Kitaev interactions of the spin-orbit coupled magnet UO2

Abstract

Uranium dioxide, UO$_2$, is a canonical example of a magnetic material with strong spin-orbit coupling. Here, we present a study of the magnetic diffuse scattering measured on a polycrystalline sample of UO$_2$, which we interpret in terms of its magnetic interactions between U$^{4+}$ magnetic moments. By refining values of the magnetic interaction parameters to magnetic diffuse-scattering data measured above the magnetic ordering transition temperature, we show that the dominant magnetic coupling in UO$_2$ is a bond-dependent interaction analogous to the Kitaev model of honeycomb magnets. We compare our experimental results with published theoretical predictions and experimental measurements of the magnetic excitation spectrum. Our results suggest that magnetic materials with $f$-electron magnetic ions, particularly actinides, may be promising candidates for realising Kitaev magnetism, and highlight the role that magnetic diffuse-scattering data can play in identifying such materials.