ZnFe2O4 Nanotubes: Microstructure and Magnetic Properties

Employing an electron energy-loss spectrum (EELS), we have found that the structure of ZnFe2O4 nanotubes deviated from the normal spinel structure as the calcination temperature decreases. More Fe3+ ions migrate to the tetrahedral sites (A sites) rather than staying in their equilibrium octahedral sites (B sites). This results in the enhanced superexchange interactions between Fe3+ ions, thus affecting the magnetic properties of the nanotubes, i.e., higher blocking temperature (T-B) and larger saturation magnetization (M-S), etc. On the other hand, we have also found that deviation of the Fe/Zn from 2 affects the magnetic properties of the nanotube samples. This should be caused by the enhanced superexchange interactions resulting from the extra Fe3+ ions in the nonstoichiometric sample.