Observation of a Bi-Domain State and Nucleation Free Switching in Mesoscopic Ring Magnets

Abstract

We present the results of a study of the magnetic properties of an array of 34-nm thick Co(100) epitaxial ring magnets, with inner and outer diameters of d(in) = 1.3 microm and d(out) = 1.6 microm, respectively. Magnetic measurements and micromagnetic simulations show that a two step switching process occurs at high fields, indicating the existence of two different stable states. In addition to the vortex state, which occurs at intermediate fields, we have identified a new bi-domain state, which we term the onion state, corresponding to opposite circulation of the magnetization in each half of the ring. The onion state is stable at remanence and undergoes a simple and well characterized nucleation free switching.

Closure magnetization configuration around a single hole in a magnetic film

“…2 One common feature in many of these magnetic nanostructures, such as magnetic nanorings, [3][4][5][6] thin films patterned with arrays of antidots, [7][8][9][10][11][12] or magnetic disks with controlled defects, 13 is the existence of nonmagnetic holes within the magnetic material. Most of the attention has been devoted to the analysis of the different magnetic configurations corresponding to each different kind of structure, such as the transitions between in-plane axial and vortex states in nanorings, 14 or the different kinds of periodic closure domain structures in magnetic films with antidots.…”

Vortex core size in interacting cylindrical nanodot arrays

“…Common structures are arrays of wires, [1,2] cylinders, [3,4] rings, [5,6] and tubes. [7,8] Such structures can be tailored to display different stable magnetized states, depending on their geometric details.…”

Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations

“…Generally, the domain wall moves around the perimeter of the rings. 13 As a domain wall starts to move, its stray field can trigger the domain wall motion in an adjacent ring. Thus, the ring with the lowest switching field can cause a cascade of switching inside of the tri-ring structure.…”

“…In the course of field relaxation, the ring switches into a bidomain state referred as an onion state. 13 Here, the magnetization follows the circumference of the ring with opposite senses of circulation in the two halves of the ring. Two opposite head-tohead Néel domain walls are formed generating a stray field.…”

“…14,15 After removing the field, the onion state remains stable at remanence. 13 When a reverse field is applied, ideally both domain walls should move in the same direction around the ring. However, due to imperfections in patterned rings, which always exist in real experiments, one wall will be more strongly pinned than the other.…”