Effect of Cu–Al substitution on the structural and magnetic properties of Co ferrites

In this work copper aluminum substituted cobalt nanocrystalline spinel ferrites having general formula Co1−xCuxFe2−x AlxO4, with 0.0≤x≤0.8 have been synthesized by using a co-precipitation method. The Cu–Al substituted samples were annealed at 600 °C and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). XRD analysis confirmed a single phase spinel structure and the crystalline size calculated using Scherrer׳s formula found to be in the range of 14−24 nm. This crystalline size is small enough to achieve the suitable signal to noise ratio in the high density recording media. The FTIR spectra reveal two prominent frequency bands in the wave number range 350–600 cm−1, which confirm the cubic spinel structure and completion of chemical reaction. Magnetic studies reveal that the coercivity (Hc) attains a maximum value of 1142 Oe at 14 nm. The increasing trend of magnetic parameters (coercivity and retentivity) is consistent with crystallinity. The role played by the Cu–Al ions in improving the structural and magnetic properties are analyzed and understood. The optimized magnetic parameters suggest that the material with composition Co0.6Cu0.4Fe1.6Al0.4O4 may have a potential application for high density recording media. Our simple, economic and environmental friendly preparation method may contribute towards the controlled growth of high quality ferrite nanopowder, potential candidates for recording.