MAGNETIC PROPERTIES OF BINARY DISORDERED ALLOY

Abstract

A model binary alloy Ax B1−x where A and B represent ferromagnetic and paramagnetic transition metal respectively is considered within the framework of periodic Anderson model, and the effects of d-level disorder and variation of electron concentration due to alloying on the magnetic properties are investigated. The phase boundary, thermal behavior of magnetization and susceptibility of the alloy are obtained using HF approximation for the Coulomb interaction and the virtual crystal approximation for d-level disorder. The ferromagnetic state of alloy vanishes at a critical concentration xc which depends on d-band width, strength of s-d hybridization and the Coulomb interaction. The re-entrant magnetic phase is found within a small region of x for alloy with narrow d-band. For x≲xc, the magnetic properties resemble that of spin-glass system. For x≪xc, the alloy behaves like a Pauli paramagnet. The re-entrant and spin-glass-like phases are associated with the increase in d-level population as temperature decreases. Local moment for x≃1 decreases with temperature up to Tc whereas the reverse is the situation for alloy exhibiting spin-glass-like behavior.