Curvature induced magnetization of altermagnetic films

TL;DR

This paper demonstrates that curvature gradients in altermagnetic films induce a local tangential magnetization, with the magnitude and direction depending on bending geometry, confirmed by analytical and numerical methods.

Contribution

It introduces the concept that curvature gradients in altermagnetic films generate magnetization, linking magnetic properties to geometric deformation, a novel insight in the field.

Findings

Curvature gradients induce tangential local magnetization.

Total magnetic moment scales with bending amplitude and wave vector.

Bending direction determines the magnetization's sign and magnitude.

Abstract

We consider a thin film of $d$-wave altermagnet bent in a stretching-free manner and demonstrate that gradients of the film curvature induce a local magnetization which is approximately tangential to the film. The magnetization amplitude directly reflects the altermagnetic symmetry and depends on the direction of bending. It is maximal for the bending along directions of the maximal altermagnetic splitting of the magnon bands. A periodically bent film of sinusoidal shape possesses a total magnetic moment per period $\propto\mathscr{A}^2q^4$ where $\mathscr{A}$ and $q$ are the bending amplitude and wave vector, respectively. The total magnetic moment is perpendicular to the plane of the unbent film and its direction (up or down) is determined by the bending direction. A film roll up to a nanotube possesses a toroidal moment directed along the tube $\propto \delta_r/r^2$ per one coil, where $r$ and $\delta_r$ are the coil radius and the pitch between coils. All these analytical predictions agree with numerical spin-lattice simulations.