Thermally-Assisted Magnetic Recording Head Flying Height Setting
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Solution Overview
Problem
In thermally-assisted magnetic recording, achieving a precise flying height for the magnetic recording head is challenging due to the protrusion of the medium opposed surface caused by near-field light generation, which can lead to difficulties in detecting touch down and potentially damage the head and medium.
Innovation Solution
A method and device for setting the flying height of a thermally-assisted magnetic recording head that involves determining a tentative optimum drive current and heater power, adjusting drive currents sequentially to detect touch down, and calculating correlations to ensure the head can achieve a target flying height without damaging the medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive current for near-field light generation is increased to achieve precise flying height control, then the protrusion of the medium opposed surface increases, but this makes touch down detection difficult and may damage the head and medium
Solution Approach 1:
The patent applies preliminary action by performing touch down detection at multiple drive current levels (first through fourth drive currents) before final flying height setting. The system sequentially increases drive current from a first level to a fourth level, detecting touch down at each stage. This gradual approach allows the system to adapt to medium protrusion progressively, avoiding sudden large protrusions that would make detection difficult or cause damage.
Solution Approach 2:
The system dynamically adjusts the drive current for near-field light generation based on detected touch down points. By varying the drive current across multiple levels (first, second, third, fourth drive currents) and correlating these with touch down detection results, the system optimizes the balance between achieving sufficient medium protrusion for precise flying height control and maintaining touch down detectability.
2Length of moving object
If the medium opposed surface protrusion is increased to reduce flying height for high recording density, then the flying height decreases, but the risk of head and medium damage increases
Solution Approach 1:
The patent implements preliminary action by conducting a series of touch down detections at progressively increasing drive current levels before final operation. The system performs detections at first, second, third, and fourth drive currents, allowing gradual medium protrusion that reduces the risk of sudden contact damage while achieving the desired low flying height for high recording density.
Solution Approach 2:
The system provides beforehand cushioning by establishing a correlation between multiple drive current levels and their corresponding touch down detection results. This correlation data serves as a protective guide, allowing the system to select appropriate drive current and heater power combinations that have been pre-validated to avoid excessive protrusion and potential damage, while still achieving sufficiently low flying heights.
3Reliability
If sequential drive current adjustment is performed to detect touch down accurately, then touch down detection reliability improves, but the time required for flying height setting increases
Solution Approach 1:
The patent applies partial action by performing touch down detection at selective drive current levels (first through fourth) rather than continuously scanning all possible current values. The system identifies correlation points at these discrete levels, which is sufficient to establish the necessary correlation for reliable flying height setting without requiring exhaustive measurement, thus reducing time while maintaining reliability.
Solution Approach 2:
The system uses feedback by correlating touch down detection results from multiple drive current levels to establish a relationship between drive current, heater power, and medium protrusion. This correlation feedback allows the system to predict optimal settings and reduce the need for extensive sequential testing in normal operation, thereby reducing time loss while maintaining high detection reliability.
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 allows for precise setting of the flying height, ensuring reliable touch down detection and preventing damage to the magnetic recording head and medium, thereby enabling stable operation at extremely small flying heights for high recording density.
Implementation Method 1
light propagated through the waveguide is coupled with a plasmon-generator in a surface plasmon mode, and excites the surface plasmon. Propagation of such surface plasmon in the plasmon-generator causes the generation of near-field light
Implementation Method 2
a heater part that heats the vicinity of the medium opposed surface in order to protrude the medium opposed surface toward the magnetic recording medium side
Implementation Method 3
a magnetic recording medium is heated by irradiating the magnetic recording medium with the near-field light generated at the near-field light generating portion of the plasmon-generator, and information is recorded by applying a magnetic field under a state where the anisotropy field of the magnetic recording field is decreased
Data Source
AI summary
While a plurality of drive currents for flying height setting with current values smaller than a tentative optimum drive current are supplied to a light source, respectively, heater power is supplied to a heater part, and touch down of a thermally-assisted magnetic recording head is detected. Tentative optimum heater power is determined based on a correlation between the heater power when the touch down is detected and each drive current for flying height setting. The tentative optimum drive current is supplied to the light source part; the tentative optimum heater power is supplied to the heater part; a reference signal is recorded in a magnetic recording medium; and flying height of the thermally-assisted magnetic recording head is set by determining whether or not the reference signal is recorded with the desired signal intensity.