Magnetic spin states and vortex stability control in elongated Ni 80Fe20 nanorings

Abstract

We present the results of a systematic characterization of the magnetization reversal mechanism of arrays of elongated Ni80 Fe20 nanorings using focused magneto-optical Kerr effect measurements. The long axis of the rings was varied from 850 nm to 1.60 μm while the aspect ratio, ring width, and thickness were fixed at 2, 150 nm, and 25 nm, respectively. We observed an increase in the range of stability of the intermediate vortex state with both increasing length (l) of the ring and varying field orientations. Interestingly, for l he reversal process drastically changes from a two-step switching to a single step switching without the formation of a vortex state and from a one-step switching to a double step switching with the formation of a vortex state when the applied field is (±5°) away from the easy and hard axes of the ring, respectively. There is a good agreement between the experimental results and micromagnetic simulations. © 2009 American Institute of Physics.