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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.29: Poster

Mittwoch, 24. März 2010, 14:00–18:00, Poster D1

Multiple phase transitions in YbPd — •Stefanie Grünheit, Jeevan S. Hirale, Yoshifumi Tokiwa, and Philipp Gegenwart — I. Physik. Institut, Georg-August Universität Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen

Cubic YbPd is an interesting strongly-correlated electron system, as previous ¹⁷⁰Yb-Mössbauer measurements have suggested two different Yb charge states at low temperatures; one magnetic and the other one nonmagnetic in equal proportions [1]. We have synthesized large YbPd polycrystals and investigate their physical properties by electrical resistivity, magnetic susceptibility, specific heat and thermal expansion at temperatures down to 20 mK. Four phase transitions at 0.6 K, 1.9 K, 105 K and 125 K are found. While the two higher ones are presumably related to a structural distortion, which may result in two inequivalent Yb-sites, the two lower ones are of clear antiferromagnetic origin. At lowest temperatures, the Sommerfeld coefficient amounts to 200 mJ/(mol K²) and a reduced entropy of about one quarter of Rlog2 at 1.9 K is found. These results are discussed in terms of a coexistence of mixed-valent and magnetic Yb-sites. To investigate the microscopic origin of the various transitions, synchroton and neutron scattering experiments are under way.

Work supported by DFG through research unit 960 (Quantum phase transitions).

[1] P. Bonville et al., Phys. Rev. Lett. 57 (1986) 2733.