Magnetoresistive Element Leakage Field Cancellation
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Solution Overview
Problem
In magnetoresistive elements with perpendicular magnetization, the leakage magnetic field from the reference layer affects the storage layer, leading to decreased thermal stability and increased switching current values, making it difficult to fabricate elements with reduced thickness and manufacturing costs.
Innovation Solution
A magnetoresistive element with a stack structure including a storage layer, a reference layer, and shift adjustment layers, where the thickness of the upper shift layer is reduced while the lower shift layer is increased, effectively canceling the leakage magnetic field and optimizing the thickness for easier fabrication and reduced switching currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shift adjustment layer is provided to cancel the leakage magnetic field from the reference layer, then the thermal stability is improved, but the element thickness increases making fabrication difficult
Solution Approach 1:
The patent changes the material parameters of the shift adjustment layer by using a magnetic layer with perpendicular magnetic anisotropy and controlled saturation magnetization. By adjusting the composition (e.g., CoFeB, CoFe) and thickness of the shift adjustment layer, the leakage magnetic field is effectively canceled while keeping the total element thickness within acceptable fabrication limits.
Solution Approach 2:
The patent employs composite magnetic layer structures where the shift adjustment layer is composed of specific magnetic materials (CoFeB, CoFe) with perpendicular magnetization. This composite structure allows the shift adjustment layer to generate a magnetic field that opposes and cancels the leakage field from the reference layer, achieving field cancellation without excessive thickness increase.
2Object-generated harmful factors
If the shift adjustment layer is made larger in thickness than the reference layer to cancel the leakage magnetic field, then the leakage field cancellation is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent optimizes the thickness parameter of the shift adjustment layer to be greater than that of the reference layer (e.g., reference layer 3 nm, shift adjustment layer 4-6 nm) to ensure adequate magnetic field cancellation. This parameter optimization achieves effective leakage field compensation while maintaining manufacturability through precise thickness control in the fabrication process.
3Area of stationary object
If perpendicular magnetization configuration is used, then the element size is reduced, but the leakage magnetic field from the reference layer increases affecting the storage layer
Solution Approach 1:
The patent extracts and addresses the harmful leakage magnetic field effect by introducing a separate shift adjustment layer specifically designed to cancel the leakage field from the reference layer. This layer is positioned between the reference layer and storage layer to counteract the unwanted magnetic field while preserving the benefits of perpendicular magnetization for miniaturization.
Solution Approach 2:
The shift adjustment layer acts as an intermediary magnetic layer between the reference layer and storage layer. It mediates the magnetic field interaction by generating a field that opposes the leakage field from the reference layer, thereby protecting the storage layer from harmful magnetic field effects while allowing the perpendicular magnetization configuration to maintain small element size.
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 reduces the leakage magnetic field, lowers the switching current values, and minimizes the total thickness of the magnetoresistive element, thereby simplifying manufacturing and reducing costs.
Implementation Method 1
a writing (spin transfer torque writing) method that uses spin-momentum-transfer (SMT) has been proposed
Implementation Method 2
When magnetocrystalline anisotropy is used in a perpendicular magnetization configuration
Implementation Method 3
A magnetoresistive element having a ferromagnetic tunnel junction is also called a magnetic tunnel junction (MTJ) element
Data Source
AI summary
According to one embodiment, a magnetoresistive element includes the following configuration. First nonmagnetic layer is provided between the first magnetic layer (storage layer) and the second magnetic layer (reference layer). Third magnetic layer is formed on a surface of the storage layer, which is opposite to a surface on which the first nonmagnetic layer is formed. Fourth magnetic layer is formed on a surface of the reference layer, which is opposite to a surface on which the first nonmagnetic layer is formed. The third and fourth magnetic layers have a magnetization antiparallel to the magnetization of the storage layer. Second nonmagnetic layer is located between the storage and third magnetic layers. Third nonmagnetic layer is located between the reference and fourth magnetic layers. The thickness of the fourth magnetic layer is smaller than that of the third magnetic layer.