Precession dynamics in NiFe thin films, induced by short magnetic in-plane field pulses generated by a photoconductive switch.

Abstract

Short magnetic in-plane field pulses were used to pull the magnetic spin system of a NiFe film out of its equilibrium state and to initiate coherent magnetisation dynamics. This field induced dynamics was investigated by means of a time-resolved pump-probe experiment, measuring the linear Kerr effect with a balanced photodiode scheme. Precession frequencies of several GHz and relaxation-times in the nanosecond range were observed. Emphasis is on the generation of the short magnetic in-plane field pulses. They were generated using an ultrafast photoconductive switch based on GaAs and launched by a waveguide to the sample. The waveguide and the photoswitch were designed to yield as large as possible magnetic field strengths. The field pulses used in this work had a rise time of 10-60ps, a decay time of 500-700ps and a maximum field strength of 9Oe.