Spin excitations in a 4f-3d heterodimer on MgO

TL;DR

This study investigates the magnetic properties of HoCo dimers on MgO, revealing spin excitations and ferromagnetic coupling, combining experimental STM data with theoretical analysis to understand their magnetic interactions.

Contribution

It provides the first detection of spin excitations in 4f-3d heterodimers and characterizes their magnetic interactions using combined experimental and theoretical methods.

Findings

Detection of spin excitations in HoCo dimers.

Identification of ferromagnetic coupling in the dimer.

Determination of magnetic level distribution and exchange interaction.

Abstract

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.