The nanotube-based composite MWNT-Fe2+ was prepared through coordination action of the carboxylic acid groups from the oxidized multi-walled carbon nanotubes (MWNTs). The magnetic behavior of this composite was measured as a function of the magnetic field strength at 5 K and a function of temperature (5-300 K) at 30 kOe. A hysteresis loop at 5 K with a small coercivity of 260 Oe was observed. The experimental results show that the MWNT-Fe2+ composite possesses special ferromagnetic interaction between nanotubes and iron ions. (c) 2005 Elsevier B.V. All rights reserved.