Institute of High Pressure Physics

CaKFe₄As₄ is already superconducting without chemical doping, unlike most iron-based superconductors. This unique characteristic makes it an ideal platform for investigating the effects of selective elemental substitution within the superconducting FeAs layers.

In this context, Prof. Shiv J. Singh’s research team (from NL-6 Laboratory of Superconductors and Hydrogen Technologies) systematically investigated the influence of Mn substitution combined with high-pressure synthesis on the superconducting properties of CaKFe₄As₄. Mn-doped CaK(Fe_1-xMn_x)₄As₄ bulk samples were successfully synthesized using both conventional solid-state processing and high-pressure synthesis techniques.

Although Mn doping is generally known to suppress superconductivity in iron-based systems, the application of high-pressure synthesis was found to partially counteract this detrimental effect. As a result, a significant enhancement of the superconducting transition temperature (T_c) by approximately 3–7 K was observed for samples with 2–3% Mn substitution. Moreover, the study reveals unique behaviour in Mn-doped CaKFe₄As₄, where an increase in T_c can be achieved through the combined effects of controlled doping and high-pressure processing.

For more details, please refer to the publication: Manasa Manasa, Mohammad Azam, Tatiana Zajarniuk, Svitlana Stelmakh, Tomasz Cetner, Andrzej Morawski & Shiv J. Singh entitled “Enhancement of the Superconducting Transition Temperature in Mn-doped CaKFe₄As₄ Processed by the High gas-pressure and High-temperature Synthesis Method” Journal of Superconductivity and Novel Magnetism 39, 10 (2026). https://doi.org/10.1007/s10948-025-07115-2

Figure: A comparative summary of the superconducting transition temperatures (T_c) of CaK(Fe_1-xMn_x)₄As₄ bulks prepared by CSP at ambient pressure, and High gas pressure and high temperature synthesis (HP-HTS) methods, together with reported Mn-doped CaKFe₄As₄ single-crystals grown by the conventional method at ambient pressure [22], is shown with Mn concentration (x). The transition temperature values are determined from both the resistivity (R(T)) and magnetic (M(T)) measurements.