Hitachi, Ltd.

Hitachi Maxell, Limited

Other

Hitachi Maxwell, Ltd.

Sanyo Electric Co., Ltd.

Hitachi Cable, Inc.

Norio Ohta

Katsusuke Shimazaki

Masafumi Yoshihiro

Harukazu Miyamoto

Toshio Niihara

Hitoshi Watanabe

Yutaka Sugita

Masahiko Takahashi

Satoru Ohnuki

Hiroyuki Awano

Hiroki Takao

Hirofumi Sukeda

Fumiyoshi Kirino

Motoyasu Terao

Keiji Kataoka

Seiji Yonezawa

Toshiaki Tsuyoshi

Tetsuya Nishida

Keikichi Ando

Tadashi Ikeda

Shinkichi Horigome

Yukinori Yamada

Katsuji Nakagawa

Yuzuru Hosoe

Hideo Fujiwara

Yoshinori Miyamura

Yoshitane Tsuburaya

Ryo Suzuki

Atsushi Yamaguchi

Toshimitsu Kaku

Kazuo Shigematsu

Yasushi Miyauchi

Teruaki Takeuchi

Keikichi Andoo

Satoshi Sumi

Osamu Ishizaki

Toshinori Sugiyama

Tsuneo Suganuma

Akito Sakemoto

Hiroshi Yasuoka

Hiroshi Shirai

Noriyuki Ogihara

Fumihiko Ishida

Kazuko Ishitsuka

Akiyoshi Itou

Yoshio Suzuki

Yumiko Anzai

Masahiro Ojima

Hiroyoshi Matsumura

Takashi Toyooka

Eiji Koyama

Ryo Imura

Naoyuki Takagi

Kazuyuki Nagatsuma

Yoshiharu Uchihara

Shigenori Okamine

Masaki Sekine

Masatoshi Hashimoto

Susumu Imai

Yoshinori Shirai

Junko Nakamura

Hitoshi Furusho

Akiyoshi Ito

Takeshi Maeda

Toshio Kobayashi

Hisashi Takano

Shigeru Nakamura

Atsushi Saito

Yoshihiro Shiroishi

Tsuneo Terasawa

Yoshito Tsunoda

Nobuyuki Inaba

Hiroaki Miwa

Kazuo Shiiki

Kunikazu Ohnishi

Masaru Ito

Kazumasa Takagi

Mikio Kishimoto

Takeshi Nakao

Ryoichi Sudo

Toshio Katsuyama

Masaaki Kurebayashi

Fumio Kugiya

Tetsuo Tajima

Satoshi Matsunuma

Kouichirou Wakabayashi

Yosuke Seo

Akira Gotoh

Nobuhiro Umebayashi

Kenzo Susa

Akira Yano

Masashi Suenaga

Takashi Tamura

Hajime Fukke

Kazuya Fukunaga

Manabu Tani

Takanobu Takayama

Keizo Kato

Tetsunori Koda

Shuhei Nakamichi

A magnetic recording medium comprises a first magnetic film and a second magnetic film on a substrate. The second magnetic film is composed of a magnetic material preferred for recording and reproduction, and the first magnetic film is composed of a ferrimagnetic material excellent in thermal stability. Information is recorded in the second magnetic film by using a magnetic head. The first magnetic film is heated by being irradiated with a laser beam to lower coercivity, and the information in the second magnetic film is magnetically transferred to the first magnetic film. The recorded information is stabilized, because the first magnetic film is excellent in thermal stability. The magnetic recording medium is highly resistant to thermal fluctuation, and it has high reliability. A magnetic domain of about 0.1 &#x3bc;m, formed by magnetic recording at a super high density of 50 Gb/inch, is successfully and stably allowed to exist.

Method for recording information data to a recording medium by irradiation with a light beam and application of a magnetic field

A magneto-optical recording medium and a method for recording and reproduction thereon are provided in order to reproduce information recorded by multi-valued recording at a high S/N ratio. Disclosed is a magneto-optical recording medium including two magnetic layers capable of four-valued recording based on four combined magnetization states. Magnitudes of reproduction signals concerning the four magnetization states, obtained upon reproduction at a wavelength &#x3bb;, are different from those obtained upon reproduction at a wavelength &#x3bb;. The two magnetic layers, on which a signal (a) is recorded, are irradiated with light beams having the wavelengths &#x3bb;and &#x3bb;respectively. Signals (d), (e) reproduced from respective reflected light beams are sliced by using at least one slice level to obtain two-valued or higher multi-valued reproduction signals respectively. The two-valued or higher multi-valued reproduction signals (f), (g) from the respective wavelengths are mutually subjected to logical operation to reproduce recorded information (i).

Method for recording and reproduction on a magneto-optical recording medium

A magneto-optical recording medium has magneto-optical recording layers () and reproducing layers (). The information recorded in the reproducing layers are reproduced by means of reproducing light beams () of different wavelengths, respectively. In reproduction, magnetic domains () recorded in the recording layers are transferred in the reproducing layers formed on the respective recording layers, the transferred magnetic domains () are enlarged with an external magnetic field, and the information is reproduced. Since information is recorded and reproduced for each recording layer, the recording density is improved. Further since the reproduction signals are amplified by the magnetic domain enlargement, the C/N is improved.

Magneto-optical reproducing method using a plurality of different reproducing beams

A magnetic recording medium comprises an information-recording film and a ferromagnetic film on a substrate. The information-recording film is composed of, for example, an amorphous ferrimagnetic material having perpendicular magnetization. Further, the ferromagnetic film is composed of a magnetic material which has saturation magnetization larger than that of the information-recording film. Accordingly, the leak magnetic flux from the ferromagnetic film is larger than that from the information-recording film. The magnetic recording medium and a magnetic recording apparatus are obtained, which are excellent in thermal stability and which are preferred to perform super high density recording.

Magnetic recording medium with high thermal stability, method for producing the same, and magnetic recording apparatus

A magneto-optical recording medium which includes a reproducing layer. When a laser beam is irradiated to the magneto-optical recording medium, a magnetic domain in a recording layer is transferred, through enlargement, to a reproducing layer increased in temperature. The magneto-optical recording medium further includes a calibration area that has a calibration magnetic domain recorded in a predetermined pattern in the recording layer. In a reproducing apparatus, a laser beam of an optical head is adjusted in output depending upon a reproduced signal obtained by reproducing the calibration magnetic domain.

Magneto-optical recording medium including a calibration magnetic domain recorded in a predetermined pattern in a recording layer

External magnetic fields H(x) or reproducing light beams L(x) having different intensity patterns are applied to an identical recording position on a magneto-optical recording medium so that different pieces of information corresponding to the patterns are reproduced from the identical recording position. A function H(x) or L(x) is a password for obtaining the information. Only a person, who knows the function, can access specified information recorded on the magneto-optical recording medium. The function H(x) or L(x) is a function in which the magnetic field intensity or the light intensity is modulated with respect to the recording position x so that magnetic domains may be thinned out to perform reproduction at a specified cycle from continuous magnetic domains in a recording area. Other than the use for the purpose of security, reproduced C/N can be remarkably improved by performing reproduction n times while radiating a reproducing light beam P /P which is power-modulated so that the high power P is applied at every cycle which is not less than n times the recording clock, to a specified magneto-optical recording medium capable of magnetic domain-magnifying reproduction.

Reproducing method and reproducing apparatus for magneto-optical recording medium

A magneto-optical recording medium comprises, on a substrate, a dielectric layer, a GdFeCo reproducing layer, a non-magnetic layer, and a TbFeCo recording layer. Upon reproduction, a DC magnetic field Hex is applied in the recording direction, and a reproducing light beam is radiated while being modulated to have a low power and a high power in synchronization with a reproducing clock. The reproducing layer is a magnetic film which changes from in-plane magnetization into perpendicular magnetization at a critical temperature Tcr, which has a compensation temperature Tcomp between room temperature and a Curie temperature Tc, and which satisfies Troom<Tcr<Tcomp<Tco<Tc in relation to a Curie temperature Tco of the recording layer. Magnetic domain transfer and magnetic domain magnification occur if the transfer magnetic field of the recording layer and the coercive force of the reproducing layer have the relationship of relative magnitude as shown in FIG. in temperature areas (a) and (b) when the reproducing light beam having the low power is radiated. The magnified magnetic domain is reliably extinguished if the transfer magnetic field of the recording layer and the coercive force of the reproducing layer have the relationship of relative magnitude as shown in FIG. in a temperature area (c) when the reproducing light beam having the high power is radiated. A minute magnetic domain, which is smaller than the reproducing light spot on the magneto-optical recording medium, can be subjected to reproduction independently to produce an amplified reproduced signal.

Magneto-optical recording medium and reproduction method therefor

A magneto-optical recording medium has magneto-optical recording layers ( ) and reproducing layers ( ). The information recorded in the reproducing layers are reproduced by means of reproducing light beams ( ) of different wavelengths, respectively. In reproduction, magnetic domains ( ) recorded in the recording layers are transferred in the reproducing layers formed on the respective recording layers, the transferred magnetic domains ( ) are enlarged with an external magnetic field, and the information is reproduced. Since information is recorded and reproduced for each recording layer, the recording density is improved. Further since the reproduction signals are amplified by the magnetic domain enlargement, the C/N is improved.

Magneto-optical reproducing method using a plural of different reproducing beams

A reproducing apparatus for a magneto-optical recording medium has, at one end of a swing arm, a magneto-optical head provided with a slider and a solid immersion lens. A reproducing light beam-detecting system is installed to the other end of the swing arm. During reproduction on a magneto-optical recording medium, an alternating magnetic field is applied while radiating a reproducing light beam which is power-modulated to have a low power and a high power in synchronization with a reproducing clock. The reproducing light beam having the low power causes transfer of a magnetic domain in the information-recording layer to the reproducing layer and magnification thereof. The reproducing light beam having the high power extinguishes the magnified magnetic domain. Minute magnetic domains can be individually reproduced at high C/N.

Reproducing method and reproducing apparatus using plural light beam powers for transferring a magnetic domain

Reproducing method and reproducing apparatus for magneto-optical recording medium using different radiation patterns

A plate spring is provided on a back surface of a shutter of a cartridge. When the shutter is closed, the plate spring presses a disk in a cartridge case against an inner wall surface of a lower case so that the disk is immovable in the case. When the shutter is open, the plate spring is retracted into a space between an inner surface of the shutter and a surface of an upper case. The disk is supported immovably and uniformly in the cartridge. Therefore, deformation such as warpage of the disk hardly occurs. Even when the cartridge is stored in any posture, it is possible to avoid deformation such as warpage and flexure of the disk in the cartridge during the storage.

Cartridge for information-recording media having deformable elastic pressing member urged by projection on shutter

A magneto-optical recording medium has, in order from the laser irradiation side, a second auxiliary magnetic film first auxiliary magnetic film and magneto-optical recording film First and second auxiliary magnetic films and change from in-plane magnetization to perpendicular magnetization when their respective critical temperatures T and T are exceeded. The Curie temperatures T , T and T of the magneto-optical recording film and the first and the second auxiliary magnetic films and their critical temperatures T and T satisfy the relationship: room temperature<T <T <T , T ,T . The first auxiliary magnetic layer has a film thickness greater than the thickness of the magnetic wall. In response to irradiation by the reproducing light beam, recording magnetic domain of magneto-optical recording film is transferred, with size reduction, to first auxiliary magnetic film and is then transferred, with magnification, to second auxiliary magnetic film This is ideal for reproduction of a high-density recording medium since an amplified reproduction signal is obtained from magnified magnetic domains

Magneto-optical recording media having an auxiliary magnetic layer

A magneto-optical disk apparatus and an adjustment method of a head mechanism are provided for strictly and quickly adjusting a setting position of a magnetic head with respect to an optical axis of an optical head. The adjustment method is executed by the following steps. A magnetic super resolution type magneto-optical disk is mounted to the magneto-optical disk apparatus provided with the optical head and the magnetic head. Then, an external magnetic field from the magnetic head is applied onto the magneto-optical disk as applying a laser beam of a reproduction level onto the magneto-optical disk. Then, a reproduction signal output read from the magneto-optical disk is detected concurrently with the application of the external magnetic field. Next, a fine adjustment mechanism is operated so that the reproduction signal output is made maximum with respect to the direction of the external magnetic field, for the purpose of sequentially changing a setting position of the magnetic head with respect of the optical axis of the optical head.

Magneto-optical disk apparatus having an adjustment mechanism for setting the position of magnetic heads

The magneto-optical recording medium has a magnetic domain magnification reproducing layer and an information recording layer. Clock marks are formed on the information recording layer, making it possible to generate a reproducing clock on the basis of these. The clock marks are detected either by irradiating directly with light of wavelength &lgr; (&lgr; &ne;&lgr; ), being different from the light of wavelength &lgr; which is used for reproducing the recording marks, or by applying a direct-current magnetic field, transferring and enlarging the clock marks on to the magnetic domain magnification reproducing layer, and detecting the reproduction signals from this magnetic domain magnification reproducing layer. Since the reproducing clock is in exact synchronisation with the recording marks, it is eminently suitable as a clock for pulse-modulated reproducing light and reproducing magnetic fields used when reproducing the reproducing layer.

Magneto-optical recording medium having clock-marks on recording layer and apparatus for recording and reproducing same

A magneto-optic recording medium includes a second auxiliary magnetic film, a first auxiliary magnetic film and a magneto-optic recording film on a substrate. The auxiliary magnetic films change from in-plane magnetization to vertical magnetization at critical temperatures T and T . Since they have the relation T >T , the magnetic domain transferred from the magneto-optic recording film to the first auxiliary magnetic film at the time of reproduction is expanded in diameter and is transferred to the second auxiliary magnetic film when the temperature profiles of the auxiliary magnetic films inside an optical spot are utilized. The magnetic domain of the magneto-optic recording film can be expanded and transferred, too, by means of magnetostatic coupling by using a non-magnetic film in place of the first auxiliary magnetic film. Pulse reproduction light subjected to power modulation in synchronism with a reproduction clock can be used at the time of reproduction. Even when a very small magnetic domain is recorded, the intensity of an amplified reproduction signal can be detected and excellent C/N can be obtained.

Magneto-optical recording medium and reproducing method for reproducing magnetic domain in enlarged form on a reproducing layer

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Yawara-mura, Japan

Norio Ohta