Abstract:
Embodiments of the invention provide solutions to a problem, in which a reduced peripheral speed resulting from a trend toward a magnetic disk having a smaller diameter makes it more and more difficult to achieve a lifting force that allows a magnetic head slider to fly stably. According to one embodiment, in a magnetic head slider comprising a leading edge, a trailing edge, and an air bearing surface, the air bearing surface includes a plurality of leading side rail surfaces, a trailing side rail surface disposed in the same plane as the leading side rail surfaces and having a magnetic head mounted thereon, a stepped bearing surface having a predetermined depth δ 1  from the leading side rail surface, and a negative-pressure groove surface having a depth δ 2  from the leading side rail surface, the depth δ 2  being even deeper than the stepped bearing surface. The leading side rail surfaces include first stepped surfaces having a predetermined height h 1  and second stepped surfaces having a predetermined height h 2  from the first stepped surfaces, the first stepped surfaces and the second stepped surfaces having continuity in a longitudinal direction of the magnetic head slider.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application claims priority from Japanese Patent Application No. JP2005-201215, filed Jul. 11, 2005, the entire disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a magnetic head slider capable of maintaining a stable fly height even with a peripheral speed reduced due to the reduction in diameter of a magnetic disk, and a manufacturing method therefor.  
         [0003]     A magnetic disk drive uses a magnetic head slider that flies above a spinning magnetic disk recording medium (magnetic disk), while maintaining a microscopic distance (a flying height) therefrom. The magnetic disk drive is required to make the magnetic head slider fly in a low flying state, in which the magnetic head slider is as close as possible to the magnetic disk, in order to increase storage capacity. To achieve such a stringent requirement for the low flying height, a negative pressure type magnetic head slider is currently used. The negative pressure type magnetic head slider offers outstanding flying stability by making use of negative pressure acting on the slider to attract the slider onto the magnetic disk.  
         [0004]     The slider disclosed in Patent Document 1 (Japanese Patent Laid-open No. 2000-260015) is well-known, wherein the slider includes micro-protrusions disposed on an air bearing surface thereof, each being independent of each other on the air bearing surface. The micro-protrusions are intended to allow a magnetic head included in the slider to be proximate to a smooth magnetic disk surface with a gap of substantially zero therebetween. Each of the micro-protrusions has a diameter of about 1 μm or less as measured in a slider traveling direction. The total area of vertices of all micro-protrusions is 0.02 mm 2  or less.  
         [0005]     The magnetic head slider disclosed in Patent Document 2 (Japanese Patent Laid-open No. 2001-297421) is arranged to keep the flying height substantially uniform throughout the entire magnetic disk surface, reduce variations in the flying height at high altitudes, and let the head slider glide smoothly in contact with the magnetic disk should the slider contact the magnetic disk. To achieve these ends, the magnetic head slider includes a magnetic head mounting surface, a slider rail surface, a slider stepped bearing surface, and a negative-pressure groove. The magnetic head mounting surface forms a first surface disposed proximately to the magnetic disk. The slider rail surface forms a second surface disposed further away from the magnetic disk than the magnetic head mounting surface. The slider stepped bearing surface forms a third surface disposed further away from the magnetic disk than the slider rail surface. The negative-pressure groove forms a fourth surface disposed the farthest away from the magnetic disk.  
         [0006]     Conventional magnetic disk drives have had a large housing, allowing a magnetic disk used therewith to have a sufficiently large diameter and thus spin at a sufficiently high speed. This in turn has allowed the magnetic head slider flying above the surface of the magnetic disk to generate a sufficiently large lifting force so as to achieve a stable flying height. In recent years, however, the size of the magnetic disk drive has been progressively reduced because of a trend toward adopting magnetic disk drives in portable devices, and the like. Because the peripheral speed becomes lower for the magnetic disks having smaller diameters, therefore, it is becoming more difficult to achieve a sufficient flying force of the magnetic head slider. Accordingly, a need arises for a magnetic head slider that generates a sufficient lifting force even with a reduced peripheral speed of the magnetic disk and maintains a stable fly height.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     The techniques of the prior art described above are intended for reducing or making uniform the flying height. The techniques, however, do not address whatsoever the problem of the reduced lifting force generated by the magnetic head slider due to the slower peripheral speed which results from the trend toward smaller diameters of the magnetic disks. The magnetic head sliders of the prior art do not solve this problem.  
         [0008]     The present invention has been made to solve the foregoing problem. It is therefore a feature of the present invention to provide a magnetic head slider capable of generating a large lifting force even with a reduced peripheral speed of a magnetic disk.  
         [0009]     It is another feature of the present invention to provide a manufacturing method for the magnetic head slider.  
         [0010]     A magnetic head slider according to an embodiment of the present invention is characterized in that a leading side rail surface includes a first stepped surface and a second stepped surface that continues from the first stepped surface. A typical magnetic head slider includes a leading edge, a trailing edge, and an air bearing surface. The air bearing surface includes a plurality of leading side rail surfaces, a trailing side rail surface disposed in the same plane as the leading side rail surfaces and having a magnetic head mounted thereon, a stepped bearing surface having a predetermined depth δ 1  from the leading side rail surfaces, and a negative-pressure groove surface having a depth δ 2  that is even deeper than the stepped bearing surface. The leading side rail surfaces include the first stepped surface having a predetermined height h 1  and the second stepped surface having a predetermined height h 2  disposed on the first stepped surface.  
         [0011]     According to the present invention, it is possible to generate a large lifting force for the magnetic head slider and thereby achieve a stable fly height of the magnetic head slider even with a reduced peripheral speed resulting from the trend toward magnetic disks having smaller diameters. Furthermore, it is possible to provide a manufacturing method for the magnetic head slider. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a plan view showing a magnetic head slider according to a first embodiment of the present invention.  
         [0013]      FIG. 2  is a cross-sectional view taken along line A-A′ of  FIG. 1 .  
         [0014]      FIG. 3  is a view showing a general construction of a magnetic disk drive, in which a magnetic head slider is mounted.  
         [0015]      FIG. 4  is a chart showing a relationship between a peripheral speed of a magnetic disk and a lifting force, representing an effect achieved by the first embodiment of the present invention.  
         [0016]      FIG. 5  is a chart showing a relationship between a ratio of the length of a second stepped surface to the length of a first stepped surface and the lifting force.  
         [0017]      FIG. 6  is a cross-sectional view for illustrating a manufacturing method of the magnetic head slider according to the first embodiment of the present invention.  
         [0018]      FIG. 7  is a cross-sectional view for illustrating another manufacturing method of the magnetic head slider according to the first embodiment of the present invention.  
         [0019]      FIG. 8  is a plan view showing a magnetic head slider according to a second embodiment of the present invention.  
         [0020]      FIG. 9  is a plan view showing a magnetic head slider according to a second embodiment of the present invention.  
         [0021]      FIG. 10  is a plan view showing a magnetic head slider according to a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Specific embodiments to which the present invention is applied will be described below with reference to the accompanying drawings. A general construction of a magnetic disk drive, in which a magnetic head slider is mounted, will be first described with reference to  FIG. 3 . A magnetic disk drive  20  includes a base  22 , a spindle motor  24  fixed to the base  22 , and an actuator  30 . The spindle motor  24  is mounted with at least one magnetic disk  26 . The actuator  30  includes a head arm  34  that swings about a pivot  32  and a voice coil motor (VCM)  36 . One end of a suspension  38  is mounted on the head arm  34 , while a magnetic head slider  40  is mounted on the other end of the suspension  38 . A lift tab  42  is formed at a leading end of the other end of the suspension  38 . In addition, a load/unload mechanism  28  is secured to the base  22 . When current is passed through the VCM  36 , the head arm  34  swings about the pivot  32 . This correctly locates the magnetic head slider  40  mounted on the suspension  38  at any arbitrary position in a radial direction of the magnetic disk  26  so that data is written or read. When reading or writing of data is completed or a power of the magnetic disk drive  20  is shut down, the magnetic head slider  40  is driven by the VCM  36  so that the lift tab  42  climbs up a ramp slope of the load/unload mechanism  28  to reach a retraction region.  
         [0023]     The magnetic head slider according to an embodiment of the present invention will be described in detail below.  FIG. 1  is a plan view showing the magnetic head slider  40  according to a first embodiment of the present invention as viewed from the side of the air bearing surface.  FIG. 2  is a cross-sectional view taken along line A-A′ of  FIG. 1 . The magnetic head slider  40  includes a leading edge  1 , a trailing edge  2 , and an air bearing surface  3 . The magnetic head slider  40  is a so-called pico slider measuring 1.25 mm long×1 mm wide×0.3 mm thick. The air bearing surface  3  includes a leading stepped bearing surface  4 , a leading side rail surface  11 , a trailing side rail surface  7 , a trailing stepped bearing surface  8 , a negative-pressure groove surface  10 , first stepped surfaces  5 ,  6 , and second stepped surfaces  12 ,  13 . The trailing side rail surface  7  includes a magnetic head  9 . The first stepped surfaces  5 ,  6  and the second stepped surfaces  12 ,  13  are formed on the leading side rail surface  11 .  
         [0024]     The leading stepped bearing surface  4  has a depth (step) of δ 1  from the leading side rail surface  11 . The negative-pressure groove surface  10  has a depth (step) of δ 2  from the trailing side rail surface  11 . The first stepped surfaces  5 ,  6  have a height (step) of h 1  from the leading side rail surface  11 . The second stepped surfaces  12 ,  13  have a height of h 2  (step) from the first stepped surfaces  5 ,  6 . The leading side rail surface  11  and the trailing side rail surface  7  are on the same level. The leading side rail surface  11  and the trailing side rail surface  7  act as what is called a positive pressure rail surface. The positive pressure rail surface generates pressure using an air stream flowing through a gap between the magnetic head slider  40  and the magnetic disk  26 . The positive pressure rail surface thereby makes the magnetic head slider  40  fly above the magnetic disk  26 . The leading stepped bearing surface  4  and the trailing stepped bearing surface  8  are in plane of the same height. A depth from the leading side rail surface  11  or the trailing side rail surface  7  is about 200 nm.  
         [0025]     An air stream (not shown) flowing from the side of the leading edge  1  is compressed, and the pressure thereof is boosted, by the step δ 1  between the leading stepped bearing surface  4  and the leading side rail surface  11 . The air stream is then compressed, and the pressure thereof is built up, by the step h 1  between the leading side rail surface  11  and the first stepped surfaces  5 ,  6 . There is then generated a high pressure. The air stream is further compressed, and the pressure thereof is further boosted, by the step h 2  between the first stepped surfaces  5 ,  6  and the second stepped surfaces  12 ,  13 . An even higher pressure is thereby created. As such, a large lifting force can be generated by providing the two stepped surfaces of the first stepped surfaces  5 ,  6  and the second stepped surfaces  12 ,  13  in the magnetic head slider having the same outline.  
         [0026]      FIG. 4  is a chart showing an increase in the lifting force as calculated when the height h 2  of the second stepped surfaces  12 ,  13  is varied with the height h 1  of the first stepped surfaces  5 ,  6  fixed at 30 nm in the magnetic head slider  40  according to the first embodiment of the present invention. Values on the ordinate of the chart represent normalized lifting forces when the lifting force generated only with the first stepped surfaces  5 ,  6  is 1. The abscissa of the chart represents a peripheral speed of the magnetic disk  26  (magnetic head slider  40 ). The chart shows the normalized lifting forces when the height h 2  of the second stepped surfaces  12 ,  13  is varied among 0, 20, 30, and 35 nm. The chart tells that providing the second stepped surfaces  12 ,  13  in addition to the first stepped surfaces  5 ,  6  contributes to a greater lifting force as compared with the case of providing only the first stepped surfaces  5 ,  6 . The chart also indicates that the slower the peripheral speed, the greater the lifting force. This indicates that the arrangement of the second stepped surfaces  12 ,  13  produces a great effect on the peripheral speed reduced due to reduction in the magnetic disk size. From a qualitative viewpoint, the ratio of the height (h 2 ) of the second stepped surfaces  12 ,  13  to the height (h 1 ) of the first stepped surfaces  5 ,  6  (h 2 /h 1 ) is preferably set to about 3 or less. This is because the ratio of height of about 2 to 3 results in the lifting force being the greatest. Any ratio greater than about 2 to 3 decreases the lifting force.  
         [0027]      FIG. 5  is a chart showing an increase in the lifting force as calculated when a length (L 2 ) of the second stepped surfaces  12 ,  13  is varied with a length (L 1 ) of the first stepped surfaces  5 ,  6  fixed in the magnetic head slider  40  according to the first embodiment of the present invention. Values on the ordinate of the chart represent normalized lifting forces when the length of the second stepped surfaces  12 ,  13  is taken as 1 when the same is 54% of the length of the first stepped surfaces  5 ,  6 . The abscissa of the chart represents a ratio of the length of the second stepped surfaces  12 ,  13  to the length of the first stepped surfaces  5 ,  6 . The chart shows the normalized lifting forces when the peripheral speed of the magnetic disk  26  (magnetic head slider  40 ) is varied among 11.30, 8.29, 5.28, and 3.77 m/s. The chart tells that elongating the second stepped surfaces  12 ,  13  contributes to a greater lifting force. The chart also indicates that the slower the peripheral speed, the smaller the lifting force. To generate the lifting force by forming the second stepped surfaces  12 ,  13 , the length of the second stepped surfaces  12 ,  13  needs to be about 20% or more of the length of the first stepped surfaces  5 ,  6 . Accordingly, an expected lifting force can be obtained if a boundary of the second stepped surfaces  12 ,  13  with respect to the first stepped surfaces  5 ,  6  is situated at a position that falls within the range between about 20% and 90% from a rear end of the first stepped surfaces  5 ,  6 .  
         [0028]     The first stepped surfaces  5 ,  6  and the second stepped surfaces  12 ,  13  may be formed by the following method. Specifically, referring to  FIG. 6  which corresponds to FIG.  2 , an approx.-3-nm-thick air bearing surface protective film (not shown) is first formed on the air bearing surface  3  before machining the magnetic head slider  40 . Then, through etching, such as ion milling or the like, the leading side rail surface  11  and the trailing side rail surface  7 , the leading stepped bearing surface  4  and the trailing stepped bearing surface  8 , and the negative-pressure groove surface  10  are formed. Next, a silicone tight contact layer (not shown) is formed on the leading side rail surface  11  by sputtering and a carbon layer is formed on the silicone tight contact layer to form the first stepped surface  6  ( 5 ). This is followed by formation of the second stepped surface  12  ( 13 ) by forming a carbon layer on the first stepped surface  6  ( 5 ) through sputtering. In accordance with the foregoing method, the first stepped surface  6  ( 5 ) and the second stepped surface  12  ( 13 ) are formed of the carbon layer of the same material. A different material may nonetheless be used. As shown in  FIG. 7 , it is appropriate that the first stepped surface  6  ( 5 ) of a silicone layer be formed on the leading side rail surface  11  through sputtering and the second stepped surface  12  ( 13 ) of a carbon layer be formed on the silicone first stepped surface  6  ( 5 ). In accordance with these methods, the magnetic head slider can be manufactured through a simple method by simply additionally forming the stepped surfaces on the leading side rail surface  11  after having formed the air bearing surface without having to modify the existing method of forming the slider air bearing surface.  
         [0029]     A third method is to form the second stepped surface  12  ( 13 ) and the first stepped surface  6  ( 5 ) through etching, such as ion milling or the like, when the air bearing surface  3  is formed. The method flows specifically as detailed in the following. An air bearing surface protective film is first formed on the air bearing surface. The second stepped surface  12  ( 13 ) having the step h 2  is formed through ion milling and then the first stepped surface  6  ( 5 ) having the step h 1  from a lower portion of the second stepped surface  12  ( 13 ) is formed. Then, the leading side rail surface  11  at the depth of δ 1  from a lower portion of the first stepped surface  6  ( 5 ) is formed. This is followed by formation of the negative-pressure groove surface  10  that has the depth of δ 2  from a lower portion of the leading side rail surface  11  and the trailing side rail surface  7 , namely, from the leading stepped bearing surface  4  and the trailing stepped bearing surface  8 .  
         [0030]     A magnetic head slider according to a second embodiment of the present invention will be described with reference to  FIGS. 8 and 9 . The magnetic head slider according to the second embodiment differs from the magnetic head slider according to the first embodiment shown in  FIG. 1  in the shape of the boundary between the first stepped surfaces  5 ,  6  and the second stepped surfaces  12 ,  13 . In the magnetic head slider  40  according to the first embodiment of the present invention, the boundary between the first stepped surfaces  5 ,  6  and the second stepped surfaces  12 ,  13  is formed by a straight line. The shape of the boundary is not necessarily a straight line. Rather, the boundary may be U-shaped as shown in  FIG. 8 , toothed as shown in  FIG. 9 , or otherwise shaped in many varied ways. These arrangements reduce a side flow of air flowing into the second stepped surfaces  12 ,  13  from the first stepped surfaces  5 ,  6 , thereby allowing an even greater lifting force to be generated.  
         [0031]     A magnetic head slider according to a third embodiment of the present invention is shown in  FIG. 10 . The magnetic head slider according to the third embodiment differs from the magnetic head slider according to the first embodiment in the following point. Specifically, the magnetic head slider according to the third embodiment includes a third stepped surface  14  ( 15 ) formed, as a third step, on the second stepped surface  12  ( 13 ). It is preferable that the third stepped surface  14  ( 15 ) be formed of a carbon layer like the second stepped surface. A step h 3  between the second stepped surface  12  ( 13 ) and the third stepped surface  14  ( 15 ) further compresses, and further boosts the pressure of, the air stream compressed by the step h 2  between the first stepped surface  6  ( 5 ) and the second stepped surface  12  ( 13 ). An even greater lifting force than in the magnetic head slider according to the first embodiment is thereby generated.  
         [0032]     The present invention has been described as the preferred embodiments using a pico slider measuring 1.25 mm long×1 mm wide×0.3 mm thick. It should be apparent to those skilled in the art that it is not so limited, but the present invention may be applied to a femto slider measuring 0.85 mm long×0.7 mm wide×0.23 mm thick or an even more compact slider. In particular, the present invention exhibits an outstanding effect for a reduced peripheral speed due to magnetic disks having smaller diameters and a reduced lifting force due to smaller magnetic head sliders.  
         [0033]     It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.