Probing the atomic-scale magnetism of single molecules and engineered organometallic nanostructures with electron spin resonance STM*

Single atoms and molecules constitute the ultimate spatial limit for magnetic data storage, quantum information units, quantum sensors and spintronic devices. Recently, developments in Electron Spin Resonance spectroscopy using Scanning Tunneling Microscopes (STM-ESR) have enabled simultaneous atomic spatial resolution and ~ 100 neV energy resolution of adsorbate spin excitations. Previous STM-ESR studies have focused on magnetic 3d transition metal atoms, but the domain of organic spin radicals and complex organometallic structures remains unexplored. Here we report on efforts to extend the detection of STM-ESR to single magnetic molecules and spin radicals stabilized by a thin insulating layer grown on a metal substrate. The intensity of the ESR signal, Rabi rate and coherence times are compared to single metal atom benchmark systems, providing new insights into the mechanisms of STM-ESR. Further, we demonstrate novel organometallic compounds fabricated by tip manipulation with precise control over ligand binding site and orientation. These results present exciting new opportunities for exploring atomic scale magnetism through deliberate engineering of organometallic nanostructures.