A novel complex of SWNT-PDTEN-Nd3+ was prepared though coordination action of polymer to introduce Nd3+ in SWNT-PDTEN system. The magnetic behavior of the complex was measured as a function of the magnetic field strength (0-60 kOe) at 5 K and a function of temperature (5-300 K). New magnetic phenomena of temperature dependence of magnetization for SWNT-PDTEN-Nd3+ are observed. The ferromagnetism of polymeric complex directly turns to diamagnetism at transition temperature of 125 K. It exhibits a hysteresis loop at 5 K with small coercivity (165 Oe) and remnant magnetization of 0.008 emu/g, which indicates that this complex possesses soft ferromagnetic property. (C) 2004 Elsevier B.V. All rights reserved.