Structural, thermal, morphological, surface, chemical, and magnetic analysis of Al3+-doped nanostructured mixed-spinel cobalt ferrites

Abstract The effect of Al3+ substitution into nanocrystalline cobalt ferrite that was prepared via a thermal treatment method was investigated. The average ferrite nanoparticle diameters are found to be in the range between 5.86 and 15.91 nm when polyvinylpyrrolidone (PVP) was used as a capping agent. The importance of the thermal treatment process in capitulating as-produced aluminum-doped cobalt ferrite on the nanostructured scale is in excellent agreement with the results of structural, thermal, quantitative, dimensional and morphological characterizations, which included X-ray diffraction (XRD), particle size analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The lattice strain and lattice constants were determined by employing the Scherrer and Williamson-Hall extrapolation methods. XRD pattern analysis was used to examine various structural characteristics, which included oxygen positional parameters, radii of octahedral and tetrahedral sites, hopping lengths, bond lengths and bond angles, site bonds, and edge lengths. The disparity in the theoretically anticipated bond angle demonstrates the enhancement of A-B superexchange interactions. This enhancement was supported by the results of Magnetic-Hysteresis (M-H) measured by vibrating-sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS) studies. The XPS results demonstrated that iron is present as FeIII and cobalt is present as CoII. XPS analysis represents a powerful tool for investigating the composition, chemical state and inversion degree of doped cobalt ferrites, thereby contributing to the understanding of their properties. The reduction of both saturation magnetization (Ms) and remnant magnetization (Mr), which is demonstrated by the hysteresis loop that was obtained at room temperature (RT) with an ultimate magnetic field of 1.8 T, is due to spin noncollinearity and delicate interactions among sublattices.