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Coupled Film Device with Minimum Stray Fields

IP.com Disclosure Number: IPCOM000093976D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Keefe, GE: AUTHOR [+2]

Abstract

Undesirable stray fields in a coupled-film memory device can be eliminated or minimized. This is effected by providing additional magnetic layers which are magnetostatically coupled to the storage layers.

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Coupled Film Device with Minimum Stray Fields

Undesirable stray fields in a coupled-film memory device can be eliminated or minimized. This is effected by providing additional magnetic layers which are magnetostatically coupled to the storage layers.

Drawing A shows, in cross-section, a conventional coupled-film memory device in which the magnetic field of each storage film closes partially through a stray-field path. The stray field of each film tends to demagnetize the film and thus weakens the coupled-film magnetization so that the films are more disturb- sensitive or subject to creep. The stray fields also penetrate nearby conductors and generate eddy currents in them when the memory device is switched. Energy losses and delays due to the trapped-flux effect are thus caused.

This condition can be remedied by providing, in proximity to each storage film, an additional magnetic layer. The latter is separated from its adjacent storage film by a thin nonmagnetic layer to induce magnetostatic coupling as shown in drawing B. Thus, the stray fields no longer have a demagnetizing effect upon the storage films and the stability of the device is increased. The additional magnetic layers are just thick enough to absorb the stray field of the storage films, so that they do not generate stray fields of their own. The coercivity of these layers must be low enough so that they absorb and are magnetized by the relatively weak stray fields of the storage films. This construct...