JP2000155925A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium for further improving a coercive force and an SN rate. SOLUTION: In this magnetic recording medium, an amorphous Ni/Zr layer is formed as a seed layer on a glass substrate, and the surface of this Ni/Zr layer is oxidized. Moreover, a Cr base film is formed on the surface of the oxidized Ni/Zr layer, and a C0CrPt magnetic film is formed on the Cr base film, and a C protecting film is formed on the C0CrPt magnetic film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium used as a recording medium for a hard disk drive, for example.

[0002]

2. Description of the Related Art A general recording medium for a hard disk drive comprises a nonmagnetic substrate, such as an Al-Mg alloy substrate or a smooth polished glass substrate, which is provided with a Cr layer via a buffer layer.
A system base layer, a Co system magnetic layer, a C system protective film, and a lubricating film are sequentially formed.

Recently, there has been proposed a technique for miniaturizing the crystal of the Cr-based underlayer and, consequently, the crystal of the Co-based magnetic layer to realize high coercive force and low noise.
525, JP-A-10-74619 and JP-A-10-74620, European Patent No. 7048
No. 39 publication.

JP-A-63-217525 discloses a non-magnetic substrate (a buffer layer if a buffer layer is provided) and C
Proposals have been made to form an amorphous Ni-P alloy layer as a seed layer between an r-based underlayer. Also, Japanese Patent Application Laid-Open
No. 74619 discloses that Ni—Cr, N
i-Cr-W and Ni-Cr-Mo are described.
No. 74620 describes Ni-Cu as a seed layer, and EP-A-704839 describes Ni-Al, Al-Co, Fe-Al, Fe as seed layers.
-Ti, Co-Fe, Co-Ti, Co-Hf, Co-Zr, Ni
-Ti, Cu-Be, Cu-Zn, Al-Mn, Al-Re, Ag
-Mg, Al ₂ -Fe-Mn ₂ are described.

[0005]

For high-density recording on a hard disk, it is essential to improve the recording / reproducing characteristics (R / W characteristics) of the recording medium, that is, to improve the coercive force and the SN ratio. In order to improve the magnetic layer, it is required to further miniaturize the magnetic layer. In addition, with the development of a magnetoresistive element head (MR head) that detects the direction of recording magnetization by the magnetoresistance effect, recording media are required to have lower noise (higher S / N ratio) than ever before. However, the seed layer having the conventional configuration described above does not provide a sufficient effect.

[0006]

It has been confirmed that Ni-Zr alloys become amorphous over a wide range by rapid solidification. The present inventor paid attention to the characteristics of the Ni-Zr-based alloy and tried to apply the Ni-Zr-based alloy to the seed layer.

As a result, the present invention has been made, and a magnetic recording medium according to the present invention is a magnetic recording medium in which a seed layer, a base film, and a magnetic film are sequentially formed on a nonmagnetic substrate surface. The seed layer is made of an amorphous alloy containing Ni as a main component, and the surface of the seed layer is oxidized. As the non-magnetic substrate, a polycarbonate, a silicone wafer, or the like can be considered in addition to the Al-Mg alloy and the glass substrate.

As an amorphous alloy containing Ni as a main component,
Ni-Zr, Ni-Zr-Al, Ni-Zr-Ti, Ni-Zr-
V, Ni-Zr-Cu, Ni-Zr-Nb, Ni-Zr-Mo,
Ni-Zr-Ta and Ni-Zr-W can be exemplified.

There is an appropriate range for the thickness and oxygen content of the oxidized portion of the seed layer surface. That is,
When the thickness of the oxidized portion is increased, a crystalline metal Ni phase exhibiting ferromagnetism is precipitated. Therefore, as the thickness of the oxidized portion, a thickness in which the crystal structure of the oxide cannot be substantially recognized, for example, And a thickness of several atomic layers is preferable. If a large amount of oxygen impurities is present in the seed layer, a crystalline metal Ni phase exhibiting ferromagnetism may be precipitated inside the seed layer. It is preferable to use one that does not.

[0010] The oxygen content of the oxidized portion of the surface of the seed layer is preferably 1.0 atomic% to 10 atomic%. If the content is less than 1.0 atomic%, the fineness of the Cr-based underlayer and the Co-based magnetic layer becomes insufficient. On the other hand, if the content exceeds 10 atomic%, a crystalline ZrO ₂ -X (X <1) oxide is formed. Progresses, and there is a possibility that a crystalline metal Ni phase exhibiting ferromagnetism may precipitate. Since the surface of the seed layer has fine irregularities, for example, when measuring the oxygen concentration on the surface by secondary ion mass spectrometry (SIMS), the depth from the surface layer to about 5 nm is analyzed.

Further, the configuration of the magnetic recording medium according to the present invention includes a configuration in which a buffer layer or a texture layer is formed between the surface of the non-magnetic substrate and the seed layer, and the surface of the magnetic film usually has A protective film and a lubricating film are formed.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view of the magnetic recording medium according to the present invention, and FIG. 2 is a graph showing the relationship between the oxygen ion concentration and the etching time of the layer formed on the substrate of the magnetic recording medium according to the present invention. As shown in FIG. 1, in the magnetic recording medium according to the present invention, an amorphous Ni-Zr layer is formed as a seed layer on the surface of a glass substrate.
The surface of the Zr layer is oxidized, and a Cr underlayer is formed on the surface of the oxidized Ni-Zr layer.
An oCrPt magnetic film is formed, and a C protective film is formed on the CoCrPt magnetic film.

(Example 1) Ni is 90 atomic% and Zr is 10
Using an atomic% Ni-Zr alloy as a target, a Ni-Zr thin film was formed on the glass substrate surface by an in-line type sputtering apparatus. Next, the glass substrate on which the Ni-Zr thin film has been formed is taken out into a clean room (in the air) and left for 1 hour.
The Ni-Zr thin film surface was oxidized. The temperature in the clean room was 22 ° C. and the humidity was 40%. Also, Ni-Zr
As a means for oxidizing the surface of the thin film, a method of exposing the substrate to oxygen plasma, a method of heating in a vacuum device, and the like can be considered in addition to the above. Next, the substrate left in the clean room is returned to the in-line type sputtering apparatus again, and after evacuation, a Cr underlayer, a CoCrPt magnetic layer, and a C protective film are sequentially formed. A medium sample was formed by forming a perfluorocarbon-based lubricating layer on the surface of. When the structure of the Ni-Zr thin film was measured by X-ray diffraction (XD) measurement, it was microscopically amorphous.

Comparative Example 1 After a Ni—Zr thin film was formed on the surface of a glass substrate in the same manner as in Example 1, it was not taken out to a clean room (in the air), but a Cr underlayer, a CoCrPt magnetic layer and a C A protective film was sequentially formed to prepare a medium sample. When the structure of the Ni-Zr thin film was measured by X-ray diffraction (XD) measurement, it was microscopically amorphous as in Example 1.

(Comparative Example 2) A glass substrate was put into an in-line type sputtering apparatus, and after evacuation, a Cr underlayer, a CoCrPt magnetic layer, and a C protective film were sequentially formed. A medium sample was prepared by forming a perfluorocarbon-based lubricating layer on the surface of the protective film.

The following Table 1 summarizes the thicknesses and the film forming conditions of each layer of Example 1 and Comparative Examples 1 and 2.

[0017]

[Table 1]

On the other hand, FIG. 2 is a graph showing the relationship between the oxygen ion concentration and the etching time of the layers formed on the substrates of the respective media samples of Example 1 and Comparative Example 1. FIG. In contrast, the amount of oxygen impurities in the Ni—Zr layer and the Cr layer is reduced in the vicinity of the interface (half width at about 1).
(0 nm), the detected value of the amount of oxygen impurities was large, and in Comparative Example 1 in which the surface of the Ni-Zr layer was not oxidized, no change was observed in the amount of oxygen impurities near the interface.

Next, the amount of oxygen impurities near the interface of Example 1 and Comparative Example 1 shown in FIG. 2 and the thickness of the oxidized portion are estimated. First, according to the impurity analysis results of the target materials used in Example 1 and Comparative Example 1, the oxygen impurity in the Cr target was about 500 atomic ppm, and the oxygen impurity in the Ni-Zr alloy target was about 50 atomic ppm. . The back pressure of the in-line type sputtering apparatus used in Example 1 and Comparative Example 1 was 2 × 10 ⁻⁵ Pa or less, and the result of the residual gas analysis (RGA) performed separately showed that the oxygen partial pressure was 2 × 10 ⁻⁵ Pa. ^-7 Pa or less. In Example 1 and Comparative Example 1, the amount of oxygen impurities taken in from the vacuum atmosphere during film formation is described below (Appendix A: The amount of oxygen taken into the film from the vacuum atmosphere based on gas molecule kinetics). Estimate), it can be estimated to be 50 atomic ppm at the maximum, and oxygen impurities (about 50 atomic pp) in the Ni-Zr target can be estimated.
m), the oxygen impurity in the Cr target (about 500
1/10 of atomic ppm).

(Appendix A) Based on gas molecule kinetics,
Estimating the amount of oxygen molecules incident on the thin film surface at room temperature,
(0.005 to 0.01 nanometers / square nm / second). On the other hand, assuming that the atomic density of the Ni—Zr film surface is substantially the same as the atomic density of the Ni (111) plane, metal Ni has a face-centered cubic lattice structure and a lattice constant of 0.352 nm.
There are two atoms in the m equilateral triangle, and the atomic density is 37.3 / nm. The distance between atomic planes is 0.20 nm. When the same estimation is performed for Cr, in the case of the closest-packed (110) plane of the body-centered cubic lattice,
Since the lattice constant is 0.288 nm, the atomic density is 1
7.1 pieces / square nm, and the distance between atomic planes is 0.20 nm. Under the film thickness and film forming conditions of Comparative Example 1, the film forming time in the in-line type sputtering apparatus was about 8 seconds.
The layer is about 43 atomic layers per second, and the Ni-Zr layer is about 25 atomic layers per second.
A film equivalent to an atomic layer is formed. Therefore, the amount of oxygen taken in from the vacuum atmosphere is estimated as follows. Cr layer = 0.01 (molecule / sec) / {43 (atomic layer / sec) x 17.1 (piece / atomic layer)} = 0.02 (atom / sec) / {43 (atom layer / sec) x 17.1 (piece / atomic layer) )｝ = 27.2 (atomic ppm) Ni-Zr layer = 0.01 (molecule / sec) / {25 (atomic layer / sec) × 37.3 (pieces / atomic layer)} = 0.02 (atom / sec) / ｛25 (atomic layer) /S)×37.3 (pieces / atomic layer)｝ = 21.4 (atomic ppm) These numerical values are small and negligible compared to the amount of impurity oxygen in the target.

The above description relates to the amount of oxygen impurities taken in from the vacuum atmosphere during the film formation. Next, after the Ni-Zr layer is formed, the film is exposed to the vacuum atmosphere until the Cr layer is formed. Since the exposure time was 30 seconds, the amount of oxygen impurities taken in on the surface of the Ni-Zr layer was as shown in (Appendix
From A), it is estimated that 1.6 atomic% of oxygen impurities enter the surface of the Ni-Zr layer. However, oxygen impurities were taken in by the getter function during the film formation described above. However, after the Ni-Zr layer was formed, there was no getter function during the film formation, and it was considered that the adsorbed oxygen impurities were easily desorbed again. Therefore, the actual oxygen impurity uptake should be significantly less than 1.6 atomic%.

From the above, it can be estimated that the oxygen impurity in the vicinity of the interface in Comparative Example 1 is 0.1 atomic% or less. It can be estimated from atomic% to 10 atomic%.

Next, the measurement results of the magnetostatic properties of the medium samples produced in Example 1, Comparative Examples 1 and 2, and MR
The measurement results of the recording / reproducing characteristics measured using the head are shown in the following (Table 2). From this (Table 2), the magnetic recording medium of Example 1 according to the present invention has improved coercive force, reduced noise, and improved SN ratio compared to the magnetic recording media of Comparative Examples 1 and 2. .

[0024]

[Table 2]

[0025]

According to the present invention as described above,
A seed layer formed between the nonmagnetic substrate surface and the underlayer,
It is composed of an amorphous alloy containing Ni as a main component, such as Ni-Zr, and oxidizes the surface of the seed layer, which promotes the miniaturization of the Cr-based underlayer and the Co-based magnetic layer, and increases the coercive force and It is possible to provide a magnetic recording medium having a high SN ratio and capable of sufficiently responding to perpendicular magnetization.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetic recording medium according to the present invention.

FIG. 2 is a graph showing a relationship between an oxygen ion concentration and an etching time of a layer formed on a substrate of a medium sample according to Example 1 and a medium sample according to Comparative Example 1;

Claims (5)

[Claims] 1. A magnetic recording medium comprising a seed layer, a base film, and a magnetic film sequentially formed on a surface of a non-magnetic substrate, wherein the seed layer is made of an amorphous alloy containing Ni as a main component. A magnetic recording medium characterized in that the surface of the layer is oxidized. 2. The magnetic recording medium according to claim 1, wherein the amorphous alloy containing Ni as a main component is Ni-Zr,
Ni-Zr-Al, Ni-Zr-Ti, Ni-Zr-V, Ni-
Zr-Cu, Ni-Zr-Nb, Ni-Zr-Mo, Ni-Zr-
A magnetic recording medium characterized by being one of Ta and Ni-Zr-W. 3. The magnetic recording medium according to claim 1, wherein the thickness of the oxidized portion on the surface of the seed layer is such that the crystal structure of the oxide cannot be substantially recognized. A magnetic recording medium, comprising: 4. The magnetic recording medium according to claim 1, wherein the oxygen content of the portion from the surface of the seed layer to 5 nm is 1.0 at% to 10 at%. Magnetic recording medium. 5. The magnetic recording medium according to claim 1, wherein a buffer layer and a texture layer are formed between the surface of the non-magnetic substrate and the seed layer, and the surface of the magnetic film is protected. A magnetic recording medium comprising a film and a lubricating film.