JP3044571B2 - Magnetic recording media - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a magnetic recording medium for high-density recording that can be used as a magnetic memory in an external storage device (magnetic disk device) of a computer and the like. It is.

(Prior Art) Magnetic recording media have been used as storage media such as computers. Conventionally, a magnetic tape coated with magnetic powder has been widely used as the magnetic recording medium. However, this magnetic tape has disadvantages such as low storage density and long access time. Disc-shaped magnetic disks that can be randomly accessed instead of tapes have been developed as the above-mentioned magnetic recording media. Among them, a magnetic recording layer having a thickness of about 1 μm is formed on a hard substrate such as aluminum. Configured magnetic recording media have begun to be used. By the way, the magnetic recording layer of such a magnetic recording medium was initially obtained by mixing a magnetic powder such as iron oxide with a binder, and applying this to a substrate by a technique such as spin coating. A magnetic recording medium including a magnetic recording layer obtained by this method has a limit in the magnitude of saturation magnetization. Therefore, recently, a magnetic recording medium using a metal thin film having a higher saturation magnetization as a magnetic recording layer has been proposed. Such a magnetic recording layer is formed by depositing a thin film made of cobalt or a cobalt-based alloy by vacuum evaporation, sputtering, or the like. It is obtained by forming it by a vacuum film forming technique, or by forming an alloy thin film of cobalt-phosphorus, cobalt-nickel-phosphorus or the like by a wet method such as electroless plating. However, the following problems have been pointed out in such a magnetic recording medium. That is, in order to obtain high output and high resolution electromagnetic conversion characteristics in a high recording density region, the coercive force (S), the coercive force, and the coercive force (Hc) and residual magnetization (Mr) of the magnetic recording medium are increased. The squareness ratio (S *) must also be increased. On the other hand, when the squareness ratio (S) or the holding force squareness ratio (S *) is improved, the output increases while the medium noise increases rapidly. ,
As a result, there is a problem that the SN ratio is deteriorated, and it is difficult to obtain a high output and a high SN ratio with good balance.

(Problems to be Solved by the Invention) An object of the present invention is to provide a high recording density, excellent output
An object of the present invention is to provide a magnetic recording medium having an SN ratio.

(Means for Solving the Problem) The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the magnetic recording layer was composed of a CoCrTa-based alloy having a specific composition, and further a specific substrate was formed. By providing concentric scratches of roughness (hereinafter referred to as texturing), it is possible to suppress medium noise while obtaining high output, thereby providing an excellent medium suitable for high recording density.
It has been found that a magnetic recording medium having an SN ratio can be obtained, and the present invention has been completed. That is, the present invention provides a magnetic recording medium comprising a substrate coated with a nonmagnetic underlayer, a magnetic recording layer provided on the nonmagnetic underlayer, and a protective layer for protecting the magnetic recording layer. There the following composition formula, an alloy thin film represented by _{Co 1-xy Cr x Ta y} 0.05 ≦ x ≦ 0.2 0.005 ≦ y ≦ 0.1, subjected to texturing in its circumferential direction on the substrate, the average surface of the substrate A magnetic recording medium having a roughness (Ra) of 8 to 12 nm.

Hereinafter, the present invention will be described in detail with reference to the drawings. First
The figure shows a partial sectional view of an example of the magnetic recording medium of the present invention.
As shown in FIG. 1, the magnetic recording medium of the present invention includes a magnetic recording layer 3 and a protective layer 4 for protecting the magnetic recording layer on the substrate 1 covered with the specific magnetic underlayer 2. The substrate 1 may be made of, for example, a ceramic such as an aluminum alloy, a silicon nitride sintered body, or an aluminum oxide sintered body coated with a nickel-phosphorous plating film or an anodized alumite film, or a metal such as stainless steel or a titanium alloy, or a glass. it can. The substrate is textured in the circumferential direction so that the average surface roughness (Ra) of the substrate is 8 to 12 nm. Here, when the average surface roughness (Ra) of the substrate is less than 8 nm, a signal from the obtained magnetic recording medium cannot be obtained with a high output, and
When the value exceeds, the medium noise of the obtained magnetic recording medium increases, and the SN ratio decreases. The substrate 1 is covered with a non-magnetic underlayer 2. The non-magnetic underlayer 2 can be made of a non-magnetic metal thin film such as chromium. The thickness of the nonmagnetic underlayer 2 is determined as appropriate, but is preferably about 500 to 5000 °. Then composition formula on the nonmagnetic underlayer 2, a _{Co 1-xy Cr x Ta y} 0.05 ≦ x ≦ 0.2 0.005 ≦ y ≦ 0.1 magnetic recording layer 3 composed of a CoCrTa alloy film represented by 300 It is formed with a thickness of about 1000 mm. Here, when the composition of the magnetic recording layer is represented by the above composition formula, the coercive force and the SN ratio of the magnetic recording medium of the present invention are high. The magnetic recording medium of the present invention includes a protective layer 4 for protecting the magnetic recording layer 3, and this protective layer can be made of, for example, carbon or the like, and has a thickness of 100 to 400.
Å is preferred. Further, when using the magnetic recording medium of the present invention, a liquid lubricant, a solid lubricant or a composite lubricant of these may be applied as necessary to form the lubricating layer 5 before use.

As described above, in forming a thin film of a metal or an inorganic substance from the nonmagnetic underlayer 2 to the protective layer 4, a vacuum film forming technique such as DC or RF sputtering or vacuum evaporation is effectively used.

Since the magnetic recording medium of the present invention has the above-described configuration, the medium noise can be suppressed while obtaining a high output, and thus, an excellent, suitable for high recording density can be obtained.
The magnetic recording medium having the SN ratio is considered to be due to the occurrence of balanced anisotropy in the magnetic properties of the magnetic recording layer with respect to the substrate in the circumferential direction and the radial direction. That is, in the magnetic recording medium of the present invention, the coercive force squareness ratio (S * c) measured by applying an external magnetic field in the circumferential direction of the magnetic recording medium and the measurement by applying the external magnetic field in the radial direction. Coercive force squareness ratio (S * r)
The ratio (S * c / S * r) is approximately 1.05 to 1.25, indicating a well-balanced anisotropy.

(Examples) Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 A magnetic recording medium having a sectional structure shown in FIG. 1 was produced. For the substrate 1, a disk-shaped aluminum alloy coated with a nickel-phosphorus plating film is mirror-polished, and then textured in the circumferential direction so that the average surface roughness (Ra) is 10 nm. Was. First, this board 1
A nonmagnetic underlayer 2 made of a chromium film of 3000 ° is formed thereon by a DC sputtering method, and a cobalt-chromium-tantalum alloy film containing chromium of 12 atom% and tantalum of 2 atom% is formed thereon as a magnetic recording layer 3. It was formed to a thickness of 600 mm by DC sputtering. Further, a carbon film was formed thereon as a protective layer 4 by DC sputtering to a thickness of 300 mm.
A liquid lubricant was formed thereon as a lubricating layer 5 by a dipping method to produce a magnetic recording medium.

Thereafter, the magnetic characteristics and electromagnetic conversion characteristics of the magnetic disk obtained as described above were measured. The magnetic characteristics were measured using a vibration sample magnetometer (VSM), and the electromagnetic conversion characteristics were measured using a certifier under the conditions shown in Table 1. Table 2 shows the measurement results.

Table 1 Measurement radius 30.5mm Rotation speed 2400rpm 1F frequency 1.25MHz 2F frequency 5.00MHz Head Track width 20μm Gap length 0.6μm Flying height 0.20μm Comparative example 1 As the magnetic recording layer 3, nickel was 20 atom% and chromium was
A magnetic recording medium was manufactured in the same manner as in the example except that a cobalt-nickel-chromium alloy film containing 10 atomic% was used, and its magnetic characteristics and electromagnetic conversion characteristics were measured. Table 2 shows the measurement results. The obtained magnetic recording medium had a large medium noise and a low SN ratio.

Comparative Example 2 A magnetic recording medium was manufactured in the same manner as in the example, except that a mirror-finished substrate without texturing was used as the substrate 1, and its magnetic characteristics and electromagnetic conversion characteristics were measured. Table 2 shows the measurement results. The obtained magnetic recording medium had low output and SN ratio.

Comparative Example 3 A magnetic recording medium was prepared in the same manner as in Example 1, except that a substrate subjected to texturing so that the average surface roughness (Ra) was 20 nm was used as the substrate 1. The conversion characteristics were measured. Table 2 shows the measurement results. The obtained magnetic recording medium had a large medium noise and a low SN ratio.

Hc: Coercive force Mr * t: Product of residual magnetization and thickness of magnetic recording layer S: Square ratio S *: Coercive force square ratio S * c: Measured by applying an external magnetic field in the circumferential direction of the magnetic recording medium S * r: Coercive force squareness ratio measured when an external magnetic field is applied in the radial direction of the magnetic recording medium. Res: 2F output / 1F output. The magnetic recording medium of the present invention has a high recording density area. It can be seen that the increase in noise can be suppressed while obtaining a high output, and as a result, an excellent SN ratio can be obtained.

(Effects of the Invention) As described above, the magnetic recording medium of the present invention is suitable for high recording density and has excellent output and SN ratio.

[Brief description of the drawings]

FIG. 1 is a diagram showing a partial cross section of an example of the magnetic recording medium of the present invention. In the figure, 1... Substrate, 2... Non-magnetic underlayer 3... Magnetic recording layer, 4... Protective layer 5.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-303601 (JP, A) JP-A-1-133217 (JP, A) JP-A-2-154323 (JP, A) JP-A-62-162 60119 (JP, A) JP-A-2-273315 (JP, A) JP-A-3-125325 (JP, A) JP-A-61-202324 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/64

Claims (1)

(57) [Claims] A non-magnetic underlayer made of a chromium film provided on the substrate; a magnetic recording layer provided on the nonmagnetic underlayer; and a protective layer made of a carbon film for protecting the magnetic recording layer. in the magnetic recording medium comprising the above magnetic recording layer the following composition _{formula, Co 1-xy Cr x Ta} y an alloy thin film represented by 0.05 ≦ x ≦ 0.2 0.005 ≦ y ≦ 0.1, the circle on the substrate The concentric scratches are made in the circumferential direction, and the average surface roughness (Ra) of the substrate
Is 8 to 12 nm.