JP2001266326A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium of high recording density at a low price. SOLUTION: In the magnetic recording medium provided with a Co based alloy magnetic recording layer on a non-magnetic substrate, a lanthanoid series rare earth transition metal is incorporated into the Co based alloy magnetic recording layer. The magnetic recording medium whole noise is reduced can be obtained by further adding Cr and/or B to the layer.

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 such as a hard disk, and more particularly to a longitudinal magnetic recording medium having a Co-based alloy magnetic recording layer formed by a sputtering method.

[0002]

2. Description of the Related Art In response to a rapid increase in the amount of information handled in the field of information communication, magnetic recording devices are required to have higher recording densities. Therefore, a magnetic recording medium (hereinafter, also simply referred to as a medium) used in a magnetic recording apparatus has a high coercive force (H
c) A low remanence film thickness product (tMr) is essential. The problem of increasing the coercive force has been addressed by adding Pt to the magnetic recording layer. In addition, a high-sensitivity reproducing head has been used as the reproducing head, and in order to cope with this, it has been required to reduce the noise of the medium itself. As a countermeasure, a method of increasing the amount of Cr in the magnetic recording layer has been generally adopted. Was. It is also well known that adding B to a magnetic recording layer is effective.

[0003]

Hc increases as the amount of Pt added to the magnetic recording layer increases, but the media price increases because Pt is expensive. Further, there is a limit to the increase in Hc by adding Pt. For example, in the longitudinal magnetic recording method, Hc of about 5000 Oe is required for a recording density of 40 Gbits / in ² or more, but at the same time, tMr which determines the magnitude of output is 0.3 memu / cm.
^It needs to be reduced to about ² . The thickness of the magnetic recording layer is usually 15 nm to 20 nm, and such a thin film has a thickness of 500 nm.
It is difficult to obtain Hc of about 0 Oe. The present invention has been made in view of the above points, and has as its object to provide a low-price, high-density medium.

[0004]

According to the present invention, there is provided a magnetic recording medium comprising a Co-based alloy magnetic recording layer on a non-magnetic substrate, wherein the Co-based alloy magnetic recording layer includes a lanthanoid-based magnetic recording layer. The problem is solved by including a rare earth transition metal. The present inventor has improved the coercive force of the medium,
Various studies were conducted on additives to the magnetic recording layer for the purpose of reducing the product of the residual magnetization film thickness, and it was found that the addition of a lanthanoid-based rare earth transition metal instead of Pt was effective. The addition amount of the lanthanoid series rare earth transition metal is 5
Atomic% to 30 atomic% is desirable. Among the lanthanoid series rare earth transition metals, S in terms of magnetic anisotropy energy
m, Eu, Gd, Tb and Dy are particularly preferred.

[0005] It is preferable that the Co-based alloy magnetic recording layer contains Cr and a lanthanoid-based rare-earth transition metal, because the noise is reduced. Further, it is preferable that the Co-based alloy magnetic recording layer contains Cr, a lanthanoid-based rare-earth transition metal and B to further reduce noise. The material composition of the magnetic recording layer is desirably in the range of 15 atomic% to 25 atomic% of Cr, 5 atomic% to 30 atomic% of lanthanoid series rare earth transition metal, 0 atomic% to 6 atomic% of B, and the balance of Co.

[0006]

FIG. 1 is a schematic sectional view showing an example of a layer structure of a medium according to the present invention. An underlayer 2, a magnetic layer 3 as a magnetic recording layer, and a protective layer 3 are formed on a nonmagnetic substrate 1. The film 4 and the lubricating film 5 are sequentially formed. As the substrate 1, any substrate of a commonly used material such as an aluminum alloy substrate and a glass substrate can be used.

The base film 2 is formed by a sputtering method, and may have a single layer or a multilayer structure of two or more layers. The material of the base film may be any of commonly used materials such as a Cr alloy and a Ni alloy, but it is preferable that at least one or more Cr alloy films are formed. As the Cr alloy, for example, an alloy with Mo, V, W, Mn, Ti, or the like is used. The thickness is 5 nm to 30 nm.

The magnetic film 3 is formed by a sputtering method, and includes a Co alloy containing a lanthanoid-based rare earth transition metal,
Or a Co alloy containing a lanthanoid series rare earth transition metal and Cr, or a lanthanoid series rare earth transition metal,
It is made of a Co alloy containing Cr and B. The addition amount of the lanthanoid series rare earth transition metal is 5 atomic% to 30 atomic%,
The addition amount of r is 15 atomic% to 25 atomic%, and the addition amount of B is 0 atomic%.
The range is from atomic% to 6 atomic%. The film thickness is 10 nm to 4
0 nm.

The protective film 4 is formed by depositing carbon by sputtering or CVD. The film thickness is 5 nm to 1
5 nm. Sputtering is 5mTorr ~ 40
It is performed in a vacuum of mTorr, and the substrate temperature is from room temperature to 500
° C, preferably 220 ° C to 280 ° C. A liquid lubricant is applied to a thickness of 10 nm to 20 nm on the protective film 4 to form a lubricating film 5 to produce a medium.

[0010]

Embodiments Hereinafter, specific embodiments will be described. Example 1 On a substrate 1 of an aluminum alloy disk having a Ni-P film formed on its surface, 10 mTorr was formed by a sputtering method.
Under a vacuum of r and a substrate temperature of 250 ° C., a Cr alloy base film 2 of Cr ₈₀ Mo ₂₀ composition, a Co alloy magnetic film 3 of Co ₆₄ Cr ₂₄ Sm ₁₀ B ₂ composition, and a carbon protective film 4 are continuously formed. A film is formed, and a liquid lubricant is applied thereon to form a lubricating film 5 to produce a medium. The thickness of the Cr alloy base film 2 is 20 n
m, the thickness of the carbon protective film 4 is 10 nm, the thickness of the lubricating film 5 is 20 nm, and the thickness of the Co alloy magnetic film 3 is 10 nm.
Ten kinds of media were prepared by changing within a range of ４０40 nm.

Example 2 In Example 1, the composition of the Co alloy magnetic film 3 was changed to Co ₆₈ C
to prepare a medium except for changing the r ₂₀ Eu ₁₀ B ₂ in the same manner as in Example 1. Example 3 In Example 1, the composition of the Co alloy magnetic film 3 was changed to Co ₆₁ C
to prepare a medium except for changing the r ₂₃ Gd ₁₂ B ₄ in the same manner as in Example 1.

Example 4 In Example 1, the composition of the Co alloy magnetic film 3 was changed to Co ₆₄ C
A medium was prepared in the same manner as in Example 1, except that r ₂₄ Tb ₁₀ B ₂ was used. Example 5 In Example 1, the composition of the Co alloy magnetic film 3 was changed to Co ₆₄ C
A medium was prepared in the same manner as in Example 1, except that r ₂₄ Dy ₁₀ B ₂ was used.

Comparative Example 1 In Example 1, the composition of the Co alloy magnetic film 3 was changed to Co ₆₄ C
to prepare a medium except for changing the r ₂₀ Pt ₁₃ Ta ₃ in the same manner as in Example 1. Comparative Example 2 In Example 1, the composition of the Co alloy magnetic film 3 was changed to Co ₆₄ C
A medium was produced in the same manner as in Example 1 except that r ₁₉ Pt ₁₅ Ta ₂ was used.

The film thickness was measured with a stylus step meter. The magnetic properties of the media thus obtained in the examples and comparative examples were measured with a calibrated vibrating sample magnetometer (VSM).
The relationship between the coercive force in the longitudinal direction (recording direction) and the product of the residual magnetization film thickness was examined. The results are shown in the diagram of FIG. As can be seen in FIG. 2, each medium of the example is different from each medium of the comparative example.
In particular, the product of the residual magnetization film thickness is 0.3 memu / cm ^{2 to} 0.6.
It shows a very large coercive force exceeding 4,500 Oe in the range of memu / cm ² , which indicates that the medium has a high recording density. The effect of the present invention in which a lanthanoid-based rare earth transition metal is added to the magnetic film 3 is clear.

[0015]

According to the present invention, Co on a non-magnetic substrate
A magnetic recording medium comprising a base alloy magnetic recording layer,
By adding a lanthanoid-based rare earth transition metal to the magnetic recording layer, a high coercive force and a low remanence film thickness product can be obtained without using expensive Pt. Obtained at a low price. By adding Cr or B to the Co-based alloy magnetic recording layer, or by adding Cr and B together, a medium excellent in high coercive force, low remanence film thickness product, and low noise can be obtained. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a layer configuration of a medium according to the present invention.

FIG. 2 is a diagram showing a relationship between a coercive force and a product of a residual magnetization thickness of each medium of an example and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Underlayer 3 Magnetic film 4 Protective film 5 Lubricating film

Claims (3)

[Claims] 1. A magnetic recording medium comprising a Co-based alloy magnetic recording layer formed on a non-magnetic substrate by a sputtering method, wherein the magnetic recording layer contains a lanthanoid-based rare earth transition metal. Medium. 2. A magnetic recording medium comprising a Co-based alloy magnetic recording layer formed on a non-magnetic substrate by a sputtering method, wherein the magnetic recording layer contains Cr and a lanthanoid-based rare earth transition metal. Magnetic recording medium. 3. A magnetic recording medium comprising a Co-based alloy magnetic recording layer formed on a non-magnetic substrate by a sputtering method, wherein said magnetic recording layer contains Cr, a lanthanoid-based rare earth transition metal and B. Magnetic recording medium.