Symmetry of the dissipation of surface acoustic waves by ferromagnetic resonance

TL;DR

This study investigates the symmetry properties of energy dissipation in surface acoustic waves interacting with ferromagnetic resonance in a magnetic film, revealing an unexpected 2-fold symmetry influenced by in-plane anisotropy.

Contribution

It uncovers the origin of the 2-fold symmetry in SAW absorption, linking it to in-plane uniaxial anisotropy in ultrathin magnetic films, expanding understanding of magnetoelastic interactions.

Findings

Discovery of unexpected 2-fold symmetry in SAW absorption.

Identification of in-plane uniaxial anisotropy as a key factor.

Persistence of symmetry effects in ultrathin films.

Abstract

We study the symmetry of the coupling between surface acoustic waves and ferromagnetic resonance in a thin magnetic film of CoFeB deposited on top of a piezoelectric Z-cut LiNbO3 substrate. We vary the orientation of the applied magnetic field with respect to the wavevector of the surface acoustic wave. Experiments indicate an unexpected 2-fold symmetry of the absorption of the SAW energy by the magnetic film. We discuss whether this symmetry can arise from the magnetoelastic torque of the longitudinal strain and the magnetic susceptibility of ferromagnetic resonance. We find that one origin of the 2-fold symmetry can be the weak in-plane uniaxial anisotropy present within the magnetic film. This phenomena adds to the previously identified other source of 2-fold symmetry but shall persist for ultrathin films when the dipolar interactions cease to contribute to the anisotropy of the slope of the spin wave dispersion relation.