Impact of interfacial coupling on the structural, magnetic, and dielectric properties of CoFe2O4/NiO nanocomposites

We report the synthesis and comprehensive characterization of CoFe${}_{\text{2}}$O${}_{\text{4}}$/NiO nanocomposites prepared via a modified co-precipitation method followed by thermal treatment. Structural and morphological analyses confirm the coexistence of pure CoFe${}_{\text{2}}$O${}_{\text{4}}$ and NiO phases with well-defined interfaces. Mössbauer spectroscopy indicates a partially inverted spinel structure. Magnetic measurements revealed particle-size-dependent magnetic ordering, and a transition from single- to multi-domain behavior with increasing particle size, and strong interfacial effects, including exchange bias and wasp-waisted hysteresis loops, as evidenced by $\Delta H$ vs. $M$ plots. AC susceptibility shows frequency-dependent peaks in the imaginary component, with Vogel–Fulcher analysis suggesting cluster-glass-like behavior due to strong interphase interactions. Dielectric measurements demonstrate a marked enhancement of the dielectric constant in the composites, attributed to interfacial polarization at the CoFe${}_{\text{2}}$O${}_{\text{4}}$/NiO boundary. These findings highlight the critical role of interfacial coupling in tailoring the multifunctional properties of oxide-based nanocomposites.