JPH05143972A - Metal thin film magnetic recording medium and its production - Google Patents

Abstract

(57) [Summary] [Object] To provide a metal thin film type magnetic recording medium having excellent durability and capable of high density recording. [Structure] A Cr underlayer 2, a magnetic recording layer 3 and a C layer 4 are formed on a non-magnetic substrate 1 in the same order by sputtering. The C layer 4 is reverse sputtered in an N ₂ gas atmosphere after the film formation, or Ar and N are formed when the C layer is formed.
_The film was formed by bias sputtering in a mixed gas atmosphere with ₂ . Therefore, at least the surface layer of the C layer 4 has N atoms mixed in with the C atoms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film type magnetic recording medium for in-plane recording used in a magnetic disk device.

[0002]

2. Description of the Related Art In recent years, a Co alloy having uniaxial crystal magnetic anisotropy such as CoNiCr and CoCrTa is formed on a non-magnetic substrate by sputtering through a Cr underlayer along with the increase in density of magnetic recording media. A metal thin film magnetic recording medium for in-plane recording is used.

One of the technical problems in the magnetic recording medium is to reduce the contact resistance between the surface of the medium and the magnetic head and improve the wear resistance and durability. Conventionally, in order to improve durability, unevenness processing called texture is applied to the substrate surface to make the medium surface uneven so as to reduce the contact resistance. Further, a C (carbon) layer is formed as a protective layer on the magnetic recording layer made of Co alloy, and a liquid lubricating layer is further formed thereon.

[0004]

Despite the above-mentioned durability improving means, when the magnetic recording medium is repeatedly rotated and stopped, the medium surface and the magnetic head surface are repeatedly brought into contact with each other. As a result, the friction coefficient increases, rotation start becomes impossible, and the C layer wears and causes a head crash, so that the durability (life) of the medium has a certain limit. ..

Recently, the demand for high-density recording has been increasing more and more, and in order to reduce the distance between the magnetic recording layer and the head, thinning of the C layer is required. The present invention has been made in view of the above problems, and an object of the present invention is to provide a metal thin film magnetic recording medium having excellent durability and capable of high-density recording, and a suitable manufacturing method thereof.

[0006]

The metal thin film type magnetic recording medium of the present invention is a metal thin film type magnetic recording medium in which a Cr underlayer, a magnetic recording layer and a C layer are laminated in the same order on a non-magnetic substrate. In the above, N atoms are mixed in at least the surface layer of the C layer. The manufacturing method is the same as the method for manufacturing a metal thin film magnetic recording medium in which a Cr underlayer, a magnetic recording layer, and a C layer are laminated in the same order on a nonmagnetic substrate by sputtering. Later N ₂
Reverse sputtering in a gas atmosphere, or C layer with Ar and N
_A film is formed by bias sputtering in a mixed gas atmosphere with ₂ .

[0007]

After the C layer is formed by sputtering, reverse sputtering is performed in an N ₂ gas atmosphere, and the C layer is bias sputtered in a mixed gas atmosphere of Ar and N ₂ (a negative voltage is applied to the substrate). Method of spattering in a wet condition)
By doing so, nitrogen gas ions are taken into the C layer at a negative potential to form a layer in which N atoms are mixed in the surface layer or all layers of the C layer. When performing bias sputtering,
Argon gas ions are also taken into the C layer, but since they do not have an affinity for C like N, they are rapidly desorbed from the C layer and are hardly mixed into the C layer.

When a layer containing N atoms is formed on the surface layer of the C layer, the shear strength with the head surface is smaller in the continuous contact state with the magnetic head than the C layer containing no N atoms. Therefore, the coefficient of friction is reduced and the durability is improved. Further, the inclusion of N atoms in the C layer distorts the crystal structure and improves hardness, which also contributes to improvement in durability.

The C crystal structure of the C layer is amorphous carbon having a high SP ² property, and the crystal structure does not change substantially even when N atoms are mixed.

[0010]

EXAMPLES The production of the magnetic recording medium shown in FIG. 1 will be described below as an example. This medium is on the non-magnetic substrate 1,
A Cr underlayer 2, a magnetic recording layer 3 and a C layer 4 are laminated in this order, and a liquid lubricating layer 5 is formed on the C layer 4 by coating.

As the substrate 1, an amorphous Ni substrate of about 10 to 20 μm is formed on the Al alloy substrate 1 in order to secure rigidity.
-A P-plated layer is usually used, but the structure is not limited to this, and a glass substrate, a ceramic substrate, or the like may be used.
Any non-magnetic material having a certain degree of rigidity can be used. Incidentally, the upper surface of the substrate is usually provided with an unevenness process called a texture in order to reduce the contact frictional resistance with the magnetic head.

The Cr underlayer 2 formed on the substrate 1 is
Co alloy showing uniaxial crystal magnetic anisotropy formed thereon
It is formed to orient the c-axis (crystal axis showing crystal magnetic anisotropy) of (crystal structure hcp) in the plane, and
It is formed by sputtering to a thickness of about 500 to 2000Å. As described above, the magnetic recording layer 3 is made of CoNiC.
It is formed by sputtering using a Co alloy exhibiting uniaxial crystal magnetic anisotropy such as r, CoCrPa, and CoCrPt. The magnetic recording layer 3 is not limited to a single layer of Co alloy, but may be a multilayer of alternating layers of Co alloy layers and Cr layers (the uppermost layer is a Co alloy layer). Magnetic recording layer
The thickness of layer 3 (the thickness of the Co alloy single layer, the total thickness of the Co alloy layer if it is multiple layers) is usually 600 to 800 Å. In order to secure reproduction output and reduce noise, B as a magnetic recording medium is used.
This is because rδ of about 400 to 600 G · μ is required.

A C layer is formed on the magnetic recording layer 3 as a protective layer.
The layer 4 is formed on the order of 200 to 400 Å, and the liquid lubricating layer 5 is formed on the upper surface thereof by application of a liquid lubricant such as fluorinated polyether on the order of 20 to 50 Å. The C layer 4
Has N atoms mixed into at least its surface layer.
As a method of mixing N atoms, a C layer is formed on the magnetic recording layer 3 by sputtering, and then a negative voltage is applied to the substrate (C layer) side in an N ₂ gas atmosphere to perform reverse sputtering. Further, when the C layer is formed, it can be realized by applying a negative bias voltage to the substrate (C layer) side in a mixed gas atmosphere of Ar and N ₂ and performing sputtering (bias sputtering).

FIG. 2 shows the principle of a sputtering apparatus for carrying out bias sputtering, and this apparatus can also perform reverse sputtering. In the figure, in the lower part of the vacuum container 21, a target 22 for emitting C layer (also applicable to magnetic layer and Cr layer) film forming atoms is installed, and an annular anode 23 is attached around it. Therefore, a negative voltage (generally -1 KV or less) is applied by the sputtering power source 24. On the other hand, a holder 25 for attaching the substrate 3 is provided on the upper portion, and a negative voltage is applied to the substrate 3 attached to the holder 25 by the bias power supply 26 via the holder 25. 27 is an exhaust pipe, which is connected to a vacuum pump by piping.
28 is a sputtering gas supply pipe for Ar gas or the like. In order to perform reverse sputtering with this sputtering device, a negative bias voltage is applied to the substrate with the minimum power for generating plasma applied to the target. In this case, the target atoms are not deposited on the substrate, and the Ar or ion strikes the substrate or the surface of the film deposited thereon to perform reverse sputtering.

FIG. 3 shows the principle of the DC bipolar sputtering apparatus. When sputtering is performed, a negative high voltage of the power supply for sputtering is applied to the terminal A connected to the target 22 to mount it on the substrate. The terminal B connected to the holder 25 is grounded. On the other hand, in the case of performing the reverse sputtering, contrary to the case of performing the sputtering, by applying a positive potential to the terminal A and a negative voltage to the terminal B, plasma is generated and the substrate or the substrate is formed by Ar ions. Reverse sputtering is performed by hitting the surface of the film.

As the sputtering apparatus, for example, a heater for heating the substrate may be provided in a vacuum container. Alternatively, a magnetron sputtering device having a magnet on the back surface of the target may be used. Further, the power supply for sputtering and the bias power supply are not limited to direct current, and a high frequency (RF) power supply may be used. However, for forming the C layer, it is necessary to be able to perform bias sputtering and reverse sputtering.

The sputtering conditions for the Cr underlayer, magnetic recording layer, and C layer differ depending on the sputtering apparatus used, substrate, target material, etc., but generally Ar gas partial pressure is 1 to 10 ×.
The substrate temperature is about 10 ⁻³ Torr and the substrate temperature is about 150 to 300 ° C. Next, specific examples will be given. (1) A Ni-P electroless plating layer (20 μm) is formed on the surface of an aluminum alloy substrate, the surface is polished and textured, and then DC magnetron sputtering is performed to form Cr in an Ar atmosphere of 7 × 10 ⁻³ Torr. Underlayer 10
00Å, magnetic recording layer (Co alloy single layer) 600Å, C layer 200Å
Was deposited in this order to obtain Sample A (conventional example). (2) In addition, the sample A was subjected to N ₂ gas atmosphere (7.0 × 10 ^-3 Tor).
Reverse sputtering was performed under r) to obtain Sample B (Example 1). (3) After depositing the Cr underlayer and the magnetic recording layer under the same conditions as in (1), a negative bias voltage (-300 V) is applied to the substrate in a mixed gas atmosphere of Ar and N _2. Sample C (Example 2) was obtained by sputtering C while applying voltage. (4) Table 1 shows the results of a drag test (disk rotation speed 100 rpm) performed on Samples A, B and C using a thin film head. The values in the table are μf (dynamic friction coefficient).

[0018]

[Table 1]

From Table 1, μf is considered to have a favorable low friction coefficient.
The test time for = 1 is about 2 for sample A (conventional example).
In contrast to 3 hours, Samples B and C (Examples 1 and 2) have 6 to 8 hours, and the example is more than twice as durable as the conventional example. (5) Also, apply 20 liters of liquid lubricant to Samples A, B and C,
A CSS (Constant Start Stop) test was performed using a thin film head. Table 2 shows the measurement results of μf during the CSS test.

[0020]

[Table 2]

From Table 2, the samples B and C according to the embodiment are 300
The value of μf after 00 times is about 0.3, which is a low coefficient of friction, whereas the sample A according to the conventional example has a C of about the same value of μf.
The number of SSs was about 10,000 to 15,000, and it was confirmed that the example had durability twice or more.

[0022]

As described above, in the metal thin film magnetic recording medium of the present invention, the C layer formed by sputtering is reverse-sputtered in the N ₂ gas atmosphere, and when the C layer is formed, the C layer is formed by Ar sputtering. By bias sputtering in a mixed gas with N ₂ , at least N atoms were mixed into the surface layer of the C layer, so that the friction coefficient between the surface of the magnetic head and the surface of the C layer can be lowered. It is possible to improve hardness, which in turn can improve durability,
Further, the recording density can be improved by reducing the layer thickness of the C layer.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a metal thin film magnetic recording medium according to an example.

FIG. 2 is a principle view showing an example of a sputtering apparatus for bias sputtering.

FIG. 3 is a principle view showing an example of a sputtering apparatus capable of reverse sputtering.

[Explanation of symbols]

 1 Nonmagnetic Substrate 2 Cr Underlayer 3 Magnetic Recording Layer 4 C Protective Layer 5 Liquid Lubrication Layer 22 Target 24 Sputtering Power Supply 26 Bias Power Supply

Claims (3)

[Claims] 1. A metal thin film magnetic recording medium in which a Cr underlayer, a magnetic recording layer and a C layer are laminated in the same order on a non-magnetic substrate, wherein the C layer has N atoms mixed in at least its surface layer. A metal thin film type magnetic recording medium characterized in that 2. A method of manufacturing a metal thin film magnetic recording medium in which a Cr underlayer, a magnetic recording layer and a C layer are laminated in the same order by sputtering on a non-magnetic substrate, wherein N is formed after the formation of the C layer. _A method for manufacturing a metal thin film magnetic recording medium, characterized by performing reverse sputtering in a _two- gas atmosphere. 3. A method of manufacturing a metal thin film magnetic recording medium in which a Cr underlayer, a magnetic recording layer and a C layer are laminated in the same order on a non-magnetic substrate by sputtering, wherein the C layer is Ar and N ₂ A method of manufacturing a metal thin film magnetic recording medium, characterized in that the film is formed by bias sputtering in a mixed gas atmosphere with.