JPH01149218A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a perpendicular magnetic recording medium which is uniform in envelope by forming a perpendicular magnetized film in such a manner that the film has a curved columnar structure and the oxygen concn. distribution in the film thickness direction within the perpendicular magnetized film does not have the peak exceeding the average value of the oxygen concn. in the film and providing specific coercive force to this film. CONSTITUTION:The perpendicular magnetized film is formed to have the curved columnar structure. In addition, the film is so formed that the oxygen concn. distribution in the film thickness direction within the perpendicular magnetized film does not have the peak exceeding the average value of the oxygen concn. in the film. Moreover, the coercive force Hc(theta) of the perpendicular magnetized film measured with the angle between the traveling direction of a magnetic head and the measuring magnetic field as theta within the plane inclusive of the direction where the magnetic head and the perpendicular magnetized film move relatively and the normal direction of the substrate face is determined to satisfy the equation I. The floppy disk having the excellent uniformity of the envelope is thus obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a thin film type perpendicular magnetic recording medium. .

[Prior Art] A method for obtaining a perpendicularly magnetized film mainly composed of a ferromagnetic material and its oxide with good productivity is disclosed in Japanese Patent Laid-Open No. 59-1987.
07, JP-A-61-80521, and other reactive vacuum deposition methods have been proposed. These have a fast film deposition rate;
Therefore, since a perpendicularly magnetized film can be continuously formed on a long substrate at high speed, it is extremely excellent industrially.

However, a perpendicular magnetic recording medium with a perpendicular magnetization film formed on a moving substrate by reactive vacuum deposition has a large non-uniformity in the reproduction output (envelope) during one revolution of the medium when used as a floppy disk. It was found that this occurs. Further, when a tape is used, there is a problem in that the playback output varies depending on the running direction of the tape. That is,
There has been a problem in that the reproduction output varies greatly depending on the combination of a specific position on the perpendicular magnetic recording medium and the traveling direction of the magnetic head at that position.

, the cause of this cannot be found in the magnetic anisotropy and coercive force in the thickness direction of the perpendicularly magnetized film, the coercive force in the in-plane direction, and the nonuniformity of the film thickness, but it is necessary to control the fine structure of the perpendicularly magnetized film. The present inventors' studies have revealed that this is necessary.

Conventionally, the structure of a perpendicularly magnetized film is as shown in FIG. 6, in which multilayered magnetized films 3 and 4 having a columnar structure are laminated on a base 2 so as to be inclined to each other and facing in opposite directions. has been proposed (JP-A-57-3223, JP-A-56-
94520. (Japanese Unexamined Patent Publication No. 61-26926, etc.).

However, when these techniques are applied to reactive vacuum evaporation, there is a problem that the reproduction output decreases. That is, in the reactive vacuum deposition method, a highly oxidized layer is formed in the early and late stages of film deposition, particularly in the late stage of film deposition, and this highly oxidized layer is nonmagnetic and does not contribute to the reproduction output.

At the initial stage of film deposition, crystal orientation is difficult to occur. It is important for a perpendicularly magnetized film to have large magnetic anisotropy in the film thickness direction, and this magnetic anisotropy is largely due to the expression of anisotropy due to crystal orientation. Therefore, having to repeat the initial stage of film deposition, in which the crystals are difficult to orient, several times degrades the performance of the perpendicularly magnetized film and makes it difficult to perform high-density recording.

In order to roughly orient the fine structure of a perpendicularly magnetized film perpendicularly to the substrate, a method was proposed in Japanese Patent Laid-Open No. 5 (1972) in which the incident angle of the ferromagnetic vapor flow to the substrate is set small to form the perpendicularly magnetized film by vacuum evaporation.
Although proposed in Japanese Patent No. 8-14326, the present inventors have found that it is possible to obtain a perpendicular magnetic recording medium with a uniform envelope by reactive vapor deposition even if the incident angle is made small at the expense of a considerable film deposition rate. I couldn't.

[Problems to be Solved by the Invention] The present invention was devised in view of the various drawbacks of the prior art, and its purpose is to solve various problems regardless of the position on the medium or the running direction of the magnetic head. The object of the present invention is to provide a perpendicular magnetic recording medium equipped with a perpendicularly magnetized film made of a partial oxide that can express an envelope, and also to provide a perpendicular magnetic recording medium that does not cause a decrease in reproduction output or magnetic anisotropy in the thickness direction of the perpendicularly magnetized film. An object of the present invention is to provide a perpendicular magnetic recording medium equipped with a magnetized film.

[Means for Solving the Problems] The object of the present invention is to provide a perpendicular magnetic recording medium in which a perpendicular magnetization film having magnetic anisotropy in the film thickness direction, which is mainly made of a ferromagnetic material and its oxide, is disposed on a substrate. The perpendicularly magnetized film has a curved columnar structure, and the oxygen concentration distribution in the film thickness direction inside the perpendicularly magnetized film does not have a peak exceeding the average value of the oxygen concentration inside the film, and the magnetic This is achieved by setting the angle between the traveling direction of the magnetic head and the measurement magnetic field to be θ in a plane that includes the direction in which the head and the perpendicular magnetic recording medium move relative to each other and the normal direction to the substrate surface.

Examples of the substrate that can be used in the present invention include metals such as aluminum, copper, iron, and stainless steel, inorganic materials such as glass and ceramics, and organic polymer materials such as plastic films. In particular, organic polymer materials are suitable for tapes, flexible disks, and other applications where processability, moldability, and flexibility are important. 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 substrate may be drum, disk, sheet, tape, card, etc., but disk and tape shapes are particularly suitable for high-density recording applications.

The thickness of the substrate is not particularly limited, but in the case of sheets, tapes, cards, etc., the thickness is 2 μm to 500 μm, especially 4 μm to 20 μm, in terms of workability and dimensional stability.
A range of 0 μm is preferred.

Prior to the formation of the magnetized film, the substrate 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 abrasion resistance, etc. . Furthermore, one or more underlayers may be laminated between the substrate and the perpendicularly magnetized film for the purpose of improving the magnetic properties, corrosion resistance, and adhesion of the perpendicularly magnetized film. In particular, it is preferable to provide a soft magnetic film as an underlayer because it has a great effect in increasing the recording/reproducing sensitivity.

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 is measured by the method shown in JIS C-2561.

A tangent line is drawn from the origin to this hysteresis loop, and the value of the externally applied magnetic field at the point where the magnetization value on this tangent line is the same as the saturation magnetization is called an anisotropic magnetic field. The larger the anisotropic magnetic field, the easier it is to magnetize in the perpendicular direction. In the present invention, a perpendicularly magnetized film has an anisotropic magnetic field of 2 km/hr or more.

The perpendicularly magnetized film of the present invention mainly consists of a ferromagnetic material and its oxide. The ferromagnetic material is not particularly limited, but it is preferably cobalt alone or cobalt and iron and/or nickel. These composition ratios are not particularly limited, but when cobalt and iron are used, a weight ratio of 97 to 85:3 to 15 increases reproduction output and reduces magnetic anisotropy. Preferable from the point of view of prevention;
The range of 95-90:5-10 is roughly preferred.

Also, when using cobalt and nickel, the weight ratio is 9
A ratio of 7 to 60:3 to 40 is preferred from the viewpoint of increasing reproduction output and corrosion resistance, and a range of 95 to 70:5 to 30 is more preferred.

Furthermore, when using cobalt, iron and nickel, when the weight is expressed as P and QSR respectively as a percentage, 65≦P≦
98.1≦Q≦15.1≦R≦30, P+Q+R=10
It is preferable to set the value within the range of 0 from the viewpoint of increasing reproduction output and S/N and preventing a decrease in magnetic anisotropy, and 75≦P≦94.
The range of 1≦Q≦10.1≦R≦15 is generally preferred.

Oxides contained in the perpendicular magnetization film include C00 and CO2O.
3. Co3O4, Fe01Fe203, Fe5st, N
io etc. are the main ones, but in addition to these, Coa
x, Fe0y, N ioz (x.

Non-stoichiometric suboxides and peroxides represented by y and z are numbers between O and 2 may also be included.

Nitride and hydroxide may be contained within a range that does not impair the magnetic properties of the perpendicularly magnetized film.

The magnetic recording layer also contains elements and compounds other than the above-mentioned cobalt, iron, and nickel, such as copper, chromium, aluminum, carbon, fluorine, silicon, vanadium, titanium, zinc, manganese, tantalum, and oxides and nitrides thereof. A hydroxide or the like may be contained within a range that does not impair the magnetic properties of the magnetic recording layer.

In addition, it is preferable from the viewpoint of magnetic properties that the magnetic recording layer contains 10 to 50% by volume of voids.

The thickness of the magnetic recording layer is not particularly limited, but from the viewpoint of reproduction output, flatness, and flexibility, it is preferably in the range of 0.05 μm to 2 μm, and most preferably in the range of 0.1 μm to 0.5 μm.

The magnetic recording layer may be provided on one side or both sides of the substrate.

In the present invention, the perpendicularly magnetized film formed on the substrate has a curved columnar structure. FIG. 1 illustrates this. Reference numeral 1 denotes a columnar structure constituting a perpendicularly magnetized film, which is formed in a curved shape on a base 2. In FIG. Reference numeral 5 indicates a normal line to the base, and reference numeral 6 indicates a line (center line) connecting the cross-sectional center of the columnar structure in its length direction.

In this case, it is preferable for the columnar structure to be curved so that the direction intersecting the substrate normal 5 changes once in the film thickness direction, as shown in the figure, in order to make the envelope more uniform. That is, the angle α1 between the center line 6- and the substrate normal 5 at the early stage of forming the perpendicularly magnetized film and the angle α2 between the center line 6' and the substrate normal 5 at the later stage of forming the perpendicularly magnetized film form the substrate normal. It is preferable to have a structure in which the angle between the center line 6 and the substrate normal 5 changes monotonically from α1 to α2 from the substrate side toward the surface layer side of the perpendicularly magnetized film.

The sizes of α1 and α2 are not particularly limited, as simply determining them does not necessarily lead to uniformity of the envelope. However, in order to make the envelope uniform, it is better to make them small, and on the other hand, the deposition speed of the perpendicularly magnetized film In order to increase the efficiency of using evaporation material, the larger the number, the better. Also α
It is not preferable to reduce the value of 2 because the oxidation formed on the surface layer of the perpendicularly magnetized film particularly progresses, making the layer thinner and reducing its abrasion resistance and corrosion resistance. Therefore, α1 and α2 are each preferably in the range of 2 degrees to 12 degrees, and more preferably in the range of 3 degrees to 10 degrees. It is preferable that α1>α2 because the envelope can be made more uniform.

The perpendicular magnetization film of the present invention has an oxygen concentration distribution in the film thickness direction inside the film excluding the surface layer on the substrate side (initial layer portion) and the surface layer (outer layer portion) of the perpendicular magnetization film. It has no peak to exceed.

This will be explained below with reference to FIGS. 2 and 7, which illustrate the oxygen concentration distribution in the film thickness direction.

In a perpendicularly magnetized film mainly made of a ferromagnetic material and its oxide, a highly oxidized layer is generally formed in the initial layer on the substrate side and in the surface layer. The present invention is characterized in that the oxygen concentration distribution inside the film excluding these portions is set to a specific distribution.

That is, the oxygen concentration distribution in the film thickness direction of the perpendicularly magnetized film is measured at predetermined intervals (or continuously) by a combination of Auger electron spectroscopy and etching. Next, a portion from the base side surface to a depth of 400 mm and a portion from the surface side surface to a depth of 400 mm.
If we add these data in the film thickness direction and take the average oxygen concentration for the inside of the film (between points A and B) excluding the part up to the depth of 0.00 mm, the oxygen concentration distribution in the film thickness direction is as follows. As shown in FIG. 2, there is no peak within the film that exceeds the average value of oxygen concentration (average oxygen m degrees). That is, as shown in FIG. 7, it can be clearly distinguished from the case where the oxygen concentration distribution in the film thickness direction has a peak that exceeds the average value of the oxygen concentration inside the film.

The perpendicularly magnetized film in the present invention must have a coercive force as described below.

In other words, when HC(θ) is the coercive force measured in a plane including the normal direction of the substrate surface and the running direction of the head, where θ is the angle between the head running direction and the measuring magnetic field, the ratio becomes significantly smaller. Moreover, the effect of improving the envelope becomes smaller, which is undesirable.On the other hand, if the value exceeds 1.2, the envelope inconsistency becomes large, and the shape of the running direction of the magnetic head becomes extremely difficult to design the signal processing circuit. When the angle changes, that is, when the medium is a floppy disk or multiple magnetic heads with different azimuth angles are used, the angle between the running direction of the substrate and the running direction of the magnetic head at the time of manufacturing the medium on the medium should be changed. We need to follow the changes. In other words, if the medium is a floppy disk, the circumference called a track must fall within the aforementioned range.

As a method for forming the magnetic recording layer, a reactive sputtering method, a reactive ion blating method, a reactive vapor deposition method, etc. can be used, but the reactive vapor deposition method is particularly preferable because it has a fast film formation rate and good mass production. .

Next, an example of a method for manufacturing a perpendicularly magnetized film according to the present invention will be described with reference to the accompanying drawings.

FIG. 4 is a schematic cross-sectional view showing an example of an apparatus used in manufacturing the perpendicularly magnetized film of the present invention, in which 7 is a vacuum chamber, which is a substrate unwinding device capable of supporting and moving a long film-like substrate 8. A substrate traveling system including a shaft 9, a substrate support drum 10, and a substrate winding shaft 11 is provided.

12 is an evaporation source provided vertically below the center of the axis of the drum 4; 13 is three nozzles for supplying an oxygen-containing mixed gas provided near the downstream side of the evaporation source in the direction of substrate travel; are oriented at a predetermined angle as shown so that the oxygen-containing gaseous fluid is incident generally parallel to the vapor flow.

14 is an exhaust port, 15 is a barrier pull leak valve, 16.
Reference numeral 16' denotes a shielding plate for regulating the angle of incidence of ferromagnetic vapor evaporated from the evaporation source onto the substrate, and the angle between the incident vapor and the normal to the substrate at the start and end points of incidence on the substrate. is installed so that it is less than a predetermined angle, preferably less than 45°.

17.17' is a partition provided between a predetermined position on the intermediate side of each upper surface of the shielding plate 16.16' and the substrate support drum 10, and the substrate support drum 10, the side partition wall 17.17', and the shielding plate, The space extending in the axial direction of the drum surrounded by 16 and 16' surrounds the position where the vapor flow is incident on the substrate, so that the oxidation of the film can proceed efficiently.

To form a perpendicularly magnetized film using such an apparatus, first, the vacuum chamber 7 is evacuated through the exhaust port 14, and then the valve 15 is operated to blow out oxygen-containing gas from the nozzle 13 toward the substrate.

Next, the material mainly consisting of ferromagnetic material is evaporated from the evaporation source 12, and the vapor flow is incident on the substrate moving along the drum cooled to a predetermined temperature, thereby removing the ferromagnetic material and the oxide of the ferromagnetic material. A main perpendicular magnetization film is formed.

The mixed gas containing oxygen is ejected from the nozzles 13 into the vacuum chamber with directionality, but at this time, the direction of each nozzle is
It is directed toward a point 19 where a line 18 connecting approximately the axis of the drum and the center of the evaporation source intersects the substrate.

In the present invention, in order to inject the oxygen-containing gas fluid almost parallel to the vapor flow, the angle (β) between the nozzle and the straight line connecting the center of the drum and the center of the evaporation source must be It is preferable that the absolute value is 30 degrees or less in a plane including a straight line connecting the centers of and the direction in which the substrate travels.

The perpendicularly magnetized film of the present invention can also be obtained by using the apparatus shown in FIG.

That is, in the apparatus shown in FIG. 5, the oxygen-containing mixed gas introduction nozzle 21 is provided to penetrate the partition wall 17, and the oxygen-containing mixed gas is supplied from the upstream side in the substrate running direction. 22 and 23 are provided to face each other through partition walls 17 and 17', and inert gas is supplied to the magnetic layer forming zone from the upstream and downstream sides in the substrate running direction, respectively. By adjusting the amount of gas ejected, the perpendicularly magnetized film that is the object of the present invention can be easily obtained. In addition, in Figure 5,
The same reference numerals as in FIG. 4 indicate the same parts.

[Effects of the Invention] Since the present invention is configured as described above, a floppy disk with excellent envelope uniformity can be obtained. Furthermore, when made into a tape, a tape with small differences in the magnitude of the reproduced output depending on the running direction of the tape can be obtained. The details of this reason are not clear, but it is speculated that there is a relationship between the direction of the magnetic lines of force generated by the ring-type magnetic head and the spatial distribution of density, and the distribution in the film thickness direction of the easy axis of magnetization of the perpendicular magnetic recording medium. be done.

Furthermore, compared to a medium with a perpendicular magnetization film in which the concentration distribution in the film thickness direction has a peak exceeding 11 degrees of average oxygen inside the film, the medium of the present invention can obtain a larger reproduction output and significantly improve productivity. can be increased.

The magnetic recording medium of the present invention can be formed into a tape, sheet, card, disk, drum, or the like, and can be widely used for magnetic recording purposes such as audio, video, and digital signals.

[Method of measuring characteristics, evaluation criteria] The characteristic values of the present invention are based on the following measurement method.

(2) Measurement of magnetic anisotropy of perpendicularly magnetized film The hysteresis loop in the film surface direction is measured by the method shown in JIS C-2561. The value of magnetization at the saturation point of the hysteresis loop is called saturation magnetization. A tangent line is drawn from the origin to this hysteresis loop, and the value of the external magnetic field at the point on this tangent line where the value of magnetization becomes the same as the saturation magnetization is called an anisotropic magnetic field (Hk). In the present invention, a perpendicularly magnetized film having an Hk of 2 kilometrested or more is used. A sample vibrating magnetometer (manufactured by Riken Denshi Co., Ltd., BHV-30) was used for the measurement.

■ After approximately 50 people applied fluorocarbon-based lubricant to the envelope measurement sample, 3.
It is shaped into a 5-inch diameter micro-floppy disk, placed in a jacket, and used as a measurement sample.

A sample was placed on a commercially available single-sided head floppy disk drive (Sony Corporation'!jOA-D32V), and the
Rotate at 0 rpm and record 500k) 12 signals. Next, the playback output from the head is amplified and the vA is measured using a synchroscope. Floppy disk - playback output waveform (envelope) for each cycle is JIS C6291
According to the definition of modulation, evaluate using the following formula.

((A-B) / (A+B)) A smaller value of average output voltage modulation means a more uniform envelope.

■ Observation of the cross-sectional microstructure of a perpendicularly magnetized film An ultra-thin section of the sample was cut along the substrate running direction, and the cross-sectional microstructure was observed using a transmission electron microscope (Hitachi's Fracture H-600).
) to observe.

■ Measurement of coercive force The sample vibrating magnetometer described above was used. A sample is cut out from a tape- or disk-shaped medium, and the head is measured in a plane that includes the normal direction of the sample substrate surface and the running direction of the head. Set the sample so that the angle between the traveling direction and the measuring magnetic field is θ. The hysteresis loop is measured by the method shown in JISC-2561, and the point where this hysteresis loop intersects with the external magnetic field axis is defined as the coercive force HC(θ) at an angle θ, where θ=75°, 80°, 85°, 900.95 °, 1
Measurements are made sequentially for 000.105°.

Figure 7 is drawn based on the measurement results, and it is found that for the planar disk-shaped media in the areas from θ=75° to 90' and from 90' to 105°, the above values change depending on the position on the circumferential track. At this time, measurements are taken over the entire circumference of the track at intervals of 30', and the values are determined as the maximum value.

■ Measurement of oxygen concentration distribution in the film thickness direction The oxygen concentration distribution in the film thickness direction of the perpendicularly magnetized film was measured by combining Auger electron spectroscopy and argon ion etching. JAMP-103 manufactured by JEOL Ltd. was used for the measurement.

Of the measured oxygen concentration distribution, the inside of the membrane excluding the part at a depth of up to 400 mm from the oxidized surface of the substrate and the part at a depth of up to 400 mm from the surface on the opposite side of the substrate was After measuring at each interval and adding these data in the film thickness direction, the average concentration is calculated by dividing by the number of added data.

It is important that the oxygen concentration distribution in the film thickness direction inside the film does not have a peak that exceeds the average value of the oxygen concentration inside the film.

[Example] The invention will be explained in greater detail by the following examples.

Example 1 Using the apparatus shown in FIG. 4, an ingot containing cobalt, nickel, and iron in a weight ratio of 80:15:5 was filled into the evaporator [12]. An electron beam heater was used as the evaporation source, and the substrate was a biaxially stretched polyethylene terephthalate film with a thickness of 50 μm.

The diameter of the drum is 400 mm, and the evaporation surface of the evaporation source is 60 mm in diameter.
mm circle, and the distance between the evaporation surface and the substrate is approximately 300 m.
mL, ta. In addition, the effective evaporation length in the direction of the drum axis is 200m.
It was set as m.

Three nozzles were installed in the direction of the drum axis, and the center nozzle was arranged at an angle of 15 degrees with respect to the direction connecting the center of the drum and the center of the evaporation source. the other 2
The book nozzles were each placed 7 Qmm apart from the center nozzle in the axial direction, and were oriented parallel to the center nozzle.

After the inside of the vacuum chamber was evacuated to 5×10 −5 Torr or less, a mixed gas of oxygen and nitrogen (volume ratio: 10:90) was jetted out from the valve 15 and nozzle 13 at a rate of if/min. Next, cobalt, nickel, and iron are evaporated from the evaporation source 12, and the cobalt, nickel, and iron are deposited on the substrate moving along the drum 10.
Perpendicularly magnetized films consisting primarily of nickel, iron, and their oxides were deposited to a thickness of 3000 nm at a rate of approximately 5 μm/min.

Similarly, a perpendicular magnetization film was attached to the other surface of the substrate.

The anisotropic magnetic field Hk of the perpendicularly magnetized film obtained was 3 kOersted.

Next, a lubricant was applied to the perpendicularly magnetized film sample, and the sample was shaped into a 3.degree. 5-inch floppy disk, and the envelope and reproduction output were measured. The modulation was extremely good at 5%. Further, the reproduction output was 0.5 Vpp.

An ultra-thin section of the sample was cut out along the direction of travel of the forehead base on the circumference measured along the direction of travel of the head, and the fine structure of the perpendicularly magnetized film was observed using a transmission electron microscope, as shown in Figure 1. Thus, although there was some curvature, a columnar structure was obtained in which the film thickness direction as a whole was quite parallel to the normal direction of the substrate. When α1 and α2 were measured, they were 7 degrees and 6 degrees, respectively.

When the oxygen concentration distribution in the film thickness direction was measured, it was found to have a distribution similar to that shown in FIG. 400mm deep from the surface of the base and 400mm deep from the surface opposite the base.
Inside the membrane (between points A and B) excluding the depth part up to the human body
When we measured the oxygen concentration of every 200 people, integrated these data, and calculated the average value, we found that 16
．． It was 7 at%. The oxygen concentration distribution in the film thickness direction had no peak within the film that exceeded the average value of oxygen concentration within the film (16°7 at.%). The boundary between the substrate and the perpendicularly magnetized film was set at the intersection (C) of the concentration distribution curve of carbon contained in the polyethylene phthalate film of the substrate and the concentration distribution curve of oxygen contained in the perpendicularly magnetized film.

Example 2 This was carried out using the apparatus shown in FIG. A mixed gas of 20:80 by volume of oxygen and nitrogen is supplied from the nozzle 21 at a rate of 0.52/min, nitrogen gas is supplied from the nozzle 22 at a rate of O,iff/min, and further from the nozzle 23. Nitrogen gas 0. IQ
,/minute, and the other conditions were the same as in Example 1 to form a perpendicularly magnetized film. .

The obtained perpendicularly magnetized film had a Hk of 3 kOersted.

Also, when the envelope was measured, the modulation was 7%, which was very good. Further observation of the fine structure of the perpendicularly magnetized film of the head revealed that it had a curved columnar structure similar to that of Example 1, with α1 being 5 degrees and α2 being 3 degrees.

Further, the average value of oxygen mrx inside the film was 22.3 atomic %, and when the oxygen concentration distribution in the film thickness direction was measured, there was no peak of oxygen concentration exceeding the above average value.

Comparative Example 1 In the apparatus shown in FIG. 4, the nozzle 13 was installed upstream in the direction of movement of the substrate from the incident position of the ferromagnetic vapor flow (the nozzle was provided through the partition wall 17), and oxygen and nitrogen were mixed. A perpendicularly magnetized film was formed in the same manner as in Example 1, except that gas (volume ratio 10:90) was supplied from the upstream side.

The Hk of the obtained perpendicularly magnetized film was 3.2 kOersted.

Also, when I measured the envelope, the modulation was 21%, which was not good.

The average value of the oxygen concentration inside the film is 23 at.%, and when we measured the oxygen concentration distribution in the film thickness direction, there was no peak of oxygen concentration exceeding the above average value. The circumference measured along the line was 1.3.

Furthermore, when the fine structure of the perpendicularly magnetized film was observed, as shown in FIG. 8, a perpendicularly magnetized film 28 with a columnar structure that was curved on the substrate 27 and tilted from the normal direction of the substrate in the film thickness direction as a whole was observed. α1 was 7 degrees and α2 was 14 degrees.

Comparative Example 2 The apparatus shown in FIG. 4 used in Comparative Example 1 is configured so that the substrate running direction is reversed (the positions of the substrate winding shaft 11 and the substrate unwinding shaft 13 are exchanged), and the nozzle 13 is made of ferromagnetic material. The partition wall 17 is installed upstream in the direction of movement of the base body from the incident position of the body vapor flow and facing the position where the vapor flow enters the base body.
A device with a nozzle penetrating through it was used.

The substrate running speed was controlled so that the thickness of the perpendicularly magnetized film was 1,500 mm, and the conditions were the same as in Comparative Example 1 to form a perpendicularly magnetized film.

The obtained perpendicularly magnetized film had a Hk of 2.4 oersteds. When the envelope was measured, the modulation was 13%, but the playback output was 7% for the medium of Example 1.
・0% of 0.35VppL was small.

The oxygen concentration distribution in the film thickness direction shows the same distribution as in Figure 7,
The average value of the oxygen concentration inside the film is 25 at%, and the oxygen concentration distribution in the film thickness direction has a peak inside the film that exceeds the average value of the oxygen concentration inside the film (25 at%). was.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one example of the perpendicular magnetic recording medium of the present invention, FIG. 2 is an explanatory diagram showing the oxygen concentration distribution in the film thickness direction of the perpendicularly magnetized film of the present invention, and FIG. FIG. 6 is a schematic cross-sectional view of iPR showing an example of an apparatus for producing a perpendicularly magnetized film of the present invention, FIG. 6 is a schematic cross-sectional view showing an example of a conventional perpendicular magnetic recording medium, and FIG. 7 is shown in FIG. An explanatory diagram showing the oxygen concentration distribution in the film thickness direction of a perpendicularly magnetized film, and FIG. 8 is a schematic cross-sectional view showing another example of a conventional perpendicular magnetic recording medium. 1: Columnar structure of perpendicular magnetization film 2.8: Substrate 12: Evaporation source 13.21-23: Gas introduction nozzle 17.17": Shielding plate Patent applicant Azuma Shi Co., Ltd. No. 2 [21 No. 5 Figure 6 Depth from surface (^) Figure 7 75 80 8590 95 too 105θ (°
) Figure 3 Figure 8 Figure 1, Indication of the case Patent Application No. 308036, filed in 1988 Address: 2-2-1-5 Nihonbashi Muromachi, Chuo-ku, Tokyo Number of inventions increased by amendment None 6, Description subject to amendment Column 7 of "Detailed Description of the Invention", Contents of Amendment (1) "6'" on page 10, line 13 of the specification is amended to "6'". (2) On page 28 of the specification, lines 4 to 13, "A perpendicularly magnetized film was formed using the method shown in FIG. 4 used in Comparative Example 1." was corrected as follows. do. [A perpendicularly magnetized film was formed in the same manner as in Comparative Example 1, except that the substrate traveling speed was controlled so that the film thickness was 1500 mm. Next, with the elongated substrate on which the perpendicularly magnetized film was formed mounted as it was on the substrate traveling system, a perpendicularly magnetized film was laminated on the perpendicularly magnetized film in the following manner. That is, in FIG. 4 used in Comparative Example 1, the substrate traveling direction is configured to be reversed (the positions of the substrate winding shaft 11 and the substrate winding shaft 9 are exchanged), and the nozzle 13 is configured to rotate the ferromagnetic vapor flow. (the partition wall 17
The substrate running direction was controlled so that the thickness of the perpendicularly magnetized film was 1,500 mm using a device with a nozzle penetrating the A perpendicularly magnetized film was formed on the perpendicularly magnetized film that had been formed in advance to form a perpendicularly magnetized film with a total thickness of 3,000 people. ”

Claims (1)

[Claims] (1) In a perpendicular magnetic recording medium equipped with a perpendicularly magnetized film on a substrate that is mainly made of a ferromagnetic material and its oxide and has magnetic anisotropy in the film thickness direction, the perpendicularly magnetized film has a curved columnar structure. , and the oxygen concentration distribution in the film thickness direction inside the perpendicularly magnetized film does not have a peak exceeding the average value of the oxygen concentration inside the film, and the magnetic head and the perpendicular magnetic recording medium move relative to each other. The coercive force Hc(θ) of the perpendicularly magnetized film measured in a plane including the direction and the normal direction of the substrate surface, where θ is the angle between the magnetic head running direction and the measurement magnetic field, is expressed by the following formula: 0.83≦▲ , chemical formulas, tables, etc. A perpendicular magnetic recording medium characterized by satisfying ▼≦1.2.