MRAM Recording Layer Segmentation for Data Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MRAM devices face challenges in achieving high uniaxial magnetic anisotropy and low switching magnetic fields, leading to unstable data storage due to the use of ferromagnetic materials with high exchange-coupling forces, which result in intermediate electric resistance values and data instability when accessing memory cells.
Innovation Solution
A nonvolatile memory device with a magnetoresistive element featuring a pinned layer, a recording layer with an exchange-coupling layer and ferromagnetic layers of different materials, where the exchange-coupling layer includes two ferromagnetic layers with opposing magnetizations to cancel each other, allowing for independent selection of materials for uniaxial magnetic anisotropy and exchange-coupling force, thereby reducing the switching magnetic field and enhancing data stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferromagnetic materials with high exchange-coupling forces are used to achieve low switching magnetic fields, then switching magnetic field is reduced, but uniaxial magnetic anisotropy decreases leading to intermediate electric resistance values and data instability
Solution Approach 1:
The recording layer is segmented into multiple ferromagnetic layers (first recording layer and second recording layer) with different materials and magnetic properties. The first recording layer provides high uniaxial magnetic anisotropy for stable data storage, while the second recording layer provides high exchange-coupling force for low switching magnetic field. This segmentation allows each layer to specialize in one function, resolving the contradiction between data stability and switching field magnitude.
Solution Approach 2:
Different regions of the magnetoresistive element are assigned different local qualities: the first recording layer has high uniaxial magnetic anisotropy optimized for data stability, while the second recording layer has high exchange-coupling force optimized for switching. The pinned layer also has specifically engineered magnetic properties to pin against the composite recording layer. This local differentiation of magnetic properties allows simultaneous optimization of both data stability and switching characteristics.
2Adaptability or versatility
If a single ferromagnetic layer is used in the recording layer, then device complexity is reduced, but it is impossible to independently optimize uniaxial magnetic anisotropy and exchange-coupling force
Solution Approach 1:
The recording layer is divided into multiple ferromagnetic layers with different materials (e.g., CoFeB and CoFe). This segmentation enables independent optimization of each layer's magnetic properties: one layer can be optimized for uniaxial magnetic anisotropy while another is optimized for exchange-coupling force. The multi-layer structure provides the adaptability to independently select materials for each functional requirement.
Solution Approach 2:
The recording layer uses composite ferromagnetic materials with different compositions and magnetic characteristics. By combining materials like CoFeB (high anisotropy) and CoFe (high exchange-coupling), the structure achieves properties that cannot be obtained with a single material. This composite approach enables independent optimization of uniaxial magnetic anisotropy and exchange-coupling force, providing versatility in material selection despite increased structural 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 configuration enables a nonvolatile memory device with high uniaxial magnetic anisotropy and low switching magnetic fields, improving data stability and reducing power consumption during data write operations, while maintaining the selectivity of memory cells and error margin during data read.
Implementation Method 1
a second ferromagnetic layer (18) and a third ferromagnetic layer (22) which form an exchange-coupling layer and have magnetization directions coupled in an antiparallel orientation by exchange interaction
Implementation Method 2
changes in an electric resistance value are classified into the tunnel magnetoresistive effect, the giant magnetoresistive effect, and the like, according to the principles thereof
Implementation Method 3
changes in an electric resistance value are classified into the tunnel magnetoresistive effect, the giant magnetoresistive effect, and the like, according to the principles thereof
Implementation Method 4
a pinned layer having a fixed magnetization direction irrespective of the write magnetic field
Data Source
AI summary
Ferromagnetic layers have magnetizations oriented to such directions as to cancel each other, so that the net magnetization of the ferromagnetic layers is substantially zero. That is, the ferromagnetic layers are exchange-coupled with a nonmagnetic layer interposed therebetween, thereby forming an SAF structure. Since the net magnetization of the ferromagnetic layers forming the SAF structure is substantially zero, the magnetization of a recording layer is determined by the magnetization of a ferromagnetic layer. Therefore, the ferromagnetic layer is made of a CoFeB alloy having high uniaxial magnetic anisotropy, and the ferromagnetic layers are made of a CoFe alloy having a high exchange-coupling force.