According to one embodiment, a disk device includes a disk-shaped recording medium, a base accommodating the recording medium, the base including a bottom wall, a sidewall on a peripheral portion of the bottom wall, and a rib on a part of an upper surface of the sidewall, a first cover on a part of the upper surface of the sidewall, and a second cover on a first surface of the rib and above the first cover. The rib includes a first region with a first width, a second region with a second width less than the first width, and the first surface with a fixed width around an entire circumference of the rib. The first region and the second region are located corresponding to a side portion of the recording medium.

According to one embodiment, a disk device includes two magnetic disks opposing each other at intervals of 1.2 to 1.5 mm, and at least two suspension assemblies movable respectively between the two magnetic disks. Each of the suspension assemblies includes a base plate, a load beam extending from the base plate, a tab extending from a distal end of the load beam, a wiring member on the load beam and the base plate, including a gimbal portion, and a magnetic head on the gimbal portion, abutting on a dimple of the load beam via the gimbal portion. The ratio of a distance from a bendable location of the load beam to a center of the dimple with respect to a distance from the center of the dimple to a tip of the tab is 2.8 to 3.8.

According to one embodiment, a disk device includes a disk-shaped recording medium, a base accommodating the recording medium, the base including a bottom wall, a sidewall on a peripheral portion of the bottom wall, and a rib on a part of an upper surface of the sidewall, a first cover on a part of the upper surface of the sidewall, and a second cover on a first surface of the rib and above the first cover. The rib includes a first region with a first width, a second region with a second width less than the first width, and the first surface with a fixed width around an entire circumference of the rib. The first region and the second region are located corresponding to a side portion of the recording medium.

Embodiments provide a polishing composition for a magnetic disk substrate containing colloidal silica, a water-soluble polymer, and water. The water-soluble polymer compound is a copolymer containing a monomer having a carboxylic acid group, a monomer having an amide group, and a monomer having a sulfonic acid group as essential monomers. The water-soluble polymer compound has a weight average molecular weight of 1,000 to 1,000,000.

According to one embodiment, a disk device includes a disk-shaped recording medium, a base accommodating the recording medium, the base including a bottom wall, a sidewall on a peripheral portion of the bottom wall, and a rib on a part of an upper surface of the sidewall, a first cover on a part of the upper surface of the sidewall, and a second cover on a first surface of the rib and above the first cover. The rib includes a first region with a first width, a second region with a second width less than the first width, and the first surface with a fixed width around an entire circumference of the rib. The first region and the second region are located corresponding to a side portion of the recording medium.

Embodiments relate to a polishing composition is an aqueous composition containing at least colloidal silica, wet-process silica particles, and a water-soluble polymer compound. The water-soluble polymer compound is a copolymer containing a monomer having a carboxylic acid group, a monomer having an amide group, and a monomer having a sulfonic acid group as essential monomers.

According to one embodiment, a disk device includes two magnetic disks opposing each other at intervals of 1.2 to 1.5 mm, and at least two suspension assemblies movable respectively between the two magnetic disks. Each of the suspension assemblies includes a base plate, a load beam extending from the base plate, a tab extending from a distal end of the load beam, a wiring member on the load beam and the base plate, including a gimbal portion, and a magnetic head on the gimbal portion, abutting on a dimple of the load beam via the gimbal portion. The ratio of a distance from a bendable location of the load beam to a center of the dimple with respect to a distance from the center of the dimple to a tip of the tab is 2.8 to 3.8.

An apparatus includes a plurality of storage media mounted on a rotatable spindle. The apparatus also includes an actuator with at least one actuator arm configured to translate among the plurality of storage media and at least two heads supported on the at least one actuator arm. Each of the at least two heads is configured to communicate with the plurality of storage media.

A magnetic disk device includes a disk, a head configured to write data on the disk based on a write current, and a controller configured to determine whether a write error occurs when data is written on the disk, based on a change in a heating value of the head, and upon determining that the write error occurs, read the data written on the disk.

A pattern is pre-written using a pre-erase or pre-conditioning magnetic field applied within at least part of a target track of a hard disk via a first write transducer prior to the target track being written. Subsequent to the pre-writing, target user data is written to the part of the target track.