Shaping magnetization dynamics in a planar square dot by adjusting its surface anisotropy

TL;DR

This paper investigates how adjusting surface anisotropy on the edges of a simple square magnetic dot can control its spin wave modes and stray fields, aiding in the design of magnetic nanostructures.

Contribution

It demonstrates how surface anisotropy tuning influences fundamental spin wave modes and stray fields in a planar square dot, providing a method to tailor magnetic interactions.

Findings

Surface anisotropy shifts the fundamental mode frequency.

Asymmetric surface anisotropy creates asymmetric stray field profiles.

Finite-element method effectively models these effects.

Abstract

A planar square dot is one of the simplest structures confined to three dimensions. Despite its geometrical simplicity, the description of the spin wave modes in this structure is not trivial due to the competition of dipolar and exchange interactions. An additional factor that makes this description challenging are the boundary conditions depend both on non-local dipolar interactions and local surface parameters such as surface anisotropy. In the presented work, we showed how the surface anisotropy applied at the lateral faces of the dot can tune the frequency of fundamental mode in the planar CoFeB dot, magnetized in an out-of-plane direction. Moreover, we analyzed the spin wave profile of the fundamental mode and the corresponding dynamic stray field. We showed that the asymmetric application of surface anisotropy produces an asymmetric profile of dynamic stray field for square dot and can be used to tailor inter-dot coupling. The calculations were performed with the use of the finite-element method.