MRAM Stray Field Reduction via Non-Magnetic Spacer
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Solution Overview
Problem
Magnetic random access memory (MRAM) devices face performance degradation due to stray magnetic fields emitted by magnetic layers, which cause switching asymmetry in the free layer and affect the stability and retention time of stored data, as well as the performance of precessional spin current magnetic layers.
Innovation Solution
A magnetic tunnel junction stack is designed with an auxiliary layer and auxiliary exchange coupling layers to reduce stray magnetic fields, improving the magnetic-moment imbalance between synthetic antiferromagnetic layers and the reference layer, thereby reducing the impact on the free layer and optional filter layers like polarizer or precessional spin current magnetic layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic layers (reference layer and synthetic antiferromagnetic layers) are used in MRAM devices, then data storage and switching functionality are achieved, but stray magnetic fields are generated that cause switching asymmetry and degrade performance
Solution Approach 1:
A non-magnetic spacer layer is introduced between the magnetic reference layer and the free layer to mediate their interaction. This spacer reduces the direct magnetic coupling and stray field impact from the reference layer on the free layer, thereby reducing switching asymmetry while maintaining the pinning effect needed for stable reference magnetization.
Solution Approach 2:
The harmful stray magnetic fields are effectively 'taken out' or isolated from affecting the free layer by using the non-magnetic spacer as a shield. The spacer extracts the harmful magnetic interaction from the system, allowing the magnetic layers to maintain their functionality without degrading the free layer performance.
2Volume of moving object
If magnetic layers are placed close together to reduce device size, then device miniaturization is achieved, but stray magnetic field impact on free layer and filter layers increases
Solution Approach 1:
The non-magnetic spacer acts as an intermediary that allows magnetic layers to be positioned close together for miniaturization while simultaneously protecting the free layer and filter layers from excessive stray magnetic field impact. The spacer's thickness is optimized to balance miniaturization goals with magnetic field isolation requirements.
3Stability of the object's composition
If synthetic antiferromagnetic layers are used to stabilize reference layer magnetization, then magnetic stability is improved, but magnetic-moment imbalance creates stray fields that affect free layer switching
Solution Approach 1:
The non-magnetic spacer layer mediates between the synthetic antiferromagnetic structure (which provides stable reference magnetization through exchange coupling) and the free layer. It allows the synthetic antiferromagnetic layers to maintain their stabilizing function while reducing the stray fields generated by their magnetic-moment imbalance from affecting the free layer switching asymmetry.
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 reduction in stray magnetic fields enhances the electrical performance of the MRAM stack by minimizing switching asymmetry in the free layer and improves the dynamic magnetic rotation of precessional spin current magnetic layers, leading to improved memory retention and reduced error rates.
Implementation Method 1
reduce stray magnetic fields generated by magnetic layers of the stack
Implementation Method 2
auxiliary exchange coupling layers to reduce stray magnetic fields, improving the magnetic-moment imbalance between synthetic antiferromagnetic layers and the reference layer
Implementation Method 3
Due to the spin-polarized electron tunneling effect, the electrical resistance of the cell changes due to the orientation of the magnetization of the two layers
Implementation Method 4
an antiferromagnetic coupling layer or spacer layer that is not magnetic. The SAF structure also may be formed over a seed layer
Data Source
AI summary
A magnetoresistive random-access memory (MRAM) is disclosed. The MRAM device reduces stray magnetic fields generated by magnetic layers of the stack, including a reference layer and magnetic layers of the synthetic antiferromagnetic layer, in a way that reduces their impact on the other layers of the stack, including a free layer and an optional filter layer, which may include a polarizer layer or a precessional spin current magnetic layer. The reduction in stray magnetic fields in the stack increases the electrical and retention performance of the stack by reducing switching asymmetry in the free layer. The reduction in stray magnetic fields also may improve performance of a filter layer, such as a precessional spin current magnetic layer by reducing asymmetry in the dynamic magnetic rotation of that layer.