Thickness-Dependent Evolution of Magnetization Reversal in Micron-Scale Polycrystalline Fe Rings

The evolution of magnetic switching mechanism is investigated for micron-scale polycrystalline Fe ring arrays with Fe layer thickness, t Fe , varying between 10 nm and 50 nm. Single-step and double-step switching are observed for the 10 nm and 50 nm rings, with the 30 nm sample showing a transient behavior. As thickness increases, the first-step switching field, H c1 , increases, while the second-step switching field, H c2 , and remanent magnetization, M r decreases. Magnetic force microscopy imaging and micromagnetic simulations reveal that in the reversal process, H c1 and H c2 correspond to the switching fields of two distinct halves of the ring. The relative separation between these two fields decides the switching behavior of the ring.