Abstract:
The embodiments disclosed generally relate to a read head in a magnetic recording head. The read head utilizes a sensor structure having: a pinned magnetic structure recessed from a media facing surface; and a reader gap structure. The reader gap structure has a spacer layer recessed from the media facing surface and disposed on top of the pinned magnetic structure, a recessed first free layer partially recessed from the media facing surface and disposed on top of the barrier layer, a second free layer extending to the media facing surface an disposed on top of the barrier layer, and a cap layer extending to the media facing surface disposed atop the second free layer. The pinned magnetic structure, the spacer, and the first free layer have a common face which is on an angle relative to the media facing surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments disclosed herein generally relate to a magnetic read head for use in a hard disk drive. 
     2. Description of the Related Art 
     At the heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent to a media facing surface (MFS), such as an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions corresponding to host data. The read and write heads are connected to a signal processing circuitry that operates according to a computer program to implement the writing and reading functions. 
     Modern HDDs use tunnel magneto resistance (TMR) read heads. The TMR read head uses magnetic tunnel junctions for sensing magnetically written data on a HDD. The direction of magnetization for a ferromagnetic “free layer” can be switched by an external magnetic field. If the magnetization is in a parallel orientation to a second pinned ferromagnetic film, it is more likely that electrons will tunnel through the insulating film separating them than if they are in an anti-parallel orientation. Consequently, such a junction can be switched between two states of electrical resistance, one with low and one with very high resistance. 
     The need for ever increased data density is pushing researchers to develop data recording systems that can read and record ever smaller bit lengths in order to increase the density of data recorded on a magnetic medium. The size of a reader gap thickness in the read head is related to the size of the bit length the read head can sense. This has led to a push to decrease the reader gap thickness for the read heads. However, the amount by which the reader gap thickness can be decreased has been limited by physical limitations of sensors and also by the limitations of currently available manufacturing methods. 
     Future read heads for high density media require a very narrow reader gap. The reader gaps for conventional TMR/CPP read heads cannot meet the requirements for future high density media simply by thinning the functional layers of the read head. Recently, alternative read head structures, such as recessed pinned layers and scissor sensors, have been the focus of development for narrowing the reader gap of the read heads. 
     The conventional read heads using recessed pinned layers have been considered with various configurations of the pinned layer recessed back from the MFS. As a result, the size of the reader gap can be shrunk approximately 7 nm to about 18 nm. However, aside from fabrication challenges, the reduction in the pinning energy and the stability of the pinned layer at the MFS has been problematic for read heads using the recessed pinned layers. 
     Read heads using the scissor sensor structure has been developed for many years. Using this technology, the reader gap can be reduced approximately 10 nm to about 14 nm. However, a great challenge related to yield and the sensor stability still remains. 
     Therefore, there is a need to further reduce the reader gap while still preserving the stability and reliability of the magnetic read head sensor. 
     SUMMARY OF THE INVENTION 
     The embodiments disclosed herein relate to a sensor structure having a pinned magnetic structure recessed from a media facing surface and a reader gap structure. The reader gap structure has a spacer layer fully recessed from the media facing surface and disposed on top of the pinned magnetic structure; a first part of free layer partially recessed from the media facing surface and disposed on top of the spacer layer; a second part of free layer extending to the media facing surface an disposed on top of the recessed first free layer; and a cap layer extending to the media facing surface disposed atop the second part of free layer. The seed layer, pinned magnetic structure, the spacer, and the first free layer have a common face which is on an angle relative to the media facing surface. 
     In another embodiment, a magnetic read head has a bottom shield, a top shield; and a sensor structure disposed between the bottom and top shield. The sensor structure has a pinned magnetic structure recessed from a media facing surface and a reader gap structure. The reader gap structure has a spacer layer fully recessed from the media facing surface and disposed on top of the pinned magnetic structure; a first part of free layer partially recessed from the media facing surface and disposed on top of the spacer layer, a second part of free layer extending to the media facing surface an disposed on top of the recessed first free layer; and a cap layer extending to the media facing surface disposed atop the second free layer. The seed layer, pinned magnetic structure, the spacer, and the first free layer have a common face which is on an angle relative to the media facing surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features can be understood in detail, a more particular description of the invention, briefly summarized above, may be reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  illustrates an exemplary magnetic disk drive, according to one embodiment. 
         FIG. 2  is a side view of a read/write head and magnetic disk of the disk drive of  FIG. 1 , according to one embodiment. 
         FIG. 3  is a schematic illustration of the read head of  FIG. 2 , according to one embodiment. 
         FIG. 4  is a schematic illustration of the read head of  FIG. 2 , according to a second embodiment 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     In the following, reference is made to embodiments of the invention. However, it should be understood that the invention is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement and practice the invention. Furthermore, although embodiments of the invention may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the invention. Thus, the following aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the invention” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s). As used herein, a “stitched” layer is a layer formed in two or more separate steps, such as later deposited and joined (“stitched”). 
       FIG. 1  illustrates a top view of an exemplary hard disk drive (HDD)  100 , according to an embodiment of the invention. As illustrated, HDD  100  may include one or more magnetic disks  110 , an actuator  120 , actuator arms  130  associated with each of the magnetic disks  110 , and a spindle motor  140  affixed in a chassis  150 . The one or more magnetic disks  110  may be vertically arranged and coupled with the spindle motor  140 . 
     Magnetic disks  110  may include circular tracks of data on both the top and bottom surfaces of the magnetic disk  110 . A magnetic read/write head  180  mounted on a slider may be positioned on a track. As each magnetic disk  110  spins, data may be written on to, and/or read from, the data track. Magnetic read/write head  180  may be coupled to an actuator arm  130  as illustrated in  FIG. 1 . Actuator arm  130  may be configured to swivel around actuator axis  131  to place magnetic read/write head  180  on a particular data track. 
       FIG. 2  is a fragmented, cross-sectional side view through the center of the magnetic read/write head  180  facing the magnetic disk  110 . The magnetic read/write head  180  and magnetic disk  110  may correspond to the magnetic read/write head  180  and magnetic disk  110 , shown in  FIG. 1 . 
     In some embodiments, the magnetic disk  110  may be a “dual-layer” medium that includes a perpendicular magnetic data recording layer (RL)  204  on a “soft” or relatively low coercivity magnetically permeable under-layer (PL)  206  disposed atop a non-magnetic material  219 . The RL  204  is illustrated with perpendicularly recorded or magnetized regions  234 , with adjacent regions having magnetization directions, as represented by the arrows  236  located in the RL  204 . 
     The magnetic read/write head  180  includes an MFS  260 , such as an ABS, such that the MFS  260  is facing the magnetic disk  110 . The magnetic read/write head  180  also includes a magnetic write head  250  and a magnetic read head  230 . The magnetic read head  230  is disposed between a bottom shield S 2  and a top shield S 1 . Additionally, the bottom shield S 2  may be disposed between the magnetic write head  250  and the magnetic read head  230 . The write head  250  includes a magnetic circuit made up of a main pole  212  and a thin film coil  218  shown in the section embedded in the non-magnetic material  219 . 
     In  FIG. 2 , the magnetic disk  110  moves past the magnetic read/write head  180  in the direction indicated by the arrow  232 . The magnetic write head  250  writes bits of information in the adjacent magnetized regions  234  for recording data on the magnetic disk  110 . The magnetized bits are detectable by the read head  230  which senses the recorded (magnetized) bits. 
       FIGS. 3 and 4  are schematic illustrations of read heads  300 ,  400  according to separate embodiments of the invention. The read heads  300 ,  400  may correspond to the magnetic head  230  shown in  FIG. 2 . The read heads  300 ,  400  may have a sensor structure  306  with a pinned magnetic structure  320 , disposed between the bottom shield S 2  and the top shield S 1 . The pinned magnetic structure  320  has a trapezoidal shape which enhances the shielding effect and permits the reduction of a width  352  for a reader gap  354 . The following discussion will be in reference to  FIG. 3  but is equally germane to  FIG. 4 . 
     In  FIG. 3 , the bottom shield S 2  may comprise a ferromagnetic material such as nickel (Ni), iron (Fe), cobalt (Co), nickel-iron alloy (NiFe), nickel-iron-cobalt alloy (NiFeCo), nickel-cobalt alloy (NiCo), cobalt-iron alloy (CoFe), combinations thereof, or other suitable materials. The bottom shield may have a thickness in or about the micrometer level. The sensor structure  306  is disposed on the bottom shield S 2 . 
     The sensor structure  306  may optionally include a seed layer  318 . The seed layer  318  may be disposed on the bottom shield S 2 . The seed layer may comprise ruthenium (Ru), tantalum (Ta), Ru, Ta, Ni(Co)Fe, Ni(Fe)Cr, Co(Ni)FeB, Co(Ni) Fe(Ta, Hf, Zr, W, Nb)(B) and their combination, or other suitable material. The seed layer  318  may have a thickness of about 10 Angstroms to about 500 Angstroms. A thin film deposition process such as DC magnetron sputtering may deposit the seed layer  318 . 
     The pinned magnetic structure  320  is disposed atop the seed layer  318 , or the bottom shield S 2 . The pinned magnetic structure  320  comprises an antiferromagnetic (AFM) layer  322 , a first ferromagnetic pinned (AP1) layer  324 , a pin spacer layer  326 , and a second anti-parallel pinned (AP2) ferromagnetic layer  328 . The seed layer  318  and the pinned magnetic structure  320  may be stitched together and recessed from the MFS  302  along with spacer layer  330 . A first free layer  332  may additionally be recessed from the MFS  302  and disposed atop the spacer layer  330 . The first part of free magnetic layer  332 , the spacer layer  330 , the pinned magnetic structure  320  and the seed layer  318  share a common face  310 . A front shield  342  and a front isolation layer  344  are disposed between the common face  310  and the MFS  302 . Although the sensor structure  306  is bottom pinned in  FIG. 3 , it should be appreciated that the sensor structure  306  may be configured as a top pinned sensor structure. 
     The AFM layer  322  may be formed on the seed layer  318  and annealed in an aligning magnetic field to pin the orientation of the magnetic field of the AFM layer  322 . The AFM layer  322  may comprise platinum (Pt), iridium (Ir), rhodium (Rh), nickel (Ni), iron (Fe), magnesium (Mn), or combinations thereof such as platinum-manganese (PtMn), PtPdMn, NiMn or Iridium-Manganese (IrMn). In one embodiment, the AFM layer  322  is comprised of IrMn and has a thickness of between about 30 Angstroms and about 400 Angstroms such as about 60 Angstroms. 
     The AP1 layer  324  may be deposited on the AFM layer  322 . The AP1 layer  324  may comprise one or more magnetic materials such as, for example NiFe, Co, CoFe, CoFeB, or diluted magnetic alloys. In one embodiment, several magnetic materials may be layered to form the AP1 layer  324 . For example, the AP1 layer  324  may be formed from a Co layer disposed atop a CoFe layer which in turn is disposed atop a second Co layer. The AP1 layer  324  may have an overall thickness between about 10 Angstroms and about 100 Angstroms such as about 20 Angstroms. 
     The pin spacer layer  326  is deposited on the AP1 layer  324 . The pin spacer layer  326  may comprise Ruthenium (Ru), rhodium (Rh), iridium (Ir), combinations thereof, or other suitable materials. In one embodiment, the pin spacer layer  326  may be formed from Ru having a thickness between about 3 Angstroms and about 25 Angstroms such as about 4.5 Angstroms. 
     The AP2 layer  328  may be deposited on the pin spacer layer  326 . The inclusion of the AP2 layer  328  on the pin spacer layer  326  may reverse the magnetic field orientation for the pinned magnetic structure  320 . Optionally, the pinned magnetic structure  320  may not include the AP2 layer  328  and the pin spacer layer  326 . Therefore, the AP2 layer  328  may be used to determine the pinning direction of the pinned magnetic structure  320 . For example, the pinned magnetic structure  320  includes AP2 layer  328  and the pinning direction for the pinned magnetic structure  320  may be anti-parallel to the pinning direction of the AP1  324  that is pinned by AFM layer  322 . In another example, the pinned magnetic structure  320  does not include an AP2 layer  328  and the pinning direction of the pinned magnetic structure  320  is determined by AP1  324  pinning direction. 
     The AP2 layer  328  may comprise one or more magnetic materials such as Co(Fe)(Ta, Zr, Hf, W, Nb), Co(Fe)(Ta, Zr, Hf, W, Nb)B, Fe(Co)(Ta, Zr, Hf, W, Nb), Ta, Zr, Hf and their alloys. The AP2 layer  328  has a top surface  329  and may be formed from one or more layers of materials having a thickness between about 10 Angstroms and about 100 Angstroms such as about 20 Angstroms. In one embodiment, several magnetic alloys may be layered to form the AP2 layer  328 . For example, the AP2 layer  328  may be formed from a Co(Fe) layer, disposed atop a CoFeB layer, disposed atop a CoFeBTa layer, and finally disposed atop a second Co layer. 
     The front shield  342  is disposed atop the bottom shield S 2  and between the common face  310  and the MFS  302 . The front shield  342  has a top surface  343  and may comprise one or more of NiFe, Ni, Co, Fe, their alloys and laminates as well as other suitable materials. The top surface  343  of the front shield  342  may or may not be coplanar with the top surface  329  of the AP2 layer  328 . The front shield  342  may have a thickness between about 50 Angstroms and about 500 Angstroms such as about 100 Angstroms. The front shield  342  separates the pinned magnetic structure  320  from the magnetic disk  110  and prevents magnetic interference between the pinned magnetic structure  320  and the magnetic disk  110  (shown in  FIGS. 1 and 2 ). Along the common face  310  of the front shield  342 , the front shield  342  tapers in a direction towards the MFS  302  when moving along the common face  310  in a direction from the bottom shield S 2  to the top surface  343  of the front shield  342 . Thus, in the pinned magnetic structure  320 , the AP2 Layer  328  is a closer distance to, or less recessed from, the MFS  302  than the AFM layer  322  is to the MFS  302 . 
     The spacer layer  330  is recessed from the MFS  302  and deposited on top of the sensor structure  320 . As the second spacer layer  330  becomes thinner, the magnetic interlayer coupling between adjacent layers increases. In the case of a TMR sensor, the second spacer layer  330  may be formed from material such as MgO, AlO, ZnO, Mg, Zn, GaO, IZO, ITO, Cu, Ag, AnSn, AlCu and their alloys which are dielectric or metal. In one embodiment, the spacer layer  330  comprises MgO with a thickness between about 5 Angstroms and about 100 Angstroms, such as about 10 Angstroms. 
     The first free magnetic layer  332  is recessed from the MFS  302  and deposited on the spacer layer  330 . The first free magnetic layer  332  may comprise one or more of Co, Fe, B, Ta, Hf, Zr, CoB, CoFe, CoFeB, NiFe, and their alloys and/or other suitable materials. The first free magnetic layer  332  has a top surface  333  and may comprise a single layer of magnetic material or multiple layers. For example, the first free magnetic layer  332  may be multilayered and formed from a Co(Fe)B layer deposed atop a CoFe layer. In one embodiment, the first free magnetic layer  332  may have an overall thickness between about 10 Angstroms and about 60 Angstroms such as about 15 Angstroms. 
     The front isolation layer  344  is disposed atop the front shield  342  and extends from the MFS  302  to the first free magnetic layer  332 . The front isolation layer  344  has a top surface  345  wherein the top surface  345  may be coplanar with the top surface  333  of the first free magnetic layer  332 . The front isolation layer  344  may comprise one or more of MgO, AlO, TaO, SiN and other dielectric materials and/or metal dielectric laminations. In one embodiment, the front isolation layer  344  may comprise MgO and have a thickness between about 15 Angstroms and about 160 Angstroms such as about 50 Angstroms. As will be discussed below, the dielectric material of the front isolation layer  344  improves the data integrity from electronic and magnetic noise for both the first free magnetic layer  332  and a second free magnetic layer  334 . 
     The common face  310  extends linearly from the bottom shield S 2  to the intersection of the top surfaces  333 ,  345  of the front isolation layer  344  and the first free magnetic layer  332 . The common face  310  and the MFS  302  are divergent. The common face  310  may be at an angle  312  from the MFS  302  as shown by phantom line  314 . The angle  312  may be between an angle equal or greater than 0 degrees and an angle less than 90 degrees, such as about 30 degrees. In the embodiment shown in FIG.  3 , the angle  312  of the common face  310  provides a wider portion  350  of the front shield  342  at the intersection with the bottom shield S 2  and a narrower portion at the top surface  343 . Thus, the recess of the layers from the MFS  302  decreases from the pinned magnetic structure  320  to the first free magnetic layer  332 . This places the first free magnetic layer  332  closer than the pinned magnetic structure  320  to the MFS  302  and also to external magnetic influences. The trapezoidal shape enhances shielding effects to reduce noise. 
     The second free magnetic layer  334  is deposited on top of the first free magnetic layer  332  and the front isolation layer  344 . Unlike the first free magnetic layer  332 , the second free magnetic layer  334  is not recessed from the MFS  302 . The second free magnetic layer  334  has a top surface  335  and may comprise one or more of Co, Fe, B, Ta, Hf, Zr, CoB, CoFe, CoFeB, NiFe, and their alloys and other suitable materials. The second free magnetic layer  334  may comprise one or more layers. For example, the second free magnetic layer  334  may be multilayered and formed from a NiFe layer deposed atop a Ta, Hf or their alloy with CoFe layer, and deposed atop a Co(Fe)B layer. In one embodiment, the second free magnetic layer  334  may have a thickness between about 10 Angstroms and about 100 Angstroms such as about 50 Angstroms. 
     The first free magnetic layer  332  and the second free magnetic layer  334  are stitched together. The stitching of the first free magnetic layer  332  and the second free magnetic layer  334  has a combined thickness greater than that of the first antiferromagnetic layer  322 . 
     A cap layer  336  extends from the MFS  302  and is disposed on and extends along the top surface  335  of the second free magnetic layer  334 . The cap layer  336  may comprise one or more of Ru, Ta, Ti, Ni(Co)Fe, Hf their alloys, or other suitable materials. The cap layer  336  may comprise a single layer or multiple layers, i.e. laminates. In one embodiment, the cap layer  336  may have a thickness between about 10 angstroms and about 100 angstroms such as about 15 Angstroms. 
     The first free magnetic layer  332 , the spacer layer  330 , the second free magnetic layer  334 , and the cap layer  336  have in common a backside  311 . The backside  311  may be recessed from a rear surface  321  of the read head  300 . The backside  311  may or may not be nearly parallel with both the MFS  302  and the rear surface  321 . 
     A back isolation layer  346  is formed in the space from the backside  311  to the rear surface  321 . Thus, the back isolation layer  332  is formed between the rear surface  321  of the read head  300  and the first free magnetic layer  332 , the spacer layer  330 , the second free magnetic layer  334 , and the cap layer  336 . Material from the first free magnetic layer  332  and the second free magnetic layer  334  and the cap layer  336  may be removed, exposing a portion of the AP2 layer  328 . The material removal may be performed by etching, milling or any suitable material removal method. In one embodiment, the first free magnetic layer  332 , the second free magnetic layer  334  and the cap layer  336  is milled to form the back isolation layer  346 . The back isolation layer  346  may be adjacent to the backside  311  and extend to the rear surface  321  of the read head  300 . The back isolation layer  346  may comprise one or more of AlO, TaO, SiN, MgO or other dielectric suitable material. In one embodiment, the back isolation layer  346  is comprised of AlO and has a thickness between about 80 angstroms and about 200 angstroms, such as 100 angstroms. 
     A top shield S 1  may be disposed on the cap layer  336  and the back isolation layer  346  of the sensor structure  306 . The top shield S 1  may comprise a ferromagnetic material such as nickel (Ni), iron (Fe), cobalt (Co), nickel-iron alloy (NiFe), nickel-iron-cobalt alloy (NiFeCo), nickel-cobalt alloy (NiCo), cobalt-iron alloy (CoFe), combinations thereof, or other suitable materials either through PVD sputtering or plating. In one embodiment, the top shield S 1  may be similar in material and thickness to the bottom shield S 2 . In another embodiment, the top shield S 1  may be dissimilar in material and thickness to the bottom shield S 2 . 
     The reader gap  354  comprises the cap  336 , second free magnetic layer  334 , first free magnetic layer  332 , and the spacer  330 . This width  352  of the reader gap  354  determines the density of the readable material. For example, the reader gap  354  having a small or narrow width  352  is capable of reading higher density media then a reader gap  354  with a larger or wider width  352 . The width  352  of the reader gap  354  may be between about 4 nm and about 12 nm such as about 8 nm. The reader gap  354  of the sensor structure  306  is capable of achieving 4 nm and smaller widths  352 . The reader gap  354  is much narrower than current (conventional) scissor designed read heads, allowing for greater media density without the stability issues found in the scissor designed read heads. 
       FIG. 4  shows a read head  400  similarly configured to the read head  300 . The read head  400  has a common face  410  that extends from the bottom shield S 2  to the intersection of the top surfaces  333 ,  345  of the front isolation layer  344  and the first free magnetic layer  332 . The common face  410  is similar to common face  310  of  FIG. 3  and is divergent with the MFS  302 . The common face  410  may have an angle  412  from the MFS  302  as shown by phantom line  314 . The angle  412  may be in a negative angle in the range between about 0 degrees and about greater than negative 90 degrees, such as about negative 30 degrees. Thus, where the angle  312  swings in a positive direction, or counter clockwise, from phantom line  314 , angle  412  swings in a negative direction, or clockwise, from the phantom line  314 . 
     Along the common face  410  of the front shield  342 , the front shield  342  tapers in a direction away from the MFS  302  when moving along the common face  410  in a direction from the bottom shield S 2  to the top surface  343  of the front shield  342 . Thus, in the pinned magnetic structure  320  of read head  400 , the AP2 layer  328  is a farther distance to, or more recessed from, the MFS  302  than the AFM layer  322  is to the MFS  302 . 
     A reader gap  354  for the read head  400  is similar to that of read head  300  shown in  FIG. 3 . The width  352  of the reader gap  354  is very narrow and capable of reading high density media. The reader gap  354  may have a width  352  between about 4 nm and about 12 nm. The reader gap  354 , for the read head  400 , is capable of obtaining the widths  352  of 4 nm and smaller. 
     Therefore, it has been shown where the reader gap of  FIG. 3  and  FIG. 4  may be significantly narrowed by recessing the pinning structure along with the first of the two free magnetic layers. The stitching of a recessed first free magnetic layer with a second free magnetic layer which extends to the MFS advantageously extends the capabilities of the sensor structure by narrowing the reader gap for use with media having ultra-high recording densities. The trapezoidal structure of the sensor structure enhances the shielding effect while the two free layers have equal or greater amplitude than that found in conventional sensors. The novel sensor structure maintains the integrity of the pinning strength and the pinning field while eliminating the problems associated with a reduction in the pinning strength found in a conventional stitching processes. 
     While the foregoing is directed to exemplified embodiments, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.