NMR Shift Measurements of⁶⁹Ga in Unconventional Superconductor PuRhGa₅

The NMR shift ( K ) at the Ga(2) site (the 4 i site) has been measured in PuRhGa 5 , a compound which shows anisotropic superconductivity below T c ≈9 K. In the normal state, K ( T ) is very nearly independent of T below ∼30 K. This result is consistent with the relaxation rate measurements. This Korringa-like behavior indicates the formation of Fermi-liquid state below ∼30 K. The transferred hyperfine coupling constants have been estimated from the relation between K and the bulk susceptibility, showing a strong anisotropy. Measurements of K ( T ) in the superconducting state have also been performed. A decrease of K in the superconducting state has been observed, which strongly suggests a spin-singlet pairing.