Ferromagnetic Cr-Doped ZnO for Spin Electronics via Magnetron Sputtering

Through nonequilibrium rf magnetron cosputtering of ZnO and Cr metal on a-plane Al 2 O 3 we find ferromagnetic ordering with a room-temperature saturation moment of 1.4 μ B per Cr ion at a doping concentration of ~9.5 at. % after UHV postanneal. No secondary phases are detected in the films via x-ray diffraction (XRD). Increased Cr doping causes disorder within the films resulting in decreased overall, and per Cr, moment. The Curie temperature exceeds 365 K, the maximum temperature reached in our experiment. All films are dielectric with a resistivity higher than 10 6 Ω cm at room temperature. The lack of carriers indicates that the ferromagnetic mechanism is not carrier mediated.