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US3964035A
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Magnetic devices utilizing garnet epitaxial materials
Assignee: AT&T Inc
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Filing: 1974-09-23
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Granted: 1976-06-15
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Expires: 1994-09-23
Abstract
Abstract Members of a particular class of magnetic garnet compositions show characteristics useful for incorporation in magnetic memory devices which depend for their operation on the positioning of single wall domains ("bubbles"). Such compositions, ordinarily in the form of a supported layer, manifest high limiting bubble velocity, thereby making possible high record and access rates. Tetrahedral iron sites in the concerned compositions are occupied by non-magnetic ions in amount such as to result in magnetically balanced iron sub-lattices so that the magnetic moment contribution is made primarily by dodecahedral site ions. Europium is a necessary dodecahedral site occupant. High limiting velocity is attributed to the high value of the gyromagnetic ratio (g value) associated with europium.
Inventors
- 👤 Stuart Lawrence Blank
- 👤 Roy Conway Le Craw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 05:14
CPC Classifications
H; H01; H01F; H01F10/00; H01F10/08; H01F10/10; H01F10/18; H01F10/20; H01F10/24
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
109 words
Memory device comprising a substrate supporting at least a first epitaxial layer, the said layer being capable of evidencing uniaxial magnetic anisotropy capable of supporting local enclosed regions of magnetic polarization opposite to that of surrounding material, provided with first means for magnetically biasing said layer to stabilize said regions, second means for positioning such oppositely polarized local and enclosed regions, and third means for propagating such local regions, said material being of the garnet structure, characterized in that at least 75 percent of the total net moment of the material is contributed by europium as a dodecahedral site occupant, the said net moment being at least 100 Gauss.
Claim 2
Dependent Claim
109 words
Memory device comprising a substrate supporting at least a first epitaxial layer, the said layer being capable of evidencing uniaxial magnetic anisotropy capable of supporting local enclosed regions of magnetic polarization opposite to that of surrounding material, provided with first means for magnetically biasing said layer to stabilize said regions, second means for positioning such oppositely polarized local and enclosed regions, and third means for propagating such local regions, said material being of the garnet structure, characterized in that at least 75 percent of the total net moment of the material is contributed by europium as a dodecahedral site occupant, the said net moment being at least 100 Gauss.
Claim 3
Dependent Claim
24 words
Memory device of claim 1 in which the magnetic moment 4πM of the said first layer is from about 100 Gauss to 500 Gauss.
Claim 4
Dependent Claim
52 words
Memory device of claim 2 in which the magnetic moment contribution of the iron sub-lattice is reduced by partial substitute of iron by at least one of the ions selected from the group consisting of Si 4 + , Ge 4 + , V 5 + , and Ga 3 + .
Claim 5
Dependent Claim
23 words
Memory device of claim 3 in which valence compensation is accomplished by inclusion of Ca 2 + as a partial dodecahedral site occupant.
Claim 6
Dependent Claim
18 words
Memory device of claim 4 in which the said unaxial magnetic anisotropy is at least partially growth induced.
Claim 7
Dependent Claim
18 words
Memory device of claim 4 in which the said unaxial magnetic anisotropy is at least partially strain induced.
Claim 8
Dependent Claim
138 words
Memory device of claim 1 in which the composition of the said material of the said first layer may be represented by the atom formula: Eu x Ca y RE 3-x-y (A) z Fe 5-z O 12 , in which RE is yttrium, lanthanum, or a rare earth selected from the lanthanide series of element numbers 58-62 and 64-71 of the Periodic Table; in which A is at least one element selected from the group consisting of Si, Ga, Ge, Al, and V; x is at least 0.5; z is from 1.00-1.20 where A is Si, Ge, or V, or a combination thereof and z is from 1.20-1.50 where A is Ga; in which y is essentially equal to z where A is Si, Ge, or a combination thereof and is equal to 2z where A is V.
Claim 9
Dependent Claim
21 words
Memory device of claim 7 in which A is silicon or germanium and in which z is approximately equal to 1.1.
Claim 10
Dependent Claim
26 words
Memory device of claim 7 in which the said substrate consists essentially of a material of the atom formula Sm 3 Ga 5 O 12 .
Claim 11
Dependent Claim
26 words
Memory device of claim 7 in which the said substrate consists essentially of a material of the atom formula Gd 3 Ga 5 O 12 .
Claim 12
Dependent Claim
25 words
Memory device of claim 10 in which a o of the said first layer is within the range of from 12.370 A to 12.401 A.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-06-15 | 1979-12-15 | 1980-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-06-15 | 1983-12-15 | 1984-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-06-15 | 1987-12-15 | 1988-06-15 | $7700.00 | Window Closed / Lapsed |