JPH07141641A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having high coercive force and high squareness ratio by forming a magnetic film and implanting ions into the film. CONSTITUTION:A magnetic film is formed by sputtering on a nonmagnetic circular substrate and ions are implanted into the magnetic film to obtain a magnetic recording medium. The compsn. of the magnetic film is represented by the formula Co100-a-b-c-dNiaCrbPtcMd (where M is one or more kinds of substances selected from among B, Ta, Ti, W and oxides, 0<=a<=10at.%, 0<=b<=15at.%, 0<c<=20at.% and 0<=d<=10at.%). When SiO2 or CoO is used as M in the compsn. of the magnetic film, squareness ratio and coercive force in the hysteresis loop are simultaneously enhanced and the objective high density magnetic recording medium having superior magnetic characteristics is obtd. This method is effectively and easily applicable even to an isotropically textured substrate of glass, etc., which cannot utilize a magnetic orienting effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density magnetic recording medium such as a magnetic disk.

[0002]

2. Description of the Related Art At present, there is an ever-increasing demand for high-density recording in hard magnetic disks, and a magnetic disk having a diameter of 95 mm, for example, has achieved a recording capacity of 300 Mbytes or more. In order to achieve such high density magnetic recording, it is very important to increase the coercive force (Hc) and the squareness ratio in the magnetic hysteresis curve of the Co-based alloy magnetic film that is the magnetic recording medium. The half-width of isolated reproduction wave (PW50), which represents high-density recording performance, is expressed as a function of Hc and coercive force squareness ratio (S ^* ), and PW50 decreases with higher Hc and S ^* [17th AIP Conference Proceeding , Part 1, No.
5 (1971) 738]. That is, even if the recording is performed at a higher density, the reproduction characteristics are less deteriorated and the recording characteristics are excellent. If the squareness ratio (S), which is the ratio of the residual magnetization to the saturation magnetization, can be increased, a reproduction output that is proportional to the residual magnetization film thickness product can be secured even with a magnetic film having a small saturation magnetization film thickness product. It becomes possible. This means that the geometric thickness of the magnetic film having the same reproduction output can be reduced. Such reduction of the magnetic film thickness also has the effect of reducing PW50 [17t
h AIP Conference Proceeding, Part 1, No.5 (1971) 73
8].

Currently, as a method for increasing the Hc of a magnetic film,
CoPt type alloy [IEEE Trans. Magn., MAG-19 (1983) 1514, J.
Appl.Phys., 54 (1983) 7089, IEEE Trans. Magn., MAG-1
9 (1983) 1638] and CoCr alloys and other magnetic film alloys
[J.Vac.Sci.Technol., A4 (1986) 1], a sputtered NiP film as a base film [US Pat. No. 4,786,564, IEEE Trans.m.
agn., MAG27 (1991) 4727] and Cr film [J.Vac.Sci.Technol.,
A4 (1986) 1] has been proposed. When using a CoCr alloy, the sputtering condition is, for example, 200 ° C.
It has been reported that increasing the film-forming energy by heating the substrate or applying a substrate bias during film formation is effective in increasing Hc [IEEE Trans. Magn., MAG26 (1990).
1282]. Also, Ta or B [14th Japan Society for Applied Magnetics 8pB-18 (1990), Japanese Patent Application No. 3-359511] or oxide such as SiO ₂ [Japanese Patent Application No. 3-282301] is added to the magnetic alloy. Such a method has been proposed. As a physical mechanism for increasing Hc by these methods, first, it is considered that the in-plane orientation of the Co hexagonal lattice of the magnetic film and the crystal magnetic anisotropy thereof are increased. In addition, PinningS that prevents domain wall movement such as stacking fault
It is also possible to introduce ite. Microscopically, these magnetic films are aggregates of crystal particles, and by physically separating the crystal particles, their magnetic isolation is enhanced,
As a result, it is theoretical that Hc increases [J.Appl.Phys., 6
3 (1988) 3248] experimentally [IEEE Trans.Magn.MAG24 (1988)
2700], using the NiP underlayer described above,
It is understood that the high-energy film formation, the effect of additional elements, etc. are all due to the promotion of such magnetic separation structure. However, when Hc is increased due to such magnetic separation between crystal grains, the squareness ratio is essentially reduced [J.Appl.Phys., 63 (1988) 3248], and PW50 is practically used. It is not always preferable in terms of magnetic recording characteristics because it will cause deterioration.

In addition, a CoCr alloy magnetic film is laminated on a Cr underlayer, and the substrate texture direction is set by setting a substrate temperature of about 200 ° C. or more and a substrate bias application of about −200V as sputtering conditions during film formation. It is well known that, in so-called oriented media, which induces uniaxial magnetic anisotropy, a high coercive force and a high squareness ratio can be obtained in the circumferential texture direction, which is the head traveling direction, in the so-called oriented media. [The Journal of Applied Magnetics of Japan Vol.
13 (1989) 493]. However, it has the following problems. In other words, for the next-generation high-density magnetic recording, it is important to minimize the spacing between the head and the magnetic film in order to increase the read output of the head and reduce the PW50 [17th AIP Conference Proceeding, Par
t 1, No. 5 (1971) 738]. In order to reduce such spacing, it is necessary to use a glass substrate having high rigidity, a so-called zone texture in which a head / disk sliding area having a texture and a recording area having a smooth surface are separated without providing a texture. The glass substrate is chemically treated to the minimum required roughness [JP-A-6437718], fine particle coating [JP-A-1-194128], or low melting point metal [JP-A-
3-73419], oxides thereof [Japanese Patent Application No. 5-76219], and other methods have been proposed, and the texture created by these methods is anisotropic in shape in the circumferential direction. It is an isotropic texture with no property. It is clear that the zone texture has a smooth recording surface, and the above magnetic orientation effect cannot be applied to both.

[0005]

As described above, in order to realize higher density magnetic recording in the future, it is necessary to increase the coercive force, the squareness ratio, and the isolated reproduction wave time half width. is there. An object of the present invention is to provide a magnetic recording medium having a high coercive force and squareness ratio, including a glass substrate having no groove-like texture in the circumferential direction.

[0006]

The present invention provides a magnetic recording medium characterized by forming a magnetic film on a non-magnetic circular substrate by a sputtering method, and then implanting ions into the magnetic film. To do.

Particularly, in the present invention, the magnetic film composition is Co
_100-abcd Ni _a Cr _b Pt _c M _d (M is one or more substances selected from B, Ta, Ti, W or oxides), and 0 ≤ a
≤10 atomic%, 0 ≤b ≤15 atomic%, 0 <c ≤20 atomic%, 0
There is provided a magnetic recording medium characterized in that ≤d ≤10 atomic%.

In the present invention, SiO ₂ or Co is used as the M _d.
You can choose O.

Further, the magnetic film is preferably formed on a base film made of Cr, NiP or NiB formed by a sputtering method.

In the present invention, ions of a rare gas element such as argon and a non-metal element such as nitrogen, oxygen, hydrogen and carbon can be used as the implanted ions.

Further, in the present invention, ions of metal elements such as Cr and W can be used as the implanted ions.

[0012] In the present invention, the injection amount of the implanted ions to 1 × 10 ¹⁶ / cm ² or more, can be selected in the range of 1 × 10 ¹⁹ / cm ² or less.

In the present invention, the ion concentration in the film thickness direction of the magnetic film is changed by controlling the energy of the implanted ions, so that the magnetic film having substantially different magnetic characteristics such as coercive force in the film thickness direction is formed. A formed magnetic recording medium is provided.

Further, according to the present invention, in a magnetic recording medium having a magnetic film formed on a non-magnetic circular substrate, ions are implanted into the film after forming the magnetic film to enhance the coercive force and squareness ratio in the magnetic hysteresis curve. A magnetic recording medium characterized by the above.

In the present invention, the implantation energy of the implanted ions can be selected within the range of 5 keV or more and 50 keV or less.

Further, the present invention is, in an in-line type sputtering apparatus, after forming a magnetic film on a non-magnetic circular substrate,
Provided is a method for manufacturing a magnetic recording medium, characterized in that ion implantation is continuously performed without breaking the vacuum, and a protective film is further formed on the magnetic film that has been ion-implanted continuously.

In order to solve the above-mentioned problems, the present inventors implant ions of a rare gas element such as argon or a non-metal element such as nitrogen or oxygen in a vacuum after forming the magnetic film. By investigating the above and examining the magnetic film composition, the type and concentration of implanted ions, the energy, etc. in detail,
We have found a phenomenon in which the coercive force and the squareness ratio on the magnetic hysteresis curve are significantly increased at the same time. Furthermore, such an effect is particularly _caused by Co _100-abcd Ni _a Cr _b Pt _c M _d (M is B, Ta, T
i, W or one or more substances selected from oxides), 0 ≤ a ≤ 10 atomic%, 0 ≤ b ≤ 15 atomic%, 0 <c
In a magnetic film having a composition of ≦ 20 atomic% and 0 ≦ d ≦ 10 atomic% (where a and b do not become 0 at the same time), 1 × 10 ¹⁶ pieces / cm ² or more, 1 × 10 ¹⁹ pieces / It was clarified that it was particularly remarkable when ions such as argon, nitrogen, and oxygen below cm ² were implanted. Of course, this effect is also exhibited in other magnetic films, the type and concentration of implanted ions. It was also clarified that this effect can be applied to a so-called magnetically isotropic medium on a glass substrate. Japanese Patent Laid-Open No. 5-20
No. 5257 describes a method of forming discrete magnetic recording tracks by locally implanting nitrogen ions into a magnetic film to reduce saturation magnetization and form magnetically different regions. Among them, an example in which an increase in the coercive force of the CoCrTa magnetic film was observed by ion implantation is described, but in this case, the saturation magnetization was simultaneously reduced to less than half by ion implantation. It is concluded that this is a completely different phenomenon. That is, the coercive force Hc can be expressed as Hc = α (2Ku / Ms) by using the in-plane magnetic anisotropy constant Ku of the crystal grains forming the magnetic film and the saturation magnetization Ms. Where α
Is a constant representing the magnetic separation degree of crystal grains. That is, if the saturation magnetization is halved, the coercive force will be remarkably increased. According to the example, the saturation magnetization is reduced to less than half by the ion implantation, and the increase in coercive force at that time is about 10% at most (1600
Since it is Oe to 1800 Oe), it can be explained by a sufficient reduction effect of saturation magnetization. In other words, in order to utilize the above described items for our purpose, it is necessary to increase the thickness of the magnetic film in advance in order to secure a practically important reproduction output.
That is, since the saturation magnetization is halved, it is necessary to double the film thickness of the magnetic film, and it is considered that the obtained Hc will be much lower. There is no description about the squareness ratio.

On the other hand, according to the present invention, by optimizing the composition of the magnetic film, the implanted ion species and the amount thereof, or the energy thereof, it is possible to reduce the saturation magnetization by about 10% as described in the examples. As a result, a coercive force increase of about 40% was obtained, which cannot be explained by a simple saturation magnetization reducing effect. Moreover, the effect of significantly increasing the squareness ratio could be found for the first time.

[0019]

The magnetic recording medium formed by the above-mentioned ion implantation method has a high coercive force and squareness ratio in the magnetic hysteresis curve at the same time, and has excellent magnetic characteristics as a high density magnetic recording medium such as a hard magnetic disk in the future. It became clear to have. Further, the present invention can be effectively and easily applied to an isotropic textured substrate such as glass in which a so-called magnetic orientation effect, which is exhibited in a conventional substrate subjected to a circumferential texture treatment, cannot be used.

[0020]

Example: A circular glass disk substrate with a diameter of 65 mm and a plate thickness of 0.889 mm was precision cleaned and sputtered with Co ₈₁ with a film thickness of 500 Å.
A Ni ₇ Pt ₁₂ magnetic film was formed. Then, argon ions generated by a bucket type ion source were injected into the magnetic film. At the time of ion implantation, the degree of vacuum in the chamber was evacuated to 2 × 10 ^-6 Torr. The degree of vacuum during ion implantation is 5 × 10 ⁻⁵ T
It was controlled to 8 × 10 ⁻⁵ Torr from orr. The substrate was not heated actively during the ion implantation, and the temperature rise of the magnetic film due to the ion implantation was up to 80 ° C. Argon ions were injected with an energy of 18 keV, and the injection concentration was controlled by changing the injection time. The magnetic hysteresis curve of the prepared medium was measured by applying a maximum external magnetic field of 5 kOe with a vibrating sample magnetometer. Table 1 shows the magnetic hysteresis characteristics of the samples with different implanted ion concentrations. The magnetic hysteresis curve measured when argon ions were injected at 5 × 10 ¹⁷ ions / cm ² is shown in FIG. 1 in comparison with the case where it was not injected. Coercive force by ion implantation
Significant increase from 1233 Oe to 1612 Oe, and squareness ratio
S was 0.74 to 0.81 and S ^* was 0.91 to 0.95. That is, the coercive force and the squareness ratio in the magnetic hysteresis curve could be increased at the same time by implanting ions into the film after forming the magnetic film. At this time, the decrease in saturation magnetization is about 10%, and the increase in the squareness ratio S shows almost no decrease in the residual magnetization that practically determines the reproduction output. Therefore, excellent magnetic recording characteristics can be obtained by the effect of improving the coercive force and the squareness ratio without lowering the reproduction output.

[0021]

[Table 1]

[0022]

According to the present invention, high coercive force and high squareness ratio, which are extremely effective for improving magnetic recording characteristics, can be obtained at the same time by performing ion implantation after forming a magnetic film. A magnetic recording medium that can be used for recording can be provided. In addition, this technology cannot achieve the high coercive force and high squareness technology due to the conventional circumferential texture-induced magnetic orientation effect of Cr underlayer. It can also be applied to improve the mold ratio. Further, in the present ion implantation method, the ion concentration center value can be set at an arbitrary position in the magnetic film thickness direction by controlling the energy of the implanted ions. By using this method, it is possible to change the implanted ion concentration in the film thickness direction of the magnetic film and easily form a magnetic multi-layer film having substantially different magnetic properties such as coercive force in the film thickness direction. The magnetic characteristics of such a magnetic multilayer film are also superior to those of a magnetic film in which ions are not implanted.
Further, the ion implantation energy and the ion implantation density effective for improving the magnetic characteristics shown in the present invention can be easily applied to an in-line type sputtering apparatus having very high mass productivity. Furthermore, by the ion implantation energy control method described above, by implanting ions near the interface between the substrate surface and the magnetic film or underlayer film, the effect of increasing the mechanical adhesion of the magnetic film or underlayer film to the substrate is also added. Was obtained.

[Brief description of drawings]

FIG. 1 shows the change in magnetic hysteresis curve of a CoNiPt magnetic film before and after ion implantation.

Claims (13)

[Claims] 1. A magnetic recording medium comprising a magnetic film formed on a non-magnetic circular substrate by a sputtering method and then ion-implanted into the magnetic film. 2. The composition of the magnetic film is Co _100-abcd Ni _a Cr _b Pt _c.
M _d (M is one or more kinds of substances selected from B, Ta, Ti, W or oxides), and 0 ≤ a ≤ 10 atomic%, 0 ≤ b ≤
The magnetic recording medium according to claim 1, wherein 15 atomic%, 0 <c ≤ 20 atomic%, and 0 ≤ d ≤ 10 atomic%. 3. The magnetic recording medium according to claim 2, wherein the magnetic M _d is SiO ₂ or CoO. 4. The magnetic recording medium according to claim 1, wherein the magnetic film is formed on any one kind of sputter base film selected from Cr, NiP and NiB. 5. The implanted ions are He ⁺ , Ne ⁺ , Ar ⁺ , Kr ⁺ or
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a rare gas ion selected from Xe ⁺ . 6. The magnetic recording medium according to claim 1, wherein the implanted ions are non-metal element ions such as oxygen ions, nitrogen ions, hydrogen ions or carbon ions. 7. The magnetic recording medium according to claim 1, wherein the implanted ions are ions of a metal element such as Cr and W. 8. The implantation amount of the implanted ions is 1 × 10 ¹⁶ / cm 2.
^2. The magnetic recording medium according to claim 1, wherein the number is ² or more and 1 × 10 ¹⁹ pieces / cm ² or less. 9. By controlling the energy of the implanted ions, the concentration of implanted ions in the film thickness direction of the magnetic film is changed to form a magnetic film having substantially different magnetic properties such as coercive force in the film thickness direction. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a vertical structure. 10. A magnetic recording medium having a magnetic film formed on a non-magnetic circular substrate, wherein ions are implanted into the film after the magnetic film is formed to enhance coercive force and squareness ratio in a magnetic hysteresis curve. The magnetic recording medium according to claim 1. 11. The implantation energy of the implanted ions is 5 keV.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is 50 keV or less. 12. By controlling the energy of the implanted ions, the concentration of the implanted ions in the film thickness direction of the magnetic film is changed to form a magnetic multilayer film in which magnetic properties such as coercive force are substantially different in the film thickness direction. The method of manufacturing a magnetic recording medium according to claim 1, wherein 13. An in-line type sputtering apparatus,
After forming a magnetic film on a non-magnetic circular substrate, ion implantation is continuously performed without breaking the vacuum, and further, a protective film is formed on the ion-implanted magnetic film. Production method.