Unoccupied energy bands, exchange splitting, and self-energy of iron

Unoccupied energy bands of iron are mapped by inverse photoemission from Fe(100), Fe(110), and Fe(111). The ferromagnetic exchange splitting Eex of the uppermost d band is measured for the H25 point, where the minority- and majority-spin subbands are both empty (Eex=1.8 eV with H25 at 1.9 eV and H25 at 0.12 eV above EF). Several other critical points are determined, such as the minority-spin 12 and P3 points, the majority-spin N3 point, and the higher-lying H15,H1 points of s,p character. Critical points and exchange splitting are compared with first-principles, local-density calculations. The real part of the self-energy is obtained from this comparison, and the imaginary part by measuring the liftime broadening. In the d-band region, the self-energy causes a 10% compression of the bands and a linear broadening (E)0.6E-EF. © 1991 The American Physical Society.