JPH07141639A - Magnetic recording medium and magnetic recorder - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having the magnetic film improved in crystal orientability so as to make the medium fit for high density magnetic recording. CONSTITUTION:A 1st base film 13 having a body-centered cubic structure is formed on a 2nd base film 14 having a CaF2 type crystal structure formed directly on a nonmagnetic substrate 15 or through a certain base film and a magnetic film 12 having a hexagonal close-packed structure is formed on the 1st under film 13. The coercive force and squareness ratio of the resulting magnetic recording medium in the intrasurface direction are enhanced and higher density magnetic recording is enabled.

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 having a magnetic film suitable for high density magnetic recording and a magnetic recording device using the same.

[0002]

[Outer 1]

[0003]

2. Description of the Related Art As a recording medium suitable for high density magnetic recording, a magnetic recording medium having a continuous magnetic film formed on a non-magnetic substrate is known. The magnetic film is a thin film of an alloy containing a ferromagnetic metal such as Co as a main component, and is formed by a method such as a sputtering method, a vacuum deposition method, a chemical plating method, or the like. It is known that the characteristics as a magnetic recording medium are closely related to the fine structure of the magnetic film, and attempts have been made to improve the magnetic film in order to improve the magnetic recording characteristics. In particular, in order to develop preferable magnetic characteristics such as high coercive force and high squareness ratio for a magnetic recording medium and to obtain sufficient reproduction characteristics even when high density recording is performed, it is necessary to further improve the crystal orientation of the magnetic film. Is.

Generally, the crystal structure of a Co alloy used in a magnetic recording medium is an hcp (hexagonal close-packed) structure similar to that of simple substance Co, and has an easy axis of magnetization in the c-axis direction ([0001] direction). . When a Co alloy is used as the in-plane magnetic recording medium, it is necessary to direct the easy axis of magnetization of each crystal grain parallel to the magnetic film surface, or to have as many components as possible parallel to the magnetic film surface. Become. However, since the densest plane of the hcp structure is the (0001) plane, this plane is likely to be preferentially oriented. In this case, since the c-axis is oriented in the direction perpendicular to the film surface, it is not suitable for an in-plane magnetic recording medium as it is.

However, there is a bcc between the magnetic film and the substrate.
By providing a metal underlayer having a (body-centered cubic) structure, the direction of the c-axis of the Co alloy can be tilted in the in-plane direction. For example, IEEE Magnetics Society, Vol. 22, 334.
~ 336 (1986) [IEEE Trans. Magn., MAG-2
2, pp.334-336. (1986)].
In the paper of (en), the orientation direction of the CoNiCr alloy formed on the Cr underlayer film is different from the orientation direction of the film of the same composition formed without providing the Cr underlayer film. It is shown that the 1101} plane grows on the {110} plane of the Cr underlayer. That is, {110}
If a bcc base film with preferential orientation is used, it is about 28 from the film surface.
A {1101} preferentially oriented hcp magnetic film having an easy axis of magnetization in a tilted direction can be obtained.

[0006]

As described above, when a Co alloy is used for the in-plane magnetic recording medium, in order to increase the component of the easy axis of magnetization of individual crystal grains in the direction parallel to the film surface, {11
It is effective to provide a bcc base film having a 0} preferential orientation. This {110} preferentially oriented bcc underlayer film is achieved by preferentially crystallizing the {110} plane which is the closest packed surface. However, in the initial stage of growth, crystal grains having other orientations were inevitably formed at the same time, and thus far, sufficient {110} orientation could not be obtained. Therefore, even if a magnetic film is formed on this underlayer, it has been difficult to obtain a magnetic thin film medium composed of highly oriented crystal grains. An object of the present invention is to provide a magnetic recording medium in which the crystal orientation of a magnetic film is improved and a magnetic recording device using the same.

[0007]

In order to achieve the above object, the magnetic recording medium of the present invention comprises a non-magnetic substrate and a two-layer structure provided directly or through some underlayer on the non-magnetic substrate. It has an underlayer film and a magnetic film provided on the two-layer underlayer film, and the magnetic film has a hexagonal close-packed structure.
Among the underlayer films of the layer, the first underlayer film provided directly below the magnetic film has a body-centered cubic structure, and the second underlayer film provided immediately below the first underlayer film has a CaF ₂ type crystal structure. Configure to have.

FIG. 1 is a schematic diagram showing an example of the magnetic recording medium of the present invention. Magnetic film 12 having an hcp structure
Are formed on the first base film 13 having the bcc structure. The first base film 13 is formed on the second base film 14 having a CaF ₂ type crystal structure. The second base film 14 is formed on the non-magnetic substrate 15 directly or has a hexagonal close-packed structure.
It is formed through a thin base film of i, Zn, Ru, or the like. It is preferable to form a protective film 11 such as a carbon film on the magnetic film 12.

The magnetic film 12 has a preferred orientation of {110
1}, and the first base film 13 has a preferred orientation of {11
0}, and the second base film 14 has a preferred orientation of {11
1} is preferable. In addition, the first base film and the second
It is preferable that each of the base films is made of a nonmagnetic material. Furthermore, the magnetic film 12 is preferably made of Co or an alloy containing Co as a main component, such as a CoCrPt alloy or a CoCrTa alloy. As the alloy containing Co as a main component, various alloys have been conventionally used as the magnetic film, and such alloy can be used in the present invention. It is practically desirable that the thickness of the magnetic film be in the range of 10 to 100 nm. The magnetic film can be formed by a method such as a vacuum vapor deposition method or a sputtering method.

The material of the first underlayer is Cr, Mo,
At least one material selected from the group consisting of W, V, Nb, Ta and alloys containing these elements as main components can be used. Of course, the material of the first base film is not limited to these materials, and other metals or alloys having a bcc structure can be used. It is practically desirable that the thickness of the first base film is in the range of 2 to 100 nm. The first underlayer film can also be formed by a method such as a vacuum vapor deposition method or a sputtering method as with the magnetic film.

The material of the second underlayer film is CaF ₂ , S.
At least one material selected from the group consisting of rF ₂ , BaF ₂ , SrCl ₂ and mixed crystals containing these inorganic compounds as the main components can be used. The material of the second base film is not limited to these materials, and C
It is also possible to use other compounds having an aF ₂ type crystal structure or mixed crystals. It is practically desirable that the thickness of the second base film is in the range of 2 to 300 nm. The second base film can be formed by a method such as a vacuum vapor deposition method, a sputtering method, a chemical vapor deposition method, an ion plating method or the like.

When the magnetic film is made of Co or an alloy containing Co as a main component, the first underlayer is preferably made of Cr or an alloy containing Cr as a main component. When the first undercoating film is made of Cr or an alloy containing Cr as a main component, the second undercoating film is preferably made of CaF ₂ , SrF ₂ or a mixed crystal containing these inorganic compounds as main components. The magnetic recording apparatus of the present invention includes a magnetic recording medium as described above, a holder for holding the magnetic recording medium, a magnetic head arranged on the magnetic film of the magnetic recording medium for recording and reproducing information, The magnetic head and the magnetic recording medium are configured in a known manner from a moving means for moving the relative position and a control means for controlling them.

[0013]

[Function] On the {110} plane of a metal having a bcc structure, h
It is known that the {1101} plane of a metal having a cp structure is epitaxially grown. hcp structure {110
The 1} crystal plane is shown in FIG. In addition, the hcp structure {110
FIG. 3 shows the matching relationship between the 1} plane and the {110} plane of the bcc structure. For the non-magnetic underlayer material having the bcc structure, Cr, M
Although o, W, V, Nb, Ta and alloys containing these elements as main components are conceivable, the interatomic distance on the {110} plane is determined by the atoms in the {1101} plane of the magnetic film material. It is preferable to select it so as to match the inter-distance. Specifically,
As will be understood from the following, the following equations (1) and (2) are set to values as close as possible. a (hcp) × 2 (1) a (bcc) × 3 ^1/2 (2)

Where a (bcc) is the a-axis lattice constant of the bcc structure, and a (hcp) is the a-axis lattice constant of the hcp structure. If the ratio of the difference between the values of the formula (1) and the formula (2) to the formula (2), that is, the value of the following formula (3) exceeds ± 0.1, epitaxial growth does not occur well and crystallinity is disturbed. ± 0.1 or less is preferable, ± 0.03
The following is more preferable. {A (hcp) × 2-a (bcc) × 3 ^1/2 } / a (bcc) × 3 ^1/2 (3)

For example, when Co is used for the magnetic film and the underlayer is changed, the value of the equation (3) is about 0.004 when the underlayer is Cr, and about -0.043 when V is V, and Mo. In the case of, it becomes about -0.080, and in the case of W, it becomes about -0.085. C
The lattice constant of the o alloy is almost the same as that of Co even if the composition is changed. When the magnetic film is a CoCrTa alloy and the base film is Cr, the difference is about 0.005.

In the present invention, the bcc base film (first base film)
Is controlled by the second underlayer film having a CaF ₂ type crystal structure provided immediately below. This is because, as shown in FIG. 4, the {110} plane of the bcc structure is easily epitaxially grown on the {111} plane of the CaF ₂ type crystal structure. In addition, CaF ₂ type crystals generally have a property of being easily oriented in {111}. Therefore, by epitaxially growing a bcc crystal on the surface thereof, it is possible to easily obtain a film of a bcc crystal having a sufficiently {110} orientation.

When the hcp magnetic film was epitaxially grown on the above-mentioned bcc first underlayer having a sufficient {110} orientation, {1101} orientation was achieved, and the easy axis of magnetization of each crystal grain was inclined about 28 ° from the film surface. A magnetic film is obtained. In the magnetic film thus obtained, as compared with the case where only the bcc underlayer film is formed on the substrate and the hcp magnetic film is formed thereon,
It exhibits a higher coercive force and squareness ratio in the in-plane direction of the film, and can be used as an in-plane magnetic recording medium capable of recording and reproducing at higher density.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 A magnetic recording medium having a cross-sectional structure as shown in FIG. 5 was produced by a high frequency magnetron sputtering method using a glass substrate having a diameter of 3.5 inches. That is, on both surfaces of the glass substrate 55, CaF ₂ base films 54 and 54 ′ having a CaF ₂ type crystal structure and Cr having a bcc structure are formed.
The base films 53 and 53 ', the Co alloy magnetic films 52 and 52' having the hcp structure, and the carbon protective films 51 and 51 'are formed in this order.

Argon gas was used to form the CaF ₂ base films 54 and 54 ', and the gas pressure was 0.5 to 1.5 Pa.
It was formed under the conditions of a substrate temperature of 200 ° C. and a film forming rate of 3 to 5 nm per minute. Cr underlayer films 53, 53 ', Co alloy magnetic film 5
2, 52 ′ and the carbon protective films 51, 51 ′ were formed using argon gas under the conditions of a gas pressure of 0.7 Pa, a substrate temperature of 150 ° C., and a film forming rate of 50 nm / min. The composition of the target used to form the magnetic films 52 and 52 'is C
o-15 at. % Cr-7 at. % Pt. The film thickness of each film is 50 nm for the CaF ₂ underlayer film and 50 for the Cr underlayer film.
nm, Co alloy magnetic film 30 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 produced sample was measured by X-ray diffraction, and the magnetic characteristics were measured by using a sample vibrating magnetometer (VSM). As a result, the magnetic recording medium of this example has a Cr underlayer {11} compared to a magnetic recording medium produced under exactly the same conditions except that the CaF ₂ underlayer is not provided.
0} orientation and the {1101} orientation of the Co alloy magnetic film were remarkably improved, and the coercive force in the in-plane direction of the film was 7.0% (105
Oe) was improved, and the squareness ratio was improved by 9.8% (0.08). The value of the above equation (3) calculated from each crystal structure of the Co alloy magnetic film and the Cr underlayer of this magnetic recording medium is
It is 0.004.

Example 2 Using a glass substrate having a diameter of 3.5 inches, a magnetic recording medium having a sectional structure as shown in FIG. 5 was produced by a high frequency magnetron sputtering method. On both surfaces of the glass substrate 55, SrF ₂ base films 54 and 54 ′ having a CaF ₂ type crystal structure, Cr base films 53 and 53 ′ having a bcc structure, Co alloy magnetic films 52 and 52 ′ having an hcp structure, and carbon. The protective films 51 and 51 'are formed in this order.

Argon gas was used to form the SrF ₂ base films 54 and 54 ', and the gas pressure was 0.5 to 1.5 Pa.
It was formed under the conditions of a substrate temperature of 200 ° C. and a film forming rate of 3 to 5 nm per minute. Cr underlayer films 53, 53 ', Co alloy magnetic film 5
The film formation of 2, 52 'and the carbon protective films 51, 51' was performed under the same conditions as in Example 1. The composition of the target used for forming the magnetic films 52 and 52 'is Co-12 at. % Cr
-4 at. % Ta. The film thickness of each film was 50 nm for the SrF ₂ underlayer film, 50 nm for the Cr underlayer film, 30 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 produced sample was measured by X-ray diffraction, and the magnetic characteristics were measured by using a sample vibrating magnetometer (VSM). As a result, the magnetic recording medium of this example has a Cr underlayer film {11} compared with the magnetic recording medium produced under exactly the same conditions except that the SrF ₂ underlayer film is not provided.
0} orientation and the {1101} orientation of the Co alloy magnetic film were significantly improved, and the coercive force in the in-plane direction of the film was 11% (120O).
e) improved, and the squareness ratio improved by 8.6% (0.07).

Further, in the above-mentioned embodiment, V, Mo, W or Cr-3 at. A magnetic recording medium was prepared in exactly the same manner except that a% Si alloy was used. With respect to each of these magnetic recording media, improvement in both the {110} orientation of the bcc underlayer and the {1101} orientation of the Co alloy magnetic film was observed as compared with the respective comparative examples in which the SrF ₂ underlayer was not provided. The squareness ratio has also improved. The results are shown in Table 1.

[0025]

[Table 1]

Further, Nb, Ta, Cr-5 is used as the first underlayer film.
at. % Nb alloy or Cr-10 at. It was also found that the magnetic recording medium using the% Mo alloy has improved orientation and magnetic properties as compared with the respective comparative examples in which the SrF ₂ underlayer is not provided.

[Embodiment 3] Using a glass substrate having a diameter of 3.5 inches, a magnetic recording medium having a sectional structure as shown in FIG. 5 was produced by a high frequency magnetron sputtering method as in the above embodiment. C on both sides of the glass substrate 55
CaF ₂ base films 54, 54 ′ having an aF ₂ type crystal structure,
Cr underlayer films 53 and 53 ′ having a bcc structure, Co alloy magnetic films 52 and 52 ′ having an hcp structure, and carbon protective films 51 and 51 ′ are formed in this order.

The CaF ₂ base films 54 and 54 'were formed by using argon gas under the conditions of a gas pressure of 0.5 to 1.5 Pa, a substrate temperature of 200 ° C., and a film forming rate of 3 to 5 nm per minute.
Cr underlayer films 53, 53 ', Co alloy magnetic films 52, 52'
The carbon protective films 51 and 51 ′ were formed under the same conditions as in Example 1. The composition of the target used for forming the magnetic films 52 and 52 ′ is Co-16 at. % C
r-6 at. % Pt. The film thickness of each film was 50 nm for the CaF ₂ underlayer film, 50 nm for the Cr underlayer film, 30 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.

Under the same conditions as above, instead of the CaF ₂ underlayer, BaF ₂ having the same CaF ₂ type crystal structure,
A magnetic recording medium using SrCl ₂ was prepared. 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). As a result, the magnetic recording medium of this example has a Cr underlayer film {11} compared with the magnetic recording medium produced under exactly the same conditions except that no underlayer film having a CaF ₂ type crystal structure is provided.
Both the 0} orientation and the {1101} orientation of the Co alloy magnetic film were remarkably improved, and the coercive force in the in-plane direction and the squareness ratio were improved. The results are shown in Table 2.

[0030]

[Table 2]

Further, (Ca, Sr) F _{2 is formed on} the second base film.
A magnetic recording medium using a mixed crystal was manufactured. It was found that this magnetic recording medium also has the same effect.

[Embodiment 4] FIG. 6 is a schematic view of an embodiment of the magnetic recording apparatus. The magnetic recording medium 61 is held by a holder rotated by a motor, and a magnetoresistive effect element reproducing composite head 62 for writing and reading information is arranged corresponding to each magnetic film. The magnetic recording medium 61 of the magnetoresistive effect element reproducing composite head 62
The position with respect to is moved by the actuator 63 and the voice coil motor 64. Further, a recording / reproducing circuit 65, a positioning circuit 66, and an interface control circuit 67 are provided to control these. When the magnetic recording medium manufactured in each of the above-mentioned Examples was used and applied to this magnetic recording apparatus, all of them were capable of high-density recording with a high S / N ratio.

[0033]

According to the present invention, the coercive force in the in-plane direction and the squareness ratio are improved by orienting the easy axis of magnetization of the crystal grains of the magnetic film highly in the direction inclined by about 28 ° from the film surface. A magnetic recording medium suitable for high-density magnetic recording can be provided. Further, it is possible to provide a magnetic recording device capable of high density recording with a high S / N ratio.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a {1101} plane in the hcp structure.

FIG. 3 is a plan view showing the matching relationship between the {1101} plane of the hcp structure and the {110} plane of the bcc structure.

FIG. 4 is a plan view showing a matching relationship between a {110} plane of a bcc structure and a {111} plane of a CaF ₂ type structure.

FIG. 5 is a sectional view of the magnetic recording medium according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram of an embodiment of a magnetic recording device according to the present invention.

[Explanation of symbols]

11 ... Protective film 12 ... Magnetic film 13 ... 1st Underlayer film 14 ... 2nd Underlayer film 15 ... Nonmagnetic substrate 51, 51 '... Protective film 52, 52' ... Magnetic film 53, 53 '... hcc structure bcc structure Underlayer film 54, 54 'having ... CaF ₂ type underlayer film 55 Glass substrate 61 Magnetic recording medium 62 Magnetoresistive element reproducing composite head 63 Actuator 64 Voice coil motor 65 Recording reproducing circuit 66 Positioning circuit 67 ... Interface control circuit

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

Claims (11)

[Claims] 1. A magnetic recording medium comprising a non-magnetic substrate, at least two underlayer films provided on the non-magnetic substrate, and a magnetic film provided on the two underlayer films, the magnetic film Has a hexagonal close-packed structure, and a first underlayer film provided directly under the magnetic film of the two-layer underlayer film has a body-centered cubic structure and a second underlayer film provided directly under the first underlayer film. The base film is C
A magnetic recording medium having an aF ₂ type crystal structure. 2. A preferred orientation plane of the magnetic film is {1101}.
2. The magnetic recording medium according to claim 1, wherein the first underlayer has a preferential orientation plane of {110} and the second underlayer has a preferential orientation plane of {111}. 3. The first base film and the second base film,
Both are made of a non-magnetic material.
Or the magnetic recording medium according to 2. 4. The magnetic recording medium according to claim 1, wherein the magnetic film is made of Co or an alloy containing Co as a main component. 5. The first underlayer is made of Cr, Mo, W,
5. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is made of at least one material selected from the group consisting of V, Nb, Ta, and alloys containing these elements as a main component. 6. The second underlayer film is made of CaF ₂ , Sr.
F _2, BaF _2, SrCl ₂ or any one of claims 1 to 5, characterized in that it consists of at least one material selected these inorganic compounds from the group consisting of a mixed crystal whose main component Magnetic recording medium. 7. The magnetic film is made of Co or an alloy containing Co as a main component, and the first underlayer is made of Cr or an alloy containing Cr as a main component. 2. A magnetic recording medium according to item 1. 8. The first underlayer film is made of Cr or an alloy containing Cr as a main component, and the second underlayer film is made of CaF ₂ , Sr.
The magnetic recording medium according to any one of claims 1 to 3, which is composed of F ₂ or a mixed crystal containing these inorganic compounds as a main component. 9. When the a-axis lattice constant of the crystal structure of the magnetic film is a (hcp) and the a-axis lattice constant of the crystal structure of the first underlayer is a (bcc), −0. 1 ≦ {a (hcp) × 2-a (bcc) ×
The magnetic recording medium according to claim 1, wherein 3 ^1/2 } / a (bcc) × 3 ^1/2 ≦ 0.1. 10. The magnetic recording medium according to claim 1, further comprising a protective film on the magnetic film. 11. A magnetic recording medium according to claim 1, a holder for holding the magnetic recording medium, and a magnetic film of the magnetic recording medium for recording information. A magnetic recording apparatus comprising: a magnetic head for reproducing, a moving means for moving a relative position between the magnetic head and the magnetic recording medium, and a control means for controlling these.