ST-MRAM Storage Element With Inclined Ferromagnetic Layers
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Solution Overview
Problem
The existing spin torque magnetic random access memory (ST-MRAM) technologies face challenges in completing magnetization reversal within a writing period, leading to writing errors due to the dependence on magnetization angles and thermal stability issues, especially when the magnetization angle aligns with the easy magnetization axis, resulting in prolonged reversal times.
Innovation Solution
The proposed solution involves a storage element with a magnetization fixed layer and a magnetization free layer, where the ferromagnetic layers are inclined relative to each other, and a coupling layer is used to enhance magnetic coupling, allowing for magnetization reversal within a predetermined time frame. This structure includes a magnetization fixed layer with a perpendicular magnetization direction, a magnetization free layer with multiple ferromagnetic layers laminated together, and a nonmagnetic layer between them, facilitating spin torque magnetization reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the magnetization angle aligns with the easy magnetization axis in conventional ST-MRAM, then thermal stability is improved, but the magnetization reversal time becomes excessively long leading to writing errors
Solution Approach 1:
The storage layer is divided into multiple ferromagnetic sublayers (first and second ferromagnetic layers) with different magnetization directions. The first ferromagnetic layer has magnetization inclined at a first angle from the perpendicular direction, while the second ferromagnetic layer has magnetization inclined at a second angle. This segmentation allows the system to maintain thermal stability through perpendicular magnetization components while reducing reversal time through the combined effect of multiple layers with optimized angles.
Solution Approach 2:
The invention optimizes the magnetization angles of the ferromagnetic layers relative to the perpendicular direction. By setting specific inclination angles for the first and second ferromagnetic layers, the system achieves a balance between thermal stability (requiring perpendicular magnetization) and reversal speed (benefiting from angled magnetization). The coupling layer strength and layer thicknesses are also adjusted as parameters to achieve optimal performance.
2Adaptability or versatility
If conventional ST-MRAM uses spin torque magnetization reversal, then rewriting capability is improved, but writing errors occur when magnetization angle alignment causes prolonged reversal time
Solution Approach 1:
The storage layer is segmented into multiple ferromagnetic layers with different magnetization orientations. This segmentation enables the system to maintain rewriting capability through spin torque while improving writing reliability by distributing the reversal process across multiple layers with optimized angle configurations, preventing the prolonged reversal time that causes writing errors in conventional single-layer structures.
Solution Approach 2:
The invention uses a composite magnetic structure consisting of multiple ferromagnetic layers coupled through a coupling layer. This composite structure combines layers with different magnetization characteristics to achieve both rewriting capability and writing reliability. The coupling layer mediates the interaction between layers, enabling controlled magnetization reversal while maintaining thermal stability.
3Reliability
If the magnetization reversal time is extended to ensure thermal stability, then reliability is improved, but the writing operation exceeds the predetermined time frame causing writing errors
Solution Approach 1:
The storage layer is segmented into multiple ferromagnetic layers with optimized magnetization angles. This segmentation enables the system to achieve thermal stability through perpendicular magnetization components while reducing the overall reversal time by distributing the magnetization reversal process across multiple layers, thereby improving writing speed without sacrificing reliability.
Solution Approach 2:
The invention optimizes multiple parameters including the inclination angles of magnetization in each ferromagnetic layer, the thickness of each layer, and the coupling strength between layers. By adjusting these parameters, the system achieves a balance where thermal stability is maintained through perpendicular magnetization components while the writing operation completes within the predetermined time frame through optimized reversal dynamics.
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 reduces the time required for magnetization reversal, minimizes writing errors, and maintains thermal stability, enabling high-speed and reliable writing operations while reducing the current needed for magnetization reversal.
Implementation Method 1
the phenomenon that a spin polarized electron passing through a magnetic layer of which magnetization is fixed in a direction gives a torque to another free magnetic layer (of which magnetization is not fixed) when entering this free magnetic layer (also called spin transfer torque) is utilized
Implementation Method 2
a coupling layer formed between each pair of adjacent ferromagnetic layers
Data Source
AI summary
A storage element includes a magnetization fixed layer, and a magnetization free layer. The magnetization fixed layer includes a plurality of ferromagnetic layers laminated together with a coupling layer formed between each pair of adjacent ferromagnetic layers. The magnetization directions of the ferromagnetic layers are inclined with respect to a magnetization direction of the magnetization fixed layer.