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TT: Fachverband Tiefe Temperaturen

TT 55: Correlated Electrons: Quantum-Critical Phenomena - Experiment II

TT 55.4: Vortrag

Mittwoch, 2. April 2014, 12:00–12:15, HSZ 204

Binary Cr-Ge systems close to a magnetic quantum critical point — •Katharina Weber, Marcus Peter Schmidt, Walter Schnelle, Michael Baenitz, Helge Rosner, and Christoph Geibel — Max Planck Institute for Chemical Physics of Solids, Dresden

Systems close to the transition between a magnetic-ordered (MO) and a paramagnetic (PM) ground state are of strong interest, because some very peculiar phenomena, like unconventional superconductivity, quantum critical points, and non-Fermi liquids haven been observed in connection with such transitions. While quite a lot of research has been devoted to compounds based on late transition metals, as Fe or Cu, only limited work has been published on Cr-based systems. Here we present a deeper investigation of CrGe and Cr₁₁Ge₈. Previous studies indicate both compounds to be close to a magnetic instability, but information on physical properties were limited. CrGe single crystals were grown by vapor phase transport, while polycrystalline Cr₁₁Ge₈ was prepared by arc melting and subsequent annealing. Physical properties were studied by means of susceptibility χ(T), resistivity, and specific heat measurements. Both compounds show a Curie-Weiss behavior at high temperatures, with sizeable effective moments of about 2µ_B/Cr. CrGe presents a broad, but clear maximum in χ(T) at about 60 K, while in Cr₁₁Ge₈ χ(T) increases continuously down to low T. This suggest both compounds to be in the PM regime, Cr₁₁Ge₈ being extremely close to the transition to a MO state, while CrGe is slightly further away. The Sommerfeld coefficients are quite large for 3d systems, of the order of 20 mJ/K² mol-Cr, supporting strong correlations.