Magnetization dynamics in NiFe thin films induced by short in-plane magnetic field pulses

The magnetization dynamics in a thin NiFe film was investigated by applying short in-plane magnetic field pulses while probing the response using a ti me-resolved magneto-optical Kerr effect setup. In-plane magnetic field puls es, with duration shorter than the relaxation of the system, were generated using a photoconductive switch and by subsequent propagation of current pu lses along a waveguide. The field pulses with typical rise and decay times of 10-60 and 500-700 ps, respectively, have a maximum field strength of 9 O e, by which Permalloy elements of 16 nm thickness and lateral dimensions of 10 x 20 mum were excited. The observed coherent precession of a ferromagne tic NiFe system had precession frequencies of several GHz and relaxation ti mes on a nanosecond time scale. The dynamic properties observed agree well the Gilberts's precession equation and the static magnetic properties of th e elements (C) 2001 American Institute of Physics.