JP2000322724A - Magnetic disk recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both of S/N and thermal stability and to obtain high density by forming an intraplane magnetization recording layer as a multilayer and forming a controlling layer for exchange coupling force between the recording layers. SOLUTION: This magnetic disk recording medium includes an Al or glass substrate 1, a base layer 2 such as Cr and a diamond like carbon surface protective film 5, and the medium has two layers of intraplane magnetization recording layers 3, 5 and a controlling layer 4 for exchange coupling force between these layers. The intraplane magnetization recording layers 3, 5 are formed from CoCr in high vacuum of a DC magnetron sputtering device, and the controlling layer 4 for exchange coupling force is formed from an alloy of Co and nonmagnetic elements, such as CoCr, CoNiCr, CoNiAl and CoSi. The compsn. ratio of Co in the controlling layer 4 for exchange coupling force is specified to 40 to 70%, and its film thickness preferably ranges from 0.5 to 10 nm. Thus, the product of the saturation magnetization and the coercive force of the controlling layer 4 for exchange coupling force is specified to be equal to or smaller than the product of the saturation magnetization and the coercive force of the intraplane magnetization recording layers 3, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk recording medium, and more particularly to a means for reducing grain boundary noise associated with bit boundaries due to magnetic particles by inserting an exchange coupling force adjusting layer between magnetic layers having a multilayer structure. And a magnetic disk recording medium having the following characteristics.

[0002]

2. Description of the Related Art Research and development of hard disk devices capable of high-density magnetic recording have been rapidly progressing along with recent demands for miniaturization and large capacity of hard disk devices. Has also become narrower as the recording density increases.

In order to form smaller recording bits on a magnetic disk recording medium, it is important to increase the coercive force and reduce noise of the magnetic disk recording medium itself, as well as the performance of the recording head.

As a recording layer of such a magnetic disk recording medium, CoCr such as CoCrPtTa or the like utilizing in-plane magnetization, ie, magnetization in a direction parallel to a plane of the magnetic layer, instead of a direction perpendicular to the plane of the magnetic layer. Since a system alloy is used, such a conventional magnetic disk recording medium will be described with reference to FIG.

[0005] See Figure 4. Figure 4 is a schematic cross-sectional view of a conventional magnetic disk recording medium, first, the mechanical strength of the Al substrate 31 by a Ni ₈₁ P ₁₉ plating layer 32 provided on the surface of the Al substrate 31 After being raised, Ni ₈₁ P
_After depositing a Cr underlayer 33 and a Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ recording layer 34 having a thickness of, for example, 25 nm on the ₁₉ plating layer 32, using a plasma CVD method,
DLC (Diamond L) having a thickness of, for example, 8 nm
By forming the (ike Carbon) layer 35, the basic structure of the magnetic disk recording medium can be obtained.

However, in the in-plane recording using the CoCr-based material, if the recording density is increased, the S / N ratio of the reproduced signal is reduced, and there is a problem that an error occurs at the time of reading the recorded signal. Will be described with reference to FIG.

FIG. 5 (a) is an enlarged view schematically showing a part of the magnetic disk recording medium by emphasizing a part of the magnetic disk recording medium. It is composed of fine Co-rich magnetic particles of about 20 to 50 nm, and has a configuration in which nonmagnetic Cr is segregated around the magnetic particles 45 to 47.

When data is recorded on such a magnetic disk recording medium, the magnetization directions of the recording bits 42, 43, and 44 are alternately reversed, and a bit boundary 41 is formed at the boundary. The boundary 41 is a bit boundary 41
Are disturbed by the influence of the grain boundaries of the magnetic particles 45 to 47, and the disturbance becomes noise of the reproduction signal, that is, grain boundary noise, and the S / N ratio is reduced.

In order to prevent such a decrease in the S / N ratio due to the increase in the recording density, the thickness of the recording layer is reduced and the bit boundary 4
1, a method of reducing the demagnetizing field, and a method of reducing noise by reducing the crystal grain size of the magnetic particles 45 to 47 to reduce the magnetic clusters to which the exchange coupling force is exerted. This situation will be described with reference to FIG.

FIG. 5B shows each recording bit 4 in one track.
2, 43, and 44 are schematically shown.
The area of 1 is represented by S, and the interval between the recording bits 42, 43, 44 is represented by d. In such a state, the influence of the demagnetizing field is determined by the area S of the bit boundary 41 and the distance d between the recording bits 42 to 44. In the case of a long columnar magnet such as a needle-like magnet, the area S Is small and d is relatively long, so that the influence of the demagnetizing field is small. However, in the case of a disk-shaped magnet, the area S of the bottom surface is large and d is small, so that the influence of the demagnetizing field is large.

In such an in-plane recording magnetic disk recording medium, recording bits 42 to 44 are used to increase the recording density.
When the interval d of is shortened, the shape of the bit becomes a disc shape,
The effect of the demagnetizing field increases. Since this demagnetizing field has a direction opposite to the magnetization of the recording bit to be read, it acts in a direction to erase the recorded magnetization, and the recording bit on which data is recorded becomes unstable. Therefore, since the reduction in the thickness of the recording layer reduces the area S of the recording bit, it has an effect of reducing the demagnetizing field, thereby improving the S / N ratio.

[0012]

However, although it is possible to improve the S / N ratio by the above method, the storage reliability of recorded data becomes a problem. That is, there is a problem of thermal fluctuation caused by the vibration of the magnetization direction due to the vibration of atoms constituting the magnetic particles due to heat.

[0013] The effect of this thermal fluctuation, the anisotropy constant of the K _u recording layer, the volume of the unit magnetization of the V recording layer, k the Boltzmann constant, the absolute temperature and T, K _u · V / kT The larger the value, the more thermally stable. Therefore, this thermal fluctuation becomes remarkable as the temperature rises, and when the magnetic cluster is made smaller to improve the S / N ratio, V becomes smaller and the influence of the thermal fluctuation increases. Further, when the recording layer is made thinner, the volume of the magnetic cluster becomes smaller as a result, so that the influence of thermal fluctuation also increases.

Therefore, when the recording layer is made thinner or the magnetic cluster is made smaller in order to improve the S / N ratio, the influence of thermal fluctuation increases, and the recorded data is destroyed due to the reversal of the magnetization direction. And it becomes very unstable thermally.

The temperature in the drive of the HDD device is 6
Since the temperature becomes higher than 0 ° C., the influence of the thermal fluctuation depending on the temperature T further increases and the thermal instability increases, and the improvement of the S / N ratio and the thermal stability are in a conflicting relationship. Was.

Accordingly, an object of the present invention is to achieve both improvement of the S / N ratio and thermal stability.

[0017]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. In the drawings, reference numeral 1 denotes a substrate such as an Al substrate or a glass substrate, reference numeral 2 denotes a base layer of Cr or the like, and reference numeral 5 denotes a diamond-like carbon film serving as a surface protective film. See FIG. 1. (1) In the present invention, in the magnetic disk recording medium, the in-plane magnetization recording layers 3 and 5 are composed of two or more layers, and between the multi-layered in-plane magnetization recording layers 3 and 5, An exchange coupling force adjusting layer 4 for controlling the exchange coupling force between layers is provided.

As described above, the multi-layered in-plane magnetization recording layer 3,
By providing the exchange coupling force adjusting layer 4 for optimizing the exchange coupling force between the layers 5, a good S / N ratio and thermal stability can be compatible with good reproducibility.

(2) Further, according to the present invention, in the above (1), the in-plane magnetization recording layers 3 and 5 are composed of two layers.
The exchange coupling force adjusting layer 4 provided between the layers is an in-plane magnetization film, and the product of the saturation magnetization and the coercive force of the exchange coupling force adjusting layer 4 is set to be equal to or less than the product of the saturation magnetization and the coercive force of the in-plane magnetization recording layers 3 and 5. It is characterized by having done.

As described above, the product M _s4 · H _c4 of the saturation magnetization M _s4 of the exchange coupling force adjusting layer 4 and the coercive force H _c4 is determined by the product M _s3 of the saturation magnetization of the in-plane magnetization recording layers 3 and 5 and the coercive force. By setting _Hc3 or less, that is, 0 < _Ms4 · _Hc4 ≦ _Ms3 · _Hc3 , both good S / N ratio and good thermal stability can be achieved with good reproducibility.

In this case, when M _s4 · H _c4 is extremely small, the exchange coupling force adjusting layer 4 becomes close to non-magnetic and the exchange coupling force between the layers becomes almost zero. In the recording layers 3 and 5, separate magnetic clusters are formed and become too small, thereby improving the S / N ratio, but increasing the influence of thermal fluctuation and reducing thermal stability. On the other hand, when M _s4 · H _c4 becomes large, the volume of the magnetic cluster becomes too large, and the S / N ratio decreases. Therefore, by appropriately adjusting the value of M _s4 · H _{c4 in} the range of 0 <M _s4 · H _{c4 ≤M s3} · H _c3 , it is possible to achieve both good S / N and thermal stability with good reproducibility. Can be.

(3) In the present invention, in the above (1) or (2), the in-plane magnetization recording layers 3 and 5 may be made of CoCr or a material obtained by adding at least one kind of Pt or Ta to CoCr. And the exchange coupling force adjusting layer 4 is formed of an alloy of Co and a nonmagnetic element.

As described above, the in-plane magnetization recording layers 3 and 5 are made of CoCr or a material obtained by adding at least one kind of Pt or Ta to CoCr, for example, CoCr.
Pt, CoCrPtTa, CoCrPtTaNb, or the like is preferable. The exchange coupling force adjusting layer 4 is made of an alloy of Co and a nonmagnetic element, for example, CoCr, CoNiC.
r, CoNiAl, CoSi and the like are preferable.

(4) In the present invention, in the above (3), the Co composition ratio of the exchange coupling force adjusting layer 4 is 40 to 70%.
It is characterized by being.

As described above, the Co composition ratio of the exchange coupling force adjusting layer 4 is preferably 40 to 70%. If the Co composition ratio is too small, M _s4 · H _c4 becomes small and the thermal stability becomes small. On the other hand, if the Co composition ratio is too large, M _s4 · H _c4
Becomes large and the S / N ratio decreases.

(5) The present invention is characterized in that in any one of the above (1) to (4), the exchange coupling force adjusting layer 4 has a layer thickness of 0.5 to 10 nm.

As described above, the layer thickness of the exchange coupling force adjusting layer 4 is preferably 0.5 to 10 nm. If the layer thickness is too large, M _s4 · H _c4 becomes small and thermal stability becomes poor. On the other hand, if the layer thickness is too thin, M _s4 · H _c4 increases and S /
The N ratio decreases.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic disk recording medium according to a first embodiment of the present invention will now be described with reference to FIG. FIG. 2 is a schematic sectional view of a magnetic disk recording medium according to the first embodiment of the present invention. First, for example, a 3.5-inch (≒ 8.9 cm) Al substrate 11 is A Ni ₈₁ P ₁₉ plating layer 12 having a thickness of, for example, about 10 μm is provided.
The mechanical strength of the Al substrate 11 is increased to ensure contact reliability with the magnetic head during high-speed rotation.

Then, if necessary, texture processing using abrasive grains is performed to form fine grooves along the circumferential direction of the surface of the Ni ₈₁ P ₁₉ plating layer 12, or irregular processing is performed. To form irregularities. The grooves formed by the texture processing or the concavities and convexities formed by the concavo-convex processing reduce the friction between the magnetic head and the magnetic disk recording medium to prevent the magnetic head from being attracted. , The magnetic anisotropy in the in-plane recording direction can be increased.

Next, a DC magnetron using Ar gas
1 × 10 using a sputtering device^-FiveHigh vacuum over Pa
Degree, for example, 5 × 10^-6At a vacuum of Pa, Ni₈₁
P₁₉On the plating layer 12, a thickness of 15 to 30 nm, for example,
20 nm Cr₉₀Mo_TenUnderlayer 13 and thickness 10
20 nm, for example, 12 nm of Co₆₉Cr_{twenty one}Pt₈Ta
_TwoThe first recording layer 14 is deposited.

Next, from Co and Cr which is a nonmagnetic element,
Become Co₅₅Cr₄₅Using alloy as target, thickness
0.5-10 nm, for example, 5 nm of Co₅₅Cr₄₅Adjustment
After forming the layer 15, the thickness is again 10 to 20 nm, for example.
For example, 12 nm of Co₆₉Cr _{twenty one}Pt₈Ta_TwoSecond recording layer
16 is deposited.

Next, a thickness of 5
After depositing a DLC layer 17 having a thickness of 15 nm, for example, 8 nm, a lubricant is applied to the surface of the DLC layer 17 by a method such as dipping to obtain a basic configuration of the magnetic disk recording medium.

As described above, in the first embodiment of the present invention, the in-plane magnetization recording layer is formed of Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ first recording layer 14 and Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ second recording layer. Co ₆₉ Cr ₂₁ Pt is composed of two layers 16, and a Co ₅₅ Cr ₄₅ adjustment layer 15, which is an in-plane magnetized film, is provided between both layers so that the S / N ratio and the thermal stability are compatible. ₈ Ta ₂ first recording layer 14 and Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ second recording layer 1
6 is controlled so as to optimize the exchange coupling force, and a magnetic disk recording medium having good magnetic characteristics can be manufactured with good reproducibility.

In this case, Co₅₅Cr₄₅Adjustment layer 15
Is greater than 10 nm, M _s・ H_cProduct is small
Too much and thermal stability is reduced, while Co₅₅Cr₄₅Key
When the thickness of the alignment layer 15 becomes 0.5 nm or less, M_s・ H_c
Becomes too large and the magnetic cluster becomes large and S /
Since the N ratio decreases, the range of 0.5 to 10 nm is preferable.
is there.

The composition ratio of the exchange coupling force adjusting layer is Co.₅₅
Cr₄₅Is not limited to Co₄₀Cr₆₀~ Co₇₀
Cr₃₀And the Co composition ratio should be 40% or less.
Then, M_s・ H_cProduct is too small and thermal stability
On the other hand, when the Co composition ratio becomes 70% or more, M_s
・ H_cThe product becomes too large and the S / N ratio decreases. Cause
And Co₄₀Cr₆₀M_s・ H_cThe product is about 1kOe ・ emu
/ Cc and Co ₇₀Cr₃₀M_s・ H_cThe product is about 50k
Oe · emu / cc.

Next, a magnetic disk recording medium according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, a glass substrate is used as a substrate, and Cr ₉₀ Mo is used as a layer for increasing mechanical strength.
_It is the same as the above-described first embodiment except that a _ten sputtered layer is used. FIG. 3 is a schematic sectional view of a magnetic disk recording medium according to a second embodiment of the present invention. First, for example, a 2.5-inch (≒ 6.35 cm) glass substrate 21 is placed on a glass substrate 21. A sputtering method is used to provide a Ni ₈₁ P ₁₉ sputtered layer 22 having a thickness of, for example, about 100 nm.
The mechanical strength of is increased.

Thereafter, similarly to the above-described first embodiment, texturing using abrasive grains is performed as necessary, so that fine particles are formed along the circumferential direction of the surface of the Ni ₈₁ P ₁₉ sputtered layer 22. An irregular groove is formed, or irregularities are formed to form irregularities.

Next, using a DC magnetron sputtering apparatus with an Ar gas, Ni _{81 at} a high degree of vacuum of 1 × 10 ⁻⁵ Pa or more, for example, 5 × 10 ⁻⁶ Pa.
On the P ₁₉ sputtered layer 22, a thickness of 15 to 30 nm, e.g., 20 nm of Cr ₉₀ Mo ₁₀ underlayer 23 and the thickness 1
0 to 20 nm, for example, 12 nm Co ₆₉ Cr ₂₁ Pt ₈
The Ta ₂ first recording layer 24 is deposited.

Next, from Co and Cr which is a non-magnetic element,
Become Co₅₅Cr₄₅Using alloy as target, thickness
0.5-10 nm, for example, 5 nm of Co₅₅Cr₄₅Adjustment
After forming the layer 25, the thickness is again 10 to 20 nm, for example.
For example, 12 nm of Co₆₉Cr _{twenty one}Pt₈Ta_TwoSecond recording layer
26 is deposited.

Next, a thickness of 5
After depositing a DLC layer 27 of １５15 nm, for example, 8 nm, a lubricant is applied to the surface of the DLC layer 27 by a method such as dipping to obtain the basic configuration of the magnetic disk recording medium.

As described above, according to the second embodiment of the present invention,
A glass substrate 2 harder than an Al substrate
1 and Ni₈₁P₁₉Ni thinner than plating layer 12
₈₁P ₁₉Further hardness is obtained by using the sputter layer 22.
2.5 inches for high impact use
Suitable as a magnetic disk recording medium for notebook computers
become. In addition, the matters relating to the magnetic characteristics are described in the first section above.
Regarding the magnetic characteristics of the magnetic disk recording medium of the embodiment
The matter is exactly the same.

The embodiments of the present invention have been described above. However, the present invention is not limited to the configurations and conditions described in the embodiments, and various changes can be made. For example, in each of the above embodiments, the Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ magnetic film is used as the magnetic film constituting the magnetization recording layer, but a CoCrPtTa magnetic film having another composition ratio may be used. CoCr such as Co ₇₄ Cr ₁₅ Pt ₄ Ta ₄ Nb ₃ magnetic film or Co _76.3 Cr ₁₇ Pt _6.7 magnetic film
PtTaNb magnetic film, CoCrPt film, or CoC
An r film may be used.

In each of the above embodiments, the magnetic recording layer has a two-layer structure. However, the magnetic recording layer may have a multilayer structure of three or more layers. What is necessary is just to interpose an exchange coupling force adjustment layer.

In the description of the above embodiments, the exchange coupling force adjusting layer has a Co composition ratio of 40 to 70.
% CoCr layer is used, but the present invention is not limited to the CoCr layer, and Ni, Al, S
i, etc. may be used, and CoNiCr, CoNiAl, CoSi, or the like made of an alloy of such an element and Co may be used. In this case, the Co composition ratio may also be 40.
７０70%, and the layer thickness is 0.5〜
It is desirable to set it to 10 nm.

In the description of each of the above embodiments, in order to prevent surface oxidation of the formed magnetic recording layer,
Although sputtering is performed under a high vacuum of 1 × 10 ⁻⁵ Pa or less, in some cases, in order to eliminate the influence of oxidation,
Before depositing the exchange-coupling-force adjusting layer, the surface of the first recording layer may be etched by reverse sputtering using Ar gas, whereby the gap between the first recording layer and the second recording layer may be removed. Can be adjusted.
Further, before depositing the second recording layer, the surface of the exchange coupling force adjusting layer may be etched by reverse sputtering using Ar gas.

Further, the substrate is not limited to an Al substrate or a glass substrate, but other substrates such as a Si substrate may be used, and Ni ₈₁ P may be used as a mechanical strength enhancement layer.
The composition is not limited to _19, and NiP having another composition ratio may be used. Further, another alloy such as NiAl may be used. Further, even if the underlying layer is not limited to Cr ₉₀ Mo _10, may also CrMo other composition ratio, and further, it is permissible to use other metals such as Cr.

[0047]

According to the present invention, the in-plane magnetization recording layer has a multilayer structure, and an exchange coupling force adjusting layer for optimizing the exchange coupling force between the multilayer in-plane magnetization recording layers is provided between the layers. As a result, a good S / N ratio and thermal stability can be compatible with good reproducibility, thereby contributing to an increase in the capacity of a magnetic disk recording device such as a hard disk device and a high-density magnetic recording. But big.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is a schematic sectional view of the magnetic disk recording medium according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of a magnetic disk recording medium according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view of a conventional magnetic disk recording medium.

FIG. 5 is an explanatory diagram of a problem in a conventional magnetic disk recording medium.

[Explanation of symbols]

1 substrate 2 underlayer 3 plane magnetic recording layer 4 exchange coupling force control layer 5 plane magnetic recording layer 6 diamond-like carbon layer 11 Al substrate 12 Ni ₈₁ P ₁₉ plating layer 13 Cr ₉₀ Mo ₁₀ underlayer 14 Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ first recording layer 15 Co ₅₅ Cr ₄₅ adjustment layer 16 Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ second recording layer 17 DLC layer 21 glass substrate 22 Ni ₈₁ P ₁₉ sputtering layer 23 Cr ₉₀ Mo ₁₀ underlayer 24 Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ first recording layer 25 Co ₅₅ Cr ₄₅ adjustment layer 26 Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ second recording layer 27 DLC layer 31 Al substrate 32 Ni ₈₁ P ₁₉ plating layer 33 Cr underlayer 34 Co ₆₉ Cr ₂₁ Pt ₈ Ta ₂ recording layer 35 DLC layer 41 bit boundary 42 recording bit 43 recording bit 44 recording bit 45 magnetic particle 46 magnetic particle 47 magnetic particle

Claims (5)

[Claims] 1. An in-plane magnetization recording layer comprising two or more multilayers, and an exchange coupling force adjusting layer for controlling an exchange coupling force between the multilayered in-plane magnetization recording layers. A magnetic disk recording medium characterized by the above-mentioned. 2. An in-plane magnetization recording layer comprising two layers, an exchange coupling adjustment layer provided between said layers being an in-plane magnetization film, and a product of a saturation magnetization and a coercive force of said exchange coupling adjustment layer. 2. The magnetic disk recording medium according to claim 1, wherein the value is equal to or less than a product of a saturation magnetization and a coercive force of the in-plane magnetization recording layer. 3. The in-plane magnetization recording layer is made of CoCr or a material obtained by adding at least one of Pt and Ta to CoCr, and the exchange coupling force adjusting layer is made of an alloy of Co and a non-magnetic element. The magnetic disk recording medium according to claim 1, wherein the magnetic disk recording medium is constituted by: 4. The Co composition ratio of the exchange coupling force adjusting layer is as follows:
4. The magnetic disk recording medium according to claim 3, wherein the ratio is 40 to 70%. 5. A layer thickness of the exchange coupling force adjusting layer is set to 0.5
The magnetic disk recording medium according to any one of claims 1 to 4, wherein the thickness is set to 10 to 10 nm.