Shape of magnetic domain walls formed by coupling to mobile charges

TL;DR

This paper explores how the shape of magnetic domain walls in itinerant magnets is influenced by the electronic band structure and electron filling, revealing directional preferences and induced electric currents due to mobile charge coupling.

Contribution

It introduces a theoretical and numerical analysis of the impact of mobile charge coupling on magnetic domain wall shapes in the Kondo lattice model, highlighting the role of band structure and electron filling.

Findings

Domain wall shape depends on electronic band structure and electron filling.

Noncoplanar spin states exhibit directional preferences in domain wall formation.

Electric currents are induced along domain walls via the spin Berry phase mechanism.

Abstract

Magnetic domain walls, which are crucially important in both fundamental physics and technical applications, often have a preference in their form due to many different origins, such as the crystalline shape, lattice symmetry, and magnetic anisotropy. We theoretically investigate yet another origin stemming from the coupling to mobile charges in itinerant magnets. Performing a large-scale numerical simulation in a minimal model for itinerant magnets, i.e., the Kondo lattice model with classical localized spins, we show that the shape of magnetic domain walls depends on the electronic band structure and electron filling. While Neel and 120 antiferromagnetic states do not show a strong preference in the shape of domain walls, noncoplanar spin states with scalar chiral ordering have distinct directional preferences of the domain walls depending on the electron filling. We find that the directional preference is rationalized by the wave-number dependence of the effective magnetic interactions induced by the mobile charges, which are set by the band structure and electron filling. We also observe that, in the noncoplanar chiral states, an electric current is induced along the domain walls owing to the spin Berry phase mechanism, with very different spatial distributions depending on whether the bulk state is metallic or insulating.