Dynamics of magnetization reversal in thin polycrystallineNi80Fe20films

Abstract

The dynamic magnetization reversal behavior of polycrystalline ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ films (thickness 60 and 200 \AA{}) was studied in the temperature range 90--300 K by applying a magnetic field along the easy magnetization axis of the samples. The loop area A is found to follow the scaling relation $A\ensuremath{\propto}{H}_{0}^{\ensuremath{\alpha}}{\ensuremath{\Omega}}^{\ensuremath{\beta}}{T}^{\ensuremath{-}\ensuremath{\gamma}}$ with $\ensuremath{\alpha}\ensuremath{\approx}0.9,$ $\ensuremath{\beta}\ensuremath{\approx}0.8,$ and $\ensuremath{\gamma}=0.38$ for both thicknesses. This behavior is only qualitatively consistent with theoretical models if the magnetization reversal mechanism is identical for both films, independently of the applied field and sample temperature. The observed scaling exponent values indicate that domain nucleation and domain-wall motion process dominate the magnetization reversal process, which is not included in current theoretical models based on coherent rotation. Furthermore, the exponents \ensuremath{\alpha} and \ensuremath{\beta} are found to be independent of the temperature, indicating that the dynamic reversal mechanism is unchanged in this temperature range.