Spin-polarized tunneling in room-temperature mesoscopic spin valves

We study optimization of spin injection and detection both at 4.2 K and at room temperature using a metallic mesoscopic spin valve structure with tunneling interfaces between the ferromagnetic electrodes (CoFe or NiFe) and the central metallic conductor (Al). We investigate the influence of the barrier transparency on the spin polarization of the tunneling electrons by varying the O-2 exposure of the Al film before depositing the ferromagnetic electrodes. An increase of the polarization from similar to10% to 16% (25% at 4.2 K) is observed as the resistance of the junction is increased from 100 to 700 Omegamum(2). A spin transresistance as high as 2.5 Omega is obtained at 4.2 K. (C) 2004 American Institute of Physics.