Magnetoresistive Element Oxygen Gettering Layer Exchange Bias
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Solution Overview
Problem
Existing spintronic devices, such as MRAM cells, face challenges with reduced exchange bias and increased surface resistance due to manganese diffusion and oxygen incorporation during the deposition and annealing processes, affecting their performance and stability over temperature cycles.
Innovation Solution
Incorporating a magnesium-based oxygen gettering layer between the second magnetic layer and the antiferromagnetic layer to prevent manganese diffusion and oxygen insertion, thereby enhancing exchange bias and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an antiferromagnetic layer is used to pin the magnetization of the ferromagnetic layer, then exchange bias is achieved below the critical temperature, but manganese diffusion into the ferromagnetic layer reduces exchange bias and increases coercivity
Solution Approach 1:
A magnesium oxide barrier layer is introduced between the antiferromagnetic layer (containing manganese) and the ferromagnetic layer to act as an intermediary that blocks manganese diffusion while allowing exchange coupling to occur. This mediator prevents the harmful diffusion of manganese atoms into the ferromagnetic layer, thereby maintaining exchange bias and reducing coercivity.
Solution Approach 2:
The structure is segmented by introducing a distinct barrier layer between the antiferromagnetic and ferromagnetic layers. This segmentation separates the manganese-containing antiferromagnetic layer from the ferromagnetic layer, preventing direct contact and diffusion while still allowing the necessary magnetic interaction through the thin oxide barrier.
2Reliability
If residual oxygen atoms are present during deposition, then oxidation of the antiferromagnetic layer occurs, but this reduces exchange bias
Solution Approach 1:
The magnesium oxide barrier layer is deposited beforehand to prevent oxygen from reaching and oxidizing the antiferromagnetic layer. This preliminary protective action blocks the harmful oxidation process before it can occur, preserving the exchange bias properties of the antiferromagnetic layer.
Solution Approach 2:
The magnesium oxide layer serves as an intermediary barrier that prevents oxygen atoms from diffusing into the antiferromagnetic layer. This mediator blocks the harmful oxidation process while allowing the necessary magnetic exchange interaction to occur through the thin oxide layer.
3Reliability
If manganese diffusion is prevented by a barrier layer, then exchange bias is maintained, but the device structure becomes more complex
Solution Approach 1:
A thin magnesium oxide film (typically 1-3 nm thick) is used as the barrier layer. This thin film approach provides effective manganese diffusion blocking and oxidation prevention while minimizing the increase in structural complexity and maintaining compatibility with standard spintronic device fabrication processes.
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 solution results in improved exchange bias, increased resistance to temperature cycles, and extended lifespan of the magnetoresistive elements by maintaining magnetic coupling and preventing galvanic corrosion.
Implementation Method 1
an oxygen gettering layer which comprises material that has better oxygen gettering properties than the antiferromagnetic layer and/or the second magnetic layer
Implementation Method 2
the oxygen gettering layer is arranged in the magnetoresistive element such that it blocks diffusion of manganese from the antiferromagnetic layer into the second magnetic layer
Implementation Method 3
The exchange-coupling is occurring via a so-called exchange bias appearing when the antiferromagnetic layer is in contact with the ferromagnetic layer
Implementation Method 4
an antiferromagnetic layer, which comprises manganese, exchanged coupling the second magnetic layer such that the second magnetization is pinned below a critical temperature of the antiferromagnetic layer
Data Source
Figure 1~2
AI summary
Magnetic element (1) comprising a first magnetic layer (21) having a first magnetization (210); a second magnetic layer (23) having a second magnetization (230); a tunnel barrier layer (22) comprised between the first and the second magnetic layers (21, 23); and an antiferromagnetic layer (24) exchanged coupling the second magnetic layer (23) such that the second magnetization (230) is pinned below a critical temperature of the antiferromagnetic layer (24), and can be freely varied when the antiferromagnetic layer (24) is heated above that critical temperature; the magnetic element (1) further comprising an oxygen gettering layer (25) between the second magnetic layer (23) and the antiferromagnetic layer (24), or within the second magnetic layer (23). The magnetic element has reduced insertion of oxygen atoms in the antiferromagnetic layer and possibly reduced diffusion of manganese in the second magnetic layer resulting in an enhanced exchange bias and/or enhanced resistance to temperature cycles and improved life-time.