Magnetic hysteresis dynamics in Ni80Fe20 thin films

Abstract

The dynamic magnetization reversal behavior of polycrystalline Ni80Fe20 films (thickness 60 and 200 Angstrom) was studied in the temperature range 90 similar to 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 proportional to H(0)(alpha)Omega T-beta(-gamma) with alpha approximate to 0.9, beta approximate to 0.8, and gamma = 0.38 for both thicknesses, where H-0 is the magnetic field amplitude, Omega is frequency, and T is temperature, 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 exponents alpha and beta are found to be independent of the temperature, indicating that the dynamic reversal mechanism is unchanged in this temperature range. The hard-axis loop also evolves with increasing frequency, and the loop areas of the hard axis obey the scaling relation with beta (HA) = 0.47 +/- 0.02.