THE UNIVERSITY OF TOKYO
Nomura Group
Applied Chemistry and Radiation Safety
School of Engineering
Tokyo
http://so.t.u-tokyo.ac.jp/nomura/

From left: Toru Ohkubo, Cesar Barrero, Kiyoshi Nomura, Satoshi Iio, Junko Sakuma, and Yosuki Suzuki

Names and Titles of Researchers Associate Professor Kiyoshi Nomura – Radioanalytical Chemistry and Applied Chemistry for Material Science Dr. Cesar Barrero – Guest Researcher (Universidad de Antioquia, Colombia) Mr. Toru Ohkubo – Technician Mr. Satoshi Iio – Technician Junko Sakuma – Graduate Student Yosuke Suzuki – Student

Description and Areas of Research

The Mössbauer Group at the School of Engineering, University of Tokyo, has been working in the following areas.

Development of conversion electron and resonant X-ray Mössbauer spectroscopy (CEMS and XMS): Dual counters for CEMS and XMS have been developed to study the characterization of corrosion and surface finishing of iron and steel. Measuring ⁵⁷Fe CEMS and XMS simultaneously can easily perform the layer-by-layer analysis. CEMS and XMS provide Mössbauer information of about 200 nm and 10 µm thick layers, respectively. It is possible to measure a depth selective CEMS (DCEMS) of less than 100 nm thin layers by discriminating the energy of emitted electrons even with a He+10%CH₄ gas counter.

Corrosion process and structure analysis of oxide layers on iron and weathering steel by CEMS: The rust layers produced on steel surface in various solutions have been characterized by CEMS. γ-FeOOH is initially formed as a corrosion product and later Fe₃O₄ is formed as an intermediate layer in oxidative NO₃^- solutions. In addition to γ-FeOOH, green rust of Fe(OH)₂ and Fe(OH)₃ are formed in SO₄^2- solutions, and β-FeOOH is additionally formed in Cl^- solutions. Low temperature CEMS can distinguish these compounds easily. The samples prepared by wet corrosion process should be freeze-dried for CEMS measurement in order to detect the unstable and initial corrosion products. Both CEMS and XMS are useful for direct observation of thick rust layers on weathering steel from the viewpoints of practical layer analysis.

Structural analysis of phosphate coating on steel and black coating on steel by CEMS: Iron, zinc, and manganese phosphate coatings, among others, have been used in the automobile and other industries. The different formation processes and structures of each deposited coating have been characterized by CEMS. It was clarified that the interface between coatings and substrate can be estimated from the peak area ratio of a magnetic sextet of the substrate in addition to the analysis of iron states in many coatings. The black coating of steel, treated in hot alkaline solutions, consists of small particles of magnetite. Measuring CEMS spectra at a low temperature of 78K has done the detail analysis.

Analysis and chemical application of ultra thin layers on stainless steel and thin films of stainless steel by DCEMS: The group has studied thin oxide films on various stainless steels heated at high temperature or treated chemically. The thin layer structures have been clarified by CEMS with the help of other surface analysis tools, such as glow discharge optical spectroscopy and X-ray photoelectron spectroscopy. It is further found that oxide films on a certain stainless steel are useful as a solid-state pH sensor. It can provide the rapid response and good tolerance factor against the other cations in a solution between pH=1 and pH=13. Thin stainless steels have been prepared by DC and RF sputtering and pulsed laser ablation. It was found from the CEMS analysis that these films consist of martensite phase even if austenite steel is used as the target, and that the direction of magnetic moments on the film planes was different between films deposited by DC sputtering and by RF sputtering.

Surface analysis of soft magnetic materials and noise filters for high frequency bands: Soft magnetic material films, such as Sendust [Fe₃(Si,Al)], have been analyzed by CEMS. The material is practically used as a surface cover film of magnetic memory cards. The composite polymer thick films using Sendust have been recently developed as noise filters for high frequency bands (NEC-Tokin).

Structural chemistry of perovskite for partial oxidation catalysis and for CO₂ absorption: Perovskite of Co-Fe mixed oxides prepared by a sol-gel method is useful for the catalysis for oxidative coupling of methane. In this study, the group was aware of the properties for rapid absorption of CO₂ at high temperature and developed CO₂ absorption materials. Various A(Fe,Co)O₃ perovskites with A=(Ba, Sr) or (Sr, Ca) have the possibility of controlling the absorption temperature ranges by varying the compositions. The group has also studied the mechano-chemical effect for activation of the CO₂ absorbents, and it was found that the activation can be realized by pretreatment of ball milling for only five minutes. A(Fe, Mg) oxides with A=(Ba, Sr) or (Sr, Ca) also show the rapid CO₂ absorptions at more than 400^o C. It is considered that brownmillerite of ABO_2.5 contributes a skeletal structure with lattice vibration induced by different ionic radius in site A, and the rapid absorption of CO₂ is promoted due to the valence change at site B of perovskite.

Structural chemistry of transparent semiconductors such as indium tin oxide (ITO) films by ¹¹⁹Sn CEMS: The electronic properties of ITO and SnO₂ transparent films depend on the preparation conditions. The different properties have been clarified by characterization of tin chemical states in these films using ¹¹⁹Sn CEMS. The transparent semiconductors are used for solar cell electrodes. The iron oxide films formed on these semiconductors by spray pyrolysis have been clarified by ⁵⁷Fe CEMS. It is found that iron oxide thin films with large grains are formed on SnO₂ film, while iron oxide thin films with small grains are formed on ITO film due to chemical reaction at the interface with the solution.

Gas selectivity and sensitivity of a SnO₂ based sensor: The gas sensitivity and selectivity of a SnO₂ based sensor with some dopants have been studied, and the spillover effect of H₂ gas has been clarified, using Pd doped SnO₂ mixed with and without Ni or Mn oxides. The group has shown that gas selectivity could be directly observed by in situ CEMS using a gas flow proportional 2π counter loaded with a heater.

Development and characterization of spintronics materials: The chemical pressure effect of double perovskite Sr_1-xA_x(Fe,Mo)O₃ (x = 0.05, A = Ba, Ca), which shows colossal magneto-resistance, has been studied by temperature dependence Mössbauer spectrometry. The chemical pressure effect of Sr_1-xA_x(Ru_0.5Fe_0.5)O₃ perovskites (x = 0.05, A = Ba, Ca) also are studied, and the spin glass behavior is directly shown by in field Mössbauer spectroscopy (in Czech). It is reported recently that the dilute magneto transparent semiconductor (DMS) of TiO₂ doped with Co shows ferromagnetism at room temperature. The thin films of ⁵⁷Fe doped TiO₂ deposited by a pulsed laser ablation were analyzed by CEMS. CEMS is a very nice tool for characterization of micro-magnetism to consider the macro-magnetism of DMS. However, the preparation methods of spintronics materials are not well enough established at this point. The group is also developing various transparent oxide semiconductors doped with Fe using a sol-gel method.

Nuclear resonant scattering using synchrotron radiation: Phonon densities of states (DOS) on perovskite and brownmillerite have been studied by measuring nuclear inelastic scattering spectra, using synchrotron radiation at Spring-8. The temperature dependency of Mössbauer-Lamb factors can be determined directly using the inelastic scattering spectra measured. For example, the Mössbauer-Lamb factors of perovskite related oxides become small after absorption of CO₂. Together with Dr. A. Rykov, who was a visiting researcher in the group, they have studied many kinds of perovskite and related oxides, and found that the soft phonons are created with the increase of oxygen defects. They are now focusing on the study of DMS materials by nuclear inelastic scattering.

The group’s publication list is available from its Web site (see above for address).

Dr. Kiyoshi Nomura collaborates with the following researchers to accomplish Mössbauer studies for material science:

• Professor Z. Hommonay, Professor E. Kuzmann, and Professor A. Vertes – Laboratory of Nuclear Chemistry, Eotvos Lorand University, Budapest, Hungary

• Professor M. Mashlan and Professor R. Zboril – Department of Inorganic and Physical Chemistry and Department of Experimental Physics, Palacky University, Olomouc, Czech Republic

• Professor I. Felner – The Racah Institute of Physics, The Hebrew University of Jerusalem, Israel

• Professor M. Takeda and Professor M. Takahashi – Department of Inorganic Chemistry, Toho University, Chiba

• Professor S. Hasegawa and Professor S. Ohgoshi – Department of Chemistry, School of Science, The University of Tokyo, Tokyo

• Professor K. Hashimoto – Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo

• Professor T. Terai – Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, Tokyo

• Professor Y. Yamada – Department of Chemistry, Science University of Tokyo, Tokyo

• Professor T. Yajima – Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Engineering, Saitama

• Professor K. Takehira – Department of Chemistry and Chemical Engineering, Graduate School of Engineering, Hiroshima University, Hiroshima

• Dr. A. Rykov – Siberian Synchrotron Radiation Center, Novosibirsk, Russia

• Dr. T. Ohki – Kobelco Research Institute, Inc., Koube

TOHO UNIVERSITY
Inorganic and Radiochemistry Laboratory and Coordination Chemistry Laboratory
Department of Chemistry, Faculty of Science
Funabashi

Names of Researchers Professor Masuo Takeda – Inorganic and Radiochemistry Laboratory Professor Masashi Takahashi – Inorganic and Radiochemistry Laboratory Professor Takafumi Kitazawa – Coordination Chemistry Laboratory

From left: Professor Takafumi Kitazawa, Professor Masuo Takeda, and Professor Masashi Takahashi

Description and Areas of Research

The Mössbauer activities of the group at Toho University started in 1979 with studies on the stereochemical activity of the lone pair in the Sb(III) compounds by Professor Takeda; in 1984 Dr. Takahashi joined Professor Takeda with his research. Since then, many Mössbauer spectroscopic studies using ⁵⁷Fe, ¹¹⁹Sn, ¹²¹Sb, ¹²⁷I, ¹⁵⁵Gd, ¹⁶¹Dy, ¹⁶⁶Er, ¹⁹⁷Au, and ²³⁷Np have been carried out. The research interests are widely spread from organoheteroatom compounds to inorganic solids including organometallic complexes. The research interests have been shifting to spin-crossover compounds and f-block elements compounds.

p-Block Compounds. The research group prepared and measured ¹²¹Sb Mössbauer spectra for more than 50 Sb(III) compounds having different coordinating spheres and showed a linear relationship between isomer shifts and quadrupole coupling constants. The p character of the lone pair was found to correlate strongly with the coordination configuration. They then began investigation on the hypervalent compounds using ¹²¹Sb and ¹²⁷I Mössbauer spectroscopy. They have worked on a large number of hypervalent organoantimony(V) and organoiodine(III) compounds having one and two hypervalent bonds (3c-4e bond).

Spin-Crossover Iron(II) Cyanides. In 1992 Dr. Kitazawa, who has now moved to the Coordination Chemistry Laboratory, joined the research group and soon after two-dimensional cyano coordination polymer FeNi(CN)₄(py)₂ was found to show spin-crossover behavior. Although to date numerous spin-crossover materials have been developed, FeNi(CN)₄(py)₂ is the first example of the cyano-bridged two-dimensional materials. Since then, a considerable number of two-dimensional cyano-bridged iron(II) polymer complexes have been investigated, and recently the FeL₂Ni(CN)₄ and FeL₂Ag(CN)₂ systems have been the focus.

Actinide Compounds. ²³⁷Np Mössbauer spectroscopy is a powerful tool to investigate the physicochemical properties of neptunium compounds, through which we can extract the indispensable chemical information on actinide compounds. The wide range spread in ²³⁷Np isomer shifts (more than 80 mm s^–1) is well recognized and clearly correlated with the oxidation state and coordination number. Recently, the research group has collaborated with Dr. Saeki’s group at the Japan Atomic Energy Research Institute (presently the Japan Atomic Energy Agency) to find that the isomer shift for neptunyl(VI) complexes reflects the covalency; there are some contribution of 5f electrons in the NpO₂²⁺–L bond.

Lanthanide Compounds. The research group is interested in the structure and bonding of the lanthanide compounds, including Gd, Dy, and Er. A number of coordination compounds with organic chelate have been synthesized and their crystal structures have been determined. They have shown some 6s character in the Gd(III)–L bond by the ¹⁵⁵Gd spectra on more than 30 compounds. They also have applied ¹⁵⁵Gd spectroscopy to structural studies on Gd₂O₃–ZrO₂ solid solutions and related system in connection with an ionic conductor and back-end process of nuclear fuel as a joint research program with Dr. Akio Nakamura of the Japan Atomic Energy Agency. They have also worked on the magnetic interactions in Er(III) complexes by ¹⁶⁶Er spectroscopy and lattice dynamics of the Dy-Fe cyano complex using ¹⁶¹Dy spectroscopy.

The research group has active collaborations with several research institutions:

• Department of Chemistry, Toho University (Professor Tomoyuki Mochida): Solid-state chemistry of biferrocene charge-transfer complexes

• School of Medicine, Toho University, Tokyo (Professor Mikio Nakamura and Dr. Yoshiki Ohgo): Spin states in iron(III) non-planar porphyrin complexes

• Department of Applied Science, RMIT University, Melbourne (Professor S. K. Bhargava) and School of Chemistry, Australian National University, Canberra (Emeritus Professor M. A. Bennett): Coordination chemistry of the cycloaurated complexes

• Division of Materials Chemistry, Ruder Boskovic Institute, Zagreb, Croatia (Dr. B. Grzeta): Structural studies of nanocrystalline Sb(III)-doped SnO₂ using XRD and Mössbauer spectroscopy.

KYOTO UNIVERSITY
Nuclear Radiation Physics Laboratory
Research Reactor Institute
Osaka

Left to right: Professor Makoto Seto, Dr. Yasuhiro Kobayashi, Dr. Shinji Kitao, Ryo Masuda, Satoshi Higashitaniguchi, Chika Inaba

Names and Titles of Researchers Professor Makoto Seto  – Group Leader Dr. Shinji Kitao – Assistant Professor Dr. Yasuhiro Kobayashi – Assistant Professor Ryo Masuda – Graduate Student Satoshi Higashitaniguchi – Graduate Student Chika Inaba – Graduate Student

Description and Areas of Research

The Nuclear Radiation Physics Laboratory at the Research Reactor Institute of Kyoto University is involved in the studies of condensed matter physics with nuclear methods and the development of measuring methods. In particular, the main interests of the laboratory are Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation.

As for Mössbauer spectroscopic research, ⁵⁷Fe and ¹⁵¹Eu Mössbauer effects have been measured using long-lived radioisotope sources. In addition to these long-lived radioisotopes, the group can obtain short-lived radioisotopes by neutron irradiation in the Kyoto University Reactor (KUR) and the Mössbauer studies using them have been performed extensively for ¹²⁵Te, ¹²⁹I, ¹⁹³Ir, ¹⁹⁷Au, etc. Current Mössbauer studies are focused on topics in nanoparticles, carbon nanotubes, high-T_c superconductors, conducting organic polymers, mixed-valence complexes, and low-dimensional materials. Furthermore, a Fixed Field Alternating Gradient (FFAG) accelerator is now being constructed at the Research Reactor Institute of Kyoto University for an accelerator-driven subcritical reactor (ADSR) project. This will increase the available Mössbauer sources at the laboratory.

Synchrotron radiation attracted attention at first as an alternative source for nuclear excitation in Mössbauer spectroscopy. However, it has become a unique and powerful tool for nuclear resonant scattering and has built a new field, which is one of the most cutting-edge methods in materials science at present. The Nuclear Radiation Physics Laboratory played a central role in the first observation of nuclear resonant inelastic scattering of synchrotron radiation. As this method uses the resonant excitation process, element-specific phonons in complex compounds and local vibrational properties of dilute atoms in metals and semiconductors can be obtained. Furthermore, the laboratory developed a new method that permits them to measure site-specific phonon density of states. Nuclear resonant inelastic scattering measurements are now being extensively performed at the third-generation synchrotron radiation facilities (ESRF, APS, SPring-8). For studies of nuclear resonant scattering of synchrotron radiation, the laboratory is engaged in various topics in condensed matter physics, and the measurements are performed at SPring-8 and PF-AR (KEK). In addition, the laboratory is involved in the development of X-ray optics and X-ray detectors for nuclear resonant scattering measurements.

Professor Seto is also affiliated with the Japan Atomic Energy Agency (JAEA) as a group leader of the X-ray Structural Physics Group in the Synchrotron Radiation Research Center. The X-ray Structural Physics Group in JAEA and the Nuclear Radiation Physics Laboratory in Kyoto University are cooperatively working in the nuclear resonant scattering research.

TOKYO INSTITUTE OF TECHNOLOGY
Yamauchi-Karppinen Group
Materials and Structures Laboratory
Yokohama

Names and Titles of Researchers Professor Hisao Yamauchi – Head of Laboratory, and Professor and Head of the Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering
Professor Maarit Karppinen – Visiting Professor, and Head of the Laboratory of Inorganic and Analytical Chemistry at Helsinki University of Technology

The Yamauchi-Karppinen Group Members of the Tokyo Institute of Technology (July 2005)

Description and Areas of Research

The Mössbauer activities of the Yamauchi-Karppinen Group at the Tokyo Institute of Technology are focused on electro-functional perovskite-derived iron-oxide materials. An important example is the recently highlighted halfmetallic double-perovskite oxide, Sr₂FeMoO₆. Halfmetals are conducting ferromagnets with 100% spin-polarized carriers (in an ideal case) and form the bases for tunneling-type magnetoresistance (TMR) devices, the application of which is found in the presently emerging new technology called spintronics. For Sr₂FeMoO₆, a model for the electronic structure was initially assumed based on localized 3d⁵ electrons of high-spin Fe^III and an itinerant 4d¹ electron of Mo^V. Based on ⁵⁷Fe Mössbauer spectroscopy data, they elaborated this picture by showing that Fe in Sr₂FeMoO₆ possesses a mixed-valence state, expressed as Fe^II/III. Accordingly, Mo possesses a mixed-valence state of Mo^V/VI. This view (the valence-mixing concept) is now widely accepted. Moreover, since fractional B-cation valence states were later confirmed for other halfmetallic double perovskites, it seems that the valence-mixing phenomenon is inherent to these materials. Utilizing a series of thoroughly characterized samples of the (Ca,Sr,Ba)₂FeMoO₆ system, they moreover revealed that the precise valence of Fe^II/III species may be fine-tuned (within 2.2 ~ 2.5) by means of varying the effective ionic radius at the A-cation site.

Mössbauer data for Sr₂FeMoO₆ revealed another type of iron species, i.e., trivalent Fe atoms sitting at the lattice site reserved for Mo in the completely ordered double-perovskite structure. Also obtained was the first experimental evidence for so-called antiphase boundaries in Sr₂FeMoO₆. Both types of lattice defect are common for B-site ordered double perovskites. They elaborated their Mössbauer spectroscopy approach to a highly quantitative level to be able to follow the concentration of such defects in their differently synthesized Sr₂FeMoO₆ samples.

For samples with very small Sr₂FeMoO₆ particles, evidence for superparamagnetism was obtained from the ⁵⁷Fe Mössbauer spectroscopy data. At the same time, large enhancement in the technologically important low-field magnetoresistance (LFMR) effect was achieved. They could therefore conclude that superparamagnetic (insulating) portions coexist with the ferromagnetic (halfmetallic) ones, and the suppression of the superparamagnetism upon submitting the sample to external magnetic fields makes an additional contribution to the significant LFMR. They utilized this observation by preparing “homocomposites” consisting of two single-phase Sr₂FeMoO₆ components of different grain sizes. In their homocomposites, the smaller (nanoscale) particles of Sr₂FeMoO₆ with superparamagnetic behaviour act as the “tunneling barrier” for the larger-sized Sr₂FeMoO₆ halfmetallic crystals. As a matter of fact, very large LFMR effect was achieved for such composite materials.

NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY (AIST)
The Iijima Research Group
Ibaraki

Dr. Seiichiro Iijima

Professor Masaaki Kojima

Professor Naohide Matsumoto

• Dr. Seiichiro Iijima – Senior Research Scientist, Division of Biological Resources and Functions

Collaborating Scientists

• Professor Masaaki Kojima, Department of Chemistry, Faculty of Science, Okayama University

• Professor Naohide Matsumoto, Department of Chemistry, Faculty of Science, Kumamoto University

Description and Areas of Research

The Iijima group has extensively investigated iron complexes with interesting properties, such as spin-crossover, mixed valency, and molecule-based magnetism, by using ⁵⁷Fe Mössbauer spectroscopy. The group is carrying out research in close collaboration with two powerful inorganic chemistry groups – Professor Matsumoto’s laboratory at Kumamoto University and Professor Kojima’s laboratory at Okayama University – experts in molecular design and the synthesis and characterization by X-ray crystallography and cryomagnetic measurement of metal coordination compounds.

Spin-Crossover Compounds. A tripod ligand with three imidazole groups H₃L (tris[2-(((imidazol-4-yl)methylidene)amino)ethyl]amine) and its methyl-derivative H₃L^Me can afford several kinds of 2D iron complexes, [Fe^IIH₃L][Fe^IIIL](X)₂, [Fe^IIH₃L^Me][Fe^IIIL^Me] (X)₂, [Fe^IIH₃L^Me][Fe^IIL^Me]X, [Fe^IIH₃L^Me]Cl·X, etc., which exhibit thermal and photo-induced spin-crossover (SCO) phenomena. ⁵⁷Fe Mössbauer spectroscopy was employed to understand their complicated SCO behaviors, combined with magnetic susceptibility measurements. A two-step SCO process, LS Fe^II-LS Fe^III → HS Fe^II-LS Fe^III → HS Fe^II-HS Fe^III (LS = low spin, HS = high spin), was revealed for the mixed-valence systems, [Fe^IIH₃L][Fe^IIIL](X)₂  and [Fe^IIH₃L^Me][Fe^IIIL^Me](X)₂. The LS→HS transition of the Fe^II unit is suggested to trigger the SCO of the otherwise LS Fe^III unit. The [Fe^IIH₃L^Me]Cl·X system showed a variety of SCO behaviors depending on the counter anion, including one-step HS + LS → 2HS, two-step 2LS → HS + LS → 2HS with slow thermal relaxation, gradual one-step LS → HS, and a steep one-step LS → HS with a hysteresis.

Molecule-Based Magnets. Bulk magnetic transitions in oxalate-bridged mixed-valence assemblies [AM(II)M’(III)(ox)₃] were evidenced by ⁵⁷Fe Mössbauer spectroscopy (ox^2- = oxalate ion, A⁺ = organic cations such as quarternary ammonium and phosphonium ions). The direction of internal magnetic field, i. e., the direction of spin alignment, was estimated for the compounds from their magnetically-split Mössbauer patterns, and it was revealed that the direction can be controlled by the M-M’ combination and by the size of A⁺ cation. Molecule-based magnets consisting of cyclam complexes and Schiff-base complexes were also investigated by the spectroscopy.

Other Main Research Objects. Superparamagnetism was studied for iron oxides supported on silica gels and for tetraalkylammonium hexacyanoferrates(III). The importance of counter anion’s structure was indicated for the interaction between Fe(II) and Fe(III) sites in mono-oxidized binuclear ferrocenes.

TOKYO METROPOLITAN UNIVERSITY
Department of Chemistry
Graduate School of Science and Engineering
Tokyo

Description and Areas of Research

Professor Katada started Mössbauer spectroscopic study of tin compounds in 1968 at Hiroshima University. He then joined Professor Sano’s group at Tokyo Metropolitan University (TMU) as faculty staff in 1975. The TMU group has studied: (1) the mixed-valence state of binuclear ferrocene derivatives and trinuclear iron carboxylates, (2) the lattice dynamics of iron and tin complexes, (3) the chemical state of gold complexes and ruthenium compounds, and (4) the chemical effects of nuclear transformations in coordination compounds, using ⁵⁷Fe-, ⁹⁹Ru-, ¹¹⁹Sn-, ¹²⁹I- , ¹⁵¹Eu-, and ¹⁹⁷Au-Mössbauer spectroscopy.

Current research of the TMU group includes: (i) the mixed-valence state of trinuclear iron carboxylates, (ii) the lattice dynamics of alkylammonium hexacyanoferrates(III), (iii) the synthesis and characterization of new rare earth-iron complexes, (iv) the fluorescence behavior of solid europium β-diketonates and their lattice dynamical properties, (v) the synthesis and characterization of new borate-vanadate mixed glasses, and (vi) radiation-induced synthesis of new iron complexes. More recently, the group found that oxo-centered mixed-valence trinuclear iron dicarboxylic acid complex iron fumarate showed a temperature dependent mixed-valence state. At low temperature, two quadrupole split doublets were observed and a complete averaged valence state was observed at about 270 K.

The TMU group is also involved in joint studies with many other groups, including Nagoya University, Osaka University, and the National Institute for Materials Science.

HIROSHIMA UNIVERSITY
Radiochemistry Group
Natural Science Center for Basic Research and Development
Higashi-Hiroshima

Names and Titles of Researchers Associate Professor Satoru Nakashima – Head of Laboratory Masaki Atsuchi – Student

Description and Areas of Research

The Radiochemistry Group at Hiroshima University studies organometallic chemistry and coordination chemistry using Mössbauer spectroscopy. This group is currently working in the following areas:

• Mixed-Valence States of Binuclear Ferrocenes. The group studies electron transfer in mixed-valence binuclear ferrocenes to understand relations between structure and mixed-valence state. To know this, they study binuclear ferrocenes having chiral substituent.

• Synthetic Study of Organometallic Compounds. The group synthesizes novel azaferrocenes, arene complexes, or piano-stool complexes to synthesize redox-active supramolecules.

• Spin-Crossover Phenomena of Assembled Complexes. Spin-crossover complexes of transition metals have the ability to switch between two spin states by temperature, pressure, or light. The group is interested in the phenomena of the porous self-assembled complexes. They succeeded in changing the spin state by introducing an organic molecule to the pore of a self-assembled complex. They are now studying the difference in spin-crossover phenomena among the assembled structures.

RIKEN (INSTITUTE OF PHYSICAL AND CHEMICAL RESEARCH)
Applied Nuclear Physics Laboratory
Nishina Center for Accelerator Based Science
Wako, Saitama

Dr. Yoshio Kobayashi

Names and Titles of Researchers Professor Koichiro Asahi – Division Director Dr. Yoshio Kobayashi – Senior Scientist Dr. Fumitoshi Ambe – Emeritus Scientist

• Professor Yutaka Yoshida (Shizuoka Institute of Science and Technology)

• Professor Michael Kenya Kubo (International Christian University)

• Professor Yasuhiro Yamada (Tokyo University of Science)

• Dr. Jun Miyazaki (Tokyo University of Science)

• Dr. Wataru Sato (Osaka University)

• Dr. Satoshi Tsutsui (SPring8, Harima)

• Dr. Masaki Murata (University of Tokyo/Sony Co.)

• Professor Hiroshi Nishihara (University of Tokyo)

• Professor Yujiro Nagata (Aoyama Gakuin University)

• Dr. Takuya Okada (Gakushuin University)

• Professor Yasuaki Einaga (Keio University)

• Dr. Mototsugu Mihara (Osaka University)

• Professor Saburo Nasu (Osaka University/JAEA)

Students

• Mr. Yoji Tsuruoka (International Christian University)

• Mr. Guillaume Pedoussaut (International Christian University)

• Mr. Kunifumi Suzuki (Shizuoka Institute of Technology)

• Mr. Kazuhiro Kato (Tokyo University of Science)

• Ms. Kaori Taguchi (Tokyo Metropolitan University)

Description and Areas of Research

There has been a long and unique history of Mössbauer spectroscopic studies in RIKEN (the previous name in English was the Institute of Physical and Chemical Research, Wako). Here is presented a description of the Mössbauer studies using unstable nuclei related to the RIKEN accelerator facility.

In the middle of the 1960s, Dr. Fumitoshi Ambe (the former Chief Scientist of the Nuclear Chemistry Laboratory) and his co-workers began Mössbauer studies, especially the emission Mössbauer spectra of various compounds, including ⁵⁷Co, in order to understand systematically hot-atom chemistry from the viewpoint of anomalous valence states after nuclear decay and nuclear reaction. In the 1970s, ⁶¹Ni and ¹¹⁹Sn Mössbauer spectroscopic studies were carried out using the source nuclides ⁶¹Cu and ¹¹⁹Sb produced by the cyclotron in RIKEN. Fumitoshi Ambe and Shizuko Ambe identified the defect in ¹¹⁹Sn atoms, decaying from ¹¹⁹Sb (T_1/2 = 38.2 h) and ^119mTe (T_1/2 = 16.3 h), occupying the lattice sites in Sn¹¹⁹Sb, Sn¹¹⁹ⁿTe, and Sb₃¹¹⁹ⁿTe₃ from the ¹¹⁹Sn-emission Mössbauer spectra. The results were utilized to estimate the final state of energetic ¹¹⁹Sb and ^119mTe after proton and alpha particle reactions in SnSb and SnTe. The recoil atoms were found in scarcely perturbed lattice points. Their distribution in the lattice was as expected from the electronegativities of the recoil atoms and the lattice components. These emission studies might be considered to be the origin of the present in-beam Mössbauer technique at RIKEN.

Since the end of the 1990s, the group has focused on in-beam Mössbauer spectroscopic studies with the aim of applications of short-lived RI beams to condensed matter studies. RI beams in RIKEN are produced as secondary beams via the nuclear fragmentation reaction between a stable primary beam and an appropriate target. Emission Mössbauer spectroscopy offers unique information concerning the site occupation, dynamical behavior, and chemical states of extremely diluted atoms in a material. A large number of emission studies have been performed by the processes of chemical treatment or low-energy ion implantation for doping the radioactive Mössbauer probes into materials.

The RIKEN Ring Cyclotron at Nishina Center for Accelerator Based Science

The RI beams now acquire an increasing importance in materials science compared to the conventional ion implantation techniques. Thus, RI beam particles can be applied not only as Mössbauer probes to obtain atomistic information on processes immediately after the implantation, but also as an effective tool to create “exotic chemical species” and/or valence states in materials. The on-line Mössbauer technique using an energetic RI beam provides a number of advantageous features over the conventional implantation. It is possible to implant Mössbauer probes into much deeper positions within straggling widths as narrow as a few mm. The time range for measurement can be selected by choosing probe nuclide of the appropriate half-life. In the case of ⁵⁷Mn, for instance, which decays to ⁵⁷Fe with a half-life of 1.45 minutes, a Mössbauer measurement can be started about a few “minutes” after the implantation, while the on-line Mössbauer experiment using Coulomb excitation and recoil implantation provides the time range of several hundred “nanoseconds” after implantation.

In the group’s studies, ⁵⁷Mn ions were implanted into samples of two different types, namely, a semiconductor of Si and chemical samples of KMnO₄ and solid O₂. First, a Fe atom has been known to be one of the notorious impurities in a Si wafer. The on-line Mössbauer spectroscopy using an RI beam is considered to be one of the most powerful techniques to obtain atomistic information concerning the final lattice positions and dynamic behavior of Fe atoms in Si, because the concentration of the implanted nuclear probes is extremely low. Second, numbers of emission Mössbauer studies have been carried out to investigate ⁵⁷Fe species produced by EC decay of ⁵⁷Co implanted into various matrices. Mn occurs in various oxidation states in solids. Therefore, it is interesting to find out unusual valence states for ⁵⁷Fe arising from the ⁵⁷Mn decay, compared with those reached from ⁵⁷Co, in an appropriate matrix.

Unstable isotopes of ⁵⁷Mn were separated and implanted into FZ- and CZ-Si wafers using the RIKEN projectile nuclear fragment separator (RIPS). Subsequently, Mössbauer spectra of ⁵⁷Fe in Si were measured between 12 and 800 K, in order to study the charge states and the diffusion processes of interstitial and substitutional Fe atoms in Si matrix. The spectra could be fitted with two components of singlets up to about 650 K. Above 600 K, both the disappearance of the interstitial component and the simultaneous relaxation effects on the centre shifts were clearly observed. These dynamical behaviors could be interpreted as a reaction process of interstitial Fe atoms jumping into vacancies, which were accompanied by changes in the charge states. Above 650 K, a line broadening of the singlet could be also seen, indicating an enhanced diffusion of the Fe atoms due to the excess vacancies.

The implantation Mössbauer study of ⁵⁷Mn into KMnO₄ was the first chemical application of a RI beam to the study of valence states after nuclear transformation. The obtained Mössbauer spectra of KMnO₄ could be analyzed with two components, a doublet and a singlet. From the calculations of the molecular orbital wave functions (Gaussian 98, DV-Xα), the singlet is suggested to be substitutional ⁵⁷Fe atoms for Mn sites in tetrahedral [MnO₄]^- with an unusually high valence state of Fe(VIII). In more reactive matrices, Fe species with extraordinarily higher oxidation states and “exotic chemical structures” are expected to be produced under non-equilibrium conditions. The well-defined in-beam ⁵⁷Fe (⁵⁷Mn) Mössbauer spectra of solid O₂ were measured at 18, 30, and 42 K. The spectrum obtained at 18 K can be analyzed by four components of doublets. They are preliminarily assigned to be novel species of Fe(O₂), FeO, (O₂)FeO₂, and (O₂)Fe(O₂), respectively.

The group has developed another type of in-beam Mössbauer study using neutron beams in the Tokai Institute of the Japan Atomic Energy Agency. The advantage of this technique is that it is possible to investigate non-destructively the chemical effects and the dynamics of a hot atom produced just after the nuclear reaction of ⁵⁶Fe(n,γ)⁵⁷Fe*. The Mössbauer spectrometer using the prompt γ-rays was newly designed and installed at a neutron beamline connected with JRR-3M in the Tokai Institute. The in-beam Mössbauer spectra of a stainless steel, a pure Fe foil, and FeS₂ (pyrite and marcasite) were obtained at 77 K and room temperature. In the case of a pyrite-type of FeS₂, the spectrum could be fitted two doublets. One was originated from host matrix of FeS₂; the other was suggested to be a novel Fe species produced by neutron capture reaction.

In the off-line absorption measurements, some Mössbauer source nuclides (for example ⁶¹Cu (T_1/2 = 3.3 h) for ⁶¹Ni and ⁹⁹Rh (T_1/2 = 16.1 d) for ⁹⁹Ru Mössbauer spectroscopy) produced by the RIKEN cyclotron have been applied to various investigations concerning materials science and chemistry. By means of ⁶¹Ni Mössbauer measurements, the hyperfine magnetic field H_hf of ⁶¹Ni²⁺ ions in the compressed tetrahedral sites of the spinel chromite Cu_0.9Ni_0.1Cr₂O₄ was found to be 800 kOe, which is the largest ever reported for ⁶¹Ni. The large H_hf could be elucidated on the basis of the orbital angular momentum in the degenerate ground state of Ni²⁺ ions. The group has studied the electron configurations of anhydrous ruthenium trichlorides or ruthenocene derivatives, the magnetic ground state and the antiferromagnetic ordering mechanism of Ca_xSr_1-xRu_yM_1-yO₃ (M = Fe, Rh, Ti) system, and the characterizations of a skutterudite of SmRu₄Sb₁₂ by ⁹⁹Ru Mössbauer spectroscopy, magnetization, and µSR measurements.

Finally, the expansion plan of the current RIKEN accelerator facility, the RI Beam Factory Project (RIBF) as a next generation facility, is currently underway. When completed, it will produce the world’s highest intensity RI beams over the whole atomic mass range, from elements of hydrogen through to uranium, which will be applied to research in a wide variety of fields. The advent of RI beams will open up a fascinating field in materials science research.

KINKI UNIVERSITY
School of Humanity-Oriented Science and Engineering
Iizuka, Fukuoka
http://web.fuk.kindai.ac.jp/

Kinki University is a private university composed of 11 Faculties (41 Departments), 11 Graduate Schools, and 16 Institutes, and with campuses in Osaka, Nara, Wakayama, and Fukuoka Prefecture, Japan. The total number of students is nearly 30,000. There are two groups performing Mössbauer research, as follows:

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Laboratory of Environmental Material Chemistry (Nishida Laboratory)
Department of Biological and Environmental Chemistry
http://web.fuk.kindai.ac.jp/~biochem/labo/nishida/english.htm

Names and Titles of Researchers Professor Tetsuaki Nishida (Removed from Kyushu University April 1, 2000) Mr. Jun Tamaki – Ph.D. Student Mr. Yasuki Toita – Ph.D. Student Mr. Daigo Hisajima – Ph.D. Student Mr. Masaaki Yasuhara – Ph.D. Student Mr. Hiroki Yasumitsu – Ph.D. Student Mr. Shohei Yamashita – Ph.D. Student Others: Seven undergraduate students

Professor Tetsuaki Nishida

Description and Areas of Research

The Nishida Laboratory (the Laboratory of Environmental Material Chemistry) in the Department of Biological and Environmental Chemistry, School of Humanity-Oriented Science and Engineering, at Kinki University has available two spectrometers (both Japanese made) – one for ⁵⁷Fe Mössbauer measurements, and the other for ¹⁵¹Eu measurements. The group has published 150 papers, six reviews, and six book chapters.

The group’s research interests include:

• Local structure and physical properties of several new glasses, including semiconducting vanadate glass, IR-transmitting aluminate glass, etc.

• Preparation and characterization of new cathode material for lithium-ion batteries

• Preparation and characterization of heavy metal waste glasses, porous ceramics, etc.

• Water purification with glass, glass-ceramics, ceramics, polymer gels, etc.

Recent coworkers and collaborators include:

• Tokyo Metropolitan University, Tokyo: Professor Motomi Katada

• Musashi Institute of Technology, Tokyo: Professor Tamotsu Toriyama

• Kyushu University, Fukuoka: Professor Jyun-ichi Yamaki, Professor Shigeto Okada, and Professor Kazuhiro Hara

• Ube National College of Technology, Ube: Professor Shiro Kubuki

• Eötvös Loránd University, Budapest: Professor Attila Vertes, Professor Zoltan Homonnay, and Professor Erno Kuzmann

• Al-Azhar University, Cairo: Professor Mohamed Yousry Hassaan Hassaan

• Bangladesh University of Engineering and Technology, Dhaka: Professor A.S.M.A. Haseeb

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Laboratory of Inorganic Material Chemistry (Arakawa Laboratory)
Department of Biological and Environmental Chemistry
http://web.fuk.kindai.ac.jp/~biochem/labo/arakawa/

Names and Titles of Researchers

• Professor Tsuyoshi Arakawa

• Mr. Kentaro Takebe – Ph.D. Student

• Others: Seven undergraduate students

Description and Areas of Research

• Gas sensors containing rare-earth elements

• Nanotechnology

TOKYO UNIVERSITY OF SCIENCE
Department of Chemistry
Tokyo

Description and Areas of Research

The research group at the Tokyo University of Science is working on the synthesis and characterization of novel unstable species, clusters, and films unavailable in normal conditions.  The study of reactions of single atoms or small clusters provides useful information for understanding the mechanism of reactions on surfaces and on heterogeneous catalysts by providing simple models of larger and more complex systems. Mössbauer spectroscopy is a very useful technique to study electronic structures of iron species to provide the direct information of chemical states of the iron species.

Currently, particular attention is being directed to studying the reactions of laser-evaporated iron atoms, which have high translational and electronic energy and react with various reactant gases without additional excitation to produce novel compounds. The group has reported the reaction of laser-evaporated iron atoms with O₂, N₂, N₂O, SF₆, CH₃I, and CH₄ using a matrix-isolation technique. The reaction products were trapped in low-temperature Ar matrices and observed by Mössbauer and infrared spectroscopy. The assignments of these species were performed with the aid of ab initio molecular orbital calculations or density functional calculations.

The group is also studying the films produced by laser-deposition of Fe metal onto Al or Si substrates at various temperatures, and the formation of Fe-Al alloy or Fe-Si compounds was observed at the boundary between the Fe-films and the Al or Si substrate. They found that the unreacted iron metal has a tendency to have spin-orientation parallel to the substrate surface. Laser-deposition of iron oxides, hematite or magnetite, onto substrates produced iron oxide films whose composition varied depending on the substrate temperature. Laser-deposition has the possibility of producing functional films whose chemical compositions and physical properties can be controlled.

The group is exploring the exotic chemical states using in-beam Mössbauer spectroscopy in collaboration with Dr. Yoshio Kobayashi of RIKEN and Professor Michael Kenya Kubo of the International Christian University. In-beam Mössbauer spectroscopy coupled with ion implantation of secondary ⁵⁷Mn particles is being studied using the RIKEN Accelerator Research Facility. Neutron in-beam Mössbauer spectroscopy is being studied to investigate the chemical and physical behaviors of the trace species formed by the neutron capture reaction ⁵⁶Fe(n, γ) ⁵⁷Fe using the JRR-3M reactor at JAEA.

MUSASHI INSTITUTE OF TECHNOLOGY
Quantum Beams Applications Laboratory for Materials Engineering
Tokyo

Front row, from left to right: Kazuma Akita, Toshiaki Iizuka, Takehiro Kubota, Toshiaki Kawabata, Yuuta Maeda, and Aya Takahashi Back row, from left to right: Yuuya Miyamoto, Proofessor Tamotsu Toriyama, Taku Katoh, and Masato Yamashiro Inset: Associate Professor Hidehiko Wakabayashi

Names and Titles of Researchers

Description and Areas of Research

The Mössbauer Group at the Musashi Institute of Technology is working in the following themes:

• Preparation and characterization of sputtered iron-oxide thin films for semiconductor photoelectrodes

• High-density growth of α-iron nano-particles by multi-step implantation of iron ions into alumina

• Conversion electron Mössbauer spectroscopy (CEMS) study with applied magnetic field on iron states in a sequentially implanted FeCo alloy-Al₂O₃ granular layer

• Development of CEMS and conversion X-ray Mössbauer Spectroscopy (CXMS) with applied magnetic field systems

• Analysis of Ru atoms in catalysis electrodes of polymer electrolyte fuel cell (PEFC) using particle induced X-ray emission (PIXE) spectroscopy and Rutherford backscattering spectroscopy (RBS)

• Development of wave dispersive particle-induced X-ray emission spectroscopy (WD-PIXE) system for analyzing S atoms in catalysis electrodes of PEFC and direct methanol fuel cell (DMFC)

SHIZUOKA INSTITUTE OF SCIENCE AND TECHNOLOGY
Fukuroi, Shizuoka
http://www.sist.ac.jp/~yoshida/

Back row, left to right: Kunifumi Suzuki, Kazumasa Sakata, Yutaka Suzuki, Kazuo Hayakawa, Tomohiro Kamimura, and Masahiko Adachi Middle Row, left to right: Kennichi Yukihira and Namiko Miura Front: Professor Yutaka Yoshida

Names and Titles of Researchers

• Professor Yutaka Yoshida

• Kazuo Hayakawa – Technician

• Kennichi Yukihira – Technician

• Masahiko Adachi – Student

• Tomohiro Kamimura – Student

• Namiko Miura – Student

• Kazumasa Sakata – Student

• Kunifumi Suzuki – Student

• Yutaka Suzuki – Student

Description and Areas of Research

Research at the Shizuoka Institute of Science and Technology is presently focused on iron segregation and diffusion processes in silicon materials and nanomaterials. The group combines different experimental methods and instruments for Mössbauer spectroscopy, which the group has been continuously developing. A high temperature furnace, an Instron-type tensile-test machine, and a conversion electron detector using micro-channel plates (MCP) connected to a UHV deposition chamber are in operation at the laboratory. In addition, as a joint venture with Dr. Yoshio Kobayashi at RIKEN, the group is working with in-beam Mössbauer spectroscopy immediately after Coulomb excitation and recoil-implantation, (d, p) reaction and implantation of projectile nuclear fragments using an on-line isotope separator at RIKEN. Two excellent technicians, Kenichi Yukihira and Kazuo Hayakawa, and students in masters and undergraduate courses contribute strongly to the research projects. The final goal is to achieve an in situ observation of iron atoms in different materials to understand atomic motions, chemical reactions, and formation processes of nano-structures under different circumstances, such as high temperatures, uniaxial stress, and highly energetic ion irradiation (several GeV). For characterization, they employ a wide range of techniques, including X-ray diffraction and microscopies such as SEM, TEM, AFM, STM, MFM, and infrared spectrometer.

Although the study of iron in silicon has a long history for more than half a century, there exists still many open questions, such as the solubility, the lattice sides of iron, etc. Combining two completely different methods in Mössbauer spectroscopy – high-temperature measurements and highly energetic implantation of ⁵⁷Mn/ ⁵⁷Fe – they study iron impurities in silicon materials, such as multicrystalline silicon wafers. The problem is directly connected to the solar cell efficiency, and therefore it is very important to find “a gettering method” to remove the impurities from the device regions. Furthermore, they are developing a ⁵⁷Fe Mössbauer microscope (two-dimensional position-sensitive spectrometer) using microcapillary X-ray lens, the results of which were presented in the last Seeheim Workshop.

CHUKYO UNIVERSITY
Ecomaterials Laboratory
School of Life System Science and Technology (LSST)
Kaizu, Toyota

• Professor Toru Nonami – Head of the Laboratory

• Dr. Junhu Wang

Description and Areas of Research

The main research lines at the Ecomaterials Laboratory at LSST, Chukyo University, involve the development and application of novel photocatalytic materials and multifunctional biomaterials on an experimental basis. The photocatalytic materials developed are used for environmental purification, and the multifunctional biomaterials developed are for dental surgery as well as the fabrication of artificial bone scaffolds with controlled bore size. The laboratory is headed by Professor Toru Nonami, a distinguished material scientist.

Dr. Wang, a research fellow, is primarily studying the development of highly efficient mono-dispersed photocatalytic nanoparticles by soft chemical solution process at low temperature. The photocatalytic nanoparticles are applied for lightening unpleasant smells in one’s living environment on an experimental basis, such as in nursing homes and karaoke rooms. He is also researching the development of novel apatitic biomaterials that have not only good biocompatibility but also photo-oxidation ability for deodorization, antibacterial properties, and self-cleaning by modifying a simulated body solution. Dr. Wang teaches the course “Ceramics Materials Experiment” to all of the undergraduate students of LSST. In addition, 14 undergraduate students belong to the Ecomaterials Laboratory. Dr. Wang also conducts seminars regularly to staff at Nonami Science Produce Co., Ltd., Japan, on the characterization of functional materials and also provides scientific assistance to product users as a senior advisor.

At Chukyo University, Dr. Wang plays a central role in Mössbauer spectroscopic studies on the mechanism of photocatalytic activities and multifunction of novel materials by collaborating with Professor Takahashi and Professor Takeda of Toho University and Dr. Iijima of AIST. The photocatalytic activities of two kinds of mono-dispersed antimonic acid single crystal nanoparticles have been reported recently, and the differences in their photocatalytic properties have been concluded to be mainly due to the existence of a little Sb³⁺ with d⁸ electron configuration observed by ¹²¹Sb Mössbauer spectroscopy. Substitution effects of Sb by Ta, Nd, Bi, and Y on structural and photo-absorption properties of the antimonic acid fine nanoparticles will also be published. In addition, the role of trace iron elements in bone and teeth has been investigated using ⁵⁷Fe Mössbauer spectroscopy by doping trace-enriched ⁵⁷Fe into hydroxyapatite (HAp). Here, the ⁵⁷Fe-doped HAp sample used was synthesized by simulating the natural formation process of bone and tooth. It was interesting here that tooth black in East Asia, “ohaguro” in Japanese, was traditionally applied, and the agent used contained iron, which could have contributed to caries prevention.

Current and past collaborators of Dr. Wang include:

• Toho University: Professor Masuo Takeda, Professor Takahashi Masashi, and Associate Professor Takafumi Kitazawa

• Institute for Materials Research (IMR), Tohoku University: Associate Professor Toetsu Shishido and Dr. Kunio Yubuta

• National Institute of Advanced Industrial Science and Technology (AIST): Dr. Seiichiro Iijima and Dr. Zhigang Zou

• Graduate School of Human Life Science, Sugiyama Jogakuen University: Ms. Hiroko Hase

• National Institute for Materials Science (NIMS): Dr. Jinhua Ye and Dr. Kiyoshi Ozawa

• Japan Atomic Energy Research Institute (JAERI): Dr. Akio Nakamura, Mr. Masami Nakada, and Mr. Haruyoshi Otobe

KURUME INSTITUTE OF TECHNOLOGY
Department of Mechanical Systems Engineering
Fukuoka

Name of Researcher Professor Nobuyuki Hayashi

Professor Hayashi (standing) in his laboratory with a graduate student, T. Moriwak, who is now studying for his Ph.D. degree under Professor Taniwaki and the Kochi Institute of Technology

Description and Areas of Research

The group at the Kurume Institute of Technology has been working on the material modification by ion beams using ⁵⁷Fe implantation with conversion electron Mössbauer spectroscopy (CEMS). The work is being done in cooperation with groups from the Musashi Institute of Technology (Professor Tamotsu Toriyama), the Kochi Institute of Technology (Professor Masafumi Taniwaki), and Dr. Isao Sakamoto of the National Institute of AIST.

In recent years, the group has been involved in research relating to nano-composite materials in insulating metal-oxides synthesized by high dose implantation of magnetic ions. The metal-insulator nanocomposite layers provide attractive structures since they exhibit peculiar optical and magnetic properties, such as giant magnetic tunneling junctions. An eminent tunneling magnetoresistance (TMR) effect was observed in α-Al₂O₃ single crystals implanted with 100 keV Fe⁺ ions, where the implanted layers exhibit a magnetoresitance (MR) ratio of about 7 ~ 8%. The obtained value was about twice as large as that observed for similar granular Fe/Al₂O₃ films prepared by rf sputtering. Furthermore, they have succeeded in synthesizing nanosized clusters of FeCo alloys in the Al₂O₃ matrices by sequential implantation of Fe and Co ions. It is demonstrated in the FeCo granular layers that the alloying leads to an increase in the iron magnetic moment. From the result, the MR ratio is expected to increase to a value of more than 10% at room temperature.

Through these studies, the group obtains detailed information on the aggregation states of implanted Fe ions by means of CEMS, combined with glancing angle X-ray diffraction (GXRD) and magnetization (VSM) measurements. CEMS is highly sensitive and effective in characterizing the properties of the nanocomposite, especially when it is combined with the mass-selected ⁵⁷Fe implantation and the projectile’s energies are selected to be comparable to the penetration depth of the conversion electrons. Thus, they have observed an eminent enhancement of TMR effect by changing the relative amount of Fe and Co ions implanted in Al₂O₃ matrices and presented the largest MR ratio of more than 13% at room temperature among the values reported in the Fe-, Co-, and FeCo granular films.

The group has also observed the formation of Fe-Cu nano-clusters in crystalline Al₂O₃ and SiO₂ by implantation of Fe and Cu ions up to a total dose of 1.5 × 10¹⁷ ions/cm². It is shown that the addition of Cu ions into both Fe/Al₂O₃ and Fe/SiO₂ granules promotes the transition from superparamagnetic to ferromagnetic states, indicating the formation of the metastable Fe-Cu alloy nano-clusters.

UBE NATIONAL COLLEGE OF TECHNOLOGY
Material Science Laboratory
Department of Chemical and Biological Engineering
Ube, Yamaguchi

Name and Title of Researcher Dr. Shiro Kubuki – Associate Professor

Description and Areas of Research

Starting his international research career by presenting at a Pac Rim conference in Hawaii in 1993, Dr. Shiro Kubuki has energetically obtained unique research results concerning the structure of new glass-ceramics by applying ⁵⁷Fe Mössbauer spectroscopy. In the themes, verification of the T_g-∆ rule and discovery of the E_a-δ rule have been accomplished in infrared-transmitting calcium gallate and aluminate glasses under collaboration work with Professor Tetsuaki Nishida of Kinki University. These half-experimental rules are very important for characterizing or fabricating functional glasses-ceramics.

The unique research results have been organized into around 30 papers and presented at many international conferences. Dr. Kubuki is now exploring recycling procedures of iron-containing inorganic wastes into functional materials, e.g., wastewater purifier or semi-conductor, by utilizing the “T_g-∆” and “E_a-δ” rules.

Dr. Kubuki’s chemical interests and enthusiasm extend over the waters and has given him the opportunity to find many collaborators. Especially in the period from March of 2005 to March of 2006, he was selected as a visiting researcher and dispatched from the Ministry of Education, Science, and Technology in Japan to Eötvös Loránd University, Budapest. He experienced an extremely fruitful time discussing upcoming experimental data and future plans of research projects together with Hungarian colleagues. Themes of collaborative works and his collaborators are as follows.

Research work:

• Characterization of semi-conducting BaO-V₂O₅-Fe₂O₃ glasses by reverse Monte Carlo simulation

• The co-relationship between water purifying ability and local structure of iron-containing waste glasses

• Lithium-ion battery containing FePO₄ as a cathode material

• Mössbauer spectra and electrical conductivity of fly ash-recycled glass

• Mössbauer studies of novel oxygen-bridged compounds formed in the solid matrix of β-Fe^IIPc

Collaborators include:

• Kinki University (Iizuka, Japan): Professor Tetsuaki Nishida

• Eötvös Loránd University (Budapest, Hungary): Professor Zoltán Homonnay, Professor Erno Kuzmann, and Professor Attila Vértes

• Al-Azhar University (Cairo, Egypt): Professor Mohammad Y. Hassaan and Professor Salah H. Sarah

• University of North Carolina (North Carolina, USA): Professor Amar Nath

TOHO UNIVERSITY SCHOOL OF MEDICINE
Department of Chemistry
Tokyo

Names and Titles of Researchers Professor Mikio Nakamura Assistant Professor Yoshiki Ohgo Dr. Akira Ikezaki – Research Associate

The group’s major interest is to reveal the electronic structure of iron(III) complexes of porphyrin and its analogues, such as chlorin, bacteriochlorin, porphycene, corrphycene, hemiporphycene, diazaporphyrin, etc. They are especially interested in the highly deformed porphyrin complexes, because they exhibit some unusual electronic structures; the (d _xz, d _yz) ⁴(d _xy) ¹ electron configuration in highly ruffled low-spin complexes, two different electron configurations in the intermediate-spin complexes with ruffled and saddled porphyrin rings, and the novel spin crossover between S=3/2 and S=1/2 in highly saddled complexes. They are using various spectroscopic methods including Mössbauer spectroscopy to characterize these complexes.

NAGOYA INSTITUTE OF TECHNOLOGY
Graduate School of Engineering
Nagoya

Left to right: Dr. Wei Zhang, Yusuke Yamanishi, Professor Ko Mibu, and Daisuke Gondo

Names and Titles of Researchers

• Professor Ko Mibu – Group Leader

• Dr. Wei Zhang – Research Fellow

• Mr. Daisuke Gondo – B.Eng. Student

• Mr. Yusuke Yamanishi – B.Eng. Student

• Ms. Kayo Nozawa – B.Eng. Student

Description and Areas of Research

Professor Ko Mibu was formerly in Professor Teruya Shinjo’s group at Kyoto University. He moved to the Nagoya Institute of Technology (NIT), which is one of the smallest National University Corporations in Japan, in February 2005. Two sets of Mössbauer spectrometers, together with cryostats and a split-coil superconducting magnet, were also moved from Kyoto to Nagoya. Now a small but active research group on magnetism of metallic thin films and nanostructures is being built up at NIT.

Before his arrival, NIT already had Mössbauer facilities with two sets of spectrometers and ⁵⁷Co sources. These facilities were run by groups headed by Professor Takeshi Moriya and Professor Kenji Sumiyama. Professor Moriya retired in March 2004, whereas Professor Sumiyama is still active in the field of nano-particles.

The main studies of Professor Mibu’s group at Kyoto University, which continue at NIT, are on magnetism of metallic thin films and nano-structures. The key research concept is “control of magnetic structures using interfacial and shape-induced effects.” The research interests of the group are as follows:

• Creation of novel artificial super-structures and novel alloys that do not exist in nature

• Design of model magnetic systems useful for fundamental studies on magnetism

• Search for new materials and new phenomena for the development of spin-electronics

The successful studies published so far include (i) control of domain-wall-type magnetic structures using exchange-spring multilayers, (ii) control of spin-density waves in Cr-based multilayers, (iii) control of magnetic vortex structures in elliptical NiFe nano-dots, and so on.

The group uses Mössbauer spectroscopy for the studies on magnetic thin films and nano-structures. The recent works rely on ¹¹⁹Sn nuclei, rather than ⁵⁷Fe. These series of studies are classified into the following three subjects:

• Detection of electron spin-polarization in nonmagnetic layers of magnetic/nonmagnetic multilayers

• Investigation of magnetism of anti- ferromagnetic Cr in multilayer systems

• Exploration of local magnetism of half-metallic Heusler alloy films

Professor Mibu is also a member of a CREST-JST research project on nuclear resonant scattering in Japan, which is led by Professor Makoto Seto at Kyoto University. His sub-group is in charge of the research on thin films and nano-structures.

The research group is still small, with only one postdoctoral research fellow and three undergraduate students. In spite of this, it is expected that the group will become more active in the next few years.

NATIONAL INSTITUTE FOR MATERIALS SCIENCE
Tsukuba, Ibaraki

Names and Titles of Researchers Dr. Takao Furubayashi – Senior Researcher
Dr. Hiroaki Mamiya – Senior Researcher

Description and Areas of Research

Mössbauer studies at the National Institute for Materials Science are mainly focused on nano-structured magnetic materials including iron, such as nano particles, magnetic fluids, granular films, and amorphous materials. Recent research topics are as follows:

• Characterization and magnetic properties of nano particles, magnetic fluids, and granular films

• Magnetoresistance of nano-granular magnetic films

• Magnetic oxide films

• Exchange anisotropy in nano-granular magnetic films

• Cooperative magnetization reversal in assembled nano particles with dipolar interactions

• Magnetic relaxation in non-interacting and interacting nano particles

DAIDO INSTITUTE OF TECHNOLOGY
Department of Chemistry / Collaborative Research Center
Nagoya

Names and Titles of Researchers

Professor Yoichi Sakai – Group Leader	Associate Professor Tsutomu Takayama	Visiting Professor Yasuo Watanabe

Description and Area of Research

The group of Mössbauer spectroscopy at the Daido Institute of Technology, located in Nagoya, is headed by Professor Yoichi Sakai, and started in January 1996. It is affiliated with the Department of Chemistry as well as with the Collaborative Research Center of the Institute. Recently, Associate Professor Tsutomu Takayama and Visiting Professor Yasuo Watanabe joined the group. The group’s research attention is devoted to wide chemical fields, such as (1) environmental and geochemical sciences, (2) materials technologies, and (3) chemical education.

Their Mössbauer research activities are described by introducing some of the titles of their published or submitted papers for the present decade together with a brief comment:

• Environmental and Geochemical Sciences

“Comparison of antimony behavior with arsenic under various soil redox conditions.” This study was performed in collaboration with a group from Hiroshima University. The physicochemical states of iron in soil were examined by Mössbauer spectroscopy in connection with adsorption of antimony and arsenic species to soil.

“Concentration and oxidation states of iron related to sediment-water interaction in Lake Biwa, Japan.” The group studied the concentration and oxidation states of iron at the sediment-water interface to reveal the relation of nutrient pollution of Lake Biwa to oxidation potential in the lake water. This was a cooperation project with a group from Aichi Medical University.

• Materials Technology

“In-situ ⁵⁷Fe Mössbauer investigation of solid-state redox reactions of lithium insertion electrodes for advanced batteries.” A collaboration with a group from Osaka City University, the iron oxidation states in the electrode in a lithium-ion secondary battery were investigated using an in situ Mössbauer measurement cell developed by the group.

“Structure comparison between Th₂Zn₁₇-type and TbCu₇-type Sm-Fe intermetallic compounds and their nitrides by means of ⁵⁷Fe-Mössbauer spectroscopy.” The iron states in rare-earth transition metal magnet materials were characterized by Mössbauer spectroscopy. This research project was in collaboration with a research team from Daido Steel Co.

“Mossbauer characterization of calcium-ferrite oxides prepared by calcining Fe₂O₃ and CaO.” This was a collaboration with a group from Nagoya University.

“Nanocomposite powders of Fe-C system produced by the flowing gas plasma processing.” A collaboration with another group from the Institute; the Mössbauer spectroscopic study was progressed.

“Neutron in-beam Mossbauer spectroscopic study of iron disulfide.” The experiments for this research have been carried out using the neutron-beam guide of JRR-3 at the Japan Atomic Energy Agency (JAEA), as a collaboration project named “SH” consisting of many groups: RIKEN, the International Christian University, the Tokyo University of Science, JAEA, and Daido Institute of Technology. The aim of this work is to clarify the in situ chemical states of energetic (hot) ⁵⁷Fe atoms produced via the ⁵⁶Fe(n, γ)⁵⁷Fe reaction in solid phase.

• Application to Chemical Education

“Research of reactions and products in the Evance’s experiment by ⁵⁷Fe-Mossbauer spectroscopy.”

“Mössbauer spectroscopic study of chemical reaction products of iron in a disposable body warmer.” This research project has been promoted by the group. Iron is one of the most popular elements from a chemical education viewpoint. They have applied Mössbauer spectroscopy to characterizing iron states of materials treated often in chemistry laboratories in junior-high and high schools and in general chemistry classes in colleges.

The group’s facilities include the following equipment:

• Three Mössbauer spectrometers

• A conversion electron Mössbauer counter

• A liquid nitrogen refrigeration cryostat controllable to 310.0 K from 77.4 K

Collaboration researchers include:

• Hiroshima University: Dr. Y. Takahashi and Mr. S. Mitsunobu

• Aichi Medical University: Dr. S. Kojima

• Osaka City University: Dr. T. Ohzuku and Dr. K. Ariyoshi

• Nagoya University: Dr. M. Sano, Dr. Hirabayashi, Dr. Suzuki

• RIKEN: Dr. Yoshio Kobayashi

• International Christian University: Dr. Michael Kenya Kubo

• Tokyo University of Science: Dr. Yasuhiro Yamada

• Japan Atomic Energy Agency: Dr. H. Matsue

SUMITOMO METAL INDUSTRIES, LTD.
Corporate Research and Development Laboratories
Hyogo

Name and Title of Researcher Dr. Takayuki Kamimura – Senior Researcher, Plate and Structural Steel R&D Department

Description and Area of Research

The Corrosion Protection Group consists of six members, led by the group leader Dr. Hideaki Miyuki, and mainly focuses on the corrosion protection technologies for steel plate used for ships and bridges. Recently, weathering steel containing small amounts of Cr, Cu, Ni, and P has been widely noticed in Japan from the viewpoint of reduction in maintenance cost of steel structures. Dr. Kamimura has been interested in the corrosion protection mechanism of the rust layer formed on steels, and actively advanced collaborative researches by ⁵⁷Fe Mössbauer spectroscopy with Professor Saburo Nasu and Dr. Shotaro Morimoto of Osaka University. The detailed phase analyses have been performed on rust layers formed on steels exposed for more than 30 years, and it was found that the protectiveness of the rust layer is closely related to formation of α-FeOOH. Moreover, ⁵⁷Fe Mössbauer spectroscopy has been applied for the phase analysis of the rust formed on the weathering steel coated with a surface pretreatment promoting protective rust formation (Weather-Act).

IBARAKI UNIVERSITY
Ibaraki

Names of Researchers Professor Y. Nishihara Dr. H. Kawanaka

Description and Area of Research

The Ibaraki University group consists of two permanent staff members, one masters and three bachelor course students (2006). The permanent staff is Professor Y. Nishihara and Dr. H. Kawanaka, who is a senior researcher at the National Institute of Advanced Industrial Science and Technology at Tsukuba.

The study of magnetic and transport properties of transition-metal oxides is a recent research project in the group. One of the recent studies is “metal-insulator transition in Fe-substituted SrRuO₃ bad metal system.” Professor C. Bansal, a visiting professor from the University of Hyderabad, India, performed this work. Professor Bansal made clear that the quadrupole splitting shows a clear increase from the metallic to the insulating state and that the metal-insulator transition in this system is a kind of Mott transition in a small carrier mean free path system. Another work recently performed is entitled “small plaron transport and glassy ferromagnetism in (LaSr)Co_1-xFe_xO₄.” This work was performed by a doctoral course student A. Tabuchi. He measured the valence of Fe in this system and proposed a model that explains glassy ferromagnetism induced by a variable range hopping of small polaron.

Even though the group is very small, they would like to continue their efforts to make clear microscopic electronic states of transition-metal oxide systems.