Spin injection efficiency from two adjoining ferromagnetic metals into a   two-dimensional electron gas
  In order to enhance spin injection efficiency from ferromagnetic (FM) metal into a two-dimensional electron gas (2DEG), we introduce another FM metal and two tunnel barriers (I) between them to investigate the current polarization in such ballistic FM/I/FM/I/2DEG junction. Our treatment is based on the free-electron scattering theory. It is found that due to quantum interference effect, the magnitude and sign of the current polarization exhibits periodical oscillating behavior with variation of the thickness of the middle FM metal layer or its exchange energy strength. For some suitable parameters, the spin injection efficiency may arrive over 80% in this junction and can also be controlled by the electron density of 2DEG. Our results may shed light on the development of new spin-polarized device. 
Jun Wang, D.Y. Xing, and H.B. Sun