Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena

TT 6.71: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Low-temperature heat capacity of Yb(Rh_0.93Co_0.07)₂Si₂ — •Alexander Steppke, Niels Oeschler, Cornelius Krellner, Manuel Brando, Christoph Geibel, and Frank Steglich — Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany

Exotic non-Fermi liquid behavior of the Sommerfeld coefficient C/T was reported for the heavy-fermion compound YbRh₂Si₂ [1]. It exhibits antiferromagnetic ordering at T_N=72 mK and a quantum critical point (QCP) can be induced by a magnetic field of µ₀H_c=60 mT. The application of hydrostatic pressure yields a shift of T_N to higher temperatures and the appearence of a second phase transition at T_L [2].
Instead of using hydrostatic pressure, similar behavior can be achieved by slightly substituting isoelectronic Co on the Rh site without introducing much disorder. At 7% Co substitution T_N is shifted to 400 mK and T_L to 70 mK.
We investigated the specific heat of a Yb(Rh_0.93Co_0.07)₂Si₂ high-quality single crystal in magnetic fields and in the temperature range between 0.05 and 4 K. The T − H phase diagram has been explored by means of thermodynamics. The nature of the lower transition and the behaviour of C/T close to the QCP at µ₀H_c≈200 mT has been studied in detail.

[1] J. Custers et al. Nature 424, 524 (2003).

[2] S. Mederle et al., J. Phys. Condens. Matter 14, 10731 (2002).