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A Green's function method is used to obtain the spectrum of excitations of two neighboring impurities in a semi-infinite ferromagnet. The equations of motion for Green's functions are determined in the framework of the Heisenberg model. The energies of non-resonant localized modes are calculated as a function of the interaction parameters for the exchange coupling between impurity–spin pairs, host–spin pairs, and impurity–host neighbors, as well as the effective field parameter at the impurity sites. With two impurities the system is less symmetric and has more localized modes when compared with a single impurity case.

A finite-temperature perturbation formalism is employed to study the nonlinear processes for interactions between the discrete spin waves (SW) in ultrathin antiferromagnetic films, taking account of both dipole–dipole and exchange coupling between the spins. Within a microscopic Hamiltonian approach we obtain the dominant three- and four-magnon interactions at low temperatures, and their contributions to the frequency shift and damping (or reciprocal lifetime) of the discrete SW are evaluated. Numerical results applied to MnF2 are presented.

We present calculations for the dipole-exchange spin wave spectrum of two ferromagnetic thin films separated by a non-magnetic spacer. We employ a microscopic model that takes into account the position dependence of the spin sites in each media. The results show the frequency shift and mode mixing caused by the dipolar interaction between the films as a function of spacer thickness, for films with parallel magnetization.

A theory is presented for the effect of surface orientation on the spectra of localized surface spin waves in antiferromagnetic films. The calculations apply to the exchange-dominated regime and exploit properties of banded matrices to find analytic expressions for the spin-wave frequencies.Results are presented for films with a simple-cubic structure for (0 0 1), (0 1 1), and (1 1 1) orientations of the surface planes. The spin-wave characteristics are found to be quite distinct in the three cases.