MULTIPLE-SCATTERING APPROACH TO THE S-F MODEL IN FERROMAGNETIC SEMICONDUCTORS ABOVE THE CURIE-TEMPERATURE

For the s-f model in ferromagnetic semiconductors, it is necessary to treat simultaneously multiple scattering on the same site and scatteri ng due to f spin correlation between different sites. In this paper, o ne-site multiple scattering is taken into account using a t-matrix for malism, and the exchange scattering via f spin correlation between dif ferent sites is treated using a two-spin correlation function and an a ppropriate decoupling scheme. The results show good agreement with tho se of the coherent potential approximation in the high-temperature lim it. The calculated energy of the bottom of the band is reasonable, eve n at the Curie temperature (T-c), for a wide range of IS/W, where W is the bandwidth of the conduction band and IS is the exchange interacti on energy.