Pinning properties of 1144 polycrystalline samples with aliovalent doping

The 1144 Iron-Based Superconductors (IBSC), characterized by the A 1 AE 1 Fe 4 As 4 chemical composition (A=Alkaline, AE=Alkaline-Earth), has gained significant interest in the recent years due to their crystalline structure character-ized by an intrinsic modulation of the strain along the c-axis and by the proneness in forming crystalline defects with a positive impact on flux pinning. Moreover, it has been proved that the compound is compatible with the cost-effective powder-in-tube (PIT) manufacturing process. In our recent experiments, we have showed that the A 1 AE 1 Fe 4 As 4 structure can be tailored to obtain a 1144 com-pound characterized by different (A x AE 1-x )(AE y A 1-y )Fe 4 As 4 chemical formulae without any depression in the critical temper-ature value. On the other hand, it has been recently shown that the doping with selected elements on both A and AE sites has a clear influence on the pinning and the grain boundary properties of poly-crystalline samples. In this work we report the results of the extensive magnetic characterization performed on pristine Ca 1 K 1 Fe 4 As 4 and doped (A x Ca 1-x )(AE y K 1-y )Fe4As4 with Ba as dopant on the K site and ei-ther La or Na as dopant on the Ca site. In particular, the magnet-ization hysteresis loops recorded at different temperatures M(H, T) and the critical current density dependences extracted from the M(H) using the Bean model, J c (B, T), have been analyzed in order to assess the effect of aliovalent doping on the quality of the produced samples in terms of grain boundary properties and pinning efficiency.