Ion-Implanted $^8$Li Nuclear Magnetic Resonance in Highly Oriented Pyrolytic Graphite

• DOI: 10.48550/arxiv.2301.07821
• Publication Date: 2023-11-29
• Authors: John O. Ticknor; Jonah R. Adelman; Aris Chatzichristos; Martin H. Dehn; Luca Egoriti; Derek Fujimoto; Victoria L. Karner; Robert F. Kiefl; C. D. Philip Levy; Ruohong Li; Ryan M. L. McFadden; Gerald D. Morris; Mohamed Oudah; Monika Stachura; Edward Thoeng; W. Andrew MacFarlane
• Keywords: Condensed Matter - Other Condensed Matter; Condensed Matter - Materials Science; Condensed Matter - Mesoscale and Nanoscale Physics; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; Other Condensed Matter (cond-mat.other)

We report $β$-detected nuclear magnetic resonance of ultra-dilute $^{8}$Li$^{+}$ implanted in highly oriented pyrolytic graphite (HOPG). The absence of motional narrowing and diffusional spin-lattice relaxation implies Li$^+$ is not appreciably mobile up to 400 K, in sharp contrast to the highly lithiated stage compounds. However, the relaxation is remarkably fast and persists down to cryogenic temperatures. Ruling out extrinsic paramagnetic impurities and intrinsic ferromagnetism, we conclude the relaxation is due to paramagnetic centers correlated with implantation. While the resulting effects are not consistent with a Kondo impurity, they also differ from free paramagnetic centers, and we suggest that a resonant scattering approach may account for much of the observed phenomenology.