Electronic Properties of Ferromagnetic Pyrite Compounds Fe_<i>x</i>Co_1-<i>x</i>S₂

Abstract

Explanations of the physical properties of solid solutions Fe x Co 1- x S 2 are given by the use of models taking account of the observation that Fe is a highly repulsive impurity atom for 3 d e g electrons on Co atoms. True Fe concentration dependence of the saturation magnetization and of the electronic-specific-heat coefficient are explained by a calculation using the CPA combined with Hartree-Fock approximation. A simple argument making use of the Friedel sum rule is given to discuss the change in the electrical resistivity by Fe impurities in CoS 2 . A density-of-states curve for the e g band of CoS 2 is proposed to account for these properties.