Magnetic junction, TMR element, TMR element array, magnetic sensor, magnetic sensor for linear encoder, and magnetic rotary encoder

Abstract

This magnetic joint body comprises a first free layer (11), a tunnel barrier layer (12), and a second free layer (13). The tunnel barrier layer (12) is sandwiched between the first free layer (11) and the second free layer (13). The first and second free layers (11, 13) each contain a ferromagnetic metal. A detection target magnetic field is configured to have a component that is to be applied in the hard magnetization axis direction of the first and second free layers (11, 13). Magnetization of the first and second free layers (11, 13) becomes stabilized in an array in which the layers are antiparallel to each other under a non-magnetic field, and becomes stabilized in an array in which magnetization of the first and second free layers (11, 13) are parallel to each other in a state where the intensity of an external magnetic field applied in the hard magnetization axis direction of the first and second free layers (11, 13) reaches a saturation magnetic field.

Description

[Technical Field]

[0001] This disclosure relates to a magnetic junction, a TMR element, a TMR element array, a magnetic sensor, a magnetic sensor for a linear encoder, and a magnetic rotary encoder. This application claims priority to Japanese Patent Application No. 2022-127029, filed on August 9, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] A position and rotation detection device using an artificial lattice giant magnetoresistance element has been proposed (see Patent Document 1). FIG. 16A shows an example of an artificial lattice giant magnetoresistance element. The artificial lattice giant magnetoresistance element shown in FIG. 16A has a layered structure in which an electrode 160, an underlayer 161, a ferromagnetic layer 162, a nonmagnetic layer 163, a ferromagnetic layer 164, a nonmagnetic layer 165, a repeat stack 166, and a ferromagnetic layer 167 are stacked in this order. In FIG. 16A, the magnetization directions of ferromagnetic layers 162, 164, and 167 are indicated by arrows. The repeat stack 166 is formed by repeatedly stacking ferromagnetic layers and nonmagnetic layers. In this laminated structure, by utilizing the antiparallel magnetic coupling between ferromagnetic layer 162 and ferromagnetic layer 164, the magnetizations of the adjacent ferromagnetic free layers are aligned antiparallel when no external magnetic field is applied. When a magnetic field to be detected is applied to the artificial lattice giant magnetoresistive element, the magnetization of the ferromagnetic free layer rotates, changing the resistance of the laminated structure. This phenomenon utilizes the giant magnetoresistive (GMR) effect, and this effect is used to sense magnetic fields. As shown in Figure 16B, this element exhibits symmetric resistance changes with respect to the positive and negative directions of the external magnetic field applied to the element (hereinafter referred to as even-function resistance-magnetic (RH) characteristics). By exhibiting this characteristic, this element can detect position and rotation with higher accuracy than sensors with odd-function RH characteristics, as described below, and is therefore used in encoders.

[0003] However, in the case of a GMR sensor, the resistance change rate, which corresponds to the output value of the sensor, is at most about 50%. To achieve higher-precision position and rotation detection, it is desirable to use a tunnel magnetoresistance (TMR) sensor, which exhibits a resistance change rate of about 150% to 200%. Here, the resistance change rate (R max -R min ) / R min is defined by R max and R min are the maximum and minimum resistance values ​​of the GMR or TMR element, respectively. In contrast, in a TMR sensor, antiparallel magnetic coupling does not occur between the two ferromagnetic layers (free layers) sandwiching the tunnel barrier layer. Therefore, in order to align the magnetizations of the ferromagnetic layers in a TMR sensor antiparallel, a device such as the soft-pin type described below is required.

[0004] A typical spin-valve TMR sensor used in magnetic heads and the like has a multilayer structure of an antiferromagnetic layer 170, a fixed layer 171, a tunnel barrier layer 172, and a first free layer 173, as shown in Figure 17. Figure 17(A) shows the magnetization directions of the fixed layer 171 and the first free layer 173 when the external magnetic field is saturated in the positive direction. Figure 17(B) shows the magnetization directions of the fixed layer 171 and the first free layer 173 when the external magnetic field is zero. Figure 17(C) shows the magnetization directions of the fixed layer 171 and the first free layer 173 when the external magnetic field is saturated in the negative direction. The magnetization of the pinned layer 171 is pinned by an exchange bias with the adjacent antiferromagnetic layer 170. The magnetization of the first free layer 173 is stabilized in a direction perpendicular to the magnetization of the pinned layer 171 when no external magnetic field is applied (see Non-Patent Documents 1 and 2). The magnetization direction of the first free layer 173 can be determined by a bias magnetic field from a permanent magnet or induced magnetic anisotropy by heat treatment in a magnetic field. However, in a spin-valve TMR sensor, the element resistance increases in a positive magnetic field and decreases in a negative magnetic field, exhibiting an RH characteristic close to a linear response. Note that when the element resistance decreases in a positive magnetic field, the element resistance also increases in a negative magnetic field, exhibiting an RH characteristic close to a linear response. Deterioration of this linear response poses a problem: the position detection accuracy of the sensor deteriorates.

[0005] FIG. 18 is a diagram showing an example of a single soft pinned TMR sensor (see Non-Patent Documents 3 and 4). The single soft pinned TMR sensor has a layer structure in which a fixed layer 181, a tunnel barrier layer 182, and a free layer 183 are stacked. (A) of FIG. 18 is a diagram showing the magnetization directions of the fixed layer 181 and the free layer 183 when an external magnetic field sufficiently large in the positive direction relative to the anisotropy magnetic field of the free layer 183 is applied and the magnetization of the free layer 183 is saturated in the positive direction. (B) of FIG. 18 is a diagram showing the magnetization directions of the fixed layer 181 and the free layer 183 when the external magnetic field is zero. (C) of FIG. 18 is a diagram showing the magnetization directions of the fixed layer 181 and the free layer 183 when the magnetization of the free layer 183 is saturated in the negative direction. In the single soft-pinned TMR sensor, the magnetization of the free layer 183 is stabilized (soft-pinned) in the opposite direction to the magnetization of the fixed layer 181, and the sensor exhibits an even-function RH characteristic. min is the resistance when the magnetization of the free layer 183 and the magnetization of the fixed layer 181 are orthogonally aligned, so the resistance change rate is smaller than that of the spin valve type, at about 110%. In a single soft pin type TMR sensor, if the direction of the magnetic field to be detected deviates from the hard axis of magnetization of the free layer, which is the original direction, the even function RH characteristic of the element, which was originally strictly symmetrical with respect to the positive and negative of the detected magnetic field, becomes asymmetric. Therefore, a problem with this sensor is that high alignment precision is required when mounting the sensor.

[0006] 19 shows the magnetoresistance characteristics of a granular TMR element in which ferromagnetic nanoparticles are dispersed in an insulating matrix. The granular TMR element exhibits even-function RH characteristics that are strictly symmetrical with respect to the positive and negative sides of the detection magnetic field applied to the element. However, the resistance change rate of the granular TMR element is small, at around 10%, making it unsuitable for a highly sensitive magnetic sensor (see Non-Patent Document 5). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-71334 [Patent Document 2] US 2017 / 0154643 A1 [Non-patent literature]

[0008] [Non-Patent Document 1] Journal of Applied Physics 92, 4722 (2002) [Non-patent document 2] J. Appl. Phys. 111, 07C710 (2012) [Non-patent document 3] The 45th Annual Meeting of the Magnetic Society of Japan 01aB-11 [Non-patent document 4] Journal of the Japan Institute of Metals, Vol. 75 (2011) 419-423 [Non-patent document 5] Journal of the Japan Institute of Metals, Vol. 76 (2012) 375-379 Summary of the Invention [Problem to be solved by the invention]

[0009] To summarize the above, the drawbacks and problems of the background art are as follows: The artificial lattice type GMR element has a small resistance change rate of 50% at most, which makes it difficult to achieve high sensitivity. Since the spin-valve TMR element has odd-function RH characteristics, achieving highly accurate linear response is a challenge for highly accurate position detection. The single soft pin type TMR element has a resistance change rate of about 110%, which is smaller than that of the spin valve type (about 150% to 200%). Furthermore, when the direction of the detection magnetic field shifts, the single soft pin type TMR element's RH characteristics become asymmetric, and the position detection accuracy deteriorates. Granular TMR elements have a small resistance change rate of about 10%.

[0010] The present disclosure is intended to solve such problems, and aims to provide a magnetic junction, a TMR element, a magnetic sensor, a TMR element array, a magnetic sensor, a magnetic sensor for a linear encoder, and a magnetic rotary encoder that have a large rate of resistance change and are less likely to have asymmetric RH characteristics due to a shift in the direction of the detected magnetic field. [Means for solving the problem]

[0011] [1] A magnetic junction according to a first aspect includes a first free layer 11 having an easy axis and a hard axis perpendicular to the easy axis, a tunnel barrier layer 12, and a second free layer 13 having an easy axis and a hard axis perpendicular to the easy axis. The tunnel barrier layer 12 is sandwiched between the first free layer 11 and the second free layer 13. The first free layer 11 and the second free layer 13 include a ferromagnetic metal. A magnetic field to be detected is configured to have a component applied in the hard axis direction of the first free layer and the second free layer. The magnetization of the first free layer 11 and the magnetization of the second free layer 13 are stabilized in an antiparallel arrangement with each other when no external magnetic field is applied. Furthermore, the magnetization of the first free layer 11 and the magnetization of the second free layer 13 are aligned parallel to each other when the strength of the external magnetic field applied in the hard-magnetization axis direction of the first free layer 11 and the second free layer 13 reaches the saturation magnetic field. Here, antiparallel alignment refers to a magnetization alignment state in which the angle between the magnetization of the first free layer and the magnetization of the second free layer is at its maximum (180 degrees), maximizing the resistance of the element. As the external magnetic field increases, the angle between the magnetization of the first free layer and the magnetization of the second free layer decreases, and the magnetizations of the first free layer and the second free layer become aligned in the same direction, i.e., parallel. At this time, the resistance of the element is minimized.

[0012] [2] In the magnetic junction body according to the above embodiment, when the strength of the external magnetic field applied in the direction of the hard magnetization axis of the first free layer 11 and the second free layer 13 reaches the saturation magnetic field, the magnetization of the first free layer 11 and the magnetization of the second free layer 13 rotate symmetrically with respect to the direction in which the external magnetic field is applied. As the strength of the external magnetic field increases, the angle between the magnetization of the first free layer 11 and the magnetization of the second free layer 13 becomes smaller, and the resistance magnetic field characteristics exhibit an even function type characteristic that is symmetric with respect to the positive and negative directions in which the external magnetic field is applied. [3] In the magnetic junction according to the above embodiment, the tunnel barrier layer 12 may include any one selected from the group consisting of MgO, Mg—Al—O, and Al2O3, and the first free layer 11 and the second free layer 13 may include a layer made of at least CoFeB. [4] In the magnetic junction according to the above aspect, at least one of the first free layer and the second free layer may be a stack including multiple layers. This stack includes a layer made of CoFeB, a layer made of CoFe, and a central layer. The layer made of CoFe is located farther from the tunnel barrier layer 12 than the layer made of CoFeB, and the central layer is located between the layer made of CoFeB and the layer made of CoFe. The central layer includes any one selected from the group consisting of NiFe, CoFeSiB, and CoFeBTa. The layer made of CoFe is provided to improve magnetic coupling, and the central layer is provided to improve soft magnetic properties.

[0013] [5] The TMR element according to the second aspect may include the magnetic junction according to the above aspect. [Ferromagnetic layer A i / bonding layer A i ] n / ferromagnetic layer A n+1 / Intermediate layer A / First free layer / Tunnel barrier layer / Second free layer / Intermediate layer B / [Ferromagnetic layer B j / Binding layer B j ] n+1 / Ferromagnetic layer B n+2 / Or, [Ferromagnetic layer A j / bonding layer A j ]n+1 / ferromagnetic layer A n+2 / Intermediate layer A / First free layer / Tunnel barrier layer / Second free layer / Intermediate layer B / [Ferromagnetic layer B i / Binding layer B i ] n / Ferromagnetic layer B n+1 / The laminated structure has the following structure: Here, n is an integer equal to or greater than 0, and when n≠0, i=1,...,n and j=1,...,n+1, and [ferromagnetic layer A j / bonding layer A j ] n+1 The notation "ferromagnetic layer A" j / bonding layer A j " is repeatedly stacked n+1 times, and the ferromagnetic layer B i / Binding layer B i ] n The notation "ferromagnetic layer B i / Binding layer B i " is stacked n times. [6] In the TMR element according to the above aspect, the ferromagnetic layer A i , ferromagnetic layer A n+1 , ferromagnetic layer B j , ferromagnetic layer B n+2 , ferromagnetic layer A j and the ferromagnetic layer B i may be CoFe, and the bonding layer A i , bonding layer B j , bonding layer A j and bonding layer B i may be Ru, intermediate layer A and intermediate layer B may have at least one selected from the group consisting of Cu, Ag, Cr, Ru, and AgSn, the tunnel barrier layer may have any one selected from the group consisting of MgO, Mg—Al—O, and Al2O3, and the first free layer and the second free layer may have a layer made of at least CoFeB.

[0014] [7] The TMR element according to the above aspect may include the magnetic junction according to the above aspect. First antiferromagnetic layer / First ferromagnetic layer / First exchange coupling layer / First free layer / Tunnel barrier layer / Second free layer / Second exchange coupling layer / Second ferromagnetic layer / Second antiferromagnetic layer / The laminate structure has the following structure: The first exchange coupling layer and the second exchange coupling layer may be Ru or Cr, and one of the magnetic coupling between the first ferromagnetic layer and the first free layer and the magnetic coupling between the second ferromagnetic layer and the second free layer may be antiferromagnetic coupling and the other may be ferromagnetic coupling. [8] In the TMR element according to the above aspect, the first and second antiferromagnetic layers may be at least one of IrMn, PtMn, FeMn, and NiMn, the first and second ferromagnetic layers may be CoFe, the first and second exchange coupling layers may be Ru, the tunnel barrier layer may be one selected from the group consisting of MgO, Mg—Al—O, and Al2O3, and the first and second free layers may have at least a layer made of CoFeB.

[0015] [9] The TMR element according to the above aspect may include the magnetic junction according to the above aspect. Antiferromagnetic layer A / dust layer A / ferromagnetic layer A i / bonding layer A i ] n / First free layer / Tunnel barrier layer / Second free layer / [Coupling layer B j / Ferromagnetic layer B j ] n+1 / Dust layer B / Antiferromagnetic layer B / Or, Antiferromagnetic layer A / dust layer A / ferromagnetic layer A j / bonding layer A j ] n+1 / First free layer / Tunnel barrier layer / Second free layer / [Coupling layer B i / Ferromagnetic layer B i ] n / Dust layer B / Antiferromagnetic layer B / The laminated structure may be represented by the following formula: Here, n is an integer equal to or greater than 0, and when n≠0, i=1,...,n and j=1,...,n+1, and [ferromagnetic layer Aj / bonding layer A j ] n+1 The notation "ferromagnetic layer A" j / bonding layer A j " is laminated n+1 times, and the bonding layer B i / Ferromagnetic layer B i ] n The notation is "bonding layer B i / Ferromagnetic layer B i " is stacked n times.

[10] In the TMR element according to the above embodiment, the antiferromagnetic layer A and the antiferromagnetic layer B may each contain at least one material selected from the group consisting of IrMn, PtMn, FeMn, and NiMn, and the ferromagnetic layer A may contain at least one material selected from the group consisting of IrMn, PtMn, FeMn, and NiMn. i , ferromagnetic layer B j , ferromagnetic layer A j , ferromagnetic layer B i may be CoFe, and the bonding layer A i , bonding layer B j , bonding layer A j , bonding layer B i may be Ru, dust layer A and dust layer B may be Ru with a thickness of 1 nm or less, the tunnel barrier layer may have at least one selected from the group consisting of MgO, Mg—Al—O, and Al2O3, and the first free layer and the second free layer may have at least a layer made of CoFeB.

[0016]

[11] The TMR element according to the above aspect may exhibit a maximum resistance when the magnetic field to be detected is zero, and the magnetization of the first free layer and the magnetization of the second free layer may be antiparallel. Furthermore, the resistance of the TMR element may decrease when the magnetic field to be detected is applied, the magnetizations of the first free layer and the second free layer may both rotate, and the angle between the magnetization of the first free layer and the magnetization of the second free layer may decrease as the strength of the magnetic field to be detected increases.

[12] In the TMR element according to the above aspect, when the direction of the magnetic field to be detected is tilted by 10° from the hard axis direction of the first free layer and the second free layer, the magnetic field asymmetry of the resistance value with respect to the positive and negative directions of the magnetic field H1 may be within 1%, more preferably 0.5%. Here, the magnetic field H1 is a magnetic field in which a tangent to a curve based on experimental data of the resistance magnetic field (RH) characteristics is determined at the point where the differential (dR / dH) of the curve based on the experimental data is maximized, and the difference between the curve based on the experimental data and the tangent is divided by the maximum resistance value of the experimental data to normalize the difference to 20%. Furthermore, when the element resistance R is expressed as a function of the magnetic field H as R(H), the magnetic field asymmetry is defined as the asymmetry of the RH curve at H=H' (>0). Asy(H')=[R(H')-R(-H')] / [(R(H')+R(-H')](%) and defines the asymmetry of the resistance to the magnetic field H1.

[0017]

[13] In the TMR element according to the above embodiment, the stacked structure may be located between a first structure consisting of a substrate / lower electrode / underlayer / antiferromagnetic layer and a second structure consisting of an antiferromagnetic layer / cap layer.

[14] In the TMR element according to the above aspect, the stacked structure may be located between a third structure made up of a substrate / lower electrode / underlying layer and a fourth structure made up of a cap layer.

[15] In the TMR element according to the above aspect, the substrate may be a silicon wafer or a ceramic wafer made of AlTiC or alumina, the underlayer may have a laminated structure of Ta and Ru, the antiferromagnetic layer may be any one selected from the group consisting of IrMn, PtMn, FeMn, and NiMn, and the cap layer may be Ru.

[0018]

[16] A magnetic sensor according to a third aspect has a bridge circuit using four TMR elements according to the above aspect.

[17] A TMR element array according to a fourth aspect is formed by connecting a plurality of TMR elements according to the above aspect in at least one of series and parallel.

[18] The magnetic sensor according to the above aspect may be configured by connecting the TMR element array according to the above aspect in a bridge circuit.

[19] A magnetic sensor for a linear encoder according to a fifth aspect or a magnetic rotary encoder according to a sixth aspect includes the TMR element according to the above aspect or the magnetic sensor according to the above aspect. [Effects of the Invention]

[0019] The TMR element of the present disclosure exhibits even-function RH characteristics and exhibits a resistance change rate of over 150%, equivalent to that of odd-function spin-valve TMR sensors. This resistance change rate is approximately 1.5 times that of a single soft-pin TMR sensor. Therefore, magnetic sensors using the TMR element of the present disclosure are highly sensitive and can detect positions with higher accuracy. The TMR element of the present disclosure has less asymmetry in the RH characteristics than the conventional single soft pin type, even when the direction of the magnetic field to be detected deviates from the hard axis of magnetization of the free layer, allowing for more accurate position detection and excellent mountability. In the TMR element of the present disclosure, the saturation magnetic field can be adjusted according to the position detection magnetic field by adjusting the thickness of the intermediate layer, the coupling exchange layer, or the dust layer. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are diagrams illustrating the magnetization state and resistance magnetic field characteristics of the magnetic junction body according to the first embodiment, showing the magnetization direction of the free layer (ferromagnetic layer) in three typical types of magnetization modes. [Figure 2A] 3 is a diagram showing a stacked structure of a first example (n=0) of a first stacked type of the magnetic sensor according to the first embodiment. FIG. [Figure 2B] 4 is a diagram showing a stacked structure of a second example (n≧1) of the first stacked type of the magnetic sensor according to the first embodiment. FIG. [Figure 2C] 4 is a diagram showing a stacked structure of a first example (n≧1) of a second stacked type of the magnetic sensor according to the first embodiment. FIG. [Figure 3A] 10 is a diagram showing a stacked structure of a first example (n=0) of a first stacked type of a magnetic sensor according to a second embodiment. FIG. [Figure 3B] 10 is a diagram showing a stacked structure of a second example (n≧1) of the first stacked type of the magnetic sensor according to the second embodiment. FIG. [Figure 3C] 10 is a diagram showing a stacked structure of a third example (n≧1) of the second stacked type of the magnetic sensor according to the second embodiment. FIG. [Figure 4] 10A and 10B are diagrams illustrating a first example of a laminate structure of a third laminate type of the magnetic sensor according to the third embodiment. [Figure 5A] FIG. 10 is a diagram showing a stacked structure of a first example (n=0) of a fourth stacked type of the magnetic sensor according to the fourth embodiment. [Figure 5B] 10 is a diagram showing a stacked structure of a second example (n≧1) of a fourth stacked layer type of the magnetic sensor according to the fourth embodiment. FIG. [Figure 5C] 10 is a diagram showing a stacked structure of a first example (n≧1) of a fifth stacked layer type of the magnetic sensor according to the fourth embodiment. FIG. [Figure 6] 1A to 1C are diagrams showing the stacked structure of a TMR sensor using magnetic sensors of the first to fifth stacked types. [Figure 7] This figure shows the resistance-magnetic field curve of a laminate of the first stack type having the stack structure shown in Table 1, which is one embodiment of the present invention, and the dashed and solid lines represent combinations of different thicknesses of intermediate layer A and intermediate layer B. [Figure 8A] FIG. 10 shows the magnetization curve of the first free layer of the stack of the first stack type (n=0). [Figure 8B] FIG. 10 is a diagram showing the relationship between the intermediate layer thickness and the soft pinning field strength Hpin of the free layer in various stacked configurations. [Figure 9] FIG. 10 is a diagram illustrating the definition of a magnetic field H1 in a resistance-magnetic field curve. [Figure 10A] FIG. 10 is a diagram showing the deviation angle (θ) of the magnetic field application angle of the magnetic sensor having the configuration shown in Table 1. [Figure 10B] FIG. 10 is a diagram showing changes in the resistance-magnetic field curve when the magnetic sensor having the configuration shown in Table 1 has different deviation angles (θ) in the angle at which the magnetic field is applied. [Figure 10C] FIG. 10 is an explanatory diagram of the rate of resistance change depending on the annealing temperature of the third laminate type laminate. [Figure 11]FIG. 10 is a diagram showing the change in asymmetry in the magnetic field H1 depending on the angle of deviation (θ) of the magnetic field application angle of the magnetic sensor for the example and the comparative example. [Figure 12A] FIG. 10 is a diagram showing simulation results of H1 asymmetry of the dual soft-pinned TMR sensor according to the present embodiment. [Figure 12B] FIG. 10 is a diagram showing simulation results of H1 asymmetry for a single soft-pinned TMR sensor as a comparative example. [Figure 13A] FIG. 10 is a diagram showing a simulation result of the resistance-magnetic field curve of the dual soft-pinned TMR sensor according to the embodiment. [Figure 13B] FIG. 10 is a diagram showing the simulation results of the resistance-magnetic field curve of a single soft-pinned TMR sensor as a comparative example. [Figure 14A] FIG. 1 is a perspective view showing a configuration of an example in which a plurality of TMR element portions of the dual soft pin TMR sensor according to the present embodiment are connected in series. [Figure 14B] FIG. 10 is a perspective view showing the configuration of an example in which a plurality of TMR element parts of the dual soft pin TMR sensor according to the present embodiment are connected in parallel and in series. [Figure 15] FIG. 1 is a circuit diagram of an encoder using a bridge configuration according to an embodiment of the present invention. [Figure 16A] This is a cross-sectional view of the multilayer structure of an artificial lattice GMR sensor, and also shows the magnetization directions of the ferromagnetic layers. [Figure 16B] 1 shows the resistance-magnetic field curve of the multilayer structure of the artificial lattice type GMR sensor. [Figure 17] This is a diagram showing the resistance-magnetic field curve of a spin-valve TMR sensor, along with the magnetization direction of the free layer (ferromagnetic layer) in three typical magnetization modes. [Figure 18] This figure shows the resistance-magnetic field curve of a soft-pinned TMR sensor, along with the magnetization direction of the free layer (ferromagnetic layer) in three typical magnetization modes. [Figure 19] FIG. 10 is a graph showing an example of a resistance change rate-magnetic field curve of granular TMR. [Figure 20]1 is a perspective view of the configuration of a magnetic linear encoder to which the magnetic sensor according to the present embodiment is applied; [Figure 21] 1 is a configuration diagram of a magnetic rotary encoder to which a magnetic sensor according to an embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0021] Best modes for carrying out the present disclosure will be described in detail below. The magnetic sensor of the present disclosure may use a tunneling magnetoresistance (TMR) element, which is based on a three-layer structure consisting of a first free layer (ferromagnetic metal), a tunnel barrier layer (insulating oxide), and a second free layer (ferromagnetic metal). The tunnel barrier layer is sandwiched between the first free layer and the second free layer and magnetically separates the first free layer from the second free layer. The TMR element exhibits the tunneling magnetoresistance effect, and when a voltage is applied between the first free layer and the second free layer, the resistance of the sensor changes depending on the relative angle between the magnetizations of the first free layer and the second free layer.

[0022] As shown in FIGS. 1A to 1C, the magnetic sensor of the present disclosure includes a first free layer 11, a tunnel barrier layer 12, and a second free layer 13. The tunnel barrier layer 12 is sandwiched between the first free layer 11 and the second free layer 13. The first free layer 11 and the second free layer 13 are ferromagnetic layers, preferably made of, but not limited to, CoFeB. The tunnel barrier layer 12 preferably uses at least one material selected from the group consisting of MgO, Mg—Al—O, and Al2O3. The first free layer 11 or the second free layer 13 may be a stacked structure including multiple layers. The stacked structure may include, for example, a layer made of CoFeB, a layer made of CoFe, and a central layer. CoFeB, which has excellent TMR characteristics, is preferably located near the tunnel barrier layer 12, and CoFe may be located near the interface with another layer located away from the tunnel barrier layer 12. The central layer is disposed between these layers and may be made of NiFe, CoFeSiB, CoFeBTa, or the like, which has excellent soft magnetic properties.

[0023] 1B, the magnetizations of the first free layer 11 and the second free layer 13 sandwiching the tunnel barrier layer 12 are stabilized in an antiparallel arrangement in the absence of a magnetic field. The magnetic sensor is positioned so that the magnetic field to be detected is applied in a direction perpendicular to the magnetic field (the hard axis direction of the free layer). When an external magnetic field is applied in the hard-magnetization direction of the first free layer 11 and the second free layer 13 (the direction perpendicular to the magnetization direction of the first free layer 11 and the second free layer 13 in the absence of a magnetic field), the magnetization of the first free layer 11 and the second free layer 13 rotates symmetrically with respect to the external magnetic field. As the external magnetic field strength increases, the angle between the magnetizations of the first free layer 11 and the second free layer 13 decreases, resulting in the state shown in FIG. 1A or 1C. In the states shown in FIG. 1A and 1B, the element resistance is lower than in the state shown in FIG. 1C. The magnetic anisotropy of the magnetization of the first free layer 11 and the second free layer 13 in one direction is set to a strength appropriate for the magnitude of the magnetic field to be detected, as described below. The magnitude of the saturation magnetic field and the magnetic permeability of the free layer are determined by the strength of the magnetic anisotropy (soft-pinned magnetic field strength).

[0024] FIG. 1D shows the relationship between magnetic field and resistance in the magnetic sensor of the present disclosure. As shown in FIG. 1D, the magnetic resistance of the element is maximized in the absence of a magnetic field and decreases as the external magnetic field strength increases. When an external magnetic field is applied in the hard-magnetization axis direction of the first free layer 11 and the second free layer 13, the magnetizations of the first free layer 11 and the second free layer 13 rotate symmetrically with respect to the external magnetic field. As the external magnetic field strength increases, the angle between the magnetization of the first free layer 11 and the magnetization of the second free layer 13 decreases. The magnetic sensor of the present disclosure exhibits even-function resistance magnetic field characteristics that are symmetric with respect to the sign of the external magnetic field. For example, the sign of the external magnetic field is defined as positive in one direction along the hard-magnetization axis and negative in the opposite direction.

[0025] The following are possible examples of specific stacked structures of the TMR sensor in the magnetic sensor of the present disclosure: In the present specification, the magnetic sensor according to the present disclosure will be referred to as a "dual soft-pin TMR sensor." Typical materials for each layer of the magnetic sensor of the present disclosure are as follows: The underlayer can be a laminated structure of Ta and Ru. The antiferromagnetic material can be one or more selected from the group consisting of IrMn, PtMn, FeMn, and NiMn. The ferromagnetic layer can be CoFe. The coupling layer can be Ru. The intermediate layer can be a non-magnetic material such as Cu, Ag, Cr, or Ru, preferably AgSn. The cap layer can be Ru. In the following first and second stacked layer types, the bottom and top ferromagnetic layers of the stacked structure may be replaced with hard magnetic films such as CoPt without using antiferromagnetic layers.

[0026] The free layers (first free layer 11 and second free layer 13) may have a single-layer structure of a layer made of CoFeB, or may have a laminated structure to further improve magnetic properties. The laminated structure of the free layer may have, for example, a layer made of CoFeB, a layer made of CoFe, and a central layer. The layer made of CoFeB, which has excellent TMR, is provided closer to the tunnel barrier layer 12 than the layer made of CoFe. NiFe, CoFeSiB, CoFeBTa, or the like, which has excellent soft magnetic properties, is used for the central portion between the layer made of CoFeB and the layer made of CoFe.

[0027] FIG. 2A is a diagram showing a first example (n=0) of a first stack type laminate structure according to the first embodiment. The stacked structure of the first example (n=0) of the first stacking type has a stacked structure represented by the following: electrode 20 / underlayer 20a / antiferromagnetic layer 21 / ferromagnetic layer 22 / intermediate layer 23 / first free layer 24 / tunnel barrier layer 25 / second free layer 26 / intermediate layer 27 / ferromagnetic layer 28 / coupling layer 28a / ferromagnetic layer 28b / antiferromagnetic layer 29 / cap layer (not shown). Here, " / " indicates the stacking interface of each layer, and the layers are stacked in this order with " / " between them. The intermediate layers 23 and 27 are made of, for example, AgSn. Ferromagnetic interlayer coupling acts between the ferromagnetic layer 22 and the first free layer 24, sandwiching the intermediate layer 23, and ferromagnetic interlayer coupling acts between the ferromagnetic layer 28 and the second free layer 26, sandwiching the intermediate layer 27. The coupling layer 28a is made of, for example, Ru, and strongly antiparallel-couples the ferromagnetic layers 28 and 28b on both sides of the coupling layer 28a.

[0028] FIG. 2B is a diagram showing a second example (n≧1) of the first lamination type laminate structure according to the first embodiment. The stacked structure of the second example (n≧1) of the first stacked type has a stacked structure represented by electrode 20 / underlayer 20a / antiferromagnetic layer 21 / stacked body 22p (=[ferromagnetic layer 22a / coupling layer 22b] repeated n times) / ferromagnetic layer 22 / intermediate layer 23 / first free layer 24 / tunnel barrier layer 25 / second free layer 26 / intermediate layer 27 / ferromagnetic layer 28 / stacked body 28p (=[coupling layer 28a / ferromagnetic layer 28b] repeated n+1 times) / antiferromagnetic layer 29 / cap layer (not shown).

[0029] 2C is a diagram showing a first example (n≧1) of a stack structure of the second stack type according to the first embodiment, in which the stacking order of [ferromagnetic layer 22 a / coupling layer 22 b]n and [coupling layer 28 a / ferromagnetic layer 28 b]n+1 in the stack of the first stack type shown in FIG. The first example (n≧1) of the second stack type has a stack structure represented by electrode 20 / underlayer 20a / antiferromagnetic layer 21 / stack 22p′ (=[ferromagnetic layer 22c / coupling layer 22d] repeated n+1 times) / ferromagnetic layer 22 / intermediate layer 23 / first free layer 24 / tunnel barrier layer 25 / second free layer 26 / intermediate layer 27 / ferromagnetic layer 28 / stack 28p′ (=[coupling layer 28c / ferromagnetic layer 28d] repeated n times) / antiferromagnetic layer 29 / cap layer (not shown).

[0030] Here, the laminate structure of the first laminate type (n≧1) shown in FIG. 2B can also be expressed as the following general formula. First stacking type: Underlayer / antiferromagnetic layer A / ferromagnetic layer A i / bonding layer A i ] n / ferromagnetic layer A n+1 / Intermediate layer A / First free layer / Tunnel barrier layer / Second free layer / Intermediate layer B / [Ferromagnetic layer B j / Binding layer B j ] n+1 / Ferromagnetic layer B n+2 / Antiferromagnetic layer B / Cap layer The laminate structure of the second laminate type (n≧1) shown in FIG. 2C can also be expressed as the following general formula: Second stacking type: Underlayer / antiferromagnetic layer A / ferromagnetic layer A j / bonding layer A j ] n+1 / ferromagnetic layer A n+2 / Intermediate layer A / First free layer / Tunnel barrier layer / Second free layer / Intermediate layer B / [Ferromagnetic layer B i / Binding layer B i ] n / Ferromagnetic layer B n+1 / Antiferromagnetic layer B / Cap layer Here, n is an integer equal to or greater than 0, and when n≠0, i=1,...,n and j=1,...,n+1. [Ferromagnetic layer A j / bonding layer A j ] n+1 "Ferromagnetic layer A j / bonding layer A j This means that the two-layer structure of [ferromagnetic layer A] is repeatedly stacked n+1 times. j / bonding layer A j ] n+1 / ferromagnetic layer A n+2 This refers to a stack of ferromagnetic layer A1 / coupling layer A1 / ferromagnetic layer A2 / coupling layer A2 / ferromagnetic layer A3.

[0031] The operation of the device configured in this way will be explained. The magnetization of the first free layer and the magnetization of the second free layer are antiparallel in the absence of a magnetic field. This is achieved as follows: Ferromagnetic layer A is stacked on antiferromagnetic layer A. Antiferromagnetic layer B is stacked on ferromagnetic layer B. When n≠0, either the number of stacked ferromagnetic layers / coupling layers in the stack including magnetic layer A or the number of stacked ferromagnetic layers / coupling layers in the stack including magnetic layer B is even and the other is odd. Furthermore, the magnetizations of the ferromagnetic layers on both sides of the coupling layer are magnetically coupled in an antiparallel manner. After forming this stacked structure, it is heat-treated (at about 300°C) under a magnetic field and then returned to room temperature, whereupon the magnetizations of ferromagnetic layer A and ferromagnetic layer B are fixed in the same direction due to unidirectional magnetic anisotropy. Through the antiparallel magnetic coupling of the coupling layer, the magnetization of the first free layer and the magnetization of the second free layer have unidirectional magnetic anisotropy in opposite directions, and the magnetization of the first free layer and the magnetization of the second free layer are arranged antiparallel in the absence of a magnetic field.

[0032] In the first and second stacking types, when an external magnetic field is applied in the hard axis direction of the first and second free layers (a direction perpendicular to the magnetization direction of the first and second free layers in the absence of a magnetic field), the magnetization of the first and second free layers rotates symmetrically with respect to the external magnetic field. As the external magnetic field strength increases, the angle between the magnetization of the first and second free layers decreases, and the device resistance decreases. As a result, the stacked structures of the first and second stacking types exhibit even-function resistance-magnetic field characteristics that are symmetric with respect to the positive and negative directions of the applied external magnetic field. The magnitude of the saturation magnetic field and the magnetic permeability of the free layers are determined by the soft-pinning strength of the first and second free layers, but these can be adjusted to the desired value by adjusting the thickness and material (e.g., AgSn) of the intermediate layer.

[0033] Fig. 3A is a diagram showing a first example (n=0) of a laminate structure of a first laminate type according to the second embodiment. The laminate structure shown in Fig. 3A is a modified example of the laminate structure of the first laminate type (n=0) shown in Fig. 2A. A first example (n=0) of the first stack type according to the second embodiment has a stack structure represented by an electrode 30 / underlayer 30a / antiferromagnetic layer 31 / ferromagnetic layer 32 / intermediate layer 33 / first free layer 34 / tunnel barrier layer 35 / second free layer 36 / intermediate layer 37 / ferromagnetic layer 38 / coupling layer 38a / ferromagnetic layer 38b / antiferromagnetic layer 39 / cap layer (not shown).

[0034] 3B is a diagram showing a second example (n≧1) of the first stack type laminate structure according to the second embodiment. The laminate structure shown in FIG. 3B is a modified example of the first stack type (n≧1) laminate structure shown in FIG. 2B. A second example (n≧1) of the first stack type according to the second embodiment has a stack structure represented by electrode 30 / underlayer 30a / antiferromagnetic layer 31 / stack 32p (=[ferromagnetic layer 32a / coupling layer 32b] repeated n times) / ferromagnetic layer 32 / intermediate layer 33 / first free layer 34 / tunnel barrier layer 35 / second free layer 36 / intermediate layer 37 / stack 38p (=ferromagnetic layer 38 / [coupling layer 38a / ferromagnetic layer 38b] repeated n+1 times) / antiferromagnetic layer 39 / cap layer (not shown).

[0035] Fig. 3C is a diagram showing a first example (n≧1) of a second stack type laminate structure according to the second embodiment. The laminate structure shown in Fig. 3C is a modified example of the second stack type (n≧1) laminate structure shown in Fig. 2C. A first example (n≧1) of the second stack type according to the second embodiment is an electrode 30 / underlayer 30a / antiferromagnetic layer 31 / stack 32p′ (=[ferromagnetic layer 32c / coupling layer 32d] repeated n+1 times) / ferromagnetic layer 32 / intermediate layer 33 / first free layer 34 / tunnel barrier layer 35 / second free layer 36 / intermediate layer 37 / ferromagnetic layer 38 / stack 38p′ (=[coupling layer 38c / ferromagnetic layer 38d] repeated n times) / antiferromagnetic layer 39 / cap layer (not shown).

[0036] 3A to 3C, the names of the layers shown in Figures 2A to 2C are the same, and the same configuration as in Figures 2A to 2C can be used. The stack shown in Figures 3A to 3C differs from the stack shown in Figures 2A to 2C in that the magnetization directions of ferromagnetic layers 32, 38 are antiparallel to first free layer 34, tunnel barrier layer 35, and second free layer 36, respectively.

[0037] FIG. 4 is a diagram showing a stack structure of a third stack type according to the third embodiment. The stacking structure of the third stacking type has a stacking structure represented by an electrode 40 / underlying layer 40a / antiferromagnetic layer 41 / ferromagnetic layer 42 / exchange coupling layer 43 / first free layer 44 / tunnel barrier layer 45 / second free layer 46 / exchange coupling layer 47 / ferromagnetic layer 48 / antiferromagnetic layer 49 / cap layer (not shown). The exchange coupling layers 43 and 47 are made of Ru, Cr, Ir, Rh, or the like. Depending on the thickness of the exchange coupling layer 43, the interlayer coupling between the ferromagnetic layer 42 and the first free layer 44 can be either antiferromagnetic or ferromagnetic. Depending on the thickness of the exchange coupling layer 47, the interlayer coupling between the ferromagnetic layer 48 and the second free layer 46 can be either antiferromagnetic or ferromagnetic. If the thickness of the exchange coupling layer 43 is such that the interlayer coupling between the ferromagnetic layer 42 and the first free layer 44 is antiferromagnetic, the thickness of the exchange coupling layer 47 is set to such that the interlayer coupling between the ferromagnetic layer 48 and the second free layer 46 is ferromagnetic. If the thickness of the exchange coupling layer 43 is such that the magnetization arrangement of the layers sandwiching the exchange coupling layer 43 is ferromagnetically coupled, the thickness of the exchange coupling layer 47 is set to such that the magnetization arrangement of the layers sandwiching the exchange coupling layer 47 is antiferromagnetically coupled. The characteristics of the third stacking type will be explained later with reference to FIG.

[0038] FIG. 5A is a diagram showing a first example (n=0) of a fourth stack type laminate structure according to the fourth embodiment. The first example (n=0) of the fourth stack type has a stack structure represented by an electrode 50 / underlayer 50a / antiferromagnetic layer 51 / dust layer 53 / first free layer 54 / tunnel barrier layer 55 / second free layer 56 / coupling layer 57 / ferromagnetic layer 58 / dust layer 58a / antiferromagnetic layer 59 / cap layer (not shown). The dust layers 53 and 58a are non-magnetic layers made of Ru or the like with a thickness of 1 nm or less, and act to weaken the exchange bias of the antiferromagnetic material.

[0039] FIG. 5B is a diagram showing a second example (n≧1) of the fourth stack type laminate structure according to the fourth embodiment. A second example (n≧1) of the fourth stack type has a stack structure represented by electrode 50 / underlayer 50a / antiferromagnetic layer 51 / dust layer 53 / stack 53p (=[ferromagnetic layer 53a / coupling layer 53b] repeated n times) / first free layer 54 / tunnel barrier layer 55 / second free layer 56 / stack 58p (=[coupling layer 57 / ferromagnetic layer 58] repeated n+1 times) / dust layer 58a / antiferromagnetic layer 59 / cap layer (not shown).

[0040] FIG. 5C is a diagram showing a first example (n≧1) of a fifth stack type stack structure according to the fourth embodiment. A first example (n≧1) of the fifth stack type has a stack structure represented by the following: electrode 50 / underlayer 50a / antiferromagnetic layer 51 / dust layer 53 / stack 53p′ (=[ferromagnetic layer 53c / coupling layer 53d] repeated n+1 times) / first free layer 54 / tunnel barrier layer 55 / second free layer 56 / stack 58p′ (=[coupling layer 57c / ferromagnetic layer 58c] repeated n times) / dust layer 58a / antiferromagnetic layer 59 / cap layer (not shown).

[0041] Here, the laminated structure of the second example (n≧1) of the fourth laminated type shown in FIG. 5B can also be expressed as the following general formula. Fourth stacking type: Underlayer / antiferromagnetic layer A / dust layer A / ferromagnetic layer A i / bonding layer A i ] n / First free layer / Tunnel barrier layer / Second free layer / [Coupling layer B j / Ferromagnetic layer B j ] n+1 / dust layer B / antiferromagnetic layer B / cap layer The first example (n≧1) of the fifth stacking type stacking structure shown in FIG. 5C can also be expressed as the following general formula. Fifth stacking type: Underlayer / antiferromagnetic layer A / dust layer A / ferromagnetic layer A j / bonding layer A j ] n+1 / First free layer / Tunnel barrier layer / Second free layer / [Coupling layer B i / Ferromagnetic layer B i ] n / dust layer B / antiferromagnetic layer B / cap layer Here, n is an integer greater than or equal to 0, and when n≠0, i=1,...,n and j=1,...,n+1.

[0042] FIG. 6 is a diagram showing the configuration of a TMR sensor using the stacked structures of the first to fifth stacked types. The TMR sensor has a laminated structure of a substrate 600, a lower electrode 602, a laminated layer 604C, and an upper electrode 606. The laminated layer 604C is one of the laminated structures of the first to fifth laminated types. The laminated layer 604C is obtained by laminating each layer and then patterning it into a predetermined shape using photolithography or the like. The substrate 600 is a silicon wafer or a ceramic wafer made of AlTiC or alumina, and the lower electrode 602 and the upper electrode 606 are made of Cu, Au, Ru, or the like. Insulating layers 604L and 604R are provided in adjacent regions on the left and right of the laminate layer 604C.

[0043] <Magnetic property evaluation example 1: Film structure and RH characteristics> We fabricated a TMR sensor with a structure of stacking type 1 (n=0) shown in Table 1. This TMR sensor has a stacking structure of the first stacking type (n=0) shown in Figure 2A. We also fabricated a TMR sensor with a stacking structure of the second stacking type (n=1, 2) shown in Figure 8B. After deposition and microfabrication, the elements were subjected to a magnetic field heat treatment at 300°C for 1 hour. Figure 7 shows the RH characteristics. Here, the resistance value is normalized to the resistance change rate. Figure 7 also shows the characteristics of two samples with different thicknesses of intermediate layers A (AgSn) and B. Both exhibit even-function RH characteristics and a resistance change rate of approximately 160%, but the saturation magnetic field value and the slope of the resistance change rate relative to magnetic field change (i.e., sensitivity) are adjusted by varying the thicknesses of intermediate layers A and B. Note that this resistance change rate is equivalent to that of a spin-valve TMR sensor fabricated under the same heat treatment conditions and is an improvement over the 110% resistance change rate of the conventional single soft pin type TMR element shown in Figure 18. [Table 1]

[0044] <Magnetic property evaluation example 2: soft pinning magnetic field control of the free layer> Figures 8A and 8B show that the saturation magnetic field and permeability of the first and second free layers in the stack structures of the first and second stack types can be controlled by the thickness of the intermediate layer A and intermediate layer B. First, Figure 8A shows the magnetization curve of the first free layer in the stack structure of the first stack type (n = 0). The magnetization curve was measured for each sample with different thicknesses of the intermediate layer A (made of AgSn). The materials and thicknesses of each layer are the same as those in Table 1. The center of the hysteresis curve of the first free layer shifts from zero magnetic field. The magnitude of this shift represents the magnitude of the unidirectional magnetic anisotropy relative to the first free layer, which we refer to here as the soft pinning field Hpin. Controlling the magnitude of Hpin allows us to control the operating magnetic field range of the TMR sensor. Figure 8 plots the soft pinning field Hpin versus the thickness of the intermediate layer made of AgSn for various stack structures. In all cases, Hpin decreases with increasing intermediate layer thickness. From these data, we can determine the appropriate thickness of the intermediate layer to obtain the desired Hpin. It is also easy to predict that even larger Hpin can be obtained by making the AgSn intermediate layer thinner than the 2.2 or 2.3 nm shown here.

[0045] Magnetic property evaluation example 3: Asymmetry of RH properties (experiment) First, we define the magnetic field H1 using the method shown in Figure 9. This is because it is difficult to define the magnetic field at which the resistance R value becomes constant, i.e., the saturation magnetic field, with the RH characteristics shown in Figures 1, 7, and 9, so we define the magnetic field H1 as a substitute for the saturation magnetic field. We draw a tangent to the experimental data at the point where the differential of the experimental data for the RH characteristics, dR / dH, is maximum, and then divide the difference between the experimental data and the tangent by the maximum resistance value of the experimental data to normalize the value (Δ / Rmax) to 20%, thereby defining the magnetic field H1 as the magnetic field at which this normalized value (Δ / Rmax) is 20%. The magnetic field H1 for this experimental data is 7.0 mT. Figure 10A shows the state in which an external magnetic field H is tilted by a misalignment angle θ with respect to the hard axis of magnetization (orthogonal to the easy axis EA) of the free layer of the dual soft pinned TMR sensor. Figure 10B shows the R-H curve when an external magnetic field is applied to the free layer of the dual soft pinned TMR sensor with the misalignment angle θ shown in Figure 10A. This indicates how much the output waveform of the sensor is distorted when the sensor is positioned off-axis from the appropriate direction (the hard axis of the free layer) when implemented as a position detection sensor, and this directly affects position detection errors.

[0046] The asymmetry of the RH curve is defined as follows: When the element resistance R is expressed as R(H) as a function of the magnetic field H, the asymmetry of the RH curve when H=H' (>0) is defined by the following equation. Asy(H')=[R(H')-R(-H')] / [(R(H')+R(-H')](%) In the following, the asymmetry at H=H1, that is, the value of Asy(H1) (referred to as H1 asymmetry) is used. As an example, a dual soft-pinned TMR sensor shown in Table 1 was prepared, and as a comparative example, a single soft-pinned TMR sensor shown in Table 2 was prepared. Figure 11 shows the dependence of H1 asymmetry on the misalignment angle θ in the example and the comparative example. The comparative example has a stacked structure of underlayer / antiferromagnetic A / ferromagnetic layer A / intermediate layer A / first free layer / tunnel barrier layer / ferromagnetic layer B2 / coupling layer B / ferromagnetic layer B2 / antiferromagnetic layer B / cap layer. In both the comparative example and the example, the H1 asymmetry increases linearly with increasing misalignment angle θ. However, the example has a smaller asymmetry value in the magnetic field H1 than the comparative example. The asymmetry value in H1 in the example up to θ = 20° is approximately 1 / 30 of that in the comparative example. [Table 2]

[0047] 10C is an explanatory diagram illustrating the dependence of the resistance change rate on the annealing temperature of the third stacking type stack structure according to the third embodiment. When the annealing temperature of the third stacking type sensor is 300°C, the maximum value of the resistance change rate (dR / Rmin) is 170% when the external magnetic field is 0 mT. In contrast, when the annealing temperature is 350°C, the maximum value of the resistance change rate (dR / Rmin) is 210% when the external magnetic field is 0 mT. In other words, when the external magnetic field is 0 mT, the characteristic of the maximum value of the resistance change rate (dR / Rmin) exceeding 200% is obtained when the annealing temperature is 335°C or higher and 360°C or lower.

[0048] <Magnetic property evaluation example 4: Asymmetry of RH properties (simulation)> The asymmetry of the RH curve was simulated. Figure 12A shows the H1 asymmetry of the dual soft-pinned TMR sensor according to this embodiment. It is desirable for the Hpin values ​​of the first and second free layers to be the same. To achieve the same Hpin values ​​for the first and second free layers, the thickness of the intermediate layer or dust layer must be precisely controlled. Here, the Hpin asymmetry was calculated by varying the Hpin ratio between the first and second free layers from 6:6 to 6:3. When the Hpin ratio is 6:6, i.e., the same value, the H1 asymmetry is zero for any value of the misalignment angle θ. On the other hand, as the asymmetry between the Hpin values ​​of the first and second free layers increases, the H1 asymmetry of the RH curve also increases. Furthermore, the H1 asymmetry increases linearly with the misalignment angle θ.

[0049] Figure 12B shows the H1 asymmetry of a comparative single soft-pin TMR sensor. The H1 asymmetry of the single soft-pin TMR sensor increases linearly with the misorientation angle θ, but its magnitude is much larger than that of the dual soft-pin TMR sensor. For example, the H1 asymmetry of the single soft-pin TMR sensor at θ = 10° is 9.6%, which is much larger than the H1 asymmetries of the dual-pin TMR sensor at θ = 10°, which are 0.6%, 1.4%, and 2.4% (corresponding to Hpin ratios of 6:6, 6:5, and 6:3, respectively). In practice, it is quite possible to achieve a difference of approximately 6:5 between the first and second free layers. As seen in the experimental data in Figures 12A and 12B, the dual soft-pin TMR sensor can suppress the H1 asymmetry at θ = 10° to less than 1% and exhibits highly symmetric RH characteristics of the resistance with respect to the sign of the external magnetic field (the direction of the applied external magnetic field).

[0050] Figures 13A and 13B show the calculated RH curves for a dual soft-pin TMR sensor and a single soft-pin TMR sensor, respectively. Figure 13A shows the RH curve for the dual soft-pin TMR sensor, and Figure 13B shows the RH curve for the single soft-pin TMR sensor. In the case of a dual soft-pin TMR sensor, even when the misalignment angle θ is not zero, when a magnetic field (saturation magnetic field) sufficiently larger than H1 is applied, the resistance values ​​are nearly identical regardless of the sign of the magnetic field, provided that the absolute value of the magnetic field is the same. In contrast, in the case of a single soft-pin TMR sensor, when the misalignment angle θ is not zero, the resistance values ​​are different depending on the sign of the magnetic field, even if the absolute value of the magnetic field is the same. One of the features of a dual soft-pin TMR sensor is that the element resistance is consistent regardless of the sign of the saturation magnetic field, provided that the absolute value of the magnetic field is the same, regardless of the misalignment angle θ. From the above, it can be seen that the use of a dual soft-pin TMR sensor can reduce the asymmetry of the RH characteristics of the sensor compared to a conventional single soft-pin TMR sensor, even if an angular deviation occurs in the sensor orientation with respect to the measurement magnetic field when the sensor is mounted.

[0051] <TMR element array configuration> Fig. 14A is a perspective view showing an embodiment in which a plurality of TMR elements 100 of a dual soft pin TMR sensor are connected in series. The TMR elements 100 shown in Fig. 14 are connected in series via an upper electrode E1 and a lower electrode E2. Fig. 14B is a perspective view showing an embodiment in which a plurality of TMR elements 100 of a dual soft pin TMR sensor are connected in parallel and in series via an upper electrode E1 and a lower electrode E2. The TMR element array may be configured by connecting multiple TMR elements 100 of the dual soft-pin TMR sensor in series, in parallel, or in a combination of these. This allows the bias voltage applied to each TMR element 100 to be distributed, thereby alleviating the problem of a decrease in the rate of resistance change due to a high bias voltage.

[0052] <Bridge configuration> When using a dual soft pin TMR element as a position detection sensor, it is preferable to use the bridge circuit configuration shown in FIG. 15. FIG. 15 is a circuit diagram of an encoder using the bridge configuration according to this embodiment. Elements 157a to 157d each represent the dual soft pin TMR sensor shown in FIG. 1. Current flows in parallel from current source 155 to ground 156 through a line connecting elements 157a and 157b and a line connecting elements 157c and 157d. The encoder detects intermediate potential 153 between elements 157a and 157b and intermediate potential 154 between elements 157c and 157d as sensor outputs.

[0053] Next, a magnetic linear encoder and a magnetic rotary encoder using the TMR element and magnetic sensor according to this embodiment will be described. 20 is a perspective view of the configuration of a magnetic linear encoder to which a magnetic sensor 200 according to this embodiment is applied. The magnetic linear encoder has a permanent magnet sheet on which N poles and S poles are alternately magnetized as a magnetic scale 201. The magnetic sensor 200 detects the position on the surface of this magnetic scale 201 (permanent magnet sheet). 21 is a perspective view of the configuration of a magnetic rotary encoder to which the magnetic sensor 300 according to this embodiment is applied. The magnetic rotary encoder has a permanent magnet region 301, in which N poles and S poles are alternately magnetized, provided on the circumferential surface of a rotor 302. The magnetic rotary encoder detects the rotation angle of this permanent magnet region 301 using the magnetic sensor 300.

[0054] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Industrial Applicability]

[0055] According to the TMR element and magnetic sensor using the same disclosed herein, the maximum value of the resistance change rate is 210% when the stacking structure is optimized, and the maximum value obtained when manufactured within a typical range is large, at approximately 160%, and a TMR sensor is obtained that can suppress asymmetry in the RH characteristics due to a shift in the direction of the detection magnetic field, making it suitable for use in position and rotation detection devices. [Explanation of symbols]

[0056] 11 First Freedom Layer 12 Tunnel Barrier Layer 13 The Second Freedom Layer 20, 30, 40, 50 electrodes 20a, 30a, 40a, 50a Base layer 21, 31, 41, 51 antiferromagnetic layer 22, 32, 42, 52 ferromagnetic layer 23, 33 Middle class 24, 34, 44, 54 First free layer 25, 35, 45, 55 Tunnel barrier layer 26, 36, 46, 56 Second free layer 27, 37 Middle class 28, 38, 48, 58 ferromagnetic layer 29, 39, 49, 59 antiferromagnetic layer 22a, 28b, 32a, 32c, 38b, 38d, 53a, 53c, 58c ferromagnetic layer 22b, 28a, 32b, 32d, 38a, 38c, 53b, 53d, 57, 57c bonding layer 43, 47 exchange coupling layer 53, 58a Dust layer 160 electrodes, 161 Base layer, 162, 164, 167 ferromagnetic layer 163, 165 non-magnetic layer, 166 repeated stacking

Claims

1. An antiferromagnetic layer, a ferromagnetic layer whose magnetization is fixed by being magnetically coupled to the antiferromagnetic layer; a first free layer having an easy axis and a hard axis perpendicular to the easy axis, the magnetization of which is rotatable relative to the magnetization of the ferromagnetic layer; a tunnel barrier layer; a second free layer having an easy axis of magnetization and a hard axis of magnetization perpendicular to the easy axis of magnetization, the second free layer having a rotatable magnetization with respect to the magnetization of the ferromagnetic layer; the tunnel barrier layer is sandwiched between the first free layer and the second free layer; the first free layer and the second free layer include a ferromagnetic metal; a magnetic field to be detected is configured to have a component applied in a hard axis direction of the first free layer and the second free layer; the magnetization of the first free layer and the magnetization of the second free layer are stabilized in an antiparallel arrangement with each other in a state where no external magnetic field is applied; A magnetic junction in which the magnetization of the first free layer and the magnetization of the second free layer are aligned parallel to each other when the strength of an external magnetic field applied in the hard-magnetization axis direction of the first free layer and the second free layer reaches a saturation magnetic field of the first free layer and the second free layer.

2. until the external magnetic field applied in the hard axis direction of the first free layer and the second free layer reaches a saturation magnetic field, the magnetization of the first free layer and the magnetization of the second free layer rotate symmetrically with respect to the direction in which the external magnetic field is applied, As the strength of the external magnetic field increases, the angle between the magnetization of the first free layer and the magnetization of the second free layer decreases, 2. The magnetic junction according to claim 1, wherein the resistance magnetic field characteristic exhibits an even function type characteristic that is symmetric with respect to the positive and negative directions of the external magnetic field application.

3. The tunnel barrier layer is made of MgO, Mg—Al—O, and Al ２ O ３ and at least one selected from the group consisting of 2. The magnetic junction according to claim 1, wherein the first free layer and the second free layer each include at least a layer made of CoFeB.

4. at least one of the first free layer and the second free layer is a stack including multiple layers; the laminate includes a layer made of CoFeB, a layer made of CoFe, and a central layer; the layer made of CoFe is located farther from the tunnel barrier layer than the layer made of CoFeB, the central layer is located between the layer of CoFeB and the layer of CoFe, and includes any one selected from the group consisting of NiFe, CoFeSiB, and CoFeBTa; The magnetic joint according to claim 3 .

5. A first free layer having an easy axis and a hard axis perpendicular to the easy axis; a tunnel barrier layer; a second free layer having an easy axis and a hard axis perpendicular to the easy axis; the tunnel barrier layer is sandwiched between the first free layer and the second free layer; the first free layer and the second free layer include a ferromagnetic metal; a magnetic field to be detected is configured to have a component applied in a hard axis direction of the first free layer and the second free layer; the magnetization of the first free layer and the magnetization of the second free layer are stabilized in an antiparallel arrangement with each other in a state where no external magnetic field is applied; a magnetic junction structure in which the magnetization of the first free layer and the magnetization of the second free layer are aligned parallel to each other when the strength of an external magnetic field applied in the hard axis direction of the first free layer and the second free layer reaches a saturation magnetic field of the first free layer and the second free layer; The magnetic joint body is [Ferromagnetic layer A ｉ / Binding layer A ｉ ] ｎ / ferromagnetic layer A ｎ＋１ / Intermediate layer A / First free layer / Tunnel barrier layer / Second free layer / Intermediate layer B / [Ferromagnetic layer B ｊ / Binding layer B ｊ ] ｎ＋１ / Ferromagnetic layer B ｎ＋２ / Or, [Ferromagnetic layer A ｊ / Binding layer A ｊ ] ｎ＋１ / ferromagnetic layer A ｎ＋２ / Intermediate layer A / First free layer / Tunnel barrier layer / Second free layer / Intermediate layer B / [Ferromagnetic layer B ｉ / Binding layer B ｉ ] ｎ / Ferromagnetic layer B ｎ＋１ / The laminate structure has the following structure: Here, n is an integer equal to or greater than 0, and when n≠0, i=1, . . . , n and j=1, . . . , n+1. ｊ / Binding layer A ｊ ] ｎ＋１ The notation "ferromagnetic layer A" ｊ / Binding layer A ｊ " is repeatedly stacked n+1 times. ｉ / Binding layer B ｉ ] ｎ The notation "ferromagnetic layer B ｉ / Binding layer B ｉ " is a two-layer structure that is repeatedly stacked n times.

6. The ferromagnetic layer A ｉ , the ferromagnetic layer A ｎ＋１ , the ferromagnetic layer B ｊ , the ferromagnetic layer B ｎ＋２ , the ferromagnetic layer A ｊ and the ferromagnetic layer B ｉ is CoFe, The bonding layer A ｉ , the bonding layer B ｊ , the bonding layer A ｊ and the bonding layer B ｉ is Ru, the intermediate layer A and the intermediate layer B each contain at least one selected from the group consisting of Cu, Ag, Cr, Ru, and AgSn, The tunnel barrier layer is made of MgO, Mg—Al—O, and Al ２ O ３ and the first free layer and the second free layer each include at least a layer made of CoFeB; 6. The TMR element according to claim 5.

7. A first free layer having an easy axis and a hard axis perpendicular to the easy axis; a tunnel barrier layer; a second free layer having an easy axis and a hard axis perpendicular to the easy axis; the tunnel barrier layer is sandwiched between the first free layer and the second free layer; the first free layer and the second free layer include a ferromagnetic metal; a magnetic field to be detected is configured to have a component applied in a hard axis direction of the first free layer and the second free layer; the magnetization of the first free layer and the magnetization of the second free layer are stabilized in an antiparallel arrangement with each other in a state where no external magnetic field is applied; a magnetic junction structure in which the magnetization of the first free layer and the magnetization of the second free layer are aligned parallel to each other when the strength of an external magnetic field applied in the hard axis direction of the first free layer and the second free layer reaches a saturation magnetic field of the first free layer and the second free layer; The magnetic joint body is First antiferromagnetic layer / first ferromagnetic layer / first exchange coupling layer / the first free layer / the tunnel barrier layer / the second free layer / second exchange coupling layer / second ferromagnetic layer / second antiferromagnetic layer / The laminate structure has the following structure: the first exchange coupling layer and the second exchange coupling layer are made of Ru or Cr; A TMR element, wherein one of the magnetic coupling between the first ferromagnetic layer and the first free layer and the magnetic coupling between the second ferromagnetic layer and the second free layer is antiferromagnetic coupling and the other is ferromagnetic coupling.

8. the first antiferromagnetic layer and the second antiferromagnetic layer are made of at least one of IrMn, PtMn, FeMn, and NiMn; the first ferromagnetic layer and the second ferromagnetic layer are CoFe; the first exchange coupling layer and the second exchange coupling layer are made of Ru; The tunnel barrier layer is made of MgO, Mg—Al—O, and Al ２ O ３ The present invention relates to a method for manufacturing a pharmaceutical composition comprising the steps of:

8. The TMR element of claim 7, wherein the first free layer and the second free layer each include at least a layer made of CoFeB.

9. A first free layer having an easy axis and a hard axis perpendicular to the easy axis; a tunnel barrier layer; a second free layer having an easy axis and a hard axis perpendicular to the easy axis; the tunnel barrier layer is sandwiched between the first free layer and the second free layer; the first free layer and the second free layer include a ferromagnetic metal; a magnetic field to be detected is configured to have a component applied in a hard axis direction of the first free layer and the second free layer; the magnetization of the first free layer and the magnetization of the second free layer are stabilized in an antiparallel arrangement with each other in a state where no external magnetic field is applied; a magnetic junction structure in which the magnetization of the first free layer and the magnetization of the second free layer are aligned parallel to each other when the strength of an external magnetic field applied in the hard axis direction of the first free layer and the second free layer reaches a saturation magnetic field of the first free layer and the second free layer; The magnetic joint body is Antiferromagnetic layer A / dust layer A / [ferromagnetic layer A ｉ / Binding layer A ｉ ] ｎ / the first free layer / the tunnel barrier layer / the second free layer / [coupling layer B ｊ / Ferromagnetic layer B ｊ ] ｎ＋１ / dust layer B / antiferromagnetic layer B / Or, Antiferromagnetic layer A / dust layer A / [ferromagnetic layer A ｊ / Binding layer A ｊ ] ｎ＋１ / the first free layer / the tunnel barrier layer / the second free layer / [coupling layer B ｉ / Ferromagnetic layer B ｉ ] ｎ / dust layer B / antiferromagnetic layer B / The laminate structure has the following structure: Here, n is an integer equal to or greater than 0, and when n≠0, i=1, . . . , n and j=1, . . . , n+1. ｊ / Binding layer A ｊ ] ｎ＋１ The notation "ferromagnetic layer A" ｊ / Binding layer A ｊ " is repeatedly stacked n+1 times. ｉ / Ferromagnetic layer B ｉ ]n is the notation for "bonding layer B ｉ / Ferromagnetic layer B ｉ " is a two-layer structure that is repeatedly stacked n times.

10. the antiferromagnetic layer A and the antiferromagnetic layer B each contain at least one material selected from the group consisting of IrMn, PtMn, FeMn, and NiMn; The ferromagnetic layer A ｉ , the ferromagnetic layer B ｊ , the ferromagnetic layer A ｊ and the ferromagnetic layer B ｉ is CoFe, The bonding layer A ｉ , the bonding layer B ｊ , the bonding layer A ｊ and the bonding layer B ｉ is Ru, the dust layer A and the dust layer B are made of Ru and have a thickness of 1 nm or less; The tunnel barrier layer is made of MgO, Mg—Al—O, and Al ２ O ３ At least one selected from the group consisting of 10. The TMR element of claim 9, wherein the first free layer and the second free layer each include at least a layer made of CoFeB.

11. a maximum resistance is exhibited when the magnetic field to be detected is zero, and the magnetization of the first free layer and the magnetization of the second free layer are antiparallel to each other; 6. The TMR element of claim 5, wherein the resistance decreases upon application of the magnetic field to be detected, the magnetizations of the first free layer and the second free layer both rotate upon application of the magnetic field to be detected, and the angle between the magnetization of the first free layer and the magnetization of the second free layer decreases as the strength of the magnetic field to be detected increases.

12. When the application direction of the magnetic field to be detected is tilted by 10° from the direction of the hard magnetization axis of the first free layer and the second free layer, the magnetic field asymmetry of the resistance value with respect to the positive and negative of the application direction of the magnetic field H1 is within 1%, Here, the magnetic field H1 is a magnetic field in which a tangent to a curve based on experimental data of resistance magnetic field (R-H) characteristics is determined at a point where the differential (dR / dH) of the curve based on said experimental data is maximum, and the difference between the curve based on said experimental data and the tangent is divided by the maximum resistance value of said experimental data to obtain a standardized value of 20%; The magnetic field asymmetry is defined as the asymmetry of the RH curve at H=H' (>0) when the element resistance R is expressed as R(H) as a function of the magnetic field H. Asy(H')=[R(H')-R(-H')] / [(R(H')+R(-H')](%) 12. The TMR element according to claim 11, wherein the asymmetry of the resistance to the magnetic field H1 is defined as follows:

13. 6. The TMR element according to claim 5, wherein the laminated structure is located between a first structure consisting of a substrate / lower electrode / underlayer / antiferromagnetic layer and a second structure consisting of an antiferromagnetic layer / cap layer.

14. 8. The TMR element according to claim 7, wherein the laminated structure is located between a third structure consisting of a substrate / lower electrode / underlying layer and a fourth structure consisting of a cap layer.

15. the substrate is a silicon wafer or a ceramic wafer made of AlTiC or aluminum oxide; the underlayer has a laminated structure of Ta and Ru, the antiferromagnetic layer is any one selected from the group consisting of IrMn, PtMn, FeMn, and NiMn; the cap layer is Ru; The TMR element according to claim 13.

16. A TMR element array comprising a plurality of TMR elements according to claim 5 connected in at least one of series and parallel.

17. A magnetic sensor having a bridge circuit using four TMR elements according to claim 5.

18. A magnetic sensor comprising the TMR element array according to claim 16 connected in a bridge circuit.

19. A magnetic sensor for a linear encoder, comprising the TMR element according to claim 5.

20. A magnetic rotary encoder having the TMR element according to claim 5.

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