Transition metals ferromagnetism

SWCNTs have been produced by carbon arc discharge and laser ablation of graphite rods. In each case, a small amount of transition metals is added to the carbon target as a catalyst. Therefore the ferromagnetic catalysts resided in the sample. The residual catalyst particles are responsible for a very broad ESR line near g=2 with a linewidth about 400 G, which obscures the expected conduction electron response from SWCNTs. 

Zener, C. 1951. Interaction between the (/-shells in the transition metals. II. Ferromagnetic compounds of manganese with perovskite structure. Physical Review 82 403-405. 

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