Effect of iron doping on the structural and magnetic properties of ZnO nanoparticles prepared by pulsed electron beam evaporation

Nanocrystalline ZnO, ZnO–Zn, and ZnO–Zn–Fe powders with a specific surface area up to 45 m$^2$/g and a low Fe concentration (no more than 0.619 wt%) have been prepared using pulsed electron beam evaporation. The crystal structure, morphology, and size of the nanoparticles have been determined using X-ray powder diffraction, transmission electron microscopy, and scanning electron microscopy. It has been found that the magnetization of the ZnO-Zn and ZnO–Zn–Fe nanopowders increases after annealing in an oxidizing atmosphere. An elemental mapping with energy-dispersive X-ray analysis has revealed the absence of Fe clusters in the ZnO–Zn–Fe sample. A thermal analysis has demonstrated that dopants of Fe in ZnO increase the temperature of complete oxidation of Zn nanoparticles to 600$^\circ$C, which creates favorable conditions for an increase in the density of structural defects upon oxidation of Zn to ZnO. The absence of clusters and secondary magnetic Fe phases in pure and doped ZnO-based nanopowders indicates the intrinsic nature of ferromagnetism at room temperature in nanopowders prepared by pulsed electron beam evaporation.