Magnetic And Electronic Properties Of Transition Metal-graphene Nanoribbons

Transition metal (TM) atoms adsorbed graphene or graphene nanoribbons (GNR)are of great research interest for their varied magnetic and electronic properties. Themagnetic property of transition metal monolayer (ML) adsorbed on carbon substrateis important to researchers for its potential application as spintronic device.In this article, spin-polarized density functional theory (DFT) calculation wascarried out to study structure, electronic and magnetic properties of n=6,8,10armchair graphene nanoribbons (AGNRs) coated with3d transition metal (TM) atomsand n=6,8,10zigzag graphene nanoribbons (ZGNRs) coated with Co, Ni atoms. Wefound that1D nature of GNR would affect the magnetism of adsorbed TM atoms,provide different properties from TM atoms adsorbed on2D graphene substrate.Besides, the edge shape of GNR, whether it is armchair or zigzag, would affect theordering and magnetism of adsorbed TM atoms.The research results are summarized as follows:1. In TM-AGNR systems, AGNRs are curved by adsorbing single layer3dtransition metal atoms in vacuum environment, and the metal layers are mostly rough.Due to1D nature of GNR, adsorbed TM atoms would form topologies that aredifferent from bulk structures. As the AGNR width increases the TM-AGNR systemstend to be more metallic. Diverse magnetic states are presented for differentTM-AGNR systems, and the antiferromagnetic (AFM) systems have different TMatomic orderings from the ferromagnetic (FM) systems. The1D nature of GNRaffected the magnetism of adsorbed TM atoms, too. Cr and Fe atoms tend to form3Dclusters above AGNR.2. In Co, Ni-ZGNR systems, ZGNRs are curved by adsorbing single layer3dtransition metal atoms in vacuum environment too, and the metal layers are mostlyrough. Besides, there are3D clusters in n=8,10Co, Ni-ZGNR. After adsorbing TMatoms, the H atoms’ magnetic moments and the magnetic coupling of edges of ZGNR are affected by TM atoms’ magnetic moments, different from pristine ZGNR’scondition. All the Co, Ni-ZGNR systems are metallic. As the width of ZGNR changes,the ordering of TM atoms changes too, causing different magnetism.3. While comparing Co, Ni-ZGNR systems with Co, Ni-AGNR systems, wefound that the edge shape and symmetry of GNR would affect the topology of metallayer adsorbed on GNR surface. Co and Ni atoms tend to form3D clusters whileadsorbing on ZGNR surface, but they tend to be uniformly distributed on AGNRsurface. TM atoms of one species would produce different electronic structures whileadsorbed on different kinds of GNRs. The electronic structure of original GNR andhybridization of GNR and TM atoms would affect the electronic properties ofTM-GNR systems. TM atoms of one species adsorbing on different kinds of GNRswould result in different TM atom orderings, thus produce different magneticproperties. The magnetism difference is in fact caused by the shape and symmetrydifference of GNR edge, too.