Flux Closure Structures in Cobalt Rings

Abstract

Measurements are reported on the magnetization reversal in submicron magnetic rings fabricated by high-resolution electron beam lithography and lift-off from cobalt thin films. For all dimensions investigated, with diameters of 300-800 nm and a thickness of 10-50 nm, the flux closure state is the stable magnetization configuration. However, with increasing diameter and decreasing film thickness a metastable near single domain state can be obtained during the reversal process in an in-plane applied field.

Magnetization Reversal in Submicron Disks: Exchange Biased Vortices

“…1(a). The constricted loop shape is typical of magnetization reversal via a vortex state [5][6][7][8]. For this sample, no significant differences in the shape of the loop were observed when measuring at different in-plane angles, indicating that the anisotropy of the FM and interdot dipolar interactions were negligible.…”

“…When the size of a magnetic element becomes of the same order as magnetic length scales, such as the domain wall width or the critical single domain size, the multidomain structure encountered in the bulk material becomes energetically unfavorable and either single domain or inhomogeneous magnetization configurations develop instead [1][2][3][4]. A case of particular interest is the formation of vortex states in circular or ring-shaped soft magnetic nanostructures [5][6][7][8]. When the Zeeman energy becomes sufficiently low, the magnetization curls up along the edges of the nanostructure to minimize the lateral stray fields, leading to a flux closure arrangement.…”

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.…”

Ferromagnetic Nanorings

“…As mentioned previously, micrometre size magnetic rings fall into two distinct magnetic states during the magnetization process. While these were originally inferred from MOKE magnetometry and from micromagnetic simulations [6,37], they were subsequently imaged using scanning electron microscopy with polarization analysis (SEMPA) and photoemission electron microscopy (PEEM) [38]. The spin structure of the 180 • domain walls was also determined, and found to be identical to those found by micromagnetic simulations in straight wires [39,40]: while narrow rings exhibit transverse walls (with a fairly uniformly magnetized triangular region separated by sharper 90 • domain walls), wider rings exhibit vortex walls (consisting of a full magnetization vortex); see f gure 3.…”