Magneto-transport flipping induced by surface oxidation in Co films

Abstract

We have performed low temperature magnetoresistance (MR) and magnetization measurements for a series of thin Co films with different degrees of oxidation to investigate the role of surface oxidation on magnetic properties. For films with less oxidation, magneto-transport exhibits the typical anisotropic magnetoresistance behavior. However, magneto-transport flips completely in films with severe oxidation. The inverse MR is replaced by the normal MR when the applied magnetic field is a long the current. The normal MR is changed to the inverse MR when the applied magnetic field is perpendicular to the current. Since the disorder will enhance the spin-orbital interaction and electron-electron interaction in thin films, we suggest that both mechanisms may be responsible for the flipping in anisotropic MR induced by surface oxidation.