MRAM Magnetization Free Layer Domain Wall Stabilization
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Solution Overview
Problem
Current MRAM technologies face challenges in achieving stable magnetization of the magnetization fixed region during data writing, particularly with miniaturization, as the write current required can be high and may lead to thermal disturbance and instability of the domain wall, limiting the write margin and durability of the memory cell.
Innovation Solution
A magnetoresistance effect element and MRAM based on the domain wall motion method, featuring a magnetization free layer with a magnetization switching region and two magnetization fixed regions forming three-way intersections, which stabilizes the magnetization when a write current is supplied, allowing for a higher write current limit and improved write margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the write current is increased to ensure stable magnetization switching, then the magnetization switching reliability is improved, but the thermal disturbance resistance deteriorates and the magnetization fixed region becomes unstable
Solution Approach 1:
The magnetization free layer is segmented into a magnetization switching region and a magnetization fixed region, with the fixed region having opposite magnetization directions at its ends. This segmentation allows the fixed region to stabilize the domain wall while the switching region undergoes magnetization reversal, resolving the contradiction between switching reliability and fixed region stability.
Solution Approach 2:
Different regions of the magnetization free layer are given different magnetic properties: the magnetization switching region has reversible magnetization for switching operations, while the magnetization fixed region has stable magnetization with opposite directions at ends to pin the domain wall. This local differentiation allows each region to perform its specific function without interfering with the other.
2Area of stationary object
If the magnetoresistance effect element is miniaturized to increase integration density, then the area is reduced, but the write current required increases
Solution Approach 1:
The invention uses a domain wall motion mechanism where a domain wall is formed at the interface between the magnetization switching region and the magnetization fixed region. By applying a write current, the domain wall moves to switch the magnetization state. This dynamic domain wall motion mechanism is more efficient than coherent rotation, allowing miniaturization without proportional increase in write current.
Solution Approach 2:
The magnetization fixed region acts as an intermediary that stabilizes the domain wall position. The opposite magnetization directions at the ends of the fixed region create a pinning effect that holds the domain wall in place, enabling reliable switching at smaller dimensions without requiring excessive write current.
3Object-affected harmful factors
If the write current is increased to overcome thermal disturbance, then the thermal disturbance resistance is improved, but the magnetization fixed region becomes unstable due to excessive current
Solution Approach 1:
The magnetization fixed region with opposite magnetization directions at its ends creates a counterbalancing magnetic field that pins the domain wall in place. This counterweight effect stabilizes the fixed region against thermal disturbance without requiring excessive write current, preventing the instability that would occur with high current operation.
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 enables stable retention of magnetization during data writing, increasing the upper limit of the write current and enlarging the write margin, while also reducing the write current required, thus enhancing the durability and efficiency of the memory cell.
Implementation Method 1
a magnetoresistance effect element that exhibits a magnetoresistance effect such as a TMR (Tunnel MagnetoResistance) effect is used as a memory cell
Implementation Method 2
a spin-polarized current is injected into a magnetization free layer, and direct interaction between spin of conduction electrons of the current and magnetic moment of the conductor causes the magnetization to be switched
Implementation Method 3
a data write method replacing the current magnetic field method, a spin transfer method using spin transfer is recently proposed... According to the domain wall motion method, a current-driven domain wall motion has been actually observed
Data Source
AI summary
A magnetoresistance effect element according to the present invention comprises a magnetization free layer 1 and a magnetization fixed layer 3 connected to the magnetization free layer 1 through a nonmagnetic layer 2. The magnetization free layer 1 includes a magnetization switching region 13, a first magnetization fixed region 11 and a second magnetization fixed region 12. The magnetization switching region 13 having reversible magnetization overlaps with the magnetization fixed layer 3. The first magnetization fixed region 11 having first fixed magnetization is connected to one end 13a of the magnetization switching region 13. The second magnetization fixed region 12 having second fixed magnetization is connected to the other end 13b of the magnetization switching region 13. The first magnetization fixed region 11 and the magnetization switching region 13 form a three-way intersection, and the second magnetization fixed region 12 and the magnetization switching region 13 form another three-way intersection.