CoFe Composition for Exchange Coupling in Magnetic Sensors
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Solution Overview
Problem
Conventional magnetic sensing elements with an antiferromagnetic layer made of IrMn and a pinned magnetic layer made of CoFe experience a small exchange coupling field, leading to a higher possibility of magnetization inversion, particularly in top spin-valve giant magnetoresistive elements.
Innovation Solution
An exchange coupling film is formed with an antiferromagnetic layer of IrMn and a ferromagnetic layer of CoFe, where the CoFe composition is adjusted within specific atomic percent ranges (30% to 90%) to enhance the exchange coupling field, reducing magnetization inversion in the pinned magnetic layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an antiferromagnetic layer made of IrMn and a pinned magnetic layer made of CoFe are used, then the magnetic sensing element structure is established, but the exchange coupling field is small leading to high magnetization inversion possibility
Solution Approach 1:
The invention changes the compositional parameters of the ferromagnetic layer by adjusting the Fe content to 30-90 atomic percent in CoFe alloy, which fundamentally alters the exchange coupling field strength between the IrMn antiferromagnetic layer and the ferromagnetic layer, resolving the contradiction between structural establishment and magnetization stability
Solution Approach 2:
The invention uses a composite structure of IrMn antiferromagnetic layer combined with CoFe ferromagnetic layer with specific composition ratios, creating a material system that achieves both structural integrity and strong exchange coupling field to prevent magnetization inversion
2Force
If the CoFe composition is adjusted within specific atomic percent ranges, then the exchange coupling field increases to 64 kA/m or more, but the manufacturing precision requirements increase
Solution Approach 1:
The invention defines a broad compositional range (30-90 atomic percent Fe in CoFe) that achieves the target exchange coupling field of 64 kA/m or more, providing manufacturing flexibility while meeting performance requirements, thus balancing force enhancement with manufacturability
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 adjusted CoFe composition achieves an exchange coupling field of 64 kA/m or more, reducing the rate of magnetization inversion in magnetic sensing elements to 5% or less, and an exchange coupling field of 80 kA/m or more with optimal composition ranges.
Implementation Method 1
An exchange coupling field occurs between the two layers to align the magnetization of the ferromagnetic layer in a predetermined direction
Data Source
AI summary
A magnetic sensing element and exchange coupling film is disclosed. The magnetic sensing element has a free magnetic layer, nonmagnetic material layers disposed on the top and bottom of the free magnetic layer, pinned magnetic layers disposed on the top of one nonmagnetic material layer and on the bottom of the other nonmagnetic material layer, and antiferromagnetic layers containing IrMn disposed on the top of one pinned magnetic layer and on the bottom of the other pinned magnetic layer. The magnetization of the free magnetic layer is aligned in a direction orthogonal to the magnetization direction of the pinned magnetic layers. The exchange coupling film is formed by the antiferromagnetic layer and the pinned magnetic layer above the free magnetic layer. At least an interfacial portion of the ferromagnetic layer which is adjacent to the antiferromagnetic layer contains Co100-xFex wherein 30%≦x≦90% in atomic percent.