JP4557277B2 - Method for manufacturing perpendicular magnetic recording medium - 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]
An aspect of the present invention for solving the above-described problems is that at least an underlayer, an orientation control layer, a magnetic domain control layer, an exchange coupling magnetic field control layer, a soft magnetic backing layer, an intermediate layer, a magnetic recording layer, and a protective layer are formed on a nonmagnetic substrate. And a method of manufacturing a perpendicular magnetic recording medium in which liquid lubricant layers are sequentially laminated, wherein a soft magnetic layer made of a Co-based amorphous alloy is used as the soft magnetic backing layer, and is in contact with the magnetic domain control layer at the interface and exchange coupled In order to adjust the magnitude of the magnetic field, an exchange coupling magnetic field control layer made of an alloy containing at least Co and Fe is used, and an antiferromagnetic layer made of an Mn alloy containing at least Ir is used as the magnetic domain control layer. In order to control the crystal orientation of the layer, an orientation control layer made of a NiFe-based alloy containing Cr is used as a lower layer, and in order to control the microstructure of the orientation control layer, an underlayer made of Ta is used as the lowermost layer. , The antiferromagnetic layer at least as the magnetic domain control layer, during the formation of the exchange coupling magnetic field control layer and the soft magnetic layer, in the manufacturing method of the perpendicular magnetic recording medium by applying a magnetic field radially in the radial direction of the substrate is there.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As a result of intensive studies on perpendicular magnetic recording media, a soft magnetic layer made of a Co-based amorphous alloy was used as the soft magnetic backing layer, and the magnitude of the exchange coupling magnetic field between the soft magnetic backing layer and the antiferromagnetic layer as the magnetic domain control layer was large. In order to adjust the thickness, an exchange coupling magnetic field control layer made of a CoFe-based alloy is used, an IrMn alloy is used as an antiferromagnetic layer as a magnetic domain control layer, and an antiferromagnetic material is used to control the crystal orientation of the antiferromagnetic layer. An orientation control layer made of a NiFe alloy containing Cr is provided below the layer, and an underlayer is provided below the orientation control layer for the purpose of controlling the microstructure of the orientation control layer. By applying a magnetic field in the radial direction of the substrate during the formation of the ferromagnetic layer, exchange coupling magnetic field control layer, and soft magnetic layer, a large exchange coupling can be obtained without performing heat treatment after the film formation. It was effectively found that perform the control of the magnetic wall of the soft magnetic underlayer.
[0009]
FIG. 1 is a schematic sectional view of a perpendicular magnetic recording medium of the present invention. On the nonmagnetic substrate 1, at least the underlayer 2, the orientation control layer 3, the antiferromagnetic layer as the magnetic domain control layer 4, the exchange coupling magnetic field control layer 5, the soft magnetic layer 6, the intermediate layer 7, the magnetic recording layer 8, and the protective layer 9 has a structure in which 9 is formed in order, and a liquid lubricant layer 10 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 exchange coupling magnetic field control layer 5 is made of an alloy containing at least Co and Fe. In order to obtain a large exchange coupling magnetic field, it is better not to add a nonmagnetic element to this CoFe alloy. In order to reduce noise caused by the exchange coupling magnetic field control layer 5, the film thickness should be as thin as possible, and preferably about 1 nm to 10 nm. As the soft magnetic layer 6, a Co-based amorphous alloy is used. Although the optimum value of the thickness of the soft magnetic layer 6 varies depending on the structure and characteristics of the magnetic head used for recording, it is preferably 50 nm or more and 300 nm or less from the viewpoint of productivity.
[0011]
The intermediate layer 7 is used for preferably controlling the crystal orientation and crystal grain size of the magnetic recording layer 8. Examples of materials that can be used as the material for the intermediate layer include Ti and TiCr alloys. The magnetic recording layer 8 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 perpendicular 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 9. In addition, for example, a perfluoropolyether lubricant can be used for the liquid circulating agent layer 10.
[0012]
In manufacturing the magnetic recording medium shown in FIG. 1 having the layer structure as described above, at least the antiferromagnetic layer, the exchange coupling magnetic field control layer 5 and the soft magnetic layer 6 as the magnetic domain control layer 4 are formed. In this case, for example, as shown in FIG. 2, it is necessary to apply the magnetic field in the radial direction of the substrate. As a result, the magnetization of the antiferromagnetic layer as the magnetic domain control layer 4 is fixed in the radial direction of the substrate, and the magnetization easy axes of the exchange coupling magnetic field control layer 5 and the soft magnetic layer 6 that are subsequently laminated also face the radial direction of the substrate. Therefore, effective domain wall 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. After forming a 2 nm exchange coupling magnetic field control layer using a CoFe alloy target, a soft magnetic layer was formed to 100 nm using a CoZrNb alloy target. When forming the antiferromagnetic layer, the exchange coupling magnetic field control layer, and the soft magnetic layer as the magnetic domain control 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 effects of applying the underlayer, the orientation control layer, and the exchange coupling magnetic field control layer, in the manufacturing method shown in the above embodiment, a soft magnetic backing layer is formed from a nonmagnetic substrate without adding a Ta, NiFeCr, or CoFe layer. The laminated structure up to was produced. 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 and the exchange coupling magnetic field control layer, in the manufacturing method shown in the above embodiment, the laminated structure from the nonmagnetic substrate to the soft magnetic backing layer without providing the Ta and CoFe layers. Produced. 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]
Comparative Example 3
In order to verify the effect of providing an exchange coupling magnetic field control layer, a laminated structure from a nonmagnetic substrate to a soft magnetic backing layer was prepared without applying a CoFe 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.
[0018]
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).
[0019]
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, CoFe layers) shown in Comparative Example 1, no exchange coupling magnetic field is obtained. By using the medium layer structure (without Ta, CoFe layers) of Comparative Example 2 provided with an orientation control layer, an exchange coupling magnetic field appears and an exchange coupling magnetic field of about 8 Oe is obtained. By using the medium layer structure shown in Comparative Example 3 (without the CoFe layer) using an underlayer to control the fine structure of the orientation control layer, a larger exchange coupling magnetic field of about 15 Oe can be obtained.
[0020]
By adopting the layer structure according to the present invention to which the exchange coupling magnetic field control layer was added, the exchange coupling magnetic field increased rapidly and a large value of 32 Oe was obtained.
[0021]
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.
[0022]
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, the exchange coupling magnetic field control layer, and the soft magnetic layer as the magnetic domain control layer. There is.
[0023]
【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. A base alloy layer for controlling the microstructure of the orientation control layer, and an exchange coupling magnetic field between the soft magnetic backing layer and the antiferromagnetic layer as the magnetic domain control layer. By using an exchange coupling magnetic field control layer made of a CoFe-based alloy to adjust the size, the magnetization of the soft magnetic layer is pinned by exchange coupling with an antiferromagnetic layer as a magnetic domain control layer, and becomes a noise source It is possible to suppress the domain wall formation of the soft magnetic layer. When the antiferromagnetic layer is used as the magnetic domain control layer of the present invention, a very simple manufacturing method in which a magnetic field is applied to the substrate during the formation of the antiferromagnetic layer, the exchange coupling magnetic field control layer, and the soft magnetic backing layer. Because the required uniform and high exchange coupling is obtained, it is also 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 layer 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 Exchange coupling magnetic field control layer 6 Soft magnetic backing layer 7 Intermediate layer 8 Magnetic recording layer 9 Protective layer 10 Liquid lubricant layer

Claims (1)

Perpendicular magnetism in which at least an underlayer, an orientation control layer, a magnetic domain control layer, an exchange coupling magnetic field 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. A method of manufacturing a recording medium, wherein a soft magnetic layer made of a Co-based amorphous alloy is used as the soft magnetic backing layer, and at least Co and Fe are used to adjust the magnitude of an exchange coupling magnetic field in contact with the magnetic domain control layer at the interface. In order to control the crystal orientation of the antiferromagnetic layer, Cr is used in the lower layer, using an exchange coupling magnetic field control layer made of an alloy containing Ni, using an antiferromagnetic layer made of a Mn alloy containing at least Ir as the magnetic domain control layer. an alignment control layer composed of NiFe alloy containing, further using a base layer made of Ta in the lowest layer in order to control the microstructure of the orientation control layer, an antiferroelectric as at least the magnetic domain control layer Sex layer, during the formation of the exchange coupling magnetic field control layer and the soft magnetic layer, a method of manufacturing a perpendicular magnetic recording medium and applying a magnetic field radially in the radial direction of the substrate.

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