Magnetic Tunnel Junction Free Layer Segmentation
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Solution Overview
Problem
Magnetoresistive sensors in data storage devices face challenges with low tunnel magnetoresistance (TMR), increased interlayer coupling, and decreased signal-to-noise ratio (SNR) due to thinner designs and higher recording densities, which degrade sensor performance.
Innovation Solution
A magnetoresistive device with a multilayer free layer structure, including Co or FCC FeCo layers sandwiched between a BCC CoFe50 nanolayer and an amorphous CoFeB layer, and incorporating ferromagnetic and boron layers with specific thicknesses and configurations to reduce interlayer coupling and enhance TMR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If sensor thickness is reduced to achieve higher recording densities, then device miniaturization is improved, but tunnel magnetoresistance (TMR) decreases and interlayer coupling increases
Solution Approach 1:
The free layer is segmented into multiple sub-layers including BCC CoFeB nanolayer, amorphous CoFeB layer, and Co or FCC FeCo insertion layers. This segmentation allows each sub-layer to contribute differently to the overall magnetic properties, enabling thin total thickness while maintaining high TMR through optimized interface effects and reduced interlayer coupling between segmented portions.
Solution Approach 2:
The invention uses composite material structure combining different crystalline phases (BCC and FCC) and amorphous phases in the free layer. The BCC CoFeB provides high spin polarization, the amorphous CoFeB reduces magnetocrystalline anisotropy, and the Co/FCC FeCo insertion layers create nanocrystalline disorder that suppresses interlayer coupling, collectively achieving high TMR in a thin profile.
2Volume of moving object
If sensor thickness is reduced to achieve higher recording densities, then device miniaturization is improved, but interlayer coupling increases
Solution Approach 1:
Co or FCC FeCo insertion layers are introduced as intermediary layers between the BCC CoFeB nanolayer and the amorphous CoFeB layer. These intermediary layers create nanocrystalline disorder that acts as a buffer to reduce direct magnetic coupling between adjacent ferromagnetic layers, thereby suppressing harmful interlayer coupling effects while maintaining the thin overall structure.
3Reliability
If amorphous CoFeB layer thickness is reduced to improve TMR, then tunnel magnetoresistance is improved, but structural stability deteriorates
Solution Approach 1:
Different regions of the free layer are assigned different local qualities: the BCC CoFeB nanolayer provides high spin polarization at the barrier interface, the Co or FCC FeCo insertion layers provide nanocrystalline disorder to reduce coupling, and the amorphous CoFeB layer provides low magnetocrystalline anisotropy. This local optimization allows the amorphous layer to be thin enough for high TMR while the combined structure maintains overall stability.
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 increases TMR and reduces interlayer coupling, leading to improved sensor performance and signal-to-noise ratio, enabling higher recording densities and reliability in data storage devices.
Implementation Method 1
utilize sensors in relation to hard disk drives that are thinner, have high recording densities, and have lower resistance-area product (RA) in order to attempt to achieve higher volumes of data that can be stored and processed by computers. However, using such sensors can lower tunnel magnetoresistance (TMR)
Implementation Method 2
lower magnetic moments, and decrease signal-to-noise ratio (SNR). Such issues can degrade sensors and hinder sensor performance and resolution. Therefore, there is a need for sensors that facilitate higher TMR with reduced interlayer coupling (Hint), and sensor asymmetry.
Data Source
AI summary
The present disclosure generally relates to magnetoresistive device apparatus and methods. The magnetoresistive device includes a read head. The read head is a tunneling magnetoresistive reader that includes a multilayer free layer structure. The multilayer structure includes one or more layers of Co or FCC FeCo sandwiched between a BCC CoFe50 nanolayer and an amorphous CoFeB layer. The one or more layers of Co or FCC FeCo create nanocrystalline disorder that allows the thickness of the amorphous CoFeB layer to be reduced while retaining or even improving TMR and reducing the interlayer coupling field.