Ce valence state probed by XAFS study in Ce2Fe17 − xGaxHy compounds

Abstract This system is a good probe for the study of the effect of Fe → Ga substitution and hydrogen insertion, on the degree of localization of the 4f states of cerium. We tried to correlate the electronic state of cerium with the changes in the magnetic properties. The studied compounds crystallize in the Th 2 Zn 17 type of structure. Most of them are ferromagnetic with Curie temperatures near room temperature. Insertion of hydrogen or Fe → Ga substitution leads to spectacular changes in the ordering temperature. Both, hydrogen and gallium atoms take part in the cerium coordination leading to a change of the local environment of cerium. Measurements of X-ray absorption spectroscopy have been combined with magnetization measurements in order to probe the magnetic properties of the Ce 2 Fe 17 − x Ga x H y system. X-ray absorption near edge spectroscopy XANES has been measured at the Ce L 2.3 edges. The Ce 5d magnetic moment has been estimated using polarized X-ray absorption spectroscopy. We discuss the effect of hydrogen on the rare earth 6s electronic states in the light of earlier Mossbauer Spectroscopy.