Patent Application
20170154647
Hard disk drives read from and write to magnetic patterns on magnetic storage media, which can be used to store data. Hard disk drives offer low cost, high recording capacity, and relatively rapid data retrieval. While the basic principle of reading and writing magnetic patterns on rotating disks (e.g., media disks) remains the same, components of the disk drive, particularly the magnetic storage media have significantly evolved requiring thinner layers formed on the media disks. A magnetic storage medium may be implemented by a PMR media stack that includes various layers.
In one example, perpendicular magnetic recording (PMR) has been used to increase the areal recording density of magnetic storage media. A PMR media stack generally includes a substrate, an antiferromagnetic coupled soft magnetic underlayer (AFC-SUL), a seed layer, an intermediate layer (IL), a grain isolation initiation layer (GIIL), and a magnetic layer stack. The magnetic layer stack includes a number of magnetic layers separated by a number of exchange-break layers (EBLs). The main role of seed layer is to control grain size and develop preferred orientation for ILs and magnetic layers. The IL is used to improve orientation further and to provide a proper template for the magnetic layer so that grain isolation of magnetic layers is enhanced and intergranular magnetic coupling is substantially reduced. Ruthenium (Ru) has been widely used for the IL in PMR media since no alternative shows better properties than Ru.
However, since areal density of magnetic storage media continues to increase, grain size and intergranular magnetic coupling need to be reduced further. The current IL used in PMR media stacks is unable to meet this requirement. Thus, there is a need to provide a PMR media stack that is able to reduce the core grain size of the magnetic layers and widen grain boundaries to result in a signal-to-noise (SNR) gain mainly due to reduction of grain size and intergranular magnetic coupling.
In the following detailed description, various aspects of a PMR media stack and method of manufacture will be presented. These aspects are well suited for reducing the core grain size of the magnetic layers and widening grain boundaries to result in a SNR gain due to reduction of grain size and intergranular magnetic coupling. Those skilled in the art will realize that these aspects may be extended to all types of media disks such as optical disks, floppy disks, or any other suitable disk capable of storing data through various electronic, magnetic, optical, or mechanic changes to the surface of the disk. Accordingly, any reference to a specific system, apparatus, or method is intended only to illustrate the various aspects of the present invention, with the understanding that such aspects may have a wide range of applications.
One aspect of a PMR media stack includes two intermediate layers, and a spacer layer formed between the two intermediate layers, wherein a surface energy of the spacer layer is lower than a surface energy of the two intermediate layers.
One aspect of a method of forming a PMR media stack includes forming two intermediate layers, and forming a spacer layer between the two intermediate layers, wherein a surface energy of the spacer layer is lower than a surface energy of the two intermediate layers.
The detailed description set forth below in connection with the appended drawings is intended as a description of various exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the present invention.
The word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiment” of a system, apparatus, or method does not require that all embodiments of the invention include the described components, structure, features, functionality, processes, advantages, benefits, or modes of operation.
It will be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only several embodiments of the invention by way of illustration. As will be realized by those skilled in the art, the present invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the invention. For example, while embodiments related to PMR are discussed below, other embodiments (e.g., for shingled magnetic recording or other types of recording technologies) are possible.
According to one aspect, the PMR media stack 100 may include a substrate 102, one or more soft magnetic underlayers (SUL) such as an antifermagnetically-coupled SUL (AFC SUL) 104, a seed layer 106, two or more intermediate underlayers (ILs) 108a, 108b, a spacer layer 110, a number of magnetic layers (e.g., Mag1, Mag2, Mag3) 114a-114c each separated from one another by an exchange-break layer (EBL) 116a-116c, a cap 118, and a carbon overcoat (COC) layer 120.
The seed layer 106 and the two or more ILs 108a, 108b may be used to improve crystallographic orientation and to control grain size and distribution of magnetic recording layers 114a-114c. By way of example, Ru or an Ru alloy (Rux) may be selected for use as the ILs 108a, 108b since Ru may help grain orientation of magnetic layers 114a-114c. In addition, Ru may also suppress magnetic coupling of the magnetic recording layers 114a-114b by providing a growth template with a rougher surface. Alternatively, cobalt (Co), a Co alloy (Cox), platinum (Pt), or a Pt alloy (Ptx) may be selected for one or more of the ILs 108a, 108b. In an aspect, formation of each of the ILs 108a, 108b may include a two step process, where the first Rux layer is sputtered at low pressure (Rux L) and the second Rux layer is sputtered at high pressure (Rux H). The Rux L (not illustrated in
The insertion of a spacer layer 110 in between IL 108a and IL 108b may reduce the size of the grains in the ILs 108a, 108b and magnetic recording layers 114a-114c when the surface energy of the spacer layer 110 is selected to lower than the surface energies of the ILs 108a, 108b. For example, the ILs 108a, 108b may be formed from Ru or Rux, and the spacer layer 110 be copper (Cu). Since the surface energy of Cu is relatively low compared to Ru and/or Rux, and the lattice parameter of Cu is similar to Ru, using Cu as the spacer layer 110 may result in epitaxial growth of IL 108b without orientation degradation. Thus, the PMR media stack 100 may include an Ru—Cu—Ru stacked IL configuration, which may allow the grains of magnetic layers 114a-114c to include a small grain size, narrow size distribution, and be well decoupled magnetically for SNR improvement.
In addition, the AFC SUL 104 may be used to reduce noise when reading and writing data to/from the PMR media stack 100. The GIIL 112 and EBLs 116a-116c may control and improve segregation of magnetic grains in each of the magnetic layers 114a-114b, while the cap 118 and COC 120 may be used to may used to protect the PMR media stack 100 against corrosion.
As illustrated in
Referring now to
Referring now to
In this way, the Cu SL 204 may be used to refine grain size and widen grain boundary thickness of the ILs 108a, 108b and magnetic layers 114a-114c illustrated in
As represented by block 302, a substrate can be formed. For example, referring to
As represented by block 304, a soft magnetic underlayer can be formed on the substrate. For example, referring to
As represented by block 306, a seed layer can be formed on the soft magnetic underlayer layer. For example, referring to
As represented by block 308, two intermediate layers can be formed on the seed layer, and as represented by block 310, a spacer layer can be formed between the two intermediate layers. In one aspect, each of the two intermediate layers include at least one of Ru, Co, or Pt, and the spacer layer includes at least one of Cu, Al, Ag, or Au. In an aspect, the forming the two intermediate layers includes forming a first of the two intermediate layers by sputtering a first layer at a first pressure and forming a second of the two intermediate layers by sputtering a second layer at a second pressure onto the first layer, the first pressure being lower than the second pressure. For example, the first pressure includes a range of 2-10 mTorr, and the second pressure includes a range of 40-150 mTorr. In another aspect, the first of the two intermediate layers includes a plurality of grains, each of the plurality of grains being formed with a domed portion such that a valley is formed at a grain boundary between each of the plurality of grains. In a further aspect, the forming the spacer layer comprises forming the spacer layer in the valley located at the grain boundary between each of the plurality of grains. In still a further aspect, the spacer layer is not formed on the domed portion of the plurality of grains. In another aspect, the forming the two intermediate layers further includes forming a second of the two intermediate layers on the domed portion of each of the plurality of grains of the first of the two intermediate layers. For example, referring to
As represented by block 312, a grain isolation initiation layer can be formed on the two intermediate layers. For example, referring to
As represented by block 314, a plurality of magnetic layers can be formed on the grain isolation initiation layer. For example, referring to
As represented by block 316, an exchange breaking layer can be formed on each the plurality of magnetic layers. For example, referring to
A represented by block 318, at least one capping layer can be formed on one of the exchange breaking layers, and as represented by block 320, at least one overcoat layer can be formed on the at least one capping layer. For example, referring to
In this way, a PMR media stack may be formed that includes an Ru—Cu—Ru stacked IL configuration, which may allow the grains of magnetic layers to include a small grain size, narrow size distribution, and be well decoupled magnetically for SNR improvement.
The various aspects of this disclosure are provided to enable one of ordinary skill in the art to practice the present invention. Various modifications to exemplary embodiments presented throughout this disclosure will be readily apparent to those skilled in the art, and the concepts disclosed herein may be extended to other magnetic storage devices. Thus, the claims are not intended to be limited to the various aspects of this disclosure, but are to be accorded the full scope consistent with the language of the claims. All structural and functional equivalents to the various components of the exemplary embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112(f), unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”
