Patent Application
20140355152
The present invention relates to data storage systems, and more particularly, this invention relates to magnetic read heads having an interlayer coupled free layer with out of plane magnetic orientation relative to a plane of deposition thereof, and method for forming.
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.
One such obstacle is the need for hard and/or soft bias materials in conventional magnetic read heads. The read head sensor must be adequately biased and stabilized by providing deposition of appropriate hard or soft bias materials to form a contiguous junction between the sensor and bias layer. However, hard and/or soft bias materials in conventional magnetic read heads take up valuable space and inhibit the reduction in size thereof. Furthermore, biasing layers bias the magnetic orientation of the free layer to be in the plane of deposition thereof, which may be undesirable, e.g., as the size of data tracks continue to become smaller.
In one embodiment, a magnetic head includes a reference layer having magnetic orientation about aligned with a plane of deposition thereof; a first free layer having a magnetic orientation out of a plane of deposition thereof; a spacer layer between the reference layer and the first free layer; a second free layer having a magnetic orientation out of a plane of deposition thereof; and an inserting layer between the first and second free layers.
In another embodiment, a magnetic head includes a reference layer having magnetic orientation about aligned with a plane of deposition thereof; a first free layer having a magnetic orientation about perpendicular to a plane of deposition thereof; a spacer layer between the reference layer and the first free layer; a second free layer having a magnetic orientation about perpendicular to a plane of deposition thereof; and a nonmagnetic inserting layer between the first and second free layers.
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. Such embodiments may also be implemented in magnetic sensor and magnetic memory application.
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 well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc.
Moreover, unless otherwise specifically defined herein, conventional materials may be used to form any of the components of the various embodiments.
It must also be noted that, as used in the 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 which address poor readback quality in conventional magnetic read heads, as well as operation and/or component parts thereof.
As described above, conventional magnetic read heads suffer from degradation of writing quality as they require one or more biasing layers which establish a biasing magnetic orientation in the plane of deposition thereof. However, these limitations impede the further miniaturization of magnetic read heads, and reading improvements thereof.
In sharp contrast, various embodiments described and/or suggested herein introduce ferromagnetic coupling between free layers; moreover, the interlayer ferromagnetic coupling influences a desirable magnetic orientation out of the plane of deposition, thereby eliminating the need for hard bias layers as seen in conventional products. Also, a perpendicular free layer configuration could be more favorable for future head generations with very narrow track width.
In one general embodiment, a magnetic head includes a reference layer having magnetic orientation about aligned with a plane of deposition thereof; a first free layer having a magnetic orientation out of a plane of deposition thereof; a spacer layer between the reference layer and the first free layer; a second free layer having a magnetic orientation out of a plane of deposition thereof; and an inserting layer between the first and second free layers
In another general embodiment, a magnetic head includes a reference layer having magnetic orientation about aligned with a plane of deposition thereof; a first free layer having a magnetic orientation about perpendicular to a plane of deposition thereof; a spacer layer between the reference layer and the first free layer; a second free layer having a magnetic orientation about perpendicular to a plane of deposition thereof; and a nonmagnetic inserting layer between the first and second free layers.
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., of 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 slider 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 desired 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 formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write portion. 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.
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 underlying 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 ABS 318.
In
Except as otherwise described herein, the various components of the structures of
As described above, the free layer of a magnetic recording head may be a composite free layer, e.g., including at least two free layers separated by a thin non-magnetic spacer. The portions of the free layer on each side of spacer may each, independently of the other, have a single ferromagnetic layer or multiple ferromagnetic layers. Moreover, various embodiments described and/or suggested herein may exhibit ferromagnetic coupling between such free layers through the spacer layer, thereby preferably influencing a magnetic orientation, e.g., out of a plane of deposition thereof. As a result, the hard magnetic biasing layer can be eliminated, and a high TMR ratio can be obtained. Moreover, potential free layer noise reduction can be expected through damping reduction due to the inserting layer provides magnetic damping reduction of both the first and second free layer.
According to an exemplary embodiment, which is in no way intended to limit the invention, “a” layer in the following paragraph is intended to include a structural block that can have a single layer or multiple layers.
The seed layer 544 is a layer deposited to modify the crystallographic texture or grain size of the subsequent layers, and may not be needed depending on the subsequent layer. A first MTJ stack deposited over the seed layer 544 comprises a first antiferromagnetic (AFM1) layer 546, a first AP-pinned layer 547, a spacer layer 554 which may be an electrically insulating tunnel barrier layer or a metal spacer layer, and a first free layer 555. The AP-pinned layer structure 547 is formed of two ferromagnetic layers 548 and 552 separated by an antiparallel coupling (APC) layer 550. The APC layer is formed of a nonmagnetic material, preferably ruthenium (Ru) that allows the two ferromagnetic layers 548 and 552 to be strongly antiparallel-coupled together. The AFM1 layer 546 has a thickness at which the desired exchange properties are achieved, typically 30-300 Å.
The AFM1 layer 546 is exchange-coupled to the first AP-pinned layer 547 to provide a pinning magnetic field to pin the magnetizations of the two ferromagnetic layers of the AP-pinned layer structure 547 in the planes of deposition thereof, as indicated by arrow 549 and arrow 553, respectively. The AP-pinned layer 552 closest to the first free layer 555 is the reference layer of the sensor 530.
Illustrative materials for the AP pinned layers 548, 552 are CoFex and/or NiFex alloys where x is 0 at % to 100 at %. Moreover, the AP pinned layers may each be a single layer or laminated layers. Illustrative thicknesses of the AP pinned layers 548, 552 are between about 10 Å and 50 Å. The antiparallel coupling layer 550 can be formed of Ru at a thickness about 3-12 Å. Referring to
The magnetic head also includes a spacer layer 554 positioned between the reference layer 552 and the first free layer 555. The spacer layer 554 may be a tunnel barrier layer 554 formed of a dielectric barrier material, such as Al2O3, MgOx etc. The tunnel barrier layer 554 is very thin such that the electric current passing through the sensor 530 “tunnels” through the tunnel barrier layer. An illustrative thickness of the tunnel barrier layer is 3-10 Å. The spacer layer may alternatively be a metal layer, such as Cu, Ag, AgSn etc., with a thickness typically in the range of 20-100 Å.
With continued reference to
The first free layer 555 may have a magnetic orientation (signified by the arrow 557) out of a plane of deposition (X-Y plane) when there is no applied field, for example, a field from media. In one preferred approach, the magnetic orientation of the first free layer 555 may be about perpendicular to the plane of deposition thereof (X-Y plane) and about perpendicular to the magnetic orientation of the reference layer 552. In other approaches, the magnetic orientation of the first free layer 555 may be perpendicular to the plane of deposition or have a magnetic orientation in between in-plane and perpendicular to the plane. Moreover, according to a preferred approach, the magnetic orientation of the first free layer 555 when at rest in the head can also be induced by the magnetic orientation of the second free layer 560, as will soon become apparent.
With continued reference to
Additionally, an inserting layer 559 is positioned between the first and second free layers 555, 560. The inserting layer 559 is characterized as tuning (inducing) ferromagnetic coupling between the first and second free layers 555, 560, and also acting as a growth template for the second free layer, thereby promoting growth of the second free layer. The second free layer 560 has a higher anisotropy than the first free layer 555. The ferromagnetic coupling induced by the inserting layer 559 causes the first free layer 555 to have an out of plane magnetization induced by the interlayer ferromagnetic coupling and stronger out of plane (e.g., perpendicular) anisotropy of the second free layer 560.
In some embodiments, the first and second free layers 555, 560 may have different compositions. In a preferred approach, the first free layer 555 may have a higher spin polarization and a lower perpendicular anisotropy than the second free layer 560. As a result, the magnetic orientation of the second free layer 560 may induce the magnetic orientation of the first free layer 555 through the interlayer coupling formed by the inserting layer 559. However, in various approaches, the ferromagnetic coupling between the first and second free layers 555, 560 may depend on the thickness, material, growth, etc. of the inserting layer 559 relative to both the first and second free layers 555, 560. Moreover, in another approach, the overall perpendicular anisotropy of the combined free layers 555, 560 may be adjusted by the selected of a low perpendicular anisotropy of the first free layer 555 and a high perpendicular anisotropy of the second free layer 560.
According to an exemplary embodiment, which is in no way intended to limit the invention, the smaller the thickness t1 of the inserting layer 559 the stronger the interlayer ferromagnetic coupling between the first and second free layers 555, 560. Moreover, the smaller the thickness t3 of the first free layer 555, the greater effect the second free layer has on the first free layer 555. Thus, different relationships between the characteristics thereof may result in a stronger or weaker ferromagnetic coupling between the first and second free layers 555, 560. In some approaches, the first free layer 555 may be formed with a magnetic orientation about aligned with a plane of deposition thereof, and the ferromagnetic coupling with the second free layer 560 is sufficient to reorient the magnetization direction of the first free layer 555 to the desired orientation.
According to various approaches, the inserting layer 559 is nonmagnetic, and may be electrically conductive or nonconductive. Illustrative materials for the inserting layer 559 include metal oxides such as MgO, Ta, Ti, heavy metals or light metals, etc. or any other suitable spacer material which would be apparent to one skilled in the art upon reading the present description. The insertion material is not only used to tune the coupling field between the first and second free layer, it also can be engineered to reduce magnetic damping constants of both the first and second free layers, potentially leading to noise reduction and head signal to noise gain.
It follows that the thickness, materials, growth, etc. of the inserting layer 559, and/or of the first and second free layers 555, 560 may be tuned to achieve the desired ferromagnetic coupling between the first and second free layers 555, 560, thereby causing the magnetic orientation of the first free layer 555 to be out of a plane of deposition (X-Y plane) when at rest in the sensor 530. As a result, a sensor, e.g., such as that illustrated in
As described above, the first free layer 555 has a magnetic orientation out of a plane of deposition thereof, and in some approaches, about perpendicular to the plane of deposition thereof, when at rest in the head in the absence of external magnetic forces. The magnetic orientation of the first free layer 555 is biased in right configuration with respect to the ABS without the use of one or more hard bias material layers. Thus, as illustrated in
Moreover, by removing the one or more biasing layers seen in conventional products, the complexity of magnetic read head fabrication processes is desirably reduced, while maintaining efficient performance thereof.
Referring again to
Any of the approaches described and/or suggested herein may be formed using various methods. However,
Referring now to
According to various approaches, the thickness or any other characteristic of the first free layer, second free layer and/or inserting layer may be determined using and/or in light of program code; modeling; user input; predetermined values, e.g., from a user, stored in memory (e.g., a lookup table), etc.; based on the operating conditions; etc.
With continued reference to
Note that operations 702 and 704 may be performed concurrently, in dependence upon one another to select the appropriate combination of physical characteristics.
The method 700 further includes forming the reference layer in operation 706, forming the spacer layer above the reference layer in operation 708, forming the first free layer above the spacer layer in operation 710, forming the inserting layer above the first free layer in operation 712 and forming the second free layer above the inserting layer in operation 714. Conventional fabrication techniques may be used in operations 706-714.
Moreover, according to various other approaches, the layers formed in operations 706-714 may include any of the illustrative materials, dimensions, thickness characteristics, etc. described above, depending on the desired embodiment. However, in a preferred approach, the thickness of the first free layer and the material of the second free layer as determined in operations 702 and 704, are implemented in their corresponding formation operations 710, 714 of method 700, respectively.
It should be noted that methodology presented herein for at least some of the various embodiments may be implemented, in whole or in part, in computer hardware, software, by hand, using specialty equipment, etc. and combinations thereof.
Moreover, any of the structures and/or steps may be implemented using known materials and/or techniques, as would become apparent to one skilled in the art upon reading the present specification.
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.
