SPIN-WAVE SPECTRA IN SEMIINFINITE MAGNETIC SUPERLATTICES WITH NONUNIAXIAL SINGLE-ION-ANISOTROPY

A microscopic theory, based on the Heisenberg model, is employed to investigate the spin wave spectra in a semi-infinite superlattice made up of two ferromagnetic materials, where the constituents may present both the uniaxial and nonuniaxial components of the single-ion anisotropy. Our calculations are carried out for the exchange-dominated regime, and a transfer-matrix approach is used to simplify the algebra, which otherwise could be quite heavy. The calculated spectra show that, in addition to bulk spin wave modes, there may be surface modes associated with the truncation of the superlattice.