Thermally-Assisted Magnetic Recording Head Gap Design
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Solution Overview
Problem
Thermally-assisted magnetic recording systems face challenges in achieving sufficient heating ability and write magnetic field due to the thermal expansion of near-field optical devices and reduced light use efficiency, which affects data writing and reading capabilities.
Innovation Solution
A thermally-assisted magnetic recording head with a waveguide and a near-field optical device configured in a surface plasmon mode, where the magnetic pole is shaped in a hook form to maintain a controlled gap with the near-field optical device, ensuring efficient heating and write field generation by optimizing the gap size and shape for near-field light generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the near-field optical device is directly irradiated with laser light, then heating ability is improved, but thermal expansion causes the read head to depart from the medium surface and light use efficiency degrades
Solution Approach 1:
The optical device is divided into two separate components: a waveguide that transmits laser light and a near-field optical device that generates heat. The waveguide delivers light to the interface between the near-field optical device and the magnetic recording medium, allowing the near-field optical device to be heated indirectly through thermal conduction from the waveguide, thereby avoiding direct laser irradiation and its harmful thermal expansion effects.
Solution Approach 2:
The waveguide acts as an intermediary element that transfers energy from the laser source to the near-field optical device through thermal conduction rather than direct optical irradiation. This intermediary mechanism allows the near-field optical device to achieve the necessary heating for thermal-assisted magnetic recording while avoiding the harmful effects of direct laser heating on the read head positioning.
2Temperature
If the gap between magnetic pole and near-field optical device is reduced to improve heating efficiency, then heating ability is improved, but write magnetic field generation is affected
Solution Approach 1:
The magnetic pole is designed with non-uniform gap characteristics: a first gap region with smaller gap width for efficient heating, and a second gap region with larger gap width for adequate write magnetic field generation. This local variation in gap quality allows simultaneous optimization of both heating efficiency and write field strength in different spatial regions of the same magnetic pole structure.
Solution Approach 2:
The magnetic pole structure extends in multiple dimensions with varying gap widths at different positions. By creating a three-dimensional structure where the gap width changes along the length of the magnetic pole, the design accommodates both heating and write field requirements in different spatial zones, effectively using dimensional variation to resolve the contradiction.
3Manufacturing precision
If magnetic micro particle size is decreased to improve recording density, then recording density is improved, but thermal stability of magnetization degrades
Solution Approach 1:
The patent employs thermal-assisted magnetic recording that temporarily changes the temperature parameter of the magnetic recording medium. By heating the medium to a Curie temperature or near-Curie temperature, the magnetic anisotropy energy is reduced, allowing small magnetic particles with improved recording density to be written. After cooling, the thermal stability is restored, thus resolving the contradiction between small particle size and thermal stability.
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 configuration provides both sufficient heating ability and write magnetic field, enabling stable thermally-assisted magnetic recording with improved light use efficiency and reduced thermal fluctuations, enhancing data writing and reading performance.
Implementation Method 1
a near-field optical device configured to be coupled with the light in a surface plasmon mode and to emit near-field light
Implementation Method 2
laser light is coupled with the near-field optical device in a surface plasmon mode to cause excited surface plasmon to propagate to the opposed-to-medium surface, thereby providing near-field light
Implementation Method 3
a magnetic pole for generating write field from its end on the opposed-to-medium surface side
Data Source
AI summary
A thermally-assisted magnetic recording head includes a waveguide, a near-field optical device which emits near-field light from a near-field-light-generating end surface that forms a portion of an opposed-to-medium surface, and a magnetic pole generates write field from its end on the opposed-to-medium surface side. The near-field optical device includes a contact-to-waveguide surface, and a propagation edge configured to propagate there on the surface plasmon excited by the light. A gap between a near-field optical device-opposed surface of the magnetic pole and the propagation edge of the near-field optical device is larger at a section far from the end on the opposed-to-medium surface side than that at a section near the opposed-to-medium surface side.