Abstract:
One embodiment of the present invention is directed to a read head for a data storage device including a sensor for reading data from a data storage medium, a first shield disposed adjacent to the sensor and characterized as moment-compensated, and a second shield disposed adjacent to the sensor, the second shield being moment-compensated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Hard disk storage devices are used in many computer system operations. In fact, most computing systems are not operational without some type of hard disk drive or similar storage device to store the most basic computing information such as the boot operation, the operating system, applications, and the like.  
         [0002]     The basic hard disk drive model includes a storage disk or hard disk that spins at a designed rotational speed. An actuator arm is utilized to reach out over the surface of the disk. The arm carries a head assembly that has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The transducer is attached to a slider, such as an air-bearing slider, which is supported adjacent to the data surface of the disk by a cushion of air generated by the rotating disk. The transducer can also be attached to a contact-recording type slider. In either case, the slider is connected to the actuator arm by means of a suspension. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA).  
         [0003]     In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.  
         [0004]     Over the years, the disk and the head have undergone great reductions in their size. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that).  
         [0005]     This continual reduction in size has placed steadily increasing demands on the technology used in the HGA, particularly in terms of power consumption, shock performance, and disk real estate utilization. One recent advance in technology has been the development of the Femto slider, which is roughly one-third of the size and mass of the older Pico slider, which it replaces; over the past 23 years, slider size has been reduced by a factor of five, and mass by a factor of nearly 100.  
         [0006]     Some of the recent improvement has resulted from reduction in the size of the read head.  FIG. 1  shows a cross section of a common read head  100 . Read head  100  typically comprises a sensor  110 , shields  121  and  122 , and conductive leads  131 - 132 . For the purposes of illustration, thickness will refer to horizontal dimensions in  FIG. 1 , height will refer to vertical dimensions in the figure, and width will refer to dimensions going into the page. In today&#39;s read heads, sensors are commonly on the order of 300 Å thick, whereas shields are typically 1-2 microns thick and 50-100 microns wide. Thus, shields  121  and  122  are significantly larger than sensor  110 . Furthermore, the separation between the head  100  and disk  140  is typically only around 1-2 nm.  
         [0007]     During head operation, the head is excited with high current, causing the temperature in the head to rise. This rise in temperature can cause shields  121  and  122  to thermally expand. Thus, shields  121  and  122 , which are commonly made of NiFe, will actually protrude, causing sensor  110  to become recessed. In come cases, shields have been known to protrude as much as 1 nm. This is quite significant considering the small distance between the air bearing surface  150  and the disk  140 . Protrusion of the shields hinders the reliability of the sensor interface as well as the sensitivity of the sensor.  
         [0008]     Thus, it is desirable to restrict shield thickness to less than 100 nm. However, reducing the size of shields can adversely affect their ability perform their two primary functions: providing resolution by shielding the sensor from fields of bits other than the bit directly below; and providing contacts for external an current supply. First, when the shield material becomes thin, it can easily saturate and will no longer act as a shield. Second, the shield material does not have a high degree of conductivity, so making a shield thinner will only increase its resistivity. Furthermore, decreasing the size of a shield can cause it to become magnetically unstable.  
       BRIEF SUMMARY OF INVENTION  
       [0009]     Accordingly, one embodiment of the present invention is directed to a read head for a data storage device including a sensor for reading data from a data storage medium, a first shield disposed adjacent to the sensor and characterized as moment-compensated, and a second shield disposed adjacent to the sensor, the second shield being moment-compensated.  
         [0010]     Another embodiment of the present invention is directed to a data storage device including a disk with a data surface, a rotator for rotating the disk, and a read/write head for reading and writing data with respect to the data surface. The read/write head includes a sensor for reading data from a data storage medium, a first shield disposed adjacent to the sensor and characterized as moment-compensated, and a second shield disposed adjacent to the sensor and characterized as moment-compensated.  
         [0011]     Another embodiment of the present invention is directed to a read head for a data storage device including a sensor for reading data from a data storage medium, a first shield disposed adjacent to the sensor, a second shield disposed adjacent to the sensor, a first antiferromagnet disposed adjacent to the first shield, and a second antiferromagnet disposed adjacent to the second shield.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1 a  side view of a prior art read head design.  
         [0013]      FIG. 2  is a side view of a hard disk drive and a controller unit in block form, in accordance with one embodiment of the present invention.  
         [0014]      FIG. 3  is a top view of a hard disk drive system, in accordance with one embodiment of the present invention.  
         [0015]      FIG. 4  is an air bearing surface view of a read head for a data storage device, in accordance with an embodiment of the present invention.  
         [0016]      FIG. 5  is an air bearing surface view of a read head for a data storage device, in accordance with an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     A head assembly and a data recording device configured to use a head assembly are disclosed. Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the claims. Furthermore, in the detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.  
         [0018]     With reference now to  FIGS. 2 and 3 , a side and top view of a hard disk drive  210  is shown. Drive  210  has a disk pack having at least one media or magnetic disk  212 , mounted to a spindle  214 . A spindle motor  216  rotates the spindle  214  and the disk or disks  212 . The spindle motor  214  and an actuator shaft  230  are attached to the chassis  220 . A hub assembly  232  rotates about the actuator shaft  230  and supports a plurality of actuator arms  234 , referred to as a “comb.” A rotary voice coil motor  140  is attached to the chassis  220  and to a rear portion of the actuator arms  234 .  
         [0019]     A plurality of suspension assemblies  250  are attached to the actuator arms  234 . A plurality of transducer heads or sliders  252  are attached respectively to the suspension assemblies  250 . The sliders  252  are located proximate to the disks  212  for reading and writing. The rotary voice coil motor  240  rotates actuator arms  234  about the actuator shaft  230  in order to move the suspension assemblies  250  to the desired radial position on disks  212 . The shaft  230 , hub  232 , arms  234 , and motor  240  may be referred to collectively as a rotary actuator assembly.  
         [0020]     A controller unit  260  provides overall control to system  210 . Controller unit  260  typically includes (not shown) a central processing unit (CPU), a memory unit and other digital circuitry, although it should be apparent that one skilled in the computer arts could also enable these aspects as hardware logic. Controller  260  is connected to an actuator control/drive unit  266  that in turn is connected to the rotary voice coil motor  240 . This configuration allows controller  260  to control rotation of the disks  212 . A host system  280 , typically a computer system, is connected to the controller system  260 . The host system  280  may send digital data to the controller  260  to be stored on disks  212 , or it may request that digital data at a specified location be read from the disks  212  and sent to the system  280 . The basic operation of DASD units is well known in the art and is described in more detail in The Magnetic Recording Handbook, C. Dennis Mee and Eric D. Daniel, McGraw-Hill Book Company, 1990, hereby incorporated by reference as background.  
         [0021]     With reference now specifically to the read head, as stated above, decreasing the thickness of sensor shields lowers the conductivity of the shields and also makes them more susceptible to saturation. One solution to the saturation problem is to put an antiferromagnet material in contact with the read-head&#39;s shield.  FIG. 4  shows an example of a read head  400 , as viewed from the air bearing surface, that utilizes an antiferromagnet, in accordance with an embodiment of the present invention. In one embodiment, read head  400  includes a sensor  410 . In one embodiment, sensor  410  is a current perpendicular to the plane of the layers type sensor. Read head  400  also includes two shields  420  and  425  disposed adjacent to sensor  410 . The shield material can be NiFe, CoFe, iron nitride, or any other appropriate shield material.  
         [0022]     Read head  400  also includes antiferromagnets  430  and  435  disposed adjacent to shields  420  and  425  and conductive leads  440  and  445  disposed adjacent to antiferromagnets  430  and  435 . Antiferromagnets  430  and  435  comprise an antiferromagnet material such as iron-magnesium or platinum-magnesium alloys. It should be appreciated that other antiferromagnet materials could be used as well. Placing antiferromagnets  430  and  435  in contact with shields  420  and  425  develops exchange coupling between the materials, causing the saturation field of shields  420  and  425  to increase. Raising the saturation fields of shields  420  and  425  allows for the shields to be much thinner while still maintaining their functionality. In one embodiment, shields  420  and  425  are equal to or less than 50 nm thick, and the combined thickness of shields  420  and  425  and their respective antiferromagnets  430  and  435  is equal to or less than 100 nm. In  FIG. 4 , the thickness dimension should be understood as the vertical dimension of the page.  
         [0023]     In another embodiment, the saturation problem is solved by anti-parallelly coupling the shield material with anti-parallel coupling material.  FIG. 5  shows an example of a read head  500  as viewed from the air bearing surface that utilizes anti-parallel coupling, in accordance with an embodiment of the present invention. Read head  500  includes sensor  510 . In one embodiment, sensor  510  is a current perpendicular to the plane of the layers type sensor. Read head  500  also includes two shields  520  and  530  disposed adjacent to sensor  510  and two conductive leads  540  and  550  disposed adjacent to shields  520  and  530 . Shields  520  and  530  each include a first layer of shield material  521  and  531  having a magnetic moment and a second layer of shield material  522  and  532  having a magnetic moment that is anti-parallel to its respective first layer  521  and  531 . The shield material can be NiFe, CoFe, iron nitride, or any other appropriate shield material. Shields  520  and  530  also include a layer of anti-parallel coupling material  525  and  535  disposed between their respective first layers  521  and  531  and second layers  522  and  532 . In one embodiment, coupling material  525  and  535  comprises ruthenium. The conductivity problem can be solved by adding another high-conductivity, non-magnetic material in contact with the shield to lower its resistivity. However, this does not resolve any saturations issues with the shields. The shield material can be NiFe, CoFe, iron nitride, or any other appropriate shield material. Disposed between the first layers  521  and  531  and the second layers  522  and  532 . Anti-parallelly coupling first layers  521  and  531  and second layers  522  and  532  significantly increases the saturation fields of shields  520  and  530 . Raising the saturation fields of shields  520  and  530  allows for the shields to be much thinner while still maintaining their functionality. In one embodiment, shields  520  and  530  are equal to or less than 100 nm thick. In a preferred embodiment, layers  521 - 522  and  531 - 532  are equal to or less than 200 angstrom thick. In one embodiment, shields  520  and  530  are also equal to or less than 100 microns in height and equal to or less than 100 microns in width. In  FIG. 5  it should be understood that the thickness dimension is the vertical dimension of the page, the width dimension is the horizontal dimension of the page, and the height dimension is the dimension into the page.  
         [0024]     Furthermore, using anti-parallel coupling in the manner illustrated in  FIG. 5  also serves to solve the resistivity problem as well. Ruthenium and other similar materials are highly conductive. Thus, putting such materials in contact with shield materials  521 - 522  and  531 - 532  as a coupling material significantly lowers the overall resistivity of shields  520  and  530 .  
         [0025]     Thus, embodiments of the present invention provide a means and structure for reduced thickness of read head shields while at the same time avoiding the saturation and resistivity problems associated with thinner shields. As a consequence of the reduced thickness, the shields will protrude much less due to thermal expansion. Therefore, the tolerances between the read head and the disk surface may be reduced, contributing to a reduction in the overall size of a storage device in multiple dimensions.  
         [0026]     Embodiments of the present invention are thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.