Institute of High Pressure Physics

Generally, the presence of impurity phases in a superconductor reduces its properties. Dr. Singh's research group (NL-6) has just published a new study in the Journal of Physics and Chemistry of Solids (Impact factor: 4.0) that shows the impact of impurities on high-T_c iron-based superconductors grown under ambient and applied pressure conditions.

The conclusion of this research is that the high-pressure synthesis of the stoichiometric CaKFe₄As₄ (1144) superconductor increases the transition temperature (T_c) by 2K and the critical current density (J_c) by one order of magnitude in the whole magnetic field range of 9 T as compared to that of the 1144 bulks prepared by conventional synthesis method at ambient pressure (CSP). Moreover, the superconducting onset transition temperature of this stoichiometric CaKFe₄As₄ (1144) family is robust with the presence of the common 122 (CaFe₂As₂ or KFe₂As₂) impurity phases. This study is published by “Manasa Manasa, Mohammad Azam, Tatiana Zajarniuk, Ryszard Diduszko, Tomasz Cetner, Andrzej Morawski, Andrzej Wiśniewski, Shiv J. Singh” entitled “Effect of impurity phase and high-pressure synthesis on the superconducting properties of CaKFe₄As₄”  DOI: https://doi.org/10.1016/j.jpcs.2024.111996

Figure: The variation of (a) an amount of the impurity CaFe₂As₂ phase, (b) the onset transition temperature T_c^onset, (c) the room temperature resistivity (ρ_300K), (d) Residual resistivity ratio (RRR = ρ_{300 K}/ρ_{40 K}), (e) transition width (ΔT) and (f) the critical current density (J_c) at 5 K and self-field with respect to CaKFe₄As₄ bulks prepared by high pressure and high temperature synthesis (HP-HTS) method with  1144 sample prepared by CSP method.