Absolute value and temperature dependence of the magnetic penetration depth in Ba(Co0.074Fe0.926)(2)As-2
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Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
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Abstract
The absolute value and temperature dependence of the in-plane magnetic penetration depth λ have been measured on a single crystal of Ba(Co0.074Fe0.926)2As2 using low-energy muon-spin rotation and microwave cavity perturbation. The magnetic field profiles in the Meissner state are consistent with a local London model beyond a depth of 15 nm. We determine the gap symmetry through measurements of the temperature dependence of the superfluid density which follows a two-gap s-wave model over the entire temperature range below Tc. While the intermediate to high temperature data is well fit by an energy gap model in the BCS-like (weak-coupling) limit, a second smaller gap becomes apparent at low temperatures.
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This article is published as Ofer, Oren, J. C. Baglo, M. D. Hossain, R. F. Kiefl, W. N. Hardy, A. Thaler, H. Kim et al. "Absolute value and temperature dependence of the magnetic penetration depth in Ba (Co 0.074 Fe 0.926) 2 As 2." Physical Review B 85, no. 6 (2012): 060506. DOI: 10.1103/PhysRevB.85.060506. Posted with permission.