Structural and magnetic phase transitions occurring in Pr$_{0.7}$Sr$_{0.3}$MnO$_3$ manganite at high pressures

The crystal and magnetic structures and the vibrational spectra of Pr$_{0.7}$Sr$_{0.3}$MnO$_3$ manganite are studied within the pressure range up to $25$ GPa by methods of X-ray diffraction and Raman spectroscopy. Neutron diffraction studies have been performed at pressures up to $4.5$ GPa. The magnetic phase transition from the ferromagnetic phase ($T_{\text{C}}=273\,$K) to the A-type antiferromagnetic phase ($T_{\text{N}}=152\,$K) is found at $P\approx2\,$GPa. This transition is characterized by a broad pressure range corresponding to the phase separation. The Raman spectra of Pr$_{0.7}$Sr$_{0.3}$MnO$_3$ measured under high pressures significantly differ from the corresponding spectra of the isostructural doped A$_{1-x}$A'$_x$MnO$_3$ manganites, (where A is a rare-earth ion and A$'$ is an alkaline-earth ion) with the smaller average ionic radius $\langle r_{\text{A}}\rangle$ of A and A$'$ cations. Namely, the former spectra do not include clearly pronounced stretching phonon modes. At $P\sim7\,$GPa, there appears the structural phase transition from the orthorhombic phase with the $Pnma$ space group to the orthorhombic high-pressure phase with the $Imma$ symmetry. In the vicinity of the phase transition, anomalies in the pressure dependences of the lattice parameters, unit cell volume, and phonon frequencies corresponding to the characteristic lattice vibration modes are observed.