We report the first high pressure measurement of the Fe K-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 phase transitions of Fe2O3 is discussed and it is shown that ligand hybridization significantly reduces the critical high-spin/low-spin pressure.
@article{arxiv.1006.2612,
title = {High pressure evolution of Fe$_{2}$O$_{3}$ electronic structure revealed by X-ray absorption},
author = {Shibing Wang and Wendy L. Mao and Adam P. Sorini and Cheng-Chien Chen and Thomas P. Devereaux and Yang Ding and Yuming Xiao and Paul Chow and Nozomu Hiraoka and Hirofumi Ishii and Yong Q. Cai and Chi-Chang Kao},
journal= {arXiv preprint arXiv:1006.2612},
year = {2010}
}