G. Fabbris, T. Matsuoka, J. Lim, J. R. L. Mardegan, K. Shimizu, D. Haskel, J. S. Schilling
We demonstrate that the pressure-induced volume collapse transitions observed in Gd and Tb metals have different origins, despite their neighboring location in the periodic table. While the collapse in Gd is caused by s->d electron transfer without involvement of 4f electrons, that in Tb is largely driven by an enhanced negative exchange interaction between local 4f and conduction electrons under pressure (Kondo resonance). These findings are derived from element- and orbital-selective x-ray absorption and emission spectroscopic measurements on Tb and Gd metals together with electrical resistivity measurements of the superconducting transition temperature of Y(Tb) and Y(Gd) dilute alloys carried out under high pressure to 120 GPa. The results highlight the richness of behavior behind the volume collapse transition in lanthanide metals where, unlike assumed in most prevalent models, 4f electron involvement may or may not be a key ingredient.
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http://arxiv.org/abs/1305.3852
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