Temperature gradient-driven magnetic skyrmion motion

TL;DR

This paper explores how temperature gradients influence skyrmion motion, revealing different behaviors in single-layer and multilayer ferromagnets due to entropic torques and material parameter scaling.

Contribution

It advances the understanding of temperature gradient-driven skyrmion dynamics by identifying entropic torque effects and contrasting behaviors in different multilayer structures.

Findings

Skyrmions move towards higher temperatures in single-layer ferromagnets.

In multilayers, skyrmions move towards lower temperatures.

The opposite behaviors are due to different scaling of magnetic parameters and magnetostatic fields.

Abstract

The static and dynamic properties of skyrmions have recently received increased attention due to the potential application of skyrmions as information carriers and for unconventional computing. While the current-driven dynamics has been explored deeply, both theoretically and experimentally, the theory of temperature gradient-induced dynamics - Skyrmion-Caloritronics - is still at its early stages of development. Here, we move the topic forward by identifying the role of entropic torques due to the temperature dependence of magnetic parameters. Our results show that, skyrmions move towards higher temperatures in single-layer ferromagnets with interfacial Dzyaloshinski-Moriya interactions, whereas, in multilayers, they move to lower temperatures. We analytically and numerically demonstrate that the opposite behaviors are due to different scaling relations of the material parameters as well as a non-negligible magnetostatic field gradient in multilayers. We also find a spatially dependent skyrmion Hall angle in multilayers hosting hybrid skyrmions due to variations of the thickness dependent chirality as the skyrmion moves along the temperature gradient.