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.
@article{arxiv.2512.16612,
title = {Controlling Spin-Waves by Inhomogeneous Spin-Transfer Torques},
author = {Lorenzo Gnoatto and Jean F. O. da Silva and Artim L. Bassant and Rai M. Menezes and Rembert A. Duine and Milorad V. Milossevic and Reinoud Lavrijsen},
journal= {arXiv preprint arXiv:2512.16612},
year = {2025}
}