Near-field transducer thermal sensor write clock synchronization
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Solution Overview
Problem
In patterned-media thermal-assisted recording (TAR) disk drives, there is a need for an accurate method to detect data islands to generate a precise write-clock signal, ensuring accurate writing to the patterned data islands, as conventional methods lack synchronization with the precise locations of individual islands.
Innovation Solution
A near-field transducer (NFT) with a primary tip that concentrates oscillating charge to heat magnetic data islands and a secondary tip that forms a thermal probe to detect changes in optical power, used in conjunction with a temperature sensor and sensor circuitry to generate a write clock signal synchronized with the location of data islands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If patterned media with data islands are used to increase data density, then storage capacity is improved, but synchronization of write operations with island locations becomes necessary and complex
Solution Approach 1:
The patent employs a radiation detector that detects reflected radiation from data islands to generate a write-clock signal, creating a feedback mechanism that automatically synchronizes write operations with island positions. This feedback approach eliminates the need for complex external synchronization systems while maintaining precise writing alignment with the patterned media structure.
Solution Approach 2:
The system uses the reflected radiation from the data islands themselves to generate the synchronization signal, allowing the media structure to provide its own positioning information. This self-service approach converts the passive patterned media into an active participant in the synchronization process, reducing external control complexity.
2Manufacturing precision
If a radiation detector is used to detect data islands and generate write-clock signal, then writing accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The radiation detector serves multiple functions: it detects data island positions, generates the write-clock signal, and provides feedback for synchronization. This multi-functionality consolidates what could be separate complex subsystems into a single integrated component, improving writing accuracy while limiting the increase in overall device complexity.
Solution Approach 2:
Radiation acts as an intermediary between the data islands and the detection system, carrying positional information from the media to the detector. This intermediary approach allows indirect detection of island positions without requiring direct physical contact or complex sensing mechanisms at the media surface.
3Manufacturing precision
If the write head must be synchronized with individual island positions, then data writing precision is improved, but operation speed may be reduced due to synchronization requirements
Solution Approach 1:
The radiation detection and write-clock generation operate continuously as data islands pass beneath the detector, creating a continuous synchronization signal stream. This continuous operation eliminates gaps or interruptions in the writing process, maintaining high productivity while ensuring precise synchronization with each island position through the ongoing feedback mechanism.
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 solution allows for accurate synchronization of write pulses with the location of magnetic data islands, enabling precise writing on patterned media by detecting changes in optical power and surface topography, thereby enhancing data writing accuracy in patterned-media TAR disk drives.
Implementation Method 1
an oscillating charge in the NFT is concentrated at a primary tip of the NFT to create an intense near-field pattern that is directed onto a substrate
Implementation Method 2
The radiation heats the magnetic material locally to near or above its Curie temperature to lower the coercivity enough for writing to occur
Implementation Method 3
The secondary tip also concentrates the charge in the NFT to create an intense near-field pattern, but this heats the temperature sensor
Implementation Method 4
a secondary tip that forms part of a thermal probe. The secondary tip on the NFT detects the amplitude of the charge oscillation in the NFT
Implementation Method 5
The output signal from the sensor circuitry is directed to control circuitry and thus represents changes in dissipated optical power as islands and spaces pass the primary tip of the NFT
Data Source
AI summary
A near-field transducer (NFT) has a primary tip that concentrates the oscillating charge of the NFT onto a substrate, such as magnetic recording medium, to heat regions of the medium, and a secondary tip. The secondary tip is located close to a temperature sensor, such as an electrical conductor whose resistance varies with temperature. The temperature sensor senses heat from the secondary tip and thus properties of the substrate like surface topography and the presence or absence of metallic material. The NFT can be part of a bit-patterned media (BPM) thermally-assisted recording (TAR) disk drive. The temperature sensor output is used to control the write pulses from the disk drive's write head so the magnetic write field is synchronized with the location of the magnetic data islands.