1997 Fiscal Year Final Research Report Summary
Orbital ordering and magnetism of fluoride and chloride compounds at high pressures
| Project/Area Number |
08454088
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Chiba University |
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Principal Investigator |
YAMADA Isao Chiba University, Physics, Professor, 理学部, 教授 (90037820)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAYAMA Takashi Chiba University, Physics, Associate Professor, 理学部, 助教授 (70189075)
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| Project Period (FY) |
1996 – 1997
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| Keywords | orbital ordering / fluoride compound / chloride compound / high pressure |
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| Research Abstract |
Although the layred compounds K_2CuF_4 and La_2CuO_4 have a K_2NiF_4-type crystal structure, the former is a ferromagnet while the latter is an antiferromagnet. Such a difference of magnetism is due to the antiferrodistortive and ferrodistortive orbital orderings of 3d-holes, respectively. Under a high pressure, we expect that K_2CuF_4 turns into an antiferromagnet because of a change of orbital ordering from antiferrodistortive to ferrodistortive.
From the magnetic susceptibility measurements at low temperatures under hydrostatic high pressures, we found a magnetic change from ferromagnetism to antiferromagnetis around 9 GPa. To confirm that this magnetic change was surely due to a change of orbital ordering, we performed X-ray diffraction and phonon-Raman scattering experiments under high pressures. As a result, we found that the crystal structure changed around 9 GPa. This structurql transition was found to bring about a change of orbital ordering from antifferrodistortive to ferrodistortive.
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