Abstract
Single crystals of Na1-delta Fe1-xTxAs with T = Co, Rh have been grown using a self-flux technique. The crystals were thoroughly characterized by powder x-ray diffraction, magnetic susceptibility, and electronic transport with particular focus on the Rh-doped samples. Measurements of the specific heat and ARPES were conducted exemplarily for the optimally doped compositions. The spin-density wave transition (SDW) observed for samples with low Rh concentration (0 <= x <= 0.013) is fully suppressed in the optimally doped sample. The superconducting transition temperature (T-c) is enhanced from 10 K in Na1-delta FeAs to 21 K in the optimally doped sample (x = 0.019) of the Na1-delta Fe1-xRhxAs series and decreases for the overdoped compounds, revealing a typical shape for the superconducting part of the electronic phase diagram. Remarkably, the phase diagram is almost identical to that of Co-doped Na1-delta FeAs, suggesting a generic phase diagram for both dopants.