フェライト薄膜磁気記録媒体の磁場中冷却処理効果

抄録

Magnetic annealing treatments were applied to Co doped ferrite thin film media on heat- resistant flexible substrates, which were deposited through a process including direct formation of Fe₃O₄ films by sputtering sintered targets of Co doped Fe₃O₄.
Conditions to achieve the best effects of the treatment were invstigated to be a static magnetic field greater than 1 kOe and cooling-start temperature above 150°C. Under such optimum conditions, squareness S and coercive squareness S* increased to 0.8 and 0.9, respectively, coercive force Hc also increased and pressure demagnetization decreased markedly to 3∼4%.
It has been revealed that, through the treatment, uniaxial magnetic anisotropy Ku (3 × 10⁴∼2 × 10⁵ erg/cc) was induced parallel to the applied magnetic field.
The induced uniaxial magnetic anisotropy, whose origin is considered to be the same as bulk cobalt ferrites, improves magnetic properties, stabilizes the magnetization and thus decreases the pressure demagnetization.