Multilayer Near Field Transducer Thermal Stability

The patent applies composite materials by constructing the NFT with multiple distinct material layers: a tungsten peg providing thermal stability, a rhodium intermediate layer enhancing adhesion, and a gold disc maintaining plasmonic properties. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both thermal stability and adhesion without using a single complex material.

The patent segments the NFT into functionally distinct components: the peg (tungsten), the intermediate layer (rhodium), and the disc (gold). Each segment performs a specific function - the peg provides thermal anchor, the intermediate layer provides adhesion, and the disc provides plasmonic activity. This segmentation allows optimization of each component independently, achieving overall reliability without requiring a single complex material.

The patent introduces a rhodium intermediate layer between the tungsten peg and gold disc. This intermediary layer serves as a buffer that prevents direct thermal stress and material migration between the two main components under high-power laser irradiation, thereby maintaining NFT integrity while enabling high-power operation.

The patent converts the harmful thermal effects of high-power lasers into a beneficial thermal management strategy. The tungsten peg acts as a thermal anchor that conducts heat away from the plasmonic disc, while the rhodium intermediate layer prevents thermal degradation. The high temperature that would normally cause degradation is instead managed through the thermal properties of the composite structure.

The patent changes the material parameters of the NFT components to withstand high-temperature operation. Tungsten is selected for the peg due to its high melting point and thermal stability, rhodium is chosen for its adhesion properties at elevated temperatures, and gold is used for the disc to maintain plasmonic functionality. These parameter changes enable the NFT to maintain adhesion and functionality at HAMR operating temperatures.

The composite structure combines materials with complementary high-temperature properties: tungsten provides thermal stability, rhodium provides adhesion at elevated temperatures, and gold provides plasmonic activity. This composite approach allows the NFT to achieve both high-temperature operation and extended service life by distributing the thermal stress across materials optimized for different functions.