Relation of structure, magnetism, doping and pressure in AFe$_{2-x}$T$_x$As$_2$ (T=Co,Rh,Ru)

We present an overview of our recent investigations on the SrFe$_{2-x}$T$_x$As$_2$ (T = Co, Ru, Rh) compounds. In our joint experimental and theoretical study, we report the influence of hydrostatic pressure and substitution at 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$_{2-x}$Co$_x$As$_2$ for pressures of 2.6GPa. In our analysis, we attempt to disentangle the interplay of charge doping and structural changes induced by the substitution and by external pressure.