Vector Magnetometer Research Articles

Macapá, a Brazilian equatorial magnetometer station: installation, data availability, and methods for temperature correction

Abstract. In the last 60 years, the largest displacement of the magnetic equator (by about 1100 km northwards) occurred in the Brazilian longitudinal sector. The magnetic equator passed by Tatuoca magnetic observatory (TTB) in northern Brazil in 2012 and continues to move northward. Due to the horizontal geomagnetic field geometry at the magnetic equator, enhanced electric currents in the ionosphere are produced – the so-called equatorial electrojet (EEJ). The magnetic effect of the EEJ is observed in the range of ±3° from the magnetic equator, where magnetic observatories record an amplified daily variation of the H component. In order to track the spatial and temporal variation of this phenomena, a new magnetometer station was installed in Macapá (MAA), which is about 350 km northwest of TTB. In this paper, we present the setup and data analysis of MAA station from November 2019 until September 2021. Because of its special configuration, we develop a method for temperature correction of the vector magnetometer data.

Simultaneous vector magnetometry based on fluorescence polarization of NV centers ensemble in diamond

The nitrogen-vacancy (NV) centers ensemble has extensive application prospects in vector-magnetic-field measurement due to its accurate and fixed spatial orientations along the crystallographic axes of diamonds. However, to address signals of NV centers along all four axes, a large bias magnetic field sufficient to spectrally separate their resonances is typically inevitable, which may affect the magnetic substance under test and require multiple-frequency microwaves to interrogate signals of the four axes. Here, we demonstrate an NV-based simultaneous vector magnetometer that works at a bias field as low as just separating the resonant peaks of |ms=±1 states and utilizes a single-frequency microwave. By simultaneously detecting the fluorescence at specific optical polarization angles in three orthogonal directions and determining the transformation matrix in advance, all the Cartesian components of the magnetic field under test are distinguished. The experimentally achieved magnetic-field sensitivity is 63 nT/Hz, and the bias field is reduced to around 11 Gauss (still reducible by narrowing the linewidth) in ambient conditions. The proposed methods dramatically reduce the bias field for NV-based simultaneous vector magnetometers and potentially expand their applications in biological science, materials science, and industrial noninvasive detection.

Microscale fiber-integrated vector magnetometer with on-tip field biasing using N - V ensembles in diamond microcrystals

In quantum sensing of magnetic fields, ensembles of nitrogen-vacancy centers in diamond offer high sensitivity, high bandwidth and outstanding spatial resolution while operating in harsh environments. Moreover, the orientation of defect centers along four crystal axes forms an intrinsic coordinate system, enabling vector magnetometry within a single diamond crystal. While most vector magnetometers rely on a known bias magnetic field for full recovery of three-dimensional (3D) field information, employing external 3D Helmholtz coils or permanent magnets results in bulky, laboratory-bound setups, impeding miniaturization of the device. Here, a novel approach is presented that utilizes a fiber-integrated microscale coil at the fiber tip to generate a localized uniaxial magnetic field. The same fiber-tip coil is used in parallel for spin control by combining dc and microwave signals in a bias tee. To implement vector magnetometry using a uniaxial bias field, the orientation of the diamond crystal is preselected and then fully characterized by rotating a static magnetic field in three planes of rotation. The measurement of vector magnetic fields in the full solid angle is demonstrated with a shot-noise-limited sensitivity of 19.4nT/Hz1/2 and microscale spatial resolution while achieving a fiber sensor head cross section of less than 1mm2. Published by the American Physical Society 2024

Processing of unmanned underwater vehicle vector magnetometer data

AbstractMarine magnetometry very close to the targeted sources, even in very deep waters, is today a reality with the advent of autonomous underwater vehicles. We argue that a successful approach is to fully integrate the magnetometer onboard the autonomous underwater vehicle and to deal with its static magnetic noise, that is induced and permanent fields of the drone, with a 3‐axis vector measurement of the Earth's magnetic field. This argument is supported by results from three magnetic surveys performed with different fluxgate magnetic sensors embedded in autonomous underwater vehicles of increasing sizes. They show that simple specifically defined figures of merit coupled to an optimized scalar calibration procedure derived from aeromagnetic and satellite‐borne developments produce reliable magnetic measurements from autonomous underwater vehicles for geophysical mapping or detection applications. Results are impressive and show that even weak magnetic anomalies smaller than 10 nT can be highlighted even though the magnetic signatures of autonomous underwater vehicles can be orders of magnitude higher.

Integrated NV (Nitrogen Vacancy) Vector Magnetometer in Real-Time Utilizing Frequency-Hopping Method

Integrated NV (Nitrogen Vacancy) Vector Magnetometer in Real-Time Utilizing Frequency-Hopping Method

Searching for exotic spin-dependent interactions with diamond-based vector magnetometer

We propose a new method to search for exotic spin-spin interactions between electrons and nucleons using a diamond-based vector magnetometer. The vector magnetometer can be constructed from ensembles of nitrogen-vacancy centers along different axes in a diamond. The N14 nuclear spins of nitrogen-vacancy centers in the same diamond can be polarized through the dynamic nuclear polarization method to serve as spin sources. With the vector magnetometer, the sought-after exotic interactions can be distinguished from the magnetic dipole-dipole interaction. For the axion-mediated interaction VPP, new upper bounds of the coupling |gPegPN| are expected within the force range from 10 nm to 100 μm. For the Z′-mediated interaction VAA, new upper bounds of the coupling |gAegAN| are expected within the force range from 10 nm to 1 cm. The new upper bounds for VPP and VAA are both expected to be more than 5 orders of magnitude more stringent than existing constraints at the force range of 1 μm with the total measurement time of 1 day. Published by the American Physical Society 2024

Three-Axis Vector Magnetometer with a Three-Dimensional Flux Concentrator.

This research proposes a magnetic field sensor with spatial orientation ability. Through the assistance of a magnetic flux concentrator, out-of-plane magnetic flux can be concentrated and guided into the planar magnetic cores of a fluxgate sensor. A printed circuit board is used to construct the basic planar structure, on which the proposed three-dimensional magnetic flux concentrator and magnetic cores are assembled. This reduces the alignment error of the coils and improves the reliability of the sensor. Three-axis sensing is achieved by using the second harmonic signals from selected sensing coil pairs. The magnetometer exhibits a linear range to 130 μT. At an excitation frequency of 50 kHz, the measured sensitivities are 257.1, 468.8, and 258.8 V/T for the X-, Y-, and Z-axis sensing modes, respectively. This sensor utilizes only one sensing mechanism for the vector field, making it suitable for IoT applications, especially for assessing mechanical posture or position.

In Situ Spin Polarization Measurement Method and Identification of Optimal Spin Polarization Range in Atomic Magnetometer

AbstractIn this study, an in situ measurement method of spin polarization in single‐beam atomic magnetometer is presented. Modeling magnetic linewidth by incorporating nonlinear attenuation along the propagation direction of light and employing the output response equation of magnetometers at zero‐field resonance. Utilizing the model for fitting to extract relaxation rate information, the photon absorption cross‐sections at three temperatures are estimated to be , , and , respectively. Further, the spin polarization curves are obtained by introducing the spin polarization equations. Given the diminishing marginal utility resulting from the enhancement of performance through increased spin polarization, long‐term sensitivity is employed to determine optimal spin polarization range. The optimal long‐term sensitivity for four displayed states is (@31.5Hz), while the ultimate minimum sensitivity is 10.7 (@31.5Hz). The optimal spin polarization ranges at three temperatures are 78.9%–87.1%, 82.3%–88.5%, and 84.5%–88.4%, respectively. The measurement method applied to single‐beam magnetometer can be easily extended to multi‐axis vector magnetometer. The determination of optimal spin polarization range is of great significance for the performance and stability of the magnetometer system, improving the sensitivity of magnetic field measurement, and ensuring its widespread application in bio‐magnetic measurement.

Far-Field Spatial Response of Off-Diagonal GMI Wire Magnetometers. Application to Magnetic Field Sources Sensing

Studying the spatial response of a single-axis magnetometer could be the key parameter to optimize the ultimate performances of magnetic heads of detection. Indeed, the problem of non-orthogonality, misalignment, and 3D spatial response could be improved based on the knowledge of the 3D sensor spatial response. In that way, we have investigated the latter for our giant magneto-impedance (GMI) magnetometer, as a far-field pattern, by using a three-axis Helmholtz coil system. Firstly, we calibrate our device and secondly, we apply a specific 3D magnetic field to obtain this pattern. The latter helps to observe the directional or angular dependence of the sensor sensitivity versus the applied magnetic field, as we exemplified. The results confirm the excellent directivity of our off-diagonal GMI magnetometer. The evaluation of the associated error compared to an ideal vector magnetometer is also given and discussed.

Underwater target correlation detection and location method based on normalized magnetic moment

For the dynamic magnetic detection platform represented by airborne magnetic anomaly detection, the magnetic field measured by the vector magnetometer is easily affected by the rapid attitude change. Therefore, traditional anti-submarine aircraft are equipped with scalar magnetometers that are less affected by changes in the carrier attitude. However, the scalar magnetometer can only measure the total magnetic field signal, and its measurement information is single. It contains a time-varying environmental magnetic field signal, including the geomagnetic field, which is difficult to effectively reject. This brings great difficulties to the single real-time location of a magnetic anomaly target. This paper proposes a target correlation detection method based on the normalized magnetic moment that can effectively solve the above problems, considering the rotational invariance of magnetic anomaly measurements for dynamic magnetic exploration platforms and the efficient detection methods required for the single real-time positioning of targets. Correlation detection based on the normalized magnetic moment characteristic function and characteristic time search based on the correlation detection are included. Simulation and experimental results verify the single-point real-time positioning ability of the improved detection method within an effective operating distance. This method has strong usability for actual magnetic anomaly detection of underwater targets.

Attitude-Independent Route Tracking for Subsea Power Cables Using a Scalar Magnetometer under High Sea Conditions

To overcome the shortcoming wherein the accuracy of subsea cable detection can be affected by the determination of the bias vector, scale factors, and non-orthogonality corrections of the vector magnetometer, a real-time attitude-independent route tracking method for subsea power cables is investigated theoretically and experimentally by means of scalar magnetic field checking. The measurement of the magnetic field Bc produced by the current in a cable is made immune to the influence of the platform attitude by extracting the component of Bc along the geomagnetic field using a high-bandwidth self-oscillating optically pumped magnetometer. The self-oscillating frequency is proved to be independent of the attitude of the magnetometer with the theoretical model. Experiments are carried out to test the attitude-independent performance, and the effectiveness of route tracking is verified by the results of the sea experiment. The proposed method will effectively improve the ability to locate subsea cables under high sea conditions.

Tensor gradiometry with a diamond magnetometer

Vector magnetometry provides more information than scalar measurements for magnetic surveys utilized in space, defense, medical, geological, and industrial applications. These areas would benefit from a mobile vector magnetometer. Here we present a scanning fiber-coupled nitrogen-vacancy (N-V) center vector magnetometer. Feedback control of the microwave excitation frequency is used to improve dynamic range and maintain sensitivity during movement of the sensor head. Tracking of the excitation frequency shifts for all four orientations of the N-V center allows us to image the vector magnetic field of a damaged steel plate. We calculate the magnetic tensor gradiometry images in real time, and they allow us to detect smaller damage than is possible with vector or scalar imaging. Published by the American Physical Society 2024

AC vector magnetometer for space-based applications using low-resource magneto-impedance sensor

AC vector magnetometer for space-based applications using low-resource magneto-impedance sensor

In situ measurement of magneto-optical non-orthogonality in miniaturized atomic magnetometer

Miniaturized atomic magnetometers (M-AMs) are important tools for bio-magnetic measurements, but their performance is limited by magneto-optic non-orthogonality (MON). In this study, a response signal model considering MON is established, and an in situ measurement method combining this model and the magneto-optical relationship is proposed. Considering this, the MON of five M-AMs are measured. We found that MON over 1° is common. The measurement results verify the accuracy of the principle derived from the model. Compared with only compensating the residual magnetism and after additional compensation of the light shift caused by MON, the M-AM calibration coefficient with large MON improves by 44.6%, and the sensitivity increases from 25.29 to 16.25 fT/Hz1/2 (@31.5Hz). The calibration coefficient with small MON improves by 10%, and the sensitivity increases from 14.10 to 12.15 fT/Hz1/2 (@31.5Hz). With a minimum bandwidth of 140 Hz, it fully satisfies the requirements of the magnetometer. This study completed the in situ measurement of MON without auxiliary equipment, which can be easily applied to other multi-axis vector magnetometers. The measurement and evaluation of MON is crucial for the efficient operation and pursuit of higher sensitivity magnetometers.

Machine learning assisted vector atomic magnetometry

Multiparameter sensing such as vector magnetometry often involves complex setups due to various external fields needed in explicitly connecting one measured signal to one parameter. Here, we propose a paradigm of indirect encoding for vector atomic magnetometry based on machine learning. We encode the three-dimensional magnetic-field information in the set of four simultaneously acquired signals associated with the optical rotation of a laser beam traversing the atomic sample. The map between the recorded signals and the vectorial field information is established through a pre-trained deep neural network. We demonstrate experimentally a single-shot all optical vector atomic magnetometer, with a simple scalar-magnetometer design employing only one elliptically-polarized laser beam and no additional coils. Magnetic field amplitude sensitivities of about 100 {{{{{{{rm{fT}}}}}}}}/sqrt{{{{{{{{rm{Hz}}}}}}}}} and angular sensitivities of about 100 sim 200,mu rad/sqrt{{{{{{{{rm{Hz}}}}}}}}} (for a magnetic field of around 140 nT) are derived from the neural network. Our approach can reduce the complexity of the architecture of vector magnetometers, and may shed light on the general design of multiparameter sensing.

Angular magnetic field dependence of a doubly clamped magnetoelectric resonator

Angular dependence of magnetic field response of fully suspended resonant microelectromechanical double-clamped magnetoelectric beams was investigated as the basis for a vector magnetometer utilizing the magnetically induced change in fundamental resonance frequency. Strain-coupled magnetostrictive iron cobalt (FeCo) and piezoelectric aluminum nitride layers together constitute a magnetoelectric heterostructure with a high magnetic field sensitivity of 70 Hz/mT along the beam axis and a transfer function of 47 V/T at 10 Hz. The fundamental frequency shift to an external magnetic field is found to be strongly anisotropic with a relative variation of more than 3% between perpendicular and parallel field orientations with respect to the long axis of the beam at a field of 100 mT. This design can form the basis for an on-chip high sensitivity vector magnetometer operating with ultra-low power when multiplexed with two or more resonators.

Nanoscale Vector Magnetometry with a Fiber‐Coupled Diamond Probe

AbstractA nanoscale vector magnetometer is demonstrated by integrating a microfabricated diamond probe with a nanopillar on top of a single‐mode optical fiber. Based on the recently developed self‐aligned patterning techniques, ≈80 nitrogen vacancies are concentrated at a 100 nm2 area at the center of nanopillars to maximize the excitation and collection efficiencies. The spatial resolution of such a fiber‐coupled diamond magnetometer can reach 100 nm for the first time with a sensitivity of 11.27 µT/ for DC magnetic field sensing. In addition, the probe can provide deterministic oriented diamond nanopillars for simplified vector magnetometry. This fiber‐coupled diamond probe is applied to demonstrate the magnetic field imaging of charged electrodes in a confined box. These results mark a decisive step toward fiber‐based applications with nanoscale vector magnetometry capabilities.

On a Novel Approach to Correcting Temperature Dependencies in Magnetic Observatory Data

High-quality geomagnetic measurements are widely used in both fundamental research of the magnetic field and numerous industrial applications. However, vector data measured by fluxgate sensors show a dependency on temperature due to sensitive coil core material and components of the sensor electronics. Here, we propose a new method for detecting and eliminating temperature dependence in magnetic observatory data. The method is designed to correct temperature drifts in variation vector magnetometer measurements when preparing quasi-definitive data according to an INTERMAGNET standard. A special feature of the method is the semi-automatic adjustment of localization intervals for temperature correction, which prevents boundary jumps and discontinuities in the course of sequential data processing over long intervals. The conservative nature of the approach implies the minimization of the original data amount subjected to correction. The described method is successfully applied in the routine monthly preparation of quasi-definitive data of the Saint Petersburg Observatory (IAGA-code SPG) and can be efficiently introduced at other magnetic observatories worldwide.

In-flight vector magnetometer calibration for FY-3E satellite

In-flight vector magnetometer calibration for FY-3E satellite

Extended Kalman Filter Design to Estimate the Attitude of the Nanosatellite System Using Magnetometer

The problem of estimating nonlinear systems is an important issue in many engineering applications. One of these applications is in the nanosatellite for Vehicle-to-everything (V2X) communications, which is used to replace sensors in the event of failure or error. Therefore, the accuracy of pre-filter estimation is of great importance. To control the orientation of a satellite, it is important to estimate the attitude accurately. Time-series estimation is especially important in micro and nanosatellites, whose sensors are usually low-cost and have higher noise levels than high-end sensors. Also, the algorithms should be able to run on systems with very restricted computer power. In this paper, an overview of the algorithms used to determine the attitude of nanosatellites, and especially using only the magnetometer sensor, will be discussed. This paper aims to simulate a nanosatellite system to estimate the magnetic field derivative vector using only the magnetometer data with the desired accuracy. The estimated vectors in the pre-filter, along with the magnetometer sensor data, are used to estimate the attitude of the satellite. The estimation of the state vector consisting of the vector part of quaternion and the angular velocity vector is used for the control calculation. To evaluate the accuracy of this pre-filter, a comparison of the magnetometer vector estimator with the body sensor data has been used.