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 delta-E(ex) of the uppermost d band is measured for the H'25 point, where the minority- and majority-spin subbands are both empty (delta-E(ex) = 1.8 eV with H'25 down at 1.9 eV and H'25 up at 0.12 eV above E(F)). Several other critical points are determined, such as the minority-spin GAMMA-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 lifetime broadening. In the d-band region, the self-energy causes a 10% compression of the bands and a linear broadening GAMMA(E) almost-equal-to 0.6\E - E(F)\.