Near Field Transducer Thermal Protrusion Compensation
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Solution Overview
Problem
In energy-assisted magnetic recording (EAMR) heads, near field transducers (NFTs) experience heat-induced protrusion due to inefficient optical energy conversion, leading to potential damage and reduced reliability.
Innovation Solution
An iterative heat-and-remove process is employed to modify the air-bearing surface (ABS) of the EAMR head, where increasing levels of optical power are applied to the NFT to generate heat and subsequently remove the resulting protrusions, creating a smooth, concave surface that compensates for heat-induced distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If optical power is applied to the near field transducer to concentrate energy for magnetic writing, then the magnetic writing capability is improved, but heat-induced protrusion of the NFT occurs leading to potential damage
Solution Approach 1:
The air-bearing surface is pre-modified with a recessed region before the NFT is installed or before operational heating occurs. This preliminary geometric modification creates a compensation structure that anticipates and counteracts the thermal protrusion that will occur during operation, allowing the NFT to maintain proper positioning despite heat-induced expansion
Solution Approach 2:
A recessed region is created in the air-bearing surface that provides a compensatory depression. This preliminary anti-action structure is designed to offset the protrusion caused by thermal heating, creating a balance where the recess compensates for the expected thermal expansion and maintains the NFT at the correct height above the medium
2Quantity of substance
If optical power is applied to the near field transducer to heat the magnetic medium, then the areal storage density is increased, but thermal protrusion of surrounding materials occurs
Solution Approach 1:
The air-bearing surface is modified with a localized recessed region specifically positioned around the NFT. This local geometric modification concentrates the compensation effect precisely where thermal protrusion occurs, without affecting other regions of the air-bearing surface. The recessed region has specific dimensional characteristics (depth and width) tailored to counteract the localized thermal expansion of the NFT and surrounding materials
3Loss of energy
If the NFT is positioned close to the air bearing surface for efficient energy transfer, then the optical conversion efficiency is improved, but heat-related protrusion and damage risk increase
Solution Approach 1:
The geometric parameters of the air-bearing surface are modified by creating a recessed region with specific depth and width dimensions. This parameter change allows the NFT to be positioned closer to the medium for efficient energy transfer while the recessed geometry compensates for thermal protrusion, maintaining the optimal gap distance despite thermal expansion during operation
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 method enhances the reliability of EAMR heads by preventing damage from heat-induced protrusions and maintaining a smooth, efficient optical path, ensuring consistent performance and increased areal storage density.
Implementation Method 1
a near field transducer (NFT) is used to concentrate optical energy in the near field to dimensions much smaller than the diffraction limit would otherwise allow
Implementation Method 2
a small spot where data is to be written is locally heated to reduce the coercivity of the magnetic grains therein
Implementation Method 3
some of the optical energy provided on the NFT is absorbed by the materials near an air-bearing surface (ABS) surrounding the NFT, and heat-related protrusion and of the NFT and the surrounding materials may occur
Data Source
AI summary
An energy assisted magnetic recording head comprises a slider having a leading edge, a trailing edge, and an air bearing surface (ABS), and a near field transducer (NFT) disposed in the slider and having a distal end proximate the ABS. The distal end is recessed from the ABS when no optical power is applied to the NFT, and is co-planar with the ABS when a predetermined amount of optical power is applied to the NFT. A portion of the slider surrounding the distal end forms a concave surface having a continuously varying slope when no optical power is applied to the NFT, and a flat surface coplanar with the ABS and the distal end when the predetermined amount of optical power is applied to the NFT. Applying optical power comprises coupling light into a waveguide formed in the head and directing the coupled light to the NFT via the waveguide.