We report on the magnetic properties of HoCo dimers as a model system for the smallest intermetallic transition metal-lanthanide compound. The dimers are adsorbed on ultrathin MgO(100) films grown on Ag(100). New for 4f elements, we detect inelastic excitations with scanning tunneling microscopy and prove by their behaviour in applied magnetic field that they are spin-excitations. In combination with density functional theory and spin Hamiltonian analysis we determine the magnetic level distribution, as well as sign and magnitude of the exchange interaction between the two atoms. In contrast to typical 4f−3d bulk compounds, we find ferromagnetic coupling in the dimer.
@article{arxiv.1807.09316,
title = {Spin excitations in a 4f-3d heterodimer on MgO},
author = {A. Singha and F. Donati and F. D. Natterer and C. Wäckerlin and S. Stavrić and Z. S. Popović and {Ž}. {Š}ljivan{č}anin and F. Patthey and H. Brune},
journal= {arXiv preprint arXiv:1807.09316},
year = {2018}
}