Structural, dielectric, and magnetic properties of Al³⁺-doped nickel spinel ferrite nanomaterials for technological applications

A sol–gel auto-combustion technique was employed to synthesize Al³⁺-doped nickel spinel ferrite nanomaterials with the chemical composition Ni(Al_xFe_1-x)_1.8La_0.2O₄. The face-centered cubic (FCC) crystalline structure was verified through X-ray diffraction (XRD), affirming the material’s crystallinity. The calculate value of the crystallite size was found from 7 to 9 nm. This smallest crystallite size nanomaterial can be helpful in sensors. Aluminum substitution prominently influenced structural parameters such as lattice strain, microstrain, stacking fault, and dislocation density, with a slight alteration in lattice constant observed from 8.33 to 8.38 Å as Al³⁺ concentration increased. Fourier transform infrared radiation (FTIR) analysis confirmed the prepared materials have the band variations at the octahedral and tetrahedral sites. The particle size and their distribution of the prepared materials were analyzed using transmission electron microscopy (TEM). The significant agglomeration found at aluminum concentrations of x = 0.20 provides unambiguous proof of the presence of magnetic particles. Dielectric properties were examined using impedance analyzer for frequencies ranging from 1 MHz to 3 GHz. Dielectric parameters were analyzed, including both the real (ԑʹ) and imaginary (ԑʹʹ) parts of dielectric constant, AC conductivity (σ_ac), tangent loss (tanδ), and real (Zʹ) and imaginary Zʹ parts of electric impedance. Additionally, the real (Mʹ) and imaginary (Mʹʹ) parts of electric modulus Cole–Cole plots of the prepared nanomaterials were investigated. These all parameters showed significant variations with Al³⁺ doping concentration. The vibrating sample magnetometer (VSM) technique was employed to assess the magnetic characteristics. The magnetic properties such as coercive field (H_c), saturation magnetization (M_s), and remanent magnetization (M_r) were studied. These all quantities showed have decreased with increasing Al³⁺ content, suggesting a transition toward paramagnetic behavior. Its magnetic properties would indicate that it is suitable for a wide range of technical applications. The high dielectric constant and low dielectric loss values indicate that the synthesized material holds potential for use in high-frequency devices and microwave applications.