Phase transitions and p–T phase diagram of the multiferroic TbFe3(BO3)4 crystal

The structural phase transitions in multiferroic TbFe3(BO3)4 with change hydrostatic pressures and temperatures have been studied by Raman spectroscopy and calculation within density functional theory. Lattice dynamics calculations in the TbFe3(BO3)4 crystal in the R32 phase under various values of applied hydrostatic pressure (from 0 up to 5 GPa with 1 GPa step) were performed. The calculation performed in this work in a TbFe3(BO3)4 crystal showed that the applied pressure can increase the phase transition temperature. Raman spectra of the TbFe3(BO3)4 crystal have been investigated at simultaneously high temperature and high pressure (up to 5.14 GPa and 465 K). The appearance of a soft mode was observed with decreasing temperature at normal pressure. The manifestations of the interaction of the structural and magnetic order parameters in the range from 13 to 50 K were observed at normal pressure. With increasing pressure and a fixed temperature, recovery of the soft modes is also observed. The experimental p–T phase diagram of TbFe3(BO3)4 was established. An increase in pressure leads to an increase in the temperature of transition. The structural phase transitions in multiferroic TbFe3(BO3)4 under hydrostatic pressures and various temperatures have been investigated by density functional theory (DFT) calculation and Raman spectroscopy. The experimental p–T phase diagram was established. The manifestations of the interaction of the structural and magnetic order parameters in the range from 13 to 50 K were observed.