Middle Shields Two-Dimensional Magnetic Recording Read Heads

The present disclosure generally relates to a dual free layer two dimensional magnetic recording read head. The read head comprises a first lower shield, a first sensor disposed over the first lower shield, a first upper shield disposed over the first sensor, a read separation gap (RSG) disposed on the first upper shield, a second lower shield disposed over the RSG, a second sensor disposed over the second lower shield, and a second upper shield disposed over the second sensor. In some embodiments, the second lower shield comprises a CoFeHf layer. In another embodiment, the second lower shield is a synthetic antiferromagnetic multilayer comprising a first shield layer, a second shield layer, and a CoFe/Ru/CoFe anti-ferromagnetic coupling layer or a Ru layer disposed therebetween, the first and second shield layers comprising NiFe and CoFe. In yet another embodiment, the second lower shield comprises layers of Ru, IrMn, and NiFe.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

Embodiments of the present disclosure generally relate to a dual free layer (DFL) two dimensional magnetic recording (TDMR) read head.

Description of the Related Art

Two dimensional magnetic recording (TDMR) read heads generally have a first sensor, oftentimes referred to as a lower reader and a second sensor, oftentimes referred to as an upper reader. The readers each have lower and upper shields with an insulating reader separation gap (RSG) therebetween. Both the top reader and the bottom reader are substantially identical, each comprising two free layers to be dual free layer (DFL) readers or sensors. In DFL reader operation, the two free layers or each reader are individually stabilized longitudinally by an anti-ferromagnetically coupled (AFC) soft bias (SB) and biased transversally by a permanent magnet or a rear hard bias (RHB) structure from the stripe back edge of the sensor.

A transverse bias field of TDMR read heads is determined by the remnant magnetization (Mr) times thickness (t) product (i.e., Mr*t) of the RHB structure. Since a saturation magnetization, Ms, and thus, the Mr of the RHB is quite limited (e.g., as compared to the Ms of the soft bias), a thicker RHB is generally required to achieve the desired transverse bias field. The thicker RHB needed results in an increased topography along the reader stripe height (SH) direction. The large topography poses a challenge to TDMR DFL reader designs, as the large topography limits the read head's capacity in down track spacing (DTS), somewhat offsetting the intrinsic narrow shield-shield (S-S) advantage of DFL readers. A wide DTS can cause the two readers to become misaligned at large skew, thereby limiting the fraction of the disk accessible in TDMR mode. As such, the lower reader and the upper reader may perform asymmetrically with different performance and reliability.

A middle shield (MS) in TDMR read heads serves as both a bottom shield and a bottom lead for the upper reader (UR). The middle shield contributes to down track spacing (DTS) physically, UR performance stability magnetically, and lead resistance electrically. The large topography of the lower reader (LR) and deep over milling (OM) of the UR, specifically from a TDMR dual free layer (DFL) read head, result in an uneven middle shield with varying magnetic shield thicknesses. A single NiFe layer has currently been used for the MS and is not robust magnetically due to its uneven thickness and the nature of NiFe known intrinsically with more magnetic domain activities. While the topography of the LR needs to be improved, a MS with constant magnetic thickness and magnetic robustness has to be used with simplicity for implementation in TDMR read head fabrications.

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

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a dual free layer (DFL) two dimensional magnetic recording (TDMR) read head. The read head comprises a first lower shield, a first sensor disposed over the first lower shield, a first upper shield disposed over the first sensor, a read separation gap (RSG) disposed on the first upper shield, a second lower shield disposed over the RSG, a second sensor disposed over the second lower shield, and a second upper shield disposed over the second sensor. In some embodiments, the second lower shield comprises a layer of CoFeHf. In another embodiment, the second lower shield comprises a first shield layer, a second shield layer, and a Ru layer disposed therebetween, where the first and second shield layers comprising CoFe and NiFe. In another embodiment, the second lower shield comprises a Ru layer, an IrMn layer, and a NiFe layer.

In one embodiment, a read head comprises a first lower shield, a first sensor disposed over the first lower shield, a second sensor disposed over the first sensor, a first upper shield disposed over the second sensor, and a middle shield disposed between the first sensor and the second sensor. The middle shield comprises a second upper shield disposed over the first sensor, a read separation gap disposed on the second upper shield, and a second lower shield disposed between the read separation gap and the second sensor, the second lower shield being a multilayer shield comprising a CoFe/Ru/CoFe anti-ferromagnetic coupling (AFC) layer or a Ru layer.

In another embodiment, a read head comprises a first lower shield, a first sensor disposed over the first lower shield, a first upper shield disposed over the first sensor, a read separation gap disposed on the first upper shield, the read separation gap being substantially planar, a second lower shield disposed over the read separation gap, the second lower shield comprising CoFeHf, a second sensor disposed over the second lower shield, and a second upper shield disposed over the second sensor.

In yet another embodiment, a read head comprises a first lower shield, a first dual free layer (DFL) sensor disposed over the first lower shield, a DFL second sensor disposed over the first DFL sensor, a first upper shield disposed over the second DFL sensor, and a substantially planar middle shield disposed between the first DFL sensor and the second DFL sensor. The substantially planar middle shield comprises a second upper shield disposed over the first DFL sensor, a read separation gap disposed on the second upper shield, a seed layer disposed on the read separation gap, the seed layer comprising Ru, NiFe, NiCr, SiO2, or combinations thereof, and a second lower shield disposed between and in contact with the seed layer and the second DFL sensor, the second lower shield being a multilayer shield comprising a first shield layer disposed on the seed layer, a CoFe/Ru/CoFe anti-ferromagnetic coupling (AFC) layer or a Ru layer disposed on the first shield layer, and a second shield layer disposed on the AFC layer or the Ru layer.

DETAILED DESCRIPTION

The present disclosure generally relates to a dual free layer (DFL) two dimensional magnetic recording (TDMR) read head. The read head comprises a first lower shield, a first sensor disposed over the first lower shield, a first upper shield disposed over the first sensor, a read separation gap (RSG) disposed on the first upper shield, a second lower shield disposed over the RSG, a second sensor disposed over the second lower shield, and a second upper shield disposed over the second sensor. In some embodiments, the second lower shield comprises a layer of CoFeHf. In another embodiment, the second lower shield comprises a first shield layer, a second shield layer, and a Ru layer disposed therebetween, where the first and second shield layers comprising CoFe and NiFe. In another embodiment, the second lower shield comprises a Ru layer, an IrMn layer, and a NiFe layer.

FIG.1illustrates a disk drive100embodying this disclosure. As shown, at least one rotatable magnetic media112is supported on a spindle114and rotated by a disk drive motor118. The magnetic recording on each disk is in the form of any suitable patterns of data tracks, such as annular patterns of concentric data tracks (not shown) on the magnetic media112.

At least one slider113is positioned near the magnetic media112, each slider113supporting one or more magnetic head assemblies121. As the magnetic media rotates, the slider113moves radially in and out over the media surface122so that the magnetic head assembly121may access different tracks of the magnetic media112where desired data are written. Each slider113is attached to an actuator arm119by way of a suspension115. The suspension115provides a slight spring force which biases the slider113toward the media surface122. Each actuator arm119is attached to an actuator means127. The actuator means127as shown inFIG.1may be a voice coil motor (VCM). The VCM includes a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by control unit129.

During operation of the disk drive100, the rotation of the magnetic media112generates an air bearing between the slider113and the media surface122which exerts an upward force or lift on the slider113. The air bearing thus counter-balances the slight spring force of suspension115and supports slider113off and slightly above the media112surface by a small, substantially constant spacing during normal operation. In the case of EAMR, a DC magnetic field generated from an assist element of the magnetic head assembly121enhances the write-ability so that the write element of the magnetic head assembly121may efficiently magnetize the data bits in the media112.

The above description of a typical magnetic disk storage system and the accompanying illustration ofFIG.1are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders.

It is to be understood that the embodiments discussed herein are applicable to a data storage device such as a hard disk drive (HDD) as well as a tape drive such as a tape embedded drive (TED) or an insertable tape media drive, such as those conforming to the LTO (Linear Tape Open) standards. An example TED is described in co-pending patent application titled “Tape Embedded Drive,” U.S. application Ser. No. 16/365,034, filed Mar. 31, 2019, assigned to the same assignee of this application, which is herein incorporated by reference. As such, any reference in the detailed description to an HDD or tape drive is merely for exemplification purposes and is not intended to limit the disclosure unless explicitly claimed. For example, references to disk media in an HDD embodiment are provided as examples only, and can be substituted with tape media in a tape drive embodiment. Furthermore, reference to or claims directed to magnetic recording devices or data storage devices are intended to include at least both HDD and tape drive unless HDD or tape drive devices are explicitly claimed.

FIG.2is a fragmented, cross sectional side view through the center of a read/write head200facing the magnetic media112, according to one embodiment. The read/write head200may correspond to the magnetic head assembly121described inFIG.1. The read/write head200includes a media facing surface (MFS)212, such as an air bearing surface (ABS), a magnetic write head210, and a magnetic read head211, and is mounted such that the MFS212is facing the magnetic media112. The read/write head200may be an energy-assisted magnetic recording (EAMR) head or a perpendicular magnetic recording (PMR) head. InFIG.2, the magnetic media112moves past the write head210in the direction indicated by the arrow232and the read/write head200moves in the direction indicated by the arrow234.

In some embodiments, the magnetic read head211is a SOT differential reader204located between the shields S1and S2. In other embodiments, the magnetic read head211is a magnetoresistive (MR) read head that includes an MR sensing element204located between MR shields S1and S2. In some other embodiments, the magnetic read head211is a magnetic tunnel junction (MTJ) read head that includes a MTJ sensing element204located between MR shields S1and S2. The magnetic fields of the adjacent magnetized regions in the magnetic media112are detectable by the MR (or MTJ) sensing element204as the recorded bits.

The write head210includes a return pole206, a main pole220, a trailing shield240, and a coil218that excites the main pole220. The coil218may have a “pancake” structure which winds around a back-contact between the main pole220and the return pole206, instead of a “helical” structure shown inFIG.2. A trailing gap (not shown) and a leading gap (not shown) may be in contact with the main pole and a leading shield (not shown) may be in contact with the leading gap. A recording magnetic field is generated from the main pole220and the trailing shield240helps making the magnetic field gradient of the main pole220steep. The main pole220may be a magnetic material such as a FeCo alloy. The main pole220may include a trailing surface222which may be parallel to a leading surface236of the trailing shield240. The main pole220may be a tapered write pole (TWP) with a trailing edge taper (TET) configuration. In one embodiment, the main pole220has a saturated magnetization (Ms) of 2.4 T and a thickness of about 300 nanometers (nm). The main pole220may comprise ferromagnetic materials, typically alloys of one or more of Co, Fe, and Ni. The trailing shield240may be a magnetic material such as NiFe alloy. In one embodiment, the trailing shield240has an Ms of about 1.2 T to about 1.6 T.

FIGS.3A-3Billustrate various views of a conventional dual free layer (DFL) two dimensional magnetic recording (TDMR) read head300comprising two sensors or readers302,304, according to one embodiment.FIG.3Aillustrates a media facing surface (MFS) view of the DFL TDMR read head300, andFIG.3Billustrates a cross-sectional view of the DFL TDMR read head300.

The DFL TDMR read head300comprises a first lower shield306, a first insulation layer308disposed on the first shield306, a first sensor or reader302disposed on the first lower shield306between portions of the first insulation layer308, a first upper shield312disposed over the first sensor302, a read separation gap (RSG)316disposed on the first upper shield312, a second lower shield318disposed on the RSG316, a second insulation layer320disposed on the second lower shield318, a second sensor or reader304disposed on the second lower shield318between portions of the second insulation layer320, and a second upper shield324disposed over the second sensor304. The RSG316may comprise AlOx, where x is an integer greater than or equal to 1. The first and second sensors302,304may each individually be tunnel magnetoresistance (TMR) sensors or magnetic tunnel junction (MTJ) sensors. The first and second sensors302,304may be interchangeably referred to as a first reader302and a second reader304throughout.

The first reader302comprises a seed layer330a, a first free layer332adisposed on the seed layer330a, a barrier layer334adisposed on the first free layer332a, a second free layer336adisposed on the barrier layer334a, and a cap layer338adisposed on the second free layer336a. The second reader304comprises a seed layer330b, a first free layer332bdisposed on the seed layer330b, a barrier layer334bdisposed on the first free layer332b, a second free layer336bdisposed on the barrier layer334b, and a cap layer338bdisposed on the second free layer336b.

A first soft bias layer310is disposed on the first insulation layer308for the first reader302and an anti-ferromagnetically coupled (AFC) layer314ais disposed between the first soft bias layer310and a second soft bias layer311. Similarly, a first soft bias layer322is disposed on the first insulation layer320for the second reader and an AFC layer314bis disposed between the first soft bias layer322and a second soft bias layer323. The first upper shield312and the second upper shield324may each individually comprise a magnetic material similar to the soft bias material, such as NiFe, NiFe/CoFe laminates, NiFe/NiFeCr laminates, or NiFe/W laminates, for example (“/” as used here denotes separate layers in a multi-layer stack). The first upper shield312and the second upper shield324may also each individually comprise a magnetic material similar to the soft bias material exchange biased by an antiferromagnet, such as IrMn, IrCrMn. The first upper shield312and the second upper shield324connect seamlessly to the second soft bias layers311,323, respectively. The first insulation layer308extends in the y-direction on each side of the first sensor302to prevent the first sensor302from contacting the first soft bias layer310, the AFC layer314a, and the second soft bias layer311. Similarly, the first insulation layer320extends in the y-direction on each side of the second sensor304to prevent the second sensor304from contacting the second soft bias layer322, and the AFC layer314b, and the second soft bias layer323. The AFC layers314aand314bcomprise a CoFe/Ru/CoFe tri-layer.

As shown inFIG.3B, a down-track spacing (DTS)340between the first barrier layer334aof the first sensor302and the second barrier layer334bof the second sensor304is about 90 nm to about 95 nm. A first rear hard bias (RHB) structure342ais disposed behind the first reader302, recessed from the MFS in the z-direction. A second insulation layer366ais disposed between the first RHB structure342aand the first reader302, and between the first RHB structure342aand the first lower shield306. A third insulation layer344ais disposed behind the first RHB structure342a. The first RHB structure342aand the second insulation layer366aextend above the first sensor302a distance354in the y-direction of about 10 nm to about 15 nm. The first RHB structure342aand the second insulation layer366aextend below the first sensor302a distance352in the −y-direction of about 5 nm to about 10 nm. The first, second, and third, insulation layers308,366a, and344amay each individually comprise MgO, AlOx, SiNx, SiOx and their laminates, where x is an integer greater than or equal to 1.

A second RHB structure342bis disposed behind the second reader304, recessed from the MFS in the z-direction. A second insulation layer366bis disposed between the second RHB structure342band the second reader304, and between the second RHB structure342band the second lower shield318. The third insulation layer344bis disposed behind the first RHB structure342b. The second RHB structure342bextends below the second sensor304a distance356in the −y-direction of about 5 nm to about 10 nm. The first RHB structure342aand the second insulation layer366aextending above the first sensor302the distance354, and the second RHB structure342bextending below the second sensor304the distance356, causes the DTS between the sensors302,304to widen in the y-direction.

Because the first RHB structure342aand the second insulation layer366aextend above the first sensor302the distance354, neither the RSG316nor the first upper shield312is linear in the z-direction. As a result, the RSG316comprises a first portion316adisposed at the MFS extending in the z-direction, a second portion316bextending in the yz-direction, and a third portion316cextending in the z-direction that is unaligned with the first portion316ain the y-direction. Similarly, the first upper shield312comprises a first portion312adisposed at the MFS extending in the z-direction, a second portion312bextending in the yz-direction, and a third portion312cextending in the z-direction that is unaligned with the first portion312ain the y-direction. Additionally, the second lower shield318varies in thickness in the y-direction. A first portion318aof the second lower shield318aligned with the second sensor304in the y-direction has a first thickness360of about 30 nm to about 35 nm greater than a second thickness358of about 10 nm to about 15 nm of a second portion318bof the second lower shield318disposed between the RSG316and the second insulation layer366b.

FIGS.4A-4Billustrate various views of a DFL TDMR read head400comprising two sensors or readers302,304, according to one embodiment.FIG.4Aillustrates an MFS view of the DFL TDMR read head400, andFIG.4Billustrates a cross-sectional view of the DFL TDMR read head400. The DFL TDMR read head400ofFIGS.4A-4Bmay be within the disk drive100ofFIG.1. The DFL TDMR read head400ofFIGS.4A-4Bmay be the magnetic read head211ofFIG.2. The DFL TDMR read head400is similar to the DFL TDMR read head300ofFIGS.3A-3B; however the first RHB structure442a, the second insulation layer466a, the first upper shield412, the RSG416, the second lower shield418, the second RHB structure442b, and the second insulation layer466bvary. The first upper shield412, the RSG416, the second lower shield418may collectively be referred to herein as middle shields415.

Like the DFL TDMR read head300ofFIGS.3A-3B, the DFL TDMR read head400comprises the first sensor or reader302and the second sensor or reader304. A first upper shield412is disposed over the first reader302and the second soft bias layer311. As shown inFIG.4B, a first surface443aof the first RHB structure442adisposed adjacent to the first upper shield412is substantially flush or aligned with a first surface402aof the first reader302. In other words, the first RHB structure442aand the second insulating layer466aare substantially flush or aligned with the top surface402aof the cap layer338aof the first sensor302in the z-direction. Similarly, a first surface443bof the second RHB structure442bis substantially flush or aligned with a first surface404aof the second reader304in the z-direction. In other words, the second RHB structure442bis substantially flush or aligned with the bottom surface404aof the seed layer330bof the second sensor304in the z-direction.

Rather than the first RHB structure442aextending above the first reader302in the y-direction, the first RHB structure442ais recessed further into the first lower shield306in the −y-direction than the first RHB structure342aof the DFL TDMR read head300ofFIGS.3A-3B. The first RHB structure442aof the read head400is recessed into the first lower shield306a distance452of about 15 nm to about 20 nm, which is greater than the distance352ofFIGS.3A-3B. Because the first RHB structure442ais substantially flush or aligned with the first reader302, the first upper shield412and the RSG416of the DFL TDMR read head400each extends substantially linearly along the z-axis from the MFS into the read head400such that the first upper shield412and the RSG416are planar.

Additionally, because the first upper shield412and the RSG416of the DFL TDMR read head400are each planar or extend substantially linearly along the z-axis, the second lower shield418comprises only two portions. As shown inFIG.4B, a first portion419aof the second lower shield418disposed at the MFS adjacent to the second reader304has a first thickness460in the y-direction of about 20 nm to about 30 nm, and a second portion419bof the second lower shield418disposed between the RSG416and the second insulation layer444bhas a second thickness458in the y-direction of greater than or equal to about 10 nm, such as about 15 nm to about 20 nm.

Comparing the second lower shield418of the read head400to the second lower shield318of the read head300, the first thickness360of the first portion318aof the second lower shield318of the read head300and the second thickness358of the second portion318bof the second lower shield318of the read head300differ in thickness by about 15 nm to about 25 nm. However, the first portion419aand the second portion419bof the second lower shield418of the read head400only differ in thickness by about 5 nm to about 10 nm. As such, the DTS440between the first sensor302and the second sensor304in the read head400is between about 75 nm to about 85 nm, which is less than the DTS340of the DFL TDMR read head300ofFIGS.3A-3B.

Because the first surface443aof the first RHB structure442ais aligned with the first surface402aof the first sensor302, and because the first surface443bof the second RHB structure442bis aligned with the first surface404aof the second sensor304, the first and second sensors or readers302,304are physically asymmetric, where a bulk or majority of the first RHB structure442ais disposed below (i.e., the −y-direction) the first sensor302, and where a bulk or majority of the second RHB structure442bis disposed above (i.e., the y-direction) the second sensor304. As such, the DTS440between the first and second readers302,304is decreased, enabling a larger fraction of the disk to be operated in TDMR mode hence improving the performance and reliability, both magnetically and electronically, of the read head400.

FIGS.5A-5Dillustrate MFS views of various embodiments of middle shields415a,415b,415c,415dutilized in the read head400ofFIGS.4A-4B. Each middle shield415a,415b,415c,415dofFIGS.5A-5Dmay be individually used as the middle shield415in the read head400ofFIGS.4A-4B. While not shown inFIGS.5A-5D, each middle shield415a,415b,415c,415dmay further comprise the first upper shield412ofFIGS.4A-4Bdisposed below the RSG416. In some embodiments, each middle shield415a,415b,415c,415dmay be the second lower shield418of the read head400ofFIGS.4A-4B.

The middle shield415aofFIG.5Aillustrates an embodiment of a pinned middle shield415a. The pinned middle shield415acomprises the RSG416, a middle shield (MS) seed layer417disposed on the RSG416, and a multilayer shield418adisposed on the MS seed layer417. The multilayer shield418amay be the second lower shield418ofFIGS.4A-4B. The RSG416may comprise Al2O3. The MS seed layer417may comprise two layers, an underlayer serving as chemical mechanical polishing (CMP) stopping layer during the planarization post MS seed depositions, and a seed layer composed of magnetic or non-magnetic metallic materials. A Ru/NiFe bilayer is used as a MS seed layer417in one embodiment, where Ru is used as an underlayer and NiFe is used as is the seed layer. The underlayer of the MS seed layer417can also be Ru and/or SiO2, and may have a thickness in the y-direction of about 20 Å to about 30 Å. The seed layer of the MS seed layer417can also be NiFe and/or NiCr, and may have a thickness in the y-direction of about 80 Å to about 150 Å. In some embodiments, the MS seed layer417may be considered part of the multilayer shield418a.

The multilayer shield418acomprises a seed layer550disposed on the MS seed layer417, an antiferromagnetic (AFM) layer552disposed on the seed layer550, and a pinned layer554disposed on the AFM layer552. The seed layer550comprises Ta, Ru, NiCr, or NiFe, or combinations thereof, the AFM layer552comprises IrMn, and the pinned layer554comprises NiFe, Co, CoFe, or combinations thereof. The seed layer550has a thickness556in the y-direction of about 15 Å to about 30 Å, the AFM layer552has a thickness558in the y-direction of about 40 Å to about 60 Å, and the pinned layer554has a thickness560in the y-direction of about 150 Å to about 300 Å.

The middle shield415bofFIG.5Bcomprises the RSG416, the MS seed layer417disposed on the RSG416, and a shield418bdisposed on the MS seed layer417. The shield418bmay be the second lower shield418ofFIGS.4A-4B. The RSG416may comprise Al2O3. The MS seed layer417may comprise a Ru/NiFe bilayer in one embodiment, and a NiCr single layer in another embodiment. The thickness of the MS seed layer417may have a thickness in the y-direction of about 50 Å to about 150 Å. In some embodiments, the MS seed layer417may be considered part of the shield418b. As a comparison, a shield (like the shield418bshown) comprises NiFe in prior art. The shield418bcan also comprise CoFeHf in another embodiment. The shield418bhas a thickness562in the y-direction of about 200 Å to about 250 Å. CoFeHf is magnetically soft due to being amorphous or microcrystalline in nature. CoFeHf has a high anisotropic magnetic field (Hk). For example, as shown below in the chart650ofFIG.6B, CoFeHf has a Hk of about 63 Oe, whereas NiFe has a Hk of about 4 Oe.

The middle shield415cofFIG.5Ccomprises the RSG416, the MS seed layer417disposed on the RSG416, and a synthetic antiferromagnetic (SAF) multilayer shield418cdisposed on the MS seed layer417. The multilayer shield418cmay be the second lower shield418ofFIGS.4A-4B. The RSG416may comprise Al2O3. The MS seed layer417may comprise Ru/NiFe, Ru/NiCr, SiO2/NiFe, or SiO2/NiCr bilayers, or NiCr as a single layer. The Ru or SiO2underlayer of the MS seed layer417may have a thickness in the y-direction of about 20 Å to about 30 Å, and the NiFe or NiCr seed layer of the MS seed layer417may have a thickness in the y-direction of about 40 Å to about 70 Å. In some embodiments, the MS seed layer417may be considered part of the multilayer shield418c.

The multilayer shield418ccomprises a first shield layer (SL1)564, an anti-ferromagnetic coupling (AFC) layer or a single Ru layer566disposed on the first shield layer564, and a second shield layer (SL2)568disposed on the AFC layer or the Ru layer566. The SL1564comprises NiFe, CoFe, and/or combinations thereof, and has a total thickness570in the y-direction of about 40 Å to about 60 Å. The layer566comprises an AFC CoFe/Ru/CoFe trilayer, or a Ru single layer and has a thickness572in the y-direction of about 28 Å, with about 10 Å for each CoFe layer, and about 8 Å for the Ru layer. The SL2568comprises NiFe, CoFe, and combinations thereof, and has a total thickness574in the y-direction of about 150 Å to about 200 Å.

The middle shield415dofFIG.5Dcomprises the RSG416, the MS seed layer417disposed on the RSG416, and a SAF multilayer shield418ddisposed on the MS seed layer417. The multilayer shield418dmay be the second lower shield418ofFIGS.4A-4B. The RSG416may comprise Al2O3. The MS seed layer417may comprise Ru/NiFe, Ru/NiCr, SiO2/NiFe, or SiO2/NiCr bilayers, or a NiCr single layer. The Ru or SiO2underlayer of the MS seed layer417may have a thickness in the y-direction of about 20 Å to 30 Å, and the NiFe or NiCr seed layer of the MS seed layer417may have a thickness in the y-direction of about 40 Å to about 70 Å. In some embodiments, the MS seed layer417may be considered part of the multilayer shield418d.

The multilayer shield418dcomprises a first shield layer (SL1)576, an anti-ferromagnetic coupling (AFC) layer or a single Ru layer578disposed on the first shield layer576, and a second shield layer (SL2)580disposed on the AFC layer or the Ru layer578. The SL1576comprises NiFe, CoFe, and/or combinations thereof, and has a total thickness582in the y-direction of about 90 Å to about 110 Å. The layer578comprises an AFC CoFe/Ru/CoFe trilayer or a Ru single layer, and has a thickness584in the y-direction of about 28 Å, with about 10 Å for each CoFe layer and about 8 Å for the Ru layer. The SL2580comprises NiFe, CoFe, and/or combinations thereof, and has a total thickness586in the y-direction of about 120 Å to about 160 Å. The multilayer shield418dofFIG.5Dvaries from the multilayer shield418cofFIG.5Cin that the SL1576of multilayer shield418dis much larger than the SL1564, where the thickness582of the SL1576of multilayer shield418dis about equal to the thickness586of the SL2580.

Each middle shield415a,415b,415c, and415dofFIGS.5A-5Dis magnetically robust and have a high magnetic anisotropy. Multilayer shields415cand415dare two variations from one embodiment of a SAF middle shield with different AFC positions or Ru positions along the y-direction. As such, read heads utilizing one of the middle shields415a,415b,415c, and415dhave improved signal to noise ratios, error rates and higher areal density capacities (ADC).

FIG.6Aillustrates a chart600comparing various SAF middle shields602,604,606,608,610, according to one embodiment, with the middle shield seed layer being considered part of the middle shields. Each of the middle shields602,604,606,608,610shown in the chart600may be individually utilized in the read head400ofFIGS.4A-4B.

The chart600compares various different embodiments of middle shields602-610that are each magnetically robust and have a high magnetic anisotropy. In each middle shield602-610, the first Ru layer and a portion of the first NiFe layer may be the MS seed layer417ofFIGS.5A-5D. Middle shields602,606,608, and610are similar; however, the thicknesses of the various NiFe layers within each vary.

The middle shield602comprises a first Ru layer of about 30 Å, a first NiFe layer of about 80 Å disposed on the first Ru layer, a first CoFe layer of about 10 Å disposed on the first NiFe layer, a second Ru layer of about 8 Å disposed on the first CoFe layer, a second CoFe layer of about 10 Å disposed on the second Ru layer, and a second NiFe layer of about 260 Å disposed on the second CoFe layer. The middle shield602may be the middle shield415cofFIG.5C, where the second Ru layer is the Ru layer566. The middle shield604comprises a first Ru layer of about 30 Å, a first NiFe layer of about 110 Å disposed on the first Ru layer, a second Ru layer of about 8 Å disposed on the first NiFe layer, and a second NiFe layer of about 215 Å disposed on the second Ru layer.

The middle shield606comprises a first Ru layer of about 30 Å, a first NiFe layer of about 100 Å disposed on the first Ru layer, a first CoFe layer of about 10 Å disposed on the first NiFe layer, a second Ru layer of about 8 Å disposed on the first CoFe layer, a second CoFe layer of about 10 Å disposed on the second Ru layer, and a second NiFe layer of about 205 Å disposed on the second CoFe layer. The middle shield608comprises a first Ru layer of about 30 Å, a first NiFe layer of about 130 Å disposed on the first Ru layer, a first CoFe layer of about 10 Å disposed on the first NiFe layer, a second Ru layer of about 8 Å disposed on the first CoFe layer, a second CoFe layer of about 10 Å disposed on the second Ru layer, and a second NiFe layer of about 175 Å disposed on the second CoFe layer. The middle shield610comprises a first Ru layer of about 30 Å, a first NiFe layer of about 150 Å disposed on the first Ru layer, a first CoFe layer of about 10 Å disposed on the first NiFe layer, a second Ru layer of about 8 Å disposed on the first CoFe layer, a second CoFe layer of about 10 Å disposed on the second Ru layer, and a second NiFe layer of about 155 Å disposed on the second CoFe layer. The middle shield610may be the middle shield415dofFIG.5D, where the second Ru layer is the Ru layer578.

In the chart600, column612identifies the middle shields602-610, column614shows the various film layers of each middle shield602-610and their respective thicknesses in Å, column616shows a change in thickness (ΔThk) in Å between the second and the first NiFe layers, column618shows the antiferromagnetic coupling strength (JRu) in erg/cm2, and column620shows the net moment (Δm) between the second and the first NiFe layers in mem u/cm2.

As shown in column618, middle shield604, which does not comprise any CoFe layers, has the lowest coupling strength of about 0.07 erg/cm2. However, middle shields602,606,608, and610all have relatively high coupling strengths of around 0.4 erg/cm2. Additionally, middle shield610, which has the lowest ΔThk also has the lowest Δm, whereas the middle shields602,604, and606each have a higher Δm and a higher ΔThk. The Δm or the ΔThk of the middle shield is not limited to only positive values, as described by afore-illustrated embodiments, and its value can also be zero or negative in some other embodiments.

FIG.6Billustrates a chart650comparing a middle shield comprising CoFeHf to a conventional middle shield comprising only NiFe, according to one embodiment. The middle shield comprising CoFeHf may be the middle shield415bofFIG.5B. As shown in the chart650, post annealing of the read head, the middle shield comprising CoFeHf has a significantly higher high anisotropic magnetic field (Hk), about 63 Oe, than the middle shield comprising only NiFe, about 4 Oe.

FIGS.7A-7Cillustrate magnetic hysteresis or magnetization versus magnetic field (M-H) loops700,750,775comparing the saturated magnetization (Bs) in nano Weber (nW) versus the magnetic field in Oe, according to various embodiments. The M-H loop700ofFIG.7Aillustrates a conventional middle shield comprising only NiFe, like discussed above inFIG.6B, the M-H loop750ofFIG.7Billustrates the middle shields600-610of chart600ofFIG.6A, and the M-H loop775illustrates the middle shield comprising CoFeHf, such as the middle shield415bofFIG.5B.

As shown in the M-H loop700, when a magnetic field is applied, the magnetic response of the conventional middle shield comprising only NiFe is hysteretic along the easy axis and has a magnetic anisotropy field (Hk) about 5 Oe measured along the hard axis. Comparatively, each of the middle shields602-610shown in the M-H loop750have a non-hysteretic magnetic response with saturation at fields about −100 Oe or about 100 Oe in one embodiment, and about −1300 Oe or about 1300 Oe in other embodiments, and the middle shield comprising CoFeHf shown in the M-H loop775has a magnetic anisotropy field of about 60 Oe measured along the hard axis. Thus, each middle shield602-610and the middle shield comprising CoFeHf all achieve a higher magnetic anisotropy field than a conventional middle shield comprising only NiFe.

Thus, a middle shield comprising IrMn, a middle shield comprising CoFeHf, and a multilayer middle shield comprising a Ru layer are each magnetically robust and have a high magnetic anisotropy. As such, read heads utilizing one of such middle shields have improved signal to noise ratio, error rates and a higher ADC.

In one embodiment, a read head comprises a first lower shield, a first sensor disposed over the first lower shield, a second sensor disposed over the first sensor, a first upper shield disposed over the second sensor, and a middle shield disposed between the first sensor and the second sensor. The middle shield comprises a second upper shield disposed over the first sensor, a read separation gap disposed on the second upper shield, and a second lower shield disposed between the read separation gap and the second sensor, the second lower shield being a multilayer shield comprising a CoFe/Ru/CoFe anti-ferromagnetic coupling (AFC) layer or a Ru layer.

The second lower shield further comprises a first shield layer and a second shield layer, the AFC layer or the Ru layer being disposed between the first shield layer and the second shield layer. The first shield layer and the second shield layer each individually comprises NiFe, CoFe, and combinations thereof. The second shield layer has a greater thickness than the first shield layer. The first shield layer has a thickness substantially equal to or smaller than the second shield layer. The second upper shield and the read separation gap are substantially planar, extending into the read head substantially perpendicular to a media facing surface. The second lower shield comprises the Ru layer, and the second lower shield further comprises an antiferromagnetic (AFM) layer disposed on the Ru layer, and a pinned layer disposed on the AFM layer. A thickness of the AFM layer is greater than a thickness of the Ru layer, and wherein a thickness of the pinned layer is greater than the thickness of the AFM layer. A magnetic recording device comprises the read head.

In another embodiment, a read head comprises a first lower shield, a first sensor disposed over the first lower shield, a first upper shield disposed over the first sensor, a read separation gap disposed on the first upper shield, the read separation gap being substantially planar, a second lower shield disposed over the read separation gap, the second lower shield comprising CoFeHf, a second sensor disposed over the second lower shield, and a second upper shield disposed over the second sensor.

The read head further comprises a seed layer disposed between the second lower shield and the read separation gap, the second lower shield having a greater thickness than the seed layer. The second lower shield comprises a layer of CoFeHf having a thickness of about 200 Å to about 300 Å. The first sensor and the second sensor are each a dual free layer sensor. The read head further comprises a first rear hard bias (RHB) structure disposed adjacent to the first sensor, the first sensor being disposed at a media facing surface (MFS) and the first RHB structure being recessed from the MFS, and a second RHB structure disposed adjacent to the second sensor, the second sensor being disposed at the MFS and the second RHB structure being recessed from the MFS. The first upper shield, the read separation gap, and the second lower shield are disposed between the first RHB structure and the second RHB structure. A magnetic recording device comprises the read head.

In yet another embodiment, a read head comprises a first lower shield, a first dual free layer (DFL) sensor disposed over the first lower shield, a DFL second sensor disposed over the first DFL sensor, a first upper shield disposed over the second DFL sensor, and a substantially planar middle shield disposed between the first DFL sensor and the second DFL sensor. The substantially planar middle shield comprises a second upper shield disposed over the first DFL sensor, a read separation gap disposed on the second upper shield, a seed layer disposed on the read separation gap, the seed layer comprising Ru, NiFe, NiCr, SiO2, or a combination thereof, and a second lower shield disposed between and in contact with the seed layer and the second DFL sensor, the second lower shield being a synthetic antiferromagnetic multilayer shield comprising a first shield layer disposed on the seed layer, a CoFe/Ru/CoFe anti-ferromagnetic coupling (AFC) layer or a Ru layer disposed on the first shield layer, and a second shield layer disposed on the AFC layer or the Ru layer.

The first shield layer and the second shield layer are each an individually single or multilayer structure comprising NiFe, CoFe, and combinations thereof with the middle shield seed being considered part of the first shield layer. A thickness of the AFC layer or the Ru layer is less than the thickness of the first shield layer. The AFC layer or the Ru layer has a thickness of about 8 Å, the first shield layer has a thickness of about 80 Å to about 160 Å, and the second shield layer has a thickness of about 160 Å to about 260 Å. A magnetic recording device comprises the read head.