Composite Magnetic Shield for MR Sensor Grain Growth
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Solution Overview
Problem
Contemporary magnetic read sensors face instability in magnetic domain configuration under strong magnetic fields and elevated temperatures, leading to unwanted noise and reduced spatial resolution due to magnetic grain growth in the ferromagnetic shield.
Innovation Solution
A composite magnetic shield comprising two ferromagnetic anisotropic layers separated by a grain growth suppression layer, which inhibits structural changes and stabilizes the anisotropic magnetic domain structure during high-temperature annealing, ensuring stable anisotropy and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ferromagnetic shield is exposed to strong magnetic fields at elevated temperatures during processing, then the sensor can be manufactured, but the magnetic anisotropy of the shield becomes unstable due to magnetic grain growth
Solution Approach 1:
The patent applies composite materials by creating a layered shield structure consisting of a first ferromagnetic layer, a nonmagnetic layer, and a second ferromagnetic layer. This composite structure prevents magnetic grain growth in individual layers while maintaining overall magnetic shielding function. The nonmagnetic layer acts as a barrier that stabilizes the magnetic anisotropy of adjacent ferromagnetic layers during high-temperature processing, thus resolving the contradiction between manufacturability and compositional stability.
Solution Approach 2:
The shield is segmented into multiple distinct layers with different magnetic properties. By dividing the originally single ferromagnetic shield into separate ferromagnetic and nonmagnetic layers, the patent prevents unwanted magnetic interactions and grain growth that would occur in a monolithic structure. Each layer can be independently optimized for its specific function while collectively providing stable magnetic shielding.
2Device complexity
If the magnetic shield uses a single ferromagnetic layer, then the structure is simple, but the areal density capabilities are limited due to unstable magnetic domain configuration under strong fields
Solution Approach 1:
The patent employs composite materials by combining ferromagnetic and nonmagnetic layers to create a multi-layered shield structure. This composite approach enhances magnetic domain stability under strong fields while maintaining reasonable structural complexity. The nonmagnetic layers prevent magnetic coupling between ferromagnetic layers, ensuring stable magnetic domain configuration for improved areal density capabilities.
Solution Approach 2:
Different layers in the shield structure are assigned different local qualities - ferromagnetic layers provide magnetic shielding while nonmagnetic layers provide structural stability and prevent grain growth. This local differentiation allows each layer to optimize its specific function, with the overall structure achieving both reliability and controlled complexity.
3Manufacturing precision
If high annealing temperatures are applied to set magnetic orientation, then the magnetic anisotropy can be established, but magnetic grain growth occurs causing unwanted noise
Solution Approach 1:
The patent uses composite materials with alternating ferromagnetic and nonmagnetic layers to enable high-temperature annealing for precise magnetic anisotropy control while preventing magnetic grain growth. The nonmagnetic layers act as diffusion barriers that suppress grain growth during annealing, allowing the ferromagnetic layers to achieve stable magnetic orientation without generating unwanted noise.
Solution Approach 2:
The nonmagnetic layers serve as intermediaries between ferromagnetic layers during high-temperature processing. These intermediary layers prevent direct magnetic interaction and grain growth between adjacent ferromagnetic layers, enabling precise magnetic anisotropy control while eliminating the harmful effect of magnetic noise that would otherwise result from grain growth.
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 composite shield maintains stable anisotropy at elevated temperatures, enhancing the areal density capabilities of magneto-resistive readers and improving their sensitivity and reliability by preventing grain growth and maintaining optimal magnetic orientation.
Implementation Method 1
a grain growth suppression layer, which inhibits structural changes and stabilizes the anisotropic magnetic domain structure during high-temperature annealing
Implementation Method 2
two ferromagnetic anisotropic layers separated by a grain growth suppression layer
Implementation Method 3
a tunneling magneto-resistive sensor stack separating the first magnetic shield element from the second magnetic shield element
Data Source
AI summary
A magneto-resistive reader includes a first magnetic shield element, a second magnetic shield element and a magneto-resistive sensor stack separating the first magnetic shield element from the second magnetic shield element. The first shield element includes two ferromagnetic anisotropic layers separated by a grain growth suppression layer.