Exchange coupling between two ferromagnetic electrodes separated by a graphene nanoribbon

TL;DR

This paper investigates the oscillatory exchange coupling between two ferromagnetic electrodes separated by graphene nanoribbons, revealing dependence on Fermi energy and nanoribbon length through numerical analysis.

Contribution

It introduces a self-energy and total energy calculation approach to analyze exchange coupling in FM/GNR/FM junctions, highlighting oscillatory behavior and parameter dependencies.

Findings

Exchange coupling oscillates with Fermi energy and nanoribbon length.

Coupling strength varies between ferromagnetic and antiferromagnetic states.

Numerical results demonstrate dependence on junction geometry and electronic properties.

Abstract

In this study, based on the self-energy method and the total energy calculation, the indirect exchange coupling between two semi-infinite ferromagnetic strips (FM electrodes) separated by metallic graphene nanoribbons (GNRs) is investigated. In order to form a FM/GNR/FM junction, a graphitic region of finite length is coupled to the FM electrodes along graphitic zigzag or armchair interfaces of width $N$. The numerical results show that, the exchange coupling strength which can be obtained from the difference between the total energies of electrons in the ferromagnetic and antiferromagnetic couplings, has an oscillatory behavior, and depends on the Fermi energy and the length of the central region.