Ferromagnetism and exchange bias in Fe-doped ZnO nanocrystals

Zn1−xFexO (x = 0.03, 0.05, 0.08, 0.1) nanocrystals were synthesized from Zn nitrate and Fe nitrate reduced by citrate. The X-ray diffraction (XRD) shows that Zn1−xFexO (x ≤ 0.08) samples are single phase with the ZnO-like wurtzite structure, while the secondary phase ZnFe2O4 is observed in Zn0.9Fe0.1O sample. Magnetic measurements indicate that Zn1−xFexO (x = 0.03, 0.05, 0.08) are ferromagnetic at room temperature and appear exchange bias varies with Fe concentration. The origin of the ferromagnetic is given by exchange and Zn vacancies in samples.