JP2000215444A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a texture with a precisely controlled interval and depth on the surface of a magnetic disk substrate and to obtain a magnetic disk having high reliability due to the enhanced adhesive strength of the substrate to a medium and improved contact at the interface between a head and the disk. SOLUTION: An inorganic compound film 2 having crystal grains comprising one oxide selected from chromium oxide, iron oxide and nickel oxide and at least one oxide deposited on the grain boundaries of the grains and selected from silicon dioxide, aluminum oxide, titanium dioxide, tantalum oxide and zinc oxide is formed on a disk substrate 1, the oxide grains are at least partly removed by etching the surface of the inorganic oxide film and a magnetic film 3 comprising magnetic grains is formed in the oxide grains-freed parts to produce the objective magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium for storing a large amount of information quickly and accurately, and more particularly to a structure of a magnetic disk having high performance and high reliability and a magnetic disk using the same. It relates to a disk device.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in the advanced information society, and multimedia in which various forms of information are integrated has rapidly spread. One of the information recording devices that support this is a magnetic disk device. At present, the magnetic disk drive is being downsized while improving the recording density. At the same time, the cost of disk devices has been rapidly reduced. By the way, in order to realize the high density of the magnetic disk, 1) shorten the distance between the disk and the magnetic head, 2) increase the coercive force of the medium,
3) It is an essential technology to devise a signal processing method.

[0003] Above all, in a magnetic recording medium, an increase in coercive force is indispensable in order to realize high-density recording. In addition, in order to achieve a recording density exceeding 10 Gb / in ² , the unit in which magnetization reversal occurs must be reduced. For that purpose, it is necessary to reduce the size of the magnetic particles. For that purpose, it is known to reduce magnetic interaction between magnetic particles. As an example of this, JP-A-7-50008 can be mentioned. At the same time, in terms of reliability, suction occurs between the head and the magnetic recording medium. As a result, the rotation may stop. On the other hand, irregularities called textures are formed on the substrate surface. As a known example of this, Patent Registration 19
86300 can be given.

[0004]

In the above prior art,
Non-magnetic elements are segregated at grain boundaries in order to reduce magnetic interaction between magnetic particles. However, as the magnetic particles become finer, the magnetic properties are significantly reduced, and there is a limit to the concentration that can be added. Further, it is difficult to reduce the size distribution of the magnetic particles, and there is a limit to the reduction of medium noise, thermal fluctuation and thermal demagnetization. Also, in terms of disk reliability,
In some cases, it is difficult to accurately and stably form the texture formed on the disk surface. In particular, it has been difficult to form irregularities (textures) of an arbitrary height on the substrate surface and to precisely control the shape and arrangement on the substrate. Further, variation between substrates cannot be fully controlled, and the structure of the magnetic film formed on the substrate is different, which sometimes causes variation in magnetic characteristics. As a result, when performing ultra-high-density recording exceeding 10 GB / inch ² , stable recording and reproduction may not be performed.

Accordingly, a first object of the present invention is to provide a medium structure capable of reducing the magnetic interaction between magnetic particles without deteriorating the magnetic characteristics of the magnetic film, and a method of manufacturing the same. Further, the second object of the present invention is to provide a texture that is controlled with high precision by forming a texture of concavities and convexities simultaneously with the production of a magnetic film, and to provide a simple manufacturing process, and to provide high performance and low cost. Another object of the present invention is to provide a simple magnetic disk device. As for the texture, it is possible to control the arbitrary size and the height of the arbitrary unevenness with high accuracy. Further, a third object of the present invention is to provide a magnetic disk substrate having high reliability by increasing the adhesion between the substrate and the magnetic recording medium. Further, a fourth object of the present invention is to provide a magnetic disk having high corrosion resistance and high stability of magnetic characteristics of a magnetic film by controlling diffusion of alkali metal ions and the like leached from a substrate. Thereby, an ultra-high density magnetic recording medium exceeding 20 GB / inch ² can be provided.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide, on a disk substrate, crystal grains made of one kind of oxide selected from chromium oxide, iron oxide or nickel oxide and crystal grain boundaries of the crystal grains. Forming an inorganic compound film having at least one oxide selected from precipitated silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, or zinc oxide, and etching the surface of the inorganic compound by etching the surface of the inorganic compound. By removing at least a part of the crystal grains of the above, and forming a magnetic film composed of magnetic particles on the portion from which the crystal grains of the oxide have been removed, a magnetic recording medium can be realized. Further, in a magnetic disk having at least a circular disk substrate and a magnetic film for recording information, one type of oxide selected from chromium oxide, iron oxide or nickel oxide is formed on the disk substrate surface.
(Solute) is dissolved in at least one oxide (solvent) selected from silicon oxide, aluminum oxide, titanium oxide, tantalum oxide or zinc oxide, and the solute substance is an inorganic compound precipitated as crystal particles. It can be realized by forming a magnetic film after selectively removing a part of a crystalline chromium oxide, iron oxide or nickel oxide phase (solute) by etching after forming a thin film.

Further, when the magnetic recording medium is formed after etching the surface of the inorganic compound film, the magnetic recording medium may be formed such that the portion of the solvent substance at the crystal grain boundaries relatively becomes convex. . Thereby, the texture can be produced simultaneously with the production of the magnetic film.

Here, the difference (depth) between the top and bottom of the irregularities formed on the substrate surface is determined by the film thickness of the formed inorganic compound layer and / or the etching time. It can be controlled by utilizing the difference between the etching rates of the amorphous portion and the amorphous portion (grain boundary portion).
As a result, the texture can be formed simultaneously with the production of the magnetic film, so that the process can be simplified. By the way, the structure of the inorganic compound layer after film formation is such that the crystal phase is a solute compound and the solvent compound is amorphous at the grain boundaries of the crystal grains. The crystalline phase is an oxide of cobalt, iron or nickel. There is no change in the film structure or particle size after etching, and the magnetic film is epitaxially grown from this crystal phase. In this case, since the solvent substance present at the crystal grain boundaries serves as a barrier, the crystal growth of the magnetic recording medium to be formed can be suppressed, so that magnetic particles having the same crystal particle size as the inorganic compound layer can be formed.

Here, the magnetic material is mainly composed of this element in addition to cobalt, iron or nickel.
An alloy containing at least two kinds of elements selected from r, Pt, Ta, and Nb may be used. Further, in this ferromagnetic thin film, the crystal grains are at least one element selected from Co, Ni or Fe, and at least one element selected from Cr, Ta and Nb is located near or at the crystal grain boundary. The types of elements may be segregated.

A magnetic disk device comprising such a magnetic recording medium, a magnetic disk, a magnetic head, or an electric circuit. Then, various types of information are recorded, reproduced or erased in this device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described with reference to embodiments.

(Example 1) FIG. 1 shows a schematic view of a cross-sectional structure of a manufactured magnetic disk. First, a 2.5 ″ diameter glass substrate was used as a substrate for a magnetic disk. The glass substrate used here is only one example, and a disk substrate of any size can be used. Even if a substrate is used, the effect of the present invention is not affected.On the substrate (1), a mixture of CoO and SiO2 in a ratio of 2: 1 as an inorganic compound layer (2) is used as a target. By sputtering method
It was formed to a thickness of 30 nm. The surface of the inorganic compound layer (2) is
FIG. 2 shows a schematic diagram of the results observed by M. From this figure,
It can be seen that this is an aggregate of 8 nm regular hexagonal fine crystal particles. The width of the crystal grain boundary was 0.5 nm or less from TEM observation. There was almost no variation in the particle size of this crystal phase, and the standard deviation σ was 3 or less. Etching was performed from the surface of this film to selectively etch the cobalt oxide crystal phase. Here, the difference in etching rate between the oxide of cobalt and the silicon oxide was used. here,
The etching depth is 15 nm. No change was found in the form or structure of the inorganic compound film even after etching.
Thereafter, a magnetic layer (3) was formed in a concave portion of the inorganic compound layer (2) generated by etching to a thickness of 15 nm by a sputtering method. The magnetic material used is Co. The sputtering conditions are as follows: input DC power density is 1 kW / 150 mmφ, and discharge gas pressure is 3 mTorr. During sputtering, the substrate was heated to 300 ° C. Here, Ar was used as the sputtering gas. A Co film was epitaxially grown from the crystal phase surface of the inorganic compound layer. At the same time, the surface of the substrate was milled so that a film was not deposited on the crystal grain boundary portions, which were convex portions of the inorganic compound layer. As a result, no film is deposited on the crystal grain boundaries of the projections. When the magnetic film exists in the crystal grain boundary portion, the interaction between the magnetic particles is strengthened, and the microscopic distribution of the magnetic characteristics occurs due to the presence of the unevenness. This is because it causes medium noise, thermal fluctuation and thermal demagnetization. Protective film on the surface of this film
As (4), a C film was formed to a thickness of 5 nm. The sputtering conditions are as follows: input DC power density is 0.5 kW / 150 mmφ, and discharge gas pressure is 5 mTorr. Here, the sputtering gas is Ar
However, it goes without saying that a gas containing nitrogen may be used. This is because the particles become finer, and the resulting film becomes denser, and the protective performance can be improved. As for the film quality of this film, in addition to such a sputtering method, since the properties of the obtained film greatly depend on the apparatus, these conditions and methods are not absolute.

Next, the structure of the magnetic film was examined. According to X-ray diffraction, the (102) plane of Co was strongly oriented in this film. Further, from the observation of the plane by electron microscopy, the average particle size was 9 nm, and the particle size distribution was determined.
Was 3 or less. The particles of this magnetic film are finer and the particle size distribution is smaller. From the cross-sectional observation, it was found that the cross-sectional structure of the magnetic film (3) had a good columnar structure, and the crystal grain size did not change from the substrate surface to the medium surface. In addition, since the inorganic compound layer is present between the substrate and the magnetic particles, alkali ions do not diffuse from the glass substrate into the magnetic recording medium during film formation, etc. It was also found that there was no decline. Next, the magnetic characteristics of the magnetic film were measured. The obtained magnetic properties are as follows: coercive force 3.5 kOe, Isv 2.
5 × 10 ⁻¹⁶ emu, S, which is an index of the squareness of the hysteresis in the MH loop, was 0.8, and S ^† was 0.86, indicating good magnetic properties.

Next, a lubricant was applied to the medium surface of a magnetic disk using a magnetic film having such magnetic characteristics, and the recording / reproducing characteristics of the disk were evaluated. For recording, a magnetic head using a soft magnetic film having a high saturation magnetic flux density of 2.1 T was used as the recording head. Reproduction was performed using a magnetic head having a giant magnetoresistance effect. The distance between the head surface and the magnetic film is 20 nm. A signal equivalent to 20 GB / inch ² was recorded on this disk and the S / N of the disk was evaluated.
Was obtained. Here, when the magnetization reversal unit was measured by a magnetic force microscope (MFM), it was found that the size was about 3 particles from 2 and sufficiently small. At the same time, the zigzag pattern existing in the magnetization transition region was significantly smaller than that of the conventional medium. In addition, thermal fluctuation and demagnetization due to heat did not occur. This is attributable to the fact that the crystal grain size distribution of the magnetic film is small and, in addition, the magnetic interaction is reduced by providing a grain boundary phase between crystal grains. Further, when the defect rate of this disk was measured, the value obtained when no signal processing was performed was 1
× 10 ^-5 or less. Further, by forming a texture with the inorganic compound layer of this example, stable flying characteristics were obtained.

Here, an example was described in which chromium oxide was used as the solute substance in the inorganic compound layer (2), but the same effect was obtained by using iron oxide or nickel oxide. Further, although silicon oxide was used as the solute oxide, similar effects were obtained by using aluminum oxide, titanium oxide, tantalum oxide, or zinc oxide. In addition, Co, Ni or F
By using an alloy containing at least two elements selected from Cr, Pt, Ta, and Nb in addition to the main elements such as e,
The magnetic properties can be adjusted. In this case, at least one element selected from Cr, Ta, and Nb may be segregated near or at the crystal grain boundaries. As a result, there is an effect that matching between the magnetic head and the magnetic recording medium can be easily achieved.

(Embodiment 2) In this embodiment, the texture is formed simultaneously with the production of the magnetic film. FIG. 3 shows a schematic diagram of a cross-sectional structure of the manufactured magnetic disk. First, a 2.5 ″ diameter glass substrate was used as a substrate for a magnetic disk. The glass substrate used here is only one example, and any size disk substrate can be used.
The use of an alloy substrate does not affect the effects of the present invention. On this substrate (1), as an inorganic compound layer (2), CoO
Using a mixture of ZnO and ZnO at a ratio of 3: 1 as a target, a film having a thickness of 35 nm was formed by a sputtering method. This film was subjected to dry etching to remove a part of the crystal grains. As a result, unevenness having a depth of 25 nm was formed on the substrate. This depth is
It can be arbitrarily selected by selecting the thickness of the inorganic compound layer (2), the etching time, and the etching gas. afterwards,
A magnetic layer (3) was formed to a thickness of 15 nm by a sputtering method in a concave portion of the inorganic compound layer (2) generated by the etching. As a result, irregularities of 10 nm can be formed on the medium surface, and this becomes the texture. Needless to say, the desired depth can be easily obtained by appropriately combining the thickness of the inorganic compound, the etching depth, and the thickness of the magnetic film. Here, the magnetic material used is Co. Sputtering conditions are as follows: input DC power density is 1kW / 150m
mφ and discharge gas pressure is 3 mTorr. During sputtering, the substrate was heated to 300 ° C. Here, the sputtering gas is Ar
It was used. A Co film was epitaxially grown from the crystal phase surface of the inorganic compound layer. At the same time, the surface of the substrate was milled so that a film was not deposited on the crystal grain boundary portions, which were convex portions of the inorganic compound layer. As a result, no film is deposited on the crystal grain boundaries of the projections. When the magnetic film exists in the crystal grain boundary portion, the interaction between the magnetic particles is strengthened, and the microscopic distribution of the magnetic characteristics occurs due to the presence of the unevenness. This is because it causes medium noise, thermal fluctuation and thermal demagnetization. Finally, a C film was formed to a thickness of 5 nm as a protective film (4). Sputtering conditions are as follows: input DC power density is 1 kW / 15
0 mmφ and discharge gas pressure is 5 mTorr. Here, Ar is used as the sputtering gas, but it goes without saying that a gas containing nitrogen may be used. This is because the particles become finer, and the resulting film becomes denser, and the protective performance can be improved. As for the film quality of this film, in addition to such a sputtering method, since the properties of the obtained film greatly depend on the apparatus, these conditions and methods are not absolute.

Next, the structure of the magnetic film was examined. According to the X-ray diffraction method, (102) of Co was strongly oriented in this film. From the observation of the medium surface, the average particle size was 8 nm. When the particle size distribution of the particles was determined, the value of σ was 3 or less. Thus, the particles are finer, and
The distribution was found to be small. The grain boundary width is 0.5nm
It was below. From the cross-sectional observation, it was found that the inorganic compound layer and the magnetic film were epitaxially grown.
The structure also had a good columnar structure, and it was found that the crystal grain size did not change from the substrate surface to the medium surface.
In addition, since the inorganic compound layer is present, alkali ions do not diffuse from the glass substrate into the magnetic recording medium, so that magnetic characteristics and reliability are not deteriorated. The magnetic properties of this magnetic film were measured. The obtained magnetic properties are
The coercive force is 3.5 kOe, Isv is 2.5 × 10 ^-16 emu, S is 0.81 which is an index of the squareness of the hysteresis in the MH loop, and S ^†
Was 0.85, indicating good magnetic properties. When the magnetic recording medium was observed by TEM, the crystal grain size was the same as that of the inorganic compound layer, it was an aggregate of 8 nm regular hexagonal crystal grains, and the distribution was extremely small with σ of 3 or less. It is presumed to reflect this.

Next, a lubricant was applied to the medium surface of a magnetic disk using a magnetic film having such magnetic characteristics, and the recording / reproducing characteristics of the disk were evaluated. For recording, a magnetic head using a soft magnetic film having a high saturation magnetic flux density of 2.1 T was used as the recording head. Reproduction was performed by a head having a giant magnetoresistance effect. The distance between the head surface and the magnetic film is 20nm
It is. When a signal corresponding to 20 GB / inch ² was recorded on this disc and the S / N of the disc was evaluated, a reproduction output of 32 dB was obtained. Here, when the magnetization reversal unit was measured by a magnetic force microscope (MFM), it was found that the size was about 3 particles from 2 and sufficiently small. At the same time, the zigzag pattern existing in the magnetization transition region was significantly smaller than that of the conventional medium. In addition, thermal fluctuation and demagnetization due to heat did not occur. This is attributable to the fact that the crystal grain size distribution of the magnetic film is small and, in addition, the magnetic interaction is reduced by providing a grain boundary phase between crystal grains. When the defect rate of this disk was measured, the value was 1 × 10 ⁻⁵ or less when no signal processing was performed. Further, by forming a texture with the inorganic compound layer of this example, stable flying characteristics were obtained.

Here, an example in which chromium oxide is used as the solute substance has been described, but the same effect was obtained by using iron oxide or nickel oxide. Further, although silicon oxide was used as the solute oxide, similar effects were obtained by using aluminum oxide, titanium oxide, tantalum oxide, or zinc oxide. Furthermore, by forming an alloy containing at least two elements selected from Cr, Pt, Ta, and Nb in addition to the main elements such as Co, Ni, and Fe in the magnetic film after the reduction treatment, the magnetic properties are improved. Can be adjusted. In that case, Cr, Ta,
At least one element selected from Nb may be segregated. As a result, there is an effect that matching between the magnetic head and the magnetic recording medium can be easily achieved.

[0020]

According to the present invention, ultra-high density magnetic recording exceeding 20 GB / inch ² can be achieved because the size of magnetic particles can be reduced and the size distribution can be reduced, and the magnetic interaction between magnetic particles can be reduced. Can be realized. In addition, a texture with a precisely controlled spacing and depth can be formed on the surface of the magnetic disk substrate, and high reliability such as improved adhesion between the substrate and the medium and improved contact at the head-disk interface can be achieved. A magnetic disk having the same can be obtained. In addition, stable flying characteristics were obtained. Further, since the texture and the magnetic film can be formed at the same time, and the number of laminations can be reduced, the manufacturing process can be simplified, and the disk cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a magnetic disk.

FIG. 2 is a schematic view illustrating a structure of an inorganic compound layer.

FIG. 3 is a schematic diagram showing a cross-sectional structure of a magnetic disk.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Inorganic compound film, 3 ... Magnetic film, 4 ...
· Protective film.

Continued on the front page (72) Inventor Hiroki Yamamoto 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Takashi Naito 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Motoyasu Terao, Inventor: 1-280, Higashi-Koigakubo, Kokubunji-shi, Tokyo Within Central Research Laboratory, Hitachi, Ltd. (72) Inventor: Ken Takahashi Hitachi, Ltd.Hitachi Research Laboratories (72) Inventor Sumio Hosaka 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Prefecture Hitachi, Ltd.Basic Research Laboratories Co., Ltd. Hitachi Maxell Co., Ltd. (72) Inventor Hiroki Kuramoto 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Technology Research Laboratories F-term (reference) BB02 BB05 BB06 BD03 BD04 FA04 GA02 GA20

Claims (6)

[Claims] 1. A disk substrate, comprising: a crystal particle made of one kind of oxide selected from chromium oxide, iron oxide, and nickel oxide; and silicon oxide, aluminum oxide, and oxide oxide precipitated at a crystal grain boundary of the crystal particle. Forming an inorganic compound film having at least one oxide selected from titanium, tantalum oxide or zinc oxide, and removing at least a part of crystal particles of the oxide by etching the surface of the inorganic compound; And forming a magnetic film composed of magnetic particles in the portion from which the crystal grains of the oxide have been removed. 2. The magnetic film according to claim 1, wherein a portion of a crystal grain boundary of the oxide crystal particle is relatively convex with respect to a portion from which the oxide crystal particle is removed. The method for manufacturing a magnetic recording medium according to claim 1. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein magnetic particles constituting the magnetic film are epitaxially grown from crystal grains of the oxide in the inorganic compound film. 4. The method according to claim 1, wherein the magnetic film contains at least one element selected from Co, Ni and Fe. 5. The magnetic film mainly comprises at least one element selected from Co, Ni or Fe, and Cr, Pt, Ta, N
5. The method for manufacturing a magnetic recording medium according to claim 4, wherein an alloy containing at least two kinds of elements selected from b is used. 6. The magnetic film comprises: magnetic particles comprising at least one element selected from Co, Ni or Fe;
6. The method according to claim 5, further comprising at least one element selected from the group consisting of Cr, Ta, and Nb segregated at the grain boundaries of the magnetic particles.