Nuclear magnetic resonance in the LaX3 intermetallic compounds

Abstract

The La139 nuclear-magnetic-resonance (NMR) Knight shift and spin-lattice relaxation time (T1) in LaPb3 were measured from 1.5 to 300°K. The isotropic and anisotropic Pb207 Knight shifts were measured at 1.5, 4.2, and 77 °K and T1 was measured at 1.55°K. Also presented are measurements of the La T1 in LaIn3 from 1.5 to 300°K which are more complete than previously reported. These measurements are compared with previously reported measurements for LaSn3. The La139 Knight shift (+0.010% at 4.2°K) in LaPb3 has a temperature dependence roughly five times that found in LaSn3 and LaIn3 even though the bulk susceptibility is considerably smaller. For LaPb3, the La T1T product is nearly temperature independent (T1T=0.59 sec °K at 4.2°K) and is about half that found in LaSn3. For LaIn3, T1T increases by 50% between 1.5 and 300°K and has a temperature dependence similar to LaSn3. The isotropic and anisotropic Pb Knight shifts (Kiso=+0.70% and 3Kax=+0.43% at 4.2°K) are nearly temperature independent. The Pb relaxation time in LaPb3 (T1T=63×10-4 sec°K) is about four times faster than in Pb metal, indicating a larger s-contact contribution than in Pb metal and a large negative Knight-shift component. The La NMR and bulk-susceptibility data are partitioned using the customary approximation for transition metals. We find the results for LaIn3 and LaSn3 are quite similar suggesting that in both these materials the La d-orbital susceptibility is much larger than the d-spin susceptibility and that exchange-enhancement effects are probably not important. For LaPb3, d-orbital effects are less important than the d-spin contributions. In all three compounds the La d-spin contributions to the NMR properties and the bulk susceptibility are of similar magnitude. © 1972 The American Physical Society.