Probing divacancy defects in a zigzag graphene nanoribbon through RKKY exchange interaction

TL;DR

This study explores how divacancy defects influence the electronic and magnetic properties of zigzag graphene nanoribbons, revealing that defect location and density significantly alter RKKY exchange interactions and magnetic states.

Contribution

It provides a detailed analysis of the impact of divacancy defects on RKKY interactions in zGNRs using Green's function and tight-binding models, highlighting the importance of defect positioning.

Findings

Edge defects greatly enhance exchange coupling magnitude.

Interior defects result in weaker RKKY interactions.

Periodic divacancies can change the magnetic ground state.

Abstract

We investigate the effect of vacancy defects on the electronic and magnetic properties of zigzag graphene nanoribbons (zGNRs) by making use of the Green's function formalism in combination with the tight-binding Hamiltonian. The evolution of the indirect exchange coupling, known as Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, including single, double, and multiple 5-8-5 divacancy defects is explained. Our numerical calculations show that the changes in the electronic structure and the exchange coupling of zGNRs depend significantly on the location of the divacancy defects with respect to the ribbon edges and on the number of the divacancy defects. In the case both the impurities are located on the edge, the magnitude of the exchange coupling is several orders of magnitude strengthen that result when they are placed on the interior of the nanoribbon. Furthermore, a periodic divacancy causes a dramatic change in the magnetic ground state of the ribbon. In the limit of high vacancy potential, the strength of the RKKY interaction is approximately independent of the Fermi energy.