Abstract:
A later spin valve multi-reader includes at least two spin detectors, a spin injector and a spin diffusion medium. The spin diffusion medium bridges the spin detectors and the spin injector. Each of the spin detectors detects a unique spin accumulation signal.

Description:
SUMMARY 
     A lateral spin valve (LSV) multi-reader includes at least two spin detectors, a spin injector and a spin diffusion medium. The spin diffusion medium bridges the spin detectors and the spin injector. Each of the spin detectors detects a unique spin accumulation signal. 
     A lateral spin valve multi-reader includes a means for injecting a polarized current, a means for both receiving the injected current and for producing a polarized spin accumulation associated with the injected current, and at least two means for detecting. Each means for detecting detects a portion of the spin accumulation. 
     A process for reading by a lateral spin valve multi-reader includes the steps of injecting a polarized spin current into a spin diffusion medium to produce an associated spin accumulation, detecting a first portion of the spin accumulation and detection a second portion of the spin accumulation. 
     The above summary is not intended to describe each embodiment or every implementation. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an example of a CPP bottom spin valve. 
         FIGS. 2A-2C  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 2A  providing a top view,  FIG. 2B  providing an air barrier surface (ABS) view, and  FIG. 2C  providing a side view. 
         FIG. 3  illustrates the circuit created by the lateral spin valve multi-reader of  FIGS. 2A-2C . 
         FIGS. 4A-4C  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 4A  providing a top view,  FIG. 4B  providing an ABS view, and  FIG. 4C  providing a side view. 
         FIGS. 5A-5C  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 5A  providing a top view,  FIG. 5B  providing an ABS view, and  FIG. 5C  providing a side view. 
         FIGS. 6A-6C  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 6A  providing a top view,  FIG. 6B  providing an ABS view, and  FIG. 6C  providing a side view. 
         FIGS. 7A-7B  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 7A  providing an ABS view and  FIG. 7B  providing a side view. 
         FIGS. 8A-8B  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 8A  providing an ABS view and  FIG. 8B  providing a side view. 
         FIGS. 9A-9C  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 9A  providing a top view,  FIG. 9B  providing an ABS view, and  FIG. 9C  providing a side view. 
         FIG. 10  illustrates the circuit created by the lateral spin valve multi-reader of  FIGS. 9A-9C . 
         FIGS. 11A-11C  depict a lateral spin valve multi-reader according to various embodiments with  FIG. 11  A providing a top view,  FIG. 11B  providing an ABS view, and  FIG. 11C  providing a side view. 
     
    
    
     The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number. 
     DETAILED DESCRIPTION 
     The desire to store more electronic data and to access that data more quickly is ever increasing. As such, various technologies have been developed to help meet these desires. For example, progress in the development of giant magnetoresistive (GMR) spin valve materials and high-sensitivity spin valve read heads has allowed a continuous increase of areal recording density in hard disk drives. 
     One type of spin valve currently being used within the read head of a disk drive is a current perpendicular to the plane (CPP) bottom spin valve. An example of a CPP bottom spin valve  50  is shown in  FIG. 1 . The CPP bottom spin valve  50  comprises a stack that includes a bottom shield  51 , a seed layer  52 , an anti-ferromagnetic layer (AFM)  53 , a pinned ferromagnetic layer  54 , a coupling layer  55  of Ru, a ferromagnetic reference layer  56 , a spacer  57 , a ferromagnetic free layer  58 , a cap  59  and a top shield  60 . In this configuration, the magnetization direction of the pinned ferromagnetic layer  54  is fixed by exchange coupling with the adjacent AFM  53 . The ferromagnetic free layer  58  provides a layer in which the magnetization vector can rotate in response to electromagnetic fields. The rotation of magnetization in the free layer  58  relative to the fixed layer magnetization generates a resistance change that is detected as a voltage change when a sense current is passed through the structure in a direction that is perpendicular to the stack. The length of the spin valve  50 , i.e., the distance between shields, defines downtrack readback resolution. The width of the free layer approximately defines the crosstrack readback width. 
     While spin valve readers have assisted in the ability to read electronic data, they are not without their limitations. Because spin valves are comprised of a vertical heterostructure they present a physical configuration that is difficult to integrate with other devices. Specifically, spin valve readers are limited in shield-to-shield spacing by the need to include synthetic anti-ferromagnetic layer pinned by an anti-ferromagnetic layer. Multi-reader spin valve concepts, such as a two-dimensional magnetic recording (TDMR), are similarly limited in shield-to-shield spacing and are also challenged by difficulties for narrow cross-track spaced readers. 
     The present disclosure describes various embodiments of lateral spin valve multi-reader configurations which allow for reduced shield-to-shield spacing and narrow cross-track spacing for areal densities above 1 Tbpsi. The various embodiments provide compact geometries for readers aligned along either downtrack or crosstrack directions. 
     Referring now to  FIGS. 2A-C , an example embodiment of a lateral spin valve multi-reader  200  is depicted. The diagram in  FIG. 2B  is a view from the media facing surface, and  FIGS. 2A and 2C  are respective cross sections taken along lines  2 A- 2 A and  2 C- 2 C. The reader  200  includes a spin injector  202 , two individual free layer spin detectors  204  for sensing nearby hard disk tracks, and a spin diffusion medium, e.g., channel  206  (with arrow indicating the direction of charge current flow), that bridges the spin injector  202  and spin detectors  204 . The spin injector  202  includes an injector contact  208 , a seed layer  209 , an anti-ferromagnetic layer  210 , and a ferromagnetic layer  212 . The spin injector  202  may optionally include a barrier layer  214  between the ferromagnetic layer  212  (with direction of magnetization indicated by the arrow) and the channel  206  to optimize the signal-to-noise ratio. In addition the injector may utilize a pinned SAF structure by substituting the simple ferromagnetic layer  212  with a SAF formed from FM/Ru/FM, where FM designates a suitable ferromagnetic material such as Co, FeCo with high spin polarization. 
     Each of spin detectors  204  includes a ferromagnetic free layer  216  (with direction of magnetization indicated by the arrow), an isolation cap  218 , and an optional barrier  220  to optimize the signal-to-noise ratio. Side shields  217 , or permanent magnets, are provided to either side of each of the detectors  204 . The channel  206  is a high quality conductor with a long spin diffusion length and is of a nonmagnetic metal, e.g., Cu, Ag, Al. Alternatively, the channel  206  may comprise a doped semiconductor material or other long spin mean free path material such as graphene. An isolation cap  222  is provided across portions of the bottom surface of the channel  206  as shown. The lateral spin valve multi-reader  200  further includes a current drain  224  to conduct charge, a bottom shield  226  and a top shield  228  that serves as the contact for the spin detectors  204 . Note that the top shield is electrically split into a first portion  230  and a second portion  232  to allow detection of two reader signals against a common potential The circuit created by the embodiment of  FIGS. 2A-2C  is illustrated in  FIG. 3 . As shown, the multiple spin detectors  204  are provided with a common channel  206  and an injector/drain circuit. The application of a voltage, VI, between the spin injector  202  and the current drain  224  produces a charge current in the channel  206  and an associated spin accumulation in the channel  206 . The spin accumulation can be measured as a voltage potential change, V 1  and V 2 , at the spin detectors  204  which varies according to the relative orientation of the spin detectors&#39;  204  and spin injector&#39;s  206  magnetization/spin directions. The configuration of the present embodiment presents a large injector area for a high injection current. The channel thickness is made thin, e.g., 10 nm or less, to provide higher spin density. The reduced stack thickness relative to common spin valves provides reduced shield-to-shield spacing with improved linear density resolution and the ability to more easily process adjacent reader stacks. 
     Referring now to  FIGS. 4-6 , variations on the embodiment of lateral spin valve multi-reader  200  are shown.  FIGS. 4A-4C  depict a lateral spin valve multi-reader  300  that includes a spin injector  302 , two spin detectors  304  and a spin diffusion medium, i.e., channel  306  (with arrow indicating the direction of charge current flow) with indicated isolation cap  322 , along with a current drain  324 , top shield  328  and bottom shield  326 . The spin injector  302  once again includes an injector contact  308 , a seed layer  309 , an anti-ferromagnetic layer  310  and a ferromagnetic layer  312  (with direction of magnetization indicated by the arrow). Each of the spin detectors  304  includes a ferromagnetic free layer  316  (with direction of magnetization indicated by the arrow), an isolation cap  318 , and optional barrier  320 . A side shield  317 , or permanent magnet, is provided to either side of the detectors  304 . However, different in this configuration, is that each of spin detectors  304  is in contact with a separate electrical lead/contact  321  and both spin detectors  304  and leads  321  are isolated from a solid top shield  328 . The individual detector leads  321  enable individual sensing of detector voltage potentials without the use of the split top shield used in  FIGS. 2A-2C . As in the previous embodiment, voltage, V I , is applied between the spin injector  302  and the current drain  324  to produce a charge current and associated spin accumulation in channel  306 . The spin accumulation is measured as a voltage potential change, V 1  and V 2  (not shown), by respective detectors  304 . 
       FIGS. 5A-5C  depict a lateral spin valve multi-reader  400  with two distinct reader injector/channel/detector circuits. Specifically, lateral spin valve multi-reader  400  includes two spin injectors  402 , two spin detectors  404  and two spin diffusion mediums, i.e., channels  406  (with arrow indicating the direction of charge current flow) with indicated isolation caps  422 , and two current drains  424 . A single, un-split top shield  428  and a single bottom shield  426  are also included. The spin injectors  402  each include an injector contact  408 , an isolation cap layer  409 , an anti-ferromagnetic layer  410  and a ferromagnetic layer  412  (with direction of magnetization indicated by the arrow). Each of the spin detectors  404  includes a ferromagnetic free layer  416  (with direction of magnetization indicated by the arrow), an isolation cap  418 , an optional barrier  420 , and a detector contact  421 . A side shield  417 , or permanent magnet, is provided to either side of the detectors  404 . In this embodiment, voltage, V I , is applied between each of the spin injectors  402  and its corresponding current drain  424  to produce a current charge and associated spin accumulation in each of the channels  406 . The spin accumulation is measured as a voltage potential change, V 1  and V 2  (not shown), by respective detectors  404 . The two distinct reader injector/channel/detector circuits of the present embodiment enable better separation of signal between readers and less dilution of the spin density due to the narrower crosstrack dimension of each of the channels  406 . 
       FIGS. 6A-6C  depict a lateral spin valve multi-reader  500  that includes a spin injector  502 , two spin detectors  504  and a common spin diffusion medium, i.e., channel  506  with indicated isolation cap  522 , along with a current drain  524 , a top shield  528  and a bottom shield  526 . The spin injector  502  once again includes an injector contact  508 , an isolation cap layer  509 , an anti-ferromagnetic layer  510  and a ferromagnetic layer  512  (with direction of magnetization indicated by the arrow). Each of the spin detectors  504  includes a ferromagnetic free layer  516  (with direction of magnetization indicated by the arrow), an isolation cap  518 , and barrier  520 . A side shield  517 , or permanent magnet, is provided to either side of the detectors  504 . Each of the spin detectors  504  additionally includes an integrated in-stack shield  527  that functions as the electrical lead to the contact  521  for the spin detector  504  and functions as a local magnetic shield enabling easier processing and lower lead resistance than the embodiment of  FIGS. 5A-5C . The in-stack shield  527  is an oriented, permeable thin magnetic layer or synthetic anti-ferromagnetic with low resistance which is isolated from the un-split, top shield  528 . Voltage, V I , is applied between the spin injector  502  and the current drain  524  to produce a current charge and associated spin accumulation in channel  506 . The spin accumulation is measured as a voltage potential change, V 1  and V 2  (not shown), by respective detectors  504 . 
       FIGS. 7A-B  and  8  illustrate additional embodiments of the lateral spin valve multi-reader. In these embodiments stacked detectors utilize a shared magnetic shield. Specifically, with reference to  FIGS. 7A-7B , lateral spin valve multi-reader  600  includes a central spin injector  602 , two spin detectors  604 , two spin diffusion mediums, i.e., two channels  606  (with arrow indicating the direction of charge current flow), two current drains  624 , a bottom shield  626 , a shared shield  625  and a top shield  628 . The spin injector  602  includes a central injector contact  608  and, to either side of the contact  608 , a cap/seed layer  609 , an anti-ferromagnetic layer  610 , a ferromagnetic layer  612  (with direction of magnetization indicated by the arrow), and an optional barrier  614  between layer  612  and the proximate channel  606 . The first of channels  606  presents a lower surface with an isolation cap  622  proximate bottom shield  626 . The upper surface of the first of the channels  606  is in contact with the lower current drain  624 , the spin injector  602  and the lower positioned spin detector  604 , which incorporates optional barrier  620 , free layer  616  (with direction of magnetization indicated by the arrow), and isolation cap  618 . 
     The second of the channels  606  presents a lower surface, with an isolation cap  622  as illustrated, in contact with the central spin injector  602  and the second of the current drains  624 . The upper surface of the second of the channels  606  is in contact with the upper spin detector  604 , which incorporates barrier  620 , free layer  616 , and isolation cap  618 . The top shield  628  is positioned above the upper spin detector  604 . A side shield  617 , or permanent magnet, is provided to either side of each of the detectors  604 . The shared shield  625  lies between the bottom of the second of the channels  606  and the lower spin detector  604 . In this configuration, the top shield  628  serves as the contact for the upper spin detector  604  while the shared shield  625  serves as the contact for the lower spin detector  604 . Because the shared magnetic shield  625  serves as a contact for only one of the two spin detectors  604  the free-layer to free-layer spacing can be made thinner than in a stacked tunneling magnetoresistive (TMR) configuration where two independent shields/contacts are required. In the present embodiment, voltage, VI, is applied between the common spin injector  602  and the current drains  624  to produce a current charge and associated spin accumulation in channel  606 . The spin accumulation is measured as a voltage potential change, V 1  and V 2 , by respective detectors  604 . 
     Referring now to  FIGS. 8A-8B , the lateral spin valve multi-reader once again utilizes stacked detectors and a shared magnetic shield, however, in this embodiment each reader of the lateral spin valve multi-reader is provided with its own injector/channel/detector circuit. Specifically, lateral spin valve multi-reader  700  includes two spin injectors  702 , two spin detectors  704 , and two spin diffusion mediums, i.e. two channels  706  (with arrow indicating the direction of charge current flow), along with two current drains  724 , a bottom shield  726 , a shared shield  725 , and a top shield  728 . Each spin injector  702  includes an injector contact  708 , an isolation cap layer  709 , an anti-ferromagnetic layer  710 , a ferromagnetic layer  712  (with direction of magnetization indicated by the arrow), and a barrier  714 . Each spin detector  704  includes a barrier  720 , a free layer  716  (with direction of magnetization indicated by the arrow), and an isolation cap  718 . 
     The bottom shield  726  is proximate the lower surface of the lower channel  706 , with lower isolation cap  722 , while the top shield is proximate the upper surface of the upper channel  706 , with upper isolation cap  722 . Shared shield  725  lies between the isolation caps  718  of each of the spin detectors  704 . A side shield  717 , or permanent magnet, is provided to either side of each of the detectors  704 . 
     The present embodiment provides a mirrored detector configuration where the lower detector  704  has the channel  706  and spin injector  702  below the free layer  716  and the upper detector  704  has the channel  706  and the spin injector  702  above the free layer  716 . The shared shield  725  serves as the detector contact for both of the spin detectors  704 . The stacked configuration of the reader  700  presents an opportunity of reducing thickness by reducing the free-layer to free-layer spacing. In the present configuration, voltage, VI 1 , is applied between the lower spin injector  702  and the lower current drain  724  to produce a current charge and associated spin accumulation in lower channel  706 . Voltage, VI 2 , is applied between the upper spin injector  702  and the upper current drain  724  to produce a current charge and associated spin accumulation in the upper channel  706 . The spin accumulation is measured as a voltage potential change, V 1  and V 2 , by the lower and upper detectors  704 , respectively. 
       FIGS. 9A-9C  illustrate another embodiment of the lateral spin valve multi-reader. In this configuration, stacked spin detectors utilize a common channel. Specifically, lateral spin valve multi-reader  800  includes a spin injector  802 , two spin detectors  804 , a spin diffusion medium, i.e., channel  806  (with arrow indicating the direction of charge current flow) with isolation cap  822 , a current drain  824 , a bottom shield  826  and a top shield  828 . The spin injector  802  includes an injector contact  808 , an isolation cap layer  809 , an anti-ferromagnetic layer  810 , and a ferromagnetic layer  812  (with direction of magnetization indicated by the arrow). Each spin detector  804  includes an optional barrier  820  proximate the channel  806 , a free layer  816 , and an isolation cap  818 . The isolation cap  818  of the lower spin detector  804  presents the bottom shield  826 , which operates as the contact of the lower detector  804 . The isolation cap  818  of the upper spin detector presents to the top shield  828 , which operates as the contact for the upper detector  804 . A side shield  817 , or permanent magnet, is provided to either side of the detectors  804 . The present configuration, with a single common channel  806  and free layers  816  (with direction of magnetization indicated by the arrow) of the detectors  804  in a top and bottom orientation, provides a simpler geometry with low shield-to-shield spacing and the stacked detectors  804  in a downtrack direction. The circuit created by multi-reader  800  is illustrated in  FIG. 10 . In the circuit, voltage, VI, is applied between the spin injector  802  and the current drain  824  to produce a current charge and associated spin accumulation in channel  806 . The spin accumulation is measured as a voltage potential change, V 1  and V 2 , by the lower and upper detectors  804 , respectively. 
       FIGS. 11A-11C  illustrate another embodiment of the lateral spin valve multi-reader. In this configuration a separating, critical tunnel barrier may be eliminated allowing the spin accumulation interface to be upon any face of the detector. Specifically, lateral spin valve multi-reader  900  includes a spin injector  902 , two spin detectors  904 , a spin diffusion medium, i.e., channel  906 , a current drain  924 , a bottom shield  926 , and an upper shield  928 . The spin injector  902  includes an injector contact  908 , a seed layer  909 , an anti-ferromagnetic layer  910 , and a ferromagnetic layer  912  (with direction of magnetization indicated by the arrow). Each spin detector  904  comprises only a free layer  916  (with direction of magnetization indicated by the arrow) with a contact  921  to the outer edge of each free layer  916 . The channel  906  resides between the inner edges of the free layers  916 . The channel  906  is provided with a lower isolation cap  922 , as illustrated, and an upper isolation cap  923 . Optionally, additional seed and cap layers may be included, which may be helpful to produce optimal channel layer properties. 
     The present configuration provides two detector free layers  916  arranged in the crosstrack direction with a central channel  906 , thus, very narrow shield-to-shield and crosstrack spacing is enabled. Alternatively, the channel  906  may contact the free layers  916  at the back of the stack or the back and sides to allow detection of the electric potential change. The free layer stabilization of this embodiment may be achieved by creating uniaxial anisotropy parallel to the air bearing surface (ABS) direction through a Controlled Incidence Sputtering (CIS or sometimes referred to as Oblique Angle Sputtering) deposition technique. In the present embodiment, voltage, VI, is applied between the spin injector  902  and the current drain  924  to produce a current charge and associated spin accumulation in channel  906 . The spin accumulation is measured as a voltage potential change, V 1  and V 2  (not shown), by respective detectors  904 . 
     Systems, devices or methods disclosed herein may include one or more of the features structures, methods, or combination thereof described herein. For example, a device or method may be implemented to include one or more of the features and/or processes above. Or, layers described in one embodiment may be incorporated into another embodiment without specific recitation. Or, the lateral spin valve multi-reader may include any number of readers rather than being limited to two. It is intended that any device or method described above need not include all of the features and/or processes described herein, but may be implemented to include selected features and/or processes that provide useful structures and/or functionality. 
     Various modifications and additions can be made to the disclosed embodiments discussed above. Accordingly, the scope of the present disclosure should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.