JPH06104113A - Metal thin film magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a metal thin film magnetic recording medium which has high coercive force and excellent electric characteristics by forming a base layer of CrB alloy composed of specific chemical composition. CONSTITUTION:On a non-magnetic board 1, a base layer 2 composed of CrB alloy of specific composition is formed, a magnetic layer 3 composed of ferromagnetic Co alloy which has uniaxial crystal magnetic anisotropy is formed on the layer 2 and a protecting film 4 is laminated on the layer 3. The base layer 2 is formed for internally blending the C axis of the Co alloy, which is formed on the base layer 2 with uniaxial crystal magnetic anisotropy, and CrB alloy composed of Cr100-xBx, X:1-10 (atom %) is formed. Therefore, internal orientation of the magnetic layer is improved, not only coercive force but also electric characteristics, especially O/W(overwrite) characteristics, are remarkably improved and recording density is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-plane recording metal thin film type magnetic recording medium used as a hard disk.

[0002]

2. Description of the Related Art In recent years, along with the trend toward high density recording of magnetic recording media, metal thin film magnetic recording media in which the magnetic recording system is an in-plane magnetization system have been used. The magnetic recording medium according to this method is one in which a magnetic layer, which is a thin film of a ferromagnetic metal such as CoNiCr or CoCrTa, is formed on a non-magnetic substrate via an underlayer for introducing in-plane anisotropy. In general, a protective layer is further formed on the magnetic layer.

The underlayer is usually made of Cr,
The magnetic layer is epitaxially grown on the Cr layer.
Each of the above-mentioned layers is usually formed by a sputtering method to improve the coercive force of the magnetic layer.
As disclosed in Japanese Patent No. 4323, a negative bias voltage is also applied to the substrate when the magnetic layer is formed by sputtering.

[0004]

The magnetic recording medium is
Although high-density recording is possible, further improvement in recording density is required for next-generation magnetic recording media.
To improve the recording density, not only the coercive force but also
It is also necessary to improve electrical characteristics such as overwrite (O / W).

The present invention has been made in view of the above problems, and an object of the present invention is to provide a metal thin film type magnetic recording medium having a high coercive force and excellent electrical characteristics.

[0006]

The magnetic recording medium of the present invention is a metal thin film type magnetic recording medium in which a magnetic layer made of a ferromagnetic metal is laminated on a non-magnetic substrate via an underlayer. The formation has a chemical composition of atomic%, and is formed of a CrB alloy composed of Cr _100-X B _X , X: 1 to 10.

[0007]

In the conventional underlayer composed of only Cr, there is a limit to the improvement of coercive force. In the present invention, Cr has a specific range of B
By containing, it is possible to enhance the coercive force, improve the electrical characteristics, particularly the O / W characteristics, and thus increase the recording density. At this time, when X is less than 1 or more than 10 in the Cr _100-X B _X alloy forming the underlayer, the above-mentioned improving effect becomes too small. Also,
By forming the underlayer by sputtering with a negative bias voltage applied to the substrate, the above-mentioned improving effect is remarkably exhibited.

The reason why the inclusion of B improves the coercive force and the like has not been clearly clarified, but the lattice constant of the crystal forming the underlayer changes, which facilitates the epitaxial growth of the magnetic layer, and It is considered that the crystal mismatch between the magnetic layer and the magnetic layer is reduced.

[0009]

EXAMPLE FIG. 1 is a cross-sectional view of a main part of a magnetic recording medium according to an example, in which an underlayer 2 made of a CrB alloy having a predetermined composition is formed on a nonmagnetic substrate 1. A magnetic layer 3 made of a ferromagnetic Co alloy having uniaxial crystal magnetic anisotropy is formed thereon, and a protective layer 4 is further laminated thereon.

As the substrate 1, a substrate having an amorphous Ni-P plating layer of about 10 to 20 μm formed on the A1 alloy substrate 1 is usually used. It is also possible to use non-magnetic materials such as ceramic substrates. Incidentally, the upper surface of the substrate is usually provided with a textured process called texture in order to reduce the contact frictional resistance with the magnetic head.

The underlayer 2 formed on the substrate 1 is a c-axis (crystal axis exhibiting crystal magnetic anisotropy) of a Co alloy (crystal structure hcp) having uniaxial crystal magnetic anisotropy formed thereon. ) Is formed for in-plane orientation.
_A CrB alloy consisting of _100- XB _X , X: 1 to 10 (atomic%) is usually formed to a thickness of about 500 to 2000Å. When forming the underlayer, a negative bias voltage (-
It is preferable to apply a voltage of about 50 to −400 V). This is because the in-plane alignment action can be remarkably exhibited.

As described above, the magnetic layer 3 is made of a ferromagnetic metal having uniaxial crystal magnetic anisotropy, such as CoNiCr or C.
It is formed of a Co alloy such as oCrTa. During film formation, a negative bias voltage (−50
~ -400 V) may be applied. The magnetic layer is C
The o alloy is not limited to a single layer as shown in the figure, but a Co alloy layer and a Cr layer (or the CrB alloy layer) may be alternately laminated and the uppermost layer may be a Co alloy layer. Good. The thickness of the magnetic layer (the total thickness of the Co alloy single layer and the total thickness of the Co alloy layers if it is multiple layers) is usually 400 to 800 Å
It is considered as a degree. To secure playback output and reduce noise,
As a magnetic recording medium, the product B of the residual magnetic flux density Br and the film thickness δ
This is because rδ of about 300 to 500 G · μ is required.

A protective layer 4 of about 150 to 400 Å is formed on the magnetic layer 3 by a carbide such as WC or SiC, diamond-like carbon, amorphous carbon or the like. Furthermore,
If necessary, a lubricant such as a fluorinated polyether may be applied as a lubricant layer thereon in an amount of about 20 to 50 Å. When the magnetic recording medium is industrially produced, the underlayer 2, the magnetic layer 3, and the protective layer 4 are formed by sequentially moving the substrate in a sputtering apparatus equipped with a target material for forming a desired layer. Laminated films may be formed. The sputtering conditions are usually
Ar gas pressure 1-40 × 10 ^-3 Torr, substrate temperature 200-300
Approximately ℃.

Next, specific examples will be given. Example A (1) 1400Å Co ₈₆ Cr ₁₂ Ta, an underlayer having the composition shown in Table 1 below was formed on a substrate having a Ni—P plating layer formed on an Al plate.
_A magnetic layer consisting of a single alloy layer of 600 Å was formed, and a carbon protective layer was further formed on the magnetic layer of 250 Å. A DC magnetron sputtering device is used as the film forming device, and the film forming condition is Ar gas pressure 1
The substrate temperature was set to × 10 ^-2 Torr and the substrate temperature was 240 ° C.

When the underlayer and the magnetic layer were formed, the bias voltage shown in the table was applied to the substrate.

[0016]

[Table 1]

(2) Coercive force Hc of the obtained magnetic recording medium
Table 1 also shows the results of the measurement. (3) Evaluation Table 1 shows that the underlayer formed of CrB alloy within the scope of the present invention has a coercive force of 20 to 20% compared to the conventional film formed of Cr.
It is recognized that the improvement is about 100 Oe. Example B (1) In order to examine the electrical characteristics, a magnetic recording medium was manufactured by adjusting the sputtering conditions so that the residual magnetic flux and coercive force were the same. However, the layer structure is the same as in Example A. In consideration of the possibility of variation in electrical characteristics due to bias voltage application, in Example B, an underlayer was formed without applying a bias voltage, and characteristics were compared.

[0018]

[Table 2]

(2) HF average read voltage (HF-TAA), resolution (Res.), O / W characteristic of the obtained magnetic recording medium,
The pulse width (half-value width, PW ₅₀ ) was measured. The head used was a thin film head, and the measurement conditions were a disk rotation speed of 3600.
rpm, HF 5.0MHz, LF 1.25MHz. Table 2 shows the measurement results.
Are also shown. (3) Evaluation From Table 2, it was confirmed that all of the electrical characteristics of the example were better than those of the conventional example, and particularly the O / W characteristics were significantly improved.

[0020]

As described above, in the metal thin film type magnetic recording medium of the present invention, since the underlayer is made of the CrB alloy having the specific composition, the in-plane orientation of the magnetic layer can be improved and the coercive force can be improved. The electrical characteristics, particularly the O / W characteristics, can be remarkably improved, and the recording density can be further improved by improving both characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a magnetic recording medium of the present invention.

[Explanation of symbols]

 1 Substrate 2 Underlayer 3 Magnetic layer 4 Protective layer

Claims (2)

[Claims] 1. A metal thin film type magnetic recording medium having a magnetic layer comprising a ferromagnetic metal is laminated via an underlying layer on the nonmagnetic substrate, wherein the undercoat layer has a chemical composition in atomic%, Cr _{100- X} B _{X, X:} metal thin film type magnetic recording medium characterized in that it is formed by CrB alloy comprising 1 to 10. 2. The metal thin film magnetic recording medium according to claim 1, wherein the underlayer is formed by sputtering with a negative bias voltage applied.