Magnetism of Covalently Functionalized Carbon Nanotubes

TL;DR

This study reveals that covalent functionalization of carbon nanotubes induces a universal magnetic moment of 1.0 μB per molecule, driven by defect states at the Fermi energy, with magnetic interactions depending on adsorption sites.

Contribution

It introduces a universal mechanism of bonding-induced magnetism in covalently functionalized carbon nanotubes, highlighting the role of defect states and sublattice-dependent magnetic coupling.

Findings

A spin moment of 1.0 μB per molecule is induced at low coverage.

Adsorption creates defect states at the Fermi energy localized in the carbon wall.

Magnetic coupling depends on the sublattice adsorption site.

Abstract

We investigate the electronic structure of carbon nanotubes functionalized by adsorbates anchored with single C-C covalent bonds. We find that, despite the particular adsorbate, a spin moment with a universal value of 1.0 $\mu_B$ per molecule is induced at low coverage. Therefore, we propose a mechanism of bonding-induced magnetism at the carbon surface. The adsorption of a single molecule creates a dispersionless defect state at the Fermi energy, which is mainly localized in the carbon wall and presents a small contribution from the adsorbate. This universal spin moment is fairly independent of the coverage as long as all the molecules occupy the same graphenic sublattice. The magnetic coupling between adsorbates is also studied and reveals a key dependence on the graphenic sublattice adsorption site.