Ferromagnetism above room temperature in Mn-doped ZnO thin films

Ferromagnetism has been investigated up to 500 K in Mn-doped ZnO thin films grown by pulsed laser deposition starting from targets of different Mn atomic concentrations (CMn) (4-10 at.%) and varying the oxygen pressure and the substrate temperature. The films with the largest saturation magnetization (Ms) (0.36-1 emu/g) and coercive field (Hc) (80-200 Oe) were grown at O2 pressure of 2×10−3 mbar and at substrate temperature ranging from 480∘C to 600∘C, depending on the Mn content. At room temperature Ms decreases with increasing the Mn content, whereas Hc increases. Magnetic measurements, performed at 500 K (Ms≈0.3emu/g) indicate a Curie temperature above 500 K. The observed high temperature ferromagnetism is attributed to the defects in the base materials, intrinsic or induced by the Mn dopant atoms.