According to one embodiment, a magnetic disk device includes a first disk having a first user data region and a first system area, a second disk having a second user data region and a second system area, a first head that writes data to the first disk, a second head that writes data to the second disk, a first actuator having the first head, a second actuator having the second head, a first controller that controls the first disk, the first head, and the first actuator, and a second controller that controls the second disk, the second head, and the second actuator, wherein the first controller records first information related to the first head and the first disk in the second system area.

According to one embodiment, a magnetic disk device includes a first disk having a first user data region and a first system area, a second disk having a second user data region and a second system area, a first head that writes data to the first disk, a second head that writes data to the second disk, a first actuator having the first head, a second actuator having the second head, a first controller that controls the first disk, the first head, and the first actuator, and a second controller that controls the second disk, the second head, and the second actuator, wherein the first controller records first information related to the first head and the first disk in the second system area.

An apparatus, according to one embodiment, includes a write transducer having: a bottom yoke, a top yoke, a nonmagnetic write gap positioned between the top and bottom yokes, a bottom pole extending from the bottom yoke toward the write gap, and a top pole extending from the top yoke toward the write gap. A width of a media facing side of the bottom pole is about the same as a width of a media facing side of the top pole. The media facing side of the bottom pole is aligned with the media facing side of the top pole along a thickness direction. A method, according to one embodiment, includes performing bidirectional writing to a magnetic recording tape using a write transducer as described above.

An apparatus, according to one embodiment, includes a write transducer having: a bottom yoke, a top yoke, a nonmagnetic write gap positioned between the top and bottom yokes, a bottom pole extending from the bottom yoke toward the write gap, and a top pole extending from the top yoke toward the write gap. A width of a media facing side of the bottom pole is about the same as a width of a media facing side of the top pole. The media facing side of the bottom pole is aligned with the media facing side of the top pole along a thickness direction. A method, according to one embodiment, includes performing bidirectional writing to a magnetic recording tape using a write transducer as described above.

According to one embodiment, a magnetic disk device includes a base that includes a bottom wall and side walls standing along a circumference of the bottom wall, a housing that includes a cover facing the bottom wall and closing the base, an actuator assembly that is housed inside the housing and is rotatable around a rotation axis, a head movably supported by the actuator assembly, a control circuit board provided outside of the housing, a first sensor disposed on the control circuit board, and a second sensor disposed inside the housing.

According to one embodiment, a monitoring unit of a magnetic disk device monitors a supply voltage supplied to a plurality of actuators by a first threshold value at which power supply by back electromotive force of a motor is started, and a second threshold value that is larger than the first threshold value. In a case where the supply voltage is lower than or equal to the second threshold value and is higher than the first threshold value, a controller interrupts execution of processing of reading/writing data to a magnetic disk in at least one of the actuators according to a predetermined condition based on execution status of the processing in the actuators.

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of data tracks, including a first data track and a second data track. In connection with writing to at least part of the first data track, a quality metric is measured for at least part of the first data track. In connection with writing to at least part of the second data track, a refresh metric is updated based on the write to at least part of second data track and the quality metric measured for the first data track, and at least the first data track is refreshed based on the refresh metric.

According to one embodiment, a magnetic disk device includes a first actuator which actuates a magnetic head portion including a magnetic head, a second actuator which adjusts a position of the magnetic head on a magnetic disk in a radial direction of the magnetic disk, and a control portion which determines a second measurement signal amplitude when a second transfer function is measured in accordance with a first gain estimated value of the second actuator and an amplitude of a first measurement signal amplitude to the second actuator applied when a first transfer function is measured, which calculates a second gain estimated value of the second actuator based on the first transfer function and the second transfer function, and which updates the first gain estimated value, using the calculated second gain estimated value.

The magnetic tape includes a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, in which the magnetic layer has a servo pattern, and an absolute value N of a difference between a refractive index Nxy measured regarding an in-plane direction of the magnetic layer and a refractive index Nz measured regarding a thickness direction of the magnetic layer is 0.25 to 0.40, a magnetic tape cartridge and a magnetic tape apparatus including this magnetic tape.

According to one embodiment, a magnetic disk device includes an actuator assembly including an actuator block including a rotatable bearing unit, a plurality of heads movably supported by the actuator assembly, a first sensor provided to the actuator block, and a second sensor provided at a position different from the first sensor.