JP2007188637A - Magneto-optical recording medium and its reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain sufficient reproduced signals even when recording and reproducing using small diameter recording bits with still smaller recording bit spacings. <P>SOLUTION: This recording medium has at least a reproducing layer 1 having signal reproducing areas magnetized perpendicularly, and a recording layer 4 consisting of a perpendicular magnetic recording film magnetically coupling to the reproducing layer 1. Further, it has an in-plane magnetizing layer 3 provided apart from the reproducing layer 1 to suppress the coupling between the recording layer 4 and the reproducing layer 1 at least in room temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magneto-optical recording medium such as a magneto-optical disk, a magneto-optical tape, and a magneto-optical card applied to a magneto-optical recording / reproducing apparatus, and a reproducing method thereof.

  Conventionally, a magneto-optical recording medium has been put to practical use as a rewritable optical recording medium. In such a magneto-optical recording medium, the recording bit diameter and recording bit interval, which are recording magnetic domains, become smaller than the beam diameter of the light beam emitted from the semiconductor laser focused on the magneto-optical recording medium. When this happens, there is a disadvantage that the reproduction characteristics deteriorate.

  Such drawbacks are caused by the fact that adjacent recording bits fall within the beam diameter of the light beam focused on the target recording bit, so that individual recording bits cannot be separated and reproduced. It is.

  In order to eliminate the above drawbacks, in Patent Document 1, a nonmagnetic intermediate layer is provided between a reproducing layer and a recording layer which are in-plane magnetization at room temperature and become perpendicularly magnetized as the temperature rises. A magneto-optical recording medium having a structure in which the recording layer is magnetostatically coupled has been proposed.

  As a result, the recorded magnetic domain information of the portion in the in-plane magnetization state is masked, and even when adjacent recording bits enter the beam diameter of the focused light beam, individual recording bits can be separated and reproduced. (1st conventional example).

Further, Non-Patent Document 1 discloses that in a similar configuration in which a nonmagnetic intermediate layer is sandwiched between a recording layer and a reproducing layer, a magnetic domain larger than the magnetic domain of the recording layer is caused in the reproducing layer by a magnetic field generated from the recording layer. A magnetic domain enlarging method for transferring and reproducing while forming a film is shown (second conventional example).
JP-A-6-150418 JP-A-8-287537 JP-A-6-295479 JP-A-8-106662 Appl. Phys. Lett. 69 (27) p4257-4259, “Magnetic domain expansion readout for amplification of an ultra high density magneto-optical recording signal”

  However, in the above-described first conventional example, when recording / reproduction is performed with a smaller recording bit diameter and a smaller recording bit interval, there is a problem that the reproduction signal intensity is lowered and a sufficient reproduction signal cannot be obtained. confirmed.

  Also in the second conventional example, when the recording density is high and there are a large number of bits under the reproducing magnetic domain, the reproducing layer receives magnetic fields from a plurality of bits of the recording layer, and the true reproduction is performed. There is a problem that the reproducing layer cannot correctly receive the magnetic field from the power bit.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to obtain a sufficient reproduction signal even when recording / reproduction is performed with a small recording bit diameter and a smaller recording bit interval. There is.

  In order to achieve the above object, the present invention has the following configuration.

  The magneto-optical recording medium according to claim 1 is a magneto-optical recording medium comprising: a reproducing layer in which at least a signal reproducing region is in a perpendicular magnetization state; and a recording layer comprising a perpendicular magnetization film that is magnetically coupled to the reproducing layer. A magnetic mask layer is provided apart from the reproducing layer and suppresses magnetic coupling between the recording layer and the reproducing layer at least at room temperature.

  The magneto-optical recording medium according to claim 2 has a reproducing layer in which at least the signal reproducing region is in a perpendicular magnetization state, and a recording layer made of a perpendicular magnetization film that is magnetically coupled to the reproducing layer, and is irradiated with a light beam. In a magneto-optical recording medium in which a magnetic domain larger than the recording magnetic domain of the recording layer is formed in the reproducing layer, the magnetic layer is arranged apart from the reproducing layer and suppresses magnetic coupling between the recording layer and the reproducing layer at least at room temperature. It has a mask layer.

  A magneto-optical recording medium according to a third aspect is the magneto-optical recording medium according to the first or second aspect, wherein the magnetic mask layer comprises an in-plane magnetic layer whose magnetization decreases at a high temperature.

  A magneto-optical recording medium according to claim 4 is the magneto-optical recording medium according to claim 3, wherein the magnetization of the magnetic mask layer is larger than the magnetization of the recording layer at room temperature.

  The magneto-optical recording medium according to claim 5 is the magneto-optical recording medium according to claim 3 or 4, wherein the Curie temperature of the magnetic mask layer is lower than the Curie temperature of the recording layer.

  The magneto-optical recording medium according to claim 6 is the magneto-optical recording medium according to any one of claims 3 to 5, wherein the Curie temperature of the recording layer is lower than the Curie temperature of the reproducing layer. And

  The magneto-optical recording medium according to claim 7 is the magneto-optical recording medium according to any one of claims 3 to 6, wherein a transparent dielectric layer, the reproducing layer, the nonmagnetic intermediate layer, A magnetic mask layer, the recording layer, and a protective layer are sequentially formed.

  The magneto-optical recording medium according to claim 8 is the magneto-optical recording medium according to claim 7, wherein the thickness of the magnetic mask layer is 2 nm or more and 40 nm or less.

  The magneto-optical recording medium according to claim 9 is the magneto-optical recording medium according to claim 7 or claim 8, wherein the magnetic mask layer is a GdFe alloy, GdFeAl alloy, GdFeTi alloy, GdFeTa alloy, GdFePt alloy, GdFeAu alloy, GdFeCu alloy. It is made of any one of an alloy, a GdFeAlTi alloy, and a GdFeAlTa alloy.

The magneto-optical recording medium according to claim 10 is the magneto-optical recording medium according to any one of claims 7 to 9, wherein the magnetic mask layer is composed of (Gd _0.11 Fe _0.89 ) _X Al _1-X. X (atom ratio) is 0.30 or more and 1.00 or less.

  The magneto-optical recording medium according to claim 11 is the magneto-optical recording medium according to any one of claims 7 to 10, wherein the Curie temperature of the magnetic mask layer is 60 ° C. or higher and 220 ° C. or lower. And

  The magneto-optical recording medium according to claim 12 is the magneto-optical recording medium according to claim 7, wherein the thickness of the reproducing layer is 10 nm or more and 80 nm or less.

  A magneto-optical recording medium according to claim 13 is the magneto-optical recording medium according to claim 7, wherein the film thickness of the nonmagnetic intermediate layer is 1 nm or more and 80 nm or less.

  The magneto-optical recording medium according to claim 14 is the magneto-optical recording medium according to claim 7, wherein a reflective layer is formed adjacent to the non-magnetic intermediate layer on the recording layer side of the non-magnetic intermediate layer. It is characterized by that.

  A magneto-optical recording medium according to a fifteenth aspect is the magneto-optical recording medium according to the fourteenth aspect, wherein the reflective layer is made of Al and has a thickness of 2 nm to 40 nm.

  A magneto-optical recording medium according to claim 16 is the magneto-optical recording medium according to claim 14, wherein the reflective layer is made of an alloy of Al and a magnetic metal.

The magneto-optical recording medium according to claim 17 is the magneto-optical recording medium according to claim 16, wherein the reflective layer is represented by a composition formula of Al _1-X Fe _X , and X (atom ratio) is 0.02 or more. It is 0.50 or less.

The magneto-optical recording medium according to claim 18 is the magneto-optical recording medium according to claim 16, wherein the reflective layer is represented by a composition formula of Al _{1 -X} Ni _X and X (atom ratio) is 0.02 or more. It is 0.50 or less.

  The magneto-optical recording medium according to claim 19 is the magneto-optical recording medium according to claim 14, wherein the reflective layer is made of an alloy of Al and a nonmagnetic metal.

  The magneto-optical recording medium according to claim 20 is the magneto-optical recording medium according to claim 19, wherein the nonmagnetic metal is any one element of Ti, Ta, Pt, Au, Cu, and Si. .

The magneto-optical recording medium according to claim 21 is the magneto-optical recording medium according to claim 19, wherein the reflective layer is represented by a composition formula of Al _1-X Ti _X and X (atom ratio) is 0.02 or more and 0. .98 or less.

  The magneto-optical recording medium according to claim 22 is the magneto-optical recording medium according to claim 7, wherein a heat dissipation layer is formed on the opposite side of the substrate with respect to the protective layer.

  The magneto-optical recording medium according to claim 23 is the magneto-optical recording medium according to any one of claims 1 to 22, wherein the reproducing layer is in an in-plane magnetization state at room temperature and in a perpendicular magnetization state at high temperature. It is characterized by becoming.

  The magneto-optical recording medium according to claim 24 is the magneto-optical recording medium according to claim 1, 2, or 3, wherein the reproducing layer is composed of a multilayer film in which Co and Pt are alternately laminated. And

  A magneto-optical recording medium reproducing method according to claim 25 is the reproducing method for reproducing information from the magneto-optical recording medium according to any one of claims 1 to 24, wherein the magneto-optical recording medium is reproduced during signal reproduction. The recording medium is irradiated with a light beam in pulses.

  A magneto-optical recording medium reproducing method according to claim 26 is a reproducing method for reproducing information from the magneto-optical recording medium according to claim 3, wherein the magneto-optical recording medium is irradiated with a light beam during reproduction, The magnetic mask layer is heated to the vicinity of the Curie temperature or higher.

  The magneto-optical recording medium according to claim 27 is the magneto-optical recording medium according to any one of claims 1 to 7, wherein the magnetic mask layer is magnetostatically coupled to the recording layer.

  A magneto-optical recording medium according to claim 28 is the magneto-optical recording medium according to claim 27, wherein a non-magnetic intermediate layer is formed between the magnetic mask layer and the recording layer, and the film of the non-magnetic intermediate layer The thickness is not less than 2 nm and not more than 80 nm.

  (1) In the magneto-optical recording medium of the present invention, it is possible to suppress the leakage magnetic flux from the recording layer to the reproducing layer at least at room temperature. Only the information from the magnetic domain can be extracted, and the recording density can be increased. In addition, recording / reproduction can be performed with a smaller bit diameter and a smaller recording bit interval.

  (2) Also, by forming a magnetic domain larger than the recording magnetic domain of the recording layer in the reproducing layer, in addition to the effect of (1), the amount of reproduced signal can be increased and the signal quality can be improved.

  (3) Furthermore, when the in-plane magnetic layer is used as a magnetization mask, the in-plane magnetic layer can absorb the magnetic field generated from the recording layer at room temperature and block the magnetic field from the recording layer in the reproducing layer. On the other hand, when heated by irradiation with a reproducing laser beam, the magnetization of the in-plane magnetized layer decreases, so that the magnetic field blocking effect is lost, and the magnetic flux from the recording layer leaks to the reproducing layer in the heated region. Thus, the reproducing layer can be perpendicularly magnetized according to the recorded information. Here, since information from only the heated minute region is transmitted to the reproducing layer, a sufficient reproduction signal can be obtained even when recording / reproduction is performed with a small recording bit length and a small recording bit interval. .

  (4) If the magnetization of the in-plane magnetic layer at room temperature is made larger than the magnetization of the recording layer at room temperature, the magnetic field blocking effect can be reliably achieved.

  (5) Further, it is desirable to keep the in-plane magnetic layer at or above the Curie temperature due to heating during reproduction, the magnetization disappears, and the recording layer at or below the Curie temperature in order to retain the information recorded at that time. That is, it is desirable to set the Curie temperature of the recording layer to be higher than the Curie temperature of the in-plane magnetic layer.

  (6) Further, since the reproducing layer is required to have reproducing characteristics, it is advantageous that the Curie temperature is higher than that of the recording layer.

  (7) If a transparent dielectric layer, a reproducing layer, a nonmagnetic intermediate layer, an in-plane magnetic layer, a recording layer, and a protective layer are sequentially formed on the substrate, a part of bit information recorded on the recording layer is It can be selected by a magnetization mask with an in-plane magnetic layer, and can be greatly enlarged and reproduced in the magnetic domain of the reproducing layer, and a sufficiently large signal intensity can be obtained even in high-density recording. In addition, the nonmagnetic intermediate layer completely cuts off the exchange coupling between the reproducing layer and the in-plane magnetized layer, thereby realizing a good magnetostatic coupling between the reproducing layer and the recording layer.

  (8) If the film thickness of the in-plane magnetic layer is set to 2 nm or more and 40 nm or less in (7) above, the masking effect of the recording layer by the in-plane magnetic layer is set to a good state. Also, stable magnetic domain expansion reproduction is possible.

  (9) In the above (7) and (8), the magnetic mask layer is made of any one of GdFe alloy, GdFeAl alloy, GdFeTi alloy, GdFeTa alloy, GdFePt alloy, GdFeAu alloy, GdFeCu alloy, GdFeAlTi alloy and GdFeAlTa alloy. Thus, it is possible to form a stable magnetic domain in the reproducing layer, to react correctly to the magnetic field coming out of the recording layer, and to realize good magnetic domain expansion reproduction.

(10) In the above (7) and (8), when the magnetic mask layer is (Gd _0.11 Fe _0.89 ) _X Al _1-X and X (atom ratio) is 0.30 or more and 1.00 or less, the magnetic mask By optimizing the magnetic properties of the layer (in-plane magnetic layer), a good exchange coupling state between the recording layer and the in-plane magnetic layer can be realized, and a good magnetic domain expansion reproduction can be realized.

  (11) In the above (7) to (10), if the Curie temperature of the magnetic mask layer is set to 60 ° C. or higher and 220 ° C. or lower, the Curie temperature of the magnetic mask layer is optimized, whereby the Curie temperature of the magnetic mask layer is optimized. At the following temperatures, the magnetization of the recording layer is shielded from the reproducing layer by in-plane magnetization (magnetically masked), and the magnetostatic coupling between the recording layer and the reproducing layer is good at a temperature equal to or higher than the Curie temperature of the magnetic mask layer. Thus, stable magnetic domain expansion reproduction can be realized.

  (12) In the above (7), if the thickness of the reproducing layer is 10 nm or more and 80 nm or less, the magnetic domain in the reproducing layer can be stabilized and the interference effect of light becomes large, and a good reproduction signal is obtained. It becomes possible.

  (13) If the thickness of the nonmagnetic intermediate layer is set to 1 nm or more and 80 nm or less, the nonmagnetic intermediate layer thickness is optimized, thereby realizing a good magnetostatic coupling state and magnetic super-resolution reproduction. As well as an optical interference effect.

  (14) In (7) above, if a reflective layer is formed adjacent to the recording layer side of the nonmagnetic intermediate layer, the thickness of the reproducing layer is reduced, and the reproducing light beam transmitted through the reproducing layer is reduced. Information reproduction from the recording layer that is reflected by the reflection layer and is unnecessary for signal reproduction can be optically completely blocked, and the signal reproduction characteristics are improved.

  (15) In the above (14), when the reflective layer is made of Al and the film thickness is made 2 nm to 40 nm, the thickness of the reflective layer made of Al is optimized, so that the reproducing light beam is reflected by the reflective layer. Thus, the magnetic super-resolution reproduction signal reproduction characteristics are improved, and the magnetostatic coupling force acting between the reproduction layer and the recording layer can be maintained in a good state.

  (16) In the above (14), if the reflective layer is made of an alloy of Al and a magnetic metal, the reflective layer alloy has a lower thermal conductivity than Al, so that the medium temperature distribution during heating by the laser beam is steep. It is possible to provide a magneto-optical recording medium capable of realizing good magnetic amplification reproduction, improving the magnetic characteristics of the recording layer formed on the reflective layer, and erasing with a smaller erasing magnetic field. Is possible.

(17) In (16) above, if the reflective layer is Al _1-X Fe _X and X (atom ratio) is 0.02 or more and 0.50 or less, it is possible to realize good magnetic amplification reproduction. In addition, the magnetic characteristics of the recording layer formed on the reflective layer are optimized, and a magneto-optical disk that can be erased with a smaller erasing magnetic field can be provided.

(18) In the above (16), if the reflective layer is Al _1-X Ni _X and X (atom ratio) is 0.02 or more and 0.50 or less, it is possible to realize good magnetic amplification reproduction. In addition, the magnetic characteristics of the recording layer formed on the reflective layer are optimized, and a magneto-optical recording medium that can be erased with a smaller erasing magnetic field can be provided.

  (19) In the above (14), if the reflective layer is made of an alloy of Al and a nonmagnetic metal, it is possible to realize good magnetic amplification reproduction and magnetic characteristics of the recording layer formed on the reflective layer. Thus, it becomes possible to provide a magneto-optical disk that can be erased with a smaller erasing magnetic field.

  (20) In the above (19), if the nonmagnetic metal is any one element of Ti, Ta, Pt, Au, Cu, and Si, it is possible to realize good magnetic amplification reproduction and a reflection layer. The magnetic characteristics of the recording layer formed thereon are improved, and a magneto-optical disk that can be erased with a smaller erasing magnetic field can be provided.

(21) In the above (19), if the reflective layer is made of Al _1-X Ti _X and X (atom ratio) is 0.02 or more and 0.98 or less, it is possible to realize good magnetic amplification reproduction. In addition, the magnetic characteristics of the recording layer formed on the reflective layer are optimized, and a magneto-optical disk that can be erased with a smaller erasing magnetic field can be provided.

  (22) In (7) above, if a heat dissipation layer is formed on the opposite side of the substrate with respect to the protective layer, the temperature distribution in the light beam applied to the magneto-optical recording medium becomes steeper and the magnetic The mask effect of the magnetic field from the recording layer in the reproducing layer by the mask layer can be emphasized, and the reproducing characteristics are further improved.

  (23) In the above (1) to (22), if the reproducing layer is in the in-plane magnetization state at room temperature, it is not necessary to reproduce an extra signal, which is advantageous. The outside of the magnetic domain generated in the reproducing layer may be a noise component, but if a reproducing layer showing in-plane magnetization at room temperature is used, only the magnetic domain transferred from the recording layer becomes perpendicular magnetization. Thus, signal reproduction only in the vertical region is possible.

  (24) In the above (1), (2) and (3), if the reproducing layer is a multilayer film of Co and Pt, it is possible to obtain a good C / N ratio even when a short wavelength laser is used. It becomes.

  (25) When information is reproduced from the magneto-optical recording media of (1) to (24) above, erasing the magnetic domains formed in the reproducing layer once leads to a smooth reproducing operation. If the beam is pulsed, the magnetic domain disappears while the laser is extinguished, and the medium temperature is raised while the laser emits light, and the recording magnetic domain of the recording layer is transferred to the reproducing layer to reproduce the signal. The reproduction signal quality can be made higher.

  (26) When reproducing information from the magneto-optical recording medium of (3) above, if the magnetic mask layer is heated to a temperature equal to or higher than the Curie temperature, the magnetization of the magnetic mask layer can be lost, and the information is reproduced from the recording layer at the time of reproduction. It becomes possible to transfer the magnetization to the layer smoothly.

  (27) In the above (1) to (7), if the magnetic mask layer is magnetostatically coupled to the recording layer, exchange coupling between the magnetic mask layer and the recording layer can be cut off, thereby obtaining a higher mask effect. And better signal strength can be obtained.

  (28) In the above (27), if a nonmagnetic intermediate layer having a thickness of 2 to 80 nm is disposed between the magnetic mask layer and the recording layer, the effect of the above (27) can be appropriately obtained.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a reproduction principle of the magneto-optical disk of the present invention, and FIG. 16 shows a sectional view of a magneto-optical recording medium for explaining the reproduction principle of a conventional magneto-optical disk.

  First, a conventional super-resolution reproduction operation will be described. As shown in FIG. 16, the conventional reproducing system receives a magnetic field generated from the recording layer 4 by the reproducing layer 1 and transfers it to the magnetic domain of the reproducing layer 1. Therefore, at least when the temperature rises, there is a reproducing layer 1 made of an alloy of a rare earth metal and a transition metal that is in a perpendicular magnetization state, and a recording layer 4 made of an alloy of a rare earth metal and a transition metal having a compensation temperature at room temperature. A non-magnetic intermediate layer 2 is formed between them, and the reproducing layer 1 and the recording layer 4 are magnetostatically coupled.

  Here, when the light beam 5 is condensed and irradiated from the reproducing layer side, a Gaussian distribution-like temperature distribution corresponding to the intensity distribution of the light beam 5 is formed on the medium. As the temperature distribution is formed, the magnetization of the recording layer 4 increases and the magnetic field generated from the recording layer 4 increases, and the magnetization direction of the reproducing layer 1 is determined by the magnetic field. The magnetization of the layer 4 is transferred. The super-resolution reproduction operation is realized by reproducing the information of the transferred portion.

  In this reproducing method, as shown in FIG. 2A, when the magnetic domain size existing in the reproducing layer 1 is, for example, a reproducing laser having a wavelength of 680 nm, the beam spot size is about 1 μm. If the size is set to be larger than the size of the magnetic domain of the recording layer 4, the signal generated from the reproducing layer 1 during reproduction increases.

  However, the direction of magnetization in the reproducing layer 1 is determined by the magnetic field from the recording layer 4, and when information is recorded on the recording layer 4 at a high density, as shown below, from the recording layer 4 The magnetization transfer cannot be performed satisfactorily. That is, although the isolated bit 100 is formed in the entire erase state as shown in FIG. 2A, the direction of the perpendicular magnetization in the reproducing layer 1 is influenced only by the magnetic field from the isolated bit 100, but functions effectively. When recording is performed at a high density, the influence of the adjacent recording bits 101 appears as shown in FIG. Since the magnetization direction of the adjacent bit 101 is opposite to that of the recording bit 100, the magnetization to be reproduced is weakened, and magnetic transfer and magnetic expansion become extremely difficult. For this reason, the information in the target range cannot be correctly reproduced, and is easily affected by an external stray magnetic field or the like.

  On the other hand, in the magnetic domain expansion magneto-optical recording medium of the present invention shown in FIG. 1, an in-plane magnetic layer 3 (a magnetic mask layer in claims) is formed adjacent to the recording layer 4. This masks the magnetization from the portion 11 of the recording layer 4 that is not heated above a predetermined temperature (hereinafter referred to as critical temperature). That is, the in-plane magnetization layer 3 prevents the magnetization of the portion 11 of the recording layer 4 from affecting the reproducing layer 1 (suppresses leakage of magnetic flux generated from the portion 11 to the reproducing layer 1). In short, the magnetic coupling force between the recording layer 4 and the reproducing layer 1 is suppressed.

  As described above, by realizing the magnetic mask, it becomes possible to remove only the mask above the critical temperature, and the size of the magnetic domain existing in the reproducing layer 1 is larger than the size of the recording magnetic domain as shown in FIG. Even when the recording layer 4 is large, it is possible to reproduce only information of a desired recording magnetic domain heated to a critical temperature or higher in the recording layer 4.

  Here, the in-plane magnetic layer 3 does not have magnetization at a temperature equal to or higher than the critical temperature in order to effectively cause magnetostatic coupling between the recording layer 4 and the reproducing layer 1 in a portion heated to the critical temperature or higher. Alternatively, it is desirable that the magnitude of magnetization is smaller than the magnitude of magnetization at a temperature below the critical temperature, and the Curie temperature of the in-plane magnetic layer 3 is desirably lower than the Curie temperature of the recording layer 4. Further, in order to prevent the magnetic flux from the recording layer 4 from affecting the reproducing layer 1 at room temperature, it is desirable that the magnetization size of the in-plane magnetic layer 3 is larger than the magnetization size of the recording layer 4 at room temperature. .

  In addition, when the reproducing layer 1 is reproduced by a laser beam, it is preferable that the size of the magnetic domain is large because the amount of signal increases and the cause of noise decreases. Further, the domain wall needs to move in accordance with the magnetic field from the recording layer 4, and a characteristic with a small coercive force is advantageous.

  Further, when information is reproduced from this magneto-optical recording medium, once the magnetic domain created in the reproducing layer 1 is erased, it leads to a smooth reproducing operation, so that the reproducing laser beam can be emitted in pulses. For example, the magnetic domain disappears while the laser is extinguished, the medium temperature is raised while the laser emits light, and the recording magnetic domain of the recording layer is transferred to the reproducing layer to perform signal reproduction. The reproduction signal quality can be made higher.

  The first embodiment of the present invention will be described more specifically with reference to FIG. 3 as follows. In the following, a case where a magneto-optical disk is applied as the magneto-optical recording medium will be described.

  As shown in FIG. 3, the magneto-optical disk according to the present embodiment includes a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, an in-plane magnetic layer 3, a recording layer 4, and a protective layer 8. The overcoat layer 9 has a disc body laminated in this order.

  In such a magneto-optical disk, the Curie temperature recording system is used as the recording system, and the light beam 5 emitted from the semiconductor laser is narrowed down to the reproducing layer 1 by the objective lens, which is known as the polar Kerr effect. Information is recorded and reproduced by the magneto-optical effect. The polar Kerr effect is a phenomenon in which the direction of rotation of the polarization plane of reflected light rotates due to magnetization perpendicular to the incident surface, and the direction of rotation changes depending on the direction of magnetization.

  The board | substrate 6 consists of transparent base materials, such as a polycarbonate, for example, and is formed in disk shape.

The transparent dielectric layer 7 is preferably made of a material having a large refractive index such as AlN, SiN, AlSiN, TiO ₂ , and the film thickness realizes a good interference effect with respect to the incident laser light. The Kerr rotation angle of the medium needs to be set to increase. When the wavelength of the reproduction light is λ and the refractive index of the transparent dielectric layer 7 is n, the film thickness of the transparent dielectric layer 7 is (λ / 4n). For example, when the wavelength of the laser beam is 680 nm, the film thickness of the transparent dielectric layer 7 may be set to about 30 nm to 100 nm.

  The reproducing layer 1 is a magnetic film made of a rare earth transition metal alloy, and its magnetic properties are in-plane magnetization state at room temperature, and the composition is adjusted so that it becomes a perpendicular magnetization state as the temperature rises.

  The nonmagnetic intermediate layer 2 is composed of one layer of a dielectric such as AlN, SiN, AlSiN, or one layer of a nonmagnetic metal alloy such as Al, Ti, Ta, or two layers of the dielectric and the metal. The total film thickness is set to 1 to 80 nm so that the reproducing layer 1 and the recording layer 4 are magnetostatically coupled.

  The in-plane magnetized layer 3 is a magnetic film mainly composed of a rare earth transition metal alloy, a rare earth metal, or a transition metal, and is a film having magnetization in a direction parallel to the film surface. As described with reference to FIG. 1, the in-plane magnetic layer 3 masks the magnetic field generated from the perpendicular magnetization of the recording layer 4 at a temperature lower than the critical temperature with the in-plane magnetization to prevent leakage of the magnetic field to the reproducing layer 1. Above the critical temperature, the composition is adjusted so that the masking effect of magnetization is lost and the magnetic flux generated from the recording layer 4 is easily transmitted to the reproducing layer.

  The recording layer 4 is made of a perpendicular magnetization film made of a rare earth transition metal alloy, and the film thickness is set in the range of 20 to 80 nm.

  The protective layer 8 is made of a dielectric such as AlN, SiN, AlSiN, SiC, or a nonmagnetic metal alloy such as Al, Ti, Ta, etc., and prevents oxidation of the rare earth transition metal alloy used for the reproducing layer 1 and the recording layer 4. The film thickness is set in the range of 5 nm to 60 nm.

  The overcoat layer 9 is formed by applying an ultraviolet curable resin or a thermosetting resin by spin coating and irradiating with ultraviolet rays or heating.

  Hereinafter, specific examples of the magneto-optical disk having the above-described structure will be described separately for (1) forming method and (2) recording / reproducing characteristics.

(1) Formation method First, a polycarbonate made of a disc having pregrooves and prepits in a sputter apparatus provided with an Al target, a GdFeCo alloy target, a GdFeAl alloy target, and a GdDyFeCo alloy target, respectively. The substrate 6 is placed on the substrate holder. After the inside of the sputtering apparatus is evacuated to 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen is introduced, power is supplied to the Al target, and the substrate 6 is subjected to a gas pressure of 4 × 10 ⁻³ Torr. A transparent dielectric layer 7 made of AlN was formed with a film thickness of 80 nm.

Next, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, and then argon gas is introduced to supply power to the GdFeCo alloy target to obtain a gas pressure of 4 × 10 ⁻³ Torr. On the body layer 7, the reproducing layer 1 made of Gd _0.30 (Fe _0.80 Co _0.20 ) _0.70 was formed with a film thickness of 20 nm. The reproducing layer 1 was in the in-plane magnetization state at room temperature and had a property of being in a perpendicular magnetization state at a temperature of 120 ° C., its compensation temperature was 300 ° C., and its Curie temperature was 320 ° C.

Next, a mixed gas of argon and nitrogen is introduced, electric power is supplied to the Al target, and the nonmagnetic intermediate layer 2 made of AlN is formed on the reproducing layer 1 under the condition of a gas pressure of 4 × 10 ⁻³ Torr. Formed at 20 nm.

Next, power is supplied to the GdFeAl alloy target so that the gas pressure is 4 × 10 ⁻³ Torr, and the in-plane magnetic layer 3 made of (Gd _0.11 Fe _0.89 ) _0.75 Al _{0.25 is formed} on the nonmagnetic intermediate layer 2. The film was formed with a thickness of 30 nm. The in-plane magnetic layer 3 was an in-plane magnetic layer having a Curie temperature of 120 ° C. and having magnetization in a direction parallel to the film surface from room temperature to the Curie temperature.

Next, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, and then argon gas is introduced to supply power to the GdDyFeCo alloy target to obtain a gas pressure of 4 × 10 ⁻³ Torr. A recording layer 4 made of (Gd _0.50 Dy _0.50 ) _0.23 (Fe _0.80 Co _0.20 ) _0.77 was formed on the magnetic layer 3 to a thickness of 40 nm. The recording layer 4 had a compensation temperature at 25 ° C. and a Curie temperature of 275 ° C.

Next, a mixed gas of argon and nitrogen is introduced, electric power is supplied to the Al target, and the protective layer 8 made of AlN is formed to a thickness of 20 nm on the recording layer 4 under the condition of a gas pressure of 4 × 10 ⁻³ Torr. Formed.

  Next, an ultraviolet curable resin was applied onto the protective layer 8 by spin coating, and an overcoat layer 9 was formed by irradiating with ultraviolet rays.

(2) Recording / Reproducing Characteristics FIG. 4 shows the mark length dependence of CNR (signal to noise ratio) measured on the above disk by an optical pickup using a semiconductor laser having a wavelength of 680 nm. Here, the magneto-optical recording medium of the present embodiment described above is shown as Example 1.

  For comparison, the mark length dependency of CNR of a magneto-optical disk having a configuration in which the in-plane magnetic layer 3 does not exist is also shown in FIG. The medium of the magneto-optical disk having no in-plane magnetic layer has a configuration in which the in-plane magnetic layer 3 is removed from the medium configuration of the present embodiment. The CNR mark length dependency shown here represents a signal-to-noise ratio when a recording magnetic domain having a length corresponding to the mark length is continuously formed at a recording magnetic domain pitch twice as long as the mark length. is there.

  Comparing the CNRs of both marks having a mark length of 0.3 μm, it is 34.0 dB in the case of the comparative example 1, whereas an increase in CNR of 41.5 dB and 7.5 dB is observed in the case of the first example. This is because the in-plane magnetic layer 3 works as a magnetization mask for the recording layer 4 to increase the reproduction resolution.

  Next, Table 1 shows the results of measuring the CNR at 0.3 μm by changing the film thicknesses of the reproducing layer 1 and the in-plane magnetic layer 3 in Example 1.

  In Table 1, the in-plane magnetic layer thickness 0 nm indicates the result of Comparative Example 1 in which the in-plane magnetic layer 3 is not formed. Even when the film thickness of the in-plane magnetic layer 3 is as extremely thin as 2 nm, the CNR increases by 1 dB by realizing the strengthening of the in-plane magnetization mask. As for the film thickness of the in-plane magnetization layer 3, the CNR increases as the in-plane magnetization mask is strengthened up to 30 nm, but the CNR decreases as the thickness increases further. This means that the recording layer and the reproducing layer are separated. This is considered to be due to the fact that the complete perpendicular magnetization state of the reproducing layer cannot be obtained due to the effect that the in-plane magnetization mask is strengthened too much and the magnetic aperture is difficult to open. From the above, it can be seen that the film thickness of the in-plane magnetic layer 3 that provides a higher CNR than Comparative Example 1 is in the range of 2 to 40 nm.

  Further, when the film thickness of the reproduction layer 1 is 8 nm, the reproduction signal becomes small and its CNR becomes lower than that of the comparative example 1. Furthermore, when the film thickness of the reproducing layer 1 is 120 nm, the domain wall energy generated in the reproducing layer 1 increases, and a complete perpendicular magnetization state cannot be obtained in the portion where the temperature has risen, and its CNR is lower than that of Comparative Example 1. End up. From Table 1, it can be seen that the thickness of the reproducing layer 1 that provides a higher CNR than Comparative Example 1 is in the range of 10 to 80 nm.

  Next, Table 2 shows the results of measuring the CNR at 0.3 μm and the magnetic field necessary for erasing (erasing magnetic field) by changing the film thickness of the nonmagnetic intermediate layer 2 in Example 1. .

  From Table 2, it can be seen that when the film thickness of the nonmagnetic intermediate layer 2 is 0.5 nm, the CNR is remarkably lowered. This is considered to be because a good magnetostatic coupling state was not obtained because the film thickness of the nonmagnetic intermediate layer 2 was too thin. When the film thickness of the nonmagnetic intermediate layer 2 is 1 nm, the maximum CNR is obtained. As the film thickness of the nonmagnetic intermediate layer 2 increases, the magnetostatic coupling force decreases and the CNR decreases. . It can be seen that in order to obtain a higher CNR than Comparative Example 1, it is necessary to set the film thickness of the nonmagnetic intermediate layer 2 in the range of 1 to 80 nm.

  Further, it can be seen that by increasing the film thickness of the nonmagnetic intermediate layer 2, the magnetostatic coupling force between the reproducing layer 1 and the recording layer 4 is reduced, thereby reducing the erasing magnetic field. In order to make the erasing magnetic field within a practical range of 31 kA / m or less, it is more desirable that the film thickness of the nonmagnetic intermediate layer 2 is 4 nm or more.

(Embodiment 2)
In the present embodiment, an example in which the in-plane magnetic layer 3 having a different composition in the specific example of the magneto-optical disk shown in the first embodiment will be described.

In the first embodiment, the recording / reproduction characteristics in the case where (Gd _0.11 Fe _0.89 ) _0.75 Al _0.25 having a Curie temperature of 120 ° C. is used as the in-plane magnetic layer 3 are shown. The result of investigating the recording / reproducing characteristics by changing the Al content of the magnetic layer 3 will be described.

Table 3 shows that the in-plane magnetic layer 3 is (Gd _0.11 Fe _0.89 ) _X Al _1-X with a film thickness of 30 nm, the value of X (atom ratio) is changed, and the Curie temperature T _C2 of the in-plane magnetic layer 3 is The result of having measured CNR (signal to noise ratio) in 0.3 micrometer measured with the optical pick-up using a semiconductor laser with a wavelength of 680 nm is shown.

  In Table 3, a CNR higher than the CNR (34.0 dB) obtained in Comparative Example 1 in which the in-plane magnetic layer 3 is not formed is in the range of 0.30 <X <1.00. I understand that. The reproducing layer 1 used in the present embodiment is the same as that in the first embodiment, and is in a perpendicular magnetization state at a temperature of 120 ° C. That is, the in-plane magnetic layer 3 only needs to be able to mask the magnetic field of the recording layer in the in-plane magnetization at a temperature of 120 ° C. or less, and the optimum value of the Curie temperature of the in-plane magnetic layer 3 is approximately 120 ° C. Become. However, as shown in this embodiment, when the Curie temperature of the in-plane magnetic layer 3 is 60 ° C. or higher and 220 ° C. or lower, a CNR higher than that of Comparative Example 1 is obtained, and the Curie temperature of the in-plane magnetic layer is By setting the temperature to 60 ° C. or higher and 220 ° C. or lower, a magnetization mask can be formed.

  In this embodiment, the result of using GdFeAl as the in-plane magnetization layer 3 is described. However, if the in-plane magnetization is satisfied in the Curie temperature range (60 ° C. to 220 ° C.), In addition, it is possible to use an in-plane magnetic layer 3 made of NdFe, NdFeAl, DyFe, or DyFeAl.

(Embodiment 3)
In the present embodiment, an example in which another material is used as the in-plane magnetic layer 3 in the specific example of the first embodiment will be described.

In the first embodiment, the recording / reproducing characteristics in the case where (Gd _0.11 Fe _0.89 ) _0.75 Al _0.25 having a Curie temperature of 120 ° C. is used. However, in this embodiment, the in-plane magnetic layer 3 is made of Al. Describe the results using other metal elements.

Table 4 shows an optical pickup using a Curie temperature T _C2 of the in-plane magnetic layer 3 and a semiconductor laser having a wavelength of 680 nm when (Gd _0.11 Fe _0.89 ) _0.75 Z _0.25 having a film thickness of 20 nm is used for the in-plane magnetic layer 3. The CNR (signal-to-noise ratio) measured at 0.3 μm measured in (1) is shown. Here, as Z, Ti, Ta, Pt, Au, Cu, Al _0.5 Ti _0.5 , and Al _0.5 Ta _0.5 were used.

From Table 4, it is understood that CNR higher than that of Comparative Example 1 is obtained in all cases where Ti, Ta, Pt, Au, Cu, Al _0.5 Ti _0.5 , and Al _0.5 Ta _0.5 are used as Z. As described in the second embodiment, the in-plane magnetic layer 3 only needs to have a Curie temperature in the range of 60 ° C. to 220 ° C. In addition, an in-plane magnetic layer made of NdFeTi, NdFeTa, DyFeTi, DyFeTa is used. Is possible.

(Embodiment 4)
The following describes Embodiment 4 of the present invention with reference to FIG. In the present embodiment, a case where a magneto-optical disk is applied as the magneto-optical recording medium will be described. However, description of the same parts as those in the first to third embodiments will be omitted.

  As shown in FIG. 5, the magneto-optical disk according to Embodiment 4 includes a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a reflective layer 10, an in-plane magnetic layer 3, and a recording layer. 4, a protective layer 8 and an overcoat layer 9 have a disk body laminated in this order.

  In the first embodiment, when the film thickness of the in-plane magnetic layer 3 is smaller than 10 nm, the light beam 5 transmitted through the reproducing layer 1 and the nonmagnetic intermediate layer 2 is reflected by the recording layer 4 to be a reproduction signal. Information of the recording layer 4 is mixed.

  The magneto-optical disk according to the fourth embodiment has a configuration in which the reflective layer 10 is formed between the nonmagnetic intermediate layer 2 and the in-plane magnetic layer 3 in the magneto-optical disk described in the first embodiment. ing. By doing so, the light beam 5 transmitted through the reproducing layer 1 is reflected by the reflecting layer 10, and it is possible to prevent unnecessary information from the recording layer 4 from being mixed in the reproduced signal.

  Hereinafter, specific examples of the magneto-optical disk of the present embodiment will be described by dividing into (1) formation method and (2) recording / reproduction characteristics.

(1) Formation Method The magneto-optical disk of this embodiment is the same as the magneto-optical disk formation method of Embodiment 1, except that the reflective layer 10 made of Al is interposed between the nonmagnetic intermediate layer 2 and the in-plane magnetization layer 3. The substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the nonmagnetic intermediate layer 2, the in-plane magnetic layer 3, the recording layer 4, the protective layer 8, and the overcoat layer 9 are the same as those in the first embodiment. Similarly, the reproducing layer 1 was formed with a thickness of 17.5 nm, and the in-plane magnetic layer 3 was formed with a thickness of 7.5 nm.

Here, after forming the nonmagnetic intermediate layer 2, the Al reflective layer 10 is evacuated again to 1 × 10 ⁻⁶ Torr inside the sputtering apparatus, and then argon gas is introduced to supply power to the Al target. Then, the reflective layer 10 made of Al was formed to a thickness of 2 to 80 nm on the nonmagnetic intermediate layer 2 with a gas pressure of 4 × 10 ⁻³ Torr.

(2) Recording / reproducing characteristics Table 5 shows a CNR (signal at 0.3 μm) measured by an optical pickup using a semiconductor laser having a wavelength of 680 nm while changing the film thickness of the reflective layer 10 in the magneto-optical disk of the present embodiment. To noise ratio).

  In Table 5, the reflective layer thickness of 0 nm indicates the result of Comparative Example 2 in which the reflective layer 10 is not formed. Even when the thickness of the reflective layer 10 is as extremely thin as 2 nm, the effect of blocking information reproduction from the recording layer 4 is observed, and the CNR increases by 1.0 dB. By increasing the thickness of the reflective layer 10, the CNR gradually increases, and the CNR becomes maximum at the thickness of 20 nm. This is because the effect of blocking information reproduction from the recording layer 4 becomes more significant as the thickness of the reflective layer increases. Although the CNR is reduced when the film thickness is 30 nm or more, this is because the magnetostatic coupling force acting between the recording layer 4 and the reproducing layer 1 becomes weaker as the distance between the recording layer 4 and the reproducing layer 1 increases. From the above, it can be seen that in order to obtain a higher CNR than in Comparative Example 2, it is necessary to set the film thickness of the reflective layer 10 in the range of 2 to 50 nm.

(Embodiment 5)
In the present embodiment, the case where a different material is used as the reflective layer 10 in the specific example of the fourth embodiment will be described.

  In the fourth embodiment, reproduction characteristics using Al are described. However, in this embodiment, an alloy of Al and a metal other than Al is used as the reflective layer 10 in order to improve the recording characteristics. Describe the results.

Table 6 shows that the CNR at 0.3 μm measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm with the reflective layer 10 made of Al _1-X Fe _X having a thickness of 20 nm and changing the value of X (atom ratio). (Signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 6, the CNR gradually decreases as the Fe content increases, that is, as X increases from 0.10, but both CNRs are larger than those in Comparative Example 2, and the reflective layer 10 The effect which formed is seen. On the other hand, looking at the erasing magnetic field, when the reflection layer 10 made of pure Al is used, an erasing magnetic field as large as 50 kA / m is required, whereas X is set to 0.02 or more and 0.50 or less. Thus, the erasing magnetic field can be reduced.

Next, Table 7 shows that the reflective layer 10 is Al _1-X Ni _X having a film thickness of 20 nm, the X (atom ratio) value is changed, and the measurement is performed with an optical pickup using a semiconductor laser having a wavelength of 680 nm. The CNR (signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 7, as in the case of containing Fe, it was possible to reduce the erasing magnetic field by setting X to 0.02 or more and 0.50 or less.

  In addition to Fe and Ni, a magnetic metal such as Co, Gd, Tb, Dy, and Nd is similarly contained in Al, so that the erasing magnetic field can be reduced.

(Embodiment 6)
In the present embodiment, a case will be described in which a different material is used as the reflective layer 10 in the specific example of the fourth embodiment.

  In the fifth embodiment, the result of including a magnetic metal element in Al as the reflective layer 10 is described, but in this embodiment, the recording characteristics when a nonmagnetic metal element is included in Al. Describe improvement.

Table 8 shows the CNR at 0.3 μm measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm, with the reflective layer 10 made of Al _1-X Ti _X having a film thickness of 20 nm and changing the value of X (atom ratio). (Signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 8, as the Ti content increases, that is, as X becomes larger than 0.10, the CNR gradually decreases. However, both CNRs are larger than those in Comparative Example 2, and the reflective layer 10 The effect which formed is seen. On the other hand, looking at the erasing magnetic field, when the reflection layer 10 made of pure Al is used, an erasing magnetic field as large as 50 kA / m is required, whereas X is set to 0.02 to 0.98. Thus, the erasing magnetic field can be reduced.

Next, Table 9 shows the erasing magnetic field reduction effect when a nonmagnetic element other than Ti is contained in Al as the reflective layer 10, where the reflective layer 10 is Al _0.5 Z _0.5 and Z is other than Ti. The figure shows the CNR (signal-to-noise ratio) at 0.3 μm and the magnitude of the erasing magnetic field measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm when a nonmagnetic metal is used.

  From Table 9, in the case where Ta, Pt, Au, Cu, and Si, which are nonmagnetic metals, are used as Z, all the CNRs are larger than those in Comparative Example 2, and the effect of forming the reflective layer 10 is seen. On the other hand, looking at the erasing magnetic field, it was possible to reduce the erasing magnetic field as in the case where Al was contained in Ti.

  In the above first to sixth embodiments, a magnetic layer that is in-plane magnetized at room temperature and perpendicularly magnetized at high temperature is used as the reproducing layer 1, but at least the signal reproducing region (predetermined temperature (reproducing at reproduction) Any material can be used as long as it is in a perpendicular magnetization state in the region heated above (temperature).

  In the first to sixth embodiments, the in-plane magnetic layer 3 is used. Instead of this layer, (1) a magnetic layer that is in the in-plane magnetization state at room temperature and becomes a perpendicular magnetization state at a high temperature (reference form 5). 9) and (2) perpendicular to which the direction of the transition metal sublattice magnetization is the same as that of the recording layer 4 and the sum of the transition metal sublattice magnetization and the rare earth metal sublattice magnetization is opposite to the recording layer 4 A magnetized layer (see Reference Embodiments 1 to 4) can be used. Further, the in-plane magnetic layer 3 of the first to sixth embodiments and the magnetic layer (1) need not be adjacent to the recording layer 4, and (3) are magnetostatically coupled to the recording layer 4. It may be present (see Embodiment 7 and Reference Embodiment 10).

(Reference form 1)
Hereinafter, this reference embodiment will be described in detail with reference to the drawings.

  FIG. 6 shows the principle of magnetic domain expansion reproduction operation of this embodiment.

  In the magneto-optical recording medium, the magnetic field generated from the recording layer in the low temperature region is canceled by the magnetic field in the opposite direction. For example, in the magnetic domain expansion reproducing magneto-optical recording medium shown in FIG. 6, a blocking layer 3 ′ (magnetic mask layer in the claims) made of an alloy of a rare earth metal and a transition metal is formed adjacent to the recording layer 4 and exchanged. Are connected. The blocking layer 3 'has a rare earth metal sublattice moment greater than the transition metal sublattice moment at room temperature (rare earth metal rich), and the recording layer 4 has a transition metal sublattice moment greater than the rare earth metal sublattice moment from room temperature to the Curie temperature (transition Metal rich).

  In the magneto-optical recording medium having such a configuration, the recording layer 4 and the blocking layer 3 ′ are exchange-coupled at room temperature, and the directions of the transition metal sublattice moments are aligned. The magnetization direction (rare earth metal sublattice moment direction) and the total magnetization direction (transition metal sublattice moment direction) of the recording layer 4 are opposite to each other. In the magneto-optical recording medium of the present embodiment, the direction of the magnetic field that affects the reproducing layer 1 is determined by the overall magnetization direction of the recording layer 4 and the blocking layer 3 '. Therefore, by using the blocking layer 3 'as described above, the magnetic field from the recording layer 4 can be reduced by the magnetic field of the blocking layer 3' at least at room temperature. In short, the magnetic coupling between the recording layer 4 and the reproducing layer 1 can be suppressed.

  Further, if the total magnetization of the blocking layer 3 ′ and the total magnetization of the recording layer 4 are balanced so as to be substantially the same in a low temperature region near room temperature, the magnetic flux leaking to the reproducing layer 1 can be made substantially zero. Possible and desirable.

  On the other hand, as the temperature rises from room temperature, the blocking layer 3 ′ has a smaller difference between the magnitudes of the rare earth metal sublattice moment and the transition metal sublattice moment, and the total magnetization decreases. The difference in magnitude between the rare earth metal sublattice moment and the transition metal sublattice moment increases and the total magnetization increases. Accordingly, the total magnetization between the recording layer 4 and the blocking layer 3 ′ cannot be balanced by heating during reproduction, and the reproduction layer 1 is affected by the magnetic field generated from the recording layer 4. As a result, the magnetization of the recording layer 4 is transferred to the reproducing layer 1.

  As described above, in the magneto-optical recording medium of the present embodiment, during reproduction, the magnetization of the low temperature portion of the recording layer 4 is masked by the blocking layer 3 ′, and the recording layer 4 in the high temperature portion (the central portion of the light beam spot). Only the magnetic flux from the magnetic field leaks and the recording signal is transferred to the reproducing layer 1. For this reason, even when the recording bit interval is narrowed and an adjacent recording bit enters the enlarged magnetic domain region of the reproducing layer 1, no magnetic field is generated from the adjacent recording bit. Since the direction is determined only by the recording bit of the portion heated to the central high temperature, good reproduction characteristics can be obtained.

  In addition, when information is reproduced from this magneto-optical recording medium, once the magnetic domain created in the reproducing layer 1 is erased, it leads to a smooth reproducing operation. The magnetic domain disappears while the laser is extinguished, and the medium temperature is raised while the laser emits light, so that the recording magnetic domain of the recording layer can be transferred to the reproducing layer and signal reproduction can be performed. The signal quality can be made high.

  Below, the specific example of this reference form is demonstrated based on FIG. Here, a case where a magneto-optical disk is applied as the magneto-optical recording medium will be described.

  As shown in FIG. 7, the magneto-optical disk according to the present embodiment includes a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a blocking layer 3 ′, a recording layer 4, a protective layer 8, an overlayer. The coat layer 9 has a disk main body laminated in this order.

  In such a magneto-optical disk, the Curie temperature recording system is used as the recording system, and the light beam 5 emitted from the semiconductor laser is narrowed down to the reproducing layer 1 by the objective lens, which is known as the polar Kerr effect. Information is recorded and reproduced by the magneto-optical effect. The polar Kerr effect is a phenomenon in which the direction of rotation of the polarization plane of reflected light is reversed due to the direction of magnetization perpendicular to the incident surface.

  The board | substrate 6 consists of transparent base materials, such as a polycarbonate, for example, and is formed in disk shape.

  The transparent dielectric layer 7 is preferably made of a material that does not contain oxygen, such as AlN, SiN, AlSiN, etc., and its film thickness realizes a good interference effect on the incident laser light, The Kerr rotation angle needs to be set to increase. When the wavelength of the reproduction light is λ and the refractive index of the transparent dielectric layer 7 is n, the film thickness of the transparent dielectric layer 7 is about (λ / 4n). Set to For example, when the wavelength of the laser beam is 680 nm, the film thickness of the transparent dielectric layer 7 may be set to about 30 nm to 100 nm.

  The reproduction layer 1 is a rare earth transition metal alloy, or a magnetic film containing a rare earth metal or a transition metal as a main component, and its magnetic properties are adjusted so that the coercive force becomes small near the reproduction temperature. .

  The nonmagnetic intermediate layer 2 is made of a dielectric such as AlN, SiN, or AlSiN, or a nonmagnetic metal alloy such as Al, Ti, or Ta, and the reproducing layer 1, the blocking layer 3 ′, and the recording layer 4 are magnetostatically coupled. Therefore, the film thickness is set to 1 to 80 nm.

  The blocking layer 3 ′ is a magnetic film made of a rare earth transition metal alloy. As described with reference to FIG. 6, the barrier layer 3 'has a composition adjusted so that the rare earth metal sublattice moment is larger than the transition metal sublattice moment at room temperature, and the magnetic field generated from the recording layer 4 is masked at room temperature. Further, the direction of the transition metal sublattice moment always follows the direction of the transition metal sublattice moment of the recording layer 4 described later from room temperature to the Curie temperature. That is, the composition is adjusted so as to be determined by the direction of the transition metal sublattice moment of the recording layer 4.

  The recording layer 4 is made of a perpendicular magnetization film made of a rare earth transition metal alloy, and the transition metal sublattice moment is larger than the rare earth metal sublattice moment from room temperature to the Curie temperature, and the film thickness is set in the range of 20 to 80 nm. . The area of the recording magnetic domain is set smaller than the area of the magnetic domain existing in the reproducing layer 1 during reproduction.

  The protective layer 8 is made of a dielectric such as AlN, SiN, or AlSiN, or a nonmagnetic metal alloy such as Al, Ti, or Ta, and is intended to prevent oxidation of the rare earth transition metal alloy used for the reproducing layer 1 and the recording layer 4. The film thickness is set in the range of 5 nm to 60 nm.

  The overcoat layer 9 is formed by applying an ultraviolet curable resin or a thermosetting resin by spin coating and irradiating with ultraviolet rays or heating.

  Hereinafter, specific examples of this embodiment will be described in the order of (1) magneto-optical disk forming method and (2) recording / reproducing characteristics.

(1) Method for Forming Magneto-Optical Disk A method for forming the magneto-optical disk having the above configuration will be described.

First, a substrate 6 is made of a polycarbonate substrate 6 having a pregroove and a prepit and formed in a disk shape in a sputtering apparatus having an Al target, a GdFeCo alloy target, a GdDyFe alloy target, and a GdDyFeCo alloy target. To place. After the inside of the sputtering apparatus is evacuated to 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen is introduced, power is supplied to the Al target, and the substrate 6 is subjected to a gas pressure of 4 × 10 ⁻³ Torr. A transparent dielectric layer 7 made of AlN was formed with a film thickness of 80 nm.

Next, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, and then argon gas is introduced to supply power to the GdFeCo alloy target to obtain a gas pressure of 4 × 10 ⁻³ Torr. On the body layer 7, the reproducing layer 1 made of Gd _0.30 (Fe _0.80 Co _0.20 ) _0.70 was formed with a film thickness of 40 nm. The reproducing layer 1 was in the in-plane magnetization state at room temperature and had a property of being in a perpendicular magnetization state at a temperature of 120 ° C., its compensation temperature was 300 ° C., and its Curie temperature was 320 ° C.

Next, a mixed gas of argon and nitrogen is introduced, electric power is supplied to the Al target, and the nonmagnetic intermediate layer 2 made of AlN is formed on the reproducing layer 1 under the condition of a gas pressure of 4 × 10 ⁻³ Torr. The film was formed with a thickness of 20 nm.

Next, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, and then argon gas is introduced to supply power to the GdDyFe alloy target to obtain a gas pressure of 4 × 10 ⁻³ Torr. On the intermediate layer 2, a blocking layer 3 ′ made of (Gd _0.50 Dy _0.50 ) _0.28 Fe _0.72 was formed with a film thickness of 30 nm. The blocking layer 3 ′ had a Curie temperature of 140 ° C. and was a rare earth metal rich perpendicular magnetization film from room temperature to the Curie temperature.

Next, power is supplied to the GdDyFeCo alloy target so that the gas pressure is 4 × 10 ⁻³ Torr, and the recording layer 4 made of (Gd _0.50 Dy _0.50 ) _0.23 (Fe _0.80 Co _0.20 ) _{0.77 is formed} on the blocking layer 3 ′. Was formed with a film thickness of 40 nm. The recording layer 4 had a Curie temperature of 275 ° C.

Next, a mixed gas of argon and nitrogen is introduced, electric power is supplied to the Al target, and the protective layer 8 made of AlN is formed to a thickness of 20 nm on the recording layer 4 under the condition of a gas pressure of 4 × 10 ⁻³ Torr. Formed.

  Next, an ultraviolet curable resin was applied onto the protective layer 8 by spin coating, and an overcoat layer 9 was formed by irradiating with ultraviolet rays.

(2) Recording / Reproduction Characteristics FIG. 8 shows the mark length dependence of CNR (signal to noise ratio) measured on the above disk with an optical pickup using a semiconductor laser having a wavelength of 680 nm.

  For comparison, the dependency of CNR on the mark length of a magnetic domain expansion reproducing magneto-optical disk having a configuration without the blocking layer 3 ′ is also shown in FIG. The results for the magneto-optical disk described above will be described as Example 2. Incidentally, the medium of the magneto-optical disk having no blocking layer has a configuration in which the blocking layer 3 'is removed from the medium configuration described in this embodiment. The CNR mark length dependency shown here represents a signal-to-noise ratio when a recording magnetic domain having a length corresponding to the mark length is continuously formed at a recording magnetic domain pitch twice as long as the mark length. is there.

  Comparing the CNR of both marks having a mark length of 0.3 μm, it is 34.0 dB in the case of the comparative example 1, whereas an increase in CNR of 41.5 dB and 7.5 dB is observed in the case of the second embodiment. . This is due to the fact that adjacent bits are masked by the blocking layer 3 'and the reproduction resolution is increased.

  The recording / reproducing characteristics when the conditions of each layer in Example 2 are changed are shown below.

  (A) Film thickness of reproduction layer 1 and blocking layer 3 ′ Next, Table 10 shows the result of measuring the CNR at 0.3 μm by changing the film thickness of the reproduction layer 1 and blocking layer 3 ′ in Example 2. Is shown.

  In Table 10, the blocking layer thickness of 0 nm indicates the result of Comparative Example 1 in which the blocking layer 3 'is not formed. As the film thickness of the blocking layer 3 ′, the mask effect appears and the CNR increases when the thickness is 10 nm or more, but the CNR decreases when the thickness is 60 nm or more. This is presumably because the magnetic field transfer from the recording layer 4 is less likely to occur due to a decrease in the leakage magnetic field at the high temperature portion. From the above, it can be seen that the film thickness of the blocking layer 3 ′ that provides a higher CNR than Comparative Example 1 is in the range of 10 to 60 nm.

  Further, when the film thickness of the reproduction layer 1 is 8 nm, the reproduction signal becomes small and its CNR becomes lower than that of the comparative example 1. Furthermore, when the film thickness of the reproducing layer 1 is 100 nm, it becomes difficult to enlarge and transfer the magnetic domain, and the CNR becomes lower than that of the first comparative example. From the above, it can be seen that the thickness of the reproducing layer 1 that provides a higher CNR than Comparative Example 1 is in the range of 10 to 80 nm.

  (B) Film thickness of nonmagnetic intermediate layer 2 Next, Table 11 shows the results of measuring the CNR at 0.3 μm while changing the film thickness of the nonmagnetic intermediate layer 2 in Example 2.

  As can be seen from Table 11, when the film thickness of the nonmagnetic intermediate layer 2 is 0.5 nm, the CNR is remarkably reduced. This is considered to be because a good magnetostatic coupling state was not obtained because the film thickness of the nonmagnetic intermediate layer 2 was too thin. When the film thickness of the nonmagnetic intermediate layer 2 is 1 nm, the maximum CNR is obtained. As the film thickness of the nonmagnetic intermediate layer 2 increases, the magnetostatic coupling force decreases and the CNR decreases. . It can be seen that in order to obtain a higher CNR than Comparative Example 1, it is necessary to set the film thickness of the nonmagnetic intermediate layer 2 in the range of 1 to 80 nm.

  Further, it can be seen that by increasing the film thickness of the nonmagnetic intermediate layer 2, the magnetostatic coupling force between the reproducing layer 1 and the recording layer 4 is reduced, thereby reducing the erasing magnetic field. In order to make the erasing magnetic field within a practical range of 31 kA / m or less, it is desirable that the film thickness of the nonmagnetic intermediate layer 2 be 4 nm or more.

(C) Curie temperature of blocking layer 3 ′ In the above, the recording / reproducing characteristics when (Gd _0.50 Dy _0.50 ) _0.28 Fe _0.72 having a Curie temperature of 140 ° C. is used as the blocking layer 3 ′ are shown below. The result of investigating the recording / reproducing characteristics by changing the Gd content of the blocking layer 3 ′ will be described.

Table 12 shows that the blocking layer 3 ′ is (Gd _X Dy _1-X ) _0.28 Fe _0.72 with a film thickness of 30 nm, and the value of X (atom ratio) is changed, and the Curie temperature T _C3 of the blocking layer 3 ′ and the wavelength of 680 nm 2 shows a result of measuring a CNR (signal-to-noise ratio) at 0.3 μm measured by an optical pickup using the above semiconductor laser.

  In Table 12, a CNR higher than the CNR (34.0 dB) obtained in Comparative Example 1 in which the blocking layer 3 ′ is not formed is in the range of 0.20 ≦ X ≦ 1.00. I understand.

  The recording layer 4 used in Table 12 has the maximum magnetization at a temperature of 140 ° C. (heating temperature during reproduction). That is, the blocking layer 3 ′ only needs to be able to mask the leakage magnetic field from the recording layer at a temperature of 140 ° C. or lower, and the optimal value of the Curie temperature of the blocking layer 3 ′ is about 140 ° C. (near the heating temperature during reproduction). It will be. However, as shown in Table 12, when the Curie temperature of the blocking layer 3 ′ is 80 ° C. or higher and 220 ° C. or lower, a higher CNR than that of Comparative Example 1 is obtained, and the Curie temperature of the blocking layer 3 ′ is 80 ° C. By setting the temperature to 220 ° C. or lower, it is possible to obtain a mask effect at a low temperature.

  In addition, here, the result of using GdDyFe as the blocking layer 3 ′ is described. It is possible to use a perpendicular magnetization film made of an alloy including any one of an alloy, a GdFe alloy, a GdTbFe alloy, a DyFeCo alloy, and a TbFeCo alloy.

  (D) Compensation temperature of blocking layer 3 ′ Further, it has been described above that the blocking layer 3 ′ preferably has a Curie temperature of 80 ° C. to 220 ° C. However, even if the compensation temperature is 80 ° C. to 220 ° C. In addition, the effect of the present embodiment (blocking of the magnetic field from the recording layer 4 at room temperature) can be obtained. This specific example will be described below.

CNR (signal to noise ratio) at 0.3 nm was measured with an optical pickup using a semiconductor laser with a wavelength of 680 nm, using (Gd _0.8 Dy _0.2 ) _0.26 Fe _0.74 with a film thickness of 30 nm as the blocking layer 3 ′. The blocking layer 3 ′ had a compensation temperature of 140 ° C. and a Curie temperature of 200 ° C.

  In this case, the CNR was 41.5 dB, and substantially the same characteristics as in Example 2 were obtained. That is, even when the blocking layer 3 ′ has a compensation temperature, the masking effect of the leakage magnetic field from the recording layer 4 can be obtained. The compensation temperature is preferably set to 140 ° C. (near the heating temperature at the time of reproduction) at which the magnetization of the recording layer is maximized. However, if the compensation temperature is other than 80 ° C. to 220 ° C., the mask effect It is possible to obtain If the compensation temperature is 80 ° C. to 220 ° C., a perpendicular magnetization film made of an alloy containing any of GdDyFe alloy, TbFe alloy, DyFe alloy, GdFe alloy, GdTbFe alloy, DyFeCo alloy, and TbFeCo alloy in addition to GdDyFe. Can be used.

(Reference form 2)
The second embodiment of the present invention will be described with reference to FIG. In this embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described.

  As shown in FIG. 9, the magneto-optical disk according to the second embodiment has a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a recording layer 4, a blocking layer 3 ′, a protective layer 8, The overcoat layer 9 has a disc body laminated in this order.

  The magneto-optical disk of the second embodiment has a configuration in which the formation order of the blocking layer 3 ′ and the recording layer 4 is reversed in the magneto-optical disk described in the first embodiment.

  Hereinafter, specific examples of this embodiment will be described in the order of (1) magneto-optical disk forming method and (2) recording / reproducing characteristics.

(1) Magneto-optical disk forming method The magneto-optical disk of the present embodiment is formed by reversing the formation order of the blocking layer 3 'and the recording layer 4 in the magneto-optical disk forming method described in the first embodiment. The substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the nonmagnetic intermediate layer 2, the protective layer 8, and the overcoat layer 9 were formed in the same manner as in Example 2.

(2) Recording / reproduction characteristics Table 13 shows a CNR (signal at 0.3 μm) measured by an optical pickup using a semiconductor laser having a wavelength of 680 nm with the film thicknesses of the reproduction layer 1 and the blocking layer 3 ′ in this reference embodiment being changed. To noise ratio).

  In Table 13, the blocking layer film thickness of 0 nm indicates the result of Comparative Example 1 in which the blocking layer 3 ′ is not formed. In addition, the recording layer 4 and the blocking layer 3 'in Example 2 shown in Reference Mode 1 are simply replaced as Example 3.

  As the film thickness of the blocking layer 3 ′, the mask effect appears and the CNR increases when the thickness is 10 nm or more, but the CNR decreases when the thickness is 100 nm or more. This is presumably because the effect of the mask is reduced and it is affected by the adjacent recording signal. From the above, it can be seen that the film thickness of the blocking layer 3 ′ that provides a higher CNR than Comparative Example 1 is in the range of 10 to 80 nm.

  Compared to the case of the first embodiment, since the blocking layer is present on the side opposite to the incidence of the light beam 5, the mask effect is weakened and the CNR is relatively low. The film thickness range of the blocking layer 3 ′ necessary for realizing it is widened.

  Note that (a) the thickness of the reproducing layer 1, (b) the thickness of the nonmagnetic intermediate layer 2, (c) the Curie temperature of the blocking layer 3 ′, and (d) the compensation temperature of the blocking layer 3 ′ are reference forms. Results similar to those shown in 1 were obtained.

(Reference form 3)
The third embodiment of the present invention will be described with reference to FIG. In this embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described.

  As shown in FIG. 10, the magneto-optical disk according to the third embodiment includes a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a reflective layer 10, a blocking layer 3 ′, a recording layer 4, The protective layer 8 and the overcoat layer 9 have a disc body laminated in this order.

  In Reference Embodiment 1 and Reference Embodiment 2, when the thickness of the reproduction layer 1 is smaller than 40 nm, the light beam 5 transmitted through the reproduction layer 1 is reflected by the blocking layer 3 ′ or the recording layer 4 and recorded in the reproduction signal. As a result, the information of the adjacent recording bit signal of the layer 4 is mixed, and the reproduction signal characteristic is deteriorated.

  The magneto-optical disk according to the third embodiment has a configuration in which the reflective layer 10 is formed between the nonmagnetic intermediate layer 2 and the blocking layer 3 'in the magneto-optical disk described in the first embodiment. By doing so, even when the film thickness of the reproducing layer 1 is as thin as 40 nm or less, the light beam 5 transmitted through the reproducing layer 1 is reflected by the reflecting layer 10 and the recording signal adjacent to the recording layer 4 is recorded on the reproduced signal. It becomes possible to prevent the bit signal information from being mixed, and the magnetic domain expansion reproduction by the reproduction layer 1 can be made more complete.

  Hereinafter, specific examples of the magneto-optical disk of the present embodiment will be described by dividing into (1) a method of forming the magneto-optical disk and (2) recording / reproducing characteristics.

(1) Method for Forming Magneto-Optical Disk The magneto-optical disk of the present embodiment is a reflection made of Al between the nonmagnetic intermediate layer 2 and the blocking layer 3 ′ in the method for forming a magneto-optical disk described in the first embodiment. The layer 10 is formed. The substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the nonmagnetic intermediate layer 2, the blocking layer 3 ′, the recording layer 4, the protective layer 8, and the overcoat layer 9 are the same as in Example 2. Similarly, the reproducing layer 1 was formed with a film thickness of 25 nm.

Here, after forming the nonmagnetic intermediate layer 2, the Al reflective layer 10 is evacuated again to 1 × 10 ⁻⁶ Torr inside the sputtering apparatus, and then argon gas is introduced to supply power to the Al target. Then, the reflective layer 10 made of Al was formed to a thickness of 2 to 80 nm on the nonmagnetic intermediate layer 2 with a gas pressure of 4 × 10 ⁻³ Torr.

(2) Recording / reproduction characteristics Table 14 shows the CNR (signal-to-noise ratio) at 0.3 μm measured by an optical pickup using a semiconductor laser having a wavelength of 680 nm while changing the film thickness of the reflection layer 10 of this embodiment described above. ).

  In Table 14, the reflective layer thickness of 0 nm indicates the result of Comparative Example 3 in which the reflective layer 10 is not formed. Even when the thickness of the reflective layer 10 is as extremely thin as 2 nm, the effect of blocking information reproduction from the recording layer 4 is seen, and the CNR increases by 0.5 dB. By increasing the thickness of the reflective layer 10, the CNR gradually increases, and the CNR becomes maximum at the thickness of 20 nm. This is because the effect of blocking information reproduction from the recording layer 4 becomes more significant as the thickness of the reflective layer increases. Although the CNR is reduced when the film thickness is 20 nm or more, this is because the magnetostatic coupling force acting between the recording layer 4 and the reproducing layer 1 becomes weaker as the distance between the recording layer 4 and the reproducing layer 1 increases. From the above, it can be seen that in order to obtain a higher CNR than Comparative Example 3, it is necessary to set the film thickness of the reflective layer 10 in the range of 2 to 40 nm.

  In the above description, the reproducing characteristics using Al as the reflective layer 10 are described. However, as the reflective layer 10, an alloy of Al and a metal other than Al may be used.

Table 15 shows that the CNR at 0.3 μm measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm with the reflective layer 10 being Al _1-X Fe _X having a thickness of 20 nm and changing the value of X (atom ratio). (Signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 15, as the Fe content increases, that is, as X becomes larger than 0.10, the CNR gradually decreases. However, both CNRs are larger than those in Comparative Example 3 described above. The effect of forming the layer 10 is seen. On the other hand, looking at the erasing magnetic field, when the reflection layer 10 made of pure Al is used, an erasing magnetic field as large as 50 kA / m is required, whereas X is set to 0.02 or more and 0.50 or less. Thus, the erasing magnetic field can be reduced.

Next, Table 16 shows that the reflective layer 10 is Al _1-X Ni _X with a film thickness of 20 nm and the value of X (atom ratio) is changed and measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm. The CNR (signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 16, as in the case of containing Fe, it was possible to reduce the erasing magnetic field by setting X to 0.02 or more and 0.50 or less.

  In addition to Fe and Ni, a magnetic metal such as Co, Gd, Tb, Dy, and Nd is similarly contained in Al, so that the erasing magnetic field can be reduced.

  Next, description will be made on improvement in recording characteristics when a nonmagnetic metal element is contained in Al as the reflective layer 10.

Table 17 shows that the CNR at 0.3 μm measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm, with the reflective layer 10 made of Al _1-X Ti _X having a thickness of 20 nm and changing the value of X (atom ratio). (Signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 17, as the Ti content increases, that is, as X becomes larger than 0.10, the CNR gradually decreases. However, both CNRs are larger than those in Comparative Example 3, and the reflective layer 10 The effect which formed is seen. On the other hand, looking at the erasing magnetic field, when the reflection layer 10 made of pure Al is used, an erasing magnetic field as large as 50 kA / m is required, whereas X is set to 0.02 to 0.98. Thus, the erasing magnetic field can be reduced.

Next, Table 18 shows the erasing magnetic field reduction effect when a nonmagnetic element other than Ti is contained in Al as the reflective layer 10, where the reflective layer 10 is Al _0.5 Z _0.5 and Z is other than Ti. The figure shows the CNR (signal-to-noise ratio) at 0.3 μm and the magnitude of the erasing magnetic field measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm when a nonmagnetic metal is used.

  From Table 18, in the case where Ta, Pt, Au, Cu, and Si, which are nonmagnetic metals, are used as Z, all the CNRs are larger than those of Comparative Example 3 described above, and the effect of forming the reflective layer 10 is seen. On the other hand, looking at the erasing magnetic field, it was possible to reduce the erasing magnetic field as in the case where Al was contained in Ti.

  Here, the case where the reflective layer is applied to the magneto-optical disk described in the reference embodiment 1 is described, but it goes without saying that the same result can be obtained even if it is applied to the reference embodiment 2.

  Note that (a) the thickness of the reproducing layer and the blocking layer, (c) the Curie temperature of the blocking layer 3 ′, and (d) the compensation temperature of the blocking layer 3 ′ are the same as those shown in the first and second embodiments. Results were obtained.

(Reference form 4)
Reference embodiment 4 of the present invention will be described below with reference to FIG. In this embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described.

  As shown in FIG. 11, the magneto-optical disk according to the fourth embodiment has a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a blocking layer 3 ′, a recording layer 4, a protective layer 8, The heat dissipating layer 110 and the overcoat layer 9 have a disc body laminated in this order.

  The magneto-optical disk of the fourth embodiment has a configuration in which the heat dissipation layer 110 is formed between the protective layer 8 and the overcoat layer 9 in the magneto-optical disk described in the first embodiment.

  Hereinafter, (1) a magneto-optical disk forming method and (2) recording / reproducing characteristics will be described for a specific example of the present embodiment.

(1) Method for Forming Magneto-Optical Disk The magneto-optical disk of this embodiment is the same as the method for forming a magneto-optical disk described in Example 2, except that the heat dissipation layer 110 made of Al is interposed between the protective layer 8 and the overcoat layer 9. The substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the nonmagnetic intermediate layer 2, the blocking layer 3 ′, the recording layer 4, the protective layer 8, and the overcoat layer 9 are described in Reference Example 1. Similarly to the method, the protective layer 8 was formed with a film thickness of 5 nm.

Here, after forming the recording layer 4, the Al heat dissipation layer 110 is again evacuated to 1 × 10 ⁻⁶ Torr in the sputtering apparatus, and then introduced argon gas to supply power to the Al target. A gas pressure of 4 × 10 ⁻³ Torr was set, and a heat dissipation layer 110 made of Al was formed on the recording layer 4 to a thickness of 20 nm.

(2) Recording / reproducing characteristics As a result of measuring the CNR (signal to noise ratio) at 0.3 μm with an optical pickup using a semiconductor laser having a wavelength of 680 nm, the CNR was 42.5 dB, which is 1 dB better than that in the second embodiment. became.

  If there is a heat dissipation layer 110 made of Al with high thermal conductivity as in this reference embodiment, the spread of heat in the lateral direction can be released to the heat dissipation layer side, that is, the thickness direction of the layer, and the heat in the lateral direction can be released. Can be reduced. Accordingly, the temperature distribution in the light beam becomes steeper, the masking effect of the magnetic field from the recording layer in the reproducing layer by the blocking layer can be emphasized, and the reproducing characteristics can be further improved.

  Al, which is a material of the heat dissipation layer 110, has a higher thermal conductivity than the rare earth transition metal alloy film used for the reproducing layer 1 and the recording layer 4, and is a material suitable for the heat dissipation layer. It is also a very inexpensive material.

  As a material of the heat dissipation layer 110, any material other than Al in the above example may be used as long as it has a higher thermal conductivity than a reproducing layer or recording layer such as Au, Ag, Cu, SUS, Ta, Cr.

  Since Au is excellent in oxidation resistance, moisture resistance and pitting corrosion resistance, long-term reliability can be improved.

  If Ag is used, since it is excellent in oxidation resistance, moisture resistance, and pitting corrosion resistance, long-term reliability can be improved.

  Since Cu is excellent in oxidation resistance, moisture resistance, and pitting corrosion resistance, long-term reliability can be improved.

  If SUS, Ta, or Cr is used, these materials are extremely excellent in oxidation resistance, moisture resistance, and pitting corrosion resistance. Therefore, it is possible to provide a magneto-optical disk having excellent long-term reliability.

  In this reference embodiment, the thickness of the heat dissipation layer 110 is 20 nm. However, the thicker the heat dissipation effect, the longer the reliability. However, since it also affects the recording sensitivity of the magneto-optical disk, it is necessary to set the film thickness according to the thermal conductivity and specific heat of the material, and the range of 5 to 200 nm is good. In particular, 10 to 100 nm is preferable. If the material has a relatively high thermal conductivity and excellent corrosion resistance, the film thickness can be as thin as about 10 to 100 nm, and the time required for film formation can be shortened.

  Here, the case where the radiation layer is applied to the magneto-optical disk described in Reference Embodiment 1 is described. However, the present invention is applied to Embodiments 1 to 6, Reference Embodiments 2 and 3, and Reference Embodiments 5 to 9 described later. It goes without saying that a similar result can be obtained.

  In Reference Mode 4, (a) the thickness of the reproducing layer 1 and the blocking layer 3 ′, (b) the thickness of the nonmagnetic intermediate layer 2, (c) the Curie temperature of the blocking layer 3 ′, (d) the blocking layer 3 Regarding the compensation temperature of ', (e) the thickness of the reflective layer, and the material, the same results as those shown in Reference Examples 1 to 3 were obtained.

  In Reference Embodiments 1 to 3 described above, a magnetic layer that is in-plane magnetized at room temperature and perpendicularly magnetized at high temperature is used as the reproducing layer. However, at least the signal reproducing region (heated to a predetermined temperature or higher during reproduction). Any region can be used as long as it is in a perpendicular magnetization state.

(Reference form 5)
Hereinafter, Reference Embodiment 5 of the present invention will be described in detail with reference to the drawings.

  FIG. 12 shows the principle of magnetic domain expansion reproduction according to this embodiment.

  In the magneto-optical recording medium of the present embodiment, a transfer layer 3 ″ (magnetic mask layer in claims) that is magnetostatically coupled to the reproducing layer 1 is provided between the reproducing layer 1 and the recording layer 4. "" Indicates in-plane magnetization at room temperature and perpendicular magnetization above a predetermined temperature. Then, the transfer layer 3 ″ masks the magnetization from the portion 11 that is not heated above the predetermined temperature (hereinafter referred to as a critical temperature) in the recording layer 4. That is, the transfer layer 3 ″ allows the recording layer 4 to The magnetization from the portion 11 is prevented from being transmitted to the reproducing layer 1.

  On the other hand, since the transfer layer 3 ″ exhibits perpendicular magnetization in the portion above the critical temperature, it is possible to remove the mask, and it is possible to reproduce information only in the range above the critical temperature of the target recording layer 4.

  Accordingly, the heating temperature of the transfer layer 3 ″ at the time of reproduction is set so that only the magnetic flux from one recording bit in the recording layer 4 is leaked by the transfer layer 3 ″ and the magnetic flux from the other recording bits is masked. For example, even if the recording bit interval is narrowed, the influence of the adjacent bits 11 is suppressed, and only information of one recording bit can be transferred to the reproducing layer 1, and good reproduction characteristics can be obtained.

  Here, the transfer layer 3 ″ needs to have a Curie temperature above the critical temperature in order to make the magnetostatic coupling between the recording layer 4 and the reproducing layer 1 effective in the range above the critical temperature. By setting the temperature lower than the Curie temperature of the layer 4, there is no magnetic influence during recording, so that stable recording can be performed.

  In addition, when the reproducing layer 1 is reproduced by a laser beam, it is preferable that the size of the magnetic domain is large because the amount of signal increases and the cause of noise decreases. Further, the domain wall needs to move in accordance with the magnetic field from the recording layer 4, and a characteristic with a small coercive force is advantageous.

  In addition, when information is reproduced from this magneto-optical recording medium, erasing the magnetic domain created in the reproducing layer 1 leads to a smooth reproducing operation, so that a reproducing laser beam is emitted in pulses. Is desirable. In this way, the magnetic domain disappears while the laser is extinguished, and the medium temperature is raised while the laser emits light, so that the recording magnetic domain of the recording layer 4 is transferred to the reproducing layer 1 to reproduce the signal. The reproduction signal quality can be made higher.

  Below, the specific example of this reference form is demonstrated based on FIG. Here, a case where a magneto-optical disk is applied as the magneto-optical recording medium will be described.

  As shown in FIG. 13, the magneto-optical disk according to the present embodiment includes a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a transfer layer 3 ″, a recording layer 4, a protective layer 8, an overlayer. The coat layer 9 has a disk main body laminated in this order.

  In such a magneto-optical disk, the Curie temperature recording system is used as the recording system, and the light beam 5 emitted from the semiconductor laser is narrowed down to the reproducing layer 1 by the objective lens, which is known as the polar Kerr effect. Information is recorded and reproduced by the magneto-optical effect. The polar Kerr effect is a phenomenon in which the direction of rotation of the polarization plane of reflected light rotates due to magnetization perpendicular to the incident surface, and the direction of rotation changes depending on the direction of magnetization.

  The board | substrate 6 consists of transparent base materials, such as a polycarbonate, for example, and is formed in disk shape.

The transparent dielectric layer 7 is preferably made of a material having a large refractive index such as AlN, SiN, AlSiN, TiO ₂ , and the film thickness realizes a good interference effect with respect to the incident laser light. The Kerr rotation angle of the medium needs to be set to increase. When the wavelength of the reproduction light is λ and the refractive index of the transparent dielectric layer 7 is n, the film thickness of the transparent dielectric layer 7 is (λ / 4n). For example, when the wavelength of the laser beam is 680 nm, the film thickness of the transparent dielectric layer 7 may be set to about 30 nm to 100 nm.

  The reproducing layer 1 is a magnetic film made of a rare earth transition metal alloy, and its magnetic characteristics are in the in-plane magnetization state at room temperature, approaching the compensation composition as the temperature rises, the total magnetization becomes smaller, and the effect of the demagnetizing field The composition is adjusted so as to become weak and become a perpendicular magnetization state.

  The nonmagnetic intermediate layer 2 is composed of one layer of dielectric such as AlN, SiN, AlSiN, or one layer of nonmagnetic metal alloy such as Al, Ti, Ta, or two layers of dielectric and metal. 1 and the recording layer 4 are set to be magnetostatically coupled.

  The transfer layer 3 ″ is a rare earth transition metal alloy, or a magnetic film containing a rare earth metal or a transition metal as a main component, exhibits in-plane magnetization at room temperature, and perpendicular magnetization above a predetermined temperature (critical temperature). 12, the transfer layer 3 ″ masks the magnetic field generated from the perpendicular magnetization of the recording layer 4 with the in-plane magnetization at a temperature lower than the critical temperature, thereby preventing the magnetic field to the reproducing layer 1 from occurring. . Above the critical temperature, the composition is adjusted so that the mask effect is lost due to the perpendicular magnetization and the magnetic field generated from the recording layer 4 is easily transmitted to the reproducing layer.

  The recording layer 4 is made of a perpendicular magnetization film made of a rare earth transition metal alloy, and the film thickness is set in the range of 20 to 80 nm.

  The protective layer 8 is made of a dielectric such as AlN, SiN, AlSiN, SiC, or a nonmagnetic metal alloy such as Al, Ti, Ta, etc., and prevents oxidation of the rare earth transition metal alloy used for the reproducing layer 1 and the recording layer 4. The film thickness is set in the range of 5 nm to 60 nm.

  The overcoat layer 9 is formed by applying an ultraviolet curable resin or a thermosetting resin by spin coating and irradiating with ultraviolet rays or heating.

  Hereinafter, specific examples of the magneto-optical disk of the present embodiment will be described by dividing into (1) forming method and (2) recording / reproducing characteristics.

(1) Formation Method A formation method of the magneto-optical disk having the above-described configuration will be described.

First, a pre-groove and a pre-pit are formed in a disc shape in a sputtering apparatus equipped with an Al target, two types of GdFeCo alloy targets corresponding to the reproduction layer 1 and the transfer layer 3 ″, and a GdDyFeCo alloy target. The polycarbonate substrate 6 is placed in the substrate holder, and after the inside of the sputtering apparatus is evacuated to 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen is introduced, power is supplied to the Al target, and the gas pressure is increased. A transparent dielectric layer 7 made of AlN was formed on the substrate 6 with a film thickness of 80 nm under the condition of 4 × 10 ⁻³ Torr.

Next, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, and then argon gas is introduced to supply power to the GdFeCo alloy target to obtain a gas pressure of 4 × 10 ⁻³ Torr. On the body layer 7, the reproducing layer 1 made of Gd _0.30 (Fe _0.80 Co _0.20 ) _0.70 was formed with a film thickness of 40 nm.

  The reproducing layer 1 was in the in-plane magnetization state at room temperature and had a property of being in a perpendicular magnetization state at a temperature of 120 ° C., its compensation temperature was 300 ° C., and its Curie temperature was 320 ° C.

Next, a mixed gas of argon and nitrogen is introduced, electric power is supplied to the Al target, and the nonmagnetic intermediate layer 2 made of AlN is formed on the reproducing layer 1 under the condition of a gas pressure of 4 × 10 ⁻³ Torr. Formed at 20 nm.

Next, electric power is supplied to the GdFeCo alloy target to set the gas pressure to 4 × 10 ⁻³ Torr, and a transfer layer 3 ″ made of Gd _0.30 (Fe _0.85 Co _0.15 ) _{0.70 is formed} on the nonmagnetic intermediate layer 2 with a film thickness. The transfer layer 3 ″ was formed in the in-plane magnetization state at room temperature, had a property of being in a perpendicular magnetization state at a temperature of 120 ° C., and its Curie temperature was 250 ° C.

Next, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, and then argon gas is introduced to supply power to the GdDyFeCo alloy target to obtain a gas pressure of 4 × 10 ⁻³ Torr. On 3 ″, a recording layer 4 made of (Gd _0.50 Dy _0.50 ) _0.23 (Fe _0.80 Co _0.20 ) _0.77 was formed with a film thickness of 40 nm. The recording layer 4 had a compensation temperature at 25 ° C. and had a Curie temperature. It was 275 ° C.

Next, a mixed gas of argon and nitrogen is introduced, electric power is supplied to the Al target, and the protective layer 8 made of AlN is formed to a thickness of 20 nm on the recording layer 4 under the condition of a gas pressure of 4 × 10 ⁻³ Torr. Formed.

  Next, an ultraviolet curable resin was applied onto the protective layer 8 by spin coating, and an overcoat layer 9 was formed by irradiating with ultraviolet rays.

(2) Recording / Reproducing Characteristics FIG. 14 shows the mark length dependence of CNR (signal to noise ratio) measured on the above disk by an optical pickup using a semiconductor laser having a wavelength of 680 nm. In this figure, the magneto-optical disk of this reference embodiment described above is described as Example 4.

  For comparison, the mark length dependency of the CNR of a magneto-optical disk having a structure without the transfer layer 3 ″ is also shown in the same figure as Comparative Example 1. Note that the medium of the magneto-optical disk without the transfer layer 3 ″ is shown in FIG. Is a configuration in which the transfer layer 3 ″ is removed from the medium configuration described in the present embodiment. The dependency of the CNR shown here on the mark length is that the recording magnetic domain having a length corresponding to the mark length is equal to 2 of the mark length. It represents the signal-to-noise ratio when continuously formed with a recording magnetic domain pitch of double length.

  When the CNR of both marks having a mark length of 0.3 μm is compared, it is 34.0 dB in the case of the comparative example 1, whereas an increase in CNR of 41.0 dB and 7.0 dB is observed in the case of the fourth embodiment. . This is because the transfer layer 3 ″ works as a magnetization mask for the recording layer 4 to increase the reproduction resolution.

  Next, Table 19 shows the result of measuring the CNR at 0.3 μm while changing the film thickness of the reproducing layer 1 and the transfer layer 3 ″ in Example 4.

  In Table 19, the transfer layer thickness of 0 nm indicates the result of Comparative Example 1 in which the transfer layer 3 ″ was not formed. Even when the transfer layer 3 ″ was extremely thin, the in-plane magnetization was 2 nm. As the mask is strengthened, the CNR increases by 1.5 dB. As the film thickness of the transfer layer 3 ″, the CNR increases by realizing the enhancement of the in-plane magnetization mask up to 30 nm, but the CNR decreases as the thickness increases further. This is due to the fact that the in-plane magnetization mask is over-strengthened and the magnetic aperture is difficult to open, and the complete perpendicular magnetization state of the reproducing layer cannot be obtained. Here, it can be seen from Table 19 that the film thickness of the transfer layer 3 ″ that provides a higher CNR than Comparative Example 1 is in the range of 2 to 40 nm.

  Further, when the film thickness of the reproduction layer 1 is 8 nm, the reproduction signal becomes small and its CNR becomes lower than that of the comparative example 1. Furthermore, when the film thickness of the reproducing layer 1 is 120 nm, the domain wall energy generated in the reproducing layer 1 increases, and a complete perpendicular magnetization state cannot be obtained in the portion where the temperature has risen, and its CNR is lower than that of Comparative Example 1. End up. From Table 19, it can be seen that the thickness of the reproducing layer 1 that provides a higher CNR than Comparative Example 1 is in the range of 10 to 80 nm.

  Next, Table 20 shows the results of measuring the CNR at 0.3 μm and the magnetic field necessary for erasing (erasing magnetic field) by changing the film thickness of the nonmagnetic intermediate layer 2 in Example 4. .

  As can be seen from Table 20, when the thickness of the nonmagnetic intermediate layer 2 is 0.5 nm, the CNR is remarkably reduced. This is considered to be because a good magnetostatic coupling state was not obtained because the film thickness of the nonmagnetic intermediate layer 2 was too thin. When the film thickness of the nonmagnetic intermediate layer 2 is 1 nm, the maximum CNR is obtained. As the film thickness of the nonmagnetic intermediate layer 2 increases, the magnetostatic coupling force decreases and the CNR decreases. . It can be seen that in order to obtain a higher CNR than Comparative Example 1, it is necessary to set the film thickness of the nonmagnetic intermediate layer 2 in the range of 1 to 80 nm.

  Further, it can be seen that by increasing the film thickness of the nonmagnetic intermediate layer 2, the magnetostatic coupling force between the reproducing layer 1 and the recording layer 4 is reduced, thereby reducing the erasing magnetic field. In order to make the erasing magnetic field within a practical range of 31 kA / m or less, it is desirable that the film thickness of the nonmagnetic intermediate layer 2 be 4 nm or more.

(Reference form 6)
In the present embodiment, an example in which the transfer layer 3 ″ having a different composition in the specific example of the magneto-optical disk shown in the above embodiment 5 will be described.

In Reference Mode 6, the recording / reproducing characteristics when Gd _0.30 (Fe _0.85 Co _0.15 ) _0.70 having a temperature of transition from in-plane magnetization to perpendicular magnetization (hereinafter referred to as T _trans ) of 120 ° C. is used as the transfer layer 3 ″. However, in this embodiment, the result of examining the recording / reproducing characteristics by changing the composition of the transfer layer 3 ″ will be described.

Table 21 shows that the transfer layer 3 ″ is Gd _X (Fe _0.80 Co _0.20 ) _1-X with a film thickness of 30 nm, the value of X (atom ratio) is changed, the T _{trans of the} transfer layer 3 ″, and the semiconductor with a wavelength of 680 nm. The result of having measured CNR (signal to noise ratio) in 0.3 micrometer measured with the optical pick-up using a laser is shown.

In Table 21, a CNR higher than the CNR (34.0 dB) obtained in Comparative Example 1 in which the transfer layer 3 ″ is not formed is in the range of 0.22 ≦ X ≦ 0.35. The reproduction layer 1 used in this embodiment is the same as that in Example 4, and is in a perpendicular magnetization state at a temperature of 120 ° C. That is, the transfer layer 3 ″ is reproduced at a temperature of 120 ° C. or less. It is sufficient if the in-plane magnetization mask of the layer 1 can be emphasized. However, if T _trans is too low, the mask effect is diminished, and preferably X ≧ 0.22. If T _trans is too high, it can be transferred to the reproducing layer 1 to some extent, but if it is too high, recorded information cannot be transferred to the reproducing layer 1 sufficiently. Accordingly, the transfer layer 3 ″ remains in the masked state when it becomes perpendicularly magnetized at a temperature higher than the temperature at which the reproducing layer 1 becomes the perpendicularly magnetized film. Therefore, it is desirable that the transfer layer 3 ″ be perpendicularly magnetized at the reproducing temperature.

In Reference Embodiments 5 and 6, as the transfer layer 3 ″, it is sufficient that T _trans satisfies the above-mentioned conditions. However, by setting the Curie temperature to be equal to or lower than the Curie temperature of the recording layer, a magnetic influence during recording is obtained. In Reference Embodiments 5 and 6, the results using GdFeCo are described, but it is sufficient that T _trans satisfies the above-mentioned conditions, and in addition, GdNdFe, GdNdFeCo, GdTbFe , GdTbFeCo, GdDyFeCo, GdDyFe, GdFe and the like can be used.

  The same results as in Reference Example 5 were obtained with respect to the thickness of the reproducing layer 1, the transfer layer, and the thickness of the nonmagnetic intermediate layer 2.

(Reference form 7)
Reference Embodiment 7 of the present invention will be described below with reference to FIG. In this embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described. However, the description of the same parts as those of the reference embodiments 5 to 6 is omitted.

  As shown in FIG. 15, the magneto-optical disk according to the seventh embodiment has a substrate 6, a transparent dielectric layer 7, a reproducing layer 1, a nonmagnetic intermediate layer 2, a reflective layer 10, a transfer layer 3 ″, a recording layer 4, The protective layer 8 and the overcoat layer 9 have a disc body laminated in this order.

  In the reference mode 5, when the thickness of the transfer layer 3 ″ is smaller than 10 nm, the light beam 5 transmitted through the reproducing layer 1 and the nonmagnetic intermediate layer 2 is reflected by the recording layer 4, and the recording layer receives the reproduced signal. As a result, the effect of the mask due to the in-plane magnetization of the reproducing layer 1 and the transfer layer 3 ″ is deteriorated.

  The magneto-optical disk of the seventh embodiment has a configuration in which a reflective layer 10 is formed between the nonmagnetic intermediate layer 2 and the transfer layer 3 ″ in the magneto-optical disk described in the fifth embodiment. By doing so, the light beam 5 transmitted through the reproducing layer 1 is reflected by the reflecting layer 10, and it is possible to prevent the information of the recording layer 4 from being mixed into the reproducing signal.

  Hereinafter, specific examples of the magneto-optical disk of the present embodiment will be described by dividing into (1) forming method and (2) recording / reproducing characteristics.

(1) Forming Method The magneto-optical disk of this reference embodiment is the same as the magneto-optical disk forming method of Reference Embodiment 5 except that a reflective layer 10 made of Al is formed between the nonmagnetic intermediate layer 2 and the transfer layer 3 ″. The substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the nonmagnetic intermediate layer 2, the transfer layer 3 ″, the recording layer 4, the protective layer 8, and the overcoat layer 9 are reproduced in the same manner as in Example 4. The film thickness of the layer 1 was 25 nm, and the film thickness of the transfer layer 3 ″ was 20 nm.

Here, after forming the nonmagnetic intermediate layer 2, the Al reflective layer 10 is evacuated again to 1 × 10 ⁻⁶ Torr inside the sputtering apparatus, and then argon gas is introduced to supply power to the Al target. Then, the reflective layer 10 made of Al was formed to a thickness of 2 to 80 nm on the nonmagnetic intermediate layer 2 with a gas pressure of 4 × 10 ⁻³ Torr.

(2) Recording / reproduction characteristics Table 22 shows the CNR (signal-to-noise ratio) at 0.3 μm measured by an optical pickup using a semiconductor laser having a wavelength of 680 nm while changing the film thickness of the reflective layer 10 in Example 3. It is shown.

  In Table 22, the reflective layer thickness of 0 nm indicates the result of Comparative Example 4 in which the reflective layer 10 is not formed. Even when the thickness of the reflective layer 10 is as extremely thin as 2 nm, the effect of blocking information reproduction from the recording layer 4 is observed, and the CNR increases by 1.0 dB. By increasing the thickness of the reflective layer 10, the CNR gradually increases, and the CNR becomes maximum at the thickness of 20 nm. This is because the effect of blocking information reproduction from the recording layer 4 becomes more significant as the thickness of the reflective layer increases. Although the CNR is reduced when the film thickness is 30 nm or more, this is because the magnetostatic coupling force acting between the recording layer 4 and the reproducing layer 1 becomes weaker as the distance between the recording layer 4 and the reproducing layer 1 increases. From the above, it can be seen that in order to obtain a CNR higher than that of Comparative Example 4, it is necessary to set the thickness of the reflective layer 10 in the range of 2 to 50 nm.

(Reference form 8)
In the reference form 7, reproduction characteristics using Al as the reflective layer 10 are described. However, in this reference form, in order to improve the recording characteristics, the reflective layer 10 is made of a metal other than Al and Al. Describes the results of using the above alloys.

Table 23 shows that the CNR at 0.3 μm measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm with the reflective layer 10 as Al _1-X Fe _X having a thickness of 20 nm and changing the value of X (atom ratio). (Signal to noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 23, as the Fe content increases, that is, as X becomes larger than 0.10, the CNR gradually decreases. However, both CNRs are larger than those in Comparative Example 4, and the reflective layer 10 The effect which formed is seen. On the other hand, looking at the erasing magnetic field, when the reflection layer 10 made of pure Al is used, an erasing magnetic field as large as 50 kA / m is required, whereas X is set to 0.02 or more and 0.50 or less. Thus, the erasing magnetic field can be reduced.

Next, Table 24 shows that the reflective layer 10 is Al _1-X Ni _X having a film thickness of 20 nm, the X (atom ratio) value is changed, and the measurement is performed with an optical pickup using a semiconductor laser having a wavelength of 680 nm. The CNR (signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 24, it was possible to reduce the erasing magnetic field by setting X to 0.02 or more and 0.50 or less as in the case of containing Fe.

  In addition to Fe and Ni, a magnetic metal such as Co, Gd, Tb, Dy, and Nd is similarly contained in Al, so that the erasing magnetic field can be reduced.

(Reference form 9)
In this reference embodiment, a case where a different material is used as the reflective layer 10 in the specific example of the reference embodiment 7 will be described.

  In Reference Form 8, the result of including a magnetic metal element in Al as the reflective layer 10 is described. However, in this Reference Embodiment, recording characteristics are improved when a nonmagnetic metal element is included in Al. Describe.

Table 25 shows that the CNR at 0.3 μm measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm with the reflective layer 10 made of Al _1-X Ti _X having a thickness of 20 nm and changing the value of X (atom ratio). (Signal-to-noise ratio) and the magnitude of the erasing magnetic field are shown.

  From Table 25, as the Ti content increases, that is, as C becomes larger than 0.10, the CNR gradually decreases. However, both CNRs are larger than those in Comparative Example 4, and the reflective layer 10 The effect which formed is seen. On the other hand, looking at the erasing magnetic field, when the reflection layer 10 made of pure Al is used, an erasing magnetic field as large as 50 kA / m is required, whereas X is set to 0.02 to 0.98. Thus, the erasing magnetic field can be reduced.

Next, Table 26 shows the erasing magnetic field reduction effect when a nonmagnetic element other than Ti is contained in Al as the reflective layer 10, where the reflective layer 10 is Al _0.5 Z _0.5 and Z is other than Ti. The figure shows the CNR (signal-to-noise ratio) at 0.3 μm and the magnitude of the erasing magnetic field measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm when a nonmagnetic metal is used.

  From Table 26, when Ta, Pt, Au, Cu, and Si, which are nonmagnetic metals, are used as Z, any CNR is larger than that of Comparative Example 4, and the effect of forming the reflective layer 10 is seen. On the other hand, looking at the erasing magnetic field, it was possible to reduce the erasing magnetic field as in the case where Al was contained in Ti.

  In Reference Embodiments 7 to 9, the same results as Reference Embodiments 5 and 6 were obtained with respect to the thickness of the reproducing layer 1, the transfer layer, and the thickness of the nonmagnetic intermediate layer 2.

  In the above reference embodiments 5 to 9, a magnetic layer that is in-plane magnetized at room temperature and perpendicularly magnetized at high temperature is used as the reproducing layer 1, but at least the signal reproducing region (at or above a predetermined temperature (reproducing temperature) during reproduction). Any region can be used as long as it is in a perpendicular magnetization state in the region heated to a high temperature.

  In Reference Embodiments 5 to 9, the transfer layer 3 ″ is adjacent to the recording layer 4, but may be magnetostatically coupled to the recording layer 4 (see Reference Embodiment 10). By providing a nonmagnetic intermediate layer between the recording layer 4 and the recording layer 4, the mask effect can be enhanced.

  In Embodiments 1 to 6 and Reference Embodiments 1 to 9 described above, a recording auxiliary layer may be provided between the recording layer 4 and the protective layer 8. For example, the auxiliary recording layer is made of a material that exhibits perpendicular magnetization, has a Curie temperature higher than that of the recording layer, and reverses magnetization in a lower magnetic field than the recording layer. In this case, recording can be performed with a lower magnetic field by first reversing the magnetization of the recording auxiliary layer during recording and reversing the magnetization of the recording layer by the exchange coupling force.

  In Embodiments 1 to 6 and Reference Embodiments 1 to 9, a laminated film of Co and Pt may be used as the reproducing layer 1. For example, a total of 30 layers of 0.4 nm Co layers and 0.9 nm Pt layers stacked alternately can be used (total film thickness is 19.5 nm, Curie temperature is 300 ° C.). As described above, when the Co and Pt laminated film is used, the Kerr rotation angle can be increased when the short wavelength light is used, and the reproduction signal quality can be further improved.

(Embodiment 7)
The following describes an embodiment of the present invention with reference to FIG. In the present embodiment, a case where a magneto-optical disk is applied as the magneto-optical recording medium will be described.

  As shown in FIG. 17, the substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the first nonmagnetic intermediate layer 20, the in-plane magnetic layer 3, the second nonmagnetic intermediate layer 30, the recording layer 4, the protective layer 8, The overcoat layer 9 has a disc body laminated in this order. Basic characteristics of each layer other than the second nonmagnetic intermediate layer 30 are the same as those described in the first to sixth embodiments.

The second nonmagnetic intermediate layer 30 is made of one layer of dielectric such as AlN, SiN, AlSiN, or SiO ₂ , or one layer of nonmagnetic metal alloy such as Al, Ti, or Ta, or the dielectric and the above The in-plane magnetized layer 3 and the recording layer 4 are configured so as to be magnetostatically coupled with each other.

  Hereinafter, specific examples of the magneto-optical disk having the above-described structure will be described separately for (1) forming method and (2) recording / reproducing characteristics.

(1) Formation method The formation method is substantially the same as the formation method described above, and only different portions are described. The method of forming the transparent dielectric layer 7, the reproducing layer 1, the first nonmagnetic intermediate layer 20, and the in-plane magnetic layer 3 is the same as that of the previous embodiments. The method for forming the second nonmagnetic intermediate layer 30 is as follows.

After the in-plane magnetic layer 3 is formed, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen is introduced, power is supplied to the Al target, and the gas pressure is 4 × 10 ^{−. A} second nonmagnetic intermediate layer 30 made of AlN was formed on the in-plane magnetic layer 3 under the condition of ³ Torr.

Subsequently, after the inside of the sputtering apparatus was again evacuated to 1 × 10 ⁻⁶ Torr, the recording layer 4 and the protective layer 8 made of AlN were formed on the second nonmagnetic intermediate layer 30 in the same manner as in the above-described embodiment. Formed.

  Next, an ultraviolet curable resin was applied onto the protective layer 8 by spin coating, and an overcoat layer 9 was formed by irradiating with ultraviolet rays.

(2) Recording / reproduction characteristics The above disk was measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm. Table 27 shows the result of measuring the CNR at 0.3 μm while changing the film thickness of the second nonmagnetic intermediate layer 30.

  In Table 27, the film thickness of 0 nm of the second nonmagnetic intermediate layer 30 indicates the result when the second nonmagnetic intermediate layer 30 is not formed. As can be seen from this, a high CNR is obtained by providing the second nonmagnetic intermediate layer 30 to a thickness of 80 nm.

  This will be described below. When the second nonmagnetic intermediate layer 30 is not provided, the magnetization of the in-plane magnetic layer 3 is in a state in which the magnetization is easily oriented in the vertical direction due to the exchange coupling force from the recording layer 4. When the temperature rises during reproduction, when the magnetization of the in-plane magnetic layer 3 becomes small, the magnetization of the in-plane magnetic layer 3 is oriented in the vertical direction due to the exchange coupling force from the recording layer 4. For this reason, the magnetization from the recording layer 4 is leaked to the reproducing layer 1 even in the region serving as a mask layer at a predetermined temperature or lower.

  On the other hand, when the second nonmagnetic intermediate layer 30 is provided, the in-plane magnetic layer 3 and the recording layer 4 are not exchange coupled. Therefore, even if the temperature rises during reproduction, the magnetization of the in-plane magnetic layer 3 remains in the in-plane direction in the region below the predetermined temperature. For this reason, the mask effect can be further obtained in a region below a predetermined temperature.

  However, if the thickness of the second nonmagnetic intermediate layer 30 is too large, the magnetostatic coupling force with the reproducing layer 1 becomes weak, and information on the recording layer 4 is not transferred to the reproducing layer 1. Therefore, the film thickness of the second nonmagnetic intermediate layer 30 is preferably 2 nm or more and 80 nm or less.

  The second nonmagnetic intermediate layer 30 may be anything as long as it blocks the exchange coupling force between the in-plane magnetic layer 3 and the recording layer 4, but the transparent dielectric layer 7 or the first nonmagnetic intermediate layer 20 If it is made the same as either or both (for example, if it is unified with AlN as in this embodiment), the manufacturing process can be simplified.

(Reference form 10)
The reference embodiment of the present invention will be described with reference to FIG. In this embodiment, a case where a magneto-optical disk is applied as a magneto-optical recording medium will be described.

  As shown in FIG. 17, the substrate 6, the transparent dielectric layer 7, the reproducing layer 1, the first nonmagnetic intermediate layer 20, the transfer layer 3 ″, the second nonmagnetic intermediate layer 30, the recording layer 4, the protective layer 8, over The coat layer 9 has a disk main body laminated in this order.

  The basic characteristics of the respective layers other than the second nonmagnetic intermediate layer are the same as those described in the reference embodiments 5 to 9 described above.

The second nonmagnetic intermediate layer 30 is made of one layer of dielectric such as AlN, SiN, AlSiN, or SiO ₂ , or one layer of nonmagnetic metal alloy such as Al, Ti, or Ta, or the dielectric and the above It consists of a combination of two or more layers of metal, and is set so that the transfer layer 3 ″ and the recording layer 4 are magnetostatically coupled.

  Hereinafter, specific examples of the magneto-optical disk having the above-described structure will be described separately for (1) forming method and (2) recording / reproducing characteristics.

(1) Formation method The formation method is substantially the same as the formation method described above, and only different points are described. The formation method of the transparent dielectric layer 7, the reproduction layer 1, the first nonmagnetic intermediate layer 20, and the transfer layer 3 ″ is the same as the reference embodiment so far. The formation method of the second nonmagnetic intermediate layer 30 is as follows. It is.

After forming the transfer layer 3 ″, the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, a mixed gas of argon and nitrogen is introduced, power is supplied to the Al target, and the gas pressure is 4 × 10 ^−3. Under the condition of Torr, the second nonmagnetic intermediate layer 30 made of AlN was formed on the transfer layer 3 ″.

Subsequently, after the inside of the sputtering apparatus is again evacuated to 1 × 10 ⁻⁶ Torr, the recording layer 4 and the protective layer 8 made of AlN are formed on the second nonmagnetic intermediate layer 30 in the same manner as in the reference embodiment described above. did. Next, an ultraviolet curable resin was applied onto the protective layer 8 by spin coating, and an overcoat layer 9 was formed by irradiating with ultraviolet rays.

(2) Recording / reproduction characteristics The above disk was measured with an optical pickup using a semiconductor laser having a wavelength of 680 nm. Table 28 shows the result of measuring the CNR at 0.3 μm while changing the film thickness of the second nonmagnetic intermediate layer 30.

  In Table 28, the film thickness of 0 nm of the second nonmagnetic intermediate layer 30 indicates the result when the second nonmagnetic intermediate layer 30 is not formed. As can be seen from this table, a high CNR is obtained by providing the second nonmagnetic intermediate layer 30 to a thickness of 80 nm.

  This will be described below. When the second nonmagnetic intermediate layer 30 is not provided, the magnetization of the transfer layer 3 ″ is in a state in which the magnetization is easily oriented in the vertical direction due to the exchange coupling force from the recording layer 4. When the temperature rises during reproduction, When the magnetization of the transfer layer 3 ″ is reduced, the magnetization of the transfer layer 3 ″ is directed in the vertical direction due to the exchange coupling force from the recording layer 4. For this reason, even in the region acting as a mask layer at a predetermined temperature or lower, the recording layer 4 Is leaked to the reproducing layer 1.

  On the other hand, when the second nonmagnetic intermediate layer 30 is provided, the transfer layer 3 ″ and the recording layer 4 are not exchange-coupled. It remains facing inward, and transitions to perpendicular magnetization above a predetermined temperature. For this reason, the mask effect can be further obtained in a region below a predetermined temperature.

  However, if the thickness of the second nonmagnetic intermediate layer 30 is too large, the magnetostatic coupling force with the reproducing layer 1 becomes weak, and information on the recording layer 4 is not transferred to the reproducing layer 1. Therefore, the film thickness of the second nonmagnetic intermediate layer 30 is preferably 2 nm or more and 80 nm or less.

  The second nonmagnetic intermediate layer 30 may be anything as long as it blocks the exchange coupling force between the transfer layer 3 ″ and the recording layer 4, but the transparent dielectric layer 7 or the first nonmagnetic intermediate layer 20 If they are the same as either or both (for example, if they are unified with AlN as in the present embodiment), the manufacturing process can be simplified.

It is a figure explaining the reproduction principle of the magneto-optical disk which concerns on Embodiment 1-6 of this invention. It is a figure explaining the conventional magneto-optical disk. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on Embodiment 1 of this invention. It is a figure which shows the recording / reproducing characteristic of the magneto-optical disk based on Embodiment 1 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on Embodiment 4 of this invention. It is a figure explaining the reproduction principle of the magneto-optical disc which concerns on the reference forms 1-4 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on the reference form 1 of this invention. It is a figure which shows the recording / reproducing characteristic of the magneto-optical disk which concerns on the reference form 1 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on the reference form 2 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on the reference form 3 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on the reference form 4 of this invention. It is a figure explaining the reproduction principle of the magneto-optical disc which concerns on the reference forms 5-9 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on the reference form 5 of this invention. It is a figure which shows the recording / reproducing characteristic of the magneto-optical disk which concerns on the reference form 5 of this invention. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on the reference form 7 of this invention. It is a figure explaining the reproduction principle of the conventional super-resolution recording medium. It is a figure which shows the film | membrane structure of the magneto-optical disk which concerns on Embodiment 7 of this invention, and Reference Embodiment 10. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reproducing layer 2 Nonmagnetic intermediate layer 3 In-plane magnetized layer 3 'Blocking layer 3 "Transfer layer 4 Recording layer 5 Light beam 6 Substrate 7 Transparent dielectric layer 8 Protective layer 9 Overcoat layer 10 Reflective layer 20 First nonmagnetic intermediate Layer 30 Second nonmagnetic intermediate layer 110 Heat dissipation layer

Claims (28)

In a magneto-optical recording medium having a reproducing layer in which at least a signal reproducing region is in a perpendicular magnetization state and a recording layer made of a perpendicular magnetization film magnetically coupled to the reproducing layer,
A magneto-optical recording medium comprising: a magnetic mask layer that is disposed away from the reproducing layer and suppresses magnetic coupling between the recording layer and the reproducing layer at least at room temperature. A reproducing layer having at least a signal reproducing region in a perpendicular magnetization state, and a recording layer comprising a perpendicular magnetization film magnetically coupled to the reproducing layer, and a magnetic domain larger than the recording magnetic domain of the recording layer by light beam irradiation In the magneto-optical recording medium in which the reproducing layer is formed,
A magneto-optical recording medium comprising: a magnetic mask layer that is disposed away from the reproducing layer and suppresses magnetic coupling between the recording layer and the reproducing layer at least at room temperature. The magneto-optical recording medium according to claim 1 or 2,
The magneto-optical recording medium according to claim 1, wherein the magnetic mask layer comprises an in-plane magnetization layer whose magnetization decreases at a high temperature. The magneto-optical recording medium according to claim 3,
A magneto-optical recording medium, wherein the magnetization of the magnetic mask layer is larger than the magnetization of the recording layer at room temperature. In the magneto-optical recording medium according to claim 3 or 4,
A magneto-optical recording medium, wherein a Curie temperature of the magnetic mask layer is lower than a Curie temperature of the recording layer. The magneto-optical recording medium according to any one of claims 3 to 5,
The magneto-optical recording medium, wherein the recording layer has a Curie temperature lower than the Curie temperature of the reproducing layer. The magneto-optical recording medium according to any one of claims 3 to 6,
A magneto-optical recording medium comprising a substrate, a transparent dielectric layer, the reproducing layer, a nonmagnetic intermediate layer, the magnetic mask layer, the recording layer, and a protective layer formed in this order. The magneto-optical recording medium according to claim 7,
A magneto-optical recording medium, wherein the magnetic mask layer has a thickness of 2 nm to 40 nm. The magneto-optical recording medium according to claim 7 or 8,
The magneto-optical recording medium, wherein the magnetic mask layer is made of any one of a GdFe alloy, a GdFeAl alloy, a GdFeTi alloy, a GdFeTa alloy, a GdFePt alloy, a GdFeAu alloy, a GdFeCu alloy, a GdFeAlTi alloy, and a GdFeAlTa alloy. The magneto-optical recording medium according to any one of claims 7 to 9,
The magneto _- optical recording medium, wherein the magnetic mask layer is represented by a composition formula of (Gd _0.11 Fe _0.89 ) _X Al _1-X , and X (atom ratio) is 0.30 or more and 1.00 or less. The magneto-optical recording medium according to any one of claims 7 to 10,
The magneto-optical recording medium, wherein the magnetic mask layer has a Curie temperature of 60 ° C. or higher and 220 ° C. or lower. The magneto-optical recording medium according to claim 7,
A magneto-optical recording medium, wherein the reproducing layer has a thickness of 10 nm to 80 nm. The magneto-optical recording medium according to claim 7,
A magneto-optical recording medium, wherein the non-magnetic intermediate layer has a thickness of 1 nm to 80 nm. The magneto-optical recording medium according to claim 7,
A magneto-optical recording medium, wherein a reflection layer is formed adjacent to the nonmagnetic intermediate layer on the recording layer side of the nonmagnetic intermediate layer. The magneto-optical recording medium according to claim 14,
The magneto-optical recording medium, wherein the reflective layer is made of Al and has a thickness of 2 nm to 40 nm. The magneto-optical recording medium according to claim 14,
The magneto-optical recording medium, wherein the reflective layer is made of an alloy of Al and a magnetic metal. The magneto-optical recording medium according to claim 16,
The magneto-optical recording medium, wherein the reflective layer is represented by a composition formula of Al _1-X Fe _X , and X (atom ratio) is 0.02 or more and 0.50 or less. The magneto-optical recording medium according to claim 16,
The magneto-optical recording medium, wherein the reflective layer is expressed by a composition formula of Al _{1 -X} Ni _X and X (atom ratio) is 0.02 or more and 0.50 or less. The magneto-optical recording medium according to claim 14,
The magneto-optical recording medium, wherein the reflective layer is made of an alloy of Al and a nonmagnetic metal.   20. The magneto-optical recording medium according to claim 19, wherein the nonmagnetic metal is any one element of Ti, Ta, Pt, Au, Cu, and Si. The magneto-optical recording medium according to claim 19,
The magneto-optical recording medium, wherein the reflective layer is represented by a composition formula of Al _1-X Ti _X and X (atom ratio) is 0.02 or more and 0.98 or less. The magneto-optical recording medium according to claim 7,
A magneto-optical recording medium, wherein a heat dissipation layer is formed on the opposite side of the substrate with respect to the protective layer. The magneto-optical recording medium according to any one of claims 1 to 22,
The magneto-optical recording medium according to claim 1, wherein the reproducing layer is in an in-plane magnetization state at room temperature and is in a perpendicular magnetization state at a high temperature. In the magneto-optical recording medium according to claim 1, claim 2, or claim 3,
The magneto-optical recording medium according to claim 1, wherein the reproducing layer comprises a multilayer film in which Co and Pt are alternately laminated. A reproduction method for reproducing information from a magneto-optical recording medium according to any one of claims 1 to 24,
A method for reproducing a magneto-optical recording medium, comprising: irradiating the magneto-optical recording medium with a light beam in a pulsed manner during signal reproduction. A reproduction method for reproducing information from a magneto-optical recording medium according to claim 3,
A method of reproducing a magneto-optical recording medium, comprising: irradiating the magneto-optical recording medium with a light beam at the time of reproduction to heat the magnetic mask layer to a temperature close to or above its Curie temperature. The magneto-optical recording medium according to any one of claims 1 to 7,
The magneto-optical recording medium, wherein the magnetic mask layer is magnetostatically coupled to the recording layer. The magneto-optical recording medium according to claim 27,
A magneto-optical recording medium, wherein a nonmagnetic intermediate layer is formed between the magnetic mask layer and the recording layer, and the film thickness of the nonmagnetic intermediate layer is 2 nm or more and 80 nm or less.

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