Magnetic Memory Device Using Moving Domain Walls for Multi-Bit Storage
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Solution Overview
Problem
Existing magnetic memory devices face challenges in accurately reading and writing information due to limited resistance change rates in magnetic tunneling junction (MTJ) cells when the insulating layer is not clean, and they can only store 1-bit information per memory area, making it difficult to manufacture large capacity devices.
Innovation Solution
The magnetic memory device employs a structure with parallel metal lines on a substrate, where magnetic domains with variable magnetization directions are moved and switched using input units, and sensing units detect an electromotive force to read and write information, allowing for multi-bit storage by forming magnetic domains and domain walls on a plastic substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MTJ cells are used for magnetic memory devices, then reading and writing information is enabled through resistance changes, but the resistance change rate is limited to about 40% and reduces to 20-30% when the insulating layer is not sufficiently clean, resulting in inaccurate information reading
Solution Approach 1:
The patent replaces the electrical resistance-based read/write mechanism of MTJ cells with a magnetomotive force-based mechanism using moving magnetic domain walls. Instead of relying on resistance changes that are sensitive to insulating layer cleanliness, the invention uses the motion of magnetic domain walls to generate magnetomotive forces that can be detected by sensing units, thereby eliminating the reliability issue associated with resistance change rate variations
Solution Approach 2:
The invention changes the fundamental parameter used for information storage and reading from electrical resistance to magnetic domain wall position and motion. By using the position of magnetic domain walls along metal lines and their induced magnetomotive forces as the storage and readout parameters, the system achieves more stable and accurate information handling that is not affected by insulating layer quality
2Productivity
If only 1-bit information is stored in a single memory area, then the memory structure is simple, but manufacturing large capacity magnetic memory devices is relatively difficult
Solution Approach 1:
The patent divides each memory area into multiple magnetic domains along the metal lines, where each domain can independently store information. By creating multiple magnetic domains within a single memory area and using their relative positions to encode information, the system achieves multi-bit storage capacity without requiring proportional increases in the number of physical memory cells, thus improving storage capacity while maintaining structural simplicity
Solution Approach 2:
The invention transitions from storing information in a single point (1-bit per memory area) to storing information along the length of metal lines by creating multiple magnetic domains in sequence. This one-dimensional arrangement of magnetic domains along the metal line allows multiple bits of information to be stored in what would traditionally be a single memory area, effectively increasing storage capacity without adding vertical or lateral complexity
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 improves reading and writing accuracy and increases storage capacity per unit area by detecting electromotive forces and enabling multi-bit data storage, making it easier to manufacture and stack magnetic memory devices.
Implementation Method 1
Sensing units may be connected to the plurality of second metal lines and may sense an electromotive force caused by magnetic domain walls passing through the tunnels
Implementation Method 2
First input units may be connected to the plurality first metal lines and may supply a current to drag or move the plurality of magnetic domains
Implementation Method 3
Second input units may be connected to the plurality of second metal lines to apply a current for switching the magnetization directions of the plurality of magnetic domains inside the tunnels
Data Source
AI summary
A magnetic memory device includes a plurality of first metal lines arranged in parallel on a substrate and including a plurality of magnetic domains with variable magnetization directions. A plurality of second metal lines is arranged on the substrate perpendicular to the first metal lines. The plurality of second metal lines each has a tunnel through which the plurality of first metal lines pass. First input units are connected to the plurality of first metal lines and supply a current to drag or move the plurality of magnetic domains. Second input units are connected to the plurality of second metal lines to supply a current for switching the magnetization directions of magnetic domains inside the tunnels. Sensing units are connected to the plurality of second metal lines for sensing an electromotive force caused by magnetic domain walls passing through the tunnels.