Band structure measurements and multi-electron effects (satellites) for nearly-filled d-band metals: Fe, Co, Ni, Cu, Ru, and Pd (invited)

Abstract

Angle-resolved photoelectron spectroscopy has been used to determine energy band dispersions E(k↘) along symmetry lines. A complete description of the ferromagnetic energy bands of Ni at the X-point has been obtained. We observed that the ferromagnetic exchange splitting δEex for the d-like valence bands of Fe, Co, and Ni depends on the symmetry character of the wave functions. In particular, states derived from t2g tight binding orbitals (e.g., Γ25′, X5) exhibit a larger exchange splitting than eg-derived orbitals (e.g., Γ12, X2). This agrees with theoretical estimates based on self-energy calculations. The d-band widths as observed in photoemission are smaller than those determined by ab initio ground state calculations. This effect increases from Fe to Co to Ni, and is small for Cu, Ru and Pd. We correlate this apparent d-band narrowing to the position and strength of two-electron excitations which are seen as satellite structures to the valence band emission.