MAGNETIC PROPERTIES OF IRON-NITRIDE-ALUMINA NANOCOMPOSITE MATERIALS PREPARED BY HIGH-ENERGY BALL MILLING

摘要

The structural and magnetic properties of the granular iron nitride-alumina composite materials, (Fe_xN)_(0.2)(Al_2O_3)_(0.8) and (Fe_xN)_(0.6)(Al_2O_3)_(0.4), fabricated using high-energy ball milling have determined using x-ray diffraction, transmission electron microscopy, and magnetization measurements. The coercive fields as high as 325 and 110 Oe are obtained for (Fe_xN)_(0.2)(Al_2O_3)_(0.8) at 5 and 300 K, respectively; the increase the coercive field upon cooling indicates the presence of small superparamagnetic particles. The coercive field increases with milling time because of the reduced particle size. The saturation magnetization decreases with increased milling because of the increased superparamagnetic fraction.