Frustration and anisotropic exchange in ytterbium magnets with edge-shared octahedra

TL;DR

This paper analyzes anisotropic exchange interactions in ytterbium-based magnets with edge-sharing octahedra, providing a framework to understand magnetic regimes and implications for various compounds.

Contribution

It introduces a qualitative method to determine anisotropic exchange regimes in ytterbium magnets and tests it against known compounds, extending understanding to new lattice structures.

Findings

Extended regime of weak anisotropy with dominant antiferromagnetic Heisenberg interactions

Regions with strong anisotropy identified in the parameter space

Implications for known and novel ytterbium-based magnetic materials

Abstract

We consider the structure of anisotropic exchange interactions in ytterbium-based insulating rare-earth magnets built from edge-sharing octahedra. We argue the features of trivalent ytterbium and this structural configuration allow for a qualitative determination of the different anisotropic exchange regimes that may manifest in such compounds. The validity of such super-exchange calculations is tested through comparison to the well-characterized breathing pyrochlore compound Ba$_3$Yb$_2$Zn$_5$O$_{11}$. With this in hand, we then consider application to three-dimensional pyrochlore spinels as well as two-dimensional honeycomb and triangular lattice systems built from such edge-sharing octahedra. We find an extended regime of robust emergent weak anisotropy with dominant antiferromagnetic Heisenberg interactions as well as smaller regions with strong anisotropy. We discuss the implications of our results for known compounds with the above structures, such as the spinels AYb$_2$X$_4$ (A = Cd, Mg, X = S, Se), the triangular compound YbMgGaO$_4$, which have recently emerged as promising candidates for observing unconventional magnetic phenomena. Finally, we speculate on implications for the R$_2$M$_2$O$_7$ pyrochlore compounds and some little studied honeycomb ytterbium magnets.