Magnetization dynamics and domain reversal in electrodeposited permalloy thin films: impact of thickness and annealing treatment

The domain reversal and magnetization dynamics of electrodeposited permalloy (Fe20Ni80) thin films on conducting ITO/glass substrate was investigated using Magneto-optic Kerr effect microscopy and ferromagnetic resonance. Permalloy thin films were electrodeposited with thickness ranging from 66 nm to 330 nm. Synchrotron XRD confirmed the deposited permalloy in FCC phase without any impurity. The squared hysteresis with very low coercivity (Hc similar to 5 Oe) established soft magnetic nature of the films. Further, angular MOKE hysteresis measurements with simultaneous domain imaging revealed four-fold surface anisotropy in as-deposited film ensuing magnetization reversal via branched and ripple domains. The annealing treatment in Ar+H2 atmosphere removed surface anisotropy and renovated the magnetization reversal through 180 degrees branched domains with rapid magnetization switching. Ferromagnetic resonance spectroscopy discloses reduction in the gyromagnetic ratio (gamma) as well as in Gilbert damping parameter (alpha) as the film thickness increases. The lowest Gilbert damping for 330 nm film measured at 0.022, which further reduced to 0.018 after annealing. The combination of rapid magnetization switching and low Gilbert damping in the electrodeposited permalloy thin films render them promising for implementation in high-frequency microwave devices devices and magnetic sensors.