JP3141436B2 - Perpendicular magnetic recording media - Google Patents

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 on which information is recorded by magnetization in the thickness direction of a recording layer, and more particularly to a C magnetic recording medium.
The present invention relates to a perpendicular magnetization recording medium having an oPtBO-based magnetic layer.

[0002]

2. Description of the Related Art In the field of information recording in recent years, studies on perpendicular magnetic recording have been conducted in various places in order to meet demands for higher recording density and higher recording capacity. In perpendicular magnetic recording, even when the recording wavelength is a short wavelength equal to or less than the film thickness of the magnetic layer, demagnetization is suppressed by approaching the different poles, stabilization of magnetostatic is achieved, It has such advantages that the induced electromotive force of the reproducing head can be increased due to the formation of a magnetic transition region, which is essentially a method suitable for high-density recording.

As a magnetic layer of this perpendicular magnetic recording medium,
An alloy magnetic thin film of CoCr, CoMo, CoV, CoRu or the like is known.

[0004] Among these alloys, a Co-Cr alloy magnetic layer formed by high frequency sputtering is known as a material having the most excellent perpendicular magnetic characteristics.

However, the Co-Cr alloy magnetic layer requires a protective lubricating layer because the durability thereof is insufficient when the magnetic layer is in sliding contact with the magnetic head. It is necessary to form the film very thinly, but there are problems such as difficulty, a relatively low saturation magnetic flux density, and a high coercive force cannot be obtained unless the substrate temperature during film formation is increased. .

[0006] On the other hand, the present applicant has previously disclosed in Japanese Patent Laid-Open No.
In the publication No. 74012, sufficient Hc can be obtained even if the film thickness is large.
And it is not necessary to raise the substrate temperature during film formation.
In addition, a CoPtBO-based alloy that easily obtains a sufficient saturation magnetic flux density Bs has been proposed. This CoPtBO-based alloy has a composition formula of (Co _a Pt _b B _c ) _100-x O _x , and the composition range is a = 100-bc, 0 ≦ b ≦ 50, 0.1 ≦
c ≦ 30, 0 <x ≦ 15 (where a, b, c, and x are atomic%). The magnetic thin film is formed at a relatively low substrate temperature of about room temperature. and even relatively large thickness, as high as 3kOe perpendicular coercivity Hc _v,
High saturation magnetic flux density Bs of about 10 to 12 kG (4πM
s), a high perpendicular anisotropy magnetic field Hk of about 15 kOe is obtained.

Further, the applicant of the present application has proposed that in order to obtain better perpendicular magnetic characteristics in the CoPtBO-based polar layer, the CoPtBO-based polar layer must be related to the fine structure such as the shape, size, orientation state and arrangement state of the crystals constituting the magnetic layer. A perpendicular magnetic recording medium having stable characteristics by controlling these factors has been proposed in Japanese Patent Application Laid-Open No. 3-58316.

However, as a result of further diligent studies, investigations, and analyzes, the present inventors have come to know the crystal structure, orientation state, etc., which can obtain more accurate perpendicular magnetic characteristics.

Here, the perpendicular magnetization film as a recording magnetic layer of the perpendicular magnetic recording medium means that the relationship between the perpendicular anisotropy magnetic field Hk of the above-mentioned magnetic thin film and the saturation magnetic flux density 4πMs has a unit of Hk of kOe. When the unit of 4πMs is indicated by kG, it is considered that these values should satisfy the relationship expressed by the following equation (1).

[Formula 1] Hk ≧ 4πMs

[0010]

The present invention provides a magnetic recording medium having a high perpendicular anisotropic magnetic field and a high perpendicular coercive force, based on the above-mentioned new findings.

[0011]

According to the present invention, a CoPtBO-based magnetic layer is formed on a non-magnetic support.

The CoPtBO-based magnetic layer is composed of acicular crystals having a hexagonal structure and having a diameter of 4 to 8 nm, and each acicular crystal is oriented with the <001> axis direction perpendicular to the surface of the nonmagnetic support. At the same time, a configuration is adopted in which adjacent needle-like crystals are arranged with a gap of 1 to 4 nm therebetween.

[0013]

According to the present invention, demagnetization is suppressed by finely arranging a single magnetic domain according to the acicular crystals and the arrangement state of the crystal structure described above. Further, the <001> direction is an easy axis of magnetization in the hexagonal crystal, and It is the major axis direction of the acicular crystal, and therefore the above-mentioned orientation is high perpendicular magnetic anisotropy as a perpendicular magnetic recording layer from both crystal magnetic anisotropy and shape magnetic anisotropy,
The vertical coercive force is increased.

That is, according to the present invention, the crystal orientation of the CoPtBO-based magnetic layer having good perpendicular magnetic anisotropy was examined by pole figure measurement, and the cross-sectional structure was observed with a transmission electron microscope. In the case of a columnar crystal having both components of cubic and face-centered cubic, good perpendicular magnetic anisotropy is unlikely to appear.In contrast, individual needles having a hexagonal crystal have a long axis through a certain gap. It has been found that good perpendicular magnetic anisotropy appears when the structure is oriented perpendicular to the film surface and the hexagonal <001> direction is perpendicular to the film surface.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a CoPtBO-based magnetic layer is formed of a needle-like crystal having a hexagonal structure and having a diameter of 4 to 8 nm on a non-magnetic support. It is formed so as to be oriented perpendicular to the body surface and arranged with a gap of 1 to 4 nm between adjacent needle crystals.

Under this CoPtBO-based magnetic layer, a Pt underlayer can be formed.

The Pt underlayer is made of Pt of the X-ray diffraction image.
(111) orientation degree [Delta] [theta] ₅₀ determined from rocking curve peaks, and [Delta] [theta] ₅₀ ≦ 10 °.

The composition formula of the CoPtBO-based magnetic layer is (Co _a Pt _b B _c ) _{100 -x} O _x (a, b,
c and x are atomic%), and a = 100−b−c 0 ≦ b ≦ 50 0.1 ≦ c ≦ 300 0 <x ≦ 15.

Example 1 A Pt base film and a CoPtBO-based magnetic layer were sequentially sputtered on a slide glass substrate by a magnetron sputtering apparatus. These sputtering conditions were set as follows. Background vacuum: 1.3 × 10 ⁻⁴ Pa Substrate temperature: room temperature Input power: DC 300 W

The sputtering of the Pt underlayer film was performed under the following conditions: sputtering gas pressure: 2.0 Pa (gas was argon gas); total gas flow rate: 50 sccm; and film thickness: 100 nm. For the sputtering of the CoPtBO-based magnetic layer, sputtering gas pressure: 2.0 Pa (gas is a mixed gas of argon and oxygen) Total gas flow rate: 50 sccm Oxygen partial pressure: 0.035 Pa Film thickness: 100 nm Target composition: Co ₆₈ Pt ₂₃ B ₉ (atomic%) Target shape: 10 cm in diameter and 3 mm in thickness.

Example 2 A CoPtBO-based magnetic layer was formed directly on a slide glass substrate. In this case, the Pt base film was not provided, and all other conditions were the same as in the first embodiment.

Comparative Example 1 A perpendicular magnetic recording medium having a CoPtB-based magnetic layer containing no oxygen was manufactured. The film forming conditions were the same as in Example 1 except that an argon gas containing no oxygen was used as a sputtering gas.

Comparative Example 2 A CoPtB-based magnetic layer was formed directly on a slide glass substrate in the same manner as in Comparative Example 1.

When the perpendicular magnetic anisotropy magnetic field Hk of the magnetic layers according to Examples 1 and 2 and Comparative Examples 1 and 2 was measured,
The Hk was 14 kOe and 10 kOe in Examples 1 and 2, respectively, and the Hk was 7 kOe in Comparative Examples 1 and 2, respectively.
e and 3 kOe.

Since 4πMs is 10 to 12 kG, Hk ≧ 4πMs is satisfied in Examples 1 and 2, and it is understood that a perpendicular magnetization film is realized in Examples 1 and 2. .

Next, the crystallographic structures of Examples 1 and 2 and Comparative Examples 1 and 2 will be described. X of the magnetic layer in the case of the second embodiment
FIG. 1 shows an X-ray diffraction chart by the X-ray diffractometer. FIG. 2 is a table showing the analysis results. This measurement was performed using a powdered CoPtBO-based thin film. In FIG. 1, reference numerals 2 to 7 indicate peak numbers. FIG. 2 shows the calculated face-centered cubic (fc)
c) and lattice spacing d of hexagonal crystal (hcp) and measured value d
It is shown. The calculated value in this case is 2.112 ° of the actually measured value (peak No. 2 in FIG. 1), respectively, fc
It is obtained as the lattice spacing between the c (111) crystal plane and the hcp (002) crystal plane. According to this actual measurement,
The CoPtBO-based magnetic layer has face-centered cubic fcc and hexagonal hcc.
cp. That is, as is clear from the comparison between the measured value and the calculated value, peaks 1 and 5 which should not exist in fcc are actually measured, and it is understood that at least hexagonal hcp is generated. . In hcp, the (200) plane and the (20) plane
1) Although the peak due to the plane is not actually measured, the peak does not always occur on all the crystal planes, so that the existence of hcp is not denied.

As described above, in the measurement by the diffractometer, the CoPtBO-based magnetic layer was subjected to a pole figure measurement to confirm whether the magnetic field was fcc or hcp. FIG.
5 to 5 show the results of pole figure measurement in the case of Example 1 according to the present invention, and FIGS. 6 to 8 show the results of pole figure measurement when oxygen was not contained in Comparative Example 1, where FIG. 2 shows the diffraction intensity distribution for An elevation angle of 0 ° indicates an in-plane direction of the film, and an elevation angle of 90 ° indicates a normal direction of the film surface. The diffraction intensity in each figure B is obtained by correcting the change in volume, the change in detection efficiency, and the contribution of scattering due to the Pt underlayer that contribute to diffraction during measurement.

4B and FIG. 5B are shown as relative intensities when the maximum intensity of 132 cps in FIG.

For an ideal hcp (001) orientation, h
In the cp (001) pole figure, a diffraction peak appears in the direction of the elevation angle of 90 °, and in the hcp (101) pole figure, a diffraction peak appears in the direction of the elevation angle of 28 °. On the other hand, in the case of an ideal fcc (111) orientation, diffraction peaks appear at an elevation angle of 90 ° and an elevation angle of 19.5 ° in the fcc (111) pole figure, and an elevation angle of 3 in the fcc (100) pole figure.
A diffraction peak appears in the direction of 4.5 °.

FIGS. 3 and 5 show an ideal hcp (001).
This is consistent with the diffraction intensity distribution of the pole figure. The ratio of the maximum intensity in FIG. 4 to the maximum intensity in FIG. 3 is 0.0078. On the other hand, the ratio of the maximum intensity in FIG. 5 to the maximum intensity in FIG.
60.

Next, in the case of Comparative Example 1 shown in FIGS. 6 to 8, the characteristics of the ideal hcp (001) orientation and the ideal fcc (111) orientation are the same as described above.
For comparison between FIG. 7B and FIG. 8B, the maximum strength 6 shown in FIG.
The relative intensity when 3 cps is set to 1 is shown.

FIG. 7 shows the characteristics of the fcc (100) pole figure in the seemingly ideal fcc (111) orientation.
However, according to FIG. 6, there is no peak at an elevation angle of 90 °. Further, FIG. 8 does not show the characteristics of the ideal hcp (001) orientation. The ratio of the maximum intensity in FIG. 7 to the maximum intensity in FIG. 6 is 0.017. On the other hand, FIG.
Has a maximum intensity ratio of 0.021. Even when the peak at an elevation angle of 20 ° in FIG. 8 is calculated assuming the hcp (101) polar component of the hcp (001) orientation, the ratio of the hcp (001) orientation is as shown in FIG. 35%.
On the other hand, the fcc (111) orientation component is about twice as large as that of FIG.

FIGS. 9 and 11 are diagrams A and B, respectively.
9 shows a pole figure of a measurement result of Example 2 according to the present invention and a diffraction intensity distribution with respect to an elevation angle. Figures A and B in Figures 12-14
The figure shows a pole figure of the same measurement result of Comparative Example 2 and a diffraction intensity distribution with respect to the elevation angle.

FIGS. 9 and 11 show an ideal hcp (00
1) It matches the diffraction intensity distribution of the pole figure. The ratio of the maximum intensity in FIG. 10 to the maximum intensity in FIG.
The maximum intensity ratio of FIG.
It is.

FIG. 13 shows the characteristics of the fcc (100) pole figure in the seemingly ideal fcc (111) orientation. However, in FIG. 12, the peak at an elevation angle of 90 ° is dominant. FIG. 14 does not show the feature of the hcp (001) orientation.

The maximum intensity ratio of FIG. 13 to the maximum intensity of FIG. 12 is 0.0349, and the ratio of the maximum intensity of FIG.
Has a maximum intensity ratio of 0.051.

Fcc (11) in FIG.
1) The orientation component is increased to about 3.4 times that in the case of FIG. At this time, the elevation angle is 20 ° in FIG.
Is assumed to be the hcp (101) polar component of the hcp (001) orientation, the ratio of the hcp (001) orientation is almost the same as that of Example 2 (FIG. 11).

As is apparent from the above description, Comparative Examples 1 and 2 are different from Examples 1 and 2 of the present invention in that hcp ｛1.
The 11 ° orientation is weak, and an fcc {200} orientation component is also observed. That is, it can be said that the reason why the large perpendicular anisotropy magnetic field Hk is obtained in the embodiment of the present invention is that the crystal magnetic anisotropy due to the hcp {001} orientation contributes.

The cross section of Example 1 and Comparative Example 1 was observed using a transmission electron microscope (TEM). In Example 1, fine grains having a cross-sectional structure perpendicular to the film surface were observed. In the comparative example 1, the needle-like crystals have a columnar structure in comparison with the needle-like crystals having a diameter (major axis direction) of 4 to 8 nm, which are arranged at intervals of 1 to 4 μm. Was observed. Thus, in the case of the embodiment of the present invention, the shape is formed so as to increase the shape magnetic anisotropy, and therefore, the perpendicular anisotropy magnetic field Hk is increased.

Further, as described above, the Pt underlayer has an orientation Δθ ₅₀ determined from the rocking curve of the Pt (111) peak of the X-ray diffraction image of 10 ° or less. Δθ ₅₀ is the so-called θ of X-ray diffraction.
In a surface analysis method using a −2θ scan, the angle range in which the rocking curve intensity obtained by fixing 2θ on the (111) crystal plane of the Pt underlayer 2 is I / 2 or more when the maximum intensity is I Is shown.

[0041] As in FIG. 15 shows the measurement results of the relationship between [Delta] [theta] ₅₀ and Hk of Pt underlayer, the [Delta] [theta] ₅₀ as described above 1
By setting the angle to 0 ° or less, a high perpendicular anisotropy magnetic field Hk can be obtained.

In general, the larger the Δθ ₅₀ is, the worse the crystallinity becomes. Therefore, by keeping the Δθ ₅₀ relatively small as described above, the crystallinity of the Pt underlayer 2 can be maintained well. As a result, the magnetic properties of the magnetic layer above this,
For example, when the magnetic anisotropy increases, the above-described Hk ≧ 4πMs
It is considered that the condition for satisfying the condition (1) is relaxed.

In the above example, the non-magnetic support is a slide glass substrate. However, as described above, since the substrate temperature in the formation of the underlying Pt and the sputtering of the magnetic layer can be room temperature, it is limited to a glass substrate. Alternatively, a support having low heat resistance, such as polyethylene terephthalate, may be used.

[Brief description of the drawings]

FIG. 1 is a diffraction chart of an X-ray diffractometer of a CoPtBO-based thin film.

FIG. 2 is a table showing lattice spacings of fcc and hcp obtained by actual measurement values and calculation values of the diffraction chart in FIG.

FIG. 3 shows hcp (001) or fc in Example 1.
It is a figure which shows a c (111) pole figure and the diffraction intensity with respect to an elevation angle.

FIG. 4 is a diagram showing an fcc (100) pole figure and a diffraction intensity with respect to an elevation angle in Example 1.

FIG. 5 is a diagram showing a hcp (101) pole figure and a diffraction intensity with respect to an elevation angle in Example 1.

FIG. 6 shows hcp (001) or fc in Comparative Example 1.
It is a figure which shows a c (111) pole figure and the diffraction intensity with respect to an elevation angle.

FIG. 7 is a diagram showing a fcc (100) pole figure and a diffraction intensity with respect to an elevation angle in Comparative Example 1.

8A and 8B are a hcp (101) pole figure and a diffraction intensity diagram with respect to an elevation angle in Comparative Example 1.

FIG. 9 shows hcp (001) or fc in Example 2.
It is a figure which shows a c (111) pole figure and the diffraction intensity with respect to an elevation angle.

FIG. 10 is a diagram showing a fcc (100) pole figure and a diffraction intensity with respect to an elevation angle in Example 2.

FIG. 11 is a diagram showing an hcp (101) pole figure and a diffraction intensity with respect to an elevation angle in Example 2.

FIG. 12 shows hcp (001) or f in Comparative Example 2.
It is a figure which shows a diffraction intensity with respect to a cc (111) pole figure and an elevation angle.

13 is a diagram showing a fcc (100) pole figure and a diffraction intensity with respect to an elevation angle in Comparative Example 2. FIG.

FIG. 14 is a diagram showing a hcp (101) pole figure and a diffraction intensity with respect to an elevation angle in Comparative Example 2.

FIG. 15 is a diagram showing a relationship between Δθ _{50 of a} Pt underlayer and a perpendicular anisotropic magnetic field Hk.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-74012 (JP, A) JP-A-3-58316 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 10/16 C23C 14/08 G11B 5/66 H01F 41/18

Claims (1)

(57) [Claims] A CoPtBO-based magnetic layer is formed on a non-magnetic support, wherein the CoPtBO-based magnetic layer has a hexagonal structure and a diameter of 4 mm.
８8 nm, each needle-like crystal being <001>
A perpendicular magnetic recording medium characterized by being oriented in a direction perpendicular to the surface of a nonmagnetic support in the axial direction, and being arranged with a gap of 1 to 4 nm between adjacent needles.