ABSTRACT
This chapter describes the early development of spin injection in metals and related phenomena prior to the year 2000. It focuses on the application of the spin-injection technique, using the lateral spin valve geometry, to observe the Datta—Das conductance oscillation in a gated two-dimensional electron system structure. Researchers invoke fundamental concepts such as spin injection, spin accumulation, spin-polarized currents in ferromagnet/nonmagnet structures, and pure spin currents. Many of the advances in the field of spin-polarized transport in the solid state have involved tunneling, and experimental studies began with superconducting tunneling spectroscopy about 30 years ago. The physics of spin accumulation and spin diffusion are closely related to the principles of electron spin resonance, and there are similarities in the techniques for measuring spin-diffusion lengths and spin-relaxation times. Pictures of nonequilibrium populations of spin-polarized electrons have been introduced in the context of transmission electron spin resonance experiments.
