Theory of a Disordered Heisenberg Model by the Coherent Potential Approximation

抄録

The averaged magnon Green function in a random Heisenberg ferromagnet which has two kinds of exchange integrals J_A and J_B randomly distributed is calculated by the coherent potential approximation. The density of states of magnon is calculated for various cases, and the correct localized mode is obtained in the low concentration limit. The critical concentration is obtained for two cases, J_A>0, J_B<0 and J_A>0, J_B=0. The magnetic properties for the two cases at the critical concentration are different from each other.