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Strip Film Memory Device With Isolated Bit Cells

IP.com Disclosure Number: IPCOM000094152D
Original Publication Date: 1966-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Keefe, GE: AUTHOR

Abstract

Magnetic memory devices using elongated strip films can be made to perform as though they were composed of discrete bit cells. In a closed-easy-axis type of memory device having coupled magnetic films M1 and M2 disposed on a bit-sense line B, the portions of the films lying between the word lines W may acquire remanent magnetizations. These can differ from those of the neighboring bit storage areas that lie directly beneath the word lines. Under these conditions, the sense signal voltage which is induced in a bit storage area of the line B during readout can be opposed and partially weakened by a spurious signal voltage induced in an adjoining section of the bit-sense line B between the word lines W.

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Strip Film Memory Device With Isolated Bit Cells

Magnetic memory devices using elongated strip films can be made to perform as though they were composed of discrete bit cells. In a closed-easy- axis type of memory device having coupled magnetic films M1 and M2 disposed on a bit-sense line B, the portions of the films lying between the word lines W may acquire remanent magnetizations. These can differ from those of the neighboring bit storage areas that lie directly beneath the word lines. Under these conditions, the sense signal voltage which is induced in a bit storage area of the line B during readout can be opposed and partially weakened by a spurious signal voltage induced in an adjoining section of the bit-sense line B between the word lines W.

To eliminate the adverse effects of these spurious signal voltages, shorting bars S of highly conductive material, such as copper, are placed upon upper film M2 in the spaces between word lines W. Bars S are narrower than bit-sense line B and are separated from each other by narrow gaps running lengthwise of line B, thus minimizing eddy-current effects.

The conductivity of bars S is materially greater than that of the magnetic films
M. The latter generally are made of a material such as permalloy having considerable resistivity. Any voltage which is induced in a portion of line B beneath bars S is shorted out by these bars, so that it contributes nothing to the resultant sense signal. The effect is to isolate the bit...