HAMR Disk Drive Laser Stabilization Gap Optimization
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Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) disk drives, the time required for laser power stabilization exceeds the gap length between data sectors, leading to a significant loss of disk real estate due to the need for longer gaps to accommodate stabilization, which reduces storage capacity.
Innovation Solution
The method involves identifying the servo sectors preceding and following the data sectors to be written, combining old and new data, and writing continuously between these servo sectors, allowing the laser power to stabilize with only one gap per servo sector, thereby eliminating the need for additional gaps between data sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the laser is turned on to heat the recording material for HAMR writing, then the coercivity of the magnetic material is reduced enabling writing to occur, but several microseconds are required for the laser power to stabilize which exceeds the gap length between data sectors
Solution Approach 1:
The laser is activated during the gap period between data sectors to pre-stabilize the laser power before the write head begins writing data. This preliminary action ensures that when writing commences, the laser power is already stable, eliminating the need for extended stabilization time during actual data writing operations.
Solution Approach 2:
The system dynamically controls the laser activation timing to coincide with the gap periods between data sectors. By making the laser operation dynamic and synchronized with the data sector timing, the system optimizes the balance between achieving stable laser power for reliable HAMR writing and maintaining efficient use of disk space by minimizing gap lengths.
2Reliability
If longer gaps are introduced between data sectors to accommodate laser power stabilization, then the laser power can stabilize properly, but there is a large loss of disk real estate reducing storage capacity
Solution Approach 1:
Laser power stabilization is performed in advance during the gap periods between data sectors, rather than during the data writing process. This preliminary stabilization action confines the space-consuming stabilization period to non-data areas, thereby preserving maximum disk real estate for actual data storage while ensuring reliable laser power stability.
Solution Approach 2:
The system maintains continuous useful action by utilizing the gap periods between data sectors for laser stabilization, ensuring that no disk space is wasted. The laser power stabilization occurs continuously during these natural transition periods, maximizing storage capacity while maintaining writing reliability.
3Reliability
If high-Ku magnetic recording material is used to ensure thermal stability of stored magnetization, then thermal stability is improved, but the coercivity increases beyond the write field capability of the write head
Solution Approach 1:
The system changes the temperature parameter of the magnetic recording material by heating it with the laser during the writing process. This parameter change temporarily reduces the coercivity of high-Ku magnetic material, making it writable by the write head while maintaining high thermal stability at ambient temperature, thus resolving the contradiction between writability and thermal stability.
Solution Approach 2:
The laser heating induces a temporary phase transition or state change in the magnetic recording material, reducing its coercivity from a high stable state to a writable low-coercivity state. After writing, the material returns to its high-Ku stable state, ensuring thermal stability of the stored data while enabling the writing process to occur.
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 reduces the disk real estate required for laser power stabilization, enabling efficient data writing without compromising storage capacity by allowing continuous writing between servo sectors, thus optimizing disk usage.
Implementation Method 1
the magnetic recording material is heated locally during writing by the write head to lower the coercivity enough for writing to occur
Implementation Method 2
heat-assisted magnetic recording (HAMR), wherein high-Ku magnetic recording material is heated locally during writing by the write head
Implementation Method 3
A "near-field" transducer is an optical device with subwavelength features that is used to concentrate the light delivered by the waveguide into spot smaller than the diffraction limit
Data Source
AI summary
A heat-assisted magnetic recording (HAMR) disk drive has a laser, a transducer coupled to the laser and a rotatable disk. The disk has a recording layer with concentric or spiral data tracks, servo sectors extending across the tracks, a laser power gap adjacent each servo sector, and data sectors between the laser power gaps and the servo sectors. The servo sector preceding the first data sector to be written and the servo sector following the last data sector to be written are identified. Any old data in the data sectors between said first and last servo sectors is acquired, and the old and new data is combined. The laser is turned on when the laser power gap adjacent the first servo sector rotates past the transducer. The combined old and new data is then written in all of the data sectors continuously between said first and last servo sectors.