Twin-boundary-induced nonrelativistic spin splitting

TL;DR

This paper demonstrates that twin boundaries in magnetic materials can induce nonrelativistic spin splitting, expanding possibilities for spintronic applications through symmetry engineering.

Contribution

It reveals that twin boundaries can induce NRSS in materials where it is otherwise forbidden, supported by DFT and tight-binding calculations.

Findings

Twin boundaries induce NRSS similar to d-wave altermagnets.

NRSS depends on twin boundary type and coexistence with ferromagnetic domains.

Transport properties scale with domain size and density.

Abstract

Nonrelativistic spin splitting (NRSS) in compensated magnetic materials is drawing considerable attention due to its potential impact in next-generation spintronic devices. While NRSS is typically restricted to materials with particular symmetry constraints, here we demonstrate, using density functional theory (DFT) and tight-binding transport calculations, that twin boundaries can induce NRSS in magnetic systems where it is otherwise forbidden. We focus on two representative material systems: the tetragonal perovskite oxide BiCoO$_3$ with $90^{\circ}$ ferroelastic domain walls, and the rhombohedral layered delafossite-type oxide CoO$_2$, supporting $71^{\circ}$, $109^{\circ}$, and $135^{\circ}$ twin boundaries. Our results reveal that, if these boundaries coexist with ferromagnetic domain walls, they consistently produce NRSS similar to that of d-wave altermagnets, with nodal surfaces dictated by the underlying symmetry of the supercell containing the twin boundary. Tight-binding models further elucidate how the NRSS and derived transport properties scale with domain size and density. Our results put forward twin boundary engineering as a versatile route to realize and control spin splitting in a broader class of materials.