  The application of Brillouin light scattering to the study of the spin-wave
spectrum of one- and two-dimensional planar magnonic crystals consisting of
arrays of interacting stripes, dots and antidots is reviewed. It is shown that
the discrete set of allowed frequencies of an isolated nanoelement becomes a
finite-width frequency band for an array of identical interacting elements. It
is possible to tune the permitted and forbidden frequency bands, modifying the
geometrical or the material magnetic parameters, as well as the external
magnetic field. From a technological point of view, the accurate fabrication of
planar magnonic crystals and a proper understanding of their magnetic
excitation spectrum in the GHz range is oriented to the design of filters and
waveguides for microwave communication systems.
