Dynamic magnetization properties of a superferromagnetic metal-insulator multilayer observed by magneto-optic Kerr microscopy

摘要

Longitudinal magneto-optical Kerr effect (MOKE) magnetometry and microscopy have been performed on a superferromagnetic (SFM) metal-insulator multilayer of [Co_(80)Fe_(20)(t_n=1-3 nm)/ Al_2O_3(3 nm)]_(10) to understand the dynamic behavior of the SFM domains. Frequency dependent hysteresis loops measured by MOKE show that the coercive field H_c increases as the rate (frequency) of magnetization reversal is increased similar to dynamic hysteresis loops observed on conventional ferromagnetic ultrathin films. This dynamic hysteresis behavior arises due to SFM friction-controlled domain wall motion which is observed by MOKE microscopy. We see that the nucleation field for SFM domains increases for hysteresis loops with higher frequency as expected for a ferroic system.