Removal of Ferrimagnetic ZnFe2O4 Impurity Phase by Li Co-Doping in Fe Doped ZnO

Abstract

A simple approach is presented to remove the impurity phase of ZnFe2O4 from Fe doped ZnO. Gradual incorporation of non-magnetic Li ions reduced 5.6% phase contamination of ZnFe2O4 to negligible limit (<0.01%) from 4 at% (atomic %) Fe doped ZnO. X-ray absorption near edge spectroscopy (XANES) revealed that the most of the Fe ions were in Fe3+ state. The optical absorption spectra of Fe doped ZnO samples exhibited d-d transition between Fe ions. It also indicated the signature of ZnFe2O4 phase, which reduced gradually on Li increment. ZnFe2O4 contained samples exhibited strong magnetic ordering with spin-glass character at low temperature and weak ferromagnetism (FM) at the room temperature with disordered inverse spinel structure. However, 6 at% Li incorporated sample did not show any significant FM in the entire temperature range of 2-300K. ZnFe2O4 is supposed to be the possible source of the observed strong magnetic ordering i.e., FM has extrinsic origin. The gradual removal of impurity phase ZnFe2O4 by increasing Li doping without damaging any intrinsic property of Fe doped ZnO is primarily due to gradual increase of tetrahedral coordination of Fe ions.