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种具有巨大电子比热系数γ的重费米子。当 3d 电子系统表现出巨大的自旋涨落时，预计伽马也会出现类似的增强。我们研究了几种合金和拉夫斯相化合物的低温比热。结果如下： 1．由于自旋涨落，近反铁磁性的 Y_<1-X> Sc_XMn_2 化合物显示出 150mJ/K^2mol 的巨大伽玛值。增强因子定义为 gamma/gamma_b，其中 gamma_b 是频带计算中预期的理论伽玛值，约为 15。这种增强可与典型 5f 重费米子 UPt_3 的增强因子 20.2 相媲美。近铁磁Laves相化合物，如NbFe_2和Y(Co_<1-X>Al_X)_2也表现出γ增强。增强因子至多为5，小于Y_<1-X>Sc_XMn_2.3。 betaMn 没有低至 1.4 K 的磁序。已知这种金属具有 70mJ/K^2mol 的大伽马值，被认为是 3d 重费米子的候选者。通过用 Al 代替 Mn，我们发现局部矩特性得到了发展。这表明 betaMn 中的电子态正处于局部矩开始的边缘，类似于 4f 和 5f 重费米子。从这些结果中，我们得出结论，受挫结构中的反铁磁自旋涨落显着增强了 3d 电子系统中的伽马值。