Simple explanation of tunneling spin-polarization of Fe, Co, Ni and its alloys

Values of the electron spin-polarization and their proportionality to bulk moments are easily explained by realizing that they are due to the itinerant d-like electrons. The proportionality of the tunneling current of superconductors and ferromagnets to the three-dimensional density-of-states is seen to occur naturally in the independent particle model. In contrast to tunneling, photoelectrons are dominated by localized electrons; these are also seen to be in agreement with calculated band structure.