JPS61120332A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a thin soft magnetic underlying layer and to improve the flexibility of a recording medium by forming said underlying layer of a thin Co-Fe film. CONSTITUTION:e thin Co-Fe alloy film having large saturation magnetization is adopted for the material of the soft magnetic underlying layer of a multi-layered vertical magnetic recording medium. The Co-Re alloy has fairly larger saturation magnetization then the satura tion magnetization of 'Permalloy(R)' and Co-base amorphous material and consequently the film thickness of the soft magnetic underlying larger of the two-layered film medium can be decreased. The flexibility of the magnetic recording medium such as flexible disk and magnetic tape is improved. The Co-Fe alloy has a small anisotropy constant in an ade quate compsn. ratio and has therefore a small anisotropic magnetic field and large magnetic permeability. The compsn. of a vapor source changes in the case of forming continuously the underlying layer consisting of 'Permalloy(R)' for a long period of time by vapor deposition and therefore the underlying layer having the consistent quality is not obtainable with the underlying layer formed in a initial period and the underlying layer formed after lapse of some time. The Co-Fe alloy has a small compsn. flucuation and yields the underlying layer having the stable quality in the above-mentioned respect. The substrate temp. may be about 150 deg.C in the case of forming the underlying layer. The selection range for the substrate is thus widened.

Description

[Detailed Description of the Invention] [Field of Application of the Invention and Object of the Invention] The present invention relates to improvement of a soft magnetic underlayer of a multilayer perpendicular magnetic recording medium, and provides a perpendicular magnetic recording medium with excellent flexibility. The purpose is to

[Conventional technology]

Double-layer media for perpendicular magnetic recording, in which a perpendicular magnetic anisotropic film is provided on a soft magnetic underlayer, are superior to single-layer media in which only a perpendicular magnetic anisotropic film is provided on a non-magnetic substrate.

It is possible to reduce the recording current and significantly improve the reproduction output. The above two improvements in the recording and reproducing characteristics of the double-layer film medium for perpendicular magnetic recording are achieved by the soft magnetic underlayer having the role of effectively focusing the magnetic flux generated from the magnetic head onto the recording area, and at the same time, This is because it plays a role in making the magnetization recorded in the direction more stable exist in the perpendicular direction. In order for the soft magnetic underlayer to function effectively as described above, its magnetic permeability, saturation magnetization, and film thickness must be large enough to effectively focus the magnetic flux generated from the magnetic head onto the recording area. Ru.

Conventionally, permalloy thin [, Go-based amorphous thin films, etc.] have been mainly studied as soft magnetic underlayer materials for double-layer media for perpendicular magnetic recording, but their saturation magnetization is 900
Gaussian, and in order to effectively focus the magnetic flux generated from the magnetic head onto the recording area, it is necessary to increase the film thickness of the underlayer. When applied to other flexible magnetic recording media, the rigidity of the medium increases, making it impossible to obtain stable contact of the magnetic head with the surface of the magnetic recording medium, and insufficient magnetic properties.

Means for Solving Problem C] Therefore, in order to solve the drawbacks of the conventional technology, the present invention adopts a Go-Fe alloy thin film with large saturation magnetization as the soft magnetic underlayer material of a multilayer perpendicular magnetic recording medium. are doing.

As a result, the Go-Fe alloy has a considerably larger saturation magnetization than Permalloy or Go-based amorphous.

The thickness of the soft magnetic underlayer of a two-layer film medium can be significantly reduced. As mentioned above, this can improve the flexibility of magnetic recording media such as flexible disks and magnetic tapes, and can greatly improve the contact state of the magnetic recording head with the surface of the magnetic recording medium.

Furthermore, since the Go-Fe alloy has a small anisotropy constant in an appropriate composition range, the anisotropic magnetic field is small and the magnetic permeability is large.

Furthermore, when forming a permalloy base layer continuously for a long period of time by vapor deposition, the composition of the permalloy base layer changes between the one formed initially and the one formed after a certain period of time because the composition of the evaporation source changes. In this respect, the G o -F s alloy has a small compositional variation and can provide an underlayer with stable quality. Furthermore, when forming a permalloy underlayer by vapor deposition, it is necessary to raise the substrate temperature to about 350 degrees Celsius, which requires the substrate to be heat resistant, which limits the range of substrate selection and ultimately increases costs. Becomes high. In this respect, as in the present invention, Co-F
When forming an e-alloy base layer, the substrate temperature is approximately 350°C.
As a result, the selection range of substrates is widened, and the cost can be reduced after all.

However, if a thin Go-Fe alloy film is used as an underlayer and a perpendicularly anisotropic film such as a Co-Cr alloy thin film is provided directly on the underlayer, it will be possible to form a thin film directly on a non-magnetic substrate such as a base film or a glass substrate. Compared to the case.

The crystallographic orientation of the perpendicular magnetic anisotropic film tends to deteriorate, and the magnetic properties in the direction perpendicular to the film surface, such as coercive force and squareness ratio, tend to deteriorate. Therefore, the present inventors provided a soft magnetic underlayer of Go-Fa alloy on a non-magnetic substrate, and then
A thin intermediate layer was formed on the Go-Fe alloy thin film, and a perpendicular magnetic anisotropy film was formed on the intermediate layer. Various nonmagnetic thin films were considered as the intermediate layer, but in particular, thin films made of materials that have a hexagonal close-packed structure and whose lattice constant is close to that of the perpendicular magnetic anisotropic film 1, for example, a perpendicular magnetic anisotropic film. In the case of a co-Cr alloy thin film, a non-magnetic thin film such as Ti or Zn does not interfere with the crystallographic orientation of the Co-Cr alloy thin film, and a good perpendicular magnetization film can be obtained. Also, C.

The material of the intermediate layer, which is amorphous after forming the -Fa soft magnetic underlayer, is not particularly limited in material, and does not interfere with the crystallographic orientation of the perpendicular magnetic anisotropic film.

In this case, there is almost no difference in the degree of crystallographic orientation from the case where the vertically anisotropic film is provided directly on the base film or glass substrate.

Note that the G o -F a alloy thin film in the present invention can be formed by a physical vapor deposition method such as a sputtering method or a vacuum evaporation method, and a preferable alloy composition has a CO content of 20 to 20.
Even if the a Co content, which is in the range of 60 atomic %, does not reach or exceed this appropriate alloy composition range, the saturation magnetization of the alloy decreases, and the effect of the present invention is slightly reduced. Further, the optimum film thickness range of the above-mentioned intermediate layer is in the range of 50A to 100OA, and below 50A, the effect of the intermediate layer is weak and too thick.
.

Above A, especially in the case of flexible magnetic recording media.

The rigidity of the recording medium increases, and the contact stability of the magnetic head with the surface of the recording medium deteriorates.

As described above, in a perpendicular magnetic recording medium equipped with a soft magnetic underlayer, by using a Go-Fe alloy thin film as the soft magnetic underlayer, the surface of the magnetic recording medium can be improved without impairing the electromagnetic conversion characteristics of the recording medium. The contact stability of the magnetic head against the magnetic head can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 CoogNblx Zr4 as a soft magnetic underlayer
An amorphous layer or a Go-Fe alloy 2 (Go gold content 0 at%) is added to a polyethylene terephthalate film.
(film thickness: 50 μm) and a Ti layer with a thickness of 0.01 μm as an intermediate layer 3. Furthermore, C with a film thickness of 0.15 μm
An o-Cr alloy layer 4 (Cr content: 20% by weight) was formed. The method for forming the thin films was all high-frequency sputtering. Note that whether the soft magnetic underlayer is a CoNbZr amorphous layer or a Co-Fe alloy, C is formed through the Ti group.

Large differences in crystallographic orientation and magnetic properties of the -Cr alloy layer are not a curse.

Note that 1 in Fig. 2 is a substrate. 0 The perpendicular magnetic recording medium with a multilayer structure obtained in the above manner was evaluated using a main pole excitation type perpendicular head (main pole thickness 0.7 μm, track width 120 μm). Figure 2 shows the results of measuring the dependence of output on the thickness of each soft magnetic underlayer, and the measured recording density is 2k.
In BPI, curve 1 in the figure is a recording medium using a soft magnetic layer of Go-Fe alloy layer, and curve 2 is Go-Nb.
-Zr It is a characteristic curve of a recording medium using a soft magnetic layer of an amorphous layer.

From the results in this figure, what is the thickness of the soft magnetic underlayer for the reproduction output to be saturated for a given recording current?

Compared to the case of Go-Nb-Zr amorphous thin film, Go-F
It can be seen that in the case of an e-alloy thin film, a film thickness of 1/2 to 1/3 is sufficient. This shows that if the Go-F@alloy thin film is used as a soft magnetic underlayer, the thickness of the underlayer can be reduced and the flexibility of the recording medium can be improved. Under the present experimental conditions, the soft magnetic underlayer thickness was 0.3~
If it exceeds 0.4 μm, the contact state of the magnetic head with the recording medium surface becomes unstable, and the reproduction output envelope becomes non-uniform, but l! ! Co-F with a thickness of 0.3 pm or less
In the case of the e-alloy base layer, a homogeneous reproduction output envelope with a large output was obtained.

〔Effect of the invention〕

As explained above, by using a Go-Fs thin film as the soft magnetic underlayer of the multilayer perpendicular magnetic recording medium,
The thickness of the underlayer can be reduced and the flexibility of the recording medium can be greatly improved.

In particular, as shown in the examples, when forming a perpendicular magnetic anisotropic film such as a Co-Cr alloy thin film on a Co-Fe alloy underlayer, one problem is the disturbance of the crystallographic orientation of the perpendicular anisotropy. ,
This problem can be solved by providing a specific intermediate layer between the Co--Fe alloy underlayer and the perpendicular magnetic anisotropy film.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the soft magnetic underlayer thickness and reproduction output of a perpendicular magnetic recording medium, and FIG. 2 is a sectional view of a perpendicular magnetic recording medium according to an embodiment of the present invention. 1...Substrate, 2...G o -F a
Alloy layer, 3...Ti layer, 4--Ca-Cr
layer.

Claims (1)

[Claims] 1. A multilayer perpendicular magnetic recording medium in which a soft magnetic layer is formed on a substrate and a recording magnetic layer having perpendicular magnetic anisotropy is formed above the soft magnetic layer. A perpendicular magnetic recording medium characterized in that a cobalt-iron alloy thin film is provided as a geological layer. 2. In the magnetic recording medium according to claim 1, the cobalt content of the cobalt-iron alloy thin film is 20 to 60.
A perpendicular magnetic recording medium characterized by being regulated within an atomic percent range. 3. In claim 1, between the soft magnetic underlayer and the recording magnetic layer having perpendicular magnetic anisotropy,
A perpendicular magnetic recording medium characterized in that a nonmagnetic intermediate layer is formed. 4. Claim 3, characterized in that the intermediate layer is made of a material having a hexagonal close-packed structure and a lattice constant close to that of the perpendicular magnetic anisotropic recording magnetic layer. perpendicular recording medium. 5. Claim 3, wherein the soft magnetic underlayer is a cobalt-iron alloy thin film, the intermediate layer is one or more thin films selected from the group of titanium and zinc, and a perpendicular magnetic anisotropic recording magnetic layer. 1. A perpendicular magnetic recording medium, comprising a cobalt-chromium alloy thin film.