Spin waves in a periodically layered magnetic nanowire

We report a simple theoretical derivation of the spectrum and damping of spin waves in a cylindrical periodically structured magnetic nanowire (cylindrical magnonic crystal) in the “effective-medium” approximation. The dependence of the “effective” magnetic parameters upon the individual layer parameters is shown to be different from the arithmetic average over the volume of the superlattice. The formulas that are obtained can be applied firstly in the description of spin-wave dispersion in the first allowed band of the structure and secondly in the design of a magnonic crystal with band gaps in an arbitrary part of the spin-wave spectrum.