Relation of structure, magnetism, doping and pressure in AFe{2-x}TxAs2 (A=Ca,Sr,Ba,Eu; T=Co,Rh,Ru)

In a joint experimental and theoretical study we present an overview of recent results for the '122' compound family. We show thermodynamical measurements and band structure results for the undoped Sr-compound under ambient conditions, and also the influence of hydrostatic pressure and doping on the A site as well as the Fe site on the magneto-structural and superconducting transitions. The magnetism is weakened upon the application of pressure as indicated by resistivity, X-ray data and density functional band structure calculations. Similar to substitution on the Sr site, substitutions on the Fe-site quench the magnetic transition and induce bulk superconductivity with T_c up to 20 K for ambient pressure and up to 27 K for underdoped SrFe_2-xCo_xAs₂ for pressures of 2.6 GPa. In our analysis, we attempt to disentangle the interplay of charge doping and structural changes induced by the substitution and by external pressure.