Current Sensor Using Perpendicular Bias for Stable Miniaturization
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Solution Overview
Problem
Magnetic sensors and current sensors using GMR elements face challenges in achieving stable and precise detection of weak magnetic fields and currents while maintaining a compact configuration, as they become susceptible to noise from external sources during miniaturization.
Innovation Solution
The implementation of a magnetoresistive element with a pinned layer, a free layer, and an intermediate layer, along with a bias applying means that provides a bias magnetic field with both parallel and orthogonal components, enhances uniaxial anisotropy without relying on shape anisotropy, allowing for precise and stable detection of magnetic fields and currents in a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a GMR element is used in a compact configuration, then miniaturization is achieved, but noise susceptibility increases and detection stability deteriorates
Solution Approach 1:
The patent changes the magnetic field orientation parameter from in-plane to out-of-plane by applying a perpendicular bias magnetic field. This parameter change enables the use of perpendicular magnetic anisotropy (PMA) in the free layer, which provides stronger magnetic stability and higher detection sensitivity even in miniaturized configurations, thereby resolving the contradiction between miniaturization and detection stability.
Solution Approach 2:
The patent employs a composite multilayer structure including pinned layer, intermediate layer, and free layer with specific material compositions. The free layer uses materials exhibiting perpendicular magnetic anisotropy (PMA), and the combination of these layers creates a composite structure that maintains high detection stability while enabling miniaturization through enhanced magnetic field response.
2Measurement precision
If shape anisotropy is used to enhance uniaxial anisotropy, then detection precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the fundamental parameter from shape anisotropy to perpendicular magnetic anisotropy (PMA) by modifying the magnetic field orientation and material composition. This eliminates the need for complex elongated shapes while achieving the desired uniaxial anisotropy for precise detection, thereby improving detection precision without increasing structural complexity.
Solution Approach 2:
The patent substitutes the mechanical shape-based anisotropy (requiring elongated geometries) with a magnetic field-based perpendicular anisotropy mechanism. By applying a perpendicular bias field and using PMA materials, the system achieves uniaxial anisotropy through magnetic properties rather than mechanical shape, simplifying the device structure while maintaining detection precision.
3Measurement precision
If the magnetization direction of the free layer is changed to be parallel to the pinned layer, then sensitivity is improved, but responsiveness to high frequency signals deteriorates
Solution Approach 1:
The patent changes the magnetization orientation parameter from in-plane (parallel) to out-of-plane (perpendicular) configuration. This perpendicular configuration reduces magnetic damping and enhances precession dynamics, thereby improving high-frequency responsiveness while maintaining detection sensitivity through the strong perpendicular magnetic anisotropy effect.
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
This configuration enables high-precision and stable detection of magnetic fields and currents, reducing noise susceptibility and enabling miniaturization without compromising sensitivity or responsiveness.
Implementation Method 1
a giant magnetoresistive element (hereinbelow, GMR element) producing giant magnetoresistive effect is disposed in the current magnetic field generated by control current and the gradient of the current magnetic field is detected
Implementation Method 2
enhances uniaxial anisotropy without relying on shape anisotropy
Implementation Method 3
a first anti-ferromagnetic material layer, a first ferromagnetic material layer (pinned layer) which receives bias magnetic field caused by exchange coupling with the first anti-ferromagnetic material layer
Data Source
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AI summary
The present invention provides a current sensor (10) capable of detecting a current magnetic field generated by a current to be detected with high precision and stability while realizing a compact configuration. The current sensor has: first and second magnetoresistive elements (1A,1B) each including a pinned layer having a magnetization direction pinned in a predetermined direction, a free layer whose magnetization direction changes according to applied magnetic fields, and an intermediate layer sandwiched between the pinned layer and the free layer; and first and second permanent magnets (HM1,HM2) for applying bias magnetic fields to the first and second magnetoresistive elements. The bias magnetic field has a parallel component parallel to a magnetization direction under no magnetic field and an orthogonal component orthogonal to the parallel component. Consequently, uniaxial anisotropy of the free layer can be enhanced without using shape anisotropy. Therefore, the current magnetic field to be detected can be detected with high precision and stability irrespective of the shapes of the magnetoresistive elements, and the invention is favorable for miniaturization.