Heavy Fermions in 3d Electron Systems

3d 电子系统中的重费米子

基本信息

批准号：
63540249
负责人：
WADA Hirofumi
金额：
$ 1.22万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

项目摘要

Recently, A heavy fermion, characterized by a huge electronic specific heat coefficient, gamma, has been found in 4f and 5f electron systems. Similar enhancement of gamma can be expected for 3d electron systems, when they show giant spin fluctuations. We have investigated the low temperature specific heat of several alloys and Laves phase compounds. The results are as follows.1. The nearly antiferromagnetic Y_<1-X> Sc_XMn_2 compounds show a giant gamma-value of 150mJ/K^2mol due to spin fluctuations. The enhancement factor, defined as gamma/gamma_b, where gamma_b is the theoretical gamma-value expected from the band calculation is about 15. This enhancement is comparable to that of a typical 5f heavy fermion UPt_3, 20.2. The nearly ferromagnetic Laves phase compounds, such as NbFe_2 and Y(Co_<1-X>Al_X)_2 also show an enhancement of gamma. The enhancement factor is at most 5, which is smaller than that of Y_<1-X>Sc_XMn_2.3. betaMn has no magnetic order down to 1.4 K. This metal is known to have a large gamma-value of 70mJ/K^2mol and is considered as a candidate for 3d heavy fermions. By substitution Al for Mn, we have found that the local moment character develops. This suggests that an electronic state in betaMn is on the verge for the onset of local moment, similarly to 4f and 5f heavy fermions. From these results, we conclude that antiferromagnetic spin fluctuations in a frustrative structure significantly enhances gamma-value in 3d electron systems.

最近，在4F和5F电子系统中发现了一个以巨大的电子特异性热系数Gamma为特征的沉重费米昂。当3D电子系统显示出巨大的自旋波动时，伽马系统也可以预期类似的增强。我们已经研究了几种合金和薰衣草相化合物的低温特异性热。结果如下1。由于自旋波动而导致的几乎抗铁磁性Y__ <1-X> SC_XMN_2化合物显示出150mj/k^2mol的巨型伽马值。增强因子定义为伽马/伽马_b，其中γ_b是从频带计算中预期的理论伽马值约为15。这种增强与典型的5F繁重的Fermion upt_3，20.2相当。几乎铁磁液相化合物，例如NBFE_2和Y（CO_ <1-x> al_x）_2也显示了伽玛的增强。增强因子最多为5，比y_ <1-x> sc_xmn_2.3小。 Betamn没有磁性降低至1.4K。已知这种金属的γ值为70MJ/k^2mol，被认为是3D重费米子的候选者。通过替代MN，我们发现当地时刻的特征是发展的。这表明，betamn中的电子状态在本地力矩开始时处于边缘，类似于4F和5F重型费米子。从这些结果中，我们得出的结论是，令人沮丧的结构中的抗磁性自旋波动显着增强了3D电子系统中的伽马值。