HAMR Pre-Write Clearance Offset Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) devices, maintaining consistent head-to-media spacing is challenging due to high coercivity of the magnetic medium and variations in thermal protrusion caused by multiple heat-generating components, leading to suboptimal writability metrics, especially during the first few sectors of a write operation.
Innovation Solution
A method and apparatus that calibrate the target pre-write clearance offset by measuring writability metrics while sweeping laser diode current for different clearance offsets, adjusting the offset to reach a predetermined threshold, and performing subsequent write operations using the adjusted offset to maintain optimal head-to-media spacing and improve writability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed target pre-write clearance is used for all write operations, then the device complexity is reduced, but the writability metric deteriorates due to variations in thermal protrusion and laser-induced writer protrusion
Solution Approach 1:
The patent implements dynamic adjustment of the target pre-write clearance based on measured thermal protrusion and laser-induced writer protrusion values. The clearance is no longer fixed but varies according to actual operating conditions, allowing the system to adapt to different thermal and mechanical states of the writer components.
Solution Approach 2:
The patent changes the clearance parameter dynamically by calculating adjusted target pre-write clearance values based on measured thermal protrusion and laser-induced writer protrusion. This parameter adjustment allows optimization of the writability metric for each specific operating condition rather than using a universal fixed value.
2Ease of operation
If thermal protrusion and laser-induced writer protrusion are not compensated for, then the device operation is simpler, but the head-to-media spacing becomes inconsistent leading to poor writability
Solution Approach 1:
The patent implements feedback mechanisms by measuring actual thermal protrusion and laser-induced writer protrusion during operation, then using these measurements to adjust the target pre-write clearance. This closed-loop feedback ensures that head-to-media spacing remains consistent despite variations in thermal and mechanical conditions.
Solution Approach 2:
The patent performs preliminary measurements of thermal protrusion and laser-induced writer protrusion before the actual write operation. These preliminary actions allow the system to pre-calculate and set an optimized target pre-write clearance that accounts for expected variations, ensuring consistent head-to-media spacing from the start of the write operation.
3Reliability
If the target pre-write clearance is adjusted for each head, then the writability metric improves, but the calibration process becomes more complex and time-consuming
Solution Approach 1:
The patent implements self-service calibration where the system automatically measures thermal protrusion and laser-induced writer protrusion, then self-adjusts the target pre-write clearance without requiring external intervention. This automated self-calibration reduces the need for manual calibration procedures while still achieving optimized writability metrics for each head.
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 enhances the writability of the first few sectors of a write operation by adjusting the target pre-write clearance offset on a head-by-head basis, compensating for unique laser-induced writer protrusion variations, thereby improving the reliability and performance of HAMR devices.
Implementation Method 1
heat-assisted magnetic recording (HAMR) devices
Implementation Method 2
The laser heats a small spot on the medium during recording. The heat lowers magnetic coercivity at the spot
Implementation Method 3
variations in thermal protrusion caused by multiple heat-generating components
Data Source
AI summary
An apparatus comprises a slider configured for heat-assisted magnetic coupled to a controller. The slider comprises a writer, a heater, a near-field transducer, and an optical waveguide for communicating light from a laser diode to the near-field transducer. The controller is configured to set a target pre-write clearance of the slider prior to performing a write operation, set a target write clearance of the slider for performing the write operation, and determine a difference between the target pre-write and write clearances to define a target pre-write clearance offset. The controller is also configured to measure, for a plurality of different target pre-write clearance offsets, a writability metric for the slider while sweeping a laser diode current, and adjust the target pre-write clearance offset so that the writability metric reaches a predetermined threshold. The controller is further configured to perform subsequent write operations using the adjusted target pre-write clearance offset.