Spin hydrodynamics in amorphous magnets

TL;DR

This paper proposes amorphous magnets as promising materials for coherent spin transport by developing a hydrodynamic theory that accounts for their disordered structure and potential for superfluid spin flow.

Contribution

It introduces a nonlinear hydrodynamic framework for spin in amorphous magnets, including dissipation and interface effects, enabling analysis of coherent spin dynamics in disordered systems.

Findings

Amorphous magnets can support superfluid spin transport.

The theory predicts distinct regimes of coherent spin dynamics.

Framework applicable to nonlocal magneto-transport experiments.

Abstract

Spin superfluidity, i.e., coherent spin transport mediated by topologically stable textures, is limited by parasitic anisotropies rooted in relativistic interactions and spatial inhomogeneities. Since structural disorder in amorphous magnets can average out the effect of these undesired couplings, we propose this class of materials as platforms for superfluid spin transport. We establish nonlinear equations describing the hydrodynamics of spin in insulating amorphous magnets, where the currents are defined in terms of coherent rotations of a noncollinear texture. Our theory includes dissipation and nonequilibrium torques at the interface with metallic reservoirs. This framework allows us to determine different regimes of coherent dynamics and their salient features in nonlocal magneto-transport measurements. Our work paves the way for future studies on macroscopic spin dynamics in materials with frustrated interactions.