Dielectric and magnetic properties of rare-earth-doped cobalt ferrites and their first-order reversal curve analysis

The present study focuses on the effects of rare-earth (R) ion substitutions namely Y, Sm and Pr ions on the structural, magnetic and electrical properties of cobalt ferrite (CFO) and the nature of their magnetic domains using the first-order reversal curve (FORC) analysis. These samples were synthesized using the sol-gel auto-combustion method. The powder X-ray diffraction analysis reveals that the Pr-substituted CFO crystallizes in a single-phase spinel structure, while a few traces of RFeO3 appear as minor phases in Sm- and Y-doped CFO. The scanning electron micrographs show that the substitution of R3+ ions causes a considerable reduction in the grain size. The studies on magnetic properties reveal that the saturation magnetization of R-substituted CFO decreased. The FORC analysis was done to know the domain state of magnetization and the nature of magnetic interactions among the grains. All the FORC diagrams depict a single peak with a single contour suggesting that all the synthesized samples have single domain particles and are comprised only of mono-magnetic phase. The electrical properties of the R-doped CFO compounds exhibit high values of dielectric constant at room temperature with the highest value for Pr-doped CFO. The activation energy determined using electrical properties is found to decrease with R doping.