According to one embodiment, a magnetic disk device includes a disk having a first area, and a second area to which data is temporary written, a head including a write head which writes data to the disk, and an assisting element which generates energy which improves write performance of the write head, and a controller which writes data to the first area by supplying energy having a first value to the assisting element, and writes data to the second area by supplying energy having a second value different from the first value to the assisting element.

A recording head includes a channel waveguide that delivers light to a media-facing surface. A near-field transducer (NFT) is at an end of the channel waveguide and proximate to the media-facing surface. A laser including an active region has a longitudinal axis corresponding to a propagation direction of the channel waveguide. The active region includes a back facet and a front facet proximate the NFT. The front facet has a surface shape configured to suppress back reflection of the light.

A disk drive apparatus determines a pattern of bits of a data signal applied to a magnetic write transducer of a heat-assisted magnetic recording apparatus. The magnetic write transducer applies a magnetic field to a recording medium in response to the data signal. A laser power signal is applied to a laser that heats the recording medium while the magnetic field is applied. The laser power signal is modulated based on the pattern of bits. The modulation reduces differences between track widths of recorded marks having different elapsed time values and/or increases a signal-to-noise ratio of the recorded marks having different elapsed time values.

The magnetic recording medium disclosed in the present application includes a non-magnetic support, an undercoat layer, a magnetic layer containing magnetic particles, and a back coat layer. The coercive force Hc of the magnetic layer in the thickness direction at 25° C. is not 4100 oersteds (Oe) or more, and the coercive force Hc of the magnetic layer in the thickness direction at a temperature between 55° C. and 80° C. inclusive is not less than 1200 oersteds (Oe) and not more than 3700 oersteds (Oe).

The magnetic recording medium disclosed in the present application includes a non-magnetic support, an undercoat layer, a magnetic layer containing magnetic particles, and a back coat layer. The coercive force Hc of the magnetic layer in the thickness direction at 25° C. is not 4100 oersteds (Oe) or more, and the coercive force Hc of the magnetic layer in the thickness direction at a temperature between 55° C. and 80° C. inclusive is not less than 1200 oersteds (Oe) and not more than 3700 oersteds (Oe).

An apparatus includes a substrate. A laser is formed on a non-self supporting structure and bonded to the substrate. A waveguide having a gap portion is deposited proximate the laser. The waveguide is configured to communicate light from the laser to a near-field transducer (NFT) that directs energy resulting from plasmonic excitation to a recording medium. An optical isolator is disposed over the gap portion.

A laser beam is directed through a transmissive axicon telescope or a reflective axicon telescope such as in a magneto-optic Kerr effect metrology system. With the transmissive axicon telescope, a Gaussian beam profile is directed through a first axicon lens and a second axicon lens. The first axicon lens and second axicon lens transfer the Gaussian beam profile of the laser beam to a hollowed laser ring. The laser beam with a hollowed laser ring can be directed through a Schwarzschild reflective objective. With the reflective axicon telescope, the laser beam is directed through two conical mirrors that are fully reflective. One of the conical mirrors defines a central hole that the laser beam passes through.

A recording head includes a substrate, a read transducer, a waveguide core, and a near-field transducer at an end of the waveguide core proximate a media-facing surface. The recording head includes a magnetic write pole and coil. A laser diode unit with one or more non-self-supporting layers of crystalline material region is transfer printed between layers of the recording head.

An apparatus includes a substrate and a reader deposited on the substrate. A laser is formed on a non-self supporting structure and bonded to the substrate. A plurality of heat sink layers are deposited between the reader and the laser and configured to provide thermal coupling between the substrate and the laser and sink heat away from the laser. A waveguide is deposited proximate the laser. The waveguide is configured to communicate light from the laser to a near-field transducer that directs energy resulting from plasmonic excitation to a recording medium.

According to one embodiment, a magnetic disk device includes: a disk; a head including a main magnetic pole, a write shield that faces the main magnetic pole in a first direction and is separated from the main magnetic pole by a gap, a first assist element that is disposed in the gap and a second assist element that is disposed in the gap and is positioned relative to the first assist element in a second direction intersecting the first direction; and a controller configured to: cause a first assist energy from the first assist element to be applied to the disk and affect a coercive force of the disk; and cause a second assist energy from the second assist element to be applied to the disk and affect a coercive force of the disk, wherein the first assist energy is different from the second assist energy.