Adatoms and clusters of 3d transition metals on graphene: Electronic and magnetic configurations

TL;DR

This study explores the electronic and magnetic behaviors of individual and clustered 3d transition metal adatoms on graphene, revealing site preferences, magnetic states, and the influence of hybridization through combined experimental and theoretical methods.

Contribution

It provides new insights into the magnetic and electronic configurations of Fe, Co, and Ni adatoms and clusters on graphene, supported by experimental data and ab initio calculations.

Findings

Fe and Co adatoms are paramagnetic with out-of-plane easy axes.

Ni monomers are nonmagnetic, but larger clusters show magnetic moments.

Hybridization and charge transfer significantly affect adatom and cluster properties.

Abstract

We investigate the electronic and magnetic properties of single Fe, Co, and Ni atoms and clusters on monolayer graphene (MLG) on SiC(0001) by means of scanning tunneling microscopy (STM), x-ray absorption spectroscopy, x-ray magnetic circular dichroism (XMCD), and ab initio calculations. STM reveals different adsorption sites for Ni and Co adatoms. XMCD proves Fe and Co adatoms to be paramagnetic and to exhibit an out-of-plane easy axis in agreement with theory. In contrast, we experimentally find a nonmagnetic ground state for Ni monomers while an increasing cluster size leads to sizeable magnetic moments. These observations are well reproduced by our calculations and reveal the importance of hybridization effects and intra-atomic charge transfer for the properties of adatoms and clusters on MLG.