JPS6174133A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent S/N of high-density recording and reproduction by forming a magnetic layer coated with Co onto the area larger than the specific area of the surface of pulverous iron oxide crystal particles on a substrate. CONSTITUTION:The substrate 4 (1 in the separate figure) consisting of a polyethylene terephthalate film, etc. is fed from a delivery shaft 5 along a cylindrical can 7 toward an arrow and while the substrate is taken up on a take-up shaft 6, an Fe3O4 film is formed thereon by using a cathode I8 and cathode II9 disposed on a magnetic field generator 10 with Fe3O4 as a target in a gaseous mixture composed of Ar and O2. High-frequency sputter vapor deposition is then executed with Co as a target to deposit Co onto the surface of >=1/3 the pulverous crystal particles of the Fe3O4 film thereby providing the magnetic layer 2. A protective layer 3 is thereafter provided thereon. The Co is deposited onto the magnetic layer in the above-mentioned manner, by which the magnetic recording medium having the improved S/N of the thin iron oxide film having high coercive force is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium having a magnetic recording layer comprising an iron oxide thin film suitable for high-density magnetic recording and reproduction.

Conventional structure and its problems In order to improve the information recording density, efforts have been made to make the magnetic recording layer thinner, and iron oxide thin film, Co-Ni gold layer, Co-
Cr gold film has been studied, and iron oxide thin film is superior to the above two types in terms of practical reliability, and has been put into practical use in some cases.

In order to improve the recording density of this thin film, the saturation magnetization amount is Fe.
Since the choice depends on whether 3O4 or r-Fe203 is selected, the only option is to improve the coercive force and the squareness ratio.

To do this, high temperature processing is required during thin film formation or post-processing, so the substrate material is limited and requires a hard disk using AQ alloy or the like, or a special substrate such as polyimide for flexible disks. It lacks versatility.

In particular, as a polymer substrate, polyesters have good surface properties for magnetic recording media, and this good surface property is important for improving the signal-to-noise ratio (S/N ratio) at high recording densities. This is extremely important, and it would be very promising if it were possible to construct iron oxide thin films with high coercive force on polyester substrates.

OBJECTS OF THE INVENTION The present invention was made in view of the above circumstances, and an object of the present invention is to improve the S/N ratio in high-density recording and reproduction of a magnetic recording layer made of an iron oxide thin film.

Components of the Invention The magnetic recording medium of the present invention is characterized in that Co atoms are arranged on the surface of more than % of the iron oxide microcrystalline particles, which improves squaring and, in combination with high coercive force, enables high recording density. Reproduction S
/N is improved.

Description of examples Examples of the present invention will be described below.

FIG. 1 is an enlarged sectional view of the magnetic recording medium of the present invention.

FIG. 2 shows a sputtering apparatus used to obtain the magnetic recording medium of the present invention.

In FIG. 1, 1 is a substrate such as a polymer substrate or a nonmagnetic metal substrate, 2 is a magnetic recording layer, and 3 is a protective layer.

In Figure 2, 4 is the substrate, 6 is the feed shaft, 6 is the winding shaft, and 7
is a cylindrical can, 8 is a cathode 1.9 is a cathode■, 1
0 is a magnetic field generator.

The magnetic recording layer of the present invention is γ-Fe 203 or Fe3
CO atoms are arranged on the surface of a microcrystalline particle made of O4.

% or less, the properties are unstable, so it is preferable to cover more than 10%.

% or more, the characteristics are almost constant, so it is not necessarily necessary to make efforts to increase the coverage, so it can be said that the manufacturing method is relatively easy.

The most reliable method for obtaining the magnetic recording layer of the present invention is Fe3O
4 or r F lB2O3, then C.

This is a method of sputter deposition using a sputtering method such as high frequency sputtering.

At this time, if there is an inconvenience due to too much Co adhering to the surface,
Adjustment can be made by using it together with etching.

Alternatively, the formation of the magnetic recording layer may be divided into two or three times in the thickness direction, and the iron oxide thin film formation and CO sputter deposition may be performed alternately.

In the magnetic recording layer obtained in this way, CO exists within the crystal in the thickness direction, but in terms of characteristics, CO exists on the surface of the microcrystal.
plays an important role, so if necessary, the same characteristics can be obtained using this method.

In particular, since a plurality of targets are used to form a thin film on a mass production scale, in that case it can be said that manufacturing using the above method is efficient.

It should be noted that the fact that the presence of Co improves the squareness and increases the coercive force is predicted to be due to the magnitude of the magnetocrystalline anisotropy of CO, but the details of the surface effect are particularly important. is not clear.

Materials that can be used for the substrate and the protective layer can be freely selected within known ranges, but it goes without saying that the desired magnetic properties can be sufficiently obtained even if a polyester substrate is used as described above.

An example will be described in more detail below.

〔Example〕

On a polyethylene terephthalate film with a thickness of 12 μm and a surface roughness of 120, F
Targeting es○4 (Targera) 1) Fes○
4 films were formed with a thickness of 0.26 μm. Cylindrical can has a diameter of 60
The surface temperature was kept constant at 15°C at α.

After forming the Fe30a film, target Co (target ■
) and CO by high-frequency sputtering in Ar.
was sputter deposited. The Co coverage was estimated by Auger electron spectroscopy and electron probe microanalysis.

In the comparative example, a polyamide substrate having a thickness of 12.degree. 5 .mu.m and a surface roughness of 60 was used, a Fes.sub.4 film was formed by sputtering, and then heat-treated at 240.degree. C. in 4B atmosphere.

For S/N comparison, the recording wavelength is 0.7 μm and the trunk width is 2Q.
It was performed in μm.

As is clear from the table, the magnetic recording medium of the present invention has an excellent S/N ratio in high-density recording.

The reason why the difference is larger than the difference predicted from the magnetic properties is due to increased noise due to uneven shrinkage of the substrate due to heat treatment, and even if starting from a substrate with small surface roughness, the result is inferior to the product of the present invention. You can only get things.

Effects of the Invention As described above, the magnetic recording medium of the present invention improves coercive force and squareness ratio by disposing CO on the surface of iron oxide microcrystal particles, and achieves high-density recording and reproduction with an excellent VN ratio. It can be done and its practicality is extremely large.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of the magnetic recording medium of the present invention, and FIG. 2 is a diagram of the main groove FiX of the medium manufacturing apparatus. 4...Substrate, 8...Target (iron oxide), 9...Target (Co) Name of agent Patent attorney Toshio Nakao and 1 other person 1st
Figure 2

Claims (1)

[Claims] A magnetic recording medium characterized in that Co atoms are arranged on 1/3 or more of the surface of iron oxide microcrystal particles.