Controlled anisotropic dynamics of tightly bound skyrmions in a synthetic ferrimagnet due to skyrmion-deformation mediated by induced uniaxial in-plane anisotropy

TL;DR

This paper investigates how in-plane uniaxial anisotropy influences the shape, speed, and deflection of tightly bound skyrmions in synthetic ferrimagnets, revealing tunable anisotropic dynamics through skyrmion deformation.

Contribution

It introduces a method to control skyrmion dynamics via induced anisotropy, combining micromagnetic simulations and analytical models to demonstrate tunability.

Findings

Skyrmion deformation affects speed and deflection.

Induced anisotropy enables wide-range skyrmion tunability.

Deformation can cause deflection unrelated to topological charge.

Abstract

We study speed and skew deflection-angle dependence on skyrmion deformations of a tightly bound two-skyrmion state in a synthetic ferrimagnet. We condsider here, an in-plane uniaxial magnetocrystalline anisotropy-term in order to induce lateral shape distortions and an overall size modulation of the skyrmions due to a reduction of the effective out-of-plane anisotropy, thus affecting the skyrmion speed, skew-deflection and inducing anisotropy in these quantities with respect to the driving current-angle. Because of frustrated dipolar interactions in a synthetic ferrimagnet, sizeable skyrmion deformations can be induced with relatively small induced anisotropy constants and thus a wide range of tuneability can be achieved. We also show analytically, that a consequence of the skyrmion deformation can, under certain conditions cause a skyrmion deflection with respect to driving-current angles, unrelated to the topological charge. Results are analyzed by a combination of micromagnetic simulations and a compound particle description within the Thiele-formalism from which an over-all mobility tensor is constructed. This work offers an additional path towards in-situ tuning of skyrmion dynamics.