JP3523834B2 - Magnetic field sensor and magnetic field sensing system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field sensor including a thin film magneto-impedance effect element.

[0002]

2. Description of the Related Art In recent years, measurement of magnetic fields generated from electric / electronic devices and their constituent devices, substrates, and elements, motion capture, magnetic field measurement for nondestructive inspection of various articles, control and position information, etc. Displacement / angle measurement or magnetic recording such as magnetic head,
In particular, there is a strong demand for higher sensitivity, wider bandwidth, and smaller size.

As a conventional magnetic field sensor, an element utilizing a Hall effect or a magnetoresistive (MR) effect and an element using an air-core coil are generally used. Development of an element using a magnetic impedance effect using a magnetic thin film is in progress. Further, in the magneto-impedance element, with consideration for use in a region where the carrier current frequency is high, studies are being made on making the element into a microstrip line.

The above-mentioned "magnetic impedance element" is a phenomenon in which the electrical impedance of the element changes as the magnetic permeability of the magnetic material changes due to an externally applied magnetic field, and various types utilizing this have been proposed. . For example, FIG. 10 shows a conventional magnetic field sensor structure in which the above-mentioned amorphous wire is used as a sensing element and the voltage across the element when a high-frequency current is directly applied to the sensing element changes according to the strength of an external magnetic field. It is shown. Journal of Applied Magnetics of Japan (Vo
1.18, No. 2, 493, 1994), a magnetic field change induces a change in element impedance, and as a result, the carrier voltage is amplitude-modulated by a high-frequency current (but a constant amplitude), so that the magnetic field is detected.

This sensor has a simple element structure because it does not require the windings found in fluxgate type magnetic field sensors and the like, and the magnetic flux changes in the circumferential direction of the wire without demagnetizing field,
That is, since the element impedance changes due to the change in magnetic permeability, it is possible to drive with low carrier power, so that a small and highly sensitive sensor can be constructed. The change in permeability is 10 due to the skin effect up to a carrier frequency of about 10 MHz.
It is considered that the magnetization component that rotates following the high-frequency current magnetic field changes up to about 0 MHz. 100MHz
Above a certain level, the impedance change due to resonance is small.
Since the upper limit of the frequency of the magnetic field that can be detected by amplitude modulation is about 1/10 of the carrier frequency, the detection band of this element is about 10 MHz.

On the other hand, in a magnetic field sensor or the like as a magnetic head used in a magnetic recording apparatus, it is necessary to miniaturize the element and realize a high detection resolution. For this purpose, application of thin film technology is essential.

FIG. 11 shows the IEEE Trans.Magn.V, which was also published in the 96th Research Meeting Material 96-6, 37, 1996 of the Japan Society for Applied Magnetics.
The magnetic field sensor using the magnetic-impedance effect using the magnetic thin film of o1.30, No.6, 4611, 1994 is illustrated. In this magnetic field sensor, a magnetic thin film is arranged so as to surround the thin film conductor, and the magnetic thin film serves as a core of a magnetic head and is magnetized by a signal magnetic field from a recording medium such as a hard disk. It changes. UH for impedance matching between elements and peripheral circuits
By using a high frequency signal in the F band (several hundred MHz) as a carrier, the bandwidth of 80 MHz (50 Ω matching, -3 dB band) (40 MHz as the signal frequency band) and more than 10 times that of the spin valve giant magnetoresistive element Signal output (127 mVpp / μm).

In addition to this, an element having a structure in which a high frequency current is directly applied to a magnetic thin film (see: Journal of Japan Society for Applied Magnetics VO1.
19, No.2, 481, 1995) and a device with high sensitivity by using electric resonance phenomenon (see: Journal of Japan Society for Applied Magnetics Vol.10, No.
2,93 1986; Proceedings of the Japan Society for Applied Magnetics 20pB-11,
45, 1996), and a magnetic field sensor (see Japanese Patent No. 3001452) using a microstrip line type element for the purpose of highly efficient use in a high frequency carrier region.

[0009]

In order to realize a broadband magnetic field sensor, it is necessary to increase the frequency of the high frequency current (carrier current) that flows through the element. For example, in measurement of magnetic fields generated from electric / electronic devices and their constituent devices, substrates, and elements, the drive frequencies of these constituents are shifting to the GHz band.

As another example, even in a hard disk device in the field of magnetic recording, the data transfer rate will be GH in the near future.
It is considered to be the z band. For example, in order to realize the measurement of these high-frequency magnetic fields using a method such as amplitude modulation, the frequency of the carrier current (carrier frequency) needs to be several times the frequency of these signals, that is, several GHz.
Therefore, the basic characteristics of the magneto-impedance element at the carrier current in the GHz band are important.

According to the Journal of Applied Magnetics of Japan (Vol. 21, 789. 1997), a magnetic thin film having a uniaxial anisotropic magnetic field strength Hk in the film plane is subjected to AC excitation with a small amplitude in the easy axis direction,
The resonance magnetic field strength Hdc with respect to the carrier angular frequency when a DC magnetic field is applied in the hard axis direction is represented by the following equation when the applied magnetic field strength is larger than the anisotropic magnetic field strength Hk.

Hdc = (μ0 · ω0 ² ) / ( γ ² · Ms ) + Hk (Equation 1) where ω0 is the resonance angular frequency (carrier angular frequency) , γ is the gyro magnetic constant, Ms is the saturation magnetization , Hk is the anisotropic magnetic field, and μ
It is assumed that 0 is the magnetic permeability in vacuum .

In the conventional magneto-impedance element, since the carrier current frequency used is in the MHz band, the influence of the first term on the left side of (Equation 1) is small, and the resonance is on the second side of the left side.
The terms were important. However, when the GHz band carrier current is used, it is expected that the first term on the left-hand side of (Equation 1) becomes the main factor that determines Hdc.

FIG. 12 shows a NiFe thin film magneto-impedance element having a total magnetic film thickness of 1 μm and a line width of 100.
In the case of an element of μm, the applied magnetic field dependence of the absolute value (| S21 |) of the S21 parameter representing the characteristics as a sensor is shown for carrier current frequencies 1, 2, 3, 4, and 5 GHz.

The magnetic field (Hdip) at the point of hitting the bottom of the depression in the magnetic field characteristics at each frequency corresponds to Hdc in (Equation 1) above. FIG. 13 shows the results of this experiment and the values expected from the above (Equation 1). The characteristics of the device this time were in accordance with the above (formula 1). Also,
As the value of Hdip increases in the conventional element, as shown in FIG.
It is unavoidable that the response to the applied magnetic field corresponding to the steepness of the characteristic curve in 1 becomes slow.

As described above, in the conventional device, when a carrier frequency in the GHz band is used, it is necessary to use the device in a very high magnetic field region in order to obtain a large usable signal for the magnetic field. It also shows that a large magnetic field change is required.

In other words, in the conventional element, when the carrier frequency in the GHz band is used, the sensitivity is low and a very high bias magnetic field is required to obtain a large change. In addition, a very high bias magnetic field is required to obtain linear response.

However, the document IEEE Trans.Magn., Vo1.29, N
In o.6,3867.1993, it is proposed that a device using a Co-P1anar type waveguide obtains a signal output in a carrier frequency range of 2 to 6 GHz. However, in this method, since the standing wave in the waveguide is used, there are large restrictions on the element size, and the element size cannot be reduced to the extent that it can be applied to a high-density hard disk device. There was a practical problem.

Therefore, an object of the present invention is to use a high frequency carrier in the GHz band for the magneto-impedance element in a high frequency region including the GHz band which enables operation in a low magnetic field region and realizes a sharp impedance change. A high-sensitivity magnetic field sensor and a magnetic field sensing system are provided.

[0020]

The present invention has been made in view of the above-mentioned current situation, and takes the following means in order to solve the above problems and achieve the object. For example, a magnetic field sensor including a thin film magneto-impedance effect element using a magnetic thin film among magnetic impedance elements serving as a magnetic field sensor using the magneto-impedance effect, and when a current frequency to be conducted is 1 GHz or more, , The most remarkable magnetic field strength of the magnetic resonance of the magnetic sensitive part is
A magnetic field sensor is proposed in which the size of the magnetic body of the magnetic sensing section in the direction substantially perpendicular to the magnetic field sensing direction is made small to the extent that it falls below the obtained resonance magnetic field strength Hdc . Hdc = (μ0 · ω0 ² ) / (γ ² · Ms ) + Hk where ω0 is the resonance angular frequency (carrier angular frequency) and γ is the
Gyro magnetic constant, Ms is saturation magnetization, Hk is anisotropic magnetic field, μ
0 is the magnetic permeability in vacuum . Then, a magnetic field sensor is proposed in which the magnetic body of the magnetic sensing section is made of a soft magnetic material.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A plurality of embodiments of a magnetic field sensor according to the present invention and a magnetic field sensing system using the same and modifications thereof will be described in detail below. In this description, the absolute value of the voltage transmission coefficient S21 when the transmission line is regarded as a two-aperture circuit for element evaluation |
The difference between this value and the value of zero magnetic field for each magnetic field with respect to S21 |
(ΔS21) is used as the amount of change in the voltage transmission coefficient.

(First Embodiment) FIG. 1 shows the structure of a magnetic field sensor according to the first embodiment of the present invention.
The characteristics of this magnetic field sensor are shown in the graphs shown in FIG.

The magnetic field sensor of the first embodiment is characterized in that a magnetic thin film which is elongated and thinned (oblong stripe pattern) is used as a magnetic sensing part as shown in FIG. 1, and a high frequency is directly applied to the magnetic thin film. It is a sensor. The specific structure is that, for example, a magnetic strip 6 made of a magnetic thin film and conductor electrode pads 5a, 5b made of a Cu conductor thin film are sequentially formed on one surface of a substrate 1 made of glass and having a thickness of 1 mm, and a ground conductor is formed on the other surface. This is a structure in which Cu having a thickness of 2 μm and having a thickness of 2 is deposited by a sputtering method.

Both ends of the elongated striped pattern of the magnetic thin film forming the magnetic strip 6 are connected to the Cu conductor thin films of the conductor electrode pads 5a and 5b, respectively. In operation, the conductor electrode pads 5a and 5b are connected to the electrodes 3a and 4a, respectively, and one of the electrodes 3b and 4b is connected.
Is connected to the ground conductor 2. Then, it is magnetized by the supply of a predetermined voltage, and changes in current and voltage at this time are also detected.

The former method for forming one surface is performed as follows. First, a Ta layer having a thickness of 5 nm is formed by a sputtering method, and then a magnetic thin film having a thickness of 100 is formed.
The NiFe magnetic film of 5 nm and the Cu film of 5 nm are alternately deposited by a sputtering method to form a NiFe layer having a total film thickness of 1 μm, and then a Ta layer having a thickness of 5 nm is formed by the sputtering method.
Ten layers of NiFe separated by nine Cu layers between layers a
A thin film having a layer is formed (step S1), and the width is 1 μm using the photolithographic technique and the ion milling device.
Etching is performed on a stripe pattern having a length of m and a length of 1.6 mm (step S2). At this time, the width direction is set to be the easy axis of magnetization.

Next, a 1 μm thick Cu film is formed on the photoresist by patterning the photoresist into the shape of an electrode pad, and unnecessary portions of the Cu thin film are removed by a lift-off method to form conductor electrode pads 5a and 5b. (Step S3). At this time,
The magnetic strip and the conductor electrode pad are partially overlapped with each other to ensure electrical continuity. The distance between the conductor electrode pads 5a and 5b is set to about 1 mm.

When a carrier current is caused to flow in the line illustrated in FIG. 1 and a magnetic field is applied in the longitudinal direction (current-carrying direction) of the magnetic strip, the impedance of the magnetic sensing section changes depending on the strength of the applied magnetic field. The amount of change ΔS21 of | S21 | is a amount that reflects this amount of change and serves as a magnetic field detection signal.

The graph of FIG. 2 shows a carrier frequency of 2 GHz,
This is the dependence of the external magnetic field on ΔS21 of this magnetic field sensor at a carrier power of 3.16 mW and a sensor with a line width of 100 μm manufactured by the same method described in the above-mentioned [Problems to be solved by the invention]. Similarly, the graph of FIG. 3 is the result when the carrier frequency is 3 GHz.

(Effect 1) As shown in the graph of FIG. 2, Hdip is about 5 in a sensor having a line width of 100 μm.
It is 0 Oe, and the slope of the curve with respect to the magnetic field is gradual as a whole, which means poor sensitivity of the sensor to the magnetic field, and this is confirmed even in a relatively low magnetic field region.

On the other hand, according to the magnetic field sensor of this embodiment, 20
A change in absolute value | S21 | of the voltage transmission coefficient of 0.1 or more can be realized in a low and narrow applied magnetic field region of Oe or less.

Further, as shown in the graph of FIG.
With a conventional sensor with a track width of 100 μm, Hdip is about 100
It is Oe, and it is confirmed that the sensitivity to the magnetic field is further deteriorated. On the other hand, in the magnetic field sensor of this embodiment, 3 GHz
Even at a high carrier frequency, a high | S21 | change of 0.1 or more can be realized in a low and narrow applied magnetic field region of 20 Oe or less.

As described above, by bringing the magnetic resonance magnetic field of the magnetic material forming a part of the magnetic sensing part and the magnetic field causing the magnetization change close to or substantially matching with each other, a steep change in impedance due to a steep change in magnetization is caused. can get. By using a magnetic material that causes a change in magnetization in a relatively low magnetic field region, when the above-described condition (positional condition of magnetic field) is satisfied, use in the low magnetic field region is also possible.

In a similar device having the same structure, the total number of magnetic layers was 200 and the total thickness of the magnetic layers was 200 nm while the thickness of each NiFe magnetic layer was fixed at 100 nm. In the measurement, the most remarkable decrease in the magnetic field (Hdip) of the magnetic resonance of the magnetic material of the magnetically sensitive portion is hardly seen. The cause of this may be either the film thickness or the decrease in the total number of the film thicknesses, or both.

From this, it is considered necessary to reduce the line width in order to bring about a remarkable decrease in Hdip along with the reduction of the causative factor. On the contrary, it is conceivable that with the increase of the factors that cause this, the line width wider than that of the present embodiment may cause a remarkable decrease in Hdip.

(Modification 1) The first embodiment described above can be modified as follows. For example, by shortening the length of the magnetic field sensor illustrated in the present embodiment, the magnetic field sensor as a whole is made sufficiently smaller than a predetermined electric / electronic device and a device, a substrate, and an element which are its constituent elements, and the magnetic field The sensor is arranged in the immediate vicinity of the electric / electronic device and its constituent devices, substrates, and elements.

By applying the magnetic field sensor as described above to the measurement of the high-frequency near-field magnetic field generated by the electric / electronic device and the devices, substrates, and elements that are its constituent elements, the magnetic-field sensor can operate in the near-high-frequency field. A magnetic field sensing system can be configured as the primary sensor for measurement.

(Second Embodiment) Next, a magnetic field sensor as a second embodiment of the present invention will be described. The graphs of FIGS. 4 and 5 show the characteristics of the magnetic field sensor of the second embodiment. The magnetic field sensor of the second embodiment has the same structure as that of the first embodiment, and has a stripe width of 2 μm in step S2.

The graph of FIG. 4 shows that the carrier frequency is 2 GHz,
The dependence of the external magnetic field on ΔS21 of the present magnetic field sensor with a carrier power of 3.16 mW and a conventional magnetic field sensor with a line width of 100 μm manufactured by the same method as mentioned in the problem is shown. Similarly, the graph of FIG. 5 shows the result when the carrier frequency is 3 GHz.

(Effect 2) As shown in the graph of FIG. 4, in comparison with the conventional sensor having a line width of 100 μm, the magnetic field sensor of this embodiment has a Hdip value of about 500 e, which is the same as that of the conventional sensor. The spread of the dent due to the dispersion of the magnetic characteristics in the body is large, and the resonance and non-resonance state changes are realized by the magnetization change in the low magnetic field region, and the low and narrow applied magnetic field region of 200 e or less has a high value of about 0.15. The change of S21 | can be realized.

As shown in the graph of FIG. 5, 3 GHz
The same tendency can be seen at high carrier frequencies,
A high | S21 | change of about 0.1 can be realized in a low and narrow applied magnetic field region of 200 e or less.

(Third Embodiment) The magnetic field sensor of the third embodiment has the same structure as that of the first embodiment described above, and here, in particular, a hard magnetic material or a semi-magnetic material is used as the magnetic sensing section magnetic body. Using a hard magnetic material, the coercive force H
It is used at a carrier frequency where magnetic resonance is realized in the magnetic field region around c. However, the stripe does not necessarily have to be thinned.

The graph of FIG. 6 shows an expected measurement result when the magnetic field is increased from a sufficiently small value of Hc or less to a value of Hc or more in this magnetic field sensor.

(Effect 3) According to the magnetic field sensor of the third embodiment, the steep | S21 | (voltage transmission coefficient) change reflecting the steepness of the magnetization reversal with respect to the applied magnetic field in the vicinity of the coercive force Hc. Can be expected to be realized. Further, it becomes possible to detect a minute magnetic field change in a region equivalent to the coercive force.

(Fourth Embodiment) The graphs of FIGS. 7 and 8 show the characteristics of the magnetic field sensor of the fourth embodiment. The magnetic sensor of this embodiment has the same structure as that of the second embodiment. However, the magnetic layer portion is a single layer.

FIG. 7 shows the present magnetic field sensor with a carrier frequency of 2 GHz and a carrier power of 3.16 mW and ΔS21 of a conventional magnetic field sensor with a line width of 100 μm manufactured by the method of Example 1 mentioned in the above-mentioned problem. It is the dependence of the external magnetic field. Similarly, FIG. 8 shows the result when the carrier frequency is 3 GHz.

(Operation and Effect 4) As shown in the graph of FIG. 7, the fourth sensor is compared with the conventional sensor having a line width of 100 μm.
In the magnetic field sensor of the embodiment, the value of Hdip is reduced from about 500e to about 350e, and further, the spread of the recess due to the dispersion of the magnetic characteristics in the magnetic body is expanded, and the addition of these two effects reduces the low value. Resonance and non-resonance can be realized by changing the magnetization in the magnetic field region, and a high | S21 |

Further, as shown in the graph of FIG. 8, the same tendency is observed at a carrier frequency as high as 3 GHz.

In the magnetic field sensor element of the present invention, the magnetic element pattern size in the direction substantially perpendicular to the direction to be detected is reduced with respect to the magnetically sensitive partial magnetism of the sensor element utilizing the magnetic impedance effect. Either use of an increased characteristic dispersion of the magnetic body part, use of a hard magnetic material having coercive force equivalent to the resonance magnetic field region, or
By combining two or more of these, it is possible to realize high sensitivity to a minute magnetic field even in the GHz band high frequency by bringing the resonance magnetic field of the magnetic field sensing member and the magnetic field in which the magnetization change occurs close to each other. .

(Fifth Embodiment) FIGS. 9A and 9B show
The magnetic field sensor as 5th Embodiment of this invention is illustrated.
The difference of the fifth embodiment from the above-described first to fourth embodiments is that the magnetic thin film does not form a part of the conductor strip, and the magnetic thin film is arranged separately from the conductor strip.

That is, in the structure illustrated in FIG. 9A, the magnetic thin film 10 is arranged on one surface of the conductor electrode pads 7a and 7b and the magnetic thin film is arranged on one surface of the conductor strip. A two-layer structure similar to the above is formed, and conductor electrode pads 7a and 7b that are elongated in the longitudinal direction are formed in both directions of the magnetic thin film 10a formed from above in the center. During operation, each of these conductor electrode pads 7 (7a, 7b) is connected to the electrodes 3a and 4a, and one of the electrodes 3b and 4b is connected to the ground conductor 2. Then, it is magnetized by the supply of a predetermined voltage, and changes in current and voltage at this time can also be detected.

The structure illustrated in FIG. 9B is an example of a structure in which the magnetic thin films 10a and 10b are arranged on both surfaces of the conductor electrode pads 7a and 7b in addition to the above-described structure and the circumference is surrounded. Is. The magnetic strips of the first to fourth embodiments have the same structure as those of the magnetic strips.

(Function and Effect 5) The former (FIG. 9 (a)) has a characteristic that the structure is extremely simple, and the latter (FIG. 9 (b)) has a closed magnetic circuit structure against the magnetic field generated by the high frequency current. Therefore, high sensitivity can be expected.

(Other Modifications) The present invention can be variously modified in addition to the above-described embodiments without departing from the scope of the invention. For example, the structure does not necessarily have to be a microstrip structure, and the magnetic anisotropy direction and magnetic characteristics of the exemplified magnetic strip according to the present invention, whether it is a laminated film or a single layer film, or an external magnetic field Not only the direction of application to the magnetic strip, but also the shape, size, material of each part, the number of laminated magnetic layers, etc. can be variously changed as necessary, and the shape can be a straight line or a curved line. In addition to being present, an appropriate combination with another is possible.

[0054]

As described above, according to the magnetic field sensor of the present invention, it is possible to obtain the effect of using the magneto-impedance effect and exhibiting high sensitivity especially in a high frequency region of GHz band level. Therefore, it is possible to provide a highly sensitive magnetic field sensor and magnetic field sensing system that can be easily used at various operating magnetic field points including a low magnetic field region.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance and a layer structure of a magnetic field sensor according to a first embodiment of the present invention.

FIG. 2 is a graph showing characteristics of the magnetic field sensor according to the first embodiment.

FIG. 3 is a characteristic graph of the magnetic field sensor of the first embodiment, similarly.

FIG. 4 is a graph showing characteristics of a magnetic field sensor according to a second embodiment of the present invention.

FIG. 5 is a characteristic graph of the magnetic field sensor according to the second embodiment.

FIG. 6 is a graph showing characteristics of a magnetic field sensor according to a third embodiment of the present invention.

FIG. 7 is a graph showing characteristics of a magnetic field sensor according to a fourth embodiment of the present invention.

FIG. 8 is a characteristic graph of the magnetic field sensor of the fourth embodiment.

9 (a) and 9 (b) show a magnetic field sensor as a fifth embodiment of the present invention, and FIG. 9 (a) is a perspective view showing the appearance and layer structure of the magnetic field sensor. FIG. 6B is a perspective view showing an appearance and a layer structure as a modified example of the magnetic field sensor.

FIG. 10 is an explanatory diagram showing an outline of the configuration and size of a conventional magnetic field sensor.

FIG. 11 is an explanatory diagram showing the configuration and size of a conventional magnetic field sensor.

FIG. 12 is a graph showing magnetic field characteristics in a high frequency region by a conventional magnetic field sensor.

FIG. 13 is a graph showing measured values and theoretical values of magnetic field characteristics of a conventional magnetic field sensor.

[Explanation of symbols]

1 ... Substrate (glass substrate), 2 ... Ground conductor, 3a, 3b ... Electrode (application electrode), 4a, 4b ... Electrode (output electrode), 5a, 5b ... Conductor electrode pad (Cu conductor thin film), 6 ... Magnetic strip (Magnetic thin film: stripe pattern), 7 ... Conductor electrode pad (non-magnetic conductor electrode pad), 7a, 7b ... Conductor electrode pad (electrode pad portion), 10 ... Magnetic thin film.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Kazuhiro Ouchi Inventor Kazuhiro Ouchi 4-21 Sunaya, Aya, Akita-shi, Akita Prefectural Institute of Advanced Technology (72) Masahiro Yamaguchi 2 Katahira, Aoba-ku, Sendai, Miyagi 1-1-1, Tohoku University Institute of Electrical Communication (72) Inventor Kenichi Arai 2-1-1, Katahira, Aoba-ku, Sendai-shi, Miyagi Prefecture In-house Institute of Electrical Communication (72) Tohoku University Hiroshi Shimada Aoba-ku, Sendai-shi, Miyagi Prefecture 2-1-1 Katahira, Institute of Scientific Measurement, Tohoku University (56) Reference JP-A-9-113590 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 33/02- 33/10 H01L 43/00

Claims (7)

(57) [Claims] 1. A magnetic field sensor comprising a thin film magneto-impedance effect element using a magnetic thin film among magnetic impedance elements as a magnetic field sensor using the magneto-impedance effect, when a current frequency to be conducted is 1 GHz or more, On the other hand, the size of the magnetic sensing portion magnetic body in the direction substantially perpendicular to the magnetic field sensing direction is made small so that the most remarkable magnetic field strength of the magnetic resonance of the magnetic sensing portion magnetic material is lower than the resonance magnetic field strength Hdc obtained by the following equation. A magnetic field sensor comprising: Hdc = (μ0 · ω0 ² ) / (γ ² · Ms) + Hk where ωO is the resonance angular frequency (carrier angular frequency), γ is the gyromagnetic constant, Ms is the saturation magnetization, Hk is the anisotropic magnetic field, μ
0 is the magnetic permeability in vacuum. 2. The magnetic field sensor according to claim 1, wherein the magnetic body of the magnetic sensing section is made of a soft magnetic material. 3. A magnetic field sensor comprising a thin-film magneto-impedance effect element, wherein a hard magnetic material causes a change in impedance with respect to a magnetic field, which reflects a change in magnetization of a magnetic body of a magnetically sensitive portion, when a frequency of a current to be applied is 1 GHz or higher. Alternatively, a magnetic field sensor characterized in that a semi-hard magnetic material is used as the magnetic body of the magnetic sensing section. 4. A magnetic field sensor comprising a thin film magneto-impedance effect element, wherein a resonance magnetic field region in a magnetically sensitive portion in which a magnetic thin film that changes magnetization due to an external magnetic field is overlapped with a magnetic field region that changes magnetization. Or a part having a magnetic thin film made of a hard magnetic material having a coercive force substantially the same as the resonance magnetic field region. A magnetic field sensor, characterized in that it is configured in any one of a form using an element. 5. The magnetic body of the magnetic sensing part is characterized in that a plurality of magnetic thin films are laminated with a non-magnetic thin film interposed therebetween.
The magnetic field sensor according to claim 1 . 6. The magnetic body of the magnetic sensing part is composed of a single-layer magnetic thin film without a non-magnetic thin film interposed therebetween.
The magnetic field sensor according to claim 1 . 7. The magnetic material of the magnetic sensing part is NiFe or NiF.
4. A magnetic thin film formed of either a multilayer film of e and Cu, a multilayer film of NiFe and Ta, or a multilayer film of NiFe, Cu and Ta. Magnetic field sensor according to.