JPH0421921A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a coercive force and residual magnetization quantity by forming the magnetic layers of the magnetic recording medium of alloys consisting of specific compds. CONSTITUTION:The plural magnetic layers laminated on a nonmagnetic sub strate 1 are formed of one or >=2 kinds of alloys selected from a group consisting of Co-Cr-Ta, Co-Cr-Hf, Co-Cr-Zr. These magnetic layers 3, 5, 7, 9 are alternately laminated with a 1st Cr layer 2, a 2nd Cr layer 4, a 3rd Cr layer 6 and a 4th Cr layer 8. Since plural layers of the magnetic layers are laminated by inserting Cr layers as underlying layers between these layers and, therefore, the residual magnetization quantity is equal to the residual magnetization quantity of the single magnetic layer having the thickness corre sponding to the sum of the thicknesses of the plural magnetic layers even if the thicknesses of the respective magnetic layers are reduced so as to obtain the sufficiently high coercive force. The hysteresis curve which is high in both of the coercive force and the residual magnetization quantity and is clean even if the Cr layers are relatively thin, is therefore, obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium having a plurality of magnetic layers,
In particular, the present invention relates to a magnetic recording medium that has high coercive force, enables high-density recording, and has excellent information recording group □ production characteristics.

[Prior Art] In recent years, as the amount of information has increased, there has been a strong demand for the development of magnetic recording media with high recording density and excellent information recording and reproducing characteristics. For this reason, active research and development is being carried out on magnetic recording media having alloy magnetic thin films with high coercivity. In such magnetic recording media, the magnetic layer is usually formed by sputtering. Furthermore, in order to further improve the coercive force, a magnetic disk in which a plurality of magnetic layers are formed has been proposed (Japanese Unexamined Patent Publication No. 63-244309). That is, in a magnetic recording medium in which a magnetic thin film medium layer with a single layer structure is formed by the plating method, as the film thickness increases, there is a relationship between the film thickness of the magnetic thin film medium layer and the coercive force and residual magnetization amount. There is a relationship in which the amount of residual magnetization increases, but the coercive force decreases. For this reason, it is difficult to obtain a magnetic recording medium that is excellent in both the amount of residual magnetization and the coercive force. Therefore, in the above-mentioned conventional technology, by stacking a plurality of magnetic thin film media layers with non-magnetic layers interposed between them, the thickness of the unit magnetic layer is reduced to increase the coercive force, and the unit magnetic layer is The amount of residual magnetization is increased by integrally laminating a plurality of magnetic layers.

[Problems to be Solved by the Invention] However, in conventional magnetic recording media in which each magnetic layer itself is thinned and multiple magnetic layers are laminated, the coercive force is at most 800 (Oe), which is lower than the current high coercivity. This does not fully satisfy the demand for increased recording density. Therefore, there is an urgent need to develop a magnetic recording medium that has extremely high coercive force and can fully meet the demands for higher recording densities.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a magnetic recording medium that has extremely high coercive force and residual magnetization, and can significantly improve recording density.

[Means for Solving the Problems] A magnetic recording medium according to the present invention is a magnetic recording medium in which a laminate in which a plurality of Cr layers and a plurality of magnetic layers are alternately stacked on a non-magnetic substrate is arranged. The magnetic layer is Co-Cr
-Tat Co-Cr-HfzCo-Cr-Zr and C
It is characterized by being made of one or more alloys selected from the group consisting of o-Cr-Hf-Zr.

In this case, the thickness of the Cr layer disposed between the magnetic layers is preferably 5 to 600 mm.

[Operation] In the present invention, a plurality of magnetic layers are stacked with a Cr layer as an underlayer sandwiched between them, so the thickness of each magnetic layer is made thin so as to obtain a sufficiently high coercive force. However, the amount of residual magnetization is equivalent to the amount of residual magnetization of a single magnetic layer having a thickness corresponding to the sum of the thicknesses of a plurality of magnetic layers. Therefore, in the present invention, both the coercive force and the amount of residual magnetization are high.

Moreover, in the present invention, the magnetic layer is made of Co-Cr-Ta.
5 Co-Cr-Hf1Co-Cr-Zr or Co-
It is formed of any alloy of Cr-Hf-Zr,
A Cr layer is arranged as a nonmagnetic layer between these magnetic layers. However, if another layer such as carbon is placed between the magnetic layers, the hysteresis curve will be distorted, but if a Cr layer is placed between the magnetic layers as in the present invention, this Cr layer will be distorted. A clean hysteresis curve can be obtained even if it is relatively thin. In this way, Co-Cr-T
Due to the synergistic effect of the magnetic layer such as the a-alloy and the Cr layer, the amount of residual magnetization can be maintained high and the coercive force can be made much higher than before.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the layer structure of a magnetic recording medium according to an embodiment of the present invention. The nonmagnetic substrate 1 is an aluminum alloy substrate coated with a Ni--P alloy, and has an appropriate surface smoothness. A first Cr layer 2 is formed on this nonmagnetic substrate 1 as an underlayer. Furthermore, this 1st C
A first magnetic layer 3 is formed on the r layer 2. Then, on this first magnetic layer 3, a second Cr layer is formed as an intermediate base Cr layer.
A Cr layer 4 is formed. Further, a second magnetic layer 5 is formed on the second Cr layer 4, and the second magnetic layer 5 is further covered with a protective film layer 10. Both the first and second magnetic layers 3 and 5 are, for example, CoCrt4Ta3.
The magnetic layer is made of an alloy having the following composition (Cr: 14 atomic %, Ta: 3 atomic %, and the balance is Co. Hereinafter, the magnetic layer alloy composition is similarly expressed in atomic %). Further, the protective film layer 10 has a thickness of about 300 nm and is made of carbon. Each of these layers can be formed by sputtering.

The thickness of the base Cr layer 2 is usually 500 to 4000, but preferably about 1500.

Further, it is preferable that the thickness of each magnetic layer 3, 5 is 200 to 600 layers. In the case of a single magnetic layer, the thickness is preferably 200 to 1500 mm in order to balance both the coercive force and the amount of residual magnetization, but in the present invention, the amount of residual magnetization is Since this is ensured by laminating the magnetic layer, the magnetic layer can be made thin enough to obtain a sufficiently high coercive force. Therefore, in order to increase the coercive force, the thickness of the magnetic layer 3.5 is made 200 to 600 thick, which is thinner than in the case of a single layer. More preferably, the thickness of each magnetic layer 3, 5 is 300 to 400 layers, for example, 380 layers.

When forming the second magnetic layer 5, the total thickness of the first and second magnetic layers 3.5 is substantially the same as the thickness of a single-layer magnetic layer having a predetermined amount of residual magnetization. Set it as follows.

As mentioned above, the magnetic recording medium of this example has a laminate of the first Cr layer 2 and the first magnetic layer 3 and a laminate of the second Cr layer 4 and the second magnetic layer 5 on the nonmagnetic substrate 1. It is composed of layers. Generally, the amount of residual magnetization is determined by the magnetic film 3,
5, and this total thickness approximately corresponds to the thickness of the magnetic layer in the case of a single layer.

In Figure 2, the horizontal axis shows Co　Cr　14MX　(M is Ta.

Hf + Zr, X indicates atomic % of atoms M), and the vertical axis represents the coercive force and residual magnetization [residual magnetic flux density x film thickness (G・μ)]. FIG. 3 is a graph showing the relationship between the thickness of the magnetic layer, coercive force (06), and amount of residual magnetization when the magnetic layer is a single layer. For example, if the magnetic layer is C0Crt
In the case of 4Hfs, the coercive force is extremely high at about 1900 (Oe) when the thickness of the magnetic layer is 380. However, the amount of residual magnetization is as low as 320 G·μm. On the other hand, when the thickness of the magnetic layer is 760, the amount of residual magnetization is about 570.
Although it has a high recording/reproducing property of G.μm and has good recording and reproducing characteristics, its holding force is about 1500 (Oe), and it cannot be said that it has the holding force capable of achieving the high recording density that is required these days.

For this reason, after forming the second Cr layer, which is an intermediate underlayer, on the first magnetic layer 3 with a film thickness of 380, the second Cr layer is
A second magnetic layer 5 having a thickness of 380 nm is formed on layer 4.

Then, a carbon protective layer 10 with a thickness of 3 (10 λ) is formed on the uppermost layer. Then, a magnetic recording medium having a high residual magnetization of about 800 G·μm and a high coercive force of 1900 (Oe) is obtained.

The thickness of the second Cr layer 4, which is an intermediate underlying Cr layer formed between the first magnetic layer 3 and the second magnetic layer 5, is 5 to 600 mm.
Preferably a person. If the thickness of the second Cr layer 4 is less than 5 layers, the effect of stacking multiple layers by thinning the magnetic layer and interposing a non-magnetic layer between them is small, and extremely high coercive force is obtained. I can't say that. On the other hand, if the thickness of the second Cr layer 4 exceeds 800 layers, the effect of improving the coercive force is small even though it takes a long time to form the Cr layer, and the manufacturing efficiency of the magnetic recording medium deteriorates. Furthermore, when the thickness of the intermediate Cr layer 4 exceeds 600 Å, the distance between the magnetic head point and the magnetic layer increases due to the presence of the Cr intermediate layer 4, resulting in a spacing loss. This reduces recording density.

For this reason, it is preferable that the thickness of the intermediate base Cr layer 4 is 5 to 800 layers.

The magnetic recording medium configured as described above has extremely high coercive force and residual magnetization, and therefore has excellent recording and reproducing characteristics and extremely high recording density.

FIG. 3 is a sectional view showing a magnetic recording medium according to another embodiment of the present invention. In this magnetic recording medium, a third magnetic layer 7 is formed on the second magnetic layer 5 via a third Cr layer 6 as an intermediate base Cr layer, and further on the third magnetic layer 7. , a fourth magnetic layer 9 is formed with a fourth Cr layer 8 as an intermediate underlying Cr layer interposed therebetween. And this fourth
A protective film layer 10 made of carbon is formed on the magnetic layer 9. Moreover, each magnetic layer 3.5, 7.9 is made of C0Cr
It is made of t4Hfs alloy.

In this way, the first to fourth four magnetic layers 3,5°7.9
and four Cr layers 2.4.8. between the first to fourth layers.
A magnetic recording medium stacked with 8 interposed therebetween also exhibits the same effect as the magnetic recording medium shown in FIG. Further, since the magnetic layer 4 is composed of four layers, the thickness of each magnetic layer 3, 5, 7.9 can be made half the thickness of the case of 190 people and FIG. 1, for example. Therefore, the holding force can be further increased. Further, in the magnetic recording medium of this embodiment, the coercive force as a magnetic recording medium also changes depending on the thickness of the intermediate Cr layer. In this embodiment as well, the thickness of this intermediate base Cr layer is preferably 5 to 800 layers, more preferably 10 to 500 layers.

The constituent material of the magnetic layer in the present invention is not limited to the CoCr□4Ta3 alloy or GoCrt4Hft alloy of each of the above embodiments, but also C0-Cr-Ta, Go-Cr-Hf, Co-Cr-Zr, and Co. Various magnetic alloys can be used as long as they are -Cr-Hf-Zr alloys.

Table 1 below shows C0Crt4Ta3, C00rtaHft and CoC as representative alloys of these systems.
r14Zr□ was selected and the measured value of its saturation magnetic flux density is listed. As can be seen from Table 1, the alloys constituting each of the above-mentioned magnetic layers have extremely high saturation magnetic flux densities. However, this Table 1 is data for a magnetic recording medium in which 760 single-layer magnetic layers were formed on an underlying Cr layer. The magnetic recording medium of each of the above embodiments is, for example,
These are two or four laminated layers of 380 or 190 thin magnetic layers with a Cr layer sandwiched between them, and the saturation magnetic flux density of each magnetic layer is determined based on the data in Table 1. can do.

Table 1 Next, the results of actually manufacturing magnetic recording media according to examples of the present invention and evaluating their characteristics will be explained in comparison with comparative examples.

: The surface of an aluminum alloy substrate (external diameter: 95 mm, inner diameter: 25 mm, thickness: 1.3 mm) with N1-P plating was precisely polished using a lapping machine, and then subjected to texturing treatment to obtain a nonmagnetic substrate. This non-magnetic substrate was placed in a DC magnetron sputtering device, and after evacuation at an initial vacuum level of 7 x 10-7 torr or less, the first Cr layer 2, which was a base Cr layer, was sputtered at a sputtering pressure of 5 x 10'' torr to 1,500 torr. Formed with the thickness of a person.

Next, under the same sputtering conditions, C0Cr, 4T a
The first magnetic layer 3 of No. 3 was formed to have a thickness of 380 mm.

Furthermore, the film thickness shown in Table 2 below (first example Na1-7;
5 to 600 people, first comparative example Na1-2; 0 or 8
A second Cr layer 4, which was an intermediate base Cr layer, was formed using the following methods. The magnetic recording medium of Comparative Example 1 in which the second Cr layer 4 of the intermediate underlying Cr layer has a thickness of 0 is a single layer (thickness of 760) in which the first magnetic layer 3 and the second magnetic layer 5 are in direct contact with each other. It has a magnetic layer of

After that, repeat the same operation to create C0Crt4Ta3
After forming the second magnetic layer 5 with a thickness of 380 mm, a carbon protective film of 300 mm was formed.

The measurement results of the coercive force of the magnetic recording medium thus obtained are shown in Table 2 in correspondence with the thickness of the second Cr layer 4.

As is clear from this Table 2, as in this example, C
By forming a laminate of the r layer and the magnetic layer, an extremely high coercive force can be obtained compared to the conventional maximum of 800 (Oe). Furthermore, the magnetic recording media of Examples Nα1-7 in which the thickness of the second Cr layer 4 is in the range of 5 to 600 Oe have an extremely high coercive force of 650 Oe or more.

Table 2: As in the first example, a non-magnetic substrate was prepared by subjecting an N1-P plated aluminum alloy substrate to a predetermined treatment.

Table 3 Then, the sputtering operation was repeated under the same conditions as in the first example except that the material of the magnetic layer was GOCrt4Hfs alloy instead of C0Cr+4Hf1 alloy.
Second Example 1- The thickness of the second Cr layer 4 is shown in Table 3 above.
Magnetic recording media of Comparative Example 7 and Second Comparative Example 1-2 were obtained. Table 3 also shows the measurement results of the coercive force of this magnetic recording medium.

As is clear from Table 3, the magnetic layer is C0Cr+4
Even in the case of Hf1, a high coercive force of 1510 (Oe) (Comparative Example 1) or more can be obtained by forming a laminate of this magnetic layer and a Cr layer. Furthermore, in the case of the magnetic recording medium of Example Na1-7 in which the thickness of the second Cr layer 4 is 5 to 600, the coercive force is extremely high at 1880 (Oe) or more.

: Similarly to the first example, a non-magnetic substrate was prepared by subjecting a Ni-P plated aluminum alloy substrate to a predetermined treatment. The material of the magnetic layer is C.

Co Cr 14Zr instead of Cr 14T a 3
The sputtering operation was repeated under the same conditions as in the first example except that s was used, and the magnetic recording of the third example N (11-7 and the third comparative example N [L12) with the film thickness shown in Table 4 below was performed. Got the medium.

The measurement results of the coercive force of each magnetic recording medium of the third example Na1-7 and the third comparative example Na1-2 are also shown in Table 4.

Table 4 As shown in Table 4, the magnetic layer is C0Cr14Zr□
Even in the case where the coercive force is 1480 (Oe) or more, especially when the thickness of the second Cr layer 4 is 5 to 600 mm, an extremely high coercive force of 1880 (Oe) or more can be obtained. .

: Similar to the second example, after a predetermined treatment was performed on an NLP-plated aluminum alloy substrate, layers up to the second magnetic layer 5 were formed by sputtering. After that, further intermediate base Cr
After forming a third Cr layer 6 as a layer, a third magnetic layer 7 made of CoCr 14Hfl, a fourth Cr layer 8 as an intermediate underlying Cr layer, and a fourth magnetic layer 9 made of COCr 14Hfl under similar sputtering conditions. A magnetic recording medium was prepared by forming a carbon protective film layer 10 with a thickness of 300 layers.

At that time, a second Cr layer 4, which is an intermediate base Cr layer. 3rd Cr
Fourth Example N11-1 shown in Table 5 below by changing the film thicknesses of the layer 6 and the fourth Cr layer 8 in the range from IO to 600.
0 magnetic recording media were obtained. In addition, these intermediate base C
A magnetic recording medium of a fourth comparative example Nα1-4 was obtained by setting the film thickness of one of the Cr layers among the r layers to O or 800 mm.

Table 5 and, Measurement of the coercive force of each of these magnetic recording media The results are shown in Table 5.

As is clear from Table 5, the three Cr layers 4°6.
When the film thickness of No. 8 is either 10.50.100 or 800, the coercive force is extremely high at 1800 (Oe) or more.

In addition, in the case of the comparative example in which the film thickness of either of these Cr layers is 800 mm, although the coercive force is high, the manufacturing process is long, and the effect of increasing the coercive force is small in comparison, so it is useless. . Furthermore, if the thickness of the Cr layer is increased by 800 mm, the spacing loss will increase and the recording density will decrease, which is not preferable.

[Effects of the Invention According to the present invention, Co-Cr-Ta5 Co-Cr-H
f1 A plurality of magnetic layers formed of one or more alloys selected from the group consisting of Co-Cr-Zr and Co-Cr-Hf-Zr, and an intermediate base Cr disposed between each of the magnetic layers. Since it is composed of a laminated body of layers, an extremely high coercive force can be obtained, and the amount of residual magnetization is also extremely high.

Therefore, the present invention is extremely useful as a magnetic recording medium that has excellent recording and reproducing characteristics and enables high recording density.

[Brief explanation of the drawing]

1 is a cross-sectional view showing a magnetic recording medium according to an embodiment of the present invention, 2rXJ is a graph showing the relationship between magnetic film thickness, coercive force, and residual magnetization amount, and FIG. 1 is a cross-sectional view showing a magnetic recording medium according to an example. 1; Non-magnetic substrate, 2; First Cr layer, 3; First magnetic layer, 4
; second Cr layer, 5; second magnetic layer, 6; third Cr layer, 7;
Third magnetic layer, 8; Fourth Cr layer, 9; Fourth magnetic layer, 10;
protective film layer

Claims (2)

[Claims] (1) In a magnetic recording medium in which a laminate in which a plurality of Cr layers and a plurality of magnetic layers are alternately laminated on a nonmagnetic substrate, the magnetic layer is Co-Cr-Ta, Co-Cr-H
A magnetic recording medium characterized in that it is formed of one or more alloys selected from the group consisting of f, Co-Cr-Zr, and Co-Cr-Hf-Zr. (2) The magnetic recording medium according to claim 1, wherein each of the Cr layers disposed between the magnetic layers has a thickness of 5 to 600 Å.