JPS61276116A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain the title medium having large S/N and high saturation magnetic flux density by forming a magnetic film with a cobaltnickel alloy having prescribed composition and characteristic. CONSTITUTION:A magnetic film layer is formed on a discoid substrate to obtain a magnetic recording medium. The magnetic film is formed with a Co-Ni alloy contg. 10-35 atom% Ni, consisting essentially of crystal grains having 100-500Angstrom grain diameter and having 60-95% relative density. Namely, a substrate layer is formed on the discoid substrate which has been heated to a temp. ranging from ordinary temp. to <=250 deg.C, then a thin film of a Co-Ni alloy is formed in the atmosphere of gaseous Ar contg. N2 and/or O2 and then the material is heat-treated. Consequently, a magnetic film composed of a Co-Ni alloy contg. 10-35 atom% Ni, consisting essentially of crystal grains having 100-500Angstrom grain diameter and having 60-95% relative density is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium and a method for manufacturing the same, and in particular, to a magnetic recording medium and a method for manufacturing the same.
The present invention relates to a magnetic recording medium having a cobalt-nickel (CONi) alloy magnetic film layer with a high /N ratio, and a method for manufacturing the same.

[Prior Art] In recent years, as computers have become smaller and their processing power has increased, there has been a demand for further increases in the storage capacity of external memory devices. In order to satisfy this demand, it is necessary to further increase the recording density of magnetic disks used in external memory devices, and for this purpose, it is necessary to improve the magnetic properties of the magnetic thin film that forms the recording layer and to improve the recording density of the recording layer. We must promote further thinning of the film.

Therefore, as one method to satisfy such requirements, as shown in Japanese Patent Publication No. 55-14058,
A method of forming a recording layer by sputtering has been developed. This method uses iron or iron alloy as a target and deposits Fe onto the disk substrate by reactive sputtering.
A thin film layer of 304 was formed and then thermally oxidized to form γ-
F 620 g. In addition, cobalt or cobalt nickel (CoNi) can be made by sputtering method.
A thin film layer of an alloy has been proposed (
J, Appl, Phys, 53 (5).

1982, Japanese Unexamined Patent Publication No. 57-7230, etc.), and others.
Cobalt-platinum (Co-Pt) and cobalt-nickel-platinum (Co-Ni-Pt) systems are also known. Further, it is also known that a Go-P or Go-Ni-P film is formed by electroless plating.

[Problems to be solved by the invention] Among the conventionally used magnetic films, γ-F e 2 O
The a-type magnets have the advantage of a high S/N ratio, but have the disadvantages of a low saturation magnetic flux density and low output.

On the contrary, Co-Ni, co-pt, Co-Nt
-Pt, Co--P, and Co--Ni--P have a high saturation magnetic flux density and a large output, but have a problem of a low S/N ratio at high recording densities of 20 KPCI or higher.

[Means for Solving the Problems 1] In order to solve the problems of the prior art described above, the present invention provides a magnetic recording medium in which a magnetic film layer is formed on the plate surface of a disk-shaped substrate, in which the magnetic film is made of Ni. A magnetic recording medium characterized in that it is a CoNi alloy with a CoNi content of 10 to 35 at. After forming a base layer on the plate surface of a disk-shaped substrate heated to below ℃, a Go-Nt alloy thin film is formed in an Ar gas atmosphere containing N2 and/or 02, and then heat treatment is performed to form a Ni-containing layer. Magnetic recording, characterized in that it is a Co-Ni alloy with a Co-Ni alloy having a ratio of 10 to 35 at. Method of manufacturing media.

The main points are as follows.

The present invention will be explained in more detail below.

In the magnetic recording medium of the present invention, a magnetic film layer is formed on a substrate such as an aluminum-based alloy.

As the material of the substrate, it is preferable to use aluminum or a material whose main component is aluminum, with the addition of other metal elements to improve one or more of the properties such as strength, rigidity, and corrosion resistance. For example, magnesium content is 7% by weight or less.

For example, one containing 3 to 4% by weight is used. Note that since silicon tends to precipitate as silicon dioxide, impurities with a low silicon content are preferred.

On this substrate, a hard underlayer of alumite, Ni-P, or the like is usually provided. If this underlayer is too thin, it has low strength against head collisions, which may cause a so-called head crash.On the other hand, if it is too thick, internal thermal stress may occur due to temperature rises and falls during manufacturing. Since there is a risk that the amount becomes too large and causes cracks, it is preferable to set the amount to about several pm to several 1101 L.

The magnetic layer formed on the underlayer is (a) Nl
A CoNi alloy having a content of 1O to 35 atomic %, (b) mainly consisting of crystal grains with a grain size of 100 to 500 A, and (c) a relative density of 60 to 95% is used.

The requirements (a) to (c) will be explained below.

(b) By substituting a part of Go with Ni, Hc
It is possible to easily adjust Hc according to the required characteristics of the medium. When the Ni content is lower than 10 at%, this effect is small; on the other hand, when the Nt content is over 35 at%, the saturation magnetic flux density Bs decreases, and the crystal system changes from hcp to fcc. As a result, the in-plane squareness ratio S of the film decreases.

In addition, in the present invention, in the Co-Ni alloy thin film medium (
7) Part of Co is replaced by Ti, Cr, Hf, and Ru.

Pt may be substituted alone or in combination of two or more of these in a total amount of 2 to 20 aL, %.

(b) By mainly containing crystal grains with a grain size of 100 to 500 A, excellent magnetic properties can be obtained. That is,
If the main part of the crystal grains is smaller than 100A, Hc will be small, while if it is larger than 500A, noise will increase, making it unsuitable for high-density recording. Particularly preferred is 200 to 300 people, resulting in a magnetic film layer with high Hc and low noise.

In addition, in this specification, "subject" means.

This means that 50% or more of the particles fall within the particle size range, and the particle size is measured by observing with an electron microscope.

(c) By setting the relative density to 60 to 95%, 4π
Characteristic properties of the present invention, such as a high Ms and a high S/N ratio, are exhibited.

That is, the present inventors have repeatedly studied the relationship between the relative density and magnetic properties of this magnetic film, and have found that when the relative density is 95% or less, the S/N ratio is significantly improved, and
It has been found that when the relative density is 6096 or more, 4πMs is high and a large output can be obtained. In other words, in the present invention, when the relative density of the magnetic film is less than 60%, 4πMs is low and the output is small, and when it exceeds 95%, noise increases and the S/N ratio becomes small.

Particularly preferred relative densities are 65-90%, especially 70-90%.
It is 85%.

The reason why the characteristics are improved by setting the relative density to 60% to 95% is that the width of the magnetization transition region becomes smaller due to the presence of bores, resulting in a sharper signal. It is assumed that this effect is strengthened by keeping the crystal grain size within a predetermined small grain size range.

Next, a method for measuring the relative density of a magnetic film will be described.

The principle of measuring relative density in the present invention is that Co
, the theoretical magnetic flux density M+ that the magnetic film should have is determined from the Ni content and their respective saturation magnetizations. Then, the ratio (M
2/M I) X I OO is calculated and used as the relative density. That is, the theoretical magnetic flux density M1 of the actually measured magnetic flux density M2
It is assumed that the sagging or drop from the surface is caused by pores in the membrane.

When calculating M+, the saturation magnetization of Co and Ni is 181 emu/g, 54 emu/g, and 4 emu/g, respectively, and Go
and the density d of Ni are 8 and 71 g/c, respectively.
c, 8.80 g/cc. The content rate was assumed to be equal to the composition of the target used for sputtering to form the film (as a result of various measurements, it was confirmed that the target composition and the magnetic film composition matched). The calculation of 0M1 was performed using Slater-Pauling. Based on Curve, C
o, NLty) content atomic % of both 4πMs (unit is Gauss, Ms is calculated as (fs
c. ) and calculated the sum.

To give a specific example of calculation, when a target having a composition of 85 atomic % Co and 15 atomic % Ni is used, the magnetic film composition will be the same. And 4 tc M s of Co is M
s is dX□, B is 8.71 (g/c c) X 16
1 (e mu/g), so it is further multiplied by 4π to get 17900 (G).Similarly, Ni's 4πM
From the Slater-Pauling Curve, s is 8.80X54.4X4π=6084(G),
The theoretical magnetic flux density M+ of this film is 17900X (85/10
0) +6084X (15/100) M+ = 16
130 (G), in this case, the actually measured magnetic flux density M2
If (4πM s ) is 12000 (G), then
The relative density is (M2/MI)X100, (1200
0/16130)X100=75%. The results of measuring the saturation magnetic flux densities of bulk samples of Co--Nt gold alloys with various Ni contents confirmed that the above method for calculating the theoretical magnetic flux densities was almost correct.

The Slater-Pauling Curve is described in “Introduct 10n” by Cullity.
to Magne CM Materials'' 1st edition (
Publisher, Add 1son-Wes leyPubli
shing Company) P, l'48, etc.

Such a magnetic recording medium of the present invention can be manufactured according to the method of the present invention, for example, as follows.

That is, a base layer is formed on the substrate by Co-P electroless plating or anodizing an aluminum or aluminum-based alloy substrate, and then Co-P is formed by a method such as sputtering in an Ar gas atmosphere containing N2. A Ni alloy thin film is formed on a substrate and then heat treated to release N.

To perform this sputtering, 1. A normal spar phthaling device, that is, a device casing with a target and a sample installation stage, a heater to heat the inside of this casing, a vacuum pump to reduce the pressure inside this casing, and a connection to the casing. A gas cylinder configured with a gas cylinder is preferably used. This target preferably has an alloy composition that completely or almost matches the alloy composition of the film to be formed.

Sputtering is performed in an atmosphere containing 02 and/or N2 in addition to Ar. What is the atmospheric pressure?

Total pressure l~roomTorr, especially 5~50mT
It is preferable to set it to orr. In addition, before forming the planned sputtering atmosphere, once to-5T
It is preferable to reduce the pressure to a vacuum of orr or less. The partial pressure of 02 and/or N2 with respect to the total pressure during sputtering is 1
0-100%, especially 20-80% is preferred.

When performing spartering, the substrate may be heated or left at room temperature.
The sputtering time, which is preferably 250°C or lower, particularly 220°C or lower, depends on the thickness of the film to be formed.
Determined by dividing by the average film formation rate.

As the sputtering apparatus, one that can adjust various conditions such as temperature, atmosphere, and atmospheric pressure as described above is suitable. Well-known sputtering equipment includes:
Examples include a high frequency magnetron sputtering device, a circular magnetron sputtering device, a flat plate magnetron sputtering device, a coaxial cylindrical electrode magnetron sputtering device, an ion beam sputtering device, a high frequency sputtering device, a direct current two-pole sputtering device, and the like.

In the manufacturing method of the present invention, the N content in the magnetic alloy thin film formed on the substrate is 20 atomic % or more, for example, 25 to 50 atomic %.
When a large amount of N, preferably atomic %, is included in the thin film during sputtering, a thin film consisting of an amorphous or microcrystalline substance with a grain size of about 50A to 150A is formed, and this thin film is subjected to heat treatment in the post-process. The magnetic recording medium undergoes crystallization or grain growth to a grain size of about 100 to 500 A, and forms a magnetic recording medium having an appropriate Hc and a high squareness ratio. Also,
The membrane becomes porous due to the action of removing N.

The temperature of this heat treatment is preferably about 300 to 600°C. If the temperature of the heat treatment is lower than 300°C,
When the heat treatment temperature exceeds 600°C, the de-N
progresses too quickly, and the crystal grain size increases, resulting in a decrease in the holding force Ha. Particularly preferable heat treatment conditions are 320-5
00° C. for about 0.5 to 3 hours, and by doing so, it becomes possible to manufacture products with excellent magnetic properties at low cost.

According to research conducted by the present inventors, the magnetic recording medium of the present invention could be manufactured in exactly the same manner even if O2 was used instead of N2 during sputtering. It was also recognized that a mixed gas of N2 and 02 may be used instead of N2.

As the substrate used in the present invention, various conventionally used non-magnetic substrates can be used, and the above-mentioned aluminum or aluminum-based alloy substrate (
For example, a substrate made of an alloy made of aluminum with Mg added in an amount of several percent or less or a titanium alloy, as well as various glass or ceramic substrates can be used.

In addition to the underlayer between the substrate and the magnetic thin film, there are various intermediate layers that increase the adhesion strength of the magnetic thin film, specifically Cr,
A layer of carbon, polysilicate, A fL, etc. may be provided on the magnetic thin film.
N, SiaN4, Cr.

A protective film consisting of a single layer or multiple layers (multilayers) of Au, Pt, Ru, etc. may be provided.
IFa top lubricant, A body nitli OMBLIN Z
A mixture of -25 rate and perfluoroalkyl polyether may also be applied.

[Function] In the magnetic recording medium of the present invention, the relative density of the magnetic film is 60 to 9.
5% and has a grain size of 100 to 500 A, the S/N ratio is high and the saturation magnetic flux density is high.

Moreover, the magnetic recording medium of the present invention has excellent properties such as squareness ratio and coercive force. Therefore, according to the present invention, a highly practical recording medium having characteristics as a high-density recording medium is provided.

The present invention can be applied to magnetic recording media ranging from extremely small disk diameters of 1 inch to 2 inches to large disk diameters of 10 inches or more.

[Example] Hereinafter, the present invention will be explained in detail using specific examples.

Although the embodiment described below uses a magnetron r, f, and sputtering device, it is of course possible to obtain the effects of the present invention by ion beam sputtering, etc., which can be said to be similar in terms of ion technology.

Example 1 An aluminum alloy substrate (size: diameter 130 mm, inner diameter 40 mm, thickness 1.9 mm) containing 4% magnesium was electrolytically treated in an acid bath containing chromic acid, and a thickness of 1.
A base layer of 0 pm alumite was formed, and its surface was polished by approximately 24 meters to make it flat.

Next, using a flat plate magnetron r, f, sputtering device,
Go-Ni containing 35 atomic % of N on the underlayer under the following conditions
-N thin film was formed.

Initial exhaust 2XlO-'Torr total atmospheric pressure (Ar+N2) 20mTorr N2 gas concentration in atmosphere (% of N2 partial pressure to total pressure) 50% Input power 1kw Target composition Go-Ni (Ni 15 atomic%) Pole spacing 108mm Film thickness
800A thin film formation rate 200A/min substrate temperature
After this film formation treatment at 100° C., heat treatment was performed at 350° C. for 3 hours in a vacuum to crystallize the film or grow crystal grains and release nitrogen. This G
.

- When we took a transmission electron micrograph of the cross section of the Ni@ film and measured the crystal grain size, we found that the crystal grain size was 100 to 500.
It was accepted that A's property should be the main subject.

Thereafter, a carbon protective film was formed by sputtering to a thickness of 60 OA to obtain a magnetic recording medium.

The relative density and magnetic properties of this magnetic recording medium are shown in Table 1 along with conditions other than those mentioned above.

Example 2 After sputtering, the substrate temperature was set to 250°C so that the N content in the film was 25 atomic %, and the film thickness was set to 70°C.
A magnetic recording medium was manufactured in the same manner as in Example 1 except that Example A was used.

Table 1 shows the measurement results of its characteristics.

Example 3.4 The substrate temperature during sputtering was set to room temperature, and the N contained in the film after sputtering was 40 atomic % (Example 3
), 46 atom % (Example 4) A magnetic recording medium was manufactured in the same manner as in Example 1, except that the content was adjusted to 46 at % (Example 4).

Table 1 shows the measurement results of its characteristics.

In the present invention, the recording density of the S/N ratio is 23.6 KPCI
shows the S/N ratio with respect to noise during signal recording, where S: O-P value of noise power during signal recording, N: effective value of noise voltage during signal recording. The measurement conditions are as follows.

Head used: M n -Z n mini Winchester type Track width 19 m Gap length 0.8 Bm Number of turns 16TX2 Head flying height: 0. IILm Measurement point: Measured at a track top speed of 4.7 m/sec at a point with a disk radius R = 50 mm Op value of recording current Iw: 15 mA Bw: 1 OKHz Video filter: 10 Hz Span: 5 MHz Comparative example 1 Composition is Ni 10 atoms %, Pt1O atomic%, balance CO target was used, and the sputtering atmosphere was Ar.
100%, and heat treatment was omitted. A magnetic recording medium was formed under the same conditions as in Example 1 except for the following conditions. Results first
Shown in the table.

Comparative Example 2 On the same substrate as in Example 1, approximately 30% of the Ni-P underlayer was applied.
It was formed to a thickness of 1 Lm by electroless plating and finished to a mirror finish. Further, on this base layer, a plating solution having the following composition was used to form a G film with a thickness of 800 Å.

A -Ni-P magnetic film was formed by electroless plating.

Co SO4.7 H200, 06 m ol /
fLN i SO4' 7 H200, 04//N
a HP O2” H200, 2//(NH4)250
4 0.1 tt Sodium bronate
0,3 7/sodium malate 0.
4 Sodium succinate 0.5 P
H8,9-59.3 Liquid temperature 75-85°C A carbon protective film was formed on this film by sputtering to a thickness of 50 OA to form a magnetic recording medium.

Table 1 shows the measurement results of its characteristics.

From Table 1, it is clear that all the samples according to the present invention exhibit high values for both the S/N ratio and 4πMs.

Incidentally, the conventionally used γ-F e 203-based magnetic film has a 4πMs of about 3.3KG and an S/N ratio of 35d.
It was about B. In Comparative Example 1.2, 4πMg is γ-
Although it is higher than the Fe2O3-based magnetic film, the S/N ratio is quite low.

Further, from Table 1, it is recognized that the material according to the present invention also has a high St.

[Effect of the invention] As detailed above, the magnetic recording medium of the present invention is as follows.

The magnetic recording medium of the present invention has a high S/N ratio and a high saturation magnetic flux density, and is also excellent in properties such as squareness ratio and coercive force. Therefore, according to the present invention, a highly practical recording medium having characteristics as a high-density recording medium is provided.

Therefore, such a magnetic recording medium of the present invention can be easily manufactured by the method of the present invention.

Claims (1)

[Claims] (1) In a magnetic recording medium in which a magnetic film layer is formed on the plate surface of a disk-shaped substrate, the magnetic film has a Ni content of 10 to 3.
It is a cobalt-nickel alloy with a content of 5 at% and 100~
Mainly composed of crystal grains with a grain size of 500 Å, with a relative density of 60~
95% magnetic recording medium. (2) The magnetic recording medium according to claim 1, wherein the substrate is an aluminum substrate or an aluminum-based alloy substrate. (3) The magnetic recording medium according to claim 2, wherein the substrate is an aluminum-based alloy substrate containing 7% by weight or less of magnesium. (4) The magnetic recording medium according to any one of claims 1 to 3, characterized in that an underlayer is formed on the substrate. (5) The magnetic recording medium according to claim 4, wherein the underlayer is made of alumite. (6) The magnetic recording medium according to claim 4 or 5, characterized in that a layer for increasing the adhesion strength of the magnetic film is provided between the underlayer and the magnetic film. (7) Any one of claims 1 to 6, characterized in that a protective film is provided on the magnetic film.
The magnetic recording medium described in section. (8) The magnetic recording medium according to claim 7, wherein a lubricant is applied on the protective film. (9) After forming a base layer on the plate surface of the disk-shaped substrate heated to room temperature to 250℃ or less, N_2 and/or O
By forming a Co-Ni alloy thin film in an Ar gas atmosphere containing _2 and then heat-treating it, the Ni content was reduced to 10
~35 at% Co-Ni alloy, 100~5
Mainly composed of crystal grains with a grain size of 00 Å and a relative density of 60 to 9
1. A method for manufacturing a magnetic recording medium, comprising forming a magnetic film of 5%. (10) Claim 9, characterized in that the substrate is an aluminum alloy containing 7% by weight or less of magnesium.
A method for manufacturing a magnetic recording medium according to paragraph 1. (11) The method for manufacturing a magnetic recording medium according to claim 9 or 10, wherein the underlayer is formed by Ni-P electroless plating or anodization of the substrate. (12) A method for manufacturing a magnetic recording medium according to any one of claims 9 to 11, characterized in that the Co--Ni alloy thin film is formed by sputtering. (13) N in the deposited Co-Ni alloy thin film before heat treatment
The method for manufacturing a magnetic recording medium according to any one of claims 9 to 12, wherein the O content is 20 to 50 atomic %. (14) The method for manufacturing a magnetic recording medium according to any one of claims 9 to 13, wherein the heat treatment temperature is 300 to 600°C. (15) The method for manufacturing a magnetic recording medium according to claim 14, wherein the heat treatment conditions are 320 to 500°C for 0.2 to 3 hours. (16) A layer for increasing the adhesion strength of the magnetic film is provided between the underlayer and the magnetic film, according to any one of claims 9 to 15. A method of manufacturing a magnetic recording medium. (17) The method for manufacturing a magnetic recording medium according to any one of claims 9 to 16, characterized in that a protective film is provided on the magnetic film. (18) The method for manufacturing a magnetic recording medium according to claim 17, wherein a lubricant is applied on the protective film. (19) The method for manufacturing a magnetic recording medium according to claim 12, wherein the sputtering is performed using a magnetron sputtering device or an ion beam sputtering device.