Investigations on the charge transport in LaMnO3 +δat low temperatures

Publisher Website
Google Scholar
Abstract
Samples of LaMnO3 +δ with 0.08 ⩽δ⩽ 0.16 have been synthesized in order to study the effect of non-stoichiometry, δ, which is related to the concentration of MnIV ions, on the physical properties of the material. For δ⩽ 0.10 the compound crystallizes in the orthorhombic perovskite-type structure, while for δ > 0.10 a rhombohedral cell is formed. All LaMnO3 +δsamples with δ⩽ 0.12 are paramagnetic, or, below TC ferromagnetic semiconductors, while samples with larger values of δ exhibit a discontinuity in the temperature dependence of the resistivity, indicating a transition to a ferromagnetic metallic-like state at low temperatures. Upon further lowering of the temperature the charge carriers become localized again. These results are consistent with thermopower measurements. All samples are ferromagnetic at low temperatures. The magnetic properties can be interpreted on the basis of Goodenough's superexchange model.