Single-crystal growth of YbRh₂Si₂ and YbIr₂Si₂

Abstract

We report on the single-crystal growth of the heavy-fermion compounds YbRh₂Si₂ and YbIr₂Si₂ using a high-temperature indium-flux technique. The optimization of the initial composition and the temperature–time profile lead to large (up to 100 mg) and clean (ρ₀ ≈ 0.5 µΩ cm) single crystals of YbRh₂Si₂. Low-temperature resistivity measurements revealed a sample-dependent temperature exponent below 10 K, which for the samples with highest quality deviates from a linear-in-T behaviour. Furthermore, we grew single crystals of the alloy series Yb(Rh_1−x Ir _x )₂Si₂ with 0 ≤ x ≤ 0.23 and report the structural details. For pure YbIr₂Si₂, we establish the formation of two crystallographic modifications, where the magnetic 4f electrons have different physical ground states.

Keywords:

• YbRh₂Si₂
• YbIr₂Si₂
• metal-flux technique
• Kondo-lattice systems
• quantum critical point

Acknowledgements

The authors thank U. Burkhardt and P. Scheppan for energy dispersive X-ray analysis of the samples as well as N. Caroca-Canales and R. Weise for technical assistance. The presented low-temperature susceptibility measurements were performed with the help of C. Klausnitzer. We acknowledge valuable discussions with M. Brando, M. Deppe, J. Ferstl, S. Friedemann, P. Gegenwart, A. Rosch, and F. Steglich. The DFG (Research Unit 960, ‘Quantum phase transitions’) is acknowledged for financial support.