Magnetic Sensor

Abstract

To increase the sensitivity of a magnetic sensor by using a magnetic impedance effect.SOLUTION: A magnetic sensor 1 includes: a non-magnetic substrate 10; and a receiving element 30 on the substrate 10, the sensitive element having a longer direction and a shorter direction and also having the uniaxial magnetic anisotropy in a direction that intersects with the longer direction, and including a soft magnetic body layer 101 of an amorphous alloy mainly containing Co of which saturation magnetization is in the range from 300 emu / cc to 650 emu / cc, both inclusive, the sensitive element receiving a magnetic field by the magnetic impedance effect.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic sensor. [Background technology]

[0002] The prior art described in the publication includes a magneto-impedance effect element that includes a thin-film magnet made of a hard magnetic film formed on a non-magnetic substrate, an insulating layer covering the thin-film magnet, and a magnetic sensing part made of one or more rectangular soft magnetic films that have been given uniaxial anisotropy and are formed on the insulating layer (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-249406 A Summary of the Invention [Problem to be solved by the invention]

[0004] A magnetic sensor equipped with a sensing element that senses a magnetic field by the magneto-impedance effect utilizes the change in impedance relative to the magnetic field. To improve the sensitivity of the magnetic sensor, it is required that the change in impedance relative to the magnetic field is large.

[0005] An object of the present invention is to improve the sensitivity of a magnetic sensor that uses the magnetoimpedance effect. [Means for solving the problem]

[0006] The magnetic sensor to which the present invention is applied comprises a non-magnetic substrate, a magnetic field sensor provided on the substrate, having a longitudinal direction and a transverse direction, having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, sensing a magnetic field by the magneto-impedance effect, and having a saturation magnetization of 300 emu / cc or more. 550 emu / cc or less, and a sensing element including a soft magnetic layer of an amorphous alloy mainly composed of Co. where , soft The magnetic layer may be characterized by a saturation magnetization of greater than or equal to 300 emu / cc and less than or equal to 450 emu / cc.

[0007] From another perspective, a magnetic sensor to which the present invention is applicable comprises a non-magnetic substrate, and a sensing element provided on the substrate, having a longitudinal direction and a transverse direction, having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and sensing a magnetic field by magneto-impedance effect, the sensing element including a soft magnetic layer of an amorphous alloy containing 3 at % Zr, 17 at % or more and less than 21 at % Nb, and the remainder Co. Here, the soft magnetic layer can be characterized in that Nb is more than 17 at % and less than 21 at %. The soft magnetic layer may also be characterized by having Nb greater than 18 at % and less than 21 at %.

[0008] In such a magnetic sensor, the sensing element can be characterized in that it includes a plurality of soft magnetic layers, and includes a magnetic domain suppression layer between the plurality of soft magnetic layers that suppresses the generation of closure domains in the soft magnetic layers. The sensitive element may also be characterized in that it includes a plurality of soft magnetic layers, and includes a non-magnetic conductive layer between the plurality of soft magnetic layers, the non-magnetic conductive layer having a higher conductivity than the soft magnetic layers. The sensor element can be characterized in that it includes a plurality of soft magnetic layers, and includes an antiferromagnetic coupling layer of a non-magnetic material between the plurality of soft magnetic layers, which antiferromagnetically couples the soft magnetic layers. Effect of the Invention

[0009] According to the present invention, it is possible to improve the sensitivity of a magnetic sensor that uses the magneto-impedance effect. [Brief description of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams illustrating an example of a magnetic sensor to which the present embodiment is applied, where (a) is a plan view and (b) is a cross-sectional view taken along line IB-IB in (a). [Diagram 2] 10 is a diagram illustrating the relationship between a magnetic field applied in the longitudinal direction of a sensing part of a sensing element and the impedance of the sensing element. FIG. [Diagram 3] FIG. 1 is a diagram showing an example of a measurement circuit for measuring impedance changes. [Figure 4] 1 is a diagram showing the relationship between the Nb ratio and the sensitivity and anisotropy magnetic field, where (a) is the sensitivity and (b) is the anisotropy magnetic field. [Diagram 5] FIG. 4 is a graph showing the relationship between the Nb ratio and saturation magnetization in a soft magnetic layer. [Figure 6] 4 is a diagram illustrating the relationship between saturation magnetization and the sensitivity of a magnetic sensor. FIG. [Figure 7] Cross-sectional views of modified magnetic sensors: (a) is a magnetic sensor in which the sensing part of the sensing element is composed of one soft magnetic layer, (b) is a magnetic sensor in which the sensing part of the sensing element is composed of two soft magnetic layers with a magnetic domain suppression layer sandwiched therebetween, and (c) is a magnetic sensor in which the sensing part of the sensing element is composed of two soft magnetic layers with a conductive layer sandwiched therebetween. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention (hereinafter, referred to as the present embodiment) will be described with reference to the accompanying drawings. (Configuration of magnetic sensor 1) Fig. 1 is a diagram illustrating an example of a magnetic sensor 1 to which the present embodiment is applied. Fig. 1(a) is a plan view, and Fig. 1(b) is a cross-sectional view taken along line IB-IB in Fig. 1(a). In Fig. 1(a), the right direction on the paper is the x-direction, the upward direction on the paper is the y-direction, and the surface direction on the paper is the z-direction. In Fig. 1(b), the right direction on the paper is the x-direction, the upward direction on the paper is the z-direction, and the back direction on the paper is the y-direction.

[0012] As shown in FIG. 1(b), a magnetic sensor 1 to which this embodiment is applied includes a non-magnetic substrate 10 and a sensing element 30 that is provided on the substrate 10 and includes a soft magnetic layer that senses a magnetic field. The cross-sectional structure of the magnetic sensor 1 shown in FIG. 1(b) will be described in detail later.

[0013] Here, the soft magnetic material is a material that is easily magnetized by an external magnetic field, but quickly returns to a state in which there is no magnetization or only a small amount of magnetization when the external magnetic field is removed, that is, has a small coercive force.

[0014] The planar structure of the magnetic sensor 1 will be described with reference to FIG. 1(a). The magnetic sensor 1 has a rectangular planar shape, for example. The planar shape of the magnetic sensor 1 is a few mm square. For example, the length in the x direction is 4 mm to 6 mm, and the length in the y direction is 3 mm to 5 mm. The size of the planar shape of the magnetic sensor 1 may be other values. The planar shape of the magnetic sensor 1 may also be a shape other than a rectangle.

[0015] Next, the sensing element 30 provided on the substrate 10 will be described. The sensing element 30 has a plurality of sensing parts 31, each of which has a rectangular shape with a longitudinal direction and a lateral direction in plan view. In FIG. 1(a), the x direction is the longitudinal direction of the sensing element 30. The plurality of sensing parts 31 are arranged so that their longitudinal directions are parallel to each other. The sensing element 30 has a connection part 32 that connects the adjacent sensing parts 31 in series in a zigzag manner, and a terminal part 33 to which an electric wire for supplying current is connected. The sensing part 31 senses a magnetic field or a change in the magnetic field to generate a magneto-impedance effect. That is, the change in the magnetic field or the magnetic field is measured by the impedance change of the sensing element 30 to which the sensing part 31 is connected in series. Hereinafter, the impedance of the sensing element 30 may be referred to as the impedance of the magnetic sensor 1.

[0016] Although eight sensing parts 31 are illustrated in Fig. 1(a), the number of sensing parts 31 does not have to be eight. Therefore, in Fig. 1(a), a dashed line is drawn between the four parts on the upper side of the page and the four parts on the lower side of the page, indicating that the number is not limited to eight.

[0017] The connection portions 32 are provided between the ends of adjacent sensing portions 31, and connect the adjacent sensing portions 31 in series in a zigzag manner. The terminal portion 33 (terminal portions 33a, 33b) is provided at each of the two ends of the sensing portion 31 that are not connected by the connection portion 32. The terminal portion 33 functions as a pad portion for connecting an electric wire that supplies electric current. The terminal portion 33 may be of any size that allows an electric wire to be connected. Although the terminal portion 33 (terminal portions 33a, 33b) is provided on the right side of the paper in FIG. 1(a), it may be provided on the left side, or may be provided separately on the left and right sides.

[0018] Here, the length of the sensing portion 31 in the longitudinal direction (x direction) is defined as length L. The width of the sensing portion 31 in the lateral direction is defined as width W. The interval between adjacent sensing portions 31 is defined as interval G. The length L of the sensing portion 31 is, for example, 1 mm to 10 mm, the width W is, for example, 10 μm to 150 μm, and the interval G is, for example, 10 μm to 150 μm. The size of each sensing portion 31 (length L, width W, thickness, etc.), the number of sensing portions 31, the interval G between the sensing portions 31, etc. may be set depending on the sensing, i.e., the magnitude of the magnetic field to be measured. The number of sensing portions 31 may be one.

[0019] Next, the cross-sectional structure of the magnetic sensor 1 will be described with reference to FIG. The substrate 10 is a substrate made of a non-magnetic material, and examples of such substrates include oxide substrates such as glass and sapphire, semiconductor substrates such as silicon, and metal substrates such as aluminum, stainless steel, and metals plated with nickel-phosphorus. If the substrate 10 has high conductivity, an insulating layer that electrically insulates the substrate 10 from the sensing element 30 may be provided on the surface of the substrate 10 on which the sensing element 30 is provided. Examples of insulators that constitute such an insulating layer include oxides such as SiO2, Al2O3, and TiO2, and nitrides such as Si3N4 and AlN. Here, the substrate 10 is described as being glass.

[0020] As an example, the sensor element 30 includes four soft magnetic layers 101a, 101b, 101c, and 101d from the substrate 10 side. The sensor element 30 includes a magnetic domain suppression layer 102a between the soft magnetic layers 101a and 101b, which suppresses the generation of closure domains in the soft magnetic layers 101a and 101b. The sensor element 30 also includes a magnetic domain suppression layer 102b between the soft magnetic layers 101c and 101d, which suppresses the generation of closure domains in the soft magnetic layers 101c and 101d. The sensor element 30 also includes a conductive layer 103 between the soft magnetic layers 101b and 101c, which reduces the resistance (here, this refers to electrical resistance) of the sensor element 30. When the soft magnetic layers 101a, 101b, 101c, and 101d are not distinguished from one another, they are referred to as soft magnetic layers 101. When the magnetic domain suppression layers 102a and 102b are not distinguished from one another, they are referred to as magnetic domain suppression layers 102.

[0021] The soft magnetic layer 101 is made of a soft magnetic material of an amorphous alloy that exhibits a magneto-impedance effect. The thickness of the soft magnetic layer 101 is, for example, 100 nm to 1 μm. In the sensing element 30 to which this embodiment is applied, the soft magnetic layer 101 is made of a soft magnetic material of an amorphous alloy mainly composed of Co, with saturation magnetization of 300 emu / cc or more and 650 emu / cc or less. The soft magnetic layer 101 will be described in detail later. In this specification, the term "amorphous alloy" and "amorphous metal" refer to those which have a structure that does not have a regular arrangement of atoms as in crystals, and which are formed by a method such as sputtering.

[0022] The magnetic domain suppression layer 102 suppresses the generation of closure domains in the upper and lower soft magnetic layers 101 that sandwich the magnetic domain suppression layer 102 . In general, a plurality of magnetic domains with different magnetization directions are easily formed in the soft magnetic layer 101. In this case, a closure magnetic domain with a ring-shaped magnetization direction is formed. When the external magnetic field becomes stronger, the magnetic domain walls move, and the area of ​​the magnetic domains with the same magnetization direction as the external magnetic field becomes larger, and the area of ​​the magnetic domains with the opposite magnetization direction to the external magnetic field becomes smaller. When the external magnetic field becomes even stronger, magnetization rotation occurs in the magnetic domains with the magnetization direction different from the external magnetic field so that the magnetization direction becomes the same as the external magnetic field. Finally, the magnetic domain walls existing between adjacent magnetic domains disappear, and one magnetic domain (single magnetic domain) is formed. In other words, when a closure magnetic domain is formed, the Barkhausen effect occurs in which the magnetic domain walls constituting the closure magnetic domains move discontinuously in a step-like manner as the external magnetic field changes. This discontinuous movement of the magnetic domain walls becomes noise in the magnetic sensor 1, and there is a risk of causing a decrease in the S / N ratio in the output obtained from the magnetic sensor 1. The magnetic domain suppression layer 102 suppresses the formation of multiple small magnetic domains in the soft magnetic layers 101 provided above and below the magnetic domain suppression layer 102. This suppresses the formation of closure domains and suppresses the generation of noise caused by discontinuous movement of domain walls. Note that it is sufficient for the magnetic domain suppression layer 102 to have the effect of forming fewer magnetic domains, i.e., larger magnetic domains, compared to a case where the magnetic domain suppression layer 102 is not included.

[0023] Examples of such a magnetic domain suppression layer 102 include non-magnetic materials such as Ru and SiO2, and non-magnetic amorphous metals such as CrTi, AlTi, CrB, CrTa, CoW, etc. The thickness of such a magnetic domain suppression layer 102 is, for example, 10 nm to 100 nm.

[0024] The conductive layer 103 reduces the resistance of the sensing element 30. In other words, the conductive layer 103 has a higher conductivity than the soft magnetic layer 101, and reduces the resistance of the sensing element 30 compared to the case where the conductive layer 103 is not included. The magnetic field or change in the magnetic field caused by the sensing element 30 is measured by a change (ΔZ) in impedance (hereinafter, referred to as impedance Z) when an AC current is passed between the two terminals 33a and 33b. In this case, the higher the frequency of the AC current, the larger the change rate ΔZ / ΔH of the impedance Z (hereinafter, referred to as impedance change rate ΔZ / ΔH) with respect to the change in the external magnetic field (here, referred to as ΔH). However, if the frequency of the AC current is increased without including the conductive layer 103, the impedance change rate ΔZ / ΔH is reduced due to the stray capacitance in the magnetic sensor 1. In other words, if the resistance of the sensing element 30 is R, the stray capacitance is C, and the sensing element 30 is a parallel circuit of the resistance R and the stray capacitance C, the relaxation frequency f0 of the magnetic sensor 1 can be expressed by equation (1).

[0025]

number

[0026] As can be seen from formula (1), when the stray capacitance C is large, the relaxation frequency f0 is small. Therefore, when the frequency of the AC current is made higher than the relaxation frequency f0, the impedance change rate ΔZ / ΔH decreases. Therefore, the conductive layer 103 is provided to reduce the resistance R of the sensing element 30 and to increase the relaxation frequency f0.

[0027] As the conductive layer 103, it is preferable to use a metal or alloy having high conductivity, and it is more preferable to use a metal or alloy having high conductivity and non-magnetic. As the conductive layer 103, metals such as Al, Cu, Ag, and Au can be used. The thickness of the conductive layer 103 is, for example, 10 nm to 1 μm. The conductive layer 103 may be any layer that reduces the resistance of the sensing element 30 compared to a case where the conductive layer 103 is not included.

[0028] The upper and lower soft magnetic layers 101 sandwiching the magnetic domain suppression layer 102, and the upper and lower soft magnetic layers 101 sandwiching the conductive layer 103 are antiferromagnetically coupled (AFC) to each other. The antiferromagnetic coupling between the lower and upper soft magnetic layers 101 suppresses the demagnetizing field, and the sensitivity of the magnetic sensor 1 is improved.

[0029] The magnetic sensor 1 is manufactured as follows. First, a photoresist pattern is formed on the surface of the substrate 10 by a known photolithography technique, covering the surface of the substrate 10 except for the planar shape of the sensing element 30. Next, the soft magnetic layer 101a, the magnetic domain suppression layer 102a, the soft magnetic layer 101b, the conductive layer 103, the soft magnetic layer 101c, the magnetic domain suppression layer 102b, and the soft magnetic layer 101d are deposited on the substrate 10 in this order, for example, by a sputtering method. Then, the soft magnetic layer 101a, the magnetic domain suppression layer 102a, the soft magnetic layer 101b, the conductive layer 103, the soft magnetic layer 101c, the magnetic domain suppression layer 102b, and the soft magnetic layer 101d deposited on the photoresist are removed together with the photoresist. Then, a laminate consisting of the soft magnetic layer 101a, the magnetic domain suppression layer 102a, the soft magnetic layer 101b, the conductive layer 103, the soft magnetic layer 101c, the magnetic domain suppression layer 102b, and the soft magnetic layer 101d, which has been processed into the planar shape of the sensor element 30, remains on the substrate 10. In other words, the sensor element 30 is formed.

[0030] The soft magnetic layer 101 is provided with uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, for example, in the transverse direction (y direction in FIG. 1(a)). The direction intersecting the longitudinal direction may have an angle of more than 45° and not more than 90° with respect to the longitudinal direction. The uniaxial magnetic anisotropy can be provided by subjecting the sensing element 30 formed on the substrate 10 to, for example, heat treatment at 400° C. in a rotating magnetic field of 3 kG (0.3 T) (heat treatment in a rotating magnetic field) followed by heat treatment at 400° C. in a static magnetic field of 3 kG (0.3 T) (heat treatment in a static magnetic field). Instead of providing the uniaxial magnetic anisotropy by the heat treatment in a rotating magnetic field and the heat treatment in a static magnetic field, the magnetron sputtering method may be used when depositing the soft magnetic layer 101 constituting the sensing element 30. That is, the magnetic field generated by a magnet used in magnetron sputtering imparts uniaxial magnetic anisotropy to the soft magnetic layer 101 at the same time as the soft magnetic layer 101 is deposited.

[0031] In the manufacturing method described above, the connection part 32 and the terminal part 33 are formed integrally at the same time as the sensing part 31. The connection part 32 and the terminal part 33 may be formed of a conductive metal such as Al, Cu, Ag, Au, etc. Also, a conductive metal such as Al, Cu, Ag, Au, etc. may be laminated on the connection part 32 and the terminal part 33 formed integrally at the same time as the sensing part 31.

[0032] (Operation of sensing element 30) The function of the sensing element 30 will now be described. 2 is a diagram illustrating the relationship between the magnetic field H applied in the longitudinal direction (x direction in FIG. 1(a)) of the sensing part 31 of the sensing element 30 and the impedance Z of the sensing element 30. In FIG. 2, the horizontal axis represents the magnetic field H, and the vertical axis represents the impedance Z. The impedance Z is measured by passing an AC current between the terminals 33a, 33b of the sensing element 30 shown in FIG. 1(a).

[0033] As shown in FIG. 2, the impedance Z of the sensing element 30 increases as the magnetic field H applied in the longitudinal direction of the sensing part 31 increases. Conversely, the impedance Z of the sensing element 30 decreases when the applied magnetic field H becomes larger than the anisotropic magnetic field Hk. In a range smaller than the anisotropic magnetic field Hk, by using a portion where the change amount ΔZ of the impedance Z is large relative to the change amount ΔH of the magnetic field H, that is, a portion where the impedance change rate ΔZ / ΔH is steep (large), a weak change in the magnetic field H can be extracted as the change amount ΔZ of the impedance Z. In FIG. 2, the center of the magnetic field H where the impedance change rate ΔZ / ΔH is large is shown as the magnetic field Hb. In other words, the change amount ΔH of the magnetic field H in the vicinity of the magnetic field Hb (the range indicated by the arrow in FIG. 2) can be measured with high accuracy. Here, the sensitivity is the part where the change amount ΔZ of the impedance Z is the steepest (the impedance change rate ΔZ / ΔH is the largest), that is, the change amount Zmax of the impedance per unit magnetic field in the magnetic field Hb is divided by the impedance Z in the magnetic field Hb (written as impedance Zb), (Zmax / Zb). The higher the sensitivity Zmax / Zb, the greater the magnetic impedance effect, and the easier it is to measure the magnetic field or the change in the magnetic field. In other words, the steeper the change in the impedance Z with respect to the magnetic field H, the higher the sensitivity Zmax / Zb. For this, the smaller the anisotropic magnetic field Hk, the better. In other words, in the magnetic sensor 1, it is preferable that the sensitivity Zmax / Zb is high, and for this, it is preferable that the anisotropic magnetic field Hk is small. The magnetic field Hb is sometimes called a bias magnetic field. Hereinafter, the magnetic field Hb is written as a bias magnetic field Hb.

[0034] (Method of measuring sensitivity Zmax / Zb) FIG. 3 is a diagram showing an example of a measurement circuit for measuring impedance changes. The measurement circuit shown in FIG. 3 is a bridge circuit 50. The bridge circuit 50 includes terminals A, B, C, and D. An impedance Z is set between the terminals AB, CD, and DA. A sample S with a variable impedance is provided between the terminals BC. That is, the impedance Z is set on three of the four sides constituting the bridge, and the sample S is provided on the remaining side. An AC power source P for supplying an AC current is connected between the terminals AC. A voltage Vin is applied between the terminals AC. In the bridge circuit 50, a voltage ΔV between the terminals BD is measured.

[0035] Here, it is assumed that the impedance of the sample S changes from Z to Z+ΔZ. When the sample S has impedance Z, the four sides of the bridge circuit 50 have impedance Z. Therefore, the bridge circuit 50 is in a balanced state, and no voltage is generated between the terminals BD. In other words, ΔV is 0V. On the other hand, when the sample S has impedance Z+ΔZ, ΔV becomes ΔZ / (4Z)×Vin (ΔV ≒ ΔZ / (4Z)×Vin).

[0036] When the sample S is the magnetic sensor 1, the above ΔZ / Z when ΔH=1 corresponds to the sensitivity Zmax / Zb (ΔZ / Z=Zmax / Zb). In this manner, the sensitivity Zmax / Zb of the magnetic sensor 1 is measured by the bridge circuit 50. Note that the sensitivity Zmax / Zb of the magnetic sensor 1 may be measured by a method other than the bridge circuit 50.

[0037] (Relationship between Nb ratio and sensitivity Zmax / Zb) As described in the prior art document 1, the soft magnetic material constituting the soft magnetic layer 101 of the magnetic sensor 1 using the magneto-impedance effect is a Co alloy containing 12 at % Nb, 3 at % Zr, and the remainder Co. 85 Nb 12Zr3 (sometimes written as Co12Nb3Zr) has been used. However, it was discovered that increasing the ratio of Nb improved the sensitivity Zmax / Zb. In the following, when the ratios of Co, Nb, and Zr are not stated, it will be written as CoNbZr.

[0038] Fig. 4 is a diagram showing the relationship between the Nb ratio and the sensitivity Zmax / Zb and the anisotropic magnetic field Hk. Fig. 4(a) shows the sensitivity Zmax / Zb, and Fig. 4(b) shows the anisotropic magnetic field Hk. In Fig. 4(a), the horizontal axis shows the Nb ratio (at%), and the vertical axis shows the sensitivity Zmax / Zb ( / Oe). In Fig. 4(b), the horizontal axis shows the Nb ratio (at%), and the vertical axis shows the anisotropic magnetic field Hk (Oe).

[0039] In the magnetic sensor 1, the number of sensitive portions 31 in the sensitive element 30 was 24, the length L of the sensitive portion 31 was 4 mm, the width W of the sensitive portion 31 was 100 μm, and the interval G between the sensitive portions 31 was 50 μm.

[0040] The soft magnetic layers 101a, 101b, 101c, and 101d (see FIG. 1(b)) were made of CoNbZr, an amorphous alloy mainly composed of Co, with the Nb ratio varied from 12, 17, 18, 19, and 20 at%. The Zr ratio was fixed at 3 at%. In other words, the Co ratio was decreased in accordance with the increase in the Nb ratio. The thickness of each of the soft magnetic layers 101a, 101b, 101c, and 101d was 500 nm.

[0041] The magnetic domain suppression layers 102a and 102b (see FIG. 1(b)) are made of CrTi with an atomic ratio of 1:1. The magnetic domain suppression layers 102a and 102b each had a thickness of 25 nm.

[0042] The conductive layer 103 (see FIG. 1(b)) is made of Ag and has a thickness of 400 nm.

[0043] As shown in Figure 4(a), when the Nb ratio increases, the sensitivity Zmax / Zb improves. On the other hand, as shown in Figure 4(b), when the Nb ratio increases, the anisotropic magnetic field Hk decreases. In other words, as the anisotropic magnetic field Hk decreases, the change in impedance Z with respect to the magnetic field H becomes steeper. This is thought to improve the sensitivity Zmax / Zb.

[0044] (Relationship between Nb ratio and saturation magnetization Ms) Fig. 5 is a diagram showing the relationship between the Nb ratio and saturation magnetization Ms in the soft magnetic layer 101. In Fig. 5, the horizontal axis is the Nb ratio (at%) and the vertical axis is the saturation magnetization Ms (emu / cc). Here, the soft magnetic layer 101 was provided on the substrate 10, and the saturation magnetization Ms was measured. A state in which the domain wall disappears due to the magnetic field is said to be saturated with magnetization. The magnetization in the saturated state is called the saturation magnetization Ms.

[0045] In FIG. 5, in addition to CoNbZr (black circles), an amorphous alloy containing Co as the main component, indicated as CoFeCrMnSiB (white circles), is added. Note that CoFeCrMnSiB contains 1.4 at% Fe, 13.8 at% Si, 3.6 at% Mn, 5 at% Cr, 9.5 at% B, and the remainder is Co. In other words, CoFeCrMnSiB shown here is a 66.7 Fe 1.4 Cr5Mn 3.6 S 13.8 B 9.5 (It is sometimes written as Co1.4Fe5Cr3.6Mn13.8Si9.5B.) FIG. 5 also shows the case where the Nb ratio in CoNbZr is 21 at %.

[0046] As shown in Figure 5, in CoNbZr, the saturation magnetization Ms decreases as the Nb ratio increases. In other words, the magnetization is easily saturated by the magnetic field. The saturation magnetization Ms of CoFeCrMnSiB is 390 emu / cc, which is close to the 421 emu / cc of CoNbZr with 19 at% Nb and the 365 emu / cc of CoNbZr with 20 at% Nb.

[0047] Incidentally, CoNbZr with 21 at% Nb has a small saturation magnetization Ms of 284 emu / cc, but when used as magnetic sensor 1, the anisotropy magnetic field Hk was too small and it did not function as a magnetic sensor. This is thought to be because when the saturation magnetization Ms is too small, it becomes difficult to impart uniaxial anisotropy.

[0048] (Relationship between saturation magnetization Ms and sensitivity Zmax / Zb) FIG. 6 is a diagram for explaining the relationship between saturation magnetization Ms and sensitivity Zmax / Zb of the magnetic sensor 1. In FIG. 6, the horizontal axis is saturation magnetization Ms (emu / cc), and the vertical axis is sensitivity Zmax / Zb ( / Oe). Here, CoNbZr (black circles) and CoFeCrMnSiB (white circles) with different Nb ratios (at%) are shown. For CoNbZr, the Nb ratio (at%) is shown in parentheses. Furthermore, the magnetic sensor 1 using CoFeCrMnSiB has the structure shown in FIG. 1. However, the thickness of each of the soft magnetic layers 101a, 101b, 101c, and 101d is set to 250 nm.

[0049] As shown in FIG. 6, when the saturation magnetization Ms is 300 emu / cc or more and 650 emu / cc or less, the sensitivity Zmax / Zb is improved compared to when the saturation magnetization Ms is 801 emu / cc with an Nb ratio of 12 at%. This is not limited to when the soft magnetic layer 101 is made of CoNbZr, but also applies to when the soft magnetic layer 101 is made of CoFeCrMnSiB. This shows that in the magnetic sensor 1 using the magneto-impedance effect, if the saturation magnetization Ms of the soft magnetic layer 101 containing Co as the main component is 300 emu / cc or more and 650 emu / cc or less, the sensitivity Zmax / Zb is improved. Here, Co being the main component means that the Co ratio is 60 at% or more. As mentioned above, if the saturation magnetization Ms is less than 300 emu / cc, the anisotropic magnetic field Hk becomes too small, which is not preferable.

[0050] Also, as shown in Fig. 4(b), when the Nb ratio exceeds 17 at%, the anisotropic magnetic field Hk is further reduced. On the other hand, as shown in Fig. 6, when the Nb ratio exceeds 17 at%, the saturation magnetization Ms is 550 emu / cc or less, so it is better to use a soft magnetic layer 101 whose main component is Co and whose saturation magnetization Ms is 300 emu / cc or more and 550 emu / cc or less. Furthermore, as shown in Fig. 6, when the saturation magnetization Ms is 450 emu / cc or less, the sensitivity Zmax / Zb becomes higher, so it is even better to use a soft magnetic layer 101 whose main component is Co and whose saturation magnetization Ms is 300 emu / cc or more and 450 emu / cc or less.

[0051] In CoNbZr, the Nb ratio is preferably 17 at% or more and less than 21 at%. As described above, if the Nb ratio is 21 at% or more, the anisotropic magnetic field Hk becomes too small, which is not preferable. Furthermore, as shown in FIG. 4(b), if the Nb ratio is more than 17 at%, the anisotropic magnetic field Hk is further reduced, so it is more preferable that the Nb ratio is more than 17 at% and less than 21 at%. Furthermore, as shown in FIG. 6, if the Nb ratio is more than 18 at%, the sensitivity Zmax / Zb becomes higher, so it is even more preferable that the Nb ratio is more than 18 at% and less than 21 at%.

[0052] (Modification) Fig. 7 is a cross-sectional view of a modified example of the magnetic sensor 1. Fig. 7(a) shows a magnetic sensor 2 in which the sensing part 31 in the sensing element 30 is composed of a single soft magnetic layer 101, Fig. 7(b) shows a magnetic sensor 3 in which the sensing part 31 in the sensing element 30 is composed of two soft magnetic layers 101 sandwiching a magnetic domain suppression layer 102, and Fig. 7(c) shows a magnetic sensor 4 in which the sensing part 31 in the sensing element 30 is composed of two soft magnetic layers 101 sandwiching a conductive layer 103. In Figs. 7(a), 7(b), and 7(c), the same parts as those in the magnetic sensor 1 shown in Fig. 1 are denoted by the same reference numerals.

[0053] The sensing section 31 may be composed of one soft magnetic layer 101 as shown in Fig. 7(a), may be composed of two soft magnetic layers 101 sandwiching a magnetic domain suppression layer 102 as shown in Fig. 7(b), or may be composed of two soft magnetic layers 101 sandwiching a conductive layer 103 as shown in Fig. 7(c). The sensing section 31 may also be provided with three or more soft magnetic layers 101. Also, instead of the magnetic domain suppression layer 102 in FIG. 7(b), an antiferromagnetic coupling layer that antiferromagnetically couples the upper and lower soft magnetic layers 101 may be used. Also, the magnetic domain suppression layers 102a and 102b in the magnetic sensor 1 shown in FIG. 1 may be antiferromagnetic coupling layers. As described above, the magnetic domain suppression layer 102 suppresses the generation of closure domains and antiferromagnetically couples the upper and lower soft magnetic layers 101. The antiferromagnetic coupling layer is a layer that does not have a function of suppressing the generation of closure domains or has a weak function of suppressing the generation of closure domains. By having the antiferromagnetic coupling layer, the upper and lower soft magnetic layers 101 are antiferromagnetically coupled, suppressing the demagnetizing field and improving the sensitivity Zmax / Zb of the magnetic sensor. Such an antiferromagnetic coupling layer can be made of Ru or a Ru alloy. The sensing section 31 may include a plurality of layers, including a magnetic domain suppression layer 102, a conductive layer 103, and an antiferromagnetic coupling layer.

[0054] Furthermore, in the magnetic sensors 1 to 4, a magnet (hereinafter referred to as a thin-film magnet) composed of a hard magnetic layer that applies a bias magnetic field Hb (see FIG. 2) may be provided between the substrate 10 and the sensing element 30. A hard magnetic material is a material with a large coercive force, that is, when magnetized by an external magnetic field, the magnetized state is maintained even when the external magnetic field is removed. The thin-film magnet may be provided such that the magnetic poles N and S pass magnetic flux in the longitudinal direction of the sensing part 31 in the sensing element 30. Even when a thin-film magnet is provided between the substrate 10 and the sensing element 30, the substrate 10 and the thin-film magnet are collectively referred to as the substrate.

[0055] Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various modifications and combinations may be made as long as they are not contrary to the spirit of the present invention. [Explanation of symbols]

[0056] 1, 2, 3, 4...magnetic sensor, 10...substrate, 30...sensing element, 31...sensing portion, 32...connection portion, 33, 33a, 33b...terminal portion, 50...bridge circuit, 101, 101a, 101b, 101c, 101d...soft magnetic layer, 102, 102a, 102b...magnetic domain suppression layer, 103...conductive layer, H...magnetic field, Hb...bias magnetic field, Hk...anisotropic magnetic field, Ms...saturation magnetization, P...AC power supply, Z...impedance

Claims

1. A non-magnetic substrate; a sensing element provided on the substrate, having a longitudinal direction and a transverse direction, having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and sensing a magnetic field by a magneto-impedance effect, the sensing element including a soft magnetic layer of an amorphous alloy containing Co as a main component and having a saturation magnetization of 300 emu / cc or more and 550 emu / cc or less; A magnetic sensor comprising:

2. 2. The magnetic sensor according to claim 1, wherein the soft magnetic layer has a saturation magnetization of 300 emu / cc or more and 450 emu / cc or less.

3. A non-magnetic substrate; a sensing element provided on the substrate, having a longitudinal direction and a transverse direction, having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and sensing a magnetic field by a magneto-impedance effect, the sensing element including a soft magnetic layer of an amorphous alloy containing 3 at % Zr, 17 at % or more and less than 21 at % Nb, and the remainder being Co; A magnetic sensor comprising:

4. 4. The magnetic sensor according to claim 3, wherein the soft magnetic layer contains more than 17 at % and less than 21 at % Nb.

5. 5. The magnetic sensor according to claim 4, wherein the soft magnetic layer contains more than 18 at % and less than 21 at % Nb.

6. The sensing element includes a plurality of the soft magnetic layers, 6. The magnetic sensor according to claim 1, further comprising a magnetic domain suppression layer between the soft magnetic layers, the magnetic domain suppression layer suppressing the generation of closure domains in the soft magnetic layers.

7. The sensing element includes a plurality of the soft magnetic layers, 7. The magnetic sensor according to claim 1, further comprising a non-magnetic conductive layer between the plurality of soft magnetic layers, the non-magnetic conductive layer having a higher conductivity than the soft magnetic layers.

8. The sensing element includes a plurality of the soft magnetic layers, 8. The magnetic sensor according to claim 1, further comprising an antiferromagnetic coupling layer made of a non-magnetic material between the soft magnetic layers, for antiferromagnetically coupling the soft magnetic layers.

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