DFL reader signal side bump imbalance reduction

Abstract

A dual free layer (DFL) read head or reader typically has side bumps in a signal amplitude and cross-track profile. The side bump is an additional magnetic signal of the reader in response to the magnetic field of the limited thickness magnetic medium. The side bump has a magnitude much lower than the main magnetic signal of the reader and is offset from the center of the track in a cross-track direction. The presence of the side bumps indicates that the magnetic signal of the reader is out of phase. When there is a pair of side bumps (one on each side of the center of the track), the side bumps typically and ideally should be offset symmetrically in the cross-track direction, which would otherwise negatively impact reader performance. To achieve offset symmetry, synthetic antiferromagnetic (AFM) (SAF) shielding may be used, the magnetic moment of the soft bias layer may be adjusted, and the spacing between the free layer and the soft bias layer of the DFL read head may also be adjusted.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to a dual free layer (DFL) read head. Background Art

[0002] Central to the function and capability of a computer is the storage and writing of data to a data storage device, such as a magnetic media drive (e.g., a hard disk drive (HDD)). An HDD has a head including a reader (e.g., a read head) and a writer (e.g., a write head), each with shielding to capture stray fields (e.g., in a read head) or improve field gradients (e.g., in a write head).

[0003] Over the past few years, various magnetic recording methods have been investigated to increase the areal density of magnetic media devices. The magnetic heads in an HDD can have a significant impact on the overall performance and reliability of the recording device. The magnetic heads can be designed to achieve specific advantages, such as improved performance.

[0004] One example design involves a dual free layer (DFL) read head or reader. In DFL reader operation, the two free layers are stabilized longitudinally by an antiferromagnetic coupling (AFC) soft bias (SB) and laterally biased by a permanent magnet or a rear hard bias structure (RHB) from the rear edge of the sensor strip. Ideally, a DFL read head has a symmetrical side bump offset in the output signal when measured in the cross-track direction. However, due to manufacturing and geometric controllability, symmetrical offset does not always occur. This asymmetrical side bump offset will introduce additional operational complexity to the HDD, especially during shingled magnetic recording (SMR).

[0005] Therefore, there is a need in the art for an improved DFL read head. Summary of the invention

[0006] A dual free layer (DFL) read head, or more generally any reader, typically has side bumps in the signal amplitude versus cross-track distribution plot. Side bumps are out-of-phase magnetic signals of the reader in response to the magnetic field of a finite thickness magnetic medium. The amplitude of the side bumps is much lower than the main magnetic signal of the reader and is typically offset from the center of the reader in the cross-track direction. The presence of side bumps indicates that the magnetic signal of the reader is somewhat out of phase. When a pair of side bumps are present (one on each side of the center of the track), the side bumps are typically and ideally should be symmetrically offset in the cross-track direction, otherwise it can negatively impact the reader performance, especially during SMR operation. To obtain offset symmetry, a synthetic antiferromagnetic (SAF) undershield can be used, the magnetic moment of the soft bias layer can be adjusted, and the spacing between the free layer and the soft bias layer of the DFL read head can also be adjusted.

[0007] In one embodiment, a magnetic read head includes: a synthetic antiferromagnetic (AFM) (SAF) shield; a first free layer disposed on the SAF shield; a barrier layer disposed on the first free layer; a second free layer disposed on the barrier layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer; a back bias structure recessed from the MFS; and a second shield disposed on the second free layer and the soft bias structure.

[0008] In another embodiment, a magnetic read head includes: a first shield; a first free layer disposed on the first shield; a first insulating layer disposed on the first free layer; a second free layer disposed on the first insulating layer; a soft bias structure, disposed laterally in a cross-track direction at a medium facing surface (MFS), adjacent to the first free layer and the second free layer, wherein the soft bias structure includes: a first soft bias layer having a first magnetic moment; and a second soft bias layer having a second magnetic moment different from the first magnetic moment; a back bias structure recessed from the MFS; and a second shield disposed on the second free layer and the soft bias structure.

[0009] In another embodiment, a magnetic read head includes: a first shield; a first free layer disposed on the first shield; a first insulating layer disposed on the first free layer; a second free layer disposed on the first insulating layer; a soft bias structure, disposed laterally in a cross-track direction at a medium facing surface (MFS), adjacent to the first free layer and the second free layer, wherein the soft bias structure includes: a first soft bias layer spaced a first distance from the first free layer; and a second soft bias layer spaced a second distance from the second free layer, wherein the second distance is different from the first distance; a back bias structure recessed from the MFS; and a second shield disposed on the second free layer and the soft bias structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to be able to understand the above-mentioned features of the present disclosure in detail, the present disclosure briefly summarized above may be described in more detail with reference to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings only illustrate typical embodiments of the present disclosure and are therefore not to be considered as limiting the scope thereof, as the present disclosure may allow other equally effective embodiments.

[0011] Figure 1 A disk drive embodying the invention is shown.

[0012] Figure 2 is a fragmentary cross-sectional side view through the center of a read / write head facing a magnetic media according to one embodiment.

[0013] Figure 3A is a graph illustrating side tab offset in the cross-track direction according to one embodiment.

[0014] Figure 3B is a graph illustrating the maximum side bump value and the side bump increment.

[0015] Figure 4A is a schematic diagram of the medium facing surface (MFS) of the read head.

[0016] Figure 4B yes Figure 4A Schematic diagram of the scissor axis offset of the read head.

[0017] Figure 5A is a top view of a read head according to one embodiment. Figure 5B yes Figure 5A MFS view of the read head.

[0018] Fig. 6A is a top view of a read head according to one embodiment. Figure 6B yes Fig. 6A MFS view of the read head.

[0019] Figure 7 is a graph illustrating the effect on the side bump maximum value versus the side bump increment between the left bump and the right bump.

[0020] Fig. 8A is a view of an MFS of a read head according to another embodiment.

[0021] Figure 8B is a graph illustrating the maximum reduction of underbump and the underbump imbalance according to using different magnetic moments for the soft bias layer.

[0022] Fig.9A is a view of an MFS of a read head according to another embodiment.

[0023] Fig. 9B and 9C The diagram shows the right bump ( Fig. 9B ) and the left bump ( Fig. 9C ) is a graph showing the influence of the cumulative probability of the bump ratio.

[0024] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. DETAILED DESCRIPTION

[0025] Reference is made below to embodiments of the present disclosure. However, it should be understood that the present disclosure is not limited to the specifically described embodiments. On the contrary, any combination of the following features and elements, whether or not related to different embodiments, is considered to be able to implement and practice the present disclosure. In addition, although the embodiments of the present disclosure can achieve advantages over other possible solutions and / or prior art, whether a specific advantage is achieved by a given embodiment does not limit the present disclosure. Therefore, the following aspects, features, embodiments and advantages are merely illustrative and are not considered to be elements or limitations of the appended claims unless explicitly stated in the claim(s). Similarly, reference to the "present disclosure" should not be interpreted as a generalization of any inventive subject matter disclosed herein, and should not be considered to be elements or limitations of the appended claims unless explicitly stated in the claim(s).

[0026] A double free layer (DFL) read head, or more generally any reader, typically has side bumps in the signal amplitude vs. cross-track distribution plot. Side bumps are additional magnetic signals that the reader responds to the magnetic field of a finite thickness magnetic medium. The amplitude of the side bumps is much lower than the reader's magnetic signal and is offset from the center of the reader in the cross-track direction. The presence of side bumps indicates that the reader's magnetic signal is somewhat out of phase. When a pair of side bumps are present (one on each side of the center of the track), the side bumps should typically and ideally be offset symmetrically in the cross-track direction, otherwise it will negatively affect the reader performance. This offset asymmetry often occurs in DFLs. To obtain offset symmetry, synthetic antiferromagnetic (SAF) shields can be used, the magnetic moment of the soft bias layer can be adjusted, and the spacing between the free layer and the soft bias layer of the DFL read head can also be adjusted.

[0027] Figure 1 1 is a schematic diagram of a magnetic recording device 100 according to one implementation. The magnetic recording device 100 includes a magnetic recording head, such as a write head. The magnetic recording device 100 is a magnetic media drive, such as an HDD. Such a magnetic media drive may be a single drive / device, or may include multiple drives / devices. For ease of description, in Figure 1 In the illustrated implementation, a single disk drive is shown as the magnetic recording device 100. The magnetic recording device 100 (e.g., a disk drive) includes at least one rotatable disk 112 supported on a spindle 114 and rotated by a drive motor 118. The magnetic recording on each rotatable disk 112 is in the form of any suitable data track pattern, such as an annular pattern of concentric data tracks on the rotatable disk 112.

[0028] At least one slider 113 is located near the rotatable magnetic disk 112. Each slider 113 supports a head assembly 121. The head assembly 121 includes one or more magnetic recording heads (e.g., read / write heads), such as a write head. As the rotatable magnetic disk 112 rotates, the slider 113 moves radially in and out on the disk surface 122 so that the head assembly 121 can access different tracks of the rotatable magnetic disk 112 to write desired data on these tracks. 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 disk surface 122. Each actuator arm 119 is attached to an actuator 127. As shown in FIG. Figure 1 The actuator 127 shown may be a voice coil motor (VCM). The VCM includes a coil that can move within a fixed magnetic field, and the direction and speed of the coil movement are controlled by a motor current signal provided by the control unit 129.

[0029] The head assembly 121, such as a write head of the head assembly 121, includes a medium facing surface (MFS), such as an air bearing surface (ABS), that faces the disk surface 122. During operation of the magnetic recording device 100, the rotation of the rotatable disk 112 generates an air or gas bearing between the slider 113 and the disk surface 122, which exerts an upward force or lift on the slider 113. Thus, the air or gas bearing counteracts the slight spring force of the suspension 115 and supports the slider 113 a small, substantially constant spacing outside and slightly above the disk surface 122 during operation.

[0030] The various components of the magnetic recording device 100 are controlled in operation by control signals generated by a control unit 129, such as access control signals and internal clock signals. The control unit 129 includes logic control circuits, storage devices, and a microprocessor. The control unit 129 generates control signals to control various system operations, such as drive motor control signals on line 123 and head positioning and seek control signals on line 128. The control signals on line 128 provide the desired current distribution to optimally move and position the slider 113 to the desired data track on the rotatable disk 112. The write and read signals are communicated to the head assembly 121 through the recording channel 125. In an embodiment that can be combined with other embodiments, the magnetic recording device 100 can also include multiple media or disks, multiple actuators, and / or multiple sliders.

[0031] Figure 2 For the purpose of one implementation Figure 1 1 is a schematic diagram of a cross-sectional side view of a head assembly 200 for a rotatable disk 112 or other magnetic storage medium. The head assembly 200 may correspond to Figure 1The magnetic head assembly 121 described in the above. The magnetic head assembly 200 includes an MFS 212, such as an ABS, facing the rotatable magnetic disk 112. Figure 2 As shown, the rotatable magnetic disk 112 moves relatively in the direction indicated by arrow 232 , and the head assembly 200 moves relatively in the direction indicated by arrow 234 .

[0032] In one embodiment that may be combined with other embodiments, the magnetic head assembly 200 includes a magnetic read head 211. The magnetic read head 211 may include a sensing element 204 disposed between shields S1 and S2. The sensing element 204 is a magnetoresistive (MR) sensing element, such as an element that applies a tunnel magnetoresistive (TMR) effect, a gravitational magnetoresistive (GMR) effect, an abnormal magnetoresistive (EMR) effect, a spin track torque (SOT) effect, or a spin torque oscillator (STO) effect. The magnetic field of a magnetized region in the rotatable magnetic disk 112, such as a perpendicular recording bit or a longitudinal recording bit, may be detected as a recording bit by the sensing element 204. Here, the magnetic read head 211 is a simplified representation of various disclosed embodiments, which will include multiple sensing elements and shields, as further described below.

[0033] The magnetic head assembly 200 includes a write head 210. In one embodiment that can be combined with other embodiments, the write head 210 includes a main magnetic pole 220, a front shield 206, and a rear shield (TS) 240. The main magnetic pole 220 serves as a first electrode. Each of the main magnetic pole 220, the front shield 206, and the rear shield (TS) 240 has a front portion at the MFS.

[0034] The main pole 220 includes a magnetic material such as CoFe, CoFeNi or FeNi, as well as other suitable magnetic materials. In one embodiment that can be combined with other embodiments, the main pole 220 includes small particles of a magnetic material with a random texture, such as a body-centered cubic (BCC) material formed with a random texture. In one example, the random texture of the main pole 220 is formed by electrodeposition. The write head 210 includes a coil 218 surrounding the main pole 220, and the coil 218 excites the main pole 220 to generate a write magnetic field for affecting the magnetic recording medium of the rotatable disk 112. The coil 218 can be a spiral structure or one or more groups of flat structures.

[0035] In one embodiment that can be combined with other embodiments, the main pole 220 includes a rear cone 242 and a front cone 244. The rear cone 242 extends from a position recessed from the MFS 212 to the MFS 212. The front cone 244 extends from a position recessed from the MFS 212 to the MFS 212. The rear cone 242 and the front cone 244 can have the same degree of taper or different degrees of taper relative to the longitudinal axis 260 of the main pole 220. In one embodiment that can be combined with other embodiments, the main pole 220 does not include the rear cone 242 and the front cone 244. In such an embodiment, the main pole 220 includes a rear side and a front side, wherein the rear side and the front side are substantially parallel.

[0036] TS240 includes a magnetic material, such as FeNi or other suitable magnetic materials, and serves as a return pole and a second electrode of the main pole 220. The front shield 206 can provide electromagnetic shielding and is separated from the main pole 220 by a front gap 254. A rear gap 252 exists between the main pole 220 and TS240. Figure 2 As shown, one or more structures 250 for energy assisted writing may be present in the back gap 252. Alternatively, in heat assisted magnetic recording (HAMR), a near field transducer (NFT, not shown) may be disposed near the main pole 220, where the NFT is coupled to a waveguide coupled to a light source to provide local heating to the medium, thereby reducing its coercivity for assisted writing.

[0037] Figure 3A is a graph showing the side bump distribution according to one embodiment by plotting the reader signal output as a function of cross-track position. The signal here is normalized to the maximum amplitude at the center of the track. There are usually two out-of-phase signal (side bump) peaks to the left and right of the main signal peak (position C). Large side bumps have a negative impact on read head performance. Figure 3A As shown, the DFL side bumps are generally asymmetric between the left side bump A and the right side bump B. The amplitude of the left side bump A is shown to be about 12.5% ​​of the peak amplitude at cross-track offsets between about -50 nanometers and about -80 nanometers, while the amplitude of the right side bump B is shown to be about 7.5% of the peak amplitude at cross-track offsets between about 50 nanometers and about 80 nanometers. C is the main signal. The side bump maximum is defined as the maximum side bump of the left or right bump amplitude, and the side bump delta is defined as the amplitude (normalized) difference between the left and right bumps. Figure 3B is a graph illustrating the maximum side bump versus the side bump increment. Figure 3B As shown, the imbalance of the two bumps, in terms of amplitude difference, is closely related to the maximum bump of A and B. Reducing the bump imbalance should result in a reduction in the maximum bump. In this particular example, most of the bump occurs to the left of center.

[0038] Figure 4A is a schematic MFS view of a DFL read head 400. The read head 400 includes a main shield or bottom shield 402, which may be referred to as a magnetic seed layer. In some embodiments, the bottom shield 402 includes a recess 404. The recess 404A exists due to manufacturing conditions such as defining the DFL layer. Suitable materials for the bottom shield 402 include magnetic materials such as CoFe, CoFeNi, NiFe or FeNiRe, CoB, CoHf or other suitable magnetic materials.

[0039] On the recess 404, the layers of the DFL sensor are disposed. Specifically, a first free layer 406 exists as does a second free layer 408. The first free layer 406 is spaced from the recess 404 by a nonmagnetic buffer layer 420. Suitable materials for the buffer layer 420 include Ta, Ru, CoHf, NiFeTa, NiFeGe, RuAl, NiAl, and combinations thereof. Suitable materials for the first free layer 406 and the second free layer 408 may each individually include cobalt iron (CoFe), cobalt boron (CoB), cobalt iron boron (CoFeB), cobalt hafnium (CoHf), ​​cobalt iron hafnium (CoFeHf), and combinations thereof. The first free layer 406 is separated from the second free layer 408 by a barrier layer 409, which includes an insulating material such as MgO, SiOx, SiNx, AlOx, HfOx, TiOx, and combinations thereof, where x is greater than 1. On top of the second free layer 408 and in contact with the upper shield 414 is a capping layer 422. The capping layer 422 includes a non-magnetic material, such as Ta, Ru, Ti, CoHf, NiFeTa, NiFeGe, RuAl, NiAl, and combinations thereof.

[0040] There is also a soft bias structure including a first soft bias layer 410 and an antiferromagnetic coupling (AFC) layer 407 formed thereon, and a second soft bias layer 412 formed on the AFC layer 407. Suitable materials for the first soft bias layer 410 and the second soft bias layer 412 include, for example, NiFe, a NiFe / CoFe stack, a NiFe / NiFeCr stack, or a NiFe / W stack (the " / " used here indicates a separate layer in a multilayer stack). Suitable materials for the AFC layer 407 include Ru or a CoFe / Ru / CoFe three-layer structure. The soft bias structure is spaced apart from the layers of the DFL sensor along the cross-track direction (X direction) and is also spaced apart from the bottom shield / recess 402 along the downtrack direction (Y direction) by an insulating material 405. The soft bias structure is in contact with an upper shield 414.

[0041] The upper shield 414 is disposed above both the soft bias structure and the second free layer 408. On top of the second free layer 408, there may be a capping layer 422, which may include Ta, Ru, Ti, CoHf, NiFeTa, NiFeGe, RuAl, and NiAl, and combinations thereof. The upper shield 414 includes NiFe, a NiFe / CoFe stack, a NiFe / NiFeCr stack, a NiFe / W stack, CoFe, CoFeNi, NiFe, or FeNiRe, or other suitable magnetic materials. Sometimes, an AFC coupling structure may be implemented in the upper shield 414. An antiferromagnetic magnet 416 is disposed on the upper shield 414, which includes, for example, IrMn, IrCrMn, or a combination thereof.

[0042] The side bump signal imbalance problem of the read head 400 is now further explained. As shown by the matching direction of the arrow with the -X direction, the first soft bias layer 410 biases the first free layer 406 in a first direction (-X). In contrast, the second soft bias layer 412 biases the second free layer 408 in a second direction (+X) opposite to the first direction. Generally, the bias applied by the first soft bias layer 410 is equal to (and opposite to) the bias applied by the second soft bias layer 412. In fact, if the recess 404 is not present, the equal and opposite biases applied by the respective soft bias layers should result in fewer side bumps and at least symmetrical side bumps. In the presence of the recess 404, Figure 4A The recess is shown to have surface edges 404A / 404B that contribute fringe fields that are additional to the bias of the first free layer 406 (as indicated by the curved arrows from the recess 404 to the free layer 406). In fact, the recess 404 produces a higher first free layer 406 bias, making the bias of the first free layer 406 greater than the bias of the second free layer 408.

[0043] Figure 4B yes Figure 4A Schematic diagram of the scissor axis offset of the read head 400. "Scissors" refers to the conceptual figure or shape produced by the relative magnetization of the two free layers. Due to the different biases, the scissor axis is tilted away from the vertical direction (Z). As a result, the magnetization offset angles of the first free layer 406 (labeled FL1) and the second free layer 408 (labeled FL2) relative to the vertical axis will be different, and when the reader moves to the left and right sides of the written track, this will result in different magnetic moments from the magnetic medium field, and thus corresponding asymmetric side bumps and higher maximum bumps (see Figure 3A and 3B). This difference is due to the fringing magnetic field from the recess 404 being added to the bias provided by the first soft bias layer 410. Since the second free layer 408 is biased only from the second soft bias layer 412, the bias of the first free layer 406 is greater than the bias of the second free layer 408. It should also be noted that the bias provided to the first free layer 406 by the first soft bias layer 410 is substantially equal to the bias provided to the second free layer 408 by the second soft bias layer 412, and in the opposite direction. It is necessary to design the reader structure appropriately to achieve perpendicular scissor axes and therefore symmetrical / equal biasing of the first and second free layers.

[0044] Figure 5A is a top view of a read head 500 according to one embodiment. Figure 5B yes Figure 5A MFS view of the read head 500. The read head 500 includes a pinned synthetic antiferromagnetic (AFM) (SAF) shield, rather than having a Figure 4A The conventional lower shield or bottom shield or magnetic seed layer shown. The SAF shield includes an AFM layer 502, which includes, for example, IrMn, IrCrMn, or a combination thereof. The SAF shield also includes a first magnetic seed layer 504, an AFM coupling (AFC) layer 506, and a second magnetic seed layer 508 having a recess 512. Suitable materials for the first magnetic seed layer 504 and the second magnetic seed layer 508 include NiFe, CoFe, Co, and / or combinations thereof. Suitable materials for the AFC layer 506 include a CoFe / Ru / CoFe trilayer or a Ru monolayer. As shown in FIG. Figure 5A As shown, a post-hard bias structure 510 is also present and disposed on the second magnetic seed layer 508. Suitable materials for the post-hard bias structure 510 include CoPt, NiFe, CoFe, and combinations thereof. The post-hard bias structure 510 is both recessed from the MFS and located behind the first free layer 406 and the second free layer 408. The post-hard bias structure 510 is separated from the second magnetic seed layer 508, the first free layer 406, and the second free layer 408 by the insulating material 405. The post-hard bias structure 510 is separated from the upper shield 414 by a non-magnetic layer 520, which may be an insulating material or a simple non-magnetic, non-insulating material. Figure 5B As shown, the recess 512 is disposed under the first free layer 406 , and the second magnetic seed layer 508 is disposed under the first soft bias layer 410 .

[0045] Due to the pinned SAF shielding, the orientation of the second magnetic seed layer 508 and the recess 512 is pinned to match the orientation of the first free layer 406, as shown in FIG. Figure 5B. In the pinned SAF shield, the first magnetic seed layer 504 is pinned in the +X direction and the second magnetic seed layer 508 is pinned in the -X direction. As previously described, the first free layer 406 is biased in the -X direction by the first soft bias layer 410 and the second free layer is biased in the +X direction by the second soft bias layer 412. Pinning the second magnetic seed layer 508 (and thus the recess 512) in the same orientation as the first free layer 406 eliminates the Figure 4A The fringe field addition effect that occurs in the first free layer 406 is reduced, and sometimes even some subtraction effect is introduced. Therefore, the bias of the first free layer 406 can be significantly reduced and more closely matched to the opposite bias of the second free layer 408 through the second soft bias layer 412. In this way, if present, Figure 3A The amplitude and position of the side bumps in the cross-track direction shown in will be substantially the same. It should be noted that Figure 5B The various magnetization orientations in the other figures below are intended to illustrate the concepts, and as a whole they can be oppositely oriented while maintaining the same reduction in side lug imbalance.

[0046] Fig. 6A is a top view of a read head 600 according to one embodiment. Figure 6B yes Fig. 6A FIG. 6 is an MFS view of a read head 600. The read head 600 is similar to the read head 500, except that the second magnetic seed layer is present only under the sensor stack, or more specifically, under the first free layer 406, as a recess 612, but not under the soft bias structure or the first soft bias layer 410, and not under the post hard bias layer 510. In contrast, the read head 500 has the second magnetic seed layer 508 under the first free layer 406 and the first soft bias layer 410 and the RHB layer 510. Thus, in the read head 500, the entire shield is a pinned SAF shield. However, the read head 600 is a pinned SAF shield only at locations under the first free layer 406, while the remaining areas of the shield are single pinned.

[0047] In other words, in the read head 600, the second magnetic seed layer (e.g., recess 612) has substantially the same width as the first free layer 406 and the second free layer 408 in the X direction at the MFS. The second magnetic seed layer as recess 612 has substantially the same height as the first free layer 406 and the second free layer 408 in the Z direction at the vertex. Compared with the read head 500, only the recess 512 has substantially the same width as the first free layer 406 and the second free layer 408 in the X direction at the MFS, while the second magnetic seed layer 508 has a greater width in the X direction at the MFS than the first free layer 406 and the second free layer 408. In this way, the first soft bias layer 410 is spaced apart from the AFC coupling layer 506 by the insulating material 405 instead of by both the insulating material 405 and the second magnetic seed layer. Similarly, the read hard bias 510 is spaced apart from the AFC coupling layer 506 by the insulating material 405 instead of by both the insulating material 405 and the second magnetic seed layer.

[0048] Due to the pinned SAF shield recess and the single pinned remaining portion of the shield, the orientation of the second magnetic seed layer as recess 612 is pinned in an orientation parallel to the orientation of the first free layer 406 (i.e., the -X direction). In other words, due to the pinned SAF shield, the first magnetic seed layer 504 is pinned in the +X direction, the second magnetic seed layer as recess 612 is pinned in the -X direction, the first free layer 406 is biased in the -X direction by the first soft bias layer 410, and the second free layer is biased in the -+X direction by the second soft bias layer 412. The parallel orientation of the second magnetic seed layer as recess 612 and the first free layer 406 does not produce Figure 4A Thus, the bias of the first soft bias layer 410 on the first free layer 406 can be significantly reduced and can be equal and opposite to the bias of the second soft bias layer 412 on the second free layer 408. In doing so, the underbump shown in FIG. 3 , if present, will be substantially the same in both magnitude and position in the cross-track direction.

[0049] Figure 7 is a simulation result illustrating the effect on the maximum side bump and the side bump increment. The graph shows how not using a pinned SAF (i.e., conventional shielding) will result in a larger maximum side bump (on the left in this case), while using a pinned SAF ( Figure 5A-5B configuration) or using a pinning SAF just below the sensor ( Figure 6A-6B configuration) will result in a significant reduction in side bump imbalance and maximum value.

[0050] Fig. 8A8 is a MFS view of a read head 800 according to another embodiment. Rather than using a pinned SAF shielding approach, the read head 800 uses the magnetic moment of a soft bias structure to ensure that any side bumps are minimized and symmetrical. In the read head 800, a first soft bias layer 810 has a first magnetic moment, and a second soft bias layer 812 has a second magnetic moment, and the first magnetic moment is different from the second magnetic moment.

[0051] For the read head 800, the fringing magnetic field (from the recess 404) added to the bias from the first soft bias layer 810 generates a first bias in the first free layer 406. The bias from the second soft bias layer 812 generates a second bias in the second free layer 408. The first bias and the second bias are substantially equal even though the magnetic moments of the first soft bias layer 810 and the second soft bias layer 812 are different. The different magnetic moments of the first soft bias layer 810 and the second soft bias layer 812 can be achieved by having different materials for these layers. More specifically, the first magnetic moment is smaller than the second magnetic moment.

[0052] Fig. 8A The configuration in contrast to read head 400, in which the magnetic moment of first soft bias layer 410 is substantially the same as the magnetic moment of second soft bias layer 412. As described above, in read head 400, the first bias is greater than the second bias due to the addition of the fringe magnetic field from recess 404 to the bias from first soft bias layer 410. Although this additive effect in the recess also exists in Fig. 8A However, the difference in magnetic moments of the first soft bias layer 810 and the second soft bias layer 812 compensates for this effect to equalize the bias difference between the first and second free layers and result in equal signal side bumps. Figure 8B is a graph illustrating the reduction of the side bump maximum and the shift of the bump imbalance toward zero when using different magnetic moments for the soft bias layer. More specifically, the moment of the first bias layer is less than the moment of the second soft bias layer (dM<0).

[0053] Fig.9A is a MFS view of a read head 900 according to another embodiment. Rather than using a pinned SAF shielding approach, the read head 900 varies the separation distance between the first and second free layers 406, 408 and the first and second soft bias layers 910, 912 to ensure that any underboost is minimized and symmetrical.

[0054] In the read head 900, the first soft bias layer 910 has an end 918 facing an end 920 of the first free layer 406. The ends 918, 920 are separated by a first distance by the insulating material 405. The second soft bias layer 912 has an end 924 facing an end 922 of the second free layer 408. The ends 922, 924 are separated by a second distance by the insulating material 405. The second distance is different from the first distance and is Fig.9AIn the illustrated embodiment, the second distance is less than the first distance. In addition, the AFC layer 807 is spaced apart from the DFL sensor stack portion by the second distance. In other words, both the second soft bias layer 912 and the AFC layer 807 have a greater width in the X direction at the MFS than the first soft bias layer 910. The difference in separation distance mitigates the fringe field effect of the recess 404 described above.

[0055] In some embodiments, the spacing is adjusted by partially removing the insulating material 405 from the vicinity of the second free layer 408 to obtain different separation distances. Fig. 9B and 9C is a diagram showing the right convex ( Fig. 9B ) and left convex ( Fig. 9C ) of the bump ratio. The more removals that occur (e.g. Fig. 9B As shown in the direction of the middle arrow, the smaller the second distance becomes, the stronger the bias of the second free layer 408 becomes, the smaller the difference between the bias of the second free layer 408 and the bias of the first free layer 406 becomes, the more balanced the bias becomes, and the smaller the side bump becomes. There is almost no effect on the first free layer 406, so there is no effect on the left bump ( Fig. 9C ), because the removal can occur after forming the first soft bias layer 910, so that the first soft bias layer 910 can protect the insulating material 405 between the first soft bias layer 910 and the first free layer 406. In some embodiments, the general process is to define the first free layer 406 and the second free layer 408 by material removal, deposit the insulating material 405 and the first soft bias layer 910, remove the insulating material on the sidewalls of the second free layer 408, and then deposit the AFC layer 807 and the second soft bias layer 910. In other embodiments, other manufacturing methods and configurations can be used, as long as the above-mentioned difference in separation distance is achieved to compensate for the recess edge field effect.

[0056] It is contemplated that pinned SAF shields can be combined with different magnetic moment options, different distance options, or both to obtain symmetrical underbumps. Similarly, it is contemplated that different magnetic moment options can be combined with different distance options to obtain symmetrical underbumps. By using SAF shields, adjusting the magnetic moment of the SB layer, and / or adjusting the spacing between the free layer and the SB layer of the DFL read head, the DFL underbumps are symmetrical and can be minimized.

[0057] In one embodiment, a magnetic read head includes: a synthetic antiferromagnetic (AFM) (SAF) shield; a first free layer disposed on the SAF shield; a barrier layer disposed on the first free layer; a second free layer disposed on the barrier layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer; a back bias structure recessed from the MFS; and a second shield disposed on the second free layer and the soft bias structure. The SAF shield includes: an AFM layer; a first magnetic layer disposed on the AFM layer; an antiferromagnetic coupling layer disposed on the first magnetic layer; and a second magnetic layer disposed on the antiferromagnetic coupling layer, wherein the second magnetic layer is disposed below the back bias structure. The SAF shield includes: an AFM layer; a first magnetic layer disposed on the AFM layer; an antiferromagnetic coupling layer disposed on the first magnetic layer; and a second magnetic layer disposed on the antiferromagnetic coupling layer, wherein the second magnetic layer has a stripe height from the MFS no greater than an amount by which the back bias structure is recessed from the MFS. The soft bias structure is disposed on the antiferromagnetic coupling layer. The SAF shield includes a recess. The SAF shield includes: an AFM layer; a first magnetic layer disposed on the AFM layer and having a first width in a cross-track direction at an MFS; an antiferromagnetic coupling layer disposed on the first magnetic layer; and a second magnetic layer disposed on the antiferromagnetic coupling layer and having a second width in a cross-track direction at the MFS, wherein the first width is greater than the second width. The first free layer has a third width at the MFS, and wherein the second width and the third width are substantially equal. A magnetic recording device including a magnetic read head is also contemplated.

[0058] In another embodiment, a magnetic read head includes: a first shield; a first free layer disposed on the first shield; a first insulating layer disposed on the first free layer; a second free layer disposed on the first insulating layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer, wherein the soft bias structure includes: a first soft bias layer having a first magnetic moment; and a second soft bias layer having a second magnetic moment different from the first magnetic moment; a back bias structure recessed from the MFS; and a second shield disposed on the second free layer and the soft bias structure. The second soft bias layer is disposed on the first soft bias layer, and wherein the second magnetic moment is greater than the first magnetic moment. The first shield includes a recess, and wherein a width of the recess at the MFS in the cross-track direction is substantially equal to a width of the first free layer at the MFS. The recess provides an additional bias to the first free layer, and wherein the additional bias plus the bias provided to the first free layer by the first soft bias layer is substantially equal to the bias provided to the second free layer by the second soft bias layer. The first soft bias layer includes a first magnetic material, wherein the second soft bias layer includes a second magnetic material different from the first magnetic material. The first soft bias layer is spaced a first distance from the first free layer, wherein the second soft bias layer is spaced a second distance from the second free layer, and wherein the first distance and the second distance are different. The first distance is greater than the second distance. A magnetic recording device including a magnetic read head is also contemplated.

[0059] In another embodiment, a magnetic read head includes: a first shield; a first free layer disposed on the first shield; a first insulating layer disposed on the first free layer; a second free layer disposed on the first insulating layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer, wherein the soft bias structure includes: a first soft bias layer spaced a first distance from the first free layer; and a second soft bias layer spaced a second distance from the second free layer, wherein the second distance is different from the first distance; a back bias structure recessed from the MFS; and a second shield disposed on the second free layer and the soft bias structure. The second distance is less than the first distance. The soft bias structure also includes a ruthenium layer disposed between the first soft bias layer and the second soft bias layer. The ruthenium layer is spaced a second distance from the second insulating layer disposed between the first free layer and the second free layer. The first soft bias layer has a first magnetic moment, wherein the second soft bias layer has a second magnetic moment, and wherein the first magnetic moment is substantially equal to the second magnetic moment. A magnetic recording device including a magnetic read head is also contemplated.

[0060] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the same is determined by the claims that follow.

Claims

1. A magnetic reading head, include: synthetic antiferromagnetic (AFM)(SAF) shielding; a first free layer disposed on the SAF shield; a barrier layer disposed on the first free layer; a second free layer disposed on the barrier layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer; a rear offset structure recessed from the MFS; and A second shield is disposed on the second free layer and the soft bias structure.

2. The magnetic reading head according to claim 1, in, The SAF shielding includes: AFM layer; a first magnetic layer disposed on the AFM layer; an antiferromagnetic coupling layer disposed on the first magnetic layer; and A second magnetic layer is disposed on the antiferromagnetic coupling layer, wherein the second magnetic layer is disposed below the back bias structure.

3. The magnetic reading head according to claim 1, in, The SAF shielding includes: AFM layer; a first magnetic layer disposed on the AFM layer; an antiferromagnetic coupling layer disposed on the first magnetic layer; and A second magnetic layer is disposed on the antiferromagnetic coupling layer, wherein a stripe height of the second magnetic layer from the MFS does not exceed an amount by which the back-bias structure is recessed from the MFS.

4. The magnetic reading head according to claim 3, in, The soft bias structure is arranged on the antiferromagnetic coupling layer.

5. The magnetic reading head according to claim 1, in, The SAF shield includes a recessed portion.

6. The magnetic reading head according to claim 1, in, The SAF shielding includes: AFM layer; a first magnetic layer disposed on the AFM layer and having a first width in a cross-track direction at the MFS; an antiferromagnetic coupling layer disposed on the first magnetic layer; and A second magnetic layer is disposed on the antiferromagnetic coupling layer and has a second width in the cross-track direction at the MFS, wherein the first width is greater than the second width.

7. The magnetic reading head according to claim 6, in, The first free layer has a third width at the MFS, and wherein the second width and the third width are substantially equal.

8. A magnetic recording device comprising the magnetic reading head according to claim 1.

9. A magnetic reading head, include: First shield; a first free layer disposed on the first shield; a first insulating layer disposed on the first free layer; a second free layer disposed on the first insulating layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer, wherein the soft bias structure comprises: a first soft bias layer having a first magnetic moment; and a second soft bias layer having a second magnetic moment different from the first magnetic moment; a rear biasing structure recessed from the MFS; and A second shield is disposed on the second free layer and the soft bias structure.

10. The magnetic reading head according to claim 9, in, The second soft bias layer is disposed on the first soft bias layer, and wherein the second magnetic moment is greater than the first magnetic moment.

11. The magnetic reading head according to claim 9, in, The first shield includes a recessed portion, and wherein a width of the recessed portion in the cross-track direction at the MFS is substantially equal to a width of the first free layer at the MFS.

12. The magnetic reading head according to claim 11, in, The recess provides an additional bias to the first free layer, and wherein the additional bias plus the bias provided to the first free layer by the first soft bias layer is substantially equal to the bias provided to the second free layer by the second soft bias layer.

13. The magnetic reading head according to claim 9, in, The first soft bias layer includes a first magnetic material, wherein the second soft bias layer includes a second magnetic material different from the first magnetic material.

14. The magnetic reading head according to claim 9, in, The first soft bias layer is spaced a first distance from the first free layer, wherein the second soft bias layer is spaced a second distance from the second free layer, and wherein the first distance and the second distance are different.

15. The magnetic reading head according to claim 14, in, The first distance is greater than the second distance.

16. A magnetic recording device comprising the magnetic reading head according to claim 9.

17. A magnetic reading head, include: First shield; a first free layer disposed on the first shield; a first insulating layer disposed on the first free layer; a second free layer disposed on the first insulating layer; a soft bias structure disposed laterally in a cross-track direction at a medium facing surface (MFS) adjacent to the first free layer and the second free layer, wherein the soft bias structure comprises: a first soft bias layer spaced a first distance from the first free layer; and a second soft bias layer spaced a second distance from the second free layer, wherein the second distance is different from the first distance; a rear biasing structure recessed from the MFS; and A second shield is disposed on the second free layer and the soft bias structure.

18. The magnetic reading head according to claim 17, in, The second distance is smaller than the first distance.

19. The magnetic reading head according to claim 17, in, The soft bias structure also includes a ruthenium layer disposed between the first soft bias layer and the second soft bias layer.

20. The magnetic reading head according to claim 19, in, The ruthenium layer is spaced apart from a second insulating layer disposed between the first free layer and the second free layer by the second distance.

21. The magnetic reading head according to claim 17, in, The first soft bias layer has a first magnetic moment, wherein the second soft bias layer has a second magnetic moment, and wherein the first magnetic moment is substantially equal to the second magnetic moment.

22. A magnetic recording device comprising the magnetic reading head according to claim 17.

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