TAMR Write Head with Integrated HDI Sensor
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Solution Overview
Problem
Current magnetic recording technologies face challenges in achieving high areal data densities due to conflicting requirements of stronger writing fields and smaller write heads, which lead to thermal instability and mechanical stress issues in thermally assisted magnetic recording (TAMR) systems, particularly in detecting impending head-disk interference (HDI) events and monitoring temperature changes.
Innovation Solution
An integrated HDI sensor with a high temperature coefficient of resistivity material, such as nickel or nickel iron alloys, is embedded within the write-head portion of the TAMR structure, providing both touchdown detection and temperature monitoring capabilities with high spatial resolution, enabling reliable thermal-mechanical reliability monitoring and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a stronger writing field is used to write on high coercivity magnetic media, then writing capability is improved, but thermal instability and head-disk interference increase
Solution Approach 1:
The patent segments the writing field generation into two parts: a strong localized field from the write head pole and a thermal field from the laser heater. This allows the magnetic media to be written to through combined thermal and magnetic effects without requiring the entire system to operate at high magnetic field strengths continuously, thereby improving thermal stability while maintaining writing capability.
Solution Approach 2:
The patent changes the operating parameters of the magnetic recording system by introducing thermal assistance. The laser heater raises the temperature of the magnetic media locally, changing its magnetic properties (reducing coercivity and anisotropy), which allows writing to occur at lower magnetic field strengths, thus resolving the contradiction between writing field strength and thermal stability.
2Area of moving object
If the write head size is reduced to achieve high areal densities, then recording density is improved, but field gradient and writing capability deteriorate
Solution Approach 1:
The patent segments the field generation function between the write head (providing localized magnetic field) and the laser heater (providing thermal energy). This allows the write head to be miniaturized for high density while the thermal field compensates for the reduced magnetic field gradient, maintaining writing capability despite smaller head dimensions.
Solution Approach 2:
The patent employs a composite approach combining thermal energy (laser heating) with magnetic field energy (write head). This composite energy delivery system allows the use of smaller write heads while maintaining effective writing capability through the synergistic effect of thermal softening and localized magnetic field application.
3Force
If laser heating is applied to enable TAMR, then writing capability on high coercivity media is improved, but temperature monitoring and HDI detection become critical challenges
Solution Approach 1:
The patent merges the temperature monitoring function and HDI detection function into the write head structure itself by integrating sensors directly into the write head assembly. This integration allows simultaneous monitoring of temperature and detection of head-disk interference events, resolving the difficulty of detecting and measuring these critical parameters during TAMR operation.
Solution Approach 2:
The patent implements feedback mechanisms where sensors monitor temperature and HDI conditions in real-time, and this information is fed back to the control system. This allows dynamic adjustment of laser power and write head positioning to maintain optimal writing conditions while preventing thermal damage and detecting interference events, thereby improving both writing capability and safety.
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
The integrated sensor effectively detects impending touchdowns and monitors temperature changes, enhancing the reliability and operational stability of the TAMR system by providing real-time feedback on thermal and mechanical conditions, thus preventing unwanted erasures and extending the lifespan of magnetic and optical components.
Implementation Method 1
An integrated HDI sensor with a high temperature coefficient of resistivity material, such as nickel or nickel iron alloys, is embedded within the write-head portion
Implementation Method 2
The integrated sensor effectively detects impending touchdowns and monitors temperature changes
Implementation Method 3
The heating effect of TAMR works by raising the temperature of a small region of the magnetic medium to essentially its Curie temperature (TC), at which temperature both its coercivity and anisotropy are significantly reduced
Data Source
AI summary
A DFH (dynamic fly height) equipped TAMR (Thermal Assisted Magnetic Recording) write head uses optical-laser excited surface plasmons to locally heat a magnetic recording medium so that writing is enabled, while a DFH heater allows the head to fly very close to the magnetic medium. The write head includes an integral HDI sensor with a narrow track width for high spatial resolution. The HDI sensor is calibrated to obtain a relationship between its resistance and heater power. When the TAMR head is operated, measurement of high frequency voltage across the HDI sensor as a function of heater power indicates impending touchdowns, while use of the calibrated resistance curve enables the sensor to monitor temperature variations within components of the TAMR write head.