Magnetoresistive elements, magnetic sensors, and detectors

Abstract

To provide a magnetoresistive element that can respond to a wide range of magnetic fields. [Solution] The magnetoresistive element 100 comprises a first magnetic layer 11, a second magnetic layer 12, and a third magnetic layer 13 whose magnetization direction changes in response to an external magnetic field, a first non-magnetic layer 31 located between the first magnetic layer 11 and the third magnetic layer 13, and a dielectric layer 20 located between the first magnetic layer 11 and the second magnetic layer 12. The first magnetic layer 11 is located between the second magnetic layer 12 and the third magnetic layer 13. The first magnetic layer 11 and the third magnetic layer 13 are antiferromagnetically exchanged-coupled via the first non-magnetic layer 31. The magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 are stabilized in an antiparallel state when no external magnetic field is applied.

Description

Technical Field

[0001] The present disclosure relates to a magnetoresistive element, a magnetic sensor, and a detector.

Background Art

[0002] Magnetic sensors using a TMR (Tunnel MagnetoResistance) structure are known. Patent Document 1 describes a magnetic sensor having two free layers made of a magnetic material and a tunnel barrier layer as a TMR structure. In the TMR structure described in Patent Document 1, the magnetization directions of the two free layers are stably antiparallel to each other in a state where no external magnetic field is applied. As the external magnetic field strength increases, the magnetization directions of the two free layers approach the direction of the external magnetic field.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The magnetic sensor described in Patent Document 1 functions as a sensor by utilizing the change in electrical resistance according to the magnitude of an external magnetic field. In the magnetic sensor described in Patent Document 1, most of the resistance change occurs when the external magnetic field is in the range of -10 mT to 10 mT. Therefore, no resistance change occurs due to a change in the external magnetic field with a large absolute value exceeding this range, and it cannot be used as a sensor.

[0005] Therefore, the present disclosure provides a magnetoresistive element or the like that can respond to a wide range of magnetic fields.

Means for Solving the Problems

[0006] A magnetoresistive element according to one aspect of the present disclosure is a first magnetic layer, a second magnetic layer, and a third magnetic layer whose magnetization direction changes in response to an external magnetic field, wherein the first magnetic layer comprises a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked so as to be located between the second magnetic layer and the third magnetic layer, a first non-magnetic layer located between the first magnetic layer and the third magnetic layer, and a dielectric layer located between the first magnetic layer and the second magnetic layer, wherein the first magnetic layer and the third magnetic layer are antiferromagnetically exchanged-coupled via the first non-magnetic layer, and the magnetization direction of the first magnetic layer and the magnetization direction of the second magnetic layer are stabilized in an antiparallel state when no external magnetic field is applied.

[0007] A magnetoresistive element according to one aspect of the present disclosure has a laminated structure in which a first antiferromagnetic layer, a fourth magnetic layer, a second non-magnetic layer, a third magnetic layer, a first non-magnetic layer, a first magnetic layer, a dielectric layer, a second magnetic layer, a third non-magnetic layer, a fifth magnetic layer, and a second antiferromagnetic layer are stacked in this order, wherein the first non-magnetic layer is formed such that the first magnetic layer and the third magnetic layer exhibit a first-order antiferromagnetic RKKY (Ruderman, Kittel, Kasuya, Yosida) interaction.

[0008] A magnetic sensor according to one aspect of the present disclosure comprises a magnetoresistive element, a first electrode electrically connected to one end of the magnetoresistive element, and a second electrode electrically connected to the other end of the magnetoresistive element.

[0009] A detector according to one aspect of the present disclosure comprises the magnetic sensor and a magnetic scale having at least one north pole and a south pole aligned, and detects a change in position between the magnetic sensor and the magnetic scale.

[0010] A detector according to one aspect of the present disclosure comprises the magnetic sensor and a magnetic scale having at least one north pole and a south pole aligned, and detects the rate of change in position between the magnetic sensor and the magnetic scale.

[0011] A detector according to one aspect of the present disclosure comprises the magnetic sensor and a magnetic scale having at least one north pole and a south pole aligned, and detects the acceleration of a change in position between the magnetic sensor and the magnetic scale. [Effects of the Invention]

[0012] This disclosure provides a magnetoresistive element and the like that can respond to a wide range of magnetic fields. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a cross-sectional view showing a magnetoresistive element according to Embodiment 1. [Figure 2] Figure 2 is a top view showing a magnetoresistive element according to Embodiment 1. [Figure 3] Figure 3 shows an example of the magnetization direction in a magnetic tunnel junction structure. [Figure 4] Figure 4 is a diagram illustrating the change in resistance of a magnetoresistive element due to an external magnetic field. [Figure 5] Figure 5 is a conceptual diagram showing the dependence of the strength of the exchange coupling energy due to the RKKY interaction on the thickness of the non-magnetic layer. [Figure 6] Figure 6 is a cross-sectional view showing a modified magnetoresistive element according to Embodiment 1. [Figure 7] Figure 7 is a perspective view showing a magnetic sensor according to Embodiment 2. [Figure 8] Figure 8 is a perspective view showing a first example of a magnetic sensor according to a modified embodiment of the second embodiment. [Figure 9] Figure 9 is a perspective view showing a second example of a magnetic sensor according to a modification of Embodiment 2. [Figure 10] Figure 10 is a perspective view showing a third example of a magnetic sensor according to a modification of Embodiment 2. [Figure 11] Figure 11 is a perspective view showing a detector according to Embodiment 3. [Figure 12] Figure 12 is a schematic diagram showing the stacked structure of the magnetic sensors in Examples 1 to 4. [Figure 13]FIG. 13 is a diagram schematically showing the stacked structure of the magnetic sensor in Comparative Example 1. [Figure 14] FIG. 14 is a diagram showing the relationship between the exchange coupling energy due to the RKKY interaction and the thickness of the non-magnetic layer. [Figure 15] FIG. 15 is a diagram showing the magnetoresistive characteristics of the magnetic sensors in Example 2 and Comparative Example 1. [Figure 16] FIG. 16 is a diagram showing the maximum value of the resistance change rate of the magnetic sensors in Examples 1 to 4 and Comparative Example 1 and the magnetic field strength representing the degree of the magnetic field to which the sensors can respond.

Embodiments for Carrying Out the Invention

[0014] (Summary of the Present Disclosure) As a summary of the present disclosure, examples of the magnetoresistive element, magnetic sensor, and detector according to the present disclosure are shown below.

[0015] For example, the magnetoresistive element according to the first aspect of the present disclosure includes a first magnetic layer, a second magnetic layer, and a third magnetic layer whose magnetization directions change in response to an external magnetic field, wherein the first magnetic layer is a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked so as to be positioned between the second magnetic layer and the third magnetic layer, a first non-magnetic layer positioned between the first magnetic layer and the third magnetic layer, and a dielectric layer positioned between the first magnetic layer and the second magnetic layer. The first magnetic layer and the third magnetic layer are antiferromagnetically exchange-coupled via the first non-magnetic layer, and the magnetization directions of the first magnetic layer and the second magnetic layer are stabilized in an antiparallel state when no external magnetic field is applied.

[0016] As a result, when the first magnetic layer and the third magnetic layer are antiferromagnetically coupled, the magnetization directions of the first magnetic layer and the third magnetic layer rotate so as to maintain an antiferromagnetic coupling. As a result, the rotation of the magnetization direction of the first magnetic layer when the external magnetic field is increased becomes gentle. Thus, in the magnetoresistive element according to this aspect, a resistance change can be obtained even when the magnitude of the external magnetic field changes in a region where the external magnetic field is large. Therefore, the magnetoresistive element according to this aspect can respond to a wide range of magnetic fields.

[0017] Furthermore, for example, a magnetoresistive element according to a second aspect of this disclosure is a magnetoresistive element according to a first aspect, wherein the dielectric layer mainly comprises magnesium oxide, aluminum oxide, or magnesium-aluminum oxide.

[0018] This makes it possible to improve the TMR characteristics of the magnetoresistive element.

[0019] Furthermore, for example, a magnetoresistive element according to a third aspect of the present disclosure is a magnetoresistive element according to the first or second aspect, wherein each of the first magnetic layer and the second magnetic layer has an alloy layer mainly composed of an alloy of cobalt, iron, and boron.

[0020] This makes it possible to improve the TMR characteristics of the magnetoresistive element.

[0021] Furthermore, for example, the magnetoresistive element according to the fourth aspect of this disclosure is a magnetoresistive element according to any one of the first to third aspects, wherein the first non-magnetic layer contains ruthenium as the main component, and the thickness of the first non-magnetic layer is 0.6 mm or more and 0.9 mm or less.

[0022] This effectively expands the range of magnetic fields to which the magnetoresistive element can respond.

[0023] Furthermore, for example, a magnetoresistive element according to a fifth aspect of the present disclosure is a magnetoresistive element according to any one of the first to fourth aspects, further comprising a fourth magnetic layer and a fifth magnetic layer whose magnetization direction is fixed in one direction, wherein the fourth magnetic layer faces the first non-magnetic layer via the third magnetic layer, and the fifth magnetic layer faces the dielectric layer via the second magnetic layer.

[0024] This makes it easy to define the magnetization directions of the first, second, and third magnetic layers when no external magnetic field is applied.

[0025] Furthermore, for example, the magnetoresistive element according to the sixth aspect of this disclosure is a magnetoresistive element according to the fifth aspect, wherein the third magnetic layer and the fourth magnetic layer are antiferromagnetically exchanged and coupled, and the second magnetic layer and the fifth magnetic layer are antiferromagnetically exchanged and coupled.

[0026] This defines the magnetization direction of the second and third magnetic layers.

[0027] Furthermore, for example, a magnetoresistive element according to a seventh aspect of the present disclosure is a magnetoresistive element according to a fifth or sixth aspect, further comprising a first antiferromagnetic layer facing the third magnetic layer via the fourth magnetic layer, and a second antiferromagnetic layer facing the second magnetic layer via the fifth magnetic layer.

[0028] This makes it easy to fix the magnetization direction of the fourth and fifth magnetic layers.

[0029] Furthermore, for example, the magnetoresistive element according to the eighth aspect of this disclosure is the magnetoresistive element according to the seventh aspect, wherein the first antiferromagnetic layer and the second antiferromagnetic layer each mainly contain a manganese-iridium alloy, a manganese-platinum alloy, or a manganese-nickel alloy.

[0030] This makes it possible to generate strong exchange bias magnetic fields between the first antiferromagnetic layer and the fourth magnetic layer, and between the second antiferromagnetic layer and the fifth magnetic layer.

[0031] Furthermore, for example, a magnetoresistive element according to the ninth aspect of this disclosure has a laminated structure in which a first antiferromagnetic layer, a fourth magnetic layer, a second non-magnetic layer, a third magnetic layer, a first non-magnetic layer, a first magnetic layer, a dielectric layer, a second magnetic layer, a third non-magnetic layer, a fifth magnetic layer, and a second antiferromagnetic layer are stacked in this order, and the first non-magnetic layer is formed such that the first magnetic layer and the third magnetic layer exhibit a first-order antiferromagnetic RKKY (Ruderman, Kittel, Kasuya, Yosida) interaction.

[0032] As a result, a first-order antiferromagnetic RKKY interaction is generated between the first magnetic layer and the third magnetic layer, causing the magnetization directions of the first magnetic layer and the third magnetic layer to rotate in an antiparallel state. Consequently, the rotation of the magnetization direction of the first magnetic layer becomes slower when the external magnetic field is increased. Therefore, in the magnetoresistive element according to this embodiment, a change in resistance can be obtained even when the magnitude of the external magnetic field changes in the region where the external magnetic field is large. Thus, the magnetoresistive element according to this embodiment can respond to a wide range of magnetic fields.

[0033] Furthermore, for example, a magnetic sensor according to the tenth aspect of this disclosure comprises a magnetoresistive element according to any one of the first to ninth aspects, a first electrode electrically connected to one end of the magnetoresistive element, and a second electrode electrically connected to the other end of the magnetoresistive element.

[0034] This allows magnetic fields to be detected using the magnetoresistive element described above, which can respond to a wide range of magnetic fields.

[0035] Furthermore, for example, the magnetic sensor according to the 11th aspect of this disclosure is a magnetic sensor according to the 10th aspect, which detects a magnetic field component in a direction different from the magnetization direction of the first magnetic layer and the magnetization direction of the second magnetic layer when no external magnetic field is applied.

[0036] This improves the accuracy of detecting magnetic field components.

[0037] Furthermore, for example, a magnetic sensor according to a twelfth aspect of the present disclosure is a magnetic sensor according to a tenth or eleventh aspect, comprising a plurality of magnetoresistive elements, wherein the plurality of magnetoresistive elements are electrically connected to each other in at least one form, such as series and parallel.

[0038] This allows the voltage applied to the magnetoresistive element to be distributed when measuring its electrical resistance.

[0039] Furthermore, for example, a detector according to a 13th aspect of this disclosure comprises a magnetic sensor according to any one of the 10th to 12th aspects and a magnetic scale having at least one N pole and S pole aligned, and detects changes in the position of the magnetic sensor and the magnetic scale.

[0040] This makes it possible to detect changes in the position between a magnetic sensor and a magnetic scale using a magnetic sensor equipped with the above-mentioned magnetoresistive element that can respond to a wide range of magnetic fields.

[0041] Furthermore, for example, a detector according to a 14th aspect of this disclosure comprises a magnetic sensor according to any one of the 10th to 12th aspects and a magnetic scale having at least one N pole and S pole aligned, and detects the rate of change of position between the magnetic sensor and the magnetic scale.

[0042] This makes it possible to detect the rate of positional change between a magnetic sensor and a magnetic scale using a magnetic sensor equipped with the above-mentioned magnetoresistive element that can respond to a wide range of magnetic fields.

[0043] Furthermore, for example, a detector according to a 15th aspect of this disclosure comprises a magnetic sensor according to any one of the 10th to 12th aspects and a magnetic scale having at least one N pole and a S pole aligned, and detects the acceleration of the positional change between the magnetic sensor and the magnetic scale.

[0044] This makes it possible to detect the acceleration of the positional change between the magnetic sensor and the magnetic scale using a magnetic sensor equipped with the above-mentioned magnetoresistive element that can respond to a wide range of magnetic fields.

[0045] Embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are either comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure. The various embodiments described herein can be combined with each other as long as they do not conflict. Furthermore, components in the following embodiments that are not described in an independent claim will be described as optional components. In the following description, components having substantially the same function will be indicated by a common reference numeral and their description may be omitted. Also, to avoid making the drawings excessively complex, some elements may be omitted from the illustration.

[0046] Furthermore, the various elements shown in the drawings are for illustrative purposes only, and their dimensional ratios and appearance may differ from those of the actual object. In other words, each drawing is a schematic representation and not necessarily a strictly accurate depiction. Therefore, for example, the scale in each drawing may not necessarily match.

[0047] Furthermore, in this specification, terms indicating relationships between elements, such as parallel or coincident, terms indicating the shape of elements, such as circular, and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0048] Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upward (vertically upward) and downward (vertically downward) directions in absolute spatial perception, but rather to terms defined by the relative positional relationship based on the stacking order in a stacked configuration. Terms such as "upper" and "lower" are used solely to specify the relative arrangement between components and are not intended to limit the orientation when using magnetoresistive elements, magnetic sensors, and detectors. The same applies to the terms "lower surface" and "upper surface," which do not refer to the upper and lower surfaces in absolute spatial perception. Moreover, the terms "upper" and "lower" apply not only when two components are spaced apart and another component exists between them, but also when two components are placed in close proximity and touching each other.

[0049] In this specification and in the drawings, the X, Y, and Z axes represent the three axes of a three-dimensional Cartesian coordinate system. Below, the negative side of the Z axis is referred to as "downward," and the positive side of the Z axis is referred to as "upward." The surface on the negative side of the Z axis is referred to as the "bottom surface," and the surface on the positive side of the Z axis is referred to as the "top surface." The Z-axis direction is the thickness direction of each layer in the magnetoresistive element, and also the stacking direction.

[0050] (Embodiment 1) The magnetoresistive element according to Embodiment 1 will be described below. The magnetoresistive element according to Embodiment 1 can be used, for example, in a magnetic sensor.

[0051] [composition] First, the configuration of the magnetoresistive element according to this embodiment will be described. Figure 1 is a cross-sectional view showing the magnetoresistive element according to this embodiment. Figure 2 is a top view showing the magnetoresistive element according to this embodiment. In Figure 1, a cross-section is shown at the position indicated by line II in Figure 2. Also in Figure 1, the magnetization directions D1, D2, and D3 of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 when no external magnetic field is applied are schematically shown by dashed arrows. Note that in Figure 1, the length in the thickness direction is exaggerated for clarity.

[0052] As shown in Figure 1, the magnetoresistive element 100 according to this embodiment comprises a first magnetic layer 11, a second magnetic layer 12, and a third magnetic layer 13, a dielectric layer 20, and a first non-magnetic layer 31. The first magnetic layer 11, the second magnetic layer 12, the third magnetic layer 13, the dielectric layer 20, and the first non-magnetic layer 31 are each thin film structures. The magnetoresistive element 100 has a laminated structure in which the third magnetic layer 13, the first non-magnetic layer 31, the first magnetic layer 11, the dielectric layer 20, and the second magnetic layer 12 are stacked in this order from the bottom along the Z axis. In the magnetoresistive element 100, no other layers are arranged between each layer of the laminated structure, but other layers may be arranged within a range that does not significantly degrade the TMR characteristics. Furthermore, another layer may be stacked above or below the magnetoresistive element 100.

[0053] In the example shown in Figure 2, the plan view shape of the magnetoresistive element 100, when viewed from above, is circular. The plan view shape of the magnetoresistive element 100 is not particularly limited and may be elliptical or polygonal. The maximum width (or diameter if the plan view shape is circular) of the plan view shape of the magnetoresistive element 100 is, for example, 0.01 μm or more and 100 μm or less.

[0054] In the magnetoresistive element 100, the portion where the first magnetic layer 11, the dielectric layer 20, and the second magnetic layer 12 are stacked is a magnetic tunnel junction structure. The first magnetic layer 11 and the second magnetic layer 12 are joined to the dielectric layer 20 and are in contact with the dielectric layer 20. The first magnetic layer 11 is located between the second magnetic layer 12 and the third magnetic layer 13.

[0055] The magnetization directions D1, D2, and D3 of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 change in response to an external magnetic field. Furthermore, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 are stabilized in an antiparallel state when no external magnetic field is applied. The external magnetic field is the magnetic field that is detected by the magnetic sensor using the magnetoresistive element 100, and the magnitude of the magnetic field that the magnetoresistive element 100 receives from the external magnetic field changes when the magnetic sensor is used. The magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 may be stabilized in an antiparallel state by a constant magnetic field applied to the magnetoresistive element 100 separately from the external magnetic field to be detected, or they may be stabilized in an antiparallel state by laminating another magnetic layer on the magnetoresistive element 100 as described later.

[0056] The first magnetic layer 11 and the third magnetic layer 13 are antiferromagnetically exchanged. The magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D3 of the third magnetic layer 13 are antiparallel, regardless of whether an external magnetic field is applied or not. Therefore, the apparent magnetic moment of the laminated structure of the first magnetic layer 11, the first non-magnetic layer 31, and the third magnetic layer 13 is the resultant vector (direction and magnitude) of the magnetic moment of the first magnetic layer 11 and the magnetic moment of the third magnetic layer 13. Here, let m1 represent the magnetic moment of the first magnetic layer 11 and m3 represent the magnetic moment of the third magnetic layer 13. Since the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D3 of the third magnetic layer 13 are antiparallel, the apparent magnitude of the magnetic moment of the laminated structure of the first magnetic layer 11, the first non-magnetic layer 31, and the third magnetic layer 13 is |m1-m3|, and the magnetization direction of the entire laminated structure coincides with the magnetization direction of the one with the larger magnetic moment between the first magnetic layer 11 and the third magnetic layer 13. Also, if the magnetic moment of the second magnetic layer 12 is represented as m2, then for example, the relationship m2>|m1-m3| holds.

[0057] The magnetic moment referred to here means the magnetic moment per unit area. The usual unit of magnetic moment is, for example, Tcm. 3This is in tesla cubic centimeters. Dividing this by the area gives the magnetic moment per unit area, which can be expressed in units such as Tnm (tesla nanometers).

[0058] In the example shown in Figure 1, the magnetization directions D1, D2, and D3 of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 are parallel to the X-axis when no external magnetic field is applied. Also, the magnetization directions D1, D2, and D3 of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 are parallel to the upper and lower surfaces of the magnetoresistive element 100.

[0059] Each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 may be a layer composed of a single material, or it may have a laminated structure of multiple layers including two or more layers composed of different materials. Each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 includes at least a layer composed of a ferromagnetic material. Each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 may also include a layer composed of a non-magnetic material (e.g., a paramagnetic material). Even if the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 have a laminated structure of multiple layers, the magnetization direction in the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 is uniquely determined. In this specification, magnetic layers such as the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 are layers in which the magnetization direction of one or more layers composed of ferromagnetic materials contained within them is unified. In each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13, the magnetization direction of one or more layers composed of ferromagnetic material contained within them changes in the same direction in response to the external magnetic field.

[0060] Each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 contains a ferromagnetic material as its main component. Each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 contains, for example, at least one of iron, cobalt, and nickel. Each of the first magnetic layer 11 and the second magnetic layer 12 has an alloy layer containing, for example, an alloy of iron, cobalt, and boron as its main component as the magnetic material. This can improve the TMR characteristics of the magnetoresistive element 100. The alloy layer containing the alloy of iron, cobalt, and boron as its main component is, for example, located closest to the dielectric layer 20. An example of the composition ratio of the alloy of iron, cobalt, and boron is Co:Fe:B = 40:40:20.

[0061] The third magnetic layer 13 has an alloy layer mainly composed of an alloy of iron and cobalt. The first magnetic layer 11 and the second magnetic layer 12 may also have an alloy layer mainly composed of an alloy of iron and cobalt. An example of the composition ratio of the iron and cobalt alloy is Co:Fe = 50:50.

[0062] Furthermore, examples of non-magnetic materials included in the first magnetic layer 11 and the second magnetic layer 12 include tantalum, ruthenium, or alloys containing tantalum or ruthenium. In addition, the third magnetic layer 13 does not include a layer made of a non-magnetic material, but may include a layer made of a non-magnetic material.

[0063] In this specification, "main component" means that the content of the material in question is greater than 50 mass%. The content of the main component material may be 90 mass% or more, 95 mass% or more, or 99 mass% or more. The content of the main component material may be substantially 100%. In this case, the main component material may contain unavoidable impurities.

[0064] The thickness of each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 is, for example, between 0.1 nm and 100 nm. The thickness of each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 may be 1 nm or more. Alternatively, the thickness of each of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 may be 10 nm or less.

[0065] The dielectric layer 20 is located between the first magnetic layer 11 and the second magnetic layer 12. The dielectric layer 20 mainly contains a dielectric material. For example, the dielectric layer 20 mainly contains magnesium oxide, aluminum oxide, or magnesium-aluminum oxide. The compositional formulas of magnesium oxide, aluminum oxide, and magnesium-aluminum oxide are MgO, Al2O3, and MgAl2O4, respectively.

[0066] The thickness of the dielectric layer 20 is, for example, 0.1 nm or more and 10 nm or less.

[0067] The first non-magnetic layer 31 is located between the first magnetic layer 11 and the third magnetic layer 13. The first non-magnetic layer 31 mainly contains a non-magnetic material (e.g., a paramagnetic material). The non-magnetic material contained in the first non-magnetic layer 31 is, for example, a non-magnetic metal. The first non-magnetic layer 31 mainly contains ruthenium. The thickness of the first non-magnetic layer 31 will be described later.

[0068] [Resistance change characteristics of magnetoresistive elements] Next, the resistance change characteristics of the magnetoresistive element 100 according to this embodiment will be described.

[0069] In the magnetoresistive element 100 according to this embodiment, the electrical resistance between the third magnetic layer 13 and the second magnetic layer 12 is measured during use. The method for measuring the electrical resistance may be DC measurement or AC measurement. In the case of DC measurement, the method for measuring the electrical resistance may be constant voltage application measurement or constant current application measurement.

[0070] A structure in which a first magnetic layer 11, a dielectric layer 20, and a second magnetic layer 12 are stacked is called a TMR structure or magnetic tunnel junction structure. The dielectric layer 20 is a barrier layer that acts as a tunnel barrier. The first magnetic layer 11 and the second magnetic layer 12 are both free layers whose magnetization direction changes due to an external magnetic field.

[0071] Figure 3 shows an example of magnetization direction in a magnetic tunnel junction structure. In Figure 3, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 are shown when the magnetoresistive element 100 is viewed from above. In a magnetic tunnel junction structure, the resistance value between the first magnetic layer 11 and the second magnetic layer 12 is determined by the angle θ between the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12. Ideally, the resistance value depends on cosθ. Specifically, the resistance value is minimized when the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 are parallel (i.e., θ is 0 degrees). The resistance value is maximized when the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 are antiparallel (i.e., θ is 180 degrees).

[0072] In the magnetoresistive element 100 according to this embodiment, the magnetization direction of each layer changes when an external magnetic field is applied. When the angle θ between the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 changes due to the external magnetic field, the resistance value of the magnetoresistive element 100 changes.

[0073] Figure 4 is a diagram illustrating the change in resistance of the magnetoresistive element 100 due to an external magnetic field. In Figure 4, the vertical axis represents the resistance of the magnetoresistive element 100, and the horizontal axis represents the external magnetic field applied to the magnetoresistive element 100. As shown in Figure 4, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 change in response to the external magnetic field. Specifically, when the direction of the external magnetic field is constant and the strength of the external magnetic field changes, as the external magnetic field increases, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 approach the direction of the external magnetic field, and the angle θ decreases.

[0074] As shown in Figure 4(a), when no external magnetic field is applied, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 are stabilized in an antiparallel state, so the resistance value of the magnetoresistive element 100 is the maximum resistance value Rmax. When an external magnetic field is applied and the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 approach the direction of the external magnetic field, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 approach a parallel state, so the resistance value of the magnetoresistive element 100 decreases. In other words, the magnetoresistive element 100 exhibits a behavior in which its resistance value decreases when an external magnetic field is applied. As shown in Figures 4(b) and 4(c), when the external magnetic field increases and the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 coincide with the direction of the external magnetic field, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 become parallel, and the resistance value of the magnetoresistive element 100 becomes the minimum resistance value Rmin.

[0075] Here, the maximum value MR of the resistance change rate of the magnetoresistive element 100 can be expressed as MR = (Rmax - Rmin) / Rmax, and the larger the maximum value MR of the resistance change rate, the more accurate magnetic field detection becomes possible using the magnetoresistive element 100. The maximum value MR of the resistance change rate of the magnetoresistive element 100 is, for example, 50% or more. The maximum value MR of the resistance change rate of the magnetoresistive element 100 may be 55% or more. There is no particular upper limit to the maximum value MR of the resistance change rate of the magnetoresistive element 100, but the maximum value MR of the resistance change rate of the magnetoresistive element 100 is, for example, 80% or less.

[0076] Since the above behavior occurs regardless of the direction of the external magnetic field, the magnetoresistive element 100 yields a bell-shaped, even-function resistance change curve when the horizontal axis is the magnetic field and the vertical axis is the resistance. Furthermore, as shown in Figure 4, the magnetic field strength Hk at which the inner tangent line of the resistance change curve drawn from the peak of the resistance change curve (i.e., the maximum resistance value Rmax) is the minimum resistance value Rmin can be used as an indicator of the range of magnetic fields to which the magnetoresistive element 100 can respond. The larger the magnetic field strength Hk, the wider the range of magnetic fields to which the magnetoresistive element 100 can respond. In the case of the magnetoresistive element 100, it is possible to increase the magnetic field strength Hk, and the magnetic field strength Hk of the magnetoresistive element 100 is, for example, 20 mT or more. The magnetic field strength Hk of the magnetoresistive element 100 may also be 25 mT or more. There is no particular upper limit to the magnetic field strength Hk of the magnetoresistive element 100, but the magnetic field strength Hk of the magnetoresistive element 100 is, for example, 80 mT or less.

[0077] The following explains why the magnetoresistive element 100 can respond to a wide range of magnetic fields.

[0078] As described above, when the direction of the external magnetic field is constant and the external magnetic field changes, as the external magnetic field increases, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 approach the direction of the external magnetic field.

[0079] Furthermore, as described above, the resistance value of the magnetoresistive element 100 is determined by the angle θ formed by the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12. Therefore, the way in which the resistance of the magnetoresistive element 100 changes with respect to the magnitude of the external magnetic field is determined by the rotation of the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12.

[0080] In the magnetoresistive element 100 according to this embodiment, the first magnetic layer 11 and the third magnetic layer 13 are antiferromagnetically coupled, so that the laminated structure of the first magnetic layer 11, the first non-magnetic layer 31, and the third magnetic layer 13 becomes one, and the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D3 of the third magnetic layer 13 rotate in such a way that they maintain an antiferromagnetic coupling state. As a result, the rotation of the magnetization direction D1 of the first magnetic layer 11 becomes gradual when the external magnetic field is increased. Therefore, even when the external magnetic field increases, the magnetization direction D1 of the first magnetic layer 11 is less likely to become parallel to the direction of the external magnetic field, and the resistance change of the magnetoresistive element 100 due to the increase in the external magnetic field continues. As a result, the magnetoresistive element 100 can obtain a resistance change even when the magnitude of the external magnetic field changes in the region where the external magnetic field is large. Therefore, the magnetoresistive element 100 can be used even in environments with strong external magnetic fields, and for example, the distance to the source of the external magnetic field to be detected can be reduced, thus enabling miniaturization of devices or systems using the magnetoresistive element 100. Furthermore, by making the first magnetic layer 11 thinner and reducing the magnetic moment of the first magnetic layer 11 without using the third magnetic layer 13, it is also possible to make it more difficult for the magnetization direction D1 of the first magnetic layer 11 to rotate due to the external magnetic field; however, in this case, the maximum value MR of the resistance change rate becomes smaller. With the magnetoresistive element 100, the magnetization direction D1 of the first magnetic layer 11 becomes less likely to rotate regardless of the thickness of the first magnetic layer 11, making it possible to increase the maximum value MR of the resistance change rate.

[0081] Furthermore, the magnetic moment m1 of the first magnetic layer 11 is greater than, for example, the magnetic moment m3 of the third magnetic layer 13 (i.e., m1 > m3). This makes it possible to increase the maximum value MR of the resistance change rate of the magnetoresistive element 100. Note that the magnetic moment m1 of the first magnetic layer 11 may be the same as or smaller than the magnetic moment m3 of the third magnetic layer 13.

[0082] The exchange coupling between the first magnetic layer 11 and the third magnetic layer 13 may be due to an antiferromagnetic RKKY (Ruderman, Kittel, Kasuya, Yosida) interaction via the first non-magnetic layer 31. Figure 5 is a conceptual diagram showing the dependence of the strength of the exchange coupling energy due to the RKKY interaction on the thickness of the non-magnetic layer. In Figure 5, the vertical axis represents the exchange coupling energy of the magnetic layers in a laminated structure of magnetic layers and non-magnetic layers. In Figure 5, the horizontal axis represents the thickness of the non-magnetic layer.

[0083] As shown in Figure 5, the exchange coupling energy exhibits damped oscillations with increasing thickness of the non-magnetic layer. Within a certain range of non-magnetic layer thickness, antiferromagnetic interactions occur between magnetic layers, while within a range other than that, ferromagnetic interactions occur between magnetic layers. The exchange coupling energy shows multiple peaks in its dependence on the non-magnetic layer thickness for both antiferromagnetic and ferromagnetic coupling energies. Of these multiple peaks, the peak at the position with the smallest non-magnetic layer thickness is called the first-order peak, and the order of the peaks increases as the non-magnetic layer thickness increases. The antiferromagnetic interaction corresponding to the Nth-order peak of the antiferromagnetic coupling energy is also called the Nth-order antiferromagnetic RKKY interaction. Similarly, the ferromagnetic interaction corresponding to the Mth-order peak of the ferromagnetic coupling energy is also called the Mth-order ferromagnetic RKKY interaction. Here, N and M are integers greater than or equal to 1.

[0084] In the magnetoresistive element 100 according to this embodiment, the first non-magnetic layer 31 is formed such that, for example, the first magnetic layer 11 and the third magnetic layer 13 exhibit a first-order antiferromagnetic RKKY interaction. The thickness of the first non-magnetic layer 31 required to exhibit a first-order antiferromagnetic RKKY interaction between the first magnetic layer 11 and the third magnetic layer 13 varies depending on the type of non-magnetic metal constituting the first non-magnetic layer 31. For example, when ruthenium is used as the non-magnetic metal, a first-order antiferromagnetic RKKY interaction can be obtained with a layer thickness of 0.6 nm to 0.9 nm.

[0085] [Differentiation] The following describes a magnetoresistive element according to a modification of Embodiment 1. In the following description of the modification, the differences from Embodiment 1 will be the main focus, and the similarities will be omitted or simplified.

[0086] Figure 6 is a cross-sectional view showing a magnetoresistive element according to this modified example. In Figure 6, the magnetization directions D1, D2, and D3 of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 when no external magnetic field is applied are schematically shown by dashed arrows. Also in Figure 6, the magnetization directions D4 and D5 of the fourth magnetic layer 14 and the fifth magnetic layer 15 are schematically shown by solid arrows. Note that in Figure 6, the length in the thickness direction is exaggerated for clarity.

[0087] As shown in Figure 6, the magnetoresistive element 101 according to this modified example differs from the magnetoresistive element 100 according to Embodiment 1 mainly in that it further comprises a fourth magnetic layer 14, a fifth magnetic layer 15, a second non-magnetic layer 32, a third non-magnetic layer 33, a first antiferromagnetic layer 41, and a second antiferromagnetic layer 42. Each of the fourth magnetic layer 14, fifth magnetic layer 15, second non-magnetic layer 32, third non-magnetic layer 33, first antiferromagnetic layer 41, and second antiferromagnetic layer 42 is a thin film structure.

[0088] The magnetoresistive element 101 has a laminated structure in which a first antiferromagnetic layer 41, a fourth magnetic layer 14, a second non-magnetic layer 32, a third magnetic layer 13, a first non-magnetic layer 31, a first magnetic layer 11, a dielectric layer 20, a second magnetic layer 12, a third non-magnetic layer 33, a fifth magnetic layer 15, and a second antiferromagnetic layer 42 are stacked in this order from the bottom along the Z axis. The portion where the third magnetic layer 13, the first non-magnetic layer 31, the first magnetic layer 11, the dielectric layer 20, and the second magnetic layer 12 are stacked is the same as the magnetoresistive element 100 according to Embodiment 1. In the magnetoresistive element 101, no other layers are arranged between each layer of the above laminated structure, but other layers may be arranged within a range that does not significantly degrade the TMR characteristics. Furthermore, another layer may be stacked above or below the magnetoresistive element 101.

[0089] The fourth magnetic layer 14 faces the third magnetic layer 13 via the second non-magnetic layer 32. The third magnetic layer 13 and the fourth magnetic layer 14 are antiferromagnetically exchanged via the second non-magnetic layer 32. The fourth magnetic layer 14 also faces the first non-magnetic layer 31 via the third magnetic layer 13. The fifth magnetic layer 15 faces the second magnetic layer 12 via the third non-magnetic layer 33. The second magnetic layer 12 and the fifth magnetic layer 15 are antiferromagnetically exchanged via the third non-magnetic layer 33. The fifth magnetic layer 15 also faces the dielectric layer 20 via the second magnetic layer 12. Note that the exchange coupling between the third magnetic layer 13 and the fourth magnetic layer 14, and the exchange coupling between the second magnetic layer 12 and the fifth magnetic layer 15, may be ferromagnetic instead of antiferromagnetic.

[0090] Each of the fourth magnetic layer 14 and the fifth magnetic layer 15 may be a layer composed of a single material, or it may have a laminated structure of multiple layers composed of different materials. Each of the fourth magnetic layer 14 and the fifth magnetic layer 15 includes at least a layer composed of a ferromagnetic material. Each of the fourth magnetic layer 14 and the fifth magnetic layer 15 may include a layer composed of a non-magnetic material (e.g., a paramagnetic material). Each of the fourth magnetic layer 14 and the fifth magnetic layer 15 as a whole contains a ferromagnetic material as its main component. Each of the fourth magnetic layer 14 and the fifth magnetic layer 15 has, for example, an alloy layer containing an alloy of iron and cobalt as its main component.

[0091] The thickness of the fourth magnetic layer 14 and the fifth magnetic layer 15 is, for example, between 0.1 nm and 100 nm. The thickness of the fourth magnetic layer 14 and the fifth magnetic layer 15 may be 1 nm or more. Alternatively, the thickness of the fourth magnetic layer 14 and the fifth magnetic layer 15 may be 10 nm or less.

[0092] The magnetization direction D4 of the fourth magnetic layer 14 and the magnetization direction D5 of the fifth magnetic layer 15 are each fixed in one direction. In this specification, "fixed in one direction" means substantially fixed, indicating that the magnetization direction does not change due to the magnetic field applied in the environment in which the magnetoresistive element 101 is used. The magnetization direction D4 of the fourth magnetic layer 14 and the magnetization direction D5 of the fifth magnetic layer 15 do not change when an external magnetic field of magnitude from -100mT to 100mT is applied, for example. By comprising the fourth magnetic layer 14 and the fifth magnetic layer 15, the magnetoresistive element 101 can easily define the magnetization directions D1, D2, and D3 of the first magnetic layer 11, the second magnetic layer 12, and the third magnetic layer 13 when no external magnetic field is applied.

[0093] In the example shown in Figure 6, the magnetization directions D4 and D5 of the fourth magnetic layer 14 and the fifth magnetic layer 15 are parallel to the X-axis. Also, the magnetization directions D4 and D5 of the fourth magnetic layer 14 and the fifth magnetic layer 15 are parallel to the upper and lower surfaces of the magnetoresistive element 101. Furthermore, the magnetization direction D4 of the fourth magnetic layer 14 and the magnetization direction D5 of the fifth magnetic layer 15 are the same (parallel).

[0094] One method for fixing the magnetization directions D4 and D5 of the fourth magnetic layer 14 and the fifth magnetic layer 15 is to use the exchange bias magnetic field generated between the fourth magnetic layer 14 and the first antiferromagnetic layer 41, and between the fifth magnetic layer 15 and the second antiferromagnetic layer 42.

[0095] To generate a unidirectional exchange bias magnetic field, the heat treatment may be performed with an external magnetic field applied in one direction. The magnitude of the external magnetic field during the heat treatment is, for example, 100 mT to 1000 mT. The heat treatment temperature is, for example, 300 degrees Celsius to 400 degrees Celsius.

[0096] The first antiferromagnetic layer 41 faces the third magnetic layer 13 via the fourth magnetic layer 14. The second antiferromagnetic layer 42 faces the second magnetic layer 12 via the fifth magnetic layer 15. Each of the first antiferromagnetic layer 41 and the second antiferromagnetic layer 42 contains an antiferromagnetic material as its main component. Each of the first antiferromagnetic layer 41 and the second antiferromagnetic layer 42 contains, for example, a manganese-iridium alloy, a manganese-platinum alloy, or a manganese-nickel alloy as its main component.

[0097] Furthermore, if the magnetization direction D4 of the fourth magnetic layer 14 and the magnetization direction D5 of the fifth magnetic layer 15 are fixed in one direction, the magnetoresistive element 101 does not need to include the first antiferromagnetic layer 41 and the second antiferromagnetic layer 42.

[0098] The thickness of the first antiferromagnetic layer 41 and the second antiferromagnetic layer 42 is, for example, between 1 nm and 100 nm.

[0099] The second non-magnetic layer 32 faces the first non-magnetic layer 31 via the third magnetic layer 13. The second non-magnetic layer 32 is located between the third magnetic layer 13 and the fourth magnetic layer 14. The third non-magnetic layer 33 faces the dielectric layer 20 via the second magnetic layer 12. The third non-magnetic layer 33 is located between the second magnetic layer 12 and the fifth magnetic layer 15. Each of the second non-magnetic layer 32 and the third non-magnetic layer 33 contains, for example, a non-magnetic material (e.g., a paramagnetic material) as its main component. The non-magnetic material contained in each of the second non-magnetic layer 32 and the third non-magnetic layer 33 is, for example, a non-magnetic metal. Each of the second non-magnetic layer 32 and the third non-magnetic layer 33 contains, for example, ruthenium as its main component.

[0100] The thickness of the second non-magnetic layer 32 and the third non-magnetic layer 33 is, for example, between 1.0 nm and 5.0 mm.

[0101] The second non-magnetic layer 32 is formed such that, for example, the third magnetic layer 13 and the fourth magnetic layer 14 exhibit a second-order or higher-order antiferromagnetic RKKY interaction. The third non-magnetic layer 33 is formed such that, for example, the second magnetic layer 12 and the fifth magnetic layer 15 exhibit a second-order or higher-order antiferromagnetic RKKY interaction. This prevents the antiferromagnetic exchange coupling with the second magnetic layer 12 and the third magnetic layer 13 from becoming too strong, thereby improving the TMR characteristics of the magnetoresistive element 101. For example, when ruthenium is used as the non-magnetic metal for the second non-magnetic layer 32 and the third non-magnetic layer 33, a second-order or higher-order antiferromagnetic RKKY interaction can be obtained at layer thicknesses of 1.0 nm or more.

[0102] (Embodiment 2) The following describes a magnetic sensor according to Embodiment 2. Specifically, Embodiment 2 describes a magnetic sensor equipped with a magnetoresistive element according to the present disclosure.

[0103] Figure 7 is a perspective view showing a magnetic sensor according to this embodiment. In Figure 7, the position of the dielectric layer 20 in the magnetoresistive element 110 is indicated by a dashed line. Also, the magnetization directions D1 and D2 of the first magnetic layer 11 (not shown in Figure 7) and the second magnetic layer 12 (not shown in Figure 7) when no external magnetic field is applied to the magnetoresistive element 110 are indicated by dashed arrows.

[0104] As shown in Figure 7, the magnetic sensor 200 according to this embodiment comprises a magnetoresistive element 110, a lower electrode 121, and an upper electrode 122. The magnetoresistive element 110 is, for example, a magnetoresistive element 101 according to a modified example of Embodiment 1, but is not particularly limited as long as it is a magnetoresistive element that includes the structure of the magnetoresistive element 100 according to Embodiment 1.

[0105] The magnetic sensor 200 detects the magnetic field component of the external magnetic field to be detected. The magnetic field component of the external magnetic field to be detected is detected, for example, as a signal indicating the electrical resistance of the magnetoresistive element 110. In the example shown in Figure 7, the direction of the magnetic field component of the external magnetic field to be detected detected by the magnetic sensor 200 is different from the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 when no external magnetic field is applied.

[0106] For example, the direction of the magnetic field component of the external magnetic field detected by the magnetic sensor 200 may be perpendicular to the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 when no external magnetic field is applied.

[0107] The lower electrode 121 and the upper electrode 122 are, for example, thin-film structures. In the magnetic sensor 200, the electrical resistance of the magnetoresistive element 110 is measured by passing an electric current between the lower electrode 121 and the upper electrode 122. In other words, the lower electrode 121 and the upper electrode 122 are used as electrodes for measuring the electrical resistance of the magnetoresistive element 110. The signal indicating the electrical resistance of the magnetoresistive element 110 is output as a voltage signal or a current signal via, for example, the lower electrode 121 and the upper electrode 122.

[0108] The lower electrode 121 is an example of a first electrode and is electrically connected to one end of the magnetoresistive element 110. In the example shown in Figure 7, the lower electrode 121 is joined to the lower surface of the magnetoresistive element 110. The upper electrode 122 is an example of a second electrode and is electrically connected to the other end of the magnetoresistive element 110. In the example shown in Figure 7, the upper electrode 122 is joined to the upper surface of the magnetoresistive element 110. The plan view shapes of the lower electrode 121 and the upper electrode 122 are, for example, the same as the plan view shape of the magnetoresistive element 110, but may also be different from the plan view shape of the magnetoresistive element 110.

[0109] Each of the lower electrode 121 and the upper electrode 122 is, for example, a metal layer or a semiconductor layer. Each of the lower electrode 121 and the upper electrode 122 may be a layer composed of a single material, or it may have a laminated structure of multiple layers composed of different materials. Furthermore, the lower electrode 121 and the upper electrode 122 may be plate-shaped electrodes or thin-film electrodes formed on a substrate.

[0110] [Differentiation] The following describes a modified magnetic sensor according to Embodiment 2. In the following description of the modified sensor, the differences from Embodiment 2 will be the main focus, and the similarities will be omitted or simplified.

[0111] Figure 8 is a perspective view showing a first example of the magnetic sensor according to this modified example. Figure 9 is a perspective view showing a second example of the magnetic sensor according to this modified example. Figure 10 is a perspective view showing a third example of the magnetic sensor according to this modified example.

[0112] As shown in Figures 8 to 10, the magnetic sensors 201A, 201B, and 201C according to this modified example differ from the magnetic sensor 200 according to Embodiment 2 mainly in that they have multiple magnetoresistive elements 110 and that they have a lower electrode 125 and an upper electrode 126 instead of the lower electrode 121 and upper electrode 122. In the magnetic sensors 201A, 201B, and 201C, the electrical resistance of the magnetoresistive elements 110 is measured by passing a current between the lower electrode 125 and the upper electrode 126.

[0113] As shown in Figures 8 to 10, in magnetic sensors 201A, 201B, and 201C, multiple magnetoresistive elements 110 are electrically connected to each other in at least one form, in series and parallel, by one or more lower electrodes 125 and one or more upper electrodes 126. This allows the voltage applied to the magnetoresistive elements 110 to be distributed when measuring the electrical resistance of the magnetoresistive elements 110.

[0114] Specifically, in magnetic sensor 201A, the multiple magnetoresistive elements 110 are all electrically connected to each other in series by the lower electrode 125 and the upper electrode 126. In magnetic sensors 201B and 201C, the multiple magnetoresistive elements 110 are electrically connected to each other in a combination of series and parallel by the lower electrode 125 and the upper electrode 126. Alternatively, all of the multiple magnetoresistive elements 110 may be electrically connected to each other in parallel. For example, in magnetic sensor 201B, all of the multiple magnetoresistive elements 110 may be electrically connected to each other in parallel by the electrical connection of the lower electrodes 125 to each other.

[0115] Multiple magnetoresistive elements 110 are arranged, for example, on the same plane (the XY plane in Figures 8 to 10). The multiple magnetoresistive elements 110 may be arranged in a single row, as in magnetic sensor 201A, or in an array, as in magnetic sensors 201B and 201C. Furthermore, the multiple magnetoresistive elements 110 are arranged such that, for example, the magnetization directions D1 of the first magnetic layer 11 and the magnetization directions D2 of the second magnetic layer 12 are the same when no external magnetic field is applied.

[0116] The lower electrode 125 is an example of a first electrode and is connected to one end of at least one magnetoresistive element 110. In the examples shown in Figures 8 to 10, the lower electrode 125 is bonded to the lower surface of at least one magnetoresistive element 110. The upper electrode 126 is an example of a second electrode and is connected to the other end of at least one magnetoresistive element 110. In the examples shown in Figures 8 to 10, the upper electrode 126 is bonded to the upper surface of at least one magnetoresistive element 110. In magnetic sensors 201A, 201B, and 201C, at least one of the lower electrode 125 and the upper electrode 126 is connected to two or more magnetoresistive elements 110.

[0117] Each of the lower electrode 125 and the upper electrode 126 is, for example, a plate-shaped or foil-shaped conductive member. Each of the lower electrode 125 and the upper electrode 126 is formed using a conductive metallic material or semiconductor material. At least one of the lower electrode 125 and the upper electrode 126 does not need to be made entirely of a conductive material; it is sufficient if the portion that is joined to the magnetoresistive element 110 is made of a conductive material.

[0118] Furthermore, magnetic sensors 201A, 201B, and 201C may further include at least one of the lower electrode 121 and upper electrode 122 provided by the magnetic sensor 200. In this case, the lower electrode 121 may be positioned between the magnetoresistive element 110 and the lower electrode 125, and the upper electrode 122 may be positioned between the magnetoresistive element 110 and the upper electrode 126.

[0119] (Embodiment 3) The detector according to Embodiment 3 will be described below. Specifically, Embodiment 3 will describe a detector equipped with a magnetic sensor according to the present disclosure.

[0120] Figure 11 is a perspective view showing the detector according to this embodiment. In Figure 11, for clarity, the south pole of the magnetic scale 220 is marked with a dot pattern. Also, in Figure 11, the magnetic sensor 210 is schematically shown as a rectangular parallelepiped.

[0121] As shown in Figure 11, the detector 300 according to this embodiment comprises a magnetic sensor 210 and a magnetic scale 220. The magnetic sensor 210 is, for example, the magnetic sensors 200, 201A, 201B, or 201C described above, but is not particularly limited as long as it is a magnetic sensor that includes the structure of the magnetoresistive element 100 according to Embodiment 1.

[0122] The magnetic scale 220 generates the external magnetic field to be detected by the magnetic sensor 210. By equipping the detector 300 with a magnetic sensor 210 that includes a magnetoresistive element 100 capable of responding to a wide range of magnetic fields, the distance between the magnetic sensor 210 and the magnetic scale 220 can be shortened, allowing for miniaturization of the device or system in which the detector 300 is installed.

[0123] The magnetic scale 220 is composed of a permanent magnet having a structure in which at least one north pole and one south pole are aligned. In the example shown in Figure 11, the magnetic scale 220 has multiple north poles and south poles aligned. Also, in the example shown in Figure 11, the north poles and south poles are aligned linearly along the Y axis. Although not shown in Figure 11, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 when no external magnetic field is applied are, for example, parallel to the X axis. In other words, in the example shown in Figure 11, the magnetization direction D1 of the first magnetic layer 11 and the magnetization direction D2 of the second magnetic layer 12 when no external magnetic field is applied are orthogonal to the direction in which the north poles and south poles are aligned. The north poles and south poles may be aligned in a curved shape, for example, in a circular shape. In the example shown in Figure 11, the magnetic scale 220 is located below the magnetic sensor 210.

[0124] The magnetic sensor 210 moves relative to the magnetic scale 220. Of the magnetic sensor 210 and the magnetic scale 220, only the magnetic sensor 210 may move, only the magnetic scale 220 may move, or both the magnetic sensor 210 and the magnetic scale 220 may move. The direction Dm of movement of the magnetic sensor 210 relative to the magnetic scale 220 is parallel to the direction in which the north and south poles of the magnetic scale 220 are aligned. In other words, the magnetic sensor 210 moves relative to the magnetic scale 220 along the direction in which the north and south poles of the magnetic scale 220 are aligned. At least one of the magnetic sensor 210 and the magnetic scale 220 is driven by, for example, a drive mechanism (not shown). The drive mechanism is, for example, a motor or an actuator.

[0125] The detector 300 detects at least one of the following: the change in position between the magnetic sensor 210 and the magnetic scale 220, the speed of the change in position, and the acceleration of the change in position. The detector 300 includes, for example, a detection circuit (not shown), which acquires a signal indicating the electrical resistance of the magnetic sensor 210 (the magnetoresistive element 110 provided by the magnetic sensor 210). The magnetic sensor 210 moves relative to the magnetic scale 220 along the direction in which the north and south poles are aligned on the magnetic scale 220. As a result, the magnitude of the external magnetic field applied to the magnetic sensor 210 by the magnetic scale 220 oscillates, and the above signal also oscillates.

[0126] When the detector 300 detects a change in position between the magnetic sensor 210 and the magnetic scale 220, it detects the change in position, for example, by detecting the number of vibrations of the above signal. Furthermore, if the magnetic scale 220 is annular and the magnetic sensor 210 or the magnetic scale 220 is rotated by a motor, the detector 300 can also detect the rotational position of the motor.

[0127] Furthermore, when the detector 300 detects the rate of positional change between the magnetic sensor 210 and the magnetic scale 220, it detects the rate of positional change by, for example, detecting the frequency of vibration of the above signal (the frequency or period of the above signal).

[0128] Furthermore, when the detector 300 detects the acceleration of the position change between the magnetic sensor 210 and the magnetic scale 220, it detects the acceleration of the position change by, for example, detecting the amount of change in the frequency of the vibration of the above signal (the amount of change in the frequency or period of the above signal).

[0129] (Examples) The present disclosure will be described in more detail below with reference to the following embodiments. In the embodiments, a magnetic sensor comprising a magnetoresistive element was fabricated and its characteristics were evaluated.

[0130] [Fabrication of magnetoresistive elements] Magnetic sensors equipped with magnetoresistive elements in the examples and comparative examples were fabricated as described below.

[0131] (1) Examples 1 to 4 A structure of Ta(2) / Ru(20) / Ta(2) / Ru(2) / IrMn(6) / CoFe(4) / Ru(1.7) / CoFe(X) / Ru(0.8) / CoFe(0.7) / CoFeB(0.5) / Ta(0.2) / CoFeB(2) / MgO(1.8) / CoFeB(2) / Ta(0.2) / CoFeB(0.5) / CoFe(0.7) / Ru(1.7) / CoFe(2.5) / IrMn(8) / Ru(8) was formed on a substrate by sputtering. The " / " indicates that the layers of the materials listed to the left and right of the " / " are stacked adjacent to each other. The material of each layer is indicated by its element symbol. Furthermore, when two or more element symbols are listed together, such as IrMn, it indicates that the material is an alloy composed of those two or more elements. Furthermore, the number in parentheses next to the element symbol indicates the layer thickness in nanometers. This convention will also be followed in subsequent explanations.

[0132] After stacking the above layers, they were processed into a predetermined shape using photolithography or the like. Subsequently, a Ta(5) / Au(100) structure was formed on the above stacked structure by sputtering and processed into a predetermined shape using photolithography or the like. Furthermore, as a heat treatment in a magnetic field, the magnetic sensors of Examples 1 to 4 were obtained by heating to 350 degrees Celsius while applying an external magnetic field of 700 mT in one direction.

[0133] Figure 12 schematically shows the stacked structure of the magnetic sensor in Examples 1 to 4. Ta(2) / Ru(20) / Ta(2) / Ru(2) on the substrate is the lower electrode for signal extraction. IrMn(6) above it is the first antiferromagnetic layer. CoFe(4) above it is the fourth magnetic layer. Ru(1.7) above it is the second non-magnetic layer. CoFe(X) above it is the third magnetic layer. Ru(0.8) above it is the first non-magnetic layer. CoFe(0.7) / CoFeB(0.5) / Ta(0.2) / CoFeB(2) above it is the first magnetic layer. MgO(1.8) above it is the dielectric layer. CoFeB(2) / Ta(0.2) / CoFeB(0.5) / CoFe(0.7) above it is the second magnetic layer. Ru(1.7) above it is the third non-magnetic layer. The CoFe(2.5) above it is the fifth magnetic layer. The IrMn(8) above it is the second antiferromagnetic layer. The Ru(8) above it is the capping layer. The Ta(5) / Au(100) above it is the upper electrode for signal extraction.

[0134] In Example 1, X in CoFe(X) of the third magnetic layer was 2.8, in Example 2 it was 3.0, in Example 3 it was 3.2, and in Example 4 it was 3.6. In other words, in Examples 1 through 4, magnetic sensors were fabricated by varying the thickness of the third magnetic layer to 2.8, 3.0, 3.2, and 3.6, respectively.

[0135] (2) Comparative Example 1 A structure consisting of Ta(2) / Ru(20) / Ta(2) / Ru(2) / IrMn(6) / CoFe(2) / Ru(2.6) / CoFe(1) / CoFeB(4) / Ta(0.3) / CoFeB(2) / MgO(1.8) / CoFeB(2) / Ta(0.3) / CoFeB(4) / CoFe(1) / Ru(1.7) / CoFe(2) / IrMn(8) / Ru(8) was formed on a substrate by sputtering.

[0136] After stacking the above layers, they were processed into a predetermined shape using photolithography or the like. Subsequently, a Ta(5) / Au(100) structure was formed on the above stacked structure by sputtering and processed into a predetermined shape using photolithography or the like. Furthermore, as a heat treatment in a magnetic field, the magnetic sensor of Comparative Example 1 was obtained by heating to 350 degrees Celsius while applying an external magnetic field of 700 mT in one direction.

[0137] Figure 13 schematically shows the stacked structure of the magnetic sensor in Comparative Example 1. Ta(2) / Ru(20) / Ta(2) / Ru(2) on the substrate is the lower electrode for signal extraction. IrMn(6) is the first antiferromagnetic layer. CoFe(2) is the fourth magnetic layer. Ru(2.6) above it is a non-magnetic layer. CoFe(1) / CoFeB(4) / Ta(0.3) / CoFeB(2) above it is the first magnetic layer. MgO(1.8) above it is a dielectric layer. CoFeB(2) / Ta(0.3) / CoFeB(4) / CoFe(1) above it is the second magnetic layer. Ru(1.7) above it is the third non-magnetic layer. CoFe(2) above it is the fifth magnetic layer. IrMn(8) above it is the second antiferromagnetic layer. Ru(8) above it is a capping layer. The Ta(5) / Au(100) above it is the upper electrode for signal extraction. The magnetic sensor in Comparative Example 1 has a laminated structure in which the first non-magnetic layer, third magnetic layer, and second non-magnetic layer of the magnetic sensors in Examples 1 to 4 are replaced with non-magnetic layers of Ru(2.6).

[0138] [Magnetic direction in magnetic sensors] Figure 14 shows the relationship between the exchange coupling energy due to RKKY interaction and the thickness of the non-magnetic layer. Figure 14 shows the result of plotting the exchange coupling energy due to RKKY interaction in a CoFe / Ru / CoFe structure (an exchange coupling structure of a magnetic layer using ruthenium as the non-magnetic layer) against the thickness of the ruthenium. When the exchange coupling energy is negative, the CoFe layers in the CoFe / Ru / CoFe structure are antiferromagnetically coupled. In other words, it is stable when the magnetization directions of the two CoFe layers are antiparallel. When the exchange coupling energy is positive, the CoFe layers in the CoFe / Ru / CoFe structure are ferromagnetically coupled. In other words, it is stable when the magnetization directions of the two CoFe layers are parallel. For example, the magnitude of the exchange coupling energy when the exchange coupling energy is negative can be determined as follows. For example, the magnetization directions of the two CoFe layers in a CoFe / Ru / CoFe structure are in a stable antiparallel state when no external magnetic field is applied, but when the applied external magnetic field is increased, the magnetization directions of the two CoFe layers become parallel due to the energy from the external magnetic field. Whether the magnetization directions of the two CoFe layers are parallel can be determined by magnetization measurement. The exchange coupling energy can be obtained by dividing the magnitude of the magnetic field when they are parallel by the magnetic moment of the CoFe layer.

[0139] As shown in Figure 14, when the ruthenium layer thickness is 0.8 nm, a strong antiferromagnetic coupling (first-order antiferromagnetic RKKY interaction) occurs. When the ruthenium layer thickness is 1.7 nm, a weak antiferromagnetic coupling (second-order antiferromagnetic RKKY interaction) occurs. When the ruthenium layer thickness is 2.6 nm, a weak ferromagnetic coupling (second-order ferromagnetic RKKY interaction) occurs. Therefore, in the magnetic sensors of Examples 1 to 4, the first non-magnetic layer is designed to exhibit a strong antiferromagnetic coupling. In addition, in the magnetic sensors of Examples 1 to 4, both the second magnetic layer and the third non-magnetic layer are designed to exhibit a weak antiferromagnetic coupling. In the magnetic sensor of Comparative Example 1, the third non-magnetic layer is designed to exhibit a weak antiferromagnetic coupling, and the non-magnetic layer is designed to exhibit a weak ferromagnetic coupling.

[0140] As described above, the thickness of the ruthenium layer is set, and an exchange bias magnetic field is generated between the fourth magnetic layer and the first antiferromagnetic layer, and between the fifth magnetic layer and the second antiferromagnetic layer. As a result, when no external magnetic field is applied, the magnetization direction of each magnetic layer is in the direction indicated by the arrows in Figures 12 and 13.

[0141] [Magnetic moment of the magnetic layer] The magnetic moments of the first, second, and third magnetic layers in Examples 1 to 4 and Comparative Example 1 were measured. The magnetic moments were determined by magnetization measurements of only the first magnetic layer, only the second magnetic layer, and only the third magnetic layer in Examples 1 to 4 and Comparative Example 1. The measurement results are shown in Table 1.

[0142] The magnetic moment referred to here means the magnetic moment per unit area. The unit of magnetic moment is Tcm. 3 This is expressed in tesla cubic centimeters. By dividing this by the area, the magnetic moment per unit area is obtained and expressed in units of Tnm (tesla nanometers).

[0143] Furthermore, in the magnetic sensors of Examples 1 to 4, the first magnetic layer and the third magnetic layer are strongly antiferromagnetically coupled. Therefore, the effective magnetic moment of the laminated structure of the first magnetic layer, the first non-magnetic layer, and the third magnetic layer can be expressed as m1-m3, using the magnetic moment m1 of the first magnetic layer and the magnetic moment m3 of the third magnetic layer. In Examples 1 to 4, the effective magnetic moment of the laminated structure of the first magnetic layer, the first non-magnetic layer, and the third magnetic layer is adjusted by changing the thickness of the third magnetic layer.

[0144] Furthermore, the magnetic sensor in Comparative Example 1 does not include a structure in which the first magnetic layer and the third magnetic layer are strongly antiferromagnetically coupled, as is the case with the magnetic sensors in Examples 1 to 4. Therefore, in the case of the magnetic sensor in Comparative Example 1, m3 is set to zero in m1-m3.

[0145] [Evaluation of magnetoresistance properties] A constant voltage of 30 mV was applied between the upper and lower electrodes of the magnetic sensor obtained above, and the resistance was measured. During the resistance measurement, the magnitude of the uniform magnetic field applied using an electromagnet was varied in a direction perpendicular to the direction of magnetic field application during heat treatment in the magnetic field. Figure 15 shows the magnetoresistance characteristics (resistance-magnetic field characteristics) of the magnetic sensors measured in Example 2 and Comparative Example 1. In Figure 15, the vertical axis represents the resistance change rate, and the horizontal axis represents the magnetic field applied to the magnetic sensor. Here, the resistance change rate is calculated by (Rmax-R) / Rmax. Rmax is the maximum resistance value Rmax explained using Figure 4, and R is the measured resistance value. Furthermore, from the measured magnetoresistance characteristics, the maximum value of the resistance change rate MR and the magnetic field strength Hk, explained using Figure 4 as an index representing the degree of magnetic field to which the magnetoresistance element of the magnetic sensor can respond, were also determined. Table 1 and Figure 16 show the maximum value of the resistance change rate MR and the magnetic field strength Hk for Examples 1 to 4 and Comparative Example 1. Table 1 shows the maximum value of the resistance change rate MR and the magnetic field strength Hk, as well as the thickness of the third magnetic layer and the magnetic moments m1, m2, m3, and m1-m3 mentioned above. In Figure 16, the horizontal axis represents m1-m3, and the vertical axis represents the maximum value of the resistance change rate MR (left vertical axis) and the magnetic field strength Hk (right vertical axis).

[0146] [Table 1]

[0147] As shown in Figure 15, most of the resistance change of the magnetoresistive element in the magnetic sensor in Comparative Example 1 occurs in the magnetic field range of -10mT to 10mT. On the other hand, most of the resistance change of the magnetoresistive element in the magnetic sensor in Example 2 occurs in the magnetic field range of -50mT to 50mT. Therefore, the magnetic sensor in Example 2 can obtain resistance changes over a wider range of magnetic fields than the magnetic sensor in Comparative Example 1, and thus can respond to a wider range of magnetic fields.

[0148] Furthermore, as shown in Table 1 and Figure 16, while the magnetic sensor in Comparative Example 1 has an Hk of 4mT, all magnetic sensors in Examples 1 to 4 have an Hk of 30mT or higher, indicating a significant increase in Hk. In other words, all magnetic sensors in Examples 1 to 4 are capable of responding to a wide range of magnetic fields. This is because, as explained above, in the magnetic sensors in Examples 1 to 4, the presence of a third magnetic layer that is strongly antiferromagnetically coupled to the first magnetic layer slows down the rotation of the magnetization direction of the first magnetic layer when the external magnetic field is increased. On the other hand, in the magnetic sensor in Comparative Example 1, because there is no third magnetic layer, the magnetization direction of the first magnetic layer rotates more easily in response to the external magnetic field than in the magnetic sensors in Examples 1 to 4, and the resistance is more easily changed by the external magnetic field.

[0149] (Other embodiments) The magnetoresistive elements, magnetic sensors, and detectors relating to this disclosure have been described above based on embodiments (including modifications) and examples. However, this disclosure is not limited to these embodiments and examples. Without departing from the spirit of this disclosure, various modifications to the embodiments that a person skilled in the art could conceive, as well as other forms constructed by combining some of the components of the embodiments, are also included in the scope of this disclosure.

[0150] Furthermore, each of the above embodiments can be modified, replaced, added, or omitted in various ways within the scope of the claims or their equivalents. [Industrial applicability]

[0151] The magnetoresistive element relating to this disclosure can be used in various applications for detecting magnetic fields, such as magnetic sensors. [Explanation of symbols]

[0152] 11 First magnetic layer 12 Second magnetic layer 13 Third magnetic layer 14 4th magnetic layer 15 5th magnetic layer 20 Dielectric layer 31 First nonmagnetic layer 32 Second nonmagnetic layer 33 Third nonmagnetic layer 41 First antiferromagnetic layer 42 Second antiferromagnetic layer 100, 101, 110 magnetoresistive elements 121, 125 Lower electrode 122, 126 upper electrode 200, 201A, 201B, 201C, 210 Magnetic Sensors 220 Magnetic Scale 300 detectors D1, D2, D3, D4, D5 Magnetization direction

Claims

1. A first magnetic layer, a second magnetic layer, and a third magnetic layer whose magnetization direction changes in response to an external magnetic field, wherein the first magnetic layer is laminated so as to be located between the second magnetic layer and the third magnetic layer, A first non-magnetic layer located between the first magnetic layer and the third magnetic layer, A dielectric layer located between the first magnetic layer and the second magnetic layer, The first magnetic layer and the third magnetic layer are antiferromagnetically exchanged and coupled through the first nonmagnetic layer. The magnetization direction of the first magnetic layer and the magnetization direction of the second magnetic layer stabilize in an antiparallel state when no external magnetic field is applied. Magnetoresistive element.

2. The dielectric layer mainly comprises magnesium oxide, aluminum oxide, or magnesium-aluminum oxide. The magnetoresistive element according to claim 1.

3. Each of the first magnetic layer and the second magnetic layer has an alloy layer mainly composed of an alloy of cobalt, iron, and boron. The magnetoresistive element according to claim 1.

4. The first non-magnetic layer contains ruthenium as its main component, The thickness of the first non-magnetic layer is 0.6 mm or more and 0.9 mm or less. The magnetoresistive element according to claim 1.

5. The present invention further comprises a fourth magnetic layer and a fifth magnetic layer whose magnetization direction is fixed in one direction, The fourth magnetic layer faces the first non-magnetic layer via the third magnetic layer, The fifth magnetic layer faces the dielectric layer via the second magnetic layer, The magnetoresistive element according to claim 1.

6. The third magnetic layer and the fourth magnetic layer are antiferromagnetically exchanged and coupled. The second magnetic layer and the fifth magnetic layer are antiferromagnetically exchanged and coupled. The magnetoresistive element according to claim 5.

7. A first antiferromagnetic layer facing the third magnetic layer via the fourth magnetic layer, The present invention further comprises a second antiferromagnetic layer facing the second magnetic layer via the fifth magnetic layer, The magnetoresistive element according to claim 5.

8. Each of the first antiferromagnetic layer and the second antiferromagnetic layer mainly contains a manganese-iridium alloy, a manganese-platinum alloy, or a manganese-nickel alloy. The magnetoresistive element according to claim 7.

9. The first antiferromagnetic layer, The fourth magnetic layer, The second non-magnetic layer, The third magnetic layer, The first non-magnetic layer, The first magnetic layer and Dielectric layer and The second magnetic layer and The third non-magnetic layer, The fifth magnetic layer, It has a stacked structure in which a second antiferromagnetic layer and a second antiferromagnetic layer are stacked in this order. The first non-magnetic layer is formed such that the first magnetic layer and the third magnetic layer exhibit a first-order antiferromagnetic RKKY (Rudeman, Kittel, Kasuya, Yoshida) interaction. Magnetoresistive element.

10. A magnetoresistive element according to any one of claims 1 to 9, A first electrode electrically connected to one end of the magnetoresistive element, A second electrode electrically connected to the other end of the magnetoresistive element, Magnetic sensor.

11. The system detects magnetic field components in directions different from the magnetization direction of the first magnetic layer and the magnetization direction of the second magnetic layer when no external magnetic field is applied. The magnetic sensor according to claim 10.

12. The system comprises a plurality of the aforementioned magnetoresistive elements, The plurality of magnetoresistive elements are electrically connected to each other in at least one form, such as in series and in parallel. The magnetic sensor according to claim 10.

13. The magnetic sensor according to claim 10, It comprises a magnetic scale with at least one north pole and one south pole aligned, The positional change between the magnetic sensor and the magnetic scale is detected. Detector.

14. The magnetic sensor according to claim 10, It comprises a magnetic scale with at least one north pole and one south pole aligned, The speed of the positional change between the magnetic sensor and the magnetic scale is detected. Detector.

15. The magnetic sensor according to claim 10, It comprises a magnetic scale with at least one north pole and one south pole aligned, The acceleration of the change in position between the magnetic sensor and the magnetic scale is detected. Detector.

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