Effect of bimetallic (Ni and Co) substitution on magnetic properties of MnFe2O4 nanoparticles

Abstract Nickel and cobalt substituted manganese ferrite nanoparticles (NPs) with the chemical composition Ni x Co x Mn 1–2x Fe 2 O 4 (0.0≤x≤0.5) NPs were synthesized by one-pot microwave combustion route. The effect of co-substitution (Ni, Co) on structural, morphological and magnetic properties of MnFe 2 O 4 NPs was investigated using XRD, FT-IR, SEM, VSM and Mossbauer spectroscopic techniques. The cation distribution of all products were also calculated. Both XRD and FT-IR analyses confirmed the synthesis of single phase spinel cubic product for all the substitutions. Lattice constant decreases with the increase in concentration of both Co and Ni in the products. From 57 Fe Mossbauer spectroscopy data, the variations in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values with Mn 2+ , Ni 2+ and Co 2+ substitution have been determined. While the Mossbauer spectra collected at room temperature for the all samples are composed of magnetic sextets, the superparamagnetic doublet is also formed for MnFe 2 O 4 and Ni 0.2 Co 0.2 Mn 0.6 Fe 2 O 4 NPs. The magnetization and Mossbauer measurements verify that MnFe 2 O 4 and Ni 0.2 Co 0.2 Mn 0.6 Fe 2 O 4 NPs have superparamagnetic character. The saturation and remanence magnetizations, magnetic moment and coercive field were determined for all the samples. Room temperature VSM measurements reveals saturation magnetization value close to the bulk one. It has been observed that the saturation magnetization and coercive field increase with respect to the Ni and Co concentrations.