Perpendicular Magnetic Recording Medium With Coupling Layer
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Solution Overview
Problem
Conventional perpendicular magnetic recording media face challenges in achieving high recording densities while maintaining thermal stability and ease of recording, as finer magnetization reversal units lead to increased magnetic field intensity and reduced recording ability.
Innovation Solution
A perpendicular magnetic recording medium with a three-layer structure, featuring a soft magnetic backing layer, an underlayer, and a magnetic recording layer with different uniaxial anisotropy constants, where the first and second magnetic recording layers are ferromagnetically coupled via a thin coupling layer, allowing for controlled magnetization reversal and improved thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetization reversal unit is reduced to increase recording density, then the recording resolution is improved, but the thermal stability is diminished
Solution Approach 1:
The patent changes the uniaxial anisotropy constant Ku as a key parameter to resolve the contradiction. By increasing Ku in the magnetic recording layer while maintaining a reduced magnetization reversal unit size, the patent achieves both high recording resolution and improved thermal stability. The relationship KuVa (where Va is activation volume) is used as the thermal stability index, and increasing Ku compensates for the reduced Va caused by finer magnetization reversal units.
Solution Approach 2:
The patent employs a composite magnetic recording layer structure consisting of multiple layers with different uniaxial anisotropy constants Ku. This includes a first magnetic recording layer with Ku1, a second magnetic recording layer with Ku2, and optionally a third magnetic recording layer with Ku3, where Ku1 < Ku2 < Ku3. This composite structure allows optimization of both thermal stability and recording resolution by combining materials with different magnetic properties.
2Reliability
If Ku is increased to maintain thermal stability, then the thermal stability is improved, but the magnetic field intensity necessary during recording increases
Solution Approach 1:
The patent optimizes the distribution of uniaxial anisotropy constant Ku across multiple magnetic recording layers to resolve this contradiction. By creating a gradient structure where Ku increases from the first to the third layer (Ku1 < Ku2 < Ku3), the patent achieves high overall thermal stability while the lower-Ku layers require less magnetic field intensity for magnetization reversal, thus reducing the overall recording field requirement.
Solution Approach 2:
The patent applies local quality by assigning different uniaxial anisotropy constants to different regions (layers) of the magnetic recording layer. The first magnetic recording layer with lower Ku1 requires less magnetic field for recording, while the third magnetic recording layer with higher Ku3 provides enhanced thermal stability. This spatial variation in magnetic properties allows simultaneous optimization of both recording ease and thermal stability.
3Measurement precision
If the magnetization reversal unit is reduced to increase recording density, then the recording resolution is improved, but the ease of recording is reduced
Solution Approach 1:
The patent changes the uniaxial anisotropy constant Ku to resolve this contradiction. By increasing Ku in the magnetic recording layer, the patent achieves both high recording resolution (through reduced magnetization reversal unit size) and improved ease of recording (through increased thermal stability that prevents unwanted magnetization changes). The optimized Ku value allows finer magnetic domains to be maintained stably.
Solution Approach 2:
The patent uses a composite magnetic recording layer structure with multiple layers having different uniaxial anisotropy constants (Ku1, Ku2, Ku3 where Ku1 < Ku2 < Ku3). This composite structure enables the system to achieve high recording resolution through fine magnetization reversal units while maintaining ease of recording through the cumulative thermal stability provided by the higher-Ku layers.
4Ease of operation
If a two-layer magnetic recording structure is used to improve ease of recording, then the ease of recording is improved, but the recording density is limited
Solution Approach 1:
The patent extends the two-layer composite structure to a three-layer magnetic recording layer structure with uniaxial anisotropy constants Ku1, Ku2, and Ku3 where Ku1 < Ku2 < Ku3. This three-layer composite material structure allows further optimization of both ease of recording and recording density by providing a more gradual transition in magnetic properties across the layers, enabling finer magnetization reversal units while maintaining recording ease.
Solution Approach 2:
The patent segments the magnetic recording layer into three distinct layers with progressively increasing uniaxial anisotropy constants. This segmentation allows each layer to contribute differently to the overall magnetic properties, with the first layer facilitating ease of recording, the second layer providing intermediate properties, and the third layer enhancing thermal stability to support higher recording densities.
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 lowers the switching magnetic field, enhances recording density, and maintains thermal stability, while improving noise and signal-to-noise characteristics, facilitating easier recording.
Implementation Method 1
the first magnetic recording layer and second magnetic recording layer are ferromagnetically coupled via the coupling layer
Implementation Method 2
the first magnetic recording layer, second magnetic recording layer, and third magnetic recording layer have directions of easy axis of magnetization in the direction perpendicular to the plane of the nonmagnetic substrate
Implementation Method 3
the problem of the 'thermal fluctuation' phenomenon due to which recorded signals cannot be held with stability
Data Source
AI summary
A perpendicular magnetic recording medium, which includes a first magnetic recording layer, a second magnetic recording layer, and a third magnetic recording layer disposed sequentially on a nonmagnetic substrate, and a coupling layer formed between the first and second magnetic recording layers. The first, second and third magnetic recording layers have an easy axis of magnetization in a direction perpendicular to a film plane of the nonmagnetic substrate. The first and second magnetic recording layers are ferromagnetically coupled via the coupling layer.