Direct measurement of the spin diffusion length by Andreev spectroscopy

The application of point contact Andreev spectroscopy for the measurement of the spin diffusion length is demonstrated by studying the spin relaxation in platinum thin films grown on the top of a ferromagnetic cobalt layer. Using this local probe technique, the temperature dependence of the spin diffusion length was determined, and various sources of the spin relaxation in platinum were identified. At low temperatures the spin lifetime is found to be three orders of magnitude larger than the momentum lifetime. The applied method is selectively sensitive to spin-flip processes even in the presence of a huge background of momentum scattering.