JPH06162472A - Magnetic recording medium with multilayered film and magnetic storage - Google Patents

Abstract

PURPOSE:To increase the strength of a magnetic recording medium with a multilayered film to sliding on a magnetic head as well as to prevent the reduction of the coercive force of the medium. CONSTITUTION:The objective magnetic recording medium has a nonmagnetic substrate 11, plural magnetic layers 13, 15 formed on the substrate 11 and nonmagnetic middle layers 14 each interposed between the magnetic layers 13, 15. At least a region in each of the middle layers 14 in the thickness direction is made of a layer of C, B, Si, Ge or an Ni-P alloy, a layer based on C, B, Ge, Si or an Ni-P alloy, a layer of nitride of C, B, Si, Ge or an Ni-P alloy or a layer of oxide of B, Ge or an Ni-P alloy. By this structure, noise can be reduced without reducing the coercive force of the magnetic recording medium, the strength of the medium can be increased by 20-30% as compared with that of a conventional medium and the objective high density and high reliability magnetic storage having >=600 megabit/in<2> recording density and >=150,000hr MTBF is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer magnetic recording medium and a magnetic storage device, and more particularly to a magnetic storage device having an ultrahigh recording density of 600 megabits per square inch or more for use as an auxiliary storage device of a computer and the like. The present invention relates to a magnetic recording medium suitable for realizing a recording density.

[0002]

2. Description of the Related Art As the information-oriented society advances, the amount of information that can be dealt with on a daily basis is increasing. Along with this, the demand for higher recording density and higher storage capacity for magnetic storage devices is increasing. In the case of increasing the recording density of a magnetic disk device which is a typical magnetic storage device, generally, in a conventional electromagnetic induction type magnetic head, the reproduction output is lowered and the reproduction becomes difficult. Therefore, as described in JP-A-51-44917, a high output can be obtained even if the recording magnetic head and the reproducing magnetic head are separated and the reproducing magnetic head has a high recording density. The use of a magnetic head utilizing the magnetoresistive effect has been studied. The magnetoresistive effect type magnetic head has a high reproducing sensitivity and a small resistance of the head, so that the thermal noise generated is small. For this reason, the noise caused by the magnetic recording medium, which has been hidden by the large noise generated from the electromagnetic induction type magnetic head in the related art, now accounts for a large proportion of the noise of the entire apparatus.

Therefore, in order to realize a high recording density by using a magnetoresistive magnetic head, it is necessary to reduce noise (medium noise) caused by the magnetic recording medium.
As a method of reducing medium noise, Japanese Patent Laid-Open Publication No. 63-146219 discloses a magnetic recording medium having a multilayer structure including a plurality of magnetic layers and a non-magnetic intermediate layer for reducing magnetic coupling between the magnetic layers. Is disclosed.

[0004]

The intermediate layer used in the above-mentioned magnetic recording medium having a multilayer structure (hereinafter also referred to as a multilayer magnetic recording medium) is suitable when used as an underlayer of a Co-based alloy thin film magnetic recording medium. Cr, which provides various characteristics, has been widely studied. In the multilayer magnetic recording medium using the Cr intermediate layer,
Although medium noise is reduced as compared with a magnetic recording medium having a single magnetic film, there is a problem that coercive force is lowered.
When the coercive force decreases, the width of the magnetization transition region generally increases, which makes it difficult to increase the recording density.

Another major problem in increasing the recording density of a magnetic disk device is the strength of the magnetic recording medium against sliding by a magnetic head. When the recording density is increased by shortening the bit interval, the amount of magnetic flux leaking from the medium to the external space rapidly decreases with the distance from the medium surface.
Therefore, in order to obtain a sufficient reproduction output, it is necessary to reduce the distance between the magnetic recording medium and the magnetic head. In addition, it is necessary to reduce the distance between the magnetic recording medium and the magnetic head in order to obtain the steep recording magnetic field distribution required for recording a minute bit. When the distance between the magnetic recording medium and the magnetic head becomes small, the probability that the medium and the magnetic head will come into contact with each other becomes high at the time of start and stop or due to slight disturbance. Therefore, higher strength is required for the magnetic recording medium. This point has not been sufficiently taken into consideration in the conventional multilayer magnetic recording medium.

A first object of the present invention is to provide a magnetic recording medium which prevents a decrease in coercive force of the multilayer magnetic recording medium and at the same time enhances the strength against sliding of the magnetic head, and which is suitable for high density recording. . A second object is to provide a highly reliable magnetic storage device capable of recording and reproducing high density information by using this magnetic recording medium.

[0007]

The first object is a multilayer having a non-magnetic substrate, a plurality of magnetic layers formed on the non-magnetic substrate, and a non-magnetic intermediate layer arranged between the magnetic layers. In the film magnetic recording medium, at least a part of the non-magnetic intermediate layer in the layer thickness direction is C, B, Si, Ge, Ni-P.
Alloy layer, layer containing C, B, Ge, Ni-P alloy as the main component, or nitride layer of C, B, Si, Ge, Ni-P alloy or B, Ge, Ni-P alloy This is achieved by using an oxide layer. The second object has a magnetic recording medium, a drive unit for rotationally driving the magnetic recording medium, a recording / reproducing magnetic head, and means for moving the magnetic head relative to the magnetic recording medium. In the magnetic storage device, a reproducing portion of the recording / reproducing magnetic head is constituted by a magnetoresistive effect magnetic head, and further, the magnetic recording medium is constituted by a magnetic recording medium capable of achieving the first object. It is achieved by

[0008]

In a multi-layer magnetic recording medium, various techniques for ensuring sufficient mechanical strength and preventing a decrease in coercive force due to the multi-layered magnetic film have been studied. Intermediate layer is C, B, Si, Ge, Ni-P alloy layer, or layer containing C, B, Ge, Ni-P alloy as a main component, or C, Si, B, Ge, Ni-P alloy It was found that sufficient mechanical strength can be ensured and reduction in coercive force can be prevented by using the nitride layer or the oxide layer of B, Ge or Ni-P alloy. Curve 1 in FIG. 1 is the relationship between the thickness of the intermediate layer and the coercive force when the intermediate layer is C. In this magnetic recording medium, a CoPt alloy magnetic layer having a thickness of 20 nm is laminated on two surfaces of a Ni-P plated Al-Mg alloy substrate with a C intermediate layer interposed therebetween, and further a C layer having a thickness of 70 nm is formed thereon. The layers are laminated as a protective film.
The point where the thickness of the intermediate layer is zero corresponds to the CoPt alloy single layer film having a thickness of 40 nm. Also, the Pt concentration in the CoPt alloy is 20 at.
%. Curve 2 in FIG. 1 shows, for comparison, the result when Cr, which is widely studied at present, is used as the intermediate layer.

As shown in FIG. 1, when the intermediate layer is made of Cr, the coercive force is sharply lowered by the insertion of the intermediate layer, whereas when the intermediate layer is made of C, the coercive force is decreased. Is not seen. As a result of comparing the noises generated from these media, the media in which the two-layer magnetic film is laminated has about 30% lower media noise than the single-layer magnetic film media, and the difference between when the intermediate layer is Cr and C is different. Was not seen. Further, the strength of these media was evaluated by a spherical sliding test using a sapphire spherical slider having a curvature of 30 mm. The pressing load of the spherical slider is 10 gf, and the relative velocity with the magnetic recording medium is 1
The magnetic disk was rotated at 0 m / s. Comparing the number of sliding passes until the magnetic film is peeled off, the medium using the C intermediate layer is 2 to 3 more than the medium using the Cr intermediate layer.
A relatively long life was obtained. As described above, by using C as the intermediate layer, it is possible to obtain a low noise multilayer magnetic recording medium having higher coercive force and sliding strength than those of the conventional ones.
As a magnetic film, instead of CoPt, CoNi, CoFe, C
oCr, CoIr, CoW, CoRe, CoNiZr, CoCrP
The same effect was obtained when a Co-based alloy magnetic film containing t, CoCrTa or CoNiCr as a main component was used.

Regarding the above-mentioned prevention of decrease in coercive force, the same effect was obtained when a B, Ge or Ni-P intermediate layer was used instead of the C intermediate layer. Also, C, B, S
At least one element or alloy selected from the first group consisting of i, Ge, and Ni-P alloys is added with Zr, Nb, Ti,
A compound to which at least one element selected from the second group consisting of Hf, Ta, Cr, Mo and W is added, or T
Oxides such as a2O5 and ZrO2, or (Zr-Nb)
The same effect was obtained when a nitride such as N or Si3N4 was used as the intermediate layer. In this case, the addition amount of the element selected from the second group with respect to the C, B, Si, Ge or Ni-P alloy is preferably less than 50 at% and preferably 20 at% or less.

Si and Ge used in place of C, like C, are elements having a diamond lattice structure. Also,
B and the Ni-P alloy have an amorphous structure. Any of these elements or compounds, oxides, nitrides, and other intermediate layers that have been effective in preventing a decrease in coercive force have a structure that is completely different from the dense hexagonal lattice structure of the Co-based alloy magnetic layer. There is no epitaxial relationship, that is, crystalline connection between the magnetic layers formed above and below the intermediate layer. On the other hand, it is known that a Co-based alloy magnetic layer having a dense hexagonal lattice structure is epitaxially grown on a Cr layer having a body-centered cubic lattice structure. From this, it is considered that the mechanism for preventing the decrease in the coercive force is related to breaking the crystalline connection between the magnetic layers. In connection with this, compared with the case where the conventional Cr or Cr alloy is used as the intermediate layer, the medium noise can be reduced by 10 to 20% even if the multilayer structure is the same.

Regarding the sliding strength of the medium, even when using the intermediate layer, which is effective in preventing the above-mentioned decrease in coercive force, a strength equal to or higher than that when using the Cr intermediate layer was obtained. Among them, when a C, B, Si, Ge, Ni-P alloy layer or an intermediate layer containing C, B, Si, Ge, Ni-P alloy as a main component is used, a particularly remarkable increase in sliding strength is obtained. was there. Among the above-mentioned intermediate layers, the intermediate layer composed of C, B, Si, Ge, and Ni-P exhibits particularly high hardness and adhesion. Therefore, the hardness of the intermediate layer is a mechanism for increasing the sliding strength. Is considered to be related to adhesion.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 2 is a sectional view showing the layer structure of an embodiment of the multilayer magnetic recording medium according to the present invention. The multilayer magnetic recording medium of the present embodiment has an Al-plated Ni-P alloy surface.
-A first magnetic layer 13, an intermediate layer 14, and a second magnetic layer 13 which are sequentially formed by a sputtering method on a non-magnetic substrate 11 made of Mg alloy, Ti alloy, tempered glass, organic resin, ceramics or the like. The magnetic film 15 and the C protective layer 16 and the lubricating layer 17 formed thereon. Here, the first magnetic film 13 and the second magnetic film 15 are Co-10 at% Cr-8 at% Pt alloy layers having a thickness of 20 nm, and the intermediate layer 14 is a C layer having a thickness of 10 nm. The thickness of the C protective layer 16 was 40 nm. The lubricating layer 17 is an adsorbent perfluoroalkylalkyl polyether.

The coercive force measured by a sample vibrating magnetometer was 2100 Oersted. This value is a single layer prepared by replacing the above three layers of the first and second magnetic layers and the intermediate layer with one Co-10 at% Cr-8 at% Pt alloy layer having a thickness of 40 nm for comparison. A value equal to or higher than that of the coercive force of 2080 Oersted of the film magnetic recording medium was obtained. Next, the recording / reproducing characteristics were measured. Relative speed of medium and magnetic head is 12m / s, levitation spacing is 80nm
Then, the evaluation was performed using a magnetic head in which an electromagnetic induction type thin film magnetic head for recording having an effective gap length of 350 nm and a magnetoresistive effect type magnetic head for reproduction were combined. As a result, the medium noise was reduced by about 30% as compared with the comparative single-layer magnetic recording medium. Further, the medium noise was about 20% smaller than the case where Cr having the same layer thickness instead of C was used as the intermediate layer.
The half-power recording density (D50) was 76 kFCI, which was equivalent to that of the single-layer magnetic recording medium. Further, a test (contact start / stop: hereinafter abbreviated as CSS) in which the magnetic head is brought into contact with the magnetic recording medium by repeating the rotation / stop of the magnetic disk was performed 30,000 times, and then the error rate of recording / reproducing was measured. As a result, no increase in error rate was observed after CSS.

As a material for the intermediate layer 14, instead of C, B, Si, Ge, Ni-P alloy, Ta2O5,
Similar effects were obtained when ZrO2, (Zr-Nb) N, Si3N4, etc. were used. Also, C, B, Si, Ge, Ni
At least one element or alloy selected from the first group consisting of -P alloys with Zr, Nb, Ti, Hf, Ta, C
at least 1 selected from the second group consisting of r, Mo and W
The same effect was obtained when the compound to which the seed element was added was used as the intermediate layer 14. As the material of the magnetic film,
Instead of CoCrPt, CoPt, CoNi, CoFe,
CoCr, CoIr, CoW, CoRe, CoNiZr, CoCrT
The same effect was obtained when a or CoNiCr was used.

The above-mentioned multilayer magnetic recording medium has an intermediate layer 14
With two layers of magnetic films laminated 13 and 15. If the thickness of each of the magnetic layers 13 and 15 is 14 nm and the intermediate layer and the magnetic layer are inserted in this order between the second magnetic layer 15 and the C protective layer 16 to form three magnetic layers, the medium It is possible to further reduce noise by about 20%. Also in this case, no increase in error rate was observed after CSS 30,000 times.

<Embodiment 2> FIG. 3 is a sectional view showing the layer structure of another embodiment of the multilayer magnetic recording medium according to the present invention.
The multilayer magnetic recording medium of the present embodiment is similar to the first embodiment in that the surface is plated with a Ni—P alloy, Al—Mg alloy, Ti alloy, tempered glass, or non-magnetic material composed of organic resin, ceramics, or the like. It is formed on the substrate 11. A Cr underlayer 12, a first magnetic layer 13, an intermediate layer 14, a second magnetic film 15 and a C protective layer 16 are sequentially formed on the non-magnetic substrate 11 by a sputtering method, and lubrication is further performed thereon. It is a structure in which the layer 17 is formed by coating. Example 1
Similarly to the above, the first magnetic film 13 and the second magnetic film 15 are a Co-10 at% Cr-8 at% Pt alloy layer having a thickness of 20 nm,
The intermediate layer 14 was a C layer having a thickness of 10 nm, the C protective layer 16 had a thickness of 40 nm, and the lubricating layer 17 was an adsorptive perfluororoalkylpolyether. The Cr underlayer 12 has a thickness of 50 nm.

The coercive force measured by the sample vibrating magnetometer was 2200 Oersted. This value is 3 for the first and second magnetic layers 13 and 15 and the intermediate layer for comparison.
40nm thick Co-10at% Cr-8at%
A value equal to or higher than the coercive force of 2140 Oersted of the single-layer magnetic recording medium produced by replacing with one Pt alloy layer was obtained. Next, the recording / reproducing characteristics were measured under the same conditions as in Example 1. The medium noise was reduced by about 30% as compared with the comparative single-layer magnetic recording medium. The half-power recording density (D50) was 80 kFCI, and a value equivalent to that of the single-layer magnetic recording medium was obtained. As a result of measuring the error rate after CSS was performed 30,000 times, no increase in the error rate after CSS was observed.

As a material for the intermediate layer, instead of the above C,
The same effect was obtained when B, Si, Ge or Ni-P alloy was used. Also, C, B, Si, Ge, Ni-
Zr, Nb, Ti, Hf, Ta, Cr, at least one element or alloy selected from the first group of P alloys,
The same effect was obtained when the compound containing at least one element selected from the second group consisting of Mo and W was used as the intermediate layer 14. In addition, NbO, MgO,
The same effect was obtained when ZrN, TiN, HfN, etc. were used. As the material of the magnetic film, instead of CoCrPt, CoPt, CoNi, CoFe, CoCr, CoMo, C
oW, CoRe, CoNiZr, CoCrTa or CoNiCr
The same effect was obtained by using. Similar to the method described in Example 1, when the number of magnetic layers was three, the medium noise was further reduced by about 20% as compared with the case of two magnetic layers. Also in this case, no increase in error rate was observed after CSS 30,000 times.

<Embodiment 3> FIG. 4 is a diagram showing the construction of an embodiment of a magnetic memory device according to the present invention. FIGS. 4 (a) and 4 (b) are a schematic plan view and a sectional view, respectively. A magnetic storage device was manufactured by incorporating four multilayer magnetic recording media 1 and 2. This apparatus has a well-known configuration including a magnetic recording medium 18, a drive unit 19 for rotationally driving the magnetic recording medium 18, a magnetic head 20 and a driving unit 21 therefor, and a recording / reproducing signal processing unit 22 of the magnetic head 20. It is a magnetic storage device. In this magnetic storage device, the magnetic recording medium 1
8 is composed of the multilayer magnetic recording medium of Examples 1 and 2, and a composite magnetic head in which a recording electromagnetic induction type thin film magnetic head and a reproducing magnetoresistive effect type magnetic head are combined is used as the magnetic head 20. When the device was made into a device, the intermediate layer 14 of the multilayer magnetic recording medium of the present embodiment was set to Cr.
As compared with the magnetic storage device configured by using the conventionally known multi-layered magnetic recording medium replaced by, the output half-recording density is increased by about 30%, so that the capacity can be increased 1.3 times or more. In particular, since the medium noise is low in the present embodiment, by using a magnetoresistive effect type magnetic head as the reproducing head instead of the electromagnetic induction type magnetic head, it is possible to realize a larger capacity than ever.

By performing signal processing on the input / output signals of the magnetic head, it was possible to record / reproduce information of 600 megabits per square inch with a head flying height of 70 nm. Moreover, by using the magnetic head of the present invention,
The life of the device was extended, and MTBF was able to reach 150,000 hours. When the recording density was 300 megabits per square inch, it was possible to record and reproduce with a head flying height of 110 nm, and MTBF could achieve 300,000 hours.

[0022]

The magnetic recording medium of the present invention can reduce the noise of the magnetic recording medium without lowering the coercive force. By combining with a magnetoresistive effect type magnetic head having high reproducing sensitivity, recording / reproducing is possible even at a high recording density of 600 megabits per square inch or more. Further, according to the present invention, the sliding strength of the medium can be increased by 20 to 30% as compared with the conventional one, and therefore, 600 per 1 square inch can be obtained.
With a high recording density of megabits, a mean failure interval of 150,000 hours or more (hereinafter abbreviated as MTBF) can be realized. When the recording density is 300 megabits per square inch, MTBF of 300,000 hours or more can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an intermediate layer thickness and a coercive force in a multilayer magnetic recording medium of the present invention and a conventional multilayer magnetic recording medium.

FIG. 2 is a cross-sectional view showing the layer structure of an example of a multilayer magnetic recording medium according to the present invention.

FIG. 3 is a cross-sectional view showing the layer structure of another embodiment of the multilayer magnetic recording medium according to the present invention.

4A and 4B are respectively a plan view and an AA ′ sectional view of an embodiment of a magnetic storage device according to the present invention.

[Explanation of symbols]

1: Curve showing the relationship between the intermediate layer thickness and the coercive force in the multilayer magnetic recording medium of the present invention 2: Curve showing the relationship between the intermediate layer thickness and the coercive force in the multilayer magnetic recording medium of the comparative example 11: Nonmagnetic Substrate 12: Cr underlayer 13: First magnetic layer 14: Intermediate layer 15: Second magnetic film 16: C protective layer 17: Lubrication layer 18: Magnetic recording medium 19: Magnetic recording medium drive unit 20: Magnetic head 21 : Magnetic head drive unit 22: Recording / reproducing signal processing system

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Yamamoto 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Masatoshi Takeshita 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Inside the Central Research Laboratory (72) Inventor Yasuo Yaku 1-280, Higashi Koigokubo, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Akira Ozaki 1-280, Higashi Koigokubo, Kokubunji, Tokyo Hitachi, Ltd. Central Research Center (72) Researcher, Tanahashi Researcher, Central Research Laboratory, Hitachi, Ltd. 1-280, Higashi Koigokubo, Kokubunji, Tokyo

Claims (11)

[Claims] 1. A magnetic recording medium having a plurality of magnetic layers formed directly on a non-magnetic substrate or via an underlayer and a non-magnetic intermediate layer arranged between the magnetic layers, wherein the non-magnetic intermediate layer is provided. Of at least a partial region in the layer thickness direction of C, B, S
i, Ge, Ni-P alloy layer, or C, B, Ge, Ni-P
A layer containing an alloy as a main component, or C, B, Si, Ge,
A multilayer magnetic recording medium comprising a nitride of Ni-P alloy or an oxide layer of B, Ge, Ni-P alloy. 2. At least a partial region in the layer thickness direction of the non-magnetic intermediate layer is made of at least one element or alloy selected from the first group consisting of C, B, Si, Ge and Ni-P alloys. 2. The multi-layer film according to claim 1, comprising a compound layer to which at least one element selected from the second group consisting of Zr, Nb, Ti, Hf, Ta, Cr, Mo and W is added. Magnetic recording medium. 3. At least a partial region of the non-magnetic intermediate layer in the layer thickness direction is C, B, Si, Ge, Ni-P alloy, Zr, N.
2. The multilayer magnetic recording medium according to claim 1, comprising a nitride layer of at least one element or alloy selected from the group consisting of b, Ti, Hf, Ta, Cr, Mo and W. 4. The multilayer magnetic recording medium according to claim 1, 2 or 3, wherein the plurality of magnetic layers are Co-based alloy layers. 5. The multilayer magnetic recording medium according to claim 1, 2, 3 or 4, wherein the surface of said non-magnetic substrate is an amorphous layer. 6. The multilayer magnetic recording medium according to claim 1, 4 or 5, wherein at least a part of the non-magnetic intermediate layer comprises C or a layer containing C as a main component. 7. The nonmagnetic intermediate layer comprises at least a portion of Ni.
6. The multilayer magnetic recording medium according to claim 1, which is composed of a layer containing a -P alloy or a Ni-P alloy as a main component. 8. A magnetic storage comprising a magnetic recording medium, a drive unit for rotationally driving the magnetic recording medium, a recording / reproducing magnetic head, and means for moving the magnetic head relative to the magnetic recording medium. In the apparatus, the magnetic recording medium comprises the multilayer magnetic recording medium according to claim 1, 2, 3, 4, 5, 6 or 7. 9. The magnetic storage device according to claim 8, wherein the recording / reproducing magnetic head comprises an inductive magnetic head for recording and a magnetoresistive effect magnetic head for reproduction. 10. A high recording density of 600 per square inch.
10. The magnetic storage device according to claim 8, wherein a mean time between failures (MTBF) is 150,000 hours or more at megabits or more. 11. A high recording density of 300 per square inch.
10. The magnetic storage device according to claim 8, wherein a mean time between failures (MTBF) is 300,000 hours or more at megabits or more.