Investigation of flux turbulence in iron-based superconductors

We explore the magnetic flux penetration in single crystals of the 122-type iron-based superconductors after remagnetization using magneto-optical imaging. We find evidence for turbulence at the boundary between vortices and antivortices. The turbulenceis characterized by increased fingering of the flux front.Moreover, steps in local magnetic induction are observed at the flux boundary. Our results show that flux turbulence is observed even for low-anisotropy type-II superconductors and is not confined to the cuprates.