Arrays of epitaxial Co submicron particles: Critical size for single-domain formation and multidomain structures

Abstract

Arrays of Co particles with well-defined geometry and lateral sizes in the range 0.1–0.5 μm were prepared by electron beam lithography and studied by magnetization measurements and magnetic force microscopy. The starting materials were epitaxial Co films, with in-plane magnetic anisotropy, having thicknesses in the range 10–50 nm. The particles change from multidomain behavior to that of stable single domains in zero field, as the lateral dimension decreases within these ranges. For particles of circular shape, i.e., without in-plane shape anisotropy, the critical size for forming single domains was found to be about 200 nm in lateral extension and 20 nm thickness. Elliptical particles prepared with 20 nm thickness and lateral dimensions 150 by 450 nm were found to be stable single domains, of good uniformity, in zero field. The switching of these particles from one magnetization direction along the long axis to the other, requires an applied field BS≈(100±20)mT. A comparison with other published results leads to the conclusion that although the critical volume for single domains may be about the same, the final microscopic magnetic structure and the processes for magnetic switching for particles in the actual range of sizes, are strongly governed by the intrinsic properties of the Co films, which may vary widely.

Magnetic domain states in nano-sized Co nuclei electrodeposited onto monocrystalline silicon

“…5 give valuable experimental information on the influence of the shape, through h and D, on the magnetic domain states of the nuclei. This is in concordance with previous works in which the special importance of shape anisotropy in determining the magnetic properties of nanostructured elements has been emphasized [11,27,28].…”

Fabrication of a Class of Nanostructured Materials Using Carbon Nanowalls as the Templates

“…The curves in both directions exhibit typical characteristics of nanomagnetic arrays. [12] The curve along the nanowall direction is more highly sheared as compared to that in the sample surface direction, suggesting a strong magnetostatic interaction in the wall direction. This is understandable because the nanospheres are closely packed on the walls, whereas the distance between the nanospheres in the sample surface direction is relatively large, as it is determined by the spacing between the walls.…”

Energetics of magnetic ring and disk elements: Uniform versus vortex state

“…In this context, the onset of quasi-uniform magnetic states as a function of the element size and geometry is of particular interest as is the determination of the boundary that separates the stability regions of such states, since this allows one to controllably select a given magnetic state by choosing adequate geometrical parameters. [21][22][23][24][25][26][27] However, such a boundary depends on a whole range of intrinsic and extrinsic factors, such as the physical dimensions, material, edge and surface roughness, defects, temperature, etc., and the extent to which a given magnetic state may depend on these factors is key. For example, the equilibrium states of rings and disks are now understood to depend strongly on the presence of defects which act as pinning sites for the magnetization, thereby stabilizing magnetic states which are not the lowest in energy; 28 this is case with the "onion" state in rings 14,15 and the diamond and triangle state in disks.…”