Anisotropy of the iron pnictide superconductor Ba(Fe1xCox)2As2 (x=0.074,Tc=23K)

M. A. Tanatar, N. Ni, C. Martin, R. T. Gordon, H. Kim, V. G. Kogan, G. D. Samolyuk, S. L. Bud’ko, P. C. Canfield, and R. Prozorov
Phys. Rev. B 79, 094507 – Published 5 March 2009

Abstract

Anisotropies of electrical resistivity, upper critical field, London penetration depth, and critical currents have been measured in single crystals of the optimally doped iron pnictide superconductor Ba(Fe1xCox)2As2 (x=0.074 and Tc23K). The normal-state resistivity anisotropy was obtained by employing both the Montgomery technique and direct measurements on samples cut along principal crystallographic directions. The ratio γρ=ρc/ρa is about 4±1 just above Tc and becomes half of that at room temperature. The anisotropy of the upper critical field, γH=Hc2,ab/Hc2,c, as determined from specific-heat measurements close to Tc is in the range of 2.1–2.6, depending on the criterion used. A comparable low anisotropy of the London penetration depth, γλ=λc/λab, was recorded from tunnel diode resonator measurements and found to persist deep into the superconducting state. An anisotropy of comparable magnitude was also found in the critical currents, γj=jc,ab/jc,c, as determined from both direct transport measurements (1.5) and from the analysis of the magnetization data (3). Overall, our results show that iron pnictide superconductors manifest anisotropies consistent with essentially three-dimensional intermetallic compounds and bear little resemblance to cuprates.

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  • Received 6 January 2009

DOI:https://doi.org/10.1103/PhysRevB.79.094507

©2009 American Physical Society

Authors & Affiliations

M. A. Tanatar1,*, N. Ni1,2, C. Martin1, R. T. Gordon1,2, H. Kim1,2, V. G. Kogan1, G. D. Samolyuk1,†, S. L. Bud’ko1,2, P. C. Canfield1,2, and R. Prozorov1,2,‡

  • 1Ames Laboratory, Ames, Iowa 50011, USA
  • 2Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

  • *tanatar@ameslab.gov
  • Present address: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
  • prozorov@ameslab.gov

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Vol. 79, Iss. 9 — 1 March 2009

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