針状性フェライトの合成と特性に関する研究 Studies on Preparation of Acicular Ferrites and Their Properties
Acicular barium ferrite, cobalt ferrite and crystal oriented manganese zinc ferrite particles were prepared using the acicular α-FeOOH as the starting material. The crystal structure and magnetic characteristics of these fine particles were investigated in detail. Acicular barium ferrite fine particles doped with Co<SUP>2+</SUP> ions and Ti<SUP>4+</SUP> ions were fabricated by a conventional sintering method. The BaCo<SUB>x</SUB>TixFe<SUB>12-2x</SUB>O<SUB>19</SUB> particles consisted of some grains and their c-axis were aligned along the short axis of the acicular particles. The output waveform of the acicular barium ferrite magnetic tape signified that it had perpendicular magnetic anisotropy. Acicular cobalt ferrite fine particles were prepared from acicular α-FeOOH and C<SUB>10</SUB>H<SUB>14</SUB>O<SUB>4</SUB>Co⋅2H<SUB>2</SUB>O. The particles had coercivity of 1 kOe (80kA/m) and magnetization values of 67 emu/g (0.45Wb/m<SUP>2</SUP>). The output of the magnetic tape made of the acicular particles, with long axis of 0.4μm was greatlly enhanced in the high density recording. The acicular Mn-Zn ferrite fine particles composed of 65.6mol. %Fe, 21.9mol. %Mn and 12.5mol. %Zn were made by conventional sintering method. The fine particle was made up of several crystallites with long axis of 0.2-1.0μm. These fine particles were pressed in an applied magnetic field and then sintered at 1250°C for 4hrs in air. The oriented Mn-Zn ferrite exhibited strong crystal orientation similar to the single crystal of it.
粉体および粉末冶金 45(1), 42-52, 1998-01-15
Japan Society of Powder and Powder Metallurgy