Tuning magneto-electric properties in Al-Gd co-doped nickel ferrite nanoparticles fabricated by sol-gel route

Spinel ferrite nanomaterials co-substituted with multivalent cations have attracted considerable research interest due to their tunable structural, magnetic, and electrical properties. The incorporation of trivalent rare-earth elements into spinel ferrites holds great potential for diverse technological fields. In this work, we explored trivalent Al3+-Gd3+ co-substituted nickel ferrite nanoparticles formulated as NiFe_2-2xAl_xGd_xO₄ (x = 0.00, 0.03, 0.05, 0.07, 0.10). These nanoparticles were prepared via a sol-gel auto-combustion process using citric acid as a complexing agent. Rietveld-refined X-ray diffraction (XRD) profiles confirmed the pure cubic spinel phase of the nanoparticles. Field emission scanning electron microscopy (FE-SEM) revealed spherical particle shapes. Energy-dispersive X-ray (EDAX) analysis verified the stoichiometric composition and purity of the materials. Infrared spectroscopy displayed characteristic bands confirming the spinel framework. Vibrating sample magnetometry (VSM) demonstrated soft ferromagnetic characteristics with reduced coercivity. DC resistivity decreased with increasing Al3+-Gd3+ substitution. Dielectric properties exhibited enhancement upon higher co-substitution levels. These findings demonstrate that Al3+-Gd3+ co-substitution effectively tunes the magneto-electric properties of nickel ferrite, making these materials suitable for functional device applications. The synthesized nanoparticles may be suitable for applications in high-frequency electronic components, magnetic sensors, EMI shielding, microwave absorption, and surface-related processes such as sensing and catalysis.