Electronic Structure of Gadolinium and Terbium at Extreme Pressure

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Date/Time:Friday, 11 Apr 2014 - Friday, 11 Apr 2014
Location:ROOM 18/19 PHYSICS Hall
Phone:515-294-5630
Channel:Condensed Matter Physics
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Gilberto Fabbris
Advanced Photon Source, Argonne National Laboratory
Department of Physics, Washington University in St. Louis

The 4f electrons in heavy lanthanides are atomic-like at ambient pressure. Their exchange interaction with the conduction electrons sets up an indirect, long-range RKKY interaction between the lanthanide cations leading to magnetic order below a critical temperature. Upon increased pressure, the reduced volume is expected broaden the 4f states and bring it closer to the Fermi level, leading to a plethora of possible novel ground states. In particular, the high-pressure volume collapse observed in many lanthanides may signal the onset of 4f-conduction electron hybridization and/or direct 4f-4f interactions. In this talk I will discuss the effect of pressure on the 4f electrons of gadolinium and terbium. Through a combination of x-ray spectroscopy and transport measurements on the pure lanthanide metals and their dilute magnetic alloys with Y, we conclude that the volume collapse in Gd is unrelated to 4f electron interactions, whereas that in Tb seems to be due to increased hybridization (covalent mixing) between 4f and conduction electrons as manifested by the apparent onset of Kondo effect phenomena [1]. Furthermore, preliminary studies on the high-pressure magnetic order of these lanthanides and Dy will be discussed.

[1] G. Fabbris, T. Matsuoka, J. Lim, J. R. L. Mardegan, K. Shimizu, D. Haskel, and J. S. Schilling, Physical Review B 88, 245103 (2013).