JPH0388114A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium which is less decreased in output in a high-frequency region and has a high resolving power by providing a magnetic recording layer having a two-layered structure consisting of a ferromagnetic material layer and a diamagnetic material layer on a substrate coated with a nonmagnetic underlying layer. CONSTITUTION:The surface of a substrate is coated with the nonmagnetic underlying layer, on which the diamagnetic material layer consisting of a diamagnetic material and the ferromagnetic material layer consisting of a ferromagnetic material are formed to constitute the magnetic recording layer. A protective layer is formed on this magnetic recording layer. The magnetic recording medium constituted in such a manner is subjected to writing by a magnetic head. Magnetization Md in a -x direction is generated in the diamagnetic material layer when the magnetization Mf in a +x direction is written in the ferromagnetic layer, where Mf>Md. The magnetic flux in the lower part of the ferromagnetic layer is looped and excess magnetic fields do not exist in the lower part of the magnetization inversion region of the medium; therefore, the magnetic charge distribution and the magnetization inversion region are narrowed. The half-amplitude level of the reproduced and isolated waves is, therefore, diminished. The degradation in the output by an interference effect is reduced and the resolving power is improved even if the recording frequency increases.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides an external storage device for a computer, etc.
The present invention relates to a magnetic recording medium used as a magnetic storage medium.

(Prior technology) Conventionally, tapes coated with magnetic powder have been widely used as storage media for computers, etc. However, this storage tape method has drawbacks such as low storage density and long access times, so tape Instead, disk-shaped magnetic disks that allow random access have been used. Among these, a magnetic disk constructed by forming a magnetic recording layer about 1 μm thick on a hard substrate about 2 μm thick has been widely used. The magnetic recording layer of such magnetic disks was obtained by coating a mixture of magnetic powder such as iron oxide with a binder onto the disk substrate using a technique such as a spin cord. The magnetic recording layer has a limit on the magnitude of saturation magnetization. Therefore, recently, magnetic recording media have been proposed that use a metal thin film with large saturation magnetization as a magnetic recording layer, and such a magnetic recording layer is formed by vacuum deposition, sputtering, etc. of a thin film made of cobalt or a cobalt-based alloy. It can be formed by film technology, or by forming an alloy thin film such as Co-PSCo-Ni-P by a wet method such as electroless plating. However, such magnetic recording media have problems in resolution, and in particular, it is difficult to maintain output at high frequencies.

(Problems to be Solved by the Invention) An object of the present invention is to provide a magnetic recording medium with excellent resolution.

(Means for Solving the Problems) In order to solve the above problems, the present inventors conducted intensive studies on magnetic recording layers. As a result, they discovered that a magnetic recording medium with excellent resolution can be obtained by forming the magnetic recording layer into a two-layer structure, and have completed the present invention. That is, the present invention provides a magnetic recording medium in which a magnetic recording layer and a protective layer are provided on a substrate coated with a non-magnetic underlayer, in which the magnetic recording layer has a two-layer structure of a ferromagnetic layer and a diamagnetic layer. This is a magnetic recording medium with special characteristics. The present invention will be explained in detail below.

FIG. 2 shows a cross-sectional view of the magnetization reversal region of a conventional magnetic recording medium in which the magnetic recording layer has a single-layer structure.

As shown in the figure, leakage magnetic flux diverges from the magnetic charges distributed in the magnetization reversal region in the magnetic recording medium to the top and bottom of the medium. Of these magnetic fluxes, only the magnetic flux that diverges upward actually contributes to the reproduction signal, and this magnetic flux induces a reproduction voltage through the magnetic head. On the other hand, although the magnetic charge located at the bottom of the medium does not contribute to reproduction, the magnetic charge distribution tends to spread more as the absolute amount of magnetic charge increases. As a result, the magnetization reversal region was wider than necessary. Therefore, in conventional magnetic recording media, the width of the induced reproduction solitary wave is wide, the interference effect becomes large in the high frequency region, and it is difficult to maintain the output at high frequencies, that is, the resolution.

On the other hand, FIG. 3 is a cross-sectional view of the magnetic recording layer of the magnetic recording medium of the present invention in which the first layer is a diamagnetic layer and the second layer is a ferromagnetic layer, and shows the state of magnetization during writing by a magnetic head. It is something that When magnetization (Mf) in the +χ direction is written in the ferromagnetic layer of the magnetic recording medium of the present invention, magnetization (Md) in the 1χ direction is generated in the diamagnetic layer. where l Mfl > l
It is Mdl. FIG. 4 shows a cross-sectional view of the magnetization reversal region of this medium. Since the magnetic recording layer of the magnetic recording medium of the present invention has a diamagnetic layer, the magnetic flux below the ferromagnetic layer is reduced as shown in the figure. It becomes a loop, and there is no extra magnetic charge below the reversal region of the medium. As a result, the magnetic charge distribution and the magnetization reversal region become narrower, and the magnetic flux distribution becomes sharper and has a steeper change. Therefore, in the magnetic recording medium of the present invention, the half value of the solitary wave to be reproduced is reduced, and even if the recording frequency becomes high, the output decrease due to the interference effect is reduced, and the resolution is improved.

In the present invention, the diamagnetic layer below the magnetic recording layer is made of boron,
It is preferably made of a metal selected from silicon, phosphorus, sulfur, copper, zinc, germanium, indium, cadmium, silver, gold, and lead, and has a thickness of 50 to 500 people. The upper ferromagnetic layer is made of a magnetic metal selected from cobalt and cobalt-nickel alloys, or platinum or platinum.
It is made of a material to which at least one metal selected from rhodium, titanium, chromium, samarium, tantalum, rhenium, and tungsten is added, and its thickness is 200 to 1.
It is preferable to set the number to 500 people.

Next, one embodiment of the present invention will be described based on the drawings. 1st
The figure is a partial sectional view showing an embodiment of a magnetic disk made of the magnetic recording medium of the present invention. The magnetic recording medium of the present invention is constructed on a substrate 1, and the substrate 1 is made of, for example, an alumina alloy coated with an N1-P plating film, an anodized alumite film, etc., or a silicon nitride sintered body, an aluminum oxide sintered body, etc. ceramics or metals such as stainless steel and titanium alloys,
Made of glass or plastic. Further, on the substrate 1, a non-magnetic underlayer 2 made of chromium etc.
A diamagnetic layer 3 made of a diamagnetic material and a ferromagnetic layer 4 made of a ferromagnetic material are placed on top of this to form a magnetic recording layer. Furthermore, a protective layer 6 is formed on the magnetic recording layer, and this protective layer 6 is made of an inorganic material such as carbon, aluminum oxide, or zirconia, and has a thickness of 50 mm.
~400 people is appropriate. Further, a surface layer 5 may be added between the magnetic layer 4 and the protective layer 6 as necessary.
is made of a thin film of metal such as chromium, titanium, vanadium, etc., and its thickness is suitably between 50 and 200. As described above, in forming the thin films from the non-magnetic underlayer 2 to the protective layer 6, vacuum film forming techniques such as DC and RF sputtering methods and vacuum evaporation are effectively used. Furthermore, when using the magnetic recording medium of the present invention, a liquid lubricant, a solid lubricant, or a combination of these lubricants can be applied on the protective layer 6 to form a lubricating layer.

(Example) Hereinafter, specific examples of the present invention will be described. Note that the present invention is not limited to the following examples.

Examples 1-4. Comparative Example 1 A magnetic recording medium shown in FIG. 1 was produced. An aluminum alloy coated with an N1-P plating film polished to an average surface roughness of 100 mm was used as the base body 1, and a 3000 mm thick chromium film was deposited on the base body 1 as the base layer 2 by DC sputtering. It was formed by a sputtering method. Next, silver is formed as a diamagnetic layer 3 on the underlayer 2 by DC sputtering, and on top of this, a cobalt alloy containing 20 atom% of nickel and 10 atom% of chromium is formed as a ferromagnetic layer 4 by DC sputtering. It was formed to a thickness of 700 people. On this magnetic recording layer, chromium was formed as a surface layer 5 to a thickness of 100A by DC sputtering method,
Furthermore, 300 carbon layers were formed as protective Frl6 on this layer by the same DC sputtering method to produce a magnetic recording medium.

Here, the electromagnetic conversion characteristics of magnetic recording media obtained by changing the thickness of the diamagnetic layer 3 as shown in Table 2 were evaluated and compared under the conditions shown in Table 1. The results are shown in Table 2. Further, as Comparative Example 1, a magnetic recording medium was produced without forming the diamagnetic layer 3, and its electromagnetic conversion characteristics were evaluated and compared using the same method as in the example. The results are also shown in Table 2. Furthermore, FIG. 5 shows the magnetic recording medium obtained in Example 3 and Comparative Example 1.
The correlation between the recording density and output of the magnetic recording medium obtained in the above is shown.

Table 1 Evaluation conditions Radius: 35 mm Rotation speed: 3600 RPM 1F frequency: 1.25 MHz 2F frequency: 2.50 MHz Track width = 20 μm Gap length: 0.9 μm Head flying height: 0.25 μm Table 2 Examples 5 to 8 Example 1 and A magnetic recording medium with the same structure was manufactured using the same method. However, in the case of this embodiment, the thickness of the diamagnetic layer 3 is 100 mm.
The electromagnetic conversion characteristics of the obtained magnetic recording medium were evaluated and compared in the same manner as in Example 1, with the thickness of the ferromagnetic layer 4 being varied while keeping the thickness constant. The results are shown in Table 3.

Table 3 (Effects of the Invention) As described above, the magnetic recording medium of the present invention having a two-layer structure of a first magnetic layer made of a diamagnetic material and a second magnetic layer made of a ferromagnetic material has a read-isolated The half-width of the wave can be made small, resulting in a magnetic recording medium with little output drop in the high frequency region, that is, a high resolution with high<D50.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing one embodiment of a magnetic disk made of the magnetic recording medium of the present invention. FIG. 2 is a cross-sectional view of a magnetization reversal region portion of a conventional magnetic recording medium. FIG. 3 is a diagram showing the state of magnetization during writing by a magnetic head in a cross section of the magnetic recording layer of the magnetic recording medium of the present invention. FIG. 4 is a sectional view of the magnetization reversal region portion of the magnetic recording medium of the present invention. FIG. 5 is a diagram showing the correlation between recording density and output of the magnetic recording medium obtained in Example 3 and the magnetic recording medium obtained in Comparative Example 1. In the figure, 1... base body 2... base layer 3... diamagnetic layer 4... ferromagnetic layer 5... surface layer 6... protective layer, respectively.

Claims (1)

[Claims] (1) A magnetic recording medium in which a magnetic recording layer and a protective layer are provided on a substrate coated with a non-magnetic underlayer, characterized in that the magnetic recording layer has a two-layer structure of a ferromagnetic layer and a diamagnetic layer. magnetic recording media.