MAGNON BAND-STRUCTURE OF PERIODIC COMPOSITES

We calculate the spin-wave spectra of two-dimensional composite materi als consisting of periodic square arrays of parallel cylinders made of a ferromagnetic material embedded in a ferromagnetic background. Each material is described by its spontaneous magnetization M(S) and excha nge constant A. An external static magnetic field is applied along the direction of the cylinders and both ferromagnetic materials are assum ed to be magnetized parallel to this magnetic field. We consider the s pin-waves propagation in the plane perpendicular to the cylinders. We reveal the existence of gaps in the magnon band structure of composite systems such as the periodic array of Fe cylinders in an EuO matrix. We investigate the existence of these gaps in relation to the physical parameters of the materials involved. We also study the influence of the lattice parameter (i.e., the square array periodicity) and the eff ect of the filling fraction of the cylinders on the magnon band struct ure.