JPH05109040A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the vertical magnetic recording medium whose noise is small by a method wherein a substratum film which is laminated on a nonmagnetic support body is formed so as to have a prescribed composition. CONSTITUTION:The vertical magnetic recording medium is constituted by sequentially laminating a substratum film and a vertical magnetization film on a nonmagnetic support body; the substratum film is set as in Formula I. In Formula I, M represents at least one kind selected from Co, Fe, Ni and Mn, and L represents at least one kind out of elements in Formula II. In addition, N represents nitrogen, O represents oxygen, (x), (y), (z) and (w) represent respective ratios in terms of atomic % of the individual elements and the ratios are set to values within ranges indicated in Formula III. Thereby, the substratum thin film can be obtained in a fine crystal state, and a coercive force can be controlled by means of oxygen to be added. As a result, it is possible to obtain the vertical magnetic recording medium which is provided with a proper coercive force and whose noise is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium in which a base film and a perpendicular magnetization film are sequentially laminated on a non-magnetic support, and more particularly to a base film for a magnetic recording medium.

[0002]

2. Description of the Related Art For example, in a magnetic recording / reproducing apparatus,
Magnetic recording media are being improved in order to improve recording density, etc., but in order to achieve higher densities, it is effective to use a perpendicular magnetic recording method in which the magnetic recording medium is magnetized in a direction perpendicular to the film surface. It has been known. As a medium for perpendicular magnetic recording, a thin film medium such as CoCr is under study. However, when recording / reproducing is performed by using a conventional ring type magnetic head using a perpendicular magnetic recording medium, the reproduced signal becomes a dipulse signal, which is inconvenient for signal processing. In order to solve this problem, it has been studied to arrange a soft magnetic layer such as NiFe in the underlayer of the perpendicular magnetic recording medium, that is, the so-called backing layer. Further, even when a single magnetic pole head is used as a magnetic head for perpendicular magnetic recording, a similar underlayer film is required to improve recording efficiency and reproducing efficiency. However, NiFe
When a soft magnetic film such as is used as the underlayer, noise is generated due to magnetic domains peculiar to the soft magnetic material, which causes a problem in recording and reproduction.
It has been reported that a semi-hard magnetic material having a certain coercive force is preferable as the magnetic property of the underlayer. However, a film having a large crystal grain size is not preferable because noise is generated at the crystal grain boundary. However, at present, there is no optimum material for a base film for a perpendicular magnetic recording medium, and a NiFe film or a CoP film is used.
It is being studied by using a plating film.

[0003]

By the way, in the perpendicular magnetic recording medium, there is a demand for an underlayer film having an appropriate coercive force and generating no noise as described above. Amorphous is preferable in order to reduce noise due to crystal grain boundaries, but it is difficult to wait an appropriate coercive force. However, in recent years, a microcrystalline material having a very small crystal grain size has been attracting attention as a soft magnetic material. However, the crystallite size of the microcrystalline material is much smaller than that of crystalline permalloy, and the underlayer film of the perpendicular magnetic recording medium is When used as, it is considered that the generation of noise is small. Furthermore, it is considered that the coercive force can be controlled by controlling the crystallinity. Therefore, the present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide a perpendicular magnetic recording medium having an appropriate coercive force as an underlayer and less noise.

[0004]

The present inventor has conducted intensive studies to achieve the above-mentioned object, and as a result, Co, Fe,
It was found that it is possible to control the coercive force while maintaining the microcrystalline state by adding oxygen to the microcrystalline magnetic film composed of at least one of the magnetic elements of Ni and Mn, the specific element and nitrogen.

The present invention has been completed on the basis of such knowledge, and in a perpendicular magnetic recording medium in which a base film and a perpendicular magnetization film are sequentially laminated on a non-magnetic support, the base film is MxLyNzOw ( However, in the formula, M is Co, Fe,
Represents at least one selected from Ni and Mn, and L is N
b, Zr, Ta, Hf, Y, Mo, W, Cr, Ti,
V, La, Sm, Dy, Er, Ho, Pr, Ce, E
u, Tb, Ru, Pt, Ir, Rh, Cu, Zn, S
i, Al, Sn, Ga, Ge, Pd, Ag, In, B,
Represents at least one of C, N represents nitrogen, O represents oxygen, and x, y, z, and w each represent the ratio of each element in atomic%. ), And the composition range thereof is 40 <x <97 1 <y <40 1 <z <20 0.3 <w <20.

In the underlayer film of the perpendicular magnetic recording medium of the present invention, at least one of ferromagnetic alloys Co, Fe, Ni and Mn, Nb, Zr, Ta, Hf, Y and Mo,
W, Cr, Ti, V, La, Sm, Dy, Er, Ho,
Pr, Ce, Eu, Tb, Ru, Pt, Ir, Rh, C
u, Zn, Si, Al, Sn, Ga, Ge, Pd, A
A microcrystalline state is obtained in a thin film composed of at least one of g, In, B, and C and nitrogen. The composition x of the magnetic element M is 40 <x <97 atomic%, and the element L
The composition ratio y of 1 is 1 <y <40, and the composition z of nitrogen is 1 <z <2.
When it is set to 0, a microcrystalline magnetic film is produced. When the element L or the nitrogen N is 1% or less, the state of microcrystal does not occur, and the element L
Is 40% or more or nitrogen N is 20% or more, the magnetization is remarkably reduced, and the effect as a base film of the perpendicular magnetic recording medium cannot be expected.

When oxygen is added to this microcrystalline magnetic film,
The coercive force increases. The amount of nitrogen added is in the range that the composition ratio w of oxygen atoms in the film is 0.3 <w <20 atom%. If the amount of oxygen added is too small, an appropriate coercive force cannot be obtained, and conversely, if it is too large, the decrease in magnetization becomes large. The underlayer film of the perpendicular magnetic recording medium of the present invention is manufactured by a so-called vapor phase plating technique such as sputtering. Sputtering may be performed using an alloy target adjusted to have a desired composition ratio, or a target for each atom may be individually prepared, and the area and applied output may be adjusted to control the composition. You may go. In particular, when the former method is adopted, the film composition is almost uniquely determined by the target composition, which is suitable for mass production, for example.

As a method of adding nitrogen, a method of introducing nitrogen or ammonia gas into the atmosphere and performing sputtering can be considered. As a method of adding oxygen, a method of using an oxide target or introducing oxygen-containing gas such as oxygen or carbon dioxide into the atmosphere to form a film can be considered.

[0009]

[Function] At least one of ferromagnetic alloys Co, Fe, Ni and Mn, and Nb, Zr, Ta, Hf, Y and Mo,
W, Cr, Ti, V, La, Sm, Dy, Er, Ho,
Pr, Ce, Eu, Tb, Ru, Pt, Ir, Rh, C
u, Zn, Si, Al, Sn, Ga, Ge, Pd, A
A microcrystalline state is obtained in a thin film composed of at least one of g, In, B, and C and nitrogen. The coercive force can be controlled by adding oxygen to the microcrystalline film, and a perpendicular magnetic recording medium having an appropriate coercive force as an underlayer and less noise can be obtained.

[0010]

[Examples] Film formation was carried out by RF magnetron sputtering using an alloy target (diameter 100 mm). Nitrogen addition was carried out while introducing a mixed gas of Ar, N ₂ gas and O ₂ gas into the sputtering. went. The conditions during film formation were as follows. —Sputtering Conditions— Ultimate Vacuum 2 × 10 ⁻⁴ Pa Ar Gas Pressure 0.1 Pa Input Power 300 W Film thickness is 1 μm.

The coercive force Hc was measured by a BH loop tracer and a sample vibrating magnetometer. The saturation magnetic flux density was measured by a sample vibrating magnetometer. The experiment of recording / reproducing characteristics was conducted as follows. The underlying film had a thickness of 0.5 μm, and a 100 nm thick CoPtBO sputtered film was used as the perpendicular magnetization film. The magnetic properties of the perpendicular magnetization film are perpendicular coercive force 1
50 kA / m. The recording / reproducing head is a single magnetic pole head using an iron-based soft magnetic thin film, and the saturation magnetic flux density of the magnetic pole material is 2 tesla. The linear velocity at the time of recording / reproducing is 1 m / sec, and the recording frequency is 1 MHz.

Co ₈₅ Z as a sputtering target
FIG. 1 shows the relationship between the oxygen partial pressure, the coercive force, and the magnetic anisotropy energy when a film was formed by fixing the nitrogen partial pressure to 0.01 Pa using r ₁₅ and changing the oxygen partial pressure. When the amount of oxygen is small, both anisotropic energy and coercive force are small and typical soft magnetism is exhibited, but as oxygen is increased, anisotropic energy,
The coercive force also increases, and the coercive force can be arbitrarily controlled by the amount of oxygen. Further, the anisotropy is a uniform vertical anisotropy in the plane, which is advantageous as a base film of a perpendicular magnetic recording medium.

Next, using a Ni ₈₀ Fe ₂₀ target,
Films were formed by changing the amount of oxygen using a film formed in an atmosphere of only r gas and several alloy targets. Table 1 shows the composition and coercive force of these films. Next, a comparison of the signal-to-noise ratio (C / N) at the time of recording / reproducing characteristics in perpendicular magnetic recording when the NiFe alloy thin film is used as the underlayer and when the thin film made of CoZrNO of the present invention is used as the underlayer. It shows in Table 2.

When the underlayer film of the present invention is used, NiFe
It shows a better signal-to-noise ratio than when using alloys,
It can be seen that the magnetic material of the present invention is effective as a base film material for a perpendicular magnetic recording medium.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

As is apparent from the above description, in the present invention, at least one of ferromagnetic alloys Co, Fe, Ni and Mn, Nb, Zr, Ta, Hf, Y and Mo,
W, Cr, Ti, V, La, Sm, Dy, Er, Ho,
Pr, Ce, Eu, Tb, Ru, Pt, Ir, Rh, C
u, Zn, Si, Al, Sn, Ga, Ge, Pd, A
It is obtained in a microcrystalline state in a thin film composed of at least one of g, In, B, and C and nitrogen, and the coercive force can be controlled by adding oxygen. It is possible to provide a perpendicular magnetic recording medium having a suitable coercive force and low noise when used.

[Brief description of drawings]

FIG. 1 Oxygen partial pressure dependence of coercive force when a Co ₈₅ Zr ₁₅ target is deposited in argon, nitrogen and oxygen.

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[Procedure amendment]

[Submission date] November 21, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (1)

[Claims] 1. A perpendicular magnetic recording medium in which a base film and a perpendicular magnetization film are sequentially laminated on a non-magnetic support, wherein the base film is MxLyNzOw (where M is Co or F).
represents at least one selected from e, Ni, and Mn, and L
Is Nb, Zr, Ta, Hf, Y, Mo, W, Cr, T
i, V, La, Sm, Dy, Er, Ho, Pr, Ce,
Eu, Tb, Ru, Pt, Ir, Rh, Cu, Zn, S
i, Al, Sn, Ga, Ge, Pd, Ag, In, B,
Represents at least one of C, N represents nitrogen, O represents oxygen, and x, y, z, and w each represent the proportion of each element in atomic%. ), The composition range is 40 <x <97 1 <y <40 1 <z <20 0.3 <w <20.