Li Y K, Lin X, Zhou T, Shen J Q, Tao Q, Cao G H, Xu Z A
Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
J Phys Condens Matter. 2009 Sep 2;21(35):355702. doi: 10.1088/0953-8984/21/35/355702. Epub 2009 Aug 10.
Superconductivity with a T(c) of about 10 K is observed in the Ni-doped SmFe(1-x)Ni(x)AsO system. The measurements of resistivity and magnetic susceptibility show that the spin-density wave (SDW) order is quickly suppressed with increasing Ni content, and superconductivity emerges as x≥0.04. T(c)(mid) shows a maximum of 10.8 K at x = 0.06, and it drops to lower than 2 K as x>0.12. Meanwhile, the upper critical field (H(c2)(0)) is estimated to be about 40 T for the optimally-doped sample (x = 0.06). The normal state thermopower is negative for all the Ni-doped samples, indicating that an electron-type charge carrier dominates in the transport properties. Moreover, the magnitude of the room-temperature thermopower increases with increasing Ni content, and then shows a broad peak around x = 0.06. We found that there is an obvious correlation between the anomalously enhanced thermopower and superconductivity. A phase diagram is derived based on the transport measurements and a dome-like T(c)(x) curve is established.
在镍掺杂的SmFe(1-x)Ni(x)AsO体系中观察到了临界温度（Tc）约为10K的超导性。电阻率和磁化率测量表明，随着镍含量的增加，自旋密度波（SDW）序被迅速抑制，当x≥0.04时出现超导性。Tc（中值）在x = 0.06时达到最大值10.8K，当x>0.12时降至低于2K。同时，对于最佳掺杂样品（x = 0.06），上临界场（Hc2(0)）估计约为40T。所有镍掺杂样品的正常态热功率均为负，这表明在输运性质中电子型载流子占主导。此外，室温热功率的大小随镍含量的增加而增加，然后在x = 0.06附近出现一个宽峰。我们发现异常增强的热功率与超导性之间存在明显的相关性。基于输运测量得出了相图，并建立了类似穹顶的Tc(x)曲线。
