| Project/Area Number |
04640338
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Osaka University |
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Principal Investigator |
NASU Saburo Osaka University, Faculty of Eng. Science, Associate prof., 基礎工学部, 助教授 (00030057)
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| Co-Investigator(Kenkyū-buntansha) |
ENDO Shoichi Osaka University, research Center for Extreme Materials, Professor, 極限物質研究センター, 教授 (10001843)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1992: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | diamond-anvil-cell / ^<57>Fe Mossbauer spectroscopy / material properities under pressure / iron exides / high-and low-spin transition / pressure induced structual transition / pressure induced ferromagnet / Nuclear resonance forward scattering with synchrotron radiation / ^<57>Feメスバウアー分法 / メスバウァー分光 / ペロブスカイト鉄酸化物 / Fe_3O_4 / FeO / 圧力相転移 / 磁気構造転移 / 高スピン低スピン転移 |
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| Research Abstract |
It is well recognized that the high-pressure Mossbarer spectroscopy using a diamond anvil cell is one of powerful methods to elucidate the material properties under pressure, especially for the magnetic properties. In this project, we have performed the Fe Mossbauer measurements under high-pressure and low temperature for the typical iron oxides meterials in order to elucidate the magnetic properties under high-pressure. Results obtained in this project are summarized as follows.
(1) Perovskite iron oxides, SrFeO_3 and caFeO_3 : Since these iron oxides have an abnormally high valence as Fe, it is intresting to investigate the effects of high pressure on the electronic stucture of these exides. We found the appreciable increases of the Neel temperatures as an increase of the external pressure. SrFeO_3 did not show any structural trasformation up to 77 GPa. However the magnetic stucture changes form helical-spin to colinear ferromagnetic structure by the external high pressure. On the oth
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er hand, CaFeO_3 shows the structural transformation and simultaneously the spin-cross-over transition from high-spin to low-spin state by the external high-pressure. (2) Magnetite, Fe_3O_4 : Magnetite is the oldest known magnetic naterial and we have found that the high pressure phase appeared at 29 GPa. This high-pressure magnetite has 2 non-equivalent iron sites whose number ratio is 1 : 2 and they are para-(or non-) magnetic at 300 K.(3) Wustite, Fe _<1-3>O : Up to 80 gPa high-pressure ^<57>Fe Mossbauer investigation has been performed using a specimen Fe_<0.977>O which is the closest composition to the stoichiometry. We found the appreciable increase of the Neel temperature by the pressure and an extraordinary large magnetic hyperfine nagnetic field of 48 T at 300 K.(4) High-pressure Mossbauer spectroscopy using a synchrotron radiation : Muclear resonance forward scattering has been successfully obserbed for SrFeO_3 at 44 GPa and 74 GPa at 300 K.
DAC can offer us a very high-pressure field, but the specimen should be restricted to be an extremely small amounts and usually it is rather difficult to get a spectrum having a good-quality. In order to eliminate the difficulty for the measurements, we optimexed the measurement conditions and can get a high-quality spectrum. However, the measurements at low temperatures between 4.2 K and 300 k have just begun using a liquid-helium cryastat and it is measurements at liw temperatures between 4.2 K and 300 K have just begun using a liquid-helium cryastat and it is essential to continue this research project in order to accomplish the high-pressure and low-temperature measurements by DAC. Less
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