PHOTOEMISSION-STUDY OF COMPOSITION-INDUCED AND TEMPERATURE-INDUCED METAL-INSULATOR TRANSITIONS IN CR-DOPED V2O3

The variety and complexity of the metal-insulator transitions that V2O 3 undergoes, in both pure form and when doped with other transition-me tal ions, have resulted in widespread interest in the electronic struc ture of this oxide. We report here the results of a photoemission stud y of the electronic structure of Cr-doped V2O3 in metallic and insulat ing states. At room temperature, insulating Cr-doped V2O3 exhibits a l ow emission intensity at E(F). When cooled, a transition to a metallic state is observed at 210 K. The emission intensity at E(F) and the wi dth of the V 3d emission increase below this transition. Additionally, the O 1s and V 2p core-level structure changes, resembling that of th e metallic state of pure V2O3. When cooled further, another transition occurs from the metallic state to a second insulating state. The emis sion intensity at E(F) decreases and the V 3d emission narrows. The co re-level emission structure reverted to that of the room-temperature i nsulating state. The changes in density-of-states and bandwidth were f ound to be consistent with a Fermi-liquid theory of these transitions; the changes in core-level emission are identified with different core -hole screening in the metallic and insulating states.