PERPENDICULAR MAGNETIC RECORDING MEDIA WITH LATERAL EXCHANGE CONTROL LAYER
A magnetic media having a lateral exchange control layer formed on a magnetic oxide layer of a magnetic recording layer. A cap layer is formed over the lateral exchange control layer. The lateral exchange control layer can be an alloy comprising Co and one or more of W, Ru, Hf, Ta, Nb and Fe. The lateral exchange control layer has the highest magnetic saturation moment among all the recording layers, and increases spacing between magnetic grains (e.g. increased non-magnetic boundary width), thereby reducing lateral exchange sigma. The presence of lateral exchange control increases signal to noise ratio and reduces bit error rate and increases areal density.
The present invention relates to magnetic data recording and more particularly to a magnetic media having a lateral exchange control layer in a magnetic recording layer for increased lateral exchange and reduced magnetic exchange sigma.
BACKGROUNDAt the heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head includes at least one coil, a write pole and one or more return poles. When current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the coil, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic media, thereby recording a bit of data. The write field then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head.
A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the magnetic media.
In a perpendicular magnetic recording system, the magnetic media on which data is written can be formed with a soft magnetic under-layer and a magnetic recording layer formed over the soft magnetic recording layer. The magnetic recording layer can be formed as individual magnetic grains that are separated by non-magnetic oxide layers. In order to increase data density, it is desirable to decrease the size of the magnetic grains. However certain engineering constraints have made it difficult to further reduce the size of magnetic grains and increase the magnetic data density while also maintaining high signal resolution and data integrity.
SUMMARYThe present invention provides a magnetic data recording media that includes a magnetically soft under-layer and a magnetic recording layer formed over the magnetically soft under-layer. The magnetic recording layer includes a granular magnetic layer, a lateral exchange control layer positioned on the granular magnetic layer and a cap layer formed over the lateral exchange control layer, wherein the lateral exchange control layer comprises an alloy that includes Co and at least one of W, Ru, Hf, Ta, Nb and Fe.
The presence of the lateral exchange control layer advantageously increases the magnetic saturation moment while also increasing the non-magnetic boundary width. This provides reduced bit error rate and also increased signal to noise ratio, thereby allowing for increased areal density.
The lateral exchange control layer can be formed as islands over magnetic grains of the granular magnetic layer. The material of the lateral exchange control layer has a high surface energy which causes it to deposit on the individual grains of the granular magnetic layer, but not on the non-magnetic boundary material.
These and other features and advantages of the invention will be apparent upon reading of the following detailed description of the embodiments taken in conjunction with the figures in which like reference numeral indicate like elements throughout.
For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale.
The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein.
Referring now to
At least one slider 113 is positioned near the magnetic disk 112, each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, slider 113 moves in and out over the disk surface 122 so that the magnetic head assembly 121 can access different tracks of the magnetic disk where desired data are written. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force which biases the slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127 as shown in
During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122, which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of the suspension 115 and supports the slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation.
The various components of the disk storage system are controlled in operation by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, the control unit 129 comprises logic control circuits, and a microprocessor. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position the slider 113 to the desired data track on the media 112. Write and read signals are communicated to and from write and read heads 121 by way of recording channel 125.
The magnetic recording layer includes a granular oxide layer 210 and a non-oxide top layer 219 formed over the granular oxide layer 210. The non-oxide top layer 219 includes a novel lateral exchange control layer 212 formed over the magnetic oxide layer 210, and a magnetic cap layer 214 formed over the lateral exchange control layer 212. The magnetic recording layer and its grain structure are shown in greater detail in
It can also be seen in
For line 502 (the case without the lateral exchange control layer) it can be seen that, achieving the desired amount of lateral exchange coupling puts the media in a relatively steep portion of the curve, causing a very high lateral exchange coupling sigma for a given amount of boundary layer thickness variation. It is desirable to have a low amount of lateral exchange sigma, and this could be achieved by increasing the grain boundary width. However, this would result in an unacceptably low lateral exchange coupling, resulting in poor writeability and thermal stability.
For line 504 however, the presence of the lateral exchange control layer increases the average saturation magnetization Ms of non-oxide top layer 219 (
This effect is further verified by
The table of
In order to form a lateral exchange control layer 212 (
In order to exhibit high Ms as well as a high surface energy, the lateral exchange control layer can be formed of an alloy of Co or Fe and X, where X is a non-magnetic material, and wherein the concentration of X is less than 25%. If the concentration of non-magnetic material in the lateral exchange control layer is more than 25%, magnetic saturation moment will not be sufficiently high. A specific preferable example of an advantageous alloy for use as the lateral exchange layer is Co—Cr—Ru—W where the combined concentration of Ru and W is at least 10 atomic percent and the combined concentration of non-magnetic elements (i.e. Ru, Cr and W) is less than 25 atomic percent.
Therefore, the lateral exchange control layer includes at least 10 atomic percent of an material having a high surface energy, which can be one or more of W, Ru, Hf, Ta, Nb, and Fe, and also includes a non-magnetic material in a concentration of up to 25 atomic percent. More preferably, the concentration of non-magnetic material is more than 10% because it is difficult to sputter deposit thin films if the concentration of non-magnetic material is less than 10%. The capping layer 214 (
While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the inventions should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
Claims
1. A magnetic media, comprising:
- a magnetically soft under-layer; and
- a magnetic recording layer formed over the magnetically soft under-layer, the magnetic recording layer further comprising:
- a granular magnetic layer;
- a magnetic lateral exchange control layer positioned on the granular magnetic layer; and
- a magnetic cap layer formed over the lateral exchange control layer, wherein the magnetic cap layer comprises magnetic grains separated by non-magnetic grain boundaries;
- wherein the lateral exchange control layer comprises an alloy that includes Co and at least one of W, Ru, Hf, Ta, Nb and Fe.
2. The magnetic media as in claim 1, wherein the concentration of non-magnetic material in the lateral exchange control layer is less than 25 atomic percent.
3. The magnetic media as in claim 1, wherein the concentration of non-magnetic material in the lateral exchange control layer is greater than 10 atomic percent and less than 25 atomic percent.
4. The magnetic media as in claim 1, wherein the concentration of one or more of W, Ru, Hf, Ta, Nb and Fe is at least 10 atomic percent.
5. The magnetic media as in claim 1 wherein the lateral exchange control layer has a higher magnetic saturation than the granular magnetic layer or the cap layer.
6. The magnetic media as in claim 1 wherein the lateral exchange control layer has a magnetic saturation of between 650 emu/cc and 800 emu/cc.
7. The magnetic media as in claim 1, wherein the lateral exchange control layer contains no oxide.
8. The magnetic media as in claim 1, wherein the lateral exchange control layer has a thickness of 0.1 nm to 0.5 nm.
9. The magnetic media as in claim 1, wherein the non-magnetic grain boundaries have a thickness that gradually decreases with increasing distance from the lateral exchange control layer.
10. The magnetic media as in claim 9 wherein the cap layer is at least 1.0 nm thick and wherein the non-magnetic grain boundaries have a width of at least 0.5 nm at a location 1.0 nm from the lateral exchange control layer.
11. The magnetic media as in claim 1, wherein the lateral exchange control layer is formed as islands on the granular magnetic layer.
12. The magnetic media as in claim 1, wherein the lateral exchange control layer is formed as islands separated by non-magnetic boundary layers, and wherein the boundary layers at the location of the lateral exchange control layer have a width of at least 1 nm.
13. A magnetic media, comprising:
- a magnetic recording layer formed as a plurality of magnetic structures separated by non-magnetic boundary layers extending vertically between the magnetic structures, the magnetic structures comprising;
- a magnetic oxide structure;
- a magnetic lateral exchange control layer having a surface energy higher than that of Co causing it to be formed as an island on the magnetic oxide structure; and
- a magnetic cap layer formed over the magnetic oxide structure.
14. The magnetic media as in claim 13, wherein the lateral exchange control layer is an alloy comprising Co and at least one of W, Ru, Hf, Ta, Nb and Fe.
15. The magnetic media as in claim 13, wherein the lateral exchange control layer has a higher magnetic saturation than the magnetic oxide structure or the magnetic cap layer.
16. The magnetic media as in claim 13, wherein the lateral exchange control layer has a magnetic saturation of between 650 emu/cc and 800 emu/cc.
17. The magnetic media as in claim 13, wherein the non-magnetic boundary layers have a width of at least 1 nm at the location of the lateral exchange control layer.
18. The magnetic media as in claim 13, wherein the non-magnetic boundary layers have a width of at least 0.5 nm at a location within the cap layer that is 1.0 nm above the lateral exchange control layer.
19. A magnetic data recording system, comprising:
- a housing;
- a magnetic media mounted within the housing; and
- a magnetic read write transducer mounted within the housing for movement adjacent to a surface of the magnetic media;
- wherein the magnetic media comprises:
- a magnetically soft under-layer;
- a magnetic recording layer formed over the magnetically soft under-layer, the magnetic recording layer further comprising:
- a granular magnetic layer;
- a magnetic lateral exchange control layer positioned on the granular magnetic layer; and
- a magnetic cap layer formed over the lateral exchange control layer wherein the magnetic cap layer comprises magnetic grains separated by non-magnetic grain boundaries;
- wherein the lateral exchange control layer comprises an alloy that includes Co and at least one of W, Ru, Hf, Ta, Nb and Fe.
Type: Application
Filed: Nov 19, 2015
Publication Date: May 25, 2017
Inventors: Shun Tonooka (Odawara), Masayoshi Shimizu (Chigasaki), Miki Nishida (Fujisawa), Hiroyuki Katada (Odawara)
Application Number: 14/946,648