Magnetic shield having improved resistance to the hard bias magnetic field

In one embodiment, a magnetic head includes a magnetoresistance effect sensor including a free layer, a hard bias magnetic film adapted for performing magnetic domain control of the free layer by biasing a magnetization direction of the free layer towards a predefined direction that is positioned on both sides of the free layer in a track-width direction, an upper shield positioned above the hard bias magnetic film and the magnetoresistance effect sensor; and an antiferromagnetic (AFM) layer positioned above the upper shield. The upper shield includes first and second upper shield layers, and an AFM coupling layer positioned between the first upper shield layer and the second upper shield layer that is adapted for antiferromagnetically coupling the first upper shield layer and the second upper shield layer, wherein a magnetization of the first upper shield layer is antiparallel with a magnetization of the hard magnetic bias layer.

FIELD OF THE INVENTION

The present invention relates to magnetic recording, and more particularly to a magnetic head having a tunneling magnetoresistance (TMR) sensor and a magnetic shield that has improved resistance to a hard bias magnetic field produced by a hard bias film of the magnetic head.

BACKGROUND

Typically, a hard bias film is positioned at an end of a free layer of a magnetic head, and is constructed to apply a hard bias magnetic field to the free layer. This hard bias magnetic field converts the magnetization of the free layer to a single magnetic domain, thereby suppressing noise. If the magnetization of the free layer is not converted to a single magnetic domain, but has a multitude of domains, noise is generated.

Conventionally, with increased recording density, the read gap, i.e., the vertical separation of the magnetic shield from the read sensor, is narrowed, with the consequence that the hard bias magnetic field is more readily absorbed by the magnetic shield, which causes the hard bias magnetic field to be decreased as a result of this absorption. As a result, noise such as Barkhausen noise is generated in the magnetic head, which is undesirable.

A portion of a magnetic head500is shown inFIG. 5according to the prior art. A conventional magnetic head500comprises a magnetic shield502, a protective layer504between the magnetic shield502and a hard bias film514, and a sensor512, such as a tunneling magnetoresistance (TMR) sensor. In some magnetic heads500, an insulating layer506, a first underlayer508and a second underlayer510may be positioned below the hard bias film514. As shown, magnetization513of the hard bias film514(the hard bias magnetic field) and magnetization503of the magnetic shield502are parallel (e.g., they have the same direction). This results in the hard bias magnetic field tending to be absorbed by the magnetic shield502, which also causes noise to occur.

Accordingly, it would be beneficial to have a magnetic head design which has a high recording density but which also reduces the amount of the hard bias magnetic field which is absorbed by the magnetic shield.

SUMMARY

In one embodiment, a magnetic head includes a magnetoresistance effect sensor including a free layer, a hard bias magnetic film positioned on both sides of the free layer in a track-width direction, wherein the hard bias magnetic film is adapted for performing magnetic domain control of the free layer by biasing a magnetization direction of the free layer towards a predefined direction, an upper shield positioned above the hard bias magnetic film and the magnetoresistance effect sensor; and an antiferromagnetic (AFM) layer positioned above the upper shield, wherein the upper shield includes a first upper shield layer, a second upper shield layer positioned above the first upper shield layer, and an AFM coupling layer positioned between the first upper shield layer and the second upper shield layer, the AFM coupling layer being adapted for antiferromagnetically coupling the first upper shield layer and the second upper shield layer, wherein a magnetization of the first upper shield layer is antiparallel with a magnetization of the hard magnetic bias layer.

In another embodiment, a method for forming a magnetic head includes forming a magnetoresistance effect sensor including a free layer, forming a hard bias magnetic film on both sides of the free layer in a track-width direction, wherein the hard bias magnetic film is adapted for performing magnetic domain control of the free layer by biasing a magnetization direction of the free layer towards a predefined direction, forming a first upper shield layer above the hard bias magnetic film and the magnetoresistance effect sensor, forming a second upper shield layer above the first upper shield layer, forming an AFM coupling layer between the first upper shield layer and the second upper shield layer, the AFM coupling layer being adapted for antiferromagnetically coupling the first upper shield layer and the second upper shield layer, wherein the first upper shield layer, the AFM coupling layer, and the second upper shield layer together form an upper shield, and forming an AFM layer above the upper shield, wherein a magnetization of the first upper shield layer is antiparallel with a magnetization of the hard magnetic bias layer.

Any of these embodiments may be implemented in a magnetic data storage system such as a disk drive system, which may include a magnetic head, a drive mechanism for passing a magnetic medium (e.g., hard disk) over the magnetic head, and a controller electrically coupled to the magnetic head.

DETAILED DESCRIPTION

The following description discloses several preferred embodiments of disk-based storage systems and/or related systems and methods, as well as operation and/or component parts thereof.

In one general embodiment, a magnetic head includes a magnetoresistance effect sensor including a free layer, a hard bias magnetic film positioned on both sides of the free layer in a track-width direction, wherein the hard bias magnetic film is adapted for performing magnetic domain control of the free layer by biasing a magnetization direction of the free layer towards a predefined direction, an upper shield positioned above the hard bias magnetic film and the magnetoresistance effect sensor; and an antiferromagnetic (AFM) layer positioned above the upper shield, wherein the upper shield includes a first upper shield layer, a second upper shield layer positioned above the first upper shield layer, and an AFM coupling layer positioned between the first upper shield layer and the second upper shield layer, the AFM coupling layer being adapted for antiferromagnetically coupling the first upper shield layer and the second upper shield layer, wherein a magnetization of the first upper shield layer is antiparallel with a magnetization of the hard magnetic bias layer.

In another general embodiment, a method for forming a magnetic head includes forming a magnetoresistance effect sensor including a free layer, forming a hard bias magnetic film on both sides of the free layer in a track-width direction, wherein the hard bias magnetic film is adapted for performing magnetic domain control of the free layer by biasing a magnetization direction of the free layer towards a predefined direction, forming a first upper shield layer above the hard bias magnetic film and the magnetoresistance effect sensor, forming a second upper shield layer above the first upper shield layer, forming an AFM coupling layer between the first upper shield layer and the second upper shield layer, the AFM coupling layer being adapted for antiferromagnetically coupling the first upper shield layer and the second upper shield layer, wherein the first upper shield layer, the AFM coupling layer, and the second upper shield layer together form an upper shield, and forming an AFM layer above the upper shield, wherein a magnetization of the first upper shield layer is antiparallel with a magnetization of the hard magnetic bias layer.

Referring now toFIG. 1, there is shown a disk drive100in accordance with one embodiment of the present invention. As shown inFIG. 1, at least one rotatable magnetic disk112is supported on a spindle114and rotated by a drive mechanism which may include a disk drive motor118. The magnetic recording on each disk is typically in the form of an annular pattern of concentric data tracks (not shown) on the disk112.

At least one slider113is positioned near the disk112, each slider113supporting one or more magnetic read/write heads121. As the disk rotates, slider113is moved radially in and out over disk surface122so that heads121may access different tracks of the disk where desired data are recorded and/or to be written. Each slider113is attached to an actuator arm119by means of a suspension115. The suspension115provides a slight spring force which biases slider113against the disk surface122. Each actuator arm119is attached to an actuator127. The actuator127as shown inFIG. 1may be a voice coil motor (VCM). The VCM comprises 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 controller129.

During operation of the disk storage system, the rotation of disk112generates an air bearing between slider113and disk surface122which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension115and supports slider113off and slightly above the disk surface by a small, substantially constant spacing during normal operation. Note that in some embodiments, the slider113may slide along the disk surface122.

The various components of the disk storage system are controlled in operation by control signals generated by controller129, such as access control signals and internal clock signals. Typically, control unit129comprises logic control circuits, storage (e.g., memory), and a microprocessor. The control unit129generates control signals to control various system operations such as drive motor control signals on line123and head position and seek control signals on line128. The control signals on line128provide the desired current profiles to optimally move and position slider113to the desired data track on disk112. Read and write signals are communicated to and from read/write heads121by way of recording channel125.

An interface may also be provided for communication between the disk drive and a host (integral or external) to send and receive the data and for controlling the operation of the disk drive and communicating the status of the disk drive to the host, all as will be understood by those of skill in the art.

In a typical head, an inductive write head includes a coil layer embedded in one or more insulation layers (insulation stack), the insulation stack being located between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write head. The pole piece layers may be connected at a back gap. Currents are conducted through the coil layer, which produce magnetic fields in the pole pieces. The magnetic fields fringe across the gap at the ABS for the purpose of writing bits of magnetic field information in tracks on moving media, such as in circular tracks on a rotating magnetic disk.

The second pole piece layer has a pole tip portion which extends from the ABS to a flare point and a yoke portion which extends from the flare point to the back gap. The flare point is where the second pole piece begins to widen (flare) to form the yoke. The placement of the flare point directly affects the magnitude of the magnetic field produced to write information on the recording medium.

FIG. 2Aillustrates, schematically, a conventional recording medium such as used with magnetic disc recording systems, such as that shown inFIG. 1. This medium is utilized for recording magnetic impulses in or parallel to the plane of the medium itself. The recording medium, a recording disc in this instance, comprises basically a supporting substrate200of a suitable non-magnetic material such as glass, with an overlying coating202of a suitable and conventional magnetic layer.

FIG. 2Bshows the operative relationship between a conventional recording/playback head204, which may preferably be a thin film head, and a conventional recording medium, such as that ofFIG. 2A.

FIG. 2Cillustrates, schematically, the orientation of magnetic impulses substantially perpendicular to the surface of a recording medium as used with magnetic disc recording systems, such as that shown inFIG. 1. For such perpendicular recording the medium typically includes an under layer212of a material having a high magnetic permeability. This under layer212is then provided with an overlying coating214of magnetic material preferably having a high coercivity relative to the under layer212.

FIG. 2Dillustrates the operative relationship between a perpendicular head218and a recording medium. The recording medium illustrated inFIG. 2Dincludes both the high permeability under layer212and the overlying coating214of magnetic material described with respect toFIG. 2Cabove. However, both of these layers212and214are shown applied to a suitable substrate216. Typically there is also an additional layer (not shown) called an “exchange-break” layer or “interlayer” between layers212and214.

In this structure, the magnetic lines of flux extending between the poles of the perpendicular head218loop into and out of the overlying coating214of the recording medium with the high permeability under layer212of the recording medium causing the lines of flux to pass through the overlying coating214in a direction generally perpendicular to the surface of the medium to record information in the overlying coating214of magnetic material preferably having a high coercivity relative to the under layer212in the form of magnetic impulses having their axes of magnetization substantially perpendicular to the surface of the medium. The flux is channeled by the soft underlying coating212back to the return layer (P1) of the head218.

FIG. 2Eillustrates a similar structure in which the substrate216carries the layers212and214on each of its two opposed sides, with suitable recording heads218positioned adjacent the outer surface of the magnetic coating214on each side of the medium, allowing for recording on each side of the medium.

FIG. 3Ais a cross-sectional view of a perpendicular magnetic head. InFIG. 3A, helical coils310and312are used to create magnetic flux in the stitch pole308, which then delivers that flux to the main pole306. Coils310indicate coils extending out from the page, while coils312indicate coils extending into the page. Stitch pole308may be recessed from the ABS318. Insulation316surrounds the coils and may provide support for some of the elements. The direction of the media travel, as indicated by the arrow to the right of the structure, moves the media past the lower return pole314first, then past the stitch pole308, main pole306, trailing shield304which may be connected to the wrap around shield (not shown), and finally past the upper return pole302. Each of these components may have a portion in contact with the ABS318. The ABS318is indicated across the right side of the structure.

Perpendicular writing is achieved by forcing flux through the stitch pole308into the main pole306and then to the surface of the disk positioned towards the ABS318.

FIG. 3Billustrates a piggyback magnetic head having similar features to the head ofFIG. 3A. Two shields304,314flank the stitch pole308and main pole306. Also sensor shields322,324are shown. The sensor326is typically positioned between the sensor shields322,324.

FIG. 4Ais a schematic diagram of one embodiment which uses looped coils410, sometimes referred to as a pancake configuration, to provide flux to the stitch pole408. The stitch pole then provides this flux to the main pole406. In this orientation, the lower return pole is optional. Insulation416surrounds the coils410, and may provide support for the stitch pole408and main pole406. The stitch pole may be recessed from the ABS418. The direction of the media travel, as indicated by the arrow to the right of the structure, moves the media past the stitch pole408, main pole406, trailing shield404which may be connected to the wrap around shield (not shown), and finally past the upper return pole402(all of which may or may not have a portion in contact with the ABS418). The ABS418is indicated across the right side of the structure. The trailing shield404may be in contact with the main pole406in some embodiments.

FIG. 4Billustrates another type of piggyback magnetic head having similar features to the head ofFIG. 4Aincluding a looped coil410, which wraps around to form a pancake coil. Also, sensor shields422,424are shown. The sensor426is typically positioned between the sensor shields422,424.

InFIGS. 3B and 4B, an optional heater is shown near the non-ABS side of the magnetic head. A heater (Heater) may also be included in the magnetic heads shown inFIGS. 3A and 4A. The position of this heater may vary based on design parameters such as where the protrusion is desired, coefficients of thermal expansion of the surrounding layers, etc.

FIG. 6depicts a portion of a magnetic head600for sensing a magnetization of a magnetic medium, in accordance with one embodiment. As an option, the present magnetic head600may be implemented in conjunction with features from any other embodiment listed herein, such as those described with reference to the otherFIGS. 1-5. Of course, however, such magnetic head600and others presented herein may be used in various applications and/or in permutations which may or may not be specifically described in the illustrative embodiments listed herein. Further, the magnetic head600presented herein may be used in any desired environment.

According to one embodiment, and with reference toFIG. 6, an upper magnetic shield602may be isolated using an AFM layer622, which may comprise ruthenium (Ru) or some other suitable material known in the art. The magnetization of the upper magnetic shield602may be antiferromagnetically coupled. Furthermore, the magnetization617of the upper magnetic shield602at a position that is closest to the hard bias film614(denoted as the first upper shield layer616) may be caused to be antiparallel (oriented in the opposite direction) to the magnetization613of the hard bias film614. This causes the upper magnetic shield602to absorb less of the hard bias magnetic field (HBF) emanating from the hard bias film614since it is more difficult for the upper magnetic shield602to absorb the HBF.

Referring again toFIG. 6, by making the magnetization617of the first layer of the upper magnetic shield616at a position that is closest to the hard bias film614antiparallel (oriented in the opposite direction) with respect to the magnetization613of the hard bias film614, it is more difficult for the HBF to be absorbed by the upper magnetic shield602. As a result, the magnetization613of the hard bias film614is increased. This technique does not affect the magnetization603of the second layer624of the upper magnetic shield602.

In one embodiment, a magnetic head600comprises a magnetoresistance effect sensor612comprising a free layer, a hard bias magnetic film614positioned on both sides of the free layer in a track-width direction (e.g., on the sides of the magnetoresistance effect sensor612as shown inFIG. 6), wherein the hard bias magnetic film614is adapted for performing magnetic domain control of the free layer by biasing a magnetization direction of the free layer towards a predefined direction which is often in alignment with the direction of magnetization of the hard bias magnetic film, an upper shield602positioned above the hard bias magnetic film614and the magnetoresistance effect sensor612, wherein the upper shield602comprises a first upper shield layer616, a second upper shield layer624positioned above the first upper shield layer616, and an AFM coupling layer622positioned between the first upper shield layer616and the second upper shield layer624. The AFM coupling layer622is adapted for antiferromagnetically coupling the first upper shield layer616and the second upper shield layer624. The magnetic head600also comprises an AFM layer618positioned above the upper shield602, wherein a magnetization617of the first upper shield layer616is antiparallel with a magnetization613of the hard magnetic bias layer614.

In various embodiments, the magnetic head600may further comprise a lower shield620positioned below the magnetoresistance effect sensor612and the hard bias magnetic film614, an insulating layer606positioned above the lower shield620and on both sides of the magnetoresistance effect sensor612in the track-width direction, a first underlayer608positioned above the insulating layer606and on both sides of the magnetoresistance effect sensor612in the track-width direction, and/or a second underlayer610positioned above the first underlayer608, below the hard bias magnetic film614, and on both sides of the magnetoresistance effect sensor612in the track-width direction.

In some further embodiments, any or all of the following may exist in the magnetic head600. An AFM coupling constant (Jex) of the upper shield602may be at least about 0.25 erg/cm2, the magnetoresistance effect sensor612may utilize tunneling magnetoresistance (TMR) to sense, the insulating layer606may comprise alumina, the first underlayer608may comprise NiTa, the second underlayer610may comprise CrMo, the hard bias magnetic film614may comprise CoCrPt, the first upper shield layer616and the second upper shield layer624may comprise NiFe, the AFM coupling layer622may comprise Ru, and/or the AFM layer618may comprise MnIr.

FIG. 7shows a method700for forming a magnetic head, in accordance with one embodiment. As an option, the present method700may be implemented to construct structures such as those shown inFIGS. 1-4and6. Of course, this method700and others presented herein may be used to form magnetic structures for a wide variety of devices and/or purposes which may or may not be related to magnetic recording. Further, the methods presented herein may be carried out in any desired environment. It should also be noted that any aforementioned features may be used in any of the embodiments described in accordance with the various methods.

In operation702, a magnetoresistance effect sensor is formed. The magnetoresistance effect sensor may be of any type, and in one embodiment it may be a TMR sensor which utilizes TMR to sense. In any embodiment, the magnetoresistance effect sensor comprises a free layer.

In operation704, a hard bias magnetic film is formed on both sides of the free layer in a track-width direction. The hard bias magnetic film is adapted for performing magnetic domain control of the free layer by controlling a magnetization direction of the free layer, as would be understood by one of skill in the art upon reading the present descriptions.

In one approach, the hard bias magnetic film may comprise CoCrPt or some other suitable material.

In operation706, a first upper shield layer is formed above the hard bias magnetic film and the magnetoresistance effect sensor. The first upper shield layer, in some embodiments, may comprise NiFe or some other suitable material.

In operation708, a second upper shield layer is formed above the first upper shield layer. The second upper shield layer, in some embodiments, may comprise NiFe or some other suitable material.

In operation710, an AFM coupling layer is formed between the first upper shield layer and the second upper shield layer, the AFM coupling layer being adapted for antiferromagnetically coupling the first upper shield layer and the second upper shield layer, as would be understood by one of skill in the art. The first upper shield layer, the AFM coupling layer, and the second upper shield layer together form an upper shield.

In preferred embodiments, a magnetization of the first upper shield layer is antiparallel with a magnetization of the hard magnetic bias layer.

In some approaches, the AFM coupling layer may comprise Ru or some other suitable material.

In operation712, an AFM layer is formed above the upper shield. In some embodiments, the AFM layer may comprise MnIr or some other suitable material.

According to one embodiment, an AFM coupling constant (Jex) of the upper shield may be at least about 0.25 erg/cm2. When the term “about” is used in this context, what is intended is plus or minus 10%.

In more approaches, the method700may further comprise forming a lower shield below the magnetoresistance effect sensor and the hard bias magnetic film. Furthermore, in some approaches, the method700may also include forming an insulating layer above the lower shield and on both sides of the magnetoresistance effect sensor in the track-width direction, forming a first underlayer above the insulating layer and on both sides of the magnetoresistance effect sensor in the track-width direction, and forming a second underlayer above the first underlayer, below the hard bias magnetic film, and on both sides of the magnetoresistance effect sensor in the track-width direction. In addition, a surface of the first underlayer may be oxidized prior to forming the second underlayer in some approaches.

According to one embodiment, the insulating layer may comprise alumina, the first underlayer may comprise NiTa, and the second underlayer may comprise CrMo.

A magnetic head600, according to one embodiment, was manufactured according to the following description, and with reference toFIG. 6. First, a TMR sensor612was formed above a lower shield620, the TMR sensor comprising a free layer. A resist was then formed full film above the TMR sensor612and the lower shield620, and then removed to expose the lower shield620by milling or some other suitable technique known in the art. An insulating layer606comprising an insulating material such as Al2O3was then formed above the lower shield620and along sides of the TMR sensor612. A first underlayer608comprising NiTa or some other suitable material known in the art was then formed above the insulating layer606. Next, a second underlayer610comprising CrMo or some other suitable material was formed above the first underlayer608, after oxidizing the surface of the first underlayer608using a suitable oxidizing gas, such as Ar+O2gas or some other suitable gas known in the art.

Then, hard magnetic material, such as CoCrPt, was formed above the second underlayer610and on both sides of the TMR sensor612as a hard bias film614. Then, a protective layer604was formed above the hard bias film614and on both sides of the TMR sensor612, the protective layer604comprising Cr, Ta, or some other suitable material or combination of materials known in the art in order to protect the hard bias film614. After this, the resist was removed from above the TMR sensor612and a first upper shield layer616comprising NiFe or some other suitable material known in the art was formed above the TMR sensor612and the protective layer604. Thereafter, an antiferromagnetic (AFM) coupling layer622comprising Ru or some other suitable material known in the art was formed on the first upper shield layer616, a second upper shield layer624comprising NiFe or some other suitable material known in the art was formed above the AFM coupling layer622, and an AFM layer comprising MnIr or some other suitable material known in the art was formed above the second upper shield layer624. Annealing was then conducted on the structure600in a magnetic field.

After this magnetic head was manufactured, an evaluation of the magnetization of the hard bias film (HBF) was conducted. For the upper shield602, NiFe/FeCo/Ru/FeCo/NiFe was employed. Also, MnIr was used for the AFM layer618that was formed on the upper shield602. The magnetization of the hard bias film614comprising CoCrPt and the magnetization of the first upper shield layer616were made antiparallel by annealing in a magnetic field.

FIG. 8shows the HBF when the AFM coupling constant (Jex) is varied. FromFIG. 8, it is seen that HBF has a dependency on Jex: e.g., when Jex is increased, HBF is increased. Furthermore, when Jex is at least about 0.25 erg/cm2, the HBF exceeds that of conventional structures. Jex may be increased by varying a film thickness of the AFM coupling layer (which may comprise Ru) between the first upper shield layer and the second upper shield layer, and shows a peak at a certain AFM coupling layer film thickness, assuming the AFM coupling layer comprises Ru. If the AFM coupling layer comprises a different material or a combination of Ru and some other material(s), then the peak may occur at a different thickness.

Also, Jex may be increased by varying a material of the layers that contact the AFM coupling layer (Ru). For example, Jex may be increased by employing a laminated film structure comprising a layer of NiFe and a layer of FeCo for the material of the first upper shield layer and second upper shield layer, respectively. In this embodiment, the FeCo material portion contacts the Ru film of the AFM coupling layer. This laminated film structure may be used in this embodiment instead of the single layer of NiFe, as in other structures.