WO2007007130A1

WO2007007130A1 - Weak magnetostatic field electronic sensor

Info

Publication number: WO2007007130A1
Application number: PCT/GR2006/000034
Authority: WO
Inventors: Evangelos Hristoforou; Panayiotis D. Dimitropoulos
Original assignee: Evangelos Hristoforou; Dimitropoulos Panayiotis D
Priority date: 2005-07-14
Filing date: 2006-07-14
Publication date: 2007-01-18
Also published as: GR20050100365A

Abstract

Weak magnetostatic field electronic sensor comprising a magnetic film (1) being mounted onto a substrate (7) containing the electronic sensor's response-signal processing circuit. An artificial magnetic field that rotates at frequency f0 is induced in film (1), the intensity vector thereof being co-planar with the film and having a magnitude higher than the sum of the magnitudes of the measured ambient field-intensity plus the apparent saturation field-intensity along any direction in the film's plane whatsoever. The resulting rotation of the film's magnetization vector (2) leads to approaching the value of magnetization saturation and to coincidence of the direction of the projection thereof on the film's plane with the direction of the resultant sum of the rotating excitation field-intensity vector plus the projection of the measured ambient field- intensity vector on the film's plane. The phase difference between the rotating excitation magnetic field (4) and the phase of the rotating magnetization induced into the film being detected by detecting medium (3) is used in the measurement of the ambient field-intentsity around film (1).

Description

Weak Magnetostatic Field Electronic Sensor

THE FIELD OF THE ART

The present invention relates to the field of the art of weak magnetostatic field sensors and in particular to such sensors comprising magnetic films exhibiting a nearly-isotropic behavior and low demagnetization factor along any direction whatsoever in the plane of the film, wherein following induction of magnetization in said films by means of applying a rotating excitation field therein, the projection of the film's magnetization vector at an axis parallel to the plane thereof becomes a periodical function of time, the phase and width of which are monitored by means of either galvanometric or HALL devices and they are functions of the intensity of the ambient magnetic field being measured.

THE PRIOR ART

Measuring instruments of weak magnetostatic fields, hereinafter being referred to as magnetometers are being increasingly employed in a plurality of industrial and medical applications, wherein technological requirements impose improvement of the measuring accuracy, repeatability, reliability, and spatial measuring resolution of magnetic sensors incorporated in such magnetometers, along with the reduction of sensor size and cost, as well as the integration of the sensor together with the electronic signal-conditioning circuit that in combination compose the magnetometer assembled by means of standard CMOS technologies. SQUID magnetometers (Super-Conducting Quantum Interference Devices), magnetometers based on the NMR (Nuclear Magnetic Resonance) or EMR (Electronic Magnetic Resonance) technique fall within the class of weak magnetostatic field-measuring instruments, such magnetometers typically providing a measuring accuracy of the order of Iff⁷ A/m at a frequency bandwidth of up to 1 Hz. The aforementioned magnetometers constitute bulky and complicated relatively high cost devices that in the case of SQUID function in cryogenic temperatures. Moreover, they are capable of gauging only the magnitude - and not the direction - of the magnetic field vector, whilst, due to their size, they provide limited spatial measuring resolution. Due to the aforementioned characteristics of such magnetometers, their use is limited in special scientific applications. The so-called FLUXGATE magnetometers typically provide a measuring accuracy in the order of Iff⁴ A/m at a frequency bandwidth of up to 1 Hz. Despite their capability of providing satisfactory accuracy and capacity of estimating both the magnitude and the direction of the ambient field vector, they cannot be optimally employed in microsystem applications requiring 34

miniature sensor size and/or CMOS integration because of the proportional relationship correlating the signal-to-noise ratio with the volume of the receiving coil of such instruments, such relationship being responsible for the dramatic degradation of FLUXGATE performance when scaling-down of size is attempted. The magnetic noise - generated due to the discrete changes of random magnitude (Barkhausen jumps) that the magnetization vector undergoes within the magnetic core, when the latter is subjected to induced magnetization by means of the primary instrument coil - constitutes an additional accuracy-limiting factor that does not depend on the receiving-coil size.

The use of magnetostatic field sensors based on the Hall effect facilitates the development of integrated magnetometers by means of standard CMOS technologies. However, HALL magnetometers suffer from limited measuring accuracy that is typically no better than 1 A/m at a frequency bandwidth of up to 1 Hz, thereby rendering such devices inappropriate for measuring the intensity of weak magnetostatic fields. The accuracy of HALL magnetometers can be improved using magnetic flux concentrators comprising magnetic films that have a large demagnetization factor, so that non-linear phenomena due to the saturation of the magnetic film may be avoided. In this particular case, however, the hysteretic behaviour of the film employed, that becomes pronounced when the ambient field intensity exceeds, typically, icf A/m causes repeatability errors in the response of such magnetometers. Additional repeatability errors are further being induced in these instruments, due to the strong dependence of the intensity of Hall- effect on ambient temperature.

Instruments that incorporate magnetostatic field sensors based on the physical and/or geometrical magnetoresistance effect can also be integrated by means of standard CMOS technologies, whilst typically providing a measuring accuracy of the order of Iff³ A/m at a frequency bandwidth of up to IHz. Magnetoresistive devices comprise a magnetic film having an easy anisotropy axis (uniaxial anisotropy) in the film plane, the electrical resistance of this film being a function of the direction of the magnetization vector projected on the film-plane that, in turn, depends on the measured ambient field intensity. Such magnetometers, however, suffer from severe repeatability errors due to the random orientation of the magnetization vector that is caused either due to the hysteretic behaviour of the magnetic film resulting from the exposure thereof to field intensities higher than, typically, 10³ A/m, or due to rapid temperature variations (thermal shock). To improve the repeatability of such instruments, the film is periodically subjected -in regular time-intervals, during which sensor operation is temporarily interrupted - to magnetization induced along its easy anisotropy axis that restores the specified performance characteristics of the instrument. It is an object of the present invention to advantageously overcome the aforementioned deficiencies of the prior art by providing an electronic sensor, capable of measuring the intensity of weak magnetostatic fields that, on the one hand, facilitates manufacturing by means of standard CMOS technologies, while, on the other hand, achieves elimination of magnetic noise and repeatability errors due to either hysteretic behavior or to temperature variation. Magnetometers incorporating this sensor may provide a measuring accuracy within the range of Iff⁵ A/m at a frequency bandwidth of up to 1 Hz, thereby approaching the corresponding performance of SQUID magnetometers whilst keeping manufacturing cost at the corresponding levels of magnetoresistive and HALL sensors; thus employment of these devices in a wide variety of industrial and medical applications is made possible.

The object of the invention is achieved by the induced magnetization of a magnetic film exhibiting nearly-isotropic behavior and small demagnetization factor along any direction whatsoever at the plane thereof by means of a rotating excitation field, the intensity vector of which is co-planar with the film and has a magnitude higher than the sum of the magnitudes of the measured ambient field-intensity and of the apparent saturation field-intensity vectors along any direction in the plane of the film.

Another object of the invention is to propose alternative modes of generation and application on the film of the aforementioned rotating excitation field, i.e. a) by employing one or a plurality of pairs of electrical conductors in orthogonal orientation, b) by employing one or a plurality of pairs of planar coils in orthogonal orientation, and c) by employing one or a plurality of pairs of solenoids in orthogonal orientation.

Another object of the invention is to propose alternative means of detection of the rotation phase φ_M(t) of the film's magnetization vector, i.e.: a) by means of galvanic measurements in one or multiple pairs of points on the magnetic film, given that the latter exhibits pronounced geometrical and/or physical magnetoresistance effect, or b) by measurement of the flux-density component perpendicularly oriented onto the film plane, or of the flux-density component that is coplanar with the film plane, such flux-density being induced by the magnetization of the film at one or multiple points near the edges thereof by means of HALL devices located at said points.

Another object of the invention is to propose alternative ways of deriving the information relating to the magnitude and orientation of the projection of the measured ambient field-intensity vector on the plane of the film from the φ(t) signal, i.e. from the difference [φftj = φ_M(t) - φ_EftJ\ of the phase φ_M(t) of the rotation of the film's magnetization vector from the phase φ_E(t) of the rotating vector of the intensity of the excitation magnetic field, i.e.: a) by measuring respectively the amplitude and phase-angle of the φ(t) signal that results from demodulation of electrical signals having the form: x_o-cos(φ_M(t)), x_o-cos(2ψ_M(t)), y_o-sin(φ_M(t)), and y_o-sin(2φ_M(t)), or b) by measuring the phase difference between signals having the form: x₀-cos(φ_M(t))_f x_o-cos(2φ_M(t)), y_o-sin(φ_M(t)), y_o-sin(2φ_M(t)) and signals having the form: cos(φ,=(t)), cos(2φ_E(t)), sinCφεit)), sin(2φ_E(t)) respectively, or c) by measuring respectively the amplitude and phase-angle of the even-order harmonics of signals having the form: x₀-cos(φ_M(t)), y_o-sin(φ_M(t)) and/or of the odd- order harmonics of signals having the form: x₀-cos(2φ_M(t)), y_o-sin(2φ_M(t)).

Another object of the invention is to propose a manner in which the projection of the intensity of the measured ambient magnetic field along an axis perpendicular to the plane of the film is determined by means of measurement of the magnitude of the projection of the magnetization vector at the plane of the film, such magnitude being a function of the intensity component of the measured ambient magnetic field that is oriented perpendicularly along the film.

These and other objects, characteristics and advantages of the present invention will be made apparent in the detailed description hereinunder. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be made apparent to those skilled in the art by reference to the accompanying drawings wherein the invention is depicted in an illustrative manner.

Fig. 1 presents a planar view of an illustrative embodiment of the basic sensing device of the weak magnetostatic filed-measuring sensor of the invention, comprising the magnetic film 1, the rotatable magnetization vector 2 of the film, a medium to detect the rotation phase 3 of the film magnetization and a medium to generate the rotating excitation magnetic field 4.

Fig. 2 presents the magnetic film that preferably has a circular shape, the dimensions of which ensure isotropic behavior with small demagnetization factor along any direction in the film's plane whatsoever. Figures 3a, 3b, and 3c illustratively present the sensing device of Figure 1 subjected, respectively, to excitation by means of: a) a pair of current conductors in orthogonal orientation, b) a pair of planar coils in orthogonal orientation, and c) a pair of solenoids in orthogonal orientation.

Figures 4a and 4b illustratively present the sensing device of Fig. 1, wherein the sensor-response signal is detected, respectively: a) by galvanic measurements at one or multiple points of the film, provided that the film exhibits pronounced geometrical and/or physical magnetoresistance effect, or b) by measuring the flux-density induced by the film magnetization at one or multiple points at the edges of the perimeter of the film by means of HALL devices located at such points.

Fig. 5a presents the signal φ = φ_M - φ_E plotted against the signal φ_E for an ambient field- intensity magnitude HfH₀ = 0.1 and direction θ = CP, 9CP, 18CP, and 270", whereas Fig. 5b presents the signal φ = φ_M - φ_E plotted against the signal φ_E for an ambient field-intensity magnitude HfH₀ = 0.2, OA, 0.6, and 0.8 and direction θ = CP. Fig. 6 presents the phase difference between x₂(t), cos(φ_E) and y₂(t) , sinfφ^ signal-pairs, as measured at the time instances at which φ_E = O, plotted against the direction θ of the measured excitation magnetic field.

Fig. 7 presents the plurality of harmonics of x/t) and cos(2-φ_E) signals for H/H_o = 0.1 and θ= CP. Fig. 8 presents the plurality of harmonics of x₂(t) and cosfφ^ signals, for H/H_o = 0.1 and θ = CP.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As presented in Fig. 1, the weak magnetostatic field electronic sensor of the invention comprises a magnetic film 1 that exhibits a nearly-isotropic behavior and a small demagnetization factor along any direction in the plane thereof. The magnetic film 1 is subjected to induced magnetization by means of a rotating excitation magnetic field, generated by the excitation medium 4. The intensity vector of this induced rotating excitation magnetic field is co-planar with the film 1 and has a magnitude that is larger than the sum of magnitudes of the measured ambient field-intensity and the apparent saturation field-intensity vectors along any direction in the film's plane whatsoever. The apparent saturation field-intensity along a certain direction in the film's plane is herein defined as the magnitude of the field-intensity vector that must be applied onto the film along a given direction, so that the magnitude of the film magnetization vector-component along that given direction has a magnitude equal to 90% of the value of saturation magnetization. The apparent saturation field-intensity along a given direction is proportional to the demagnetization factor along that given direction, the demagnetization factor being dependent on the shape and thickness of the film. Under the influence of the rotating excitation magnetic field, the film magnetization vector is forced to rotate, as indicated by arrow 2, in such a way that the magnitude of the film magnetization vector takes nearly the saturation magnetization value, whilst the direction of the projection thereof on the film's plane coincides with the direction of the sum of the rotating excitation magnetic field-intensity vector and the projection of the measured ambient field-intensity vector on the film plane. The difference, φ = φ_M ~ φ_a between the rotation phase φ_M of the film magnetization vector and the phase φ_E of the rotating excitation field-intensity vector is a periodical function of time t, the frequency of which is equal with the rotation frequency f₀ of the excitation field vector, or, equivalents, the phase difference φ is a periodical function of φ_E that, in turn, is a periodical function of time t with the same frequency. It is herein defined that at the time instances t_π = n/f_0l where n e Z₁ φ_E(n/f₀) = θ_El where θ_Ei is a phase-angle expressing the phase-delay of the periodical excitation field waveform, as measured with regard to a given time-instance of reference. In the special case of a harmonically rotating excitation field, the function φ_E(t) becomes ψ_E(t) = 2-π-f_tit + Θ_E. The amplitude of the periodical function φ(t) and the phase-angle thereof, namely the phase-delay with regard to a given time-instance of reference, are respectively functions of the magnitude and direction of the projection of the measured ambient field-intensity vector on the film plane.

The sensing device depicted in Fig. 1 is based on a substrate 7 that comprises the electronic signal-conditioning circuit of the sensor. The substrate 7 may be a ceramic plate or epoxy resin film or other suitable material onto which are incorporated the response signal conditioning circuitry of the sensor, or it might be a silicon-die with or without additional insulating layers, such as silicon oxide and nitride, within which said electronic circuits may be incorporated by means of standard CMOS technologies. The magnetic film may be attached onto the substrate 7, prior to, or after incorporation of the aforementioned electronic circuits therein, by means of: a) gluing of an amorphous or nanocrystalline magnetic foil, which may subsequently be subjected to thinning or grinding by chemical and/or mechanical means, or b) by depositing a thin film of appropriate magnetic material by means of a Chemical Vapor Deposition technique, or c) by depositing a thin film of appropriate magnetic material by means of a Physical Vapor Deposition technique, or d) by depositing a thick film of appropriate magnetic material by means of a Screen Printing technique, or e) by depositing a thick film by electrochemical techniques. The magnetic film 1 consists preferably of an amorphous or nanocrystalline alloy belonging to the Fe- Ni or Fe-Si systems, the magnetic properties of which may be optimized by means of annealing, wherein it is preferably patterned in a circular shape by means of lithography and wet or dry etching techniques. The film dimensions and shape provide small demagnetization factor along any direction in the film's plane and, consequently, a small apparent saturation field-intensity H_k, of the order of H_k* 1000 A/m.

The excitation medium 4 may in accordance with the invention attain a variety of configurations. As presented in Figure 3a, the excitation magnetic field, that rotates with frequency f₀ and phase φ_E(t) having a phase-delay Θ_E with regard to a given time-instance of reference - namely φdn/Q = Θ_E, where n e Z - is induced by a pair of conductors 5 and 6 in orthogonal orientation, that are respectively supplied with two similar electric current-waveforms having a constant phase shift of 9CP. Mediums 5 and 6 induce the orthogonal H_eχ and H_ey excitation field intensity components respectively, which are co-planar with the film and define a two- dimensional, rectangular reference system on the film plane. The components H_x = Hcos(θ) and H_y = Hsin(θ) of the projection of the measured ambient field-intensity vector on the film plane are respectively superimposed to the aforementioned excitation-field components H_ex and H_ey, where H and θ denote, respectively, the magnitude and the direction of the projection of the measured ambient field-intensity vector on the film plane. In the special case, in which the excitation current-waveforms comprise harmonic functions of time, the conductors 5 and 6 induce a magnetic field, the intensity of which is respectively H_ex = H_o-cos(2-πf_o-t+θ_E) and H_eγ = H_o-sinfeπf_o t+θε). Provided that the magnitude H₀ of the rotating excitation field-intensity exceeds the sum of the magnitudes of the measured ambient field-intensity plus the apparent saturation field-intensity along any direction in the film plane (H₀ > H + H_kl), the film magnetization magnitude takes nearly the saturation value and the magnetization vector thereof rotates with frequency f₀ and phase (PM(Q that in case of harmonic excitation is given by: φ_M = arg{(H₀- cos(2- π- f_ϋ t+θ_E)+H cos(θ))+i- (H_ύsin(2 n f_ύ t+θ_E)+Hsin(θ))}. As presented in Figure 5, the difference, φ = φ_M - φ_El between the magnetization phase φ_M and the excitation field phase φ_E - that in case of harmonic excitation is given by φ_E = 2nf_o-t + Θ_E- is a periodical function of time t with frequency f_0l or - in other words - φ is a periodical function of φ_E. The amplitude and phase-angle of φ(Q signal, are, respectively, functions of the magnitude H and direction-angle θ, of the projection of the measured ambient field-intensity on the film plane. The higher the magnitude H₀ becomes - compared to the apparent saturation field-intensity - the closer the magnetization vector follows the resultant sum of the excitation and ambient field vectors. In the ideal case that H₀ » H_k, magnetic noise and repeatability errors are eliminated.

Alternatively, as presented in Fig. 3b, the excitation field may be generated by means of two pairs of planar coils 8 and 9 in orthogonal orientation, or, as presented in Figure 3c, by means of two pairs of solenoid coils 11 and 10 also in orthogonal orientation; in both cases the effects on the magnetization rotation and the sensor response are the same as in the conductor-pair case described previously.

In order to derive the information relating to the magnitude and direction of the projection of the intensity of the measured ambient magnetic field at the plane of the film out of the signal of the phase-difference time-function φ(t), it is essential to detect the phase-signal φ_M(t), namely the current direction of the film magnetization vector and subtract from the latter the given rotating excitation-field phase-signal φ_E(t). The φ_M(t) phase detection device 3, presented in Fig. 1, may be alternatively implemented by means of a variety of configurations. As presented in Fig. 4a, in the case that the magnetic film of the sensor exhibits geometrical and/or physical magnetoresistance effect, the value of the ohmic resistance, measured between two diametrically opposite points 12 in the perimeter of the film, is given by R(Q = R₀ + 2ΔR cos(φ_M(Qf = R₀ + ΔR + ΔR-cos(2φ_M(Q). The DC component of the abovementioned signal R(t) can be eliminated, either by means of an electronic high-pass filter, or by connecting multiple film-devices 1 and excitation media 4 in a WHEATSTONE bridge configuration, thereby the residual electric signal taking the form: X₁(U) = x_ύcos(2φ_M(t)) = x_o-cos(2φ_E(Q+2φ(Q), which in the specific case of harmonic excitation becomes: X₁(Q - x₀-cos(4π-f₀-t+2-θ_E+2φ(Q). The φ(Q signal can be extracted from the X₁(Q waveform by means of a phase-demodulation technique. The amplitude and phase-delay of the detected φ(Q signal are respectively related with the magnitude and the direction of the projection of the measured ambient filed-intensity vector on the film plane. Alternatively, an additional pair of diametrically opposite points 12 - in orthogonal orientation with respect to the original pair - may be used to measure the resistance, in order to extract the y/tj = y_o-sin(2φ_M(t)) signal, in addition to the X₁Ct) one. The phase difference between X₁(Q ^vA cosC2φ_E(t)) signals, as measured at the time instances, at which φ_E = 0, is proportional to the magnitude of the component of projection of the measured ambient field-intensity vector on the film plane, which is parallel with the H_ey excitation field component. Respectively, the phase difference between y/t) and sin(2-φ^t)) signals, as measured at the time instances, at which φ_E = O₁ is proportional to the magnitude of the component of projection of the measured ambient field-intensity vector on the film plane, which is parallel with the H_ex excitation field component. In the aforementioned case, the ambient field-intensity vector is determined by the detection of its two perpendicular components along the directions of /4* and /%_ythat define a two-dimensional rectangular reference system onto the plane of the film.

Alternatively, the aforementioned perpendicular components of the measured ambient field- intensity vector - along the directions of H_ex and H_ey - can be respectively determined by the detection of the magnitude and phase-delay of odd-order harmonics contained in X₁Ct) and y_x(t) signals. As depicted in Fig. 7, the spectra of the aforementioned signals contain a series of odd- order harmonics, in contrast with cos(2φ_E(t)) and sin(2φ_E(t)) signals that contain only even- order harmonics. Moreover, the harmonics of X₁(Q and y_x(t) signals have a constant 90° phase- difference, so that they can be independently detected. The amplitude and phase-delay of odd- order harmonics of X₁Ct) and y/t) signals are respectively related with the components of the projection of the measured ambient filed-intensity vector on the film plane along the direction of H_exand H_ey components.

In addition to galvanometric techniques, the φ(t) phase-signal can also be deected by measuring the flux-density component oriented perpendicularly or parallel to the film's plane by means of HALL devices 13 positioned near the edges of the film's perimeter, as shown in Figure 4b. A HALL device 13 detects the flux-density induced by the magnetization of the film, so that the device response signal has the form X₂Ct) = x_o-cos(φ_M(t)) = x_o-cosCφ_E(t)+φ(t)). The φ(t) signal can be extracted from X₂Ct) waveform by means of any phase-demodulation technique whatsoever. The amplitude and phase-delay of the detected demodulated φ(t) signal are respectively related to the magnitude and the direction of the projection of the measured ambient filed-intensity vector on the film plane. Alternatively, an additional HALL device positioned appropriately so as to detect the flux-density induced by the film magnetization with 9CP phase-delay may be used to extract the y₂(t) = y_o-sin(φ_M(t)) signal, in addition to the X₂Ct) one. The phase difference between x/t) and cos(φ_E(t)) signals, as measured at the time instances, at which φ_E = O₁ is proportional to the magnitude of the component of the projection of the measured ambient field-intensity vector on the film plane, which is parallel with the H_ey excitation field component. Respectively, the phase difference between y₂(t) and sinCφε(t)) signals, as measured at the time instances, at which φ_ε = 0, is proportional to the magnitude of the component of the projection of the measured ambient field-intensity vector on the film plane, which is parallel with the H_ex excitation field component. In the aforementioned case, the ambient field-intensity vector is determined by the detection of its two perpendicular components along the directions of H_ex and H_ey that define a two-dimensional rectangular reference system on the film's plane. Fig. 6 presents the phase difference between x₂(t), y₂(t) in comparison with the

sin(φ_E(t)) signals respectively for different magnitudes and different directions of the projection of the measured ambient field-intensity vector on the film plane. It follows from Fig. 6 that the phase difference between x₂(t) and cos(φ_E(t)) signals is zero if the ambient field is parallel with the H_ex component, whereas the phase difference between y₂(t) and sin(φ_E(t)) signals is zero if the ambient field is parallel with the H_ey component. Alternatively, the aforementioned components of the measured ambient field- intensity vector - along the directions of H_ex and H_ey - can be respectively determined by the detection of the magnitude and phase-delay of even-order harmonics contained in x₂(t) and y₂(t) signals. As depicted in Fig. 8, the spectra of the aforementioned signals contain a series of even- order harmonics, in contrast with cos(φ_E(t)) and sin(φ_E(t)) signals that contain only odd-order harmonics. Moreover, the harmonics of x₂(t) and y₂(t) signals have a constant 9CP phase- difference, so that they can be independently detected. The amplitude and phase-delay of even- order harmonics of x₂(t) and y₂(t) signals are respectively related with the components of the projection of the measured ambient filed-intensity vector on the film plane along the direction of H_exand H_ey components.

Further to the abovementioned techniques of signal processing, the amplitudes X₀₁ and y_olf x_oz and y₀₂ of the signals X₁(Q₁ y/tj, X₂CtJ and y₂(t) respectively may be used for the determination of the projection of the intensity of the measured ambient magnetic field along an axis perpendicularly oriented to the plane of the film, given that this perpendicular component is a function of the magnitude of the magnetization vector at the plane of the film.

Claims

1. Electronic sensor capable of measuring the intensity of weak magnetostatic fields, comprising a sensing device of a magnetic film (1) with a nearly-isotropic behavior and low demagnetization factor along any direction of the plane thereof whatsoever, said film being mounted onto a substrate (7) containing the electronic sensor's response-signal processing circuit, characterized by that it comprises an excitation medium (4) generating an artificial magnetic field that rotates at frequency f_Ol the intensity vector thereof being co-planar with the film and having a magnitude higher than the sum of the magnitudes of the measured ambient field-intensity plus the apparent saturation field-intensity along any direction in the film's plane whatsoever, wherein under the influence of said artificial magnetic field, the film's magnetization vector (2) is forced to rotate in a way such that the magnitude thereof approaches the value of magnetization saturation, whereas the direction of the projection thereof on the film's plane coincides with the direction of the resultant sum of the rotating excitation field-intensity vector plus the projection of the measured ambient field-intensity vector on the film's plane and a medium (3) for the detection of the induced film magnetization rotation phase φ_M, the difference ψ = φ_M - φ_E between phase φ_E of the rotating magnetic field being induced by said excitation medium (4) and phase φ_M of the rotating magnetization induced into film (1) is a periodical function of time with frequency f₀, the amplitude and phase-delay of which are respectively functions of the magnitude and direction of the projection of the measured ambient field- intentsity vector on the plane of film (1).

2. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claim 1, characterized by the magnetic film (1) comprising amorphous or nanocrystalline alloy of the Fe-Si or Fe-Ni systems, wherein the magnetic properties of said film may be optimized by means of annealing, said film having circular shape and dimensions being patterned by means of lithography and wet or dry etching techniques.

3. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claim 1, characterized by said excitation medium (4) comprising an arrangement of one or multiple pairs of conductors (5), (6) in orthogonal orientation, wherein said conductors, being supplied by two similar periodical electric current waveforms having frequency f₀ and constant 9CP phase-difference, generate in combination two periodical magnetic field components perpendicular to each other and co-planar with said film (1), said magnetic field components defining a rectangular two-dimensional reference system (x,y) at the plane of said film (1), whilst the sum of their vectors constitutes said rotating excitation magnetic field.

4. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claim 1, characterized by said excitation medium (4) comprising an arrangement of one or multiple pairs of planar coils (8), (9) in orthogonal orientation, wherein said planar coils being supplied by two similar, periodical electric current waveforms having frequency f₀ and constant 9CP phase-difference generate in combination two periodical magnetic field components perpendicular to each other and co-planar with said film (1), said magnetic field components defining a rectangular two-dimensional reference system (x,y) at the plane of said film (1), whilst the sum of their vectors constitutes said rotating excitation magnetic field.

5. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claim 1, characterized by said excitation medium (4) comprising an arrangement of one or multiple pairs of solenoid coils (10), (11) in orthogonal orientation, wherein said solenoid coils being supplied by two similar, periodical electric current waveforms having frequency f₀ and constant 9CP phase-difference generate in combination two periodical magnetic field components perpendicular to each other and co-planar with said film (1), said magnetic field components defining a rectangular two-dimensional reference system (x,y) at the plane of said film (1), whilst the sum of their vectors constitutes said rotating excitation magnetic field.

6. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claim 1, characterized by said medium (3) for the detection of the magnetization rotation phase φ_M, induced in film (1) comprising, in the case that the film exhibits a pronounced geometrical and/or physical magnetoresistance effect, one or multiple pairs of points (12) for galvanic measurements positioned in the perimeter of film (1) along with the appropriate - for the measurements - electronic circuits, or one or multiple pairs of points (12) for galvanic measurements positioned in the perimeter of a plurality of films (1) connected in a WHEATSTONE bridge configuration, wherein electrical signals of the form x/t) = x_Oi-cos(2-φ_M) and Y₁Ct) = γoi-sin(2-φ_M) are produced at the said points of galvanic measurements.

7. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claim 1, characterized by said medium (3) for the detection of the magnetization rotation phase φ_Mι induced in film (1) comprising one or more HALL devices (13) located at one or multiple points of the perimeter of film (1) along with the appropriate - for the measurements - electronic circuits, wherein the flux density component due to magnetization of the film oriented perpendicularly or parallel along the plane of the film is being detected through said HALL devices (13) that produce electrical signal of the form X₂Ct) = Xoz∞s(φ_M) και γ₂(t) = YozSin(φ_M).

8. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claims 1, 6, and 7, characterized by said electronic sensor response-signal processing circuit comprising a medium, by means of which at least one of said signals X₁Ct), YiCOi x/t)_> and y/t) is being subjected to phase demodulation, with the scope of using the demodulated periodical signal φ(t) = φ_M(t) - ψε(V for the determination of the magnitude and direction of the projection of the measured ambient magnetic field-intensity vector onto the plane of film (1).

9. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claims 1, 3, 4, 5 and 6, characterized by that it comprises a medium by means of which the phase difference between two signal-pairs X₁Ct)₁ cos(2-ψ_E) and ytft) , sin(2-φ_E) is being detected at time instances at which φ_E = 0, the detected phase difference being used in the determination of the two components of the projection of the measured ambient magnetic field- intensity vector onto the plane of film (1), said two components being parallel to the perpendicular components of the rotating excitation field being produced by said excitation medium (4) and defining a two-dimensional, orthogonally oriented reference system (x,y) on the plane of film (1).

10. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claims 1, 3, 4, 5, and 7, characterized by that it comprises a medium by means of which the phase difference between two signal-pairs x₂(t), cos(φ_E) and y₂(t), sin(φ_E) is being detected at time instances at which φ_E = 0, the detected phase difference being used in the determination of the two components of the projection of the measured ambient magnetic field- intensity vector onto the plane of film (1), said two components being parallel to the perpendicular components of the rotating excitation field being produced by said excitation medium (4) and defining a two-dimensional, orthogonally oriented reference system (x,y) on the plane of film (1).

11. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claims 1, 3, 4, 5, and 6, characterized by that it comprises a medium by means of which the magnitude and phase-delay of the odd-order harmonics of signals X₁(Q and y/Q is being detected, the detected values being used in the determination of the two components of the projection of the measured ambient magnetic field-intensity vector onto the plane of film (1), said two components being parallel to the perpendicular components of the rotating excitation field being produced by said excitation medium (4) and defining a two-dimensional, orthogonally oriented reference system (x,y) on the plane of film (1).

12. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claims 1, 3, 4, 5, and 7, characterized by that it comprises a medium by means of which the magnitude and phase-delay of the even-order harmonics of signals x₂(t) and y₂(t) is being detected, the detected values being used in the determination of the two components of the projection of the measured ambient magnetic field-intensity vector onto the plane of film (1), said two components being parallel to the perpendicular components of the rotating excitation field being produced by said excitation medium (4) and defining a two-dimensional, orthogonally oriented reference system (x,y) on the plane of film (1).

13. Electronic sensor, capable of measuring the intensity of weak magnetostatic fields, according to claims 1, 6, and 7, characterized by said electronic sensor response-signal processing circuit comprising a medium by means of which at least one of said signals X₁Ct), Y₁(U), x₂(t), and y₂(t) is being subjected to amplitude demodulation with the scope of using the detected values of x_olf y₀₁, x_02t and y_O2 respectively for the determination of the magnitude of the projection of the measured ambient magnetic field-intensity vector along an axis that is perpendicularly oriented with respect to the plane of film (1).