Magnetic Properties of LaSn3

The normal-state nuclear-magnetic-resonance (NMR) Knight shifts and spin-lattice relaxation times are reported for ${\mathrm{La}}^{139}$ and ${\mathrm{Sn}}^{119}$ in La${\mathrm{Sn}}_3$ from 1.6 to 300 °K. New susceptibility data on higher-purity samples are reported for 4.2-700 °K which allow a more accurate determination of the susceptibility $\chi$ than previously reported. Above 100 °K, $\chi$ is Curie-Weiss, but it increases by only 6% below 77 °K. The ${\mathrm{Sn}}^{119}$ relaxation time ($T_{1}T=0.033\mathrm{}$ sec °K) and isotropic Knight shift (+0.640%) are temperature independent, while the anisotropic Knight shift is strongly temperature dependent. The ${\mathrm{La}}^{139}$ Knight shift (+0.207% at 4.2 °K) and relaxation time ($T_{1}T=1.25\mathrm{}$ sec °K at 4.2 °K) have a temperature dependence more than an order of magnitude smaller than expected in the case of a strong exchange enhancement of the La $d$-spin susceptibility. Various partitions of the NMR and $\chi$ data are discussed using the customary approximations for transition metals. We find that the assumption of a dominant La $d$-orbital susceptibility which has the same temperature dependence as the La $d$-spin susceptibility gives the most reasonable results, although with the large number of assumptions involved the fit is not unique. Finally, we discuss the nature of this orbital susceptibility and point out that paramagnetic contributions exist which usually are neglected and which may have the observed magnitude and temperature dependence.