Spin superstructure and noncoplanar ordering in metallic pyrochlore magnets with degenerate orbitals

TL;DR

This paper investigates how the directional dependence of t2g orbitals in pyrochlore and spinel structures causes unique Fermi surfaces, leading to complex spin arrangements and noncoplanar magnetic orders in metallic pyrochlore magnets.

Contribution

It reveals the role of orbital anisotropy in inducing spin superstructures and noncoplanar orderings in double-exchange models on pyrochlore lattices.

Findings

Unusual Fermi surfaces due to t2g orbital dependence

Induction of spin superstructures and noncoplanar orderings

Relevance to materials ZnV2O4 and Cd2Os2O7

Abstract

We study double-exchange models with itinerant t2g electrons in spinel and pyrochlore crystals. In both cases the localized spins form a network of corner-sharing tetrahedra. We show that the strong directional dependence of t2g orbitals leads to unusual Fermi surfaces that induce spin superstructures and noncoplanar orderings for a weak coupling between itinerant electrons and localized spins. Implications of our results to ZnV2O4 and Cd2Os2O7 are also discussed.