Abstract

Manganese oxides of spinel structure, based on nickel (NiMn2O4) or lithium (LiMn2O4), were studied by magnetic measurements. Manganese was partially substituted by either chromium or iron, showing substantial variations of the magnetic properties with respect to the non-substituted compounds. Chromium enhances the antiferromagnetic interactions in both NiMn2-xCr xO4 and LiMn2-xCr xO4, while iron enhances the ferromagnetic ones, increasing Tc well above room temperature in NiMn2xFe xO4 and LiMn2-xFe xO4 (0