Competition between Kondo screening and exchange interaction in pairs of atoms

A. Spinelli, M. Gerrits, R. Toskovic, B. Bryant, M. Ternes, A. F. Otte

Published 2014-11-17Version 1

Individual magnetic atoms on a metal substrate are known to be Kondo-screened, but little is known about how this screening is affected when multiple magnetic atoms are coupled to each other through exchange interactions. We use a low-temperature scanning tunneling microscope to assemble, with atomic precision, a set of Co dimers on Cu$_2$N/Cu(100) with various orientations. By performing local inelastic electron tunneling spectroscopy and fitting the observed spectra to simulated conductance curves, we are able to map the exchange interaction between the atoms in the pair as a function of relative position and distance. In addition, modeling the spin-spin interactions up to third order enables us to determine to what extent Kondo correlations play a role in each dimer. We find that this role steadily diminishes as the exchange coupling is increased.