Equation of State and High Pressure Irreversible Amorphization in $\mathrm{Y_3Fe_5O_{12}}$

The change of crystal structure in the yttrium iron garnet $\mathrm{Y_3Fe_5O_{12}}$ was studied at room temperature at high pressures up to $\sim55\,$GPa by the X-ray diffraction technique in diamond anvil cells. At the pressure about $\sim50$ GPa the drastic change in the X-ray diffraction pattern was observed indicating a transition into an amorphous-like state. At the pressure increase the bulk modulus of YIG was found to be $193\pm4\,$GPa. It was also found that the amorphous state was retained after decompression down to ambient pressure. From the shape of X-ray patterns in “amorphous” phase, it was concluded that the local atomic structure consists of iron-oxygen $\mathrm{FeO_6}$ octahedral complexes with disordered orientations of local axis and of the randomly arranged others ions fragments with the overall $\mathrm{Y_3Fe_5O_{12}}$ composition. For amorphous phase it was evaluated that the bulk modulus of $\mathrm{FeO_6}$ octahedral complexes is about 260 GPa.