JPS62189622A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide wear resistance sufficient for practical use by forming the surface layer of the vertically magnetized film with a layer consisting essentially of Co2O3. CONSTITUTION:The surface layer of the vertically magnetized film is formed with a layer consisting essentially of Co2O3. The layer consisting essentially of Co2O3 can be recognized by the fact that a peak characteristic of Co, CoO, Co3O4, and Co(OH)2 is not seen or is not predominant in the measurement of a cobalt atom by XPS (X-ray Photoelectron Spectroscopy) and only the peak characteristic of Co2O3 can be observed. Although the thickness of the layer consisting essentially of Co2O3 is preferably decreased not to increase a spacing loss, some thickness is needed to impart sufficient wear resistance. Accordingly, the thickness is preferably controlled to 50-500Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perpendicular magnetic recording medium. For more details,
The present invention relates to a thin film type perpendicular magnetic recording medium having a perpendicular magnetization film mainly composed of cobalt and cobalt oxide and having improved wear resistance.

[Prior Art] As a perpendicularly magnetized film constituting a perpendicular magnetic recording medium, an alloy thin film of cobalt and other metals such as cobalt-chromium is known as a typical film.

These perpendicularly magnetized films are usually formed on a substrate by sputtering or vacuum deposition. However, cobalt alloy films formed by sputtering have a slow film formation rate, and
The method of electron beam evaporation of cobalt alloys has a problem in that it is difficult to control the alloy composition. In addition, in both methods, in order to obtain 1 q of film with good magnetic properties, the substrate must be 150 to 300
It has the disadvantage that it must be heated to a high temperature of about 1000 ft, which is a major hindrance especially when using a plastic substrate.

As a method to improve this problem, a method of obtaining a perpendicularly magnetized film consisting of cobalt and cobalt oxide 1- on a cooled substrate has been proposed (Collection of Abstracts of the 7th Academic Conference of the Japan Society of Applied Magnetics).

Although these thin perpendicularly magnetized films have characteristics suitable for high-density recording, they are easily scratched or peeled off when they come into contact with magnetic heads, guides, etc., so it is important to improve their wear resistance for practical use. This is considered to be the biggest challenge in doing so.

Various attempts have been made to improve wear resistance, but it is believed that oxidizing the surface layer of the perpendicularly magnetized film itself is effective. Among them, the method of forming a perpendicularly magnetized film and then oxidizing its surface layer is a method that reduces the volume expansion caused by oxidation.
: It is said that the surface layer becomes denser and the wear resistance can be greatly improved.
It has been proposed to form a protective layer made of 3O4 (Japanese Unexamined Patent Publication No. 58-41439).

[Problems to be solved by the invention] However, in the case of this technology, the perpendicularly magnetized film surface layer is co
It has become clear that despite being oxidized to a state consisting mainly of o, Co3O4, it does not have sufficient wear resistance for practical use.

The present inventors have conducted intensive studies to obtain a perpendicularly magnetized film mainly composed of cobalt and cobalt oxide, which have excellent wear resistance, and have finally arrived at the present invention.

Means for Solving the Problems Namely, the present invention provides a perpendicular magnetic recording medium comprising, on a substrate, a perpendicular magnetization film mainly made of cobalt and cobalt oxide and having magnetic anisotropy in the film thickness direction. , a perpendicular magnetic recording medium characterized in that the surface layer of the perpendicular magnetic film is formed of a layer mainly composed of Co2O3.

In the present invention, the layer mainly composed of Co2O3 means
P S (X-ray Photoelectron
In the peak measurement of cobalt atoms by 5pectroscopy, C01coo, Co3O4 and Co
This is determined based on the fact that (OH)2-specific peaks are not observed or are not dominant, and only Co2O3-specific peaks are observed.

The thickness of the layer mainly made of Co2O3 should be thinner to avoid increasing spacing loss, and it needs to be thick enough to fit into the layer to provide sufficient wear resistance. The number of participants is preferably in the range of 700 to 700, and more preferably 50 to 500. Most preferably, the number ranges from 50 to 300 people.

The thickness of the layer mainly composed of Co2O3 was determined by repeated XPS measurements and sample etching.
, Co3O4, Go Co, Coo, Co
3O4, refers to the edging depth to the position where the unique peak of Co(OH)2 begins to appear.

A layer mainly composed of Co2O3 means an element or compound other than Co2O3, such as iron, nickel, copper, chromium, aluminum, carbon, silicon, vanadium, titanium, zinc, manganese metal oxide, etc., with an atomic ratio of 20%.
The content may preferably be 10% or less. Further, cobalt oxide, cobalt hydroxide, and cobalt other than Co2O3 may be contained as long as they are in extremely small amounts of about 5% or less in terms of atomic number ratio.

A dome-shaped protrusion is formed on the surface of the perpendicularly magnetized film.

Regarding the dome-shaped protrusion referred to in the present invention, FIGS. 1 and 2
This will be explained using figures. FIG. 1 is a model diagram showing the surface shape of an example of a perpendicularly magnetized film of the invention, and FIG. 2 is a cross-sectional model of an example of a perpendicular magnetic recording medium of the invention.

In the figure, 1 is a substrate, 2 is a perpendicularly magnetized film formed on the substrate, and fine dome-shaped protrusions 3 are formed on the surface thereof. The cross section of the protrusion does not have an acute-angled protrusion, as shown in the model in FIG. 2, and has a generally circular shape when viewed from the membrane surface side.

In the present invention, the grain size of the dome-shaped protrusions refers to the maximum width of each grain as indicated by the arrow in FIG.

If the grain size of the dome-shaped protrusions is too small, the surface will become too flat, leading to an increase in the coefficient of friction, and if it is too large, the force applied to a single protrusion will increase when it comes into contact with a head, etc., resulting in damage to the perpendicularly magnetized film. Since this can easily cause damage, a range of 50 to 1000 people is preferable, and more preferably a range of 80 to 800 people.

Further, it is desirable that the particle diameters of the dome-shaped protrusions be irregular within the above-mentioned preferred range in order to improve wear resistance.

Similarly, the density of the dome-shaped protrusions is set from I×108 pieces/mm2 to 4×10 to reduce the cause of damage to the perpendicularly magnetized film.
The range of 10 pieces/mm2 is preferable, and the range of 1.5×10
A range of 8 pieces/mm2 to 1.5×101° pieces/mm2 is preferable.

The perpendicularly magnetized film mainly composed of cobalt and cobalt oxide in the present invention is composed mainly of cobalt and cobalt, except for the surface layer.
It is composed of cobalt oxides such as Co3O4 and Co3O4. Cobalt oxide also includes non-stoichiometric oxides and peroxides represented by C00X (X is a number greater than O and less than 1.5).

The perpendicularly magnetized film mainly composed of cobalt and cobalt oxide contains elements and compounds other than these, such as iron, nickel, copper, chromium, aluminum, carbon,
Silicon, vanadium, titanium, zinc, manganese, metal oxides, metal nitrides, metal hydroxides, etc. may be contained within the range that does not impair magnetic properties.

The perpendicularly magnetized film having magnetic anisotropy in the film thickness direction as used in the present invention is defined as follows.

The hysteresis loop in the film surface direction and film thickness direction is measured by the method shown in JIS C-2561. The area surrounded by each hysteresis loop is calculated, and the area surrounded by the hysteresis loop in the film surface direction is defined as S, and the area surrounded by the hysteresis loop in the film thickness direction is defined as S. S
Let H/S// be the magnetic anisotropy coefficient, and this value is 1J:
The perpendicular magnetization film is preferably larger than 1.2, most preferably 1°4 or larger.

The thickness of the perpendicularly magnetized film is not particularly limited, but practically it is 0.
．． A range of 0.02μm to 5μm is best, especially 0.03μm.
A range of m to 3 μm, particularly 0.05 μm to 2 μm is most preferable in terms of flexibility and good head touch.

Furthermore, it is permissible to laminate one or more other protective layers or lubricating layers on the surface of the perpendicularly magnetized film for the purpose of improving running properties, wear resistance, etc.

Substrates that can be used in the present invention include, but are not particularly limited to, metals such as aluminum, copper, iron, and stainless steel, inorganic materials such as glass and ceramics, and organic polymer materials such as plastic films. can be mentioned. Particularly in tapes, flexible disks, etc., where flexibility, formability, and flexibility are important,
Suitable materials include polyesters such as polyethylene terephthalate, polyethylene pphthalate, and polyethylene dicarboxylate, polyolefins such as polyethylene, polypropylene, and polybutene, and polymethyl methacrylate. , polycarbonate, polysulfonate, polyamide, aromatic polyamide, polyphenylene sulfide, bolifluoride, polyamideimide, polyimide, polyvinyl chloride,
Polyvinylidene chloride, polyvinylidene fluoride, polytetrafluoroethylene, cellulose acetate, cellulose methyl, cellulose ethyl, epoxy resin, urethane resin, or mixtures and copolymers thereof are suitable. In particular, biaxially stretched films and sheets are most suitable due to their excellent flatness and dimensional stability, and among them, polyester, polyphenylene sulfide, aromatic polyamide, etc. are most suitable.

The shape of the base body may be any shape such as a drum shape, a disk shape, a sheet shape, a tape shape, a card shape, etc., and the thickness is not particularly limited. In the case of sheets, tapes, cards, etc., the thickness should be 2 to 500μ in terms of processability and dimensional stability.
m, preferably in the range of 4 to 200 μm.

Prior to forming a magnetic film, etc., the single substance used in the present invention may be subjected to various surface treatments or pretreatments for the purpose of facilitating adhesion, improving flatness, coloring, preventing static electricity, imparting wear resistance, etc. .

It should be noted that between the perpendicular magnetization film and the substrate described in the present invention, it is not allowed to laminate one or more underlayers for the purpose of improving the magnetic properties and ti of the perpendicular magnetization film, improving corrosion resistance, improving adhesive strength, etc. Permitted as appropriate. In particular, it is preferable to provide a soft magnetic film as an underlayer because it has a great effect on increasing the recording/reproducing sensitivity.

Perpendicular magnetization! 3 and the base layer may be formed on either one side or both sides of the substrate.

Methods for forming a perpendicularly magnetized film mainly made of cobalt and cobalt oxide include, but are not necessarily limited to, vacuum deposition methods such as reactive evaporation, reactive ion blasting, and reactive sputtering. An example of a method for producing a perpendicularly magnetized film mainly made of cobalt and cobalt oxide using a reactive vapor deposition method will be shown below.

1) Cobalt was applied to a biaxially stretched polyethylene terephthalate film substrate placed in a vacuum system by electron beam evaporation in an oxygen atmosphere of 10 Torr to 10 Torr. Vapor deposition is performed at a rate of 0.1 μm to 20 μm per minute to form a perpendicularly magnetized film mainly composed of cobalt and cobalt oxide. At this time, the back side of the substrate is cooled to 50°C or less, and when the cobalt vapor hits the film substrate, the evaporation is carried out so that the angle between the inlet vapor and the normal direction of the substrate is 45° or less. Place a shield plate between the source and the source.

A method of forming dome-shaped protrusions on the surface of a perpendicularly magnetized film mainly composed of cobalt and cobalt oxide and making the surface layer of the perpendicularly magnetized film a layer mainly composed of Co2O3 is as follows:
A method of etching the surface of a perpendicular magnetization film mainly made of cobalt and cobalt oxide to form dome-shaped protrusions using a wet or dry method, and then further oxidizing the surface layer of the perpendicular magnetization film to Co2O3 by thermal oxidation or anodic oxidation. There is a method of simultaneously forming a dome-like structure and Co2O3 by irradiating the surface of the magnetized film with high-energy particles containing oxygen using an ion source Yasbatta etching method.
It is not necessarily limited to these. An example of a method of forming a dome-shaped protrusion on the surface of a perpendicularly magnetized film mainly made of cobalt and cobalt oxide, and making the surface layer of the perpendicularly magnetized film a layer mainly made of Co2O3 will be described below.

A substrate on which a perpendicularly magnetized film mainly made of cobalt and cobalt oxide is pre-formed is installed in a vacuum (a), and an ion source is installed to irradiate the surface of the perpendicularly magnetized film with ions. After evacuation to
Preheat for 1 minute at a density of μA/d. In this way, a perpendicularly magnetized film having dome-shaped protrusions on the surface and whose surface layer is mainly composed of cobalt mainly composed of Co2O3 and cobalt oxides 1 to 1 is obtained.

[Function] By oxidizing the surface layer of the perpendicularly magnetized film, which is mainly composed of cobalt and cobalt oxide, to a higher degree of oxidation to Co2O3, the surface becomes denser due to volume expansion accompanying oxidation and hardness can be increased; By forming dome-shaped protrusions of appropriate size and shape on the surface, the thickness coefficient can be reduced and the cause of damage to the perpendicularly magnetized film can be reduced. It is presumed that the wear resistance of the perpendicular magnetic recording medium equipped with the film could be greatly improved. Further, even if the thickness of the layer mainly composed of Co2O3 is 700 Å or less, it is sufficiently effective in improving wear resistance, so that spacing loss can be kept small.

[Effects of the Invention] In the present invention, a dome-shaped protrusion is formed on the surface of a perpendicularly magnetized film mainly made of cobalt and cobalt oxide, and the surface layer of the perpendicularly magnetized film is made a layer mainly made of Co2O3. A perpendicular magnetic recording medium with extremely excellent wear resistance can be obtained.

The perpendicular magnetic recording medium obtained by the present invention is
It can be used for magnetic recording of audio, video, digital signals, etc. in the form of cards, disks, drums, etc.

Measurement method and evaluation criteria for properties (1) Wear resistance test method A sample was punched into a 5.25-inch flexible disk, and a fluorocarbon-based lubricant (RYTOX142AC manufactured by DuPont) was applied to a thickness of approximately 200 mm. Apply it and put it in the jacket. This was applied to a commercially available single-sided head type flexible disk drive, and recording and reproduction was performed after 300 rotations.

The reproduction output (E, o) at this time is measured, and then the vehicle is run on the same track while measuring the reproduction output. The playback output is E. Abrasion resistance is evaluated based on the running speed when the speed decreases to 70% of the speed.

(2) Measurement of recording density A sample was punched into a 5.25-inch flexible disk, and a lubricant (RYTOX143^C manufactured by DuPont) was applied.
Apply it to a thickness of about 200 people and store it in a jacket. While rotating this sample at 300 rpm, the gap length was set to 0.
A square wave is recorded with a 25 μm ring head, and the reproduced output is amplified and measured on a synchroscope. Recording and reproduction are performed while changing the wavelength of the square wave generated by a pulse generator, and the recording density is determined by the magnetization reversal density per inch (FCPI) corresponding to the wavelength of the recording square wave at which the reproduction output drops to half of the maximum value. (D5o).

(3) Observation of protrusions on the surface of the perpendicularly magnetized film The sample surface was observed using a field emission scanning electron microscope (Model S-800, manufactured by Hitachi, Ltd.), and the grain size and density of the protrusions were determined. We also cut ultra-thin sections of the sample and examined the cross-sectional shape using a transmission electron microscope.
Observation was made using H-600 model (manufactured by Hitachi, Ltd.).

(4) Composition analysis of perpendicular magnetization film surface layer The composition and bonded layer of the sample surface layer were analyzed using XPS (ESCALAB5 manufactured by VG Scientific Limited). The thickness of the layer mainly composed of Co2O3 was determined by repeatedly etching the sample and measuring by XPS. A layer mainly composed of Co2O3 means Co, coo,
Co3O4, Co(OH)2-specific peaks are not observed or are not dominant, and are identified by the observation of only Co2O3-specific peaks. For more information, see Co.
It is identified by the fact that the main peak of Co"(7) and the Co" (7) satellite peak are not observed or are not dominant, and only a peak specific to Co2O3 is observed.The thickness of the layer mainly composed of Co2O3 is From the outermost layer of the sample where only peaks are observed, Co, CoO1Co30
4. The etching depth is set to the position where a peak unique to Co(OH)2 begins to appear.

[Examples] Example 1 A biaxially stretched polyethylene terephthalate film with a thickness of 50 μm was used as the substrate.

After filling the vacuum chamber to 1 x 10'l, a mixed gas of oxygen and nitrogen with a partial pressure ratio of 50:50 (volume %) was added.
The pressure inside the vacuum chamber was set to 1X10' Torr by introducing oxygen up to X10-4 and separately blowing oxygen to the position where the formation of the perpendicularly magnetized film was completed. Next, electron beam evaporation 6
The cobalt is evaporated by evaporation, and the substrate is continuously moved along the drum at a speed of 10μr/min to a thickness of about 0.
．． A perpendicularly magnetized film mainly consisting of 25 .mu.rn cobal 1 to cobal oxide 1 was formed on the substrate.

The substrate was placed in close contact with a holder cooled to 5°C.
A water-cooled shielding plate was installed over the entire surface of the substrate to block large sword particles exceeding 45 degrees so that the angle between the cobalt vapor and the normal to the substrate surface was 45 degrees or more.

On the surface of the perpendicularly magnetized film thus obtained, relatively sharp protrusions with a grain size of about 200 were observed at a density of about 2.5 x 109 pieces/mm2.

Next, after placing the substrate with the perpendicular magnetization film in close contact with a holder cooled to 5°C, oxygen gas is supplied to the ion source so that the inside of the vacuum chamber becomes 2 x 10' torr to form an ion beam. Then, the perpendicularly magnetized film was irradiated with this. The ion source is a magnetron discharge ion source (MIS-25
0 (manufactured by JEOL Ltd.) was used. Ion irradiation 0=+ density is approximately 150μA/cJ, ion acceleration voltage is 1.5K
ey, the ion beam irradiation time was 1 minute.

On the surface of the perpendicularly magnetized film after ion beam irradiation, irregular dome-shaped protrusions with a grain size of 300 to 600 particles were observed at a density of about 4×10 8 /mm 2 .

When the outermost layer of the perpendicularly magnetized film was measured using XPS, it was found that Co2O
Only a peak specific to 3 was observed. When etching the sample and measuring by XPS were repeated, the peak specific to Co2O3 became smaller when the etching depth reached approximately 300 mm, and CO1CoO, Co3
O4,C.

A peak of (OH1)2 began to be observed. That is, Co2
The thickness of the layer consisting mainly of O3 was about 300 people.

When a lubricant was applied to the perpendicularly magnetized crotch of an ion beam irradiated model and a wear resistance test was conducted, the wear resistance was significantly improved after 1 million cycles compared to a model that was not irradiated with an ion beam.

Further, the recording density (D5o) was 78 kg FCPI.

Example 2 A perpendicularly magnetized film mainly composed of cobalt 1 and cobalt oxide was formed in the same manner as in Example 1.

Next, the perpendicularly magnetized film was irradiated with an ion beam in the same manner as in Example 1, except that the ion acceleration voltage was 500 cV and the ion beam irradiation time was 5 minutes.

The surface of the perpendicularly magnetized film obtained in this way contains 300 to 60
Irregular dome shaped protrusions with particle size of 0 are about 4X10
8 with a density of 1 m”.

When the outermost layer of the perpendicularly magnetized film was measured using XPS, it was found that Co2O
Only the peak specific to I2 was observed. As the sample etching and XPS measurements were repeated, the peak specific to Co2O3 became smaller when the etching depth reached approximately 200 people, and Co, coo, Co3
Peaks of O4, Co (OFl)2 began to be observed.

That is, the thickness of the layer mainly composed of Co2O3 is about 200
It was a person.

When a lubricant was applied to the perpendicular magnetization crotch after ion beam illumination and a wear resistance test was conducted, the wear resistance was greatly improved to 2 million cycles.

Also, D50 was 80 Giro FCPI.

Example 3 A perpendicularly magnetized film mainly composed of cobalt and cobalt oxide was formed in the same manner as in Example 1.

Next, the perpendicularly magnetized film was irradiated with an ion beam in the same manner as in Example 1, except that argon gas was used as the gas supplied to the ion source.

The surface of the perpendicularly magnetized film obtained in this way has 300 to 50
Relatively uniformly sized dome-like protrusions with a grain size of 0.05 mm were observed at a density of approximately 1 x 109 particles/llll112.

Next, this perpendicularly magnetized film was anodized in an electrolytic solution containing n-methylacetamide and 0.04N of potassium nitrate. Yang 4ii! The oxidation current was set to 7 mA/QTf, and oxidation was continued until the anodic oxidation voltage increased three times the initial value.

Thus, on the surface of the perpendicularly magnetized film after 1q, dome-shaped protrusions of relatively uniform size were observed, with a diameter of 300 to 500 mm, which was not much different from that before anodization.

When the outermost layer of the perpendicularly magnetized film was measured using XPS, it was found that Co2O
3.'t:j Only the peak on the right is visible? It was done. After repeating the first trial etching and XPS measurements, it was found that when the number of graves reached approximately 350, C
The peaks specific to o2O3 become smaller, and co, c
Peaks of oo, Co3O4, and C0(OH)2 began to be observed.

When a lubricant was applied to the perpendicularly magnetized film thus obtained and a wear resistance test was conducted, the wear resistance was good at 1 million cycles. Also, the D50 was 75 kg FCPI.

Comparative Example 1 A perpendicularly magnetized film mainly composed of cobalt and cobalt oxide was formed on a substrate in the same manner as in Example 1.

Next, a lubricant was applied to this perpendicularly magnetized film and a wear resistance test was conducted, and the wear resistance was 10,000 times, which was poor.

When the outermost layer of the perpendicularly magnetized film was measured using XPS, coo,
The peaks of Co3O4 and Co(OH1)2 were predominantly observed.

Comparative Example 2 A perpendicularly magnetized film mainly composed of cobalt and cobalt oxide was formed on a substrate in the same manner as in Practical Example 1.

Next, the perpendicularly magnetized film was irradiated with an ion beam in the same manner as in Example 1, except that argon gas was used as the gas supplied to the ion source.

The surface of the perpendicularly magnetized film obtained in this way has 300 to 50
Relatively uniformly sized dome-like projections with a diameter of 0.0 cm were observed at a density of approximately 1 x 109 pieces/city 2.

When the outermost layer of the perpendicularly magnetized film was measured using XPS, it was found that Coo,
The peaks of Co3O4 and Co(OH)2 were predominantly observed. ``We applied a lubricant to the perpendicularly magnetized film after ion beam irradiation and conducted a wear resistance test. Despite the formation of dome-shaped protrusions, the wear resistance was 0.4 million times, which was remarkable. It was inferior.

Comparative Example 3 A perpendicularly magnetized film mainly composed of cobalt and cobalt oxide was formed on a substrate in the same manner as in Example 1.

Next, the ion acceleration voltage was set to 3008V, and the ion irradiation density was set to 1.
The perpendicularly magnetized film was irradiated with an ion beam in the same manner as in Example 1, except that the ion beam irradiation time was 00 μA/aK and 5 minutes.

On the surface of the perpendicularly magnetized film thus obtained, sharp protrusions were reduced, but dome-shaped protrusions were not formed. The density of protrusions was approximately 2×109 f/mm2.

When the outermost layer of the perpendicular magnetization film was measured by XPS, it was 1, C01.
Twelve peaks of coo, Co3O4, and Go(OH)2 were dominantly observed.

When a lubricant was applied to the perpendicularly magnetized film after ion beam irradiation and an abrasion resistance test was conducted, the abrasion resistance was 10,000 times and there was almost no improvement effect.

Example 4 A perpendicularly magnetized film mainly composed of cobalt and cobalt oxide was formed on a substrate in the same manner as in Example 1.

Next, the perpendicular magnetization was carried out in the same manner as in Example 2, except that a voltage of -10 KV was applied to the substrate on which the perpendicular magnetization film was provided and a holder that was in close contact with the back surface of the substrate, and the ion irradiation density was set to about 50 μA/clTF. The membrane was irradiated with ions.

After ion beam irradiation, the surface of the perpendicularly magnetized film has an indistinct 30
Irregular dome-like projections with diameters ranging from 0 to 600 mm were found at a density of approximately 2 x 10 9 /mm 2 .

When the outermost layer of the perpendicularly magnetized film was measured using XPS, it was found that Co2O
Only a peak specific to 3 was observed. As the sample etching and XPS measurements were repeated, the peak specific to Co2O3 became smaller when the etching depth reached approximately 800 people, and the peaks specific to Co2O3 became smaller.
4, co (.

The peaks of 1) and 2 began to be predominantly observed.

When a lubricant was applied to the perpendicularly magnetized film after ion beam irradiation and a wear resistance test was conducted, the wear resistance was greatly improved to 2 million cycles. On the other hand, the D50 was somewhat smaller at 40km FCPI.

[Brief explanation of drawings]

FIG. 1 is a model diagram showing the surface shape of an example of a perpendicular magnetization film of the present invention, and FIG. 2 is a cross-sectional diagram showing an example of a perpendicular magnetic recording medium of the invention. 1: Base 1 provisional 2: Perpendicular magnetization film 3: Dome-shaped protrusion

Claims (3)

[Claims] (1) A perpendicular magnetic recording medium comprising, on a substrate, a perpendicular magnetization film mainly composed of cobalt and cobalt oxide and having magnetic anisotropy in the film thickness direction, wherein the surface layer of the perpendicular magnetization film is C
A perpendicular magnetic recording medium characterized in that it is formed of a layer mainly consisting of o_2O_3. (2) The perpendicular magnetic recording medium according to claim (1), characterized in that the surface of the perpendicularly magnetized film has dome-shaped projections having a grain size of 50 Å to 1000 Å. (3) The thickness of the layer mainly composed of Co_2O_3 is 20
The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium has a thickness in the range of Å to 700 Å.