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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.15: Poster

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

Low-temperature magnetization measurements on Yb(Rh_0.93Co_0.07)₂Si₂ — •Luis Pedrero, Manuel Brando, Cornelius Krellner, Christoph Geibel, and Frank Steglich — Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany

In the heavy-fermion compound Yb(Rh_0.93Co_0.07)₂Si₂ a detailed study of the thermodynamic and transport properties at low temperature has shown that the energy scale T^*(H), associated with the Fermi surface reconstruction, vanishes inside the magnetic phase T_N(H), where T_N=0.4 K at zero field [1]. This discovery raises questions as (i) which energy scale is more relevant for quantum criticality in this system, (ii) where are located the strongest signatures of quantum fluctuations (at the critical field of T^* or of T_N) and (iii) which is their intrinsic nature.
To get more insights, we have performed several isofield M(T) and isothermal M(H) magnetization measurements on a high-quality single crystal of Yb(Rh_0.93Co_0.07)₂Si₂, to obtain a magnetization grid M(T,H) across the magnetic phase diagram. According to the definition of the Grüneisen ratio Γ_H = −(dM/dT)_H/C_H and the Maxwell relation (dM/dT)_H=(dS/dH)_T we could then map the entropy S(H) in and outside the magnetic phase and - supported by specific heat measurements - analyse the divergence of Γ_H(T) at both critical fields for T^* and T_N. A direct comparison with the theory will be presented.
[1] S. Friedemann et al., Nat. Phys. 5 (2009) 465.