Isostructural Phase Transition of Fe_{2}O_{3} under Laser Shock Compression.
Amouretti A., Crépisson C., Azadi S., Brisset F., Cabaret D., Campbell T., Chin DA., Collins GW., Hansen L., Fiquet G., Forte A., Gawne T., Guyot F., Heighway P., Heriprë E., Cunningham E., Lee HJ., McGonegle D., Nagler B., Pintor J., Polsin DN., Rousse G., Shi Y., Smith E., Wark JS., Vinko SM., Harmand M.
We present in situ x-ray diffraction and velocity measurements of Fe_{2}O_{3} under laser shock compression at pressures between 38-122 GPa. None of the high-pressure phases reported by static compression studies were observed. Instead, we observed an isostructural phase transition from α-Fe_{2}O_{3} to a new α^{'}-Fe_{2}O_{3} phase at a pressure of 50-62 GPa. The α^{'}-Fe_{2}O_{3} phase differs from α-Fe_{2}O_{3} by an 11% volume drop and a different unit cell compressibility. We further observed a two-wave structure in the velocity profile, which can be related to an intermediate regime where both α and α^{'} phases coexist. Density functional theory calculations with a Hubbard parameter indicate that the observed unit cell volume drop can be associated with a spin transition following a magnetic collapse.