JPH10208936A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the magnetic efficiency of a magnetic recording medium and simplify the manufacturing process of the medium by constituting the magnetic recording layer of the medium mainly of a hard magnetic phase associated with a subordinate nonmagnetic phase or a composite phase of a nonmagnetic phase and a magnetic phase and specifying the inclination of the axis of easy magnetization of the magnetic recording layer against the surface of the recording layer. SOLUTION: A magnetic medium layer 2 composed of a yoke layer 3 coating the upper surface of a substrate 1, a magnetic recording layer 4 formed on the surface of the layer 2, and a boundary section formed between the layers 3 and 4 is formed on the upper surface of the substrate 1. When the yoke layer 3 is made of a soft magnetic material or a ferromagnetic material having an axis in the direction of the surface of the substrate 1, vertical anisotropy is given to the magnetic recording layer 4 so that the inclination θ of the axis of easy magnetization from the surface of the substrate 1 may become 1<=θ<=900 deg.. The yoke layer 3 and recording layer 4 are not separated definitely from each other by the boundary section 5, but are intermixed together and the composition of one layer is gradually reduced toward the other layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording device which is an external storage device of a computer and a magnetic recording medium used for storing music and images.

[0002]

2. Description of the Related Art Magnetic recording media are widely used not only as recording media for music and image data but also as external storage devices for computers. Considering, for example, an external storage device of a computer, in recent years, various methods have been devised in a recording method and a recording medium in order to enable high-density recording in a magnetic recording device. As an example, as a recording method, a perpendicular recording method has been proposed with respect to the conventional longitudinal recording. Further, in the recording medium, a two-layer or three-layer medium having different materials and magnetic properties is used in part.

[0003]

In the case of a perpendicular recording medium in which a soft magnetic permalloy or the like magnetic film is formed as a lower layer and a hard magnetic Co—Cr based film is formed as an upper layer, the hard magnetic film is Due to the influence of the crystallinity of the lower layer, it is difficult to have perpendicular anisotropy with respect to the film surface. Therefore, the film is formed by strictly controlling the alloy composition and sputtering conditions. Alternatively, a thin buffer layer is provided at the interface between the upper layer and the lower layer in order to eliminate the influence of the lower layer. In any case,
Not only does this increase the number of steps, but also significantly lowers the magnetic efficiency, which is a factor that lowers the recording / reproducing efficiency, the signal-to-noise ratio, and impairs the stability of the recording magnetization state. The present invention has been made in view of the above-mentioned problems, and its purpose is to
It is an object of the present invention to provide a novel magnetic recording medium for the purpose of improving magnetic efficiency and simplifying a manufacturing process.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a yoke layer on a substrate of a magnetic recording medium that allows a magnetic flux to pass in substantially the same direction as the surface of the substrate, and an upper surface of the yoke layer. In a magnetic recording medium having a magnetic recording layer to be formed, an alloy film composed of the magnetic recording layer and the yoke layer is integrally formed, and 3 to 15 at% of Y, L
a, a composition containing one or more rare earth elements of the lanthanide element, 0.02 to 20 at% element M, and the remaining iron as essential elements, and the component composition gradually decreases from one layer to the other layer And the magnetic recording layer further comprises a composite phase of a main hard magnetic phase and a subordinate nonmagnetic phase or a magnetic phase having a lower coercive force than the hard magnetic phase, and furthermore, the inclination θ of the axis of easy magnetization of the magnetic recording layer. Is 0 with respect to the film surface.
≤ θ ≤ 90 °. However, the element M is Co, Ni, A
1, Si, Ti, V, Cr, Mn, Zr, Nb, Mo,
Any one or more of Ga, Sn, Hf, Ta, and W.

It is assumed that the axis of easy magnetization of the magnetic recording layer is substantially perpendicular or parallel to the film surface. Further, the magnetic recording layer is composed of a composite phase of a main hard magnetic phase and a secondary nonmagnetic phase or a hard phase having a lower coercive force than the hard magnetic phase. Further, the alloy film composed of the magnetic recording layer and the yoke layer is
h ₂ Zn ₁₇ , Th ₂ Ni ₁₇ , TbCu ₇ , ThMn ₁₂ ,
It has any one of the crystal structures of R ₃ (Fe, M) ₂₉ type.
Further, a protective film is provided on the upper surface of the magnetic recording layer.

The structural principle of the magnetic recording medium according to the present invention in which the magnetic recording layer and the yoke layer are integrally formed is as follows. For example, by sputtering, S
forming an Sm ₂ Fe ₁₇ film using an m-Fe target,
An Fe—Ti target is added on the way, and binary simultaneous sputtering with Sm—Fe is performed to form an SmFe ₁₁ Ti film as an upper layer. In this case, C-axis of the soft magnetic Sm ₂ Fe ₁₇ crystal form so that the substrate surface and perpendicular to, the hard magnetic SmFe ₁₁
The Ti upper layer is formed so that the crystal C axis is parallel to the substrate surface, and therefore, the easy magnetization direction of the hard magnetic recording layer is parallel to the film surface. In addition, by appropriately selecting the crystal structure and the component composition of the alloy, it is possible to manufacture a magnetic film in which both hard and soft magnetism and anisotropy are controlled.

As the film forming method of the present invention, sputtering, vapor deposition, plating, laser deposition, CVD and the like can be used. Regarding the components of the alloy film, one or more rare earth elements of the lanthanide genus, iron, and the element M (Co, Ni, Al, Si, Ti, V, Cr, M
n, Zr, Nb, Mo, Ga, Sn, Hf, Ta, W)
If the rare earth element is less than 3%, the coercive force is small and the coercive force required for the magnetic recording layer cannot be obtained. Meanwhile, 1
If it exceeds 5%, the saturation magnetization decreases, and the rare earth content increases, so that the oxidation resistance of the film is impaired. Further, by adding one or more elements M, the crystal structure of the alloy can be stabilized and the magnetic characteristics can be adjusted. However, if the total amount of the element M is less than 0.02%, the effect of adjusting the magnetic properties is hardly observed, while if it exceeds 20%, the original crystal structure of the alloy cannot be maintained, and the magnetic properties are significantly impaired.

The alloy film of the present invention is made of Th ₂ Zn ₁₇ , T
h ₂ Ni ₁₇ , TbCu ₇ , ThMn ₁₂ , R ₃ (Fe,
M) It is constituted by selecting various compounds such as type ₂₉ . For example, on the C-plane (001) of an alloy having a composition of Sm ₂ Fe ₁₇ having a crystal structure of Th ₂ Zn ₁₇ , Sm ₂ Fe ₁₇ Ti ₂ containing Ti is added.
When an upper alloy film having a composition is formed, the upper layer has a ThMn ₁₂ type crystal structure and its C axis is parallel to the film surface due to the advantage of crystal stacking. In another example, N having a ThMn ₁₂ structure
An upper layer film of NdFe ₁₀ VMo composition having the same crystal structure is formed on the C-plane (001) of the alloy having dFe ₁₁ V composition. In this case, the lower layer shows intermediate magnetism between soft magnetism and hard magnetism,
The upper layer exhibits hard magnetism and has an easy axis of magnetization perpendicular to the film surface.

Further, the hard magnetic upper layer has one of the above crystal structures as a main phase and has a nonmagnetic or low coercivity second layer.
Alternatively, by forming a composite with the third magnetic phase, separation of recording bits can be promoted, and high-density recording can be advantageously performed. For example, a conventional Co—Cr alloy medium is composed of a composite of a Co-rich phase and a Cr-rich phase finer than a single magnetic domain particle size. Also in the present invention, Sm ₂ (Fe, Ti) is selected by selecting the alloy composition and devising the heat treatment.
A non-magnetic phase such as Fe ₂ Ti or Sm ₂ O ₃ or a low coercive force phase such as (Sm, Ce) ₂ Fe ₁₇ phase is present in the grain boundaries or in the crystal of the ₁₇ or Nd (Fe, V) ₁₂ hard magnetic phase. Can be provided. In general, since a rare-earth iron-based alloy is chemically active, a protective film such as silicon oxide, carbon, or a polymer for preventing oxidation or wear is deposited on the alloy film in practical use. . The magnetic recording medium configured as described above has no disturbance at the boundary between the upper and lower layers.
In addition to being excellent in smoothness, since there is no magnetic gap seen in the conventional two-layer film, the recording / reproducing characteristics and the signal noise ratio are high, and the stability of the recording magnetization state is also excellent.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial sectional view of a magnetic recording medium according to the present invention. In FIG. 1, reference numeral 1 denotes a substrate made of glass or the like. On the upper surface of the substrate 1, a magnetic medium layer 2 is formed. The magnetic medium layer 2 comprises a yoke layer 3 attached on a substrate, a magnetic recording layer 4 on the surface, and a boundary portion 5 formed therebetween.

The substrate 1 is made of SiO ₂ glass having high mechanical strength and small expansion and contraction due to temperature change. The yoke layer 3 is made of a soft magnetic material or a ferromagnetic material having a uniform magnetic anisotropy axis in the plane direction of the substrate 1, and both pass a magnetic flux in the same direction as the plane of the substrate 1. It is configured to be able to. Magnetic recording layer 4
Indicates that the yoke layer 3 is made of a soft magnetic material or the substrate 1
When the yoke layer 3 is made of a soft magnetic material, it can have anisotropy in the direction perpendicular to the plane of the substrate 1. The magnetic recording layer can have anisotropy in the plane direction and exhibit excellent hard magnetic characteristics in any case. The boundary portion 5 is not clearly separated from the yoke layer 3 and the magnetic recording layer 4 by a plane, but is in a state in which both are intermingled. The boundary between the two layers is formed by a configuration in which the composition of the other layer gradually decreases, and the details will be described later. The thickness of the magnetic recording layer is approximately 2 to 50% of the thickness of the entire yoke layer at the boundary between the magnetic recording layers.

The substrate 1 can be made of glass as described above. Alternatively, as shown in FIG. 2, the substrate 6 can be made of aluminum. In this case, the substrate 6 and the magnetic medium layer 2 It is preferable to form a base film 7 made of a non-magnetic metal to repair defects on the surface of the aluminum substrate and absorb physical strain generated between the magnetic medium layer 2 and the substrate 6 at the same time. Further, the substrate 1 can be made of silicon.

[0013]

【Example】

Embodiment 1 FIG. Sm for facing target type sputtering equipment
An alloy target having an Fe—Co—V composition was mounted, and a glass substrate having a thickness of 0.7 mm and a diameter of 3.5 inches was placed on a glass substrate having a thickness of 11.3 mm.
A lower magnetic film of at% Sm-5.4 at% Co-13.4 at% V-remaining Fe composition was formed. The deposition conditions are as follows: a power density of 6 W / cm ² is applied between the target and the substrate;
The test was performed at a substrate heating temperature of 350 ° C. while flowing an argon gas at 50 cc / min. Subsequently, an Fe-Co-V target is added, and a magnetic field is applied in a direction perpendicular to the substrate surface.
9.8 at% Sm-7.6a
An upper magnetic film having a composition of t% CO-18.5at% V-remaining Fe was formed, and further heat-treated at 420 ° C. for 90 minutes. The total thickness of the obtained magnetic film is 500 nm, and the total component composition is 1
0.7 at% Sm-6.3 at% Co-15.4 at%
V—residual Fe, which was designated as Sample (A) of the present invention. In addition, for the magnetic property measurement, a reference sample of only the upper layer film or the lower layer film, and a 400 nm thick glass substrate for the comparative example.
(B) on which a permalloy film of No. 1 and a Co—Cr—Ta film of 80 nm were formed.

[0014] Samples (A) has a crystal structure of _12-inch ThMn, lower film C-axis of the crystal is formed in parallel with the substrate surface, the upper portion is C-axis substrate surface and vertical crystals due to the influence of the magnetic field applied Was formed. In addition, as a result of observation of the microstructure by a transmission electron microscope, it was found that Sm-Co-V having a diameter of 20 to 40 nm was used.
SmFe ₇ soft magnetic sub-phase of 10 nm or less and a small amount of amorphous samarium oxide phase were observed around the -Fe main phase. Further, both the upper layer and the lower layer showed hard magnetism, and the upper layer had anisotropy in a direction perpendicular to the film surface and the lower layer had anisotropy in a direction parallel to the film surface. The coercive force of the alloy films of these samples is shown in FIG.
As a result, the sample of the present invention exhibited high coercive force characteristics, and a film suitable for high recording density was obtained. In the sample of the present invention in which both the upper and lower layers show hard magnetism, the lower layer plays the role of a yoke layer for passing magnetic flux.

Next, a fluorocarbon film was coated on the film surfaces of the samples (A) and (B) to a thickness of 5 nm, and the recording / reproducing characteristics were measured using a perpendicular magnetic head. Generally, diamond-like carbon (DLC) or silicon oxide is used as the protective film, and graphite or a polymer film having a small friction coefficient is used as the lubricating film.

FIG. 4 shows recording / reproducing characteristics when the samples (A) and (B) are used as a medium and a single pole head generally used for perpendicular magnetic recording is used. The track width is 10 μm, the number of coil turns is 26 turns, and the peripheral speed is 10 m /
s. As a result, sample (A) has a higher compared to reproduction output (B), and also, D ₅₀ is high which is a measure of the high recording density. In order to increase the reproduced output and D ₅₀ is at the same time as the higher coercive force, the magnetization transition region of the recording layer is narrow, i.e. the dispersion of coercive force is small is required. Accordingly, in the sample (A), the boundary between the recording layer and the yoke phase is inseparable and smooth, and the hard magnetic phase, which carries the recording information, is finely separated. It turns out that it is a medium. Further, the SN ratio, which is the ratio of signal to noise, was -47 dB in (A) and -36 dB in (B), indicating a good value. This is because the medium of the present invention is formed in a continuous process from the lower layer to the upper layer,
This is due to the stronger magnetostatic coupling.

In this embodiment, as shown in FIG. 5, a hard magnetic yoke layer 3 having anisotropy in the horizontal direction with respect to the substrate surface is formed on the upper layer of the substrate 1, and the uppermost film is formed on the substrate surface with respect to the substrate surface. A magnetic recording layer 4 of a hard magnetic material exhibiting anisotropy in the vertical direction is formed.
The intermediate boundary portion 5 has a configuration in which the composition of the other layer gradually decreases toward one of the layers. Reference numeral 8 denotes a protective film.

Embodiment 2 FIG. After performing initial sputtering in argon gas in the same manner as in Example 1 using an Sm-Fe target, an additional Fe-Ti target was added, and binary simultaneous sputtering with Sm-Fe was performed without applying a magnetic field. 8.3 at% Sm-5.4 at% on silicon substrate
An alloy film having a Ti-residual Fe composition was formed to obtain a sample (C) of the present invention. The lower layer of this film had a Th ₂ Zn ₁₇ type crystal structure, the approximate composition was Sm ₂ Fe ₁₇ , and the C axis of the crystal was formed parallel to the substrate surface. On the other hand, the upper layer has a ThMn ₁₂ type crystal structure, and the approximate composition is Sm.
Fe ₁₁ Ti, and the C axis of the crystal was formed parallel to the substrate surface. In addition, as a result of observing the fine structure of the upper layer, 20
About 10 nm around the Sm-Ti-Fe main phase having a diameter of -50 nm
Fe ₂ Ti nonmagnetic subphase was observed. Further, the lower layer showed soft magnetism, while the upper layer showed hard magnetism, and its anisotropic direction was parallel to the film surface. The coercive force of this sample (C) was 2630 Oe for the upper layer and 1.1 Oe for the lower layer.

Using the sample (C) as a medium, a recording / reproducing characteristic was evaluated using a single pole head generally used in perpendicular magnetic recording. The track width was 10 μm, the number of coil turns was 26 turns, and the peripheral speed was 10 m / s. As a result, sample (C) Comparative Example Sample (B) compared to the reproduction output and 74% higher, also D ₅₀ which is a measure of the high recording density 38
% Higher. Further, the SN ratio was a good value at -44 dB.

In this embodiment, as shown in FIG. 6, the lower layer film becomes the yoke layer 3 which exhibits soft magnetism and allows magnetic flux to pass. The upper layer film forms the magnetic recording layer 4 which is hard magnetic and has anisotropy in the direction parallel to the film surface. Further, the yoke layer 3 and the magnetic recording layer 4 are formed integrally and inseparably, and their boundary portions 5
Has a configuration in which the composition of the other layer gradually decreases toward one of the layers. 8 is a protective film.

Embodiment 3 FIG. Sm-Ce-Fe and Fe-Mo
Sputtering was performed in an argon gas while applying a magnetic field in a direction perpendicular to the substrate surface using the two types of targets. At this time, as time elapses, Sm-Ce-Fe
A film is formed by increasing the sputtering rate from the Fe-Mo target by narrowing the opening area of the target, and 6.4 at% Sm is formed on an aluminum substrate subjected to electroless nickel plating.
An alloy film having a composition of -1.8 at% Ce-6.5 at% Mo-remaining Fe was formed to obtain a sample (D) of the present invention. This membrane
The lowermost layer was mainly composed of a Th ₂ Zn ₁₇ type compound phase, and the C axis of the crystal was formed parallel to the substrate surface due to the effect of applying a magnetic field. On the other hand, the uppermost layer was mainly composed of a ThMn ₁₂ type compound phase, and the C axis of the crystal was formed in a direction perpendicular to the substrate surface. In addition, as a result of observation of the fine structure of the upper layer, 10-
Around the main phase of Sm-Ce-Mo-Fe having a diameter of 30 nm, about 2
An α-Fe soft magnetic subphase having a diameter of 0 to 50 nm was observed. As a result, the magnetism changed from soft magnetic to hard magnetic from the lower layer to the upper layer, and the direction of anisotropy was inclined in the direction perpendicular to the film surface.

Using the sample (D) as a medium, the recording / reproducing characteristics were evaluated using a single pole head generally used in perpendicular magnetic recording. The track width was 10 μm, the number of coil turns was 26 turns, and the peripheral speed was 10 m / s. As a result, the reproduction output of the sample (D) was 62% higher than that of the sample (B) of the comparative example, and D _{50 which} is a measure of high recording density was also 28.
% Higher. Furthermore, the SN ratio showed a good value at -42 dB.

In this embodiment, as shown in FIG. 7, the lowermost film becomes the yoke layer 3 exhibiting anisotropy in a direction parallel to the substrate, and the boundary portion 5 becomes anisotropic from the lower film toward the upper film. Is gradually turned from the horizontal direction to the vertical direction, and the uppermost layer becomes the magnetic recording layer 4 exhibiting anisotropy in the direction perpendicular to the substrate. 8 is a protective film.

Although the present invention has been described with reference to the above-described embodiments and examples, various modifications and applications are possible within the scope of the gist of the present invention, and these modifications and applications are excluded from the scope of the present invention. It does not do.

[0025]

As described above, according to the magnetic recording medium of the present invention in which the compositions of the magnetic recording layer and the yoke layer change and are integrally formed, hard and soft bimagnetism and By controlling the anisotropy, it has excellent magnetic properties not found in the conventional two-layer film. The feature is that there is no disturbance at the boundary surface, the smoothness is excellent, and there is no magnetic gap, which is effective for improving the recording / reproducing characteristics and the signal-to-noise ratio. Further, since it is not necessary to form two types of magnetic layers, it contributes to simplifying the manufacturing process.

[Brief description of the drawings]

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

FIG. 2 is a partial cross-sectional view of another magnetic recording medium of the present invention.

FIG. 3 is a comparison table diagram between the first embodiment of the present invention and a conventional example.

FIG. 4 is a comparison chart of recording densities between the first embodiment of the present invention and a conventional example.

FIG. 5 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is a sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 1 ... substrate 2 ... magnetic medium layer 3 ... yoke layer 4 ... magnetic recording layer 5 ... boundary 6 ... substrate 7 .... Undercoat 8 ... Protective film

Claims (5)

[Claims] 1. A magnetic recording medium comprising: a yoke layer on a substrate of a magnetic recording medium that allows a magnetic flux to pass in substantially the same direction as the substrate surface; and a magnetic recording layer formed on an upper surface of the yoke layer. An alloy film composed of the magnetic recording layer and the yoke layer is integrally formed as an integral part, and 3 to 15 at% of one or more rare earth elements of any one of Y, La, and lanthanide elements is added to the alloy film.
The magnetic recording layer contains 2 to 20 at% of the element M and the remaining iron as essential elements, and the component composition gradually decreases from one layer to the other layer. The magnetic recording layer is composed of a non-magnetic phase or a composite phase with a magnetic phase having a lower coercive force than the hard magnetic phase, and the inclination θ of the axis of easy magnetization of the magnetic recording layer is 0 ≦ θ ≦ 90 ° with respect to the film surface. A magnetic recording medium characterized by the above-mentioned. Where the element M is
Co, Ni, Al, Si, Ti, V, Cr, Mn, Z
Any one or more of r, Nb, Mo, Ga, Sn, Hf, Ta, and W. 2. The magnetic recording medium according to claim 1, wherein the direction of the axis of easy magnetization of said magnetic recording layer is substantially parallel to the film surface. 3. The magnetic recording medium according to claim 1, wherein the direction of the axis of easy magnetization of the magnetic recording layer is substantially perpendicular to the film surface. 4. An alloy film comprising the magnetic recording layer and the yoke layer is made of Th ₂ Zn ₁₇ , Th ₂ Ni ₁₇ , TbCu ₇ , Th.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a crystal structure of any one of Mn ₁₂ and R ₃ (Fe, M) ₂₉ type. Where R is Y, La,
Indicates a lanthanide-based rare earth element. 5. A magnetic recording medium according to claim 1, wherein a protective film is provided on an upper surface of said magnetic recording layer.