Towards spintronics: superparamagnetism of nanoparticles in carbon nanotubes

For the first time the anomaly temperature dependence of the anisotropy field H_A in carbon single-walled nanotubes (SWNTs) with magnetic nanoclusters was observed. It is shown that the reason of this phenomenon can be caused by a competition between dipolar interaction and anisotropy. It is found that the assembly of Ni nanoparticles shows the crossover to a collective magnetic ordering both initial and diluted SWNTs at the temperatures smaller than about 50 K.