JP3494947B2 - MI element control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an MI element, and more particularly to a control device for a magneto-impedance element capable of obtaining a detected magnetic field over a wide range with high sensitivity.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a magnetic sensor that is small in size, low in cost, high in sensitivity and fast in response. Along with that, MI that can detect a weak external magnetic field with high sensitivity
Elements are needed. In addition, there is an increasing demand for high-sensitivity sensors that can be used for nondestructive inspection and bill inspection. Further, there is an increasing demand for a current sensor having high sensitivity and capable of sensing over a wide detection magnetic field as a current sensor for automobiles.

Here, the MI effect will be briefly described. The MI effect is an electromagnetic phenomenon in which, when a high-frequency current of several MHz or more or a pulse current that causes a skin effect on a high-permeability magnetic material is applied, the magnitude of its impedance changes greatly due to an external magnetic field. . A highly sensitive MI element utilizing this phenomenon was proposed by Professor Mohri of Nagoya University in 1993. The MI element utilizing this MI effect is of the amorphous magnetic wire type shown below. When a high frequency current of MHz order is passed through an amorphous magnetic wire of FeCoSiB, not only the amplitude of the induced voltage but also the wire end Shows a significant change due to the external magnetic field Hex in the wire length direction. This is because Hex changes not only the inductance inside the wire but also the ohmic resistance due to the skin effect. This MI effect also appears remarkably in a sample with a small size of several tens of μm in diameter and 1 to 2 mm long when an amorphous wire of zero magnetostriction or negative magnetostriction is used, and an excitation or detection coil is completely unnecessary. Further, the MI effect does not require a circuit for canceling the ohmic voltage, so that the sensor structure can be simplified and the exciting frequency can be up to several hundred MHz, so that a high frequency device can be formed.

As a characteristic thereof, since a magnetic flux in the circumferential direction (closed magnetic circuit) is changed by energization, there is no demagnetizing field due to excitation, the head is not only micro-sized, but also magnetic flux due to excitation is not generated outside. No coil for excitation and detection is required, and there is no problem of stray capacitance in high frequency excitation. It is possible to suppress the characteristic change of the magnetic wire due to the temperature change. Since it has advantages such as the above and high detection sensitivity, it is expected to be applied to a magnetic head or a high-precision magnetic head for a rotary encoder of an HDD or FDD spindle motor.

Further, in order to reduce the size and weight of the MI element, the MI element is formed of a thin magnetic material thin film and a further improved type of soft magnetic material thin film such as a CoFeB film. An MI element with a directional film has also been proposed.
In order to configure the magnetic field sensor with the MI element, the MI effect is symmetrical with respect to the positive and negative of the external magnetic field, and therefore it is necessary to use the DC bias magnetic field of the coil or the permanent magnet to make the characteristics asymmetric. In particular, a magnetic thin film MI element generally has a magnetic field detection sensitivity of 1/3 to 1 as compared with an amorphous wire.
Since it is as low as / 4, power consumption increases when a DC bias magnetic field is generated by a coil current. Further, there is a problem that the element becomes large by winding a coil or disposing a permanent magnet.

The latter cross-type magnetic thin film MI element is a cross-type magnetic anisotropic film MI element having a magnetic anisotropy that intersects by utilizing the easy axis of the soft magnetic thin film.
It was possible to obtain an MI effect asymmetric with respect to the positive and negative of the external magnetic field. This made it possible to construct a magnetic field sensor without using a DC bias magnetic field. Low power consumption by not requiring a coil to generate a DC bias magnetic field,
It became possible to miniaturize. In addition, the magnitude of the magnetic field that maximizes the magnitude of the impedance is ⅕ of that of the magnetic thin film MI element, so it can be expected to manufacture a sensor with higher sensitivity.

However, although the above-mentioned MI element has high sensitivity, linearity cannot be obtained over a wide range of detection magnetic field, and it is necessary to improve its control device.
FIG. 17 shows a block diagram of a conventional controller 30 for an MI element 31. A bias magnetic field is applied by the DC bias coil 32, amplified by an amplifier 35 via a detection circuit 34, a negative feedback resistor 37, and a wound negative feedback bias coil 33.
Negative feedback is applied via to obtain an output 36. The external magnetic field H _ex [Oe] -output voltage E _OUT [V] has linearity as shown in FIG.

As described above, in the conventional control device 30 for the MI element 31, although the MI characteristic of the MI element 31 is symmetrical and highly sensitive, the MI characteristic is symmetrical and the peak of the change rate of each impedance is obtained. It is ± several [Oe], and it is asymmetrical by applying a bias magnetic field to shift it. Since one of the peaks of the asymmetrical characteristic is around +3 [Oe], the linear region is narrowed to ± 3 [Oe]. Even with the conventional control device 30 for the MI element 31, the linearity can be obtained only in the range of ± 3 [Oe] as shown in FIG. Moreover, output detection was impossible in the region where the output was saturated at ± 4 [Oe] and ± 5 [Oe].

The applicant of the present invention detects a wide range (infinity) of high sensitivity without saturating the output of any MI element having any MI characteristic by using a new MI element controller. It has become possible to provide a control device for an MI element capable of detecting a magnetic field over a magnetic field.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems as a control device for MI elements, the present invention is directed to a magnetic wire MI.
As a control device for an element, a thin-film MI element, and a laminated thin-film crossing MI element, there is provided an MI element control device capable of obtaining linearity over a wide range of detected magnetic fields with high sensitivity. Further, the present invention provides a control device that obtains a similar effect without requiring a bias coil.

[0011]

In the present application, in a control device for a magnetic impedance element (MI element), the MI
Negative feedback bias coil for canceling magnetic flux and DC
A bias coil is wound and connected to a negative feedback bias coil from both ends of the MI element via a detection circuit by an external magnetic field Hex [Oe], and the detection circuit outputs the voltage V changed from both ends of the MI element. When reading, a current that becomes I _I is generated and supplied to the negative feedback bias coil wound around the MI element, and H _{I at} which the total magnetic field becomes zero is generated.
_I is always balanced, and in the DC bias coil, it may be wound to shift the operating point at which the maximum sensitivity is obtained, and the end of the negative feedback bias coil is connected to one end of the output detection element. However, it is an application of a control device characterized in that the output is detected at both ends of the output detection element. Further, in the control device for the magneto-impedance element, the generated current is supplied to the negative feedback bias coil in advance from both ends of the MI element through the detection circuit and the initial offset circuit, and ΔH [Oe ] The operating point at which the maximum sensitivity is shifted is shifted by the generated external magnetic field Hex,
The detector circuit reads the changed voltage V from both ends of the MI element, generates a current I _I , connects it to a negative feedback bias coil wound around the MI element, and supplies it, so that the total magnetic field becomes zero. the H _I is generated, and always balance the I _I, it is connected to one end of the output detection element the end of the negative feedback bias coil, and outputs the HI as an output at both ends of the output detecting device It is also an application of a control device characterized by.

According to a first aspect of the present invention, in a control device for a magnetic impedance element (MI element), the MI element is a cross type magnetic anisotropic thin film MI element, and the external magnetic field Hex [O
e], the negative feedback bias coil is connected from both ends of the MI element through the detection circuit, and the detection circuit
The changed voltage V is read from both ends of the element, a current that becomes I _I is generated and supplied to the negative feedback bias coil wound around the MI element, and H _{I at} which the total magnetic field becomes zero is generated, and I _I It is always balanced, and the terminal of the negative feedback bias coil is connected to one end of the output detecting element, and the output is detected at both ends of the output detecting element.
By providing a control device for the I element, the external magnetic field Hex
The problem is solved by providing a control device that does not depend on the relationship between [Oe] and the rate of change (%) of impedance, and that detects the output regardless of the saturated region. In the MI element, the voltage across the MI element which changes according to an external magnetic field is read by the detection circuit to generate a current, which is supplied to the negative feedback bias coil, so that the external magnetic fields Hex and H _I
Is an application of the control device characterized in that it is possible to detect linearly even in a region where the voltage change is saturated by generating a magnetic field in which the total magnetic field becomes zero and balancing the current. In claim 2, MI characteristics of the MI element are asymmetrical,
The measurement can be performed even in the saturation region.
The problem is solved by providing the described MI element control device.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Here, an embodiment will be described by using an MI element using a magnetic thin film.
The same effect can be obtained with the I element. Embodiments of the present invention will be described with reference to the drawings. As a first embodiment, FIG.
FIG. 4 is a diagram showing a configuration of a thin film MI element using a magnetic impedance (hereinafter MI) effect according to the present invention. Figure 2a
Is MI when the external magnetic field Hex [Oe] is applied from the positive side and when the external magnetic field Hex [Oe] is applied from the negative side.
It is a figure which shows MI characteristic of an element. FIG. 2b is a diagram showing MI characteristics of MI elements having different MI characteristics. In FIG. 2B, the MI characteristic is represented only by the impedance change rate when the external magnetic field Hex [Oe] is applied from the positive side for simplification of description. FIG. 3 is a configuration diagram of the magnetic thin film MI element when a bias magnetic field _Hb is applied. FIG. 4a is a characteristic diagram of the thin film MI element when a bias magnetic field _Hb is applied. FIG. 4b shows different M
It is a characteristic view of a thin film MI element when a bias magnetic field _Hb is applied to an MI element having I characteristics. FIG. 5 is a diagram schematically showing a control device for a thin film MI element using the MI element according to the present invention. FIG. 6 is a schematic block diagram of an electronic circuit of the MI element control device according to the present invention.
FIG. 7 shows the relationship between the external magnetic field H _ex [Oe] and the output voltage E _OUT [V] of the MI device controller.

A thin film MI element 1 is shown in FIG. 1, and a substrate is omitted in the drawing. The thin film MI element 1 is
Al ₂ O ₃ ceramic wafers, Si wafers, glass wafers, and other non-magnetic substrates with enhanced surface smoothness, plated films of CoFeNi, NiFe, etc., which are soft magnetic thin films, or FeCoSiB, CoZrNb, FeSiB, CoSi
The magnetic characteristics can be improved by forming a soft magnetic thin film such as an amorphous sputtered film of B or the like, a NiFe sputtered film, etc., and then performing heat treatment in a rotating magnetic field and a static magnetic field. Further, a non-magnetic substrate may be used even if the surface smoothness is not improved.

A thin-film MI element 1 which obtains a skin effect by applying a time-varying current is rebonded to both ends by aluminum wire bonding, electrodes made of Au wires, or direct soldering.
Dozens of [MHz] (10-40 [MH
z]) is applied to both ends of the high frequency current. At this time,
The relationship (MI characteristic) between the external magnetic field Hex [Oe] and the impedance change rate (%) is shown in FIG. 2a. In FIG. 3, DC
A bias magnetic field H _b [Oe] is applied in order to shift the operating point where the bias coil 2 is wound N times and the maximum sensitivity is obtained. The MI characteristic at this time is shown in FIG. 4a. Referring to FIG. 5, at this time, the DC bias coil 2 wound around the thin film MI element 1 is insulation-coated, or the outer peripheral portion of the coil is insulation-coated, and the negative feedback bias coil 3 is the same as the DC bias coil. It is wound N times. Next, an external magnetic field is applied to H _ex
When [Oe] is set, the voltage of the thin film MI element 1 is changed by H _ex [Oe]. From both ends of the MI element 1 described above, the detection circuit 4
The voltage V changed by is read, a current that becomes I ₁ is generated and supplied to the negative feedback bias coil 3 wound around the thin film MI element 1, H ₁ that makes the total magnetic field zero is generated, and I ₁ is Always equilibrate. This H ₁ is the detecting element 5
The output is measured via (resistor R ₁ ). The DC bias coil 2 and the negative feedback bias coil 3 are disclosed in the main part of the MI element 1 in this figure. Further, an example of the electronic circuit at this time is schematically shown in a block diagram in FIG.

Since the total magnetic field of the external magnetic fields H _ex and H ₁ becomes zero, the magnetic field in the region where the voltage change of the thin film MI element 1 with respect to the external magnetic field H _ex is saturated can be detected linearly. Therefore, although the magnetic field could be detected only in a narrow magnetic field range of ± several [Oe] as shown in FIG. 4a, as shown in FIG. 7, it can be detected over a wide range (physically infinite) of the external magnetic field H _ex . Thus, it is possible to obtain the magnetic field balanced control device 10 that obtains a linear output voltage. Next, the different MI shown in FIG.
The control device was verified with an MI element having characteristics a and MI characteristics b. Since the MI characteristic of the MI element varies depending on the element, the MI element having such different characteristics was used for the experiment. FIG. 4b is a diagram in which the bias magnetic field H _b [Oe] is applied to the MI characteristics a and b of FIG. 2b and shifted. Although detailed description has not been given above, both the MI characteristic a indicated by the solid line and the MI characteristic b indicated by the dotted line are shown in FIG.
It was verified that the control device 10 is a magnetic field balanced type that obtains a linear output voltage over a very wide range (physically infinite) of the external magnetic field H _ex as shown in FIG.

Next, as a second embodiment of the present invention, a control device for a thin film MI element will be described with reference to the drawings. Figure 8
FIG. 6 is a diagram showing a configuration of a thin-film MI element using the MI effect according to the present invention. FIG. 9a shows the external magnetic field H from the positive side.
External magnetic field Hex when ex [Oe] is applied and from the negative side
It is a figure which shows MI characteristic of the MI element when [Oe] is applied. FIG. 9b is a diagram showing MI characteristics c and d of MI elements having different MI characteristics. In FIG. 9b, the MI characteristic is represented only by the impedance change rate when the external magnetic field Hex [Oe] is applied from the positive side for the sake of simplicity. FIG. 10 a shows an initial offset circuit 7
Shows a characteristic diagram in which an electric current is made to flow in the negative feedback bias coil 3 in advance and ΔH [Oe] is shifted to make the MI characteristic asymmetric. FIG. 10b is a characteristic diagram in which the MI characteristics are made asymmetric by previously passing a current through the negative feedback bias coil 3 in the initial offset circuit 7 to MI elements having different MI characteristics c and d. FIG. 11 shows the MI according to the present invention.
It is the figure which showed typically the control apparatus of the thin film MI element using an element. FIG. 12 is a block diagram showing an example of an electronic circuit of the MI device control apparatus according to the present invention.
Further, the external magnetic field H _ex [Oe] − of the control device 10 for the MI element 1
Since the diagram showing the relationship of the output voltage E _OUT [V] is the same as that of the first embodiment, it will be described with reference to FIG. 7.

FIG. 11 shows a thin film M using the MI element 1 according to the present invention for applying a time-varying current to obtain a skin effect.
It is the figure which showed the structure of the control apparatus 10 of I element 1 typically, and is a principle figure of the external magnetic field detection by MI element in detail. When the MI element 1 whose voltage changes symmetrically with respect to the direction of the magnetic field as shown in FIG. 9a is used, the current generated by the initial offset circuit 7 is supplied to the negative feedback bias coil in advance, as shown in FIG. 10a. The MI characteristic to Δ
Only H [Oe] is shifted to keep it asymmetric. If the external magnetic field generated is _Hex [Oe], then MIx is generated by _Hex [Oe].
The voltage of element 1 changes. The voltage V changed by the detection circuit 4 is read from both ends of the MI element 1 described above, a current that becomes I ₁ is generated and supplied to the negative feedback bias coil 3 wound around the MI element 1, and the total magnetic field becomes zero. H ₁ is generated and I ₁ is always in equilibrium. This H ₁ is measured as an output through the output detection element 5 (resistor R ₁ ). Further, FIG. 12 is a schematic block diagram showing an example of the electronic circuit at this time.

Therefore, in the prior art, as shown in FIG.
Although the magnetic field could be detected only in the narrow magnetic field range of e],
As shown in FIG. 7, it was possible to obtain the magnetic field balanced control device 10 that obtains a linear output voltage over a wide range of the external magnetic field H _ex [Oe]. Further, it is possible to obtain an asymmetric characteristic as shown in FIG. 10a without requiring a DC bias coil, and to read the voltage V changed by the detection circuit 7 from both ends of the thin film MI element 1 only by the negative feedback bias coil 3.
A current that becomes I ₁ is generated and supplied to the negative feedback bias coil 3 wound around the thin film MI element 1, H ₁ that makes the total magnetic field zero is generated, and I ₁ is always balanced. And the process is not complicated. Next, an MI having different MI characteristics a and b shown in FIG.
The element was used to verify the control device 10. Although detailed description has not been given above, both the MI characteristic c indicated by the solid line and the MI characteristic d indicated by the dotted line are asymmetrical by causing a current to flow in advance in the initial offset circuit 7 and shifting by ΔH [Oe] as shown in FIG. 10b. It has a characteristic. As described above, even with different MI characteristics c and d, as shown in FIG. 7, a linear output voltage E _OUT [V] is generated over the same wide range (physically infinite) of the external magnetic field H _ex [Oe]. It was verified that the controller 10 is a magnetic field balanced type controller that obtains

Next, a third embodiment according to the present invention will be described with reference to the drawings. FIG. 13 is a diagram showing the structure of a crossed magnetic thin film MI element 21 laminated so as to cross the directions of magnetic anisotropy of the soft magnetic thin film according to the present invention. Figure 14a shows
It is a figure which shows the MI characteristic of the cross type magnetic anisotropic thin film MI element 21 when the external magnetic field Hex [Oe] is applied from the plus side and when the external magnetic field Hex [Oe] is applied from the minus side.
FIG. 14b shows MI characteristics e and f of the cross-type magnetic anisotropy thin film MI element with different variations. Figure 14b
Is the external magnetic field Hex from the positive side to simplify the explanation.
It is a figure which shows MI characteristic when [Oe] is applied. Figure 1
FIG. 5 is a diagram schematically showing the structure of a control device for the crossed magnetic anisotropic thin film MI element 21. FIG. 16 is a schematic block diagram showing an electronic circuit of a control device for the crossed magnetic anisotropic thin film MI element 21. Further, the diagram showing the external magnetic field H _ex [Oe] -output voltage E _OUT [V] of the control device for the cross-type magnetic anisotropic thin film MI element 21 is the same as in the first and second embodiments. Now, it will be explained with reference to FIG.

As shown in FIG. 13, a thin film MI element 21 having a structure in which the directions of magnetic anisotropy of a soft magnetic thin film are crossed is a substrate such as an Al ₂ O ₃ ceramic wafer, a Si wafer, or a glass wafer, although not particularly shown. C, which is a soft magnetic thin film on top
Plating film of oFeNi, NiFe, or FeCoS
iB, CoZrNb, FeSiB, CoSiB, and other amorphous sputtered films, and NiFe sputtered films and other soft magnetic thin films are stacked so that the directions of magnetic anisotropy intersect.

In the cross-type thin film MI element 21 which applies a time-varying current to obtain the skin effect, a DC bias or an initial offset circuit is used because its MI characteristic is asymmetrical as shown in FIG. 14a. Not only has the advantage of not being necessary, but its detection sensitivity is also very good. FIG. 15 shows a cross-type magnetic anisotropic thin film MI according to the present invention.
FIG. 3 is a diagram schematically showing the structure of a control device using the element 21, and specifically is a principle diagram for detecting an external magnetic field by the cross magnetic anisotropic thin film MI element 21.

FeCoSiB, CoZrNb, FeSi
B, CoSiB and other amorphous sputtered films, NiFe
The cross-type MI element 21 using the easy axis of magnetization of a laminated soft magnetic thin film using an amorphous thin film of a soft magnetic material such as a sputtered film is not particularly shown, but aluminum wire bonding on both ends, Au wire Connected to the lead wire with an electrode composed of etc. or directly with solder, and dozens of [MH
z] or more, and preferably a high frequency current of 10 to 40 [MHz] is applied to both ends. External magnetic field Hex [O at this time
The relationship between e] and the impedance change rate [%] is shown in FIG. When using the magnetic cross type magnetic anisotropic thin film MI element 21 in which the voltage changes asymmetrically with respect to the direction of the magnetic field as shown in FIG. 14A, the MI characteristic is made asymmetric by a DC bias or an initial offset circuit. No need to leave.

Assuming that the external magnetic field generated is H _ex [Oe], the voltage of the cross-type magnetic anisotropic thin film MI element 21 changes due to H _ex [Oe]. The voltage V changed by the detection circuit 24 is read from both ends of the MI element 1 described above, a current I ₁ is generated and supplied to the negative feedback bias coil 23 wound around the cross magnetic anisotropic thin film MI element 21. H ₁ is generated so that the total magnetic field becomes zero, and I ₁ is always balanced. This H ₁ is measured as an output through the output detection element 25 (resistor R ₁ ). Since the total magnetic fields of the external magnetic fields H _ex and H ₁ become zero, it is possible to linearly detect even a magnetic field in a region where the voltage change with respect to the magnetic field of the cross type MI element 21 is saturated. 16 is a schematic block diagram showing an example of the electronic circuit at this time.
Is.

Therefore, although the magnetic field could be detected only in a narrow magnetic field range of ± several [Oe] as shown in FIG.
It was possible to obtain the magnetic field balanced type control device 20 that obtains a linear output voltage over a wide range of external magnetic field H _ex generated as shown in FIG. Further, the asymmetrical characteristic as shown in FIG. 14A can be obtained without the need for the DC bias coil and the initial offset circuit, and the detection circuit 2 is provided from both ends of the cross MI element 21 only by the negative feedback bias coil 23.
The voltage V changed by 4 is read, a current that becomes I ₁ is generated and supplied to the negative feedback bias coil 23 wound around the MI element 21, H ₁ that makes the total magnetic field zero is generated, and I ₁ is Since it is always in equilibrium, the cost can be reduced and the process is not complicated. Next, FIG.
The control device 20 of the MI element was verified with the cross-type magnetic anisotropic thin film MI element having different MI characteristics e and f shown in b. A detailed explanation is given above, so I will not mention it,
Both the MI characteristic e shown by the solid line and the MI characteristic f shown by the dotted line are asymmetrical. Even in such MI characteristics e and f, as shown in FIG. 7, in the magnetic field balanced type control device 20 which obtains a linear output voltage over the external magnetic field H _ex of the same wide range (physically infinite). I was able to verify that there is. Also, use a coil with insulation coating,
It is self-evident that the element is insulated and wound around the coil. Further, although not particularly shown, stabilizing the characteristics by using an initial offset circuit for the crossed magnetic anisotropic thin film MI element 21 is also included in the present application. in this case,
It is preferable that an electric current is made to flow in advance by the initial offset to shift to the position of maximum sensitivity.

Therefore, although the MI element and its MI characteristics have been verified, the MI element control apparatus according to the present invention always generates a magnetic field that makes the total magnetic field zero, so that the voltage with respect to the external magnetic field H _ex is reduced. It can detect linearly even the magnetic field in the region where the change is saturated. As a result, it is a device that can obtain linearity over a wide range of detection magnetic field (physically infinite) with high sensitivity, and can be achieved without applying a bias magnetic field. Furthermore, the output can be detected without being affected by the variations in the MI characteristics of the MI element.

[0028]

As described above, according to the present invention, what MI
Even a MI element with characteristics has a total magnetic field that is always zero by the control device, and by maintaining an equilibrium state, it is possible to obtain a super-sensitive and wide-range detection magnetic field (physically infinite). You can get linearity across. Furthermore, the same effect can be achieved without applying a bias magnetic field.

[Brief description of drawings]

FIG. 1 is a magnetic thin film MI using the MI effect according to the present invention.
It is a figure showing composition of an element.

FIG. 2a is a diagram showing MI characteristics when an external magnetic field is applied to the magnetic thin film MI element according to the present invention from the positive side and when an external magnetic field is applied from the negative side.

FIG. 2b is a diagram showing MI characteristics of magnetic thin film MI elements having different characteristics according to the present invention.

FIG. 3 shows a configuration diagram of a magnetic thin film MI element when a bias magnetic field H _{b according} to the present invention is applied.

FIG. 4a is a characteristic diagram of a thin film MI element when a bias magnetic field H _b is applied to the magnetic thin film MI element according to the present invention.

FIG. 4b is a characteristic diagram of a thin film MI element when a bias magnetic field H _b is applied to magnetic thin film MI elements having different MI characteristics according to the present invention.

FIG. 5 is a schematic view showing a control device of a magnetic thin film MI element using a soft magnetic thin film according to a first embodiment of the present invention.

FIG. 6 is a diagram showing an example of an electronic circuit of a controller for a magnetic thin film MI element using a soft magnetic thin film according to a first embodiment of the present invention.

FIG. 7 shows an external magnetic field H _ex [O of the MI device control apparatus of the present invention.
It is a graph which shows the relationship of e] -output voltage _EOUT [V].

FIG. 8 is a diagram showing a configuration of a magnetic thin film MI element using the MI effect of a second embodiment according to the present invention.

FIG. 9a is a diagram showing MI characteristics when an external magnetic field is applied to the magnetic thin film MI element according to the second embodiment of the present invention from the positive side and when an external magnetic field is applied from the negative side.

FIG. 9b is a diagram showing MI characteristics of magnetic thin film MI elements having different characteristics according to the second embodiment of the present invention.

FIG. 10a is a characteristic diagram of a thin film MI element when a bias magnetic field H _Δ is applied to the magnetic thin film MI element according to the second embodiment of the present invention by an initial offset circuit.

FIG. 10b is a thin film MI when a bias magnetic field H _Δ is applied to the magnetic thin film MI device according to the second embodiment of the present invention having different MI characteristics by an initial offset.
It is a characteristic view of an element.

FIG. 11 is a diagram schematically showing a control device of a magnetic thin film MI element using a soft magnetic thin film according to a second embodiment of the present invention.

FIG. 12 is a diagram showing an example of an electronic circuit of a controller for a magnetic thin film MI element using a soft magnetic thin film according to a second embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of a cross-type magnetic thin film MI element in which a soft magnetic thin film according to a third embodiment of the present invention is laminated so as to cross the directions of magnetic anisotropy.

FIG. 14a is a diagram showing a case where an external magnetic field is applied from the positive side to a cross-type magnetic thin film MI element laminated so as to cross the directions of magnetic anisotropy of a soft magnetic thin film according to a third embodiment of the present invention; M when an external magnetic field is applied from the negative side
It is a figure which shows I characteristic.

FIG. 14b is a diagram showing MI characteristics of a cross-type magnetic thin film MI element having different MI characteristics according to the third embodiment of the present invention.

FIG. 15 is a cross-type magnetic thin film M in which the magnetic anisotropy of the soft magnetic thin film of the third embodiment according to the present invention is crossed and laminated.
It is the figure which showed the control apparatus of I element typically.

FIG. 16 shows an example of an electronic circuit of a controller for a crossed magnetic thin film MI element in which a soft magnetic thin film according to a third embodiment of the present invention is laminated so as to cross the directions of magnetic anisotropy. Is a figure

FIG. 17 is a block diagram showing an electronic circuit of a conventional MI element control device.

FIG. 18 shows an external magnetic field H generated by a conventional MI element control device.
It is a figure which shows _ex -output (voltage) _EOUT characteristic.

[Explanation of symbols]

1, 21, 31 ... MI element 2, 32 ... DC bias coil 3, 23, 33 ... Negative feedback bias coil 4, 24, 34 ... Detection circuit 5, 25 ... Output detection element (resistor R ₁ ) 6, 26, 36 ... output 7, ... initial offset circuit 35 ... control device of the amplifier 37 ... negative feedback resistor 10, 20, 30 ... MI element H _b ... bias field H _ex ... external magnetic field I ₁ ... negative feedback current (balanced current) H ₁ ... Equilibrium magnetic field (negative feedback magnetic field) where the total magnetic field with the external magnetic field becomes zero

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Hatsumi 1-3-1 Eda Nishi, Aoba-ku, Yokohama-shi, Kanagawa Stanley Electric Co., Ltd. Inside the Yokohama Technology Center (72) Inventor Chiyo Funaoka Aoba-ku, Yokohama-shi, Kanagawa 1-3-1 Edanishi Stanley Electric Co., Ltd. Technical Research Institute (72) Inventor Katsura Tsukada 1-3-1 Edanishi, Aoba-ku, Yokohama, Kanagawa Prefecture Stanley Electric Co., Ltd. Technical Research Institute (72) Hiroyuki Sano 1-3-1 Edanishi, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Stanley Electric Co., Ltd. Technical Research Laboratory (72) Inventor Hiroo Yokoyama 2-9-13 Nakameguro, Meguro-ku, Tokyo Stanley Electric Co., Ltd. (72) Inventor Kimihiro Iritono 1-3-1 Edanishi, Aoba-ku, Yokohama-shi, Kanagawa Stanley Electric Co., Ltd. Technical Research Institute (56) References JP-A-2000-55996 (JP, A) JP-A-2000-30921 (JP, A) JP-A-2001-91608 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 33 / 02-33/10 H01L 43/00

Claims (2)

(57) [Claims] 1. A magneto-impedance element (MI element) control device, wherein the MI element is a cross-type magnetic anisotropic thin film MI element, and is controlled by an external magnetic field Hex [Oe].
Both ends of the MI element are connected to a negative feedback bias coil through a detection circuit, and the detection circuit reads the changed voltage V from both ends of the MI element and generates a current I _I to cause the MI element to have a current. It is supplied to the wound negative feedback bias coil to generate H _I that makes the total magnetic field zero and II is always balanced, and the end of the negative feedback bias coil is connected to one end of the output detection element, An MI element control device, wherein an output is detected at both ends of the output detection element. 2. The MI element control device according to claim 1, wherein the MI element has an asymmetric MI characteristic and can be measured even in a saturation region thereof.