JPS6477593A - Magnetic card - Google Patents

Abstract

PURPOSE: To protect a magnetic recording layer from the external magnetic field by mounting a magnetic shield layer made of a superconductive material on a surface of the magnetic recording layer. CONSTITUTION: A magnetic recording layer 2 is protected from the external magnetic field by a magnetic shield layer 1 and a magnetic shield layer 3. In the case where a signal is recorded and reproduced on the magnetic recording layer 2, a magnetic head and the magnetic recording layer 2 are magnetically shielded from each other by the magnetic shield layer 1, so that the recording and reproduction cannot be performed as it is. In the recording and reproducing, the magnetic shield layer 1 made of the superconductive material is heated to more than a critical temperature by a heater 5, and a part indicated by the slash is changed from the superconductive state to the non-superconductive state. In the non-superconductive state, the Meissner effect cannot be found, and the magnetic shield action disappears only in the part of the slash, whereby the signal can be recorded and reproduced on the magnetic recording layer 2. The magnetic shield layer 3 is mounted adjacent to the magnetic recording layer 2 in this case, but the same effect can be obtained when it is mounted on a rear face of a base.