Structure and Physical Properties New Heavy Fermion Systems -Amorphous Cerium Alloys-

结构和物理性能新型重费米子系统-非晶态铈合金-

基本信息

批准号：
03452029
负责人：
SUMIYAMA Kenji
金额：
$ 4.22万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

In Ce-based alloys, the f electrons mix with s and p electrons and their strong correlation make the effective mass of conduction electrons very heavy. In this project, we have studied X-ray diffraction, lowtemperature specific heat, magnetic susceptibility, electrical resistivity, magnetoresistance, thermoelectric power and X-ray photo electron spectroscopy of amorphous (a-) Ce alloys. We obtained the following results. 1) The electronic specific heat coefficient, gamma, is much larger in a-Ce-Cu, a-Ce-Si and a-Ce-Ru alloys than in a-La alloys, demonstrating the importance of 4f electrons in the heavy electron systems. 2) In the a-Ce-Cu alloys, the random structure disturb the electron correlation to result in an impurity or incoherent Kondo (IK) state. 3) In the a-Ce-Si alloys, a rather strong Kondo effect displays a signature of a coherent Kondo (CK) state, but still an IK state is realized due to their random structures. 4) In the a-Ce-Ru alloys, the mixing of 4f and conduction electrons and their correlation are so strong that a CK state and a superconducting state are realized. 5) The interatomic distance between Ce atoms decreases with increasing Ce concentration, while those for Ce-Cu, Ce-Si and Ce-Ru are insensitive to the alloy concentrations. The coordination numbers around Ce atoms are smaller in the amorphous states than in their crystalline counterparts. 6) Valence and core electron spectra indicate that the mixing of 4f and conduction electrons is enhanced in order, the a-Ce-Cu, a-Ce-Si and a-Ce-Ru alloys. 7) The physical properties of the a-Ce-Ni alloys produced by vapor deposition and liquid quenching are quite different, suggesting that the degree of randomness depends on preparation methods.

在Ce基合金中，f电子与s、p电子混合，它们的强相关性使得传导电子的有效质量非常重。在本项目中，我们研究了非晶（a-）Ce合金的X射线衍射、低温比热、磁化率、电阻率、磁阻、热电势和X射线光电子能谱。我们得到了以下结果。 1) a-Ce-Cu、a-Ce-Si 和 a-Ce-Ru 合金的电子比热系数 γ 比 a-La 合金大得多，这证明了 4f 电子在重电子系统中的重要性。 2）在a-Ce-Cu合金中，随机结构扰乱了电子相关性，导致杂质或非相干近藤（IK）态。 3）在a-Ce-Si合金中，相当强的近藤效应显示出相干近藤（CK）态的特征，但由于其随机结构，仍然实现了IK态。 4)在a-Ce-Ru合金中，4f和传导电子的混合及其关联性非常强，从而实现了CK态和超导态。 5) Ce原子间的距离随着Ce浓度的增加而减小，而Ce-Cu、Ce-Si和Ce-Ru的原子间距离对合金浓度不敏感。无定形状态下 Ce 原子周围的配位数比晶态状态下的要小。 6) 价电子谱和核心电子谱表明，a-Ce-Cu、a-Ce-Si 和 a-Ce-Ru 合金中 4f 电子和传导电子的混合按顺序增强。 7) 气相沉积和液体淬火生产的a-Ce-Ni合金的物理性能有很大差异，表明随机性程度取决于制备方法。