Shingled TAR Disk Drive Adjacent Track Erasure Control
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Solution Overview
Problem
Shingled-recording thermally-assisted recording (TAR) disk drives with wide-area heaters face significant adjacent track erasure (ATE) due to heat extending into adjacent tracks, leading to increased bit error rates and data degradation.
Innovation Solution
Implement a system that counts the number of writes to each band and re-writes adjacent tracks when a predetermined threshold is reached, based on calculated magnetization decay time to minimize thermal instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wide-area heater is used to heat the disk during writing, then the coercivity is lowered enough for writing to occur, but the heat extends into adjacent tracks causing adjacent track erasure
Solution Approach 1:
The patent applies local quality by selectively heating only the track being written while leaving adjacent tracks at lower temperatures. This is achieved through precise control of the heater's thermal field to create a localized temperature zone that enables writing in the target track without causing erasure in neighboring tracks, thus resolving the contradiction between writing capability and adjacent track erasure
Solution Approach 2:
The patent implements preliminary action by pre-heating the track before writing occurs. The heater is positioned and activated to heat the specific track area prior to the writing process, ensuring the coercivity is reduced at the correct moment and location, while avoiding excessive heat propagation to adjacent tracks that would cause erasure
2Productivity
If the magnetic grains are made smaller to increase areal data density, then more bits can be recorded per unit area, but the grains become thermally unstable and prone to demagnetization
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the temperature parameter during the writing process. By heating the magnetic grains to elevated temperatures during writing, the coercivity is reduced enabling smaller grain sizes, while the grains are then cooled and stabilized at lower temperatures during storage, maintaining both high areal data density and thermal stability
Solution Approach 2:
The patent implements periodic action through the cyclic process of heating during writing and cooling during storage. The magnetic grains undergo periodic temperature variations - heated to enable writing of smaller, denser grains, then cooled to stabilize them for long-term storage, thus maintaining both high density and thermal stability
3Stability of the object's composition
If high magneto-crystalline anisotropy is used to improve thermal stability, then the magnetization retains its state better, but the switching field required to reverse magnetization increases beyond write capability
Solution Approach 1:
The patent applies parameter changes by temporarily altering the temperature parameter during writing. By heating the magnetic material, the coercivity and switching field are reduced to levels that can be overcome by the write head's magnetic field, enabling reversal of magnetization in high-anisotropy materials. After writing, the material cools and regains its high anisotropy and stability, thus resolving the contradiction between magnetization retention and switching field requirement
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 effectively reduces magnetization decay in adjacent tracks, maintaining data integrity and reducing bit error rates by strategically re-writing data before excessive thermal decay occurs.
Implementation Method 1
A waveguide coupled to a laser and with an output end near the media
Implementation Method 2
the magnetic recording material is heated locally during writing to lower the coercivity
Implementation Method 3
it is known that the coercivity of the magnetic material of the recording layer is temperature dependent
Implementation Method 4
one proposed solution to the thermal stability problem is thermally-assisted recording (TAR), also called heat-assisted magnetic recording (HAMR)
Implementation Method 5
the switching field cannot exceed the write field capability of the recording head
Implementation Method 6
the field required to reverse the magnetization direction
Implementation Method 7
The recorded data is then read back at ambient temperature by a conventional magnetoresistive (MR) read head
Data Source
AI summary
A thermally-assisted recording (TAR) disk drive that uses “shingled” recording and a rectangular waveguide as a “wide-area” heat source includes a controller that counts the number of writes to each annular band of data tracks. The wide-area heater generates a heat spot that extends across multiple tracks, so that each time an annular band is written, the data in tracks in adjacent bands are also heated. Because the bands are written independently, the number of passes of the heat spot and thereby the number of times the data tracks in a band are exposed to elevated temperatures without being re-written is related to the number of re-writes of the adjacent bands. The number of writes to each band is counted and when that count reaches a predetermined threshold value, one or more tracks in an adjacent band are re-written to avoid reaching an unacceptable level of magnetization decay in the tracks of the adjacent band.