Phase-separated states in high-pressure LaMn1-xGaxO3 manganites

High-pressure (P) Raman (0 <= P <= 12 GPa) and Infrared (0 <= P <= 24 GPa) spectra are collected on two samples of the LaMn1-xGaxO3 series: x=0.2 and 0.6 with cooperative Jahn-Teller distorted and regular MnO6 octahedra, respectively. Raman spectra are also collected at P=0 on varying Ga-content (0 <= x <= 0.8). A remarkable octahedral symmetrization is observed on increasing P in the x=0.2 sample, as well as x at P=0. The x-driven symmetrization process is homogeneous whereas, compressing the lattice, a phase-separated regime (regular/distorted MnO6) is observed at intermediate P. The comparison between the spectra of the two samples in the high-pressure regime strongly suggests the presence of small residual distortion in the x=0.2 even at the highest P. Infrared data show that P is effective only in the x=0.2 sample (P-driven band-gap filling) suggesting the relevance of orbital and magnetic order on the metallization process. Our results provide a unique experimental base to clarify the origin of the peculiar pressure behavior of the parent LaMnO3.