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

The magnetization configurations and reversal dynamics of Ni₈₀Fe₂₀ thin film elements are investigated by magnetic force microscopy (MFM), magneto-optical Kerr effect (MOKE) and micromagnetic simulations. The results from MOKE experiments indicate that there is a striking difference in the switching behavior between "Pac man" shaped elements (PM-I and EPM-I). For the PM-I, the hysteresis loop shows an intermediate jump, which is an indication of the vortex driven reversal process. In contrast to this, the EPM-I element undergoes a coherent switching process, which is characterized by a simple jump from one magnetization state to the other, and the loop shape approaches a perfect square. Micromagnetic simulations based on Landau Liftshitz-Gilbert equation further explain how the magnetic switching dynamics is influenced by distinct as-patterned magnetization state for given element geometries, when the elements undergo ultrafast magnetization reversal. It is found that the half-select switching is strongly dependent on the relative time delay between word and digital pulses.