Electric transport and magnetic properties of perovskitesLaMn1−xCoxO3 up to 900 K

Abstract

The structural, magnetic and transport properties of theLaMn1−xCoxO3 system were investigated over a wide temperature range, 10–900 K. Two structural types, depending onx, weredetected—orthorhombic Pbnm () and rhombohedral (x>0.6), separated by thebi-phasic sample x = 0.6.At both ends of the LaMn1−xCoxO3 system, the respective substituents are unambiguously characterized asCo2+ () and Mn4+ (). On the Mn-rich side, up to x<0.5, we infer on the basis of high temperature transport and magnetic data the gradual increase of theCo2+ valence towardsthe prevailing Co3+, while for the Co-rich samples (), the Co3+ states tend to disproportionate at high temperatures toCo2++Co4+, which probably controls both the transport and magnetic properties. At low temperatures,the long range ferromagnetic order was confirmed by means of neutron diffraction for thex = 0.4 sample. A non-uniform magnetic state was detected at higher cobalt substitution up tox = 0.8 and was associated with FM clusters that are formed below K and coagulate below K.