US3621382A
Expired / Lapsed
US
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Anistropic thin ferromagnetic film magnetometer
Assignee: Commissariat à l'Énergie Atomique et Aux Énergies Alternatives
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Filing: 1969-10-07
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Granted: 1971-11-16
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Expires: 1989-10-07
Abstract
Abstract A thin bistable ferromagnetic film of the inverted type (i.e. for which the coercive forces Hc and Hct are smaller than the anisotropy field Hk) is used as sensor and is associated with a pumping coil which submits the film to an alternating field (frequency f) along the easy axis and with a detection coil wound around the easy axis. A steady biasing field is applied along the hard axis, at least if the thin film is a flat strip. The value of the field component along the easy axis is deduced from the time difference between successive reversals of the magnetic vector in the strip from the amplitude of the harmonic 2 f of the signal in the detection coil. The magnetometer makes it possible to detect fields as low as 0.1 gamma since reversal of the magnetic vector in the film is made without wall movement and consequently without Barkhausen noises.
Inventors
- 👤 Jean-Yves Valet
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:58
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/02; G01R33/04; G01R33/05
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
96 words
A device for measuring the magnitude of the component along a direction of an external weak magnetic field, comprising a thin ferromagnetic film of the reversed type having an easy axis of magnetization along said direction and a hard axis and having a square hysteresis loop, means for subjecting said film to an alternating magnetic field at frequency f parallel to the easy axis and of sufficient amplitude to reverse the magnetic vector in said thin film, a detection coil about said thin film and means for analyzing the electric signals collected by said detection coil.
Claim 2
Independent Claim
96 words
A device for measuring the magnitude of the component along a direction of an external weak magnetic field, comprising a thin ferromagnetic film of the reversed type having an easy axis of magnetization along said direction and a hard axis and having a square hysteresis loop, means for subjecting said film to an alternating magnetic field at frequency f parallel to the easy axis and of sufficient amplitude to reverse the magnetic vector in said thin film, a detection coil about said thin film and means for analyzing the electric signals collected by said detection coil.
Claim 3
Dependent Claim
43 words
Device according to claim 1, wherein said analyzing means are constructed and arranged to measure the amplitude of the harmonic at frequency 2f of the electrical signal collected by the detection coil and due to reversal of the magnetic vector in the film.
Claim 4
Dependent Claim
20 words
Device according to claim 2, having means for applying to the film a polarizing field directed along the hard axis.
Claim 5
Dependent Claim
40 words
Device according to claim 3, wherein the polarizing field which is directed along the hard axis of the film is a steady field and has an intensity of the same order of magnitude as the amplitude of the alternating field.
Claim 6
Dependent Claim
46 words
Device according to claim 3, wherein the polarizing field which is directed along the hard axis of the film is an alternating field and consists of the component along the hard axis of an alternating field whose component along the easy axis constitutes the alternating field.
Claim 7
Dependent Claim
30 words
Device according to claim 5, wherein said alternating field is generated by a coil having its axis located at an angle comprised between 30* and 60* with the easy axis.
Claim 8
Dependent Claim
59 words
Device according to claim 2, having two thin films mounted with their easy axes in parallel relation, a winding for the pumping field, the pumping and detection windings associated with one film being wound in the same direction and those associated with the other film in opposite direction, both detection windings being in series and supplying the analyzing means.
Claim 9
Dependent Claim
11 words
Device according to claim 7, wherein said films are flat strips.
Claim 10
Dependent Claim
15 words
Device according to claim 7, wherein said films are tubular and deposited on conducting wires.
Claim 11
Dependent Claim
19 words
Device according to claim 9, wherein said conducting wires carry a direct current which generates a tangential polarizing field.
Claim 12
Dependent Claim
108 words
In a device for measuring the magnitude of a weak external magnetic field, a sensor comprising: a thin ferromagnetic film having easy and hard axes of magnetization perpendicular to each other and having a square hysteresis loop; a first coil wound about said film along said easy axis; means for circulating in said coil an alternating current generating a field sufficient to reverse the magnetic vector in said film; means for subjecting said film to a steady field directed along said hard axes; and means including another coil wound about said film along said easy axis for detecting the magnitude along said easy axis of the external field.
Claim 13
Dependent Claim
108 words
In a device for measuring the magnitude of a weak external magnetic field, a sensor comprising: a thin ferromagnetic film having easy and hard axes of magnetization perpendicular to each other and having a square hysteresis loop; a first coil wound about said film along said easy axis; means for circulating in said coil an alternating current generating a field sufficient to reverse the magnetic vector in said film; means for subjecting said film to a steady field directed along said hard axes; and means including another coil wound about said film along said easy axis for detecting the magnitude along said easy axis of the external field.
Claim 14
Dependent Claim
149 words
In a device for measuring the magnitude of a weak external magnetic field, a sensor comprising: a thin ferromagnetic film having easy and hard axes of magnetization perpendicular to each other and having a square hysteresis loop; a first coil wound about said film along said easy axis; means for circulating in said coil an alternating current generating a field sufficient to reverse the magnetic vector in said film; means for subjecting said film to a steady field directed along said hard axis; and means including another coil wound about said film along said easy axis for detecting the magnitude along said easy axis of the external field, wherein the film consists of an annular layer on an electrically conductive wire and having easy and hard axes of magnetization directed longitudinally and circumferentially respectively and wherein a DC current is circulated in said wire to generate said steady field.
Claim 15
Dependent Claim
149 words
In a device for measuring the magnitude of a weak external magnetic field, a sensor comprising: a thin ferromagnetic film having easy and hard axes of magnetization perpendicular to each other and having a square hysteresis loop; a first coil wound about said film along said easy axis; means for circulating in said coil an alternating current generating a field sufficient to reverse the magnetic vector in said film; means for subjecting said film to a steady field directed along said hard axis; and means including another coil wound about said film along said easy axis for detecting the magnitude along said easy axis of the external field, wherein the film consists of an annular layer on an electrically conductive wire and having easy and hard axes of magnetization directed longitudinally and circumferentially respectively and wherein a DC current is circulated in said wire to generate said steady field.
Claim 16
Dependent Claim
134 words
In a device for measuring the magnitude of a weak external magnetic field, a sensor comprising: a thin ferromagnetic film having easy and hard axes of magnetization perpendicular to each other and having a square hysteresis loop; a first coil wound about said film along said easy axis; means for circulating in said coil an alternating current generating a field sufficient to reverse the magnetic vector in said film; means for subjecting said film to a steady field directed along said hard axis; and means including another coil wound about said film along said easy axis for detecting the magnitude along said easy axis of the external field, having a coil wound about said film along said hard axis and means circulating a direct current in said second coil for generating said steady field.
Claim 17
Dependent Claim
134 words
In a device for measuring the magnitude of a weak external magnetic field, a sensor comprising: a thin ferromagnetic film having easy and hard axes of magnetization perpendicular to each other and having a square hysteresis loop; a first coil wound about said film along said easy axis; means for circulating in said coil an alternating current generating a field sufficient to reverse the magnetic vector in said film; means for subjecting said film to a steady field directed along said hard axis; and means including another coil wound about said film along said easy axis for detecting the magnitude along said easy axis of the external field, having a coil wound about said film along said hard axis and means circulating a direct current in said second coil for generating said steady field.
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) | 1974-11-15 | 1975-05-17 | 1975-11-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-15 | 1979-05-17 | 1979-11-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-15 | 1983-05-17 | 1983-11-16 | $7700.00 | Window Closed / Lapsed |