Pressure effects on the phase separation of Pr0.6Ca0.4MnO3 thin films

Micro-Raman measurements under high hydrostatic pressures (up to ∼6.5 GPa) have been carried out on Pr0.6Ca0.4MnO3 thin film grown on LaAlO3 substrate at room and low temperatures (down to 80 K). We had investigated in detail the temperature and hydrostatic pressure dependence of the Raman phonons and calculated their β = d lnω/dp values and the Gruneisen parameters. Under the external pressure, certain peaks attributed to metallic phase gain intensity and become narrower. The charge ordered insulating phase, characterized by the orthorhombic-type Jahn-Teller broad band, is suppressed up to a critical pressure pc1∼2 GPa, and the diffuse electronic scattering intensity decreases, implying that the compound becomes more conductive. However, the pressure is not enough to melt the charge ordered phase, while upon further increase (pc2∼4 GPa) the macroscopic state remains insulating, at least up to the magnitudes studied. The behaviour of the system is ascribed to the electronic phase separation between a ferromagnetic metallic phase and an antiferromagnetic charge ordered insulating one.