Temperature Sensor in Thermally Assisted Magnetic Recording Head

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Solution Overview

Problem

Magnetic data storage systems face limitations due to the superparamagnetic limit, where random thermal fluctuations can erase data, and existing solutions like thermally assisted recording (TAR) require precise temperature control to maintain data stability without damaging the write heads.

Innovation Solution

Incorporating a temperature sensor proximate to an optical transducer in a disk drive's write head to control the power of a heating laser, allowing for real-time adjustment of optical energy based on measured temperature, thereby maintaining optimal heating of the magnetic media while preventing head damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the power of the heating laser is increased to maintain data stability above the superparamagnetic limit, then the magnetic media can be heated to sufficient temperature for reliable recording, but the write head may overheat and suffer damage

Engineering Contradiction:

Improvedata stabilityVSAvoidhead overheating

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback control system where a temperature sensor monitors the thermal condition of the write head and sends signals to adjust the laser power accordingly. When the sensor detects temperatures approaching dangerous thresholds, it automatically reduces laser power to prevent head damage while maintaining sufficient heating for data recording stability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The temperature sensor acts as an intermediary between the heating laser and the write head, providing real-time thermal information that enables indirect control of the heating process. This intermediary monitoring system allows the controller to adjust laser power based on actual thermal conditions rather than operating at fixed high power levels.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the temperature of the magnetic media is lowered to maintain data stability, then thermal fluctuations are reduced, but the coercivity increases requiring higher magnetic moment materials or perpendicular recording

Engineering Contradiction:

Improvedata stabilityVSAvoidmedia temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The system employs periodic or pulsed laser heating rather than continuous heating, allowing the magnetic media to be heated only during the recording window when data writing occurs. Between pulses, the media cools to ambient temperature where data remains stable, thus achieving both data stability and sufficient heating for recording by using time-dependent temperature control.

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If a temperature sensor is placed very close to the optical transducer for accurate temperature measurement, then real-time temperature control is improved, but the sensor may interfere with the optical transducer function or become damaged

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidsensor interference or damage

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The temperature sensor is positioned at a specific optimal location that balances measurement accuracy with functional compatibility. Rather than placing it directly in the optical path where it would interfere with the transducer, the sensor is located in a nearby region where it can still accurately monitor the thermal environment of the write head without disrupting the optical heating function.

Inventive Principle:

Principle #3Local quality

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 solution enhances data stability by maintaining the magnetic media at a sufficient temperature for reliable recording while protecting the write head from overheating, thus overcoming the superparamagnetic limit and ensuring reliable data storage.

Implementation Method 1

transmitting optical energy from a laser to an optical transducer... heating the media

Methodology Applied

Scientific EffectOptical absorption and conversion to thermal energy: Absorption (EM radiation)

Implementation Method 2

measuring the electrical resistance of a temperature sensor that is thermally coupled to the optical transducer where the electrical resistance correlates to a temperature of the sensor

Methodology Applied

Scientific EffectElectrical resistance correlation with temperature: Electrical Resistance

Implementation Method 3

the temperature sensor and the optical transducer are spaced apart by a first distance... thermally coupled

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8451696B2Temperature sensor in a thermally assisted magnetic recording head

Publication Date: 2013.05.28 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A method and apparatus for providing a signal for driving a heating element in a TAR or HAMR enabled disk storage system that includes an optical transducer (or near-field optical source) for further focusing the beamspot of a laser onto a magnetic media, thereby heating the media. The storage system includes a temperature sensor proximate to the near-field transducer which provides a feedback loop to the laser driver to adjust the power of the laser.