JPS60251511A - Vertically magnetized recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium suitable for recording and reproduction at high density by providing a high permeability thin film layer consisting of an Fe-Ni alloy in such a manner that the direction of the axis of easy magnetization in said layer coincides approximately with the direction of the magnetic lines of force within the film layer and providing a vertically magnetized recording layer consisting of Co-Cr on said layer. CONSTITUTION:The high permeability magnetic thin film layer 2 consisting of an Fe-Ni alloy (''Permalloy(R)'') is so formed on a non-magnetic substrate 1 that the direction of the axis of easy magnetization in the film 2 coincides approximately with the direction of the magnetic lines of force (the longitudinal direction of the vertically magnetized recording medium 10) in the layer 2. The vertically magnetized recording layer 3 consisting of Co-Cr is then formed on the layer 2. A thin Ti film 4 may be formed if necessary on the layer 2 within a 100-500Angstrom thickness range in order to increase the film growing speed for formation of the layer 3 by vapor deposition. The temp. at which the film 4 and the layer 3 are formed by vapor deposition is enough at <=180 deg.C and therefore the high-density recording medium 10 having an excellent surface characteristic and excellent recording and reproducing efficiency is obtd. by using polyimide, polyester, etc. for the substrate 1.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a perpendicular magnetic recording layer formed of a Co-Cr alloy and a high permeability magnetic thin film formed of an F"e-Ni alloy (so-called permalloy). The present invention relates to a perpendicular magnetization recording medium that has a two-layer film (in-plane magnetization layer) and records information using residual magnetization perpendicular to the magnetic surface of the recording medium. This relates to the improvement of high magnetic permeability magnetic thin film layers. [Background technology and problems thereof] Conventionally, in magnetic recording and reproducing devices such as audio table recorders and video table recorders, magnetic thin film layers are generally deposited on a substrate. Recording is performed by magnetizing the magnetic recording layer in the horizontal direction (in-plane direction magnetization).

However, in the case of recording using in-plane direction magnetization, as the wavelength of the recording signal becomes shorter, that is, as the recording density increases, the demagnetizing field within the medium increases and the residual magnetic flux density attenuates.
This has the disadvantage that the reproduction output decreases.

Therefore, a perpendicular magnetization recording method has been proposed in which recording is performed by magnetization in the thickness direction of the recording layer of a magnetic recording medium. According to this perpendicular magnetization recording method, the demagnetizing field decreases as the recording wavelength becomes shorter. It is known that it is more advantageous than the above-mentioned recording using in-plane direction magnetization, especially in short wavelength recording and high-density recording, because it is smaller.

The perpendicular magnetization recording medium used in this type of recording method is a C
A single-layer perpendicular magnetic recording medium in which a perpendicular magnetic recording layer is formed using an o-Cr alloy, or a two-layer perpendicular magnetic recording medium in which a high permeability magnetic thin film layer made of a Fe''Ni alloy is provided between the nonmagnetic substrate and the perpendicular magnetic recording layer. Film perpendicular magnetization recording media have been considered, but two-layer film perpendicular magnetization recording media are attracting particular attention because of their excellent recording efficiency and reproduction efficiency.

By the way, in this two-layer film perpendicular magnetization recording medium, the magnetic properties of the high permeability magnetic thin film are important; for example, if the permeability of the high permeability magnetic thin film decreases, it becomes difficult to magnetize the high permeability magnetic thin film. , the recording efficiency and reproduction efficiency will decrease. Therefore, F''c-Ni alloy having high magnetic permeability is used as the material of the above-mentioned high magnetic permeability magnetic thin film, but it is still unclear what kind of magnetic properties this Fe-Ni alloy film should exhibit. For example, in Japanese Patent Application Laid-Open No. 58-68226, it is stated that the axis of easy magnetization of the above-mentioned high permeability magnetic thin film is not in the plane, but is preferably oriented almost perpendicular to the plane. There is a description that highly efficient perpendicular magnetization recording is possible in the high frequency region when the direction is almost perpendicular to the magnetic field lines flowing in the high permeability magnetic thin film layer even in the plane. According to experiments 1
0~1001! It has been found that such an effect cannot be expected in the practical frequency range of about viT(z).

[Purpose of the invention]

Therefore, the present invention has been proposed in order to eliminate the drawbacks of the above-mentioned conventional ones, and uses Fe-Ni, which exhibits excellent magnetic properties, as a high permeability magnetic thin film layer of a two-layer perpendicular magnetization recording medium. The present invention aims to provide a perpendicular magnetization recording medium with high recording efficiency and high reproduction efficiency by providing an alloy thin film.

[Summary of the invention]

That is, the perpendicular magnetization recording medium according to the present invention has F on the substrate.
High permeability magnetic thin film layer made of e-Ni alloy and Co-C
In a perpendicular magnetic recording medium formed by vapor-depositing perpendicular magnetic recording layers made of r alloy, the direction of the axis of easy magnetization of the high magnetic permeability magnetic thin film layer substantially coincides with the direction of the magnetic force lines in the high magnetic permeability magnetic thin film layer. Fe-N which is easily magnetized in the longitudinal direction of the perpendicular magnetization recording layer body.
i By forming an alloy thin film, it is intended to improve recording efficiency and reproduction efficiency.

As shown in FIG. 1, a perpendicular magnetization recording medium 10 according to the present invention includes a high permeability magnetic thin film 2 made of an Fe-Ni alloy and a perpendicular magnetization recording layer 3 made of a Co-Cr alloy on a nonmagnetic substrate 1. It is constructed by laminating layers with a Ti thin film 4 interposed therebetween.
What is important here is that the direction of the easy axis of magnetization of the Fe-Ni alloy thin film constituting the high permeability magnetic thin film layer 2 is determined by the direction of the magnetic force lines within this high permeability magnetic thin film layer 2 (normally perpendicular magnetic recording medium). 10).

In other words, in the perpendicular magnetization recording medium 10),
As shown in FIG. 2, a perpendicular magnetic head 20 comprising a main magnetic pole 5 and a complementary magnetic pole 6 is slid in the direction of the arrow X in the figure (the longitudinal direction of the perpendicular magnetization recording medium 10), and the main magnetic pole 5 is The perpendicular magnetization recording layer 3 is magnetized in the thickness direction by magnetic lines of force (indicated by broken lines in the figure) emanating from the magnetic field, and the lines of magnetic force are passed through the high permeability magnetic thin film layer 2, which is an in-plane magnetization layer, to the auxiliary magnetic pole 6. Recording and playback are performed by streaming,
Since the Fe-Ni alloy thin film is magnetized mainly by domain wall movement, it is most easily magnetized when the direction of the applied magnetic field and the axis of easy magnetization are parallel. This makes it easier to flow. According to the experiments conducted by the present inventors, as shown in Fig. 3, in the practical frequency range of 100h-1z or less, the coercive force Hc of the Pe-Ni alloy thin film is small in the direction of the easy axis of magnetization. The magnetic permeability (curve a in the figure) is higher in the direction of the hard magnetization axis where the coercive force Hc is larger (the curve b in the figure).
) and was found to be easily magnetized.

In order to produce uniaxial magnetic anisotropy in the Fe-Ni alloy thin film constituting the high permeability magnetic thin film layer 2 and to set the axis of easy magnetization in the direction in which the above-mentioned lines of magnetic force flow, that is, in the longitudinal direction of the perpendicular magnetization recording medium 10. When producing the Fe--Ni alloy thin film using a vacuum deposition technique such as a spuck method or an evaporation method, a magnetic field of approximately several oersteds may be applied in the longitudinal direction of the perpendicular magnetization recording medium 10. Alternatively, in a vacuum evaporation apparatus using an electron beam heating method using a magnetic field deflection type electron gun, a magnetic field is applied in a direction perpendicular to the electron beam, so the position of the substrate 1 is appropriately selected and this magnetic field is used to facilitate magnetization. The direction of the axis may also be set.

The high permeability magnetic thin film layer 2 is formed, for example, by using an Ii''e-Ni alloy ingot as an evaporation source and by a spuck method, a vapor deposition method, etc., and its film thickness is usually 0.2 to 1.
It is set to about 0μ.

On the other hand, the perpendicular magnetization recording layer 3 can be fabricated by depositing a Co-Cr alloy consisting of 10 to z5 atoms of Cr and the remainder Co by sputtering or vapor deposition. A product with excellent orientation can be obtained.

The Ti thin film 4 is provided to improve the film growth rate of the perpendicular magnetization recording layer 3 and form an excellent Co-Cr alloy film, and has a thickness of ]00 to 500.
λ is selected. If the film thickness of the Ti thin film 4 is less than 00 λ, it will be difficult to form a continuous film of T1, and the effect of Ti as a base film may become opaque. No further effects were observed on the magnetic properties or mechanical properties of the Cr alloy film. Note that this Ti thin film 4 may be omitted depending on the case.

Furthermore, the temperature of the substrate 1 when depositing the Ti thin film 4, the perpendicular magnetic recording layer 3, etc. is sufficient to be 180°C or less, and the material of the substrate 1 may be polyimide or other materials that are inexpensive and have excellent surface properties. Polyethylene terephthalate, etc. can be used.

In the perpendicular magnetization recording medium 10 configured in this manner, the high permeability magnetic thin film layer 2, which is an in-plane magnetization layer, is easily magnetized in the longitudinal direction, and therefore recording efficiency and reproduction efficiency are increased.

By the way, for example, in a rotary head type recording/reproducing device, the moving direction of the perpendicular magnetic head 20 is set to the perpendicular magnetization recording medium 1.
In some cases, the axis of easy magnetization of the high permeability magnetic thin film layer 2 may not coincide with the longitudinal direction of 0, but it goes without saying that the direction of the easy axis of magnetization of the high permeability magnetic thin film layer 2 may be set parallel to the direction of the lines of magnetic force.

Hereinafter, specific examples of the present invention will be described.

〔Example〕

On the polyimide substrate, F”e-Ni alloy Inkotsuto (F
e21.5%, Ni7L5%) evaporation source, vacuum degree 2. OX 10-6 Torr, substrate temperature 260°
At a C5 deposition rate of 39A/(8), a film thickness of 0.39 was obtained without applying a magnetic field of 0 O in the longitudinal direction of the substrate.
A Fe-Ni alloy thin film of μm thickness was formed by vapor deposition.

Next, on this Fe-Ni alloy film, a vacuum degree of 2°Q was applied.
A Ti thin film having a film thickness of 30 oi was formed under the following conditions: X ] ] Q-6 Torr substrate temperature 180° C1 evaporation rate 14 λ/.

Furthermore, on the above 'pi thin film, vacuum degree 2.0X10-6
”, rorr, substrate temperature 180°C1 deposition rate 32A/
A sample tape was prepared by depositing a Co--Cr alloy film with a thickness of 0.1 μm under eec conditions.

The coercive force Hc of the obtained sample tape and the magnitude of the magnetic field required for magnetization were examined in the tape longitudinal direction and tape width direction. The results are shown in the table below. In addition, in the table, H(0,8Is) is the magnitude of the magnetic field required to magnetize to 80% of the saturation magnetization, and H(0,9Is) is the magnitude of the magnetic field required to magnetize to the 90th factor of the saturation magnetization. be.

From this table, it can be seen that the recording efficiency and reproduction efficiency of the obtained sample tapes are high.

〔Effect of the invention〕

As described above, in the present invention, the direction of the axis of easy magnetization of the high permeability magnetic thin film layer, which is an in-plane magnetization layer, is made to match the direction of the magnetic lines of force within this thin film layer. A perpendicular magnetization recording medium in which the layer exhibits excellent magnetic properties and high recording efficiency and high reproduction efficiency can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part schematically showing the configuration of a perpendicular magnetization recording medium according to the present invention, and FIG. 2 is a schematic diagram illustrating a perpendicular magnetization recording method. FIG. 3 is a characteristic diagram showing the magnetic permeability frequency characteristics of the Fe--Ni alloy thin film in the easy axis direction and the hard axis direction. 1...Substrate 2...High permeability magnetic thin film layer 3...
...... Perpendicular magnetization recording layer patent applicant Sony Corporation representative Patent attorney Kodo Koike 1) Sakae Mura - Figure 1 1 Convex Figure 2 Figure 3 ↑

Claims (1)

[Claims] In a perpendicular magnetization recording medium in which a high permeability magnetic thin film layer made of an Fe-Ni alloy and a perpendicular magnetization recording layer made of a Co-Cr alloy are formed on a substrate by vapor deposition, the easy axis of magnetization of the high permeability magnetic thin film layer is A perpendicular magnetization recording medium characterized in that the direction of the magnetic field lines substantially coincides with the direction of the magnetic lines of force within the high permeability magnetic thin film layer.