JPH04117624A - Production of magnetic recording medium and magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the nonuniformity of the magnetic characteristics within the plane of a magnetic layer by using a target essentially consisting of Fe and forming a sputtered film on a rigid substrate by a DC sputtering method in an oxidative atmosphere. CONSTITUTION:The target essentially consisting of the Fe is used and the sputtered film is formed on the rigid substrate 2 by the DC sputtering method in the oxidative atmosphere in the process for production of the magnetic recording medium 1 of a hard type having the magnetic layer 3 of a continuous thin film type essentially consisting of gamma-Fe3O4 on the rigid substrate 2. The spread of plasma decreases and the atmosphere near the substrate 2 hardly receives the influence of the plasma in the DC sputtering method. The fluctuation in the concn. of gaseous O2 near the substrate 2 is, therefore, suppressed. The nonuniformity of the magnetic characteristics in the intra-surface direction of the magnetic layer is improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention provides a method for manufacturing a so-called hard type magnetic recording medium having a continuous thin film type magnetic layer mainly composed of γ-Felon on a rigid substrate; The present invention relates to a magnetic recording medium manufactured by this method.

<Prior Art> A hard type magnetic disk in which a magnetic layer is formed on a rigid substrate and a floating magnetic head are used in magnetic disk drives used in computers and the like.

Conventionally, such magnetic disk drives have used magnetic disks with coated magnetic layers.
As the capacity of magnetic disks increases, thin-film magnetic disks have a continuous thin-film magnetic layer formed by a vapor phase deposition method such as sputtering because they are advantageous in terms of magnetic properties, recording density, etc. is now used.

Thin-film magnetic disks are produced by forming an Nf-P underlayer on a helium-based disk-shaped metal plate by plating, or by oxidizing the surface of this metal plate to form alumite. A Cr layer, a metal magnetic layer such as Co-Ni.

Furthermore, a protective lubricant film of C or the like is generally formed by sequentially depositing layers using a sputtering method.

However, a metal magnetic layer such as Co--Ni has low corrosion resistance and low hardness, causing problems in reliability. On the other hand, Japanese Patent Application Laid-Open Nos. 62-43819 and 63-17521
The magnetic thin film containing iron oxide as a main component as described in Publication No. 9 is chemically stable, so there is no fear of corrosion (and has sufficient hardness).

On the other hand, a flying type magnetic head is a magnetic head having a slider that generates buoyancy, and a composite type in which the core is integrated with the slider, or a monolithic type in which the core also serves as a slider is usually used.

Furthermore, in addition to these, so-called floating thin film magnetic heads are attracting attention because they are capable of high-density recording.
A floating thin film magnetic head has a magnetic pole layer, a gap layer, a coil layer, etc. formed on a substrate by a vapor phase deposition method or the like. In such a floating thin film magnetic head, the base body functions as a slider.

In a magnetic disk device using a floating magnetic head, the flying surface of the floating magnetic head (surface on the magnetic disk side of the slider) and the magnetic disk come into contact during contact start/stop (CSS), and the magnetic layer receives an impact.

In particular, when using a floating thin-film magnetic head, the distance between the magnetic disk and the magnetic head (flying bite) is set extremely small because high-density recording is possible.
The impact received by the magnetic layer during C8S becomes larger.

Furthermore, if the flying bite is small, an accidental contact between the magnetic disk and the flying magnetic head may occur due to vibration of the magnetic disk or impact from outside the drive device.

JP-A-62-43819, JP-A No. 63-175219
A magnetic disk having a magnetic thin film mainly composed of iron oxide as described in the above publication uses a glass substrate with a mirrored surface, and the surface roughness of the magnetic layer (Rmax
) is very small, less than 100 Å.
In such a magnetic disk, since the flying bite can be set extremely small, the damage to the magnetic layer increases during C8S or in the event of a head contact accident.

Therefore, in order to improve the C8S durability, the present inventors investigated Rwax on the glass substrate surface and Rmax on the medium surface.
Proposal to set each x within a predetermined range (Patent application No. 1-1
．． 10390), and γ-F contained in the magnetic layer.
In addition to the proposal (Japanese Patent Application No. 1-113135) that stipulated the area ratio of a predetermined peak of etch, α-Fe2 was added to the magnetic layer.
A proposal has been made to incorporate O3 (Japanese Patent Application No. 1-113136).

However, in order to achieve high-density recording, there is a tendency for flying hides to become lower and lower, and a magnetic recording medium with even higher C8S durability is desired. Furthermore, in order to perform high-density recording, it is required that the electromagnetic conversion characteristics decrease little at high frequencies, that is, the frequency characteristics of the electromagnetic conversion characteristics are required to be flat.

Therefore, the present inventors proposed a magnetic recording medium in which the specific resistance ρ of the magnetic layer is 0.03 to 3 Ω·cm as a magnetic recording medium that has high durability and has good electromagnetic conversion characteristics and frequency characteristics. (Patent application No. 1-290925)
issue).

<Problems to be Solved by the Invention> The above-described continuous thin film type magnetic layer containing Fe2O3 as a main component is formed by a direct method or an indirect method.

In the direct method, a FeJ4 film is first formed and then oxidized to form γ.
-This is a method for obtaining a Fe2O3 film. Direct methods include a direct oxidation method, a direct oxidation method, and a direct neutralization method.

Among these, in the direct oxidation method, a Fe504 film is formed by using a target containing Fe as a main component and performing reactive sputtering in an Ar gas atmosphere containing O2 gas. Since the direct oxidation method has a simple process, high productivity can be obtained.

In addition, in the indirect method, 0. In an Ar gas atmosphere containing gas, reactive sputtering is performed using a target containing Fe as the main component to form an α-Fezes film, which is reduced to a Fe50+ film, and further oxidized to form a γ-Fezes film. A Fe2O3 film is obtained.

That is, the direct oxidation method and the indirect method use reactive sputtering in an oxidizing atmosphere.

Conventionally, a high frequency sputtering method has generally been used for reactive sputtering. However, the present inventors have discovered that when high-frequency sputtering is used for reactive sputtering in such an oxidizing atmosphere, the magnetic properties tend to become non-uniform within the plane of the magnetic layer. It has been found that when the magnetic layers are formed at the same time, the in-plane magnetic properties become significantly non-uniform. If the magnetic properties are non-uniform within the plane of the magnetic layer, output fluctuations during reproduction (reproduction output modulation) will occur.

The present invention has been made under these circumstances, and γ-
The purpose of this invention is to improve the non-uniformity of magnetic properties within the plane of the magnetic layer in a magnetic recording medium having a continuous thin film type magnetic layer containing FeOOs as the main component.

<Means for Solving the Problems> Such objects are achieved by the present invention described in (1) to (11) below.

(1) A method for manufacturing a magnetic recording medium having a continuous thin film type magnetic layer containing γ-Fee's as a main component on a rigid substrate.

A method for manufacturing a magnetic recording medium, comprising the step of forming a sputtered film on the rigid substrate by DC sputtering in an oxidizing atmosphere using a target containing Fe as a main component.

(2) The method according to (1) above, wherein in the step, targets containing Fe as a main component are provided opposite to each other on both main surfaces of the rigid substrate, and sputtered films are simultaneously formed on both main surfaces of the rigid substrate. A method for manufacturing a magnetic recording medium.

(3) The sputtered film is a film whose main component is FezO4, and by oxidizing this sputtered film, γ-Fe
The method for manufacturing a magnetic recording medium according to (1) or (2) above, wherein a continuous thin film type magnetic layer containing tus as a main component is formed.

(4) The specific resistance ρ of the sputtered film is 10"4 to 10-1
Ω・Cff1, and the specific resistance ρ of the magnetic layer is 0.08.
The method for manufacturing a magnetic recording medium according to (3) above, wherein the magnetic recording medium has a resistance of ˜3 Ω·am.

(5) The above method using a glass plate as the rigid substrate (1)
) to 4). The method for manufacturing a magnetic recording medium according to any one of 4).

(6) A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to any one of (1) to 5) above.

(7) In the X-ray diffraction chart of the magnetic layer, y-Fet
The peak of the plane index (311) of Os is 35.43 to 35.
The magnetic recording medium according to (6) above, which appears at an angle of 80°.

(8) In the X-ray diffraction chart of the magnetic layer, 7-F
The peak areas of the plane index (311), plane index (400), and plane index (222) of etOs are expressed as P(311
), P(400) and P(222), O≦P(400)/P(311)≦1.00≦P(2
22) The magnetic recording medium according to (6) or (7) above, wherein /P(311)≦0.5.

(9) The above (6) wherein the magnetic layer contains α-Fe and O.
) to 8). The magnetic recording medium according to any one of 8).

(10) The magnetic recording medium according to (9) above, wherein the content of α-Fe2O3 on the side opposite to the substrate in the magnetic layer is higher than the content of α-Fe*0- on the substrate side.

(11) In the X-ray diffraction chart of the magnetic layer, α-
The peak area of the plane index (104) of FezOs is P(10
4), and the peak areas of the plane index (311), plane index (400), and plane index (222) of y-FetOs are P(311), P(400), and P(222), respectively.
When 0,02≦P(104)/P(311)≦0,
200≦P(400)/P(311)≦1.00≦P(
222)/P(311)≦0.5, the magnetic recording medium according to (9) or (10) above.

Effects> In the present invention, reactive sputtering in an oxidizing atmosphere in the above-described direct oxidation method or indirect method is performed by a DC sputtering method. Therefore, the non-uniformity of the magnetic properties in the in-plane direction of the magnetic layer is improved compared to when high frequency sputtering is used.

This is considered to be due to the following reasons.

In the sputtering method, Ar gas or the like is turned into plasma, and atoms and molecules are ejected from a target by ions derived from the plasma and attached to the substrate surface. In reactive sputtering in an oxidizing atmosphere, atoms and molecules flying from the target are oxidized before they adhere to the substrate surface.

In the DC sputtering method, the spread of plasma is smaller than in the high frequency sputtering method, and it is thought that the atmosphere near the substrate is less affected by the plasma. Therefore, fluctuations in the 02 gas concentration near the substrate are suppressed, and the oxidation degree distribution within the plane of the sputtered film becomes more uniform.

In the direct oxidation method, the Fear< film is formed by reactive sputtering.
In the indirect method, an α-Fezes film is formed by reactive sputtering, and this is further oxidized or reduced to form γ-Fe2O3.
However, in these methods, the finally obtained γ-F
The degree of oxidation of ezes depends on the degree of oxidation of Fe50< and α-Fe2O3 produced in the intermediate step. For this reason, Fe504 films formed by reactive DC sputtering and α-
The γ-Fe2O3 film obtained from the Fe*Ox film has small non-uniformity in the degree of oxidation within the plane, and as a result, uniform magnetic properties can be obtained within the plane.

Furthermore, when sputtering films are simultaneously formed on both surfaces of a substrate using the high-frequency sputtering method, sputter targets are placed facing each side of the substrate, and a high-frequency electric field is applied to each target independently. In this case, plasma corresponding to each high frequency electric field is generated on both sides of the substrate.

However, since there is usually a central hole penetrating the substrate at the center of the substrate, these electric fields interfere with each other near the substrate, making plasma discharge unstable. Therefore, the oxygen concentration near the substrate becomes unstable. Moreover, the instability of plasma discharge exhibits different aspects on both sides of the substrate, resulting in a difference in oxygen concentration on both sides of the substrate.

In reactive sputtering using the direct oxidation method or the indirect method, when the oxygen concentration near the substrate changes, the degree of oxidation of the sputtered film varies locally, resulting in non-uniform magnetic properties in the plane.

To alleviate this problem, a plug is inserted into the center hole of the board to prevent mutual interference between the electric fields on both sides of the board, but fitting the plug takes time and reduces productivity. . Furthermore, interference between the electric fields on both sides of the substrate occurs not only in the center hole of the substrate but also in the gap between the substrate and the holder or tray that holds the substrate during sputtering.

However, since the present invention uses a DC sputtering method, mutual interference of high frequency electric fields does not occur, and non-uniformity of magnetic properties caused by this can be prevented.

The magnetic layer mainly composed of γ-FeJs produced according to the present invention has extremely high durability when it has a resistivity ρ in the above range.

Such specific resistance ρ and surface index of γ-Fe2O3 (311
) has a correlation with the peak position of
The peak position of the γ-Feign plane index (311) of the magnetic layer having .

Further, there is also a correlation between the specific resistance ρ of the magnetic layer and the coercive force Hc, and the coercive force He increases as the specific resistance ρ increases.

The coercive force of the magnetic layer having a specific resistance ρ in the above range is about 6 times that of a conventional γ-Felon magnetic layer or a Co-containing -Fe2O3 magnetic layer containing Co equivalent to the conventional one. Therefore, the recording density D7°, at which the playback output decreases by 70%, is 2.5 degrees compared to the conventional one.
It is possible to improve it to about twice as much.

Therefore, the magnetic recording medium manufactured according to the present invention is capable of high-density recording, and moreover, C8
S durability is also extremely good.

In addition, in a continuous thin film type magnetic layer containing γ-Fe2O3 as a main component, the range of specific resistance ρ that has been conventionally reported is, for example, in the Journal of the Institute of Electronics and Communication Engineers 112/IVo1. J65-C
According to No. 1 p, 24-31, when the direct method described later is used, the resistivity is about 102 to 103 Ω·c11, which is extremely larger than the specific resistance ρ in the present invention. This is considered to be because the degree of oxidation of Fe2O3 in the present invention is lower than that in the conventional case.

When the magnetic layer is formed by a direct oxidation method and has a specific resistance ρ in the above range, the specific resistance ρ of Fex04 in the previous step
is usually about 10-' to 10-'Ω·cIfi. This value is based on the conventionally reported specific resistance ρ of Fe3O4 by direct oxidation method of about 3Ω・Cl11 (Transactions of Institute of Electronics and Communication Engineers '82/IVo1.J65-C: No, i
p, 24-31), which is extremely small.

Furthermore, in the present invention, in an X-ray diffraction chart of a magnetic layer obtained with an X-ray diffraction apparatus having an optical system arrangement as shown in FIG. If it is within this range, the durability will be higher.

Further, the magnetic layer is made of α-Fe, 0. In particular, when the area ratio of the predetermined peaks of α-Fetus and γ-Fe2rg in the X-ray diffraction chart of the magnetic layer is within the above range, the durability becomes even higher. improves.

These configurations significantly improve C8S durability and improve cssit durability at low temperatures.

Further, even if an accident such as contact with a magnetic head occurs, the deterioration of the magnetic layer is extremely small.

Note that conventionally, γ-FeO0. It has been thought that the presence of α-Fetus in the magnetic layer is undesirable because it lowers the magnetic properties and lowers the recording and reproducing output.

However, in magnetic recording media such as magnetic disks used in computers and the like, it is most important to ensure durability and improve reliability even if the recording/reproducing output is slightly reduced. Moreover, according to the present invention, there is almost no deterioration in magnetic properties and high durability can be obtained.

<Specific configuration> Hereinafter, a specific configuration of the present invention will be explained in detail.

A magnetic recording medium 1 of the present invention shown in FIG. 1 has a continuous thin film type magnetic layer 3 on a rigid substrate 2. The magnetic recording medium 1 shown in FIG.

The substrate 2 used in the present invention simplifies the manufacturing process since there is no need to provide an underlayer, etc., is easy to polish, and the surface roughness can be easily controlled, and is suitable for heat treatment during the formation of the magnetic layer. It is preferable to use glass because of its durability.

As the glass, it is preferable to use tempered glass, particularly surface-strengthened glass obtained by chemical strengthening. Regarding surface-strengthened glass, see JP-A-62-43819 and JP-A-62-43819.
It is described in Japanese Patent No. 3-175219.

The glass substrate preferably has a contact angle with water of at least the surface on the magnetic layer side of 20'' or less, particularly preferably 10'' or less.

By setting the contact angle with water within such a range, the adhesion of a continuous thin film type magnetic layer containing iron oxide as a main component as described later is improved. Note that there is no particular restriction on the lower limit of the contact angle, but it is usually about 2° or more.

The contact angle with water may be measured, for example, after dropping pure water on the surface of the glass substrate and 30 seconds later.

The measurement atmosphere is approximately 18 to 23°C and 40 to 60% RH.

In order to obtain such a contact angle, the glass substrate surface is polished, then subjected to the above-mentioned strengthening treatment, the glass substrate surface is polished again, washed with pure water, and then [detergent cleaning] It is preferable to perform the cleaning in the following order: pure water cleaning - organic solvent vapor drying.

The surface roughness (Rmax) of the rigid substrate is preferably 10 to
The number of participants is 100 people, preferably 40 to 80 people, and even more preferably 40 to 60 people.

By setting the RIllax of the rigid board within this range,
The durability of the magnetic recording medium is improved, and Rwax on the surface of the magnetic layer side of the medium as described later can be easily obtained.

Note that Rmax may be measured according to JIS B 0601.

Such surface roughness is described, for example, in Japanese Patent Application Laid-Open No. 62-4381.
It can be obtained by mechanochemical polishing as described in Japanese Patent No. 9 and Japanese Patent No. 63-175219.

There are no particular restrictions on the material of the glass substrate (it can be appropriately selected from glasses such as borosilicate glass, aluminosilicate glass, quartz glass, titanium silicate glass, etc., but aluminosilicate glass is particularly suitable for its high mechanical strength). It is preferable to use

Although there are no particular restrictions on the shape and dimensions of the glass substrate, it is usually disk-shaped, with a thickness of about 0.5 to 5 mm and a diameter of about 25 to 300 mfl.

A continuous thin film type magnetic layer containing γ-Fezes as a main component is formed on the rigid substrate.

The specific resistance ρ of this magnetic layer is preferably 0.08 to 3 Ω·cm. The specific resistance ρ of the magnetic layer is 0.1 to 0.9
Even more preferable results can be obtained when it is Ω·cm.

The specific resistance ρ may be measured by the usual four-point needle method or the like.

In a magnetic layer having a resistivity ρ within the above range, the peak of the plane index (311,) of γ-FexOm in an X-ray diffraction chart is usually 35.43 to 35.80', preferably 35.52 to 35. Appears on 71@.

In the present invention, when such a magnetic layer is subjected to X-ray diffraction, X! In the line diffraction chart, y-Fe2O3
The surface index (311), the surface index (400) and the surface index (
222) are expressed as P(3111, P(
400) and P(222), 0≦P(400)/PC311)≦1.00≦P(22
2)/P(311)≦0.5, and 0≦P(400)/P(311)≦0.60≦P(2
22)/P(311)≦0.3.

When the magnetic layer has such a peak area ratio,
Durability is further improved.

To explain in more detail, an increase in P(222) means that the (222) plane and (1,1
1) It shows that the proportion of faces that exist increases. Ni Fe2O3 has a spinel structure, and in the spinel structure, the (111) plane is the most slippery plane.

Therefore, if the peak area of the (222) plane parallel to the (111) plane is large, that is, P(222)/P(311)
If the value of is large, it is considered that the knee Fe2O3 constituting the magnetic layer is likely to slip due to sliding with the magnetic head, resulting in decreased durability.

When P(222)/P(311) exceeds the above range, durability is critically reduced.

The (100) plane that exists parallel to the (400) plane is (11
1) Since it is thought that slippage is likely to occur next to the surface, P(
If 400)/P(311) exceeds the above range, durability will be critically reduced.

In the present invention, it is preferable that the magnetic layer contains α-Fe2O3. When the magnetic layer contains α-Fe2O3, durability is improved.

In the X-ray diffraction chart of the magnetic layer, α-Fe
The peak area of the plane index (104) of 2O3 is P (104)
When, 0.02≦P(104)/P(311)≦0.200
≦P(400)/P(311)≦1,00≦P (22
2)/P C311)≦0.5, preferably 0.05≦P(104)/P(311)≦0.150
≦P(400)/P(311)≦0.60≦P(22
2)/P(311)≦0.3 is more preferable.

When the magnetic layer has such a peak area ratio,
Durability is further improved.

To explain in more detail, P(104)/P(311)
is less than the above range, the durability improvement effect is relatively low (,
When the above range is exceeded, the recording and reproducing output decreases.

X II! It is preferable that the diffraction chart is created, for example, as follows.

FIG. 2 shows an example of an X-ray diffraction apparatus.

In FIG. 2, the X-rays irradiated from the X-ray source 101 are
Magnetic recording medium 10 via divergence slit DS
It enters the magnetic layer of No. 2 and is diffracted, scattering into the scatter slit S.
After passing through S and receiving slit RSI, it is reflected by a monochromator MM to become monochromatic light, and then enters a counter tube 103 via a receiving slit RS2, where the X-ray intensity is counted. Usually, a rate meter or the like is used. recorded.

Note that during measurement, the magnetic recording medium 102 has a scanning speed dθ
/dt, the members constituting the optical path below the scatter slit SS are rotated at a scanning speed of 2dθ/dt.

For each peak in the obtained X 1@ diffraction chart, a portion excluding the background is integrated to calculate the above-mentioned area ratio.

In addition, in the optical arrangement shown in FIG. 2 using CuKα as the X-ray source, the plane index of α-Fe2O3 (1,0
4) peak appears around 33.3°,
The peaks of plane index (400) and plane index (222) of 3 appear around 435° and 37.3°, respectively. The peak of the plane index (311) of γ-Fe2O3 appears in the range described above. The peak position is determined as the centroid position of the peak after background removal.

Although α-Fe2O3 may be contained uniformly in the magnetic layer, it is preferable that the content is higher on the surface side of the magnetic layer, that is, on the side opposite to the substrate.

By containing α-Fe2rs in this way, it is possible to further strengthen the surface part of the magnetic layer, which is easily damaged by the sliding of the magnetic head, and it is possible to further strengthen the surface part of the magnetic layer, which is easily damaged by the sliding of the magnetic head. The content of α-Fe2rs can be kept low.

In this case, α-Fe2rs may gradually increase toward the surface of the magnetic layer, or may not exist on the substrate side but only on the surface side.

It is preferable to analyze the content of α-Fe2O3 near the surface of the magnetic layer, for example, as follows.

FIG. 3 shows an example of a low incidence angle X-ray diffraction device.

In FIG. 3, the X-rays irradiated from the X-ray source 101 are
The light passes through the solar slit Sl, enters the magnetic layer of the magnetic recording medium 102 at an angle β with the surface thereof, and is diffracted.

After passing through the solar slit S2, the diffracted X-rays are reflected by a monochromator MM to become monochromatic light,
Furthermore, the X-rays enter the counter tube 103 through the receiving slit R8, and the X-ray intensity is counted.

In this low-incident-angle X-ray diffraction apparatus, unlike the apparatus shown in FIG. /dt.

In this device, by changing the angle β between the incident X-ray and the magnetic layer surface, a-
The distribution of Fe2O3 can be determined. Specifically, in order to analyze a portion close to the surface, it is sufficient to reduce β, and as β becomes larger, analysis results deeper into the magnetic layer can be obtained.

In the present invention, in such low incident angle X-ray diffraction, β
It is preferable that P(104)/P(311) becomes larger as P(104)/P(311) becomes smaller. For example, P(104)/P(311) measured when β=0.5° is changed to P (104)/P (1 of 3111)
It is preferably 5 to 10 times, particularly 1.5 to 5 times.

Note that the average crystal grain size of γ-Fetus constituting the magnetic layer is usually about 100 to 800, particularly about 200 to 500.

The average crystal grain size can be determined by observing the surface using a scanning electron microscope (SEM).

Next, a method for forming the magnetic layer will be explained.

In the present invention, a continuous thin film type magnetic layer containing γ-Fezes as a main component is formed on a rigid substrate. The step of forming this magnetic layer includes the step of forming a sputtered film by DC sputtering in an oxidizing atmosphere using a target containing Fe as a main component.

In the present invention, a direct oxidation method or an indirect method is used to form a continuous thin film type magnetic layer containing γ-Fe2O3 as a main component.

In the direct oxidation method, a Fe504 film is formed by reactive sputtering using a target containing Fe as the main component in an Ar gas atmosphere containing 0□ gas, and this is oxidized to form a γ-Fe2O3 film. .

In addition, in the indirect method, an α-Fezes film is formed by reactive sputtering in an Ar gas atmosphere containing 2O3 gas using Targera, whose main component is Fe, and this is reduced to form an Fe5O4 film. Further oxidation is performed to obtain a γ-Feign film.

Among these, it is preferable to use the direct oxidation method because the process is simple and high productivity can be obtained, and the above-mentioned peak area ratio can be easily obtained.

In the direct oxidation method, O is used as a reaction gas in an Ar gas atmosphere.
, gas is added to perform sputtering, but in the present invention, a DC sputtering method is used at this time.

There are no particular restrictions on the conditions for DC sputtering, but in order to obtain the above-mentioned peak ratio of γ-Fe2O3 in X-ray diffraction, it is necessary to Let the partial pressure of the gas be POl, Ar gas and 0.
When the total pressure with gas is P (Ar+0*), 0
□Gas concentration PO1/P (Ar+Oz) is 40-90%
It is preferable that Further, P (Ar+Oz) is preferably 0.8X10-' to 10, OX 10-'Pa. And the total flow rate of Ar gas and 0□ gas is 15-80 SCCM, especially 20-50 SCCM
It is preferable that

Note that the specific resistance ρ can be changed by changing the total flow rate of the gas, but it is also possible to change the specific resistance ρ by appropriately selecting the heat treatment conditions for oxidizing to γ-Fe2O3.

There is no particular restriction on the sputtering power, and it may be determined as appropriate.

For details on FejO4 thin film formation by direct method, see Journal of the Institute of Electronics and Communication Engineers '80/9 Vol. J63-CNa 9 p.
, 609-616, and in the present invention, it is preferable to form the magnetic layer according to this method. However, in this case, it is essential to use the DC sputtering method, and the gas flow rate as described above is It is preferable to perform sputtering at a gas pressure of , and a gas concentration of 0.03.

The Fe504 film formed by sputtering is γ-Fez
Oxidized to Os.

This oxidation occurs at a partial pressure of 02 gas of about 0.05 to 0.8 atm.
The heat treatment may be carried out in an atmosphere with a total pressure of about 0.5 to 2 atmospheres, and it is usually preferable to carry out the heat treatment in the atmosphere.

The holding temperature during heat treatment is 200 to 400°C, especially 25°C.
The temperature is preferably 0 to 350°C, and the temperature holding time is
The time period is preferably 10 minutes to 10 hours, particularly 1 hour to 5 hours.

In the present invention, during this heat treatment, the temperature increase rate is set to 0.5 to b It is preferable that

By setting the temperature to such a rate, α-Feign
The peak area ratio as described above can be easily obtained.

Note that the temperature increase rate may be constant, gradually increased or decreased, or a plurality of temperature increase rates may be combined to increase the temperature to the holding temperature.

The magnetic layer formed in this way has a coercive force of 400 to 3, although it varies depending on the amount of CO added and the value of specific resistance ρ.
Magnetic properties of 000 0e, residual magnetization 1700 to 3000G, and squareness ratio of about 0.55 to 0.85 are obtained, and α
- Even when Fezes is contained, there is almost no deterioration in magnetic properties.

Co, Ti, Cu, etc. may be added to the magnetic layer as necessary, and Ar, etc. contained in the film forming atmosphere may be contained.

Co is useful for controlling coercivity. The content of Co is preferably such that it replaces 10 wt% or less of Fe. Furthermore, when the magnetic layer contains CO, an Fe target containing Go may be used.

The layer thickness of the magnetic layer is set at 20 mm in consideration of productivity, magnetic properties, etc.
The number of participants is preferably about 0 to 2,000.

Preferably, a lubricating film 4 is provided on such a magnetic layer.

The lubricating film 4 preferably contains an organic compound, and particularly preferably contains an organic compound having a polar group, a hydrophilic group, or a hydrophilic portion.

The organic compound used is not particularly limited, and may be liquid or solid (e.g., fluorine-based organic compounds, such as European Patent Publication No. 0165650 and its corresponding Japanese application, JP-A-61-4727). Perfluoropolyethers such as those described in European Patent Publication No. 0165649 and its corresponding Japanese application, JP-A-61-155345, or various known fatty acids,
An appropriate one may be selected from various esters, various alcohols, etc.

There is no particular restriction on the method for forming the lubricating film, and a coating method or the like may be used.

The thickness of the lubricating film varies depending on the film forming method and the compound used, but is preferably about 4 to 300.

When the thickness is 4 Å or more, durability is improved, and when it is 300 Å or less, adsorption and crashes of the magnetic head are reduced. In addition,
A more preferable thickness is 4 to 100 people, and an even more preferable thickness is 4 to 80 people.

The magnetic recording medium of the present invention having the magnetic layer as described above is
If the surface roughness (Rmax) on the magnetic layer side is 50 to 200, the durability is further improved. In this case, Rll1a
A more preferable range of x is 80 to 150 people, an even more preferable range is 80 to 120 people, and an especially preferable range is 90 to 120 people.
There are 120 people.

If Rwax on the magnetic layer side is within the above range, not only the durability will be improved, but also recording and reproducing can be performed while keeping the distance between the medium surface and the floating surface of the floating magnetic head at 0.1 μm or less. Furthermore, there is no adhesion between the floating magnetic head and the magnetic recording medium, making high-density recording possible.

In addition, in order to obtain such Rmax on the magnetic layer side,
From Fe504 described above to γ-Fe, 0. When oxidizing to , the heat treatment temperature and time may be controlled.

The magnetic recording medium of the present invention is effective when recording and reproducing is performed using a known composite type floating magnetic head, monolithic type flying magnetic head, etc., but is particularly effective when used with a thin film type flying magnetic head. Extremely effective when used in combination.

FIG. 4 shows an example of a thin film floating type magnetic head.

The floating magnetic head 10 shown in FIG. 4 has an insulating layer 31, a lower magnetic pole layer 4, a gap layer 50, an insulating layer 33, a coil layer 60, an insulating layer 35, an upper magnetic pole layer 45 on a base 20.
and a protective layer 70 in this order. Further, at least the front surface, ie, the floating surface, of such a floating magnetic head IO may be provided with a lubricating film similar to the above, if necessary.

Note that the Rtax of the front surface is 200 Å or less, especially 5
It is preferable that it is 0-150 people. This more Rm
C
The 8S durability improvement effect is further improved.

There are no restrictions on the material, winding pattern, winding density, etc. of the coil layer 60, and known materials may be selected and used as appropriate.

The base body 20 may be made of a known material such as Mn-Zn ferrite, but when used for the magnetic recording medium of the present invention, the base body 20 has a Vickers hardness of 1000 kgf.
/mm1 or more, especially 1000 to 3000 kgf/mm
It is preferable that the C8S is made of a ceramic material of approximately 100%.

Vickers hardness 1000 kgf/ma! As the two or more ceramic materials, ceramics containing AlxOsTiC as a main component, ceramics containing ZrOt as a main component, ceramics containing SiC as a main component, or ceramics containing AβN as a main component are suitable. These also contain Mg, Y, Zr0z,
TiC2 etc. may be contained.

Particularly preferred among these are AQ*Ox-T
Ceramics containing iC as a main component, ceramics containing SiC as a main component, or ceramics containing AAN as a main component are the most suitable among these, and the most suitable one is based on the relationship with the hardness of the thin film magnetic layer containing iron oxide as a main component. Since it is optimal, it is a ceramic whose main component is 8ρ*Om-TiC.

As the material for the lower and upper magnetic pole layers 41, 45, any conventionally known material can be used, such as permalloy.

The magnetic poles are usually provided as a lower magnetic pole layer 41 and an upper magnetic pole layer 45 as shown, and a gap layer 50 is formed between the lower magnetic pole layer 41 and the upper magnetic pole layer 45.

The gap layer 50 may be made of a known material such as AI2*Os or SiOx.

The patterns, film thicknesses, etc. of the pole layers 41, 45 and the gap layer 50 may be any known ones.

Furthermore, in the illustrated example, the coil layer 60 is of a so-called spiral type, and the upper and lower magnetic pole layers 41 are arranged in a spiral shape.
．． 45, and an insulating layer 33.35 is provided between the coil layer 60 and the upper and lower magnetic pole layers 41.45.

Further, an insulating layer 31 is provided between the lower magnetic pole layer 41 and the base body 20.

Any conventionally known material can be used for the insulating layer; for example, when a thin film is formed by sputtering, SiO□, glass, Al2zOs, etc. can be used.

Further, a protective layer 70 is provided on the upper magnetic pole 45 . As the material for the protective layer, any conventionally known material can be used; for example, A.degree. C. to 8, etc. can be used. Further, various resin coat layers or the like may be laminated thereon.

Such a floating magnetic head is used in combination with a conventionally known assembly such as an arm.

To perform recording and reproducing using the magnetic recording medium of the present invention, particularly a magnetic disk, recording and reproducing are performed while rotating the disk and making the magnetic head fly.

Disk rotation speed is about 2000 to 6000 rpm,
In particular, it is set to 2000 to 4000 rpI11.

In addition, the floating height is 0.2 μ or less, especially 0.15 or less, and even 0.1- or less, for example, 0.01 to 0.09 IjJ.
In this case, good flying characteristics and C
8S durability can be obtained.

The flying height is adjusted by changing the slider width and the load on the magnetic head.

<Example> Hereinafter, the present invention will be specifically explained with reference to Examples.

<Preparation of magnetic disk samples> The magnetic disk samples shown in Table 1 below were prepared by the method shown below.

An aluminosilicate glass substrate with an outer diameter of 130 mm, an inner diameter of 40 mm, and a thickness of 1.27 mm was polished and further subjected to chemical strengthening treatment. The chemical strengthening treatment was performed by immersing it in molten potassium nitrate at 450°C for 10 hours.

Next, the surface of the glass substrate was smoothed by mechanochemical polishing. A polishing liquid containing colloidal silica was used for mechanochemical polishing.

Surface roughness of glass substrate used for each sample (Rmax)
There were 50 people.

Note that Rff1ax was measured using a stylus type surface roughness meter.

After cleaning the glass substrate, a magnetic layer was formed on its surface in the following manner.

First, preliminary sputtering is performed in an Ar gas atmosphere.
．． The oxide film on the surface of the 0wt% Co--Fe alloy target was removed. Then 0. A gas was introduced and reactive sputtering was performed to form a Fe5O4 film.

Reactive sputtering was performed by DC magnetron sputtering or high frequency magnetron sputtering.

The conditions for DC magnetron sputtering are: Ar gas flow rate: 15 SCCM O gas flow rate: 20 SCCM P(Ar+Ox): 1.5X10-'Pa, and the conditions for high frequency magnetron sputtering are: Ar gas flow rate: 1.4 SCCM 02 Gas flow rate: 19 SCCM P (Ar+Oz): 8. Qx 10-”P
It was set as a.

The specific resistance ρ of the Fe5Oa film is 0.02 to 0.03Ω'
It was cm.

After forming the FeJ4 film, it was oxidized by heat treatment in the atmosphere under the following conditions to obtain a γ-Fe2O3 magnetic layer.

(Heat treatment conditions) Temperature increase rate: 2℃/win Processing temperature: 270-330℃ Processing time: 3hr The thickness of the magnetic layer was 1000.

For the magnetic layer of each sample obtained in this way,
Linear diffraction was performed and an X-ray diffraction chart was created. Note that X-ray diffraction was performed using the apparatus shown in FIG.

As a result of X-ray diffraction chart analysis, the y-Fe2 of each sample
The peak position of the plane index (311) of O3 is sample No.
1 to 4, it was 35.47 to 35.78°, and sample N005 was 35.86°.

Also, P(104)/P(311)=0, 08~0.12
, P(400)/P(311)=0, 40~0.50
, P(222)/P(311)=0 to 0.05.

Further, the magnetic layer of each sample was analyzed using a low-incidence-angle X-ray diffractometer shown in Fig.
．． As a result of performing X-ray diffraction at 0'', P(104)/P(311) at β=o, 5° is approximately 2.0 to P(1041/P(311) at β=2.0'') It was confirmed that the α-Fezes content was 3.5 times higher on the surface side of the magnetic layer.

In addition, the average crystal grain size of the magnetic layer of each sample was 100~
There were 800 people.

Furthermore, the following measurements were performed for each sample.

(specific resistance ρ) It was measured by the four-point needle method. The measurement conditions are shown below.

Probe material: titanium carbide Needle spacing = IIIlffl Needle tip radius: 40pmR Needle pressure: 100g/piece Note that the specific resistance is an index indicating the degree of oxidation of the magnetic layer.

The specific resistance is 30 mm, 40 mm, 50 mm and 6
0 mm respectively, angles 0 @ 90° 180° and 27
A total of 16 points were measured at the 0° position, and the average value and distribution width (maximum value - minimum value) were calculated and shown in Table 1. The smaller the distribution width, the better the uniformity in the in-plane direction of the film.

(Modulation of reproduction output) A lubricant film was formed on the magnetic layer of each sample, and the modulation of reproduction output was measured at a flying height of 0.1 μm using the thin film magnetic head described below.

The lubricating film was formed using a 0.1 wt % solution of a compound having a molecular weight of 200 degrees expressed by the following formula to a thickness of 20 mm by a spin code method. The contact angle of the surface of this lubricating film with water (30 seconds after dropping water) was 100°.

(Formula) %Formula% Note that Rwax on the magnetic layer side of each sample is 80 to 150
It was a person.

The configuration of the magnetic head used is as follows.

Flight! air! = Futakami Vickers hardness 2200 kgf/mm”Aj!0n
- After forming a thin film magnetic head element on a TiC substrate, it was processed into a magnetic head shape and attached to a support spring (gimbal) to produce an air bearing type floating magnetic head.

The Rwax of this magnetic head floating surface was 130 people.

The flying height was adjusted to 0.1 by adjusting the slider width and gimbal load.
I made it become a door.

(Coercive force) Measured using a vibrating sample magnetometer (VSM). The maximum applied magnetic field was 5 koe.

(Reproduction output and values.) Reproduction output and values of a sample in which the above-mentioned lubricant film was formed on the magnetic layer. I asked for

The playback output is 21kPCI (kilo flux cha
The following evaluations were made using the recording and playback output using NGGE per Inch).

0: Practically preferable output ○: Practical output ×: Practically problematic output. is the recording density when the reproduction output decreases to 70% of the reproduction output at low recording density, kF (:
Represented by I.

The measurement was performed using the thin film magnetic head described above at a flying height of 0.1-.

The results of these measurements are shown in Table 1.

From the results shown in Table 1, the effects of the present invention are clear.

In other words, in samples using DC sputtering, the distribution width of p is narrower than in samples using high-frequency sputtering.
Playback output modulation is small.

Furthermore, a sliding durability test was conducted on the samples shown in Table 1 at 25° C. and 50% relative humidity.

The magnetic head used was manufactured using the same method as the magnetic head described above, but the slider width was 150 μm so that the magnetic disk and magnetic head were always in sliding contact.
, the gimbal load was 25 g.

This magnetic head was pressed against the magnetic disk sample, and the magnetic disk was rotated such that the relative speed between the magnetic disk and the magnetic head was 20 m/s. At this time, the fact that the magnetic head is constantly sliding without floating means that the AE
(Acoustic Emission) Confirmed by sensor.

Note that this sliding durability test is a more severe durability test method than the C8S durability test.

As a result, it was confirmed that Samples Nos. 1 to 4 had excellent durability, with no scratches occurring for more than 2 hours.

<Effects of the Invention> According to the present invention, the reproduction output modulation of a continuous thin film magnetic layer containing γ-Fe-Ox as a main component can be made extremely small.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing a preferred embodiment of the magnetic recording medium of the present invention. FIG. 2 is a schematic diagram of the X-ray diffraction apparatus. FIG. 3 is a schematic diagram of a low incidence angle X-ray diffraction device. FIG. 4 is a partial cross-sectional view of the magnetic head. Explanation of symbols l...Magnetic recording medium 2...Substrate 3...Magnetic layer 4...Lubricating film 101...X-ray source 102...Magnetic recording medium 103...Counter DS...・Divergence slit SS...Scatter slit R3, RSI, R52...Receiving slit MM...Monochromator SL, S2...Solar slit 10...Floating type magnetic head Applicant TDC-K Co., Ltd. Company Representative Patent Attorney Yo Ishii - Patent Attorney Increase 1) Tatsuya FIG, 1 FrG, 4

Claims (1)

[Claims] (1) A method for manufacturing a magnetic recording medium having a continuous thin film type magnetic layer containing γ-Fe_2O_3 as a main component on a rigid substrate, using a target containing Fe as a main component, A method for manufacturing a magnetic recording medium, comprising the step of forming a sputtered film on the rigid substrate by DC sputtering in an oxidizing atmosphere. (2) The magnetic field according to claim 1, wherein in the step, targets containing Fe as a main component are provided opposite to both main surfaces of the rigid substrate, and sputtered films are simultaneously formed on both main surfaces of the rigid substrate. A method for manufacturing a recording medium. (3) The sputtered film is a film whose main component is Fe_3O_4, and by oxidizing this sputtered film, γ-
3. The method for manufacturing a magnetic recording medium according to claim 1, wherein a continuous thin film type magnetic layer containing Fe_2O_3 as a main component is formed. (4) The specific resistance ρ of the sputtered film is 10^-^4 to 10
＾-＾1Ω・cm, and the specific resistance ρ of the magnetic layer is 0.
4. The method for manufacturing a magnetic recording medium according to claim 3, wherein the magnetic recording medium has a resistance of 0.8 to 3 Ω·cm. (5) The method for manufacturing a magnetic recording medium according to any one of claims 1 to 4, wherein a glass plate is used as the rigid substrate. (6) A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to any one of claims 1 to 5. (7) The magnetic recording medium according to claim 6, wherein the peak of the plane index (311) of γ-Fe_2O_3 appears at 35.43 to 35.80° in the X-ray diffraction chart of the magnetic layer. (8) In the X-ray diffraction chart of the magnetic layer, γ-F
The peak areas of the plane index (311), plane index (400), and plane index (222) of e_2O_3 are expressed as P(3
11), P(400) and P(222), a claim where: 0≦P(400)/P(311)≦1.0 0≦P(222)/P(311)≦0.5 8. The magnetic recording medium according to 6 or 7. (9) The magnetic recording medium according to any one of claims 6 to 8, wherein the magnetic layer contains α-Fe_2O_3. (10) The magnetic recording medium according to claim 9, wherein the content of α-Fe_2O_3 on the side opposite to the substrate in the magnetic layer is higher than the content of α-Fe_2O_3 on the substrate side. (11) In the X-ray diffraction chart of the magnetic layer, α-
The peak area of the plane index (104) of Fe_2O_3 is defined as P(
104) and the plane index of γ-Fe_2O_3 (311)
, P(311), P(400) and P(
222), then 0.02≦P(104)/P(311)≦0.200≦
The magnetic recording medium according to claim 9 or 10, wherein P(400)/P(311)≦1.0 0≦P(222)/P(311)≦0.5.