A comparative study on the ferromagnetic properties of undoped and Mn-doped ZnO

We have investigated the origin of the ferromagnetic ordering in undoped and Mn-doped ZnO thin films. A systematic comparison is presented between two sets of films grown by pulsed laser deposition from targets prepared under the same conditions. We show that ferromagnetic ordering in both compounds is directly related to the concentration of oxygen vacancies. The incorporation of Mn dramatically increases the magnetic moment in highly oxygen-deficient films. By analyzing the photoluminescence spectra and the structural properties of the films, we can exclude that magnetic ordering in our films originates from unintentional doping. (C) 2012 Elsevier B. V. All rights reserved.