Ferromagnetism above room temperature in Mn-doped ZnO thin films

Ferromagnetism has been investigated up to 500K 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 480C to 600C, depending on the Mn content. At room temperature Ms decreases with increasing the Mn content, whereas Hc increases. Magnetic measurements, performed at 500K (Ms 0.3emu/g) indicate a Curie temperature above 500K. The observed high temperature ferromagnetism is attributed to the defects in the base materials, intrinsic or induced by the Mn dopant atoms.