Anisotropy of the iron pnictide superconductor Ba(Fe1-xCo x)2As2 (x=0.074, Tc = 23 K)

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, R. Prozorov

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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(Fe1-xCo x)2As2 (x=0.074 and Tc ∼ 23 K). 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 = ρca is about 4 ± 1 just above T c 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 = λcab, 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.

Original languageEnglish
Article number094507
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume79
Issue number9
DOIs
StatePublished - Mar 3 2009

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