JP4353654B2 - Perpendicular magnetic recording medium and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a perpendicular magnetic recording medium mounted on various magnetic recording apparatuses and a manufacturing method thereof.
[0002]
[Prior art]
As a technique for realizing a high density magnetic recording, a perpendicular magnetic recording system is drawing attention in place of the conventional longitudinal magnetic recording system.
[0003]
The perpendicular magnetic recording medium is composed of a magnetic recording layer made of hard magnetic material and a backing layer made of soft magnetic material which is used for recording on the recording layer and plays a role of concentrating magnetic flux generated by the magnetic head. It is known that spike noise, which is one of the noises problematic in the perpendicular magnetic recording medium having such a structure, is caused by a domain wall formed in a soft magnetic layer as a backing layer. Therefore, in order to reduce the noise of the perpendicular magnetic recording medium, it is necessary to prevent the domain wall formation of the soft magnetic underlayer.
[0004]
As for the control of the domain wall of the soft magnetic backing layer, for example, as disclosed in Japanese Patent Laid-Open No. 6-180834 and Japanese Patent Laid-Open No. 10-214719, the upper and lower layers of the soft magnetic backing layer are made of a Co alloy or the like. There are proposed a method in which a ferromagnetic layer is formed and magnetized so as to be magnetized in a desired direction, and a method in which an antiferromagnetic thin film is formed and magnetization is pinned using exchange coupling.
[0005]
The method of controlling the domain wall by exchange coupling with the soft magnetic backing layer using the antiferromagnetic layer as the magnetic domain control layer prevents the domain wall formation of the soft magnetic backing layer when the exchange coupling is sufficiently obtained. Can be very effective. However, in order to obtain sufficient exchange coupling, for example, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 10-214719, a heat treatment after film formation is necessary in order to obtain the characteristics of the soft magnetic backing layer. Since this heat treatment is a treatment that must be performed for a long time while applying a magnetic field in the radial direction, it is very disadvantageous for mass production.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a perpendicular magnetic recording medium with reduced noise by effectively controlling a domain wall of a soft magnetic underlayer by using an antiferromagnetic layer as a magnetic domain control layer, and It is an object of the present invention to provide a manufacturing method suitable for mass production of magnetic recording media.
[0007]
[Means for Solving the Problems]
The first aspect of the present invention for solving the above problems is that at least an underlayer, an orientation control layer, a magnetic domain control layer, a soft magnetic backing layer, an intermediate layer, a magnetic recording layer, a protective layer, and a liquid lubrication layer are provided on a nonmagnetic substrate The magnetic domain control layer is an antiferromagnetic layer in which magnetization is fixed in the radial direction of the substrate, and the soft magnetic backing layer has an easy axis of radius of the substrate. The soft magnetic layer is a Co-based amorphous alloy, the antiferromagnetic layer is a Mn alloy containing at least Ir, the orientation control layer is a NiFe-based alloy containing Cr, and the underlayer is Ta The orientation control layer located under the magnetic domain control layer controls the crystal orientation of the antiferromagnetic layer, and the underlayer located at the bottom layer controls the microstructure of the orientation control layer. Vertical characterized by Similarly, the second embodiment is a method for manufacturing the perpendicular magnetic recording medium, in which a magnetic field is radially applied in the radial direction of the substrate at least when the antiferromagnetic layer and the soft magnetic layer are formed. It is a manufacturing method of a perpendicular magnetic recording medium by applying.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As a result of diligent studies on perpendicular magnetic recording media, a soft magnetic layer made of a Co-based amorphous alloy was used as the soft magnetic underlayer, and IrMn was used as the antiferromagnetic layer as the magnetic domain control layer formed between the nonmagnetic substrate and the soft magnetic layer. In order to control the crystal orientation of the antiferromagnetic layer using an alloy, an orientation control layer made of a NiFe alloy containing Cr is provided under the antiferromagnetic layer, and the microstructure of the orientation control layer is further controlled. An underlayer is provided under the orientation control layer, and at least when the antiferromagnetic layer and the soft magnetic layer as the magnetic domain control layer are formed, a magnetic field is applied in the radial direction of the substrate, so that heat treatment is performed after the film formation. It has been found that a large exchange coupling can be obtained without performing the control, and that the domain wall of the soft magnetic underlayer can be controlled effectively.
[0009]
FIG. 1 is a schematic sectional view of a perpendicular magnetic recording medium of the present invention. A structure in which at least an underlayer 2, an orientation control layer 3, an antiferromagnetic layer as a magnetic domain control layer 4, a soft magnetic layer 5, an intermediate layer 6, a magnetic recording layer 7 and a protective layer 8 are sequentially formed on a nonmagnetic substrate 1. The liquid lubricant layer 9 is further formed thereon.
[0010]
As the nonmagnetic substrate 1, an Al alloy, tempered glass, crystallized glass, or the like subjected to NiP plating, which is used for a normal magnetic recording medium, can be used. The underlayer 2 is made of Ta. The film thickness is not particularly limited, but is preferably about 3 nm to 50 nm in order to be suitable for mass production. The orientation control layer 3 is made of a NiFe alloy containing at least Cr. The film thickness is not particularly limited, but is preferably about 3 nm to 50 nm in order to be suitable for mass production. The antiferromagnetic layer as the magnetic domain control layer 4 is made of an IrMn alloy. The film thickness is not particularly limited, but is preferably about 5 nm to 50 nm in order to obtain appropriate exchange coupling and to be suitable for mass production. The soft magnetic layer 5 is made of a Co-based amorphous alloy. The optimum value of the thickness of the soft magnetic layer 5 varies depending on the structure and characteristics of the magnetic head used for recording, but it is preferably 50 nm or more and 300 nm or less in view of productivity.
[0011]
The intermediate layer 6 is used for preferably controlling the crystal orientation and crystal grain size of the magnetic recording layer 7. Examples of materials that can be used as the material for the intermediate layer include Ti and TiCr alloys. The magnetic recording layer 7 is preferably made of a ferromagnetic material of an alloy containing at least Co and Cr, and the c-axis of the hexagonal close-packed structure is oriented perpendicularly to the film surface for use as a perpendicular magnetic recording medium. Is necessary. For example, a thin film mainly composed of carbon is used for the protective layer 8. The liquid circulating agent layer 9 can be made of, for example, a perfluoropolyether lubricant.
[0012]
In manufacturing the magnetic recording medium shown in FIG. 1 having the layer structure as described above, at least the antiferromagnetic layer and the soft magnetic layer 5 as the magnetic domain control layer 4 are formed, for example, FIG. As shown in FIG. 2, it is necessary to apply the magnetic field in the radial direction of the substrate. Thereby, the magnetization of the antiferromagnetic layer as the magnetic domain control layer 4 is fixed in the radial direction of the substrate, and the easy magnetization axis of the soft magnetic layer 5 to be subsequently laminated is also oriented in the radial direction of the substrate. Control, that is, prevention of domain wall formation becomes possible. From the viewpoint of controlling the domain wall, the strength of the magnetic field to be applied is not limited. However, if an extremely strong magnetic field is applied during film formation, there is a risk of film formation by sputtering. Is desirable.
[0013]
【Example】
Examples of the present invention will be described below.
[0014]
EXAMPLE A chemically strengthened glass substrate (for example, N-5 glass substrate manufactured by HOYA) having a smooth surface was used as a nonmagnetic substrate, and this was introduced into a sputtering apparatus after cleaning, and a Ta underlayer was formed to 5 nm using a Ta target. Then, using a NiFe-based alloy target to which Cr is added, a NiFeCr alloy thin film is formed to a thickness of 5 nm, and an antiferromagnetic layer as a magnetic domain control layer is formed to a thickness of 5 nm using an IrMn alloy target. A soft magnetic layer was formed to a thickness of 100 nm using a CoZrNb target. When forming these antiferromagnetic layers and soft magnetic layers, a magnetic field of 50 Oe was applied in parallel to the radial direction of the substrate in the same sputtering apparatus. As a sample for measuring an exchange coupling magnetic field, which will be described later, a laminated structure up to the soft magnetic backing layer taken out from the sputtering apparatus at this time was used. For other tests, a perpendicular magnetic recording medium having a liquid lubricant layer formed thereon was used. When the remaining layer was formed to produce the perpendicular magnetic recording medium of the present invention, the substrate surface temperature was heated to 250 ° C. using a lamp heater in the same sputtering apparatus as described above. Thereafter, a Ti intermediate layer was formed to 10 nm, and subsequently a CoCrPt magnetic recording layer was formed to 30 nm. Finally, a carbon protective layer was formed to 10 nm, and then removed from the vacuum apparatus. All these films were formed by DC magnetron sputtering under Ar gas pressure of 5 mTorr. Thereafter, a liquid lubricant layer 2 nm made of perfluoropolyether was formed by a dip method to obtain a perpendicular magnetic recording medium.
[0015]
Comparative Example 1
In order to verify the effect of applying the underlayer and orientation control layer, in the manufacturing method shown in the above example, a laminated structure from a nonmagnetic substrate to a soft magnetic backing layer was prepared without providing Ta and NiFeCr layers. . In this comparative example, as described in the examples, the magnitude of the exchange coupling magnetic field described below was measured with the laminated structure so far, and the other magnetic recording media were formed up to the liquid lubricant layer for other tests. Was used. In the case of producing a perpendicular magnetic recording medium, a Ti intermediate layer, a magnetic recording layer, a carbon protective layer, and a liquid lubricant layer are subsequently formed in the same sputtering apparatus as in the embodiment, and the perpendicular magnetic recording medium is formed. It was.
[0016]
Comparative Example 2
In order to verify the effect of applying the underlayer, a laminated structure from a nonmagnetic substrate to a soft magnetic backing layer was prepared without applying the Ta layer in the manufacturing method shown in the above example. In this comparative example, as described in the examples, the magnitude of the exchange coupling magnetic field described below was measured with the laminated structure so far, and the other magnetic recording media were formed up to the liquid lubricant layer for other tests. Was used. In the case of producing a perpendicular magnetic recording medium, a Ti intermediate layer, a magnetic recording layer, a carbon protective layer, and a liquid lubricant layer are subsequently formed in the same sputtering apparatus as in the embodiment, and the perpendicular magnetic recording medium is formed. It was.
[0017]
In each of the above Examples and Comparative Examples, the magnetization curve in the substrate radial direction of the sample taken out from the sputtering apparatus without forming the intermediate layer, the magnetic recording layer, the protective layer and the liquid circulating agent layer was measured with a vibrating sample magnetometer. The exchange coupling magnetic field was measured. In addition, in order to confirm the presence or absence of the domain wall formed in the soft magnetic underlayer of the completed perpendicular magnetic recording medium, the rate of variation with respect to the average value of the output waveform when no signal is written using a spin stand tester The presence or absence of spike noise was investigated by measuring (COV).
[0018]
FIG. 3 shows the value of the exchange coupling magnetic field when the layer configuration is changed. In the case of the medium layer configuration (without Ta, NiFeCr layer) shown in Comparative Example 1, no exchange coupling magnetic field is obtained. By using the medium layer configuration (without the Ta layer) shown in Comparative Example 2 to which the orientation control layer is provided, an exchange coupling magnetic field appears and an exchange coupling magnetic field of about 8 Oe can be obtained. Furthermore, a large exchange coupling magnetic field of about 15 Oe can be obtained by adopting the medium layer structure according to the present invention using an underlayer for controlling the fine structure of the orientation control layer.
[0019]
FIG. 4 shows a COV value as an index indicating the presence of spike noise for each layer configuration. For reference, the intensity of the exchange coupling magnetic field in each layer configuration shown in FIG. 3 is also shown in the same graph. When the exchange coupling magnetic field is 0, the COV value is large due to spike noise, but the COV decreases as the exchange coupling magnetic field increases. When the exchange coupling magnetic field is 10 Oe or more, there is no medium with a soft magnetic backing layer ( The value is almost equivalent to (no spike noise). Thus, spike noise can be completely suppressed by using the perpendicular magnetic recording medium according to the present invention.
[0020]
FIG. 5 shows one rotation of a perpendicular magnetic recording medium to which a magnetic field is applied and a perpendicular magnetic recording medium which has been formed without applying a magnetic field during the formation of an antiferromagnetic layer and a soft magnetic layer as magnetic domain control layers. The output waveform of the minute is shown. Spike noise does not occur at all in perpendicular magnetic recording media in which the direction of the exchange coupling magnetic field is aligned in the radial direction by performing film formation in a magnetic field, but perpendicular magnetic recording was performed without applying a magnetic field. It can be seen that spike noise occurs non-uniformly over the entire circumference of the medium. This is because the domain wall is generated at the boundary because the direction of unidirectional anisotropy due to the exchange coupling magnetic field is not aligned, and this is observed as spike noise. Thus, in order to eliminate spike noise, it is necessary to apply a magnetic field radially in the radial direction of the substrate when forming the antiferromagnetic layer and the soft magnetic layer as the magnetic domain control layer.
[0021]
【The invention's effect】
As described above, according to the present invention, a soft magnetic layer made of a Co-based amorphous alloy is used as the soft magnetic backing layer, and NiFeCr is used to improve the crystal orientation of the IrMn-based alloy antiferromagnetic layer as the magnetic domain control layer. By using an alloy-based orientation control layer and further using an underlayer made of Ta to control the microstructure of the orientation control layer, the magnetization of the soft magnetic layer is exchanged with an antiferromagnetic layer as a magnetic domain control layer. It is possible to suppress the formation of the domain wall of the soft magnetic layer that is pinned and becomes a noise source. Furthermore, when using the antiferromagnetic layer as the magnetic domain control layer of the present invention, it is required by a very simple manufacturing method in which a magnetic field is applied to the substrate during the formation of the antiferromagnetic layer and the soft magnetic backing layer. Uniform and high exchange coupling is obtained, so it is very suitable for mass production.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the configuration of a magnetic recording medium according to the present invention.
FIG. 2 is a schematic diagram illustrating a state in which a magnetic field is applied in a radial direction of a substrate for explaining an embodiment of the present invention.
FIG. 3 is a diagram for explaining an example of the present invention, and shows a change in the value of the exchange coupling magnetic field when the layer structure of the laminated structure from the nonmagnetic substrate to the soft magnetic backing layer produced in the example is changed. It is the graph which showed.
FIG. 4 is a graph for explaining an example of the present invention, and shows a change in the value of the COV and the exchange coupling magnetic field when the layer configuration of the perpendicular magnetic recording medium manufactured in the example is changed.
FIG. 5 is a diagram for explaining an embodiment of the present invention, and a perpendicular magnetic recording medium to which a magnetic field was applied during film formation of an antiferromagnetic layer and a soft magnetic layer as a magnetic domain control layer, and a film formed without it. It is the figure which showed the output waveform for 1 round by the spin stand tester of the perpendicular magnetic recording medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nonmagnetic base | substrate 2 Underlayer 3 Orientation control layer 4 Magnetic domain control layer 5 Soft magnetic backing layer 6 Intermediate layer 7 Magnetic recording layer 8 Protective layer 9 Liquid lubricant layer

Claims (2)

A perpendicular magnetic recording medium in which at least an underlayer, an orientation control layer, a magnetic domain control layer, a soft magnetic backing layer, an intermediate layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate, the magnetic domain control layer is an antiferromagnetic layer in which magnetization is fixed in a radial direction of the substrate, and the soft magnetic backing layer is a soft magnetic layer whose magnetization easy axis oriented in the radial direction of the substrate, the soft magnetic layer is Co The amorphous control alloy, the antiferromagnetic layer is an Mn alloy containing at least Ir, the orientation control layer is a NiFe alloy containing Cr, and the underlayer is made of Ta , and the orientation control layer is located below the magnetic domain control layer. Controls the crystal orientation of the antiferromagnetic layer, and the underlayer located in the lowermost layer controls the fine structure of the orientation control layer . 2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein a magnetic field is applied radially in the radial direction of the substrate at least when the antiferromagnetic layer as the magnetic domain control layer and the soft magnetic layer are formed. A method of manufacturing a perpendicular magnetic recording medium.

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