Thermally-Assisted Magnetic Recording Head Plasmon Generator Design
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Solution Overview
Problem
Thermally-assisted magnetic recording heads face challenges in efficiently using light propagated through a waveguide due to temperature rise in the plasmon generator, which affects the positioning of the write magnetic field and near-field light, leading to reduced efficiency and servo signal read issues during write operations.
Innovation Solution
A thermally-assisted magnetic recording head design that includes a waveguide with a core and clad, where evanescent light generates surface plasmons on a plasmon generator with extended portions for heat dissipation, allowing the write magnetic field and near-field light to be positioned close to each other while minimizing plasmon generator temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a plasmon antenna is used to generate near-field light by direct irradiation with light, then near-field light can be generated, but the transformation efficiency of applied light into near-field light is very low and the plasmon antenna temperature increases significantly
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the light source and the plasmon generator. The dielectric layer guides light through total internal reflection and generates evanescent light that couples with the plasmon generator, preventing direct irradiation and reducing temperature increase while improving transformation efficiency
Solution Approach 2:
The patent replaces direct optical irradiation with a waveguide-based light delivery system. The waveguide uses total internal reflection and evanescent field coupling to transfer energy to the plasmon generator, substituting the direct mechanical/optical coupling with an intermediary waveguide mechanism
2Temperature
If the plasmon antenna absorbs thermal energy and increases in temperature, then near-field light generation continues, but the plasmon antenna expands in volume and protrudes from the medium facing surface, causing the read head to get farther from the magnetic recording medium
Solution Approach 1:
The dielectric layer acts as a thermal and optical intermediary, preventing direct light absorption by the plasmon generator and reducing temperature increase. This maintains the positioning stability of the read head relative to the magnetic recording medium, ensuring servo signal readability
Solution Approach 2:
The patent designs the waveguide structure to anticipate and prevent excessive temperature rise before it occurs. By using evanescent light coupling instead of direct irradiation, the system preemptively limits thermal energy absorption, preventing thermal expansion and positioning drift
3Productivity
If magnetic fine particles are made smaller to reduce asperities and improve recording density, then recording density increases, but the thermal stability of magnetization of the magnetic fine particles decreases
Solution Approach 1:
The patent changes the physical state of the magnetic recording medium by locally increasing temperature during writing. This temporary parameter change reduces coercivity, allowing data writing in high-coercivity media with small magnetic particles that maintain thermal stability
Solution Approach 2:
The patent utilizes a temporary phase transition in the magnetic recording medium's magnetic properties through thermal assistance. The localized heating temporarily alters the magnetic state, enabling writing operations on media with high anisotropic energy and small particle sizes
4Stability of the object's composition
If high coercivity magnetic recording medium is used to maintain thermal stability, then thermal stability of magnetization is maintained, but it becomes difficult to perform data writing with existing magnetic heads
Solution Approach 1:
The patent temporarily changes the coercivity parameter of the magnetic recording medium by applying localized heat during the writing process. This allows standard magnetic heads to write data on high-coercivity media by reducing the coercivity barrier only during the writing operation
Solution Approach 2:
The patent employs periodic or pulsed heating to temporarily reduce coercivity during writing operations. The heating is applied in controlled bursts that coincide with the writing process, temporarily facilitating data writing while maintaining high coercivity for thermal stability during storage
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 enhances the transformation of light into near-field light with high efficiency, suppresses plasmon generator temperature rise, and maintains effective write magnetic field positioning, improving data writing capabilities and servo signal readability.
Implementation Method 1
a core (32) and a clad (31, 33), the core having an evanescent light generating surface that generates evanescent light based on light propagated through the core
Implementation Method 2
a plasmon generator (34)... Surface plasmons are excited on the plasmon exciting part (341) through coupling with the evanescent light generated from the evanescent light generating surface (32c)
Implementation Method 3
a first sidewall part (34A1) and a second sidewall part (34A2)... and at least one extended portion (34B, 34C)... having a heat sink function of dissipating heat from the plasmon generator (34) to outside
Data Source
AI summary
An outer surface of a plasmon generator includes: a plasmon exciting part that faces an evanescent light generating surface with a predetermined distance therebetween; and a front end face located in a medium facing surface. The plasmon generator has: first and second sidewall parts that are connected to the plasmon exciting part and increase in distance from each other with increasing distance from the plasmon exciting part; and at least one extended portion connected to an edge of at least one of the first and second sidewall parts opposite from the plasmon exciting part. A magnetic pole has a portion interposed between the first and second sidewall parts. The front end face includes first and second portions lying at ends of the first and second sidewall parts and connected to each other into a V-shape. An end face of the magnetic pole has a portion interposed between the first and second portions of the front end face.