XPS and X-BPS studies of Gd monopnictides

We have studied the electronic structures of GdX (X: P, As, Sb, Bi) by means of the X-ray photoemission, X-ray bremsstrahlung isochromat and vacuum ultraviolet inverse photoemission spectroscopy. We have found monotonous energy shifts of the Gd 3d, 4d and 4f levels from GdP to GdBi. Such systematic energy shifts are attributed to the reduced crystal field splitting of the Gd 5d state through GdX. The occupied valence band is dominated by the X p state. The energy shifts of the valence band are found to be much different from those of the Gd-derived states, but consistently interpreted by the band calculation.