Co-based Magneto-sensitive Wire with Composite Structure for High-Temperature Stability
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Solution Overview
Problem
Conventional magneto-sensitive wires for magnetic sensors rely on adjusting the anisotropic magnetic field through internal stress, which is prone to relaxation under high-temperature environments, limiting their heat resistance and durability, and do not effectively expand the measurement range without compromising sensitivity.
Innovation Solution
A Co-based alloy magneto-sensitive wire with a composite structure where fine crystal grains are dispersed in an amorphous phase, generating internal stress and pinning spin magnetization rotation, thereby stabilizing the anisotropic magnetic field and enhancing heat resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal stress is used to adjust the anisotropic magnetic field in conventional amorphous wires, then the anisotropic magnetic field can be controlled, but the internal stress relaxes under high-temperature environments, reducing heat resistance and durability
Solution Approach 1:
The invention utilizes phase transition by introducing crystal grains into the amorphous phase through controlled heat treatment. The crystal grains remain stable at high temperatures unlike internal stress, providing a stable anisotropic magnetic field while maintaining the magneto-impedance effect. This resolves the contradiction by replacing the unstable internal stress mechanism with a stable crystal phase structure.
Solution Approach 2:
The invention creates a composite structure with both amorphous phase and crystal grains coexisting in the wire. The amorphous phase provides the magneto-impedance effect while the crystal grains provide stable anisotropic magnetic field through their crystallographic structure. This composite structure simultaneously achieves high heat resistance and stable magnetic properties.
2Adaptability or versatility
If the measurement range of MI sensor is widened by reducing anisotropic magnetic field, then larger magnetic field range is achieved, but sensitivity decreases
Solution Approach 1:
The invention applies local quality by creating regions with different magnetic properties through controlled crystal grain distribution. The crystal grains are introduced locally to provide stable anisotropic magnetic field regions, while the amorphous regions maintain high sensitivity. This allows simultaneous achievement of wide measurement range and high sensitivity through spatial differentiation of material properties.
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 solution provides a stable anisotropic magnetic field, expands the measurement range, and improves reliability under high-temperature conditions, while maintaining sensitivity and durability of the magnetic sensor.
Implementation Method 1
internal stress is generated in accordance with the density difference between the amorphous phase and the crystal grains
Implementation Method 2
the anisotropic magnetic field of a magneto-sensitive wire can be adjusted by dispersing (or precipitating) fine crystal grains in an amorphous phase
Implementation Method 3
the crystal grains have a higher density than that of the amorphous phase, and when the crystal grains are formed, the internal stress (compressive stress) in the contraction direction acts on the magneto-sensitive wire
Implementation Method 4
the magnitude of magnetization rotation occurring in the circumferential direction in response to the strength of the surrounding magnetic field is detected as a change in impedance or a voltage
Data Source
AI summary
A magneto-sensitive wire (magneto-sensitive body) made of a Co-based alloy having a composite structure in which crystal grains are dispersed in an amorphous phase. The Co-based alloy is, for example, a Co—Fe—Si—B-based alloy, and the total amount of Si and B is preferably 20 to 25 at % with respect to the Co-based alloy as a whole. Preferably, the average diameter of the crystal grains is 70 nm or less and the area ratio of the crystal grains is 10% or less to the composite structure as a whole. The magneto-sensitive wire has a circular cross section and the wire diameter is about 1 to 100 μm. Such a magneto-sensitive wire can be obtained, for example, through a heat treatment step of heating an amorphous wire composed of a Co-based alloy at a temperature equal to or higher than a crystallization start temperature and lower than a crystallization end temperature.