US4983025A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magneto-optical thin film
Assignee: Fujifilm Holdings Corp
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Filing: 1989-02-01
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Granted: 1991-01-08
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Expires: 2009-02-01
Abstract
Abstract A magneto-optical thin film comprising a substrate having thereon at least two ferromagnetic thin layers alternating with at least two dielectric thin layers to form a laminate the ferromagnetic thin layers each having a thickness of from 30 to 260 Å.
Inventors
- 👤 Shizuo Umemura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:17
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; G11B11/10589; G11B11/10593
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
138 words
A magneto-optical recording medium including an ultrathin magneto-optical film capable of attaining a commercially satisfactory carrier to noise (C/N) ratio and having an improved figure of merit so that the Kerr rotation angle is enhanced while the reflectance is not substantially reduced, wherein said thin film comprises a substrate supporting a laminate formed of at least two ferromagnetic alloy thin layers, each of said layers having a thickness of from 30 to 260 Å alternately layered with at least two dielectric thin layers each having a thickness of from 30 to 500 Å and made of a material with a complex refractive index, wherein the real part of said index is 2.5 or less and the imaginary part of said index is 0.2 or less, and the total thickness of said laminate is from 300 to 2000 Å.
Claim 2
Dependent Claim
138 words
A magneto-optical recording medium including an ultrathin magneto-optical film capable of attaining a commercially satisfactory carrier to noise (C/N) ratio and having an improved figure of merit so that the Kerr rotation angle is enhanced while the reflectance is not substantially reduced, wherein said thin film comprises a substrate supporting a laminate formed of at least two ferromagnetic alloy thin layers, each of said layers having a thickness of from 30 to 260 Å alternately layered with at least two dielectric thin layers each having a thickness of from 30 to 500 Å and made of a material with a complex refractive index, wherein the real part of said index is 2.5 or less and the imaginary part of said index is 0.2 or less, and the total thickness of said laminate is from 300 to 2000 Å.
Claim 3
Dependent Claim
24 words
A magneto-optical thin film as claimed in claim 1, wherein said ferromagnetic thin layers each has a thickness of from 80 to 160 Å.
Claim 4
Dependent Claim
40 words
A magneto-optical thin film as claimed in claim 1, wherein said dielectric thin layers each is made of a material having a real part of complex refractive index of 2.1 or less and the imaginary factor of 0.1 or less.
Claim 5
Dependent Claim
55 words
A magneto-optical thin film as claimed in claim 1, wherein said ferromagnetic thin layers each is made of an amorphous alloy of a system consisting of a rare earth metal and a transition metal, and said dielectric thin layers each is made of a material selected from the group consisting of nitrides, sulfides and fluorides.
Claim 6
Dependent Claim
23 words
A magneto-optical thin film as claimed in claim 4, wherein said ferromagnetic thin layers each is made of TbFeCo alloys and DyFeCo alloys.
Claim 7
Dependent Claim
28 words
A magneto-optical thin film as claimed in claim 4, wherein said dielectric thin layers each is made of Si 3 N 4 , ZnS or MgF 2 .
Claim 8
Dependent Claim
27 words
A magneto-optical recording medium as described in claim 1, wherein the thickness of each said dielectric thin layer is within the range from 50 to 250 Å.
References Cited (Backward Citations)
US3472575A
Cited
US3650601A
Cited
GB2020842A
Cited
US4525028A
Cited
US4637953A
Cited
US4556291A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-01-07 | 1994-07-09 | 1995-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-01-07 | 1998-07-09 | 1999-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-01-07 | 2002-07-09 | 2003-01-08 | $7700.00 | Window Closed / Lapsed |