DC Magnetic Field Detection Research Articles

High-sensitivity DC magnetic field detection with ensemble NV centers by pulsed quantum filtering technology.

Continuous wave optically detected magnetic resonance (CW-ODMR) is a practical way to study the sensitivity of the DC magnetic field. However, in large ensemble nitrogen-vacancy (NV) defects, the simultaneous excitation of microwave and laser will deteriorate the parameters of the ODMR spectrum and some unwanted sideband excitations caused by P1 electron spins will also bring challenges to further improve the sensitivity and signal quality. Here, we first achieve the CW-ODMR and acquire DC photon-shot-noise-limited magnetic sensitivity of 12nT/Hz. Different from the conventional method, we take advantage of pulsed quantum filtering (PQF) technology to eliminate such impacts above and demonstrate a sensitivity of about 1nT/Hz, which an order of magnitude enhancement over CW-ODMR. We find this method provides simple but effective support for relevant high-sensitivity DC magnetometry and obtains pure resonance signal when using large ensemble NV- defects.

Self-biased vector magnetic sensor based on a Love-type surface acoustic wave resonator

Magnetic sensors based on the interaction between the delta-E effect and surface acoustic waves (SAWs) are promising devices due to their simple driving circuits. In this study, a magnetic sensor composed of a (Fe90Co10)78Si12B10 magnetic layer and Love-type SAW resonator was investigated. The resonance frequency sensitivities (RFS) of the sensor resulting from the delta-E effect are 76.06 Hz/μT and 364.28 Hz/μT in the L-direction (along the easy axis) and W-direction (along the hard axis), respectively. The maximum RFS achieved by this magnetic sensor is 663.98 Hz/μT along the hard axis, with a resonance frequency of 221.76 MHz. The shift of resonance frequency shows a good linearity along with the external magnetic field in the L-direction. The curves of frequency response demonstrate point symmetry rather than the expected axial symmetry in both directions, due to the existence of residual magnetization. Non-zero RFS at zero magnetic field also appears in this device, because of the non-zero change of the Young's modulus at zero magnetic field. The good linearity and high sensitivity mean that the investigated magnetic sensor can be applied for weak DC magnetic field detection.

Lorentz force induced magnetoelectric effect in cylindrical composites with PZT/magnetostrictive and nonmagnetic metal layers

Lorentz force-piezoelectric coupled magnetoelectric (ME) effect and piezomagnetic-piezoelectric coupled ME effect were compared in PZT/nonmagnetic and PZT/magnetostrictive metal cylindrical layered composites under axial magnetic fields. While only the Lorentz force-piezoelectric ME effect is observed in PZT/brass and PZT/Al cylinders, both ME effects are present in PZT/magnetostrictive Ni cylinder. The ME voltage linear dependence on DC magnetic field and constant −90° ME voltage phase reflect the Lorentz force-piezoelectric ME effect. For the PZT/Ni cylinder under low DC magnetic field, the ME voltages from the two ME effects tend to be anti-phase, and the piezomagnetic-piezoelectric ME voltage is much higher than the Lorentz force-piezoelectric ME voltage. However, under high DC magnetic field, the Lorentz force-piezoelectric ME effect plays a dominant role. These results indicate that the PZT/Ni cylinder is favorable to DC magnetic field detection in wide range.

A magnetoelectric flux gate: new approach for weak DC magnetic field detection

The magnetic flux gate sensors based on Faraday’s Law of Induction are widely used for DC or extremely low frequency magnetic field detection. Recently, as the fast development of multiferroics and magnetoelectric (ME) composite materials, a new technology based on ME coupling effect is emerging for potential devices application. Here, we report a magnetoelectric flux gate sensor (MEFGS) for weak DC magnetic field detection for the first time, which works on a similar magnetic flux gate principle, but based on ME coupling effect. The proposed MEFGS has a shuttle-shaped configuration made of amorphous FeBSi alloy (Metglas) serving as both magnetic and magnetostrictive cores for producing a closed-loop high-frequency magnetic flux and also a longitudinal vibration, and one pair of embedded piezoelectric PMN-PT fibers ([011]-oriented Pb(Mg,Nb)O3-PbTiO3 single crystal) serving as ME flux gate in a differential mode for detecting magnetic anomaly. In this way, the relative change in output signal of the MEFGS under an applied DC magnetic anomaly of 1 nT was greatly enhanced by a factor of 4 to 5 in comparison with the previous reports. The proposed ME flux gate shows a great potential for magnetic anomaly detections, such as magnetic navigation, magnetic based medical diagnosis, etc.

Ultra-sensitive NEMS magnetoelectric sensor for picotesla DC magnetic field detection

We report a highly sensitive NEMS DC/low frequency magnetic field sensor consisting of an AlN/FeGaB resonator, with a ΔE effect-based sensing principle. Unlike previously reported magnetic field detection schemes, such as observing induced magnetoelectric voltage, or monitoring impedance, we designed a system to directly measure the reflected output voltage from the sensor as a function of magnetic field. The AlN/FeGaB resonator shows a resonance frequency shift of 3.19 MHz (1.44%), which leads to a high DC magnetic field sensitivity of 2.8 Hz/nT and a limit of detection of 800pT in an unshielded, room temperature and pressure, lab environment.

Room-temperature detection of a single 19 nm super-paramagnetic nanoparticle with an imaging magnetometer

We demonstrate room temperature detection of isolated single 19 nm super-paramagnetic nanoparticles (SPNs) with a wide-field optical microscope platform suitable for biological integration. The particles are made of magnetite (Fe3O4) and are thus non-toxic and biocompatible. Detection is accomplished via optically detected magnetic resonance imaging using nitrogen-vacancy defect centers in diamond, resulting in a DC magnetic field detection limit of 2.4 μT. This marks a large step forward in the detection of SPNs, and we expect that it will allow for the development of magnetic-field-based biosensors capable of detecting a single molecular binding event.

Self-biased 215 MHz magnetoelectric NEMS resonator for ultra-sensitive DC magnetic field detection.

High sensitivity magnetoelectric sensors with their electromechanical resonance frequencies < 200 kHz have been recently demonstrated using magnetostrictive/piezoelectric magnetoelectric heterostructures. In this work, we demonstrate a novel magnetoelectric nano-electromechanical systems (NEMS) resonator with an electromechanical resonance frequency of 215 MHz based on an AlN/(FeGaB/Al2O3) × 10 magnetoelectric heterostructure for detecting DC magnetic fields. This magnetoelectric NEMS resonator showed a high quality factor of 735, and strong magnetoelectric coupling with a large voltage tunable sensitivity. The admittance of the magnetoelectric NEMS resonator was very sensitive to DC magnetic fields at its electromechanical resonance, which led to a new detection mechanism for ultra-sensitive self-biased RF NEMS magnetoelectric sensor with a low limit of detection of DC magnetic fields of ~300 picoTelsa. The magnetic/piezoelectric heterostructure based RF NEMS magnetoelectric sensor is compact, power efficient and readily integrated with CMOS technology, which represents a new class of ultra-sensitive magnetometers for DC and low frequency AC magnetic fields.

Self-powered, hybrid antenna-magnetoresistive sensor for magnetic field detection

A self-powered hybrid sensor integrating a resonant antenna with a magnetoresistive spin valve sensor was microfabricated. The device is activated by a radiofrequency (rf) external electromagnetic source. This hybrid sensor is capable of detecting dc and ac external magnetic fields in the thermal noise regime. For an excitation rf field of 17 dB m at 130 MHz, the sensitivity to a transverse magnetic field normalized by the current induced in the device was 812 V (T A)−1 for dc magnetic field detection and 918 V (T A)−1 for the ac field measurement.

Hybrid Magnetic Tunnel Junction-MEMS High Frequency Field Modulator for 1/f Noise Suppression

A dc to ac magnetic field transformer was developed using a magnetic tunnel junction (MTJ)/microelectromechanical system (MEMS) mixed device. A MEMS torsionator was fabricated with an incorporated magnetic flux guide, that when actuated by a gate electrode, modulates an external dc field into the same frequency of the micro-torsionator oscillation. Attached to it a MgO based MTJ was fabricated, performing the detection of the generated ac magnetic field. This dc to ac field transformation enables the detection of dc magnetic fields in the high frequency thermal noise regime, where the 1/f noise is typically two orders of magnitude lower. Measurements show the detection of a modulated field at 460 kHz, coming from the MEMS torsionator designed to exhibit high modulation efficiency. This efficiency was of 11%, i.e., 11% of the external dc field is modulated. As a result, from a MTJ exhibiting a noise of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MTJ</sup> =4.4 nT/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> at 460 kHz, this hybrid device enables a dc magnetic field detection of 40 nT/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> . This work acts as a major improvement to a previous one , mainly through the optimization of the MEMS magnetic field modulation efficiency.

Hybrid magnetoresistive∕microelectromechanical devices for static field modulation and sensor 1∕f noise cancellation

Low frequency 1∕f noise in magnetoresistive (MR) spin valve sensors was suppressed by modulating an external dc magnetic field at high frequency microelectromechanical system using a (MEMS) microcantilever structure with an integrated magnetic flux guide. With this hybrid MR∕MEMS device, direct detection of dc magnetic fields in the sensor high frequency thermal noise regime was achieved. The microcantilever was actuated using a gate electrode by applying an ac voltage with frequency f, causing it to oscillate at 2f. Measurements show detection of a dc magnetic field at 2f frequency (400kHz), where sensor 1∕f noise is two orders of magnitude lower than dc.

Phase shift of electric-field-induced magnetization in magnetoelectric laminate composite

A magnetoelectric laminate composite with electric-field-induced magnetization (EIM) effect was prepared. It was found that the phase shift of EIM in the laminate was highly sensitive to the dc magnetic field near resonance frequency. The dependence of the phase shift of EIM on the dc magnetic field was theoretically and experimentally investigated. This work demonstrates that the phase shift of EIM in the magnetoelectric composite has potential for application of small dc magnetic field detection.