JPH05182171A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having large coercive force and decreased noise by forming the magnetic film from an alloy consisting, by atomic% of 7-15 Cr, 7-15 Pt, 0.5-3 B, and the balance Co with inevitable impurities. CONSTITUTION:The magnetic recording medium is film-formed by successively laminating a Cr base film, Co-Cr-Pt-B alloy magnetic film, and C protective film. The magnetic film added of B by 0.5-3 atomic% has >=2100 Oe coercive force, however, if the added amt. thereof exceeds 3 atomic%, the coercive force decreases. By adding 0.5-3 B, the squareness ratio increases to >=0.8, which is preferable for the output. However, if the add amt. of B exceeds 3 at.%, disk noise increases. It is pareferable to add 7-15 Pt and 7-15 Cr concerning the coercive force. Thus, the coercive force increases and the 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 a magnetic recording medium for recording and reproducing information with, for example, a magnetic head, and more particularly to a magnetic recording medium having improved coercive force by reducing noise.

[0002]

2. Description of the Related Art In a magnetic disk device, a magnetic head is opposed to a magnetic recording medium at minute intervals so that the magnetic head reads magnetic information recorded on the magnetic recording medium or magnetically records the magnetic information from the magnetic head onto the magnetic recording medium. It is supposed to do. The magnetic recording medium uses Co-Ni-Cr, C as the substrate material.
It is formed by depositing a magnetic film made of an alloy such as o-Cr-Ta or Co-Cr-Pt. Recently, in order to make the magnetic recording medium have a high recording density, it is necessary to increase the coercive force of the magnetic film. Have been proposed.

For example, Japanese Patent Laid-Open No. 1-256017 discloses a magnetic recording medium in which a magnetic film is made of a quaternary alloy of Co--Cr--Ta--Pt. When the amount of Pt added is 1 to 15 at%, the coercive force is larger than about 1200 Oe and the squareness ratio is 0.8 or more. In the 14th Japan Society for Applied Magnetics (1990), Co-C
It has been announced that the coercive force is affected by adding B to r-Ta and Co-Cr-Pt.
The coercive force monotonously decreases when B is added to Co-Cr-Ta, and the coercive force increases with the addition of B in the case of Co-Cr-Pt. It is also stated that a high coercive force of about 3000 Oe can be obtained by adding 3 to 7 at% of B to Co-Cr-Pt.

[0004]

As described in the above-mentioned prior art, the coercive force can be improved in a magnetic recording medium in which a magnetic film is made of an alloy of a quaternary element of Co-Cr-Pt-B. It has been known. The present inventors have developed Co-Cr
When a magnetic film is formed by using an alloy in which 3 to 7 at% of B is added to -Pt to prepare a magnetic recording medium, coercive force is improved, but when the added amount of B exceeds 3 at%, it tends to decrease. It was found that the addition of B did not lead to an improvement in the coercive force depending on the ratio of. In addition, the disk noise decreases monotonously until the amount of B added reaches 2.5 at%.
I learned that it tends to increase above 2.5 at%. Therefore, it is an object of the present invention to improve the coercive force of a magnetic recording medium and reduce noise.

[0005]

The present inventors have found that Co--C
A magnetic film was made from an alloy in which the component ratio of r-Pt was changed and the addition amount of B was variously changed, and it was studied to improve coercive force and reduce noise as a disk. Then, by various experiments, B was set to 3 at% or less,
The present invention was completed to improve coercive force and reduce noise. That is, the present invention provides a magnetic recording medium in which a magnetic film made of a magnetic material is provided on the surface of a substrate made of a non-magnetic material via an undercoat film made of a non-magnetic material, and the magnetic film contains Cr of 7 to 15% in atomic%, Pt7-15
%, B 0.5 to 3%, the balance Co and unavoidable impurities.

[0006]

In the above magnetic recording medium, the magnetic film is Co--Cr--.
It is composed of Pt-B quaternary elements, and B is 0.5 to 3 atom%.
Since it is contained, the coercive force is as large as 2000 Oe or more, the recording density is improved, and the noise is 3 μVrm.
It becomes s or less, and noise can be reduced.

[0007]

Example The surface of a substrate made of an aluminum alloy containing 4% by weight of magnesium was formed into a smooth surface by turning, to obtain a substrate having an outer diameter of 95 mm, an inner diameter of 25 mm and a thickness of 1.27 mm. Next, a Ni-P alloy plating film having a thickness of 5 to 15 μm is formed on the surface of this substrate, and the contact sliding characteristics (CSS) with the magnetic head or slider at the time of starting and stopping the magnetic recording medium are measured. Secure. The surface of the plated film deposited as described above is polished to be smooth, and texture processing is performed to prevent adsorption to the magnetic head or slider.

Next, after cleaning the substrate, a base film made of Cr and Co--
A magnetic film made of a Cr-Pt-B alloy and a protective film made of C are sequentially stacked to form a film. In this case, for forming the base film, after exhausting the inside of the sputtering chamber to 1 × 10 ⁻⁵ Toor or less,
The substrate was heated at 200 ° C. for 30 minutes, Ar gas was introduced to maintain the inside of the sputtering chamber at 5 mToor, and a film having a thickness of 100 nm was formed under conditions of an input power of 2000 W and a film forming rate of 40 nm / min. Next, on this base film, Cr1
2 atomic%, Pt 12 atomic%, B addition amount 0 to 3 atomic%,
With various balance magnetic films made of Co—Cr—Pt—B with different Co additions and different in B addition amount, the applied power 2000
A film having a thickness of 50 nm was formed under the conditions of W and the film forming speed of 100 nm / min. A bias voltage of -4 is used for sputtering this magnetic film
00V was applied. In addition, the protective film is 1000 W input power,
A film thickness of 30 n is formed on the magnetic film under the condition that the film forming speed is 8 nm / min.
The film was formed at m.

The coercive force of various magnetic recording media produced as described above was measured and shown in FIG. As can be seen from FIG. 1, a magnetic film containing 0.5 to 3 atomic% of B has a coercive force of 2100 Oe or more, and the addition amount of B is 3 or more.
It can be seen that the coercive force tends to decrease when the atomic percentage is exceeded. Similarly, the squareness ratios of the magnetic films of the various magnetic recording media were measured and shown in FIG. It can be seen from FIG. 2 that the squareness ratio is 0.8 or more when the addition amount of B is 0.5 to 3 atom%, which is desirable for output. Further, the output and disk noise of each of the various magnetic recording media were measured and shown in FIG. For each magnetic recording medium, a thin film head with a cap length of 0.5 μm was used, with a flying height of 0.11 μm and a recording linear density of 24 KFCI.
Then, signal recording and reproduction were performed, and the reproduction output signal and media noise were obtained. From FIG. 3, the addition amount of B is 0.5 to 3 atom%.
It can be seen that the output is desirable to be 120 μVrms or more, and the disk noise is desirably 3 μVrms or less. When the addition amount of B exceeds 3 at%, the disk noise tends to increase.

In the magnetic recording medium, the magnetic film is made of Cr.
Various magnetic films were prepared by changing the Pt amount to 12 at%, B2 at%, and the balance Co, and the coercive force of each was measured and shown in FIG. From FIG. 4, the Pt addition amount is 7 to 15
At coercive force, the coercive force becomes 1300 Oe or more, and it is considered preferable to set Pt in this range. Similarly, various magnetic films were prepared by changing the amount of Cr with Pt at 10 at%, B2 at% and (remainder Co) as the magnetic film, and the coercive force of each was measured and shown in FIG. From FIG. 5, the amount of Cr is 7 to
At 15 at%, the coercive force becomes 2000 Oe or more, and it is considered desirable to set it in that range.

[0011]

The magnetic recording medium of the present invention is a Co-Cr-
Since the magnetic film is made of an alloy in which B is 0.5 to 3 at% with a quaternary element of Pt-B, the coercive force is large and
The one with reduced noise can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of B added and the coercive force in a magnetic film made of a quaternary element according to the present invention.

FIG. 2 is a relationship diagram between the B addition amount and the squareness ratio in the magnetic film made of the quaternary element of the present invention.

FIG. 3 is a graph showing the relationship between the amount of B added to the magnetic film made of the quaternary element of the present invention, and the output and noise of the disk.

FIG. 4 is a diagram showing the relationship between the amount of Pt added and the coercive force in a magnetic film made of a quaternary element according to the present invention.

FIG. 5 is a graph showing the relationship between the amount of added Cr and the coercive force in a magnetic film made of a quaternary element according to the present invention.

Front Page Continuation (72) Inventor Hajime Shinohara 5200 Sankejiri, Kumagaya City, Saitama Hitachi Metals Co., Ltd.

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic film made of a magnetic material is provided on a surface of a substrate made of a non-magnetic material via an undercoat film made of a non-magnetic material, the magnetic film being C in atomic%
A magnetic recording medium characterized by being formed of an alloy comprising r7-15%, Pt7-15%, B0.5-3%, the balance Co and inevitable impurities.