Perpendicular MTJ with Modulated Moment Density Layer
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Solution Overview
Problem
Conventional perpendicular magnetic tunnel junction (pMTJ) devices face challenges in optimizing switching speed, switching current, and thermal barrier height, with limitations in controlling stray fields and electronic coupling due to uniform filter layer size and shape matching the free layer, leading to suboptimal performance.
Innovation Solution
A precessional spin current layer with a non-uniform moment density and offset design relative to the free layer, allowing for varying size, shape, and moment density distribution to control stray field injection and electronic coupling, enhancing switching speed and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a uniform filter layer size and shape matching the free layer is used, then the device structure is simple and easy to manufacture, but the switching speed and stability are suboptimal due to inability to control stray fields and electronic coupling
Solution Approach 1:
The filter layer is designed with non-uniform moment density distribution, where different regions of the layer have different magnetic moment densities. This allows specific regions to provide stronger or weaker stray field injection and electronic coupling to the free layer, enabling optimized switching speed and stability control in different areas of the device.
Solution Approach 2:
The filter layer is designed with an offset configuration relative to the free layer, creating an asymmetric structure. This asymmetry enables better control over the distribution of stray fields and electronic coupling, improving switching performance by creating favorable magnetic field gradients and spin torque distribution that are not achievable with symmetric coaxial alignment.
2Reliability
If a uniform moment density is used in the filter layer, then the manufacturing process is simpler, but the control over stray field injection and electronic coupling is limited
Solution Approach 1:
The filter layer incorporates regions with different moment densities to provide localized control over magnetic properties. High moment density regions enhance stray field injection for reliable switching, while low moment density regions provide stability and prevent unwanted magnetic effects, achieving both switching reliability and stability through spatially varying material composition.
Solution Approach 2:
The moment density parameter is varied across the filter layer to optimize device performance. By changing the magnetic moment density from high to low in different regions, the patent achieves improved control over switching characteristics and thermal stability, demonstrating how parameter variation can resolve the contradiction between reliability and manufacturability.
3Ease of operation
If the filter layer is coaxial with the free layer, then the alignment is straightforward, but the control over stray field injection location is limited
Solution Approach 1:
The filter layer is intentionally offset from coaxial alignment with the free layer, creating an asymmetric configuration. This offset design enables precise control over the location where stray fields are injected into the free layer, allowing the magnetic field to be applied at specific positions that optimize switching performance and stability.
Solution Approach 2:
The patent introduces lateral displacement (offset) as an additional degree of freedom beyond radial and vertical positioning. By moving the filter layer center relative to the free layer center in the lateral direction, the invention achieves precise control over stray field injection location and electronic coupling, adding a dimensional parameter for optimization.
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 non-uniform precessional spin current layer design improves switching speed and stability by optimizing stray field injection and electronic coupling, allowing for better control over switching current and thermal barrier height, thereby enhancing the overall performance of MRAM devices.
Implementation Method 1
a precessional spin current layer in a seventh plane that is physically separated from the free magnetic layer and coupled to the free magnetic layer by a filter coupling layer
Implementation Method 2
allowing for varying size, shape, and moment density distribution to control stray field injection and electronic coupling
Implementation Method 3
coupled to the free magnetic layer by a filter coupling layer that may induce ferromagnetic or antiferromagnetic coupling between the free magnetic layer and the filter layer
Implementation Method 4
A precessional spin current layer with a non-uniform moment density and offset design relative to the free layer, allowing for varying size, shape, and moment density distribution
Data Source
AI summary
A magnetoresistive random-access memory (MRAM) is disclosed. The MRAM device includes a perpendicular magnetic tunnel junction device having a reference layer, a free layer, and a precessional spin current magnetic layer. The precessional spin current magnetic layer has a non-uniform moment density, and may have a moment density at its center that is greater than a moment density at its perimeter. The device is designed to provide control over the injection of stray fields and the electronic coupling between the precessional spin current magnetic layer and the free layer. Switching speed, switching current, and thermal barrier height for the device can be adjusted. The decreased moment density at the perimeter of the precessional spin current layer helps to stabilize the free layer when the effective magnetic field of the precessional spin current layer is high. Spin accumulation can be increased near the center of the precessional spin current layer, helping to switch the free layer