Crystal growth of the iron pnictide superconductor NdFeAsO${}_{1-x}$F${}_x$

The single crystal growth of the iron pnictide superconductor NdFeAsO in a NaCl/KCl-salt flux at ambient pressure has been improved optimizing growth temperature settings and profiles and developing a new growth geometry. Single crystaline samples of the 1111-system NdFeAsO${}_{1-x}$F${}_x$ were investigated with structural, magnetic and transport methods and are in overall agreement with the polycrystalline material. For lower doping levels (up to about x = 0.1) the system shows a spin density wave transition (below 154 K), which is suppressed strongly with increased doping, and with higher doping levels yields unconventional superconductivity (T${}_C$ = 50 K for x = 0.2). We will present details of the optimization procedure of the crystal growth together with structural and magnetic characterization down to 2 K.