Generation of Large Spin Accumulation in S/N/S Josephson Junctions

We have studied the generation of spin accumulation much larger than the conventional value in lateral spin valves. The accumulation can be used as an alternative means to apply the exchange field in the Josephson junction to induce exotic superconductive phenomena such as 0-pi transition. In Cu/MgO/permalloy (Py) lateral spin valve devices, the MgO interface layer enhances the spin accumulation at 10 K by a factor of ten. The spin diffusion length of 1.3 mu m at 10 K for Cu assures homogeneous spin polarization in the region of interest. Thereby we intend to inject the spin current with the large spin accumulation into superconductor(S)/normal metal(N)/superconductor Josephson junctions. As a primary attempt, we fabricated in-situ samples for spin injection into Josephson junction with Ohmic contact between Cu and Py. The clear suppression of the critical current of the Josephson junction is observed as the spin injection current increases.