Charge Transfer and Spin Susceptibility in a Binary Alloy: The Wolff Model

Abstract

The coherent-potential approximation has been employed to discuss itinerant-electron magnetism of binary alloys by use of diagram techniques, which make clear the meanings of, and the differences between, the formulations by Hasegawa and Kanamori (HK), Levin etal. and Harris and Zuckermann. These diagram techniques make it easy to obtain the wave-vector and frequency-dependent susceptibility for the Wolff model at finite impurity concentrations. The results reduce to that of HK in the uniform and static limit. The formula enables us to discuss on the same footing both local exchange enhancement and paramagnons by changing the concentration of magnetic atoms. It is also shown that the charge transfer has some important consequences. By use of this susceptibility, the possibility of the spin-density-wave state has been discussed in similar ways as Penn's argument for pure systems. It is found that the occurrence of magnetic states is essentially related not to the total density of states but to the local density of states. In addition to the static properties, the diffusion constant of spin fluctuations is discussed in relation to the electronic specific heat.