PRESSURE-DEPENDENCE OF THE RESISTIVITY AND MAGNETORESISTANCE IN SINGLE-CRYSTAL ND0.62PB0.30MNO3-DELTA

We have measured the resistivity and magnetoresistance of single-cryst al Nd0.62Pb0.30MnO3-delta as a function of hydrostatic pressure up to 12 kbar. The pressure dependence of the resistivity at temperatures ne ar the metal-insulator transition exceeds d(ln rho)/dP similar to 3 kb ar(-1), greater than that observed in the normal state of high-tempera ture superconductors. The extreme pressure sensitivity of the resistiv ity below the transition temperature provides evidence that the low-te mperature phase is not a simple metal. The metal-insulator transition temperature T-MI decreases by 2.6 K kbar(-1), in accord with an expect ation for greater pressure sensitivity in lower-doped materials with l ower T-MI. The peak magnetoresistance defined as [rho(0 T) - rho(7 T)] /rho(7 T) decreases with increasing pressure as the metal-insulator tr ansition becomes less abrupt. The influence of thermal expansion upon the resistivity is expected to be large.