FIELD OF THE INVENTION 
     The present invention relates to a head slider which is used in a magnetic disk drive or the like. The head slider mounts a recording/reproducing element and is also arranged on a recording medium to fly over the recording medium owing to the airflow generated by movement of the recording medium. 
     In more specific, the present invention relates to a head slider having projections at the sliding surface, which are suitable for avoiding the stiction between the head slider and the recording medium. 
     BACKGROUND OF THE INVENTION 
     FIGS.  1 ( a )-( c ) show a magnetic head slider of the prior art. In the prior art, the magnetic head slider has floating rails  41  and  42 , in the longitudinal direction, just opposed to a magnetic disk  3  when it is built into a magnetic disk drive. The magnetic head slider flies over the magnetic disk  3  when the airflow generated by rotation of the magnetic disk  3  enters into an air inflow end  5  and affects the floating rails  41 - 43 , and then conducts the recording/reproducing operation to and from the magnetic disk  3  with an electromagnetic transducer  2  arranged at the area near the air outflow end  7 . 
     It is effective to reduce the contact area of the magnetic head slider in order to prevent the stiction at the time of contacting with a CSS (Contact Start Stop) zone, therefore, projections  61 - 64  are provided on the rail surfaces of the floating rails  41  and  42 . As shown in FIG.  1 ( b ), in order to effectively prevent the stiction while the projections  61 - 64  are contacting with the magnetic recording, the height H of the projections  61 - 64  must be necessarily at least 20 nm for the magnetic disk  3  having Ra (average roughness) of about 2 nm. It has been verified experimentally that the stiction cannot be prevented if the height H is less than such value. 
     However, the prior art explained above has following disadvantages. The magnetic head slider takes a flying condition that the flying height of the air inflow end  5  is higher than one of the air outflow end  7  as shown in FIG.  1 ( c ). If the electro-magnetic transducer  2  is attempted to be located near the magnetic disk  3  by reducing the flying height δ of the magnetic head slider in view of enhancing the recording/reproducing sensitivity, the projections  63  and  64  near the air outflow end  7  may interfere with the surface of the magnetic disk  3 . Moreover, in order to prevent the interference of the projections  63  and  64 , it is thought to set up the pitch angle of the magnetic head slider, but it is disadvantage in the viewpoint of balance of the flying condition. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the present invention to provide a head slider suitable for preventing the stiction to a recording medium. 
     It is another object of the present invention to provide a head slider which realizes the small flying height while preventing the stiction to a recording medium. 
     It is further object of the present invention to provide a head slider which achieves the small flying height and improves the recording/reproducing sensitivity to a recording medium. 
     The objects explained above can be achieved by a head slider which mounts a recording/reproducing element and flies over the recording medium with the airflow generated when the recording medium moves. This head slider comprises a slider body having the air inflow end and an air outgoing end, a rail which is projected from the slider body to define an air bearing surface extended to the outflow end, a projection formed on the rail and between the inflow end and the outflow end, and a recess formed at the outflow end of the rail to make narrow the width of the rail. 
     According to the present invention, when the recording medium stops to move, the head slider and the recording medium are in contact each other at the projection and the air outflow end of the rail. Since the air outflow end of the rail is rather narrow in width, the stiction can be prevented. Moreover, it is no longer required to form a projection near the outflow end of the rail and therefore the flying height of the recording/reproducing element can be lowered to improve the recording/reproducing sensitivity. 
     According the other aspect of the present invention, the width of the recording/reproducing element at the surface opposed to the recording medium is narrower than the width of the outflow end of the rail. According to this aspect, the recording/reproducing element is never exposed to the side wall of the recess of the rail and thereby the corrosion of the recording/reproducing element can be prevented. 
     According to still another aspect of the present invention, the rail comprises a couple of rails, and the width of one rail, where the recording/reproducing element is formed, at the outflow end is wider than the corresponding one of the other rail. According to this aspect, the width of the outflow end of the one rail is set so that the recording/reproducing element is never exposed. Moreover the width of the outflow end of the other rail can be set so that the stiction never occurs. 
     Moreover, according to still further aspect of the present invention, the recess isolates an area, where the recording/reproducing element is formed, from the air bearing surface of the rail and thereby the area is formed like an island. According to this aspect, the phenomenon that the lubricant creeps up can be prevented, therefore, the stiction can be prevented effectively. 
     Moreover, according to still further aspect of the present invention, a forward projection and a backward projection are provided on the rail. According to this aspect, the area in which the head slider is in contact with the recording medium can be reduced, therefore, the stiction can be prevented effectively. Namely, the head slider is in contact with the recording medium in the following three condition, first the inflow end and the forward projection, secondly the forward projection and the backward projection, and thirdly the backward projection and the outflow end are in contact with the recording medium. Even in any type of contact condition, the contact area between the head slider and recording medium can be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS.  1 ( a )-( c ) show a head slider of the prior art. 
     FIG.  1 ( a ) is a front elevation viewed from a side of the floating rail forming surface, 
     FIG.  1 ( b ) is a side elevation illustrating the contacting condition to the magnetic disk, and 
     FIG.  1 ( c ) is a side elevation illustrating a flying condition. 
     FIGS.  2 ( a )-( c ) show a head slider of the present invention. 
     FIG.  2 ( a ) is a front elevation viewed from a side of the floating rail forming surface, 
     FIG.  2 ( b ) is a side elevation illustrating the contacting condition to the magnetic disk, and 
     FIG.  2 ( c ) is a cross-sectional view along the line  1 C— 1 C of FIG.  2 ( b ). 
     FIGS.  3 ( a )-( c ) show an electro-magnetic transducer. 
     FIG.  3 ( a ) is a front elevation viewed from a side of the air outflow end, 
     FIG.  3 ( b ) is a cross-sectional view along the line  2 B— 2 B of FIG.  3 ( b ), and 
     FIG.  3 ( c ) is a cross-sectional view along the line  2 C— 2 C of FIG.  3 ( a ). 
     FIGS.  4 ( a ) and  4 ( b ) show a modification example of the electromagnetic transducer. 
     FIG.  4 ( a ) is a front elevation of the electro-magnetic transducer viewed from a side of the air outflow end, and 
     FIG.  4 ( b ) is a cross-sectional view along the line  3 C— 3 C of FIG.  4 ( a ). 
     FIG. 5 shows a head slider of the second embodiment of the present invention. 
     FIG. 6 shows a head slider of the third embodiment of the present invention. 
     FIGS.  7 ( a )-( c ) show a header slider of the fourth embodiment of the present invention. 
     FIG.  7 ( a ) is a front elevation viewed from a side of the floating rail forming surface, 
     FIG.  7 ( b ) is a side elevation illustrating the contacting condition to the magnetic disk, and 
     FIG.  7 ( c ) is a side elevation illustrating the flying condition. 
     FIGS.  8 ( a ) and  8 ( b ) show the process of manufacturing a thin film magnetic head. 
     FIG.  8 ( a ) is a perspective view of a wafer, and 
     FIG.  8 ( b ) is a perspective view illustrating a condition where a bar is cut out. 
     FIGS.  9 ( a )-( e ) show the process of forming the floating rail. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS.  2 ( a )- 2 ( c ) show a head slider of the present invention. A magnetic head slider is manufactured by forming an electro-magnetic transducer  2  on slider body  1  using the thin film process and by forming floating rails  41 - 43  on the surface opposing to magnetic disk  3 . The floating rails are formed of a couple of side rails  41  and  42  and a center rail  43 . The slider body  1  is formed, for example, of alumina-titanium-carbide (Al 2 O 3 TiC). 
     The magnetic head slider flies over the magnetic disk  3  at the predetermined height with the airflow in the direction of an arrow mark A in FIG.  2 ( b ) due to the rotation of the magnetic disk  3 . Moreover, the magnetic head slider has a sloping surface  8  at the air inflow end  5  of the slider body  1  and the floating rails  41  to  43 . 
     The projections  61  and  62  are formed at the boundary between the sloping surface  8  and a rail surface  8 ′ of the floating rails  41  and  42 , and are projected toward the magnetic disk  3 . With respect to the size of the projections  61  and  62 , the contacting area to the magnetic disk  3  are as small as not causing the stiction and are as large as not being worn out easily due to the friction with the magnetic disk  3 . For example, the projections  61  and  62  are formed as an elongated column having the minor axis length of about 50-70 μm, while the width of the floating rails  41  and  42  is about 300 μm. 
     As explained above, the projections  61  and  62  are required to have the sufficient height to show stiction-free, for example, about 20 nm in minimum or about 30 nm assuming a margin for the magnetic disk  3  having the surface roughness Ra of about 2 nm. In FIGS.  2 ( a ) and  2 ( b ), the projections  61  and  62  are formed at the boundary between the sloping surface  8  and the rail surface  8 ′ but these may also be formed on only the rail surface  8 ′. 
     FIGS.  3 ( a )-( c ) show the electro-magnetic transducer. In these figures, the electro-magnetic transducer  2  is a composite type head which is generally called an MR head and which is formed integrally an inductive element for recording and a magneto-resistive element for reproducing. The electro-magnetic transducer  2  is formed by utilizing the thin film process and the magneto-resistive element and the inductive element are formed in this sequence from the side of slider body (substrate)  1 . 
     The magneto-resistive element is composed, as shown in FIGS.  3 ( b ) and  3 ( c ), of a magneto-resistive layer (MR layer)  2   f , a non-magnetic gap layer  2   a  formed for surrounding the MR layer  2   f , and an upper magnetic shield  2   c  and a lower magnetic shield  2   d  formed for sandwiching the MR layer  2   f  and the gap layer  2   a.    
     The inductive element is composed of a lower magnetic pole (the upper shield)  2   c , an upper magnetic pole  2   b , a non-magnetic gap layer  2   a ′ for forming an interval between the upper and lower magnetic poles  2   b  and  2   c  and at the rail surface, a non-magnetic insulating layer  2   i  formed between both magnetic poles  2   b  and  2   c , and a coil  2   e  formed in the non-magnetic insulating layer  2   i.    
     In the electro-magnetic transducer  2 , as shown in FIG.  3 ( b ), a protection film  2   h  is formed on the upper magnetic pole  2   b  of the inductive element and a protection film  10   a  is formed in the floating surface side of the inductive element and magneto-resistive element. 
     As shown in FIGS.  2 ( a )-( c ), the electro-magnetic transducer  2  is arranged at the air outflow end  7  of the floating rail  41  and a part of the electro-magnetic transducer  2  is appearing on the rail surface of the floating rail  41 . In the floating rail  41 , at the air outflow end  7 , both sides of the electromagnetic transducer  2  are engraved along the longitudinal direction of the floating rail  41 , and thereby a narrow width portion  4   a  and recesses  9  are formed. 
     Namely, the floating rail  41  is narrowed in width at the air outflow end  7  for the contact with the magnetic disk  3 . When the magnetic disk  3  having the surface roughness Ra of about 2 nm is considered, it is desirable that the depth d of the recesses  9  of the floating rail  41  be 20 nm or more and the width w of the narrow portion  4   a  be about 50 to 100 μm. 
     In this embodiment, when contacting with the CSS zone, the projection  61  near the air inflow end Sand the narrow portion  4   a  at the air outflow end  7  are in contact with the surface of the magnetic disk  3  as shown in FIGS.  2 ( b ) and  2 ( c ). The narrow portion  4   a  is as narrow as 50 to 100 μm in width in comparison with the floating rail  41  of 300 μm and therefore there is no fear for the stiction to the magnetic disk  3 . Moreover, even in the case of the floating condition, since the projection is not provided near the narrow portion  4   a , the flying height from the magnetic disk can be reduced. 
     FIGS.  4 ( a ) and  4 ( b ) show a modification example of the electro-magnetic transducer. In the electro-magnetic transducer shown in FIGS.  3 ( a )-( c ), since the floating rail  41  where the electro-magnetic transducer  2  is arranged is engraved, the upper and lower shields  2   c  and  2   d  are exposed to the side wall of the engraved portion. Therefore, the electro-magnetic transducer  2  potentially has the possibility of corrosion. 
     This problem can be eliminated, as shown in FIGS.  4 ( a ) and  4 ( b ), by forming the upper and lower shields  2   c  and  2   d  of the electromagnetic transducer  2  to such a size as can be accommodated within the narrow portion  4   a . Namely, in this embodiment, the magnetic shields  2   c  and  2   d  are formed so as to have a step that their tip portions opposed to the magnetic disk  3  are narrowed in width, and the floating rail  41  is engraved at the position adequately isolated from the side edge of the magnetic shields  2   c  and  2   d . As a result, the side wall of the narrow portion  4   a  is covered with the protection film  2   h  which is also covering the electromagnetic transducer  2 . Thereby, the exposure to the outside can be prevented. 
     FIG. 5 shows a head slider of a second embodiment of the present invention. For the explanation of the second embodiment, the elements which are substantially same as the above-mentioned embodiment are designated by the same reference numerals, and the explanation is omitted here. In this embodiment, the width w 1  of the narrow portion  4   a  of the floating rail  41  where the electromagnetic transducer  2  is arranged is formed wide and the width w 2  of the narrow portion  4   a  of the floating rail  42  where the electro-magnetic transducer  2  is not arranged is formed narrow. 
     Since the narrow portion  4   a  of the floating rail  41  where the electro-magnetic transducer  2  is arranged is formed in the width not interring the magnetic shields  2   c  and  2   d , the magnetic shields  2   c  and  2   d  are never exposed to the outside. Therefore, there is no fear for the corrosion. Moreover, since the narrow portion  4   a  where the electromagnetic transducer  2  is not arranged is formed narrow, in comparison with the first embodiment, as much as the widening of the narrow portion  4   a  of the floating rail  41  where the electro-magnetic transducer is arranged. Therefore, the total contacting area is never enlarged. 
     FIG. 6 shows a head slider of a third embodiment of the present invention. This embodiment is a modification for effectively preventing the stiction. The recesses  9  in both right and left sides of the narrow portions  4   a  are coupled with second recesses  9 ′ crossing the floating rails  41  and  42 . As a result, the narrow portion  4   a  is formed like an island which is capable of preventing that the lubricant creeps up by the capillarity. The second recess  9 ′ has the same depth to both right and left recesses and the width wc of about 5 μm. 
     FIGS.  7 ( a )- 7 ( c ) show a head slider of a fourth embodiment of the present invention. In this embodiment, each floating rail  41  and  42  is provided with the backward projections  63  and  64 , in addition to the forward projections  61  and  62  in the side of the air inflow end  5 . The backward projections  63  and  64  as shown in FIG.  7 ( b ) have the height of 20 nm or more not to cause the stiction at the time of contacting with the magnetic disk  3 . 
     Moreover, it is preferable, as shown in FIG.  7 ( c ) that the backward projections  63  and  64  are provided at the area so that they are not in contact with the magnetic disk  3  when the magnetic head slider flies. In this embodiment, the backward projections  63  and  64  has the height almost equal to the forward projections  61  and  62  provided near the air inflow end  5 , and are arranged at the center of each floating rail  41  and  42 . 
     Therefore, in this embodiment, since the projection  61 - 64  are in contact with the CSS zone of the magnetic disk  3  under normal condition as shown in FIG.  7 ( b ), the contacting area with the magnetic disk  3  can be reduced and thereby the stiction can be prevented. In addition, even if the air outflow end  7  is in contact with to the CSS zone as shown by a chain line in FIG.  7 ( b ), the angle Θ to the magnetic disk  3  becomes large. Therefore, the contacting area becomes small and the possibility for the stiction is also lowered. 
     FIGS.  8 ( a ) and  8 ( b ) show the process of manufacturing the magnetic head slider. The magnetic head slider can be obtained by forming a plurality of electro-magnetic transducers  2  on a ceramic wafer  10  such as alumina-titanium-carbide (Al 2 O 3 TiC) using the thin film process as shown in FIG.  8 ( a ), then cutting the wafer by a dicing saw into bars that the electromagnetic transducers  2  are arranged in a line as shown in FIG.  8 ( b ), then forming the floating rails  41  and  42  on the cutting surface A of the magnetic pole side of each bar by the process explained later, and then separating from the bar. If a sloping surface  8  as shown in FIG. 2 is formed at the air inflow end  5 , the chamfering process applies to the edge of the bar after the cutting process of the wafer into the bar and before the forming process of the floating rails. 
     FIG. 9 shows the process of forming the floating rails to the bar. First, the floating rails are formed by etching the floating rail forming surface (surface A of FIG.  8 ( b )) of the bar. Thereafter, as shown in FIG.  9 ( a ), an adhesion layer  10   a  of about 2 nm in thickness is formed on the rail surface of the floating rail by the sputtering of Si or SiC, and then a protection layer  10   b  is laminated thereon. The protection layer  10   b  is formed with the diamond-like carbon (DLC) film by the plasma CVD process and its thickness is about 20 nm or more, for example, of about 30 nm. 
     Thereafter, as shown in FIG.  9 ( b ), the resist  10   c  is formed on the area of the protection layer  10   b  to form the projections  61  and  62 . The resist  10   c  is coated corresponding to the projections  51  and  62  in the side of the air inflow end  5  and, if necessary, to the backward projections  63  and  64 . Thereafter, the remaining portion not covered with the resist  10   c  is etched by the ion milling process or the like, and thereby the projections  61  and  62  consisting of DLC are formed as shown in FIG.  9 ( c ). 
     Moreover, as shown in FIG.  9 ( d ), the surface of floating rail is coated with the resist  10   d , except the area corresponding to the recess  9 . Thereafter, as shown in FIG.  9 ( e ), the narrow portion  4   a  is formed on the floating rail by etching the area corresponding the to the recess  9  and then the resist  10   d  is removed. With the processes explained above, the magnetic head slider as shown in FIGS.  2 ( a )- 2 ( c ) can be obtained. In the magnetic head slider, the floating rail including the narrow portion  4   a  is covered with the adhesion layer  10   a  which is also working as the protection film, and the projections  61  and  62  consisting of DLC are provided in the predetermined positions. 
     INDUSTRIAL APPLICABILITY 
     As will be apparent from above explanation, the present invention can provide the small flying height and can prevent the stiction to the magnetic disk. 
     The head slider of the present invention can realize the small flying height while preventing the stiction to the magnetic disk. Therefore, the recording/reproducing sensitivity to the recording medium can be improved and therefore the high density recording can be realized. 
     Particularly, the magnetic disk drives have been greatly improved in the recording capacity and is still required to further increase the recording capacity. From this point of view, the head slider of the present invention is very effective. Moreover, the present invention is also effective not only to the magnetic disk drive but also to an optical disk drive using the head slider.
The head slider mounts a recording/reproducing element and flies over a recording medium with the airflow generated when the recording medium moves. The head slider comprises a slider body having an air inflow end and an air outflow end, a rail projected from the slider body to define an air bearing surface extended to the outflow end, a projection formed on the rail and between the inflow end and the outflow end, and a recess formed at the outflow end of the rail to make narrow the width of the rail. When the recording medium stops, the head slider and the recording medium are in contact at the projection and the air outflow end of the rail. Since the outflow end of the rail is narrow in width, the stiction can be prevented. Moreover, it is unnecessary to form a projection near the outflow end of the rail and thereby the flying height of the recording/reproducing element can be lowered to improve the recording/reproducing sensitivity.