Room temperature ferromagnetism of Fe-doped ZnO and MgO thin films prepared by ink-jet printing

ABSTRACTRoom temperature magnetic properties of un-doped, as well as 10 at.% Fe-doped ZnO and MgO single-pass layer of ink-jet printed thin films have been investigated to obtain insight into the role of the band gaps and mechanisms for the origin of ferromagnetic order in these materials. It is found that on doping with Fe, the saturation magnetization is enhanced by several-fold in both systems when compared with the respective un-doped thin films. For a “28 nm thick film of Fe-doped ZnO (Diluted Magnetic Semiconductor, DMS) we observe an enhanced moment of 0.465μB /Fe atom while it is around 0.111μB/Fe atom for the doped MgO (Diluted Magnetic Insulator, DMI) film of comparable thickness. Also, the pure ZnO is far more ferromagnetic than pure MgO at comparable low film thicknesses which can be attributed to defect induced magnetism originating from cat-ion vacancies. However, the film thickness dependence of the magnetization and the defect concentrations are found to be significantly different in the two systems so that a comparison of the magnetism becomes more complex for thicker films.