Damped free oscillations of the magnetization have been clearlyobserved at the completion of 180° flux reversal along both the easyand the hard axis in Ni-Fe thin films. The flux component perpendicularto the applied pulse field was observed using a single turn pickuploop around the film. The frequency of the oscillation was studiedas a function of applied pulse field and compared with the results obtainedby ferromagnetic resonance. The frequency of the damped freeoscillation agreed quite well with that obtained by resonance when thefrequency was measured after the oscillation had damped to small amplitude.The damping constant obtained from the decay of the oscillationagreed quite well with that obtained from the half-power line-widthof the resonance curve.
The Landau-Lifshitz equation proposed for the coherent rotation,using the value of the damping constant obtained by resonance, coulddescribe the initial part of the magnetization reversal and the dampedfree oscillation in the films with low angular dispersion. Agreementbetween the experimental and the calculated transverse flux change forthe entire waveform could not be obtained by using the value of dampingconstant obtained by resonance. The agreement was better at bothhigher applied field or lower anisotropy dispersion. The effect ofeddy currents was negligible on the flux reversal but appeared as aslight increase of the damping constant obtained by resonanceexperiment.
