Electron correlation effects in the exchange coupling at the Fe/CoO/Ag(001) ferro-/antiferro-magnetic interface

TL;DR

This study uses AR-APECS to analyze how electron correlations influence exchange coupling at the Fe/CoO/Ag(001) interface, revealing enhanced Coulomb and exchange interactions linked to electron confinement and interlayer coupling.

Contribution

It provides the first experimental determination of effective correlation energies for different orbitals and spins at this magnetic interface, highlighting the role of electron correlation effects.

Findings

Enhanced Coulomb interaction for e_g orbitals at the interface.

Increased exchange interaction for t_2g orbitals compared to Fe/Ag.

Correlation effects are linked to electron confinement and interlayer exchange.

Abstract

Angle resolved-Auger-photoelectron coincidence spectroscopy (AR-APECS) has been exploited to investigate the role that electron correlation plays in the exchange-coupling at the ferromagnetic/antiferromagnetic interface of a Fe/CoO bilayer growth on Ag(001). The effective correlation energy U$_{\textrm{eff}}$, usually employed to assess the energy distribution of core-valence-valence Auger spectra, has been experimentally determined for each possible combination of the orbital (e$_g$ or t$_{2g}$) and the spin (majority or minority) of the two valence electrons involved in the Auger decay. Coulomb and exchange interactions have been identified and compared with the result obtained on the Fe/Ag system. The presented analysis reveals in the Fe/CoO interface an enhancement of the Coulomb interaction for the e$_g$ orbital and of the exchange interaction for the t$_{2g}$ orbital with respect to the Fe/Ag case that can be associated to the stronger electron confinement and to the exchange coupling between the two layers, respectively.