Patent Publication Number: US-2011075297-A1

Title: Patterned magnetic media having an exchange bridge structure connecting islands

Description:
RELATED APPLICATIONS 
     This non-provisional patent application is a continuation of U.S. patent application Ser. No. 11/964,685 filed on Dec. 26, 2007, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to the field of magnetic disk drive systems and, in particular, to patterned magnetic media having an exchange bridge structure connecting the islands of a perpendicular magnetic recording layer. 
     2. Statement of the Problem 
     Many computer systems use magnetic disk drives for mass storage of information. Magnetic disk drives typically include one or more magnetic recording heads (sometimes referred to as sliders) that include read elements and write elements. An actuator/suspension arm holds the recording head above a magnetic disk. When the magnetic disk rotates, an air flow generated by the rotation of the magnetic disk causes an air bearing surface (ABS) side of the recording head to ride a particular height above the magnetic disk. The height depends on the shape of the ABS. As the recording head rides on the air bearing, an actuator moves the actuator/suspension arm to position the read element and the write element over selected tracks of the magnetic disk. 
     One type of magnetic disk presently used in magnetic disk drives provides for longitudinal recording. A magnetic disk for longitudinal recording includes a magnetic recording layer having an easy axis of magnetization parallel to the substrate. The easy axis of magnetization is the crystalline axis that is aligned along the lowest energy direction for the magnetic moment. Another type of magnetic disk provides for perpendicular recording. A magnetic disk for perpendicular recording includes a magnetic recording layer having an easy axis of magnetization oriented substantially perpendicular to the substrate. 
     A perpendicular magnetic disk is generally formed with a soft magnetic underlayer (SUL), an interlayer, a perpendicular magnetic recording layer, and a protective layer or overcoat for protecting the surface of the perpendicular magnetic recording layer, which are formed on a substrate. The soft magnetic underlayer (SUL) serves to concentrate a magnetic flux emitted from a main pole of a write element and to serve as a flux return path back to a return pole of the write element during recording on the magnetic recording layer. The interlayer serves to control the size of magnetic crystal grains and the orientation of the magnetic crystal grains in the magnetic recording layer. The interlayer also serves to magnetically de-couple the SUL and the magnetic recording layer. 
     On a longitudinal or perpendicular magnetic disk, the magnetic recording layer is divided into small magnetic regions, each of which is used to encode a single binary unit of information. The magnetic regions include multiple magnetic grains, possibly small in number (10 to 100), which generates a highly localized magnetic field. The write element magnetizes a magnetic region by generating a strong local magnetic field. 
     As the areal density of magnetic disks increase, the super-paramagnetic effect causes problems for disk manufacturers. The super-paramagnetic effect occurs when the microscopic magnetic grains on the disk become so tiny that ambient temperature can reverse their magnetic orientations. The result is that the bit is erased and the data is lost. 
     One solution to the problems posed by the super-paramagnetic effect is to pattern the magnetic disk (also referred to as bit patterned recording). A patterned disk is created as an ordered array of highly uniform islands, with each island capable of storing an individual bit. A patterned disk may allow ultra-high density recording to be achieved. Because each island represents an individual magnetic domain, the patterned disk is thermally stable and higher densities may be achieved. 
     However, the magnetic stability of the islands as well as their switching field distribution may be adversely affected by magnetostatic interaction fields. The adverse effects of magnetostatic interaction fields are a problem especially when the media is patterned with high densities of islands. As the size of the islands decrease with increased density, the width of the write element (i.e., pole tip) also decreases. Smaller pole tips lead to reduced write fields. Thus, the switching field (Hs) of the islands needs to be decreased, which leads to decreased energy barriers against thermal reversal or demagnetization-induced reversal. 
     The islands on a perpendicular magnetic disk are patterned as discrete magnetic islands, meaning that there is no magnetic material connecting the islands. Although there is no magnetic material connecting the islands, there is still magnetostatic coupling between the islands. Magnetostatic coupling tends to cause antiparallel (AP) coupling between neighboring islands. As the densities increase and the islands are patterned closer together, the magnetostatic coupling between the islands increases. The increase in magnetostatic coupling can de-stabilize the island magnetization. 
     SUMMARY 
     Embodiments of the invention solve the above and other related problems by connecting the islands of a patterned magnetic recording media with an exchange bridge structure formed from magnetic material. Connecting the islands with magnetic material increases exchange coupling between the islands. The exchange coupling tends to cause parallel coupling between neighboring islands, which counteracts or offsets the magnetostatic coupling between the islands. The result is that the islands are more magnetically stable against thermal reversal or demagnetization-induced reversal. 
     One embodiment of the invention comprises a method of fabricating a patterned magnetic recording media. One step of the method includes fabricating a perpendicular magnetic recording layer that is patterned into a plurality of discrete magnetic islands. Another step of the method includes fabricating an exchange bridge structure formed from magnetic material that connects the islands of the perpendicular magnetic recording layer. These steps may be performed in either order. In one example, the exchange bridge structure may be fabricated first, with the perpendicular magnetic recording layer patterned on top of the exchange bridge structure. The exchange bridge structure thus connects the bottoms of the islands of the perpendicular magnetic recording layer. In another example, the perpendicular magnetic recording layer may be patterned first, with the exchange bridge structure fabricated on top of the islands of the perpendicular magnetic recording layer. The exchange bridge structure thus connects the tops of the islands of the perpendicular magnetic recording layer. In yet another example, the perpendicular magnetic recording layer may be patterned first, with the exchange bridge structure fabricated between the islands of the perpendicular magnetic recording layer. The exchange bridge structure thus connects the sides of the islands of the perpendicular magnetic recording layer. 
     The invention may include other exemplary embodiments described below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The same reference number represents the same element or same type of element on all drawings. 
         FIG. 1  illustrates a magnetic disk drive system. 
         FIG. 2  is a cross-sectional view of a typical patterned magnetic recording media for perpendicular recording. 
         FIG. 3  is a flow chart illustrating a method of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention. 
         FIG. 4  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure fabricated under islands in an exemplary embodiment of the invention. 
         FIG. 5  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure fabricated on top of islands in another exemplary embodiment of the invention. 
         FIG. 6  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure fabricated between islands in another exemplary embodiment of the invention. 
         FIG. 7  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure only partially filling the spaces between islands in an exemplary embodiment of the invention. 
         FIG. 8  is a flow chart illustrating a method of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention. 
         FIG. 9  is a cross-sectional view of a patterned magnetic recording media with an SUL deposited in an exemplary embodiment of the invention. 
         FIG. 10  is a cross-sectional view of patterned a magnetic recording media with an interlayer deposited in an exemplary embodiment of the invention. 
         FIG. 11  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure deposited in an exemplary embodiment of the invention. 
         FIG. 12  is a cross-sectional view of a patterned magnetic recording media with a perpendicular magnetic recording layer deposited in an exemplary embodiment of the invention. 
         FIG. 13  is a cross-sectional view of a patterned magnetic recording media with an etch mask patterned in an exemplary embodiment of the invention. 
         FIG. 14  is a cross-sectional view of a patterned magnetic recording media after the etching process in an exemplary embodiment of the invention. 
         FIG. 15  is a cross-sectional view of a patterned magnetic recording media with an etch mask removed in an exemplary embodiment of the invention. 
         FIG. 16  is a flow chart illustrating another method of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention. 
         FIG. 17  is a cross-sectional view of a patterned magnetic recording media with an SUL deposited in an exemplary embodiment of the invention. 
         FIG. 18  is a cross-sectional view of a patterned magnetic recording media with an interlayer deposited in an exemplary embodiment of the invention. 
         FIG. 19  is a cross-sectional view of a patterned magnetic recording media with a perpendicular magnetic recording layer deposited in an exemplary embodiment of the invention. 
         FIG. 20  is a cross-sectional view of a patterned magnetic recording media with an etch mask patterned in an exemplary embodiment of the invention. 
         FIG. 21  is a cross-sectional view of a patterned magnetic recording media after an etching process in an exemplary embodiment of the invention. 
         FIG. 22  is a cross-sectional view of a patterned magnetic recording media with a refill material deposited in an exemplary embodiment of the invention. 
         FIG. 23  is a cross-sectional view of a patterned magnetic recording media with an etch mask removed in an exemplary embodiment of the invention. 
         FIG. 24  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure deposited in an exemplary embodiment of the invention. 
         FIG. 25  is a flow chart illustrating another method of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention. 
         FIG. 26  is a cross-sectional view of a patterned magnetic recording media with an SUL deposited in an exemplary embodiment of the invention. 
         FIG. 27  is a cross-sectional view of a patterned magnetic recording media with an interlayer deposited in an exemplary embodiment of the invention. 
         FIG. 28  is a cross-sectional view of a patterned magnetic recording media with a perpendicular magnetic recording layer deposited in an exemplary embodiment of the invention. 
         FIG. 29  is a cross-sectional view of a patterned magnetic recording media with an etch mask patterned in an exemplary embodiment of the invention. 
         FIG. 30  is a cross-sectional view of a patterned magnetic recording media after an etching process in an exemplary embodiment of the invention. 
         FIG. 31  is a cross-sectional view of a patterned magnetic recording media with an exchange bridge structure deposited in an exemplary embodiment of the invention. 
         FIG. 32  is a cross-sectional view of a patterned magnetic recording media with an etch mask removed in an exemplary embodiment of the invention. 
         FIG. 33  illustrates a patterned magnetic recording media with refill material deposited before an exchange bridge structure in an exemplary embodiment of the invention. 
         FIG. 34  illustrates a patterned magnetic recording media with refill material deposited after an exchange bridge structure in an exemplary embodiment of the invention. 
         FIG. 35  illustrates a multi-layer exchange bridge structure in an exemplary embodiment of the invention. 
         FIG. 36  is a cross-sectional view of a patterned magnetic recording media with islands fabricated on a SUL in an exemplary embodiment of the invention. 
         FIG. 37  is a cross-sectional view of a patterned magnetic recording media with islands fabricated on an exchange control layer in an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a magnetic disk drive system  100 . Magnetic disk drive system  100  includes a spindle  102 , a magnetic recording disk  104 , a motor controller  106 , an actuator  108 , an actuator/suspension arm  110 , and a recording head  114 . Spindle  102  supports and rotates magnetic recording disk  104  in the direction indicated by the arrow. A spindle motor (not shown) rotates spindle  102  according to control signals from motor controller  106 . Recording head  114  is supported by actuator/suspension arm  110 . Actuator/suspension arm  110  is connected to actuator  108  that is configured to rotate in order to position recording head  114  over a desired track of magnetic recording disk  104 . Magnetic disk drive system  100  may include other devices, components, or systems not shown in  FIG. 1 . For instance, a plurality of magnetic disks, actuators, actuator/suspension arms, and recording heads may be used. 
     When magnetic recording disk  104  rotates, an air flow generated by the rotation of magnetic disk  104  causes an air bearing surface (ABS) of recording head  114  to ride on a cushion of air at a particular height above magnetic disk  104 . The height depends on the shape of the ABS. As recording head  114  rides on the cushion of air, actuator  108  moves actuator/suspension arm  110  to position a read element (not shown) and a write element (not shown) in recording head  114  over selected tracks of magnetic recording disk  104 . 
       FIG. 2  is a cross-sectional view of a typical patterned magnetic recording media  200  for perpendicular recording, such as magnetic disk  104 . Patterned magnetic recording media  200  includes a soft magnetic underlayer (SUL)  202 , an interlayer  204 , and a perpendicular magnetic recording layer  206  formed on a substrate  201 . Patterned magnetic recording media  200  may include other layers not shown in  FIG. 2  for the sake of brevity, such as one or more protective layers or an overcoat formed on perpendicular magnetic recording layer  206 , one or more seed layers, one or more layers between SUL  202  and interlayer  204 , or one or more layers between interlayer  204  and magnetic recording layer  206 , etc. 
     Perpendicular magnetic recording layer  206  is formed from one or more materials that have an easy axis of magnetization oriented substantially perpendicular to substrate  201 . Perpendicular magnetic recording layer  206  may be formed from a Co-alloy and may include elements such as Cr and Pt as well as oxides such as SiO 2 . Interlayer  204  controls the orientation and grain diameter of the perpendicular magnetic recording layer  206 . SUL  202  acts in conjunction with the write element to increase the perpendicular field magnitude and improve the field gradient generated by a recording head passing over magnetic recording media  200 . SUL  202  may be a single layer structure formed from materials such as CoFeTaZr. SUL  202  may alternatively have an antiparallel (AP) structure, where two SULs are antiparallel coupled across an AP coupling layer. 
     Perpendicular magnetic recording layer  206  is patterned into a plurality of discrete magnetic islands  208 . Islands  208  are separated from one another by refill material  210 , which is some type of non-magnetic material such as alumina. Although there is no magnetic material connecting islands  208 , there is still magnetostatic coupling between islands  208 . Magnetostatic coupling tends to cause AP coupling between neighboring islands  208 . As densities increase and islands  208  are patterned closer together, the magnetostatic coupling between islands  208  increases. The increase in magnetostatic coupling leads to magnetic instability in islands  208 . Improved patterned magnetic recording media and associated methods of fabrication are described below to overcome the problems of magnetostatic coupling. 
       FIGS. 3-37  and the following description depict specific exemplary embodiments of the invention to teach those skilled in the art how to make and use the invention. For the purpose of teaching inventive principles, some conventional aspects of the invention have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific embodiments described below, but only by the claims and their equivalents. 
     In the following embodiments of patterned magnetic recording media, a soft magnetic underlayer (SUL) is described as one of the layers used to form the media, as that is common in present technology. However, the patterned magnetic recording media in the following embodiments may include a SUL as described below, may include a substantially thinner SUL or a SUL with significantly less permeability than is presently implemented, or no SUL. 
       FIG. 3  is a flow chart illustrating a method  300  of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention. Method  300  may be used to fabricate magnetic recording disk  104  as shown in  FIG. 1 . 
     Step  302  comprises fabricating a soft magnetic underlayer (SUL) on a substrate. Step  304  comprises fabricating an interlayer on the SUL. Step  306  comprises fabricating a perpendicular magnetic recording layer. The perpendicular magnetic recording layer may be fabricated in a variety of ways. In one example, the material for the layer is deposited, and then is patterned. The perpendicular magnetic recording layer may be patterned by first patterning a master tool using electron beam lithography. An etch layer may then be deposited on the perpendicular magnetic recording layer, which is imprinted with the master tool. An etching process, such as ion beam etching, may then be performed to remove the portions of the perpendicular magnetic recording layer that are exposed by the etch layer. This patterns the perpendicular magnetic recording layer into a plurality of discrete magnetic islands. 
     In another example, additional substrate material may be deposited before the perpendicular magnetic recording layer. An etch layer may then be deposited on the substrate material, which is imprinted with the master tool. An etching process may then be performed to remove the portions of the substrate material that are exposed by the etch layer. This patterns the substrate material into a plurality of discrete islands. The perpendicular magnetic recording layer is then deposited on top of the patterned substrate material. Those skilled in the art will appreciate that there may be additional ways of patterning a perpendicular magnetic recording layer. 
     Step  308  comprises fabricating an exchange bridge structure. An exchange bridge structure comprises any structure that connects neighboring islands of a patterned perpendicular magnetic recording layer with magnetic material. The exchange bridge structure increases exchange coupling between the islands. The exchange coupling tends to cause the magnetizations of neighboring islands to align in parallel, which counteracts or offsets the magnetostatic coupling between the islands. As a result, the islands are more magnetically stable against thermal reversal or demagnetization-induced reversal. 
     The steps of method  300  are not provided in any particular order. As a result, the exchange bridge structure may be fabricated before the perpendicular magnetic recording layer, or after the perpendicular magnetic recording layer. Thus, the exchange bridge structure may be fabricated underneath the perpendicular magnetic recording layer in order to connect the bottoms of the islands. In one alternative, the exchange bridge structure may be fabricated on top of the perpendicular magnetic recording layer in order to connect the tops of the islands. In yet another alternative, the exchange bridge structure may be fabricated in between the islands. Examples of these structures are shown in  FIGS. 4-6 . 
       FIG. 4  is a cross-sectional view of a patterned magnetic recording media  400  with an exchange bridge structure fabricated under the islands in an exemplary embodiment of the invention. Patterned magnetic recording media  400  includes a soft magnetic underlayer (SUL)  402  formed on a substrate  401 , with an interlayer  404  formed on SUL  402 . Patterned magnetic recording media  400  further includes an exchange bridge structure  406  formed on interlayer  404 . Patterned magnetic recording media  400  further includes a perpendicular magnetic recording layer  408  formed on exchange bridge structure  406 . Patterned magnetic recording media  400  may include other layers not shown in  FIG. 4  for the sake of brevity, such as one or more protective layers formed on perpendicular magnetic recording layer  408 , one or more seed layers, one or more layers between SUL  402  and interlayer  404 , etc. 
     Patterned magnetic recording layer  408  is patterned into a plurality of islands  410 . Because islands  410  are formed on exchange bridge structure  406 , the bottom of islands  410  are connected to one another with magnetic material. Exchange bridge structure  406  provides exchange coupling between islands  410 , which counteracts the demagnetization fields from neighboring islands  410 . The interaction field can decrease or increase the switching field of an island  410  depending on relative orientation. Exchange bridge structure  406  filters out the switching field fluctuations that are due to magnetostatic coupling. Further, exchange bridge structure  406  connects islands  410  with different intrinsic switching fields (e.g., due to anisotropy fluctuations, moment fluctuations, defects, etc), which helps to smooth these fluctuations. Exchange bridge structure  406  may also allow the use of an increased anisotropy of islands  410  without raising the write field requirement. 
       FIG. 5  is a cross-sectional view of a patterned magnetic recording media  500  with an exchange bridge structure fabricated on top of the islands in another exemplary embodiment of the invention. Patterned magnetic recording media  500  includes a SUL  502  formed on a substrate  501 , with an interlayer  504  formed on SUL  502 . Patterned magnetic recording media  500  further includes a perpendicular magnetic recording layer  506  formed on interlayer  504 . Patterned magnetic recording layer  506  is patterned into a plurality of islands  508 . Refill material  510  is deposited between islands  508  in order to create a planarized surface. Patterned magnetic recording media  500  further includes an exchange bridge structure  512  formed on patterned magnetic recording layer  506 . Because exchange bridge structure  406  is formed on patterned magnetic recording layer  506 , the top of islands  508  are connected to one another with magnetic material. 
       FIG. 6  is a cross-sectional view of a patterned magnetic recording media  600  with an exchange bridge structure fabricated between the islands in another exemplary embodiment of the invention. Patterned magnetic recording media  600  includes a SUL  602  formed on a substrate  601 , with an interlayer  604  formed on SUL  602 . Patterned magnetic recording media  600  further includes a perpendicular magnetic recording layer  606  formed on interlayer  604 . Patterned magnetic recording layer  606  is patterned into a plurality of islands  608 . Patterned magnetic recording media  600  further includes an exchange bridge structure  610  formed between islands  608  of patterned magnetic recording layer  606 . 
     Patterned magnetic recording media  600  as illustrated in  FIG. 6  shows exchange bridge structure  610  completely filling the spaces between islands  608 . However, exchange bridge structure  610  may only partially fill the spaces between islands  608  in other embodiments.  FIG. 7  is a cross-sectional view of a patterned magnetic recording media  600  with exchange bridge structure  610  only partially filling the spaces between islands  608 . A non-magnetic material  702  is deposited between islands  608 , and exchange bridge structure  610  is deposited on top of non-magnetic material  702 . In other embodiments, exchange bridge structure  610  may be deposited first with non-magnetic material  702  deposited on top of exchange bridge structure  610 . 
     Patterned magnetic recording media as described herein may be fabricated in a variety of ways. Three examples are shown in  FIGS. 8-34 , but those skilled in the art will appreciate that many variations of these fabrication methods may be employed. 
       FIG. 8  is a flow chart illustrating a method  800  of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention.  FIGS. 9-15  illustrate a patterned magnetic recording media  900  being fabricated according to method  800 . 
     Step  802  comprises depositing a SUL  902  on a substrate  901  (see  FIG. 9 ).  FIG. 9  is a cross-sectional view of patterned magnetic recording media  900  with SUL  902  deposited according to step  802 . As previously mentioned, SUL  902  may comprise a single layer structure or an AP coupled structure. Step  804  comprises depositing an interlayer  1002  on SUL  902  (see  FIG. 10 ).  FIG. 10  is a cross-sectional view of patterned magnetic recording media  900  with interlayer  1002  deposited according to step  804 . The material for interlayer  1002  may comprise NiCr, NiWCr, or a similar alloy. 
     Step  806  comprises depositing an exchange bridge structure  1102  on interlayer  1002  (see  FIG. 11 ).  FIG. 11  is a cross-sectional view of patterned magnetic recording media  900  with exchange bridge structure  1102  deposited according to step  806 . Exchange bridge structure  1102  may be deposited in a variety of ways. In one example, exchange bridge structure  1102  may be deposited by depositing an exchange bridge layer of magnetic material, such as Permalloy, Co-alloys, or soft ferromagnetic materials. In another example, exchange bridge structure  1102  may be deposited by depositing an exchange bridge layer of magnetic material, and then depositing an exchange control layer of non-magnetic material, such as Ru, Pt, C, Pd, Si, SiOx, SiNx, Cu, Ta, Au, Ag, Mg, MgOx, Ti, TiOx, Cr, etc, or of attenuated magnetic materials by forming mixtures of aforementioned materials with addition of one or more of the magnetic elements such as Co, Fe, and Ni. The exchange control layer controls the amount of exchange coupling between subsequently-formed islands of a perpendicular magnetic recording layer and the exchange bridge layer. 
     Step  808  comprises depositing a perpendicular magnetic recording layer  1202  on exchange bridge structure  1102  (see  FIG. 12 ).  FIG. 12  is a cross-sectional view of patterned magnetic recording media  900  with perpendicular magnetic recording layer  1202  deposited according to step  808 . The material for the perpendicular magnetic recording layer  1202  may comprise CoPtCr—SiOx or other similar materials or multilayers of Co, Fe, Pt, Pd, or similar materials. 
     Step  810  comprises patterning an etch mask  1302  on perpendicular magnetic recording layer  1202  (see  FIG. 13 ).  FIG. 13  is a cross-sectional view of patterned magnetic recording media  900  with etch mask  1302  patterned according to step  810 . Step  812  comprises performing an etching process, such as ion beam etching, to remove the portions of perpendicular magnetic recording layer  1202  exposed by etch mask  1302  (see  FIG. 14 ).  FIG. 14  is a cross-sectional view of patterned magnetic recording media  900  after the etching process according to step  812 . The etching process of step  812  defines discrete magnetic islands  1402  out of perpendicular magnetic recording layer  1202 . 
     Step  814  comprises removing etch mask  1302  (see  FIG. 15 ).  FIG. 15  is a cross-sectional view of patterned magnetic recording media  900  with etch mask  1302  removed according to step  814 . At this point, refill material may be deposited to fill in the spaces between islands  1402 , and the top surface planarized to create a flat surface for the recording head to fly over. An overcoat layer may then be deposited to protect islands  1402 . Method  800  fabricates a patterned magnetic recording media  900  much as is illustrated in  FIG. 4 , with exchange bridge structure  1102  fabricated underneath islands  1402 . Exchange bridge structure  1102  thus creates exchange coupling between islands  1402 . 
     One variation of method  800  is to remove interlayer  1002 , and allow SUL  902  to act as the exchange bridge structure. The SUL  902  may then serve as the magnetic layer that creates exchange coupling between islands  1402 . These embodiments are described in  FIGS. 36-37 . 
       FIG. 16  is a flow chart illustrating another method  1600  of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention.  FIGS. 17-24  illustrate a patterned magnetic recording media  1700  being fabricated according to method  1600 . 
     Step  1602  comprises depositing a SUL  1702  on a substrate  1701  (see  FIG. 17 ).  FIG. 17  is a cross-sectional view of patterned magnetic recording media  1700  with SUL  1702  deposited according to step  1602 . Step  1604  comprises depositing an interlayer  1802  on SUL  1702  (see  FIG. 18 ).  FIG. 18  is a cross-sectional view of patterned magnetic recording media  1700  with interlayer  1802  deposited according to step  1604 . 
     Step  1606  comprises depositing a perpendicular magnetic recording layer  1902  on interlayer  1802  (see  FIG. 19 ).  FIG. 19  is a cross-sectional view of patterned magnetic recording media  1700  with perpendicular magnetic recording layer  1902  deposited according to step  1606 . Step  1608  comprises patterning an etch mask  2002  on perpendicular magnetic recording layer  1902  (see  FIG. 20 ).  FIG. 20  is a cross-sectional view of patterned magnetic recording media  1700  with etch mask  2002  patterned according to step  1608 . Step  1610  comprises performing an etching process to remove the portions of perpendicular magnetic recording layer  1902  exposed by etch mask  2002  (see  FIG. 21 ).  FIG. 21  is a cross-sectional view of patterned magnetic recording media  1700  after the etching process according to step  1610 . The etching process of step  1610  defines discrete magnetic islands  2102  out of perpendicular magnetic recording layer  1902 . Step  1612  comprises depositing refill material  2202  (see  FIG. 22 ).  FIG. 22  is a cross-sectional view of patterned magnetic recording media  1700  with refill material  2202  deposited according to step  1612 . Refill material  2202  is used to fill the spaces between islands  2102 . Refill material  2202  may comprise alumina or some other non-magnetic material. Step  1614  comprises removing etch mask  2002  (see  FIG. 23 ).  FIG. 23  is a cross-sectional view of patterned magnetic recording media  1700  with etch mask  2002  removed according to step  1614 . At this point, the top surface of patterned magnetic recording media  1700  may be planarized, or may be left slightly uneven from the previous processes. 
     Step  1616  comprises depositing an exchange bridge structure  2402  on the top surface of patterned magnetic recording media  1700  (see  FIG. 24 ).  FIG. 24  is a cross-sectional view of patterned magnetic recording media  1700  with exchange bridge structure  2402  deposited according to step  1616 . Exchange bridge structure  2402  is in contact with the top surfaces of islands  2102 . An overcoat layer may then be deposited to protect exchange bridge structure  2402 . 
     In the embodiment described in  FIG. 16 , perpendicular magnetic recording layer  1902  was etched to form islands  2102 . However, those skilled in the art will appreciate that there are different ways of forming islands  2102 . For example, substrate material may be deposited in the place of perpendicular magnetic recording layer  1902 , and then patterned as described above. A perpendicular magnetic recording layer may then be deposited on top of the islands formed out of the substrate material. After the perpendicular magnetic recording layer and the refill material  2202  is deposited, exchange bridge structure  2402  may then be deposited. 
       FIG. 25  is a flow chart illustrating another method  2500  of fabricating a patterned magnetic recording media in an exemplary embodiment of the invention.  FIGS. 26-34  illustrate a patterned magnetic recording media  2600  being fabricated according to method  2500 . 
     Step  2502  comprises depositing a SUL  2602  on a substrate  2601  (see  FIG. 26 ).  FIG. 26  is a cross-sectional view of patterned magnetic recording media  2600  with SUL  2602  deposited according to step  2502 . Step  2504  comprises depositing an interlayer  2702  on SUL  2602  (see  FIG. 27 ).  FIG. 27  is a cross-sectional view of patterned magnetic recording media  2600  with interlayer  2702  deposited according to step  2504 . 
     Step  2506  comprises depositing a perpendicular magnetic recording layer  2802  on interlayer  2702  (see  FIG. 28 ).  FIG. 28  is a cross-sectional view of patterned magnetic recording media  2600  with perpendicular magnetic recording layer  2802  deposited according to step  2506 . Step  2508  comprises patterning an etch mask  2902  on perpendicular magnetic recording layer  2802  (see  FIG. 29 ).  FIG. 29  is a cross-sectional view of patterned magnetic recording media  2600  with etch mask  2902  patterned according to step  2508 . Step  2510  comprises performing an etching process to remove the portions of perpendicular magnetic recording layer  2802  exposed by etch mask  2902  (see  FIG. 30 ).  FIG. 30  is a cross-sectional view of patterned magnetic recording media  2600  after the etching process according to step  2510 . The etching process of step  2510  defines discrete magnetic islands  3002  out of perpendicular magnetic recording layer  2802 . 
     Step  2512  comprises depositing an exchange bridge structure  3102  (see  FIG. 31 ).  FIG. 31  is a cross-sectional view of patterned magnetic recording media  2600  with exchange bridge structure  3102  deposited according to step  2512 . Exchange bridge structure  3102  is deposited between islands  3002  and contacts the sides of islands  3002 . 
     Step  2514  comprises removing etch mask  2902  (see  FIG. 32 ).  FIG. 32  is a cross-sectional view of patterned magnetic recording media  2600  with etch mask  2902  removed according to step  2514 . At this point, the top surface of patterned magnetic recording media  2600  may be planarized, or may be left slightly uneven from the previous processes. An overcoat layer may then be deposited to protect islands  3002  and exchange bridge structure  3102 . 
       FIG. 32  illustrates the exchange bridge structure  3102  having a thickness equal to islands  3002 . If exchange coupling between islands  3002  is too strong to allow islands  3002  to switch independently from one another, then a composite material for exchange bridge structure  3102  may be used. For instance, there may be microscopic regions of magnetic material interspersed among regions of non-magnetic material. Strong exchange coupling may alternatively be reduced by adjusting the thickness of exchange bridge structure  3102  as shown in  FIGS. 33-34 . The spaces between islands  3002  may be filled with refill material (i.e., a non-magnetic material) and exchange bridge structure  3102  to adjust the thickness of exchange bridge structure  3102 .  FIG. 33  illustrates patterned magnetic recording media  2600  with refill material  3302  deposited before exchange bridge structure  3102 . In this example, the exchange bridge structure  3102  is thinner than in  FIG. 32  and contacts the top portions of islands  3002 .  FIG. 34  illustrates patterned magnetic recording media  2600  with refill material  3402  deposited after exchange bridge structure  3102 . In this example, the exchange bridge structure  3102  is again thinner than in  FIG. 32  and contacts the bottom portions of islands  3002 . 
     The exchange bridge structure in the above embodiments may be fabricated in a variety of ways. In one example, the exchange bridge structure may be fabricated as a layer of magnetic material, such as Permalloy, Co-alloys, or soft ferromagnetic materials. In another example, the exchange bridge structure may be a multi-layer structure of non-magnetic material and magnetic material. In another example, the exchange bridge may include attenuated magnetic materials formed from mixtures of non-magnetic material, including Ru, Pt, C, Pd, Si, SiOx, SiNx, Cu, Ta, Au, Ag, Mg, MgOx, Ti, TiOx, Cr, etc, and one or more of the magnetic elements such as Co, Fe, and Ni. 
       FIG. 35  illustrates a multi-layer exchange bridge structure  3500  in an exemplary embodiment of the invention. Multi-layer exchange bridge structure  3500  includes an exchange bridge layer  3502  of magnetic material, such as Permalloy, Co-alloys, or soft ferromagnetic materials. The thickness of the exchange bridge layer  3502 , in one example, is between about 0.3-12 nanometers, depending on the material used and what type of exchange control layer, if any, is used. A high thickness of the exchange bridge layer  3502  is achieved with attenuated magnetic materials where magnetic materials are attenuated by the addition of non-magnetic materials including Ru, Pt, C, Pd, Si, SiOx, SiNx, Cu, Ta, Au, Ag, Mg, MgOx, Ti, TiOx, Cr, etc. Thinner thickness of the exchange bridge layer  3502  is achieved by adding less, if any, of the non-magnetic materials to the magnetic materials. 
     Multi-layer exchange bridge structure  3500  further includes an exchange control layer  3504  of non-magnetic material, such as Ru, Pt, C, Pd, Si, SiOx, SiNx, Cu, Ta, Au, Ag, Mg, MgOx, Ti, TiOx, Cr, etc, or of attenuated magnetic materials by forming mixtures of aforementioned materials with addition of one or more of the magnetic elements such as Co, Fe, and Ni. Islands  3506  of a perpendicular magnetic recording layer are illustrated as being patterned on top of exchange control layer  3504 . Exchange control layer  3504  controls the amount of exchange coupling between islands  3506  of a perpendicular magnetic recording layer and exchange bridge layer  3502 . Exchange control layer  3504  is sufficiently thin to allow some exchange coupling to be mediated. An exemplary thickness of exchange control layer  3504  is between about 0.5-2 nanometers, depending on the material used. A low thickness of exchange control layer  3504  may be achieved with non-magnetic materials or highly-attenuated magnetic materials with small addition of the magnetic elements to the non-magnetic materials. Larger thickness of exchange control layer  3504  may be achieved by adding more of the magnetic elements to the non-magnetic materials. 
     In  FIG. 35 , exchange control layer  3504  is illustrated as deposited on top of exchange bridge layer  3502 . Such a configuration may be used in the method of  FIG. 8 . Exchange control layer  3504  is used to separate exchange bridge layer  3502  from the islands  3506  of the perpendicular magnetic recording layer. Thus, exchange bridge layer  3502  may be deposited on top of exchange control layer  3504  in other embodiments if exchange bridge structure  3500  is fabricated on top of the islands. 
     As previously mentioned, the SUL may act as the exchange bridge layer is some embodiments, which is illustrated in  FIGS. 36-37 .  FIG. 36  is a cross-sectional view of a patterned magnetic recording media  3600  with islands fabricated on a SUL in an exemplary embodiment of the invention. Patterned magnetic recording media  3600  includes a soft magnetic underlayer (SUL)  3602  formed on a substrate  3601 , with a perpendicular magnetic recording layer  3608  formed on SUL  3602 . Patterned magnetic recording layer  3608  is patterned into a plurality of islands  3610 . Because islands  3610  are formed on SUL  3602 , the bottoms of islands  3610  are connected to one another with magnetic material. SUL  3602  in this embodiment acts as an exchange bridge layer to provide exchange coupling between islands  3610 . 
     In order to avoid excessive coupling between the islands  3610  in this embodiment, a thinner SUL  3602  or a SUL  3602  with a lower permeability is used. A typical SUL is between about 20-50 nanometers thick. A thinner or lower permeability SUL may be used when a write element, which is used to write to the media, is less reliant on flux conductance through the SUL. An example of a thinner SUL is about 2-5 nanometers. When a thinner SUL  3602  or a SUL  3602  having a lower permeability is used in the media, the islands  3610  may be formed directly on SUL  3602 , which then acts as the exchange bridge layer. 
     If a thicker SUL is used, then an exchange control layer may be implemented between the islands and the SUL.  FIG. 37  is a cross-sectional view of a patterned magnetic recording media  3700  with islands fabricated on an exchange control layer in an exemplary embodiment of the invention. Patterned magnetic recording media  3700  includes a soft magnetic underlayer (SUL)  3702  formed on a substrate  3701 , with an exchange control layer  3706  formed on SUL  3702 . Patterned magnetic recording media  3700  also includes a perpendicular magnetic recording layer  3708  formed on exchange control layer  3706 . Patterned magnetic recording layer  3708  is patterned into a plurality of islands  3710 . Again, SUL  3702  in this embodiment acts as an exchange bridge layer to provide exchange coupling between islands  3710 . 
     Exchange control layer  3706  is formed from non-magnetic material, such as Ru, Pt, C, Pd, Si, SiOx, SiNx, Cu, Ta, Au, Ag, Mg, MgOx, Ti, TiOx, Cr, etc, or of attenuated magnetic materials by forming mixtures of aforementioned materials with addition of one or more of the magnetic elements such as Co, Fe, and Ni. Exchange control layer  3706  controls the amount of exchange coupling between islands  3710  and SUL  3702 . Exchange control layer  3706  is sufficiently thin to allow some exchange coupling to be mediated. An exemplary thickness of exchange control layer  3706  is between about 0.5-2 nanometers, depending on the material used. A low thickness of exchange control layer  3706  may be achieved with non-magnetic materials or highly-attenuated magnetic materials with small addition of the magnetic elements to the non-magnetic materials. Larger thickness of exchange control layer  3706  may be achieved by adding more of the magnetic elements to the non-magnetic materials. 
     Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents thereof.