Flux Channeling Layer for Patterned Perpendicular Magnetic Recording
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Solution Overview
Problem
Patterned perpendicular magnetic recording media face challenges with wide variation in coercive field among magnetic islands, leading to decreased bit-addressability and increased likelihood of overwriting due to fringing fields, and require improved readback signal and signal-to-noise ratio.
Innovation Solution
Incorporating a flux channeling layer (FCL) below the recording layer in discrete data islands, with a soft underlayer and nonmagnetic exchange break layer to prevent magnetic coupling, and a nonmagnetic separation layer to prevent magnetic coupling between the FCL and recording layer, utilizing a soft magnetic material with anisotropy field lower than the recording layer to channel magnetic flux and enhance readback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flux channeling layer is added below the recording layer in discrete data islands, then the external field required for writing is reduced and bit-addressability is improved, but the device complexity increases due to additional layers and fabrication steps
Solution Approach 1:
The magnetic recording medium is segmented into discrete data islands with a flux channeling layer in each island, separating the magnetic recording function from the flux channeling function. This segmentation allows independent optimization of each layer's properties to improve bit-addressability while managing complexity through functional decomposition.
Solution Approach 2:
The flux channeling layer acts as an intermediary between the write head and the recording layer, channeling and concentrating the magnetic flux to the desired location. This intermediary layer improves writing efficiency and bit-addressability by directing flux precisely to the target data island while minimizing fringing fields that cause overwriting of adjacent dots.
2Quantity of substance
If the size of magnetic islands is reduced to increase data density, then the achievable density increases, but the switching field distribution broadens and coercive field variation increases
Solution Approach 1:
The flux channeling layer provides locally optimized magnetic flux distribution within each data island, creating a more uniform and controlled magnetic field environment. This local quality control compensates for the reduced size effects in smaller islands, maintaining more consistent coercive fields and switching characteristics across the array even as island size decreases to increase density.
3Quantity of substance
If track density is increased to achieve ultra-high areal density, then the areal density increases, but fringing fields from the write head leak into adjacent dots causing inadvertent switching
Solution Approach 1:
The flux channeling layer serves as a magnetic flux intermediary that confines and directs the write head's magnetic field primarily to the intended target dot. By channeling the flux through high-permeability material with controlled anisotropy, the layer reduces fringing field leakage into adjacent tracks and dots, enabling higher track densities without excessive overwriting of neighboring data.
Solution Approach 2:
The flux channeling layer's magnetic parameters (permeability, anisotropy field, thickness) are optimized to change the flux distribution pattern. By selecting materials and dimensions that create strong in-plane or out-of-plane anisotropy, the layer confines magnetic flux laterally, reducing the angular spread of fringing fields and minimizing interference with adjacent dots when track density is increased.
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 reduces the external field required for writing, improves bit-addressability by minimizing inadvertent switching of adjacent dots, and enhances the readback signal and signal-to-noise ratio, thereby addressing the limitations of bit density and overwriting in patterned perpendicular media.
Implementation Method 1
The FCL has an anisotropy field low enough to assure that the FCL is saturated at a much lower field than the RL and thus can channel the magnetic flux from the write head through the island positions
Implementation Method 2
the dipolar fields from the RL above it are able to align the magnetization of the FCL parallel to the magnetization direction of the RL
Implementation Method 3
a nonmagnetic exchange break layer (EBL) on the SUL that breaks the magnetic exchange between the SUL and the FCL in the islands
Implementation Method 4
A nonmagnetic separation layer (SL) is located between the FCL and the RL in the islands to prevent magnetic coupling between the RL and the FCL
Data Source
AI summary
A patterned perpendicular magnetic recording medium, such as a disk for use in hard disk drives, has a flux channeling layer (FCL) located below the recording layer (RL) in each of the discrete data islands. The disk includes a substrate, a soft underlayer (SUL) of soft magnetically permeable material on the substrate, and a nonmagnetic exchange break layer (EBL) on the SUL. A nonmagnetic separation layer (SL) is located between the FCL and the RL in the islands. The FCL has an anisotropy field substantially lower than the anisotropy field of the RL, and a magnetization equal to or higher than the magnetization of the RL. The FCL is saturated at a much lower field than the RL and thus channels the magnetic flux from the write head through the island positions. The dipolar fields from the RL above the FCL polarize the magnetization of the FCL parallel to the magnetization direction of the RL in the absence of an external field, to thereby enhance the readback signal.