Heat-Assisted Magnetic Head With Asymmetric Light Waveguide
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Solution Overview
Problem
Current heat-assisted magnetic recording techniques face challenges in achieving high line recording density and signal-to-noise ratio due to limitations in placing near-field light generating elements close to the main magnetic pole, leading to issues with magnetization transition regions and thermal stability.
Innovation Solution
A thin-film magnetic head with a waveguide for leading heat-assisted light and a write magnetic field profile having a projecting region on the leading side, where the anisotropy field profile traverses the write magnetic field profile, allowing for steep magnetization transition regions and improved recording density without using a near-field light generating element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a near-field light generating element is placed close to the main magnetic pole to achieve heat-assisted magnetic recording, then the coercive force of the magnetic recording medium can be reduced for writing, but the distance constraint (less than or equal to 50 nm) makes the device structure extremely complex and difficult to manufacture
Solution Approach 1:
The patent extracts the light generating function from the traditional near-field light probe structure and integrates it into the electromagnetic transducer's magnetic pole. The light emitting unit is formed by making the leading side end surface of the main magnetic pole transparent to light, eliminating the need for separate complex near-field light generating elements while maintaining the required heating function.
Solution Approach 2:
The patent merges the light emitting function with the magnetic pole writing function into a single integrated structure. The main magnetic pole serves dual purposes: generating the write magnetic field and emitting light for heat-assisted recording, thereby simplifying the overall head structure while achieving both functions effectively.
2Manufacturing precision
If the irradiating center of near-field light is placed close to the main magnetic pole to achieve high recording density, then spatial resolution improves, but the magnetization transition regions become disturbed by higher write magnetic field after writing
Solution Approach 1:
The patent positions the light emitting unit on the leading side of the main magnetic pole, creating an asymmetric arrangement where the light emission point is separated from the magnetic field application region. This asymmetric positioning allows the light to heat the medium before the magnetic field acts on it, preventing disturbance of magnetization transition regions while maintaining high spatial resolution.
Solution Approach 2:
The patent implements preliminary heating of the magnetic recording medium by emitting light from the leading side before the write magnetic field is applied. This preliminary action reduces the coercive force in advance, allowing the subsequent magnetic field to write data without causing excessive disturbance to the magnetization transition regions.
3Manufacturing precision
If magnetic microparticles are decreased in size to improve recording density, then more particles fit per bit, but the thermal stability of magnetization is degraded
Solution Approach 1:
The patent changes the temperature parameter locally at the recording spot by emitting light to heat the magnetic recording medium. This temporary temperature increase reduces the magnetic anisotropy energy and coercive force, enabling stable magnetization switching in small magnetic microparticles that would otherwise be thermally unstable, thereby achieving high recording density with maintained stability.
4Stability of the object's composition
If the magnetic anisotropy energy KU is increased to improve thermal stability, then magnetization becomes more stable, but the coercive force increases beyond the maximum write magnetic field capability
Solution Approach 1:
The patent temporarily changes the temperature parameter of the magnetic recording medium by light-induced heating during the writing process. This temperature increase dynamically reduces the coercive force and magnetic anisotropy energy, enabling the write magnetic field to overcome the high KU barrier and switch magnetization in particles with high thermal stability, thus resolving the contradiction between stability and writability.
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 the formation of stable recording bits with steep magnetization transitions, achieving high line recording density and improved signal-to-noise ratio, while preventing adjacent track erasure and maintaining magnetization stability.
Implementation Method 1
a magnetic head writes data to a magnetic recording medium formed of a material with large magnetic anisotropy energy KU by supplying a heat to the medium to reduce the coercive force of the medium
Implementation Method 2
an electromagnetic transducer for writing data signals
Data Source
AI summary
In a heat-assisted magnetic recording, a thin-film magnetic head, which can form stable recording bits pattern having steep magnetization transition regions without using a near-field light generating element, is provided. The head is formed on an element forming surface of a substrate, and has a waveguide for leading a light for heat-assist to a magnetic medium and a write element formed on a trailing side of the waveguide and having a magnetic pole for applying a write field to the medium. Here, a write field profile, which is an intensity distribution of the write field from the pole along a track in a recoding layer of the medium, has a projecting region on a leading side. Further, an anisotropy field profile, which is a distribution of an anisotropy field when the anisotropy field is reduced by irradiating the light on a part of the recoding layer, traverses the projecting region.