Christopher B. Wolf

Effect of Carbon Overcoat on Heat-Assisted Magnetic Recording Performance

Heat-assisted magnetic recording (HAMR) is a promising approach for enabling large increases in the magnetic data storage density. Amorphous carbon is the principal overcoat material of thin-film disks and magnetic heads in the HAMR systems. In this paper, we investigated the recording performance of media with a chemical vapor deposition (CVD) carbon overcoat (COC) and a sputtered COC. We observed that the carbon type has a significant impact on the HAMR recording performance and the heat absorption. Tunneling current atomic force microscopy analysis results show higher surface roughness and peak current in the disk with the sputtered carbon. Track profile and magnetic signal measurement results indicate 90% of the optimized laser current is not enough to fully write the disk with the CVD carbon, while the tracks on the sputtered carbon disk can be written using the same laser current. The difference in the two types of COC can be attributed to the difference in the carbon bonding structure, the optical and electrical properties, the roughness, and the heat absorption behavior.

Optical and thermal analysis of the light-heat conversion process employing an antenna-based hybrid plasmonic waveguide for HAMR

We investigate a tapered, hybrid plasmonic waveguide which has previously been proposed as an optically efficient near-field transducer (NFT), or component thereof, in several devices which aim to exploit nanofocused light. We numerically analyze how light is transported through the waveguide and ultimately focused via effective-mode coupling and taper optimization. Crucial dimensional parameters in this optimization process are identified that are not only necessary to achieve maximum optical throughput, but also optimum thermal performance with specific application towards heat-assisted magnetic recording (HAMR). It is shown that existing devices constructed on similar waveguides may benefit from a heat spreader to avoid deformation of the plasmonic element which we achieve with no cost to the optical efficiency. For HAMR, our design is able to surpass many industry requirements in regard to both optical and thermal efficiency using pertinent figure of merits like 8.5% optical efficiency.