Insulator–Metal Transitions, Giant Magnetoresistance, and Related Aspects of the Cation-Deficient LaMnO3Compositions La1−δMnO3and LaMn1−δ′O3

Electron transport and magnetic properties of the cation-deficient compositions of LaMnO3with the nominal formulae La1−δMnO3(0.0 ≤ δ ≤ 0.2) and LaM1−δ′O3(0.0 ≤ δ′ ≤ 0.2) were investigated after their defect structures were examined. La1−δMnO3(δ = 0.1) contains more than one defect structure involving both La and Mn vacancies. La1−δMnO3(0.0 ≤ δ ≤ 0.2) compositions are all ferromagnetic and show insulator–metal (I–M) transition, with the resistivity decreasing with increasing δ. LaMn1−δ′O3compositions show ferromagnetism and the I–M transition only up to δ′ = 0.05, with the resistivity increasing with δ′. All compositions showing the I–M transitions exhibit giant magnetoresistance.