Biographical Sketch of T. Shinjo
Reprinted from the April 2005 edition of the Mössbauer Spectroscopy Newsletter, published as part of Volume 28, Issue 4 of the Mössbauer Effect Reference and Data Journal

Teruya Shinjo was born August 18, 1938, in Kyoto, Japan, and grew up in Hyogo prefecture. In 1957, he entered Kyoto University and graduated in 1961. He then entered the graduate course in chemistry and was awarded a doctoral degree in 1966. In 1961, two groups of nuclear physicists initiated the Mössbauer effect experiment in Japan: Atsuko Ito and Kazuo Ono at the Institute for Solid State Physics (ISSP), University of Tokyo; and Naomoto Shikazono at the Japan Atomic Energy Research Institute (JAERI). The Kyoto group, consisting of Yoji Nakamura, Masayuki Shiga, and Teruya Shinjo, began their Mössbauer spectroscopic studies in 1962, using the facilities at JAERI.

The first object for Nakamura and Shiga was Invar alloys, and for Shinjo was ordered Fe-Si alloys. Prof. Shinjo’s first paper, a Mössbauer study on Fe3Si, was published in the Journal of the Physical Society of Japan in 1963.

Professor Toshio Takada was the leader of the inorganic chemistry group at the Institute for Chemical Research at Kyoto University, and his group had the skill to synthesize ultrafine particles with controlled particle sizes. Teruya Shinjo applied Mössbauer spectroscopy to investigate the magnetic properties of iron oxide particles and observed for the first time the superparamagnetic relaxation in Mössbauer spectra. Namely, in ultrafine particles of antiferromagnetic oxides (actually FeOOH and Fe2O3), the rate of superparamagnetic fluctuation can be faster than the nuclear Larmor frequency, and therefore the hyperfine splitting has collapsed. This result was the main focus of his doctoral thesis, entitled “Mössbauer studies on antiferromagnetic ultrafine particles.”

After completing the doctoral course in 1966, he became a Research Associate with Prof. Takada’s group in the Institute for Chemical Research, Kyoto University. He was promoted to an Associate Professor in 1977 and to full Professor in 1984. There, he organized a group for Mössbauer spectroscopic studies and has been involved extensively in the research on magnetic materials. Magnetic characteristics of many iron compounds prepared by the Takada group were identified by Mössbauer measurements. In collaboration with Mikio Takano, the antiferromagnetic ordering in jarosite was confirmed for the first time. This mineral has attracted recent attention as a part of the evidence that water once existed on the surface of Mars.

Studies on iron oxides with exotic valences – Fe4+, Fe5+, and Fe6+ – were also carried out with Mikio Takano and Toshiro Ichida. It was unique to Prof. Shinjo’s group to use 57Fe or 57Co as a probe to investigate magnetic properties of materials originally including no Fe. Successful results, for example, included:

  • the behavior of precipitated Co particles embedded in a Cu or Au matrix was elucidated by using 57Co source doping, which was a collaboration with Saburo Nasu;
  • antiferromagnetic orderings in vanadium oxides were observed using 57Fe impurities, in cooperation with Koji Kosuge; and
  • the magnetic ordering in CrO2 was confirmed to be ferromagnetic using 57Fe impurity, with Nobuyasu Tamagawa. 

Around 1970, studies on surface/interface magnetism utilizing Mössbauer spectroscopy were initiated. In the first step, 57Co was deposited electrolytically on ferromagnetic metal surfaces. The Mössbauer source spectra showed nearly bulk hyperfine fields at the surface layers, which denied the existence of a magnetically dead layer on ferromagnetic metal surfaces proposed from magnetization measurements.

Professor Uli Gonser's group at Universität Saarbrucken in 1975. Besides Uli and Teruya, you can find Ali Trautwein and Werner Keune.
In 1974 and 1975, for 14 months, he worked in the laboratory of Uli Gonser, Universitat des Saarlandes, Germany. In collaboration with Werner Keune and Achim Lauer, interface magnetism studies were carried out using thin films prepared by ultrahigh vacuum deposition. Interface-selectively enriched samples were prepared by depositing 57Fe on an Fe layer, which was then covered by Cu. Using thusly prepared samples, interface hyperfine fields were again observed to be close to the bulk value.

Since his return from Germany, the Mössbauer spectroscopic studies for interface magnetism at Kyoto have been developed using 56Fe/57Fe multilayers, instead of natural Fe, to make surface-enrichment more efficient (in cooperation with Shiro Hine and Nobuyoshi Hosoito). Prof. Keune moved from Saarbruken to Duisburg, and there established the equipment to measure hyperfine fields at clean surfaces in vacuum. Studies by Shinjo in Kyoto and Keune in Duisburg were complementary and, in order to keep a close connection, an agreement of cooperation was contracted between the Institute for Chemical Research at Kyoto University and Fachbereich Physik at Duisburg University.

His stay in Saarbrucken gave Prof. Shinjo the opportunity to become acquainted with Mössbauer spectroscopists around the world. At that time, the laboratory of Prof. Gonser was one of the most active centers for Mössbauer studies, and not only European but also many American and Asian guests visited the lab. Prof. Shinjo attended the International Conference on the Applications of the Mössbauer Effect (ICAME) held in France in 1974, which was during his stay in Germany. It was his first experience joining the ICAME series. In 1978, ICAME was organized in Kyoto and he presented a paper on the interface magnetism; his first invited talk in the ICAME series.

Photos from ICAME 1978 in Kyoto
Among those pictured, from left to right,
are Uli Gonser, F.E. Fujita, and Teruya Shinjo.
Professor Shinjo at the podium.
J.C. Walker, Teruya Shinjo, and R.W. Hoffman.

Interface-selectively enriched samples were prepared by ultrahigh vacuum deposition techniques and the obtained results suggested the possibility of controlling the thickness on an atomic scale. If two (or more) metals are deposited alternately, artificial superstructures may be constructed, and such multilayers seem to be new materials that do not exist in nature. As an extension of interface magnetism studies, the preparation of multilayers with artificial superstructures was initiated around 1980. Multilayers prepared in the early stages included Fe as one component in order to use Mössbauer spectroscopy as a tool for characterization, but afterwards many kinds of multilayers were prepared extensively, including even superconducting multilayers. In the 1980s, Prof. Shinjo’s group was one of the pioneers in the field of metallic multilayer studies. The principal coworkers were Kenji Kawaguchi, Noriaki Nakayama, Kazushi Kanoda,  and Ko Mibu. Cooperative works were carried out with Yasuo Endoh (Sendai), Yasuhiko Fujii (Osaka), and Hiroshi Yasuoka (Tokyo), and some other groups.

In 1988, a French group discovered the giant magnetoresistance (GMR) effect in Fe/Cr multilayers. Prof. Shinjo and Hiefumi Yamamoto demonstrated in 1990 that a non-coupled GMR multilayer, whose structure may be Co/Cu/NiFe/Cu for instance, exhibits sensitive resistance change in moderate magnetic fields. Thus, the possibility of GMR for applications was evidenced. Today a non-cooled type GHR head (spin valve system invented by the IBM group) is widely used in the hard disks of computers.  

It was in the middle of the 1990s that the group of Prof. Shinjo (Teruo Ono, Kunji Shigeto, Takuya Okuno, and Ralf Hassdorf) began the application of microfabrication techniques for magnetic materials. Using electron-beam lithography equipment, nanoscale dots and wires have been fabricated from ferromagnetic thin films. Several novel observations, such as the confirmation of a perpendicularly magnetized spot at the center of a vortex magnetic structure, the estimation of domain wall propagation velocity in a nanowire, and the observation of domain wall motion driven by electric current, were made.

ICAME 2001 in Oxford. From left to right are Namdeo Gajbhiye, Teruya Shinjo, and Werner Keune.

However, the group has not yet been successful in obtaining clear Mössbauer spectra from nanofabricated samples. It has been a wish of Prof. Shinjo to compare the Mössbauer results on recent nano-fabricated systems with those on fine particles from 40 years ago, but it is not yet realized.

Another of Prof. Shinjo’s research topics for a rather long time was Mössbauer measurements at very low temperatures. Using a dilution refrigerator, in collaboration with Kunihide Okada, a 57Co spectrum in CoO was measured down to 80 mK and, from the nuclear polarizability, the hyperfine field at the mother nuclei (Co) was estimated, in 1974. About 10 years later, lower temperatures were achieved by using an improved refrigerator. A 57Fe absorption spectrum for natural Fe foil showed a clear asymmetry of absorption intensity due to the nuclear polarization, and from the polarizability the temperature of the absorber was determined to be 5 mK, which seems to be one of the lowest temperature records for Mössbauer measurements.

The most recent Mössbauer study is 119Sn measurements on Cr layers, in collaboration with Ko Mibu. Impurity Sn can act as a probe for the complicated antiferromagnetic structure of ultrathin Cr layers. After Prof. Shinjo’s retirement, Dr. Ko Mibu is leading the studies on Cr layers, serving as his successor.

In the 40 years of his career, Prof. Shinjo published 320 original scientific papers on magnetic materials research. Over 220 publications were registered by the Mössbauer Effect Data Center, which is ranked to be the top among Japanese Mössbauer spectroscopists and in the top 15 of overall Mössbauer researchers in terms of number of publications.

In addition to the visit to Saarbrucken in 1974/1975, Prof. Shinjo visited Strasbourg, France, for two months with J. M. Friedt, and made short visits to many places in the world. He received financial support for international cooperation between his group and researchers in Duisburg, Arizona, and Orsay. He gave many invited talks at the ICAME conference series, the International Conference on Magnetism (ICM), the International Colloquium on Magnetic Films and Surfaces (ICMFS), the Materials Research Society Meetings (MRS), and others.

Prof. Shinjo served as a chair of the ICMFS International Advisory Committee for three years. He organized ICMFS twice, and the International Symposium on Metallic Multilayers (MML) once. He was also the program chair of the International Symposium on Industrial Applications of the Mössbauer Effect (ISIAME) held in Otsu, Japan, in 1992.

Prof. Shinjo served as a member of the organizing committee and the program committee for many conferences. For many years he was an Associate Editor of the Mössbauer Effect Reference and Data Journal. He is a member of editorial board for the Journal of Physics D, Applied Physics and the Journal of Magnetism and Magnetic Materials. Prof. Shinjo was recently elected to be a fellow of the United Kingdom Institute of Physics.

Prof. Shinjo served as the Director of the Institute for Chemical Research, Kyoto University, from 1996 to 1998. He also served as a science advisor of the Ministry of Education (Monbusho) from 1992 to 2000. Prof. Shinjo was awarded the Japanese Medal of Honor with Purple Ribbon (Shijuhosho) in November 2000. The Medal of Honor, given by the government of Japan, is bestowed upon individuals who have made outstanding achievements in their respective fields of society; the Medal with Purple Ribbon is awarded to individuals who have contributed to academic and artistic developments, improvements, and accomplishments. He was also awarded prizes by the Magnetics Society of Japan and the Japan Society of Applied Physics.

Professors Teruya Shinjo and Saburo Nasu in the Mössbauer laboratory at Osaka University (December 2004).
The Mössbauer Group at Osaka University.

After his retirement at the end of March 2002, he has been Professor Emeritus of Kyoto University, and is a Fellow at the International Institute for Advanced Studies, which is located in the new science town near Nara. At the same time, he serves Osaka University as a guest professor. There, he is joining the research group of Prof. Saburo Nasu and keeping in touch with Mössbauer spectroscopic studies. After his retirement, having more free time, he is enjoying playing tennis and golf frequently.

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