  Transmission of microwave spin waves through a microstructured magnonic
crystal in the form of a permalloy waveguide of a periodically varying width
was studied experimentally and theoretically. The spin wave characteristics
were measured by spatially-resolved Brillouin light scattering microscopy. A
rejection frequency band was clearly observed. The band gap frequency was
controlled by the applied magnetic field. The measured spin-wave intensity as a
function of frequency and propagation distance is in good agreement with a
model calculation.

Mesoscale and Nanoscale Physics;Other Condensed Matter