The electromagnetic wave absorption properties of epsilon-Fe3N/Y2O3 nanocomposites were characterized in a frequency range of 0.05-20.05 GHz. The imaginary part of relative permeability mu(r) exhibited two types of resonance mechanisms: the domain wall and spin rotational resonances, over a 0.5-10 GHz range. The real part (epsilon(r)') and imaginary part (epsilon(r)") of relative permittivity almost kept a low constant in a region of 0.5-10 GHz, respectively. As a result, the resin composites with 80 wt % epsilon-Fe3N/Y2O3 powders exhibited excellent electromagnetic wave absorption properties (RL< -20 dB) in a frequency range of 0.6-4.4 GHz, with thickness of 3.3-19.3 mm. A minimum reflection loss of -55 dB was observed at 1.8 GHz with an absorber thickness of 7.05 mm. (C) 2004 The Electrochemical Society.