Fabrication of Antiferromagnetic α-Cr2O3(0001) Thin Film and Influence on Magnetism of Ultrathin Co Film

We have investigated the fabrication of α-Cr2O3(0001) thin film on a Au(111) surface and the effect of the antiferromagnetic feature of α-Cr2O3(0001) on the magnetic properties of ultrathin Co film on α-Cr2O3(0001). Highly oriented α-Cr2O3(0001) thin film is fabricated by oxidizing Cr(110) thin film grown on a Au(111) surface. Upon the oxidization of threefold symmetric Cr(110) thin film, the α-Cr2O3(0001) thin film is produced. On α-Cr2O3(0001) thin film, ultrathin Co film is epitaxially grown at 473 K to form fcc-Co(111) film. The antiferromagnetic feature of α-Cr2O3 affects the magnetic properties of the ultrathin Co film. Exchange bias is only observed when the magnetic field is applied perpendicular to the film surface, i.e., the direction parallel to the Cr spin. Additionally, in the temperature dependence of magnetization, the clear signature of a Neel temperature of approximately 300 K is observed. The obtained results indicate the collinear coupling of Co and Cr spins.