Spin-filtering and Disorder Induced Giant Magnetoresistance in Carbon Nanotubes: Ab Initio Calculations

TL;DR

This study uses ab initio calculations to demonstrate that nitrogen-doped carbon nanotubes with specific transition metal defects can act as highly effective spin filters and exhibit giant magnetoresistance effects.

Contribution

The paper introduces a detailed analysis of transition metal bonded defects in N-doped carbon nanotubes, revealing their potential for spin filtering and magnetoresistance applications.

Findings

Heme B-like defect (iron bonded to four nitrogens) is most stable.

Single defects can achieve near 100% polarization current.

Giant magnetoresistance up to 20000% observed in long nanotubes.

Abstract

Nitrogen-doped carbon nanotubes can provide reactive sites on the porphyrin-like defects. It's well known that many porphyrins have transition metal atoms, and we have explored transition metal atoms bonded to those porphyrin-like defects in N-doped carbon nanotubes. The electronic structure and transport are analyzed by means of a combination of density functional theory and recursive Green's functions methods. The results determined the Heme B-like defect (an iron atom bonded to four nitrogens) as the most stable and with a higher polarization current for a single defect. With randomly positioned Heme B-defects in a few hundred nanometers long nanotubes the polarization reaches near 100% meaning an effective spin filter. A disorder induced magnetoresistance effect is also observed in those long nanotubes, values as high as 20000% are calculated with non-magnectic eletrodes.