Strained Ferromagnetic SOT Layer for Low-Current MTJ Switching
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Solution Overview
Problem
Existing STT-MRAM technologies require substantial current for magnetic switching, which limits their suitability for fast access and low-power applications such as cache memory, and external assist fields complicate the cell structure.
Innovation Solution
Employing a strained ferromagnetic SOT induction structure with perpendicular magnetic anisotropy and high spin Hall angle, integrated without a heavy metal seed layer, and utilizing a spacer layer to modulate magnetic coupling, enabling efficient SOT switching within the MTJ film stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If STT-MRAM is used for magnetic switching, then magnetic random access memory functionality is achieved, but substantial current is required which limits suitability for low-power applications
Solution Approach 1:
The patent combines the SOT induction structure and MTJ stack into a single integrated device, allowing the spin-orbit torque generated in the Hall metal to directly switch the magnetization in the MTJ free layer. This integration eliminates the need for separate external field generation systems and reduces the overall current requirement compared to conventional STT-MRAM approaches.
Solution Approach 2:
The patent utilizes strain engineering to modify the magnetic anisotropy parameters of the Hall metal layer, inducing perpendicular magnetic anisotropy that enhances the spin Hall angle. This parameter change enables more efficient spin-charge conversion and reduces the critical current density required for magnetization switching in the MTJ stack.
2Device complexity
If external assist fields are used for SOT switching, then magnetic field assistance is provided, but cell structure becomes complicated
Solution Approach 1:
The patent merges the function of external field assistance into the intrinsic properties of the Hall metal layer by inducing perpendicular magnetic anisotropy through strain. The Hall metal itself generates the necessary magnetic field configuration through spin Hall effect, eliminating the need for separate external field generation components and simplifying the overall cell structure.
Solution Approach 2:
The strained Hall metal layer provides self-generated magnetic field assistance through its perpendicular magnetic anisotropy and spin Hall effect. The structure serves its own switching assistance function without requiring external magnets or field generation systems, thereby simplifying the device architecture while maintaining reliable switching.
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
Reduces write current requirements and simplifies the design by internally generating the necessary magnetic field for switching, offering faster and more energy-efficient SOT-MRAM operations.
Implementation Method 1
a strained PMA (perpendicular magnetic anisotropy) Hall metal SOT induction structure
Implementation Method 2
spin-orbit torque (SOT) induction structure...high spin Hall angle
Data Source
AI summary
A magnetic memory device includes a spin-orbit torque (SOT) induction structure which may be strained and seedless and formed with a perpendicular magnetic anisotropy. A magnetic tunnel junction (MTJ) stack is disposed over the SOT induction structure. A spacer layer may decouple layers between the SOT induction structure and the MTJ stack or decouple layers within the MTJ stack. One end of the SOT induction structure may be coupled to a first transistor and another end of the SOT induction structure coupled to a second transistor.