Heat-Assisted Magnetic Recording Head Plasmon Generator Shape
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Solution Overview
Problem
Heat-assisted magnetic recording heads face challenges in efficiently generating near-field light with a small spot diameter due to low light use efficiency and temperature issues with existing plasmon antennas, which affect data writing precision and recording density.
Innovation Solution
A heat-assisted magnetic recording head design featuring a plasmon generator with a shape-changing portion where the radius of curvature of the propagation edge decreases towards the medium facing surface, coupled with a waveguide and magnetic pole configuration to enhance light transformation into near-field light and prevent thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a plasmon antenna is used to generate near-field light, then near-field light can be generated, but the light transformation efficiency is very low and the antenna temperature increases significantly
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the light source and the plasmon generator. This dielectric layer guides light to the plasmon generator, enabling efficient light transformation into near-field light while preventing direct irradiation that would cause temperature increase. The dielectric layer acts as a mediator that optimizes the interaction between light and the plasmon generator.
Solution Approach 2:
The patent changes the structural parameters of the plasmon generator by forming it with a specific shape (such as a needle-like or conical structure) and controlling its size to be smaller than or equal to the wavelength of light. This parameter optimization enables efficient near-field light generation while managing thermal effects.
2Illumination intensity
If the plasmon antenna absorbs thermal energy, then near-field light is generated, but the antenna temperature increases and causes volume expansion and protrusion
Solution Approach 1:
The dielectric layer serves as a thermal isolator and light guide, preventing direct thermal coupling between the light source and the plasmon generator. This intermediary structure allows the plasmon generator to be excited by evanescent light from the dielectric layer without direct thermal irradiation, thereby reducing temperature increase and volume expansion.
Solution Approach 2:
The patent separates the light guidance function (performed by the dielectric layer) from the near-field light generation function (performed by the plasmon generator). This functional separation allows the plasmon generator to operate at lower temperatures while still achieving efficient near-field light generation through the extracted and guided light.
3Illumination intensity
If the plasmon generator protrudes from the medium facing surface, then near-field light can be generated, but the read head end gets farther from the magnetic recording medium causing servo signal reading failure
Solution Approach 1:
The patent optimizes the size and shape parameters of the plasmon generator, making it smaller than or equal to the wavelength of light. This size optimization allows the plasmon generator to generate near-field light effectively while minimizing its protrusion from the medium facing surface, thereby maintaining proper spacing between the read head and the magnetic recording medium for accurate servo signal reading.
4Productivity
If magnetic fine particles are made smaller to reduce asperities, then recording density improves, but thermal stability of magnetization decreases
Solution Approach 1:
The patent utilizes the phase transition concept in the form of heat-assisted magnetic recording. By applying localized heat to the magnetic recording medium during the writing process, the coercivity of the magnetic material is temporarily reduced, allowing data to be written to high-coercivity, thermally stable magnetic fine particles. After the heat source is removed, the magnetization is stabilized, achieving both high recording density 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 design achieves high light use efficiency and generates near-field light with a small spot diameter, improving data writing precision and recording density while preventing thermal issues that affect the head's operation.
Implementation Method 1
The core has an evanescent light generating surface that generates evanescent light based on the light propagated through the core
Implementation Method 2
A surface plasmon is excited on the propagation edge through coupling with the evanescent light generated from the evanescent light generating surface
Implementation Method 3
The surface plasmon is propagated along the propagation edge to the near-field light generating part. The near-field light generating part generates near-field light based on the surface plasmon
Implementation Method 4
When writing data, a magnetic field and heat are simultaneously applied to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing
Data Source
AI summary
A plasmon generator has an outer surface including a propagation edge, and has a near-field light generating part lying at an end of the propagation edge and located in a medium facing surface. The propagation edge faces an evanescent light generating surface of a waveguide's core with a predetermined distance therebetween and extends in a direction perpendicular to the medium facing surface. The propagation edge is arc-shaped in a cross section parallel to the medium facing surface. The plasmon generator includes a shape changing portion in which a radius of curvature of the propagation edge in the cross section parallel to the medium facing surface continuously decreases with decreasing distance to the medium facing surface.