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Synthesis of the two-dimensional orthogonal dieter compound with an exact dieter ground state and investigation of its magnetic properties

具有精确基态的二维正交Dieter化合物的合成及其磁性研究

基本信息

批准号：
13640352
负责人：
KAGEYAMA Hiroshi
金额：
$ 2.62万
依托单位：
KYOTO UNIVERSITY (2003)The University of Tokyo (2001-2002)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

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.

这个项目的目的是实验实现Shastry-Sutherland模型，即我大约5年前发现的二维正交二元系统SrCu_2(BO_3)_2，是为了阐明与其特殊拓扑相关的磁特性，并利用一些化学和物理方法来诱导量子相变。结果发现，物理压力对于调整基态非常有效。即使施加约10kbar的压力，也会导致自旋间隙的减少，其减少量是没有压力时的一半，并且当施加进一步的压力时，我们发现了相分离的趋势。该结果与理论建议一致，即该化合物中的 Dieter 自旋单线态非常接近某些其他状态的相界。与其他小组的合作也很成功：使用我生长的优质晶体进行的高场核磁共振研究揭示了1/8平台态的磁性超结构以及作为温度和磁场函数的奇异相变的性质，其结果发表在《Science》杂志上。这项研究促使理论家重新考虑他们的理论，因为现有的理论无法重现实验确定的上层建筑。我们还寻找在拓扑上等价于 Shastry-Suhherland 模型的自旋化合物。发现 Nd_2BaZnO_5 对应于此类模型的另一个例子，但具有经典自旋。我们通过中子衍射实验确定了这种材料的磁结构。对SrCu_2(BO_3)_2等方晶格新型磁阻系统进行了探索。通过利用离子交换反应，我们新合成了低维磁性材料，如(CuCl)Ca_2Ta_3O_<10>和(FeCl)Ca_2Ta_3O_<10>，其中一些材料表现出有趣的磁特性，可能是由磁性离子的低维网络产生的。