FePtRh Magnetic Recording Medium Lowering Curie Temperature
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Solution Overview
Problem
Current magnetic recording media with FePt and added Cu have high Curie temperatures, making it difficult to achieve lower recording temperatures while maintaining thermal stability, as they require high magnetic fields and can lead to deterioration of protective films and recording heads.
Innovation Solution
A magnetic recording medium with a laminated structure comprising a first magnetic layer with a higher magnetic anisotropy constant (Ku) than the second magnetic layer, where the second layer is an FePtRh ordered alloy, allowing for a granular structure that lowers recording temperature and magnetic field requirements while maintaining thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If FePt with Cu is used to lower Curie temperature, then recording temperature is reduced, but Curie temperature remains comparatively high (650K with 10at% Cu)
Solution Approach 1:
The patent uses a composite magnetic layer structure combining FePt and FePtRh alloys. The FePtRh ordered alloy specifically lowers the Curie temperature to 550K while maintaining thermal stability through controlled composition (Fe: 40-50at%, Pt: 40-50at%, Rh: 5-20at%). This composite approach resolves the contradiction by achieving both lower recording temperature and maintained thermal stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the magnetic alloy by introducing Rhodium (Rh) as a third element in FePtRh ordered alloy. This parameter change specifically targets the Curie temperature reduction to 550K while maintaining adequate thermal stability, thereby resolving the contradiction between lowering recording temperature and maintaining reliability.
2Force
If high magnetic field is applied for recording, then magnetization reversal is achieved, but protective film and recording head deteriorate
Solution Approach 1:
The patent changes the magnetic properties parameter by using FePtRh ordered alloy with Curie temperature of 550K, which reduces the coercive force compared to conventional FePt. This parameter change allows magnetization reversal at lower magnetic field strength, thereby reducing the harmful effects on protective films and recording heads while still achieving successful recording.
3Reliability
If FePt ordered alloy is used, then thermal stability is improved, but coercive force is high and recording cannot be performed with ordinary recording head
Solution Approach 1:
The patent creates a composite magnetic layer system where FePt ordered alloy provides thermal stability and FePtRh ordered alloy provides lower coercive force. The combination maintains thermal stability while enabling recording with ordinary recording heads by reducing the required magnetic field strength.
Solution Approach 2:
The patent applies local quality by having different magnetic layers with different properties: FePt ordered alloy layer for thermal stability and FePtRh ordered alloy layer for reduced coercive force. Each layer performs its specific function locally, resolving the contradiction between thermal stability and coercive force.
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
The proposed structure enables recording at lower temperatures with reduced magnetic fields, ensuring thermal stability and extending the lifespan of the recording medium by minimizing heat-assisted magnetic recording system's adverse effects on protective films and recording heads.
Implementation Method 1
the second magnetic layer comprises an FePtRh ordered alloy... it has become possible to perform recording at a low temperature of 550 K
Implementation Method 2
a first magnetic layer having a magnetic anisotropy constant (Ku) at room temperature larger than Ku at room temperature of the second magnetic layer
Implementation Method 3
A heat-assisted magnetic recording system is a recording system in which a magnetic recording layer is irradiated with laser to heat and lower the coercive force
Data Source
AI summary
The present invention aims at providing a magnetic recording medium capable of realizing lowering of recording temperature. A magnetic recording medium comprises a substrate, and a magnetic recording layer comprising a first magnetic layer and a second magnetic layer, in which the second magnetic layer comprises an FePtRh ordered alloy, and the first magnetic layer has Ku at room temperature larger than Ku of the second magnetic layer at room temperature.