JPS59148120A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is suitable for vertical magnetic recording at a high density and has excellent mechanical strength, chemical stability, etc. by forming a magnetic layer of a granular material consisting essentially of an iron oxide having a prescribed magnetizing characteristic. CONSTITUTION:A magnetic field is formed in the direction perpendicular to the surface of targets T1, T2 in a vacuum vessel 1 of a sputtering device to form high density plasma. The target material is deposited as a magnetic material on a substrate 6. A continuous magnetic layer 10 in which small grain lumps consisting essentially of an iron oxide are joined to the target material in the state in contact with the grain boundary is formed on the substrate 6 by using Fe (contg. 1atom% Co) and Ar+O2 for the gas to be introduced. The ratio of the residual magnetization in the direction perpendicular to the plane of the layer 10 with respect to the residual magnetization in the direction within the plane of said layer is made >=0.5. The magnetic recording medium in which the small grain boundaries are arranged in the direction perpendicular to the plane of the layer 10 and which is suitable for vertical magnetic recording at a high density and has excellent mechanical strength, chemical stability, etc. is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field 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 No.

192). 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, to perform such perpendicular recording efficiently, LS
I1: The recording layer of the magnetic recording medium must have an axis of easy magnetization in the 1u direction (thickness direction of the magnetic layer). As such magnetic recording media, 5. On the base (support),
A coated type medium is known in which a magnetic paint containing magnetic powder and a binder as main components is coated and the magnetic layer is oriented so that its axis of easy magnetization is oriented in the perpendicular direction. This coated medium includes Co, Fe30I1. , T Fe2O3, Co-added Fe30q, Co-added -Fe2es, hexagonal ferrite (e.g. barium ferrite), MnBi, etc. are used as magnetic powders (JP-A-52-4680).
No. 3, No. 53-67406, No. 52-L78403, No. 55-86103, No. 52-78403, No. 5
4-87202). However, since these coated media contain a non-magnetic binder in the magnetic layer, there is a limit to increasing the packing density of magnetic powder, and it is difficult to increase the S/N ratio sufficiently high. Since the size is limited by the dimensions of the magnetic particles, a medium having a magnetic layer made of 4M coating is unsuitable for perpendicular magnetization recording in LIE.

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 -F without using a binder, are attracting attention as suitable for high-density recording. has been done.

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. In addition, a magnetic recording medium having a magnetic layer formed by adding rhodium of 30% or less to a co-01 alloy film is disclosed in Japanese Patent Laid-Open No. 111/1983 and No. 10, and furthermore, a cobal I-vanadium alloy film is disclosed. film(
For example, the American Institute of Electrical and Electronics Communication Engineers (abbreviated as IEEE) is an academic journal published by 'Transaction on Magnet'.
ism" 1982 Vol. 18 No. 6.1116) and cobalt-ruthenium alloy films (for example, the (3) 18th Tohoku University Research Symposium [Perpendicular Magnetic Recording Cobra Collection] held in March 1982). Magnetic recording media are known.

Among these, the co-Or alloy film has been shown to be promising for perpendicular magnetization, but it has been found that it has the following drawbacks.

(I) 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” Torr or higher, and the substrate must be subjected to advanced cleaning treatment and low Conditions such as sputtering speed are required, and the control factors for vertical alignment become very 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 and scratches occur 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) The corrosion resistance of the magnetic recording medium is not sufficient, 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 actual situation as described in -F, the inventor has made extensive studies and has obtained a magnetic recording medium that is suitable for high-density perpendicular magnetic recording and has excellent mechanical strength, chemical stability, etc. It was extremely successful.

4. Structure of the invention and its effects, that is, the present invention provides a magnetic recording medium in which a magnetic layer is provided on a substrate, in which the magnetic layer comprises (a) a large number of small particles mainly composed of iron oxide; A continuous magnetic layer is formed by bonding each other with grain boundaries.

(b) The ratio (Mv/MH) of the residual magnetization in the in-plane direction of the magnetic layer (M+-+) to the residual magnetization (Mv) in the direction perpendicular to the plane of the magnetic layer is 0.5 or more. Be a good person.

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 its main component, excellent properties unique to oxides (i.e. mechanical strength, chemical stability, etc.) can be obtained, which are necessary for conventional alloy thin films. The surface protective film that was previously used 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.

Furthermore, the residual magnetization ratio (MV/M?l) in the in-plane direction and the perpendicular direction of the magnetic layer containing iron oxide as the main component is 0°5 or more.
Since the iron oxide magnetic material has a high temperature, the magnetic moment of the iron oxide magnetic material rises more than 30 degrees perpendicular to the in-plane direction.
It has a structure that can fully realize perpendicular magnetization. The magnetization amounts Mv and M+ can be measured, for example, with a sample vibrating magnetometer (manufactured by Toei Kogyo Co., Ltd.).

Moreover, in the magnetic layer, a large number of small grains mainly composed of iron oxide each have grain boundaries and are bonded to each other to form a continuous layer. It is possible to obtain a magnetic layer in which magnetization characteristics are effectively produced and excellent perpendicular magnetic recording and retention/7S performance. In particular, it is preferable that each of the small agglomerates has a columnar structure or a needle-like structure, and the length direction of the structure is oblique to the in-plane direction of the magnetic layer (or the plane of the substrate). You can, but
Ideally, it should be vertical.

As described above, the magnetic layer according to the present invention is composed of a continuous aggregate of small grains mainly composed of iron oxide, and has a magnetization ratio that allows perpendicular magnetization. It did not exist at all and was thought to be impossible to create.

The magnetic layer according to the present invention is fundamentally different from conventional coated magnetic layers in that it does not use a binder and is made of iron oxide (e.g. Fe).
5 0 B, r Fe 2 O 3 , or a non-stoichiometric composition intermediate between them) 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.
It is preferably at least 70% by weight, and more preferably at least 70% by weight. The ratio of iron to oxygen is preferably the number of oxygen atoms/the number of iron atoms - 1 to 3, more preferably 4/3 to 2, and the iron oxides listed above are suitable. be.

However, metals other than iron and oxygen or their oxides, nonmetals, semimetals, or compounds thereof are added to the magnetic layer, thereby improving the magnetic properties of the magnetic layer (e.g. coercive force, saturation magnetization, residual magnetization). amount), its crystallinity, and the orientation of the crystal in a specific axial direction. Examples of such additive elements or compounds include A1. ,co,,co-Mn1Z
n, , co-Zn1LiSCrsTi, , Li-CrX
Mg, Mg-Ni, Mn-Zn, NiXNi-
A11Ni-Zn%Cu-, CuMn,,
Examples include Cu, Zn-, V, etc., but it is preferable to use other than rare earth elements.

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

To produce this magnetic recording medium, the substrate can be closely supported on a fixed plate, or the magnetic material can be applied while the substrate is running. For this purpose, a sputtering method is used in which a magnetic material target is sputtered in a processing chamber connected to an evacuation system such as a vacuum pump, or the material is evaporated from a magnetic material evaporation source and deposited on the substrate. Vapor deposition method etc. can be applied.

In either case, the elements constituting the magnetic layer are made to fly,
A continuous thin film is formed on the substrate.

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

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

FIG. 1 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 10 to 10' Torr. This is a gas introduction system. The target electrodes are configured as opposed target electrodes in which a pair of target electrodes (T1% T2) are arranged facing each other in parallel with each other separated from each other by a target holder 4.

Between these targets is a magnetic field generating means (not shown).
A magnetic field is formed by 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 holder 5.

In the sputtering apparatus configured in this way, a magnetic field is formed in a direction perpendicular to each surface of the two targets T1 and T2 that face each other in parallel, and this magnetic field generates a cathode falling area (i.e., between the target nodes L and T+m). The γ electrons emitted by the impact of the sputtering gas ions accelerated by the electric field on the target surface in the region (11) between the plasma atmosphere and each target T1 and T2 are trapped in the space between the targets, and the Move towards the other target. The γ electrons that have moved to the other target surface are reflected at the cathode fall section nearby. In this way, the γ electrons repeatedly move back and forth between the targets T1 and T2 while being bound by the magnetic field. During this reciprocating motion, the γ 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, a high-density plasma is formed in the space between the targets TI-='Th, and accordingly, the target material is sufficiently sputtered, and the magnetic material*' is sputtered onto the side substrate 6.
It will continue to accumulate as a result.

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, since the incident energy of the magnetic film material sputtered onto the substrate by the facing target sputtering device is smaller than that of a normal sputtering device, the material is easily deposited directionally in the desired direction, making it possible to record perpendicular magnetization. It becomes easier to obtain a membrane with a structure that passes through the membrane.

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

The conditions for this preparation were as follows.

Target material Iron (contains 1 atomic% Co) base
Glass-facing target spacing 100mm Magnetic field in sputtering space 1400e Target shape 100mm diameter disk (5mm
Thickness) Distance between substrate and target end 30mm Back pressure in vacuum chamber 10Torr Introduced gas Ar →-02 Introduced gas pressure
4 X 10 Torr (12) Sputter input power 420 W In this way, as shown in FIG.
A magnetic recording medium having an iron oxide-based magnetic layer 10 was obtained. For this medium, the characteristics of the magnetic layer were evaluated by identifying the composition by X-ray microanalysis (XMA), the state of iron oxide by X-ray diffraction, and the magnetic properties by 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 Mν/MH≧0.5
Met. That is, as illustrated in FIG. 3, a hysteresis curve during magnetization in the in-plane direction shown by the broken line and a hysteresis curve during magnetization in the perpendicular direction shown by the solid line were obtained, but when the applied magnetic field is zero, The amount of magnetization at each time was defined as MH, , Mv. According to this, the former hysteresis curve is smaller than the latter hysteresis curve, Mν≧0.5 MH,
It is clear that the magnetic layer is suitable for perpendicular magnetization. This is a surprising fact for iron oxide-based magnetic layers.

In addition, the composition of this magnetic recording medium was analyzed using XMA (X-ray microanalyzer: rX-556JKEVEX manufactured by Hitachi, Ltd.).
-7000 model), it was found that Fe was the main peak and a small amount of CO was contained. Furthermore, in order to investigate the state of iron oxide, measurements were performed using an X-ray diffraction device (rJDχ-10RAj manufactured by JEOL Ltd., using a CuKα tube), and as shown in the table below, it was found that the magnetic layer mainly consisted of iron oxide. It turned out that it was an ingredient.

Furthermore, it was observed using an electron microscope that this magnetic layer had a substantially ordered structure in the direction perpendicular to the in-plane direction.

That is, as shown in FIG.
10, a large number of columnar or acicular small grains 11 mainly composed of iron oxide are arranged substantially perpendicularly to the surface of the base 6, each having a grain boundary 12 (boundary). It was found that they had a structure in which they were joined or fixed to each other.

The short axis of each small agglomerate 11 was 100 to 200 on average, and a continuous magnetic layer 10 with a thickness of about 2,500 was formed.

A magnetic layer consisting of small grains with a columnar or needle-like structure is
Because individual small agglomerates oriented substantially vertically have the property of being easily and sufficiently magnetized in the vertical direction,
It has excellent perpendicular magnetization characteristics, and exhibits the desired hysteresis curve magnetization characteristics as shown in FIG. On the other hand, if the grain boundaries between small grain agglomerates are unclear or the grain size is too large, the amount of magnetization in the horizontal direction increases too much (15), and as shown in Figure 5, the relative Mv decreases, M
It was confirmed that v/MH<0.5.

It is clear that this makes it impossible to achieve the desired perpendicular magnetization.

[Brief explanation of the drawing]

The drawings illustrate the present invention, and FIG. 1 is a schematic sectional view of a facing target sputtering apparatus, FIG. 2 is a sectional view of a magnetic recording medium, FIG. 3 is a hysteresis curve diagram of the magnetic recording medium, and FIG. The figure is an enlarged cross-sectional view of the magnetic layer, and FIG. 5 is a hysteresis curve diagram of a magnetic recording medium having a magnetic layer not based on the present invention. In addition, in the symbols shown in the drawings, ■--Vacuum chamber 2-11--Exhaust system 3--Gas introduction system 4.5--Holder 6-- ---One substrate (16) 10-1.-Magnetic layer 11-m.--Small grain agglomerates 12.--Grain boundaries T1, T2.--Target.

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer is provided on a substrate, wherein the magnetic layer (a) has a large number of small grains mainly composed of iron oxide, each of which has a grain boundary. A continuous magnetic layer is formed by bonding each other in a state. (b) The ratio (MV/MH) of the residual magnetization (MH) in the in-plane direction of the magnetic layer to the residual magnetization (Mv) in the direction perpendicular to the plane of the magnetic layer is 0.5 or more. . What is claimed is: 1. A magnetic recording medium comprising: