JPH11111524A - Magnetic recording medium, magnetic alloy film and sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having a high coercive force and a low noise, by using a magnetic film formed by adding an appropriate quantity of Zr to a CoCrPtTa four-element alloy. SOLUTION: A magnetic film is made of a CoCrPtTaZr alloy containing Cr at 10 to 26 at.%, Pt at 1 to 16 at.%, Ta at 1 to 7 at.%, Zr at 0.5 to 4 at.%, and Co substantially for the remaining part. In a working example, after texturing with a surface roughness Ra of 1.5 nm is carried out on a Ni-P plated Al substrate, the Al substrate is set in a DC magnetron sputtering device. Next, after evacuation is carried out to an ultimate vacuum of 2×10<7> Torr, a film of Cr85W15 (at.%) is formed to 15 nm as an underlying film, and subsequently, a magnetic film is formed by using a sintered alloy target having a composition of Co69Cr18Pt9Ta2Zr2 (at.%). The thickness of the magnetic film is equal to the product (Br.t) of the residual magnetization density (Br) and the thickness thereof (t), that is, 115 G.μm. The Ar pressure at the formation of film is 3 mmTorr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium used for a magnetic recording device such as a magnetic disk device and a floppy disk device.

[0002]

2. Description of the Related Art In recent years, as the recording density of a magnetic disk device and the like has increased, a magnetic recording medium suitable for a magnetic head (hereinafter, referred to as an MR head) using a magnetoresistive effect having high reproduction sensitivity has been required. . An MR head usually has a product (Br · t) of the residual magnetization density (Br) of the magnetic film and its thickness (t).
Is suitable for a magnetic disk having a thickness of 250 (Gm) or less.

On the other hand, as a magnetic disk which can be used in an MR head, CoCrPtTa4 is used as a magnetic film.
Base alloy, CoCr with W added as the fifth element
A magnetic disk using a PtTaW pentagonal alloy has been proposed (for example, Japanese Patent Application Laid-Open No. 9-147343). These proposed MR magnetic disks have the advantage that the characteristics can be controlled by changing the composition of elements other than Co.

[0004]

Since the MR head has a lower head noise than the electromagnetic induction type magnetic head, it is necessary to improve the signal-to-noise ratio (S / N) of the entire magnetic disk drive by using a magnetic head. Reducing the noise of the recording medium has become a very important issue. In the above quaternary and quinary alloys, a high coercive force (H
Although c) is obtained, there is a problem that the noise increases when the added amount of Pt is increased. Therefore, an object of the present invention is to provide a magnetic recording medium having high coercive force (Hc) and low noise.

[0005]

The inventor of the present invention has proposed CoCrPt.
When the fifth element added to the Ta quaternary alloy was examined, it was found that a magnetic recording medium with high coercive force (Hc) and low noise could be obtained by using a magnetic film to which an appropriate amount of Zr was added. The magnetic recording medium of the present invention has been made based on this finding. In a magnetic recording medium having a non-magnetic substrate, a non-magnetic base film, a magnetic film, and a protective film as a basic structure, the magnetic film has 10 to 26 atoms of Cr. %, Pt1
~ 16%, Ta1 ~ 7at%, Zr0.5 ~ 4at%,
The balance is characterized by being substantially an alloy of Co.

The non-magnetic substrate used in the present invention, which will be described in further detail below, is an Al alloy substrate (hereinafter referred to as NiP) having a NiP plating film, which is generally used as a substrate for a magnetic recording medium. In addition to a plated Al substrate, a glass substrate having excellent surface smoothness, a single crystal silicon substrate, or the like can be used.

[0007] The non-magnetic substrate is preferably used after being textured according to a conventional method. If necessary, chemical etching or electrolytic etching (electropolishing) can be performed as a finishing process for removing burrs and burrs after the texturing process. Further, in order to remove a natural oxide film and a contaminant adsorbed substance formed on the substrate surface after the above-described processing, it is also effective to expose the substrate film to RF plasma in vacuum immediately before forming the base film.

In a magnetic recording medium for an MR head,
As the recording density is improved, the flying height of the head is required to be lower, so that the substrate surface is required to have higher smoothness than in the past. Therefore, it is desirable that the non-magnetic substrate used in the present invention has an average surface roughness Ra of 2 nm or less.

The underlayer formed on the nonmagnetic substrate may be a conventionally known nonmagnetic underlayer such as Cr, Ti, Ni, S
A single-composition film such as i, Ta, W or the like, or an alloy containing other elements within a range that does not impair the crystallinity thereof can be used. However, in relation to the magnetic film of the present invention, Cr-5 is used.
It is desirable to use a ６０60 at% W alloy. Further, the base film is not limited to a single-layer structure, and may have a multilayer structure in which a plurality of films having the same composition or different compositions are stacked as necessary. The thickness of the underlayer is 1 to 200
nm, preferably 2 to 100 nm.

[0010] The magnetic film is made of a CoCrPtTaZr alloy, and contains 10 to 26 atomic% of Cr, 1 to 16% of Pt,
It is important that the alloy is composed of Ta 1 to 7 atomic%, Zr 0.5 to 4 atomic%, and the balance substantially Co. The preferred ranges are respectively 12 to 22 atomic% of Cr, 3 to 10% of Pt,
Ta is 2 to 6 atomic%, Zr is 1 to 3 atomic%, and Co is 6 atomic%.
It is preferably in the range of 5 to 85 atomic%. By using a CoCrPtTaZr alloy having such a specific composition, a magnetic recording medium having high coercive force (Hc) and low noise can be obtained.

The reason why the content of Cr is set to 10 to 26 at% is 10
If the amount is less than atomic%, the dispersion of the Co particles is insufficient due to the segregation of Cr, and if it exceeds 26 atomic%, the coercive force (Hc) tends to be remarkably reduced, and it tends to be unsuitable for MR media. Pt is set to 1 to 16% because a high coercive force (Hc) cannot be obtained at less than 1 atomic%.
If it exceeds 6 atomic%, the noise tends to increase.

The reason for making Ta 1 to 7 atomic% is 1 atomic%.
If it is less than 7, the noise tends to increase, and if it exceeds 7 atomic%, it becomes difficult to obtain a high coercive force (Hc). The reason why Zr is set to 0.5 to 4 atomic% is that noise tends to increase when it is less than 0.5 atomic%, and when it exceeds 4 atomic%, a high coercive force (Hc) is obtained.
Is difficult to obtain.

Although the thickness of the magnetic film is not particularly limited, in the case of a magnetic recording medium for an MR head, the product (Br · t) of the residual magnetization density (Br) and its thickness (t) is used. ) Is desirably adjusted to fall within the range of 50 to 150 G · μm. Residual magnetization density (Br) and its film thickness (t)
If the product (Br · t) is less than 50 G · μm, it is difficult to obtain an appropriate output, and if it exceeds 150 G · μm, it becomes difficult to obtain characteristics suitable for MR media.

The magnetic film can be formed by a sputtering method in the same manner as the underlayer film and the like. In this case, Cr is 10 to 26 atomic%, Pt is 1 to 16%, Ta is 1 to 7 atomic%, Zr is 0.5 to 0.5 atomic%.
An alloy target, preferably a sintered alloy target, made by a smelting method comprising 4 atomic% and the balance substantially consisting of Co is used.
This sintered alloy target is an alloy powder of the final target composition,
Alternatively, it can be manufactured by a conventionally known sintering method such as HIP (Hot Isostatic Press) or Hot Press using a plurality of alloy powders and single metal powders having the final target composition. Alloy powders and metal powders can also be produced by a conventionally known method such as a gas atomizing method.

In the magnetic recording medium of the present invention, a protective film is formed on the magnetic film in order to prevent damage due to contact between the head and the medium surface. As a material constituting the protective film, a conventionally known material may be used, and for example, a single component such as C, SiO ₂ , ZrO ₂ or a film mainly containing each component can be used. The thickness of the protective film is usually 2 to 20 nm. A lubricating film may be formed on the surface of the protective film, if necessary. As the lubricant, a fluorinated liquid lubricant such as PFPE (perfluoropolyether) or a solid lubricant such as a fatty acid is used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the scope. (Example 1) Surface roughness Ra was applied to a Ni-P plated Al substrate.
After texturing of 1.5 nm, it was set in a DC magnetron sputtering apparatus. Next, after evacuating to an ultimate vacuum of 2 × 10 ⁻⁷ Torr, Cr was used as a base film.
A film of 85 W15 (atomic%, hereinafter the same) was formed to a thickness of 15 nm, and subsequently a magnetic film was formed using a sintered alloy target having a composition of Co69Cr18Pt9Ta2Zr2. The thickness of the magnetic film is determined by the product of the residual magnetization density (Br) and its thickness (t) (Br ·
At t), it was 115 G · μm. The Ar pressure during film formation was 3 mmTorr.

When the magnetic characteristics of the magnetic recording medium prepared as described above were measured using a vibration type magnetic characteristic device (VSM), the coercive force (Hc) was 2918 Oe, and the coercive force squareness ratio (S *). Was 85.0%. In addition, the noise characteristics in recording / reproducing were measured by using a composite type thin film magnetic head having an MR element in a reproducing section and a linear recording density of 148.5 KFC.
It was 2.31 μV when measured at I.

(Embodiment 2) The magnetic film is made of Co69Cr18Pt9.
A magnetic recording medium was prepared in the same manner as in Example 1 except that the alloy was a Ta5Zr1 alloy. When the magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1, the coercive force (Hc) 2862 Oe and the coercive force squareness ratio (S *) 8
2.2%, and noise during recording and reproduction was 2.21 μV.

(Embodiment 3) The magnetic film is made of Co69Cr18Pt9.
A magnetic recording medium was prepared in the same manner as in Example 1, except that the alloy was Ta1Zr3. The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1. As a result, the coercive force (Hc) was 2875 Oe and the coercive force squareness (S *) was 8
6.3%, and noise in recording and reproduction was 2.21 μV.

Example 4 A magnetic recording medium was prepared in the same manner as in Example 1 except that the underlayer was Cr85Ti15.
The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1, and the coercive force (Hc) was 2878.
Oe, the coercive force squareness ratio (S *) was 83.3%, and the noise during recording and reproduction was 2.35 μV.

Example 5 A magnetic recording medium was prepared in the same manner as in Example 1 except that the underlayer was Cr85Mo15.
The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1, and the coercive force (Hc) 2836
Oe, the coercivity squareness ratio (S *) was 81.8%, and the noise during recording and reproduction was 2.37 μV.

(Comparative Example 1) Ni-P plated Al substrate
After texturing with a surface roughness Ra of 1.5 nm, the resultant was set in a DC magnetron sputtering apparatus. Next, after evacuation was performed to an ultimate vacuum of 2 × 10 ⁻⁷ Torr, a Cr85W15 film was formed as a base film to a thickness of 15 nm, and a Co70Cr18Pt9Ta3 alloy magnetic film was formed. The thickness of the magnetic film was 115 G · μm as the product (Br · t) of the residual magnetization density (Br) and its thickness (t). The Ar pressure during film formation was 3 mmTorr.

The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1, and the coercive force (H
c) 2815 Oe, coercivity squareness ratio (S *) 83.1%,
The noise during recording and reproduction was 2.58 μV.

(Comparative Example 2) Co64Cr18P as a magnetic film
A magnetic recording medium was prepared in the same manner as in Comparative Example 1 except that a t9Ta3Zr6 alloy magnetic film was formed. The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1. As a result, the coercive force (Hc) was 2584 Oe, the coercive force squareness ratio (S *) was 80.7%, and the noise in recording / reproducing was 2.
It was 49 μV.

(Comparative Example 3) Co69Cr18P as a magnetic film
A magnetic recording medium was prepared in the same manner as in Comparative Example 1 except that a t9Ta2W2 alloy magnetic film was formed. The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1. As a result, the coercive force (Hc) was 2584 Oe, the coercive force squareness ratio (S *) was 84.8%, and the noise in recording / reproducing was 2. 6
It was 3 μV.

(Comparative Example 4) Cr is 60 nm as a base film
A magnetic recording medium was prepared in the same manner as in Comparative Example 1, except that a film was formed and subsequently a Co79Cr16Ta5 alloy magnetic film was formed as a magnetic film. The magnetic characteristics and recording / reproducing characteristics of this magnetic recording medium were measured in the same manner as in Example 1. As a result, the coercive force (Hc) was 1829 Oe and the coercive force squareness (S ^* ) was 71.5.
%, And noise in recording and reproduction was 2.59 μV.

The evaluation results of Examples 1 to 5 and Comparative Examples 1 to 4 are summarized below. Examples 1 to 5 are 2800
It can be seen that it has a high coercive force (Hc) of Oe or more and has excellent characteristics of noise of less than 2.40 μV. Also, comparing Example 1 with Examples 4 and 5, it can be seen that superior characteristics can be obtained by using a CrW alloy as the underlayer.

Underlayer Magnetic film Hc S * Neuss ゛ Br · t (atomic%) (atomic%) (Oe) (%) (μV) (G · μm) Example 1 Cr85W15 Co69Cr18Pt9Ta2Zr2 2918 85.0 2.31 115 Example 2 Cr85W15 Co67Cr18Pt9Ta5Zr1 2862 82.2 2.21 115 Example 3 Cr85W15 Co75Cr18Pt9Ta1Zr3 2875 86.3 2.32 115 Example 4 Cr85Ti15 Co69Cr18Pt9Ta2Zr2 2878 83.3 2.35 115 Example 5 Cr85Mo15 Co69Cr18Pt9Ta2Zr2 2836 81.8 2.37115 Cr8P8 Cr3W82.55 815 Cr3W82.58 Cr3P8 2.58 Example 3 Cr85W15 Co69Cr18Pt9Ta2W2 2544 84.8 2.63 115 Comparative Example 4 Cr Co79Cr16Ta5 1829 71.5 2.59 115

[0029]

As described above, a magnetic recording medium having a high coercive force (Hc) and low noise can be obtained by using a CoCrPtTaZr alloy having a predetermined composition as the magnetic film.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Sakai 5-1 Yawata Kaigandori, Ichihara City, Chiba Prefecture Showa Denko HD Research & Development Center Co., Ltd.

Claims (7)

[Claims] 1. A magnetic recording medium having a non-magnetic substrate, a non-magnetic base film, a magnetic film and a protective film as a basic structure, wherein the magnetic film comprises 10 to 26 atomic% of Cr, 1 to 16 atomic% of Pt,
A magnetic recording medium comprising Ta 1 to 7 atomic%, Zr 0.5 to 4 atomic%, and the balance substantially Co. 2. A magnetic film comprising: 12 to 22 atomic% of Cr;
2. The magnetic recording medium according to claim 1, wherein the content is 10 to 10 atomic%, Ta is 2 to 6 atomic%, and Zr is 1 to 3 atomic%. 3. The magnetic recording medium according to claim 1, wherein the non-magnetic underlayer is composed of 5 to 60 atomic% of W and the balance substantially of Cr. 4. A magnetic alloy film comprising 10 to 26 atomic% of Cr, 1 to 16 atomic% of Pt, 1 to 7 atomic% of Ta, 0.5 to 4 atomic% of Zr, and the balance substantially Co. 5. The magnetic alloy film according to claim 4, wherein Cr is 12 to 22 atomic%, Pt is 3 to 10 atomic%, Ta is 2 to 6 atomic%, and Zr is 1 to 3 atomic%. 6. A sputtering target characterized by being a sintered body composed of 10 to 26 atomic% of Cr, 1 to 16 atomic% of Pt, 1 to 7 atomic% of Ta, 0.5 to 4 atomic% of Zr, and the balance substantially Co. . 7. The sputtering target according to claim 6, wherein Cr is 12 to 22 atomic%, Pt is 3 to 10 atomic%, Ta is 2 to 6 atomic%, and Zr is 1 to 3 atomic%.