ABSTRACT
This chapter discusses the experimental developments of nonlocal spin injection in metallic systems and the related phenomena after the year 2000. It describes the basic aspect of spin injection, spin accumulation, and spin current in lateral devices comprised of non-magnetic and ferromagnetic metals. The chapter introduces the concept of the spin resistance, that is, a measure of impedance against spin relaxation; thereby lateral spin valve structures can be expressed by equivalent spin-resistance circuits in analogy with cascaded transmission lines. It focuses on the effect of the device structure, including the junction size, on the magnitude of the spin accumulation stored in the nonmagnet and also the magnitude of the spin current flowing in it. The Hanle effect is the manifestation of dephasing process in precessional motion of diffusively traveling collective electronic spins. Spin transfer torques arise whenever the flow of spin angular momentum is throwing a portion of its angular momentum while passing through a ferromagnet.
