Spin-Orbit Torque Magnetic Field Sensor
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Solution Overview
Problem
Conventional magnetic field sensors, such as anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) sensors, face complexity and high costs due to the need for additional magnetic biasing layers and complex processing steps, and suffer from non-linearity and noise issues, making them inefficient for accurate magnetic field detection.
Innovation Solution
A spin-orbit torque magnetic field sensor using a magnetic layer with a switchable state is employed, where an alternating current creates an oscillatory spin-orbit torque to switch the magnetic state between two states, generating a time-varying anomalous Hall voltage that is averaged to measure the magnetic field, eliminating the need for offset compensation and transverse magnetic bias, and providing a linear output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MR sensors (AMR, GMR, TMR) are used for magnetic field detection, then high sensitivity can be achieved, but device complexity increases due to additional magnetic biasing layers and complex processing steps
Solution Approach 1:
The patent removes the complex magnetic biasing layers (soft adjacent layers, barber pole strips, or longitudinal bias layers) from conventional MR sensor structures. By extracting these unnecessary components, the invention achieves magnetic field detection functionality while significantly reducing device structure complexity and fabrication process complexity, directly resolving the contradiction between sensitivity and structural complexity
Solution Approach 2:
The invention changes the operating parameters of the MR sensor by applying an alternating current to generate an oscillating spin-orbit torque that dynamically switches the magnetization state. This parameter change approach eliminates the need for static magnetic biasing layers while maintaining high sensitivity, thereby reducing device complexity without sacrificing measurement precision
2Manufacturing precision
If soft adjacent layer (SAL) scheme is used to bias magnetization at 45°, then non-linearity is reduced, but current shunting effect and domain stabilization issues occur
Solution Approach 1:
The patent extracts and removes the soft adjacent layer component entirely from the sensor structure. Instead of using SAL to achieve 45° magnetization bias, the invention employs an alternating current-driven spin-orbit torque mechanism that dynamically controls magnetization switching, thereby eliminating the current shunting effect while maintaining precise magnetization angle control
Solution Approach 2:
The invention replaces the static mechanical/structural biasing approach (SAL providing fixed 45° bias through layer orientation) with a dynamic electromagnetic control approach. By using alternating current to generate oscillating spin-orbit torque, the system achieves magnetization control without the harmful current shunting effect inherent in SAL structures
3Measurement precision
If Wheatstone bridge is used to suppress zero-field output, then offset is reduced, but process complexity and costs increase
Solution Approach 1:
The patent implements a self-service mechanism where the alternating current-driven spin-orbit torque automatically generates symmetric magnetization switching between upward and downward states. This inherent symmetry causes the zero-field output to naturally cancel out over a full cycle, eliminating the need for external Wheatstone bridge circuits while maintaining excellent offset suppression and reducing overall device complexity
4Manufacturing precision
If conventional MR sensors are fabricated with additional magnetic biasing layers, then sensor linearization is achieved, but fabrication time and costs increase
Solution Approach 1:
The patent extracts and eliminates the time-consuming fabrication steps for depositing magnetic biasing layers (soft adjacent layers, barber pole strips, or longitudinal bias layers). By removing these unnecessary fabrication steps while maintaining sensor linearization through alternating current-driven spin-orbit torque, the invention significantly reduces fabrication time and associated costs
Solution Approach 2:
The invention changes the approach to achieving sensor linearization from a structural parameter (adding magnetic biasing layers during fabrication) to an operational parameter (applying alternating current to generate dynamic spin-orbit torque). This parameter change eliminates complex fabrication steps while maintaining excellent linearity, thereby reducing fabrication time and costs
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 approach allows for zero-offset and negligible hysteresis magnetic field detection with reduced manufacturing time and costs, while suppressing noise and enabling direct read-off of magnetic field values, improving the operational ease and accuracy of magnetic field sensing.
Implementation Method 1
providing an alternating current to the spin-orbit torque magnetic field sensor for creating an oscillatory spin-orbit torque in the magnetic layer to switch the switchable magnetic state between two magnetic states
Implementation Method 2
measuring an output voltage of the spin-orbit torque magnetic field sensor, the output voltage being dependent on the magnetic field, wherein the output voltage is a time average of a time-varying anomalous Hall voltage generated in the magnetic layer
Data Source
AI summary
A method for detecting a magnetic field using a spin-orbit torque magnetic field sensor is described. The spin-orbit torque magnetic field sensor comprises a magnetic layer having a switchable magnetic state. The method comprises: (i) providing an alternating current to the sensor for creating an oscillatory spin-orbit torque in the magnetic layer to switch the switchable magnetic state between two magnetic states; and (ii) measuring an output voltage of the sensor, the output voltage being dependent on the magnetic field and is a time average of a time-varying anomalous Hall voltage generated in the magnetic layer in response to the oscillatory spin-orbit torque and the magnetic field. The time-varying anomalous Hall voltage is a function of the alternating current and a Hall resistance of the magnetic layer, and the Hall resistance is associated with a duration in which the switchable magnetization is in each of the two magnetic states and the duration is associated with a magnitude and a polarity of the magnetic field. An apparatus for performing the method is also described.