We describe the effect of nonmagnetic impurity on the superconductivity behavior of the NdFeAsO 0.8 F 0.2 iron-based superconductor. The resistivity measurements show that the superconductivity is suppressed upon increasing the low amounts of calcium impurity ( x ≤ 0.05). Also, the T C decreases with the increase in the residual resistivity. Such behavior is qualitatively described by the Abrikosov–Gorkov theory and confirms that these impurities act as scattering centers. Moreover, we present the phase diagram of our synthesized samples for the various calcium dopings. We find that according to the increase in the calcium impurities and the decrease in the spin-density wave transition tempeθrature ( T SDW ), Fe ions are arranged stripe-antiferromagnetic at lower temperatures and also the superconducting transition temperature ( T C ) declines. Based on our results and in agreement with the available theories as is explained in the text, since the S ++ state has no effect on the impurity-doped samples, and for low amounts of calcium, the S ± state that is attributed to the spin-fluctuations causes the superconductivity suppression. So, it confirms the role of the spin-fluctuations as a dominant pairing mechanism in our synthesized samples.

中文翻译：

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钙掺杂Nd-1111铁基超导体的超导机理

我们描述了非磁性杂质对 NdFeAsO 0.8 F 0.2 铁基超导体的超导行为的影响。电阻率测量表明，增加少量钙杂质 (x ≤ 0.05) 会抑制超导性。此外，TC 随残余电阻率的增加而降低。这种行为由 Abrikosov-Gorkov 理论定性描述，并证实这些杂质充当散射中心。此外，我们展示了各种钙掺杂的合成样品的相图。我们发现随着钙杂质的增加和自旋密度波转变温度（T SDW ）的降低，Fe 离子在较低温度下呈条状反铁磁性排列，超导转变温度（ TC ）下降。根据我们的结果并与文中解释的可用理论一致，由于 S ++ 状态对掺杂杂质的样品没有影响，并且对于少量钙，S ± 状态归因于自旋波动导致超导抑制。因此，它证实了自旋波动作为我们合成样品中主要配对机制的作用。