We present in-situ x-ray diffraction and velocity measurements of Fe2O3 under laser shock compression at pressures between 38-116 GPa. None of the phases reported by static compression studies were observed. Instead, we observed an isostructural phase transition from α-Fe2O3 to a new α′-Fe2O3 phase at a pressure of 50-62 GPa. The α′-Fe2O3 phase differs from α-Fe2O3 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.
@article{arxiv.2402.18432,
title = {Phase transitions of Fe$_2$O$_3$ under laser shock compression},
author = {A. Amouretti and C. Crépisson and S. Azadi and D. Cabaret and T. Campbell and D. A. Chin and B. Colin and G. R. Collins and L. Crandall and G. Fiquet and A. Forte and T. Gawne and F. Guyot and P. Heighway and H. Lee and D. McGonegle and B. Nagler and J. Pintor and D. Polsin and G. Rousse and Y. Shi and E. Smith and J. S. Wark and S. M. Vinko and M. Harmand},
journal= {arXiv preprint arXiv:2402.18432},
year = {2025}
}