Spin Wave Optics

TL;DR

This paper introduces a mathematical framework that transforms magnetostatic equations into a wave equation, enabling the application of optics-like analysis techniques to spin wave phenomena in magnetic materials.

Contribution

It develops a novel wave equation formalism for spin waves by defining a magnetic refractive index and demonstrates its practical manipulation via magnetic storage technology.

Findings

Magnetic refractive index can be controlled by bias magnetic field or saturation magnetization.

The formalism allows the use of optics-inspired analytical and numerical methods for spin wave analysis.

Potential for designing magnetic analogues of optical devices using this wave equation approach.

Abstract

We propose a mathematical apparatus which converts magnetostatic (Walker) equations into a wave equation by introducing a specific definition of the magnetic refractive index. Its value can be manipulated by adjusting spatial distribution of the saturation magnetization or the bias magnetic field. We demonstrate that the latter can be accomplished efficiently by utilizing the bias field produced by magnetization patterns recorded onto a neighboring hard magnetic film using the current magnetic storage technology; there is a specific algorithm by which one can convert a two dimensional optical device into its magnetic analogue. The wave equation formalism opens the possibility to adopt a number of optics-like analytical and numerical techniques, including those applicable to scattering, near field, diffraction and geometric (Eikonal equation) optics, as well as a generic finite difference time domain (FDTD) algorithm.