Structural and Transport Study of La$_{0.9}$MnO$_{3}$ Under Pressure.

The detailed transport and structural properties of the self-doped system La$_{0.9}$MnO$_{3}$ have been studied under hydrostatic pressures extending to 6GPa and 11GPa, respectively.~ Like the doped manganite systems previously studied by our group, in the La deficiency (x=0.9) system a maximum shift of the peak resistivity is obtained at around 3.4GPa.~~ A crossover from metallic to insulating behavior is observed above this optimum pressure.~ The x-ray diffraction study results show that the self-doped system is compatible with a single phase of monoclinic space group up to 11 GPa. The detailed changes in the lattice parameters, volume, bond distances and bond angles have been obtained.~Comparisons with pressure dependent measurements on the doped manganites will be made.~ This work was supported by NSF DMR-0209243 and DMR-0512196.