Spin-Dependent Density of States in Ferromagnetic Ni-Fe Alloys

Experimental spectra of spin-polarized photoemission from well-defined ${\mathrm{Ni}}_{1-x}{\mathrm{Fe}}_x$ (100) surfaces for $x=0.2\mathrm{} \mathrm{and} 0.6$ are presented. They reflect the difference between occupied up- and down-spin densities of states of the bulk near the Fermi energy. It is shown that the majority bands are not full for $x=0.6\mathrm{}$, in contrast to $x=0.2\mathrm{}$ and pure Ni, and that the majority density of states dominates at the Fermi energy for $x=0.6\mathrm{}$. Current theories of ferromagnetic alloys do not fully account for the observed spin polarization.