Epitaxial Exchange Coupling Layer for FePt Magnetic Recording Media
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Solution Overview
Problem
FePt-based perpendicular magnetic recording media with high magnetic anisotropy faces challenges in being recordable due to exceeding coercivity thresholds, as existing exchange coupling methods for L10 ordered alloys are uncontrolled and lack an exchange coupling interlayer.
Innovation Solution
Incorporation of an epitaxial exchange coupling layer (EECL) between magnetic recording layers to provide controllable and tunable exchange coupling, enabling epitaxial texture transfer and adjusting the degree of coupling, thereby maintaining high anisotropy while reducing the media writing field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high magnetic anisotropy is used in L10 ordered alloy to resist demagnetization effects and maintain thermal stability, then thermal stability and noise reduction are improved, but coercivity exceeds the recording head threshold and recordability deteriorates
Solution Approach 1:
The magnetic recording layer is segmented into multiple sub-layers with different magnetic properties: a hard magnetic layer (L10 FePt) providing high anisotropy and thermal stability, and a soft magnetic layer providing ease of recording. This segmentation allows each layer to fulfill its specific function without compromise
Solution Approach 2:
The patent employs a composite magnetic structure combining L10 FePt hard magnetic layer with soft magnetic layers, creating an exchange-coupled composite media. The composite structure integrates the advantages of both hard and soft magnetic materials to achieve high thermal stability and recordability simultaneously
2Ease of operation
If exchange coupling is implemented without an exchange coupling interlayer in L10 FePt-based media, then soft magnetic layer can assist switching of hard magnetic layer, but exchange coupling is uncontrolled and cannot be tuned
Solution Approach 1:
A nonmagnetic exchange coupling layer is introduced as an intermediary between the hard and soft magnetic layers. This intermediary layer provides controlled exchange coupling by allowing spin polarization transfer while preventing direct magnetic interaction, enabling tunable coupling strength through thickness adjustment
Solution Approach 2:
The exchange coupling strength is controlled by changing the thickness parameter of the nonmagnetic exchange coupling layer. By adjusting this geometric parameter, the degree of exchange coupling between hard and soft layers can be precisely tuned to optimize recording performance
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 EECL allows for high coercivity and low saturation magnetic fields, enhancing the recordability of FePt-based media by amplifying the write field and stabilizing the magnetic orientation, thus overcoming the coercivity threshold limitations.
Implementation Method 1
epitaxial exchange coupling layer (EECL) between a first magnetic recording layer and a second magnetic recording layer to provide controllable and tunable exchange coupling between the first and second magnetic recording layers while also enabling epitaxial transfer of texture from the first magnetic recording layer to the second magnetic recording layer
Implementation Method 2
provide controllable and tunable exchange coupling between the first and second magnetic recording layers
Data Source
AI summary
FePt-based perpendicular magnetic recording (PMR) media including an epitaxial exchanged coupling layer (EECL) between FePtX magnetic recording layers. The degree of exchange coupling may be modulated by the EECL while the texture is transferred between the magnetic recording layers. With an EECL of proper composition and thickness, the FePt-based composite media has high anisotropy field and low saturation magnetic field.