Magnetic Memory Spin Orbit Interaction Writing
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Solution Overview
Problem
Magnetic memory technologies face challenges with high electric power consumption due to large writing currents required for data writing, especially in miniaturized elements, and the need for domain wall introduction in spin orbit interaction-based methods.
Innovation Solution
A magnetic memory configuration using a magnetization free layer with broken space symmetry, where a writing current flows in-plane to generate a Rashba magnetic field, allowing for data inversion without domain walls and reducing the writing current significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current induced magnetic field is used for data writing in conventional magnetic memory, then data can be written to the memory cell, but the writing current becomes large leading to high power consumption
Solution Approach 1:
The patent replaces the conventional current-induced magnetic field mechanism with a spin-orbit interaction mechanism. Instead of using a writing current flowing through a wiring line to generate a magnetic field, the invention uses a writing current flowing through the magnetization free layer to generate a Rashba magnetic field via spin-orbit interaction, which then acts on the magnetization to invert it. This substitution fundamentally changes the physical mechanism from electromagnetic induction to spin-dependent scattering and spin-orbit coupling, enabling lower writing currents.
Solution Approach 2:
The patent changes the physical parameters of the magnetization free layer to enable spin-orbit interaction. Specifically, it introduces a broken space symmetry in the magnetization free layer by making the upper side boundary different from the lower side boundary (different materials or structures). This structural parameter change enables the generation of a Rashba magnetic field when writing current flows through the layer, allowing for efficient spin-orbit interaction-based magnetization inversion with much lower currents than conventional methods.
2Use of energy by moving object
If spin orbit interaction is used for magnetization inversion, then writing current can be reduced, but domain wall introduction becomes necessary complicating the process
Solution Approach 1:
The patent applies asymmetry by making the upper side boundary of the magnetization free layer different from the lower side boundary. This broken space symmetry is achieved by using different materials or structures above and below the magnetization free layer (e.g., different barrier layers or base layers). This asymmetric structure enables the generation of a Rashba magnetic field that acts uniformly on the magnetization without requiring domain wall formation, simplifying the writing process while maintaining low current requirements.
3Device complexity
If the magnetization free layer has uniform magnetization, then data storage is simplified, but breaking space symmetry is required to generate Rashba magnetic field
Solution Approach 1:
The patent applies local quality by creating different structures or materials only at the boundaries of the magnetization free layer (upper and lower sides) while keeping the bulk of the magnetization free layer uniform. The broken space symmetry is localized to the boundary regions where different barrier layers or base layers are used, while the magnetization free layer itself maintains uniform magnetization for simplified data storage. This localized structural asymmetry enables Rashba magnetic field generation without compromising the uniformity of the magnetization in the storage region.
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 solution enables efficient data writing with a remarkably smaller writing current and eliminates the need for domain wall introduction, improving device specifications and reducing power consumption.
Implementation Method 1
A magnetic memory configuration using a magnetization free layer with broken space symmetry, where a writing current flows in-plane to generate a Rashba magnetic field
Implementation Method 2
A magnetic memory using spin orbit interaction
Data Source
AI summary
A magnetic memory includes: a base layer; a magnetization free layer; a barrier layer; and a magnetization reference layer. The magnetization free layer, with which the base layer is covered, has invertible magnetization and is magnetized approximately uniformly. The barrier layer, with which the magnetization free layer is covered, is composed of material different from material of the base layer. The magnetization reference layer is arranged on the barrier layer and has a fixed magnetization. When the magnetization of the magnetization free layer is inverted, a first writing current is made to flow from one end to the other end of the magnetization free layer in an in-plane direction without through the magnetization reference layer.