Strong Flux Pinning Caused by Phase Distribution Characteristics in (Ba,K)Fe₂As₂ Films

We report that the strong flux pinning of (Ba,K)Fe₂As₂ thin films is induced by superconducting phase distribution characteristics. Our thin films present a diverse distribution of the compositional fluctuation, depending on growth conditions. This distribution was achieved by the electron probe microanalyzer elemental mapping and analyzed by the overlay method. The broad transition in magnetic susceptibility indicates that the flux pinning force arises from a distinct range of the concentration of potassium in (Ba,K)Fe₂As₂. We compare the activation energy of two different distributions having temperatures of 16780 K and 5027 K at 0.1 T, respectively. The higher activation energy film forms a randomly textured distribution whose stronger pinning potential originates from a rapid spatial Trmc change compared to the homogeneous plain film. We conclude that the superconducting phase distribution in the (Ba,K)Fe₂As₂ film is strongly related to a macroscale vortex interaction, i.e., δ Trm pinning.