Disentangling electric field effect on spin waves in ferromagnetic insulators

TL;DR

This paper extends micromagnetic theory to include electric field effects on spin waves in ferromagnetic insulators, identifying two main influences: the Ahronov-Casher effect and symmetry-breaking exchange interactions, supported by experimental comparisons.

Contribution

It introduces a comprehensive theoretical framework that distinguishes two electric field effects on spin wave dispersion in ferromagnetic insulators, highlighting the importance of crystal symmetry breaking.

Findings

The Ahronov-Casher effect influences spin wave dispersion.

Electric field induced symmetry breaking affects exchange interactions.

Experimental data supports the distinct contributions of the two effects.

Abstract

In this paper we extend the micromagnetic theory of magnetostatic surface waves in insulating ferromagnetic thin films to include the applied electric field effects. We start by identifying the two main effects on the dispersion relation: the first one is of relativistic nature and emerges as a consequence of the Ahronov-Casher effect, while the second one is a consequence of the electric field induced symmetry breaking operating at the level of magnetic exchange interactions. We support our theory by comparing its predictions with experimental data on ittrium iron garnet thin films taken from the literature. The main result is to evidence the limitations of using the same value of the applied electric field to address both effects and to emphasize that crystal symmetry breaking due to the applied electric field brings about the contributions of the crystal field and determines different amplitudes for the two effects.