The variety and complexity of the metal-insulator transitions that ${\mathrm{V}}_2$${\mathrm{O}}_3$ undergoes, in both pure form and when doped with other transition-metal ions, have resulted in widespread interest in the electronic structure of this oxide. We report here the results of a photoemission study of the electronic structure of Cr-doped ${\mathrm{V}}_2$${\mathrm{O}}_3$ in metallic and insulating states. At room temperature, insulating Cr-doped ${\mathrm{V}}_2$${\mathrm{O}}_3$ exhibits a low emission intensity at ${\mathit{E}}_{\mathit{F}}$. When cooled, a transition to a metallic state is observed at 210 K. The emission intensity at ${\mathit{E}}_{\mathit{F}}$ and the width of the V 3d emission increase below this transition. Additionally, the O 1s and V 2p core-level structure changes, resembling that of the metallic state of pure ${\mathrm{V}}_2$${\mathrm{O}}_3$. When cooled further, another transition occurs from the metallic state to a second insulating state. The emission intensity at ${\mathit{E}}_{\mathit{F}}$ decreases and the V 3d emission narrows. The core-level emission structure reverted to that of the room-temperature insulating state. The changes in density-of-states and bandwidth were found 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.

• Received 16 March 1994

DOI:https://doi.org/10.1103/PhysRevB.50.1382