Re-investigation of Moment Direction in a Kitaev Material α-RuCl_3

We report X-ray diffraction and resonant elastic X-ray scattering (REXS) studies on two α-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 R3̅. Notwithstanding, both samples exhibit an identical zigzag magnetic structure, with magnetic moments pointing away from the honeycomb plane by α=31(2)^∘. We argue that the identical ordered moment directions in these samples suggest that the intralayer magnetic Hamiltonian remains mostly unchanged regardless of T_N.