Thermal decomposition of the Kitaev material $α$-RuCl$_3$ and its influence on low-temperature behavior

Abstract

We explore the effect of heat treatment in argon atmosphere under various temperatures up to 500 • C on single crystals of α-RuCl3 by study of the mass loss, microprobe energy dispersive x-ray spectroscopy, powder x-ray diffraction, 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.