ELECTRICAL-PROPERTIES IN THE SYSTEM (ND0.1CA0.9-XSRX)MNO2.97 (0 LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO 0.4)

The electrical resistivity of (Nd0.1Ca0.9-xSrx)MnO2.97 (0 ≤ x ≤ 0.4) was measured in the temperature range 80 to 700 K. At low temperature, manganates are n-type semiconductors, and the electrical resistivity follows Mott's T- 1 4 law, indicating the possible occurrence of variable range hopping of electrons due to Anderson localization. At high temperature, manganates exhibit a metal-insulator transition with no crystallographic change. The metal-insulator transition temperature linearly increased with increasing x. Since both the number of 4f electrons in rare earth ions and the Mn3+/Mn4+ ratio are independent of x, the increase of the metal-insulator transition temperature depends on the cell constants. © 1991.