Nanostructured magnonic crystal with magnetic-field tunable bandgap

Most experimental investigations into magnonic bandgaps are based on structures composed of single-constituent magnetic materials. Here we report Brillouin and numerical studies of the spin dynamics of a bi-component magnonic crystal, viz. a one-dimensional periodic array of alternating permalloy and cobalt 150 nm-wide nanostripes. Our measurements, together with those for a similar crystal composed of 250 nm-wide nanostripes, suggest that for a stripe width ratio of 1:1, the bandgap width of such magnonic arrays increases with crystal lattice constant. The bandgap parameters are strongly dependent on external magnetic field. This magnetic-field tunability of the bandgap is expected to be a crucial property of devices based on magnonic crystals. The agreement between numerical calculations, based on finite element analysis, and the experimental data is generally good.