Signatures of electronic correlations and spin-susceptibility anisotropy in nuclear magnetic resonance

We present a methodology for probing the details of electronic susceptibility through minimally-invasive nuclear magnetic resonance techniques. Specifically, we classify electron-mediated long-range interactions in an ensemble of nuclear spins by revealing their effect on simple spin echo experiments. We find that pulse strength and applied field orientation dependence of these spin echo measurements resolves the spatial extent and anisotropy of electronic spin susceptibility. These nuclear-nuclear interactions provide an alternate explanation to unusual NMR results in superconducting and magnetically-ordered systems, commonly attributed to heating effects. The methodology has direct applications for sensing and characterizing spin structure in correlated electronic phases.