Abstract: Provided is an optical disk apparatus which has high read retry ability and high compatibility by performing a proper verify for other apparatuses. The optical disk apparatus includes a playback system capable of arbitrarily changing playback performance, and means which detects and determines a factor causing a read error. Moreover, a read retry is performed by use of playback parameters corresponding to the factor causing the read error. Furthermore, a verify is performed with the playback performance of the playback system lowered.

Abstract: A magnetic recording/reproducing apparatus is disclosed with high storage capability. The apparatus also prevents fluctuation of readback output and decay of magnetization or erasure of recorded magnetization in the recording layer. A soft magnetic underlayer and a perpendicular recording layer are formed in specific order on the substrate of a magnetic disk. The soft magnetic underlayer has a triple-layered structure in which a domain control layer, including an anti-ferromagnetic layer, is sandwiched between two first and second soft magnetic layers. The thickness of the first and second soft magnetic layers (d1, d2) is between 25 nm and 150 nm and a ratio of d1/d2 is within a range of 0.3 to 1.5. Accordingly, magnetic domains in the soft magnetic underlayer of a perpendicular magnetic recording medium can be controlled and magnetic domain wall motion can be inhibited.

Abstract: This invention involves irradiating an optical disk with laser light, pulse-driven by a high-frequency signal from an HF oscillator, and converting the output of a photo-detector that receives laser light reflected from the optical disk into an electronic pulse readout signal using a current amplifier. The pulse readout signal is converted into a temporally continuous readout signal by a peak hold circuit. The invention solves the problems of SNR deterioration of the readout signal and the difficulty of removing the impact of high-frequency modulation accompanying the increase in the readout speed factor in optical disk devices.

Abstract: A perpendicular magnetic recording medium which has been improved to be suitable for high-density magnetic recording and a magnetic recording apparatus using the medium are provided. The magnetic back film of a dual-layer perpendicular recording medium is caused to be constituted by a plurality of layers, and a keeper layer 17 for keeping perpendicular magnetization and layers 13 and 15 for improving the recording efficiency of a recording head are functionally separated from one another. Further, the magnetization orientations of the soft magnetic films excluding the keeper layer are defined to be in the circumferential direction of the disk, whereby the frequency of occurrence of noise is decreased.

Abstract: A soft magnetic underlayer includes a first amorphous soft magnetic layer to which an exchange bias magnetic field is applied directly from an antiferromagnetic layer or via a ferromagnetic layer, and a second amorphous soft magnetic layer which is formed on the first amorphous soft magnetic layer via a non-magnetic layer. The first amorphous soft magnetic layer and the second amorphous soft magnetic layer are antiferromagnetically coupled.

Abstract: Provided are a double-layer perpendicular magnetic recording medium having a high medium S/N at an areal recording density of 50 Gbits or more per square inch, and a magnetic storage apparatus having excellent reliability with a low error rate. The perpendicular magnetic recording medium is formed by sequentially laminating a domain control layer, an amorphous soft magnetic underlayer, an intermediate layer, and a perpendicular recording layer on a substrate. The domain control layer is a triple-layer film formed by laminating a first polycrystalline soft magnetic layer, a disordered antiferromagnetic layer, and a second polycrystalline soft magnetic layer from a substrate side.

Abstract: An optical disk read signal processing system for Blu-ray disc systems to ensure stable phase-locked locked operation even with a low signal-to-noise ratio. This system changes a loop configuration of a phase lock loop circuit according to the operating state, and utilizes a FIR equalizer for phase detection. This system attains a low error rate even when the signal-to-noise ratio of an input signal is low, and avoids pulse edges with low phase detection accuracy or signal pulse streams with a high possibility of being mistakenly detected as an edge in conventional methods, and also supports diverse types of input signals.

Abstract: A perpendicular magnetic recording medium which has been improved to be suitable for high-density magnetic recording and a magnetic recording apparatus using the medium are provided. The magnetic back film of a dual-layer perpendicular recording medium is caused to be constituted by a plurality of layers, and a keeper layer 17 for keeping perpendicular magnetization and layers 13 and 15 for improving the recording efficiency of a recording head are functionally separated from one another. Further, the magnetization orientations of the soft magnetic films excluding the keeper layer are defined to be in the circumferential direction of the disk, whereby the frequency of occurrence of noise is decreased.

Abstract: A double layer perpendicular magnetic recording medium having a high medium S/N ratio at a recording density of 50 Gb/in2 or higher and a magnetic storage apparatus with a lower error rate and excellent reliability are provided. In a perpendicular magnetic recording medium in which a soft magnetic underlayer 12, an intermediate layer 13, and a perpendicular magnetic recording layer 14 are sequentially formed on a substrate 11, the intermediate layer 13 is made to be a non-magnetic amorphous alloy, in which Ni is a main component and Zr is contained, and the soft magnetic underlayer 12 is constituted of ferromagnetic nan-crystals precipitated by annealing.

Abstract: With the objective of providing a stable PLL circuit and improving readout performance of an optical disk apparatus equipped with PRML, using the PLL circuit, phase detectors are respectively provided with respect to signals prior and subsequent to an FIR filter, and the phase detectors are selectively used according to an operating condition of a PLL to thereby stabilize the operation of the PLL circuit. There can be provided such an optical disk apparatus that readout performance is improved so as to extract an operating limit of a Viterbi decoder.

Abstract: A perpendicular recording medium includes a perpendicular recording layer formed over a substrate through a soft magnetic underlayer, the soft magnetic underlayer then being arranged to include a plurality of soft magnetic layers physically separated by a non-magnetic layer, and further, the soft magnetic layers being formed of nanocrystals, with these arrangements, local magnetic loops are formed between the soft magnetic layers that are adjacent to each other through the non-magnetic layer, thereby suppressing spike noise and modulation that arises from the soft magnetic underlayer.

Abstract: An optical disc apparatus implementing a PRML and capable of recording and reading a plurality of disc media with different recording densities, wherein read compatibility between drives is ensured without relying solely on the error correction capability of the ECC (error correction code). A phase comparator provided in a PLL compares each value of an input signal sequence with a designated threshold value in order to determine an edge. The optical disc apparatus can record and read a plurality of disc media with different recording densities while ensuring read compatibility.

Abstract: An object is to automatically detect the positions of spike noise, create a distribution diagram, and perform pass/fail decisions. The cross-correlation function of the signal waveform from a magnetic head 1 and a reference waveform simulating spike noise is used in extraction of spike noise. The number of peaks in the cross-correlation function exceeding a threshold value is counted, and quantitative evaluation of spike noise is performed.

Abstract: Embodiments of the invention prevent demagnetization or degaussing of recorded magnetizations, even if a stray field is applied. In one embodiment, an output of a read head including a magneto-resistive effect element is inputted to a stray field detector through a DC amplifier and a DC filter. The stray field detector monitors dc components of the output from the read head, and escapes a head from above a magnetic recording medium.

Abstract: Embodiments of the invention provide a countermeasure against spike noise maintaining the data reliability of a magnetic recording layer. In one embodiment, the magnetic domain state right below and around the read head of the soft magnetic layer in the recording medium is locally and temporarily equalized using the write head, whereby, the effect of the spike noise caused by the magnetic domain boundaries (magnetic domain walls) of the soft magnetic layer on the read waveform is prevented. The read retry action of the magnetic hard disk drive is used as the trigger for the timing of the magnetic field application, thereby shortening the time for the magnetic field application.

Abstract: An object is to automatically detect the positions of spike noise, create a distribution diagram, and perform pass/fail decisions. The cross-correlation function of the signal waveform from a magnetic head 1 and a reference waveform simulating spike noise is used in extraction of spike noise. The number of peaks in the cross-correlation function exceeding a threshold value is counted, and quantitative evaluation of spike noise is performed.

Abstract: An object is to automatically detect the positions of spike noise, create a distribution diagram, and perform pass/fail decisions. The cross-correlation function of the signal waveform from a magnetic head 1 and a reference waveform simulating spike noise is used in extraction of spike noise. The number of peaks in the cross-correlation function exceeding a threshold value is counted, and quantitative evaluation of spike noise is performed.

Abstract: The chemical conversion film containing, at least as the constituent components thereof, (a) at least one of the metals selected from molybdenum, zirconium, vanadium, and tungsten; (b) a rare earth metal constituting the magnet; and (c) oxygen, which is formed on the surface of a rare earth metal-based permanent magnet according to the present invention, contains a composite metal oxide provided on the surface of the R-rich phase having a lower oxidation-reduction potential through a preferential reaction of the metallic ions that are present in the form of complex ions or oxide ions, such as of molybdenum, contained in the treatment solution, with the rare earth metals that elute from the magnet. Thus formed composite metal oxide reduces the difference in corrosion potential as to realize a uniform surface potential, and effectively suppresses the corrosion based on potential difference.

Abstract: The chemical conversion film containing, at least as the constituent components thereof, (a) at least one of the metals selected from molybdenum, zirconium, vanadium, and tungsten; (b) a rare earth metal constituting the magnet; and (c) oxygen, which is formed on the surface of a rare earth metal-based permanent magnet according to the present invention, contains a composite metal oxide provided on the surface of the R-rich phase having a lower oxidation-reduction potential through a preferential reaction of the metallic ions that are present in the form of complex ions or oxide ions, such as of molybdenum, contained in the treatment solution, with the rare earth metals that elute from the magnet. Thus formed composite metal oxide reduces the difference in corrosion potential as to realize a uniform surface potential, and effectively suppresses the corrosion based on potential difference.

Abstract: There is provided a perpendicular magnetic recording medium comprising a non-magnetic layer having a face-centered cubic structure, an antiferromagnetic layer provided on the non-magnetic layer, a soft magnetic underlayer provided on the antiferromagnetic layer, and a perpendicular recording layer provided on the soft magnetic underlayer, which magnetic recording medium makes it possible to realize a recording density not less than 50 Gb/in2 and makes the error rate thereof low while suppressing the spike noise.