Abstract: Disclosed herein is a magnetic head including a main magnetic pole and a return yoke. The magnetic head can suppress a side writing at an edge of the return yoke even if the soft magnetic layer of a disk is saturated. The magnetic head further includes a single-pole type head that is used as write head.

Abstract: A disk drive having a magnetic shield which can avoid effect of an external magnetic field is disclosed. The drive comprises a housing which contains a disk drive mechanism including a head and a disk medium. The housing has a structure wherein a tape-like or foil-like magnetic shield member is provided to shield an external magnetic field, in particular, in the vicinity of the head. The magnetic shield member is wound around the housing so as to cover each partial region of an upper surface facing a movement range of the head on the disk medium, lower surface and side surfaces.

Abstract: A servo track write method is disclosed in which, in a disk drive of a perpendicular magnetic recording system, servo data is written with the use of a single magnetic pole type head of the disk drive itself. In this method, the servo data is recorded on a disk in those servo areas with the use of the single magnetic hole type head mounted on the disk drive. A head mounted as the single magnetic pole type head is position-controlled relative to the servo area by a servo track writer. The servo data is recorded with perpendicular magnetization under a recording magnetic field from the single magnetic pole type head in accordance with the magnetic pole thickness of the single magnetic pole type head.

Abstract: There is disclosed a disk drives of the perpendicular magnetic recording system capable of using a data channel of the longitudinal magnetic recording system. The drive has a preamplifier including a differentiation circuit which differentiates a read signal output from a read head. The preamplifier includes an adjusting circuit which adjusts low cut-off frequency for restricting waveform deformation of a read signal of rectangular waveform, as a front stage of the differentiation circuit.

Abstract: In a data recording system used for a magnetic disk drive, a write amplifier feeds a write head with a recording current that corresponds to the data to be recorded on the disk. A recording current controller selects a current value to be fed to the write head from the write amplifier according to the recording pattern detected by a pattern detection circuit. Thus, an effective recording track width can be selected without relying on the recording wavelength of the data to be recorded. Therefore, the influence of the cross talk from adjacently located tracks can be effectively reduced without unnecessarily reducing the recording track width.

Abstract: In a self-servo writing mode, parameters such as a moving amount of a head, a time delay and the like are measured and detected by using preservo information recorded beforehand on, for instance, an outermost periphery of a disk. In accordance with the detected parameters, the head is positioned in a predetermined radial position on the disk and virtual servo information and servo information are written. Then, in accordance with at least either the virtual servo information or the servo information, the head is positioned in a next predetermined radial position and the virtual servo information and the servo information are written. After writing on a full surface of the disk is completed, a normal mode is switched ON and writing/reading of data via the head can be performed.