Spin-hedgehog-derived electromagnetic effects in itinerant magnets

TL;DR

This paper investigates the formation of magnetic hedgehog lattices in itinerant magnets using a neural network approach, revealing their topological Hall effects and magneto-optic Kerr responses.

Contribution

It introduces a neural network method to study magnetic hedgehog lattices in noncentrosymmetric itinerant magnets, advancing beyond traditional Monte Carlo simulations.

Findings

Identification of stable magnetic hedgehog lattice configurations

Demonstration of topological Hall conductivity due to scalar spin chirality

Evidence of magneto-optic Kerr effect associated with the hedgehog lattice

Abstract

In itinerant magnets, the indirect exchange coupling of Ruderman-Kittel-Kasuya-Yosida type is known to stabilize incommensurate spin spiral. Whereas an account of higher order spin interactions favors the formation of a noncoplanar magnetic texture. This is manifested by the finite Berry phase the conduction electrons accumulate when their spins follow this texture, leading thus to the topological Hall effect. We herein utilize the effective spin model with bilinear-biquadratic exchange interactions for studying the formation of the magnetic hedgehog lattice, that represents a periodic array of magnetic anti- and monopoles and has been recently observed in the B20-type compounds, in a three-dimensional itinerant magnet. As opposed to widely used Monte Carlo simulations, we employ a neural-network-based approach for exploring the ground state spin configuration in a noncentrosymmetric crystal structure. Further, we address the topological Hall conductivity, associated with nonzero scalar spin chirality, in the itinerant magnet due to the coupling to the spin hedgehog lattice, and provide the evidence of magneto-optic Kerr effect.