Compositionally Graded NFT Antenna for HAMR Thermal Stability
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Solution Overview
Problem
In magnetic disk devices employing heat-assisted magnetic recording (HAMR) heads, near-field transducers (NFTs) made of gold face deformation issues due to high temperatures, and using alloys can counteract benefits with increased temperature and reduced thermal conductivity.
Innovation Solution
The NFT antenna is composed of a compound with a varying composition based on location, with the highest additive material concentration at the apex to enhance thermal stability and minimize temperature, achieved through the use of a primal material and additive materials like Au and Rh, with the additive material distribution gradient optimizing thermal conductivity and refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If gold is used for the NFT material to achieve high optical efficiency, then optical efficiency is improved, but the NFT deforms due to low melting point and atomic diffusion at high temperatures
Solution Approach 1:
The patent applies local quality by creating a compositionally graded structure where the NFT material has different compositions at different locations. The region near the apex (highest temperature) contains higher concentration of thermally stable alloying elements, while other regions have different compositions optimized for optical efficiency. This spatial variation in material composition allows each region to be optimized for its specific functional requirements.
Solution Approach 2:
The patent uses composite materials by combining gold with other metals (such as Cu, Ag, Al, Ni, Co, Pt, Pd, Rh, Ir, Ru, Mo, W, Ti, B, Hf, Ta, or Nb) to create an alloy NFT material. The composite structure provides both the optical efficiency of gold and the thermal stability of the alloying elements, resolving the contradiction between optical performance and thermal stability.
2Reliability
If an alloy is used for the NFT material to improve thermal stability, then reliability is improved, but the NFT temperature increases due to increased light absorption and reduced thermal conductivity
Solution Approach 1:
The patent applies local quality by creating a compositionally graded structure where the NFT material has different compositions at different locations. The region near the apex (highest temperature) contains higher concentration of thermally stable alloying elements, while other regions have different compositions optimized for optical efficiency. This spatial variation in material composition allows each region to be optimized for its specific functional requirements.
Solution Approach 2:
The patent uses parameter changes by varying the composition of the NFT material along its length, specifically changing the concentration of alloying elements as a function of position. This continuous parameter change allows optimization of both thermal stability and thermal conductivity properties at different locations within the NFT structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This compositionally graded approach improves the reliability of HAMR heads by maintaining thermal stability while minimizing temperature rise, balancing thermal conductivity and refractive index, thus addressing deformation and efficiency challenges.
Implementation Method 1
a near-field transducer (NFT) may be utilized to locally heat magnetic media
Implementation Method 2
the imaginary part of the dielectric constant is large, and more light is absorbed by the NFT
Implementation Method 3
the thermal conductivity of the NFT is lowered due to phonon scattering by dopant atoms, and the heat flow inside the NFT is reduced
Implementation Method 4
a near-field transducer (NFT) may be utilized to locally heat magnetic media having high coercivity during recording to lower the coercivity of the localized region
Data Source
AI summary
Embodiments disclosed herein generally relate to a HAMR head. The HAMR head includes a main pole, a waveguide and a NFT disposed between the main pole and the waveguide. The NFT includes an antenna, and the antenna is made of a compound that has a composition that varies based on the location within the antenna. In one embodiment, the antenna has a surface at a media facing surface (MFS) and the surface has an apex, and the composition of the compound varies from the apex in a direction away from the apex. The apex has the highest temperature during the operation of the HAMR head, and having a composition that is thermally stable at the apex helps achieve higher reliability.