Low-Temperature Synthesis by Autocombustion and Investigation of Structural and Magnetic Properties of Mn0.5Cu0.5−xNixFe2O4 Nanocrystallites

A series of single-phase nanocrystalline Mn_0.5Cu_0.5-xNi_xFe₂O₄ spinel ferrites with x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 was successfully synthesized by sol-gel autocombustion method, at a temperature as low as 300°C. X-ray diffraction, scanning electron microscopy, and room-temperature vibrating sample magnetometry studies have been carried out in order to understand the structural, morphological, and magnetic properties as a function of nickel concentration. The lattice parameters did not show any consistent decreasing or increasing trend, but crystallite size was decreased due to the incorporation of Ni contents at Cu sites in the structure. Large-sized grains were evident for the composition Mn_0.5Cu_0.5Fe₂O₄; however, the grain size was significantly reduced as the Ni was substituted. It was observed that with increasing nickel concentration, saturation magnetization increased, but coercivity decreased, which could be attributed to the substitution of soft ferromagnetic Ni²⁺ ions in place of diamagnetic Cu²⁺ ions.