According to an embodiment, a manufacturing method includes: estimating a distribution of an initial value of a clearance of a magnetic head on a first recording surface; and recording first spiral signals on the first recording surface while controlling a clearance using the distribution of the initial value of the estimated clearance. The manufacturing method includes measuring a distribution of an initial value of a clearance of a magnetic head on a second recording surface under positioning control using the first spiral signals recorded on the first recording surface. The manufacturing method includes recording the first spiral signals on the second recording surface while controlling a clearance using the distribution of the initial value of the measured clearance of the magnetic head on the second recording surface. The manufacturing method includes recording the second spiral signals on a third recording surface under positioning control using the first spiral signals recorded on the second recording surface.

A data storage device is disclosed comprising a head actuated over a disk. A spiral track is written on the disk, and a disk locked clock (DLC) is synchronized to the spiral track. The spiral track is read to generate a spiral track crossing signal, and the spiral track crossing signal is processed to generate a position error signal (PES) representing a position of the head over the disk. When the DLC indicates a first part of the spiral track crossing signal is corrupt, the corruption is compensated in order to generate a compensated PES. While servoing the head over the disk based on the PES, a plurality of concentric servo sectors are written on the disk based on the DLC.

Various illustrative aspects are directed to a data storage device, comprising: one or more disks; an actuator assembly comprising a head, and configured to position the head over a corresponding disk surface; and one or more processing devices, the head comprising: a write element; a laser unit; and a fly height control element, and wherein the one or more processing devices are configured to: iteratively perform spiral write operations of spiral patterns comprising a plurality of sync marks with the head on the corresponding disk surface, wherein the spiral write operations are performed at: a plurality of values of laser pre-bias current, write backoff, and/or start disk phase; detect pattern signal amplitudes of the spiral patterns on the corresponding disk surface; and determine a relation of write backoff to laser pre-bias current for the head, based on the pattern signal amplitudes of the spiral patterns.

A method for writing servo information in a disk drive that includes a write head and one or more recording surfaces includes: writing a first portion of a first spiral with the write head on a first recording surface of the one or more recording surfaces while controlling a radial position of the write head with a controller that is configured with a first set of controller parameter values; after the read head crosses a second spiral formed on a second recording surface of the one or more recording surfaces, determining a radial position error for the write head based on information associated with the second spiral; and in response to the radial position error exceeding a disturbance threshold value, writing a second portion of the first spiral with the write head while controlling the radial position of the write head with the controller while the controller is configured with a second set of controller parameter values.

According to an embodiment, a manufacturing method includes: estimating a distribution of an initial value of a clearance of a magnetic head on a first recording surface; and recording first spiral signals on the first recording surface while controlling a clearance using the distribution of the initial value of the estimated clearance. The manufacturing method includes measuring a distribution of an initial value of a clearance of a magnetic head on a second recording surface under positioning control using the first spiral signals recorded on the first recording surface. The manufacturing method includes recording the first spiral signals on the second recording surface while controlling a clearance using the distribution of the initial value of the measured clearance of the magnetic head on the second recording surface. The manufacturing method includes recording the second spiral signals on a third recording surface under positioning control using the first spiral signals recorded on the second recording surface.

A magnetic disk device includes a disk, first and second heads, a motor, and a controller. The disk includes a first surface and a second surface opposite to the first surface. The first head is configured to perform reading and writing with respect to the first surface. The second head is configured to perform reading and writing with respect to the second surface. The motor is configured to move the first and second heads with respect to the first and second surfaces, respectively, along a radial direction of the disk. The controller is configured to alternately activate the first and second heads to perform writing of a plurality of spiral patterns on the first and second surfaces of the disk, respectively, while controlling the motor to move the first and second heads at a predetermined constant speed with respect to the first and second surfaces in the radial direction.

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 reference spiral is written on a recording surface of a hard disk drive. By launching writing of fine guide spirals from a launch point that is disposed on a pre-existing coarse guide spiral, writing of the fine guide spiral can be launched in response to a write head crossing the pre-existing coarse guide spiral, rather than in response to a precisely timed event. To enable launch points being disposed on pre-existing coarse guide spirals, launch points are not all located at the same radial position on the recording surface.

A method for positioning a magnetic head having first and second read sensors and one write head includes: while the magnetic head is at a first position relative to a disk medium, reading first magnetic servo information written on a first surface of the disk medium, with the first read sensor, and reading second magnetic servo information written on the first surface of the disk medium with the second read sensor; determining a position error of the magnetic head based on the first and second magnetic servo information; and repositioning the magnetic head to a second position relative to the disk medium to compensate for the determined position error of the magnetic head.