Insulator-metal transitions, giant magnetoresistance, and related aspects of the cation-deficient LaMnO3 compositions La1-delta MnO3 and LaMn1-delta O3

Electron transport and magnetic properties of the cation-deficient compositions of LaMnO3 with the nominal formulae La1-deltaMnO3 (0.0 less than or equal to 6 less than or equal to 0.2) and LaMn1-delta'O-3 (0.0 less than or equal to delta'less than or equal to 0.2) were investigated after their defect structures were examined. La1-deltaMnO3 (delta=0.1) contains more than one defect structure involving both La and Mn vacancies. La(1-delta)GMnO(3) (0.0 less than or equal to delta 0.2) compositions are all ferromagnetic and show insulator-metal (I-M) transition, with the resistivity decreasing with increasing delta. LaM(1-delta')O(3) compositions show ferromagnetism and the I-M transition only up to delta'=0.05, with the resistivity increasing with delta'. All compositions showing the I-M transitions exhibit giant magnetoresistance. (C) 1996 Academic Press, Inc.