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

在ce基合金中，f电子与s和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大。本课题研究了非晶（a-） Ce合金的x射线衍射、低温比热、磁化率、电阻率、磁阻、热电功率和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gamma比a-La合金大得多，说明4f电子在重电子体系中的重要性。2)在a-Ce-Cu合金中，随机结构干扰了电子相关，导致杂质或非相干近藤（IK）态。3)在a- ce - si合金中，具有较强的近藤效应，表现为相干近藤（CK）态，但由于其结构的随机性，仍然实现IK态。4)在a- ce - ru合金中，4f与传导电子的混合及其相关性很强，实现了CK态和超导态。5) Ce原子间距离随Ce浓度的增加而减小，而Ce- cu、Ce- si和Ce- ru原子间距离对合金浓度不敏感。在无定形状态下，Ce原子周围的配位数比在晶体状态下要小。6)价电子能谱和芯电子能谱表明，a-Ce-Cu、a-Ce-Si和a-Ce-Ru合金中4f和传导电子的混合程度依次增强。7)气相沉积法和液相淬火法制备的a-Ce-Ni合金的物理性能差异较大，表明其随机性程度取决于制备方法。

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.