title: Atomic-scale sensing of the magnetic dipolar field from single atoms.
abstract: Spin resonance provides the high-energy resolution needed to determine biological and material structures by sensing weak magnetic interactions. In recent years, there have been notable achievements in detecting and coherently controlling individual atomic-scale spin centres for sensitive local magnetometry. However, positioning the spin sensor and characterizing spin-spin interactions with sub-nanometre precision have remained outstanding challenges. Here, we use individual Fe atoms as an electron spin resonance (ESR) sensor in a scanning tunnelling microscope to measure the magnetic field emanating from nearby spins with atomic-scale precision. On artificially built assemblies of magnetic atoms (Fe and Co) on a magnesium oxide surface, we measure that the interaction energy between the ESR sensor and an adatom shows an inverse-cube distance dependence (r-3.01±0.04). This demonstrates that the atoms are predominantly coupled by the magnetic dipole-dipole interaction, which, according to our observations, dominates for atom separations greater than 1 nm. This dipolar sensor can determine the magnetic moments of individual adatoms with high accuracy. The achieved atomic-scale spatial resolution in remote sensing of spins may ultimately allow the structural imaging of individual magnetic molecules, nanostructures and spin-labelled biomolecules.
authors.affiliation: IBM Almaden Research Center, San Jose, California 95120, USA.
authors.forename: Taeyoung
authors.identifier: 0000-0001-5681-807X
authors.initials: T
authors.lastname: Choi
authors.affiliation: IBM Almaden Research Center, San Jose, California 95120, USA.
authors.forename: William
authors.initials: W
authors.lastname: Paul
authors.affiliation: Max Planck Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany.|Max Planck Institute for Solid State Research, Stuttgart 70569, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Rolf-Pissarczyk
authors.affiliation: University of British Columbia &Quantum Matter Institute, Vancouver, BC V6T 1Z4, Canada.
authors.forename: Andrew J
authors.identifier: 0000-0002-7274-5701
authors.initials: AJ
authors.lastname: Macdonald
authors.affiliation: IBM Almaden Research Center, San Jose, California 95120, USA.|Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Fabian D
authors.identifier: 0000-0002-2488-5988
authors.initials: FD
authors.lastname: Natterer
authors.affiliation: IBM Almaden Research Center, San Jose, California 95120, USA.|School of Physical Sciences and Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Kai
authors.identifier: 0000-0002-5863-3666
authors.initials: K
authors.lastname: Yang
authors.affiliation: IBM Almaden Research Center, San Jose, California 95120, USA.|IV. Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
authors.forename: Philip
authors.initials: P
authors.lastname: Willke
authors.affiliation: IBM Almaden Research Center, San Jose, California 95120, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Lutz
authors.affiliation: Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea.|Physics Department, Ewha Womans University, Seoul, Republic of Korea.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Heinrich