High-temperature magnetic anomaly in the Kitaev hyperhoneycomb compound β−Li2IrO3

We report the existence of a high-temperature magnetic anomaly in the three-dimensional Kitaev candidate material, $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Li}}₂{\mathrm{IrO}}₃$. Signatures of the anomaly appear in magnetization, heat capacity, and muon spin relaxation measurements. The onset coincides with a reordering of the principal axes of magnetization, which is thought to be connected to the onset of Kitaev-like correlations in the system. The anomaly also shows magnetic hysteresis with a spatially anisotropic magnitude that follows the spin-anisotropic exchange anisotropy of the underlying Kitaev Hamiltonian. We discuss possible scenarios for a bulk and impurity origin.