Anisotropic Magnetic Fluctuations in the Ferromagnetic Superconductor UCoGe Studied by Direction-Dependent ~(59)Co NMR Measurements

摘要

We have carried out direction-dependent ~(59)Co NMR experiments on a single crystal sample of the ferromagnetic superconductor UCoGe in order to study the magnetic properties in the normal state. The Knight-shift and nuclear spin-lattice relaxation rate measurements provide microscopic evidence that both static and dynamic susceptibilities are ferromagnetic with strong Ising anisotropy. We discuss that superconductivity induced by these magnetic fluctuations prefers spin-triplet pairing state.