Breakdown of the Mott-Hubbard state in Fe2O3:: A first-order insulator-metal transition with collapse of magnetism at 50 GPa

Electronic and structural properties of the high-pressure phase of Fe2O3 were determined by combining the methods of Mossbauer spectroscopy, x-ray diffraction, and electrical resistance, R(P, T), to 80 GPa. Because of a first-order phase transition taking place in the 50-75 GPa range and accompanied by a volume decrease of similar to 10%, a breakdown of the electronic d-d correlation occurred, leading to a Mott transition, a metallic and a nonmagnetic single Fe3+ electronic state. The high-pressure structure is of the distorted Rh2O3-II type. The accommodation of the denser phase within this six-coordinated structure is attributable to the metallic state. [S0031-9007(99)09286-8].