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Magneto Optic Memory Switch

IP.com Disclosure Number: IPCOM000080502D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Argyle, BE: AUTHOR [+2]

Abstract

Present day magneto-optic memories rely on material switching of the magnetization (M) in a local spot which is readable by the Faraday rotation approx. +M(1), Which contrasts against a background of rotation from magnetization (-M(1)) oriented opposite to an applied bias field +H(1). The effect described herein allows magneto-optic switching without changes in the local total magnetization, thus allowing inherently greater stability against spontaneous reversal. An observed effect of reversal in the sign of the Faraday rotation with increasing magnetic field, is attributed to a phase change in orientation of two sublattices of spins in the sample, only one of which contributes to the Faraday rotation. A thermomagnetic writing technique for using this effect is suggested, using a heat source such as a laser or electron beam.

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Magneto Optic Memory Switch

Present day magneto-optic memories rely on material switching of the magnetization (M) in a local spot which is readable by the Faraday rotation approx. +M(1), Which contrasts against a background of rotation from magnetization (-M(1)) oriented opposite to an applied bias field +H(1). The effect described herein allows magneto-optic switching without changes in the local total magnetization, thus allowing inherently greater stability against spontaneous reversal. An observed effect of reversal in the sign of the Faraday rotation with increasing magnetic field, is attributed to a phase change in orientation of two sublattices of spins in the sample, only one of which contributes to the Faraday rotation. A thermomagnetic writing technique for using this effect is suggested, using a heat source such as a laser or electron beam.

Features of the magneto-optic memory switch are:
1) Uniaxial magneto-optic switchable material capable of

working in the presence of a bias field;
2) Uniaxial magneto-optic switch in which the initial and final

state of the total magnetization are the same or

approximately the same, while the orientation of the

sublattice's magnetization is not the

same after switching occurs; and,
3) Temperature sensitive magneto-optic switch capable

of working in a bias field, and possessing a switching

field that changes with heating and exhibits open-loop

behavior.

In the materials amorphous Gd-Co and crystalline gadolinum iron garnet, it is possible to observe the following Faraday loop (Fig. 1). The effect is understood as being related to sublattice magnetization almost exclusively so that the total magnetization M(1) + M(2) behavior, according to Fig. 3, does not exhibit the switching at the higher field near +/-H(S). A model for the switching phenomenon in Gd-Co is presented in Fig. 4, and a model for the switching phenomenon in Gd-IG is presented in Fig. 5. In Gd-Co films M(1) = sublattice magnetization of Co M(2) = sublattice magnetization of Gd theta(F) (M(1)) >> theta(F) (M(2)) In Gd-IG M(1) = tetrahedral sublattice of Fe M(2) = octagonal sublatt...