US4586161A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Permanent thermo-magnetic recording of binary digital information
Assignee: MOVID INFORMATION TECHNOLOGY Inc A CORP OF DE
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Filing: 1983-05-11
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Granted: 1986-04-29
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Expires: 2003-05-11
Abstract
Abstract A thermo-magnetic method for recording of a bit of information in each domain of an amorphous alloy thin-film layer supporting small stable domains. Each domain in the recording layer is first magnetized in a first direction, corresponding to a first binary state, by exposure to a saturation magnetic field. The remaining binary state is temporarily or permanently recorded in a particular domain by heating (to a lower or higher temperature) that domain volume of the recording layer above a predetermined temperature, but less than the melting temperature of the layer material, and thereafter cooling the heated domain in the presence of a bias magnetic field of direction opposite to, and magnitude less than, the saturation field. The binary state of each domain is read by interrogation with a beam of energy and utilization of differential effects between the interrogation beam and the direction of the magnetic field in the interrogated domain.
Inventors
- 👤 Raymond E. Skoda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:29
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/10504; G11B11/10515; G11B11/10532; G11B11/10534
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
142 words
A method for non-erasable storage of binary digital information, comprising the steps of: (a) providing a planar thin-film recording layer of a thermo-magnetic recording material; (b) temporarily subjecting the layer to a bias magnetic field, of magnitude less than a saturation field magnitude and passing through at least a domain in which a bit of information is to be recorded; (c) temporarily heating the layer in at least the area thereof defining a domain in which a binary state is to be recorded, while the bias magnetic field is present, to a temperature within a range predetermined to cause a bit of information to be substantially permanently stored in that domain; and (d) cooling the heating domain in the presence of the bias magnetic field, to induce in that domain a net magnetic field of direction aligned with the bias magnetic field.
Claim 2
Independent Claim
142 words
A method for non-erasable storage of binary digital information, comprising the steps of: (a) providing a planar thin-film recording layer of a thermo-magnetic recording material; (b) temporarily subjecting the layer to a bias magnetic field, of magnitude less than a saturation field magnitude and passing through at least a domain in which a bit of information is to be recorded; (c) temporarily heating the layer in at least the area thereof defining a domain in which a binary state is to be recorded, while the bias magnetic field is present, to a temperature within a range predetermined to cause a bit of information to be substantially permanently stored in that domain; and (d) cooling the heating domain in the presence of the bias magnetic field, to induce in that domain a net magnetic field of direction aligned with the bias magnetic field.
Claim 3
Dependent Claim
102 words
The method of claim 1, wherein step (a) further comprises the step of: temporarily subjecting the recording layer to a saturation field, in a first direction substantially normal to the plane of the layer, to provide a residual magnetic field defining a first binary state in each of at least one magnetic domain in the layer; step (b) further comprises the step of: providing the bias magnetic field in a direction opposite to the direction of the saturation field; and steps (c) and (d) are utilized only for each domain in which a remaining binary state is to be substantially permanently recorded.
Claim 4
Independent Claim
55 words
The method of claims 1 or 2, further comprising the steps of: interrogating at least one layer domain with a beam of energy; and analyzing the effect of the magnetic field in the interrogated domain upon the beam of energy to read the state of the bit of digital information stored in the interrogated domain.
Claim 5
Dependent Claim
16 words
The method of claim 3, wherein the interrogating energy beam is a beam of light energy.
Claim 6
Dependent Claim
27 words
The method of claim 4, further comprising the step of: substantially planar-polarizing the interrogating light beam prior to the impingement of that beam upon the recording layer.
Claim 7
Dependent Claim
86 words
The method of claim 5, wherein the impinging light beam is reflected from the magnetic layer prior to the analyzing step, and further comprising the steps of: fabricating a layer of a substantially transparent material upon that surface of the recording layer from which the interrogating light beam is to be reflected; and establishing the thickness of the substantially transparent layer to be about one-quarter of the wavelength, corrected for the refractive index of the material of the substantially transparent layer, of the interrogating light beam.
Claim 8
Dependent Claim
50 words
The method of claim 5, wherein the analyzing step includes the steps of: determining the direction of rotation of the substantially planar polarized light reflected from the recording layer; and assigning different ones of the binary states to opposite directions of rotation thereof, with respect to a reference polarization plane.
Claim 9
Dependent Claim
52 words
The method of claim 5, wherein said recording layer includes a multiplicity of domains, each having a different bit of digital information stored therein, and including the step of: sequentially directing light energy upon a sequential portion of the multiplicity of domains for at least one of the heating and interrogation steps.
Claim 10
Dependent Claim
28 words
The method of claim 1, wherein the predetermined temperature range extends from about 200° C. to a temperature less than the melting temperature of the recording layer material.
Claim 11
Independent Claim
35 words
The method of claims 1 or 2, wherein the heating step comprises the step of focussing a beam of light energy upon the domain in which a bit of digital information is to be recorded.
Claim 12
Dependent Claim
28 words
The method of claim 10, wherein the light beam is focussed to heat a domain of diameter in the range from about 0.5 micron to about 3 microns.
Claim 13
Dependent Claim
31 words
The method of claim 11, wherein the focussed light beam is pulsed for a time interval of between about 10 nanoseconds and about 50 microseconds to heat the domain being recorded.
Claim 14
Independent Claim
25 words
The method of claims 1 or 2, wherein the saturation field is provided at a magnitude of between about 1000 Oersteds and about 2000 Oersteds.
Claim 15
Dependent Claim
24 words
The method of claim 13, wherein the bias magnetic field is provided at a magnitude of between about 50 Oersteds and about 500 Oersteds.
Claim 16
Independent Claim
35 words
The method of claims 1 or 2, wherein the recording layer is provided by R.F. sputtering an amorphous alloy of at least one rare-earth element and at least one transition-metal element on a non-magnetic substrate.
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) | 1989-04-28 | 1989-10-28 | 1990-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-28 | 1993-10-28 | 1994-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-28 | 1997-10-28 | 1998-04-29 | $7700.00 | Window Closed / Lapsed |