Patent Application
20130280556
Magnetic media are widely used in various applications, particularly in the computer industry for data/information storage and retrieval applications, typically in disk form, and efforts are continually made with the aim of increasing the areal recording density, i.e., bit density of the magnetic media. Conventional thin-film type magnetic media, wherein a fine-grained polycrystalline magnetic alloy layer serves as the active recording layer, are generally classified as “longitudinal” or “perpendicular”, depending upon the orientation of the magnetic domains of the grains of magnetic material.
In perpendicular magnetic recording media, residual magnetization is formed in a direction (“easy axis”) perpendicular to the surface of the magnetic medium, typically a layer of a magnetic material on a suitable substrate. Very high to ultra-high linear recording densities are obtainable by utilizing a “single-pole” magnetic transducer or “head” with such perpendicular magnetic media.
Provided herein, is an apparatus that includes a nonmagnetic substrate having a surface; and a plurality of overlying thin film layers forming a layer stack on the substrate surface. The layer stack includes a magnetically hard perpendicular magnetic recording layer structure and an underlying soft magnetic underlayer (SUL), wherein the sum of a magnetic thickness of the layer stack is a magnetic thickness of up to about 2 memu/cm̂2.
These and other features and advantages will be apparent from a reading of the following detailed description.
Various embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.
Before various embodiments are described in greater detail, it should be understood that the embodiments are not limited to the particular embodiments described and/or illustrated herein, as elements in such embodiments may vary. It should likewise be understood that a particular embodiment described and/or illustrated herein has elements which may be readily separated from the particular embodiment and optionally combined with any of several other embodiments or substituted for elements in any of several other embodiments described herein.
It should also be understood that the terminology used herein is for the purpose of describing embodiments, and the terminology is not intended to be limiting. Unless indicated otherwise, ordinal numbers (e.g., first, second, third, etc.) are used to distinguish or identify different elements or steps in a group of elements or steps, and do not supply a serial or numerical limitation on the elements or steps of the embodiments thereof. For example, “first,” “second,” and “third” elements or steps need not necessarily appear in that order, and the embodiments thereof need not necessarily be limited to three elements or steps. It should also be understood that, unless indicated otherwise, any labels such as “left,” “right,” “front,” “back,” “top,” “bottom,” “forward,” “reverse,” “clockwise,” “counter clockwise,” “up,” “down,” or other similar terms such as “upper,” “lower,” “aft,” “fore,” “vertical,” “horizontal,” “proximal,” “distal,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. It should also be understood that the singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
An apparatus is described herein for embodiments of a perpendicular media with a thin SUL. The features of the disclosed embodiments are based upon recognition that perpendicular media with thin SUL's, exhibiting good writability, can be achieved by appropriate selection of the structure, composition, and thickness of the magnetically hard recording layer structure. In addition, the performance of magnetic recording systems comprising perpendicular media with thin SUL's is materially improved by use of single pole write heads equipped with front shields adjacent the main pole thereof, thereby enhancing the perpendicular field component and controlling the field angle, hence enhancing the effective write field for providing optimal recording performance.
The various embodiments will now be described in greater detail.
A perpendicular recording system 10 with a perpendicularly oriented magnetic medium 1 and a magnetic transducer head 9 is schematically illustrated in
Furthermore, according to an embodiment, reference numerals 9M and 9A, respectively, indicate the main (writing) and auxiliary poles of the magnetic transducer head 9. The relatively thin interlayer 5, comprised of one or more layers of non-magnetic materials, serves to (1) prevent magnetic interaction between the magnetically soft underlayer 4 and the magnetically hard recording layer 6; and (2) promote desired microstructural and magnetic properties of the magnetically hard recording layer 6.
As shown by the arrows in the figure indicating the path of the magnetic flux φ, flux φ emanates from the main writing pole 9M of magnetic transducer head 9, enters and passes through the vertically oriented, magnetically hard recording layer 6 in the region below main pole 9M, enters and travels within soft magnetic underlayer (SUL) 4 for a distance, and then exits therefrom and passes through the perpendicular hard magnetic recording layer 6 in the region below auxiliary pole 9A of transducer head 9. The relative direction of movement of perpendicular magnetic medium 21 past transducer head 9 is indicated in the figure by the arrow in the figure.
Completing the layer stack of medium 1 is a protective overcoat layer 7, such as of a diamond-like carbon (DLC), formed over magnetically hard layer 6, and a lubricant topcoat layer 8, such as of a perfluoropolyether (PFPE) material, formed over protective overcoat layer 7.
According to an embodiment,
The thickness of substrate 2 is not critical; however, in the case of magnetic recording media for use in hard disk applications, substrate 2 must be of a thickness sufficient to provide the necessary rigidity. Substrate 2 typically comprises Al or an Al-based alloy, e.g., an Al—Mg alloy, or glass or glass-ceramics, and, in the case of Al-based substrates, includes a plating layer, typically of NiP, on the surface of substrate 2 (not shown in the figure for illustrative simplicity). An optional adhesion layer 3, typically a less than about 100 Å thick layer of an amorphous metallic material or a fine-grained material, such as a metal or a metal alloy material, e.g., Ti, a Ti-based alloy, Ta, a Ta-based alloy, Cr, or a Cr-based alloy, may be formed over the surface of substrate 2 or the NiP plating layer thereon.
Overlying substrate 2 or optional adhesion layer 3 is a thin magnetically soft underlayer (SUL) 4′ formed according to an embodiment. According to embodiments, the SUL 4′ is substantially thinner than a conventional SUL and comprises a layer of a magnetically soft material up to about 100 Å thick, selected from the group consisting of: Co, Fe, an Fe-containing alloy such as NiFe (Permalloy), FeN, FeSiAl, FeSiAlN, a Co-containing alloy such as CoZr, CoZrCr, CoZrNb, or a Co—Fe-containing alloy such as CoFeZrNb, CoFe, FeCoB, and FeCoC.
As in medium 1, an optional adhesion layer 3 may be included in the layer stack of medium 11 between the surface of substrate surface 2 and the SUL 4′, the adhesion layer 3 being less than about 200 Å thick and comprised of a metal or a metal alloy material such as Ti, a Ti-based alloy, Ta, a Ta-based alloy, Cr, or a Cr-based alloy.
Furthermore, in
According to an embodiment, the multilayer perpendicular magnetic recording structure 6′ is, for example, comprised of a granular perpendicular magnetic recording layer 6G adjacent interlayer 5A and an overlying continuous perpendicular magnetic recording layer 6C. The resultant multilayer structure 6′, termed a “coupled granular-continuous”, or “CGC” structure, exhibits high areal recording densities with enhanced magnetic performance characteristics. According to such multilayer stacked CGC structure, the granular perpendicular recording layer, wherein the magnetic grains are only weakly exchange coupled together, and the continuous perpendicular recording layer, wherein the magnetic grains are strongly exchange coupled laterally, are ferromagnetically coupled together.
Typically, the granular perpendicular magnetic recording layer 6G is from about 5 to about 30 nm thick and comprised of a Co-based alloy wherein segregation of magnetic grains occurs via formation of oxides, nitrides, or carbides at the boundaries between adjacent grains. The oxides, nitrides, or carbides may be formed by introducing a minor amount of at least one reactive gas, e.g., oxygen (O2), nitrogen (N2), or a carbon (C)-containing gas to the inert gas (e.g., Ar) atmosphere during deposition (e.g., sputter deposition) thereof. For example, the granular perpendicular magnetic recording layer 6G may be comprised of a CoCrPt—X material, wherein X is selected from the group consisting of oxides, nitrides, and carbides, e.g., CoCrPt—SiO2, CoCrPt—SiNx, and CoCrPt—SiC.
Typically, the continuous perpendicular magnetic recording layer 6C is from about 2 to about 15 nm thick and comprised of one or more layers of a Co-based alloy, e.g., a CoCrPtX alloy, where X may be selected from the group consisting of: Pt, Fe, Tb, Ta, B, C, Mo, V, Nb, W, Zr, Re, Ru, Ag, Hf, Ir, Si, and Y. Preferably, the perpendicular magnetic recording layer 6C comprises a fine-grained hcp alloy with a preferred c-axis perpendicular growth orientation.
Finally, the layer stack of medium 11 includes a protective overcoat layer 7 above the multilayer perpendicular magnetic recording structure 6′ and a lubricant topcoat layer 8 over the protective overcoat layer 7. Preferably, the protective overcoat layer 7 comprises a carbon-based material, e.g., diamond-like carbon (“DLC”), and the lubricant topcoat layer 8 comprises a fluoropolymer material, e.g., a perfluoropolyether compound.
According to an embodiment, each of the layers 3, 4′, 5, 6′, 7 may be deposited or otherwise formed by techniques typically utilized for formation of thin film layers, e.g., physical vapor deposition (“PVD”) techniques, including but not limited to, sputtering, vacuum evaporation, ion plating, cathodic arc deposition (“CAD”), etc., or by any combination of various PVD techniques. The lubricant topcoat layer 8 may be provided over the upper surface of the protective overcoat layer 7 in any convenient manner, e.g., as by dipping the thus-formed medium into a liquid bath containing a solution of the lubricant compound.
Moreover,
According to an embodiment,
In
According to an embodiment,
Additional advantages afforded by the thin SUL perpendicular recording media, according to an embodiment, include increased flexibility m accommodating different write head designs and clearance specifications by varying the SUL thickness as to optimize the effective field strength and angle for achieving improved recording performance, relative to the currently available thick SUL media.
The effectiveness of an SUL as a guide for magnetic flux is determined primarily by its magnetic thickness (Bs*t) and its permeability (p). Bs is the saturation magnetic moment of the material and t is the thickness of the SUL layer. Permeability is the ability to carry magnetic current or flux, much like an electrical conductivity, and is given by B/H, where H is the applied field.
In SUL designs, the focus has been on materials having very high permeability >˜100, and the highest possible Bs (often ˜1.5-2.0 Tesla) consistent with manufacturing and film growth requirements because designs called for as thick of an SUL as was reasonable possible to manufacture. In this regime, the flux guiding capability was primarily defined by the SUL film thickness. With this paradigm, it is natural and convenient to describe relative SUL flux guiding capability in terms of a simple layer thickness (e.g., physical thickness). According to an embodiment, a physical thickness of an SUL may be approximately 100 A. This thickness may describe an SUL with, for example, 20 times less flux guiding capacity than a more conventional 2000 A SUL.
Therefore, as design implementations are reduced from, for example, a 2000 A SUL to, for example, a 100 A SUL with 20 times less flux carrying capacity the SUL is optimized and many of the manufacturing limitations on thickness are reduced and/or removed. Furthermore, the requirements to maximize Bs (e.g., permeability) of the material, so other materials issues relating to film growth, corrosion resistance, substrate heating, and/or particle generation, is no longer required and can be optimized along with reducing Bs of the SUL material. Thus, the permeability is correspondingly reduced as it is proportional to Bs. Moreover, the flux carrying/guiding capability of the materials that continue to be designed to optimally perform the limited flux guiding function of a high Bs, <100 A SUL are optimized on a per/Angstrom basis.
Thus, according to another embodiment, a flux guiding capacity may be defined by a magnetic thickness (Bs*t) even in the case of the physical thickness. Therefore, the flux carrying capacity of a 400 A thick layer of an SUL material having a Bs=0.5t exhibits a similar thickness, or an even lower thickness, than, for example, a 100 A SUL having a Bs approximately 2.0t. Therefore, the sum of a magnetic thickness of the layer stack may be represented as a magnetic thickness of up to about 2 memu/cm̂2.
Thus, performance, high areal density, magnetic alloy-based perpendicular magnetic media and data/information recording, storage, and retrieval systems, which media include very thin soft magnetic underlayers (SUL's) exhibit improved performance characteristics when utilized in combination with single pole magnetic transducer heads. The media enjoys particular utility in high recording density systems for computer-related applications. In addition, the inventive media can be fabricated by means of media manufacturing technologies, e.g., sputtering.
While embodiments have been described and/or illustrated by means of examples, and while these embodiments and/or examples have been described in considerable detail, it is not the intention of the applicant(s) to restrict or in any way limit the scope of the embodiments to such detail. Additional adaptations and/or modifications of the embodiments may readily appear in light of the described embodiments, and, in its broader aspects, the embodiments may encompass these adaptations and/or modifications. Accordingly, departures may be made from the foregoing embodiments and/or examples without departing from the scope of the embodiments. The implementations described above and other implementations are within the scope of the following claims.
This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/606,998, filed 1 Dec. 2006.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11606998 | Dec 2006 | US |
| Child | 13919983 | US |
