JPH0944837A - Magnetic recording media - Google Patents

Abstract

(57) Abstract: To provide a magnetic recording medium having improved corrosion resistance without lowering the coercive force. In a magnetic recording medium 10 of the present invention having a non-magnetic substrate 12 and a magnetic layer 14 provided on the non-magnetic substrate 12, the magnetic layer 14 is made of an alloy represented by the following formula (1). It is characterized by Co _a Sm _b R _c (1) (In the formula, R represents a rare earth metal other than Sm, b and c are 5 to 25 at% in total, and b / c is 3 to 50.
And a is 95 to 75 at%. )

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having an improved corrosion resistance of a magnetic layer.

[0002]

2. Description of the Related Art With the recent increase in recording density of magnetic recording media, a method of using a metal magnetic thin film as a magnetic layer to further increase the coercive force of the magnetic layer is widely used. . And, as such a metal magnetic thin film, for example, Co-Pt, Co-Ni, Co formed using a vacuum film forming technique such as vacuum deposition or sputtering.
A cobalt-based alloy thin film such as -Sm is used.

For example, Japanese Patent Laid-Open No. 2-103717 discloses a magnetic recording medium having an improved coercive force in which a magnetic layer made of a Co--Sm binary alloy is formed on a non-magnetic substrate via a non-magnetic metal underlayer. The magnetic recording medium formed is described. Further, in JP-A-5-54358, a magnetic layer having a high S / N ratio is obtained by using an amorphous magnetic alloy layer composed of Co and / or Fe and at least one rare earth metal such as Sm as the magnetic layer. It is suggested that a recording medium be obtained. In JP-A-7-7496, by using a thin film alloy in which one or more rare earth elements such as Sm are added as an additive metal to Co, Ni or Fe for the magnetic layer, the oxidation resistance and hardness of the magnetic layer are improved. It has been suggested to do so.

However, the Co-
The magnetic layer made of an Sm-based alloy thin film has a drawback that it is inferior in corrosion resistance because it contains Sm. On the other hand, Co-
If the concentration of Sm is reduced in order to improve the corrosion resistance of the Sm-based alloy thin film, the coercive force of the magnetic layer will decrease. Further, in each of the above publications, a rare earth metal is added to a Co—Sm alloy to improve the corrosion resistance of the magnetic layer, and Sm and Sm.
Concentration ratios of rare earth metals other than the above and concentrations of rare earth metals in the entire alloy are not specified.

Accordingly, it is an object of the present invention to provide a magnetic recording medium having improved corrosion resistance without lowering the coercive force.

[0006]

The present inventors have developed Co-Sm.
As a result of diligent studies on the corrosion resistance of the Al-based alloy, Co-S
By further adding a rare earth alloy R other than Sm to the m-based alloy, setting the concentration of Sm / R within a specific range, and reducing the concentration of rare earth metal (Sm + R) in the entire alloy, the coercive force is reduced. It was found that a magnetic layer having good corrosion resistance can be obtained without this.

The present invention has been made based on the above findings, and in a magnetic recording medium having a non-magnetic substrate and a magnetic layer provided on the non-magnetic substrate, the magnetic layer is represented by the following formula (1). The present invention has achieved the above object by providing a magnetic recording medium characterized by comprising an alloy. Co _a Sm _b R _c (1) (In the formula, R represents one or more rare earth metals other than Sm, b and c are 5 to 25 at% in total, and b / c is 3 to 50. And a is 95 to 75 at%.)

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described in detail below with reference to the drawings. Here, FIG. 1 is a schematic diagram showing the configuration of the first embodiment of the magnetic recording medium of the present invention, and FIG. 2 is a schematic diagram showing the configuration of the second embodiment of the magnetic recording medium of the present invention. Is.

In the first embodiment of the magnetic recording medium of the present invention shown in FIG. 1, the magnetic recording medium 10 comprises a non-magnetic substrate 12 and a magnetic layer 14 provided on the non-magnetic substrate 12.

As the non-magnetic substrate 12, for example, A
l substrate, NiP plated Al alloy substrate, tempered glass substrate,
Crystallized glass substrate, ceramics substrate, Si alloy substrate,
A Ti substrate, a Ti alloy substrate, a plastic substrate, a carbon substrate, a substrate made of a composite material of these, or the like can be used. In particular, the carbon substrate, especially the glassy carbon substrate is advantageous in reducing the diameter / thin plate, has excellent heat resistance, and has electrical conductivity, and thus is preferably used in the present invention.

The magnetic layer 14, which is a feature of the present invention, will now be described. The magnetic layer 14 is made of an alloy represented by the following formula (1). Co _a Sm _b R _c (1) (In the formula, R represents one or more rare earth metals other than Sm, b and c are 5 to 25 at% in total, and b / c is 3 to 50. And a is 95 to 75 at%.)

In the above formula (1), R is not particularly limited as long as it is a rare earth metal other than Sm. Among the rare earth metals represented by R, preferred are lanthanoid metals, and particularly preferred are Ce, Pr, Gd and H.
o, Nd, Tb and Dy. Further, R may be one kind or a combination of two or more kinds as long as it is a rare earth metal other than Sm.

In the magnetic recording medium of the present invention, the magnetic layer 14 is made of an alloy of Co, Sm and a rare earth metal R other than Sm, and in addition, the rare earth metal (Sm + R) in the alloy. ) Concentration (= b + c),
And the concentration ratio of Sm and R in the alloy (= b / c)
Is important to be within a specific range.

That is, the concentration (= b + c) of the rare earth metal (Sm + R) in the alloy represented by the above formula (1) is 5
Is about 25 at%. When (b + c) is less than 5 at%, a high coercive force cannot be obtained, and when (b + c) exceeds 25 at%, corrosion resistance deteriorates. Such (b + c) is 10-2
It is preferably 5 at%.

The concentration ratio (= b / c) of Sm and R in the alloy represented by the above formula (1) is 3 to 50. If (b / c) is less than 3, high coercive force cannot be obtained, and even if (b / c) exceeds 50, high coercive force cannot be obtained. Such (b / c) is preferably 3 to 20.

The magnetic layer 14 generally has a thickness of 5 to 5.
It is preferably 40 nm. Such a magnetic layer is preferably formed by a thin film forming means such as physical vapor deposition (PVD) such as vacuum deposition, sputtering and ion plating.

Next, a second embodiment of the magnetic recording medium of the present invention shown in FIG. 2 will be described. Note that, in FIG. 2, the same points as in FIG. 1 will not be described in detail, but the description in detail with respect to FIG. 1 is appropriately applied. In FIG. 2, the same members as those in FIG. 1 are denoted by the same reference numerals.

In the magnetic recording medium 10 shown in FIG.
A first underlayer 20 is provided on a non-magnetic substrate 12, a second underlayer 22 is provided thereon, and a magnetic layer 14 made of the above alloy is provided thereon. A protective layer 24 and a lubricant layer 2 are formed on the magnetic layer 14.
6 are sequentially provided.

The first underlayer 20 in the magnetic recording medium 10 shown in FIG. 2 is provided for the purpose of further reducing medium noise, and is preferably made of Ti or a Ti alloy. On the other hand, the second underlayer 22 provided on the first underlayer 20 is provided for the purpose of improving the magnetostatic characteristics of the magnetic layer 14, and for this purpose, its material is Magnetic layer 1
It is preferable to use a material having a lattice constant close to that of the substance forming No. 4. In particular, it is preferable that the second underlayer 22 is made of Cr or a binary alloy containing Cr from the viewpoints of improving magnetostatic characteristics and reducing medium noise. Examples of the binary alloy containing Cr include CrTi, CrMo, CrW and Cr.
Nb, CrSi, CrCo, CrTa, etc. can be mentioned. The thicknesses of the first underlayer 20 and the second underlayer 22 are preferably 5 to 200 nm and 5 to 150 nm, respectively.

Next, the protective layer 24 provided on the magnetic layer 14 will be described. The protective layer is used to protect the magnetic layer 14. The protective layer is preferably formed of a material having high mechanical strength from the viewpoint of wear resistance, and for example, Al, Si, T
Oxides of metals such as i, Cr, Zr, Nb, Mo, Ta, W (silicon oxide, zirconium oxide, etc.); nitrides of the metal (boron nitride, etc.); carbides of the metal (silicon carbide, tungsten carbide, etc.) ); It is preferable to use one or more selected from the group consisting of carbon such as diamond-like carbon and boron nitride.
Among the above materials, carbon, silicon carbide, tungsten carbide, silicon oxide, zirconium oxide, boron nitride or a composite material thereof is preferable, carbon is more preferable, and diamond-like carbon and glassy carbon are particularly preferable. Generally, the thickness of the protective film is preferably 5 to 25 nm.

The lubricant layer 26 provided on the protective layer 24 will be described. The lubricant layer is used for improving the running property and durability of the magnetic recording medium, and has a thickness of, for example. A method of applying a lubricant so as to be about 5 to 100Å, or a method of vapor phase polymerization of a fluorocarbon compound and oxygen (especially photo-CVD) (for example, the method described in Japanese Patent Application No. 6-286940). Can be formed by. As the lubricant, a fluoropolymer can be preferably used. As the fluorine-based polymer, both those having a polar group in the molecule and those not having a polar group can be used alone or in combination. Examples of the fluoropolymer having a polar group in the molecule include-
Has a (CF ₂ CF ₂ O) n- (CF ₂ O) m- skeleton,
It has an aromatic ring or OH group at the terminal and has a molecular weight of 200.
It is preferably 0 to 4000. On the other hand, as the fluorine-based polymer having no polar group in the molecule, CF _3-
A compound represented by (CF ₂ CF ₂ O) n- (CF ₂ O) m-CF ₃ and having a molecular weight of 2,000 to 10,000 is preferable.

Although the magnetic recording medium of the present invention has been described above in detail, the description of the conventional magnetic recording medium can be applied to the points not particularly described in detail other than the above description.

The magnetic recording medium of the present invention is useful as, for example, a magnetic drum, a magnetic tape, a magnetic card and a magnetic disk, and particularly useful as a magnetic disk such as a fixed disk.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to such examples.

Example 1 An amorphous carbon substrate (size 2.5 ″) having a density of 1.5 g / cm ³ was polished to have an average surface roughness Ra of 0.5 to 1.0 nm. Was precisely cleaned, and then set in a batch type sputtering apparatus having 4 cathodes, and each layer was sequentially formed under the following conditions.
A Co target having chips of Sm and rare earth metal having a thickness of × 5 × 1 mm was used, and the concentration of the alloy forming the magnetic layer was controlled by increasing or decreasing the number of the chips. Also,
The composition of the magnetic layer was measured by ICP by depositing only the magnetic layer on a slide glass.

(1) First underlayer-Material: Ti-Substrate temperature: room temperature-Ar gas pressure: 5 mTorr-Substrate bias voltage: 0 V-Film thickness: 50 nm (2) Second underlayer-Material: Cr-Substrate temperature : Room temperature-Ar gas pressure: 5 mTorr-Substrate bias voltage: 0 V-Film thickness: 50 nm (3) Magnetic layer-Material: Co _78.7 Sm _18.1 Ce _3.2 at% -Substrate temperature: Room temperature-Ar gas pressure: 5 mTorr-Substrate bias voltage : 0V ・ Film thickness: 30nm

(4) Intermediate layer-Material: Cr-Substrate temperature: room temperature-Ar gas pressure: 5 mTorr-Substrate bias voltage: 0 V-Film thickness: 7 nm (5) Protective layer-Material: Amorphous carbon-Substrate temperature: Room temperature- Ar gas pressure: 5 mTorr-Substrate bias voltage: 0 V-Film thickness: 10 nm

After forming the protective layer, the Ar gas was stopped, the inside of the sputtering chamber was leaked with N ₂ and the carbon substrate having the protective layer formed was taken out. In addition, tape burnish, followed by the lubricant Fomblin AM2001
(Manufactured by Aojimont Co., Ltd.) was applied to a film thickness of 2 nm to obtain a magnetic disk.

For the obtained magnetic disk, VSM
The magnetostatic characteristic (coercive force Hc) was evaluated with a (vibrating sample magnetometer). In addition, the obtained magnetic disk is
After leaving it in an atmosphere of 80% RH for 2 weeks, measure Hc-after with VSM, and compare it with the Hc-before in the initial state.
(Hc-after / Hc-before) was used as an index of corrosion resistance. Table 1 shows the results.

Examples 2 to 4 and Comparative Examples 1 to 3 Examples other than forming the magnetic layer by using the alloys shown in Table 1 in place of the alloy used for the magnetic layer in the magnetic disk of Example 1. A magnetic disk was obtained by the same procedure as in 1. The same measurement as in Example 1 was performed on the obtained magnetic disk. Table 1 shows the results.

[0031]

[Table 1]

As is clear from the results shown in Table 1, C
The magnetic disks obtained in Examples 1 to 4 having a magnetic layer made of an alloy of o, Sm, and a rare earth metal other than Sm and having a specific concentration have corrosion resistance while maintaining a high coercive force. You can see that it has been improved. On the other hand, in the magnetic disk having the magnetic layer made of a Co-Sm binary alloy (Comparative Example 1), a relatively high coercive force can be obtained, but the corrosion resistance is poor. Further, in the same manner as in Comparative Example 1, in the magnetic disk (Comparative Example 2) having the magnetic layer made of the Co—Sm binary alloy and having the Sm concentration lower than that of Comparative Example 1, the corrosion resistance is improved, High coercive force cannot be obtained. Also, Co, Sm and S
A magnetic disk (Comparative Example 3) having a magnetic layer made of an alloy having a high Sm concentration, although it is an alloy made of a rare earth metal (Ce) other than m, has improved corrosion resistance but does not have high coercive force. .

[0033]

As described above in detail, according to the present invention,
By further adding a rare earth alloy R other than Sm to the Co-Sm alloy and setting the concentration of Sm / R within a specific range and reducing the concentration of rare earth metal (Sm + R) in the entire alloy, the coercive force A magnetic recording medium having good corrosion resistance without deterioration is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a first embodiment of a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram showing the configuration of a second embodiment of the magnetic recording medium of the present invention.

[Explanation of symbols]

 10 magnetic recording medium 12 non-magnetic substrate 14 magnetic layer

Claims (2)

[Claims] 1. A magnetic recording medium having a non-magnetic substrate and a magnetic layer provided on the non-magnetic substrate, wherein the magnetic layer is made of an alloy represented by the following formula (1). Medium. Co _a Sm _b R _c (1) (In the formula, R represents one or more rare earth metals other than Sm, b and c are 5 to 25 at% in total, and b / c is 3 to 50. And a is 95 to 75 at%.) 2. R in the above formula (1) is Ce, P
r, Gd, Ho, Nd, Tb or Dy.
The magnetic recording medium described.