PNNL

Abstract

Through nonequilibrium rf magnetron co-sputtering of ZnO and Cr metal on a-plane Al2O3 we find ferromagnetic ordering with a room-temperature saturation moment of 1.4 mB 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 sXRDd. 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 106 V cm at room temperature. The lack of carriers indicates that the ferromagnetic mechanism is not carrier mediated.