%0 Journal Article
%T Phase Diagram and Calorimetric Properties of NaFe$_{1-x}$Co$_x$As
%A A. F. Wang
%A X. G. Luo
%A Y. J. Yan
%A J. J. Ying
%A Z. J. Xiang
%A G. J. Ye
%A P. Cheng
%A Z. Y. Li
%A W. J. Hu
%A X. H. Chen
%J Physics
%D 2012
%I arXiv
%R 10.1103/PhysRevB.85.224521
%X We measured the resistivity and magnetic susceptibility to map out the phase diagram of single crystalline NaFe$_{1-x}$Co$_x$As. Replacement of Fe by Co suppresses both the structural and magnetic transition, while enhances the superconducting transition temperature ($T_{\rm c}$) and superconducting component fraction. Magnetic susceptibility exhibits temperature-linear dependence in the high temperatures up to 500 K for all the superconducting samples, but such behavior suddenly breaks down for the non-superconducting overdoped crystal, suggesting that the superconductivity is closely related to the T-linear dependence of susceptibility. Analysis on the superconducting-state specific heat for the optimally doped crystal provides strong evidence for a two-band s-wave order parameter with gap amplitudes of $\Delta_1(0)/k_{\rm B}T_{\rm c}$= 1.78 and $\Delta_2(0)/k_{\rm B}T_{\rm c}$=3.11, being consistent with the nodeless gap symmetry revealed by angle-resolved photoemission spectroscopy experiment.
%U http://arxiv.org/abs/1204.3522v2