JPH0573879A - Magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE:To provide the magnetic recording medium having the structure to prevent a head clash and further prevent the sticking of a magnetic head to the magnetic recording medium and the process for production thereof. CONSTITUTION:This magnetic recording medium has circular cone-shaped projecting parts on the surface of a magnetic recording film 2 provided directly or via a substrate film on a substrate. A protective film 5 of carbon, etc., is formed on the extreme surface. This magnetic recording medium can be formed by providing films of Ti, etc., partially varying in etching resistant characteristics and etching the films from above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium widely used as a main memory of an electronic computer or the like which handles digital data, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional magnetic recording medium having a sputtered thin film has carbon or the like on its surface in order to prevent the magnetic recording medium from colliding with a magnetic head for recording / reproducing information and destroying the magnetic recording film. Was provided with a protective film made of a relatively hard material. In addition, in order to prevent the magnetic head from sticking to the magnetic head due to water adsorbed on the surface of the magnetic recording medium, a so-called textured magnetic recording medium having minute grooves on the surface has been used. .. Further, a lubricant having a buffering effect at the time of collision has been applied to the surface thereof. Note that the technology relating to these is described in US Reissue Patent 32,464 and US Patent 4,73.
5,840.

[0003]

The magnetic recording medium is designed to have a high recording density as one of the performance improvements.
Therefore, the distance between the magnetic recording medium and the magnetic head is getting closer. Then, the above-mentioned conventional technique has a problem that an accident due to a so-called head crash, in which the magnetic head and the magnetic recording medium come into contact with each other, easily occurs. An object of the present invention is to provide a magnetic recording medium capable of preventing the magnetic recording film from being damaged by a head crash and also preventing so-called head adhesion, which is a phenomenon in which a magnetic head and a magnetic recording medium are adhered to each other. A second object of the present invention is to provide a method for manufacturing such a magnetic recording medium.

[0004]

The above object is (1) in a magnetic recording medium comprising a substrate, a magnetic recording film provided on the substrate, and a protective film provided on the magnetic recording film,
(2) A magnetic recording medium having a substantially conical convex portion on the surface of the magnetic recording film, (2) In the magnetic recording medium according to the above-mentioned 1, a half of the concave portion formed by the conical convex portion. A magnetic recording medium having an average value range of 5 nm or more and 200 nm or less, (3) above 1
Or the magnetic recording medium according to 2, wherein the average value of the distance between the centers of the recesses formed by the conical protrusions is in the range of 5 nm to 600 nm. ) The magnetic recording medium as described in any one of 1 to 3 above, characterized in that an underlayer film is provided between the substrate and the magnetic recording film, (5) any one of 1 to 4 above (1) The magnetic recording medium according to any one of (1) to (5) above, wherein the magnetic recording film is a laminated film of at least two layers made of materials having different coercive forces. In the magnetic recording medium as described above, the protective film is carbon, (7) In the magnetic recording medium as described in any one of 1 to 6, the surface of the magnetic recording medium is lubricated. Agent Is achieved by a magnetic recording medium, characterized by.

The second object is (8) a step of forming a magnetic recording film on a substrate, a step of forming a thin film having a partially different etching resistance on the magnetic recording film, and etching the thin film. A method of manufacturing a magnetic recording medium, comprising: forming a recess in a thin film, further continuing etching to form a recess in the magnetic recording film, and forming a protective film on the magnetic recording film. (9) In the method of manufacturing a magnetic recording medium as described in 8 above, the thin film is a polycrystalline body, and grain boundaries of crystal grains thereof are portions that are easily etched. , (10)
In the method of manufacturing a magnetic recording medium according to the above 8 or 9,
The thin film is made of Ti, Al, Si, V, Cr, Mn, F.
e, Co, Ni, Cu, Zn, Ge, Zr, Nb, M
o, Tc, Ru, Rh, Pd, Ag, In, Sn, S
b, Te, Hf, Ta, W, Re, Os, Ir, Pt,
(11) A method for manufacturing a magnetic recording medium, which is a film made of a material containing at least one selected from the group consisting of Au, Tl, Pb, Bi and C as a main component. In the method for producing a magnetic recording medium according to any one of the aspects, the concave portion formed in the magnetic recording film has an average half-width of 5 nm or more and 200 nm or less. Method, (12)
In the method of manufacturing a magnetic recording medium according to any one of 8 to 11 above, the recess formed in the magnetic recording film is
The average value of the distance between the center and the adjacent recess is 5n.
The method for producing a magnetic recording medium is characterized by being in the range from m to 600 nm, (13) In the method for producing a magnetic recording medium according to any one of 8 to 12, the etching is ion etching. (14) In the method for manufacturing a magnetic recording medium according to any one of (8) to (13) above,
The magnetic recording film is formed on a base film after the base film is formed on the substrate. (15) A substantially conical projection on the substrate And a step of forming a magnetic recording film having a substantially conical projection on the thin film and a step of forming a protective film on the magnetic recording film. (16) In the method of manufacturing a magnetic recording medium according to the above (15), the thin film is Ti,
Al, Si, V, Cr, Mn, Fe, Co, Ni, C
u, Zn, Ge, Zr, Nb, Mo, Tc, Ru, R
h, Pd, Ag, In, Sn, Sb, Te, Hf, T
a, W, Re, Os, Ir, Pt, Au, Tl, Pb,
A method for producing a magnetic recording medium, which is a film made of a material whose main component is at least one selected from the group consisting of Bi and C, (17) The production of the magnetic recording medium as described in 15 or 16 above. In the method, in the concave portion formed on the magnetic recording film by the convex portion, the average half-width is 5n.
m is a range of 200 nm or less, and (18) the method of manufacturing a magnetic recording medium according to any one of 15 to 17, wherein the convex portion forms a magnetic recording film. The average value of the distance between the center of the formed recess and the center of the adjacent recess is 5 nm or more 6
In the method for producing a magnetic recording medium according to any one of the items 15 to 18, the thin film is formed on the substrate. This is achieved by a method for manufacturing a magnetic recording medium, which comprises performing the formation on the base film after forming the base film.

In the present invention, the substantially conical convex portion is not limited to a circular shape in plan view, and may be a polygonal shape or an elliptical shape. The upper part may be flat and close to a cylinder.

Various methods can be used for providing the convex portion on the surface of the magnetic recording medium. For example, it is possible to use a method in which the recording medium is made into a fine polycrystalline state and is etched from the grain boundaries. The etching is preferably reactive ion etching (sputter etching with reactive gas or inert gas, ion beam etching, ion milling). Or as a thin film for a mask,
A thin polycrystalline film is provided, this thin film is etched, and the recesses are formed by utilizing the fact that the etching speed of the grain boundaries is faster than others, and further, the fine irregularities are formed on the surface of the magnetic recording film through this thin film. Can also be formed. As a material of the thin film used for the mask, a method of forming a cohesive metal or a metal having a high melting point by vapor deposition or sputtering is effective.

The magnetic recording medium of the present invention may be provided after forming a non-magnetic metal underlayer on the substrate, or may be directly formed on the substrate without providing the underlayer. When providing the base film, it is preferable to use Cr or a compound containing Cr, and the thickness thereof is preferably in the range of 20 nm to 500 nm. It is preferable to use carbon as the protective film. The thickness is preferably in the range of 5 nm to 50 nm.

[0009]

By providing minute irregularities on the surface of the magnetic recording medium, it is possible to prevent minute dust, which causes a head crash, from entering the concave portion and causing a head crash.
Improved reliability can be expected. Further, since the interface between the magnetic head and the magnetic recording film is not flat, the phenomenon that the magnetic head and the magnetic recording film adhere to each other, that is, head sticking can be prevented. When a lubricant is used, the lubricant is trapped in the recesses and gradually bleeds out on the surface to protect the magnetic recording film.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 First, a method of manufacturing a magnetic recording medium of this example will be described.
As shown in FIG. 3, a Cr film as a base film 3 having a thickness of about 150 nm is formed on the disk-shaped glass substrate 4 by magnetron sputtering to correct macroscopic unevenness of the substrate and to improve the magnetic characteristics of the magnetic recording film. Formed, and having a thickness of about 30 nm Co-12.5 at% Cr-2.5 at
A magnetic recording film 2 made of% Ta was formed, and a Ti film having an average thickness of about 20 nm was formed as a thin film 1 for a mask. This Ti film is a granular polycrystalline film, the plan view of which is shown in FIG. 1, and has a partially different ion etching resistance characteristic. The polycrystal of Ti is formed so as to overlap with the polycrystal constituting the magnetic recording film thereunder, and the grain size (average value, hereinafter the same) of the Ti polycrystal is about 50 nm. It was almost equal to the particle size.

Next, this disk was treated with argon gas,
Sputter etching was performed at a gas pressure of 10 mTorr. At this time, the portions of the thin film 1 for a mask between the crystals were particularly etched, and the thin film 1 became an island. By further continuing the etching, the magnetic recording film 2 in the portion between the Ti islands was etched. At this time, the thin film 1 remaining in an island shape is gradually etched and thinned, but the etching was completed when a small amount of Ti islands remained or disappeared completely. As a result, the magnetic recording film 2 has irregularities as shown in a part of its cross section in FIG. 2, and the depth of the concave portions is at least larger than 1/2 of the crystal grain size constituting the magnetic recording film. Part of the recess reaches the underlayer film 3. At this time, the average film thickness of the magnetic recording film 2 was 25 nm. Note that argon-oxygen gas may be used for etching, or CCl ₂ F ₂ or the like may be added to the argon-oxygen gas. After etching, as shown in FIG. 4, a carbon thin film having a thickness of about 10 nm, which is the protective film 5, was further formed by magnetron sputtering.

Information was recorded / reproduced on / from the magnetic recording medium manufactured as described above. The magnetic recording medium was rotated at 3600 rpm, the reference signal was recorded by the recording magnetic head, and the signal was obtained by the reproducing magnetic head. As a result, the device S / N 2.2 was obtained. At this time, similar results were obtained even when the same head was used instead of separate heads.

An experiment was conducted in which the crystal grain size of the Ti film was changed by changing the conditions for forming the Ti film and the heat treatment conditions after the formation. The substrate temperature during Ti film formation is usually 100 ° C. to 250 ° C.
It is preferable to carry out at a temperature of ℃, the higher the temperature, the larger the crystal grain size. Sputter etching was performed using these films as masks to change the shape of the irregularities of the magnetic recording film. As a result, the full width at half maximum of the recess formed in the magnetic recording film (width at half maximum depth, average value, the same applies hereinafter) is 5
In the range of 5 nm or more and 200 nm or less, and the distance between the recesses (the distance between the centers of two adjacent recesses, the average value, the same applies below) is 5 nm or more and 600 nm or less, the magnetic head may have sticking or head crashes compared to conventional disks. The frequency of accidents has decreased. In addition, the full width at half maximum of the recess is 10 nm or more 1
50 nm or less, the distance between the recesses is 10 nm or more and 450
In the range of nm or less, the effect is further remarkable and the reliability is remarkably improved.

A magnetic recording medium having two layers of magnetic recording film may be manufactured. This magnetic recording medium is performed up to formation of a base film in the same manner as described above, and then, as shown in FIG.
5 nm Co-12.5 at% Cr-2.5 at% Ta
The first magnetic recording film 16 made of Co and having a thickness of 15 nm
A second magnetic recording film 17 made of 12 at% Cr-8 at% Pt is formed, and as in the above, the unevenness is formed in the two layers of the magnetic recording film by using a thin film for a mask. Then, a protective film (not shown) was formed to obtain a magnetic recording medium having substantially the same effect as above. The output was increased by forming the magnetic recording film by laminating two layers of materials having different saturation magnetization and coercive force.

Further, the magnetic recording medium of this embodiment may be coated with a lubricant on its surface. When a compound containing silicon was applied as a lubricant to the magnetic recording medium obtained by the above method and recording / reproducing of information similar to the above was performed, almost the same effect was observed.

Another film forming method will be described. A base film was formed in the same manner as above, and then a Ti film having an average thickness of about 5 nm was formed as a thin film 1 on the surface of the base film. The Ti film has an island shape as shown in FIG. 8 when it has the above thickness. When a magnetic recording film is formed on this island-shaped Ti film by vacuum vapor deposition, the magnetic recording film selectively grows on the island-shaped Ti film over the entire surface in the initial stage of vapor deposition, and irregularities are formed on the surface. We could obtain the magnetic recording film we had. The formation of the protective film was carried out in the same manner as above to manufacture a magnetic recording medium. This magnetic recording medium has almost the same recording / reading characteristics and reliability as above.

A part or all of Ti used as the mask thin film 1 is made of Al, Si, V, Cr, Mn, Fe,
Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, T
c, Ru, Rh, Pd, Ag, In, Sn, Sb, T
e, Hf, Ta, W, Re, Os, Ir, Pt, Au,
Substantially similar characteristics were obtained even when substituting at least one selected from the group consisting of Tl, Pb, Bi and C as a main component. Of these, Ti, V, Cr, Fe,
Co, Ni, Zr, Nb, Tc, Ru, Rh, Pd, H
Especially preferred are f, Ta, W, Re, Os, Ir, Pt and C.

Part or all of the Ti used as the island-shaped thin film 1 is Al, Si, V, Cr, Mn, Fe, C.
o, Ni, Cu, Zn, Ge, Zr, Nb, Mo, T
c, Ru, Rh, Pd, Ag, In, Sn, Sb, T
e, Hf, Ta, W, Re, Os, Ir, Pt, Au,
Substantially similar characteristics were obtained even when substituting at least one selected from the group consisting of Tl, Pb, Bi and C as a main component.

When forming the above-mentioned base film and magnetic recording film, FIG.
When the Cr target 13 and the CoCrTa target 14 are lined up using the in-line sputtering apparatus shown in FIG. 1 and the substrate 4 is moved in the sputtering chamber 15 while moving in the direction of the arrow C, one sputtering chamber A laminated film of a base film and a magnetic recording film can be easily obtained. The composition continuously changes between these layers. With such a magnetic recording medium, almost the same recording / reading characteristics and reliability were obtained.

Example 2 A magnetic recording medium was formed in the same manner as in Example 1, but the magnetic recording film was Co-20 at having perpendicular magnetic anisotropy.
A film of% Cr was used. As shown in FIG. 6, a Fe—Ni film having a film thickness of 500 nm was formed as the base film 3 on the same substrate as in Example 1 by magnetron sputtering.
A 100 nm-thick Co-20 at% Cr film was formed thereon as a first magnetic recording film 16, and then a Ti film was formed on the surface thereof as a thin film (not shown) for a mask.
In the same manner as above, on the surface of the magnetic recording film 16, the film thickness of about 1
After forming the unevenness having the concave portion with the depth of / 3, the second
Magnetic recording film 17 with a thickness of 50 nm of Co-12 at
A film of% Cr-8 at% Pt was formed. Further Example 1
A protective film (not shown) was laminated in the same manner as in.

Information was recorded / reproduced on / from the magnetic recording medium formed as described above. The magnetic recording medium was rotated at 3600 rpm, the reference signal was recorded by the recording magnetic head, and the signal was obtained by the reproducing MR magnetic head. As a result, the device S / N3.6 was obtained. Also,
The frequency of accidents such as magnetic head sticking and head crashes is lower than with conventional disks.

Needless to say, other materials may be used for the magnetic recording layer. As an example, the second
On the magnetic recording film 17 of Co-12 at% Cr-3 at% T
The film of a was used, but the results were almost the same.

Example 3 In substantially the same manner as in Example 1, as shown in FIG. 3, a Cr layer having a thickness of about 200 nm was first formed as a base film 3 on the glass substrate 4 by magnetron sputtering. On top of that, Co-12.5 at% Cr-4.0 having a thickness of about 40 nm.
A magnetic recording film 2 made of at% Ta was formed, and a Ti film having an average thickness of about 5 nm was formed as a thin film 1 for a mask. The Ti film has an island shape as shown in FIG. 8 when it has the above thickness.

Next, an argon gas containing 20 mol% of oxygen was used to perform reverse sputtering (ion etching) at a gas pressure of 20 mTorr to etch the magnetic recording film 2 in the portion between the Ti islands. At this time, the Ti islands are gradually etched and become smaller, but the etching is completed before the Ti islands are completely removed. As a result, the magnetic recording film 2 is formed with a concave portion as shown in FIG.
Part of it reaches the base film 3. At this time, the average thickness of the magnetic recording film was about 35 nm. Etching may be continued until the Ti islands are exhausted. Pure argon gas may be used instead of argon-oxygen gas, and CCl ₂ F ₂ or the like may be added to argon-oxygen.

After etching, a carbon layer having a thickness of about 10 nm as a protective film was further formed by magnetron sputtering. Finally, a magnetic recording film and the like were formed on the back surface of the substrate in the same manner. As a result of observing the cross section of the magnetic recording medium with a scanning electron microscope, it was possible to confirm the uneven shape formed on the magnetic recording film by ion etching. Recording and reproduction of information on the disk formed as described above were performed in the same manner as in Example 1. Recording similar to that of Example 1
Readout characteristics and reliability were obtained.

An experiment was conducted in which the shape of the recess of the magnetic recording film was changed by changing the conditions for forming the Ti film, which is the thin film 1 for the mask, and the heat treatment conditions after the formation. The preferable half-value width of the recess and the value of the space between the recesses were almost the same as in Example 1.

As another film forming method, as in the case of Example 1, an island-shaped Ti film is formed on the surface of the base film 3, and a magnetic recording film is formed thereon by vacuum evaporation. In addition, a magnetic recording film having irregularities on the surface could be obtained. The protective film was formed in the same manner as in Example 1, and the same recording / recording was performed.
A magnetic recording medium having read characteristics and reliability was obtained.

Although the disk-shaped magnetic recording medium has been described in the above embodiments, the present invention can be applied to other magnetic recording media such as a tape and a card.

[0030]

As described above, according to the present invention, the head crush can be prevented by providing the minute projections on the surface of the magnetic recording medium. Even if a minute dust that would cause a crash were to enter, it traps between the irregularities and keeps the atmosphere of the disk head in a clean space.

Further, the concave portion on the surface of the magnetic recording medium can prevent adhesion with the magnetic head. A conventional magnetic recording medium by texture processing may not have a recess at the portion of the magnetic head that contacts the slider, but the magnetic recording medium of the present invention has a recess at the portion of the magnetic head that contacts the slider. The prevention effect is better.

Therefore, it is possible to cope with the low flying height of the magnetic head of 0.1 μm or less, which is essential for increasing the density of the magnetic disk device, and the reliability at the time of recording / reproducing information is greatly improved. ..

[Brief description of drawings]

FIG. 1 is a plan view of a polycrystalline Ti film that is a thin film for a mask used in a method of manufacturing a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of the magnetic recording medium for explaining the manufacturing process of the magnetic recording medium of the embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of the magnetic recording medium for explaining the manufacturing process of the magnetic recording medium of the embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a magnetic recording medium according to an embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of a sputtering apparatus having a plurality of targets.

FIG. 6 is a partial cross-sectional view of a magnetic recording medium of another embodiment of the present invention.

FIG. 7 is a partial cross-sectional view of a magnetic recording medium according to still another embodiment of the present invention.

FIG. 8 is a plan view of an island-shaped thin film used in a method of manufacturing a magnetic recording medium according to an example of the present invention.

FIG. 9 is a partial cross-sectional view of a magnetic recording medium according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Thin film 2 Magnetic recording film 3 Underlayer film 4 Substrate 5 Protective film 13, 14 Target 15 Sputtering chamber 16 First magnetic recording film 17 Second magnetic recording film C Arrow (moving direction of substrate)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Inaba 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Central Research Laboratory, Hitachi, Ltd. (72) Motoyasu Terao 1-280 Higashi Koikeku Ku, Kokubunji, Tokyo Hitachi Ltd. Central research institute

Claims (19)

[Claims] 1. A magnetic recording medium comprising a substrate, a magnetic recording film provided on the substrate, and a protective film provided on the magnetic recording film, wherein the surface of the magnetic recording film has a substantially conical shape. A magnetic recording medium having a convex portion. 2. The magnetic recording medium according to claim 1, wherein the average value of the half-value widths of the concave portions formed by the conical convex portions is in the range of 5 nm to 200 nm. 3. The magnetic recording medium according to claim 1, wherein an average value of distances between centers of the concave portions formed by the conical convex portions is 5 nm or more and 600 nm or less. And a magnetic recording medium. 4. The magnetic recording medium according to claim 1, further comprising a base film between the substrate and the magnetic recording film. 5. The magnetic recording medium according to any one of claims 1 to 4, wherein the magnetic recording film is a laminated film of at least two layers of materials having different coercive forces. .. 6. The magnetic recording medium according to any one of claims 1 to 5, wherein the protective film is carbon. 7. The magnetic recording medium according to claim 1, further comprising a lubricant on the surface of the magnetic recording medium. 8. A step of forming a magnetic recording film on a substrate, a step of forming a thin film having partially different etching resistance on the magnetic recording film, the thin film being etched to form a recess in the thin film, A method of manufacturing a magnetic recording medium, further comprising: a step of continuing the etching to form a recess in the magnetic recording film; and a step of forming a protective film on the magnetic recording film. 9. The method of manufacturing a magnetic recording medium according to claim 8, wherein the thin film is a polycrystal, and grain boundaries of crystal grains thereof are portions easily etched. Production method. 10. The method of manufacturing a magnetic recording medium according to claim 8, wherein the thin film is Ti, Al, Si, V,
Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Z
r, Nb, Mo, Tc, Ru, Rh, Pd, Ag, I
n, Sn, Sb, Te, Hf, Ta, W, Re, Os,
A method of manufacturing a magnetic recording medium, which is a film made of a material containing at least one selected from the group consisting of Ir, Pt, Au, Tl, Pb, Bi and C as a main component. 11. The method of manufacturing a magnetic recording medium according to claim 8, wherein the recess formed in the magnetic recording film has an average half-width of 5 nm or more.
A method of manufacturing a magnetic recording medium, which is in a range of 0 nm or less. 12. The method for manufacturing a magnetic recording medium according to claim 8, wherein the recess formed in the magnetic recording film has an average value of the distance between the center of the recess and the center of the recess adjacent thereto. Is in the range of 5 nm or more and 600 nm or less. 13. The method of manufacturing a magnetic recording medium according to claim 8, wherein the etching is performed.
A method for manufacturing a magnetic recording medium, which is ion etching. 14. The method of manufacturing a magnetic recording medium according to claim 8, wherein the magnetic recording film is formed on the substrate after forming the underlying film on the substrate. And a method of manufacturing a magnetic recording medium. 15. A step of forming a thin film having a substantially conical convex portion on a substrate, a step of forming a magnetic recording film having a substantially conical convex portion on the thin film, and the magnetic layer. A method of manufacturing a magnetic recording medium, comprising a step of forming a protective film on a recording film. 16. The method of manufacturing a magnetic recording medium according to claim 15, wherein the thin film is made of Ti, Al, Si, V or C.
r, Mn, Fe, Co, Ni, Cu, Zn, Ge, Z
r, Nb, Mo, Tc, Ru, Rh, Pd, Ag, I
n, Sn, Sb, Te, Hf, Ta, W, Re, Os,
A method of manufacturing a magnetic recording medium, which is a film made of a material containing at least one selected from the group consisting of Ir, Pt, Au, Tl, Pb, Bi and C as a main component. 17. The method of manufacturing a magnetic recording medium according to claim 15, wherein the concave portion formed in the magnetic recording film by the convex portion has an average half-width of 5 nm or more and 200 nm or more.
A method of manufacturing a magnetic recording medium, which is in the range of nm or less. 18. The method of manufacturing a magnetic recording medium according to claim 15, wherein the concave portion formed in the magnetic recording film by the convex portion is a distance between the center of the concave portion and the center of the adjacent concave portion. The average value of is in the range of 5 nm or more and 600 nm or less. 19. The method of manufacturing a magnetic recording medium according to claim 15, wherein the thin film is formed on the base film after forming the base film on the substrate. And a method for manufacturing a magnetic recording medium.