Hard Bias Layer Stabilizes Magnetic Shield Domains
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Solution Overview
Problem
Magnetic hysteresis in magnetic shields deteriorates the linearity of output in magnetic balance type current sensors using magnetoresistance effect elements.
Innovation Solution
Incorporating a hard bias layer on or above the magnetic shield to put its magnetic domain structure into a single magnetic domain state, reducing the influence of magnetic hysteresis and enhancing the linearity of the magnetoresistance effect element output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic shield is provided to attenuate the induction magnetic field and enhance the cancelling magnetic field, then the sensitivity and response of the current sensor are improved, but the linearity of the output is deteriorated due to magnetic hysteresis
Solution Approach 1:
A hard bias layer is introduced as an intermediary component between the magnetic shield and the external environment. This hard bias layer acts as a mediator that stabilizes the magnetic domains in the magnetic shield, preventing hysteresis effects while preserving the shield's ability to attenuate induction magnetic fields and enhance cancelling magnetic fields.
Solution Approach 2:
The magnetic properties of the shield structure are changed by adding the hard bias layer, which alters the magnetic domain configuration. This parameter change transforms the magnetic shield from a state prone to hysteresis to a state with stabilized magnetic domains, thereby improving linearity while maintaining shielding effectiveness.
2Reliability
If a magnetic shield is used to enhance the cancelling magnetic field, then the sensor's ability to detect current is improved, but the output linearity deteriorates
Solution Approach 1:
The hard bias layer serves as an intermediary that decouples the relationship between the magnetic shield and the magnetoresistance effect element. It allows the magnetic shield to perform its function of enhancing the cancelling magnetic field while preventing direct hysteresis effects from reaching the sensing element, thus maintaining both reliability and measurement precision.
3Measurement precision
If a magnetic shield is provided to attenuate the induction magnetic field, then the sensor performance is enhanced, but magnetic hysteresis causes nonlinearity in the output
Solution Approach 1:
The magnetic shield structure is transformed into a composite structure by combining the magnetic shield material with the hard bias layer. This composite structure leverages the high permeability of the magnetic shield for field attenuation while utilizing the hard magnetic properties of the bias layer to stabilize domains and eliminate hysteresis, achieving improved measurement precision without significant increase in device complexity.
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 hard bias layer improves the linearity of the output by suppressing magnetic hysteresis, allowing for more accurate current measurement in magnetic balance type current sensors.
Implementation Method 1
a magnetoresistance effect element whose characteristic changes owing to an induction magnetic field from a current to be measured flowing through a conductor
Implementation Method 2
a feedback coil configured to be disposed in the vicinity of the magnetoresistance effect element and generate a cancelling magnetic field cancelling out the induction magnetic field
Implementation Method 3
a magnetic shield configured to attenuate the induction magnetic field and enhance the cancelling magnetic field
Implementation Method 4
Since a material forming a magnetic shield is a magnetic material and has a magnetic hysteresis, there occurs a problem that the linearity of the output of a magnetoresistance effect element is deteriorated owing to the influence of the magnetic hysteresis of the magnetic shield
Data Source
AI summary
A magnetic balance type current sensor includes a magnetic balance type current sensor including a magnetoresistance effect element whose characteristic changes owing to an induction magnetic field from a current to be measured flowing through a conductor, a feedback coil configured to be disposed in the vicinity of the magnetoresistance effect element and generate a cancelling magnetic field cancelling out the induction magnetic field, a magnetic shield configured to attenuate the induction magnetic field and enhance the cancelling magnetic field, and a hard bias layer configured to be provided on or above the magnetic shield.