Local metallic and structural properties of the strongly correlated metal LaNiO3 using 8Li β-NMR

We report beta-detected NMR of ion-implanted Li-8 in a single crystal and thin film of the strongly correlated metal LaNiO3. Spin-lattice relaxation measurements reveal two distinct local environments, both metallic as evident from T-linear Korringa 1/T-1 below 200 K with slopes comparable to other metals. A small approximately temperature-independent Knight shift of similar to 74 ppm is observed, yielding a normalized Korringa product characteristic of substantial antiferromagnetic correlations. We find no evidence for a magnetic transition from 4 to 310 K. The similarity of these features in the two very different samples indicates that they are intrinsic and unrelated to dilute oxygen vacancies. We attribute the two environments to two distinct but similar crystallographic Li-8 sites and not to any form of phase inhomogeneity, but this is inconsistent with the conventional rhombohedral structure of LaNiO3, and also cannot be simply explained by the common alternative orthorhombic or monoclinic distortions.