JPH0554359A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium of a high coercive force, low noise and high output by forming a magnetic layer contg. cobalt, platinum, zirconium, and boron on a substrate at specific ratios. CONSTITUTION:The surface of the substrate 1 is lapped and a hard layer 2 of nickel-phosphorus is provided as a nonmagnetic metallic layer by an electroless plating method thereon. After this hard layer 2 is polished to a specular surface, a texture is formed. A substrate layer 3 consisting of nonmagnetic chromium is then formed on this electroless plating layer of the nickel-phosphorus. A magnetic layer 4 consisting of cobalt-chromium-platinum- zirconium-boron is formed by a sputtering method on this chromium substrate layer 3. The zirconium and the boron are incorporated therein at the specific ratios.

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.

[0002]

2. Description of the Related Art In recent years, it has become possible to record even on a magnetic recording medium having a high coercive force by improving the material of the head and reducing the flying height of the head. High-density recording is required. In the magnetic recording medium manufactured by the conventional sputtering method, a CoCrTa magnetic layer formed on an underlayer made of Cr is not used as CoCrNi on the underlayer made of Cr.
It has excellent magnetic characteristics as compared with a magnetic layer formed of CoNi or the like. Further, a magnetic layer of CoNiPt or CoCrPt to which Pt is added is formed on an underlayer made of Cr, which is disclosed in JP-A-62-1141628 and JP-A-63-1628.
253622, JP-A-59-88806 and JP-A-6.
3-187414 and JP-A-1-283803.

However, in Japanese Patent Laid-Open No. 59-88806, the coercive force is 1000 Oe or less.
No. 253622 also has a coercive force of 1000 Oe or less. Further, in JP-A-63-187414, 17 atomic% or more of Cr is added to reduce noise.
Therefore, it is difficult to produce high output. Further, in JP-A-1-283803, the Cr film thickness is made as thick as 2000Å in order to obtain a high coercive force, which is not preferable from the viewpoint of productivity and the like.

Further, increasing the Pt concentration is also an effective method for obtaining a high coercive force (reference: IEEE TRANSACTION).
S ON MAGNETICS, VOL. MAG-22, NO.5, SEPTEMBER 1986;
It is the same VOL. MAG-19, NO.4, JULY 1983), but it is costly and has practical problems.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art.

[0006]

The present invention has been made to solve the above-mentioned problems, and has a magnetic layer made of cobalt, platinum, chromium, zirconium and boron on a substrate, and is included in the magnetic layer. And zirconium (Zr) and boron (B) are in the range of 0.5 at% ≤Zr ≤5 at% 1 at% ≤B ≤5 at% respectively. ..

In the present invention, a non-magnetic layer may be provided on the substrate side of the magnetic layer as an underlayer adjacent to the magnetic layer.

In the present invention, the nonmagnetic layer may be made of chromium. The thickness of the nonmagnetic layer made of chromium is not particularly limited, but it is not preferable to make it extremely thick from the viewpoints of economical efficiency of the target, maintenance of the device, productivity, and the like, and for the purpose of the present invention, it may be about 500Å. Good. In the present invention, another film, for example, a Ni-P electroless plating film can be provided between the substrate and the underlayer.

[0009]

The present invention will now be described in detail with reference to the drawings and examples, but the present invention is not limited thereto.

FIG. 1 is a partial sectional view of an embodiment of the magnetic recording medium of the present invention. In FIG. 1, the non-magnetic substrate 1 of the magnetic recording medium has an outer diameter of 95 mm, an inner diameter of 25 mm, and a thickness of 1.
A 27 mm aluminum disk was prepared and the surface of the substrate 1 was lapped. Next, on this substrate 1, a hard layer (nickel-phosphorus electroless plating layer) 2 made of nickel-phosphorus having a thickness of 25 μm was formed as a non-magnetic metal layer by electroless plating.
Was provided, the hard layer 2 was mirror-polished, and then the texture was formed by a usual means.

Next, an underlayer 3 made of chromium was formed as a nonmagnetic underlayer 3 on the nickel-phosphorus electroless plating layer 2 by a sputtering method. Next, a magnetic layer 4 made of cobalt-chromium-platinum-zirconium-boron was formed on the chromium underlayer 3 by sputtering.
Next, a protective film 5 made of carbon was provided on the magnetic layer 4 by a sputtering method. As the sputtering, a co-sputtering method in which a CoCrPt target and a ZrB target were used for sputtering was used.

Example 1 On a chromium underlayer having a thickness of 100Å, 12 atom% of chromium, 10 atom% of platinum, 2 atom% of zirconium and 2 atom of boron were used.
A cobalt alloy magnetic layer containing atomic% was formed to a thickness of 600Å, and a carbon protective film was further formed thereon to a thickness of 300Å. Coercive force Hc, product of magnetization and thickness tMr, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1000 Oe and 3.5 × 10 ⁻³ em, respectively.
It was u / cm ² , 0.9, 0.92, and 32 dB.

Example 2 On a chromium underlayer having a thickness of 200Å, 12 atom% of chromium, 10 atom% of platinum, 2 atom% of zirconium, 2 boron of 2
A cobalt alloy magnetic layer containing atomic% was formed to a thickness of 600Å, and a carbon protective film was further formed thereon to a thickness of 300Å. Coercive force Hc, product of magnetization and thickness tMr, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1200 Oe and 3.5 × 10 ⁻³ emu, respectively.
/ Cm ² , 0.9, 0.91, 32 dB.

Example 3 On a chromium underlayer having a thickness of 300Å, 12 atomic% of chromium, 10 atomic% of platinum, 2 atomic% of zirconium and 2 atomic% of boron were formed.
A cobalt alloy magnetic layer containing atomic% was formed to a thickness of 600Å, and a carbon protective film was further formed thereon to a thickness of 300Å. Coercive force Hc, product of magnetization and thickness tMr, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1500 Oe and 3.5 × 10 ⁻³ emu, respectively.
/ Cm ² , 0.9, 0.91, 32 dB.

Example 4 On a chromium underlayer having a thickness of 300Å, 12 atom% of chromium, 10 atom% of platinum, 3 atom% of zirconium, and 3 boron of boron were formed.
A cobalt alloy magnetic layer containing atomic% was formed to a thickness of 600Å, and a carbon protective film was further formed thereon to a thickness of 300Å. Coercive force Hc, product of magnetization and thickness tMr, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1600 Oe and 3.2 × 10 ⁻³ emu, respectively.
/ Cm ² , 0.9, 0.93, 33 dB.

Example 5 12 atomic% of chromium, 10 atomic% of platinum, 3 atomic% of zirconium and 3 boron of boron were formed on a chromium underlayer having a thickness of 500Å.
A cobalt alloy magnetic layer containing atomic% was formed to a thickness of 600Å, and a carbon protective film was further formed thereon to a thickness of 300Å. Coercive force Hc, product of magnetization and thickness tMr, squareness ratio (Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1800 Oe and 3.2 × 10 ⁻³ emu / c, respectively.
It was m ² , 0.9, 0.93, and 34 dB.

Example 6 Table 1 shows the values of coercive force Hc (Oe) with respect to the added atomic% (at%) when Zr-B was added to Co-Cr-Pt. For comparison, in the case of only Co-Cr-Pt, Zr
Table 2 shows the values when B was added alone and when B was added alone. However, chromium film thickness: 500Å (constant), magnetic film thickness: 600Å (constant), tMr = 3.5 ×
It is 10 ^-3 emu / cm ² .

[0018]

[Table 1]

[0019]

[Table 2]

Comparative Example 1 A cobalt alloy magnetic layer containing 12 atomic% of chromium and 10 atomic% of platinum was formed on a chromium underlayer having a thickness of 100Å to a thickness of 6
It was formed with 00Å, and a carbon protective film with a thickness of 300Å was further provided thereon. Coercive force Hc, product of magnetization and thickness tM
r, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 700 Oe and 3.5 × 10, respectively.
^-3 emu / cm ² , 0.9, 0.90, 29 dB.

Comparative Example 2 A cobalt alloy magnetic layer containing 12 atom% of chromium and 10 atom% of platinum was formed on a chromium underlayer having a thickness of 200Å to a thickness of 6
It was formed with 00Å, and a carbon protective film with a thickness of 300Å was further provided thereon. Coercive force Hc, product of magnetization and thickness tM
r, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 800 Oe and 3.5 × 10, respectively.
^-3 emu / cm ² , 0.9, 0.90, 29 dB.

Comparative Example 3 A cobalt alloy magnetic layer containing 12 atomic% of chromium and 10 atomic% of platinum was formed on a chromium underlayer having a thickness of 300Å to a thickness of 6
It was formed with 00Å, and a carbon protective film with a thickness of 300Å was further provided thereon. Coercive force Hc, product of magnetization and thickness tM
r, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1000 Oe and 3.5 × 1 respectively.
It was 0 ^-3 emu / cm ² , 0.9, 0.90, and 30 dB.

Comparative Example 4 A cobalt alloy magnetic layer containing 12 atomic% of chromium and 10 atomic% of platinum was formed on a chromium underlayer having a thickness of 500Å to a thickness of 6
It was formed with 00Å, and a carbon protective film with a thickness of 300Å was further provided thereon. Coercive force Hc, product of magnetization and thickness tM
r, squareness ratio (S = Mr / Ms), coercive force squareness ratio S ^* , and medium signal-to-noise ratio are 1200 Oe and 3.5 × 1 respectively.
It was 0 ^-3 emu / cm ² , 0.9, 0.90, and 30 dB.

[0024]

The magnetic recording medium of the present invention has a high coercive force, low noise and high output. Further, since the amount of Pt in the magnetic layer can be reduced, an economic effect can be recognized. Further, since the Cr film thickness as the underlayer can be reduced, the productivity is improved, and the economical effect can be recognized from this point as well.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an embodiment of a magnetic recording medium of the present invention.

[Explanation of symbols]

 1 substrate 2 nickel-phosphorus electroless plating layer 3 chromium layer 4 magnetic layer 5 protective film

Claims (4)

[Claims] 1. A magnetic layer made of cobalt, platinum, chromium, zirconium, and boron is provided on a substrate, and zirconium (Zr) and boron (B) contained in the magnetic layer are each 0.5 atomic% ≦ Zr ≦. A magnetic recording medium characterized by being in the range of 5 at% 1 at% ≤ B ≤ 5 at%. 2. The magnetic recording medium according to claim 1, further comprising a non-magnetic layer as a base layer adjacent to the magnetic layer on the substrate side of the magnetic layer. 3. The magnetic recording medium according to claim 2, wherein the non-magnetic layer is made of chromium. 4. The magnetic recording medium according to claim 2, wherein the nonmagnetic layer has a thickness of 500 Å or less.