JP2001351226A - Magnetic recording medium, method for producing the same and magnetic recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium, which ensures low noise, low thermal fluctuations and low thermal demagnetization by making the grains of a magnetic film fine and suppressing the dispersion of the size and to provide a magnetic recorder, which attains ultrahigh density recording at exceeding 20 Gb/in2. SOLUTION: In the magnetic recording medium obtained by forming a first under film comprising a chromium-base nonmagnetic material, a second under film contains inorganic compounds, a cobalt-base magnetic film and a protective film in this order on a substrate, the second under film forms an underlayer containing a first oxide, comprising an oxide containing at least one element selected from nickel, cobalt and magnesium as the principal component or an antiferromagnetic Cr-base alloy and a second oxide comprising an oxide containing at least one element selected from silicon, aluminum, titanium, tantalum and zinc as the principal component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and a magnetic storage device capable of recording large-capacity information, and more particularly to a magnetic recording medium suitable for high-density magnetic recording and a small and large-capacity magnetic recording medium using the same. The present invention relates to a magnetic storage device.

[0002]

2. Description of the Related Art At present, demands for increasing the capacity of magnetic storage devices are increasing more and more. In response to this demand, in recent years, a composite head using a magnetoresistive head having high sensitivity for reproduction by separating the recording and reproduction heads has been rapidly advancing. In order to improve the sensitivity of a magnetoresistive head using the fact that the electric resistance of the head element changes with the change in the magnetic flux leakage from the medium, a magnetic layer of a type in which multiple magnetic films are stacked via a non-magnetic film is used. Higher sensitivity heads utilizing an extremely large magnetoresistance change (giant magnetoresistance effect or spin valve effect) generated in the film have also been put to practical use. This is because the relative magnetization directions of the plurality of magnetic films via the non-magnetic film change due to the leakage magnetic field from the medium,
It utilizes the fact that the magnetic resistance changes.

On the other hand, factors necessary for increasing the density of the magnetic recording medium include (1) compatibility between flattening the surface due to the low flying height of the magnetic head and avoiding the head sticking phenomenon when the magnetic head is stopped, and (2) It is mentioned that a change in reproduction output with time due to noise and thermal fluctuation is reduced, and (3) stable magnetic characteristics with a large process margin are realized.

In order to achieve both flattening of the surface due to the low flying height of the magnetic head and avoidance of the head sticking phenomenon at the time of stopping the magnetic head, the head is retracted to the outside of the disk when the rotation of the disk is stopped. An apparatus equipped with a mechanism for preventing sticking is disclosed in JP-A-11-11093.
No. 3 proposes this. This mechanism is called a load / unload mechanism, and by adopting this mechanism, it is possible to achieve both low flying height of the magnetic head and prevention of adhesion. However, when this mechanism is adopted, when the magnetic head slider is placed (loaded) on the magnetic disk, or when it is separated from the magnetic disk (unloaded), the magnetic disk rotating at high speed and the magnetic head slider come into contact with each other. Therefore, it is necessary to design reliability considering this.

Also, as described in Japanese Patent Application Laid-Open No. 6-267053, a contact start / stop (CS
S) In a magnetic recording medium having a Co alloy magnetic thin film on a substrate as a magnetic recording medium having excellent characteristics, a metal having a thickness between 5 nm and 500 nm between the substrate and the magnetic film;
There is disclosed a magnetic recording medium in which a semi-metallic or semiconductor oxide thin film is formed, and a part of the oxide is reduced. Here, for example, A
It has been proposed to use oxides of l, Zn, Co, Ni and Mg. 20Gb / inch2 for magnetic disk media
In order to realize a recording density exceeding the above, in addition to increasing the coercive force, it is necessary to reduce the unit in which the magnetization reversal of the magnetic film occurs. For that purpose, it is necessary to reduce the size of the magnetic grains constituting the magnetic film. Further, it has become important from the viewpoint of thermal fluctuation to make the size distribution of the magnetic grains fine and to make the size distribution uniform at the same time.

[0006] As a method for controlling the size of the magnetic grains in the magnetic film and the distribution of the size, Japanese Patent Publication No. 4-16884 discloses a method.
No. 8 (Japanese Unexamined Patent Publication No. 62-257618, US Pat.
It has also been proposed to provide a base film of a magnetic film as described in Japanese Patent No. 652499). Also, JP-A-11-9653
No. 4, as described in Japanese Patent Application Laid-Open No. 4 (1999) -2002, a first underlayer made of a nonmagnetic material whose main component is chromium, a body-centered cubic antiferromagnetic material having a Neel temperature of at least 60 ° C., Further, when the crystal lattice of the material is compared with the crystal lattice of the body-centered cubic structure of the first underlayer, the former (10)
One side of the lattice of the (0) plane is substantially equal to the length of the diagonal line of the lattice of the (100) plane, and therefore, the second underlayer that can be epitaxially grown on the first underlayer, and its main layer. There has been proposed a magnetic recording medium characterized by sequentially providing a recording film made of a magnetic material whose component is cobalt.

Further, Digests of Intermag 99
(Digests of INTERMAG 99, 1999 IEEE INTERNATIONAL
MAGNETICS CONFERENCE DIGESTS OF TECHNICAL PAPERS,
(IEEECatalog Number: 99CH36359, ISBN: 0-7803-5555-5)
Announcement number DR-01 indicates that a Cr
Forming a Mn alloy film, then a CoCrPt alloy magnetic film,
Further, a laminated film on which a CrMn protective film is formed is shown.
After forming a CrMn alloy film on a NiAl underlayer, CoC
When the rPt alloy magnetic film was formed, the crystal grain size of the CoCrPt alloy film was about 16 nm. This average crystal grain size is determined by forming CoCrPt after forming a Cr film on a NiAl base film.
It is smaller than 21 nm when an alloy magnetic film is formed. However, the coercive force of the magnetic film largely depends on the subsequent heat treatment, and the dispersion of the crystal grain size of the magnetic film is NiAl.
CrM formed between underlayer and CoCrPt alloy magnetic film
It is considered that the thickness largely depends on the thickness of the n-alloy film and the subsequent heat treatment.

[0008]

In the above prior art, there is a limit to the control of the crystal grain size distribution of the magnetic film constituting the magnetic disk medium, and fine and coarse crystal grains coexist in the magnetic film. Was. In such a magnetic film, when information is recorded, the magnetic film is affected by the leakage magnetic field from the surrounding magnetic grains, or conversely, the large magnetic crystal grains interact with each other, so that the high density exceeding 20 Gb / inch2 is obtained. When performing recording, there were cases where stable signal reproduction could not be performed.

Accordingly, a first object of the present invention is to provide a high-performance magnetic recording medium with small noise by reducing the magnetic particle size in a magnetic film.

A second object of the present invention is to provide a magnetic recording medium having low thermal fluctuation and low thermal demagnetization by controlling the distribution of magnetic particle diameters to be small.

A third object of the present invention is to provide a magnetic recording medium suitable for high-density recording by controlling the crystal orientation of a magnetic film.

Further, a fourth object of the present invention is to provide a method for manufacturing such a magnetic recording medium.

[0013] A fifth object of the present invention is to provide a 20 Gb / inc.
An object of the present invention is to provide a large-capacity magnetic recording device capable of high-density recording exceeding h2.

[0014]

SUMMARY OF THE INVENTION A first object of the present invention is to:
A substrate, a first base film formed on the substrate and made of a nonmagnetic material whose main component is chromium, and Cr containing at least one element selected from Mn, Re, Ru, and Rh as an additive element In a magnetic recording medium in which a second base film made of a base alloy and an inorganic compound, a magnetic film mainly containing cobalt is formed thereon, and a protective film is formed in this order, the second base film Can be realized by using an oxide containing at least one element selected from silicon, aluminum, titanium, tantalum and zinc as a main component. Alternatively, as the second base film, a first oxide made of an oxide containing at least one element selected from nickel, cobalt, and magnesium as a main component and silicon, aluminum, titanium, tantalum, and zinc are selected. The first object can also be achieved by forming a film containing a second oxide composed of an oxide containing at least one element as a main component.

Here, it is preferable to further form a protective film containing carbon as a main component on the magnetic film in order to improve the sliding resistance.

Further, in the second undercoating film containing the polycrystalline inorganic compound, an oxide containing at least one element selected from silicon, aluminum, titanium, tantalum and zinc as a main component is provided. By forming a magnetic recording medium in which the concentration of the substance is high at the crystal grain boundary of the second underlayer, the crystal grain size and crystal orientation of the magnetic layer can be controlled simultaneously.

The average particle diameter <d> of the crystal constituting the magnetic film is
7 nm or more, more preferably 10 nm or more and 15 nm or less, and the ratio σ / <of the standard deviation σ of the crystal grain size to the average grain size <d>.
A film in which d> 0.28 or less can be realized by a laminated base film in which the crystal grain size and the crystal orientation are controlled simultaneously. Here, the average particle diameter <d> of the crystal constituting the magnetic film was calculated by the following method. That is, a sample for transmission electron microscope observation was prepared by the method described later in Example 1. 200
Observe more than one crystal grain, find the area of each crystal grain,
The diameter d of the circle that is equal to this was determined as the diameter of the crystal grain. Then, the arithmetic average value <d> of the values of d of all the observed crystal grains was defined as the average crystal grain size. The square of the standard deviation σ of the crystal grain size was calculated by taking the sum of the squares of the difference between each crystal grain size used in calculating the average grain size <d> and the average grain size <d>.

The coercive force measured by applying a magnetic field in the direction of travel of the magnetic head relative to the magnetic recording medium is 240 k
If it is not less than A / m and not more than 350 kA / m, a magnetic recording medium suitable for high-density magnetic recording can be provided. Where the coercivity is
A maximum magnetic field of 1,040 kA / m was applied at 25 ° C., and measurement was performed with a sample vibration type magnetometer. By using the second underlayer as described above, it is possible to reduce the noise and reduce the temporal change of the reproduction output due to the thermal fluctuation, thereby achieving the second object of the present invention.

When a magnetic film is formed on the second underlayer of such a magnetic recording medium, an inorganic compound film composed of an oxide containing at least one element selected from nickel, cobalt and magnesium as a main component is used. Since it is also possible to epitaxially grow a magnetic film having a close-packed hexagonal filling (hcp) structure on the crystal grains of the present invention, the third object of the present invention can be achieved.

An oxide containing at least one element selected from silicon, aluminum, titanium, tantalum, and zinc as a main component is predominantly precipitated at the crystal grain boundary of the second underlayer. The magnetic film grows epitaxially on crystal grains in the second underlayer, and epitaxial growth of the magnetic film may be hindered at grain boundaries in the second underlayer. As described above, since the growth mode of the magnetic film is different between the crystal grains of the second base film and the crystal grain boundaries, the crystal orientation and structure of the magnetic film formed thereon can be controlled. The size of the crystal grains in the second base film can be easily controlled by changing the composition of the inorganic compound added to the target.

In order to form such a second underlayer,
It is also possible to use a target having a Neel temperature of at least 80 ° C. or higher and a mixture of an antiferromagnetic material having a NaCl type structure or a body-centered cubic (bcc) structure and a nonmagnetic oxide and sintered. Neel temperature is at least 80 ° C., and as an antiferromagnetic material having a NaCl type structure or a body-centered cubic structure, (1) an oxide containing at least one element selected from nickel and cobalt or (2) Cr
It is preferable to use an alloy in which at least one element selected from Mn, Re, Ru, and Rh is added as an additional element.

An antiferromagnetic material having a Neel temperature exceeding 80 ° C. can be formed only by adding a small amount of an element selected from Mn, Re, Ru, and Rh to Cr. That is, 5 for Cr
When Mn is added alone up to about 0 at.%, The Neel point is about 800K. Therefore, when Mn is added to Cr, the addition concentration is 0.4 at.% Or more and 50 at.%.
The following is preferred. When Re is added alone to Cr, if 0.5 at.% Or more is added, an antiferromagnetic material having a Neel temperature exceeding 80 ° C. (353 K) can be formed.
However, over 18 at.
Alone, the Neel temperature drops below 80 ° C. (353 K). When Re is added alone to Cr,
It is preferable that the addition amount be 0.5 at.% Or more and 18 at.% Or less. When adding Ru alone to Cr,
When 0.2 at.% Or more is added, the Neel temperature becomes 80 ° C. (35%).
An antiferromagnetic material exceeding 3K) can be formed. When Ru alone is added in excess of 14 at.% With respect to Cr, the Neel temperature becomes 80 ° C. (353 K) or less. Therefore, when Ru is solely added to Cr, the addition amount is preferably 0.5 at.% Or more and 14 at.% Or less. When Rh alone is added to Cr, an antiferromagnetic material having a Neel temperature exceeding 80 ° C. (353 K) can be formed if 0.2 at.% Or more is added. The change in Neel temperature for these additional elements is described in Physical Review 1 by WC Koehler et al.
51, 1966, p. 405 [Phys. Rev. 151 (1966) 40
5-413.], Y. Hamaguchi and N. Kunitomi, Journal of the Physical Society of Japan, 1964, 1964, p. 1849 [J. Phys. Soc. J
apan 19 (1964) 1849-1856.].

When such a target in which an antiferromagnetic material and a nonmagnetic material are mixed is used, a base film made of an inorganic compound in which an antiferromagnetic material and a nonmagnetic material are mixed can be formed without simultaneous sputtering of two or more sources. Can be formed. If the non-magnetic material is hardly dissolved in the polycrystalline anti-ferromagnetic material, the non-magnetic material precipitates at the crystal grain boundary of the anti-ferromagnetic material. If the non-magnetic substance is added beyond the solid solubility limit of the anti-ferromagnetic substance, the non-magnetic substance which is not dissolved in the anti-ferromagnetic substance precipitates at the grain boundary of the poly-crystalline anti-ferromagnetic substance. Here, as the nonmagnetic material, an oxide containing at least one element M selected from silicon, aluminum, titanium, tantalum and zinc as a main component is selected. When these nonmagnetic materials are added to an antiferromagnetic material made of a Cr-based alloy, the concentration of M in the crystal grain boundary of the antiferromagnetic material is smaller than the concentration of M contained in the crystal of the antiferromagnetic material made of the Cr-based alloy. It was found that the concentration of M was increased.

Nickel, as a main component of the second underlayer,
It is also possible to use, as a mother phase, crystal grains mainly composed of a first oxide containing at least one element selected from cobalt and magnesium. If this mother phase is made of polycrystal and the second phase containing M can be precipitated at the grain boundary in the film plane, the mother phase that causes concentration fluctuation is not limited to antiferromagnetic. If such a concentration fluctuation occurs in the film plane, the second
The crystal grain size of the underlayer can be easily controlled. It has been found that if the thickness of the magnetic film is not too thick compared to the second underlayer, the crystal grains of the magnetic film can be controlled by reflecting the crystal grain size of the second underlayer.

When a magnetic recording medium using such an inorganic compound as a base film is incorporated in a magnetic storage device and operated, the maximum temperature during operation of the actual machine is close to 70 ° C. In order to obtain the effect of reducing the temporal change of the reproduction output even at such a high temperature, it is necessary to mix an antiferromagnetic material having a Neel temperature of at least 80 ° C. or more into the target. The difference between the nail temperature of the material used as the target raw material and the maximum temperature during operation of the actual machine is as follows. When a base film in which antiferromagnetism and nonmagnetism are mixed is formed, the Neel temperature of the antiferromagnetic material included in the base film is not necessarily equal to the Neel temperature of the antiferromagnetic material of the target raw material. This is presumably because the element which forms the non-magnetic oxide is slightly contained in the portion which becomes the antiferromagnetic material. The fourth object of the present invention can also be achieved by forming a thin film using such a sputter target.

The substrate has a diameter of 65 mm and a thickness of 0.635 m.
m aluminosilicate substrate was used. The substrate may be soda glass or the like, and it is desirable that the surface of the substrate has been chemically strengthened to enhance reliability. Other than the glass substrate,
A rigid substrate such as a silicon substrate is also used. The outer diameter of the board is also 65
It is not limited to mm. After cleaning such a substrate, the substrate was evacuated to form a first underlayer containing Cr as a main component, heated, and the second underlayer was formed by high-frequency sputtering.

As an additive element, an alloy containing at least one element selected from Mn, Re, and Ru added to Cr and an alloy containing at least one element selected from silicon, aluminum, titanium, tantalum, and zinc. When sputtering a target to which a substance is added, the second underlayer can be formed by a DC magnetron sputtering method. In order to form the second base film with a short tact, a plurality of sputtering chambers may be provided. After the formation of the second base film, it is necessary to control the substrate temperature. Therefore, the substrate was heated again after the formation of the second base film. Heating is not necessarily required before the formation of the second base film, but it is preferable to perform heating in order to enhance adhesion. Thereafter, a magnetic film and a protective film were formed and taken out into the atmosphere.

The magnetic film is preferably a ferromagnetic thin film made of an alloy mainly containing Co and containing Pt. For example, a Co-Cr-Pt-Ta alloy, a Co-Cr-Pt alloy, a Co-Pt-SiO2 alloy, a Co-Pt-O alloy,
An o-Cr-Pt-Ge-B alloy may be used. Cr, which lowers the residual magnetic flux density and promotes magnetic separation, may not always be added.

A magnetic film formed on the substrate, wherein the average grain size <d> of the crystal grains constituting the magnetic film is 7 nm
Above, more preferably 10 nm or more and 15 nm or less, the ratio σ / <d> of the standard deviation σ of the crystal grain size of the magnetic film to the average particle size <d> of the magnetic film is 0.28 or less, and the coercive force measured at 25 ° C. Is 24
It is also preferable that it is 0 kA / m or more and 350 kA / m or less in order to reduce thermal fluctuation. As the thickness of the magnetic film decreases, the influence of thermal fluctuation increases. For example, C containing Cr
When the thickness of the magnetic film made of the o-Pt alloy is 20 nm, the average crystal grain is 10 nm, and the standard deviation of the average crystal grain size is 3 nm, that is, σ / <d> = 0. It has been estimated that the residual magnetization of the medium thus obtained is reduced by about 40% when left at room temperature for 5 years. The average crystal grain of the magnetic film is 12n
If m, the standard deviation of the average crystal grain size is 3 nm, that is, σ / <
When d> = 0.25, the residual magnetization can be reduced by about 10%.

By optimizing the formation conditions and composition of the second underlayer and controlling the crystal grain size of the second underlayer, the crystal grains in the second underlayer are refined. The particle size dispersion can be reduced to about 2 nm, and the crystal grains of the oxide are two-dimensionally arranged, so that the crystal grains of the magnetic film formed thereon are also miniaturized. As a result, the particle size distribution of the magnetic film becomes small, and the ratio of the standard deviation σ of the particle size to the average particle size <d> of the magnetic film can be controlled to 0.28 or less. Therefore, noise, thermal fluctuation and thermal demagnetization caused by the magnetic recording medium can be reduced. In this manner, the crystal grain size of the second underlayer and the magnetic film grown heteroepitaxially can be controlled,
The second object of the present invention is achieved. Further, when the second underlayer is partially composed of an antiferromagnetic material, the frequency of magnetization reversal due to thermal fluctuations is reduced, and a signal recorded for a long time can be stably held. preferable.

A magnetic recording medium formed by the above method, a driving unit for driving the magnetic recording medium, a magnetic head comprising a recording unit and a reproducing unit, and means for moving the magnetic head relative to the magnetic recording medium And a mechanism for ramping the head, a signal input means to the magnetic head, and a recording / reproducing signal processing means for reproducing an output signal from the magnetic head. The reproducing unit includes a plurality of conductive magnetic films that generate a large resistance change when their magnetization directions change relative to each other due to an external magnetic field, and a conductive nonmagnetic film disposed between the conductive magnetic films. If the magnetic recording medium is constituted by a resistance sensor and uses the above-described magnetic recording medium, higher reliability can be obtained by adopting the load / unload mechanism, and the fifth aspect of the present invention
Can be achieved.

In the magneto-resistance effect type magnetic head, the magneto-resistance sensor portion may be formed between two shield layers made of a soft magnetic material separated from each other by a distance of not less than 0.06 μm and not more than 0.12 μm. desirable. If the distance between the shield layers is larger than 0.12 μm, sufficient reproduction output cannot be obtained in the maximum linear recording density region exceeding 500 kFCI. If the distance between the shield layers is smaller than 0.06 μm, it is not easy to maintain the insulation between the shield layers and the magnetoresistive sensor. The product Br × t of the thickness t of the magnetic film of the magnetic recording medium and the residual magnetic flux density Br measured by applying a magnetic field in the direction of travel of the magnetic head relative to the magnetic recording medium during recording is 2.4 mA. (30G
μm) or more and 6.4 mA (80 G · μm) or less. If Br × t is smaller than 2.4 mA (30 G · μm), the danger of reproducing incorrect information increases due to a decrease in the reproduction output due to long-term storage after recording, and 6.4 mA (80 G · μm). ), It becomes difficult to overwrite during recording.

In the magnetic storage device described above, a plurality of conductive magnetic films that cause a large change in resistance due to a relative change in their magnetization directions due to an external magnetic field as a reproducing portion of the magnetic head; With a magnetoresistive sensor that includes a conductive non-magnetic film disposed between the films, 40
It is preferable because a signal recorded at the highest linear recording density exceeding 0 kFCI can be reproduced stably. Further, it is desirable to form the magnetic head on a magnetic head slider having a flying surface rail area of 1.4 mm 2 or less and a mass of 2 mg or less. As a result, the probability of collision between the magnetic head and the projections described above can be reduced, and at the same time, the impact in the event of a collision can be reduced.
High recording density of 20 Gb / inch2 or more and high impact reliability can both be achieved.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described in detail with reference to the drawings.

Example 1 FIG. 1 is a sectional structural view of an embodiment of a magnetic recording medium according to the present invention. As the substrate 11, an aluminosilicate glass substrate having a thickness of 0.635 mm and a diameter of 2.5 inches whose surface was chemically strengthened was used. After cleaning this substrate, place it on it.
The following multilayer film was formed in 9 seconds using a single-wafer sputtering apparatus (MDP250B). FIG. 2 shows a chamber configuration of this sputtering apparatus.

First, a 15 nm-thick first base film 12 containing Cr as a main component was formed on both surfaces of a substrate 11 in a first base film forming chamber 22. Further, after that, the heating chamber 2
After the temperature of the substrate was heated to about 230 ° C. by a lamp heater in Step 3, nickel oxide (NiO) and silicon oxide (SiO 2) were mixed in a molar ratio of 7: 3 in the second base film forming chambers 24 and 25. The sintered target was subjected to high frequency sputtering to form a second base film 13 having a thickness of 16 nm. On top of this, a 16 nm thick Co-22 at.
Forming a magnetic film 15 made of a -14 at.% Pt alloy,
On top of this, the two protective film forming chambers 29 and 29 ′ have a thickness of 3 n.
A protective film 18 having a total thickness of 6 nm was formed for each m. afterwards,
The substrate was taken out of the sputtering apparatus, and a lubricant mainly composed of perfluoroalkyl polyether was applied on the protective film to form a 2 nm-thick lubricating film 19.

As shown in Table 1, the first underlayer 12
Ar was used as a discharge gas for forming the second underlayer 13 and the magnetic film 15 all at a gas pressure of 0.93 Pa (7 mT
orr). Further, when forming the protective film 18 made of carbon, Ar containing nitrogen was used as a discharge gas, and the gas pressure was 1.33 Pa (10 mTorr).

[0038]

[Table 1]

The magnetic recording medium thus formed is cut, and the laminated thin film portion is formed into a mortar-shaped thin film vertically from the direction perpendicular to the film surface by an ion thinning method. Observed under a microscope. The area of each crystal grain was determined, and the diameter d of a circle equivalent to this area was determined as the diameter of the crystal grain. Then, the arithmetic average value <d> of the values of d of all the observed crystal grains was defined as the average crystal grain size. The average grain size <d> of the obtained magnetic film is 13.2 nm, and the standard deviation σ of the grain size of the magnetic film and the average grain size of the magnetic film are as follows.
The ratio σ / <d> of <d> was 0.27.

The magnetic characteristics of the obtained magnetic disk medium were evaluated using a sample vibration magnetometer. For evaluation, a disc piece cut into an 8 mm square was used. Magnetic field application up to 1,140k
A / m, and a magnetic field was applied in the relative running direction of the magnetic head during recording on the recording medium. Here, both surfaces of the medium were scraped off from the surface to a thickness of about 1 μm, and the magnetization curve of the sample from which the thin films formed on both surfaces of the substrate were removed was measured in advance with a sample vibration magnetometer, and the influence of the substrate was subtracted. As a result, the coercive force was 262 kA / m, the coercive force squareness ratio was 0.75, and the product Br × t of the thickness t of the magnetic film and the residual magnetic flux density Br was 4 mA.
(50 Gm).

As the substrate 11, besides chemically strengthened aluminosilicate, soda lime glass, silicon,
Ceramics made of borosilicate glass, glass-glazed ceramics, or Ni-P
-Electroless plated Al-Mg alloy substrate or Ni-
A rigid substrate made of glass or the like in which P is electrolessly plated can be used. Samples in which the first underlayer 12 and the second underlayer 13 were formed on the substrate, and no magnetic film and subsequent layers were formed were also manufactured. This sample was subjected to ion thinning in a mortar shape from the substrate side to obtain an observation sample of a transmission electron microscope.
Point analysis was performed on constituent elements in the grains of the second underlayer and grain boundaries using an energy dispersive X-ray fluorescence spectrometer at an acceleration voltage of 200 kV. As a result, the concentration of Ni was higher in the grains of the second underlayer than at the grain boundaries. Further, since the selected area diffraction image was a broken ring, which was a collection of discrete diffraction spots, it was confirmed that the second underlayer was a polycrystalline thin film composed of many crystal grains.

The second underlayer 13 is made of silicon oxide (SiO 2).
In addition to 2), an oxide of at least one element selected from Ti, Al, Ta, and Zn or an oxide containing a plurality of these elements may be simultaneously contained.

As the second underlayer 13, the following (1) to
Example 1 except that the target composition of (6) was used.
Was produced. (1) NiO and TiO
2 in a molar ratio of 7: 3, (2) NiO and Ta2O5 in a molar ratio of 7: 3, (3) NiO and ZnO in a molar ratio of 9: 1,
(4) CoO and SiO2 in a molar ratio of 7: 3, (5) MgO and SiO2 in a molar ratio of 7: 3, (6) CoO, NiO and S
iO2 in a molar ratio of 2: 2: 1. The coercive force H of these media
c, Table 2 shows the average crystal grain size <d> of the magnetic film and the ratio σ / <d> of the standard deviation σ of the magnetic film grain size to the average crystal grain size <d> of the magnetic film. The evaluation of the coercive force Hc of the medium is based on a disc piece cut into an 8 mm square. The magnetic field was applied at a maximum of 1,140 kA / m, and a magnetic field was applied at 25 ° C. in the relative running direction of the magnetic head during recording on the recording medium.

[0044]

[Table 2]

The second underlayer 13 is used as an underlayer for controlling the crystal orientation of a magnetic film formed thereon and controlling the magnetization reversal due to thermal fluctuation of the magnetic film. At the same time the second
May be antiferromagnetic. As a result, the average grain size of the crystals constituting the magnetic film is reduced to 15 n, which is suitable for reducing noise.
m, and at the same time, the direction of the axis of easy magnetization is controlled in a direction parallel to the film surface suitable for in-plane magnetic recording, and the retention of recorded signals after a long period of time is guaranteed. We were able to.

The magnetic film is made of not only a Co—Cr—Pt alloy but also Co as a main component.
Cr, T to contain t and to further reduce medium noise
A multi-element alloy system to which a, SiO2, aluminum oxide, Nb, or the like is added can be used. Especially Ta, Nb,
The addition of V, Ti, Ge, and P is preferable because the melting point of the target is lowered, and the composition separation of the magnetic film containing Cr is facilitated. However, excessive addition of Cr lowers the residual magnetic flux density of the magnetic film, so that Cr that promotes magnetic separation need not always be added. In a Co-based alloy system to which Pt, Ni, Ge or Mn is added, the decrease in magnetic anisotropy energy is small compared to other added elements, and it is practical. Specifically, Co-Cr-
In addition to Pt, Co-Cr-Pt-Ge-B, Co-Cr
-Pt-Ta, Co-Cr-Pt-SiO2, Co-C
r-Pt-Al2O3, Co-Cr-Pt-Mn, Co
-Cr-Nb-Pt, Co-Cr-V-Pt, Co-C
r-Ti-Pt, Co-Cr-Nb-Ta-Pt, Co
Alloys such as -Pt-Ni-SiO2 and Co-Pt-O can be used. Providing a protective film containing carbon as a main component on the magnetic film is preferable in improving the sliding resistance.

Embodiment 2 In the configuration of the magnetic recording medium described in Embodiment 1, the constituent material of the second underlayer 13 is as follows.
A magnetic recording medium formed using a target obtained by mixing magnesium oxide (MgO) and silicon oxide (SiO2) at a molar ratio of 7: 3 and sintering the same was prototyped.

The magnetic properties of the obtained magnetic disk were evaluated using a sample vibration magnetometer, and the coercive force was 258 kA.
/ m, coercive force squareness ratio is 0.73, and product Br × t of magnetic film thickness t and residual magnetic flux density Br is 4.1 mA (51.5 G · μ).
m), which is almost the same as the magnetostatic characteristics of the magnetic recording medium formed by using a target obtained by mixing nickel oxide (NiO) and silicon oxide (SiO 2) at a molar ratio of 7: 3 and sintering in Example 1. was gotten.

A head having a shield gap length of 0.11 μm and a write gap length of 0.2 μm was mechanically levitated from the magnetic recording medium by 18 nm, and these mediums were air-conditioned in air at 65 nm.
Using a spin stand controlled at a temperature of ° C., the change over time in the output of the reproduced wave after recording was measured. As a result, nickel oxide (N
In a magnetic recording medium formed using a target obtained by mixing and sintering iO) and silicon oxide (SiO2) at a molar ratio of 7: 3, the output of the reproduced wave recorded at 207.5 kFCI after 96 hours has decreased by 3 hours. %, Whereas in the magnetic recording medium described in the second embodiment, after 96 hours,
Degradation of output of reproduced wave recorded at 7.5kFCI is about 5%
As a result of measuring the byte error rate of these magnetic disks, no decrease in performance was observed even after 96 hours.

Example 3 FIG. 3 is a sectional structural view of an embodiment of a magnetic recording medium according to the present invention, and FIG. 4 is a chamber configuration of a sputtering apparatus.

The thickness of the first magnetic film 15 is set to 10 nm,
On top of this, Co-37 at.
An intermediate film 16 made of an alloy is formed, and a Co-21 at.
A magnetic recording medium was formed in the same manner as in Example 1, except that a second magnetic film 17 made of a 12 at.% Pt-3 at.% Ta alloy was formed. Table 3 shows the relationship between FIG. 4 and FIG.

[0052]

[Table 3]

The thickness of the intermediate film 16 is set to 0.4, 0.8, 1.
When the above medium is formed by changing to 2, 2, 3, 4 nm,
The thickness t of the magnetic film of the magnetic recording medium and the residual magnetic flux density Br measured with a sample vibration type magnetometer by applying a magnetic field of 1,040 kA / m in the relative running direction of the magnetic head to the magnetic recording medium during recording. The product Br × t is 4.8 mA (60 G ·
μm) and the coercive force squareness ratio is also 0.73 to 0.75.
The value was almost constant between the two. However, the coercive force measured by the sample vibrating magnetometer while applying a magnetic field of 1,040 kA / m in the relative running direction of the magnetic head with respect to the magnetic recording medium at the time of recording, as shown in FIG. Decreased with increasing thickness.

The medium noise Nd of the magnetic recording medium thus formed was measured using a head having a shield gap length of 0.11 μm and a write gap length of 0.2 μm. 13-nm mechanically levitated from magnetic recording medium and 5 to 436 kF
The band corresponding to CI was integrated and Nd was measured. When the thickness of the intermediate film is less than 1.2 nm, the effect of improving S / Nd is not remarkable. When the intermediate film was formed to a thickness of 2 nm, S / Nd was improved by 1.1 dB. When the thickness was further increased to 3 nm, the S / Nd was further improved. However, the reproduction signal intensity ratio Re of 20 kFCI with respect to the reproduction output of the signal recorded at 207.5 kFCI.
MF decreased with increasing interlayer thickness. When no intermediate film was formed, ReMF was 51%. On the other hand, when the intermediate film was formed to a thickness of 4 nm, ReMF was reduced to about 45%, and ReMF decreased as the intermediate film thickness increased. From these results,
In the configuration of the present embodiment, it is preferable that the thickness of the intermediate film be 2 nm to 3 nm in combination of (ReMF, S / Nd).

Instead of the Co-37% Cr alloy described in the third embodiment, the same oxide-based intermediate film as the second underlayer can be used as a material for forming the intermediate film 16.
In this case, as the thickness of the intermediate film increases, a coercive force Hc measured by a sample vibration type magnetometer by applying a magnetic field of 1,040 kA / m in a relative running direction of the magnetic head with respect to the magnetic recording medium during recording, The product Br × t with the residual magnetic flux density Br,
Both the squareness ratio S and the coercive force squareness ratio S * decreased.

As an oxide-based intermediate film, nickel oxide
When a target obtained by mixing (NiO) and silicon oxide (SiO 2) at a molar ratio of 7: 3 and sintering is subjected to high frequency sputtering to form the second underlayer 13, the intermediate layer of ReMF has a thickness of 0.3 mm. When the thickness was 4 to 0.8 nm, ReMF was the largest, and when the 0.8 nm intermediate film was formed, the S / Nd was the largest. Then, when the intermediate film is formed to have a thickness of 1.2 nm, the S / Nd when the intermediate film is formed to have a thickness of 0.4 nm is improved. When the same oxide-based intermediate film as the second underlayer is used, By using an intermediate film having a thickness of 0.4 to 1.2 nm, favorable characteristics in terms of electromagnetic conversion were obtained.

Other intermediate films include Cr or Cr-Ti, Cr-Mo, Cr-Ti-M containing Cr as a main component.
o, Cr-V, Cr-W alloy, Co-Ru, Co-Cr
-A Ru alloy or Ru can also be used.

Embodiment 4 FIG. 6 is a sectional structural view of an embodiment of the magnetic recording medium of the present invention. FIG. 7 shows a chamber configuration of a sputtering apparatus used for forming a medium.

First, a first underlayer 12 made of Cr and having a thickness of 15 nm was formed on both surfaces of the substrate 11 in a first underlayer formation chamber 22 on the substrate 11. Thereafter, nickel oxide (NiO) and silicon oxide are used in the two second base film forming chambers 24 and 25.
A target obtained by mixing (SiO2) at a molar ratio of 7: 3 and sintering was subjected to high-frequency sputtering to form a second underlayer 13 having a total thickness of 16 nm. Here, after forming a second base film having a thickness of 8 nm in the second base film formation chamber 24, the temperature of the substrate is heated to about 230 ° C. by a lamp heater in the heating chamber 23,
Thereafter, a second base film having a thickness of 8 nm was formed in the second base film forming chamber 25. A third underlayer 14 made of a Cr-20 at.% W alloy having a thickness of 10 nm is formed thereon in a third underlayer formation chamber 32, and then a magnetic film and a protective film are formed in the same manner as in the first embodiment. Then, a magnetic recording medium was obtained. Table 4 shows the relationship between FIG. 6 and FIG.

[0060]

[Table 4]

The magnetic recording medium thus formed is
mm, and a magnetic field of 1,040 kA / is applied in the direction of travel of the magnetic head relative to the magnetic recording medium during recording.
m was applied, and the magnetic properties were measured at 25 ° C. using a sample vibration magnetometer. Product Br × of coercive force Hc and residual magnetic flux density Br ×
t, squareness ratio S, coercive force squareness ratio S * are each 271 k
A / m, 3.6 mA, 0.71 and 0.74.

The crystal structure of the third underlayer 14 has a body-centered cubic structure, and is preferably a nonmagnetic metal. For example,
A thin film such as a non-magnetic Cr-based alloy that forms a (100) -oriented solid solution, which is expected to have good crystal matching with the magnetic film, is used. Here, the (100) orientation refers to the (100) orientation of the crystal.
The plane is oriented parallel to the substrate plane. As a material of the third underlayer, a Cr-Ti alloy or a Cr-Ti
-Mo alloy, Cr-Mo alloy, etc., Cr-W alloy, C
An r-Ni alloy or the like can be used. The thickness of the third underlayer is preferably 4 nm or more and 50 nm or less. When the thickness is less than 4 nm, it is difficult to control the crystallinity and crystal orientation of the magnetic film formed thereon, and when the thickness is more than 50 nm, the efficiency of mass production is reduced, which is preferable. Absent. The third underlayer is made of Cr-Ti
In the case of an alloy, the Ti concentration is 18 at. % To 2
3 at. % Is preferable. The third C
The concentration of Ti added to the r-Ti alloy underlayer is 18 at. %, The crystal consistency with the magnetic film formed thereon is reduced. On the other hand, when the Ti addition concentration is 23 at. %, The crystal grains of the underlayer become large, and the crystal grains of the magnetic film formed continuously on this underlayer also become large, which undesirably increases the medium noise.

The third underlayer 14 is made of Ru, a Co alloy containing Ru, a Co—Cr alloy, a Co—Cr—R
A u-alloy may be used. However, no matter which material is used, if the film thickness is too large, the crystal grains become coarse, and the crystal grains of the magnetic film formed on these third underlayers are formed. Also increases. From the viewpoint of particle size control, the thickness of the third underlayer is 5
0 nm or less is preferable, and 4 nm or more is preferable from a viewpoint of film thickness control. By forming the third base film, the second
It is desirable to select a material that improves the crystal matching with the underlying film and at the same time improves the adhesion.

Comparative Example 1 A magnetic recording medium having the cross-sectional structure shown in FIG. 8 was manufactured using a sputtering apparatus having the structure shown in FIG.

In the medium of this comparative example, the first underlayer 12 is not formed on both sides of the substrate in the first underlayer formation chamber 22 on the substrate 11, and the second underlayer 12 is formed on the substrate 11. The magnetic recording medium was formed in the same manner as in Example 4 except that the magnetic recording medium was formed directly.

As a result of performing a dust injection test on the magnetic recording medium thus formed, the magnetic recording medium of Example 4 was compared with the magnetic recording medium of Comparative Example 1 in which the first underlayer 12 was not formed.
In the magnetic recording medium on which the first underlayer 12 was formed, the number of seeks until a crash was increased by a factor of three or more, resulting in excellent sliding resistance.

Example 5 Instead of the target obtained by mixing nickel oxide (NiO) and silicon oxide (SiO 2) at a molar ratio of 7: 3 and sintering them as shown in Example 1, the targets shown in Table 5 were used. Was used to form a magnetic recording medium.

[0068]

[Table 5]

When a nickel oxide (NiO) target to which silicon oxide (SiO 2) is not added is subjected to high frequency sputtering,
As shown in Comparative Example 2 of Table 5, the average particle size <d> of the magnetic film was 13.5 nm, and the ratio σ / <d> of the standard deviation σ to the average particle size <d> of the magnetic film was about 0.306. Met.

Silicon oxide to nickel oxide (NiO)
The concentration of (SiO2) added is 20 mol.% (Example 5-1)
By increasing the coercive force to 40 mol.% (Example 5-2), the coercive force was reduced from 271 kA / m to 241 kA / m, and the average particle size <
d> also decreased from 13.2 nm to 12.6 nm. On the other hand, as the concentration of silicon oxide (SiO 2) increased, the decrease in output measured by the same method as in Example 2 was reduced to 5% to 3%.

Silicon oxide (Si) used as the second underlayer
Even when the molar ratio of O2) was changed, the dependence of the residual magnetic flux density, the coercive force squareness, and the squareness ratio on the silicon oxide (SiO2) mole ratio was small.

As shown in Table 5, (NiO-30 mol.
% SiO 2) (Example 5-3) or 10 mol.% CoO (Example 5-4), and even when the material of the second underlayer is changed, 240 kA is added.
A magnetic recording medium having a coercive force exceeding / m was obtained.

As shown in Comparative Example 2 in Table 5, the output reduction of the medium using nickel oxide (NiO) as the second underlayer was 10%. On the other hand, the output decrease measured with the medium of the above example was as small as 3 to 5%.

Example 6 Nickel oxide (NiO) and silicon oxide (SiO 2) shown in Example 1 were mixed at a molar ratio of 7: 3 and sintered instead of (1) nickel oxidation Product, aluminum oxide (Al2O3) and silicon oxide mixed at a molar ratio of 7: 1: 2 and sintered and mixed.
l.% Al2 O3 -20 mol.% A target having a composition of SiO2 (Example 6-1), (2) a nickel oxide, an aluminum oxide, and a titanium oxide in a molar ratio of 7: 1:
10 mol.% Al2O3-
20 mol.% TiO2 target (Example 6-2), (3) Ni sintered by mixing nickel oxide, titanium oxide and zinc oxide at a molar ratio of 7: 2: 1.
A magnetic recording medium was formed in the same manner as in Example 1, except that a target having a composition of O-10 mol.% ZnO-20 mol.% TiO2 (Example 6-3) was used. Table 6 shows the magnetic properties when these second underlayers are used.

[0075]

[Table 6]

Even if the material of the above-mentioned oxide underlayer is changed, when the thickness of the second underlayer is 16 nm, a magnetic field is generated in the direction of travel of the magnetic head relative to the magnetic recording medium during recording. The value of the coercive force Hc measured by a sample vibration magnetometer by applying 1,040 kA / m exceeds 240 kA / m, and the coercive force squareness ratio S * is in the range of 0.7 to 0.75;
The value of the product Br × t with the residual magnetic flux density Br is also 3.8 mA to 4.
2 mA.

[0094] The measurement was performed in the same manner as in Example 2
Nd and output decrease were 25.3 as shown in Table 6, respectively.
dB to 26.2 dB, 2% to 6%.

Example 7 Three types of magnetic recordings having the same structure as the magnetic recording medium described in Example 1 except that the thicknesses of the magnetic films are different, and the thicknesses of the magnetic films are 16 nm, 20 nm, and 24 nm A medium was produced in the same manner as in Example 1.

As a result of performing the CSS sliding resistance test 50,000 times, the magnetic recording medium and the magnetic head are destroyed in any of the magnetic recording media having the thickness of the magnetic film of 16 nm, 20 nm and 24 nm. No good sliding reliability was obtained.

By reducing the thickness of the magnetic film, the product Br × t of the thickness t of the magnetic film and the residual magnetic flux density Br is greatly reduced. As shown in Table 7, the in-plane coercive force Hc was approximately 262 k
A / m-273 kA / m, coercive force squareness ratio S * is 0.69-
At 0.75, a magnetic recording medium having a substantially constant value of about 0.72 could be formed. These magnetic properties were measured at 25 ° C. using a sample vibration magnetometer at a maximum applied magnetic field of 1040 kA / m.

[0081]

[Table 7]

The electromagnetic conversion characteristics of these magnetic recording media were the same as those of the spin valve type reproducing element described in Example 8 in which the shield gap length Gs was 0.11 μm, and the gap length was 0.1 μm.
The measurement was performed using a magnetic head composed of a 2 μm electromagnetic induction type writing element. The sense current of the read element was 3 mA, and the write current Iw was 34 mA. Isolated reproduction wave half width PW
50 was measured with a digital oscilloscope (Tektronix TDS544A). The PW50 was smaller as the magnetic film was thinner. The magnetic film thickness is 16 nm and the flying height of the head is 2
In the case of 2 nm, a small value of 170 nm was obtained.
When the flying height of the head is 9 nm, PW50 is 13
Shortened to 5 nm.

The output at the maximum linear recording density of 415 kFCI measured by the spectrum analyzer was 2 to 5% of the output of the isolated reproduction wave at 20 kFCI measured by the digital oscilloscope. The output at the maximum linear recording density of 415 kFCI measured by the spectrum analyzer was obtained by integrating the odd-order waveform output until it exceeded 100 MHz. Further, 0-p output of isolated reproduction wave (Siso)
The ratio Siso / Nd of integrated medium noise (Nd) when signals of 415 kFCI and 415 kFCI were recorded was evaluated. Here, the flying height of the head was 22 nm, and Nd was 5 kFCI to 436.
A value obtained by integrating noise in a band corresponding to kFCI was used.
In each medium, a high Siso / Nd of 24.7 dB or more was obtained at a high recording density of 415 kFCI.

The head having the shield gap length of 0.11 μm and the write gap length of 0.2 μm described in Example 2 was mechanically levitated from the magnetic recording medium by 18 nm, and the head was controlled at 65 ° C. with a spin stand of 207.5 kFCI. The change over time in the reproduction output of a signal recorded at a density of was measured.
As a result, as shown in Table 7, in the magnetic recording medium described in Example 1, the output reduction after 96 hours from the reproduction output after 1 second from the recording was about 3%. The thickness of the magnetic film is from 16 nm (Example 1) to 24 nm (Example 7-2)
As the power increased, the decrease in power decreased from 3% to 2%.

Example 8 In Example 1, the targets used for forming the second underlayer in the second underlayer formation chambers 24 and 25 were Cr-25 at.% Mn alloy and silicon oxide (S
iO2) was mixed at a molar ratio of 7: 3 to obtain a sintered target. Further, the thickness of the second underlayer was set to 10 nm and 20 n.
A magnetic recording medium was formed in the same manner as in Example 1 except that m and 30 nm were used.

The time-dependent change in the reproduction output of the magnetic recording medium thus manufactured was measured in the same manner as in Example 2. As a result, in the magnetic recording medium described in Example 1, the output reduction after 96 hours had elapsed was about 3% based on the reproduction output after one second had elapsed from recording. In the present example, when the second underlayer was 5 nm, an output decrease of about 5% was observed, and when the second underlayer was 10 nm thick, about 4% of output decrease was observed. Was done. On the other hand, the second underlayer is
The output decrease when the thickness was 0 nm or 30 nm was 3% or less. The crystal grain size of these magnetic films was evaluated in the same manner as in Example 1. 5 nm, 10 nm,
FIG. 9 shows the average crystal grain size of the magnetic film formed in each case of 20 nm and 30 nm. By increasing the thickness of the second base film, the average crystal grain size of the magnetic film is 8.4 to 12 nm.
It became big. By increasing the thickness of the second base film,
Ratio σ / <d> of standard deviation σ of these media and average particle size <d>
Decreased from 0.30 to 0.27.

Comparative Example 3 In Example 1, the target used for forming the second base film in the second base film forming chambers 24 and 25 was Cr-25a to which silicon oxide (SiO 2) was not added.
A magnetic recording medium was manufactured in the same manner as in Example 1, except that the target of the t.% Mn alloy was used and the thickness of the second underlayer was set to 20 nm. The average particle size <d> of the obtained magnetic film was 14.5 nm, and the ratio σ / <d> of the standard deviation σ to the average particle size <d> of the magnetic film was 0.31. This value of σ / <d> was larger than that of Example 8 in which the second underlayer was formed to 20 nm.

Example 9 In Example 1, the target used in the second base film formation chambers 24 and 25 was nickel oxide.
A magnetic recording medium was formed in the same manner as in Example 1, except that (NiO), silicon oxide (SiO2), and zinc oxide (ZnO) were changed to a mixture. Nickel oxide (NiO) and silicon oxide (S
Table 8 shows the molar ratio between iO2) and zinc oxide (ZnO).

[0089]

[Table 8]

The crystal grain size of the magnetic film of the obtained medium was evaluated in the same manner as in Example 1. As the concentration of zinc oxide added during the formation of the second underlayer increases, the average crystal grain size of the magnetic film increases from 12.9 nm to 1 with the increase of the concentration of ZnO.
It increased to 5.2 nm, and the ratio σ / <d> of the standard deviation σ to the average particle size <d> of the magnetic film was 0.27 to 0.28.

[0091] The ratio of SiO / Nd increased with an increase in the concentration of ZnO. When ZnO was added in an amount of 10 mol.% Or more, the output reduction measured in the same manner as in Example 2 was 5% or more. Example 1, Example 9-1, and Example 9-2
In the magnetic recording medium described in (1), the output decrease after 96 hours from the reproduction output after 1 second from the recording was about 3%.

Example 10 In Example 1, the composition of the alloy target for forming the magnetic film 15 was changed to Co-21 at.% Cr-1.
4at.% Pt, Co-21at.% Cr-16at.%
Pt, Co-20at.% Cr-18at.% Pt alloy, Brt 2.4 mA (30 G
.Mu.m), except that the magnetic recording medium was formed in the same manner as in Example 1. A magnetic field of 1,040 is applied in the running direction of the magnetic head relative to the magnetic recording medium during recording.
The value of the coercive force Hc measured by a sample vibrating magnetometer at 25 ° C. while applying kA / m was 306 to 365 kA / m. If it exceeds 350 kA / m, the head having a shield gap length of 0.11 μm and a write gap length of 0.2 μm described in Example 2 is mechanically moved from the magnetic recording medium by 18 μm.
-30 nm when the overwrite characteristic was measured using a spin stand controlled at 5 ° C. in the air.
Only overwriting characteristics of dB or more were obtained. The frequency of 1F when measuring the overwrite characteristic was set to 1/6 of the frequency corresponding to the maximum linear recording density of 415 kFCI.

Applying an external magnetic field of 1,040 kA / m
The value of the coercive force Hc measured at 5 ° C. with a sample vibration magnetometer was about 350 kA / m at the maximum. The crystal constituting the magnetic film of the medium according to the present example had a mean particle size <d> of 7 nm or more and 15 nm as a result of observation of the particle size by transmission electron microscope observation.
The standard deviation σ of the crystal grain size of the magnetic film and the average grain size <
The ratio σ / <d> of d> was 0.25 to 0.28.

From these results, taking into account the overwrite characteristics at low temperature, the substrate and the magnetic film formed on the substrate have an average particle diameter <d> of 7 nm or more which constitutes the magnetic film. 15 nm or less, the ratio σ / <d> of the standard deviation σ of the crystal grain size of the magnetic film to the average grain size <d> is 0.28 or less, and the coercive force measured by a sample vibration magnetometer at 25 ° C. is 240 kA /
It became clear that it is preferable that it is more than m and 350 kA / m or less.

<< Embodiment 11 >> In forming the magnetic recording medium described in Embodiment 8, the second underlayer and the magnetic film were changed as follows without changing the conditions for forming the first underlayer and the protective film. Thus, a magnetic recording medium was formed. A sintered target having the following composition was used as the second target for forming a base film.

(Cr-50at.% Mn) -20mol.% SiO2 (Cr-40at.% Mn) -20mol.% SiO2 (Cr-50at.% Mn) -30mol.% SiO2 (Cr-5at.% Re) -20 mol.% SiO2 (Cr-10 at.% Ru) -20 mol.% SiO2 (Cr-1 at.% Rh) -20 mol.% SiO2 (Cr-50 at.% Mn) -10 mol.% Ta2O5 (Cr-50 at.%) Mn) -10 mol.% TiO2 (Cr-50 at.% Mn) -20 mol.% ZnO (Cr-50 at.% Mn) -20 mol.% SiO2-
6 mol.% ZnO The thickness of the second underlayer made of these Cr-containing alloys is 4
nm, 8 nm, 16 nm, 20 nm, 25 nm,
A magnetic film containing cobalt as a main component was formed thereon. The alloy target for forming the magnetic film had the following composition.

% Pt Co-12 at.% Pt Co-10 at.% Cr-12 at.% Pt Co-20 at.% Cr-12 at.% Pt Co-22 at.% Cr-12 at.% Pt Co -22at.% Cr-14at.% PtCo-20at.% Cr-12at.% Pt-2at.% TaCo-20at.% Cr-5at.% Ge Co-20at.% Cr-5at.% Ge-4at .% Pt-4a
% B Co-20at.% Cr-2at.% Ta Co-20at.% Ni-10at.% Cr-12at.% Pt
% BCo-20at.% Cr-14at.% Pt-4at.% BCo-22at.% Cr-12at.% Pt-4at.% BCo-7at.% Ge-10at.% Pt-6at % B When the magnetic film is formed using the above alloy target, the thickness is changed and the product Br of the residual magnetic flux density Br and the thickness t of the magnetic film is changed.
It was formed by controlling the value of × t to the following three levels.

(1) From 2 mA (25 G · μm) to 2.4 mA
(30 Gm), (2) From 4 mA (50 Gm) to 4.8
mA (60 G · μm), (3) A piece of a disk cut from 6.4 mA (80 G · μm) to 6.8 mA (85 G · μm), 8 mm square was measured at 25 ° C. using a sample vibration type magnetometer. Br × t
Was determined. The magnetic field application is set to 1,040 kA / m at maximum,
A magnetic field was applied in the relative running direction of the magnetic head during recording on the recording medium.

[0099] The change over time of the output of the reproduction wave of these magnetic recording media was measured using the spin stand described in Example 2. As a result, 2 mA (25 G · μm) to 2.
Some media having a current of 4 mA (30 G · μm) have a low reproduction output, so that the value of Siso / Nd may be 24 dB or less. On the other hand, when the Br × t value is 2.4 mA or more and 6.4 mA or less, the output reduction of the reproduced wave recorded at 200 kFCL after 96 hours does not exceed 10%, and at least Siso / Nd is obtained at 24 dB or more. . When the Br × t value of the magnetic recording medium is 2.4 mA or more and 6.4 mA or less, the average particle diameter <d> of the magnetic film is 7 nm or more and 15 nm or less.
And the standard deviation σ with respect to the average particle diameter <d> of the magnetic film.
Was 0.238 to 0.28.

However, when the Br × t value exceeds 6.4 mA, there arises a problem that overwriting cannot be performed sufficiently. That is, when recording with a signal having a linear recording density (1F) of about 1/6 of the maximum linear recording density exceeding 500 kFCI and then overwriting a signal (2F) with the maximum linear recording density, 1
The erasure remaining of the F signal was -30 dB or more, and sufficient overwriting could not be performed.

When the Br × t value exceeds 6.4 mA and the magnetic film is thicker than the second underlayer, the average particle size of the magnetic film
Magnetic recording media in which the ratio σ / <d> of the standard deviation σ to <d> exceeded 0.28 were also included.

The Mn concentration of the Cr—Mn—SiO 2 alloy was changed to obtain (Cr-50 at.% Mn) -20 mol.
Instead of (Cr-40at.% Mn) -20mol.%
Even when SiO2 was used, when the value of Br × t was less than 2.4 mA, there was a case where Siso / Nd was 24 dB or less.

Cr-50 at.% M for forming second underlayer
The concentration of SiO2 added to the n alloy is (Cr-50 at.%
Mn) -20 mol.% SiO2 to (Cr-50 at.
% Mn) -30 mol.% SiO2 was compared with the second underlayer.

A magnetic recording medium on which a second underlayer was formed to a thickness of 16 nm was ion-milled in a mortar shape in the film thickness direction in the same manner as in Example 1, and a transmission electron microscope and an energy dispersive elemental analyzer were used together. And the element distribution was measured.
As a result, from the observation of the selected area diffraction image, the crystal grains composed of the Cr-containing alloy are polycrystals composed of many crystal grains.
Cr concentration is low at the grain boundaries of the crystal grains made of the alloy containing
It became clear that grain boundaries with high concentration were formed. SiO2 added to Cr-50at.% Mn alloy
This tendency became clearer when the concentration was increased from 20 mol.% To 30 mol.%. When Mn exceeded the solid solubility limit with respect to the parent phase, it also precipitated at the grain boundaries.

In addition to the above, (Cr-X) -20mo
Elemental analysis was similarly performed on l.% SiO2 (X = Re, Ru, Rh). X is Re, R instead of Mn
Also when u and Rh are used, polycrystalline
The second phase mainly composed of silicon oxide was precipitated at the grain boundaries of the matrix mainly composed of (Cr-X) alloy.

(Cr-50 at.% Mn) -20 mol.
When ZnO was further added in an amount of 6 mol.% As compared with% SiO2, the crystal grain size of the second underlayer was increased by the addition of ZnO. When the thickness of the underlayer is 8 nm, 6 mo
The addition of ZnO in an amount of 1 to 20 mol.% was effective in increasing the grain size of the second underlayer as compared with the case where another oxide was added to the Cr alloy. (Cr-50at.% M
n) compared to -20 mol.% SiO2 (Cr-50 at.
% Mn) -20 mol.% ZnO in the range of 8 nm to 1
When formed to have a thickness of 6 nm, the crystal grain size of the second underlayer was large.

Embodiment 12 The magnetic recording medium 91 described in Embodiments 1 to 11, a driving unit 92 for driving the magnetic recording medium, and a magnetic head 9 including a recording unit and a reproducing unit
3, a means 94 for moving the magnetic head relative to the magnetic recording medium, a signal input means for the magnetic head, a recording / reproducing signal processing means 95 for reproducing an output signal from the magnetic head, and an amplifier. Mechanical unit 9 to save during loading
6 was constructed as shown in FIG.

The reproducing section of the magnetic head is constituted by a magnetoresistive head. FIG. 11 is a schematic perspective view showing the structure of the magnetic head. This head is a composite head having both an electromagnetic induction type head for recording and a magnetoresistive head for reproduction formed on a substrate 401. The recording head was composed of an upper recording magnetic pole 403 sandwiching a coil 402 and a lower recording magnetic pole and upper shield layer 404, and the gap length between the recording magnetic poles was 0.2 μm. Further, copper having a thickness of 3 μm was used for the coil. The reproducing head includes a magnetoresistive sensor 405 and electrode patterns 406 on both ends thereof. The magnetoresistive sensor is sandwiched between a lower recording magnetic pole / upper shield layer 404 and a lower shield layer 407.
The distance between the two shield layers was 0.10 μm. In this figure, the gap layer between the recording magnetic poles and the gap layer between the shield layer and the magnetoresistive sensor are omitted.

FIG. 12 shows a sectional structure of the magnetoresistive sensor. The signal detection region 500 of the magnetic sensor includes a plurality of conductive magnetic films that generate a large resistance change when their magnetization directions relatively change due to an external magnetic field, and a conductive film disposed between the conductive magnetic films. It is constituted by a magnetoresistive sensor (spin-valve type reproducing element) including a nonmagnetic film. The structure of this magnetic sensor is such that a Ta buffer layer 502, a first magnetic film 503, an intermediate layer 504 made of copper, a second magnetic film 505,
This is a structure in which an antiferromagnetic film 506 made of a 50 at.% Mn alloy is sequentially formed. The first magnetic film has Ni-2
A 0 at.% Fe alloy was used, and cobalt was used for the second magnetic film. Due to the exchange magnetic field from the antiferromagnetic film, the second
The magnetization of the magnetic film is fixed in one direction. On the other hand, the direction of magnetization of the first magnetic film that is in contact with the second magnetic film via the non-magnetic film changes due to a leakage magnetic field from the magnetic recording medium, and thus a resistance change occurs.

At both ends of the signal detection area, there are tapered portions 507 processed into a tapered shape. The tapered portion is used to make the first magnetic film a single magnetic domain.
8 and a pair of electrodes 406 for extracting signals formed thereon. The permanent magnet layer must have a large coercive force and the magnetization direction must not change easily.
-A Pt alloy was used.

By combining the magnetic recording medium of the present invention described in Examples 1 to 11 with the above-described head shown in FIG. 11, a magnetic storage device shown in FIG. 10 was formed. When using any of the above-mentioned media, a recording density of 20 Gb / inch2 or more could be realized by the magnetic storage device configured as described above.

In this embodiment, the area of the air bearing surface rail is 1.
A magnetic head having a magnetoresistive effect type magnetic head formed on a magnetic head slider having a size of 4 mm2 or less and a mass of 2 mg or less was used. By setting the area of the slider's floating surface rail to 1.4 mm 2 or less and the mass to 2 mg or less, the impact resistance can be improved. This allows
High recording density and high impact can be achieved at the same time.
A mean time between failures (MTBF) of 300,000 hours or more was realized at a recording density of 0 Gb / inch2 or more.

[0113]

According to the present invention, a high-performance magnetic recording medium with small noise can be realized by reducing the magnetic particle size in the magnetic film. At the same time, by controlling the distribution of the magnetic particle size to be small, a magnetic recording medium with low thermal fluctuation and low thermal demagnetization can be provided. Further, by controlling the crystal orientation of the magnetic film, a magnetic recording medium suitable for high-density recording can be provided. The magnetic recording medium of the present invention also has a feature of low noise in a high recording density region, and realizes a small-sized magnetic storage device having a large storage capacity and high reliability capable of high-density recording exceeding 20 Gb / inch2. Suitable for

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram illustrating an example of a chamber configuration of a sputtering apparatus.

FIG. 3 is a schematic sectional view showing an example of the magnetic recording medium of the present invention.

FIG. 4 is a schematic view illustrating an example of a chamber configuration of a sputtering apparatus.

FIG. 5 is a diagram showing a relationship between a thickness of an intermediate film and a coercive force.

FIG. 6 is a schematic sectional view showing an example of the magnetic recording medium of the present invention.

FIG. 7 is a schematic diagram illustrating an example of a chamber configuration of a sputtering apparatus.

FIG. 8 is a schematic diagram illustrating an example of a chamber configuration of a sputtering apparatus.

FIG. 9 is a diagram showing the relationship between the thickness of a second underlayer and the average grain size of a magnetic film.

FIG. 10 is a schematic diagram of a magnetic storage device of the present invention.

FIG. 11 is a schematic diagram showing an example of a cross-sectional structure of a magnetoresistive sensor of a magnetic head in the magnetic storage device of the present invention.

FIG. 12 is a schematic sectional view showing an example of a sectional structure of a magnetoresistive sensor of a magnetic head in the magnetic storage device of the present invention.

[Explanation of symbols]

11 ... substrate, 12 ... first under film, 13 ... second under film, 14 ... third under film, 15 ... first magnetic film, 1
6 ... intermediate film, 17 ... second magnetic film, 18 ... protective film,
19: lubrication film, 21: preparation chamber, 22: first base film formation chamber, 23: heating chamber, 24, 25 ... second base film formation chamber, 26 ... 1st magnetic film forming chamber, 27 ... intermediate film forming chamber, 28 ... second magnetic film forming chamber, 29, 29 '... protective film forming chamber, 30 ... take-out chamber, 31 ... Main chamber, 32 ... Third base film, 91 ... Magnetic recording medium, 92
... Driving unit for driving the magnetic recording medium, 93 ... Magnetic head, 94 ... Means for moving the magnetic head relative to the magnetic recording medium, 95 ... Recording / reproducing signal processing means, 96 ...・
Mechanism for retreating during unloading, 401...
2 ... coil, 403 ... upper recording magnetic pole, 404 ... lower recording pole and upper shield layer, 405 ... magnetic resistance sensor, 406 ... electrode pattern, 407 ... lower shield layer, 500 ... Signal detection area of magnetic sensor, 501 ... Gap layer, 502 ... Ta buffer layer, 503 ... First magnetic film, 504 ... Intermediate layer, 505 ... Second magnetism Membrane, 5
06: antiferromagnetic film, 507: tapered portion, 508:
Permanent magnet layer.

Continued on the front page (72) Inventor Yasuo Yakuo 2880 Kozu, Kodawara-shi, Kanagawa Prefecture, Ltd.Storage Systems Division, Hitachi, Ltd. (72) Inventor Joe Hosoe 2880 Kozu, Kozu, Odawara-shi, Kanagawa Storage System Business, Hitachi, Ltd. (72) Inventor Akira Ishikawa 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (72) Inventor Takashi Naito 7-1-1, Omikamachi, Hitachi City, Hitachi City, Ibaraki Prefecture Hitachi Research, Ltd. In-house F-term (reference) 4K029 AA09 BA06 BA07 BA13 BA21 BA43 BA46 BD11 CA05 DC02 5D006 BB01 BB07 CA01 CA05 CA06 FA00 5D112 AA03 BD02 FA04 FB02

Claims (12)

[Claims] 1. A substrate, a first base film formed on the substrate and made of a nonmagnetic material whose main component is chromium, and at least one kind selected from Mn, Re, Ru, and Rh as an additive element. A second underlayer made of a Cr-based alloy containing an element and an inorganic compound, a magnetic film containing cobalt as a main component formed thereon, and a protective film formed in this order; The inorganic compound contained in the underlayer is silicon,
A magnetic recording medium comprising an oxide containing at least one element selected from aluminum, titanium, tantalum, and zinc as a main component. 2. The magnetic recording medium according to claim 1, wherein the concentration of the inorganic compound contained in the second underlayer has a fluctuation in an in-plane direction of the film. 3. The method according to claim 1, wherein the second underlayer is formed of a large number of crystal grains made of a Cr-based alloy, and at least one selected from silicon, aluminum, titanium, tantalum, and zinc at grain boundaries of the crystal grains. 2. The magnetic recording medium according to claim 1, wherein the concentration of the oxide containing one kind of element is higher than the concentration inside the crystal grains. 4. An average particle diameter <d> of a crystal constituting the magnetic film.
Is not less than 7 nm and not more than 15 nm, and the ratio σ / <d> of the standard deviation σ of the crystal grain size of the magnetic film to the average grain size <d> is 0.28 or less, 2
The coercive force measured by a sample vibration magnetometer at 5 ° C. is 240
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a kA / m of 350 kA / m or more. 5. A substrate, a first underlayer made of a nonmagnetic material whose main component is chromium formed on the substrate, a second underlayer containing an oxide, and cobalt on the second underlayer. In a magnetic recording medium in which a magnetic film having a main component is formed, and a protective film is further formed in this order, the second underlayer film has an oxide containing at least one element selected from nickel, cobalt and magnesium as a main component. And an oxide containing at least one element selected from silicon, aluminum, titanium, tantalum and zinc as a main component.
A magnetic recording medium characterized by containing an oxide of: 6. The magnetic recording medium according to claim 5, wherein the concentration of the second oxide contained in the second underlayer has a fluctuation in an in-plane direction of the film. 7. The second base film is composed of a large number of crystal grains, and the concentration of the second oxide at a grain boundary of the crystal grains is higher than the concentration in the crystal grains. 6. The magnetic recording medium according to claim 5, wherein: 8. An average particle diameter <d> of a crystal constituting the magnetic film.
Is not less than 7 nm and not more than 15 nm, and the ratio σ / <d> of the standard deviation σ of the crystal grain size of the magnetic film to the average grain size <d> is 0.28 or less, 25
The coercive force measured by a sample vibrating magnetometer at 240 ° C is 240k
6. The magnetic recording medium according to claim 5, wherein the magnetic recording medium is not less than A / m and not more than 350 kA / m. 9. The magnetic recording medium according to claim 1, wherein an antiferromagnetic material having a Neel temperature of at least 80 ° C. is contained in a sputter target for forming the second underlayer. A method for manufacturing a magnetic recording medium. 10. A magnetic recording medium according to claim 5, wherein an antiferromagnetic material having a Neel temperature of at least 80 ° C. is contained in a sputter target for forming said second underlayer. A method for manufacturing a magnetic recording medium. 11. A magnetic recording medium, a driving unit for driving the magnetic recording medium, a magnetic head including a recording unit and a reproducing unit,
Means for moving the magnetic head relative to the magnetic recording medium, a mechanism for ramping the magnetic head,
In a magnetic storage device having a signal input means to the magnetic head and a recording / reproducing signal processing means for reproducing an output signal from the magnetic head, the reproducing units of the magnetic head can be configured such that their magnetization directions are relative to each other by an external magnetic field. A magnetic recording medium comprising: a plurality of conductive magnetic films that generate a large resistance change due to a change in resistance; and a magnetoresistive sensor including a conductive nonmagnetic film disposed between the conductive magnetic films. Item 2. A magnetic storage device, which is the magnetic recording medium according to Item 1. 12. A magnetic recording medium, a driving unit for driving the magnetic recording medium, a magnetic head including a recording unit and a reproducing unit,
Means for moving the magnetic head relative to the magnetic recording medium, a mechanism for ramping the magnetic head,
In a magnetic storage device having a signal input means to the magnetic head and a recording / reproducing signal processing means for reproducing an output signal from the magnetic head, the reproducing units of the magnetic head can be configured such that their magnetization directions are relative to each other by an external magnetic field. A magnetic recording medium comprising: a plurality of conductive magnetic films that generate a large resistance change due to a change in resistance; and a magnetoresistive sensor including a conductive non-magnetic film disposed between the conductive magnetic films. Item 6. A magnetic storage device, which is the magnetic recording medium according to Item 5.