Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jeurceramsoc.2023.07.035

researchmap

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.23-00019

researchmap

Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Millimeter wave absorption exceeding 70 GHz has been performed in a Co-substituted Ca–La magnetoplumbite (M-type) ferrite. A polymerized complex method was used to increase the substitution of La and Co ions in the M-type ferrite. The increase in the magnetic anisotropy field combined with the remaining significant saturation magnetization results in good magnetic resonance absorption in the millimeter range of 70–100 GHz. Above 70 GHz, good millimeter wave absorption of more than −20 dB was achieved in 0.25 mm thickness plates of Ca0.46La0.54Fe11Co0.28O19-η and Ca0.42La0.58Fe11Co0.58O19-η. Highly Co-substituted Ca–La M-type ferrites may, thus, be promising candidates for magnetic absorption materials operating in frequencies of up to 100 GHz.

DOI： 10.1063/5.0133578

researchmap

Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

An epitaxial film of YbFe2O4, a candidate for oxide electronic ferroelectrics, was fabricated on yttrium-stabilized zirconia (YSZ) substrate by magnetron sputtering technique. For the film, second harmonic generation (SHG), and a terahertz radiation signal were observed at room temperature, confirming a polar structure of the film. The azimuth angle dependence of SHG shows four leaves-like profiles and is almost identical to that in a bulk single crystal. Based on tensor analyses of the SHG profiles, we could reveal the polarization structure and the relationship between the film structure of YbFe2O4 and the crystal axes of the YSZ substrate. The observed terahertz pulse showed anisotropic polarization dependence consistent with the SHG measurement, and the intensity of the emitted terahertz pulse reached about 9.2% of that emitted from ZnTe, a typical nonlinear crystal, implying that YbFe2O4 can be applied as a terahertz wave generator in which the direction of the electric field can be easily switched.

DOI： 10.3390/ma16051989

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Recently, Fe2O3 has been considered as an alternative anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity (approximately 1000 mA h g-1), low cost, and nontoxicity. However, its rate performance remains poor relative to that of the conventional graphite anode. In this study, Fe2O3-based anodes were prepared through the annealing of biogenous Fe2O3 (L-BIOX) samples produced by an aquatic Fe-oxidizing bacterium. The effect of the annealing temperature on the performance of the synthesized Fe2O3-based material as the anode of an LIB was investigated. Electrochemical measurements revealed that the annealed L-BIOX samples at 300-700 degrees C exhibited higher rate performances than the unannealed material. Particularly, the sample annealed at 700 degrees C exhibited the highest capacity among the synthesized materials and showed a higher performance than the previously reported Fe2O3-based anodes. It exhibited a capacity of 923 mA h g-1 even at a high current density of 2 A g-1. After annealing at 700 degrees C and discharging, the synthesized biogenous material had a uniform nanocomposite structure composed of alpha-Fe2O3 nanoparticles dispersed in an amorphous matrix of Li-Si-P oxide. To form this uniform nanostructure, the solid-state diffusion resistance of the Li+ ions in the active material was reduced, which consequently improved the rate performance of the electrode. Therefore, this study provides substantial insights into the development and improvement of the performance of novel Fe2O3-based nanomaterials as the anode of LIBs.

DOI： 10.1021/acs.jpcc.2c08380

Web of Science

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.inorgchem.2c02843

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Inorganic pigments have been widely used due to their low cost of production, strong hiding power, and chemical resistance; nevertheless, they have limited hue width and chromaticity. To eliminate these disadvantages, we herein propose the use of an ingenious biotemplate technique to produce Al-enriched biogenic iron oxide (BIOX) materials. Spectrophotometric color analysis showed that high levels of Al inclusion on heat-treated BIOX samples produced heightened yellowish hues and lightness. The Al-enriched BIOX sheaths exhibited a stable tubular structure and excellent thermal stability of color tones after heating at high temperatures and repetitive heat treatments. Ultrastructural analysis and mechanical destruction experiments revealed that the highly chromatic orange-hue of these pigments are ascribed probably to an ingenious cylindrical nanocomposite architecture composed of putative Fe-included low crystalline Al oxide regions and hematite particles embedded therein. The present work therefore demonstrates that the bioengineered material can serve as an epochal orange-hued inorganic pigment with low toxicity and marked thermostability that should meet large industrial demand.

DOI： 10.1021/acsomega.1c07390

PubMed

researchmap

Publishing type：Research paper (scientific journal)  

We report an attempt valence control of the mixed valence iron triangular oxide YbFe2O4 to develop an effective technique controling the frustration of charges in strongly correlated electron systems. The electrochemical doping of Li + into YbFe2O4 was examined on a cell-type sample similar to the Li-ion secondary battery cell. Systematic changes in the lattice constant and Fe – Fe and Fe–Yb distance were observed with Li doping. Maximum value of the doping was over 300 mAh/g. An EXAFS experiment indicated that Li positioned between Yb octahedron layer (U-layer) and Fe-bipyramidal layer (W-layer). However, detailed change of iron valence state of YbFe2O4was not clearly observed because of the superimpose of the signal from iron metal nano particles in XANES observation. We discuss that the uncertainty might arise from the inhomogeneous distribution of the sample particle size, which might prevent the homogeneous doping of Li because the doping occurs on the surface of each nano-particles.

DOI： 10.1016/j.jpcs.2021.110468

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

DOI： 10.1063/5.0066289

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

YbFe<INF>2</INF>O<INF>4</INF> is a charge-ordered ferroelectric that exhibits coupling between magnetization and electric polarization near room temperature and crystallizes in a rhombohedral structure (R3m). This study presents an attempt to fabricate stoichiometric and epitaxial YbFe<INF>2</INF>O<INF>4-delta</INF> films with a nearly single-domain structure using an RF magnetron sputtering method. The (0001)-oriented epitaxial films of YbFe<INF>2</INF>O<INF>4-delta</INF> on YSZ (111) substrates via reactive sputtering method exhibited clear three-fold symmetry normal to the substrate without the formation of twin domains rotated by 60 degrees. The oxygen stoichiometry of the epitaxial YbFe<INF>2</INF>O<INF>4-delta</INF> was improved by controlling an oxygen partial pressure (P<INF>O<INF>2</INF></INF>) during the deposition. The films showed a sharp ferrimagnetic transition, and the transition temperature (T<INF>N</INF>) increased linearly to approximately 245 K with decreasing P<INF>O<INF>2</INF></INF>. The magnitude of magnetization of the obtained films was comparable to that of bulk single crystals. Further, the electron diffraction pattern of the stoichiometric films confirmed the presence of three-dimensional charge order, which is consistent with the behavior of the bulk crystals as well.

DOI： 10.1039/d1ce00834j

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We report the band structure of Ba-deficient BaTiO3 as a p-type semiconductor, studied by a combination of light reflectance and photoelectron yield spectroscopy. Two acceptor levels were observed at the tail of a valence band. As the quantity of Ba vacancies increased, the density of state of the two acceptor levels also increased. The levels of the conduction band minimum and the valence band maximum shifted far away from the vacuum level, but the bandgap seems to be independent of Ba deficient concentration. For classical semiconductors such as Si and GaAs, the observation of impurity levels is restricted to low temperatures (similar to 20K) owing to their narrow bandgaps. Oxide semiconductors have now been demonstrated with wide bandgaps and acceptor levels, at normal operating temperatures, which could lead to new device designs in the future.

DOI： 10.1063/5.0033761

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

A mixture of a lead-free multicomponent alkali borosilicate glass frit containing zinc ions and hematite was heat-treated under various conditions to elucidate the reaction between the two components, which is essentially important for controlling the color of red overglaze enamels. Above the glass transition temperature, the interaction between the frit fluid and hematite was evident, as the viscosity of the frit decreased. Moreover, hematite dissolved, the iron ions diffused into the glass matrix and they precipitated on residual hematite, resulting in enhanced crystal growth through Ostwald ripening. Concurrently, the iron and zinc ions reacted to form zinc ferrite. During cooling, the supersaturated iron ions were consumed for precipitation of hematite and zinc ferrite. Because frit and hematite dramatically react during heat treatment, conventional modification of hematite alone is insufficient. Development of the frit exhibiting low reactivity toward hematite through precise control of physical properties is a future challenging issue.

DOI： 10.1016/j.jeurceramsoc.2020.08.037

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE RESEARCH  

Skewed band structures have been empirically described in ferroelectric materials to explain the functioning of recently developed ferroelectric tunneling junction (FTJs). Nonvolatile ferroelectric random access memory (FeRAM) and the artificial neural network device based on the FTJ system are rapidly developing. However, because the actual ferroelectric band structure has not been elucidated, precise designing of devices has to be advanced through appropriate heuristics. Here, we perform angle-resolved hard X-ray photoemission spectroscopy of ferroelectric BaTiO3 thin films for the direct observation of ferroelectric band skewing structure as the depth profiles of atomic orbitals. The depth-resolved electronic band structure consists of three depth regions: a potential slope along the electric polarization in the core, the surface and interface exhibiting slight changes. We also demonstrate that the direction of the energy shift is controlled by the polarization reversal. In the ferroelectric skewed band structure, we found that the difference in energy shifts of the atomic orbitals is correlated with the atomic configuration of the soft phonon mode reflecting the Born effective charges. These findings lead to a better understanding of the origin of electric polarization.

DOI： 10.1038/s41598-020-67651-w

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Inspired by a bacteriogenic, iron-based oxide material and a traditional Japanese red pigment, a bright yellowish-red pigment was prepared by heating an Al-containing iron oxyhydroxide precursor. The obtained red pigment had a unique porous disk-like structure, comprising Al-substituted hematite particles and crystalline alumina nanoparticles. Although these disk-like structures loosely gathered to form an aggregate in powder, they can be easily dispersed into a single, disk-like structure by simple ultrasonic irradiation. The powder exhibited a bright yellowish-red color and high thermostability, making it attractive as a coloring material for various industrial products needing a bright-red color, high weather resistance, and durability. Quantitative color measurements revealed extremely high L*, a*, and b* values that are much greater than those of commercially available hematite. The thermostability test showed that even after exposure to high temperatures, the pigment retained the red color, indicating its high thermostability. The unique microstructure should be strongly related to the bright yellowish-red color and the high thermostability of the developed red pigment.

DOI： 10.1021/acsomega.9b04297

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Intermittent parathyroid hormone (PTH) administration is known to promote bone healing after surgical procedures. However, the mechanism and influence of PTH on the mineral and collagen quality of the jaw are not well understood. Most studies have focused on analyzing the bone density and microstructure of the mandible, and have insufficiently investigated its mineral and collagen quality. Oxidative stress activates osteoclasts, produces advanced glycation end products, and worsens mineral and collagen quality. We hypothesized that PTH induces oxidation and affects the mineral and collagen quality of newly formed mandibular bone. To test this, we examined the mineral and collagen quality of newly formed mandibular bone in rats administered PTH, and analyzed serum after intermittent PTH administration to examine the degree of oxidation. PTH administration reduced mineralization and worsened mineral and collagen quality in newly formed bone. In addition, total anti-oxidant capacity in serum was significantly decreased and the oxidative-INDEX was increased among PTH-treated compared to vehicle-treated rats, indicating serum oxidation. In conclusion, intermittent administration of PTH reduced mineral and collagen quality in newly formed mandibular bone. This effect may have been induced by oxidation.

DOI： 10.1038/s41598-019-44389-8

researchmap

Other Link： http://www.nature.com/articles/s41598-019-44389-8

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

Nanometric amorphous iron-based oxides of bacterial origin show a great potential as an Fe3+/Fe-0 conversion anode material for lithium-ion batteries. By means of in situ Mossbauer spectroscopy, chemical states of Fe ions were examined under the discharge-charge process of the bacterial iron-oxide electrode in a lithium-ion half-cell. As for the first discharge process, the successive reduction of Fe3+-> Fe2+-> Fe-0 occurred in the electrode as a function of the cell voltage. While on the charge process, Fe-0 in the electrode was oxidized directly to Fe3+ without going through Fe2+.

DOI： 10.1007/s10751-019-1639-y

Web of Science

researchmap

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Cobalt blue is one of the most chemically and thermally stable blue pigments. However, cobalt is scarce and expensive. To minimize the use of cobalt and reduce production costs and toxicity, cobalt blue core-shell pigments were synthesized by a solid-state method, which is cheaper than a liquid-phase reaction. Small cobalt hydroxide particles and large -alumina particles, in various ratios, were used as the starting materials. The dry mixed powders were calcined at 1200 degrees C for 2hours. Elemental mappings of the surfaces and cross sections of the synthesized particles showed that the cobalt blue had a core-shell structure. X-ray diffraction patterns showed that the synthesized cobalt blue consisted of an -alumina core and a cobalt aluminate shell. The color tone of the synthesized cobalt blue was evaluated from the lightness (L*) and chroma (C*) values. The color tone of the cobalt blue synthesized in this study was almost same as those of commercially available samples although the cobalt molar fraction was lower than the stoichiometric ratio (Co/(Co+Al)=0.33, Co/Al=0.5) which was calculated from the chemical reaction formula.

DOI： 10.1111/jace.16191

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

An oxide system Sc2-xFexO3 prepared by a conventional solid-state reaction method was found to change its color from the well-known reddish color at x = 2.0 to a yellowish color at x approximate to 0.6 and to a greenish-yellow color at 0.2 <= x <= 0.4. According to the structural characterization results for this system, the monophasic corundum phase region persists for 1.6 <= x <= 2.0, whereas the bixbyite-type phase is monophasic for 0 <= x <= 1.0. The intermediate region of 1.2 <= x <= 1.4 is a mixed region. Because green is a rare color for iron oxides, powder of the most typical composition, x = 0.4, with (L*, a*, b*) coordinates of (77.3, - 0.5, 51.0) was tested as a pigment for a Japanese-style painting and also as an overglaze enamel on porcelain; reasonably good results were obtained.

DOI： 10.1016/j.materresbull.2018.09.035

Web of Science

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

The color tone of pigments is affected by various factors such as crystal structure and particle size. These characteristics should be determined by synthesis condition. In this study, the influence of cobalt source on the color tone of cobalt blue pigment was investigated. Cobalt blue (CoAl2O4) was synthesized by solid-state reaction method. Co3O4 and Co(OH)2 with two different particle sizes were used as the cobalt source, and γ-Al2O3 was used as the aluminum source. The products were characterized by spectrophotometry, XRD, SEM, and TG/DTA. It was revealed that the chroma of the synthesized cobalt blue depends on the cobalt source. The cobalt blue synthesized using smaller size Co(OH)2 showed most vivid color. It was suggested that the number of the contact points between the starting materials increased with decreasing the particle size, leading to the progress of the reaction.

DOI： 10.4164/sptj.56.446

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Cathepsin K inhibitors are new drugs with the potential for the treatment of osteoporosis because they sustain bony remodelling better than bone resorption inhibitors such as bisphosphonates. The treatment of osteoporosis with inhibitors of bony resorption is associated with osteonecrosis of the jaw, as the deterioration in bony quality that they induce is thought to be one of its causes. The quality of bone is delineated by structural and material characteristics (which include the degree and quality of mineralisation, and depends on the content of proteoglycan and the structural integrity of the bony collagen).1,2 Animal and clinical studies have shown that cathepsin K inhibitors improve the mineral density and structural characteristics of bone, but their effect on the rest remains unknown. We therefore hypothesised that these inhibitors will affect the material characteristics of newly-formed mandibular bone. To verify our hypothesis, we used Raman microspectroscopy to examine such bone in rats that were given a cathepsin K inhibitor, and found unusual crystallinity and an increased substitution of carbonate (CO32-) in its crystal structure.

DOI： 10.1016/j.bjoms.2018.08.003

PubMed

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2497/jjspm.65.585

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Bone quality is defined by structural and material characteristics. Most studies on the mandible have focused on the analysis of structural characteristics, with insufficient investigation of material characteristics. This study tested whether zoledronate affects the material characteristics of newly formed mandibular bone. Thirty-six female Wistar rats were assigned to three groups: sham-ovariectomized rats (SHAM, n=12), ovariectomized rats (OVX, n=12), and ovariectomized rats treated with zoledronate (ZOL, n=12). The left side of the mandibular ramus of all rats was drilled bicortically. Twenty-eight days after surgery, all surviving rats were euthanized and all mandibles were removed. Raman microspectroscopy was performed, and five spectra per specimen of newly formed mandibular bone were analysed. Compared with OVX rats, the mineral/matrix ratio in ZOL rats was significantly increased (5.43±1.88 vs. 7.86±2.05), while crystallinity (0.055±0.002 vs. 0.050±0.002), relative proteoglycan content (0.43±0.10 vs. 0.31±0.05), and collagen structural integrity (1.16±0.21 vs. 0.72±0.06) were significantly decreased. These changes in material characteristics may explain why rats that received zoledronate exhibited peculiar biological phenomena such as bisphosphonate-related osteonecrosis of the jaw.

DOI： 10.1016/j.ijom.2018.02.002

PubMed

researchmap

Publishing type：Research paper (scientific journal)   Publisher：The Royal Society  

This paper reports the structural and optical investigations of the structural colour of the weevil
<italic>Lamprocyphus</italic>
<italic>augustus</italic>
. The photonic crystal structure within the weevil's scales was investigated using sequential focused ion-beam milling and scanning electron microscopy imaging. We carefully analysed the reconstructed three-dimensional structure to determine the unit cell of the photonic crystal. It was found that the cuticle network of the cubic unit cell perfectly matches the previously reported diamond-based network. However, different results were obtained for the crystal orientations of the small crystal domains that comprise the entire photonic crystal structure in the scales:
<monospace>&lt;111&gt;</monospace>
directions are highly preferred along the surface normal of the scale. This finding explains the fact that the scale is almost uniformly coloured despite the multi-domain structure. It is confirmed experimentally and theoretically that the wavelength range of the reflection band corresponds to the gap of the photonic band.

DOI： 10.1098/rsif.2018.0360

researchmap

Other Link： https://royalsocietypublishing.org/doi/full-xml/10.1098/rsif.2018.0360

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.73.1.0_2571

CiNii Article

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.72.2.0_2307

CiNii Article

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_2691

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_2708

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_2543

CiNii Article

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_2545

CiNii Article

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Ferroelectric barium titanate, BaTiO3 (BT) was coated on lithium cobaltate, LiCoO2 (LC), as an artificial solid electrolyte interface (SEI), via the simple sol-gel route. The high charge-discharge rate capabilities of the composite cathodes were evaluated up to 10C. The LC loaded with 1 mol% of BT had a measured capacity of 146 mAh/g, which was the highest value measured at 10C. This capacity was 78% of its initial value, and was 238% of the capacity of bare LC over the same number of cycles. (C) 2015 The Electrochemical Society. All rights reserved.

DOI： 10.1149/2.0041512eel

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_2704

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_2743

CiNii Article

CiNii Books

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The high charge-discharge rate characteristics of composite cathodes consisting of ferroelectric BaTiO3 (BT)-coated LiCoO2 (LC), synthesized via a simple sol-gel route, were evaluated, and the rate showed stepwise increases to as high as 5C. The LC-BT composite cathode annealed at 600 degrees C, LC-BT-600, notably retained high capacities, i.e., 122 mAh/g at 30 cycles, 5C and 99 mAh/g at 60 cycles, 5C. These capacities corresponded to 83% and 67% of the initial values and were as high as 158% and 245% of the capacities of bare LC over the same cycles, respectively. The ferroelectricity of the coated BT contributed to the improvement in high-rate performance. (c) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4898006

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER  

Ilmenite-type FeGeO3 was prepared by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus at 23.5 GPa and 500 A degrees C. The effects of post annealing on the high-pressure synthesized samples were investigated by XRD analysis, Mossbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity and increased the crystallite size of the ilmenite-type FeGeO3. The room temperature Mossbauer spectrum was composed of sharp paramagnetic doublets assigned to Fe2+. The well-crystallized ilmenite-type FeGeO3 showed typical antiferromagnetic behavior with the N,el temperature of 79 K, while the as-prepared sample without annealing demonstrated the superparamagnetic characteristics with larger magnetization.

DOI： 10.1007/s10751-014-1014-y

Web of Science

Scopus

researchmap

Other Link： http://orcid.org/0000-0002-5422-7396

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

To clarify the detailed features of the red bengala samples excavated from the Shimo-ohgibaru archaeological site in the late Yayoi period (2^nd to 3^rd century A.D.) from the viewpoint of materials science, colorimetric measurements, X-ray fluorescence analyses, X-ray diffraction measurements, transmission electron microscope observations, and surface area measurements of the ancient bengala samples were achieved. The ancient bengala sample was found to be high purity α - Fe₂O₃. The features of the color tone and particle size of the ancient bengala were clarified by comparing with those of commercially available bengala, Fukiya bengala, and synthesized α-Fe₂O₃. In addition, the starting materials and synthesis processes of the ancient bengala were discussed by applying the elutriation experiments of representative natural hematite and heat-treated natural iron hydroxide (Oniita).

DOI： 10.2497/jjspm.60.146

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/10018736921?from=CiNii

Language：Japanese   Publisher：Japan Society of Powder and Powder Metallurgy  

In the natural aquatic environment, there are various types of biogenic manganese oxide (BMO) precipitates which are produced by manganese oxidizing microorganisms, at ambient temperature, atmosphere and neutral pH.BMO is a very interesting and useful functional material because of its unique property; hollow globule shape formed by nanosheets, large surface area and photocatalytic characteristics. In this study, thermally-processed BMO at 100 − 1000 °C was analyzed by XRD, XANES, SEM, TEM and nitrogen adsorption method to reveal the effects of heat-treatment on its crystal structure, Mn valence state, globule morphology, microstructure, pore size distribution and specific surface area. In the result, morphology of BMO is maintained below 800 °C, while nanosheets composing BMO were changed into nanoparticles at 600 °C. The crystal structure was transformed from birnessite into hausmannite (Mn₃O₄) at 600 °C. The specific surface area was increased by heat-treatment between 300 and 500 °C. In cases of artificial manganese oxides, such changes of crystal structure and specific surface area were not observed, and combustion of organic materials produced by microorganisms in BMO probably has a large effect on them.

DOI： 10.2497/jjspm.60.92

CiNii Article

CiNii Books

J-GLOBAL

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Synthesis of Sr3Zn2Fe24O41 Z-type ferrite was investigated. Precursors of ferrite were prepared by polymerizable complex method. Identification of formed phases in the obtained samples and determination of lattice parameters of Z-type ferrite were performed by powder X-ray diffraction (XRD). Single-phase of Sr3Zn2Fe24O41 Z-type ferrite was synthesized by heating at 1463 K for 5hours in air. M-H curve of prepared single-phase Sr3Zn2Fe24O41 Z-type ferrite was measured by using vibrating sample magnetometer (VSM). It was revealed that Sr3Zn2Fe24O41 Z-type ferrite has larger saturation magnetization (23.5 mu(B)/formula unit) than that of Sr3Co2Fe24O41 (22.7 mu B/formula unit) and shows characteristic two-step saturation of magnetization as well as Sr3Co2Fe24O41 Z-type ferrite.

DOI： 10.4028/www.scientific.net/KEM.566.231

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Synthesis of U-type hexaferrite was investigated in the various strontium-based systems (Sr-Me-Fe-O system, Me = Co, Zn, Cu, and Ni). Precursors of ferrites were prepared by polymerizable complex method. Sr4Me2Fe36O60 (Me = Co and Zn) U-type hexaferrites were synthesized at the temperature range between 1423 and 1483 K in air. Coercivity of obtained ferrite was decreased with increasing heat treatment temperatures. Cu substitution reduced formation temperature of U-type hexaferrite.

DOI： 10.4028/www.scientific.net/KEM.566.227

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

By heating an amorphous iron oxide produced by Leptothrix ochracea, an iron-oxidizing bacterium species, at 600-1100 degrees C in air for 2 h, vivid red-colored powdered materials including alpha-Fe2O3 (hematite) and amorphous silicate with high thermostability were prepared which offer potential for use as over-glaze enamels on porcelain. The precise color tone of the materials greatly depends on the heat-treatment temperature. The most strikingly beautiful sample, heat-treated at 800 degrees C, is light yellowish-red in color (L* = 47.3, a* = 34.1, and b* = 34.6), has a unique microstructure, and does not fade in color even with reheating at 800 degrees C, which is the firing temperature for over-glaze enamel on porcelain. The sample primarily consists of crystalline hematite particles similar to 40 nm in diameter with slightly longer axis unit-cell parameters than those of pure hematite. The particles are covered with amorphous silicate phase similar to 5 nm in thickness and are intricately interconnected into microtubules with an average diameter of 1.26 mu m. The attractive color of this material is due to the following structural features: small particle size (similar to 40 nm). nanocomposite of hematite and amorphous silicate, and a microtubule structure that inhibits aggregation of individual hematite particles and microtubules. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2012.06.024

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

Formation mechanism of β-Fe₂O₃ particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO₄)₂ and Na₃Fe(SO₄)₃ to NaCl and the heat treatment temperature. The heat treatment temperature strongly affected the particle shapes and sizes. β-Fe₂O₃ was found to be formed by two different reactions; one is a solid state reaction below 490 °C, and another is a liquid phase-mediated reaction above 490 °C. β-Fe₂O₃ had granular shape with a diameter of about 50 to 100 nm below 490 °C, while at high temperatures above 490 °C cubic particles with relatively large size of about 500 nm to 2 μm were produced. We found that this dramatically change of particle morphology including their sizes and shapes was caused by the effects of the liquid phase in the reaction.

DOI： 10.2497/jjspm.58.529

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00384211894?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER  

Formation of LaFeO3 nanoparticles obtained from thermal decomposition of organometallic precursors was investigated as a function of the heat-treatment temperature. The precursors heat-treated below 300 degrees C were amorphous, but above 350 degrees C a single-phase of nanocrystalline LaFeO3 was formed. The LaFeO3 nanoparticles showed the superparamagnetic behavior in both magnetization and Mossbauer measurements. With increasing heat-treatment temperature, the crystallite size of LaFeO3 nanoparticles was gradually increased. The quadrupole splitting and isomer shift of paramagnetic doublet pattern were affected by the growth of LaFeO3 particles.

DOI： 10.1007/s10751-011-0423-4

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Synthesis of La-Co substituted M-type Calcium hexaferrite was studied. Samples were prepared by polymerizable complex method. High purity reagent of strontium carbonate, iron (III) nitrate ennnahydrate, cobalt (II) nitrate hexahydrate and lanthanum oxide were used as starting materials. Prepared aqueous solution was heated for dehydration and gelling. Thermal pyrolysis was carried out by heating the gel. The obtained precursor powders were ground with an alumina mortar and compacted by uniaxial pressing into disk specimens and then heated at temperature range between 1173 K and 1573 K in air. Phase identification and determination of lattice parameters were carried out by powder X-ray diffraction (XRD). Scanning Electron Microscope (SEM) was utilized to investigate the microstructure of the polycrystalline ferrites. Magnetic properties were discussed by magnetization measurements by measuring of M-H curve with vibrating sample magnetometer (VSM). Single-phase of M-type hexaferrite was obtained at lower temperature relative to by conventional synthesis.

DOI： 10.1088/1757-899X/18/9/092040

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Formation mechanism of nano-crystalline β-Fe O particles was investigated by controlling the preparation conditions such as the mixing ratio of NaFe(SO ) to NaCl and heating treatment temperature. A single phase of β-Fe O was formed regardless of the mixing ratio. The heat treatment temperature strongly affected the particle shapes and sizes. Below 490 °C, they had granular shape with a diameter of about 50 to 100 nm. While, above 490 °C, cubic particles with increased size of about 1 μm were produced. All samples were antiferromagnetic at low temperature. The Néel temperature (T ) of 119 K for the large cubic particles was decreased to 113 K for the nanoparticles. © 2010 IOP Publishing Ltd. 2 3 4 2 2 3 N

DOI： 10.1088/1742-6596/200/8/082003

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Ilmenite (FeTiO ) is an antiferromagnetic insulator with Néel temperature (T ) of 55 K. The magnetic structure of FeTiO is known to be easily frustrated by cation substitution. In the present study we tried to prepare the Ge-substituted FeTiO . The samples were prepared by the conventional solid state reaction technique under the controlled oxygen pressure. Formation of a single phase of FeTi Ge O with x=0.01 was confirmed by X-ray diffraction (XRD) method. The Ge-substituted FeTiO had a smaller lattice volume than that of un-doped one. SQUID magnetometer and Mössbauer spectroscopy measurements indicated that the Ge-substitution reduced the T slightly. Moreover the magnetic hyperfine fields of Ge-substituted FeTiO seemed to be increased in spite of the decreased magnetic moments. © 2010 IOP Publishing Ltd. 3 N 3 3 1-x x 3 3 N 3

DOI： 10.1088/1742-6596/200/1/012144

Web of Science

Scopus

researchmap

Language：English   Publisher：INT UNION CRYSTALLOGRAPHY  

DOI： 10.1107/S0108767308094683

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.61.1.3.0_435_1

CiNii Article

CiNii Books

researchmap

Publishing type：Research paper (international conference proceedings)  

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

Well-crystallized Y-type hexagonal ferrite films with highly c-axis orientation were successfully preparated on Ag substrates by polymerized complex method. The Co-2-Y phase started to form at 780 degrees C and nearly single-phase Of Co-2-Y was formed when the films heat-treated above 820 degrees C. The films had large in-plane magnetic anisotropy with small in-plane Hc of about 300 Oe. When it was heat-treated at 860 degrees C, the Ms had maximam value of 192 emu/cm(3). The heat-treatment time also influence the magnetic properties of the films. The films with nearly the single-phase Of Co-2-Y were formed when the films had stoichiometric Ba:Co:Fe ratio of 1:1:6.

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

Thin films of the hematite-ilmenite solid solution (ot-Fe2O3-FeTiO3) are one of the candidates for practical magnetic semiconductors with a high Curie temperature (Tc). We have successfully prepared well-crystallized epitaxial Fe1.2Ti0.8O3 films on alpha-Al2O3 substrates by using a reactive helicon plasma sputtering technique. Only the films having the R3 symmetry had large ferrimagnetic moments, where the Fe-rich and the Ti-rich cation layers were alternately stacked along the c-axis. To obtain the order structure (R3) for the Fe1.2Ti0.8O3 films, a higher substrate temperature and/or post annealing at 600 degrees C were very effective. Unfortunately the Fe1.2Ti0.8O3 solution has the lower Tc of about 250 K in bulk form. Trying to raise up the Tc of Fe1.2Ti0.8O3 multilayered films of alpha-Fe2O3/Fe1.2Ti0.8O3 were also prepared. At the moment, though, we did not success the preparation of high-Tc multilayered films beyond the room temperature. Low temperature magnetization measurements and Mossbauer spectroscopy suggested that the exchange coupling between alpha-Fe2O3 and Fe1.2Ti0.8O3 seemed to provide a large possibility to increase the Tc of Fe1.2Ti0.8O3 layers beyond the room temperature.

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

Hematite (alpha-Fe2O3) is one of the most primitive and attractive red pigments. The particle size of hematite seriously influences the reddish tone. The particle with the smallest size of about 100 nm had yellowish red color. With increasing the particle size, the tone color changed systematically from yellowish red to red, dark red, and dark purple. To control the tone color of hematite we prepared Al-substituted Hematite (alpha-(Fe1-xAlx)(2)O-3) by polymerized complex method using iron nitrate (Fe(NO3)(3)-9H(2)O) and aluminum nitrate (Al(NO3)(3)-9H(2)O) as starting materials. The precursors were heat-treated at the temperature between 500 degrees C and 1100 degrees C for 2 hours. When the samples were heat-treated at 1100 degrees C, the solubility limit of Al in hematite up to 13%. The particle size of the sample heat-treated at 1000 degrees C without Al substitution was about 2 pm, while the one with 10% Al-substitution was about 200 nm. The Al substitution suppressed the grain growth of hematite. With increasing the Al content, the temperature at which the color of hematite changed from yellowish red to dark purple increased monotonically. Moreover the Al-substitution seemed to stabilize the maghemite phase (gamma-Fe2O3) at higher temperature.. The XRD pattern of Al-substituted samples heat-treated at 700 degrees C showed some diffraction lines assigned to gamma-Fe2O3. This would be a reason to suppress the grain growth of hematite.

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

Magnetic properties of La-Co substituted M-type Sr ferrite powders were studied. Samples were prepared from the citrate precursors. High purity reagent of Sr(NO3)(2), Fe(NO3)(3)(.)9H(2)O, Co(NO3)(2)(6H2O)-H-. and La2O3 were used as starting materials. They were dissolved in distilled water with citric acid. The nominal molar ratio of the mixed solutions were I : 5 of metal : citric acid. Prepared aqueous solution was heated at 120 degrees C for dehydration and gelling. Thermal pyrolysis was carried out by heating the gel at the temperature range between 300 degrees C and 350 degrees C for 1h in air. The obtained precursor powders were ground with an alumina mortar and compacted by uniaxial pressing into disk specimens, 20 mm in diameter and I mm thick, and then heated at temperature range between 750 degrees C and 900 degrees C in air. Phase identification and determination of lattice parameters were carried out by powder X-ray diffraction (XRD). Scanning Electron Microscope (SEM) was utilized to investigate the microstructure of the polycrystalline ferrites. Magnetic properties were discussed by magnetization measurements by using a vibration sample magnetometer (VSM) at a maximum applied field of 16 kOe. Magnetization and coercive force were measured at room temperature. Temperature dependence of residual magnetization was measured for determine the Curie temperature. The La-Co substituted SrM ferrite powders prepared in this study showed typical magnetic hysterisis of hard ferrite. Extreme enhancement of coercive force was performed by La-Co substitution. Maximum value of coercive force achieved in this study is 8.0 kOe. This enhancement of coercive force is realized by mainly increase of magnetocrystal line anisotropy caused by La-Co substitution.

Web of Science

researchmap

Synthesis and magnetic properties of M-type hexagonal ferrites with chemical composition of AFe12O19 (A = Ba and Sr) were studied. Nitrates of barium, strontium and iron were used as starting materials. The precursor of M-type ferrites was prepared mainly by the polymerization of metal-citric complex with various amounts of ethylene glycol, and heating the gel at 300 oC. The precursor was ground, pressed by uniaxial compression in a die and heated at 750-950 oC in air. From these results, large coercive force of the samples in this study is probably caused by achievement of small grain size under the single domain size by polymerized complex method.

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：MATERIALS RESEARCH SOCIETY  

Since the beginning of the 18th century A.D., an artificial iron oxide pigment (hematite, called "bengara" in Japanese) and having a beautiful yellowish red color, has been produced in Japan and applied to pottery, textiles and paintings. However, in 1965 the traditional "bengara" could not be produced anymore, mainly because of environmental pollution. The purpose of this study is to make clear the features of traditional "bengara" and to reproduce high quality "bengara" using modern high-purity reagents. Traditional "bengara" has been characterized as hematite containing a small amount of Al. The average size of the "bengara" particles is approximately 100 nm. The color becomes more yellowish-red with increasing Al content. A monophase of hematite prepared by heating a mixture FeSO -7H O and α-Al O to about 680°C included a small amount of Al substituted in a solid solution. The particle size greatly decreased as the heat treatment temperature was decreased : 100 nm at 770°C but 50 nm at 650°C. The color of the particles becomes more vivid as the temperature is decreased, but within bounds this color is independent of the amount of Al in solid solution. 4 2 2 3

DOI： 10.1557/proc-712-ii8.2

Web of Science

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

In an attempt to obtain wustite Fe O as epitaxial films on MgO(100), NO -assisted molecular-beam epitaxy was applied. At low NO fluxes, the low-energy electron diffraction and reflection high-energy electron diffraction images indeed indicate the formation of a rocksaltlike structure. In addition, Mössbauer spectroscopy provides evidence for the formation of a phase that is paramagnetic at room temperature. However, the layers are not pure oxides but are well-ordered oxynitrides with composition Fe O N . The nitrogen atoms occupy substitutional sites on the oxygen-anion sublattice. Similarly, at slightly higher NO fluxes, magnetitelike oxynitride films with composition Fe O N are obtained. By correlating x-ray photoelectron spectroscopy spectra with the intensity oscillation periods observed during reflection high-energy electron diffraction, it is possible to derive the complete stoichiometry of the films. We propose that the abrupt incorporation of nitrogen atoms only occurs if the atomic oxygen provided by the NO flux is insufficient to form a stoichiometric Fe O . 1-x 2 2 1-x 1-y y 2 3+δ 4-y y 2 3 4

DOI： 10.1103/physrevb.63.125409

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 粉体粉末冶金協会  

Bi-2223 bulk superconductors were irradiated with 290MeV/n Ar ions. Ar irradiation effects on flux pinning of Bi-2223, which were estimated as ΔM from magnetic hysteresis loops measured by SQUID and VSM, were discussed. Irradiated samples had enlarged magnetic hysteresis loops than unirradiated samples. Moreover, the increment of ΔM depended on depth from the irradiation surface. Microstructure of irradiated samples were observed by high-resolution transmission electron microscopy (HR-TEM). However, irradiation defects such as the columnar defects were not observed in these samples. 40 18+ 40 18+

DOI： 10.2497/jjspm.46.994

Scopus

CiNii Article

J-GLOBAL

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevb.59.3195

researchmap

Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.59.3195/fulltext

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Publishing type：Research paper (international conference proceedings)  

We have made a study of the use of NO as the source of oxygen in the MBE-growth of iron oxides thin films. It is found that NO is a much more efficient oxidizing agent than molecular O . As indicated by Moessbauer spectroscopy, performed on Fe probe layers, NO is not only capable of forming stoichiometric magnetite Fe O , but also all non-stoichiometric Fe O phases. Even the metastable maghemite phase γ-Fe O (Fe O with δ = 1/3) can be formed. All iron oxides grow layer-by-layer-like, as indicated by strong RHEED intensity oscillations. When small doses of NO are used, new wustite Fe O and Fe O phases are formed. In contrast to the Fe O films, these phases have nitrogen incorporated into the crystal lattice. Similar compounds are obtained when NO is used as the source of oxygen. The use of N O does not lead to the formation of iron oxides. It does, however, alter the growth mode of Fe on MgO(100). Whereas Fe deposited under UHV conditions forms 3D islands, the N O acts as a surfactant and induces 2D layer-by-layer growth. 2 2 2 2 3 4 3-δ 4 2 3 3-δ 4 2 1-x 3 4 3-δ 4 2 2 57

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

Co Fe O (0. 1≤×≤1.0) films and a Co Fe O /Zn Fe O double layered film were prepared on soda-lime glass substrate (a=87×10 /deg) by plasma enhanced MOCVD and their microstructures and magnetic properties were studied. The Co ferrite films consisted of a random orientated initial layer (thickness < 100 nm) and an <100> orientated columnar layer. Conversion electron Mossbauer spectra and magnetization curves of the films indicated that the films had an easy axis perpendicular to the film plane. The Co ferrite film with higly perpendicular magnetic anisotropy could be obtained by using Zn ferrite film (thickness:210 nm) as a buffer layer between the Co ferrite film and the substrate. © 1993, Japan Society of Powder and Powder Metallurgy. All rights reserved. x a-x 4 0.1 2.9 4 0.5 2.5 4 -7

DOI： 10.2497/jjspm.40.618

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

The 720 and 780 cm components of the deconvoluted Raman spectra of glasses in the systems R O-TeO (R=Li, Na, K, Ba, Zn) were attributed to TeO groups and the 665 cm band was to TeO groups. The theoretical values of the molar ratio TeO /TeO derived from an assumed vitrification reaction were compared with the ratio derived from the intensity ratios of the Raman bands, I(720) /I(665) and I(780)/I(665). It was indicated that [O Te=O] and [O Te(=O)-O] units were induced by the addition of network modifying oxides in the composition range of lower atomic ratio O/Te. It was proposed that the decrease in the rate of increase of the ratio TeO /TeO in the range of larger O/Te was due to the equilibrium TeO ↔[O12/2Te=O] favoring the former unit. © 1993, The Society of Materials Science, Japan. All rights reserved. -1 -1 - n 2 3 4 3 4 2/2 1/2 3 4 4/2

DOI： 10.2472/jsms.42.473

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

Aqueous solutions of calcium nitrate stabilized with EDTA, ammonium dihydrogen orthophosphate and iron (III) nitrate were mixed before they were subject to ultrasonic spraying and to subsequent pyrolysis in an electric furnace, and particles of 0.45μm in average diameter consisting of hydroxyapatite and hematite were obtained. Surface morphology and microstructure of the particles were examined. A nucleus (hematite)-shell (hydroxyapatite) type structure was observed for larger particles (>0.8μm in diameter) though the particles of medium size apparently had a uniform microstructure. Such structural difference due to the particle size was explained in terms of decomposition of the Ca-EDTA chelating bond at lowest temperatures and temperature distribution in the sprayed mists. © 1992, Japan Society of Powder and Powder Metallurgy. All rights reserved.

DOI： 10.2497/jjspm.39.239

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

As studied in our previous works, a proportional counter filled with pure helium gas works well at low temperatures near 4.2 K. The helium-filled proportional counter (HFPC) provides us with a new method to detect nuclear radiations at low temperatures. A typical application of this counter is resonance-electron Mössbauer spectroscopy (REMS) at low temperatures (< ∼ 30 K). In this article some examples of REMS measurements with HFPC are given. © 1989.

DOI： 10.1016/0168-9002(89)90918-2

Scopus

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：English   Publisher：MDPI  

Iron oxide minerals, schwertmannite and goethite, which are naturally occurring in acidic environments are attractive nanostructured materials because of the potential diverse applications. Although the biosynthesis of schwertmannite by acidophilic Fe(II)-oxidizing microorganisms has been investigated, little is known about goethite biosynthesis under acidic conditions. To examine a biological approach to the synthesis of these minerals, bioreactor experiments were conducted with a newly isolated acidophilic betaproteobacterium. The bioproducts were characterized by powder X-ray diffraction, cryogenic Mossbauer spectroscopy, and electron microscopy. The cultures growing at 25 degrees C and pH 3.0 or at 37 degrees C and pH 2.5 oxidized Fe(II) and precipitated schwertmannite rapidly. Increasing pH at each temperature resulted in the concomitant production of goethite, and 90% pure goethite was obtained at 37 degrees C and pH 3.5. The goethite phase was nano-sized and had relatively large specific surface area (133 m(2).g(-1)), leading to high sorption capacity for metal oxyanions. Schwertmannite was also a good adsorbent for oxyanions, regardless of the smaller specific surface area. Our results indicate that these acidophilic microbial cultures serve as a simple rapid system for the synthesis of nanostructured goethite as well as schwertmannite.

DOI： 10.3390/min8030098

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Cobalt blue is an inorganic pigment with an intense blue color, and consists mainly of cobalt aluminate (CoAl2O4) spinet. Many synthesis methods for cobalt blue have been reported, but there are no reports on the color tone of cobalt blue synthesized from different starting materials. Thus, the relationship between starting material and the color tone of the resulting product has not yet been clarified. We experimentally investigate the influence of different starting materials on the color tone of cobalt blue, synthesized by solid-state reaction. Cobalt oxide (Co3O4) was used as the cobalt source, and three types of aluminum source, Al(OH)(3), gamma-Al2O3, and alpha-Al2O3, were used. The color tone of cobalt blue was evaluated by the lightness L-* and Chroma 0 values, based on CIE L(*)a(*)b(*) color coordinates. The properties of the products were characterized by spectrophotometry, X-ray diffraction, scanning electron microscopy (SEM), particle size distribution analysis, and thermal gravimetric-differential thermal analyses. SEM images and particle size distribution analysis revealed that the lightness L-* value depends on the mass median diameter of the cobalt blue. The Chroma C-* value is affected by the crystallinity of the aluminum source. These results suggest that the lightness and Chroma values of cobalt blue can be controlled by the particle size and crystallinity of the starting materials. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.powtec.2016.06.021

Web of Science

Scopus

researchmap

Language：English   Publisher：IOP PUBLISHING LTD  

Well-crystallized epitaxial YbFe2O4 films were prepared on an alpha-Al2O3(001) substrate using an Fe3O4 buffer layer. Fe3O4 has a relatively small lattice mismatch with both YbFe2O4 and alpha-Al2O3. Electron diffraction analysis combined with transmission electron microscopy revealed the epitaxial relationship to be alpha-Al2O3[110](001) parallel to Fe3O4[211](111) parallel to YbFe2O4[110](001). Moreover, superlattice spots due the Fe2+-Fe3+ charge order state of YbFe2O4 were clarified. The Fe2+/Fe3+ ratio in YbFe2O4 was nearly stoichiometric. The film exhibited a ferrimagnetic transition at similar to 220K and a nonlinear current-voltage characteristic at room temperature. These results confirmed the good crystallinity and stoichiometry of the obtained YbFe2O4 films. (C) 2018 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.57.010305

Web of Science

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

Language：Japanese   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

Y-Type ferrite substituted with a combination of non-magnetic lithium and aluminum, Ba2Zn2-2xLixAlxFe12O22, was synthesized by polymerized complex method and the effects of substitution on their magnetic properties were investigated. The monophasic Y-Type ferrite was obtained at the composition range up to x = 0.6 and their lattice parameters decreased isotropically by the substitution. The saturation magnetization at 10 K decreased and Curie temperature increased with increasing composition x. As a result, the saturation magnetization at room temperature showed maximum at x = 0.2 and the relative complex permeability of sintered Y-Type ferrite also showed same tendency. The substituion with a combination of non-magnetic ions could enhanced the magnetic properties of Y-Type ferrite through lattice contraction and/or site occupation of iron ions.

DOI： 10.2497/jjspm.64.378

Scopus

researchmap

Language：Japanese   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

The Japanese traditional red overglaze ceramic ware, akae, a composite in which hematite particles are dispersed in a glass-frit layer, has become extremely popular with porcelain lovers all over the world. Recently, development of hematite powders dedicated to akae is strongly desired by various porcelain producers. Inspired by Fukiya bengala, a high-quality old red pigment produced in Japan in the early 18th century, we produced Al-substituted hematite powder through wet-process in a large scale. In this study, we investigated the effect of dispersion and aggregation of hematite particles on the color tone of the resultant powder, and developed a technique to produce high-quality akae using the hematite powder. The prepared powder is primarily composed of hematite nanoparticles 3 similar to 10nm in diameter that contains 5 mol% of Al3+ in the structure, and these primary particles are aggregated to form secondary particles 30-70nm in diameter. The powder showed dark brown color regardless of its nanometric character because the secondary particles form large aggregated particles with high volume fraction of hematite, leading to prevent transmission of visible light. Applying ultrasonic and silica-coating treatments that realize low volume fraction of hematite, we obtained the hematite powder exhibiting yellowish red color. In addition, high-quality akae test pieces having highly dispersive hematite particles in a glass layer were successfully prepared using ball-milling technique and subsequent combination process with the submicron-sized lead-free frit. (C) 2017 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.17031

Web of Science

researchmap

Language：Japanese   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

The Japanese traditional red overglaze ceramic ware, akae, a composite in which hematite particles are dispersed in a glass-frit layer, has become extremely popular with porcelain lovers all over the world. Recently, development of hematite powders dedicated to akae is strongly desired by various porcelain producers. Inspired by Fukiya bengala, a high-quality old red pigment produced in Japan in the early 18th century, we produced Al-substituted hematite powder through wet-process in a large scale. In this study, we investigated the effect of dispersion and aggregation of hematite particles on the color tone of the resultant powder, and developed a technique to produce high-quality akae using the hematite powder. The prepared powder is primarily composed of hematite nanoparticles 3 similar to 10nm in diameter that contains 5 mol% of Al3+ in the structure, and these primary particles are aggregated to form secondary particles 30-70nm in diameter. The powder showed dark brown color regardless of its nanometric character because the secondary particles form large aggregated particles with high volume fraction of hematite, leading to prevent transmission of visible light. Applying ultrasonic and silica-coating treatments that realize low volume fraction of hematite, we obtained the hematite powder exhibiting yellowish red color. In addition, high-quality akae test pieces having highly dispersive hematite particles in a glass layer were successfully prepared using ball-milling technique and subsequent combination process with the submicron-sized lead-free frit. (C) 2017 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.17031

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCI LTD  

Polycrystalline powder samples of the zinc-substituted strontium cobalt Z-type hexaferrite: Sr3Co2-xZnxFe24O41 (x = 0, 0.5, 1.0, 1.5 and 2.0) were prepared by the polymerizable complex method. Their Mossbauer spectra were measured at room temperature with conventional constant-acceleration spectrometer. Obtained Mossbauer spectra were numerically separated into six discrete components. The relationship between Mossbauer parameters and magnetic properties has been discussed. From the values of the isomer shift, it was found that the iron ion in Sr3Co2-xZnxFe24O41 is trivalent with high spin. The value of the quadrupole splitting increased and changed the sign from negative to positive for the sample with x = 1.5. From the results mentioned above and the analysis of the complex permeability spectra, the magnetocrystalline anisotropy of Sr3Co2-xZnxFe24O41 is changed from c-plane to c-axis at Zn content between x = 1.0 and 1.5. The compositional dependence of the areas of each subspectra showed that Zn2+ ions occupy the sites with down spin at the compositional range of x = 0.0-1.0.

DOI： 10.1016/j.ceramint.2017.05.264

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

&lt;p&gt;自発分極は試料内部の静電ポテンシャルを傾斜させる。強誘電体の原子軌道エネルギーはこの傾斜に応じて系統的に変化すると考えられる。この現象はバンドベンディングと呼ばれ40年以上に渡り予想されてきた。今回，BaTiO_3_においてバンドベンディング現象を直接的に観測したので報告する。本研究において得られた実験結果は，エピタキシャル製膜された強誘電体薄膜試料と深さ分解光電子分光実験を組み合わせることで初めて達成できた。&lt;/p&gt;

DOI： 10.11316/jpsgaiyo.72.1.0_2725

CiNii Article

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

&lt;p&gt;強誘電体に金属ナノ粒子を接合させると強誘電体の分極により金属の電子状態が変調すると考えられる。電子状態変化が触媒作用に影響することが示唆されているが、電子状態異常の直接的な観測例はない。今回、強誘電体BaTiO_3_表面に担持したPdO_x_ナノ粒子に対してX線吸収微細構造(XAFS)測定を行い、粒子表面で異常な価数状態をとることを見出した、またその発現機構についての考察を行ったので報告する。&lt;/p&gt;

CiNii Article

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

A high-capacity and high-rate-capability anode material for lithium-ion batteries, silicon-doped iron oxyhydroxide or 2-line ferrihydrite (2Fh), was prepared by mixing iron nitrate powder, tetraethyl orthosilicate, 2-propanol, and ammonium hydrogen carbonate powder at room temperature. The design of this material was inspired by a bacteriogenic product, a nanometric amorphous iron-based oxide material containing small amounts of structural Si. The atomistic structure of the prepared Si-doped 2Fh was strongly affected by the Si molar ratio [x = Si/(Fe + Si)]. Its crystallinity gradually decreased as the Si molar ratio increased, with a structural variation from nanocrystalline to amorphous at x = 0.25. The sample with x = 0.20 demonstrated the best Li storage performance. The developed material exhibited a high capacity of similar to 400 mAh g(-1) at the 25th cycle in the voltage range of 0.3-3.0 V and at a current rate of 9 A g(-1), which was three times greater than that of the Si-free 2Fh. This indicates that Si-doping into the 2Fh structure realizes good rate capability, which are presumably because of the specific nanocomposite structure of iron-based electrochemical centers embedded in the Si-based amorphous matrix, generated by reversible Li insertion/deinsertion process. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2016.08.037

Web of Science

researchmap

Language：English   Publisher：AMER INST PHYSICS  

Levels of the conduction band minimum and the valence band maximum in ion-deficient BaTiO3 particles were investigated with optical band gap and ionization energy measurements. Though it is known that the quantification of the band structure in an insulator is difficult, due to the poor electrical conductivity of BaTiO3, systematic variation in the band energy levels was found that correlated with the introduction of vacancies. Photoelectron yield spectroscopy provided direct observation of the occupancy level of electrons, which is altered by the presence of oxygen and barium vacancies. In addition, the conduction band deviation from the vacuum level was determined by optical reflectance spectroscopy. Our results show that: (1) Introduction of oxygen vacancies forms a donor level below the conduction band. (2) The conduction band is shifted to a lower level by a larger number of oxygen vacancies, while the valence band also shifts to a lower level, due to the reduction in the density of O 2p orbitals. (3) Introduction of barium vacancies widens the band gap. Since barium vacancies can induce a small number of oxygen vacancies with accompanying charge compensation, this behavior suppresses any large formation of donor levels in the gap states, indicating that cation vacancies can control the number of both donor and acceptor levels. Published by AIP Publishing.

DOI： 10.1063/1.4964803

Web of Science

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：AMER INST PHYSICS  

Rare-earth iron oxides (RFe2O4) have attracting attention as new electronic device materials because of their numerous functionalities, such as electronic ferroelectricity, ferrimagnetism, and high infrared absorption. In this paper, nearly monophasic YbFe2O4 films were prepared on alpha-Al2O3 (001) substrates by the spin coating method using an aqueous-based YbFe2O4 solution. The solution was composed of a stoichiometric ratio of Yb(CH3COO)(3) and Fe(NO3)(3) with excess chelating agents. After heat treatment above 800 degrees C, well-crystallized and highly (001)-oriented YbFe2O4 started to epitaxially form on the substrate under controlled oxygen partial pressure with H-2/CO2 gas mixtures. X-ray pole figure analysis confirmed the following epitaxial relationship: YbFe2O4[100](001)//alpha-Al2O3[100](001). Moreover formation of an Fe3O4 interracial layer between YbFe2O4 and alpha-Al2O3 was detected by high-resolution transmission electron microscopy. Presence of the Fe3O4 interracial layer seemed to release the lattice misfit with the substrate. The Fe2+/Fe3+ ratio in the obtained YbFe2O4 films was nearly stoichiometric and the indirect bandgap assigned to Fe2+ -> Fe3+ charge transfer excitation was found to be similar to 0.4 eV by optical spectroscopy. A clear magnetic transition from the paramagnetic state to the ferrimagnetic state occurred at similar to 230 K. (C) 2016 Author(s).

DOI： 10.1063/1.4961639

Web of Science

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Akae porcelain, an artistic Japanese traditional overglaze ceramic typically known for Kakiemon-style ware, has fascinated porcelain lovers around the world for over 400 years because of the graceful red color displayed by akae that matches so well with white porcelain bodies. In this work, we clarified the factors that control the color of akae and those that are conventionally controlled by artisans based on empirical experience. Inspired by a recent particle-design method, we also developed a practical facile process to prepare red paints that yields high-quality akae. Various akae samples were prepared from a combination of lead-free alkali borosilicate glass frits with different particle sizes and hematite powders with differing dispersibilities. Polarized light microscopy, scanning electron microscopy, and transmission electron microscopy analyses indicate that considering only the dispersibility of hematite powders is not sufficient, but the frit-particle size must be controlled to obtain high-quality akae with a high reflectance value for >= 580 nm visible light. In addition, we developed a process for preparing high-quality red paints that uses a large-particle frit powder and a strongly aggregated-hematite powder, both of which are easily obtainable. The red paint composed of frit, hematite, and the solvent is mixed until the paint is drying. By adding more solvent and repeating this process three times, we obtained high-quality akae with a higher reflectance value than for the akae prepared from a frit with submicron-sized particles and weakly aggregated-hematite powder. On the basis of transmission electron microscopic observations, we consider the red paint to consist of a core/shell-like composite structure of frit and hematite, forming a three-dimensional network in the akae glass layer. The good dispersibility of these particles leads to high-quality akae.

DOI： 10.1021/acsami.6b01549

Web of Science

researchmap

Language：Japanese  

J-GLOBAL

researchmap

J-GLOBAL

researchmap

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.1.0_2709

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_2505

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：ELSEVIER SCIENCE SA  

Ilmenite-hematite solid solution (Fe2-xTixO3) is one of the candidates for high-temperature magnetic semiconductors. Well-crystallized and epitaxially formed Fe2-xTixO3 films on alpha-Al2O3 (11 (2) over bar0) single-crystalline substrates were tried to fabricate by using reactive sputtering technique. The detailed structural properties of (11 (2) over bar0)-oriented epitaxial Fe1.4Ti0.6O3 films were analyzed by using transmission electron microscope (TEM). The films showed large magnetization and typical semiconductive conduction at room temperature. However their anisotropic properties were rather small than expected, though the films had good crystallinity with preferred orientation. The TEM observations clearly revealed that the (11 (2) over bar 0)-oriented Fe1.4Ti0.6O3 films on alpha-Al2O3(11 (2) over bar0) were partly composed of the (0001)-oriented grains. Formation of the (0001)-oriented grains could reduce the anisotropic properties of the (11 (2) over bar0)-oriented films. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2015.04.028

Web of Science

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Inspired by a nanometric iron-based oxide material of bacterial origin, silicon (Si)-doped iron oxyhydroxide nanopartides or 2-line ferrihydrites (2Fhs) were prepared and their lithium (Li) storage properties were investigated. The structures of the Si-doped 2Fhs strongly depended on the Si molar ratio [x = Si/(Fe + Si)] whose longrange atomic ordering gradually vanished as the Si molar ratio increased, with a structural change from nanocrystalline to amorphous at x = 0.30. The most striking properties were observed for the sample with x = 0.30. Over the voltage range of 1.5-4.0 V at a current rate of 500 mA/g, this material exhibited a relatively high reversible capacity of similar to 100 mAh/g, which was four times greater than that of the Si-free 2Fh and indicated a good rate capability and cyclability. The large capacity and good rate and cycle performances are presumably because of the amorphous structure and the strong and stabilizing covalent Si-O bonds, respectively. The minor amount of Si4+ in the structure of the iron oxyhydroxides is considered to improve the electrochemical properties. Use of more appropriate doping elements and fabrication of more appropriate nanostructures could drastically improve the Li storage properties of the developed bioinspired material.

DOI： 10.1021/acs.inorgchem.5b01165

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE SA  

A bacterial siliceous iron oxide microtubule (diameter: ca. 1 mu m, 15Fe(2)O(3)center dot 8SiO(2)center dot P2O6 center dot 30H(2)O) produced by Leptothrbc ochracea was heat treated in air and its structural transformation was investigated in detail by microscopy, diffractometry, and spectroscopy. Although the heat-treated bacterial iron oxide retained its original microtubular structure, its nanoscopic, middle-range, and local structures changed drastically. Upon heat treatment, nanosized pores were formed and their size changed depending on temperature. The Fe O Si linkages were gradually cleaved with increasing temperature, causing the progressive separation of Fe and Si ions into iron oxide and amorphous silicate phases, respectively. Concomitantly, global connectivity and local structure of FeO6 octahedra in the iron oxide nanoparticles systematically changed depending on temperature. These comprehensive investigations clearly revealed various structural changes of the bacterial iron oxide which is an important guideline for the future exploration of novel bio-inspired materials. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2015.01.067

Web of Science

researchmap

Language：English   Publisher：ELSEVIER  

Lithium-ion discharge/charge properties of a nanometric amorphous iron-based oxide material of bacterial origin, L-BIOX, in a voltage range of 1.5-4.0 V were studied. X-ray absorption fine structure measurements confirmed that Fe3+ -><- Fe2+ reactions dominate in this voltage range. Cycle characteristics with a capacity exceeding 70 mAh/g at a current rate of 1670 mA/g are considerably higher than those achieved by known simple iron-oxides such as alpha-Fe2O3. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2014.10.126

Web of Science

researchmap

J-GLOBAL

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Inspired by the traditional Japanese pigment Fukiya bengala, nanocomposite materials were synthesized using a polymer complex method, comprising Al-substituted a-Fe-2O3 (hematite) particles with diameters ranging from 40 to 100 nm and ultrafine Fe-substituted a-Al2O3 (corundum) particles smaller than 10 nm in diameter. The obtained powders exhibited a vivid yellowish-red color and high thermostability, making them attractive as potential overglaze enamels on porcelain. Quantitative color measurements revealed that, when heated to 700, 800, and 900 degrees C, samples displayed high lightness (L*) and color-opponent dimensions (a* and b*) at 10 mol % Al. For the same particle size samples, L*, a*, and b* values increased with the Al molar ratio, revealing that Al substitution in the hematite structure intrinsically enhances lightness and chroma in hematite color. These samples mostly retained their color upon reheating at 900 degrees C, indicating their high thermostability. This thermostability should originate from the Al substitution-induced enhancement in lightness and chroma in hematite color, which should counter color fading caused by particle growth. These composite materials are expected to find application in the porcelain industry, cosmetics, and nanotechnology.

DOI： 10.1021/am505820b

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Amorphous Fe3+-based oxide nanoparticles produced by Leptothrix ochracea, aquatic bacteria living worldwide, show a potential as an Fe3+/Fe-0 conversion anode material for lithium-ion batteries. The presence of minor components, Si and P, in the original nanoparticles leads to a specific electrode architecture with Fe-based electrochemical centers embedded in a Si, P-based amorphous matrix.

DOI： 10.1021/am500905y

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

Rare-earth iron oxides (RFe2O4) have attracting attention as new electronic device materials because of their abundant functionalities such as ferroelectricity, ferrimagnetism, and high infrared absorption. These properties are strongly related to the mixed iron valance states between Fe2+ and Fe3+. We tried to prepare RFe2O4 films by using soft chemical method. The films were prepared by spin-coating of viscous aqueous solutions of Yb(CH3COO)3 and Fe(NO3)3 with citric acid. The molar ratio between Yb:Fe was 1:2 and the citric acid: metal ratio was set to 3.75:1. After the coating, the films dried at 100�C for 10 min in air were, heat-treated at 900�C for 0.2 h in H2/CO2 gases to control oxygen partial pressure, and quenched. The obtained films were characterized by using XRD, SEM, EDS, M�ssbauer, and optical-absorption spectra. The XRD pattern clearly indicated the well-crystallized and nearly monophasic YbFe2O4 formed on the substrates above 900�C to control the oxygen partial pressure. Equal amount of Fe2+ and Fe3+ ions was present in the films. The films showed small band-gap and large optical absorbance in infrared region.

DOI： 10.2497/jjspm.61.S327

Scopus

researchmap

Language：English   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

Ilmenite-hematite solid solution (Fe2-xTixO3) is known to have unique magnetic and electric properties. It is one of the candidates for novel magnetic semiconductors with the high Curie temperature (Tc). The carrier type of Fe2-xTixO3 is controllable by changing the Ti content x. In order to fabricate the semiconductor devices, epitaxial thin films having good crystallinity with precise control of their carrier type are required. We have already succeeded in preparing well-crystallized epitaxial Fe2-xTixO3 (x=0.7) films on α-Al2O3 (110) single-crystalline substrates by reactive helicon plasma-sputtering technique. The films are expected to have n-type conduction, while the films having the higher Ti content could be p-type conduction. In this research, we tried to prepare (110)-oriented solid solution films over a wide composition range.

DOI： 10.2497/jjspm.61.S330

Scopus

researchmap

Language：English   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

Iron oxide microtubules produced by a species of iron-oxidizing bacteria, Leptothrix ochracea, have been expected to be useed as unique multifunctional materials such as catalysts scaffolds, pigments, and magnetic materials. However, their structural characteristics and formation mechanism are still ambiguous. The detailed features of the microtubules were characterized through electron microscopies, X-ray diffractometory, and energy dispersive X-ray spectroscopy. We found that the microtubules have hierarchical microstructures with aggregates of amorphous iron oxide nanoparticles. Statistical analysis of distributions of the tubule diameters and the wall thicknesses suggested that the tubule layer could grow from outside to inside.

DOI： 10.2497/jjspm.61.S90

Scopus

researchmap

DOI： 10.4164/sptj.51.629

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：English   Publisher：NATURE PUBLISHING GROUP  

We report the unprecedented square-planar coordination of iridium in the iron iridium arsenide Ca-10(Ir4As8)(Fe2As2)(5). This material experiences superconductivity at 16 K. X-ray photoemission spectroscopy and first-principles band calculation suggest Ir(II) oxidation state, which yields electrically conductive Ir4As8 layers. Such metallic spacer layers are thought to enhance the interlayer coupling of Fe2As2, in which superconductivity emerges, thus offering a way to control the superconducting transition temperature.

DOI： 10.1038/srep03101

Web of Science

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

We prepared nano-micrometer-architectural acidic silica from a natural amorphous iron oxide with structural silicon which is a product of the iron-oxidizing bacterium Leptothrix ochracea. The starting material was heat-treated at 500 degrees C in a H-2 gas flow leading to segregation of alpha-Fe crystalline particles and then dissolved in 1 M hydrochloric acid to remove the alpha-Fe particles, giving a gray-colored precipitate. It was determined to be amorphous silica containing some amount of iron (Si/Fe = similar to 60). The amorphous silica maintains the nano-microstructure of the starting material-similar to 1-mu m-diameter micrometer tubules consisting of inner globular and outer fibrillar structures several tens of nanometer in size and has many large pores which are most probably formed as a result of segregation of the alpha-Fe particles on the micrometer tubule wall. The smallest particle size of the amorphous silica is similar to 10 nm, and it has a large surface area of 550 m(2)/g with micropores (0.7 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, we found that it has relatively strong Bronsted and Lewis acidic centers that do not desorb pyridine, even upon evacuation at 400 degrees C. The acidity of this new silica material was confirmed through representative two catalytic reactions: ring-opening reaction and Friedel-Crafts-type reaction, both of which are known to require acid catalysts.

DOI： 10.1021/am401029r

Web of Science

Scopus

PubMed

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

A novel route in the synthesis of magnetite nanoparticles is reported. This synthesis is based on autoclaving of iron choline citrate dissolved in mixed water/ethanol or water solution and neutralized with NH4OH solution. The magnetite precipitates were characterized by XRD, Mossbauer, FT-IR, HRTEM and magnetometric measurements. All the precipitated magnetite particles were in the nanosize range as shown by HRTEM. They did not contain organic residues or any other iron (hydrous) oxide phase. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2013.03.013

Web of Science

researchmap

Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

To develop novel magnetic composites with acid functionalities, iron oxide produced by iron-oxidizing bacterium, Leptothrix ochracea, was used as a precursor. The composites were prepared by thermal treatment and subsequent reduction of the bacterial iron oxide. alpha-Fe2O3 nanoparticles obtained in air were thermally reduced to Fe3O4 and gradually oxidized to gamma-Fe2O3. The obtained composites with Fe3O4 and gamma-Fe2O3 have high magnetization values that are approximately half those of pure Fe3O4 and gamma-Fe2O3. All samples have an interesting nano-micro-architectural structure: similar to 40-nm-diameter crystalline particles covered with similar to 8-nm-thick amorphous silicate are intricately interconnected into similar to 1-mu m-diameter microtubules. Pyridine adsorption spectra indicate that the surface amorphous silicate has both Bronsted and Lewis acid properties. (c) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.materresbull.2012.12.022

Web of Science

Scopus

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Microporous and mesoporous silica derived from biogenous iron oxide is an attractive catalyst for various organic reactions. Biogenous iron oxide contains structural silicon, and amorphous silica remains after iron oxide is dissolved in concentrated hydrochloric acid. The amorphous silica containing slight amounts of iron (Si/Fe = similar to 150) is composed of similar to 6-nm-diameter granular particles. The amorphous silica has a large surface area of 540 m(2)/g with micropores (1.4 nm) and mesopores (<3 nm). By using pyridine vapor as a probe molecule to evaluate the active sites in the amorphous silica, it was found that this material has strong Bronsted and Lewis acid sites. When the catalytic performance of this material was evaluated for reactions including the ring opening of epoxides and Friedel Crafts-type alkylations, which are known to be catalyzed by acid catalysts, this material showed yields higher than those obtained with common silica materials.

DOI： 10.1021/am302837p

Web of Science

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

beta-Fe2O3 is the scarce polymorph of Fe2O3 phases and is transformed easily into alpha-Fe2O3 at high temperature. However, its crystal structure and the transformation, mechanism to alpha-Fe2O3 are still unclear because of the difficulty in obtaining monophasic beta-Fe2O3 crystals. We established a synthesis method of the monophasic beta-Fe2O3. It was synthesized by a two-step reaction: heating a mixture of Na2SO4 and Fe-2(SO4)(3) in air at 250 degrees C to form NaFe(SO4)(2), and subsequent heating the resultant phase with NaCl in air at 500 degrees C. The crystal structure was refined to a bixbyite-type cubic structure (Ia (3) over bar) with alpha = 9.4039(1) angstrom by the Rietveld method. Single crystalline beta-Fe2O3 particles of approximately 1 mu m in size were topotactically transformed into single alpha-Fe2O3 crystals. Electron diffraction analysis revealed the crystallographic orientation relationships between beta-Fe2O3 and alpha-Fe2O3 to be [100](beta)//[0001](alpha), [010](beta)//[10 (1) over bar0](alpha), and [001](beta)//[(1) over bar2 (1) over bar0](alpha).

DOI： 10.1021/cg301493a

Web of Science

researchmap

Language：English   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

We synthesized well-crystallized ilmenite-type FeGeO3 to investigate its structural and magnetic properties. Ilmenite-type FeGeO3 were synthesized by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus. Their structural and magnetic properties were examined by XRD analysis with Rietveld refinement, transmission electron microscopy, Mossbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity of the ilmenite-type FeGeO3. The primary particle size of ilmenitetype FeGeO3 was similar to 15 nm. Some particles seemed to be covered with non- or poorly crystalline phase even after the annealing, and others showed a lamellar microstructure parallel to the (0 0 1) plane. Theilmenite-type FeGeO3 showed typical antiferromagnetic behavior with the Neel temperature of 79 K. (c) 2012 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jssc.2012.11.020

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE SA  

In nature, there are various iron oxides produced by the water-habitant bacterial group called "iron-oxidizing bacteria". These iron oxides have been studied mainly from biological and geochemical perspectives. Today, attempts are made to use such iron oxides as novel functional materials in several applications. However, their quantitative structural characteristics are still unclear. We studied the structure of iron oxide of microtubular form consisting of amorphous nanoparticles formed by an iron-oxidizing bacterium, Leptothrix ochracea, using a combination of high-energy X-ray diffraction and reverse Monte Carlo simulation. We found that its structure consists of a framework of corner- and edge-sharing distorted FeO6 octahedral units, while SiO4 tetrahedral units are isolated in the framework. The results reveal the atomic arrangement of iron oxide of bacterial origin, which is essential for investigating its potential as a functional material. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2012.10.002

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE SA  

Magnetic nanocomposites containing magnetite (Fe3O4) nanoparticles were prepared from iron oxide microtubules produced by Leptothrix ochracea, a species of water-habitant iron-oxidizing bacteria. The microtubules were mainly composed of Si-containing ferric hydroxide that shows a broad X-ray diffraction pattern similar to that of 2-line ferrihydrite. After moderate heat treatment in a reductive atmosphere above 325 degrees C, the ferric ions were partially reduced to a ferrous state, and nanocrystalline Fe3O4 with a spinel-type structure was formed in a noncrystalline silicate matrix. The average crystallite size of the Fe3O4 nanoparticles was estimated to be in the order of a few nanometers. The sample heat-treated at 500 degrees C exhibited considerable magnetization together with superparamagnetic behavior at room temperature, and super-spin-glass interaction occurred at low temperature. On further heat treatment above 530 degrees C, Fe3O4 was reduced to wustite (Fe1-xO) and finally crystallized into iron metal (alpha-Fe) and ferrous silicate (Fe2SiO4). (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2012.08.070

Web of Science

researchmap

Language：English   Publisher：NATURE PUBLISHING GROUP  

Calcium carbonate (CaCO3) in the presence of single-walled carbon nanotube (SWCNT) /fullerodendron supramolecular nanocomposites was crystallized with a CO2 diffusion method under ambient conditions and in aqueous environments to produce monodisperse spherical SWCNT/CaCO3 hybrids with a core-shell structure. The crystals nucleate at the carboxyl groups on the surface of the SWCNT/fullerodendron supramolecular nanocomposites grow around a spherical scaffold consisting of the SWCNTs, and finally form spherical calcite crystals embedded with and covered by the SWCNTs. Owing to of the phase transition from vaterite to calcite through a solvent-mediated process, the morphology of the microspheres is unique; the shell is primarily composed of calcite crystals of CaCO3, and a greater amount of SWCNTs is embedded in the core moiety. Polymer Journal (2012) 44, 620-624; doi:10.1038/pj.2012.36; published online 18 April 2012

DOI： 10.1038/pj.2012.36

Web of Science

researchmap

Language：English   Publisher：ROYAL SOC CHEMISTRY  

Nano- and micro-architectural manganese oxide produced by microorganisms catalyses the selective monobromination of hydrocarbons in excellent yield under irradiation of fluorescent room light. The knowledge gained from investigating natural materials will lead to unprecedented catalyst designing toward efficient organic reactions.

DOI： 10.1039/c2ra20896b

Web of Science

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

Language：English   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

The microstructure and conditions for the formation of the reddish color referred to as hi-iro on Japanese ceramics were investigated through model experiments. The hi-iro marking was found to be formed by the reaction between clay and alkali ions supplied from the glaze. When a mixture of porcelain clay and 20 wt % KCl was heated in air at 1250 degrees C and then cooled slowly to 800 degrees C, hi-iro clearly appeared on the sample surface. In hi-iro, corundum [alpha-(Al,Fe)(2)O-3], hematite (alpha-Fe2O3) and a liquid phase are formed. Upon heating until 1250 degrees C, corundum is firstly precipitated as hexagonal plate-like crystals. During the cooling process, hematite precipitates on the edges of the corundum crystals to form specific composite particles. When rapidly cooled from 1250 degrees C to room temperature, a brownish red color appeared on the sample surface, which was found to be caused by the formation of approximately 50 mu m Al-substituted hematite (Fe1.9Al0.1O3) particles. The relationship between the microstructure of the phases formed and the color is discussed. (C)2011 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.119.942

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE SA  

Nanocrystalline LaFeO3 particles were synthesized at low temperatures by using hot soap technique. The synthesis was based on the thermal decomposition of organometallic compounds precipitated in a hot coordinating solvent. Moderate heat treatment at low temperature far below the combustion point of organic compounds produced spherical LaFeO3 nanoparticles with average diameter of about 15 nm. The crystalline phase, structure and particle size of obtained products were characterized by Xray diffraction, infrared spectroscopy and transmission electron microscopy observations. In spite of the antiferromagnetic nature of bulk LaFeO3, the obtained nanoparticles exhibited anomalous large magnetization. Superparamagnetic behavior with a blocking temperature of about 30 K was observed in both magnetization and Mossbauer spectroscopic analyses. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2011.05.015

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Synthesis of single-phase Sr3Co2Fe24O41 Z-type (Sr(3)CO(2)Z) ferrite was realized by adopting the polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase Sr(3)Co(2)Z ferrite was obtained by heating at 1473 K for 5 h in air. Magnetic properties were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). Sr(3)CO(2)Z ferrite prepared by polymerizable complex method showed typical M-H curve of soft ferrite, with a saturation magnetization of 21.5 mu(B)/formula unit (50.5 emu/g) and a coercive force of 0.0141 at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.materresbull.2011.03.004

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

A series of high-resolution Ti K beta X-ray emission spectra were measured for various isomorphous titanium oxides with composition MTiO3, where M was divalent Mg, Mn, Fe, Co, or Ni. The detailed spectral features of Ti K beta lines for MTiO3 were intermediate between those of TiO2 and Ti2O3 depending on the coexisting cation species M, though the formal valence states of all Ti ions in MTiO3 were consistent with those in TiO2. Especially in the case of FeTiO3, the features in both main and satellite lines had many similarities of Ti2O3. The Ti K beta X-rays of FeTiO3 seemed to be emitted by the transition from Ti3+-like states. Because of the small difference in energies and the large overlap between Ti 3d and Fe 3d orbitals, intermediate core-hole states occurring on the X-ray emission process might produce the inter-valence charge transfer from Fe2+ to Ti4+ to form the Ti3+-like states. The DV X alpha calculations based on the molecular orbital theory can reproduce the satellite structures to assume the increasing 3d electron densities on Ti for FeTiO3. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2010.10.003

Web of Science

researchmap

Language：English   Publisher：ELSEVIER SCIENCE SA  

On the synthesis of nano-structural hydrogenated graphite by ball-milling under H atmosphere, iron contamination was mingled from steel balls during ball-milling. It is clarified by spectroscopic measurements that the mingled iron formed a non-stoichiometric iron-carbon (Fe-C) compound. The Fe-C phase was transformed to a well-ordered phase with H desorption at 450 °C, suggesting that the hydrogen atoms were anomalously trapped at the Fe-C phase. With respect to hydrogen absorbing properties, the mingled iron enhanced the hydrogen capacity by about 50% compared with iron free hydrogenated graphite, where H/Fe was about 13 mass%. Therefore, if the hydrogen absorption site originated in the Fe-C phase could be synthesized independently, it should be recognized as a promising hydrogen storage system. © 2010 Elsevier B.V. All rights reserved. 2 2

DOI： 10.1016/j.jallcom.2010.07.221

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Magnetic properties of La-Co substituted M-type strontium hexaferrites were studied. The samples were prepared by polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase M-type strontium hexaferrites with chemical composition of Sr La Fe Co O (x=0-0.4) were formed by heating at 1173 K for 24 h in air. Magnetic properties were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). La-Co substituted M-type strontium hexaferrites prepared by polymerizable complex method showed typical magnetic hysteresis of hard ferrite. The coercive force increased significantly by La-Co substitution with polymerizable complex method. Maximum coercive force achieved in this study is 8.0 kOe (640 kA/m). Scanning electron microscopy revealed that the prepared ferrite particles have plate-like shape of diameter range between 20 and 500 nm. © 2010 Elsevier B.V. All rights reserved. 1.05-x x 12-x x 19

DOI： 10.1016/j.jmmm.2010.02.041

Web of Science

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

A new layered iron hydroxide was synthesized by a wet chemical technique, by which aqueous ferrous sulfate solution was gradually oxidized by using sodium carbonate at 283 ∼ 333 K. Obtained yellowish precipitates identified by X-ray powder diffraction had a similar structure to the layered double hydroxides. The observed interlayer spacing was about d=0.74 nm. Electron micrographs showed that the particles had plate-like morphology. Electron diffraction pattern of the plate-like particles had hexagonal symmetry, when the electron beam was aligned normal to the planes. Mössbauer spectrum suggested that all iron ions were paramagnetic Fe states with large quadrupole splittings at room temperature. These results show that the obtained new layered iron hydroxide cotains only Fe(III) ion species. Water vapor adsorption curves of the sample oxidized át 291 K showed high adsorption value (19 wt%) by unit weight. 3+

DOI： 10.2497/jjspm.57.76

Scopus

researchmap

Language：Japanese  

A new layered iron hydroxide was synthesized by a wet chemical technique, by which aqueous ferrous sulfate solution was gradually oxidized by using sodium carbonate at 283 ∼ 333 K. Obtained yellowish precipitates identified by X-ray powder diffraction had a similar structure to the layered double hydroxides. The observed interlayer spacing was about d=0.74 nm. Electron micrographs showed that the particles had plate-like morphology. Electron diffraction pattern of the plate-like particles had hexagonal symmetry, when the electron beam was aligned normal to the planes. Mössbauer spectrum suggested that all iron ions were paramagnetic Fe3+ states with large quadrupole splittings at room temperature. These results show that the obtained new layered iron hydroxide cotains only Fe(III) ion species. Water vapor adsorption curves of the sample oxidized át 291 K showed high adsorption value (19 wt%) by unit weight.

DOI： 10.2497/jjspm.57.76

Scopus

researchmap

Language：English   Publisher：ROYAL SOC CHEMISTRY  

The biogenous iron oxide (BIO) from Leptothrix ochracea was transformed to an organic-inorganic hybrid support to prepare an excellent immobilized enzyme showing high catalytic performance. © 2010 The Royal Society of Chemistry.

DOI： 10.1039/b919497e

Web of Science

Scopus

PubMed

researchmap

Language：English   Publisher：IOP PUBLISHING LTD  

Solid solutions between ilmenite (FeTiO ) and hematite (α-Fe O ) are one of the candidates for high-temperature magnetic semiconductors. Well-crystallized epitaxial xFeTiO -(1-x)Fe O (0.5<x<1) films were prepared on both α-Al O (001) and (110) single-crystalline substrates by reactive sputtering technique. The (110)-oriented films provided more restricted preparation conditions than the (001)-oriented ones. Both films with x<0.7 had large saturation magnetization at room temperature. The magnetic easy plane lay in the (001) crystallographic plane regardless of the film orientations. The magnetic properties of (001)- and (110)-oriented films seemed to be affected not only by the crystalline orientation but also by the lattice strains induced in the films. © 2010 IOP Publishing Ltd. 3 2 3 3 2 3 2 3

DOI： 10.1088/1742-6596/200/7/072029

Web of Science

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：WILEY  

The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets covered lightly with rice straw as a coloring assistant. When heated in flowing nitrogen, the model pellet turned blackish owing to the formation of α-Fe particles coated with graphite. However, schreibersite (Fe P), which is also blackish, was formed specifically on the pellet surface in direct contact with the straw. The rice straw seems to have generated a strongly reducing atmosphere, strong enough for the metallization to α-Fe, and also to have provided phosphorus through contact. When oxygen content in the surrounding gas atmosphere was raised to N /O =99/1, the pellet surface turned yellowish brown because the main coloring material was Fe -containing mullite. At oxygen contents of N /O =98/2 or more, the formtion of hematite (α-Fe O ) pushed the color to deep red. © 2009 The American Ceramic Society. 3 2 2 2 2 2 3 3+

DOI： 10.1111/j.1551-2916.2009.03125.x

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

We report the synthesis and magnetic properties of the AgI-intercalated misfit-layer cobalt oxide Bi Ca Co O . The AgI-intercalated Bi Ca Co O was prepared by the guest exchange reaction from the I -intercalated one. SEM-EDX analysis exhibited the stoichiometric ratio of Ag/I and the guest concentration as (AgI)Bi Ca Co O on the basis of Co = 2. After the AgI intercalation, the lattice parameter along the c-axis calculated from X-ray diffraction patterns was 21.68 Å, which was drastically increased not only from the non intercalated host phase (14.68 Å) but also from the I -intercalated phase (18.08 Å). After the AgI intercalation, magnetic susceptibility measurements revealed that the antiferromagnetic Weiss temperature and the effective magnetic moment in Co ion simultaneously decreased compared with the non-intercalated host compound. © 2008 Elsevier B.V. All rights reserved. 1.8 2 2 z 1.8 2 2 z 2 1.8 2 2 z 2

DOI： 10.1016/j.matlet.2008.10.032

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

DOI： 10.1016/j.jmmm.2008.01.046

Web of Science

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：IOP PUBLISHING LTD  

Well-crystallized epitaxial FeTiO films were prepared on the sapphire substrate by reactive sputtering technique. A wide range of oxygen nonstoichiometry from FeTiO to FeTiO was successfully controlled by controlling the sputtering conditions. All films had uniform structure without phase separation even for the highly oxidized FeTiO film. Structures, magnetic and electronic properties of the FeTiO films were seriously influenced by the oxygen nonstoichiometry. The nearly stoichiometric FeTiO films had a R structure, while the nonstoichiometric FeTiO had a R c structure. With increasing the oxygen nonstoichiometry, the valence states of Fe ions in FeTiO were examined to be changed from Fe to Fe by means of both Mössbauer and XPS spectroscopy. The Ti 2p core-level XPS spectra clearly confirmed the valence states of Ti ions in nonstoichiometric FeTiO . However the Ti ions in stoichiometric FeTiO suggested the abundant electron density than the conventional Ti ions due to the Fe to Ti intervalence charge transfer. © 2008 IOP Publishing Ltd. 3+δ 3 3.5 3.5 3+δ 3 3.5 3+δ 3.5 3 2+ 3+ 4+ 4+ 2+ 4+

DOI： 10.1088/1742-6596/100/1/012043

Web of Science

Scopus

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

In the course of our study on a Japanese traditional stoneware called "Bizen", we have found that ε-Fe O , which has been classically known but recently limelighted for its magnetic potentiality, crystallizes epitaxially on needlelike crystals of mullite, 3(Al,Fe) O ·2SiO . This interesting reaction occurred when a pellet of Bizen clay powder was covered with rice straw and then heated to 1250 °C in a stream of nitrogen containing 1-2 vol % of oxygen. It is known that mullite forms from the clay on heating and that the rice straw provides potassium to induce partial melting in the pellet surface to a depth of ∼50/im. The ε-Fe O -on-mullite particles formed in this molten region, changing their morphology with the oxygen partial pressure. Square-columnar single-crystalline particles with prismatic ends grew to ∼0.1 × 0.1 × 0.5 μm at N /O = 99/1, while dendritic finlike crystals of ∼0.3 × 0.1 × 0.8 μm , which was then the biggest size ever reported, grew at N /O = 98/2, The relative ε-Fe O -to-mullite orientation also changed with the oxygen partial pressure. This discovery suggests morphological controllability of this metastable but magnetically interesting iron oxide as a function of the oxygen partial pressure. © 2008 American Chemical Society. 2 3 2 3 2 2 3 2 2 2 2 2 3 3 3

DOI： 10.1021/cm7023247

Web of Science

Scopus

researchmap

Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The influence of composition on the structural ordering and magnetism in the V Nb S system has been investigated by X-ray diffraction and magnetic measurements. Stoichiometric V NbS did not exhibit the structural ordering of vanadium between the NbS layers. In the ordered structure, the vanadium composition deviated from the ideal value of x = frac(1, 3) to both higher and lower values, while the niobium composition was in the range of 0.05≤y≤0.18. Excess niobium, y>0, is thought to play an essential role in the structural ordering in this system. For samples with excess niobium and ordered structures, a magnetic transition was observed at 20-50 K, depending on the composition. The spontaneous magnetization of 3-5×10 μ /V atom is thought to be intrinsic to this system. The magnetization curves consisted of a constant and a proportional parts of the magnetic field, which correspond to the spontaneous magnetization and high-field susceptibility, respectively. The magnetization curves and the temperature dependencies of the high-field susceptibility were quite similar to those of the canted antiferromagnetic NiS . A correlation between the structural and magnetic ordering is suggested. © 2007 Elsevier Ltd. All rights reserved. x 1+y 2 1/3 2 2 B 2 -3

DOI： 10.1016/j.jpcs.2007.07.124

Web of Science

Scopus

researchmap

Language：English   Publisher：AMER INST PHYSICS  

Thin films of ilmenite-hematite solid solution 0.6FeTi O 0.4 Fe O were prepared on α- Al O (001) and (110) single-crystalline substrates. The oxide phases formed in the thin films strongly depended on the oxygen partial pressure (PO ) during deposition. At PO =1.3× 10 Pa, regardless of thesubstrate orientation, well-ordered 0.6FeTi O 0.4 Fe O films with R 3- symmetry were epitaxially formed. Large saturation magnetization at room temperature was observed in both (001)- and (110)-oriented films. The differences in the magnetization and electrical resistivity curves between the (001)- and (110)-oriented films indicated the anisotropic nature of 0.6FeTi O 0.4 Fe O . © 2008 American Institute of Physics. 3 2 3 2 3 2 2 3 2 3 3 2 3 -3

DOI： 10.1063/1.2951589

Web of Science

Scopus

researchmap

On traditional Japanese stoneware called "Bizen", we found that ε-Fe O crystallizes epitaxially on needle-like mullite crystals. This interesting reaction occurred when a pellet of Bizen clay powder was heated with rice straw to 1250°C in a stream of N containing 1∼2 vol% of O . It is known that mullite forms from the clay on heating and that the rice straw provides potassium to induce partial melting in the pellet surface. The ε-Fe O -on- mullite particles formed in this molten region, changing their morphology and the relative ε-Fe O -to-mullite orientation with oxygen partial pressure. This discovery suggests morphological controllability of ε-Fe O as a function of oxygen partial pressure. 2 3 2 2 2 3 2 3 2 3

Scopus

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Characterization of biogenic iron oxide sheaths produced by Leptothrix ochracea (L. ochracea) was investigated. The sheaths had average inner- and outer-diameters of 1.08 ± 0.15 and 1.35 ± 0.14 μm, respectively. Their length ranged from 10-2000 μm. Outer and inner surface of each sheath were composed of fibrous and spherical particles, respectively. The width of fibrous particles was approx. 20 nm, while the diameter of spherical particles was 20-120 nm. The chemical composition of the sheaths was Fe: Si: P = 73: 22: 5 with the exception of H and O. The sheaths had similar structure to that of 2-line ferrihydrite.

Scopus

researchmap

Thin films of ilmenite-hematite solid solution, Fe Ti O were prepared on α-A1 O (001) and (110) single-crystalline substrates by reactive helicon plasma-sputtering technique. The oxide phases formed in the thin films and the degree of cation ordering in the ilmenite phase strongly depended on the preparation conditions. At the optimized preparation conditions, regardless of the substrate orientation, well-ordered Fe Ti O films with R3 symmetry were epitaxially formed on the substrates. Large saturation magnetization at room temperature was observed in both (001)- and (110)-oriented films. The ordered Fe Ti O films were ferrimagnetic semiconductors at room temperature. The (110)-oriented film had uniaxial in-plane magnetic and electric anisotropies, because Fe Ti O had a magnetic easy plane and predominant conduction in the (001) crystallographic plane. The differences in magnetization and electrical resistivity curves between the (001)- and (110)-oriented films indicated the anisotropic nature of Fe Ti O . 1.4 0.6 3 2 3 1.4 0.6 3 1.4 0.6 3 1.4 0.6 3 1.4 0.6 3

Scopus

researchmap

Language：English   Publisher：AMER INST PHYSICS  

An ilmenite-hematite solid solution (Fe2-x Tix O3) is one of the candidates for practical magnetic semiconductors with a high Curie temperature. We have prepared well-crystallized epitaxial Fe2-x Tix O3 films with a wide range of Ti concentrations- x=0.50, 0.60, 0.65, 0.76, 0.87, and 0.94-on α -Al2 O3 (001) substrates. The films are prepared by a reactive helicon plasma sputtering technique to evaporate Fe and TiO targets simultaneously under optimized oxygen pressure conditions. The structural characterizations of the films reveal that all films have a single phase of the ordered structure with R 3- symmetry, where Ti-rich and Fe-rich layers are stacked alternately along the c axis. All films have large ferrimagnetic moments at low temperature, and room temperature magnetization is clearly observed at x<0.7. The inverse temperature dependence of the resistivities of the films indicates their semiconducting behavior. The film resistivities decrease with decreasing Ti concentration. © 2008 American Institute of Physics.

DOI： 10.1063/1.2966298

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

The polymeric complex method has been employed to investigate the effects of substitution by lanthanum into hematite powder on structures, morphology and color tone properties. X-ray diffraction measurements evidenced the existence of Fe La O at 1000 °C-1200 °C by shifting peaks to lower angles. At higher temperature, lattice parameters and cell volume were found to expand due to the incorporation of La ion into the hematite in the range 301.98-303.87 Å . Crystalline size decreased when increasing the amount of La ion in the reaction process. Suppression of particle growth was observed by the Field Emission Scanning Electron Microscopy studies at higher temperatures. Brighter yellowish-red color than that of pure hematite was obtained and it grew into deeper color tone rapidly by increasing the amount of La ion into the hematite. © 2007. 2 - x x 3 3+ 3 3+ 3+

DOI： 10.1016/j.matlet.2006.12.032

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Ilmenite-hematite solid solution (Fe Ti O ) is one of the candidates for practical magnetic semiconductors with the high Curie temperature (T ). We have successfully prepared well-crystallized and epitaxial Fe Ti O films by using a reactive helicon plasma sputtering technique. The structural characterizations indicated that the films had the order structure (R over(3, -) symmetry), where Ti- and Fe-rich layers were stacked alternately along the c-axis, without any secondary phase. The subsequent annealing of the films in vacuum at 700 °C promoted the R over(3, -) symmetry. Only the films having the good R over(3, -) symmetry had large ferrimagnetic moments at room temperature. The resistivities of the films clearly showed semiconducting behavior, i.e., logarithmic resistivity showed a monotonous increase with increasing the inverse temperature. The minimum room temperature resistivity of the films was about 10 Ω cm. From the Hall effect measurement all films had n-type conduction. The carrier concentration was estimated to be about 10 -10 cm , depending on the annealing conditions. © 2006 Elsevier B.V. All rights reserved. 2-x x 3 C 1.4 0.6 3 -1 19 21 -3

DOI： 10.1016/j.jmmm.2006.10.783

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Nominal valence states of Ti ions in FeTiO are generally considered to be Ti . However, due to the close energy levels between Fe and Ti states, there are some possibilities of intervalence charge transfer from Fe to Ti . In order to clarify the real electronic structures of Ti ions in FeTiO , we performed resonant photoemission spectroscopy (RPES) and X-ray magnetic circular dichroism (XMCD) across the Ti 2p→3d excitation. The RPES spectra clearly indicated the partial density of states derived from the Ti 3d states on the valence band. The Ti 3d states appearing at the top of the valence bands were overlapped with the Fe 3d states. Moreover, the XMCD spectra at Ti L edges suggested large magnetic polarization of Ti ions in FeTiO in spite of nonmagnetic natures of Ti ions in common sense. The Ti ions in FeTiO seemed to have some 3d electron densities caused by the electron transfer from the Fe 3d t ↓ states. © 2006 Elsevier B.V. All rights reserved. 3 3 2,3 3 3 2g 4+ 2+ 4+ 2+ 4+ 4+

DOI： 10.1016/j.jmmm.2006.10.469

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Some features of characteristic iron oxide sheaths which the iron oxidizing bacteria Leptothrix ochracea (L. oceracea) formed were studied in order to make clear their morphology microstructure, chemical composition, and crystal structure through scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD). Each sheath was a hollow tube with average outer and inner diameters of 1.1 and 1.4 μm, respectively. Their length ranged from 10 to 200 μm and the aspect ratio was 10-200. Each sheath was constructed by very small particles with a diameter of less than 100 nm. The hollow sheaths were mainly composed of Fe and O with small amounts of Si and P. The chemical composition analyzed by EDX was roughly Fe:Si:P=80:15:5 with the exception of O. XRD measurement revealed that crystal structures of the sheath were similar to that of 2-line ferrihydrite. The sheath showed spin-glass-like magnetic properties. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.793

Web of Science

Scopus

researchmap

Language：Japanese  

Cerium doped hematite powders obtained by polymeric complex method following the hydrolysis of FeCl · 6H O and Ce(NH ) (NO )6. X-ray diffraction pattern of cerium doped samples obtained at 1000°C̃ 1200°C for two hours in air revealed some solubility of cerium ion in α-Fe O over the composition range of 5%̃15 at% that were characterized by the shifting of X-ray diffraction peaks compared with the internal silicon standard. X-ray Photoelectron Spectra investigations revealed the existence of Ce ion at higher temperature. Unit cell parameters were found to expand due to the incorporation of cerium ions into the hematite lattice. Field Emission Scanning Electron Microscopy studies showed that the growth of particles was suppressed in the appearance of cerium ions into the α-Fe O lattice. Fe Ce O exhibits much lower magnetization due to the incorporation of non-magnetic cerium ions into the α-Fe O . Spectroscopy measurement evidenced that cerium doped hematite samples exhibited brighter yellowish red color tone than that of pure α-Fe O . 3 2 4 2 3 2 3 3+ 2 3 2-x x 3 2 3 2 3

DOI： 10.2497/jjspm.54.112

Scopus

researchmap

Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Single-phases of Pb-substituted Bi-Ca-Co-O misfit-layer cobaltites with various Pb concentrations have been synthesized and the Pb-substitution effects on the structural, electrical and magnetic properties have been systematically investigated. Powder X-ray diffraction analysis showed that the single-phases of Bi Pb Ca Co O were obtained up to x = 0.6 - 0.7 under the optimized synthesis conditions. The lattice parameters of Bi Pb Ca Co O continuously changed with increasing Pb concentration. The electron diffraction analysis suggested that the structure consisted of two different sublattices with a rock salt structure (RS) and a hexagonal CdI structure (H), respectively, without modulation. In combined with the chemical composition analysis, the chemical formulas of the x = 0 and x = 0.6 samples were determined approximately as [Bi Co Ca O ] [CoO ] and [Bi Pb Co Ca O ] [CoO ] , respectively. The electrical resistivity became more metallic with increasing the Pb concentration up to x = 0.6. Moreover, the Pb-substitution simultaneously increased the antiferromagnetic Weiss temperatures and decreased the effective magnetic moments of the Co ions. © 2006 Elsevier Ltd. All rights reserved. 1.8-x/2 x 2 2 z 1.8-x/2 x 2 2 z 2 1.74 0.31 2.01 4 2 1.69 1.47 0.38 0.29 1.98 4 2 1.71 RS RS

DOI： 10.1016/j.ssc.2006.10.015

Web of Science

Scopus

researchmap

Language：English   Publisher：Faculty of Engineering, Okayama University  

CiNii Article

CiNii Books

researchmap

Publisher：THE CARBON SOCIETY OF JAPAN  

We have prepared Carbon/Fe-Ni-Cu ternary alloy composites by polymerized complex method. A single-phase Fe-Ni-Cu alloy could be obtained in carbon matrix by controlling pH of the citrate complex solution. It was revealed that the chemical compositions of metals in composites were maintained well by adding ethylene glycol into the complex solution. Crystallinity of both carbon matrix and Fe-Ni-Cu alloy particles were enhanced with increasing the carbonized temperature. The composite carbonized at 700°C had larger saturation magnetization and smaller coercivity than that carbonized at 500°C, which correlated with metal content and crystallite size of alloy. The composite carbonized at 700°C exhibited larger permeability and permittivity than carbon/Fe-Co alloy composites at frequency of GHz range.

DOI： 10.7209/tanso.2007.158

CiNii Article

researchmap

Language：English   Publisher：SPRINGER WIEN  

The measurement of soft X-ray spectra, Ti Kα , Lα and O Kα, of Ti in several titanium oxide compounds was carried out by FE-WD-EPMA (wavelength dispersive - electron probe micro-analyzer with field emission type electron gun) and HRXRF (high-resolution X-ray fluorescence spectroscopy). From the results of measurements, it was found that the valence state of Ti in FeTiO (ilmenite) was at least partially Ti , might be the mixed state of Ti and Ti . And, Ti in MgTiO (ilmenite system) was confirmed as Ti . From the discussion, it can be presumed that the effective charge of the oxygen should be not-uniform and should be different subtlety by the cationic difference, Fe or Mg, even if it had equal crystal structure of the ilmenite system, and that this subtlety difference gave any effects on the valence state of Ti. 1,2 1,2 3 3 III IV III IV

DOI： 10.1007/s00604-006-0532-y

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER  

Ferroxplana type hexagonal ferrite with composition Ba Co Fe O (Co Y) was prepared by polymeric sol-gel method from the aqueous solution of their corresponding metal salts. All the samples were characterized by using X-ray diffraction and scanning electron microscopic technique. The formation and the microstructure of the Ba Co Fe O was studied as a function of heat treatment temperature and it was observed that well defined hexagonal plate-like fine particles with particle sizes between 130 and 400 nm were formed at relatively lower temperature (900 °C) as compared to conventional solid state reaction method (1100 °C). Magnetic properties of the samples were also studied as a function of heat treatment temperature and it showed large saturation magnetization (M ) ranging from 30.9 to 47.6 emu/g and a wide range of coercivity (130∼1566 Oe) depending on the heat treatment temperature. The very high saturation magnetization at relatively lower temperature (say 800 °C) arises due to the presence of several high magnetic impurities, such as BaFe O and CoFe O . The saturation magnetization increases with increasing heat treatment temperature above 900 °C, while the coercivity showed a reversed order. © 2006 Elsevier B.V. All rights reserved. 2 2 12 22 2 2 2 12 22 s 12 19 2 4

DOI： 10.1016/j.matlet.2006.01.077

Web of Science

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

researchmap

Iodine intercalation and deintercalation of a Sr-free Bi-based cuprate, Bi (La,Na) CuO:, have been investigated. It has been confirmed by powder X-ray diffraction and thermogravimetric analysis that the stage-1 iodine-intercalated compound Bi (La,Na) CuO l with x=1.0 was formed. As in the case of a Bi (Sr,La) CuO: (Bi-2201) specimen, expansion of the c-length of the stage-1 iodine-intercalated compound was 3.6 Å, compared with one half that of host compound. After deintercalation of the intercalated iodine, the stage-1 iodine-intercalated compound returned reversibly to the host compound. The powder X-ray diffraction pattern showed the formation of the intermediate phase containing a certain amount of iodine, not assigned to the stage-2 intercalated compound, during the deintercalation. Neither host compound nor iodine-intercalated compound exhibited superconductivity down to 2 K. 2 2 2 2 7 x 2 2

Scopus

researchmap

Thin films of hematite-ilmenite (α-Fe O -FeTiO ) solid solution series are proposed to be one of the new high-temperature magnetic semiconductors, We have successfully prepared well-crystallized epitaxial Fe Ti O films with various Ti content, x, between 0.6 and 1.0. The films were epitaxially formed on α-Al O (0001) single-crystalline substrates by reactive helicon plasma sputtering technique. The films prepared at lower substrate temperature below 700°C had the R3̄c structure, in which the Fe and Ti ions randomly occupied octahedral interstices. While the films prepared at higher substrate temperature above 700°C had the R3̄ structure, in which the octahedral interstices occupied by the Fe and Ti ions were arranged in an ordered way along the c-axis. Moreover the films prepared at the higher substrate temperature consisted of nearly stoichiometric oxygen concentration. However, with decreasing the substrate temperature the films seemed to have large cation vacancies and Fe ions were gradually oxidized to Fe . With decreasing the Ti content from x=1.0 to 0.6, the electric resistivity of the stoichiometric films was sharply decreased from 10 to 0.1 Ωcm because of the formation of mixed valence states between Fe and Fe . The stoichiometric films with x=0.6 were ferrimagnetic semiconductors at room temperature when the films had the R̄̄3 structure. 2 3 3 2-x x 3 2 3 2+ 3+ 2+ 3+

Scopus

researchmap

researchmap

Carbon/Fe-Ni-Cu alloy composites were synthesized by carbonization of organometallic polymers obtained from ion exchanged chelate resins. The carbonization was performed at 900 °C in a N gas flow. The composition of the Fe-Ni-Cu alloy in a carbon matrix can be controlled by the adjusting solution compositions in the ion exchange process. The carbon obtained from the organometallic polymer was crystallized to a turbostratic structure. X-ray diffraction patterns revealed that the Cu, Fe and Ni elements in the ion exchanged chelate resins were crystallized to a Fe-Ni-Cu alloy after carbonization at 900°C. This result indicates that the formation of the ternary alloy in the carbon matrix is coincident with the crystallization of the well-ordered turbostratic structure of the carbon matrix. The alloy particles with an average size of about 200-700 nm were widely dispersed in the carbon matrix. The saturation magnetization and coercivity of the composites depended on the alloy composition. The saturation magnetization and coercivity of the carbon/Fe Ni Cu alloy composite were 7.9 emu/g and 167 Oe, respectively. 2 0.52 0.42 0.06

Scopus

researchmap

In this study, low temperature preparation conditions for Co Z (3BaO·2CoO·12Fe O ) particles were investigated by using alkaline halide method. The obtained particles were characterized by using X-ray diffraction and scanning electron microscopy techniques. Many factors such as the metal compositions, heating temperature, heating and cooling rates, and amount of flux reagents were changed for the preparation. The X-ray diffraction analysis indicated that (1) the metal compositions, (2) flux reagent, and (3) heating rate were important to obtain Co Z at low temperature using the alkaline halide method. Nearly monophasic Co Z was formed under the following conditions: metal compositional ratio of Ba : Co: Fe = 3.0 : 1.5 : 24 with 10wt% BaCl flux and rapid heating to 1200 °C for 6 hours. Co Z powders mixed with an EPDM rubber were pressed to a sheet form. The electromagnetic properties of rubber sheets were examined to apply to use as an electromagnetic wave absorber. 2 2 3 2 2 2 2

Scopus

researchmap

The ilmenite-hematite solid-solution, xFeTiO -(1-x) α-Fe O samples with x=0.7-1.0. were prepared by standard solid state reaction technique in an evaculated quartz tube. The sample pellets were heated at 1200°C for 24 hr, then furnance cooled to room temperature . All samples consisted of a single phase of ilmenite structure. Lattice parameters of these samples estimated from the XRD patterns varied linearly with decreasing the Ti concentration on the basis of the Vegard's law. The saturating magnetization at 78 K was obtained at x=0.8 (Fe Ti O ), and the sample with x=0.7 (Fe Ti O ) was ferrimagnetic at room temperature. The carrier type measured by Seebeck coefficient was changed from p-type to n-type at about x=0.78 with decreasing the Ti concentration. Electronic states of Fe and Ti ions in FeTiO seemingly had the characteristic features of Fe and Ti respectively. However the Ti 2p→3p resonant valence band photoemission spectra of FeTiO had a clear density assigned to the Ti 3 d derived states. The small density appeared just below the Fermi edge was intrinsic for the FeTiO crystals because of identical x-ray absorption spectrum at Ti L edges between constant initial state and total electron yield mode. 3 2 3 1.2 0.8 3 1.3 0.7 3 3 3 3 2,3 1 2+ 4+

Scopus

researchmap

The formation process of Z-type hexagonal ferrite, Ba Co Fe O , prepared by polymerized complex method and the effects of pH control of citrate complex solution were investigated. By heating a precursor, a pyrolyzed complex polymer, spinel phase, M-type ferrite and Y-type ferrite were formed sequently with increasing the heating temperature. By heating up to 1200°C, monophasic Z-type ferrite was not synthesized in usual preparation procedures. So pH of citrate complex solution was changed and the effects on formation process were examined. As ammonia solution was added to change the complex solution from acidic to basic, the phases in the pyrolysate changed form barium carbonate to barium nitrate and the crystallinity of the constituent phases decreased. By controlling pH to 11, monophasic Z-type ferrite was obtained by heating at 1200°C. On the other hand, pH control of the complex solution toward basic condition suppressed the formation of Y-type ferrite. It was revealed that the optimum conditions for preparing the complex solution depended on phases even for same Ba-Co-Fe-O system. 3 2 24 41

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Fine particles of cerium substituted hematite with different compositions were prepared by the sol-gel method from the aqueous solution of their corresponding metal salts. Mixed hydroxides of Fe and Ce were obtained by reacting aqueous NH with the aqueous solution of FeCl and Ce(NH ) (NO ) at pH 2.5-3.0) and they were heat treated at different temperatures between 400 and 1200°C in air for 2 h to get the mixed oxide product. Thermal analysis and X-ray diffraction studies revealed the coexistence of Fe O and CeO phase separately up to 900°C, and covalent interaction between them above 1000°C, which was evidenced by the shifting of the XRD peaks. Unit cell parameters and the cell volumes (V) of the samples derived between 1000 and 1200°C were found to be in the range a = 5.045-5.048 ± 0.007 Å, c = 13.774-13.815 ± 0.041 Å and V = 303.608-304.874 Å respectively. It was observed that both the lattice parameters and the cell volumes were higher than that of the pure α-Fe O (a = 5.036 Å, c = 13.749 Å, V = 301.976 Å ) system. The expansion of lattice parameters further supported the incorporation of the large Ce ion into the α-Fe O matrix. The lattice parameter increased with increasing Ce ion loading. FESEM studies showed the growth of the particles with increasing temperature though it was suppressed due to the presence of Ce ions as compared to the pure system. © 2005 Elsevier B.V. All rights reserved. 3+ 4+ 3 3 4+ 4+ 4+ 3 3 3 2 3 6 2 3 2 2 3 2 3

DOI： 10.1016/j.matlet.2005.06.056

Web of Science

Scopus

researchmap

Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Site-specific valence-band X-ray photoelectron spectra of SrTiO (111) were successfully obtained by using X-ray standing wave technique. Contributions of the Ti and SrO derived states to the valence-band spectra were clearly separated. The spectra provided not only site-specific but also bulk-sensitive information on the SrTiO crystal because of the use of a high-energy synchrotron X-ray source (hν=4750 eV) for photoelectron excitation with the large escape depth. The electronic structures calculated by the DV-Xα method using a (Sr Ti O ) cluster model well reproduced the observed structures in the valence-band spectra. The partial density of states of both Ti and Sr ions in SrTiO were mainly distributed over the bottom of the valence-band to produce the covalent bonding with O ions. © 2005 Elsevier Ltd. All rights reserved. 3 3 3 8 27 108 3 92-

DOI： 10.1016/j.ssc.2005.09.013

Web of Science

Scopus

researchmap

Language：English   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Hematite-ilmenite (α-Fe O -FeTiO ) solid solution system is one of the candidates for high-temperature magnetic semiconductors. The intermediate composition, Fe Ti O , is known to have the maximum saturation magnetization at low temperature. We have successfully prepared well-crystallized Fe Ti O and Fe Ti Fe O bilayered films by using reactive helicon plasma sputtering. The Fe Ti O films without Fe O layers showed lower T of about 200 K, while the T of Fe Ti O layers in the bilayered films increased to about 220 K. The bilayered films had a sharp interface between Fe Ti O and α-Fe O . The strong magnetic coupling between two layers seemed to increase the T of the attached Fe Ti O layers. © 2005 IEEE. 2 3 3 1.2 0.8 3 1.2 0.8 3 1.2 0.8 2 3 1.2 0.8 3 2 3 C C 1.2 0.8 3 1.2 0.8 3 2 3 C 1.2 0.8 3

DOI： 10.1109/TMAG.2005.854820

Web of Science

Scopus

researchmap

The traditional Japanese red pigment called "bengara" has vivid yellowish red coloras compared with the pure hematite powder. The traditional "bengara" is composed of mainly hematite, for impurities, a small amount of quartz and corundum. The color of reproduced "bengara" was great influenced by the particles shape and size of hematite powder.

Scopus

researchmap

Language：Japanese  

We have successfully prepared Carbon/Fe-Co alloy composites starting from metal organic precursors synthesized by polymerized complex method. The carbon/Fe-Co alloy composites were obtained after the carbonization of the precursors heat-treated at ambient pressure and lower temperatures ranging from 500 to 700°C in N gas flow. Crystalline sizes of both carbon matrix and Fe-Co alloy particles were determined by X-ray diffraction measurements as a function of the Co concentration and the carbonized temperature. The alloy particles were widely dispersed in the carbon matrix and the particle size carbonized at 600°C was about 20-50nm observed by scanning electron microscopy. The composite carbonized at 600°C had very small coercivity of 14 Oe and exhibited relatively large permeability spectra at frequency of GHz range. 2

DOI： 10.2497/jjspm.52.640

Scopus

researchmap

Language：English   Publisher：SPRINGER  

A stable precursor for CoFe O thin film was prepared by sol-gel technique from the aqueous solution of FeCl •6H O and CoCl •6H O. Sol was deposited on a naturally oxidized silicon-substrate by spinning technique (2000 rpm) and heat treated at different temperatures ranging from 700 to 1100°C. Thickness of the films was controlled in the range of 400-500 nm and all the films were characterized by using XRD and SEM. The effects of temperature and the composition on the formation of CoFe O thin film were also studied. Films obtained at relatively lower temperature showed multi-phases of α-Fe O , CoFe O and CoO while the formation of CoFe O phase increases with increasing temperature. Furthermore, the composition of the solution in mol% has great role on the formation of CoFe O films and the film containing 50 mol% of Co exhibited CoFe O mono-phase. Surface morphology of the films was studied by scanning electron microscope (SEM). Magnetic properties of the films, studied by using vibrating sample magnetometer (VSM), showed relatively high saturation magnetization (8.04-22.21 kWb/m ) as well as high coercivity (44.59-63.30 kA/m). Saturation magnetization also increases with increasing heat treatment temperature. © 2005 Springer Science + Business Media, Inc. 2 4 3 2 2 2 2 4 2 3 2 4 2 4 2 4 2 4 2+ 2

DOI： 10.1007/s10853-005-3819-1

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Nanograined hexagonal barium ferrite (BaFe O ) thin films have been developed on naturally oxidized Si substrates by sol-gel technique using aqueous solution of metal chlorides. Coated films were heat treated at different temperatures ranging from 450 to 900°C, and all the films were characterized by using X-ray diffraction (XRD), inductive coupled plasma (ICP) spectroscopy, and field emission scanning electron microscopy (FESEM). The effects of temperature on the formation of BaFe O thin film were studied, and it was observed that hexagonal barium ferrite thin films with grain sizes of about 50 nm were formed above 700°C. Study on the magnetic properties of the films by vibrating sample magnetometer (VSM) showed that films exhibited large saturation magnetization and high coercivity in the range 247-355 emu/cm and 2.70-4.22 kOe, respectively, while the Curie temperatures (□ ) were in the range 443-457°C. The effects of temperatures on the magnetic properties were also studied. © 2004 Elsevier B.V. All rights reserved. 12 19 12 19 c 3

DOI： 10.1016/j.matlet.2004.10.026

Web of Science

Scopus

researchmap

Language：English   Publisher：JAPAN INST METALS  

A homogeneous layer of molybdenum alumininosilicide Mo(Si,Al) with C(40) structure was made on the sample surface of molybdenum by dip-coating technique using Al-25mass%Si liquid at 1123K. Adherent Al-Si was removed by soaking the dipped samples in the NaOH saturated hydraulic solution. The Mo samples coated with the Mo(Si,Al) layer were found to have excellent oxidation resistance in air even at 1473 K due to formation of a dense alumina film on the sample surface during oxidation. The formation of Mo (Si,Al) layer was also observed at the interface between the Mo substrate and the Mo(Si,Al) layer. ©2005 The Japan Institute of Metals. 2 2 5 3 2

DOI： 10.2320/matertrans.46.215

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Spinel-type Co Fe O (x=0-0.5) thin films (∼450 nm thickness) on SiO glass substrate were prepared by the sol-gel method using spinning technique (2000 rpm) from the aqueous solution of FeCl .6H O and CoCl .6H O. All the films were heat treated at different temperatures ranging from 700 to 1100°C. The films were structurally characterized by using the X-ray diffraction technique (XRD), and the morphology was studied by field emission scanning electron microscope (FESEM). The effects of temperature and the composition ([Co ]/ [Fe ] ratio) on the formation of Co Fe O thin films were also studied. The films obtained at relatively low temperature showed mixed phases of α-Fe O , CoO, along with CoFe O , while the formation of the CoFe O phase increases with increasing temperature. Furthermore, the composition of the solution in terms of [Co ]/[Fe ] plays a great role on the formation and magnetic properties of the films. The magnetic properties of the films, studied using vibrating sample magnetometer (VSM), showed relatively small saturation magnetization, and coercivity was observed to be low as compared with that of other reports. Saturation magnetization also increases with increasing heat treatment temperature. © 2004 Elsevier B.V. All rights reserved. 1+x 2-x 4 2 3 2 2 2 1+x 2-x 4 2 3 2 4 2 4 2+ 3+ 2+ 3+

DOI： 10.1016/j.matlet.2004.09.023

Web of Science

Scopus

researchmap

Language：English   Publisher：ROYAL SOC CHEMISTRY  

The effect of Co ion on the magnetic properties of the sol-gel derived cobalt ferrite thin films (400 nm thickness) was studied. Films with different solution composition ([Co ]/[Fe ] = 0.5-1.0) were deposited on a Si substrate from the precursor containing an aqueous solution of FeCl ·6H O and CoCl · 6H O. Deposited films were heat treated at different temperatures (700-1100 °C) and were characterized by X-ray diffraction using Cu Kα radiation. The films containing a nonstoichiometric α-(Fe Co ) O phase were obtained in addition to a small amount of CoO at relatively lower temperatures. With increasing heat treatment temperature, nonstoichiometric α-(Fe Co ) O was decomposed to stoichiometric α-Fe O and the CoFe O phase was intensified. Only the films obtained from the solution enriched with Co showed the single phase of CoFe O , though the Co to Fe content ratio analyzed by inductive coupled plasma spectroscopy (ICP) and energy dispersive X-ray spectroscopy (EDX) was nearly consistent with that of the starting solutions. The study of surface morphology of the films by using field emission scanning electron microscope (FESEM) showed that films were homogeneously distributed throughout the surface of the substrate and the grain sizes were in the range of 60 to 140 nm. Magnetic properties of the films, including the Curie temperature, were studied by using a vibrating sample magnetometer (VSM) and conversion electron Mössbauer spectroscopy (CEMS). The Curie temperature and the magnetic hyperfine fields of the films slightly decreased with increasing molar ratio of the Co and Fe ions while the saturation magnetization reached a maximum value with the film composition of x = 0.28. 2+ 2+ 3+ 2+ 3+ 3 2 2 2 1-x x 2 3 1-x x 2 3 2 3 2 4 2 4

DOI： 10.1039/b410163d

Web of Science

Scopus

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

The formation process of Hidasuki, a characteristic reddish coloring pattern on traditional Japanese unglazed stoneware called Bizen, was studied through model experiments. Pellets of the same type of clay used to form Bizen stoneware were heated to 1250 °C with and without contact with rice straw and then were cooled at different rates. A reddish color appeared for relatively slowly cooled samples when rice straw was present. Owing to the presence of potassium in the rice straw, the mullite (3(Al,Fe) O ·2SiO ) the major phase formed in the absence of rice straw, was replaced by corundum (α-Al O ), hematite (α-Fe O ), and others in the surface region of about 50 μm in depth. The corundum precipitated as hexagonal platelike crystals, and on the edges of these crystals the hematite grew epitaxially. The growth continued so that the primary corundum crystals were wholly covered by hematite to form a specific single crystalline α-Fe O /α-Al O /α-Fe O structure. The contribution of this unique microstructure to coloring is discussed. On the basis of these analytical results, the Hidasuki pattern was reproduced artificially in the form of written characters. 2 3 2 2 3 2 3 2 3 2 3 2 3

DOI： 10.1021/cm0352145

Web of Science

Scopus

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Unique magnetic and electric properties of solid solutions of ilmenite (FeTiO ) and hematite (α-Fe O ) can be expected for new electronics, optics and spintronics applications. We have successfully prepared well-crystallized and epitaxial Fe Ti O (001) films on α-Al O (001) substrates by reactive helicon plasma-sputtering technique. Structure, magnetic and electric properties of the films were seriously dependent on both the oxygen pressure and the substrate temperature during the sputtering deposition. The subsequent annealing of the films in vacuum at high temperature (600 °C) promoted the order (R3̄) structure of Fe Ti O , where the Ti and Fe ions occupied the cation sites alternatively along the c-axis. Only the films having the R3̄ symmetry had large ferrimagnetic moments at low temperature (78 K), although the magnetization values were depending on not only the order parameter between the R3̄ and the R3̄c structures but also the oxidization states of Fe ions in Fe Ti O . The film prepared at an oxygen partial pressure ratio of 1.4% and substrate temperature of 400 °C had considerably large spontaneous magnetization of 275 emu/cm at 78 K after the subsequent annealing at 600 °C. However, highly oxidized nonstoichiometirc Fe Ti O films with the R3̄c symmetry could not give the ordered structure with the R3̄ symmetry. © 2004 Elsevier B.V. All rights reserved. 3 2 3 1.23 0.77 3+δ 2 3 1.23 0.77 3+δ 1.23 0.77 3+δ 1.23 0.77 3+δ 3

DOI： 10.1016/j.ssi.2004.02.051

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Well-crystallized Y-type hexagonal ferrite films with highly c-axis orientation were successfully prepared on Ag, Au and Pt substrates by polymerized complex method. The films prepared on Ag had considerably low formation temperature of 800°C, while those on An and Pt were formed at above 1000°C. The films had large in-plane magnetic anisotropy, with small coercivity. Hexagonal grains structures were developed on the substrates. © 2003 Published by Elsevier B.V.

DOI： 10.1016/j.jmmm.2003.12.885

Web of Science

Scopus

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

Epitaxial FeTiO (001) films were prepared on α-Al O (001) substrates by helicon plasma sputtering technique. Structure and magnetic properties of FeTiO film were largely dependent on the residual oxygen pressure (Po ) during the sputtering deposition. The films prepared at lower Po had an ilmenite (R3̄) structure, while a corundum (R3̄c) structure was observed in the case of higher Po . The oxidation state of Fe in FeTiO films changed monotonically from Fe to Fe with increasing the Po . The films with the R3̄ symmetry were ferrimagnitic at low temperature, while the nonstoichiometric FeTiO with the R3̄c symmetry were antiferromagnetic at room temperature. © 2003 Elsevier B.V. All rights reserved. 3+λ 2 3 3+λ 2 2 2 3+λ 2 3+λ 2+ 3+

DOI： 10.1016/j.jmmm.2003.12.793

Web of Science

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：表面分析研究会  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：養賢堂  

CiNii Article

CiNii Books

researchmap

researchmap

Language：Japanese   Publisher：日本材料学会  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：日本材料学会  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：日本材料学会  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：Journal of the Japan Society of Powder and Powder Metallurgy  

Human beings have been using "bengara" (α-Fe O ) as red pigment ever since ancient times. As for Japan, the first artificial "bengara" was manufactured at Fukiya town in 1707, and it was mainly used for red painting of porcelain and other objects for about 300 years. However this "Fukiya bengara" cannot be manufactured anymore because of the environment pollution in spite of eagerness of potters to use it for producing bright yellowish red. At first step, we characterized traditional "Fukiya bengara" and found that α-Al O existed. It is probably due to the formation of Al substituted α-Fe O . Then next step, we prepared red pigment of Fe O -Al O system to investigate the Al substitution effect, by using both solid-state and polymerized complex methods. The red tone color depended on the particle size; the yellowish red pigment had the smallest size. Al substitution seemed to suppress the grain growth of hematite. The red tone color was controllable with the amount of Al substitution. α-(Fe Al ) O prepared at 1000°C for 2 hours presented as bright yellowish red color as that of "Fukiya Bengara". 2 3 2 3 2 3 2 3 2 3 0.9 0.1 2 3

DOI： 10.2497/jjspm.50.1062

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

researchmap

researchmap

J-GLOBAL

researchmap

CiNii Article

CiNii Books

researchmap

Epitaxial thin films of (001)-oriented FeTiO were prepared on α-Al O (001) single crystalline substrates by helicon plasma sputtering technique. The FeTiO films had large oxygen nonstoichiometry, which seriously depended on both substrate temperature and oxygen pressure during the sputtering deposition. The valence states of Fe ions in FeTiO changed monotonically from Fe to Fe with decreasing the substrate temperature from 900 to 400°C or with increasing the oxygen pressure from 0.9 to 1.8×10 Pa. The change of Fe valence states from Fe to Fe induced the magnetic phase transition only for the films prepared at 900°C. The films containing Fe were paramagnetic while those with Fe were antiferromagnetic at room temperature. The oxygen nonstoichiometry of the FeTiO films was probably produced by cation vacancies and disarrangement of Fe and Ti ions, which randomly occupied both interstitial and substitutional sites of the FeTiO related structure. 3+δ 2 3 3+δ 3+δ 3+δ 3 2+ 3+ -6 2+ 3+ 2+ 3+ 3+ 4+

DOI： 10.1557/proc-746-q6.10

Scopus

researchmap

Language：English   Publisher：MATERIALS RESEARCH SOCIETY  

Well-crystallized Ba Zn Fe O (Zn -Y) films with high c-axis oritentation were successfully formed on Ag substrates at low temperature by the polymeric precursor method. A precursor solution with stoichiometric Ba , Zn , and Fe ions was deposited on the substrates by a dip-coating. The films were then heat-treated at temperatures ranging from 700 to 900°C. The crystallization process of c-axis-oriented Zn -Y films occurred at the considerably low temperature of 750°C, though a small amount of spinel oxides contaminated them. The films had hexagonal grain structures which were developed by increasing the heat-treatment temperature. Magnetization curves of the Zn -Y film heated at 900°C clearly indicated that the film had large in-plane magnetic anisotropy and had small in-plane coercivity. 2 2 12 22 2 2 2 2+ 2+ 3+

DOI： 10.1557/JMR.2001.0338

Web of Science

Scopus

researchmap

Language：English   Publisher：AMER PHYSICAL SOC  

In an attempt to obtain wustite Fe1-xO as epitaxial films on MgO(100), NO2-assisted molecular-beam epitaxy was applied. At low NO2 fluxes, the low-energy electron diffraction and reflection high-energy electron diffraction images indeed indicate the formation of a rocksaltlike structure. In addition, Mossbauer spectroscopy provides evidence for the formation of a phase that is paramagnetic at room temperature. However, the layers are not pure oxides but are well-ordered oxynitrides with composition Fe1-xO1-yNy. The nitrogen atoms occupy substitutional sites on the oxygen-anion sublattice. Similarly, at slightly higher NO2 fluxes, magnetitelike oxynitride films with composition Fe3+deltaO4-yNy are obtained. By correlating x-ray photoelectron spectroscopy spectra with the intensity oscillation periods observed during reflection high-energy electron diffraction, it is possible to derive the complete stoichiometry of the films. We propose that the abrupt incorporation of nitrogen atoms only occurs if the atomic oxygen provided by the NO2 flux is insufficient to form a stoichiometric Fe3O4.

Web of Science

researchmap

CoFe O /α-Fe O (ferrimagnetic/antiferromagnetic) bilayered films were prepared on α-Al O (102) single-crystalline substrates by helicon plasma sputtering. A well-crystallized epitaxial α-Fe O (102) layer was formed on the substrate, while CoFe O grown on α-Fe O (102) was a polycrystalline layer with a (100)-preferred orientation. The α-Fe O (102) films without CoFe O layers clearly showed a spin-flip transition at about 400 K. The spins aligned perpendicular to the film plane at room temperature changed their direction within the film plane above 400 K. However the α-Fe O base layers of CoFe O /α-Fe O bilayered films did not show any spin-flip transition. The CoFe O layer on α-Fe O had a large in-plane magnetic anisotropy, while the spin axis of the α-Fe O (102) base layer was directed perpendicular to the film plane. The magnetization of ferrimagnetic CoFe O layers was coupled perpendicularly to the spin axis of antiferromagnetic α-Fe O layers due to the exchange coupling at the interface between CoFe O and α-Fe O . 2 4 2 3 2 3 2 3 2 4 2 3 2 3 2 4 2 3 2 4 2 3 2 4 2 3 2 3 2 4 2 3 2 4 2 3

DOI： 10.1557/proc-674-t1.10

Scopus

researchmap

Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Effects of Pb-substitution on the electrical and magnetic properties and the microstructure of the Bi-based cuprate superconductors, especially Bi-2212 (Bi Sr CaCu O ) polycrystalline phase, have been studied by XRD, SEM, TEM and magnetic measurements. The larger hysteresis loops of the Pb-substituted Bi-2212 phase in M-H curves were observed in comparison with the Pb-free Bi-2212 phase. The disorder of the structural modulation and the formation of micro-twins were found in the Pb-doped Bi-2212 phase by TEM observations. These results were caused by inhomogeneity of Pb concentration in the crystal. 2 2 2 8+δ

Web of Science

Scopus

researchmap

Well-crystallized Y-type hexagonal ferrite (Me -Y, Me=Zn and Co) films with highly c-axis orientation were successfully prepared on Ag substrates by dip coating technique. The procedure consisted of preparation of homogeneous metal-organic solution by polymerized complex method, dip coating and subsequent heat-treatment. The films deposited on α-Al O easily reacted with the substrate, while the films deposited on Ag formed hexagonal planar structures. The formation temperature of Me -Y structures on Ag was 800 °C, which was much lower than that of Me -Y bulk crystals. The Me -Y films on Ag had a large in-plane magnetic anisotropy. The observed anisotropy field of the Zn -Y film was about 13 kOe and that of Co -Y was too large beyond our experimental limits. © 2001 Materials Research Society. 2 2 3 2 2 2 2 2

Scopus

researchmap

In order to develop wide-band microwave absorbers we tried to prepare composite absorbers between the magnetic loss (Ni-Zn-ferrite) and the dielectric loss (SiC) materials. The dry or wet mixtures of Ni-Zn-ferrite and polycarbosilane (PCS) were cured in air and were then subjected to pyrolysis forming of the ferrite composites. The composites produced by the wet mixing had granular structure: the PCS surrounding the ferrite particles suppressed the sintering and the grain growth of the ferrite composites during pyrolysis. The matching frequency due to the magnetic loss linearly increased with increasing the PCS content. Moreover the ferrite/SiC hemi-crystallized composite cured at 473 K for 24 hours showed wide-band absorption spectrum having the both magnetic and dielectric losses. © 2001 Materials Research Society.

Scopus

researchmap

Language：English   Publisher：Elsevier Science Publishers B.V.  

The magnetization of V S and V Se was measured in pulsed high magnetic fields up to 39 T. The anomalies were observed in the magnetization curves for both V S and V Se . For V S , the anomaly at lower field is thought to correspond to spin flopping. The magnetization curves exhibited saturation for both compounds and the values of the ordered moments for V S and V Se were estimated to be 1.5 and 1.2 μ /V from the saturation moments, respectively. Our results support the magnetic structure of V S proposed by neutron diffraction measurements. 5 8 5 8 5 8 5 8 5 8 5 8 5 8 B 5 8 I

DOI： 10.1016/S0304-8853(00)00509-6

Scopus

researchmap

Language：Japanese   Publisher：Funtai Funmatsu Yakin Kyokai  

Ni-Zn ferrite/SiC sintered composite was prepared as electromagnetic wave absorber through pre-ceramics method and subsequent annealing at 1273 K. Amorphous SiC particles dispersed uniformly in Ni-Zn ferrite matrix and the density of the composites decreased with increasing the amount of SiC particles. The absorption characteristics of the sintered composite were found to depend upon the amount of SiC particles. The matching frequency of the composites shifted toward higher frequency, from about 100 MHz to 1 GHz, with increasing the amount of SiC particles.

DOI： 10.2497/jjspm.47.927

Scopus

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：English   Publisher：Elsevier Science Publishers B.V.  

The magnetization of V5S8 and V5Se8 was measured in pulsed high magnetic fields up to 39 T. The anomalies were observed in the magnetization curves for both V5S8 and V5Se8. For V5S8, the anomaly at lower field is thought to correspond to spin flopping. The magnetization curves exhibited saturation for both compounds and the values of the ordered moments for V5S8 and V5Se8 were estimated to be 1.5 and 1.2 μB/VI from the saturation moments, respectively. Our results support the magnetic structure of V5S8 proposed by neutron diffraction measurements.

DOI： 10.1016/S0304-8853(00)00509-6

Scopus

researchmap

Solid solution films of the α-Fe O -FeTiO series are one of the candidates for noble half-metallic oxides. They were epitaxially formed on α-Al O (001) single crystalline substrates by O -reactive evaporation method. The Fe Ti O films prepared at higher T =973 K and with larger Ti content x ≥ 0.4 had the ilmenite structure with R3̄ symmetry. Other films at lower T or with smaller x possessed the corundum structure with R3̄c. Only the films with R3̄ symmetry had large ferrimagnetic moments, though the observed spontaneous magnetization was less than half of the ideal value expected from the fully ordered structure. Room temperature resistivity of intermediate composites dropped to 10 Ωcm due to the formation of the mixed valence states between Fe and Fe . However the Fe content of the films was rather small as compared with stoichiometric Fe Ti O . The Ti-rich films had large oxygen nonstoichiometry of about δ=0.3. 2 3 3 2 3 2 2-x x 3+δ S S 2-x x 3 -1 2+ 3+ 2+

DOI： 10.1557/PROC-623-191

Scopus

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：Funtai Funmatsu Yakin Kyokai  

The effects of lithium doping by solid state reaction on the electrochemical intercalation into the Bi-2212 phase with lithium were investigated through the structure and superconducting properties. The expansion rates of lattice parameters with respect to the amount of lithium intercalated by electrochemical reaction decreased with increasing the amount of lithium doped by solid state reaction. The change of superconducting critical temperature with respect to average valence of copper became small with increasing the amount of lithium doped by solid state reaction. The electrochemical reaction removed lithium from Bi-2212 phase as much as the amount of lithium intercalated by electrochemical reaction. The result supports the possibility that lithium doped by solid state reaction and electrochemical reaction occupies the different sites in the Bi-2212 phase.

DOI： 10.2497/jjspm.46.990

Scopus

researchmap

Language：Japanese   Publisher：Funtai Funmatsu Yakin Kyokai  

FeTiO -α-Fe O solid solution films were epitaxially formed on an α-Al O (001) single crystalline substrate by activated reactive evaporation method. The films prepared at low substrate temperature of 500°C had the corundum structure where Fe and Ti ions occupied the cation sites randomly. While the Fe Ti O films with x ≥ 0.4 prepared at 700°C had the ilmenite structure where Fe and Ti ions were arranged in order. Only the films with the ordered Fe and Ti ions had large ferrimagnetic moments, though the observed spontaneous magnetization was less than a half of the ideal value expected from the fully ordered ions. Moreover the resistivity of the solid solution films dropped to 10 Ωcm due to the formation of the mixed valence states between Fe and Fe . We revealed this system was one of the candidates for new oxide magnetic semiconductor films. 3 2 3 2 3 2-x x 3 -1 2+ 3+

DOI： 10.2497/jjspm.46.643

Scopus

researchmap

Language：English  

We report on a systematic analysis of x-ray photoelectron spectroscopy (XPS) core- and valence-level spectra of clean and well-characterized iron oxide films, i.e., (Formula presented) (Formula presented) (Formula presented) and (Formula presented) All iron oxide films were prepared epitaxially by (Formula presented)-assisted molecular-beam epitaxy on single crystalline MgO(100) and (Formula presented) substrates. The phase and stoichiometry of the films were controlled precisely by adjusting the (Formula presented) pressure during growth. The XPS spectrum of each oxide clearly showed satellite structures. These satellite structures were simulated using a cluster-model calculation, which could well reproduce the observed structures by considering the systematic changes in both the Fe (Formula presented) to O (Formula presented) hybridization and the (Formula presented) electron-correlation energy. The small difference in the satellite structures between (Formula presented) and (Formula presented) resulted mainly from changes in the Fe-O hybridization parameters, suggesting an increased covalency in (Formula presented) compared to (Formula presented) With increasing reduction in the (Formula presented) system, the satellite structures in XPS became unresolved. This was not only due to the formation of (Formula presented) ions, but also to nonhomogeneous changes in the hybridization parameters between octahedral and tetrahedral (Formula presented) ions. © 1999 The American Physical Society.

DOI： 10.1103/PhysRevB.59.3195

Scopus

researchmap

Language：English  

We report on a systematic analysis of x-ray photoelectron spectroscopy (XPS) core- and valence-level spectra of clean and well-characterized iron oxide films, i.e., (Formula presented) (Formula presented) (Formula presented) and (Formula presented) All iron oxide films were prepared epitaxially by (Formula presented)-assisted molecular-beam epitaxy on single crystalline MgO(100) and (Formula presented) substrates. The phase and stoichiometry of the films were controlled precisely by adjusting the (Formula presented) pressure during growth. The XPS spectrum of each oxide clearly showed satellite structures. These satellite structures were simulated using a cluster-model calculation, which could well reproduce the observed structures by considering the systematic changes in both the Fe (Formula presented) to O (Formula presented) hybridization and the (Formula presented) electron-correlation energy. The small difference in the satellite structures between (Formula presented) and (Formula presented) resulted mainly from changes in the Fe-O hybridization parameters, suggesting an increased covalency in (Formula presented) compared to (Formula presented) With increasing reduction in the (Formula presented) system, the satellite structures in XPS became unresolved. This was not only due to the formation of (Formula presented) ions, but also to nonhomogeneous changes in the hybridization parameters between octahedral and tetrahedral (Formula presented) ions. © 1999 The American Physical Society.

DOI： 10.1103/PhysRevB.59.3195

Scopus

researchmap

We report on the molecular beam epitaxial growth of single-crystalline, stoichiometric Fe O and γ-Fe O films on MgO(100), using NO as the oxidizing agent. Mössbauer spectroscopy on Fe probe layers is used to determine accurately the stoichiometry of the films. It is found that also all intermediate nonstoichiometric Fe O phases can be obtained. The formation of the metastable compound γ-Fe O clearly demonstrates the large oxidizing power of NO . Although the shape anisotropy dictates that the zero-field magnetization direction should lie entirely in the plane of the film, this is never observed. Stoichiometric Fe O has large out-of-plane components and only in the case of highly oxidized Fe O does the magnetization approach the film plane. Upon further oxidation to stoichiometric γ-Fe O , however, it rotates back, and finally becomes almost completely perpendicular to the plane of the film. Furthermore, in the case of (near-) stoichiometric Fe O , the magnetizations of the A and B sublattices are not completely coupled antiparallel. On average, the magnetization of the B site ions is 4° closer to the film plane than the magnetization of the A site ions. All the as-grown films exhibit a (√2x √2)R45° surface reconstruction, independent of the stoichiometry. Using simple electrostatic considerations, we propose three possible surface terminations: a half-filled A layer, a B layer with oxygen vacancies and a B layer with hydroxyl groups. Upon annealing, the (√2x √2)R45° reconstruction irreversibly transforms to a 3x1 reconstruction, caused by Mg outdiffusion from the substrate. Strong reflection high-energy electron diffraction intensity oscillations give direct, unambiguous evidence that Fe O has a two-dimensional layer-by-layer growth mode over the entire temperature range studied, i.e., from 273 to 723 K, guaranteeing atomically flat surfaces and interfaces in multilayer structures. The largest oscillations are obtained on ex situ cleaved, UHV-annealed MgO(100) substrates, or on in situ annealed Fe O /MgO(100) films. Deposition above ∼700 K is accompanied by rapid Mg outdiffusion. ©1999 The American Physical Society. 3 4 2 3 2 3-δ 4 2 3 2 3 4 3-δ 4 2 3 3 4 3 4 3 4 57

DOI： 10.1103/PhysRevB.60.11193

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

J-GLOBAL

researchmap

The structural, electric and magnetic properties of (100)-oriented Fe O /NiO and Fe O /CoO superlattices on MgO(100) have been studied. The films were prepared by an activated reactive evaporation method. The lattice constants of each layers were a little changed from the bulk values due to a lattice mismatch with the substrate. The Fe 2p XPS of both Fe O /NiO and Fe O /CoO interfaces suggested the formation of stoichiometric Fe O . The saturation magnetizations (Ms) of Fe O /MO superlattices were compared with that of a Fe O thin film as a function of the thickness of MO layers. The reduction in Ms of Fe O /NiO could be linked with the large exchange coupling with NiO. While the increase in Ms of Fe O /CoO was probably caused by the ferromagnetic coupling of the CoO interface with the Fe O layer. 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 4

DOI： 10.2497/jjspm.45.58

Scopus

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Effects of electrochemical Li-doping to the Pb-substituted Bi-2212 phase on its structural and superconducting properties were studied. Bi Pb Sr Ca Cu O was lithiated through an electrochemical method at constant applied potential at room temperature. In the electrochemically Li-doping samples, the original crystal symmetry, tetragonal structure, was maintained and any secondary phase was not formed. The amount of doped Li for Bi Pb Sr Ca Cu O was much lager than that for Bi Sr Ca Cu O at the same reaction periods. Analysed maximum Li content y for Li Bi Pb Sr Ca Cu O was found to be 0.53, which was remarkably high in comparison with y=0.37 for Li Bi Sr Ca Cu O . The lattice parameters (a,c) of Li Bi Pb Sr Ca Cu O increased continuously in a similar trend to that of Li Bi Sr Ca Cu O . Tc remains almost constant around 85K as the Li content y increased. 1.8 0.2 1.5 1.5 2 z 1.8 0.2 1.5 1.5 2 z 2 1.5 1.5 2 z y 1.8 0.2 1.5 1.5 2 z y 2 1.5 1.5 2 z y 1.8 0.2 1.5 1.5 2 z y 2 1.5 1.5 2 z

DOI： 10.2497/jjspm.44.792

Scopus

researchmap

Language：English   Publisher：Elsevier  

Effects of lithium intercalation into the Bi-2212 phase on its structural and superconducting properties were studied using monophasic samples of Bi Sr Ca Cu O lithiated through an electrochemical method at a constant applied voltage at room temperature. The amount of doped lithium was found by ICP analysis to be in the range of 0 ≤ y ≤ 0.37 for Li Bi Sr Ca Cu O depending upon experimental conditions. However, the oxygen content determined by coulometric titration remained almost unchanged after the lithiation. The electrochemical lithium intercalation led to a very interesting change in T , though the original tetragonal structure and oxygen content remained essentially the same: T first increased rapidly as y increased, reached a maximum of 94 K, and then decreased to zero. The drastic T change is ascribed to a decrease in the hole concentration. Thus, the electrochemical lithium-doping provides us with a great advantage of easily controlling T at room temperature by changing electrochemical conditions while keeping the original crystal symmetry. © 1997 Elsevier Science B.V. 2 1.5 1.5 2 z y 2 1.5 1.5 2 z c c c c

DOI： 10.1016/S0921-4534(97)00177-9

Scopus

researchmap

Language：English   Publisher：Elsevier  

Effects of lithium intercalation into the Bi-2212 phase on its structural and superconducting properties were studied using monophasic samples of Bi2Sr1.5Ca1.5Cu2Oz lithiated through an electrochemical method at a constant applied voltage at room temperature. The amount of doped lithium was found by ICP analysis to be in the range of 0 ≤ y ≤ 0.37 for LiyBi2Sr1.5Ca1.5Cu2O z depending upon experimental conditions. However, the oxygen content determined by coulometric titration remained almost unchanged after the lithiation. The electrochemical lithium intercalation led to a very interesting change in Tc, though the original tetragonal structure and oxygen content remained essentially the same: Tc first increased rapidly as y increased, reached a maximum of 94 K, and then decreased to zero. The drastic Tc change is ascribed to a decrease in the hole concentration. Thus, the electrochemical lithium-doping provides us with a great advantage of easily controlling Tc at room temperature by changing electrochemical conditions while keeping the original crystal symmetry. © 1997 Elsevier Science B.V.

DOI： 10.1016/S0921-4534(97)00177-9

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Thin films of c-axis oriented Ba- and Sr-hexaferrits (BaM and SrM) were prepared by reactive evaporation method without any post heat treatments. Subsequently growth of BaM/SrM multilayered films was tried and the sidebands in XRD clearly appeared. According to magnetization measurements all films had the perpendicular magnetic anisotropy. However the M for BaM film was only 55% of that for the bulk. A broad background in Mössbauer spectrum for the BaM suggested the fluctuating magnetic moments. Though the M for SrM film was improved it had some inplane magnetization components. To combine the advantages of BaM and SrM individual films, the BaM/SrM multilayered film exhibited good magnetic properties: The M was recovered to about 80% of the bulk value and the inplane magnetization components disappeared in both the magnetization curves and the Mössbauer spectrum. s s s

DOI： 10.1051/jp4:19971197

Scopus

researchmap

Epitaxial single crystalline films of iron oxides have been grown on MgO(100) substrates by means of MBE. Natural Fe or Fe was evaporated from alumina crucibles, and oxidized simultaneously with a dosed flux of NO . The resulting oxide layers have been characterized in situ with RHEED, LEED, XPS, and AES. RHEED intensity oscillations, observed during deposition of the oxides, indicate a layer-by-layer growth for all substrate temperatures between 373 and 673 K. A stoichiometry analysis with CEMS, performed ex situ, shows that it is straightforward to prepare both the stable magnetite Fe O and the metastable maghemite γ-Fe O phases. Moreover, also all solid solutions in between these two extreme phases, i.e. Fe O with 0<δ<1/3, could be formed. Ion beam channelling has been used to examine the epitaxy of the films. It was found that the films grow coherent on MgO(100). 57 2 3 4 2 3 3-δ 4

Scopus

researchmap

Epitaxial single crystalline films of iron oxides have been grown on MgO(100) substrates by means of MBE. Natural Fe or Fe was evaporated from alumina crucibles, and oxidised simultaneously with a dosed flux of NO . The resulting oxide layers have been characterised in situ with RHEED, LEED, XPS, and AES. RHEED intensity oscillations, observed during deposition of the oxides, indicate a layer-by-layer growth for all substrate temperatures between 373 and 673 K. A stoichiometry analysis with CEMS, performed ex situ, shows that it is straightforward to prepare both the stable magnetite Fe O and the metastable maghemite γ-Fe O phases. Moreover, also all solid solutions in between these two extreme phases, i.e. Fe O with 0<δ<1/3, could be formed. Ion beam channelling has been used to examine the epitaxy of the films. It was found that the films grow coherent on MgO(100). 57 2 3 4 2 3 3-δ 4

Scopus

researchmap

The effects of Li doping on the formation process of the 2212 phase in the Bi-Sr-Ca-Cu-O system, and its structural and superconducting features were studied. Samples with nominal compositions of Bi : Sr: Ca: Cu: Li = 2: 1.5: 1.5: 2: x where 0 ≤ x ≤ 0.6 were heated in air at temperatures ranging between 560°C and 850°C. Li doping greatly promoted the formation of the 2212 phase; the monophasic samples were rapidly obtained for x ≤ 0.4 by firing even at 730°C, which is about 100°C lower than that of the non-doped 2212 phase. A newly found oxide phase containing Li, which was formed below 710°C, is considered to play an important role as a precursor to accelerate the formation of the 2212 phase. The Li content in the monophasic samples determined by ICP analysis decreased to about a half of the nominal composition due to partial Li escape during heating. Monophasic composition range of the Li-doped 2212 phase was 0 ≤ y ≤ 0.19 as Bi Sr Ca Cu Li O . Increase in both lattice parameter c and oxygen content z with increasing Li content y in the 2212 phase was accompanied with a rise of T up to 90 K. 2 1.5 1.5 2 y z c

DOI： 10.1016/S0921-4534(96)00689-2

Scopus

researchmap

Language：Japanese   Publisher：Funtai Funamtsu Yakin Kyokai/Japan Soc. of Powder Metallurgy  

The effects of electrochemical Li-doping on superconducting properties of the Bi-2212 phase have been investigated. The electrochemical Li-doping into the 2212 phase was first succeed with remaining the original crystal structure and without formation of any second phase. Maximum Li content y as Li Bi Sr Ca Cu O by this electrochemical reaction was found to be 0.37. The Li content increased with increasing in reaction time and applied potential. The lattice parameters (a, c) of the Bi-2212 crystals increased continuously from (5.397Å, 30.69Å) for y=0.0 to (5.411Å, 30.89Å) for y=0.37. Tc of the doped samples continuously decreased to 0K for around y=0.27. y 2 1.5 1.5 2 z

DOI： 10.2497/jjspm.44.142

Scopus

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

In situ RHEED and XPS measurements of epitaxial α-Fe O (0001) films are reported as a function of the number of deposited monolayers. The films were prepared on α-Al O (0001) substrates by MBE. The RHEED patterns suggest that layer-by-layer growth of α-Fe O (0001) occurs for the first few monolayers. Subsequently, the growth mode changes to three-dimensional growth. The in-plane lattice constant of the first monolayer of α-Fe O (0001) is expanded relative to that of the bulk, although in the case of lattice matching between α-Al O and α-Fe O a contraction would be expected. This can be explained by assuming a basic hexagonal structure for the first monolayer with a random distribution of ferric ions over the octahedral sites between the close-packed oxygen layers. Beyond the first monolayer, the ordered corundum structure is formed. The lineshapes of the XPS Fe 2p core level spectra are also found to be thickness-dependent. The deviation of the Madelung potential at the surface shifts the positions of the Fe 2p peaks to lower binding energies. For the first few monolayers, the satellite intensity is reduced because the interplanar contraction leads to a shorter Fe-O distance. 2 3 2 3 2 3 2 3 2 3 2 3

DOI： 10.1016/0039-6028(96)00844-8

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Epitaxial layers of iron oxides have been grown on a MgO(001) substrate by evaporating natural Fe or 57Fe from Knudsen cells in the presence of a NO flow directed to the substrate. The resulting layers have been investigated in situ with LEED, RHEED, AES and XPS and ex situ with CEMS and ion beam analysis. For substrate temperatures between 200 and 400°C we observe RHEED oscillations during deposition, indicative of layer-by-layer growth. By adjusting the flux of NO at the surface, all stable and mctastable cubic phases in the Fe-O system could be grown: FeO (wustite), Fe O (magnetite), γ-Fe O (maghcmitc) and solid solutions between the latter two phases. Rutherford backscattering spectra show a relatively high minimum yield in the channel directions. © J.C. Baltzer AG, Science Publishers. 2 2 3 4 2 3

DOI： 10.1007/bf02150170

Scopus

researchmap

Magnetic properties of small particles of iron oxide on an aluminum foil and a single crystal of MgO are studied by conversion electron Mössbauer spectroscopy (CEMS) at low temperature. The average thickness of the oxide layers is 3.0 nm on aluminum and 1.2 nm on MgO. The CEMS spectra are observed at 15-300 K with a gas-filled proportional counter which was developed in our laboratory. The hyperfine fields in the surface layer and in the core of the particles are separated. The diameter and magnetic anisotropy energy constant are 3.7 nm and 0.87 × 10 J/m , and 3.5 nm and 2.4 × 10 J/m , respectively, for small particles on aluminum and MgO. The large difference in the anisotropy constants of small particles on aluminum and MgO is attributed to the enhanced surface anisotropy, which may be caused by diffusion of magnesium ions into the lattice of iron oxide. The superparamagnetic blocking temperatures of these particles are 71 and 94 K, respectively. © 1995. 5 3 5 3

DOI： 10.1016/0304-8853(94)00864-7

Scopus

researchmap

Language：English  

(100)- and (111)-oriented Fe O /CoO superlattices were prepared on MgO(100) and α-Al O (0001) singlecrystalline substrates, respectively, by activated reactive vapor deposition method. X-ray diffraction analysis suggests that the lattice spacing along the growth direction was contracted for the CoO layer but expanded for the Fe O layer probably due to the lattice mismatch between these layers. The magnetostriction of CoO layers induced in-plane and perpendicular magnetic anisotropy in (100)- and (111)-oriented superlattices, respectively. Coercive force along the magnetic easy axis was increased with increasing the thickness of the CoO layer but decreased with increasing that of the Fe O layer. Strong magnetic coupling between Fe O and CoO layers made the Néel temperature of the CoO layer higher and showed the ferrimagnetic/antiferromagnetic exchange anisotropy. © 1995, Japan Society of Powder and Powder Metallurgy. All rights reserved. 3 4 2 3 3 4 3 4 3 4

DOI： 10.2497/jjspm.42.34

Scopus

researchmap

Language：English  

The spin-flip transition of 1000 Å-thick α-Fe O films was investigated by conversion electron Mössbauer spectroscopy from 2.5 to 673 K. The films were epitaxially formed on α-Al O single-crystalline substrates by a reactive vapor deposition method. Not only the transition temperature but also the spin axis were found to strongly depend upon the film orientation, probably as a result of anisotropic lattice strains caused by interactions with the substrate. For a (102)-oriented film the transition takes place at about 400 K, much higher the Morin transition temperature (260 K) of the free crystal, and the spin axis lying within the (102) plane above 400 K changes almost normal to the plane at room temperature and below: the normal makes 57.6° with the spin axis of the free crystal. A (001)-oriented film, on the other hand, does not show any transition at least down to 2.5 K. © 1994. 2 3 2 3

DOI： 10.1016/0304-8853(94)90351-4

Scopus

researchmap

Language：English  

Titanium di- and sesquioxide films were epitaxially grown on the (001) surface of sapphire single-crystalline substrates by an activated reactive evaporation method. Formation range for each titanium oxide was determined as a function of oxygen pressure (Po2) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at Po^.OX 10 4 Torr were stoichiometric (lOO)-oriented rutile of Ti02, and with decreasing Po2 they would accommodate more and more Ti3+ ions in the rutile structure. At P02 = 0.6 X 10~4 Torr, on the other hand, (OOl)-oriented Ti203 was formed and an electrical transition was clearly detected at about 400 K. However, the large lattice mismatch between the substrate and these films leads to a periodic introduction of misfit dislocations in the case of the Ti02 films and a mixing of stacking sequences for the Ti203 films. © 1994, Materials Research Society. All rights reserved.

DOI： 10.1557/JMR.1994.1468

Scopus

researchmap

Language：English  

Stoichiometric Fe O films have formed epitaxially on α-Al O and MgO single-crystal substrates by a reactive vapor deposition method. In order to apply conversion electron Mössbauer spectroscopy depth-selectively, a 5-7 Åthick probe layer containing Fe was formed at various depths in inactive Fe O matrix films. At the topmost surfaces and also at the interfaces, the essential electronic features of bulk Fe O are retained, including a rapid electron hopping between the Fe and Fe ions at B sites. Minor depth-dependent changes are confined to a few outermost atomic layers, and the changes depend on the orientation and the lattice mismatch with the substrate. For (111) growth on α-Al O , the surface layer seems to be strongly relaxed to reduced the electric polarization, while a high density of defects seems to be concentrated at the interface with α-Al O . For (001) growth on MgO, the surface retains the spinel lattice though slightly oxidized, while the interface with MgO has good crystallinity and stoichiometry. An enhanced thermal fluctuation of the Fe -spins in contact with the MgO substrate and in the topmost surface layer can be seen in their reduced magnetic hyperfine field at 300 K. © 1994. 3 4 2 3 3 4 3 4 2 3 2 3 57 56 2+ 3+ 3+

DOI： 10.1016/0304-8853(94)90683-1

Scopus

researchmap

Language：English  

Titanium di- and sesquioxide films were epitaxially grown on the (001) surface of sapphire single-crystalline substrates by an activated reactive evaporation method. Formation range for each titanium oxide was determined as a function of oxygen pressure (Po2) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at Po^.OX 10 4 Torr were stoichiometric (lOO)-oriented rutile of Ti02, and with decreasing Po2 they would accommodate more and more Ti3+ ions in the rutile structure. At P02 = 0.6 X 10~4 Torr, on the other hand, (OOl)-oriented Ti203 was formed and an electrical transition was clearly detected at about 400 K. However, the large lattice mismatch between the substrate and these films leads to a periodic introduction of misfit dislocations in the case of the Ti02 films and a mixing of stacking sequences for the Ti203 films. © 1994, Materials Research Society. All rights reserved.

DOI： 10.1557/JMR.1994.1468

Scopus

researchmap

Language：English  

Stoichiometric Fe3O4 films have formed epitaxially on α-Al2O3 and MgO single-crystal substrates by a reactive vapor deposition method. In order to apply conversion electron Mössbauer spectroscopy depth-selectively, a 5-7 Åthick probe layer containing 57Fe was formed at various depths in inactive 56Fe3O4 matrix films. At the topmost surfaces and also at the interfaces, the essential electronic features of bulk Fe3O4 are retained, including a rapid electron hopping between the Fe2+ and Fe3+ ions at B sites. Minor depth-dependent changes are confined to a few outermost atomic layers, and the changes depend on the orientation and the lattice mismatch with the substrate. For (111) growth on α-Al2O3, the surface layer seems to be strongly relaxed to reduced the electric polarization, while a high density of defects seems to be concentrated at the interface with α-Al2O3. For (001) growth on MgO, the surface retains the spinel lattice though slightly oxidized, while the interface with MgO has good crystallinity and stoichiometry. An enhanced thermal fluctuation of the Fe3+-spins in contact with the MgO substrate and in the topmost surface layer can be seen in their reduced magnetic hyperfine field at 300 K. © 1994.

DOI： 10.1016/0304-8853(94)90683-1

Scopus

researchmap

Language：English  

The spin-flip transition of 1000 Å-thick α-Fe2O3 films was investigated by conversion electron Mössbauer spectroscopy from 2.5 to 673 K. The films were epitaxially formed on α-Al2O3 single-crystalline substrates by a reactive vapor deposition method. Not only the transition temperature but also the spin axis were found to strongly depend upon the film orientation, probably as a result of anisotropic lattice strains caused by interactions with the substrate. For a (102)-oriented film the transition takes place at about 400 K, much higher the Morin transition temperature (260 K) of the free crystal, and the spin axis lying within the (102) plane above 400 K changes almost normal to the plane at room temperature and below: the normal makes 57.6° with the spin axis of the free crystal. A (001)-oriented film, on the other hand, does not show any transition at least down to 2.5 K. © 1994.

DOI： 10.1016/0304-8853(94)90351-4

Scopus

researchmap

A new helium-filled proportional counter was constructed for conversion electron Mössbauer spectroscopy under strong magnetic fields. The counter was specially designed to be inserted into superconducting electromagnets placed at the bottom of a liquid helium cryostat. The operation of the counter was stable enough in magnetic fields up to 3 T at 4.2 K and it seemed to be little influenced by the strong magnetic field. A high performance of the present counter was demonstrated by observing a field-induced magnetic spin rotation of an α-Fe film. © 1993.

DOI： 10.1016/0168-583X(93)95182-5

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English  

DOI： 10.2497/jjspm.39.985

Scopus

researchmap

Language：English  

DOI： 10.2497/jjspm.39.981

Scopus

researchmap

Language：English  

Stoichiometric Fe3O4 films have been epitaxially formed on both =α-Al2O3 and MgO single-crystalline substrates by a reactive vapor deposition method. A few-A-thick probe layer containing 57Fe was formed at a desired depth of an inactive S6Fe3O4 matrix film to apply a depth selective Mossbauer spectroscopy. Even at the topmost layer and also at the interface, the electronic state retained the essential features of Fe304 bulk so that the Verwey transition was clearly detected. Any minor depth-dependent changes in electronic state were confined in a few outermost atomic layers. The nature of the changes depended on the orientation of the films and the lattice mismatch between the substrate and the film. © 1992, Japan Society of Powder and Powder Metallurgy. All rights reserved.

DOI： 10.2497/jjspm.39.143

Scopus

researchmap

Language：English  

DOI： 10.2497/jjspm.39.981

Scopus

researchmap

Language：English  

DOI： 10.2497/jjspm.39.985

Scopus

researchmap

Language：English  

DOI： 10.2497/jjspm.39.985

Scopus

researchmap

Language：English  

DOI： 10.2497/jjspm.39.981

Scopus

researchmap

Very recently, an artificial new material “bismuth iron garnet” was prepared for the first time with a reactive ion-beam-sputterring method. A magnetic characterization of this single crystalline garnet film was achieved by applying conversion electron Mössbauer spectroscopy (CEMS). To examine the temperature dependence of sublattice magnetization, CEMS measurments were made at 6, 78, 290, and 670 K, i.e. in both the ferrimagnetic and paramagnetic regions. The magnetic and quadrupole hyperfine interactions as compared with YIG indicated continuous effects of lattice expansion owing to the large spherical size of Bi ions. The temperature dependence of sublattice magnetization has been explained by the two-sublattice molecular field model with a molecular field constant N slightly modified from that of YIG. © 1991, Japan Society of Powder and Powder Metallurgy. All rights reserved. 3+ ad

DOI： 10.2497/jjspm.38.427

Scopus

researchmap

Language：English  

Stoichiometric Fe3O4 films have been epitaxially formed on both =α-Al2O3 and MgO single-crystalline substrates by a reactive vapor deposition method. A few-A-thick probe layer containing 57Fe was formed at a desired depth of an inactive S6Fe3O4 matrix film to apply a depth selective Mossbauer spectroscopy. Even at the topmost layer and also at the interface, the electronic state retained the essential features of Fe304 bulk so that the Verwey transition was clearly detected. Any minor depth-dependent changes in electronic state were confined in a few outermost atomic layers. The nature of the changes depended on the orientation of the films and the lattice mismatch between the substrate and the film. © 1992, Japan Society of Powder and Powder Metallurgy. All rights reserved.

DOI： 10.2497/jjspm.39.143

Scopus

researchmap

A magnetic characterization of a single crystalline bismuth iron garnet film was done by applying conversion electron Mössbauer spectroscopy (CEMS). To examine the temperature dependence of sublattice magnetization, CEMS measurements were made at 6, 78, 290 and 670 K, i.e. in both the ferrimagnetic and paramgnetic regions. The magnetic and quadrupole hyperfine interactions as compared with those in other garnets like YIG indicated continuous effects of lattice expansion. The temperature dependence of the sublattice magnetization has been explained at the present stage by the two-sublattice molecular field model using parameters slightly modified from those of YIG. © 1990.

DOI： 10.1016/0304-8853(90)90640-C

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Stoichiometric Fe O films have been epitaxially formed on both α-Al O and MgO single-crystalline substrates by a reactive vapor deposition method. Their crystalline qualities were examined by various methods including conversion electron Mössbauer spectroscopy (CEMS). A large lattice mismatch of Fe O with the α-Al O substrate resulted in a granular particle growth. But with Fe O /MgO, where the mismatch was only 0.3%, the structural and magnetic properties were found to be very sensitive to an excellent interfacial lattice matching. © 1990. 3 4 2 3 3 4 2 3 3 4

DOI： 10.1016/0022-0248(90)90592-9

Scopus

researchmap

Language：English  

Several (111) oriented Fe O films containing a 5-Å-thick Fe O probe layer at or below the surface were grown epitaxially on the α-Al O (0001) surface by a reactive vapor deposition method. Conversion electron Mössbauer spectroscopy was applied at 6, 78, and 300 K by using a recently developed helium-filled proportional counter. The well-crystallized surface has been found to be surprisingly stable even in air as characterized by the Mössbauer parameters that are almost the same as for the bulk. Moreover, the Verwey transition was detected clearly even in the 5-Å-thick surface layer. However, the ferrous components seem to have changed their Mössbauer parameters probably because of their sensitivity to any crystalline field modifications in the surface. Generally speaking, the quality of epitaxial Fe O films is very high: Any unusual surface state, if present, is confined in a shallow depth of ≤ 5 Å. 56 57 3 4 3 4 2 3 3 4

DOI： 10.1063/1.346602

Scopus

researchmap

Language：English  

Several (111) oriented 56Fe3O4 films containing a 5-Å-thick 57Fe3O4 probe layer at or below the surface were grown epitaxially on the α-Al 2O3 (0001) surface by a reactive vapor deposition method. Conversion electron Mössbauer spectroscopy was applied at 6, 78, and 300 K by using a recently developed helium-filled proportional counter. The well-crystallized surface has been found to be surprisingly stable even in air as characterized by the Mössbauer parameters that are almost the same as for the bulk. Moreover, the Verwey transition was detected clearly even in the 5-Å-thick surface layer. However, the ferrous components seem to have changed their Mössbauer parameters probably because of their sensitivity to any crystalline field modifications in the surface. Generally speaking, the quality of epitaxial Fe3O4 films is very high: Any unusual surface state, if present, is confined in a shallow depth of ≤ 5 Å.

DOI： 10.1063/1.346602

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Article

CiNii Books

researchmap

Language：English  

The operation of the helium-filled proportional counter (HFPC) has been investigated at low temperatures below liquid-helium temperature, 4.2 K. It has been found that the gas gain as a function of the anode voltage is not appreciably changed by the temperature of the filling gas, but continuous electric discharges are induced at lower anode voltages as the gas temperature is decreased. The present counter technique has been applied to resonance-electron Mössbauer spectroscopy in the temperature region below 4.2 K.

DOI： 10.1063/1.1140562

Scopus

researchmap

Language：English  

Films of various iron oxides including FeO, Fe O , and α-Fe O were formed on the α-Al O (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (T ) and oxygen partial pressure (P ). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of T =523∼623 K and P =1.0-5.0×10 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe O resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, Fe, only at the deepest layers. On the other hand, by depositing Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation. 3 4 2 3 2 3 s O2 s O2 3 4 -4 57 57

DOI： 10.1063/1.344154

Scopus

researchmap

Language：English  

Films of various iron oxides including FeO, Fe3 O4, and α-Fe2 O3 were formed on the α-Al 2 O3 (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (Ts) and oxygen partial pressure (PO2). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of Ts =523∼623 K and PO2 =1.0-5.0×10-4 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe 3 O4 resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, 57 Fe, only at the deepest layers. On the other hand, by depositing 57 Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation.

DOI： 10.1063/1.344154

Scopus

researchmap

Language：English  

The operation of the helium-filled proportional counter (HFPC) has been investigated at low temperatures below liquid-helium temperature, 4.2 K. It has been found that the gas gain as a function of the anode voltage is not appreciably changed by the temperature of the filling gas, but continuous electric discharges are induced at lower anode voltages as the gas temperature is decreased. The present counter technique has been applied to resonance-electron Mössbauer spectroscopy in the temperature region below 4.2 K.

DOI： 10.1063/1.1140562

Scopus

researchmap

Event date： 2018.12.18 - 2018.12.20

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：北九州市  

researchmap