"High-pressure evolution of Fe2O3 electronic structure revealed by x-ray absorption"

Shibing Wang: Wendy L. Mao, Adam P. Sorini, Cheng-Chien Chen, Thomas P. Devereaux, Yang Ding, Yuming Xiao, Paul Chow, Nozomu Hiraoka, Hirofumi Ishii, Yong Q. Cai, and Chi-Chang Kao; Phys. Rev. B , 10/19/10.

Additional Authors: Wendy L. Mao, Adam P. Sorini, Cheng-Chien Chen, Thomas P. Devereaux, Yang Ding, Yuming Xiao, Paul Chow, Nozomu Hiraoka, Hirofumi Ishii, Yong Q. Cai, and Chi-Chang Kao

Abstract:

We report the high-pressure measurement of the Fe‚ÄČK edge in hematite (Fe2O3) by x-ray absorption spectroscopy in partial fluorescence yield geometry. The pressure-induced evolution of the electronic structure as Fe2O3 transforms from a high-spin insulator to a low-spin metal is reflected in the x-ray absorption pre-edge. The crystal-field splitting energy was found to increase monotonically with pressure up to 48 GPa, above which a series of phase transitions occur. Atomic multiplet, cluster diagonalization, and density-functional calculations were performed to simulate the pre-edge absorption spectra, showing good qualitative agreement with the measurements. The mechanism for the pressure-induced electronic phase transitions of Fe2O3 is discussed and it is shown that ligand hybridization significantly reduces the critical high-spin/low-spin transition pressure.