JPH0757233A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce disk noise by forming a nonmagnetic underlayer on each side of a substrate and then forming an alloy film having a close-packed hexagonal structure and a prescribed compsn. and magnetic layers each having a prescribed compsn. CONSTITUTION:A substrate 11 of an Al alloy contg. 4% Mg is prepd., Ni-12wt.% P plating is formed on both sides of the substrate 11 in 20mum thickness and the surface of the plating is finely grooved and ground to 15mum thickness. This substrate 11 is washed, dried and set in a sheet feed type film forming device using a DC magnetron cathode, Ni-P is sputtered to form underlayers 12, 12' in 50nm thickness and Co-15at.% Cr-8at.% Pt films are formed as lower magnetic layers 13, 13' in 12nm thickness. Alloy films 14, 14' of Co-20at.% Cr-4at.% Ta-0.2at.% Nb are further formed in 0.5nm thickness, Co-Cr-Pt films having the same compsn. as the magnetic layers 13, 13' are formed as upper magnetic layers 15, 15' in 12nm thickness and carbon films are formed as protective layers 16, 16'. A lubricant such as perfluoroalkyl polyether is stuck on the layers 16, 16'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic recording medium, and particularly to a thin film magnetic recording medium excellent in low noise and high recording density characteristics, and a read magnetic head and a write inductive head using a magnetoresistive effect. The present invention relates to a magnetic recording medium suitable for use in a combined magnetic storage device.

[0002]

2. Description of the Related Art As a material of a medium capable of high density recording, a Co alloy film formed on a pure Cr film or a Co-N film is used.
An i-Pt-based thin film has been proposed and partially put into practical use. The Co alloy magnetic film is, for example, Eye Triple E
・ Transaction on Magnetics (IEEE Tr
An Co.-Cr-Ta type thin film is used as described in ans. Magn.) Volume 23 (1987), page 122.

There is also a movement to further improve the reproduction output by using a thin film medium having a magnetic layer having a multilayer structure (for example, JP-A-1-173313 and JP-A-1-173313). 217723). By stacking a magnetic layer and a non-magnetic layer, an output improvement can be expected in a Co-based alloy containing Ni, a Co-Pt alloy, or the like.

However, as described in JP-A-3-283016, in these media, noise and bit shift, which are considered to be derived from the transition area between adjacent bits at the time of recording, are larger than those in the conventional coating type media. However, it is necessary to improve noise and bit shift in order to achieve higher recording density. Against this background, Co-
A magnetic recording medium has been proposed in which a Cr-Ta based magnetic layer and a Cr based thin film non-magnetic layer are alternately repeated.

In addition, Co-Cr-P is used as a material for the magnetic layer.
When using a t-alloy, i-triple-e-Transaction on Magnetics (IEEE Trans.
n.) As described in Volume 26 (1990), page 2706, when the thickness of the magnetic thin film which is alternately repeated is constant,
It has also been shown that increasing the number of non-magnetic intermediate layers reduces noise.

[0006]

In the medium according to the prior art, since it is necessary to form a non-magnetic metal intermediate layer, at least one Cr-based thin film non-magnetic layer is formed after the non-magnetic underlayer and the magnetic layer are formed. The intermediate layer and the magnetic layer must be formed. Therefore, there is a drawback that the crystallinity of the upper magnetic layer is lowered due to the formation of the non-magnetic intermediate layer having a different crystal structure, and the magnetic characteristics are lowered. Further, there is a limit to the reduction of medium noise at high recording density, and there is a restriction to increase the capacity per unit volume of the magnetic storage device. Further, in mass production, it is necessary to control the film thickness of the non-magnetic intermediate layer from the viewpoint of reducing the fluctuation of the electromagnetic conversion characteristics for each medium.

An object of the present invention is to provide a magnetic recording medium of high output and low noise without deteriorating the crystallinity and magnetic characteristics of the upper magnetic layer.

[0008]

In the magnetic recording medium of the present invention, after a non-magnetic underlayer is formed on a substrate, a Co-Cr-Ta alloy film having a dense hexagonal crystal structure is formed as a ferromagnetic layer, for example. Then, a crystal structure also has a close-packed hexagonal structure on the surface, and after forming a paramagnetic Co-Cr-Ta-T alloy intermediate layer, a ferromagnetic Co-Cr-Ta magnetic layer is further formed.

As described above, one feature of the present invention is to use the paramagnetic intermediate layer having the same crystal structure as the magnetic layer and to eliminate the conventional non-magnetic metal intermediate layer process having a different crystal structure.

As the non-magnetic underlayer, Ni-P thin film, C
It is preferable to use an underlayer composed of a thin film containing r or Cr as a main component.

At least one element of the element T contained in the paramagnetic Co-Cr-Ta-T alloy intermediate layer is mainly contained in a region of a paramagnetic material in the element group M constituting the medium. It is desirable that the alloy component contains only.

In the magnetic layer, a medium in which the layers are repeatedly stacked so as to include a plurality of regions having a low Co concentration and a high Cr concentration between the regions having a high Co concentration and mainly a paramagnetic substance in the film thickness direction between the regions having a high Co concentration in the magnetic layer In comparison with a medium in which a region having a low Co concentration and a high Cr concentration between the regions having a high Co concentration so as to include one region mainly in the film thickness direction in the film thickness direction is compared, the latter further reduces the medium noise. it can.

Residual magnetization Br [G] and film thickness t [μ of the magnetic layer
The magnetic head for reading using the magnetoresistive effect by using at least one medium having a product value of m] of 100 G · μm or more and 400 G · μm or less, more preferably 150 G · μm or more and 280 G · μm or less. A magnetic storage device is configured by combining the above and the writing inductive head. It is desirable that the read magnetic head and the write inductive head using the magnetoresistive effect are formed on the same element.

It is also possible to construct at least one magnetic recording medium of the present invention with an inductive head to form a magnetic storage device.

[0015]

The present inventor has found that it is possible to reduce medium noise at the time of recording / reproducing in a magnetic recording medium in which at least one region having a high Cr concentration and mainly a paramagnetic substance is included between the magnetic layers. It is considered that this is because the magnetic interaction can be reduced. Therefore, a non-magnetic underlayer and a thin film magnetic layer containing Co as a main component are sequentially formed on the substrate, and the Co concentration is low and the Cr concentration is high between the regions having a high Co concentration in the magnetic layer. It was considered that the structure including one region in the film thickness direction is very effective in reducing noise. Further, even in a structure in which a plurality of regions having a low Co concentration and a high Cr concentration and mainly a paramagnetic material are included in the film thickness direction between regions having a high Co concentration in the magnetic layer, magnetic interaction in the film thickness direction is caused. It was also found that the medium noise during recording and reproduction is further reduced. It is considered that this effect is also because the magnetic interaction between the ferromagnetic layers can be reduced mainly by forming the paramagnetic layer.

Furthermore, in a magnetic recording medium including at least one region having a high Cr concentration and mainly a paramagnetic substance between the magnetic layers, among the elements T contained in the region having a high Cr concentration and mainly a paramagnetic substance. , At least one element is included in the element group M that constitutes the medium, so that the alloy component T mainly contained only in a region that is a paramagnetic substance is included, so that the film thickness in this region can be easily controlled during mass production. Is possible.

When a plurality of regions, which are mainly paramagnetic substances, are provided in the film thickness direction, each Cr concentration is high and mainly the paramagnetic substance is obtained by mixing more than that number of additional elements T in each region independently. It is possible to evaluate the amount of each area.

When forming a region that is mainly a paramagnetic material, two types of intermediate layers can be formed mainly by adjusting the Cr composition in the Co alloy. For example Co-25at.
When the Co-23at.% Cr alloy film is formed under the thin film forming condition (1) such that the% Cr alloy film is a paramagnetic material, a film in which a ferromagnetic material and a paramagnetic material are mixed can be formed. Thin film forming conditions (1)
Compared with the above, by increasing the substrate temperature or decreasing the discharge gas pressure during thin film formation, the volume ratio of the ferromagnetic material having a lower Cr concentration than the average composition of the film tends to be higher.

Through such an intermediate layer mainly made of paramagnetic material, for example, the paramagnetic material and the ferromagnetic material are allowed to coexist or the ratio thereof is changed, whereby the magnetic mutual relation between the upper magnetic material and the lower magnetic material is made. It has become possible to reduce the action. The tendency that the existence ratio of the ferromagnetic material changes depending on the conditions for forming the intermediate layer is not limited to the Co-Cr binary system, and is the same when a few atomic% of the third element is added. It was Considering the lattice mismatch, the composition of the intermediate layer can be selected according to the average atomic size of the lower magnetic layer. Additive element T is 10 ⁹ / c per unit area of film surface
If it is contained in m ² or more, it can be quantitatively evaluated by total reflection fluorescent X-ray analysis or the like. Therefore, in order to form a region containing the additive element T, it is only necessary to add a trace amount of T. The reason why T is preferably Nb, Ti or the like is as follows. The energy values of these characteristic X-rays used for detecting the elements constituting other media do not overlap with the energy values of the characteristic X-rays of Nb and Ti, and Nb and Ti are mixed when other constituent layers are formed. Because there is no fear of.

On the other hand, when a Co-30 at.% Cr alloy film having a higher Cr composition than Co-25 at.% Cr is formed under the thin film forming condition (1), it is a paramagnetic substance and a non-magnetic amorphous film. Was mixed. Compared to the thin film forming condition (1), by lowering the substrate temperature or increasing the discharge gas pressure during thin film formation, for example, “Sputtering Phenomenon, The University of Tokyo Press, 1984, Yu Kanehara, p. As described above, the "self-shading effect" is generated, and the proportion of amorphous is higher than that of the paramagnetic material. However, by lowering the discharge gas pressure when forming the upper magnetic layer, It became possible to reduce the magnetic interaction of the lower magnetic body.

The reason why the underlayer made of a Cr-based thin film is used as the non-magnetic underlayer is that the easy axis of magnetization of the in-plane magnetized film continuously formed on the underlayer is highly oriented in the in-plane direction.

When reproducing using a read magnetic head utilizing the magnetoresistive effect, in the medium according to the present invention, the product of the residual magnetization Br [G] of the magnetic layer and the film thickness t [μm] is 100 G.・ Μ
m or more, 400 G ・ μm or less, more preferably 150 G ・ μm or more, 2
It must be 80 G · μm or less. The reason for this is to obtain a high S / N. The product of remanent magnetization Br and film thickness t is 400G ・ μ
If it is set to m or more, the S / N decreases. On the other hand, the film thickness t
When the value of the product of the residual magnetization Br and the residual magnetization Br is 100 G · μm or less, the output decreases.

When reproducing using an inductive head, the medium according to the present invention has a residual magnetization Br of the magnetic layer.
The value of the product of [G] and the film thickness t [μm] must be 100 G · μm or more and 400 G · μm or less, more preferably 300 G · μm or more and 400 G · μm or less. The value of the product of G] and the film thickness t [μm] is 100 G · μm or more because the film thickness t and the residual magnetization B
This is because the output decreases when the product of r is 100 G · μm or less.

[0024]

The present invention will be described with reference to the following examples.

Example 1 FIG. 1 is a sectional view showing a magnetic recording medium according to this example. In FIG. 1, 11 is tempered glass, plastic,
Substrate such as Ni-P plated Al alloy, 12, 12 'is Ni-
Metal underlayers such as P, Cr, Mo, W, Cr-Ti, Cr-Si, Cr-W, 13 and 13 'are Co-Ni-Cr, Co-Cr-Ta, Co-
Cr-Pt, Co-Cr-Zr, Co-Cr-Zr-Hf, Co-Ni-Z
Lower magnetic layer of r, Co-Ni-Ta, Co-Ni-Cr-Pt, etc., 1
4, 14 'is a region having a higher Cr concentration and a lower Co concentration than 13, 13', 15, 15 'is an upper magnetic layer similar to 13, 13', 16, 16 'is C, B, B ₄ C, Si-C, Co ₃ O ₄ , Si
A protective layer made of O ₂ , Si ₃ N ₄ , WC, Zr-WC, W-Mo-C-Ni, etc., each of which is formed as in the following example.

An aluminum alloy disk substrate 11 having a diameter of 130 mm, an inner diameter of 40 mm, and a thickness of 1.9 mm and containing 4% of magnesium is plated with Ni-12 wt.% P having a thickness of 20 μm on both surfaces, and then the plated surfaces are substantially concentric. To form fine grooves. The center line average surface roughness is 10 nm, and the Ni-12 wt.% P plating film thickness is 15
Polished to be μm. This kind of surface processing is generally called texture processing, but the groove direction of the texture is not limited to the circumferential direction, but if it is a structure that can avoid sticking of the head even with eccentric processing, Even if the thin film recording medium is formed on the substrate, there is no problem in electromagnetic conversion characteristics.

After washing and drying these substrates, the underlayer 1 was formed by using a single-wafer type film forming apparatus using a DC magnetron cathode.
Ni-P which becomes 2 and 12 'is sputtered to a thickness of 50 nm, and further Co-15at.% Cr-8at.% Pt film which becomes lower magnetic layers 13 and 13' is made to have thickness
2 nm is formed, and Co-20 at.% Cr-4 at.% Is formed on the surface of this magnetic layer.
Ta-0.2 at.% Nb alloy films 14 and 14 'were formed to a thickness of 0.5 nm.
A Co-Cr-Pt film having the same composition as 13 and 13 'was formed to a thickness of 12 nm as the upper magnetic layers 15 and 15', and a C film was formed as the protective layers 16 and 16 '. A lubricant such as perfluoroalkylpolyether was adhered on the C protective film.

Comparative Example 1 C / (Co-15at.% Cr-8at.% Pt) / where the magnetic film was formed as a single layer
A Cr medium was formed and the electromagnetic conversion characteristics were evaluated by a head utilizing the magnetoresistive effect. As a result, the magnitude of the solitary wave reproduction output of the medium formed in Comparative Example 1 was equal to the magnitude of the solitary wave reproduction output formed in Example 1. On the other hand, when signals were recorded at the same recording density on the medium formed in Comparative Example 1, the disk noise was 22% larger than the disk noise formed in Example 1.

Example 2 4 magnesium having a diameter of 130 mm, an inner diameter of 40 mm and a thickness of 1.27 mm was used.
% On both sides of aluminum alloy disc substrate 11 20
After applying Ni-12 wt.% P plating of μm, the same texture processing as in Example 1 was performed.

After the substrate was washed and dried, Cr was formed to a thickness of 50 nm as the underlayers 12 and 12 'in a single wafer type film forming apparatus, and further Co-10at.% Cr-4at.% Was formed as the lower magnetic layers 13 and 13'. 13n Ta film
m, and on the surface of this magnetic layer Co-21at.% Cr-4at.% Ta-0.
4 at.% Ti films 14 and 14 'were formed to a thickness of 4 nm. After this, further Co-10a having the same composition as 13, 13 'is formed as the upper magnetic layers 15, 15'.
A t.% Cr-4at.% Ta film was formed to a thickness of 13 nm, and a C film was formed as the protective layers 16 and 16 ′. The thickness of the C protective layer was 25 nm. A lubricant such as phenoxyamine was adhered to the C protective film.

Comparative Example 2 4 magnesium having a diameter of 130 mm, an inner diameter of 40 mm and a thickness of 1.27 mm was used.
% On both sides of aluminum alloy disc substrate 11 20
After applying Ni-12 wt.% P plating of μm, the same texture processing as in Example 1 was performed.

After washing and drying this substrate, Cr was formed in a thickness of 50 nm as the underlayers 12 and 12 'by a single-wafer type film forming apparatus, and further Co-10at.% Cr-4at.% Was formed as the lower magnetic layers 13 and 13'. 13 Ta film
Non-magnetic C immediately after the formation of nm without oxidizing the surface
An intermediate layer having a thickness of 4 nm was formed. Further, successively, as the upper magnetic layers 15 and 15 ', Co-10 at.% C having the same composition as that of 13 and 13'
A r-4 at.% Ta film is formed to a thickness of 13 nm, and the protective layers 16 and 16 'are made of C
A film was formed. The thickness of the C protective layer is 25 nm as in the second embodiment.
And A lubricant such as phenoxyamine was adhered to the C protective film. The value of the coercive force of these laminated films measured by a vibrating magnetometer was 1430 Oe in the laminated film described in Example 2, whereas it was 1160 Oe in the case where a non-magnetic Cr intermediate layer was provided. Was decreasing.

Example 3 (Cr-Ti) alloy underlayers 12 and 12 'were formed on a glass disk 11 having a diameter of 3.5 inches and a thickness of 0.8 mm in the same manner as in Example 1. Co-15.4 at.% When forming the magnetic layers 13 and 13 'to 20 nm
When a Cr-8 at.% Pt alloy is formed to a thickness of 4 nm for the intermediate layers 14 and 14 ', a Co-23 at.% Cr-4 at.% Ta-0.3 at.% Nb alloy is used to form a magnetic layer 15 and 15' for 20 nm. When doing Co-12 at.% Cr-4 at.
A magnetic recording medium was formed in the same manner as in Example 1 except that the% Ta alloy was used.

Comparative Example 3 After forming 13 and 13 'as the magnetic layer described in Example 3, Co-
Non-magnetic Cr intermediate layers 14 and 14 'are provided at 4 nm in place of the 25 at.% Cr-4 at.% Ta-0.3 at.% Nb alloy intermediate layer, and then the magnetic layer 1 is formed.
Formed 5, 15 '. A magnetic recording medium was formed in the same manner as in Example 3 except this. Samples of 8 mm square were cut out from these discs and subjected to θ-2θ scanning with an X-ray diffractometer to evaluate crystallinity. As a result, in the sample manufactured in Example 3, 11 of the Co alloy magnetic layer having the hcp structure was obtained.
The 0 diffraction integrated intensity was 1.8 times or more higher than that of the sample prepared in Comparative Example 3, and it was revealed that the crystallinity of the upper magnetic layer can be improved by using the intermediate layer having the same crystal structure as the ferromagnetic material.

Example 4 As shown in FIG. 2, using an in-line sputtering device,
A 50 nm thick Cr underlayer 12, 12 ', a lower magnetic film 13, a lower magnetic film 13, on the glass-carbon substrate 11 by DC magnetron sputtering.
After forming a Co-12 at.% Cr-2 at.% Ta film having a thickness of 9 nm as 13 ', a Co-23 having a thickness of 0.5 nm is used as the intermediate layers 14 and 14'.
At.% Cr-2 at.% Ta-0.1 at.% Fe-0.5 at.% Nb film is formed. Further, the magnetic layer 2 having the same thickness as the lower magnetic layers 13 and 13 '
5,12 'as Co-12at.% Cr-2at.% Ta film, intermediate layer 2
4,24 '0.5-nm thick Co-23 at.% Cr-2 at.% Ta-
After forming a 0.1 at.% Fe-0.5 at.% Ti film, Co-12 is formed as upper magnetic layers 15 and 15 'having the same thickness as the lower magnetic layers 13 and 13'.
At.% Cr-2 at.% Ta film and C film were formed as protective films 16 and 16 '.

Example 5 Example 5 was repeated except that the medium thickness was changed so that the product of the magnetic layer thickness and the residual magnetization used in the medium described in Example 1 had a value of 360 G · μm. In the same manner as in No. 1, the electromagnetic conversion characteristics were evaluated using the inductive head. As a result, compared with the case where the magnetic layer is formed as a single layer film, the solitary-wave reproduction output does not change in the medium described in this example, but when a signal is recorded at the same recording density, the disk noise is reduced by about 20%. did. By combining at least one of this medium with a magnetic read head and a write inductive head using the magnetoresistive effect on the same element, a 70 kFCI
The above high-density magnetic recording was realized.

[0037]

The disk noise at high recording density can be reduced without deteriorating the magnetostatic characteristics and crystallinity. Further, by using the magnetic recording medium of the present invention, it is possible to provide a large-capacity magnetic storage device having a good S / N.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a magnetic recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 11 Substrate 12, 12 'Metal underlayer 13, 13' Lower magnetic layer 14, 14 'Intermediate layer 15/15' having a higher Cr concentration than that of 13, 13 'Upper magnetic layer 16, 16' Protective layer 24, 24 '13, 13' Intermediate layer with higher Cr concentration than 25, 25 'Magnetic layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Yonekawa 2880, Kozu, Odawara, Kanagawa Stock Company Hitachi Storage Systems Division (72) Inventor Atsushi Takagaki 2880, Kozu, Odawara, Kanagawa Hitachi, Ltd. Storage System Division (72) Inventor Naoto Endo 2880 Kozu, Odawara, Kanagawa Stock Company Hitachi Storage Systems Division (72) Inventor Katsuo Abe 2880 Kozu, Kanagawa Prefecture Storage Systems Division, Hitachi Co., Ltd.

Claims (6)

[Claims] 1. A nonmagnetic underlayer and a thin film alloy magnetic layer containing Co as a main component are sequentially formed on a substrate, and Co is formed in the magnetic layer.
A region having a low Co concentration and a high Cr concentration between the high-concentration regions mainly includes a paramagnetic substance in the film thickness direction, and is mainly a paramagnetic substance in the element group M constituting the medium. A magnetic recording medium comprising at least one alloy component T contained only in a region. 2. A nonmagnetic underlayer and a thin film alloy magnetic layer containing Co as a main component are sequentially formed on a substrate, and Co is formed in the magnetic layer.
A plurality of regions having a low Co concentration and a high Cr concentration, which are mainly paramagnetic substances, are included in the film thickness direction between the high concentration regions, and are mainly paramagnetic substances in the element group M constituting the medium. A magnetic recording medium comprising at least one alloy component T contained only in a region. 3. The magnetic recording medium according to claim 1 or 2, wherein the alloy component T mainly contained only in the paramagnetic material is selected from at least one element group consisting of Nb and Ti. . 4. The magnetic recording medium according to claim 1, wherein the non-magnetic underlayer is made of Cr or a thin film containing Cr as a main component. 5. The magnetic recording medium according to claim 1, wherein a value of a product of the residual magnetization Br and the film thickness t of the magnetic layer is 100 G · μm or more and 400 G · μm or less. 6. The magnetic recording medium according to claim 1, wherein the value of the product of the residual magnetization Br and the film thickness t of the magnetic layer is 150 G · μm or more and 280 G · μm or less.