Abstract
A first-order metal-insulator transition with no change in long-range order occurs in the mixed oxides with increasing or decreasing pressure (at kbar for at 298 °K). In a preliminary letter it was shown that the transition had all the qualitative features expected of a Mott transition, i.e., a transition from band to localized behavior. The present paper reports the detailed experimental results. Single crystals of mixed oxides have been made by reaction of , , and VN in molten KF. Electrical resistivity and powder x-ray diffraction measurements made as a function of temperature and pressure in oxides with establish a temperature-pressure-composition phase diagram with three clearly defined phases: metal (M), insulator (I), and antiferromagnetic insulator (AF). The I-M transition is marked by a drop of over two orders of magnitude in the electrical resistivity and a discontinuous decrease in volume of % with no change in crystal structure. For the sequence AF→ M→ I is observed with increasing temperature at 1 atm. At 4.2 K an AF→ M transition occurs with increasing pressure ( kbar for ). The phase diagram is compared with other transition-metal oxides, and the differences between the transition in and V are discussed.
- Received 24 April 1970
DOI:https://doi.org/10.1103/PhysRevB.2.3734
©1970 American Physical Society