JP3157806B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a magnetic film suitable for high-density magnetic recording.

[0002]

2. Description of the Related Art A conventional magnetic disk drive which has been put to practical use employs an in-plane magnetic recording system. The in-plane magnetic recording method is a recording method in which an in-plane magnetic domain parallel to a substrate is formed on a magnetic recording medium which is easily magnetized in a direction parallel to a disk substrate surface, and its recording density is rapidly increasing. The improvement of the recording density of the longitudinal magnetic recording medium is mainly achieved by improving the coercive force and decreasing the magnetic film thickness.

As a means for improving the coercive force of a magnetic film made of a Co alloy, a material having a body-centered cubic structure (hereinafter referred to as "bcc structure") such as Cr or a Cr alloy between the magnetic film and the substrate or NiAl is used. For example, a method of providing a base film made of a material having a B2 structure such as, for example, U.S. document "Journal of Magnetism and Magne
tic Materials) "Vol. 155 (issued in 1996) No. 1
Pages 46 to 150 (David E. Laughlin et al., “Design an
d crystallography of multilayered media ”).

When a bcc structure underlayer is employed, it is effective to further improve the coercive force by adjusting the condition of the lattice constant between the epitaxially grown Co alloy magnetic film and the underlayer. "Journal of
Applied Physics (Journal of Applied Physi)
cs) Vol. 79, No. 8, (issued in 1996) p.
5356 (N. Inaba et al. “Magnetic and crystallog
raphic properties ofCoCrPt thin films formed on Cr
-Ti single crystalline underlayers ”)).

To improve the coercive force, it is effective to further improve the crystallinity of the Co alloy magnetic film. Therefore, a hexagonal film having the same crystal structure as the Co alloy magnetic film between the underlayer and the magnetic film is effective. It is effective to add a new base film made of a non-magnetic material having a dense structure (hereinafter referred to as "hcp structure") (see, for example, JP-A-4-321919), which is one of typical magnetic films. A Co-35at (atomic)% Cr film or the like is used as an additional underlayer for the Co-Cr-Pt magnetic film [for example, see US Transactions "IEEE Transaction.
On Magnetics (IEEE Transactions on Magne
tics) Vol. 32 No. 5 (issued in 1996) pp. 3789 to 3794 (M. Futamoto et al. “High Density Magnet
ic Recording on Highly Oriented CoCr-Alloy Perpend
icular RigidDisk Media ”).

[0006]

The longitudinal magnetic recording medium is
At present, it has reached 10 Gb / in ² , but in order to obtain a recording density exceeding this, it is necessary to further increase the coercive force and to improve the heat fluctuation characteristics. As described above, it is necessary to reduce the magnetic film thickness together with the improvement of the recording density. However, if the film thickness is too small, the problem that the recording magnetization decreases with the passage of time due to the influence of heat and disappears in some cases is encountered. I do. The magnetic film thickness at which the influence of the thermal fluctuation of magnetization becomes remarkable is usually 20 nm or less in a Co alloy system which is frequently used in magnetic disk devices.

If the trend of the improvement of the recording density is extended, it is expected that the thickness of the magnetic film must be reduced to 20 nm or less in order to realize the recording density of 10 Gb / in ² or more. Inevitable.

An object of the present invention is to solve the above-mentioned problems caused by the extension of the prior art, to increase the coercive force and to improve the thermal fluctuation characteristics, thereby achieving 10 Gb / in ^2.
It is an object of the present invention to provide a novel magnetic recording medium that can be put to practical use with the above high density recording.

[0009]

As a result of a detailed examination of the heat fluctuation characteristics of the conventional in-plane magnetic recording medium, a region having low magnetic anisotropy energy and poor crystallinity was formed in a part of the magnetic film. It has been found that the crystallinity deteriorates from the region and the recording magnetization decreases. The magnetic anisotropy energy of the portion where the crystallinity has deteriorated is low, and the magnetic anisotropy energy is a factor that forms the coercive force of the medium. Will be. That is, the recording magnetization decreases. Therefore, it is important to prevent the formation of a region having poor crystallinity.

From this point of view, a Co alloy material having an hcp structure which is most commonly used and studied for a longitudinal magnetic recording medium is examined. It was found that the region having a low value exists in the initial growth region of the film, and the crystallinity of this region was strongly affected by the underlying film in contact with the magnetic film. Therefore, it has become clear that it is important to set the structure and composition of the underlayer so that the crystallinity of the magnetic film is good.

Further, as a result of an investigation focusing on the process of forming the magnetic film, it was found that at least one ultra-thin layer having a composition different from that of the magnetic film was introduced during the process of forming the magnetic film, thereby forming the magnetic film. It has been found that the magnetic anisotropy energy of the growing crystal grains increases.

The present invention has been made based on the above findings and investigation results. The magnetic recording medium of the present invention has two layers: a lower base film in which the base film contacts the substrate and an upper base film in contact with the magnetic film. C having an upper base film having an hcp structure
A o-Cr _x -M _y alloy film, Cr + in addition concentration is 25at% ≦ x + y ≦ 50at % of the non-magnetic element M, and the added amount of the element M is 0.5 at% ≦ y, further, Element M is B, Si,
Ge, C, Al, P, Ti, V, Nb, Zr, Hf, Mn, R
h, Os, Ir, Re, Pd, Pt, Mo, Ta, W, Ag, Au
The biggest feature is that either.

Furthermore, the magnetic recording medium of the present invention is a very thin film according to Co-Cr _x -M _y alloy of at least one layer having a hcp structure, the addition concentration of Cr + M is 25at% ≦ x + y ≦ 5
0 at%, the amount of M added is 0.5 at% ≦ y, and the nonmagnetic element M is B, Si, Ge, C, Al, P, Ti, V, N
b, Zr, Hf, Mn, Rh, Os, Ir, Re, Pd, Pt, M
Another feature is that the Co alloy magnetic film is separated by an ultrathin film of any of o, Ta, W, Ag, and Au.

FIG. 1 shows an example of a sectional structure of a magnetic recording medium having such characteristics. A lower underlayer 12a is formed on the non-magnetic substrate 11. The lower underlayer 12a is used for epitaxially growing the crystal of the magnetic film and controlling the crystal orientation and grain size. Such a lower underlayer 12a
A material having a B2 structure consisting of NiAl, FeAl, FeV, CuZn, CoAl or CuPd ordered phase, or C
Use a material having a bcc structure composed of r, Cr-Ti, Cr-Mo, Cr-W, Cr-Nb, Cr-V, or a material obtained by laminating a material having a B2 structure and a material having a bcc structure. Is appropriate.

When a film made of these materials is formed on the substrate 11, the film has such a property that an alignment film whose (211) plane or (100) plane is parallel to the substrate is easily grown. Furthermore, the distribution of crystal grains constituting a film made of a material having such a B2 structure or a bcc structure can be controlled by adjusting the substrate temperature and the film forming speed when forming a film by a sputtering method or the like. it can.

When a Co alloy film having the hcp structure is formed on the (211) orientation film or the (100) orientation film, the epitaxial growth allows

[0017]

(Equation 1)

Grows parallel to the substrate 11. In this case, the axis of easy magnetization of the Co alloy becomes parallel to the substrate, and the coercive force is improved, which is a desirable characteristic for an in-plane magnetic recording medium.

Next, on the lower base layer 12a, Co-Cr _x -M _y of the non-magnetic or weakly magnetic made of alloy material upper base film 12b having a hcp structure is formed, Co alloy magnetic layer thereon 14 and a protective film 15 are formed.

Here, the additive concentration of Cr + M is 25 at% ≦
x + y ≦ 50 at% is set. 25 at% of Cr + M in Co
When added as described above, the material becomes weak or non-magnetic. When Cr + M is added at 50 at% or more, the h
Instability of the cp structure occurs. Therefore, in the Co alloy system, the range in which the nonmagnetic or weak magnetic hcp structure can be stably maintained is 25 at% ≦ x + y ≦ 50 at%. The effect of addition can be obtained when the amount of the nonmagnetic element M is 0.5 at% ≦ y.

The metal atom radius of Co is 1.26 angstroms, and the metal atom radius of Cr is 1.26 angstroms.
Since they are close to 28 angstroms, the Co—Cr alloy has an almost constant average atomic radius independent of the Cr concentration. On the other hand, Co—Cr—Ta, Co used for the recording magnetic film 14 are used.
-Cr-Pt, Co-Cr-Pt-Ta, Co-Cr-Pt-Ta-Nb, C
The average atomic radius of o-Cr-Pt-Ta-B and the like was found to be in the range of 1.265 to 1.290 angstroms according to experiments performed by the present inventors.

Among these, particularly in a medium in which Pt is added to Co as an alloy element, the metal atomic radius of Pt is 1.
Since it is as large as 38 angstroms, the average metal atom radius increases almost in proportion to the added amount of Pt. The amount of Pt added to a Co—Cr-based material as a high-density magnetic recording medium is in the range of 5 at% to 30 at%. In order to realize good epitaxial growth of the underlayer and the magnetic film, it is desirable that the average metal atom radius of the underlayer be close to the value of the magnetic film.

The first measure of the present invention is to use Co-C
The purpose is to adjust the average metal atom radius of the base film material by adding an appropriate amount of an element having a metal atom radius larger than Co and Cr to the r alloy. Rh, Os, Re, Hf having the same hcp crystal structure as Co or Ir, Pd, Pt having a face-centered cubic structure (fcc structure) have a larger metal atom radius than Co and have a wider solid solution range. , Are suitable as additional elements. Ti having the hcp structure and Au and Ag having the face-centered cubic structure have a solid solution range not large because the metal atom radius is 14% or more larger than Co, but form a solid solution in a small range where the addition amount is 20% or less. It is possible. In addition, metal elements suitable as additional elements include V, Mo, and b having a bcc structure.
Examples thereof include Ta, W, Nb, and Mn having a cubic crystal structure.

According to an experiment conducted by the present inventors on these additional elements, Pt was measured for a Co—Cr—Pt magnetic material.
When the amount is changed in the range of 5 at% to 30 at%, Co-Cr
Be necessary to be adjusted so that the difference between that of ₂₅ -M _y underlayer average metal atom radius of Co-Cr-Pt-based magnetic material of the material is within 3% to obtain a relationship between good epitaxial growth, amount of non-magnetic material Co-Cr ₂₅ -M _y underlayer material therefor, the following ranges have been found to be particularly preferred.

That is, Mn: 3 at% ≦ y ≦ 25 at%, Rh: 3
at% ≦ y ≦ 25 at%, Os: 3 at% ≦ y ≦ 25 at%, Ir: 3
at% ≦ y ≦ 25 at%, V: 3 at% ≦ y ≦ 25 at%, Re: 3 at
% ≦ y ≦ 25 at%, Pd: 3 at% ≦ y ≦ 25 at%, Pt: 3 at
% ≦ y ≦ 25 at%, Mo: 3 at% ≦ y ≦ 22 at%, Ta: 3 at
% ≦ y ≦ 21 at%, W: 3 at% ≦ y ≦ 15 at%, Au: 3 at%
≤ y ≤ 16 at%, Ti: 3 at% ≤ y ≤ 15 at%, Nb: 3 at%
≦ y ≦ 12at%, Zr: 2at% ≦ y ≦ 20at%, Hf: 3at%
≤ y ≤ 16 at%, Ag: 3 at% ≤ y ≤ 16 at%, Al: 3 at%
.Ltoreq.y.ltoreq.14 at%. In such a range of the addition amount, Co-
Even when the amount of Cr added in Cr ₂₅ -M _y underlayer material is varied from 35 at%, the average of the metal atomic radius hardly changed.

Another related measure of the present invention is Co-Cr _x-
M _y alloy film metal atomic radii as the non-magnetic element M constituting the is less than that of Co and Cr B, C, Si, Ge , P
Is to employ at least one element of In this case, the Co alloy magnetic film 14 and the Co—Cr _x −
M _y underlayer 12b expanding difference between the average atomic radius of, for both film interface crystal strains is formed.

However, in this case, Cr, which has a smaller atomic radius than Co constituting the base alloy and is easily moved between crystal lattices compared to B, C, Si, Ge, P, or Co, is the Co alloy magnetic film. By diffusing and moving to the crystal grain boundaries, an effect of alleviating the strain entering both films is produced. Thereby, a high magnetic anisotropic energy state can be realized.

[0028] Co-Cr _x -M _y optimum amount ranging M alloy film in this case, when the Cr amount is 25 at%, B:
2 at% ≦ y ≦ 14 at%, C: 1 at% ≦ y ≦ 12 at%, Si:
0.5at% ≦ y ≦ 15at%, Ge: 0.5at% ≦ y ≦ 16at
%, P: 0.5 at% ≦ y ≦ 10 at%. Even if the amount of added Cr was changed in the range of 15 to 30 at%, the range of the appropriate amount of added M was hardly changed.

The range of the weak magnetism that can be accepted as the underlayer is as follows.
The saturation magnetization Ms is 30 emu / cc or less. Co-Cr ₂₅
When film the -M _y underlayer material at high substrate temperature, segregation of the grain boundaries of Cr is sometimes magnetization occurs occurs, Co-Cr ₂₅ -M _y underlayer of the additional element M plus the amount of the In the material,
There is a feature that the saturation magnetization Ms can be kept at 30 emu / cc or less.

The above, as the upper base film 12b in contact with the recording magnetic film 14 of Co alloy, by providing a Co-Cr ₂₅ -M _y alloy film described above, the crystal grains of the crystalline constituting the recording magnetic film 14 It can be improved and the coercive force can be increased. So that the difference between that of the upper base film 12b mean metal atom radius of the magnetic film 14 is within 3%, M in Co-Cr ₂₅ -M _y film (Al, Ti, V, Nb ,
Zr, Hf, Mn, Rh, Os, Ir, Re, Pd, Pt, Mo,
These effects can be amplified by adjusting the amount of Ta, W, Au, Ag) added.

[0031] When providing the Co-Cr ₂₅ -M _y as a base film, is particularly effective magnetic film material for recording, a Co alloy including Pt, among others added weight range of 5at% to 30 at% Pt
It is a Co alloy containing. C containing Pt in this range
The o-alloy magnetic film has high magnetic anisotropy energy and good heat fluctuation resistance, and therefore has a high coercive force and is suitable as a high-density magnetic recording medium. In addition, Co-
Cr _x -M _y M where the alloy film having a smaller atomic radius than Co (B, C, Si, Ge, P) in the case of the difference between its average atomic radius of Co M is within 4% It is desirable.

[0032] The thickness of the Co-Cr ₂₅ -M _y film, 0.5
nm or more and 100 nm or less, a particularly desirable range is:
1 nm or more and 30 nm or less. At 0.5 nm or less,
Co-Cr ₂₅ -M _y for the effect of the alloy film becomes insufficient, and because the surface undulations generated in association with the film thickness becomes more than 100nm becomes thicker increases, medium required as a high-density magnetic recording medium It becomes difficult to ensure surface smoothness.

Next, the crystal strain and stress in the magnetic film are relaxed,
As a further measure of high magnetic anisotropy energy with the present invention for achieving the holding force, at least a Co-Cr _x -M _y alloy film having a different composition than the magnetic film in the process of forming the magnetic film It is effective to introduce layers. FIG. 2 shows an example of a cross-sectional structure of a medium incorporating this measure.

As the base film 22, a bcc structure material such as Cr, V and an alloy thereof is used. After forming a magnetic film 24a made of a Co alloy, an ultra-thin Co-Cr
_x -M _y alloy film 23 is formed. Co-Cr _x -M _y alloy film 2
The composition of 3 is preferably as described above. In addition, Co again
A magnetic film 24b made of an alloy is formed, and a protective film 25 is formed thereon. Here, Co-Cr _x -M _y magnetic layer 24a provided on the upper and lower film 23, the composition of 24b may but be the same or different, a Pt least 5at%, at most 30 at%
It is desirable to have an hcp structure that includes it.

[0035] The thickness of the Co-Cr _x -M _y alloy film 23 is 0.2
The thickness is suitably not less than 5 nm and not more than 5 nm. Hereinafter 0.2nm, Co-Cr _x -M _y alloy film small effect of introducing and undesirable effects arise as a high-density magnetic recording medium such as a coercive force of the magnetic film is decreased becomes more than 5 nm.

By simultaneously applying the above-described countermeasures for making the underlayer two layers, more desirable characteristics as a high-density magnetic recording medium can be obtained. An example is shown in FIG. Bcc structure material layer is provided as a lower base film 32a, are formed an upper base film 32b made of Co-Cr _x -M _y alloy film having a hcp structure thereon. Further Co alloy magnetic layer 34a thereon, Co-Cr _x -M _y alloy film ultrathin layer 33, Co alloy magnetic layer 34b, the protective film 35 is formed. Lower base film 32a
A plurality of films such as an adhesion strengthening layer, a crystal grain size control layer, and a soft magnetic film may be formed between the substrate and the substrate 31 according to the purpose.

FIG. 4 shows a structural cross section of a magnetic recording medium in which the grain size distribution of the crystal constituting the recording magnetic film is controlled in addition to the above effects. Cr or Cr on the non-magnetic substrate 41
After providing the adhesion strengthening layer 46 made of an alloy, MgO, LiF
A lower base film 42a having a NaCl type crystal structure is formed. For a material film such as MgO or LiF, a (100) oriented film is easily obtained, and the distribution of crystal grain sizes is easily uniform. By adjusting the film formation conditions (substrate temperature, film formation speed, etc.), it is possible to easily form a base film having a crystal grain size of about 10 nm, which is desirable for realizing a recording density of 10 Gb / in ² or more. The intermediate underlayer 42c is made of a material having a B2 structure, and the upper underlayer 42b is made of Co-
Consisting cr _x -M _y alloy film. C with hcp structure on this
o Magnetic layer 44a for recording layer made of alloy, ultra-thin Co-Cr _x
A -My alloy film layer 43, a magnetic film 44b for a recording layer made of a Co alloy having an hcp structure, and a protective film 45 are formed.

In order to realize high-density magnetic recording, it is necessary to make the crystal grain size finer and narrow the crystal grain size distribution in accordance with the improvement in recording density. It satisfies the condition.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a magnetic recording medium according to the present invention will be described in more detail with reference to some embodiments of the present invention.

[0040]

Example 1 An in-plane magnetic recording medium having a cross-sectional structure shown in FIG. 1 was manufactured by a DC magnetron sputtering method using a glass substrate having a diameter of 2.5 inches. Substrate 1
On the substrate 1, a lower underlayer 12a, an upper underlayer 12b, a recording magnetic film 14, and a protective film 15 were formed in this order.

As a target for forming each film, a NiAl target for the lower base film 12a and an upper base film 12b
Co-Cr _x -M _y target use, for the recording magnetic film 14 Co-
A carbon target was used for the 21 at% Cr-15 at% Pt target and the protective film 15.

[0042] as a Co-Cr _x -M _y target, Co-25at
% Cr-6at% B, Co-25at% Cr-8at% Si, Co-25at% Cr-10
at% Ge, Co-25at% Cr-4at% Al, Co-25at% Cr-6at%
P, Co-25at% Cr-6at% Ti, Co-25at% Cr-10at% V, C
o-25at% Cr-4at% Zr, Co-25at% Cr-8at% Nb, Co-25at
% Cr-6at% Hf, Co-25at% Cr-10at% Mn, Co-25at% Cr-
12at% Rh, Co-25at% Cr-18at% Ir, Co-25at% Cr-14at
% Re, Co-25at% Cr-8at% Pd, Co-25at% Cr-6at% Pt,
Co-25at% Cr-4at% Mo, Co-25at% Cr-8at% W, Co-25a
t% Cr-4at% Ag and Co-25at% Cr-6at% Au were used.

Under the conditions of a sputtering Ar gas pressure of 3 mTorr, a sputtering power of 10 W / cm ² , and a substrate temperature of 250 ° C., the NiAl film of the lower underlayer 12 a is 15 nm, the upper underlayer 12 b is 5 nm, and the magnetic film 14 is 16 nm. Membrane 15
Was formed to a thickness of 8 nm. Protective film 1
5 was coated with a perfluoropolyether-based film (not shown) as a lubricating film.

As a comparative sample, Co-21at% Cr-15at was directly provided on the NiAl lower base film 12a without providing the upper base film 12b.
A sample in which the% Pt magnetic film 14 is formed (Comparative Example 1), and the upper underlayer 12b are provided, but the element M is not added to the film.
A nonmagnetic upper underlayer made of -35 at% Cr is formed on the NiAl lower underlayer 12a, and Co-21at% Cr-15at% Pt is formed thereon.
A sample on which the magnetic film 14 was formed (Comparative Example 2) was manufactured.

The coercive force of these samples was measured using a vibrating magnetometer (V
SM), and the recording / reproducing characteristics were evaluated using a recording / reproducing separated magnetic head. The gap length of the recording head is 0.2 μm, and the shield interval of the spin valve head for reproduction (highly sensitive magnetoresistive read head) is 0.2.
μm, and the spacing at the time of measurement (the distance between the recording medium and the head) was 0.04 μm. The measurement of the change over time of the recording signal was performed by measuring the reproduction output (St _{= 0} ) immediately after recording of the magnetic recording signal of 350 kFCI (FCI: change in magnetization per inch) and the reproduction output (St _{= 100} ) after 100 hours. It was evaluated as a ratio.

Table 1 shows the measurement results of the coercive force and the remaining ratio of the recorded signal ( _{St = 100} / _{St = 0} ) of the prepared sample.

[0047]

[Table 1]

The magnetic recording medium of the present invention has a high coercive force of 2.7 kOe or more, and has a recording signal remaining ratio of 0.9 or more. On the other hand, the coercive force of each of the samples of Comparative Examples 1 and 2 is 2.5 kOe or less, and the residual ratio of the recording signal is as low as 0.85 or less. Thus, it was confirmed that the magnetic recording medium according to the present invention was effective as a high-density magnetic recording medium with little deterioration of a recording signal.

Example 2 Using a glass substrate having a diameter of 2.5 inches, an in-plane magnetic recording medium having a cross-sectional structure shown in FIG. 2 was manufactured by DC magnetron sputtering. On the substrate 21, the base film 22, the side of the Co alloy system recording magnetic film 24a close to the substrate 21, a non-magnetic or weakly magnetic having an hcp structure ultrathin Co-Cr _x -M _y alloy film 23, closer to the surface Co on the side
The alloy-based recording magnetic film 24b and the protective film 25 were formed in this order.

For forming the under film 22, Cr and Cr-15at% T
Using two types of targets i, a 5 nm-thick Cr film was formed on the substrate 21 side, and a 5 nm-thick Cr-15at% Ti film was formed thereon, thereby forming the base film 22 into two layers. Further, Co-21 is used for forming the Co alloy-based recording magnetic film 24a.
An at% Cr-8at% Pt target was used.

[0051] Co-Cr _x -M as deposition target _y film 23, Co-30at% Cr- 5at% B, Co-30at% Cr-4at% Si,
Co-30at% Cr-6at% Ge, Co-30at% Cr-4at% Al, Co-30
at% Cr-6at% P, Co-30at% Cr-4at% Ti, Co-30at% Cr-
10at% V, Co-30at% Cr-4at% Zr, Co-30at% Cr-6at% N
b, Co-30at% Cr-6at% Hf, Co-30at% Cr-10at% Mn, C
o-30at% Cr-8at% Rh, Co-30at% Cr-8at% Ir, Co-30at
% Cr-7at% Re, Co-30at% Cr-8at% Pd, Co-30at% Cr-6
at% Pt, Co-30at% Cr-4at% Mo, Co-30at% Cr-4at%
W, Co-30at% Cr-3at% Ag and Co-30at% Cr-4at% Au were used.

For forming the Co alloy-based recording magnetic film 24b, C
An o-21at% Cr-10at% Pt target was used.

Under the conditions of a sputtering Ar gas pressure of 3 mTorr, a sputtering power of 10 W / cm ² , and a substrate temperature of 270 ° C., the base film 22 is formed of Cr-15at% Ti (5 nm) / Cr (5n
m), a total of 10 nm, a magnetic film 24a of 8 nm, Co-Cr _x -M
The y film 23 was formed to a thickness of 0.5 nm, the magnetic film 24b was formed to a thickness of 8 nm, and the carbon film 25 was formed to a thickness of 10 nm. A perfluoropolyether film was applied as a lubricating film on the protective film 25.

[0054] As comparative samples, very thin Co-Cr _x -M _y film 2
A magnetic recording medium having the same structure except that No. 3 was not formed was manufactured.

As in the case of Example 1, the coercive force of these samples was measured with a vibrating magnetometer, and the recording / reproducing characteristics were evaluated using a recording / reproducing separated magnetic head. The gap length of the recording head was 0.2 μm, the shield interval of the spin valve head for reproduction was 0.2 μm, and the spacing at the time of measurement was 0.04 μm. The measurement of the change over time of the recording signal was evaluated as the ratio of the reproduction output (St _{= 0} ) immediately after recording of the magnetic recording signal of 350 kFCI and the reproduction output (St _{= 100} ) after 100 hours.

Table 2 shows the measurement results of the coercive force of the prepared sample and the remaining ratio of the recorded signal ( _{St = 100} / _{St = 0} ).

[0057]

[Table 2]

The magnetic recording medium of the present invention has a high coercive force of 2.5 kOe or more, and the residual ratio of the recording signal is 0.9 or more. On the other hand, the coercive force of the sample of the comparative example is 2.3 kOe or less, and the residual ratio of the recording signal is as low as 0.8. Thus, it was confirmed that the magnetic recording medium according to the present invention was effective as a high-density magnetic recording medium with little deterioration of a recording signal.

Example 3 Using a glass substrate having a diameter of 2.5 inches, an in-plane magnetic recording medium having a sectional structure shown in FIG. 3 was produced by a DC magnetron sputtering method. On the substrate 31, a lower base film 32a, a non-magnetic or weakly magnetic having an hcp structure Co-Cr _x -M _y upper base film 32b, the substrate 31
Magnetic or weakly magnetic ultrathin Co-Cr _x -M _y film 33, the closer to the surface side Co alloy system recording magnetic film 34b having the side of Co alloy system recording magnetic film 34a, an hcp structure close to and, Protective film 3
5 were formed in this order.

[0060] As a target for the formation of the film, Cr target for the lower base film 32a, Co-Cr _x -M _y target for the upper base film 32b and the very thin film 33, the recording magnetic film 34a, for 34b A Co-21at% Cr-8at% Pt target was used.

[0061] as a Co-Cr _x -M _y target, Co-20at
% Cr-14at% B, Co-20at% Cr-14at% Si, Co-20at% Cr-
10at% Ge, Co-20at% Cr-10at% Al, Co-20at% Cr-10at
% P, Co-20at% Cr-14at% Ti, Co-20at% Cr-13at% V,
Co-20at% Cr-6at% Zr, Co-20at% Cr-10at% Nb, Co-2
0at% Cr-12at% Hf, Co-20at% Cr-16at% Mn, Co-26at%
Cr-12at% Rh, Co-26at% Cr-12at% Ir, Co-26at% Cr-
8at% Re, Co-26at% Cr-8at% Pd, Co-26at% Cr-6at% P
t, Co-20at% Cr-4at% Mo, Co-20at% Cr-8at% W, Co-
26at% Cr-6at% Ag and Co-26at% Cr-4at% Au were used.

Under the conditions of an Ar gas pressure for sputtering of 3 mTorr, a sputtering power of 10 W / cm ² and a substrate temperature of 270 ° C., the Cr of the lower underlayer 32 a is 10 nm, the upper underlayer 32 is
b of Co-Cr _x -M _y film 5 nm, the lower magnetic film 34a 8n
m, again Co-Cr _x -M _y film of the same kind as the very thin film 33 0.
3 nm, the upper magnetic film 34b was formed to a thickness of 8 nm, and the carbon film 35 was formed to a thickness of 10 nm. A perfluoropolyether film was applied as a lubricating film on the protective film 35.

[0063] As comparative samples, Co-Cr _x -M _y film 32b,
A magnetic recording medium having the same structure except that no 33 was formed was produced.

As in the case of Example 1, the coercive force of these samples was measured with a vibrating magnetometer, and the recording / reproducing characteristics were evaluated using a recording / reproducing separation type magnetic head. The gap length of the recording head was 0.2 μm, the shield interval of the spin valve head for reproduction was 0.2 μm, and the spacing at the time of measurement was 0.04 μm. The measurement of the change over time of the recording signal was evaluated as the ratio of the reproduction output (St _{= 0} ) immediately after recording of the magnetic recording signal of 350 kFCI and the reproduction output (St _{= 100} ) after 100 hours.

Table 3 shows the measurement results of the coercive force of the prepared sample and the remaining ratio of the recording signal ( _{St = 100} / _{St = 0} ).

[0066]

[Table 3]

The magnetic recording medium of the present invention has a high coercive force of 2.5 kOe or more, and the residual ratio of the recording signal is 0.9 or more. On the other hand, the coercive force of the sample of the comparative example is 2.3 kOe or less, and the residual ratio of the recording signal is as low as 0.8. Thus, it was confirmed that the magnetic recording medium according to the present invention was effective as a high-density magnetic recording medium with little deterioration of a recording signal.

Example 4 Using a glass substrate having a diameter of 2.5 inches, an in-plane magnetic recording medium having a sectional structure shown in FIG. 4 was produced by a DC magnetron sputtering method and a high-frequency magnetron sputtering method. On a substrate 41, an adhesion reinforcing layer 46, a lower base film 42a having a NaCl structure, an intermediate base film 42c, and a nonmagnetic or weak magnetic Co-Cr _x -having an hcp structure.
Upper base film 42b made of M _y film, closer to the substrate 41 side C
o alloy system recording magnetic film 44a, ultrathin Co-Cr _x nonmagnetic or weakly magnetic having an hcp structure -M _y film 43, the closer to the surface side C
o An alloy-based recording magnetic film 44b and a protective film 45 were formed in this order.

As targets for forming the respective films, a Cr target for the adhesion reinforcing layer 46, an MgO target for the lower base film 42a having a NaCl structure, and an intermediate base film 42c
Cr target use, Co-23at% Cr-10at % M as Co-Cr _x -M _y target for the upper base film 42b and the very thin film 43
n target, Co-21at% Cr-5at% Pt for magnetic film 44a,
A Co-20at% Cr-8at% Pt target was used for the magnetic film 44b, and a carbon target was used for the protective film 45.

Under the conditions of a sputtering Ar gas pressure of 3 mTorr, a sputtering power of 10 W / cm ² and a substrate temperature of 270 ° C., the Cr of the adhesion reinforcing layer 46 is 10 nm, and the lower underlayer 42 a
MgO film of 5 nm, and Cr film of the intermediate underlayer 42 c of 5 nm
m, 5 nm of Co-23at% Cr-10at% Mn film of the upper underlayer 42b.
m, 7.5n of Co-21at% Cr-5at% Pt film of the magnetic film 44a.
m, the Co-23at% Cr-10at% Mn film of the very thin film 43 is 1 nm,
As the magnetic film 44b, a Co-20at% Cr-8at% Pt film was formed to a thickness of 8 nm, and a carbon film 45 was formed to a thickness of 10 nm. High frequency magnetron sputtering was used to form the MgO film as the lower underlayer 42a.

As in the case of Example 1, the coercive force of the prepared sample was measured by a vibrating magnetometer, and the recording / reproducing characteristics were evaluated using a recording / reproducing separated magnetic head. The gap length of the recording head was 0.2 μm, the shield interval of the spin valve head for reproduction was 0.2 μm, and the spacing at the time of measurement was 0.04 μm. The measurement of the change over time of the recording signal was evaluated as the ratio of the reproduction output (St _{= 0} ) immediately after recording of the magnetic recording signal of 350 kFCI and the reproduction output (St _{= 100} ) after 100 hours.

The coercive force of the sample was as high as 3.6 kOe, and the residual ratio of the recording signal was 0.95 or more.
It has been confirmed that the recording medium of the present invention has excellent properties as a high-density magnetic recording medium having a high coercive force and a small deterioration of a recording signal.

<Embodiment 5> Upper underlayer 32b of Embodiment 3
And in the non-magnetic or weakly magnetic in Co-Cr _x -M _y film having a hcp structure is extremely thin film 33, the additional element M to one type of Mn, the composition Cr: 0~50at%, Mn: 0~50at %, Thereby producing a plurality of magnetic recording media. The manufacturing conditions are the same as in Example 3, and the cross-sectional structure of the manufactured recording medium is the same as that in FIG. Co-Cr _x
As -mn _y film forming target, by placing the pellets of Cr and Mn chip over the Co target was performed to adjust the composition.

As in the case of Example 3, the coercive force of the prepared sample was measured with a vibrating magnetometer, and the recording / reproducing characteristics were evaluated using a recording / reproducing separated magnetic head. The gap length of the recording head was 0.2 μm, the shield interval of the spin valve head for reproduction was 0.2 μm, and the spacing at the time of measurement was 0.04 μm. The measurement of the change over time of the recording signal was evaluated as the ratio of the reproduction output (St _{= 0} ) immediately after recording of the magnetic recording signal of 350 kFCI and the reproduction output (St _{= 100} ) after 100 hours.

The measurement results of the coercive force and the residual ratio of the reproduction output ( _{St = 100} / _{St = 0} ) of the prototype medium are shown in FIGS. 5 and 6, respectively. Co-Cr _x -Mn composition range of _y is 25 at% ≦ x
When + y ≦ 50 at% and 0.5 at% ≦ y, it was confirmed that a particularly high coercive force and a high residual ratio of reproduction output were achieved, and the above composition range was particularly effective for a high-density magnetic recording medium. It was confirmed that there was.

[0076]

According to the present invention, the high coercive force of the magnetic recording medium and the stability of the thermal fluctuation can be ensured, so that high-density magnetic recording of 10 Gb / in ² or more can be achieved, and the size of the apparatus can be reduced. It is easy to increase the capacity and increase the capacity.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view for explaining a second embodiment of the present invention.

FIG. 3 is a sectional view for explaining a third embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining a fourth embodiment of the present invention.

[5] curves for explaining the relationship between Co-Cr _x -Mn _y composition and medium coercivity.

[6] curve diagram for explaining a relationship between residual ratio of Co-Cr _x -Mn _y composition and the recording signal.

[Explanation of symbols]

11, 21, 31, 41 ... substrate, 12a, 32a, 42a
... lower underlayer, 12b, 32b, 42b ... Co -Cr x -M y upper base film 22 ... base film, 42c ... intermediate underlayer, 14 ...
Recording magnetic film, 24a, 34a, 44a ... substrate side recording magnetic film, 24b, 34b, 44b ... surface side recording magnetic _{film, 23,33,43 ... Co-Cr x -M} y alloy ultrathin Membrane, 1
5, 25, 35, 45: protective film, 46: adhesion reinforcing layer.

Continued on the front page (72) Inventor Teruaki Takeuchi 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside Hitachi, Ltd. Central Research Laboratory (72) Inventor Yukio Honda 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi, Ltd. (56) References JP-A-10-334444 (JP, A) JP-A-10-233016 (JP, A) JP-A-7-57233 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/738 G11B 5/64-5/673

Claims (4)

(57) [Claims] A lower base film having 1. A bcc structure or B2 structure, and an upper base film formed on the lower base film and a upper underlayer magnetic film formed on the upper bottom The ground film is made of Co-C with a hexagonal close-packed structure containing the non-magnetic element M.
r-M film, and the non-magnetic element M is B, S
i, Ge, an element selected from C and P or Ranaru group, and also the composition of the Co-Cr-M film Co-Cr _x -
When expressed as _{M y, 25at% ≦ x +} y ≦ 50at%, 0.
A magnetic recording medium, wherein 5 at% ≦ y. 2. The method according to claim 1, wherein the lower underlayer is made of NiAl, FeAl,
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is made of a material having a B2 structure selected from the group consisting of FeV, CuZn, CoAl, and CuPd. 3. The method according to claim 1, wherein the lower underlayer is made of Cr, Cr—Ti, C
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is made of a material having a bcc structure selected from the group consisting of r-Mo, Cr-W, Cr-Nb, and Cr-V. 4. Co-C having a hexagonal close-packed structure containing a nonmagnetic element M
an upper magnetic film and the lower magnetic film separated the magnetic film by the r-M film, the non-magnetic element M, B, Si, Ge, C
And P or Ranaru an element selected from the group, and the C
When the composition of the o-Cr-M film was expressed as the Co-Cr _x -M _y, 2
A magnetic recording medium, wherein 5 at% ≦ x + y ≦ 50 at% and 0.5 at% ≦ y.