Local Measurement of the Superfluid Density in the Pnictide Superconductor Ba(Fe1-xCox)2As2 across the Superconducting Dome

We measure the penetration depth lambda(ab)(T) in Ba(Fe1-xCox)(2)As-2 using local techniques that do not average over the sample. The superfluid density rho(s)(T) equivalent to 1/lambda(ab)(T)(2) has three main features. First, rho(s)(T = 0) falls sharply on the underdoped side of the dome. Second, lambda(ab)(T) is flat at low T at optimal doping, indicating fully gapped superconductivity, but varies more strongly in underdoped and overdoped samples, consistent with either a power law or a small second gap. Third, rho(s)(T) varies steeply near T-c for optimal and underdoping. These observations are consistent with an interplay between magnetic and superconducting phases.