Eddy current loss behavior of MS/Fe3O4 nanocomposites and M-doped Fe3O4 nanoparticles (M = Mn, Zn) analyzed through dielectric and magnetic studies

The critical parameter of eddy current change plays a crucial role in analyzing the characteristics and defects of materials used in industry. Following the successful co-precipitation synthesis of magnetite (Fe₃O₄) nanoparticles (NPs), this study employed X-ray diffraction to analyze the sample's structure and phases. Morphological FESEM testing revealed diameters of 9 nm, 18 nm, 14 nm, 12 nm, and 20 nm for the pure Fe₃O₄, Zn-doped Fe₃O₄, Mn-doped Fe₃O₄, ZnS/Fe₃O₄, and MnS/Fe₃O₄ nanoparticles, respectively. Moreover, dielectric and eddy current investigations of the synthesized samples were conducted at ambient temperature over a frequency range of 10^-3 to 10⁶ Hz. The data analysis shows that the resistive and capacitive properties of the samples are primarily attributed to processes associated with grains and grain boundaries. Additionally, across all samples, a decrease in frequency resulted in increased capacitance and dielectric parameters. The variation of dielectric properties and AC conductivity with frequency indicates that the dispersion is mainly due to Maxwell-Wagner interfacial polarization and charge hopping between Fe²⁺ and Fe³⁺ ions at octahedral sites. Frequency-dependent magnetic parameters and electric modulus were observed in all samples. The analysis of magnetic parameters μ' and μ″, along with eddy currents, suggests that Mn and Zn doping, as well as ZnS and MnS nanoparticles, enhance these parameters compared to their effects on dielectric properties. Manganese sulfide had the greatest impact on eddy currents, while pure magnetite displayed the lowest eddy current and the highest loss tangent. Examination of M-H hysteresis loops revealed that the saturation magnetization (M_s) of multi-domain iron oxide magnetite increases with zinc doping. Conversely, manganese doping and the presence of manganese sulfide and zinc sulfide nanoparticles lead to a decrease in saturation magnetization. The hysteresis loop data also allowed for the extraction of other magnetic properties, including the anisotropy constant (K), anisotropy field (H_k), and magnetic moment (n_B).