Magnetic properties of Cr-substituted Co-ferrite nanoparticles synthesized by citrate-gel autocombustion method

Abstract A series of Co-Cr nanoferrites having the chemical formula CoCr _x Fe_{2 − x} O₄ (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) were synthesized by citrate-gel autocombustion method at a very low temperature (180°C). The X-ray diffraction analysis of as-synthesized powders and sintered powders has confirmed the formation of single-phase cubic spinel structure. The average particle size of the synthesized ferrites was 6 to 12 nm. Magnetic susceptibility measurements using Faraday magnetic susceptibility balance showed the paramagnetic nature of the ferrites. Magnetic properties of Co-Cr nanoferrites were measured using a vibrating sample magnetometer at room temperature in the applied field of 15 kOe. The saturation magnetization decreased from 33.84 to 13.83 emu/g with increase in Cr³⁺ concentrations, indicating the fact that the lesser magnetic Cr³⁺ ions substitute Fe³⁺ ions in the octahedral sublattice of the ferrite. With improvement in the magnetic properties, the synthesized nanoferrites become soft magnetic materials. Such materials are useful in transformer and motor cores to minimize the energy dissipation with the alternating fields associated with AC electrical applications. The coercivity of pure CoFe₂O₄ was larger than that of the Cr-doped cobalt ferrites.