Abstract Submitted for the MAR10 Meeting of The American Physical Society Evolution of the absolute value of the London penetration depth in single crystals of Ba(Fe1−xCox)2As2 upon cobalt doping RYANGORDON,

Submitted for the MAR10 Meeting of The American Physical Society Evolution of the absolute value of the London penetration depth in single crystals of Ba(Fe1−xCox)2As2 upon cobalt doping RYANGORDON, NI NI, MAKARIY TANATAR, VLADIMIR KOGAN, SERGEY BUD’KO, PAUL CANFIELD, RUSLAN PROZOROV, Iowa State University and Ames Laboratory, NICHOLAI SALOVICH, RUSSELL GIANNETTA, University of Illinois at UrbanaChampaign — The absolute value of the London penetration depth, λ0, has been measured in single crystals of Ba(Fe1−xCox)2As2 over a wide range of cobalt doping levels using a tunnel diode resonator (TDR) [1]. Normally, the TDR technique can only measure the relative change, ∆λ(T), but the absolute value is needed to construct λ(T) and the superfluid density, ρs=[λ0/λ(T)] 2, which can be compared to theory. A more elaborate approach in which the samples are coated with a thin film of Al allows for a direct estimate of λ0 by using the same TDR apparatus [2]. The resulting doping-dependent λ0(x) as well as the calculated ρs(T,x) curves will be discussed within current theoretical models. In particular, attention will be devoted to the effects of possible strong pair breaking predictions which state ∆λ ∝T/Tc , with n≈2 [3]. [1] R. T. Gordon et al., Phys. Rev. B 79, 100506(R) (2009). [2] R. Prozorov et al., Appl. Phys. Lett. 77, 25 (2000). [3] V. G. Kogan, arXiv:0910.4728 Ryan Gordon Iowa State University and Ames Laboratory Date submitted: 18 Nov 2009 Electronic form version 1.4