JP2902872B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable magneto-optical disk (magneto-optical recording medium) formed by alternately laminating a noble metal and a transition metal on a substrate. C / N improvement.

[0002]

2. Description of the Related Art As shown in FIG. 2, as a recording layer (perpendicular magnetization film) for a magneto-optical disk (magneto-optical recording medium) which can be repeatedly recorded / reproduced, Pt and Co are alternately formed by several Å each. Have been proposed. This alternately laminated film 1 becomes a perpendicular magnetization film in an ultra-thin film region having a total film thickness of several hundreds degrees or less. By changing conditions such as a lamination period or a film thickness, it is possible to change characteristics of a coercive force and a car rotation angle. Can be. In some cases, a dielectric film 20 of amorphous SiN or the like is formed as a base layer between the alternately laminated film 1 and the substrate 3 for the purpose of improving the coercive force and the Kerr effect. In addition, there is a case where an etching process 21 is applied for smoothing (the 14th Annual Meeting of the Japan Society of Applied Magnetics P65).

[0003] Information on such a magneto-optical recording medium is reproduced using the magneto-optical Carr effect. That is, when the linearly polarized light is reflected by the surface of the medium having the magnetization, the polarization plane is θ _K or − depending on whether the magnetization is upward or downward.
Using the phenomenon of rotation by θ _K , this is detected by an analyzer and reproduced.

[0004]

The values of the rotation angles θ _K and −θ _{K in} the magneto-optical Kerr effect are extremely small, approximately 0.3 ° to
It is about 1 °. For this reason, if the reflected light fluctuates or fluctuates, erroneous detection will occur and signal noise will occur, and the C / N of the reproduced signal will decrease.

However, in the magneto-optical recording medium of FIG. 2, since the Pt / Co alternating laminated film 1 is formed on the amorphous SiN layer 20, the Pt / Co
At the beginning, the t-layer is also not clearly stacked in the [111] direction.
As a result, the growth direction of the alternately laminated film 1 is also disturbed as shown in FIG. 4, and the reflected light fluctuates or fluctuates. That is, the C / N of the reproduced signal decreases. The present invention has been made in view of the above circumstances, and has as its object to reduce fluctuations and variations in reflected light during information reproduction and improve the C / N of a reproduced signal.

[0006]

According to the present invention, there is provided a magneto-optical recording medium comprising an alternately laminated film in which layers having a noble metal and layers having a transition metal are alternately laminated on a substrate. A magneto-optical recording medium wherein the half-width of a locking curve of X-ray diffraction of the noble metal of the alternately laminated film is 18 deg or less.

Further, the present invention provides a magneto-optical recording method comprising forming an alternately laminated film in which layers having a noble metal and layers having a transition metal are alternately laminated on a substrate via a light-transmitting underlayer. The medium is a magneto-optical recording medium in which the underlayer is formed of a compound which shows a peak on a certain surface of a crystal when subjected to X-ray diffraction. As the compound, Zn in which the half width of the underlayer locking curve is 20 deg or less is used.
Any of O, Al ₂ O ₃ , AlN, SiC, BeO, CoS and the like can be used.

[0008]

When the half-width of the rocking curve for X-ray diffraction is reduced to 18 deg or less by improving the orientation of the noble metal in the alternately laminated film, fluctuations and variations in reflected light during information reproduction are reduced, and reproduction is performed. Signal noise is reduced and C / N
Is improved. The improvement in the orientation of the noble metal can also be realized, for example, by interposing, as an underlayer, a compound that shows a peak on a certain surface of the crystal by X-ray diffraction between the substrate and the alternately laminated film. Further, when the above-described compound is interposed between the underlayers, the fluctuation and variation in the reflected light from the underlayer are reduced. This effect is remarkable when the half width of the X-ray diffraction rocking curve of the underlayer is set to 20 deg or less.

[0009]

Embodiments of the present invention will be described below. FIG.
1 schematically illustrates a cross section of a magneto-optical recording medium according to an example. As shown in the figure, in the present magneto-optical recording medium, ZnO
The underlayer 2 is formed, and the Pt / Co alternately laminated film 1 is formed thereon. The thickness of the ZnO underlayer 2 is 2
It is about 00-3000 °. The thickness of one Pt layer is about 5 to 20 °, the thickness of one Co layer is 10 ° or less, and the total thickness of the alternate laminated film 1 is 50 to 40 °.
It is about 0 °.

In the above magneto-optical recording medium, a ZnO underlayer 2 is formed on the surface of a substrate 3 using a sputtering apparatus shown in FIG. 3, and then Pt and Co are alternately formed on the surface of the underlayer 2. It is created by forming a film on the substrate.

The apparatus shown in FIG. 3 includes a vacuum chamber 4, a substrate holder 7 rotatably disposed above the vacuum chamber 4, and a vacuum chamber 4.
And a shielding plate 5 for partitioning the inside, and sputtering is performed by RF or DC power supplied from a power supply 8. The rotation speed of the substrate holder 7 can be controlled. Also,
The substrate 3 is held on the lower surface side of the substrate holder 7 so as to be eccentric from the axis of rotation.

The sputtering target 6 is held on each holding plate below each space in the vacuum chamber 4 divided by the shielding plate 5. As a target, Zn or ZnO is used when the underlayer 2 is formed, and Pt and Co are used when the Pt / Co alternately stacked film is formed. Ar + O ₂ or Ar is used as a sputtering gas, which is supplied from a cylinder 9 via a valve, a pipe, or the like.

The underlayer 2 made of ZnO is (000
2) The film is formed with good crystallinity so that peaks on the surface appear. This ZnO is hexagonal, and its (0001) plane is arranged in the same manner as the (111) plane of Pt. That is, the Pt crystal is a face-centered cubic lattice as shown in FIG. 5, and has a close-packed structure as shown in FIG. 6 when viewed from the [111] direction. For this reason, when the underlayer 2 is formed as described above, the crystallinity and orientation of the Pt layer are also improved, and fluctuations and variations in reflected light are reduced.
Noise during information reproduction is reduced, and C / N is improved.

The conditions for forming the underlayer 2 include, for example, a power input to the target of 300 W and an Ar gas pressure of 7 mTorr.
It is. The conditions for forming the alternately laminated film 1 are, for example, 100 W or less of electric power applied to the target. The film formation conditions can be adjusted by the heating temperature of the substrate in addition to the input power and gas pressure.

An X-ray diffraction image of the underlayer formed in this manner and the underlayer of the conventional magneto-optical recording medium shown in FIG. 2 were measured. The results are shown in FIG. 7 (this embodiment) and FIG.
(Conventional example). As shown in the figure, in the magneto-optical recording medium of the embodiment, a peak of the (0002) plane of ZnO appears. The half width of the ZnO rocking curve is 11 de.
g, indicating good orientation.

The rocking curves of X-ray diffraction were measured for Pt of the alternately laminated film 1 of the two magneto-optical recording media. The results are shown in FIG. 9 (this embodiment), FIG.
(Conventional example). As shown in the drawing, in the magneto-optical recording medium of the embodiment, the half width of the locking curve is 15 deg and the orientation is good, but in the magneto-optical recording medium of the conventional example, it is 19.5 deg.

FIG. 11 shows the result of measuring the C / N for the two magneto-optical recording media. As shown in the figure, the carriers are almost the same, but the noise level is small in the magneto-optical recording medium of the embodiment plotted by squares in the figure. Therefore, good C / N is obtained.
Incidentally, as described above, the good C / N is obtained by the Pt of the alternately laminated film 1.
It was also obtained when the half-width of the rocking curve for X-ray diffraction was 18 deg or less, and when the half-width of the rocking curve for X-ray diffraction of ZnO was 20 deg or less.

In the above embodiment, the magneto-optical recording medium is prepared by a sputtering method. However, the present invention can be also applied by using another method, for example, a vacuum deposition method or an MBE (Molecular Beam Epitaxy) method. Is obtained. Further, in the above embodiment, the case where Pt / Co is used as the alternately laminated film of the noble metal / transition metal is described, but for example, Pd / Co, PtPd / Co, Pt / Fe
Even when Co, Pd / FeCo, Pt / Fe, or the like is used, the same effect as described above is obtained. Further, in the above-described embodiment, the same effect can be obtained also when a known dielectric film, ultraviolet curing resin film, or reflection film is provided on the surface of the alternate laminated film 1 on the side not in contact with the substrate 3.

[0019]

As described above, the half value width of the rocking curve of X-ray diffraction is increased by improving the orientation of the noble metal of the alternately laminated film.
According to the present invention in which the deg or less is set, the fluctuation and variation of the reflected light at the time of reproducing the information are reduced, and the C / N of the reproduced signal is improved. Further, in the present invention using a compound in which a peak on a certain surface of a crystal appears by X-ray diffraction as an underlayer, fluctuations and variations in reflected light from the underlayer are reduced, and the noble metal of the alternately laminated film is reduced. Is also improved,
Fluctuations and variations in the reflected light are further reduced, and the C / N of the reproduced signal is further improved. This effect is more remarkable when the half width of the underlayer locking curve is 20 deg or less. Further, when the crystallinity and orientation of the alternately laminated film are improved, the coercive force, the perpendicular magnetic anisotropy, etc. are also improved, and the recording bit is stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a cross-sectional structure of a magneto-optical recording medium according to an example.

FIG. 2 is a schematic diagram showing a cross-sectional structure of a conventional magneto-optical recording medium.

FIG. 3 is a configuration diagram of an apparatus for producing a magneto-optical recording medium according to an embodiment.

FIG. 4 is a schematic view showing a crystal of a conventional magneto-optical recording medium.

FIG. 5 is a crystal structure diagram of Pt.

FIG. 6 is a structural view of the stack viewed from the [111] direction.

FIG. 7 is an X-ray diffraction image of a magneto-optical recording medium underlayer of an example.

FIG. 8 is an X-ray diffraction image of a conventional magneto-optical recording medium underlayer.

FIG. 9 is a X-ray diffraction locking curve of the magneto-optical recording medium of the embodiment.

FIG. 10 shows a locking curve for X-ray diffraction of a conventional magneto-optical recording medium.

FIG. 11 is a characteristic diagram showing carriers and noise of the magneto-optical recording medium of the embodiment and a conventional magneto-optical recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pt / Co alternating laminated film 2 ZnO underlayer 20 Amorphous SiN underlayer 3 Substrate

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 11/10 506

Claims (4)

(57) [Claims] 1. A magneto-optical recording medium comprising an alternately laminated film in which layers having a noble metal and layers having a transition metal are alternately laminated on a substrate, wherein X of the noble metal in the alternately laminated film is A magneto-optical recording medium having a half-width of a rocking curve for line diffraction of 18 deg or less. 2. A magneto-optical recording medium comprising an alternately laminated film in which layers having a noble metal and layers having a transition metal are alternately laminated on a substrate via a light-transmitting underlayer. A magneto-optical recording medium, wherein the underlayer is formed of a compound that shows a peak on a certain surface of the crystal when subjected to X-ray diffraction. 3. The X-ray diffraction rocking curve of the underlayer according to claim 2, wherein the half width of the rocking curve is 2.
A magneto-optical recording medium having 0 deg or less. 4. The method according to claim 2, wherein the compound of the underlayer is ZnO, Al ₂ O ₃ , AlN,
A magneto-optical recording medium that is any compound selected from SiC, BeO, and CoS.