Tunneling Magnetic Sensor With IrMn Protective Layer
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Solution Overview
Problem
Tunneling magnetic sensing elements face challenges in achieving a high rate of change in resistance (ΔR/R) without increasing magnetostriction λ, which affects detection sensitivity and stability due to interdiffusion issues between protective layers and magnetic layers during the fabrication process.
Innovation Solution
A tunneling magnetic sensing element is designed with a pinned magnetic layer, an insulating barrier layer, and a first protective layer composed of iridium-manganese (IrMn) on the free magnetic layer, which prevents diffusion and maintains crystallinity, and optionally a second protective layer of tantalum (Ta) to further enhance the rate of change in resistance (ΔR/R) without altering the composition or thickness of the free magnetic layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Fe content at the interface with the insulating barrier layer is increased, then spin polarizability and rate of change in resistance (ΔR/R) are increased, but magnetostriction λ has a large positive value causing noise and decreasing stability
Solution Approach 1:
An IrMn layer is introduced as an intermediary between the free magnetic layer and the Ta protective layer. This intermediary layer prevents direct interdiffusion between Ta and the free magnetic layer, allowing the free magnetic layer to maintain high Fe content for high spin polarizability and ΔR/R without Ta contamination degrading its magnetic properties and causing noise
Solution Approach 2:
The invention uses a CoFeB layer as a template or copying layer with specific magnetic properties, then protects it with IrMn to preserve these properties. The CoFeB layer provides the desired magnetic characteristics while the IrMn layer copies/protects these properties by preventing degradation from interdiffusion
2Reliability
If Ta protective layer is used, then oxidation protection is provided, but Ta diffuses into the free magnetic layer and insulating barrier layer during heat treatment, causing strain and preventing high rate of change in resistance (ΔR/R)
Solution Approach 1:
The protective layer is segmented into two distinct layers: an inner IrMn layer that prevents interdiffusion and maintains crystallinity, and an outer Ta layer that provides oxidation protection. This segmentation allows each layer to perform its specific function without interfering with the other, solving both the protection and ΔR/R requirements
Solution Approach 2:
The IrMn layer serves as an intermediary barrier between the Ta protective layer and the free magnetic layer. It mediates the interaction by blocking Ta diffusion while allowing the Ta layer to maintain its oxidation protection function, thus preserving the high rate of change in resistance
3Measurement precision
If compositions of the free magnetic layer and pinned magnetic layer are changed to increase rate of change in resistance (ΔR/R), then detection sensitivity is improved, but other magnetic properties are changed affecting overall performance
Solution Approach 1:
The invention applies local quality by having the enhancement layer with high Fe content specifically at the interface with the insulating barrier layer where it is most needed for spin polarizability, while the bulk composition remains controlled. The IrMn protective layer then preserves this localized high Fe content without allowing Ta contamination to degrade it
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 effectively increases the rate of change in resistance (ΔR/R) while maintaining stability and sensitivity by preventing interdiffusion and maintaining the crystallinity of the free magnetic layer, thereby improving the performance of magnetic sensing devices.
Implementation Method 1
In a tunneling magnetic sensing element (tunneling magnetoresistance element), the change in resistance is caused by a tunneling effect
Implementation Method 2
a first protective layer composed of iridium-manganese (IrMn) disposed on the free magnetic layer... which prevents diffusion and maintains crystallinity
Data Source
AI summary
A tunneling magnetic sensing element includes a pinned magnetic layer whose magnetization direction is pinned in one direction, an insulating barrier layer disposed on the pinned magnetic layer, a free magnetic layer whose magnetization direction varies in response to an external magnetic field disposed on the insulating barrier layer, and a first protective layer composed of iridium-manganese (IrMn) disposed on the free magnetic layer. Consequently, a high rate of change in resistance is obtained and the magnetostriction of the free magnetic layer is low, compared with a tunneling magnetic sensing element which is not provided with a first protective layer.