Localized GHz frequency electrodynamic behavior of an optimally-doped Ba(Fe1−xCox)2As2 epitaxial film

High frequency (several GHz) electrodynamic properties of a high-quality epitaxial, single-crystal Iron-Pnictide Ba(Fe1−xCox)2As2 thin film near optimal doping (x = 0.08) are measured under a localized and strong RF magnetic field created by a near-field microwave microscope. Linear response and third harmonic electrodynamic measurements are performed to understand the electromagnetic properties of Ba(Fe1−xCox)2As2 and contrasts are drawn with similar measurements on Nb. Our measurement results show that Ba(Fe1−xCox)2As2 has nonlinear response potentially arising from a number of mechanisms and may show evidence of a multi-gap nature.