Ultrafine Sm-Fe-N Particles Prepared by Planetary Ball Milling
Department of Physics and Astronomy, University of DE, Newark, DE, USA
Ultrafine magnetically hard particles are needed for the bottomup fabrication of anisotropic exchangedcoupled permanent magnets. In this study we have chosen Sm2Fe17Nx because of its high anisotropy field and large saturation magnetization. A multistage planetary ball milling process was used. The key is to find the right balance of energy used to mill the precursor particles; it must be high enough to break the particles and reduce their size but, not so high as to destroy the crystal structure of the nanoparticles that would lead to deterioration of the magnetic properties. First the coarse powders were subjected to a wet milling with 2.0 mm diameter media. In each subsequent stage the media size was reduced to maintain the milling balance. Using such a process produced particles in a size range from 100 - 800 nm with a coercivity as high as 10 kOe at room temperature.
© Owned by the authors, published by EDP Sciences, 2013