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Browse Prior Art Database

Storage of Confidential Information

IP.com Disclosure Number: IPCOM000082535D
Original Publication Date: 1974-Dec-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Wieder, H: AUTHOR

Abstract

By use of materials exhibiting an unusual "coercive force hysteresis", magnetic information can be stored in a way that avoids unauthorized readout.

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Storage of Confidential Information

By use of materials exhibiting an unusual "coercive force hysteresis", magnetic information can be stored in a way that avoids unauthorized readout.

Materials, such as MnAlGe and MnGaGe, exhibit a normal saturation M-H loop 1. However, when heated to the Curie temperature, such materials are demagnetized. Upon remagnetization in an external field, these materials exhibit a saturation M-H loop 2; i.e., they will switch at a value of applied field H(0) significantly less than the value of applied field required for saturation when operating on M-H loop 1.

Using materials with this characteristic, the information is encoded bit-wise by heating the material to the Curie point whenever a "1" bit is desired, following the standard thermomagnetic writing technique of laser addressed storage. Where, however, stored information is periodically updated, readout need not be by an optically focused beam; hence, instead of a beam addressed magneto-optic readout technique, a magnetic head or large-field magnetooptic display may be preferable.

The information can be stored on a flexible tape, disk, card, etc. depending on the application. A "laser pen" may be used to write non-coded information;
i.e., an authorized magnetic signature. Such a pen would contain lenses and be so constructed that when the pen is in contact with the magnetic film, the laser beam will be automatically focused on the film. In such case, even a pulsed room temperature GaAs laser would have a sufficient repetition rate to write continuous lines.

By heating and thus demagnetizing only portions of the film, a...