JP2002197643A - Magnetic recording medium, method of manufacturing for the same and magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is capable of recording and reproducing high-density information by improving recording and reproduc ing characteristics and a method for manufacturing the same and a magnetic recording and reproducing device. SOLUTION: The surface of a nonmagnetic substrate 1 is provided with a soft magnetic ground surface film 2 consisting of a soft magnetic material, an alignment control film 3 which controls the alignment characteristic of the film right thereabove, a vertical manufacturing film 4 of which the axis of easy magnetization is aligned mainly vertically to the substrate and a protective film 5. Part or the whole of the surface of the soft magnetic ground surface film 2 on the alignment control film 3 is oxidized and the thickness of the oxidized film 2a is >=0.1 to <3 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium, a method for manufacturing the same, and a magnetic recording / reproducing apparatus using the magnetic recording medium.

[0002]

2. Description of the Related Art Most magnetic recording media currently on the market are in-plane magnetic recording media in which the axis of easy magnetization in a magnetic film is mainly oriented horizontally to a substrate. In such an in-plane magnetic recording medium, when the recording density is increased, the bit volume becomes too small, and the recording / reproducing characteristics may be deteriorated due to the thermal fluctuation effect. Further, when the recording density is increased, the medium noise increases due to the influence of the demagnetizing field at the recording bit boundary.
In contrast, a so-called perpendicular magnetic recording medium in which the easy axis of magnetization in the magnetic film is mainly oriented vertically, even when the recording density is increased, the influence of the demagnetizing field at the bit boundary is small, and the boundary is sharp. Since the recording magnetic domain is formed, it is possible to reduce noise, and even if the bit volume is relatively large, it is possible to increase the recording density, so it has a strong thermal fluctuation effect. A medium structure suitable for magnetic recording has been proposed. JP-A-7-73429 discloses that
There has been proposed a magnetic recording medium characterized by providing an oxide layer having excess oxygen and poor crystallinity. It is considered that the thickness of the oxide layer is preferably 3 to 10 nm. However, providing an oxide layer having a thickness of 3 nm or more significantly deteriorates the orientation of the perpendicular magnetic film, significantly deteriorates the thermal fluctuation resistance, and increases the surface roughness of the soft magnetic underlayer. For this reason, it is difficult to reduce the flying height of the magnetic head, and it is difficult to increase the recording density.

[0003]

In recent years, there has been a demand for further increasing the recording density of a magnetic recording medium, and in order to use a single-pole head having excellent writing capability for a perpendicular magnetic film, a perpendicular magnetic recording layer has been required. A magnetic recording medium has been proposed in which a layer made of a soft magnetic material called a backing layer is provided between the film and the substrate to improve the efficiency of the magnetic flux between the single-pole head and the magnetic recording medium. I have. However, even when a magnetic recording medium provided with the above-mentioned backing layer is used as a conventional magnetic recording medium, the recording / reproducing characteristics are not satisfactory, and a magnetic recording medium excellent in these characteristics has been demanded. The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic recording medium capable of recording and reproducing high-density information by improving recording and reproducing characteristics, a method for manufacturing the same, and a magnetic recording and reproducing apparatus. I do.

[0004]

In order to achieve the above object, the present invention employs the following constitution. The magnetic recording medium of the present invention has a soft magnetic underlayer made of at least a soft magnetic material on a non-magnetic substrate, an orientation control film for controlling the orientation of the film immediately above, and an axis of easy magnetization mainly perpendicular to the substrate. And a protective film is provided, and a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized,
The oxide film has a thickness of 0.1 nm or more and less than 3 nm. Further, the thickness of the oxide film is 0.1 nm.
It is preferably at least 2.2 nm. Further, it is more preferable that the thickness of the oxide film is 0.2 nm or more and 1.8 nm or less. In the magnetic recording medium of the present invention, the saturation magnetic flux density Bs (T) of the soft magnetic underlayer and the thickness t
(Nm) is 40 (T · n)
m) or more. Further, the product Bs · t (T · nm) of the saturation magnetic flux density Bs (T) of the soft magnetic underlayer and the thickness t (nm) of the soft magnetic underlayer is 60 (T · n).
m) or more. In the magnetic recording medium of the present invention, the soft magnetic underlayer contains 80 at% or more of Co,
Zr, Ta, Nb and Y contain at least one element of at least 2 at% and a saturation magnetic flux density Bs (T) of 0.8
(T) or more, and the soft magnetic underlayer preferably has an amorphous structure. The soft magnetic underlayer is made of Fe 6
0 at% or more, at least one element of Ta, Zr, Al, Si, and Hf at 2 at% or more, and a saturation magnetic flux density Bs (T) of 0.8 (T) or more. can do. The soft magnetic underlayer is made of Fe 6
0 at% or more, at least one element of O, N, B, and C at 2 at% or more, and a saturation magnetic flux density Bs (T) of 0.8 (T) or more. Can also. In the magnetic recording medium of the present invention, the orientation control film is T
It is preferable to use a material containing one or more or two or more of i, Zn, Y, Zr, Ru, Re, Gd, Tb, and Hf as main components. Further, in the magnetic recording medium of the present invention, the orientation control film may include a first orientation control layer having a B2 structure, Ti,
A configuration including a second orientation control layer made of a material containing one or more or two or more of Zn, Y, Zr, Ru, Re, Gd, Tb, and Hf as main components may be employed. The first orientation control layer is made of NiAl, FeAl, CoFe, CoZ.
r, one of NiTi, AlCo, AlRu, and CoTi
It is preferably made of a material mainly containing one or more alloys. The thickness of the first orientation control layer is:
The thickness is preferably 0.1 to 20 nm. In the magnetic recording medium of the present invention, it is preferable that a non-magnetic intermediate film made of a non-magnetic material is provided between the orientation control film and the perpendicular magnetic film. The method of manufacturing a magnetic recording medium according to the present invention includes the steps of: forming a soft magnetic underlayer made of at least a soft magnetic material on a non-magnetic substrate, an orientation control film for controlling the orientation of the film immediately above, and an axis of easy magnetization relative to the substrate. A method of manufacturing a magnetic recording medium comprising a vertically oriented perpendicular magnetic film and a protective film, comprising a step of oxidizing the surface of a soft magnetic underlayer. In order to oxidize the surface of the soft magnetic underlayer, a method of oxidizing the surface of the soft magnetic underlayer by exposing the surface to oxygen-containing gas after forming the soft magnetic underlayer can be adopted. When oxidizing the surface of the soft magnetic underlayer, a gas containing oxygen may be used for only a part of the soft magnetic underlayer. A magnetic recording / reproducing apparatus according to the present invention is a magnetic recording / reproducing apparatus including a magnetic recording medium and a magnetic head for recording / reproducing information on / from the magnetic recording medium, wherein the magnetic head is a single-pole head, However, a soft magnetic under film made of at least a soft magnetic material on a non-magnetic substrate, an orientation control film for controlling the orientation of the film immediately above, and a perpendicular magnetic film whose easy axis is mainly oriented perpendicular to the substrate. And a protective film, wherein a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized, and the thickness of the oxide film is 0.1 nm or more and less than 3 nm. .

[0005]

FIG. 1 shows a first embodiment of a magnetic recording medium according to the present invention. The magnetic recording medium shown in FIG. An orientation control film 3, a perpendicular magnetic film 4, a protective film 5, and a lubricating film 6 are sequentially formed. Examples of the nonmagnetic substrate 1 include a metal substrate made of a metal material such as aluminum and an aluminum alloy, and a nonmetal substrate made of a nonmetal material such as glass, ceramic, silicon, silicon carbide, and carbon. . As the glass substrate, there are amorphous glass and crystallized glass, and as the amorphous glass, general-purpose soda lime glass,
Aluminosilicate glass and aluminosilicate glass can be mentioned. Further, as the crystallized glass, for example, a lithium-based crystallized glass can be used. Examples of the ceramic substrate include general-purpose sintered bodies mainly containing aluminum oxide, aluminum nitride, silicon nitride, and the like, and fiber-reinforced products thereof. As the non-magnetic substrate 1, a substrate in which a NiP film is formed on the surface of the above-mentioned metal substrate or non-metal substrate by plating or sputtering can also be used. The average roughness Ra of the surface of the substrate 1 is:
0.01 to 2 nm (preferably 0.05 to 1.5 nm)
Is preferred. If the surface average roughness Ra is less than 0.01 nm, the magnetic head tends to vibrate, and if it exceeds 2 nm, the glide characteristics tend to be insufficient.

[0006] The soft magnetic underlayer 2 increases the component of the magnetic flux emitted from the magnetic head in the direction perpendicular to the substrate, and more firmly fixes the magnetization of the perpendicular magnetic film 4 in which information is recorded in the direction perpendicular to the substrate 1. It is provided for the purpose.
This effect is particularly remarkable when a single-pole head for perpendicular recording is used as the magnetic head for recording and reproduction.

The outermost surface (the surface on the orientation control film 3 side) of the soft magnetic underlayer 2 is an oxide film 2a in which the material constituting the soft magnetic underlayer 2 is partially or completely oxidized. The oxide film 2a is formed on the surface of the soft magnetic underlayer 2 (the surface on the orientation control film 3 side) and in the vicinity thereof (region having a predetermined depth from the surface).
However, it is preferable that the material forming the soft magnetic underlayer 2 is formed by partially or entirely oxidizing the material. The oxide film 2a can suppress magnetic fluctuations on the surface of the soft magnetic underlayer 2, so that noise due to the magnetic fluctuations can be reduced and the recording / reproducing characteristics of the magnetic recording medium can be improved. it can. Also, the oxide film 2a
The orientation control film 3 formed on the soft magnetic under film 2
Can be refined to improve the recording / reproducing characteristics. In addition, the oxide film 2a can prevent the corrosive substance from moving from the soft magnetic underlayer 2 or the non-magnetic substrate 1 to the surface of the medium due to the function of a barrier layer, thereby suppressing the corrosion of the medium surface.

The thickness of this oxide film 2a is 0.1 nm or more and less than 3 nm (preferably 0.1 nm or more and 2.2 nm or less, more preferably 0.2 nm or more and 1.8 nm or less).
It is said. The outermost surface of this soft magnetic underlayer 2 (the orientation control film 3
When the oxide film 2a is oxidized so that the oxide film 2a has a thickness exceeding 3 nm, the orientation of the orientation control film 3 provided thereon is disturbed, and as a result, the recording / reproducing characteristics are deteriorated. If the surface of the soft magnetic underlayer 2 is excessively oxidized, the surface average roughness Ra increases (for example, 2 nm).
), Which is not preferable because the flying height of the magnetic head during recording and reproduction may not be sufficiently reduced. The thickness of the oxide film 2a is set to 0.1
When the thickness is less than nm, the fluctuation of the magnetization of the surface of the soft magnetic underlayer 2 tends to occur, and the effect of improving the recording / reproducing characteristics becomes insufficient.

The oxidized portion of the surface of the soft magnetic underlayer 2 is formed, for example, by forming the soft magnetic underlayer 2 and then exposing it to an atmosphere containing oxygen, or forming a portion close to the surface of the soft magnetic underlayer 2. It can be formed by a method of introducing oxygen during the film forming process. Specifically, when the surface of the soft magnetic underlayer 2 is exposed to oxygen, the disk (the one on which the soft magnetic underlayer 2 is formed on the substrate 1) is exposed to pure oxygen or a gas such as argon or nitrogen. In a gas atmosphere diluted with.
It may be left for about 1 to 30 seconds. Further, the disc can be exposed to the atmosphere. By appropriately setting the amount of oxygen to be introduced and the time of exposure to oxygen, the degree of oxidation of the soft magnetic underlayer 2 can be adjusted. For example, 1
A predetermined degree of oxidation can be obtained by exposing the disk to an atmosphere having an oxygen gas pressure of 10 ^-3 Pa or more for a vacuum degree of 0 ^-4 to 10 ^-6 Pa for 0.1 to 30 seconds. In particular, when a diluent gas obtained by diluting oxygen with a gas such as argon or nitrogen is used, the degree of oxidation of the surface of the soft magnetic underlayer 2 can be easily adjusted by appropriately setting the degree of dilution of oxygen. Stable production can be performed. When oxygen is introduced into a gas for forming the soft magnetic underlayer 2, for example, if a sputtering method is used as a film forming method, a process gas in which oxygen is introduced into only a part of the film forming time is used. May be performed by sputtering. As the process gas, for example, 0.05% by volume of oxygen is added to argon.
A mixed gas of about 50% (preferably 0.1-20%) is suitably used.

The thickness of the oxide film can be determined, for example, from a cross-sectional view obtained by observation with a transmission electron microscope (TEM). The oxidized state can be confirmed by Auger electron spectroscopy, SIMS, or the like.

The saturation magnetic flux density Bs (T) of the soft magnetic underlayer 2
Of the soft magnetic underlayer 2 and the thickness t (nm) of the soft magnetic underlayer Bs · t (T
.Nm) is 40 (T.nm) or more (preferably 60 (T
· Nm) or more). If Bs · t is less than the above range, the reproduced waveform will be distorted, which is not preferable.

The material of the soft magnetic underlayer 2 is Co
Co containing at least 0 at%, at least one element of Zr, Ta, Nb, and Y at 2 at% or more, having a saturation magnetic flux density Bs (T) of at least 0.8 (T), and having an amorphous structure. It is preferable to use an alloy. As this material, CoZr, CoZrNb, CoZrTa,
CoZrCr, CoNbY-based alloys and the like can be mentioned as preferable ones. Further, as a material of the soft magnetic underlayer 2, Fe is contained at 60 at% or more, and Ta, Zr,
l, at least one element among Si, Hf is contained at 2 at% or more, and the saturation magnetic flux density Bs (T) is 0.8 at%.
It is preferable to use an Fe alloy that is (T) or more.
This material includes FeAlSi, FeTaC, FeA
lSiRuTi, FeHfO, FeTaN, FeZrO
A suitable alloy can be given as an example. The material of the soft magnetic underlayer 2 is Fe at 60 at%.
And at least one of O, N, B and C
Saturation magnetic flux density Bs
It is preferable to use an Fe alloy in which (T) is 0.8 (T) or more. This material includes FeN, FeTaC,
FeHfO, FeTaN, FeAlO, FeB, FeZ
Materials having a fine crystal structure such as an rN-based alloy or a granular structure in which fine crystal particles are dispersed in a matrix can be mentioned as preferable materials.

The coercive force Hc of the soft magnetic underlayer 2 is 200 (O
e) It is preferably not more than 50 (preferably not more than 50 (Oe)). If the coercive force Hc exceeds the above range, the soft magnetic characteristics become insufficient, and the reproduced waveform becomes a waveform having a distortion from a so-called rectangular wave, which is not preferable. The maximum magnetic permeability of the soft magnetic underlayer 2 is 1000 to 1,000,000.
(Preferably 100,000 to 500,000). If the maximum magnetic permeability is less than the above range, writing on the magnetic recording medium during recording becomes insufficient, and sufficient recording and reproducing characteristics may not be obtained. Note that the magnetic permeability is a value expressed in a CGS unit system.

Since the surface shape of the soft magnetic underlayer 2 affects the surface shapes of the perpendicular magnetic film 4 and the protective film 5, the surface unevenness of the magnetic recording medium is reduced, and the flying height of the magnetic head during recording and reproduction is reduced. In order to reduce the surface roughness, it is preferable that the average surface roughness Ra of the alignment control film 3 is 2 nm or less. If the surface of the soft magnetic underlayer 2 is excessively oxidized, this surface average roughness R
a is likely to exceed 2 nm, which is not preferable.
By setting the surface average roughness Ra to 2 nm or less, the surface irregularities of the magnetic recording medium can be reduced, the flying height of the magnetic head during recording and reproduction can be sufficiently reduced, and the recording density can be increased.

The orientation control film 3 controls the orientation and the grain size of the perpendicular magnetic film 4 provided immediately above. The orientation control film 3 is made of a first orientation control layer made of a material having a B2 structure. 3a, Ti, Zn, Y, Zr, Ru, Re, G
It is preferable to have a two-layer structure provided with a second orientation control layer 3b made of a material containing one or more of d, Tb, and Hf as main components. As a material of the first alignment control film 3a having the B2 structure, NiAl, FeA
1, CoFe, CoZr, NiTi, AlCo, AlR
One or two or more alloys of u and CoTi can be used as the main component. In addition, Cr, N
Materials to which elements such as b, V, W, Mo, B, O, N, Ru, and Nd are added can also be used. The above binary alloys (NiAl, FeAl, CoFe, CoZr, NiT
When using i, AlCo, AlRu, and CoTi), the content of each of the two components constituting the alloy is preferably 40 to 60 at% (preferably 45 to 55 at%).

The thickness of the first orientation control layer 3a is preferably determined as follows. FIG. 2 shows the thickness of the first orientation control layer 3a and the perpendicular magnetic film 4 in the magnetic recording medium having the above-described configuration.
4 is a graph showing the relationship between the (0002) plane and the orientation. In this graph, the horizontal axis represents the thickness of the first orientation control layer 3a, and the vertical axis represents the X-ray diffraction intensity corresponding to the (0002) plane of the perpendicular magnetic film 4. As shown in this graph,
The X-ray diffraction intensity is such that the thickness of the first orientation control layer 3a is 0.1 to
It shows a high value when it is 20 nm, and thereafter becomes lower as the thickness of the first orientation control layer 3a increases. According to this graph, the perpendicular orientation of the perpendicular magnetic film 4 is such that the thickness of the first orientation control layer 3a is 0.1 to 20 nm (particularly 1.5 to 10 n).
It can be seen that the height increases when m), and gradually decreases when the thickness is further increased. Therefore, in the magnetic recording medium of the present embodiment, the thickness of the first orientation control layer 3a is set to 0.1
It is preferable to set it to 20 nm. When the thickness is less than the above range, the perpendicular orientation of the perpendicular magnetic film 4 is reduced, and the noise characteristics and the thermal fluctuation resistance are deteriorated. Also,
If the thickness exceeds the above range, the perpendicular orientation of the perpendicular magnetic film 4 decreases, and the noise characteristics and the thermal fluctuation resistance deteriorate. Further, since the distance between the magnetic head and the soft magnetic underlayer 2 during recording becomes large, the resolution of a reproduced signal is undesirably reduced. When the thickness of the first orientation control layer 3a is in the range of 1.5 to 10 nm, the perpendicular magnetic film 4
In particular, and the distance between the magnetic head and the soft underlayer 2 during recording can be reduced, so that the recording / reproducing characteristics can be improved without lowering the resolution of the reproduced signal.

The thickness of the second orientation control layer 3b is 0.1 to 5
It is preferably 0 nm (preferably 2 to 25 nm). If this thickness is less than the above range, the perpendicular orientation of the perpendicular magnetic film 4 is reduced, and the recording / reproducing characteristics and the resistance to thermal fluctuation are deteriorated. If this thickness exceeds the above range,
Crystal grains are coarsened in the second orientation control layer 3b, crystal grains are coarsened in the perpendicular magnetic film 4, and the recording / reproducing characteristics are deteriorated. In addition, since the distance between the magnetic head and the soft magnetic underlayer 2 at the time of recording / reproducing is increased, the resolution of a reproduced signal is undesirably reduced.

In forming the orientation control film 3, oxygen or nitrogen is introduced into a gas for forming the first orientation control layer 3a or the second orientation control layer 3b, and an oxide film or a nitride film is formed on the surface. It may be formed. For example, if a sputtering method is used as a film forming method, as a process gas, a gas in which oxygen is mixed with argon at a volume ratio of about 0.05 to 50% (preferably 0.1 to 20%), and a nitrogen gas is argon. 0.01 by volume ratio
A mixed gas of about 20% (preferably 0.02 to 10%) is suitably used.

In the present invention, the orientation control film is not limited to a two-layer structure, but may have a single-layer structure made of a single material. In this case, Ti, Zn, Y,
It is preferable to use a material containing one or more of Zr, Ru, Re, Gd, Tb, and Hf as main components. In particular, it is preferable that the use of Ru particularly enhances the perpendicular orientation of the perpendicular magnetic film 4. For this material, considering the lattice matching with the perpendicular magnetic film,
Alloys obtained by adding Co, Cr, Fe, Ni, and the like to these materials can be used. Also, as this material, C, O, N, S
An alloy to which i and B are added can also be used. The thickness of the orientation control film in the case of a single-layer structure is 0.1 to 50 nm.
(Preferably 1 to 25 nm, more preferably 2 to 25 n
m) is preferred. If the thickness is less than the above range, the perpendicular orientation of the perpendicular magnetic film 4 is reduced, and the recording / reproducing characteristics and the resistance to thermal fluctuation are deteriorated. If the thickness exceeds the above range, the crystal grains become coarse, the crystal grains in the perpendicular magnetic film 4 become coarse, and the recording / reproducing characteristics deteriorate. In addition, since the distance between the magnetic head and the soft magnetic underlayer 2 at the time of recording / reproducing is increased, the resolution of a reproduced signal is undesirably reduced.

The perpendicular magnetic film 4 has an easy axis of magnetization with respect to the substrate.
Mainly vertically oriented magnetic film, made of magnetic material
And can be. As a material of the perpendicular magnetic film 4,
CoCr, CoCrPt, CoCrTa, CoC
rPtX₁System, CoPtX₁System (X₁: Ta, Zr, N
b, Cu, Re, Ni, Mn, Ge, Si, O, N,
And one or more of B)
preferable. In particular, the perpendicular magnetic anisotropy of the perpendicular magnetic film 4 is increased.
In order to use CoCrPtX₁System, CoPtX₁System alloy
In this case, a Pt content of 8 to 24 at% is used.
Is preferred. The perpendicular magnetic film 4 includes a transition metal (C
o, Co alloy, Fe, Fe alloy, etc.) and noble metal materials (P
d, Pd alloy, Pt, Pt alloy)
A laminated structure can be adopted. For example, Co, CoX_Two,
Fe, FeX_TwoAnd Pd, Pd
X_Two, Pt, PtX_Two(X_Two: Cr, Pt, Ta, B,
O, Ru, or one or more of Si)
Adopts a structure in which layers consisting of
be able to. CoCr-based, CoCrPt listed above
System, CoCrTa system, CoCrPtX ₁System, CoPtX₁
The system and the laminated structure type perpendicular magnetic film are all composed of polycrystals.
However, the magnetic recording medium of the present invention has a perpendicular magnetic structure having an amorphous structure.
A membrane can also be applied. Specifically, it is particularly limited
Rare earth elements such as TbFeCo alloys
Alloys containing silicon.

The thickness of the perpendicular magnetic film 4 is 3 to 100 nm.
(Preferably 5 to 50 nm). If the thickness of the perpendicular magnetic film 4 is less than the above range, a sufficient magnetic flux cannot be obtained, and the reproduction output decreases. The perpendicular magnetic film 4
If the thickness exceeds the above range, the magnetic particles in the perpendicular magnetic film 4 become coarse, and the recording / reproducing characteristics are deteriorated.

The coercive force of the perpendicular magnetic film 4 is 3000 (O
e) or more. The coercive force is 3000 (O
e) Smaller magnetic recording media are not preferred because they are unsuitable for high recording densities and have poor thermal fluctuation resistance.

The perpendicular magnetic film 4 has an average crystal grain size of 5
It is preferably from 15 to 15 nm (preferably from 7 to 10 nm). The average particle diameter can be determined, for example, by observing crystal particles of the perpendicular magnetic film 4 with a TEM (transmission electron microscope) and image-processing the observed image.

The perpendicular magnetic film 4 may be formed by laminating two or more layers having different compositions and structures. For example, the perpendicular magnetic film 4 includes a plurality of magnetic layers and an intermediate layer formed between the magnetic layers, and the intermediate layer has a crystal structure of a B2 structure or a structure of an hcp structure. Can be. At this time, the composition of the magnetic layer,
The structures may be the same or different from each other. The material of the intermediate film is not limited,
Considering the lattice matching, Ru, Ru are Co, Cr,
Alloys to which Fe, Ni, C, O, N, Si, B, etc. are added, and Co, Cr, Fe, Ni, Ru, Pt, Ta, C,
It is particularly preferable to use an alloy to which O, N, Si, B, etc. are added.

The protective film 5 serves to prevent corrosion of the perpendicular magnetic film 4 and also to prevent damage to the medium surface when the magnetic head comes into contact with the medium. Conventionally known materials such as C and SiO ₂ can be used. , ZrO ₂ can be used. It is desirable that the thickness of the protective film 5 be 1 to 10 nm. As the lubricant 6, it is preferable to use perfluoropolyether, fluorinated alcohol, fluorinated carboxylic acid, or the like.

To manufacture the magnetic recording medium having the above configuration,
On a substrate 1, a soft magnetic base film 2, an orientation control film 3, and a perpendicular magnetic film 4 are sequentially formed by sputtering, vacuum deposition, ion plating, or the like. Next, the protective film 5 is formed preferably by a plasma CVD method, an ion beam method, or a sputtering method. In order to form the lubricant 6, a conventionally known method such as a dipping method and a spin coating method can be adopted.

In the magnetic recording medium having the above configuration, the material constituting the soft magnetic underlayer 2 is partially or completely oxidized on the outermost surface (the surface on the side of the orientation control film 3) of the soft magnetic underlayer 2. Oxide film 2a is formed, and the thickness of oxide film 2a is 0.1 nm or more and less than 3 nm (preferably 0.1 nm
Or more and 2.2 nm or less, more preferably 0.2 nm or more and 1.8 nm or less). Thereby, the soft magnetic underlayer 2
Magnetic fluctuations on the surface of the magnetic recording medium can be suppressed, so that noise due to the magnetic fluctuations can be reduced and the recording / reproducing characteristics of the magnetic recording medium can be improved. Also,
By making the crystal grains of the orientation control film 3 formed on the soft magnetic underlayer 2 fine, the recording / reproducing characteristics can be improved.

Further, the thickness of the first orientation control layer 3a is set to 0.
By setting the thickness to 1 to 20 nm, the recording / reproducing characteristics can be further improved. By setting the thickness of the first orientation control layer 3a within the above range, the recording / reproducing characteristics can be improved because the second orientation control layer 3b grown under the influence of the first orientation control layer 3a, In the magnetic film 4,
This is considered to be due to the progress of miniaturization, isolation, and uniformization of crystal grains.

The recording resolution can be improved by setting the thickness of the first orientation control film 3a in the above range (0.1 to 20 nm). This is considered to be because the perpendicular orientation of the perpendicular magnetic film 4 can be increased without increasing the distance between the magnetic head and the soft magnetic film 2.

FIG. 3 shows a second embodiment of the magnetic recording medium of the present invention.
In the magnetic recording medium shown here, the orientation
A non-magnetic intermediate film 7 is provided between the control film 3 and the perpendicular magnetic film 4.
Have been killed. The nonmagnetic intermediate film 7 has an hcp structure
It is preferable to use a non-magnetic material. Non-magnetic interlayer 7
Is a non-magnetic CoCr alloy or CoCrX_ThreeAlloys and CoX_Three
Alloy (X _Three: Pt, Ta, Zr, Ru, Nb, Cu, R
e, one of Ni, Mn, Ge, Si, O, N and B
(Or two or more species). Non-magnetic
The thickness of the interlayer 7 depends on the coarseness of the magnetic particles in the perpendicular magnetic film 4.
Deterioration of recording / reproducing characteristics due to
Low recording resolution due to increase in distance to ground film 2
20 nm or less (preferably,
Or less than 10 nm). This embodiment
In the magnetic recording medium described above, the non-magnetic intermediate film 7 may be provided.
By this, the perpendicular orientation of the perpendicular magnetic film 4 can be enhanced.
Since the coercive force Hc of the perpendicular magnetic film 4 can be increased,
The raw properties and heat fluctuation resistance can be further improved.
Wear.

FIG. 4 shows a third embodiment of the magnetic recording medium according to the present invention. In the magnetic recording medium shown in FIG. A hard magnetic film 8 whose properties mainly face the in-plane direction is provided. A CoSm alloy or a CoCrCoX ₄ alloy (X ₄ : Pt, Ta, Zr, Nb, Cu, Re, Ni,
One or two of Mn, Ge, Si, O, N and B
Or more). The hard magnetic film 8 has a coercive force Hc of 500 (Oe) or more (preferably 1000 (Oe).
e) above). The thickness of the hard magnetic film 8 is preferably 20 to 150 nm (preferably 40 to 70 nm). The thickness of the hard magnetic underlayer 8 is 20 n
If it is less than m, the effect of lowering the error rate decreases, and if it exceeds 150 nm, the surface average roughness Ra of the orientation control film 3 becomes undesirably large. The hard magnetic film 8
It is preferable to adopt a configuration in which exchange coupling with the soft magnetic underlayer 2 is performed so that the magnetization direction can be directed in the radial direction of the substrate. By providing the hard magnetic underlayer 8, the formation of a huge magnetic domain in the soft magnetic underlayer 2 can be suppressed more effectively. Therefore, the generation of spike noise due to the domain wall is prevented, and the error rate during recording / reproduction is reduced. Can be made sufficiently low.

FIG. 5 shows a fourth embodiment of the magnetic recording medium of the present invention. In the magnetic recording medium shown in FIG. 5, the magnetization formed by a soft magnetic film between the perpendicular magnetic film 4 and the protective film 5 is shown. A stable film 9 is provided. Examples of the material of the magnetization stabilizing film 9 include a FeCo-based alloy (FeCo, FeCoV, etc.), F
eNi alloys (FeNi, FeNiMo, FeNiC)
r, FeNiSi, etc.), FeAl-based alloys (FeAl,
FeAlSi, FeAlSiCr, FeAlSiTiR
u, FeAlO, etc.), FeCr-based alloys (FeCr, F
eCrTi, FeCrCu, etc.), FeTa-based alloys (F
eTa, FeTaC, FeTaN, etc.), FeMg-based alloy (FeMgO, etc.), FeZr-based alloy (FeZrN, etc.), FeC-based alloy, FeN-based alloy, FeSi-based alloy,
FeP-based alloy, FeNb-based alloy, FeHf-based alloy, Fe
B-based alloys and the like can be mentioned. In addition, Fe
FeAlO, FeMgO, FeTa containing at least t%
A material having a fine crystal structure such as N or FeZrN or a granular structure in which fine crystal particles are dispersed in a matrix may be used. As a material of the magnetization stable film 9,
In addition to the above, Zr, N
A Co alloy containing at least one of b, Ta, Cr, Mo and the like and having an amorphous structure can be used. This material includes CoZr, CoZrNb,
CoZrTa, CoZrCr, CoZrMo-based alloys and the like can be mentioned as suitable ones.

The coercive force Hc of the magnetization stabilizing film 9 is 200 (O
e) It is preferably not more than 50 (preferably not more than 50 (Oe)). The saturation magnetic flux density Bs of the magnetization stable film 9 is 0.4 T
Or more (preferably 1 T or more). Further, the saturation magnetic flux density Bs (T) of the magnetization stabilizing film 9 and the film thickness t
(Nm), the product Bs · t (T · nm) is 7.2 (T · n
m) If the value of Bs · t exceeds the above range, the reproduction output is undesirably reduced.
The maximum magnetic permeability of the magnetization stable film 9 is 1000 to 100.
0000 (preferably 100,000 to 500,000).

The magnetization stable film 9 is preferably formed by partially or completely oxidizing the material constituting the magnetization stable film 9. That is, the surface of the magnetization stable film 9 (the surface on the side of the protective film 5 or the perpendicular magnetic film 4) and its vicinity (a region at a predetermined depth from the surface) are partially or entirely formed of the material constituting the magnetization stable film 9. It is preferably oxidized. Thus, magnetic fluctuations on the surface of the magnetization stabilizing film 9 can be suppressed, so that noise due to the magnetic fluctuations can be reduced and the recording / reproducing characteristics of the magnetic recording medium can be improved.

By providing the magnetization stabilizing film 9 made of a soft magnetic film between the perpendicular magnetic film 4 and the protective film 5, it is possible to improve the thermal fluctuation resistance and increase the reproduction output. This is considered to be because the magnetization fluctuation existing on the surface of the perpendicular magnetic film 4 is stabilized by the magnetization stabilizing film 9 so that the leakage magnetic flux is not affected by the fluctuation and the reproduction output increases. Can be Further, since the magnetization stabilizing film 9 is provided, the magnetization of the perpendicular magnetic film 4 in the direction perpendicular to the substrate 1 and the magnetization of the soft magnetic underlayer 2 and the magnetization stabilizing film 9 in the in-plane direction are closed. To form It is considered that the magnetization of the perpendicular magnetic film 4 is more firmly fixed by this action, and the thermal fluctuation resistance is improved.

The magnetic recording medium having the structure shown in FIGS.
1. The manufacturing process of the magnetic recording medium shown in FIG. 1 (the surface of the soft magnetic underlayer 2 is subjected to oxidation treatment during or after the formation of the soft magnetic underlayer 2 by sputtering or the like, Then, the perpendicular magnetic film 4 is formed by a sputtering method or the like, and then the protective film 5 is formed by a CVD method, an ion beam method, a sputtering method, or the like.
Forming a lubricating film 6 by a spin coating method or the like), a step of forming a hard magnetic film 8 between the substrate 1 and the soft magnetic underlayer 2 as necessary, or a step of forming the orientation control film 3 and the perpendicular magnetic film 4.
A step of forming a non-magnetic intermediate film 7 between them, a step of forming a magnetization stable film 9 between the perpendicular magnetic film 4 and the protective film 5,
It can be manufactured by performing the process including the step of oxidizing the surface of the magnetization stable film 9.

FIG. 6 shows an example of a magnetic recording / reproducing apparatus using the above magnetic recording medium. The magnetic recording / reproducing apparatus shown here includes a magnetic recording medium 10, a medium driving unit 11 for driving the magnetic recording medium 10 to rotate, a magnetic head 12 for recording / reproducing information on / from the magnetic recording medium 10, and a head driving unit 1.
3 and a recording / reproducing signal processing system 14. The recording / reproducing signal processing system 14 can process input data and send a recording signal to the magnetic head 12, or can process a reproducing signal from the magnetic head 12 and output data. As the magnetic head 12, a single pole head for perpendicular recording can be exemplified. As shown in FIG. 6B, the single magnetic pole head includes a seed magnetic pole 12a.
A structure having an auxiliary magnetic pole 12b and a coil 12d provided in the connecting portion 12c can be suitably used.

According to the magnetic recording / reproducing apparatus, since the magnetic recording medium 10 is used, the recording / reproducing characteristics can be improved. Therefore, troubles such as data loss can be prevented beforehand, and higher recording density can be achieved. In this specification, the main component refers to the component at 50 at.
% Is included.

[0039]

The following examples are provided to clarify the operation and effect of the present invention. However, the present invention is not limited to the following examples. (Example 1) A cleaned glass substrate 1 (manufactured by OHARA, 2.5 inch in outer diameter) was housed in a film forming chamber of a DC magnetron sputtering apparatus (C-3010, manufactured by Anelva), and the ultimate vacuum degree was 1 After exhausting the inside of the film forming chamber until the pressure becomes × 10 ⁻⁵ Pa, 89 at% Co
Using a target consisting of -4 at% Zr-7 at% Nb, a soft magnetic underlayer 2 having a thickness of 100 nm was formed by sputtering at a substrate temperature of 100 ° C or lower. The product Bs · t of the saturation magnetic flux density Bs (T) of this film and the film thickness t (nm)
(T · nm) was confirmed to be 200 (T · nm) by a vibrating magnetic property measuring apparatus (VSM). Next, pure oxygen (100 vol% O ₂ ) was introduced into the chamber, and the surface of the soft magnetic underlayer 2 was exposed to oxygen (exposure step) to form an oxide film 2 a on the surface of the soft magnetic underlayer 2. Next, the substrate is heated to 200 ° C., and 50 μm
a first orientation control layer (thickness: 8 nm) made of at% Ni-50 at% Al and a second orientation control layer (thickness: 2 nm) made of Ru.
0 nm) was formed. Then 6
2 at% Co-20 at% Cr-14 at% Pt-4a
A perpendicular magnetic film 4 (thickness: 30 nm) made of t% B was formed. In the sputtering step, the film was formed at a gas pressure of 0.5 Pa using argon as a process gas for film formation. Next, a protective film 5 having a thickness of 5 nm was formed by a CVD method. Next, a lubricating film 6 made of perfluoropolyether was formed by dipping to obtain a magnetic recording medium (see Table 1).

(Examples 2 to 6) In the exposure step, Example 1 was repeated except that the thickness of the oxide film 2a was changed by changing the time for exposing the soft magnetic underlayer 2 to oxygen.
A magnetic recording medium was produced in the same manner as described above (see Table 1).

(Examples 7 to 9) In the exposure step, the gas for exposing the soft magnetic underlayer 2 was replaced with pure oxygen as shown in Table 1.
A magnetic recording medium was produced in the same manner as in Example 1 except that the gases shown in Table 1 were used (see Table 1).

(Examples 10 and 11) Without performing the exposure step,
Instead of this, the process was performed in the same manner as in Example 1 except that the oxide film 2a was formed by using an oxygen-containing argon gas shown in Table 1 as a process gas used in the film forming process for forming the soft magnetic underlayer 2. A magnetic recording medium was manufactured (Table 1).
See).

Comparative Examples 1 and 2 As Comparative Example 1, a magnetic recording medium was prepared in which the surface of the soft magnetic underlayer 2 on the side of the perpendicular magnetic film was not oxidized. Further, as Comparative Example 2, a magnetic recording medium was manufactured in which the surface of the soft magnetic underlayer 2 on the side of the perpendicular magnetic film was excessively oxidized (see Table 1).

(Examples 12 to 18) In Examples 12 to 18, magnetic recording was performed in the same manufacturing process as in Example 1 except that the material shown in Table 2 was used for the soft underlayer film 2. A medium was prepared (see Table 2).

Examples 19 to 21 In Examples 19 to 21, the product Bs · t of the saturation magnetic flux density Bs of the soft magnetic underlayer 2 and the thickness t of the soft magnetic underlayer 2 is shown in Table 3. A magnetic recording medium was manufactured in the same manufacturing steps as in Example 1 except for the settings (see Table 3).

(Examples 22 to 30) Production examples 22 to 30 were the same as those in Example 1 except that the orientation control layer 3 had a single-layer structure and the material and thickness were as shown in Table 4. A magnetic recording medium was manufactured in the process (see Table 4).

(Examples 31 to 38) In Examples 31 to 38, a manufacturing process was performed in the same manner as in Example 1 except that the material and thickness of the first alignment control film 3a were set as shown in Table 5. A magnetic recording medium was manufactured (see Table 5).

(Examples 39 to 46) Magnetic recording was performed in the same manner as in Example 1 except that the material and thickness of the perpendicular magnetic film 4 were set as shown in Table 6 as Examples 39 to 46. A medium was prepared (see Table 6).

(Examples 47 to 52) In Examples 47 to 52, a non-magnetic intermediate film 7 was provided between the orientation control layer 3 and the perpendicular magnetic film 4, and the material and thickness were as shown in Table 7. A magnetic recording medium was manufactured in the same manufacturing process as in Example 1 except for performing the above (see Table 7).

(Examples 53 to 57) As Examples 53 to 57, a hard magnetic film 8 was provided between the substrate 1 and the soft magnetic underlayer 2, and the material and thickness of the hard magnetic film 8 are shown in Table 8. Except as shown, a magnetic recording medium was manufactured in the same manufacturing process as in Example 1 (see Table 8).

(Examples 58 to 63) As Examples 58 to 63, a magnetization stable film 9 was provided between the perpendicular magnetic film 4 and the protective film 6, and the material and thickness of the magnetization stable film 9 are shown in Table 9. Except as shown, a magnetic recording medium was manufactured in the same manufacturing process as in Example 1 (see Table 9).

The magnetostatic property of the magnetic recording medium is represented by kerr.
It measured using the effect measuring device. The recording / reproducing characteristics and the resistance to thermal fluctuation of these magnetic recording media were measured using a read / write analyzer RWA1632 manufactured by GUZIK and a spin stand S1701MP. For evaluation of recording / reproducing characteristics, a single-pole head for perpendicular recording similar to that shown in FIG. 6B was used as a magnetic head, and an error rate was measured at a linear recording density of 600 kFCI. The thermal fluctuation resistance was evaluated by heating the substrate to 70 ° C., writing at a linear recording density of 50 kFCI, and decreasing the output with respect to the reproduction output one second after writing (% /
decade) is (So-S) × 100 / (So ×
It was calculated based on 3). In this equation, So represents the reproduction output one second after the signal recording on the magnetic recording medium, and S
Indicates the reproduction output after 1000 seconds. Tables 1 to 9 show the measurement results of the magnetostatic characteristics and the recording / reproducing characteristics of each magnetic recording medium.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

[Table 5]

[0058]

[Table 6]

[0059]

[Table 7]

[0060]

[Table 8]

[0061]

[Table 9]

From the results shown in Table 1, an oxide film 2a is formed on the surface of the soft magnetic underlayer 2, and the thickness of the oxide film 2a is set to 0.1
It can be seen that in the magnetic recording medium having a thickness of not less than 3 nm and less than 3 nm, good recording / reproducing characteristics and thermal fluctuation resistance were obtained.

From the results shown in Table 2, it can be seen that excellent recording / reproducing characteristics and heat fluctuation resistance were obtained even when the material shown in Table 2 was used as the material of the soft magnetic underlayer 2.

From the results in Table 3, the value of Bs · t was set to 40T · t.
It can be seen that good recording / reproducing characteristics were obtained by setting the thickness to at least nm, and that the recording / reproducing characteristics and thermal fluctuation resistance could be further improved by setting the value of Bs · t to at least 60 T · nm. .

From the results shown in Table 4, it can be seen that excellent recording / reproducing characteristics and heat fluctuation resistance were obtained even when the material shown in Table 4 was used as the material of the orientation control film 3.

From the results shown in Table 5, it can be seen that excellent recording / reproducing characteristics and resistance to thermal fluctuation could be obtained by setting the thickness of the first orientation control layer 3a to 0.1 to 20 nm. Also, it was found that excellent recording / reproducing characteristics and thermal fluctuation resistance were obtained even when the materials shown in Table 5 were used as the material of the first orientation control layer 3a (Examples 35 to 3).
8).

From the results shown in Table 6, the thickness of the perpendicular magnetic film 4 is
It can be seen that good recording and reproduction characteristics were obtained by setting the thickness to 3 to 100 nm. Further, the perpendicular magnetic film 4
It can be understood that better recording / reproducing characteristics were obtained by setting the thickness to 5 to 50 nm. It can also be seen that excellent recording / reproducing characteristics and thermal fluctuation resistance were obtained even when the materials shown in Table 6 were used as the material of the perpendicular magnetic film 4 (Examples 44 to 46).

From the results shown in Table 7, it can be seen that the provision of the non-magnetic intermediate film 7 improved the recording / reproducing characteristics and the resistance to thermal fluctuation.

From the results shown in Table 8, it can be seen that the provision of the hard magnetic film 8 has improved the recording / reproducing characteristics and the resistance to thermal fluctuation.

From the results shown in Table 9, it can be seen that the provision of the magnetization stabilizing film 9 improved the recording / reproducing characteristics and the resistance to thermal fluctuation.

[0071]

As described above, in the magnetic recording medium of the present invention, at least the soft magnetic underlayer made of a soft magnetic material and the alignment for controlling the alignment of the film immediately above are formed on the nonmagnetic substrate. A control film, a perpendicular magnetic film whose easy axis is mainly oriented perpendicular to the substrate, and a protective film are provided, and a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized. Since the thickness of the oxide film is 0.1 nm or more and less than 3 nm, the recording / reproducing characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a first embodiment of a magnetic recording medium according to the present invention.

FIG. 2 is a graph showing the relationship between the thickness of a first orientation control layer 3a and the orientation of the (0002) plane of a perpendicular magnetic film 4;

FIG. 3 is a partial sectional view showing a second embodiment of the magnetic recording medium of the present invention.

FIG. 4 is a partial sectional view showing a third embodiment of the magnetic recording medium of the present invention.

FIG. 5 is a partial cross-sectional view showing a fourth embodiment of the magnetic recording medium of the present invention.

FIGS. 6A and 6B are schematic diagrams showing an example of a magnetic recording / reproducing apparatus according to the present invention, wherein FIG. 6A shows the entire configuration, and FIG. 6B shows a magnetic head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Non-magnetic substrate, 2 ... Soft magnetic base film, 3 ... Orientation control film,
3a: first orientation control layer, 3b: second orientation control layer, 4: perpendicular magnetic film, 5: protective film, 6: lubricating film, 7: non-magnetic intermediate film, 8: hard magnetic film, 9: magnetization stable film Reference numeral 10: magnetic recording medium, 11: medium drive unit, 12: magnetic head, 12a: main magnetic pole, 12b: auxiliary magnetic pole, 12c: coupling unit, 12d: coil, 13: head drive unit, 14: recording / reproducing signal processing system

Claims (19)

[Claims] 1. A soft magnetic underlayer made of at least a soft magnetic material on a nonmagnetic substrate, an orientation control film for controlling the orientation of the film directly above, and an easy axis of magnetization oriented mainly perpendicular to the substrate. A perpendicular magnetic film and a protective film are provided, and a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized, and the thickness of the oxide film is 0.1 nm or more and 3 n
m, which is less than m. 2. The thickness of an oxide film is 0.1 nm or more and 2.2 n.
2. The magnetic recording medium according to claim 1, wherein m is equal to or less than m. 3. An oxide film having a thickness of 0.2 nm or more and 1.8 n or more.
3. The magnetic recording medium according to claim 1, wherein m is equal to or less than m. 4. The saturation magnetic flux density Bs (T) of the soft magnetic underlayer.
Of the soft magnetic underlayer and the thickness t (nm) of the soft magnetic underlayer.
The magnetic recording medium according to any one of claims 1 to 3, wherein (nm) is 40 (T-nm) or more. 5. A saturation magnetic flux density Bs (T) of a soft magnetic underlayer.
Of the soft magnetic underlayer and the thickness t (nm) of the soft magnetic underlayer.
5. The magnetic recording medium according to claim 1, wherein (nm) is 60 (T · nm) or more. 6. The soft magnetic underlayer contains at least 80 at% of Co, at least one element of Zr, Ta, Nb, and Y at least 2 at%, and has a saturation magnetic flux density Bs (T) of 0.8 at%. 6. The magnetic recording medium according to claim 1, wherein the soft magnetic underlayer has an amorphous structure. 7. A soft magnetic underlayer containing at least 60 at% of Fe, at least one element of at least one of Ta, Zr, Al, Si, and Hf at 2 at% or more, and a saturation magnetic flux density Bs (T) 6. The magnetic recording medium according to claim 1, wherein is equal to or more than 0.8 (T). 8. The soft magnetic underlayer contains at least 60 at% of Fe, at least one element of O, N, B, and C at 2 at% or more, and has a saturation magnetic flux density Bs (T) of 0 or more. The magnetic recording medium according to any one of claims 1 to 5, wherein the magnetic recording medium is equal to or more than 0.8 (T). 9. An alignment control film comprising Ti, Zn, Y, Zr, R
The magnetic recording medium according to any one of claims 1 to 8, wherein the magnetic recording medium is made of a material containing at least one of u, Re, Gd, Tb, and Hf as a main component. 10. An orientation control film comprising: a first orientation control layer having a B2 structure; and Ti, Zn, Y, Zr, Ru, Re, and G.
9. The magnetic recording according to claim 1, comprising a second orientation control layer made of a material containing one or more of d, Tb, and Hf as main components. Medium. 11. The first orientation control layer is made of NiAl, FeA
1, CoFe, CoZr, NiTi, AlCo, AlR
11. The magnetic recording medium according to claim 10, wherein the magnetic recording medium is made of a material mainly containing one or more alloys of u and CoTi. 12. The thickness of the first orientation control layer is from 0.1 to 2
The magnetic recording medium according to claim 10, wherein the magnetic recording medium has a thickness of 0 nm. 13. The magnetic device according to claim 1, wherein a non-magnetic intermediate film made of a non-magnetic material is provided between the orientation control film and the perpendicular magnetic film. recoding media. 14. A non-magnetic substrate on which a soft magnetic underlayer made of at least a soft magnetic material, an orientation control film for controlling the orientation of the film immediately above, and an axis of easy magnetization oriented mainly perpendicular to the substrate. A method for manufacturing a magnetic recording medium provided with a perpendicular magnetic film and a protective film, comprising a step of oxidizing a surface of a soft magnetic underlayer. 15. The magnetic recording medium according to claim 14, further comprising a step of oxidizing a surface of the soft magnetic underlayer by exposing the surface of the soft magnetic underlayer to a gas containing oxygen after forming the soft magnetic underlayer. Production method. 16. The method for manufacturing a magnetic recording medium according to claim 15, wherein when oxidizing the surface of the soft magnetic underlayer, a gas containing oxygen is used only for a part of the soft magnetic underlayer. 17. A magnetic recording / reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording / reproducing information on / from the magnetic recording medium, wherein the magnetic head is a single-pole head, and the magnetic recording medium is a non-magnetic A soft magnetic underlayer made of at least a soft magnetic material on the substrate, an orientation control film for controlling the orientation of the film immediately above, a perpendicular magnetic film in which the easy axis is oriented mainly perpendicular to the substrate, and a protective film. Wherein a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized, and the thickness of the oxide film is 0.1 nm or more and less than 3 nm. . 18. A magnetic recording / reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording / reproducing information on / from the magnetic recording medium, wherein the magnetic head is a single-pole head, and the magnetic recording medium is a non-magnetic A soft underlayer consisting of at least a soft magnetic material on the substrate, an orientation control film for controlling the orientation of the film immediately above, a perpendicular magnetic film in which the easy axis is mainly oriented perpendicular to the substrate, and a protective film. Wherein a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized, and the thickness of the oxide film is 0.1 nm or more and 2.2 nm or less. Playback device. 19. A magnetic recording / reproducing apparatus comprising: a magnetic recording medium; and a magnetic head for recording / reproducing information on / from the magnetic recording medium, wherein the magnetic head is a single-pole head, and the magnetic recording medium is a non-magnetic A soft underlayer consisting of at least a soft magnetic material on the substrate, an orientation control film for controlling the orientation of the film immediately above, a perpendicular magnetic film in which the easy axis is mainly oriented perpendicular to the substrate, and a protective film. Wherein a part or the entire surface of the soft magnetic underlayer on the orientation control film side is oxidized, and the thickness of the oxide film is 0.2 nm or more and 1.8 nm or less. Playback device.