β-NMR study of isolated 8Li ⁺ in the enhanced paramagnet platinum

We report β-detected nuclear magnetic resonance (β-NMR) measurements of 8Li ⁺ implanted into high purity Pt. The frequency of the 8Li β-NMR resonance and the spin-lattice relaxation rates 1/T ₁ were measured at temperatures ranging from 3 to 300 K. Remarkably, both the spin-lattice relaxation rate and the Knight shift K depend linearly on temperature T although the bulk susceptibility does not. K is found to scale with the Curie-Weiss dependence of the Pt susceptibility extrapolated to low temperatures. This is attributed to a defect response of the enhanced paramagnetism of Pt, i.e., the presence of the interstitial Li ⁺ locally relieves the tendency for the Curie-Weiss susceptibility to saturate at low T. We propose that the low temperature saturation in χ of Pt may be related to an interband coupling between the s and d bands that is disrupted locally by the presence of the Li ⁺.