Chemical pressure effects and valence fluctuations in Yb 0.6Ca 0.4Al 2 and YbAl 2 alloys: A photoemission investigation
We present angle integrated X-ray photoemission studies of Yb 0.6Ca 0.4Al 2 and YbAl 2 alloys. Mixed valence behaviour was observed for Yb in both compounds with room temperature valence estimated at 2.28 ± 0.03 for Yb 0.6Ca 0.4Al 2 and 2.33 ± 0.03 for YbAl 2. The lower intermediate valence for Yb in the pseudo-binary compound Yb 0.6Ca 0.4Al 2 is related to chemical pressure effects. Results at liquid nitrogen temperature indicate further reduction (about 10%) in the trivalent state contribution.