Anisotropic Transferred Hyperfine Interaction in a Heavy-Fermion Compound: Paramagnetic NMR Line Shift in a CeCu6 Single Crystal

We report on single crystal nuclear magnetic resonance spectroscopy for 63Cu at the Cu(5) sites in the heavy-fermion paramagnet CeCu6 for constant external magnetic field strength (7 T) applied along the “hardest” magnetic direction b and varied temperature (5 − 100 K). The transferred field coupling constant αb(5) =  +  3.40(31) kOe/μB is derived from the van Vleck like paramagnetic line shift. These results establish the predominance of anisotropic spin and orbital polarization acting on the Cu sites neighbouring the Ce 4f local moment. Because magnetically induced electric quadrupolar interaction at this Cu site is not unusually enhanced, we conclude that the exchange polarization mechanism at the Ce site is the source of the observed anisotropy. Impact of the substitution of Cu(2) by Au on the Ce3+ single-ion ground state properties and magnetic characteristics of CeCu6-xAux is discussed.