The spin-split Fermi level crossings of the conduction band in Ni are mapped out by high-resolution photoemission and compared to the equivalent crossing in Cu. The area of the quasiparticle peak decreases rapidly below Ef in Ni, but not in Cu. Majority spins have larger spectral weight at Ef than minority spins, thereby enhancing the spin-polarization beyond that expected 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-band begins to hybridize with the dz 2 state. However, it is quite possible that the intensity drop in Ni is reinforced by a transfer of spectral weight from single-particle to many-electron excitations. The results suggest that the matrix element should be considered for explaining the enhanced spin polarization observed for Ni in spin-polarized tunneling.

Angle-resolved photoemission is used to determine the change in the electronic states of Ni induced by doping with Fe and Cr. Well-defined spin and k states are selected using high energy and k resolution combined with single crystal alloys. Iron suppresses the mean free path of minority spins only, while chromium suppresses both spins and decreases the magnetic splitting. The strong variation of these effects from one impurity to the other supports the concept of magnetic doping.

The k-space electronic structure of Co x Ni 1Ϫx alloy films epitaxially grown on Cu͑100͒ has been investigated with changing stoichiometry in angle-resolved photoemission, and is compared to the electronic structure of fcc films of Co and Ni, and single-crystalline Cu. We have monitored changes in the Fermi surface with changing stoichiometry and changing magnetic behavior. The measurements show that the sp band is a prominent feature of the Fermi surface throughout k space for all of the alloys and the magnetic 3d pseudomorphic fcc films. A band-structure calculation of Ni allows us to identify d-hole pockets which increase in size with changing stoichiometry. Minority spin states highlight specific regions of k space associated with key spanning vectors that determine the oscillatory exchange coupling, which underpins the giant magnetoresistance effect in heterostructures. ͓S0163-1829͑99͒03948-X͔