Controlling Spin-Waves by Inhomogeneous Spin-Transfer Torques

TL;DR

This paper demonstrates how inhomogeneous spin-transfer torques, shaped by device geometry, can deterministically control the phase and velocity of spin waves in nanostructured magnetic waveguides, advancing magnonic computing.

Contribution

It introduces the first experimental demonstration of phase modulation of spin waves using engineered nonuniform spin-transfer torques in nanostructures.

Findings

Spin-wave phase can be modulated by inhomogeneous spin-transfer torques.

Narrower constrictions enhance current-density gradients and influence spin-wave dynamics.

The work enables scalable magnonic interferometry and control of spin-wave behavior in complex current landscapes.

Abstract

We investigate the interplay between spin currents and spin waves in nanofabricated Permalloy waveguides with geometrical constrictions. Using propagating spin-wave spectroscopy, micromagnetic simulations, and analytical modeling, we provide experimental evidence that spin-wave phase can be modulated by inhomogeneous spin-transfer torques generated by current-density gradients shaped by the constriction geometry. Narrower constrictions enhance these gradients and modify the internal field for Damon-Eshbach spin waves, resulting in pronounced changes in spin-wave group velocity and phase. To our knowledge, this constitutes the first demonstration of deterministic phase modulation via engineered nonuniform spin-transfer torques. Beyond enabling a scalable route to magnonic interferometry - a building block for spin-wave-based computing - our findings establish a platform to control spin-wave dynamics in spatially varying current landscapes, relevant for analogue-gravity experiments in condensed matter systems.