Spin injection in mesoscopic silver wires: experimental test of resistance mismatch.

The spin polarization of current injected from a Permalloy electrode into a mesoscopic Ag wire is measured for samples with very low interface resistance. The observed value of 22.3% +/- 1.6% at 79 K is an order of magnitude larger than values previously reported for low resistance interfaces and about 4 times larger than predictions of the common resistance mismatch model. These results demonstrate that high resistance barriers are not necessary for efficient spin injection.