Magnetic Field Change Research Articles

Crack detection in metallic materials using a mobile robot

Cracks and flaws are typical failure modes in mechanical structures such as oil and gas pipeline networks, buildings, aircraft fuselages, and spacecraft. Early detection of these failures is critical for safety, timely replacement of damaged or corroded parts, accident prevention, and resource and cost savings. This requires low-cost, easy-to-implement, non-destructive, and reliable testing. For this purpose, we developed an embedded system in a Zumo 32U4 mobile robot for the magnetic detection of cracks in metal plates. Two AVR microcontrollers were used. One controls the magnetic sensing, signal processing, and data acquisition, and the other controls the robot’s displacement. A graphical user interface (GUI) was also implemented. Low-cost commercial magnetoresistive sensors (Sparkfun MAG3110) were used to monitor the variations of the 3D magnetic field around the cracks. Our detection method is based on the magnetic memory method, where local magnetic distortions are expected around a crack in a metallic material. Such distortions are due to the breaking of the symmetry of the crystal in the region where cracks appear. Experimental tests were carried out on a steel plate with machine-induced cracks of depth and width variations. The magnetic field changes associated with these cracks were analyzed and compared. This crack detection method could be used for structural health monitoring of mechanical infrastructure.

Excitation of Quasiperiodic Fast-propagating Waves in the Early Stage of the Solar Eruption

We propose a mechanism for the excitation of large-scale quasiperiodic fast-propagating magnetoacoustic (QFP) waves observed on both sides of the coronal mass ejection. Through a series of numerical experiments, we successfully simulated the quasi-static evolution of the equilibrium locations of the magnetic flux rope in response to the change of the background magnetic field, as well as the consequent loss of the equilibrium that eventually gives rise to the eruption. During the eruption, we identified QFP waves propagating radially outward of the flux rope, and tracing their origin reveals that they result from the disturbance within the flux rope. Acting as an imperfect waveguide, the flux rope allows the internal disturbance to escape to the outside successively via its surface, invoking the observed QFP waves. Furthermore, we synthesized the images of QFP waves on the basis of the data given by our simulations and found consistency with observations. This indicates that the leakage of the disturbance outside the flux rope could be a reasonable mechanism for QFP waves.

Scale and Time Dependence of Alfvénicity in the Solar Wind as Observed by the Parker Solar Probe

Alfvénicity is a well-known property, common in the solar wind, characterized by a high correlation between magnetic and velocity fluctuations. Data from the Parker Solar Probe (PSP) enable the study of this property closer to the Sun than ever before, as well as in the sub-Alfvénic solar wind. We consider scale-dependent measures of Alfvénicity based on second-order functions of the magnetic and velocity increments as a function of time lag, including the normalized cross helicity σ c and residual energy σ r . Scale-dependent Alfvénicity is strongest for lags near the correlation scale and increases when moving closer to the Sun. We find that σ r typically remains close to the maximally negative value compatible with σ c . We did not observe significant changes in measures of Alfvénicity between sub-Alfvénic and super-Alfvénic wind. During most times, the solar wind was highly Alfvénic; however, lower Alfvénicity was observed when PSP approached the heliospheric current sheet or other magnetic structures with sudden changes in the radial magnetic field, non-unidirectional strahl electron pitch angle distributions, and strong electron density contrasts. These results are consistent with a picture in which Alfvénic fluctuations generated near the photosphere transport outward, forming highly Alfvénic states in the young solar wind, and subsequent interactions with large-scale structures and gradients lead to weaker Alfvénicity, as commonly observed at larger heliocentric distances.

Changes in Photospheric Lorentz Force in Eruptive and Confined Solar Flares

Solar flares are known to leave imprints on the magnetic field in the photosphere, often manifested as an abrupt and permanent change in the downward-directed Lorentz force in localized areas inside the active region. Our study aims to differentiate eruptive and confined solar flares based on the variations in vertical Lorentz force. We select 26 eruptive and 11 confined major solar flares (stronger than the GOES M5 class) observed during 2011–2017. We analyze these flaring regions using SHARP vector magnetograms obtained from NASA’s Helioseismic and Magnetic Imager. We also compare data corresponding to two synthetic flares from a δ-sunspot simulation reported by Chatterjee et al. We estimate the change in the horizontal magnetic field and the total Lorentz force integrated over an area around the polarity inversion line (PIL) that encompasses the location of the flare. Our results indicate a rapid increase in the horizontal magnetic field along the flaring PIL, accompanied by a significant change in the downward-directed Lorentz force in the same vicinity. Notably, we find that all the confined events under study exhibit a total change in Lorentz force of <1.8 × 1022 dyn. This threshold plays an important role in effectively distinguishing eruptive and confined flares. Further, our analysis suggests that the change in total Lorentz force also depends on the reconnection height in the solar corona at the associated flare onset. The results provide significant implications for understanding the flare-related upward impulse transmission for the associated coronal mass ejection.

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.

Characteristics of blood flow velocity in the radial artery and finger capillaries using magnetoplethysmogram and photoplethysmogram

The Hall element and optical sensor, which can detect the magnetic field change caused by the minute fluctuations of the permanent magnet according to the periodic movement of the radial artery and the light absorption and reflection intensity according to the change in wrist blood flow, respectively, are used as key elements in digital healthcare devices. The pulse waves of the radial artery inside the wrist were measured and analyzed using a clip-type pulsimeter, magnetoplethysmogram (MPG). The pulse wave, which is the change in blood flow obtained by photoplethysmogram (PPG), was measured on the dorsal side of the wrist or the fingers simultaneously with MPG. The ABFV (artery blood flow velocity) is a few ten cm/s as DH (distance between MPG and PPG) divided by ΔT(a) which is the time difference between the first peaks of MPG and PPG waveforms on the dorsal side of the wrist. The PBFV (peripheral blood flow velocity) is a few mm/s as LH (hand length) divided by ΔT(p), which is the time difference between the first peak of MPG waveform and the third peak PPG waveform on the finger. For four subjects of 20s, SPWV was approximately 0.98∼1.19 m/s, ABFV in the radial artery was approximately 0.40∼0.44 m/s, and finger capillary PBFV was approximately 6.3∼8.6 cm/s. These results show reasonable values similar to the blood velocity of many blood vessels flowing through the human body.

Toward a New Theory of the Fractional Quantum Hall Effect

The fractional quantum Hall effect was experimentally discovered in 1982. It was observed that the Hall conductivity σyx of a two-dimensional electron system is quantized, σyx=e2/3h, in the vicinity of the Landau level filling factor ν=1/3. In 1983, Laughlin proposed a trial many-body wave function, which he claimed described a “new state of matter”—a homogeneous incompressible liquid with fractionally charged quasiparticles. Here, I develop an exact diagonalization theory that allows one to calculate the energy and other physical properties of the ground and excited states of a system of N two-dimensional Coulomb interacting electrons in a strong magnetic field. I analyze the energies, electron densities, and other physical properties of the systems with N≤7 electrons continuously as a function of magnetic field in the range 1/4≲ν&lt;1. The results show that both the ground and excited states of the system resemble a sliding Wigner crystal whose parameters are influenced by the magnetic field. Energy gaps in the many-particle spectra appear and disappear as the magnetic field changes. I also calculate the physical properties of the ν=1/3 Laughlin state for N≤8 and compare the results with the exact ones. This comparison, as well as an analysis of some other statements published in the literature, show that the Laughlin state and its fractionally charged excitations do not describe the physical reality, neither at small N nor in the thermodynamic limit. The results obtained shed new light on the nature of the ground and excited states in the fractional quantum Hall effect.

Magnetic properties and large low-field cryogenic magnetocaloric effect in the divalent europium borate Eu2B2O5 compound

We herein investigated the divalent europium borate Eu2B2O5 compound regarding its structural, magnetic and magnetocaloric properties by means of experimental determinations and first principal calculations. The Eu2B2O5 compound was found to crystallize in a monoclinic structure (P21/c space group) and order ferromagnetically at ground state. A large cryogenic reversible MCE was observed in the Eu2B2O5 compound around 2.7 K. The maximum values of magnetic entropy change of Eu2B2O5 compound reach 13.7, 28.2 and 46.9 J/kgK under the magnetic field changes of 0–1, 0–2, and 0–5 T, respectively. The corresponding values of adiabatic temperature change and refrigerant capacity are obtained to be 3.3, 7.0, and 13.3 K and to be 37.8, 102.5, and 317.3 J/kg. These magnetocaloric parameters, especially under relatively low-field changes, are better than those of the reported candidate materials, which makes the Eu2B2O5 compound attractive for cryogenic MR applications.

Relationship of Magnetic Domain and Permeability for Clustered Soft Magnetic Narrow Strips with In-Plane Inclined Magnetization Easy Axis on Distributed Magnetic Field.

A unique functionality was reported for a thin-film soft magnetic strip with a certain angle of inclined magnetic anisotropy. It can switch magnetic domain by applying a surface normal field with a certain distribution on the element. The domain switches between a single domain and a multi-domain. Our previous study shows that this phenomenon appears even in the case of the adjacent configuration of multiple narrow strips. It was also reported that the magnetic permeability for the alternating current (AC) magnetic field changes drastically in the frequency range from 10 kHz to 10 MHz as a function of the strength of the distributed magnetic field. In this paper, the correspondence of AC permeability and the magnetic domain as a function of the intensity of the distributed field is investigated. It was confirmed that the extension of the area of the Landau-Lifshitz-like multi-domain on the clustered narrow strips was observed as a function of the intensity of the distributed magnetic field, and this domain extension was matched with the permeability variation. The result leads to the application of this phenomenon to a tunable inductor, electromagnetic shielding, or a sensor for detecting and memorizing the existence of a distributed magnetic field generated by a magnetic nanoparticle in the vicinity of the sensor.

Magnetic properties and large cryogenic magnetocaloric effects in the RE2SiO5 (RE = Gd, Dy, Ho, and Er) silicates

We herein investigated four rare earth (RE)-based oxides, the RE2SiO5 (RE = Gd, Dy, Ho, and Er) silicates, regarding their structural and cryogenic magnetic properties. All the RE2SiO5 silicates are found to crystallized in a monoclinic structure. X-ray photoemission spectroscopy spectra illustrate that RE, Si and O elements in RE2SiO5 silicates are present as RE3+, Si4+, and O2−, respectively. The Dy2SiO5 reveals a first-order magnetic transition around 4.5 K. The magnetic phase transition temperatures are probably below 2 K for the RE2SiO5 (RE = Gd, Ho, and Er) silicates. Large cryogenic magnetocaloric effects (MCE) and good magnetocaloric performances were observed in the RE2SiO5 silicates. The MCE parameters in terms of the maximum magnetic entropy changes, the temperature-averaged entropy change (5 K-lift) and refrigerant capacity under a magnetic field change of 0–5 T are determined to be 35.5, 30.4 J/kgK, and 215.7 J/kg for Gd2SiO5, to be 13.3, 12.9 J/kgK, and 190.5 J/kg for Dy2SiO5, to be 15.3, 15.1 J/kgK, and 274.1 J/kg for Ho2SiO5 and to be 17.9, 16.5 J/kgK, and 181.14 J/kg for Er2SiO5, respectively. These derived values of MCE parameters of the RE2SiO5 silicates, especially for Gd2SiO5, are at similarly high level with or better than those of the updated candidate materials, making them also of potential for practical magnetic refrigeration applications.

Levitation performance evolution of high-temperature superconducting maglev vehicle under electromagnetism-heat-force strong coupling

ABSTRACT High-temperature superconducting (HTS) maglev is considered suitable for high-speed maglev systems because of its self-stability characteristic. However, when the HTS maglev vehicle vibrates, alternating current loss occurs in the onboard superconductor due to the change in the external magnetic field. It leads to the decrease of vehicle levitation height and seriously affects the safe and stable operation of the vehicle. So, in this paper, the levitation performance evolution of HTS maglev vehicle under the electromagnetism-heat-force strong coupling model is studied. The parameter of the air spring is optimized according to the ride index and levitation height decay. The effects of random irregularity at different speeds on vehicle levitation performance are compared. The influence of periodicity geometric irregularity on the levitation performance and ride comfort of HTS maglev vehicle are studied. This paper can provide data reference for the HTS maglev vehicle system in future engineering applications.

Exploring the magnetic and magnetocaloric behavior of nanocrystalline melt-spun R2Fe17 (R = Pr, Nd) ribbons

Single-phase nanocrystalline R2Fe17 (R = Pr and Nd) ribbons with rhombohedral Th2Zn17-type crystalline structure (space group R3̅m) have been fabricated by melt-spinning technique. The microstructure of the polycrystalline ribbons is composed of quasi-spherical grains with an average size below 100 nm. Transmission electron microscopy reveals that these grains are formed by agglomeration of smaller nanocrystalline entities around 15 nm in diameter, separated by disordered boundaries where the long-range crystalline order is lost. Two different ferro-to-paramagnetic phase transitions are observed, one of them coincides with that of the parent bulk alloy (290 and 326 K for R = Pr and Nd, respectively), and the other one can be ascribed to the disordered boundaries (323 and 350 K for R = Pr and Nd, respectively). For R= Pr, this fact gives rise to a significant broadening (c.a. 120 K under a magnetic field change of 2 T) of the full-width at the half-maximum of the magnetic entropy change curve, |∆SM(T)| (that adopts a "table-like" shape), resulting in a considerable increase of the refrigerant capacity.

Electrodeposited Heusler Alloys-Based Nanowires for Shape Memory and Magnetocaloric Applications.

In this article, the downsizing of functional Heusler alloys is discussed, focusing on the published results dealing with Heusler alloy nanowires. The theoretical information inspired the fabrication of novel nanowires that are presented in the results section of the article. Three novel nanowires were fabricated with the compositions of Ni66Fe21Ga13, Ni58Fe28In14, and Ni50Fe31Sn19. The Ni66Fe21Ga13 nanowires were fabricated, aiming to improve the stoichiometry of previous functional Ni-Fe-Ga Heusler nanomaterials with a functional behavior above room temperature. They exhibit a phase transition at the temperature of ≈375 K, which results in a magnetocaloric response of |ΔSM| ≈ 0.12 J·kg-1·K-1 at the magnetic field change of only μ0ΔH = 1 T. Novel Heusler alloy Ni58Fe28In14 nanowires, as well as Ni50Fe31Sn19 nanowires, are analyzed for the first time, and their magnetic properties are discussed, introducing a simple electrochemical approach for the fabrication of nanodimensional alloys from mutually immiscible metals.

Polarization losses from the nonadiabatic passage of hyperpolarized solutions through metallic components

From complex-mixture analysis to in vivo molecular imaging, applications of liquid-state nuclear spin hyperpolarization have expanded widely over recent years. In most cases, hyperpolarized solutions are generated ex situ and transported from the polarization instrument to the measurement device. The sample hyperpolarization usually survives this transport, since the changes in magnetic fields that are external to the sample are typically adiabatic (slow) with respect to the internal nuclear spin dynamics. The passage of polarized samples through weakly magnetic components such as stainless steel syringe needles and ferrules is not always adiabatic, which can lead to near-complete destruction of the magnetization. To avoid this effect becoming “folklore” in the field of hyperpolarized NMR, we present a systematic investigation to highlight the problem and investigate possible solutions. Experiments were carried out on: (i) dissolution-DNP-polarized [1-13C]pyruvate with NMR detection at 1.4T, and (ii) 1.5-T-polarized H2O with NMR detection at 2.5μT. We show that the degree of adiabaticity of solutions passing through metal parts is intrinsically unpredictable, likely depending on many factors such as solution flow rate, degree of remanent ferromagnetism in the metal, and nuclear spin species. However, the magnetization destruction effects can be suppressed by application of an external field on the order of 0.1–10mT.

Magnetocaloric properties of Mn5(Si,P)B2 compounds for energy harvesting applications

The magnetocaloric properties of Mn5Si1-xPxB2 (0 ≤ x ≤ 1) compounds were studied for energy harvesting applications. The crystal structure and the magnetic structure were characterized by powder X-Ray Diffraction and powder Neutron Diffraction. The results indicate that these magnetocaloric materials crystallize in the tetragonal Cr5B3-type crystal structure. The introduction of P causes a stretching of the c axis and compression of the a-b plane, leading to a decrease in the unit-cell volume V. In the ferromagnetic state the magnetic moments align within the a-b plane, and the magnetic moment of the Mn1 atom on the 16 l site is larger than that of the Mn2 atom on the 4c site. The Curie temperature TC can be adjusted continuously from 305 K (x = 1) to 406 K (x = 0) by replacing Si with P. The corresponding magnetic entropy change varies from 1.90 Jkg−1K−1 (x = 0) to 1.35 Jkg−1K−1 (x = 1) for a magnetic field change of 1 T. The PM-FM transition in these compounds corresponds to a second-order phase transition. Mn5Si1-xPxB2 compounds exhibit a magnetization difference of 28.1 - 31.3 Am2kg−1 for a temperature span of 30 K around TC in an applied magnetic field of 1 T. The considerable change in magnetization, the tunable TC near and above room temperature and the absence of thermal hysteresis make these compounds promising candidates for magnetocaloric energy harvesting materials.

Emergent magneto-inductance effect in permalloy thin films on flexible polycarbonate substrates at room temperature

Emergent inductance has attracted significant interest for its relevance in both interesting fundamental physics and practical applications in magnetic devices that demand miniaturization without compromising inductance. In this Letter, we report the discovery of a stepwise magnetic field-induced emergent magneto-inductance (EML) effect in Permalloy (Py) thin films deposited on polycarbonate (PC) substrates. Remarkably, Py/PC devices exhibit an exceptionally large inductance variation exceeding 1 μH at room temperature, and intriguingly, a sign reversal of inductance occurs around the zero magnetic field. The dependencies of the EML effect on frequency, step magnetic field changes, and film width can be explained from the theory based on the spin motive force driven by transient domain wall motion. This study opens up exciting avenues for advancing our understanding of emergent inductance in fundamental physics and paves the way for practical applications in flexible magnetic devices.

Reversal of drift direction during the Laschamp geomagnetic excursion

Earth's magnetic field changes in both space and time: the temporal changes are called geomagnetic and paleomagnetic secular variations. Westward drift has been noted as a feature of secular variation for several centuries, but eastward drift has received less attention. We use three global geomagnetic field models covering the past 100 kyr to extend temporal coverage for tracking the zonal (azimuthal) motion of the radial magnetic field. The models we use are GGF100k (100–0 ka), GGFSS70 (70–15 ka), LSMOD.2 (50–30 ka); the extent of the models enables the inclusion of the extreme secular variations found during excursions, particularly the Laschamp excursion (42–40 ka). GGFSS70 and LSMOD.2 have higher temporal resolution than GGF100k, but their underlying data have poorer spatial coverage. Spatial structure is greatly diminished in all models for spherical harmonic degrees l>4.We use two types of time-longitude plots, one of the full radial field to expose reverse and intense flux patches at the core-mantle boundary. The second time-longitude plot is processed to enhance zonal motion signatures and allows us to use Radon drift analyses to uncover characteristic time scales of both westward and eastward drift at mid to high latitudes in both the northern and southern hemispheres. Our results differ across the three models, which we attribute to varying degrees of resolution, accuracy, and data distribution. Nevertheless, recurrent episodes of both eastward and westward drift ranging from ±0.05o/yr to ±0.18o/yr occur in both the northern and southern hemispheres. Westward drift dominates. We also observe 8–20 kyr intervals between occurrences of high-latitude reverse flux patches correlated with strong drift signals. Focusing on the period 50–30 ka, we observe dominant eastward drift preceding the Laschamp excursion and westward drift subsequently. In a period not associated with an excursion, 90–80 ka, we see strong mid to high latitude drift signatures in the northern hemisphere.

Assessing rapid solidification processing to produce magnetocaloric RFeSi alloys (R= Tb, Dy) for natural gas liquefaction

This work addressed the synthesis of melt-spun ribbons of the ternary intermetallic ferromagnetic phases RFeSi with R = Tb and Dy, presenting a thorough characterization of their structural, magnetic, and magnetocaloric behavior. Both compounds have been referred to as suitable magnetic refrigerants in the natural gas liquefaction temperature range. The primary phase in ribbon samples of both compounds shows the CeFeSi-type tetragonal crystal structure (space group P4/nmm), with Curie temperatures of 124 K and 89 K for TbFeSi and DyFeSi, respectively. Notably, a sizeable increase in the coercive field appeared below 20 K. However, for a magnetic field change of 2 T, the maximum values of the magnetic entropy change (|ΔSM|max) were 3.4 J kg−1 K−1 and 3.8 J kg−1 K−1 for TbFeSi and DyFeSi ribbon samples, respectively, reflecting a reduction of approximately 60% compared to reported findings for bulk alloys. In contrast, the refrigerant capacity under a magnetic field change of 2 T measured 120 J kg−1 for TbFeSi and 109 J kg−1 for DyFeSi. The reduction in |ΔSM|max is mainly due to a broader magnetic transition compared to the previous results for bulk alloys. Based on the RFeSi ribbons obtained, a biphasic magnetocaloric composite with a broad table-like magnetic entropy change curve, as that required for an Ericsson-type refrigeration cycle, is designed.

Обзор факторов, воздействующих на оптоволоконные линии связи при грозовых разрядах, и моделирование лабораторных установок, предназначенных для изучения влияния магнитного поля на параметры оптоволокна

The article provides an overview of the known effects that influence the transmission of information over optical fiber and that arise as a result of lightning discharges: the electro-optical Kerr effect, the Faraday effect, the influence of ionizing radiation. It is indicated that there is preliminary empirical data according to which the magnetic field changes such an optical fiber parameter as attenuation. In order to verify these preliminary empirical data, further experimental studies of the supposed influence of the magnetic field on attenuation are proposed, for which it is necessary to build a laboratory installation. This article is also devoted to a comparison of various options for laboratory installations and the preliminary selection of a parameter for comparison. As a result of modeling two options for a laboratory installation and comparing them according to the accepted parameter, one of two installation options is selected.

Sudden Commencements and Geomagnetically Induced Currents in New Zealand: Correlations and Dependance

AbstractChanges in the Earth's geomagnetic field induce geoelectric fields in the solid Earth. These electric fields drive Geomagnetically Induced Currents (GICs) in grounded, conducting infrastructure. These GICs can damage or degrade equipment if they are sufficiently intense—understanding and forecasting them is of critical importance. One of the key magnetospheric phenomena are Sudden Commencements (SCs). To examine the potential impact of SCs we evaluate the correlation between the measured maximum GICs and rate of change of the magnetic field (H′) in 75 power grid transformers across New Zealand between 2001 and 2020. The maximum observed H′ and GIC correlate well, with correlation coefficients (r2) around 0.7. We investigate the gradient of the relationship between H′ and GIC, finding a hot spot close to Dunedin: where a given H′ will drive the largest relative current (0.5 A nT−1 min). We observe strong intralocation variability, with the gradients varying by a factor of two or more at adjacent transformers. We find that GICs are (on average) greater if they are related to: (a) Storm Sudden Commencements (SSCs; 27% larger than Sudden Impulses, SIs); (b) SCs while New Zealand is on the dayside of the Earth (27% larger than the nightside); and (c) SCs with a predominantly East‐West magnetic field change (14% larger than North‐South equivalents). These results are attributed to the geology of New Zealand and the geometry of the power network. We extrapolate to find that transformers near Dunedin would see 2000 A or more during a theoretical extreme SC (H′ = 4000 nT min−1).