title: Magnetic properties of iron nitride-silica nanocomposite materials prepared by high-energy ball milling.
abstract: Powder mixtures of (FexN)y and (SiO2)1-y, with x between 3 and 4 and y equal to 0.2 or 0.6, were ball-milled for 4, 8, 16, 32, and 64 h. X-ray diffraction, thermal analysis, and magnetization measurements allowed an investigation of structural and magnetic properties to be carried out. The samples consist of nanostructured Fe3N and Fe4N particles in a SiO2 matrix. As the milling time increases, the Fe4N phase is eliminated from the particles in favor of Fe3N. Coercive fields as high as 270 and 84 Oe are obtained for (FexN)0.2(SiO2)0.8 at 5 and 300 K, respectively. This higher coercive field, upon cooling, indicates the presence of small superparamagnetic particles. The coercive field also increases with milling time, which is due to the reduced particle size and induced stain. The saturation magnetization decreases with increased milling time as a consequence of an increase in the superparamagnetic fraction and increased strain. Hard and soft magnetic properties are observed for y = 0.2 and y = 0.6 samples, respectively.
mesh_terms: D000497:Alloys / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008280:Magnetics; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D000497:Alloys; D012822:Silicon Dioxide; D007501:Iron; D009584:Nitrogen