US3883892A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making magnetic recordings which cannot be altered without it being noticed
Assignee: BASF SE
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Filing: 1973-10-16
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Granted: 1975-05-13
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Expires: 1993-10-16
Abstract
Abstract The invention relates to a method of recording magnetic signals on magnetic recording media containing an exchange-anisoptropic material at a temperature lower than, equal to or higher than the Neel temperature of this magnetic material. After the recording has been made, the magnetic recording medium is heated to a temperature equal to, or higher than, the Neel temperature, then cooled down to a temperature below the Neel temperature and the recording temperature, following which it is provided with an indicator which betrays re-heating. The method is suitable for the space-saving and, at the same time, authentic recording and storage of all data and images which are to be preserved without risk of falsification.
Inventors
- 👤 Eckart Kneller
- 👤 Eberhard Koester
- 👤 Gerd Wunsch
- 👤 Paul Deigner
- 👤 Dieter Graw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 13:37
CPC Classifications
G; G11; G11B; G11B23/00; G11B23/28; G11B23/281; G03; G03G; G03G5/00; G03G5/16; G11B5/00; G11B5/62; G11B5/64; G11B5/68; G11B5/70; G11B5/706
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
278 words
A method of making magnetic recordings on magnetic recording media which cannot be altered without it being noticed, wherein on a magnetic recording medium containing exchange-anisotropic magnetizable material, which material consists of a ferri- or ferromagnetic component to which there is coupled an antiferromagnetic component in respect of which, below a given temperature TS lower than the Neel temperature TN of the antiferromagnetic component, the critical magnetic field required to bring about the irreversible rotation of the antiferromagnetic axis and, in addition, the magnetic field needed for the production of any magnetizing structure leading to the irreversible rotation of the antiferromagnetic axis are stronger than the strongest magnetic field Hsm that can be produced with the technical means used in the magnetic recording of signals, so that all magnetization structures capable of being produced in magnetic fields smaller than, or equal to, Hsm vanish again partly or completely after the magnetic field has been turned off, such that the signals previously fixed at a temperature above TS will either be completely or partly regenerated automatically or can be restored a. the signals are recorded at a temperature above or below the temperature TS and the magnetic recording medium, after the recording has been made, is heated to a temperature above this temperature TS and at least to a temperature TAFS; b. the magnetic recording medium is then cooled to a temperature below the temperature TS, and c. is subsequently provided with an indicator irreversibly indicating the fact that the magnetic recording medium has been reheated to a temperature equal to or above TS, and d. the recording is then marked at both ends by physical or chemical means.
Claim 2
Independent Claim
278 words
A method of making magnetic recordings on magnetic recording media which cannot be altered without it being noticed, wherein on a magnetic recording medium containing exchange-anisotropic magnetizable material, which material consists of a ferri- or ferromagnetic component to which there is coupled an antiferromagnetic component in respect of which, below a given temperature TS lower than the Neel temperature TN of the antiferromagnetic component, the critical magnetic field required to bring about the irreversible rotation of the antiferromagnetic axis and, in addition, the magnetic field needed for the production of any magnetizing structure leading to the irreversible rotation of the antiferromagnetic axis are stronger than the strongest magnetic field Hsm that can be produced with the technical means used in the magnetic recording of signals, so that all magnetization structures capable of being produced in magnetic fields smaller than, or equal to, Hsm vanish again partly or completely after the magnetic field has been turned off, such that the signals previously fixed at a temperature above TS will either be completely or partly regenerated automatically or can be restored a. the signals are recorded at a temperature above or below the temperature TS and the magnetic recording medium, after the recording has been made, is heated to a temperature above this temperature TS and at least to a temperature TAFS; b. the magnetic recording medium is then cooled to a temperature below the temperature TS, and c. is subsequently provided with an indicator irreversibly indicating the fact that the magnetic recording medium has been reheated to a temperature equal to or above TS, and d. the recording is then marked at both ends by physical or chemical means.
Claim 3
Dependent Claim
21 words
A method according to claim 1, wherein the magnetic signals are recorded above the Neel temperature TN of the antiferromagnetic substance.
Claim 4
Dependent Claim
50 words
A method according to claim 1, wherein a magnetic recording medium with signals recorded below the Neel temperature TN of the antiferromagnetic substance is heated to a temperature above the Neel temperature TN of the antiferromagnetic substance and is provided with the indicator after cooling to below the temperature TS.
Claim 5
Dependent Claim
39 words
A method according to claim 1, wherein either during or after the recording of the magnetic signals a control signal is recorded which enables subsequent editing of the recording or cutting of the magnetic recording medium to be detected.
Claim 6
Dependent Claim
22 words
A method according to claim 1, wherein the Neel temperature TN of the exchange-anisotropic material is between approximately 40* and approximately 500*C.
Claim 7
Dependent Claim
49 words
A method according to claim 1, wherein the exchange-anisotropic magnetizable material consists of an alloy containing the elements Co and Ni and having the composition CoxNi(1 x), to which an oxide layer having the approximate composition CoO)x(NiO)(1 X) has been applied, x denoting any value between 0 and 1.
Claim 8
Dependent Claim
50 words
A method according to claim 1 wherein the critical magnetic field required to bring about the irreversible rotation of the antiferromagnetic axis and, in addition, the magnetic field needed for the production of any magnetizing structure leading to the irreversible rotation of the antiferromagnetic axis are stronger than 800 kiloamps/meter.
Claim 9
Dependent Claim
215 words
Magnetic recording media for recordings that cannot be altered without it being noticed, characterized in that they contain an exchange-anisotropic magnetizable material consisting of a ferri- or ferromagnetic component and an antiferromagnetic component, in respect of which, below a given temperature TS lower than the Neel temperature TN of the antiferromagnetic component the critical magnetic field required to bring about the irreversible rotation of the antiferromagnetic axis and, in addition, the magnetic field needed for the production of any magnetization structure leading to the irreversible rotation of the antiferromagnetic axis are stronger than the strongest magnetic field Hsm that can be produced with the technical means used in the magnetic recording of signals, so that all magnetization structures capable of being produced in magnetic fields smaller than, or equal to, Hsm vanish again partly or completely after the magnetic field has been turned off, such that the signals previously fixed at a temperature above TS will either be completely or partly regenerated automatically or can be restored, that they are heated, during or after the recording has been made, to a temperature above TS and, after cooling to a temperature below this temperature TS, are provided with an indicator which indicates irreversibly any renewed heating of the recording media to or above the temperature TS.
Claim 10
Dependent Claim
215 words
Magnetic recording media for recordings that cannot be altered without it being noticed, characterized in that they contain an exchange-anisotropic magnetizable material consisting of a ferri- or ferromagnetic component and an antiferromagnetic component, in respect of which, below a given temperature TS lower than the Neel temperature TN of the antiferromagnetic component the critical magnetic field required to bring about the irreversible rotation of the antiferromagnetic axis and, in addition, the magnetic field needed for the production of any magnetization structure leading to the irreversible rotation of the antiferromagnetic axis are stronger than the strongest magnetic field Hsm that can be produced with the technical means used in the magnetic recording of signals, so that all magnetization structures capable of being produced in magnetic fields smaller than, or equal to, Hsm vanish again partly or completely after the magnetic field has been turned off, such that the signals previously fixed at a temperature above TS will either be completely or partly regenerated automatically or can be restored, that they are heated, during or after the recording has been made, to a temperature above TS and, after cooling to a temperature below this temperature TS, are provided with an indicator which indicates irreversibly any renewed heating of the recording media to or above the temperature TS.
Claim 11
Dependent Claim
52 words
A magnetic recording media according to claim 8 wherein the critical magnetic field required to bring about the irreversible rotation of the antiferromagnetic axis and, in addition, the magnetic field needed for the production of any magnetizing structure leading to the irreversible rotation of the antiferromagnetic axis are stronger than 800 kiloamps/meter.
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) | 1978-05-12 | 1978-11-11 | 1979-05-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-12 | 1982-11-11 | 1983-05-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-12 | 1986-11-11 | 1987-05-13 | $7700.00 | Window Closed / Lapsed |