One ‐step synthesis of composite materials based on polytetrafluoroethylene microgranules and Co@ Fe ₂ O ₃ ‐FeF ₂ nanoparticles

This paper investigates the structure and magnetic characteristics of Co@Fe 2 O 3 ‐FeF 2 nanoparticles localized on the surface of polytetrafluoroethylene microgranules. It is the first time that nanocomposite materials of this composition were obtained. The average size of the nanoparticles was established by transmission electron microscopy and amounted to 10.9 nm. According to the data of energy dispersive analysis, Mössbauer spectroscopy, X‐ray emission spectroscopy, and EXAFS, it was found that the particles consist of a metallic cobalt core surrounded by a surface shell of Fe 2 O 3 and FeF 2 , due to the oxidation of surface iron atoms and their interaction with the polymer matrix, respectively. The studies of magnetic properties showed that the material has blocking temperature of 200 K and residual magnetization in the temperature range from 4.2 to 300 K.