Thickness-dependent evolution of magnetization reversal in micron-scale polycrystalline Fe rings

Abstract

The evolution of magnetic switching mechanism is investigated for micron-scale polycrystalline Fe ring arrays with Fe layer thickness, tFe, 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, Hc1, increases, while the second-step switching field, Hc2, and remanent magnetization, Mr decreases. Magnetic force microscopy imaging and micromagnetic simulations reveal that in the reversal process, Hc1 and Hc2 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.