Self-Referenced TAS-MRAM Cell With Segmented Sense Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing self-referenced MRAM cells face challenges in reducing power consumption during reading operations while maintaining effective magnetization switching and resistance measurement, as the dipolar coupling between the sense and storage layers affects the read magnetic field and write magnetic field requirements.
Innovation Solution
The MRAM cell incorporates a magnetic tunnel junction with a sense layer, a storage layer, and an antiferromagnetic layer, where the sense layer comprises two sense layers with a spacer layer introducing RKKY coupling, allowing for scissoring switching and fine-tuning of apparent magnetocrystalline anisotropy, enabling low-power reading by adjusting the spacer layer thickness and using read magnetic fields to measure resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the net moment of the synthetic antiferromagnetic storage layer is reduced to decrease dipolar coupling, then the read power consumption is reduced, but the write magnetic field increases
Solution Approach 1:
The sense layer is divided into two separate sense layers (first sense layer and second sense layer) with a non-magnetic spacer layer between them. This segmentation allows independent control of each sense layer's magnetization direction, enabling differential reading without requiring high read magnetic fields, thus reducing read power consumption while maintaining acceptable write conditions
Solution Approach 2:
A non-magnetic spacer layer is introduced as an intermediary between the first and second sense layers. This spacer layer prevents direct ferromagnetic coupling between the two sense layers while allowing controlled RKKY coupling through the spacer thickness, enabling independent magnetization switching at lower read fields
2Use of energy by stationary object
If the dipolar coupling between sense and storage layer is decreased, then the read magnetic field is reduced, but the write magnetic field increases
Solution Approach 1:
The invention uses dynamic control of the sense layers' magnetization directions during read operations. By switching the magnetization of the first and second sense layers in opposite directions (scissoring switching), the system creates a time-varying magnetic field configuration that reduces the required read magnetic field strength while maintaining differential signal detection capability
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 configuration allows for low-power consumption reading with improved magnetization switching and resistance measurement accuracy, canceling out apparent magnetocrystalline anisotropy without material composition changes, and optimizing read field currents.
Implementation Method 1
an antiferromagnetic layer exchange-coupling the storage layer such that the storage magnetization can be pinned when the antiferromagnetic layer is below a critical temperature and freely varied when the antiferromagnetic layer is heated at or above the critical temperature
Implementation Method 2
the spacer layer can have a thickness such that no direct ferromagnetic coupling occurs between the first and second sense layers
Implementation Method 3
the spacer layer has a thickness being greater than about 2 nm, but preferably greater than about 2.5 nm. The spacer layer can further have a thickness such that RKKY coupling is minimal
Implementation Method 4
The read magnetic field used for switching the sense magnetization depends on the magnetostatic coupling (or dipolar coupling) between the synthetic antiferromagnetic storage layer and the sense layer. The read magnetic field depends further on the magnetocrystalline anisotropy of the sense layer
Implementation Method 5
comparing the resistance of the magnetic tunnel junction measured for the two directions of the sense magnetization
Data Source
Figure 1
Figure 2(a)~3(c)
Figure 4(a)~5(c)
AI summary
Self-referenced magnetic random access memory (MRAM) cell (1) comprising a magnetic tunnel junction (2) including a sense layer (21); a storage layer (23) having a storage magnetization (230); a tunnel barrier layer (22) comprised between the sense and the storage layers (21, 23); and an antiferromagnetic layer (24) exchange-coupling the storage layer (23) such that the storage magnetization (230) can be pinned when the antiferromagnetic layer (24) is below a critical temperature and freely varied when the antiferromagnetic layer (24) is heated at or above the critical temperature; said sense layer (21) comprising a first sense layer (211) having a first sense magnetization (213), a second sense layer (212) having a second sense magnetization (214) and spacer layer (215) between the first and second sense layers (211, 212). The MRAM cell can be read with low power consumption.