Vortex polarity switching in magnets with surface anisotropy

Abstract

Vortex core reversal in magnetic particle is essentially influenced by a surface anisotropy. Under the action of a perpendicular static magnetic field the vortex core undergoes a shape deformationof pillow-or barrel-shaped type, depending on the type of the surface anisotropy. This deformation plays a key point in the switching mechanism: We predict that the vortex polarity switching is accompanied (i) by a linear singularity in case of Heisenberg magnet with bulk anisotropy only and (ii) by a point singularities in case of surface anisotropy or exchange anisotropy. We study in details the switching process using spin-lattice simulations and propose a simple analytical description using a wired core model, which provides an adequate description of the Bloch point statics, its dynamics and the Bloch point mediated switching process. Our analytical predictions are confirmed by spin-lattice simulations for Heisenberg magnet and micromagnetic simulations for nanomagnet with account of a dipolar interaction.

Boundary conditions for the Néel order parameter in a chiral antiferromagnetic slab

“…4(i). Note, that a similar shape distortion is observed for vortices in easy-plane ferromagnets with surface anisotropy [66,67].…”

Experimental observation of the curvature-induced asymmetric spin-wave dispersion in hexagonal nanotubes

“…While many of the aforementioned effects have been investigated mostly in bulk or in flat thin-film samples, over the last decade, curvature induced effects have been uncovered as a new way to manipulate magnetic equilibria as well as spin dynamics. Numerous theoretical and numerical works have already shown that the surface curvature of magnetic membranes leads to phenomena which are not present in flat geometries of the same material [19][20][21][22][23][24][25][26][27][28]. As a result of the bending, in conventional soft magnetic materials exotic non-collinear magnetic textures such as skyrmions [29] may be stabilized or magnetisation dynamics can be influenced, leading to left-right symmetry breaking of domain wall motion [19,20], asymmetric spin-wave transport [25,30] or the emergence of a topological Berry phase [31].…”