Pressure-driven structural phase transitions and metallization in the two-dimensional ferromagnetic semiconductor CrBr.

High-pressure structural, magnetic and electrical transport characteristics of CrBr were synthetically investigated using Raman scattering, electrical conductivity, high-resolution transmission electron microscopy (HRTEM) and first-principles theoretical calculations during compression and decompression under different hydrostatic conditions. Upon pressurization, CrBr underwent a second-order structural transition at 9.5 GPa, followed by the semiconductor-to-metal and magnetic switching at 25.9 GPa under non-hydrostatic conditions, whereas, an obvious pressure hysteresis of ∼3.0 GPa was detected in the occurrence of structural transitions and metallization under hydrostatic conditions due to the deviatoric stress. Upon decompression, the structural and electronic transitions of CrBr under different hydrostatic conditions were of good reversibility with a considerable pressure sluggishness of ∼5.0 GPa, which was corroborated well by the microstructural observation with HRTEM. Our systematic high-pressure investigation on CrBr not only reveals its underlying application in spintronic, magnetic and electronic devices but also advances the understanding of the physicochemical behaviors for 2D magnetic materials.