Detection Of Weak Magnetic Fields Research Articles

Ni80Fe20 thickness optimization of magnetoplasmonic crystals for magnetic field sensing

A promising approach to enhance the transverse Kerr effect with potential applications in the detection of weak magnetic fields is the use of magnetoplasmonic crystals based on ferromagnetic metals. The sensitivity, measuring field range, and limit-of-detection of 1D magnetoplasmonic crystals with 5–20 nm thick Ni80Fe20 layers are analyzed in this study based on magnetic, optical, and magneto-optical characterization. The magnetoplasmonic crystal with 10 nm-thick Ni80Fe20 layer provided a sensitivity of 21.9 µV/mOe, a limit-of-detection of 3.6 mOe, and a measuring field range of 1.134 Oe. This sample was also utilized as a magnetic field probe to reconstruct the magnetic configuration of a multicore cable and a planar induction coil, thereby highlighting its potential for the visualization of DC magnetic fields.

Study on the frequency response characteristic of superconducting/tunnel magnetoresistance composite magnetic sensors

The superconducting/tunnel magnetoresistance (TMR) composite magnetic sensor is expected to have great application prospects in the field of weak magnetic field detection due to its ultra-high detectivity. For some special applications such as bio-magnetic measurement, it is of necessity to study the frequency response characteristic. Therefore, a superconducting/TMR composite sensor was fabricated and its frequency response was systematically studied in this paper. Firstly, the sensitivity of composite magnetic sensors was found to decrease rapidly with the magnetic field frequency. After excluding the influence of the TMR device itself at different temperatures, the sensitivity decay with magnetic field frequency was attributed to the AC loss of the superconducting loop. Finally, the minimum detectable field of the composite magnetic sensor was obtained by combining the sensitivity and noise spectrum. The sensor exhibits superior magnetic field detectivity, particularly in the low-frequency range, which indicates the suitability for the application of bio-magnetic field detection.

Driver circuit with high-voltage pulse and high-frequency excitation for the cell of optically pumped sensors.

Helium optically pumped sensor is widely used in the application for the detection of weak magnetic fields, and the cell is the core component of that, which needs an external excitation signal to ignite and maintain its luminosity, and its luminosity affects the sensitivity performance of the sensor. To improve the performance of the cell and reduce the power consumption of the system, which is the largest power consumption component in the sensor, this study presents the design of a driver circuit for a helium cell based on a high-voltage pulse source and high-frequency excitation source and uses a T-type impedance matching circuit to realize the efficient transmission of energy. The experimental results demonstrate that the driver circuit can effectively light up the helium cell, in which the pulse voltage of the high-voltage excitation is more than 1.0kV, the output power of the high-frequency excitation signal is in the range of 0-6W, and it is easy to adjust the output power of the high-frequency excitation signal to optimize the sensitivity of the sensor with an the optimal power density of 1.1 W/cm2 and a sensitivity of 29.4 pT/Hz1/2 is obtained. The driver circuit method designed in this study is also suitable for other inert gases to generate metastable atoms.

Optical fiber weak magnetic sensing system based on strip-ring sensing structure and PGC-Improved algorithm

The detection of weak magnetic fields is integral to applications in geophysical monitoring, biomagnetism, and remote sensing. This paper presents a new sensing unit structure and signal demodulation algorithm for optical fiber weak magnetic sensing system. The system uses a strip-ring sensing unit structure that combines magnetostrictive effects with optical fibers through 3D printing technology. This integration facilitates the conversion of magnetostrictive displacement into optical phase. An improved Phase Generated Carrier (PGC) algorithm is employed to demodulate the phase information, enhancing the signal to noise ratio (SNR) by 4.33 dB compared to the traditional PGC algorithm, and achieving a phase resolution of 29.51 µrad/Hz1/2 at 500 Hz. Experimental results demonstrate that the suggested sensing system can detect a minimum magnetic field of 140 nT, with an AC magnetic field phase resolution of 15.78 nT/Hz1/2 at 500 Hz. The demodulation sensitivity reaches 1.87 × 10−6 rad/nT under a magnetic field of 140–1400 nT. The capability of the proposed system demonstrated great potential as an efficient approach for detecting weak magnetic signals in many practical applications.

TMR-high-temperature superconductor composite magnetic sensor and its performance optimization

Tunnel magnetoresistance (TMR), recognized for its high sensitivity and low power consumption, holds significant promise in the domain of weak magnetic field detection. Using superconducting materials as magnetic concentrators can achieve several hundred to even a thousandfold amplification of magnetic fields, making it one of the most effective approaches to enhance the magnetic field resolution of TMR sensors. This paper utilized the flip-chip bonding process to integrate TMR with the high-temperature superconductor YBCO (YBa2Cu3O7-δ), and successfully developed TMR-YBCO composite magnetic sensor. Building upon this foundation, through optimization of the fabrication process and the pioneering use of a structural design incorporating the filling of annular holes with superconducting concentrators, the sensitivity of the sensor was further enhanced. Finally, the magnetic field resolution was increased by 1030 times compared to TMR sensors, reached to 2.9pT/Hz1/2 at 1 Hz. Simultaneously, results from frequency band testing indicated excellent frequency band characteristics, with a frequency response range exceeding kHz.

Fabrication and performance enhancement of TMR-Superconducting composite magnetic sensors for weak magnetic field detection

The tunneling magnetoresistance (TMR) effect, utilizing the CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) structure, has seen a surge in research interest owing to its pronounced sensitivity to magnetic fields. However, advancements in TMR technology have plateaued in recent times. In response, this study explores the integration of TMR with superconductivity to form a TMR-superconducting composite magnetic sensor, aiming to amplify the external magnetic field effect and improve sensor performance. Such sensors offer significant promise for applications in detecting feeble magnetic fields due to their compact dimensions, minimal energy consumption, and exceptional magnetic field resolution. Despite their potential, manufacturing challenges persist. This paper focuses on the meticulous fabrication of the TMR's critical thin film layer and its subsequent patterning. Moreover, we propose an innovative technique utilizing magnetron sputtering to deposit a niobium (Nb) layer atop the TMR structure, followed by intricate patterning to successfully construct a TMR-superconducting composite film. This novel approach importantly diminishes the interspace between TMR and superconducting layers compared to traditional bonding methods, thereby enhancing device performance. Experimental assessments of the device constructed superconducting loops, contrasted with traditional bonding process, demonstrate that sputtering-based sensor exhibit better magnetic field resolution. Consequently, TMR-superconducting composite sensors realized via the sputtering technique hold distinct advantages in weak magnetic field detection.

Capacitive Bionic Magnetic Sensors Based on One-Step Biointerface Preparation.

Magnetic biomolecule-based bionic magnetic field sensors are anticipated to open up novel pathways for magnetic field detection. The detection range and accuracy of current bionic magnetic field sensors are limited, and little work is based on the capacitive response principle. We successfully developed a biochemical interface with an extralarge target-receptor size ratio, which can be manufactured in a single step for weak magnetic field detection across a wide frequency range, and we used electrochemical capacitance as a magnetic field change conduction strategy. The thickness-controllable nanoscale bovine serum albumin/graphene layer on an indium tin oxide working electrode combines with the one-step preparation method to immobilize the MagR/Cry4 complex. This capacitive bionic magnetic sensor can achieve the detection range of 0-120 mT. This biointerface design strategy obtains the further improvement of the performance of this bionic magnetic field sensor. Furthermore, the biointerface construction and optimization methodology in this proposal has potential applications in the design of other medical biosensors.

Research and simulation of fiber sensor for weak magnetic field detection

Research and simulation of fiber sensor for weak magnetic field detection

Two-dimensional synchronous motion modulation MEMS structure for suppressing 1/f noise in magnetoresistive sensors

Magnetoresistive (MR) sensors have great application prospects in the field of weak magnetic field detection due to their high sensitivity, small size, and low power consumption. However, 1/f noise greatly limits the low-frequency detectivity of MR sensors. In order to suppress 1/f noise, this paper proposes a two-dimensional synchronous motion modulation (TDSMM) structure based on microelectromechanical systems (MEMS). This structure can effectively reduce 1/f noise by modulating the frequency of the measured magnetic field in the high-frequency band. Theoretical analysis and finite element simulation were conducted on three different modulation models: TSDMM, magnetic flux concentrators motion modulation, and MR components longitudinal motion modulation. The results showed that the modulation efficiency of the TDSMM reached as high as 127%, which is currently the highest value in MR-MEMS sensors. The TDSMM MEMS structure has been successfully manufactured, and the resonant frequency of the transverse resonator is twice that of the longitudinal resonator, enabling extremely high modulation efficiency. The noise spectral density of giant-magnetoresistive components on a silicon-on-insulator substrate was tested, and the noise level in the high-frequency band was three orders of magnitude lower than that in the low-frequency band. These results position MR-MEMS sensors with TDSMM structures as highly competitive candidates in the field of ultra-weak magnetic field detection.

Highly Sensitive Detection of Weak Low Frequency Magnetic Fields Using Single Nanoscale Orthogonal MgO Magnetic Tunnel Junctions under a Large Bias Field

Highly Sensitive Detection of Weak Low Frequency Magnetic Fields Using Single Nanoscale Orthogonal MgO Magnetic Tunnel Junctions under a Large Bias Field

A high magnetic field sensitivity PCF‐SPR sensor working in the near‐infrared wavelength band

AbstractA novel form of photonic crystal fiber (PCF) magnetic field sensor, utilizing surface plasmon resonance, has been developed and investigated. By depositing a layer of gold onto the interior surface of the left‐sided air hole and introducing magnetic fluid into the aperture to detect magnetic field changes, the plasma resonance effect was ingeniously combined with a dual‐core PCF to achieve magnetic field measurement. The displacement of the loss peak in the output spectrum was observed to gain insights into the magnetic field changes. By means of modulations in the thickness of the gold film, and the spacing and size of the air holes, the optimal parameters for the sensor were obtained. The optimized sensor exhibited a maximum magnetic field sensitivity of up to 6.23 nm/Oe, and the magnetic field detection resolution was approximately 10 μT, enabling precise detection of weak magnetic fields. This fiber sensor boasts a simple structure, ease of production, high sensitivity, and robust environmental adaptability, making it an attractive option for implementation.

Enhanced Performance of Weak Magnetic Field Sensor Based on Laminated Cantilever: Theoretical Analysis and Experimental Verification

The present study introduces a weak magnetic field sensor that utilizes a laminated cantilever structure, consisting of a magnetostrictive layer, a piezoelectric layer, and a substrate layer. Consequently, the transformation from the magnetic signal to the electrical signal is accomplished through the consistent mechanical stress in both layers. A comprehensive theoretical model has been developed to evaluate the impact of key structural parameters on the magnetoelectric sensing performance, enabling the optimization of the device design. By incorporating vanadium (V) as a dopant element, a Zn-V-O film with a piezoelectric coefficient as high as 35 pm/V is fulfilled. Furthermore, the high piezomagnetic properties of Galfenol make it a suitable candidate as a magnetostrictive layer. Sensor prototypes were fabricated for experimental verification through the utilization of MEMS technology. The film was characterized using techniques such as XRD, TEM, and PFM. The magnetoelectric testing experiments indicated that the magnetostrictive coefficient could achieve about 9.32 kV/(cm∙Oe) at resonant frequencies for sensors with varying lengths and a 20 μm thick Si substrate. The proposed sensor exhibits promising potential for improving weak magnetic field detection performance.

The In-Plane Magnetic Field Measurement Method of SC/MR Mixed Sensor and Its Three-Axis Magnetic Sensor With Integrated Magnetic Concentrator

Superconductor/magnetoresistance (SC/MR) mixed sensor has the advantage of ultrahigh sensitivity and is thought to be a promising candidate for weak magnetic field detection. However, it has no effect on the magnetic field in the superconducting flux-to-field transformation amplifier (SFTA) plane, which limits its applications in 3-D magnetic field detection. Here, we present a new architecture of SC/MR mixed sensor with only one integrated magnetic concentrator (IMC) to realize the in-plane magnetic field measurement. Firstly, the conversion efficiency, defined as the in-plane magnetic changing to the out-plane magnetic field by the IMC and SFTA of mixed sensor, was systematically studied by the finite element analysis method, the results show that the high conversion efficiency is from the combined action of superconducting diamagnetism and magnetic concentrator of soft magnetic materials. Then, a serial prototype mixed sensors with different IMC relative configuration sizes were prepared and their experimental performances were obtained. Indeed, the mixed sensor with IMC can simultaneously measure the in-plane and out-of-plane magnetic fields, furthermore, the conversion efficiency changes as the function of the relative configuration size is consistent well with the simulation result. Finally, a three-axis SC/MR mixed sensor scheme and its corresponding three-axis magnetic field decoupling method based on this method were also proposed, showing the obvious capability of three-axis magnetic field measurement. Our work is meaningful to the development of a three-axis weak magnetic field detection.

An integrated and scalable experimental system for nitrogen-vacancy ensemble magnetometry.

Nitrogen-vacancy (NV) centers in diamond are extremely promising solid-state spin quantum sensors for magnetic field in recent years. The rapid development of NV-ensemble magnetometry has put forward higher requirements for high-speed data acquisition, real-time signal processing and analyzing, etc. However, the existing commercial instruments are bulky and expensive, which brings extra complexity to the weak magnetic field detection experiment and hinders the practicality and miniaturization of NV-ensemble magnetometry. Here, we report on an integrated and scalable experimental system based on a field-programmable-gate-array (FPGA) chip assisted with high-speed peripherals for NV-ensemble magnetometry, which presents a compact and compatible design containing high-speed data acquisition, oscilloscopes, signal generator, spectrum analyzer, lock-in amplifier, proportional-integral-derivative feedback controller, etc. To verify its applicability and reliability in experiments, various applications, such as optical magnetic resonance detection, optical cavity locking, and lock-in NV magnetometry, are conducted. We further realize the pump-enhanced magnetometry based on NV center ensembles using the optical cavity. Through the flexible FPGA design approach, this self-developed device can also be conveniently extended into atomic magnetometer and other quantum systems.

Superconductor/magnetoresistance mixed sensor with magnetic flux guides for three-dimensional magnetic field measurement

The superconductor/magnetoresistance (SC/MR) mixed sensor has the advantage of ultra-high sensitivity, but it is only sensitive to unidirectional magnetic fields that are perpendicular to the superconducting flux-to-field transformation amplifier (SFTA). This inherent characteristic limits its applications in three-dimensional magnetic field detection. This paper presents a new architecture of the SC/MR mixed sensor with magnetic flux guides to realize three-dimensional magnetic field measurement. The finite element analysis method was used to confirm the performance of the mixed sensor, which theoretically proved the feasibility of three-dimensional magnetic field measurement and analyzed the influence of the magnetic field detection errors caused by the installation errors of MFGs. Finally, a mixed sensor composed of a whole-SFTA, four tunneling magnetoresistances, and two layers of MFGs was prepared, and experimental performances were obtained. Indeed, the mixed sensor can measure the three-dimensional magnetic field. This work is a meaningful contribution to the development of three-dimensional weak magnetic field detection.

Optical fiber-based magnetically-tuned graphene mechanical resonator

In this study, an optical fiber-based magnetically-tuned graphene mechanical resonator (GMR) is demonstrated by integrating superparamagnetic iron oxide nanoparticles on the graphene membrane. The resonance frequency shift is achieved by tuning the tension of the graphene membrane with a magnetic field. A resonance frequency tunability of 23 kHz using a 100 mT magnetic field is achieved. The device provides a new way to tune a GMR with a non-contact force. It could also be used for weak magnetic field detection in the future with further improvements in sensitivity.

High-temperature multiferroic magnetoelectric sensors

Magnetoelectric (ME) sensors are an important tool to detect weak magnetic fields in the industry; however, to date, there are no high-quality ME sensors available for high-temperature environments such as engines, deep underground, and outer space. Here, a 0.364BiScO3–0.636PbTiO3 piezoelectric ceramic and Terfenol-D alloy with a Curie temperature of 450 and 380 °C, respectively, were bonded together by an inorganic glue to achieve a high-temperature ME sensor. The ceramic shows a piezoelectric d33 coefficient of 780 pC/N at 420 °C, and the inorganic glue has a high maximum stress of 9.12 MPa even at 300 °C. As a result, the sensor exhibits the maximum ME coefficient αE of 2.008, ∼1.455, and ∼0.906 V cm−1 Oe−1 at 20, 200, and 350 °C, respectively. Most importantly, the magnetic field detecting precision is as small as 42 nT at 20–350 °C. The ME sensor provides an effective solution for the detection of weak magnetic fields in harsh environments.

Ultra-low anisotropy magnetoelectric sensor in ferrite/piezoelectric toroidal composites

An ultra-low anisotropy magnetoelectric (ME) magnetic field sensor consisting of strictly concentric toroidal nickel-zinc ferrite/piezoelectric composite with toroidal solenoid was developed, and its sensitivity and resolution under different angles of planar AC/DC magnetic field were systemically characterized. The experimental results demonstrate that the induced voltage output strength was constant along the angles between the ME magnetic sensor and the planar DC/AC magnetic field due to toroidal structure had ultra-low shape-induced anisotropy. Consequently, for the DC case its sensitivity and resolution could reach about 15 mV/Oe and 2 × 10−7T under a low excitation of ƒ=111.42 kHz circumferential AC magnetic field, respectively. Correspondingly, for the AC case its sensitivity and resolution could reach about 56.9 mV/Oe and 7 × 10−9T under a 2.25Oe circumferential DC bias magnetic field. These findings provided more flexibility of the device design for weak magnetic field detection.

Modeling and experimental investigation of magnetic anomaly detection using advanced triaxial magnetoelectric sensors

Magnetoelectric (ME) sensors have been proven to have great performance on weak magnetic field detection with high sensitivity, low noise, broad bandwidth and low power consumption. In this work, a self-designed ME detection system consisting of a high-performance triaxial ME sensor was used for magnetic anomaly detection (MAD). As the core sensing element of the ME sensor, the laminated ME composites were made of Metglas laminates and Mn-doped PMN-PT single crystal fibers with in-plane series connection. The noise equivalent magnetic induction (NEB) of the ME sensors were below 6.28pT/Hz1/2 @ 1 Hz, and the limit detection of magnetic field is about 5 × 10−10 T, representing great performance to detect weak magnetic field. An experiment of detecting a real ship was conducted to test the performance of the triaxial ME detection system. To analyze the magnetic anomaly signal induced by the ship, a 3D finite element model (FEM) about the magnetic field distribution of the moving ship is developed. The estimated signals of the scalar total magnetic field and the motion parameters of the ship simulated by the proposed FEM match well with the experimental data, which proves the reliability of the model. The error analysis of the simulation was also discussed in detail. The experimental investigation reveals a promising application of ME sensor in MAD, while the proposed finite element model can be further modified to meet the analysis requirements on the detection of the magnetic anomaly induced by ferromagnetic targets with large dimension.

A superconductor/TMR composite magnetic sensor for pico-Tesla magnetic field detection

A highly sensitive superconductor/tunnel magnetoresistance (TMR) composite magnetic sensor was designed and fabricated to satisfy the demands of detecting weak magnetic fields down to the pT range at low frequencies. First, analysis of the 1/f noise provided an optimized design scheme for the TMR unit to reduce the noise level. Then, the key structural parameters of the superconducting flux transformation amplifier (SFTA) were optimized with focus on the bonding quality between SFTA and TMR units using the finite element method to enhance the magnetic field magnification factor. An SFTA–TMR composite method with secondary alignment and multi-step bonding was proposed to fabricate the composite magnetic sensor and ensure the designed bonding gap and alignment accuracy. Experiments showed that the magnetic field sensitivity reached 5 pT/Hz0.5 (@ 13 Hz), which is beyond the highest level of superconductor/TMR composite magnetic sensors reported to date and is a further step toward the application of weak magnetic field detection.