Vortex MTJ Magnetic Gradiometer for Weakly Magnetic Material Defect Detection
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Solution Overview
Problem
Current nondestructive testing (NDT) methods, particularly magnetic flux leakage (MFL) testing, lack the spatial and depth resolution to detect small material defects or inhomogeneities in weakly magnetic materials, such as magnetic cement, at distances required in real-world applications.
Innovation Solution
A magnetic tunnel junction in magnetic vortex state (vortex MTJ) sensor-based magnetic gradiometer system is developed, which includes a printed circuit board with an excitation coil and differential sensor arrays. This system generates a magnetic field and detects small fluctuations in magnetic fields produced by weakly magnetic materials, enabling the detection of defects or inhomogeneities of small size and at certain depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic flux leakage testing equipment is used, then the testing process is simple, but the spatial and depth resolution is insufficient to detect small defects in weakly magnetic materials
Solution Approach 1:
The patent replaces conventional mechanical/electromagnetic sensing systems with vortex MTJ-based magnetic tunnel junction sensors that operate at the quantum level. The vortex MTJ sensors utilize quantum tunneling effects to achieve extremely high sensitivity to magnetic field changes, enabling detection of small defects in weakly magnetic materials that conventional equipment cannot detect.
Solution Approach 2:
The patent changes the operating parameters by using alternating current (AC) excitation at specific frequencies and measuring the resulting magnetic field variations. The vortex MTJ sensors are designed to operate in a specific magnetic field range and response mode that optimizes their sensitivity to small magnetic changes, allowing detection of defects that would be invisible to conventional MFL equipment.
2Reliability
If conventional MFL testing is used, then the equipment is relatively simple, but the detection capability for defects in weakly magnetic materials like magnetic cement is limited
Solution Approach 1:
The patent replaces conventional electromagnetic induction-based MFL testing with vortex MTJ sensor technology that detects magnetic field changes through quantum tunneling effects. This substitution enables reliable detection of defects in weakly magnetic materials such as magnetic cement, where conventional MFL equipment fails to provide sufficient detection capability.
Solution Approach 2:
The vortex MTJ sensors act as an intermediary between the excitation magnetic field and the detection system. These sensors convert subtle magnetic field variations caused by defects in weakly magnetic materials into measurable electrical signals through quantum tunneling, bridging the gap between the weak magnetic signals from the material and the detection capabilities of the testing equipment.
3Measurement precision
If the sensor is positioned closer to the material to improve resolution, then the spatial resolution improves, but the standoff distance required for real-world applications is reduced
Solution Approach 1:
The patent uses vortex MTJ sensors that detect magnetic field changes through quantum tunneling effects, enabling high spatial resolution at larger standoff distances. The sensors' extreme sensitivity to magnetic field variations allows them to resolve small defects even when positioned at practical distances from the material surface, eliminating the need to place sensors in direct contact or very close to the material.
Solution Approach 2:
The patent changes the detection parameter from direct contact-based measurement to remote magnetic field sensing. By using AC excitation and measuring magnetic field variations through the material thickness, the system achieves high spatial resolution without requiring the sensor to be positioned close to the material surface, thus maintaining practical standoff distances for real-world applications.
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 MTJ sensor-based magnetic gradiometer system significantly enhances the spatial and depth resolution for detecting material defects and inhomogeneities in weakly magnetic materials, allowing for effective nondestructive testing even in harsh environments and at larger standoff distances.
Implementation Method 1
an excitation coil encircling at least a portion of the PCB and configured to deliver an alternating current (AC) to generate an excitation magnetic field
Implementation Method 2
a differential sensor. The differential sensor can include a reference vortex MTJ sensor array proximal to the first end to generate a voltage based on the excitation magnetic field; and a signal vortex MTJ sensor array proximal the second end to generate another voltage based on the excitation magnetic field due to a composition of a measurement target
Data Source
AI summary
A magnetic gradiometer can be used in systems or methods for nondestructive testing, even when the material being tested is weakly magnetic. The magnetic gradiometer can include a printed circuit board (PCB) comprising a first end and a second end separated by a base length; an excitation coil encircling at least a portion of the PCB and configured to deliver an alternating current (AC) to generate an excitation magnetic field; and a differential sensor. The differential sensor can include a reference magnetic tunneling junction in magnetic vortex state (vortex MTJ) sensor array at the first end to generate a voltage based on the excitation magnetic field; and a signal vortex MTJ sensor array at the second end to generate another voltage based on the excitation magnetic field due to a composition of the measurement target. The second end of the PCB can be oriented towards the measurement target.