JPH08180360A - Perpendicular magnetic recording medium and magnetic recorder - Google Patents

Abstract

PURPOSE: To provide a medium excellent in crystal orienting property and having high perpendicular magnetic anisotropy by forming an under film with a Co-Ru alloy. CONSTITUTION: A Co-Ru alloy forms a solid soln. over the entire compsn. range at ordinary temp. and the crystal structure is a hexagonal close-packed structure. An under film 12 of the Co-Ru alloy is formed on a nonmagnetic substrate 11 such as a glass substrate or an NiP coated Al alloy substrate. In the film 12, (0001) faces become parallel to the substrate and c-axes are liable to orient perpendicularly. A perpendicularly magnetized film 13 of a Co-based alloy and a protective film 14 are then formed on the film 12 to obtain the objective perpendicular magnetic recording medium. The proper concn. of Ru is >=40at.% because a compsn. having >=40at.% concn. of Ru gives <=0 deg.C Curie temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium provided with a magnetic film suitable for high density magnetic recording and a magnetic recording apparatus using the same.

[0002]

2. Description of the Related Art With the development of information-oriented society, there is an increasing demand for a magnetic recording device capable of accumulating a large amount of information and inputting / outputting at high speed. In order to compactly record more information, the perpendicular magnetic recording method has attracted attention as a new recording method that can further improve the recording density in place of the in-plane magnetic recording method that has been conventionally used.

Perpendicular magnetic recording is a recording system in which the magnetization formed in the direction perpendicular to the surface of the recording medium is used as a recording unit.
Since the influence of the demagnetizing field is small in the magnetization reversal portion, it is considered suitable for high density recording. This is IEE Transactions on Magnetics (IEEE
Transactions on Magnetics), MAG-13 (1977) 1
It is described in the article on page 272. The recording medium used for this perpendicular magnetic recording must have an easy axis of magnetization in the direction perpendicular to the medium surface and have a large magnetic anisotropy. For this reason, research and development have been conducted on thin film media in which a perpendicularly magnetized film is formed on a substrate.

It has been conventionally studied to use a Co alloy having a large magnetic anisotropy for the recording film of the perpendicular magnetic recording medium. Co alloys such as CoCr alloys have a hexagonal close-packed structure and exhibit uniaxial magnetic anisotropy with the c-axis as the easy axis of magnetization. When a Co alloy thin film is formed on the surface of an amorphous substrate such as glass, the (0001) plane, which is the closest packed atom plane, tends to be parallel to the substrate surface, and a [0001] oriented polycrystalline thin film is obtained. . Although this film exhibits perpendicular magnetic anisotropy, it was necessary to have a larger magnetic anisotropy in order to use it as a perpendicular magnetic recording medium.

Therefore, attempts have been made to improve the c-axis orientation of the Co alloy magnetic film by providing a base film on the substrate. A thin film having a hexagonal close-packed structure such as Ti is [000
1] Since it is easily oriented, it is used as a base film and Co
It has been reported that the orientation of the alloy magnetic film can be improved. Regarding a perpendicular magnetic recording medium using a Ti underlayer,
IEEE Transactions on Magnetics, MAG-19 (19
83) p. 1644.

However, the magnitude of the c-axis dispersion of the Co alloy magnetic film formed on the Ti underlayer has not been sufficiently small. It is considered that this is because the difference between the lattice constants of Ti and Co alloy is as large as 15%, and the orientation is disturbed during the initial growth of Co alloy. Therefore,
It has been desired to develop a new undercoating film for further improving the c-axis orientation of the Co alloy magnetic film.

[0007]

An object of the present invention is to provide a perpendicular magnetic recording medium which is more excellent in crystal orientation and has a large perpendicular magnetic anisotropy as compared with a conventional Co alloy film formed on a base film. It is to provide and a magnetic recording device using the same.

[0008]

As shown in FIG. 1, a perpendicular magnetic recording medium of the present invention comprises a non-magnetic substrate 11, a base film 12 formed on the substrate, and a Co film formed on the base film. A perpendicular magnetic recording medium comprising a perpendicularly magnetized film 13 of an alloy containing as a main component and a protective film 14 formed on the perpendicularly magnetized film, wherein the material of the underlayer is an alloy of Co and Ru. And

The second feature of the perpendicular magnetic recording medium of the present invention is, as shown in FIG. 2, a non-magnetic substrate 21, a first underlayer film 22 formed on the substrate, and a first underlayer film. A second underlayer film 23 formed on the second underlayer film, a perpendicular magnetization film 24 of an alloy containing Co as a main component formed on the second underlayer film, and a protective film 25 formed on the perpendicular magnetization film. In the perpendicular magnetic recording medium, the first underlayer film is made of either Ti or Ru, and the second underlayer film is made of an alloy of Co and Ru.

In the perpendicular magnetic recording medium having the second structure of the present invention, (1) the underlayer film made of an alloy of Co and Ru is composed of two layers having different Ru concentrations, and is located immediately below the perpendicular magnetization film. The Ru concentration of the layer
It is smaller than the u concentration, or (2) the Ru film concentration is continuously decreased from the side close to the substrate to the side of the perpendicular magnetization film in the base film made of an alloy of Co and Ru. It may be configured to satisfy that.

The perpendicular magnetic recording medium of the first and second configurations of the present invention is characterized in that the underlying film made of an alloy of Co and Ru has a Ru concentration of 40 at% Ru or more.

Further, in the perpendicular magnetic recording medium of the first and second configurations of the present invention, the perpendicular magnetization films 13 and 24 and the base film 1 are used.
Each of 2, 22, and 23 is characterized by having a [0001] preferential azimuth orientation.

Further, the perpendicular magnetic recording medium of the first and second configurations of the present invention may have a configuration in which fine undulations are provided on the surfaces of the substrates 11 and 21.

The magnetic recording apparatus of the present invention has the perpendicular magnetic recording medium having the above-described first and second configurations, a holder for holding the perpendicular magnetic recording medium, and information recording / reproducing on / from the perpendicular magnetic recording medium. A magnetic head for moving the magnetic head, a moving means for moving the relative position of the magnetic head and the perpendicular magnetic recording medium, and a control means for controlling each of these parts.

[0015]

It is known that the CoRu alloy used in the above structure forms a solid solution over the entire composition range at room temperature. The crystal structure is a hexagonal close-packed structure like Co and Ru. When a thin film of this alloy is formed on a substrate having an amorphous surface such as a glass substrate or a NiP-coated Al alloy substrate, the (0001) plane becomes parallel to the substrate, and the c-axis is easily oriented vertically. Therefore, it can be used as a base film for improving the c-axis vertical orientation of the Co alloy magnetic film used as the recording film of the perpendicular magnetic recording medium. In the composition range where the Ru concentration is 40 at% or higher, the Curie temperature is 0 ° C. or lower, so that this alloy does not exhibit ferromagnetism. When used as a non-magnetic underlayer, it is suitable to use Ru in a concentration of 40 at% Ru or more.

The lattice constant of CoRu alloy continuously changes in proportion to the composition of the alloy. The a-axis lattice constants of Co and Ru are 0.251 nm and 0.270 nm, respectively.
The lattice constant of Co-40 at% Ru is 0.259 nm. Therefore, if an alloy of Co-40at% Ru is used for the underlayer film, the Co alloy magnetic film (the lattice constant of the a-axis is about 0.
25 nm) and the difference in lattice constant are as small as -3% based on the CoRu alloy. Therefore, when this alloy is used as the base film, the disorder of the orientation of the Co alloy during the initial growth can be prevented, and the perpendicular magnetization film having a high c-axis perpendicular orientation can be manufactured.

Ru and Ti are likely to be vertically oriented on the c-axis, but the difference in the lattice constant of the a-axis from the Co alloy magnetic film is -7% when Ru is used as the underlayer, and when Ti is used,
-15%, which is larger than that of CoRu alloy. Therefore, by forming a Ti or Ru underlayer and then forming a CoRu alloy underlayer on the surface thereof, it is possible to alleviate the difference in lattice constant and produce an underlayer having a lattice constant close to that of Co alloy. it can.

Further, the CoRu alloy base film is constituted by two layers of films having different Ru concentrations, and Ti or Ru is used.
Layer with a high Ru concentration is formed on the underlayer film of
By forming the layer having a low u concentration, the difference in lattice constant can be effectively mitigated. The lattice constant difference can also be relaxed by continuously decreasing the Ru concentration of the CoRu alloy underlayer film from the side closer to the substrate toward the side of the perpendicular magnetization film.

As described above, by using the CoRu alloy having a lattice constant close to that of the a-axis of the Co alloy magnetic film for the underlayer, the c-axis vertical orientation of the Co alloy magnetic film is enhanced, and the CoRu alloy magnetic film has a higher orientation than the conventional one. A perpendicular magnetic recording medium suitable for high density recording can be provided.

[0020]

【Example】

Example 1 A magnetic recording medium having a cross-sectional structure as shown in FIG. 3 was produced by a DC magnetron sputtering method using a glass substrate having a diameter of 2.5 inches. Board 3
CoRu alloy base films 32 and 32 ', Co alloy magnetic films 33 and 33', and carbon protective films 34 and 34 'are formed in this order on both surfaces of No. 1 in this order.

Argon gas was used for film formation, the gas pressure was 0.7 Pa, the substrate temperature was 260 ° C., and the film formation rate was 50 n / min.
It was formed under the condition of m. The composition of the target used for forming the underlayer film is Co-40 at% Ru, and the composition of the target used for forming the magnetic film is Co-15 at% Cr-5 at% T.
a. The a-axis length of the Co alloy magnetic film having this composition was 0.251 nm. The film thickness of each film was 50 nm for the CoRu alloy base film, 100 nm for the Co alloy magnetic film, and 10 nm for the carbon protective film. The above film formation was continuously performed in the same vacuum chamber without breaking the vacuum.

The crystal orientation of the prepared sample was measured by X-ray diffraction, and the magnetic characteristics were measured by using a sample vibrating magnetometer (VSM). In X-ray diffraction, a 0002 diffraction peak of the CoRu alloy underlayer film and the Co alloy magnetic film was observed, and it was found that this film had a [0001] orientation. Co
When the rocking curve of the X-ray 0002 diffraction peak of the alloy magnetic film was measured, the rocking curve of the magnetic recording medium of this example was higher than that of the magnetic recording medium manufactured under the same conditions without using the underlayer film. The full width at half maximum has decreased and Co
The [0001] orientation of the alloy magnetic film was improved. The coercive force in the direction perpendicular to the film surface was improved by 38% (420 Oe).

Further, when the Co-50 at% Ru alloy and the Co-75 at% Ru alloy were used for the underlayer film, the improvement effect was recognized. Table 1 shows the results.

[0024]

[Table 1]

Example 2 A magnetic recording medium having a cross-sectional structure as shown in FIG. 4 was produced by a DC magnetron sputtering method using an Al alloy substrate coated with NiP having a diameter of 1.8 inches. On both sides of the substrate 41,
First underlayer films 42, 42 'made of Ru, second underlayer films 43, 43' made of CoRu alloy, Co alloy magnetic film 4
4, 44 'and carbon protective films 45, 45' are formed in this order.

Argon gas was used for film formation, the gas pressure was 0.7 Pa, the substrate temperature was 260 ° C., and the film formation rate was 50 n / min.
It was formed under the condition of m. The composition of the target used to form the CoRu alloy underlayer film is Co-40 at% Ru, and the composition of the target used to form the magnetic film is Co-12 at% Cr.
It was set to -10 at% Pt. The a-axis length of the Co alloy magnetic film having this composition was 0.255 nm. The thickness of each film is
Ru base film 30 nm, CoRu alloy base film 50 n
m, Co alloy magnetic film 100 nm, carbon protective film 1
It was set to 0 nm. The above film formation was continuously performed in the same vacuum chamber without breaking the vacuum.

The crystal orientation of the prepared sample was measured by X-ray diffraction, and the magnetic characteristics were measured by using a sample vibrating magnetometer (VSM). In X-ray diffraction, Ru underlayer, CoRu
0002 diffraction peaks of the alloy underlayer film and the Co alloy magnetic film were observed, and it was found that this film had a [0001] orientation. When the rocking curve of the X-ray 0002 diffraction peak of the Co alloy magnetic film was measured, the magnetic recording medium of this example was compared with a magnetic recording medium produced under exactly the same conditions without using the CoRu alloy underlayer film. The half-width of the rocking curve was reduced, and the [0001] orientation of the Co alloy magnetic film was improved. The coercive force in the direction perpendicular to the film surface is 13% (1
90 Oe) improved.

Further, when the Ti underlayer film was used instead of the Ru underlayer film, the improvement effect was recognized. Table 2 shows the results.

[0029]

[Table 2]

Using such a perpendicular magnetic recording medium, a magnetic recording apparatus according to the perpendicular magnetic recording system as schematically shown in FIG. 5 was manufactured. The perpendicular magnetic recording medium 51 is held by a holder rotated by a motor, and a magnetic head 52 for writing and reading information is arranged corresponding to each magnetic film. The position of the magnetic head 52 with respect to the magnetic recording medium 51 is moved by the actuator 53 and the voice coil motor 54. Further, in order to control these, a recording / reproducing circuit 55, a positioning circuit 56,
An interface control circuit 57 is provided. Co
It was confirmed that high density recording is possible with a perpendicular magnetic recording medium using a Ru underlayer.

Example 3 Using a glass substrate having a diameter of 1.8 inches, a magnetic recording medium having a cross sectional structure as shown in FIG. 4 was produced by the ion beam sputtering method. The first base film 4 made of Ru is formed on both surfaces of the substrate 41.
2, 42 ', a second base film 43 made of a CoRu alloy,
43 ', Co alloy magnetic films 44 and 44', and carbon protective films 45 and 45 'are formed in this order.

Argon gas was used for the film formation, and the substrate temperature was 260 ° C. and the film formation rate was 50 nm / min. C
Two ion guns were used to form the oRu alloy base film,
A Co target and a Ru target were independently sputtered and deposited simultaneously. By controlling the Ru film formation rate, the Ru concentration in the film was continuously changed in the film thickness direction. The composition of the target used for forming the magnetic film is C
It was o-12 at% Cr-10 at% Pt. The length of the a-axis of the Co alloy magnetic film having this composition was 0.255 nm. The film thickness of each film was 30 nm for the Ru underlayer film, 50 nm for the CoRu alloy underlayer film, 100 nm for the Co alloy magnetic film, and 10 nm for the carbon protective film. The above film formation was continuously performed in the same vacuum chamber without breaking the vacuum.

The crystal orientation of the prepared sample was measured by X-ray diffraction, the change in composition in the film thickness direction was measured by Auger electron spectroscopy, and the magnetic characteristics were measured by a sample vibrating magnetometer (VSM). In X-ray diffraction, 0002 diffraction peaks of the Ru underlayer film, the CoRu alloy underlayer film, and the Co alloy magnetic film were observed, and it was found that this film had a [0001] orientation. Co
The rocking curve of the X-ray 0002 diffraction peak of the alloy magnetic film was measured, and it was found that the magnetic recording medium of this example had CoR
The full width at half maximum of the rocking curve is 35% compared to the magnetic recording medium produced under exactly the same conditions without using the u alloy underlayer.
And the [0001] orientation of the Co alloy magnetic film was improved. The compositional distribution in the film thickness direction of the CoRu alloy underlayer film has a gradually decreasing Ru concentration toward the film surface, and Co-72at% R near the interface with the Ru underlayer film.
Co-46 at% R near the interface with the u and Co alloy magnetic film
It was u.

The length of the a-axis of the CoRu alloy of this composition was estimated to be 0.265 nm near the interface with the Ru underlayer.
The thickness is 0.260 nm near the interface with the Co alloy magnetic film.
The amount of lattice misfit estimated from this value is Ru
At the interface between the base film and the CoRu alloy base film, -4.0%, Co
It is -1.8% at the interface between the Ru alloy base film and the Co alloy magnetic film. The coercive force in the direction perpendicular to the film surface was also improved by 21% (310 Oe).

Example 4 Using a glass substrate having a diameter of 1.8 inches, a magnetic recording medium having a cross sectional structure as shown in FIG. 6 was produced by the DC magnetron sputtering method. On both surfaces of the substrate 61, Ti base films 62, 62 ', C
o-70 at% Ru alloy base film 63, 63 ', Co-4
The 0 at% Ru alloy base films 64 and 64 ', the Co alloy magnetic films 65 and 65', and the carbon protective films 66 and 66 'are formed in this order. Prior to film formation, the surface of the substrate was sputtered with argon ions to form fine undulations having an average depth of about 2 nm. Argon gas was used for the film formation, and the substrate temperature was 250 ° C. and the film formation rate was 50 nm / min.

The composition of the target used for forming the magnetic film was Co-15 at% Cr-5 at% Ta. The a-axis length of the Co alloy magnetic film having this composition was 0.251 nm. Regarding the film thickness of each film, the Ti underlayer film is 30 nm, Co-70
at% Ru alloy base film is 25 nm, Co-40 at% R
u alloy underlayer film is 25 nm, Co alloy magnetic film is 100 n
m, the carbon protective film was 10 nm. The above film formation was continuously performed in the same vacuum chamber without breaking the vacuum.

The crystal orientation of the produced sample was measured by X-ray diffraction, and the magnetic characteristics were measured by using a sample vibrating magnetometer (VSM). In X-ray diffraction, 0002 diffraction peaks of the Ti underlayer film, the CoRu alloy underlayer film, and the Co alloy magnetic film were observed, and it was found that this film had a [0001] orientation.

The rocking curve of the X-ray 0002 diffraction peak of the Co alloy magnetic film was measured, and the magnetic recording medium of this example was compared with the magnetic recording medium prepared under exactly the same conditions without using the CoRu alloy underlayer. As a result, the full width at half maximum of the rocking curve is reduced by 27%, and the [0
001] orientation was improved. In this case, the amount of lattice misfit is -10% at the interface between the Ti underlayer and the Co-70at% Ru alloy underlayer, and at the interface between the Co-70at% Ru alloy underlayer and the Co-40at% Ru alloy underlayer- 2.
2%, Co-40 at% Ru-2.9% at the interface between the Ru alloy underlayer and the Co alloy magnetic film. The coercive force in the direction perpendicular to the film surface was also improved by 8% (130 Oe) as compared with the magnetic recording medium manufactured under exactly the same conditions without using the CoRu alloy base film.

Using this perpendicular magnetic recording medium, a magnetic recording device of the perpendicular magnetic recording system as schematically shown in FIG. 5 was produced. Due to the effect of fine undulations on the substrate surface, stable recording and reproduction could be performed without the magnetic head sticking to the medium surface.

[0040]

As in the present invention, by using a CoRu alloy for the underlayer film, the c-axis vertical orientation of the Co alloy magnetic film is enhanced, and a high-performance perpendicular magnetic recording medium suitable for high-density recording as compared with the prior art. Can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a sectional structure of a perpendicular magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a sectional structure of a perpendicular magnetic recording medium of a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a cross-sectional structure of the perpendicular magnetic recording medium of the first embodiment of the present invention.

FIG. 4 is an explanatory view of a sectional structure of a perpendicular magnetic recording medium according to a second embodiment of the invention.

FIG. 5 is a block diagram of a magnetic recording device of the present invention.

FIG. 6 is an explanatory diagram of a sectional structure of a perpendicular magnetic recording medium according to a third embodiment of the invention.

[Explanation of symbols]

11 ... Non-magnetic substrate, 12 ... CoRu alloy base film, 13 ...
Co alloy magnetic film, 14 ... Protective film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takanobu Takayama 1-280 Higashi Koikekubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (8)

[Claims] 1. A non-magnetic substrate, a base film formed on the non-magnetic substrate, a perpendicular magnetization film formed on the base film and made of an alloy containing Co as a main component, and a perpendicular magnetization film on the perpendicular magnetization film. A perpendicular magnetic recording medium comprising a protective film formed on the underlayer, wherein the underlayer film is made of an alloy of Co and Ru. 2. A non-magnetic substrate, a first base film formed on the non-magnetic substrate, a second base film formed on the first base film, and the second base film. Co formed on top
In a perpendicular magnetic recording medium comprising a vertically magnetized film of an alloy containing as a main component and a protective film formed on the vertically magnetized film, the first underlayer is made of either Ti or Ru. A perpendicular magnetic recording medium, wherein the second underlayer film is made of an alloy of Co and Ru. 3. The underlayer film made of an alloy of Co and Ru is formed of two layers having different Ru concentrations, and the Ru concentration of a layer located immediately below the perpendicularly magnetized film is:
A perpendicular magnetic recording medium having a Ru concentration lower than that of a layer located thereunder. 4. The perpendicular film of the perpendicular magnetic recording medium according to claim 2, wherein R is a base film made of an alloy of Co and Ru.
A perpendicular magnetic recording medium in which the concentration of u continuously decreases from the side closer to the non-magnetic substrate toward the side of the perpendicular magnetization film. 5. The perpendicular magnetic recording medium according to any one of claims 1 to 4, wherein in the underlayer film made of an alloy of Co and Ru, the Ru concentration is 40 at% Ru or more. 6. A perpendicular magnetic recording medium according to claim 1, 2, 3 or 4, wherein the preferred orientation azimuth of each underlayer and the preferred orientation azimuth of the perpendicular magnetization film are both [0001]. 7. The perpendicular magnetic recording medium according to claim 1, 2, 3 or 4, wherein fine undulations are provided on the surface of the non-magnetic substrate. 8. A perpendicular magnetic recording medium according to claim 1, 2, 3, 4, 5, 6 or 7, a holder for holding the perpendicular magnetic recording medium, and information recorded on the perpendicular magnetic recording medium. A magnetic recording device having a magnetic head for reproducing, a moving means for moving the relative position of the magnetic head and the perpendicular magnetic recording medium, and a control means for controlling each of these parts.