Magnetic hysteresis dynamics in Ni80Fe20 films

The dynamic magnetization reversal behavior of polycrystalline Ni80Fe20 films (thickness 60 and 200 A) 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 ∝ HoαΩβT-γ with α = 0.9, β = 0.8, and γ = 0.38 for both thicknesses, where Ho is the magnetic field amplitude, Ω 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 α and β 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 βHA = 0.47 ±0.02