ABSTRACT
Spin accumulation is the deviation of spin population in nanostructures from its thermal equilibrium state. It is nowadays considered as one of the most important phenomena in the scienti c and technological eld of the so-called spintronics, which has emerged as a new branch of electronics since the 1990s and includes rich spin-related physics (Wolf et al. 2001, Awschalom et al. 2002, Zutic et al. 2004, Maekawa et al. 2006). e rst example of primary functional properties in which spin accumulation plays an important role is currentperpendicular-to-plane giant magnetoresistance (CPP-GMR) investigated intensively in the early 1990s (e.g., Pratt 1991). Magnetoresistance (MR) e ect is a change in resistance according to the magnetization con guration, and CPP-GMR occurs in metallic multilayers consisting of ferromagnetic layers separated by nonmagnetic spacers when an electrical current ows in the direction perpendicular to the layer planes. Physics of CPP-GMR is well described by the macroscopic model proposed by Valet and Fert (1993), considering spin accumulation around the interfaces in multilayers as well as spin-dependent bulk and interface scattering. Note that GMR has already been used for technical applications such as reading heads of highdensity hard disc drives (HDD), and researches and development of GMR are continued for the demands of higher density HDD (e.g., Tsang et al. 1998, Takagishi et al. 2002).
