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Research of the electronstates on strongly correlated electron systems under static and dynamic extreme condition

静态和动态极端条件下强相关电子系统的电子态研究

基本信息

批准号：
10440111
负责人：
DOMI Gendo
金额：
$ 6.14万
依托单位：
KYUSHU UNIVERSITY (2000)Kumamoto University (1998-1999)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

(1) Effect of pressure and magnetic field on the perovskite manganese oxidesMagnetostriction and magnetization of Eu_<0.58>Sr_<0.42>MnO_3 were measured under hydrostatic pressures up to 2 GPa in order to investigate the effect of pressure on the metal-insulator (M-I) transition. At ambient pressure, around 2 T and 6 K, where the field-induced M-I transition was previously reported, the observed magnetostriction was to be 0.04 %. With increasing pressure, the saturation magnetization increased at a field of 0.5 T, whereas it decreased at field of 1.5 and 5.0 T.On the other hand, the influence of hydrostatic pressure on electrical resistance of La_<0.1>Ce_<0.4>Sr_<0.5>MnO_3 were investigated under pressures up to 1.8 GPa. With increasing pressure, Curie temperature increases. It is also found that the coefficient of -logT term originated from Kondo-like effect decreases with increasing pressure and the resistance maximum temperature shifts largely to lower temperature. Though the origin of the large negative pressure coefficient cannot be clearly solved, it can be said that the peculiar phenomenon is ascribed to some kind of magnetic interactions.(2) High-pressure studies on the magnetic phase transitions and related phenomena in the single crystalline UNi_2Si_2Measurement of electrical resistance and thermal expansion under high pressure and high magnetic field were performed. We found that the analogy between the p-T and B-T magnetic phase diagrams. From the results, the critical pressure for suppression of simple antiferromagnetism in UNi_2Si_2 was determined as 3.2 GPa. It is also found that a small anomaly appears around 100 K.The resistance anomaly can be attributed to the pressure-induced magnetic order-order phase transition between ILSDW and UAF phases. In terms of magnetoelastic phenomena, thermodynamic equations and theoretical approach, it is deduced that this intermediate phase would be suppressed by applying pressure.

(1)为了研究压力对钙钛矿锰氧化物<0.58><0.42>金属-绝缘体（M-I）转变的影响，在2GPa的静水压力下测量了Eu_ Sr_MnO_3的磁致伸缩和磁化强度。在环境压力下，约2 T和6 K，其中场诱导的M-I转变是以前报道的，观察到的磁致伸缩是0.04%。随着压力的增加，在0.5T磁场下饱和磁化强度增加，而在1.5和5.0T磁场下饱和磁化强度降低。另一方面，在1.8GPa压力下研究了静水压对La_<0.1>Ce_<0.4>Sr_<0.5>MnO_3电阻的影响。随着压力的增加，居里温度升高。研究还发现，由近藤效应引起的-logT项系数随压力的增加而减小，电阻最大温度向低温方向移动。虽然大的负压系数的来源还不能很清楚地解决，但可以说这种奇特的现象归因于某种磁相互作用。(2)对单晶UNi_2Si_2的磁相变及相关现象进行了高压研究，测量了高压和强磁场下的电阻和热膨胀。我们发现，p-T和B-T磁相图之间的相似性。根据实验结果，确定了UNi_2Si_2的简单反铁磁性被抑制的临界压力为3.2GPa。研究还发现，在100 K附近出现了一个小的异常。电阻异常可以归因于ILSDW和UAF相之间的压力诱导磁有序相变。根据磁弹性现象、热力学方程和理论方法，推导出施加压力可以抑制该中间相。