Investigation of the Metal-Insulator Transition inV2O3by Nuclear Magnetic Resonance

The metal-to-insulator phase transitions have been investigated in Cr- and Al-doped ${\mathrm{V}}_2$ ${\mathrm{O}}_3$ by nuclear magnetic resonance. Two distinct transitions exist in this system: a low-temperature antiferromagnetic insulator-metal transition, and a high-temperature metal-insulator transition. An abrupt change in the Knight shift is noted at the high-temperature transition, while the resonance signal completely vanishes in the low-temperature antiferromagnetic phase. A theoretical model is developed which explains the existence of both transitions, and the anomalous properties of the metallic state. The magnitude of the magnetic moment in the antiferromagnetically ordered state is discussed.