ИСТИНА

Nanostructures are a crucial component of modern technologies, with applications spanning from data storage to biomedicine. Magnetic nanoparticles based on spinel ferrites attract particular attention due to the diversity of their physical and chemical properties [1]. Among them, ferrites of the composition MnxCo1₋xFe2O4 stand out because of the similarity of ionic radii and electronic structures of the constituent metal atoms. Compared to cobalt and iron, manganese possesses a higher magnetic moment, and substituting cobalt with manganese could significantly enhance the magnetic properties of ferrites in this system. One promising application for such nanoferrites is the development of cost-effective permanent magnets to fill the gap between conventional ferrite magnets and rare-earth-based magnets such as NdFeB [2,3]. In this study, MnxCo1₋xFe2O4 nanoparticles were synthesized using the sol–gel method, self combustion reaction with heating up to 350 °C. After cooling, the samples were annealed in the temperature range from 500 to 700 °C. The manganese concentration was varied within the range x = 0.15–0.35. The resulting materials were characterized using magnetic measurements, X-ray diffraction (XRD), and Mössbauer spectroscopy. It was found that manganese incorporation alters the distribution of metal cations among the spinel sublattices, leading to a non-monotonic change in magnetic properties. Additionally, an increase in manganese concentration, combined with annealing at temperatures up to 600 °C, promotes the segregation of hematite from the ferrite structure. This segregation results in a decrease in the saturation magnetization of the ferrite nanoparticles.