HAMR Near-Field Transducer Dithering for Smear Detection
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Solution Overview
Problem
The challenge in heat-assisted magnetic recording (HAMR) hard disk drives is the detection and mitigation of contamination, or 'smear', at the head-disk interface, which affects thermal and mechanical reliability and recording performance due to its nanoscale dimensions and high precision requirements, exceeding the precision of existing disk contact detection techniques.
Innovation Solution
A method involving a head slider with a near-field transducer (NFT) that applies an oscillating signal to a heat source to dither the spacing between the NFT and the disk, allowing for precise detection of contamination through changes in contact detection signals, and subsequent burnishing of contamination by bringing the slider into contact with the disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal fly height control systems are used for disk contact detection, then the system can maintain basic flying height control, but the measurement precision is insufficient to detect nanoscale contamination at the head-disk interface
Solution Approach 1:
The patent applies dithering (mechanical vibration) to the head-disk interface by oscillating the relative spacing between the NFT and disk at a specific frequency. This vibration modulates the contact detection signal in response to contamination presence, enabling precise nanoscale detection that exceeds the capability of static thermal fly height control systems alone.
Solution Approach 2:
The patent employs periodic oscillation of the head-disk spacing at a defined frequency to create a modulated contact detection signal. This periodic action transforms the static contact detection into a dynamic measurement that is highly sensitive to contamination, achieving the required measurement precision without proportionally increasing system complexity.
2Reliability
If the head slider is brought into contact with the disk to remove contamination, then contamination can be burnished off the slider, but the risk of damaging the NFT or disk surface increases
Solution Approach 1:
The patent performs preliminary detection of contamination using the dithering-based contact detection method before initiating any contact with the disk. This allows the system to identify contamination presence and initiate burnishing only when necessary, avoiding unnecessary contact that could damage the NFT or disk surface while ensuring contamination is removed when present.
Solution Approach 2:
The patent uses the modulated contact detection signal as feedback to determine both the presence of contamination and the appropriate timing for burnishing operations. The feedback mechanism allows the system to monitor the head-disk interface condition continuously and initiate contact-only when contamination is detected, thereby removing contamination while minimizing the risk of damage to the NFT or disk surface.
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 early detection and removal of contamination with precision on the order of a few hundred nanometers, preventing accumulation and maintaining recording performance by increasing the sensitivity of disk contact sensing techniques beyond existing thermal fly height control systems.
Implementation Method 1
applying an oscillating signal to a heat source associated with a HAMR near-field transducer (NFT) that is located in the slider to dither the spacing between the NFT and the disk
Implementation Method 2
applying an oscillating signal to a heat source associated with a HAMR near-field transducer (NFT) that is located in the slider to dither the spacing between the NFT and the disk
Implementation Method 3
determining, based on change to a contact detection signal, that contamination has accumulated on the slider
Data Source
AI summary
A procedure for detecting the presence of contamination at a head-disk interface in a heat- assisted magnetic recording (HAMR) hard disk drive involves flying a head slider over a magnetic-recording disk at a particular fly height, applying an oscillating signal to a heat source associated with a HAMR near-field transducer (NFT) that is located in the slider to dither the spacing between the NFT and the disk, and determining, based on change to a contact detection signal, that contamination has accumulated on the slider, generally, or on the NFT, specifically. Burnishing the contamination from the slider may then be performed, by bringing the slider into contact with the disk.