2001 Fiscal Year Final Research Report Summary
FORMATION OF AN EXCITONIC FERROMAGNETIC MOMENT IN THE LOW DENSITY-CARRIER BORIDES
| Project/Area Number |
12640353
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | HIROSHIMA UNIVERSITY |
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Principal Investigator |
IGA Fumitoshi Hiroshima University, Graduated School of Advanced Sciences of Matter, Dept. of Quantum Matter, Associate Prof., 大学院・先端物質科学研究科, 助教授 (60192473)
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| Co-Investigator(Kenkyū-buntansha) |
UMEO Kazunori Hiroshima University, Graduated School of Advanced Sciences of Matter, Dept. of Quantum Matter, Research Associate, 大学院・先端物質科学研究科, 助手 (10223596)
TAKABATAKE Toshiro Hiroshima University, Graduated School of Advanced Sciences of Matter, Dept. of Quantum Matter, Prof., 大学院・先端物質科学研究科, 教授 (40171540)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Low density-carrier system / Borides / ferromagnet / Lattice defect / Heat treatment / Excitonic Insulator / Muon Spin Relaxation / Internal field |
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| Research Abstract |
We have found that Yb_<1-x>La_xB_6 (x<0.006) has a very similar electronic structure as that of the excitonic ferromagnet Ca_<1-x>La_xB_6 and that this alloy system shows ferromagnetic transition at Curie point Tc = 150-200 K by manetization and muon spin-relaxation (μSR).
1. Single crystal growth : YbB_6 single-crystal samples were grown by a floating-zone method using an image furnace equipped with four-xenon lamps. In order to eliminate impurity phase YbB_<50> from the crystals of YbB_6, a nominal composition of Yb_<1.1>B_6 was chosen for sintered polycrystalline rods for the single-crystal growth. This as-cast sample shows diamagnetism. After heat treatment to introduce Yb-defect we have found that large paramagnetic moment was formed.
2. polycrystalline sample : Sintered polycrystalline sample has a sponge-like surface that has been sintered in vacuum by using a radi-frequency induction-furnace. The high-resolution x-ray diffraction analysis and EPMA revealed that both polycrystals and single crystals have no impurities of FeB and Fe_2B except for a small amount of paramagnetic YbB_4 (【less than or equal】0.001 at%). After acid etching treatment, polycrystalline sample shows ferromagnetism with Tc = 150-200 K. In the next research, we will study the surface effect of this sintered sample for magnetic property.
3. μSR : we have performed μ^+SR measurement for both single crystals and polycrystals from 300 K down to 10 K. Relaxation spectra shows typical paramagnetic pattern. Internal fields deduced from relaxation rate are 0.2 mT at room temperature, and do not change down to 150 K. On cooling further, the internal field increases strongly and reaches a value of 0.6 mT at 10 K. this temperature depence is very similar to that of the magnetic susceptibility.
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Research Products
(12 results)
