magnetic sensor

Abstract

The present invention relates to a magnetic sensor. The object of the present invention is to improve the sensitivity of a magnetic sensor utilizing the magnetoimpedance effect. The solution of the present invention is that a magnetic sensor (1) is provided with a non-magnetic substrate (10), and a sensing element (30) provided on the substrate (10), the sensing element (30) comprising a soft magnetic layer (101) of an amorphous alloy with Co as the main component, having a saturation magnetization of 300 emu / cc or more and 650 emu / cc or less, and the sensing element (30) having a long side direction and a short side direction, having uniaxial magnetic anisotropy in a direction intersecting the long side direction, and sensing a magnetic field by the magnetoimpedance effect.

Description

TECHNICAL FIELD

[0001] The present application relates to a magnetic sensor. BACKGROUND

[0002] As the prior art described in the publication, there is a magnetic impedance effect element which has a thin film magnet formed on a non-magnetic substrate and formed of a hard magnetic film, an insulating layer covering an upper portion of the thin film magnet, and a magnetic sensing portion formed on the insulating layer, imparted with uniaxial anisotropy, and formed of one or more rectangular soft magnetic films (see Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2008-249406 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Further, a magnetic sensor which has a sensing element that senses a magnetic field by a magnetic impedance effect utilizes the fact that an impedance changes with respect to a magnetic field. In order to improve the sensitivity of the magnetic sensor, it is required that the change of the impedance with respect to the magnetic field be increased.

[0008] An object of the present application is to improve the sensitivity of a magnetic sensor which utilizes a magnetic impedance effect.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] A magnetic sensor to which the present application is applied has a non-magnetic substrate, and a sensing element provided on the substrate, the sensing element including a soft magnetic layer of an amorphous alloy having Co as a main component and having a saturation magnetization of 300 emu / cc or more and 650 emu / cc or less, and having a long side direction and a short side direction, having uniaxial magnetic anisotropy in a direction intersecting the long side direction, and sensing a magnetic field by a magnetic impedance effect.

[0011] Here, it can be characterized that the saturation magnetization of the soft magnetic layer is 300 emu / cc or more and 550 emu / cc or less.

[0012] Further, it can be characterized that the saturation magnetization of the soft magnetic layer is 300 emu / cc or more and 450 emu / cc or less.

[0013] The magnetic sensor to which the present application is applied has a non-magnetic substrate and a sensing element provided on the substrate, the sensing element including a soft magnetic layer of an amorphous alloy containing Zr at 3 at%, Nb at 17 at% or more and less than 21 at%, and Co as a balance, and having a long side direction and a short side direction, uniaxial magnetic anisotropy in a direction intersecting the long side direction, and sensing a magnetic field by a magnetoimpedance effect, from another viewpoint.

[0014] Here, it can be characterized that the Nb is higher than 17 at% and lower than 21 at% in the soft magnetic layer.

[0015] Further, it can be characterized that the Nb is higher than 18 at% and lower than 21 at% in the soft magnetic layer.

[0016] For such a magnetic sensor, it can be characterized that the sensing element includes a plurality of soft magnetic layers, and a magnetic domain suppressing layer that suppresses generation of a closed magnetic domain in the soft magnetic layer is included between the plurality of soft magnetic layers.

[0017] Further, it can be characterized that the sensing element includes a plurality of soft magnetic layers, and a non-magnetic electrically conductive layer that is higher in electrical conductivity than the soft magnetic layer is included between the plurality of soft magnetic layers.

[0018] Moreover, it can be characterized that the sensing element includes a plurality of soft magnetic layers, and a non-magnetic antiferromagnetic coupling layer that antiferromagnetically couples the soft magnetic layers is included between the plurality of soft magnetic layers.

[0019] Effects of Invention

[0020] According to the present application, it is possible to improve the sensitivity of a magnetic sensor that utilizes a magnetoimpedance effect. BRIEF DESCRIPTION OF DRAWINGS

[0021] [ Figure 1 ] is a drawing for explaining an example of a magnetic sensor to which the present embodiment is applied. (a) is a plan view, and (b) is a cross-sectional view along the IB-IB line in (a).

[0022] [ Figure 2 ] is a drawing for explaining the relationship between a magnetic field applied in the long side direction of the sensing portion of the sensing element and the impedance of the sensing element.

[0023] [ Figure 3 ] is a drawing showing an example of a measurement circuit that measures the change in impedance.

[0024] [ Figure 4 ] is a drawing showing the relationship between the Nb ratio and the sensitivity and the anisotropic magnetic field. (a) is the sensitivity, and (b) is the anisotropic magnetic field.

[0025] [ Figure 5Fig. 1 is a graph showing the relationship between the ratio of Nb in the soft magnetic layer and the saturation magnetization.

[0026] [ Figure 6 Fig. 2 is a graph illustrating the relationship between the saturation magnetization and the sensitivity of the magnetic sensor.

[0027] [ Figure 7 Fig. 3 is a sectional view of a modification of the magnetic sensor. (a) is a magnetic sensor in which the sensing portion in the sensing element is composed of one layer of soft magnetic layer, (b) is a magnetic sensor in which the sensing portion in the sensing element is composed of two layers of soft magnetic layer sandwiching a magnetic domain suppression layer, and (c) is a magnetic sensor in which the sensing portion in the sensing element is composed of two layers of soft magnetic layer sandwiching a conductor layer.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] 1, 2, 3, 4... magnetic sensor, 10... substrate, 30... sensing element, 31... sensing portion, 32... connecting 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... conductor layer, H... magnetic field, Hb... bias magnetic field, Hk... anisotropic magnetic field, Ms... saturation magnetization, P... alternating current power source, Z... impedance DETAILED DESCRIPTION

[0030] Hereinafter, an embodiment of the present application (hereinafter, described as the present embodiment) will be described with reference to the drawings.

[0031] (Configuration of the magnetic sensor 1)

[0032] Figure 1 Fig. 4 is a graph illustrating one example of the magnetic sensor 1 to which the present embodiment is applied. Figure 1 (a) is a plan view, Figure 1 (b) is a sectional view along Figure 1 the IB-IB line in (a). Figure 1 In (a), the right direction of the paper is taken as the x direction, the upward direction of the paper is taken as the y direction, and the surface direction of the paper is taken as the z direction. Figure 1 In (b), the right direction of the paper is taken as the x direction, the upward direction of the paper is taken as the z direction, and the back direction of the paper is taken as the y direction.

[0033] As shown in (b), the magnetic sensor 1 to which the present embodiment is applied is provided with a non-magnetic substrate 10 and a sensing element 30 provided on the substrate 10, the sensing element 30 including a soft magnetic layer that senses a magnetic field. Figure 1 Note that, regarding the magnetic sensor 1 to which the present embodiment is applied, the same applies to the magnetic sensor 1 to which the present embodiment is applied.

[0034] Figure 1 ​(b) a cross-sectional structure of the magnetic sensor 1 shown, which is described in detail later.

[0035] Here, the soft magnetic body is a so-called material having a small coercive force, that is, a material that is easily magnetized by an external magnetic field but quickly returns to a state of no magnetization or a small magnetization if the external magnetic field is removed.

[0036] With Figure 1 (a), a planar structure of the magnetic sensor 1 is described. As an example, the magnetic sensor 1 has a planar shape of a quadrangle. The planar shape of the magnetic sensor 1 is several 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. Note that the size of the planar shape of the magnetic sensor 1 can also be other values. In addition, the planar shape of the magnetic sensor 1 can also be a shape other than a quadrangle.

[0037] Next, the sensing element 30 provided on the substrate 10 is described. The sensing element 30 has a plurality of sensing portions 31 having a planar shape of a long strip shape having a long side direction and a short side direction. Figure 1 In (a), the x direction is the long side direction of the sensing element 30. The plurality of sensing portions 31 are arranged in parallel in the long side direction. Furthermore, the sensing element 30 has a connection portion 32 connecting adjacent sensing portions 31 in series in a meandering shape, and a terminal portion 33 to which an electric wire for supplying a current is connected. The sensing portion 31 senses a magnetic field or a change in a magnetic field to generate a magneto-impedance effect. That is, the sensing portion 31 measures a magnetic field or a change in a magnetic field using a change in the impedance of the sensing element 30 connected in series. Hereinafter, the impedance of the sensing element 30 is sometimes described as the impedance of the magnetic sensor 1.

[0038] In Figure 1 In (a), eight sensing portions 31 are illustrated, but the number of sensing portions 31 can not be eight. Therefore, Figure 1 In (a), the number of sensing portions 31 is not limited to eight, as indicated by the broken line between the four sensing portions 31 on the upper side of the paper and the four sensing portions 31 on the lower side of the paper.

[0039] The connection portion 32 is provided between the end portions of adjacent sensing portions 31 to connect the adjacent sensing portions 31 in series in a meandering shape.

[0040] The terminal portion 33 (terminal portions 33a, 33b) is provided at the two end portions of the sensing portion 31 that are not connected by the connection portion 32. The terminal portion 33 functions as a pad portion to which an electric wire for supplying a current is connected. The terminal portion 33 can be as large as the electric wire can be connected. Note that the terminal portion 33 (terminal portions 33a, 33b) is provided on the right side in the plane of (a), but can be provided on the left side, and can be provided separately on the left and right sides. Figure 1 (a) is provided on the right side in the plane of (a), but can be provided on the left side, and can be provided separately on the left and right sides.

[0041] Here, the length of the inductive portion 31 in the long direction (x direction) is set to a length L. Also, the width of the inductive portion 31 in the short direction is set to a width W. The interval between adjacent inductive portions 31 is set to an interval G. The length L of the inductive 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. Note that the size (length L, width W, thickness, etc.) of each inductive portion 31, the number of inductive portions 31, the interval G between inductive portions 31, etc. can be set in accordance with the size of the magnetic field to be induced, i.e., the magnetic field to be measured, etc. Note that the inductive portion 31 can also be one.

[0042] Next, the cross-sectional structure of the magnetic sensor 1 will be described with reference to FIG. 2B. Figure 1 (b).

[0043] The substrate 10 is a substrate formed of a non-magnetic material, and examples include an oxide substrate such as glass or sapphire, a semiconductor substrate such as silicon, or a metal substrate such as aluminum, stainless steel, or a metal on which nickel-phosphorus plating has been performed. Note that in the case where the substrate 10 is highly conductive, it is preferable to provide an insulator layer that electrically insulates the substrate 10 from the inductive element 30 on the surface of the substrate 10 on the side on which the inductive element 30 is provided. As the insulator that constitutes such an insulator layer, oxides such as SiO2, Al2O3, and TiO2, or nitrides such as Si3N4 and AlN can be used. Here, the substrate 10 will be described as being formed of glass.

[0044] As an example, the inductive element 30 includes four soft magnetic layers 101a, 101b, 101c, and 101d from the side of the substrate 10. Also, the inductive element 30 includes a magnetic domain suppression layer 102a between the soft magnetic layer 101a and the soft magnetic layer 101b that suppresses the generation of closed magnetic domains in the soft magnetic layer 101a and the soft magnetic layer 101b. Furthermore, the inductive element 30 includes a magnetic domain suppression layer 102b between the soft magnetic layer 101c and the soft magnetic layer 101d that suppresses the generation of closed magnetic domains in the soft magnetic layer 101c and the soft magnetic layer 101d. Also, the inductive element 30 includes a conductor layer 103 between the soft magnetic layer 101b and the soft magnetic layer 101c that reduces the resistance (here, referred to as the resistance value) of the inductive element 30. In the case where the soft magnetic layers 101a, 101b, 101c, and 101d are not distinguished from one another, they are referred to as soft magnetic layers 101. In the case where the magnetic domain suppression layers 102a and 102b are not distinguished from one another, they are referred to as magnetic domain suppression layers 102.

[0045] The soft magnetic layer 101 is composed of a soft magnetic body of an amorphous alloy exhibiting a magnetoimpedance effect. The thickness of the soft magnetic layer 101 is, for example, 100 nm to 1 μm. In the inductive element 30 to which the present embodiment is applied, the soft magnetic layer 101 is composed of a soft magnetic body of an amorphous alloy having a saturation magnetization of 300 emu / cc or more and 650 emu / cc or less and having Co as a main component. The soft magnetic layer 101 will be described in detail later.

[0046] Note that, in the present specification, the amorphous alloy and the amorphous metal mean a substance having a structure in which atomic order arrangement like a crystal is not present and formed by a sputtering method or the like.

[0047] The magnetic domain suppressing layer 102 suppresses the formation of a closed magnetic domain in the soft magnetic layers 101 above and below the magnetic domain suppressing layer 102.

[0048] Generally, in the soft magnetic layer 101, a plurality of magnetic domains in which the directions of magnetization are different from each other are easily formed. In this case, a closed magnetic domain in which the directions of magnetization are annular is formed. If the external magnetic field becomes large, the magnetic wall moves, the area of the magnetic domain in which the direction of the external magnetic field is the same as the direction of magnetization becomes large, and the area of the magnetic domain in which the direction of the external magnetic field is opposite to the direction of magnetization becomes small. Further, if the external magnetic field further becomes large, in the magnetic domain in which the direction of magnetization is different from the direction of the external magnetic field, magnetization rotation occurs in such a manner that the direction of magnetization and the direction of the external magnetic field are oriented in the same direction. Further, finally, the magnetic wall present between the adjacent magnetic domains disappears, and one magnetic domain (single magnetic domain) is formed. That is, if a closed magnetic domain is formed, the Barkhausen effect in which the magnetic wall constituting the closed magnetic domain discontinuously moves in steps in accordance with the change in the external magnetic field occurs. The discontinuous movement of the magnetic wall becomes noise in the magnetic sensor 1, and it is possible that the S / N in the output obtained from the magnetic sensor 1 is reduced. The magnetic domain suppressing layer 102 suppresses the formation of a plurality of magnetic domains having a small area in the soft magnetic layers 101 provided above and below the magnetic domain suppressing layer 102. Thereby, the formation of a closed magnetic domain can be suppressed, and the generation of noise caused by the discontinuous movement of the magnetic wall can be suppressed. Note that, for the magnetic domain suppressing layer 102, the effect in which the number of magnetic domains formed is reduced, that is, the size of the magnetic domain is increased, can be obtained compared to the case in which the magnetic domain suppressing layer 102 is not included.

[0049] As such a magnetic domain suppressing layer 102, a non-magnetic body such as Ru, SiO2, a non-magnetic amorphous metal such as CrTi, AlTi, CrB, CrTa, and CoW can be given. The thickness of such a magnetic domain suppressing layer 102 is, for example, 10 nm to 100 nm.

[0050] The electrically conductive layer 103 reduces the resistance of the inductive element 30. That is, the electrically conductive layer 103 has higher electric conductivity than the soft magnetic layer 101, and thus the resistance of the inductive element 30 is reduced compared to the case where the electrically conductive layer 103 is not included. The magnetic field or the change in the magnetic field induced by the inductive element 30 is measured using the change in the impedance (hereinafter, referred to as impedance Z) when an alternating current flows between the two terminal portions 33a, 33b. At this time, the higher the frequency of the alternating current, the larger the change rate ΔZ / ΔH (hereinafter, referred to as impedance change rate ΔZ / ΔH) of the impedance Z with respect to the change ΔH in the external magnetic field. However, if the frequency of the alternating current is increased in the state where the electrically conductive layer 103 is not included, the impedance change rate ΔZ / ΔH is reduced due to the parasitic capacitance of the magnetic sensor 1. That is, if the resistance of the inductive element 30 is R, and the parasitic capacitance is C, and the inductive element 30 is a parallel circuit of the resistance R and the parasitic capacitance C, the relaxation frequency f0 of the magnetic sensor 1 is represented by Expression (1).

[0051] [Mathematical Expression 1]

[0052]

[0053] As is clear from Expression (1), the relaxation frequency f0 is reduced if the parasitic capacitance C is large. Therefore, if the frequency of the alternating current is higher than the relaxation frequency f0, the impedance change rate ΔZ / ΔH is reduced. Therefore, the electrically conductive layer 103 is provided to reduce the resistance R of the inductive element 30, and thus the relaxation frequency f0 is increased.

[0054] As such an electrically conductive layer 103, a metal or an alloy having high electric conductivity is preferably used, and a metal or an alloy having high electric conductivity and being non-magnetic is more preferably used. As such an electrically conductive layer 103, metals such as Al, Cu, Ag, and Au can be given. The thickness of the electrically conductive layer 103 is, for example, 10 nm to 1 μm. For the electrically conductive layer 103, it is only necessary to reduce the resistance of the inductive element 30 compared to the case where the electrically conductive layer 103 is not included.

[0055] Note that 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 electrically conductive layer 103 are antiferromagnetically coupled (AFC). By antiferromagnetically coupling the upper and lower soft magnetic layers 101, the demagnetizing field is suppressed, and the sensitivity of the magnetic sensor 1 is improved.

[0056] The magnetic sensor 1 can be manufactured as described below.

[0057] First, a photoresist pattern covering the portion of the sensing element 30 (excluding its planar shape) is formed on the substrate 10 using a known photolithography technique. Next, a soft magnetic layer 101a, a domain suppression layer 102a, a soft magnetic layer 101b, a conductive layer 103, a soft magnetic layer 101c, a domain suppression layer 102b, and a soft magnetic layer 101d are sequentially deposited on the substrate 10 using, for example, sputtering. Then, the soft magnetic layers 101a, 102a, 101b, 103, 101c, 102b, and 101d deposited on the photoresist are removed along with the photoresist. Thus, a stack formed of a soft magnetic layer 101a, a magnetic domain suppression layer 102a, a soft magnetic layer 101b, a conductive layer 103, a soft magnetic layer 101c, a magnetic domain suppression layer 102b, and a soft magnetic layer 101d, which has been processed into a planar shape for the sensing element 30, remains on the substrate 10. That is, the sensing element 30 is formed.

[0058] For the soft magnetic layer 101, along the direction intersecting the long side direction, for example, the short side direction ( Figure 2 (a) The y-direction imparts uniaxial magnetic anisotropy. It should be noted that the direction intersecting the long side direction is an angle greater than 45° and less than 90° relative to the long side direction. Uniaxial magnetic anisotropy can be imparted 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). Alternatively, the imparting of uniaxial magnetic anisotropy can be achieved during the deposition of the soft magnetic layer 101 constituting the sensing element 30 using magnetron sputtering, instead of heat treatment in a rotating magnetic field and heat treatment in a static magnetic field. That is, the magnetic field formed by the magnet (magnet) used in magnetron sputtering imparts uniaxial magnetic anisotropy to the soft magnetic layer 101 during deposition.

[0059] In the manufacturing method described above, the connecting portion 32, the terminal portion 33, and the sensing portion 31 are formed integrally. It should be noted that the connecting portion 32 and the terminal portion 33 can be formed using conductive metals such as Al, Cu, Ag, and Au. Alternatively, conductive metals such as Al, Cu, Ag, and Au can be laminated onto the connecting portion 32 and the terminal portion 33, which are integrally formed with the sensing portion 31.

[0060] (Operation of sensing element 30)

[0061] The function of the sensing element 30 will be explained.

[0062] Figure 1 For the long side direction of the sensing part 31 of the sensing element 30 ( Figure 2 The figure illustrates the relationship between the magnetic field H applied in the x-direction (a) and the impedance Z of the sensing element 30. Figure 1 In the diagram, the horizontal axis represents the magnetic field H, and the vertical axis represents the impedance Z. It should be noted that, for the impedance Z, in... Figure 2 (a) The alternating current is passed between the terminals 33a and 33b of the sensing element 30 shown in the figure to measure the current.

[0063] like Figure 2 As shown, the impedance Z of the sensing element 30 increases as the magnetic field H applied in the long side direction of the sensing section 31 increases. Furthermore, the impedance Z of the sensing element 30 decreases when the applied magnetic field H is larger than the anisotropic magnetic field Hk. Within a range smaller than the anisotropic magnetic field Hk, when using the portion where the change in impedance Z ΔZ is large relative to the change in magnetic field H ΔH—that is, the portion where the impedance change rate ΔZ / ΔH is steep (large)—it is possible to extract the slight change in magnetic field H as the change in impedance Z ΔZ. Figure 2 In this context, the center of a magnetic field H with a large impedance change rate ΔZ / ΔH is denoted as magnetic field Hb. That is, the vicinity of magnetic field Hb can be measured with high precision. Figure 3 The change in magnetic field H (ΔH) within the range indicated by the middle arrow is the amount of change in magnetic field H. Here, the value (Zmax / Zb) obtained by dividing the steepest part of the change in impedance Z (the part with the largest rate of change in impedance ΔZ / ΔH), i.e., the change in impedance per unit magnetic field in magnetic field Hb, by the impedance Z at magnetic field Hb (referred to as impedance Zb) is the sensitivity. The higher the sensitivity Zmax / Zb, the greater the magnetoresistance effect, and the easier it is to measure the magnetic field or the change in magnetic field. In other words, the steeper the change in impedance Z relative to magnetic field H, the higher the sensitivity Zmax / Zb. Therefore, the smaller the anisotropic magnetic field Hk, the better. That is, in magnetic sensor 1, a high sensitivity Zmax / Zb is preferred, and for this reason, a small anisotropic magnetic field Hk is preferred. Magnetic field Hb is sometimes called the bias magnetic field. Hereinafter, magnetic field Hb will be referred to as bias magnetic field Hb.

[0064] (Method for determining sensitivity Zmax / Zb)

[0065] Figure 3 This diagram illustrates an example of a measuring circuit for measuring impedance changes. Figure 4The illustrated measurement circuit is a bridge circuit 50. The bridge circuit 50 has terminals A, B, C, and D. Further, the impedance Z is set between terminals A and B, between terminals C and D, and between terminals D and A. The sample S, whose impedance changes, is provided between terminals B and C. That is, of the four sides of the bridge, the impedance Z is set in three sides, and the sample S is set in the remaining one side. The alternating current power source P, which supplies an alternating current, is connected between terminals A and C. The voltage Vin is between terminals A and C. Further, in the bridge circuit 50, the voltage AV between terminals B and D is measured.

[0066] Here, for the sample S, the impedance is changed from Z to Z+ΔZ. When the sample S is the impedance Z, the four sides of the bridge circuit 50 are the impedance Z. Therefore, the bridge circuit 50 is in a balanced state, and no voltage is generated between terminals B and D. That is, AV is 0 V. On the other hand, when the sample S becomes the impedance Z+ΔZ, AV becomes ΔZ / (4Z) x Vin (AV = ΔZ / (4Z) x Vin).

[0067] In a state where the sample S is the magnetic sensor 1 to which the bias magnetic field Hb is applied, ΔH = 1, the above ΔZ / Z corresponds to the sensitivity Zmax / Zb (ΔZ / Z = Zmax / Zb). Thus, the sensitivity Zmax / Zb of the magnetic sensor 1 can be measured using the bridge circuit 50. Note that the sensitivity Zmax / Zb of the magnetic sensor 1 can also be measured by a method other than the bridge circuit 50.

[0068] (Relationship between Nb ratio and sensitivity Zmax / Zb)

[0069] Prior to this, as a soft magnetic body that constitutes the soft magnetic body layer 101 of the magnetic sensor 1 that utilizes the magneto-impedance effect, a Co 85 Nb 12 Zr3 (sometimes written as Co12Nb3Zr). However, it was found that the sensitivity Zmax / Zb is improved when the ratio of Nb is increased. Hereinafter, when the ratios of Co, Nb, and Zr are not written, it is written as CoNbZr.

[0070] Figure 4 A graph showing the relationship between the Nb ratio and the sensitivity Zmax / Zb and the anisotropic magnetic field Hk. Figure 4 (a) is the sensitivity Zmax / Zb, Figure 4 (b) is the anisotropic magnetic field Hk. Figure 4 In (a), the horizontal axis is the Nb ratio (at%), and the vertical axis is the sensitivity Zmax / Zb ( / Oe). Figure 1In (b), the horizontal axis is the Nb ratio (at%), and the vertical axis is the anisotropic magnetic field Hk (Oe).

[0071] For the magnetic sensor 1, the number of the sensing portions 31 in the sensing element 30 was made 24, the length L of the sensing portion 31 was made 4 mm, the width W of the sensing portion 31 was made 100 μm, and the interval G between the sensing portions 31 was made 50 μm.

[0072] The soft magnetic layers 101a, 101b, 101c, 101d (see Figure 1 (b)) were CoNbZr as an amorphous alloy having Co as a main component, and the Nb ratio was changed to 12, 17, 18, 19, and 20 at%. Note that the Zr ratio was fixed at 3 at%. That is, the Co ratio was decreased in correspondence with the increase in the Nb ratio. The thickness of each of the soft magnetic layers 101a, 101b, 101c, 101d was made 500 nm.

[0073] The magnetic domain suppressing layers 102a, 102b (see Figure 1 (b)) were CrTi with an atomic ratio of 1:1. The thickness of each of the magnetic domain suppressing layers 102a, 102b was made 25 nm.

[0074] The conductor layer 103 (see Figure 4 (b)) was Ag. The thickness of the conductor layer 103 was made 400 nm.

[0075] As shown in Figure 4 (a), if the Nb ratio is increased, the sensitivity Zmax / Zb is improved. On the other hand, as shown in Figure 5 (b), if the Nb ratio is increased, the anisotropic magnetic field Hk becomes small. That is, since the anisotropic magnetic field Hk becomes small, the change in the impedance Z with respect to the magnetic field H becomes steep. Thus, it is considered that the sensitivity Zmax / Zb is improved.

[0076] (Relationship between the Nb ratio and the saturation magnetization Ms)

[0077] Figure 5 A graph showing the relationship between the Nb ratio in the soft magnetic layer 101 and the saturation magnetization Ms. Figure 5 In the graph, the horizontal axis is the Nb ratio (at%), and the vertical axis is the saturation magnetization Ms (emu / cc). Here, the saturation magnetization Ms was measured with the soft magnetic layer 101 provided on the substrate 10. The state in which the magnetic wall disappears due to the magnetic field is referred to as the magnetization saturation. Further, the magnetization in the state in which the magnetization has been saturated is referred to as the saturation magnetization Ms.

[0078] Figure 5In the present embodiment, in addition to CoNbZr (black circles), an amorphous alloy described as CoFeCrMnSiB (white circles) is added, which is an amorphous alloy having Co as a main component. Note that in CoFeCrMnSiB, Fe is 1.4 at%, Si is 13.8 at%, Mn is 3.6 at%, Cr is 5 at%, B is 9.5 at%, and the balance is Co. That is, CoFeCrMnSiB shown here is Co 66.7 Fe 1.4 Cr5Mn 3.6 Si 13.8 B 9.5 (sometimes described as Co1.4Fe5Cr3.6Mn13.8Si9.5B).

[0079] In addition, Figure 5 In the present embodiment, a case where the Nb ratio in CoNbZr is 21 at% is also shown.

[0080] As Figure 6 shown, for CoNbZr, as the Nb ratio becomes larger, the saturation magnetization Ms becomes smaller. That is, saturation of magnetization caused by a magnetic field is likely to occur. In addition, the saturation magnetization Ms of CoFeCrMnSiB is 390 emu / cc, which is close to 421 emu / cc for CoNbZr with Nb of 19 at% and 365 emu / cc for CoNbZr with Nb of 20 at%.

[0081] Note that for CoNbZr with Nb of 21 at%, the saturation magnetization Ms is as small as 284 emu / cc, but in the case where a magnetic sensor 1 is made, the anisotropic magnetic field Hk becomes too small to function as a magnetic sensor. It is considered that this is because if the saturation magnetization Ms is too small, it is difficult to impart uniaxial anisotropy.

[0082] (Relationship between saturation magnetization Ms and sensitivity Zmax / Zb)

[0083] Figure 6 is a graph for explaining the relationship between the saturation magnetization Ms and the sensitivity Zmax / Zb of the magnetic sensor 1. Figure 1 In the present embodiment, the horizontal axis is the saturation magnetization Ms (emu / cc), and the vertical axis is the sensitivity Zmax / Zb ( / Oe). Here, CoNbZr (black circles) with different Nb ratios (at%) and CoFeCrMnSiB (white circles) described above are shown. Note that for CoNbZr, the Nb ratio (at%) is shown in (). In addition, the magnetic sensor 1 using CoFeCrMnSiB has the structure shown in Figure 6 . Here, each of the thicknesses of the soft magnetic layers 101a, 101b, 101c, and 101d is 250 nm.

[0084] like Figure 4 As shown, when the saturation magnetization Ms is 300 emu / cc or higher and 650 emu / cc or lower, the sensitivity Zmax / Zb is improved compared to the case where the saturation magnetization Ms is 801 emu / cc when the Nb ratio is 12 at%. This is not limited to the case where the soft magnetic layer 101 is composed of CoNbZr, but also holds true when the soft magnetic layer 101 is composed of CoFeCrMnSiB. This indicates that for the magnetic sensor 1 utilizing the magnetoresistance effect, if the saturation magnetization Ms of the soft magnetic layer 101 with Co as the main component is 300 emu / cc or higher and 650 emu / cc or lower, the sensitivity Zmax / Zb is improved. Here, "Co as the main component" means that the Co ratio is 60 at% or higher. It should be noted that, as mentioned above, if the saturation magnetization Ms is lower than 300 emu / cc, the anisotropic magnetic field Hk becomes too small, which is therefore not preferred.

[0085] In addition, such as Figure 6 As shown in (b), if the Nb ratio is higher than 17 at%, the anisotropic magnetic field Hk further decreases. On the other hand, as Figure 6 As shown, when the Nb ratio is higher than 17 at%, the saturation magnetization Ms is 550 emu / cc or less. Therefore, it is more preferable to use a soft magnetic layer 101 with a saturation magnetization Ms of 300 emu / cc or more and 550 emu / cc or less, which is mainly composed of Co. Furthermore, as... Figure 4 As shown, if the saturation magnetization Ms is below 450 emu / cc, the sensitivity Zmax / Zb becomes higher. Therefore, it is even more preferable to use a soft magnetic layer 101 with Co as the main component and a saturation magnetization Ms of 300 emu / cc or more and 450 emu / cc or less.

[0086] In CoNbZr, the Nb ratio is preferably 17 at% or higher and less than 21 at%. It should be noted that, as mentioned earlier, if the Nb ratio is 21 at% or higher, the anisotropic magnetic field Hk becomes too small, and therefore is not preferred. Furthermore, if... Figure 6 As shown in (b), if the Nb ratio is higher than 17 at%, the anisotropic magnetic field Hk further decreases; therefore, an Nb ratio higher than 17 at% and lower than 21 at% is more preferred. Furthermore, as... Figure 7 As shown, if the Nb ratio is higher than 18 at%, the sensitivity Zmax / Zb becomes even higher. Therefore, it is further preferred that the Nb ratio is higher than 18 at% and lower than 21 at%.

[0087] (Modified Example)

[0088] Figure 7 This is a cross-sectional view of a modified example of magnetic sensor 1.Figure 7 (a) is a magnetic sensor 2 in which the sensing portion 31 in the sensing element 30 is composed of one soft magnetic layer 101, Figure 7 (b) is a magnetic sensor 3 in which the sensing portion 31 in the sensing element 30 is composed of two soft magnetic layers 101 sandwiching a magnetic domain suppressing layer 102, Figure 7 (c) is a magnetic sensor 4 in which the sensing portion 31 in the sensing element 30 is composed of two soft magnetic layers 101 sandwiching a conductive layer 103. Note that, in Figure 7 (a), Figure 7 (b), Figure 1 (c), the same parts as the magnetic sensor 1 shown in Figure 7 are labeled with the same reference numerals.

[0089] The sensing portion 31 can be composed of one soft magnetic layer 101 as shown in Figure 7 (a), or can be composed of two soft magnetic layers 101 sandwiching a magnetic domain suppressing layer 102 as shown in Figure 7 (b), or can be composed of two soft magnetic layers 101 sandwiching a conductive layer 103 as shown in Figure 7 (c). In addition, the sensing portion 31 can be provided with three or more soft magnetic layers 101.

[0090] In addition, instead of the magnetic domain suppressing layer 102 in Figure 1 (b), an antiferromagnetic coupling layer that antiferromagnetically couples the upper and lower soft magnetic layers 101 can be used. In addition, the magnetic domain suppressing layers 102a, 102b in the magnetic sensor 1 shown in Figure 2 (b) can be used as the antiferromagnetic coupling layer. As described above, the magnetic domain suppressing layer 102 suppresses the generation of closed magnetic domains, and antiferromagnetically couples the upper and lower soft magnetic layers 101. The antiferromagnetic coupling layer is a layer that does not have the function of suppressing the generation of closed magnetic domains, or has a weak function of suppressing the generation of closed magnetic domains. By having the antiferromagnetic coupling layer, the upper and lower soft magnetic layers 101 are antiferromagnetically coupled, whereby the demagnetizing field is suppressed, and the sensitivity Zmax / Zb of the magnetic sensor is improved. As such an antiferromagnetic coupling layer, Ru or a Ru alloy can be given.

[0091] Furthermore, the sensing portion 31 can include a plurality of layers such as the magnetic domain suppressing layer 102, the conductive layer 103, and the antiferromagnetic coupling layer.

[0092] In addition, in the magnetic sensors 1 to 4, a bias magnetic field Hb can be applied between the substrate 10 and the sensing element 30 (see ​magnet composed of a hard magnetic layer (hereinafter, referred to as a thin film magnet). The hard magnetic body is a so-called material with a large coercive force, that is, if magnetized by an external magnetic field, it maintains the magnetized state even if the external magnetic field is removed. For the thin film magnet, the magnetic poles N and S are disposed in a manner that the magnetic flux passes in the long side direction of the induction portion 31 in the induction element 30. Note that even if the thin film magnet is disposed between the substrate 10 and the induction element 30, the substrate 10 and the thin film magnet are collectively regarded as a substrate.

[0093] The above describes the embodiment of the present application, but the present application is not limited to the embodiment. Various modifications and combinations can be made as long as the gist of the present application is not violated.

Claims

1. A magnetic sensor comprising: a non-magnetic substrate; and a sensing element provided on the substrate, the sensing element including a soft magnetic layer of an amorphous alloy having Co as a main component and having a saturation magnetization of 300 emu / cc or more and 550 emu / cc or less, and the sensing element having a long side direction and a short side direction, having uniaxial magnetic anisotropy in a direction intersecting the long side direction, and sensing a magnetic field by a magnetoimpedance effect. The amorphous alloy having Co as a main component is CoNbZr in which Zr is 3 at%, Nb is higher than 17 at% and lower than 21 at%, and the balance is Co, or CoFeCrMnSiB in which Fe is 1.4 at%, Si is 13.8 at%, Mn is 3.6 at%, Cr is 5 at%, B is 9.5 at%, and the balance is Co. The saturation magnetization of the soft magnetic layer is 300 emu / cc or more and 450 emu / cc or less.

3. A magnetic sensor comprising: a non-magnetic substrate; and a sensing element provided on the substrate, the sensing element including a soft magnetic layer of an amorphous alloy in which Zr is 3 at%, Nb is higher than 17 at% and lower than 21 at%, and the balance is Co, and the sensing element having a long side direction and a short side direction, having uniaxial magnetic anisotropy in a direction intersecting the long side direction, and sensing a magnetic field by a magnetoimpedance effect.

2. The magnetic sensor of claim 1, wherein, In the soft magnetic layer, Nb is higher than 18 at% and lower than 21 at%. The sensing element includes a plurality of the soft magnetic layers, Between the plurality of the soft magnetic layers, a magnetic domain suppression layer that suppresses generation of a closed magnetic domain in the soft magnetic layer is included. The sensing element includes a plurality of the soft magnetic layers, 4. The magnetic sensor of claim 3, wherein, Between the plurality of the soft magnetic layers, a non-magnetic electrically conductive layer having higher electrical conductivity than the soft magnetic layer is included.

5. The magnetic sensor of any one of claims 1 to 4, wherein, The sensing element includes a plurality of the soft magnetic layers, Between the plurality of the soft magnetic layers, a non-magnetic antiferromagnetic coupling layer that causes the soft magnetic layers to be antiferromagnetically coupled is included.

6. The magnetic sensor of any one of claims 1 to 4, wherein, ​ ​ 7. The magnetic sensor of any one of claims 1 to 4, wherein, ​ ​

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