Resolution of the Discrepancy between the Variation of the Physical Properties of Ce₁₋ₓYbₓCoIn₅ Single Crystals and Thin Films with Yb Composition


Extraordinary electronic phenomena including an Yb valence transition, a change in Fermi surface topology, and suppression of the heavy fermion quantum critical field at a nominal concentration x ≈ 0.2 have been found in the Ce1-xYbxCoIn5 system. These phenomena have no discernable effect on the unconventional superconductivity and normal-state non-Fermi liquid behaviour that occur over a broad range of x up to ~0.8. However, the variation of the coherence temperature T* and the superconducting critical temperature Tc with nominal Yb concentration x for bulk single crystals is much weaker than that of thin films. To determine whether differences in the actual Yb concentration of bulk single crystals and thin film samples might be responsible for these discrepancies, we employed Vegard's law and the spectroscopically determined values of the valences of Ce and Yb as a function of x to determine the actual composition xact of bulk single crystals. This analysis is supported by energy-dispersive X-ray spectroscopy, wavelength-dispersive X-ray spectroscopy, and transmission X-ray absorption edge spectroscopy measurements. The actual composition xact is found to be about one-third of the nominal concentration x up to x ~ 0.5, and resolves the discrepancy between the variation of the physical properties of Ce1-xYbx CoIn5 single crystals and thin films with Yb concentration.




National Science Foundation, Grant 1005568

Keywords and Phrases

Chemical Substitution; Energy-Dispersive X-Ray Spectroscopy; Heavy Fermion Behaviour; Intermediate Valence; Kondo Lattice; Transmission X-Ray Absorption Edge Spectroscopy; Unconventional Superconductivity; Valence Transition; Vegard's Law; Wavelength-Dispersive X-Ray Spectroscopy

International Standard Serial Number (ISSN)

1478-6443; 1478-6435

Document Type

Article - Journal

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Publication Date

22 Dec 2014