The present invention relates to magnetic data storage devices, and more particularly, this invention relates to a magnetic data storage device that utilizes a tunneling magnetoresistive (TMR) sensor having a soft bias layer.
The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
The further miniaturization of the various components, however, presents its own set of challenges and obstacles. As areal density increases the read transducers need to be produced to be smaller and closer together, which results in cross-talk, interference, and/or degradation of performance of the various components, such as sensors, within the magnetic heads.
An apparatus according to one embodiment includes a read sensor. The read sensor has an antiferromagnetic layer (AFM), a first antiparallel magnetic layer (AP1) positioned above the AFM layer in a first direction oriented along a media-facing surface and perpendicular to a track width direction, a non-magnetic layer positioned above the AP1 in the first direction, a second antiparallel magnetic layer (AP2) positioned above the nonmagnetic layer in the first direction, a barrier layer positioned above the AP2 in the first direction, and a free layer positioned above the barrier layer in the first direction. A soft bias layer is positioned behind at least a portion of the free layer in an element height direction normal to the media-facing surface, the soft bias layer including a soft magnetic material configured to compensate for a magnetic coupling of the free layer with the AP2.
A method for forming a sensor according to one embodiment includes forming a first antiparallel magnetic layer (AP1), forming a second antiparallel magnetic layer (AP2) above the AP1 in a first direction oriented along a media-facing surface and perpendicular to a track width direction, forming a barrier layer above the AP2 in the first direction, and forming a free layer above the barrier layer in the first direction, wherein the AP1, the AP2, the free layer, and the barrier layer together form a read sensor. A soft bias layer is formed behind at least a portion of the free layer in an element height direction normal to the media-facing surface, the soft bias layer having a soft magnetic material configured to compensate for a magnetic coupling of the free layer with the AP2.
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.
Other aspects and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings.
The following description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations.
Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as web as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc.
It must also be noted that, as used in specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified.
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, an apparatus includes a read sensor having an antiferromagnetic layer (AFM), a first antiparallel magnetic layer (AP1) positioned above the AFM layer in a first direction oriented along a media-facing surface and perpendicular to a track width direction, a non-magnetic layer positioned above the AP1 in the first direction, a second antiparallel magnetic layer (AP2) positioned above the non-magnetic layer in the first direction, a barrier layer positioned above the AP2 in the first direction and a free layer positioned above the barrier layer in the first direction. A soft bias layer is positioned behind at least a portion of the free layer in an element height direction normal to the media facing surface, the soft bias layer including a soft magnetic material configured to compensate for a magnetic coupling of the free layer with the AP2.
In another general embodiment, a method tier forming a sensor includes forming a first antiparallel magnetic layer (AP1), forming a second antiparallel magnetic layer (AP2) above the AP1 in a first direction oriented along a media-facing surface and perpendicular to a track width direction, forming a barrier layer above the AP2 in the first direction, and forming a free layer above the barrier layer in the first direction, wherein the AP1, the AP2, the free layer, and the barrier layer together form a read sensor. A soft bias layer is formed behind at least a portion of the free layer in an element height direction normal to the media-facing surface, the soft bias layer having a soft magnetic material configured to compensate for a magnetic coupling of the free layer with the AP2.
Referring now to
At least one slider 113 is positioned near the disk 112, each slider 113 supporting one or more magnetic read/write portions 121, e.g., a magnetic head according to any of the approaches described and/or suggested herein. As the disk rotates, slider 113 is moved radially in and out over disk surface 122 so that portions 121 may access different tracks of the disk where desired data are recorded and/or to be written. Each slider 113 is attached to an actuator arm 119 by means of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator 127. The actuator 127 as shown in
During operation of the disk storage system, the rotation of disk 112 generates an air bearing between slide 113 and disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation. Note that in some embodiments, the slider 113 may slide along the disk surface 122.
The various components of the disk storage system are controlled in operation by control signals generated by controller 129, such as access control signals and internal clock signals. Typically, control unit 129 comprises logic control circuits, storage (e,g., memory), and a microprocessor. In a preferred approach, the control unit 129 is electrically coupled (e.g., via wire, cable, line, etc.) to the one or more magnetic read/write portions 121, for controlling operation thereof. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desires current profiles to optimally move and position slider 113 to the desired data track on disk 112. Read and write signals are communicated to and from read/write portions 121 by way of recording channel 125.
The above description of a typical magnetic disk storage system, and the accompanying illustration of
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 portion 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 firmed between the first and second pole piece layers of the write portion by a gap layer at or near a media facing side of the head (sometimes referred to as an ABS in a disk drive). 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 media facing side 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.
In this structure, the magnetic lines of flux extending between the poles of the perpendicular head 218 loop into and out of the overlying coating 214 of the recording medium with the high permeability under layer 212 of the recording medium causing the lines of flux to pass through the overlying coating 214 in a direction generally perpendicular to the surface of the medium to record information in the overlying coating 214 of magnetic material preferably having a high coercivity relative to the under layer 212 in 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 under layer 212 back to the return layer (P1) of the head 218.
Perpendicular writing is achieved by forcing flux through the stitch pole 308 into the main pole 306 and then to the surface of the disk positioned towards the media facing side 318.
In
Except as otherwise described herein, the various components of the structures of
Referring to
The side shield 506 may comprise any suitable material known in the art, such as soft magnetic materials, hard magnetic materials, composite magnetic materials (multiple magnetic layers with non-magnetic layer(s) interspersed therein), etc., such as CoCrPt, CoFe, CoCrNb, NiFe, etc.
The soft bias layer 504 may comprise any suitable soft magnetic material(s) known in the art, such as Nife, CoFe, etc. In other embodiments, the soft bias layer 504 may comprise a hard magnetic material, and/or a soft/hard magnetic composite with one or more soft magnetic layers stacked with one or more hard magnetic layers, as would be understood by one of skill in the art.
As shown in
In one particular embodiment, as shown in
As shown in
As shown in
As shown in
As shown in
The free layer 606 has a magnetization that is oriented parallel with a media-facing surface 508 of the read sensor 502 and parallel with a plane of deposition of the free layer 606, such that it points either into the plane of the paper or out from the plane of the paper. The magnetization of the free layer 606 may be affected by magnetic fields external to the structure, such as from a magnetic medium having data stored thereon.
The AP1 602 has magnetization that is oriented antiparallel with the magnetization of the AP2 604, as indicated by the arrows labeled “AP1 ” and “AP2 ” in
In these embodiments, the magnetic moment of the soft bias layer 504 may be selected to compensate for the magnetic coupling of the free layer 606 with the AP2 604, In order to accomplish this compensation, material, thickness, and/or height of the soft bias layer 504 may be adjusted at the back edge of the free layer 606, as would be understood by one of skill in the art upon reading the present descriptions. The back edge of the free layer 606 is an edge of the free layer 606 opposite the media-facing surface 508 of the free layer 606.
Also, as shown in
The AP2 604 may be separated from the AP1 602 by an antiparallel coupling (APC) layer 626, a thickness of this APC layer 626 being chosen such that an antiparallel coupling is established between the AP1 602 and the AP2 604 so that the magnetization directions of AP1 602 and AP2 604 are aligned parallel and opposite to each other. The APC layer 626 may comprise any suitable material known in the art, such as non-magnetic metals, Ru, Ta, etc.
In further embodiments, the barrier layer 608 may comprise any suitable material known in the art, such as MgO, AlO, alumina, etc.
The soft bias layer 504 may be positioned behind at least a portion of the free layer 606 in an element height direction 616. The soft bias layer 504 may comprise any suitable soft magnetic material known in the art, such as nickel alloys such as Nife, cobalt alloys such as CoFe, etc. The magnetic moment of the soft bias layer 504 may be in a direction antiparallel to and/or against the magnetic moment of the AP2 604, in certain embodiments.
Also, in each magnetic head structure, the AP1 602 may extend below the AP2 604 and the soft bias layer 504 in the element height direction 616. Furthermore, in some approaches, at least a portion of the AP2 604 may extend below the soft bias layer 504 in the element height direction 616. According to various embodiments, all, some, or none of the AP2 604 may extend below the soft bias layer 504 in the element height direction 616 beyond a closest point of the soft bias layer 504 to the media-facing surface 508.
Furthermore, in some embodiments, the magnetic head structure may include a spacer layer 610 positioned above the free layer 606 and the soft bias layer 504 in the first direction, and, in some approaches, an upper shield 612 positioned above the spacer layer 610 in the first direction.
Any suitable materials known in the art may be used for the AP1 602, the AP2 604, the free layer 606, the barrier layer 608, the spacer layer 610, and/or the upper shield 612. Furthermore, different embodiments may utilize different materials in order to provide certain benefits of such materials, as would be understood by one of skill in the art.
As shown in
In a next embodiment, as shown in
In another embodiment, as shown in
According to more embodiments, an insulating layer 618 may be positioned between the soft bias layer 504 and any and/or all of: the barrier layer 608, the free layer 606, and/or the AP2 604. The insulating layer 618 may comprise any suitable electrically insulating material known in the art, such as alumina, MgO, SiO2, ZrN, etc.
In yet another embodiment, as shown in
Although it is not shown in any of the figures, it is noted that the spacer layer 610 may be configured such that it separates the free layer 606 and bias layer 504 from the upper shield 612, but such that it does not extend laterally over the side shield 506 (as shown in
In a further embodiment, a magnetic data storage system, such as that shown in
For a conventional TMR read head with an area resistance (RA) below 0.5, the orange-peel coupling field (Hf) may be on the order of several hundred Oersted (Oe), which is a dominating force for the free layer along the stripe height (SH) direction and comparable to a typical longitudinal bias field in magnitude. As a consequence, at a zero external field, the free layer is not sufficiently biased along the track width direction, resulting in movement of the bias point. In other words, with reference to
A simple Stoner-Wolfarth model calculation shows that with increasing Hf, the TMR sensor suffers substantially from Asymmetry/Utilization loss due to a bias point shift resulting from uncompensated Hf. This trend may be seen in the plot shown in
Now referring to
According to experiments conducted on various read sensors, according to one embodiment, the soft bias layer magnetic field may be set to be about equal to the Hf.
In operation 1002, a first antiferromagnetic layer (AFM) is formed, such as above a lower shield, a substrate, or some other suitable layer known in the art. The AFM may comprise any suitable material known in the art, such as IrMn, FeMn, PtMn, etc., among others. Furthermore, the AFM may be formed via any formation technique known in the art, such as sputtering, plating, atomic layer deposition (ALD), etc.
In operation 1004, a first antiparallel magnetic layer (AP1) is formed, such as above the AFM layer, a lower shield, a substrate, or some other suitable layer known in the art, in a first direction oriented along a media-facing surface and perpendicular to a track width direction. The AP1 may comprise any suitable material known in the art, such as CoFe, NiFe, CoCrPt, among others, or some combination of suitable materials. Furthermore, the AP1 may be formed via any formation technique known in the art, such as sputtering, plating, atomic layer deposition (ALD), etc.
In operation 1006, a second antiparallel magnetic layer (AP2) is formed above the AP1 in the first direction. The AP2 may comprise any suitable material known in the art, such as CoFe, NiFe, CoCrPt, among others, or some combination of suitable materials, and may comprise the same material as the AP1 or some other material. Furthermore, the AP2 may be formed via any formation technique known in the art, such as sputtering, plating, atomic layer deposition (ALD), etc. It should be noted that the AP2 may be separated from the AP1 by a thin layer of a non-magnetic material, the thickness of this layer being chosen such that an antiparallel coupling is established between the AP1 and the AP2 so that the magnetization directions of AP1 and AP2 are aligned parallel and opposite to each other. This non-magnetic material may comprise any suitable material known in the art, such as non-magnetic metals, Ru, Ta, etc.
In operation 1008, a barrier layer is formed above the AP2 in the first direction. The barrier layer may comprise any suitable material known in the art, such as MgO, AlO), alumina, etc.
In operation 1010, a free layer is formed above the barrier layer in the first direction. The free layer may comprise any suitable material known in the art (such as CoFe, CoFeB, NiFe, alloys thereof, etc.) or some combination of suitable materials known in the art and may be formed via any formation technique known in the art, such as sputtering, plating, ALD), etc. The AP1, the AP2, the barrier layer, and the free layer together form a read sensor.
In operation 1012, a soft bias layer is formed behind at least a portion of the free layer in the element height direction. The soft bias layer comprises a soft magnetic material of a type known in the art, such as NiFe, NiFeCo, CoFe, etc., or some combination of suitable materials know in the art. The soft bias layer may be formed via any formation technique known in the art, such as sputtering, plating, ALD, etc.
In one embodiment, the soft magnetic material may be chosen to correspond to the magnetic moment of the AP2. For example, for a range of between about 1 T and about 1.4 T, NiFe may be chosen. For a range of between about 1.4 T and about 2.0 T, NiFeCo may be chosen. Furthermore, for a range of between about 2.0 T and 2.4 T, CoFe may be chosen. Of course, other soft magnetic materials may be chosen to substantially cancel out the Hf to the free layer, in more approaches.
In each embodiment, the magnetic moment of the soft bias layer may be selected to compensate for the magnetic coupling of the free layer with the AP2. In order to accomplish this compensation, material, thickness, and/or height of the soft bias layer may be adjusted at the back edge of the free layer, as would be understood by one of skill in the art upon reading the present descriptions.
In a further embodiment, a hard bias layer may be formed, at least a portion thereof being formed behind the soft bias layer in the element height direction. The hard bias layer may comprise a hard magnetic material (of a type known in the art) configured to provide unidirectional anisotropy to the soft bias layer, and may be formed via any formation technique known in the art, such as sputtering, plating, ALD, etc. In a further embodiment, at least a portion of the hard bias layer may be in direct contact with a back edge of the soft bias layer, and at least a portion of the hard bias layer may extend at least to sides of the read sensor and the soft bias layer in a track width direction.
In another embodiment, method 1000 may include forming a soft side shield or hard magnet (HM) on one or more sides of the read sensor in a track width direction. In this embodiment, the soft bias layer may extend to at least one of an extent of the side shield on both sides of the read sensor in the track width direction, and/or beyond a back edge of the read sensor in the element height direction.
When the soft bias layer extends beyond the back edge of the read sensor in the element height direction, and the width of the soft bias layer is not greater than a width of the reader sensor, the side shield may also extend to about an extent of the soft bias layer in the element height direction.
In another approach, the soft bias layer may have shape anisotropy in a direction perpendicular to a media-facing surface of the read sensor (such as an ABS) that is achieved by forming the soft bias layer to have a length in the element height direction which is at least twice a width in a track width direction to form the shape anisotropy. In more embodiments, the length may be about three times the width, four times the width, five times the width, or more. Also, the width of the soft bias layer may be greater than or equal to a width of the read sensor in the track width direction.
In yet another approach, the AP1 may extend below the AP2 and the soft bias layer in the element height direction. In a further approach, at least a portion of the AP2 may extend below the soft bias layer in the element height direction.
The method 1000 may also include forming a spacer layer above the free layer and the soft bias layer in the first direction and/or forming an upper shield above the spacer layer in the first direction. The upper shield may be electrically isolated from the soft bias layer by the spacer layer or some other layer suitable for such a purpose. The spacer layer may comprise any suitable material known in the art, such as Ru, Ta2O5, etc., and may be formed using any formation technique known in the art. Also, the upper shield may comprise any suitable material known in the art, such as CoFe, NiFe, etc., and may be formed using any formation technique known in the art.
In another embodiment, method 1000 may also include forming an insulating layer between the soft bias layer and one, several, or all of: the barrier layer, the free layer, and the AP2. The insulating layer may comprise any suitable material known in the art, such as alumina, MgO, SiO2, etc., and may be formed using any formation technique known in the art.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of an embodiment of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.