Pressurizing the HgCr2Se4 spinel at room temperature

The cubic HgCr2Se4 spinel undergoes two structural transitions upon pressure increase. Initially, the ambient-pressure Fd-3m phase transforms into a tetragonal I4(1)/amd structure above 15 GPa. We speculate that this Fd-3m-I4(1)/amd transition is accompanied by an insulator-to-metal transition, resulting in the vanishing of the Raman signal after the structural transformation. Further compression of HgCr2Se4 leads to structural disorder beyond 21 GPa. Our spin-resolved band structure calculations reveal significant changes in the electronic structure of HgCr2Se4 after the Fd-3m-I4(1)/amd transition, whereas the ferromagnetic interactions are found to dominate in both structures. (C) 2014 AIP Publishing LLC.