Thermally-Assisted Magnetic Recording Head Near-Field Optical Device
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Solution Overview
Problem
In magnetic recording systems, the decrease in magnetic grain size for higher recording densities leads to thermal stability issues due to increased anisotropic magnetic fields, making it difficult to write data when the coercive force exceeds the write field limit, and existing near-field optical systems face challenges in light use efficiency and thermal management.
Innovation Solution
A thermally-assisted magnetic recording head is designed with a waveguide, a near-field optical device configured to emit NF-light from a propagation edge opposite to the waveguide, and a magnetic pole, where the NF-optical device is positioned close to the magnetic pole to generate NF-light with high intensity, using a silver alloy and an Otto configuration to optimize light coupling and reduce thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic grain size is decreased to increase recording density, then recording density is improved, but thermal stability of magnetization deteriorates due to increased anisotropic magnetic field
Solution Approach 1:
The patent changes the physical state of the magnetic recording medium by heating it to temporarily reduce the anisotropic magnetic field (coercive force), enabling data writing at higher recording densities where the medium would otherwise be too stable to write. After writing, the medium cools and regains its thermal stability.
2Reliability
If anisotropic magnetic field is increased to improve thermal stability, then thermal stability is improved, but write field limit is exceeded making data writing difficult
Solution Approach 1:
The patent applies periodic heating and cooling cycles to the magnetic recording medium. During the heating phase, the anisotropic magnetic field is reduced to enable writing. During the cooling phase, thermal stability is restored. This periodic modulation allows both writing capability and thermal stability to be achieved sequentially.
3Illumination intensity
If laser light is directly applied to NF-optical device to generate NF-light, then NF-light generation is achieved, but thermal expansion causes read head element to move away from medium reducing light use efficiency
Solution Approach 1:
The patent extracts the heating function from the NF-optical device by applying laser light to a separate heating region of the magnetic recording medium. The NF-optical device only generates NF-light without direct laser heating, preventing thermal expansion and maintaining optimal reading position and light use efficiency.
4Illumination intensity
If NF-optical device is positioned close to magnetic pole to generate high intensity NF-light, then NF-light intensity is improved, but thermal management becomes challenging
Solution Approach 1:
The patent segments the functional regions: the NF-optical device is positioned close to the magnetic pole for high NF-light intensity, while the laser light is applied to a separate heating region of the magnetic recording medium. This spatial segmentation allows intense NF-light generation without direct thermal coupling between the laser source and the NF-optical device, simplifying thermal management.
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 allows for reliable thermally-assisted magnetic recording with high recording density by generating NF-light with sufficient intensity and gradient, while maintaining efficient light use and minimizing thermal issues, enabling stable write operations.
Implementation Method 1
a waveguide for guiding a laser light
Implementation Method 2
a near-field optical device for converting the laser light into a surface plasmon and for generating near-field light from a propagation edge opposite to the waveguide
Implementation Method 3
causing excited surface plasmon to propagate to the opposed-to-medium surface, thereby providing NF-light
Implementation Method 4
an electromagnetic transducer including a coil and a magnetic pole, the coil being wound around a part of the magnetic pole
Implementation Method 5
anisotropic magnetic field of the medium is lowered by applying heat to a portion of the medium where data is to be written
Data Source
AI summary
There is provided a near-field-light (NFL) generating optical system in which the point where near-field (NF) light is generated can be provided sufficiently close to the end surface of a magnetic pole that generates write field. The optical system comprises: a waveguide through which a light for exciting surface plasmon propagates; and a NF-optical device configured to be coupled with the light in a surface plasmon mode. The NF-optical device comprises: an opposed-to-waveguide surface opposed to the waveguide with a predetermined distance; and a propagation edge provided on the side opposite to the opposed-to-waveguide surface, extending to the NFL-generating end surface of the device, and configured to propagate thereon the surface plasmon excited by the light. In this optical system, the point, where NF-light is generated, of the NFL-generating end surface can be located on the side opposite to the waveguide.