PMR Disk Capping Layer Curie Temperature for DC Readback Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional heat-assisted magnetic recording (HAMR) media suffer from high DC read back noise levels during the read back process, which increases as the size of the reader element shrinks, and existing solutions do not effectively address this issue.
Innovation Solution
A perpendicular magnetic recording (PMR) disk structure is introduced, featuring a capping layer with a higher Curie temperature and lower anisotropy than the magnetic recording layer, along with an exchange coupling layer to partially decouple these layers, reducing DC read back noise and improving transition jitter during the refreezing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional HAMR media structure is used with magnetic recording layer, then high coercivity magnetic materials can be written, but high DC read back noise level occurs during read back process
Solution Approach 1:
The magnetic recording layer is segmented into multiple sub-layers with different magnetic properties. The first sub-layer has high coercivity for stable data storage, while the second sub-layer has lower coercivity and serves as a reference layer to reduce read back noise. This segmentation allows the system to simultaneously achieve high coercivity for writing and noise reduction for reading.
Solution Approach 2:
A non-magnetic spacer layer is introduced as an intermediary between the first and second magnetic sub-layers. This spacer layer decouples the exchange interaction between the two sub-layers, allowing them to function independently - the first sub-layer maintains high coercivity for data storage while the second sub-layer provides a stable reference pattern to reduce DC read back noise.
2Productivity
If reader element size is shrunk to increase storage density, then higher capacity is achieved, but DC read back noise level increases
Solution Approach 1:
The non-magnetic spacer layer acts as an intermediary that decouples the reference layer from the recording layer, allowing the reader element to read the reference pattern without being affected by the high coercivity of the recording layer. This enables smaller reader elements to function effectively by providing a low-coercivity reference signal that is easier to detect.
Solution Approach 2:
The invention changes the magnetic parameter (coercivity) by introducing a second magnetic sub-layer with lower coercivity than the first sub-layer. This parameter change creates a reference signal with lower magnetic strength that can be more easily detected by shrunk reader elements, thereby reducing DC read back noise while maintaining high storage density.
3Stability of the object's composition
If capping layer with lower Curie temperature is used for magnetic stabilization, then storage stability is improved, but DC read back noise is not reduced
Solution Approach 1:
Instead of using a single capping layer, the invention segments the magnetic structure into multiple sub-layers with different functions. The first sub-layer provides magnetic stabilization with high coercivity, while the second sub-layer specifically addresses read back noise with lower coercivity. This segmentation allows independent optimization of stabilization and noise reduction functions.
Solution Approach 2:
The magnetic recording layer is constructed as a composite structure with two different magnetic sub-layers separated by a non-magnetic spacer. This composite structure combines materials with different coercivity values to achieve both magnetic stabilization and DC read back noise reduction, which a single uniform material cannot accomplish.
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 PMR disk structure significantly reduces DC read back noise and enhances the signal-to-noise ratio by aligning magnetic orientations and reducing magnetization dispersion, thereby improving the reliability and quality of the read back signal.
Implementation Method 1
The PMR disk structure significantly reduces DC read back noise and enhances the signal-to-noise ratio by aligning magnetic orientations and reducing magnetization dispersion
Implementation Method 2
an exchange coupling layer to partially decouple these layers
Implementation Method 3
The heating of a local area may be accomplished by, for example, a heat or thermal source such as a laser
Implementation Method 4
The local area is then rapidly cooled to retain the written information
Data Source
AI summary
A perpendicular magnetic recording (PMR) disk used in energy assisted magnetic recording drives is described. The PMR disk includes a substrate, a magnetic recording layer disposed above the substrate, an exchange coupling layer disposed above the magnetic recording layer, and a capping layer disposed above the exchange coupling layer. The capping layer has a Curie temperature greater than the Curie temperature of the magnetic recording layer.