Voltage-Controlled Magnetic Tunnel Junctions for Low-Energy Switching
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Solution Overview
Problem
Conventional semiconductor devices face limitations in scaling due to device reliability and increased power consumption, and magnetic tunnel junctions require external magnetic fields or currents for switching, which is inefficient.
Innovation Solution
A magnetic device with a layer stack comprising a first ferromagnetic layer, a non-magnetic spacer layer, and an oxide layer, where a voltage source applies a bias voltage to switch the magnetic orientation of the second ferromagnetic layer without an external magnetic field or current, allowing control of switching direction through the sign and magnitude of the bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional magnetic tunnel junctions use external magnetic fields or currents for switching, then magnetic orientation switching is achieved, but energy consumption increases and device efficiency decreases
Solution Approach 1:
The patent replaces the conventional magnetic field-based switching mechanism with an electric field-based mechanism. Specifically, it uses voltage-controlled magnetic anisotropy (VCMA) where an applied voltage modifies the magnetic anisotropy energy of the ferromagnetic layer, enabling magnetization switching without requiring external magnetic fields or high current pulses. This substitution of the switching mechanism fundamentally reduces energy consumption while maintaining switching efficiency.
Solution Approach 2:
The patent changes the control parameter from magnetic field or current to voltage. By applying a voltage across the magnetic tunnel junction, the magnetic anisotropy of the ferromagnetic layer is modified through electric field-induced changes in the interfacial magnetic moment. This parameter change enables low-energy switching because voltage application requires minimal energy compared to generating external magnetic fields or driving high current through the device.
2Volume of moving object
If magnetic devices are scaled down to improve integration density, then device size decreases, but thermal stability and reliability deteriorate
Solution Approach 1:
The patent employs a composite magnetic layer structure consisting of multiple ferromagnetic layers separated by non-magnetic spacer layers. This composite structure creates synthetic antiferromagnetic coupling between the ferromagnetic layers, which provides enhanced thermal stability through Néel coupling. The composite material approach allows the device to maintain high thermal stability even as the overall device volume is reduced for scaling, because the interlayer coupling energy compensates for the reduced volume.
Solution Approach 2:
The patent introduces vertical dimensionality through the layered structure of the magnetic tunnel junction. By stacking multiple ferromagnetic layers in the vertical dimension with nanoscale precision, the device achieves thermal stability through the cumulative effect of multiple interfaces. This dimensional approach allows scaling in the lateral plane while maintaining thermal stability through the vertical layering, effectively decoupling device size from thermal stability requirements.
3Productivity
If conventional semiconductor devices continue scaling, then device density increases, but power consumption increases and reliability decreases
Solution Approach 1:
The patent replaces conventional current-based switching with voltage-based switching through VCMA. In conventional devices, switching requires high current pulses that consume significant power. By using voltage to control magnetic anisotropy, the patent enables switching with minimal current flow, thereby maintaining high device density while dramatically reducing power consumption per device operation.
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 efficient switching of magnetic orientation with high speed and ultralow energy consumption, suitable for memory, logic, stochastic computing, and neural network devices, achieving bidirectional switching and improved thermal stability.
Implementation Method 1
a voltage source configured to apply a bias voltage across the layer stack to cause switching of a magnetic orientation of the second ferromagnetic layer
Data Source
AI summary
A magnetic device may include a layer stack. The layer stack may include a first ferromagnetic layer; a non-magnetic spacer layer on the first ferromagnetic layer, where the non-magnetic spacer layer comprises at least one of Ru, Ir, Ta, Cr, W, Mo, Re, Hf, Zr, or V; a second ferromagnetic layer on the non-magnetic spacer layer; and an oxide layer on the second ferromagnetic layer. The magnetic device also may include a voltage source configured to apply a bias voltage across the layer stack to cause switching of a magnetic orientation of the second ferromagnetic layer without application of an external magnetic field or a current. A thickness and composition of the non-magnetic spacer layer may be selected to enable a switching direction of the magnetic orientation of the second ferromagnetic layer to be controlled by a sign of the bias voltage.