JPH05314455A - Fixed magnetic disk - Google Patents

Abstract

(57) [Summary] [Purpose] Excellent reliability such as durability and hardness and enabling high density magnetic recording. An iron oxide magnetic thin film 2 having a columnar structure in a direction perpendicular to the surface of the disk substrate 1 and having a spinel type crystal structure containing cobalt preferentially oriented on a surface index (100) on the disk substrate 1. The protective film 3 and the lubricating layer 4 were laminated. The performance is further improved by forming an oxide thin film having a NaCl type crystal structure on the disk substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed magnetic disk which is excellent in reliability and can be used for high density magnetic recording.

[0002]

2. Description of the Related Art In the advanced information society in recent years, the amount of information to be stored has been increasing year by year, and there is an increasing demand for large capacity and high density recording devices.

Under such circumstances, a recording medium of a fixed magnetic disk used as a computer peripheral device is
Density is increased by changing from the conventional coating type in which gamma iron oxide-based acicular magnetic powder is coated on an aluminum disk substrate to the Co-Ni / Cr alloy thin film type by plating or sputtering. Came.

A conventional fixed magnetic disk will be described below. FIG. 6 is an enlarged cross-sectional view of a main part of a conventional Co-Ni / Cr alloy thin film type fixed magnetic disk. In FIG.
61 is an aluminum substrate, 62 is a Ni-P plating layer, 6
3 is a Cr layer, 64 is a Co-Ni magnetic layer, 65 is a protective film,
66 is a lubricating layer. Each layer is laminated on the aluminum substrate 61 to form a thin film type fixed magnetic disk 67 of Co—Ni / Cr alloy.

[0005]

However, in the above-mentioned conventional structure, since the Co-Ni / Cr thin film is an alloy, it has low durability and has the following problems.

(1) As the structure of the fixed magnetic disk,
It has a five-layer structure from the surface (lubricating layer / protective layer / Co—Ni magnetic layer / Cr layer / Ni—P plated layer / aluminum substrate), and the manufacturing process is complicated.

(2) The fixed magnetic disk is made of Co-Ni.
Since the magnetic layer 64 is an in-plane recording medium, if the recording wavelength is shortened to increase the recording density, recording becomes difficult due to the influence of the demagnetizing field.

In order to solve these problems, as a magnetic recording medium which enables perpendicular recording, a Co--Cr thin film medium has been actively researched although the magnetic head and the medium are in contact with each other. However, as in the case of the thin film type recording medium of Co—Ni / Cr alloy shown in FIG. 6, since the Co—Cr medium is also an alloy, there is a problem in reliability. In the case of a fixed magnetic disk, rotate the magnetic disk at high speed (3600 rotations / minute)
Therefore, the hardness of the magnetic layer is also very important in terms of ensuring reliability, but the Co—Cr thin film has a problem in hardness.

The present invention solves the above conventional problems, and provides a fixed magnetic disk having a component of perpendicular magnetic recording which is excellent in reliability such as durability and hardness and is compatible with high density magnetic recording. The purpose is to do.

[0010]

In order to achieve this object, a fixed magnetic disk of the present invention is a spinel type magnetic disk having a columnar structure in the direction perpendicular to the disk substrate surface and containing cobalt on the disk substrate. Crystal structure face index (10
It has a structure in which an iron oxide magnetic thin film preferentially oriented to 0), a protective film, and a lubricating layer are laminated.

[0011]

With this structure, the iron oxide magnetic thin film of cobalt-containing spinel type crystal structure formed on the disk substrate is oriented in (100) which is the easy axis of magnetization, and has a columnar structure. Compared with, it has excellent reliability such as durability and hardness, and has a component of perpendicular magnetic recording, which enables high density magnetic recording.

Further, by adopting a structure in which an oxide thin film of NaCl type crystal structure is used as a base film of the iron oxide magnetic thin film of spinel type crystal structure containing cobalt, the plane index (100) crystal orientation and the columnar structure property are obtained. It is possible to obtain a fixed magnetic disk that is compatible with high density magnetic recording and has excellent reliability such as durability and hardness.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fixed magnetic disk according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is an enlarged sectional view of a main part of a fixed magnetic disk according to a first embodiment of the present invention. As shown in FIG. 1, in the first embodiment, C was used as an iron oxide magnetic thin film of spinel type crystal structure having a columnar structure on the disk substrate 1 in the direction perpendicular to the substrate surface and containing Co.
The structure is such that the o ferrite film 2 is provided, the carbon thin film 3 is provided as a protective film on the Co ferrite film 2, and the lubricating layer 4 is further provided on the carbon thin film 3.

FIG. 2 shows Co of the fixed magnetic disk of this embodiment.
FIG. 3 is a schematic configuration diagram of a plasma CVD apparatus for forming a ferrite film 2. As shown in FIG. 2, the plasma CVD apparatus includes an electrode 7 and a high-frequency power source (13.5) that house a substrate heater 6 with a substrate rotating mechanism in a reaction chamber 5.
Electrodes 9 connected to 6 MHz) 8 are provided facing each other, and a glass disk substrate 1 is placed below the electrodes 7. Further, the reaction chamber 5 is provided with an exhaust system 10 and a source gas introduction port 11 for keeping the reaction chamber 5 at a low pressure.

On the other hand, vaporizers 12, 13, 14 containing raw materials
Is connected to the reaction chamber 5 via valves 15, 16 and 17, and to the vaporizers 12, 13 and 14 the valve 1
A nitrogen cylinder 22 is connected via 8, 19, 20.21, the introduction of nitrogen carrier gas is controlled by opening / closing the valves 18, 19, 20.21, and the valves 15, 16,
The opening and closing of 17 controls the introduction of the source gas and the carrier gas into the reaction chamber 5. The oxygen cylinder 23 is connected to the reaction chamber 5 via a valve 24.

A method of forming the Co ferrite film 2 using the plasma CVD apparatus shown in FIG. 2 will be described below.

Iron acetylacetonate [F
e (C ₅ H ₇ O ₂ ) ₃ ] and cobalt acetylacetonate [Co (C ₅ H ₇ O ₂ ) ₂ 2H ₂ O] were used.

Dehydrated cobalt acetylacetonate was placed in the vaporizer 12 (dehydrated at 100 ° C. for 2 hours in vacuum), and iron acetylacetonate was placed in the vaporizer 13 and heated to 90 ° C. and 130 ° C., respectively, and held. Keep it. Open valves 15, 16, 18, and 19, and use nitrogen carrier gas (flow rate 5 SCCM on vaporizer 12 side, 30 SCCM on vaporizer 13 side) to vaporize cobalt acetylacetonate vapor and iron acetylacetonate vapor as reaction gases. (Flow rate 5SC
It is introduced together with CM into the reaction chamber 5 whose pressure is reduced by the exhaust system 10 to generate plasma (power 1.4 W / c).
m ² ), the reaction is performed under reduced pressure (0.09 Torr) for 7 minutes, and the glass disk substrate 1 (120
The Co ferrite film 2 was formed on (rotation / minute).

Then, the glass disk substrate 1 having the Co ferrite film 2 formed thereon is taken out from the reaction chamber 5,
The same Co is applied to the back surface of the glass disk substrate 1 by the same method.
The ferrite film 2 was formed. Next, a carbon thin film 3 as a protective film is formed on the Co ferrite film 2 by a sputtering method.
Was formed to a thickness of 20 nm, and the glass disk substrate 1 was further immersed in a liquid tank containing a fluorine-based organic substance to form a lubricating tank 4 to prepare a fixed magnetic disk (A).

Regarding the manufactured fixed magnetic disk (A), a MIG head having a gap length (GL) of 0.25 μm and a track width (Tw) of 10 μm was used, a head current value of 50 mA was selected, and a speed of 3600 revolutions / minute was selected. Then, the electromagnetic conversion characteristics were evaluated with a circumferential track of 20.0 mm from the center of the fixed magnetic disk (A). The relative speed between the fixed magnetic disk (A) and the magnetic head was 7.5 m /
sec, the flying height of the magnetic head is 0.15
was μm.

Next, for comparison, Hc = 1000 Oe,
A fixed magnetic disk of a conventional Co-Ni / Cr alloy thin film having a magnetic layer thin film of Ms = 800 emu / cc of 80 nm, a carbon thin film of 60 nm formed thereon as a protective layer, and a lubricating layer similar to that of the present embodiment ( B) (magnetization orientation in an in-plane direction on an aluminum substrate) was produced, and the electromagnetic conversion characteristics were evaluated under the same conditions as the fixed magnetic disk (A) of this example.

FIG. 3 shows the fixed magnetic disk (A) of this embodiment.
FIG. 3 is a diagram showing the relationship between recording density and reproduction output of a Co—Ni / Cr alloy thin film fixed magnetic disk (B) and FIG. In FIG. 3, the horizontal axis represents the recording density (recording wavelength), and the vertical axis represents the reproduction output. Further, in the figure, (a) shows the characteristics of the fixed magnetic disk (A) of this embodiment, and (b) shows the characteristics of the Co—Ni / Cr alloy thin film fixed magnetic disk (B) for comparison. As shown in FIG. 3, the fixed magnetic disk (A) is Co-Ni / C.
Compared to the r-alloy thin film fixed magnetic disk (B), a high reproduction output was shown on the high recording density side. At this time, when the reproduced waveform of the recording signal of the fixed magnetic disk (A) was observed with an oscilloscope, it showed a dipulse waveform that is characteristic of including a perpendicular magnetic recording component.

A Co ferrite film 2 was formed on the glass disk substrate 1 under the same conditions as in the first embodiment, and the crystal structure was analyzed by X-ray diffraction. As a result, the Co ferrite film 2 had a spinel type crystal structure and was preferentially oriented in the plane index (100).

Next, the Co ferrite film 2 was broken and the film surface and the fracture surface were observed using a high resolution scanning electron microscope. As a result, it was found that the Co ferrite film 2 had a columnar structure, the film thickness was about 210 nm, and the column diameter was 20 to 65 nm. As a result of composition analysis by an electron beam microanalyzer, it was Co _0.10 Fe _2.90 O ₄ .

Next, the magnetic characteristics of the Co ferrite film 2 were measured using a vibrating sample type magnetometer (VSM). Coercive force Hc = 1 in the vertical direction of the Co ferrite film 2
200 Oe, in-plane coercive force Hc = 780 Oe, and magnetization Ms = 224 emu / cc.

The fixed magnetic disk (A) of this embodiment is Co
The factor that the reproduction output is higher on the high density side in the short wavelength region than that of the Ni / Cr alloy thin film fixed magnetic disk (B) is that it has a perpendicular magnetic recording component.

Further, since the Co ferrite film 2 is an oxide and is excellent in durability and weather resistance, it has sufficient reliability as a fixed magnetic disk even if the protective film 3 is not provided. By providing it, the reliability can be further improved.

As the protective film 3, instead of the carbon thin film, SiO is used.
The same results as in FIG. 3 were obtained using the ₂ film and the ZrO ₂ film.

(Embodiment 2) FIG. 4 is an enlarged sectional view of a main part of a fixed magnetic disk according to a second embodiment of the present invention. As shown in FIG. 4, in the present embodiment, a NiO film 4 is formed as an oxide thin film of a NaCl type crystal structure on a glass disk substrate 41.
2 has a columnar structure on the NiO film 42 in a direction perpendicular to the surface of the glass disk substrate 41, and C
A Co ferrite film 43 as an iron oxide magnetic thin film having a spinel type crystal structure containing o is formed, a carbon film 44 as a protective film is formed on this Co ferrite film 43, and a carbon thin film 44 is further lubricated. The layer 45 is formed. This NaCl type crystal structure oxide thin film is made of magnesium,
It is configured to include at least one element from the element group of manganese, cobalt, nickel, and cadmium, and to be crystallographically preferentially oriented to the plane index (100) plane. The protective film is a carbon thin film, a silicon oxide thin film, or a zirconia oxide thin film.

Here, a method of manufacturing the fixed magnetic disk in the second embodiment will be described. First, iron acetylacetonate [Fe (C ₅ H ₇ O ₂ ) ₃ ] and nickel acetylacetonate [Ni (C ₅ H ₇ O ₂ ) ₂ 2H were used as starting materials.
₂ O], cobalt acetylacetonate [Co (C ₅ H ₇
O ₂ ) ₂ 2H ₂ O] was used.

In the plasma CVD apparatus of FIG. 2, the vaporizer 12 is dehydrated with nickel acetylacetonate (dehydration at 100 ° C. for 2 hours), 13 is dehydrated with cobalt acetylacetonate, and 14 is iron. Add acetylacetonate, 180 ℃, 95 ℃,
Heat and keep at 130 ° C. The valves 18 and 15 are opened to introduce a nitrogen carrier gas (flow rate of 30 SCCM), nickel acetylacetonate vapor, and oxygen as a reaction gas (flow rate of 15 SCCM) into the reaction chamber 5 whose pressure is reduced by the exhaust system 10 to generate plasma ( Electric power 1.4 W / cm ² ) and reduced pressure for 5 minutes (0.12 Torr)
Then, the NiO film 42 was formed on the glass disk substrate 41 (120 revolutions / minute) heated to 400 ° C., and the valve 18 and the valve 15 were closed.

Further, the valve 1 is continued without breaking the vacuum.
9, 20, 16, 17 are opened, and the vapors of cobalt acetylacetonate and iron acetylacetonate are reacted with oxygen (flow rate 5SCCM) as a reaction gas by nitrogen carrier gas (flow rates 5SCCM and 30SCCM in vaporizers 13 and 14, respectively). After being introduced into the chamber 5, the reaction is performed under reduced pressure (0.12 Torr) in plasma (electric power 1.4 W / cm ² ) for 7 minutes to form a Co ferrite film 43 on the NiO film 42. A two-layer film of NiO was prepared.
Then, the glass disk substrate 41 having the two-layer film formed thereon was taken out from the reaction chamber 5, and the same two-layer film was formed on the back surface by the same method.

Next, a carbon thin film 44 as a protective film is formed on both surfaces of the Co ferrite film 43 by a sputtering method, and the glass disk substrate 41 is immersed in a liquid tank containing a fluorine-based organic lubricant for lubrication. The tank 45 was formed to prepare a fixed magnetic disk (C).

Regarding the manufactured fixed magnetic disk (C), a MIG head having a gap length (GL) of 0.25 μm and a track width (Tw) of 10 μm was used, a head current value of 50 mA was selected, and a speed of 3600 rotations / minute was selected. Then, the electromagnetic conversion characteristics were evaluated with a circumferential track of 20.0 mm from the center of the fixed magnetic disk (C). The relative speed between the fixed magnetic disk (C) and the magnetic head was 7.5 m /
sec, the flying height of the magnetic head is 0.15
was μm.

Next, for comparison, Hc = 1000 Oe,
A fixed magnetic disk of a conventional Co-Ni / Cr alloy thin film having a magnetic layer thin film of Ms = 800 emu / cc of 80 nm, a carbon thin film of 60 nm formed thereon as a protective layer, and a lubricating layer similar to that of this embodiment provided. (D) (Magnetic orientation in an in-plane direction on an aluminum substrate) and a fixed magnetic disk (E) prepared under the same conditions as the fixed magnetic disk (C) and having no NiO undercoating film were prepared. The electromagnetic conversion characteristics were evaluated under the same conditions as the fixed magnetic disk (C).

The relationship between the recording density and the reproduction output of the fixed magnetic disk (C), the fixed magnetic disk (D) and the fixed magnetic disk (E) is shown in FIG.

In FIG. 5, the horizontal axis is the recording density (recording wavelength) and the vertical axis is the reproduction output. Further, (c) shows the characteristics of the fixed magnetic disks (C), (d) and (e) of this embodiment, and those of the fixed magnetic disks (D) and (E) for comparison.

As shown in FIG. 5, the fixed magnetic disk (C) of this embodiment has a high reproduction output on the high recording density side as compared with both the fixed magnetic disk (D) and the fixed magnetic disk (E). showed that.

When the reproduction waveform of the recording signal of the fixed magnetic disk (C) of this embodiment was observed with an oscilloscope, it showed a dipulse waveform which is characteristic of including a perpendicular magnetic recording component.

A NiO film 42 and a Co ferrite film 43 were formed on the glass disk substrate 41 under the above film forming conditions, and the crystal structure of the sample film as a Co ferrite / NiO 2 layer film was analyzed by X-ray diffraction. As a result, the NiO film 42 formed under the above conditions was completely oriented in the plane index (100) by X-ray. The surface index of NiO (10
0) By using the perfect orientation film, the plane index (100) orientation of the Co ferrite film 43, which is the magnetic layer of the fixed magnetic disk (C), is affected by the crystal orientation of the underlayer. It was found that it was improved compared with the case where the film was formed on 41. The fixed magnetic disk (C) was also excellent in crystallinity.

Observation of the surface and fracture surface of the Co ferrite / NiO 2 layer film using a high resolution scanning electron microscope revealed that the bilayer film had a columnar structure and a film thickness of about 360.
The column diameter was found to be 35-80 nm in nm.

Further, as a result of analyzing the composition of Co ferrite by an electron beam microanalyzer, Co _0.10 Fe
It was _2.90 O ₄ .

Next, the magnetic characteristics of the Co ferrite film 43 and the Co ferrite / NiO 2 layer film were measured by a vibrating sample magnetometer (VSM). As a result, in the Co ferrite / NiO 2 layer film, the coercive force in the direction perpendicular to the film surface is Hc = 1200 Oe, and the coercive force in the in-plane direction is Hc = 79.
It was 0 Oe and Ms was 265 emu / cc. Also C
o In the ferrite film 43, the coercive force in the direction perpendicular to the film surface is Hc = 1200 Oe, and the coercive force in the in-plane direction is Hc = 80.
It was 0 Oe and Ms was 239 emu / cc.

The fixed magnetic disk (C) of this embodiment is Co
The factor that the reproduction output is higher than that of the Ni / Cr alloy thin film fixed magnetic disk (D) is that it has a perpendicular magnetic recording component. Further, the factor that the reproduction output is higher than that of the fixed magnetic disk (E) is influenced by the underlying NiO film 42, and the crystallinity and surface index (10) of the Co ferrite film 43.
0) It is considered that the orientation was improved.

M as an oxide thin film having a NaCl type crystal structure
gO thin film, CoO thin film, MnO thin film or CdO thin film
When used, or as a protective film 44 instead of a carbon thin film, S
iO ₂Membrane and ZrO₂The configuration using the membrane is the same as in FIG.
The following results were obtained.

Since the Co ferrite film 43 is an oxide and is excellent in durability and weather resistance, it has sufficient reliability as a fixed magnetic disk even if the protective film 44 is not provided. By providing it, the reliability is further improved.

[0048]

As described above, according to the present invention, the surface index (100) of the crystallographically spinel type crystal structure having a columnar structure in the direction perpendicular to the surface and containing cobalt is provided on the disk substrate. It is possible to realize an excellent fixed magnetic disk which has a structure in which a preferentially oriented iron oxide magnetic thin film, a protective film, and a lubricating layer are laminated, and which has high reliability and is compatible with a high recording density.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a main part of a fixed magnetic disk according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a plasma CVD apparatus for forming a Co ferrite film of the fixed magnetic disk.

FIG. 3 is a diagram showing a relationship between recording density and reproduction output of the fixed magnetic disk.

FIG. 4 is an enlarged view of a main part of a fixed magnetic disk according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between recording density and reproduction output of the fixed magnetic disk.

FIG. 6 is an enlarged sectional view of a main part of a conventional fixed magnetic disk.

[Explanation of symbols]

1 Disk Substrate 2 Co Ferrite Film (Iron Oxide Magnetic Thin Film Containing Cobalt) 3 Carbon Thin Film (Protective Film) 4 Lubrication Layer

Claims (4)

[Claims] 1. An iron oxide magnetic thin film, which has a columnar structure in a direction perpendicular to the surface of the disk substrate and is preferentially oriented to a plane index (100) of a spinel type crystal structure containing cobalt on the disk substrate, and protection. A fixed magnetic disk formed by laminating a film and a lubricating layer. 2. An oxide thin film having a NaCl type crystal structure on a disk substrate, an iron oxide magnetic thin film having a spinel type crystal structure having a columnar structure perpendicular to the surface of the disk substrate and containing cobalt, and a protective film. A fixed magnetic disk formed by laminating a film and a lubricating layer. 3. The fixed magnetic disk according to claim 2, wherein the oxide thin film having a NaCl type crystal structure contains at least one element selected from the group of elements of magnesium, manganese, cobalt, nickel and cadmium. 4. The fixed magnetic disk according to claim 1, wherein the protective film is a carbon thin film, a silicon oxide thin film or a zirconia oxide film.