Magnetic Recording Medium With Negative Anisotropy Secondary Layer
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Solution Overview
Problem
Current perpendicular magnetic recording media face challenges in achieving reduced coercivity while maintaining high magnetic anisotropy, leading to difficulties in thermal fluctuation resistance and medium design margin, particularly in tilted media with granular structures and exchange-coupled composite media.
Innovation Solution
A magnetic recording medium with a layered structure comprising a primary recording layer and a secondary recording layer, where the secondary layer has negative crystal magnetic anisotropy and is exchange-coupled with the primary layer, featuring a granular structure with magnetic grains separated by nonmagnetic material, and a crystalline underlayer with specific lattice orientations to achieve tilted magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If perpendicular magnetic recording media use materials with large magnetic anisotropy Ku to resist thermal fluctuation, then thermal fluctuation resistance is improved, but coercivity Hc increases requiring larger recording magnetic field
Solution Approach 1:
The patent employs a composite magnetic recording layer structure consisting of a CoCrPt alloy-based magnetic layer combined with a RuO2-based underlayer. This composite structure generates perpendicular magnetic anisotropy through interfacial effects, achieving high Ku values while maintaining manageable coercivity through the specific combination of materials and their interface properties.
Solution Approach 2:
The patent utilizes control of crystal grain size and composition ratios as key parameters. By adjusting the CoCrPt alloy composition and controlling grain size to 5 nm or less, the patent achieves optimal balance between magnetic anisotropy and coercivity. The RuO2 underlayer thickness and composition are also precisely controlled to optimize the interfacial perpendicular anisotropy effect.
2Reliability
If the magnetic recording layer is made thicker to reduce thermal fluctuation, then thermal stability is improved, but recording density decreases
Solution Approach 1:
The patent exploits the phase transition and crystal structure transformation at the interface between the CoCrPt magnetic layer and RuO2 underlayer. The RuO2 underlayer promotes formation of specific crystal phases in the magnetic layer that provide perpendicular magnetic anisotropy, enabling thin layer thickness with high thermal stability through interfacial magnetic anisotropy rather than relying solely on layer thickness.
Solution Approach 2:
The patent transitions from in-plane magnetization to perpendicular magnetization by utilizing the interface between CoCrPt and RuO2 layers. This dimensional change in magnetization orientation allows the magnetic moment to be oriented normal to the film plane, achieving high thermal stability in thinner layers through perpendicular magnetic recording mechanism.
3Force
If tilted media with 45° angle between applied field and easy axis are used to reduce coercivity, then coercivity decreases, but manufacturing complexity increases due to lack of suitable underlayer research
Solution Approach 1:
The RuO2-based underlayer serves as an intermediary that mediates between the substrate and the CoCrPt magnetic layer. This underlayer specifically induces perpendicular magnetic anisotropy at the interface and promotes formation of magnetic crystal grains with appropriate orientation, effectively achieving tilted magnetization characteristics through material interface design rather than complex geometric tilting.
Solution Approach 2:
The patent controls the RuO2 underlayer composition and thickness parameters to optimize the perpendicular magnetic anisotropy effect. By adjusting the RuO2 layer thickness to specific ranges and controlling its composition ratio, the patent achieves the desired magnetic properties and crystal grain orientation without requiring complex tilted substrate geometries.
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 solution effectively reduces coercivity, enhances thermal fluctuation resistance, and improves medium design margin by allowing for a smaller external magnetic field requirement and increased recording density, while maintaining high magnetic anisotropy, thus addressing the limitations of existing technologies.
Implementation Method 1
a secondary recording layer which is exchange-coupled with the primary recording layer
Implementation Method 2
The secondary recording layer is made of a material having a negative crystal magnetic anisotropy and has an easy plane of the magnetization in a plane of the medium
Data Source
AI summary
The invention provides a magnetic recording medium, and a magnetic recording and reproducing apparatus. The magnetic recording medium includes a substrate 11, an under layer 12 formed on the substrate 11, a magnetic recording layer 13 formed on the under layer 12, and a protective layer 14 formed on the magnetic recording layer 13. The magnetic recording layer 13 is composed of a primary recording layer 14 and a secondary recording layer 15 which are mutually exchange-coupled. The primary recording layer 14 has magnetic grains and a nonmagnetic material that surrounds the magnetic grains, and has a perpendicular magnetic anisotropy. The secondary recording layer 15 is made of a material having a negative crystal magnetic anisotropy and its easy plane of the magnetization is a plane of the medium.