Resonance and Reversal Phenomena in Ferromagnetic Films

Abstract

For fields several times the coercive force, magnetization reversal in thin films takes place by domain rotation. A phenomenological theory based on a modification of the Landau-Lifshitz equation of motion shows that the reversal time for this type of magnetization reversal will be proportional to the damping constant of the modified equation of motion. This damping constant is in turn proportional to the ferro-magnetic resonance absorption line width. Experimental measurements on evaporated films of three different alloy compositions demonstrate this predicted proportionality of the reversal time and the resonance line width.The shift in the value of the resonant field strength at constant frequency as a function of film thickness was also investigated. This shift can be attributed to a decrease in the saturation magnetization, $4\ensuremath{\pi}{M}_{0}$. The results indicate that the saturation magnetization remains reasonably constant down to a film thickness of about ${10}^{\ensuremath{-}5}$ cm, and then decreases rapidly. The resonance line widths of the thickest and the thinnest films tested of a given composition were about the same.