Magnetic properties of disordered Heisenberg binary spin system with long-range exchange

The influence of substitutional disorder on the magnetic properties of disordered Heisenberg binary spin systems with long-range exchange integrals is studied. The equation of motion for the magnon Green's function that is decoupled by the Tyablikov approximation is solved in the Blackman-Esterling-Berk (BEB) coherent potential approximation (CPA) framework, where the environmental disorder term is treated by a virtual crystal approximation. The long-range exchange integrals include a power-law decaying and an oscillating Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction. The resulting spectral density, which is calculated by the CPA self-consistent equation, is then used to estimate the magnetization and Curie temperature. The results show, in the case of the three-dimensional simple cubic systems, a strong influence of ferromagnetic long-range exchange integrals on the magnetization and Curie temperature of the systems, which is obviously different from the calculation of a short-range interaction.