The present disclosure generally relates to spin-orbit torque (SOT) device comprising a first bismuth antimony (BiSb) layer having a (001) orientation. The SOT device comprises a first BiSb layer having a (001) orientation and a second BiSb layer having a (012) orientation. The first BiSb layer having a (001) orientation is formed by depositing an amorphous material selected from the group consisting of: B, Al, Si, SiN, Mg, Ti, Sc, V, Cr, Mn, Y, Zr, Nb, AlN, C, Ge, and combinations thereof, on a substrate, exposing the amorphous material to form an amorphous oxide surface on the amorphous material, and depositing the first BiSb layer on the amorphous oxide surface. By utilizing a first BiSb layer having a (001) orientation and a second BiSb having a (012) orientation, the signal through the SOT device is balanced and optimized to match through both the first and second BiSb layers.

According to an embodiment, tracks on a magnetic disk each include a long-distance sector having a length in the circumferential direction covering two or more servo sectors. A controller executes an acquisition operation to acquire one or more evaluation amounts on the basis of a track pitch in each of the two or more servo sectors included in a portion adjacent to the long-distance sector. The controller executes a protection operation to protect data of an adjacent track in a case where a total value of the one or more evaluation amounts exceeds a first threshold value.

An apparatus includes a substrate. A laser is deposited above the substrate. The laser includes one or more non-self-supporting layers of crystalline material. The laser has a length along a light path in a range of about 40 um to about 350 um. An optical input coupler is configured to receive light from the laser. A waveguide is deposited proximate the optical input coupler. The waveguide is configured to communicate light from the laser via the optical input coupler to a near-field transducer that directs energy resulting from plasmonic excitation to a recording medium.

A data storage device may include one or more disks, an actuator arm assembly comprising one or more magnetic recording heads, a laser diode positioned inside a laser diode cavity, and one or more processing devices configured to initiate a write operation, wherein initiating the write operation comprises activating a magnetic recording head corresponding to the laser diode, and applying a forward bias to the laser diode; apply a first reverse bias to the laser diode during at least one intervening event; and transition from applying the first reverse bias to the at least one laser diode to applying the forward bias to the at least one laser diode.

A method involves forming a recording head that comprises a waveguide, a write pole, and a near-field transducer proximate the write pole. The near-field transducer has an extended portion extending towards a surface of the recording head and operable to direct plasmons to a recording medium. The surface of the recording head is lapped to form a lapped surface. A resist or hardmask is patterned on the lapped surface in a region that encompasses the extended portion. The lapped surface is etched with the resist or hardmask pattern to form a media-facing surface such that the extended portion protrudes beyond the media-facing surface by a first distance, and the resist or hardmask is removed.

A data storage device may include a media comprising a magnetic recording layer and a heat-assisted magnetic recording (HAMR) head for writing to the magnetic recording layer, the HAMR head comprising: a waveguide, a main pole comprising a main-pole surface facing the magnetic recording layer, a near-field transducer (NFT) situated between the main pole and the waveguide, and a transparent overcoat. The NFT comprises a main body and a micropillar. The micropillar comprises a micropillar surface facing the magnetic recording layer. A first distance between the micropillar surface and the media is less than a second distance between the main-pole surface and the media. The transparent overcoat is situated on the main-pole surface and the micropillar surface.

A data storage device may include a media comprising a magnetic recording layer and a heat-assisted magnetic recording (HAMR) head for writing to the magnetic recording layer, the HAMR head comprising: a waveguide, a main pole comprising a main-pole surface facing the magnetic recording layer, a near-field transducer (NFT) situated between the main pole and the waveguide, and a transparent overcoat. The NFT comprises a main body and a micropillar. The micropillar comprises a micropillar surface facing the magnetic recording layer. A first distance between the micropillar surface and the media is less than a second distance between the main-pole surface and the media. The transparent overcoat is situated on the main-pole surface and the micropillar surface.

A physical unclonable function (PUF) apparatus having magnetic particles is disclosed. The magnetic field data and the image view of the magnetic particles in the PUF apparatus are difficult to counterfeit. A PUF apparatus may be incorporated into a user-replaceable supply item for an imaging device. Further, a PUF reader may be incorporated into an imaging device to read the PUF. Other systems are disclosed.

An apparatus comprises a slider and an optical waveguide formed in the slider and configured to receive light from a laser source. A near-field transducer (NFT) is formed on the slider at or near an air bearing surface (ABS) of the slider and optically coupled to the waveguide. A bolometric sensor is positioned proximate the NFT and exposed to at least some of the light. The bolometric sensor is configured to detect changes in output optical power of the laser source and contact between the slider and a magnetic recording medium.

An apparatus and method provide for performing, using a heat-assisted magnetic recording head, multiple sequential writes to a recording medium, and recording a metric of write performance for each of the writes. The apparatus and method further provide for calculating fluctuations in the metric, detecting whether the head has a laser mode hopping problem using the metric fluctuations, and categorizing a severity of the laser mode hopping problem.