Re-investigation of Moment Direction in a Kitaev Material $\alpha$-RuCl${}_3$

Abstract

We report X-ray diffraction and resonant elastic X-ray scattering (REXS) studies on two $\alpha$-RuCl${}_3$ crystals with distinct magnetic transition temperatures: T${}_N$=7.3K and 6.5K. We find that the sample with T${}_N$=6.5K exhibits a high degree of structural twinning at low temperature, whereas the T${}_N$=7.3K sample primarily comprises a single domain of R$\bar{3}$. Notwithstanding, both samples exhibit an identical zigzag magnetic structure, with magnetic moments pointing away from the honeycomb plane by $\alpha =31(2{)}^{\circ }$. We argue that the identical ordered moment directions in these samples suggest that the intralayer magnetic Hamiltonian remains mostly unchanged regardless of T${}_N$.