${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$ spin dynamics and Knight shift in single crystals of ${\mathrm{UPt}}_3$

${}_{}{}^{195}{}_{}{}^{}\mathrm{Pt}$ nuclear-magnetic-resonance measurements were performed on aligned single-crystal whiskers of ${\mathrm{UPt}}_3$ for temperatures from 4 to 50 K. A special alignment technique allows us to produce samples with very good c-axis alignment and to work with the field parallel to the c axis with an excellent signal-to-noise ratio. Combining the Knight shift and spin-lattice-relaxation data, we show a continuous crossover from paramagnetic behavior above 40 K toward a degenerate-Fermi-liquid behavior below 5 K. Antiferromagnetic spin fluctuations appear to be responsible for this crossover process, and dominate all low-frequency magnetic properties of this compound. The anisotropy ratios of both the spin-lattice and the spin-spin relaxation rates are found to be temperature independent. Analyzing these ratios we find that the imaginary part of the dynamic spin susceptibility is slightly stronger in the basal plane.