Wednesday, November 4, 2009
Ballroom A+B (Camino Real Hotel)
Nanocrystalline Sm25Fe75 powders with high coercivity HC were prepared by mechanical milling and subsequent annealing. Annealing was carried out at temperature T equal to 800 °C, and times t ranging from 1 to 6 minutes. X-ray diffraction, magnetization measurements and scanning electron microscopy were used to study the microstructure and magnetic properties of these samples. The analisys of X-ray diffraction patterns demonstrate that the average grain size
of the nanocrystalline powders depends on the annealing time t: ranges from 15 nm (for t = 1.5 minutes) to 80 nm (for t = 6.0 minutes). In addition, scanning electron microscopy images showed a small particle size for all samples. Finally, magnetic measurements performed at room temperature indicates high coercivity values (HC > 4 kOe) for best sample, where was found a strong annealing-induced grain size dependence.