Ytterbium NMR:Yb171Nuclear Moment and Yb Metal Knight Shift

The nuclear magnetic resonance of ${\mathrm{Yb}}^{171}$ has been found in two nonmagnetic ytterbium (ous) compounds, Yb${\mathrm{Cl}}_2$ and YbS, from which a value of ${\mu }^{171}=+0.4926\mathrm{}\pm 0.0004 {\mu }_N$ is determined. From the ${\mathrm{Yb}}^{3+}$ electron paramagnetic resonance measurements of the ratio of the hfs constants $\frac{A^{171}}{A^{173}}$ we deduce ${\mu }^{173}=-0.6772\mathrm{}\pm 0.0025 {\mu }_N$. Observations of ${\mathrm{Yb}}^{171}$ NMR in elemental Yb metal and in the intermetallic compound Yb${\mathrm{Al}}_2$ at temperatures of 1.8, 4.2, and 20.4°K yield values of the Knight shift of (0.0±0.1)%, and (7.76±0.05)%, respectively. The absence of any detectable temperature dependence of the field for resonance indicates that the low-temperature increase in the magnetic susceptibilities of these metals is caused by isolated, localized magnetic impurities. In Yb${\mathrm{Al}}_2$, a constant susceptibility of 7.6×${10}^{-4\mathrm{}}$ emu/mole remains at higher temperatures. The electronic contribution to the specific heat is found to be $\gamma \cong 4\times {10}^{-3\mathrm{}}$ cal/mole °${\mathrm{K}}^2$. The nuclear spin-lattice relaxation time $T_1\cong \frac{0.12}{T}$ sec at $T=1.8\mathrm{}$°K. From these latter two measurements, in conjunction with the large positive Knight shift, we conclude that the larger part of the high-temperature $\chi$ does not arise from spin paramagnetism of the band electrons, but is orbital in origin.