Spin injection, diffusion, and detection in lateral spin-valves

We demonstrate the injection of spin-polarized electrons into paramagnetic Au nanowires by driving an electric current from a ferromagnetic permalloy (Py) electrode. The nonequilibrium spin accumulation in Au results in a difference between the chemical potentials for spin-up and spin-down electrons that is detected as a field-dependent voltage signal using a second Py electrode. The magnitude of the voltage contrast (>10%) and its coincidence with the magnetic switching of the Py electrodes attest to the spin-sensitive origin of the signals. By increasing the separation of the Py injector and detector, we observe an exponential decay of the spin signals. The measurements yield a spin-diffusion length of 63+/-15 nm and an injected spin polarization of 3% in Au at 10 K. (C) 2004 American Institute of Physics.