Magnetic Sensing Element Free Layer Lamination
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Solution Overview
Problem
Existing magnetic sensing elements face challenges in achieving a suitable configuration for the free magnetic layer, particularly in enhancing the product ΔRA of resistance variation and element area, while maintaining soft magnetic properties and detection sensitivity.
Innovation Solution
A magnetic sensing element is designed with a free magnetic layer comprising a laminate structure of a Co2MnZ alloy layer and a (NiaFe100-a)bX100-b alloy layer, where Z represents elements like Al, Sn, In, Sb, Ga, Si, Ge, or Zn, and X represents Cu, Au, Ag, Zn, Mn, Al, Cd, Zr, or Hf, with specific composition ratios to improve magnetostriction and coercive force, and a film thickness range of 10 to 60 angstroms for the (NiaFe100-a)bX100-b alloy layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a NiFe layer is deposited on a Heusler alloy layer to improve soft magnetic properties, then magnetostriction and coercive force are enhanced, but the free magnetic layer configuration becomes unsuitable and detection sensitivity deteriorates
Solution Approach 1:
The free magnetic layer is segmented into multiple sub-layers: a Heusler alloy layer (Co2MnZ) providing spin polarization and a NiFe-based alloy layer providing soft magnetic properties. This segmentation allows each layer to fulfill its specific function without compromising the overall performance, resolving the contradiction between enhancing soft magnetic properties and maintaining detection sensitivity.
Solution Approach 2:
The invention uses a composite structure combining Heusler alloy (Co2MnZ) and NiFe-based alloy layers. The Heusler alloy provides high spin polarization for sensitive detection, while the NiFe-based alloy contributes soft magnetic properties with low coercive force. This composite material approach enables simultaneous achievement of both detection sensitivity and soft magnetic characteristics.
2Measurement precision
If the free magnetic layer is made thicker to increase the product ΔRA of resistance variation and element area, then detection sensitivity improves, but the magnetization alignment and soft magnetic properties deteriorate
Solution Approach 1:
The invention optimizes the thickness parameters of each layer within specific ranges: the Heusler alloy layer is 5-20 nm thick and the NiFe-based alloy layer is 10-60 nm thick. By precisely controlling these parameter ranges, the free magnetic layer achieves both adequate ΔRA product for sensitive detection and proper magnetization alignment for stable operation, resolving the contradiction between detection sensitivity and magnetization alignment.
3Ease of manufacture
If a simple NiFe layer is deposited on Heusler alloy to form the free magnetic layer, then manufacturing is simplified, but the resulting configuration is unsuitable and performance is poor
Solution Approach 1:
Rather than using a simple single-layer structure, the free magnetic layer is segmented into functionally distinct Heusler alloy and NiFe-based alloy sub-layers. This segmentation, while adding a layer, creates a suitable configuration where each layer contributes specific properties, ultimately improving reliability without significantly complicating the manufacturing process.
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 product ΔRA of resistance variation and element area, enhances soft magnetic properties, and improves detection sensitivity to external magnetic fields, while maintaining stability and reducing noise from spin transfer torque.
Implementation Method 1
improve magnetostriction and coercive force
Implementation Method 2
An exchange coupling magnetic field is generated at the interface between the antiferromagnetic layer 3 and the pinned magnetic layer 4, and the magnetization of the pinned magnetic layer 4 is pinned in the height direction
Implementation Method 3
The magnetization of the free magnetic layer 6 is aligned in a track-width direction (X direction shown in the drawing) by longitudinal bias magnetic fields from the hard bias layers 8
Implementation Method 4
When an external magnetic field is applied to the magnetic sensing element shown in FIG. 10, the magnetization direction of the free magnetic layer is varied relative to the magnetization direction of the pinned magnetic layer, and the resistance of the multilayer film is changed
Data Source
AI summary
A magnetic sensing element exhibiting a large ΔRA is provided, in which a free magnetic layer has a small coercive force Hc and a small magnetostriction constant λs. The free magnetic layer includes a Co2MnZ alloy layer (where Z may represent at least one element selected from the group consisting of Al, Sn, In, Sb, Ga, Si, Ge, Pb, and Zn) and a (NiaFe100-a)bX100-b alloy layer (where X may represent at least one element selected from the group consisting of Cu, Au, Ag, Zn, Mn, Al, Cd, Zr, and Hf, a may represent a composition ratio satisfying 80<a≦100, and b may represent a composition ratio satisfying 60<b≦100). Consequently, the magnetostriction constant λs and the coercive force Hc of the free magnetic layer may be decreased and the soft magnetic properties of the free magnetic layer may be improved.