| 摘要 |
PURPOSE:To eliminate the erasion noises due to the change of remaining magnetization by setting the surface roughness at <=0.1-S for the magnet part of the rubbing surface of a magnetic tape of a permanent magnet erasion head main body of a reducing alternating magnetic field type. CONSTITUTION:A magnetic tape 1 travels through magnetic poles 5, 6 and 7 respectively on a tape rubbing surface and receives successively magnetic fields 94, 95 and 96. Therefore the track of the tape 1 is saturated up to a point 90 regardless of its initial position on a B-H curve and finally produces the remaining magnetization shown by a point 93 after passing through points 91 and 92. As the surface roughness of the erasion head is kept at <=0.1-S, the erasing process is equal at all points on the track of the magnetic tape to be recorded and reproduced. Therefore the remaining magnetization that is finally generated at the point 93 has the same fixed value as each point on the track. Such remaining magnetization is not produced in the form of a reproduction output with a reproduction system where the reproduction output is equal to the differential value of a leaked magnetic flux of the tape. Thus no erasion noise is produced due to the change of remaining magnetization. |
