Influence of domain wall scattering on the magnetoresistance of Co and Co₈₀Pt₂₀ film systems

Constant miniaturization of electronic devices and storage media demands a detailed understanding of transport processes and structures on the atomic scale. In particular, interfaces between magnetic domains play an important role because of domain wall pinning at the interfaces. Here, we study the anisotropic magnetoresistance and the influence of domain walls on the resistance in Co and Co₈₀Pt₂₀ films in contact with Pt leads as a function of the geometry and thickness of the ferromagnetic films. The calculations were performed by using a fully relativistic ab initio scattering approach (Korringa–Kohn–Rostoker) and the Kubo–Greenwood formalism. In particular, the relation between the width of the domain wall and its contribution to the magnetoresistance was calculated and compared to a model calculation by Levy and Zhang Phys. Rev. Lett. 79 5110 (1997). In the case of the current perpendicular to the plane geometry, the calculated decay of the domain wall magnetoresistance corresponds to the predicted 1/L² (L=̂domain wall width) scaling behavior for the case of wide domain walls. For domain walls smaller than a critical width L_min, a linear decay of the magnetoresistance is observed. A second type of domain walls with its magnetic orientation being partially out of plane was investigated. In this case, no 1/L² behavior was found.