Spin-Orbit Torque Wiring with Layered Resistivity for Low Power Memory
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Solution Overview
Problem
The increasing power consumption of magnetic memory due to high currents applied to magnetoresistance effect elements, which can lead to deterioration of their characteristics and reduced lifespan.
Innovation Solution
A magnetization rotation element with a spin-orbit torque wiring structure, where the wiring layers closer to the ferromagnetic layer have a higher product of cross-sectional area and resistivity, potentially containing compounds with a pyrochlore structure like R2Ir2O7, and a spacer layer, to reduce the current required for operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current is applied to magnetoresistance effect elements for writing data, then the magnetization directions can be controlled and data can be written, but the power consumption increases and the characteristics of the elements deteriorate
Solution Approach 1:
The patent changes the physical parameters of the spin-orbit torque wiring by creating a multilayer structure with varying cross-sectional areas. The wiring layers have different thicknesses, with the first wiring layer having a smaller thickness than the second wiring layer, which optimizes the spin-orbit torque generation efficiency and reduces the write current requirement
Solution Approach 2:
The patent uses a composite multilayer structure for the spin-orbit torque wiring consisting of different metal layers (e.g., Ta, W, Mo, Hf) with distinct properties. This composite structure leverages the spin Hall effect or Rashba effect in specific materials to generate spin-orbit torque more efficiently, thereby reducing the current needed for magnetization switching
2Speed
If a high current is applied to reverse magnetization quickly, then the writing speed increases, but the power consumption increases and element characteristics deteriorate
Solution Approach 1:
The patent optimizes the thickness parameters of the spin-orbit torque wiring layers to achieve efficient spin-orbit torque generation. The first wiring layer has a thickness of 1-5 nm and the second wiring layer has a thickness of 5-10 nm, which provides optimal spin Hall angle or Rashba effect while limiting excessive current density that would harm element characteristics
Solution Approach 2:
The spin-orbit torque wiring acts as an intermediary that converts charge current into spin-orbit torque through the spin Hall effect or Rashba effect. This intermediary mechanism allows magnetization reversal without direct current flow through the magnetoresistance effect element, enabling fast switching while preserving element characteristics
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 configuration reduces the power consumption of magnetic memory by minimizing the write current needed to reverse magnetization, thereby extending the lifespan of the magnetoresistance effect elements.
Implementation Method 1
A spin-orbit torque (SOT) is induced by a spin current generated by a spin-orbit interaction or a Rashba effect at an interface between different materials
Implementation Method 2
A spin-orbit torque (SOT) is induced by a spin current generated by a spin-orbit interaction or a Rashba effect at an interface between different materials
Implementation Method 3
One such method is a writing method using a spin-orbit torque (SOT). An SOT is induced by a spin current generated by a spin-orbit interaction
Data Source
AI summary
The magnetization rotation element includes: a spin-orbit torque wiring; and a first ferromagnetic layer which is stacked on the spin-orbit torque wiring, wherein the spin-orbit torque wiring includes a plurality of wiring layers, and wherein, in a cross section orthogonal to a length direction of the spin-orbit torque wiring, a product between a cross-sectional area and a resistivity of each of the wiring layers is larger in the wiring layer closer to the first ferromagnetic layer.