Perpendicular Magnetic Recording Medium Cr Segmentation
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Solution Overview
Problem
Current perpendicular magnetic recording media face challenges in achieving high signal-to-noise ratio (SNR), thermal stability, and write-ability due to limitations in reducing chromium (Cr) concentration, which affects magnetic anisotropy and cluster size, leading to instability and noise issues.
Innovation Solution
A perpendicular magnetic recording medium with a substrate, soft magnetic underlayer, and multiple magnetic layers comprising Co, Cr, Pt, and oxides, where the Cr concentration is optimized between 23% and 32% in adjacent layers, and the ferromagnetic metal layer does not include oxides, ensuring a granular structure with oxides surrounding ferromagnetic grains, and a nucleation field higher than 159.2 kA/m.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Cr concentration is reduced to decrease magnetic cluster size, then recording density is improved, but thermal stability deteriorates
Solution Approach 1:
The magnetic layer is divided into multiple sub-layers with different Cr concentrations. The first magnetic layer has lower Cr concentration (5-20 at.%) for small cluster size and high recording density, while the second magnetic layer has higher Cr concentration (15-30 at.%) for thermal stability. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
Different regions of the magnetic layer structure are assigned different Cr concentrations tailored to local requirements. The lower Cr concentration region (first magnetic layer) provides small magnetic clusters for high density, while the higher Cr concentration region (second magnetic layer) provides thermal stability. This local optimization resolves the global contradiction.
2Object-affected harmful factors
If Cr concentration is reduced to improve SNR, then noise is reduced, but magnetic anisotropy energy decreases
Solution Approach 1:
The magnetic layer is segmented into two sub-layers with different Cr concentrations. The first magnetic layer with lower Cr concentration (5-20 at.%) provides strong magnetic anisotropy energy for signal stability, while the second magnetic layer with higher Cr concentration (15-30 at.%) reduces noise through oxide segregation. This segmentation allows simultaneous optimization of both parameters.
3Productivity
If oxide segregation is promoted to reduce magnetic cluster size, then recording density is improved, but switching field increases making recording impossible
Solution Approach 1:
The magnetic layer is divided into two sub-layers with different oxide concentrations and granular structures. The first magnetic layer has lower oxide content for easier magnetization switching (good write-ability), while the second magnetic layer has higher oxide content for smaller magnetic clusters (high recording density). This segmentation resolves the contradiction between write-ability and recording density.
Solution Approach 2:
Different regions of the magnetic layer structure are assigned different oxide concentrations tailored to local requirements. The lower oxide concentration region provides easy magnetization switching for write-ability, while the higher oxide concentration region provides small magnetic clusters for high density. This local optimization resolves the global contradiction.
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 enhances thermal stability, reduces noise, and improves write-ability by maintaining a high SNR while allowing for thinner film thickness, reducing magnetic cluster size, and suppressing cross-erase effects.
Implementation Method 1
the magnetic layer with the lowest Cr concentration has a granular structure in which oxides surround ferromagnetic grains therein
Implementation Method 2
a ferromagnetic metal layer formed above the magnetic layer, the ferromagnetic metal layer comprising mainly Co, Cr, and Pt
Data Source
AI summary
According to one embodiment, a PMRM includes a substrate, a soft magnetic underlayer above the substrate, an underlayer above the soft magnetic underlayer, an oxide-containing magnetic layer above the underlayer, and a ferromagnetic layer above the magnetic layer having no oxides. The underlayer controls orientation and segregation of the magnetic layer. The oxide-containing magnetic layer comprises at least two or more magnetic layers, a Cr concentration of the magnetic layer adjacent to the ferromagnetic metal layer is between about 23 at. % and about 32 at. %, and a difference between the Cr concentration of the magnetic layer adjacent to the ferromagnetic metal layer and a magnetic layer having a lowest Cr concentration among the at least three magnetic layers is less than about 25 at. %, the magnetic layer with a lowest Cr concentration has a granular structure, and a nucleation field is greater than about 159.2 kA/m.