Structural, morphological and magnetic properties of Ni–Co ferrites by the Mn2+ ions substitution

Manganese substituted nickel–cobalt ferrite nanoparticles having the basic composition Ni0.2MnxCo0.8−xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized using sol–gel auto combustion method. The effect of Mn substitution on structural and magnetic properties of nickel–cobalt ferrite has been studied. All the prepared samples show that the single-phase cubic spinel structure by X-ray diffraction. The average microcrystalline size of the prepared samples is about 50 nm calculated by Scherrer equation. With the increase of Mn content, the lattice constant decreases first and then increases for the prepared samples. Fourier transform infrared measurements also confirm the formation of the cubic spinel structure of ferrite. The absorption peak of the Fe–O bond at tetrahedral position shifted to the low frequency with the increase of manganese ion content. By transmission electron microscope observation of the preparation of samples with spherical cube crystallite particles. Energy dispersive X-ray confirmed that the synthesis with pure phase and structure of ferrite, and successfully realized the Mn2+ doping. Vibration sample magnetometer measurement confirm that the Ni0.2MnxCo0.8−xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) nanoparticles have ferromagnetic behavior. It is observed that the saturation magnetization (Ms), remanent magnetization (Mr), rectangular ratio (Mr/Ms) and magnetic moment are decreasing with the increase of manganese ion content. The prepared ferrites have high coercivity, and the decrease of coercivity of samples is due to excessive Mn substitution. At the same time, the magnetization is expected to decrease because of the conversion of equivalent amounts of Fe3+ (5 µB) to Fe2+ (4 µB).