3D SOT Magnetic Sensor With Stray-Field-Insensitive Axis Detection
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Solution Overview
Problem
Current 3D magnetic field sensors using the spin-orbit torque (SOT) effect fail to perform magnetic field measurements in three different axes, and conventional MR sensors suffer from non-orthogonality and noise due to domain walls, leading to inadequate performance.
Innovation Solution
The use of a magnetic layer stack with a ferromagnetic layer and a spin orbit torque conductor layer, combined with control circuitry, allows for the detection of magnetic fields in all three axes by adjusting the magnetization direction of the ferromagnetic layer using SOT currents, enabling reliable and sensitive measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional MR sensors use flux gates to detect fields in three directions, then 3D magnetic field detection is achieved, but non-orthogonality of sensing directions occurs
Solution Approach 1:
The patent applies parameter changes by utilizing the spin-orbit torque effect to dynamically adjust the magnetization direction of the ferromagnetic layer. By changing the orientation of the magnetization vector through SOT, the sensor can achieve precise orthogonal sensing directions in three-dimensional space, resolving the non-orthogonality issue while maintaining 3D detection capability
2Manufacturing precision
If AMR sensors or anomalous Hall Effect sensors are used to minimize offset between orthogonality, then sensing direction orthogonality is improved, but domain walls are required which lead to noise and non-reproducible behaviors
Solution Approach 1:
The patent extracts and eliminates the domain wall structure from the sensor design. By using a uniform ferromagnetic layer without domain walls and relying on spin-orbit torque for magnetization control, the invention removes the source of noise and non-reproducible behavior while maintaining orthogonal sensing capability through precise magnetization orientation
3Force
If large external fields are applied to AMR or Hall Effect sensors, then sensing capability is maintained, but domain walls are annihilated resulting in alteration of sensor response or destruction of functional behavior
Solution Approach 1:
The patent implements dynamic control of the magnetization direction through spin-orbit torque. The SOT mechanism allows real-time adjustment of magnetization orientation in response to external fields, enabling the sensor to maintain functional behavior and reliability even under large external field conditions by dynamically adapting the magnetization state rather than relying on static domain wall structures
4Measurement precision
If current SOT-based 3D magnetic sensors are used, then offset reduction in two directions is achieved, but magnetic field measurements in three different axes are not performed
Solution Approach 1:
The patent achieves multi-functionality by configuring the ferromagnetic layer and SOT conductor layer to enable detection of magnetic field components along all three Cartesian axes (x, y, and z). Through appropriate orientation of the magnetization direction and application of SOT currents, the sensor can simultaneously measure fields in three different axes while maintaining offset reduction, thus achieving universal 3D magnetic field sensing capability
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 a 3D magnetic field sensor with reduced offset, insensitivity to orthogonal stray fields, tunable linear range, and sensitivity direction adjustment, allowing for accurate detection of magnetic fields in the x-, y-, and z-directions using a single domain portion and an in-plane ferromagnetic layer.
Implementation Method 1
the use of the spin-orbit torque (SOT) effect to adjust a magnetic field sensor's direction of sensitivity to magnetic fields in different directions
Implementation Method 2
detect a magnetic field acting externally to the sensor by determining a conductance of the magnetoresistive element that is dependent on the SOT current
Data Source
AI summary
The described techniques facilitate the use of a magnetic field sensor that implements the same magnetic layer stack for the detection of the x, y, and z components of an external magnetic field. The sensor advantageously is insensitive to orthogonal stray fields and operates with a reduced offset compared to conventional magnetic field sensors. The linear regime implemented by the sensor to facilitate magnetic field detection may also be adjusted per application by tuning the current strength.