Electronic structure and magnetic properties of graphitic ribbons

TL;DR

This study uses first principles calculations to show that zig-zag graphene ribbons are magnetically unstable, with long-range magnetic interactions affecting their electronic properties, and explores mechanisms influencing their stability and potential for spintronic applications.

Contribution

The paper demonstrates that magnetic polarization in zig-zag graphene ribbons is stable and long-ranged, independent of electron-electron interaction details, and rules out alternative stabilization mechanisms.

Findings

Magnetic edge states are stable and long-ranged.

Electron-electron interactions do not alter qualitative results.

Charge ordering and Peierls distortion are unfavorable for stability.

Abstract

First principles calculations are used to establish that the electronic structure of graphene ribbons with zig-zag edges is unstable with respect to magnetic polarisation of the edge states. The magnetic interaction between edge states is found to be remarkably long ranged and intimately connected to the electronic structure of the ribbon. Various treatments of electronic exchange and correlation are used to examine the sensitivity of this result to details of the electron-electron interactions and the qualitative features are found to be independent of the details of the approximaton. The possibility of other stablisation mechanisms, such as charge ordering and a Peierls distortion, are explicitly considered and found to be unfavourable for ribbons of reasonable width. These results have direct implications for the control of the spin dependent conductance in graphitic nano-ribbons using suitably modulated magnetic fields.