Abstract:
A patterned magnetic recording media and method thereof is provided. A recording layer comprises a continuous surface of more-noble elements and less-noble elements, such as CoXYZ, wherein X can be Pt, Pd, Ru, Rh, Ir, Os, or Au, wherein Y can be null or Cr, and wherein Z can be null, Cu, Ta, Ti, O, B, Ag, or TiO 2 . The recording layer is masked, shielding areas for recording domains and exposing areas between the recording domains. A voltage bias establishes the substrate as an anode in the presence of Pt cathode, in an electrolyte bath. Ions of the less-noble element are anodically removed predominantly from the exposed areas of the recording layer for a controlled time. The controlled time minimizes oxidation of the nobler element and reduces undercutting of the recording domains. The article produced can have separating areas with surfaces substantially formed of the more-noble element.

Description:
FIELD 
       [0001]    The invention relates generally to patterned magnetic recording storage media and methods for creating the recording domains of such media. 
       BACKGROUND 
       [0002]    Magnetic data storage media includes a recording layer formed on a substrate. Data is stored on the media by changing magnetic polarities among consecutive magnetic domains in the recording layer. The domains of contemporary magnetic storage media include multiple distinct grains of a magnetic material. Denser media can be provided by forming smaller domains. However, there is a practical limit as to the extent the domains can be minimized in size and yet still be comprised of a plurality of distinct grains. 
         [0003]    One particular effect that limits minimization of domain size is a super-paramagnetic effect. The super-paramagnetic effect occurs when the grain volume is too small to prevent thermal fluctuations from spontaneously reversing magnetization direction in the grains. One technique to delay the onset of the super-paramagnetic effect is to use bit patterned media, where each bit is a single magnetic switching volume (e.g., a single grain or a few strongly coupled grains), as described in R. D. Terris et al.,  J. Phys. D: Applied Physics  38, R199 (2005). In order to keep thermally activated reversal at an acceptable level, K u V/k b T, where K u  represents the magnetic anisotropy, V represents the magnetic switching volume, k b  represents the Boltzmann constant, and T represents the temperature in Kelvin. The ratio must remain greater than approximately 60 for conventional longitudinal media according to D. Weller, et al. “Thermal Effect Limits in Ultrahigh-Density Magnetic Recording”,  IEEE Trans. on Magnetics  35, 4923 (1999). To maintain a sufficient SNR, it is desirable to conserve the number of grains per bit as the density is increased. The switching volume in discrete dots is equal to the bit size, and dots smaller than 10 nm can be thermally stable. 
         [0004]    A patterning process typically consists of several steps including lithography to define the pattern, and pattern transfer onto the substrate or thin film. In general, there are two classes of pattern formation processes, additive and subtractive. In the additive process (electrodeposition and lift-off), the resist pattern is first created and then the magnetic film is deposited. In the subtractive process, the magnetic film is deposited prior to resist patterning. The pattered resist then serves as an etch mask, and the surrounding magnetic film is removed by one of a number of processes including ion milling, RIE and wet chemical etching. A commonly used process for removing magnetic materials is ion milling, which is not considered to be a selective removal process. C. Ross, “Patterned Magnetic Recording Media”  Annual. Rev. Mater. Res.  31, 203-35 (2001). 
         [0005]    The modification of magnetic films through Ga+ poisoning using FIB (Focused Ion Beam) has been described in the art. With this approach, perpendicular granular media based on CoPtCr was not etched, but rather poisoned by Ga+. Islands (dots) smaller than 70 nm in diameter were seen to have a domain remnant state. However, one drawback of this method is that FIB methods lack throughput to be a low-cost manufacturing method for patterned media. C. T. Rettner, et al. “Patterning of Granular Magnetic Media with a Focused Ion Beam to Produce Single-Domain Islands at &gt;140 Gbit/in2 ” IEEE Trans. on Magnetics  37, 1649 (2001); C. T. Rettner, et al. “Magnetic Characterization and Recording Properties of Patterned Co 70 Cr 18 Pt 12   ”, IEEE Trans. on Magnetics  38, 1725 (2002); C. T. Rettner et al.  Applies Physics Letters  80, 2 279 (2002); R. Hyndman et al. “Modification of Co/Pt Multilayers by Gallium Irradiation—Part 1: The Effect on Structural and Magnetic Properties”  J. Appl. Phys.  90, 3843 (2001). 
         [0006]    Another contemporary method deposits a recording layer that includes magnetic material separated by inherently non-magnetic regions, masking a surface of the recording layer where the mask covers areas desired to be used as recording domains, and then processing the exposed regions to reduce magnetism. The inherently non-magnetic regions serve to protect and preserve the isolation of the magnetic material regions after etching away the exposed magnetic material. However, this contemporary approach calls for provision of a recording layer with multiple different materials, which substantially increases the complexity of the manufacturing process. 
       SUMMARY 
       [0007]    A patterned magnetic recording media, and a method of producing patterned magnetic recording media is described herein. Aspects of the present invention include anodically removing, in selected regions, a comparatively less-noble component of an alloy, wherein the alloy is disposed as a continuous surface supported by a media substrate. The removal of the less-noble component in the selected regions causes the magnetic properties of the alloy in those regions to be degraded or destroyed. The areas of the continuous surface in which the less-noble component was not removed retain their magnetic characteristics and can be used as recording domains. 
         [0008]    In an example embodiment, a method for the formation of patterned media comprises modifying perpendicular Hexagonal Close Packed (HCP) structured media based on (Co or Fe)X, (Co or Fe)XY, (Co or Fe)XZ or (Co or Fe)XYZ, wherein X is an element selected from a first group comprising Pt, Pd, Ru, Rh, Ir, Os, and Au, Y is an element selected from a second group comprising Cr, and wherein Z is an element selected from a third group comprising Cu, Ta, Ti, O, B, Ag and TiO 2 . In a cobalt based recording media, selective anodic removal of Co (in forms of soluble Co +2  salts) from the media is performed in determined regions, destroying or inhibiting the magnetization of the remaining material in those regions. The timing of the anodic Co removal is controlled to avoid excessive Pt oxidation and undercut of protected regions. A rate of anodic removal is controlled by variation in the current density or applied voltage potential. An appropriate electrolyte and concentration is selected for the anodic removal, as described herein. Further, processing can be performed to neutralize galvanic corrosion at Pt/CoPt interfaces, such as by submersion in a boric acid bath at about pH 8. Reference electrodes can be used to control and monitor the process. 
         [0009]    In an embodiment, the magnetic film recording layer is deposited (e.g. by sputtering) on a Ru structured seed layer. A resist pattern is applied on the recording layer to expose the regions in which selective removal is to be performed, and to mask the areas to be used as recording domains. Resist patterns are selected to form recording domains of a desired size, in view of process characteristics. In an example, processes are described to substantially destroy magnetic properties by anodic Co removal, and to allow some Pt oxidation. Other processes are described that allow for some remaining magnetic capability in exposed regions, if the application for that media can tolerate some magnetic characteristic in those regions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a plan view of a disc drive for data storage employing media, in which the present invention is useful, in accordance with an embodiment of the present invention; 
           [0012]      FIG. 2  is a simplified cross-sectional view of a media article, e.g. a disc, over which is disposed a layer of resist, in accordance with an embodiment of the present invention; 
           [0013]      FIG. 3  is a simplified cross-sectional view of a pattern formed in the resist of the media article as in  FIG. 2 , in accordance with an embodiment of the present invention; 
           [0014]      FIG. 4  is a simplified cross-sectional view of an anodic processing step of the media as in  FIG. 2  and  FIG. 3 , in accordance with an embodiment of the present invention; 
           [0015]      FIG. 5  is a plan view of a surface section of the media article processed, in accordance with an embodiment of the present invention; 
           [0016]      FIG. 6  is a method flow diagram illustrating processing of media articles, in accordance with an embodiment of the present invention; 
           [0017]      FIG. 7  is a graphical illustration of a linear sweep voltammograms of a CoPt disc in KNO 3 , KBr, Na 2 SO 4 , and NaCl at pH 2 (5 mV/sec, no agitation, area 1 cm 2 ), in accordance with an embodiment of the present invention; 
           [0018]      FIG. 8  is a graphical illustration of ICP-OES experimental results for dissolved metal concentrations from corrosion of CoPtRu media in 1M electrolytes at pH 2, in accordance with an embodiment of the present invention; 
           [0019]      FIG. 9  is a graphical illustration of constant current removal of Co from 1 cm 2  areas in KBr 1M pH 2 at sampled current densities, in accordance with an embodiment of the present invention; 
           [0020]      FIG. 10  is a graphical illustration of potential vs. time in a preparative cell at 1 mA constant current with exposure of 1.2 cm 2 , in accordance with an embodiment of the present invention; 
           [0021]      FIG. 11  is a graphical illustration of ICP-OES results for elemental concentration (ppm) of Co and Pt at 1 mA constant current with exposure of 1.2 cm 2  at sampling points indicated in  FIG. 10 , in accordance with an embodiment of the present invention; 
           [0022]      FIG. 12  is a graphical illustration of VSM measurements of various samples after selective anodic removal of Co from Co 82 Pt 18  alloy, in accordance with an embodiment of the present invention; 
           [0023]      FIG. 13   a  is a graphical illustration of Co 2p3 spectra XPS spectra of samples after selective removal of Co from Co 82 Pt 18  alloy at pH 2 to 5, in accordance with an embodiment of the present invention; 
           [0024]      FIG. 13   b  is a graphical illustration of Pt 4f spectra XPS spectra of samples after selective removal of Co from Co 82 Pt 18  alloy at pH 2 to 5, in accordance with an embodiment of the present invention; 
           [0025]      FIG. 14  is a cross-sectional view of a TEM image of a sample, in accordance with an embodiment of the present invention; and 
           [0026]      FIG. 15  is a cross-sectional view of patterned media after anodic removal processing with a DLC coating, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following description is presented to enable a person of ordinary skill in the art to make and use various aspects of the invention. Descriptions of specific techniques, implementations and applications are provided only as examples. Various modifications to the examples described herein may be apparent to those skilled in the art from these disclosures, and the general principles defined herein may be applied to other examples and applications by those of ordinary skill without departing from the scope of the invention. Additionally, well-known elements, devices, components, methods, process steps and the like may not be set forth in detail in order to avoid obscuring the invention. 
         [0028]    A patterned magnetic recording media, and a method of producing patterned magnetic recording media is described herein.  FIG. 1  depicts a disc drive  100  employing media for data storage, in which the present invention is useful. The disk drive  100  includes a base  112  and a top cover plate  114 . The base  112  is combined with cover plate  114  to form a sealed environment to protect the internal components from contamination by elements outside the sealed environment. Disk drive  100  further includes a disk pack  116  that is mounted on a hub for rotation on a spindle motor by a disk clamp  118 . Disk pack  116  includes one or more of individual disks that are mounted for co-rotation about a central axis. It will be apparent that features of the recording media, discussion and claims may be utilized with a variety of memory systems and motors, including disc drive memory systems, and low profile disc drive memory systems. The recording media teachings herein is not limited to the disc drive  100  as shown. Further, the present invention can be utilized with a variety of recording media material including-perpendicular recording media material of discrete track recording (DTR) media or bit patterned recording media (BPM), and a hexagonal close-packed (HCP) structure. 
         [0029]    Each disk surface has an associated read/write head  120  that is mounted to the disk drive  100  for reading/writing to/from the disk surface. In the example shown in  FIG. 1 , read/write heads  120  are supported by flexures  122  that are in turn attached to head mounting arms  124  of an actuator  126 . The actuator shown in  FIG. 1  is of the type known as a rotary moving coil actuator and includes a voice coil motor, shown generally at  128 . Voice coil motor  128  rotates actuator  126  with its attached read/write heads  120  about a pivot shaft  130  to position read/write heads  120  over a desired data track along a path  132 .  FIG. 1  is shown as a general example of a usage for the articles of media that can be produced according to the disclosed methods, and  FIG. 1  implies no limitation as to the structure, components, form factor, read/write head technology or the like that may be used in devices with such media articles. 
         [0030]      FIG. 2  illustrates, in simplified cross-sectional view, a portion  200  of media, such as a data disc that can be processed to produce storage media articles, in accordance with an embodiment of the present invention. The media  200  includes a substrate  205 , a ruthenium seed layer  210 , on which is deposited a magnetic film recording layer  215 , and on which is deposited a layer  220  of resist that can, for example, be spun on and cured or dried. As an example, the recording layer  215  may be comprised of CoPt, FePt, or further alloys thereof, such as alloys of CoPt including any of Cr, Cu, Ag, Ta, Ti, O, and B. Further, in place of Pt, other elements include Pd, Ru, Rh, Ir, Os, and Au. 
         [0031]    Substrate  205  can be formed according to known methods and from known materials, and for example can be formed from aluminum and magnesium (Al—Mg), glass, silicon, quartz sapphire, and so on. Ruthenium seed layer  210  is often used as a buffer layer between substrate  205  and recording layer  215 , and helps to achieve a desired orientation in the recording layer  215 . A person of ordinary skill would be able to make suitable substitutes, and omit or add further layers for supporting recording layer  215 . For example, a variety of magnetically soft underlayers (SULs) can be used in magnetic recording media and can be disposed under the recording layer  215 . 
         [0032]      FIG. 3  illustrates a cross-sectional view of the portion  200  of media, after further processing of resist layer  220  to produce a pattern that exposes some areas of recording layer  215  and masks other areas. In particular, resist portions  320   a  through  320   n  illustrate resist mask portions, while reference number  330  identifies an exposed portion of recording layer  215 . The two-dimensional layout of a surface of recording layer  215  may have any of a variety of patterns of such masking, which is not illustrated in the cross-section of  FIG. 3 . 
         [0033]      FIG. 4  illustrates a pictorial example processing setup  400  in which recording layer  215  is modified to produce bits (recording domains) separated by non-magnetic regions in a desired pattern. Setup  400  includes a container  415  in which media portion  200  can be placed. A Pt electrode  410  is biased at a negative potential with respect to media portion  200 . A reference electrode  420  can be provided and formed, preferably, of calomel (mercury chloride), or of a suitable substitute, such as Ag/AgCl. An electrolyte, generally referenced by  430  is provided in container  415  at an amount sufficient to submerge at least portions of each of reference electrode  420  and Pt electrode  410  and at least the recording layer  215  of media portion  200 . 
         [0034]    As explained in further detail below, a controlled potential or current density is applied to the disc (e.g. via the illustrated voltage bias applied between media portion  200  and Pt electrode  410 ), which serves as an anode in an electrochemical cell with a Pt cathode and a reference electrode (such as a saturated calomel electrode). It is to be noted that a reference electrode is not a requirement of the present invention, but can allow for greater process control, and hence is desirable. 
         [0035]    The above describes a particular example of a configuration for a Pt-based recording alloy with cobalt. More generally, other aspects include using alloys comprising a more-noble component and a less-noble component, with the more-noble element better resisting oxidation in the processing setup for the media article having the recording alloy on its surface. For example, in place of Pt, an alternative noble component of the alloy can be Pd, Ru, Rh, Ir, Os, or Au. 
         [0036]      FIG. 6  illustrates steps of an example method  600  for processing articles of media according to aspects of this disclosure. Elements of method  600  are explained in further detail below, but are introduced here. Method  600  includes depositing ( 605 ) a recording layer consisting of a generally homogenous alloy of a more-noble magnetic element and a less-noble magnetic element (e.g., a CoPt alloy, such as CoPtCr, and so on) on a surface of a media article, such as a substrate (or on various intervening layers that were previously deposited on the substrate, such as a Ru seed layer). Method  600  includes establishing ( 610 ) a resist pattern on the surface of the recording layer, or on a surface of a coating, such as a carbon overcoat or a Diamond Like Carbon (DLC) coating, on the recording layer. In some examples, the DLC coating can be under 10 nm thick, and in still more particular examples, under 5 nm thick, sometimes about 4 nm thick, and sometimes 2 to 3 mm thick. The resist pattern exposes first regions and masks second regions. The media article is then placed ( 615 ) or otherwise disposed in an electrolyte bath as a working electrode in the presence of a counter electrode (e.g. Pt) and a reference electrode (see, e.g.  FIG. 4 ). 
         [0037]    Next, a controlled current density or potential can be applied ( 620 ) to the article. As explained below, the timing and amount of current density and/or potential can be varied according to a number of criteria and considerations. After processing the article can be placed in a boric acid solution to neutralize ( 625 ) protons at interfaces between the more-noble element and the alloy (e.g., at a Pt—CoPt interface. Other methods for such neutralization may be provided, and boric acid solution is an example. Method  600  also can comprise removing ( 630 ) the remaining resist, and filling ( 635 ) of areas between the now-formed domains, which comprise mostly Pt. A DLC coating also can be applied ( 640 ). Further considerations, examples, approaches, and other information about these steps is described below. 
         [0038]    It is to be apparent from this disclosure that methods according to this disclosure may exclude certain steps of method  600 , for example, in some situations resist removal may be unnecessary, and gap filling or a DLC coating may be unnecessary, or omitted. By further example variation, proton neutralization is desirable, but not strictly necessary. 
         [0039]    In an embodiment, two desired characteristics of the supporting electrolyte are (1) anodic removal occurs with minimal attack or without attack of a Ru layer, and (2) the supporting electrolyte causes little, minimal, or no detectable corrosion of CoPt or CoPtX in relatively brief intervals when there is no current density or voltage potential applied between Pt electrode  410  and media portion  200 . Examples of electrolytes that support these characteristics comprise MC1, MBr, MI, MNO 3 , MHSO 4 , M 2 SO 4 , MH 2 PO 4 , M 2 HPO 4 , and MClO 4 , wherein M comprises one of Na + , K + , H + , and NH 4   + . An electrolyte meeting these characteristics is 1M KBr solution. In other circumstances, the desired characteristics for the electrolyte may be changed or reduced. For example, if the Ru layer were encapsulated or otherwise shielded from contact with the electrolyte, then (1), above, may be less needed. A further example electrolyte that may be employed is NaCl 1M pH 6, using 0.1 to 10 mA/cm 2  for 7.5 sec to 10 sec. NaCl solutions (1M, pH 2 to 6) are also effective electrolytes for anodic removal. Further, experiments have showed that anodic removal occurs at a lower current density and a longer time (0.265 mA/cm 2 , 45 sec), as well as at higher current density and a shorter time (1 mA/cm 2 , 10 sec). In an embodiment, the same amount of Co is removed at an electrolyte pH of 6, as compared to an electrolyte pH of 2. Also, in an embodiment, the pH of the electrolyte has an effect on corrosion resistance, such that a pH of 6 shows better corrosion resistance than a pH of 2 or 4. 
         [0040]      FIG. 5  illustrates a schematic example of a surface that can result from processing according to the method of  FIG. 6 . In particular, the surface  500  after processing can have a number of dots (some identified  510   a - 510   n ) that provide recording domains, and are formed of grains of the magnetic recording material initially provided for support on the substrate. For example, the material can comprise grains of CoPt, CoPtCr, and so on. As an alternative embodiment to formation of dots on surface  500 , trenches may be formed by the processing methods described herein. Boundaries of the recording domains are formed based on the removal of Co from areas that were not shielded, such as by a resist coating. The dashed square outline  530  identifies an example of where an original resist outline can have been provided. The recording domain outline  510   c  illustrates that some removal of Co around the peripheral edges of the resist portion  530  may occur, while still preserving a central portion generally unaffected by the anodic processing. As shown, the surface areas between the recording domains can be composed predominantly of Pt, Pd, Ru, Rh, Ir, Os, or Au, and also can have other materials, as described below. Further, the anodic removal of ions can be employed to remove ions from a desired number of recording layers. 
         [0041]      FIG. 7  shows anodic linear sweep voltammograms for the dissolution of a CoPt alloy in various potential electrolytes. These results were obtained under conditions including pH 2, 5 mV/sec sweep, no agitation, with an exposed area of 1 cm 2 . For KBr electrolyte, the anodic limiting potential corresponds to the reaction 2Br − -2e − →Br 2 , which prevents the oxidation of the Ru seedlayer. 
         [0042]    With further regard to item (2) above, at paragraph [0022],  FIG. 8  graphs elemental concentration in solution, due to corrosion (i.e., without current density or potential applied), of Co, Pt, and Ru after exposure to 1M electrolytes at pH 2. In particular, it is noted that a 1M KBr electrolyte exhibits the lowest corrosion of CoPt material, among the tested electrolytes. The concentrations were determined by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). The conditions included exposure to 1M solutions of each electrolyte for 3 minutes. In sum, a 1M KBr electrolyte provides the least corrosion during anodic “off times” of those tested, thus allowing better selectivity in removal of Co from the exposed areas of recording layer  215 , as explained below. Thus, the KBr electrolyte can be preferred over the other electrolytes tested, but the others can be used as well, and more restrictive controls to limit time in the bath can be implemented as desired. 
         [0043]    Further methods of inhibiting media corrosion include electrodeposition of nonmagnetic material from the anodic removal electrolyte, plating a nonmagnetic metal or metal alloy on a media track after the anodic removal, utilizing remaining residual nonmagnetic material within a media trench, and utilizing corrosion inhibitors with the media track including benzotriazole and methyl-benzotriazole to inhibit corrosion before and after the anodic removal. In particular, Benzotriazole (BTA) at 0.01M can be used in processing solutions to inhibit media corrosion at all times before, during and after anodic removal. Further, it was found that the BTA does not significantly affect the rate of anodic removal at high potentials &gt;+0.8V. 
         [0044]    The selective removal of Co (as cobalt ions, such as Co +2 ) from alloys including Co and Pt was demonstrated by chronopotentiometry measurements, such as those depicted in  FIG. 9 . Respective lines show respective oxidation of a magnetic alloy at three different constant current densities (2 mA/cm 2 , 1 mA/cm 2 , 0.5 mA/cm 2 ) performed in 1M KBr solution at pH 2.  FIG. 9  generally illustrates respective gradual increases (higher current densities cause quicker increase in potential) in potential (with reference to a Standard Calomel Electrode (SCE)—e.g. electrode  420 ). 
         [0045]    Each current density line has plateau regions, and those of the lowest current density of 0.5 mA/cm 2  are most apparent. As explained below, these plateaus provide evidence that Co can be selectively removed in an anodic process from a CoPt alloy. The lower potential, at approximately 0.35v vs. SCE, corresponds to the selective removal of Co in its oxidized form (e.g., Co +2  ions). The higher plateau, at approximately 0.5V vs. SCE, corresponds to the oxidation of Pt. The third potential plateau, at approximately 0.7V vs. SCE corresponds to the oxidation of Bromide ions. Confining the joint selection of processing times and current density to areas where there is cobalt removal, but less platinum removal is a preferred approach. A lower current density can allow better process control, in that the process need not be as precisely timed as for higher current densities, but requires somewhat longer processing times. Also, this figure illustrates that the progress of Co removal can be monitored by monitoring the measured potential, which allows for higher throughput processes. 
         [0046]      FIG. 10  is a graphical illustration of a potential versus time, similar to the setup of  FIG. 9 , but with a finer time scale to better illustrate potential change over time. The graph of  FIG. 10  employed an exposed area of 1.2 cm 2 , and the electrolyte was 1M KBr. The arrows indicate points at which a sample of the solution was taken in order to analyze ion concentrations to confirm selective removal of Co from CoPt. The solution samples were analyzed using ICP-OES. 
         [0047]      FIG. 11  illustrates a graph of detectable ionic concentration of each of Co and Pt for the samples taken at the times illustrated in  FIG. 10 . It is shown that detectable amounts of Pt are not removed at least during the first 30 sec under these conditions, and when the measured potential is less than approximately 0.5V vs. SCE. 
         [0048]    Thus, these results show that examples of current density in the range of about 0.5 mA/cm 2  to about 2.0 mA/cm 2  can be selected. Other current densities in addition to this range can be determined as being acceptable by experimentation according to the disclosures presented, and therefore also fall within the scope of examples of the invention. 
         [0049]      FIG. 12  illustrates results of Vibrating Sample Magnetometer (VSM) measurements of different samples after selective anodic removal of Co from Co 82 Pt 18  alloy (such as by the experiment shown in  FIG. 10 ). These results demonstrate complete destruction of magnetization of the Co 82 Pt 18  films after 40 sec can be realized, and that the selective removal of cobalt functions can be used to create domains of magnetic material separated by non-magnetic material. Thus, the material remaining after selective Co removal is not capable of being magnetized to any appreciable degree, and thus can serve as a separator between magnetic domains for data storage. 
         [0050]    In particular,  FIG. 12  illustrates the progressive deterioration in magnetic capability of a processed region. The recognizable hysteresis curve identified as  1215  shows magnetic performance of the control sample, which had no processing. The curve identified as  1220  shows the magnetic performance of the processed region after 5 seconds of processing. The curve identified as  1225  shows a much degraded magnetic capability after 10 seconds of processing. The graph illustrates curves for 15 seconds ( 1230 ), 20 seconds ( 1240 ), 30 seconds ( 1210 ) and 40 seconds ( 1205 ); however, they all are clustered close to the X axis, demonstrating no appreciable magnetic capability remains in any of these samples. 
         [0051]    For these purposes, it is also the case that some platinum removal can be permitted, but such removal should be limited to what occurs incidentally to degrade the magnetic characteristics sufficiently to serve as a separation region. In some case, such degradation need not cause a degree of degradation such that no magnetizability remains, but instead, a degree of degradation appropriate for a particular purpose can be determined. For example, a particular application may only require a magnetic moment of separation regions to be ⅔ or less, or ½ or less, of the magnetic moment of the storage domains. Based on this disclosure, a person of ordinary skill would be able to select a degree of selective Co removal appropriate for the desired application. 
         [0052]      FIGS. 13   a  and  13   b  depict results of X-Ray Photoelectron Spectroscopy (XPS) analysis of non-magnetic material remaining after selective removal of Co from a Co 82 Pt 18  film.  FIG. 13   a  shows cobalt XPS spectra for a control disc and samples from a plurality of processing conditions. The unprocessed control disc results evidence a disc surface primarily comprising cobalt oxides and metallic cobalt. By contrast, all the processed samples demonstrate a large reduction in the presence of metallic cobalt on the surface of the respective samples; they also evidence reduction of cobalt oxides. However, magnetic properties are determined more by metallic cobalt than its oxides. 
         [0053]    In particular,  FIG. 13   a  depicts Co 2p3 spectra for different processed samples, and a control without processing. The control  1350  shows a strong peak associated with surface cobalt oxide, another peak associated with cobalt metal, and a lesser peak also associated with cobalt oxides. Two measurements were taken using a first disk (D 1 ) processed at different pHs, 2 and 4, respectively labeled  1365  and  1360 . These measurements show a relatively flat spectra for both samples, demonstrating that the processed areas no longer have strong spikes associated with cobalt. Two measurements were taken using a second disk having different regions processed at two different pHs, 2 and 5, respectively identified as  1370  and  1375 . The less basic pH 5 sample had a slight spike in the vicinity of what would be expected for cobalt oxide/metal. However, it also is substantially less prominent than the control. Thus, these results further demonstrate the effectiveness of the anodic processing to remove cobalt from processed regions at pHs from around 2 through 5. Of course, it is apparent that even at pH 5, substantial removal of cobalt occurs, such that pHs outside of these ranges also can be verified by further experiments according to this disclosure, and would be within the scope of such embodiments. As an example, when using an electrolyte such as KBr or NaCl, a pH of 2 to 6 is effective to remove Co, but when using NaCl, a pH of 2 can cause more corrosion than a pH of 6. 
         [0054]      FIG. 13   b  depicts Pt 4f 5  and  4   f   7  spectra for the samples described initially with respect to  FIG. 13   a . From the results of  FIG. 13   b , it appears that the surface of the D 2  pH5 ( 1305 ) sample exhibits strong Pt peaks, while the D 1  pH 4 ( 1310 ), D 2  pH2 ( 1315 ) samples all exhibit Pt peaks roughly similar to the control sample  1325 . The D 1  pH2 ( 1320 ) sample exhibits lower Pt peaks than the control and the other processed samples.  FIG. 13   b  also evidences that some impurities, such as Pt-bromides and Pt-hydroxides, can be produced during processing, as identified by the Br3d peak in the control D 2  pH 5 ( 1305 ) line.  FIGS. 13   a  and  13   b  in conjunction show that Co can be removed selectively from a CoPt alloy according to this disclosure. 
         [0055]      FIG. 14  depicts a Transmission Electron Microscopy (TEM) image of a media portion that was provided with shielding over some regions and was exposed in other regions. The white region identified as  1420  is residual resist; the dark layer disposed along the white region was a layer added for contrast, and which need not be added in a media article for actual usage. The area illustrated by arrow  1410  illustrates an area that was not protected, and hence was processed for selective Co removal, as shown by the comparative recess to the area to the right of  1410 . Arrows  1415  demarcate an area of undercut where some removal of Co occurred even though that area was protected by resist. Arrows  1425  illustrate a similar situation to the right. Arrow  1435  illustrates that a central portion of the protected area was substantially unprocessed, such that the recording material initially deposited remains in a substantially unaltered state. Arrow  1430  identifies an area near the central protected region where the columnar grains of magnetic material remain intact, also showing that the processing did not disturb the configuration of this material. Thus,  FIG. 14  illustrates that the desired formation of a dot of magnetic material, surrounded by non-magnetic material can be achieved on a surface of a media article. 
         [0056]      FIG. 14  illustrates that the organic protection ( 1420 ) (e.g. resist) may not entirely prevent undercut (processing) of regions around the periphery of the resist. An extent of undercut can be greater than what would be expected from only intentional anodic processing, with a given current density and for a given duration (i.e., an amount of undercut does not correlate precisely to what would be expected purely from processing time and current density). This result can be attributed predominantly to a corrosion process in the “off time” between anodic removal of Co and rinsing and drying of the media portion (e.g. a disc). The interface Pt/CoPt induces a galvanic cell with ΔE corr =E corr-Pt −E corr-CoPt , which increases a corrosion rate of CoPt at these interfaces. 
         [0057]    A solution for this problem involves mitigation of protons present at the Pt/CoPt interface formed during anodic removal. An example of such a solution is to transfer the anodized media (e.g. disc) to a well-stirred (e.g. ultrasonic agitation) bath with boric acid and water that has a pH of about 8, or a similar buffering solution. 
         [0058]    Thus, the above-described aspects include the fabrication of patterned (or bit patterned or discrete track) media by anodic removal of Co from selected areas (e.g. unmasked areas) of a surface composed of a substantially uniform layer of an alloy of Co and Pt, such as a CoPtX alloy in an HCP orientation in order to form data storage domains (a.k.a. dots, or trenches). The anodic removal of Co from selected areas in order to define the dots or trenches allows a processed media article to begin with a generally uniform media storage layer, rather than one which also has materials designed to shield the dots or trenches from each other, such as a silicon dioxide material. 
         [0059]    Also, the processed media can have the following characteristics. First, the material made non-magnetic during processing is recessed (e.g., 2 to 3 nm) from the magnetic dots or trenches, and fills the space between the dots or trenches. Therefore, usage of an additive filling, such as a filling with alumina, that often must be followed by Chemical Mechanical Polishing (CMP) may be rendered unnecessary, or may be reduced substantially. 
         [0060]    Second, the photoresist material, which served as a protective mask during formation of the CoPt or CoPtX dots or trenches, can be removed, and a DLC deposition can be made on the media article for final corrosion protection. In accordance with this description,  FIG. 15  depicts a cross section of a processed article of media with a DLC coating. Dots  1505  and  1510  are identified as being separated by region  1515 , which has been processed for selective removal of Co. 
         [0061]    For clarity, the above description describes examples of anodic processing of a continuous surface of a CoPt alloy for removal of Co in selected regions of the surface. Other examples and implementations comprise using different alloys. Each alloy will have a more-noble component and a less noble component. Examples of the more-noble component include Pt, Pd, Ru, Rh, Ir, Os, and Au. Examples of the less-noble component include Co and Fe. Of course, other materials can be provided in the alloy, such as Cr, Cu, Ag, Ta, Ti, O, B and TiO 2 . 
         [0062]    It would be apparent from this disclosure that a pattern of resist can be provided on the media article to account for an expected amount of undercut that would result during processing, in order to achieve an end result of a desired size of recording domain, for a given set of processing conditions. It also would be apparent that the resist pattern is not limited to formation only of dots or islands, but can be provided in any of a variety of different patterns, such as circular tracks. Further areas that can be made to contain servo patterns or other servo information also can be provided according to this disclosure. As such, a person of ordinary skill would have understood embodiments according to this disclosure to comprehend any of these alternatives alone or in combination with other examples and disclosures. 
         [0063]    Those of ordinary skill also may vary the composition of the recording layer, the selection of electrolyte, processing times, processing steps, electrode selection, and other variables, as demonstrated by the examples disclosed above, and according to further experiments and/or simulations in accordance with such disclosure, without varying from the scope of the invention as defined in the appended claims.