Institute of Molecular Physics, Polish Academy of Science, M Smoluchowskiego 17, PL-60-179 Poznań, Poland.
J Phys Condens Matter. 2012 Apr 4;24(13):136003. doi: 10.1088/0953-8984/24/13/136003. Epub 2012 Mar 9.
We report on the magnetic ac/dc susceptibility and specific heat measurements for the CeCu(4)Mn(y)Al(1-y) series of compounds with 0 ≤ y ≤ 1. All compounds investigated crystallize in the hexagonal CaCu(5)-type structure with the space group P6/mmm. The results reveal that the frustration of the interactions dominates and leads to a spin-glass (SG) behaviour with a linear change of the freezing temperature T(f) as a function of y. The SG state has been confirmed by the frequency dependence of the ac magnetic susceptibility, the relaxation of the remanent magnetization and the split of the field-cooled-zero-field-cooled dc magnetic susceptibility. The electronic specific heat coefficient γ is enhanced for all y and increases with the Al content. Below a threshold at y ≈ 0.3, γ is large even if determined for temperatures above T(f); moreover the paramagnetic Curie-Weiss temperature θ(p) changes sign to negative. These observations indicate the possible presence of the heavy fermion (HF) state, at least below y ≈ 0.3, and the possible coexistence of the SG and HF states down to y = 0, i.e. for the CeCu(4)Al compound. A tentative magnetic phase diagram for CeCu(4)Mn(y)Al(1-y) has been constructed.
我们报告了 CeCu(4)Mn(y)Al(1-y) 系列化合物的交流/直流磁磁化率和比热测量结果，其中 0 ≤ y ≤ 1。所有研究的化合物都结晶为具有空间群 P6/mmm 的六方 CaCu(5)-型结构。结果表明，相互作用的挫折占主导地位，导致自旋玻璃（SG）行为，其特征是冻结温度 T(f)随 y 的线性变化。SG 状态通过交流磁化率的频率依赖性、剩余磁化强度的弛豫和场冷却-零场冷却直流磁化率的分裂得到证实。电子比热系数 γ 对所有 y 都增强，并随 Al 含量增加而增加。在 y ≈ 0.3 的阈值以下，即使在高于 T(f)的温度下确定，γ 也很大；此外，顺磁居里-外斯温度 θ(p)变为负值。这些观察结果表明，至少在 y ≈ 0.3 以下可能存在重费米子（HF）态，并且在 y = 0 以下，即 CeCu(4)Al 化合物，可能同时存在 SG 和 HF 态。已经构建了 CeCu(4)Mn(y)Al(1-y) 的暂定磁相图。
