Enhancement of giant magnetoresistance due to spin mixing in magnetic multilayers with a superconducting contact

We study the giant magnetoresistance (GMR) ratio in magnetic multilayers wit a single superconducting contact in the presence of spin-mixing processes. It has been recently shown [F. Taddei, S. Sanvito, J.H. Jefferson, and C. J. Lambert, Phys, Rev. Lett, 82, 4938 (1999)] that the GMR ratio of magnetic multilayers is strongly suppressed by the presence of a super conducting contact when spin flipping is not allowed. In this paper we demonstrate that the GMR ratio can be dramatically enhanced by spin-orbit interaction and/or noncollinear magnetic moments. The system is described using a tight-binding model with either s-p-d or s-d atomic orbitals per site.