Impact of CNT medium on the interaction between ferromagnetic nanoparticles

We present results on low-temperature magnetization approaching the saturation law in aligned bundles of CNTs with ferromagnetic nanoparticles embedded inside inner channels of nanotubes for two directions of the magnetic field, parallel and perpendicular to the CNT axes. Elaborating experimental data, we were able to extract the explicit form of the correlation functions describing the orientation of the magnetic anisotropy axes in real space. In the parallel field the long-range coherence in the magnetic anisotropy axes is the characteristic feature. In the perpendicular direction the peculiar feature is the 2D exchange coupling. The nature of the exchange interaction and the role of the CNT medium in it is also discussed.