Optically Changeable Layer for Heat-Assisted Magnetic Recording
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Solution Overview
Problem
The challenge in magnetic recording technology is to achieve high recording density while maintaining thermal stability of magnetization, as reducing magnetic microparticle size increases anisotropic magnetic field, exceeding the write-field intensity limit, and incorporating an optical system for heat-assisted magnetic recording is complex and difficult to manufacture.
Innovation Solution
A magnetic recording medium with an optically changeable layer that generates near-field light internally when irradiated, reducing the anisotropic magnetic field and allowing for heat-assisted recording without a complex optical system in the head, using materials like antimony, lithium niobate, or terbium oxide that change refractive index with light intensity, enabling improved recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of magnetic microparticles is decreased to improve recording density, then recording density is improved, but thermal stability of magnetization degrades
Solution Approach 1:
The invention changes the magnetic anisotropy energy parameter KU by using specific magnetic materials (e.g., CoPt, CoPd, CoNi) and controlling particle composition and structure. This allows achieving high KU values that maintain thermal stability even with reduced particle size, thereby enabling high recording density without sacrificing magnetization stability
Solution Approach 2:
The invention uses composite magnetic materials combining different elements (Co-Pt, Co-Pd, Co-Ni alloys) to achieve optimal balance between magnetic properties. These composite materials provide both high magnetic anisotropy energy for thermal stability and appropriate saturation magnetization for writable coercive force, resolving the contradiction between recording density and thermal stability
2Reliability
If the magnetic anisotropy energy KU is increased to improve thermal stability, then thermal stability is improved, but anisotropic magnetic field increases exceeding write-field limit
Solution Approach 1:
The invention optimizes multiple magnetic parameters simultaneously by controlling particle size distribution, composition ratios, and crystal structure. By adjusting these parameters, the invention achieves high KU values for thermal stability while maintaining saturation magnetization Ms at levels that keep the anisotropic magnetic field Hk = 2KU/Ms within the writable range by conventional heads
Solution Approach 2:
The invention creates magnetic domains with localized high anisotropy energy regions surrounded by regions with optimized magnetization characteristics. This local quality differentiation allows maintaining thermal stability in critical regions while ensuring overall writability through appropriate Ms values in adjacent regions
3Reliability
If an optical system is incorporated for heat-assisted magnetic recording, then thermal stability is improved, but device complexity increases
Solution Approach 1:
The invention extracts the optical heating function from the magnetic head and relocates it to the recording medium itself. The medium contains optically active materials (e.g., phase-change materials, materials with strong optical absorption) that convert incident light directly into heat at the magnetic recording layer, eliminating the need for complex optical systems in the head while achieving the desired thermal effect for heat-assisted recording
4Ease of operation
If the anisotropic magnetic field is reduced with heat to enable writing, then writing becomes possible, but manufacturing precision requirements increase
Solution Approach 1:
The recording medium performs self-heating through optical absorption by materials embedded within it. When illuminated by light (from either the head or external source), the optically active materials in the medium convert light energy to heat directly at the magnetic layer, eliminating the need for precise optical focusing systems in the head. The medium itself provides the heating function, significantly reducing manufacturing precision requirements
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 solution allows for favorable heat-assisted magnetic recording with improved recording density and simplified manufacturing by generating near-field light within the medium, reducing the need for precise optical systems in the head and enhancing thermal stability.
Implementation Method 1
at least one optically changeable layer formed on a side opposite to the substrate relative to the magnetic recording layer, the at least one optically changeable layer being made transparent or a refractive index of the at least one optically changeable layer being changed when irradiated by light with an intensity not less than a predetermined intensity
Implementation Method 2
When the light irradiates the optically changeable layer in the above-described magnetic recording medium from the head, a minute opening or a refractive-index-changed area is formed within the irradiated portion on the optically changeable layer. The irradiation of the light onto the minute opening or the refractive-index-changed area enables near-field light to be generated, and the near-field light heats a portion of the magnetic recording layer
Implementation Method 3
at least one optically changeable layer being made transparent or a refractive index of the at least one optically changeable layer being changed when irradiated by light with an intensity not less than a predetermined intensity
Implementation Method 4
using materials like antimony, lithium niobate, or terbium oxide that change refractive index with light intensity
Data Source
AI summary
Provided is a magnetic recording medium that generates near-field light within itself and enables favorable heat-assisted magnetic recording with this near-field light. The medium comprises: a magnetic recording layer; and an optically changeable layer formed on the opposite side to a substrate relative to the magnetic recording layer, the optically changeable layer being made transparent or a refractive index of the layer being changed when irradiated by light with an intensity not less than a predetermined intensity. By the irradiation, a minute opening or a refractive-index-changed area is formed within the irradiated portion on the optically changeable layer. The light irradiation onto the minute opening or the refractive-index-changed area enables near-field light to be generated, which heats a portion of the magnetic recording layer. Thus, the anisotropic field of the portion is lowered to a writable value, which enables heat-assisted magnetic recording by applying write field.