Phase Transition in Y3Fe5O12 at High Pressures Observed by Raman Spectroscopy

The vibrational properties of yttrium iron garnet Y3Fe5O12 at a high quasihydrostatic pressure are studied by the Raman spectroscopy method. Raman spectra are measured in a high-pressure diamond anvil cell in the pressure range of 0–72 GPa at room temperature. A fundamental change in the character of spectra with the disappearance of sharp peaks is detected near ~50 GPa. This confirms a phase transition from the crystalline to amorphous state, which was previously detected by other experimental methods. This transition is accompanied by spin crossover in Fe3+ ions, which transit from the high-spin (HS, S = 5/2) to low-spin (LS, S = 1/2) state. The pressure dependences of phonon modes in Y3Fe5O12 are measured from atmospheric pressure to the critical phase transition pressure.