Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Correlated Electrons: Quantum-Critical Phenomena

TT 19.6: Vortrag

Dienstag, 26. Februar 2008, 15:30–15:45, H 3010

Magnetization study of stoichiometric and slightly Ir- Co-doped YbRh₂Si₂ — •Manuel Brando¹, Luis Pedrero¹, Cornelius Krellner¹, Philipp Gegenwart², Christoph Geibel¹, and Frank Steglich¹ — ¹Max-Planck-Institut für Chemische Physik fester Stoffe Nöthnitzer Str. 40, 01187 Dresden, Germany — ²Georg-August Universität Göttingen, 37077 Göttingen, Germany

Recent results on the heavy fermion compound YbRh₂Si₂ point to the presence of multiple vanishing energy scales, T_N(H), T_LFL(H) and T^*(H), at the magnetic-field-driven quantum critical point (QCP) [1]. These scales can directly be observed in thermodynamic, transport and magnetic measurements, among them the dc-magnetization M versus the magnetic field H. More precisely, M shows a kink at T_N(H) and a distinct crossover feature at T^*(H) which smears out with increasing temperature.
Slight doping with isoelectronic Co as well as with Ir on the Rh site leads to a volume change, which tunes the strength of the magnetic interaction; this shifts the T_N(H) line in the T−H phase diagram without introducing much disorder in the single crystals. However, little is known about the behavior of the T^*(H) line in the doped compounds.
We present a systematic analysis of different isothermal M vs. H curves for the stoichiometric, Co- (7%) and Ir-doped (6%) samples down to 50 mK to observe whether the two energy scales are still approaching zero at the same point in the doped compounds.

[1] P. Gegenwart et. al., Science 315, 5814 (2007).