JP2000306283A - Method and device for recording/reproducing, and magneto-optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording method capable of easily forming the recording magnetic zone of an optimal rectangular shape for superhigh-density recording. SOLUTION: A laser light is converged by a group of two lenses 6 and projected while a magneto-optical recording medium 50 is rotated at a desired rotational speed, and the thermal center (high temperature area) of a thermal spot generated based on the light intensity distribution of a laser light is formed outside an optical spot. A magnetic field generation source 3 having a narrow field generation portion in a track direction is disposed so as to be located in the thermal center outside the optical spot, and a narrow recording magnetic field is applied to the high temperature area. Thus, in the track direction, a narrow recording magnetic zone is formed in the high temperature area, and its shape becomes rectangular. Since no interference occurs in rectangular recording magnetic zones adjacent to each other in the track direction even when a gap therebetween is narrowed, high-density recording is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recording / reproducing a magneto-optical recording medium, a recording / reproducing apparatus, and a magneto-optical head.
More specifically, the present invention relates to a recording / reproducing method, a magneto-optical recording device, and a magneto-optical head suitable for ultra-high density recording.

[0002]

2. Description of the Related Art Recording media such as magneto-optical recording media are known as external memories of computers and the like. Magneto-optical recording media can handle large volumes of data such as moving images and audio, and are therefore frequently used as recording media in the multimedia age. It is desired to further increase the storage capacity of such a magneto-optical recording medium.

As a method of increasing the storage capacity of a magneto-optical recording medium, for example, a method of forming a recording magnetic domain at a high density in a recording layer by reducing the diameter of a light spot is known. In the case of optical recording, the light spot diameter is represented by λ / NA. Here, λ indicates the wavelength of light (laser light), and NA indicates the numerical aperture of the objective lens that condenses the light. Therefore, if the wavelength of the laser beam is shortened or the NA of the objective lens is increased, the light spot can be miniaturized, and a micro recording magnetic domain can be formed in the recording layer. However, when there are a plurality of such minute recording magnetic domains in the reproduction light spot, a method for identifying and reproducing them is required.

Therefore, as a method of individually reproducing a plurality of minute recording magnetic domains existing in a reproducing light spot, Japanese Patent Application No. Hei.
A magnetic domain enlarging and reproducing technique as disclosed in Japanese Patent No. 182901 has been proposed. A magneto-optical recording medium according to this technology includes a recording layer and a magnetically soft reproducing layer, and magnetically transfers a recording magnetic domain recorded on the recording layer to the reproducing layer, and reproduces the transferred magnetic domain. Information is reproduced by enlarging in layers. This makes it possible to individually detect a plurality of minute recording magnetic domains existing in the reproduction light spot by using a signal amplified from the reproduction layer.

[0005]

In order to record information on a magneto-optical recording medium, the magneto-optical recording medium is irradiated with a laser beam,
A heat spot based on the light intensity distribution is formed in the light spot. Then, the coercive force is reduced in the high-temperature area of the heat spot, and the recording magnetic field is uniformly applied to the light spot area including the high-temperature area, thereby inverting the magnetization in the high-temperature area where the coercive force is reduced to form a recording magnetic domain. are doing. To apply a magnetic field to a magneto-optical recording medium, a magnetic coil is usually used. The magnetic coil is usually arranged on the opposite side of the substrate, that is, on the side where the recording film is formed. On the other hand, a lens for condensing laser light is usually arranged on the substrate side.

When a high NA objective lens is used to miniaturize a light spot, the distance between the lens and the surface of the medium must be shortened because the focal length of the lens becomes short. Therefore, the high NA objective lens is arranged on the side where the recording film is formed, similarly to the magnetic coil. At this time, the magnetic coil is configured so as not to block light emitted from the objective lens. For example, when a solid immersion lens (SIL) is used as a high NA lens, the magnetic coil 104 is formed by winding a coil wire around the SIL 10 as shown in FIG. When such a magnetic coil 104 is used,
A magnetic field is applied to the entire area of the light spot, and the size of the recording magnetic domain formed in the recording layer is determined according to the size of the high-temperature area of the heat spot. Therefore, in order to form minute recording magnetic domains, it was necessary to miniaturize the heat spot. However, it is difficult to control the size of the high-temperature region of the heat spot because it changes depending on the light intensity and the material constituting the medium, and it is not easy to form a recording magnetic domain smaller than the heat spot. . Also, since the shape of the heat spot is reflected as the shape of the recording magnetic domain, the recording magnetic domain becomes an arrow shape when overwritten, but the arrow shape is not necessarily a preferable shape for the magnetic domain shape for high density recording. Absent.

The present invention has been made in view of the above points, and a first object of the present invention is to provide a recording method capable of ultra-high-density recording, and a recording / reproducing apparatus and a magneto-optical head suitable for the method. It is in.

A second object of the present invention is to provide a reproducing method capable of reproducing information recorded at a very high density on a magneto-optical recording medium at a high reproducing resolution.

[0009]

According to a first aspect of the present invention, a light spot which moves relative to a magneto-optical recording medium is formed on a track of the magneto-optical recording medium, and the light spot is generated by the light spot. A magneto-optical recording method for recording information by applying a magnetic field to a heat spot, wherein a high-temperature area of the heat spot is formed outside the light spot, and information is recorded by applying a magnetic field to the high-temperature area. A recording method is provided.

According to the recording method of the first aspect of the present invention, a light spot relatively moving with respect to a magneto-optical recording medium is formed on a track of the magneto-optical recording medium, and heat generated by the light spot is formed outside the light spot. Form the hot area of the spot.
Then, a recording magnetic domain is formed in the recording layer by applying a recording magnetic field to the formed high-temperature region. To apply a magnetic field only to a narrow area such as a high-temperature area of a heat spot, for example, a magnetic head in which the width of a magnetic field generating portion in the track direction is narrower than the light spot may be used. In the present specification, the “high-temperature region” means a light spot that moves on the magneto-optical recording medium relative to the magneto-optical recording medium, and the heat center of the heat spot generated by the light spot, that is, the highest temperature This is a concept that means a temperature region including a point.When information is recorded, the coercive force of the recording layer is reduced and a recording magnetic domain can be formed in the recording layer. Is an area on the reproduction layer where the coercive force of the reproduction layer is reduced and the recording magnetic domain of the recording layer is transferred. Further, in the present specification, “outside the light spot” means a radial position where 1 / e ² of the maximum value of the light intensity in the radial light intensity distribution of the light spot formed on the magneto-optical recording medium. Means outside the region defined by.

In the recording method of the present invention, for forming a high-temperature area of a heat spot outside a light spot, for example,
The linear velocity at the position where scanning is performed by the magneto-optical head may be increased by increasing the rotation speed of the magneto-optical recording medium. Alternatively, when the rotation speed of the magneto-optical recording medium is not increased, it can be realized by further reducing the light spot diameter or adjusting the light intensity.

In the recording method of the present invention, the shape of the recording magnetic domain formed in the recording layer can be made rectangular. In the conventional recording method, when the recording magnetic domain is overwritten to have a shape reflecting the heat spot, the shape becomes an arrow shape.
The arrow feather shape is not always a preferable shape, and in the case of the arrow feather-shaped recording magnetic domains adjacent in the track direction, the head part of the arrow feather and the tail part of the arrow feather sometimes interfere with each other. Therefore, noise may be generated when reproducing information. On the other hand, in the recording method of the present invention, a narrow magnetic field can be applied only to the highest temperature region of the heat spot by using a magnetic head narrower than the light spot. Can be rectangular.
Even when the rectangular recording magnetic domains are formed adjacent to each other in the track direction, interference generated between the recording magnetic domains is reduced. Therefore, the distance between the recording magnetic domains can be reduced, and ultra-high density recording can be performed.

According to a second aspect of the present invention, a light spot moving relative to the magneto-optical recording medium is formed on a track of the magneto-optical recording medium, and a magnetic field is applied to a heat spot generated by the light spot. In the magneto-optical recording method for recording information, a high-temperature area of a heat spot is formed at a position shifted in the track direction from the center of the light spot, and information is recorded by applying a magnetic field inside the high-temperature area. Is provided.

In the recording method according to the second aspect of the present invention,
A light spot moving relative to the magneto-optical recording medium is formed on the magneto-optical recording medium, and a heat spot generated based on the light intensity distribution in the light spot at a position shifted in the track direction from the center of the light spot. To form a high temperature region. Then, a recording magnetic domain is formed in the recording layer by applying a recording magnetic field to the inside of the formed high-temperature region. To apply a magnetic field only to a narrow area such as a high-temperature area of a heat spot, for example, a magnetic head in which the width of a magnetic field generating portion in the track direction is narrower than the light spot may be used. Here, “applying a recording magnetic field inside the high-temperature area” means applying a recording magnetic field inside the high-temperature area in the track direction, and a magnetic field is applied to an area wider than the high-temperature area in the track width direction. The magnetic field may be applied so that the entire area to which the magnetic field is applied is included inside the high-temperature area.

According to a third aspect of the present invention, a heat spot is formed on a magneto-optical recording medium having a recording layer and a reproducing layer so as to move relative to the magneto-optical recording medium, so that a heat is applied to the reproducing layer. In a reproducing method in which a spot is generated and a magnetic domain of a recording layer is transferred to a reproducing layer in a heat spot under an applied magnetic field to reproduce information, a high-temperature area of the heat spot is formed outside the light spot, A reproducing method is provided, in which a magnetic field is applied to a region to transfer a magnetic domain of a recording layer to a reproducing layer through a high-temperature region.

In the reproducing method according to the third aspect of the present invention,
A light spot relatively moving with respect to the magneto-optical recording medium is formed on the magneto-optical recording medium, and a high-temperature area of a heat spot is formed outside the light spot. Then, a reproducing magnetic field is locally applied to the formed high-temperature region to transfer the recording magnetic domains of the recording layer to the reproducing layer and reproduce information from the reproducing layer. As a result, the reproduction resolution is significantly improved. The reason will be described below. In the following description, MAMMOS reproduction will be described as an example.

In the conventional reproducing method, as shown in the upper part of FIG. 6, a reproducing magnetic field is uniformly applied to a region wider than a light spot by a magnetic coil. Then, a high-temperature area having substantially the same size as the recording magnetic domain formed in the recording layer is formed in the light spot, a reproducing magnetic field is applied to an area wider than the light spot, and the recording magnetic domain is magnetically applied to the reproducing layer through the high-temperature area. Transcribed and enlarged. Therefore, the reproduction resolution is determined by the size of the high-temperature area of the heat spot based on the light intensity distribution generated by light irradiation. On the other hand, in the reproducing method of the present invention, a high-temperature area of the heat spot is formed outside the light spot, and a reproducing magnetic field is locally applied to the high-temperature area in the heat spot. Therefore, the reproduction resolution is determined in the region where the magnetic field is applied. That is, as shown in the lower part of FIG. 6, when the reproducing layer is irradiated with the reproducing light, a heat distribution is formed in the light spot Sw of the reproducing layer, and a temperature region (high temperature region) where the recording magnetic domain can be transferred appears. I do. In such a temperature range,
Using a magnetic head 60 in which the width W of the magnetic field generating portion is smaller than the light spot Sw, the reproducing magnetic field is applied so that the width of the magnetic field application region becomes narrow. Thereby, the magnetic domain of the recording layer is transferred to the narrow magnetic field application region of the reproducing layer. The magnetic domain transferred to the reproducing layer expands in the light spot of the reproducing layer according to the heat distribution generated by light irradiation. Therefore, according to the reproducing method of the present invention, it is possible to reliably extract and reproduce minute recording magnetic domains from the light spot.

According to a fourth aspect of the present invention, a magneto-optical recording medium having a recording layer and a reproducing layer is provided with a light spot which moves relative to the magneto-optical recording medium, thereby providing a thermal effect on the reproducing layer. In a reproducing method in which a spot is generated and a magnetic domain of the recording layer is transferred to a reproducing layer in the heat spot under an applied magnetic field to reproduce information, the maximum of the heat spot is shifted from the center of the light spot in the track direction. By forming a temperature region and applying a magnetic field inside the high temperature region,
A reproducing method is provided, wherein a magnetic domain of a recording layer is transferred to a reproducing layer through a high-temperature region.

In the reproducing method according to the fourth aspect of the present invention,
A light spot relatively moving with respect to the magneto-optical recording medium is formed on the magneto-optical recording medium, and a high-temperature area of a heat spot is formed at a predetermined position on the reproducing layer which is shifted from the center of the light spot in the track direction. Then, a reproducing magnetic field is applied to the inside of the high-temperature region formed on the reproducing layer, the magnetic domain of the recording layer is transferred to the region in the high-temperature region of the reproducing layer to which the magnetic field is applied, and information is read from the reproducing layer. When a magnetic domain expansion reproduction layer is used as the reproduction layer, information is reproduced by enlarging the magnetic domain transferred to the magnetic domain expansion reproduction layer in a light spot based on a heat distribution generated in the reproduction layer by light irradiation. Can be.

According to a fifth aspect of the present invention, in a recording / reproducing apparatus for a magneto-optical recording medium, a light source for irradiating light to the magneto-optical recording medium, and the light from the light source is condensed to generate a magneto-optical signal. A lens for forming a light spot on the recording medium, a magnetic field source for applying a magnetic field to the magneto-optical recording medium, and a heat spot generated based on the light intensity distribution of the light spot outside the light spot. There is provided a recording / reproducing apparatus, comprising: means for forming a high-temperature region, wherein the magnetic field generating source and the lens are positioned so that a magnetic field is applied to the high-temperature region.

The recording / reproducing apparatus according to the present invention includes means for forming a high-temperature area of a heat spot generated based on the light intensity distribution of the light spot outside the light spot, and a magnetic field is applied to the high-temperature area. As such, the magnetic field source and the lens are positioned relative to each other. For example, the magnetic field source and the lens are positioned relative to each other such that the center axis of the magnetic field generating portion of the magnetic field generating source coincides with the heat center of the heat spot (the highest temperature reached). As means for forming a high-temperature region of a heat spot generated based on the light intensity distribution of the light spot outside the light spot, for example,
A rotation driving device for rotating the magneto-optical recording medium while controlling it at a desired rotation speed may be used. When light is applied to the rotating magneto-optical recording medium, a heat distribution based on the light intensity distribution occurs in the recording layer. Since the heat transfer speed of the recording layer is constant if the same medium, increasing the rotation speed of the medium,
A heat center of the heat spot is formed behind the center of the light spot. FIG. 4 shows the relationship between the distance between the heat center of the heat spot and the center of the light spot and the rotation speed of the magneto-optical recording medium. Therefore, by rotating the magneto-optical recording medium at a desired speed while controlling the rotation speed by the rotation driving device, the heat center of the heat spot can be formed outside the light spot. Then, the magnetic field generation source and the lens are arranged such that the center axis of the magnetic field generation portion of the magnetic field generation source coincides with the heat center of the heat spot formed outside the light spot. In the conventional recording / reproducing apparatus, the magnetic field generating portion of the magnetic field generating source is arranged so as to coincide with the central axis of the lens so as not to block the light emitted from the lens. In the recording / reproducing apparatus having such a configuration, since the magnetic field is applied to a wide area including the light spot, the magnetic field cannot be locally applied only to the highest temperature area of the heat spot based on the light intensity distribution.

Further, in the present invention, as another means for forming a high-temperature region of a heat spot generated based on the light intensity distribution of the light spot outside the light spot, a high NA that reduces the diameter of the light spot is used. A lens or a device for adjusting the intensity of light applied to the magneto-optical recording medium may be used. When light is irradiated while rotating the magneto-optical recording medium at a constant rotation speed, the heat transfer rate of the material forming the recording layer is constant, so the position of the heat center of the heat spot generated based on the light intensity distribution is It is formed at a position separated by a certain distance from the center of the light spot. Therefore, if the light spot is reduced by using a high NA lens, it is possible to form the heat center of the heat spot outside the light spot. The high NA lens includes, for example, a high NA lens having a numerical aperture of 0.7 to 0.95, and a double-lens lens including a solid immersion lens (SIL) and a condenser lens for condensing light on the SIL. Can be used.

The recording / reproducing apparatus of the present invention may include a rotation drive device such as a spindle motor for rotating the magneto-optical recording medium at a desired rotation speed. Further, the linear velocity is calculated from the rotational speed of the magneto-optical recording medium and the position of the magnetic field generating source on the magneto-optical recording medium, and the distance between the center of the light spot and the magnetic field application area is controlled based on the calculated linear velocity. A controller may be provided. Such a control device can be configured using, for example, a two-axis actuator used for an optical pickup. That is, the light condensing position can be changed by changing the actuator of the light condensing lens while the magnetic field application region is fixed at a predetermined position. This makes it possible to control the distance between the center of the light spot and the magnetic field application region. Alternatively, as shown in FIG. 8, a configuration may be employed in which the direction of light incident on the lens (dual lens) 6 is finely adjusted using the galvanometer mirror 4. Even with such a configuration, it is possible to adjust the focusing position of the light emitted from the lens,
It is possible to change the position of the center of the light spot.

According to a sixth aspect of the present invention, in a magneto-optical head used for recording and reproducing information on a magneto-optical recording medium, a lens for condensing light on the magneto-optical recording medium; A magnetic field generating source for applying a magnetic field to the magnetic recording medium, the magnetic field generating source having a width smaller than a light spot diameter formed on the magneto-optical recording medium by the lens in the track direction; The magnetic field source is
A magneto-optical head is provided, wherein a center axis of a magnetic field generated from the magnetic field generation source is formed on a bottom surface of the lens so as to be shifted from a center axis of the lens.

In the magneto-optical head of the present invention, for example, a magnetic field generating source constituted by a magnetic coil or the like is formed on the bottom surface of a lens for condensing light on a magneto-optical recording medium. Are arranged so that the center of the magnetic field generated from the optical axis deviates from the optical axis of the lens. The high-temperature region of the heat spot formed on the rotating magneto-optical recording medium by irradiating the medium with light deviates from the center of the light spot. In the magneto-optical head according to the present invention, the magnetic field generating portion of the magnetic field generating source can be arranged in a high-temperature region formed at a position shifted from the center of the light spot. Therefore, for example, if a magnetic head having a narrow magnetic field generating portion is used as a magnetic field generating source, it is possible to apply a magnetic field only to the highest temperature region, and to form an extremely small recording magnetic domain in the recording layer. It becomes possible.

For example, as shown in FIG. 16, the conventional magneto-optical head has a lens 10 and a lens 10 so that the center axis of the lens (SIL) 10 and the center axis of the magnetic field generating source (magnetic coil) 104 are coaxial. The magnetic coil 104 was arranged. In the magneto-optical head 200, the lens 10
Since the diameter of the magnetic coil 104 is larger than the diameter of the light spot, the magnetic field is applied to the entire area of the light spot formed on the medium by the lens 10. Therefore, a magnetic field cannot be applied only to the highest temperature region formed on the magneto-optical recording medium by light irradiation, and a fine recording magnetic domain cannot be formed on the recording layer.

In the magneto-optical head of the present invention, the magnetic field generating source is most preferably arranged on the bottom surface of the lens so as not to block the optical path of recording light or reproducing light emitted from the lens. In a case where the light use efficiency is set so as to block the light path, it is preferable that the light use efficiency is reduced so as to be 50% or less. In the present specification, "light use efficiency" means the ratio of the amount of incident light and the amount of reflected light,
The amount of incident light can be measured by a front monitor arranged before light enters the magneto-optical recording medium, and the amount of reflected light is measured by detecting the light reflected from the magneto-optical recording medium with a signal detector. Can be.

In the magneto-optical head of the present invention, for example, a thin-film magnetic head can be used as the magnetic field generating source. Such a thin-film magnetic head can be manufactured by using a lithography technique. For example, a structure having a one-turn coil as shown in FIG. 11D or a structure as shown in FIG.
A structure having a turn coil may be employed. For example, a one-turn coil type thin-film magnetic head uses a lithography technique to form a copper film and a dielectric film on a base such that a pattern shown on the right side of FIGS. 11A to 11D is formed. To be sequentially laminated. Further, the two-turn coil type thin film magnetic head has a copper film and a dielectric so as to form a pattern as shown on the right side of FIGS. 12 (A) to 12 (D) and FIGS. 13 (E) to 13 (H). The film can be manufactured by sequentially laminating a film on a substrate. In FIGS. 11 to 13, the left side diagram is a diagram schematically illustrating a cross-sectional shape when the right side plan view is viewed from the X direction. In the thin film magnetic head having such a configuration, it is preferable that the base is formed using a transparent material such as glass or plastic. The difference between the refractive index of the base and the refractive index of the lens is preferably small, and the material of the base or the lens is selected so as to be within 10% of the refractive index of either the base or the lens. preferable.

In the magneto-optical head according to the present invention, the magnetic field is generated so that the width of the magnetic field application region applied to the magneto-optical recording medium in the track direction is smaller than the light spot, and preferably less than half the diameter of the light spot. It is desirable to configure the width of the magnetic field generating portion of the source. The dimensions of the magnetic field applied to the magneto-optical recording medium may be determined, for example, by a direct observation method using a magnetic force microscope or a magnetic field detecting element having a magnetoresistance effect, or by using the recording / reproducing apparatus of the present invention and a magnetic super-resolution magneto-optical device. It can be measured by indirect measurement of a reproduced waveform using a disc. In the indirect measurement of the reproduced waveform using the recording / reproducing apparatus of the present invention and the magnetic super-resolution magneto-optical disk, the reproduced waveform is monitored while variously changing the position of the magnetic head, and the position of the magnetic head when a reproduced signal is obtained is determined. The size of the magnetic field application region can be obtained by calculation from the position of the magnetic head when a reproduction signal is not obtained.

By the way, in the magneto-optical recording medium, the recording track on which information is recorded may not be formed concentrically with the center of the magneto-optical recording medium. for that reason,
When such a magneto-optical recording medium is loaded into a recording / reproducing apparatus and a recording track is scanned by a magneto-optical head, a recording track located immediately below the magneto-optical head may fluctuate in a track width direction due to eccentricity. Therefore, it is desirable to set the length of the magnetic field generating portion of the magnetic field generating source in the track width direction to a length that can sufficiently cover the position fluctuation of the recording track in the track width direction due to eccentricity. It is desirable that the diameter be longer than the diameter of the light spot formed on the substrate. The magnetic field generation source is, for example, 2
In the case of using a turn coil type thin-film magnetic head, the configuration shown in FIG. 5 may be used. As can be seen from FIG. 5, the thin-film magnetic head 3 is configured such that the length L of the magnetic field generating portion 3a in the track width direction is longer than the light spot diameter Sw. Further, it is desirable that the thin-film magnetic head 3 is arranged such that the center of the magnetic field generating portion 3a is substantially coaxial with the heat center generated on the magneto-optical recording medium.

In the magneto-optical head of the present invention, the distance between the center of the light spot formed on the magneto-optical recording medium by the lens and the center of the magnetic field generated from the magnetic field generating source is determined based on the linear velocity of the magneto-optical recording medium. A control device for controlling may be provided. In order to control the distance between the center of the light spot formed on the magneto-optical recording medium and the center of the magnetic field, for example, the condensing position of the lens or the position of the magnetic field source with respect to the lens is controlled. Good.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings, but the present invention is not limited thereto.

[0033]

[Embodiment 1] [Magneto-optical recording / reproducing apparatus] FIG. 14 is a schematic configuration diagram of a magneto-optical recording / reproducing apparatus according to the present invention. The magneto-optical recording / reproducing apparatus 100 mainly includes the magneto-optical head 11, the first
Polarizing beam splitter (hereinafter referred to as PBS) 13, laser light source 14, phase plate 15, half-wave plate 16, second P
BS 17, photodetectors 18, 19, MO signal detection unit 20,
It comprises a head position control device 21, an external magnetic field application control device 22, and a spindle motor 23. The magneto-optical head 11 includes a slider 1, a condenser lens 12, and a solid immersion lens (SIL) 10.

In the magneto-optical recording apparatus 100 having such a configuration, the spindle motor 23 can rotate the magneto-optical recording medium at a desired rotation speed. Laser light source 14
The laser light emitted from the SIL 10 enters the SIL 10 via the first PBS 13 and the condenser lens 12, is condensed by the SIL 10, and is irradiated on the magneto-optical recording medium. The laser beam irradiated on the magneto-optical recording medium is reflected by the magneto-optical recording medium, and the reflected light returns to the first PBS 13 via the SIL 10 and the condenser lens 12 and is directed toward the phase plate 15 by the first PBS 13. Can be The reflected light is reflected by the phase plates 15 and 1
After passing through the half-wave plate 16, the light is split by the second PBS 17 toward each of the photodetectors 18 and 19. The photodetectors 18 and 19 can convert the amount of the divided light into an electric signal. The detection signals from the photodetectors 18 and 19 are input to the head position control device 21 and the MO signal detection unit 20. The MO signal detector 20 is a light detector 18
And 19, the magneto-optical reproduction signal (MO
Playback signal). The head position control device 21
The magneto-optical head 11 can be arranged at a desired position on the magneto-optical recording medium based on the signal from the O-signal detecting unit 20. Further, the head position control device 21 can obtain the rotation speed from the spindle motor 23 and calculate the linear velocity of the magneto-optical recording medium at the position where the magneto-optical head 11 is flying. Then, based on the calculated linear velocity, the angle of a galvanomirror (not shown) mounted on the magneto-optical head 11 is finely adjusted, and the irradiation position of light emitted from the magneto-optical head 11 is controlled. The external magnetic field application control device 22 can control a magnetic head mounted on the magneto-optical head 11 to apply a recording magnetic field or a reproducing magnetic field having a desired magnetic field intensity to the magneto-optical recording medium. The magnetic field applied to the medium can be a DC magnetic field or an alternating magnetic field.

[Magneto-optical head] The magneto-optical head 11 is supported by a suspension 26 as shown in FIG.
At the time of recording / reproduction, it flies above the rotating magneto-optical recording medium 50. A schematic perspective view of the magneto-optical head 11 is shown below FIG. FIG. 8 is a schematic cross-sectional view when the magneto-optical head 11 is cut in the longitudinal direction. As shown in FIG. 8, the magneto-optical head 11 mainly includes the slider 1,
It comprises a thin-film magnetic head 3, a galvanometer mirror 4, and a doublet lens 6. The slider 1 is formed with a through hole 5 for passing a laser beam.
Is provided with a doublet lens 6. Double lens 6
Is a hemispherical solid immersion lens (SIL) 10
And a condenser lens 2 for condensing and irradiating the solid immersion lens 10 with light. SIL
A notch recessed in the direction of the optical axis is formed on the bottom surface of the thin film 10, and the thin film magnetic head 3 is fitted into the notch. FIG. 9 is an enlarged schematic view of the vicinity of the doublet lens 6 of the magneto-optical head 11. As shown in FIG. 9, the thin-film magnetic head 3 includes a base 31 and a one-turn coil 3.
2 is a one-turn coil type thin film magnetic head, and can apply a magnetic field vertically to the magneto-optical recording medium 50 located immediately below. A method for manufacturing such a thin-film magnetic head 3 will be described later. The galvanometer mirror 4 is rotatable about a direction perpendicular to the plane of the drawing as a rotation axis. By slightly rotating the galvanometer mirror 4 at various angles, the angle of incidence of the laser light on the doublet lens 6 changes. As a result, the optical path of the light emitted from the SIL 10 of the doublet lens 6 changes, and the light irradiation position on the magneto-optical recording medium changes. That is, the center position of the light spot formed on the magneto-optical recording medium can be finely adjusted in the track direction.

[Thin Film Magnetic Head] Here, a method of manufacturing the one-turn coil type thin film magnetic head 3 mounted on the magneto-optical head 11 will be described with reference to FIGS. First, as shown in FIG. 11A, a plate-shaped transparent base is prepared, and a copper film 41 is formed to a desired thickness on the substrate. Next, after a photoresist (not shown) is applied on the copper film 41, the photoresist is exposed through a mask so that a copper film having a pattern as shown on the right side of FIG. Do. Next, after forming the dielectric film 42 on the copper film on which such a pattern is formed,
Further, a photoresist (not shown) is applied. Next, after exposing through a mask so as to form a dielectric film having a pattern as shown on the right side of FIG. 11C, etching is performed. Then, after a copper film 41 'is formed on the dielectric film, a photoresist (not shown) is applied to form a copper film 41' in FIG.
Exposure and etching are performed using a mask that forms a copper film having a pattern as shown on the right side of FIG. Thus, a thin-film magnetic head is manufactured.

[Magneto-optical recording medium] As a magneto-optical recording medium used in the magneto-optical recording / reproducing apparatus 100, a MAMM
A magneto-optical recording medium for OS can be used. FIG.
1 shows a schematic sectional view of a magneto-optical recording medium. The magneto-optical recording medium 50 includes a first dielectric layer 52 and a recording layer 5 on a substrate 51.
3. Nonmagnetic layer 54, Al alloy layer 55, magnetic domain expansion reproducing layer 5
6 and a protective layer 57 are sequentially laminated. In the magneto-optical recording medium 50 having such a structure, information is recorded and reproduced by irradiating light from the side opposite to the substrate 51, that is, from the side on which each film such as the recording layer 53 and the magnetic domain expansion reproducing layer 54 is formed. As the substrate 51, for example, a polycarbonate substrate can be used, and a groove portion (groove) and a space between grooves (land) can be used.
Can be configured as a land-groove type substrate on which information can be recorded. For example, SiN can be used for the first dielectric layer 52, the nonmagnetic layer 54, and the protective layer 57. The magnetic domain expansion reproduction layer 56 is a layer that can reproduce the magnetic domain transferred from the recording layer 53 while expanding the magnetic domain.
It is configured using an FeCo amorphous alloy. GdF
The composition of the eCo amorphous alloy is adjusted in advance so that the magnetic domain transferred from the recording layer 53 has a coercive force such that the magnetic domain easily expands and contracts due to domain wall movement caused by application of an external magnetic field. The recording layer 53 is a layer for recording information in a magnetized state, and is made of a TbFeCo amorphous alloy. The magnetic domain expansion reproducing layer 56 and the recording layer 53 are magnetostatically coupled by the nonmagnetic layer 54 and the Al alloy layer 55 interposed between the magnetic domain expansion reproducing layer 56 and the recording layer 53. Each of these layers 52 to 57 can be sequentially formed by a high frequency sputtering method. The magneto-optical recording medium for MAMMOS and the principle of reproduction thereof are described in detail in International Publication No. WO98 / 02878, which can be referred to.

The magneto-optical recording medium 50 is loaded in the magneto-optical recording / reproducing apparatus 100 to record and reproduce information. When the magneto-optical recording medium 50 is irradiated with recording light or reproduction light, a heat spot is formed at a position shifted from the center of the light spot. The graph of FIG. 4 shows the results obtained by calculating the distance between the center of the light spot and the center of heat when the magneto-optical recording medium is rotated at various linear velocities. In the calculation here, the wavelength of the laser light is 405 nm, the numerical aperture NA of the lens that focuses the laser light is 0.6, and the power of the laser light is 10 mW.
And Under this condition, the light spot diameter is about 0.54
μm, and the radius is about 0.27 μm. When the linear velocity is set to 10 m / s, the thermal center is located at about 0.3 μm from the center of the light spot, that is, outside the light spot from FIG. Therefore, the magneto-optical head 1 shown in FIG.
In the first configuration, the angle of the galvanometer mirror 4 is adjusted so that the edge of the light spot formed on the medium by the SIL 10 is located at the magnetic field generating portion (the center of the coil) of the thin-film magnetic head 3. Such alignment between the heat center and the magnetic coil center is performed by the galvanometer mirror 4 shown in FIG.
The magneto-optical signal from the magneto-optical recording medium is detected while changing the light condensing position of the light emitted from the SIL 10 in the track direction by changing the angle of the SIL 10, and the galvanomirror 4 is adjusted so that the obtained magneto-optical signal is maximized. This can be achieved by adjusting the angle. At this time, it is considered that the heat center of the heat spot is substantially coaxial with the center of the magnetic coil. If a thin-film magnetic head mounted on the magneto-optical head 11 has a width in the track direction of the magnetic field generating section (width d of one-turn coil in FIG. 11D) of about 0.1 μm, the above-described light is obtained. Due to the spot diameter, the positional relationship between the center of the light spot and the heat center, and the relationship between the width of the magnetic field applying portion of the magnetic head, reproduction with a resolution of 0.5 μm is possible. This is a result of improving the resolution by a factor of 5 because it is one-tenth or less of the light spot diameter.

[Method of recording and reproducing information] Next, a method of recording and reproducing information will be described. FIG. 1 is a conceptual diagram showing the arrangement of a doublet lens and a thin film magnetic head and the principle of information recording. When recording light is irradiated to the magneto-optical recording medium 50 by a two-lens lens during information recording, a heat distribution as shown in the lower part of FIG. 1 is formed on the recording layer. A recording magnetic field is applied to only a minute area including the heat center using a magneto-optical head. Since the magnetic field generating portion of the thin-film magnetic head has a cross section as shown in FIG. 11D, a narrow magnetic field is applied in the track direction to a minute region including the heat center. As a result, the recording magnetic domains formed in the recording layer have a rectangular shape.

On the other hand, at the time of reproducing information, the magneto-optical recording medium is irradiated with reproducing light to form a heat distribution on the magnetic domain enlarged reproducing layer.
The recording magnetic domain formed in the recording layer is transferred to a minute area including the thermal center of the magnetic domain enlarging and reproducing layer, and is enlarged by the reproducing magnetic field by the magnetic coil mounted on the magneto-optical head. At this time, even if recording magnetic domains exist immediately before and after the magneto-optical head in the track direction, the recording magnetic domains are transferred to the reproducing layer because no magnetic field is applied to the region where these recording magnetic domains exist. No information is accidentally reproduced.

[0041]

Embodiment 2 FIG. 2 is a schematic configuration diagram of a modification of the magneto-optical head according to the present invention. In FIG. 2, the solid immersion lens (SIL) 10 'has a structure in which the bottom surface is cut by the thickness of the base 31' of the thin-film magnetic head 3 'in the optical axis direction. SIL10 'having such a structure
Since there is no notch like the SIL mounted on the magneto-optical head of the first embodiment, the processing is easier than that of the SIL of the first embodiment. Further, the thin-film magnetic head 3 'of this embodiment
As shown in FIG. 15, the one-turn coil type thin-film magnetic head 3 and the base 33, which can be manufactured in the same manner as in the first embodiment, are bonded together so that the one-turn coil 32 is sandwiched between the bases 31 and 33. Can be manufactured. The base 33 is made of the same material as the base 31 of the thin-film magnetic head.

[0042]

[Embodiment 3] FIG. 3 shows still another configuration example of the magneto-optical head according to the present invention. The magneto-optical head shown in FIG.
The magneto-optical head 11 has a structure in which a spiral planar magnetic coil 36 is provided on the bottom surface of the SIL 10 instead of the thin-film magnetic head 3. The planar magnetic coil 36
In order not to block the light emitted from the IL 10, the coil 3
6 are arranged so that the center of the SIL 10 is shifted from the central axis (optical axis) of the SIL 10 in the track direction. The plane magnetic coil 36 and the SIL 10 are arranged so that the center of the plane magnetic coil 36 is coaxial with the heat center of the heat spot formed on the recording film by the light emitted from the SIL 10.

The magneto-optical head shown in the second and third embodiments can be mounted and used instead of the magneto-optical head 11 of the magneto-optical recording / reproducing apparatus 100 shown in FIG.

Although the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to these, and includes various changes and improvements. For example,
In the recording / reproducing apparatus of the first embodiment, information is recorded / reproduced by irradiating light from the recording film side of the magneto-optical recording medium.
Light can also be incident from the substrate side. In this case, the rotation speed of the magneto-optical recording medium is set so that the magnetic field generating portion of the magnetic head is positioned on the highest temperature area (high-temperature area including the heat center) of the heat spot formed on the magneto-optical recording medium by light irradiation. At least one of the position of the magnetic field generating portion of the magnetic head and the irradiation position of light may be controlled.

In the first embodiment, the heat center of the heat spot is formed outside the light spot. However, the heat center of the heat spot is formed inside the light spot, for example, inside the outer edge of the light spot. Can be recorded and reproduced.

Further, in the magneto-optical head of the first embodiment, as shown in FIG. 1, the thin-film magnetic head is formed such that the center axis of the thin-film magnetic coil of the thin-film magnetic head 3 is perpendicular to the bottom surface of the SIL. However, as shown in the upper part of FIG.
Thin film magnetic coil (magnetic field generating portion) of thin film magnetic head 3b
The thin-film magnetic head 3b may be arranged so that the central axis of 32 is oblique to the bottom surface of the SIL 10. In this case, as shown in the upper part of FIG.
0a is formed. The thin-film magnetic head 3b can be formed by cutting the base 31 of the thin-film magnetic head 3 shown in the lower part of FIG. 17 at a position shown by a broken line. Then, the thin-film magnetic head 3b may be disposed obliquely inside the notch 10a so as not to block the optical path. This configuration of the magneto-optical head prevents the magnetic head from blocking the laser light. Since the central axis of the magnetic field generating portion of the thin-film magnetic head 3b faces obliquely to the medium surface, an oblique magnetic field is applied to the medium.

FIG. 18 shows another modification of the magneto-optical head.
Shown in In the thin-film magnetic head 3 shown in the upper part of FIG. 18, as shown in the lower part of FIG. 18, a notch 3c for allowing the condensed laser light to pass through the base 31 and the thin-film magnetic coil 32 is provided. Is formed. Notch 3c
This prevents the thin-film magnetic head 3 from blocking the laser light, so that the laser light can be efficiently focused on the magneto-optical recording medium.

[0048]

According to the recording method of the present invention, a high-temperature region generated in the recording layer by light irradiation is formed outside the light spot, and a recording magnetic field is applied to the high-temperature region. Even if the (temperature region equal to or higher than the Curie temperature) is not miniaturized, minute magnetic domains can be formed in the recording layer by reducing the width of the magnetic field generating portion of the magnetic head in the track direction. In particular, the magnetic field generating section is shown in FIG.
By using a thin-film magnetic head having a cross section as shown in FIG. 1, a narrow magnetic field can be applied in the track direction, and the recording magnetic domain formed thereby becomes rectangular. Therefore, information can be recorded at a very high density.

According to the reproducing method of the present invention, a high-temperature region is formed outside the light spot of the reproducing layer by irradiating the reproducing light,
Since a recording magnetic domain is transferred to the reproducing layer by locally applying a reproducing magnetic field to this high-temperature region, and information can be reproduced from the reproducing layer, a conventional reproducing method in which a magnetic field is applied to a region wider than the light spot is used. In comparison, the reproduction resolution can be significantly increased. Also, in order to form a high-temperature region outside the light spot, the reading speed of information is improved by increasing the linear velocity of the magneto-optical recording medium.

The recording / reproducing apparatus according to the present invention includes a rotation drive apparatus for rotating the magneto-optical recording medium while controlling the rotation speed of the magneto-optical recording medium, and a high NA capable of forming a minute light spot on the magneto-optical recording medium. By using a means such as a lens, a high-temperature area of a heat spot can be formed outside the light spot. Further, the lens and the magnetic field generating source are positioned so that a magnetic field is applied to a high temperature region formed outside the light spot. By using a magnetic field generating source having a magnetic field applying portion that is narrow in the track direction, a very small recording magnetic domain can be formed in a high-temperature region formed in the recording layer of the magneto-optical recording medium. In addition, since the reproducing magnetic field can be locally applied to the high-temperature region located outside the light spot on the reproducing layer by the magnetic field generating source having the narrow magnetic field applying unit, the reproduction determined by the magnetic field applying region The resolution is increased, and information recorded at an ultra high density can be reliably reproduced. Therefore, it is very suitable as a recording / reproducing apparatus for ultra-high density recording.

In the magneto-optical head according to the present invention, the magnetic field generating portion of the magnetic head is disposed at a position deviated from the optical axis of the lens, and the magnetic field generating portion of the magnetic head is arranged on the magneto-optical recording medium. Since the heat spot generated outside the spot can be located in a high-temperature area, a magnetic field can be locally applied to the high-temperature area. Therefore, it is extremely suitable as a magneto-optical head for realizing the recording method and the reproducing method of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing a heat distribution generated in a recording layer by a magneto-optical head according to the present invention.

FIG. 2 is a diagram conceptually showing a heat distribution generated in a recording layer by a magneto-optical head manufactured in Example 2.

FIG. 3 is a diagram conceptually showing a heat distribution generated in a recording layer by a magneto-optical head manufactured in Example 3.

FIG. 4 is a graph obtained by calculating how the difference between the center of the light spot and the center of heat depends on the linear velocity of the magneto-optical recording medium.

FIG. 5 is a schematic plan view showing a state in which a magnetic head in which a length of a magnetic field generating part in a track width direction is longer than a light spot diameter is arranged on a track;

FIG. 6 is a diagram for conceptually explaining a conventional reproducing method and a reproducing method of the present invention.

FIG. 7 is a diagram showing a state where the magneto-optical head of the present invention is flying above a rotating magneto-optical recording medium.

8 is a schematic cross-sectional view in the longitudinal direction of the magneto-optical head shown in FIG.

9 is an enlarged schematic view of the vicinity of a doublet lens of the magneto-optical head shown in FIG. 8;

FIG. 10 is a schematic sectional view of one specific example of a magneto-optical recording medium for MAMMOS.

FIG. 11 is a diagram for explaining a step of manufacturing a one-turn coil type thin-film magnetic head.

FIG. 12 is a view for explaining a part of a process of manufacturing a two-turn coil type thin film magnetic head.

FIG. 13 is a view for explaining a part of a step of manufacturing a two-turn coil type thin-film magnetic head, and is a continuation of the manufacturing step shown in FIG. 12;

FIG. 14 is a schematic configuration diagram of a magneto-optical recording / reproducing apparatus according to the present invention.

FIG. 15 is a view for explaining a method of manufacturing the thin-film magnetic head mounted on the magneto-optical head shown in FIG. 2;

FIG. 16 is a schematic sectional view of a conventional magneto-optical head.

FIG. 17 is a diagram showing a state in which the thin-film magnetic head is formed inside the SIL such that the center axis of the thin-film magnetic coil provided in the thin-film magnetic head is oblique to the bottom surface of the SIL.

FIG. 18 is a schematic cross-sectional view of an SIL and a thin-film magnetic head mounted on the magneto-optical head, and a perspective view schematically showing a cross-sectional structure of the thin-film magnetic head when viewed obliquely from the left side of the paper.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 slider 2 condenser lens 3 thin-film magnetic head 4 galvanometer mirror 6 doublet lens 10 solid immersion lens 11 magneto-optical head 14 laser light source 23 spindle motor 50 magneto-optical recording medium 100 magneto-optical recording / reproducing device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G11B 7/12 G11B 7/12 7/135 7/135 A

Claims (26)

[Claims] An optical spot that moves relative to the magneto-optical recording medium on a track of the magneto-optical recording medium;
In a magneto-optical recording method for recording information by applying a magnetic field to a heat spot generated by a light spot, a high-temperature area of the heat spot is formed outside the light spot, and information is recorded by applying a magnetic field to the high-temperature area. A recording method characterized in that: 2. The recording method according to claim 1, wherein the center of the magnetic field is coaxial with the center of the high temperature region of the heat spot. 3. A magnetic field generating source according to claim 1, wherein a magnetic field generating portion in the track direction has a width smaller than a light spot in order to apply a magnetic field to the magneto-optical recording medium. Recording method. 4. The light source according to claim 3, wherein a part of said magnetic field generating source is positioned so as to be included in the light spot, and a reduction rate of the light use efficiency is 50% or less. Recording method. 5. The magneto-optical recording medium is rotating, a linear velocity is calculated from a rotational speed of the magneto-optical recording medium and a position of the magnetic field generating source on the magneto-optical recording medium, and based on the calculated linear velocity. The recording method according to claim 3, wherein the distance between the center of the light spot and the magnetic field application region is adjusted. 6. The recording method according to claim 1, wherein the magneto-optical recording medium includes a magnetic domain expansion reproducing layer. 7. A light spot moving relative to the magneto-optical recording medium is formed on a track of the magneto-optical recording medium,
In a magneto-optical recording method for recording information by applying a magnetic field to a heat spot generated by a light spot, a high-temperature area of the heat spot is formed at a position shifted in the track direction from the center of the light spot, A recording method characterized by recording information by applying a magnetic field. 8. A heat spot is formed on a magneto-optical recording medium having a recording layer and a reproducing layer by forming an optical spot relatively moving with respect to the magneto-optical recording medium to generate a heat spot on the magneto-optical recording medium. In a reproducing method of reproducing information by transferring magnetic domains of a recording layer to a reproducing layer in a heat spot, a high-temperature area of the heat spot is formed outside the light spot, and a magnetic field is applied to the high-temperature area. A reproducing method, wherein a magnetic domain of a recording layer is transferred to a reproducing layer through a high-temperature region. 9. The reproducing method according to claim 8, wherein the center of the magnetic field is coaxial with the center of the high temperature region of the heat spot. 10. The reproducing method according to claim 8, wherein a magnetic field is applied such that a length in a track direction of a magnetic field application region of the magneto-optical recording medium is smaller than a light spot diameter. 11. The magnetic head according to claim 8, wherein a magnetic head in which a width of a magnetic field generating portion in a track direction is smaller than a light spot is used to apply a magnetic field to the magneto-optical recording medium. The reproduction method described in the section. 12. The magneto-optical recording medium is rotating,
12. The reproducing method according to claim 8, wherein the distance between the center of the light spot and the magnetic field application region is adjusted based on the linear velocity of the magneto-optical recording medium. 13. The reproducing method according to claim 8, wherein the reproducing layer is a magnetic domain expansion reproducing layer whose magnetic domains are expanded by applying a magnetic field. 14. A heat spot is generated on a magneto-optical recording medium having a recording layer and a reproducing layer by forming an optical spot moving relative to the magneto-optical recording medium, thereby generating a heat spot on the magneto-optical recording medium. A method for reproducing information by transferring magnetic domains of a recording layer to a reproducing layer in a heat spot, wherein a maximum temperature area of the heat spot is formed at a position shifted in the track direction from the center of the light spot; Reproducing a magnetic domain of a recording layer to a reproducing layer through a high-temperature region by applying a magnetic field inside the reproducing layer. 15. A recording / reproducing apparatus for a magneto-optical recording medium, comprising: a light source for irradiating the magneto-optical recording medium with light; and condensing light from the light source to form a light spot on the magneto-optical recording medium. A lens for applying a magnetic field to the magneto-optical recording medium; and means for forming a high-temperature area of a heat spot generated based on the light intensity distribution of the light spot outside the light spot. A recording / reproducing apparatus, comprising: a magnetic field generation source and a lens positioned so that a magnetic field is applied to the high-temperature region. 16. A rotation driving device for rotating the magneto-optical recording medium, and calculating a linear velocity from the rotational speed of the magneto-optical recording medium and the position of the magnetic field generating source on the magneto-optical recording medium. The recording / reproducing apparatus according to claim 15, further comprising: a control device that controls a distance between the center of the light spot and the magnetic field application area based on the determined linear velocity. 17. The recording / reproducing apparatus according to claim 15, wherein the center of the magnetization applying section of the magnetic field generator is substantially coaxial with the center of the highest temperature region of the heat spot. 18. The recording / reproducing apparatus according to claim 15, wherein a width of the magnetic field generating portion of the magnetic field generating source in a track direction is smaller than a light spot. 19. The recording / reproducing apparatus according to claim 15, wherein the lens is a solid immersion lens. 20. A magneto-optical head used for recording and / or reproducing information on a magneto-optical recording medium, wherein a lens for condensing light on the magneto-optical recording medium, and a magnetic field is applied to the magneto-optical recording medium. A magnetic field source having a width smaller than the diameter of a light spot formed on the magneto-optical recording medium by the lens in the track direction, the magnetic field generating source comprising: A magneto-optical head, wherein a center axis of a magnetic field generated from a source is formed on a bottom surface of the lens so as to be shifted from a center axis of the lens. 21. The magneto-optical head according to claim 20, wherein the magnetic field generating source is provided on a base, and the base is formed in close contact with a lens. 22. The method according to claim 21, wherein the difference between the refractive index of the base and the refractive index of the lens is within ± 10% of the refractive index of the lens or the base having the larger refractive index. The magneto-optical head as described in the above. 23. The magneto-optical head according to claim 20, wherein the lens is a solid immersion lens. 24. The magneto-optical head according to claim 20, wherein the magnetic field generating source is a thin magnetic head formed by lithography. 25. The magneto-optical head according to claim 20, further comprising a floating slider, wherein the lens and the magnetic field generating source are mounted on the floating slider. . 26. Further, the distance between the center of the light spot formed on the magneto-optical recording medium by the lens and the center of the magnetic field generated from the magnetic field generating source is controlled based on the linear velocity of the magneto-optical recording medium. The magneto-optical head according to any one of claims 20 to 25, further comprising: