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Phys. Rev. Lett. 102, 117004 (2009) [4 pages]

Pseudoisotropic Upper Critical Field in Cobalt-Doped SrFe2As2 Epitaxial Films

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S. A. Baily1,2,*, Y. Kohama1,3, H. Hiramatsu4, B. Maiorov2, F. F. Balakirev1, M. Hirano4,5, and H. Hosono4,5
1National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
3Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, 226-8503, Japan
4ERATO-SORST, Japan Science and Technology Agency in Frontier Research Center, Tokyo Institute of Technology, Yokohama, 226-8503, Japan
5Frontier Research Center, Tokyo Institute of Technology, Yokohama, 226-8503, Japan

Received 14 November 2008; published 17 March 2009

We present resistivity measurements of the complete superconducting upper critical field (Hc2) phase diagram as a function of angle (θ) and temperature (T) for cobalt-doped SrFe2As2 epitaxial films to 0.5 K and 50 T. Although Hc2(θ) at 10 K is indistinguishable from that derived from a single-band anisotropy model, the apparent anisotropy Hc2⊥c/Hc2∥c linearly decreases to 1 at low T, with Hc2(0)=47  T. The data are well described by a two-band model with small, opposing anisotropies for the bands. This unusual relationship is confirmed by the observation of a local maximum for Hc2∥c at low T.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.102.117004
DOI:
10.1103/PhysRevLett.102.117004
PACS:
74.70.−b, 74.25.Fy, 74.25.Op, 74.78.−w

*sbaily@lanl.gov

 
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