1994 Fiscal Year Final Research Report Summary
Magneto-volume Effects in Fe-based Amorphous Alloys
| Project/Area Number |
04402045
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Physical properties of metals
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
FUKAMICHI Kazuaki Faculty of Engineering, Tohoku University, Professor, 工学部, 教授 (00005969)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIHARA Akira Research Institute for Scientific Measurements, Research associate, 科学計測研究所, 助手 (40166989)
AOKI Kiyoshi Institute for Materials Research, Associte Professor, 金属材料研究所, 助教授 (70124542)
SHIMADA Yutaka Research Institute for Scientific Measurements, Professor, 化学計測研究所, 教授 (00006157)
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| Project Period (FY) |
1992 – 1994
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| Keywords | Pressure effect / Magnetovolume effect / Law of approach to saturation / Random axial magnetic anisotoropy / Hydrogen absorption / Valence / Spin glass / Structural analysis |
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| Research Abstract |
The pressure effects on the Curie temperature and magnetization for Fe-based amorphous alloys which have large magnetovolume effects have been investigated. The magnetization curves for the alloys with a very high concentration of Fe do not follow the law of approach to saturation with 1/H but follow that with 1/H^<1/2>. The latter power law is valid for the alloy systems which have antifferomagnetic interactions. It should be noted that the curves for random axial magnetic anisotropy alloy systems do not follow the 1/H^<1/2> law.
The temperature and field dependences of linear and forced volume magnetostrictions have been investigated. These two values are markedly large and the forced-volume magnetosriction exhibits a tendency to diverge at the spin freezing and the Curie temperatures. These results are very different from those for the localized systems.
The dramatic increase in the magnetization is caused by hydrogenation for Ce-Fe amorphous alloys. We can expect a huge coercivity at low temperatures due to the random magnetic anisotropy if the valence of Ce is reduce from tetravalent to trivalent by hydrogenation. However no such a large coercivity has been confirmed. This behavior is explained by the aggregation of hydrogen atoms around Ce atoms, resulting in the altered electronic structure. Therefore, we can not assume that the expansion of volume by hydrogenation as the negative pressure.
The changes in the magnetic properties by annealing for amorphous Y-Fe alloys are correlated to the increases in the interatomic distance of Fe-Fe pairs and the coordination numbers of Fe atoms.
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