Superparamagnetic tunnel junction element and computing system
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Solution Overview
Problem
Superparamagnetic tunnel junction elements are sensitive to external magnetic fields, leading to instability in computing systems, limiting their application and requiring costly magnetic field shields.
Innovation Solution
A superparamagnetic tunnel junction element with a laminated structure of ferromagnetic layers coupled antiparallel via a nonmagnetic coupling layer, using materials like Ru, Ir, Rh, or Cu, to stabilize magnetization against external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a superparamagnetic tunnel junction element is designed with a free layer that exhibits superparamagnetism to enable probabilistic computing, then the element can generate random output signals suitable for probabilistic computing, but the element becomes sensitive to external magnetic fields, leading to operational instability
Solution Approach 1:
The free layer is divided into two separate ferromagnetic layers (first and second ferromagnetic layers) that are coupled antiferromagnetically. This segmentation allows each layer to contribute to the superparamagnetic behavior while their coupled structure provides resistance to external magnetic fields, resolving the contradiction between probabilistic computing suitability and operational stability.
Solution Approach 2:
The invention uses a composite structure combining multiple ferromagnetic layers with different magnetic properties, coupled through a nonmagnetic coupling layer. This composite approach creates a system where the antiferromagnetic coupling between layers provides both the required thermal stability for superparamagnetism and enhanced resistance to external magnetic field disturbances.
2Stability of the object's composition
If the free layer is designed with strong magnetic anisotropy to maintain stable magnetization direction, then thermal stability is improved, but the element loses superparamagnetic behavior and cannot generate random output signals
Solution Approach 1:
The invention creates a dynamic balance where the antiferromagnetic coupling between the two ferromagnetic layers provides an effective energy barrier for thermal stability, while the individual layers remain thin enough to exhibit superparamagnetic fluctuations. This dynamic structure allows the system to maintain both thermal stability and superparamagnetic behavior simultaneously.
Solution Approach 2:
The invention carefully controls the thickness and magnetic properties of each ferromagnetic layer to achieve optimal parameters. By adjusting the layer thicknesses and magnetic anisotropy values, the system achieves the right balance between thermal stability (requiring higher energy barrier) and superparamagnetic behavior (requiring lower energy barrier), resolving the contradiction between these opposing requirements.
3Reliability
If conventional magnetic field shields are used to protect the superparamagnetic tunnel junction element from external magnetic fields, then operational stability is improved, but the system complexity and cost increase significantly
Solution Approach 1:
The tunnel junction element structure itself provides magnetic field resistance through the antiferromagnetically coupled free layer configuration. The intrinsic magnetic structure of the device resists external magnetic field disturbances without requiring external shielding mechanisms, thereby reducing system complexity and cost while maintaining operational stability.
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
The element achieves robust operation against external magnetic fields, suitable for probabilistic computing systems, enhancing stability and reducing the need for magnetic field shields.
Implementation Method 1
a nonmagnetic coupling layer containing at least one of Ru, Ir, Rh, Cr, and Cu, wherein the nonmagnetic coupling layer couples magnetizations of the (1-1)th ferromagnetic layer and the (1-2)th ferromagnetic layer in an antiferromagnetic manner
Implementation Method 2
A state in which the magnetization direction fluctuates with a short time constant due to thermal disturbance is called superparamagnetism, and magnetic tunnel junction elements designed so that the free layer exhibits superparamagnetism are called superparamagnetic tunnel junction elements
Implementation Method 3
by utilizing the tunnel magnetoresistance effect, the direction of magnetization of the first ferromagnetic layer group can be detected by the level of electrical resistance
Data Source
AI summary
A superparamagnetic tunnel junction element and a computing system using same, wherein the tunnel junction element has excellent operational stability against an external magnetic field and is suitable for the computing system based on probabilistic computing. The superparamagnetic tunnel junction element includes a first ferromagnetic layer group containing a ferromagnetic material, a second ferromagnetic layer group containing a ferromagnetic material, and a barrier layer disposed between the first ferromagnetic layer group and the second ferromagnetic layer group, wherein the first ferromagnetic layer group 14 includes a (1-1)th ferromagnetic layer, a (1-2)th ferromagnetic layer, and a first nonmagnetic coupling layer, the (1-1)th ferromagnetic layer is made of a ferromagnetic material, the magnetization direction thereof changes with a first time constant, the first time constant is one second or shorter, and the first nonmagnetic coupling layer contains at least one of Ru, Ir, Rh, Cr, and Cu.