Interplay of Superconductivity and Spin Density Wave - Magnetism in PrFeAsO and Hole-doped (Pr $_{\mathrm{1-x\thinspace }}$Sr $_{\mathrm{x}})$ FeAsO: Synthesis, Structure, Thermodynamic, Magnetic, Transport, Phonon properties and Pressure effect

Hole doping in iron-pnictide (1111) PrFeAsO by substituting Pr$^{\mathrm{3+}}$ by Sr$^{\mathrm{2+}}$ creates superconducting Pr$_{\mathrm{1-}}_{x}$Sr$_{x}$FeAsO tetragonal $P_{\mathrm{4/nmm}}$ phases at room temperature. Sr doping facilitate hole transfer through Pr/Sr plane {\&} FeAs layers. Hall-effect measurements at different magnetic field {\&} temperature ($+$Ve R$_{\mathrm{H}})$ confirms hole like charge carriers. Lattice constants ($a ${\&} $c)$ increase monotonously with Sr/hole concentration. Tc (SC) varies from 12.5 K to 15.5K with a maximum of 15.5K at $x =$ 0.22 with (optimal doping) largest SC volume fraction. Temperature (1.7 K \textasciitilde 300K) {\&} Magnetic field (1T\textasciitilde 7T)-dependent resistivity, magnetic susceptibility {\&} specific heat been measured {\&} calculated Cp/T (J/mole-K2) {\&} entropy (J/mole-K). Thermoelectric power $S$ (T) of PrFeAsO have W-like shape {\&} smaller amplitude with much larger spread. $p$-drop (\textasciitilde 150 K) has been identified with SDW/ lattice instability. Coexistence of SC {\&} SDW behavior were observed {\&} pressure effects on both being investigated by resistivity measurements under hydrostatic pressure up to 1.8GPa using piston-cylinder clamp cell device {\&} compared with electron doped Sm(O$_{\mathrm{1\thinspace -\thinspace x}}$ F$_{\mathrm{x}})$ FeAs. T$_{\mathrm{c}}$ increases ($+$ dT$_{\mathrm{c}}$/dP) with pressure for under-doped (Pr $_{\mathrm{1-x}}$ Sr $_{\mathrm{x}})$FeAsO similar to high-T$_{\mathrm{c}}$ cuprates {\&} -Ve pressure effect on SDW temperature. The results suggest a symmetry between electron {\&} hole-doping Fe-pnictide superconductors.