Microscopic Investigation of the coexistence state of Magnetism and Superconductivity in Uranium-based Heavy-Fermion Superconductors

利用高质量单晶，从微观核磁共振测量的角度研究了UCoGe铁磁超导体中铁磁性和超导性的共存。在铁磁跃迁以下，样品的整个区域处于铁磁状态，在Tc以下，近一半的区域变成超导。我们还研究了化合物中的磁波动，发现在低温下，沿有序矩方向的纵向铁磁波动占主导地位。我们所观察到的磁波动从理论的角度被认为有利于自旋三重态超导。这些结果提示了在UCoGe中实现自旋三重态超导的可能性。

We have studied coexistence of ferromagnetism and superconductivity in ferromagnetic superconductor of UCoGe from the microscopic NMR measurement using a high-quality single crystal. Below the ferromagnetic transition, whole region of the sample is in ferromagnetic state, and a nearly half of the region becomes superconductive below Tc. We also have investigated magnetic fluctuations in the compound, and found that longitudinal ferromagnetic fluctuations along the ordered moments directed to the c axis is dominant at low temperatures. The magnetic fluctuations we observed have been suggested to be favorable for spin-triplet superconductivity from theoretical point of view. These results suggest the possibility that spin-triplet superconductivity is realized in UCoGe.