Coupled MTJ Pillars Using DMI Switching for Low-Energy Logic
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Solution Overview
Problem
Current spin torque majority gate (STMG) devices face challenges in scaling due to narrow domain wall widths, complex stray field profiles, and high energy consumption, particularly in achieving full electrical control and efficient domain wall motion at nanoscale dimensions.
Innovation Solution
The implementation of a magnetic device with interconnected magnetic tunnel junction (MTJ) pillars utilizing chiral coupling induced by Dzyaloshinskii-Moriya interaction (DMI), allowing for magnetization state switching without in-plane current, and utilizing spin transfer torque (STT) for logical operations, enabling faster and lower energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional spin torque majority gate devices are used for logic operations, then magnetization switching can be achieved, but high energy consumption occurs due to requirements for in-plane current to drive domain wall motion
Solution Approach 1:
The patent replaces the conventional spin-orbit torque mechanism requiring in-plane current with a spin transfer torque mechanism using perpendicular magnetization. This substitution eliminates the need for complex current paths and domain wall motion control, directly switching magnetization states through perpendicular current injection, thereby reducing energy consumption and operational complexity
Solution Approach 2:
The invention changes the magnetization orientation parameter from in-plane to perpendicular. This parameter change fundamentally alters the switching mechanism, enabling direct magnetization reversal without domain wall motion and eliminating the need for in-plane current, thus reducing energy consumption and simplifying operation
2Productivity
If domain wall motion is used for information transmission between MTJ pillars, then logic operations can be performed, but current crowding issues arise at nanoscale dimensions
Solution Approach 1:
The patent extracts and eliminates the domain wall motion mechanism from the system. By using perpendicular magnetization switching, the invention removes the intermediate domain wall transmission step, allowing direct magnetization state switching at each MTJ pillar without current crowding issues associated with nanoscale domain wall motion
Solution Approach 2:
The invention substitutes the mechanical domain wall motion process with a direct spin transfer torque switching mechanism. This replacement eliminates the need for current-driven domain wall propagation, thereby removing current crowding effects while maintaining logic operation functionality
3Volume of moving object
If narrow domain wall widths are used for scaling, then device footprint is reduced, but stray field profiles become complex and control becomes difficult
Solution Approach 1:
The patent removes the domain wall structure from the device architecture by using perpendicular magnetization switching. This extraction eliminates the associated stray field problems entirely, allowing scaling without the complexity of controlling narrow domain wall stray fields
Solution Approach 2:
The invention replaces the domain wall-based magnetic structure with a uniform perpendicular magnetization switching mechanism. This substitution eliminates complex stray field profiles while maintaining compact device footprint, as the switching occurs through uniform magnetization reversal rather than domain wall propagation
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 approach enables efficient, scalable, and low-energy logic operations with full electrical control, overcoming issues related to domain wall motion and current crowding, and allows for the implementation of minority gates with improved operational speed and reliability.
Implementation Method 1
This chiral coupling may be induced by Dzyaloshinskii-Moriya interaction (DMI) at the interface of the second free magnetic layer and the heavy metal layer.
Implementation Method 2
In some embodiments, spin transfer torque (STT) can be applied at an MTJ pillar to locally switch its magnetization state.
Implementation Method 3
In some embodiments, the change of magnetization state of an MTJ pillar may be electrically detected by tunneling magnetoresistance (TMR) read.
Implementation Method 4
The thickness of the spacer layer (also referred to as an interexchange layer) may be tuned such that the first free magnetic layer portions and the second free magnetic layer are ferromagnetically coupled through exchange interaction.
Data Source
AI summary
A magnetic device may include at least two MTJ pillars, each MTJ pillar comprising a stack of a heavy metal layer portion, a second free magnetic layer portion, a spacer portion, a first free magnetic layer portion, a tunnel barrier layer portion, and a fixed magnetic layer portion, wherein at least the heavy metal layer portions, the second free magnetic layer portions and the spacer portions extend between the MTJ pillars through respectively an interconnecting heavy metal layer portion, an interconnecting second free magnetic layer portion and an interconnecting spacer portion, and wherein the interconnecting second free magnetic layer portion has an in-plane magnetization and the second free magnetic layer portions have an out-of-plane magnetization.