Anomalous Temperature Behavior of Sn Impurities

D. Haskel, H. Shechter, E. A. Stern, M. Newville and Y. Yacoby

Department of Physics, Technion, Haifa, Israel

Department of Physics FM-15, University of Washington, Seattle, WA 98195

Racah Institute of Physics, Hebrew University, Jerusalem, Israel

Abstract:

Sn impurities in Pb and Ag hosts have been investigated by the Mössbauer effect (ME) and in Pb by x-ray absorption fine structure (XAFS). The Sn atoms are dissolved up to at least 2 at.% in Pb and up to at least 8 at.% in Ag for the temperature ranges investigated. The concentration limit for Sn-Sn interactions is 1 at.% for Pb and 2 at.% for Ag as determined experimentally by lowering the Sn concentration until no appreciable change occurs in the Mössbauer effect. XAFS measurements verify that the Sn impurities in Pb are dissolved and predominantly at substitutional sites. For both hosts the temperature dependence of the spectral intensities of isolated Sn impurities below a temperature is as expected for vibrating about a lattice site. Above the Mössbauer spectral intensity exhibits a greatly increased rate of drop-off with temperature without appreciable broadening. This drop-off is too steep to be explained by ordinary anharmonic effects and can be explained by a liquid-like rapid hopping of the Sn, localized about a lattice site. Higher entropy density regions of radii somewhat more than an atomic spacing surround such impurities, and can act as nucleation sites for 3-dimensional melting.

• introduction
• Experimental Techniques and Results
• Discussion
• Summary and Conclusions
• Acknowledgements
• References
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