JPS59157833A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a vertical magnetic recording medium having excellent characteristics by forming a foundation layer having many discontinuous projected or recessed parts on a substrate and then forming a continuous magnetic layer containing mainly iron oxide on the foundation layer with a specific ratio between the intrasurface and vertical residual magnetizations of the continuous magnetic layer. CONSTITUTION:A material such as In, Al, Bi, C, etc. having large surface energy is vacuum-deposited on a substrate 6. A foundation layer having many island-shaped projected parts 12 formed by said surface energy is formed with 10-1,000Angstrom height of projected part. Then a continuous magnetic layer 10 containing mainly iron oxide (Fe3O4 or gamma-Fe2O3) is formed by a counter target sputtering devide, etc. in the form of a vertically magnetized film having >=0.5 MV/MH between the intra-surface residual magnetization MH and the vertical residual magnetization MV of the layer 10. The magnetic particles having columnar structures are formed into recessed parts 13 of the layer 11. Thus the layer 10 is totally magnetized easily in the vertical direction. It is also possible to form the foundation layer 11 containing discontinuous island-shaped recessed parts on the substrate 6 and then the layer 10 on the layer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

2. Prior Art Conventionally, this type of magnetic recording medium has been used for video, audio,
It is widely used for recording various electrical signals such as digital ones. These have been developed as a system that uses magnetization in the in-plane longitudinal direction of a magnetic layer (magnetic recording layer) formed on a substrate. However, in recent years, with the increase in the density of magnetic recording, recording methods that use magnetization in the longitudinal direction of the plane,
As the recording signal becomes shorter in wavelength, the demagnetizing field within the medium increases, causing attenuation and rotation of the residual magnetization, resulting in a significant reduction in the reproduction output. For this reason, it is extremely difficult to reduce the recording wavelength to submicron or less.

On the other hand, a perpendicular magnetization recording method that uses magnetization in the thickness direction of the magnetic layer of a magnetic recording medium (so-called perpendicular magnetization) has recently been proposed (for example, "Nikkei Electronics J
August 7, 1978 issue 11kL192).

According to this recording method, as the recording wavelength becomes shorter, the demagnetizing field that acts on the residual magnetization in the medium decreases, so it has favorable characteristics for increasing density, and is essentially suitable for high-density recording. This is considered to be a method.

By the way, in order to perform this kind of perpendicular recording efficiently,
The recording layer of the magnetic recording medium must have an axis of easy magnetization in the perpendicular direction (&1 magnetic thickness direction). Such a magnetic recording medium is a coated type in which a magnetic coating mainly composed of magnetic powder and a binder is coated on a substrate (support), and the axis of easy magnetization is oriented in the perpendicular direction of the magnetic layer. The medium is known. This coated medium contains C
01F e 30-γ-Fe2O3, Co added F C3
o-Co-added γ-Fe2o3, hexagonal ferrite (e.g. barium ferrite), MnB1, etc. are used as magnetic powders (% 1983-46803, 53-
No. 67406, No. 52-78403, No. 55-861
No. 03, No. 52-78403 to No. 54-87202). However, in these coated media, there is a limit to increasing the packing density of magnetic powder due to the presence of a non-magnetic binder in the magnetic layer.
'/N ratio cannot be made sufficiently high. Moreover, the magnitude of the recorded signal is limited by the size of the magnetic particles, and a medium having a magnetic layer made of a magnetic thin film is unsuitable for perpendicular magnetization recording.

Therefore, continuous thin film magnetic recording media, in which a perpendicularly magnetized magnetic layer is formed by continuously depositing a magnetic material on a support without using a binder, are attracting attention as suitable for high-density recording. ing.

This continuous thin film type perpendicular magnetization recording medium has a magnetic recording layer made of an alloy film of cobalt and chromium, as disclosed in Japanese Patent Publication No. 57-17282, and has a particularly high chromium content. states that a Co--Cr alloy film containing 5 to 25% by weight is superior. Further, a magnetic recording medium having a magnetic layer formed by adding 30% by weight or less of rhodium to a Co-Cr alloy film is disclosed in Japanese Patent Application Laid-Open No. 111110/1982, and furthermore, a cobalt-vanadium alloy film (for example, Communication Society: Abbreviation IEEE, an academic journal published by
Transaction on Magnetism
” 1982 Vol.
8th Tohoku University Research Symposium ``Perpendicular Magnetic Recording'' Paper Collection)
Magnetic recording media using . Of these -C
.

Although the -Cr alloy film has been shown to be promising for perpendicular magnetization, it has been found that it has the following drawbacks.

(1) In order to orient the axis of easy magnetization perpendicular to the plane of the magnetic layer, it is necessary to create the magnetic layer in a high vacuum of 10-7 Torr or higher, and the substrate must be subjected to advanced cleaning treatment and a low sputtering speed. etc., and the control factors for vertical alignment become extremely complicated.

(2) During signal recording and reproduction, since the magnetic recording medium and the perpendicular recording/reproducing head slide relative to each other, the interface between the head and the medium is poor, causing scratches on the medium. This can easily cause damage to the head.

(3) Since the magnetic layer is hard, cracks are likely to occur when the magnetic layer is provided on a flexible substrate.

(4) Corrosion resistance as a magnetic recording medium is insufficient, so it is necessary to provide a protective film on the surface.

(5) Cobalt, a raw material, is difficult to obtain stably and is expensive.

3. Purpose of the Invention In view of the above-mentioned circumstances, the present inventor has made extensive studies and has determined to obtain a magnetic recording medium that is suitable for high-density perpendicular magnetic recording and has excellent mechanical strength, chemical stability, etc. It was a success.

4. Structure of the invention and its effects, that is, the present invention comprises a base body, an underlayer provided on the base body and having a large number of discontinuous convex portions or concave portions on the surface side;
and a magnetic layer provided on the underlayer, wherein the magnetic layer is a continuous magnetic layer containing iron oxide as a main component.

(b), residual magnetization (Ma, ) in the in-plane direction of the magnetic layer,
The ratio (MY/ME) of residual magnetization (Mv) in the direction perpendicular to the plane of the magnetic layer is 0.5 or more.

The present invention relates to a magnetic recording medium characterized by having the following configurations.

According to the present invention, since the magnetic layer has iron oxide as a main component, excellent characteristics unique to oxides (i.e., mechanical strength, chemical stability, etc.) can be obtained, and compared to conventional alloy thin films. The previously required surface protective film is no longer necessary. As a result, the distance between the magnetic head and the medium can be reduced, making it possible to perform high-density recording, and also to reduce costs in terms of materials.

Moreover, since the residual magnetization ratio (MV/MH) between the in-plane direction and the perpendicular direction of the magnetic layer containing iron oxide as the main component is set to 0.5 or more, the magnetic moment of the iron monoxide magnetic material is relative to the in-plane direction. It rises in the vertical direction by more than 30 degrees, and has a structure that can sufficiently realize one perpendicular magnetization. The residual magnetization amount MV-MH can be measured, for example, with a sample vibrating magnetometer (manufactured by Toei Kogyo Co., Ltd.). That is, if MV/MH is less than 0.5, it is difficult to obtain a magnetic moment suitable for perpendicular magnetization. What is also important in the present invention is that the magnetic layer has many convex portions or four portions on one surface side. It is installed on the base layer. That is, by forming a large number of convex portions or concave portions in the underlayer, the magnetic material deposited in each concave portion is regulated by the concave portions and adheres sequentially in the direction perpendicular to the substrate surface. However, they gradually adhere in the same direction. For this reason, the constituent grains of the obtained magnetic layer have a so-called columnar structure, and have improved shape anisotropy in terms of magnetic properties in the direction perpendicular to the in-plane direction. These columnar structures depend on the orientation of the magnetic layer,
That is, the perpendicular magnetization characteristics are improved.

On the other hand, if the underlayer is simply formed on a smooth surface, the orientation direction of the magnetic layer deposited thereon will be disturbed, making it impossible to obtain the desired columnar structure.

Note that the magnetic layer of the present invention is preferably made of iron oxide having a spinel crystal structure.

The magnetic layer according to the present invention is fundamentally different from conventional coated magnetic layers in that it does not use a binder but instead uses iron oxide (e.g. F).
e 30 γ-Fe2O3, or a bertolide compound having a non-stoichiometric composition intermediate to these) itself consists of a continuous thin film. In this magnetic layer, the sum of both elements iron and oxygen is 50% by weight of the magnetic layer.
The thickness is preferably 70 or more, and more preferably 70 or more. In addition, the ratio of iron to oxygen is preferably 1 to 3 (number of oxygen atoms/number of iron atoms), and even more preferably <-4/3 to 2 (the above-mentioned iron oxide Appropriate.

Iron oxide, which exhibits magnetism and is used as a magnetic recording medium, includes α-Fe2o3, a parasitic ferromagnetic substance with a rhombohedral crystal structure; Fe30, which has a spinel structure.
4, γ-F 8203 These bertholed compounds and their derivatives; furthermore, Ba7 elite, Sr ferrite, pb ferrite and their derivatives having a hexagonal crystal structure; and rare earth garnet type ferrites having a garnet structure. Among the oxides mentioned above, saturation magnetization, which is one of their magnetic properties, is α-Fe2o3.
In 2 Gauss II, Ba ferrite-8r ferrite, Pb hugorite, husband k 350 Gauss
-140 Gau for rare earth ganentho ferrite
ss, whereas, for example, Feg04, which is iron oxide with a spinel structure, is as large as 480 Gau and ss.
This greatly affects the magnitude of the residual magnetic flux density, that is, the reproduction output when reproducing a recorded signal.

Therefore, the magnetic film according to the present invention is preferably an iron oxide having a spinel structure.

However, metals other than iron and oxygen or their oxides, non-gold, pj%, bovine metals, or compounds thereof are added to the magnetic layer, thereby improving the magnetic properties of the magnetic layer (e.g. coercive force, saturation magnetization). , the amount of residual magnetization), its crystallinity, and the orientation of the crystal in a specific axial direction. Such additive elements or compounds include AJSCo, -Mn, Z
n, , Co-Zn, Li, Cr.

Tj, Li-Cr-Mg, Mg-Nj, Mn-
Zn-Ni-Ni-A4Ni-Zn, Cu-Cu
-Mn, Cu-Zn-V, etc., but it is preferable to use other than rare earth elements.

Further, when the base layer in the present invention is provided in an independent island pattern, IOX' to ioo are used to provide desired unevenness on the surface side.

It is desirable that the film has an average film thickness of A. If the average film thickness is less than IOA, the effect of providing the base layer will be insufficient, and if it exceeds zoooX, the base layer will become a continuous film with substantially no irregularities. Further, when the base layer is a continuous layer having a large number of concave portions, the film thickness is preferably 1 μm or less. The constituent material of the underlayer is preferably different from the base material, such as In, Ti-Cr-Al-Bi, St, Ag.
5Au-C-Mg-V-Mn-Cu, Zn, Zr,
Mo, Sn, Sb, %Nb, etc. can be used. Among these, for example, In, which has a large surface energy,
Al, Bi, and C are preferable because they facilitate the formation of the above-mentioned island pattern.

Further, the base material that can be used in the magnetic recording medium of the present invention is:
Various materials can be used as long as magnetic materials can be attached thereto. For example - polyethylene terephthalate, polypyrinized vinyl, cellulose triacetate - polycarbonate,
Plastics such as polyimide, polyamide, polymethyl methacrylate, ceramics such as glass, etc. can be used. The shape of the substrate may be a sort, a card, a disk, a drum, or a long tape.

To produce this magnetic recording medium, one substrate may be closely supported on a fixed plate, or the base material and magnetic material may be sequentially deposited while the substrate is traveling.

For this purpose, a sputtering method is used in which a target of each material is sputtered in a processing chamber connected to an evacuation system such as a vacuum pump, or the material is evaporated from an evaporation source and deposited on a substrate. Vapor deposition method etc. can be applied. In either case, the elements constituting the underlayer and the magnetic layer can be deposited on the substrate by flying them.

5. Examples The magnetic recording medium of the present invention will be explained in more detail below with reference to the drawings.

FIG. 1 shows a magnetic recording medium, in which an island-shaped discontinuous underlayer 11 is first formed on a substrate 6, and an iron oxide-based perpendicular magnetization film (magnetic layer) 10 is formed on the entire surface of this underlayer 11. It is formed.

The base layer 11 is made by depositing In, for example, by a vacuum evaporation method, and because its surface energy is large, it is deposited in independent island-like patterns.

Methods for depositing the magnetic particles used in the present invention on the substrate include vacuum evaporation methods (including electric field evaporation and ion blating methods), sputtering methods, etc., in which the atoms constituting the magnetic layer are made to fly. A method using a facing target sputtering device is desirable.

FIG. 2 shows a facing target sputtering apparatus.

In the drawing, 1 is a vacuum chamber, 2 is an exhaust system consisting of a vacuum pump etc. for evacuating the vacuum chamber 1, and 3 is an exhaust system that introduces a predetermined gas into the vacuum chamber 1 and sets the gas pressure to about 10-1 to 10 Torr. This is a gas introduction system.

The target electrodes are configured as opposed target electrodes in which a pair of targets 'rt-'rt are separated from each other by a target boulder 4 and arranged to face each other in parallel. A magnetic field is generated between these targets by magnetic field generating means (not shown). On the other hand, the substrate 6 on which the magnetic thin film is to be formed is arranged perpendicularly to the side between the opposing targets by the substrate boulder 5.

In the sputtering apparatus configured in this manner, a magnetic field is formed perpendicularly to each surface of the parallel gates 7) Tl to T2, and this magnetic field causes the cathode fall portion (i.e., the target Ts-T2 (j
The γ′ electrons emitted at i[l are trapped in the space between the targets and moved toward the other opposing target. In this way, the γ electrons repeat the reciprocating motion while being bound by the magnetic field between the targets TI and T2. During this reciprocating motion, the γ
The electrons collide with the neutral atmospheric gas to generate ions and electrons of the atmospheric gas, and these products promote the release of γ electrons from the target and the ionization of the atmospheric gas.

Therefore, high-density plasma is formed in the space between the targets Tl and T2, and the target material is sufficiently sputtered and deposited as a magnetic material on the side substrate 6.

Compared to other flying methods, this facing target sputtering device enables film formation at a high deposition rate through high-speed sputtering, and the substrate is not directly exposed to plasma, allowing film formation at low substrate temperatures. This is advantageous for forming a perpendicularly magnetized film. Moreover, the energy incident on the substrate of the magnetic film material that is ejected by the opposing target-shaped Kuta device is smaller than that of the normal Snow (Ivy device), making it easier for the material to be directionally deposited in the desired direction. , it becomes easier to obtain a film with a structure suitable for perpendicular magnetization recording.

Next, a specific example of producing a magnetic recording medium using the above sputtering apparatus will be described.

The preparation conditions were as follows: Target material Iron (containing 1 atom of Co) Substrate
Glass-facing target spacing 100mm Magnetic field in sputtering space 1400e Target shape 100mm diameter circle (5mm
Thickness) Distance between substrate and target end 30mm Back pressure in vacuum chamber 10 Torr Introduced gas Ar+
02 Introduced scum pressure: 4 x 10-3 Torr Sputter input power: 420 W In this way, as shown in FIG. 1, a magnetic recording medium having iron oxide-based magnetic Wllo on the underlayer 11 on the base 6 was obtained. Regarding this medium, the characteristics of the magnetic layer were evaluated by identifying the composition using an X-ray microanalyzer (XMA), the state of iron oxide using an X-ray diffraction method, and the magnetic properties using a sample vibrating magnetometer. The characteristics of the obtained magnetic recording medium were as follows.

First, the ratio of the residual magnetization in the in-plane direction (MH) to the residual magnetization in the perpendicular direction (Mv) is MV/MH≧0.5.
Met. That is, as illustrated in FIG. 3, a hysteresis curve for magnetization in the in-plane direction shown by the broken line and a hysteresis curve for magnetization in the perpendicular direction shown by the solid line were obtained, but when the applied magnetic field is zero The amount of residual magnetization when MH,
According to this, the former hysteresis curve is smaller than the latter hysteresis curve, and MV≧0.
．． 5MH (ie, 2.0 in MV1ME), which indicates that a magnetic layer suitable for perpendicular magnetization is formed. This is a surprising fact in iron oxide based magnetic layers.

In addition, the composition of the magnetic recording medium in the heel is measured using xMA (X Pure Micro Analyzer: Hitachi's new product "X-556JKF:, VE
As a result of measurement using an X-7000 model, it was found that Fc was the main peak and a small amount of CO was contained. Furthermore, in order to investigate the state of iron monoxide, an X-ray diffraction device (JDX-10RA j manufactured by JEOL Ltd., using a CuKα tube) was used.
As shown in the table below, it was found that the magnetic layer was mainly composed of spinel type iron oxide. Moreover, it was observed using an electron microscope that this magnetic layer had an ordered structure in the direction perpendicular to the in-plane direction.

The base layer 11 is made up of a large number of small agglomerates 12 attached to independent island-like turns, as shown in enlarged views in FIGS. It becomes a continuous convex part, and there are four parts between each small particle agglomerate. Therefore, when magnetic particles are deposited on the base layer 11, the island 1
In the recess between 2 and the island 12, the magnetic particles 13 are deposited in the S4 order as shown in FIG. It grows. At the same time, growth also occurs on each island 12 with orientation while being regulated by the deposited particles in the recesses.

As a result, the resulting magnetic layer 10 has a columnar structure that is substantially regularly deposited in the vertical direction.

This columnar structure can enhance the shape anisotropy effect and improve the magnetic properties. For this - base layer 1
The average film thickness of No. 1 needs to be set in the range of IOA to 100OA.

On the other hand, if the thickness of the base layer is less than IOA, it will be too thin and the base material 12 will only be scattered minutely as shown in FIGS. It cannot be the basis for obtaining. Also, if the thickness of the base layer exceeds 100OA, it is too thick and the fifth
As shown in FIGS. (C) and (d), the base material particles 12 become large particles and bond to each other, and do not form the uneven surface as seen, and do not form a discontinuous film.

Furthermore, in the present invention, the fact that the underlayer 11 has a large number of island-shaped (turn-circular) islands uniformly distributed makes the energy required for adhesion of the magnetic particles uniform. This is desirable because a columnar structure can be obtained uniformly.

Further, the base layer 11 can be left in the form of turns (as shown in FIG. 4) by uniformly depositing the base material over the entire surface and then etching it using a known photolithography technique.

Next, an experimental example showing the effect of the underlayer will be described. First, an underlayer made of -In was deposited on the substrate, and an iron oxide-based perpendicular magnetic layer was formed thereon by the above-mentioned facing target sputtering method. Here, when the average thickness of the underlayer was varied, the perpendicular magnetization characteristics (MY/MH) of the magnetic layer were as shown in the table below.

From this result, it is clear that the effect of providing one underlayer is clear, and that it is desirable that the thickness of the underlayer be at least IOA and the upper limit at most 1000A.

In place of the base layer pattern shown in FIG. 4, a pattern as shown in FIG. 6 can also be adopted.

In the example shown in Fig. 6, for example, after coating the entire surface with the base coating material, -
This is etched by photolithography, and contrary to the above example, a continuous base layer 11 having one or more four parts discontinuously
It is processed into Even with this underlayer, the presence of each recess allows the magnetic particles deposited there to be directional and deposited in the vertical direction, so that a desired columnar structure can be obtained. Note that the base layer 11 in FIG. 6 may be relatively thick, and its thickness can be 1 μm or less.

Next, since the magnetic recording medium according to the present invention uses a magnetic layer containing iron oxide as a main component,
It has significantly superior chemical and mechanical stability compared to Cr-based magnetic layers. Figure 7 shows the forced deterioration test (80°C, 85°C).
%RH) of a sample of the medium according to the present invention using an iron monoxide-based magnetic layer as measured by a vibrating magnetometer (manufactured by Toei Kogyo Co., Ltd.) Residual magnetic flux density (Br) over time Δ
Br is the amount of change in residual magnetic flux density). According to this, it can be seen that the deterioration of Br is significantly/lower in the iron oxide magnetic layer than in the Go-Cr magnetic layer. Note that the reason why ΔBr/B'r is somewhat reduced in the iron oxide magnetic layer is considered to be because part of Fe304, which is the composition of the film, has migrated to γ-Fe2O31c. In addition, observation results after one month (30 days) showed that spots (spots, rust, etc.) had occurred on the surface of the Co-Cr magnetic layer, but no changes were observed in the surface condition of the iron oxide magnetic layer. There wasn't.

[Brief explanation of drawings]

The drawings illustrate the present invention, and FIG. 1 is a cross-sectional view of a magnetic recording medium, FIG. 2 is a schematic cross-sectional view of a facing target sputtering apparatus, FIG. 3 is a hysteresis curve diagram of the magnetic recording medium, and FIG. figure(
, ) is an enlarged sectional view showing the underlayer - Fig. 4(b) is an enlarged sectional view of the medium with a magnetic layer formed on the underlayer, and Fig. 4(c) is a plan view of Fig. 4(a). Figure 5(a),
(c) is an enlarged cross-sectional view showing other underlying layers, and Fig. 5(b)
, (d) are the plan views of Figures 5 (, ) and (c), and Figure 6 (
a) is an enlarged cross-sectional view showing another base layer; FIG. 6(b)
is a plan view of FIG. 6 (a). FIG. 7 is a graph showing changes in perpendicular magnetization characteristics over time. In addition, in the symbols shown in the drawings, 1... ...Vacuum chamber 2...
・・・・・・・・・Exhaust system 3・・・・・・・・・・・・
...Gas introduction system 4.5...Holder 6...Base 10...
......Magnetic layer 11...
・・・・・・Base layer 13・・・・・・・・・・・・・・・
The columnar structures T1, T21 of magnetic particles are targets. Agent: Patent attorney Hiroshi Aisaka (1 other person) No. 11 Tojima 2, No. 3, Kiku, No. 41, No. 61, Liu

Claims (1)

[Claims] 1. Comprising a base, a base layer provided on the base and having a large number of discontinuous convex or concave portions on the surface side, and a magnetic layer provided on the base layer. , and the magnetic layer is a continuous magnetic layer containing (,)-iron oxide as a main component0 (b) The residual magnetization (MU) in the in-plane direction of the magnetic layer and The ratio of residual magnetization (MV) in the vertical direction (
MV/MH) must be 05 or higher. What is claimed is: 1. A magnetic recording medium comprising: