Abstract
Acicular Ni0.4Zn0.6Fe2O4 fine particles were made from acicular a-FeOOH, Ni(C5H7O2)2 and Zn(C5H7O2)2 by calcining at 750-950°C for 4 hours. The saturation magnetization and the aspect ratio of the obtained particles were 50 emu/g and 26, respectively. These particles were pressed in a die into a troidal shape. In the pressing process, they were grain-oriented by multi-layer formation or magnetic field application so that their <111> direction in the spinel structure could be aligned perpendicular to the top surface of the troidal core. In addition, the randomly oriented sample was also prepared as a reference. These pressed compacts were sintered at 1200-1300°C for 6h. The initial permeability of the grain-oriented samples were larger than that of the randomly oriented sample. Moreover, the frequency dependence of reflection loss in these grain-oriented samples were improved.
