JP2000215436A - Magnetic recording medium and magnetic disk device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce magnetic interaction between magnetic grains in a magnetic film and to control the orientation property of the magnetic film by allowing oriented grains whose grain size and grain size distribution are small in the magnetic film to exist physically independently at 0.5-1.0 nm crystal grain intervals and to obtain a magnetic recording medium which reduces noise, thermal fluctuation and thermal demagnetization. SOLUTION: An inorganic compound film 2 having crystal grains comprising one oxide selected from cobalt oxide, iron oxide and nickel oxide and at least one oxide present 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 and a magnetic film 3 containing magnetic grains at 0.5-1.0 nm grain intervals is formed on the inorganic compound film 2 to obtain 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 high-performance and highly reliable magnetic recording medium for a magnetic disk. The present invention relates to a magnetic disk and a magnetic recording device using the same.

[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, and as a method for achieving this, it has been proposed to provide a seed layer below the magnetic film. One example is USP-4652499.

[0004]

In the above prior art,
There is a limit in controlling the crystal particle size distribution of the magnetic film for information recording, and fine particles and coarse particles may coexist. These fine particles and coarse particles are used when recording information (when reversing the magnetization).
In order to be affected by the stray magnetic field from surrounding magnetic particles, and conversely, large particles
When performing ultra-high density recording of more than h ^2, there may not be performed has stable recording. Furthermore, in recording and reproducing information, there is a case where it is disadvantageous in increasing the recording density, for example, when a strong magnetic interaction between magnetic particles increases noise.

Accordingly, a first object of the present invention is to reduce the magnetic interaction between magnetic particles by physically isolating the crystal grains of the magnetic film, and to reduce the magnetic reversal region. An object of the present invention is to provide a magnetic recording medium capable of high-density recording. A second object of the present invention is to provide a high-performance magnetic recording medium with reduced noise generation by suppressing dispersion of crystal grain size in a magnetic film and miniaturizing the same. A third object of the present invention is to reduce the noise,
An object of the present invention is to provide a magnetic recording medium having low thermal fluctuation and low thermal demagnetization. Further, a fourth object of the present invention is to control the orientation of the magnetic film to facilitate the formation of minute magnetic domains, and to make the magnetic domains stable so that magnetic recording suitable for high-density magnetic recording is achieved. To provide a medium. Thereby, it is possible to provide an ultra-high density magnetic recording medium exceeding 20 GB / inch ² .

[0006]

The object of the present invention is to provide, on a disk substrate, crystal grains made of one kind of oxide selected from cobalt oxide, iron oxide or nickel oxide;
An inorganic compound film having at least one oxide selected from silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, and zinc oxide present at the crystal grain boundaries of the crystal grains is formed, and the inorganic compound film is formed on the inorganic compound film. A magnetic film containing magnetic particles is formed on the magnetic recording medium, and the distance between the magnetic particles of the magnetic film is 0.5 nm or more and 1.0 nm or less. In addition, cobalt oxide, one type of oxide (solute) selected from iron oxide or nickel oxide on the surface of the glass substrate, silicon oxide, aluminum oxide,
After forming a thin film of an inorganic compound dissolved in at least one kind of oxide (solvent) selected from titanium oxide, tantalum oxide or zinc oxide, by producing a magnetic recording medium having a structure reflecting the film structure realizable. That is, while growing epitaxially from the crystal grains of the inorganic compound layer, reflecting the spacing between the crystal grains,
That is, the magnetic crystal grains exist physically independently. Thereby, the magnetic interaction between the magnetic crystal grains can be reduced, so that the magnetization reversal can be performed independently by the grains.

Here, the thin film of the inorganic compound has a structure in which a solute substance is precipitated as crystal particles and a solvent substance is present at the crystal grain boundary. Here, it is most preferable that the produced inorganic compound film has a hexagonal honeycomb structure in which the shapes of crystal phases are regularly arranged, and that the size distribution of the crystal particles is 2 nm or less in standard deviation. Further, it is preferable that the distance between the crystal particles in the inorganic compound is about 0.5 to 1.0 nm. Further, the thickness of the inorganic compound layer is preferably 10 nm or more and about 100 nm. This is determined from the viewpoint of the deposition time and the internal stress of the film. After forming the previous inorganic compound thin film,
In order to form a magnetic recording medium, it is most preferable to epitaxially grow on an inorganic compound thin film. This is because the crystal grain size of the formed magnetic film can be made the same as the solute particles of the inorganic compound thin film, reflecting the crystal structure of the inorganic compound thin film. Furthermore, reflecting the fact that the spacing between the crystal grains of the inorganic compound thin film is about 0.5 to 1.0 nm, the spacing between the crystal grains of the magnetic film is wider than that when formed on a normal substrate. . this is,
The crystal grains are in a physically isolated state. As a result, magnetic interaction can be reduced.

A magnetic recording medium is epitaxially grown on such an inorganic compound thin film. In this case, what is important is the consistency of the lattice constant between the crystal grains and the magnetic recording medium. However, this point can be solved by selecting the material, composition, and film forming conditions of the inorganic compound thin film. Here, it is preferable that the X-ray diffraction angle of the crystal particles (solute substance) in the inorganic compound is the same as or similar to the magnetic recording medium formed thereon. It is preferable that the inorganic compound layer is X-ray crystalline and the crystal structure is the same as or similar to the structure of the magnetic recording medium. Here, “similar” means that the difference between the lattice constants of the crystals is about ± 10% or less. This is because the lattice constant mismatch between the inorganic compound layer and the magnetic recording medium does not affect the growth of the magnetic film.

Here, the magnetic recording medium to be used is most preferably a ferromagnetic thin film of an alloy mainly composed of Co and containing at least two elements selected from Cr, Pt, Ta and Nb. By the way, the structure of this ferromagnetic thin film is such that the crystal grains are Co
And at least one element selected from Cr, Ta, and Nb is segregated and present near or at the grain boundaries. In particular, it is most preferable that the orientation of the magnetic film is such that Co (102) is preferentially oriented from the viewpoint of high density recording.

A magnetic disk device comprising such a magnetic recording medium, a magnetic disk, a magnetic head, or an electric circuit. Then, information is 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 (1) for a magnetic disk. The substrate used here is only one example, and a disk substrate of any size can be used. Even if a metal substrate such as an alloy is used, the effect of the present invention does not depend on the material and size.CoO and SiO2 are used as an inorganic compound layer (2) on the substrate (1) in a ratio of 2: 1. The mixture was used as a target to form a film having a thickness of 30 nm by a sputtering method, pure Ar was used as a discharge gas, and the pressure during sputtering was 3 m.
Torr. The input RF power is 1kW / 150mmφ. During film formation, the substrate was heated to 300 ° C. Obtained inorganic compound layer (2)
FIG. 2 shows a schematic view of the result of observing the surface of the sample by TEM.
From this figure, it was an aggregate (honeycomb structure) of 9-nm regular hexagonal crystal particles. When each layer was analyzed by μ-EDX, it was found that the crystal grains were oxides of solute cobalt and silicon oxide as a solvent was present at the crystal grain boundaries. Change the ratio of Co oxide to silicon oxide to control crystal grain size, lattice constant, and crystal grain spacing
(Corresponding to changing the composition), or titanium oxide, tantalum oxide, aluminum oxide, zinc oxide, or the like may be added to silicon oxide. Further, a Ni oxide or iron oxide may be added to the Co oxide. On this inorganic compound film (2), a Co69Cr19Pt12 film was
It was formed to a thickness of nm. The target is a Co-Cr-Pt alloy,
Pure Ar was used as the discharge gas. The pressure during sputtering is 3 mTorr. The input DC power is 1kW / 150mmφ. Finally, a C film having a thickness of 5 nm was formed 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 or a gas containing nitrogen and hydrogen may be used. This is because the particles obtained are finer, the resulting film is denser, and the protection 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 results of an X-ray diffraction analysis of the structure of the magnetic recording medium and the film comprising only the inorganic compound layer (2) are shown in FIG. First, the inorganic compound layer is 2θ = 62.5
A diffraction peak was observed around °. This is CoO (220)
It corresponds to. No other clear peaks were obtained. It is considered that the very broad peak around 2θ = 44 ° is due to the superposition of the peak due to the glass substrate and the peak due to the amorphous layer at the crystal grain boundaries. Next, the profile of the magnetic recording medium shows that Co (102) is strongly oriented as shown in FIG. This is because the inorganic compound layer
The result shows that the magnetic film was epitaxially oriented on the CoO, reflecting the result of the orientation of (220) in CoO. this
The orientation of Co is most suitable for high density recording. Here, the lattice constants of the inorganic compound layer and the magnetic film were substantially the same at 0.402 nm. The average particle diameter (circular approximation) was found to be 10 nm by observing the plane with an electron microscope, and the particle diameter distribution was determined. When the inorganic compound film does not exist, the Co (102) plane is not observed, indicating that this film greatly contributes to the control of the orientation of the magnetic film. Thus, when a magnetic film is formed on the inorganic compound layer (2),
It can be seen that the crystal grains of the magnetic film become finer and the grain size distribution becomes smaller. Next, cross-sectional observation showed 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. Further, the crystal grain boundaries of the inorganic compound layer (2)
0.5 to 1.0 nm, reflecting this, it was found that crystal grains of the magnetic recording medium fabricated thereon existed physically isolated (a conceptual diagram is shown in the lower part of FIG. 2). . As a result, an effect was seen in reducing magnetic interaction between crystal grains.

The magnetic properties of the magnetic film were measured. The obtained magnetic properties are as follows: coercive force is 3.5 kOe, Isv is 2.5 × 10 ^-16 em
u, S, which is an index of the squareness of the hysteresis in the MH loop, were 0.8 and ^S0.8 were 0.86, and had good magnetic properties. This means that the crystal grain size of the magnetic film is small,
It can be seen that this is because the variation is small. In addition, since almost no fine crystal particles are present, it is understood that the medium is excellent in heat fluctuation.

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 about 3 particles from 2 particles. When the magnetization reversal unit in the magnetic film in which the orientation of the magnetic film was controlled by the Cr film without using the inorganic compound layer (2) was measured, it was as large as about 10 to 30 particles. As described above, the magnetization reversal unit is smaller because the inorganic compound film (2) of the present invention is used.
The structure of the magnetic film changes, and magnetic crystal grains are present independently of each other. As a result, it can be seen that the magnetic interaction was reduced and the magnitude of the magnetization reversal was reduced. 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 because the distribution of the crystal grain size of the magnetic film is small, and in particular, the presence of fine particles is reduced. When the defect rate of this disk was measured, the value was 1 × 10 ⁻⁵ or less when no signal processing was performed.

Here, an example in which a thin film for controlling a crystalline lattice constant is formed on a glass substrate has been described, but a substrate is manufactured using the material on which the thin film is formed, and a magnetic film is formed thereon. It goes without saying that it may be formed. Further, in this example, an example in which chromium oxide was used as the solute substance was 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.

(Example 2) A schematic diagram of a cross-sectional structure of a manufactured magnetic disk is as shown in FIG. 1 and is similar to that of the first embodiment. First, a 2.5 ″ substrate for magnetic disks
A glass substrate having a diameter was used. The glass substrate used here is only one example, and the effect of the present invention is not affected even if a disk substrate of any size is used or an Al or Al alloy substrate is used. An inorganic compound layer (2) was formed on the substrate (1) to a thickness of 30 nm by sputtering using a mixture of CoO and ZnO at a ratio of 3: 1 as a target. Pure Ar was used as the discharge gas. The pressure during sputtering is 3 mTorr. The input DC power is 1kW / 150mmφ. During film formation, the substrate was heated to 300 ° C. Observation of the surface of the inorganic compound layer (2) by TEM revealed that it was an aggregate of crystal grains having a regular hexagonal honeycomb structure of 9 nm. Zinc oxide as a solvent substance was present so as to surround the crystal grains. Here, the lattice constant of CoO of the crystal grains was almost the same as that of the magnetic film. When the structure of the film having the honeycomb structure was analyzed by μ-EDX, it was found that the film was a crystal particle of CoO as a solute substance, and ZnO as a solvent substance was present at the grain boundary. The distance between the crystal grains was 0.5-1.0 nm. Next, the structure of the inorganic compound layer (2) was examined by an X-ray diffraction method. As a result, a sharp diffraction peak was observed around 2θ = 62.5 °. This corresponds to CoO (220). No other clear peaks were obtained.

On this film, Co69Cr19P was used as a magnetic film (3).
A t12 film was formed to a thickness of 12 nm. The target is Co-Cr-Pt
An alloy was used, and pure Ar was used as a discharge gas. The pressure during sputtering is 3 mTorr. Input DC power is 1kW / 150mm
φ. Finally, a C film having a thickness of 5 nm was formed as a protective film (4). The sputtering condition is that the input DC power density is
1 kW / 150 mmφ, 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. The quality of this film is
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 recording medium was examined by an X-ray diffraction method. According to this, a peak of Co (102) was observed overlapping with a sharp CoO (220) peak around 2θ = 62.5 °. The increase in the peak intensity around 2θ = 62.5 ° indicates that Co (102) is strongly oriented. This orientation is advantageous for realizing a high-density magnetic recording medium. From observation of the medium surface, the average particle diameter was 9n
m, which was the same as the particle size of the inorganic compound film.
When the particle size distribution of these particles was determined, the standard deviation: σ was 2
nm or less. Also, there were no minute particles having a size of a few nm. Since no fine particles were present, it was found that heat resistance fluctuation was excellent. Thus, it can be seen that the particles are fine and the particle size distribution is small. In addition, cross-sectional observation showed that the magnetic film was epitaxially grown from the inorganic compound layer.
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.

The magnetic properties of the magnetic film were measured. The obtained magnetic properties show that the coercive force is 4.0 kOe and the Isv is 2.5 × 10 ^-16 em
u and S, which are indicators of the squareness of the hysteresis in the MH loop, were 0.81 and S ^† were 0.85, indicating good magnetic properties. It can be seen that this is due to the fact that the particle size is small and the variation is small.

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 because the distribution of the crystal grain size of the magnetic film is small. When the defect rate of this disk was measured, the value was 1 × 10 ⁻⁵ or less when no signal processing was performed.

Here, an example in which a crystalline thin film is formed on a glass substrate has been described. However, it is also possible that a substrate is manufactured using a material on which the thin film is formed, and a magnetic film may be formed thereon. Needless to say. Further, in this example, an example in which cobalt oxide was used as the solute substance was described, but the same effect was obtained by using iron oxide, chromium oxide, or nickel oxide. What is important here is the orientation of the crystal phase as a solute. Further, although zinc oxide was used as the solute oxide, similar effects were obtained by using aluminum oxide, titanium oxide, tantalum oxide or silicon oxide.

[0023]

According to the present invention, the grain size and the distribution thereof are extremely small, oriented, and the crystal grain spacing is reduced.
By using a 0.5 to 1.0 nm inorganic compound layer as a base film and epitaxially growing a magnetic recording medium thereon, crystal grains of the magnetic film can be physically and independently present. Thereby, the magnetic interaction between the magnetic particles can be reduced. Thereby, the unit of magnetization reversal can be miniaturized. At the same time, the orientation of the magnetic film can be controlled. In addition, the crystal grains of the magnetic film can be made finer, the distribution of the grain size can be reduced, and since there are almost no fine grains, noise reduction when forming a disc,
It is effective in reducing thermal fluctuation and thermal demagnetization. By these,
Ultra high density magnetic recording exceeding 20GB / inch ² was realized.

[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 an X-ray diffraction profile of a magnetic recording medium.

[Explanation of symbols]

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

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Yamamoto 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Takashi Naito 7-1, Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Ken Takahashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Motoyasu Terao Higashi Koikebo, Kokubunji-shi, Tokyo 1-280, Hitachi Central Research Laboratory, Ltd. (72) Inventor Sumio Hosaka 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Pref.Hitachi Ltd. No. 88 Hitachi Maxell Co., Ltd. (72) Inventor Hiroki Kuramoto 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa F-term in Hitachi, Ltd. Production Technology Laboratory (reference) 5D006 BB01 BB02 BB07 CA01 CA05 DA03 FA09 5D112 AA02 AA03 AA05 AA24 BB05 BB06 BD02 BD03 FA04 FB04 FB06

Claims (6)

[Claims] 1. A disk substrate comprising: a crystal particle made of one kind of oxide selected from cobalt oxide, iron oxide and nickel oxide; and silicon oxide, aluminum oxide existing at a crystal grain boundary of the crystal particle. At least one selected from titanium oxide, tantalum oxide or zinc oxide
An inorganic compound film having a type of oxide is formed, a magnetic film containing magnetic particles is formed on the inorganic compound film, and the distance between the magnetic particles of the magnetic film is 0.5 nm or more and 1.0 nm or less. Characteristic magnetic recording medium. 2. The inorganic compound film has a honeycomb structure,
The spacing between crystal particles in the inorganic compound film is 0.5 nm or more 1.
2. The magnetic recording medium according to claim 1, wherein the thickness is 0 nm or less. 3. The magnetic recording medium according to claim 1, wherein the distribution of the magnetic particle size of the magnetic film is 2 nm or less in standard deviation. 4. The magnetic particle according to claim 1, wherein the magnetic particles of the magnetic film reflect the size and shape of the crystal particles of the inorganic compound film and are physically isolated. recoding media. 5. The magnetic film mainly comprises Co, Cr, Pt, Ta, N
5. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is made of an alloy containing at least two kinds of elements selected from b. 6. A magnetic disk device comprising: the magnetic recording medium according to claim 1; and a magnetic head for recording or reproducing information on or from the magnetic recording medium.