Non-Rectangular Pin Cross Section Near Field Transducer
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Solution Overview
Problem
Conventional energy-assisted magnetic recording (EAMR) systems face challenges in achieving higher areal storage density due to thermal instability of magnetic grains and limitations in scaling down near field transducers (NFTs), leading to larger thermal spots and curvature issues that affect track density and signal-to-noise ratio (SNR).
Innovation Solution
A near field transducer (NFT) with a non-rectangular pin cross section, specifically a trapezoidal or triangular shape, is used in conjunction with an insulator layer between the pin section and the write pole, preventing skin-depth penetration and reducing curvature, thereby improving the trailing edge of the thermal spot and enhancing thermal gradient for more efficient writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the pin width of the NFT is reduced to achieve smaller optical spot for higher areal density, then the optical spot size is reduced, but the fabrication becomes increasingly challenging and the pin width becomes vanishingly small
Solution Approach 1:
The patent applies asymmetry by changing the pin cross-section from a conventional rectangular shape to a triangular shape. This asymmetric geometry allows the pin to achieve a smaller effective width at the distal end (facing the recording media) while maintaining structural integrity and manufacturability. The triangular cross-section with apex angle of 60-120 degrees enables the pin to be tapered, providing a larger base width for fabrication stability while achieving a smaller tip width for high areal density operation.
2Ease of manufacture
If a conventional rectangular pin cross section is used, then fabrication is easier, but the trailing edge of the thermal spot has high curvature which limits track density due to SNR degradation
Solution Approach 1:
The triangular cross-section creates an asymmetric heat distribution pattern that naturally produces a flatter trailing edge thermal profile compared to the symmetric rectangular cross-section. This geometric asymmetry transforms the heat diffusion pattern, reducing the curvature at the trailing edge and improving track density without sacrificing fabrication ease.
Solution Approach 2:
The patent applies local quality by designing the pin with a specific triangular cross-section that optimizes heat distribution in the trailing edge region. The apex angle of 60-120 degrees is specifically chosen to control the local heat diffusion characteristics, ensuring that the trailing edge maintains a flatter profile while the overall pin structure remains manufacturable.
3Stability of the object's composition
If magnetic anisotropy is increased to improve thermal stability of magnetic grains, then thermal stability is improved, but coercivity increases requiring stronger magnetic field for writing
Solution Approach 1:
The patent utilizes phase transitions by employing energy-assisted magnetic recording (EAMR) where a laser heats the recording media to transition the magnetic grains from a high-coercivity state to a low-coercivity state during the write operation. The NFT with triangular pin cross-section concentrates optical energy to create a localized thermal field that temporarily reduces coercivity, allowing magnetic field writing, followed by rapid cooling that stabilizes the written state with high thermal stability.
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
The non-rectangular pin cross section NFT arrangement results in a flatter trailing edge, improved thermal gradient, and better track performance with reduced curvature, enabling higher areal storage density and improved skew angle track performance.
Implementation Method 1
The coupled light is then routed to a near field transducer (NFT) by which the optical energy is provided to a small optical spot on the recording media a few tens of nanometers (nm) in size. The optical energy provided to the small optical spot generates a thermal spot in the recording media.
Implementation Method 2
The non-rectangular pin cross section NFT arrangement results in a flatter trailing edge, improved thermal gradient, and better track performance with reduced curvature
Data Source
AI summary
A near field transducer (NFT) for use in an energy assisted magnetic recording (EAMR) head and configured to direct energy to a recording media is disclosed. The NFT comprises a disk section; and a pin section extending towards an air bearing surface (ABS) from the disk section. The pin section has a proximal end adjoining the disk section and a distal end opposite to the proximal end and facing the ABS, wherein the distal end of the pin section has a non-rectangular cross section in a plane parallel to the ABS and the proximal end of the pin section has a rectangular cross section in the plane parallel to the ABS.