Structural and electronic evolution of Cr_2O_3 on compression to 55 GPa

摘要

Synchrotron single-crystal x-ray diffraction experiments have been performed on corundum-type Cr_2O_3 up to a pressure of 55 GPa in Ne and He pressure transmitting media. Diffraction experiments were complemented by measurements of optical absorption spectra with single crystal samples up to 60 GPa. Results of the diffraction data analysis rule out the earlier reported monoclinic distortion at 1530 GPa, but indicate evidence of two discontinuous transitions of electronic or magnetic nature, most likely associated with a change in magnetic ordering and charge transfer. The compression mechanism established from single crystal refinements indicates much smaller distortion of the Cr~3 coordination environment than was previously assumed.