Spin Torque Modulated Magnetic Field Detection Device
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Solution Overview
Problem
Current magnetic field detection devices lack the necessary resolution to accurately detect weaker magnetic fields, and existing technologies are hindered by noise interference, particularly 1/f noise in the frequency band relevant to magneto-resistive elements.
Innovation Solution
A magnetic field detection device incorporating a magnetism detection element with a modulator that imparts a spin torque with a rotational force oscillating at a specific frequency, enhancing sensitivity and using a demodulator with high-pass and phase detection circuits to remove noise and improve resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magneto-resistive element is used for magnetic field detection, then the device can detect magnetic fields, but the detection resolution is insufficient for weaker magnetic fields due to noise interference
Solution Approach 1:
The patent applies periodic action by oscillating the magnetization direction of the detection layer using a spin torque oscillating at a specific frequency (e.g., 10 kHz to 1 MHz). This periodic modulation of the magnetization state allows the sensor to operate at a frequency where 1/f noise is minimized, thereby improving detection resolution for weak magnetic fields. The alternating spin torque current causes the magnetization to oscillate between two stable states, enabling high-resolution detection through frequency-domain analysis.
Solution Approach 2:
The patent converts the harmful effect of 1/f noise by shifting the detection operation to a frequency range where this noise is minimized. By using spin torque to oscillate the magnetization at frequencies above the 1/f noise corner frequency, the harmful low-frequency noise is effectively converted into a beneficial high-frequency operation mode, where the signal-to-noise ratio is significantly improved.
2Measurement precision
If spin torque modulation is applied to enhance sensitivity, then detection resolution improves, but device complexity increases due to additional modulator and demodulator circuits
Solution Approach 1:
The patent merges the detection layer and modulation functionality into a single magnetism detection element structure. The spin torque modulator is integrated directly with the magnetoresistive sensor, and the demodulation process utilizes the same oscillation frequency that drives the modulation, creating a unified system where the modulation and detection functions are combined rather than separate, thereby reducing overall device complexity.
Solution Approach 2:
The system employs self-service through automatic demodulation where the oscillation frequency of the spin torque automatically serves as the reference frequency for the demodulator. The same oscillating signal that modulates the magnetization also provides the reference signal for extracting the magnetic field information, eliminating the need for separate external modulation and reference signal generation circuits.
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 higher detection resolution and accuracy for weaker magnetic fields while effectively removing 1/f noise, enabling highly reproducible measurements.
Implementation Method 1
The modulator is configured to impart a spin torque to the magnetism detection element. The spin torque has a rotational force and oscillates at a first frequency.
Implementation Method 2
A magneto-resistive sensor has been proposed that applies an alternating magnetic field to a giant magneto-resistive element to achieve high resolution for detecting an external magnetic field.
Data Source
AI summary
A magnetic field detection device includes a magnetism detection element, a modulator, and a demodulator. The magnetism detection element has a sensitivity axis along a first direction. The modulator is configured to impart a spin torque to the magnetism detection element. The spin torque has a rotational force and oscillates at a first frequency. The rotational force is exerted on a plane including the first direction and a second direction orthogonal to the first direction. The demodulator is configured to demodulate an output signal received from the magnetism detection element and to detect an intensity of a measurement target magnetic field exerted on the magnetism detection element on the basis of an amplitude of the output signal. The output signal has the first frequency.