Enhancement in Curie temperature of nickel substituted Co-Mn ferrite

Curie temperature of Co0.7−xNixMn0.3Fe2O4 (with X=0.00, 0.05, 0.10 and 0.15) synthesized by the double sintering ceramic method, was recorded by, Lorria Sinha (TCL), dc resistivity (TCR) and dielectric measurement (TCD). Curie temperatures obtained by three various methods are in good agreement with each other. Curie temperature measurements exhibit anomalous increasing trend with increasing nickel content for all the compositions. Three - sublattice model is used to elucidate anomalous behavior as, Neels two - sublattice model fails to explain increase in Curie temperature, even after the replacement of Co2+ ions (3 µB) by Ni2+ ions (2 µB). Decrease in lattice constant and interionic distances can be probably originated by strengthening of A-B interaction. Enhancement in Curie temperature is observed due to the strengthening of A-B interaction. Values of magnetic moments and interaction between them are not the only reasons for enhancement of Tc but change in their orientation with temperature is also important and therefore analysis of Curie temperature is given on basis of anisotropic energy.