HAMR Head Noise Power Function for Media Characterization
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Solution Overview
Problem
Data storage devices face challenges in accurately predicting the failure of near-field transducers and write pole degradation due to variations in thermal gradients and magnetic media properties, which affect the quality and reliability of magnetic recording.
Innovation Solution
The implementation of a method involving a noise power function to estimate magnetic media properties such as peak temperature, thermal gradient, and Curie temperature distribution, using a test pattern written and read with varying laser biases and write coil currents, allowing for the prediction of near-field transducer failure and write pole degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heat assisted magnetic recording (HAMR) is used to improve data writing quality by heating the disk surface, then the coercivity of the magnetic medium decreases enabling better magnetization, but the complexity of the device increases due to additional components like laser diodes and near field transducers
Solution Approach 1:
The patent combines the laser heating function and magnetic writing function into a single integrated head assembly. The near field transducer and write coil are positioned in close proximity, allowing simultaneous thermal and magnetic action on the magnetic medium without requiring separate heating and writing mechanisms.
Solution Approach 2:
The head assembly performs multiple functions: it generates heat through the near field transducer, generates magnetic fields through the write coil, and reads back data through the read element. This multi-functional design reduces the need for separate specialized components for each operation.
2Manufacturing precision
If the near field transducer operates at high power to maintain optimal recording conditions, then the quality of written data improves, but the risk of transducer failure increases due to thermal degradation
Solution Approach 1:
The patent implements preliminary characterization of the magnetic medium's Curie temperature distribution before actual data recording. By writing test patterns and measuring noise power at different laser biases, the system determines the optimal operating parameters in advance, allowing the transducer to operate at optimal power levels without excessive thermal stress.
Solution Approach 2:
The system continuously monitors noise power in read signals and uses this feedback to adjust laser bias and write coil current. This closed-loop control ensures the transducer operates within safe thermal limits while maintaining optimal recording quality, preventing thermal degradation through real-time parameter adjustment.
3Device complexity
If variations in thermal gradients and magnetic media properties are not accounted for, then the device operates simpler without complex measurement systems, but the accuracy of predicting transducer failure and write pole degradation decreases
Solution Approach 1:
The system uses its own read element and read channel to measure noise power from test patterns written on the actual magnetic medium. This self-characterization approach eliminates the need for external specialized measurement equipment, allowing the device to autonomously determine its own operating parameters and media properties.
Solution Approach 2:
The patent systematically varies laser bias and write coil current to create different thermal and magnetic conditions, measuring noise power across multiple parameter combinations. This allows construction of a noise power function that captures the relationship between operating parameters and media response, enabling accurate prediction of transducer and write pole conditions.
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 precise estimation of magnetic media properties and early detection of near-field transducer failure, improving the reliability and capacity of data storage devices by maintaining optimal recording conditions and preventing data loss.
Implementation Method 1
heating the disk surface during write operations... by fabricating a laser diode and a near field transducer (NFT) with other write components of the head
Implementation Method 2
modulating a write current in an inductive coil (write coil) to record magnetic transitions onto the disk surface
Implementation Method 3
the magnetic transitions are sensed by a read element (e.g., a magneto-resistive element)
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a magnetic media, wherein the head comprises a write coil, a laser configured to heat the magnetic media during a write operation, and a read element. A test pattern is written to the magnetic media by applying a current to the write coil and a first bias to the laser. A second bias is applied to the laser while the head passes over the test pattern, and then the test pattern is read from the magnetic media using the head to generate a first read signal. A first noise power of the first read signal is measured, and at least one parameter of a noise power function is generated based on the first noise power measurement, wherein the noise power function is a function of at least the bias applied to the laser.