JP2001332779A - Magnetic impedance effect element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve such problem of a conventional magnetic impedance effect element that the sensitivity in detection of a magnetic field drops if the aspect ratio of a magnetosensitive part is made small. SOLUTION: The sensitivity in detection of a magnetic field can be enhanced in case that the aspect ratio of a magnetosensitive part 12 is made small, by superposing direct current components Idcon drive AC currents Iac, and applying a DC bias field B in the width direction of the magnetosensitive part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-impedance effect element usable as a magnetic field sensor.
The present invention relates to a magneto-impedance effect element capable of improving the magnetic field detection sensitivity when miniaturizing the device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the rapid development of information devices, measuring devices, control devices, and the like, there has been a demand for a magnetic field sensor having a smaller size, higher sensitivity, and faster response (high-frequency operation) than the conventional magnetic flux detection type. And the magneto-impedance effect (Magn
An element (magneto-impedance effect element) having eto-Impedance-Effect has been attracting attention.

The basic principle of a magneto-impedance effect element is that an output voltage due to impedance generated by applying a small alternating current to a magnetic wire formed in a wire, ribbon, or thin film is changed by an externally applied magnetic field. Device.

The change in the impedance of the magnetically sensitive portion made of a soft magnetic material due to the application of an external magnetic field is caused by the "skin effect" in which an alternating current flows near the surface when an alternating current is applied to the magnetic material. It is known that the change is caused by an external magnetic field.

[0005] An amorphous wire was initially used for the magnetic sensing portion of the magneto-impedance effect element. However, the amorphous wire has excellent productivity as a material, but has many unsuitable characteristics for application to a magnetic field sensor.

For example, at a circular tip of several tens μm or less for a recording medium having a recording wavelength of several μm or less, magnetic flux cannot be absorbed by the element due to a shape loss at the tip.
In addition, it is difficult to form an electrode portion for connecting a wiring member for passing an alternating current, and a wire having a diameter of several tens of μm is easily bent and difficult to align elements, or is broken. There was a problem that it was easy.

Therefore, by forming the magnetic sensing part of the magneto-impedance effect element with a soft magnetic thin film or a soft magnetic thin strip, it is possible to form the magnetic sensing part with an arbitrary thickness, width and length. It has been proposed to solve the above problems.

However, when the shape of the magnetic sensing portion of the magneto-impedance effect element is changed from a wire to a thin film or a ribbon, the magnetic properties such as the magnetic domain structure change and the magneto-impedance effect properties also change. For example, when the magnetic sensing part of the magneto-impedance effect element is formed as a soft magnetic thin film,
The magnetic field detection sensitivity is reduced by a factor of ten as compared with the case where the magnetic sensing part is formed of a wire.

FIG. 13 is a perspective view of a conventional magneto-impedance effect element. The magneto-impedance effect element M shown in FIG. 13 has a magnetically sensitive portion 12 formed by forming a thin film of a soft magnetic material on a substrate 11 made of a non-magnetic material such as alumina titanium carbide by a sputtering method or a vapor deposition method. And electrode portions 13 and 1 formed of a conductive material such as Cu and joined to both ends of the magnetic sensing portion 12.
3. The magnetic sensing portion 12 is formed in a substantially rectangular or linear pattern.

The element length and the element width of the magnetosensitive portion 12 in FIG. FIG. 14 is a circuit diagram showing a magnetic field detection circuit configured using a conventional magneto-impedance effect element. In the circuit shown in FIG. 14, in a state where an alternating current Iac in the MHz band is applied to the magnetic sensing unit 12 from the power supply Eac, the external magnetic field He in the element length direction of the magnetic sensing unit 12
When x is applied, an output voltage Emi is generated at both ends of the magnetic sensing unit 12 due to the impedance inherent in the material, and the output voltage Em
The amplitude of i changes within a range of several tens of percent corresponding to the intensity of the external magnetic field Hex.

[0011]

In the conventional magneto-impedance effect element, in order to improve the magnetic permeability of the magneto-sensitive portion 12 in the longitudinal direction of the device, the magneto-sensitive portion 12 is arranged such that the width direction of the magneto-sensitive portion 12 is in the direction of the axis of easy magnetization. Had a magnetic anisotropy.

In order to improve the magnetic field detection sensitivity and the magnetic field detection resolution of the magneto-impedance effect element, the magnetic sensing unit 1
It is necessary to reduce the aspect ratio W / L of No. 2 and to form the magnetically sensitive portion 12 of a soft magnetic material having a high magnetic permeability.

However, the aspect ratio W / L of the magnetic sensing part 12
When the value is reduced, the contribution of the shape magnetic anisotropy in which the magnetization direction is directed to the element longitudinal direction increases, and
When the magnetically sensitive portion 12 is formed of a soft magnetic material having a large magnetic permeability, it becomes difficult to impart strong induced magnetic anisotropy in the element width direction, and the magnetically sensitive portion 12 has a magnetic field in which the element width direction has an easy axis direction. It tends to be difficult to provide anisotropy. Therefore, there has been a need for a magneto-impedance effect element capable of improving the magnetic field detection sensitivity even when the direction of the easy axis of magnetization of the magneto-sensitive portion 12 is a direction other than the element width direction.

An object of the present invention is to solve the above-mentioned conventional problem. By applying a DC bias magnetic field in the element width direction to the magneto-sensitive section of the magneto-impedance effect element, the axis of easy magnetization of the magneto-sensitive section 12 is improved. It is an object of the present invention to provide a magneto-impedance effect element capable of improving the magnetic field detection sensitivity even when the direction is other than the element width direction, and a method for manufacturing the same.

[0015]

According to the present invention, there is provided a substantially rectangular magneto-sensitive portion including a soft magnetic material having a magneto-impedance effect, and a driving alternating current connected to both ends of the magneto-sensitive portion in the element longitudinal direction. And a DC bias magnetic field is applied in the element width direction of the magneto-sensitive section.

In the present invention, the aspect ratio W of the magneto-sensitive portion is
/ L is reduced, and the magnetically sensitive portion is formed using a soft magnetic material having a high magnetic permeability. As a result, even when the easy axis of magnetization of the magnetically sensitive portion is oriented in the element longitudinal direction, Since a DC bias magnetic field is applied in the element width direction, the magnetic anisotropy energy in the element width direction and the element longitudinal direction can be balanced, and the magnetic anisotropy of the magneto-sensitive portion is substantially isotropic as a whole. It can be in a state.

Accordingly, it is difficult for the magnetic moment of the magnetic sensing portion to be fixed in a certain direction, and the direction of the magnetic moment tends to change when excited by an alternating current.

That is, in the present invention, while the aspect ratio W / L of the magnetically sensitive portion is reduced, the change in impedance in the magnetically sensitive portion according to the change in the external magnetic field is increased, while the magnetically sensitive portion is changed. Therefore, even if the miniaturization of the magneto-impedance effect element is advanced, it is possible to obtain a magneto-impedance effect element having improved magnetic field detection sensitivity.

In the present invention, a direct current component is superimposed on the drive alternating current flowing in the element longitudinal direction of the magneto-sensitive portion,
A magnetic field generated from this DC current component enters from the element width direction of the magnetic body of the magnetic sensing portion, and acts as the DC bias magnetic field.

Further, in the present invention, the magnetic sensing part is formed of a soft magnetic thin film or a thin strip, and a conductive layer extending in the longitudinal direction of the element via an insulating layer above or below the soft magnetic thin film or the thin strip. The soft magnetic thin film or the ribbon, and both ends of the conductive layer in the element longitudinal direction are connected to the electrode portion, and the driving AC current supplied from the electrode portion has a DC current component. Are superimposed,
It is preferable that a magnetic field generated from a DC current component flowing through the soft magnetic thin film or ribbon and / or the conductive layer acts as the DC bias magnetic field.

When the conductive layer is laminated on the soft magnetic thin film or the ribbon via the insulating layer, the drive AC current on which the DC current component is superimposed mainly has a constant magnetic field distribution. The magnitude and direction of a magnetic field (DC bias magnetic field) generated from the DC component flowing in the conductive layer are stabilized. Therefore, a uniform DC bias magnetic field can be applied to the entire soft magnetic thin film or ribbon.

Alternatively, in the present invention, the magneto-sensitive portion is formed by forming a conductive layer extending in the element longitudinal direction on an upper layer or a lower layer of the soft magnetic thin film or the ribbon with an insulating layer interposed therebetween. A conductive layer electrode portion is connected to both ends in the device longitudinal direction, and a magnetic field generated from a DC current flowing from the conductive layer electrode portion to the conductive layer enters from the device width direction of the soft magnetic thin film or the ribbon. , And more preferably act as the DC bias magnetic field.

When the conductive layer has the conductive layer electrode portion independent of the electrode portion for supplying a driving AC current to the soft magnetic thin film or the ribbon, only the DC current is applied to the conductive layer. Since the current can flow, the magnitude and direction of the magnetic field (DC bias magnetic field) generated from the DC current are more stable. Therefore, a more uniform DC bias magnetic field can be applied to the entire soft magnetic thin film or ribbon.

In the present invention, it is preferable that the element longitudinal direction of the soft magnetic thin film or the ribbon is the direction of the axis of easy magnetization.

Further, in the present invention, a protective layer made of an insulating material is formed on the magnetically sensitive portion, and the surface of the electrode portion and / or the surface of the conductive layer electrode portion is exposed on the same plane as the surface of the protective layer. Is preferred.

The DC bias magnetic field applied in the width direction of the soft magnetic thin film or the ribbon included in the magnetic sensing portion is installed at a distance in the width direction of the soft magnetic thin film or the ribbon. It may be supplied by a hard magnetic material.

The magneto-sensitive portion of the magneto-impedance effect element needs to include a ferromagnetic thin film or ribbon having soft magnetic properties. Further, the magnetic permeability μ must be high in a high frequency range of 1 MHz to several hundred MHz. Further, it is preferable that the magnetostriction constant λ is small so that a magnetic field is not stressed by an external magnetic field (a magnetic field component of a broadcast radio wave) to degrade the magnetic characteristics.

Since the magnetically sensitive part is formed as a magnetic material having such properties, the magnetically sensitive part may be formed as including a microcrystalline soft magnetic alloy thin film as described below. preferable.

1. A microcrystalline soft magnetic alloy thin film whose composition formula is represented by Fe _h M _i O _j and which mainly has an amorphous structure.

Here, M is Ti, Zr, Hf, V, N
one or two selected from b, Ta, W and a rare earth element
H, i, j are at% and 45 ≦ h
≦ 70, 5 ≦ i ≦ 30, 10 ≦ j ≦ 40, h + i + j =
What satisfies 100 relationships.

Fe is for obtaining a large saturation magnetic flux density Bs, and is bcc-Fe having an average crystal grain size of 30 nm or less.
M is present in the amorphous phase in a state of being combined with O to increase the specific resistance ρ. When h, i, and j are within the above ranges, the saturation magnetic flux density B
A soft magnetic alloy having a large s, a specific resistance ρ, and a large magnetic permeability μ can be obtained. If h, i, and j are out of the above ranges, the soft magnetic properties are deteriorated.

When the element M is one or more elements selected from rare earth elements in the above composition, h and j are at% and 50 ≦ h ≦ 70 and 10 ≦ j ≦ 3.
More preferably, it is 0.

2. Composition _{formula, (Co 1-c T c} ) x M y X z O w
A microcrystalline soft magnetic alloy thin film represented by Where the element T is
An element containing one or both of Fe and Ni, and the element M is composed of Ti, Zr, Hf, V, Nb, T
a, Cr, Mo, Si, P, C, W, B, Al, Ga,
X is one or more elements selected from Ge and rare earth elements, and X is Au, Ag, Cu, Ru, Rh, O
one or more elements selected from s, Ir, Pt, and Pd, and the composition ratio is such that c is 0 ≦ c ≦ 0.7,
x, y, z, w are atomic%, 3 ≦ y ≦ 30, 0 ≦ z ≦ 2
Those satisfying the relationship of 0, 7 ≦ w ≦ 40, 20 ≦ y + z + w ≦ 60, and the balance being x.

In the soft magnetic alloy, an amorphous phase containing a large amount of an oxide of the element M is mixed with a microcrystalline phase mainly composed of Co and the element T and having an average crystal grain size of 30 nm or less. It is more preferable to have a structure containing an oxide of the element M.

3. Composition _{formula, T 100-defg X d M} e Z f Q
_g , bcc-Fe, bcc-FeCo, bcc
-An average crystal grain size 30 mainly composed of one or more crystal grains of Co and a crystal grain of carbide or nitride of the element M;
A microcrystalline soft magnetic alloy thin film of nm or less.

The element T is an element containing one or both of Fe and Co, and the element X is S
i is an element containing one or both of Al, and the element M is Ti, Zr, Hf, V, Nb, Ta,
One or more elements selected from Mo and W, the element Z is an element containing one or both of C and N, and Q is Cr, Re, Ru, Rh, N
one or more elements selected from i, Pd, Pt, and Au, where d, e, f, and g are at% and 0 ≦ d ≦ 2
5, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, 0 ≦ g ≦ 10.

When d, e, f, and g are within the above ranges, a soft magnetic alloy thin film having a large magnetic permeability μ, a low coercive force Hc, and a small magnetostriction constant λ can be obtained.

4. The composition formula is T _100-pqefg Si _p Al
represented by _{q M e Z f Q g,} bcc-Fe, bcc-FeC
A microcrystalline soft magnetic alloy thin film having an average crystal grain size of 30 nm or less mainly composed of one or more crystal grains of o, bcc-Co and a crystal grain of carbide or nitride of the element M.

The element T is an element containing one or both of Fe and Co, and the element M is
i, Zr, Hf, V, Nb, Ta, Mo, W are one or more elements selected from the group consisting of C, N
Element containing one or both of
Are Cr, Re, Ru, Rh, Ni, Pd, Pt, Au
One or more elements selected from the group consisting of p,
q, e, f, and g are at%, 8 ≦ p ≦ 15, 0 ≦ q ≦ 1
0, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, and 0 ≦ g ≦ 10.

If p, q, e, f, and g are within the above ranges, the magnetic permeability μ is large, the coercive force Hc is low, and the magnetostriction constant λ
A soft magnetic alloy having a small size can be obtained.

Further, the magnetic sensing portion may be formed as including an amorphous soft magnetic alloy thin film or a ribbon as described below.

5. The composition formula is (Fe _1-a Co _a ) _100-xy
(Si _{1-b B b)} amorphous soft magnetic alloy thin film or ribbon represented by _x M _y.

Here, M is an element containing one or both of Cr and Ru, and a, which represents a composition ratio,
b satisfies the relationship of 0.05 ≦ a ≦ 0.1, 0.2 ≦ b ≦ 0.8, and x and y satisfy the relationship of 10 ≦ x ≦ 35 and 0 ≦ y ≦ 7 at%.

The above (Fe _1-a Co _a ) _100-xy (Si _1-b B
_{b) x} in M _y based soft magnetic alloy thin film or ribbons, a 0.0
Exceeding the range of 5 ≦ a ≦ 0.1 is not preferable because the magnetostriction increases. On the other hand, if b exceeds the range of 0.2 ≦ b ≦ 0.8, it becomes difficult to make the film amorphous, which is not preferable. Further, when x exceeds the range of 10 ≦ x ≦ 35, it becomes difficult to form an amorphous state, which is not preferable. If x> 35, the magnetic properties deteriorate, which is not preferable.

6 Composition formula, Co _l Ta _m expressed by Hf _n, amorphous soft magnetic alloy thin film was amorphous structure mainly.

Here, l, m and n are at% and 70 ≦ l
≦ 90, 5 ≦ m ≦ 21, 6.6 ≦ n ≦ 15, 1 ≦ m / n
Those satisfying the relationship of ≦ 2.5.

[0047] In the soft magnetic alloy thin film of the Co _l Ta _m Hf _n system, the saturation magnetic flux density Bs is dependent on the content of Co, in order to obtain a high saturation magnetic flux density Bs, it is 70 ≦ l is necessary. However, if l> 90, the specific resistance ρ becomes low, which is not preferable.

Ta and Hf are elements for obtaining soft magnetic properties, and when 5 ≦ m ≦ 21 and 6.6 ≦ n ≦ 15, the soft magnetic property is such that the saturation magnetic flux density Bs is large and the specific resistance ρ is large. Material can be obtained. Hf is Co
It is also an element for eliminating the negative magnetostriction constant λ generated in the -Ta system. The magnetostriction constant λ is determined by the Ta content and Hf
Depends on the content ratio, and if it is within the range of 1 ≦ m / n ≦ 2.5, the magnetostriction constant λ can be satisfactorily eliminated.

7. Composition formula, amorphous soft magnetic alloy thin film mainly composed of amorphous structure represented by Co _a Zr _b Nb _c.

However, a, b and c are at%, and 78 ≦ a
≦ 91, 0.5 ≦ b / c ≦ 0.8.

The saturation magnetic flux density Bs depends on the Co concentration.
In order to increase Bs, it is necessary to satisfy 78 ≦ a ≦ 91. When a> 91, the corrosion resistance is lowered and an amorphous structure is hardly formed, and crystallization starts, which is not preferable. Further, if a <78, the ratio of adjacent Cos decreases, and it becomes difficult to exhibit soft magnetic characteristics, which is not preferable. The magnetic permeability μ also depends on the Co concentration,
It shows a high value in the range of ≦ a ≦ 91.

The rare earth element is a lanthanide element (L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, Ln) and Sc,
It shows 17 elements of Y.

Further, the method for manufacturing a magneto-impedance effect element of the present invention comprises the steps of:
Forming a soft magnetic thin film in a no magnetic field or in a rotating magnetic field, (b) forming a pattern of the soft magnetic thin film in a substantially rectangular shape, and (c) insulating an insulating material on the soft magnetic thin film. Forming a layer; (d) forming electrode portions connected to both ends of the soft magnetic thin film in the device longitudinal direction; and (e) forming the device length of the soft magnetic thin film on the insulating layer. Forming a conductive layer extending in the direction, and having both ends connected to the electrode portion.

Incidentally, instead of the above step (e),
(F) forming a conductive layer electrode part independent of the electrode part and a conductive layer on the insulating layer, the conductive layer extending in the element longitudinal direction of the soft magnetic thin film and both ends connected to the conductive layer electrode part; It is preferred to have.

In the present invention, the steps of (d) and (e), or the steps of (d) and (f) are performed simultaneously, so that the manufacturing process of the magneto-impedance effect element can be performed. Can be simplified.

Further, in the present invention, in the step (d) and / or the step (f), the surface height of the electrode part and the conductive layer electrode part is the same as that of the above (e) or (f). Forming the conductive layer to be higher than the surface height of the conductive layer formed in the step, and (g) protecting the conductive layer from an insulating material after the step (e) or (f). Forming a layer, and (h) polishing the surface of the protective layer to expose the surface of the electrode part and / or the surface of the conductive layer electrode part on the same plane as the surface of the protective layer. preferable.

Alternatively, in the present invention, in the steps (a) and (b), instead of forming the soft magnetic thin film by a film forming process, a molten alloy of a soft magnetic material is injected onto a cooling roll to make contact. The method may include a step of forming a soft magnetic ribbon by quenching, and bonding the soft magnetic ribbon on the substrate.

The soft magnetic thin film serving as the magnetic sensing portion of the magneto-impedance effect element is a ferromagnetic thin film having a high magnetic permeability μ and a small magnetostriction constant λ in a high frequency range of 1 MHz to several hundred MHz and having soft magnetic characteristics. In order to form the soft magnetic thin film, it is preferable to form the soft magnetic thin film as a microcrystalline soft magnetic alloy thin film as described below in the step (a).

1. A microcrystalline soft magnetic alloy thin film whose composition formula is represented by Fe _h M _i O _j and which mainly has an amorphous structure.

Where M is Ti, Zr, Hf, V, N
one or two selected from b, Ta, W and a rare earth element
H, i, j are at% and 45 ≦ h
≦ 70, 5 ≦ i ≦ 30, 10 ≦ j ≦ 40, h + i + j =
What satisfies 100 relationships.

Fe is for obtaining a large saturation magnetic flux density Bs, and is bcc-Fe having an average crystal grain size of 30 nm or less.
M is present in the amorphous phase in a state of being combined with O to increase the specific resistance ρ.

[0062] 2. Composition _{formula, (Co 1-c T c} ) x M y X z O w
A microcrystalline soft magnetic alloy thin film represented by Where the element T is
An element containing one or both of Fe and Ni, and the element M is composed of Ti, Zr, Hf, V, Nb, T
a, Cr, Mo, Si, P, C, W, B, Al, Ga,
X is one or more elements selected from Ge and rare earth elements, and X is Au, Ag, Cu, Ru, Rh, O
one or more elements selected from s, Ir, Pt, and Pd, and the composition ratio is such that c is 0 ≦ c ≦ 0.7,
x, y, z, w are atomic%, 3 ≦ y ≦ 30, 0 ≦ z ≦ 2
Those satisfying the relationship of 0, 7 ≦ w ≦ 40, 20 ≦ y + z + w ≦ 60, and the balance being x.

In the soft magnetic alloy, an amorphous phase containing a large amount of an oxide of the element M is mixed with a microcrystalline phase mainly composed of Co and the element T and having an average crystal grain size of 30 nm or less. It is more preferable to have a structure containing an oxide of the element M.

3. Composition _{formula, T 100-defg X d M} e Z f Q
_g , bcc-Fe, bcc-FeCo, bcc
-An average crystal grain size 30 mainly composed of one or more crystal grains of Co and a crystal grain of carbide or nitride of the element M;
A microcrystalline soft magnetic alloy thin film of nm or less.

The element T is an element containing one or both of Fe and Co, and the element X is S
i is an element containing one or both of Al, and the element M is Ti, Zr, Hf, V, Nb, Ta,
One or more elements selected from Mo and W, the element Z is an element containing one or both of C and N, and Q is Cr, Re, Ru, Rh, N
one or more elements selected from i, Pd, Pt, and Au, where d, e, f, and g are at% and 0 ≦ d ≦ 2
5, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, 0 ≦ g ≦ 10.

4. The composition formula is T _100-pqefg Si _p Al
represented by _{q M e Z f Q g,} bcc-Fe, bcc-FeC
A microcrystalline soft magnetic alloy thin film having an average crystal grain size of 30 nm or less mainly composed of one or more crystal grains of o, bcc-Co and a crystal grain of carbide or nitride of the element M.

However, the element T is an element containing one or both of Fe and Co, and the element M is
i, Zr, Hf, V, Nb, Ta, Mo, W are one or more elements selected from the group consisting of C, N
Element containing one or both of
Are Cr, Re, Ru, Rh, Ni, Pd, Pt, Au
One or more elements selected from the group consisting of p,
q, e, f, and g are at%, 8 ≦ p ≦ 15, 0 ≦ q ≦ 1
0, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, and 0 ≦ g ≦ 10.

Alternatively, in the step (a), the soft magnetic thin film or the soft magnetic ribbon may be formed as an amorphous soft magnetic alloy thin film or a ribbon as described below.

5. The composition formula is (Fe _1-a Co _a ) _100-xy
(Si _{1-b B b)} amorphous soft magnetic alloy thin film or ribbon represented by _x M _y.

Here, M is an element containing one or both of Cr and Ru, and a, which represents a composition ratio,
b satisfies the relationship of 0.05 ≦ a ≦ 0.1, 0.2 ≦ b ≦ 0.8, and x and y satisfy the relationship of 10 ≦ x ≦ 35 and 0 ≦ y ≦ 7 at%.

6. Composition formula, Co _l Ta _m expressed by Hf _n, amorphous soft magnetic alloy thin film was amorphous structure mainly.

Where l, m and n are at% and 70 ≦ l
≦ 90, 5 ≦ m ≦ 21, 6.6 ≦ n ≦ 15, 1 ≦ m / n
Those satisfying the relationship of ≦ 2.5.

7. Composition formula, amorphous soft magnetic alloy thin film mainly composed of amorphous structure represented by Co _a Zr _b Nb _c.

Here, a, b and c are at%, and 78 ≦ a
≦ 91, 0.5 ≦ b / c ≦ 0.8.

The rare earth element is a lanthanide element (L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, Ln) and Sc,
It shows 17 elements of Y.

[0076]

FIG. 1 is a perspective view showing a magneto-impedance effect element according to a first embodiment of the present invention.

The magneto-impedance effect element M shown in FIG.
It has basically the same structure as the magneto-impedance effect element M shown in FIG. 13, and a DC bias magnetic field B is applied in the element width direction (Y direction).

The magneto-impedance effect element M shown in FIG.
A magnetically sensitive part 1 which is a thin-film soft magnetic material formed on a substrate 11 made of a nonmagnetic material such as alumina titanium carbide by a sputtering method or a vapor deposition method using a soft magnetic material.
2, and Cu, Ni, Ti, C
Electrode portion 1 formed of a conductive material such as r or Al
3 and 13. The magnetic sensing portion 12 is formed in a substantially rectangular or linear pattern. Further, the magnetic sensing part 12 may be formed in a U-shape or a zigzag shape. The element width W of the magnetosensitive portion 12 was 30 to 100 μm, and the element length L was 1 to 4 mm.

In FIG. 1, the electrode portions 13 are formed at both ends of the magneto-sensitive portion 12 in the longitudinal direction of the element, but the electrode portions 13 are located near both end portions of the upper surface of the magneto-sensitive portion 12. A conductive material such as Cu may be stacked thereover.

The direction of the easy axis of magnetization of the magneto-sensitive portion 12 is the element longitudinal direction (X direction), and is parallel to the direction in which the drive current flows.

When the soft magnetic thin film serving as the magnetic sensing portion 12 is formed, the soft magnetic thin film having no isotropic or anisotropic magnetic anisotropy can be formed by forming the film in a no magnetic field or in a rotating magnetic field. A magnetic thin film is formed. When a soft magnetic thin film having an isotropic magnetic anisotropy is patterned on a substantially rectangular shape to form the magnetically sensitive portion 12, the element longitudinal direction of the magnetically sensitive portion 12 is easily magnetized due to the shape magnetic anisotropy. Direction.

The magnetic sensing part 12 is formed by a soft magnetic thin film described later. In the present embodiment, the magnetically sensitive part 12 is a single-layer soft magnetic thin film, but the magnetically sensitive part 12 may be formed by laminating a plurality of soft magnetic thin films via an insulating layer.

In the magneto-impedance effect element shown in FIG.
The direction of the axis of easy magnetization of the magnetic sensing part 12 is oriented in the element longitudinal direction. However, since the DC bias magnetic field B is applied in the element width direction (Y direction) of the magnetic sensing unit 12, the magnetic anisotropic energy in the element width direction and the element longitudinal direction can be balanced, and the magnetic sensing unit 12 Can be made substantially isotropic as a whole.

Therefore, the magnetic moment of the magnetic sensing part 12 is hard to be fixed in a certain direction, and the direction of the magnetic moment tends to change when excited by the driving AC current.

That is, a change in impedance in the magneto-sensitive section according to a change in the external magnetic field is increased, and the magnetic field detection sensitivity is improved.

Note that a protective layer made of an insulating material may be formed on the magnetic sensing portion 12 as in a magneto-impedance effect element shown in FIG. 3 or FIG. At this time, if the surfaces of the electrode portions 13 and 13 are exposed on the same plane as the surface of the protective layer, the electrode portions 13 and 13 are connected to the printed pattern when connecting the magneto-impedance effect element on the printed circuit board. It becomes easier.

FIG. 2 is a circuit diagram of a magnetic field detection circuit constituted by using the magneto-impedance effect element of FIG.

In FIG. 2, the DC power supply Ed is connected to the AC power supply Eac.
c are connected in series and M supplied from an AC power supply Eac
A DC current component Idc of 20 to 50 mA is superimposed on the driving AC current Iac in the Hz band. This DC current component I
The drive alternating current Iac on which dc is superimposed flows through the electrodes 13 of the magneto-impedance effect element M in the element longitudinal direction of the magneto-sensitive section 12 which is a soft magnetic thin film. In FIG. 2, it is assumed that the magnetic sensing unit 12 is viewed from above.

The DC current component Idc generates a clockwise magnetic field C around the magnetic sensing part 12, as shown in FIG.
This magnetic field C enters the inside of the magnetic sensing part 12 and
2 is a DC bias magnetic field B applied in the element width direction (Y direction).

While the magnetic sensing part 12 is excited in the element width direction (Y direction) by the driving AC current Iac, an external magnetic field Hex is applied in the element length direction (X direction) of the magnetic sensing part 12. Then, the impedance of the magnetic sensing unit 12 changes.
A change in the impedance of the magnetic sensing unit 12 is extracted as a change in the amplitude of the output voltage Emi between the electrode units 13 connected to both ends of the magnetic sensing unit 12.

The direction in which the direct current component flows may be opposite to that in FIG. When the direction in which the DC current component Idc flows is reversed, the direction of the DC bias magnetic field B is also opposite to that in FIG.

FIG. 3 is a perspective view showing a magneto-impedance effect element according to a second embodiment of the present invention, and FIG.
FIG. 4 is a sectional view taken along line 4-4 of the magneto-impedance effect element of FIG.

The magneto-impedance effect element M1 shown in FIG.
Is a magnetic sensing portion 25 formed by sequentially laminating a soft magnetic thin film 22, an insulating layer 23, and a conductive layer 24 on a substrate 21, and electrode portions 26, 26 formed at both ends of the magnetic sensing portion 25.
It is constituted by. Further, a protective layer 27 made of an insulating material is formed on the magneto-sensitive portion 25.

The electrodes 26 are connected to both ends of the soft magnetic thin film 22 and the conductive layer 24 in the element longitudinal direction.
The magnetic sensing portion 25 is formed in a substantially rectangular or linear pattern. Further, the magnetic sensing part 25 may be formed in a U-shape or a zigzag shape. The element width W of the soft magnetic thin film 22 is 3
The element length L was 1 to 4 mm.

The substrate 21 is made of glass, Si, Si
O_Two, Al_TwoO_ThreeThe insulating layer 23 and the protective layer
27 is an organic material such as a polyimide resin or Si.
O_Two, Al_TwoO _ThreeAnd the like.

The electrode portions 26, 26 and the conductive layer 24 are made of Cu,
It is made of a conductive material such as Ni, Ti, Cr, and Al.

In the present embodiment, the conductive layer 24
The pattern is formed by plating, sputtering, or vapor deposition.

[0098] The soft magnetic thin film 22 is formed of a soft magnetic thin film described later. In the present embodiment, the magnetic sensing unit 25 is formed by forming the conductive layer 24 on the single-layer soft magnetic thin film 22 with the insulating layer 23 interposed therebetween.
5 may be a layer in which a plurality of soft magnetic thin films are stacked with an insulating layer interposed therebetween, and a conductive layer 24 is formed on an upper layer with an insulating layer 23 interposed therebetween. The conductive layer 24 is formed of the soft magnetic thin film 2.
2 may be formed in the lower layer.

In the magneto-impedance effect element according to the present invention, the soft magnetic thin film 22 and the insulating layer 23 are formed by a thin film process such as a sputtering method or a vapor deposition method.

The direction of the axis of easy magnetization of the soft magnetic thin film 22 is the element longitudinal direction (X direction), and is parallel to the direction in which the drive current flows.

Note that a protective layer 27 made of an insulating material is formed on the magneto-sensitive portion 25, but the surface 26a of the electrode portions 26, 26 is exposed on the same plane as the surface of the protective layer 27. Further, when connecting the magneto-impedance effect element on the printed board, it becomes easy to connect the electrode portions 26, 26 to the printed pattern.

FIG. 5 is a circuit diagram of a magnetic field detection circuit formed using the magneto-impedance effect element of FIG.

In FIG. 5, the DC power supply Ed is connected to the AC power supply Eac.
c are connected in series and M supplied from an AC power supply Eac
A DC current component Idc of 20 to 50 mA is superimposed on the driving AC current Iac in the Hz band. This DC current component I
The driving AC current Iac on which dc is superimposed is applied to the electrode portions 26,
26, the soft magnetic thin film 22 and the conductive layer 24 flow in the element longitudinal direction. In FIG. 5, the soft magnetic thin film 2
2 and the conductive layer 24 are viewed from the side.

The DC current component Idc generates a clockwise magnetic field C around the conductive layer 24 as shown in FIG.
This magnetic field C enters the inside of the soft magnetic thin film 22 and becomes a DC bias magnetic field B applied in the element width direction of the soft magnetic thin film 22.

When an external magnetic field Hex is applied in the element length direction of the magnetic sensing section 25 in a state where the magnetic sensing section 25 is excited in the element width direction (Y direction) by the drive AC current Iac, the magnetic sensing section 25 The impedance of the unit 25 changes. Magnetic sensing part 2
5 is extracted as a change in the amplitude of the output voltage Emi between the electrode units 26, 26 connected to both ends of the magnetic sensing unit 25.

Note that the direction in which the DC current component Idc flows may be reversed from that in FIG. When the direction in which the DC current component Idc flows is reversed, the direction of the DC bias magnetic field B is also opposite to that in FIG.

In the magneto-impedance effect element shown in FIG.
The direction of the axis of easy magnetization of the soft magnetic thin film 22 constituting the magnetic sensing portion 25 is oriented in the element longitudinal direction (X direction). However, since a DC bias magnetic field is applied to the soft magnetic thin film 22 in the element width direction (Y direction), the magnetic anisotropic energy in the element width direction and the element longitudinal direction can be balanced, and The magnetic anisotropy can be made almost isotropic as a whole.

Therefore, the magnetic moment of the soft magnetic thin film 22 is less likely to be fixed in a certain direction, and the direction of the magnetic moment tends to change when excited by the driving alternating current.

That is, the magnetic sensing unit 2 according to the change of the external magnetic field
5, the change in impedance is increased, and the magnetic field detection sensitivity is improved.

As in the present embodiment, when the magnetic sensing portion 25 is formed by laminating the conductive layer 24 on the soft magnetic thin film 22 via the insulating layer 23, the driving in which the DC current component Idc is superimposed is performed. The alternating current Iac is applied to the conductive layer 2 having a constant magnetic field distribution.
4, the magnitude and direction of the magnetic field (DC bias magnetic field B) generated from the DC current component are stabilized.
Therefore, a uniform DC bias magnetic field can be applied to the entire soft magnetic thin film 22. When a uniform DC bias magnetic field can be applied to the entire soft magnetic thin film 22, the magnitude of the DC current component Idc that generates the DC bias magnetic field can be reduced. That is, power consumption can be reduced.

FIG. 6 is a perspective view showing a magneto-impedance effect element according to a third embodiment of the present invention.

The magneto-impedance effect element M2 shown in FIG.
A magnetic sensing part 35 formed by sequentially laminating a soft magnetic thin film 32, an insulating layer 33, and a conductive layer 34 on a substrate 31, electrodes 36, 36 connected to both ends of the soft magnetic thin film 32,
And conductive layer electrode portions 37, 37 connected to both ends of the conductive layer 34 in the element longitudinal direction. Also,
A protective layer 38 made of an insulating material is formed on the magnetic sensing part 35.

The soft magnetic thin film 32 is formed in a substantially rectangular or linear pattern. The portion of the conductive layer 34 that overlaps the soft magnetic thin film 32 is formed in the same shape as the soft magnetic thin film 32. The soft magnetic thin film 32 may be formed in a U shape or a zigzag shape. The element width W of the soft magnetic thin film 32 is 30 to 100 μm, and the element length L is 1 to 4 mm.
Formed.

The substrate 31 is made of glass, Si, SiO ₂ , Al ₂
O ₃ is formed in such insulating layer 33 and the protective layer 38 or the SiO ₂ organic material such as polyimide resin, Al ₂ O ₃
And the like.

The electrode portions 36, 36, the conductive layer 34, and the conductive layer electrode portions 37, 37 are made of a conductive material such as Cu, Ni, Ti, Cr, or Al.

In the present embodiment, the electrode portions 36, 3
6. The conductive layer 34 and the conductive layer electrode portions 37, 37 are patterned by plating, sputtering, or vapor deposition.

The soft magnetic thin film 32 is formed by a soft magnetic thin film described later. In the present embodiment, the magnetic sensing unit 35 is formed by forming the conductive layer 34 on the single layer of the soft magnetic thin film 32 with the insulating layer 33 interposed therebetween.
5 may be formed by laminating a plurality of soft magnetic thin films with an insulating layer interposed therebetween and having a conductive layer 34 formed thereon with an insulating layer 33 interposed therebetween. The conductive layer 34 is formed of the soft magnetic thin film 3.
2 may be formed in the lower layer.

In the magneto-impedance effect element according to the present embodiment, the soft magnetic thin film 32 and the insulating layer 33 are formed by a thin film process such as a sputtering method or a vapor deposition method.

The direction of the easy axis of magnetization of the soft magnetic thin film 32 is the element longitudinal direction (X direction), and is parallel to the direction in which the drive current flows.

A protective layer 38 made of an insulating material is formed on the magnetic sensing portion 35, similarly to the magneto-impedance effect element of FIG.
36a and surfaces 37a, 37 of the conductive layer electrode portions 37, 37
If a is exposed on the same plane as the surface of the protective layer 38, the electrodes 36, 36 and the conductive layer electrodes 37, 37 will be connected when connecting the magneto-impedance effect element to the printed circuit board.
Can be easily connected to the print pattern.

FIG. 7 is a circuit diagram of a magnetic field detection circuit formed using the magneto-impedance effect element of FIG.

In FIG. 7, the AC power supply Eac is connected to the electrode section 36,
36, a driving alternating current Iac in the MHz band is supplied to the soft magnetic thin film 32. DC power supply Edc
Are connected to the conductive layer electrode portions 37, 37, and a DC current Idc of 20 to 50 mA is supplied to the conductive layer 34. In FIG. 7, the soft magnetic thin film 32 and the conductive layer 34 are viewed from the side.

As shown in FIG. 7, the DC current Idc generates a clockwise magnetic field C around the conductive layer 34. This magnetic field C enters the inside of the soft magnetic thin film 32 and becomes a DC bias magnetic field B applied in the element width direction (Y direction) of the soft magnetic thin film 32.

In the state where the soft magnetic thin film 32 is excited in the element width direction (Y direction) by the driving AC current Iac,
When an external magnetic field Hex is applied in the element length direction of the soft magnetic thin film 32, the impedance of the soft magnetic thin film 32 changes. The change in the impedance of the soft magnetic thin film 32 is extracted as the change in the amplitude of the output voltage Emi between the electrodes 36 connected to both ends of the soft magnetic thin film 32.

Note that the direction in which the DC current component flows may be reversed from that in FIG. When the direction in which the DC current component Idc flows is reversed, the direction of the DC bias magnetic field B is also opposite to that in FIG.

In the magneto-impedance effect element shown in FIG.
The direction of the easy axis of magnetization of the soft magnetic thin film 32 constituting the magnetic sensing portion 35 is oriented in the element longitudinal direction (X direction). However, since the DC bias magnetic field B is applied in the element width direction (Y direction) of the soft magnetic thin film 22, the magnetic anisotropic energy in the element width direction and the element longitudinal direction can be balanced, and the soft magnetic thin film 32 Can be made substantially isotropic as a whole.

Therefore, it is difficult for the magnetic moment of the soft magnetic thin film 32 to be fixed in a certain direction, and the direction of the magnetic moment tends to change when excited by the driving alternating current.

That is, a change in impedance in the magneto-sensitive portion according to a change in the external magnetic field is increased, and the magnetic field detection sensitivity is improved.

As in the present embodiment, the magnetic sensing part 35 is formed by laminating the conductive layer 34 on the soft magnetic thin film 32 via the insulating layer 33, and the DC current Idc is supplied only to the conductive layer 34. In this case, the magnitude and direction of the magnetic field (DC bias magnetic field) generated from the DC current Idc are stable. Therefore, since a uniform DC bias magnetic field can be applied to the entire soft magnetic thin film 32, the magnitude of the DC current Idc that generates the DC bias magnetic field can be set small. That is, power consumption can be reduced.

The magnetic sensing part 12, the soft magnetic thin film 22, and the soft magnetic thin film 32 have, for example, a composition formula of Fe _71.4 Al _{5.8.
Represented by} Si _13.1 Hf _3.3 C _4.5 Ru _1.9 (at%),
This is a microcrystalline soft magnetic alloy thin film having a crystal grain size of 5 to 30 nm mainly composed of bcc-Fe crystal grains and having HfC crystal grains around bcc-Fe.

The following soft magnetic alloys other than this composition can also be used. T-X-M-Z-Q system (element T is
The element X is an element containing either or both of Si and Al, and the element M is an element containing either or both of Fe and Co.
f, V, Nb, Ta, Mo, and W are one or more elements selected from the group consisting of C and N, and Q is Cr, R
e, Ru, Rh, Ni, Pd, Pt, Au) or other crystal grains and elements having an average crystal grain size of 30 nm or less, such as bcc-Fe, bcc-FeCo, and bcc-Co. A microcrystalline soft magnetic alloy thin film mainly composed of M carbide or nitride crystal grains.

Alternatively, a Co—T—M—X—O system (element T
Is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V, Nb,
Ta, Cr, Mo, Si, P, C, W, B, Al, G
a, Ge and one or more elements selected from rare earth elements, and X is Au, Ag, Cu, Ru, Rh,
One or two or more elements selected from Os, Ir, Pt, and Pd), and bcc-Fe, bcc-F
Crystal grain diameter of 10-30 n made of eCo, bcc-Co, etc.
A microcrystalline soft magnetic alloy thin film comprising a crystalline phase of m and an amorphous phase containing an oxide of M.

Alternatively, Fe--MO--M (M is Ti,
Zr, Hf, V, Nb, Ta, W, and one or more elements selected from rare earth elements), and bc
A microcrystalline soft magnetic alloy thin film comprising a crystal phase mainly composed of c-Fe and having a crystal grain size of 10 to 30 nm and an amorphous phase containing an oxide of M.

The rare earth element is a lanthanide element (L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, Ln) and Sc,
It shows 17 elements of Y.

Further, a Fe—Co—Si—BM system (M
Is an element containing one or both of Cr and Ru), a Co—Ta—Hf based amorphous soft magnetic alloy thin film, and a Co—Zr—Nb based non- Magnetic sensitive part 12, soft magnetic thin film 22 as a crystalline soft magnetic alloy thin film
And a soft magnetic thin film 32 may be formed.

The magnetic sensing part 12, the soft magnetic thin film 22, and the soft magnetic thin film 32 are preferably formed of a soft magnetic thin film having a magnetic permeability of 1 MHz at 1000 or more.

A method for manufacturing the magneto-impedance effect element shown in FIG. 3 will be described. First, a soft magnetic thin film 22 is formed on a substrate 21 made of a non-magnetic material.
Is formed into a substantially rectangular pattern. The element width W of the soft magnetic thin film 22 is 30 to 100 μm, and the element length L is 1 to 4 mm.
Formed.

In the method of manufacturing a magneto-impedance effect element according to the present invention, no magnetic anisotropy is induced in the soft magnetic thin film 22. The soft magnetic thin film 22 is formed without a magnetic field or in a rotating magnetic field. When the formed soft magnetic thin film is formed into a substantially rectangular pattern, the element longitudinal direction of the soft magnetic thin film 22 becomes the easy axis direction due to the shape magnetic anisotropy.

Further, an insulating layer 23 made of an insulating material is formed on the soft magnetic thin film 22 by using a sputtering method or the like. Next, electrode portions 26 connected to both ends of the conductive layer 24 and the soft magnetic thin film 22 laminated on the insulating layer 23 in the device longitudinal direction,
26 are simultaneously formed using a conductive material by a plating method, a sputtering method, or an evaporation method.

When the electrode layers 26 and 26 and the conductive layer 24 are formed so that the surface height of the electrode layers 26 and 26 from the substrate 21 is higher than the surface height of the conductive layer 24, The protective layer 2 made of an insulating material is formed on the conductive layer 24.
7 is formed, and the surface of the protective layer 27 is polished, so that the surfaces 26a, 26a of the electrode portions 26, 26 are protected.
7 can be exposed on the same plane as the surface.

The substrate 21 is made of glass, Si, Si
O_Two, Al_TwoO_ThreeThe insulating layer 23 and the protective layer
27 is an organic material such as a polyimide resin or Si.
O_Two, Al_TwoO _ThreeAnd the like.

The electrode section 26 and the conductive layer 24 are made of Cu, Al,
It is made of a conductive material such as Ni, Ti, and Cr.

The soft magnetic thin film 22 is formed by a soft magnetic thin film or a ribbon as described later.

Next, a method of manufacturing the magneto-impedance effect element shown in FIG. 6 will be described. First, a soft magnetic thin film 32 is formed on a substrate 31 made of a nonmagnetic material, and the soft magnetic thin film 32 is formed into a substantially rectangular pattern.

In the method of manufacturing a magneto-impedance effect element according to the present invention, no magnetic anisotropy is induced in the soft magnetic thin film. The soft magnetic thin film is formed in a non-magnetic field or a rotating magnetic field. When the formed soft magnetic thin film is formed into a substantially rectangular pattern, the element longitudinal direction of the soft magnetic thin film 32 becomes the easy axis direction due to the shape magnetic anisotropy. Soft magnetic thin film 32
Has an element width W of 30 to 100 μm and an element length L of 1 to 4
Formed in μm.

Further, an insulating layer 33 made of an insulating material is formed on the soft magnetic thin film 32 by using a sputtering method or the like. Next, the conductive layer 34 laminated on the insulating layer 33 and the conductive layer 3
A conductive layer electrode part 3 connected to both ends in the element longitudinal direction of the element 4
The electrodes 7, 37 and the electrodes 36, 36 connected to both ends of the soft magnetic thin film 32 in the element longitudinal direction are simultaneously formed by a plating method, a sputtering method, or a vapor deposition method using a conductive material.

The electrode portions 36, 36, the conductive layer electrode portion 3
7 and 37 and the conductive layer 34, the electrode portion 3
6, 36 and the conductive layer electrode portions 37, 37 are formed such that the surface height from the substrate 31 is higher than the surface height of the conductive layer 34, and then a protective layer 38 made of an insulating material is formed on the conductive layer 34. Is formed, and the surfaces 36a, 36a of the electrode portions 36, 36 and the surfaces 37a, 37a of the conductive layer electrode portions 37, 37 are polished by polishing the surface of the protective layer 38.
It can be exposed flush with the surface.

The substrate 31 is made of glass, Si, SiO ₂ , Al ₂
O ₃ is formed in such insulating layer 33 and the protective layer 38 or the SiO ₂ organic material such as polyimide resin, Al ₂ O ₃
And the like.

The electrode portions 36, 36, the conductive layer electrode portions 37, 3
7 and the conductive layer 34 are made of a conductive material such as Cu, Al, Ni, Ti, and Cr.

The soft magnetic thin film 32 is formed of a soft magnetic thin film or a ribbon described later.

The soft magnetic thin films 22 and 32 are, for example, composed mainly of bcc-Fe crystal grains and HfC crystal grains represented by a composition formula of Fe _71.4 Al _5.8 Si _13.1 Hf _3.3 C _4.5 Ru _1.9. It is a crystalline soft magnetic alloy thin film.

However, TX—M—Z— other than this composition
Q-based (element T is an element containing one or both of Fe and Co, element X is an element containing one or both of Si and Al, and element M is
One or more elements selected from Ti, Zr, Hf, V, Nb, Ta, Mo, and W;
Element containing one or both of N,
Q is Cr, Re, Ru, Rh, Ni, Pd, Pt, A
bcc-Fe, bcc-FeCo having an average crystal grain size of 30 nm or less of one or more elements selected from u);
It may be a microcrystalline soft magnetic alloy thin film mainly composed of crystal grains of bcc-Co or the like and crystal grains of carbide or nitride of the element M.

Further, a Co—T—M—X—O system (element T
Is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V, Nb,
Ta, Cr, Mo, Si, P, C, W, B, Al, G
a, Ge and one or more elements selected from rare earth elements, and X is Au, Ag, Cu, Ru, Rh,
One or two or more elements selected from Os, Ir, Pt, and Pd), and bcc-Fe, bcc-F
Crystal grain diameter of 10-30 n made of eCo, bcc-Co, etc.
a microcrystalline soft magnetic alloy thin film composed of a crystalline phase of m and an amorphous phase containing an oxide of M, and a Fe-MO system (M is Ti, Z
r, Hf, V, Nb, Ta, W, and one or two or more elements selected from rare earth elements).
The soft magnetic thin film 22 and the soft magnetic thin film 32 may be formed as a microcrystalline soft magnetic alloy thin film composed of a crystalline phase mainly composed of Fe and having a crystal grain size of 10 to 30 nm and an amorphous phase containing an oxide of M. Good.

The rare earth element is a lanthanide element (L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, Ln) and Sc,
It shows 17 elements of Y.

Alternatively, an Fe—Co—Si—B—M (M is an element containing one or both of Cr and Ru) amorphous soft magnetic alloy thin film, Co—Ta—H
The soft magnetic thin film 22 and the soft magnetic thin film 32 may be formed as an f-based amorphous soft magnetic alloy thin film or a Co-Zr-Nb-based amorphous soft magnetic alloy thin film. The soft magnetic thin film 22 and the soft magnetic thin film 32 are preferably formed of a soft magnetic thin film having a magnetic permeability at 1 MHz of 1,000 or more.

In the present embodiment, the soft magnetic thin film 22
And 32 were formed under the following conditions using an RF magnetron sputtering apparatus.

High frequency power: 200 to 400 (W) Ar gas pressure: 50 (sccm) Pressure during film formation: 3 to 7 (mTorr) Static magnetic field strength during film formation: 800 or more (A / m) Film formation speed: 10 ３３33.5 (nm / min)

The standard condition is that the high frequency power is 400
(W), an Ar gas pressure of 50 (sccm), a film forming pressure of 7 (mTorr), and a film forming static magnetic field strength of 4800 (A /
m), and the film formation rate is 33.5 (nm / min). Also,
The substrate was cooled by indirect cooling.

The soft magnetic thin film 22 of the magneto-impedance effect element shown in FIG. 3 and the soft magnetic thin film 32 of the magneto-impedance effect element shown in FIG. A magnetic ribbon may be used. In this case, the soft magnetic thin ribbon may be formed by injecting a molten alloy of a soft magnetic material onto a cooling roll and rapidly cooling it by contact, and bonding the soft magnetic ribbon to a substrate.

In some applications, the magnetic sensing part 12 of the magneto-impedance effect element shown in FIG. 1, the soft magnetic thin film 22 of the magneto-impedance effect element shown in FIG. 3, or the soft magnetic thin film 32 of the magneto-impedance effect element shown in FIG. As
Similarly, a soft magnetic wire made by a quenching method may be used.

FIG. 8 is a graph showing the relationship between the soft magnetic thin film constituting the magnetosensitive portion of the magneto-impedance effect element and the impedance change at both ends of the soft magnetic thin film when the aspect ratio W / L is changed. is there.

In the magneto-impedance effect element of the present invention, as the aspect ratio W / L of the soft magnetic thin film decreases, the amount of impedance change increases, and the magnetic field detection sensitivity improves. However, in the conventional magneto-impedance effect element, when the aspect ratio W / L of the soft magnetic thin film is reduced to a certain degree or more, the amount of change in impedance is reduced.

Since the soft magnetic thin film is excited by a high-frequency alternating current, a strong skin effect appears. At this time, between the element width W of the soft magnetic thin film, the element length L, the specific resistance ρ, the excitation frequency ω, the permeability μ in the element width direction, and the magnitude | Z | of the impedance of the soft magnetic thin film, There is a relationship represented by the following (Equation 1).

[0164]

(Equation 1)

From equation (1), when the element width W, the element length L, the specific resistance ρ, and the excitation frequency ω of the soft magnetic thin film are fixed, the magnitude of the impedance | Z |
Is proportional to the half power of the magnetic permeability μ in the element width direction.

When an alternating current is applied in the element longitudinal direction and an external magnetic field is applied in the element longitudinal direction of the soft magnetic thin film excited in the element width direction, the magnetic permeability of the soft magnetic thin film in the element width direction is increased. and the magnitude | Z | of the impedance of the soft magnetic thin film changes. The external magnetic field applied to the magneto-sensitive portion is detected by measuring the change in the magnitude | Z | of the impedance of the soft magnetic thin film.

As the aspect ratio W / L decreases, the rate of change of the magnitude | Z | of the impedance with respect to the change of the magnetic permeability μ in the element width direction increases. That is, the change in the magnitude of the output voltage drawn from both ends of the soft magnetic thin film increases, and the magnetic field detection sensitivity of the magneto-impedance effect element improves.

However, if the aspect ratio W / L is too small, the shape magnetic anisotropy in the element longitudinal direction becomes strong, and the element longitudinal direction of the soft magnetic thin film becomes the easy axis of magnetization.
As shown in FIG. 9, a magnetic domain S1 having a magnetization direction in the element longitudinal direction is formed in the soft magnetic thin film S. When the magnetic domain S1 having the magnetization direction in the element longitudinal direction becomes dominant inside the soft magnetic thin film S, the rate of change of the magnetic permeability μ in the element width direction decreases, and the magnetic field detection sensitivity decreases.

When the soft magnetic thin film is formed by patterning a soft magnetic thin film having a high magnetic permeability, for example, a magnetic permeability of 1000 or more at 1 MHz, the element longitudinal direction of the soft magnetic thin film is in the direction of the axis of easy magnetization. The tendency becomes stronger.

In the present invention, the soft magnetic thin film is formed by patterning a soft magnetic thin film having a magnetic permeability of 1000 or more at 1 MHz, and the soft magnetic thin film has an aspect ratio W / L of, for example, 0.0075 to 0.1. As a result, a DC bias magnetic field is applied in the element width direction of the soft magnetic thin film even when the easy axis of magnetization of the magneto-sensitive portion is oriented in the element longitudinal direction. Can be balanced, and the magnetic anisotropy of the soft magnetic thin film or ribbon can be made substantially isotropic as a whole.

That is, as shown in FIG. 10, the value of the total area of the magnetic domain S1 whose magnetization direction is in the element longitudinal direction and the value of the total area of the magnetic domain S2 whose magnetization direction is in the element width direction antagonize, and And the magnetic anisotropic energy in the element longitudinal direction balance.

Therefore, the magnetic moment of the soft magnetic thin film or ribbon is less likely to be fixed in a certain direction, and the direction of the magnetic moment tends to change when excited by an alternating current.

That is, in the present invention, the aspect ratio W / L of the soft magnetic thin film is reduced, so that the impedance change in the magneto-sensitive portion according to the change in the external magnetic field is increased, while the magneto-sensitive portion is changed. Therefore, even if the miniaturization of the magneto-impedance effect element is advanced, a magneto-impedance effect element with improved magnetic field detection sensitivity can be obtained.

FIG. 11 is a graph showing the relationship between the external magnetic field applied to the magneto-impedance effect element and the output voltage.

The magnetic field detecting circuit shown in FIG. 2 is constituted by using the magneto-impedance effect element shown in FIG. 1, and a driving alternating current Iac in which a DC current component Idc is superimposed is supplied to the magneto-impedance effect element. When only the external magnetic field Hex was supplied, the output voltage Emi of the magneto-impedance effect element was compared.

As shown in FIG. 11, the output from both ends of the magneto-sensitive section 12 is higher when the driving AC current Iac in which the DC current component Idc is superimposed is supplied to the magneto-impedance effect element than when only the driving AC current Iac is supplied. Voltage Emi
, The rate of change of the output voltage Emi with respect to the change of the external magnetic field Hex also increases, and the magnetic field detection sensitivity is improved.

The appropriate size of the DC current component to be superimposed on the driving AC current differs depending on the material forming the magnetic sensing portion of the magneto-impedance effect element, the size of the magnetic sensing portion, and the like.

When the aspect ratio W / L of the soft magnetic thin film for forming the magnetically sensitive portion of the magneto-impedance effect element is fixed to a certain value, the appropriate magnitude of the DC current component to be superimposed on the driving AC current is as follows. Can be decided as follows.

First, an external magnetic field Hex having a constant magnitude is applied to the magneto-impedance effect element. In this state, the drive alternating current Iac having a constant execution value is supplied to the magneto-impedance effect element. Further, the output voltage of the magneto-impedance effect element was measured while changing the magnitude of the DC current component Idc superimposed on the driving AC current Iac,
The magnitude of the DC current component Idc when the output voltage becomes maximum is determined.

In the embodiment of the present invention described above,
A DC bias magnetic field applied in the element width direction of the soft magnetic thin film or the ribbon included in the magneto-sensitive portion is formed by using a magnetic field generated from a DC current component flowing along the longitudinal direction of the soft magnetic thin film or the ribbon. However, as shown in FIG. 12, the magnetic field generated from the hard magnetic materials H1 and H2 installed at a distance in the element width direction (Y direction) of the soft magnetic thin film or the thin ribbon 41 is used as the DC bias magnetic field B. You may.

[0181]

According to the present invention described in detail above, a DC bias magnetic field is applied in the width direction of the soft magnetic thin film or ribbon included in the magneto-sensitive section of the magneto-impedance effect element, Even when the aspect ratio W / L of the soft magnetic thin film is reduced and the easy axis direction is oriented in the element longitudinal direction, the magnetic anisotropic energy in the element width direction and the element longitudinal direction can be balanced, and The magnetic anisotropy of the magnetic thin film or ribbon can be made almost isotropic as a whole.

Therefore, the magnetic moment of the soft magnetic thin film or ribbon is less likely to be fixed in a certain direction, and the direction of the magnetic moment tends to change when excited by an alternating current.

That is, even when the size of the magneto-impedance effect element is reduced, a magneto-impedance effect element with improved magnetic field detection sensitivity can be obtained.

In the present invention, for example, a direct current component is superimposed on the drive alternating current flowing in the element longitudinal direction of the magneto-sensitive portion, and a magnetic field generated from the direct current component is used as the direct current bias magnetic field. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a magneto-impedance effect element according to a first embodiment of the present invention;

FIG. 2 is a circuit diagram of a magnetic field detection circuit configured using the magneto-impedance effect element of FIG.

FIG. 3 is a perspective view showing a magneto-impedance effect element according to a second embodiment of the present invention;

FIG. 4 is a sectional view of the magneto-impedance effect element of FIG. 3,

5 is a circuit diagram of a magnetic field detection circuit configured using the magneto-impedance effect element of FIG. 3,

FIG. 6 is a perspective view showing a magneto-impedance effect element according to a third embodiment of the present invention;

7 is a circuit diagram of a magnetic field detection circuit configured using the magneto-impedance effect element of FIG. 6,

FIG. 8 is a graph showing the relationship between the aspect ratio W / L of the soft magnetic thin film of the magneto-impedance effect element and the amount of impedance change at both ends of the soft magnetic thin film;

FIG. 9 is a plan view showing a magnetic domain structure of a soft magnetic thin film in which a longitudinal direction of the element is an easy axis direction,

10 is a plan view showing a magnetic domain structure when a DC bias magnetic field is applied to the soft magnetic thin film of FIG. 9 in the element width direction,

FIG. 11 is a graph showing a relationship between an external magnetic field applied to a magneto-impedance effect element and an output voltage;

FIG. 12 is a circuit diagram of a magnetic field detection circuit configured using the magneto-impedance effect element according to the fourth embodiment of the present invention;

FIG. 13 is a perspective view showing a conventional magneto-impedance effect element.

14 is a circuit diagram of a magnetic field detection circuit configured using the magneto-impedance effect element of FIG.

[Explanation of symbols]

 11, 21, 31 Substrate 12, 25, 35 Magnetic sensing part 13, 26, 36 Electrode part 22, 32 Soft magnetic thin film 23, 33 Insulating layer 24, 34 Conductive layer 37 Conductive layer electrode part B DC bias magnetic field

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01F 10/06 H01F 10/16 10/14 41/18 10/16 G01R 33/06 R 41/18 H01F 1/14 C (72) Inventor Toshiro Sato 186-1 Wakasato, Nagano-shi, Nagano Pref. AC00 BA11 BA16 EB01 GC04

Claims (25)

[Claims] 1. A substantially rectangular magnetic sensing portion including a soft magnetic material having a magneto-impedance effect, and an electrode portion connected to both ends of the magnetic sensing portion in a longitudinal direction of the element for applying a driving AC current. The magneto-impedance effect element having a direct-current bias magnetic field applied in the element width direction of the magneto-sensitive portion. 2. The DC bias component according to claim 1, wherein a DC current component is superimposed on the drive AC current flowing in the element longitudinal direction of the magnetic sensing unit, and a magnetic field generated from the DC current component acts as the DC bias magnetic field. The magneto-impedance effect element as described in the above. 3. The magnetic sensing part is formed of a soft magnetic thin film or a thin strip, and a conductive layer extending in the element longitudinal direction is formed above or below the soft magnetic alloy thin film or the thin strip via an insulating layer. 3. The magneto-impedance effect element according to claim 2, wherein both ends of the soft magnetic thin film or ribbon and the conductive layer in the element longitudinal direction are connected to the electrode part. 4. The magnetic sensing part is formed by forming a conductive layer extending in the element longitudinal direction via an insulating layer on an upper layer or a lower layer of the soft magnetic thin film or the thin strip. The magneto-impedance effect element according to claim 1, wherein a conductive layer electrode portion is connected to both ends of the conductive layer, and a magnetic field generated from a DC current flowing from the conductive layer electrode portion to the conductive layer acts as the DC bias magnetic field. 5. The magneto-impedance effect element according to claim 1, wherein a longitudinal direction of the soft magnetic thin film or the ribbon is an easy axis direction. 6. A protection layer made of an insulating material is formed on the magneto-sensitive portion, and the surface of the electrode portion and / or the surface of the electrode portion of the conductive layer are exposed on the same plane as the surface of the protection layer. Item 6. A magneto-impedance effect element according to any one of Items 1 to 5. 7. The soft magnetic thin film included in the magnetically sensitive part is formed as a microcrystalline soft magnetic alloy thin film having a composition formula represented by Fe _h M _i O _j and having an amorphous structure as a main component. 7. The magneto-impedance effect element according to any one of items 6 to 6. Here, M is Ti, Zr, Hf, V, Nb,
Ta, W and one or more elements selected from rare earth elements, and h, i and j are at% and 45 ≦ h ≦ 7
0, 5 ≦ i ≦ 30, 10 ≦ j ≦ 40, h + i + j = 10
0 is satisfied. 8. A soft magnetic thin film included in the sensing section is formed as a microcrystalline soft magnetic alloy thin film having a composition formula of _{(Co 1-c T c)} x M y X z O w The magneto-impedance effect element according to claim 1. However,
The element T is an element containing one or both of Fe and Ni, and the element M is Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, Si, P, C, W, B, A
one or two selected from l, Ga, Ge and rare earth elements
X is Au, Ag, Cu, Ru,
One or more elements selected from Rh, Os, Ir, Pt and Pd, and the composition ratio is such that c is 0 ≦ c ≦
0.7, x, y, z, w are atomic%, 3 ≦ y ≦ 30, 0
≤ z ≤ 20, 7 ≤ w ≤ 40, and 20 ≤ y + z + w ≤ 60, with the balance being x. 9. soft magnetic thin film included in the sensing section is represented by a compositional formula of _{T 100-def- g X d M} e Z f Q g, bcc-
One or two of Fe, bcc-FeCo, and bcc-Co
7. The magneto-impedance effect element according to claim 1, wherein the magneto-impedance effect element is formed as a microcrystalline soft magnetic alloy thin film mainly composed of at least one kind of crystal grains. Where the element T is F
e, an element containing one or both of Co, the element X is an element containing one or both of Si and Al, and the element M is Ti, Zr, H
f, V, Nb, Ta, Mo, and W are one or more elements selected from the group consisting of C and N, and Q is Cr, R
e, Ru, Rh, Ni, Pd, Pt, Au is one or more elements selected from the group consisting of d, e, f, and g
At t%, 0 ≦ d ≦ 25, 1 ≦ e ≦ 10, 0.5 ≦ f ≦ 1
5, 0 ≦ g ≦ 10. 10. The soft magnetic thin film included in the magnetic sensing unit,
Represented by a compositional formula of _{T 100-pq- efg Si p Al} q M e Z f Q g, bcc-Fe, bcc-FeCo, microcrystalline mainly containing one or more of crystal grains of the bcc-Co 7. The magneto-impedance effect element according to claim 1, wherein the magneto-impedance effect element is formed as a soft magnetic alloy thin film. Here, the element T is an element containing one or both of Fe and Co, and the element M is Ti, Zr, Hf, V, N
one or more elements selected from b, Ta, Mo, and W; the element Z is an element containing one or both of C and N; and Q is Cr, Re, Ru,
One or more elements selected from Rh, Ni, Pd, Pt, and Au, where p, q, e, f, and g are at%
Where 8 ≦ p ≦ 15, 0 ≦ q ≦ 10, 1 ≦ e ≦ 10, 0.
It satisfies the relationship of 5 ≦ f ≦ 15 and 0 ≦ g ≦ 10. 11. The soft magnetic thin film or ribbon included in the magnetically sensitive portion has a composition formula of (Fe _1-a Co _a ) _100-xy (Si _1-b
B _{b) x} M _y in the amorphous soft magnetic alloy thin film or magnetic impedance effect element according to any one of claims 1 to 6 is formed as a thin strip shown. Where M is Cr,
Ru is an element containing one or both of Ru, and a and b representing the composition ratios are 0.05 ≦ a ≦ 0.1, 0.
2 ≦ b ≦ 0.8, and x and y are at% and 10 ≦ x ≦ 3
5, 0 ≦ y ≦ 7. 12. The soft magnetic thin film included in the magnetic sensing unit,
Represented by a compositional formula of Co _l Ta _m Hf _n, magneto-impedance effect element according to any one of claims 1 to 6 is formed as an amorphous soft magnetic alloy thin film was amorphous structure mainly. Here, l, m, and n are at% and 70 ≦
l ≦ 90, 5 ≦ m ≦ 21, 6.6 ≦ n ≦ 15, 1 ≦ m /
It satisfies the relationship of n ≦ 2.5. 13. The soft magnetic thin film included in the magnetic sensing part,
Magneto-impedance effect element according to any of the composition formula Co _a Zr _b Nb claims 1 are formed as amorphous soft magnetic alloy thin film mainly composed of amorphous structure represented by _c 6. However, a, b, and c are at%, and 78 ≦
It satisfies the relationship of a ≦ 91 and 0.5 ≦ b / c ≦ 0.8. 14. (a) On a substrate made of a non-magnetic material,
(B) forming the soft magnetic thin film in a substantially rectangular pattern; and (c) insulating the soft magnetic thin film from an insulating material on the soft magnetic thin film. Forming a layer; (d) forming electrode portions connected to both ends of the soft magnetic thin film in the device longitudinal direction; and (e) forming the device length of the soft magnetic thin film on the insulating layer. Forming a conductive layer extending in the direction and having both end portions connected to the electrode portion. 15. Instead of the step (e), (f) an electrode portion of a conductive layer independent of the electrode portion, and the soft magnetic thin film extends on the insulating layer in the element longitudinal direction, and both ends are formed by The method for manufacturing a magneto-impedance effect element according to claim 14, further comprising a step of forming a conductive layer connected to the conductive layer electrode portion. 16. The magneto-impedance effect element according to claim 14, wherein the step (d) and the step (e), or the step (d) and the step (f) are performed simultaneously. Production method. 17. In the step (d) and / or the step (f), a surface height of the electrode part and the conductive layer electrode part is formed in the step (e) or the step (f). (G) forming a protective layer made of an insulating material on the conductive layer after the step (e) or (f). And (h) polishing the surface of the protective layer to expose the surface of the electrode portion and / or the surface of the electrode portion of the conductive layer on the same plane as the surface of the protective layer.
7. The method for manufacturing a magneto-impedance effect element according to any one of 6. 18. In the steps (a) and (b), instead of forming the soft magnetic thin film by a film forming process,
18. The method according to claim 14, further comprising a step of injecting a molten alloy of a soft magnetic material onto a cooling roll and contact-quenching to form a soft magnetic ribbon, and bonding the soft magnetic ribbon to the substrate. 3. The method for manufacturing a magneto-impedance effect element according to 1. 19. The method according to claim 14, wherein in the step (a), the soft magnetic thin film is formed as a microcrystalline soft magnetic alloy thin film having a composition formula of Fe _h M _i O _j and having an amorphous structure as a main component. 18. The method for manufacturing a magneto-impedance effect element according to any one of items 17 to 17. Where M is Ti, Z
r, Hf, V, Nb, Ta, W, and one or more elements selected from rare earth elements, and h, i, and j are a
At t%, 45 ≦ h ≦ 70, 5 ≦ i ≦ 30, 10 ≦ j ≦ 4
0, h + i + j = 100. 20. The processes of the (a), a said soft magnetic thin film, a microcrystalline soft magnetic alloy thin film composition formula represented by _{(Co 1-c T c)} x M y X z O w A method for manufacturing a magneto-impedance effect element according to any one of claims 14 to 17. Here, the element T is an element containing one or both of Fe and Ni, and the element M is
i, Zr, Hf, V, Nb, Ta, Cr, Mo, Si,
P, C, W, B, Al, Ga, Ge and one or more elements selected from rare earth elements, and X is Au,
Ag, Cu, Ru, Rh, Os, Ir, Pt, Pd, and at least one element selected from the group consisting of: 0 ≦ c ≦ 0.7, x, y, z, w is atomic%
Where 3 ≦ y ≦ 30, 0 ≦ z ≦ 20, 7 ≦ w ≦ 40, 20
<Y + z + w ≦ 60 is satisfied, and the balance is x. 21. The process of the (a), the soft magnetic thin film, the composition formula is represented by _{T 100-defg X d M e} Z f Q g, bcc-Fe, bcc-FeCo, the bcc-Co 18. The method for manufacturing a magneto-impedance effect element according to claim 14, wherein the thin film is formed as a microcrystalline soft magnetic alloy thin film mainly composed of one or more crystal grains. However, the element T is an element containing one or both of Fe and Co, the element X is an element containing one or both of Si and Al, and the element M
Is one or more elements selected from Ti, Zr, Hf, V, Nb, Ta, Mo, W, and the element Z is
C is an element containing one or both of C and N, and Q is Cr, Re, Ru, Rh, Ni, Pd, P
at least one element selected from t and Au, where d, e, f, and g are at% and 0 ≦ d ≦ 25, 1 ≦ e
≦ 10, 0.5 ≦ f ≦ 15, and 0 ≦ g ≦ 10. 22. A process for the (a), wherein the soft magnetic thin film, composition formula _{T 100-pqefg Si p Al q} M e Z f
Represented by _{Q g, bcc-Fe, bcc} -FeCo, bc
14. A microcrystalline soft magnetic alloy thin film mainly comprising one or more crystal grains of c-Co.
8. The method for manufacturing a magneto-impedance effect element according to any one of 7. Here, the element T is an element containing one or both of Fe and Co, and the element M is Ti,
1 selected from Zr, Hf, V, Nb, Ta, Mo, W
A kind or two or more kinds of elements, the element Z is an element containing one or both of C and N, and Q is
One or more elements selected from the group consisting of Cr, Re, Ru, Rh, Ni, Pd, Pt, and Au;
e, f, and g are at%, 8 ≦ p ≦ 15, 0 ≦ q ≦ 10,
1 ≦ e ≦ 10, 0.5 ≦ f ≦ 15, and 0 ≦ g ≦ 10. 23. In the step (a), the soft magnetic thin film or the soft magnetic ribbon is represented by a composition formula (Fe _1-a C
preparation of _{o a) 100-xy (Si} 1-b B b) x M magneto-impedance effect element according to any one of claims 14 to 18 formed as an amorphous soft magnetic alloy thin film or ribbon represented by _y Method. Here, M is an element containing one or both of Cr and Ru, and a, which represents a composition ratio,
b satisfies the relationship of 0.05 ≦ a ≦ 0.1 and 0.2 ≦ b ≦ 0.8, and x and y satisfy the relationship of 10 ≦ x ≦ 35 and 0 ≦ y ≦ 7 in at%. . 24. A process for the (a), claims the soft magnetic thin film, the composition formula is represented by Co _l Ta _m Hf _n, formed as an amorphous soft magnetic alloy thin film was amorphous structure mainly A method for manufacturing a magneto-impedance effect element according to any one of items 14 to 17. Where l, m, n
Is at%, 70 ≦ l ≦ 90, 5 ≦ m ≦ 21, 6.6 ≦
It satisfies the relationship of n ≦ 15 and 1 ≦ m / n ≦ 2.5. 25. The process of the (a), claims the soft magnetic thin film, the composition formula is formed as an amorphous soft magnetic alloy thin film mainly composed of amorphous structure represented by Co _a Zr _b Nb _c A method for manufacturing a magneto-impedance effect element according to any one of items 14 to 17. Where a, b, c
Is at%, 78 ≦ a ≦ 91, 0.5 ≦ b / c ≦ 0.8
It satisfies the relationship.