Experimental investigation of the electronic structure ofGd5Ge2Si2 by photoemission and x-ray absorption spectroscopy

Abstract

The electronic structure of the magnetic refrigerantGd5Ge2Si2 has been experimentally investigated by photoemission and x-ray absorption spectroscopy.The resonant photoemission and x-ray absorption measurements performed across theGd N4,5 and Gd M4,5 edges identify the position of Gd 4f multiplet lines, and assess the 4f occupancy(4f7) and the character of the states close to the Fermi edge. The presence ofGd 5d states in the valence band suggests that an indirect 5d exchangemechanism underlies the magnetic interactions between Gd 4f moments inGd5Ge2Si2. From 175 to 300 K the first 4 eV of the valence band and the Gd partial density of statesdo not display clear variations. A significant change is instead detected in thephotoemission spectra at higher binding energy, around 5.5 eV, likely associated to thevariation of the bonding and antibonding Ge(Si) s bands across the phase transition.