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ESR and Cyclotron Resonance of Strongly Correlated Materials

强相关材料的 ESR 和回旋共振

基本信息

批准号：
08404022
负责人：
MOTOKAWA Mitsuhiro
金额：
$ 25.47万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1999
项目状态：
已结题

项目摘要

Continuing the experiments done last year, we have performed the magnetic resonance and cyclotron resonance on some rare-earth compounds using vector network analyzer system developed recently at ultra low temperatures and high magnetic fields. A microwave cavity has been used for high sensitivity. The frequency range is 40〜110 GHz and the temperature range is 0.5〜300 K. The obtained results are as follows :1) GdAs : The magnetic structure of this compound with easy (111) plane, which had been unknown so far, has been determined by ESR. The cyclotron resonance has been observed at 0.5 K and the effective mass of the carrier is detemined as 0.48 m0. This result suggests that the fermi surface is spherical and the effective mass is two times larger than that obtained by quantum oscillation.2) LaSb : The cyclotron resonance has been observed below 4.2 K. From the anisotropic behavior of the resonance position, this resonance occurs due to carriers with a ellipsoidal fermi surface. The effective mass obtained is 0.26 m0 along the <100> direction and is two times larger than that obtained by quantum oscillation.The difference between masses obtained by cyclotron resonance and quantum oscillaation has been observed for low dimensional organic conductors. However the former is larger than the latter and consistent with the theoretical prediction, which is against our result. In this study, we have first observed the cyclotron resonance on strongly correlated materials, which has never reported, and determined the effective mass directly. The theory to explain our result has not been done yet.

在去年实验的基础上，我们利用新近研制的矢量网络分析仪系统，在超低温强磁场条件下，对某些稀土化合物进行了磁共振和回旋共振实验。微波腔已被用于高灵敏度。频率范围为40 ~ 110 GHz，温度范围为0.5 ~ 300 K。1）GdAs：用ESR方法测定了该化合物的磁结构，其易磁化面为（111）面。在0.5K下观察到了回旋共振现象，确定了载流子的有效质量为0.48m ~ 0.这一结果表明费米面是球形的，有效质量比量子振荡法得到的大两倍。2）LaSb：在4.2K以下观察到回旋共振。从谐振位置的各向异性行为来看，这种谐振是由于具有椭圆费米面的载流子而发生的。得到的有效质量为沿着方向的0.26 m ~ 0<100>，比量子振荡法得到的质量大两倍，并对低维有机导体观察到了回旋共振法和量子振荡法得到的质量的差别。但前者大于后者，与理论预测一致，这与我们的结果相反。在本研究中，我们首次在强关联材料上观察到了从未有过的回旋共振现象，并直接确定了有效质量。解释我们结果的理论还没有做出来。