JP4418986B2 - Magnetic field detection element and magnetic field detection method using the same - Google Patents

Description

  The present invention relates to a magnetic impedance type magnetic field detection element having step response characteristics and a magnetic field detection method using the same.

  With the recent rapid development of information equipment and measurement / control equipment, there is an increasing demand for small, low-cost, high-sensitivity, high-speed response magnetic sensors. For example, in a hard disk device that is an external storage device of a computer, performance is increasing from a bulk type induction magnetic head to a thin film magnetic head and a magnetoresistive (MR) head. However, the rotary encoder, which is a rotation sensor of the motor, has a large number of magnetic rings in the magnet ring, and instead of the conventionally used magnetoresistive effect (MR) sensor, a magnetic sensor that can detect a weak surface magnetic flux with high sensitivity is required. It has become to. There is also a growing demand for high-sensitivity magnetic sensors that can be used for nondestructive inspection, banknote inspection, and biomagnetic field measurement.

  Typical magnetic sensing elements currently used include inductive reproducing magnetic heads, magnetoresistive effect (MR) elements, fluxgate sensors, Hall elements, and the like. Recently, a highly sensitive magnetic sensor using the magnetic impedance effect of an amorphous wire has been proposed (see Patent Documents 1 to 3 below), and a highly sensitive magnetic sensor using the magnetic impedance effect of a magnetic thin film has also been proposed. (See Patent Document 4 and Non-Patent Document 1 below).

  As described in Patent Documents 1 to 3 below, magneto-impedance elements have been proposed, and a significant improvement in magnetic field sensitivity has been realized. This magneto-impedance element has a basic principle of detecting only a voltage with respect to a time change of a circumferential magnetic flux generated by applying a time-varying current to a magnetic wire as a change caused by an externally applied magnetic field. As this magnetic wire, an amorphous wire having a diameter of about 30 μm with zero magnetostriction such as FeCoSiB (wire subjected to tension annealing after drawing) is used. Then, the amplitude of the voltage of the wire changes with a high sensitivity of about 100% / Oe which is 1000 times or more that of the MR element.

  The thin film type magneto-impedance elements described in the following Patent Documents 5 to 6 are formed by forming a thin film structure containing a magnetic material on a substrate by sputtering or plating, and applying a high-frequency current to the magneto-impedance effect. Have gained.

By the way, in a rotary encoder or the like for detecting the number of rotations of a motor, a method in which a magnetic field change is detected by a magnetic sensor, converted into a pulse signal through a threshold detection circuit, and then detected by a pulse counting circuit. is there.
JP-A-6-176930 JP 7-181239 A JP 7-333305 A JP-A-8-75835 JP-A-8-320362 JP-A-11-109006 JP 2003-130932 A JP 2003-282959 A Journal of Japan Society of Applied Magnetics vol. 20,553 (1996)

  However, the above-described inductive reproducing magnetic head requires a coil winding, so that the magnetic head itself becomes large, and if the magnetic head and the medium have a low relative speed when the size is reduced, the detection sensitivity is significantly lowered. is there.

  On the other hand, a magnetoresistive effect (MR) element using a ferromagnetic film detects a magnetic flux itself, not a change in magnetic flux with time, and the magnetic head has been miniaturized. However, the rate of change in electrical resistance of current MR elements is about 2%, and even in MR elements using spin valve elements, the rate of change in electrical resistance is as small as 6% or less, and a resistance change of several percent is obtained. The required external magnetic field is as large as 1600 A / m or more. Therefore, the magnetoresistive sensitivity is a low sensitivity of 0.001% / (A / m) or less. Recently, a giant magnetoresistance effect (GMR) using an artificial lattice having a magnetoresistance change rate of several tens of percent has been found. However, in order to obtain a resistance change of several tens of percent, an external magnetic field of tens of thousands of A / m is required, and it has not been put into practical use as a magnetic sensor.

  In addition, the flux gate sensor, which is another conventional high-sensitivity magnetic sensor, measures magnetism by utilizing the fact that the symmetric BH characteristics of a high-permeability magnetic core such as ferrite and permalloy are changed by an external magnetic field. It has high resolution and high directivity of ± 1 °. However, in order to increase detection sensitivity, a large magnetic core is required, and it is difficult to reduce the overall size of the sensor, and power consumption is high.

  Furthermore, in a magnetic field sensor using a Hall element, when a magnetic field is applied perpendicularly to the surface through which current flows, an electric field is generated in a direction perpendicular to both the current and applied magnetic fields, and an electromotive force is induced in the Hall element. It is a sensor using Although the Hall element is advantageous in terms of cost, the magnetic field detection sensitivity is low, and since it is made of a semiconductor such as Si or GaAs, electrons are scattered by scattering due to thermal vibration of the lattice in the semiconductor due to temperature change, or Since the mobility of holes changes, the temperature characteristic of magnetic field sensitivity is poor.

  The present invention provides an element having a function of detecting a threshold magnetic field as a characteristic of the element itself in a magneto-impedance element, which is a highly sensitive magnetic field detection element, thereby increasing a magnetic field change counter and a threshold magnetic field detector. In addition to increasing the sensitivity, it is possible to omit a threshold detection circuit that has been necessary in the past, and to provide a detection circuit with high sensitivity and low cost.

  That is, in view of the above situation, an object of the present invention is to provide a highly sensitive magnetic field detection element that generates a step phenomenon in which impedance changes abruptly in a threshold magnetic field, and a magnetic field detection method using the same.

In order to achieve the above object, the present invention provides
[1] In a magnetic field detecting element for supplying an alternating current from a high-frequency power source to an element having a magnetic thin film structure and detecting a change in electrical characteristics in accordance with an external magnetic field, the magnetic anisotropy of the magnetic thin film is easily By inducing the axis in a direction inclined from a direction perpendicular to the direction of the detection magnetic field and giving a tilt angle to the domain wall of the stripe-like domain structure resulting from this, a step phenomenon in which the impedance rapidly changes in the threshold magnetic field is generated. The magnetic field detection element configured as described above has a structure in which an energization direction of an alternating current supplied from the high-frequency power supply is matched with the detection magnetic field direction, and the direction of the easy axis is a direction that does not coincide with the energization direction. for the domain wall formed by the average less than the inclination angle of 67 ° or more 74 ° of the domain wall, below 20μm size range 10μm or more elements, thickness 2.4 And characterized in that m or more 3.1μm or less.

[2] In a magnetic field detecting element that is composed of a magnetic thin film and a conductor, supplies a high-frequency alternating current to the conductor, and detects a change in electrical characteristics in accordance with an external magnetic field, the magnetic thin film in the magnetic thin film By inducing an easy axis of direction in a direction inclined from a direction perpendicular to the direction of the detected magnetic field, and by giving an inclination angle to the domain wall of the stripe-like domain structure resulting from this, an electrical characteristic or a magnetic characteristic in the threshold magnetic field A step phenomenon in which the magnetic thin film having this characteristic and the conductor are electrically or magnetically coupled to each other and the impedance is rapidly changed by the external magnetic field. A magnetic field detection element that is generated, wherein an average inclination angle of a magnetic wall of the magnetic thin film is 67 ° or more and 74 ° with respect to a direction perpendicular to the detection magnetic field direction . The element dimensions are a width of 10 μm to 20 μm and a film thickness of 2.4 μm to 3.1 μm.

  [3] In the magnetic field detection element according to the above [2], the magnetic thin film having a magnetic property that changes in a step-like manner is disposed on one or both of the upper and lower sides of the conductor.

  [4] In the magnetic field detection element according to [3], the conductor combined with the magnetic thin film has a zigzag shape.

  [5] A magnetic field detection method, which is necessary for causing the magnetic field detection element according to any one of [1] to [4] to generate a step change in impedance according to the strength of the external magnetic field. By applying a bias magnetic field and using two step-like changes generated by different bias magnetic fields whose element impedances change in the same direction, an external magnetic field is calculated by an arithmetic average of these bias magnetic fields.

  According to the present invention, the following effects can be achieved.

  (A) With respect to a magnetic sensing element using the magneto-impedance effect, an easy axis of magnetic anisotropy is induced in a direction inclined from a direction perpendicular to the energizing direction as the detection magnetic field direction, and the inclination angle of the domain wall resulting from this is induced. A magnetic field detection element that produces a step phenomenon in which the impedance changes abruptly in a threshold magnetic field, which is produced by controlling the above, is realized. In particular, since the threshold magnetic field can be detected by the element itself without combining electric circuits, it is possible to simultaneously realize downsizing of the entire circuit and high sensitivity of the threshold magnetic field detection device.

  The magnetic field detection element of the present invention is effective when frequency frequency of a varying magnetic field is detected or presence / absence of a magnetic field exceeding a threshold magnetic field is detected.

  (B) Since it is a thin wire element, the element impedance can be increased and the drive power can be reduced. It is also effective for downsizing.

  (C) Since the element itself has a threshold detection function, the electric circuit can be simplified, and a low-cost and small-sized magnetic sensor module can be realized. For example, the present invention can be applied to a motor rotation number measurement device, a magnetic encoder, and an overcurrent detection device. Thereby, downsizing and low power consumption are possible.

The present invention provides a magnetic field detecting element for detecting a change in electrical characteristics in response to an external magnetic field by supplying an alternating current from a high-frequency power source to an element having a magnetic thin film structure. By inducing the easy axis in a direction inclined from the direction perpendicular to the direction of the detected magnetic field, and by giving an inclination angle to the domain wall of the striped domain structure, a step phenomenon in which the impedance rapidly changes in the threshold magnetic field is generated. A magnetic field detection element configured to have a structure in which an energization direction of an alternating current supplied from the high-frequency power supply is matched with a direction of the detection magnetic field, and the direction of the easy axis does not coincide with the energization direction; for the domain wall formed by the average less than the inclination angle of 67 ° or more 74 ° of the domain wall, below 20μm size range 10μm or more elements, thickness 2 4 is μm more than 3.1μm or less.

  Hereinafter, embodiments of the present invention will be described in detail.

  First, the principle of the present invention will be described below.

  Here, the energizing direction of the high-frequency current in the sensor element is the longitudinal direction, and the direction orthogonal thereto is the width direction. The magnetic material is excited by a high-frequency current that is energized, and what is important at this time is a high-frequency magnetic permeability in the width direction, which is the magnetic field direction in which the energizing current is generated. The phenomenon in which the high-frequency permeability in the thin film width direction is changed by an external magnetic field is called a bias magnetization phenomenon. In this case, the impedance of the sensor element changes greatly according to the external magnetic field. Regardless of the shape of the wire, ribbon, thin film and element, the conventional magneto-impedance element uses the characteristic that this characteristic changes continuously and symmetrically with the increase / decrease of the external magnetic field. It was.

  According to the theoretical analysis of the bias magnetization of the thin film magnetic material, in the magnetic material whose magnetization is constrained in the in-plane direction of the thin film due to the demagnetizing field, when an easy axis of magnetization inclined from the width direction to the in-plane direction is given A metastable state is generated in the magnetic energy of the thin film magnetic body due to the strength of the longitudinal external magnetic field. The stable state of magnetic energy is related to the high-frequency permeability of the magnetic material, and there is a large gap between the metastable state and the ground state in the value of the high-frequency permeability for the magnetic field generated by the current flowing in the longitudinal direction. There is.

  In the present invention, when a thin film magnetic body is finely processed to form a small magneto-impedance sensor having a stripe-like magnetic domain structure, the direction of the easy magnetization axis is formed in a direction inclined from the width direction, which is theoretically predicted. In addition, an element having a characteristic of transition from a stripe-like magnetic domain structure in which a metastable state and a ground state of magnetic energy are mixed to a single domain structure in a ground state by applying an external magnetic field has been realized.

As specific element characteristics, when the external magnetic field in the longitudinal direction is increased from 0, the impedance changes small up to the element-specific threshold magnetic field _Hth, but when the external magnetic field exceeds _Hth , the impedance rapidly increases in a stepped manner. To do. This phenomenon can be explained according to the above principle as follows.

When the external magnetic field is equal to or less than the threshold magnetic field H _th , all of the magnetic energy in which the metastable state and the ground state are mixed is transferred to the ground state when the external magnetic field exceeds the threshold magnetic field H _th . At this time, the high-frequency magnetic permeability in the element width direction also changes suddenly with the transition of the energy state, thereby realizing a magnetic impedance element having a step characteristic in impedance.

  In the present invention, the impedance step characteristic is realized by controlling the tilt angle of the easy axis of the magnetic impedance element and, as an observable phenomenon, the tilt angle of the domain wall.

  As methods for forming the gradient magnetic domains, there are the following two methods as easy methods to implement.

  (1) After inducing magnetic anisotropy in the magnetic film, the magnetic film is processed into a magnetic field detection element shape in which the anisotropy direction is inclined.

  (2) After processing the magnetic film into the shape of the magnetic field detection element, a gradient magnetic domain is formed.

  When the element characteristics of the present invention are applied to magnetic field detection, it is possible to simplify the processing circuit of a general magnetic impedance element.

  In addition, the present invention enables high-sensitivity threshold magnetic field detection, and further simplifies the detection circuit module, and thus can be applied to a wide range of applications.

  FIG. 1 is a structural diagram of a magneto-impedance element showing an embodiment of the present invention. FIG. 1 (a) is an overall perspective view, and FIG. 1 (b) is a schematic cross-sectional view taken along line AA of FIG. It is.

  In these drawings, 1 is a magnetic field detecting element, 2 is a substrate (for example, glass), 3 is a magnetic film (or a laminated film made of a magnetic material-nonmagnetic material) formed on the substrate 2, and 4 is a magnetic film thereof. Electrode pads provided at both ends of 3, 5 is a high frequency power source, 6 is the width of the magnetic film 3, 7 is the thickness of the magnetic film 3, 8 is the direction of the detected magnetic field, and 9 is the carrier current.

  FIG. 2 is a schematic diagram of a gradient magnetic domain structure in the element plane composed of the gradient domain walls in the present invention.

  In this figure, the domain wall is classified into the 180 ° domain wall 11 and the domain wall 13 of the return magnetic domain 12. However, the domain wall angle of the present invention is the inclination angle of the 180 ° domain wall 11 and it is difficult to determine the domain wall type. The average angle of the domain wall 11 is defined. Since the tilt angle of the easy magnetization axis also has anisotropic dispersion and the like and cannot be determined uniquely in practice, the average value of the dispersion state is defined as the domain wall (easy magnetization axis) tilt angle θ. Reference numeral 14 denotes an energization direction.

The tilt angle θ of the easy axis of the element of the present invention or the average tilt angle of the domain wall is defined in the claims.
[Example 1]
The material composition of the magnetic film 3 of the magnetic field detection element 1 was Co ₈₅ Nb ₁₂ Zr ₃ , and was formed on the glass substrate 2 by RF sputtering (Ar atmosphere). For patterning, a lift-off method or an ion milling method was used. The magnetic film 3 was subjected to a heat treatment in a magnetic field after the film formation to give magnetic anisotropy in the in-plane direction. The heat treatment conditions in the magnetic field are (1) heat treatment in rotating magnetic field (40 kA / m, 400 ° C., 2 hours), and (2) heat treatment in static magnetic field (40 kA / m, 400 ° C., 1 hour).

  In order to form a magnetic domain structure inclined in the width direction, which is an important point of the present invention, the direction of the magnetic field was inclined by 1 ° from the width direction during the heat treatment in the static magnetic field. The electrode pad 4 was made of Ti / Cu, and the impedance was measured by bringing the wafer probe into contact with this electrode.

Evaluation of the magnetic field detection characteristic of the magnetic field detection element was performed by measuring a change in element impedance when an external magnetic field _Hex was applied by a Helmholtz coil. This measurement was performed by a reflection method using a network analyzer (for example, HP4396B).

  The measurement result of the magnetic field detection element characteristic manufactured by the above manufacturing method will be described.

FIG. 3 is a characteristic diagram of impedance (Ω: absolute value) with respect to the external magnetic field H _ex (Oe) of the magnetic field detecting element according to the embodiment of the present invention. Here, the magneto-impedance characteristics at a carrier frequency of 50 MHz in a magnetic field detection element having an element length of 1 mm, an element width of 20 μm, and a film thickness of 3.1 μm are shown.

  As shown in FIG. 3, when the external magnetic field increases from −2.7 Oe to +2.7 Oe and when the external magnetic field decreases from +2.7 Oe to −2.7 Oe, the steps of increasing and decreasing the impedance are performed. Occurs once each.

  FIG. 4 shows a magnetic domain structure in the magnetic field detection element showing the embodiment of the present invention.

In this figure, 20 is a magnetic field detection element, 21 is a 180 ° domain wall, 22 is a return magnetic domain, 23 is a domain wall of the return magnetic domain 22, 24 is an energization direction, and θ ₁ is a domain wall average inclination angle (70 °).

As shown in FIG. 4, the average inclination angle θ ₁ of the 180 ° domain wall 21 is 70 °. The average inclination angle θ ₁ of the domain wall 21 is larger than the magnetic field direction in the heat treatment in the static magnetic field, but this is because the element width is as narrow as 20 μm and the film thickness is as thick as 3.1 μm, so It is thought that the magnetic field direction inside the magnetic material is refracted by the influence. The details of the domain wall inclination angle due to magnetic field refraction by this demagnetizing field are shown in Example 3.

  The magnetic domain structure of this magnetic field detection element is as follows. That is, a stripe-shaped domain wall is observed in a portion where the impedance is one step lower, and the stripe-like domain wall disappears in a portion where the impedance is one step higher. This is an actual confirmation of the phenomenon described in the above-described operation principle.

  There are several variations in the magnetic field detection element characteristics of the present invention.

  FIG. 5 shows a correspondence diagram of the results of measuring the magnetic-impedance characteristics at a carrier frequency of 50 MHz and the presence or absence of a stripe-shaped magnetic domain structure in an element having an element length of 2 mm, an element width of 20 μm, and a film thickness of 3.1 μm. The domain wall average inclination angle under this condition is 65 °.

  FIG. 6 shows a correspondence diagram of the results of measuring the magnetic-impedance characteristics at a carrier frequency of 50 MHz and the presence or absence of a stripe-like magnetic domain structure in an element having an element length of 3 mm, an element width of 20 μm, and a film thickness of 3.1 μm. The domain wall average inclination angle under this condition is 66 °.

  In either case, it can be seen that the impedance changes stepwise due to the appearance and disappearance of the stripe-shaped domain wall. The magnetic field detection element of the present invention also has variations as shown in FIGS. That is, as in the case of FIGS. 5 and 6, a step-like change occurs when the impedance increases or decreases, but when recovering in the opposite direction from the state, the characteristic shows a gentle continuous change. The element of FIG. 7 is a correspondence diagram of the results of measuring the magneto-impedance characteristics and the presence or absence of a stripe-like magnetic domain structure of an element having an element length of 5 mm, an element width of 10 μm, and a film thickness of 2.4 μm. The domain wall average inclination angle under this condition is 74 °.

  FIG. 8 is a correspondence diagram of the results of measuring the magneto-impedance characteristics and the presence or absence of a stripe-shaped magnetic domain structure of a device manufactured with an element length of 2 mm, an element width of 10 μm, and a film thickness of 3.0 μm. The domain wall average inclination angle under this condition is 84 °.

  In a thin-film magneto-impedance element, by adjusting the tilt angle of the domain wall or the cross-sectional aspect ratio of the element that controls the domain wall, the magneto-impedance curve has a minimum value at the point of zero external magnetic field and two values on both sides of this minimum value. It is known that it is possible to realize an element having a maximum value and an element having a monotonically decreasing profile characteristic having a single maximum value at the point of zero external magnetic field (the above-mentioned patent document). 7, Patent Document 8). The present invention relates to an element that realizes impedance step characteristics under these known conditions.

As described above, the magnetic field detecting element having impedance step characteristics according to the present invention has several characteristic variations, but they are all the same in principle and do not exclude them.
[Example 2]
The material composition of the magnetic film 3 of the magnetic field detection element 1 was Co ₈₅ Nb ₁₂ Zr ₃ , and was formed on the glass substrate 2 by RF sputtering (Ar atmosphere). For patterning, a lift-off method or an ion milling method was used. The magnetic film 3 was subjected to a heat treatment in a magnetic field after the film formation to give magnetic anisotropy in the in-plane direction. The heat treatment conditions in the magnetic field are (1) heat treatment in a rotating magnetic field (240 kA / m, 400 ° C., 2 hours), and (2) heat treatment in a static magnetic field (240 kA / m, 400 ° C., 1 hour).

  In order to form a magnetic domain structure inclined in the width direction, which is an important point of the present invention, the direction of the magnetic field was inclined by 60 ° from the width direction during the heat treatment in the static magnetic field. The electrode pad 4 was made of Ti / Cu, and the impedance was measured by bringing the wafer probe into contact with this electrode.

Evaluation of the magnetic field detection characteristic of the magnetic field detection element was performed by measuring a change in element impedance when an external magnetic field _Hex was applied by a Helmholtz coil. This measurement was performed by a reflection method using a network analyzer (for example, HP4396B).

  The measurement result of the magnetic field detection element characteristic manufactured by the above manufacturing method will be described.

FIG. 9 is a characteristic diagram of impedance (Ω: absolute value) with respect to the external magnetic field H _ex (Oe) of the magnetic field detection element according to the embodiment of the present invention. Here, the magneto-impedance characteristics at a carrier frequency of 50 MHz in a magnetic field detection element having an element length of 1 mm, an element width of 20 μm, and a film thickness of 2.1 μm are shown.

  As shown in FIG. 9, when the external magnetic field increases from −2.1 Oe to +2.1 Oe, and when the external magnetic field decreases from +2.1 Oe to −2.1 Oe, the steps of increasing and decreasing the impedance Occurs once each.

The average inclination angle θ ₁ of the 180 ° domain wall in the magnetic domain structure of the magnetic field detection element showing the embodiment of the present invention is 65 °. It is shown that the average inclination angle of the domain wall is larger than the magnetic field direction but is larger than the magnetic field direction because the processing magnetic field in the static magnetic field heat treatment is larger than that in the first embodiment.

  The magnetic field detection element characteristics of the present invention have variations common to Example 1, although the production conditions are different from those of Example 1.

  FIG. 10 shows a correspondence diagram of the measurement results of the magneto-impedance characteristics at a carrier frequency of 50 MHz and the presence or absence of a stripe magnetic domain structure in an element having an element length of 2 mm, an element width of 20 μm, and a film thickness of 2.1 μm. The domain wall average inclination angle under this condition is 63 °. The production method is the same as above.

  FIG. 11 shows a correspondence diagram of the results of measuring the magnetic-impedance characteristics at a carrier frequency of 50 MHz and the presence or absence of a stripe magnetic domain structure in an element having an element length of 3 mm, an element width of 20 μm, and a film thickness of 2.1 μm. The domain wall average inclination angle under this condition is 62 °. The production method is the same as above.

As shown in the present embodiment, it is shown that the impedance step characteristic can be realized even when heat treatment in a static magnetic field to which a strong magnetic field close to the target domain wall angle is applied.
Example 3
By applying the characteristics of the magnetic thin film described when describing the principle of the present invention, it is possible to realize a magnetic field detection element having the following structure with impedance step characteristics. That is, as shown in the principle of the present invention, it is a structure in which a magnetic thin film whose magnetic characteristics change stepwise and which is generated with the appearance / disappearance of stripe-shaped domain walls is combined.

  FIG. 12 shows a structure in which one piece of magnetic thin film and one conductive path are combined.

  In this figure, 31 is a piece of magnetic thin film, 32 is a single conductive path, and 33 is an electrode pad of the single conductive path 32.

  FIG. 13 shows a structure in which magnetic thin films having the characteristics of the present invention are arranged above and below one conductive path.

  In this figure, 41 is a lower magnetic thin film, 42 is one conductive path, 43 is an electrode pad of the one conductive path 42, and 44 is an upper magnetic thin film.

  Further, FIGS. 14 and 15 show structures in which the conductive path is formed as a meander structure as an effective structure for setting the resistance value of the magnetic field detection element large and reducing the power consumption.

  In FIG. 14, 51 is a piece of magnetic thin film, 52 is a conductive path having a meander structure, and 53 is an electrode pad of the conductive path 52.

  In FIG. 15, 61 is a lower magnetic thin film, 62 is a conductive path having a meander structure, 63 is an electrode pad of the conductive path 62, and 64 is an upper magnetic thin film.

In these laminated structures, an insulating layer may be disposed between the magnetic body and the conductor. Even with such a structure, if the magnetic properties of the magnetic thin film change stepwise according to the external magnetic field, the electric conductor is affected electromagnetically, and the impedance of the conductor changes stepwise. It becomes.
Example 4
The material composition and the manufacturing method were the same as in Example 1. The magnetic field direction of the heat treatment in the static magnetic field was also inclined by 1 ° from the width direction, and the heat treatment in the static magnetic field was performed to produce a magnetic field detection element. The produced device dimensions were made constant with a length of 2 mm and a film thickness of 2.1 μm, and the width was changed.

  16 to 18 are diagrams showing a gradient magnetic domain structure in the element plane of the magnetic field detection element according to the fourth embodiment of the present invention. The element width in FIG. 16 is 25 μm, the element width in FIG. 17 is 15 μm, The element width in FIG. 18 is 10 μm.

  As shown in FIG. 16 (domain wall average tilt angle: 17 °), FIG. 17 (domain wall average tilt angle: 43 °), and FIG. 18 (domain wall average tilt angle: 81 °), As the angle becomes narrower, the average inclination angle of the domain wall becomes larger. When the magnetic impedance characteristics of these magnetic field detection elements are measured, the tilt angle of the domain wall increases, and as shown in FIG. 19 (corresponding to FIG. 16), FIG. 20 (corresponding to FIG. 17), and FIG. 21 (corresponding to FIG. 18). In addition, the interval between the two peaks appearing in the impedance characteristic is reduced, eventually the impedance in the external magnetic field 0 is raised, and the impedance change between the bottom and the peak becomes a small impedance characteristic.

  The magnetic field detecting element having the characteristics of the present invention is realized when the average domain wall inclination angle is increased from when the peak interval immediately before the occurrence of a rise in impedance in the external magnetic field 0 is minimized.

  Table 1 summarizes the above results and other examples shown in the examples of the present invention.

From Table 1, it can be seen that the occurrence of the impedance step appears when the average inclination angle of the domain wall is 62 ° or more and less than 81 ° , the element size is 10 μm or more and 20 μm or less in width, and the film thickness is 2.1 μm or more and 3.1 μm or less. .
Example 5
The material composition and the manufacturing method are the same as those in Example 1. When the magnetic field direction of the static magnetic field heat treatment is inclined by 1 ° from the width direction and the static magnetic field heat treatment is performed, the element width and film thickness are used as parameters. FIG. 22 shows the results of experiments on the domain wall tilt angle.

  In FIG. 22, the element width and the film thickness are uniformly shown by a parameter called a cross-sectional aspect ratio (width / thickness). The cross-sectional aspect ratio is a parameter closely related to the demagnetizing field strength generated in the width direction during heat treatment in a static magnetic field. It can be inferred that this is a parameter that expresses.

  FIG. 22 shows that the domain wall inclination angle can be controlled by the cross-sectional aspect ratio when the magnetic field direction of the heat treatment in the static magnetic field is constant. The element characteristics of the present invention as shown in Example 1 are realized by setting the domain wall inclination angle to 60 ° or more and less than 90 ° by such a magnetic domain control method.

The present embodiment is an embodiment of a method for manufacturing a magnetic field detection element having a gradient magnetic domain structure.
Example 6
As an effective method for a magnetic field detection apparatus using an impedance step, there is a step point detection method using a differentiation circuit.

  FIG. 23 shows a schematic diagram of an electric circuit of the magnetic field detection device.

  In this figure, 71 is a magnetic field detecting element, 72 is a resistor, 73 is a high frequency power source, 74 is a rectifier + LPF (low pass filter) or peak hold circuit, 75 is a differentiation circuit, and 76 is an output terminal.

FIG. 24 shows a waveform in which this circuit module is placed in an alternating magnetic field having an amplitude of 2 Oe and the output voltage at this time is passed through the differentiating circuit 75. FIG. 24 shows an output voltage waveform in one cycle. One pulse is generated when the impedance step phenomenon occurs, and two pulses are generated in one cycle of the alternating magnetic field. By counting the number of pulses, frequency counting of the alternating magnetic field is realized.
Example 7
The magnetic material composition of the magnetic field detection element was Co ₈₅ Nb ₁₂ Zr ₃ , and was formed on a glass substrate by RF sputtering (Ar atmosphere). The element dimensions were 2 mm in length and 20 μm in width, and patterning was performed using a lift-off method or an ion milling method. The magnetic film was subjected to heat treatment in a magnetic field after film formation to give magnetic anisotropy. The heat treatment conditions in the magnetic field are heat treatment in a rotating magnetic field (40 kA / m, 400 ° C., 2 hours) and heat treatment in a static magnetic field (40 kA / m, 400 ° C., 1 hour).

  In order to form a magnetic domain structure inclined in the width direction, which is an important point of the present invention, the magnetic field direction was inclined by 1 ° from the width direction during the heat treatment in the static magnetic field, and the heat treatment in the static magnetic field was performed. The electrode was made of Ti / Cu, and a coplanar electrode was installed to enable impedance measurement with a wafer probe.

Evaluation of the magnetic field detection characteristics of the magnetic field detection element was performed by measuring a change in element impedance when an external magnetic field _Hex was applied using a Helmholtz coil. The measurement was performed by a reflection method using a network analyzer (for example, HP4396B).

  The measurement results of the magnetic field detection element characteristics described above will be described.

FIG. 25 is a characteristic diagram of impedance (absolute value) with respect to the external magnetic field H _ex (Oe) of the magnetic field detection element according to the embodiment of the present invention. Here, the magneto-impedance characteristics at a carrier frequency of 500 MHz in an element having a film thickness of 3.1 μm are shown.

  Here, a bias magnetic field changing from −1.5 Oe to +1.5 Oe and a bias magnetic field changing from +1.5 Oe to −1.5 Oe are applied to the magnetic field detecting element, and the moment when the element impedance increases stepwise. Hold the bias field. Let this magnetic field be H + step and H-step. This is shown in FIG. Further, a calculation process of H + step + H-step is performed, and this output is used as a sensor output.

  Note that this calculation processing may be performed on the current or voltage required to generate the magnetic field, without performing on the bias magnetic field strength.

  Further, even if the same calculation as shown in the present embodiment is performed using the portion where the impedance decreases stepwise, the same result can be obtained.

FIG. 27 shows the external magnetic field _Hex measured by this method and the result of measurement with a calibrated magnetic field measuring device. In FIG. 27, the output of the step sensor is calculated using a current value that generates a bias magnetic field, but the calibration coefficient (about 20) of the Helmholtz coil used for this measurement and the element impedance change in the same direction. Using an arithmetic method that calculates the external magnetic field by the arithmetic mean of these bias magnetic fields using two step changes generated by different bias magnetic fields, a slight offset adjustment is necessary, but the external magnetic field at the geomagnetic level is necessary. It is shown that can be measured with high accuracy. That is, it can be seen that ● is the actually measured magnetic field, and □ is the output value of the step sensor of the present invention, which is almost the same as the actually measured value.

  In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.

  The magnetic field detection element of the present invention can be used for hard disk devices, nondestructive inspection, banknote inspection, and biomagnetic field measurement.

1 is a structural diagram of a magnetic field detection element showing an embodiment of the present invention. It is a schematic diagram of the gradient magnetic domain structure in the element surface which consists of the gradient domain wall in the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic domain structure of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic (element length 2mm, element width 20micrometer, film thickness 3.1micrometer) of the magnetic field detection element which shows the Example of this invention, and the presence or absence of a stripe-like magnetic domain structure. It is a figure which shows the magnetic impedance characteristic (element length 3mm, element width 20micrometer, film thickness 3.1micrometer) of the magnetic field detection element which shows the Example of this invention, and the presence or absence of a stripe-like magnetic domain structure. It is a figure which shows the magnetic impedance characteristic (element length 5mm, element width 10micrometer, film thickness 2.4micrometer) of the magnetic field detection element which shows the Example of this invention, and the presence or absence of a stripe-like magnetic domain structure. It is a figure which shows the magnetic impedance characteristic (element length 2mm, element width 10micrometer, film thickness 3.0micrometer) of the magnetic field detection element which shows the Example of this invention, and the presence or absence of a stripe-like magnetic domain structure. It is a figure which shows the magnetic impedance characteristic (element length 1mm, element width 20micrometer, film thickness 2.1micrometer) of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic (element length 2mm, element width 20micrometer, film thickness 2.1micrometer) of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic (element length 3mm, element width 20micrometer, film thickness 2.1micrometer) of the magnetic field detection element which shows the Example of this invention. It is a schematic diagram which shows the laminated structure element of the single-sided magnetic body of the magnetic field detection element which shows the Example of this invention. It is a schematic diagram in which the magnetic body of the magnetic field detection element showing the embodiment of the present invention is a laminated structure element having upper and lower surfaces. FIG. 4 is a schematic diagram showing a laminated structure element in which a conductive path of a magnetic field detection element showing an embodiment of the present invention has a meander structure and a magnetic body is a single side. FIG. 3 is a schematic diagram showing a laminated structure element in which a conductive path of a magnetic field detection element showing an embodiment of the present invention has a meander structure and a magnetic body has upper and lower surfaces. It is a figure which shows the gradient magnetic domain structure (film thickness 2.1 micrometers and element width 25 micrometers) in the element surface of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the gradient magnetic domain structure (film thickness 2.1 micrometers and element width 15 micrometers) in the element surface of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the gradient magnetic domain structure (film thickness 2.1 micrometers and element width 10 micrometers) in the element surface of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic (film thickness 2.1 micrometers and element width 25 micrometers) of the element of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic (film thickness 2.1 micrometers and element width 15 micrometers) of the element of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the magnetic impedance characteristic (film thickness of 2.1 micrometers, element width of 10 micrometers) of the element of the magnetic field detection element which shows the Example of this invention. It is an actual measurement relation figure of element section aspect ratio of a magnetic field detection element and a domain wall inclination angle which shows an example of the present invention. It is the schematic of the electric circuit combined with the differentiation circuit of the magnetic field detection element which shows the Example of this invention. It is a figure which shows the waveform which passed the output voltage in the alternating magnetic field of the magnetic field detection element which shows the Example of this invention to the differentiation circuit. It is a characteristic view of the impedance (absolute value) with respect to the external magnetic field _Hex (Oe) of the magnetic field detection element which shows the Example of this invention. It is operation | movement explanatory drawing of the step sensor using the magnetic field detection element which shows the Example of this invention. It is a figure which shows the measurement result of the step sensor which shows the Example of this invention.

1 Magnetic field detection element 2 Substrate (for example, glass)
3 Magnetic film (or laminated film consisting of magnetic material and non-magnetic material)
4, 33, 43, 53, 63 Electrode Pad 5 High Frequency Power Supply 6 Magnetic Film Width 7 Magnetic Film Thickness 8 Detection Magnetic Field Direction 9 Carrier Current 11, 21 180 ° Domain Wall 12, 22 Reflux Domain 13, 23 Domain Wall of Reflux Domain 14, 24 Current-carrying direction 20, 71 Magnetic field detection element θ ₁ Domain wall average inclination angle 31, 51 One piece of magnetic thin film 32, 42 One conductive path 41, 61 Lower magnetic thin film 44, 64 Upper magnetic thin film 52, 62 meander structured conductive path 72 resistor 73 high frequency power supply 74 rectifier + LPF (low pass filter) or peak hold circuit 75 differentiation circuit 76 output terminal

Claims (5)

An easy axis of magnetic anisotropy in the magnetic thin film is detected in a magnetic field detection element that detects a change in electrical characteristics according to an external magnetic field by supplying an alternating current from a high frequency power source to an element having a magnetic thin film structure. By inducing in a direction inclined from a direction perpendicular to the magnetic field direction and giving an inclination angle to the domain wall of the stripe-like domain structure resulting from this, a step phenomenon in which the impedance rapidly changes in the threshold magnetic field is generated. A magnetic field detection element having a structure in which an energization direction of an alternating current supplied from the high-frequency power source is matched with the detection magnetic field direction, and the direction of the easy axis is a direction that does not coincide with the energization direction. for forming the said domain wall is less than the mean inclination angle of 67 ° or more 74 ° of the magnetic wall, 20 [mu] m or less device dimensions width 10μm or more, thickness 2.4 [mu] m Magnetic field detecting element, characterized in that at most above 3.1 .mu.m. A magnetic field detecting element, comprising a magnetic thin film and a conductor, supplying a high-frequency alternating current to the conductor and detecting a change in electrical characteristics in accordance with an external magnetic field, has a magnetic anisotropy in the magnetic thin film. By inducing the easy axis in a direction inclined from the direction perpendicular to the direction of the detected magnetic field and giving a tilt angle to the domain wall of the striped domain structure resulting from this, the electrical characteristics or magnetic characteristics are discontinuous in the threshold magnetic field. The magnetic thin film having this characteristic and the conductor are arranged at a position where they are electrically or magnetically coupled, and a step phenomenon in which the impedance changes suddenly by the external magnetic field is generated. The magnetic field detection element according to claim 1, wherein an average inclination angle of a domain wall of the magnetic thin film is 67 ° or more and less than 74 ° with respect to a direction perpendicular to the detection magnetic field direction. A magnetic field detecting element having a width of 10 μm to 20 μm and a film thickness of 2.4 μm to 3.1 μm.   The magnetic field detection element according to claim 2, wherein the magnetic thin film having magnetic properties that change in a step-like manner is disposed on one or both of the upper and lower sides of the conductor.   The magnetic field detection element according to claim 3, wherein the conductor combined with the magnetic thin film has a zigzag shape.   A bias magnetic field required to generate a step change in impedance according to the intensity of the external magnetic field is applied to the magnetic field detection element according to any one of claims 1 to 4, and the element impedance changes in the same direction. A magnetic field detection method for calculating an external magnetic field by arithmetic mean of these bias magnetic fields using two step changes generated by different bias magnetic fields.