Spin Polarized Transport of Electrons in Metal Wires

Introduction Current traveling through a material can have a spin polarization; that is, there can exist more electrons in a current with spin up than spin down or vice versa. It has been discovered that a conducting or semiconducting material can be “injected” with a spinpolarized current. Passing a current through a ferromagnetic material can induce this spin-polarization, which remains as the current passes from the ferromagnetic material into a nonmagnetic material. As the current travels through the nonmagnetic material, however, this spin-polarization dies out quickly. Because of this rapid depolarization, the spin-polarization is not usually measured in wires of macroscopic dimensions. The little spin polarization that a current may exhibit is quickly dissipated by the equalizing effects of spin scattering events within a given material. However, spin polarization is more apparent at both low temperatures and over small distances due to the highly reduced frequency of spin-flip and spin-orbit scattering, which tend to depolarize current.