Dual Waveguide Near Field Transducer for HAMR
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Solution Overview
Problem
As data density increases and data bits become smaller and more densely packed, they become thermally unstable and prone to demagnetization in conventional magnetic recording, requiring higher magnetic fields and more magnetically stiff media, which is challenging due to the reduced strength of the magnetic field from smaller write poles.
Innovation Solution
The use of a near field transducer (NFT) with a plasmonic antenna excited by two phase-shifted optical waveguides in heat assisted magnetic recording (HAMR), which locally heats the media to temporarily lower its magnetic anisotropy, allowing for recording with weaker magnetic fields and ensuring data stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data bits are made smaller and packed closer together to increase data density, then data storage capacity is improved, but thermal stability deteriorates and demagnetization becomes more prone
Solution Approach 1:
The patent changes the temperature parameter of the magnetic media by using a near field transducer to locally heat the media. This temporary temperature increase reduces the magnetic anisotropy energy barrier, allowing smaller data bits to be written without immediate demagnetization. After writing, the media cools and the anisotropy increases, freezing the magnetic state and ensuring thermal stability.
Solution Approach 2:
The patent applies preliminary heating to the magnetic media before the write operation. By pre-heating the media with the near field transducer, the magnetic anisotropy is reduced in advance, creating a window of opportunity where weaker magnetic fields from smaller write poles can successfully write data bits that would otherwise be too small to stabilize.
2Reliability
If magnetic media is made more magnetically stiff with higher magnetic anisotropy to prevent demagnetization, then thermal stability is improved, but the required recording magnetic field strength increases
Solution Approach 1:
The patent dynamically changes the temperature parameter of the media during the write operation. By heating the media locally, the magnetic anisotropy is temporarily reduced, allowing recording with weaker magnetic fields. After writing, the media cools and regains its high anisotropy, ensuring thermal stability of the recorded data.
Solution Approach 2:
The patent applies preliminary heating to reduce magnetic anisotropy before the write operation. This preliminary action creates a temporary state where the media is more susceptible to magnetic field writing, enabling the use of smaller write poles that would otherwise be insufficient for writing to high-anisotropy media.
3Quantity of substance
If write pole size is reduced to record smaller data bits, then data density is improved, but the strength of the magnetic field delivered to the disk decreases
Solution Approach 1:
The patent changes the temperature parameter of the media to reduce magnetic anisotropy during the write operation. This allows smaller write poles to generate sufficient magnetic field strength to write data bits, because the reduced anisotropy lowers the energy barrier that would otherwise require stronger fields to overcome.
Solution Approach 2:
The patent applies preliminary heating through the near field transducer to reduce magnetic anisotropy before the write operation. This enables smaller write poles to effectively write data by creating a temporary window where the reduced anisotropy allows weaker magnetic fields to successfully magnetize the media.
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 approach enables efficient recording of smaller data bits by delivering focused energy to the media, enhancing data stability and density without the need for stronger magnetic fields, while maintaining thermal reliability of the transducer.
Implementation Method 1
exciting a symmetric surface plasmon distribution on the NFT that constructively interferes as it is focused and delivered to the media
Implementation Method 2
locally heating the media through the use of a near field transducer (NFT) just at the location on the disk that is to be recorded
Implementation Method 3
One of these waveguides can be passed through an optical phase shifter, which can be as simple as a relative path-length difference between the two waveguides
Data Source
AI summary
A near field transducer (NFT) for heat assisted magnetic recording (HAMR) having a dual waveguide excitation system located adjacent to opposite sides of a plasmonic antenna. The light to one of the waveguides can be passed through a phase shifter so that its electric field is 180 degrees out of phase with that of the other waveguide. In this way, the energy from each of the waveguides can be delivered to the plasmonic antenna in an additive manner while heat-sinking schemes can be implemented in the orthogonal direction for greatly improving the optical efficiency and thermal stability of the NFT.