Design and methods for reducing baseline drift in SOT differential readers

Abstract

This disclosure generally relates to the design of a spin-orbit torque (SOT) differential reader. The SOT differential reader is a multi-terminal device comprising a first shield, a first spin Hall layer, a first free layer, a gap layer, a second spin Hall layer, a second free layer, and a second shield. The gap layer serves as an electrode and is disposed between the first and second spin Hall layers. Electrical lead connections are located around the first spin Hall layer, the second spin Hall layer, the gap layer, the first shield, and / or the second shield. These lead connections facilitate the flow of current from the negative lead to the positive lead and / or the voltage from the negative lead to the positive lead. The positioning of these lead connections and the positioning of the SOT differential layers improve the reader resolution without reducing the shield-to-shield spacing (i.e., the read gap).

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application 17 / 029,826, filed September 23, 2020, which claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 050,016, filed July 9, 2020, both of which are incorporated herein by reference in their entirety. Background Technology Technical Field

[0004] The implementation scheme disclosed herein generally relates to the read head of a data storage device.

[0005] Description of related fields

[0006] At the heart of a computer's functionality and capabilities lies the storage and writing of data to data storage devices (such as hard disk drives (HDDs)). The amount of data processed by computers is rapidly increasing. This necessitates higher recording densities in magnetic recording media to enhance computer functionality and capabilities.

[0007] To achieve higher recording densities (such as exceeding 2 terabits per inch) in magnetic recording media 2 The recording density (i.e., the width and spacing of the write tracks are narrowed, thus narrowing the corresponding magnetic recording bits encoded in each write track) has led to attempts to achieve higher recording density reads using advanced narrow-gap reader sensors that utilize magnetoresistive sensors with free layers composed of highly saturated magnetized materials to realize the read head.

[0008] A typical read head consists of a read sensor sandwiched between two shields. The shield-to-shield spacing between the two shields plays a crucial role in the read sensor's resolution. However, conventional read sensors have been minimized to approximately 25 nm and cannot be further reduced in size to decrease the shield-to-shield spacing.

[0009] Therefore, there is a need in this field for improved magnetic reading heads. Summary of the Invention

[0010] This disclosure generally relates to the design of a spin-orbit torque (SOT) differential reader. The SOT differential reader is a multi-terminal device comprising a first shield, a first spin Hall layer, a first free layer, a gap layer, a second spin Hall layer, a second free layer, and a second shield. The gap layer serves as an electrode and is disposed between the first and second spin Hall layers. Electrical lead connections are located around the first spin Hall layer, the second spin Hall layer, the gap layer, the first shield, and / or the second shield. These lead connections facilitate the flow of current from the negative lead to the positive lead and / or the voltage from the negative lead to the positive lead. The positioning of these lead connections and the positioning of the SOT differential layers improve the reader resolution without reducing the shield-to-shield spacing (i.e., the read gap).

[0011] In one embodiment, the magnetic recording head includes a first shield, a second shield, a first bias layer, a second bias layer, and a spin-orbit torque (SOT) differential reader disposed between the first and second shields and between the first and second bias layers. The SOT differential reader includes: a first free layer; a second free layer; a gap layer configured to act as a first electrical lead; a first spin Hall layer; a second spin Hall layer in contact with the first and second bias layers; and two or more insulating layers, including a first insulating layer and a second insulating layer, the first insulating layer disposed between the first spin Hall layer and the first bias layer, and the second insulating layer disposed between the first spin Hall layer and the second bias layer. The first and second free layers are configured to be independently controlled.

[0012] In another embodiment, the magnetic recording head includes a first shield, a second shield, and a SOT differential reader disposed on a medium-facing surface between the first and second shields. The SOT differential reader includes a first free layer, a second free layer, a gap layer configured to act as a first electrical lead, a first spin Hall layer, and a second spin Hall layer. A positive terminal of the first spin Hall layer is electrically connected to a positive terminal of the second spin Hall layer. The signal read from the SOT differential reader is based on the voltage difference across the negative terminal of the first spin Hall layer to the negative terminal of the second spin Hall layer. The SOT differential reader also includes an electrical lead recessed from the medium-facing surface, contacting the gap layer and the second shield, wherein the first free layer, the second free layer, the gap layer, the first spin Hall layer, and the second spin Hall layer are disposed on the medium-facing surface.

[0013] In another embodiment, a method for forming a spin-orbit torque (SOT) differential readout is disclosed. The method includes: depositing a first free layer on a first shield, depositing a first spin Hall layer on the first free layer, and depositing a gap layer on the first spin Hall layer to form a first stack, wherein the first shield has a first width extending from a surface facing a medium to a surface opposite to the surface facing the medium; removing a portion of the first free layer, a portion of the first spin Hall layer, and a portion of the gap layer to define a first track width of the first stack, the first track width of the first stack being smaller than the first width of the first shield; and depositing a first insulating layer in contact with a first surface of the first stack, the first surface of the first stack being configured to face the surface facing the medium. The method further includes: depositing a second free layer on the gap layer, depositing a second spin Hall layer on the second free layer, and depositing a second insulating layer on the second spin Hall layer to form a second stack on a first stack; and removing a central portion of the second insulating layer, a central portion of the second spin Hall layer, and a central portion of the second free layer to define a second track width of the second stack and forming electrical leads disposed on the gap layer, wherein the electrical leads are recessed from a surface facing the dielectric. A second shielding layer is deposited, which contacts the electrical leads. Attached Figure Description

[0014] Therefore, a detailed understanding of the foregoing features of this disclosure, a more specific description of this disclosure, and the foregoing brief overview can be obtained by referring to the embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the drawings only illustrate typical embodiments of this disclosure and should therefore not be considered as limiting its scope, as this disclosure allows for other equally effective embodiments.

[0015] Figure 1 A disk drive embodying this disclosure is shown.

[0016] Figure 2 This is a segmented cross-sectional side view of the center of the read / write head facing the magnetic medium, according to one embodiment.

[0017] Figures 3A to 3D SOT differential readers according to various implementation schemes are shown.

[0018] Figures 4A to 4H The formation and definition according to one embodiment are shown. Figure 3C Methods for determining the track width of SOT differential readers.

[0019] Figures 5A to 5H The formation and definition according to one embodiment are shown. Figure 3C Methods for determining the track width of SOT differential readers.

[0020] Figures 6A to 6H The formation and definition according to one embodiment are shown. Figure 3D Methods for determining the bar height of the SOT differential reader.

[0021] For ease of understanding, the same reference numerals are used where possible to denote the same elements common in the accompanying drawings. It is conceivable that elements disclosed in one embodiment may be advantageously used in other embodiments without specific description. Detailed Implementation

[0022] In the following text, reference is made to embodiments of this disclosure. However, it should be understood that this disclosure is not limited to the specifically described embodiments. Rather, consider any combination of the following features and elements (whether or not related to different embodiments) to achieve and practice this disclosure. Furthermore, while embodiments of this disclosure may achieve advantages over other possible solutions and / or over the prior art, achieving a particular advantage through a given embodiment is not a limitation of this disclosure. Therefore, the following aspects, features, embodiments, and advantages are illustrative only and should not be considered elements or limitations of the appended claims unless expressly stated in the claims. Similarly, reference to “this disclosure” should not be construed as a generalization of any inventive subject matter disclosed herein and should not be considered elements or limitations of the appended claims unless expressly stated in the claims.

[0023] This disclosure generally relates to the design of a spin-orbit torque (SOT) differential reader. The SOT differential reader is a multi-terminal device comprising a first shield, a first spin Hall layer, a first free layer, a gap layer, a second spin Hall layer, a second free layer, and a second shield. The gap layer serves as an electrode and is disposed between the first and second spin Hall layers. Electrical lead connections are located around the first spin Hall layer, the second spin Hall layer, the gap layer, the first shield, and / or the second shield. These lead connections facilitate the flow of current from the negative lead to the positive lead and / or the voltage from the negative lead to the positive lead. The positioning of these lead connections and the positioning of the SOT differential layers improve the reader resolution without reducing the shield-to-shield spacing (i.e., the read gap).

[0024] Figure 1 A disk drive 100 embodying the present disclosure is shown. As shown, at least one rotatable magnetic medium 112 is carried on a spindle 114 and rotated by a disk drive motor 118. Magnetic records on each disk are in the form of any suitable pattern of data tracks, such as a toroidal pattern of concentric data tracks (not shown) on the magnetic medium 112.

[0025] At least one slider 113 is positioned near a magnetic medium 112, and each slider 113 supports one or more head assemblies 121. As the magnetic medium rotates, the slider 113 moves radially in and out above the medium surface 122, allowing the head assembly 121 to access different tracks of the magnetic medium 112 for writing desired data. Each slider 113 is attached to an actuator arm 119 via a suspension 115. The suspension 115 provides a slight spring force that biases the slider 113 toward the medium surface 122. Each actuator arm 119 is attached to an actuator device 127. Figure 1 The actuator component 127 shown may be a voice coil motor (VCM). The VCM includes a coil capable of moving within a fixed magnetic field, the direction and speed of which the coil moves are controlled by a motor current signal supplied by the control unit 129.

[0026] During operation of the disk drive 100, the rotation of the magnetic medium 112 creates an air bearing between the slider 113 and the medium surface 122, which applies an upward force or lift to the slider 113. Thus, during normal operation, the air bearing counteracts the slight spring force of the suspension 115 and supports the slider 113 away from and slightly above the surface of the magnetic medium 112 with a small, substantially constant gap.

[0027] Various components of the disk drive 100 are controlled during operation by control signals (such as access control signals and internal clock signals) generated by the control unit 129. Typically, the control unit 129 includes logic control circuitry, storage devices, and a microprocessor. The control unit 129 generates control signals that control various system operations, such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide a desired current distribution to optimally move and position the slider 113 onto the desired data track on the magnetic medium 112. Write and read signals are transmitted via the recording channel 125 to and from the write and read heads on the head assembly 121.

[0028] The above description of a typical disk storage system and Figure 1 The accompanying description is for illustrative purposes only. It should be obvious that a disk storage system may contain a large number of disks and actuators, and each actuator may support multiple sliders.

[0029] Figure 2 This is a segmented cross-sectional side view of a read / write head 200 facing the center of a magnetic medium 112, according to one embodiment. The read / write head 200 may correspond to... Figure 1The magnetic head assembly 121 described herein. The read / write head 200 includes a media-facing surface (MFS) 212, such as an air bearing surface (ABS), a magnetic write head 210, and a magnetic read head 211, and is mounted such that the MFS 212 faces the magnetic medium 112. Figure 2 In the process, the magnetic medium 112 moves past the write head 210 in the direction indicated by arrow 232, and the read / write head 200 moves in the direction indicated by arrow 234.

[0030] In some embodiments, the magnetic read head 211 is a magnetoresistive (MR) read head, which includes an MR sensing element 204 located between MR shields S1 and S2. In other embodiments, the magnetic read head 211 is a magnetic tunnel junction (MTJ) read head, which includes an MTJ sensing element 204 located between MR shields S1 and S2. The magnetic field of adjacent magnetized regions in the magnetic medium 112 can be detected as a recording bit by the MR (or MTJ) sensing element 204.

[0031] The write head 210 includes a return pole 206, a main pole 220, a rear shield 240, and a coil 218 for activating the main pole 220. The coil 218 may have a "pancake" structure, rather than... Figure 2 The illustrated "spiral" structure, a "pancake" structure, is wound around the back contact between the master electrode 220 and the return electrode 206. A rear gap (not shown) and a front gap (not shown) may contact the master electrode, and a front shield (not shown) may contact the front gap. A recording magnetic field is generated from the master electrode 220, and the rear shield 240 helps to steepen the magnetic field gradient of the master electrode 220. The master electrode 220 may be a magnetic material, such as an FeCo alloy. The master electrode 220 may include a rear surface 222, which may be parallel to the front surface 236 of the rear shield 240. The master electrode 220 may be a tapered write electrode (TWP) with a trailing edge taper (TET) configuration. In one embodiment, the master electrode 220 has a saturation magnetization (Ms) of 2.4 T and a thickness of approximately 300 nanometers (nm). The master electrode 220 may include a ferromagnetic material, typically an alloy of one or more of Co, Fe, and Ni. The rear shield 240 may be a magnetic material, such as a NiFe alloy. In one embodiment, the rear shield 240 has Ms of about 1.2T to about 1.6T.

[0032] Figure 3A Figure 3E shows SOT differential readers according to various implementation schemes. Figure 3A and Figure 3B SOT differential readers 300A and 300B are shown, in which... Figure 3A and Figure 3BEach of these has: (1) a top stacked configuration view of the reader, and (2) a bottom abstract view showing the positioning of the free layer relative to the magnetic medium when the recording head is above the medium, wherein other layers in the stacked configuration are omitted. The SOT differential readers 300A and 300B can be located in... Figure 2 The SOT differential reader 204 is located between the two shields S1 and S2. SOT differential readers 300A and 300B have the same electrical connection configuration. However, the first SOT differential reader 300A and the second SOT differential reader 300B can be positioned perpendicular to different regions of the magnetic medium 312. The positioning of the SOT differential readers 300A and 300B around the magnetic medium 312 can change the polarity of the induced voltage of the first spin Hall layers 302a and 302b and the second spin Hall layers 304a and 304b.

[0033] like Figure 3A and Figure 3B As shown in the top stacked configuration view, a first free layer (FL) 306 is disposed above first spin Hall effect (SHE) layers 302a and 302b (collectively referred to as first SHE layer 302), a gap layer (GL) 310 is disposed above the first FL 306, a second FL 308 is disposed above the GL 310, and second SHE layers 304a and 304b (collectively referred to as second SHE layer 304) are disposed above the second FL 308. In the description herein, for illustrative purposes, the plurality of SHE layers may be referred to as a plurality of spin Hall layers (SHL). SOT differential readouts 300A and 300B may each have a bar height between about 100 angstroms and about 400 angstroms in the z-direction.

[0034] exist Figure 3A and Figure 3B In the bottom view, the first FL 306 and the second FL 308 are shown rotated 90 degrees from the stacked configuration view above and positioned vertically above the magnetic medium 312, wherein the magnetic medium 312 may be Figure 1 The magnetic medium 312 has a first FL 306 and a second FL 308 parallel to the magnetic field direction of the magnetic medium 312. The magnetic medium 312 includes a first magnetic field direction (indicated by an upward-pointing first arrow in bits 314a and 314c) and a second magnetic field direction (indicated by a downward-pointing second arrow in bits 314b and 314d). The magnetic medium 312 also includes a first bit 314a having the first magnetic field direction, a second bit 314b having the second magnetic field direction, a third bit 314c having the first magnetic field direction, and a fourth bit 314d having the second magnetic field direction. Although four bits 314a-314d are shown, the magnetic medium may have any number of bits.

[0035] exist Figure 3AIn the top stacked configuration view, the positive terminal or pole 305b of the first SHL 302a is electrically connected to the positive terminal or pole 305b of the second SHL 304a, and the negative terminal or pole 305a of the first SHL 302a is electrically connected to the negative terminal 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 terminal or pole 305b and the negative terminal or pole 305a) depends on the positioning of the first FL 306 and the second FL 308 around the magnetic medium, as described below. In another embodiment, the voltage polarity of the first SHL 302a and / or the second SHL 304a may be reversed. The listed voltage polarities of the first SHL 302a and the second SHL 304a are not intended to be limiting, but rather to provide examples of possible implementations. Reference Figure 3A In the bottom abstract view, when both the first FL 306 and the second FL 308 are vertically positioned above a single position (such as the third position 314c) among the plurality of positions 314a-314d of the magnetic medium 312, the magnetic field of the third position 314c exerts a magnetic force on the first FL 306 and the second FL 308. Due to the magnetic force exerted on the first FL 306 and the second FL 308, the magnetic moments of the first FL 306 and the second FL 308 are in the same direction as the magnetic field of the third position 314c.

[0036] exist Figure 3B In the top stacked configuration view, the positive terminal or pole 309b of the first SHL 302b is electrically connected to the negative terminal or pole 307a of the second SHL 304b, and the negative terminal or pole 309a of the first SHL 302b is electrically connected to the positive terminal or pole 307b of the second SHL 304b. The voltage polarity of the first SHL 302b and the second SHL 304b (i.e., positive terminals or poles 307b, 309b and negative terminals or poles 307a, 309) depends on the positioning of the first FL 306 and the second FL 308 around the magnetic medium, as described below. In another embodiment, the voltage polarity of the first SHL 302b and / or the second SHL 304b may be reversed. The listed voltage polarities of the first SHL 302b and the second SHL 304b are not intended to be limiting, but rather to provide examples of possible implementations. In the description herein, the positions of the negative and positive terminals or poles of the SHLs mentioned may be reversed. Therefore, unlisted implementation schemes are envisioned, and these implementation schemes are relevant to the current description. References Figure 3BIn the bottom abstract view, when the first FL 306 and the second FL 308 are each positioned above adjacent positions (such as the third position 314c and the fourth position 314d) of the plurality of positions 314a-314d of the magnetic medium 312, the magnetic field of the second position 314b exerts a magnetic force on the first FL 306, and the third position 314c exerts a magnetic force on the second FL 308, which is opposite to the magnetic force exerted on the first FL 306. Due to the magnetic forces exerted on the first FL 306 and the second FL 308, the magnetic moment of the first FL 306 is in the same direction as the magnetic field of the second position 314b, and the magnetic moment of the second FL 308 is in the same direction as the magnetic field of the third position 314c. Figure 3B In this context, because the first FL 306 and the second FL 308 are located above adjacent positions among the multiple positions 314a-314d of the magnetic medium 312, the first FL 306 has a magnetic field direction opposite to that of the second FL 308.

[0037] exist Figure 3A and Figure 3B In this embodiment, the first SHL layers 302a, 302b and the second SHL layers 304a, 304b each comprise the same material and have the same thickness in the y-direction. The first SHL layers 302a, 302b and the second SHL layers 304a, 304b may be formed of a non-magnetic heavy metal material selected from the group consisting of Ta, Pt, W, Hf, Bi, and alloys thereof. Furthermore, it should be understood that while Ta, Pt, W, Hf, Bi, and alloys thereof have been exemplified as materials for the first SHL layers 302a and 304a, other materials are contemplated, and the embodiments discussed herein are not limited. For example, BiSb and BiSe may be used as materials for the first SHL layers 302 and 304. The first SHL layers 302 and 304 may have a wider width in the x-direction than the first FL layers 306 and 308, as well as GL 310. In one embodiment, the first SHL layers 302 and 304 have the same width in the x-direction. In another embodiment, the first SHL 302 and the second SHL 304 have different widths in the x-direction.

[0038] exist Figure 3A In this process, the first SHL 302a and the second SHL 304a each generate a transverse voltage signal (i.e., a SHE signal) within their respective first SHL 302a and second SHL 304a. The generated transverse voltage signal may be due to the spin Hall effect. The polarity of the transverse voltage signal may depend on the direction of electron flow and magnetic orientation of the first FL 306 and the second FL 308. For example, in Figure 3AIn the bottom view, the first FL 306 and the second FL 308 are each vertically positioned above the same position (such as the third position 314c). The first SHL 302a and the second SHL 304a have the same SHE voltage polarity, with the side in the negative x direction being the negative terminal 305a and the side in the positive x direction being the positive terminal 305b.

[0039] Furthermore, the negative terminals 305a of the first SHL 302a and the second SHL 304a are connected, such that the negative terminals 305a of the first SHL 302a and the second SHL 304a share equal voltage potentials. The reader signal output can be determined by the voltage difference or differential voltage 311 (which can be the SOT differential reader signal output) between the positive terminals 305b of the first SHL 302a and the second SHL 304a. Because the first SHL 302a and the second SHL 304a each comprise the same material and the same current flow direction, the SHE voltage induced by the first SHL 302a can be equal in both polarity and magnitude to the SHE voltage induced by the second SHL 304a. The differential voltage 311 between the two positive terminals 305b can be canceled out or reduced. The differential voltage 311 can be a net differential output of approximately zero.

[0040] A first current 313 travels from the first SHL 302a to GL 310, and a second current 315 travels from GL 310 to the second SHL 304a. By independently controlling the first current 313 and the second current 315, the amplitudes of the differential voltage (dVsh) of the upper reader (e.g., the section of the SOT differential reader 300A in contact with the second current 315) and the lower reader (e.g., the section of the differential reader 300A in contact with the first current 313) can be matched. Furthermore, a dust removal layer (not shown) can be arranged around the lower reader so that the first current 313 can be shunt. Therefore, the SOT differential reader 300A is a multi-terminal device. Because the first SHL 302a and the second SHL 304a have the same voltage polarity, the signal output can be greatly reduced or substantially canceled. By greatly reducing or substantially canceling the signal output, baseline drift can be reduced.

[0041] exist Figure 3BIn the bottom view, the first FL 306 and the second FL 308 are positioned above adjacent bits, for example, the first FL 306 is vertically positioned above the second bit 314b and the second FL is vertically positioned above the third bit 314c. The first FL 306 and the second FL 308 have different and opposite magnetizations. For example, the first SHL 302b has a first SHE voltage, where the side in the negative x direction is the positive terminal 309b and the side in the positive x direction is the negative terminal 309a. Similarly, the second SHL 304b has a second SHE voltage, where the side in the negative x direction is the negative terminal 307a and the side in the positive x direction is the positive terminal 307b.

[0042] Furthermore, the positive terminal 309b of the first SHL 302b and the negative terminal 307a of the second SHL 304b are connected and share equal voltage potentials. The differential voltage 311 is determined by the difference between the voltage at the positive terminal 307b of the second SHL 304b and the voltage at the negative terminal 309a of the first SHL 302b; this differential voltage can be the SOT differential reader signal output. Because the induced voltages of the first SHL 302b and the second SHL 304b are in opposite directions, the differential voltage 311 effectively doubles the output signal. A first current 313 travels from the first SHL 302b to GL 310, and a second current 315 travels from GL 310 to the second SHL 304b. Therefore, the SOT differential reader 300B is a multi-terminal device. Because the first SHL 302b and the second SHL 304b have opposite voltage directions, the signal output can be effectively doubled or greatly increased. Therefore, a larger signal output can effectively improve linear resolution.

[0043] Figure 3C An MFS view of an SOT differential reader 360 according to one embodiment is shown. The SOT differential reader 360 can be... Figure 3A SOT differential reader 300A and / or Figure 3B The SOT differential reader 300B. Furthermore, the first SHLs 302a and 302b can be the first SHL 302, and the second SHLs 304a and 304b can be the second SHL 304. In the description herein, for illustrative purposes, the SHL may be referred to as an SHE layer.

[0044] The SOT differential reader 360 also includes a first shield 322a disposed beneath the first insulating layer 330, wherein the first SHL 302 is disposed on the first insulating layer 330. Furthermore, a second insulating layer 332a is disposed along the top left edge of the SHL 302 (i.e., between the first SHL 302 and the first bias layer 324a) and on the left side of the first FL 306, GL 310, and second FL 308 (i.e., adjacent to the first bias layer 324a). A third insulating layer 332b is deposited along the top right edge of the SHL 302 (i.e., between the first SHL 302 and the second bias layer 324b) and on the right side of the first FL 306, GL 310, and second FL 308 (i.e., adjacent to the second bias layer 324b). The first bias layer 324a is disposed on the second insulating layer 332a. The second bias layer 324b is disposed on the third insulating layer 332b. A fourth insulating layer 320 is disposed above the first bias layer 324a, the second bias layer 324b, and the second SHL 304. A second shielding member 322b is disposed on the fourth insulating layer 320. The first bias layer 324a and the second bias layer 324b may include hard bias materials or soft bias materials.

[0045] Insulating layers 330, 332a, 332b, and 320 can be placed within the SOT differential reader 360 to prevent electrical short circuits between the first shield 322a, the first SHL 302, the first FL 306, GL 310, the second FL 308, the second SHL 304, the second shield 322, the first bias layer 324a, and the second bias layer 324b. Suitable materials for insulating layers 330, 332a, 332b, and 320 include dielectric materials such as aluminum oxide, silicon oxide, magnesium oxide, and silicon nitride. Insulating layers 330, 332a, 332b, and 320 can be formed by well-known deposition methods, such as atomic layer deposition (ALD), physical vapor deposition (PVD), ion beam deposition (IBD), or sputtering. Insulating layers 330, 332a, 332b, and 320 can have a thickness between about 10 angstroms and about 100 angstroms.

[0046] In some embodiments, the first FL 306 and the second FL 308 comprise the same material and have the same thickness in the y-direction. The first FL 306 and the second FL 308 have a greater thickness in the y-direction than the first SHL 302 and the second SHL 304. Each of the first FL 306 and the second FL 308 comprises a CoFe / CoFeB / Ta / NiFe multilayer stack. The CoFe layer may have a thickness between about 3 angstroms and about 10 angstroms. The CoFeB layer may have a thickness between about 10 angstroms and about 20 angstroms. The Ta layer may have a thickness between about 0.5 angstroms and about 2 angstroms. The NiFe layer may have a thickness between about 3 angstroms and about 100 angstroms, such as between about 3 angstroms and about 10 angstroms or between about 10 angstroms and about 100 angstroms. The first FL 306 and the second FL 308 may be formed by a well-known deposition method, such as sputtering. Furthermore, it should be understood that while CoFe / CoFeB / Ta / NiFe has been exemplified as the material for the first FL 306 and the second FL 308, other materials are contemplated, and the embodiments discussed herein are not limited to CoFe / CoFeB / Ta / NiFe used in the first FL 306 and the second FL 308. Additionally, the previously mentioned dimensions are not intended to be limiting, but rather to provide examples of possible embodiments.

[0047] GL 310 has a smaller thickness in the y-direction than the first SHL 302 and the second SHL 304. GL 310 may be formed of a non-magnetic conductive material (such as Cr) with a thickness between about 10 angstroms and about 50 angstroms. In some embodiments, GL 310 may have a thickness between about 0 angstroms and about 20 angstroms. It should be understood that while Cr is exemplified as GL 310, other materials are contemplated, and the embodiments discussed herein are not limited to Cr used for GL 310. In some embodiments, an insulating material may be used for the GL 310 material, such as when GL 310 has a thickness of less than about 1 nm. In one embodiment, GL 310 includes electrodes to allow independent adjustment of the spin Hall angle characteristics of the first SHL 302 and the second SHL 304.

[0048] The first shield 322a and the second shield 322b each comprise a conductive material selected from the group consisting of Cu, W, Ta, Al, NiFe, CoFe, and alloys thereof. The shielding material may include NiFe alloys, CoFe alloys, or combinations of NiFe alloys or CoFe alloys with Cu, W, Ta, and Al. The thickness of each of the first shield 322a and the second shield 322b may be between about 20 nm and about 500 nm. Furthermore, it should be understood that while NiFe, CoFe, Cu, W, Ta, Al, and alloys thereof have been exemplified as materials for the first shield 322a and the second shield 322b, other materials are contemplated, and the embodiments discussed herein are not limited to NiFe, CoFe, Cu, W, Ta, Al, and alloys thereof used for the first shield 322a and the second shield 322b.

[0049] In some embodiments, the first bias layer 324a and the second bias layer 324b are respectively a first hard bias layer and a second hard bias layer. The first and second hard bias layers may comprise a multilayer structure including a seed layer and a host layer. In one embodiment, the hard bias layer includes a Ta seed layer, a Cr or W seed layer disposed on the Ta seed layer, and a CoPt host layer disposed on the Cr or W seed layer. In some embodiments, the hard bias layer comprises multiple layers of the aforementioned materials. Furthermore, it should be understood that while Ta, W, Cr, and CoPt have been exemplified as materials for the first and second hard bias layers, other materials are contemplated, and the embodiments discussed herein are not limited to Cu, Ta, W, Cr, and CoPt for the first and second hard bias layers.

[0050] In some embodiments, the first bias layer 324a and the second bias layer 324b are respectively a first soft bias layer and a second soft bias layer. The first and second soft bias layers may comprise a multilayer structure comprising a soft magnetic material. In one embodiment, the soft bias layer comprises a material selected from the group consisting of NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and / or multilayers thereof. Furthermore, it should be understood that while NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and / or multilayers thereof have been exemplified as 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 multilayers thereof for use as soft bias layers.

[0051] When the SOT differential reader 360 includes a soft bias layer instead of a hard bias layer, an antiferromagnetic (AFM) / capping layer (not shown) is deposited between each soft bias layer and the insulating layer 320. The AFM / capping layer includes a material selected from a group of AFM materials, including IrMn, FeMn, PtMn, and other nonmagnetic conductive layers. Furthermore, the AFM / capping layer may include a group of AFM materials and one or more materials from the group consisting of IrMn, FeMn, PtMn, Ta, Ru or Ti, other nonmagnetic materials, and / or multilayers thereof. The AFM / capping layer can be formed by a well-known deposition method, such as sputtering. The AFM / capping layer may have a thickness between about 40 angstroms and about 150 angstroms. In addition, it should be understood that while IrMn, FeMn, PtMn, Ta, Ru, Ti and their multilayers have been exemplified as AFM / capping layer materials, other materials are also contemplated, and the embodiments discussed herein are not limited to IrMn, FeMn, PtMn, Ta, Ru or Ti or their multilayers for use as AFM / capping layers.

[0052] Electrical leads are positioned around the first SHL 302, the second SHL 304, and GL 310. For example, the first SHL 302 includes a first negative voltage terminal (V1-), a first positive voltage terminal (V1+), and a first positive current terminal (I1+). The second SHL 304 includes a second negative voltage terminal (V2-), a second positive voltage terminal (V2+), and a second negative current terminal (I2-) located on either side of the second SHL 304. Furthermore, GL 310 includes a first negative current terminal (I1-) and a second positive current terminal (I2+). It should be understood that the indicated polarities of the voltage terminals of the first SHL 302 and the second SHL 304 are for illustrative purposes, and the voltage polarities of the first SHL 302 and the second SHL 304 may depend on the direction of the current and the positioning of the first FL 306 and the second FL 308 relative to the magnetic medium 312 (such as positions 314a-314d). In addition, the first negative voltage terminal (V1-) and the second negative voltage terminal (V2-) may be electrically short-circuited together to provide a common voltage terminal.

[0053] The differential voltage (e.g., differential voltage 311) between the first positive voltage terminal (V1+) of the first SHL 302 and the second positive voltage terminal (V2+) of the second SHL 304 is the SOT differential reader signal output. Because GL 310 includes separate current terminals, the current applied to the first FL 306 and the second FL 308 can be adjusted independently of each other. Therefore, the magnetic responses of the first FL 306 and the second FL 308 can be matched when the first FL 306 and the second FL 308 have different characteristics (such as different materials or thicknesses). Figure 3AThe direction of current and voltage can be represented Figure 3C The direction of current and voltage.

[0054] The first SHL 302 has a first track width 318 that is substantially equal to or less than the width of the first shield 322a, and the second SHL 304 has a second track width 328 that is substantially equal to the width of the stack including the first FL 306, GL 310, and the second FL 308. In some embodiments, the width of the first track width 318 is less than the width of the first shield 322a. The first track width 318 may be from about 200 angstroms to about 2000 angstroms wide. The second track width 328 may be from about 100 angstroms to about 400 angstroms wide. Because the first track width 318 of the first SHL 302 is greater than the second track width 328 of the second SHL 304, the signal output of the lower reader (i.e., the first FL 306) is greater than the signal output of the upper reader (i.e., the second FL 308).

[0055] Asymmetric signal output between the lower and upper reader can cause baseline drift (e.g., signal outputs are not canceled out). However, by independently controlling the first current 313 and the second current 315 (i.e., three lead circuits), the signal outputs of the lower and upper reader can be matched, thereby reducing the likelihood of baseline drift. A dust removal layer (not shown) can be arranged around the lower reader to incorporate a shunt design, reducing the electron flow of the first current 313. Furthermore, by selecting a material or appropriate thickness for the second SHL 304 that includes a larger spin polarization angle, resulting in a higher spin Hall angle, the signal output of the upper reader can also be increased. Similarly, reducing the thickness of the second SHL 304 can increase the signal output of the upper reader.

[0056] Figure 3D A cross-sectional side view of a SOT differential reader 370 according to one embodiment is shown. The SOT differential reader 370 includes a first insulating layer 330 disposed on a first shield 322a, a first SHL 302 disposed above the first insulating layer 330, a first FL 306 disposed above the first SHL 302, a GL 310 disposed above the first FL 306, a second FL 308 disposed above the GL 310, and a second SHL 304 disposed above the second FL 308. In the present embodiment, the second FL 308 and the second SHL 304 comprise two separate portions or segments, wherein a first segment 301 is adjacent to a medium-facing surface (MFS) 355, and a second segment 303 is disposed on a side 357 opposite to the MFS 355 in the z-direction. GL 310 extends from the MFS 355 to the side 357 opposite to the MFS 355 and contacts the second segment 303.

[0057] A fourth insulating layer 320 is disposed above the second SHL 304. Furthermore, a fifth insulating layer 326a is disposed between the first shield 322a and GL 310. A sixth insulating layer 326b is disposed between GL 310 and the second shield 322b, and between the first segment 301 and the second segment 303. The second shield 322b is disposed above the fourth insulating layer 320 and the second segment of the second SHL 304. The second shield 322b is in contact with the second segment of the second SHL 304.

[0058] Figures 4A to 4H The formation and definition according to one embodiment are shown. Figure 3C The method for determining the track width of the SOT differential reader 360. Although in Figures 4A to 4H Different reference numerals may be used in the accompanying drawings, but the material of the layers forming the SOT differential reader 360 is the same as described above. Figure 3C The materials described are the same. Figures 4A to 4H The MFS view is shown during the manufacturing process of the SOT differential reader 360.

[0059] exist Figure 4A In this configuration, a first insulating layer 430 is deposited on a first shield 422a, a first SHL 402 is deposited on the first insulating layer 430, a first FL 406 is deposited on the first SHL 402, a GL 410 is deposited on the first FL 406, a second FL 408 is deposited on the GL 410, a second SHL 404 is deposited on the second FL 408, and a second insulating layer 420a is deposited on the second SHL 404 to form a stack 440. In some embodiments, the GL 410 includes electrodes to allow independent adjustment of the magnetic properties of the first FL 406 and the second FL 408.

[0060] exist Figure 4B In this process, a photoresist or photo-stencil 434 is deposited on a second insulating layer 420a above the stack 440 to define the track width of the stack 440. Then, portions of the second insulating layer 420a, the second SHL 404, the second FL 408, the GL 410, and the first FL 406 that are not covered by the photo-stencil 434 (i.e., the outer ends of the stack 440) are removed to expose refill layers 436a and 436b disposed behind the stack 440. Removing the outer ends of the stack 440 defines the track width or horizontal width of the stack 440. Figure 4BIn this structure, a first insulating material thin layer 432a and a second insulating material thin layer 432b are deposited on the top surface 402a of the first SHL 402 and on either side of the first FL 406, GL 410, and second FL 408. The first insulating layer 432a is disposed adjacent to the refill layer 436a, and the second insulating layer 432b is disposed adjacent to the refill layer 436b. Figure 4C In this process, an additional insulating material thin layer 432 is deposited on any one side of the second SHL 404, the second insulating layer 420a, and the photoelectric template 434 (e.g., the side in contact with the refill layers 436a, 436b). The additional insulating material thin layer 432 connects the first insulating layer 432a to the second insulating layer 432b.

[0061] exist Figure 4D In this process, hard bias layers 424a and 424b are deposited above the first SHL 402 (e.g., on the first insulating material layer 432a and the second insulating material layer 432b) and on both sides of the first FL 406, GL 410 and the second FL 408, respectively. Then, portions of the additional insulating material 432 and the refill layers 436a and 436b configured to contact the second SHL 404, the second insulating layer 420a, and the photoelectric template 434 are removed (e.g., by ion milling). Thus, the first insulating layer 432a and the second insulating layer 432b remain in contact with the first SHL 402, the first FL 406, GL 410, and the second FL 408, such that the first insulating layer 432a and the second insulating layer 432b are disposed between the first SHL 402, the first FL 406, GL 410, and the second FL 408 and the hard bias layers 424a and 424b. In other words, the first SHL 402, the first FL 406, GL 410, and the second FL 408 are not in direct contact with the hard bias layers 424a and 424b. The first hard bias material 424a is deposited on the first insulating layer 432a at a horizontal height below the second SHL 404, and the second hard bias material 424b is deposited on the second insulating layer 432b at a horizontal height below the second SHL 404. In one embodiment, the horizontal height is flush with the bottom edge of the second SHL 404.

[0062] exist Figure 4E In this process, an additional hard bias material 424c is deposited around and in contact with the second SHL 404, the second insulating layer 420a, and the optoelectronic template 434. The additional hard bias material 424c and the hard bias layers 424a and 424b form an adhesive hard bias layer, and are collectively referred to as hard bias layer 424 or hard bias material 424. Figure 4F In this process, a portion of the photoelectric template 434 and the hard bias layer 424 that are in contact with the photoelectric template 434 are removed by a process such as CMP-assisted stripping and shut-off.

[0063] exist Figure 4G In this process, the track width and strip height of the SOT differential reader are defined through the steps discussed earlier, and then a fourth insulating layer 420b is deposited on and in contact with the second insulating layer 420a and the hard bias layer 424. Figure 4H In this configuration, a second shield 422b is deposited on and in contact with a fourth insulating layer 420b to form an SOT differential reader 360. In one embodiment, the first shield 422a and the second shield 422b comprise the same or similar materials. In another embodiment, the first shield 422a and the second shield 422b comprise different materials.

[0064] Suitable materials for insulating layers 420a, 420b, 430, 432a, and 432b include dielectric materials such as alumina, silicon oxide, and silicon nitride. Insulating layers 420a, 420b, 430, 432a, and 432b can be formed by well-known deposition methods such as atomic layer deposition (ALD) or sputtering. Insulating layers 420a, 420b, 430, 432a, and 432b can have a thickness between about 10 angstroms and about 700 angstroms.

[0065] Figures 5A to 5H The formation and definition according to one embodiment are shown. Figure 3C Method for determining the track width of the SOT differential reader 360. Figures 5A to 5H An MFS view is shown during the manufacturing process of the SOT differential reader 360. Although in Figures 5A to 5H Different reference numerals may be used in the accompanying drawings, but the material of the layers forming the SOT differential reader 360 is the same as described above. Figure 3C The materials described herein are the same. Figure 5A In this configuration, a first insulating layer 530 is deposited on a first shield 522a, a first SHL 502 is deposited on the first insulating layer 530, a first FL 506 is deposited on the first SHL 502, a GL 510 is deposited on the first FL 506, a second FL 508 is deposited on the GL 510, a second SHL 504 is deposited on the second FL 508, and a second insulating layer 520a is deposited on the second SHL 504 to form a stack 540. In one embodiment, the GL 510 includes electrodes to allow independent adjustment of the magnetic properties of the first FL 506 and the second FL 508.

[0066] exist Figure 5BIn this process, a photoresist or photo-stencil 534 is deposited on a second insulating layer 520a above the stack 540 to define the track width of the stack 540. Then, portions of the second insulating layer 520a, the second SHL 504, the second FL 508, the GL 510, and the first FL 506 that are not covered by the photo-stencil 534 (i.e., the outer ends of the stack 540) are removed to expose refill layers 536a and 536b disposed behind the stack 540. Removing the outer ends of the stack 540 defines the track width or horizontal width of the stack 540. Figure 5C In this structure, a first insulating material thin layer 532a and a second insulating material thin layer 532b are deposited on the top surface 502a of the first SHL 502 and around the first FL 506, GL 510 and the second FL 508. The first insulating layer 532a is disposed adjacent to the refill layer 536a, and the second insulating layer 532b is disposed adjacent to the refill layer 536b. A third insulating material thin layer 532c is deposited around the second SHL 504, the second insulating layer 520a and the photoelectric template 534, and is connected to the first insulating layer 532a and the second insulating layer 532b.

[0067] exist Figure 5D In this process, side shielding layers 524a and 524b are deposited above the first SHL 502 (e.g., on the first insulating layer 532a and the second insulating layer 532b) and on both sides of the first FL 506, GL 510 and the second FL 508, respectively. Then, portions of the third insulating layer 532c and refill layers 536a and 536b configured to contact the second SHL 504, the second insulating layer 520a, and the photoelectric template 534 are removed (e.g., by milling). Thus, the first insulating layer 532a and the second insulating layer 532b remain in contact with the first SHL 502, the first FL 506, GL 510, and the second FL 508, such that the first insulating layer 532a and the second insulating layer 532b are disposed between the first SHL 502, the first FL 506, GL 510, and the second FL 508 and the side shielding layers 524a and 524b. In other words, the first SHL 502, the first FL 506, GL 510 and the second FL 508 do not directly contact the side shielding layers 524a and 524b.

[0068] Side shielding layers 524a, 524b may include a soft bias material. In one embodiment, the soft bias includes a material selected from the group consisting of NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and / or multilayers thereof. Furthermore, it should be understood that while NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and / or multilayers thereof have been exemplified as soft bias materials, other materials are contemplated, and the embodiments discussed herein are not limited to NiFe, CoFe, CoNi, CoFeNi, CoFeB, Co, alloys thereof, and / or multilayers thereof for soft bias.

[0069] exist Figure 5E In this configuration, an AFM / capping layer 542 is deposited on and in contact with the side shielding layers 524a and 524b, as well as the second SHL 504, the second insulating layer 520a, and the optoelectronic template 534. The AFM / capping layer 542 comprises a material selected from a group of AFM materials, including IrMn, FeMn, PtMn, and other non-magnetic conductive layers. Furthermore, the AFM / capping layer 542 may include a group of AFM materials and one or more materials from the group consisting of Ta, Ru, or Ti, other non-magnetic materials, conductive materials, and multilayers thereof. The AFM / capping layer 542 can be formed using well-known deposition methods, such as sputtering. The AFM / capping layer 542 may have a thickness between about 40 angstroms and about 150 angstroms. Furthermore, it should be understood that while IrMn, FeMn, PtMn, Ta, Ru, Ti, and their multilayers have been exemplified as AFM / capping layer 542 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 use in AFM / capping layer 542. Figure 5F In this process, a portion of the photoelectric template 534 and the AFM / capping layer 542 that is in contact with the photoelectric template 534 is removed using a process such as CMP-assisted stripping.

[0070] exist Figure 5G In this process, the track width and strip height of the SOT differential reader are defined through the steps previously discussed, and then a fourth insulating layer 520b is deposited on and in contact with the second insulating layer 520a and the AFM / capping layer 542. Figure 5H In this configuration, a second shield 522b is deposited on and contacts a fourth insulating layer 520b to form an SOT differential reader 360. In one embodiment, the first shield 522a and the second shield 522b comprise the same or similar materials. In another embodiment, the first shield 522a and the second shield 522b comprise different materials.

[0071] Figures 6A to 6EThe formation and definition according to one embodiment are shown. Figure 3D The method for determining the bar height of the SOT differential reader 370. Figures 6A to 6E A cross-sectional side view of the SOT differential reader 370 is shown. Although in Figures 6A to 6E Different reference numerals may be used in the accompanying drawings, but the material of the layers forming the SOT differential reader 370 is the same as described above. Figure 3D The materials described herein are the same. Figure 6A In the first insulating layer 630, a first SHL 602 is deposited on the first insulating layer 630, a first FL 606 is deposited on the first SHL 602, and a first GL 610a is deposited on the first FL 606 to form a first portion 640a of the stack 640.

[0072] exist Figure 6B In this process, a first photoresist or photodiode 634a is deposited over a portion of the first GL 610a of the first stacked portion 640a to define a first height 636a (i.e., in the z-direction) of the first stacked portion 640a. Then, portions of the first GL 610a, the first FL 606, and the first SHL 602 that are not covered by the first photodiode 634a (i.e., the rear end of the first stacked portion 640a recessed from the MFS 655) are removed to expose the first insulating layer 630 disposed above the first shield 622a. Figure 6C In this process, a second insulating layer 626 is deposited on the back surface 641 of the first stack portion 640a (i.e., the surface 641 of the first stack portion 640a recessed from the MFS 655) on the first insulating layer 630, and the first optoelectronic template 634a is removed. The second insulating layer 626 is deposited on the removed portion of the first stack portion 640a recessed from the MFS 655. The second insulating layer 626 is in contact with the first SHL 602, the first FL 606, and the first GL 610a.

[0073] exist Figure 6DIn this process, the portion of the second insulating layer 626 aligned with the first GL 610a is removed, and the second GL 610b is deposited on the remaining portion of the second insulating layer 626, adjacent to and in contact with the first GL 610a. The second GL 610b and the first GL 610a form an adhesive GL 610 having a uniform thickness in the y-direction. The GL 610 has a length or width in the z-direction equal to the length or width of the first shield 622a. In some embodiments, the GL 610 includes electrodes to allow independent adjustment of the spin Hall angle characteristics of the first SHL 602 and the second SHL 604. A second FL 608 is deposited on the GL 610, a second SHL 604 is deposited on the second FL 608, and a third insulating layer 620 is deposited on the second SHL 604. The second FL 608, the second SHL 604, and the third insulating layer 620 form the second portion 640b of the stack 640. The first stack portion 640a and the second stack portion 640b together form a stack 640, which is located at MFS 655.

[0074] The second photoresist or photoelectric template 634b is deposited on the third insulating layer 620, and the central portion 644a of the second photoelectric template 634b is removed, such as... Figure 6D Further illustrated. The center portion 646 of the second stacked portion 640b, aligned with the removed center portion 644a of the second optoelectronic template 634b, is then etched and removed to define a second height 636b of the second stacked portion 640b. The second height 636b is substantially the same as the first height 636a, resulting in a stack 640 with a uniform stripe height 636. The uniform stripe height 636 may be between about 10 nm and about 20 nm. In some embodiments, portions of GL610 aligned with the removed center portions 644a, 646 may be removed; however, the majority of GL 610 is not etched or removed.

[0075] Removing the central portion 646 of the second stack portion 640b further forms an electrical lead 650 recessed from the MFS 655 (i.e., Figure 3D The second portion 303 forms an electrical lead 650. The electrical lead 650 includes portions of GL 610, the second FL 608, and the second SHL 604. A portion of the third insulating layer 620 is disposed above the electrical lead 650. The electrical lead 650 is formed to contact GL 610, and thus allows GL 610 to function as the electrical lead 650. In some embodiments, the electrical lead 650 has a strip height or width 638 greater than the strip height 636 of the stack 640. The removed center portion 646 has a width in the z-direction greater than both the electrical lead 650 and the stack 640.

[0076] exist Figure 6EIn the process, the second photoelectric template 634b is removed, and a fourth insulating layer 628 is disposed between the second stack portion 640b and the electrical lead 650, in the removed central portion 646. The fourth insulating layer 628 is spaced apart from the second insulating layer 626 by GL 610. Due to the electrical lead 650, the second insulating layer 626 has a larger width in the z-direction than the fourth insulating layer 628. The fourth insulating layer 628 has a larger width in the z-direction than both the electrical lead 650 and the stack 640. The second insulating layer 626, the third insulating layer 620, and the fourth insulating layer 628 may comprise the same material.

[0077] exist Figure 6F In this process, a third photoresist or photo-stencil 634c is deposited on a third insulating layer 620 and a fourth insulating layer 628. Then, a second portion 644b of the third photo-stencil 634c disposed at MFS 655 is removed. The removed second portion 644b of the third photo-stencil 634c is aligned with a stack 640 and has a width in the z-direction equal to the width of the stack 640 (i.e., equal to the strip height or width of the strip height 636 of the stack 640). The track width of the stack 640 in the x-direction can then be defined, as described above. Figures 4B to 4H and Figures 5B to 5H As described in the text. Once the track width of stack 640 is defined, the third optoelectronic template 634c is removed.

[0078] exist Figure 6G In this process, a fourth photoresist or photoresist 634d is deposited on the third insulating layer 620 and the fourth insulating layer 628. A third portion 644c of the fourth photoresist 634d, which is at least partially aligned with or overlaps with both the electrical lead 650 and the fourth insulating layer 628, is removed. The removed third portion 644c of the fourth photoresist 634d has a smaller width or dimension than the fourth insulating layer 628, at least in the z-direction. The removed third portion 644c of the fourth photoresist 634d may have a smaller width in the z-direction than the width 638 of the electrical lead 650. Then, the portions 648 of the third insulating layer 620 and the fourth insulating layer 628 aligned with the removed third portion 644c of the fourth photoresist 634d are etched (e.g., by wet etching with alumina) and removed to open one or more electrical lead connections. Finally, the fourth photoresist 634d is removed.

[0079] exist Figure 6HIn this configuration, a second shield 622b is deposited on and in contact with the electrical lead 650, the third insulating layer 620, and the fourth insulating layer 628. By removing portions 648 of the third and fourth insulating layers 620 and 628 respectively, the second shield 622b can contact the electrical lead 650. Therefore, the second shield 622b can serve as or be used as an electrical lead connection. The first shield 622a and the second shield 622b comprise the same material.

[0080] By incorporating electrical lead connections for each layer of these SHLs, from the gap layer to the SOT differential reader, each free layer of the SOT differential reader can be independently adjusted to match the magnetic properties of each free layer. Furthermore, better reader resolution can be achieved while maintaining the shield-to-shield spacing. Therefore, it is not necessary to reduce the shield-to-shield spacing of the shields clamping the SOT differential reader to improve reader resolution, as the SOT differential reader allows for a wider shield-to-shield spacing without reducing resolution. By increasing the shield-to-shield spacing of the SOT differential reader, flux can be increased, free layers can be independently controlled, and the strip height of the SOT differential reader layers can be increased to reduce magnetic noise.

[0081] In one embodiment, the magnetic recording head includes a first shield, a second shield, a first bias layer, a second bias layer, and a SOT differential reader disposed between the first and second shields and between the first and second bias layers. The SOT differential reader includes: a first free layer; a second free layer; a gap layer configured to act as a first electrical lead; a first spin Hall layer; a second spin Hall layer in contact with the first and second bias layers; and two or more insulating layers, including a first insulating layer and a second insulating layer, the first insulating layer disposed between the first spin Hall layer and the first bias layer, and the second insulating layer disposed between the first spin Hall layer and the second bias layer. The first and second free layers are configured to be independently controlled.

[0082] A first spin Hall layer is disposed on a first shield, a first free layer is disposed on the first spin Hall layer, a gap layer is disposed on the first free layer, a second free layer is disposed on the gap layer, and a second spin Hall layer is disposed on the second free layer. A magnetic recording head is configured to receive current injected into the first spin Hall layer and output current through the gap layer, and to receive current injected into the gap layer and output current through the second spin Hall layer, wherein a first spin Hall effect voltage is induced through the first spin Hall layer, and a second spin Hall effect voltage is induced through the second spin Hall layer. The first spin Hall layer includes a second electrical lead, and the second spin Hall layer includes a third electrical lead. One or more of the first, second, and third electrical leads are used to control the signal output of the second free layer to match the signal output of the first free layer.

[0083] The electrode is configured to contact the gap layer. A first free layer, a second free layer, a gap layer, a first spin Hall layer, and a second spin Hall layer are disposed on the surface facing the dielectric. The electrode is recessed from the surface facing the dielectric. The electrode further contacts a second shield. The first spin Hall layer has a first track width on the surface facing the dielectric, and the second spin Hall layer has a second track width on the surface facing the dielectric that is smaller than the first track width. The positive terminal of the first spin Hall layer is electrically connected to the negative terminal of the second spin Hall layer, and the voltage difference across the negative terminal of the first spin Hall layer to the positive terminal of the second spin Hall layer is a signal read from the SOT differential reader.

[0084] In another embodiment, the magnetic recording head includes a first shield, a second shield, and a SOT differential reader disposed on a medium-facing surface between the first and second shields. The SOT differential reader includes a first free layer, a second free layer, a gap layer configured to act as a first electrical lead, a first spin Hall layer, and a second spin Hall layer. A positive terminal of the first spin Hall layer is electrically connected to a positive terminal of the second spin Hall layer. The signal read from the SOT differential reader is based on the voltage difference across the negative terminal of the first spin Hall layer to the negative terminal of the second spin Hall layer. The SOT differential reader also includes an electrical lead recessed from the medium-facing surface, contacting the gap layer and the second shield, wherein the first free layer, the second free layer, the gap layer, the first spin Hall layer, and the second spin Hall layer are disposed on the medium-facing surface.

[0085] A first spin Hall layer is disposed on a first shield, a first free layer is disposed on the first spin Hall layer, a gap layer is disposed on the first free layer, a second free layer is disposed on the gap layer, and a second spin Hall layer is disposed on the second free layer. The first spin Hall layer has a longer length than the second spin Hall layer at the surface facing the medium. The magnetic recording head is configured to receive a first current injected into the first spin Hall layer and output the first current through the gap layer, wherein a first spin Hall effect voltage is sensed through the first spin Hall layer. The magnetic recording head is also configured to receive a second current injected into the gap layer and output the second current through the second spin Hall layer, wherein a second spin Hall effect voltage is sensed through the second spin Hall layer. The SOT differential reader also includes a capping layer disposed above the second spin Hall layer. The magnetic recording head is configured to independently control the first and second free layers.

[0086] A first current and a first spin Hall effect voltage generate a first signal output from the first free layer, and a second current and a second spin Hall effect voltage generate a second signal output from the second free layer. The first signal output from the first free layer and the second signal output from the second free layer are independently controllable. The SOT differential readout has a bar height between approximately 10 nm and approximately 20 nm.

[0087] In another embodiment, a method for forming a SOT differential reader is disclosed. The method includes: depositing a first free layer on a first shield, depositing a first spin Hall layer on the first free layer, and depositing a gap layer on the first spin Hall layer to form a first stack, wherein the first shield has a first width extending from a dielectric-facing surface to a surface opposite to the dielectric-facing surface; removing a portion of the first free layer, a portion of the first spin Hall layer, and a portion of the gap layer to define a first track width of the first stack, the first track width of the first stack being smaller than the first width of the first shield; and depositing a first insulating layer in contact with a first surface of the first stack, the first surface of the first stack being configured to face the dielectric-facing surface. The method further includes: depositing a second free layer on the gap layer, depositing a second spin Hall layer on the second free layer, and depositing a second insulating layer on the second spin Hall layer to form a second stack on the first stack; and removing a central portion of the second insulating layer, a central portion of the second spin Hall layer, and a central portion of the second free layer to define a second track width of the second stack and forming electrical leads disposed on the gap layer, wherein the electrical leads are recessed from the dielectric-facing surface. A second shielding layer is deposited, which is in contact with the electrical leads.

[0088] The width of the first track is approximately equal to the width of the second track, and the electrical leads are recessed from the surface facing the medium. The first and second free layers are independently controlled.

[0089] While the foregoing describes embodiments of this disclosure, other and additional embodiments of this disclosure may be contemplated without departing from the basic scope of this disclosure, the scope of which is defined by the appended claims.

Claims

1. A sensing element comprising: a first bias layer; a second bias layer; and a spin orbit torque differential reader disposed between the first bias layer and the second bias layer, the spin orbit torque differential reader comprising: a first free layer; a second free layer, wherein the first free layer and the second free layer are configured to be independently controlled; a gap layer configured to act as a first electrical lead; a first spin hall layer; a second spin hall layer in contact with the first bias layer and the second bias layer; and two or more insulating layers comprising a first insulating layer disposed between the first spin hall layer and the first bias layer and a second insulating layer disposed between the first spin hall layer and the second bias layer; and wherein the first spin hall layer is disposed on a first shield, the first free layer is disposed on the first spin hall layer, the gap layer is disposed on the first free layer, the second free layer is disposed on the gap layer, and the second spin hall layer is disposed on the second free layer; and wherein a first terminal of the first spin hall layer is electrically connected to a first terminal of the second spin hall layer, and a voltage difference across a second terminal of the first spin hall layer to a second terminal of the second spin hall layer is a signal read from the spin orbit torque differential reader.

2. The sensing element of claim 1, wherein the sensing element is configured to receive a current injected into the first spin hall layer and output a current through the gap layer, and receive a current injected into the gap layer and output a current through the second spin hall layer, wherein a first spin hall effect voltage is induced through the first spin hall layer, and a second spin hall effect voltage is induced through the second spin hall layer.

3. The sensing element of claim 2, wherein the first spin hall layer comprises a second electrical lead, and the second spin hall layer comprises a third electrical lead, and wherein one or more of the first electrical lead, the second electrical lead, and the third electrical lead are used to control a signal output of the second free layer to match a signal output of the first free layer.

4. The sensing element of claim 1, further comprising an electrode disposed in contact with the gap layer, wherein the first free layer, the second free layer, the gap layer, the first spin hall layer, and the second spin hall layer are disposed at a media-facing surface, and wherein the electrode is recessed from the media-facing surface.

5. The sensing element of claim 4, wherein the electrode is further in contact with a second shield.

6. The sensing element of claim 4, wherein the first spin hall layer has a first track width at the media-facing surface, and the second spin hall layer has a second track width at the media-facing surface that is less than the first track width.

7. The sensing element of claim 1, wherein a positive terminal of the first spin hall layer is electrically connected to a negative terminal of the second spin hall layer, and a voltage difference across a negative terminal of the first spin hall layer to a positive terminal of the second spin hall layer is a signal read from the spin orbit torque differential reader.

8. A magnetic recording head comprising the sensing element of claim 1.

9. A sensing element comprising: a spin orbit torque differential reader disposed at a media-facing surface, the spin orbit torque differential reader comprising: a first free layer; a second free layer; a gap layer; a first spin hall layer; a second spin hall layer, a positive terminal of the first spin hall layer is electrically connected to a positive terminal of the second spin hall layer, wherein a signal read from the spin orbit torque differential reader is based on a voltage difference across a negative terminal of the first spin hall layer to a negative terminal of the second spin hall layer; and an electrical lead recessed from the media-facing surface, the electrical lead in contact with the gap layer, wherein the first free layer, the second free layer, the gap layer, the first spin hall layer, and the second spin hall layer are disposed at the media-facing surface; and wherein the first spin hall layer is disposed on a first shield, the first free layer is disposed on the first spin hall layer, the gap layer is disposed on the first free layer, the second free layer is disposed on the gap layer, and the second spin hall layer is disposed on the second free layer.

10. The sensing element of claim 9, wherein the first spin hall layer has a longer length at the media-facing surface than the second spin hall layer, and wherein the electrical lead is further in contact with a second shield.

11. The sensing element of claim 10, further comprising a capping layer disposed over the second spin hall layer.

12. The sensing element of claim 9, wherein the sensing element is configured to: receive a first current injected into the first spin hall layer; output the first current through the gap layer, wherein a first spin hall effect voltage is induced by the first spin hall layer; receive a second current injected into the gap layer; and output the second current through the second spin hall layer, wherein a second spin hall effect voltage is induced by the second spin hall layer.

13. The sensing element of claim 12, wherein the first current and the first spin hall effect voltage produce a first signal output of the first free layer, and the second current and the second spin hall effect voltage produce a second signal output of the second free layer.

14. The sensing element of claim 13, wherein the first signal output of the first free layer and the second signal output of the second free layer are independently controllable.

15. The sensing element of claim 9, wherein the spin orbit torque differential reader has a stripe height between 10 nm and 20 nm.

16. A magnetic recording head comprising the sensing element of claim 9.

17. A method of forming a spin orbit torque differential reader, comprising: depositing a first spin hall layer on a first shield, depositing a first free layer on the first spin hall layer, and depositing a gap layer on the first free layer to form a first stack, wherein the first shield has a first width extending from a media facing surface to a surface opposite the media facing surface; removing a portion of the first free layer, a portion of the first spin hall layer, and a portion of the gap layer to define a first track width of the first stack, the first track width of the first stack being less than the first width of the first shield; depositing a first insulator layer in contact with a first surface of the first stack, the first surface of the first stack disposed opposite the media facing surface; depositing a second free layer on the gap layer, depositing a second spin hall layer on the second free layer, and depositing a second insulator layer on the second spin hall layer to form a second stack on the first stack; removing a central portion of the second insulator layer, a central portion of the second spin hall layer, and a central portion of the second free layer to define a second track width of the second stack and form an electrical lead disposed on the gap layer, wherein the electrical lead is recessed from the media facing surface; and depositing a second shield layer in contact with the electrical lead; and wherein a first terminal of the first spin hall layer is electrically connected to a first terminal of the second spin hall layer, and a voltage difference across a second terminal of the first spin hall layer to a second terminal of the second spin hall layer is a signal read from the spin orbit torque differential reader.

18. The method of claim 17, wherein the first track width is approximately equal to the second track width, and wherein the first free layer and the second free layer are independently controlled.

19. A magnetic recording device comprising a spin orbit torque differential reader formed by the method of claim 17.

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