Pressure dependence of the resistivity and magnetoresistance in single-crystal Nd_0.62Pb_0.30MnO_3-δ

We have measured the resistivity and magnetoresistance of single-crystal Nd_0.62Pb_0.30MnO_3-δ as a function of hydrostatic pressure up to 12 kbar. The pressure dependence of the resistivity at temperatures near the metal-insulator transition exceeds d(Inρ)/dP ∼ 3 kbar^-1, greater than that observed in the normal state of high-temperature superconductors. The extreme pressure sensitivity of the resistivity below the transition temperature provides evidence that the low-temperature phase is not a simple metal. The metal-insulator transition temperature T_M1 decreases by 2.6 K kbar^-1, in accord with an expectation for greater pressure sensitivity in lower-doped materials with lower T_M1 . The peak magnetoresistance defined as [ρ(0 T) - ρ(7 T)]/ρ(7 T) decreases with increasing pressure as the metal-insulator transition becomes less abrupt. The influence of thermal expansion upon the resistivity is expected to be large.