Effective anisotropy of thin nanomagnets: beyond the surface anisotropy approach

TL;DR

This paper investigates the effective anisotropy in thin nanomagnets caused by nonlocal dipole interactions, simplifying the energy to an inhomogeneous onsite anisotropy and validating the model with simulations.

Contribution

It introduces a simplified model for effective anisotropy in nanomagnets that accounts for nonlocal dipole effects beyond surface anisotropy, validated by simulations.

Findings

Vortex solutions are ground states in the model.

Good agreement between spin-lattice and micromagnetic simulations.

Effective anisotropy can be modeled as an inhomogeneous onsite anisotropy.

Abstract

We study the effective anisotropy induced in thin nanomagnets by the nonlocal demagnetization field (dipole-dipole interaction). Assuming a magnetization independent of the thickness coordinate, we reduce the energy to an inhomogeneneous onsite anisotropy. Vortex solutions exist and are ground states for this model. We illustrate our approach for a disk and a square geometry. In particular, we obtain good agreement between spin-lattice simulations with this effective anisotropy and micromagnetic simulations.