Soft Magnetic Underlayer Antiferromagnetic Coupling for High Permeability
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Solution Overview
Problem
Current magnetic recording media with soft magnetic underlayers face challenges in achieving both high magnetic permeability and antiferromagnetic coupling, which are necessary for low noise characteristics and effective magnetization stabilization, as the conditions for enhancing permeability and antiferromagnetic coupling do not necessarily coincide.
Innovation Solution
A magnetic recording medium is developed with a soft magnetic underlayer composed of Fe, Co, and Ta, antiferromagnetically coupled using the second peak of the antiferromagnetic coupling force, achieving a magnetic permeability of not less than 1,000 H/m, and a Fe:Co ratio of 60:40 to 70:30 with 13 to 16 atomic % Ta, to enhance both magnetic permeability and antiferromagnetic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a soft magnetic underlayer is provided to improve magnetic flux efficiency, then recording magnetic field gradient is increased, but leaked magnetic flux enters the reproducing head causing noise
Solution Approach 1:
An orientation control layer is introduced as an intermediary between the soft magnetic underlayer and the perpendicular magnetic layer. This layer has perpendicular magnetic anisotropy and controls the magnetization orientation, preventing leaked magnetic flux from domain walls in the soft magnetic underlayer from entering the reproducing head while maintaining the mirror image effect for field concentration.
Solution Approach 2:
The magnetic recording medium uses a composite structure with multiple layers having different magnetic properties: a soft magnetic underlayer (Fe-Co-B alloy) for high permeability and field concentration, an orientation control layer (CoFeB alloy with perpendicular anisotropy) for magnetization control, and a perpendicular magnetic layer for data storage. Each layer contributes specific properties to resolve the contradiction.
2Quantity of substance
If the magnetic recording density is increased, then storage capacity is improved, but the effect of demagnetizing field at bit boundaries increases causing noise
Solution Approach 1:
The invention changes the magnetization orientation parameter from in-plane to perpendicular magnetization. This parameter change fundamentally alters the demagnetizing field distribution, reducing its effect at bit boundaries even at high recording densities, thereby suppressing noise while maintaining high storage capacity.
3Power
If the magnetic permeability of the soft magnetic underlayer is increased, then magnetic flux extraction is improved, but the conditions for antiferromagnetic coupling are compromised
Solution Approach 1:
The invention applies local quality by giving different regions of the magnetic structure different properties: the soft magnetic underlayer has high permeability for flux extraction, while the orientation control layer has perpendicular magnetic anisotropy for stabilizing magnetization orientation and enabling antiferromagnetic coupling effects. Each layer is optimized for its specific function.
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 approach allows for low noise characteristics and effective stabilization of magnetization, preventing leaked magnetic flux from entering the reproducing head and enhancing the extraction of the writing magnetic field, resulting in improved recording and reproduction properties.
Implementation Method 1
a soft magnetic underlayer formed by antiferromagnetic coupling of a plurality of soft magnetic layers
Implementation Method 2
the mirror image effect of the soft magnetic underlayer has the function of strengthening the recording magnetic field from the main magnetic pole of the magnetic recording head, thereby spatially concentrating the recording magnetic field and increasing the gradient of the recording magnetic field
Implementation Method 3
perpendicular magnetic recording media in which the axis of easy magnetization within the magnetic film is mainly oriented perpendicularly
Implementation Method 4
the reduction in the recording bit volume accompanying the increase in recording density can be kept to a minimum, meaning the medium is also resistant to the heat fluctuation effect
Data Source
AI summary
A magnetic recording medium that is capable of realizing both high magnetic permeability and antiferromagnetic coupling for a soft magnetic underlayer. Namely, a magnetic recording medium including at least a non-magnetic substrate on which is laminated a soft magnetic underlayer formed by antiferromagnetic coupling of a plurality of soft magnetic layers, and a perpendicular magnetic layer for which the axis of easy magnetization is oriented mainly perpendicularly to the non-magnetic substrate, wherein the soft magnetic layers contain Fe as a first main component, Co as a second main component, and also contain Ta, the soft magnetic underlayer is antiferromagnetically coupled using the second peak or a subsequently appearing peak of the antiferromagnetic coupling force, which changes according to the thickness of a spacer layer sandwiched between the plurality of soft magnetic layers, and the magnetic permeability of the soft magnetic underlayer is not less than 1,000 H/m.