Patent Application
20090190267
1. Field of the Invention
This invention relates to perpendicular magnetic recording media, including continuous and patterned recording media, and more particularly to apparatus and methods for reducing the thickness and cost of an exchange break layer of perpendicular magnetic recording media.
2. Description of the Related Art
Hard-disk drives provide data storage for data processing systems in computers and servers, and are becoming increasingly pervasive in media players, digital recorders, and other personal devices. Advances in hard-disk drive technology have made it possible for a user to store an immense amount of digital information on an increasingly small disk, and to selectively retrieve and alter portions of such information almost instantaneously. Particularly, recent developments have simplified hard-disk drive manufacture while yielding increased track densities, thus promoting increased data storage capabilities at reduced costs.
In a hard-disk drive, rotating high precision aluminum or glass disks are coated on both sides with a special thin film media designed to store information in the form of magnetic patterns. Electromagnetic read/write heads suspended or floating only fractions of micro inches above the disk are used to either record information onto the thin film media, or read information from it.
A read/write head may write information to the disk by creating an electromagnetic field to orient a cluster of magnetic grains, known as a bit, in one direction or the other. In longitudinal magnetic recording media applications, a magnetic recording layer has a magnetic c-axis (or easy axis) parallel to the disk plane. As the Hard-Drive industry is transitioning to perpendicular recording technology, adjustments are being made to adapt the disk media so that the magnetic c-axis of the Cobalt alloy grows perpendicular to the disk plane. Hexagonal Close Packed (HCP) cobalt alloys are typically used as a magnetic recording layer for perpendicular recording. Most media manufacturers now rely on a Cobalt alloy with the incorporation of an oxide segregant to promote the formation of small and uniform grains.
To read information, magnetic patterns detected by the read/write head are converted into a series of pulses which are sent to the logic circuits to be converted to binary data and processed by the rest of the system. To write information, a write element located on the read/write head generates a magnetic write field that travels vertically through the magnetic recording layer and returns to the write element through a soft underlayer. In this manner, the write element magnetizes vertical regions, or bits, in the magnetic recording layer. Because of the easy axis orientation, each of these bits has a magnetization that points in a direction substantially perpendicular to the media surface. To increase the capacity of disk drives, manufacturers are continually striving to reduce the size of bits and the grains that comprise the bits.
The ability of individual magnetic grains to be magnetized in one direction or the other, however, poses problems where grains are extremely small. The superparamagnetic effect results when the product of a grain's volume (V) and its anisotropy energy (Ku) fall below a certain value such that the magnetization of that grain may flip spontaneously due to thermal excitations. Where this occurs, data stored on the disk is corrupted. Thus, while it is desirable to make smaller grains to support higher density recording with less noise, grain miniaturization is inherently limited by the superparamagnetic effect. To maintain thermal stability of the magnetic grains, material with high Ku may be used for the magnetic layer. However, material with a high Ku requires a stronger magnetic field to reverse the magnetic moment. Thus, the ability of the write head to write on magnetic material may be reduced where the magnetic layer has a high Ku value.
The perpendicular magnetic recording medium is generally formed with a substrate, a soft magnetic underlayer (SUL), an interlayer, an exchange break layer, a perpendicular magnetic recording layer, and a protective layer for protecting the surface of the perpendicular magnetic recording layer. The exchange break layer and the interlayer comprise a plurality of Ruthenium layers which serve to control the size and orientation of the magnetic crystal grains in the magnetic recording layer. The exchange break layer and the interlayer also serve to magnetically de-couple the SUL and the perpendicular magnetic recording layer. Ruthenium is a rare material and therefore adds substantially to the overall cost involved with creating the perpendicular recording medium.
Accordingly, a need exists for a practical, attainable apparatus, system, and method for reducing thin film media layer thickness. Beneficially, such an apparatus, system and method would reduce the amount of Ruthenium used in the layers on a thin film media. Such apparatuses, systems and methods are disclosed and claimed herein.
The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available apparatus, systems and methods. Accordingly, the present invention has been developed to provide apparatus, system and methods for reducing thin film media layer thickness while simultaneously reducing the use of Ruthenium in the layers on a thin film media.
In one embodiment in accordance with the invention, a recording medium for perpendicular recording applications includes a soft magnetic underlayer deposited on a nonmagnetic substrate and a perpendicular magnetic recording layer deposited below an overcoat layer. A flash layer is deposited between the soft magnetic underlayer and the perpendicular magnetic recording layer. The perpendicular magnetic recording layer has an axis of magnetic anisotropy substantially perpendicular to the surface thereof. The flash layer comprises a RuTi alloy.
In certain embodiments, the concentration of Ti in the RuTi alloy is in the range of about 5 to about 20 atomic percent. In select embodiments, the concentration of Ti is about 10 atomic percent. In certain embodiments the thickness of the flash layer is in the range of about 5 to about 20 angstroms.
In another embodiment in accordance with the invention, a recording medium for perpendicular recording applications includes a substrate comprising a rigid support structure for depositing a plurality of layers thereon, an overcoat layer comprising a protective coating, a soft magnetic underlayer disposed between the overcoat layer and the substrate, an interlayer deposited on the soft magnetic underlayer, an exchange break layer disposed on the interlayer, and a perpendicular magnetic recording layer disposed between the exchange break layer and the overcoat layer. The soft underlayer comprises a cobalt containing alloy and the exchange break layer comprises a flash layer and a seed layer. The flash layer comprises a RuTi alloy wherein the concentration of Ti is in the range of about 5 to about 20 atomic percent. The seed layer comprises Ru. The perpendicular magnetic recording layer has a coercivity and an axis of magnetic anisotropy substantially perpendicular to the surface thereof.
In certain embodiments the crystal structure of the flash layer comprises a hexagonal-close-packed structure that orients the c-axis of the grains of the perpendicular magnetic recording layer perpendicular to the flash layer.
In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:
Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are disclosed to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
Referring now to
A read/write head 110 may be moved across the disk surface by an actuator assembly 106, allowing the head 110 to read or write magnetic data to a particular track 104. The actuator assembly 106 may pivot on a pivot 114. The actuator assembly 106 may form part of a closed loop feedback system, known as servo control, which dynamically positions the read/write head 110 to compensate for thermal expansion of the perpendicular magnetic recording media 102 as well as vibrations and other disturbances. Also involved in the servo control system is a complex computational algorithm executed by a microprocessor, digital signal processor, or analog signal processor 116 that receives data address information from an associated computer, converts it to a location on the perpendicular magnetic recording media 102, and moves the read/write head 110 accordingly.
Specifically, read/write heads 110 periodically reference servo patterns recorded on the disk to ensure accurate head 110 positioning. Servo patterns may be used to ensure a read/write head 110 follows a particular track accurately, and to control and monitor transition of the head 110 from one track 104 to another. Upon referencing a servo pattern, the read/write head 110 obtains head position information that enables the control circuitry 116 to subsequently re-align the head 110 to correct any detected error.
Servo patterns may be contained in engineered servo sectors 112 embedded within a plurality of data tracks 104 to allow frequent sampling of the servo patterns for optimum disk drive performance. In a typical perpendicular magnetic recording media 102, embedded servo sectors 112 extend substantially radially from the perpendicular magnetic recording media 102 center, like spokes from the center of a wheel. Unlike spokes however, servo sectors 112 form a subtly arc-shaped path calibrated to substantially match the range of motion of the read/write head 110.
The platter or substrate 202 may comprise an AlMg or glass platter which provides a rigid support structure upon which the recording media is deposited. In certain embodiments ion beam deposition or magnetron sputtering may be utilized to deposit the various layers comprising the perpendicular magnetic recording media 102.
In one embodiment, the first layer deposited on substrate 202 is an adhesion layer 204. The adhesion layer 204 may comprise an AlTi layer to aid in the adhesion of subsequent layers. In certain embodiments the adhesion layer 204 may be omitted and a soft underlayer 206 may be deposited directly on the substrate 202.
The material comprising the soft underlayers 206 and 208 is a soft, magnetic, cobalt containing alloy located under the interlayer 214. In certain embodiments the material comprising the soft underlayers 206 and 208 may be CoFeTaZr.
An antiferromagnetic coupling layer 210 may be disposed between the soft underlayers 206 and 208 to couple the two soft underlayers 206 and 208. The antiferromagnetic coupling layer 210 may be used to reduce magnetic signals originating from the soft underlayers 206 and 208 where such signals are undesirable in the perpendicular magnetic recording media 102.
The magnetic recording medium 102 may include a magnetic recording layer 218, to store data. The magnetic recording layer 218 may comprise a plurality of magnetic grains 224 each having a magnetic easy axis substantially perpendicular to the media surface, thereby allowing the grains 224 to be vertically magnetized. The magnetic grains 224 may comprise a magnetic material such as CoPt or CoPtCr. To maintain a highly segregated magnetic layer 218, one or more segregants may be added to the magnetic material.
Referring now to
Because of the ability to utilize soft underlayers 206 and 208 in the perpendicular geometry, write fields generated by the perpendicular write head 110 may be substantially larger than conventional longitudinal recording write fields. This allows use of media 102 having a higher coercivity (Hc) and anisotropy energy (Ku), which is more thermally stable. Furthermore, unlike longitudinal recording, where the magnetic fields between two adjacent bits have a destabilizing effect, the magnetic fields of magnetization 306 of bits in perpendicular recording media 102 stabilize each other, enhancing the overall stability of perpendicular magnetic recording media even further. This allows for closer bit packing.
Capping layer 220 is deposited on top of the perpendicular magnetic recording layer 218 which may comprise a Co alloy. Capping layer 220 serves to improve writeability of the media and to planarize the media to create a smooth surface upon which overcoat layer 222 is disposed. The Overcoat layer 222 may comprise a plurality of carbon layers to protect the perpendicular magnetic recording layer 218 and capping layer 220 against damage.
An intermediate layer 212 may comprise a nonmagnetic layer disposed between the soft underlayer 208 and the perpendicular magnetic recording layer 218. The intermediate layer 212 may comprise an interlayer 214 and an exchange break layer 216. The intermediate layer 212 may serve to prevent the soft underlayer 208 from magnetically coupling with the perpendicular magnetic recording layer 218. The intermediate layer 212 may also comprise a hexagonal-close-packed (HCP) crystalline structure to orient the magnetic grains 224 on the perpendicular magnetic recording layer 218 such that the magnetic c-axis or easy axis is parallel to the disk plane.
Turning now to
With reference to
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
