Abstract:
A magnetic head including first and second magnetic head units for recording to and reproducing from a first and second flexible rotating recording medium; the second flexible rotating recording medium having a coercive force lower than a coercive force of the first flexible rotating recording medium; a slider, supporting the first magnetic head unit, and having a central groove separating first and second air bearing surfaces, at which the first and second magnetic heads, respectively, are provided. The slider generates an elevating force from air currents generated in a space between the first and second air bearing surfaces and the flexible rotating recording media. The first air bearing surface has a width dimension A 1  located on a leading edge side of the magnetic head and substantially perpendicular to a rotating direction from which the first or second flexible rotating recording medium approaches the magnetic head, and a width dimension A 2  located on a trailing edge side thereof and substantially perpendicular to the rotating direction, the width dimension A 1  being larger than the width dimension A 2 . An elevating force control slot formed on at least the first air bearing surface can extend in a direction substantially perpendicular to the rotating direction, from which the first or second flexible rotating recording medium approaches the magnetic head, which is essentially identical to the direction from the leading edge toward the trailing edge of the magnetic head, the elevating force control slot having a depth D 1 , adjacent the central groove, and a depth D 2 , adjacent the leading edge, the dimension of D 2  being greater than the dimension D 1.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a magnetic head, and more particularly, to a magnetic head for recording and reproducing data in a state in which the magnetic head floats over a rotating recording medium, that is, a rotating magnetic disk, due to a change in air flow arising between the magnetic head and the magnetic disk. 
     2. Description of the Related Art 
     Generally, an ordinary magnetic disk drive that uses a flexible magnetic disk having a coercive force of 900 oersted (Oe) or less as a magnetic recording medium allows a relatively low rotational speed of for example 300 rpm in this case, magnetic recording and reproduction is performed by causing the magnetic bead to be in direct sliding contact with the magnetic disk. 
     However, with advances in recent years in high-density recording on magnetic disks, the rotation speed of the magnetic disk has been increased to for example 3000 rpm, with the coercive force of the magnetic disk being increased to 1500 Oe or more. As a result, in order to accommodate such so-called high-capacity magnetic disks a magnetic disk drive has appeared in which the magnetic head is provided with a narrow gap. Hereinafter such a magnetic disk drive will be referred to as a high-capacity magnetic disk drive. 
     Since a high-capacity magnetic disk drive allows the magnetic disk to be rotated at high speeds, the magnetic disk and the magnetic head used therein may be easily damaged if the magnetic head were to be caused to be in direct contact with the magnetic disk, as is done in the conventional magnetic disk drive. 
     As a result, the high-capacity magnetic disk drive is designed so that the magnetic head floats in an elevated state over the surface of the high-capacity magnetic disk due to an elevating force arising as a result of a change in an air flow caused by a relative speed between a slider surface of the magnetic head and the magnetic disk. Magnetic recording and reproduction is performed while a state of non-contact between the magnetic head and the magnetic disk is maintained. 
     FIGS. 1,  2 ,  3 ,  4  and  5  show a magnetic head used in the conventional high-capacity magnetic disk drive. As shown in FIGS. 1 and 2, the conventional high-capacity magnetic head  1  generally comprises a slider  2  and a magnetic head unit  3  The slider  2  supports the magnetic head unit  3  and causes the magnetic head unit  3  to float over the magnetic disk  6 . 
     The top surface of the slider  2  forms an air bearing surface for forming an air bearing with respect to the magnetic disk  6 . Additionally, a central groove  2   a  is formed at a central position of the top surface of the slider  2 . As shown in FIG. 1, the central groove  2   a  divides the air bearing surface into a first air bearing surface  2   b  located to the right side of the central groove  2   a  and a second air bearing surface  5  located to the left side. 
     The magnetic head magnetic head unit  3  and a pair of grooves or slots  4  are provided at the first air bearing surface  2   b . The magnetic head unit  3  for performing magnetic recording and reproducing is formed by sandwiching a gap member between thin plates of magnetic cores. 
     The slots  4  extend in a tangential direction of the magnetic disk  6 , that is, in the direction of arrow X in FIG. 1, and provide a vent for an air flow produced between the magnetic disk  6  and the first air bearing surface  2   b . By providing a vent to the air flow produced between the magnetic disk  6  and the first air bearing surface  2   b , an elevating force exerted on the magnetic head  1  is reduced. Accordingly, by providing the slots  4 , the elevating force of the magnetic head  1  can be controlled. 
     As described above, the second air bearing surface  5  is formed to the left of the central groove  2   a  located on the top surface of the slider  2  as shown in FIG.  2 . Like the first air bearing surface  2   b , the second air bearing surface  5  also produces a force for elevating the magnetic head  1 . 
     FIG. 3 is a lateral cross-sectional view from a radial direction of disk approach. As shown in the drawing, a pair of magnetic heads are supported so as to be opposite each other within the magnetic disk drive. The elevating force generated by the second air bearing surface  5  described above exerts a force that pushes the magnetic disk  6  in the direction of the first air bearing surface  2   b , that is, in the direction of the magnetic head unit  3 , of the opposite magnetic head  1 . Accordingly, the second air bearing surface  5  also functions as a pressure pad for pressing the magnetic disk  6  toward the opposite magnetic head  1 . 
     Additionally, as described above slots  4  are formed in the first air bearing surface  2   b . The slots  4  provide a vent for the air flow produced between the magnetic disk  6  and the first air bearing surface  2   b , thus reducing the elevating force exerted on the magnetic head  1 . Accordingly, the magnetic disk  6  is deformed by a negative pressure generated in the slots  4  and a pressure generated at the second air bearing surface  5  due to a change in air flow so as to warp toward a gap  3   a  as the magnetic disk  6  rotates between the pair of magnetic heads  1 . With this construction, optimum recording to and reproduction from the magnetic disk  6  is ensured even with floating magnetic heads  1  A description will now be given of how the magnetic heads  1  face the magnetic disk  6 , with reference to FIG.  4  and FIG.  5 . FIGS. 4 and 5 show views of a state in which the magnetic head  1  is recording to or reproducing from a magnetic disk  6 , from a radial Y direction of the magnetic disk  6 . 
     FIG. 4 shows the magnetic disk  6  in a state of optimal approach to the magnetic head  1 . 
     As shown in FIG. 4, a pair of slots  4  are formed in the first air bearing surface  2   b  in which the first magnetic head unit  3  is provided. These slots  4  are formed along an entire length of the first air bearing surface, that is, a direction indicated in the drawing by the double-headed arrow X, from a leading edge  7  of the magnetic head  1 , that is, an edge side of the magnetic head  1  at which the magnetic disk  6  enters the magnetic head  1 , to a trailing edge  8  of the magnetic head  1 , that is, an edge side of the magnetic head  1  at which the magnetic disk  6  exits the magnetic head  1 . As a result, a reduction in the elevating force due to the presence of the slots  4  is generated over the entire extent of the length of the first air bearing surface  2   b.    
     Accordingly, even in a state of optimal approach a distance H between the magnetic disk  6  and the leading edge  7  of the magnetic head  1  in the above-described construction in which the slots  4  are provided is smaller than a corresponding distance in a construction in which the slots  4  are not provided. 
     Moreover, with such a construction the magnetic disk  6  is maintained in close proximity to the magnetic head unit  3  as a result of the reduction in elevating force by the slots  4 , thus providing optimal magnetic recording and reproduction. 
     By contrast, FIG. 5 shows a state in which the magnetic disk  6  approaches the magnetic head  1  at a height position lower than that of an optimal approach. Such a small-clearance state of approach results from the flexibility of the magnetic disk  6  or from inevitable errors in the production process thereof. 
     When the height of the magnetic disk  6  upon approach to the magnetic head  1  is lower than a standard optimum height position as described above, the distance H is reduced to such an extent that the magnetic disk  6  may come into contact with the leading edge  7  of the magnetic head  1 , and the magnetic disk  6  or the leading edge  7  of the magnetic head  1  may be damaged as a result. 
     At the same time, although the magnetic disk  6  is ordinarily enclosed in a hard case so as to prevent particles of dirt and dust from adhering to the surface of the magnetic disk  6 , it is impossible to completely prevent the attachment of dust thereto, with the result that, inevitably, dust collects on the surface of the magnetic disk  6 . If magnetic recording to and reproducing from a magnetic disk  6  to the surface of which dust has adhered is performed using a magnetic head  1 , the dust may break loose from the surface of the magnetic disk  6  by the air flow generated at the first and second air bearing surfaces  2   b ,  5  and adhere to the magnetic heads  1 . 
     As a result, because the width dimension of the slots  4  in the conventional magnetic head  1  is small the flow of air is restricted and thus dust accumulates in the slots  4 . If this accumulated dust then breaks loose from the first and second air bearing surfaces  2   b ,  5 , the magnetic disk  6 , which is rotating at high speed, may be damaged by collision with the dust or the flow of air may be impaired by the dust, thus impairing proper magnetic recording and reproduction. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide an improved and useful magnetic head in which the disadvantages described above are eliminated. A more specific object of the present invention is to provide a magnetic head capable of reliably preventing contact between the slider and the recording medium while maintaining a state of optimum magnetic recording and reproduction by preventing the adherence of dust. 
     The above-described objects of the present invention are achieved by a magnetic head comprising: 
     a first magnetic head unit for recording to and reproducing from a first flexible rotating recording medium. 
     a second magnetic head unit for recording to and reproducing from a second flexible rotating recording medium having a coercive force lower than a coercive force of the first flexible rotating recording medium; 
     a slider supporting the first magnetic head unit, the slider having a central groove separating a first air bearing surface at which the first magnetic head unit is provided and a second air bearing surface at which the second magnetic head unit is provided, the slider generating an elevating force from an a flow generated in a space between the first and second air bearing surfaces and the flexible rotating recording media; 
     the first air bearing surface having a width dimension A 1  located on a leading edge side of the magnetic head and substantially perpendicular to a direction from which the first or second flexible rotating recording medium approaches the magnetic head, and a width dimension A 2  located on a trailing edge side thereof and substantially perpendicular to said direction, the width dimension A 1  being larger than the width dimension A 2 ; and 
     an elevating force control slot formed on at least the first air bearing surface so as to extend in a direction substantially perpendicular to the direction from which the first or second flexible rotating recording medium approaches the magnetic head, the elevating force control slot having an inside depth D 1  and an outside depth D 2  greater than the inside depth D 1 . 
     According to the invention described above, by making the width dimension A 1  larger than the width dimension A 2 , contact between the leading side edge of the slider and the magnetic disk can be prevented and, further, the first magnetic head unit and the recording medium can be brought into close proximity to each other. 
     Additionally, by forming the elevating force control slot on at least the first air bearing surface so as to extend in a direction substantially perpendicular to the direction from which the first or second flexible rotating recording medium approaches the magnetic head, the elevating force can be reduced because the air flow arising between the bearing surface and the recording medium can be vented via the elevating force control slot. 
     Additionally, by making the outside depth D 2  greater than the inside depth D 1 , the air flow generated at the slider flows from inside the elevating force control slot to outside the elevating force control slot. Therefore, dust that has broken loose from the recording media is transported from the inside to the outside via the air flow inside the elevating force control slot, that is, is exhausted to the outside of the magnetic head. As a result, adherence of dust to the magnetic head can be prevented, and further, damage to the recording media can be prevented. At the same time, optimum magnetic recording and reproduction can be maintained. 
     Further, by adjusting the internal and external depths D 1  and D 2 , respectively, the speed with which air flows through the interior of the elevating force control slot can be controlled, and it is possible to easily set the air flow to a speed that provides optimal elevating force and dust exhaust. 
     Additionally, the above-described objects of the present invention are also achieved by the magnetic head as described above, wherein a bottom surface of the elevating force control slot is a slanting surface Additionally, the above-described objects of the present invention are also achieved by the magnetic head as described above, wherein at least one step portion is formed on the bottom surface of the elevating force control slot. 
     According to the inventions described above, the flow of air inside the elevating force control slot from the inside to the outside can be made smooth, and thus the adherence of dust to the magnetic heads can be more effectively prevented. 
     Additionally,the above-described objects of the present invention are also achieved by the magnetic head as described above, herein a portion of the central groove in the vicinity of the first magnetic head penetrates in a direction of a height of the slider. 
     According to the invention described above, the volume of air flow can be increased because air flows along a rear surface of the slider as well as the sides of the slider. Accordingly, reduction of the elevating force with respect to the recording medium and the exhaust of dust can be performed more effectively. 
     Additionally, the above-described objects of the present invention are also achieved by a magnetic head comprising: 
     a first magnetic head unit for recording to and reproducing from a first flexible rotating recording medium; 
     a second magnetic head unit for recording to and reproducing from a second flexible rotating recording medium having a coercive force lower than a coercive force of the first flexible rotating recording medium; 
     a slider supporting the first magnetic head unit, the slider having a central groove separating a first air bearing surface at which the first magnetic head unit is provided and a second air bearing surface at which the second magnetic head unit is provided, the slider generating an elevating force from air currents generated in a space between the first and second air bearing surfaces and the flexible rotating recording media; 
     the first air bearing surface having a width dimension A 1  located on a leading edge side of the first magnetic head and substantially perpendicular to a direction from which the first or second flexible rotating recording medium approaches the magnetic head, and a width dimension A 2  located on a trailing edge side thereof and substantially perpendicular to said direction, the width dimension A 1  being larger than the width dimension A 2 ; and 
     an elevating force control slot formed on at least the first air bearing surface so as to extend in a direction perpendicular to the direction from which the first or second flexible rotating recording medium approaches the magnetic head and at the same time penetrate in a direction of the height of the slider. 
     According to the invention described above, by making the width dimension A 1  greater than the width dimension A 2 , contact between the leading side edge of the slider and, further, the first magnetic head unit and the recording medium can be brought into close proximity to each other. 
     Additionally, by forming the elevating force control slot on at least the first air bearing surface so as to extend in a direction substantially perpendicular to the direction from which the first or second flexible rotating recording medium approaches the magnetic head, the elevating force can be reduced because the air flow arising between the bearing surface and the recording medium can be vented via the elevating force control slot. Thus it is possible to control the elevating force for each bearing surface. 
     Additionally, by forming the elevating force control slot formed on at least the first air bearing surface so as to extend in a direction perpendicular to the direction from which the first or second flexible rotating recording medium approaches the magnetic head and at the same time penetrate in a direction of the height of the slider, the volume of air flow can be increased because air flows through the elevating force control slot along a back space and both sides of the slider. Accordingly, reduction of the elevating force with respect to the recording medium and the exhaust of dust can be performed more effectively. 
     Additionally, the above-described objects of the present invention are also achieved by the magnetic head as described above, wherein a depth of the central groove gradually increases as the central groove extends from a formation position of the elevating force control slot toward a trailing edge side of the first or second magnetic heads. 
     According to the invention described above, the flow of air inside the central groove flows easily from the position at which the elevating force control slot is formed toward the trailing edge side. Thus, dust that has broken loose from the recording media is exhausted from the magnetic heads toward the trailing edge by this flow of air flowing inside the central groove. As a result, the adherence of dust to the magnetic head can be prevented, and further, damage to the recording media can be prevented at the same time as optimum magnetic recording and reproduction can be maintained. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a conventional magnetic head for explaining the problems thereof; 
     FIG. 2 is a plan view of the conventional magnetic head; 
     FIG. 3 is a lateral cross-sectional view of the conventional magnetic head from a direction of approach of a disk; 
     FIG. 4 is a lateral cross-sectional view of the conventional magnetic head from a radial Y direction of a disk for explaining a state of approach of the disk; 
     FIG. 5 is a lateral cross-sectional view of the conventional magnetic head for explaining a state in which a height of approach of a disk is lower than a standard optimum height; 
     FIG. 6 is a perspective view of a first embodiment of a magnetic head according to the present invention; 
     FIG. 7 is a plan view of a first embodiment of is the magnetic head according to the present invention; 
     FIG. 8 is a cross-sectional view of the magnetic head shown in FIG. 7 along a line Y—Y therein; 
     FIG. 9 is an enlarged view of the slanting surface provided on a first embodiment of the magnetic head according to the present invention; 
     FIG. 10 is a cross-sectional view of the magnetic head shown in FIG. 7 along a line X—X therein; 
     FIG. 11 is a cross-sectional view of a variation of a first embodiment of the magnetic head according to the present invention; 
     FIG. 12 is a perspective view of a second embodiment of a magnetic head according to the present invention; 
     FIG. 13 is a plan view of a second embodiment of the magnetic head according to the present invention; and 
     FIG. 14 is a cross-sectional view of the magnetic head shown in FIG. 13 along a line Y—Y therein. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description will now be given of an embodiment of the present invention with reference to the accompanying drawings. 
     FIGS. 6,  7 ,  8 ,  9  and  10  show a first embodiment of a magnetic head  10 A according to the present invention. FIG. 6 is a perspective view of a first embodiment of a magnetic head  10 A according to the present invention. FIG. 7 is a plan view of a first embodiment of the magnetic head  10 A according to the present invention. FIG. 8 is a cross-sectional view of the magnetic head  10 A shown in FIG. 7 along a line Y—Y therein. FIG. 9 is an enlarged view of the slanting surface provided on a first embodiment of the magnetic head  10 A according to the present invention. FIG. 10 is a cross-sectional view of the magnetic head  10 A shown in FIG. 7 along a line X—X therein. 
     The magnetic head  10 A generally comprises a first magnetic head unit  12 , a second magnetic head unit  14  and a slider  16 A. The first and second magnetic head units  12 ,  14  are provided on air bearing surfaces  20 ,  22  formed on the slider  16 A. Of the pair of magnetic head units  12 ,  14 , the first magnetic head unit  12  is a high-capacity magnetic head for magnetic recording and reproduction, and is adapted for magnetic disks, or recording media, having a coercive force of 1500 Oe or more. The second magnetic head unit  14  is a magnetic head for ordinary magnetic recording and reproduction, and is adapted, for example, for magnetic disks having a coercive force of approximately 600-700 Oe. The second magnetic head unit  14  is constructed so that a read/write gap (R/W gap) and an erase gap (E gap) are formed by sandwiching a gap member between magnetic head cores  30 . In other words, the magnetic head  10 A according to this first embodiment of the present invention has a so-called compatible-type magnetic head structure, capable of performing both ordinary magnetic recording and reproduction as well as high-capacity magnetic recording and reproduction. 
     The slider  16 A is a block member formed, for example, of a ceramic. The slider  16 A supports the first and second magnetic head units  12 ,  14  and also provides a force for elevating the first and second magnetic head units  12 ,  14  so that the first and second magnetic head units  12 ,  14  float over a magnetic disk  32 . Additionally, the slider  16 A is provided with a central groove  18 , a first air bearing surface  20 , a second air bearing surface  22 , an incision  24 , a slanting surface  26 , a chamfered part  28  and an elevating force control slot  34 A. 
     The central groove  18  is formed at a position in a center of a width of a top surface of the slider  16 A, that is, in a direction indicated by arrows Y 1 -Y 2  in the drawing, so as to extend longitudinally in a direction of travel of the magnetic disk  32 , that is, in a direction indicated by the arrows X 1 -X 2  in the drawing. By forming the central groove  18 , the first and second air bearing surfaces are formed so as to sandwich the central groove of the slider  16 A. 
     In order for the magnetic head  10 A to float properly over the magnetic disk  32 , the air flow generated between the slider  16 A and the magnetic disk  32  must be smooth. It is for this purpose that the first and second air bearing surfaces  20 ,  22  are formed as highly flat surfaces 
     Additionally, as shown in the enlarged view presented in FIG. 9, the slanting surface  26  extending across a predetermined range is formed on the leading edge of the slider  16 A, that is, the X 2  edge, from which the magnetic disk  32  approaches. This slanting surface  26  forms an angle of for example 60 minutes or less with respect to the first and second air bearing surfaces  20 ,  22 . By forming the slanting surface  26  on the leading edge of the slider  16 A facing the approaching magnetic disk  32 , a hard collision between the magnetic disk  32  and the slider  16 A can be prevented. 
     It should be noted that, in the following description, the X 1  edge of the slider  16 A facing the magnetic disk  32  as it withdraws is referred to as a trailing edge  17 B. Additionally, the X 2  edge of the slider  16 A facing the magnetic disk  32  as it approaches is referred to as the leading edge  17 A. 
     Additionally, a chamfered part  28  is formed on an outer periphery of the first and second air bearing surfaces  20 ,  22 . Providing the chamfered part  28  also prevents the magnetic disk  32  from colliding hard against the slider  16 A when the magnetic head  10 A is in a floating state. 
     That is, the slider  16 A in a floating state with respect to the magnetic disk  32  affects the magnetic disk  32  such that a movement such as rolling, pitching and the like inevitably occurs depending on the condition of the air flow between the slider  16 A and the magnetic disk  32 . When this movement is large, it is the periphery portion of the first and second air bearing surfaces  20 ,  22  that is the first to contact the magnetic disk  32 . Thus, by forming the chamfered part  28  on the periphery of the first and second air bearing surfaces  20 ,  22 , the magnetic disk  32  is prevented from colliding hard against the slider  16 A. 
     At the same time, the incision  24  is formed on the X 1  side, that is, the trailing edge side, of the central groove  18  formed on the slider  16 A. The incision  24  is configured so as to penetrate a thickness direction of the slider, that is, a direction indicated by arrows Z 1 -Z 2  in the drawing The incision  24  is formed so as to control the width of the first air bearing surface  20 . 
     The above-described magnetic head  10 A floats over the magnetic disk  32  due to en elevating force generated by a change in air flow caused by a relative speed between the first and second air bearing surfaces  20 ,  22  of the slider  16 A and the magnetic disk  32 . As shown in FIG. 8, magnetic recording and reproduction is performed while a state of non-contact between the magnetic head and the magnetic disk  32  is maintained. 
     A description will now be given of the first air bearing surface  20  formed in the slider  16 A of the magnetic head  10 A. 
     As described above, according to the first embodiment the magnetic head  10 A is provided with an incision  24  so as to penetrate the thickness of the slider  16 A. By forming the incision  24  and by controlling a width thereof in the Y 1 -Y 2  direction, the width A 2  of the trailing edge  17 B of the first air bearing surface  20  can be controlled. 
     According to the first embodiment, the incision  24  is formed such that the width A 2  of the trailing edge  17 B of the first air bearing surface  20  is smaller than the width A 1  of the leading edge  17 A of the first air bearing surface  20 , that is A 1 &gt;A 2 . More specifically, the width A 2  at the trailing edge  17 B is set to be less than or equal to one-third the width A 1  at the leading edge  17 A, that is, A 2  (2·A 1 /3). 
     By setting the width A 1  of the first air bearing surface  20  to be equal to or larger than the width A 2  at the trailing edge  178  contact between the leading edge  17 A and the magnetic disk  32  can be prevented and at the same time the magnetic disk  32  can be maintained in close proximity to the first magnetic head unit  12 . 
     A description will now be given of the reason for the above-described advantages. 
     The elevating force generated between the first air bearing surface  20  and the magnetic disk  32  is related to the surface area of the first air bearing surface  20 . That is, the elevating force is generated as a result of the air flow between two opposed parts, the first air bearing surface  20  and the magnetic disk  32 . As a result, the larger the surface area of the first air bearing surface  20 , the larger the elevating force. 
     Accordingly, by setting the width A 2  of the trailing edge  17 B of the first air bearing surface  20  to be smaller than the width A 1  of the leading edge  17 A thereof, the surface area of the trailing edge  17 B of the first air bearing surface  20  is made smaller than the surface area of the leading edge  17 A thereof. That is, the elevating force generated between the first air bearing surface  20  and the magnetic disk  32  is greater at the leading edge  17 A of the first air bearing surface  20  and smaller at the trailing edge thereof 
     Accordingly, as shown in FIG. 8, a state arises in which the magnetic disk  32  is distant from the first air bearing surface  20  at the leading edge  17 A of the first air bearing surface  20  while the magnetic disk  32  is in close proximity to the first air bearing surface  20  at the trailing edge  17 B thereof, that is, a position near the first and second magnetic head units  12 ,  14 , 
     By thus keeping the magnetic disk  32  and the first air bearing surface  20  widely separated at the leading edge  17 A, the leading edge  17 A can be prevented from contacting the magnetic disk  32  even when the magnetic disk  32  approaches the magnetic head  10 A at a smaller than optimal clearance, that is, lower than a standard optimum height position, and thus the magnetic disk  32  can be prevented from being damaged. 
     Additionally, it is possible to bring the magnetic disk  32  into close proximity to the first magnetic head unit  12  because the elevating force decreases at the trailing edge. By bringing the first magnetic head unit  12  and the magnetic disk  32  into close proximity to each other, it is possible to perform strong magnetic recording when recording and it is possible to obtain strong reproduction signals when reproducing. 
     At the same time, according to the magnetic head  10 A of the present embodiment, an elevating force control slot  34 A is formed on the first and second air bearing surfaces  20 ,  22  so as to extend in a direction perpendicular to the direction of travel of the magnetic disk  32 , that is, in a Y 1 -Y 2  direction. More specifically, the elevating force control slot  34 A is formed so as to extend from a side part of a magnetic head core  30  toward the first air bearing surface  20 . 
     By forming the elevating force control slot  34 A the elevating force is reduced, because the flow of air between the air bearing surfaces  20 ,  22  and the magnetic disk  32  at a position at which the elevating force control slot  34 A is formed is vented via the elevating force control slot  34 A. 
     Additionally, by making a bottom surface of the elevating force control slot  34 A into a slanting surface according to the first embodiment, an outside depth D 2  at an outer periphery of the slider  16 A is set to be greater than an inside depth D 1  at a position adjacent to the magnetic head core  30 , that is, D 2  D 1 . According to this construction, the surface area of the passageway through which the air flows expands from the inside toward the outside, so the air flow generated between the first and second air bearing surfaces  20 ,  22  and the magnetic disk  32  flows from the inside toward the outside via the elevating force control slot  34 A, that is, in a direction indicated by a dotted-line arrow shown in FIG.  10 . 
     However, as previously noted, although the magnetic disk  32  is enclosed in a hard case so as to prevent particles of dirt and dust from adhering to the surface of the magnetic disk  32 , it is impossible to completely prevent the attachment of dust thereto, with the result that, inevitably, dust collects on the surface of the magnetic disk  32 . Additionally, if the magnetic disk  32  is used for an extended period of time, magnetic particles may come loose from the magnetic disk  32 . Hereinafter, such magnetic particles and other particles of dirt and dust are referred to as simply dust. If this dust adheres to and accumulates at and breaks loose from a surface of the slider  16 A that is opposite the magnetic disk  32 , then, as noted previously, the magnetic disk  32  may be damaged and it may become impossible to perform optimum magnetic recording and reproduction. 
     However, by providing the elevating force control slot  34 A having an outside depth D 2  greater than an inside depth D 1 , dust that has broken loose from the magnetic disk  32  is borne from the inside to the outside by the flow of air inside the elevating force control slot  34 A, that is, the dust is exhausted to the outside of the magnetic head  10 A in particular, according to the present embodiment the flow of air can be made smooth because the bottom surface of the elevating force control slot  34 A is a slanting surface. 
     As a result, the adherence and accumulation of dust on the magnetic head  10 A can be prevented and the occurrence of damage to the magnetic disk  32  caused by dust can be prevented. At the same time, optimum magnetic recording and reproduction can be achieved because a steady flow of air can be obtained and the separation distance between the first magnetic head unit  12  and the magnetic disk  32  can be stabilized. 
     Additionally, in a state of formation of the elevating force control slot  34 A, for example by mechanical processing or the like, it is relatively easy to control the extent of the inside depth D 1  and the  315  outside depth D 2  thereof. As described above, the speed and volume of air flow through the interior of the elevating force control slot  34 A can be controlled by the shape of the elevating force control slot  34 A, that is, the surface area of the passageway. Thus, by shaping the elevating force control slot  34 A as appropriate during the a fabrication thereof, it is possibly to easily achieve an air flow speed and volume optimal for both the elevating force and the elimination of dust. 
     A description will now be given of a variation of a first embodiment of a magnetic head according to the present invention. 
     FIG. 11 is a cross-sectional view of a variation of a first embodiment of the magnetic head according to the present invention, at a point identical to the cross-sectional view shown in FIG.  10 . 
     The above-described magnetic head  10 A according to the first embodiment has an outside depth D 2  greater than an inside depth D 1 , so the bottom surface of the elevating force control slot  34 A comprises a smoothly continuous slanting surface. 
     By contrast, the magnetic head  10 B according to the present variation of the first embodiment has a first step portion  35   a  that is shallower than the central groove  18 , the first step portion  35   a  being formed on the second air bearing surface  22 , and similarly, a second step portion  35   b  that is deeper than the central groove  18 , the second step portion  35   b  being formed on the first air bearing surface  20 . Thus, the distinctive feature of the present variation is that the elevating force control slot  34 A comprises the first step portion  35   a , the second step portion  35   b  and the central groove  18  as described above. 
     Like the first embodiment of the magnetic head  10 A according to the present invention, the construction of the magnetic head  10 B according to the present variation of the first embodiment as described above also provides an outside depth D 2  of the elevating force control slot  34 A that is greater than an inside depth D 1  thereof, thus smoothing the flow of air from the inside toward the outside within the elevating force control slot  34 A. As a result, the magnetic head  10 B according to the present variation achieves the same effect as does the magnetic head  10 A according to the first embodiment. 
     It should be noted that, although in the above-described embodiment and variation the elevating force control slots  34 A and  34 B are formed so as to extend from a position adjacent to the magnetic head core  30  toward the first air bearing surface  20 , the elevating force control slots  34 A and  34 B are not limited to the above-described formation positions but may instead be formed so as to extend from the central groove  18  toward the first air bearing surface  20 , or extend along only the first air bearing surface  20 . 
     Next, a description will be given of a second embodiment of a magnetic head  10 C according to the present invention, with reference to FIGS. 12,  13  and  14 . FIG. 12 is a perspective view of the magnetic head  10 C, FIG. 13 is a plan view of the magnetic head  10 C and FIG. 14 is a cross-sectional view of the magnetic head  10 C of FIG. 13 along a line Y—Y therein. It should be noted that, in FIGS. 11,  12  and  13 , those parts identical to the corresponding parts of the magnetic head  10 A of the first embodiment shown in FIGS. 6,  7 ,  8 ,  9  and  10  are given identical reference numerals and a description thereof is omitted. 
     Like the magnetic head  10 A according to the first embodiment, the magnetic head  10 C of the second embodiment of the present invention has an elevating force control slot  34 C extending in a direction perpendicular to the direction of travel of the magnetic disk  32 , that is, in the Y 1 -Y 2  direction. Therefore the elevating force can be reduced because the air flow between the first and second air bearing surfaces  20 ,  22  and the magnetic disk  32  is vented through this elevating force control slot  34 C, and so the magnetic disk  32  can be brought into close proximity with the first magnetic head unit  12  during magnetic recording and reproduction. 
     However, in contrast to the magnetic head  10 A according to the first embodiment, in which the bottom surface of the elevating force control slot  34 C is a slanting surface or a stepped surface, the magnetic head  10 C according to the second embodiment has an elevating force control slot  34 C that penetrates in a direction of a height of the slider  16 B, that is, in a direction indicated by arrows Z 1 -Z 2 . 
     By providing an elevating force control slot  34 C that penetrates in the Z 1 -Z 2  direction according to the second embodiment, the air flow generated between the first and second air bearing surfaces  20 ,  22  and the magnetic disk  32  can be made to flow, that is, escape, along a rear surface as well as both sides of the slider  16 B. As a result, the volume of air flow can be increased, and thus it is possible to reduce the elevating force exerted on the magnetic disk  32  and more reliably exhaust dust broken loose from the magnetic disk  32 . 
     Additionally, in the magnetic head  10 C according to the second embodiment a slanting slot  36  is formed in place of the incision  24  provided on the magnetic head  10 A according to the first embodiment. In the second embodiment the slanting slot  36  is formed so as to be continuous with the central groove  18  and to have a depth which gradually increases from a position of formation of the elevating force control slot  34 C toward a trailing direction, that is, a trailing edge side of the first or second magnetic head units  12 ,  14 . 
     By providing the slanting slot  36 , the air flow generated between the first and second air bearing surfaces  20 ,  22  and the magnetic disk  32  and flowing through the interior of the central groove  18  is guided by the slanting slot  36  so as to flow easily from the formation position of the elevating force control slot  34 C toward the trailing direction. As a result, dust that has broken loose from the magnetic disk  32  is exhausted from the magnetic head  10 C toward the trailing direction via the air flow over the slanting slot  36 . 
     Accordingly, the adherence and accumulation of dust on the magnetic head  10 C as well as damage to the magnetic disk  32  due to dust can be prevented. At the same time, optimum magnetic recording and reproduction can be achieved because a steady flow of air can be obtained and the separation distance between the first magnetic head unit  12  and the magnetic disk  32  can be stabilized. 
     The above description is provided in order to enable any person skilled in the art to make and use the invention and sets forth the best mode contemplated by the inventors of carrying out the invention. 
     The present invention is not limited to the specifically disclosed embodiments and variations, and modifications may be made without departing from the scope of the present invention.