Carrier Density and Magnetism in Graphene Zigzag Nanoribbons

TL;DR

This study investigates how changing carrier density affects magnetism in zigzag graphene nanoribbons, revealing charge and spin variations, suppression of magnetism at high doping, and potential multiferroic order at low doping.

Contribution

It introduces a mean-field Hubbard model analysis of carrier density effects on magnetism and multiferroic tendencies in zigzag graphene nanoribbons.

Findings

Magnetism decreases with increased doping density.

Charge and spin polarization vary across the ribbon.

Multiferroic order may occur at low doping levels.

Abstract

The influence of carrier density on magnetism in a zigzag graphene nanoribbon is studied in a $\pi$-orbital Hubbard-model mean-field approximation. Departures from half-filling alter the magnetism, leading to states with charge density variation across the ribbon and parallel spin-alignment on opposite edges. Finite carrier densities cause the spin-density near the edges to decrease steadily, leading eventually to the absence of magnetism. At low doping densities the system shows a tendency to multiferroic order in which edge charges and spins are simultaneously polarized.