Closed Loop Magnetic Sensor with AMR and PHE Effects
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Solution Overview
Problem
Conventional magnetic sensors using either anisotropic magnetoresistance or planar Hall effects face limitations in sensitivity, linearity, and measurement range, particularly when detecting broadband DC and AC magnetic fields, and are prone to hysteretic behavior and reduced sensitivity in nano-sized forms.
Innovation Solution
A magnetic sensor with a closed loop shape incorporating both anisotropic magnetoresistance and planar Hall effects, utilizing a ferromagnetic film with exchange coupling, which adjusts the output voltage ratio through the R/W ratio of the loop's radius and width, and includes internal or external magnetic layers to minimize demagnetization factors and hysteretic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If giant magnetoresistance material or tunneling magnetoresistance material is used to increase the magnetoresistance ratio, then the output signal increases, but the linearity in the zero magnetic field range deteriorates
Solution Approach 1:
The patent combines two different magnetic sensing mechanisms (anisotropic magnetoresistance effect and planar Hall effect) into a single integrated sensor structure. This merging allows the sensor to achieve both high output signal from the planar Hall effect and good linearity from the anisotropic magnetoresistance effect, resolving the contradiction between signal strength and linearity in the zero magnetic field range
Solution Approach 2:
The patent employs a composite magnetic layer structure consisting of multiple ferromagnetic layers with different magnetization directions. This composite structure enables simultaneous exploitation of both AMR and PHE effects, achieving enhanced output signal while maintaining linearity through the complementary characteristics of the different material layers
2Volume of moving object
If the magnetic sensor is miniaturized to nano size, then the device size decreases, but the sensitivity and performance deteriorate
Solution Approach 1:
The patent transitions from conventional planar sensor geometry to a three-dimensional closed-loop cylindrical structure. This dimensional change allows the magnetic sensing path to be extended along the cylindrical perimeter, maintaining high sensitivity and signal output even when the overall device footprint is miniaturized to nano scale
Solution Approach 2:
The patent implements a nested multi-layer cylindrical structure where magnetic sensing layers are arranged concentrically. This nesting approach maximizes the magnetic sensing path length within a compact volume, enabling high sensitivity performance in a miniaturized device configuration
3Device complexity
If conventional magnetic sensor structures are used, then the structure is simple, but the measurement range and sensitivity are limited
Solution Approach 1:
The patent introduces adjustable geometric parameters (radius R and width W of the closed loop) that allow dynamic optimization of the sensor's measurement range and sensitivity. By varying these dimensions, the sensor can be adapted to different application requirements without changing the fundamental structure, achieving both versatility and controlled complexity
Solution Approach 2:
The patent utilizes parameter changes in the closed-loop geometry (specifically the R/W ratio) to control the relative contributions of AMR and PHE effects. This parameter adjustment enables tuning of the measurement range and sensitivity while maintaining a relatively simple closed-loop structure, resolving the contradiction between structural simplicity and measurement versatility
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 sensor achieves superior linearity, enhanced sensitivity, and adjustable measurement range for broadband DC and AC magnetic fields, eliminating hysteretic behavior and maintaining performance in nano-sized forms, enabling detection of ultra-low magnetic fields with improved signal characteristics.
Implementation Method 1
Anisotropic magnetoresistance (AMR) is a phenomenon which appears in a single magnetic layer. It has a characteristic of depending on the angle between the directions of current and magnetization
Implementation Method 2
the AMR phenomena can be separated two different effects such as anisotropic magnetoresistance effect (AME) and planar Hall effect (PHE), which are defined by the measurement geometry
Data Source
AI summary
Provided is a magnetic sensor for detecting a magnetic field. The magnetic sensor includes a magnetic layer of a closed loop shape; a pair of current terminals which face each other contacting with the closed loop and through which current is input/output; and a pair of voltage terminals which face each other contacting with the closed loop and from which output voltage is detected. Both an anisotropic magnetoresistance effect (AME) and a planar Hall effect (PHE) contribute to the output voltage and a hysteresis of the output voltage is eliminated by exchange coupling of a ferromagnetic layer by a ferromagnetic-antiferromagnetic layer structure and a ferromagnetic-metal-antiferromagnetic layer structure. Accordingly, it is possible to minimize a hysteresis due to a demagnetization factor of the closed loop, stabilize the output voltage of the magnetic sensor and enhance sensitivity.