Spin precession in lateral all-metal spin valves: Experimental observation and theoretical description

Mesoscopic all-metal spin-valve devices containing two ferromagnetic permalloy electrodes and an interconnecting aluminum strip have been studied experimentally and theoretically in nonlocal geometry. Spin-valve devices have been fabricated by thermal evaporation of permalloy electrodes, formation of tunnel barriers by natural oxidation in air or in pure oxygen, and subsequent deposition of an aluminum strip on top of the electrodes. Transport measurements at temperatures of liquid helium have been performed. Spin-dependent phenomena, namely the nonlocal spin-valve effect and spin precession, are observed. A theoretical description of spin-dependent transport is presented including spin diffusion, spin relaxation, spin precession, and tunnel barriers at the interfaces between the electrodes and the aluminum strip. From the comparison of the experimentally observed spin precession to the theoretical description, we obtain a spin-relaxation time of 111 ps and a spin-relaxation length of 1034 nm in aluminum.