Indirect Exchange Interaction in Fully Metal-Semiconductor Separated   SWCNTs Revealed by ESR
  The ESR response from highly metal-semiconductor(M-SC) separated SWCNTs for temperatures T between 0.39 and 200 K is characteristically different for the two systems. The signal originates from defect spins but interaction with free electrons leads to a larger line width for M tubes. The latter decreases with increasing T whereas it increases with T for SC tubes. The spins undergo a ferromagnetic phase transition below around 10 K. Indirect exchange is suggested to be responsible for the spin-spin interaction, supported by RKKY interaction in the case of M tubes. For SC tubes spin-lattice relaxation via an Orbach process is suggested to determine the line width. 
M. Havlicek, W. Jantsch, Z. Wilamowski, K. Yanagi, H. Kataura, M. H.   Rummeli, H. Malissa, A. Tyryshkin, S. Lyon, A. Cherno...
cond-mat.mtrl-sci