  Carbon nanotubes (CNT) belong to the most promising new materials which can
in the near future revolutionize the conventional electronics. When sandwiched
between ferromagnetic electrodes, the CNT behaves like a spacer in conventional
spin-valves, leading quite often to a considerable giant magneto-resistance
effect (GMR). This paper is devoted to reviewing some topics related to
electron correlations in CNT. The main attention however is directed to the
following effects essential for electron transport through nanotubes: (i)
nanotube/electrode coupling and (ii) inter-tube interactions.It is shown that
these effects may account for some recent experimental reports on GMR,
including those on negative (inverse) GMR.
