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The vibration of a transformer core induced by magnetostriction is closely related to the environment and safety of devices. The DC bias excitation leads to the over saturation of the transformer core and causes more severe vibration. In this paper, a magnetic-mechanical strong coupling model based on a fixed-point time-periodic 2D finite element method with excitation voltage and DC bias current as the input is established in which the vector magnetic potential A, winding current I, and displacement in the core u are simultaneously taken as solution variables, and the fixed-point reluctivity is introduced to deal with the nonlinear problem of the core. In this model, the magnetic field and mechanical field are associated with the piezomagnetic equations and variational principle, and the circuit and magnetic fields are connected through the law of electromagnetic induction. The equivalent thickness of the core model and the determination of the initial value are discussed. A test transformer with a laminated core is made for experimental measurement. The accuracy and efficiency of the model proposed are verified by comparing the calculated results with the experimental results, and the influence of DC bias components on the magnetic characteristics and vibration of the transformer core is analyzed. [ABSTRACT FROM AUTHOR]

Spintronic terahertz (THz) emitters have been shown to be a cost-efficient source for use in time-domain THz spectroscopy. The use of external magnetic fields to control the polarity of the THz emission provides an opportunity to measure the magnetization of spintronic materials as well as shaping THz emission. Here, we demonstrate an efficient method of measuring magnetic hysteresis with material sensitivity and speed several orders of magnitude greater than typical magnetometry methods. In addition, we utilize the rapid control of material magnetization for lock-in detection in time-domain THz spectroscopy of spintronic emitters. The ability to rapidly control and measure the material magnetization on very small volumes provides an opportunity to study magnetic hetero-structures with sub-micron spatial resolution. [ABSTRACT FROM AUTHOR]

The topology of the applied magnetic field is an important design aspect of Hall thrusters. For modern Hall thrusters, the magnetic field topology most often features curved lines with a concave (negative) curvature upstream of the field's peak and a convex (positive) curvature downstream. Additionally, the advent of the magnetic shielding technique has resulted in Hall thruster designs with non-conventional field topologies that exhibit high degrees of concavity upstream of the field's peak. In this article, a detailed study is carried out on the effects that the magnetic field curvature has on the plasma discharge in a 2D configuration representative of a Hall thruster's radial–azimuthal cross section. The analyses are performed for discharges of three propellants of high applied interest: xenon, krypton, and argon. For each propellant, high-fidelity electrostatic reduced-order particle-in-cell (PIC) simulations are performed with various degrees of positive and negative curvatures of the magnetic field. Corresponding 1D radial PIC simulations are also performed for xenon to compare the observations against the 2D results. Most notably, it is observed that the instability spectra in the positive-curvature cases are mostly dominated by electron cyclotron drift instability, whereas the modified two stream instability is dominant in the negative-curvature cases. The distributions of electron and ion temperatures, in particular, as well as the contribution of various mechanisms to electrons' cross-field transport show notable variations between the positive and negative curvature values. Finally, the field curvature is observed to majorly influence the ion beam divergence along the radial and azimuthal coordinates. [ABSTRACT FROM AUTHOR]

We extend some of the well-established self-interaction correction (SIC) schemes of density-functional theory—the Perdew–Zunger SIC and the average-density SIC—to the case of systems with noncollinear magnetism. Our proposed SIC schemes are tested on a set of molecules and metallic clusters in combination with the widely used local spin-density approximation. As expected from the collinear SIC, we show that the averaged-density SIC works well for improving ionization energies but fails to improve more subtle quantities like the dipole moments of polar molecules. We investigate the exchange-correlation magnetic field produced by our extension of the Perdew–Zunger SIC, showing that it is not aligned with the local total magnetization, thus producing an exchange-correlation torque. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated red light (∼ 660 nm) and magnetic field dependence of impedance across (100 − x)% ZnO(zinc oxide)– x % rGO(reduced graphene oxide)/La 0.7 Sr 0.3 MnO 3 (LSMO)/ITO (x =0,0.6,0.8,100) heterostructure devices. Field-induced scattering due to the spin filter effect and spin polarized tunneling (SPT) have been extracted from the zinc oxide–reduced graphene oxide nanocomposite/LSMO space charge region (ZnO–rGO/LSMO SCR) and the LSMO active region of the devices, respectively. Higher SPT leads to higher LSMO SCR scattering across the devices. Devices with higher rGO contents could not be fitted with two RC circuits as resistance values because the two phenomena are incomparable with each other. Light-induced scattering has been observed at the ZnO–rGO nanocomposite active region and ZnO–rGO/LSMO SCR of the devices. For composite devices with x =0.8 and 0.6, higher photocarrier generation at ZnO–rGO nanocomposite active layer leads to enhanced scattering at LSMO SCR with light illumination. Light-dependent scattering at both regions, however, follows almost same decreasing trend for bare devices with x =0, 100. The decreasing trend of light-dependent scattering for ZnO/LSMO/ITO and rGO/LSMO/ITO bare devices suddenly gets reversed and, eventually, follows an increasing trend at magnetic field ambiance of 0.5 and 1 kOe, respectively. The LSMO SCRs of the bare devices got enhanced with the field, leading to a light-dependent response similar to composite devices at the higher field. [ABSTRACT FROM AUTHOR]

In this study, the influence of carrier doping on the thermo- and galvano-magnetic effects of Bi–Sb alloys was investigated. Seven types of Bi88Sb12 alloys, namely, the undoped and 0.01, 0.02, and 0.04 at. % Te- and Sn-doped alloys, were fabricated via the spark plasma sintering method and solid phase reaction. The magnetic field dependencies of the diagonal resistivity, Hall resistivity, thermal conductivity, Seebeck thermopower, and Nernst thermopower were measured in the range of −5–5 T at 300 K, and the dimensionless figures of merit for the Seebeck and Nernst effects, i.e., the zST and zNT, respectively, were determined. As a result, both the zT values in the magnetic field were improved by the addition of a trace amount of Te. To better understand this behavior, a computational model that qualitatively describes the Seebeck, Nernst, magnetoresistance, and Hall effects, as well as the carrier thermal conductivity of Bi in the magnetic field, was developed based on the Boltzmann equation by considering the relaxation time approximation. The influence of carrier doping on the thermo-magnetic effect was considered by shifting the chemical potential with the rigid-band model in the established computational model. The computational results demonstrated that zST and zNT in the magnetic field were improved by shifting the chemical potential. These findings revealed that carrier doping could be a promising approach to improve the zT, namely, the zST for the Seebeck effect and zNT for the Nernst effect in Bi–Sb alloys in a magnetic field. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally and numerically the control of magnetization circulation of the closure domain state in thin permalloy squares divided diagonally into four dipolar-coupled isosceles triangles. The control over the magnetization circulation was achieved by the mutual application of a suitable external in-plane magnetic field and interaction with a magnetic force microscopy (MFM) tip. Numerical simulations confirm that the proposed switching protocol is valid for the broad range of MFM tips. Experiments performed on four diagonally cut squares show that this method is robust against slight imperfections in the fabrication process. Moreover, by varying the polarity of the applied field and the direction of the MFM scanning, proper symmetry response of the switching method is observed. [ABSTRACT FROM AUTHOR]

Suppression of 1/f noise in tunnel magnetoresistance (TMR) sensors is a central issue in the realization of magnetic field sensors with ultrafine magnetic field detectivity. Although AC modulation with an external magnetic field has been proposed as a method to shift the operating frequency of a sensor to a high frequency and substantially suppress 1/f noise, its effects on the two types of 1/f noise, that is, magnetic and electrical 1/f noise, are not well understood. In this study, we investigated the noise characteristics and signal detection performance of TMR sensors with an even-function resistance-magnetic field curve operated by the AC modulation method. For one TMR device in which the magnetic 1/f noise was dominant, AC modulation degraded the magnetic field detectivity owing to the additional noise induced by the AC modulation field. However, in another TMR device, in which the electrical 1/f noise was artificially enhanced by introducing lattice defects in the MgO tunnel barrier, AC modulation effectively suppressed the 1/f noise and improved the magnetic field detectivity by one order. This demonstrates that the AC modulation method using an external magnetic field is effective for magnetic field sensors in which electrical 1/f noise is dominant. [ABSTRACT FROM AUTHOR]

In truncated coupled-cluster (CC) theories, non-variational and/or generally complex ground-state energies can occur. This is due to the non-Hermitian nature of the similarity transformed Hamiltonian matrix in combination with CC truncation. For chemical problems that deal with real-valued Hamiltonian matrices, complex CC energies rarely occur. However, for complex-valued Hamiltonian matrices, such as those that arise in the presence of strong magnetic fields, complex CC energies can be regularly observed unless certain symmetry conditions are fulfilled. Therefore, in the presence of magnetic fields, it is desirable to pursue CC methods that are guaranteed to give upper-bound, real-valued energies. In this work, we present the first application of unitary CC to chemical systems in a strong magnetic field. This is achieved utilizing the variational quantum eigensolver algorithm applied to the unitary coupled-cluster singles and doubles (UCCSD) method. We benchmark the method on the H2 molecule in a strong magnetic field and then calculate UCCSD energies for the H4 molecule as a function of both geometry and field angle. We show that while standard CCSD can yield generally complex energies that are not an upper-bound to the true energy, UCCSD always results in variational and real-valued energies. We also show that the imaginary components of the CCSD energy are largest in the strongly correlated region. Last, the UCCSD calculations capture a large percentage of the correlation energy. [ABSTRACT FROM AUTHOR]

We present a numerical approach to magnetic optical rotation based on real-time time-dependent electronic-structure theory. Not relying on perturbation expansions in the magnetic field strength, the formulation allows us to test the range of validity of the linear relation between the rotation angle per unit path length and the magnetic field strength that was established empirically by Verdet 160 years ago. Results obtained from time-dependent coupled-cluster and time-dependent current density-functional theory are presented for the closed-shell molecules H2, HF, and CO in magnetic fields up to 55 kT at standard temperature and pressure conditions. We find that Verdet's linearity remains valid up to roughly 10–20 kT, above which significant deviations from linearity are observed. Among the three current density-functional approximations tested in this work, the current-dependent Tao–Perdew–Staroverov–Scuseria hybrid functional performs the best in comparison with time-dependent coupled-cluster singles and doubles results for the magnetic optical rotation. [ABSTRACT FROM AUTHOR]

By electric transport measurements on high-purity bulk molybdenum single crystals at helium-temperature, it is shown that when approaching the ideal metallic crystal structure, there are deviations from Ohm's law that can exceed 30% even at low current densities ≅ 3 A / m m 2. This is due to the intrinsic circular magnetic field of the measuring current in the range of B ≅ 1 mT , which generates a magnetoresistance according to the two-band conduction model. With increasing lattice vibrations and/or crystal defects, this inherent uncertainty finally reduces to immeasurably small values. Finally, Ohm's law for a nearly ideal lattice structure can be strictly exact only in the theoretical limiting case of an infinite lattice plane, because then the magnetic fields of all electrons of the current compensate to zero. [ABSTRACT FROM AUTHOR]

Ferrimagnetic antiperovskite Mn 4 N has received growing interest due to room-temperature observation of large perpendicular magnetic anisotropy, low saturation magnetization, and ultrafast response to external magnetic fields. Comprehensive understanding of the underlying magnetic structure is instrumental in design and fabrication of computer memory and logic devices. Magneto-optical spectroscopy provides deeper insight into the magnetic and electronic structure than magnetometry. Simulations of a magneto-optical Kerr effect in biaxially strained Mn 4 N are performed using density functional theory and linear response theory. We consider three ferrimagnetic phases, two collinear and one noncollinear, which have been investigated separately by earlier studies. The simulated spectra are compared to measured magneto-optical data available in recent literature. One of the collinear ferrimagnetic phases is found to be consistent with the measured spectra. We show that an admixture of the noncollinear phase, which is the ground state of unstrained Mn 4 N, further improves the agreement with measured spectra, and at the same time, it could explain the lower than predicted net moment and magnetic anisotropy observed in thin films on various substrates. [ABSTRACT FROM AUTHOR]

Development of nanophotonics has made it possible to control the wavelength and direction of thermal radiation emission, but it is still limited by Kirchhoff's law. Magneto-optical materials or Weyl semimetals have been used in recent studies to break the time-reversal symmetry, resulting in a violation of Kirchhoff's law. Currently, most of the work relies on the traditional optical design basis and can only realize the nonreciprocal thermal radiation at a specific angle or wavelength. In this work, on the basis of material informatics, a design framework of a multilayer nonreciprocal thermal absorber with high absorptivity and low emissivity at any arbitrary wavelength and angle is proposed. Through a comprehensive investigation of the underlying mechanism, it has been discovered that the nonreciprocal thermal radiation effect is primarily attributed to excitation of the cavity mode at the interface between the metal and the multilayer structure. Moreover, the impact of factors, such as layer count, incidence angle, extinction coefficient, and applied magnetic field on nonreciprocal thermal radiation, is thoroughly explored, offering valuable insights to instruct the design process. Additionally, by expanding the optimization objective, it becomes feasible to design fixed dual-band or even multi-band nonreciprocal thermal absorbers. Consequently, this study offers essential guidelines for advancing the control of nonreciprocal thermal radiation. [ABSTRACT FROM AUTHOR]

This article employs fluid equations to analyze muon beams in gases subject to crossed electric and magnetic fields, focusing, in particular, on a scheme proposed by Taqqu [Phys. Rev. Lett. 97, 194801 (2006)], whereby transverse compression of the beam is achieved by creating a density gradient in the gas. A general criterion for maximizing beam compression, derived from first principles, is then applied to determine optimal experimental conditions for μ+ in helium gas. Although the calculations require the input of transport data for (μ+, He), which are generally unavailable, this issue is circumvented by "aliasing" (μ+, He) with (H+, He), for which transport coefficient data are available. [ABSTRACT FROM AUTHOR]

In this series, we outline a strategy for analyzing electrons and muons in gases in crossed electric and magnetic fields using the straightforward transport equations of momentum-transfer theory, plus empirical arguments. The method, which can be carried through from first principles to provide numerical estimates of quantities of experimental interest, offers a straightforward, physically transparent alternative to "off-the-shelf" simulation packages, such as Magboltz and GEANT. In this first article, we show how swarm data for electrons in helium gas subject to an electric field only can be incorporated into the analysis to generate electron swarm properties in helium gas in crossed electric and magnetic fields and to estimate the Lorentz angle in particular. The subsequent articles in the series analyze muons in crossed fields using similar transport theory, though the absence of muon swarm data requires empiricism of quite a different nature. [ABSTRACT FROM AUTHOR]

We demonstrate a real-time, single-shot vector magnetic measurement technique using synchronous coherent population trapping (SCPT) in an apparatus consisting of a small rubidium vapor cell. Vector modality of our magnetometer is enabled by designing a feedback system based on performing a peak-lock on a particularly strong 2 Ω L magnetic resonance produced in the SCPT spectrum and compensating the external magnetic field via a three-axis field coil. With its current design, this magnetometer exhibits high sensitivities of approximately 155 , 129 , and 57 pT / Hz in measuring the magnetic field vector components along the (x,y,z) axes. Sensitivities closer to the shot-noise limit can be achieved in the future by reducing the technical noise of our equipment and by employing a differential detection and polarization rotation measurement scheme in our system. [ABSTRACT FROM AUTHOR]

Using high-frequency electron paramagnetic resonance (EPR), we have observed the ferromagnetic coupling of manganese Mn2+ pairs in a layered van der Waals GaS semiconductor. The EPR spectra of Mn2+ pairs (Mn24+) [replacing covalently bonded Ga24+ pairs oriented along the chain axis (c axis) of two gallium ions and being situated in the center of the layer] were recorded at 94 and 130 GHz. The fine structure parameters for the lower multiplets with spin S = 5 and S = 4 were determined equal to D = −0.040 cm−1 and D ≅ −0.035 cm−1, respectively. Based on the observation of additional EPR lines in the region of intersection of the levels in the magnetic field of the multiplet with S = 5 and S = 4, the energy of the isotropic exchange interaction J was estimated to be ∼−0.5 cm−1. For all transitions, a well-resolved hyperfine structure was observed, due to the interaction with two equivalent 55Mn nuclei, leading to the appearance of 11 lines with a hyperfine interaction constant A = 30(1) × 10−4 cm−1, which is approximately half the hyperfine interaction constant for single Mn2+ ions. In addition, a signal from single manganese ions Mn2+ with spin S = 5/2 and a hyperfine interaction constant A = 60(1) × 10−4 cm−1 was observed, which are characterized by extremely large fine structure splitting of D = −0.15 cm−1. Simultaneously with EPR studies, the crystals were monitored by photoluminescence and micro-Raman scattering measurements using a microscope with confocal optics. [ABSTRACT FROM AUTHOR]

H−T phase diagrams for chromium oxide chloride (CrOCl) are usually obtained using data from the measurements of magnetization and specific heats. Recent works suggest that magnetic anisotropy exists in CrOCl. In this work, we use dynamic cantilever magnetometry, which is sensitive to both magnetization and magnetic anisotropy, to probe phase transitions in CrOCl flakes. Together with magnetization measurements from a Superconducting Quantum Interference Device, four major regions of the CrOCl H−T phase diagram along its c-axis are obtained, which is consistent with the previously reported works. Then, we studied magnetic field induced transitions in CrOCl flakes under four different temperatures. Several transitions in antiferromagnetic state and in incommensurate state, which have not been reported before, were recognized. We believe these transitions probably originate from magnetic anisotropy due to magnetoelastic coupling and lattice reconstruction in CrOCl. Our work provides intriguing experimental results on the intricate magnetic structure of CrOCl, making progress in understanding the rich magnetic states of CrOCl. [ABSTRACT FROM AUTHOR]

This study presents an approach to achieve a triaxial magnetic alignment through a linear drive type of modulated rotating magnetic field by using a permanent magnet array. This magnet array generates a modulated rotating magnetic field (MRF) without moving the sample and can produce an MRF of ∼ 0.8 T. By utilizing this magnet array, DyBa2Cu3Oy (Dy123, y ∼ 7) grains were biaxially aligned. After cutting the as-aligned sample that was magnetically aligned, we observed a location dependence of the orientation degree. We achieved the higher in-plane orientation degree of ∼ 8.5° and the c-axis orientation degree of ∼ 6.0°, respectively. The 3D simulation analysis played a key role in identifying the region where the uniformity of the MRF is within the magnet array. Compared to the epitaxial growth techniques, the use of the magnet array offers a cost-effective and versatile solution for achieving triaxial magnetic alignment. [ABSTRACT FROM AUTHOR]

In the present study, we have explored the absorption properties of a monolayer graphene-based photonic heterostructure, which consists of topological photonic configurations, graphene, and a Bragg mirror. The optical attributes were computed by using the 4 × 4 transfer matrix method. The results indicate that the creation of topological interface states and strong coupling between these resonant modes result in mode splitting, leading to the formation of hybrid modes known as coupled topological interface states with unity transmittance. The number of absorption modes can be modulated with an appropriate selection of cascaded photonic structures. Our proposed design with 1, 3, 5, and 7 cascaded topological photonic structures provides 1, 5, 9, and 13 absorption modes with greater than 90 % absorption. The findings also reveal that absorption peak strength is greatly influenced by Fermi-level and magnetic fields; switching of the modes from absorption to reflection and vice versa is achieved by suitable electrical and magnetic biasing. Our proposed design offers various applications, such as switchable filters, absorbers, and modulators. [ABSTRACT FROM AUTHOR]

We investigated the thermal stability and performance of AlGaN/AlN/GaN Hall-effect sensors under industry-relevant atmospheric conditions. The thermal stability and performance of Hall sensors are evaluated by monitoring Hall sensitivity, two-dimensional electron gas density, and Ohmic contact resistance during aging at 200 °C for up to 2800 h under atmospheric conditions. This was accomplished by characterizing AlGaN/AlN/GaN micro-Hall sensors, with and without contacts, and before and after being placed under different thermal aging times. Observed electrical performance was correlated with the micro-structural evolution of AlGaN/AlN/GaN Hall sensor heterostructures. Results indicate that the AlGaN/AlN/GaN Hall sensor provides stable performance for as long as 2800 h aging at 200 °C without any significant degradation of (i) Hall sensitivity, (ii) two-dimensional electron gas, and (iii) Ohmic contacts. However, there was a small change in sheet density and mobility, which is due to a decrease in polarization, resulting from local inhomogeneous strain relief at the barrier layer. During the early stage of thermal aging, a decrease in contact resistance was also observed and attributed to (i) out-diffusion of "Ga" at the vicinity of the contact interface, and (ii) a reduction in oxygen concentration and formation of Al–Ti intermediate alloy at the GaN/Ti interface, resulting in a reduced barrier and enhanced electron transport at the contacts. However, despite these small changes, results indicate that the AlGaN/AlN/GaN Hall sensor provides stable performance for as long as 2800 h thermal aging at 200 °C. [ABSTRACT FROM AUTHOR]

This work theoretically investigates the strain-mediated magnetic domain wall propagation in a magnetostrictive layer, which is perfectly attached to a thick piezoelectric layer under the combined mechanism of nonlinear viscous and dry friction dissipation. The mathematical model of this study is formulated within the framework of the one-dimensional Extended Landau-Lifshitz-Gilbert equation, considering the simultaneous action of the applied magnetic and electric fields, nonlinear dissipations and piezo-induced strains. We use the traveling wave ansatz to derive analytical expressions of the key features like threshold, breakdown, and domain wall velocity in steady and precessional regimes. More precisely, our prime focus is to examine how nonlinear viscous dissipation affects the dynamics of domain walls in both isotropic and anisotropic magnetostrictive materials. The velocity profile of the magnetic domain wall becomes nonlinear due to the inclusion of the nonlinear viscous dissipation, which also significantly affects the Walker breakdown limit, thus leading to the expansion of the steady-state regime. Finally, we present a numerical illustration of the obtained analytical results, which agree well with recent observations. [ABSTRACT FROM AUTHOR]

This article investigates the behavior of thermoelastic damping in a micro/nano beam subjected to an external magnetic field and an elastic matrix via small-scale theory. The material properties of the beam, such as Young's modulus, thermal conductivity, specific heat capacity, and coefficient of thermal expansion, are considered to analyze the physical aspects of thermoelastic damping. Further, the critical magnetic field strength of the nanobeam, which affects magnetic properties, is studied in relation to temperature, magnetic material properties, modenumber, and boundary conditions, leading to important findings for magnetomechanical systems and materials design. [ABSTRACT FROM AUTHOR]

Forced vibration is one of the essential behaviors of structures to predict the mechanical properties of various systems. Magneto-rheological (MR) or electro-rheological (ER) materials, due to many possible control-based applications, have gotten much attention in the oscillating system. Thus, in the present work, for the first time, the forced vibration of a conical shell made of three layers with an electrorheological (ER) core and reinforced composite with GPLs is investigated. The formulations are derived from the principle of Hamilton. With the aid of compatibility equations, the interfaces between the core and composite face sheets are simulated. The coupled hyperbolic differential quadrature method (HDQM) and Runge-Kutta solution procedure is employed to solve the coupled governing equations of the current system. The computational method's accuracy is confirmed by comparing computed results with those available in the literature. The results show that the number, weight fraction, thickness, and pattern of composite layers, electric/magnetic field, and geometry of the conical panel have an important role in the central deflection and phase plot of the current sandwich structure. [ABSTRACT FROM AUTHOR]

Ocean tide generated magnetic fields contain information about changes in ocean heat content and transport that can potentially be retrieved from remotely sensed magnetic data. To provide an important baseline towards developing this potential, tidal signals are extracted from 288 land geomagnetic observatory records having observations within the 50-year time span 1965–2015. The extraction method uses robust iteratively reweighted least squares for a range of models using different predictant and predictor assumptions. The predictants are the time series of the three vector components at each observatory, with versional variations in data selection and processing. The predictors fall into two categories: one using time-harmonic bases and the other that directly use lunar and solar ephemerides with gravitational theory to describe the tidal forces. The ephemerides predictors are shown to perform better (fitting more variance with fewer predictors) than do the time-harmonic predictors, which include the traditional 'Chapman–Miller method'. In fitting the oceanic lunar tidal signals, the predictants with the highest signal/noise involve the 'vertical' magnetic vector component following principle-component rotation. The best simple semidiurnal predictor is the ephemeris series of lunar azimuth weighted by the inverse-cubed lunar distance. More variance is fitted with predictors representing the lunar tidal potential and gradients calculated for each location/time. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

Electrically conductive seawater, moving in an ambient magnetic field, generates electromagnetic (EM) variations. Tsunamis are significant contributors to this phenomenon, inducing observable electric and magnetic fluctuations at seafloor and coastal observatories. While understanding of these occurrences in open oceans is robust, knowledge regarding their observation on islands remains limited. This article seeks, through the use of numerical experimentation, to enhance our understanding of tsunami-generated EM (TGEM) variations observed on islands. Utilizing simulations involving conical islands, we identify three key insights regarding EM intensity normalized by the height of incident tsunamis: (i) increased ocean depth surrounding the island amplifies tsunami EM signals, particularly for periods shorter than 20 min; (ii) magnetic field strength at the island is approximately comparable to that observed at the seafloor in the absence of the island when the island radius is smaller than 6 km; and (iii) electric field intensity at the island notably surpasses that observed at the seafloor, especially with smaller island radii (≤ 6 km). Additionally, we establish that employing the ratio of island radius to tsunami wavelength near the island coast facilitates the derivation of empirical functions for this phenomenon. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

During tsunamis, the interaction between moving seawater and the Earth's magnetic field generates a magnetic field detectable by electromagnetic sensors located on land or on the seafloor. In this study, we introduce new methods for estimating tsunami propagation direction and horizontal velocity fields using tsunami magnetic field data. We derive a transfer function that establishes a relationship between the tsunami magnetic field and the velocity field, emphasizing the alignment between the horizontal magnetic field and the tsunami's propagation direction. This transfer function was validated with data from the 2009 Samoa and 2010 Chile tsunamis. Our findings show that tsunami horizontal velocities and directions can be accurately determined from these magnetic fields. This advancement enables the use of tsunami magnetic fields to provide comprehensive data for tsunami warning systems and to improve the inversion of tsunami seismic sources. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

Ocean-bottom pressure gauges are widely used for tsunami observations due to their established accuracy and stability. Recent advancements reveal that the magnetic field fluctuates when a large tsunami passes over the ocean, suggesting potential alternatives to pressure gauges in the form of ocean-bottom electromagnetometers (OBEMs). This article offers a comprehensive synthesis of recent findings concerning tsunami magnetic fields and their utility in tsunami source estimation. In addition, we scrutinize the effectiveness of tsunami observations employing OBEMs. Despite the promise of electromagnetometers, it is worth noting that the background noise inherent in electromagnetic observations tends to be approximately 10 times greater than that of pressure observations within the critical tsunami frequency bands. The Earth's magnetic field sporadically disrupts tsunami magnetic fields, presenting a potential limitation to the utility of electromagnetometers in tsunami detection when compared with pressure gauges. Nevertheless, our investigation underscores the potential of electromagnetic observations in detecting tsunamis propagating over the ocean at magnitudes of a few centimetres. An invaluable advantage of electromagnetometers over pressure monitoring lies in their capability to observe tsunami velocity fields, suggesting a promising avenue for further research and development in tsunami observation technology. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

Electrical conductivity of the Earth's oceans is an important oceanographic parameter related through its dependence on temperature and salinity to the state of the ocean. The tidally induced magnetic field then provides a directly and globally observable physical variable affected by the ocean conductivity spatial and temporal distribution. This contribution addresses two topics of the impact of the ocean conductivity variations on the principal lunar semi-diurnal magnetic signals. First, using high-resolution forward modelling, we investigate the sensitivity of the magnetic field to seasonal conductivity variations. Here, we find that the differences between magnetic signatures calculated for individual monthly conductivity climatologies are small, and localized to the marginal seas of the global ocean. Second, we formulate an inverse method to provide a constraint for the ocean conductivity in the upper 1000 m of the ocean, and test it using a synthetic dataset, demonstrating a proof-of-concept for such an approach. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

The tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depend on the electrical properties of both seawater and the solid Earth, and thus can be used as proxies to study the seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This article presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including M2,N2,O1 and even Q1 , which was not reliably retrieved previously. Models are obtained through a robust least-squares analysis of magnetic field observations from the Swarm and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global three-dimensional (3D) electromagnetic simulations and place constraints on the conductivity of the sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

Satellite magnetic field observations have the potential to provide valuable information on dynamics, heat content and salinity throughout the ocean. Here, we present the expected spatio-temporal characteristics of the ocean-induced magnetic field (OIMF) at satellite altitude on periods of months to decades. We compare these to the characteristics of other sources of Earth's magnetic field, and discuss whether it is feasible for the OIMF to be retrieved and routinely monitored from space. We focus on large length scales (spherical harmonic degrees up to 30) and periods from one month up to 5 years. To characterize the expected ocean signal, we make use of advanced numerical simulations taking high-resolution oceanographic inputs and solve the magnetic induction equation in three dimensions, including galvanic coupling and self-induction effects. We find the time-varying ocean-induced signal dominates over the primary source of the internal field, the core dynamo, at high spherical harmonic degree with the cross-over taking place at degrees 13–19 depending on the considered period. The ionospheric and magnetospheric fields (including their Earth-induced counterparts) have most power on periods shorter than one month and are expected to be mostly zonal in magnetic coordinates at satellite altitude. Based on these findings, we discuss future prospects for isolating and monitoring long period OIMF variations using data collected by present and upcoming magnetic survey satellites. This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'. [ABSTRACT FROM AUTHOR]

The pitch-angle diffusion coefficient (PADC) quantifies the effect of pitch-angle scattering on charged particles propagating through turbulent magnetic fields and is a key ingredient in understanding the diffusion of these particles along the background magnetic field. Despite its significance, only a limited number of studies have calculated the PADC from test-particle simulations in synthetic magnetic turbulence, employing various, often quite different, techniques for this purpose. In this study, we undertake a comparative analysis of nine different methods for calculating the PADC from full-orbit simulations. Our objective is to find the strengths and limitations of each method and to determine the most reliable approach. Although all nine methods should theoretically yield comparable results, certain methods may be ill-suited for numerical investigations, while others may not be applicable under conditions of strong turbulence. Through this investigation, we aim to provide recommendations for best practices when employing these methods in future numerical studies of pitch-angle scattering. [ABSTRACT FROM AUTHOR]

This study utilised the Blume-Capel model to investigate the magnetic behaviour of a kesterite nanolattice by means of Monte Carlo simulations. The investigated nano-system, consisting of mixed spins atoms, exhibited magnetisation plateaus and level changes in response to the external magnetic field. These findings underscore the intricate interplay among the various physical parameters influencing magnetisation plateaus in the kesterite nanolattice, providing valuable insights for understanding the potential applications of this magnetic system. [ABSTRACT FROM AUTHOR]

This study reports on the electromagnetic (EM) wave absorption characteristics of M-type hexaferrite-rubber sheets, where Al was additionally substituted into high-performance permanent magnet compositions, Sr 0.2 La 0.4 Ca 0.4 Co 0.25 Fe 9.75 -x Al x O 19-d (LCCA-SrM, x = 0, 0.2, 0.4). While non-substituted SrFe 12 O 19 powder-rubber sheet had a ferromagnetic resonance frequency (f FMR) of 48.5 GHz, the LCCA-SrM (x = 0, 0.2, 0.4) rubber sheets showed increased f FMR values of 63.3, 66.2, and 68.5 GHz, respectively, with the increasing x values. The frequency of minimum reflection loss (f RLmin) also increased correspondingly with the change in f FMR. This significant increase in f FMR and f RLmin is attributed to the greatly enhanced magnetocrystalline anisotropy from the La-Ca-Co substitution in SrM and the incremental increase in magnetic anisotropy field (H ani) due to Al substitution. The absorption band (Δ f) satisfying RL < −10 dB, was 45.0–53.4 GHz for SrM, and 52.9–75, 50–75, and 59–74.2 GHz for the x = 0, 0.2, and 0.4 samples, respectively. The x = 0.2 sheets demonstrated the widest absorption, covering 50–75 GHz. This study is highly promising as it is the first to demonstrate the feasibility of developing an EM wave absorber sheet for frequencies above 50 GHz using hexaferrite powder synthesized via the solid-state method, which offers scalability and cost-efficiency for mass production. [ABSTRACT FROM AUTHOR]

Measurement of a jet geometry transition region is an important instrument of assessing the jet ambient medium properties, plasma bulk motion acceleration, parameters of a black hole, and location of a jet-launching radius. In this work, we explore the possibility of a presence of a core shift break, associated with the geometry and jet physical properties transition. We obtain the relations on the core shift offset jump due to a change in a core shift exponent. The condition of a proper frame magnetic field continuity and the core shift break can be used as an instrument to refine the magnetic field estimates upstream the break. This method is applied to the jet in NGC 315. We also argue that a local change in the plasma properties in the jet, for example due to the occurrence of a standing shock or a magnetic field reconnection, will also affect the dependence of the core shift on frequency. The properties of such a jump will be different than in the previous case. We propose to use the multifrequency core shift measurements to increase the number of sources with a detected jet shape break and to boost the accuracy of assessing the properties of a jet geometry transition region. [ABSTRACT FROM AUTHOR]

We report the results of a comprehensive study of the spectroscopic binary (SB2) system HD 34736 hosting two chemically peculiar (CP) late B-type stars. Using new and archival observational data, we characterize the system and its components, including their rotation and magnetic fields. Fitting of the radial velocities yields |$P_\mathrm{orb}=83\rm{.\!\!^{ {\rm{d}}}}219(3)$| and |$e=0.8103(3)$|⁠. The primary component is a CP He-wk star with |$T_{{\rm eff}A}$| |$\,\,=13000\pm 500$|  K and |$\upsilon _{\rm e}\sin i\,$| |$\,\,=75\pm 3$|  km s |$^{-1}\,$|⁠ , while the secondary exhibits variability of Mg and Si lines, and has |$T_{{\rm eff}B}$| |$\,\,=11500\pm 1000$|  K and |$\upsilon _{\rm e}\sin i\,$| |$\,\,=110$| –180 km s |$^{-1}\,$|⁠. Transiting Exoplanet Survey Satellite and Kilodegree Extremely Little Telescope photometry reveal clear variability of the primary component with a rotational period |$P_{\mathrm{rot}A}=1\rm{.\!\!^{ {\rm{d}}}}279\, 988\, 5(11)$|⁠ , which is lengthening at a rate of 1.26(6) s yr |$^{-1}$|⁠. For the secondary, |$P_{\mathrm{rot}B}=0\rm{.\!\!^{ {\rm{d}}}}522\, 693\, 8(5)$|⁠ , reducing at a rate of |$-0.14(3)$| s yr |$^{-1}$|⁠. The longitudinal component |$\langle B_{\rm z}\rangle$| of the primary's strongly asymmetric global magnetic field varies from |$-6$| to +5 kG. Weak spectropolarimetric evidence of a magnetic field is found for the secondary star. The observed X-ray and radio emission of HD 34736 may equally be linked to a suspected T Tau-like companion or magnetospheric emission from the principal components. Given the presence of a possible third magnetically active body, one can propose that the magnetic characteristics of the protostellar environment may be connected to the formation of such systems. [ABSTRACT FROM AUTHOR]

We present the first model aimed at understanding how the Meissner effect in a young neutron star affects its macroscopic magnetic field. In this model, field expulsion occurs on a dynamical time-scale, and is realized through two processes that occur at the onset of superconductivity: fluid motions causing the dragging of field lines, followed by magnetic reconnection. Focusing on magnetic fields weaker than the superconducting critical field, we show that complete Meissner expulsion is but one of four possible generic scenarios for the magnetic-field geometry, and can never expel magnetic flux from the centre of the star. Reconnection causes the release of up to |$\sim 5\times 10^{46}\, \mathrm{erg}$| of energy at the onset of superconductivity, and is only possible for certain favourable early-phase dynamics and for pre-condensation fields |$10^{12}\, \mathrm{G}\lesssim B\lesssim 5\times 10^{14}\, \mathrm{G}$|⁠. Fields weaker or stronger than this are predicted to thread the whole star. [ABSTRACT FROM AUTHOR]

We introduce the construction of polarized intensity cubes |$\mathbb{P}$| (RA, Dec, |$\Phi$|⁠) and their visualization as movies, as a powerful technique for interpreting Faraday structure. |$\mathbb{P}$| is constructed from maps of peak polarized intensity P(RA, Dec) with their corresponding Faraday depth maps |$\Phi$| (RA, Dec). We illustrate the extensive scientific potential of such visualizations with a variety of science use cases from ASKAP and MeerKAT, presenting models that are consistent with the data but not necessarily unique. We demonstrate how one can, in principle, distinguish between cube structures that originate from unrelated foreground screens from those due to magnetized plasmas local to the emitting source. Other science use cases illustrate how variations in the local |$n_{\rm e}$| B , and line-of-sight distance to the synchrotron emitting regions can be distinguished using Faraday rotation. We show, for the first time, how the line-of-sight orientation of active galactic nuclei (AGN) jets can be determined. We also examine the case of M87 to show how internal jet magnetic field configurations can be identified, and extend earlier results. We recommend using this technique to re-evaluate all previous analyses of polarized sources that are well-resolved both spatially and in Faraday depth. Recognizing the subjective nature of interpretations at this early stage, we also highlight the need and utility for further scientific and technical developments. [ABSTRACT FROM AUTHOR]

The design of synthetic soft matter capable of emulating the complex behaviors of living organisms, such as sensing and adapting to their environment, remains an important challenge in developing biomimetic materials. Functionalized hydrogels are ideal candidates for such materials since they are highly responsive to their environment and can be operated in water. In this work, we investigate a hybrid bonding hydrogel composed of peptide amphiphile supramolecular nanofibers covalently attached to a photoresponsive network, in which high-aspect-ratio ferromagnetic nanowires are aligned along the length of the sample, designed to swim under oscillating magnetic fields. This hybrid hydrogel swimmer can autonomously swim toward a light source by utilizing photoinduced interactions between supramolecular and covalent networks reminiscent of phototactic swimming in living systems. Using a combination of experimental techniques and a continuum model incorporating photochemistry, magnetoelasticity, and hydrodynamics, we explain the swimming mechanism and predict phototactic behavior. Our work highlights the potential role of hybrid bonding polymers, which leverage the interplay between supramolecular assemblies and covalent networks. We demonstrate how these polymers can be tailored to react dynamically to their environment, paving the way for developing intelligent and autonomous robotic systems. [ABSTRACT FROM AUTHOR]

Strong Dzyaloshinskii–Moriya interaction (DMI) and topological spin textures in two‐dimensional (2D) magnetic materials hold great potential for novel spin‐based information storage and processing. The current research efforts on topological magnetism are highly limited by insufficient magnetic strength, resulting in a narrow temperature‐external magnetic field (T‐B) phase diagram window. In this study, 2D Janus Cr2X3Y3 (X = Cl, Br, I; Y = S, Se, Te) monolayers are investigated by employing first‐principles calculations and atomic spin simulations, demonstrating desirable characteristics such as high Curie temperatures, significant DMI, and chiral spin textures benefited from the ligand substitution. Notably, stable field‐free room‐temperature magnetic skyrmions are observed in the Cr2Br3S3 monolayer and can persist under long‐range magnetic and temperature fields. Additionally, meron chains and skyrmion chains are preserved in the Cr2I3S3 monolayer under appropriate magnetic field and temperature. Based on the tight‐binding approximation, a ligand‐resolved six‐electron model is developed to distinguish superexchange interactions through X‐ and Y‐ligand hopping channels. This model elucidates the interplay between electronegativity and orbital degeneracy, shedding light on their influence on magnetic strength. This discovery highlights and expands the potential of ligand substitution for achieving high‐temperature topological magnetism in 2D magnetic materials. [ABSTRACT FROM AUTHOR]

We present 850 μ m polarization observations of the IC 348 star-forming region in the Perseus molecular cloud as part of the B-fields In STar-forming Region Observation survey. We study the magnetic properties of two cores (HH 211 MMS and IC 348 MMS) and a filamentary structure of IC 348. We find that the overall field tends to be more perpendicular than parallel to the filamentary structure of the region. The polarization fraction decreases with intensity, and we estimate the trend by power law and the mean of the Rice distribution fittings. The power indices for the cores are much smaller than 1, indicative of possible grain growth to micron size in the cores. We also measure the magnetic field strengths of the two cores and the filamentary area separately by applying the Davis–Chandrasekhar–Fermi method and its alternative version for compressed medium. The estimated mass-to-flux ratios are 0.45–2.20 and 0.63–2.76 for HH 211 MMS and IC 348 MMS, respectively, while the ratios for the filament are 0.33–1.50. This result may suggest that the transition from subcritical to supercritical conditions occurs at the core scale (∼0.05 pc) in the region. In addition, we study the energy balance of the cores and find that the relative strength of turbulence to the magnetic field tends to be stronger for IC 348 MMS than for HH 211 MMS. The result could potentially explain the different configurations inside the two cores: a single protostellar system in HH 211 MMS and multiple protostars in IC 348 MMS. [ABSTRACT FROM AUTHOR]

Although ultraluminous X-ray pulsars (ULXPs) are believed to be powered by super-Eddington accretion onto a magnetized neutron star (NS), the detailed structures of the inflow–outflow and magnetic fields are still not well understood. We perform general relativistic radiation magnetohydrodynamics (GR-RMHD) simulations of super-Eddington accretion flows onto a magnetized NS with dipole and/or quadrupole magnetic fields. Our results show that an accretion disk and optically thick outflows form outside the magnetospheric radius, while inflows aligned with magnetic field lines appear inside. When the dipole field is more prominent than the quadrupole field at the magnetospheric radius, accretion columns form near the magnetic poles, whereas a quadrupole magnetic field stronger than the dipole field results in the formation of a belt-like accretion flow near the equatorial plane. The NS spins up as the angular momentum of the accreting gas is converted into the angular momentum of the electromagnetic field, which then flows into the NS. Even if an accretion column forms near one of the magnetic poles, the observed luminosity is almost the same on both the side with the accretion column and the side without it, because the radiation energy is transported to both sides through scattering. Our model suggests that galactic ULXP Swift J0243.6+6124 has a quadrupole magnetic field of 2 × 1013 G and a dipole magnetic field of less than 4 × 1012 G. [ABSTRACT FROM AUTHOR]

In this work, I study the Casimir effect caused by a charged and massive scalar field that violates Lorentz symmetry in an aether-like and CPT even manner, by direct coupling between the field derivatives and two fixed orthogonal unit vectors. I call this a “double” Lorentz violation. The field will satisfy either Dirichlet or mixed boundary conditions on a pair of plane parallel plates. I use the generalized zeta function technique to examine the effect of a uniform magnetic field, perpendicular to the plates, on the Casimir energy and pressure. Three different pairs of mutual directions of the unit vectors are possible: timelike and spacelike perpendicular to the magnetic field, timelike and spacelike parallel to the magnetic field, spacelike perpendicular and spacelike parallel to the magnetic field. I fully examine all of them for both types of boundary conditions listed above and, in all cases and for both types of boundary conditions, I obtain simple expressions of the zeta function, Casimir energy and pressure in the three asymptotic limits of strong magnetic field, large mass, and small plate distance. [ABSTRACT FROM AUTHOR]

AbstractBackgroundMethodsResultsConclusionsHuman electromagnetic hypersensitivity (EHS) or electrosensitivity (ES) symptoms in response to anthropogenic electromagnetic fields (EMFs) at levels below current international safety standards are generally considered to be nocebo effects by conventional medical science. In the wider field of magnetoreception in biology, our understanding of mechanisms and processes of magnetic field (MF) interactions is more advanced.We consulted a range of publication databases to identify the key advances in understanding of magnetoreception across the wide animal kingdom of life.We examined primary MF/EMF sensing and subsequent coupling to the nervous system and the brain. Magnetite particles in our brains and other tissues can transduce MFs/EMFs, including at microwave frequencies. The radical pair mechanism (RPM) is accepted as the main basis of the magnetic compass in birds and other species, acting via cryptochrome protein molecules in the eye. In some cases, extraordinary sensitivity is observed, several thousand times below that of the geomagnetic field. Bird compass disorientation by radio frequency (RF) EMFs is known.Interdisciplinary research has established that all forms of life can respond to MFs. Research shows that human cryptochromes exhibit magnetosensitivity. Most existing provocation studies have failed to confirm EHS as an environmental illness. We attribute this to a fundamental lack of understanding of the mechanisms and processes involved, which have resulted in the design of inappropriate and inadequate tests. We conclude that future research into EHS needs a quantum mechanistic approach on the basis of existing biological knowledge of the magnetosensitivity of living organisms. [ABSTRACT FROM AUTHOR]

The mechanical and optical properties of liquid crystalline materials are largely dependent on the director profile. More complex soft robotic functions and programmed optical properties require spatially varying director profiles, ideally in 3D. However, it is challenging to achieve arbitrary director orientation with most established alignment techniques, as one needs to overcome surface interactions, use high electric or magnetic field strengths and temperatures. Another experimental difficulty is that there is a lack of suitable techniques that can be used to characterize the director in 3D. Here, this study first shows that the addition of 5CB to reactive mesogens permits cross‐linked liquid crystalline materials to be fabricated with a spatially varying 3D director profile using weak magnetic fields (0.13 T). This study also shows, how these can be characterized with an optical technique that uses a wedge cell to visualize the programmed 3D director profile. Interestingly, the method also permits the real‐time observation of the director. This work shows that it is possible to precisely control the director in 3D with low magnetic fields and that the dynamics can be directly observed, which facilitates potential applications of soft liquid crystalline (LC) gels and potentially also elastomers. [ABSTRACT FROM AUTHOR]

ABSTRACT We explore the potential of using magnetic cues as a novel approach to modulating ion channel expression, which could provide an alternative to traditional pharmacological interventions. Ion channels are crucial targets for pharmacological therapies, and ongoing research in this field continues to introduce new methods for treating various diseases. However, the efficacy of ion channel drugs is often compromised by issues such as target selectivity, leading to side effects, toxicity, and complex drug interactions. These challenges, along with problems like drug resistance and difficulties in crossing biological barriers, highlight the need for innovative strategies. In this context, the proposed use of magnetic cues to modulate ion channel expression may offer a promising solution to address these limitations, potentially improving the safety and effectiveness of treatments, particularly for long‐term use. Key developments in this area are reviewed, the relationships between changes in ion channel expression and magnetic fields are summarized, knowledge gaps are identified, and central issues relevant to future research are discussed. [ABSTRACT FROM AUTHOR]

Frequency tunable flexible piezo resonators exhibit significant potential for technological advances in wearable magnetic field sensing, futuristic wireless telecommunication devices, and flexible micro‐electromechanical systems. This study presents a multifunctional and flexible 0.67Pb(Mg1/3Nb2/3)O3−0.33PbTiO3(PMN‐PT)/Ni50Mn35In15 (Ni‐Mn‐In) multiferroic heterostructure‐based bulk acoustic wave (BAW) resonator fabricated over Kapton substrate. The fundamental resonance frequency (fR = 5.31 GHz) of the resonator is tunable with magnetic and electric fields. A significant change in resonance frequency (ΔfR) of 405 MHz has been achieved with 3.37 Hz nT−1 sensitivity using a direct current (DC) magnetic field of 1200 Oe, attributed to the delta‐E effect. The resonator displays a significant magnetic field tunability of 8.83%. Additionally, a substantial ΔfR of 360 MHz, 36 Hz µV−1 sensitivity and 6.78% tunability is attained with 10 V of DC bias voltage. The impact of magnetic field and DC bias voltage on the acoustic characteristics have been studied by fitting the resonance frequency curves with an equivalent modified Butterworth‐Van Dyke model. The fabricated BAW resonator exhibits outstanding flexibility with no discernible change in fR up to 2000 bending cycles. Such PMN‐PT/Ni‐Mn‐In‐based multiferroic BAW resonators displaying magnetic and electric field tunability are propitious for next‐generation flexible electronics and magnetic field sensors. [ABSTRACT FROM AUTHOR]

The synthesis of tertiary amines from alcohols (i.e. heptanol, dodecanol, cyclohexanol, benzylalcohol) and secondary amines (Me2NH (DMA), nPr2NH, nBu2NH) has been achieved in one step using trimetallic nanoparticles (NPs) displaying a magnetic core (Co4Ni6 and Fe3Ni7) and a Cu shell as both catalysts and heating agent in the presence of an alternating magnetic field. This methodology limits the redistribution reactions occurring on amines at high temperature leading to both much higher conversion and selectivity in the absence of solvent than usually observed using conventional heating. Moreover, Co4Ni6@Cu NPs were found moisture resistant, thereby allowing for performing the reaction with commercial DMA in water (40 % wt) with again high conversion and selectivity. [ABSTRACT FROM AUTHOR]

In homonuclear 1H NMR (nuclear magnetic resonance) spectra such as [1H,1H]‐NOESY (Nuclear Overhauser Enhancement spectroscopy), which is a historic cornerstone spectrum for biomolecular NMR structural biology, hundreds to thousands of cross peaks are present within a square of approximately 100 ppm2 leading to a lot of signal overlap. Spectral resolution is thus a limiting factor for unambiguous chemical shift assignment and data interpretation for dynamics and structure elucidation. Acquiring the spectra at higher magnetic fields such as at a 1.2 GHz 1H frequency helps to reduce spectral crowding, since resolution scales proportionally to the magnetic field strength. Here, we show that the linewidths of cross peaks in [1H,1H]‐NOESY and [1H,1H]‐TOCSY spectra can be further reduced by a factor of 2–3 in each dimension by super‐resolution spectroscopy. In the indirect dimension a composite exponential‐cosine weighted number of scans along the time increments are recorded and digitally smoothened by a window function, while in the direct dimension an exponential‐cosine window function is applied. Furthermore, measurement time saving by reduced‐acquisition super‐resolution (RASR) is introduced. Application to the 20 kDa protein KRAS shows that highly resolved NMR spectra suitable for automated analysis can be acquired within less than 3 hours. The method opens an avenue towards automated chemical shift assignment, dynamics and structure determination of unlabeled small and medium size proteins within 24 hours. [ABSTRACT FROM AUTHOR]

Magnetic hydrogels often suffer from low saturation magnetization and poor chemical and mechanical tolerance. Herein, we report magnetic nanoparticles (i.e. Fe3O4) grown in situ in an interpenetrating network containing both physical and covalent crosslinkages, which allowed the development of a high-water-content (∼95 wt%) and chemically (e.g. stable at extreme pH values of 1 and 12) and mechanically (Young's modulus of 550 kPa) stable magnetic hydrogel with high saturation magnetization (85 emu g−1). Moreover, the inherent high water content endowed the magnetic hydrogel with underwater superoleophobicity (OCA 160°), which enabled no-loss transport and mixing of liquid droplets as well as a cascade droplet (microliters) chemical reaction underwater through on-demand application of external magnetic field. [ABSTRACT FROM AUTHOR]