US4198689A
Expired / Lapsed
US
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Garnet magnetoresistive sensor for magnetic fields
Assignee: AT&T Inc
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Filing: 1978-08-30
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Granted: 1980-04-15
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Expires: 1998-08-30
Abstract
Abstract The discovery of a magnetoresistive effect in oriented, crystalline, semiconducting iron garnet materials is used to design devices which detect the presence or orientation of magnetic fields. The principal measure of this effect is that the resistance between two electrodes (12) on the garnet body (11) varies as an imposed magnetic field (14, 15) produces a change in the direction of the magnetization of the body (11). This effect is useful when the garnet is so constituted as to possess a resistivity from 10 3 to 10 7 ohm-centimeters. Also, the anisotropy field of the garnet body must be comparable to less than the magnitude of the magnetic field to be detected. One aspect of particular utility for magnetic "bubble" detectors (in magnetic bubble memories) is the isotropic character of the resistance when the magnetization is varied in the (111) plane but the significant change of resistance when the magnetization is moved to the [111] direction.
Inventors
- 👤 Ernst M. Gyorgy
- 👤 Roy C. Le Craw
- 👤 Raymond Wolfe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 20:53
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/127; G11B5/33; G11B5/39; G11B5/3903; G11C; G11C19/00; G11C19/02; G11C19/08; G11C19/0866
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
97 words
Apparatus for sensing a change in a magnetic field H E , comprising a semiconducting body, and at least two electrodes, spaced apart from one another and attached electrically conducting to the semiconducting body, CHARACTERIZED IN THAT the semiconducting body consists essentially of single crystal or oriented polycrystalline iron garnet in which iron atoms occupy at least 70% of the tetrahedral and octahedral lattice sites, constituted to have electrical resistivity from 10 3 ohm-cm to 10 7 ohm-cm, whereby a change of H E produces a change in the electrical resistance between the at least two electrodes.
Claim 2
Dependent Claim
97 words
Apparatus for sensing a change in a magnetic field H E , comprising a semiconducting body, and at least two electrodes, spaced apart from one another and attached electrically conducting to the semiconducting body, CHARACTERIZED IN THAT the semiconducting body consists essentially of single crystal or oriented polycrystalline iron garnet in which iron atoms occupy at least 70% of the tetrahedral and octahedral lattice sites, constituted to have electrical resistivity from 10 3 ohm-cm to 10 7 ohm-cm, whereby a change of H E produces a change in the electrical resistance between the at least two electrodes.
Claim 3
Dependent Claim
24 words
A device of claim 1 in which the semiconducting body consists essentially of a layer, at least 0.1 micrometers thick, located on a substrate.
Claim 4
Dependent Claim
27 words
A device of claim 2 in which the semiconducting body is essentially oriented to have a [111]crystallographic direction approximately parallel to the direction normal to the body.
Claim 5
Dependent Claim
15 words
A device of claim 2 in which the semiconducting body has an induced easy direction.
Claim 6
Independent Claim
26 words
A device of claims 3 or 4 in which the substrate consists essentially of a garnet material in which stable magnetic bubble domains can be propagated.
Claim 7
Dependent Claim
16 words
A device of claim 5 in which the semiconducting body is epitaxially grown on the substrate.
Claim 8
Dependent Claim
18 words
A device of claim 5 in which the semiconducting body is produced by ion implantation of the substrate.
Claim 9
Dependent Claim
14 words
A device of claim 5 in which the resistivity is approximately 10 5 ohm-centimeters.
Claim 10
Dependent Claim
29 words
A device of claim 5 in which atoms of at least one member of the group consisting of Ca and Sr are incorporated into the iron garnet semiconducting body.
Claim 11
Dependent Claim
29 words
A device of claim 5 in which atoms of at least one member of the group consisting of Si and Ge are incorporated into the iron garnet semiconducting body.
Claim 12
Dependent Claim
14 words
A device of claim 10 in which the iron garnet is yttrium iron garnet.
Claim 13
Independent Claim
73 words
A method for sensing a change in a magnetic field H E , comprising (a) imposing H E on a semiconducting layer consisting essentially of a single crystal or oriented polycrystalline iron garnet material in which iron atoms occupy at least 70% of the tetrahedral and octahedral lattice sites, consistuted to have electrical resistivity from 10 3 ohm-centimeters to 10 7 ohm-centimeters, and (b) detecting a change in resistivity of the semiconducting layer.
Claim 14
Independent Claim
73 words
A method for sensing a change in a magnetic field H E , comprising (a) imposing H E on a semiconducting layer consisting essentially of a single crystal or oriented polycrystalline iron garnet material in which iron atoms occupy at least 70% of the tetrahedral and octahedral lattice sites, consistuted to have electrical resistivity from 10 3 ohm-centimeters to 10 7 ohm-centimeters, and (b) detecting a change in resistivity of the semiconducting layer.
Claim 15
Dependent Claim
60 words
The method of claim 12 in which the semiconducting layer is so oriented with respect to H E that a change in H E produces a reorientation of the magnetization of at least part of the semiconducting layer between a direction substantially parallel to the direction normal to the layer and a direction substantially in the plane of the layer.
References Cited (Backward Citations)
US3973183A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-04-15 | 1983-10-15 | 1984-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-04-15 | 1987-10-15 | 1988-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-04-15 | 1991-10-15 | 1992-04-15 | $7700.00 | Window Closed / Lapsed |