Magnetic sensor

Abstract

To provide a magnetic sensor capable of detecting a magnetic field while suppressing cost increase.SOLUTION: The magnetic sensor is provided with a TMR film 10 whose electric resistance changes according to a magnetic field. The TMR film 10 includes first to third magnetic layers 101 to 103, an insulating layer 104 sandwiched between the first magnetic layer 101 and the second magnetic layer 102, and a nonmagnetic layer 105 sandwiched between the second magnetic layer 102 and the third magnetic layer 103. The second magnetic layer 102 and the third magnetic layer 103 are antiferromagnetically coupled via the nonmagnetic layer 105. The magnetization intensity of the first magnetic layer 101 is equal to the magnetization intensity of the third magnetic layer 103. The magnetization intensity of the second magnetic layer 102 is smaller than that of the third magnetic layer 103. The strength of the antiferromagnetic coupling between the second magnetic layer 102 and the third magnetic layer 103 is larger than either the magnetization strength of the first magnetic layer 101 or the magnetization strength of the third magnetic layer 103.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to magnetic sensors, and more particularly to magnetic sensors including TMR films. [Background technology]

[0002] Patent Document 1 describes a TMR element having a layered structure consisting of an antiferromagnetic layer, a pinned layer, a barrier layer, and a free layer. In this TMR element, a barrier layer, which is an insulating layer, is sandwiched between a pinned layer and a free layer, each of which is a ferromagnetic layer. An antiferromagnetic layer, which is an antiferromagnetic layer, is stacked on the pinned layer, fixing the magnetization direction of the pinned layer and making only the magnetization direction of the free layer variable. Therefore, the resistance of the element, and therefore the magnetic field, can be detected based on the change in the magnetization direction of the free layer in response to a magnetic field. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-198911 Summary of the Invention [Problem to be solved by the invention]

[0004] In the TMR element of Patent Document 1, the antiferromagnetic layer for fixing the magnetization direction of the pinned layer is made of rare materials such as an iridium-manganese alloy or a platinum-manganese alloy. Therefore, there is a need for a magnetic sensor that can detect magnetic fields while suppressing cost increases.

[0005] An object of the present disclosure is to provide a magnetic sensor that can detect a magnetic field while suppressing an increase in cost. [Means for solving the problem]

[0006] A magnetic sensor according to one embodiment of the present disclosure includes a TMR film whose electrical resistance changes in response to a magnetic field. The TMR film includes a first magnetic layer, a second magnetic layer, a third magnetic layer, an insulating layer sandwiched between the first magnetic layer and the second magnetic layer, and a non-magnetic layer sandwiched between the second magnetic layer and the third magnetic layer. The second magnetic layer and the third magnetic layer are antiferromagnetically coupled via the non-magnetic layer. The magnetization strength of the first magnetic layer is equal to the magnetization strength of the third magnetic layer. The magnetization strength of the second magnetic layer is smaller than the magnetization strength of the third magnetic layer. The strength of the antiferromagnetic coupling between the second magnetic layer and the third magnetic layer is greater than both the magnetization strength of the first magnetic layer and the magnetization strength of the third magnetic layer. [Effects of the Invention]

[0007] The magnetic sensor of the present disclosure has the advantage of being able to detect a magnetic field while suppressing increases in cost. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a TMR film included in a TMR sensor according to an embodiment of the present disclosure. [Figure 2] Figure 2A is a cross-sectional view schematically showing the magnetization direction of each of the first to third magnetic layers constituting the TMR film of the same, and Figure 2B is a cross-sectional view schematically showing the magnetization direction of each of the free layer, pinned layer and antiferromagnetic layer constituting the TMR element of the comparative example. [Figure 3] FIG. 3 is a schematic diagram for explaining the relationship between the magnetization direction of each of the first to third magnetic layers and the change in resistance value of the TMR film in response to an external magnetic field. [Figure 4] FIG. 4 is a schematic diagram for explaining the relationship between the magnetization direction of each of the first to third magnetic layers in the same and the change in resistance value of the TMR film in response to an external magnetic field when a bias magnetic field is applied. [Figure 5] FIG. 5 is an external view of a TMR film array in which a plurality of TMR films including the above TMR film are arranged. [Figure 6]Figure 6A is a top view showing four TMR film arrays, including the above-mentioned TMR film array, arranged on a substrate surface, Figure 6B is a top view showing a bias magnet arranged on the above-mentioned four TMR film arrays, and Figure 6C is a top view showing the above-mentioned four TMR film arrays seen from above the above-mentioned bias magnet. [Figure 7] FIG. 7 is a side view showing a specific example of the TMR sensor. [Figure 8] FIG. 8 is a top view showing a wiring layer included in the TMR sensor, as well as a bias magnet and a bias magnetic field disposed on the wiring layer. [Figure 9] FIG. 9 is a top view showing details of the wiring layer of the same. [Figure 10] FIG. 10A is an equivalent circuit diagram of a first half-bridge circuit and a third half-bridge circuit provided in the wiring layer of the same, and FIG. 10B is an equivalent circuit diagram of a second half-bridge circuit and a fourth half-bridge circuit provided in the wiring layer of the same. [Figure 11] FIG. 11 is a graph showing a change in the output voltage of the TMR sensor according to the relative position between the TMR sensor and the magnetic scale. [Figure 12] FIG. 12 is a graph showing the relationship between magnetic field strength and magnetoresistance ratio when the strength of antiferromagnetic coupling is defined as the magnetic field strength at which the resistance change of the TMR film becomes saturated. DETAILED DESCRIPTION OF THE INVENTION

[0009] (1) Overview First, an overview of a TMR (Tunnel Magneto Resistance Effect) sensor 100, which is a magnetic sensor according to an embodiment of the present disclosure, will be described with reference to FIGS. 1, 2A and 2B, 4 and 7, etc.

[0010] (1-1) TMR sensor The TMR sensor 100 (see FIG. 7) is a magnetic sensor that detects a magnetic field EH (for example, "+EH1," "0," "-EH1," etc. shown in FIG. 4) using the TMR effect. The TMR sensor 100 includes a TMR film 10 as shown in FIG.

[0011] (1-1-1)TMR membrane The TMR film 10 is a film-like element whose electrical resistance changes in response to a magnetic field. That is, when a magnetic field is applied to the TMR film 10, the electrical resistance of the TMR film 10 changes in response to the applied magnetic field EH.

[0012] Specifically, the electrical resistance of the TMR film 10, which has an insulating layer 104 sandwiched between a first magnetic layer 101 and a second magnetic layer 102, varies depending on the relationship between the magnetic moment M1 of the first magnetic layer 101 and the magnetic moment M2 of the second magnetic layer 102 (specifically, the electrical resistance is minimum when the two magnetization directions are parallel and maximum when they are antiparallel). The magnetic moment is a vector that indicates the magnetization intensity and direction. The magnetization intensity is the strength of the magnetization. The magnetization direction is the direction of the magnetization.

[0013] As shown in FIG. 1, the TMR film 10 includes a first magnetic layer 101, a second magnetic layer 102, a third magnetic layer 103, an insulating layer 104, and a non-magnetic layer 105.

[0014] (1-1-1a) First magnetic layer, second magnetic layer, and third magnetic layer Each of the first magnetic layer 101, the second magnetic layer 102, and the third magnetic layer 103 is a layer of a ferromagnetic material.

[0015] (1-1-1b) Insulating layer The insulating layer 104 is an insulating layer sandwiched between the first magnetic layer 101 and the second magnetic layer 102.

[0016] (1-1-1c) Nonmagnetic layer The non-magnetic layer 105 is a layer of a non-magnetic material sandwiched between the second magnetic layer 102 and the third magnetic layer 103.

[0017] The nonmagnetic layer 105 has a thickness that can realize antiferromagnetic coupling AC1 (see FIG. 2A ). The thickness that can realize antiferromagnetic coupling AC1 is the thickness that corresponds to the maximum value of the coupling strength (a local peak in the height of the graph) in a graph showing the relationship between the thickness of the nonmagnetic layer 105 (e.g., a ruthenium layer) and the strength of the antiferromagnetic coupling AC1.

[0018] Specifically, for example, a graph showing the relationship between thickness and the strength of antiferromagnetic coupling AC1 for ruthenium has three maxima: a first maximum corresponding to a thickness of 0.7 nanometers (hereinafter, nanometers will be abbreviated as "nm"), a second maximum corresponding to a thickness of 1.6 nm, and a third maximum corresponding to a thickness of 30 nm (where the first maximum > the second maximum > the third maximum).

[0019] From the viewpoint of detection accuracy of the magnetic field EH, the thickness of the nonmagnetic layer 105 is preferably 1.6 nm, which corresponds to the second maximum value. However, the thickness of the nonmagnetic layer 105 may also be 0.7 nm, which corresponds to the first maximum value, or 30 nm, which corresponds to the third maximum value.

[0020] (1-1-2) Antiferromagnetic coupling between the second magnetic layer and the third magnetic layer The second magnetic layer 102 and the third magnetic layer 103 are antiferromagnetically coupled via the nonmagnetic layer 105. Specifically, as shown in FIG. 2A, the magnetic moment M2 of the second magnetic layer 102 and the magnetic moment M3 of the third magnetic layer 103 are magnetically coupled by antiferromagnetic coupling AC1.

[0021] FIG. 12 shows an example of the magnetoresistance change rate when the strength of the antiferromagnetic coupling is defined as the magnetic field strength at which the resistance change of the TMR film 10 saturates. In FIG. 12, the unit of magnetic field strength is millitesla (mT), and the unit of magnetoresistance change is percent (%). In this embodiment, the magnetic field strength at which the resistance change of the TMR film 10 saturates is the magnetic field strength at which the magnetoresistance change rate becomes 0. In the example of FIG. 12, the magnetic field strength at which the resistance change of the TMR film 10 saturates is approximately ±300 mT. In this case, since no magnetoresistance change is observed at magnetic field strengths exceeding approximately ±300 mT (i.e., the magnetoresistance change rate becomes 0), the absolute value of the magnetic field strength at this time, i.e., approximately 300 mT, can be considered to be the strength of the antiferromagnetic coupling magnetic field.

[0022] When the second magnetic layer 102 and the third magnetic layer 103 are antiferromagnetically coupled, when the magnetic field EH is smaller than the threshold value, the layer of the second magnetic layer 102 or the third magnetic layer 103 with the greater magnetization strength (magnitude of the magnetic moment) faces the direction of the magnetic field EH, and the layer with the smaller magnetization strength faces the opposite direction to the magnetic field EH.

[0023] On the other hand, when the magnetic field EH is equal to or greater than the threshold value, both the second magnetic layer 102 and the third magnetic layer 103 are oriented in the direction of the magnetic field EH.

[0024] Note that antiferromagnetic coupling is possible when the nonmagnetic layer 105 (ruthenium) has a specific thickness (e.g., 1.6 nm). As the thickness deviates from the specific thickness, the antiferromagnetic coupling AC1 weakens, making it easier for the magnetization direction of the second magnetic layer 102 to rotate, thereby increasing the sensitivity of the TMR sensor 100.

[0025] (1-1-3) Magnitude relationship between the first magnetic layer, the second magnetic layer, and the third magnetic layer The first magnetic layer 101 is not magnetically coupled to any other magnetic layer (in this embodiment, neither the second magnetic layer 102 nor the third magnetic layer 103).

[0026] The magnetization strength of the first magnetic layer 101 is equal to the magnetization strength of the third magnetic layer 103. The magnetization strength of the first magnetic layer 101 is the magnitude of the magnetic moment M1 (vector) of the first magnetic layer 101, and the magnetization strength of the third magnetic layer 103 is the magnitude of the magnetic moment M3 (vector) of the third magnetic layer 103.

[0027] The term "equal strength" as used herein does not only refer to a case where the strengths are completely equal, but also to a case where the strengths are close enough to be considered equal. Close strengths refer to a case where the difference between the magnetization strength of the first magnetic layer 101 and the magnetization strength of the third magnetic layer 103 is equal to or less than a threshold. In other words, if the magnetization strength of the second magnetic layer 102 is sufficiently smaller than the magnetization strength of the third magnetic layer 103, the second magnetic layer 102 and the third magnetic layer 103 can be antiferromagnetically coupled even if the magnetization strength of the first magnetic layer 101 is slightly different from the magnetization strength of the third magnetic layer 103.

[0028] The magnetization strength of the second magnetic layer 102 is smaller than the magnetization strength of the third magnetic layer 103. The magnetization strength of the second magnetic layer 102 is the magnitude of the magnetic moment M2 (vector) of the second magnetic layer 102.

[0029] (1-1-4) Relationship between the strength of antiferromagnetic coupling and the magnetization strength of the first magnetic layer and the magnetization strength of the third magnetic layer The strength of the antiferromagnetic coupling AC1 between the second magnetic layer 102 and the third magnetic layer 103 is greater than both the magnetization strength of the first magnetic layer 101 and the magnetization strength of the third magnetic layer 103.

[0030] According to the above configuration, when the strength of the magnetic field EH is below a threshold value, the layer of the second magnetic layer 102 and the third magnetic layer 103 with the greater magnetization strength faces the direction of the magnetic field EH, and the layer with the lesser magnetization strength faces the opposite direction to the magnetic field EH. On the other hand, when the strength of the magnetic field EH is above a threshold value, both the second magnetic layer 102 and the third magnetic layer 103 face the direction of the magnetic field EH, so that the magnetic field EH can be detected without a pinned layer.

[0031] (1-2) Comparative Example A TMR element 11 according to a comparative example will now be described with reference to Fig. 2B. The TMR element 11 in Fig. 2B includes a free layer 111 and a pinned layer 112, each of which is a ferromagnetic layer, and a barrier layer 114, which is an insulating layer sandwiched between the free layer 111 and the pinned layer 112. The TMR element 11 further includes an antiferromagnetic layer 113, which is a layer of an antiferromagnetic material, stacked on one of the two major surfaces of the pinned layer 112, opposite the major surface in contact with the barrier layer 114.

[0032] In the TMR element 11, the antiferromagnetic layer 113 is stacked on the pinned layer 112, so that the magnetization direction of the pinned layer 112 (the direction of the magnetic moment M12) and the magnetization direction of the antiferromagnetic layer 113 (the directions of two antiparallel magnetic moments M13a and M13b) are fixed, and only the magnetization direction of the free layer 111 (the direction of the magnetic moment M11) is variable. Therefore, the TMR element 11 can detect the electrical resistance value of the TMR element 11, and therefore the magnetic field applied to the TMR element 11, based on the change in the magnetization direction of the free layer 111 in response to the magnetic field EH.

[0033] (2)Details Next, the TMR sensor 100 will be described in detail with reference to Figures 1 to 7 and 11. Note that in the following, descriptions of previously mentioned matters will be omitted or simplified.

[0034] (2-1) Material and thickness of each layer (2-1-1) Material and thickness of the non-magnetic layer The nonmagnetic layer 105 in this embodiment is a ruthenium (Ru) layer. By using a ruthenium layer as the nonmagnetic layer 105, it is possible to improve the strength of the antiferromagnetic coupling AC1 (see FIG. 2A) between the second magnetic layer 102 and the third magnetic layer 103.

[0035] The nonmagnetic layer 105 has a thickness d5 as shown in Fig. 1. The thickness d5 is preferably set to a value that maximizes the strength of the antiferromagnetic coupling AC1.

[0036] As described above, when the nonmagnetic layer 105 is a ruthenium layer, the strength of the antiferromagnetic coupling AC1 between the second magnetic layer 102 and the third magnetic layer 103 has three maximum values ​​with respect to the change in the thickness of the ruthenium. In this embodiment, the thickness (d5=1.6 nm) corresponding to the second maximum value is used.

[0037] That is, the strength of the antiferromagnetic coupling AC1 can be maximized by adjusting the thickness d5 of the nonmagnetic layer 105. As a result, the possibility that the strength of the antiferromagnetic coupling AC1 will be greater than both the magnetization strength of the first magnetic layer 101 and the magnetization strength of the third magnetic layer 103 can be maximized.

[0038] When the nonmagnetic layer 105 is a ruthenium layer, the thickness d5 is, for example, 1.6 nm.

[0039] In the case of the non-magnetic layer 105 made of ruthenium, the more the thickness d5 deviates from 1.6 nm, the weaker the strength of the antiferromagnetic coupling AC1 becomes, and the easier it is for the magnetization direction (magnetic moment M2: see FIG. 2A) of the second magnetic layer 102 to rotate, resulting in an increase in the sensitivity of the TMR sensor 100. Note that even if at least one of the thicknesses (d2: described below) of the second magnetic layer 102 and the third magnetic layer 103 (d3: described below) becomes smaller, the antiferromagnetic coupling AC1 also becomes weaker, resulting in an increase in the sensitivity of the TMR sensor 100.

[0040] (2-1-2) Materials and thicknesses of the first magnetic layer, second magnetic layer, and third magnetic layer In this embodiment, the first magnetic layer 101, the second magnetic layer 102, and the third magnetic layer 103 are metal layers containing the same ferromagnetic material, and have thicknesses d1, d2, and d3, respectively, as shown in FIG.

[0041] In this embodiment, the metal containing the same ferromagnetic material is an alloy containing cobalt and iron (CoFe). The alloy may further contain a non-magnetic material other than cobalt and iron, such as boron (B).

[0042] In this way, by using a common ferromagnetic material contained in the metal that constitutes the first magnetic layer 101 to the third magnetic layer 103, the number of ferromagnetic materials required to realize the TMR sensor 100 can be reduced.

[0043] In this embodiment, the first magnetic layer 101, the second magnetic layer 102, and the third magnetic layer 103 are all made of layers of an alloy containing cobalt and iron (CoFe), thereby reducing the number of ferromagnetic materials required to realize the TMR sensor 100 while improving the detection accuracy of the TMR sensor 100.

[0044] In this embodiment, the insulating layer 104 is a layer of a metal oxide such as magnesium oxide, and has a thickness d4 as shown in FIG.

[0045] Specifically, the first magnetic layer 101 is a layer of an alloy containing cobalt and iron (CoFe), and the thickness d1 is preferably 4 nm. The second magnetic layer 102 is a layer of an alloy containing cobalt, iron, and boron (CoFeB), and the thickness d2 is preferably 2 nm. The third magnetic layer 103 is a CoFeB layer, similar to the second magnetic layer 102, and the thickness d3 is preferably 4 nm. The insulating layer 104 is a layer of magnesium oxide (MgO), and the thickness d4 is preferably 1 nm.

[0046] By setting the thicknesses (d1 to d3 and d4) of each layer other than the non-magnetic layer 105 (first magnetic layer 101 to third magnetic layer 103 and insulating layer 104) as described above, the detection accuracy of the magnetic field EH can be improved.

[0047] (2-1-3) Bias magnetic field by bias magnet The magnetic field EH described above will be referred to below as the external magnetic field EH. The external magnetic field EH is, for example, the magnetic field from the magnetic scale 6 shown in FIG.

[0048] The TMR sensor 100 of this example further includes a bias magnet 5 as shown in Fig. 6B. If the strength of the antiferromagnetic coupling is defined as the magnetic field strength at which the resistance change of the TMR film 10 saturates (see Fig. 12), the bias magnet 5 applies a bias magnetic field BH of half the maximum strength (half value) to the TMR film 10 (see Figs. 1 and 5) in a direction antiparallel to the magnetization direction (direction of the second magnetic moment M2) of the second magnetic layer 102 when the strength of the antiferromagnetic coupling AC1 is maximum (when the external magnetic field EH is maximum in the second direction in Fig. 4, i.e., when "EH = -EH1").

[0049] Application of such a bias magnetic field BH from the bias magnet 5 changes the response characteristic of the resistance value to the external magnetic field EH from the graph shown in Fig. 3 to the graph shown in Fig. 4 (in other words, the operating point of the TMR film 10 drifts). As a result, when the external magnetic field EH is at its maximum in the forward direction (EH = +EH1), the magnetization direction of the first magnetic layer 101 (the direction of the magnetic moment M1) and the magnetization direction of the second magnetic layer 102 (the direction of the magnetic moment M2) are parallel, and the resistance value of the TMR film 10 is at its minimum.

[0050] Furthermore, as the external magnetic field EH approaches a maximum in the forward direction (EH=+EH1), passes through a state in which EH=0, and approaches a maximum in the reverse direction (EH=-EH1), the magnetization directions of the first magnetic layer 101 (the direction of the magnetic moment M1) and the second magnetic layer 102 (the direction of the magnetic moment M2) change from parallel to antiparallel, and the resistance value of the TMR film 10 increases monotonically, as shown in the graph in Fig. 4. Note that, as shown in Fig. 4, when EH=0, the direction of the magnetic moment M2 is perpendicular to the direction of the magnetic moment M1 (for example, pointing into the paper).

[0051] When the external magnetic field EH is at its maximum in the second direction (EH=-EH1), the magnetization direction of the first magnetic layer 101 (the direction of the magnetic moment M1) and the magnetization direction of the second magnetic layer 102 (the direction of the magnetic moment M2) are antiparallel, and the resistance value of the TMR film 10 is at its maximum.

[0052] This makes it possible to detect the resistance value of the TMR film 10 over the entire range of the external magnetic field EH ("EH=+EH1" to "EH=0" to "EH=-EH1").

[0053] When the bias magnetic field BH is not applied, the resistance of the TMR film 10 increases as the external magnetic field EH approaches zero from its maximum (+EH1) in the forward direction, and decreases as the external magnetic field EH approaches zero from its maximum (-EH1) in the second direction. In other words, when the bias magnetic field BH is not applied, the resistance of the TMR film 10 changes as an even function as the external magnetic field EH changes from +EH1 to zero and then to -EH1, as shown in the graph in Figure 3. In the graph in Figure 3, the magnetization direction of the first magnetic layer 101 (the direction of the magnetic moment M1) and the magnetization direction of the second magnetic layer 102 (the direction of the magnetic moment M2) are not uniquely determined near EH = 0, making it difficult to detect the resistance of the TMR film 10.

[0054] (2-1-4) TMR membrane array The TMR sensor 100 includes a TMR film array 10A as shown in Fig. 5. The TMR film array 10A is a component in which a plurality of TMR films 10, each of which is a TMR film 10, are arranged in an arrangement direction Dr2 that intersects with a stacking direction Dr1 of a first magnetic layer 101, an insulating layer 104, a second magnetic layer 102, a non-magnetic layer 105, and a third magnetic layer 103. A bias magnet 5 applies a bias magnetic field BH to each of the plurality of TMR films 10 included in the TMR film array 10A.

[0055] The TMR film 10 in this example has a pillar (thin cylinder) shape as shown in Fig. 5. The TMR film 10 in Fig. 5 has a diameter of 5 to 10 microns and a thickness of 12.6 (=4+2+4+1+1.6) nm.

[0056] By applying the bias magnetic field BH as described above, the resistance value of the TMR film 10 and therefore the external magnetic field EH can be detected with high sensitivity over the entire range of the external magnetic field EH ("EH=+EH1" to "EH=0" to "EH=-EH1").

[0057] (2-1-4a) Specific examples of TMR film arrays The TMR film array 10A in this example has a structure in which, between two adjacent TMR films 10 among a plurality of TMR films 10, the third magnetic layer 103 of one TMR film 10 is electrically connected to the third magnetic layer 103 of the other TMR film 10 via a connecting conductor CD1, or the first magnetic layer 101 of one TMR film 10 is electrically connected to the first magnetic layer 101 of the other TMR film 10 via the connecting conductor CD1. The connecting conductor CD1 in this example has a plate shape (I-shape) as shown in FIG. 5. However, the shape of the connecting conductor CD1 is not limited.

[0058] Among the multiple TMR films 10 arranged in the arrangement direction Dr2, in the TMR film 10 at one end side (the left end side as viewed in the drawing in the example of FIG. 5), one end side of the coupling conductor CD1, the other end side of which is in contact with the first magnetic layer 101, functions as, for example, one of a pair of electrodes (first electrode). Also, among the multiple TMR films 10 arranged in the arrangement direction Dr2, in the TMR film 10 at the other end side (the right end side as viewed in the drawing in the example of FIG. 5), the other end side of the coupling conductor CD1, the one end side of which is in contact with the first magnetic layer 101, functions as, for example, the other of the pair of electrodes (second electrode).

[0059] According to the TMR film array 10A of this example, the TMR film array 10A can be made compact.

[0060] (3) Basic structure of TMR sensor Next, the basic structure of the TMR sensor 100 will be described with reference to Figures 6A to 6C, 7, etc. Note that in the following, the description of the previously mentioned items will be omitted or simplified.

[0061] (3-1) Four TMR membrane arrays The TMR sensor 100 of this example has four TMR film arrays 1P, 1Q, 2P, and 2Q (see FIG. 6A), each of which is a TMR film array 10A. In this TMR sensor 100, as shown in FIG. 6A, on a substrate surface 73a that defines an X axis and a Y axis orthogonal to the X axis, a pair of TMR film arrays 1P and 1Q are arranged along the X axis, and a pair of TMR film arrays 2P and 2Q are arranged along the Y axis.

[0062] The magnetic moment M2 of the second magnetic layer 102 of the TMR film array 1P is oriented in the positive direction of the X-axis. The magnetic moment M2 of the second magnetic layer 102 of the TMR film array 1Q is oriented in the negative direction of the X-axis. The magnetic moment M2 of the second magnetic layer 102 of the TMR film array 1Q is oriented in the positive direction of the Y-axis. The magnetic moment M2 of the second magnetic layer 102 of the TMR film array 2Q is oriented in the negative direction of the Y-axis.

[0063] (3-2) Bias magnets and bias magnetic fields corresponding to the four TMR film arrays As shown in FIG. 6B, the bias magnet 5 corresponding to the four TMR film arrays 1P, 1Q, 2P, and 2Q has four magnetic dipoles each consisting of a north pole and a south pole. This bias magnet 5 has a two-layer structure (see FIG. 7). FIG. 6B shows two of the four magnetic dipoles in the upper layer, and there are also two magnetic dipoles in the lower layer. The arrangement of the north poles and south poles is reversed between the two magnetic dipoles in the upper layer and the two magnetic dipoles in the lower layer (see FIG. 7).

[0064] (3-3) Effects of bias magnetic field As shown in Figure 6B, the bias magnetic field BH generated by this bias magnet 5 is oriented antiparallel to the direction of the four magnetic moments M2 corresponding to the four TMR film arrays 1P, 1Q, 2P, and 2Q, and therefore the operating point drift described above occurs in each of the four TMR film arrays 1P, 1Q, 2P, and 2Q.

[0065] (4) Specific examples of TMR sensors Next, specific examples of the TMR sensor 100 will be described with reference to Figures 7 to 11. Note that in the following, descriptions of previously mentioned matters will be omitted or simplified.

[0066] (4-1) Main parts of the TMR sensor As shown in FIG. 7, the TMR sensor 100 of this example includes a substrate 73 having a substrate surface 73a, a wiring layer W1 disposed along the substrate surface 73a, and a bias magnet 5.

[0067] (4-1-1) Base material The substrate 73 is a member that serves as a signal substrate. The substrate 73 has a plate-like shape. The material of the substrate 73 is alumina, silicon, or the like.

[0068] (4-1-2) Base material surface As described above, the substrate surface 73a is a surface on which the X axis and the Y axis perpendicular to the X axis are defined. The substrate surface 73a is one of the two main surfaces of the substrate 73 (in this embodiment, the surface on which the wiring layer W1 is formed).

[0069] (4-1-3) Wiring layer 8, 9, 10A, and 10B, the wiring layer W1 includes a first half-bridge circuit 1 and a second half-bridge circuit 2. Note that Fig. 8 shows only the wiring layer W1 and the bias magnet 5, and Fig. 9 shows only the wiring layer W1.

[0070] The first half-bridge circuit 1 is a circuit including a pair of first TMR film arrays 1P and 1Q, each of which is a TMR film array 10A. The second half-bridge circuit 2 is a circuit including a pair of second TMR film arrays 2P and 2Q, each of which is a TMR film array 10A.

[0071] The pair of first TMR film arrays 1P and 1Q are arranged parallel to the Y axis as shown in Figures 8, 9, and 10A, and detect the component of the external magnetic field EH along the X axis. The pair of second TMR film arrays 2P and 2Q are arranged parallel to the X axis as shown in Figures 8, 9, and 10B, and detect the component of the external magnetic field EH along the Y axis.

[0072] As shown in Figures 8, 9, and 10A, the first half-bridge circuit 1 has a first output terminal 1T. The first output terminal 1T outputs a first output signal from a connection point between a pair of first TMR film arrays 1P and 1Q. The second half-bridge circuit 2 has a second output terminal 2T as shown in Figures 8, 9, and 10B. The second output terminal 2T outputs a second output signal from a connection point between a pair of second TMR film arrays 2P and 2Q.

[0073] (4-1-4) Bias magnet The bias magnet 5 applies a bias magnetic field BH along the positive direction of the X-axis to one of the pair of first TMR film arrays 1P, 1Q (first TMR film array 1P) and a bias magnetic field BH along the negative direction of the X-axis to the other (first TMR film array 1Q).The bias magnet 5 also applies a bias magnetic field BH along the positive direction of the Y-axis to one of the pair of second TMR film arrays 2P, 2Q (second TMR film array 2Q) and a bias magnetic field BH along the negative direction of the Y-axis to the other (second TMR film array 2P) (see FIG. 8).

[0074] As a result, for example, as shown in Figure 11, when the magnetic scale 6, on which south and north poles are arranged alternately, is displaced in the longitudinal direction, i.e., along the Y axis of the TMR sensor 100, a cosine waveform is obtained based on the first output signal, and a sine waveform is obtained based on the second output signal.

[0075] (4-2) Details of the TMR sensor (4-2-1) Protective film 7, the magnetic sensor 100 further includes a first protective film 71 and a second protective film 72 that sandwich the wiring layer W1. The first protective film 71 and the second protective film 72 are resin or inorganic films that protect the wiring layer W1.

[0076] (4-2-2) Bias Magnet Details As shown in FIGS. 6B and 7, the bias magnet 5 has a rectangular parallelepiped shape. The bias magnet 5 is a single member. The bias magnet 5 of this embodiment is a permanent magnet, such as a ferrite magnet or a neodymium magnet. However, the bias magnet 5 is not limited to a permanent magnet and may also be an electromagnet.

[0077] The bias magnet 5 has multiple (eight in this embodiment) magnetic poles 50. Four of the eight magnetic poles 50 are arranged on a first plane parallel to both the X-axis and the Y-axis. The remaining four of the eight magnetic poles 50 are arranged on a second plane parallel to the first plane.

[0078] That is, two sets of four magnetic poles 50 are provided, and in each set, the four magnetic poles 50 are provided on the same plane. The magnetic poles 50 belonging to different sets are provided at different positions in the Z-axis direction. The Z coordinates of the four magnetic poles 50 shown in FIG. 6B are greater than the Z coordinates of the remaining four magnetic poles 50.

[0079] The eight magnetic poles 50 are arranged such that adjacent magnetic poles 50 in the X-axis direction have different poles, and adjacent magnetic poles 50 in the Y-axis direction have different poles. The eight magnetic poles 50 are also arranged such that adjacent magnetic poles 50 in the Z-axis direction have different poles.

[0080] (4-2-3) Wiring layer details 7, the wiring layer W1 is formed on the substrate surface 73a. That is, the wiring layer W1 is supported by the substrate 73. The wiring layer W1 of this embodiment includes multiple layers. The multiple layers are electrically connected to each other via through holes.

[0081] As shown in FIGS. 8, 9, 10A, and 10B, the wiring layer W1 further includes a third half-bridge circuit 3 and a fourth half-bridge circuit 4.

[0082] 10A, the third half-bridge circuit 3 has a pair of third TMR film arrays 3P and 3Q and a third output terminal 3T. The pair of third TMR film arrays 3P and 3Q detect a magnetic field along the X-axis. The third output terminal 3T outputs a third output signal from the connection point between the pair of third TMR film arrays 3P and 3Q.

[0083] 10B, the fourth half-bridge circuit 4 has a pair of fourth TMR film arrays 4P and 4Q and a fourth output terminal 4T. The pair of fourth TMR film arrays 4P and 4Q detect a magnetic field along the Y axis. The fourth output terminal 4T outputs a fourth output signal from the connection point between the pair of fourth TMR film arrays 4P and 4Q.

[0084] Like the first TMR film arrays 1P and 1Q and the second TMR film arrays 2P and 2Q, the third TMR film arrays 3P and 3Q and the fourth TMR film arrays 4P and 4Q are also the TMR film array 10A shown in Fig. 5. That is, the magnetic sensor 100 includes eight TMR film arrays 10A.

[0085] 9, the wiring layer W1 further includes power supply terminals H10 and H20 and reference terminals L10 and L20. The power supply terminals H10 and H20 are high-potential side terminals electrically connected to a high-potential side electric circuit of the power supply. The reference terminals L10 and L20 are low-potential side terminals electrically connected to a low-potential side electric circuit (a reference potential electric circuit) of the power supply. In this embodiment, the reference terminals L10 and L20 are ground terminals electrically connected to a ground potential electric circuit.

[0086] A first end of the first TMR film array 1P is electrically connected to the reference terminal L20. A second end of the first TMR film array 1P is electrically connected to a first end of the first TMR film array 1Q. A second end of the first TMR film array 1Q is electrically connected to a power supply terminal H10. A first output terminal 1T is electrically connected to a connection point between the pair of first TMR film arrays 1P and 1Q.

[0087] A first end of the second TMR film array 2P is electrically connected to a power supply terminal H10. A second end of the second TMR film array 2P is electrically connected to a first end of the second TMR film array 2Q. A second end of the second TMR film array 2Q is electrically connected to a reference terminal L10. A second output terminal 2T is electrically connected to a connection point between the pair of second TMR film arrays 2P and 2Q.

[0088] A first end of the third TMR film array 3P is electrically connected to a power supply terminal H20. A second end of the third TMR film array 3P is electrically connected to a first end of the third TMR film array 3Q. A second end of the third TMR film array 3Q is electrically connected to a reference terminal L10. A third output terminal 3T is electrically connected to a connection point between the pair of third TMR film arrays 3P and 3Q.

[0089] A first end of the fourth TMR film array 4P is electrically connected to the reference terminal L20. A second end of the fourth TMR film array 4P is electrically connected to a first end of the fourth TMR film array 4Q. A second end of the fourth TMR film array 4Q is electrically connected to the power supply terminal H20. The fourth output terminal 4T is electrically connected to the connection point between the pair of fourth TMR film arrays 4P and 4Q.

[0090] In the following, when there is no need to distinguish between the first TMR film array 1P, 1Q, the second TMR film array 2P, 2Q, the third TMR film array 3P, 3Q, and the fourth TMR film array 4P, 4Q, they will be referred to as TMR film array 10A.

[0091] 8, 9, 10A, and 10B, the shape of the TMR film array 10A is illustrated as a rectangle when viewed from the Z-axis direction. However, this shape is a schematic diagram illustrating the orientation of the TMR film array 10A and does not necessarily match the shape of the actual TMR film array 10A.

[0092] As mentioned above, the electrical resistance of the TMR film array 10A changes depending on the magnitude of the applied magnetic field. The applied magnetic field is a magnetic field obtained by superposing an external magnetic field EH and a bias magnetic field BH. Since the bias magnetic field BH is known, the external magnetic field EH can be determined by detecting the applied magnetic field.

[0093] The magnetic sensor 100 outputs, as a voltage signal, a change in the electrical resistance of the TMR film array 10A in response to an applied magnetic field. The TMR film array 10A is insensitive to magnetic fields in a first direction (the direction along the long side in FIG. 8) and is sensitive to magnetic fields in a second direction (the direction along the short side in FIG. 8). The sensitivity of the TMR film array 10A is greatest for magnetic fields in the second direction.

[0094] The pair of first TMR film arrays 1P, 1Q and the pair of third TMR film arrays 3P, 3Q are arranged so as to be sensitive to a magnetic field along the X-axis. The pair of first TMR film arrays 1P, 1Q and the pair of third TMR film arrays 3P, 3Q exhibit the same change in resistance when the magnetic field is applied along the positive direction of the X-axis and when the magnetic field is applied along the negative direction of the X-axis, provided that the magnetic field magnitudes are the same.

[0095] The pair of second TMR film arrays 2P, 2Q and the pair of fourth TMR film arrays 4P, 4Q are arranged so as to be sensitive to magnetic fields along the Y axis. The pair of second TMR film arrays 2P, 2Q and the pair of fourth TMR film arrays 4P, 4Q undergo the same change in resistance when the magnetic field is applied along the positive direction of the Y axis and when the magnetic field is applied along the negative direction of the Y axis, provided that the magnetic field magnitudes are the same.

[0096] When viewed from the Z-axis direction, with the center of the magnetic sensor 100 as the reference, the TMR film arrays 10A are arranged as follows: The first TMR film array 1P and the third TMR film array 3P are arranged on the positive side of the Y-axis from the center. The first TMR film array 1Q and the third TMR film array 3Q are arranged on the negative side of the Y-axis from the center. The second TMR film array 2P and the fourth TMR film array 4P are arranged on the positive side of the X-axis from the center. The second TMR film array 2Q and the fourth TMR film array 4Q are arranged on the negative side of the X-axis from the center.

[0097] As described above, the Z coordinates of the four magnetic poles 50 shown in Fig. 8 are larger than the Z coordinates of the remaining four magnetic poles 50. In other words, of the multiple magnetic poles 50 of the bias magnet 5, the four magnetic poles 50 shown in Fig. 8 face the multiple TMR film arrays 10A and apply a bias magnetic field BH to the multiple TMR film arrays 10A. In Fig. 8, the direction of the bias magnetic field BH is indicated by a dotted arrow.

[0098] A bias magnetic field BH along the negative direction of the X-axis is applied to the first TMR film array 1P and the third TMR film array 3P. A bias magnetic field BH along the positive direction of the X-axis is applied to the first TMR film array 1Q and the third TMR film array 3Q.

[0099] A bias magnetic field BH along the negative direction of the Y axis is applied to the second TMR film array 2P and the fourth TMR film array 4P. A bias magnetic field BH along the positive direction of the Y axis is applied to the second TMR film array 2Q and the fourth TMR film array 4Q.

[0100] In this way, the single bias magnet 5 generates a bias magnetic field BH aligned along the positive direction of the X-axis and a bias magnetic field BH aligned along the negative direction of the X-axis. Furthermore, the single bias magnet 5 also generates a bias magnetic field BH aligned along the positive direction of the Y-axis and a bias magnetic field BH aligned along the negative direction of the Y-axis.

[0101] The TMR film array 10A has no sensitivity in a predetermined direction, but has isotropic sensitivity in a direction intersecting the predetermined direction.

[0102] The bias magnet 5 applies a magnetic field (bias magnetic field BH) having a strength equal to or less than half the anisotropy magnetic field of each of the plurality of TMR film arrays 10A to each of the plurality of (eight) TMR film arrays 10A, including the pair of first TMR film arrays 1P, 1Q and the pair of second TMR film arrays 2P, 2Q, thereby suppressing distortion of the output waveform of each of the plurality of TMR film arrays 10A.

[0103] (4-3) Detection of magnetic field direction The magnetic sensor 100 is placed near the magnetic scale 6. The alternating north and south poles of the magnetic scale 6 form a magnetic field. As the magnetic scale 6 moves linearly along its longitudinal direction (magnetization direction), the direction of the magnetic field applied to the magnetic sensor 100 changes. Based on the output of the magnetic sensor 100, the direction of the magnetic field applied to the magnetic sensor 100 can be determined.

[0104] As the position of the magnetic scale 6 changes in the longitudinal direction, the first output signal, the second output signal, the third output signal, and the fourth output signal each change in a sine wave or cosine wave.

[0105] The phases of the first output signal and the second output signal correspond to the direction of the magnetic field applied to the magnetic sensor 100. In other words, the direction of the magnetic field applied to the magnetic sensor 100 can be determined based on the first output signal and the second output signal.

[0106] Furthermore, the position of the magnetic scale 6 relative to the magnetic sensor 100 can be detected based on the third and fourth output signals in addition to the first and second output signals.

[0107] The direction of the magnetic field applied to the magnetic sensor 100 can be determined based on the first output signal, the second output signal, the third output signal, and the fourth output signal. The first output signal, the second output signal, the third output signal, and the fourth output signal are signals output from the first output terminal 1T, the second output terminal 2T, the third output terminal 3T, and the fourth output terminal 4T, respectively. In other words, the first output signal, the second output signal, the third output signal, and the fourth output signal are signals output from the first half-bridge circuit 1, the second half-bridge circuit 2, the third half-bridge circuit 3, and the fourth half-bridge circuit 4, respectively.

[0108] 8 and 10A, the first half-bridge circuit 1 and the third half-bridge circuit 3 have the same sensitivity direction of the TMR film array 10A and the same direction of the applied bias magnetic field BH, but the relationship between the high potential side and the low potential side is opposite to each other. Therefore, the third output signal is a signal with an opposite phase to the first output signal.

[0109] 8 and 10B, the sensitivity direction of the TMR film array 10A and the direction of the applied bias magnetic field BH are the same, but the relationship between the high potential side and the low potential side is opposite to each other. Therefore, the fourth output signal is a signal of opposite phase to the second output signal.

[0110] (5) Variations Next, various modifications of the embodiment will be described. Note that the following description will omit or simplify the description of the previously mentioned matters.

[0111] (5-1) Modification of the nonmagnetic layer (5-1-1) Variation in Ruthenium Layer Thickness The nonmagnetic layer 105 may be a ruthenium layer having a thickness other than 1.6 nm. Even if the thickness of the ruthenium layer is a value other than 1.6 nm, it may be possible to improve the strength of the antiferromagnetic coupling AC1 between the second magnetic layer 102 and the third magnetic layer 103 compared to when a layer of a nonmagnetic material other than ruthenium is used as the nonmagnetic layer 105.

[0112] However, if the thickness of the ruthenium layer is within a predetermined range including 1.6 nm, it is expected that the strength of the antiferromagnetic coupling AC1 can be increased to an intensity close to the maximum value, which is an intensity greater than both the magnetization intensity of the first magnetic layer 101 and the magnetization intensity of the third magnetic layer 103, but less than the maximum value.

[0113] This makes it possible to stabilize the detection operation of the TMR sensor 100 and maximize the strength of the antiferromagnetic coupling AC1.

[0114] The predetermined range is, for example, 1.6±0.05 nm. By ensuring that the thickness of the ruthenium layer is within this range, it is possible to ensure that the strength of the antiferromagnetic coupling AC1 is equal to or greater than a predetermined level. The strength of the antiferromagnetic coupling AC1 is greater than the magnetization strength of both the first magnetic layer 101 and the third magnetic layer 103.

[0115] (5-1-2) Modification of the material of the non-magnetic layer The nonmagnetic layer 105 may be a layer of a nonmagnetic material other than ruthenium. Examples of nonmagnetic materials other than ruthenium that can be used for the nonmagnetic layer 105 include, but are not limited to, copper (Cu), silver (Ag), chromium (Cr), and a silver-tin alloy (AgSn). Even when the nonmagnetic layer 105 is a layer of a nonmagnetic material other than ruthenium, it may be possible to maximize the strength of the antiferromagnetic coupling AC1 by adjusting the thickness of the nonmagnetic layer 105 to a thickness that maximizes the strength of the antiferromagnetic coupling AC1.

[0116] (5-2) First Modification of the Materials of the First Magnetic Layer, the Second Magnetic Layer, and the Third Magnetic Layer In the embodiment, the second magnetic layer 102 and the third magnetic layer 103 are made of CoFeB, and the first magnetic layer 101 is made of CoFe, but the first magnetic layer 101, the second magnetic layer 102, and the third magnetic layer 103 may all be made of CoFeB.

[0117] (5-3) Second Modification of the Materials of the First Magnetic Layer, the Second Magnetic Layer, and the Third Magnetic Layer The first magnetic layer 101, the second magnetic layer 102, and the third magnetic layer 103 may be metal layers containing different ferromagnetic materials. Examples of metal layers containing different ferromagnetic materials include a layer of an alloy containing cobalt, a layer of an alloy containing iron, and a layer of an alloy containing nickel, or a layer of an alloy containing cobalt and iron, a layer of an alloy containing iron and nickel, and a layer of an alloy containing nickel and cobalt.

[0118] (5-4) Modification of the insulating layer material The insulating layer 104 may be a layer of a metal oxide other than MgO, or may be a layer of an insulator other than a metal oxide, such as a ceramic layer.

[0119] (5-5) Modifications of the Thickness of the First Magnetic Layer, the Second Magnetic Layer, the Third Magnetic Layer, and the Insulating Layer The first magnetic layer 101 may have a thickness other than 4 nm. The second magnetic layer 102 may have a thickness other than 2 nm. The third magnetic layer 103 may have a thickness other than 4 nm. The insulating layer 104 may have a thickness other than 1 nm.

[0120] Even if the thickness of each layer other than the nonmagnetic layer 105 deviates from the value adopted in the embodiment within a range that does not exceed the threshold, it is possible to detect the magnetic field EH by the TMR effect.

[0121] However, if the first magnetic layer 101 has a thickness in a first range including 4 nm, the second magnetic layer 102 has a thickness in a second range including 2 nm, the third magnetic layer 103 has a thickness in a third range including 4 nm, and the insulating layer 104 has a thickness in a fourth range including 1 nm, it is expected that the detection accuracy of the magnetic field EH will be improved.

[0122] The first to fourth ranges may be determined based on "(1-1-3) The magnitude relationship between the magnetization strengths of the first magnetic layer, the second magnetic layer, and the third magnetic layer" and "(1-1-4) The magnitude relationship between the strength of the antiferromagnetic coupling and the magnetization strength of the first magnetic layer and the magnetization strength of the third magnetic layer."

[0123] In this variation, the first range is a range of 4±0.2 nm, the second range is a range of 2±0.2 nm, the third range is a range of 4±0.2 nm, and the fourth range is a range of 1±0.2 nm.

[0124] By ensuring that the thickness of the non-magnetic layer 105 is within ±0.05 nm of the value (1.6 nm) used in the embodiment, and that the thickness of each layer other than the non-magnetic layer 105 is within ±0.2 of the value used in the embodiment (first magnetic layer 101: 4 nm, second magnetic layer 102: 2 nm, third magnetic layer 103: 4 nm, insulating layer 104: 1 nm), it is expected that the detection accuracy of the TMR sensor 100 will be ensured.

[0125] (5-6) Modification of TMR film The TMR film 10 may further include one or more other magnetic layers in addition to the first to third magnetic layers 101 to 103. For example, in the TMR film 10 of the embodiment (see FIG. 1), a fourth magnetic layer may be interposed between the third magnetic layer 103 and the non-magnetic layer 105. In addition to or instead of this, a fifth magnetic layer may be interposed between the non-magnetic layer 105 and the second magnetic layer 102.

[0126] (5-7) Modified TMR film array The multiple TMR films 10 may be arranged (stacked) along the stacking direction Dr1. In this case, a conductor is interposed between the third magnetic layer 103 of the first TMR film 10 and the first magnetic layer 101 of the second TMR film 10 disposed directly above the first TMR film 10.

[0127] (5-8) First Modified Example of TMR Sensor The TMR sensor 100 may further include a processing circuit that processes the first to fourth output signals. The processing circuit is electrically connected to the first to fourth output terminals 1T to 4T.

[0128] Based on the first output signal and the second output signal, the processing circuit determines, for example, the direction of the external magnetic field EH applied from the magnetic scale 6 to the TMR sensor 100. The processing circuit may also detect the position of the magnetic scale 6 relative to the TMR sensor 100 based on the first to fourth output signals.

[0129] Specifically, the processing circuit generates a first differential signal, which is a differential signal between the first output signal and the third output signal. The waveform of the first differential signal is a waveform with double the amplitude of the first output signal. The processing circuit also generates a second differential signal, which is a differential signal between the second output signal and the fourth output signal. The waveform of the second differential signal is a waveform with double the amplitude of the second output signal.

[0130] The processing circuit determines a common phase of the first differential signal as a sine wave and the second differential signal as a cosine wave based on the first differential signal and the second differential signal, and can detect the position of the magnetic scale 6 relative to the magnetic sensor 100 based on the determined phase. The first differential signal and the second differential signal have twice the amplitude of the first output signal and the second output signal, allowing for more accurate position detection.

[0131] The processing circuit includes a computer system having one or more processors and a memory. The processor of the computer system executes a program stored in the memory of the computer system, thereby realizing the functions of the processing circuit.

[0132] (5-9) Second Modification of TMR Sensor Although the embodiment has been described as a TMR sensor 100, the present invention may be applied to various magnetic sensors that utilize the tunneling magnetoresistance (TMR) effect to detect magnetic fields and, in turn, various physical quantities that change depending on the magnetic field.

[0133] (6) Summary The magnetic sensor (100) according to the first embodiment includes a TMR film (10) whose electrical resistance changes in response to a magnetic field (EH). The TMR film (10) includes a first magnetic layer (101), a second magnetic layer (102), a third magnetic layer (103), an insulating layer (104) sandwiched between the first magnetic layer (101) and the second magnetic layer (102), and a non-magnetic layer (105) sandwiched between the second magnetic layer (102) and the third magnetic layer (103). The second magnetic layer (102) and the third magnetic layer (103) are antiferromagnetically coupled via the non-magnetic layer (105). The magnetization strength of the first magnetic layer (101) is equal to the magnetization strength of the third magnetic layer (103). The magnetization strength of the second magnetic layer (102) is smaller than the magnetization strength of the third magnetic layer (103). The strength of the antiferromagnetic coupling (AC1) between the second magnetic layer (102) and the third magnetic layer (103) is greater than both the magnetization strength of the first magnetic layer (101) and the magnetization strength of the third magnetic layer (103).

[0134] According to this aspect, when the strength of the magnetic field (EH) is equal to or less than a threshold value, the layer of the second magnetic layer (102) and the third magnetic layer (103) with the greater magnetization strength faces the direction of the magnetic field (EH), and the layer with the lesser magnetization strength faces the opposite direction to the magnetic field (EH). On the other hand, when the strength of the magnetic field (EH) is equal to or greater than the threshold value, both the second magnetic layer (102) and the third magnetic layer (103) face the direction of the magnetic field (EH), so that the magnetic field (EH) can be detected without a pinned layer. Therefore, it is possible to provide a magnetic sensor that can detect a magnetic field while suppressing an increase in cost.

[0135] In the magnetic sensor (100) according to the second embodiment, the non-magnetic layer (105) is a ruthenium layer in the first embodiment.

[0136] According to this embodiment, the strength of the antiferromagnetic coupling (AC1) between the second magnetic layer (102) and the third magnetic layer (103) can be improved.

[0137] In the magnetic sensor (100) according to the third embodiment, in the first embodiment, the nonmagnetic layer (105) has a thickness that maximizes the strength of the antiferromagnetic coupling (AC1).

[0138] According to this embodiment, the strength of the antiferromagnetic coupling (AC1) can be maximized.

[0139] In the magnetic sensor (100) according to the fourth aspect, the non-magnetic layer (105) is a ruthenium layer in the third aspect, and the thickness at which the strength of the antiferromagnetic coupling (AC1) is maximized is in the range of 1.6±0.05 nanometers.

[0140] According to this embodiment, it is possible to stabilize the detection operation of the magnetic sensor (100) and maximize the strength of the antiferromagnetic coupling (AC1).

[0141] In the magnetic sensor (100) according to the fifth aspect, in any one of the first to fourth aspects, the first magnetic layer (101), the second magnetic layer (102), and the third magnetic layer (103) are metal layers containing the same ferromagnetic material.

[0142] According to this embodiment, the number of types of ferromagnetic metals required to realize the magnetic sensor (100) can be reduced.

[0143] In the magnetic sensor (100) according to the sixth aspect, the metal containing the same ferromagnetic material as in the fifth aspect is an alloy containing cobalt and iron.

[0144] According to this embodiment, the detection accuracy of the magnetic sensor (100) can be improved.

[0145] In the magnetic sensor (100) according to the seventh aspect, in the sixth aspect, the alloy further contains boron.

[0146] According to this embodiment, the detection accuracy of the magnetic sensor (100) can be further improved.

[0147] In the magnetic sensor (100) according to the eighth aspect, in the sixth or seventh aspect, the first magnetic layer (101) has a thickness in the range of 4±0.2 nanometers. The second magnetic layer (102) has a thickness in the range of 2±0.2 nanometers. The third magnetic layer (103) has a thickness in the range of 4±0.2 nanometers. The insulating layer (104) has a thickness in the range of 1±0.2 nanometers.

[0148] According to this aspect, it is possible to improve the detection accuracy of the magnetic field (EH).

[0149] In a magnetic sensor (100) according to a ninth aspect, in any one of the first to eighth aspects, the magnetic field (EH) is an external magnetic field (EH). The magnetic sensor (100) further includes a bias magnet (5). When the strength of the antiferromagnetic coupling is defined as the magnetic field strength at which the resistance change of the TMR film (10) is saturated, the bias magnet (5) applies a bias magnetic field (BH) of half the maximum strength to the TMR film (10) in a direction antiparallel to the magnetization direction of the second magnetic layer (102) when the strength of the antiferromagnetic coupling (AC1) is maximum.

[0150] According to this embodiment, the response characteristics of the resistance value to the external magnetic field (EH) change due to the application of the bias magnetic field (BH), and the operating point of the TMR film 10 drifts, making it possible to detect the resistance value of the TMR film (10) over the entire range of the external magnetic field (EH) (“EH=+EH1” to “EH=0” to “EH=-EH1”).

[0151] When no bias magnetic field (BH) is applied, the resistance value changes as an even function in response to changes in the external magnetic field (EH), but it becomes difficult to detect the resistance value near 0.

[0152] A magnetic sensor (100) according to a tenth aspect is the same as that of the ninth aspect and includes a TMR film array (10A). The TMR film array (10A) is a component in which a plurality of TMR films (10), each of which is a TMR film (10), are arranged in an arrangement direction (Dr2) that intersects with a stacking direction (Dr1) of a first magnetic layer (101), an insulating layer (104), a second magnetic layer (102), a non-magnetic layer (105), and a third magnetic layer (103). A bias magnet (5) applies a bias magnetic field (BH) to each of the plurality of TMR films (10) included in the TMR film array (10A).

[0153] According to this embodiment, the resistance value of the TMR film (10) can be detected with high sensitivity over the entire range of the external magnetic field (EH) (from "EH=+EH1" to "EH=0" to "EH=-EH1").

[0154] In the magnetic sensor (100) according to the eleventh aspect, in the tenth aspect, the TMR film array (10A) has a structure in which, between two adjacent TMR films (10) among a plurality of TMR films (10), the third magnetic layer (103) of one TMR film (10) and the first magnetic layer (101) of the other TMR film (10) are electrically connected via a conductor (CD1).

[0155] According to this embodiment, the TMR film array (10A) can be made compact.

[0156] A magnetic sensor (100) according to a twelfth aspect is the magnetic sensor (100) of the tenth or eleventh aspect, further comprising a substrate (73) having a substrate surface (73a) and a wiring layer (W1) arranged along the substrate surface (73a). The substrate surface (73a) is a plane on which an X-axis and a Y-axis perpendicular to the X-axis are defined. The wiring layer (W1) comprises a first half-bridge circuit (1) and a second half-bridge circuit (2). The first half-bridge circuit (1) is a circuit including a pair of first TMR film arrays (1P, 1Q), each of which is a TMR film array (10A). The second half-bridge circuit (2) is a circuit including a pair of second TMR film arrays (2P, 2Q), each of which is a TMR film array (10A). The pair of first TMR film arrays (1P, 1Q) are arranged parallel to the Y-axis and detect a component of an external magnetic field (EH) along the X-axis. The pair of second TMR film arrays (2P, 2Q) are arranged parallel to the X-axis and detect the component of the external magnetic field (EH) along the Y-axis. The first half-bridge circuit (1) has a first output terminal (1T). The first output terminal (1T) outputs a first output signal from the connection point between the pair of first TMR film arrays (1P, 1Q). The second half-bridge circuit (2) has a second output terminal (2T). The second output terminal (2T) outputs a second output signal from the connection point between the pair of second TMR film arrays (2P, 2Q). The bias magnet (5) applies a bias magnetic field (BH) along the positive direction of the X-axis to one of the pair of first TMR film arrays (1P, 1Q) and a bias magnetic field (BH) along the negative direction of the X-axis to the other. In addition, the bias magnet (5) applies a bias magnetic field (BH) along the positive direction of the Y axis to one of the pair of second TMR film arrays (2P, 2Q), and a bias magnetic field (BH) along the negative direction of the Y axis to the other.

[0157] According to this embodiment, when the magnetic scale (6), on which south poles and north poles are arranged alternately, is displaced along the Y axis of the magnetic sensor (100), a cosine waveform is obtained based on the first output signal, and a sine waveform is obtained based on the second output signal. [Explanation of symbols]

[0158] 100 TMR sensor (magnetic sensor) 10A TMR membrane array 10 TMR membrane 101 First magnetic layer 102 Second magnetic layer 103 Third magnetic layer 104 Insulating layer 105 Non-magnetic layer 5 bias magnet 6 Magnetic Scale 73 Base material 73a Base material side CD1 Conductor W1 wiring layer 1 First half-bridge circuit 1P, 1Q: A pair of first TMR film arrays 1T 1st output terminal 2 Second half-bridge circuit 2P, 2Q: A pair of second TMR film arrays 2T 2nd output terminal EH(+EH1~0~-EH1) External magnetic field BH bias magnetic field

Claims

1. a TMR film whose electrical resistance changes in response to a magnetic field; The TMR film is a first magnetic layer; a second magnetic layer; a third magnetic layer; an insulating layer sandwiched between the first magnetic layer and the second magnetic layer; a non-magnetic layer sandwiched between the second magnetic layer and the third magnetic layer, the second magnetic layer and the third magnetic layer are antiferromagnetically coupled via the nonmagnetic layer, the magnetization strength of the first magnetic layer is equal to the magnetization strength of the third magnetic layer; the magnetization strength of the second magnetic layer is smaller than the magnetization strength of the third magnetic layer; a strength of antiferromagnetic coupling between the second magnetic layer and the third magnetic layer is greater than both a magnetization strength of the first magnetic layer and a magnetization strength of the third magnetic layer; Magnetic sensor.

2. the non-magnetic layer is a ruthenium layer; The magnetic sensor according to claim 1 .

3. the non-magnetic layer has a thickness that maximizes the strength of the antiferromagnetic coupling; The magnetic sensor according to claim 1 .

4. the nonmagnetic layer is a ruthenium layer, The thickness at which the strength of the antiferromagnetic coupling is maximized is in the range of 1.6±0.05 nanometers. The magnetic sensor according to claim 3 .

5. the first magnetic layer, the second magnetic layer, and the third magnetic layer are metal layers containing the same ferromagnetic material; The magnetic sensor according to claim 1 .

6. The metal containing the same ferromagnetic material is an alloy containing cobalt and iron. The magnetic sensor according to claim 5 .

7. The alloy further comprises boron. The magnetic sensor according to claim 6.

8. the first magnetic layer has a thickness in the range of 4±0.2 nanometers; the second magnetic layer has a thickness in the range of 2±0.2 nanometers; the third magnetic layer has a thickness in the range of 4±0.2 nanometers; the insulating layer has a thickness in the range of 1±0.2 nanometers; The magnetic sensor according to claim 6 .

9. the magnetic field is an external magnetic field, The magnetic recording medium further comprises a bias magnet for applying a bias magnetic field having an intensity half of the maximum intensity to the TMR film in a direction antiparallel to the magnetization direction of the second magnetic layer when the antiferromagnetic coupling intensity is maximum, where the intensity of the antiferromagnetic coupling is defined as the magnetic field intensity at which the resistance change of the TMR film is saturated. The magnetic sensor according to any one of claims 1 to 8.

10. a TMR film array in which a plurality of TMR films, each of which is the TMR film, are arranged in an arrangement direction that intersects with a stacking direction of the first magnetic layer, the insulating layer, the second magnetic layer, the non-magnetic layer, and the third magnetic layer, the bias magnet applies the bias magnetic field to each of the plurality of TMR films included in the TMR film array; The magnetic sensor according to claim 9.

11. The TMR film array has a structure in which, between two adjacent TMR films among the plurality of TMR films, the third magnetic layer of one TMR film is electrically connected to the first magnetic layer of the other TMR film via a conductor. The magnetic sensor according to claim 10.

12. A substrate having a substrate surface that is a plane on which an X axis and a Y axis perpendicular to the X axis are defined; a wiring layer disposed along the surface of the substrate; The wiring layer is a first half-bridge circuit including a pair of first TMR film arrays, each of which is the TMR film array; a second half-bridge circuit including a pair of second TMR film arrays, each of which is the TMR film array; the pair of first TMR film arrays are arranged parallel to the Y axis and detect a component of the external magnetic field along the X axis; the pair of second TMR film arrays are arranged parallel to the X-axis and detect a component of the external magnetic field along the Y-axis; the first half-bridge circuit has a first output terminal for outputting a first output signal from a connection point between the pair of first TMR film arrays; the second half-bridge circuit has a second output terminal for outputting a second output signal from a connection point between the pair of second TMR film arrays; The bias magnet is applying the bias magnetic field along the positive direction of the X-axis to one of the pair of first TMR film arrays and the bias magnetic field along the negative direction of the X-axis to the other of the pair of first TMR film arrays; the bias magnetic field is applied to one of the pair of second TMR film arrays along the positive direction of the Y axis, and the bias magnetic field is applied to the other of the pair of second TMR film arrays along the negative direction of the Y axis; The magnetic sensor according to claim 10.

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