JPS6134721A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the reproduction output in the longwave region as well as in the shortwave region by forming a Co-Pt layer, having specified Pt content and whose in-surface coercive force is more than a specified value, and a layer, having specified Co-Cr composition and whose vertical coercive force is more than a specified value, on a nonmagnetic supporting body in said order. CONSTITUTION:A Co-Pt layer 2 contg. 5-15atom% Pt is formed on a nonmagnetic supporting body 1 of plastics, glass, etc. in about 0.15-0.3mum thickness, and a magnetic recording medium whose coercive force in the in-surface direction is regulated to >=300 Oe and whose c-axis is sufficiently oriented in the vertical direction of the film surface is formed. Then a Co-Cr layer 3 contg. 20-22atom% Cr and whose vertical coercive force is regulated to >=400 Oe is formed on the layer 2. Since the c-axis of the layer 2 is vertically oriented, the vertical orientation of the layer 3 is sufficiently formed. Consequently, the magnetic recording medium, whose reproduction output in the longwave region is improved, is obtained while keeping the vertical recording system in favorable conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a lower magnetic layer made of a Co-pt alloy formed using a thin film deposition method such as a vapor deposition method, an ion blating method, a sputtering method, or a plating method; The present invention relates to a metal thin film magnetic recording medium having a laminated magnetic layer including an upper magnetic layer made of a Co--Cr alloy.

Perpendicular magnetic recording has attracted attention in recent years as a method suitable for high-density recording, and Co-C is a suitable medium for this method.
Research on media made of r-alloy thin films is being conducted in various fields.

This Co--Cr alloy thin film type medium exhibits high performance by using a so-called auxiliary pole excitation type or main pole excitation type vertical head, but it is also possible to perform recording and reproduction using a conventional ring head.

In that case, looking at the relationship between the playback output and the recording wavelength when recording and playing back using the same ring head using a perpendicular recording medium and a conventional longitudinal recording medium, the perpendicular recording medium is superior in the short wavelength region. There is a tendency for longitudinal recording media to be superior in the long wavelength region.

This decrease in playback output in the long wavelength region makes it difficult to maintain compatibility with conventional methods, such as when recording signals with a wide frequency band or when having signals for controlling a system in the long wavelength region. This has been a problem when trying to use perpendicular recording media while maintaining

One way to solve this problem is to use a perpendicular recording medium with high retention. The above Co-Cr
In order to obtain a high coercive force in an alloy thin film, it is a common method to raise the temperature of the substrate to a high temperature of 150° C. or higher when forming the film by sputtering or vapor deposition. However, when a flexible substrate such as a polymer film is used as the substrate, this method imposes extremely serious restrictions on the selection of the material for the substrate.

Furthermore, the curling of the medium due to the difference in thermal expansion coefficient between the substrate and the alloy thin film is further increased, which poses a serious problem in performing good recording.

On the other hand, a method of forming a perpendicular recording layer on top of the in-plane recording layer to supplement the reproduction output in the long wavelength region has also been considered. In this case, the problem is how to form a Co--Cr thin film with good vertical alignment on the in-plane recording layer.

That is, the Co--Cr alloy has an hcp structure, and its C axis is oriented perpendicularly to the film surface to form a perpendicularly magnetized film. If the orientation of the C-axis is disturbed, the reproduction output in the short wavelength region will be reduced, and the advantages of the perpendicular recording method will be impaired.

By the way, good C-axis orientation can be obtained when an amorphous material such as a polymer film or glass is used as the base substrate, but it is known that it usually deteriorates when a crystalline material is used as the base substrate. ing. In particular, in media made of oblique vapor deposition of Co-Ni alloy, which is currently being researched as a thin film medium for in-plane recording, the C axis of the hcp structure is tilted with respect to the film surface, and this is used as the lower layer to -Cr
Even if an upper layer made of an alloy was formed, only a Co--Cr layer with extremely poor vertical alignment was obtained, and a recording medium that took full advantage of the advantages of the perpendicular recording method could not be obtained.

11 Yutaka 11 Therefore, the present invention provides good orientation to the Co--Cr layer formed thereon, and at the same time exhibits sufficient magnetic properties as a longitudinal recording layer, mainly by selecting the longitudinal recording material for the lower layer. Overall, the object of the present invention is to provide a magnetic recording medium that improves reproduction output in the long wavelength region while taking advantage of the advantages of the perpendicular recording method in the short wavelength region.

11 The metal thin film magnetic recording medium of the present invention was developed to achieve the above objectives, and more specifically,
Co-pt alloy magnetic layer and Co-
The Cr alloy magnetic layer is formed in this order, and the Co-
The pt layer contains 5 at% or more of pt, has an in-plane coercive force of 300 Oe or more, and is made of Co-Cr.
It is characterized in that the layer contains 20 to 22 atom % of Cr and has a perpendicular coercive force of 400 Oe or more.

That is, according to the research conducted by the present inventors, a Co-pt alloy layer containing 5 at. , itself forms an in-plane magnetic recording layer having a high in-plane coercive force. Therefore, it is possible to form a Co--Cr layer having good perpendicular magnetic recording characteristics thereon by a thin film deposition method, and it is also possible to improve the output in the long wavelength region of the Co--Cr perpendicular magnetic recording medium. Also like this C
A Co-pt in-plane magnetized film with the axis oriented perpendicular to the film surface is C
Unlike an in-plane magnetized film formed by oblique deposition such as an o-Ni alloy, the film is magnetically isotropic within the film plane, so it can be preferably applied to disk-shaped media where the presence of directionality is undesirable.

Figure 1 is a schematic cross-sectional view in the thickness direction of a magnetic recording medium according to an embodiment of the present invention, and this magnetic recording medium is made of a support made of plastic such as polyethylene terephthalate or polyimide, glass, etc. 1, a Co-pt alloy magnetic layer 2 and a C0-Cr alloy magnetic layer 3 are sequentially formed by a thin film deposition method.

The magnetic properties of the Co-pt alloy magnetic layer 2 are as follows:
selected so that recording to is not prevented. In other words, if the coercive force is too small, the leakage magnetic flux from the head becomes Co-
The coercive force in the in-plane direction needs to be 300 Oe or more because it is absorbed by the PT layer and spreads, resulting in insufficient recording in the Co--Cr layer. The concentration of pt is selected within a range that maintains the hcp structure and obtains the desired coercive force,
A preferred concentration is 5 atomic % or more. That is, if it is less than 5 at %, it is difficult to obtain an in-plane coercive force of 300 Oe or more. However, as pt increases, the residual magnetic flux density decreases, and PL is also expensive, so there is no point in increasing it too much. Furthermore, as pt increases, the orientation of the C-axis tends to be disordered. In general, it is preferably 15 atom % or less. The thickness of the Co-pt film 2 is 0
．． Approximately 15-0.31 Lm is appropriate.

The Co--Cr layer 3 is formed by selecting the composition ratio and film forming conditions so that the C-axis is sufficiently oriented perpendicular to the film surface and the magnetization is directed perpendicular to the film surface. In particular, in accordance with the characteristic of the perpendicular recording method that the shorter the recording wavelength, the smaller the loss due to self-demagnetization, the reproduction output is high in the short wavelength region. In addition, the Co-Cr layer 3 is selected so that the reproduction output does not drop even in the long wavelength region to a certain extent.
It is necessary that the coercive force in the vertical direction be 400 Oe or more. In order to obtain such perpendicular magnetization characteristics, Co-
The Cr5 degree in the Cr layer 3 is preferably 20 to 22 atomic %. If Cr is less than 20%, the substrate temperature must be raised to 150°C or higher, otherwise H
It is difficult to obtain e, and if it exceeds 22%, the residual magnetic flux density decreases and the reproduction output deteriorates.

The thickness of the Co-Cr layer 3 is 0.3-0.571. It is preferable that it is m.

The magnetic recording medium of the present invention will be explained in more detail below using actual manufacturing examples and comparative examples.

``Kuto 2'' was first sputtered onto a 7 pm thick tape-shaped film made of polyimide resin at a substrate temperature of 25°C.
A Co-pt film with a thickness of 0.20 gm was formed under the conditions of sputtering power IKW and argon gas pressure 0.5 Pa, then sputtering power IKW and argon gas pressure 0.5 Pa were kept constant, and the substrate temperature was 80°C (Example 1). , 60°C (Example 2), 100°C (Example 3), 25°C (Example 4) and the thickness is 0.
．． A 45 gm Co-Cr film was formed.

At this time, the pt content in the lower Co-pt film is
By changing the area of the PT pellet placed on the get,
Cr in the upper Co-Cr film was varied in the range of 7 at%.
The content was kept constant at 20 at%.

” In the second example, instead of the underlying Co-pt film.

A Co--Ni film with a thickness of 0.15 gm was formed by an oblique evaporation method.

Co with a thickness of 0.45 meters corresponding to the upper layer of Examples 1 to 4 above
A magnetic recording medium having only a -Cr film was obtained.

[Co-N with a thickness of 0.15 pm corresponding to the lower layer of Example 5 above
A magnetic recording medium having only an i-film was obtained.

The perpendicular coercive force in the two layers and the in-plane coercive force in the lower layer of each magnetic recording medium sample obtained above are shown in the following table along with the composition of each layer (the remainder is Co).

The table also shows that for each of the above magnetic recording media, the gap length is 0.
Recording and reproduction were performed using a 3 gm Sendust ring type magnetic head at a head-medium relative speed of 3.8 m/sec.

As a result, the measurement results of the recording wavelength dependence of the reproduction output obtained for each magnetic recording medium are shown in FIGS. 2 and 3. In the figure, the numbers attached to the curves indicate the example numbers.

As is clear from FIGS. 2 and 3, media 1 and 2 corresponding to the examples of the present invention exhibit approximately the same performance and have a wider range of recording wavelengths than the other comparative examples. It shows overall excellent characteristics in the area.

As described above, according to the present invention, a wide recording wavelength can be achieved by using a two-layer structure with a Co-pt longitudinal recording layer as a lower layer and a Co-Cr perpendicular recording layer as an upper layer. Media with overall high playback output in this area can now be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view in the thickness direction of a magnetic recording medium according to an embodiment of the present invention, and FIGS. 2 and 3 are media of Examples 1 and 2 according to an embodiment of the present invention and Comparative Examples 4 to 7. This shows the recording wavelength dependence of the reproduction output of the medium.

Claims (1)

[Claims] Co-pt alloy magnetic layer and Co-
The Cr alloy magnetic layer is formed in this order, and the Co-
The pt layer contains 5 at% or more of pt, has an in-plane coercive force of 300 Oe or more, and is made of Co-Cr.
1. A metal thin film magnetic recording medium characterized in that the layer contains 20 to 22 atom % of Cr and has a perpendicular coercive force of 400 Oe or more.