Correlation between mixed valence behaviour of cerium and the magnetic and superconducting phenomena of CeFe 2 and CeRu 2

Abstract

This contribution concerns an X-ray absorption investigation of the cubic Laves phase rare earth compounds CeFe 2, CeRu 2 and their related hybrides. These compounds have been investigated by Extended X-ray Absorption Fine Structure (EXAFS) both at cerium and iron sites and by X-ray Absorption Near Edge Spectroscopy (XANES) at different edges of both ruthenium and iron species. The hydrogen absorption process is correlated with the suppression of the cerium fluctuating valence state in the case of CeFe 2, while the intermediate valence character is detected in CeRu 2 also upon the absorption process. These results and the change of 3d–5d hybridization determined by structural disorder effects in the hydridate phase of these systems can explain the anomalous magnetic behaviour of the hydridate phases when compared with those of the whole series REFe 2 and RERu 2.