Paramagnetic-ferromagnetic transition in a double-exchange model

We study the paramagnetic-ferromagnetic transition due to exchange interaction between classical localized magnetic moments and conduction electrons. We formulate the dynamical mean field approximation equations for the arbitrary electron dispersion law, concentration, and relation between exchange coupling and the electron bandwidth. Solving these equations we find an explicit formula for the transition temperature T-c. We present the results of calculations of T-c for the semicircular electron density of states.