Spin-Orbit Torque Magnetic Sensing for Low-Offset Field Detection
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Solution Overview
Problem
Conventional magnetic sensors, such as AMR, GMR, and TMR sensors, face limitations in measuring static magnetic field components with high resolution due to offset errors that depend on production variations and are difficult to compensate.
Innovation Solution
A device utilizing a layer stack with a ferromagnetic layer and a magnetic reference layer, where the ferromagnetic layer's magnetization direction is variable using the spin orbit torque effect, allowing for precise compensation of magnetic field disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If magnetoresistive sensors (AMR, GMR, TMR) are used for magnetic field detection, then the sensor structure is simple and manufacturing is easier, but the measurement precision deteriorates due to offset errors from production variations
Solution Approach 1:
The sensor is divided into multiple identical sensor elements arranged in an array, where each element contributes to the overall measurement. By segmenting the sensing function across multiple elements and using differential measurement, the offset errors from production variations are reduced while maintaining manufacturing simplicity.
Solution Approach 2:
The sensor utilizes changes in magnetization direction as a control parameter to modulate the resistance signal. By applying external magnetic fields to rotate magnetization vectors and using the resulting resistance changes, the sensor achieves higher measurement precision while compensating for offset errors through the modulation technique.
2Measurement precision
If spinning current technique is applied to compensate offset errors in magnetoresistive sensors, then measurement precision improves, but power consumption increases due to high current requirements for magnetization reversal
Solution Approach 1:
Instead of continuous high-current application for magnetization reversal, the sensor uses periodic alternating current to modulate the magnetization direction dynamically. This periodic modulation enables offset compensation through differential measurement while significantly reducing average power consumption compared to continuous spinning current techniques.
Solution Approach 2:
The patent replaces the mechanical-like magnetization reversal process (which requires high currents) with a field-based modulation approach. By using external magnetic fields to rotate magnetization vectors and measuring resistance changes, the system achieves offset compensation without the high power consumption associated with direct current-driven magnetization switching.
3Ease of operation
If high current is applied to generate AMR flipping fields for signal conditioning, then magnetization direction can be reversed for offset compensation, but power consumption increases significantly
Solution Approach 1:
The sensor introduces external magnetic fields as an intermediary to control magnetization direction instead of using high currents directly. These magnetic fields act as mediators that rotate the magnetization vectors in the sensor layers, enabling signal conditioning and offset compensation with much lower power consumption while maintaining ease of magnetization control.
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 device achieves precise detection and compensation of external magnetic fields with reduced power consumption and improved resolution, addressing the limitations of conventional magnetic sensors.
Implementation Method 1
The second magnetization direction is variable relative to the first magnetization direction, specifically with use or application of the spin orbit torque effect (or SOT effect for short). The spin orbit torque effect, or SOT effect for short, is based on the spin orbit coupling of electrons.
Implementation Method 2
Examples of phenomena that can result in a spin orbit torque effect are the so-called spin hall effect or the Rashba-Edelstein effect, which can be observed at interfaces, in particular.
Implementation Method 3
Many conventional magnetic sensors are based on materials that use the magnetoresistive effect, thus for example AMR sensors (AMR: Anisotropic Magnetoresistance), GMR sensors (GMR: Giant Magnetoresistance) or TMR sensors (TMR: Tunnel Magnetoresistance).
Data Source
AI summary
A device includes at least one layer stack including a ferromagnetic layer, at least one magnetic reference layer, and a layer arranged therebetween having a magnetic tunnel junction. The at least one magnetic reference layer has a fixed first magnetization direction, and the ferromagnetic layer has a variable second magnetization direction that is variable relative to the first magnetization direction based on a spin orbit torque effect. The device further includes a spin orbit torque conductor arranged on a first side of the layer stack adjacent to the ferromagnetic layer, and a control unit configured to provide the spin orbit torque conductor with a time-variant input signal with temporally varying polarity and at the same time to determine a conductance of the tunnel junction dependent on the time-variant input signal and, based on the conductance, to detect a magnetic field acting on the device externally.