Enhancement of spin accumulation in a nonmagnetic layer by reducing junction size

The junction size dependence of the spin accumulation in a nonmagnet is studied by using lateral spin valves geometry consisting of the Py/Cu ohmic junctions. We experimentally demonstrate that reducing the size of the junction drastically improves the efficiency of the spin injection into the Cu wire because of the enhancement of the spin resistance for the Py wire. The spin polarization in the Cu wire increases exponentially with reducing the junction area irrespective of the same spacing between the injector and the detector. The junction size dependence of the spin signal yields the spin diffusion lengths and the spin polarization which are reasonable values compared with previous experiments.