Magnetic properties of ball-milled Mn nanoparticles

Nanoparticles of Mn of sizes <500 <Angstrom> were prepared by the ball-milling technique. The temperature dependence of the magnetic susceptibility X showed systematic variation with particle size. Peaks observed in chi were attributed to the magnetic ordering of the oxides Mn3O4 and MnO. Peaks found in partial derivative(chiT)/partial derivativeT were associated with the Neel temperature of alpha -Mn. We estimated that our samples contain about 0.4% of Mn3O4. This low concentration of Mn3O4 was not detected by X-ray diffraction experiments but contributed significantly to the magnetization measurements. (C) 2001 Academic Press.