JPH05189739A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having enhanced coercive force, high S/N and low disk noise by forming a quinquenary magnetic film contg. V or Nb added to Co, Cr, Pt and B. CONSTITUTION:A magnetic film is formed with an alloy consisting of, by atom, 5-20% Cr, 1-15% Pt, 0.5-5% B, 0-8% V and/or Nb and the balance Co with inevitable impurities. Since the magnetic film contains <=8 atomic % V or Nb as well as 0.5-5 atomic % B, a magnetic recording medium having high coercive force, high S/N and reduced noise is obtd. By the combined addition of B and V or Nb, high coercive force of about 1,700Oe can be attained even in the case of a reduced expensive Pt content.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a magnetic disk,
The present invention relates to a magnetic recording medium such as a magnetic tape, in which the coercive force of a magnetic film is improved and the disk noise is reduced.

[0002]

2. Description of the Related Art As a magnetic recording medium used in a magnetic recording device or the like, a magnetic recording medium made of a CoCr-based alloy film having a Cr film as an underlayer, which is easier to manufacture than the conventional one and has a large residual magnetic flux density and coercive force, is used. (The Journal of Japan Applied Magnetics Vol.13 No.3 493 (1989). In recent years, due to the increase in capacity of magnetic recording devices, high coercive force and high S / N ratio are required to increase recording density. In the magnetic recording medium manufactured by the conventional sputtering method, Co is formed on the Cr layer.
A magnetic layer of Crta is formed on the Cr layer with CoN.
It has been found that the magnetic properties are superior to those having a magnetic layer such as i or CoNiCr formed thereon. (Japanese Patent Application Sho 62-2
91519 publication). Also, at the 6th Japan Society of Applied Magnetics in November 1983, C in binary media and ternary media
A technology for adding Pt to an o alloy has been disclosed by NEC.

Japanese Patent Laid-Open No. 1-256017 discloses that
A magnetic recording medium in which the magnetic film is made of a quaternary alloy of CoCrTaPt has been proposed, and the Pt addition amount is 1 to 15 at%.
Has a coercive force of more than 1200 Oe and a squareness ratio of 0.8
It is supposed to be over. Furthermore, in the 14th Japan Society for Applied Magnetics (1990), Co-Cr-Ta and Co-
It has been announced that the addition of B to Cr-Pt affects the coercive force. And Co-Cr-T
When B is added to a, the coercive force monotonically decreases and Co-Cr
In the case of -Pt, the coercive force increases with the addition of B. 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]

In the magnetic recording medium described above in which Pt is added to the Co alloy, a high coercive force cannot be obtained unless Pt is added at least about 15 at%, and Pt is very high. It was expensive and not very practical. Further, in a magnetic recording medium in which a magnetic film is formed of an alloy in which B is added to Co-Cr-Pt, there is a problem that the disk noise is large, and the addition amount of B is 0.
The coercive force was improved at 5 to 5 at%, but the coercive force tended to be decreased when B exceeded 5 at%. Therefore, the present invention
In a magnetic recording medium provided with a quinary magnetic film in which V or Nb is added to -Cr-Pt-B, it is possible to improve the coercive force and the S / N ratio to reduce disk noise. To aim.

[0005]

In order to achieve the above-mentioned object, the present invention provides magnetic recording in which a magnetic film made of a magnetic material is provided on the surface of a substrate made of a non-magnetic material with an undercoat film made of a non-magnetic material interposed therebetween. In the medium, the magnetic film is made of Cr5 in atomic%.
~ 20%, Pt1-15%, B0.5-5%, V and Nb
One or two of them were formed by an alloy composed of 0 to 8% and the balance Co and inevitable impurities.

In the above, Cr contained in the magnetic film is 5
If it is less than atomic%, the corrosion resistance is lowered. That is, the rate of decrease of the saturation magnetization due to the change of the environment is large, and the bit shift is increased, which is inconvenient. On the other hand, when the Cr content exceeds 20 atomic%, the output is lowered due to the decrease in the residual magnetization, and the bit shift is increased, which is not preferable. B
If the addition amount of is less than 0.5 atom%, the improvement of the coercive force is insufficient, and if it exceeds 5 atom%, the coercive force tends to decrease. The coercive force is highest when the addition amount of B is 2 to 3 at%, and the more desirable coercive force is 1 to 4 at%. Further, V and Nb contained in the magnetic film contribute to the improvement of the coercive force and the noise reduction, but if it is 8 atomic% or more, the action cannot be expected, which is not desirable. The amount of V and Nb added is 2 to 3 at.
%, The coercive force is the highest, and 1 to 6 at% provides a more desirable coercive force. The base film is preferably formed of Cr or a Cr alloy. In this case, as the Cr alloy, an alloy such as Cr-Mn, Cr-V, Cr-Mn can be used. The substrate is preferably made of aluminum or an aluminum-based alloy.

[0007]

In the above magnetic recording medium, B is added to the magnetic film in an amount of 0.5 to 0.5.
V or Nb of 5 atomic% or less and 8 atomic% or less
, The coercive force is large and the S / N ratio is large, so that noise is reduced. That is, in the magnetic film of the magnetic recording medium, CoCr having uniaxial anisotropy in the C axis is used.
The (110) plane of the Pt-based alloy film (hcp structure) is Cr
Preferential orientation is on the (100) plane of the (bcc structure). This means that the C axis of hcp coincides with the in-plane direction of the disc. Also, by adding B and V and B and Nb in combination, C
The crystal grains of the oCrPt film become finer, and the magnetic grains tend to have a single domain structure. This causes the magnetization reversal mechanism of the magnetic film to shift to the rotation mode. As a result, it is considered that a high coercive force can be obtained.

[0008]

EXAMPLES Examples and comparative examples of the present invention will be described in detail below. However, the scope of the present invention is not limited to these examples. (Example 1) A Ni-P plating film of 5 to 15 µm was formed on the surface of a 3.5-inch aluminum alloy plate (outer diameter 95 mm, inner diameter 25 mm, thickness 1.27 mm), and the surface was mirror-finished. Then, texture processing is performed to obtain surface roughness Ra =
A disk-shaped substrate having a size of 5-6 nm was prepared. After cleaning the substrate, for example, after exhausting the inside of the DC magnetron sputtering chamber to 2.66 × 10 ⁻⁴ Pa or less, Ar gas is introduced to maintain the inside of the sputtering chamber at 2.66 Pa.
A Cr underlayer having a thickness of 100 nm was formed under the condition of 0 ° C. Then, a film thickness of 50 is formed as a magnetic film on the Cr underlayer.
nm of CoCrPtVB and CoCrPtNbB were sputtered. The composition of the magnetic film was adjusted by the number of B, V, and Nb chips attached to the CoCrPt target. FIG. 1 shows the relationship between the coercive force and the V and Nb concentrations when the V concentration of the magnetic film of the magnetic recording medium thus obtained was changed.
Addition amount of V and Nb is less than 8at% and coercive force is about 1700
It is found that the coercive force becomes the highest at Oe or more and 2 to 3 at%, and the coercive force gradually decreases even if the coercive force is decreased or increased.

Example 2 Next, a substrate was prepared in the same manner as in Example 1, and a Cr underlayer film having a film thickness of 100 nm was formed on the substrate by sputtering. Further, on the Cr underlayer, CoCr with a thickness of 50 nm was formed by changing the B concentration.
PtVB and CoCrPtNbB films were formed by sputtering. The relationship between the coercive force and the B concentration of the magnetic recording medium thus obtained is shown in FIG. From FIG. 2, as with V and Nb, the coercive force is 170 when the added amount of B is 0.5 to 5 at%.
It is found that the coercive force is the largest at 0 Oe or more and 2 to 3 at%, and the coercive force gradually decreases even if the coercive force is decreased or increased.

(Embodiment 3) With respect to the magnetic recording media prepared in the above Embodiments 1 and 2, signal recording / reproduction was performed with a flying height of 0.15 μm and a recording linear density of 24 KFCI using a thin film head having a gap length of 0.5 μm. The ratio of the reproduction signal output (signal) to the media noise intensity (S / Nd
B) was determined. The obtained results are shown in Table 1 below together with the alloy composition of the magnetic film.

[0011]

[Table 1] From Table 1, the magnetic recording medium provided with the magnetic film in which V or Nb is added to CoCrPtB has a reproduction output signal slightly lower than that of the magnetic recording medium provided with the magnetic film made of CoCrPt in the comparative example. It can be seen that the N ratio becomes higher and the noise becomes smaller.

[0012]

According to the magnetic recording medium of the present invention, B and V or N
By adding b together, a high coercive force of about 1700 Oe can be realized even if the content of expensive Pt is reduced, and the saturation magnetization has a sufficient value as a magnetic recording medium. The recording medium becomes manufacturable. Further, the S / N ratio of the magnetic recording medium is increased, and noise can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the added amount of V and Nb and the coercive force in a magnetic film.

FIG. 2 is a graph showing the relationship between the amount of B added and the coercive force in the magnetic film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hajime Shinohara 5200 Mikashiri, Kumagaya, Saitama Hitachi Metals Co., Ltd.

Claims (3)

[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%
r5-20%, Pt1-15%, V0-8%, B0.5
A magnetic recording medium characterized by being formed of an alloy consisting of ˜5% and the balance Co and unavoidable impurities. 2. 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, wherein the magnetic film is C in atomic%.
r5-20%, Pt1-15%, Nb0-8%, B0.
A magnetic recording medium formed of an alloy containing 5 to 5% of balance Co and inevitable impurities. 3. 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 a base film made of a non-magnetic material, the magnetic film being C in atomic%.
r5-20%, Pt1-15%, V and Nb total 0
A magnetic recording medium formed of an alloy of 8%, B 0.5 to 5%, the balance Co and unavoidable impurities.