Neutron powder diffraction studies on Ba$_{1-x}$A$_{x}$Fe$_{2}$As$_{2}$ (A=Na, K)

In the so-called 122 iron pnictide superconductors, the SDW is suppressed and superconductivity can be induced by various means including charge doping, pressure, and isovalent substitution. Using neutron powder diffraction and SQUID magnetization measurements, we have investigated the effects of both potassium and sodium substitution on superconductivity, structural transformation and magnetic ordering in Ba$_{1-x}$A$_{x}$Fe$_{2}$As$_{2 }$(A=K,Na) producing detailed phase diagrams of both systems. We present a comparison of the similarities and differences in the various internal atomic and magnetic structural parameters as a function of temperature and composition of these two hole-doped systems.