Augmented magnetic nanoparticle assimilation in rGO sheets for tailored static and dynamic magnetic properties in surface functionalized Co0.8Zn0.2Fe2O4 nanoferrite–rGO hybrid structures

Abstract

This research explores the interplay of multifunctional properties within magnetic composite systems. Herein, we investigate the influence of optimized nanoparticle incorporation on the static and dynamic magnetic properties of surface functionalized Co_0.8Zn_0.2Fe₂O₄ (CZFO) nanoferrite/rGO hybrid structures. A facile solvothermal approach enabled efficient integration of CZFO nanoparticles onto rGO sheets, facilitated by surface functionalization of magnetic nanoparticles (MNPs), using PEG-400 to mitigate agglomeration. An optimal rGO concentration of 5 wt% yielded a remarkable saturation magnetization (M_s) of 51.06 emu g⁻¹ comparable to that of bare MNPs, demonstrating the effectiveness of the synthesis strategy. However, a further increase in rGO concentration led to a decrease in M_s due to a decrease in MNPs concentration in the hybrid structure. Comprehensive characterization revealed the formation of crystalline CZFO MNPs with spherical morphology and efficient integration with rGO sheets. Room temperature FMR spectroscopy demonstrated a complex interplay between the MNPs concentration and spin dynamics. The observed broad resonance linewidths, ranging from 1120 to 1751 G, confirmed the presence of strong dipole–dipole interactions and magnetocrystalline anisotropy within the system. The g-factor was found to be in the range of 2.07–2.21, indicating the dominance of electron spin contributions to the magnetic moment. The spin–spin relaxation time exhibits a non-monotonic dependence on the nanoparticle concentration, initially decreasing and then increasing with higher rGO concentrations, ranging from 3.56 ps to 8.28 ps. The fastest relaxation time of 3.56 ps was observed at a 5 wt% rGO concentration. This 5 wt% rGO concentration also exhibits the highest spin concentration, while higher concentrations of 10% and 15% showed a reduction. This suggests an optimal balance between exchange interactions and dipolar broadening at the optimal concentration. The observed correlation between the spin relaxation time and spin concentration highlights the critical role of nanoparticle dispersion and interaction in determining the dynamic magnetic properties of the hybrid structures.