Vortex Spin Magneto-Sensitive Wire Eliminates Hysteresis
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Solution Overview
Problem
Conventional magneto-sensitive wires with multi-magnetic domain structures exhibit degraded hysteresis characteristics due to magnetic domain walls, which affect their performance in magnetic sensors.
Innovation Solution
A magneto-sensitive wire with a vortex spin structure is developed, featuring continuous spin alignment in the surface layer and a gradual rotation of spins towards the axial direction in the inner portion, eliminating magnetic domain walls and achieving a three-dimensional structure with zero hysteresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-magnetic domain structure is used in the magneto-sensitive wire, then the wire can be manufactured with conventional methods, but the hysteresis characteristics are degraded due to magnetic domain walls
Solution Approach 1:
The invention changes the magnetic structure parameter from a multi-domain structure to a vortex spin structure with continuous spin alignment. This is achieved by controlling the wire diameter to be not more than 15 μm and applying specific thermal treatment, which transforms the magnetic domain configuration to eliminate domain walls and achieve almost zero hysteresis characteristics.
2Ease of manufacture
If the wire diameter is increased to improve manufacturing ease, then the manufacturing process becomes simpler, but magnetic domain walls form in the core portion degrading sensor performance
Solution Approach 1:
The invention establishes a specific parameter range for wire diameter (not more than 15 μm) to prevent the formation of magnetic domain walls in the core portion. This parameter control ensures that the entire wire cross-section adopts a vortex spin structure, eliminating the need for complex post-manufacturing treatments to improve hysteresis characteristics.
3Ease of manufacture
If a conventional multi-layer magnetic structure is used, then the wire can be produced with existing technology, but the boundary between layers creates discontinuous spin variation and magnetic domain walls
Solution Approach 1:
The invention creates a radially varying spin structure where the spin direction continuously changes from circumferential at the surface to axial at the center. This local variation in spin orientation throughout the wire cross-section eliminates abrupt boundaries and discontinuous spin transitions, achieving uniform vortex spin structure without layer interfaces.
Solution Approach 2:
The invention transitions from a two-dimensional planar spin structure to a three-dimensional vortex spin structure with radial variation. The spin direction varies continuously in the radial dimension, creating a smooth three-dimensional magnetic configuration that eliminates the need for discrete layers and their associated boundary problems.
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 vortex spin structure magneto-sensitive wire exhibits almost zero hysteresis and improved linearity of output voltage characteristics, enhancing the performance of magneto-impedance sensors by detecting only spin rotation without domain wall movement.
Implementation Method 1
The article 'Study of surface magnetic structure in Co-based amorphous microwires by means of off-diagonal magnetoimpedance effect' published by the Journal of Magnetism and Magnetic Materials 300 (2006) e37-e40 discloses a new method for study of the domain structure in Co-based amorphous microwires with a negative magnetostriction. The method is based on the so-called off-diagonal magnetoimpedance effect.
Implementation Method 2
Study of surface magnetic structure in Co-based amorphous microwires with a negative magnetostriction
Data Source
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Figure 3
Figure 4(a)~4(b)
AI summary
The magneto-sensitive wire of the invention has a vortex-spin structure and hence includes no magnetic domain walls, so that the magneto-sensitive wire of the invention has an excellent hysteresis characteristic exhibiting nearly zero hysteresis. Therefore, the linearity related to the output voltage characteristic for the applied magnetic field in the determination range of an MI sensor is significantly improved as compared to MI sensors using the conventional magneto-sensitive wires. Using the magneto-sensitive wire of the invention makes it possible to provide a magneto-impedance (MI) element exhibiting a higher precision than the conventional ones and further provide a sensor using such an MI element.