JP2003346334A - Vertical magnetic record medium and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve magnetic interaction among the grains of a granular magnetic recording layer, and to provided a vertical magnetic record medium that can perform high-density recording with low noise. <P>SOLUTION: The vertical magnetic record medium has a structure, where a foundation layer 2, a magnetic recording layer 3, and a protective film 4 are successively formed on a non-magnetic substrate 1, and a liquid lubricant layer 5 is formed on the structure. In the magnetic recording layer 3, there are a crystal grain having ferromagnetism and a non-magnetic grain boundary surrounding the crystal grain, and the non-magnetic grain boundary uses the granular magnetic recording layer which is a non-magnetic nonmetal. The surface of the foundation layer 2, before forming the magnetic recording layer 3, is exposed in the atmosphere of O<SB>2</SB>or N<SB>2</SB>or the atmosphere of a mixed gas, where O<SB>2</SB>or N<SB>2</SB>is added to a rare gas, and O<SB>2</SB>or N<SB>2</SB>is made to accompany as a nucleus for use in non-magnetic nonmetal formation. After that, magnetic recording layer 3 is formed, the ferromagnetic crystal grain and the non-magnetic nonmetal grain boundary are formed from an initial layer, and the magnetic recording layer, having a satisfactory segregated structure, can be formed. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 mounted on various magnetic recording devices and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a technique for realizing higher density of magnetic recording, a perpendicular magnetic recording system in which recording magnetization is perpendicular to a medium in-plane direction is attracting attention instead of a conventional longitudinal magnetic recording system. Perpendicular magnetic recording media mainly include a magnetic recording layer of a hard magnetic material, an underlayer for orienting the magnetic recording layer in a desired direction, a protective film for protecting the surface of the magnetic recording layer, and recording on the recording layer. And a backing layer of a soft magnetic material which plays a role of concentrating a magnetic flux generated by the magnetic head used for the magnetic head. The soft magnetic backing layer has higher media performance when it is present, but can be recorded even without it, and thus may be omitted in some cases. A medium without such a soft magnetic underlayer is called a single-layer perpendicular magnetic recording medium, and a medium with a soft magnetic underlayer is called a double-layer perpendicular magnetic recording medium. In the perpendicular magnetic recording medium, as in the case of the longitudinal magnetic recording medium, in order to increase the recording density, it is essential to achieve both high thermal stability and low noise.

In the conventional longitudinal magnetic recording medium, various compositions and structures of the magnetic recording layer, materials of the non-magnetic underlayer, and the like have been proposed. The magnetic recording layer that has been put to practical use uses magnetic alloys made of CoCr (hereinafter referred to as CoCr) and segregates Cr at crystal grain boundaries to obtain magnetically isolated magnetic particles. As another magnetic recording layer material, a magnetic layer called a granular magnetic recording layer has been proposed, and a nonmagnetic nonmetallic substance such as an oxide or a nitride is used as the grain boundary phase. CoCr
In the magnetic recording layer, raising the substrate temperature during film formation to 200 ° C. or more is indispensable for sufficient segregation of Cr, whereas the granular magnetic recording layer has The non-magnetic non-metallic material has a feature of causing segregation. A CoCr magnetic recording layer or a granular magnetic recording layer can also be applied to a perpendicular magnetic recording medium by causing perpendicular anisotropy to appear by controlling the crystal orientation with an underlayer, for example.

[0004]

When CoCr is used for a magnetic recording layer of a perpendicular magnetic recording medium, it is difficult to segregate Cr as seen in a longitudinal medium. It has been found that a segregation structure is easily formed as compared with that of CoCr, and as a result, magnetic interaction between grains is reduced, resulting in low noise. However, even in the granular magnetic recording layer, it is also clear that the segregation structure is insufficient in a thin region with a film thickness of 10 nm or less, that is, the separation of grains is poor and causes noise. In a perpendicular magnetic recording medium, it is ideal to perform recording with a steep head magnetic field in the vertical direction.
It is desirable that the thickness of the magnetic recording layer be thin. If there is an initial layer in which the segregation is not sufficient as described above, it is difficult to reduce the thickness of the magnetic recording layer. This has been an obstacle to further lowering the noise of the magnetic recording layer, that is, increasing the recording density.

The present invention has been made in view of such a problem, and an object of the present invention is to facilitate formation of a nonmagnetic nonmetal serving as a grain boundary phase on a surface on which a granular magnetic recording layer is formed. An object of the present invention is to propose a perpendicular magnetic recording medium in which a "nucleus" is introduced and a method of manufacturing the same.

[0006]

According to the present invention, in order to achieve the above object, the invention according to claim 1 is directed to a non-magnetic substrate comprising at least an underlayer, a magnetic recording layer, a protective film and a liquid. In the method for manufacturing a perpendicular magnetic recording medium in which a lubricant layer and a lubricant layer are sequentially laminated, the magnetic recording layer is formed by crystal grains having ferromagnetism and non-magnetic crystal boundaries of oxides or nitrides surrounding the crystal grains. After the formation of the underlayer, the substrate is
₂ or N ₂ atmosphere, or a mixed gas atmosphere in which O ₂ or N ₂ is added to a rare gas, and thereafter, the magnetic recording layer is formed.

[0007] The invention described in claim 2 is the invention according to claim 1.
3. The method according to claim 1, wherein the underlayer is made of Ru, RuW,
It is characterized by being any alloy containing at least Ru, such as RuCu, RuC, RuB, and RuCoCr. The invention according to claim 3 is the invention according to claim 1 or 2, wherein NiFe,
NiFeNb, NiFeB, NiFeCr, NiFeS
A feature is that any one of Ni-based alloys such as i is provided as a seed layer. According to a fourth aspect of the present invention, there is provided a perpendicular magnetic recording medium manufactured by the method for manufacturing a perpendicular magnetic recording medium according to the first, second, or third aspect.

According to the present invention, a ferromagnetic portion and a non-magnetic grain boundary composed of a non-magnetic non-metal are simultaneously formed from the initial layer, and the ferromagnetic crystal grains are magnetically separated.
Specifically, an oxide or nitride is used as the nonmagnetic nonmetal, and a method of exposing the substrate surface to an atmosphere containing O ₂ or N ₂ before forming the granular magnetic recording layer is used. O ₂ or N ₂ attached to the surface of the substrate by the exposure becomes a nucleus for the formation of a non-magnetic non-metal, so that the ferromagnetic crystal grains can be separated from the initial layer of the magnetic recording layer.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view for explaining an embodiment of a perpendicular magnetic recording medium according to the present invention. The perpendicular magnetic recording medium has a structure in which at least a base layer 2, a magnetic recording layer 3, and a protective film 4 are sequentially formed on a nonmagnetic substrate 1, and a liquid lubricant layer 5 is further formed thereon.
Are formed. As the non-magnetic 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. When the substrate heating temperature is kept within 100 ° C., a plastic substrate made of a resin such as polycarbonate or polyolefin can be used.

As the underlayer 2, for example, a metal having a hexagonal close-packed structure or an alloy material thereof, or a metal having a face-centered cubic lattice structure or an alloy material thereof is preferably used. Examples of the metal having the hexagonal close-packed structure include Ti, Zr, Ru, Zn, and T.
c, Re, and the like. Examples of the metal having a face-centered cubic lattice structure include Cu, Rh, Pd, Ag, Ir, Pt, and the like.
Au, Ni, Co and the like are mentioned as examples. Among the materials given as examples, Ru or an alloy containing Ru has a small reactivity with exposed O ₂ or N _2, and shows a particularly excellent effect. The film thickness is preferably thinner, but is preferably 3 nm or more where sufficient crystal growth is observed.

Further, in order to improve the orientation of the underlayer 2, a seed layer 12 can be provided directly under the underlayer 2. It may be non-magnetic, but in the case of a two-layer perpendicular magnetic recording medium, a material exhibiting soft magnetic properties is preferable so as to function as a part of the soft magnetic layer. Examples of the seed layer 12 exhibiting soft magnetic characteristics include NiFe and NiFeN.
b, N such as NiFeB, NiFeCr, NiFeSi
i-based alloys. When a seed layer 12 is provided below the underlayer 2 in order to form a two-layer perpendicular magnetic recording medium, a soft magnetic underlayer 11 serving to concentrate magnetic flux generated by a magnetic head is further provided below the seed layer 12. Can be. As the soft magnetic underlayer 11, for example, crystalline N
Microcrystalline FeTaC and CoTaZr, such as iFe alloy and sendust (FeSiAl) alloy, and CoZrNb as an amorphous Co alloy can be used.

The optimum thickness of the soft magnetic underlayer 11 varies depending on the structure and characteristics of the magnetic head used for recording. Magnetic recording layer 3
Employs a granular magnetic recording layer in which a ferromagnetic crystal grain and a non-magnetic grain boundary surrounding the ferromagnetic crystal grain are used, and the non-magnetic grain boundary is a non-magnetic non-metal. As the crystal having ferromagnetism, for example, a CoPt or FePt alloy, or an alloy obtained by adding elements such as Cr, Ni, Nb, Ta, and B to them is preferable. As the nonmagnetic nonmetal of the nonmagnetic grain boundary, an oxide or a nitride is preferable.
Co, Si, Al, Ti, Ta, Hf, Zr, Y, Ce
Oxides or nitrides are preferred. For use as a perpendicular magnetic recording medium, ferromagnetic crystal grains need to have magnetic anisotropy perpendicular to the film surface.

The surface of the substrate before the formation of the magnetic recording layer 3, ie, the surface of the underlayer 2, is placed in an O ₂ or N ₂ atmosphere or a mixed gas atmosphere in which O ₂ or N ₂ is added to a rare gas. Exposure into O ₂ or N ₂ as nuclei for non-magnetic non-metal formation. Thereafter, by forming the magnetic recording layer 3, ferromagnetic crystal grains and nonmagnetic and nonmetallic grain boundaries are formed from the initial layer, and a magnetic recording layer having a good segregation structure can be formed. The protective film 4
For example, a thin film mainly composed of carbon is used. For the liquid lubricant layer 5, for example, a perfluoropolyether-based lubricant can be used.

Hereinafter, specific embodiments of the perpendicular magnetic recording medium of the present invention will be described. [Example 1] A chemically strengthened glass substrate (for example, N-5 glass substrate manufactured by HOYA) having a smooth surface was used as a non-magnetic substrate, washed, introduced into a sputtering apparatus, and then subjected to Co5Z.
After forming a 300 nm thick CoZrNb soft magnetic layer under an Ar gas pressure of 5 mTorr using an r9Nb target, a 20 nm thick NiFeNb seed layer was formed under an Ar gas pressure of 5 mTorr using a Ni12Fe9Nb target, which is a soft magnetic Ni-based alloy. Furthermore, using a Ru target,
A Ru underlayer was formed to a thickness of 20 nm under an Ar gas pressure of 30 mTorr. Subsequently, exposure was performed for 10 seconds in an Ar gas atmosphere to which 2% O ₂ was added. At this time, the pressure of Ar + O ₂ was 5 mTorr and the flow rate was 60 sccm.

Thereafter, 91 (Co10Cr17Pt)-
CoCrPt-SiO ₂ using a 9SiO ₂ target
The magnetic recording layer was formed at an Ar gas pressure of 30 mTorr. At this time, the thickness of the magnetic recording layer was changed from 10 to 30 nm. Finally, a protective film made of carbon having a thickness of 8 nm was formed using a carbon target and then taken out of the vacuum apparatus. Thereafter, a 2 nm liquid lubricant layer made of perfluoropolyether was formed by dipping to obtain a two-layer perpendicular magnetic recording medium. RF magnetron sputtering was used to form the magnetic recording layer, and all other layers were formed by DC magnetron sputtering.

[Embodiment 2] When forming from the underlayer to the magnetic recording layer, an Ar gas pressure of 2 was used using a Ru30W target.
After forming a 15 nm RuW underlayer under 5 mTorr,
Exposure was performed for 10 seconds in an Ar atmosphere to which 3% N ₂ was added, and then 92 (Co10Cr15Pt) -8SiN
Except that the CoCrPt-SiN magnetic recording layer was formed using a target, a dual-layer perpendicular magnetic recording medium was obtained in the same manner as in Example 1. Comparative Example 1 As a comparative example of the present invention, CoCrPt-S
A two-layer perpendicular magnetic recording medium was obtained in the same manner as in Example 1 except that the exposure in the Ar + O ₂ atmosphere was not performed before the formation of the iO ₂ magnetic recording layer.

Comparative Example 2 As a comparative example of the present invention, Co
Before forming the CrPt-SiN magnetic recording layer, Ar + N ₂Atmosphere
The same as in Example 2 except that no air exposure was performed.
Thus, a two-layer perpendicular magnetic recording medium was obtained. Next, the present invention
The magnetic properties of each Example and Comparative Example
explain. Magnetic properties are measured by the magnetic Kerr effect
Was. Table 1 below shows the case where the magnetic recording layer thickness is 15 nm.
This shows the magnetic force Hc. That is, Table 1 shows Examples 1 and 2 and the ratio
Magnetic recording layer film obtained from evaluation of magnetic properties according to Comparative Examples 1 and 2
This shows the coercive force Hc when the thickness is 15 nm.
You.

[0018]

[Table 1] The squareness ratio S of each of the examples and comparative examples was 1.0. Compared with Example 1 and Comparative Example 1, in Example 1 where exposure was performed in an Ar + O ₂ atmosphere, Hc was improved as compared with Comparative Example 1 where no exposure was performed. Example 2 and Comparative Example 2
The same applies to the case of comparing. The exposure in an Ar + N ₂ atmosphere improves Hc. As described above, the segregation structure is promoted by exposure in an atmosphere containing O ₂ or N ₂ , which contributes to the improvement of Hc.

FIGS. 2 and 3 show the dependence of the diameter of the magnetic cluster size and the standard deviation on the thickness of the magnetic recording layer in each of the examples and comparative examples according to the present invention.
m], FIG. 3 is a diagram showing the case of the standard deviation σ [nm]. The magnetic cluster size was determined from MFM measurement of each AC demagnetized medium. Overall, both d and σ in Examples 1 and 2 with exposure are significantly lower than those in Comparative Examples 1 and 2 with no exposure. In particular, when focusing on the case where the thickness of the magnetic recording layer is 10 nm, in Comparative Examples 1 and 2, both the diameter d and the standard deviation σ are very large, which indicates that the ferromagnetic crystal grains are not sufficiently separated in the initial layer. This shows that the size and the variation of the magnetic cluster size are large.

On the other hand, in Examples 1 and 2 where exposure was performed,
Even when the thickness of the magnetic recording layer is 10 nm, both the diameter d and the standard deviation σ are small, indicating that O ₂ or N ₂ is a nucleus for forming a nonmagnetic nonmetal, and that ferromagnetic crystal grains are separated from the initial layer. . FIG. 4 is a diagram showing the linear recording density dependence of normalized noise obtained from the evaluation of the electromagnetic conversion characteristics when the magnetic recording layer thickness is 15 nm in each of the examples and comparative examples of the present invention. Electromagnetic conversion characteristics were obtained from measurements with a spin stand tester using a GMR head. As is clear from FIG. 4, in Example 1 or 2 where exposure was performed, noise was significantly reduced as compared with Comparative Example 1 or 2 where exposure was not performed. Considering this in combination with the above-described evaluation results of the magnetic cluster size, the noise was reduced because the magnetic particles were sufficiently separated from the initial layer by the exposure.

Table 2 below shows the linear recording densities of 400 and 60.
Shows the SNR of 0 kFCI. In other words, Table 2 shows that Example 1
2 shows the SNR at a linear recording density of 400 and 600 kFCI for a magnetic recording layer thickness of 15 nm obtained from the evaluation of the electromagnetic conversion characteristics according to Comparative Examples 1 and 2.

[0022]

[Table 2] The SNR was obtained from the same electromagnetic conversion characteristic evaluation as in the case of the above-described normalized noise. Reflecting the above-mentioned increase in Hc and noise reduction, in Examples 1 and 2 in which exposure was performed, a significant improvement in SNR was observed as compared with the comparative example in which no exposure was performed.

[0023]

As described above, according to the present invention, a granular magnetic recording layer which is a non-magnetic non-metal oxide or nitride serving as a non-magnetic grain boundary is used.
Exposure to an atmosphere containing N ₂ or N ₂ and introduction of nuclei formed of non-magnetic non-metals on the surface of the substrate can provide an effect of separating ferromagnetic crystal grains from the initial layer of the magnetic layer. As a result, the magnetic interaction between the ferromagnetic crystal grains is reduced, the medium noise is reduced, and the magnetic layer can be made thinner. Thereby, a higher recording density of the perpendicular magnetic recording medium can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view for explaining one embodiment of a perpendicular magnetic recording medium according to the present invention.

FIG. 2 is a diagram showing the dependence of the size of a magnetic cluster size determined by MFM evaluation according to Examples 1 and 2 and Comparative Examples 1 and 2 on the thickness of a magnetic recording layer.

FIG. 3 is a diagram showing the dependency of the standard deviation of the magnetic cluster size obtained from the MFM evaluation according to Examples 1 and 2 and Comparative Examples 1 and 2 on the thickness of the magnetic recording layer.

FIG. 4 is a diagram showing the linear recording density dependence of normalized noise for a magnetic recording film thickness of 15 nm obtained from the evaluation of electromagnetic characteristics according to Examples 1 and 2 and Comparative Examples 1 and 2.

[Explanation of symbols]

1 Non-magnetic substrate 2 Underlayer 3 Magnetic recording layer 4 Protective film 5 Liquid lubricant layer 11 Soft magnetic underlayer 12 Seed layer

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5D006 BB06 BB07 CA01 CA06 DA03                       DA08 EA03 FA09                 5D112 AA03 AA05 AA24 BB02 BB05                       BB06 FA04 GA05

Claims (4)

[Claims] 1. A method for manufacturing a perpendicular magnetic recording medium comprising a non-magnetic substrate and at least an underlayer, a magnetic recording layer, a protective film, and a liquid lubricant layer sequentially laminated on the non-magnetic substrate. And a nonmagnetic crystal grain boundary of an oxide or a nitride surrounding the crystal grains. After the formation of the underlayer, the substrate is placed in an O ₂ or N ₂ atmosphere, or a rare gas containing O ₂ or A method for manufacturing a perpendicular magnetic recording medium, comprising exposing in a mixed gas atmosphere to which N ₂ has been added, and thereafter forming the magnetic recording layer. 2. The method according to claim 1, wherein the underlayer is made of Ru, RuW, RuC.
u, RuC, RuB, RuCoCr, etc.
2. The method for manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is one of an alloy containing u. 3. The method according to claim 1, wherein: NiFe, NiF
3. The method for manufacturing a perpendicular magnetic recording medium according to claim 1, wherein any one of Ni-based alloys such as eNb, NiFeB, NiFeCr, and NiFeSi is provided as a seed layer. 4. A perpendicular magnetic recording medium manufactured by the method for manufacturing a perpendicular magnetic recording medium according to claim 1, 2 or 3.