Thermal decomposition of the Kitaev material α−RuCl3 and its influence on low-temperature behavior

We explore the effect of heat treatment in argon atmosphere under various temperatures up to 500∘C on single crystals of α−RuCl3 by the study of the mass loss, microprobe energy-dispersive x-ray spectroscopy, powder x-ray diffraction, and electrical resistance, as well as low-temperature magnetic susceptibility and specific heat. Clear signatures of dechlorination and oxidation of Ru appear for annealing temperatures beyond 300∘C. Analysis of the specific heat below 2 K reveals a RuO2 mass fraction of order 1% for pristine α−RuCl3 which increases up to 20% after thermal annealing, fully consistent with mass-loss analysis. The small RuO2 inclusions drastically reduce the global electrical resistance and may thus significantly affect low-temperature thermal transport and Hall effect