Enhanced spin polarization of conduction electrons in Ni explained by comparison with Cu

The spin-split Fermi-level crossings of the conduction band in Ni are mappe d out by high-resolution photoemission and compared to the equivalent cross ing in Cu. The area of the quasiparticle peak decreases rapidly below E-F i n Ni, but not in Cu. Majority spins have larger spectral weight at E-F than minority spins, thereby enhancing the spin polarization beyond that expect ed from the density-of-states. A large part of the effect can be traced to a rapid variation of the matrix element with k at the point where the s,p b and begins to hybridize with the d(z)(2) state. However, it is quite possib le that che intensity drop in Ni is reinforced by a transfer of spectral we ight from single-particle to many-electron excitations. The results suggest that the matrix element should he considered for explaining the enhanced s pin polarization observed for Ni in spin-polarized tunneling.