Spin wave propagation in spatially nonuniform magnetic fields

Spin wave pulse propagation in a magnetic thin film under static, spatially nonuniform magnetic fields has been studied. The experiment was carried out with an yttrium iron garnet film strip. The film strip was magnetized with a spatially nonuniform magnetic field parallel to the length of the film strip. Spin wave pulses were excited with a microstrip transducer at one end of the film strip. The spin wave pulse propagation along the film strip was mapped with a high-resolution time- and space-resolved inductive magnetodynamic probe. The wave number for the spin wave pulses was found to increase in a spatially increasing field and decrease in a spatially decreasing field. The wave number change in a static, general spatially varying static field is reversible for this field-film geometry. The phase velocity was found to decrease in a spatially increasing magnetic field and increase in a spatially decreasing field. The carrier frequency of the spin wave pulses remained constant throughout pulse propagation. (C) 2008 American Institute of Physics.