The effect of lattice structure on dipole-exchange spin waves in ultrathin ferromagnetic films

Calculations are reported relating to the dipole-exchange spin waves in ultrathin ferromagnetic films with different lattice structures such as simple cubic, body-centred cubic and face-centred cubic, using a microscopic, or Hamiltonian-based, theory. Both the short-range exchange and the long-range dipolar interactions are included in the Hamiltonian, together with an external magnetic field applied either parallel or perpendicular to the film surfaces. The use of phenomenological dipole-exchange boundary conditions, as in macroscopic theories, is avoided. Comparisons between our results and macroscopic theories generally give good agreement in a small wavevector limit. At larger wavevectors for the microscopic theory, it is found that the frequencies and the localization properties of the discrete spin waves show a sensitive dependence on the lattice structure.