NMR study of magnetic spin fluctuations in UTe

Tokunaga, Yo  ; Sakai, Hironori   ; Kambe, Shinsaku  ; Hattori, Taisuke; Higa, Nonoka*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; Li, D. X.*; Honda, Fuminori*; Aoki, Dai*

Recently, Ran et al. reported evidence for superconductivity in the uranium-based heavy fermion material UTe, exhibiting the rather high transition temperature of 1.6 K. The ground state of UTe is paramagnetic, not ferromagnetic. However, the compound still exhibits a very large and anisotropic upper critical field H, exceeding the Pauli limit along the three principal axes, similar to the ferromagnetic superconductors, UCoGe and URhGe. Field-induced metamagnetic transition and re-entrant superconducting behaviour have been reported under strong magnetic fields around 35 T, when a magnetic field was applied along the orthorhombic hard-magnetization b-axis. In this study, we have performed Te-NMR measurements on a newly discovered heavy fermion superconductor UTe. Our NMR data confirm a moderate Ising anisotropy for both the static (K) and dynamical susceptibilities (1/) in the paramagnetic state above about 20 K.