NUCLEAR MAGNETIC RESONANCE IN HEXAGONAL LANTHANUM METAL - KNIGHT SHIFTS SPIN RELAXATION RATES AND QUADRUPOLE COUPLING CONSTANTS

The La139 nuclear magnetic resonances in the double-hexagonal close-packed (dhcp) form of metallic lanthanum have been studied by spin-echo techniques in the frequency range 6-30 MHz and temperatures between ∼1 and 210°K. A seven-line powder pattern due to electric quadrupole interactions is observed with |e2qQ(139)h-1|=7.8±0.3 MHz. The quadrupole splittings are identical within the experimental uncertainty for the two crystallographic sites. The Knight shifts are very different, however, K+0.63%and+1.02% at 4°K, and K+0.29%and+0.92% at 210°K. The anisotropic Knight-shift contribution is estimated to be less than 10% of the measured shifts. The average spin-lattice relaxation time for the two sites is T1T=0.56±0.05 sec °K. The relaxation time for the site having the smaller Knight shift exceeds that for the other site by a factor of approximately 1.7. A comparison of the average Knight shifts and spinlattice relaxation rates in dhcp lanthanum with those in hcp scandium and yttrium leads to the conclusion that the direct s-contact interaction is the dominant magnetic-hyperfine mechanism in the Group-IIIB transition metals. © 1969 The American Physical Society.