PEM-Based Spin-Orbit Torque Measurement With Hall Effect Rejection
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Solution Overview
Problem
Existing methods for measuring spin-orbit torque (SOT) in magnetic thin films are inaccurate and time-consuming due to interference from planar Hall effects and anomalous Hall effects, making it difficult to precisely quantify SOT for applications in magnetic memory devices.
Innovation Solution
A SOT measuring apparatus and method using a photoelastic modulator (PEM) to periodically modulate polarization, combined with an AC voltage to generate an alternating current, a prism to split light, and a balanced detector to measure intensity differences, allowing for accurate calculation of SOT by measuring amplitude of frequency components, which includes a frequency component changer circuit to the frequency component changer circuit, and a balanced detector to measure the amplitude of the frequency component, and a balanced detector to measure the amplitude of the frequency component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to measure spin-orbit torque, then measurement can be performed, but measurement precision is poor due to interference from Hall effects
Solution Approach 1:
The patent extracts and separates the SOT signal from the interfering Hall effect signals by using frequency modulation and selective detection. The PEM modulates the polarization at a specific frequency, and the detection system selectively measures only the frequency component corresponding to SOT, effectively removing Hall effect interference from the measurement.
Solution Approach 2:
The patent employs periodic modulation of the light polarization direction using a photoelastic modulator (PEM) at a specific frequency. This periodic action allows the SOT signal to be encoded at a known frequency, enabling selective detection and separation from non-periodic or differently frequency-coded interference signals from Hall effects.
2Productivity
If existing methods are used to measure spin-orbit torque, then measurement can be performed, but measurement time is excessive
Solution Approach 1:
The periodic modulation by PEM encodes the measurement signal at a specific frequency, allowing rapid Fourier transformation and immediate extraction of the SOT amplitude. This eliminates time-consuming sequential measurement procedures and enables fast, direct quantification of SOT.
Solution Approach 2:
The patent replaces traditional mechanical or manual measurement procedures with an optical modulation and frequency-domain analysis system. The PEM-based optical modulation system provides rapid signal encoding and the frequency component analysis enables quick extraction of measurement data, significantly reducing measurement time compared to conventional methods.
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
Enables rapid and precise measurement of SOT by minimizing interference from Hall effects, facilitating the development of efficient magnetic memory devices like MRAM with low energy consumption.
Implementation Method 1
a photoelastic modulator (PEM) configured to periodically modulate a polarization direction of linearly polarized incident light and emit a periodically modulated light
Implementation Method 2
a prism configured to split light reflected by the sample into first light and second light having different polarization directions
Data Source
AI summary
A spin-orbit torque (SOT) measuring apparatus includes a photoelastic modulator (PEM) configured to periodically modulate a polarization direction of linearly polarized incident light and emit a periodically modulated light, a first polarization rotator configured to rotate a polarization direction of the periodically modulated light, a voltage generator configured to generate an AC current to a sample to which light with the rotated polarization direction is to be emitted, a prism configured to split light reflected into first light and second light having different polarization directions, a balanced detector configured to output a signal corresponding to an intensity difference between the first light and the second light, a changing circuit configured to change a frequency component to the intensity difference, and an amplitude measurer configured to measure an amplitude of a frequency component corresponding to a modulation frequency of the PEM with the changed frequency component.