| 摘要 |
PURPOSE:To acquire a magnetic recording medium of even frequency characteristics which is hard to erase after recorded using a magnetic powder having a good Curie point, high coercive force, high squareness ratio and stable properties by manufacturing and using a magnetic powder whose grain diameter and composition are specific. CONSTITUTION:Required materials are mixed, calcined, and ground by a vibrating mill, etc.; and burnt by an electric furnace, etc. Jet mill grinding is carried out to manufacture a magnetic powder of displacement M-type ferrite in a composition shown by an expression I, which is composed of a grain by 65% or more of an entire whose grain diameter is (0.5 to 5) X average grain diameter. Use of the magnetic powder of good Curie point, high coercive force, high squareness ratio and stable properties realizes a magnetic recording medium having even frequency characteristics which is hard to erase after recorded. In the expression, Me is one or more of Ba, Sr, Pb, Ca; and n, x, y: 4.5<=n<=6, x>=0, y>=0, x/3+y/4+z/6>=1/6, x/6+y/10+z/11<=1/6. |
