Magnetic behavior of MnCo2O4+δ spinel obtained by thermal decomposition of binary oxalates

Manganese cobaltites MnCo2O4.62 and MnCo2O4.275 having a spinel structure were studied by measuring magnetization, AC susceptibility and by XANES spectroscopy. These compounds were synthesized by decomposition of the binary oxalate Mn1/3Co2/3C2O4 center dot 2H(2)O in air at 220 and 500 degrees C, respectively. It was found that the differences in magnetic characteristics of these cation-deficient spinels are due mainly to variations in the degree of oxidation of manganese. It was shown that the complex oxide MnCo2O4.62 formed right after decomposition of the binary oxalate contains about 5 x 10(-4)mass% metallic cobalt, which determines the dependence of magnetic susceptibility chi on the magnetic field at 300 K. The magnetic transition peculiar to the stoichiometric spinel MnCo2O4 at 183 K decreases to 167.5 K for MnCo2O4.275 and 67.5 K for MnCo2O4.62. (C) 2008 Elsevier B.V. All rights reserved.