Magnetic disk

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a magnetic disk used in a computer or the like.

【0002】

[Conventional technology]

In recent years, in the field of information storage files, high recording density has been steadily improved. In a magnetic disk device, reducing the distance between a magnetic head that reads and writes information and a recording medium that holds information is one of the important factors for increasing the density. On the other hand, a protective film is provided on the recording medium for the purpose of preventing deterioration due to friction and wear between the magnetic head and the recording medium (for example, Japanese Patent Application Laid-Open No. 1-282723). In order to achieve a higher recording density, it is necessary to reduce the thickness of this protective film. In a magnetic disk device that uses a protective film with a small film thickness, contact / sliding with the magnetic head causes the protective film to peel off / damage, and the friction coefficient between the magnetic head and the disk increases, resulting in recording / playback failure. I could fall into it. In order to avoid this, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-253021, a carbon nitride film has been used as the protective film.

【0003】

[Problems to be Solved by the Invention]

However, a conventional magnetic disk using a carbon nitride film as a protective film has a carbon to nitrogen composition ratio of 1: 3. This conventional magnetic disk has a serious problem that when the protective film thickness is 20 nm or less, the protective film is peeled off or damaged due to friction and wear between the head and the disk.

【0004】

An object of the present invention is to provide a magnetic disk having a high recording density and high reliability that solves the above problems.

【0005】

[Means for solving problems]

According to the present invention, in a magnetic disk having a protective film on a magnetic layer which is a recording medium, the protective film includes an amorphous phase and a crystalline phase, and the composition of the entire protective film has an atomic ratio of carbon to nitrogen of 1: 1 to 3 pairs. It is characterized by using materials in the range of 4. Also, more preferably, β-C in the crystal phase₃N_4-xIt is a magnetic disk characterized by containing (x = 0 to 1.0).

【0006】

[Action]

The durability of the protective film of a magnetic disk is related to the hardness of the material itself, the fatigue durability when repeated stress is applied, the adhesive force between the protective film and the magnetic layer, and the like. As a new material, β-C disclosed in Niu et al., Science (C. Niu et al., Science), Vol. 261, p. 334 (1993).₃N₄Was developed. β-C₃N₄Although it has a high hardness, it has a large surface roughness because it is a crystal, and its durability decreases as the protective film becomes thinner. As a result of investigating by changing the preparation conditions and composition of the film in order to control the crystal grains, it was found that a slight nitrogen deficiency is preferable. Due to nitrogen deficiency, a part of the crystal phase is amorphized to become a mixed phase of the crystal phase and the amorphous phase, which promotes flattening and densification of the thin film surface. As a result, the hardness and adhesive force of the thin film are increased, and a magnetic disk using a highly durable protective film is realized. In addition, β-C is not always the crystal phase.₃N₄Not only can be used, β-C₃N_4-x(x = 0 to 1.0) can also be used. This is β-C₃N₄Β-C up to 1: 1 carbon to nitrogen in crystals₃N₄It is thought that the reason is that it retains the structure. Furthermore, a mixed crystal phase can also be used as the crystal phase, and α phase and β-C₃N₄Mixed crystal phase, α phase and β-C₃N_4-xMixed crystal phase, CN₃And β-C₃N₄Mixed crystal phase and CN₃And β-C₃N_4-xThere is a mixed crystal phase of. In these mixed crystal phases, the hardness and adhesive strength of the protective film are β-C.₃N₄Or β-C₃N_4-xIt was found that this is mainly due to the expression of the characteristics of. Furthermore, it was found that it is important that the atomic ratio of carbon to nitrogen is in the range of 1: 1 to 3: 4 as the composition of the entire protective film, such as hardness and adhesive strength as characteristics of the protective film.

【0007】

[Example]

Next, examples of the present invention will be described. FIG. 1 is a cross-sectional view showing the basic configuration of the recording disk of the present invention, in which 1 is a substrate, 2 is a base layer, 3 is a magnetic layer, 4 is a protective film, and 5 is a lubricating layer.

【0008】

An aluminum alloy was used for the substrate 1. For the base layer 2, Ni-P formed by the plating method was used. CoNiCr was formed into a 60 nm film on the magnetic layer 3 by a sputtering method. A perfluoropolyether-based material was used for the lubricating layer 5.

【0009】

The types and forming methods of the substrate 1, the base layer 2, the magnetic layer 3 and the lubricating layer 5 are not particularly limited, and known materials and forming methods can be used without any special restrictions.

【0010】

The protective film 4 was formed by an electronic cyclotron resonance sputtering apparatus. Carbon was used as the target of the sputtering equipment. As the sputtering gas, a mixed gas of argon and nitrogen was used. The total pressure of the sputter gas was 0.01 to 2 mtorr. The partial pressure of nitrogen is related to the amount of nitrogen deficiency, etc., and was changed between 10% and 80%. The input voltage was 300 W. The film thickness was 10 nm. C the overall composition of the protective film₃N_4-yAnd y is defined as the amount of nitrogen deficiency in the overall composition of the protective film. Formed C₃N_4-yAs a result of measuring the composition of the protective film by photoelectron spectroscopy, the nitrogen deficiency amount y = 0.0 when the nitrogen partial pressure of the sputter gas is 80%, and the nitrogen deficiency amount y = 1.0 when the nitrogen partial pressure is 10%. The value of nitrogen deficiency x decreased with the increase of. Table 1 shows the composition of the entire protective film and the composition of the precipitated crystal phase formed when the nitrogen partial pressure of the sputtering gas is changed.

【0011】

[table 1]

<img file="JP2636734B2_D0001.tif" />【0012】

X-ray diffraction measurement and atomic force microscope observation of the film surface were performed to evaluate the film quality of the formed protective film. In the film with nitrogen deficiency x = 0.0, β-phase X-ray diffraction was clearly observed, and the crystal grain size was about 0.1 micron and the average surface roughness Ra was 20 nm from the atomic force microscope observation. As the nitrogen deficiency x increased, the X-ray diffraction peak became broad and the amorphousness increased, and it became difficult to observe clear crystal grains in the surface morphology, and the surface roughness tended to decrease. .. When the nitrogen deficiency y was between 0 and 1.0, the protective film was a mixture of a crystalline phase and an amorphous phase. As a crystal phase, β phase was precipitated over all compositions, but when the nitrogen deficiency y was 0.42 or more, it was a mixed crystal phase of α phase and β phase. Furthermore, when the nitrogen deficiency y is 1.0, the β phase and CN₃It was a mixed crystal phase of.

【0013】

For comparison, a magnetic disk using carbon as a protective film was prepared. The carbon protective film magnetic disk was formed by a magnetron sputtering device. Carbon was used as the target of the sputtering equipment. Argon was used as the sputtering gas. The sputter gas pressure was 10 mtorr. The input voltage was 300 W. The protective film thickness was 10 nm. The comparative sample magnetic disk was produced in exactly the same manner as the magnetic disk shown in the examples, except for the protective film and the production conditions.

【0014】

For the protective film and comparative sample according to the present invention, the hardness related to mechanical durability was measured, and the results are shown in Table 2.

【0015】

[Table 2]

<img file="JP2636734B2_D0002.tif" />【0016】

It can be seen that the film hardness decreases as the nitrogen deficiency amount y of the protective film increases, but it has a hardness of 120 GPa at y = 1.0, which is higher than that of the carbon protective film of the comparative sample. ..

【0017】

The following mechanical durability test was performed on the magnetic memory according to the present invention. A slider with a magnetic head formed on a magnetic disk was set. The amount of levitation of the slider is 0.025 μm, and the recording density of the magnetic memory is 3 Gbit / in2. The magnetic memory is raised from a stationary state to a rotation speed of 5400 rpm in 4 seconds, rotated at a constant speed for 1 second, and then returned to a stationary state in 4 seconds. Stay stationary for 1 second. This was repeated 100,000 times as one cycle. During this test, the frictional force applied to the slider was measured with a strain gauge for each cycle, and the relationship between the friction coefficient and the durability test cycle was determined. As a result, the friction coefficient was 0.3, which was constant and did not increase up to 100,000 cycles, regardless of the nitrogen deficiency in the range of nitrogen deficiency y = 0 to 1.0. When the nitrogen deficiency is y = 0.0 to 0.27, β-C is used as the crystal phase of the protective film.₃N_4-xNo change in the coefficient of friction was observed up to the durability test of 500,000 cycles, which was particularly good.

【0018】

For comparison, a similar mechanical durability test was performed on the carbon protective film magnetic disk. In the comparative sample, the friction coefficient began to increase at 4000 cycles, and a head crash that scratched the magnetic disk occurred at 8000 cycles.

【0019】

Therefore, the magnetic disk of the present invention has achieved at least 25 times the durability as compared with the conventional magnetic disk, and can secure high recording density and high reliability.

【0020】

[Effect of the invention]

According to the present invention, in a magnetic disk having a protective film on a magnetic layer which is a recording medium, the protective film contains an amorphous phase and a crystalline phase, and the composition of the entire protective film has an atomic ratio of carbon to nitrogen of 1: 1. Use materials in the range of 3 to 4 and more preferably β-C as the crystalline phase.₃N_4-xBy using (x = 0 to 1.0), the effect of reducing friction and wear between the recording medium and the magnetic head slider and significantly improving durability and reliability in a magnetic disk having a high recording density was obtained.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing of the magnetic disk apparatus of this invention.

[Explanation of symbols]

1 board 2 Underlayer 3 Magnetic layer 4 Protective film 5 Lubricating layer