Ferromagnetic transition in a double-exchange system containing impurities

We study the ferromagnetic transition in a three-dimensional double-exchange model containing impurities. The influence of both spin fluctuations and the impurity potential on conduction electrons is described in a coherent potential approximation. In the framework of the thermodynamic approach we construct a Landau functional for the system “electrons (in disordered environment) + core spins.” Analyzing the Landau functional we calculate the temperature of the ferromagnetic transition (formula presented) and paramagnetic susceptibility χ. For (formula presented) we thus extend the result obtained by Furukawa in the framework of the dynamical mean-field approximation, with which our result coincides in the limit of zero-impurity potential. We find that alloy disorder, able to produce a gap in the density of electron states, can substantially decrease (formula presented) with respect to the case of no impurities.