EXCHANGE-FIELD PENETRATION INTO A TUNNEL BARRIER - SPIN SELECTION IN ELECTRON-TUNNELING FROM A PARAMAGNET TO A FERROMAGNET

It is shown that the tunnel barrier for electron tunneling from a paramagnet to a ferromagnet preferentially enhances the majority-spin tunneling probability, thus resulting in spin selection. This is due to the ferromagnet-exchange-field penetration into the tunnel barrier. In the context of this effect, we discuss experiments reported by Tedrow and Meservey [Phys. Rev. B 7, 318 (1973)].