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Minimizing Bit Size in Magneto Optic Memory

IP.com Disclosure Number: IPCOM000093262D
Original Publication Date: 1967-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ahn, KY: AUTHOR

Abstract

The bit size of a magneto-optic memory is inversely proportional to the bit-capacity, i.e., the larger the capacity, the smaller the bit size. The output signal from such a memory is proportional to the amount of magneto-optic rotation which, in turn, is proportional to the film thickness for Faraday rotation. As the film thickness increases, there is a corresponding increase in demagnetizing field H(d) which can destroy the stored information if the magnitude of H(d)approaches the magnitude of coercive force H(c).

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Minimizing Bit Size in Magneto Optic Memory

The bit size of a magneto-optic memory is inversely proportional to the bit- capacity, i.e., the larger the capacity, the smaller the bit size. The output signal from such a memory is proportional to the amount of magneto-optic rotation which, in turn, is proportional to the film thickness for Faraday rotation. As the film thickness increases, there is a corresponding increase in demagnetizing field H(d) which can destroy the stored information if the magnitude of H(d)approaches the magnitude of coercive force H(c).

A multilayer structure of individual layers of EuO and Eu(2)O(3) is provided which permits a smaller demagnetizing field than for a comparable thickness of EuO alone. As the output signal from a magneto-optic memory is proportional to the film thickness and is diminished by the demagnetizing field, the bit size in a magneto-optic memory is minimized by the structure now discussed.

Each layer of EuO is built up via the chemical reaction Eu + Eu(2)O(3) = 3EuO. The thicknesses of the EuO layers are chosen to give an excess amount of Eu(2)O(3) over the amount required for the stoichiometric EuO according to the foregoing chemical reaction. The excess Eu(2)O(3) does not react with Eu and remains as a nonmagnetic layer adjacent to an EuO layer.

For a 10 micron diameter bit in a single layer film of EuO having H(c) = 120 oe with a thickness of 2,800 Angstroms which gives Faraday rotation of approx. 14 at 4.2 K with...