Transport spin polarization of NixFe1-x: Electronic kinematics and band structure

We present measurements of the transport spin polarization of NixFe1-x (0 l ess than or equal to x less than or equal to 1) using the recently develope d point-contact Andreev reflection technique, and compare them with our fir st-principles calculations of the spin polarization for this system. Surpri singly, the measured spin polarization is almost composition independent. T he results clearly demonstrate that the sign of the transport spin polariza tion does not coincide with that of the difference of the densities of stat es at the Fermi level. Calculations indicate that the independence of the s pin polarization of the composition is due to compensation of density of st ates and Fermi velocity in the s and d bands.