Interface-induced magnetization in altermagnets and antiferromagnets

TL;DR

This paper demonstrates that altermagnets and antiferromagnets can exhibit surface-induced magnetization due to itinerant electrons, with implications for nanoscale spintronics, using theoretical models and calculations.

Contribution

It reveals the phenomenon of surface-induced magnetization in altermagnets and antiferromagnets, providing a phenomenological explanation and analyzing spatial dependence differences.

Findings

Surface magnetization occurs in altermagnets despite zero bulk magnetization.

Itinerant electrons cause edge magnetization through probability density redistribution.

Different spatial dependence of induced magnetization in altermagnets versus antiferromagnets.

Abstract

Altermagnets is a class of antiferromagnetic materials which has electron bands with lifted spin degeneracy in momentum space but vanishing net magnetization and no stray magnetic fields. Because of these properties, altermagnets have attracted much attention for potential use in spintronics. We here show that despite the absence of bulk magnetization, the itinerant electrons in altermagnets can generate a magnetization close to edges and vacuum interfaces. We find that surface-induced magnetization can also occur for conventional antiferromagnets with spin-degenerate bands, where the magnetization from the itinerant electrons originates from a subtle yet nonvanishing redistribution of the probability density on the unit-cell level. An intuitive explanation of this effect in a phenomenological model is provided. In the altermagnetic case, the induced magnetization has a different spatial dependence than in the antiferromagnetic case due to the anisotropy of the spin-polarized Fermi surfaces, causing the edge-induced Friedel oscillations of the spin-up and -down electron densities to have different periods. We employ both a low-energy effective continuum model and lattice tight-binding calculations. Our results have implications for the usage of altermagnets and antiferromagnets in nanoscale spintronic applications.