US5549977A
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Article comprising magnetoresistive material
Assignee: Nokia of America Corp
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Filing: 1994-04-15
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Granted: 1996-08-27
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Expires: 2014-04-15
Abstract
Abstract A magnetoresistance ratio of 200% (absolute value) or more at room temperature in a field of 6T can be achieved in a layer of material of nominal composition XMnO y (X is La and at least one of Ca, Sr and Ba, y in the range 2-3.5), if, after formation of the layer, the layer is heat treated in an oxygen-rich (O 2 partial pressure greater than that of air) atmosphere, typically in flowing O 2 . The temperature and duration of the heat treatment are in the range 300°-850°C. and 10 minutes-12 hours, and are selected to result in the desired ratio of 200% or more.
Inventors
- 👤 Sungho Jin
- 👤 Mark T. McCormack
- 👤 Ramamoorthy Ramesh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 03:07
CPC Classifications
H; H10; H10N; H10N50/00; H10N50/80; H10N50/85; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10S428/922; Y10S428/9265; Y10S428/928; Y10T; Y10T428/00; Y10T428/11; Y10T428/1107
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
118 words
An article comprising a layer of a material that exhibits magnetoresistance at 25° C. and has nominal composition XMnO y , where X is La and at least one member of the group consisting of Ca, Sr and Ba; CHARACTERIZED IN THAT the layer of material has a magnetoresistance ratio having an absolute value of at least 200% at 25° C., the magnetoresistance ratio being defined as (R(H)--R o )/R (H), where R(H) is the resistance of the layer in an applied magnetic field H of magnitude 6 Tesla, and R o is the resistance of the layer in the absence of an applied magnetic field; wherein y is selected to provide the layer with said magnetoresistance ratio.
Claim 2
Dependent Claim
118 words
An article comprising a layer of a material that exhibits magnetoresistance at 25° C. and has nominal composition XMnO y , where X is La and at least one member of the group consisting of Ca, Sr and Ba; CHARACTERIZED IN THAT the layer of material has a magnetoresistance ratio having an absolute value of at least 200% at 25° C., the magnetoresistance ratio being defined as (R(H)--R o )/R (H), where R(H) is the resistance of the layer in an applied magnetic field H of magnitude 6 Tesla, and R o is the resistance of the layer in the absence of an applied magnetic field; wherein y is selected to provide the layer with said magnetoresistance ratio.
Claim 3
Dependent Claim
21 words
Article according to claim 1, wherein the layer is disposed on a substrate and is substantially epitaxial therewith, and wherein 2<y<3.5.
Claim 4
Dependent Claim
23 words
Article according to claim 1, wherein said magnetoresistance ratio has a maximum in absolute value at a temperature substantially equal to 25° C.
Claim 5
Dependent Claim
51 words
An article according to claim 1, wherein the material has nominal composition La 1-x Ca x MnO y , with 0.25<x<0.40, or the material has nominal composition La 1-x Sr x MnO y , with 0.18<x<0.50, or the material has nominal composition La 1-x Ba x MnO y , with 0.20<x<0.45.
Claim 6
Dependent Claim
30 words
An article according to claim 1, wherein the layer was formed by a process that comprises laser ablation from a target that was sintered at a temperature above 1100° C.
Claim 7
Dependent Claim
33 words
An article according to claim 1, wherein the layer was formed by a process that comprises heat treating the layer in an atmosphere having an O 2 partial pressure greater than 100 mTorr.
Claim 8
Dependent Claim
30 words
Article according to claim 2, wherein the substrate is a compound substrate comprising a Si support body and a buffer layer, the layer being substantially epitaxial with the buffer layer.
Claim 9
Dependent Claim
148 words
Method of making an article that comprises a layer of material that exhibits magnetoresistance at 25° C., the method comprising a) forming a layer of nominal composition XMnO y , where X is La and at least one of Ca, Sr and Ba; and b) heat treating the layer in an oxygen-containing atmosphere; CHARACTERIZED IN THAT c) the oxygen partial pressure of said atmosphere is greater than the oxygen partial pressure of ambient air; and d) the heat treatment time and temperature are selected to provide material that exhibits at 25° C. a magnetoresistance ratio having an absolute value of at least 200%, said magnetoresistance ratio being defined as (R(H)--R o )/R (H), where R(H) is the resistance of the layer in an applied magnetic field H of magnitude 6 Tesla, and R o is the resistance of the layer in the absence of an applied magnetic field.
Claim 10
Dependent Claim
148 words
Method of making an article that comprises a layer of material that exhibits magnetoresistance at 25° C., the method comprising a) forming a layer of nominal composition XMnO y , where X is La and at least one of Ca, Sr and Ba; and b) heat treating the layer in an oxygen-containing atmosphere; CHARACTERIZED IN THAT c) the oxygen partial pressure of said atmosphere is greater than the oxygen partial pressure of ambient air; and d) the heat treatment time and temperature are selected to provide material that exhibits at 25° C. a magnetoresistance ratio having an absolute value of at least 200%, said magnetoresistance ratio being defined as (R(H)--R o )/R (H), where R(H) is the resistance of the layer in an applied magnetic field H of magnitude 6 Tesla, and R o is the resistance of the layer in the absence of an applied magnetic field.
Claim 11
Dependent Claim
38 words
Method according to claim 8, wherein the oxygen partial pressure is one atmosphere or more, the heat treatment temperature is in the range 300°-850° C., the heat treatment time is in the range 10 minutes-12 hours, and 2<y<3.5.
Claim 12
Dependent Claim
24 words
Method according to claim 8, the method comprising forming the layer on a substrate such that the layer is substantially epitaxial with the substrate.
Claim 13
Dependent Claim
20 words
Method according to claim 8, wherein the layer is formed such that the layer is epitaxial with a buffer region.
Claim 14
Dependent Claim
56 words
Method according to claim 8, werein the forming step comprises forming said layer such that the nominal composition is La 1-x Ca x MnO y , with 0.25≦x≦0.40, or the nominal composition is La 1-x Sr x MnO y , with 0.18≦x≦0.50, or the nominal composition is La 1-x Ba x MnO y , with 0.20≦x≦0.45.
Claim 15
Dependent Claim
126 words
An article comprising a layer of material that exhibits magnetoresistance and has nominal composition XMnO y , where X is La and at least one member of the group consisting of Ca, Sr and Ba, said layer disposed on a substrate; CHARACTERIZED IN THAT a) the layer is epitaxial with the substrate; and b) the layer has a magnetoresistance (MR) ratio having an absolute maximum value of at least 1000%, the MR ratio being defined as (R(H)--R o )/R(H), where R(H) is the resistance of the layer in an applied magnetic filed H of magnitude 6T, and R o is the resistance of the layer in the absence of an applied magnetic field, wherein y has a value that provides the layer with said MR ratio.
Claim 16
Dependent Claim
126 words
An article comprising a layer of material that exhibits magnetoresistance and has nominal composition XMnO y , where X is La and at least one member of the group consisting of Ca, Sr and Ba, said layer disposed on a substrate; CHARACTERIZED IN THAT a) the layer is epitaxial with the substrate; and b) the layer has a magnetoresistance (MR) ratio having an absolute maximum value of at least 1000%, the MR ratio being defined as (R(H)--R o )/R(H), where R(H) is the resistance of the layer in an applied magnetic filed H of magnitude 6T, and R o is the resistance of the layer in the absence of an applied magnetic field, wherein y has a value that provides the layer with said MR ratio.
Claim 17
Dependent Claim
14 words
An article according to claim 13, wherein the MR ratio is at least 10,000%.
Claim 18
Dependent Claim
16 words
An article according to claim 13, wherein said substrate comprises a substantially single crystal template layer.
Claim 19
Dependent Claim
30 words
An article according to claim 13, wherein the layer was formed by a process that comprises laser ablation from a target that was sintered at a temperature above 1100° C.
Claim 20
Dependent Claim
22 words
An article according to claim 15, wherein said template layer is disposed intermediate an amorphous layer and the layer that exhibits MR.
Claim 21
Dependent Claim
21 words
An article according to claim 17, wherein the amorphous layer is SiO 2 , and the template layer is bismuth titanate.
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) | 1999-08-27 | 2000-02-26 | 2000-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-08-27 | 2004-02-26 | 2004-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-08-27 | 2008-02-26 | 2008-08-27 | $7700.00 | Window Closed / Lapsed |