High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt
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YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of T*=0.7K, fragile antiferromagnetic order below TN=0.4K, a Kondo temperature of TK≈1K, and crystalline-electric-field splitting on the order of E/kB=1–10K. Whereas the compound has a face-centered-cubic lattice at ambient temperature, certain experimental data, particularly those from studies aimed at determining its crystalline-electric-field scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-resolution, high-energy x-ray diffraction experiments which show that, within our experimental resolution of ≈6–10×10−5Å, no structural phase transition occurs between T=1.5 and 50K. In combination with results from dilatometry measurements, we further show that the compound's thermal expansion has a minimum at ≈18K and a region of negative thermal expansion for 9≲T≲18K. Despite diffraction patterns taken at 1.6K which indicate that the lattice is face-centered cubic and that the Yb resides on a crystallographic site with cubic point symmetry, we demonstrate that the linear thermal expansion may be modeled using crystalline-electric-field level schemes appropriate for Yb3+ residing on a site with either cubic or less than cubic point symmetry.
This article is published as Ueland, B. G., S. M. Saunders, S. L. Bud'ko, G. M. Schmiedeshoff, P. C. Canfield, A. Kreyssig, and A. I. Goldman. "High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt." Physical Review B 92, no. 18 (2015): 184111. DOI: 10.1103/PhysRevB.92.184111. Posted with permission.