Superconducting properties of 1144-type iron-based superconductors by mechanochemically assisted synthesis

Among the Iron-Based Superconductors, the 1144 family attracted significant attention due to the intriguing intrinsic properties exhibited by single crystals, such as high critical fields and critical currents. Polycrystalline compounds, however, are influenced by the non-ideal nature of the material. In this work, we report the superconducting properties at high magnetic fields up to 17 T of Ca/K-1144 bulk polycrystalline compounds obtained via a mechanochemically assisted synthesis route. The material exhibits a significant robustness of intrinsic features such as the superconducting transition onset, varying from approximately 35 K in the absence of the field to approximately 33 K at 17 T. Broadening phenomena of both resistive and magnetic transitions testifies however the presence of granularity issues, most likely due to extrinsic factors such as oxidation, porosity and random orientation of the crystallites.