Hitachi, Ltd.

Hitachi Maxell, Limited

Other

Hitachi Maxwell, Ltd.

Kouichirou Wakabayashi

Hirofumi Sukeda

Takeshi Maeda

Hisataka Sugiyama

Atsushi Saito

Nobuyuki Inaba

Teruaki Takeuchi

Takeshi Shimano

Fumiyoshi Kirino

Hiroyuki Awano

Satoshi Matsunuma

Akira Yano

Tsuyoshi Onuma

Harumi Hieida

Harukazu Miyamoto

Yoshihiro Shiroishi

Hideki Saga

Takehiko Hamaguchi

Junko Ushiyama

Keikichi Andoo

Kyo Akagi

Takashi Kawabe

Masuo Umemoto

Reijiro Tsuchiya

Osamu Komoda

Takanobu Takayama

Norio Ohta

Katsuro Watanabe

Kimio Tatsuno

Mikio Suzuki

Masafumi Yoshihiro

Kiyoshi Matsumoto

Yosuke Hamada

Masaki Sekine

Manabu Tani

Tetsunori Koda

A method of reproducing information by scanning information marks, disposed with a predetermined mark pitch therebetween and recorded on tracks inside a predetermined information recording region, by an optical spot. The method includes detecting the size of the optical change resulting from the information mark, calculating a plurality of equalization coefficients used for an equalization processing for the size of the optical change detected for each of the information marks, and reducing the inter-symbol interference on the basis of the equalization coefficients by the equalization processing. The equalization coefficient used for the equalization processing of the size of the optical change by a first information mark is greater than said equalization coefficient used for the equalization processing of the size of said optical change by a second information mark which is longer than the first information mark.

Method of reproducing information with equalization coefficient for the reproduced information

A recording and reproducing apparatus including a recording magnetic head and a reproducing magnetic head with their floating height lowered for high density recordation and reproduction is provided. An information recording medium is provided on which it is possible to densely record information and from which it is possible to densely reproduce information by lowering the floating height of the recording and reproducing heads. The information recording medium includes a flat substrate and a recording layer provided on the substrate. Servo patterns and management information are recorded as magnetic marks on the recording layer in advance by a servo writer or the like. Because the substrate needs no recessed and embossed patterns formed in it, the slider of the recording and reproducing apparatus can be floated at a constant floating height lower than conventionally over the whole area of the medium. During information recordation, the position of the slider is controlled on the basis of the magneto-optical signals from the magnetic marks. During information reproduction, the reproducing magnetic head controls the slider position on the basis of the magnetic leakage fields leaking from the magnetic marks.

Information recording medium with magnetic marks, recording and reproducing apparatus therefor, and head positioning method using detected magnetic leakage fields from the magnetic marks

Method of reproducing information with equalization for the reproduced information to reduce inter-symbol interference

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 magnetic recording medium comprises, on a substrate, a soft magnetic layer, a first seed layer, a second seed layer, and a recording layer having an artificial lattice structure. The first seed layer contains oxide of Fe. The second seed layer contains one of Pd and Pt, Si, and N. The magnetic exchange coupling force in the in-plane direction of the recording layer is weakened by the first seed layer and the second seed layer. Accordingly, minute recording magnetic domains can be formed in the recording layer, and the magnetization transition area is distinct as well. Even when information is recorded at a high density, the information can be reproduced with low noise. A magnetic storage apparatus, which is provided with such a magnetic recording medium, makes it possible to achieve an areal recording density of 150 gigabits/square inch.

Magnetic recording medium, method for producing the same, and magnetic storage apparatus

A magnetic recording medium ( ) includes a substrate ( ) and on the substrate ( ) a first underlying layer ( ), a second underlying layer ( ), a magnetic layer ( ), and a protective layer ( ). Because of the existence of the first underlying layer ( ) of Hf, initial growth layer having no specific crystal structure is prevented from growing in the second underlying layer ( ). The second underlying layer ( ) has a structure in which CoO particles having a cross section of a regular hexagon and separated by SiO portion are arranged in honeycomb. Since magnetic particles are epitaxially grown from CoO particles, the size of the magnetic particles and particle size distribution can be controlled, and the magnetic interaction between magnetic particles can be lessened. The underlying layer ( ) and the protective layer ( ) are formed by ECR sputtering. Such a magnetic recording medium is free from noise and thermal fluctuation, and ultrahigh recording density over 40 Gbit/inch is realized.

Magnetic recording medium and its production method, and magnetic recorder

A magnetic recording apparatus includes a laser light source ( ), a recording magnetic head ( ) and a magnetoresistive element. The recording magnetic head includes a pair of magnetic poles ( and ), between which the magnetoresistive element is interposed. A rotary actuator (Sa) positions the recording magnetic head at a desired track of a magnetic recording medium. A laser beam can be radiated onto the magnetic recording medium to raise the temperature of a region ( ) of the medium. This region has a width of the order of the track width. The raised temperature lowers the coercive force of this region, where a recording magnetic field can be applied for high density recording. The rotary actuator may form a yaw angle (&thgr;) with a track of the magnetic recording medium. Even in this case, the recording magnetic head ( ) and the reproducing element have no tracking offset from the code track. In addition, if the size of the magnetic poles ( and ) of the recording magnetic head are set within a predetermined range, the region ( ) heated by the laser beam does not deviate from a recording magnetic field application region ( ).

Read/write head and magnetic recording device

When recording marks having various lengths are recorded to represent information on a magneto-optical recording medium, a mark length-correcting circuit is used to correct a mark length nT with a mark length correction amount Lc determined for each mark length so that the recording is performed with a shorter mark length nT&prime;&equals;nT&minus;Lc. When reproduction is performed on the magneto-optical recording medium, an appropriate reproducing light power and an appropriate reproducing magnetic field intensity can be easily selected for any recording mark having any length. Thus, the reproducing power margin is widened. The recording method is effective on a magneto-optical recording medium of the MAMMOS type comprising a recording layer and a reproducing layer, in which the light and the magnetic field are applied during the reproduction to transfer a magnetic domain from the recording layer to the reproducing layer in a magnified form.

Method for recording mark length shorter than channel bit length on magneto-optical medium

An information reproducing apparatus for reproducing information of information marks by scanning information marks recorded on tracks inside a predetermined information recording region by an optical spot, the apparatus includes a driving device, an optical head, a head driving device, a laser driving device, an automatic gain control circuit, a non-linear equalization circuit, a phase locked loop circuit, a data demodulation circuit, and a control circuit.

Information reproducing apparatus enabling equalization processing with equalization coefficient for reproduced information

An information reproducing apparatus method includes the steps of radiating an optical spots to scan information marks recorded on tracks inside a predetermined information recording region, detecting an optical change of the information marks by this scanning operation, executing a signal processing for the reproducing signal so as to reduce inter-symbol interference of an interference amount that varies for each of the information marks, and reproducing the information corresponding to the information mark. The magnitude of the optical change due to the information mark is thereby detected, and a plurality of equalization coefficients used for an equalization processing are calculated for the magnitude of the optical change detected for each information mark. The inter-symbol interference is reduced on the basis of these equalization coefficients. In consequence, the inter-symbol interference can be reduced while the equalization coefficients are changed in accordance with the level of the reproducing signal.

Method of reproducing information using a selected equalization coefficient for each signal

Magnetic recorder and magnetooptical recorder

An optical recording/reproducing method employs a recording laser beam having a first output and a first wavelength, and a reproducing laser beam having a second output lower than the first output and a second wavelength shorter than the first wavelength. A disk-like recording medium is irradiated with the recording and reproducing laser beams by use of an objective lens having an NA of about 0.55 so that a small mark equal to or smaller than about one fourth of a spot size optically defined from the wavelength of the recording laser beam and the NA of the objective lens is formed on the recording medium by a recording characteristic of the recording medium and a shielding plate provided in an optical system for irradiation with the laser beam. Two-dimensional recording is performed as a recording system to arrange marks at lattice points of a two-dimensional lattice which extend in a track direction and a track radius direction. The reproducing system detects a reproduction signal from the mark on the two-dimensional lattice point, and the reproduction signal from each mark is used to perform a signal processing, thereby detecting information.

High-density information recording/reproducing method

Growing community of inventors

Toride, Japan

Kouichirou Wakabayashi