TMR Read Head CoFe Interface Layer Annealing
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Solution Overview
Problem
High-temperature annealing of TMR read heads with thin antiparallel coupling layers leads to deterioration of the MR ratio due to increased dispersal of ferromagnetic layers, making it difficult to maintain parallelism/antiparallelism and resulting in unstable fixed layer characteristics.
Innovation Solution
A TMR read head structure is developed with a fixed layer comprising a first ferromagnetic layer, a Co-based amorphous metallic layer, and an antiparallel coupling layer, where the Co-based amorphous metallic layer is formed between the ferromagnetic layer and the insulating barrier layer, and the annealing temperature is maintained between 270° C. to 300° C. to promote crystallization and stabilize the fixed layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature annealing is performed to promote crystallization and increase MR ratio, then the MR ratio is improved, but the ferromagnetic layers become dispersed and lose parallelism/antiparallelism, causing unstable fixed layer characteristics
Solution Approach 1:
The patent introduces a Co-based amorphous metallic layer as an intermediary between the ferromagnetic layer and the insulating barrier layer. This intermediate layer acts as a buffer that prevents direct high-temperature interaction between the ferromagnetic layer and the barrier layer, thereby maintaining the stability of the fixed layer characteristics while still allowing the MR ratio to be improved through annealing.
Solution Approach 2:
The patent changes the physical state parameter of the interface layer from crystalline to amorphous. The Co-based amorphous metallic layer, being in an amorphous state, has different thermal properties compared to crystalline materials, allowing it to withstand high-temperature annealing without causing dispersal of the ferromagnetic layers, thus resolving the contradiction between improving MR ratio and maintaining stability.
2Force
If the antiparallel coupling layer is made thin to increase coupling strength, then the coupling strength is improved, but the structure becomes more sensitive to thermal effects and dispersal
Solution Approach 1:
The Co-based amorphous metallic layer serves as a protective intermediary that shields the thin antiparallel coupling layer from direct thermal exposure. This allows the coupling layer to remain thin for strong coupling while the amorphous layer absorbs thermal stress, preventing dispersal and maintaining structural reliability during high-temperature annealing.
Solution Approach 2:
The patent creates a composite structure combining the thin antiparallel coupling layer with the Co-based amorphous metallic layer. This composite material approach allows the system to benefit from both the strong coupling of the thin layer and the thermal stability of the amorphous material, resolving the contradiction between coupling strength and structural stability.
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 enhances the MR ratio by maintaining strong coupling between ferromagnetic layers and stabilizing the fixed layer, even at high temperatures, thereby improving the sensitivity and reliability of the TMR read head.
Implementation Method 1
Crystallization of the magnetic layers is promoted by the annealing treatment, and scattering of the electron spin is suppressed, whereby a high MR ratio is achieved
Implementation Method 2
TMR read heads employ a tunneling effect in a layered structure comprising an insulating layer and two ferromagnetic layers, one either side
Implementation Method 3
Annealing the magnetic layers of the TMR layered structure at high temperature is effective for achieving a high MR ratio
Data Source
AI summary
According to one embodiment, a method for producing a Tunneling Magnetoresistance (TMR) read head includes forming a fixed layer, forming an insulating barrier layer above the fixed layer, forming a free layer above the insulating barrier layer, and annealing the free layer, the fixed layer, and the insulating barrier layer. The fixed layer includes a first ferromagnetic layer having a CoxFe (0≦x≦15) interface layer and a Co-based amorphous metallic layer between the CoxFe interface layer and the insulating barrier layer, an antiparallel coupling layer below the first ferromagnetic layer, and a second ferromagnetic layer below the antiparallel coupling layer. In another embodiment, a TMR read head includes the layers described above, and may be included in a magnetic data storage system.