JP2809049B2 - Magnetic recording media - Google Patents

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 used in a magnetic recording device such as a magnetic disk device. More specifically, the magnetic characteristics and recording / reproducing characteristics are improved by improving a non-magnetic underlayer. The present invention relates to an improved magnetic recording medium.

[0002]

2. Description of the Related Art As a recording medium in magnetic recording, a so-called coating type magnetic recording medium in which a magnetic film composed of iron oxide powder and an organic binder is formed on a non-magnetic support has been used. In recent years, a metal thin film type magnetic recording medium using a ferromagnetic metal film as a record carrier has been widely used due to a demand for higher density of magnetic recording. The components and compositions of the magnetic film are determined in consideration of magnetic characteristics, recording / reproducing characteristics, environmental resistance, economy, and the like. Currently, CoNiCr alloy, CoCrTa alloy, CoNiCrT
Alloys a and the like have been studied and used. In addition, these C
Since the o-alloy is mainly composed of Co, it is known that the o-alloy has the same hexagonal crystal structure as the Co elemental metal and has magnetically uniaxial magnetic anisotropy. It is known that the direction of the magnetic anisotropy coincides with the c-axis direction of the crystal. In so-called longitudinal recording, in which the recorded magnetization is oriented in a direction parallel to the film surface, in order to improve magnetic properties such as coercive force and squareness, it is important to orient the c-axis of the crystal in the film surface direction. Therefore, conventionally, in this field, before forming a Co alloy magnetic film, a base film containing Cr or Cr as a main component is formed so as to match the atomic arrangement on the surface of the base film. A Co alloy magnetic film is grown, and Co
The crystal orientation is controlled so that the direction of the c-axis of the alloy magnetic film is oriented in the direction of the film surface, thereby improving the magnetic characteristics. Also, recently, it has been proposed to alloy a base film such as Cr in accordance with the composition of a magnetic film thereon (for example, Japanese Patent Application Laid-Open No. Hei 2-113419). Also,
It has been reported that the coercive force of a magnetic film is significantly improved by adding a noble metal such as Pt or Pd to a Co alloy. A magnetic recording medium in which Pt or Pd is mixed to improve the coercive force has a disadvantage in economical efficiency due to the high cost of such a noble metal, but is considered important for increasing the density of magnetic recording in the future. However, the atomic radii of the noble metals Pt and Pd are such that the atomic radius of Co is 1.67.
1.83 Angstroms
Angstroms, as large as 1.79 angstroms, the addition of several percent or more of Pt to improve the coercive force increases the crystal lattice constant of the Co alloy magnetic film. In order to deteriorate the alignment of the atomic arrangement with the surface of the magnetic underlayer, there is a problem that the c-axis, which is the axis of easy magnetization, does not cause in-plane orientation and the coercive force squareness and the like are deteriorated. As means for solving this, for example, a second metal for increasing the crystal lattice constant of the non-magnetic underlayer made of a Cr metal,
For example, it has been proposed to use a non-magnetic base film in which Mo or W, which is a Group 6a element same as Cr metal, is uniformly contained in the film (for example, Japanese Patent Application No. 4-124416).

[0003]

By using a non-magnetic underlayer made of a Cr metal containing a metal element having a larger atomic radius than that of the Cr metal, a noble metal such as Pt is added on the non-magnetic underlayer. When the coated Co alloy magnetic film is coated, the matching of the crystal lattices of both films is improved, and the magnetic properties of the coercive force squareness ratio are greatly improved.

[0004] However, experiments have shown that medium noise, which is another important characteristic of magnetic characteristics, increases rapidly by adding a dissimilar metal to Cr. This increase in media noise is clearly undesirable for high density magnetic recording. Observation of such a Cr underlayer with a transmission electron microscope revealed that when a metal having a large atomic radius, such as Mo, was added to a certain degree or more, the crystal grains of Cr became extremely small, and many lattices were contained in the crystal grains. Contrast considered to be a defect was confirmed, and it was found that crystallinity was significantly reduced.

That is, when a Co alloy magnetic film is coated on such a Cr alloy underlayer having poor crystallinity, the Co alloy magnetic film is epitaxially grown on the underlayer or strongly affected by the crystallinity of the underlayer. Therefore, it was found that the crystallinity of the alloy magnetic film was greatly deteriorated as in the base film. And it turned out that it was a cause of increasing the medium noise. In particular, when the magnetic film is a Co alloy magnetic film containing a noble metal having a large atomic radius such as Pt,
It has been found that it is necessary to provide a base film that matches the size of the crystal lattice and has good crystallinity in contact with the magnetic film.

The object of the present invention is based on the above-mentioned knowledge obtained by the present inventor, and it is an object of the present invention to provide a magnetic recording medium having a non-magnetic base film suitable for a Co-based alloy magnetic film containing a noble metal. It is to provide a recording medium.

[0007]

According to a first aspect of the present invention, a non-magnetic base film made of Cr metal, an alloy magnetic film containing a noble metal and containing Co as a main component, and a protective film are provided on a non-magnetic support.
Sequentially in coated magnetic recording medium, wherein between the non-magnetic undercoat layer and the alloy magnetic film is interposed a second non-magnetic undercoat layer in contact said to the non-magnetic undercoat layer and the alloy magnetic film, before
A second non-magnetic base film and the alloy magnetic film in contact therewith;
0.14 Å or less in crystal lattice spacing
And, the second non-magnetic undercoat layer has a larger lattice constant than the lattice constant of the metal, Mo, W, N
b, Ta, Ti, Zr, Hf
Also, by using a film of an alloy of one kind of second metal and the Cr metal , the second non-magnetic underlayer and the alloy non-magnetic underlayer can be compared with each other in a crystal lattice constant difference between the non-magnetic underlayer and the alloy magnetic film. A magnetic recording medium characterized in that the difference in crystal lattice constant from the alloy magnetic film is reduced.

[0008] according to the present invention, the base film provided prior to the alloy magnetic film is composed of 2-layer laminate of the non-magnetic undercoat layer and the second non-magnetic undercoat layer comprising a metal having a body-centered cubic lattice crystal structure You. The nonmagnetic base film provided on the nonmagnetic support side is not particularly limited as long as it is a metal film having good crystallinity.
A single membrane is preferred. A metal film such as this Cr film having a single composition and extremely good crystallinity and giving good magnetic properties can be obtained by a sputtering method. There is a large difference of 0.154 angstroms between the crystal lattice plane spacing of the Cr underlayer and the crystal lattice plane spacing of the Co-based alloy magnetic film containing a noble metal provided thereon.

In the first aspect of the present invention, the second nonmagnetic underlayer in contact with the alloy magnetic film is made of a metal having a larger crystal lattice plane spacing than a nonmagnetic underlayer made of a metal having a body-centered cubic lattice structure. Film. And this metal film
It is composed of an alloy or a mixture of a metal constituting the nonmagnetic underlayer and a second metal having an atomic radius larger than that of the metal. In the first aspect of the present invention, the alloy magnetic film is coated on the surface of the second non-magnetic underlayer having a value close to the crystal lattice spacing of the film. Lattice mismatch is controlled to be small, and both crystal orientation and crystallinity can be controlled so as to obtain good magnetic properties.

For the purpose of the present invention, the difference in crystal lattice spacing between the Co (100) plane of the alloy magnetic film and the Cr (110) plane of the second non-magnetic underlayer in contact with it is 0.14 Å or less. And more preferably 0.12 angstroms or less.

When the nonmagnetic underlayer is a film made of Cr metal, Mo, W, Nb, Ta, and T are used as the second metal to be added to Cr metal, which is a main component of the second nonmagnetic underlayer.
It is preferable to use any one selected from the group consisting of i, Zr, and Hf. Each of these metals has a larger atomic radius than Cr, and when formed into an alloy thin film with Cr, increases the crystal lattice constant of the film. In addition, an appropriate amount of Ti, Zr having a hexagonal close-packed crystal structure can be added.

When Cr is used as the metal of the non-magnetic underlayer film of the present invention, and Mo of the same group 6a as Cr is used as the second metal, the Mo metal can be contained in the film up to the range of 25 atomic%. , Form a solid solution in the crystal lattice without causing phase separation with Cr atoms, and the lattice constant of the crystal lattice
Assuming that the content of _Mo is x _Mo (atomic%), the lattice constant a _alloy of the CrMo _alloy is a _alloy = a _Cr · (1 + 0.00092 ·
x _Mo ).

[0013] As for the other second metal, there is a linear relationship between the amount of the second metal contained and the crystal lattice constant of the obtained second non-magnetic underlayer. The content of the second metal in the second non-magnetic underlayer in contact with the alloy magnetic film is determined so that lattice matching with the alloy magnetic film coated thereon is optimal. On the other hand, the non-magnetic underlayer is formed so that the crystallinity of the main component metal constituting the non-magnetic underlayer is not impaired.
The amount of metal can be included.

[0014] The content of the second metal contained in the second non-magnetic underlayer is appropriately adjusted by the content of the noble metal contained in the alloy magnetic film. Noble metal containing 4 to 8% by weight and C
For the alloy magnetic film containing o as a main component, the content of the second metal of 4 to 9% by weight makes it possible to provide the second non-magnetic base film with an excellent non-magnetic base film provided thereunder. This is preferable because the crystal lattice constant is kept close to the crystal lattice constant of the alloy magnetic film while maintaining the same crystallinity as the crystallinity.

C containing 8 to 12% by weight of a noble metal
For the o-alloy magnetic film, the second metal is 9 to 12% by weight.
Incorporation of the second non-magnetic underlayer can reduce the crystal lattice constant of the alloy magnetic film while maintaining the same crystallinity as that of the non-magnetic underlayer provided thereunder. Is preferable because it is close to the value of

A non-magnetic underlayer having excellent crystallinity and a second non-magnetic underlayer having a crystal lattice constant larger than that of the non-magnetic underlayer having good crystallinity affected by the crystallinity of the non-magnetic underlayer. Regarding the thickness of the nonmagnetic underlayer, the thickness of the nonmagnetic underlayer is set to 8
0 to 140 nm, the second non-magnetic underlayer is 20 to 50 nm
It is preferred that The upper and lower limits of the thickness of the non-magnetic underlayer are determined as ranges in which the crystal structure thereof has excellent crystallinity, and the upper and lower limits of the thickness of the second non-magnetic underlayer are determined by the excellent crystallinity of the underlayer. And is defined as a range that provides a lattice constant suitable for the magnetic film. The most preferable combination is a film thickness of 80 to 100 nm for the non-magnetic underlayer and 20 to 40 nm for the second non-magnetic underlayer.

The noble metal contained in the alloy magnetic film containing Co as a main component according to the present invention is at least one selected from the group consisting of Pt and Pd, and the total amount thereof is 2 to 12% by weight. Is preferred.

In addition, as long as the object of the present invention can be achieved,
The underlayer may be composed of three or more laminates having different crystal lattice constants. As the protective film used in the first embodiment of the present invention, a known material such as a carbon film, a silicon carbide film, and a silicon dioxide film can be used. The non-magnetic base film, the second non-magnetic base film, the alloy magnetic film, and the protective film of the present invention include:
Both are preferably coated by a sputtering method.

A second aspect of the present invention is that a non-magnetic base film made of a metal having a body-centered cubic lattice crystal structure is provided on a non-magnetic support.
In a magnetic recording medium in which a noble metal-containing alloy magnetic film containing Co as a main component and a protective film are sequentially coated, the nonmagnetic underlayer is a metal film containing Cr as a main component, and the nonmagnetic support side From the surface of the non-magnetic underlayer to the alloy magnetic film by continuously increasing the amount of the second metal having an atomic radius larger than that of Cr. A magnetic recording medium wherein the lattice constant is close to the crystal lattice constant of the magnetic alloy film.

In the second embodiment of the present invention, the second metal having a concentration gradient from the non-magnetic support side in the non-magnetic underlayer film toward the alloy magnetic film is Mo, W, W, as in the first embodiment of the present invention.
Any one selected from the group consisting of V, Nb, Ta, Ti, Zr, and Hf can be used. For example, the second metal is not contained at the interface with the nonmagnetic support or is contained only in a small amount, and at the interface with the alloy magnetic material, the second metal depends on the amount of the noble metal contained in the alloy magnetic film. Include. Second
Of the metal in the film is controlled so as to increase monotonously from the nonmagnetic support toward the alloy magnetic film.

The noble metal content of the alloy magnetic film is 4 to 8% by weight.
In this case, it is preferable that the amount of the second metal is 4 to 9% by weight at the interface between the non-magnetic base film and the alloy magnetic film.
When the noble metal content of the alloy magnetic film is 8 to 12% by weight, it is preferable that the second metal is 9 to 12% by weight at the interface between the nonmagnetic base film and the alloy magnetic film.
The thickness of the non-magnetic underlayer is preferably 70 to 120 nm. When the thickness is smaller than 70 nm, the crystallinity of the nonmagnetic underlayer is deteriorated, which is not preferable. When the thickness is larger than 120 nm, the crystal grain size becomes too large.

[0022]

The non-magnetic underlayer according to the first aspect of the present invention, which is provided on the non-magnetic support side, is made of a metal film having good crystallinity. The second non-magnetic base film provided in contact with and between both the non-magnetic base film and the alloy magnetic film is made of an alloy film having a crystal lattice constant larger than that of the non-magnetic base film. The non-magnetic underlayer is coated by epitaxy. Then, the alloy magnetic film is coated by epitaxy on the second non-magnetic base film having a crystal lattice constant close to that of the film and having improved crystallinity, so that the c-axis extends in the film surface direction. good growth, a good crystallinity film to improve both characteristics of the coercive magnetic force squareness ratio and medium noise.

In the nonmagnetic underlayer according to the second aspect of the present invention, the crystal lattice constant of the film continuously increases from the nonmagnetic underlayer to the alloy magnetic film, and the crystal lattice constant of the alloy magnetic film is reduced. It is getting closer. The initial step of coating the nonmagnetic underlayer film, that is, the nonmagnetic underlayer side, is composed of a metal film having a single composition with good crystallinity or a metal composition close to the single composition. Since the second metal component in the film grows in an epitaxy direction in the direction of the alloy magnetic film, a crystal lattice constant close to the crystal lattice constant of the alloy magnetic film is present near the surface thereof. In addition, the film has good crystallinity. Since the alloy magnetic film is coated by epitaxy on the non-magnetic underlayer having good crystallinity, the c-axis grows well in the film surface direction, resulting in a film having good crystallinity for improving magnetic properties.

In the present invention, noble metal-containing Co
The crystal lattice constant and crystal orientation of the main alloy magnetic film can be controlled by the non-magnetic underlayer, thereby increasing the coercive force squareness and lowering the medium noise level. A magnetic recording medium having both high recording and reproducing characteristics can be obtained.

[0025]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. Example 1 A well-cleaned glass substrate 1 of soda-lime-silica glass composition (processed into a disk shape and chemically strengthened) 1 was heated to 200 ° C. in a vacuum in a sputtering apparatus, and argon (Ar) gas was used. Ti film (gas release film from glass substrate) 2 by DC magnetron sputtering
And aluminum 3 having an island-like structure
Sputter deposition was continuously performed at 0 mTorr. The degree of vacuum before flowing argon gas before Ti film formation was 1 × 10 ⁻⁶ Torr.
r or less, and the thickness of the Ti film was about 30 nm. The Al sputtering was performed under the condition that an Al film having a thickness of about 15 nm was considered to be formed.
0 ° C. Further continuously, D using the same Ar gas
A titanium silicide (TiSi) film 4 is coated to a thickness of 30 nm by C magnetron sputtering, and the substrate is heated to 300 ° C.
After heating up to Cr film (non-magnetic underlayer) 5, Cr ₉₀ M
o ₁₀ film (second nonmagnetic under film) 6, Co ₈₁ Cr ₁₃ Pt ₆
The alloy magnetic film 7 and the carbon protective film 8 having the compositions were sequentially coated with a thickness of 120 nm, 30 nm, 56 nm, and 20 nm, respectively (the composition is indicated in atomic%). FIG. 1 shows a schematic diagram of a film cross-sectional structure of the obtained magnetic recording medium (sample 1). At this time, the coating of the Ti film 2 to the coating of the carbon film 7 was continuously performed without breaking the vacuum state by the in-line type sputtering apparatus.

[0026]

(Unit: nm) =================================== Laminated Structure Example 1 Comparison Example 1 Comparative Example 2 Example 2 Comparative Example 3 Layer Number Material ================================== 1 Substrate Glass Glass Glass Glass Glass 2 Ti 30 30 30 − − 3 Al 15 15 15 − − 4 TiSi 30 30 30 30 30 5 Cr 120 150 − − 100 6 Cr ₉₀ Mo ₁₀ 30 − 150 − − 11 Cr + Mo − − − 100 − 7 Co ₈₁ Cr ₁₃ Pt ₆ 56 56 56 − − 12 Co _63.7 Ni ₂₂ Pt ₄ − − − 51 51 Cr _9.5 Nb _0.8 8 C 20 20 20 15 15 ============ ======================= Coercive Force (Hc) 1620 1600 1650 1600 1520 Unit: Oe Coercive Force Shape ratio ^{(S *) 0.85 0.75 0.85 0.90} 0.85 ----------------------------- −−−−−− Signal strength ratio (S / N ratio) 30.2 31 28 31 30 Unit: dB ======================== =========== The layer numbers of the laminated structure correspond to FIGS.

[0027] Instead of two-layer structure of a base film of Cr film 5 and Cr ₉₀ Mo ₁₀ film 6 of Comparative Example 1 Example 1, Cr of 150nm thick as a base film
Comparative sample 1 of a magnetic recording medium was prepared in the same manner as in Example 1 except that only the film 5 having a single composition was coated.

[0028] Instead of two-layer structure of a base film of Cr film 5 and Cr ₉₀ Mo ₁₀ film 6 of Comparative Example 2 Example 1, as a base film, a 150nm thick C
except that cover only r ₉₀ Mo ₁₀ film 6, was prepared comparative sample 2 of the magnetic recording medium in the same manner as in Example 1.
FIG. 3 is a schematic diagram of a film cross-sectional structure of Comparative Sample 2.

Sample 1 prepared, Comparative samples 1-2
Table 1 summarizes the magnetic properties of Sample No. 2 and Comparative Sample 3 described below. Comparative sample 1 using only the Cr film as the underlayer had a coercive force H _C of 1600.
[Oe] , but the coercive force squareness ratio S ^* was 0.75.
The value was slightly smaller. When the recording / reproducing characteristics of the comparative sample 1 were measured by setting the distance (flying height) between the head and the surface of the magnetic recording medium to 3 micro inches, the medium noise during writing and reading of a high-frequency signal and the noise during reading were measured. The signal strength ratio (S / N ratio) is 3
It was 1 dB. In Comparative Sample 2 using only the CrMo alloy film, Hc was 1650 [Oe], which was slightly higher than Comparative Sample 1, and S ^* was significantly improved to 0.85. However, the S / N ratio was greatly reduced to 28 dB. On the other hand, in Sample 1 in which the base film is composed of two layers, Hc is about 1620 [Oe] , and S ^* is also about 0.
85, and the S / N ratio also showed a value of 30.2 dB.

Next, when these samples were analyzed by a transmission electron microscope, it was found that the Cr ₉₀ Mo ₁₀ film laminated on the pure Cr film had crystal grains almost the same as those of the Cr single composition. It has a diameter and a defect density, which are significantly different from those in which only the Cr ₉₀ Mo ₁₀ film was formed, and it was confirmed that the crystallinity was surely improved.

When the crystal orientation of the Co alloy magnetic film was examined by X-ray diffraction, the integrated intensity of the 002 reflection of the Co alloy magnetic film was found to be lower than that of Sample 1 in which the Cr ₉₀ Mo ₁₀ film and the Cr film were laminated. Compared to the comparative sample 1 in which the alloy magnetic film is coated on the film of the composition, the in-plane orientation of the easy axis of magnetization is reduced to about 1/3 as compared with the comparative sample 1 and the Cr ₉₀ Mo ₁₀ film is formed immediately below the Co alloy magnetic film. It was confirmed that this was promoted. The crystal lattice spacing of the obtained film was 2.194 angstroms for the Co alloy magnetic film and Cr ₉₀ Mo ₁₀
2.058 angstroms film, 2.040 Cr film
Angstrom.

Example 2 A glass substrate 1 of a soda-lime-silica composition (having been processed into a disk shape and chemically strengthened), which had been well washed, was heated to 200 ° C. in a vacuum of a sputtering apparatus, and argon gas was applied thereon. DC magnetron sputtering method
The iSi film 4 was coated with a thickness of 30 nm. Next, glass substrate 3
After heating to 60 ° C., a flat sputtering target 9 made of Cr metal having a tungsten (W) chip 10 as shown in FIG. 4 is used, and the glass substrate 1 is moved over the target surface in the film thickness direction. A nonmagnetic underlayer 11 having a composition gradient is formed, and a Pt having a composition of Co _63.7 Ni ₂₂ Pt ₄ Cr _9.5 Nb _0.8 is formed on the nonmagnetic underlayer 11.
The Co-containing magnetic film 12 and the carbon protective film 8 were sequentially coated to a thickness of 100 nm, 51 nm, and 15 nm, respectively, to prepare a magnetic recording medium sample 2. The coating of the protective film 8 made of carbon from the coating of the TiSi film 4 was continuously performed without breaking the vacuum state by an in-line type sputtering apparatus. FIG. 2 shows a schematic diagram of the film cross-sectional structure of Sample 2 obtained.

Comparative Example 3 A magnetic recording medium was prepared in exactly the same manner as in Example 2 except that a Cr sputter target (the one obtained by removing the tungsten chip placed on the target surface) was used. And Comparative Sample 3 were obtained.

When the magnetic characteristics of the obtained magnetic recording medium were measured, Comparative Sample 3 using a base film composed of a single Cr had a coercive force Hc of about 1520 [Oe] and showed a coercive force squareness ratio. S ^* was 0.85. On the other hand, Sample 2 having a composition gradient has Hc of 1600 [O
e], and S ^* increased to 0.90. Also,
When the recording / reproducing characteristics of the sample were measured with the distance between the magnetic head and the surface of the magnetic recording medium being about 75 nm, Comparative Sample 3 had an S / N ratio of 30.0 dB and a Pw50 (half-width of a solitary wave output) of 580 nm. However, the sample 2 had an S / N ratio of 31.0 dB and a Pw50 of 552 nm, which were characteristics suitable for high-density recording. Next, when the composition change in the film thickness direction of the non-magnetic underlayer of Sample 2 was examined by Auger electron spectroscopy, the composition was about Cr ₉₈ W ₂ on the glass substrate side of the CrW film, and the alloy magnetic film was In the vicinity of the interface, it was about Cr ₉₁ W ₉ , during which the composition was continuously and monotonously changed. X-ray diffraction revealed that the 110 diffraction peak of this CrW film was very broad, which is considered to suggest that the crystal lattice constant has a distribution in the CrW film. Was.

[0035]

According to the magnetic recording medium of the present invention, a C-containing noble metal such as Pt is formed on a conventional underlayer consisting of a single Cr.
o Compared to those formed with an alloy magnetic film, it has excellent magnetic characteristics and recording / reproducing characteristics, and has a large output and a small medium noise even in recording / reproducing in a higher frequency range. Recording and reproduction become possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a film cross-sectional structure of a magnetic recording medium obtained in Example 1.

FIG. 2 is a diagram showing a film cross-sectional structure of a magnetic recording medium obtained in Example 2.

FIG. 3 is a diagram showing a film cross-sectional structure of a magnetic recording medium obtained in Comparative Example 2.

FIG. 4 is a view for explaining a method of coating a non-magnetic base film having a composition gradient in Example 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 5 ... Non-magnetic underlayer made of Cr, 6 ... Second non-magnetic underlayer made of CrMo alloy, 7, 12 ... Contains Pt and contains Co as a main component Alloy magnetic film, 8: carbon protective film, 11: non-magnetic underlayer made of CrW having a composition gradient in the film thickness direction

Claims (9)

(57) [Claims] 1. A magnetic recording medium comprising a non-magnetic support, a non-magnetic underlayer made of Cr metal, an alloy magnetic film containing a noble metal and containing Co as a main component, and a protective film, which are sequentially coated. A second non-magnetic base film is interposed between the base film and the alloy magnetic film in contact with the non-magnetic base film and the alloy magnetic film, and is in contact with the second non-magnetic base film.
The difference in crystal lattice spacing between the alloy magnetic film and the alloy magnetic film is 0.14 on.
Gstrom or less, and the second nonmagnetic underlayer is made of a group consisting of Mo, W, Nb, Ta, Ti, Zr, and Hf having a crystal lattice constant larger than that of the metal.
By forming the film of an alloy of at least one selected second metal and the Cr metal , the second nonmagnetic layer can be made smaller than the difference in crystal lattice constant between the nonmagnetic base film and the alloy magnetic film. A magnetic recording medium characterized in that a difference in crystal lattice constant between an underlayer film and the alloy magnetic film is reduced. 2. The second non-magnetic underlayer contains 4 to 9% by weight of the second metal, and the alloy magnetic film contains at least one kind selected from a noble metal group consisting of Pt and Pd. 2. The composition according to claim 1, wherein the content is 4 to 8% by weight.
3. The magnetic recording medium according to claim 1. 3. The second non-magnetic underlayer contains 9 to 12% by weight of the second metal, and the alloy magnetic film comprises a total of at least one selected from a noble metal group consisting of Pt and Pd. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is contained in an amount of 8 to 12% by weight. 4. The method according to claim 1, wherein the thickness of the nonmagnetic underlayer is 80 to 140 n.
and m, the magnetic recording medium according to any one of claims 1-3, characterized in that the 20~50nm the second non-magnetic undercoat layer. 5. A non-magnetic base film made of a metal having a body-centered cubic lattice crystal structure on a non-magnetic support,
In a magnetic recording medium sequentially coated with an alloy magnetic film containing o as a main component and a protective film, the non-magnetic underlayer is made of Cr
And a film containing a larger amount of a second metal having an atomic radius larger than that of Cr continuously from the nonmagnetic support side to the alloy magnetic film side. A magnetic recording medium, wherein a crystal lattice constant of a surface of the non-magnetic underlayer in contact with the alloy magnetic film is close to a crystal lattice constant of the alloy magnetic film. 6. The method according to claim 1, wherein said second metal is Mo, W, V, Nb, T
6. The magnetic recording medium according to claim 5 , wherein the magnetic recording medium is any one selected from the group consisting of a, Ti, Zr, and Hf. 7. The alloy according to claim 1, wherein the second metal is contained in an amount of 4 to 9% by weight at an interface between the nonmagnetic underlayer and the alloy magnetic film, and the alloy magnetic film is selected from a noble metal group consisting of Pt and Pd. the magnetic recording medium according to claim 5 or 6, characterized in that it contains 4-8 wt% of at least one in a total amount. 8. An interface between the nonmagnetic underlayer film and the alloy magnetic film, wherein the second metal is contained in an amount of 9 to 12% by weight,
The alloy magnetic film magnetic recording medium according to claim 5 or 6, characterized in that it contains 8 to 12 wt% in total amount of at least one selected from noble metal group consisting of Pt and Pd. 9. A non-magnetic underlayer having a thickness of 70 to 120 n.
The magnetic recording medium according to any one of claims 5 to 8 , wherein m is set to m.