JPH05197944A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having high recording density and excellent recording and reproducing characteristics. CONSTITUTION:This magnetic recording medium has a magnetic thin film having a compsn. represented by a formula Co100-a-b-x-y-zNiaCrbPtxMyOz (a, b, x, y and z are in atomic % where 0<=a<=15, 0<=b<=15, 0<x<=20, 0<y<=20, 0<z<=40, y+z<=40, a+b+x+y+z<=60 and M is at least one element selected from among Si, B, Zr, Al, Y, P, Ti, Sn and In.

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.

[0002]

2. Description of the Related Art In recent years, hard magnetic disks used as high-capacity recording media for computers have been required to have a higher recording density. Generally, in order to achieve the high recording density,
It is extremely important to increase the coercive force of the in-plane magnetized magnetic thin film that is the recording medium and reduce the medium noise.

The reason why the high coercive force is required is that the length a of the magnetization transition region of the magnetic section, which is the recording bit written by the magnetic head, depends on the in-plane coercive force H _c of the magnetic film. It is expressed as a = 2tM _r f (S ^* ) / H _c . Here, t is the film thickness of the magnetic film, and M _r is the residual magnetization. The f (S ^*) is a is represents that the function of the coercive force squareness ratio S ^*, f and the value of S ^* is large (S ^*) is reduced. Therefore, it can be seen from this relational expression that if H _c and S ^* are increased, a is decreased and higher density recording is achieved. The smaller a becomes, the higher density magnetic recording becomes possible.When recording and reproducing, the voltage generated in the head by the magnetic domain written in the magnetic film is differentiated and taken out as an output signal. The small value is because the magnetization is more rapidly inverted, that is, the time width of the output pulse which is the differential waveform thereof is narrowed.

The coercive force of a magnetic film of a small magnetic disk which is generally used at present is about 900 to 1500 Oe. Moreover, it is desirable that the value of S ^* is at least 0.7 or more. The coercive force has an upper limit here because the magnetic field generated by the writing head used is limited.

However, recently, it has become possible to fly the head at a lower height, and even if a head having the same magnetic field strength is used, a large magnetic field can be applied as the strength of the magnetic field exerted on the magnetic thin film. Further, the magnetic field material used for the head itself and the precision processing of the coil part due to advances in microfabrication have made it possible to increase the magnetic field generated by the head. Therefore, if the coercive force can be increased while maintaining the squareness ratio of the coercive force of the magnetic thin film to at least 0.7 or more by combining these head technologies and low flying height of the head, a higher density magnetic recording medium can be obtained. Can be created.

Magnetic thin film materials for in-plane magnetic recording media that are widely used at present include CoPt-based materials such as CoNiPt, CoNiCrPt and CoCrPt, and CoCr-based materials such as CoNiCr and CoCrTa combined with a Cr underlayer. As the coercive force, for example, at the residual magnetization of 3.0 × 10 ⁻³ emu / cm ² required for a general magnetic recording medium, the upper limit is about 1800 Oe. Of these, CoPt-based magnetic thin films include IEEE Trans.Magn.MAG-19 (1983) 1514 and J.Appl.Phy.
s.54 (1983) 7089, IEEE Trans.Magn.MAG-19 (1983) 1638, etc., a higher coercive force can be achieved by increasing the Pt composition to about 20 to 25 atom%. However, it is not suitable because it causes a significant increase in cost. Further, addition of such a large amount of Pt element causes a large decrease in residual magnetization, which is not preferable for recording and reproduction.

Therefore, it is difficult to industrially commercialize unless a high coercive force can be achieved with a low Pt composition of about 10%, which is currently costly. As such an attempt, it was reported that a high coercive force of 2000 Oe or more was achieved by forming a CoCrPtB film (Pt 6.5 at%) with B added on the Cr underlayer (14th Japanese Application Magnetics Society of Japan 8pB-18 (1990)), the manufacturing process requires a substrate temperature of 280 ° C and a substrate bias of -300V, which is a serious problem for mass production. According to Japanese Patent Laid-Open No. 3-84723, CoPt contains P, Si, Ge, B,
It is stated that a high coercive force magnetic film of 2000 Oe or more was created by adding elements such as Ga, Al, In, Sn, Sb and sputtering in Ar gas containing oxygen. The resulting magnetic film has a very low squareness ratio and a coercive force squareness ratio of less than 0.7, which is very low in practical use, and cannot be said to be excellent as a high-density recording medium.

Further, in the actual design of a hard magnetic drive, there is an optimum value of the coercive force in terms of recording / reproducing characteristics, especially overwriting characteristics, in combination with the head, and it is necessary to adjust the coercive force of the magnetic film. is there. Therefore, it must be possible to easily adjust the high coercive force and its coercive force during mass production without significantly changing other magnetic characteristics.

Further, for a magnetic recording medium, low noise caused by the medium at the time of recording / reproducing is also very important for achieving high density magnetic recording. In general, the medium noise of thin film media is dominated by the disorder of the magnetic domain structure in the domain transition boundary region, so-called "Zig-zag Domain" formation, which is greatly influenced by the crystal grain structure of the magnetic thin film. (J. Appl. Phys., 63, 3248 (1988)).

Therefore, in order to improve the medium noise, it is necessary to study the alloy components of the magnetic film and control the sputtering process in order to modify and control the crystal grain structure of the magnetic thin film. It has been generally found that the medium noise can be reduced by using a NiP sputter base film for a CoPt-based magnetic film (US Pat. No. 4,786,564). This utilizes the effect that the crystal grain structure of the NiP underlayer controls the crystal grain structure of the magnetic film.

However, according to the results of the study by the present inventor, this method alone is not sufficient for the noise characteristics required for future high-density magnetic recording, and therefore, a CoPt-based magnetic film on which a NiP sputter film is formed as an underlayer is used. It was concluded that it is necessary to improve the material and realize the further improvement of the medium noise by the synergistic effect of both. As described above, in the CoPt-based magnetic film having the NiP sputter film as the underlying layer, if the above-mentioned high coercive force and medium noise are achieved, it is expected that magnetic recording at a higher density will be achieved.

[0012]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and has at least a coercive force squareness ratio of 0.7 which is required in the future as a high density magnetic recording medium.
With the above, the coercive force at a remanent magnetization of 3.0 × 10 ^-3 emu / cm ² is 2000.
It is an object of the present invention to newly obtain a magnetic film having Oe or more and a low medium noise characteristic and a magnetic recording medium using the magnetic film.

[0013]

The present invention has been made to solve the above-mentioned problems, and Co _100-abxyz Ni _a
Cr _b Pt _x M _y O _z (where a, b, x, y, z are atomic%), and in this composition formula, 0 ≤ a ≤ 15, 0 ≤ b ≤ 1
5, 0 <x ≤ 20, 0 <y ≤ 20, 0 <z ≤ 40, y + z ≤ 40, a + b
+ x + y + z ≦ 60 and M is Si, B, Zr, Al, Y, P, Ti, Sn, I
A magnetic recording medium characterized by using a magnetic thin film which is at least one element selected from n.

The present invention is also based on a CoNiPt alloy, a CoCrPt alloy or a CoNiCrPt alloy, on which Si, B, Zr, Al,
At least one element selected from Y, P, Ti, Sn, In (M
Co _100-abxyz Ni _a Cr _b Pt _x M _y O _z characterized by being formed by a sputtering method using a target containing in advance an oxide (MO _d , 0 <d ≦ 5)
(Where a, b, x, y, z are atomic%), and in this composition formula, 0 ≤ a ≤ 15, 0 ≤ b ≤ 15, 0 <x ≤
20, 0 <y ≤ 20, 0 <z ≤ 40, y + z ≤ 40, a + b + x + y + z ≤ 6
And a method for producing a magnetic recording medium having a magnetic thin film in which M is at least one element selected from Si, B, Zr, Al, Y, P, Ti, Sn and In. is there.

As described above, as a high density magnetic recording medium in the future, it is particularly desirable that the coercive force squareness ratio is 0.7 or more and the in-plane coercive force is at least 2000 Oe or more. In the present invention, as a means for achieving this object, based on CoNiCrPt alloy, Si, B, Zr, Al,
A magnetic film is formed by a sputtering method using a target containing an oxide containing at least one element selected from Y, P, Ti, Sn, and In in advance. As a target producing method, a sintered target obtained by mixing and sintering powders of a magnetic alloy and an oxide, or a composite target in which oxide chips are evenly placed on the magnetic alloy target is used. It is also possible to use the so-called Co-sputtering method, in which the targets of magnetic alloy and oxide are separately sputtered and the substrate is rotated at high speed in front of both targets, or two-way simultaneous sputtering in which incident sputtered particles are guided to the same substrate for film growth ..

Here, Ni and Cr are contained in the magnetic thin film of the present invention.
Need only include at least one. Therefore, a and b above do not take 0 at the same time. Further, it does not matter that the magnetic thin film contains nitrogen.

As described above, a CoPt-based magnetic film such as CoNiPt, CoNiCrPt, and CoCrPt has a coercive force of about 10% as a coercive force.
It is possible to get 1200-1500 Oe. At the time of forming these CoPt-based magnetic films, we have made the target alloy contain an oxide composed of at least one element selected from Si, B, Zr, Al, Y, P, Ti, Sn, and In beforehand. , And found that the in-plane coercive force of the magnetic film significantly increased to over 2000 Oe. In addition, the magnetic thin film thus prepared has no significant reduction in squareness ratio or remanent magnetization, has a coercive force squareness ratio of 0.7 or more, and has sufficient magnetic characteristics as a high-density magnetic recording medium. Also became clear.

If the composition of the oxide contained here exceeds 20 atomic%, the remanent magnetization begins to decrease, and especially if it exceeds 40 atomic%, the remanent magnetization decreases greatly, which is unsuitable as a high density magnetic recording medium. Especially thin film heads that are widely used today
20% or less is desirable for the type of head that reproduces by induced electromotive force such as MIG head.

Examination of the magnetic film prepared by infrared absorption spectroscopy shows that the film contains an oxide of the same MO form as in the target, which indicates that the target is also present in the sputter plasma. It is shown that the oxide contained in was hardly decomposed. When only non-oxygen elements forming the oxide were added, the coercive force sometimes increased, but the increase was at most 200%.
It was revealed that the large increase in coercive force of about Oe and 500 Oe or more is the effect of adding the additive in the form of oxide. On the other hand, when oxygen gas is introduced and reactive sputtering is carried out when sputtering a CoPt-based alloy film, the magnetic alloy is oxidized and the coercive force, saturation magnetization and remanent magnetization, squareness ratio and coercive force squareness ratio are drastically reduced. It does not become practical.

In the present invention, the oxide contained in the target in advance is not decomposed, so that it is possible to form a magnetic film having a high coercive force without causing the oxidation of the magnetic alloy. According to Japanese Patent Laid-Open No. 3-84723, CoPt
It was shown that by adding elements such as P, Si, Ge, B, Ga, Al, In, Sn, Sb, and sputtering in Ar gas containing oxygen, a high coercive force magnetic film of 2000 Oe or more was prepared. However, the magnetic film thus formed has an extremely low squareness ratio and coercive force squareness ratio of less than 0.7, which poses a serious problem in practical use and cannot be said to be excellent as a high-density recording medium. It is considered that such a difference in magnetic properties is caused by film formation by reactive sputtering with oxygen, and it can be said that the film material is essentially different from the magnetic film proposed in the present invention.

Further, as described above, in actual mass production, the coercive force of the magnetic film needs to be easily adjusted without changing the main film forming conditions. In the present invention, Co is added by adding an impurity gas such as nitrogen to the Ar gas used during the sputtering film formation and adjusting the addition amount.
_100-abxyz Ni _a Cr _b Pt _x M _y O _z A method of adjusting the coercive force of the magnetic film is used. According to this method, the holding power of the film monotonously decreases as the proportion of nitrogen gas in Ar gas increases,
It is possible to change the coercive force of the film without changing other sputtering conditions. In this way, no deterioration occurs in the magnetic properties such as saturation magnetization and remanent magnetization, squareness ratio and coercive force squareness ratio of the film formed by introducing nitrogen. Further, with respect to the ratio of nitrogen gas contained in Ar gas, if it exceeds 10%, the coercive force is remarkably reduced, which is not suitable. On the other hand, if it is less than 0.1%, it becomes difficult to control the addition amount, which is not suitable.

Further, as described above, in addition to high coercive force, low medium noise is also an important characteristic for a magnetic recording medium. We found that the Co _100-abxyz Ni _a Cr _b Pt _x M _y O _z magnetic film has a significantly improved medium noise as compared with the CoNiCrPt alloy magnetic film containing no oxide. At this time, the magnetic properties such as coercive force and squareness do not deteriorate. As a result, the bit shift value, which directly represents the magnetic recording density characteristic, is improved by including the oxide. In addition, the noise improving effect was more remarkable when the NiP sputter base film was used. As described above, the Co _100-abxyz Ni _a Cr _b Pt _x M _y O _z magnetic film produced by the target containing an oxide, which is proposed in the present invention, is very suitable as a high-density magnetic recording medium in the future. It was found to be a thing.

By the above-mentioned method, even if the Pt composition of the CoPt alloy magnetic film is about 10% and the cost is sufficiently low, the coercive force squareness ratio S ^* of 0.7 or more, which is considered necessary for high recording density, is obtained. , Remanent magnetization 3.0 × 10 ^-3 emu / cm ² at 2000 O
It has become possible to realize a high coercive force of e or higher and a significantly low medium noise characteristic.

[0024]

【Example】

[Example 1] A magnetic recording medium was formed by sequentially depositing a NiP plating film having a thickness of 15 µm on the surface and then sequentially laminating NiP / CoNiPtSiO / carbon films on a textured aluminum disk substrate by a sputtering method. did. In forming the magnetic film, Co ₈₁ Ni ₇ Pt ₁₂ chips made of SiO ₂ as an oxide on the alloy target (hereinafter, referred to as SiO ₂ oxide chips) was used a composite target placed uniformly. The NiP (15 wt% P) underlayer film thickness was 420Å and the magnetic film thickness was 500Å. At the time of film formation, Ar gas containing 0.1 volume% of nitrogen gas was used, and the pressure was set to 20 mTorr. Further, the substrate is not heated positively or the substrate bias is not applied during the film formation.

FIG. 1 shows the values of the in-plane coercive force obtained when the area ratio of the SiO ₂ oxide chip placed on the target to the target was changed to 0 to 17 area%. While the coercivity without the addition of SiO ₂ is 1400 Oe, the coercive force with the addition of SiO ₂ is rapidly increased, the case of adding SiO ₂ 9.5% 2500 Oe or more the coercive force is obtained. Here, when the composition of the actually sputtered film is analyzed by Auger electron spectroscopy, for example, SiO ₂ is used as a target and the area ratio is 9.5.
% SiO _{2 in} the film was 7.9 atom%.

The values of the saturation magnetization and the residual magnetization per unit area at this time are shown in FIG. Both decreases by the addition of SiO _2. For example, the decrease even when adding SiO ₂ 9.5% is about 20%, which according to the output decrease is adjusted by increasing the magnetic film thickness practically problematic There is no.

Further, in this case, the squareness ratio S and the coercive force squareness ratio are
The change in S ^* is shown in FIG. Even if SiO ₂ is added, there is no significant change in both, and S = 0.77, S ^* = 0.87 when 5% is added, and S = 0.77, S ^* = 0.82, which is a practically sufficient value even when 9.5% is added. It was

The effect of adding SiO ₂ to the CoNiPt alloy magnetic film is not limited to the above composition. For example Co
₇₉ Ni ₆ Pt ₁₅ alloy data - was subjected to the same SiO ₂ added to the target, the coercive force without the addition of SiO ₂ is 1700 Oe
On the other hand, the coercive force increases with the addition of SiO _2.
A maximum coercive force of 3100 Oe was obtained when 9.5% O ₂ was added.

[Example 2] As in Example 1, a magnetic recording medium was formed by sputtering, in which NiP / CoNiPtSiO / carbon films were sequentially laminated on an aluminum disk substrate by a sputtering method. When the magnetic film was formed, a composite target in which 5 area% of SiO ₂ oxide chips were placed on the Co ₈₁ Ni ₇ Pt ₁₂ alloy target was also used. Also, the NiP base film thickness is 420Å,
The magnetic film thickness was 500Å. By changing the amount of nitrogen gas in Ar gas during film formation, the coercive force of the magnetic film was adjusted according to the writing ability (head characteristic) of the head.

The electromagnetic conversion characteristics of the CoNiPtSiO magnetic film prepared in Table 1 and a CoNiPt film prepared without placing a SiO ₂ chip as a comparative example are shown.

[0031]

[Table 1]

The measurement was performed by writing and reproducing with a thin film head having a flying height of 0.1 μm. The write current was 27 mA. The frequency of the write signal was 5MHz, and 1.88MHz was used for the overwrite measurement.

According to the measurement results, the ratio of the reproduction output and the reproduction output at the writing frequency of 2.5 MHz and the reproduction output at the 5 MHz is expressed as a percentage, the resolution indicating the high frequency characteristic of the medium, and the overwrite value indicating the rewriting ability of the medium. By adding SiO ₂ as an oxide without deterioration, the S / N value representing the reproduction output / medium noise ratio has been significantly improved from about 28 dB to 33 dB.
As a result, the bit shift value representing the magnetic recording density characteristic is 1
It was improved from 1.56nsec to over 2nsec.

Further, in the case of the same SiO ₂ addition amount, the sample A having a higher coercive force shows a low bit shift value which is superior in the high density recording characteristic as compared with the sample B. It is shown that a magnetic film that is noise and has a high coercive force is suitable as a higher density magnetic recording medium.

[Embodiment 3] A magnetic recording medium in which NiP / CoCrPtSiO / carbon films were sequentially laminated on the same aluminum substrate as in Embodiment 1 was formed by the sputtering method. NiP
The base film thickness is 420Å. Co ₇₈ Cr ₁₂ is used to create the magnetic film.
A composite target in which 5 area% SiO ₂ oxide chips were placed on a Pt ₁₂ alloy target and Ar gas containing 0.1% nitrogen gas were used, and the pressure was set to 20 mTorr. Note that the substrate was not heated positively or the substrate bias was not applied during film formation.

The magnetic film thickness is changed from 250Å to 10 by changing the film formation time.
Fig. 4 shows the values of the in-plane coercive force when the value was changed to 00Å in comparison with the coercive force when SiO ₂ was not added. As compared with the case without addition of SiO _2, the coercive force is increased by the addition of SiO _2, for example, without the addition of film thickness SiO ₂ in 400 Å 1270 O
e was about 1820 Oe and 500 O due to the addition of SiO _2.
An increase in coercive force above e was obtained. Here, as a result of analyzing the composition in the actual sputtered film by Auger electron spectroscopy, for example, when the film thickness is 400 Å, the composition of SiO ₂ is 3.
It was determined to be 8 atom%. Under the sputtering conditions shown here, the maximum value of coercive force due to the addition of SiO ₂ was about 1800 Oe, but when the pressure was 30 mTorr, the maximum value was 2200 Oe.
Oe degree was obtained.

The value of the saturation magnetization in this case is shown in FIG.
The value of remanent magnetization is shown in FIG.5 (b). The saturation magnetization is decreased by the addition of SiO ₂ , but the residual magnetization is almost the same.
This is effective by improving squareness ratio S described later, SiO ₂
Is the advantage of the addition of.

FIG. 6A shows changes in the squareness ratio S in this case, and FIG. 6B shows changes in the coercive force squareness ratio S ^* . Although Without the addition of SiO ₂ S and S ^* are deteriorated to such an extent that a problem than 0.7 and the electromagnetic conversion characteristics on, by the addition of SiO ₂ 0.05 to 0.10
A significant improvement was observed and a sufficient value was obtained in terms of electromagnetic conversion characteristics.

The effect of adding SiO ₂ to the CoCrPt alloy magnetic film is not limited to the above composition. For example Co
₇₅ Cr ₁₀ Pt ₁₅ alloy data - was subjected to the same SiO ₂ added to the target, the coercive force without the addition of SiO ₂ whereas a 1550 Oe in the magnetic film thickness 400 Å, with the addition of SiO ₂ The coercive force increases, and when SiO ₂ is added at 5% by area of the tip, 20
A coercive force of 30 Oe was obtained.

[Embodiment 4] A magnetic recording medium in which NiP / CoCrPtSiO / carbon films were sequentially laminated on the same aluminum disk substrate as in Embodiment 3 was formed by the sputtering method. To prepare the magnetic film, a composite target was used in which 5 area% and 9.5 area% SiO ₂ oxide chips were placed on a Co ₇₆ Cr ₁₂ Pt ₁₂ alloy target. The NiP underlayer film thickness was 420Å and the magnetic film thickness was 500Å. The coercive force of the magnetic film was adjusted by changing the amount of nitrogen gas in Ar gas during film formation.

Table 2 shows the electromagnetic conversion characteristics of the CoCrPtSiO magnetic film prepared and the CoCrPt film for comparison.

[0042]

[Table 2]

The measurement was carried out in the same manner as in Example 2, where the flying height was 0.1 μm.
Writing and reproduction were performed with a thin film head of m 2. The write current was 27 mA. The frequency of the write signal is 5M
1.88MHz was used for Hz and overwrite measurement.

According to the measurement results, the STMNR value representing the reproduction output / medium noise ratio was improved from about 35 dB with an increase in the amount of SiO ₂ oxide added, and a value of 37 dB was obtained when 9.5% was added. In addition, the resolving power of the coercive force increased by adding SiO ₂ and the improvement of the coercive force squareness ratio were remarkably improved, and the bit shift value was improved by 1 nsec together with the media noise improving effect described above. Further, the overwrite value generally decreases as the coercive force is increased, but in the present embodiment, the degree of the decrease was very small. This is an effect resulting from the improvement of the coercive force squareness ratio.

[Embodiment 5] A magnetic recording medium in which NiP / CoNiPtMO / carbon films were sequentially laminated on the same aluminum substrate as in Embodiment 1 was formed by the sputtering method. Here, M is Si, Ti, Al, Zr or Y. When creating a magnetic film, place 1 to 5 area% of each oxide chip (SiO ₂ , TiO ₂ , Al ₂ O ₃ , ZrO ₂ or Y ₂ O ₃ ) on a Co ₈₁ Ni ₇ Pt ₁₂ alloy target. Used composite targets. NiP base film thickness is 420
Å The magnetic film thickness is 500Å. At the time of film formation, Ar gas containing 0.1% nitrogen gas was used and the pressure was set to 20 mTorr. Further, the substrate is not heated positively or the substrate bias is not applied during the film formation.

FIG. 7 shows the obtained in-plane coercive force plotted against the chip area ratio. For both oxide additives, as compared with the case of not adding, the coercive force increases with chip area ratio, that was a case about 1500 Oe without added example 5 area% in oxide, of SiO ₂ With the addition of 2400 Oe, a coercive force of 1900 Oe or more was obtained even in the case of Al ₂ O _{3 with} the smallest increase in coercive force. At this time, saturation magnetization, remanent magnetization, or a drastic decrease in the squareness ratio S and the coercive force squareness ratio S ^* were not seen, and there was no problem in practical use. Here, when the oxide composition in the actual sputtered film was analyzed by Auger electron spectroscopy, the composition was about 3.5 to 4 atom% when 5 area% was added.

[Embodiment 6] A magnetic recording medium in which NiP / CoNiCrPtSiO / carbon films were sequentially laminated on the same aluminum substrate as in Embodiment 1 was formed by the sputtering method. Ni
P Underlayer film thickness is 420Å. Co ₈₁ Ni is used to create the magnetic film.
₇ Pt ₁₂ alloy target with 5 and 9.5 area% Cr and O to 9.5 area% SiO ₂ oxide chips on the composite target and Ar gas containing 0.1% nitrogen gas were used, and the pressure was 20 mTorr. And Note that the substrate was not heated positively or the substrate bias was not applied during film formation. Magnetic film thickness is Cr
Saturation magnetization is 5 × when SiO ₂ is not added
The sputtering time was changed and adjusted so as to be 10 ⁻³ emu / cm ^2, and the film thickness was kept constant with respect to the addition of SiO ₂ .

FIG. 8 shows the effect of addition to the coercive force of SiO ₂ with respect to each Cr addition amount. At each Cr addition amount, the coercive force increases as compared to the case where SiO ₂ is not added.
% Was about 1420 Oe when SiO ₂ was not added, but it was 1690 Oe when 5% SiO ₂ was added and 1% when 9.5% was added.
An increase in coercive force was observed with 980 Oe. Also Cr 9.
5% in the was about 1270 Oe without the addition of SiO _2, an increase of 2100 Oe and significant coercivity was observed by the addition of 9.5%. As a result of Auger electron spectroscopy analysis of the composition in the actual sputtered film, the Cr composition was found to be 5%.
It is 5 atomic% with addition and 10 atomic% with 9.5% addition.
The composition of the magnetic thin film when adding 5% Cr and 9.5% SiO ₂ was calculated as Co ₇₅ Ni ₅ Cr ₅ Pt ₁₀ (SiO ₂ ) ₅ .

FIG. 9A shows the saturation magnetization value of the magnetic film, and FIG. 9B shows the residual magnetization value. Saturation magnetization and remanent magnetization decrease with the addition of SiO ₂ , but they are within the practical range.

FIG. 10A shows the change in the squareness ratio S in this case, and FIG. 10B shows the change in the coercive force squareness ratio S ^* . Cr
For added 9.5%, but if not added SiO ₂ S and S ^* is problematic 0.7 before and after the electromagnetic characteristics over, by the addition of SiO ₂ 0.
A significant improvement of about 05 to 0.10 was seen, and a sufficient value was obtained in terms of electromagnetic conversion characteristics.

[0051]

EFFECTS OF THE INVENTION According to the present invention, when the Pt composition of CoPt-based alloy magnetic film is as low as about 10% and the cost is sufficiently low, high temperature heating of the substrate, bias application, or high activity which makes sputter mass productivity extremely difficult. Difficult to control O ₂
Without using reactive sputtering, the coercive force squareness ratio required for future high recording density of magnetic recording is 0.7 or more, and the residual magnetization is
A coercive force of 2000 Oe or more can be realized at 3.0 × 10 ^-3 emu / cm ² .

Further, by combining the magnetic thin film of the present invention with the NiP sputter base film, it is possible to synergistically realize particularly low medium noise.

As described above, according to the present invention, excellent recording / reproducing characteristics can be realized, and a higher recording density can be achieved. Further, the magnetic recording medium of the present invention has an excellent feature that it can be obtained without impairing mass productivity and without significantly increasing the production cost.

[Brief description of drawings]

FIG. 1 is a graph showing changes in the coercive force of a magnetic film sputtered with a composite target in which a SiO ₂ oxide chip is placed on a Co ₈₁ Ni ₇ Pt ₁₂ alloy target, with respect to the SiO ₂ composition.

FIG. 2 is a graph showing changes in saturation magnetization and residual magnetization in a CoNiPtSiO magnetic film with respect to the amount of SiO ₂ added.

FIG. 3 is a graph showing changes in squareness ratio S (residual magnetization / saturation magnetization) and coercive force squareness ratio S ^* with respect to the amount of SiO ₂ added in a CoNiPtSiO ₂ magnetic film.

[Fig. 4] Area ratio of 5% on Co ₇₆ Cr ₁₂ Pt ₁₂ alloy target
Graph showing changes in coercive force with respect to magnetic film thickness of a magnetic film sputtered using a composite target with the SiO ₂ oxide chip of Fig. 6 and a Co ₇₆ Cr ₁₂ Pt ₁₂ magnetic film.

FIG. 5A is a graph showing a change in saturation magnetization with respect to a magnetic film thickness in a CoCrPtSiO 2 magnetic film. (B) CoCrPtSi
3 is a graph showing changes in residual magnetization with respect to magnetic film thickness in an O 2 magnetic film.

FIG. 6 (a) is a graph showing changes in the squareness ratio S with respect to the magnetic film thickness in a CoCrPtSiO 2 magnetic film. (B) CoCrPtSi
9 is a graph showing changes in coercive force squareness ratio S ^* with respect to magnetic film thickness in an O 2 magnetic film.

FIG. 7 is a graph showing changes in coercive force of a magnetic film sputtered with a composite target in which various oxide chips are placed on a Co ₈₁ Ni ₇ Pt ₁₂ alloy target, with respect to the oxide composition.

Fig. 8 Cr chip and Si on Co ₈₁ Ni ₇ Pt ₁₂ alloy target
₃ is a graph showing a change in coercive force of a magnetic film sputtered using a composite target on which an O ₂ oxide chip is placed, with respect to the SiO ₂ composition.

FIG. 9 is a graph showing changes in saturation magnetization and residual magnetization in a CoNiCrPtSiO ₂ magnetic film with respect to the amount of SiO ₂ added.

FIG. 10 (a) is a graph showing changes in the squareness ratio S with respect to the added amount of SiO ₂ in the CoNiCrPtSiO ₂ magnetic film. (B) Co
In NiCrPtSiO magnetic film, a graph showing changes in coercive force squareness ratio S ^* for additive amount of SiO _2.

Claims (6)

[Claims] 1. A _{Co 100-abxyz Ni a Cr b} Pt x M y O z ( except a,
b, x, y, z are represented by a composition formula, in which 0 ≤ a ≤ 15, 0 ≤ b ≤ 15, 0 <x ≤ 20, 0 <y ≤ 20, 0
<Z ≤ 40, y + z ≤ 40, a + b + x + y + z ≤ 60, and M is selected from Si, B, Zr, Al, Y, P, Ti, Sn, In A magnetic recording medium comprising a magnetic thin film which is at least one element. 2. The magnetic thin film contains an oxide of MO _c (0 <c ≤ 5).
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is included in the form of. 3. The magnetic recording medium according to claim 1, wherein a squareness ratio S and a coercive force squareness ratio S ^* in an in-plane magnetic hysteresis curve of the magnetic thin film are 0.7 or more. 4. The magnetic recording medium according to claim 1, wherein the magnetic thin film is formed on a NiP sputter thin film underlayer. 5. A CoNiPt alloy, a CoCrPt alloy or a CoNiCrPt alloy is used as a base, and at least one element (M) selected from Si, B, Zr, Al, Y, P, Ti, Sn and In is added to the base. oxide _{(MO d, 0 <d ≦} 5) Co 100-abxyz and forming by sputtering method using a target made in advance by incorporating the _{Ni a Cr b Pt x M y} O z ( except a, b, x, y, z
Is represented by a composition formula of 0% a), and in this composition formula, 0 ≤ a ≤ 15, 0 ≤ b ≤ 15, 0 <x ≤ 20, 0 <y ≤ 20, 0
<Z ≤ 40, y + z ≤ 40, a + b + x + y + z ≤ 60, and M is selected from Si, B, Zr, Al, Y, P, Ti, Sn, In A method of manufacturing a magnetic recording medium having a magnetic thin film which is at least one element. 6. The method of manufacturing a magnetic recording medium according to claim 5, wherein the sputtering method is a sputtering method using Ar gas containing 0.1 to 10% by volume of nitrogen gas.