Spin-Orbit Torque Random Number Generator Torque Ratio Optimization
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Solution Overview
Problem
Existing spin-orbit torque-based random number generators face challenges in achieving low switching current and high-entropy random number generation while maintaining perpendicular magnetic anisotropy.
Innovation Solution
The proposed solution involves a spin-orbit torque-based random number generator with a spin torque generation layer comprising a first and second spin torque layer, where the second spin torque layer is positioned between the magnetization-free layer and the first spin torque layer. This configuration generates field-like torque (FLT) and damping-like torque (DLT) and adjusts the torque ratio by varying the thickness of the second spin torque layer, ensuring low switching current and high entropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spin torque layer is used, then the structure is simple, but the switching current is high and entropy is insufficient
Solution Approach 1:
The spin torque layer is segmented into multiple sub-layers (first spin torque layer, second spin torque layer, third spin torque layer) with different materials and thicknesses. Each layer contributes differently to spin-orbit torque generation, allowing independent optimization of switching current and entropy characteristics without requiring a completely complex overall structure.
Solution Approach 2:
The patent employs composite material structure combining different materials (Ta, W, Pt, Pd, Mo, Hf) in the spin torque layers with CoFeB magnetic layer and MgO tunnel barrier. This composite approach enables simultaneous achievement of low switching current through spin Hall effect and high entropy through controlled magnetization switching, resolving the contradiction between structural simplicity and performance requirements.
2Device complexity
If conventional spin-transfer torque (STT) method is used, then the structure is simple, but switching speed is slow
Solution Approach 1:
The patent replaces the conventional spin-transfer torque (STT) mechanism with spin-orbit torque (SOT) mechanism induced by spin Hall effect. This substitution changes the fundamental operating principle from direct spin transfer through current to spin current generation via spin Hall effect, enabling faster switching speeds while maintaining reasonable structural complexity through the multi-layer spin torque configuration.
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 effectively reduces the switching current magnitude and enhances the switching efficiency while maintaining high entropy for the random number generation, thereby addressing the limitations of existing technologies.
Implementation Method 1
the spin-orbit torque (SOT) phenomenon inducing switching of a free layer using the spin Hall effect or Rashba effect
Implementation Method 2
Information is read using the tunneling magnetoresistance (TMR) phenomenon, in which the electrical resistance value of tunneling current passing through an insulating layer varies depending on the relative magnetization direction of the free layer and the pinned layer
Implementation Method 3
spin-orbit torque induced by in-plane current in the magnetized free layer induces magnetization in the in-plane direction
Data Source
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AI summary
The present disclosure relates to a spin-orbit torque-based random number generator and a fabricating method thereof. The spin-orbit torque-based random number generator according to an embodiment of the present disclosure includes a spin torque generation layer including a first spin torque layer and a second spin torque layer, a magnetization-free layer, a tunnel barrier layer, and a magnetization pinned layer, wherein the second spin torque layer is disposed between the magnetization-free layer and the first spin torque layer and generates field-like torque (FLT) and damping-like torque (DLT) related to the magnetization direction of the magnetization-free layer; the first spin torque layer adjusts a torque ratio according to the size of field-like torque to the size of damping-like torque in conjunction with the thickness of the second spin torque layer; in the magnetization-free layer, a magnetization direction is randomly aligned up or down based on the adjusted torque ratio; and a random number is generated based on current that is switched and output based on the randomly aligned magnetization direction.