| 摘要 |
Magnetite particles containing a silicon component inside, and having the silicon component exposed on the surface in a proportion of 0.05 to 2.0% by weight as silicon which have improved moisture resistance as indicated by moisture content of magnetite (% by weight), measured under high-temperature, high-humidity conditions (200 DEG C, Karl Fischer technique), and given by the equation (1) <MATH> where A represents the amount (% by weight) of presence of the silicon component, expressed in terms of silicon, contained in magnetite, i.e., the total amount (% by weight) of silicon in magnetite, provided that 0.3≤A≤3.0; an electrical resistance of 1x10<3> OMEGA .cm or more; a degree of aggregation of 40 or less; and low residual magnetization whereby the particles are excellent in operating efficiency, flowability and environmental resistance, without lowering the electrical resistance compared with the current standard. |
