Magnetization switching dynamics depending on as-patterned magnetization state in magnetic thin-film elements

Magnetization configuration and magnetic switching dynamics of submicrometer "Pac-man"-shaped Ni₈₀Fe₂₀ elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy (MFM), magnetooptic Kerr effect (MOKE), and micromagnetic simulations. It was found that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct magnetization configurations and magnetic switching mechanisms (in low frequencies), even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal. Fast magnetization reversal is, however, found to be slightly dependent on as-patterned domain configurations. For all elements investigated, the fast reversal leads to very complex nonequilibrium domain configurations.