SPIN-WAVES OF ANISOTROPIC FERRIMAGNETS WITH NEAREST-NEIGHBOR AND NEXT-NEAREST-NEIGHBOR INTERACTIONS

An anisotropic Heisenberg model with nearest neighbor and next-nearest neighbor interactions is introduced to study the spin wave spectra of two-sublattice ferrimagnets. The matrix Green function is applied to deal with the NaCl- and CsCl-type ferrimagnets. The results show that the spin wave spectra separate into two branches, and the numerical ca lculation at finite temperature indicates that the absolute value of t he spin wave energy increases with increasing extension and strength o f the exchange interactions. It is found that the influences of the ne xt-nearest neighbor and anisotropic interactions are quite different. Simultaneously, the influences of the structure and the temperature ar e discussed.