Electron Spin Resonance and Magnetic Resonance Imaging of Single Organic Radicals with the STM

Magnetic single atoms and molecules constitute the ultimate spatial limit for data storage, quantum sensors and quantum information units. Recently electron spin resonance spectroscopy combined with the scanning tunneling microscope (ESR-STM) has developed into a powerful tool to address magnetic adsorbates at the single atom level. Compared to other STM magnetic spectroscopy techniques, ESR-STM provides unprecedented energy resolution and allows for coherent spin manipulation. Concurrently, organic magnetism has seen a surging interest due to the exciting properties of magnetic edge states in graphene nanoribbons and magnetism induced by topological frustration in open-shell nanographenes. In today's seminar I will describe our efforts to measure the electron spin resonance of organic pi radicals adsorbed on metal-supported MgO thin films. We successfully drive delocalized electron spins with the localized RF field from an atomically sharp tip apex and characterize the spin of a molecular anion. Further, we acquire MRI scans of single molecules, revealing unexpectedly rich sub-molecular resolution detail which arises from the delocalized pi electron sensing the magnetic field from the STM tip as it scans over the molecule. Our results extend ESR-STM to the study of organic magnetism and provide new opportunities for visualizing magnetic interactions with sub-angstrom spatial resolution.

Speaker: Gregory Czap, IBM