Comprehensive scenario for single-crystal growth and doping dependence of resistivity and anisotropic upper critical fields in (Ba1xKx)Fe2As2 (0.22x1)

Y. Liu, M. A. Tanatar, W. E. Straszheim, B. Jensen, K. W. Dennis, R. W. McCallum, V. G. Kogan, R. Prozorov, and T. A. Lograsso
Phys. Rev. B 89, 134504 – Published 7 April 2014

Abstract

Large high-quality single crystals of hole-doped iron-based superconductor (Ba1xKx)Fe2As2 were grown over a broad composition range 0.22x1 by inverted temperature gradient method. We found that high soaking temperature, fast cooling rate, and an adjusted temperature window of the growth are necessary to obtain single crystals of heavily K-doped crystals (0.65x0.92) with narrow compositional distributions as revealed by sharp superconducting transitions in magnetization measurements and close to 100% superconducting volume fraction. The crystals were extensively characterized by x-ray and compositional analysis, revealing monotonic evolution of the c-axis crystal lattice parameter with K substitution. Quantitative measurements of the temperature-dependent in-plane resistivity ρ(T) found doping-independent, constant within error bars, resistivity at room temperature, ρ(300K), in sharp contrast with the significant doping dependence in electron and isovalent substituted BaFe2As2 based compositions. The shape of the temperature-dependent resistivity, ρ(T), shows systematic doping-evolution, being close to T2 in overdoped and revealing significant contribution of the T-linear component at optimum doping. The slope of the upper critical field, dHc2/dT, scales linearly with Tc for both Hc, Hc2,c, and Hab, Hc2,ab. The anisotropy of the upper critical field γHc2,ab/Hc2,c determined near zero-field Tc increases from 2 to 4–5 with increasing K doping level from optimal x0.4 to strongly overdoped x=1.

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  • Received 2 March 2014
  • Revised 27 March 2014

DOI:https://doi.org/10.1103/PhysRevB.89.134504

©2014 American Physical Society

Authors & Affiliations

Y. Liu1,*, M. A. Tanatar1,2,†, W. E. Straszheim1,3, B. Jensen1, K. W. Dennis1, R. W. McCallum1,4, V. G. Kogan1,2, R. Prozorov1,2, and T. A. Lograsso1,4

  • 1Division of Materials Sciences and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
  • 2Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
  • 3Materials Analysis and Research Laboratory, Iowa State University, Ames, Iowa 50011, USA
  • 4Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA

  • *yliu@ameslab.gov
  • tanatar@ameslab.gov

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Vol. 89, Iss. 13 — 1 April 2014

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