Heat-Assisted Rotating Disk Magnetometer for HAMR Media Characterization
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Solution Overview
Problem
Conventional methods for characterizing magnetic properties of high anisotropy media, such as those used in Heat-Assisted Magnetic Recording (HAMR), face challenges in reliability and throughput, with existing tools either being destructive or having low throughput, and failing to accurately measure critical parameters like Curie temperature distribution and anisotropy field gradient.
Innovation Solution
The development of a Heat-Assisted Rotating Disk Magnetometer (HARDM) apparatus that uses a laser-heating assisted writer and reader to non-destructively measure magnetic patterns on high coercivity media, allowing for the determination of anisotropy field temperature slope and Curie temperature distribution with high reliability and throughput, by controlling external magnetic fields and media temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods (VSM, oscillating magnetometer) are used to measure magnetic properties of high anisotropy media, then measurement capability is provided, but throughput is low and measurements are destructive or unreliable
Solution Approach 1:
The patent replaces conventional mechanical measurement systems (VSM, oscillating magnetometer) with a heat-assisted magnetic recording system that uses laser heating and magnetic field generation to non-destructively measure magnetic properties. The system writes magnetic patterns on rotating media using controlled heating and magnetic fields, then reads the patterns to extract anisotropy parameters, achieving both high throughput and reliable measurements without destructive sampling
Solution Approach 2:
The patent changes the measurement approach by varying temperature and magnetic field parameters to characterize high anisotropy media. By controlling laser heating power and applied magnetic field strength, the system measures reversal probability as a function of these parameters, enabling extraction of Curie temperature distribution and anisotropy field gradient without destroying the media
2Ease of manufacture
If high magnetic fields are applied to saturate high coercivity media, then magnetic patterns can be written, but the media may be damaged or the measurement process becomes destructive
Solution Approach 1:
The patent applies preliminary laser heating to the media before applying the magnetic field for writing. This pre-heating reduces the coercivity of the high anisotropy media, allowing magnetic patterns to be written with moderate magnetic fields rather than extreme fields that could damage the media. The heating is applied just before writing, making the media temporarily more susceptible to magnetic field changes without permanent damage
3Measurement precision
If conventional measurement tools are used for HAMR media characterization, then basic magnetic properties can be measured, but critical parameters like Curie temperature distribution and anisotropy field gradient cannot be accurately measured
Solution Approach 1:
The patent uses feedback from reading the magnetic patterns back to the media to extract critical parameters. By measuring the reversal probability at different laser powers and magnetic field strengths, and using this feedback information to fit models, the system accurately determines Curie temperature distribution and anisotropy field gradient. The feedback loop allows continuous refinement of the measurement and extraction of multiple critical parameters simultaneously
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
Enables the measurement of magnetic properties with high reliability and throughput, providing insights into media performance and facilitating the production of HAMR media with enhanced anisotropy field temperature slopes, thus improving recording density and media quality.
Implementation Method 1
A laser arrangement is configured to heat the track during the erase mode and, during the writing mode, heat the track while the track is exposed to the reversed DC magnetic field
Implementation Method 2
a magnetic field generator configured to expose a track of the medium to a DC magnetic field. The magnetic field generator is configured to saturate the track during an erase mode and reverse the DC magnetic field impinging the track during a writing mode
Implementation Method 3
A Kerr sensor configured to generate a Kerr signal using the magnetic pattern
Data Source
AI summary
An apparatus comprises a spindle to rotate a magnetic recording medium and a magnetic field generator to expose a track of the medium to a DC magnetic field. The magnetic field generator is configured to saturate the track during an erase mode and reverse the DC magnetic field impinging the track during a writing mode. A laser arrangement heats the track during the erase mode and, during the writing mode, heats the track while the track is exposed to the reversed DC magnetic field so as to write a magnetic pattern thereon. A reader reads the magnetic pattern and generates a read signal. A processor is coupled to the reader and configured to determine an anisotropy parameter using the read signal. The apparatus can further comprise a Kerr sensor that generates a Kerr signal using the magnetic pattern.