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 we re determined by combining the methods of Mossbauer spectroscopy, x-ray dif fraction, 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 nonmag netic single Fe3+ electronic state. The high-pressure structure is of the d istorted Rh2O3-II type. The accommodation of the denser phase within this s ix-coordinated structure is attributable to the metallic state. [S0031-9007 (99)09286-8].