KR100209284B1 - Magneto-optical direct recording medium - Google Patents

Abstract

The present invention relates to a direct overwrite magneto-optical disk recording medium, and more particularly, to a magneto-optical recording medium in which a protective film, a recording film and a protective film are sequentially stacked on a substrate, wherein the recording film is a first magnetic layer. Rotation angle is 0.4 Photoelectric film having a coercive force of 8 to 12 KOe, a magnetization value of 80 emu or less, an intermediate layer, and a transparent dielectric having a refractive index of n to 2.0 to 2.1 and a k value of 0.1 or less. The present invention relates to a direct recording magneto-optical recording medium in which pure magnetic films having a coercivity of 0.5 to 1 KOe and a magnetization value of 250 emu or more are sequentially stacked.

Description

Magneto-optical recording media

1 (a) and 1 (b) are cross-sectional views schematically showing an example of a recording film of a magneto-optical recording medium according to the prior art.

2 is a cross-sectional view schematically showing another example of a recording film of a magneto-optical recording medium according to the prior art.

3 is a sectional view schematically showing a recording film of a magneto-optical recording medium according to the present invention.

4 (a), 4 (b) and 4 (c) are cross-sectional views schematically showing the layer structure of the magneto-optical recording medium according to the present invention.

5 (a), 5 (b), 5 (c), 5 (d), 5 (e), and 5 (f) show the magneto-optical recording medium according to the present invention. Direct recording principle diagram schematically showing the principle of recording.

6 is a schematic diagram showing the structure of a recording / reproducing system of a magneto-optical recording medium according to the present invention.

7 is a sectional view of a magneto-optical recording medium according to Embodiment 1 of the present invention.

8 is a graph showing the reflectance changed according to the thickness of the intermediate layer of the magneto-optical recording medium of the present invention.

9 is a graph showing the Kerr rotation angle changed according to the thickness of the intermediate layer of the magneto-optical recording medium of the present invention.

* Explanation of symbols for main parts of the drawings

1, 11. 21: first magnetic layer 2, 12, 22: second magnetic layer

3, 13, 23: intermediate layer 4, 4 ', 14: recording film

15, 16, 18: protective film 17: reflective film

20: substrate surface 31: tactile magnetic field

32: recording magnetic field 33: disk

34: optical head

The present invention relates to a direct overwrite magneto-optical disk recording medium. More specifically, the conventional first-generation magneto-optical disk has been recorded through three steps of erasing / writing / verification. The present invention relates to a direct recording magneto-optical disc recording medium capable of recording / validating two levels by introducing a recording method.

In general, the magneto-optical recording technology records information by scanning a laser beam in a thin film material having perpendicular magnetism, changing the direction of the perpendicular magnetism in the magnetic domain, and rotating the recorded information in the polarization direction (Kerr effect). As a technology to read using the information, the preservation of information is semi-permanent due to the recording density of 10 to 600 times higher than the conventional magnetic recording medium and the non-contact between the head and the media. Therefore, in view of the reliability of data storage and margin between drives required by the information society, the demand for media with high recording sensitivity is increasing.

However, conventional first-generation magneto-optical disks have the disadvantage that they can be rewritten, but must be erased before recording. To solve this problem, as shown in FIG. 1, the first magnetic layer 1 and the second magnetic layer 2 A laminated intermediate layer (see also 3 and 1 (b)) for stabilization of the magnetic wall between the exchange-bonded two-layer film (see also first (a)) and the two magnetic layers (1 and 2) exchanged and bonded thereto. A magneto-optical disk having a layer film as the recording film 4 has been proposed. Further, as shown in FIG. 2, there is a magneto-optical disc having a four-layer film structure in which a reproduction layer 5 capable of improving a reproduction signal is laminated on the recording film 4 '.

By the way, in the recording films 4 and 4 'of the three-layer and four-layer film structures, the intermediate layer 3 is a metal film or the thickness of the entire recording film (600 to 1000). ), The sensitivity tends to be low, and in the case of a three-layer film, the intermediate layer 3 is a metal film, which has a disadvantage of less multi-interference effect. In addition, there is a problem that the stability of the magnetic domain according to the magnetization direction of the first magnetic layer (1) and the second magnetic layer (2) which are exchange-bonded.

Accordingly, it is an object of the present invention to provide a direct recording magneto-optical recording medium which can solve the above problems.

In the magneto-optical recording medium of the present invention for achieving the above object, in the magneto-optical recording medium in which a protective film, a recording film and a protective film are sequentially stacked on a substrate, the recording film is larger than the first magnetic layer and the rotation angle is 0.4. Photoelectric film having a coercive force of 8 to 12 KOe, a magnetization value of 80 emu or less, an intermediate layer, and a transparent dielectric having a refractive index of n to 2.0 to 2.1 and a k value of 0.1 or less. The pure magnetic film having a coercivity of 0.5 to 1 KOe and a magnetization value of 250 emu or more is laminated in this order.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

In the recording film according to the present invention, as shown in FIG. 3, the two non-ring magnetic films 11 and 12 are composed of a three-layer film of the transparent dielectric interlayer 13, wherein the dielectric protective films 15 and 17 are disposed thereon. Wrapped in a disc to make a disc. This is illustrated in more detail in FIG. 4, wherein the upper layer containing the recording film of the present invention (see FIG. 4 (a)), the four layers (see FIG. 4 (b)), and the fifth layer (FIG. Film) to form a magneto-optical disk.

The first magnetic layer 11 used in the present invention has a larger rotation angle of 0.4 It is preferable that the coercivity is 8 to 12 KOe and the magnetization value is 80 emu or less. For example, the coercivity and Curie temperature (150-200 ° C.) are slightly lower than the conventional material (TbFeCo) having a large magneto-optical effect and high coercivity. There is a TbFeCoCr magneto-optical film. The thickness of the layer 11 is 150 to 250 This is preferable, but it is difficult to meet the CNR and recording sensitivity necessary for recording and reproduction outside the above range. The intermediate layer 13 is a transparent dielectric having a thickness of 100 to 300 The preferred material is ZnS or SiNx, which has high refractive index (n value is 2.0 to 2.1 and k value is 0.1 or less) and has mass productivity. According to the present invention, as the transparent dielectric is used as the intermediate layer 13, the thermal conductivity is lowered, the sensitivity of the recording film 14 is improved, and the reproduction signal of the intensity can be optimized by adjusting the thickness of the transparent dielectric. That is, if the intermediate layer 13 is too thin, the playback signal and sensitivity are relatively bad, and if the intermediate layer 13 is too thick, a problem arises in recording. The second magnetic layer 12 has a perpendicular magnetic anisotropy, has little magneto-optic effect, has a small coercive force, and can be easily initialized to a low external magnetic field, and has a high magnetization value (Ms) and a relatively high Curie temperature for secondary recording. This is preferred. Therefore, the second magnetic layer 12 has a larger rotation angle of 0.1 Below, the coercive force is 0.5-1 KOe, the magnetization value is 250 emu or more, and the Curie temperature is 150-200 degreeC, for example, a cobalt type alloy, for example CoCr or CoPd, is preferable. On the other hand, the thickness of the recording film 14 is 1000 to maintain the recording sensitivity. It is preferable not to exceed.

The magneto-optical disc having the recording film 14 of the present invention that satisfies these conditions realizes direct recording by using the initialization magnetic field 31, the recording magnetic field 32, and two laser powers.

The recording principle of the magneto-optical disk of the present invention is shown in FIG. 5 and FIG. As can be seen from the figures, the recording principle of the disc is binary recording by the second magnetic layer 22 initializing magnetic field 31 and two powers. Hereinafter, the recording principle will be described in detail. First, the initial magnetic field 31 Bo of the initializing electromagnet is set to be larger than the coercive force Hc _{2 of} the second magnetic layer 22 so that only the second magnetic layer 22 is separated from the fifth (b) degree. Similarly, the second magnetic layer is initialized in one direction. The coercive force Hc ₁ of the first magnetic layer 21 is sufficiently large and is not affected by the initialization electromagnet. That is, the following conditions must be satisfied.

At operating temperature, Hc ₁ Bo Hc ₂

Thereafter, binary recording such as the fifth (c), fifth (d) and fifth (e) and fifth (f) degrees is performed by the recording magnetic field 32 B ₁ and the laser powers P ₁ and P _h . Here, P1 and Ph are laser powers required for each of the first magnetic layer 21 and the second magnetic layer 22 to reach a Curie temperature (150-200 ° C.). Here, P ₁ means low power and P _h means high power. That is, the temperatures at which the recording bits of the first magnetic layer 21 and the second magnetic layer 22 reach by the laser power P ₁ are respectively T ₁₁ and T ₁₂ , and the first magnetic layer 21 and the second by P _h . Assuming that the temperatures at which the recording bits of the magnetic layer 22 reach are Th ₁ and Th ₂ , the conditions for recording are as follows.

T ₁₁ ≒ Tc ₁ , T ₁₂ Tc ₂ , Th ₁ Tc ₁ , Th ₂ ≒ Tc ₂

Where Tc ₁ and Tc ₂ are the Curie temperatures of the first magnetic layer and the second magnetic layer, respectively.

At this time, the recording magnetic field 32 B ₁ is smaller than the coercive force of the second magnetic layer 22 at T ₁₂ , which is the temperature of the recording bit of the second magnetic layer 22 by the laser power P ₁ , and the second magnetic layer 22 is the first magnetic layer. The value given to (21) must be less than H ₂₁ (T ₁₂ ), the magnetic field.

B ₁ Hc ₂ (T ₁₁ ), B ₁ H ₂₁ (T ₁₂ )

In order to satisfy the above condition, the magnetization Ms (T ₁₂ ) of the second magnetic layer 22 should be sufficiently large. After that, when the magnetization of the second magnetic layer 22 passes through the initialization magnetic field 31, the magnetization of the second magnetic layer 22 is aligned in one direction again.

Although the effects of the present invention are described in more detail with reference to the following examples, the scope of the present invention is not limited to the following examples.

Example 1

Using an inline sputter, the first magnetic layer (photo magnetic film) is about 200 as shown in FIG. TbFeCoCr (Tb 19 atomic%, Fe 70 atomic%, Co 7 atomic%, Cr 4 atomic%), the second magnetic layer (pure magnetic film) of about 400 Co CoCr (Co 25 atomic%, Cr 75 atomic%) and the intermediate layer 200 SiNx, and about 400 SiNx on top And about 1000 SiNx at the bottom The magneto-optical disk of the present invention was prepared by forming a protective film with a thickness of, and the thin film manufacturing conditions were the usual conditions. The reflectance and Kerr rotation angle of the magneto-optical disk were measured and shown in FIGS. 8 and 9, respectively.

As can be seen in FIG. 8, the reflectance value changes depending on the thickness of the intermediate layer. The reflectance is usually determined by the TbFeCoCr film, but the reflectance is slightly reduced by the transparent intermediate layer. In FIG. 9, θk values varying with the thickness of the intermediate layer. The thicker the intermediate layer is, the higher the θ k value is and the thicker the layer tends to decrease.

As described above, the direct recording recording film having the transparent dielectric as an intermediate layer according to the present invention has a large signal. In addition, since the transparent dielectric material has a low thermal conductivity, not only recording at a relatively low fire is possible, but also stability of the recording bit is excellent. Finally, by forming the second magnetic layer as a pure magnetic film, the magneto-optical effect irrelevant to the recording can be eliminated. Thus, even when bonded to both sides, it can be reproduced without any problem.

Claims (8)

In a magneto-optical recording medium in which a protective film, a recording film and a protective film are sequentially stacked on a substrate, the recording film is larger than the first magnetic layer and the rotation angle is 0.4. Photoelectric film having a coercive force of 8 to 12 KOe, a magnetization value of 80 emu or less, an intermediate layer, and a transparent dielectric having a refractive index of n to 2.0 to 2.1 and a k value of 0.1 or less. A direct recording magneto-optical recording medium, characterized in that a pure magnetic film having a coercivity of 0.5 to 1 KOe and a magnetization value of 250 emu or more are sequentially stacked. The method of claim 1, wherein the thickness of the first magnetic layer is 150 ~ 250 And the thickness of the intermediate layer is 100-300 And the thickness of the second magnetic layer is 400 to 500 Direct recording magneto-optical recording medium, characterized in that. A recording medium according to claim 1, wherein the recording film has a thickness of 1000. Direct recording magneto-optical recording medium, characterized in that not exceeding. The direct recording magneto-optical recording medium of claim 1, wherein the first magnetic layer is TbFeCoCr. 2. The direct recording magneto-optical recording medium of claim 1, wherein the second magnetic layer is CoCr or CoPd. The direct recording magneto-optical recording medium of claim 1, wherein the intermediate layer is ZnS or SiNx. The direct recording magneto-optical recording medium according to claim 1, wherein a reflective film is further laminated on the protective film. 7. The direct recording magneto-optical recording medium according to claim 6, wherein a protective film is further laminated on the reflective film.