Antiferromagnetic–ferromagnetic transition in zigzag graphene nanoribbons induced by substitutional doping

Abstract

Using first-principles calculations based on density functional theory, we show that the ground state of zigzag-edged graphene nanoribbons (ZGNRs) can be transformed from antiferromagnetic (AFM) order to ferromagnetic (FM) order by changing the substitutional sites of N or B dopants. This AFM-FM transition induced by substitutional sites is found to be a consequence of the competition between the edge and bulk states. The energy sequence of the edge and bulk states near the Fermi level is reversed in the AFM and FM configurations. When the dopant is substituted near the edge of the ribbon, the extra charge from the dopant is energetically favorable to occupy the edge states in AFM configuration. When the dopant is substituted near the center, the extra charge is energetically favorable to occupy the bulk states in FM configuration. Proper substrate with weak interaction is necessary to maintain the magnetic properties of the doped ZGNRs. Our study can serve as a guide to synthesize graphene nanostructures with stable FM order for future applications to spintronic devices.

Magnetic Properties of Quasi-One-Dimensional Crystals Formed by Graphene Nanoclusters and Embedded Atoms of the Transition Metals

“…Since the pristine nanoribbons have singlet ground state, the magnetic derivatives of this material have importance for the practical realization of spin-polarized electronic transport. It is found both theoretically and experimentally that atoms of transition metals (ATM) may fill carbon vacancies in graphene clusters to form stable ATM-embedded structures [18,19]. According to Lieb's theorem, structures with periodically embedded ATM may have macroscopic values of total spin in ground state with "ferrimagnetic" spin ordering.…”