Room Temperature Ferromagnetism and Photoluminescence of Fe Doped ZnO Nanocrystals

Undoped and iron doped ZnO nanocrystals are observed to be ferromagnetic at room temperature. The role of short-range disorder in stabilizing ferromagnetism is evident from structural, optical, and electron paramagnetic resonance (EPR) measurements. The substitutional incorporation of Fe3+ at Zn sites is reflected in optical and EPR studies. Isolated as well as interacting Fe3+ ions are observed in EPR. An increase in saturation magnetization is associated with broadening of a ferromagnetic resonance feature with an increase in doping level. Co-, Mn-, and Fe-doped ZnO nanocrystals prepared by the same synthesis protocol confirm anticorrelation between photoluminescence efficiency and ferromagnetic ordering. M(T) curves indicate that the ferromagnetic nanocrystals are formed by the short-range exchange forces associated with the bound magnetic polaron at defect sites.