A Calculation of the Spin Wave Energy in fcc Fe-Ni Alloys

Abstract

An expression of the exchange stiffness constant of spin waves in disordered ferromagnetic alloys is obtained in the combined approximation of the random phase approximation and the coherent potential approximation. Both the diagonal randomness and the off-diagonal randomness are taken into account. By using the realistic band structures, the exchange stiffness constants in fcc Fe-Ni alloys are calculated numerically. The difference between the observed and calculated values of the exchange stiffness constants in fcc Fe-Ni alloys is attributed to the inter-atomic exchange interaction between d-electrons.