Cu-NMR studies of the heavy-fermion compound CeCu6 under high magnetic fields

We report a Cu NMR Knight shift K in a prototypical heavy-fermion system CeCu6 in the temperature range of 1.5 K-100 K at applied magnetic fields up to 15 T. With increasing magnetic field, the Cu-63 NMR Knight shift for HaEuro-[001] is suppressed drastically. The suppression of K with increasing field is consistent with the field dependence of the susceptibility. In order to explain this behavior, we adopted the Kondo resonance level model, where the thermodynamics at low temperatures are proportional to the density of states at the energy A mu H. The resonant model was found to correctly predict the suppression of the Knight shift with increasing magnetic field.