| 摘要 |
PURPOSE:To keep the secrecy of data, by recoding the 1st data in a magnetic field where all magnetic particles are magnetized, recording the 2nd and the n-th data while deleting magnetic particles having high coercive force and then reproducing successively the particles of low coercive force. CONSTITUTION:An original data D0 is recorded by a magnetic head R on a magnetic tape T on which particles S of single magnetic domain structure and particles M of multi-magnetic domain structure are distributed. Both particles S and M are magnetized in the same direction at the same point in response to a record magnetic field. Then a different data D1 is recorded again on the tape T by the head R. The record magnetic field has a level between the coercive force HCS of the particle S and the coercive force HCM of the particle M, and the particle M is magnetized again to change the magnetizing direction. Then an intermediate magnetic field of the force HCM is applied to the tape T which is under a scrambled state to perform demagnetization. This tape T is reproduced to pick up the data D0. Furthermore a magnetic recording medium is formed with particles having the n-stage coercive force in order to keep the secrecy of data. |
