Spin Orbit Torque MRAM Free Layer Segmentation
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Solution Overview
Problem
Spin orbit torque magnetic RAMs face challenges in maintaining opposite tendencies of magnetic damping constant and spin Hall angle in the free layer, leading to increased driving current density, which affects data processing speed and power efficiency.
Innovation Solution
A spin orbit torque magnetic RAM design with a free layer comprising a cobalt film and a permalloy layer, where the thickness of both layers is adjusted to maintain opposite tendencies of magnetic damping constant and spin Hall angle, reducing driving current density by maximizing spin transparency and minimizing two-magnon electron scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the free layer uses a single ferromagnetic material layer with high perpendicular magnetic anisotropy, then the spin transparency at the interface is high, but the driving current density increases
Solution Approach 1:
The free layer is divided into two separate ferromagnetic material layers (first and second ferromagnetic layers) with different magnetic properties. The first layer has high spin transparency while the second layer has low magnetic damping constant, allowing each layer to contribute different beneficial characteristics that collectively reduce the driving current density
Solution Approach 2:
The patent uses a composite structure of two different ferromagnetic materials (e.g., CoFeB and CoFe) stacked together. This composite free layer combines the advantages of high spin transparency from one material and low magnetic damping from another, achieving lower driving current density than single-material layers
2Stability of the object's composition
If the thickness of the ferromagnetic layer is increased to maintain magnetic stability, then the magnetic damping constant increases, but the spin Hall angle decreases
Solution Approach 1:
The free layer thickness is segmented into two layers with different thicknesses. The first ferromagnetic layer has optimized thickness for high spin transparency, while the second layer compensates for magnetic stability. This segmentation allows the system to maintain magnetic stability without sacrificing spin Hall angle
Solution Approach 2:
The patent optimizes the thickness parameters of each ferromagnetic layer independently. By adjusting the thickness of the first layer to maximize spin transparency and the second layer to provide magnetic stability, the composite structure achieves both high spin Hall angle and magnetic 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 design reduces driving current density, enhancing data processing speed and power efficiency by maintaining opposite tendencies of magnetic damping constant and spin Hall angle, thereby improving the performance of spin orbit torque magnetic RAMs.
Implementation Method 1
a spin orbit torque magnetic RAM in which a free layer of a magnetic tunnel junction (MTJ) is double-stacked at a memory cell driven by a spin orbit torque
Implementation Method 2
the spin orbit torque-based magnetic RAM causes a spin current to flow into a magnetic tunnel junction through a low line during a write operation
Implementation Method 3
the spin transfer torque-based magnetic RAM causes an electric current to directly flow into the magnetic tunnel junction (MTJ) through the row line and the column line at the time of a write operation and a read operation
Implementation Method 4
at least one row selection line positioned on a silicon substrate to induce a spin orbit interaction therein
Data Source
AI summary
A spin torque magnetic RAM according to the present invention includes at least one row selection line positioned on a silicon substrate to induce a spin orbit interaction therein; at least one first magnetic pattern positioned on the row selection line; a second magnetic pattern positioned on the first magnetic pattern; a tunnel barrier positioned on the second magnetic pattern; and a third magnetic pattern positioned on the tunnel barrier, wherein the first magnetic pattern is made of a cobalt film, the first magnetic pattern and the second magnetic pattern have a total thickness of 5 nm to form a free layer, and the third magnetic pattern is formed with a pinned layer in which a magnetization direction is fixed.