According to one embodiment, a magnetic disk includes a disk, first and second heads which write data to the disk and read data from the disk, a first actuator includes the first head, a second actuator includes the second head, first and second controllers which control the first head, the second head, the first actuator and the second actuator, an auxiliary power supply which supplies power when power from a power supply is shut off, and a power supply detection unit which makes power supplied from the auxiliary power supply to the first controller higher than the power supplied from the auxiliary power supply to the second controller when shutoff of power from the power supply is detected.

According to one embodiment, a magnetic disk includes a disk, first and second heads which write data to the disk and read data from the disk, a first actuator includes the first head, a second actuator includes the second head, first and second controllers which control the first head, the second head, the first actuator and the second actuator, an auxiliary power supply which supplies power when power from a power supply is shut off, and a power supply detection unit which makes power supplied from the auxiliary power supply to the first controller higher than the power supplied from the auxiliary power supply to the second controller when shutoff of power from the power supply is detected.

A data storage device is disclosed comprising a head actuated over an energy assisted magnetic media comprising a plurality of data tracks, wherein each data track comprises a plurality of data sectors. A write operation to a first data sector is executed by applying a first current to a write coil of the head while the head is over a second data sector preceding the first data sector, wherein the first current comprises a first amplitude. A second current is applied to the write coil while the head is over the first data sector, wherein the second current comprises a second amplitude lower than the first amplitude.

A data storage device is disclosed comprising a head actuated over an energy assisted magnetic media comprising a plurality of data tracks, wherein each data track comprises a plurality of data sectors. A write operation to a first data sector is executed by applying a first current to a write coil of the head while the head is over a second data sector preceding the first data sector, wherein the first current comprises a first amplitude. A second current is applied to the write coil while the head is over the first data sector, wherein the second current comprises a second amplitude lower than the first amplitude.

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, 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.

Illustrative aspects are directed to a data storage device comprising one or more disks; an actuator mechanism comprising one or more heads, and configured to position a head proximate to a disk surface; and one or more processing devices. The one or more processing devices are configured to: measure a read quality of a location on the disk surface; modify a refresh frequency for performing refresh writes at the location, based on the read quality at the location; in response to the refresh frequency at the location becoming stabilized, determine an integrated track interference (xTI) per write metric at the location; and, in response to determining that the xTI per write metric at the location is below a threshold for the xTI per write metric, modify an operating parameter of the head at the location to improve a longevity metric.

The present disclosure generally relates to using a data timestamp and/or a read counter to prevent data from being re-read and signal that the data has been accessed. The write assist element in the write head can be utilized to degrade the data or an allocated marker after the data has been read. The degradation functions as a read counter to indicate how many times the data has been read. Additionally and/or alternatively, a timestamp can be utilized. The timestamp is updated each time that the data has been accessed. In so doing, it is possible to determine whether data in a data storage device has been accessed.

A waveguide includes a core and a cladding. The core has an inlet on which light is incident. The core includes a front portion and a rear portion located between the front portion and the inlet. The front portion and the rear portion each have a thickness that is a dimension in a first direction and a width that is a dimension in a second direction. The first direction is orthogonal to a propagation direction of the light. The second direction is orthogonal to the propagation direction of the light and the first direction. The thickness of the front portion decreases with increasing distance from the inlet.

A waveguide includes a core and a cladding. The core has an inlet on which light is incident. The core includes a front portion and a rear portion located between the front portion and the inlet. The front portion and the rear portion each have a thickness that is a dimension in a first direction and a width that is a dimension in a second direction. The first direction is orthogonal to a propagation direction of the light. The second direction is orthogonal to the propagation direction of the light and the first direction. The thickness of the front portion decreases with increasing distance from the inlet.