Patent Grant
8218271
The present invention relates to magnetic sensors, and more particularly, this invention relates to systems and methods of making and using a tunneling magnetoresistive head with a multilayered reference layer.
The heart of a computer is a magnetic disk drive 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.
There are many different types of read and/or write magnetic heads used in magnetic disk systems. One such type of read/write head is a tunneling magnetoresistive (TMR) head. One drawback with using a typical TMR head is that there is a weak antiferromagnetic (AFM) coupling between the reference layer and keeper layer through the antiferromagnetic (AFM) coupling layer, where this AFM coupling is referred to as AFM coupling field HeP2. Previous attempts to increase HeP2 have resulted in undesirable side effects. For example, an increase in the AFM coupling between the reference layer and the keeper layer can cause an increase in the ferromagnetic coupling between the reference layer and the free layer which degrades the performance of the TMR head. In another example, tunneling magnetoresistance can decrease when the AFM coupling between the reference layer and the keeper layer increases.
Therefore, it would be beneficial to have a TMR head with increased AFM coupling between the reference layer and the keeper layer without substantially increasing the ferromagnetic coupling between the reference layer and the free layer and without substantially decreasing the tunneling magnetoresistance of the head.
According to one embodiment, a method for forming at least a portion of a magnetic head includes forming a keeper layer, forming a reference layer, and forming an AFM coupling layer which is positioned between the keeper layer and the reference layer. In addition, forming the reference layer includes forming a layer of CoFe, depositing a layer of CoFeHf which is about 20 atomic % Hf, and depositing a layer of CoFeB such that the layers of CoFeHf and CoFeB are directly adjacent.
A method for forming at least a portion of a magnetic head, according to another embodiment, includes forming a keeper layer, forming a reference layer, and forming an AFM coupling layer which is positioned between the keeper layer and the reference layer. Forming the reference layer includes forming a layer of CoFe, depositing a layer of CoFeHf by co-sputtering CoFe and Hf or by sputtering from a CoFeHf target, and depositing a layer of CoFeB by sputtering. The layers of CoFeHf and CoFeB are directly adjacent, and a ratio of respective physical thicknesses of CoFeHf to CoFeB is less than about 0.66.
In another embodiment, a magnetic head includes a keeper layer, an AFM coupling layer adjacent the keeper layer, a reference layer on an opposite side of the AFM coupling layer than the keeper layer, a free magnetic layer, and a dielectric tunnel junction layer between the free magnetic layer and the reference layer. The layer of CoFeHf is about 20 atomic % Hf, and the reference layer includes a layer of CoFe, and a layer of CoFeHf directly adjacent the layer of CoFeB.
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 well 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 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, as well as operation and/or component parts thereof.
In one general embodiment, a method for forming at least a portion of a magnetic head comprises forming a keeper layer; forming a reference layer; forming an AFM coupling layer, the AFM coupling layer being positioned between the keeper and reference layers; and wherein forming the reference layer includes forming a layer of CoFe; depositing a layer of CoFeHf, wherein the layer of CoFeHf is about 20 atomic % Hf; and depositing a layer of CoFeB, wherein the layers of CoFeHf and CoFeB are directly adjacent.
In another general embodiment, a method for forming at least a portion of a magnetic head comprises forming a keeper layer; forming a reference layer; forming an AFM coupling layer, the AFM coupling layer being positioned between the keeper and reference layers; and wherein forming the reference layer includes forming a layer of CoFe; depositing a layer of CoFeHf; and depositing a layer of CoFeB, wherein the layers of CoFeHf and CoFeB are directly adjacent, wherein depositing the layer of CoFeHf is performed by co-sputtering CoFe and Hf or sputtering from a CoFeHf target, wherein depositing the layer of CoFeB is performed by sputtering, wherein a ratio of respective physical thicknesses of CoFeHf to CoFeB is less than about 0.66.
In yet another general embodiment, a magnetic head comprises a keeper layer; an AFM coupling layer adjacent the keeper layer; and a reference layer on an opposite side of the AFM coupling layer than the keeper layer, the reference layer further comprising: a layer of CoFe; a layer of CoFeHf; and a layer of CoFeB, wherein the layers of CoFeHf and CoFeB are directly adjacent; a free magnetic layer; and a dielectric tunnel junction layer between the free magnetic layer and the reference layer, wherein the layer of CoFeHf is about 20 atomic % Hf.
Referring now to
At least one slider 113 is positioned near the disk 112, each slider 113 supporting one or more magnetic read/write heads 121. As the disk rotates, slider 113 is moved radially in and out over disk surface 122 so that heads 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 control unit 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. 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 heads 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 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.
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 coating 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
According to some embodiments and with reference to
In operation 502, a keeper layer is formed. For example, the keeper layer may be similar to that shown in
In some more embodiments, the keeper layer may be comprised of more than one material. Also, the keeper layer may be formed in more than one layer, of the same or different materials, with the same or different formation techniques, such as physical vapor deposition (PVD) including sputtering, evaporation, etc.
Referring again to
In some preferred embodiments, the reference layer is comprised of more than one layer. For example, as shown in
Referring again to
According to a preferred embodiment, in operation 508 of
Also, in operation 510, forming the reference layer includes depositing a layer of CoFeHf, wherein the layer of CoFeHf is about 20 atomic % Hf. (“about” 20 atomic % Hf includes 20 atomic % Hf±2 atomic % Hf). For example, the layer of CoFeHf may comprise CoFe9.8Hf20.
In some embodiments, the layer of CoFeHf may be deposited by co-sputtering CoFe and Hf, wherein a Hf and a CoFe deposition power are each selected and used to provide an AFM coupling field HeP2 of the reference layer and the keeper layer of greater than about 3500 Oe (where about 3500 Oe includes 3500 Oe±250 Oe). Those skilled in the art will appreciate how to vary the sputtering powers to achieve deposits having different properties. Moreover, standard tests may be used to determine the HeP2 of the resultant deposit when practicing the teachings set forth herein. Through a process of iteration, one skilled in the art can readily achieve the embodiments disclosed herein without undue experimentation. Similar results can be achieved by using a CoFeHf target of appropriate composition. More detail of what HeP2 describes is included in the description of
In more embodiments, depositing the layer of CoFeHf may be performed by co-sputtering CoFe and Hf, wherein a Hf and a CoFe deposition power are each selected and used to provide an exchange pinning field HeP1 of the keeper layer and an antiferromagnetic layer of greater than about 5900 Oe (where about 5900 Oe includes 5900 Oe±250 Oe). Similar results can be achieved by using a CoFeHf target of appropriate composition. More detail of what HeP1 describes is included in the description of
In addition, in operation 512 of
In certain embodiments, depositing the layer of CoFeHf may be performed by co-sputtering CoFe and Hf, and depositing the layer of CoFeB may be performed by sputtering, wherein a ratio of respective physical thicknesses of CoFeHf to CoFeB is less than about 0.66 and greater than 0, e.g., less than 0.66±0.066. Similar results can be achieved by using a CoFeHf target of appropriate composition. In addition, the ratio of respective physical thicknesses of CoFeHf to CoFeB may preferably be between about 0.66 and about 0.2, alternatively between about 0.33 and about 0.2, alternatively in one example about 0.22.
In further embodiments, the ratio of respective physical thicknesses of CoFeHf to CoFeB may be less than about 0.33 and greater than 0.
Now referring to
In operation 602, a keeper layer is formed. For example, the keeper layer may be similar to that shown in
In some more embodiments, the keeper layer may be comprised of more than one material. Also, the keeper layer may be formed in more than one layer, of the same or different materials, with the same or different formation techniques, such as physical vapor deposition (PVD), including sputtering, evaporation, etc.
Referring again to
In some preferred embodiments, the reference layer is comprised of more than one layer. For example, as shown in
Referring again to
According to a preferred embodiment, in operation 608 of
Also, in operation 610 of
In addition, in operation 612 of
According to some approaches, depositing the layer of CoFeHf may be performed by co-sputtering CoFe and Hf, wherein a Hf and a CoFe deposition power are each selected and used to provide a HeP2 of the reference layer and the keeper layer of greater than about 3500 Oe (where about 3500 Oe includes 3500 Oe±250 Oe). Similar results can be achieved by using a CoFeHf target of appropriate composition. More detail of what HeP2 describes is included in the description of
In some embodiments, depositing the layer of CoFeHf may be performed by co-sputtering CoFe and Hf, wherein a Hf and a CoFe deposition power are each selected and used to provide a HeP1 of the keeper layer and an antiferromagnetic layer of greater than about 5900 Oe (where about 5900 Oe includes 5900 Oe±250 Oe). Similar results can be achieved by using a CoFeHf target of appropriate composition. More detail of what HeP1 describes is included in the description of
According to more embodiments, the ratio of respective physical thicknesses of CoFeHf to CoFeB may be less than about 0.33 and greater than 0. In a more preferable approach, the ratio of respective deposition times of CoFeHf to CoFeB may be about 0.22 and greater than 0.
In a preferred embodiment, the layer of CoFeHf may be about 20 atomic % Hf. (“about” 20 atomic % Hf includes 20 atomic % Hf±2 atomic % Hf). For example, the layer of CoFeHf may comprise CoFe9.8Hf20.
Now referring to
In some embodiments, the portion of the magnetic head 700 may include additional layers, such as a seed layer 720, an antiferromagnetic layer (AFM) 722 below the keeper layer (API) 702, and a capping layer 724 above the free magnetic layer 716. Other layers may be included as well, such as shields, insulating layers, etc.
Also indicated in
In reference to the thickness of each layer shown in
By forming a portion of a magnetic head using the methods disclosed herein, such as using a 20 atomic % Hf in the layer of CoFeHf 708, and keeping the ratio of CoFeHf to CoFeB thicknesses in the reference layer 704 to about 0.22, it has surprisingly been found that the strength of HeP2 is increased by at least about 20% over prior art magnetic heads without substantially sacrificing any other desirable characteristics of the magnetic head 700, according to preferred embodiments. Also, by forming a portion of a magnetic head using the methods disclosed herein, another beneficial effect that was surprisingly found was an increase in the strength of HeP1 by about 10% over prior art magnetic heads. In addition, similar and/or the same values were discovered for the tunneling magnetoresistance of the magnetic head (TMR), the tunneling magnetoresistance of the magnetic head compared to resistance through an area of the sensor stack of the magnetic head (TMR/RA), and Hex.
The AFM coupling layer 714 may be comprised of any AFM coupling material, according to some embodiments, such as Ru, Ir, Rh, Cr, Cu, Hf, etc., and combinations thereof.
According to some embodiments, a ratio of respective physical thicknesses of CoFeHf to CoFeB may be less than about 0.66 and greater than 0. Preferably, the ratio of respective physical thicknesses of CoFeHf to CoFeB may be between about 0.66 and about 0.15, and in one approach the ratio of respective physical thicknesses of CoFeHf to CoFeB may be between about 0.33 and about 0.20. According to one example, the ratio of respective physical thicknesses of CoFeHf to CoFeB may be about 0.22.
In some embodiments, a HeP2 of the reference layer 704 and the keeper layer 702 may be greater than about 3500 Oe (where about 3500 Oe includes 3500 Oe±250 Oe).
In even more embodiments, a HeP1 of the keeper layer 702 and an antiferromagnetic layer may be greater than about 5900 Oe (where about 5900 Oe includes 5900 Oe±250 Oe).
Now referring to
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.
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