Influence of structural evolution on the magnetic behavior of the nanocrystals of Fe-doped ZnO synthesized by soft chemical route

Abstract

Soft chemical route has been used for the synthesis of nanocrystalline undoped and 5 wt% Fe-doped ZnO powder. The structural, nano/microstructural, vibrational and magnetic properties of these samples have been studied as a function of calcination temperature (400–1100 °C). X-ray diffraction studies revealed major nanocrystalline wurtzite (ZnO) phase at 400 °C only. As the calcination temperature increases to 700 °C, the evolution of the nanocrystalline secondary cubic spinel ZnFe2O4 along with major phase of ZnO is observed. Interestingly, Fe-doped ZnO calcined at 400 °C has exhibited ferromagnetic behavior at room temperature and both the magnetic parameters (M s , H c ) are larger than those of Fe-doped ZnO calcined at 700 °C. The reduction in the magnetization and coercivity has been evidenced with the increase in the grain size of the secondary cubic spinel ZnFe2O4 phase. These changes are ascribed to the degree of inversion of spinel structure, i.e., occupancy of ferric ions in both sites with different symmetries is proposed to be solely responsible for the unusual behavior. At 1100 °C, zero coercivity is observed due to paramagnetic behavior of bulk cubic spinel ZnFe2O4 phase.