Micromagnetic simulation studies of ferromagnetic part spheres

Abstract

Self-assembly techniques can be used to produce periodic arrays of magnetic nanostructures. We have developed a double-template technique using electrochemical deposition. This method produces arrays of dots which are of spherical shape, as opposed to those prepared by standard lithographic techniques, which are usually cylindrical. By varying the amount of material that is deposited electrochemically, spheres of diameter d can be grown up to varying heights h Ͻ d. Thus different spherical shapes can be created ranging from shallow dots to almost complete spheres. Using micromagnetic modeling, we calculate numerically the magnetization reversal of the soft part spherical particles. The observed reversal mechanisms range from single domain reversal at small radii to vortex movement in shallow systems at larger radii and vortex core reversal, as observed in spheres at larger heights. We present a phase diagram of the reversal behavior as a function of radius and growth height. Additionally, we compare simulation results of hybrid finite element/boundary element and finite difference calculations for the same systems.

Micromagnetic modelling of ferromagnetic cones

“…where the magnetization circulates in the yz plane and the vortex core points in the x direction) shown at point A. The same behavior is observed for the magnetization reversal of spheres [6,9] of similar size. Note that this configuration is not observed in cones in the absence of an applied field and therefore this state is not shown in figure 1.…”

“…A number of two-and threedimensional shapes have been investigated experimentally and theoretically as candidates for novel patterned media, magnetic sensors and other nanomagnetic materials and devices. This includes cylinders and discs [1][2][3][4] , spheres [5][6][7], part-spheres [8,9], triangles [10] and other polygons [10][11][12].…”

Micromagnetic simulation of ferromagnetic part-spherical particles

“…The vortex penetration for these large systems shows behavior which is related to that of spheres and will be described elsewhere. 11 We have studied size dependence by performing micromagnetic simulations on droplets of bounding sphere size between 20 and 400 nm. From this study we find that apart from a slight minimisation of the demagnetisation energy at the extremeties, the droplets behave as single domains at 130 nm and below ͑see inset, Fig.…”

Hysteresis loops and reversal modes of two‐phase nanoparticle

“…The reversal mode and magnetic properties of nanoparticles are dependent on their sizes, shapes, and the anisotropy 11, 12. Otherwise, the configurational anisotropy due to the small deviations of the magnetization from the uniform state is found to also influence the reversal mode and coercive force of the particles in some sizes 13.…”