US5173873A
Expired / Lapsed
US
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High speed magneto-resistive random access memory
Assignee: National Aeronautics and Space Administration
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Filing: 1990-06-28
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Granted: 1992-12-22
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Expires: 2010-06-28
Abstract
Abstract A high speed read MRAM memory element is configured from a sandwich of magnetizable, ferromagnetic films surrounding a magento-resistive film which may be ferromagnetic or not. One outer ferromagnetic film has a higher coercive force than the other and therefore remains magnetized in one sense while the other may be switched in sense by a switching magnetic field. The magneto-resistive film is therefore sensitive to the amplitude of the resultant field between the outer ferromagnetic films and may be constructed of a high resistivity, high magneto-resistive material capable of higher sensing currents. This permits higher read voltages and therefore faster read operations. Alternate embodiments with perpendicular anisotropy, and in-plane anisotropy are shown, including an embodiment which uses high permeability guides to direct the closing flux path through the magneto-resistive material. High density, high speed, radiation hard, memory matrices may be constructed from these memory elements.
Inventors
- 👤 Jiin-Chuan Wu
- 👤 Henry L. Stadler
- 👤 Romney R. Katti
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 04:13
CPC Classifications
G; G11; G11C; G11C11/00; G11C11/02; G11C11/16; G11C11/161; G11C11/165; G11C11/1659; G11C11/1673; G11C11/1675
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
53 words
A memory element, comprising: a pair of magnetizable layers, each said magnetizable layer having a level of magnetization; a magneto-resistive layer between the magnetizable layers for storing data as a level of resistivity; and means for altering the resistivity of the magneto-resistive layer by altering the magnetization of at least one magnetizable layer.
Claim 2
Dependent Claim
53 words
A memory element, comprising: a pair of magnetizable layers, each said magnetizable layer having a level of magnetization; a magneto-resistive layer between the magnetizable layers for storing data as a level of resistivity; and means for altering the resistivity of the magneto-resistive layer by altering the magnetization of at least one magnetizable layer.
Claim 3
Dependent Claim
23 words
The memory element claimed in claim 1 further comprising: a pair of electrically insulating layers separating the magneto-resistive layer from the magnetizable layers.
Claim 4
Dependent Claim
13 words
The memory element claimed in claim 1 wherein the magneto-resistive layer is ferromagnetic.
Claim 5
Dependent Claim
13 words
The memory element claimed in claim 1 wherein the magneto-resistive layer is non-ferromagnetic.
Claim 6
Dependent Claim
20 words
The memory element claimed in claim 1 further comprising: highly permeable means for guiding magnetic flux between the magnetizable layers.
Claim 7
Dependent Claim
19 words
The memory element claimed in claim 1 wherein one magnetizable layer has a higher coercive force than the other.
Claim 8
Dependent Claim
26 words
The memory element claimed in claim 6 further comprising: means for applying a switching field having a force between the coercive forces of the magnetizable layers.
Claim 9
Dependent Claim
15 words
The memory element claimed in claim 7 wherein the magnetizable layers surround the magneto-resistive layer.
Claim 10
Dependent Claim
26 words
The memory element claimed in claim 1 wherein the magnetizable layers are planar and exhibit anisotropy which is not confined to the planes of said layers.
Claim 11
Dependent Claim
17 words
The memory element claimed in claim 1 wherein the magnetizable layers are planar and exhibit in-plane anisotropy.
Claim 12
Dependent Claim
20 words
The memory element claimed in claim 10 further comprising: highly permeable means for guiding magnetic flux between the magnetizable layers.
Claim 13
Independent Claim
45 words
A method of storing data, comprising: positioning a pair of magnetizable layers on either side of a magneto-resistive layer; and altering the resistivity of the magneto-resistive layer to store data as a level of resistivity by altering the magnetization of at least one magnetizable layer.
Claim 14
Independent Claim
45 words
A method of storing data, comprising: positioning a pair of magnetizable layers on either side of a magneto-resistive layer; and altering the resistivity of the magneto-resistive layer to store data as a level of resistivity by altering the magnetization of at least one magnetizable layer.
Claim 15
Dependent Claim
20 words
The method of storing data claimed in claim 12 further comprising: electrically insulating the magneto-resistive layer from the magnetizable layers.
Claim 16
Dependent Claim
15 words
The method of storing data claimed in claim 12 wherein the magneto-resistive layer is ferromagnetic.
Claim 17
Dependent Claim
15 words
The method of storing data claimed in claim 12 wherein the magneto-resistive layer is non-ferromagnetic.
Claim 18
Dependent Claim
22 words
The method of storing data claimed in claim 12 further comprising: guiding magnetic flux from the magnetizable layers through the magneto-resistive layer.
Claim 19
Dependent Claim
21 words
The method of storing data claimed in claim 12 wherein one magnetizable layer has a higher coercive force than the other.
Claim 20
Dependent Claim
26 words
The method of storing data claimed in claim 17 further comprising; applying a switching field having a force between the coercive forces of the magnetizable layers.
Claim 21
Dependent Claim
17 words
The method of storing data claimed in claim 18 wherein the magnetizable layers surround the magneto-resistive layer.
Claim 22
Dependent Claim
16 words
The method of storing data claimed in claim 12 wherein the magnetizable layers exhibit perpendicular anisotropy.
Claim 23
Dependent Claim
16 words
The method of storing data claimed in claim 12 wherein the magnetizable layers exhibit in-plane anisotropy.
Claim 24
Dependent Claim
22 words
The method of storing data claimed in claim 21 further comprising: guiding magnetic flux from the magnetizable layers through the magneto-resistive layer.
References Cited (Backward Citations)
US4857418A
Cited
US4754431A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-12-22 | 1996-06-22 | 1996-12-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-12-22 | 2000-06-22 | 2000-12-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-12-22 | 2004-06-22 | 2004-12-22 | $7700.00 | Window Closed / Lapsed |