Large coercivity in Mn/sub 3/O/sub 4/ nanocrystallites

Heat treatment was applied to Mn nanoparticles to introduce Mn/sub 3/O/sub 4/ nanocrystals into the sample. X-ray diffraction spectra and the temperature dependence of the magnetization and coercivity of the Mn nanoparticles were studied. A large coercivity was observed in manganese nanocomposites containing Mn/sub 3/O/sub 4/ crystals. This coercivity, which was found to decrease almost linearly with increasing temperature, is mainly due to the small crystallite size of the ferrimagnetic Mn/sub 3/O/sub 4/.