Magnetic Memory Element With Polarizing Layer For Deterministic SOT Switching
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Solution Overview
Problem
Magnetic random access memory (MRAM) cells using spin transfer torque (STT) for magnetization reversal face high voltage across the magnetic tunnel junction (MTJ), reducing its lifetime, and require an external magnetic field for deterministic switching in high-density memory applications, which hinders commercial viability.
Innovation Solution
A magnetic memory element with a magnetic tunnel junction (MTJ) featuring a reference layer, storage layer with perpendicular magnetic anisotropy, and a current layer that passes a writing current parallel to the plane, utilizing a spin orbit torque (SOT) interaction for switching, combined with a polarizing layer generating an electric polarization orthogonal to the current layer to achieve deterministic switching without an external magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spin transfer torque (STT) is used for magnetization reversal, then magnetization reversal can be achieved, but high voltage across the magnetic tunnel junction (MTJ) reduces its lifetime
Solution Approach 1:
The invention segments the current path by introducing a separate current layer adjacent to the MTJ. The writing current flows through this current layer instead of through the MTJ, while still achieving magnetization reversal through spin orbit torque. This segmentation allows the read and write paths to be separated, protecting the MTJ from high voltage stress during write operations and extending its lifetime.
2Quantity of substance
If perpendicular magnetic anisotropy is used in high-density memory applications, then storage density is improved, but an external magnetic field is required for deterministic switching which hinders commercial viability
Solution Approach 1:
The invention introduces a polarizing layer as an intermediary between the current layer and the storage layer. This polarizing layer generates an internal electric field that polarizes the spin current, enabling deterministic switching of the storage magnetization without requiring an external magnetic field. The polarizing layer acts as a mediator that provides the necessary spin polarization internally, eliminating the need for complex external field generation equipment and making the device suitable for commercial high-density memory applications.
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 allows for low reversal current densities, extending MTJ lifetime and enabling deterministic switching without the need for external magnetic fields, enhancing the technological viability of MRAM cells for high-density memory applications.
Implementation Method 1
a current layer adjacent to the MTJ generates a spin current caused by a SOT interaction
Implementation Method 2
switching the storage magnetization by a SOT interaction
Implementation Method 3
a polarizing layer comprising an electric polarization having at least a component oriented in a second direction substantially orthogonal to the first direction, the electric polarization allowing deterministically switching of the storage magnetization
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Magnetic memory element (1), comprising a magnetic tunnel junction MTJ (2) including a reference layer (21) having a reference magnetisation (210), a tunnel barrier (22) and a storage layer (23) having a storage magnetization (230), the reference and storage layers (21, 23) having perpendicular magnetic anisotropy and the storage magnetization (230) is switchable between a first and second stable states perpendicular to a plane of the storage layer (23); a current layer (30) configured to pass a writing current (31) in a first direction (x) oriented substantially parallel to the plane of the storage layer (23), the writing current (31) being adapted for switching the storage magnetization (230) by a spin orbit torque (SOT) interaction. The magnetic memory element (1) further comprises a polarizing layer (4) comprising an electric polarization (40) having at least a component oriented in a second direction (y) orthogonal to the first direction (x) and in the plane of the current layer (30), the electric polarization (40) allowing deterministically switching of the storage magnetization (230) when the writing current (31) is passed.