Unique magnetism observed in single-wall carbon nanohorns

Abstract.

The magnetic properties of single-wall carbon nanohorns (SWNH) were studied by electron spin resonance (ESR) and static magnetic susceptibility measurements. The SWNHs were ESR active with linewidth (ΔH) of ∼6 G in vacuo at room temperature. ΔH was susceptible to the partial pressure of O₂ and became 53 G at 1 atmospheric pressure of O₂, while the integrated ESR intensity was independent on O₂ pressure and behaved as Curie-like, suggesting an intrinsic ESR origin with localized electron spin character. The diamagnetic susceptibility for SWNHs indicated a value smaller than that of randomly oriented graphite by an order of magnitude, but showing a magnitude comparable to those of C₆₀ and C₇₀. It is suggested that the large diamagnetism expecting for sp² networked carbon materials will be canceled by the Van Vleck constant paramagnetism.