Estimation of Magnetic Susceptibility Anisotropy of Carbon Nanotubes Using

Abstract

We have carried out a magnetophotoluminescence excitation spectroscopy study on micelle-suspended single-walled carbon nanotubes in high magnetic fields. By analyzing field-dependent spectral changes, we determined the degree of magnetic alignment of the observed semiconducting nanotubes at 45 T. This, together with an independently measured length distribution of the nanotubes, allowed us to estimate the magnitude of the magnetic susceptibility anisotropy � | − � ⊥ to be ∼1.4 × 10-5 emu/mol for 1-nm-diameter semiconducting nanotubes. Single-walled carbon nanotubes (SWNTs), either metallic or semiconducting, are predicted to possess novel magnetic properties. 1-3 For example, while a field applied parallel to the tube axis modifies the band structure through the Aharonov-Bohm (AB) phase, leading to a logarithmically divergent paramagnetic susceptibility for metallic tubes, a perpendicular field is predicted to induce lattice instability and distortion. At low magnetic fields (φ, φ0, where φ is the magnetic flux threading the tube and φ0) h/e is the magnetic flux quantum), semiconducting SWNTs are predicte