Structural and magnetic phase transitions in Pr0.7Ca0.3MnO3 at high pressures

Abstract

The crystal structure and Raman spectra of Pr0.7Ca0.3MnO3 manganite at high pressures of up to 30 GPa and the magnetic structure at pressures of up to 1 GPa have been studied. A structural phase transition from the orthorhombic phase of the Pnma symmetry to the high-pressure orthorhombic phase of the Imma symmetry has been observed at P ∼ 15 GPa and room temperature. Anomalies of the pressure dependences of the bending and stretching vibrational modes have been observed in the region of the phase transition. A magnetic phase transition from the initial ferromagnetic ground state (T C = 120 K) to the A-type antiferromagnetic state (T N = 140 K) takes place at a relatively low pressure of P = 1 GPa in the low-temperature region. The structural mechanisms of the change of the character of the magnetic ordering have been discussed.