JPH03237613A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics and electromagnetic conversion characteristics and to reduce medium noise by using Co(100-x-y)CrxTay (8 atomic%<=x<=20 atomic%; 2atomic%<=y<=6atomic%) as a magnetic material. CONSTITUTION:On a nonmagnetic substrate, there are successively formed a nonmagnetic metal base layer, magnetic layer, and protective layer. The magnetic layer consists of an alloy of Co(100-x-y)CrxTay (8 atomic5<=x<=20 atomic%; 2atomic%<=y<=6atomic%). Namely, by using a Co-Cr-Ta alloy, coercive force suitable for high-density recording can be obtained. By adding Ta, CoCr grains are made very small and intergranular segregation of Ta is caused, which devides individual grains well. This realizes low medium noise and high coercive force. Thereby, magnetic characteristics and electromagnetic conversion characteristics are improved and medium noise is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a magnetic recording medium such as a magnetic disk mounted in a fixed magnetic disk device.

[Conventional technology]

A magnetic recording medium (hereinafter also simply referred to as a medium) such as a magnetic disk usually has a non-magnetic metal underlayer on a non-magnetic substrate.
A magnetic layer and a protective layer are sequentially laminated. In order to improve the lubrication performance of the medium surface, a liquid lubricant layer is often further formed on the protective layer.

Such media are typically manufactured as follows. As the material of the non-magnetic substrate, various metals, alloys, glass, ceramics, etc. are used. Among these, aluminum or those whose main component is aluminum and which has other metal elements added thereto to improve strength, mechanical properties, corrosion resistance, etc. are often used. The surface of this substrate is anodized to prevent deformation of the medium surface due to collisions with magnetic heads.

A reinforced layer with high hardness is formed by N1-P alloy electroless plating. Of course, in the case of a substrate made of a material that itself has sufficient hardness, such as glass or ceramic, such a reinforcing layer may be omitted.

The surface of such a substrate is usually polished to a smooth surface with a centerline average roughness Ra of about 20 to 100 roughness, and then fine texturing, called texturing, is performed approximately along the circular layer direction. Irregularities are formed.

After precision cleaning the nonmagnetic substrate processed into the desired surface shape in this way, a sputtering method is applied to the surface to enhance the magnetic properties of the magnetic layer and to improve adhesion to the substrate. Metal base layer 3 such as Cr, Cr alloy, W
Alternatively, a layer made of Mo is formed, then a magnetic layer made of a C0 alloy is formed, and a protective layer is further formed thereon to protect the magnetic layer from the external environment and to improve the lubricating performance of the medium surface.

For example, a-C layers are formed and used as a medium.

In recent years, with the increase in processing power and miniaturization of information processing systems such as computers, there has been a demand for larger capacity and smaller fixed magnetic disk devices used as auxiliary storage devices. For density recording, there is a strong demand for improved magnetic properties, thinner magnetic layers, and improved electromagnetic conversion characteristics.

The magnetic properties and electromagnetic conversion properties of the medium are greatly affected by the magnetic material used for the magnetic layer, and the sputtering conditions during film formation [substrate temperature, sputtering power, atmospheric gas (e.g. Ar
It varies depending on the gas pressure, etc.).

Currently, Co-Ni-Cr alloys are generally used as magnetic materials, but Co-Ni alloys are also used.

Co-Ni-Pt alloys, Co-Cr alloys, etc. have been proposed, and some of them have been put into practical use. In addition, studies are being made to find suitable sputtering conditions for these magnetic materials.

[Invention tries to solve it! l! i) As mentioned above, with the aim of improving the magnetic properties and electromagnetic conversion properties of the medium, various studies are underway on the components of magnetic materials and their composition ratios, as well as on the sputtering conditions during film formation. At present, a medium with characteristics that fully satisfies the requirements has not yet been obtained.

Media using Co--Ni--Cr alloys as magnetic materials, which have been widely used in the past, have excellent tails in terms of resolution, corrosion resistance, etc., but are currently not very good in terms of media noise. In particular, when recording at a higher frequency in order to achieve high-density recording, the output signal during playback decreases and the S/N ratio deteriorates accordingly, so as a countermeasure, it is strongly recommended to improve media noise. desired.

This invention was made in view of the above points, and
The problem to be solved is to provide a magnetic recording medium with excellent magnetic properties and electromagnetic conversion properties and reduced media noise, and a method for manufacturing the same.

[Means to solve the problem]

According to the present invention, the above problem is solved by providing a non-magnetic metal underlayer and a magnetic layer that are sequentially formed on a non-magnetic substrate.

In the magnetic recording medium comprising a protective layer, the magnetic layer is made of CO(+oo-x-v)CrxT1v alloy (8 atomic %
This problem can be solved by creating a magnetic recording medium with the following relationship: ≦X<20 atomic %; 2 atomic %≦Y≦6 atomic %). and,
In the method for manufacturing a magnetic recording medium of the present invention, a nonmagnetic substrate is heated to a temperature within a range of 280°C or more and 320°C or less, and then a nonmagnetic metal underlayer is deposited on the substrate by sputtering.
A magnetic layer made of a Co-Cr-Ta alloy.

A magnetic recording medium is manufactured by sequentially forming protective layers.

[Effect]

When a Co--Cr alloy is used as the magnetic material of the medium, the medium noise becomes smaller than that of a conventional medium using a Co--Ni alloy. However, when a Co-Cr binary alloy is used, a high coercive force cannot be obtained. In addition, T as a third element
When using the Co-Cr-Ta system added with a, 33kP
A coercive force of 120006 or more, which is suitable for high-density recording of CI or higher, can be obtained. This is due to the addition of Ta, which increases the grain size of CoCr.
It is presumed that the separability of each crystal grain (grain) is improved due to the very small amount of Ta and Ta is segregated at the grain boundaries, and low medium noise and high coercive force can be achieved.

In order to achieve the low media noise required in the market, Cr
The amount added must be 8 at % or more, but if it exceeds 20 at %, the amount of magnetization tends to decrease, which is not preferable. In addition, in order to obtain a high coercive force, Ta of 2 atomic % or more is required.
However, if it exceeds 6 at %, the amount of magnetization decreases, which is not preferable.

Furthermore, when a Co-Cr-Ta alloy is used as the magnetic layer material, it is not always possible to obtain a sufficient squareness ratio if the magnetic layer is formed under the same sputtering conditions as when using a conventional Co-Ni-Cr alloy. I can't. If the squareness ratio is poor, even if a high coercive force is achieved, the resolution will drop and the signal output will decrease, resulting in a poor signal-to-noise ratio.
The excellent low medium noise properties of the a-based alloys will not be utilized. In order to achieve a good squareness ratio using a Co-Cr-Ta alloy, it is necessary to set the substrate temperature at 280° C. or higher and 320° C. or lower when forming the bottom magnetic layer by sputtering.

〔Example〕

Made of AA-Mg alloy containing 4% Mg, outer diameter 95 mm,
An N1-P alloy layer with a thickness of 15 μm was formed on the surface of a plate with an inner diameter of 25 + n + n and a thickness of 1.27 mm by electroless plating, and the surface was polished by about 4 μm to make it smooth, and then tape textured with a polishing tape. A non-magnetic substrate having a center line average roughness Ra of 70 people was prepared by applying the test. These substrates were set in a holder as shown in FIG. FIG. 2(a) shows a plurality of substrates 1 (6 in the figure).
FIG. 2(b) is a sectional view taken along line XX in FIG. 2(a).

A bottom film is formed on both sides of the substrate 1 set in the holder 2 using a sputtering apparatus as shown in the conceptual diagram of FIG. The holder 2 with the substrate set thereon is carried into the preparation chamber 11, where it is evacuated to a vacuum of I.times.10-@Torr (the evacuation system is not shown) for sufficient degassing.

Subsequently, it is transported at high speed through the door 12 to the heating zone 14 at the back of the sputtering chamber 13 (the transport mechanism is not shown).

Here, the sheath heater 15 heats from both sides.

The ambient temperature in the heating zone 14 is monitored by a thermocouple 16 and controlled to a required temperature, and the residence time of the holder 2 in the heating zone 14 can also be controlled. The ambient temperature was set to 320°C, and the substrate temperature was increased to 300°C by staying for 3 minutes.
℃. Next, set the holder 2 to ^r gas pressure 2 Xl0
While transporting in the direction of the arrow in the sputtering chamber 13 adjusted to an atmosphere of −', a Cr target 17 is used to form a Cr layer base layer (film thickness 1500A) using a DC magnetron method.
After sequentially forming a magnetic layer (thickness: 500 layers) using the Co-Cru2Ta2 alloy target 18 and a C protective layer (thickness: 250 layers) using the C target 19 on both sides of the substrate, the process passes through the door 12 to the preparation chamber 11. The prepared medium is removed from the holder 2. When the gas pressure during sputtering is lowered, the squareness ratio improves, but magnetic anisotropy that depends on the transport direction appears, making it difficult to obtain uniform magnetic properties within the medium plane, so take this into account. Therefore, it is necessary to appropriately determine the gas.

In the above manufacturing method, the atmospheric temperature of the heating zone and the residence time of the holder were varied to produce media at various substrate temperatures.

The magnetic properties of the medium thus obtained were measured by VSM. As a result, the temperature dependence of the coercive force and squareness ratio of the obtained medium is shown in the diagram of FIG. From FIG. 1, as the substrate temperature increases, both the coercive force and the squareness ratio improve, and an excellent medium having a coercive force of 14000e or more and a squareness ratio of 0.9 or more can be obtained at 280° C. or higher. On the other hand, it has been separately confirmed that if the substrate temperature exceeds 320℃, the N1-P alloy of the substrate will become magnetized, which is not desirable. be.

〔Effect of the invention〕

According to this invention, Co(too-Xy
) By using CrxTav (8 atomic % ≦ A magnetic recording medium with excellent magnetic properties and electromagnetic conversion properties and reduced media noise can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram IIi showing the relationship between the coercive force and squareness ratio of the magnetic recording medium of the present invention and the substrate temperature during manufacturing, and Fig. 2 shows an example of a holder used to carry out the manufacturing method of the present invention. 2(a) is a front view, FIG. 2(b) is a sectional view taken along line XX in FIG. 2(a), and FIG. 3 is a sputtering diagram for carrying out the method for manufacturing a medium of the present invention. It is a conceptual diagram of an example of a device. 1 Substrate, 2 Holder, 3 Sputtering chamber, 4 Heating zone, 5 Sheath heater, 180 r 1 Substrate temperature ("C)" Figure

Claims (1)

[Claims] 1) a non-magnetic metal underlayer sequentially formed on a non-magnetic substrate;
In a magnetic recording medium comprising a magnetic layer and a protective layer, the magnetic layer is Co_(_1_0_0_-_X_-_Y_)
Cr_XTa_Y alloy (8 atomic%≦X≦20 atomic%; 2
A magnetic recording medium characterized in that the magnetic recording medium is composed of atomic %≦Y≦6 atomic %. 2) After heating the non-magnetic substrate to a temperature in the range of 280° C. or higher and 320° C. or lower, a non-magnetic metal base layer, a magnetic layer made of a Co-Cr-Ta alloy, and
A method for manufacturing a magnetic recording medium, comprising the steps of sequentially forming protective layers.