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

Abstract

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.

Raman spectroscopy and X‐ray diffraction of diphenylphosphoryl azide under high pressures

“…[6][7][8][9][10][11][12] As pressure can directly change the molecular structures and bonding patterns, high-pressure techniques provide an excellent route to synthesize energetic polymeric nitrogen materials. [13][14][15][16] The highpressure studies of azides show that the electron orbital hybridization of the azide ions in inorganic azide leads to the occurrence of nitrogen polymerization. [17][18][19][20][21][22] However, the electron orbital hybridization in symmetric and linear azide ions is difficult to occur, which limits the researches and applications of polymeric nitrogen.…”