Zero-Dimensional Spin Accumulation and Spin Dynamics in a Mesoscopic Metal Island

We have measured electron spin accumulation at 4.2 K and at room temperature in an aluminum island with all dimensions (400 nm×400 nm×30 nm) smaller than the spin relaxation length. For the first time, we obtain uniform spin accumulation in a four-terminal lateral device with a magnitude exceeding the Ohmic resistance in the island. By controlling the magnetization directions of the four magnetic electrodes that contact the island, we have performed a detailed study of the spin accumulation. Spin precession measurements confirm the uniformity of our system and provide an accurate method to extract the spin relaxation time.