Controlling magnetic interactions and domain dynamics in Co2NiO4 nanorods via carbon integrated structural modulation

Nanomaterials with tailored morphology, microstructure, and carbon integration exhibit profound impacts on their optical and magnetic properties. In this study, a series of carbon-integrated Co₂NiO₄ spinel nanorods were synthesized via a hydrothermal method by systematically varying co-precursor ratios, followed by post synthesis low-temperature air annealing. Elemental analysis and Rietveld-refined XRD patterns confirmed carbon incorporation within the spinel lattice, altering unit cell parameters and crystallite size. Electron microscopic study revealed uniform nanorod morphologies with density variations correlating to carbon content, while UV–Vis spectroscopy demonstrated tunable optical bandgaps (1.85–2.08 eV), attributed to carbon-induced mid-gap states and structural defects. Magnetic characterization revealed soft ferromagnetic behavior with systematic variations in coercivity, remanent magnetization, and saturation magnetization, driven by carbon-mediated defect engineering and Co/Ni stoichiometry. First-Order Reversal Curve (FORC) mapping further uncovered tunable interaction fields and coercivity distributions, highlighting the interplay of carbon-induced pinning effects and cation-driven superexchange interactions. The controlled synthesis and annealing process enabled precise modulation of morphology, carbon content, and cation distribution, offering a pathway to engineer multifunctional spinel oxides for advanced applications.