Spin dynamics of anisotropic azimuthal modes in heterogeneous magnetic nanodisks

TL;DR

This paper investigates cubic azimuthal spin wave modes in heterogeneous magnetic nanodisks with a permalloy core and Fe shell, revealing faster vortex switching and unique core dynamics due to induced anisotropy.

Contribution

It demonstrates the emergence of fourfold symmetric cubic azimuthal modes in heterogeneous nanodisks, contrasting with traditional circular modes, and explores their impact on vortex dynamics.

Findings

Cubic azimuthal modes exhibit fourfold symmetry due to exchange and magneto-static interactions.

Vortex switching occurs faster with cubic azimuthal modes compared to circular modes.

Vortex core gyration path becomes square, with periodic oscillations in size and speed.

Abstract

It is well known that azimuthal spin wave modes of magnetic vortex state in permalloy nanodisks have circular symmetry. Intuitively, magnetic materials having magnetocrystalline anisotropy is not compatible with the circular symmetry of the azimuthal modes. In this article, however, we report cubic azimuthal modes in heterogeneous nanodisks consisting of a permalloy core and a Fe shell. The fourfold symmetry of azimuthal modes is due to the exchange, and magneto-static, interactions between the permalloy core and the Fe shell. In comparison to results of circular azimuthal mode, the vortex switching occurs considerably faster under the excitation of cubic azimuthal mode. The gyration path of vortex core turns into square under the influence of induced cubic anisotropy in the Py region. We find out periodic oscillation of the vortex core size and the gyration speed as well. Our findings may offer a new route for spintronic applications using heterogeneous magnetic nanostructures.