Domain Wall MR Element Structure for Stable Multi-State Memory
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Solution Overview
Problem
Existing magnetic domain wall movement elements face challenges in achieving a large MR ratio and high controllability, which are crucial for stable expression of multiple states.
Innovation Solution
A magnetic domain wall movement element is designed with a structure comprising a magnetoresistance effect element that includes a reference layer, a nonmagnetic layer, and a magnetic domain wall movement layer, featuring ferromagnetic layers with perpendicular magnetic anisotropy and insertion layers, along with first and second magnetization fixed layers separated by a magnetic coupling layer, allowing a write current to flow through the domain wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resistance change width (MR ratio) is increased to enable stable expression of multiple states, then the number of expressible states increases, but the device complexity and difficulty of achieving high controllability increase
Solution Approach 1:
The magnetic domain wall movement layer is segmented into multiple ferromagnetic layers (first ferromagnetic layer, second ferromagnetic layer) separated by nonmagnetic layers. This segmentation allows independent control of each layer's magnetization, enabling stable multi-state expression while maintaining manageable device complexity through modular architecture
Solution Approach 2:
Different regions of the magnetic domain wall movement layer are given different magnetic properties through the use of multiple ferromagnetic layers with potentially different compositions and thicknesses. The first and second ferromagnetic layers can have different perpendicular magnetic anisotropy characteristics, allowing localized optimization for both high MR ratio and controllability
2Quantity of substance
If the MR ratio is increased to assign more states to the resistance change width, then more states can be stably expressed, but the controllability of the magnetic domain wall operation deteriorates
Solution Approach 1:
The magnetic domain wall movement layer is designed with multiple ferromagnetic layers that can be dynamically controlled through applied currents. The spin current can selectively manipulate the magnetization state of different layers, providing dynamic controllability over the magnetic domain wall operation while maintaining a large MR ratio for multi-state expression
Solution Approach 2:
The invention utilizes changes in magnetic parameters (magnetization direction, perpendicular magnetic anisotropy) of the multiple ferromagnetic layers to achieve both large MR ratio and high controllability. By adjusting the magnetization states of individual layers through spin current, precise control over domain wall movement is achieved while maintaining distinguishable resistance states
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 achieves a large MR ratio and high controllability of the magnetic domain wall, enabling stable expression of multiple states.
Implementation Method 1
An MRAM uses a change in resistance value caused by a change in magnetization direction for data recording
Implementation Method 2
the ferromagnetic layer contains Co and Fe and has perpendicular magnetic anisotropy
Implementation Method 3
when writing is performed, a write current is allowed to flow between the first magnetization fixed layer and the second magnetization fixed layer along the magnetic domain wall movement layer
Data Source
AI summary
A magnetic domain wall movement element according to the present embodiment includes a magnetoresistance effect element that has a reference layer, a nonmagnetic layer, and a magnetic domain wall movement layer in order from a side closer to a substrate; and a first magnetization fixed layer and a second magnetization fixed layer which are each in contact with the magnetic domain wall movement layer and are separated from each other, wherein the magnetic domain wall movement layer includes a plurality of ferromagnetic layers and a plurality of insertion layers sandwiched between the plurality of ferromagnetic layers, wherein the ferromagnetic layer contains Co and Fe and has perpendicular magnetic anisotropy, and wherein, when writing is performed, a write current is allowed to flow between the first magnetization fixed layer and the second magnetization fixed layer along the magnetic domain wall movement layer.