SOT-MRAM Magnetoresistive Element with Optimized Magnetic Layer Orientation
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Solution Overview
Problem
Z type three-terminal MRAMs require an external magnetic field, have large writing currents, and exhibit abnormalities in magnetization reversal at high-current regions, making them unsuitable for high-speed, low-power memory applications without significant manufacturing complexities.
Innovation Solution
A magnetoresistance effect element with a channel layer and a recording layer containing ferromagnetic material, where the channel layer includes a first magnetic layer and a nonmagnetic spacer layer, allowing magnetization reversal without an external magnetic field by adjusting the interlayer exchange coupling strength through the spacer layer's thickness and material composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Z type three-terminal MRAM structure is used, then high-speed magnetization reversal can be achieved, but external magnetic field is required and writing current becomes large
Solution Approach 1:
The patent changes the magnetization orientation parameter from in-plane (X, Y types) or perpendicular (Z type) to a specific angle θ relative to the channel layer current direction. This parameter change enables high-speed reversal with reduced current requirements without needing external magnetic fields. The angle θ is optimized to balance between achieving high-speed reversal and minimizing the writing current magnitude.
Solution Approach 2:
Instead of applying external magnetic fields as in conventional Z type MRAM, the patent inverts the approach by using spin-orbit torque from the channel layer current to directly reverse magnetization. The magnetic field generation is inverted from external application to internal generation through spin current, eliminating the need for external magnetic field equipment.
2Speed
If Z type three-terminal MRAM structure is used, then high-speed magnetization reversal can be achieved, but abnormalities in reversal behavior occur at high-current regions
Solution Approach 1:
The patent optimizes the angle parameter θ between magnetization direction and channel layer current to a specific value that avoids the abnormal reversal behavior observed in conventional configurations. This parameter optimization ensures stable and reliable magnetization reversal across the entire operating current range, eliminating the high-current region abnormalities while maintaining high-speed performance.
3Ease of operation
If conventional MRAM structures (X, Y, Z types) are used, then magnetization reversal can be achieved, but cell area becomes large due to stray magnetic field effects
Solution Approach 1:
The patent applies local quality optimization by configuring the magnetic layers with specific magnetization angles θ relative to the channel layer current direction. This local configuration optimizes the spin-orbit torque efficiency at the interface between channel layer and magnetic layers, enabling effective magnetization reversal with reduced stray magnetic field effects, thereby reducing cell area while maintaining operational capability.
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
Enables high-speed magnetization reversal with small currents and reduced stray magnetic field effects, eliminating the need for external magnetic fields and minimizing reversal abnormalities, thus achieving a compact, efficient, and stable memory solution.
Implementation Method 1
writing of information is performed by applying a current to the channel layer to reverse the magnetization of the recording layer in the magnetic tunnel junction
Implementation Method 2
a two-terminal that writes hit information to the magnetic layer (recording layer) using spin-transfer-torque (STT)
Implementation Method 3
Bit information recorded in a magnetic layer (recording layer) of MRAM passes through a barrier layer and is read out using a TMR (Tunnel Magnetoresistance) effect
Data Source
AI summary
A perpendicular magnetization type three-terminal SOT-MRAM that does not need an external magnetic field is provided. A magnetoresistance effect element where a first magnetic layer/nonmagnetic spacer layer/recording layer are disposed in order, and the first magnetic layer and the nonmagnetic spacer layer are provided to a channel layer.