Magnetoresistive element and magnetic sensor equipped therewith

Abstract

The present invention provides a magnetoresistive element that has a magnetization free layer which is magnetized in a spiral shape in the absence of an external magnetic field and whose magnetization direction changes when an external magnetic field is applied, and which exhibits good linearity of output with respect to an external magnetic field. [Solution] The magnetoresistive element 1 has a magnetization free layer 6 that is magnetized in a spiral shape in the absence of an external magnetic field and whose magnetization direction changes when an external magnetic field is applied, a magnetization fixed layer 4 whose magnetization direction is fixed with respect to the external magnetic field, and a non-magnetic layer 5 located between the magnetization free layer 6 and the magnetization fixed layer 4, and the magnetization free layer 6, magnetization fixed layer 4 and non-magnetic layer 5 are arranged in the Z direction. The non-magnetic layer 5 has an interface surface 51 that is in contact with the magnetization free layer 6, and when viewed from the Z direction, a part 68 of the magnetization free layer 6 is outside the outer peripheral portion 53 of the interface surface 51.

Description

Technical Field

[0001] The present disclosure relates to a magnetoresistive element and a magnetic sensor including the same.

Background Art

[0002] Patent Document 1 describes a magnetoresistive element having a magnetically free layer magnetized in a spiral shape in a state without an external magnetic field (zero magnetic field state). The center (core) of the spiral shape is at the center of the magnetically free layer in the zero magnetic field state, but moves toward the periphery of the magnetically free layer when an external magnetic field is applied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the external magnetic field increases and the magnetization of the magnetically free layer approaches the saturation state, the spiral state of the magnetically free layer disappears and the whole is magnetized in the same direction. However, when the spiral state of the magnetically free layer disappears, the magnetic moment of the magnetically free layer changes discontinuously, so that the linearity of the output of the magnetoresistive element deteriorates.

[0005] An object of the present disclosure is to provide a magnetoresistive element including a magnetically free layer magnetized in a spiral shape in a state without an external magnetic field and having its magnetization direction changed by the application of an external magnetic field, and having good linearity of output with respect to the external magnetic field.

Means for Solving the Problems

[0006] The magnetoresistive element of this disclosure comprises a magnetization-free layer that is magnetized in a spiral shape in the absence of an external magnetic field and whose magnetization direction changes when an external magnetic field is applied, a magnetization-fixed layer whose magnetization direction is fixed with respect to the external magnetic field, and a non-magnetic layer located between the magnetization-free layer and the magnetization-fixed layer, and the magnetization-free layer, magnetization-fixed layer and non-magnetic layer are arranged in a first direction. The non-magnetic layer has an interface in contact with the magnetization-free layer, and when viewed from the first direction, a portion of the magnetization-free layer is outside the outer periphery of the interface. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a magnetoresistive element that has a magnetization free layer which is magnetized in a spiral shape in the absence of an external magnetic field and whose magnetization direction changes when an external magnetic field is applied, and which exhibits good linearity of output with respect to an external magnetic field. [Brief explanation of the drawing]

[0008] [Figure 1] These are schematic cross-sectional and plan views of a magnetoresistive element according to the first embodiment. [Figure 2] This is a schematic cross-sectional view of a comparative example magnetoresistive element. [Figure 3] This is a conceptual diagram showing the magnetic curve and magnetization state of the magnetized free layer. [Figure 4] This is a schematic cross-sectional view of a magnetoresistive element according to a modified example of the first embodiment. [Figure 5] This is a schematic cross-sectional view of a magnetoresistive element according to the second embodiment. [Figure 6] These are schematic cross-sectional and plan views of a magnetoresistive element according to the third embodiment. [Figure 7] These are schematic cross-sectional and plan views of a magnetoresistive element according to the fourth embodiment. [Figure 8] This is a schematic plan view of the magnetized free layer of a magnetoresistive element according to the fifth embodiment. [Figure 9] This is a schematic diagram of the magnetic sensor according to the sixth embodiment. [Figure 10] This graph shows the relationship between the diameter of the non-magnetic layer interface, the resistance of the magnetoresistive element, and the output of the magnetic sensor. [Figure 11] This graph shows the relationship between the diameter of the interface of the non-magnetic layer and the sensitivity and linearity of the magnetic sensor. [Figure 12] This graph shows the relationship between the diameter and thickness of the magnetized free layer and the rate of vortex formation. [Modes for carrying out the invention]

[0009] Several embodiments of the present disclosure will be described with reference to the drawings. In the following description and drawings, the first direction is referred to as the Z direction, the second direction as the X direction, and the third direction as the Y direction. The Z direction is the stacking direction of the laminate 2, and the X and Y directions are the in-plane directions of each layer of the laminate 2, and the X, Y, and Z directions are orthogonal to each other. The direction from the substrate 3 towards the laminate 2 is referred to as the +Z direction, and the direction from the laminate 2 towards the substrate 3 is referred to as the -Z direction. If the magnetization fixed layer 4 is magnetized in a direction orthogonal to the Z direction, the magnetization direction of the magnetization fixed layer 4 is referred to as the X direction. In the drawings, the arrows attached to the magnetization fixed layer 4 indicate the magnetization direction of the magnetization fixed layer 4.

[0010] (First embodiment) Figure 1(a) shows a cross-sectional view of a magnetoresistive element 1 according to the first embodiment of this disclosure, and Figure 1(b) shows a cross-sectional view along line AA in Figure 1(a). The magnetoresistive element 1 has a laminate 2 and a silicon substrate 3, and the laminate 2 and the substrate 3 are arranged in the Z direction. Although not shown, other layers such as electrode layers are provided between the laminate 2 and the substrate 3, and the laminate 2 is separated from the substrate 3.

[0011] The laminate 2 comprises a magnetized fixed layer 4, a non-magnetic layer 5, and a magnetized free layer 6. These layers 4-6 are arranged in the +Z direction in the order of magnetized free layer 6, non-magnetic layer 5, and magnetized fixed layer 4. The magnetized free layer 6 is located between the substrate 3 and the magnetized fixed layer 4 in the Z direction. The magnetized free layer 6 and the non-magnetic layer 5 are in contact with each other, and the non-magnetic layer 5 and the magnetized fixed layer 4 are in contact with each other. At any position in the Z direction, the cross-sectional shape of the laminate 2 is circular, and the magnetized free layer 6, non-magnetic layer 5, and magnetized fixed layer 4 form a cylinder or disk with a common central axis CL in the Z direction. The side surface 61 of the magnetized free layer 6 is formed continuously in the Z direction and does not change discontinuously. That is, there are no steps on the side surface 61 of the magnetized free layer 6.

[0012] The magnetization fixed layer 4 is a magnetic layer whose magnetization direction is fixed in the X direction with respect to an external magnetic field. The magnetization fixed layer 4 can be formed from CoFeB or the like. Although not shown in the diagram, the magnetization fixed layer 4 may also have a configuration in which an inner magnetization fixed layer in contact with the non-magnetic layer 5, an intermediate layer made of ruthenium, iridium, or the like, and an outer magnetization fixed layer are arranged in this order in the +Z direction. In this configuration, the inner and outer magnetization fixed layers are magnetized in opposite directions by synthetic antiferromagnetic coupling through the intermediate layer, so that the leakage magnetic field applied from the magnetization fixed layer 4 to the magnetization free layer 6 can be suppressed. The magnetization fixed layer 4 may also have an antiferromagnetic layer in contact with the outer magnetization fixed layer in the +Z direction. Since the magnetization direction of the outer magnetization fixed layer is firmly fixed by the antiferromagnetic layer, the magnetization direction of the outer magnetization fixed layer in a zero magnetic field state is easily stabilized.

[0013] The magnetically free layer 6 is a magnetic layer whose magnetization direction changes with respect to an external magnetic field. The magnetically free layer 6 can be formed of CoFe, CoFeB, NiFe, etc. The magnetization direction of the magnetically free layer 6 (indicated by a dashed line in Fig. 1(b)) forms a spiral shape when viewed from the Z direction in the zero magnetic field state, and the magnetization direction changes by applying an external magnetic field. What magnetization state the magnetically free layer 6 takes in the zero magnetic field state is determined by the balance between the exchange energy and the magnetostatic energy of the magnetically free layer 6. Generally, when the saturation magnetization is large, a spiral magnetization state is likely to occur. In the zero magnetic field state, the center of the spiral called the core 62 is located at the center of the magnetically free layer 6, and the magnetization direction draws concentric circles around the core 62. Generally, such a magnetically free layer 6 has a smaller hysteresis than a magnetically free layer 6 whose magnetization direction points in one direction in the zero magnetic field state.

[0014] The non-magnetic layer 5 is located between the magnetically free layer 6 and the magnetically fixed layer 4. The non-magnetic layer 5 is made of an insulating layer such as MgO or Al2O3, and the magnetoresistive element 1 of the present embodiment operates as a tunnel magnetoresistive element (TMR element). The non-magnetic layer 5 may be made of a non-magnetic metal layer such as copper or silver. In this case, the magnetoresistive element 1 operates as a giant magnetoresistive element (GMR element). A TMR element is more likely to obtain a higher output than a GMR element.

[0015] The diameter of the magnetically free layer 6 is larger than the diameters of the magnetically fixed layer 4 and the non-magnetic layer 5, and a step 7 is formed between the non-magnetic layer 5 and the magnetically free layer 6. The non-magnetic layer 5 has a circular interface 51 that contacts the magnetically free layer 6. When viewed from the Z direction, a part 68 of the magnetically free layer 6 is outside the outer peripheral part 53 of the interface 51. In other words, when viewed from the Z direction, the entire region of the interface 51 of the non-magnetic layer 5 is inside the outer periphery of the magnetically free layer 6. The outer periphery of the magnetically free layer 6 means the outer periphery of the projection of the magnetically free layer 6 in the Z direction. When viewed from the Z direction, the interface 51 of the non-magnetic layer 5 is inside the projection of the magnetically free layer 6 and does not overlap with the outer periphery of the projection.

[0016] The effects of this configuration will be described by comparing it with a comparative example. Fig. 2 shows a cross-sectional view of the magnetoresistive effect element 101 of the comparative example. In the comparative example, the magnetization free layer 106, the non-magnetic layer 5, and the magnetization fixed layer 4 are cylinders or disks having a common Z-direction central axis CL and having the same diameter. Fig. 3 shows the magnetization curve of the disk-shaped magnetization free layer 6. Fig. 3 schematically shows the magnetization of the magnetization free layer 6 at several points on the magnetization curve, specifically, the value obtained by normalizing the X-direction component of the magnetic moment of the magnetization free layer 6 by the total amount of the magnetic moment. For the sake of convenience, the upward direction in the drawing is defined as the +Y direction, and the downward direction is defined as the -Y direction.

[0017] At point A in the zero magnetization state, the magnetization of the magnetization free layer 6 forms a vortex shape, and a core 62 exists at the center. When a magnetic field in the +X direction is applied, the magnetic moment of the magnetization free layer 6 increases. The magnetization free layer 6 is magnetized in the +X direction as a whole, and the core 62 moves in the -Y direction. Although approximate linearity is maintained between the magnetic field strength and the magnetic moment, the linearity decreases as the core 62 moves in the -Y direction. When point B is reached, a jump in the magnetic moment occurs, and the magnetic moment increases discontinuously and saturates (point D). The jump in the magnetic moment occurs when the core 62 disappears (point C). When the magnetic field strength is decreased from point D, the magnetic moment rapidly decreases at point E, and the core 62 appears (point F). The same applies when a magnetic field in the -X direction is applied. Points B' to F' correspond to points B to F, and the magnetization of the magnetization free layer 6 at points B' to F' has a shape obtained by rotating the magnetization at points B to F by 180° around the center of the magnetization free layer 6. In Fig. 3, the interval between point F and point F' is shown as a single line, but actually, two different paths are taken depending on the direction of the applied magnetic field. However, in the magnetization free layer 6 magnetized in a vortex shape in the zero magnetization state, the two paths are close to each other, and the hysteresis is small compared with the magnetization free layer of other configurations.

[0018] In the comparative example, applying a magnetic field stronger than the magnetic field strength at point B reduces the linearity of the signal due to a jump in the magnetic moment, so it is practically necessary to use it between B and B'. This limits the range in which the magnetic sensor can be used as output, and thus restricts the detectable magnetic field strength. However, the abrupt jump in the magnetic moment is mainly caused by the difference in magnetization distortion near the outer edge of the magnetized free layer 6 before and after the core 62 disappears and becomes a single domain due to the external magnetic field. The region inside the magnetized free layer 6 is less affected by magnetization distortion, the magnetization direction generally points in the +X direction as the magnetic field strength increases, and the change in magnetization state is continuous. In this embodiment, the region inside the magnetized free layer 6, that is, the region facing the boundary surface 51 enclosed by the dashed line in the figure in the Z direction, is used as the effective part of the magnetized free layer 6. Since the disappearance of the core 62 of the magnetized free layer 6 occurs outside the dashed line, the jump in the magnetic moment does not have a significant effect on the output voltage of the magnetoresistive element 1. As a result, even when the magnetic field strength is increased to points D and D', the linearity of the output voltage signal does not decrease significantly, making it possible to detect a larger magnetic field than in the comparative example.

[0019] Although not shown in the diagram, as is clear from the above explanation, the interface 51 of the non-magnetic layer 5 is not limited to a circular shape. As long as a portion 68 of the magnetized free layer 6 is outside the outer periphery 53 of the interface 51 between the non-magnetic layer 5 and the magnetized free layer 6 when viewed from the Z direction, the interface 51 of the non-magnetic layer 5 may be elliptical, polygonal, or otherwise, and the center of the interface 51 may be eccentric from the center of the magnetized free layer 6.

[0020] To create the magnetoresistive element 1 of this embodiment, films that will become the magnetized free layer 6, the non-magnetic layer 5, and the magnetized fixed layer 4 are first deposited. Then, a resist mask is created on the film that will become the magnetized fixed layer 4, and the parts not covered by the resist mask are removed by etching to form the non-magnetic layer 5 and the magnetized fixed layer 4 in a predetermined shape. After that, the resist mask is removed and contaminants deposited on the surface of the magnetized fixed layer 4 are removed by reverse sputtering. At this time, since the thin non-magnetic layer 5 is protected by the magnetized fixed layer 4, the possibility of degradation of the non-magnetic layer 5 due to reverse sputtering is reduced. Since the thickness of the magnetized fixed layer 4 can be made larger than that of the non-magnetic layer 5, the effect of degradation during reverse sputtering is limited. In addition, a protective film such as tantalum can be deposited on the film that will become the magnetized fixed layer 4. In this case, the magnetized fixed layer 4 is protected by the protective film during reverse sputtering.

[0021] (Modified version of the first embodiment) As long as a portion 68 of the magnetized free layer 6 is located outside the outer periphery 53 of the interface 51 between the non-magnetic layer 5 and the magnetized free layer 6 when viewed from the Z direction, the magnetized free layer 6 can take on various shapes. Figure 4 shows cross-sectional views of several modified magnetoresistive element 1 of the first embodiment. In these modified examples, the side surface 52 of the non-magnetic layer 5 and the side surface 61 of the magnetized free layer 6 are continuously connected, and no step is formed between the non-magnetic layer 5 and the magnetized free layer 6. In addition, in these modified examples, the diameter of the magnetized free layer 6 changes in the Z direction, but the average diameter of the magnetized free layer 6 in the Z direction can be made larger than the average diameter of the non-magnetic layer 5 and the magnetized fixed layer 4 in the Z direction.

[0022] In the first modified example shown in Figure 4(a), the magnetization free layer 6 has a first portion 63 and a second portion 64. The first portion 63 and the second portion 64 have a coaxial disk or cylindrical shape and are arranged in the Z direction. The first portion 63 and the second portion 64 may be formed from the same material or from different materials. The first portion 63 has the same diameter as the non-magnetic layer 5 and is in contact with the non-magnetic layer 5. The second portion 64 is in contact with the first portion 63 and is located on the opposite side of the non-magnetic layer 5 with respect to the first portion 63. The diameter of the first portion 63 is smaller than the diameter of the second portion 64, and a step 65 is formed on the side surface 61 of the magnetization free layer 6. The thickness (Z-direction dimension) of the first portion 63 is smaller than the thickness (Z-direction dimension) of the second portion 64. This suppresses the effect of the demagnetizing field generated at the end of the first portion 63 and improves the linearity of the output. In the zero-magnetic-field state, the magnetization direction of the second portion 64 is vortex-shaped. Since the first portion 63 has a smaller volume than the second portion 64, it is affected by the magnetization of the second portion 64 and becomes magnetized in the same way as the second portion 64. Therefore, this modified example produces the same effects as the first embodiment. To create the magnetoresistive element 1 of this modified example, films that will form the magnetization free layer 6, the non-magnetic layer 5, and the magnetization fixed layer 4 are formed, and then a portion of each of these films is removed to form the magnetization free layer 6, the non-magnetic layer 5, and the magnetization fixed layer 4 in predetermined shapes.

[0023] In the second modified example shown in Figure 4(b), the magnetized free layer 6 is divided into three parts, and two steps 65 are formed on the side surface 61 of the magnetized free layer 6. The rest of the configuration is the same as in the first modified example. The number of steps 65 is not limited, and the magnetized free layer 6 may be divided into four or more parts, and three or more steps 65 may be formed. In the third modified example shown in Figure 4(c), the magnetized free layer 6 has a first part 63 and a second part 64, and the layer configuration of the laminate 2 is the same as in the first modified example. However, the magnetized fixed layer 4, the non-magnetic layer 5, and the magnetized free layer 6 have a frustoconical shape in which the diameter of the end face closer to the substrate 3 is larger than the diameter of the end face further away from the substrate 3. In the fourth modified example shown in Figure 4(d), the side surface 61 of the magnetized free layer 6 is formed continuously, and there are no steps on the side surface 61 of the magnetized free layer 6. Since there are no steps between the magnetized fixed layer 4, the non-magnetic layer 5, and the magnetized free layer 6, the manufacturing process is simplified. In the fifth modified example shown in Figure 4(e), the magnetized free layer 6 has a first portion 63 and a second portion 64, and the layer structure of the laminate 2 is the same as in the first modified example. The surface of the first portion 63 facing the second portion 64 and the surface of the second portion 64 facing the first portion 63 have the same diameter, and one corner portion 66 is formed on the side surface 61 of the magnetized free layer 6. The magnetized free layer 6 may be divided into three or more portions, as in the second modified example, to form multiple corner portions 66.

[0024] The following describes magnetoresistive element 1 in other embodiments. The following description will focus on the differences from the first embodiment. Configurations and effects that are not described are the same as in the first embodiment.

[0025] (Second embodiment) Figure 5(a) shows a cross-sectional view of a magnetoresistive element 1 according to the second embodiment. The magnetoresistive element 1 has a laminate 2 and a substrate 3, and the laminate 2 and the substrate 3 are arranged in the Z direction. In this embodiment, the magnetization fixed layer 4 is located between the substrate 3 and the magnetization free layer 6. At any position in the Z direction, the cross-sectional shape of the laminate 2 is circular, and the magnetization free layer 6, the non-magnetic layer 5, and the magnetization fixed layer 4 are cylinders or disks having a common central axis CL in the Z direction. Therefore, the side surface 61 of the magnetization free layer 6 is formed continuously, and no steps are formed on the side surface 61 of the magnetization free layer 6. The diameter of the magnetization free layer 6 is larger than the diameters of the magnetization fixed layer 4 and the non-magnetic layer 5, and a step 7 is formed between the non-magnetic layer 5 and the magnetization free layer 6. This embodiment, like the first embodiment, reduces the effect of magnetization distortion occurring in the magnetization free layer 6, and therefore produces the same effects as the first embodiment.

[0026] (Modified version of the second embodiment) Figure 5(b) shows a cross-sectional view of a magnetoresistive element 1 according to a modified example of the second embodiment. The magnetized free layer 6 has a first portion 63 and a second portion 64. The configuration of the first portion 63 and the second portion 64 is the same as the first modified example of the first embodiment. The side surface 52 of the non-magnetic layer 5 and the side surface 61 of the magnetized free layer 6 are continuously connected, and at least one (one in this modified example) step 65 is formed on the side surface 61 of the magnetized free layer 6.

[0027] In this modified example, as in the first embodiment, it is easy to ensure the integrity of the non-magnetic layer 5 during manufacturing. In the embodiment shown in Figure 5(a), films that will become the magnetized fixed layer 4 and the non-magnetic layer 5 are deposited separately, then a resist mask is created on the film that will become the non-magnetic layer 5 to form the magnetized fixed layer 4 and the non-magnetic layer 5 in a predetermined shape, and then the magnetized free layer 6 is formed. The non-magnetic layer 5 is subjected to reverse sputtering without a protective film and may deteriorate. In this modified example, films that will become the magnetized fixed layer 4, the non-magnetic layer 5, and the first portion 63 of the magnetized free layer 6 are deposited separately, and then a resist mask is created on the film that will become the first portion 63. As a result, the non-magnetic layer 5 is protected by the film that will become the first portion 63 during reverse sputtering. Since the first portion 63 of the magnetized free layer 6 can have a thicker film than the non-magnetic layer 5, the effect of deterioration during reverse sputtering is limited.

[0028] (Third embodiment) Figure 6(a) shows a cross-sectional view of the magnetoresistive element 1 according to the third embodiment, and Figure 6(b) shows a cross-sectional view along the DD line in Figure 6(a). The configuration of the magnetized free layer 6 is the same as in the first embodiment, but it may be a modified version of the first embodiment or the same as the configuration of the magnetized free layer 6 in the second embodiment. The magnetized fixed layer 4 is magnetized in the X direction and has a rectangular shape in which the length in the X direction is longer than the length in the Y direction. Since the easy magnetization axis of the shape anisotropy of the magnetized fixed layer 4 coincides with the magnetization direction (X direction) of the magnetized fixed layer 4, the resistance of the magnetized fixed layer 4 to external magnetic fields is increased, and the magnetization direction of the magnetized fixed layer 4 is less likely to rotate in the Y direction. This makes it possible to further improve the linearity of the output of the magnetoresistive element 1. Although not shown in the figures, the shape of the magnetized fixed layer 4 is not limited as long as it has an easy magnetization axis in the X direction, and may be, for example, elliptical. It is preferable that the non-magnetic layer 5 has a shape in which the length in the X direction is longer than the length in the Y direction, and it is even more preferable that it has the same planar shape, dimensions, and center as the magnetization fixing layer 4.

[0029] (Fourth embodiment) Figure 7(a) shows a schematic cross-sectional view of the magnetoresistive element 1 according to the fourth embodiment, and Figure 7(b) shows a schematic plan view of Figure 7(a) in the BB direction. In this embodiment, the magnetization fixed layer 4 is magnetized in the Z direction. In a zero magnetic field state, the magnetization free layer 6 is magnetized in a spiral shape around the core 62, but at the position of the core 62, the magnetization free layer 6 is magnetized in the Z direction. However, since both the state of being magnetized in the +Z direction and the state of being magnetized in the -Z direction are magnetically stable states, the magnetization direction of the core 62 can be reversed from the +Z direction to the -Z direction, or from the -Z direction to the +Z direction, by an external magnetic field. Once the magnetization direction is reversed, the reversed state is stably maintained, which can induce signal offset or fluctuation. Since the magnetic field generated by the magnetization fixed layer 4 can be one of the factors of such an external magnetic field, signal offset and fluctuation can be suppressed by arranging the magnetization fixed layer 4 so that the core 62 does not overlap with the magnetization fixed layer 4 when viewed in the Z direction. The magnetized free layer 6 has a first center line 67 extending in the Z direction, and when viewed from the Z direction, the magnetized fixed layer 4 is separated from the first center line 67. In other words, when viewed from the Z direction, the magnetized fixed layer 4 does not overlap with the first center line 67.

[0030] Figure 7(c) shows a schematic cross-sectional view of a magnetoresistive element 1 according to a modified example of the fourth embodiment, and Figure 7(d) shows a schematic plan view of Figure 7(c) in the CC direction. The magnetization fixed layer 4 has a through hole 41 passing through the first center line 67. That is, the magnetization fixed layer 4 has an annular cross-section. The magnetization fixed layer 4 has a second center line 42 extending in the Z direction. The second center line 42 coincides with the first center line 67, but may be separated from the first center line 67. In any of these embodiments, it is possible to ensure that the core 62 and the magnetization fixed layer 4 do not overlap when viewed in the Z direction.

[0031] (Fifth embodiment) Figure 8 is a schematic plan view of the magnetization free layer 6 of the magnetoresistive element 1 according to the fifth embodiment. A vortex-shaped magnetization state is likely to occur in the magnetization free layer 6, which is rotationally symmetric when viewed from the Z direction. Therefore, the magnetization free layer 6 may be not only circular when viewed from the Z direction, but also a polygon such as a regular hexagon (see Figure 8(a)), a square (see Figure 8(b)), or an octagon (see Figure 8(c)), or even an ellipse (Figure 8(d)). The magnetization fixed layer 4 and the non-magnetic layer 5 can also have the same shape as the magnetization free layer 6. This embodiment can be combined with any of the first to fourth embodiments described above.

[0032] (Sixth embodiment) Figure 9 shows a schematic configuration diagram of the magnetic sensor 10 according to the sixth embodiment. The magnetic sensor 10 of this embodiment has first to fourth magnetoresistive elements 11 to 14. The first to fourth magnetoresistive elements 11 to 14 may be the same as the magnetoresistive elements 1 of each embodiment described above. The first magnetoresistive element 11 and the second magnetoresistive element 12 are connected in series to form a first pair 15, and the third magnetoresistive element 13 and the fourth magnetoresistive element 14 are connected in series to form a second pair 16. One end of the first pair 15 and the second pair 16 are connected to the power supply VDD, and the other end is grounded. The first magnetoresistive element 11 and the fourth magnetoresistive element 14 are located on the power supply VDD side, and the second magnetoresistive element 12 and the third magnetoresistive element 13 are located on the ground side (GND). The magnetic sensor 10 has a differencer 17 that calculates the difference between the midpoint voltage V1 between the first magnetoresistive element 11 and the second magnetoresistive element 12 and the midpoint voltage V2 between the third magnetoresistive element 13 and the fourth magnetoresistive element 14. The magnetization directions (indicated by arrows) of the magnetization fixed layer 4 of the first magnetoresistive element 11 and the third magnetoresistive element 13 are in the same direction, while the magnetization directions (indicated by arrows) of the magnetization fixed layer 4 of the second magnetoresistive element 12 and the fourth magnetoresistive element 14 are in the opposite direction to the magnetization directions of the magnetization fixed layer 4 of the first magnetoresistive element 11 and the third magnetoresistive element 13.

[0033] The voltage drop across each magnetoresistive element 11-14 is approximately proportional to the electrical resistance of the magnetoresistive elements 11-14. Therefore, if the electrical resistances of the first to fourth magnetoresistive elements 11-14 are R1-R4, respectively, the midpoint voltage V1 is V1 = R2 / (R1+R2) × VDD, and the midpoint voltage V2 is V2 = R3 / (R3+R4) × VDD. By obtaining the differential output V1-V2 of the midpoint voltages V1 and V2 using the differencer 17, twice the sensitivity can be obtained compared to detecting the midpoint voltages V1 and V2 directly. Furthermore, even if the midpoint voltages V1 and V2 are offset, the effect of the offset can be eliminated by detecting the difference.

[0034] (Ratio of the diameter of the magnetized free layer 6 to the interface 51) For a circular magnetized free layer 6 and a circular interface 51, the preferred diameter ratio between the magnetized free layer 6 and the interface 51 was determined by analysis. A model of the magnetic sensor 10 shown in Figure 9 was created. Each magnetoresistive element 11-14 consists of a concentric, cylindrical or disc-shaped magnetized free layer 6, a non-magnetic layer 5, and a magnetized fixed layer 4 stacked together, as shown in Figure 1. The diameter of the magnetized free layer 6 was set to 0.5 μm, and the diameters of the non-magnetic layer 5 and the magnetized fixed layer 4 (i.e., the diameter φ of the interface 51) were set to 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, and 0.1 μm. The interface 51 diameter of 0.5 μm is a reference value and corresponds to a comparative example. An external magnetic field Bx was applied in the X direction, and the resistances R1-R4 of the magnetoresistive elements 11-14 were calculated based on the results of micromagnetic simulation. Resistances R1 and R3 are equal to each other, and resistances R2 and R4 are equal to each other.

[0035] Figure 10(a) shows the relationship between the external magnetic field Bx and resistors R1 and R3, Figure 10(b) shows the relationship between the external magnetic field Bx and resistors R2 and R4, and Figure 10(c) shows the relationship between the external magnetic field Bx and differential outputs V1-V2. The resistances R1-R4 and differential outputs V1-V2 on the vertical axis are all normalized values. The differential outputs V1-V2 were normalized by VDD, with the MR ratio of the magnetoresistive elements 11-14 set to 100%. The MR ratio for each of the magnetoresistive elements 11-14 is the difference between the maximum and minimum resistance values ​​divided by the minimum resistance value. When the diameter φ of the interface 51 was 0.5 μm (reference value), a jump was observed in the resistance value and differential output, but no jump was observed for diameters of 0.4 μm to 0.1 μm.

[0036] Next, the sensitivity and output linearity of the magnetic sensor 10 were determined. Figure 11(a) shows the relationship between the diameter φ of the interface 51 and the differential output sensitivity, and Figure 11(b) shows the relationship between the diameter φ of the interface 51 and the linearity index. The differential output sensitivity is the slope (derivative value) of the differential output with respect to the magnetic field, normalized by VDD at the zero magnetic field point. As shown in Figure 11(c), the linearity index is expressed as Verr, the maximum value of the difference between the line L connecting the differential output at the minimum magnetic field Bmin and the maximum magnetic field Bmax in the magnetic field application range, and the differential outputs V1-V2. Therefore, the smaller the linearity index, the better the linearity of the output of the magnetic sensor 10. Here, the minimum magnetic field Bmin is zero, and the maximum magnetic field Bmax is the magnetic field at which 75% of the output is obtained when the magnetization of the magnetized free layer 6 is saturated is used. When the diameter φ of the interface 51 is small, the sensitivity increases and the linearity improves.

[0037] Based on these results, when the interface 51 of the non-magnetic layer 5 is circular when viewed from the Z direction, it is preferable that the diameter φ of the interface 51 is 80% or less of the diameter of the magnetized free layer 6. However, since a smaller interface 51 increases manufacturing variability, it is preferable that the diameter φ of the interface 51 be 0.1 μm or larger.

[0038] (Thickness and diameter of the magnetized free layer 6) As mentioned above, whether or not a vortex-shaped magnetization state occurs depends on the balance between the exchange energy and magnetostatic energy of the magnetized free layer 6, and more specifically, on the thickness and area of ​​the magnetized free layer 6. Using micromagnetic simulations, we determined the optimal range of disk thickness and diameter for which a vortex-shaped magnetization state is likely to occur, targeting disks that simulate the magnetized free layer 6. The disk diameters were 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 7 μm, and 10 μm, and the disk thickness T was 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, and 100 nm. The saturation magnetization of the disk was 800 × 10⁻¹⁰. 3 A / m, exchange stiffness coefficient is 1 × e -11 The value was set to J / m. Since micromagnetic simulations inherently involve random elements in the analysis, multiple analyses were performed for each combination of disk thickness T and diameter to determine the proportion (probability) of vortex-shaped magnetization states occurring.

[0039] Figure 12 shows the relationship between the disk thickness T, diameter, and the rate of vortex formation. If the disk diameter is large, multiple magnetic domains will appear inside the disk, and vortex formation will not be stable, so the disk diameter is preferably 3 μm or less. If the disk thickness T is small, the inside of the disk will become a single magnetic domain and vortex formation will not be stable, so the disk thickness T is preferably 20 nm or more, and more preferably 30 nm or more. The graphs almost overlap in the range of T = 30 to 80 nm. If the disk diameter is less than 0.3 μm, it becomes difficult to stably form the disk in the manufacturing process, and if the disk thickness T exceeds 100 nm, it becomes difficult to stably form the insulating layer provided on the side of the disk. For the above reasons, the thickness of the magnetized free layer 6 is preferably 20 nm or more and 100 nm or less, and more preferably 30 nm or more and 100 nm or less. The diameter of the magnetized free layer 6 is preferably 0.3 μm or more and 3 μm or less.

[0040] (Note) This specification includes the following disclosures. [Configuration 1] A magnetization free layer that is magnetized in a spiral pattern in the absence of an external magnetic field, and whose magnetization direction changes when the external magnetic field is applied, A magnetization-fixed layer whose magnetization direction is fixed with respect to the external magnetic field, It has a non-magnetic layer located between the magnetization free layer and the magnetization fixed layer, The magnetization free layer, the magnetization fixed layer, and the non-magnetic layer are arranged in a first direction. The non-magnetic layer has an interface in contact with the magnetization-free layer, A magnetoresistive element in which, when viewed from the first direction, a portion of the magnetization free layer is located outside the outer periphery of the interface. [Configuration 2] A magnetoresistive element according to configuration 1, wherein a step is formed between the non-magnetic layer and the magnetization-free layer. [Configuration 3] The magnetoresistive element according to configuration 1, wherein the side surface of the non-magnetic layer and the side surface of the magnetization-free layer are continuously connected. [Structure 4] A magnetoresistive element according to any one of configurations 1 to 3, wherein at least one step is formed on the side surface of the magnetized free layer. [Composition 5] The magnetoresistive element according to any one of configurations 1 to 3, wherein the magnetization free layer has a first portion and a second portion arranged in the first direction, the first portion is in contact with the non-magnetic layer and has a smaller area and thickness than the second portion. [Composition 6] The magnetoresistive element according to any one of configurations 1 to 3, wherein the side surface of the magnetization free layer is formed continuously. [Composition 7] The magnetoresistive element according to configuration 6, wherein at least one corner is formed on the side surface of the magnetization free layer. [Structure 8] The magnetoresistive element according to any one of configurations 1 to 7, wherein the magnetized fixed layer is magnetized in a second direction perpendicular to the first direction, and the length of the magnetized fixed layer in the second direction is longer than the length in a third direction perpendicular to the first and second directions. [Composition 9] The magnetization fixed layer is magnetized in the first direction, The magnetization free layer has a first center line parallel to the first direction, A magnetoresistive element according to any one of configurations 1 to 8, wherein, when viewed from the first direction, the magnetization fixed layer is separated from the first center line. [Configuration 10] The magnetoresistive element according to configuration 9, wherein the magnetization fixed layer and the non-magnetic layer have a second center line parallel to the first center line. [Composition 11] The magnetoresistive element according to configuration 10, wherein the magnetization fixing layer has a through hole through which the first center line passes. [Composition 12] A magnetoresistive element according to any one of configurations 1 to 11, wherein the magnetization free layer is rotationally symmetric when viewed from the first direction. [Composition 13] The magnetoresistive element according to configuration 12, wherein the magnetization free layer is circular when viewed from the first direction. [Composition 14] The magnetoresistive element according to configuration 13, wherein the magnetization free layer has a thickness of 20 nm or more and 100 nm or less, and a diameter of 0.3 μm or more and 3 μm or less. [Composition 15] The magnetoresistive element according to configuration 13 or 14, wherein the interface is circular when viewed from the first direction, and the diameter of the interface is 0.1 μm or more and 80% or less of the diameter of the magnetized free layer. [Composition 16] The laminate comprises the magnetization free layer, the magnetization fixed layer, and the non-magnetic layer, and a substrate. The laminate and the substrate are arranged in the first direction. The magnetoresistive element according to any one of configurations 1 to 15, wherein the magnetization free layer is located between the substrate and the magnetization fixed layer. [Composition 17] The laminate comprises the magnetization free layer, the magnetization fixed layer, and the non-magnetic layer, and a substrate. The laminate and the substrate are arranged in the first direction. The magnetoresistive element according to any one of configurations 1 to 15, wherein the magnetization fixed layer is located between the substrate and the magnetization free layer. [Composition 18] A magnetic sensor having a magnetoresistive element as described in any one of configurations 1 to 17. [Explanation of Symbols]

[0041] 1. Magnetoresistive element 2 Laminate 3 circuit boards 4 Magnetization fixed layer 5 Non-magnetic layer 6 Magnetization free layer 7 steps 10 Magnetic Sensors 41 Through hole 42 Second Centerline 51 Interface 53 Outer periphery of the interface 63 Part 1 64 Part 2 65 steps 66 corners 67. First centerline Z First direction X Second direction Y Third direction

Claims

1. A magnetization free layer that is magnetized in a spiral pattern in the absence of an external magnetic field, and whose magnetization direction changes when the external magnetic field is applied, A magnetization-fixed layer whose magnetization direction is fixed with respect to the external magnetic field, It has a non-magnetic layer located between the magnetization free layer and the magnetization fixed layer, The magnetization-free layer, the magnetization-fixed layer, and the non-magnetic layer are arranged in a first direction. The non-magnetic layer has an interface in contact with the magnetization-free layer, A magnetoresistive element in which, when viewed from the first direction, a portion of the magnetization free layer is located outside the outer periphery of the interface.

2. The magnetoresistive element according to claim 1, wherein a step is formed between the non-magnetic layer and the magnetization free layer.

3. The magnetoresistive element according to claim 1, wherein the side surface of the non-magnetic layer and the side surface of the magnetization free layer are continuously connected.

4. The magnetoresistive element according to claim 1, wherein at least one step is formed on the side surface of the magnetization free layer.

5. The magnetoresistive element according to claim 1, wherein the magnetization free layer has a first portion and a second portion arranged in the first direction, the first portion is in contact with the non-magnetic layer and has a smaller area and thickness than the second portion.

6. The magnetoresistive element according to claim 1, wherein the side surface of the magnetization free layer is formed continuously.

7. The magnetoresistive element according to claim 6, wherein at least one corner is formed on the side surface of the magnetization free layer.

8. The magnetoresistive element according to claim 1, wherein the magnetized fixed layer is magnetized in a second direction perpendicular to the first direction, and the length of the magnetized fixed layer in the second direction is longer than the length in a third direction perpendicular to the first and second directions.

9. The magnetization fixed layer is magnetized in the first direction, The magnetization free layer has a first center line parallel to the first direction, The magnetoresistive element according to claim 1, wherein, when viewed from the first direction, the magnetization fixed layer is separated from the first center line.

10. The magnetoresistive element according to claim 9, wherein the magnetization fixed layer and the non-magnetic layer have a second center line parallel to the first center line.

11. The magnetoresistive element according to claim 10, wherein the magnetization fixing layer has a through hole through which the first center line passes.

12. The magnetoresistive element according to claim 1, wherein the magnetization free layer is rotationally symmetric when viewed from the first direction.

13. The magnetoresistive element according to claim 12, wherein the magnetization free layer is circular when viewed from the first direction.

14. The magnetoresistive element according to claim 13, wherein the magnetization free layer has a thickness of 20 nm or more and a diameter of 0.3 μm or more and a diameter of 3 μm or less.

15. The magnetoresistive element according to claim 13, wherein the interface is circular when viewed from the first direction, the diameter of the interface is 0.1 μm or more and 80% or less of the diameter of the magnetized free layer.

16. The laminate comprises the magnetization free layer, the magnetization fixed layer, and the non-magnetic layer, and a substrate. The laminate and the substrate are arranged in the first direction. The magnetoresistive element according to claim 1, wherein the magnetization free layer is located between the substrate and the magnetization fixed layer.

17. The laminate comprises the magnetization free layer, the magnetization fixed layer, and the non-magnetic layer, and a substrate. The laminate and the substrate are arranged in the first direction. The magnetoresistive element according to claim 1, wherein the magnetization fixed layer is located between the substrate and the magnetization free layer.

18. A magnetic sensor having a magnetoresistive element according to any one of claims 1 to 17.

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