Momentum dependence of the Stoner excitation spectrum of iron using spin-polarized electron-energy-loss spectroscopy

The electron-hole excitations with different spin configurations have been separated and studied experimentally in iron, with use of spin-resolved electron-energy-loss spectroscopy with both a source and detector of spin-polarized electrons. The data are interpreted using a two-particle, exchange scattering model, and analyzed in the 4×4 product spin space of the incident and target electrons. Stoner excitations in the form of majority-hole–minority-electron pairs are found to comprise up to one-third of the total electron-hole excitations in off-specular scattering, and exhibit a clear, broad peak due to excitations within the exchange-split d bands of iron. The width and energy loss at which this peak occurs increase with increasing wave vector of the Stoner excitation. These trends are also observed in the calculated Stoner density of states for iron.