GMR Magnetic Sensor Asymmetry for Waveform Symmetry
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Solution Overview
Problem
Magnetic sensors with giant magnetoresistive effect elements (GMR elements) face reduced detection accuracy due to deformation of output waveforms when displaced from the center of a magnetized surface, leading to inadequate magnetic sensitivity and disturbance resistance in non-sensitivity axis directions.
Innovation Solution
A magnetic sensor with a layered structure featuring a first and second magnetic layer, where magnetization directions are inclined at an angle of 90 to 180 degrees, providing improved sensitivity and disturbance resistance. The sensor includes a Co-Fe and Ni-Fe layered structure with a non-magnetic layer in between, and is arranged in an oblong shape with connecting portions, enhancing magnetic sensitivity and resistance to external fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GMR elements are arranged with predetermined intervals using the center-to-center distance between N and S poles as reference, then the magnetic sensor can detect position changes, but the output waveform becomes deformed when displaced from the center of the magnetized surface
Solution Approach 1:
The patent applies asymmetry by intentionally designing the GMR element structure with a specific magnetization configuration that compensates for the asymmetric magnetic field distribution when displaced from the magnet center. The pinned layer and free layer are arranged with specific magnetization directions that create an asymmetric response to the magnetic field, which counteracts the waveform deformation caused by displacement from the magnet center, thereby maintaining measurement precision across different positions.
2Measurement precision
If the magnetization direction of the pinned magnetic layer is pinned in a certain direction to enable magnetic field detection, then the sensor can measure external magnetic fields, but the disturbance resistance against magnetic fields in other directions is insufficient
Solution Approach 1:
The patent applies local quality by creating different magnetization characteristics in different regions of the GMR element. The pinned layer has a fixed magnetization direction optimized for sensitivity in the measurement direction, while the free layer can rotate its magnetization in response to external fields. This local differentiation of magnetic properties allows the sensor to maintain high sensitivity to external magnetic fields while being more resistant to disturbances from other directions through the anisotropic magnetization structure.
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 enhanced magnetic sensitivity in the sensitivity axis direction and improved disturbance resistance in perpendicular directions, increasing detection accuracy and output waveform symmetry, even when displaced from the center of the magnetized surface.
Implementation Method 1
A magnetic sensor including a giant magnetoresistive effect element (GMR element) is mounted in, for example, a magnetic encoder
Implementation Method 2
The GMR element has a layered structure in which a pinned magnetic layer and a free magnetic layer are stacked with a non-magnetic layer interposed therebetween
Data Source
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AI summary
[Object] To provide, in particular, a magnetic sensor and a magnetic encoder having a satisfactory magnetic sensitivity to an external magnetic field in a sensitivity axis direction and an improved disturbance resistance against a magnetic field in a direction other than the sensitivity axis direction. [Solving Means] A magnetic sensor includes a magnetic detection element having an electrical resistance value that varies in accordance with an external magnetic field in a sensitivity axis direction. The magnetic detection element includes an element portion 10 having a layered structure in which a first magnetic layer 31 and a second magnetic layer 33 are stacked with a non-magnetic layer 32 interposed therebetween. Magnetization of each of the first magnetic layer 31 and the second magnetic layer 33 is variable in accordance with the external magnetic field. In a magnetic-field-free state, the first magnetic layer 31 and the second magnetic layer 33 are magnetized in substantially antiparallel directions along a direction parallel to the sensitivity axis direction. The element portion 10 has an oblong shape that extends in the sensitivity axis direction.