The study of electron-spin transport through nonmagnetic spacer materials sandwiched in between ferromagnetic electrodes is an extremely active eld, because of the rich physics involved and the important applications in the area of magnetic sensors.1 If the spin diffusion length is larger than or comparable to the distance between the electrodes, the current through such sandwich structures can depend strongly on the mutual orientation of the magnetizations of the electrodes, which is called the spin valve effect. Switching of this orientation by an external magnetic eld, B, can then lead to a strong dependence of the current on B, an effect called giant magnetoresistance (GMR).2,3 This effect can be used in magnetic sensors, e.g., in reading magnetic information in hard disks.