Controlling the propagation of dipole-exchange spin waves using local inhomogeneity of the anisotropy

TL;DR

This paper investigates how surface inhomogeneities affect the transmission of dipole-exchange spin waves in thin magnetic films, revealing differences in backscattering between BVMSW and MSSW, and proposing a quasi-analytical scattering model.

Contribution

It introduces a quasi-analytical theory for spin-wave scattering by surface defects, validated by micromagnetic simulations, aiding the design of magnonic logic devices.

Findings

BVMSW are more susceptible to backscattering than MSSW due to surface inhomogeneities.

The developed theory accurately predicts spin-wave transmission in thin films.

Surface defects significantly influence spin-wave propagation, enabling control in magnonic devices.

Abstract

Spin waves are promising candidates to carry, transport, and process information. Controlling the propagation characteristics of spin waves in magnetic materials is an essential ingredient for designing spin-wave based computing architectures. Here, we study the influence of surface inhomogeneities on the spin-wave signals transmitted through thin films. We use micromagnetic simulations to study the spin-wave dynamics in an in-plane magnetized yttrium iron garnet thin film with a thickness in the nanometre range in the presence of surface defects in the form of locally introduced uniaxial anisotropies. These defects are used to demonstrate that the Backward Volume Magnetostatic Spin Waves (BVMSW) are more responsive to backscattering in comparison to Magnetostatic Surface Spin Waves (MSSWs). For this particular defect type, the reason for this behavior can be quantitatively related to the difference in the magnon band structures for the two types of spin waves. To demonstrate this, we develop a quasi-analytical theory for the scattering process. It shows an excellent agreement with the micromagnetic simulations, sheds light on the backscattering processes and provides a new way to analyze the spin-wave transmission rates in the presence of surface inhomogeneities in sufficiently thin films, for which the role of exchange energy in the spin-wave dynamics is significant. Our study paves the way to designing magnonic logic devices for data processing which rely on a designed control of the spin-wave transmission.