JPH09190621A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is decreased in medi um noise particularly in recording and reproducing, concerning a magnetic recording medium, such as magnetic drum, magnetic tape or magnetic disk. SOLUTION: This magnetic recording medium is constituted by forming a ternary Chromium alloy film consisting of two kinds of elements selected from among Ti, Ta, Ag, Mo and Si, and Cr as a nonmagnetic ground surface film on a nonmagnetic substrate and forming an alloy film consisting essentially of Co as a magnetic film on the Cr alloy film. The total ratio of two kinds of the elements exclusive Cr of the nonmagnetic ground surface film is 10 to 40at.%.

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 such as a magnetic drum, a magnetic tape and a magnetic disk, and more particularly to a magnetic recording medium in which medium noise during recording / reproduction is reduced.

[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. . Since the MR head has lower head noise than the conventional electromagnetic induction type head, the signal to noise ratio (S / S / S
To improve N), the reduction of medium noise has become a very important issue.

At present, as a recording medium for a magnetic disk using an Al alloy as a substrate which is generally used, Cr or Cr alloy is formed as a non-magnetic underlayer on the non-magnetic substrate, and then as a magnetic film. CoCrT containing Co as a main component
Various proposals and commercializations of a-alloy film and the like have been made. For example, in Japanese Patent Application Laid-Open No. 1-223222, Cr is used as a non-magnetic underlayer, or Cu, Nb, Ti is added to Cr.
It has been proposed to improve magnetic properties, especially coercive force, by forming an alloy containing one or more metals selected from V, Zr, Mo, Zn, W, and Ta. Further, JP-A-59-142738 proposes to use a CrAg alloy for the underlayer.

[0004]

However, in the above-mentioned JP-A-1-232522, C is used as the non-magnetic underlayer film.
Although r or Cr alloy is used, the film thickness is 500 to 3
Since it is 000Å, Cr or Cr alloy particles in the film grow. As a result, crystal grains inside the Co magnetic film epitaxially grown on the Cr or Cr alloy film also grow, so that it is difficult to reduce the medium noise. Further, in JP-A-59-142738, the CrAg alloy is used for the underlayer, but the film thickness is 500 to 300.
Since there is 0Å, alloy particles grow. If the film thickness is less than 300Å, which is formed to suppress grain growth, Cr
The coercive force of the Ag alloy film is lower than that of the Cr film, and the MR
Not suitable for media. In view of these problems, the object of the present invention is to reduce the noise during recording and reproduction,
It is to provide a magnetic recording medium that is preferably combined with a head.

[0005]

As a method for reducing medium noise, it is desirable that magnetic particles in a magnetic medium have a size equal to or larger than a critical size at which magnetism is lost and as small as possible.
That is, as a means for solving the above-mentioned problems, Ti, Ta, Ag, Mo, Si as a non-magnetic base film is formed on a non-magnetic substrate.
A ternary Cr alloy film composed of two kinds of elements selected from Cr and Cr is formed, and a Co alloy film as a magnetic film is formed thereon.
Further, as a protective film, a magnetic recording medium obtained by sequentially forming, for example, a carbon film was found, and the present invention was completed. A sputtering method is generally used as a film forming method. In the non-magnetic underlayer film, the total proportion of two elements other than Cr is 10 to 40 at%.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The non-magnetic substrate used in the present invention is an Al alloy (hereinafter, referred to as NiP) having a NiP plating film generally used as a substrate for a magnetic recording medium.
In addition to the plated Al substrate), a glass substrate, a single crystal silicon substrate or the like having excellent surface smoothness can be used. In the magnetic recording medium for the MR head, the head is required to have a lower flying height as the recording density is improved, and therefore the smoothness of the substrate surface is required as compared with the conventional case. In the non-magnetic substrate used in the present invention, the surface average roughness Ra
Is preferably 20 Å or less.

As the non-magnetic undercoat film in the present invention, a ternary Cr alloy film composed of two elements selected from Ti, Ta, Ag, Mo and Si and Cr is 25 to 350.
It can be formed with an extremely thin film thickness of Å. This Cr
Setting the film thickness of the alloy non-magnetic underlayer film is important for controlling the crystal orientation and the crystal grain size of the Co alloy magnetic film formed thereon. That is, in order to reduce the medium noise of the magnetic recording medium, it is necessary to reduce the crystal grain size of the Co alloy magnetic film or weaken the exchange coupling between the crystal grains. Conventionally used C on Cr non-magnetic underlayer
The o alloy crystal grains are made finer by thinning the film thickness of the Cr non-magnetic underlayer film, but there is a problem that the coercive force Hc decreases as the film thickness of the Cr nonmagnetic underlayer film decreases. ing. However, as a non-magnetic underlayer, Ti, Ta, Ag, M
In the case of using a ternary Cr alloy film consisting of two kinds of elements selected from o and Si and Cr, the coercive force is obtained even if the Cr alloy nonmagnetic underlayer film is formed to an extremely thin film thickness of 25 to 350 Å. It was found that the decrease in Hc was suppressed.

When the Cr alloy used as the non-magnetic underlayer is made of a binary system, some elements can suppress the decrease in coercive force when the film thickness is made thin, but it is not sufficient as compared with the ternary system, and conversely. Some elements have a significantly lower coercive force than the Cr film. In Fig. 1, CrTa with varying composition ratio of Ta
Co ₇₅ C formed on each non-magnetic base film (thickness = 300Å) of Ag ₁₀ alloy, CrTaAg ₁₅ alloy, CrTa alloy
r ₁₆ Pt ₆ Ta ₃ magnetic film (remanent magnetization film thickness product Br of the magnetic film
T = 100 Gμm), the coercive force Hc was specifically increased in the range where the composition ratio of Ta was in the range where the composition ratio of Ta was 5%. In the range of up to 25 at%, binary C
The coercive force was higher than that of the r alloy with the non-magnetic underlayer. From similar tests and other property tests on each component, it seems that the addition amount of each element of Ti, Ta, Ag, Mo and Si is preferably 5 to 25 at%. FIG.
CrTaAg ₁₀ alloy, CrTaAg ₁₅ alloy,
CrTa alloy is exactly Cr _(100-10-A) Ta _A Ag ₁₀ alloy, Cr when the composition of Ta is Aat%.
It should be described as _(100-15-A) Ta _A Ag ₁₅ alloy and Cr _(100-A) Ta _A alloy.

Further, the total proportion of two kinds of elements selected from Ti, Ta, Ag, Mo and Si in the ternary Cr alloy non-magnetic underlayer film used in the present invention is 10 to 40 at%, but from 40 at%. If it is too large, the coercive force or the coercive force squareness ratio S ^* is lowered. If it is less than 10 at%, only the physical properties similar to those of the Cr film are obtained, and the effect of alloying is hardly obtained. As described above, it is desirable that the thickness of the ternary Cr alloy non-magnetic underlayer film is 25 to 350 Å, but if the thickness is less than 25 Å, the coercive force Hc will decrease even if a Cr alloy film of any alloy composition is used. It is difficult to suppress, and if it is thicker than 350 Å, it becomes difficult to reduce the medium noise due to the coarsening of the crystal grains of the Co alloy magnetic film formed thereon.

As the magnetic film in the present invention, Co
An alloy film is used, and the composition thereof is not particularly limited, but a Co alloy containing Pt such as CoCrPt or CoCrPtTa can be preferably used. In particular, the effect of the underlayer is remarkable when CoCrPtTa is used. As described above, the ternary Cr film is used as the nonmagnetic underlayer film.
When an alloy film is used, a decrease in coercive force Hc can be suppressed in a region where the thickness of the Cr alloy nonmagnetic underlayer film is thin. This is caused by the lattice of each alloy crystal of the nonmagnetic underlayer film and the magnetic film. This is considered to be because the consistency of constants is improved. The case where CoCrPtTa is used for the Co alloy magnetic film will be described in more detail.
_(100-XYZ) Cr _X Pt _Y Ta _Z
13 at% ≦ X ≦ 20 at%, 4 at% ≦ Y ≦ 8 at
%, 2 at% ≦ Z ≦ 5 at% are desirable. C
When the r concentration exceeds 20 at%, the coercive force is remarkably reduced, and it tends to be unsuitable for MR media. Also, P
If the t concentration exceeds the upper limit, noise increases, and if the t concentration falls below the lower limit, a high coercive force tends not to be obtained. Similarly, if the Ta concentration exceeds the upper limit, a high coercive force cannot be obtained, and if the Ta concentration is lower than the lower limit, noise tends to increase.

The film thickness of the Co alloy magnetic film is preferably adjusted so that the residual magnetization film thickness product BrT is 50 to 130 Gμm, considering that it is a magnetic medium for an MR head. When the residual magnetization film thickness product BrT is less than 50 Gμm, an appropriate output cannot be obtained, and when it exceeds 130 Gμm, M
It is not possible to obtain characteristics suitable for R media.

[0012]

【Example】

<Example 1> First, a Ni-P plated Al substrate was subjected to texturing with a surface roughness Ra15Å and then set in a DC magnetron sputtering apparatus. Next, after evacuation to an ultimate vacuum of 2 × 10 ⁻⁶ Torr, the substrate is removed to 23
Cr ₈₀ Ta as a non-magnetic underlayer in a state of being heated to 0 ° C
_A 300 Å film of ₁₀ Ag ₁₀ alloy was formed, and subsequently a Co ₇₅ Cr ₁₆ Pt ₆ Ta ₃ alloy was formed as a magnetic film. Further, carbon was deposited as a protective film on the magnetic film at a thickness of 150 °. The Ar pressure during film formation was 3 mTorr. The film thickness of the magnetic film is 110 Gμm in the residual magnetization film thickness product (BrT).
Met. The magnetic characteristics of the magnetic recording medium manufactured according to Example 1 were measured using a vibration type magnetic characteristic device (VSM). The recording / reproducing characteristics of the magnetic recording medium were measured by using a composite type thin film magnetic head having a magnetoresistive (MR) element in the reproducing section and a linear recording density of 140 KFCI (measurement range: 28.14 m).
m, rotation speed 5400 rpm). The magnetic recording medium of Example 1 had a coercive force (Hc) of 2,800 Oe, a coercive force squareness ratio (S ^* ) of 84.9%, and a noise during recording / reproduction of 2.95 μV.

<Embodiment 2> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₇₀ Ta ₂₀ Ag ₁₀ was used. The coercive force (Hc) of the magnetic recording medium of Example 2 was 3010 Oe, and the coercive force squareness ratio (S
^* ) Is 82.6%, and noise during recording / playback is 2.65 μV
Met.

<Comparative Example 1> A magnetic recording medium was prepared in the same manner as in Example 1 except that the non-magnetic underlayer was made of Cr. The coercive force (Hc) of the magnetic recording medium of Comparative Example 1 is 2
011 Oe, coercive force squareness ratio (S ^* ) was 88.6%, and noise during recording and reproduction was 3.89 μV.

Comparative Example 2 The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₈₀ Ta ₂₀ was used. The coercive force (Hc) of the magnetic recording medium of Comparative Example 2 was 2111 Oe, the coercive force squareness ratio (S ^* ) was 87.8%, and the noise during recording / reproduction was 3.75 μV.

<Comparative Example 3> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was prepared in the same manner as in Example 1 except that r ₉₀ Ag ₁₀ was used. The coercive force (Hc) of the magnetic recording medium of Comparative Example 3 was 1536 Oe, the coercive force squareness ratio (S ^* ) was 86.1%, and the noise during recording and reproduction was 4.25 μV.

<Comparative Example 4> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₅₀ Ta ₃₀ Ag ₂₀ was used. The coercive force (Hc) of the magnetic recording medium of Comparative Example 4 was 1950 Oe and the coercive force squareness ratio (S
^* ) Is 80.9%, and noise during recording and playback is 4.01 μV
Met.

<Embodiment 3> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₆₅ Ta ₂₀ Ti ₁₅ was used. The coercive force (Hc) of the magnetic recording medium of Example 3 is 2866 Oe, and the coercive force squareness ratio (S
^* ) Is 89.9%, and noise during recording / playback is 2.88 μV
Met.

<Comparative Example 5> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₅₅ Ta ₃₀ Ti ₁₅ was used. The magnetic recording medium of Comparative Example 5 had a coercive force (Hc) of 1283 Oe and a coercive force squareness ratio (S
^* ) Is 61.1%, noise during recording and playback is 5.04μV
Met.

<Embodiment 4> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₇₀ Mo ₂₀ Si ₁₀ was used. The coercive force (Hc) of the magnetic recording medium of Example 4 was 2934 Oe, and the coercive force squareness ratio (S
^* ) Is 89.1%, and noise during recording / playback is 2.74 μV
Met.

<Comparative Example 6> The alloy composition of the non-magnetic underlayer is C
except that the r ₈₅ Si ₁₅ was prepared a magnetic recording medium in the same manner as in Example 1. The coercive force (Hc) of the magnetic recording medium of Comparative Example 6 was 1688 Oe, the coercive force squareness ratio (S ^* ) was 88.3%, and the noise during recording and reproduction was 4.23 μV.

<Embodiment 5> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₆₅ Ta ₂₅ Ag _{10 was used,} and the film thickness of the Co alloy magnetic film was 80 Gμm in terms of residual magnetization film thickness product (BrT). The coercive force (Hc) of the magnetic recording medium of Example 5 was 2940 Oe, the coercive force squareness ratio (S ^* ) was 83.5%, and the noise during recording and reproduction was 2.25 μV.

<Embodiment 6> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₇₀ Ta ₂₀ Ag ₁₀ and the film thickness were 100 Å. The coercive force (Hc) of the magnetic recording medium of Example 6 was 2666 Oe,
The coercive force squareness ratio (S ^* ) was 86.8%, and the noise during recording and reproduction was 2.91 μV.

<Embodiment 7> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was prepared in the same manner as in Example 1 except that r ₇₀ Ta ₂₀ Ag ₁₀ , the film thickness was 100 Å, and the film thickness of the Co alloy magnetic film was 55 Gμm in terms of residual magnetization film thickness product (BrT). The coercive force (Hc) of the magnetic recording medium of Example 7 was 2430 Oe, the coercive force squareness ratio (S ^* ) was 84.3%, and the noise during recording and reproduction was 2.97 μV.

<Embodiment 8> The alloy composition of the non-magnetic underlayer is C
A magnetic recording medium was produced in the same manner as in Example 1 except that r ₇₀ Ta ₂₀ Ag ₁₀ , the film thickness was 25 Å, and the film thickness of the Co alloy magnetic film was 110 Gμm in the residual magnetization film thickness product (BrT). The coercive force (Hc) of the magnetic recording medium of Example 8 was 2205 Oe, the coercive force squareness ratio (S ^* ) was 80.1%, and the noise during recording and reproduction was 3.02 μV.

Example 9 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the non-magnetic substrate was single crystal Si. The magnetic recording medium of Example 9 had a coercive force (Hc) of 2460 Oe, a coercive force squareness ratio (S ^* ) of 83.2%, and a recording / reproducing noise of 2.74 μV.

Example 10 A magnetic recording medium was prepared in the same manner as in Example 1 except that the non-magnetic substrate was crystallized glass (made by OHARA). The coercive force (Hc) of the magnetic recording medium of Example 10 was 2315 Oe, the coercive force squareness ratio (S ^* ) was 82.5%, and the noise during recording and reproduction was 2.91.
It was μV.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments and can be carried out in any manner as long as the configuration described in the claims is not changed.

[0029]

In the magnetic recording medium of the present invention, the coercive force Hc does not decrease even if the film thickness is reduced to 25 to 350 Å by using the ternary Cr alloy having a specific composition as the non-magnetic underlayer film. The crystal grain size of the Co alloy magnetic film can be made finer, and the Co alloy magnetic film can be used as a magnetic recording medium corresponding to an MR head with reduced medium noise.

Further, when a CoCrPtTa alloy having a specific composition is used as the Co alloy magnetic film, a particularly high coercive force can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing changes in coercive force of Co ₇₅ Cr ₁₆ Pt ₆ Ta ₃ magnetic films formed on Cr alloy non-magnetic underlayer films having different Ta compositions.

Claims (4)

[Claims] 1. T as a non-magnetic underlayer on a non-magnetic substrate
An alloy film containing Co as a main component is formed on the Cr alloy film by forming a ternary Cr alloy film containing two kinds of elements selected from i, Ta, Ag, Mo and Si and Cr. The non-magnetic underlayer film, wherein the total proportion of two kinds of elements other than Cr is 10 to 40 at%. 2. The non-magnetic underlayer film has a thickness of 25 to 35.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is 0Å. 3. The alloy composition of the magnetic film is Co _(100-XYZ) C.
In the composition formula represented by r _X Pt _Y Ta _Z , 13 at% ≦ X
≤20 at%, 4 at% ≤Y≤8 at%, 2 at% ≤Z
3. The magnetic recording medium according to claim 1, wherein ≦ 5 at%. 4. The remanence film thickness product (BrT) of the magnetic film is 5
4. The thickness is from 0 to 130 Gm.
The magnetic recording medium according to any one of 1.