Effects of pressure on electron transport and atomic structure of manganites: Low to high pressure regimes

The pressure dependence of the resistivity and structure of La0.60Y0.07Ca0.33MnO3 has been explored in the pressure range from 1 atm to similar to7 GPa. The metal to insulator transition temperature (T-MI) was found to reach a maximum and the resistivity achieves a minimum at similar to3.8 GPa. Beyond this pressure, T-MI is reduced with a concomitant increase in the resistivity. Structural measurements at room temperature show that at low pressure (below 2 GPa) the Mn-O bond lengths are compressed. Between similar to2 and similar to4 GPa, a pressure-induced enhancement of the Jahn-Teller (JT) distortion occurs in parallel with an increase in Mn-O1-Mn bond angle to similar to180degrees. Above similar to4 GPa, the Mn-O1-Mn bond angle is reduced, while the JT distortion appears to remain unchanged. The resistivity above T-MI is well modeled by variable range hopping. The pressure dependence of the localization length follows the behavior of T-MI.