Nonlinear magneto-optic measurement of flux propagation dynamics in thin Permalloy films

Time-resolved nonlinear optics are used to study the propagation of magnetic flux pulses in a 250 nm Permalloy film. The flux is generated in the film by coupling it to a coplanar waveguide structure driven with broadband voltage pulses. Flux pulses propagated in the film with a phase velocity of 4.2x10(5) m/s and a group velocity of 1.5x10(5) m/s. Both velocities are consistent with the predictions of Damon-Eshbach theory for magnetostatic surface waves with 200-300 mum wavelengths. Within 100 mum of the excitation source, flux pulses decayed monotonically but with no measurable delay. (C) 2002 American Institute of Physics.