Abstract:
A head slider arranged opposite to a storage medium, includes: a slider body, an insulating nonmagnetic layer laminated on a trailing edge of the slider body, and a head element embedded in the nonmagnetic film. A front edge of the head element is exposed at a top surface of the rail. A heater embedded in the nonmagnetic film near the head element, causes the head element to bulge at the top surface of the rail. A protection film is laminated on the top surface of the rail, and at least one protrusion is configured to protrude from a surface of the protection film and come close to the storage medium as compared with the top surface of the protection film when the head element bulges. The protrusion is used to determine how much to heat the film to bring the head element as close to the storage medium as possible.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present technique relates to head sliders arranged in storage medium drives such as hard disk drives (HDDs), and more particularly to a head slider having a heater embedded in a nonmagnetic film corresponding to a head element. 
         [0003]    2. Description of the Related Art 
         [0004]    In a head slider, for example, a nonmagnetic film made of Al 2 O 3  (alumina) is laminated on a slider body made of Al 2 O 3 —Tic (alumina-titanium carbide, AlTic). The nonmagnetic film has a head element and a heater embedded therein. The surface of the nonmagnetic film is covered with, for example, a protection film made of diamond like carbon (DLC). The head element is thus covered with the protection film. 
         [0005]    The heater applies heat to a thin-film coil pattern provided in the head element. The thin-film coil pattern linearly expands accordingly, and hence, a read gap and a write gap of the head element can come close to a magnetic disk. A flying height of the head element is determined on the basis of a bulging amount of the thin-film coil pattern. 
         [0006]    To determine the bulging amount, zero calibration is performed. Reference documents are Japanese Laid-open Patent Publication No. 2003-203321, Japanese translation of PCT international application Publication No. 2002-500798, Japanese Laid-open Patent Publication No. 2002-117509, Japanese Laid-open Patent Publication No. 05-20635, and US2005/0057841. 
         [0007]    In the zero calibration process, the bulging amount of the thin-film coil pattern is gradually increased. When the protection film comes into contact with the magnetic disk, the bulging amount of the thin-film coil pattern is obtained. A most suitable bulging amount for reading and writing can be determined on the basis of the obtained bulging amount. 
         [0008]    During the zero calibration process, the protection film comes into contact with the magnetic disk. As the contact is repeated, the protection film may be subjected to wear. The wear may reduce the thickness of the protection film. As a result, the protection film can no longer effectively protect the head element. For example, the head element may be subjected to corrosion under a high temperature and humidity environment. The characteristics of the head element may be deteriorated. 
         [0009]    The present technique is provided in light of the situations described above, and an object of the technique is to provide a head slider and a storage medium drive capable of preventing a head element from being damaged in this manner. 
       SUMMARY 
       [0010]    The disclosed technique was produced for solving the problems due to the foregoing related techniques. A head slider arranged opposite to a storage medium has a slider body, an insulating nonmagnetic layer laminated on a trailing edge of the slider body, and a rail formed on a medium-opposing surface of the slider body and extending from the slider body to the nonmagnetic film. A head element is embedded in the nonmagnetic film, a front edge of the head element being exposed at a top surface of the rail. A heater is embedded in the nonmagnetic film, the heater causing the head element to bulge at the top surface of the rail. A protection film is laminated on the top surface of the rail, and a protrusion is configured to protrude from a surface of the protection film and come closer to the storage medium than the top surface of the protection film when the head element bulges. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a plan view schematically showing the inner structure of a hard disk drive, which is a storage medium drive according to an embodiment of the present technique. 
           [0012]      FIG. 2  is a perspective view schematically showing the structure of a flying head slider arranged in the storage medium drive. 
           [0013]      FIG. 3  is a partially-enlarged perspective view schematically showing the structure of a rear rail. 
           [0014]      FIG. 4  is a partially-enlarged cross-sectional view schematically showing the structure of the rear rail. 
           [0015]      FIG. 5  is a front elevation view schematically showing the structure of an electromagnetic conversion element mounted on the flying head slider. 
           [0016]      FIG. 6  is an enlarged cross-sectional view taken along the line VI-VI in  FIG. 5 . 
           [0017]      FIG. 7  is an enlarged cross-sectional view taken along the line VII-VII in  FIG. 6 . 
           [0018]      FIG. 8  is a cross-sectional view of the rear rail for schematically showing “a bulge” formed at the flying head slider. 
           [0019]      FIG. 9  is a rear elevation of the rear rail for schematically showing “the bulge” formed at the flying head slider. 
           [0020]      FIG. 10  is a block diagram showing a control system of the hard disk drive relating to a heating wire, and the electromagnetic conversion element mounted on the flying head slider. 
           [0021]      FIG. 11  is a cross-sectional view schematically showing a state where protrusions come into contact with a magnetic disk. 
           [0022]      FIG. 12  is a rear elevation schematically showing the state where the protrusions come into contact with the magnetic disk. 
           [0023]      FIG. 13  is an enlarged cross-sectional view schematically showing the structure of a heating wire according to another embodiment. 
           [0024]      FIG. 14  is a rear elevation schematically showing a state where protrusions come into contact with a magnetic disk. 
           [0025]      FIG. 15  is a cross-sectional view schematically showing first and second regions of a nonmagnetic film. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]      FIG. 1  schematically shows the inner structure of a hard disk drive (HDD) (storage medium drive)  11  according to an embodiment of the present technique. The hard disk drive  11  includes a housing (case)  12 . The housing  12  has a box-like base  13  and a cover (not shown). The base  13  defines, for example, a flat rectangular-parallelepiped inner space, or housing space. The base  13  may be formed by casting using a metal material such as aluminum. The cover is coupled to the opening of the base  13 . The housing space is sealed with the cover and the base  13 . The cover may be formed, for example, by pressing using a plate member. 
         [0027]    The housing space houses at least a magnetic disk  14  as a storage medium. The magnetic disk  14  is mounted to a rotating shaft of a spindle motor  15 . The spindle motor  15  can rotate the magnetic disk  14  at a high speed of, for example, 5400, 7200, 10000, or 15000 rpm. The magnetic disk  14  is a perpendicular recording magnetic storage medium. 
         [0028]    The housing space further houses a carriage  16 . The carriage  16  has a carriage block  17 . The carriage block  17  is rotatably coupled to a vertically extending spindle  18 . The carriage block  17  has a plurality of carriage arms  19  horizontally extending from the spindle  18 . The carriage block  17  may be molded, for example, by extrusion using aluminum. 
         [0029]    A head suspension  21  is attached to the tip end of each of the carriage arms  19 . The head suspension  21  extends from the tip end of the carriage arm  19  to the front. A flexure is bonded to the tip end of the head suspension  21 . The flexure has a gimbal spring. As the gimbal spring works, a flying head slider  22  can change its posture relative to the head suspension  21 . Though described below, an electromagnetic conversion element (head element) is mounted to the flying head slider  22 . 
         [0030]    When an airflow is generated at the surface of the magnetic disk  14  due to the rotation of the magnetic disk  14 , a positive pressure, or a buoyant force, and a negative pressure act on the flying head slider  22  because of the effect of the airflow. The buoyant force and the negative pressure are balanced with a pressing force of the head suspension  21 , whereby the flying head slider  22  can continuously fly with a relatively high rigidity during the rotation of the magnetic disk  14 . 
         [0031]    If the carriage  16  rotates around the spindle  18  while the flying head slider  22  flies, the flying head slider  22  can move along a radial line of the magnetic disk  14 . As a result, the electromagnetic conversion element mounted on the flying head slider  22  can move across a data zone between the innermost recording track and the outermost recording track. The electromagnetic conversion element on the flying head slider  22  can be positioned at a desired recording track. 
         [0032]    The carriage block  17  is connected to a power source such as a voice coil motor (VCM)  23 . As the VCM  23  works, the carriage block  17  can rotate around the spindle  18 . The carriage arm  19  and the head suspension  21  can swing in accordance with the rotation of the carriage block  17 . 
         [0033]    As shown in  FIG. 1 , a flexible printed circuit board unit  25  is disposed on the carriage block  17 . The flexible printed circuit board unit  25  has a head IC (integrated circuit)  27  that is mounted on a flexible printed circuit board  26 . The head IC  27  is connected to a read head element and a write head element of the electromagnetic conversion element. A flexible printed circuit board  28  is used for the connection. The flexible printed circuit board  28  extends from each of the flexures. The flexible printed circuit board  28  is connected to the flexible printed circuit board unit  25 . 
         [0034]    For reading of magnetic information, sense current is supplied from the head IC  27  to the read head element of the electromagnetic conversion element. The read head element employs, for example, a current-perpendicular-to-plane (CPP) read head element. For writing of magnetic information, write current is supplied from the head IC  27  to the write head element of the electromagnetic conversion element. The write head element employs, for example, a single pole head element. The current value of the sense current is determined to a given value. The current is supplied to the head IC  27  from a small circuit board  29  disposed in the housing space, and a printed circuit board (not shown) attached to the back side of a bottom plate of the base  13 . 
         [0035]      FIG. 2  shows the flying head slider  22  according to an embodiment. The flying head slider  22  has, for example, a flat rectangular-parallelepiped slider body  31 . An element-containing film (nonmagnetic layer)  32  is laminated on a trailing edge of the slider body  31 . The above-described electromagnetic conversion element  33  is arranged in the element-containing film  32 . The details of the electromagnetic conversion element  33  will be described later. The slider body  31  may be made of a hard, nonmagnetic material, such as Al 2 O 3 —Tic (alumina-titanium carbide, AlTic). The element-containing film  32  may be made of a relatively soft, insulating nonmagnetic material, such as Al 2 O 3  (alumina). 
         [0036]    A medium-opposing surface, or an air bearing surface  34  of the flying head slider  22  faces the magnetic disk  14 . The air bearing surface  34  has a flat base surface  35  serving as a reference plane. As the magnetic disk  14  rotates, an airflow  36  acts on the air bearing surface  34  from the front edge to the rear edge of the slider body  31 . 
         [0037]    A front rail  37  is formed at the air bearing surface  34 . The front rail  37  projects from the base surface  35  near the upstream side, or the leading side of the airflow  36 . The front rail  37  extends in a slider width direction along the leading edge of the base surface  35 . Also, a rear rail  38  is formed at the air bearing surface  34 . The rear rail  38  projects from the base surface  35  near the downstream side, or the trailing side of the airflow  36 . The rear rail  38  is arranged at the center in the slider width direction. The rear rail  38  extends from the slider body  31  to the element-containing film  32 . 
         [0038]    Further, a pair of auxiliary rear rails  39  are formed at the air bearing surface  34 . The auxiliary rear rails  39  project from the base surface  35  near the trailing side. The auxiliary rear rails  39  are arranged respectively along left and right edges of the base surface  35 . Hence, the auxiliary rear rails  39  are arranged with an interval provided therebetween in the slider width direction. The rear rail  38  is arranged between the auxiliary rear rails  39 . 
         [0039]    The front rail  37 , the rear rail  38 , and the auxiliary rear rails  39  have air bearing surfaces (ABS)  41 ,  42 , and  43  at their top surfaces. Leading edges of the air bearing surfaces  41 ,  42 , and  43  are connected to the top surfaces of the rails  37 ,  38 , and  39  through steps  44 ,  45 , and  46 . The air bearing surface  34  receives the airflow  36  generated due to the rotation of the magnetic disk  14 . At this time, relatively large positive pressures, or buoyant forces are generated at the air bearing surfaces  41 ,  42 , and  43  because of the effects of the steps  44 ,  45 , and  46 . Also, a large negative pressure is generated at the rear, or the back of the front rail  37 . Accordingly, the flying posture of the flying head slider  22  is determined on the basis of the balance between the buoyant forces and the negative pressure. The configuration of the flying head slider  22  is not limited to the one described above. 
         [0040]    On the air bearing surfaces  41 ,  42 , and  43 , for example, protection films (not shown) are laminated. The top surface of the rear rail  38  is covered with the protection film at the trailing edge of the air bearing surface  42 . As shown in  FIG. 3 , the electromagnetic conversion element  33  extends in the slider width direction. The electromagnetic conversion element  33  allows the front edge of a CPP read head element  47  and a front edge of the single pole head element  48  to be exposed at the top surface of the rear rail  38 . The protection film has a pair of protection pads (protrusions)  49  vertically arranged on the surface thereof. The protection pads  49  are disposed on both left and right sides of the electromagnetic conversion element  33  in the slider width direction. That is, the protection pads  49  are disposed parallel to the trailing edge of the slider body  31  with a predetermined interval provided between the protection pads  49 . 
         [0041]    Also referring to  FIG. 4 , a protection film  51  is laminated on the front edge of the CPP read head element  47  and the front edge of the single pole head element  48 . The protection pads  49  are disposed, for example, on both sides of the single pole head element  48  in the slider width direction. The protection film  51  and the protection pads  49  may be made of, for example, diamond like carbon (DLC). 
         [0042]      FIG. 5  shows the details of the structure of the electromagnetic conversion element  33 . The CPP read head element  47 , as is well known, can detect binary data on the basis of a resistance variable according to the magnetic field applied by the magnetic disk  14 . The single pole head element  48  can write binary data on the magnetic disk  14  by using a magnetic field produced by, for example, a thin-film coil pattern (described later). The CPP read head element  47  and the single pole head element  48  are interposed between Al 2 O 3  films  57  and  58 . The Al 2 O 3  film  57  serves as an upper half layer, or overcoat film of the element-containing film  32 . The Al 2 O 3  film  58  serves as a lower half layer, or undercoat film of the element-containing film  32 . 
         [0043]    The CPP read head element  47  has a magnetoresistive film  59  such as a spin-valve film or a tunnel junction film. The magnetoresistive film  59  is interposed between an upper electrode  61  and a lower electrode  62 . The upper and lower electrodes  61  and  62  are respectively in contact with the upper and lower boundaries of the magnetoresistive film  59  at the front edge where the upper and lower electrodes  61  and  62  are exposed at the surface of the slider body  31 . The upper and lower electrodes  61  and  62  supply the magnetoresistive film  59  with sense current. The upper and lower electrodes  61  and  62  may have a conductivity, and a soft magnetic property. If the upper and lower electrodes  61  and  62  are made of a conductive and soft magnetic material such as a permalloy (Ni—Fe alloy), the upper and lower electrodes  61  and  62  can also serve as upper and lower shield layers of the CPP read head element  47 . In this way, the upper and lower electrodes  62  define a read gap. 
         [0044]    The single pole head element  48  has a main pole  64  and an auxiliary pole  65  both being exposed at the air bearing surface  42 . The main pole  64  and the auxiliary pole  65  may be made of a conductive soft magnetic material such as a permalloy. The main pole  64  and the auxiliary pole  65  together define a magnetic core of the single pole head element  48 . For example, a nonmagnetic gap layer  66  made of Al 2 O 3  is interposed between the main pole  64  and the auxiliary pole  65 . When a magnetic field is produced by the thin-film coil pattern (described below), with the effect of the nonmagnetic gap layer  66 , the magnetic flux leaks from the main pole  64  to the auxiliary pole  65 . The leaking magnetic flux forms a gap magnetic field, or a recording magnetic field. In this way, the main pole  64  and the auxiliary pole  65  define a write gap. 
         [0045]    Also referring to  FIG. 6 , the main pole  64  extends along a given reference plane  67  located above the upper electrode  61 . The reference plane  67  is defined by the surface of a nonmagnetic layer  68  made of Al 2 O 3 . The nonmagnetic layer  68  may be laminated on the upper electrode  61  with a uniform thickness. The nonmagnetic layer  68  prevents the upper electrode  61  from being magnetically connected to the main pole  64 . 
         [0046]    A thin-film coil pattern  71  is disposed on the nonmagnetic gap layer  66 . The thin-film coil pattern  71  extends along a plane in a spiral manner. The thin-film coil pattern  71  is embedded in an insulating layer  72  above the nonmagnetic gap layer  66 . The above-described auxiliary pole  65  is formed on the surface of the insulating layer  72 . The auxiliary pole  65  is magnetically coupled to the main pole  64  at the center of the thin-film coil pattern  71 . When current is supplied to the thin-film coil pattern  71 , magnetic flux circulates through the main pole  64  and the auxiliary pole  65 . 
         [0047]    The element-containing film  32  has a heater arranged therein corresponding to the electromagnetic conversion element  33 . The heater is, for example, a heating wire  73  embedded in the insulating layer  72 . The heating wire  73  extends along a plane. As shown in  FIG. 7 , the heating wire  73  extends so as not to pass through the center of the thin-film coil pattern  71 . The thin-film coil pattern  71  has a relatively large coefficient of linear expansion, and hence, when electric power is supplied to the heating wire  73 , the heating wire  73  generates heat, whereby the thin-film coil pattern  71  expands due to the heat. Then, as shown in  FIG. 8 , the thin-film coil pattern  71 , that is, the single pole head element  48  bulges at the surface of the element-containing film  32 , or at the top surface of the rear rail  38 . A bulge  74  is formed accordingly. In this way, the CPP read head element  47  and the single pole head element  48  are displaced toward the magnetic disk  14 . For example, a flying height of the single pole head element  48  is determined in accordance with a bulging amount of the single pole head element  48 . At this time, the protection pads  49  are located on both sides of the top of the bulge  74  as shown in  FIG. 9 . The top of the bulge  74  is located at the top surface of the protection film  51 . The protection pads  49  always come close to the magnetic disk  14  as compared with the top surface of the protection film  51 . 
         [0048]    As shown in  FIG. 10 , the head IC  27  has a preamplifier circuit  81 , a current supply circuit  82 , and a power supply circuit  83 . The preamplifier circuit  81  is connected to the CPP read head element  47 . Sense current is supplied from the preamplifier circuit  81  to the CPP read head element  47 . The current value of the sense current is held at a predetermined value. 
         [0049]    The current supply circuit  82  is connected to the single pole head element  48 . Write current is supplied from the current supply circuit  82  to the single pole head element  48 . The single pole head element  48  generates a magnetic field on the basis of the supplied write current. 
         [0050]    The power supply circuit  83  is connected to the heating wire  73 . Electric power is supplied from the power supply circuit  83  to the heating wire  73 . The heating wire  73  generates heat in accordance with the supplied electric power. The temperature of the heating wire  73  is determined by the electric energy. That is, the bulging amount of the bulge  74  can be controlled on the basis of the electric energy. 
         [0051]    The head IC  27  is connected to a control circuit (hard disk controller, HDC)  84 . The control circuit  84  instructs the head IC  27  to supply the sense current, write current, and electric power. In addition, the control circuit  84  detects the voltage of the sense current. Before the detection of the voltage, the preamplifier circuit  81  amplifies the voltage of the sense current. 
         [0052]    The control circuit  84  determines the binary data on the basis of the output of the preamplifier circuit  81 . Further, the control circuit  84  detects “a fluctuation” of the voltage value on the basis of the output of the preamplifier circuit  81 . For example, when the protection pads  49  come into contact with the magnetic disk  14  on account of the formation of the bulge  74 , the flying head slider  22  may be slightly vibrated. At this time, “a fluctuation” is generated in the voltage value of the sense current. The control circuit  84  detects “the fluctuation”. 
         [0053]    The control circuit  84  controls the operations of the preamplifier circuit  81 , the current supply circuit  82 , and the power supply circuit  83  corresponding to a predetermined software program. Such a software program may be stored in, for example, a memory  85 . With the software program, zero calibration (described later) is performed. Data required for the zero calibration may be also stored in the memory  85 . The software program and data may be transmitted to the memory  85  from other storage medium. The control circuit  84  and the memory  85  may be mounted on the circuit board  29 . 
         [0054]    In this hard disk drive  11 , the bulging amount of the single pole head element  48  is determined before reading or writing of magnetic information. To determine the bulging amount, zero calibration is performed. During the zero calibration, the bulging amount of the bulge  74  is measured when the protection pads  49  come into contact with the magnetic disk  14 . A bulging amount of the bulge  74  for reading or writing of information is determined on the basis of the measured bulging amount in the contact state. The bulging amount of the bulge  74  for reading or writing of information is determined, whereby the single pole head element (electromagnetic conversion element)  48  can fly over the surface of the magnetic disk  14  at a predetermined flying height. The zero calibration may be performed, for example, every time when the hard disk drive  11  is activated. 
         [0055]    To perform the zero calibration, the control circuit  84  executes the predetermined software program. When the software program is executed, the control circuit  84  performs initial setting of the hard disk drive  11 . In the initial setting, the control circuit  84  instructs the spindle motor  15  to drive. The magnetic disk  14  rotates at a predetermined rotation speed accordingly. Also, the control circuit  84  instructs the VCM  23  to drive. The carriage  16  swings around the spindle  18  accordingly. As a result, the flying head slider  22  faces the surface of the magnetic disk  14 . The flying head slider  22  flies over the magnetic disk  14  at a predetermined flying height. Further, the control circuit  84  supplies the head IC  27  with current. The control circuit  84  monitors the output of the preamplifier circuit  81 . That is, the control circuit  84  observes the voltage value of the sense current. At this time, the power supply circuit  83  suspends the supplement of the electric power. 
         [0056]    When the initial setting is completed, the control circuit  84  supplies the power supply circuit  83  with a command signal. The control circuit  84  increases the bulging amount of the bulge  74  by a given increment. In response to the reception of the command signal, the power supply circuit  83  supplies the heating wire  73  with electric power of an electric energy corresponding to the increased bulging amount. The given increment may be, for example, 0.1 nm. The electric energy may be determined in advance on the basis of the coefficient of linear expansion of the single pole head element  48 . When the bulging amount of the bulge  74  is increased, the control circuit  84  determines “contact” between the protection pads  49  and the magnetic disk  14 . For the judgment, the control circuit  84  observes the presence of “a fluctuation” appearing in the voltage value of the sense current. 
         [0057]    The control circuit  84  increases the bulging amount of the bulge  74  by the given increment until the control circuit  84  observes “the fluctuation”. The protection pads  49  always come close to the magnetic disk  14  as compared with the top of the bulge  74 , in accordance with the bulging amount of the bulge  74 . Finally, as shown in  FIG. 11 , the protection pads  49  come into contact with the magnetic disk  14 . Also referring to  FIG. 12 , the bulge  74 , or the top surface of the protection film  51  can be prevented from coming into contact with the magnetic disk  14 , in an area between the protection pads  49 . Thus, “the fluctuation” is observed. The control circuit  84  determines the contact between the protection pads  49  and the magnetic disk  14 . The control circuit  84  then determines the bulging amount of the bulge  74 . Thus, the bulging amount in the contact state can be obtained. The obtained bulging amount is stored in, for example, the memory  85 . It should be noted that a predetermined distance is provided between the tip ends of the protection pads  49  and the top of the bulge  74  in the contact state. The distance is referenced when the flying height of the single pole head element  48  is determined. The distance may be calculated in advance, for example, on the basis of a simulation. The zero calibration is thus completed. 
         [0058]    In the above-described hard disk drive  11 , the protection pads  49  come into contact with the magnetic disk  14  when the bulging amount of the bulge  74  is determined. The top surface of the protection film  51  can be prevented from coming into contact with the magnetic disk  14  in the area between the protection pads  49 . Thus, wear of the protection film  51  can be reliably prevented at the top of the bulge  74 . The protection film  51  can effectively protect the electromagnetic conversion element  33 . Thus, corrosion of the electromagnetic conversion element  33  can be reliably prevented. 
         [0059]    As shown in  FIG. 13 , the width of the heating wire  73  may be increased in the flying head slider  22 . The heating wire  73  defines meander regions  73   a  that extend in a meandering manner. The meander regions  73   a  are disposed on both sides of the thin-film coil pattern  71 , or the single pole head element  48 . Since the meander regions  73   a  extend in the meander manner, the heating wire  73  can have a sufficient length on both sides of the thin-film coil pattern  71 . With this heating wire  73 , as shown in  FIG. 14 , a bulge  74  expands in the width direction of the electromagnetic conversion element  33 . Accordingly, the interval between the protection pads  49  is increased. The protection pads  49  can come into contact with the magnetic disk  14  stably. 
         [0060]    As shown in  FIG. 15 , the nonmagnetic layer  68  has, for example, a first region  68   a  and second regions  68   b . A coefficient of linear expansion of the second regions  68   b  is larger than a coefficient of linear expansion of the first region  68   a . The second regions  68   b  may be located at positions corresponding to the meander regions  73   a  of the heating wire  73 . In particular, the second regions  68   b  may be disposed on both sides of the electromagnetic conversion element  33 . The second regions  68   b  may be made of a nonmagnetic material such as Cu. With the effects of the second regions  68   b , the expansion of the bulge  74  in the width direction can be promoted. Since the interval between the protection pads  49  is increased like the case described above, the protection pads  49  can come into contact with the magnetic disk  14  stably. 
         [0061]    With the above-described flying head slider  22 , the protection pads  49  do not have to be disposed parallel to the trailing edge of the slider body  31 . For example, one of the protection pads  49  may be disposed near the leading edge, and the other one may be disposed near the trailing edge. Otherwise, the protection pads  49  may be replaced with a protruding wall continuously surrounding the periphery of the bulge  74 . In this case, the protruding wall may have a notch. The shape of the protection pad  49  is not limited to those described above. The shape of the protection pad  49  may be modified as desired. 
         [0062]    With the above-described configuration of the present technique, the protrusions come close to the storage medium as compared with the top surface of the protection film when the head element bulges. Accordingly, the top surface of the protection film can be reliably prevented from coming into contact with the storage medium when the protrusions come into contact with the storage medium. Wear of the protection film can be prevented at the front edge of the head element. Damage of the head element can be thus effectively prevented. 
         [0063]    In addition, since the pair of protrusions are provided on the surface of the protection film, and the protrusions are disposed parallel to the trailing edge of the slider body with the predetermined interval provided between the protrusions, the pair of protrusions can come into contact with the storage medium stably. 
         [0064]    Further, since the nonmagnetic film has the first region with the first coefficient of linear expansion, and the second regions with the second coefficient of linear expansion which is larger than the first coefficient of linear expansion, the second regions being provided on both sides of the head element, the width of the bulge of the head element is increased by the effects of the heater and the second regions. The interval between the protection pads is increased. Thus, the protection pads can come into contact with the storage medium stably. 
         [0065]    With the present technique, the head slider and the storage medium drive capable of preventing the head element from being damaged can be provided.