Patent Publication Number: US-2022236344-A1

Title: Magnetic sensor

Description:
TECHNICAL FIELD 
     The present invention relates to a magnetic sensor. 
     BACKGROUND ART 
     As a conventional art described in a gazette, there is a magnetic impedance effect element including a magneto-sensitive part configured with plural rectangular soft magnetic material films provided with uniaxial anisotropy (refer to Patent Document 1). In the magnetic impedance effect element, plural magneto-sensitive parts are connected in series via conductor films. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent Application Laid-Open 
     Publication No. 2008-249406 
     SUMMARY OF INVENTION 
     Technical Problem 
     By the way, in the magnetic sensor that senses the magnetic field by the sensitive elements having the longitudinal directions and the short directions, the sensitive element having uniaxial magnetic anisotropy in the direction crossing the longitudinal direction, it is preferable to shorten the width of the sensitive element in the short direction and reduce the anisotropic magnetic field for improving the sensitivity. However, in the magnetic sensor in which the plural sensitive elements are connected in series, if the width of the sensitive element in the short direction is shortened, the impedance is increased, and thereby the sensitivity cannot be sufficiently improved in some cases. 
     An object of the present invention is to improve sensitivity while suppressing increase of the impedance in a magnetic sensor using a magnetic impedance effect as compared to the case where plural sensitive elements are connected in series. 
     Solution to Problem 
     A magnetic sensor to which the present invention is applied includes: a non-magnetic substrate; and a sensitive element part including plural sensitive elements connected in parallel, each of the sensitive elements being provided on the substrate, being composed of a soft magnetic material, having a longitudinal direction and a short direction, being provided with uniaxial magnetic anisotropy in a direction crossing the longitudinal direction, and sensing a magnetic field by a magnetic impedance effect. 
     In addition, in such a magnetic sensor, plural sensitive element parts arranged in the short direction with an interval and windingly connected in series may be provided. In this case, it is possible to improve the sensitivity of the magnetic sensor while suppressing increase in size of the magnetic sensor in the longitudinal direction. 
     Further, in such a magnetic sensor, the sensitive element part may include the plural sensitive elements arranged in the short direction with an interval, a width of the sensitive element in the short direction being smaller than the interval. In this case, for example, as compared to the case in which the width of the sensitive element in the short direction is larger than an interval between the sensitive element parts, the magnetic flux can be easily gathered to the sensitive element. 
     Still further, in such a magnetic sensor, a thin film magnet laminated between the substrate and the sensitive element part and applying a magnetic field in the longitudinal direction of the sensitive element of the sensitive element part may be provided. In this case, it is possible to measure the change in the magnetic field with high accuracy in the vicinity of the magnetic field applied by the thin film magnet. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to improve sensitivity while suppressing increase of the impedance in the magnetic sensor using the magnetic impedance effect as compared to the case where the plural sensitive elements are connected in series. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a specific example of a magnetic sensor to which the exemplary embodiment is applied; 
         FIG. 2  illustrates a specific example of a magnetic sensor to which the exemplary embodiment is applied; 
         FIG. 3  illustrates a specific example of a magnetic sensor to which the exemplary embodiment is applied; 
         FIG. 4  is a diagram illustrating a relation between a magnetic field applied in the longitudinal direction of a sensitive element part in a sensitive part of the magnetic sensor and an impedance of the sensitive part; 
         FIG. 5  shows diagrams illustrating configurations of a sensitive part in conventional magnetic sensors; 
         FIG. 6  is a diagram illustrating a relation between a magnetic field applied in the longitudinal direction of a sensitive element and an impedance of the sensitive part for the conventional magnetic sensor; and 
         FIGS. 7A to 7E  illustrate an example of a method of manufacturing the magnetic sensor. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an exemplary embodiment according to the present invention will be described with reference to attached drawings. 
       FIGS. 1 to 3  illustrate an example of a magnetic sensor  1  to which the exemplary embodiment is applied.  FIG. 1  is a plan view,  FIG. 2  is a cross-sectional view along the II-II line in  FIG. 1 , and  FIG. 3  is an enlarged view of the III part in  FIG. 1 . 
     As shown in  FIG. 2 , the magnetic sensor  1  to which the exemplary embodiment is applied includes: a thin film magnet  20  configured with a hard magnetic material (a hard magnetic material layer  103 ) provided on a nonmagnetic substrate  10 ; and a sensitive part  30  laminated to face the thin film magnet  20  and configured with a soft magnetic material (a soft magnetic material layer  105 ) to sense a magnetic field. Note that a cross-sectional structure of the magnetic sensor  1  will be described in detail later. 
     Here, the hard magnetic material has a large, so-called coercive force, the hard magnetic material being once magnetized by an external magnetic field, even upon removal of the external magnetic field, maintaining the magnetized state. On the other hand, the soft magnetic material has a small, so-called coercive force, the soft magnetic material being easily magnetized by an external magnetic field, but, upon removal of the external magnetic field, quickly returning to a state with no magnetization or a little magnetization. 
     Note that, in the present specification, an element constituting the magnetic sensor  1  (the thin film magnet  20  or the like) is indicated by a two-digit number, and a layer processed into an element (the hard magnetic material layer  103  or the like) is indicated by a number of one hundreds. Then, for a figure indicating an element, a figure indicating a layer processed into the element is written in parentheses. For example, the case of the thin film magnet  20  is written as thin film magnet  20  (hard magnetic material layer  103 ). In the figure, the case is written as  20  ( 103 ). The same is true in other cases. 
     Description will be given of a planar structure of the magnetic sensor  1  by  FIG. 1 . The magnetic sensor  1  has a quadrangular planar shape as a specific example. Here, the sensitive part  30  and yokes  40  formed at the uppermost portion of the magnetic sensor  1  will be described. The sensitive part  30  includes: plural sensitive element parts  31 ; serial connection parts  32  windingly performing serial connection of the adjacent sensitive element parts  31 ; and terminal parts  33  connected to supply the electrical current. In the sensitive part  30  of the magnetic sensor  1  shown in  FIG. 1 , the eight sensitive element parts  31  are provided. 
     Each sensitive element part  31  includes first sensitive elements  311  and second sensitive elements  312  each having the longitudinal direction and the short direction, the first sensitive elements  311  and the second sensitive elements  312  being arranged with an interval in the short direction. In addition, each sensitive element part  31  includes parallel connection parts  313  each performing parallel connection of the first sensitive element  311  and the second sensitive element  312 . Here, a horizontal direction in  FIG. 1  corresponds to the longitudinal direction, and a vertical direction in  FIG. 1  corresponds to the short direction. 
     The first sensitive element  311  and the second sensitive element  312  have, for example, the length in the longitudinal direction of 1 mm to 4 mm, the width in the short direction of 50 μm to 100 μm, and the thickness (the thickness of the soft magnetic material layer  105 ) of 0.5 μm to 5 μm. In addition, the interval between the first sensitive element  311  and the second sensitive element  312  in the short direction is 50 μm to 150 μm. Note that it is preferable that the widths of the first sensitive element  311  and the second sensitive element  312  in the short direction are small as compared to the interval between the first sensitive element  311  and the second sensitive element  312  in the short direction. 
     The parallel connection parts  313  of the sensitive element part  31  are located at both ends of the first sensitive element  311  and the second sensitive element  312  in the longitudinal direction to connect the first sensitive element  311  and the second sensitive element  312  in parallel. As shown in  FIG. 3 , each sensitive element part  31  is provided with two parallel connection parts  313 . 
     Note that the sensitive element part  31  of the exemplary embodiment includes the two sensitive elements (the first sensitive element  311  and the second sensitive element  312 ), but three or more sensitive elements may be connected in parallel. 
     The serial connection part  32  is provided between end portions of the adjacent sensitive element parts  31  and windingly performs serial connection of the adjacent sensitive element parts  31 . To additionally describe, the serial connection part  32  windingly performs serial connection of the sensitive element parts  31  each connecting the first sensitive elements  311  and the second sensitive elements  312  in parallel. 
     In the magnetic sensor  1  shown in  FIG. 1 , the eight sensitive element parts  31  are disposed side-by-side in parallel in the short direction, and therefore there are seven serial connection parts  32 . The number of serial connection parts  32  differs depending on the number of sensitive element parts  31 . For example, if there are two sensitive element parts  31 , there is one serial connection part  32 . In addition, if there is one sensitive element part  31 , no serial connection part  32  is provided. Note that the width of the serial connection part  32  may be set in accordance with the electrical current to be applied to the sensitive part  30 . In this specific example, the width of the serial connection part  32  is the same as the width of the first sensitive element  311  and the second sensitive element  312  of the sensitive element part  31  along the short direction. 
     The terminal parts  33  are provided to the (two) respective end portions of the sensitive element parts  31 , the end portions not being connected by the serial connection parts  32 . The terminal part  33  is drawn out of the end portion of the sensitive element part  31 , to which an electric wire for supplying the electrical current to the sensitive part  30  is connected. Note that, in the magnetic sensor  1  shown in  FIG. 1 , since there are eight sensitive element parts  31 , the two terminal parts  33  are provided on the right side in  FIG. 1 . In the case where the number of sensitive element parts  31  is an odd number, two terminal parts  33  may be divided to be provided into right and left. 
     Then, the sensitive element parts  31 , the serial connection parts  32  and the terminal parts  33  of the sensitive part  30  are integrally constituted by a single layer of the soft magnetic material layer  105 . The soft magnetic material layer  105  has conductivity, and therefore, it is possible to apply the electrical current from one terminal part  33  to the other terminal part  33 . 
     Note that the above-described numerical values, such as the length and the width of the first sensitive element  311  and the second sensitive element  312  and the number of sensitive elements to be disposed in parallel, are merely an example; the numerical values may be changed in accordance with the value of the magnetic field to be sensed or the soft magnetic material to be used. 
     Further, the magnetic sensor  1  includes yokes  40  each of which is provided to face the end portions of the sensitive element parts  31  in the longitudinal direction thereof. Here, there are provided two yokes  40   a  and  40   b , each of which is provided to face each of both end portions of the sensitive element parts  31  in the longitudinal direction thereof. Note that, in the case where the yokes  40   a  and  40   b  are not distinguished, the yokes are referred to as yokes  40 . The yoke  40  guides lines of magnetic force to the end portions of the sensitive elements  31  in the longitudinal direction thereof. Therefore, the yokes  40  are constituted by a soft magnetic material (the soft magnetic material layer  105 ) through which the lines of magnetic force are likely to pass. In other words, the sensitive part  30  and the yokes  40  are formed of a single layer of the soft magnetic material layer  105 . Note that, in the case where the lines of magnetic force sufficiently pass through in the longitudinal direction of the sensitive element parts  31  (the first sensitive elements  311  and the second sensitive elements  312 ), it is unnecessary to provide the yokes  40 . 
     From above, the size of the magnetic sensor  1  is several millimeters square in the planar shape. Note that the size of the magnetic sensor  1  may be other values. 
     Next, with reference to  FIG. 2 , the cross-sectional structure of the magnetic sensor  1  will be described. The magnetic sensor  1  is configured by laminating an adhesive layer  101 , a control layer  102 , the hard magnetic material layer  103  (the thin film magnet  20 ), a dielectric layer  104  and the soft magnetic material layer  105  (the sensitive part  30  and the yokes  40 ) in this order on the nonmagnetic substrate  10 . 
     The substrate  10  is composed of a non-magnetic material; for example, an oxide substrate, such as glass or sapphire, a semiconductor substrate, such as silicon, or a metal substrate, such as aluminum, stainless steel, or a nickel-phosphorus-plated metal, can be provided. 
     The adhesive layer  101  is a layer for improving adhesiveness of the control layer  102  to the substrate  10 . As the adhesive layer  101 , it is preferable to use an alloy containing Cr or Ni. Examples of the alloy containing Cr or Ni include CrTi, CrTa and NiTa. The thickness of the adhesive layer  101  is, for example, 5 nm to 50 nm. Note that, if there is no problem in adhesiveness of the control layer  102  to the substrate  10 , it is unnecessary to provide the adhesive layer  101 . Note that, in the present specification, composition ratios of alloys containing Cr or Ni are not shown. The same applies hereinafter. 
     The control layer  102  controls the magnetic anisotropy of the thin film magnet  20  constituted by the hard magnetic material layer  103  to be likely to express in the in-plane direction of the film. As the control layer  102 , it is preferable to use Cr, Mo or W, or an alloy containing thereof (hereinafter, referred to as an alloy containing Cr or the like to constitute the control layer  102 ). Specific examples of the alloy containing Cr or the like to constitute the control layer  102  include CrTi, CrMo, CrV and CrW. The thickness of the control layer  102  is, for example, 10 nm to 300 nm. 
     It is preferable that the hard magnetic material layer  103  constituting the thin film magnet  20  uses an alloy that contains Co as a main component and also contains at least one of Cr and Pt or contains both of Cr and Pt (hereinafter, referred to as a Co alloy constituting the thin film magnet  20 ). Examples of the Co alloy constituting the thin film magnet  20  include CoCrPt, CoCrTa, CoNiCr and CoCrPtB. Note that Fe may be contained. The thickness of the hard magnetic material layer  103  is, for example, 1 μm to 3 μm. 
     The alloy containing Cr or the like to constitute the control layer  102  has a bcc (body-centered cubic) structure. Consequently, the hard magnetic material constituting the thin film magnet  20  (the hard magnetic material layer  103 ) preferably has an hcp (hexagonal close-packed) structure easily causing crystal growth on the control layer  102  composed of the alloy containing Cr or the like having the bcc structure. When crystal growth of the hard magnetic material layer  103  having the hcp structure is caused on the bcc structure, the c-axis of the hcp structure is likely to be oriented in a plane. Therefore, the thin film magnet  20  configured with the hard magnetic material layer  103  is likely to have the magnetic anisotropy in the in-plane direction. Note that the hard magnetic material layer  103  is polycrystalline composed of a set of different crystal orientations, and each crystal has the magnetic anisotropy in the in-plane direction. The magnetic anisotropy is derived from crystal magnetic anisotropy. 
     Note that, to promote the crystal growth of the alloy containing Cr or the like to constitute the control layer  102  and the Co alloy constituting the thin film magnet  20 , the substrate  10  may be heated to 100° C. to 600° C. By the heating, the crystal growth of the alloy containing Cr or the like constituting the control layer  102  is likely to be caused, and thereby crystalline orientation is likely to be provided so that the hard magnetic material layer  103  having the hcp structure includes an axis of easy magnetization in a plane. In other words, the magnetic anisotropy is likely to be imparted in a plane of the hard magnetic material layer  103 . 
     The dielectric layer  104  is configured with a nonmagnetic dielectric material and electrically insulates the thin film magnet  20  and the sensitive part  30 . Specific examples of the dielectric material constituting the dielectric layer  104  include oxide, such as SiO 2 , Al 2 O 3 , or TiO 2 , or nitride, such as Si 2 N 4  or AlN. In addition, the thickness of the dielectric layer  104  is, for example, 0.1 μm to 30 μm. 
     Each of the first sensitive element  311  and the second sensitive element  312  in the sensitive element part  31  of the sensitive part  30  is provided with uniaxial magnetic anisotropy in a direction crossing the longitudinal direction, for example, the short direction intersecting the longitudinal direction (in other words, the width direction of the first sensitive element  311  and the second sensitive element  312 ). Note that the direction crossing the longitudinal direction may have an angle exceeding 45° with respect to the longitudinal direction. 
     As the soft magnetic material layer  105  constituting the sensitive part  30 , it is preferable to use an amorphous alloy, which is an alloy containing Co as a main component doped with a high melting point metal, such as Nb, Ta or W (hereinafter, referred to as a Co alloy constituting the sensitive part  30 ). Specific examples of the Co alloy constituting the sensitive part  30  include CoNbZr, CoFeTa and CoWZr. 
     The adhesive layer  101 , the control layer  102 , the hard magnetic material layer  103  and the dielectric layer  104  are processed to have a quadrangular planar shape (refer to  FIG. 1 ). Then, of the exposed side surfaces, in the two facing side surfaces, the thin film magnet  20  serves as the north pole ((N) in  FIG. 2 ) and the south pole ((S) in  FIG. 2 ). Note that the line connecting the north pole and the south pole of the thin film magnet  20  takes the longitudinal direction of the first sensitive element  311  and the second sensitive element  312  in the sensitive element part  31  of the sensitive part  30 . Here, to take the longitudinal direction means that an angle formed by the line connecting the north pole and the south pole and the longitudinal direction is less than 45°. Note that the smaller the angle formed by the line connecting the north pole and the south pole and the longitudinal direction, the better. 
     In the magnetic sensor  1 , the lines of magnetic force outputted from the north pole of the thin film magnet  20  once go to the outside of the magnetic sensor  1 . Then, a part of the lines of magnetic force passes through the first sensitive elements  311  and the second sensitive elements  312  of the sensitive element part  31  via the yoke  40   a  and goes to the outside again via the yoke  40   b . The lines of magnetic force that have passed through the first sensitive elements  311  and the second sensitive elements  312  return to the south pole of the thin film magnet  20  together with the lines of magnetic force that have not passed through the first sensitive elements  311  and the second sensitive elements  312 . In other words, the thin film magnet  20  applies the magnetic field (the bias magnetic field Hb to be described later) to the longitudinal direction of the first sensitive element  311  and the second sensitive element  312  in the sensitive element part  31 . 
     Note that the north pole and the south pole of the thin film magnet  20  are collectively referred to as both magnetic poles, and when the north pole and the south pole are not distinguished, they are referred to as a magnetic pole. 
     Note that, as shown in  FIG. 1 , the yoke  40  (the yokes  40   a  and  40   b ) is configured so that the shape thereof as viewed from the front surface side of the substrate  10  is narrowed as approaching the sensitive part  30 . This is to concentrate the magnetic field to (to gather the lines of magnetic force on) the sensitive part  30 . In other words, the magnetic field in the sensitive part  30  is strengthened to further improve the sensitivity. Note that the width of the portion of the yoke  40  (the yokes  40   a  and  40   b ) facing the sensitive part  30  may not be narrowed. 
     Here, the interval between the yoke  40  (the yokes  40   a  and  40   b ) and the sensitive parts  30  may be, for example, 1 μm to 100 μm. 
     (Action of Magnetic Sensor  1 ) 
     Subsequently, action of the magnetic sensor  1  in the exemplary embodiment will be described.  FIG. 4  is a diagram illustrating a relation between the magnetic field applied in the longitudinal direction of the sensitive element parts  31  in the sensitive part  30  of the magnetic sensor  1  and the impedance of the sensitive part  30 . In  FIG. 4 , the horizontal axis indicates the magnetic field H, and the vertical axis indicates the impedance Z. The impedance Z of the sensitive part  30  is measured by passing a high-frequency current between two terminal parts  33 . 
     Note that, in the magnetic sensor  1  with the characteristics shown in  FIG. 4 , the sensitive part  30  and the yokes  40  are configured with the soft magnetic material layer  105  composed of Co 85 Nb 12 Zr 3  with a thickness of 1.5 μm. In addition, the first sensitive element  311  and the second sensitive element  312  of the sensitive element part  31  have the width of 50 μm and the length of 3 mm. Also, the interval between the first sensitive element  311  and the second sensitive element  312  in the sensitive element part  31 , and the interval between the first sensitive element  311  and the second sensitive element  312  between the adjacent sensitive element parts  31 , is 75 μm. Further, both the serial connection part  32  and the parallel connection part  313  of the sensitive element part  31  have a width of 50 μm. 
     Moreover,  FIG. 4  shows the result measured by passing the high-frequency current of 100 MHz between the terminal parts  33  of the sensitive part  30 . 
     As shown in  FIG. 4 , the impedance Z of the sensitive part  30  is changed, increased or decreased, as the absolute value of the magnetic field H increases in the positive direction or the negative direction, with a boundary of the magnetic field H being 0 (H=0). Moreover, the amount of change in the impedance Z (in other words, the slope of the graph) in relation to the change in the magnetic field H depends on the magnitude of magnetic field H. 
     Consequently, by use of a portion where the amount of change ΔZ in the impedance Z with respect to the amount of change ΔH in the magnetic field H to be applied is steep (in other words, the portion where ΔZ/ΔH is large), it is possible to extract extremely weak change in the magnetic field H as the amount of change ΔZ in the impedance Z. In  FIG. 4 , the magnetic field H, where the amount of change ΔZ of the impedance to the amount of change ΔH of the magnetic field H (ΔZ/ΔH) is the maximum, is shown as the magnetic field Hb. In the magnetic sensor  1 , it is possible to measure the amount of change ΔH of the magnetic field H in the vicinity of the magnetic field Hb with high accuracy. The magnetic field Hb is referred to as a bias magnetic field in some cases. 
     Note that, in the following description, ΔZ/ΔH, which is the slope of the graph in the magnetic field Hb (in other words, the maximum ΔZ/ΔH), is referred to as S max  in some cases. In addition, in some cases, the impedance Z in the magnetic field Hb is referred to as the impedance Zb, and the impedance in the case where the magnetic field H is not applied (H=0) is referred to as the impedance Z0. Further, the magnetic field H, where the impedance Z takes the maximum value, is sometimes referred to as an anisotropic magnetic field Hk. 
     It can be said that the sensitivity of the magnetic sensor  1  measuring the amount of change ΔH in the magnetic field H based on the relation between the magnetic field H and the impedance Z is favorable as the value of S max /Zb is larger. Therefore, to increase the sensitivity of the magnetic sensor  1 , it is preferable to increase S max  or decrease the impedance Zb. 
     Here, in the magnetic sensor  1 , according to the relation between the magnetic field H and the impedance Z shown in  FIG. 4 , there is a tendency that, by reducing the anisotropic magnetic field Hk without changing the maximum value of the impedance Z, the amount of change ΔZ in the impedance Z becomes steep and S max  is increased. 
     In general, the sensitive element with the longitudinal direction and the short direction, the short direction being provided with uniaxial magnetic anisotropy, has magnetic shape anisotropy, which arises from the shape of the sensitive element, in the longitudinal direction. Then, as the length of the sensitive element in the short direction (hereinafter, referred to as the width of the sensitive element in some cases) is small, the magnetic shape anisotropy in the longitudinal direction is increased. In other words, as the width of the sensitive element is reduced, the anisotropic magnetic field Hk becomes smaller and S max  becomes larger. 
     However, in a conventional magnetic sensor in which plural sensitive elements are windingly and serially connected, by simply reducing the width of each sensitive element, while the anisotropic magnetic field Hk is reduced and S max  is increased, the resistance value of each sensitive element rises and the impedance Zb in the magnetic field Hb is increased. In this case, it becomes difficult to sufficiently increase S max /Zb, and thereby desired sensitivity sometimes cannot be obtained in the magnetic sensor. 
     In contrast thereto, as described above, in the magnetic sensor  1  of the exemplary embodiment, the sensitive element part  31  of the sensitive part  30  has a configuration in which the first sensitive elements  311  and the second sensitive elements  312  are connected in parallel. This makes it possible for the magnetic sensor  1  of the exemplary embodiment to decrease the anisotropic magnetic field Hk and increase S max  while suppressing the rise of the impedance Zb in the magnetic field Hb by, for example, adjusting the widths of the first sensitive element  311  and the second sensitive element  312 . Consequently, the sensitivity of the magnetic sensor  1  can be improved. 
     Subsequently, action of the magnetic sensor  1  of the exemplary embodiment will be described in more detail as compared to the conventional magnetic sensor in which the plural sensitive elements are windingly and serially connected. 
       FIGS. 5A and 5B  are diagrams illustrating configurations of the sensitive parts  30  in conventional magnetic sensors. In  FIGS. 5A and 5B , the same reference signs are used for the same configurations as the magnetic sensor  1  of the exemplary embodiment shown in  FIGS. 1 to 3 . In addition,  FIGS. 6A and 6B  illustrate, for the conventional magnetic sensors with the sensitive parts  30  having the structures shown in  FIGS. 5A and 5B , respectively, the relations between the magnetic field applied in the longitudinal direction of the sensitive element  310 , which will be described later, and the impedance of the sensitive part  30 . In  FIGS. 6A and 6B , the horizontal axis indicates the magnetic field H, and the vertical axis indicates the impedance Z. In addition, in the following description, a conventional magnetic sensor, which includes the sensitive part  30  shown in  FIG. 5A  and whose property is shown in  FIG. 6A , is referred to as a conventional magnetic sensor A. Similarly, a conventional magnetic sensor, which includes the sensitive part  30  shown in  FIG. 5B  and whose property is shown in  FIG. 6B , is referred to as a conventional magnetic sensor B. 
     As shown in  FIGS. 5A and 5B , the sensitive part  30  of the conventional magnetic sensors A and B includes: plural (in these examples, eight) sensitive elements  310 ; plural (in these examples, seven) serial connection parts  32  that windingly perform serial connection of the plural sensitive elements  310 ; and the terminal parts  33 . 
     Here, in the magnetic sensor A, the width of the sensitive element  310  and the serial connection part  32  of the sensitive part  30  is 100 μm, and the interval between the sensitive elements  310  is 150 μm. In addition, in the magnetic sensor B, the width of the sensitive element  310  and the serial connection part  32  of the sensitive part  30  is 50 μm, and the interval between the sensitive elements  310  is 75 μm. Note that the conventional magnetic sensors A and B include the same configuration as the magnetic sensor  1  of the exemplary embodiment having the property shown in  FIG. 4 , except for the shape of the sensitive part  30 . 
     Table 1 shows values of the anisotropic magnetic field Hk, the impedance Z0, the impedance Zb, S max  (=AZ/AH) and S max /Zb in each graph shown in  FIGS. 4, 6A and 6B , for the magnetic sensor  1  of the exemplary embodiment and the conventional magnetic sensors A and B. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Width of 
                 Hk 
                 Z0 
                 Zb 
                 S max   
                 S max /Zb 
               
               
                   
                 sensitive element 
                 (Oe) 
                 (Ω) 
                 (Ω) 
                 (Ω/Oe) 
                 (%/Oe) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Magnetic 
                 50 μm × 2 
                 8.8 
                 36 
                 76.9 
                 88 
                 115 
               
               
                 sensor 1 
                 (parallel) 
                   
                   
                   
                   
                   
               
               
                 Magnetic 
                 100 μm 
                 10.1 
                 32 
                 111.5 
                 74 
                 66 
               
               
                 sensor A 
                   
                   
                   
                   
                   
                   
               
               
                 Magnetic 
                  50 μm 
                 8.6 
                 66 
                 145.4 
                 174 
                 120 
               
               
                 sensor B 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1, in the magnetic sensor  1  of the exemplary embodiment, in which the first sensitive elements  311  and the second sensitive elements  312  with the width of 50 μm are connected in parallel, the anisotropic magnetic field Hk is reduced as compared to the conventional magnetic sensor A, in which the sensitive elements  310  with the width of 100 μm are connected in series. To additionally describe, in the magnetic sensor  1  of the exemplary embodiment and the conventional magnetic sensor A, irrespective of the equal sum of the widths in the short direction of the sensitive elements (the first sensitive element  311 , the second sensitive element  312 , and the sensitive element  310 ) constituting the sensitive part  30 , the anisotropic magnetic field Hk in the magnetic sensor  1  of the exemplary embodiment is reduced as compared to the conventional magnetic sensor A. As a result, in the magnetic sensor  1  of the exemplary embodiment, S max  rises and S max /Zb is improved, as compared to the conventional magnetic sensor A. 
     In other words, the magnetic sensor  1  of the exemplary embodiment has the configuration, in which the plural sensitive elements (the first sensitive elements  311  and the second sensitive elements  312 ) are connected in parallel; consequently, the sensitivity can be improved. 
     In addition, as shown in Table 1, in the magnetic sensor  1  of the exemplary embodiment, in which the first sensitive elements  311  and the second sensitive elements  312  with the width of 50 μm are connected in parallel, the impedances Zb and Z0 are reduced as compared to the conventional magnetic sensor B, in which the sensitive elements  310  with the width of 50 μm are connected in series. To additionally describe, in the magnetic sensor  1  of the exemplary embodiment and the conventional magnetic sensor B, irrespective of the equal widths in the short direction of each sensitive element (the first sensitive element  311 , the second sensitive element  312 , and the sensitive element  310 ), the impedances Zb and Z0 in the magnetic sensor  1  of the exemplary embodiment is reduced as compared to the conventional magnetic sensor B. 
     On the other hand, the anisotropic magnetic field Hk of the magnetic sensor  1  of the exemplary embodiment is at the same level as that of the conventional magnetic sensor B, and the sensitivity of the magnetic sensor  1  (S max /Zb) is also at the same level as that of the conventional magnetic sensor B. 
     In other words, in the magnetic sensor  1  of the exemplary embodiment, it is possible to set the impedances Zb and Z0 within desired ranges while suppressing decrease of the sensitivity (S max /Zb) by adjusting the widths of the first sensitive element  311  and the second sensitive element  312  in the short direction. 
     In general, in a detection circuit detecting changes in the magnetic field by use of the magnetic sensor  1 , there are preferable ranges for the impedances Zb and Z0 due to differences in the circuit configuration and the like. In the exemplary embodiment, it is possible to realize the magnetic sensor  1  tailored to the circuit configuration, etc., of the detection circuit by adjusting the widths of the first sensitive element  311  and the second sensitive element  312  in the short direction. 
     Here, in the magnetic sensor  1  of the exemplary embodiment, as compared to the width of the first sensitive element  311  and the second sensitive element  312 , the interval between the adjacent first sensitive element  311  and second sensitive element  312  is large. Consequently, for example, as compared to the case in which the interval between the adjacent first sensitive element  311  and second sensitive element  312  is smaller than the width of the first sensitive element  311  and the second sensitive element  312 , the magnetic flux can be easily gathered to each first sensitive element  311  and each second sensitive element  312 . This can further improve the sensitivity of the magnetic sensor  1 . 
     (Method of Manufacturing Magnetic Sensor  1 ) 
     Next, an example of a method of manufacturing the magnetic sensor  1  will be described. 
       FIGS. 7A to 7E  illustrate the specific example of the method of manufacturing the magnetic sensor  1 .  FIGS. 7A to 7E  show respective processes in the method of manufacturing the magnetic sensor  1 . The processes proceed in the order of  FIGS. 7A to 7E .  FIGS. 7A to 7E  show representative processes, and other processes may be included. The processes proceed in the order of  FIGS. 7A to 7E .  FIGS. 7A to 7E  correspond to the cross-sectional view cut along the II-II line in  FIG. 1  shown in  FIG. 2 . 
     As described above, the substrate  10  is composed of a non-magnetic material; for example, an oxide substrate, such as glass or sapphire, a semiconductor substrate, such as silicon, or a metal substrate, such as aluminum, stainless steel, or a nickel-phosphorus-plated metal, can be provided. On the substrate  10 , for example, streaky grooves or streaky asperities with the radius of curvature Ra of 0.1 nm to 100 nm may be provided by use of a polisher or the like. Note that it is preferable to provide the streaks of the streaky grooves or the streaky asperities in a direction connecting the north pole and the south pole of the thin film magnet  20  configured with the hard magnetic material layer  103 . By doing so, the crystal growth in the hard magnetic material layer  103  is promoted in the direction of the grooves. Consequently, the axis of easy magnetization of the thin film magnet  20  configured with the hard magnetic material layer  103  is more likely to face the groove direction (the direction connecting the north pole and the south pole of the thin film magnet  20 ). In other words, magnetization of the thin film magnet  20  is made easier. 
     Here, as an example, the substrate  10  will be described as glass having a diameter of about 95 mm and a thickness of about 0.5 mm. In the case where the planar shape of the magnetic sensor  1  is several millimeters square, plural magnetic sensors  1  are collectively manufactured on the substrate  10 , and thereafter, divided (cut) into individual magnetic sensors  1 . In  FIGS. 7A to 7E , attention is focused on one magnetic sensor  1  depicted at the center, and a part of each of the adjacent magnetic sensors  1  on the right and left sides is also shown. Note that the border between the adjacent magnetic sensors  1  is indicated by a long-dot-and-dash line. 
     As shown in  FIG. 7A , after washing the substrate  10 , on one of the surfaces (hereinafter, referred to as a front surface) of the substrate  10 , the adhesive layer  101 , the control layer  102 , the hard magnetic material layer  103  and the dielectric layer  104  are deposited (accumulated) in order, to thereby form a laminated body. 
     First, the adhesive layer  101  that is an alloy containing Cr or Ni, the control layer  102  that is an alloy containing Cr and the like, the hard magnetic material layer  103  that is a Co alloy constituting the thin film magnet  20  are continuously deposited (accumulated) in order. The deposition can be performed by a sputtering method or the like. The substrate  10  is moved to face plural targets formed of respective materials in order, and thereby the adhesive layer  101 , the control layer  102  and the hard magnetic material layer  103  are laminated on the substrate  10  in order. As described above, in forming the control layer  102  and the hard magnetic material layer  103 , the substrate  10  may be heated to, for example, 100° C. to 600° C. for accelerating the crystal growth. 
     Note that, in deposition of the adhesive layer  101 , the substrate  10  may be heated or may not be heated. To remove the moisture and so forth absorbed onto the surface of the substrate  10 , the substrate  10  may be heated before the adhesive layer  101  is deposited. 
     Next, the dielectric layer  104 , which is oxide, such as SiO 2 , Al 2 O 3 , or TiO 2 , or nitride, such as Si 2 N 4  or AlN is deposited (accumulated). Deposition of the dielectric layer  104  can be performed by a plasma CVD method, a reactive sputtering method or the like. 
     Then, as shown in  FIG. 7B , a pattern by photoresist (a resist pattern)  111 , which has an opening serving as a portion where the sensitive part  30  and the yokes  40  (the yokes  40   a  and  40   b ) are formed, is formed by a publicly known photolithography technique. 
     Then, as shown in  FIG. 7C , the soft magnetic material layer  105  that is a Co alloy constituting the sensitive part  30  is deposited (accumulated). The deposition of the soft magnetic material layer  105  can be performed by using, for example, the sputtering method. 
     As shown in  FIG. 7D , the resist pattern  111  is removed, and the soft magnetic material layer  105  on the resist pattern  111  is also removed (lifted-off). Consequently, the sensitive part  30  and the yokes  40  (the yoke  40   a  and  40   b ) constituted by the soft magnetic material layer  105  are formed. In other words, the sensitive part  30  and the yokes  40  are formed by a single deposition of the soft magnetic material layer  105 . 
     Thereafter, the uniaxial magnetic anisotropy is imparted to the soft magnetic material layer  105  in the width direction of the first sensitive element  311  and the second sensitive element  312  (for both, refer to  FIG. 3 ) in the sensitive element part  31  of the sensitive part  30 . The impartation of the uniaxial magnetic anisotropy to the soft magnetic material layer  105  can be performed by heat treatment at 400° C. in a rotating magnetic field of, for example, 3 kG (0.3 T) (heat treatment in the rotating magnetic field) and by heat treatment at 400° C. in a static magnetic field of 3 kG (0.3 T) (heat treatment in the static magnetic field) subsequent thereto. At this time, the soft magnetic material layer  105  constituting the yokes  40  is provided with the similar uniaxial magnetic anisotropy. However, the yokes  40  just have to play a role of a magnetic circuit and may not be provided with the uniaxial magnetic anisotropy. 
     Next, the hard magnetic material layer  103  constituting the thin film magnet  20  is magnetized. Magnetizing of the hard magnetic material layer  103  can be performed by, in the static magnetic field or in a pulsed magnetic field, continuously applying a magnetic field larger than a coercive force of the hard magnetic material layer  103  until magnetization of the hard magnetic material layer  103  becomes saturated. 
     Thereafter, as shown in  FIG. 7E , the plural magnetic sensors  1  formed on the substrate  10  is divided (cut) into the individual magnetic sensors  1 . In other words, as shown in the plan view of  FIG. 1 , the substrate  10 , the adhesive layer  101 , the control layer  102 , the hard magnetic material layer  103 , the dielectric layer  104  and the soft magnetic material layer  105  are cut to have a quadrangular planar shape. Then, on the side surfaces of the hard magnetic material layer  103  that has been divided (cut), magnetic poles (the north pole and the south pole) of the thin film magnet  20  are exposed. Thus, the magnetized hard magnetic material layer  103  serves as the thin film magnet  20 . The division (cutting) can be performed by a dicing method, a laser cutting method or the like. 
     Note that, before the process of dividing the plural magnetic sensors  1  into the individual magnetic sensors  1  shown in  FIG. 7E , the adhesive layer  101 , the control layer  102 , the hard magnetic material layer  103 , the dielectric layer  104 , and the soft magnetic material layer  105  between the adjacent magnetic sensors  1  on the substrate  10  may be removed by etching so that the planar shape of the magnetic sensor  1  is quadrangular (the planar shape of the magnetic sensor  1  shown in  FIG. 1 ). Then, the exposed substrate  10  may be divided (cut). 
     Moreover, after the process of forming the laminated body shown in  FIG. 7A , the adhesive layer  101 , the control layer  102 , the hard magnetic material layer  103  and the dielectric layer  104  may be processed so that the planar shape of the magnetic sensor  1  is quadrangular (the planar shape of the magnetic sensor  1  shown in  FIG. 1 ). 
     Note that the processes in the manufacturing method shown in  FIGS. 7A to 7E  are simplified as compared to these manufacturing methods. 
     In this manner, the magnetic sensor  1  is manufactured. Note that impartation of the uniaxial magnetic anisotropy to the soft magnetic material layer  105  and/or magnetization of the thin film magnet  20  may be performed on the magnetic sensor  1  or plural magnetic sensors  1  after the process of dividing the magnetic sensor  1  into the individual magnetic sensors  1  shown in  FIG. 7E . 
     Note that, in the case where the control layer  102  is not provided, it becomes necessary to impart the magnetic anisotropy in a plane by causing the crystal growth by heating the hard magnetic material layer  103  to not less than 800° C. after the hard magnetic material layer  103  was deposited. However, in the case where the control layer  102  is provided as in the magnetic sensor  1  to which the first exemplary embodiment is applied, since the crystal growth is accelerated by the control layer  102 , the crystal growth caused by high temperature, such as not less than 800° C., is not required. 
     In addition, impartation of the uniaxial magnetic anisotropy to the first sensitive element  311  and the second sensitive element  312  may be performed in depositing the soft magnetic material layer  105 , which is a Co alloy constituting the sensitive part  30 , by use of a magnetron sputtering method, instead of being performed in the above-described heat treatment in the rotating magnetic field and heat treatment in the static magnetic field. In the magnetron sputtering method, a magnetic field is formed by using magnets and electrons generated by discharge are enclosed on a surface of a target. This increases collision probability of electrons and gases to accelerate ionization of gases, to thereby improve deposition rate of a film. By the magnetic field formed by the magnets used in the magnetron sputtering method, the soft magnetic material layer  105  is deposited, and at the same time, the uniaxial magnetic anisotropy is imparted to the soft magnetic material layer  105 . By doing so, it is possible to omit the process of imparting the uniaxial magnetic anisotropy in the heat treatment in the rotating magnetic field and the heat treatment in the static magnetic field. 
     So far, the exemplary embodiment has been described; however, various modifications may be available without deviating from the gist of the present invention. 
     For example, the sensitive part  30  may be configured with plural soft magnetic material layers  105 , the soft magnetic material layers being antiferromagnetically-coupled with a demagnetizing field suppressing layer composed of Ru or an Ru alloy interposed therebetween. This improves the magnetic impedance effect by the sensitive element part  31  (the first sensitive elements  311  and the second sensitive elements  312 ), and thereby improves the sensitivity of the magnetic sensor  1 . 
     REFERENCE SIGNS LIST 
     
         
           1  Magnetic sensor 
           10  Substrate 
           20  Thin film magnet 
           30  Sensitive part 
           31  Sensitive element part 
           32  Serial connection part 
           33  Terminal part 
           40 ,  40   a ,  40   b  Yoke 
           101  Adhesive layer 
           102  Control layer 
           103  Hard magnetic material layer 
           104  Dielectric layer 
           105  Soft magnetic material layer 
           311  First sensitive element 
           312  Second sensitive element