| Project/Area Number |
13640352
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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 | KYOTO UNIVERSITY (2003)
The University of Tokyo (2001-2002) |
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Principal Investigator |
KAGEYAMA Hiroshi Kyoto Univ., Graduate School of Sci., Asso. Prof., 大学院・理学研究科, 助教授 (40302640)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2003: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2002: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2001: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Keywords | spin gap / exact dieter ground state / quantum spin system / magnetization plateaux / frustration / quantum phase transition / dimer system / ion-exchange reaction / 銅酸化物 / 直交ダイマー / シャストリー・サザーランド模型 / ジャストリーサザーランド模型 |
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| Research Abstract |
The purpose of this project on the experimental realization of Shastry-Sutherland model, the two-dimensional orthogonal dieter system SrCu_2(BO_3)_2 that I discovered about 5 years ago, is to clarify the magnetic properties which are related to its special topology and to induce quantum phase transition, utilizing some chemical as well as physical method. As a result, physical pressure was found to be very effective for tuning the ground state. Even the application of pressure about 10kbar results in the reduction of spin gap which is as half as that without pressure, and when further pressure is applied, we have found a tendency of phase separation. This result is in consistent with the theoretical suggestion that the dieter spin-singlet state in this compound resides very close to the phase boundaries to some other states. The collaboration with other groups was also successful: the high-field NMR study using the good-quality crystal grown by me has revealed the magnetic superstructure at the 1/8 plateau state and nature of exotic phase transitions as a function of temperature and magnetic field, the result of which was published in Science. This study triggered theoreticians to reconsider their theory, since existing theories could not reproduce experimentally determined superstructure. We also search for the spin compound which is topologically equivalent to the Shastry-Suhherland model. Nd_2BaZnO_5 was found to correspond to another example of such model but with classical spins. We determined the magnetic structure of this material by neutron diffraction experiment. The search for the new magnetically frustrated systems based on the square lattice as in SrCu_2(BO_3)_2 has been conducted. By utilizing the ion-exchange reaction, we newly synthesized the low-dimensional magnetic materials such as (CuCl)Ca_2Ta_3O_<10> and (FeCl)Ca_2Ta_3O_<10>, some of which show interesting magnetic properties presumably arising from the low-dimensional network of magnetic ions.
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