In this paper, we demonstrate through experiments and analysis that the most probable mechanism for the observed ferromagnetism in 2% Mn-doped ZnO thin films is a combination of intrinsic and carrier-mediated interaction of the magnetic moments. While no impurity-phase contributions were detected, a strong correlation between effective carrier densities and ferromagnetism was established. Magnetism in amorphous films with high defect densities were described by a bound magnetic polaron model whereas that in highly conducting films was consistent with a Ruderman-Kittel-Kasuya-Yosida exchange mechanism.

• Received 15 January 2010

DOI:https://doi.org/10.1103/PhysRevB.81.205202