JP2006066821A - Magnetic sensor having magneto-resistance effect element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic sensor by which a magnetization direction of each magnetic domain in a free layer is stably returned to the direction of an initial state. <P>SOLUTION: The magnetic sensor includes a magneto-resistance effect membrane having a fixed layer P with a pinned layer included, a spacer layer S and the free layer F, and a pair of end bias magnetic membranes 11b4, 11b5 below both ends of the free layer F. The magnetic membranes apply the bias magnetic field of a predetermined direction to the free layer F. Moreover, the magnetic sensor includes a central bias magnetic membrane 11d4 which is arranged between a pair of the end bias magnetic membranes 11b4, 11b5, and applies the bias magnetic field of the predetermined direction to the free layer F. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic sensor including a magnetoresistive effect element including a pinned layer and a free layer.

  Conventionally, magnetoresistive elements such as GMR elements (giant magnetoresistive elements) and TMR elements (magnetic tunnel effect elements) have been applied to magnetic sensors. These elements include a magnetoresistive effect film including a fixed layer including a pinned layer whose magnetization direction is fixed, and a free layer whose magnetization direction changes according to an external magnetic field.

  For example, the GMR element includes a free layer 102 formed on the substrate 101, a spacer layer 103 formed on the free layer 102, and a spacer layer 103, as shown in FIG. And a pinned layer 104 including a pinned layer, and exhibiting a resistance value corresponding to a relative relationship between the pinned layer pinned magnetization direction and the free layer 102 magnetization direction.

  In a magnetic sensor having such a magnetoresistive effect element, in order to detect a minute external magnetic field with high accuracy, the magnetization direction of each magnetic domain of the free layer 102 when the external magnetic field is not applied to the magnetic sensor is pinned. It is necessary to stably maintain the direction orthogonal to the direction of the fixed magnetization of the layer (hereinafter, this direction is also referred to as “the direction of the free layer in the initial state” or simply “the direction of the initial state”). is there.

  Therefore, conventionally, the shape of the free layer 102 in a plan view is a rectangle, and the long side of the rectangle (that is, the longitudinal direction of the free layer 102 and the Y-axis direction in FIG. 26) is the orientation in the initial state. To match. With this configuration, since the shape anisotropy in which the magnetization directions are aligned in the longitudinal direction can be used, the magnetization direction of each magnetic domain of the free layer 102 can be relatively easily matched to the initial state direction. Become. Further, in the conventional magnetic sensor, a pair of bias magnet films 105 and 105, which are permanent magnet films, are arranged at both ends in the longitudinal direction of the free layer 102, and the same direction as that in the initial state is provided by the bias magnet films 105 and 105. A bias magnetic field in the direction is applied to the free layer 102. According to this, when the external magnetic field disappears, the magnetization direction of each magnetic domain of the free layer 102 is stably restored to the initial state for a long time by the magnetic field applied by the bias magnet films 105 and 105.

  The state of magnetization of the free layer 102 and the bias magnet films 105 and 105 will be described with reference to FIG. 27 which is a plan view of the free layer 102 and the bias magnet films 105 and 105. At the stage where these films are formed, the magnetization direction of each magnetic domain of the free layer 102 and the bias magnet films 105 and 105 is the longitudinal direction of the free layer 102 as shown by the arrows in FIG. Are not aligned in the initial state. The GMR element in which the free layer 102 and the bias magnet films 105 and 105 are in such a state is applied with an external magnetic field whose size changes in the direction orthogonal to the longitudinal direction of the free layer 102 (X-axis direction). When the resistance value of the GMR element is examined, as shown in FIG. 27B, hysteresis occurs in the change of the resistance value.

  As is clear from this, in the magnetic sensor including the GMR element in which the magnetization directions of the free layer 102 and the bias magnet films 105 and 105 are not aligned in the longitudinal direction of the free layer 102, the external magnetic field is “0”. The resistance value in the vicinity varies within the range indicated by the arrow in FIG. As a result, such a magnetic sensor cannot accurately detect a minute magnetic field.

  Next, the bias magnet film 105 in the longitudinal direction of the free layer 102 (in this case, the Y-axis positive direction) with respect to the magnetic sensor in which the free layer 102 and the bias magnet films 105 and 105 are in the state shown in FIG. , 105 when a magnetic field larger than the holding force of the magnetic layer is applied to initialize the free layer 102 and magnetize the bias magnet films 105, 105, as shown in FIG. The direction of magnetization of each magnetic domain of the layer 102 and the bias magnet films 105 and 105 coincides with the direction of the initial state. The GMR element in this state exhibits a resistance value change without hysteresis as shown in FIG. Therefore, the magnetic sensor including the GMR element in which the free layer 102 is initialized and the bias magnet films 105 and 105 are magnetized can detect a minute magnetic field with high accuracy.

  However, for the GMR element in which the free layer 102 is initialized and the bias magnet films 105 and 105 are magnetized in this way, the holding force of the free layer 102 is smaller than the holding force of the bias magnet films 105 and 105. When an external magnetic field that has a magnitude and is opposite to the initial state (in this case, the negative Y-axis direction) is applied, even if the external magnetic field disappears thereafter, FIG. As shown in (A), the magnetization direction of each magnetic domain in the central portion of the free layer 102, particularly surrounded by the broken line DL, does not coincide with (return to) the initial state. As a result, as shown in FIG. 29B, the GMR element again exhibits a resistance value having hysteresis with respect to a change in the external magnetic field, so that the magnetic field detection accuracy by the magnetic sensor deteriorates.

In order to cope with such a problem, the conventional magnetic sensor is provided in the vicinity of the free layer 102 and applies a magnetic field in the same direction (Y-axis positive direction) as the bias magnetic field when energized under a predetermined condition. An initialization coil to be added is provided (for example, see Patent Document 1).
JP 2004-163419 (Claim 1, FIG. 1 and FIG. 2)

However, the conventional magnetic sensor has a problem that the configuration of the sensor is complicated because the initialization coil and a processing circuit for flowing current to the initialization coil must be formed in the substrate. is doing. Moreover, since a current is frequently passed through the initialization coil, there is a problem that the amount of power consumption increases.
Therefore, one of the objects of the present invention is to stably return the magnetization direction of each magnetic domain of the free layer to the initial state without using a large (large area) initialization coil. It is to provide a possible magnetic sensor.

The magnetic sensor according to the present invention comprises:
A magnetoresistive film including a pinned layer and a free layer; and a pair of end bias magnet films disposed at both ends of the magnetoresistive film and applying a bias magnetic field in a predetermined direction to the free layer; A magnetic sensor comprising a magnetoresistive effect element comprising:
The magnetic sensor further includes a central bias magnet film disposed between the pair of end bias magnet films and applying a bias magnetic field in the predetermined direction to the free layer.

  According to this, even after a relatively large external magnetic field is applied, when the external magnetic field disappears, not only the end bias magnet film but also the central bias magnet film causes the magnetization direction of a wide range of free layers. Can be restored to the initial orientation. Therefore, since the magnetoresistive effect element of this magnetic sensor stably shows a change in resistance value without hysteresis with respect to a change in the external magnetic field, the magnetic sensor can accurately detect a minute magnetic field over a long period of time. it can.

in this case,
The magnetoresistive film is formed in a narrow band shape having a longitudinal direction,
The predetermined direction is parallel to the longitudinal direction;
The central bias magnet film is preferably formed in a shape having a longitudinal direction in the same direction as the longitudinal direction.

  According to this, since the free layer has a shape having a longitudinal direction, the magnetization direction in the initial state of the free layer easily returns to the longitudinal direction due to the shape anisotropy. In addition, since the shape of the central bias magnet film has a longitudinal direction, the central bias magnet film can stably generate a large magnetic field in the longitudinal direction. Further, since the longitudinal direction of the free layer and the longitudinal direction of the central bias magnet film coincide with each other, the central bias magnet film generates a magnetic field that returns the magnetization direction of the free layer to the initial state. Therefore, the magnetoresistive effect element of this magnetic sensor can stably show a change in resistance value having no hysteresis with respect to a change in the external magnetic field over a long period of time.

  Furthermore, the magnetic sensor preferably includes at least two of the magnetoresistive effect elements, and is configured so that the fixed magnetization directions of the pinned layers of the two magnetoresistive effect elements are orthogonal to each other. is there.

  Since this magnetic sensor includes at least two magnetoresistive elements whose magnetization directions of the pinned layer are orthogonal to each other, each component of the magnetic field in the orthogonal direction can be detected. In addition, by applying magnetic fields in directions perpendicular to each other to the two magnetoresistive elements, a process for magnetizing the magnetization directions of the respective central bias magnet films in an appropriate direction can be performed at a time. .

  Note that “magnetic fields in directions orthogonal to each other” given to the two magnetoresistive elements described above are “a plurality of permanent shapes having a substantially rectangular parallelepiped shape and a cross-sectional shape perpendicular to one central axis of the rectangular parallelepiped. The bar magnets are arranged so that the center of gravity of the end faces having substantially square shapes coincide with the lattice points of the square lattice, and the polarities of the magnetic poles appearing on the same end faces of the respective permanent bar magnets arranged at the shortest distances. A magnetic array formed and arranged in the vicinity of the end face of each permanent bar magnet can be used by the “magnet array arranged and configured differently from the polarity of the magnetic poles appearing on the same end face of other adjacent permanent bar magnets”.

Embodiments of a magnetic sensor according to the present invention will be described below with reference to the drawings. This magnetic sensor includes a magnetic sensor called N type and a magnetic sensor called S type.
(Magnetic sensor structure)
The N-type magnetic sensor 10 according to the embodiment of the present invention shown in FIG. 1, which is a plan view, includes a substrate 10 a and a plurality of (in this example, eight in total) GMR elements 11 to 14, 21 to 24. The circuit unit 30 is provided.

  The substrate 10a is a thin plate having a substantially square shape having sides along the X axis and the Y axis that are orthogonal to each other in plan view, and having a small thickness in the Z axis direction orthogonal to the X axis and the Y axis.

  The GMR elements 11 to 14 and 21 to 24 are magnetic detection elements that exhibit resistance values having magnitudes corresponding to the components of the external magnetic field in the respective magnetic detection directions (magnetic field detection directions). The GMR elements 11 to 14 and 21 to 24 have substantially the same structure except that they are disposed at different positions with respect to the substrate 10a. Accordingly, the structure of the GMR element 11 will be described below as a representative example. The GMR element 11 is called a first X-axis GMR element 11, the GMR element 12 is called a second X-axis GMR element 12, the GMR element 13 is called a third X-axis GMR element 13, and the GMR element 14 is called a fourth X-axis GMR element 14. The GMR element 21 is referred to as a first Y-axis GMR element 21, the GMR element 22 is referred to as a second Y-axis GMR element 22, the GMR element 23 is referred to as a third Y-axis GMR element 23, and the GMR element 24 is referred to as a fourth X-axis GMR element 24.

  The first X-axis GMR element 11 is a schematic cross-sectional view of the first X-axis GMR element 11 cut along a plane along line 1-1 in FIGS. 2 and 2 which is an enlarged plan view, as shown in FIG. A plurality of (six in this example) narrow strip portions 11a1 to 11a6, a plurality (seven in this example) end bias magnet films 11b1 to 11b7, a pair of terminal portions 11c1 and 11c2, and a plurality of (Six in this example) central bias magnet films 11d1 to 11d6. The end bias magnet film and the center bias magnet film are also referred to as an end hard magnet film and a center hard magnet film, respectively.

  Each of the narrow strip portions 11a1 to 11a6 has a longitudinal direction in the Y-axis direction. The end of the narrow strip portion 11a1 located closest to the X-axis positive direction side on the Y-axis negative direction side is formed on the end bias magnet film 11b1. The end bias magnet film 11b1 is connected to the connection portion 11c1. The end of the narrow strip portion 11a1 on the Y axis positive direction side is formed on the end bias magnet film 11b2.

  The narrow strip portion 11a2 is disposed adjacent to the narrow strip portion 11a1 on the X axis negative side of the narrow strip portion 11a1. One end of the narrow strip portion 11a2 is formed on the end bias magnet film 11b2, and is connected to the narrow strip portion 11a1 on the end bias magnet film 11b2. The other end of the narrow strip portion 11a2 is formed on the end bias magnet film 11b3.

  The narrow strip portion 11a3 is disposed adjacent to the narrow strip portion 11a2 on the X-axis negative side of the narrow strip portion 11a2. One end of the narrow strip portion 11a3 is formed on the end bias magnet film 11b3 and is connected to the narrow strip portion 11a2 on the end bias magnet film 11b3. The other end of the narrow strip portion 11a3 is formed on the end bias magnet film 11b4.

  The narrow strip portion 11a4 is disposed adjacent to the narrow strip portion 11a3 on the X-axis negative side of the narrow strip portion 11a3. One end of the narrow strip portion 11a4 is formed on the end bias magnet film 11b4 and is connected to the narrow strip portion 11a3 on the end bias magnet film 11b4. The other end of the narrow strip portion 11a4 is formed on the end bias magnet film 11b5.

  The narrow strip portion 11a5 is disposed adjacent to the narrow strip portion 11a4 on the X-axis negative side of the narrow strip portion 11a4. One end of the narrow strip portion 11a5 is formed on the end bias magnet film 11b5 and is connected to the narrow strip portion 11a4 on the end bias magnet film 11b5. The other end of the narrow strip portion 11a5 is formed on the end bias magnet film 11b6.

  The narrow strip portion 11a6 is disposed adjacent to the narrow strip portion 11a5 on the X axis negative side of the narrow strip portion 11a5. One end of the narrow strip portion 11a6 is formed on the end bias magnet film 11b6 and is connected to the narrow strip portion 11a5 on the end bias magnet film 11b6. The other end of the narrow strip portion 11a6 is formed on the bias magnet film 11b7. The bias magnet film 11b7 is connected to the connection portion 11c2.

  The end bias magnet films 11b1 to 11b7 have a shape having a longitudinal direction in a direction (in this case, the Y-axis direction) coinciding with each longitudinal direction of the narrow strips 11a1 to 11a6 in plan view. For example, the shape of the end bias magnet films 11b2 to 11b6 is a rectangle having long sides in the Y-axis direction. The shape of the end bias magnet films 11b1 and 11b7 may be the same rectangle. Accordingly, the end bias magnet films 11b1 to 11b7 can stably generate a magnetic field having a large size in the longitudinal direction.

  The central bias magnet film 11d1 is formed on the substrate 10a immediately below the substantially central portion in the Y-axis direction (longitudinal direction) of the narrow strip portion 11a1. That is, the central bias magnet film 11d1 is disposed in the vicinity of the central part of the pair of end bias magnet films 11b1 and 11b2. The central bias magnet film 11d1 has a rectangular shape having a long side (longitudinal direction) in the Y-axis direction in plan view. The length of the short side of the central bias magnet film 11d1 is the same as or narrower than the width of the narrow strip portion 11a1 (the length in the direction orthogonal to the longitudinal direction, in this case, the length in the X-axis direction). The width is set slightly larger than the width of the belt-like portion 11a1.

  Each of the central bias magnet film 11d2 to the central bias magnet film 11d6 has the same shape as the central bias magnet film 11d1. The central bias magnet film 11d2 to the central bias magnet film 11d6 are respectively formed on the substrate 10a immediately below the central portion in the Y-axis direction (longitudinal direction) of the narrow strip portion 11a2 to the narrow strip portion 11a6.

Each of the narrow strip portions 11a1 to 11a6 is composed of a spin valve film whose film configuration is shown in FIG. This spin valve film is formed on the free layer F formed on the substrate 10a, the spacer layer S formed on the free layer F, the fixed layer P formed on the spacer layer S, and the fixed layer P. The capping layer C is formed. The substrate 10a is composed of an Si layer 10a1 and an insulating layer 10a2 of SiO ₂ (or SiN) laminated thereon. The insulating layer 10a2 includes a wiring layer.

  The free layer F is a layer whose magnetization direction changes in accordance with the direction of the external magnetic field. The free layer F includes a CoZrNb amorphous magnetic layer 11-1 having a film thickness of 8 nm (80 mm) formed directly on the substrate 10a and a film thickness of 3.3 nm formed on the CoZrNb amorphous magnetic layer 11-1. 33)) and a CoFe layer 11-3 having a thickness of about 1 to 3 nm (10 to 30 mm) formed on the NiFe magnetic layer 11-2. The CoZrNb amorphous magnetic layer 11-1 and the NiFe magnetic layer 11-2 constitute a soft ferromagnetic film.

  Since each of the narrow strip portions 11a1 to 11a6 has a longitudinal direction, the free layer F has a shape having a longitudinal direction along the Y-axis direction. Therefore, the direction of the initial state of magnetization of the free layer F is the longitudinal direction of the free layer F (in the case of the first X-axis GMR element 11, the Y-axis negative direction) due to shape anisotropy.

  The spacer layer S is a conductive film made of Cu having a film thickness of 2.4 nm (24 cm). The CoFe layer 11-3 prevents diffusion of Ni in the NiFe layer 11-2 and Cu11-4 in the spacer layer S.

  The fixed layer (fixed layer, magnetization fixed layer) P has a film thickness of 24 nm (240 mm) formed from a CoFe magnetic layer 11-5 with a film thickness of 2.2 nm (22 mm) and a PtMn alloy containing 45 to 55 mol% of Pt. The antiferromagnetic film 11-6 is superposed. The CoFe magnetic layer 11-5 is pinned so that the direction of magnetization (magnetization vector) is pinned (fixed) in the negative direction of the X-axis by being back-exchange-coupled to the antiferromagnetic film 11-6 constituting the pinning layer. Make up layer. The magnetization direction of the CoFe magnetic layer 11-5 is the fixed magnetization direction of the pinned layer of the first X-axis GMR element.

  The capping layer C is made of titanium (Ti) or tantalum (Ta) having a thickness of 1.5 nm (15 mm).

  2 and 3 again, the end bias magnet films 11b1 to 11b7 and the center bias magnet films 11d1 to 11d6 are made of a hard ferromagnetic material such as CoCrPt and have a high coercive force and a high squareness ratio. Thus, it is magnetized to form a permanent magnet film. The end bias magnet films 11b1 to 11b7 and the center bias magnet films 11d1 to 11d6 return the magnetization direction of the free layer F in the absence of an external magnetic field to the initial magnetization direction. Thus, a bias magnetic field is applied in the longitudinal direction of the free layer F (in the case of the first X-axis GMR element 11, the Y-axis negative direction). The end bias magnet films 11b1 to 11b7 and the center bias magnet films 11d1 to 11d6 are magnetically coupled to the free layer F formed immediately above them. Therefore, since the magnetization direction of the free layer F immediately above the end bias magnet films 11b1 to 11b7 and the central bias magnet films 11d1 to 11d6 does not change with respect to the external magnetic field to be measured, the resistance value of this part is external. It does not change in response to changes in the magnetic field.

  Thus, each of the narrow strip portions of the first X-axis GMR element 11 is disposed at both ends in the longitudinal direction of the free layer F (the magnetoresistive effect film including the free layer F and the fixed layer P) and is free. A pair of end bias magnet films for applying a bias magnetic field in a predetermined direction (any direction in the longitudinal direction) to the layer F, and a pair of end bias magnet films (approximately in the vicinity of the central portion). And a central bias magnet film for applying a bias magnetic field in the predetermined direction to the free layer F. Further, the central bias magnet film and the end bias magnet film are formed directly below (or directly above) the free layer F so as to be in direct contact with the free layer F without using a nonmagnetic material or the like.

  With the above configuration, the resistance value of the first X-axis GMR element 11 is acquired from the connection portion 11c1 and the connection portion 11c2 as the sum of the resistance values of the narrow strip portions 11a1 to 11a6. As a result, as shown in FIG. 5, the first X-axis GMR element 11 has a resistance value (X-axis) that changes approximately proportionally in the range of −Hc to + Hc with respect to the external magnetic field that changes along the X-axis. The resistance value increases as the magnitude of the external magnetic field in the positive direction increases, that is, the resistance value decreases as the magnitude of the external magnetic field in the X-axis negative direction increases. In addition, the first X-axis GMR element 11 exhibits a substantially constant resistance value with respect to an external magnetic field that changes along the Y-axis. That is, the magnetic detection direction of the first X-axis GMR element 11 is a direction along the fixed magnetization direction of the pinned layer.

  Referring to FIG. 1 again, the first X-axis GMR element 11 is formed in the vicinity of the X-axis negative direction end above the substantially central portion in the Y-axis direction of the substrate 10a. As described above, the fixed magnetization direction of the pinned layer of the first X-axis GMR element 11 is the negative X-axis direction. The second X-axis GMR element 12 is formed in the vicinity of the end of the X-axis negative direction below the central portion of the substrate 10a in the Y-axis direction, and the pinned layer has a fixed magnetization direction in the X-axis negative direction. . Therefore, the magnetic detection direction of the first X-axis GMR element 11 and the magnetic detection direction of the second X-axis GMR element 12 are both the X-axis direction.

  The third X-axis GMR element 13 is formed in the vicinity of the end in the X-axis positive direction above the center of the substrate 10a in the Y-axis direction, and the pinned layer has a fixed magnetization direction in the X-axis positive direction. . The fourth X-axis GMR element 14 is formed in the vicinity of the end of the X-axis positive direction at a position approximately below the center of the substrate 10a in the Y-axis direction, and the pinned layer has a fixed magnetization direction in the X-axis positive direction. . Accordingly, the magnetic detection direction of the third X-axis GMR element 13 and the magnetic detection direction of the fourth X-axis GMR element 14 are both the X-axis direction.

  The first Y-axis GMR element 21 is formed in the vicinity of the Y-axis positive direction end on the left side of the central portion of the substrate 10a in the X-axis direction, and the pinned layer has a fixed magnetization direction in the Y-axis positive direction. Yes. The second Y-axis GMR element 22 is formed in the vicinity of the Y-axis positive direction end on the right side of the central portion of the substrate 10a in the X-axis direction, and the pinned layer has a fixed magnetization direction in the Y-axis positive direction. Yes. Accordingly, the magnetic detection direction of the first Y-axis GMR element 21 and the magnetic detection direction of the second Y-axis GMR element 22 are both the Y-axis direction.

  The third Y-axis GMR element 23 is formed in the vicinity of the Y-axis negative direction end on the left side of the central portion of the substrate 10a in the X-axis direction, and the fixed magnetization direction of the pinned layer is the Y-axis negative direction. Yes. The fourth Y-axis GMR element 24 is formed in the vicinity of the Y-axis negative direction end on the right side of the central portion of the substrate 10a in the X-axis direction, and the pinned layer has a fixed magnetization direction in the Y-axis negative direction. Yes. Therefore, the magnetic detection direction of the third Y-axis GMR element 23 and the magnetic detection direction of the fourth Y-axis GMR element 24 are both the Y-axis direction.

  As shown in FIG. 1, the circuit unit 30 is formed in the substrate 10a at a substantially central portion of the substrate 10a. As will be described below, the circuit unit 30 connects the first to fourth X-axis GMR elements 11 to 14 in a full-bridge manner to extract the output Vox corresponding to the X-axis direction component of the external magnetic field, and outputs the first to fourth Y-axis GMR. The elements 21 to 24 are full-bridge connected to take an output Voy corresponding to the Y-axis direction component of the external magnetic field.

  That is, as shown in the equivalent circuit in FIG. 6A, the circuit unit 30 is a full-bridge connection of the first to fourth X-axis GMR elements 11 to 14, and the X-axis magnetic sensor (X-axis direction is the magnetic detection direction). A magnetic sensor). In FIG. 6A, the graphs shown at positions adjacent to the first to fourth X-axis GMR elements 11 to 14 are the characteristics of the GMR elements adjacent to the respective graphs (external magnetic field in the X-axis positive direction). Of the resistance value R with respect to the component Hx). Further, VB in the figure is a constant voltage generated by a constant voltage source (not shown) included in the magnetic sensor 10, and GND indicates a ground. As shown in FIG. 6B, the X-axis magnetic sensor configured in this way exhibits an output voltage Vox that changes substantially in proportion to the external magnetic field component Hx.

  In addition, as shown in the equivalent circuit in FIG. 7A, the circuit unit 30 connects the first to fourth Y-axis GMR elements 21 to 24 in a full-bridge connection, and a Y-axis magnetic sensor (Y-axis direction is a magnetic detection direction). A magnetic sensor). In FIG. 7A, the graphs shown at positions adjacent to the first to fourth Y-axis GMR elements 21 to 24 are the characteristics of the GMR elements adjacent to each graph (external magnetic field in the Y-axis positive direction). The change in resistance value R with respect to the component Hy of FIG. The meanings of VB and GND in the figure are the same as those in FIG. As shown in FIG. 7B, the Y-axis magnetic sensor configured in this way exhibits an output voltage Voy that changes approximately in proportion to the external magnetic field component Hy. The above is the configuration of the N-type magnetic sensor 10.

  Next, the magnetic sensor 50 called the S type according to the embodiment of the present invention will be briefly described. As shown in FIG. 8, the magnetic sensor 50 includes GMR elements 51 to 54 and 61 to 64 and a circuit unit 70. The configuration itself of these GMR elements is the same as that of the GMR element 11. The formation position of each GMR element, the magnetization direction of the pinned layer, and the magnetization direction of the free layer in the initial state are as shown in FIG. The magnetic sensor 50 has the same configuration as the magnetic sensor 10 and includes an X-axis magnetic sensor and a Y-axis magnetic sensor.

  That is, the X-axis magnetic sensor of the magnetic sensor 50 is formed by the first to fourth X-axis GMR elements 51 to 54 being full-bridge connected by the circuit unit 70 as shown in the equivalent circuit diagram of FIG. It is configured. Note that the meanings of the graphs and symbols in FIG. 9A are the same as those in FIG. As shown in FIG. 9B, the X-axis magnetic sensor configured in this way exhibits an output voltage Vox that changes approximately in proportion to the component Hx of the external magnetic field.

  The Y-axis magnetic sensor of the magnetic sensor 50 is configured by the first to fourth Y-axis GMR elements 61 to 64 being full-bridge connected by the circuit unit 70 as shown in the equivalent circuit diagram of FIG. ing. Note that the meanings of the graphs and symbols in FIG. 10A are the same as those in FIG. As shown in FIG. 10B, the Y-axis magnetic sensor configured in this way exhibits an output voltage Voy that changes approximately in proportion to the external magnetic field component Hy.

  Next, the state of magnetization of the free layer F, the central bias magnet film, and the end bias magnet film in each GMR element of the magnetic sensors 10 and 50 configured as described above will be described with reference to FIGS. To do. In this description, the first Y-axis GMR element 21 is selected as a representative example of the plurality of GMR elements described above. Each of FIG. 11A, FIG. 12A, and FIG. 13A shows a free layer 81 of one narrow strip portion of the plurality of narrow strip portions included in the first Y-axis GMR element 21, an end 4 is an enlarged plan view of partial bias magnet films 82 and 82 and a central bias magnet film 83. FIG.

  First, at the stage where these films are formed on the substrate, each of the free layer 81, the end bias magnet films 82 and 82, and the center bias magnet film 83, as indicated by the arrows in FIG. The magnetization directions of the magnetic domains are not aligned with the longitudinal direction of the free layer 81 (the initial state direction, the X-axis positive direction). The GMR element in such a state is applied by applying an external magnetic field H whose magnitude changes in the direction orthogonal to the longitudinal direction of the free layer 81 (magnetic field H with the Y-axis negative direction as the positive direction). When the resistance value is examined, as shown in FIG. 11B, hysteresis occurs in the change of the resistance value.

  In the magnetic sensor including the GMR element in this state, the resistance value when the external magnetic field is in the vicinity of “0” fluctuates within the range indicated by the arrow in FIG. As a result, such a magnetic sensor cannot accurately detect a minute magnetic field.

  Next, with respect to the GMR element in the state shown in FIG. 11A, the end bias magnet films 82 and 82 and the center bias magnet film 83 are arranged in the longitudinal direction of the free layer 81 (in this case, the X axis positive direction). A magnetic field having a magnitude larger than the holding force is applied, and the end bias magnet films 82 and 82 and the center bias magnet film 83 are magnetized. Thereby, as shown in FIG. 12A, the magnetization directions of the magnetic domains of the free layer 81, the end bias magnet films 82 and 82, and the central bias magnet film 83 are the magnetization directions in the initial state of the free layer 81. It corresponds to the direction (in this case, the positive direction of the X axis). The GMR element in this state exhibits a resistance value change without hysteresis as shown in FIG. Therefore, the magnetic sensor including the GMR element in which the end bias magnet films 82 and 82 and the center bias magnet film 83 are magnetized can detect a minute magnetic field with high accuracy.

  Next, with respect to the GMR element in which the end bias magnet films 82 and 82 and the center bias magnet film 83 are thus magnetized, the holding force of the end bias magnet films 82 and 82 and the center bias magnet film 83 is used. Is applied to an external magnetic field that is smaller but larger than the holding force of the free layer 81 and has the main component in the opposite direction (X-axis negative direction) to the initial state, and then extinguishes the external magnetic field .

  At this time, as shown in FIG. 13A, the free layer 81, the end bias magnet films 82 and 82, and the center bias magnet film 83 return to the same state as in FIG. That is, the magnetization directions of all the magnetic domains of the free layer 81 are returned to the initial state. In the GMR element in which the central bias magnet film 83 is not formed, as shown in FIG. 29A, the magnetization direction of each magnetic domain in the central portion surrounded by the broken line DL of the free layer 102 is in the initial state. In contrast, in the GMR element including the central bias magnet film 83, the magnetization direction of each magnetic domain reliably returns to the initial state even in the central portion surrounded by the broken line DL. As a result, as shown in FIG. 13B, the GMR element according to the embodiment of the present invention exhibits a resistance value change without hysteresis. Therefore, the magnetic sensors 10 and 50 including the GMR element can detect a minute magnetic field with high accuracy.

  Next, the magnetic coupling relationship between the free layer 81 and the central bias magnet film 83 will be described with reference to FIGS. As shown by the MH curve in FIG. 14, the central bias magnet film 83 has a large coercive force Hc (= Hc1) and does not change magnetization with respect to an external magnetic field (magnetically stable characteristic). have. As shown by the MH curve in FIG. 15, the free layer 81 has a characteristic that the coercive force Hc (= Hc2) is extremely small and changes sensitively to an external magnetic field (magnetically unstable characteristic). is doing.

  On the other hand, a film in which the free layer 81 and the central bias magnet film 83 are stacked without a nonmagnetic layer such as Ta is used, as shown by the MH curve in FIG. 16, the holding force Hc (= Hc3 ) Is large and has a characteristic that the magnetization does not change with respect to the external magnetic field (magnetically stable characteristic). That is, it is understood from FIG. 16 that when the free layer 81 is directly laminated on the magnetized central bias magnet film 83, the free layer 81 is magnetically coupled to the central bias magnet film 83 and becomes magnetically stable. Is done.

  Note that a film in which the free layer 81 and the central bias magnet film 83 are stacked via a nonmagnetic layer such as Ta has a two-fold folded magnetic hysteresis as shown by the MH curve in FIG. . This indicates that the magnetic coupling between the free layer 81 and the central bias magnet film 83 is weak. Accordingly, if a nonmagnetic layer such as Ta is interposed between the free layer 81 and the central bias magnet film 83, the central bias magnet film 83 changes the magnetization direction of the free layer 81 in the vicinity to the initial state. The ability to recover is reduced. From the above, in order to stably return the magnetization of the free layer 81 to the direction of the initial state, the free layer 81 and the central bias magnet film 83 are directly laminated without using a nonmagnetic layer such as Ta. It is understood that this is desirable.

(Production method)
Next, a method for manufacturing the magnetic sensors 10 and 50 configured as described above will be described. First, as shown in FIG. 18 which is a plan view, the GMR elements 11 to 14, 21 to 24, 51 to 54, 61 to 64 are formed on a rectangular substrate 10a-1 to be the substrates 10a and 50a later. A plurality of constituent films M are formed in an island shape. When the substrate 10a-1 is cut along the broken line in FIG. 18 and divided into the individual magnetic sensors 10 and 50 shown in FIG. 1 and FIG. -14, 21-24, 51-54, 61-64 are formed so as to be arranged at the respective positions shown in FIGS.

  Next, the magnet array MA shown in FIGS. 19 and 20 is prepared. FIG. 19 is a plan view of the magnet array MA. 20 is a cross-sectional view of the magnet array MA obtained by cutting the magnet array MA along a plane along line 2-2 in FIG. The magnet array MA includes a plate 91 made of transparent quartz glass and a plurality of permanent bar magnets 92... 92 each having a rectangular parallelepiped shape. The permanent bar magnets 92... 92 are arranged in a square lattice shape, and each upper surface is fixed to the lower surface of the plate 91. The permanent bar magnets 92... 92 are arranged so that the polarities of the magnetic poles appearing on the adjacent end faces at the shortest distance are different in the plane including the end faces of the permanent bar magnets 92.

  That is, the magnet array MA has a plurality of permanent bar magnets 92 each having a substantially rectangular parallelepiped shape and having a substantially square cross-sectional shape perpendicular to one central axis of the rectangular parallelepiped. And the polarities of the magnetic poles appearing on the same end face of each of the permanent bar magnets 92 arranged on the same end face of the other permanent bar magnets 92 adjacent to each other with a shortest distance. The magnet array is arranged and configured to be different from the polarity of the magnetic pole.

  FIG. 21 is a perspective view showing a state where only four permanent bar magnets 92... 92 are taken out. As is apparent from this figure, the direction of the end faces of the permanent bar magnets 92... 92 (the end face on which the magnetic poles are formed) is 90 degrees from one N pole to the S pole adjacent to the N pole at the shortest distance. Different magnetic fields are formed. In the present embodiment, this magnetic field is a magnetic field for fixing the magnetization direction of each of the fixed layers P (pinned layers of the fixed layers P) of the GMR elements 11 to 14, 21 to 24, 51 to 54, and 61 to 64. It is used as (magnetic field during heat treatment) and also as a magnetic field for magnetization of each end bias magnet film and center bias magnet film.

  First, as shown in FIG. 22, the substrate 10a-1 on which the film M to be a GMR element is formed is arranged so that the surface on which the film M is formed is in contact with the upper surface of the plate 91, and the plate 91 and the substrate 10a are arranged. -1 are fixed to each other by a clamp C.

  At this time, the substrate 10a-1 and the magnet array MA (plate 91) are relatively arranged as shown in FIG. 23, which is an enlarged plan view of portions that will later become the magnetic sensors 10, 50. That is, the intersection points CP of the cutting lines CL of the substrate 10a-1 serving as the sides of the magnetic sensors 10 and 50 coincide with the centers of gravity of the four permanent bar magnets 92. The substrate 10a-1 and the magnet array MA are relatively arranged. As a result, as indicated by arrows in FIG. 23, a magnetic field in a direction perpendicular to the longitudinal direction of the narrow strip portion of each film M is applied to each film M to be a GMR element.

  Then, the substrate 10a1 and the magnet array MA in this state are heated to 250 ° C. to 280 ° C. in a vacuum, and then left for about 4 hours. This treatment is called heat treatment. Thereby, the magnetization direction of the fixed layer P (the pinned layer of the fixed layer P) is fixed.

  Next, the relative positional relationship between the substrate 10a-1 on which the film M to be the GMR element is formed and the magnet array MA is changed as shown in the plan view of FIG. 24, and the film M to be the GMR element is formed. It arrange | positions so that a surface may contact | connect the upper surface of the plate 91. FIG. That is, the intersection CP of the cutting line CL of the substrate 10a-1 that becomes each side of the magnetic sensor 10, 50 is matched with the center of gravity of each end face on which the magnetic poles of the permanent bar magnets 92 ... 92 are formed. The substrate 10a-1 and the magnet array MA are relatively arranged. As a result, as indicated by the arrows in FIG. 24, the longitudinal direction of the narrow strip portion of each film M is formed on each film M to be the GMR elements 11 to 14, 21 to 24, 51 to 54, 61 to 64. The magnetic field is applied.

  As a result, the end bias magnet film and the center bias magnet film of each GMR element are magnetized. By this magnetization, the magnetization directions of the magnetic domains of these bias magnet films coincide with the magnetization directions in the initial state of the free layer F. Further, the magnetization direction of each magnetic domain in the portion to be the free layer F is also matched with the magnetization direction in the initial state of the free layer F.

  Next, the substrate 10a-1 is taken out, wiring and the like for connecting the respective films M are formed, and finally the substrate 10a-1 is cut along the broken line shown in FIG. As described above, a large number of magnetic sensors 10 and 50 shown in FIGS. 1 and 8 are manufactured at a time.

  As described above, in the embodiment of the magnetic sensor according to the present invention, the free magnetic field F is disposed at both ends in the longitudinal direction and a bias magnetic field in a predetermined direction (longitudinal direction of the free layer) is applied to the free layer. An end bias magnet film (11b1 to 11b7) made of a permanent magnet to be applied and a center bias magnet film (11d1 to 11d6) are provided. Therefore, the magnetic sensor can stably return and maintain the magnetization direction of each magnetic domain of the free layer in a state where no external magnetic field exists in a predetermined direction (initial state direction).

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, although the magnetoresistive effect element in the above embodiment is a GMR element including a spin valve film, the magnetoresistive effect element includes a free layer and a fixed layer including a pinned layer, stabilizes the magnetization direction of the magnetic domain of the free layer, and The present invention can be applied to other magnetoresistance effect elements that need to be returned to the initial state. For example, such an element includes a giant magnetoresistive element SAF of a synthetic spin valve film in which the fixed layer is replaced with a multilayer laminated fixed layer, or a magnetic layer formed by forming an insulating layer between a free layer and a fixed layer. A TMR element which is a tunnel effect element is included.

  Moreover, although the magnetic sensor of the said embodiment was comprised so that the magnetic field component of two orthogonal (X-axis and Y-axis) directions could be detected, the magnetic field of the direction of only one axis, or the direction of three or more axes. You may be comprised so that a component can be detected. The present invention can also be applied to a biaxial direction detection type magnetic sensor that can detect magnetic field components in directions intersecting each other at an angle other than 90 degrees.

  Furthermore, the GMR element included in the magnetic sensor of the above embodiment has a plurality of narrow band portions and a film shape in which these are connected in a zigzag shape, but as shown in FIG. 25 which is a plan view, You may consist of a film | membrane provided only with the linear strip | belt-shaped part. Further, the central bias magnet film need not be one between the pair of end bias magnet films. For example, as shown in FIG. 25, a pair of end bias magnets provided at both ends of the free layer 95 is provided. A plurality (two in the example of FIG. 25) of central bias magnet films 97 may be provided between the magnet films 96, 96.

  In addition, the GMR element included in the magnetic sensor of the above embodiment has a free layer formed on the center bias magnet film and the end bias magnet film formed on the substrate, but is fixed on the substrate. A layer, a spacer layer, and a free layer may be laminated in this order, and a central bias magnet film and an end bias magnet film may be formed on the free layer. In addition to the central bias magnet film of the present invention, an initialization coil that generates the bias magnetic field in a necessary portion of the free layer may be used in combination.

It is a top view of the magnetic sensor which concerns on embodiment of this invention. FIG. 2 is a partially enlarged plan view of the first X-axis GMR element shown in FIG. 1. It is the schematic sectional drawing which cut | disconnected the 1st X-axis GMR element in the plane in alignment with the 1-1 line | wire shown in FIG. It is the figure which showed the film | membrane structure of the 1st X-axis GMR element shown in FIG. 3 is a graph showing a change in resistance value of the first X-axis GMR element shown in FIG. 1. 6A is an equivalent circuit diagram of the X-axis magnetic sensor provided in the magnetic sensor shown in FIG. 1, and FIG. 6B is a graph showing the output characteristics of the sensor. FIG. 7A is an equivalent circuit diagram of the Y-axis magnetic sensor provided in the magnetic sensor shown in FIG. 1, and FIG. 7B is a graph showing the output characteristics of the sensor. It is a top view of another type of magnetic sensor concerning an embodiment of the present invention. FIG. 9A is an equivalent circuit diagram of the X-axis magnetic sensor provided in the magnetic sensor shown in FIG. 8, and FIG. 9B is a graph showing the output characteristics of the sensor. FIG. 10A is an equivalent circuit diagram of the Y-axis magnetic sensor provided in the magnetic sensor shown in FIG. 8, and FIG. 10B is a graph showing the output characteristics of the sensor. FIG. 11A is a plan view showing the magnetization state of the free layer and the bias magnet film before the bias magnet film is magnetized, and FIG. 11B is a GMR element before the bias magnet film is magnetized. It is the graph which showed the change of the resistance value with respect to the external magnetic field. FIG. 12A is a plan view showing a state of magnetization of the free layer and the bias magnet film in a state after the bias magnet film is magnetized, and FIG. 12B is a GMR element in the state after the magnetization of the bias magnet film. It is the graph which showed the change of the resistance value with respect to the external magnetic field. FIG. 13A is a plan view showing the magnetization state of the free layer and the bias magnet film after the bias magnet film is magnetized and after the application of the strong magnetic field, and FIG. 13B is the bias magnet film magnetized. It is the graph which showed the change of the resistance value with respect to the external magnetic field of the GMR element in the state after applying a strong magnetic field later. It is the graph which showed the MH curve of the center part bias magnet film. It is the graph which showed the MH curve of the free layer. It is the graph which showed the MH curve of the film | membrane which laminated | stacked the free layer directly on the center part bias magnet film | membrane. It is the graph which showed the MH curve of the film | membrane which laminated | stacked the free layer through the nonmagnetic layer on the center part bias magnet film | membrane. It is a top view of the board | substrate with which the spin valve film in the middle of manufacturing the magnetic sensor shown in FIG.1 and FIG.8 was formed. It is a top view of the magnet array used for manufacture of a magnetic sensor. It is sectional drawing of the same magnet array MA which cut | disconnected the magnet array in the plane along 2-2 of FIG. It is the perspective view which took out a part of magnet of the magnet array shown in FIG. It is the figure which showed one of the processes of manufacturing the magnetic sensor shown in FIG.1 and FIG.8. It is the conceptual diagram which showed the method of fixing the magnetization direction of the pinned layer of a GMR element. It is the conceptual diagram which showed the method of magnetizing the edge part bias magnet film and center part bias magnet film of a GMR element. It is a top view of the modification of the GMR element with which the magnetic sensor by this invention is provided. It is a longitudinal cross-sectional view of the conventional GMR element. 27A is a plan view showing the magnetization state of the free layer and the bias magnet film in the state before the bias magnet film magnetization of the GMR element shown in FIG. 26, and FIG. 27B is the GMR element. It is the graph which showed the change of the resistance value with respect to the external magnetic field. FIG. 28A is a plan view showing the magnetization state of the free layer and the bias magnet film in the state after magnetization of the bias magnet film of the GMR element shown in FIG. 26, and FIG. It is the graph which showed the change of the resistance value with respect to the external magnetic field. FIG. 29A is a plan view showing the magnetization state of the free layer and the bias magnet film in the state after the bias magnet film magnetization of the GMR element shown in FIG. B) is a graph showing a change in resistance value of the GMR element with respect to an external magnetic field.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,50 ... Magnetic sensor, 10a, 50a ... Board | substrate, 11-14, 21-24, 51-54, 61-64 ... GMR element, 11a1-11a6 ... Narrow strip | belt-shaped part, 11b1-11b7 ... End part bias magnet film , 11d1 to 11d6 ... center bias magnet film, 30, 70 ... circuit part, 81 ... free layer, 82, 82 ... end bias magnet film, 83 ... center bias magnet film, 92 ... permanent bar magnet (permanent magnet) 95: Free layer, 96, 96 ... End bias magnet film, 97 ... Center bias magnet film, 102 ... Free layer, 103 ... Spacer layer, 104 ... Fixed layer, 105, 105 ... Bias magnet film, F ... Free Layer, S ... Spacer layer, P ... Fixed layer including pinned layer, MA ... Magnet array.

Claims (3)

A magnetoresistive film including a pinned layer and a free layer; and a pair of end bias magnet films disposed at both ends of the magnetoresistive film and applying a bias magnetic field in a predetermined direction to the free layer; A magnetic sensor comprising a magnetoresistive effect element comprising:
A magnetic sensor further comprising a central bias magnet film disposed between the pair of end bias magnet films and applying a bias magnetic field in the predetermined direction to the free layer. The magnetic sensor according to claim 1,
The magnetoresistive film is formed in a narrow band shape having a longitudinal direction,
The predetermined direction is parallel to the longitudinal direction;
The center bias magnet film is a magnetic sensor formed in a shape having a longitudinal direction in the same direction as the longitudinal direction. The magnetic sensor according to claim 1 or 2, wherein
A magnetic sensor comprising at least two magnetoresistive elements, wherein the fixed magnetization directions of the pinned layers of the two magnetoresistive elements are orthogonal to each other.

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