Shear strain effects on metal–insulator transition of vanadium oxide V2O3

Abstract

Vanadium oxide V2O3 is a strongly correlated transition-metal oxide, in which electrons are strongly coupled with the lattice system. It exhibits a first-order type of metal–insulator (MI) transition at 168 K. A series of vanadium oxides VxOy, between V2O3 and VO2 with various valence states of vanadium between +3 and +4, also exhibits similar MI transitions, and the transition temperature depends on the valence. In this study, we expected a change in the valence state of vanadium in V2O3 subjected to shear under compression using the process of the high-pressure torsion (HPT). Disk-like samples were subjected to the HPT processing under pressure (PHPT = 6 GPa) for a certain number of revolutions (N) at room temperature. Originally, the MI transition occurred within a narrow temperature range of 160 ± 10 K, whereas after HPT processing with N = 10, it occurred over a wide temperature range of 180 ± 60 K. Consequently, the effects of shear resulted in the coexistence of high- and low-temperature phases in the temperature range over 120 K. Furthermore, the onset temperature of MI transition was enhanced from approximately 170 to 240 K. Thus, the HPT processing of V2O3 expanded the temperature range of low-temperature insulating phase.