Mössbauer investigations of Fe and Fe$_{3}$O$_{4}$ magnetic nanoparticles for hyperthermia applications

Magnetic nanoparticles of magnetite Fe$_{3}$O$_{4}$ and Fe synthesized by physical vapor deposition with a fast highly effective method using a solar energy have been studied. Targets have been prepared from tablets pressed from Fe$_{3}$O$_{4}$ or Fe powders. Relationships between the structure of nanoparticles and their magnetic properties have been investigated in order to understand principles of the control of the parameters of magnetic nanoparticles. Mössbauer investigations have revealed that the nanoparticles synthesized from tablets of both pure iron and Fe$_{3}$O$_{4}$ consist of two phases: pure iron and iron oxides ($\gamma$-Fe$_{2}$O$_{3}$ and Fe$_{3}$O$_{4}$). The high iron oxidability suggests that the synthesized nanoparticles have a core/shell structure, where the core is pure iron and the shell is an oxidized iron layer. Magnetite nanoparticles synthesized at a pressure of 80 Torr have the best parameters for hyperthermia due to their core/shell structure and core-to-shell volume ratio.