JPH02210614A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having a large reproducing output and an excellent C/N value by laminating >=2 magnetic recording thin- film layers consisting essentially of Co, Cr and Pt to form a multilayer structure and providing a nonmagnetic material thin-film layer between the respective thin-film layers. CONSTITUTION:The surface of a substrate 1 is coated with Ni and Pt alloys, etc., as the hard film 2. A substrate film 3 consisting essentially of Cr is formed on the hard film 2. The first magnetic thin-film layer 4 consisting essentially of Co, Cr and Pt is provided on the substrate film 3. The second magnetic thin-film layer 6 is further provided, and a nonmagnetic material thin-film layer 5 is furnished between the thin-film layers 4 and 6. The sum of the thickness of the thin-film layers 4 and 6 is controlled, for example, to 500-5,000Angstrom . The material for the thin-film layer 5 is selected from a carbonaceous material or the metals such as Cr, Mo and Al or their alloys, and the thickness is preferably controlled to 50-400Angstrom . By this method, the reproducing output is increased, and the C/N is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic disks, magnetic drums, and magnetic tapes.

(Prior art) Recently, in order to meet the demand for higher recording densities in magnetic recording media devices, a method of performing perpendicular magnetic recording on a magnetic thin film having perpendicular magnetic anisotropy has been studied, and it is possible to achieve high recording densities. It is being

As magnetic thin films having perpendicular magnetic anisotropy, alloy magnetic thin films such as cobalt-chromium alloys and cobalt-chromium-platinum alloys (Japanese Unexamined Patent Publication No. 11605/1983) produced by sputtering or vacuum evaporation are known. .

Among these alloy magnetic thin films, the present inventors have previously developed an alloy magnetic thin film that particularly improves the perpendicular coercive force and has uniform magnetic properties by using an alloy magnetic thin film whose main components are 86 at% or less of cobalt and 8 to 24 atoms of chromium. % and platinum from 6 to 25 at.%
He invented and filed a patent application for a magnetic recording medium comprising a magnetic thin film consisting of chromium and a film mainly composed of chromium as an underlayer for the magnetic thin film (Japanese Patent Application No. 185493/1983).

(Problems to be Solved by the Invention) However, such a magnetic recording medium having a magnetic thin film containing cobalt, chromium, and platinum as main components does not necessarily have sufficient reproduction output and C/N ratio. The larger the reproduction output and the higher the C/N ratio, the easier the design of the magnetic recording system becomes, and the higher the quality of magnetic recording and reproduction becomes possible.

An object of the present invention is to provide a magnetic recording medium that improves the above-mentioned invention and provides a larger reproduction output and a higher C/N ratio.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted various studies and found that when forming a magnetic thin film containing cobalt, chromium, and platinum as main components, a magnetic thin film layer is A magnetic thin film is formed by forming a magnetic thin film to a predetermined thickness, then providing a non-magnetic thin film of an appropriate thickness on top of it, and stacking these layers alternately so that the sum of the thicknesses of each magnetic thin film layer becomes the desired thickness. As a result, a magnetic thin film with a homogeneous and dense particle shape was obtained. Although the vertical alignment of this magnetic thin film was slightly deteriorated, it was found that despite this, the reproduction output was increased without lowering the recording density, and the C/N ratio was high.

That is, the present invention is characterized in that two or more magnetic thin film layers containing cobalt, chromium, and platinum as main components are laminated on a substrate to form a multilayer structure, and a nonmagnetic thin film layer is provided between each magnetic thin film layer. It is a magnetic recording medium.

The present invention will be explained in detail below with reference to the drawings.

The substrate 1 of the present invention is a hard molded body such as an aluminum plate, a glass plate, or a synthetic resin, or a soft film such as a polyester film. The surface of the substrate must be free from waviness and have sufficiently low surface roughness. If necessary, the surface of the base body may be hardened by coating a nickel-phosphorus alloy as the hard film 2, or a high magnetic permeability thin film may be provided.

In addition, if necessary, the surface of the substrate, a hard film, or
A base film 3 containing chromium as a main component may be formed on the surface of the high magnetic permeability thin film. By forming a film containing chromium as the main component as the base film in this way, the perpendicular coercive force is increased and the reproduction output is also increased. The thickness of the base film containing chromium as a main component is preferably 100 to 10,000. 100
The vertical coercive force is insufficiently high for less than 1000
The base film containing chromium as a main component, which does not particularly improve the perpendicular coercive force even if the number exceeds 0, may be provided by either a sputtering method or a vacuum evaporation method.

A first magnetic thin film layer 4 containing cobalt, chromium, and platinum as main components is provided on the substrate, hard film, high magnetic permeability film, or underlayer film containing chromium as main components.

The composition ratio is preferably in the range of 86 at % or less of Co, 8 to 24 at % of Cr, and 6 to 25 at % of pt.

If Cr is less than 8 at%, good vertical alignment cannot be obtained, and p
If t is less than 6 at %, a magnetic recording medium with high coercive force cannot be obtained. Cr exceeds 24 at% or pt is 2
If the Co content exceeds 5 atomic % or is less than 86 atomic %, not only will the coercive force not particularly increase, but the residual magnetic flux will decrease and the perpendicular magnetic anisotropy will become small.

Whether the magnetic thin film layer is formed by sputtering or vacuum evaporation, the sum of the thicknesses of the magnetic thin film layer 4.6 is important for recording and reproducing characteristics.
It is preferable to adjust the thickness of each magnetic thin film layer so that the sum thereof becomes a desired length.

Generally, the sum of the thicknesses of each magnetic thin film layer is suitably 500 to 5,000.

A nonmagnetic thin film layer 5 is provided between each magnetic thin film layer. The non-magnetic thin film layer is made of carbon, chromium, molybdenum, tungsten, titanium, zirconium, vanadium,
The material is selected from metals such as niobium, tantalum, magnesium, aluminum, germanium, and bismuth, alloys thereof, and nonmagnetic cobalt-chromium alloys Ai', O, and SiQ□. Among these, carbonaceous or chromium is preferred.

In the case of carbonaceous material, the carbonaceous target can be shared by using carbonaceous material for the protective film, and in the case of chromium, the chromium target can be shared by using chromium for the base film, so sputtering equipment or vapor deposition The device becomes simpler. The nonmagnetic thin film layer can be formed by sputtering, vacuum evaporation, or the like, but is not particularly limited. The thickness of the non-magnetic thin film is preferably 50 to 400. .

When the thickness is 50 Å or more, the reproduction output is improved and the C/N ratio also increases. If the thickness is less than 50, no sufficient effect will be obtained.On the other hand, if the thickness exceeds 400, no further improvement in properties will be observed.

Preferably, a protective film 7 is formed on the topmost magnetic thin film layer.

The protective film is particularly preferably carbonaceous. Since the carbonaceous protective film has appropriate lubricity and appropriate hardness, long-term reliability is ensured without damaging the magnetic head.

The protective film made of carbonaceous material is deposited on the surface of the magnetic thin film by a coating method, a vapor deposition method, a sputtering method, or the like. Depending on the deposition method, it can become crystalline like graphite, or
Although they are amorphous like glassy carbon, they all have the same effect as a protective film. however,
The protective film is not limited to the above films;
In addition to metals such as RLI, oxides such as Crt(h), oxides such as 5i(h, nitrides such as Si3N4, carbides such as SrC%TtC, etc.), boron, alloys of boron and carbon, polysilicate, etc. have been traditionally used as protective films. Various methods listed can be adopted.

Furthermore, a lubricant made of various organic substances may be applied onto this protective film.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Examples 1 to 4 A base made of an aluminum disk with an outer diameter of 901 m, an inner diameter of 25 m, and a thickness of 1.2 m was prepared.

After lapping the surface of the substrate, a hard layer of nickel and phosphorus with a thickness of 30 μl was provided by electroless plating. After mirror polishing the hard layer, the substrate was fixed on a sample stage of a magnetron sputtering device.

After setting the degree of vacuum to a pressure of 2 x 10''7 Torr, argon gas was introduced to reduce the argon gas pressure to I x 10.
A chromium film was deposited to a thickness of 1000 mm using metallic chromium as a target under DC sputtering conditions of -2 Torr % sputtering power 4 W/cj to form an underlayer.

Next, an alloy of cobalt, chromium, and platinum was prepared using an alloy containing 72 at.% of cobalt, 14 at.% of chromium, and 14 at.% of platinum under DC sputtering conditions at an argon gas pressure of 1 × 10-” Torrs and a sputtering power of 3 W/cd. 1st
The magnetic thin film layer was formed to a thickness of 500 nm.

Next, the argon gas pressure was set to 5·X 10-”Torr,
A nonmagnetic thin film layer made of carbonaceous material was formed using graphite as a target under the conditions of DC sputtering with a sputtering power of 3 W/cd.

Furthermore, 500 people formed a second magnetic thin film layer made of cobalt, chromium, and platinum under the same conditions as the first magnetic thin film layer, and a protective film was formed to a thickness of 200 people under the same conditions as the nonmagnetic thin film layer made of carbonaceous material. is a magnetic disk.

By repeatedly manufacturing the above-mentioned magnetic disk, and in that case, changing the sputtering time of the non-magnetic thin film layer in stages, the thickness of the non-magnetic thin film layer can be varied from 50 to 400 mm. Four magnetic disks were manufactured.

The reproduction output and noise level of these magnetic disks were measured. In these tests, a magnetic disk was inserted into a magnetic disk drive device, a magnetic head was fixed only on a certain track of the magnetic disk, and the output when a 7 MHz sine wave was recorded and reproduced was measured as the reproduction output. The noise characteristics are determined by recording and reproducing a 7 MHz signal, performing frequency analysis with a spectrum analyzer, taking the value at a frequency of 3 MHz as the noise level (NdB), and calculating the C/N ratio by taking the difference from the signal level (CdB) at 7 MHz. I asked for

The magnetic head is an amorphous metal head (ring type)
The relative speed with the magnetic disk is 10.411 I/s.
The test was carried out under the conditions of ec and track width of 20 μm.

The degree of vertical orientation was compared using the α target for Cu-, and the half width of the rocking curve of the X-ray diffraction spectrum was Δθ5°.

These results are as shown in the table.

Example 5 As a non-magnetic thin film layer, the argon gas pressure was
200 people formed a chromium film using metallic chromium as a target under the conditions of DC sputtering with an rrz sputtering power of 4 W/c+J. Other than that, magnetic disks were manufactured by the same method and under the same conditions as Examples 1 to 4, and their characteristics were measured. The results are shown in the table.

COMPARATIVE EXAMPLE A single magnetic thin film layer with a thickness of 1000 mm was formed on a chromium film on a substrate without forming the magnetic thin film layer into a multilayer structure. Other than that, magnetic disks were manufactured by the same method and under the same conditions as Examples 1 to 4, and their characteristics were measured. Result is,
As shown in the table.

From this table, it can be seen that by alternately laminating magnetic thin film layers and non-magnetic thin film layers, the reproduction output increases and the C/N ratio increases. As for non-magnetic thin films, in addition to carbonaceous films, films mainly composed of chromium were also effective. In addition, the film thickness is effective even for 50 people, and for 200 people.
Above Å, there was hardly any difference in properties.

(Effects of the Invention) As explained above, according to the present invention, two or more magnetic thin film layers mainly composed of cobalt, chromium, and platinum are laminated to form a multilayer structure, and a nonmagnetic thin film is layered between each magnetic thin film layer. A magnetic recording medium provided with this has the effect of increasing reproduction output and increasing the C/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the magnetic recording medium of the present invention. Symbols 1... Substrate, 2... Hard film, 3... Base film, 4... First magnetic thin film layer, 5... Nonmagnetic thin film layer,
6... Second magnetic thin film layer, 7... Protective film. Patent applicant Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] (1) Magnetic recording characterized in that two or more magnetic thin film layers containing cobalt, chromium, and platinum as main components are laminated on a substrate to form a multilayer structure, and a nonmagnetic thin film layer is provided between each magnetic thin film layer. Medium.