The impact of the NZFO content on the synergy effect in NZFO/f-MWCNTs nanocomposites synthesized via ex-situ method

We present a comprehensive study of the synergistic effects in as-received NZFO/f-MWCNT nanocomposites synthesized via an ex-situ method with varying contents (2, 5, 25, and 50 wt%) of Ni 0.5 Zn 0.5 Fe 2 O 4 (NZFO) nanoparticles dispersed within a matrix of functionalized multi-walled carbon nanotubes (f-MWCNTs). The structural and microstructural characteristics governing the efficiency of the synthesis process were investigated using complementary techniques, including X-ray diffraction (XRD) and Raman spectroscopy. The results reveal that the NZFO crystallite size remains nearly constant across the investigated composition range, while the structural integrity of the carbon matrix is preserved. The redistribution of cations between the A-tetrahedral and B-octahedral sites was quantified by the cation inversion parameter (δ). Magnetic characterization indicates the presence of a cluster-glass state in the NZFO nanoparticles. A core-shell-like magnetic structure, consisting of a magnetically ordered core surrounded by a disordered magnetic dead layer (MDL), is identified. The magnetic behaviour is discussed within the framework of the Yafet–Kittel model, taking into account the evolution of the cation inversion parameter. Comparative analysis of photoemission spectra highlights the contributions of magnetic trivalent iron at A and B sites and Fe-based residual species originating from the carbon matrix, irrespective of the NZFO content in the composites. These findings provide insight into the interplay between the ferrite phase and the carbon nanotube matrix, elucidating the origins of the observed synergic effects in NZFO/f-MWCNT nanocomposites.