Ferromagnetic Wire MRAM Element for Low Current Density Writing
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Solution Overview
Problem
Existing magnetic random access memory (MRAM) technologies face challenges in achieving low writing current density and simple structure while maintaining high recording density, with previous methods either requiring high current density or complex structures.
Innovation Solution
A magnetic recording element with a ferromagnetic fine wire on an Si substrate, featuring current electrodes and voltage electrodes that induce a magnetic domain wall, allowing for low current density writing and simple structure by measuring voltage across the wire to detect and move the domain wall, thereby reducing power consumption and simplifying the element's structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional MTJ element structure with ferromagnetic free layer and fixed layer is used, then data storage capability is achieved, but writing requires high current density and complex multi-layer structure
Solution Approach 1:
The patent extracts and removes the complex multi-layer MTJ structure (insulator layers, fixed ferromagnetic layers) and retains only the essential ferromagnetic body component. This extraction simplifies the device structure while maintaining the core functionality of magnetic domain wall motion for data storage, thereby reducing both structural complexity and writing current density requirements
Solution Approach 2:
The ferromagnetic body is designed to utilize its own intrinsic magnetic properties and spin-polarized current generation capability. The material itself provides the necessary magnetic anisotropy and spin polarization without requiring external magnetic fields or complex layered structures, enabling self-sufficient operation with lower writing currents
2Use of energy by moving object
If spin injection magnetization reversal technique is used, then writing current density is reduced, but device structure becomes more complex with additional layers
Solution Approach 1:
The patent extracts only the essential ferromagnetic body component and removes all additional layers (tunnel barriers, pinned layers, antiferromagnetic layers) required by spin injection techniques. This extraction achieves structural simplification while the ferromagnetic body itself provides the necessary spin polarization through its intrinsic properties
Solution Approach 2:
The ferromagnetic body serves multiple functions simultaneously: it acts as the data storage medium, generates spin-polarized current through its intrinsic properties, and provides the magnetic anisotropy needed for stable magnetization states. This multi-functionality eliminates the need for separate specialized layers required in conventional spin injection devices
3Use of energy by moving object
If magnetic domain wall motion technique is used, then writing current density is reduced, but detection and measurement becomes more difficult
Solution Approach 1:
The patent replaces direct magnetic measurement techniques with electrical resistance measurement. The magnetic domain wall position is detected indirectly through changes in electrical resistance caused by the domain wall's effect on current flow, substituting complex magnetic detection with simpler electrical measurement
Solution Approach 2:
Electrical resistance serves as an intermediary parameter that links the magnetic domain wall position to measurable electrical signals. The domain wall affects electron scattering and current flow, which in turn changes the resistance, providing a measurable signal that indicates domain wall position without requiring direct magnetic measurement
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 low current density writing and a simplified structure, achieving efficient data recording and reading with reduced power consumption and increased recording density, comparable to existing flash memory switching times.
Implementation Method 1
a magnetic domain wall is induced in ferromagnetic fine wire 1 when the element is manufactured
Implementation Method 2
current-driven magnetic domain wall motion technique of moving the magnetic domain wall in the ferromagnetic body by applying a current
Implementation Method 3
measuring the voltage between voltage electrode 4a and voltage electrode 4b when reading current 8 is applied, so as to investigate whether or not magnetic domain wall 3 is present
Data Source
AI summary
A magnetic recording element is disclosed for which current density required for writing is low and structure of the element is simple. It comprises a ferromagnetic fine wire formed on a Si substrate, current electrodes that contact ends of the ferromagnetic fine wire, and voltage electrodes joined to the ferromagnetic fine wire and current electrodes to measure voltage across part of the ferromagnetic fine wire in cooperation with the current electrodes. A magnetic domain wall is induced in the ferromagnetic fine wire when the element is manufactured. A depression is formed in the surface on top of the ferromagnetic fine wire between the voltage electrodes, and between one of the current electrodes and one of the voltage electrodes. Voltage is measured between the two voltage electrodes when reading current is applied, to determine whether the magnetic domain wall is present between the two voltage electrodes, whereby recorded data can be identified.