Patent Description:
Embodiments of the present disclosure generally relate to a read head of a data storage device.

The heart of the functioning and capability of a computer is the storing and writing of data to a data storage device, such as a hard disk drive (HDD). The volume of data processed by a computer is increasing rapidly. There is a need for higher recording density of a magnetic recording medium to increase the function and the capability of a computer.

In order to achieve higher recording densities, such as recording densities exceeding <NUM> Tbit/in<NUM> for a magnetic recording medium, the width and pitch of write tracks are narrowed, and thus the corresponding magnetically recorded bits encoded in each write track are narrowed. Attempts to achieve increasing requirements of advanced narrow gap reader sensors of read heads to achieve reading of higher recording densities have been proposed utilizing magnetoresistive sensors with free layers comprised of high saturation magnetization materials.

Typical read heads include a read sensor sandwiched between two shields. The shield-to-shield spacing of the two shields plays a crucial role in the resolution of the read sensor. However, conventional read sensors are already minimized to about <NUM>, and cannot be reduced in size much further to decrease the shield-to-shield spacing. Different reader configurations utilizing two read heads between two shields may improve reader resolution without reducing the shield-to-shield spacing (i.e., the read gap). For differential reader configurations, the materials used in the read sensor sandwiched between two shields may cause an unsymmetrical response due to different spin hall angle properties resulting in a baseline shift.

<CIT> discloses a magnetic recording head, comprising: a first shield; a second shield; and a spin orbital torque (SOT) reader disposed between the first shield and the second shield, the SOT differential reader comprising: a layer disposed over the first shield; a first spin hall effect layer disposed over the, a first interlayer layer disposed over the first spin hall effect layer; a first free layer disposed over the first interlayer layer; a seed layer disposed over the first free layer; a second free layer; a second interlayer disposed over the second free layer; a second spin hall effect layer disposed over the second interlayer layer, cap layer disposed over the second spin hall effect layer.

Therefore, there is a need in the art for an improved magnetic read head.

The present disclosure generally relates to spin-orbital torque (SOT) differential reader designs. The SOT differential reader is a multi-terminal device comprising a first seed layer, a first spin hall effect (SHE) layer, a first interlayer, a first free layer, a gap layer, a second seed layer, a second SHE layer, a second free layer, and a second interlayer. The gap layer is disposed between the first SHE layer and the second SHE layer. The materials and dimensions used for the first and second seed layers, the first and second interlayers, and the first and second SHE layers affect the resulting spin hall voltage converted from spin current injected from the first free layer and the second free layer, as well as the ability to tune the first and second SHE layers. Moreover, the SOT differential reader improves reader resolution without decreasing the shield-to-shield spacing (i.e., read-gap).

In one embodiment, a magnetic recording head comprises a first shield, a second shield, and a spin orbital torque (SOT) differential reader disposed between the first shield and the second shield. The SOT differential reader comprises a silicide seed multilayer disposed over the first shield, a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), a first interlayer layer disposed over the first spin hall effect layer, a first free layer disposed over the first interlayer layer, a seed layer disposed over the first free layer, a second free layer disposed over the seed layer, a second interlayer disposed over the second free layer, a second spin hall effect layer disposed over the second interlayer layer, the second spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), and a cap layer disposed over the second spin hall effect layer.

In another embodiment, a magnetic recording head comprises a first shield, a second shield, and a spin orbital torque (SOT) differential reader disposed between the first shield and the second shield. The SOT differential reader comprises a silicide seed multilayer disposed over the first shield, a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), a first interlayer layer disposed over the first spin hall effect layer, the first interlayer comprising a NiCu layer and a NiFeTa layer, a first free layer disposed over the first interlayer layer, a gap layer disposed over the first free layer, a seed layer disposed over the gap layer, a second free layer disposed over the seed layer, a second interlayer disposed over the second free layer, the second interlayer comprising a NiFeTa layer and a NiAl layer, and a second spin hall effect layer disposed over the second interlayer layer, the second spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>).

In yet another embodiment, a magnetic recording head comprises a first shield, a second shield, and a spin orbital torque (SOT) differential reader disposed between the first shield and the second shield. The SOT differential reader comprises a silicide seed multilayer disposed over the first shield, the silicide seed multilayer comprising a Si layer, a first Cu layer, a NiFe layer, and a second Cu layer, a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), a first interlayer layer disposed over the first spin hall effect layer, the first interlayer comprising a NiCu layer and a NiFeTa layer, a first free layer disposed over the first interlayer layer, a gap layer disposed over the first free layer, a seed layer disposed over the gap layer, the seed layer comprising NiFeTa, a second free layer disposed over the seed layer, a second interlayer disposed over the second free layer, the second interlayer comprising a NiFeTa layer and a NiAl layer, a second spin hall effect layer disposed over the second interlayer layer, the second spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), wherein the second spin hall effect layer has a greater thickness and a higher Sb concentration than the first spin hall effect layer, and a cap layer comprising a NiCu layer and a NiFeTa layer disposed over the second spin hall effect layer.

In the following, reference is made to embodiments of the disclosure. However, it should be understood that the disclosure is not limited to specific described embodiments.

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 disclosure" 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).

<FIG> illustrates a disk drive <NUM> embodying this disclosure. As shown, at least one rotatable magnetic media <NUM> is supported on a spindle <NUM> and rotated by a disk drive motor <NUM>. The magnetic recording on each disk is in the form of any suitable patterns of data tracks, such as annular patterns of concentric data tracks (not shown) on the magnetic media <NUM>.

At least one slider <NUM> is positioned near the magnetic media <NUM>, each slider <NUM> supporting one or more magnetic head assemblies <NUM>. As the magnetic media rotates, the slider <NUM> moves radially in and out over the media surface <NUM> so that the magnetic head assembly <NUM> may access different tracks of the magnetic media <NUM> where desired data are written. Each slider <NUM> is attached to an actuator arm <NUM> by way of a suspension <NUM>. The suspension <NUM> provides a slight spring force which biases the slider <NUM> toward the media surface <NUM>. Each actuator arm <NUM> is attached to an actuator means <NUM>. The actuator means <NUM> as shown in <FIG> may be a voice coil motor (VCM). The VCM includes a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by control unit <NUM>.

During operation of the disk drive <NUM>, the rotation of the magnetic media <NUM> generates an air bearing between the slider <NUM> and the media surface <NUM> which exerts an upward force or lift on the slider <NUM>. The air bearing thus counter-balances the slight spring force of suspension <NUM> and supports slider <NUM> off and slightly above the media <NUM> surface by a small, substantially constant spacing during normal operation.

The various components of the disk drive <NUM> are controlled in operation by control signals generated by control unit <NUM>, such as access control signals and internal clock signals. Typically, the control unit <NUM> comprises logic control circuits, storage means, and a microprocessor. The control unit <NUM> generates control signals to control various system operations, such as drive motor control signals on line <NUM> and head position and seek control signals on line <NUM>. The control signals on line <NUM> provide the desired current profiles to optimally move and position slider <NUM> to the desired data track on media <NUM>. Write and read signals are communicated to and from write and read heads on the assembly <NUM> by way of recording channel <NUM>.

The above description of a typical magnetic disk storage system and the accompanying illustration of <FIG> are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders.

<FIG> is a fragmented, cross sectional side view through the center of a read/write head <NUM> facing the magnetic media <NUM>, according to one embodiment. The read/write head <NUM> may correspond to the magnetic head assembly <NUM> described in <FIG>. The read/write head <NUM> includes a media facing surface (MFS) <NUM>, such as an air bearing surface (ABS), a magnetic write head <NUM>, and a magnetic read head <NUM>, and is mounted such that the MFS <NUM> is facing the magnetic media <NUM>. In <FIG>, the magnetic media <NUM> moves past the write head <NUM> in the direction indicated by the arrow <NUM> and the read/write head <NUM> moves in the direction indicated by the arrow <NUM>.

The magnetic read head <NUM> is a SOT differential reader <NUM> located between the shields S1 and S2.

The write head <NUM> includes a return pole <NUM>, a main pole <NUM>, a trailing shield <NUM>, and a coil <NUM> that excites the main pole <NUM>. The coil <NUM> may have a "pancake" structure which winds around a back-contact between the main pole <NUM> and the return pole <NUM>, instead of a "helical" structure shown in <FIG>. A trailing gap (not shown) and a leading gap (not shown) may be in contact with the main pole and a leading shield (not shown) may be in contact with the leading gap. A recording magnetic field is generated from the main pole <NUM> and the trailing shield <NUM> helps making the magnetic field gradient of the main pole <NUM> steep. The main pole <NUM> may be a magnetic material such as a FeCo alloy. The main pole <NUM> may include a trailing surface <NUM> which may be parallel to a leading surface <NUM> of the trailing shield <NUM>. The main pole <NUM> may be a tapered write pole (TWP) with a trailing edge taper (TET) configuration. In one embodiment, the main pole <NUM> has a saturated magnetization (Ms) of <NUM> T and a thickness of about <NUM> nanometers (nm). The main pole <NUM> may comprise ferromagnetic materials, typically alloys of one or more of Co, Fe and Ni. The trailing shield <NUM> may be a magnetic material such as NiFe alloy. In one embodiment, the trailing shield <NUM> has an Ms of about <NUM> T to about <NUM> T.

<FIG> illustrate a SOT differential reader, according to various embodiments. <FIG> illustrate SOT differential readers 300A, 300B, where each of <FIG> has: (<NUM>) a top stack configuration view of the reader and (<NUM>) a bottom abstract view showing the positioning of the free layers relative to a magnetic media when the recording head is over the media, with the other layers in the stack configuration omitted. The SOT differential reader <NUM> may be the SOT differential reader <NUM> located between the two shields S1 and S2 of <FIG>. The SOT differential readers 300A, 300B have the same electrical connection configuration. However, the first SOT differential reader 330A and the second SOT differential reader 300B may be positioned perpendicular to different areas of the magnetic media <NUM>. The positioning of the SOT differential readers 300A, 300B about the magnetic media <NUM> may change the induced voltage polarity of the first spin hall effect layers 302a, 302b and the second spin hall effect layers 304a, 304b.

As shown in the top stack configuration view of <FIG>, a first free layer (FL) <NUM> is disposed over a first spin hall effect (SHE) layer 302a, 302b (collectively referred to as first SHE layer <NUM>), a gap layer (GL) <NUM> disposed over the first FL <NUM>, a second FL <NUM> disposed over the GL <NUM>, and a second SHE layer 304a, 304b (collectively referred to as second SHE layer <NUM>) disposed over the second FL <NUM>. In the descriptions herein, the plurality of SHE layers may be referred to as a plurality of spin hall layers (SHLs). The SOT differential readers 300A, 300B may each have a stripe height of between about <NUM> Angstroms to about <NUM> Angstroms.

In the bottom view of <FIG>, the first FL <NUM> and the second FL <NUM> are shown rotated <NUM> degrees from the stack configuration view above, and are positioned perpendicularly over the magnetic media <NUM>, where the magnetic media <NUM> may be the magnetic media <NUM> of <FIG>. The first FL <NUM> and the second FL <NUM> are parallel with the magnetic field direction of the magnetic media <NUM>. The magnetic media <NUM> includes a first magnetic field direction, indicated by a first arrow pointing up in bits 314a and 314c, and a second magnetic field direction, indicated by a second arrow pointing down in bits 314b and 314d. The magnetic media <NUM> further includes a first bit 314a with a first magnetic field direction, a second bit 314b with a second magnetic field direction, a third bit 314c with the first magnetic field direction, and a fourth bit 314d with the second magnetic field direction. While four bits 314a-314d are shown, the magnetic media may have any number of bits.

In the top stack configuration view of <FIG>, a positive end or pole 305b of the first SHL 302a is electrically connected to a positive end or pole 305b of the second SHL 304a, and a negative end or pole 305a of the first SHL 302a is electrically connected to a negative end or pole 305a of the second SHL 304a. The voltage polarity of the first SHL 302a and the second SHL 304a (i.e., the positive end or pole 305b and the negative end or pole 305a) depends on the positioning of the first and the second FLs <NUM>, <NUM> about the magnetic media, as described below. In another embodiment, the voltage polarity of the first SHL 302a and/or the second SHL 304a may be flipped. The listed voltage polarity of the first and the second SHLs 302a, 304a are not intended to be limiting, but to provide an example of a possible embodiment. Referring to the bottom abstract view of <FIG>, when the first and second FLs <NUM>, <NUM>, respectively, are both positioned over a single bit of the plurality of bits 314a-314d, such as the third bit 314c, of the magnetic media <NUM>, the magnetic field of the third bit 314c imposes a magnetic force on the first and the second FLs <NUM>, <NUM>. As a result of the magnetic force imposed on the first and the second FLs <NUM>, <NUM>, the magnetic moment of the first and the second FLs <NUM>, <NUM> are both in the same direction as the magnetic field of the third bit 314c.

In the top stack configuration view of <FIG>, a positive end or pole 309b of the first SHL 302b is electrically connected to a negative end or pole 307a of the second SHL 304b, and a negative end or pole 309a of the first SHL 302b is electrically connected to a positive end or pole 307b of the second SHL 304b. The voltage polarity of the first SHL 302b and the second SHL 304b (i.e., the positive end or pole 307b, 309b and the negative end or pole 307a, 309a) depends on the positioning of the first and the second FLs <NUM>, <NUM> about the magnetic media, as described below. In another embodiment, the voltage polarity of the first SHL 302b and/or the second SHL 304b may be flipped. The listed voltage polarity of the first and the second SHLs 302b, 304b are not intended to be limiting, but to provide an example of a possible embodiment. In the description herein, the position of the negative ends or poles and the positive ends or poles of the SHLs referenced may be flipped. Therefore, embodiments not listed are contemplated and relevant to the current description.

Referring to the bottom abstract view of <FIG>, when the first and second FLs <NUM>, <NUM>, respectively, are each positioned over adjacent bits of the plurality of bits 314a-314d, such as the second bit 314b and the third bit 314c, of the magnetic media <NUM>, the magnetic field of the second bit 314b imposes a magnetic force on the first FL <NUM>, and the third bit 314c imposes a magnetic force on the second FL <NUM>, which is opposite to the magnetic force imposed on the first FL <NUM>. As a result of the magnetic force imposed on the first FL <NUM> and the second FL <NUM>, the magnetic moment of the first FL <NUM> is in the same direction as the magnetic field of the second bit 314b, and the magnetic moment of the second FL <NUM> is in the same direction as the magnetic field of the third bit 314c. In <FIG>, because the first and the second FLs <NUM>, <NUM> are located over adjacent bits of the plurality of bits 314a-314d of the magnetic media <NUM>, the first FL <NUM> has a magnetic field direction opposite of the second FL <NUM> magnetic field direction.

In <FIG>, the first SHL 302a, 302b and the second SHL 304a, 304b each comprises the same material and has the same thickness in the y-direction. The first and second SHLs 302a, 302b, 304a, 304b may be formed by a non-magnetic heavy metal material selected from a group that includes Ta, Pt, W, Hf, Bi, and alloys thereof. Additionally, it is to be understood that while Ta, Pt, W, Hf, Bi, and alloys thereof have been exemplified as the materials of the first and the second SHLs 302a, 304a, other materials are contemplated, and the embodiments discussed herein are not limited. For example, BiSb and BiSe may be used as the material for the first and the second SHLs <NUM>, <NUM>. The first and the second SHLs <NUM>, <NUM> may have a greater width in the x-direction than the first and second FLs <NUM>, <NUM> and the GL <NUM>. In one embodiment, the first and second SHLs <NUM>, <NUM> have the same width in the x-direction. In another embodiment, the first and second SHLs <NUM>, <NUM> have different widths in the x-direction.

In <FIG>, the first SHL 302a and the second SHL 304a each generates a lateral voltage signal (i.e., a SHE signal) inside each respective first and second SHLs 302a, 304a. The generated lateral voltage signal may be due to the spin hall effect. The lateral voltage signal polarity may depend on the electron current flow direction and the magnetic orientation of the first and second FLs <NUM>, <NUM>. For example, in the bottom view of <FIG>, the first and second FLs <NUM>, <NUM> are each positioned perpendicularly over the same bit, such as the third bit 314c. The first and second SHLs 302a, 304a have the same SHE voltage polarity, where the side in the negative x-direction is a negative end 305a and the side in the positive x-direction is a positive end 305b.

Furthermore, the negative ends 305a (e.g., the end in the negative x-direction) of the first and the second SHLs 302a, 304a are connected such that the negative ends 305a of the first and the second SHLs 302a, 304a share an equal voltage potential. The reader signal output may be determined by the voltage difference or the differential voltage <NUM> between the positive ends 305b (e.g., the end in the positive x-direction) of the first and the second SHLs 302a, 304a. Because the first and the second SHLs 302a, 304a each includes the same materials and the same current flow direction, the SHE voltage induced by the first SHL 302a may be equal in both polarity and magnitude to the SHE voltage induced by the second SHL 304a. The differential voltage <NUM> between the two positive ends 305b may be either cancelled or reduced. The differential voltage <NUM> may be a net differential output of about zero. A first current <NUM> travels from the first SHL 302a to the GL <NUM> and a second current <NUM> travels from the GL <NUM> to the second SHL 304a. As such, the SOT differential reader 300A is a multi-terminal device. Because the first and the second SHLs 302a, 304a have the same voltage polarity, the signal output may be greatly reduced.

In the bottom view of <FIG>, the first FL <NUM> and the second FL <NUM> are located over adjacent bits, such as the first FL <NUM> being positioned perpendicularly over the second bit 314b and the second FL being positioned perpendicularly over the third bit 314c. The first and the second FLs <NUM>, <NUM> have different and opposite magnetization. For example, the first SHL 302b has a first SHE voltage, where the side in the negative x-direction is a positive pole 309b and the side in the positive x-direction is a negative pole 309a. Likewise, the second SHL 304b has a second SHE voltage where the side in the negative x-direction is a negative end 307a and the side in the positive x-direction is a positive end 307b.

Furthermore, the positive pole 309b (e.g., the end in the negative x-direction) of the first SHL 302b and the negative end 307a (e.g., the end in the positive x-direction) of the second SHL 304b are connected and share an equal voltage potential. The differential voltage <NUM> is determined by the difference between the voltage of the positive end 307b of the second SHL 304b and the voltage of the negative pole 309a of the first SHL 302b. Because the induced voltage directions of the first and the second SHLs 302b, 304b are opposite of each other, the differential voltage <NUM> may effectively double the output signal. A first current <NUM> travels from the first SHL 302b to the GL <NUM>, and a second current <NUM> travels from the GL <NUM> to the second SHL 304b. As such, the SOT differential reader 300B is a multi-terminal device. Because the first and the second SHLs 302b, 304b have opposite voltage directions, the signal output may be effectively doubled or greatly increased.

<FIG> illustrates a MFS view of a SOT differential reader <NUM>, according to one embodiment. The SOT differential reader <NUM> may be the SOT differential reader 300A of <FIG> and/or the SOT differential reader 300B of <FIG>. Furthermore, the first SHLs 302a, 302b may be the first SHLs <NUM>, and the second SHLs 304a, 304b may be the second SHL <NUM>. In the descriptions herein, the SHLs may be referred to as the SHE layers for exemplary purposes.

The SOT differential reader <NUM> further includes a first shield 322a disposed below a first insulation layer <NUM>, where the first SHL <NUM> is disposed over the first insulation layer <NUM>. Furthermore, a second insulation layer 332a is disposed along the top edge of the left side of the SHL <NUM> (i.e., between the first SHL <NUM> and a first bias layer 324a) and on the left side of the first FL <NUM>, the GL <NUM>, and the second FL <NUM> (i.e., adjacent to the first bias layer 324a). A third insulation layer 332b is deposited along the top edge of the right side of the SHL <NUM> (i.e., between the first SHL <NUM> and a second bias layer 324b) and on the right side of the first FL <NUM>, the GL <NUM>, and the second FL <NUM> (i.e., adjacent to the second bias layer 324b). A first bias layer 324a is disposed over the second insulation layer 332a. A second bias layer 324b is disposed over the third insulation layer 332b. A fourth insulation layer <NUM> is disposed over the first and second bias layers 324a, 324b and the second SHL <NUM>. A second shield 322b is disposed over the fourth insulation layer <NUM>. The first and second bias layers 324a, 324b may comprise a hard bias material or a soft bias material.

The SOT differential reader <NUM> further comprises a capping layer <NUM> disposed between a first bias layer 324a, a second bias layer 324b, and the fourth insulation layer <NUM>. The first and second bias layers 324a, 324b may be soft bias layers. The capping layer <NUM> comprises a material selected from a group of anti-ferromagnetic (AFM) materials that includes IrMn, FeMn, PtMn, and other non-magnetic conducting layers. Furthermore, the capping layer <NUM> may comprise a group of AFM materials and one or more materials from a group that includes Ta, Ru, or Ti, other non-magnetic materials, and/or their multilayers. The capping layer <NUM> may be formed by well-known deposition methods, such as sputtering. The capping layer <NUM> may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. Additionally, it is to be understood that while IrMn, FeMn, PtMn, Ta, Ru, Ti and their multilayers have been exemplified as the capping layer <NUM> materials, other materials are contemplated and the embodiments discussed herein are not limited to IrMn, FeMn, PtMn, Ta, Ru, or Ti or their multilayers for the capping layer <NUM>.

The insulation layers <NUM>, 332a, 332b, <NUM> may be placed in the SOT differential reader <NUM>, such that electrical shorting between the first shield 322a, the first SHL <NUM>, the first FL <NUM>, the GL <NUM>, the second FL <NUM>, the second SHL <NUM>, the second shield <NUM>, the first bias layer 324a, and the second bias layer 324b may be avoided. Suitable materials for the insulation layers <NUM>, 332a, 332b, <NUM> include dielectric materials such as aluminum oxide, silicon oxide, magnesium oxide, and silicon nitride. The insulation layers <NUM>, 332a, 332b, <NUM> may be formed by well-known deposition methods such as atomic layer deposition (ALD), physical vapor deposition (PVD), ion bean deposition (IBD), or sputtering. The insulation layers <NUM>, 332a, 332b, <NUM> may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms.

The first FL <NUM> and the second FL <NUM> comprise the same material and have a same thickness in the y-direction. The first and the second FLs <NUM>, <NUM> have a greater thickness in the y-direction than the first and the second SHLs <NUM>, <NUM>. The first and the second FLs <NUM>, <NUM> each comprises a CoFe/CoFeB/Ta/NiFe multilayer stack. The CoFe layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The CoFeB layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The Ta layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The NiFe layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms, such as between about <NUM> Angstroms and about <NUM> Angstroms or between about <NUM> Angstroms and about <NUM> Angstroms. The first and the second FLs <NUM>, <NUM> may be formed by well-known deposition methods such as sputtering. Additionally, it is to be understood that while CoFe/CoFeB/Ta/NiFe have been exemplified as the materials of the first and the second FLs <NUM>, <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited to CoFe/CoFeB/Ta/NiFe for the first and the second FLs <NUM>, <NUM>. Furthermore, the previously mentioned dimensions are not intended to be limiting, but to provide an example of a possible embodiment.

The GL <NUM> has a smaller thickness in the y-direction than the first and the second SHLs <NUM>, <NUM>. The GL <NUM> may be formed by a non-magnetic conducting material such as Cr with a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. In some embodiments, the GL <NUM> may have a thickness of about <NUM> Angstroms to about <NUM> Angstroms. It is to be understood that while Cr is exemplified as the GL <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited to Cr for the GL <NUM>. In some embodiments, insulating materials may be used for the GL <NUM> material, such as when the GL <NUM> has a thickness of less than about <NUM>. In one embodiment, the GL <NUM> includes an electrode to allow for the independent adjustment of the spin hall angle properties of the first SHL <NUM> and the second SHL <NUM>.

The first shield 322a and the second shield 322b each comprises an electrically conductive material selected from a group that includes Cu, W, Ta, Al, NiFe, CoFe, and alloys thereof. The shield materials may either include NiFe alloy, CoFe alloy, or a combination of NiFe alloy or CoFe alloy with Cu, W, Ta, and Al. The thickness of each of the first shield 322a and the second shield 322b may be between about <NUM> and about <NUM>. Additionally, it is to be understood that while NiFe, CoFe, Cu, W, Ta, Al, and alloys thereof have been exemplified as the first shield 322a and the second shield 322b materials, other materials are contemplated, and the embodiments discussed herein are not limited to NiFe, CoFe, Cu, W, Ta, Al, and alloys thereof for the first shield 322a and the second shield 322b.

In some embodiments, the first and second bias layers 324a, 324b are first and second hard bias layers, respectively. The first hard bias layer and the second hard bias layer may comprise a multilayer structure comprising a seed layer(s) and a bulk layer. In one embodiment, the hard bias layer comprises a Ta seed layer, a Cr or a W seed layer on the Ta seed layer, and a CoPt bulk layer disposed over the Cr or the W seed layer. In some embodiments, the hard bias layer includes a multilayer of the previously mentioned materials. Additionally, it is to be understood that while Ta, W, Cr, and CoPt have been exemplified as the first hard bias layer and the second hard bias layer materials, other materials are contemplated, and the embodiments discussed herein are not limited to Cu, Ta, W, Cr, and CoPt for the first hard bias layer and the second hard bias layer. Furthermore, when the SOT differential reader <NUM> includes hard bias layers, the AFM/capping layer may not be present in the SOT differential reader.

In some embodiments, the first bias layer 324a and the second bias layer 324b are a first soft bias layer and a second soft bias layer, respectively. The first soft bias layer and the second soft bias layer may comprise a multilayer structure that includes soft magnetic materials. In one embodiment, the soft bias layers comprise a material selected from a group that includes NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and/or their multilayers. Additionally, it is to be understood that while NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and/or their multilayers have been exemplified as the soft bias layer materials, other materials are contemplated, and the embodiments discussed herein are not limited to NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and/or their multilayers for the soft bias layers.

Electrical leads are placed about the first SHL <NUM>, the second SHL <NUM>, and the GL <NUM>. For example, the first SHL <NUM> includes a first negative voltage terminal (V1-), a first positive voltage terminal (V1+), and a first negative current terminal (<NUM>-). The second SHL <NUM> includes a second negative voltage terminal (V2-), a second positive voltage terminal (V2+), and a second negative current terminal (<NUM>-) located on either side of the second SHL <NUM>. Furthermore, the GL <NUM> includes a first positive current terminal (I1+) and a second positive current terminal (<NUM>+). It is to be understood that the illustrated polarity of the voltage terminals of the first and the second SHLs <NUM>, <NUM> are for exemplary purposes and the voltage polarity of the first and second SHLs <NUM>, <NUM> may depend on the direction of the current and the positioning of the first and the second FLs <NUM>, <NUM> relative to the bits, such as the bits 314a-314d, of the magnetic media <NUM>.

Furthermore, the first negative voltage terminal (V1-) and the second negative voltage terminal (V2-) may be electrically shorted together as to provide a common voltage terminal. The differential voltage (e.g., the differential voltage <NUM>) between the first positive voltage terminal (V1+) of the first SHL <NUM> and the second positive voltage terminal (V2+) of the second SHL <NUM> is the SOT differential reader signal output. Because the GL <NUM> includes separate current terminals, the current applied to the first FL <NUM> and the second FL <NUM> may be adjusted independently of each other. Therefore, the first FL <NUM> and the second FL <NUM> magnetic response may be matched when the first FL <NUM> and the second FL <NUM> includes different properties, such as different materials or thicknesses. The current and the voltage directions of <FIG> may represent the current and the voltage directions of <FIG>. Moreover, while the SOT differential reader <NUM> of <FIG> is shown to have the same electrical leads or voltage terminals as the SOT differential reader 300A of <FIG>, the SOT differential reader <NUM> is not limited to such a configuration. In some embodiments, the electrical leads or voltage terminals of the SOT differential reader <NUM> may be the same as shown in the SOT differential reader 300B of <FIG>.

The first SHL <NUM> has a first track width <NUM> that is substantially equal to or less than the width of the first shield 322a, and the second SHL <NUM> has a second track width <NUM> that is substantially equal to the width of the stack that includes the first FL <NUM>, the GL <NUM>, and the second FL <NUM>. In some embodiments, the first track width <NUM> has a width that is less than the width of the first shield 322a. The first track width <NUM> may be about <NUM> Angstroms to about <NUM> Angstroms wide. The second track width <NUM> may be about <NUM> Angstroms to about <NUM> Angstroms wide.

<FIG> illustrates a side cross-sectional view of a SOT differential reader <NUM>, according to one embodiment. The SOT differential reader <NUM> includes a first insulation layer <NUM> disposed over the first shield 322a, a first SHL <NUM> disposed over the first insulation layer <NUM>, a first FL <NUM> disposed over the first SHL <NUM>, a GL <NUM> disposed over the first FL <NUM>, a second FL <NUM> disposed over the GL <NUM>, and second SHL <NUM> disposed over the second FL <NUM>. In the current embodiment, the second FL <NUM> and the second SHL <NUM> includes two separated portions or sections, where a first section <NUM> is adjacent to a media facing surface (MFS) <NUM> and a second section <NUM> is disposed over a side <NUM> opposite to the MFS <NUM> in the z-direction. The GL <NUM> extends from the MFS <NUM> to the side <NUM> opposite of the MFS <NUM> and is in contact with the second section <NUM>.

A fourth insulation layer <NUM> is disposed over the second SHL <NUM>. Furthermore, a fifth insulation layer 327a is disposed between the first shield 322a and the GL <NUM>. A sixth insulation layer 327b is disposed between the GL <NUM> and the second shield 322b, and between the first section <NUM> and the second section <NUM>. A second shield 322b is disposed over the fourth insulation layer <NUM> and the second section of the second SHL <NUM>. The second shield 322b is in contact with the second section of the second SHL <NUM>.

<FIG> illustrates a MFS view of a SOT differential reader <NUM>, according to another embodiment. In one embodiment, the SOT differential reader <NUM> may be the SOT differential reader 300A of <FIG>. In another embodiment, the SOT differential reader <NUM> may have different configurations of the voltage terminals or poles 305a, 305b, such that the voltage terminals match the terminals or poles 307a, 307b, 309a, 309b illustrated in the SOT differential reader 300B of <FIG>. Furthermore, the first SHLs 302a, 302b may be the first SHL <NUM> and the second SHLs 304a, 304b may be the second SHL <NUM>. Aspects of the SOT differential reader <NUM> are similar to the SOT differential reader <NUM> of <FIG>, and the reference numerals of elements of <FIG> and <FIG> are consistent to reflect this. However, unlike <FIG>, the SOT differential reader <NUM> includes a single current <NUM> rather than a first current <NUM> and a second current <NUM> as illustrated in <FIG>.

Electrical leads are placed about the first SHL <NUM> and the second SHL <NUM>. In the example shown, the first SHL <NUM> includes a first negative voltage terminal (V1-), a first positive voltage terminal (V1+), and a first positive current terminal (<NUM>+). It is to be understood that the illustrated polarity of the voltage terminals of the first and second SHLs <NUM>, <NUM> are for exemplary purposes and the voltage polarity of the first and second SHLs <NUM>, <NUM> may depend on the direction of the current and the positioning of the first and the second FLs <NUM>, <NUM> relative to the bits, such as the bits 314a-314d, of the magnetic media <NUM>. As shown, the second SHL <NUM> includes a first negative current terminal (<NUM>-), a second positive voltage terminal (V2+), and a second negative voltage terminal (V2-).

Furthermore, the first negative voltage terminal (V1-) and the second negative voltage terminal (V2-) may be electrically shorted together as to provide a common voltage terminal. The differential voltage (e.g., the differential voltage <NUM>) between the first positive voltage terminal of the first SHL <NUM> and the second positive voltage terminal of the second SHL <NUM> is the SOT differential reader signal output. Furthermore, a current <NUM> travels from the first positive current terminal (I1+) of the first SHL <NUM> to the first negative current terminal (I1-) of the second SHL <NUM>. As noted above, while the SOT differential reader <NUM> of <FIG> is shown to have the same electrical leads or voltage terminals as the SOT differential reader 300A of <FIG>, the SOT differential reader <NUM> is not limited to such a configuration. In some embodiments, the electrical leads or voltage terminals of the SOT differential reader <NUM> may be the same as shown in the SOT differential reader 300B of <FIG>.

<FIG> illustrates a MFS view of a SOT differential reader <NUM>, according to one embodiment. Aspects of the SOT differential reader <NUM> may be similar to the SOT differential readers previously described in <FIG>, and the SOT differential reader <NUM> may be any one of the SOT differential readers 300A, 300B, <NUM>, <NUM>, <NUM> of <FIG>, respectively. As such, any materials and/or dimensions of the various layers described in <FIG> may apply to the corresponding layers in <FIG>.

The SOT differential reader <NUM> includes a first shield 422a, a first insulation layer <NUM> disposed over the first shield 422a, a silicide seed multilayer <NUM> (may be referred to as seed layer <NUM> or silicide seed layer <NUM>) disposed over the first insulation layer <NUM>, a first SHL <NUM> disposed over the silicide seed multilayer <NUM>, a first interlayer 424a disposed over the first SHL <NUM>, a first FL <NUM> is disposed over the first interlayer 424a, and a gap layer <NUM> is disposed over the first FL <NUM>. The SOT differential reader <NUM> further includes a seed layer <NUM> disposed over the gap layer <NUM>, a second FL <NUM> disposed over the seed layer <NUM>, a second interlayer 424b disposed over the second FL <NUM>, a second SHL <NUM> disposed over the second interlayer 424b, a SHL capping layer <NUM> disposed over the second SHL <NUM>, a second insulation layer <NUM> disposed over the SHL capping layer <NUM>, and a second shield 422b disposed over the second insulation layer <NUM>. In some embodiments, an AFM/capping layer may be disposed on the SHL capping layer. In such embodiments, the AFM/capping layer may comprise a group of AFM materials and one or more materials from a group that includes IrMn, FeMn, PtMn, Ta, Ru, or Ti, other non-magnetic materials, and/or their multilayers.

As discussed further below, the thicknesses of the first interlayer 424a, the second interlayer 424b, the silicide seed multilayer <NUM>, and the seed layer <NUM> are each selected to vary and control the spacing between the first SHL <NUM> and the second SHL <NUM>. Controlling the spacing between the first and second SHLs <NUM>, <NUM> enables the amplitude of the first and second SHLs <NUM>, <NUM> to be tuned and matched.

The silicide seed multilayer <NUM> may be referred to as the 'E' layer, the first interlayer 424a may be referred to as the 'D' layer, the seed layer <NUM> may be referred to as the 'C' layer, the second interlayer 424b may be referred to as the 'B' layer, and the SHL capping layer <NUM> may be referred to as the 'A' layer. The SOT differential reader <NUM> may be split into a first section <NUM> and a second section <NUM>, where the first section <NUM> of the SOT differential reader <NUM> may include the layers between the "A" layer and the "C' layer, and the second section <NUM> of the SOT differential reader <NUM> may include the layers between the 'C' layer and the 'E' layer. The resulting SHE signal output from the first SHL <NUM> and the second SHL <NUM> may depend on the characteristics that each section <NUM>, <NUM> includes, such as current, voltage, the materials used, and the layer thicknesses.

The first shield 422a and the second shield 422b each comprises an electrically conductive material selected from a group that includes Cu, W, Ta, Al, NiFe, CoFe, and alloys thereof. The shield materials may either include NiFe alloy, CoFe alloy, or a combination of NiFe alloy or CoFe alloy with Cu, W, Ta, and Al. The thickness of each of the first shield 422a and the second shield 422b may be between about <NUM> and about <NUM>. Additionally, it is to be understood that while NiFe, CoFe, Cu, W, Ta, Al, and alloys thereof have been exemplified as the first shield 422a and the second shield 422b materials, other materials are contemplated, and the embodiments discussed herein are not limited to NiFe, CoFe, Cu, W, Ta, Al, and alloys thereof for the first shield 422a and the second shield 422b.

Suitable materials for the insulation layers <NUM>, <NUM> include dielectric materials such as aluminum oxide, silicon oxide, magnesium oxide, and silicon nitride. The insulation layers <NUM>, <NUM> may be formed by well-known deposition methods such as atomic layer deposition (ALD), physical vapor deposition (PVD), ion bean deposition (IBD), or sputtering. The insulation layers <NUM>, <NUM> may have a thickness of between about <NUM> Angstroms and about <NUM> Angstroms.

The SHL capping layer <NUM> comprises a NiCu/NiFeTa multilayer stack. The NiCu layer may have a thickness between about <NUM> Angstroms to about <NUM> Angstroms. The NiFeTa layer may have a thickness between about <NUM> Angstroms to about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but provide an example of a possible embodiment. The SHL capping layer <NUM> may be formed by well-known deposition methods such as ALD, PVD, IBD, or sputtering. Additionally it is to be understood that while NiCu/NiFeTa have been exemplified as the materials of the multilayer stack of the SHL capping layer <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited to NiCu/NiFeTa for the SHL capping layer <NUM>. The SHL capping layer <NUM> may aid in producing the specified texture (i.e., the (<NUM>) crystalline structure).

The first interlayer 424a comprises a NiCu/NiFeTa multilayer stack. The NiCu layer may have a thickness between about <NUM> Angstroms to about <NUM> Angstroms, such as about <NUM> Angstroms to about <NUM> Angstroms. The NiFeTa layer may have a thickness between about <NUM> Angstroms to about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but provide an example of a possible embodiment. The first interlayer 424a may be formed by well-known deposition methods such as ALD, PVD, IBD, or sputtering. Additionally it is to be understood that while NiCu/NiFeTa have been exemplified as the materials of the multilayer stack of the first interlayer 424a, other materials are contemplated, and the embodiments discussed herein are not limited to NiCu/NiFeTa for the first interlayer 424a.

The second interlayer 424b comprises a NiFeTa/NiAl multilayer stack. The NiFeTa layer may have a thickness between about <NUM> Angstroms to about <NUM> Angstroms. The NiAl layer may have a thickness between about <NUM> Angstroms to about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but provide an example of a possible embodiment. The second interlayer 424b may be formed by well-known deposition methods such as ALD, PVD, IBD, or sputtering. Additionally it is to be understood that while NiFeTa/NiAl have been exemplified as the materials of the multilayer stack of the second interlayer 424b, other materials are contemplated, and the embodiments discussed herein are not limited to NiFeTa/NiAl for the second interlayer 424b.

In one embodiment, the first FL <NUM> and the second FL <NUM> comprise the same material and have a same thickness in the y-direction. In another embodiment, the first FL <NUM> and the second FL <NUM> comprise different materials have a different thickness in the y-direction. In yet another embodiment, the first FL <NUM> and the second FL <NUM> comprise the same or different materials and the have the same or different thicknesses in the y-direction. The first and the second FLs <NUM>, <NUM> have a greater thickness in the y-direction than the first and the second SHLs <NUM>, <NUM>. The first and the second FLs <NUM>, <NUM> each includes a CoFe/CoFeB/Ta/NiFe multilayer stack. The CoFe layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The CoFeB layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The Ta layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The NiFe layer may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms, such as between about <NUM> Angstroms and about <NUM> Angstroms or between about <NUM> Angstroms and about <NUM> Angstroms.

The first and the second FLs <NUM>, <NUM> may be formed by well-known deposition methods such as sputtering. Additionally, it is to be understood that while CoFe/CoFeB/Ta/NiFe have been exemplified as the materials of the first and the second FLs <NUM>, <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited to CoFe/CoFeB/Ta/NiFe for the first and the second FLs <NUM>, <NUM>. Furthermore, the previously mentioned dimensions are not intended to be limiting, but to provide an example of a possible embodiment.

The silicide seed multilayer <NUM> comprises a Si/Cu/NiFe/Cu multilayer stack. The Si layer may have a thickness of about <NUM> Angstroms. The Cu layers may have a thickness of about <NUM> Angstrom. The NiFe layer may have a thickness of about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but provide an example of a possible embodiment. The silicide seed multilayer <NUM> may be formed by well-known deposition methods such as ALD, PVD, IBD, or sputtering. Additionally it is to be understood that while Si/Cu/NiFe/Cu have been exemplified as the materials of the multilayer stack of the silicide seed multilayer <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited to Si/Cu/NiFe/Cu for the silicide seed multilayer <NUM>. The silicide seed multilayer <NUM> thickness may be adjusted to tune the first SHL <NUM>, such that the resulting spin current of the first FL <NUM> may be matched to the spin current of the second FL <NUM>.

The seed layer <NUM> comprises a magnetic material or compound such as NiFeTa. A seed layer <NUM> comprising NiFeTa may have a thickness of between about <NUM> Angstroms to about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but provide an example of a possible embodiment. The seed layer <NUM> may be formed by well-known deposition methods such as ALD, PVD, IBD, or sputtering. Additionally it is to be understood that while NiFeTa have been exemplified as the materials of the multilayer stack of the seed layer <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited to NiFeTa for the seed layer <NUM>. The seed layer <NUM> thickness may be adjusted to tune the second SHL <NUM>, such that the resulting spin hall voltage in the second SHL <NUM> may be matched to the spin hall voltage of the first SHL <NUM>.

In one embodiment, first SHL <NUM> and the second SHL <NUM> each comprises the same material and have the same thickness in the y-direction. In another embodiment, the first SHL <NUM> and the second SHL <NUM> comprise different materials have a different thickness in the y-direction. In yet another embodiment, the first SHL <NUM> and the second SHL <NUM> comprise the same or different materials and the have the same or different thicknesses in the y-direction. The first and the second SHLs <NUM>, <NUM> may be formed by a non-magnetic heavy metal material selected from a group that includes Ta, Pt, W, Hf, Bi, and alloys thereof. Additionally, it is to be understood that while Ta, Pt, W, Hf, Bi, and alloys thereof have been exemplified as the materials of the first and the second SHLs <NUM>, <NUM>, other materials are contemplated, and the embodiments discussed herein are not limited. For example, BiSb and BiSe may be used as the material for the first and the second SHLs <NUM>, <NUM>. Furthermore, in one embodiment, the materials of the seed layers <NUM>, <NUM>, the interlayers 424a, 424b, and SHL capping layer <NUM> are selected to optimize the BiSb based topological material for specific grain orientation with improved spin hall angle for the first and second SHLs <NUM>, <NUM>.

In some embodiments, the first SHL <NUM> has a crystalline structure of (<NUM>), whereas, the second SHL <NUM> has a crystalline structure of (<NUM>). By utilizing BiSb in either the first or second SHLs <NUM>, <NUM>, the induced spin hall voltage can be tuned and matched to the other SHL <NUM>, <NUM>. For example, the first SHL <NUM> characteristics, such as the crystalline structure of (<NUM>), may improve the spin hall angle of the first SHL <NUM>, and the second SHL <NUM> characteristics, such as the crystalline structure of (<NUM>), may improve the spin hall angle of the second SHL <NUM> in order to match the spin hall voltage output of the first and second SHLs <NUM>, <NUM>. Table <NUM> below shows the spin hall angle, the conductivity, and the relative power of various compounds that may form a SHL <NUM>, <NUM>.

As shown in Table <NUM>, epitaxial BiSb (<NUM>) has a spin hall angle of <NUM>, whereas the epitaxial Bi2Se3 has a spin hall angle of <NUM>. Furthermore, the BiSb material (i.e., specifically Sb) may have a tendency to diffuse in the positive y-direction (i.e., from the first SHL <NUM> to the gap layer <NUM>, or from the second SHL <NUM> to the second shield 422b) unless a capping layer(s), such as the first interlayer 424a and SHL capping layer <NUM>, are present. By utilizing the epitaxial BiSb (<NUM>) as the material of the first SHL <NUM>, the spin hall voltage output of the first SHL <NUM> may be more easily matched to the spin hall voltage output of the second SHL <NUM>.

Because the BiSb material has a tendency to diffuse in the positive y-direction (i.e., the positive y-direction previously mentioned) when no SHL capping layer is present, such as in the case of the first SHL <NUM>, the spin hall angle of the first SHL <NUM> may need to be increased in order to compensate for the BiSb diffusion, as BiSb diffusion may result in lower spin hall angles. Thus, to compensate for a lower spin hall angle, the BiSb material used for the first SHL <NUM> can include an initial spin hall angle that may be relatively large, such as a spin hall angle of about <NUM> for an epitaxial BiSb (<NUM>) material, when compared to the BiSb material used for the second SHL <NUM>, where the second SHL <NUM> may include a non-epitaxial BiSb (<NUM>) material that includes a spin hall angle of about <NUM>. Furthermore, in one embodiment, the materials of the seed layers <NUM>, <NUM> and the interlayers 424a, 424b are selected to optimize the BiSb based topological material for specific grain orientation with improved spin hall angle for the first and second SHLs <NUM>, <NUM>.

<FIG> illustrates a graph <NUM> of the intensity of the crystalline structure of the SHL, according to one embodiment. For each case shown, the SHL comprises BiSb or a BiSbX alloy, where 'X' represents a possible material such as Cu, and where the SHL has a thickness of about <NUM> Angstroms. The SHL may be the first SHL <NUM> or the second SHL <NUM> of <FIG>. The seed layer, such as the silicide seed multilayer <NUM> or the seed layer <NUM> of <FIG>, may include several different dimensions and materials. In the descriptions herein, the listed dimensions and materials are not intended to be limiting, but to provide examples of possible embodiments.

Line <NUM> shows a seed layer, such as the silicide seed multilayer <NUM> or the seed layer <NUM> of <FIG>, comprising a Si/CuAgNi/NiFe/CuAgNi multilayer stack with a BiSbCu SHL. The Si layer may have a thickness of about <NUM> Angstroms, the first CuAgNi layer may have a thickness of about <NUM> Angstrom, the NiFe layer may have a thickness of about <NUM> Angstroms, and the second CuAgNi layer may have a thickness of about <NUM> Angstrom.

Line <NUM> shows a seed layer comprising a Si/NiFe/CuAgNi multilayer stack with a BiSb SHL. The Si layer may have a thickness of about <NUM> Angstroms, the NiFe layer may have a thickness of about <NUM> Angstroms, and the CuAgNi layer may have a thickness of about <NUM> Angstroms.

Line <NUM> shows a seed layer comprising a Si/NiFe/Si/NiFe multilayer stack with a BiSb SHL. The first Si layer may have a thickness of about <NUM> Angstroms, the first NiFe layer may have a thickness of about <NUM> Angstroms, the second Si layer may have a thickness of about <NUM> Angstroms, and the second NiFe layer may have a thickness of about <NUM> Angstroms.

Line <NUM> shows a seed layer comprising a NiFe/Si/NiFe/CuAgNi multilayer stack with a BiSb SHL. The first NiFe layer may have a thickness of about <NUM> Angstroms, the Si layer may have a thickness of about <NUM> Angstroms, and the second NiFe layer may have a thickness of about <NUM> Angstroms, and the CuAgNi layer may have a thickness of about <NUM> Angstroms.

For each seed layer, the resulting crystalline structure of the SHL is graphed, where a higher intensity reflects a higher percentage of that crystalline structure present in the SHL. For example, by appropriately selecting a multilayer seed layer stack, such as Si/CuAgNi/NiFe/CuAgNi, with a SHL comprising BiSbCu, the (<NUM>) crystalline structure of the SHL may be amplified and the resulting spin current of the relevant FL may be more easily adjusted, as shown by line <NUM>. Likewise, by including a Si/NiFe/CuAgNi multilayer seed stack with a SHL comprising BiSb, the (<NUM>) crystalline structure of the SHL is amplified, as shown by line <NUM>. The Si/NiFe/CuAgNi multilayer seed stack may be utilized for the seed layer <NUM> of the second section <NUM> of the SOT differential reader <NUM> of <FIG> to maximize the (<NUM>) crystalline structure and to match the spin current of the first section <NUM> of the SOT differential reader <NUM> to the second section <NUM>. Moreover, the Si/CuAgNi/NiFe/CuAgNi multilayer seed stack may be utilized for the silicide seed multilayer <NUM> of the first section <NUM> of the SOT differential reader <NUM> of <FIG> to maximize the (<NUM>) crystalline structure and to match the spin current of the first section <NUM> of the SOT differential reader <NUM> to the second section <NUM>.

<FIG> illustrates a graph <NUM> of the intensity of the crystalline structure of the SHL, according to another embodiment. For each case, the SHL includes BiSb, where the SHL has a thickness of about <NUM> Angstroms. The SHL may be the first SHL <NUM> or the second SHL <NUM> of <FIG>. The seed layer, such as the silicide seed multilayer <NUM> or the seed layer <NUM> of <FIG>, may include several different dimensions and materials. For each seed layer, the resulting crystalline structure of the SHL is graphed where a higher intensity reflects a higher percentage of that crystalline structure present in the SHL. In the descriptions herein, the listed dimensions and materials are not intended to be limiting, but to provide examples of possible embodiments.

Line <NUM> shows a seed layer, such as the silicide seed multilayer <NUM> or the seed layer <NUM> of <FIG>, comprising a Si/NiFe/CuAgNi multilayer stack with a BiSb SHL. The Si layer may have a thickness of about <NUM> Angstroms, the NiFe layer may have a thickness of about <NUM> Angstroms, and the CuAgNi layer may have a thickness of about <NUM> Angstroms.

Line <NUM> shows s seed layer comprising a Si/NiFe/CuAgNi multilayer stack with a BiSb SHL. The Si layer may have a thickness of about <NUM> Angstroms, the NiFe layer may have a thickness of about <NUM> Angstroms, and the CuAgNi layer may have a thickness of about <NUM> Angstroms.

For example, by appropriately selecting a multilayer seed layer stack, such as Si/NiFe/CuAgNi, where the Si layer has a thickness of about <NUM> Angstroms, the NiFe layer has a thickness of about <NUM> Angstroms, and the CuAgNi layer has a thickness of about <NUM> Angstroms, the (<NUM>) crystalline structure of the SHL may be amplified and the resulting spin current of the relevant FL may be more easily adjusted, as shown by line <NUM>. Likewise, by including a Si/NiFe/CuAgNi multilayer seed stack, where the CuX layer has a thickness of between about <NUM> Angstroms and about <NUM> Angstroms, where 'X' represents a possible material such as Cu, and the NiFe layer has a thickness of about <NUM> Angstroms, the (<NUM>) crystalline structure of the SHL is amplified, as shown by lines <NUM>, <NUM>, and <NUM>.

Thus, the Si/NiFe/CuAgNi multilayer seed stack may be utilized for the seed layer <NUM> of the second section <NUM> of the SOT differential reader <NUM> of <FIG> to maximize the (<NUM>) crystalline structure and to match the spin current of the first section <NUM> of the SOT differential reader <NUM> to the second section <NUM>. Moreover, the Si/NiFe/CuAgNi multilayer seed stack may be utilized for the silicide seed multilayer <NUM> of the first section <NUM> of the SOT differential reader <NUM> of <FIG> to maximize the (<NUM>) crystalline structure and to match the spin current of the first section <NUM> of the SOT differential reader <NUM> to the second section <NUM>.

<FIG> illustrates a graph <NUM> of the intensity of the crystalline structure of the SHL, according to another embodiment. For each case, the SHL includes BiSb, where the SHL has a thickness of about <NUM> Angstroms. Each line <NUM>, <NUM>, <NUM> illustrates a different Sb concentration percentage in the SHL. For example, line <NUM> illustrates a <NUM>% Sb concentration, line <NUM> illustrates a <NUM>% Sb concentration, and line <NUM> illustrates a <NUM>% Sb concentration. The listed percent concentrations are not intended to be limiting, but to provide examples of possible embodiments.

The SHL may be the first SHL <NUM> or the second SHL <NUM> of <FIG>. The seed layer, such as the silicide seed multilayer <NUM> or the seed layer <NUM> of <FIG>, and/or the interlayers, such as the first interlayer 424a and/or the second interlayer 424b of <FIG>, may include various different dimensions and materials. As shown by line <NUM>, a higher concentration of Sb in the SHL promotes a (<NUM>) crystalline structure. Thus, the second SHL <NUM> may have a Sb concentration of about <NUM>% to about <NUM>%, such as <NUM>%, and the first SHL <NUM> may have a Sb concentration of about <NUM>% to about <NUM>%, such as <NUM>%. By including a higher percentage of Sb in the SHL comprising BiSb, the (<NUM>) crystalline structure is promoted or increased, as shown by line <NUM>.

<FIG> illustrates a graph <NUM> of the intensity of the crystalline structure of the SHL, according to another embodiment. For each case, the SHL includes BiSbX, where 'X' represents a possible material such as Cu. Each line <NUM>-<NUM> illustrates a different SHL film thickness. For example, line <NUM> shows a SHL film thickness of about <NUM> Angstroms, line <NUM> shows a SHL film thickness of about <NUM> Angstroms, line <NUM> shows a thickness of about <NUM> Angstroms, line <NUM> shows a SHL film thickness of about <NUM> Angstroms, and line <NUM> shows a thickness of about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but to provide examples of possible embodiments.

The SHL may be the first SHL <NUM> or the second SHL <NUM> of <FIG>. The seed layer, such as the silicide seed multilayer <NUM> or the seed layer <NUM> of <FIG>, and/or the interlayers, such as the first interlayer 424a and/or the second interlayer 424b of <FIG>, may include various different dimensions and materials. As shown by line <NUM>, a thicker SHL promotes a (<NUM>) crystalline structure. Thus, the second SHL <NUM> may have thickness of about of about <NUM> Angstroms to about <NUM> Angstroms, such as <NUM> Angstroms, and the first SHL <NUM> may have a thickness of about <NUM> Angstroms to about <NUM> Angstroms, such as about <NUM> Angstroms. By including a thicker BiSbX SHL film, the (<NUM>) crystalline structure is promoted or increased.

<FIG> illustrates a graph <NUM> of the intensity of the crystalline structure of the SHL, according to another embodiment. For each line <NUM>, <NUM>, the SHL includes BiSb, where the SHL has a thickness of about <NUM> Angstroms. The SHL may be the first SHL <NUM> or the second SHL <NUM> of <FIG>. Furthermore, by including a NiFeTa as an interlayer, such as the first interlayer 424a and/or the second interlayer 424b of <FIG>, the resulting intensity of the (<NUM>) crystalline structure of the SHL may be increased. For example, line <NUM> shows an interlayer comprising a NiFeTa layer, where the NiFeTa layer has a thickness of about <NUM> Angstroms.

Furthermore, by including a NiAl layer as an interlayer, such as the first interlayer 424a and/or the second interlayer 424b of <FIG>, the resulting intensity of the (<NUM>) crystalline structure of the SHL may be increased. For example, line <NUM> shows an interlayer comprising a NiAl layer, where the NiAl layer has a thickness of about <NUM> Angstroms. The listed dimensions are not intended to be limiting, but to provide examples of possible embodiments. For each interlayer, the resulting crystalline structure of the SHL is graphed where a higher intensity reflects a higher percentage of that crystalline structure present in the SHL. By including a thin NiAl layer, such as about <NUM> Angstroms as shown by line <NUM>, the (<NUM>) crystalline structure is promoted or increased. However, by including a NiFeTa layer, such as about <NUM> Angstroms as shown by line <NUM>, the (<NUM>) crystalline structure is promoted or increased. Furthermore, by utilizing a NiFeTa layer underneath the NiAl layer, the (<NUM>) and the (<NUM>) crystalline structures (i.e., texture) of the SHLs may be enhanced.

Moreover, as discussed further below, thin seed layers can also be used to vary the degree of (<NUM>) versus (<NUM>) texture in the first and second SHLs, providing a better way to tune the SHL properties. For example, a silicide seed multilayer comprising a Si layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms, a NiFe layer having a thickness of about <NUM> Angstroms, and a CuAgNi layer having a thickness of about <NUM> Angstroms can be utilized to switch the texture of an SHL from (<NUM>) to (<NUM>) by changing the thickness of the Si layer. A primarily (<NUM>) texture in a SHL results from the Si layer having a thickness of about <NUM> Angstroms, while a primarily (<NUM>) texture in a SHL results from a Si layer having a thickness of about <NUM> Angstroms.

<FIG> illustrates a graph <NUM> of the intensity of the crystalline structure of the SHL, according to another embodiment. For each line <NUM>, <NUM>, the SHL includes BiSb. The graph <NUM> illustrates the effect of including various seed layers, specifically adjusting the thickness of the Si layer of the seed layer or the silicide seed multilayer, on the crystalline structure of the SHLs, such as the first SHL <NUM> or the second SHL <NUM> of <FIG>. Line <NUM> shows a Si/NiFe/Cu multilayer stack, where the Si layer has a thickness of about <NUM> Angstroms, the NiFe layer has a thickness of about <NUM> Angstroms, and the Cu layer has a thickness of about <NUM> Angstroms. Line <NUM> shows a Si/NiFe/Cu multilayer stack, where the Si layer has a thickness of about <NUM> Angstroms, the NiFe layer has a thickness of about <NUM> Angstroms, and the Cu layer has a thickness of about <NUM> Angstroms.

By varying the silicide layer thickness of the seed layer, the crystalline structure (i.e., the texture) of the SHL may be changed from (<NUM>) to (<NUM>), or vice-versa. For example, by including a thin layer of Si, such as about <NUM> Angstroms, as shown by line <NUM>, the (<NUM>) crystalline structure of the relevant SHL is promoted or enhanced. Likewise, when increasing the Si layer thickness to about <NUM> Angstroms, as shown by line <NUM>, the (<NUM>) crystalline structure of the relevant SHL is promoted or enhanced. In some embodiments, by decreasing the thickness of the Si layer, the amount of Si diffusing into the SHL layer decreases, thus resulting in a reduction of interfacial roughness and in an increase of thermal annealing temperature.

By utilizing seed layers and/or interlayers of various materials and dimensions, the SHLs may be tuned and the resulting spin hall voltage converted from the spin current injected from the FLs may be better matched. Selectively choosing the materials and dimensions of the seed layers and interlayers further enables the crystalline structures of the SHLs and the spacing between the SHLs to be chosen, allowing the amplitude of induced spin hall voltage inside the SHLs to be easily matched and/or tuned as needed. Moreover, while the first and second FLs may be independently controlled, utilizing the seed layers and/or interlayers of various materials and dimensions allows the power to each FL to be matched, which further enhances the ability of the SHLs to be tuned and the resulting spin hall voltage converted from spin current injected from the FLs may be better matched. Additionally, the design of the SOT differential reader improves reader resolution without decreasing the shield-to-shield spacing (i.e., read-gap).

It is to be understood that the magnetic recording head (i.e., the magnetic head assembly) discussed herein is applicable to a data storage device such as a hard disk drive (HDD) as well as a tape drive such as a tape embedded drive (TED) or an insertable tape media drive. An example TED is described in co-pending patent application titled "Tape Embedded Drive," App. No. <CIT>, assigned to the same assignee of this application. As such, any reference in the detailed description to a HDD or tape drive is merely for exemplification purposes and is not intended to limit the disclosure unless explicitly claimed. Furthermore, reference to or claims directed to magnetic recording devices are intended to include both HDD and tape drive unless HDD or tape drive devices are explicitly claimed.

It is also to be understood that aspects disclosed herein, such as the magnetoresistive devices, may be used in magnetic sensor applications outside of HDD's and tape media drives such as TED's, such as spintronic devices other than HDD's and tape media drives. As an example, aspects disclosed herein may be used in magnetic elements in magnetoresistive random-access memory (MRAM) devices (e.g., magnetic tunnel junctions as part of memory elements), magnetic sensors or other spintronic devices.

The seed layer comprises NiFeTa having a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The silicide seed multilayer comprises a Si layer having a thickness of about <NUM> Angstroms, a first Cu layer having a thickness of about <NUM> Angstrom, a NiFe layer having a thickness of about <NUM> Angstroms, and a second Cu layer having a thickness of about <NUM> Angstrom. The first interlayer comprises a NiCu layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms and a NiFeTa layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The second interlayer comprises a NiFeTa layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms and a NiAl layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms.

The first spin hall effect layer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The second spin hall effect layer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The cap layer comprises a NiCu layer and a NiFeTa layer. The magnetic recording head is configured to match an amplitude of the first spin hall effect layer to the second spin hall effect layer, and to match a spin current from the first free layer to a spin current from the second free layer. The magnetic recording head further comprises a gap layer disposed between the first free layer and the seed layer. The magnetic recording head further comprises an electrical lead recessed from a media facing surface, the electrical lead being in contact with the gap layer and the second shield, wherein the first free layer, the second free layer, the gap layer, the first spin hall effect layer, and the second spin hall effect layer are disposed at the media facing surface. The second spin hall effect layer has a Sb concentration of about <NUM>% to about <NUM>%, and the first spin hall effect layer has a Sb concentration of about <NUM>% to about <NUM>%.

In another embodiment, a magnetic recording head comprises a first shield, a second shield, and a spin orbital torque (SOT) differential reader disposed between the first shield and the second shield. The SOT differential reader comprises a silicide seed multilayer disposed over the first shield, a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), a first interlayer layer disposed over the first spin hall effect layer, the first interlayer comprising a NiCu layer and a NiFeTa layer, a first free layer disposed over the first interlayer layer, a seed layer disposed over the over the first free layer, a second free layer disposed over the seed layer, a second interlayer disposed over the second free layer, the second interlayer comprising a NiFeTa layer and a NiAl layer, and a second spin hall effect layer disposed over the second interlayer layer, the second spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>).

The magnetic recording head further comprises a cap layer disposed over the second spin hall effect layer, the cap layer comprising a NiCu layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms and a NiFeTa layer having a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The magnetic recording head further comprises a gap layer disposed between the first free layer and the seed layer, the gap layer being configured to act as an electrical lead. The silicide seed multilayer comprises a Si layer having a thickness of about <NUM> Angstroms, a first Cu layer having a thickness of about <NUM> Angstrom, a NiFe layer having a thickness of about <NUM> Angstroms, and a second Cu layer having a thickness of about <NUM> Angstrom. The seed layer comprises NiFeTa having a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The NiCu layer of the first interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms and the NiFeTa layer of the first interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The NiFeTa layer of the second interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms and the NiAl layer of the second interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The second spin hall effect layer comprises a higher Sb concentration than the first spin hall effect layer, and the second spin hall effect layer is thicker than the first spin hall effect layer.

In yet another embodiment, a magnetic recording head comprises a first shield, a second shield, and a spin orbital torque (SOT) differential reader disposed between the first shield and the second shield. The SOT differential reader comprises a silicide seed multilayer disposed over the first shield, the silicide seed multilayer comprising a Si layer, a first Cu layer, a NiFe layer, and a second Cu layer, a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), a first interlayer layer disposed over the first spin hall effect layer, the first interlayer comprising a NiCu layer and a NiFeTa layer, a first free layer disposed over the first interlayer layer, a gap layer disposed over the first free layer, a seed layer disposed over the gap layer, the seed layer comprising NiFeTa, a second free layer disposed over the gap layer, a second interlayer disposed over the second free layer, the second interlayer comprising a NiFeTa layer and a NiAl layer, a second spin hall effect layer disposed over the second interlayer layer, the second spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>), wherein the second spin hall effect layer has a greater thickness and a higher Sb concentration than the first spin hall effect layer, and a cap layer comprising a NiCu layer and a NiFeTa layer disposed over the second spin hall effect layer.

The Si layer of the silicide seed multilayer has a thickness of about <NUM> Angstroms, the first Cu layer of the silicide seed multilayer has a thickness of about <NUM> Angstrom, the NiFe layer of the silicide seed multilayer has a thickness of about <NUM> Angstroms, and the second Cu layer of the silicide seed multilayer has a thickness of about <NUM> Angstrom. The seed layer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The NiCu layer of the first interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms and the NiFeTa layer of the first interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms. The NiFeTa layer of the second interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms and the NiAl layer of the second interlayer has a thickness of about <NUM> Angstroms to about <NUM> Angstroms.

Claim 1:
A magnetic recording head, comprising:
a first shield;
a second shield; and
a spin orbital torque (SOT) differential reader disposed between the first shield and the second shield, the SOT differential reader comprising:
a silicide seed multilayer disposed over the first shield;
a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM>);
a first interlayer layer disposed over the first spin hall effect layer;
a first free layer disposed over the first interlayer layer;
a seed layer disposed over the first free layer;
a second free layer disposed over the seed layer;
a second interlayer disposed over the second free layer;
a second spin hall effect layer disposed over the second interlayer layer, the second spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (<NUM> ); and
a cap layer disposed over the second spin hall effect layer.