Integrating the structural, electro-optical, dielectric, and magnetic features of Co–Mg–La ferrites/graphene composites

Graphene nanoplatelets (GNPs) offer excellent support for a diverse array of composite applications. Herein, Co_0.5Mg_0.5Fe_1.8La_0.2O₄ (CMFL) and its composites were prepared by the sol–gel autocombustion method. X-ray diffraction confirmed the formation of a single-phase structure, with both the average crystallite size (34.33–46.30 nm) and the lattice constant (8.292–8.411 Å) increasing with GNP insertion. The presence of graphene in the nanocomposites was confirmed by Raman spectroscopy, which revealed a D band at 1376.38 cm⁻¹. The Fourier transform infrared spectra indicated the existence of absorption bands corresponding to tetrahedral (534.46–525.94 cm⁻¹) and octahedral (456.62–454.95 cm⁻¹) structures. The optical bandgap energy (E_g) varied when the compositions of the samples were changed, with the lowest value of E_g being 2.58 eV for CMFL/2.5 wt.% GNPs. The DC electrical resistivity increased from 6.73 × 10⁴ to 1.07 × 10⁶ Ω cm, indicating that the composite materials might be appropriate for use in transformers and telecommunications devices. With increasing frequency, the dielectric constant and loss decreased, whereas the AC conductivity improved. The Cole–Cole behavior showed that the conduction mechanism had non-Debye relaxation characteristics. The saturation magnetization increased from 25.86 to 42.75 emu/g for the synthesized samples, and the coercivity demonstrated a variable trend.