Hedgehog-lattice spin texture in classical Heisenberg antiferromagnets on the breathing pyrochlore lattice

TL;DR

This paper shows through Monte Carlo simulations that frustration, not Dzyaloshinskii-Moriya interaction, induces hedgehog lattice spin textures in classical Heisenberg antiferromagnets on breathing pyrochlore lattices, revealing new topological magnetic states.

Contribution

It demonstrates that frustration alone can induce hedgehog lattice states in breathing pyrochlore antiferromagnets, expanding understanding of topological spin textures beyond Dzyaloshinskii-Moriya interactions.

Findings

Hedgehog lattice is induced by frustration, not DM interaction.

The quadruple-q state becomes a hedgehog lattice for J1'/J1<1.

Magnetic field changes the lattice structure, leading to net spin chirality.

Abstract

The hedgehog lattice, a three-dimensional periodic array of magnetic monopoles and antimonopoles, is known to be realized in the presence of the Dzyaloshinskii-Moriya (DM) interaction. Here, we demonstrate by means of Monte Carlo simulations that the hedgehog lattice is induced by not the DM interaction but frustration in classical Heisenberg antiferromagnets on the breathing pyrochlore lattice. In the model, the breathing bond-alternation is characterized by the ratio of the nearest-neighbor (NN) antiferromagnetic exchange interaction for large tetrahedra to that for small ones, J1'/J1. A quadruple-q state with the ordering vector of q=(\pm 1/2,\pm 1/2,\pm 1/2), which is realized for a large third NN antiferromagnetic interaction along the bond direction J3, turns out to become the hedgehog-lattice state in the breathing case of J1'/J1 <1, while in the uniform case of J1'/J1 =1, it is a collinear state favored by thermal fluctuations. It is also found that in a magnetic field, the structure of the (1/2,1/2,1/2) hedgehog lattice is changed from cubic to tetragonal, resulting in a nonzero net spin chirality which in a metalic system, should yield a characteristic topological Hall effect.