Spin-Orbit Torque Magnetic Junctions for Reliable MRAM Switching
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Solution Overview
Problem
Conventional magnetic random access memories (MRAMs) require high currents for switching, which can damage the magnetic junction and are not suitable for small-sized, high-density memory applications, especially when an external magnetic field is not available.
Innovation Solution
Incorporating a spin-orbit interaction (SO) active layer adjacent to the free layer in magnetic junctions, allowing for in-plane current-driven switching using SO torque without an external magnetic field, with a bias structure providing magnetic bias at a nonzero acute angle to enhance switching reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high current is used to switch the magnetic moment in conventional STT-MRAM, then switching reliability is improved, but the magnetic junction may be damaged and power consumption increases
Solution Approach 1:
The patent introduces a spin-orbit interaction active layer as an intermediary component adjacent to the free layer. This layer mediates the switching process by generating spin-orbit torque through spin Hall effect or Rashba effect when current flows through it, thereby switching the free layer magnetization without requiring high current through the magnetic junction itself, thus preventing junction damage while maintaining switching reliability
Solution Approach 2:
The patent replaces the conventional spin transfer torque mechanism (which requires high current through the junction) with a spin-orbit interaction mechanism. The current flows through the SO active layer rather than through the magnetic junction, substituting the direct mechanical stress of high current through the junction with a field-mediated interaction that achieves the same switching effect without the harmful side effects
2Ease of operation
If conventional MTJ is used in STT-RAM, then magnetic switching can be achieved, but very high currents are required that may damage the junction
Solution Approach 1:
The patent segments the current path from the magnetic junction by introducing a separate SO active layer. The current flows through this dedicated active layer rather than through the magnetic junction, separating the switching function from the storage function and protecting the junction from high current damage while maintaining magnetic switching capability
Solution Approach 2:
The SO active layer serves as an intermediary that converts electrical current into spin-orbit torque, which then acts on the free layer magnetization. This intermediary mechanism enables magnetic switching without requiring the high current to pass directly through the magnetic junction, thus preserving junction durability
3Ease of operation
If external magnetic field is used for switching, then switching can be achieved, but device complexity and area increase
Solution Approach 1:
The spin-orbit interaction active layer generates the necessary spin-orbit torque internally when current flows through it, eliminating the need for external magnetic field sources. The system becomes self-sufficient by using the current itself to generate the switching mechanism through spin Hall effect or Rashba effect, thereby reducing device complexity and removing external field requirements
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 reduces the risk of junction damage, eliminates the need for external fields, and enables fast switching times, improving the performance and reliability of magnetic memories by using SO torque alone or in combination with other mechanisms.
Implementation Method 1
The SO active layer carries a current along the line length in the third direction. The SO active layer exerts a SO torque on the free layer due to the current passing through the at least one SO active layer.
Implementation Method 2
utilizing in-plane current-driven switching using SO torque
Implementation Method 3
The magnetic junction includes a biasing structure for providing a magnetic bias in a first direction
Implementation Method 4
The differences in magnetic configurations correspond to different magnetoresistances and thus different logical states
Data Source
AI summary
A magnetic memory including a plurality of magnetic junctions and at least one spin-orbit interaction (SO) active layer is described. Each of the magnetic junctions includes a reference layer, a free layer and a nonmagnetic spacer layer between reference and free layers. The magnetic junction includes a biasing structure for providing a magnetic bias in a first direction and/or the free layer has a length in the first direction and a width in a second direction. The width is less than the length. The SO active layer(s) are adjacent to the free layer and carry a current in a third direction. The third direction is at a nonzero acute angle from the first direction. The SO active layer(s) exerts a SO torque on the free layer due to the current passing through the at least one SO active layer. The free layer is switchable using the SO torque.