JPH03160616A - Double-layer perpendicular magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a double-layer tape for perpendicular magnetic recording having stable properties and to realize the production method of such tapes at high productivity by constituting the magnetic layer for magnetic recording of two-layer structure comprising a base of smaller saturation magnetization and an upper layer of larger saturation magnetization. CONSTITUTION:A layer of low coercive force having the axis of easy magnetization in its surface plane, for example, Permalloy layer B (Ni-Fe) is formed to 0.075mum thickness on a nonmagnetic substrate film A such as polyimide film by sputtering an opposite target. Then magnetic recording layers having the axis of easy magnetization perpendicular to the plane, such as Co-Cr are deposited into two layers. The first base layer C has smaller saturation magnetization with <= 0.05mum thickness, while the second upper layer D has larger saturation magnetization with such thickness that the total thickness with the lower layer becomes <=0.15mum. Since the saturation magnetization of the Co-Cr base layer adjacent to the Permalloy layer is small, a double-layer tape for perpendicular magnetic recording having good characteristics can be obtained with little deterioration of initial magnetic permeability.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to a perpendicular magnetic recording medium and a method for manufacturing the same. (Summary of the Invention) The present invention relates to a perpendicular magnetic recording dual-layer medium and a method for manufacturing the same. In a perpendicular magnetic recording medium in which a magnetic recording magnetic layer having an axis is sequentially formed, the magnetic recording magnetic layer is formed of an underlayer with a lower saturation magnetization and an upper layer with a higher saturation magnetization, and the magnetic recording layer of the series of magnetic recording layers is is formed using a sputtering method under specific conditions. In this way, a high-performance perpendicular magnetic recording medium suitable for high-density storage and an efficient manufacturing method have been realized.

(Prior Art) In recent years, with the demand for higher density magnetic recording, research has been actively conducted on so-called perpendicular magnetic recording methods in which recording is performed in the thickness direction of a magnetic layer.

These perpendicular magnetic recording media are mainly manufactured by vacuum evaporation, sputtering, or plating methods. In particular, perpendicular magnetic recording media manufactured by the sputtering method have been actively researched because the magnetic properties of the magnetic film can be easily controlled. ing.

However, when performing high-density recording, it is necessary to significantly reduce the recorded bit length, narrow tracks, and widen the band, and therefore, a high C/N is required.

For this reason, a combination of a perpendicular magnetic recording head and a so-called "perpendicular magnetic recording dual-layer medium" in which a soft magnetic layer made of a Ni-Fe alloy is formed between a perpendicular magnetic recording layer made of a Co-Cr alloy and a base film. A recording method is being researched.

According to this method, strong magnetic interaction occurs between the main pole of the perpendicular magnetic recording head and the soft magnetic layer of the perpendicular dual-layer medium, generating lines of magnetic force perpendicular to the film thickness direction. Therefore, ideal perpendicular magnetic recording can be performed even at high recording densities, and even during playback, the soft magnetic layer acts as a return bus, resulting in high playback output power. (Problem to be solved by the invention) In order to realize a perpendicular magnetic recording double layer tape, Go-C
The film thickness of the r/Ni-Fe perpendicular magnetic recording dual-layer medium was set to 0.
It needs to be about 25 μm or less. This is because when the thickness of the two-layer medium is increased, the tape itself loses its flexibility, resulting in various disadvantages in use.

Conventional perpendicular two-layer media uses a permalloy film (permalloy), which is a soft magnetic layer.
The film thickness of Ni-Fe (Ni-Fe) itself can be made thin, but if this thickness is reduced to 0.1 μm or less, the Co-Cr on it
The magnetic interaction between the hard magnetic layer and the permalloy layer causes a significant deterioration in the magnetic properties of the permalloy layer, resulting in a drawback that a two-layer tape with stable performance cannot be realized. This makes it difficult to commercialize double-layer perpendicular magnetic recording tapes. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a two-layer tape capable of perpendicular magnetic recording with stable performance and a manufacturing method for manufacturing the same with good mass productivity.

(Means for Solving the Problems) The inventors of the present invention have investigated this problem and found that in perpendicular magnetic recording dual-layer media, the saturation magnetization and film thickness of Co-Cr are 0.05 μm to 0.1 μm. It was found that there is a strong correlation between the initial magnetic permeability of Vermalloy and that the initial magnetic permeability of Permalloy decreases as the saturation magnetization of Co-Cr increases.

Therefore, Co-Cr with a saturation magnetization of 51 to 514 (emu/cc) was deposited on a vermalloy layer with a thickness of 0.075 μm.
, and further saturation magnetization of 514 (emu
/cc) of Co-Cr until the total thickness of the underlayer and upper layer is 0.15 μm, it is possible to prevent the initial magnetic permeability of permalloy from deteriorating, and how to efficiently manufacture it. I found it. In addition, by controlling the saturation magnetostriction constant λ of the permalloy film by changing the &II strength of Fe, the axis of easy magnetization of the permalloy film is within the film plane and is within the range of 60 degrees to 120 degrees with respect to the tape running direction. I was able to do something.

(Function) According to the present invention, Vermalloy 7 of the perpendicular magnetic recording dual layer medium
1. Since the saturation magnetization of the Co-Cr underlayer immediately above the (Ni-Fe) layer is smaller, its initial permeability does not deteriorate to the left, making it possible to realize a double-layer tape for perpendicular magnetic recording with good performance. Furthermore, since these layers can be manufactured efficiently using the easily controlled sputtering method, a manufacturing method with high mass productivity can be realized. (Examples) The present invention will be described in detail below by way of examples with reference to the accompanying drawings.

FIG. 1 schematically shows the basic structure of the perpendicular magnetic recording dual-layer medium according to the present invention. To explain the structure shown in FIG. 1 in more detail, first, a low coercive force magnetic layer, such as a permalloy layer (Ni-Fe) having an axis of easy magnetization in the film plane, is placed on a non-magnetic substrate film made of a polyimide film, as described below. It is deposited to a thickness of, for example, 0.075 μm by target sputtering. Subsequently, a magnetic recording layer, such as a Co--Cr layer, having an axis of easy magnetization perpendicular to the film is deposited, but in the present invention, this is deposited in two stages. That is, the IN-th Co-Cr underlayer has a smaller saturation magnetization of 50 emu/cc to 200 e+wu/cc and is shaped to a thickness of 0.05 μ- or less, and the second layer C
The o-Cr top layer has a larger saturation magnetization of 200 emu
/cc and the sum of the thickness of the base layer is 0.15 μm or less.

These film forming conditions will be explained in more detail in the specific examples given below, but at the same time, from the first to fifth specific examples, the appropriate film forming conditions for the first layer of Co-Cri are permalloy shown in the third figure. It can be determined from the initial magnetic permeability change of the film. Figure 3 is an experimental curve showing the change in the initial magnetic permeability of the Barmalow f film with respect to its predetermined film thickness using the lNth saturation magnetization of Co-Cr as a parameter.
rAppropriate film conditions for the first layer are saturation magnetization of 50 emu/
cc~200emu/cc, the film thickness is 0.05μ by taking the point where the thickness is smaller than the saturation curve of initial permeability versus film thickness.
It can be set as below.

(Specific example 1) Vermalloy target: Ni-Fe (Ni: 80 atomic%,
Sputtering argon pressure: ls+Torr Input power: 1,0 kW Fe: 20 atomic%) Substrate temperature: 115°C Film thickness: 0.075 μm Saturation magnetostriction constant
: +4 XIO-'1 of Co-Cr '131 Target: Co-Cr (Co: 67 atomic%,
Cr: 33 at%) Sputtering argon pressure: 1 mTo
rr Input power: 1.0 kW Substrate temperature: 115°C Film thickness: 0.015 to 0.075 μ
m Saturation magnetization: 51 (emu/cc)2
co-Cr, target: Co-Cr (Co: 79 atomic%,
Cr: 21 atomic%) Sputtering argon pressure: l m
Torr input power: 1. O kW Substrate temperature: 115°C Film thickness: 0.15 μm in total with Co-Cr in the 1st layer Saturation magnetization: 514 (emu/cc
) (Specific Example 2) In Specific Example 1, the target of the first layer Co--Cr film is Co: 70 atomic %, Cr: 30 atomic %, and the saturation magnetization is 160 (e+wu/cc). (Specific Example 3) In Specific Example 1, the target of the 11th Co-Cr film was Co: 73 at%, Cr: 27 at%,
The saturation magnetization is 221 (emu/cc).

(Specific Example 4) In Specific Example 1, the target of the IN-th Co-Cr film was Co: 76 at%, Cr: 24 at%,
The saturation magnetization is set to 355 (emu/cc). (Specific Example 5) In Specific Example 1, the first layer Co-Crl'J target was Co: 79 at%, Cr: 21 at%,
The saturation magnetization is set to 514 (emu/cc). As described above, a Co-Cr layer consisting of two layers with a film thickness of 0.15 μm was formed on a permalloy film with a film thickness of 0.075 μm.
An alloy film is formed. This weakens the magnetic interaction between the Vermalloy film and the first-layer Co-Cr film, which has a small saturation magnetization, so that the initial magnetic permeability of the Permalloy film can be prevented from deteriorating.

To change the saturation magnetization value of the first and second Co-Cr films, in addition to using a pair of targets with the same m for each layer as described above, it is also possible to A pair of targets facing each other like a grasshopper method
- Cr target 1 (Co: 67 atomic%, Cr:
33 at%) and Co-Cr target 2 (Co:7
9 atomic %, Cr: 21 atomic %), the first layer of Co--Cr film with low saturation magnetization and the second layer of Co--CrH with high saturation magnetization can be combined at the same time.

In FIG. 2, the angle from the center of target l-1 to the slit l in its vicinity is θ. , the angle at which the distant slit 2 is viewed is θ12, and the angle at which the nearby slit 2 is viewed from the center of the other target 2 is θ. , when the angle at which the distant slit 1 is viewed is θ2l, θl2 and θ. Arrange a max 5 whose shape is always zero. At this time, if the mask 5 is moved along the circumference of the mask 4, θ. and θ1
2 changes in conjunction with each other, and by changing the widths of slit 1 and slit 2, the film thicknesses of the first and second layers can be controlled. By controlling the position of the mask 5 and the sputtering power using the film thickness gauge 8, the film thicknesses of the IN-th and second layers can be set to desired thicknesses.

In order to confirm this, we prepared a pair of opposing Go-Cr targets with different composition ratios}1 (Co:7) as shown in Figure 4.
3 atomic%, Cr: 27 atomic%) and target 2 (C
The saturation magnetization on the substrate when sputtering O: 79 atomic %, Cr: 21 atomic %) was investigated.

Target 1: Co-Cr (Co: 73 atomic%, Cr: 27 atomic%, saturation magnetization 22Hen+u/
cc)) Target 2: Co-Cr (Co:
79 at%, Cr: 21 at%, saturation magnetization 514
(es+u/cc)) Distance between target 1 and target 2 idl:frew Spatter argon pressure: 1 sT
orr input power? 1.0 kk Substrate temperature = 115°C Film thickness: 0.15 μm Figure 5 shows the saturation magnetization distribution of the Co--Cr sputtered film formed between target 1 and target 2. "
"Distance from Target 1" is the distance measured from the surface of Target 1 in the direction of Target 2 in FIG.

FIG. 6(a) shows the Ni-Fe (Ni: 80 at%, Fe: 20 at%, saturation magnetostriction constant +4X10-
') M-H loop (magnetization curve) in the tape running direction of the film,
Figure 6 (b) shows the M-H lube of the same film in the direction perpendicular to the tape running direction. It can be seen from this figure that the direction perpendicular to the tape running direction is the axis of easy magnetization.

Further, Fig. 6(C) shows Ni-Pe (Ni: 84 at%, Pe: 16 at%, saturation magnetostriction constant -7X10-
') M-H loop in the tape running direction of the membrane, Figure 6(d)
is the M-H loop of the same film in the direction perpendicular to the tape running direction. From this figure, the tape running direction is the axis of easy magnetization. Furthermore, the saturation magnetostriction constant of the permalloy layer is increased from +2×10 to +
By setting the magnetic field to about 1×10-', the axis of easy magnetization of the vermalloy layer was within the film plane and within the range of 60 degrees to 120 degrees with respect to the tape running direction. Although the two-layer medium and the manufacturing method thereof according to the present invention have been described in detail through Examples above, the present invention is not limited thereto.
It will be obvious that various modifications and changes can be made without departing from the spirit of the invention.

(Effects of the Invention) As described above in detail, according to the present invention, the film thickness of the low coercive force magnetic layer permalloy film having an axis of easy magnetization in the film plane of a two-layer medium for perpendicular magnetic recording is reduced to 0. 0.05μm to 0.05μm
Even if the thickness is as thin as 1 μm, the magnetic recording magnetic layer Co-Cr having an axis of easy magnetization perpendicular to the film surface can be provided thereon without deteriorating its initial magnetic permeability. A perpendicular magnetic recording medium can be obtained in which the total film thickness can be suppressed to 0.25 μm or less, and which satisfies the requirements of narrow tracks, wide band, and high C/N that enable high-density recording.

Furthermore, according to the manufacturing method of the present invention, the facing target sputtering method, which is relatively easy to control, can be applied to this manufacturing method, and Co
- The base layer and the upper layer of the Cr layer have a pair of targets.
By using targets with two different compositions and controlling the use of a movable mask, the saturation magnetization and film thickness of 2IW can be easily controlled, making it possible to provide a manufacturing method with high mass productivity.

[Brief explanation of the drawing]

FIG. 1 shows a schematic structural diagram of a perpendicular magnetic recording medium according to the present invention, and FIG. 2 shows a facing target according to the present invention in which the IN layer and the second layer of Co-Cr can be simultaneously produced using a pair of targets. A schematic diagram of the sputtering apparatus is shown, and FIG. 3 shows the saturation magnetization of the l-th Co-Cr film at
514 (emu/cc) and the experimental data of the initial magnetic permeability of the permalloy film versus the Co-Cr film thickness of the 1st layer.
- shows a schematic diagram of a Cr target and a substrate film,
Figure 5 shows a pair of facing Co-Cr with different composition ratios.
The saturation magnetization distribution of a Co--Cr sputtered film formed between targets is shown, and FIGS. 6(a) to 6(d) show magnetization curves of permalloy films having different saturation magnetostriction constants. A... Substrate film C... First layer Co −
CrB...Permalloy layer D...Second layer C
o-Cr1”・Co-Cr target 1 (Co:
67 atomic%, Cr: 33 atomic%)2...Co-
Cr target 2 (Cos 79 atomic%, Cr: 21
atomic%) 3... Permalloy target (Ni: 80 atomic%, Fe: 20 atomic% 4... Mask
5...Moving mask 6...Slit l 7
...Slit 28...Film thickness gauge 9...
Supply roller 10... Take-up reroller 11... Substrate film 12... Can 13... CO-Cr target 1 (Co: 73 atomic%
, Cr: 27 atomic%) 14...Co-Cr target 2 (Co: 79 atomic%, Cr: 21 atomic%) 1
5...Substrate film)
Chin^ Figure 3 Figure 4 Figure 15 A certain 4-sided lum

Claims (1)

[Claims] 1. A magnetic field formed by sequentially forming a low coercive force magnetic layer having an easy axis of magnetization in the film plane on a non-magnetic substrate and a magnetic recording magnetic layer having an easy axis of magnetization perpendicular to the film plane. A two-layer perpendicular magnetic recording medium, characterized in that the magnetic recording layer comprises an underlayer with a lower saturation magnetization and an upper layer with a higher saturation magnetization. 2. Perpendicular magnetic recording according to claim 1, wherein the thickness of the underlayer of the magnetic recording magnetic layer and the sum of the thicknesses of the underlayer and the upper layer are 0.05 μm or less and 0.15 μm or less, respectively. Dual layer media. 3. The saturation magnetization of the underlayer and the upper layer of the magnetic recording magnetic layer are each from 50 emu/cc to 200 e
The perpendicular magnetic recording dual-layer medium according to claim 1 or 2, characterized in that the perpendicular magnetic recording dual-layer medium has a magnetic flux up to mu/cc and exceeding 200 emu/cc. 4. The perpendicular magnetic recording double layer according to any one of claims 1 to 3, wherein the low coercive force magnetic layer having an easy axis of magnetization in the film plane has a thickness of 0.05 μm to 0.1 μm. Medium. 5. The easy axis of magnetization of the low coercive force magnetic layer having an easy axis of magnetization in the film plane is between 60 degrees and 12 degrees with respect to the tape running direction.
5. The perpendicular magnetic recording dual-layer medium according to claim 1, wherein the perpendicular magnetic recording dual-layer medium is in a range of 0 degrees. 6. The saturation magnetostriction constant λ_s of the low coercive force magnetic layer having an easy axis of magnetization in the film plane is from +2×10^-^7 to +1×1
Claims 1 to 5 characterized in that the range is 0^-^6.
The perpendicular magnetic recording dual-layer medium according to any one of the above. 7. In manufacturing the perpendicular magnetic recording dual-layer medium according to any one of claims 1 to 6, the low coercive force magnetic layer and the magnetic recording magnetic layer formed in sequence are formed by a sputtering method. A method for manufacturing a perpendicular magnetic recording dual-layer medium. 8. The underlayer and the upper layer of the magnetic recording magnetic layer are formed successively by changing the compositions of the ferromagnetic materials of a pair of targets in a facing target sputtering device, respectively. A method for manufacturing a perpendicular magnetic recording dual-layer medium. 9. The angle from the center of one target 1 of the pair of targets to the slit 1 in its vicinity is θ_1_1, the angle to view the far slit 2 is θ_1_2, and the angle from the center of the other target 2 of the pair of targets to the nearby slit 1 is θ_1_1 If the angle at which the slit 2 is viewed is θ_2_2 and the angle at which the distant slit 1 is viewed is θ_2_1, then by providing a mask that always sets θ_1_2 and θ_2_1 at zero degrees and changing the position of the mask, θ_1_1 and θ_2_
9. The method of manufacturing a perpendicular magnetic recording dual-layer medium according to claim 8, wherein the thickness of the underlayer and the thickness of the upper layer are controlled by changing the thickness of the underlayer and the upper layer in conjunction with each other.