Ferromagnetism in Mn-doped ZnO due to impurity bands

We have prepared quasi-homoepitaxial Zn0.95Mn0.05O-films on ZnO substrates by pulsed laser deposition. The thin films were characterized by in situ RHEED during growth, X-ray diffraction and reflectometry, as well as transmission electron microscopy (TEM). The magnetic properties have been analyzed by SQUID magnetometry and by measuring the anomalous Hall effect. By varying the growth conditions (substrate temperature: 200-600 ∘C, deposition atmospheres: Ar, O2) a different concentration of impurities has been generated. Our results show that the films are electron doped and exhibit a ferromagnetic coupling that depends on the impurity concentration.