Intrinsic low-temperature magnetic properties on ultraclean UTe2 with T c=2.1 K revealed by Te 125 NMR

To investigate the intrinsic magnetic properties of UTe2, we performed Te125-NMR measurements on the ultraclean single-crystalline UTe2 with superconducting transition temperature Tc=2.1 K and compared the results with those of the Tc=1.6 K sample. The broadening of the linewidth of the NMR spectrum in the a-axis magnetic field and the low-temperature magnetic fluctuations observed in the 1.6 K sample are suppressed in the ultraclean sample, indicating that such magnetic properties originate from a tiny amount of U deficiency. The present results suggest that the magnetic properties in UTe2 are sensitive to the U deficiency. We also observed a peculiar angular dependence of the NMR quantities due to large magnetic anisotropy with the a axis as the magnetic easy axis.