Thermally-Assisted Magnetic Recording Head Gap Layer Design
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Solution Overview
Problem
Thermally-assisted magnetic recording heads face challenges with agglomeration of the plasmon generator due to temperature increases and stress, leading to degradation of recording properties and reduced recording density.
Innovation Solution
A thermally-assisted magnetic recording head is designed with a gap layer comprising at least two dielectric layers and one metallic layer between the magnetic pole and the plasmon generator, which relieves stress and suppresses agglomeration by detaching at the interface, while also controlling the spread of near-field light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a plasmon generator is directly applied with light to generate near-field light for thermally-assisted magnetic recording, then the magnetic disk coercivity is lowered and information recording is enabled, but the plasmon generator overheats and deforms causing practical realization difficulty
Solution Approach 1:
The patent introduces a waveguide as an intermediary component that guides light to the plasmon generator indirectly. The light source is positioned separately and couples light into the waveguide, which then directs the light to the plasmon generator at the air bearing surface. This intermediary structure allows precise spatial control of light delivery, concentrating energy where needed while keeping the light source and plasmon generator thermally separated, thus preventing overheating and deformation of the plasmon generator.
2Productivity
If magnetic microparticles are made small to increase recording density, then higher recording capacity is achieved, but thermal stability of magnetization is lowered
Solution Approach 1:
The patent employs thermally-assisted magnetic recording (TAMR) which dynamically changes the temperature parameter of the magnetic disk during the recording process. By locally heating the magnetic disk at the air bearing surface using the plasmon generator, the coercivity of the magnetic microparticles is temporarily reduced, enabling writing on high-coercivity media with small particles. After the laser is turned off, the temperature returns to ambient and the magnetization becomes stable, thus achieving both high recording density and thermal stability.
3Stability of the object's composition
If increasing anisotropy energy of magnetic microparticles is done to maintain thermal stability, then magnetization stability is improved, but coercivity increases making information recording difficult
Solution Approach 1:
The patent uses periodic (pulsed) laser action to temporarily reduce coercivity during the writing process. The laser is turned on during the write operation to lower coercivity via thermal assistance, allowing easy magnetization switching. After the pulse ends, the temperature returns to ambient and coercivity recovers to its high value, ensuring stable stored data. This periodic application of thermal energy enables writing on high-anisotropy media without permanently reducing the coercivity needed for data 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 enables higher-density magnetic recording and improves the product's lifetime by effectively managing stress and heat distribution, preventing agglomeration and maintaining recording quality.
Implementation Method 1
allowing frequency of light to coincide with a resonant frequency of plasmons that are generated in a metal, by directly applying the light to a plasmon generator
Implementation Method 2
near-field light is applied to a magnetic recording medium to lower a coercivity thereof
Implementation Method 3
the gap layer is configured of at least two dielectric layers and at least one metallic layer provided between the dielectric layers... the gap layer... relieves stress and suppresses agglomeration by detaching at the interface
Implementation Method 4
the guided light is coupled to the plasmon generator through evanescent coupling, and surface plasmon polaritons generated on a surface of the plasmon generator are used
Implementation Method 5
surface plasmon polaritons generated on a surface of the plasmon generator
Implementation Method 6
heat is applied together with the magnetic field to a section of the magnetic disk where the information is to be written to increase the temperature and to lower the coercivity of that section
Data Source
AI summary
The thermally-assisted magnetic recording head includes: a magnetic pole having an end exposed on an air bearing surface; a waveguide; a plasmon generator provided between the magnetic pole and the waveguide, and having a first region and a second region, the first region extending backward from the air bearing surface to a first position, and the second region being coupled with the first region at the first position and extending backward from the first position; and a gap layer provided between the magnetic pole and the first region of the plasmon generator and extending backward from the air bearing surface, the gap layer including at least two dielectric layers and at least one metallic layer provided between the dielectric layers.