Linear Magnetodielectric Effect and Huge Negative Magnetization in a Mixed-Valent Cobalt Manganite Spinel Oxide

Abstract

Mixed-valent cobalt manganese spinel oxide (Co2MnO4) with excess manganese (Co1.75Mn1.25O4) was synthesized using the conventional solid-state reaction method. The samples were sintered at 975 degrees C with intermediate grinding until a pure phase was formed. The synthesized samples were subjected to various characterization studies such as X-ray diffraction (XRD), magnetization against temperature and applied magnetic field, electrical resistivity, and dielectric and magnetodielectric measurements. Powder X-ray diffraction studies confirmed the formation of a cubic spinel structure with a space group of Fd3m. The Mn excess sample did not show any change in the crystal structure, but the magnetic and magnetodielectric properties showed drastic changes. The magnetic transition temperature of Co2MnO4 is 180 degrees C whereas that of Co1.75Mn1.25O4 is around 176.5 degrees C. Interestingly, the magnetization versus temperature plot for both Co2MnO4 and Co1.75Mn1.25O4 samples shows a giant negative magnetization and a concomitant linear magnetodielectric effect below the Neel temperature.