JPS60157717A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium having a very small magnetic domain, high coercive force and superior magnetic characteristics by forming a ferromagnetic metallic thin film contg. oxygen on a substrate by vapor deposition so as to make the amount of oxygen atoms contained in the surface layer and in the interfacial layer contacting with the substrate larger than that in the intermediate layer and the amount of oxygen atoms contained in the surface layer larger than that in the interfacial layer. CONSTITUTION:A substrate 4 such as a plastic film is fed from a feed roll 5 through a guide roll 6, and it is moved along the outside of a cylindrical can 3 in a vacuum vessel 1. A ferromagnetic material 10 in an evaporating source 9 placed at the lower part of the vessel 1 is evaporated by heating, and generated vapor is diagonally deposited on the substrate 4 by the action of a deposition preventing plate 11. At the same time, gaseous oxygen is blown from a pipe 12 set between the can 3 and the plate 11 so that the oxygen hits directly on the part A of the substrate 4 having the minimum incident angle. Oxygen atoms are contained in the resulting ferromagnetic metallic thin film in an ideal state, so a magnetic recording medium having superior magnetic characteristics is obtd. The amount of oxygen atoms is largest in the surface layer and small in the intermediate layer, and the amount of oxygen atoms contained in the interfacial layer contacting with the substrate is smaller than that in the surface layer and larger than that in the intermediate layer.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film layer containing a ferromagnetic metal formed by vapor deposition as a recording layer. The present invention relates to the above-mentioned magnetic recording medium containing atoms and having excellent magnetic properties.

[Background technology]

Magnetic recording media with a ferromagnetic metal thin film layer as the recording medium are usually produced by moving a base such as a plastic film along the circumferential side of a cylindrical can installed in a vacuum deposition apparatus.
It is made by vacuum-depositing ferromagnetic metals or alloys containing them on this substrate, with the aim of manufacturing the above-mentioned magnetic recording medium with excellent magnetic properties.
Oblique incidence evaporation is performed and oxygen gas is introduced toward the vapor stream from near the highest incident angle of the vapor stream (JP-A-58-83328, JP-A-58-41442), or from near the lowest incident angle. Introducing oxygen gas toward the steam flow (JP-A-58-83327, JP-A-58
-41443) is presented.

However, the method of performing oblique incidence evaporation and introducing oxygen gas toward the vapor flow from near the highest incident angle of the vapor flow has not yet been able to sufficiently improve the magnetic properties. In recording media, the effect of improving coercive force due to the introduction of oxygen atoms greatly depends on the deposition rate, and as the deposition rate increases, the concentration of oxygen atoms contained in the ferromagnetic metal thin film layer rapidly increases at the interface with the substrate. In addition, the value decreases rapidly as the distance from the substrate increases, and the effect of containing oxygen atoms is not very effective. Under relatively high-speed deposition conditions suitable for mass production, it is difficult to obtain a magnetic recording medium with excellent magnetic properties. difficult. Furthermore, in the method of performing oblique incidence evaporation and introducing oxygen gas toward the vapor flow from the vicinity of the lowest incident angle of the vapor flow,
According to Publication No. 327, it is stated that a magnetic recording medium can be obtained in which the oxygen atoms contained in the ferromagnetic metal thin film layer gradually increase as the distance from the substrate increases. is published in Japanese Unexamined Patent Application Publication No. 1983-
The method disclosed in Japanese Patent Publication No. 83327 does not produce the results described, but instead produces a magnetic recording medium in which oxygen atoms in the ferromagnetic metal thin film layer gradually decrease as the distance from the substrate increases. Since the degree of oxygen gas is smaller than that of the above-mentioned method of introducing oxygen gas toward the vapor flow from near the highest incident angle, the effect of containing oxygen atoms is not diminished in the above case, but it is sufficient. Therefore, the improvement in magnetic properties is still not satisfactory, especially under vapor deposition conditions suitable for mass production. Similarly, it is difficult to obtain a magnetic recording medium with excellent magnetic properties.

[Purpose of the invention]

In view of the current situation where this invention is difficult to achieve, it is an object of the present invention to provide a magnetic recording medium which improves the distribution of oxygen atoms contained in a ferromagnetic metal thin film layer, has extremely small magnetic domains, has high coercive force, and has excellent magnetic properties. It was made for the purpose of

[Summary of the invention]

This invention was made as a result of studying the magnetic properties of a ferromagnetic metal thin film layer and the distribution of oxygen atoms in the depth direction in the ferromagnetic metal thin film layer. In the case where oxygen atoms are contained so as to gradually decrease as they move away from the substrate, oxygen atoms are present in areas where the magnetic interaction is weak due to wide particle spacing caused by the shadow effect of obliquely incident evaporation, that is, near the interface with the substrate. Although a large amount of oxygen atoms are contained, only a small amount of oxygen atoms are contained in areas where the magnetic interaction is strong, where the particles subsequently grow and the particle spacing becomes extremely narrow, that is, near the surface. is not fully demonstrated, and as a result,
Although a high coercive force cannot be obtained and good magnetic properties cannot be obtained, the substrate of the ferromagnetic metal thin film layer that is formed by supplying sufficient oxygen when particle nuclei are formed at the highest incident angle. By appropriately adjusting the content of oxygen atoms in the interface layer with the ferromagnetic metal thin film layer, it is possible to reduce the grain size of the obliquely curved columnar grains that make up the ferromagnetic metal thin film layer, and the magnetic domain can be made smaller. Furthermore, the content of oxygen atoms in the surface layer of the ferromagnetic metal thin film layer is increased by supplying a large amount of oxygen to areas where the magnetic interaction is strong, where the particles subsequently grow and the particle spacing becomes extremely narrow, that is, near the surface. If the content is as large as possible compared to the content in the intermediate layer, a nonmagnetic oxide is formed in the surface layer, suppressing magnetic interaction, and the effect of introducing oxygen atoms is fully exhibited. This was done based on the discovery that the magnetic domains could be further refined and the coercive force could be further improved.

This invention is based on this knowledge, and the surface layer and the interface layer with the substrate of a ferromagnetic gold thin film layer containing a ferromagnetic metal formed on a substrate by strawberry adhesion have more oxygen atoms than the intermediate layer. It is characterized by containing more oxygen atoms in the surface layer than in the interface layer with the substrate, and with this distribution, the oxygen atoms in the ferromagnetic metal thin film layer are By including it, the magnetic domain can be made extremely small and the coercive force can be further improved. Note that the surface layer of the ferromagnetic metal thin film layer here is
In this specification, it refers to the surface area where oxygen atoms bonded to ferromagnetic metals are present due to the supply of oxygen gas, excluding the very surface contamination layer where organic oxygen or oxygen in the air is bonded or attached. The surface layer of the ferromagnetic metal thin film layer in the above refers to a surface layer in which all oxygen atoms bonded to the ferromagnetic metal are present.

The amount of oxygen atoms contained in a ferromagnetic metal thin film layer is the lowest in the intermediate layer, 1.5 to 6.0 times the amount of oxygen atoms contained in the intermediate layer in the surface layer, and the lowest in the intermediate layer in the interface layer with the substrate. The amount of oxygen atoms in the intermediate layer is 1.2 to 3.0 times that of the oxygen atoms contained in the layer, and the oxygen atoms in the intermediate layer are 5 times the amount of oxygen atoms contained in the intermediate layer.
~15%, and the average oxygen atoms in the entire ferromagnetic metal thin film layer account for 10% of the total constituent materials of the ferromagnetic metal thin film layer.
The content of oxygen atoms is preferably within the range of ~30%, and when the content of oxygen atoms is within this range, the coercive force is 800 F or more, and the magnetic domain size is 0.3 μ or less, a high coercive force and an extremely small magnetic domain. can be easily obtained.

On the other hand, if the content of oxygen atoms in the interface layer with the substrate is too small, the size of the core ferromagnetic metal particles will not be sufficiently small, and the amount of oxygen atoms in the surface layer will be too small. If it is too high, oxygen atoms will not be well contained in the interparticle gaps, so a high coercive force will not be obtained and the magnetic domain will not become small.

Further, if the oxygen atom content is too high, it is not preferable because it may become non-magnetic. Note that the entire ferromagnetic metal thin film layer here refers to the entire ferromagnetic metal thin film layer, excluding the very surface contamination layer where organic oxygen or oxygen in the air has bonded or adhered. It refers to the entire ferromagnetic metal thin film layer in which oxygen atoms exist, and in this specification, the entire ferromagnetic metal thin film layer refers to the entire ferromagnetic metal thin film layer in which oxygen atoms bonded to the ferromagnetic metal exist. means.

FIG. 1 shows a cross-sectional view of a vacuum evaporation apparatus used to form the ferromagnetic metal thin film layer of the present invention by blowing oxygen gas directly onto the substrate at least at the lowest incident angle. ■ is a vacuum chamber, and inside this vacuum chamber 1 is an exhaust system 2.
The vacuum is maintained by 3 is a cylindrical can disposed in the center of the vacuum chamber 1, and a base material 4 such as a plastic film is passed from a raw roll 5 through a guide roll 6 along the circumferential side of the cylindrical can 3. It moves and is wound up onto a winding roll 8 via a guide lure. During this time, the ferromagnetic material 10 is heated and evaporated in the ferromagnetic material evaporation source 9 disposed at the bottom of the vacuum chamber 1, facing the base 4 moving along the circumferential side of the cylindrical can 3, and this vapor is evaporated into the cylindrical shape. Due to the action of the deposition prevention plate 11 disposed below the can 3, oblique incidence evaporation is performed on the substrate 4, and at the same time, from the gas introduction pipe 12 disposed between the cylindrical can 3 and the deposition prevention plate 11, , oxygen gas is blown directly onto the base 4 at least at the lowest incident angle portion A. In this way, at least the lowest incident angle part A
As shown in FIG. 2, the gas introduction tube 12 that blows oxygen gas directly onto the substrate 4 has a distance from the gas outlet 12a of the gas introduction tube 12 to the lowest incident angle of the substrate 4. Within 15 cm, it is arranged at a position where the angle α with the vapor flow B directed at the lowest incident angle θ is within 30 degrees, and the gas is blown directly from the gas outlet 12a to at least the lowest incident angle part. The oxygen gas is directly blown from the lowest incident angle part A in the direction of the highest incident angle within a range E not exceeding 10 degrees at an angle β based on the center 0 of the cylindrical can 3. is preferable, and under such conditions, when oxygen gas is blown directly onto the substrate 4 at least at the lowest angle of incidence A, the oxygen gas becomes the largest near the lowest angle of incidence A of the base 4, and at the same time Since the deposition rate is slow in the vicinity of the highest incident angle portion C of the substrate 4, a large amount of oxygen gas filling the vacuum chamber 1 is likely to be taken in in large quantities. As a result, when nuclei of ferromagnetic material particles are generated on the substrate 4 in the vicinity of the highest incident angle part C, particles containing a relatively large amount of oxygen atoms and sufficiently small in size are generated; The particles grow well due to the large amount of oxygen gas near the incident angle part A, and even in the area where the magnetic interaction becomes stronger as the particles grow, oxygen atoms are well contained in the interparticle gaps, resulting in a higher coercive force. A ferromagnetic metal thin film layer with extremely small magnetic domains is formed. In addition, the ferromagnetic metal thin film layer formed in this way contains a large amount of oxygen atoms in the surface layer and the interface layer with the substrate. The balance of magnetization, which tends to be oriented in the perpendicular direction, is also maintained well, with the most oxygen atoms in the surface layer and the least in the intermediate layer (in the most ideal form, the interface layer with the substrate is less than the surface layer and more than the intermediate layer). A magnetic recording medium containing the ferromagnetic metal in the thin film layer and having excellent magnetic properties can be obtained.In particular, in this manufacturing method, at least the base 4
Since a large amount of oxygen gas is blown directly onto the lowest incident angle A of , the minimum angle of incidence of the vapor flow is 60 degrees or less,
Under deposition conditions suitable for mass production at a deposition rate of 1000 people/sec or more, a magnetic recording medium with sufficiently excellent magnetic properties can be obtained, and one with a magnetic domain size of 0.3 μm or less can be easily obtained. The incident angle θ when evaporating ferromagnetic metals or alloys containing them at oblique incidence is preferably set to 60 degrees or less because if it is larger than 60 degrees, the deposition efficiency will deteriorate and it will not be suitable for mass production.

As the substrate, a plastic film made of commonly used polymer moldings such as polyester, polyimide, polyamide, etc. and a metal film made of non-magnetic metal such as copper are used. Examples of materials include ferromagnetic metals such as C01Ni and Fe, alloys or oxides containing at least one of these ferromagnetic metals, and compounds with ferromagnetic metals such as Co-P and Co-N1-P. Anything used for vapor deposition can be used.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Using the vacuum evaporation apparatus shown in FIG. 1, a polyester base film 4 with a thickness of about 10 μm was deposited from a raw roll 5 through a guide roll 6 along the circumferential side of a cylindrical rotating can 3 with a diameter of 60 cm. Cobalt-nickel alloy (weight ratio 8:2)
I made 0 cents. Next, the inside of the vacuum chamber 1 is pumped approximately 5× using the exhaust system 2.
The vacuum was evacuated to 10-B Torr, and the cobalt-2.7 Kel alloy 10 was heated and evaporated to start oblique incidence deposition at a minimum incidence angle of 50 degrees and a deposition rate of 800 people/sec. Oxygen gas was blown onto the polyester base film 4 at the incident angle portion A at various gas pressures to form a ferromagnetic metal M-film layer made of a cobalt-nickel alloy on the polyester base film 4'.

After that, it was cut into a predetermined width to make a large number of magnetic tapes. Note that the gas introduction pipe 12 has its gas outlet 12
The distance from the tip of a to the lowest incident angle part A of the polyester base film 4 centered on the circumferential side of the cylindrical rotating can 3 is 5 cm, and the angle α formed with the vapor flow directed at the lowest incident angle is 5 cm. It was arranged so that the angle was 20 degrees. Further, the oxygen gas blown out from the gas outlet 12a of the gas introduction pipe 12 is directly irradiated from the lowest incident angle part A in the direction of the highest incident angle at an angle β of 10 degrees with respect to the center 0 of the cylindrical rotating can. It was used in this way.

Comparative Example 1 Instead of using the vacuum evaporation apparatus shown in FIG. 1, as shown in FIG. Using a vacuum evaporation device installed between the rotary can 3 and the substrate 4 so that the oxygen gas is not blown directly onto the substrate 4, and which is otherwise similar to the device shown in FIG. A ferromagnetic metal thin film layer was formed in the same manner as in Example 1 except that the gas was blown toward the vapor flow B of the ferromagnetic material at various pressures as in Example 1 as shown by the arrows, He made a large number of magnetic tapes.

Comparative Example 2 Instead of using the vacuum evaporation apparatus shown in FIG. 1, as shown in FIG. Using a vacuum evaporation apparatus similar to the apparatus shown in FIG. 1, which was placed nearby so that the oxygen gas was not blown directly onto the substrate 4, the oxygen gas was applied as shown by the arrow. A ferromagnetic metal thin film layer was formed in the same manner as in Example 1, except that the gas pressure was blown toward the stem air stream B of the ferromagnetic material at various pressures as in Example 1, and a large number of magnetic tapes were I made it.

In the examples and comparative examples, the gas pressure of oxygen gas was set to 2.
The concentration distribution of oxygen atoms in the ferromagnetic metal thin film layer was examined using an Auger electron spectrometer for the magnetic tape obtained by keeping X10-'Torr constant. Figure 5 shows the results in a graph. Graph A is the magnetic tape obtained in Example 1, graph B is the magnetic tape obtained in Comparative Example 1, and graph C is the magnetic tape obtained in Comparative Example 2. This figure shows the concentration distribution of oxygen atoms in the ferromagnetic metal thin film layer of the magnetic tape. As is clear from these graphs, the concentration distribution of oxygen atoms in the ferromagnetic metal thin film layer of the magnetic tapes obtained in Comparative Examples 1 and 2 gradually decreases as the distance from the substrate increases. The concentration distribution of oxygen atoms in the ferromagnetic metal thin film layer of the magnetic tape obtained by this invention is the highest in the surface layer, the lowest in the intermediate layer, and the interface layer with the substrate contains more oxygen atoms than the intermediate layer and less than the surface layer. I can see that it is being done.

In addition, coercive force and magnetic domain size were measured for a large number of magnetic tapes obtained in Examples and Comparative Examples. 6th
The figure is a graph showing the relationship between the coercive force measured in this way and the average oxygen content of the entire ferromagnetic metal thin film layer. , graph B shows the magnetic tape obtained in Comparative Example 1, and graph C shows the magnetic tape obtained in Comparative Example 2. Further, FIG. 7 is a graph showing the relationship between the magnetic domain size and the average oxygen content of the entire ferromagnetic metal thin film layer, where graph A is the magnetic tape obtained in Example 1, and graph B is the magnetic tape obtained in Comparative Example 1. Graph C shows the magnetic tape obtained in Comparative Example 2.

〔Effect of the invention〕

As is clear from the graphs in FIGS. 6 and 7, the magnetic tape obtained by this invention (graph A) has a higher coercive force than the conventional magnetic tape (graphs B and C). The magnetic domain size is small, which indicates that the magnetic recording medium obtained by the present invention has excellent magnetic properties. In addition, with conventional magnetic tape, even if the coercive force is high, 7
00 oersted or less, and the magnetic domain size is at least 0.5μ at the smallest. However, in the magnetic tape of the present invention, the coercive force exceeds 800 oersted and reaches loo'0 oersted, and the magnetic domain size is 0.5μ or more. It can be seen that one with a diameter of .3μ or less can be easily obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of a vacuum evaporation apparatus used to carry out the manufacturing method of the present invention, Fig. 2 is an enlarged sectional view of the same main part, and Fig. 3 is a schematic sectional view of a vacuum evaporation apparatus used to carry out the conventional manufacturing method. FIG. 4 is a schematic cross-sectional view of a vacuum evaporation device in the same place, and FIG. An explanatory diagram showing the distribution of atoms, FIG. 6 is a diagram showing the relationship between the coercive force and the average oxygen content of the magnetic tapes obtained in this invention and Comparative Examples 1 and 2, and FIG. 2 is a relationship diagram between the magnetic domain size and average oxygen content of the magnetic tape obtained in Example 2. FIG. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 0 -10 20 30 Average oxygen content (atomic %) Commissioner of the Japan Patent Office Kazuo Wakasugi) Crotch 1. Display of case Patent application (5) 2 filed on January 26, 1980, title of invention f7- IL75f' magnetic recording medium 3, person making amendment Relationship to case Patent applicant address Ushitora, Ibaraki City, Osaka Prefecture - 1-88 Chome Name (
581) Hitachi Maxell Co., Ltd. Representative Atsushi Nagai 4 Address of agent 2-41 Bakoro-cho, Higashi-ku, Osaka "Claims" column of the specification, [6, Contents of amendment (1) Specification The scope of claims from page 1 to page 2 of the book is amended as shown in the attached sheet. (2) "Distribution state of oxygen atoms contained" in the second line of page 5 of the specification is corrected to "concentration distribution of oxygen atoms in". (3) On page 5, line 9 of the specification, change ``1 minute, cloth'' to ``
"concentration distribution". (4) "Content of oxygen atoms" on page 6, line 3 of the specification is corrected to "concentration of 1 oxygen atom." (5) On page 6 of the specification, from line 10 to line 11, "If the content of oxygen atoms is increased as much as possible compared to the content in the intermediate layer" is changed to "concentration of oxygen atoms." (6) From page 6 of the specification, second line from the bottom to page 7 of the specification, line 4 from the bottom. ``Surface layer and substrate・
By containing ``, the oxygen atom concentration in the surface layer and the interface layer with the substrate is made higher than that in the intermediate layer, and the concentration of oxygen atoms in the surface layer is increased. It is characterized by having an oxygen atom concentration higher than that of the interface layer with the substrate, and with such a concentration distribution, the ferromagnetic metal thin ji! By containing oxygen atoms in layer iii, the correction is made as follows. (7) In one ferromagnetic metal thin film layer from page 7 of the specification, line 7 from the bottom to page 8 of the specification, line 3... ...If it is within this range, the oxygen atom concentration in the ferromagnetic metal thin film layer is the lowest in the intermediate layer, and the surface layer is 1.5 to 6.0 of the oxygen atom concentration in the intermediate layer. The amount is 1.2 to 3.0 times the oxygen atom concentration in the intermediate layer at the interface layer with the substrate, and the oxygen atom concentration in the intermediate J-made part is the sum of the total number of atoms constituting the intermediate layer. Against 5~
The oxygen atom concentration in the entire ferromagnetic metal thin film layer is preferably within the range of 10 to 30% of the total number of constituent atoms in the entire ferromagnetic metal thin film layer. If the atomic concentration is within this range, it is corrected as follows. (8) On page 8 of the specification, from line 6 to line 12, it says “In response to this...
If the concentration of oxygen atoms in the interface layer with the substrate is too low, the size of the ferromagnetic metal particles that form the nucleus will not become sufficiently small, and the concentration of oxygen atoms in the surface layer will decrease. If the concentration of oxygen atoms is too low, oxygen atoms will not be properly contained in the interparticle gaps, so a high coercive force will not be obtained and the magnetic domain will not become small.Furthermore, if the oxygen atom concentration is too high, the material will become non-magnetic. (9) “Surface layer and substrate... old...” from line 6 to line 12 on page 11 of the specification
・The higher the oxygen atom concentration in the surface layer and the interface layer with the substrate, the higher the oxygen atom concentration between the surface layer and the interface layer, the better the magnetization balance is. The oxygen atom concentration is highest in the surface layer, lower in the intermediate layer, and lower in the interface layer with the substrate than the surface layer and higher than the intermediate layer.'' 00) On page 16 of the specification, from the 4th line to the 5th line, "contained so as to gradually decrease by 1" is corrected to "gradually decrease". (11) It can be seen that on page 16 of the specification, line 9, "It is found that it is contained." is set to 1. ” he corrected. (12) "Average oxygen content j" from line 13 to line 14 on page 16 of the specification and "average oxygen content" from line 18 to line 19 [-average oxygen concentration ” he corrected. (13) "Average oxygen content" in the 7th and 9th lines of Specification 1, page 18, is corrected to "average oxygen concentration." (14) Figures 6 and 7 of the drawings will be corrected as shown in the attached sheet. 7. List of attached documents (1) Document stating the claims 1 copy (2) Figures 6 and 7 of the drawings 1 Claim 1: Ferromagnetic metal formed on a substrate by vapor deposition A magnetic recording medium 2 characterized in that the surface layer and the interface layer between the thin film layer and the substrate are the intermediate layer m13, Claim 1, which emphasizes the direct change of N■ oxygen atoms from the degree of difference between oxygen atoms in the interfacial layer with the substrate.
In the magnetic recording medium 3 described in Section 3, the surface layer of the ferromagnetic metal thin film layer has a low oxygen atom degree of 1 degree and an intermediate oxygen atom degree of 1.5 to 6 degrees.
0 times the amount, and the interfacial layer with the substrate has low oxygen atomic imaging once 2,
The magnetic recording medium 4 according to claim 2, the amount of which is 1.2 to 3.0 times the intermediate oxygen atom difference degree, the intermediate layer oxygen atoms 1111L of the ferromagnetic metal thin II layer.
is 5 to 15% of the total number of U atoms in the intermediate layer - about
In one magnetic metal thin film layer, the total thickness of the magnetic metal thin film layer is
The magnetic recording medium according to Claims 1 to 3, wherein the oxygen atomic difference in U'go 1Q is 10 to 30%. Figure 0 10 20 30 Average oxygen concentration (atomic%)

Claims (1)

[Claims] 1. Magnetic recording characterized in that the surface layer and the interface layer with the substrate of a ferromagnetic metal thin film layer formed by vapor deposition on the substrate contain more oxygen atoms than the intermediate layer. Medium 2: Magnetic recording medium 3 according to claim 1, in which the surface layer of the ferromagnetic metal thin film layer contains more oxygen atoms than the interface layer with the substrate. The amount of oxygen atoms contained in the surface layer of the layer is 1.5 to 6.0 times that of the oxygen atoms contained in the intermediate layer, and the amount of oxygen atoms contained in the interface layer with the substrate is 1.5 to 6.0 times that of the oxygen atoms contained in the intermediate layer. In the magnetic recording medium 4 according to claim 2, the amount of oxygen atoms contained in the intermediate layer of the ferromagnetic metal thin 115ti layer is 1.2 to 3.0 times the amount of oxygen atoms contained in the intermediate layer portion. 5 to 15% of all atoms of
and the oxygen atoms contained in the entire ferromagnetic metal thin film layer account for 10 to 30% of the total atoms.
Magnetic recording medium according to items 1 to 3