Electronic structure and magnetic properties of RCo_(5-x)M_x (R=Y, Pr and M=A1, Si) system

摘要

Detailed theoretical and experimental investigations of the electronic and magnetic properties of the RCo_(5-x)M_x compounds (R=Y, Pr and M=Si, Al) have been performed. All theoretical investigations of the electronic and magnetic properties of the system have been done using the Korringa-Kohn-Rostoker (KKR) band structure method. The Si for Co substitution in RCo_5 does not change the magnetic ordering: the RCo_(5-x)Si_x with R=Y, Nd and Pr is ferromagnetic, whilst the heavy rare-earth containing compounds are ferrimagnetic. The important modifications induced by this substitution concerns the magnetic properties of the system: the Curie temperature and the magnetic moments of Co decrease with Si content, indicating the weakening of the Co-Co exchange interaction. The band structure calculations evidence the hybridization between the 3d electronic states of Co and the 3p states of Si as possible reason for the diminishing of Co-Co exchange interaction. Also, the volume effect on the magnetic properties of the YCo_4Si was investigated using theoretical methods. The results are compared with the experimental measurements in order to distinguish the origin of magnetization reduction in YCo_4Si compared with YCo_4Al.