JP2004192782A - Perpendicular magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium which suppresses spike noise and is suitable for mass production, and a method for manufacturing the same.
SOLUTION: In a perpendicular magnetic recording medium in which at least an antiferromagnetic layer 4, a soft magnetic layer 6, a magnetic recording layer 8, a protective layer 9, and a liquid lubricant layer 10 are laminated on a non-magnetic substrate 1, at least Ni, It is made of a material containing Fe and added with at least one element of B, Nb, and Si, and is made of an orientation control layer 3 laminated just below the antiferromagnetic layer 4 and made of Ta and laminated just below the orientation control layer 3. Seed layer 2 provided.
[Selection diagram] Fig. 1

Description

  The present invention relates to a perpendicular magnetic recording medium and a method of manufacturing the same, and more particularly, to a perpendicular magnetic recording medium and a method of manufacturing the perpendicular magnetic recording medium in which domain walls of a soft magnetic layer are prevented to reduce noise.

As a technique for realizing a higher density of magnetic recording, a perpendicular magnetic recording method is attracting attention instead of a conventional longitudinal magnetic recording method. The perpendicular magnetic recording medium is composed of a magnetic recording layer of a hard magnetic material and a backing layer of a soft magnetic material used for recording on this recording layer and having a role of concentrating a magnetic flux generated by a magnetic head. It is known that spike noise, which is one of the problems in the perpendicular magnetic recording medium having such a structure, is caused by domain walls formed in a soft magnetic layer serving as a backing layer. Therefore, in order to reduce the noise of the perpendicular magnetic recording medium, it is necessary to prevent the domain walls from being formed in the soft magnetic underlayer.
Regarding the control of the domain wall of the soft magnetic underlayer, a method of forming a ferromagnetic layer of a Co alloy or the like on the upper or lower layer of the soft magnetic underlayer and magnetizing the same in a desired direction (for example, see Patent Reference 1), a method of forming an antiferromagnetic thin film and pinning the magnetization using exchange coupling (for example, see Patent Reference 2) and the like have been proposed.
JP-A-6-180834 (paragraph number [0029], FIG. 1) JP-A-10-214719 (paragraph number [0009], FIG. 2)

The method of controlling the domain wall by exchange coupling with the soft magnetic underlayer using the antiferromagnetic layer as the magnetic domain control layer is to prevent the formation of the domain wall of the soft magnetic underlayer if the exchange coupling is sufficiently obtained. Can be very effective. However, in order to obtain a sufficient exchange coupling, for example, as shown in Patent Document 2, a heat treatment after film formation is necessary in order to obtain characteristics of a soft magnetic underlayer. Since this heat treatment must be performed for a long time while applying a magnetic field in the radial direction, there is a problem that it is not suitable for mass production.
Further, for example, as shown in Patent Document 1, in a method of forming a backing layer by laminating a soft magnetic layer and an antiferromagnetic layer a plurality of times, the structure of the backing layer is complicated and is not suitable for mass production. There were also problems.
The present invention has been made in view of such a problem, and an object of the present invention is to provide a low-noise perpendicular magnetic recording medium and a method of manufacturing a perpendicular magnetic recording medium suitable for mass production. It is in.

In order to achieve such an object, the invention according to claim 1 provides at least an antiferromagnetic layer, a soft magnetic layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer on a nonmagnetic substrate. A stacked perpendicular magnetic recording medium, comprising an alignment control layer comprising a material containing at least Ni and Fe and containing at least one element of B, Nb, and Si, and stacked immediately below the antiferromagnetic layer; A seed layer made of Ta and laminated immediately below the orientation control layer.
According to a second aspect of the present invention, in the perpendicular magnetic recording medium according to the first aspect, an exchange coupling made of an alloy containing at least Fe and Co and laminated between the antiferromagnetic layer and the soft magnetic layer. It is characterized by including a magnetic field control layer.
According to a third aspect of the present invention, the antiferromagnetic layer according to the first or second aspect is made of a Mn-based alloy, and the soft magnetic layer is made of a NiFe alloy, a sendust alloy, or a Co-based amorphous alloy. Features.

According to a fourth aspect of the present invention, the magnetization of the soft magnetic layer according to the first, second, or third aspect is radially applied to a radial direction of the disk-shaped medium.
According to a fifth aspect of the present invention, in the method for manufacturing a perpendicular magnetic recording medium, at least an antiferromagnetic layer, a soft magnetic layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer are laminated on a nonmagnetic substrate. After forming the antiferromagnetic layer and the soft magnetic layer, a step of heating above the blocking temperature, and in the radial direction of the disk-shaped medium, in the static magnetic field applied radially, below the blocking temperature And a step of cooling.

According to the present invention, since the alignment control layer including a material containing at least Ni and Fe and adding at least one element of B, Nb and Si is provided, and the seed layer including Ta is provided immediately below the alignment control layer. In addition, the crystallinity and orientation of the antiferromagnetic layer can be improved, the exchange coupling magnetic field can be increased, and spike noise can be suppressed.
Further, according to the present invention, since the exchange coupling magnetic field control layer made of an alloy containing at least Fe and Co is provided between the antiferromagnetic layer and the soft magnetic underlayer, the exchange coupling magnetic field is increased and the spike noise is suppressed. Can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the perpendicular magnetic recording medium according to the present invention, an orientation control layer is provided immediately below the antiferromagnetic layer for the purpose of improving the crystallinity and orientation of the antiferromagnetic layer and increasing the exchange coupling magnetic field. As the orientation control layer, a material obtained by adding at least one element of B, Nb, and Si to NiFe is used. In addition, a seed layer made of Ta is provided to improve the crystallinity and orientation of the orientation control layer. According to this configuration, the interdiffusion of Ta atoms, Ni atoms, and Fe atoms at the interface with the seed layer is suppressed as compared with the conventional orientation control layer made of NiFe or NiFeCr. Furthermore, an initial growth layer of the orientation control layer, that is, a thin film region of 0 to 2 nm, which has a lattice defect and suppresses a portion having poor crystallinity. Therefore, the crystallinity and orientation of the antiferromagnetic layer can be improved as compared with the conventional orientation control layer.

Further, an exchange coupling magnetic field control layer is provided between the antiferromagnetic layer and the soft magnetic layer for the purpose of strengthening the exchange coupling magnetic field. As the exchange coupling magnetic field control layer, an alloy containing at least Fe and Co is used.
FIG. 1 shows the structure of a perpendicular magnetic recording medium according to one embodiment of the present invention. The perpendicular magnetic recording medium has a seed layer 2, an orientation control layer 3, an antiferromagnetic layer 4, an exchange coupling magnetic field control layer 5, a soft magnetic underlayer 6, an underlayer 7, a magnetic recording layer 8, It has a structure in which a protective layer 9 is formed in order, and a liquid lubricant layer 10 is further formed thereon. As the nonmagnetic substrate 1, a NiP-plated Al alloy, tempered glass, crystallized glass, or the like, which is used for a normal magnetic recording medium, can be used.
The seed layer 2 improves the crystallinity and orientation of the orientation control layer 3. The material is preferably Ta. The film thickness is desirably 10 nm or less that becomes amorphous or microcrystalline. The orientation control layer 3 improves the crystallinity and orientation of the antiferromagnetic layer 4. As the material, a material containing at least Ni and Fe and adding at least one element of B, Nb, and Si is used. The film thickness is desirably 3 nm or more where crystal growth is sufficiently observed. For the antiferromagnetic layer 4, a Mn-based alloy such as FeMn, CoMn, and IrMn is used. The film thickness is not particularly limited, but is preferably about 2 nm to 30 nm in order to obtain an appropriate exchange coupling and to be suitable for mass production.

The exchange coupling magnetic field control layer 5 improves the exchange coupling magnetic field. As the material, an alloy containing at least Fe and Co, such as FeCo, FeCoNi, FeCoB, and FeCoNiB, is used. The thickness is desirably 20 nm or less in consideration of productivity. As the soft magnetic underlayer 6, an amorphous Co-based alloy such as CoZrNb or CoTaZr can be used in addition to a crystalline system such as a NiFe alloy or a sendust (FeSiAl) alloy. The optimum value of the film thickness varies depending on the structure and characteristics of the magnetic head used for recording. However, it is preferable that the film thickness be 10 nm or more and 500 nm or less in view of productivity. The magnetization of the soft magnetic underlayer 6 fixed by antiferromagnetic exchange coupling is applied radially in the radial direction of the substrate as shown in FIG. 2, assuming a generally used disk-shaped medium. Is preferred.
The magnetic recording layer 8 may be a generally used CoCrPt-based material, a granular magnetic recording layer in which a nonmagnetic grain boundary surrounding a ferromagnetic crystal grain is a nonmagnetic nonmetal, or a rare earth-transition metal such as TbCo. A system alloy (RE-TM system alloy), a multilayered film of Co / Pt, Co / Pd, a FePt ordered alloy, or the like can be used. To be used as a perpendicular magnetic recording medium, the ferromagnetic crystal grains need to have perpendicular anisotropy with respect to the film surface. Further, the underlayer 7 can be provided as appropriate depending on the magnetic recording material.

As the protective layer 9, for example, a thin film mainly composed of carbon is used. For the liquid lubricant layer 10, for example, a perfluoropolyether-based lubricant can be used.
A method for manufacturing a perpendicular magnetic recording medium uses a method in which heating is performed at a temperature equal to or higher than a blocking temperature, which is a temperature at which antiferromagnetic exchange coupling is lost, and cooling is performed to a temperature equal to or lower than the blocking temperature in a static magnetic field controlled by a permanent magnet. . This method is used for the purpose of controlling the magnetization direction of the soft magnetic underlayer 6 in one direction. When heating is performed after forming the antiferromagnetic layer 4 and the soft magnetic underlayer 6 and before forming the magnetic recording layer 8, if the heating temperature exceeds the blocking temperature, the antiferromagnetic exchange is performed. The coupling is lost, and the magnetization fixing effect of the soft magnetic underlayer 6 is lost. In this state, when a slight external magnetic field is applied, the magnetization of the soft magnetic underlayer 6 is disturbed, and a domain wall is generated. Then, when exchange coupling occurs again below the blocking temperature, it is fixed as it is. Therefore, a method is used in which it is kept in a static magnetic field until it is cooled below the blocking temperature. According to this method, the magnetization fixing effect of the soft magnetic underlayer 6 can be obtained over the entire surface of the substrate. As the strength of the static magnetic field, a magnetic field that saturates the magnetization of at least the exchange coupling magnetic field control layer 5 and the soft magnetic underlayer 6 is required, and is preferably about 50 to 1,000 Oe.

Hereinafter, examples of the present invention will be described. It should be noted that the present invention is not limited to the following embodiments, and various changes can be made without departing from the gist of the present invention.
(Example 1)
A chemically strengthened glass substrate (for example, N-10 glass substrate manufactured by HOYA) having a smooth surface is used as the non-magnetic substrate, and after washing, it is introduced into a sputtering apparatus. After a Ta seed layer was formed to a thickness of 5 nm using a Ta target, a NiFeB orientation control layer was formed to a thickness of 10 nm using a Ni ₈₅ Fe ₁₂ B ₃ target. Subsequently, after heating was performed using a lamp heater so that the substrate surface temperature became 350 ° C., an IrMn antiferromagnetic layer was formed to a thickness of 10 nm using an Ir ₂₀ Mn ₈₀ target, and then Co ₈₇ Using a Zr ₅ Nb ₈ target, a CoZrNb amorphous soft magnetic underlayer was formed to a thickness of 100 nm.

Next, after forming a Ti underlayer with a thickness of 10 nm using a Ti target, a CoCrPt magnetic recording layer was formed with a thickness of 20 nm using a Co ₇₀ Cr ₂₀ Pt ₁₀ target. Subsequently, the substrate is heated again using a lamp heater so that the substrate surface temperature becomes 350 ° C., and then cooled to 150 ° C. in a fixed magnetic field of 1000 Oe. Finally, a protective layer having a thickness of 10 nm was formed using a carbon target, and then taken out of the vacuum apparatus. All of these films were formed by a DC magnetron sputtering method under an Ar gas pressure of 5 mTorr. Thereafter, a liquid lubricant layer of 2 nm made of perfluoropolyether was formed by dipping to obtain a perpendicular magnetic recording medium.
(Example 2)
An orientation control layer was formed to a thickness of 10 nm using a Ni ₇₉ Fe ₁₂ Nb ₉ target. Others are the same as the first embodiment.

(Example 3)
An orientation control layer was formed to a thickness of 10 nm using a Ni ₈₄ Fe ₁₂ Si ₄ target. Others are the same as the first embodiment.
(Example 4)
After forming the IrMn antiferromagnetic layer and before forming the CoZrNb soft magnetic underlayer, a CoFe exchange coupling magnetic field control layer was formed to a thickness of 2 nm using a Co ₉₀ Fe ₁₀ target. Others are the same as the first embodiment.
(Example 5)
After forming the IrMn antiferromagnetic layer and before forming the CoZrNb soft magnetic underlayer, a CoFe exchange coupling magnetic field control layer was formed to a thickness of 2 nm using a Co ₉₀ Fe ₁₀ target. Others are the same as the second embodiment.

(Example 6)
After forming the IrMn antiferromagnetic layer and before forming the CoZrNb soft magnetic underlayer, a CoFe exchange coupling magnetic field control layer was formed to a thickness of 2 nm using a Co ₉₀ Fe ₁₀ target. Others are the same as the third embodiment.
(Example 7)
The exchange coupling magnetic field control layer was formed using a Co ₆₅ Ni ₁₃ Fe ₂₂ target. Others are the same as the fourth embodiment.
(Example 8)
The exchange coupling magnetic field control layer was formed using a Co ₆₅ Ni ₁₃ Fe ₂₂ target. Others are the same as the fifth embodiment.

(Example 9)
The exchange coupling magnetic field control layer was formed using a Co ₆₅ Ni ₁₃ Fe ₂₂ target. Others are the same as the sixth embodiment.
(Example 10)
An exchange coupling magnetic field control layer was formed using a (Co ₆₅ Ni ₁₃ Fe ₂₂ ) ₉₄ B ₆ target. Others are the same as the fourth embodiment.
(Example 11)
An exchange coupling magnetic field control layer was formed using a (Co ₆₅ Ni ₁₃ Fe ₂₂ ) ₉₄ B ₆ target. Others are the same as the fifth embodiment.
(Example 12)
An exchange coupling magnetic field control layer was formed using a (Co ₆₅ Ni ₁₃ Fe ₂₂ ) ₉₄ B ₆ target. Others are the same as the sixth embodiment.

(Comparative Example 1)
This is the same as Example 1 except that the Ta seed layer is not formed.
(Comparative Example 2)
This is the same as Example 1 except that the NiFeB orientation control layer is not formed.
(Comparative Example 3)
Example 1 is the same as Example 1 except that the Ta seed layer, the NiFeB orientation control layer, the IrMn antiferromagnetic layer, and the CoZrNb soft magnetic underlayer were not formed.
For each of the examples and the comparative examples, in order to confirm the presence or absence of a magnetic domain wall formed in the soft magnetic underlayer, readout evaluation was performed using a spin stand tester in a state where no signal was written. Reading was performed for 100 rotations of the disk, and the ratio of the fluctuation to the average value of the output was defined as COV%. The spike noise from the domain wall is locally detected as a large signal output, and when the domain wall fluctuates, the magnitude fluctuates. Therefore, it is considered that the spike noise is generated as the COV value increases. Can be

  Further, in order to examine the magnitude of the exchange coupling magnetic field, a sample was also prepared in which the step of forming the Ti underlayer and the CoCrPt magnetic recording layer in the manufacturing process of the perpendicular magnetic recording medium was omitted. For each of the samples of Examples and Comparative Examples 1 and 2, magnetization curves in the substrate radial direction were measured by a vibrating sample magnetometer, and an exchange coupling magnetic field was calculated from the obtained MH loop. Table 1 shows the results.

The relationship between the magnitude of the exchange coupling magnetic field and the layer configuration will be described. Comparing Example 1 with Comparative Example 2, Comparative Example 2, which does not have the NiFeB orientation control layer, has an exchange coupling magnetic field of 0 and no exchange coupling occurs. is there. Comparing Example 1 with Comparative Example 1, Example 1 having a Ta seed layer has an improved exchange coupling magnetic field. In both Example 2 using NiFeNb and Example 3 using NiFeSi in place of the NiFeB orientation control layer of Example 1, exchange coupling equivalent to Example 1 occurs. Further, Examples 4 to 6 in which a CoFe exchange coupling magnetic field control layer is provided, Examples 7 to 9 in which a CoNiFe exchange coupling magnetic field control layer is provided, and Examples 10 to 12 in which a CoNiFeB exchange coupling magnetic field control layer is provided Compared with Nos. 1 to 3, the exchange coupling magnetic field is improved.
Next, the relationship between the magnitude of the exchange coupling magnetic field and COV will be described. In Comparative Example 3 having no soft magnetic underlayer, no spike noise could be generated, and the COV was 5%. On the other hand, in Examples 4 to 12 in which the exchange coupling magnetic field is 26.5 Oe or more, the spike noise is completely suppressed since the values are also 5%. From Examples 1 to 3 and Comparative Examples 1 and 2, it is understood that the larger the exchange coupling magnetic field, the smaller the COV.

FIG. 1 is a schematic diagram illustrating a structure of a perpendicular magnetic recording medium according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing a state where a magnetic field is applied in a radial direction of a substrate of a perpendicular magnetic recording medium.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 nonmagnetic substrate 2 seed layer 3 orientation control layer 4 antiferromagnetic layer 5 exchange coupling magnetic field control layer 6 soft magnetic underlayer 7 underlayer 8 magnetic recording layer 9 protective layer 10 liquid lubricant layer

Claims (5)

In a perpendicular magnetic recording medium comprising at least an antiferromagnetic layer, a soft magnetic layer, a magnetic recording layer, a protective layer and a liquid lubricant layer laminated on a nonmagnetic substrate,
An orientation control layer made of a material containing at least Ni and Fe, and added with at least one element of B, Nb, and Si, and stacked immediately below the antiferromagnetic layer;
A perpendicular magnetic recording medium, comprising: a seed layer made of Ta and laminated immediately below the orientation control layer. 2. The perpendicular magnetic recording medium according to claim 1, further comprising an exchange coupling magnetic field control layer made of an alloy containing at least Fe and Co and laminated between the antiferromagnetic layer and the soft magnetic layer. The perpendicular magnetic recording medium according to claim 1, wherein the antiferromagnetic layer is made of a Mn-based alloy, and the soft magnetic layer is made of a NiFe alloy, a sendust alloy, or a Co-based amorphous alloy. 4. The perpendicular magnetic recording medium according to claim 1, wherein the magnetization of the soft magnetic layer is radially applied in a radial direction of the disk-shaped medium. A method for manufacturing a perpendicular magnetic recording medium comprising at least an antiferromagnetic layer, a soft magnetic layer, a magnetic recording layer, a protective layer, and a liquid lubricant layer laminated on a nonmagnetic substrate.
After forming the antiferromagnetic layer and the soft magnetic layer, heating the blocking temperature or higher,
Cooling the magnetic recording medium to a blocking temperature or less in a radially applied static magnetic field in a radial direction of the disk-shaped medium.

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