According to one embodiment, a magnetic disk device includes a disk including a zone servo boundary area including a first area of a first servo frequency, a second area of a second servo frequency, and a third area of the first servo frequency, in a servo area, a head, and a controller demodulating first servo data of the first area to derive a position of the head and demodulating first corrected data of the third area to correct the position of the head. The first area, the second area, and the third area are aligned in order in a traveling direction. The first area and the second area are adjacent to each other in a circumferential direction of the disk. The second area and the third area are adjacent to each other in the circumferential direction.

According to one embodiment, there is provided a hard disk drive including a first recording surface, a second recording surface, a first magnetic head, a first actuator and a second actuator that move the first magnetic head, a second magnetic head, a third actuator and a fourth actuator that move the second magnetic head, a fifth actuator that moves the second actuator and the fourth actuator, a drive circuit that implements at least one of a first mode in which the second actuator and the fourth actuator operate differently from each other or a second mode in which the first and third actuators operate differently from each other, and a controller that controls the drive circuit.

The magnetic tape includes a magnetic layer having ferromagnetic powder and a binder on a non-magnetic support, in which a total thickness of the magnetic tape is equal to or smaller than 5.30 μm, the magnetic layer includes a timing-based servo pattern, a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, one or more components selected from the group consisting of fatty acid and fatty acid amide are included in the magnetic layer, and a C—H derived C concentration calculated from a C—H peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on the surface of the magnetic layer at a photoelectron take-off angle of 10 degrees is equal to or greater than 45 atom %.

The magnetic tape includes a non-magnetic support; a non-magnetic layer including non-magnetic powder and a binder on the non-magnetic support; and a magnetic layer including ferromagnetic powder and a binder on the non-magnetic layer, in which the total thickness of the non-magnetic layer and the magnetic layer is equal to or smaller than 0.60 μm, the magnetic layer includes a timing-based servo pattern, and logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050.

According to one embodiment, a magnetic disk device comprises a disk, a first head, a second head, a controller. The disk includes a first surface and a second surface different from the first surface. The first head carries out read and write of data from and to the first surface. The second head carries out read and write of data from and to the second surface. The controller adjusts a spiral speed of at least one of the first head and the second head according to a cylinder offset amount corresponding to a positional difference between the first head and the second head. The spiral speed is a speed at which spiral servo patterns are to be written.

Systems and methods are disclosed for phase locking of a clock. In some embodiments, a phase locked clock (PLC) module can phase-lock a write clock to a media written with multiple servo zones of different frequencies. In some implementations, this can be utilized to perform a self-servo write (SSW) of a disc surface within a hard disc drive (HDD). A PLC module can perform a method of writing with a single frequency phase coherently while a read element passes over servo zones with different frequencies. While the PLC module can perform such methods for a SSW process, the methods can also be utilized for other applications that can benefit from writing with a single frequency phase coherently based on servo zones with different frequencies.

A method for manufacturing a disk device includes the steps of measuring a first gain of a control signal of a fine motion actuator while positioning a head to a first radial position of a disk medium using a coarse motion actuator but not the fine motion actuator, based on an auxiliary servo pattern recorded on the disk medium, measuring a second gain of a control signal of the fine motion actuator while positioning the head to a second radial position of the disk medium using the coarse motion actuator but not the fine motion actuator, based on the auxiliary servo pattern recorded on the disk medium, and determining gain correction values which are to be applied to a control signal for the fine motion actuator while performing servo pattern writing on the disk medium, based on the first and second gains.

According to one embodiment, a magnetic disk device includes a disk including two first servo sectors and at least a second servo sector, a head, and a controller, wherein the first servo sector includes burst data and a first data pattern written before the circumferential direction of the burst data, the second servo sector includes the burst data, the first data pattern, and a second data pattern written after the circumferential direction of the burst data, a first frequency of the first data pattern is different from a second frequency of the second data pattern, and a first length of the first data pattern is different from a second length of the second data pattern.

This disclosure describes codes and techniques for magnetic recording. The coding schemes decrease bit error rates by decreasing total transitions in the encoded binary data compared to conventional codes. Additionally, instead of relying on a single coding scheme, an encoder and decoder are configured to switch between different coding schemes. By so doing, a variety of the coding schemes allows the encoded binary data to have a smaller bit error rate than a single coding scheme and have a maximum run-length less than or equal to a maximum run-length limitation of a magnetic disk.

A method for writing servo data includes writing servo data as a head moves outward on a disk one step at a time, so as to overwrite part of servo data that have been written in a previous step, writing servo data as the head moves inward on the disk one step at a time, so as to overwrite part of servo data that have been written in a previous step, and writing one of two-phase burst data, or address data and the other of said two-phase burst data, at the radial position, so as to overwrite at least part of servo data written in each last step of the writings as the head moves outward and inward. The same address data are written in two consecutive steps as the head moves outward and as the head moves inward.