Effect of Mn substitution on superconductivity in PrFeAs(O,F): Role of magnetic impurities

We investigate Mn substitution at the Fe site in PrFe 1- x Mn x AsO 0.7 F 0.3 (0 ≤ x ≤ 0.1) using structural, Raman, density functional theory (DFT), transport, and magnetic measurements. X-ray diffraction, Raman spectroscopy and energy-dispersive X-ray (EDX) analyses confirm preferential Mn incorporation into the FeAs superconducting planes, accompanied by lattice expansion and suppression of Fe-related vibrational modes. Electrical transport measurements reveal a systematic decrease of the superconducting transition temperature from 48 K ( x = 0) to complete suppression at x = 0.1, together with pronounced low-temperature resistivity upturns evolving toward insulating-like behavior. Magnetization and magnetotransport measurements show progressive degradation of superconducting coherence, critical current density, upper critical field, and vortex activation energy with increasing Mn content. Microstructural investigations further indicate enhanced grain-boundary disorder and secondary MnO-related impurity phases at higher Mn concentrations. The results establish Mn as an efficient magnetic impurity that strongly perturbs the electronic and magnetic environment of the FeAs layers through enhanced magnetic scattering and carrier localization. Comparative analysis with other iron pnictide systems reveals relatively enhanced robustness of superconductivity in the Pr-based system, highlighting the important role of rare-earth-dependent electronic correlations in governing impurity effects in iron-based superconductors.