Patent Publication Number: US-9899045-B2

Title: Data reader with pinned front shield

Description:
RELATED APPLICATIONS 
     The present application is a continuation of copending U.S. patent application Ser. No. 14/946,813 filed Nov. 20, 2015 which makes a claim of domestic priority to U.S. Provisional Application No. 62/094,426 filed Dec. 19, 2014, the contents of which are incorporated by reference. 
    
    
     SUMMARY 
     A data reader, in some embodiments, has a magnetoresistive stack set to a first magnetization direction by a first pinning structure separated from an air bearing surface by a front shield portion of a magnetic shield. The front shield portion is set to a different second magnetization direction by a second pinning structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block representation of an example data storage system configured and operated in accordance with some embodiments. 
         FIG. 2  displays a block representation of a portion of an example data reader capable of being used with the data storage system of  FIG. 1 . 
         FIG. 3  shows a cross-section view block representation of a portion of an example data reader configured in accordance with some embodiments. 
         FIG. 4  illustrates a cross-section view block representation of a portion of an example data reader arranged in accordance with various embodiments. 
         FIG. 5  depicts a cross-section view block representation of a portion of an example data reader configured in accordance with some embodiments. 
         FIGS. 6A-6C  respectively provide assorted views of portions of an example data reader arranged in accordance with assorted embodiments. 
         FIG. 7  plots an example data reader fabrication routine carried out in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     As data storage systems progress to accommodate increased data generation and transfer, data storage devices are striving for decreased physical size. For example, a data reader may strive for a 10 nm thickness and a 10 nm stripe height that allows for high linear data bit density resolution and greater data capacity. However, decreasing the physical size of data reading components can be magnetically volatile, which can result in degraded signal-to-noise ratio. Hence, there is an industry and consumer interest in configuring a data reader with optimized magnetic and thermal stability at a reduced physical size. 
     With these issues in mind, a data reader may have a magnetoresistive stack consisting of at least magnetically free and magnetically fixed structures with the magnetically fixed structure set to a first magnetization direction by a first pinning structure that is recessed and separated from an air bearing surface by a front shield portion of a magnetic shield while the front shield portion is set to a second magnetization direction by a second pinning structure. By setting the first and second magnetization directions differently, the front shield portion can be stabilized and the data reader can experience optimized performance. That is, the ability to tune the magnetizations of a front shield portion in a data reader with a recessed first pinning structure provides magnetic properties and repeatability conducive to reduced form factor, high data capacity data storage devices. 
     While a data reader employing a recessed pinning structure can be utilized in an unlimited variety of environments and systems,  FIG. 1  provides an example data storage system  100  in which a tuned data reader can be commissioned in accordance with some embodiments. Although not required or limiting, the data storage system  100  can have one or more data storage devices  102  that are configured with at least one data storage means. It is contemplated that various solid-state volatile and non-volatile memories can be used in a hybrid data storage device data storage means. 
     Assorted embodiments arrange at least one data storage means of the data storage system  100  as a hard disk drive with at least one transducing head  104  accessing data bits  106  stored in patterned data tracks  108  on a data storage medium  110 . The transducing head  104  can utilize one or more data writers  112  and data readers  114  to store data to and read data from the data storage medium  110 . The transducing head  104  may float on an air bearing  116  generated by rotation of the data medium  110  by a spindle motor  118 . Any number of components can be connected to the transducing head  104  to control the size of the air bearing  116 . For instance, a suspension  120 , such as a gimbal, can allow the transducing head  104  to pitch and roll in adaptation to changes induced by an actuator  122  and heater  124 . 
     At least one controller  126  can be connected to the various aspects of the data storage system  100 , as shown, to monitor, detect, and control the data storage environment to provide data access operations. A controller  126  can be local or remote, such as through a wired or wireless network  128 , and may be utilized individually or collectively with other controlling means, such as processors, servers, hosts, nodes, and application specific integrated circuits (ASICs). With the air bearing  116  and data bit density being configured on a nanometer scale, the data reader  114  can have a small window of time and narrow band of data bit magnetization to sense. 
       FIG. 2  displays a block representation of a portion of an example data reader  130  that may be employed in the data storage system  100  of  FIG. 1  to sense data on a nanometer scale or less. In accordance with assorted embodiments, the data reader  130  can have at least one magnetoresistive stack  132  disposed between bottom  134  and top  136  shields as well as between side shields  138 . It is noted that the terms “bottom” and “top ” are not limiting and are meant to denote relative position either down-track or up-track relative to a data track and the motion of the data reader  130 . 
     The magnetoresistive stack  132  can be separated from the side shields  138  by lateral nonmagnetic layers  140  and separated from the bottom  134  and top  136  shields by conductive cap and seed electrode layers, respectively. The magnetoresistive stack  132  may be configured in a variety of different manners to sense data from an adjacent data storage medium. For example, the magnetoresistive stack  132  may be a spin valve, trilayer lamination without a fixed magnetization, or a lateral spin valve with a fixed magnetization structure  142  separated from a magnetically free structure  144  by a spacer structure  146 , as shown. 
     Decreasing the shield-to-shield spacing (SSS)  148  of the data reader  130  can increase data bit linear resolution, but can correspond with increased magnetic and thermal volatility that results in degraded performance. In other words, a small SSS  148  can decrease the physical size of the various layers of the magnetoresistive stack  132 , but can also increase the risk of inadvertent magnetic behavior that can jeopardize the accuracy of data bit sensing. 
       FIG. 3  shows a cross-section view block representation of a portion of an example data reader  160  arranged in accordance with assorted embodiments to increase magnetic performance despite a small SSS. The data reader  160  has a magnetoresistive (MR) stack  162  disposed between top  164  and bottom  166  shields that define the SSS  168 . By recessing a fixed magnetization reference pinning structure  170  away from an air bearing surface (ABS), the reference structure  172  of the MR stack  162  can be set to a predetermined magnetization orientation  174  without adding to the SSS  168 . 
     It is noted that the MR stack  162  is configured as a spin valve in  FIG. 3  with a magnetically free layer  176  separated from the fixed magnetization reference structure  172  by a non-magnetic spacer layer  178 , but such configuration is not required or limiting as lateral spin valve and abutted junction configurations may be utilized. The reference structure  172  is shown as a lamination of magnetic and non-magnetic layers, but various embodiments may configure the reference structure  172  as a single magnetic layer that is set to the predetermined magnetic orientation  174  by the fixed magnetization reference pinning structure  170 . 
     Removal of the fixed magnetization reference pinning structure  170  from the ABS reduces the SSS, but leaves the front portion  180  of the bottom shield  166  vulnerable to unpredictable magnetic volatility. The lateral alignment of the fixed magnetization reference pinning structure  170  and the front portion  180  along the X axis can restrict the physical connection of the front portion  180  with the bottom shield  166 , which can result in coupling that is inadequate to control magnetization, such as with the formation of magnetic domain walls. The size, shape, and position of the front portion  180  may also be susceptible to magnetic instabilities in the bottom shield  166 . Thus, recessing the fixed magnetization reference pinning structure  170  can decrease SSS  168  at the expense of increased magnetic and thermal volatility. 
       FIG. 4  illustrates a cross-section view block representation of a portion of an example data reader  190  configured to mitigate magnetic and thermal volatility in accordance with some embodiments. An MR stack  192  has a spacer structure  194  disposed between free  196  and reference  198  structures that collectively sense data bits by providing a magnetoresistive ratio. A shield biasing structure  200  is positioned between the MR stack  192  and a top shield  202 . The shield biasing structure  200  can be one or more layers of magnetic and non-magnetic materials that can stabilize the magnetization of the top shield  202  with a magnetization oriented orthogonally to the magnetization of the reference structure  198 . 
     In comparison to the contacting length  204  of the shield biasing structure  200  with the top shield  202 , the bottom shield  206  has a front shield portion  208  that has a reduced stripe height  210 , such as  50 nm as measured from the ABS along the X axis. The reduced stripe height  210  can correspond with magnetic instability from the bottom shield core  212  or from the fixed magnetization of the laterally aligned reference pinning structure  214 . That is, the pinned magnetic layer  216  and hard magnetic layer  218  of the reference pinning structure  214 , which can be a permanent magnet or antiferromagnet, can induce magnetic and thermal instability in the front shield portion  208  alone and in concert with the magnetization of the bottom shield core  212 . 
     Accordingly, the front shield portion  208  is set to a predetermined magnetization  220  by a shield pinning structure  222  disposed between the bottom shield core  212  and the front shield portion  208 . Through tuning the magnetization of the shield pinning structure  222  to induce the predetermined magnetization  220  in the front shield portion  208  that is oriented orthogonally to the magnetization  224  of the reference structure  198  and reference pinning structure  214 , the front shield portion  208  can be stabilized without degrading the reference magnetization  224 . It is contemplated that the shield pinning structure  222  consists of a single magnetic layer, such as a permanent magnet, multiple magnetic layers, such an exchange coupled magnetic lamination, or multiple magnetic and non-magnetic layers, such as a synthetic antiferromagnet. 
     In the non-limiting embodiment shown in  FIG. 4 , the reference pinning structure  214  is separated from the front shield portion  208  by a first nonmagnetic layer  226  and from the shield pinning structure  222  by a second nonmagnetic layer  228 . The first  226  and second  228  nonmagnetic layers can be similar or dissimilar materials that allow the reference pinning structure  214  to maintain the predetermined magnetization  224  without influence from the shield pinning structure  222 . It is noted that the shield pinning structure  222  continuously extends from the ABS to a stripe height  230  that is greater than the front shield portion  208  and the free structure  196  of the MR stack  192 , but such configuration is not required as the stripe height  230  can be tuned in relation to the size of the front shield portion  208  and free structure  196  to provide optimized data sensing performance. 
     While the front shield portion  208  can be tuned for thickness  232  along the Y axis, such as 10 nm, that can match the thickness of the reference pinning structure  222 , the thickness  234  of the shield pinning structure  222  may be similar or dissimilar to the thickness  236  of the shield biasing structure  200 . In various embodiments, the shield biasing structure  200  has a matching configuration with the shield pinning structure  222  with a hard magnetic layer  238  contacting a magnetic layer  240  in either an exchange coupled lamination or a synthetic antiferromagnet. Other embodiments can configure the shield biasing structure  200  with different materials and layers than the shield pinning structure  222 . The ability to tune the respective fixed magnetization shield biasing  200  and pinning  222  structures allows the shields  202 ,  208 , and  212  to be stabilized with a reduced SSS  242  compared to a reader having the reference pinning structure  214  positioned on the ABS. 
       FIG. 5  is a cross-section view block representation of a portion of an example data reader  250  arranged in accordance with some embodiments. The data reader  250  has an MR stack  252  with free  254 , spacer  256 , and reference  258  structures each positioned on the ABS with a SSS  260  between top  262  and bottom  264  shields. As shown, the reference structure  258  is a lamination of magnetic and non-magnetic layers that provide a reference magnetization  266  set by a reference pinning structure  268  recessed from the ABS. The reference pinning structure  268  has a pinning magnetization  270  set by an antiferromagnet layer  272  and transferred to the reference structure  258  by a magnetic layer  274 . 
     The top shield  262  is stabilized by a biasing structure  276  consisting of an antiferromagnet layer  278  setting a biasing magnetization  280  in a synthetic antiferromagnet portion  282 . The bottom shield  264  has a front shield portion  284  set to a stabilizing magnetization  286  by a shield pinning structure  288  that has an antiferromagnet layer  290  contacting a synthetic antiferromagnet portion  292 . The stabilizing magnetization  286  and biasing magnetization  280  are shown to be aligned along the Z axis and respectively orthogonal to the pinning  270  and reference  266  magnetizations experienced by the MR stack  252 , but such magnetization configuration is not required or limiting. The ability to tune the magnetization strengths and orientations of at least the front shield portion  284 , reference pinning structure  268 , and reference structure  258  allows the data reader  250  to operate with minimal magnetic and thermal instability. 
     An interlayer  294  may be configured to continuously extend from the ABS between the front shield portion  284  and shield pinning structure  288  as well as between the front shield portion  284  and the reference pinning structure  268 . The interlayer  294  may be constructed of a coupling material, such as a transition metal material like Ru, that aids in the maintenance of the orthogonal relationship of the stabilizing  286  and pinning  270  magnetizations. The interlayer thickness  296  can be uniform or varying throughout the layer&#39;s stripe height from the ABS to decouple the reference pinning structure  268  with the front shield portion  284 . 
     As such, the front shield portion  284  can be concurrently coupled to the shield pinning structure  288  while maintaining the stabilizing magnetization  286  in an orthogonal relationship with the pinning  270  magnetization. The orthogonal orientation of the magnetizations  270  and  286  may be controlled by tuning the stripe height  298  of the front shield portion  284  compared to the thickness  300  of the front shield portion  284  and the angle of the rear surface  302  of the front shield portion  284  in relation to the ABS. It is contemplated that various processing means, such as oblique incidence sputtering, may also control the orientations of the respective magnetizations  270  and  286  through uniaxial anisotropy manipulation. 
       FIGS. 6A, 6B, and 6C  respectively display block representations of various views of portions of an example data reader  310  configured in accordance with some embodiments to provide more robust magnetic stability in a front shield portion  312  of a bottom shield  314 . As illustrated in  FIG. 6A , the data reader  310  has an MR stack  316  consisting of a free layer  318  having a short stripe height  320  while spacer  322  and reference  324  structures each have a long stripe height  326 . The reference structure  324  is a synthetic antiferromagnet that is pinned to a reference magnetization  328  by a reference pinning lamination  330 . 
     The reference pinning lamination  330  has a thickness  332  along the Y axis and is separated from the ABS by the front shield portion  312  and from the bottom shield core  334  by an nonmagnetic layer  336 . The front shield portion  312  has a thickness  338  that can be greater than thickness  332 . The front shield portion  312  is pinned to a front magnetization  340  by a shield pinning structure  342 . In comparison with the shield pinning structures  222  and  286  of  FIGS. 4 and 5 , the shield pinning structure  342  has a varying stripe height  344  from the ABS that contacts at least one nonmagnetic layer  346  to respectively decouple the bottom shield core  334  and reference pinning lamination  330  from the front shield portion  312 . 
     Although not limiting, the shield pinning structure  342  can be a single antiferromagnetic material (AFM), such as IrMn, or a lamination of magnetic and non-magnetic materials in the form of a synthetic antiferromagnet (SAF). For example, a SAF shield pinning structure  342  may be configured as successive layers of a seed, IrMn, NiFe, Ru, and NiFe, in some embodiments, while other embodiments configure the structure  342  as successive layers of seed, IrMn, coFe, NiFe, CoFe, Ru, CoFe, NiFe, CoFe materials. The ability to tune the shield pinning structure  342  through the selection of magnetic materials, like NiFe and CoFe, and transition metal interlayers, such as Ru, can provide magnetic characteristics conducive to high linear data bit density data storage devices. 
     With the ability to tune the size of the shield pinning structure  342  by adjusting at least the stripe height  344 , the coupling strength and susceptibility of the front magnetization  340  to the reference pinning lamination  330  and the bottom shield core  334  can be controlled. In other words, the tuned configuration of the shield pinning structure  342  can promote, eliminate, and otherwise control the coupling of the front shield portion  312  with the bottom shield core  334  and reference pinning lamination  330 . The capability of constructing the shield pinning structure  342  of a single AFM layer or as a SAF further tunes the strength, volatility, and orientation of the front magnetization  340 . The relationship of the front magnetization  340  with the reference magnetization  328 , such as, but not limited to, the orthogonal relationship shown in  FIG. 6 , allows the magnetic stability and performance of the data reader  310  to be optimized despite a shortened SSS  348  provided by recessing the reference pinning lamination  330  from the ABS. 
       FIG. 6B  illustrates an ABS view of the data reader  310  where a shield biasing structure  350  is disposed between the MR stack  316  and the top shield  352 . The shield biasing structure  350  is configured as a SAF and has protrusions  354  that extend on opposite lateral sides of the MR stack  316  as side shields with sidewalls  356  shaped to match the MR stack sidewalls  358 . The shield biasing structure  350  is completely separated from the front shield portion  312  by one or more nonmagnetic layers. 
     In the top view of  FIG. 6C , the tuned shape of the front shield portion  312  with varying stripe heights  344  from the ABS along the Z-X plane can correspond with a shaped front surface  360  of the reference pinning lamination  330 . It can be appreciated that the long stripe height  326  of the MR stack  316  can be configured as the aggregate of the stripe heights of the front shield portion  312 , reference pinning lamination  330 , and nonmagnetic layer  346 . The various views of  FIGS. 6A-6C  show how the magnetizations of the free layer  318 , shield biasing structure  350 , front shield portion  312 , and shielding pinning structure  342  can be parallel and each orthogonal to the magnetization of the reference structure  324  and reference pinning lamination  330 . 
       FIG. 7  provides a flowchart of an example data reader fabrication routine  370  that may be carried out in accordance with some embodiments. Initially, the routine  360  can form a bottom shield core on a substrate in step  372 . The underlying substrate may be any material, such as AlTiC, glass, or MgO, with any amount of texture to allow a magnetic shield material, such as CoFe or NiFe, to be formed with a predetermined thickness as measured parallel to the ABS and along the Y axis of  FIGS. 3-6 . Step  374  proceeds to deposit a stack pinning structure atop the bottom shield core. Step  374  may provide AFM or SAF magnetic structures that have uniform or varying stripe heights from the ABS. 
     It is contemplated that step  374  first removes portions of the bottom shield core before depositing the shield pinning structure, such as in the data reader configuration shown in  FIG. 6A . A front shield portion is then deposited on the shield pinning structure in step  376  before a reference pinning structure is formed as an AFM or SAF structure in lateral alignment with the front shield portion. Step  378  next forms an MR stack of magnetic and non-magnetic layers prior to a shield biasing structure, such as an AFM or SAF structure, is deposited on the MR stack in step  380 . Finally, a top shield is formed in step  382 . 
     It is noted that the various steps of routine  370  are not required or limiting. As such, any step or decision can be inserted, removed, or modified from that shown in  FIG. 7 . For example, a step or decision may be inserted that evaluates and installs an transition metal material interlayer between the shield pinning structure, the front shield portion, and the reference pinning structure. As another non-limiting example, the shield biasing structure can be configured with protrusions that are laterally aligned with at least the free layer of the MR stack to serve as side shields. 
     Through the various tuned configurations of shield pinning and reference pinning structures, a front shield portion of a bottom shield can be stabilized with a front magnetization. By tuning the size, shape, and construction of the pinning structures, the front shield magnetization can be oriented orthogonally to the reference magnetization of the MR stack, which can optimize data bit sensing. The ability to tune the materials, thicknesses, configurations, and magnetizations of the pinning structures can allow the recessed reference pinning structure arrangement to be customized for us in standard spin valve, lateral spin valve, multiple read sensors, and two-dimensional magnetic reading environments. 
     It is to be understood that even though numerous characteristics of various embodiments of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of various embodiments, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present technology to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary depending on the particular application without departing from the spirit and scope of the present disclosure.