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Topologically nontrivial magnetic structures such as skyrmion lattices are well known in materials lacking lattice inversion symmetry, where antisymmetric exchange interactions are allowed. Only recently, topological multi-q magnetic textures that spontaneously break the chiral symmetry, for example, three-dimensional hedgehog lattices, were discovered in centrosymmetric compounds, where they are instead driven by frustrated interactions. Here we show that the bilayer perovskite Sr3Fe2O7, previously believed to adopt a simple single-q spin-helical order, hosts two distinct types of multi-q spin textures. Its ground state represents a novel multi-q spin texture with unequally intense spin modulations at the two ordering vectors. This is followed in temperature by a new "spin meta-cholesteric" phase, in which the chiral symmetry is spontaneously broken along one of the crystal directions, but the weaker orthogonal modulation melts, giving rise to intense short-range dynamical fluctuations. Shortly before the transition to the paramagnetic state, vortex-crystal order spanned by two equivalent q vectors emerges. This renders Sr3Fe2O7 an ideal material to study transitions among multiple-q spin textures in a centrosymmetric host. [ABSTRACT FROM AUTHOR]

Currently, solenoids are extensively utilized in various research fields due to their flexibility of fabrication and high magnetic field strength. However, the internal magnetic field of the solenoid itself exhibits some non-uniformity defects, which limits its application in some domains. This article proposes a novel single winding tightly wound solenoid structure with an improved magnetic field uniformity. To optimize the magnetic field near the aperture of the conventional solenoid, an auxiliary solenoid with a gradually changing diameter is included at each end of the solenoid. By adjusting different parameters of the auxiliary solenoid, the edge effect of the solenoid was reduced, and its overall magnetic field uniformity was improved. The optimization of the auxiliary solenoids is achieved through GA-KAN network techniques. Finite element simulation results with the optimized parameters show that the proportion of uniform areas can be improved by more than five times. The research results are a reference for high-precision electromagnetic sensing applications based on solenoids. [ABSTRACT FROM AUTHOR]

This research delves into the magnetic properties of six transition metal dihalide monolayers including MX2 (M = Ni, Cr X = Cl, Br, I) using density functional theory. We model the ground state of these samples using a simplified Heisenberg Hamiltonian, employing a supercell approach to derive the nearest and next-nearest exchange constants. Our results illuminate the influence of the electronic configuration of the transition metal element and the mass of the halogen atom on the magnetic ground state of the monolayers. Additionally, we provide an in-depth discussion on how strain impacts both the magnetic and electronic properties of the monolayers. Our study reveals that biaxial strain does not trigger a magnetic phase transition between ferromagnetic and antiferromagnetic states. Additionally, we observe that compressive strain elevates the Curie temperature and strengthens the exchange coupling. Conversely, these properties are diminished when the monolayer is subjected to tensile strain. The study enhances our understanding of the interplay between electronic structure and magnetic properties in transition metal dihalides, offering insights that could inform future material design and application in spintronic devices. [ABSTRACT FROM AUTHOR]

A comparative specific heat (C P ) study of GdPdAl and TbPdAl compounds crystallizing in hexagonal ZrNiAl-type crystal-structure (space group P 6 ¯ 2 m) is presented. Consistent with earlier reports both the compounds show the signature of two magnetic transitions in magnetization data. The magnitude of the jump in C P at the high-temperature transition at T N 1 (∼ 47 K) in GdPdAl indicates ordering into an amplitude-modulated magnetic structure. The analysis of magnetic entropy change (S 4 f ) showed that about one-half of total S 4 f occurs below low temperature transition at T N 2 . This is in contrast to that seen in TbPdAl, where only one-third of the entropy of transition occurs below T N 2 . For both the compounds S 4 f tends to saturate to about 84% (for T > T N 1 ) of that expected for complete ordering of the rare earth moments, indicating incomplete removal of geometrical frustration. [ABSTRACT FROM AUTHOR]

Organic spintronics (OS), which focuses on utilizing the spin degree of freedom in organic materials, has been a fascinating topic because of its technological aspects and future applications. In-plane uniaxial magnetic anisotropy (UMA) is becoming increasingly important in the rapidly developing field of OS. In this study, Cobalt (Co) films were deposited with varying thicknesses on the Tris (8-hydroxyquinolinato) aluminium (Alq3) layer to investigate the evolution of magnetism and UMA. Magnetic measurements and simultaneous domain imaging have been done using the magneto-optic Kerr effect by varying the azimuthal angle between the easy axis of magnetization and the applied magnetic field. It was discovered that the bilayer exhibits a well-defined UMA in the film plane upon forming a continuous Co film with a thickness of around 10 nm. Structural and morphological properties of all the Co/Alq3 bilayers were studied using grazing-incidence small-angle X-ray scattering and wide-angle X-ray scattering measurements at synchrotron radiation source, P03 beamline PETRA-III, Germany. The combined analysis revealed that in contrast to the inorganic magnetic polycrystalline thin films, where the UMA originates mainly due to the stress, the origin of UMA in Co/Alq3 is attributed to the magnetocrystalline anisotropy caused by c-axis (Co (002)) preferential orientation. The surface free energy of Alq3 is less than that of Co; therefore, the growth of Co starts with island formation, which coalescences with increasing thickness. The observed structure orientation may be attributed to minimizing the magnetoelastic energies due to coalescence known as the zipping effect. The absence of UMA in films with lower thickness film (~5 nm) is understood in terms of random short-range stress caused by isotropic pinning due to the diffused interface. [ABSTRACT FROM AUTHOR]

The results of the spectral observation analysis in the Hα line of a site of active region NOAA 11 024, which has been in the main phase of development given its sharply increased activity, are discussed. The studied site (its length is 10 Mm) has been located in the region of a new serpentine magnetic flow emergence. An arch filament system (AFS) has been formed on it, under which an Ellerman bomb (EB) emerged and developed, and a pore formed at a distance of approximately 7.2 Mm from the EB. The evolution of the AFS is studied, and the formation and development of all Hα-ejections that formed in its magnetic loops during the observations are investigated. Spectral data with high spatial (approximately 1″) and temporal (approximately 3 s) resolution were obtained with the THEMIS French–Italian solar telescope (Tenerife, Spain) on July 4, 2009. The observation time is 20 min (to 9:52–10:11 UT). We use the spectral region that contains the central part of the Hα chromospheric line. In all spectra, Hα ejections (surges) are visible both in the long wavelength and short wavelength wings of the absorption line. The changes in the Stokes I profiles shape are studied, which are very diverse and appreciably different from the profile for the undisturbed chromosphere. Depending on whether the ejection moved to the upward direction or to the downward one, the profile component corresponding to it is projected onto the blue or red line wing. Substantially broadened and dual lobed profiles appear close to the end of the observations, which indicates that both downward and upward plasma flows exist nearby. It is found that surges can be comprised of several jets that are formed during successive and periodic magnetic reconnections. Doppler shifts of the profile components are used to calculate the line-of-sight velocities (Vlos) of chromospheric matter in surges. The changes in the Vlos along the cross section of the surge jets at the place of their maximum intensity are analyzed. The Vlos of jets are different and probably depend on the magnetic field structure in the surge and the surrounding environment. The direction of jet movement is also different, since it depends on the phase of surge development. Most of the curves of Vlos changes consist of several segments. This indicates that the large jets are composed of several smaller jets, i.e., they had a fibrous structure. The flows of ascending and descending surges often occur simultaneously and coincide in time with the increase of the EB brightness. A vortex motion of the plasma is observed in one of the surges for approximately 3 min, as evidenced by the inclined dark streaks in the spectra. At the instant of the greatest brightness of the EB, there are seven surges in the studied site of AR, and the plasma moves downward with Vlos up to 77 km/s in three of them and upward with a much lower Vlos up to –35 km/s in five of them. During our observations, the maximum upward velocities of the chromospheric matter in the surges reach –110 km/s, and the downward velocities reach 90 km/s. In the upper part of the magnetic loops, the plasma velocities vary between –25 km/s and 22 km/s. The Vlos values in the site without active formations do not exceed ±2 km/s. It is also analyzed whether the processes of AFS evolution and EB development phases are related. The study is based on a detailed analysis of observational data obtained with high spatial and temporal resolutions, which allowed the authors to better understand the dynamics of the evolution of the arch filament system under which an Ellerman bomb has emerged and developed, and to reveal the features of the formation and development of surges that form in its magnetic loops. They are probably the result of successive and periodic magnetic reconnections, which are associated with the emergence of a new serpentine magnetic flux and occur when its loops interact with the preexisting magnetic field surrounding the active region or between the magnetic loops of the flux itself. [ABSTRACT FROM AUTHOR]

Mn–Zn ferrite (Mn0.6Zn0.4Fe2O4) nanoparticles were synthesized using a modified sol–gel method at lower annealing temperature (minimum to 300 ℃). The experimental results and analysis indicate that these nanoparticles exhibit excellent soft magnetic properties with the ultra-high saturation magnetization (Ms) up to 45.1 emu/g, demonstrating the significant potential applications for biomedical industry, electronic devices, and wastewater decontamination, etc. More interestingly, Mn0.6Zn0.4Fe2O4 nanoparticles exhibit unique size-dependent magnetic property, where the saturation magnetization (Ms) decreases with the decreasing crystalline size. Furthermore, there exists a linear proportional relationship between Ms and the reciprocal of the crystalline size (1/D). A novel theoretical model is subsequently proposed in the paper to elucidate the size-dependent magnetic property. Such magnetic nanoparticles composed of small-sized nanocrystalline can be analogized to a "core–shell" structure, in which the surface or interfacial state increases rapidly in proportion to the overall system. The magnetic moments are irregularly arranged in the "shell" that consists of abundant surface or interfacial states, so-called 'magnetic disorder shell'. On the contrary, the ferrite "core" is a ferrimagnetically ordered region with a regular arrangement of magnetic moments, which is called as 'magnetic order core'. With the decrease of crystalline size, the proportion of the 'magnetic disorder shell' increases. As a result, the magnetic property of the whole ferrite nanoparticle is weakened. It is believed that the present works contribute to the advancement of comprehending the correlation between the structure and property in magnetic nanoparticles. [ABSTRACT FROM AUTHOR]

Materials exhibiting a spontaneous reversal of spin chirality have the potential to drive the widespread adoption of chiral magnets in spintronic devices. Unlike the majority of chiral magnets that require the application of an external field to reverse the spin chirality, we observe the spin chirality to spontaneously reverse in the topological magnet EuAl4. Using resonant elastic x-ray scattering we demonstrate that all four magnetic phases in EuAl4 are single-k, where the first two magnetic phases are characterized by spin density wave order and the last two by helical spin order. A single spin chirality was stabilised across the 1mm2 sample, and the reversal of spin chirality occurred whilst maintaining a helical magnetic structure. At the onset of the helical magnetism, the crystal symmetry lowers to a chiral monoclinic space group, explaining the asymmetry in the chiral spin order, and establishing a mechanism by which the spin chirality could reverse via magnetostructural coupling. The reversal of spin chirality in the absence of any externally applied field would substantially broaden the use of chiral magnets for applications in spintronic devices. In this manuscript the authors demonstrate the spontaneous reversal of spin chirality in the topological magnet EuAl4 using resonant elastic x-ray scattering. [ABSTRACT FROM AUTHOR]

Materials exhibiting a spontaneous reversal of spin chirality have the potential to drive the widespread adoption of chiral magnets in spintronic devices. Unlike the majority of chiral magnets that require the application of an external field to reverse the spin chirality, we observe the spin chirality to spontaneously reverse in the topological magnet EuAl4. Using resonant elastic x-ray scattering we demonstrate that all four magnetic phases in EuAl4 are single-k, where the first two magnetic phases are characterized by spin density wave order and the last two by helical spin order. A single spin chirality was stabilised across the 1mm2 sample, and the reversal of spin chirality occurred whilst maintaining a helical magnetic structure. At the onset of the helical magnetism, the crystal symmetry lowers to a chiral monoclinic space group, explaining the asymmetry in the chiral spin order, and establishing a mechanism by which the spin chirality could reverse via magnetostructural coupling. The reversal of spin chirality in the absence of any externally applied field would substantially broaden the use of chiral magnets for applications in spintronic devices. In this manuscript the authors demonstrate the spontaneous reversal of spin chirality in the topological magnet EuAl4 using resonant elastic x-ray scattering. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) van der Waals (vdW) magnets have sparked widespread attention due to their potential in spintronic applications as well as in fundamental physics. Ferromagnetic vdW compound Fe3GeTe2 (FGT) and its Ga variants have garnered significant interest due to their itinerant magnetism, correlated states, and high magnetic transition temperature. Experimental studies have demonstrated the tunability of FGT's Curie temperature, TC, through adjustments in quintuple layer numbers (QL) and carrier concentrations, n. However, the underlying mechanism remains elusive. In this study, we employ molecular beam epitaxy (MBE) to synthesize 2D FGT films down to 1 QL with precise layer control, facilitating an exploration of the band structure and the evolution of itinerant carrier density. Angle-resolved photoemission spectroscopy (ARPES) reveals significant band structure changes at the ultra-thin limit, while first-principles calculations elucidate the band evolution from 1 QL to bulk, largely governed by interlayer coupling. Additionally, we find that n is intrinsically linked to the number of QL and temperature, with a critical value triggering the magnetic phase transition. Our findings underscore the pivotal role of band structure and itinerant electrons in governing magnetic phase transitions in such 2D vdW magnetic materials. [ABSTRACT FROM AUTHOR]

Magnetic topological insulators exhibit unique electronic states due to the interplay between the electronic topology and the spin structure. The antiferromagnetic metal EuIn2As2 is a prominent candidate material in which exotic topological phases, including an axion insulating state, are theoretically predicted depending on the magnetic structure of the Eu2+ moments. Here, we report experimental results of the nuclear magnetic resonance (NMR) measurements of all the nuclei in EuIn2As2 to investigate the coupling between the magnetic moments in the Eu ions and the conduction electrons in In2As2 layers and the magnetic structure. The 75As and 115In NMR spectra observed at zero external magnetic fields reveal the appearance of internal fields of 4.9 and 3.6 T, respectively, at the lowest temperature, suggesting a strong coupling between the conduction electrons in the In2As2 layer and the ordered magnetic moments in the Eu ions. The 75As NMR spectra under in-plane external magnetic fields show broad distributions of the internal fields produced by an incommensurate fan-like spin structure which turns into a forced ferromagnetic state above 0.7 T. We propose a spin reorientation process that an incommensurate helical state at zero external magnetic field quickly changes into a fan state by applying a slight magnetic field. [ABSTRACT FROM AUTHOR]

The effect of plastic deformation on the structure, phase composition, and magnetic parameters of maraging steel 08Kh15N5D2T was studied. The hysteresis, electromagnetic, and magnetostrictive characteristics were measured both in a closed magnetic circuit using the Remagraph C-500 hysteresis graph and by means of attached magnetic transducers. The regions of plastic deformation are experimentally determined in which the behavior of the magnetic parameters and their relationship vary with changes in structure and phase composition. Informative parameters are proposed that can be used to control variations in the structure and phase composition of the studied steel. [ABSTRACT FROM AUTHOR]

The problem of coronal heating is one of the fundamental problems of solar physics. At present, it is again attracting great interest due to the appearance of a large amount of observational data of high spatial and temporal resolution. These data made it possible to diagnose plasma parameters from observations of waves and oscillations in coronal magnetic structures and, moreover, to introduce analytical constraints on the coronal heating function. In this paper, we propose an approach allowing us to impose constraints on the heating function based on data on the gravitational stratification of the solar atmosphere. The developed algorithm is applied to the altitude profiles of temperature and density in several regions of the solar corona obtained from direct modeling of EUV radiation from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). Assuming that the heating function is a power function of temperature and density, we determine the domain of power-index constraints allowing us to realize the observed altitude profiles. The obtained results are combined with the conditions of stability for the entropy and magnetoacoustic modes, to narrow the region of possible parameters further. [ABSTRACT FROM AUTHOR]

Ultra-small iron oxide nanoparticles (USNPs) have attracted particular attention in the past 15 years as perspective contrast agents for MRI. Unfortunately, the synthesis of such small nanoparticles with high contrast properties and water dispersibility is still challenging. This paper presents a study on the influence of synthetic conditions on the structure and the properties of hydrophilic iron oxide nanoparticles obtained by a simple single-step thermal decomposition in diethylene glycol at 230–235 °C. The samples were studied using X-ray diffraction, Mössbauer and infra-red spectroscopy, transmission electron microscopy, vibrating sample magnetometry, MRI, and dynamic light scattering. All the obtained samples are of spinel structure (Fd-3 m), specific to both magnetite and maghemite. With an increase in the synthesis time from 1 to 8 h, the crystallite size of the series with C(Fe(acac)3) = 30 mM changed from 1.8 ± 0.2 to 4.7 ± 0.5 nm, the average size according to TEM changed from 3.3 ± 0.8 to 3.8 ± 0.4 nm, and the saturation magnetization from 13.9 ± 0.3 to 83.3 ± 1.7 A•m2/kg, which is close to the values of bulk iron oxide. The same tendency was revealed with the increase in the concentration of C(Fe(acac)3) from 30 to 120 mM for 1 h of synthesis. An increase in the synthesis time for 60- and 120-mM solutions did not significantly change the crystallite size and the magnetic properties. It was shown that the samples obtained using this approach have unexpectedly high values of r2-relaxivity, up to 235 mM−1•s−1, which the highest published for USNPs. The studied method of water-soluble USNPs is promising for use in creating T2-contrast agents for MRI. [ABSTRACT FROM AUTHOR]

A dichlorophenyl substituted nitronyl nitroxide radical 2-(2,6-dichlorophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L) is prepared, its structure and magnetic properties are studied. It is shown that the interaction of bis(hexafluoroacetylacetonato)copper(II) [Cu(hfac)2] with L leads to the formation of the {[Cu(hfac)2][Cu(hfac)2L2]} heterospin complex whose crystal structure consists of pseudo-polymer chains formed by alternating single-spin [Cu(hfac)2] and three-spin [Cu(hfac)2L2] fragments. It is established that the temperature dependence of magnetic susceptibility of {[Cu(hfac)2][Cu(hfac)2L2]} is determined by ferromagnetic exchange interactions between unpaired electrons of Cu(II) ions and the axially coordinated L in three-spin fragments. [ABSTRACT FROM AUTHOR]

The study of manganese-substituted barium hexaferrite BaFe12–xMnxO19 with a degree of substitution x from 0 to 2 is presented. The samples are prepared by the solid-phase synthesis at a temperature of 1275 °C and isothermal holding for 5 h. The elemental composition of the samples is determined using energy dispersive spectroscopy, which shows good correspondence with the specified calculated compositions. Monophasicity of all synthesized samples is confirmed by powder X-ray diffraction. In addition, the effect of manganese substitution on the unit cell parameters is estimated. In the differential scanning calorimetry study of the properties, the effect of manganese substitution for iron on the Curie points of the samples obtained, which are caused by changes in the magnetic structures of the produced materials, is determined. The results indicate a significant effect of manganese substitution on the properties of barium hexaferrite and confirm the possibility to control the substitution process for the production of materials with adjustable magnetic characteristics. [ABSTRACT FROM AUTHOR]

Gold-coated magnetic iron oxide nanoparticles (ION) (Fe3O4@Au) were synthesized and utilized as catalyst for alcohol oxidation with tert-butyl hydroperoxide (TBHP). First, iron oxide magnetic nanoparticles (Fe3O4) were prepared and finally coated with a thin layer of gold. Structure and composition of Fe3O4@Au nanocatalyst were characterized by XRD, TGA, and FT-IR analysis. Size and morphology and size of particles were determined through TEM. Surface properties and topographies of coated nanoparticles were investigated by the AFM technique. The magnetic properties of Fe3O4 and Fe3O4@Au nanoparticles were measured by VSM technique. After confirming the structure of gold-coated magnetic ION, its performance for the oxidation of various aliphatic and aromatic alcohols with TBHP was studied in water. Finally, the reusability of Fe3O4@Au nanocatalyst was evaluated after five consecutive cycles in the 4-methoxybenzyl alcohol oxidation. The measured results revealed that the gold-coated iron oxide magnetic nanoparticles can be reused well in the oxidation processes of alcohols with high efficiency. [ABSTRACT FROM AUTHOR]

Adding trace Ni elements and annealing in a magnetic field improves the soft magnetic properties of the Finemet. After changing the Ni content to control the composition of the alloy system and change the pitch of stripes of the magnetic domains, Fe73.5Si14.7B7.6Nb3Cu1Ni0.2 nanocrystalline ribbon with excellent soft magnetic properties was obtained. In this work, transverse magnetic field annealing (TA) was performed on Fe73.5Si14.7B7.6Nb3Cu1Ni0.2 nanocrystalline ribbon cores (NRCs), and the magnetic properties and magnetic domain structure were compared in detail with those after non-field annealing (NA), and the mechanism of the improvement of soft magnetic properties by TA was elucidated. The soft magnetic properties of the cores were adjusted by varying the Ni composition, annealing temperature, and magnetizing temperature. The experimental results show that the core loss (Ps) of the NRCs is reduced by 24.76% (100 kHz, high frequency) and the coercivity (Hc) is 0.854 A/m after 30 min of TA at 400°C compared to the NA sample. TA optimizes the soft magnetic performance of NRCs by optimizing the domain structure and broadening the size of the domain. These results can provide a good guide for optimizing the performance of NRCs with low Ps at high frequency. [ABSTRACT FROM AUTHOR]

The study of manganese-substituted barium hexaferrite BaFe12–xMnxO19 with a degree of substitution x from 0 to 2 is presented. The samples are prepared by the solid-phase synthesis at a temperature of 1275 °C and isothermal holding for 5 h. The elemental composition of the samples is determined using energy dispersive spectroscopy, which shows good correspondence with the specified calculated compositions. Monophasicity of all synthesized samples is confirmed by powder X-ray diffraction. In addition, the effect of manganese substitution on the unit cell parameters is estimated. In the differential scanning calorimetry study of the properties, the effect of manganese substitution for iron on the Curie points of the samples obtained, which are caused by changes in the magnetic structures of the produced materials, is determined. The results indicate a significant effect of manganese substitution on the properties of barium hexaferrite and confirm the possibility to control the substitution process for the production of materials with adjustable magnetic characteristics. [ABSTRACT FROM AUTHOR]

The effects of planar biaxial strain on the stability, electronic structure, and magnetic properties of monolayer CrS2 systems doped with nitrogen group elements have been investigated based on first principles. Calculations of energy differences, formation energies, bond population, and binding energies indicate the relative stability of the system. Calculations of the electronic structure (energy band structure, density of states, and differential charge density distribution) and magnetic parameters (spin density profiles, single-atom magnetic moments, and total magnetic moments of the system) show that atomic doping in conjunction with strain induces several excellent electronic properties of the system, such as magnetic semiconductors and semimetals. The bandgap of the spin-down channel increases with tensile strain and decreases with compressive strain. In addition, we note that the total magnetic moments of the monolayer CrS2 system and the N atom-doped system decrease with tensile strain and show an increase with compressive strain. The above results provide a reference for further investigation of this material and its application in nanospin devices. [ABSTRACT FROM AUTHOR]

Although chromium trihalides are widely regarded as a promising class of two-dimensional magnets for next-generation devices, an accurate description of their electronic structure and magnetic interactions has proven challenging to achieve. Here, we quantify electronic excitations and spin interactions in CrX3 (X = Cl, Br, I) using embedded many-body wavefunction calculations and fully generalized spin Hamiltonians. We find that the three trihalides feature comparable d-shell excitations, consisting of a high-spin 4A2 ( t 2 g 3 e g 0 ) ground state lying 1.5–1.7 eV below the first excited state 4T2 ( t 2 g 2 e g 1 ). CrCl3 exhibits a single-ion anisotropy Asia = − 0.02 meV, while the Cr spin-3/2 moments are ferromagnetically coupled through bilinear and biquadratic exchange interactions of J1 = − 0.97 meV and J2 = − 0.05 meV, respectively. The corresponding values for CrBr3 and CrI3 increase to Asia = −0.08 meV and Asia= − 0.12 meV for the single-ion anisotropy, J1 = −1.21 meV, J2 = −0.05 meV and J1 = −1.38 meV, J2 = −0.06 meV for the exchange couplings, respectively. We find that the overall magnetic anisotropy is defined by the interplay between Asia and Adip due to magnetic dipole–dipole interaction that favors in-plane orientation of magnetic moments in ferromagnetic monolayers and bulk layered magnets. The competition between the two contributions sets CrCl3 and CrI3 as the easy-plane (Asia + Adip >0) and easy-axis (Asia + Adip <0) ferromagnets, respectively. The differences between the magnets trace back to the atomic radii of the halogen ligands and the magnitude of spin–orbit coupling. Our findings are in excellent agreement with recent experiments, thus providing reference values for the fundamental interactions in chromium trihalides. [ABSTRACT FROM AUTHOR]

The spontaneous formation of dynamic spiral domains, which is a type of the self-organization of a magnetic domain structure, in a thin ferromagnetic film exposed to the alternating magnetic field has been revealed in the numerical simulation within the phenomenological Ginzburg–Landau model. This simulation qualitatively reproduces the following features of the self-organization of the domain structure experimentally observed in iron garnet films: the existence of two types of spiral domains (single and double spiral domains) and the formation of the close packing of spiral domains and their chains in an inhomogeneous magnetic field. A mechanism of the formation of spiral domains without gyrotropic force has been described. [ABSTRACT FROM AUTHOR]

Purpose: Gadolinium (Gd)-based contrast agents are primarily used for contrast-enhanced magnetic resonance lymphangiography (MRL). However, overcoming venous contamination issues remains challenging. This study aims to assess the MRL efficacy of the newly developed iron-based contrast agent (INV-001) that is specially designed to mitigate venous contamination issues. The study further explores the optimal dosage, including both injection volume and concentration, required to achieve successful visualization of the popliteal lymph nodes and surrounding lymphatic vessels. Procedures. All animals utilized in this study were male Sprague–Dawley (SD) rats weighing between 250 and 300 g. The contrast agents prepared were injected intradermally in the fourth phalanx of both hind limbs using a 30-gauge syringe in SD rats. MRL was performed every 16 min on a coronal 3D time-of-flight sequence with saturation bands using a 9.4-T animal machine. Results: Contrary to Gd-DOTA, which exhibited venous contamination in most animals irrespective of injection dosages and conditions, INV-001 showed no venous contamination. For Gd-DOTA, the popliteal lymph nodes and lymphatic vessels reached peak enhancement 16 min after injection from the injection site and then rapidly washed out. However, with INV-001, they reached peak enhancement between 16 and 32 min after injection, with prolonged visualization of the popliteal lymph node and lymphatic vessels. INV-001 at 0.45 μmol (15 mM, 30 μL) and 0.75 μmol (15 mM, 50 μL) achieved high scores for qualitative image analysis, providing good visualization of the popliteal lymph nodes and lymphatic vessels without issues of venous contamination, interstitial space enhancement, or lymph node enlargement. Conclusion: In MRL, INV-001, a novel T1 contrast agent based on iron, enables prolonged enhancement of popliteal lymph nodes and lymphatic vessels without venous contamination. [ABSTRACT FROM AUTHOR]

High temporal resolution of measurements of the magnetic field and plasma of Mars is provided by observations on the Mars Atmosphere and Volatile Evolution (MAVEN; Jakosky et al., 2015) satellite, making it possible to analyze thin layers of the plasma envelope of Mars. This paper describes the magnetic structure associated with the daytime Martian magnetopause. It was shown that the solar wind passing through the shock wave on the dayside of Mars does not directly interact with the Martian ionosphere. A layer of plasma and magnetic field 200–300 km thick forms the daytime magnetosphere, which is the region between the magnetosheath and the ionosphere (Vaisberg and Shuvalov, 2020). There are two types of daytime magnetosphere: (1) the more common type of magnetosphere consists of heated and accelerated O+ ions and , located between the ionosphere and the flowing hot stream of Mars; (2) another type of daytime magnetosphere consists of accelerated O+ ions and in the magnetosheath, where they form a continuing accelerated beam, forming a plume. Between the magnetosheath and the magnetosphere there is a magnetic structure that rotates, almost without changing its size. This structure is located in the second part of the np/(np + nh) transition from ~1 to ~10–2. The transition between the magnetosheath and magnetosphere occurs smoothly, both in energy density and in ion composition, with a decrease in the proton flux and an increase in the heavy ion flux. [ABSTRACT FROM AUTHOR]

Solar loops are hot and magnetic structures that often have transverse displacements. In this research, we study the characteristics of three solar loops using the images observed in the radiation region with the Hinode/XRT telescope on 11 September 2017. Fluctuations of solar loops can be traced using two methods: image and spectral processing. In the first method, displacements and disturbances are measured in images, while in the second method, periodic patterns are searched in Doppler shifts by spectrometers. Our analysis method is based on image processing and solar loop seismology. In this method, the time slices can be prepared from the images and then analyzed using the wavelet method. The measurement results of time series for three loops with lengths of 113040, 79128, and 62800 km were obtained in the range of 3–18, 3–6, and 3–16 min, respectively. The phase velocity of these oscillations was calculated in the range of 209–1256, 438–879.2, and 130–697.7 km s−1 for three loops, respectively. Also, Alfven speeds were determined as 150–1012, 316–708.8, and 94–562.5 km s−1. The magnetic field related to these fluctuations was calculated by the seismological method with the approximation of the thin cylindrical model for the loops measuring 2.47–16.52, 3.6–11.56, and 1.1–9.18 Gauss. Our findings suggest that oscillating movements in the loops can be interpreted as Kink transverse oscillations. [ABSTRACT FROM AUTHOR]

Multiferroic Ba2CuGe2O7 was anticipated as a potential member of the exciting group of materials hosting a skyrmion or vortex lattice because of its profound Dzyaloshinskii–Moriya interaction (DMI) and the absence of single ion anisotropy (SIA). This phase, however, could not be evidenced and instead, it exhibits a complex incommensurate antiferromagnetic (AFM) cycloidal structure. Its sister compound Ba2MnGe2O7, in contrast, is characterized by a relatively strong in-plane exchange interaction that competes with a non-vanishing SIA and the weak DMI, resulting in a quasi-two-dimensional commensurate AFM structure. Considering this versatility in the magnetic interactions, a mixed solid solution of Cu and Mn in Ba2Cu1−xMnxGe2O7 can hold an interesting playground for its interactive DMI and SIA depending on the mixed spin states of the transition metal ions towards the skyrmion physics. Here, we present a detailed study of the micro- and macroscopic spin structure of the Ba2Cu1−xMnxGe2O7 solid solution series using high-resolution neutron powder diffraction techniques. We have developed a remarkably rich magnetic phase diagram as a function of the applied magnetic field and x, which consists of two end-line phases separated by a potentially quantum-critical phase at x = 0.57. An AFM conical structure at zero magnetic field is demonstrated to persist up to x = 0.50. Our results provide crucial information on the spin structure and magnetic properties, which are necessary for the general understanding and theoretical developments on multiferroicity in the frame of skyrmion type or frustrated AFM lattice where DMI and SIA play an important role. [ABSTRACT FROM AUTHOR]

In weak-coupling wireless power transmission, increasing operating frequency, and incorporating metamaterials, resonance structures or ferrite cores have been explored as effective solutions to enhance power efficiency. However, these solutions present significant challenges that need to be addressed. The increased operating frequency boosts ferrite core losses when it exceeds the working frequency range of the material. Existing metamaterial-based solutions present challenges in terms of requiring additional space for slab installation, resulting in increased overall size. In addition, limitations are faced in using Snell's law for explaining the effects of metamaterial-based solutions outside the transmission path, where the magnetic field can not be reflected or refracted. To address these issues, in this work, the concept of a negative equivalent magnetic reluctance structure is proposed and the metamaterial theory is extended with the proposed magnetic reluctance modelling method. Especially, the negative equivalent magnetic reluctance structure is effectively employed in the weak-coupling wireless power transfer system. The proposed negative equivalent magnetic reluctance structure is verified by the stacked negative equivalent magnetic reluctance structure-based transformer experiments and two-coil mutual inductance experiments. Besides, the transmission gain, power experiments and loss analysis experiments verify the effectiveness of the proposed structure in the weak-coupling wireless power transfer system. Metamaterial applications face challenges in managing magnetic fields beyond direct transmission paths where they cannot be reflected or refracted. Here, authors propose and test a Negative Equivalent Magnetic Reluctance model to improve efficiency in weak-coupling wireless power transmission. [ABSTRACT FROM AUTHOR]

The monitoring of currents in the abyssal ocean is an essential foundation of deep-sea research. The state-of-the-art current meter has limitations such as the requirement of a power supply for signal transduction, low pressure resistance, and a narrow measurement range. Here, we report a fully integrated, self-powered, highly sensitive deep-sea current measurement system in which the ultra-sensitive triboelectric nanogenerator harvests ocean current energy for the self-powered sensing of tiny current motions down to 0.02 m/s. Through an unconventional magnetic coupling structure, the system withstands immense hydrostatic pressure exceeding 45 MPa. A variable-spacing structure broadens the measuring range to 0.02–6.69 m/s, which is 67% wider than that of commercial alternatives. The system successfully operates at a depth of 4531 m in the South China Sea, demonstrating the record-deep operations of triboelectric nanogenerator-based sensors in deep-sea environments. Our results show promise for sustainable ocean current monitoring with higher spatiotemporal resolution. This study shows a self-powered deep-sea current measurement system using a triboelectric nanogenerator (TENG) that measures currents from 0.02 to 6.69 m/s and withstands over 45 MPa pressure. Successful operation at 4531 m depth in the South China Sea is demonstrated. [ABSTRACT FROM AUTHOR]

Chromium tri-iodide (CrI3) is a prototypical ferromagnetic van der Waals insulator with its genuinely two-dimensional (2D) long-range magnetic order below 45 K demonstrated recently. The underlying magnetic anisotropy has not been completely understood while both the Dzyaloshinskii-Moriya (DM) interaction and the Kitaev − Γ type interaction have been considered as the relevant magnetic Hamiltonian. In addition, the relation between the crystal structure and the magnetic order needs to be further elucidated concerning their possible coupling in few-layer samples and in the topmost surface layers of bulk samples. Here, we investigate these issues via temperature- and magnetic field-dependent terahertz spectroscopy on bulk CrI3 single crystals, focusing on the dynamics of ferromagnetic resonances (FMRs) and optical phonons in the terahertz (THz) region from 4 to 120 cm−1 (from 0.5 to 15 meV). We narrow down the possible ranges of the interaction parameters such as the off-diagonal symmetric terms and the single-ion anisotropy. The accurate values of these parameters significantly constrain the magnitude of possible Kitaev − Γ exchange interaction and the topological magnon gap. Moreover, the structure-magnetism relationship was critically analyzed based on the temperature- and field-dependences of two E u in-plane optical phonon modes, which shows that the commonly believed structural phase diagram of CrI3, derived from surface-preferential data, has to be seriously modified. [ABSTRACT FROM AUTHOR]

Spontaneous symmetry breaking and emergent polar order are each of fundamental importance to a range of scientific disciplines, as well as generating rich phase behaviour in liquid crystals (LCs). Here, we show the union of these phenomena to lead to two previously undiscovered polar liquid states of matter. Both phases have a lamellar structure with an inherent polar ordering of their constituent molecules. The first of these phases is characterised by polar order and a local tilted structure; the tilt direction processes about a helix orthogonal to the layer normal, the period of which is such that we observe selective reflection of light. The second new phase type is anti-ferroelectric, with the constituent molecules aligning orthogonally to the layer normal. This has led us to term the phases the Sm C P H and SmAAF phases, respectively. Further to this, we obtain room temperature ferroelectric nematic (NF) and Sm C P H phases via binary mixture formulation of the novel materials described here with a standard NF compound (DIO), with the resultant materials having melting points (and/or glass transitions) which are significantly below ambient temperature. The new soft matter phase types discovered herein can be considered as electrical analogues of topological structures of magnetic spins in hard matter. Spontaneous symmetry breaking and emergent polar order are key to liquid crystal phase behaviour. This study reveals two new polar liquid states with lamellar structures, providing novel insights into electrical analogues of magnetic spin structures. [ABSTRACT FROM AUTHOR]

Mononuclear nickel complexes [NiL1(NCS)2]·2DMSO (I), [NiL1(NCS)2]·DMF (II), and [NiL2(NCS)2]·0.5CH3OH·1.5H2O (III) with the distorted octahedral coordination node, where L1 and L2 are the tetradentate ligand systems derived from the products of the condensation of diacetyl with 2-hydrazinoquinoline and 2-hydrazino-4,6-dimethylpyrimidine, respectively, are synthesized. The structures of the compounds are determined by IR spectroscopy and XRD (CIF files ССDС nos. 2219793 (I), 2142035 (II), and 2219794 (III)). The quantum chemical modeling of the axial parameter of magnetic anisotropy in the zero field (D) is performed for the synthesized compounds in the framework of the SA-CASSCF+NEVPT2 method. The complexes are shown to be characterized by three-axis magnetic anisotropy close to the light magnetization plane with positive D. The axial parameter of magnetic anisotropy (Dexp = 8.79 cm−1) determined by the approximation of the magnetometry data on complex [NiL2(NCS)2]·0.5CH3OH·1.5H2O is consistent with the calculated value (Dcalc = 11.5 cm−1). [ABSTRACT FROM AUTHOR]

Structure and magnetism of CoCr2 − xFexO4 (x = 0, 1 and 2) samples have been studied using room temperature X-ray and neutron diffraction; temperature and magnetic field dependent magnetization measurements. With increasing Fe content, it is observed that the magnetic ordering temperature increases while the nature of magnetic ordering undergoes drastic changes. The highlight of the work is that the equiatomic composition CoFeCrO4 (i.e., for x = 1 sample) exhibits lowest coercivity thus making it attractive for device applications. The present study shows control of magnetic properties through substitution, making it possible to prepare materials suitable for desired applications. [ABSTRACT FROM AUTHOR]

Context: The electronic and magnetic properties of non-metallic (NM) elements doping defective graphene-like ZnO (g-ZnO) monolayer including O vacancy (VO) and Zn vacancy (VZn) are studied. The results show that VO-g-ZnO is a semiconductor and VZn-g-ZnO is a magnetic semiconductor. B, C, N, Si, P, 2S, and 2Si doping VO-g-ZnO systems present half-metal and magnetic semiconductors, and the magnetism mainly originates from the spin polarization of doping atoms. For single or double NM elements doping VZn-g-ZnO, 2P doping system presents a semiconductor, while other systems present ferromagnetic metal, half-metal, and magnetic semiconductor. The magnetism of single NM elements doping VZn-g-ZnO mainly comes from the spin polarization of O atoms near the defect point. For double NM elements doping VZn-g-ZnO, spin splitting occurs mainly in p orbitals of O atoms, dopant atoms, and d orbitals of Zn atoms. NM elements doping defect g-ZnO can effectively regulate the electronic and magnetic properties of the system. Methods: The software package VASP 5.4.1 (Vienna ab initio Simulation Package) is used for calculations in this paper. The local density approximation (LDA) is adopted as an exchange and correlation function to perform the structural optimization and analysis of electronic structure and magnetic properties. [ABSTRACT FROM AUTHOR]

Structure and magnetism of CoCr2 − xFexO4 (x = 0, 1 and 2) samples have been studied using room temperature X-ray and neutron diffraction; temperature and magnetic field dependent magnetization measurements. With increasing Fe content, it is observed that the magnetic ordering temperature increases while the nature of magnetic ordering undergoes drastic changes. The highlight of the work is that the equiatomic composition CoFeCrO4 (i.e., for x = 1 sample) exhibits lowest coercivity thus making it attractive for device applications. The present study shows control of magnetic properties through substitution, making it possible to prepare materials suitable for desired applications. [ABSTRACT FROM AUTHOR]

The core and surface structure, and magnetism of mechano-synthesized LaFeO3 nanoparticles (30–40 nm), Eu3+-doped (La0.70Eu0.30FeO3), and Eu3+/Cr3+ co-doped (La0.70Eu0.30Fe0.95Cr0.05O3) are reported. Doping results in a transition from the O′-type to the O-type distorted structure. Traces of reactants, intermediate phases, and a small amount of Eu2+ ions were detected on the surfaces of the nanoparticles. The nanoparticles consist of antiferromagnetic cores flanked by ferromagnetic shells. The Eu3+ dopant ions enhance the magnetization values relative to those of the pristine nanoparticles and result in magnetic susceptibilities compatible with the presence of Eu3+ van Vleck paramagnetism of spin–orbit coupling constant (λ = 363 cm−1) and a low temperature Curie–Weiss like behavior associated with the minority Eu2+ ions. Anomalous temperature-dependent magnetic hardening due to competing magnetic anisotropy and magnetoelectric coupling effects together with a temperature-dependent dopant-sensitive exchange bias, caused by thermally activated spin reversals at the core of the nanoparticles, were observed. [ABSTRACT FROM AUTHOR]

Magnetic materials with noncoplanar magnetic structures can show unusual physical properties driven by nontrivial topology. Topologically-active states are often multi-q structures, which are challenging to stabilize in models and to identify in materials. Here, we use inelastic neutron-scattering experiments to show that the insulating double perovskites Ba2YRuO6 and Ba2LuRuO6 host a noncoplanar 3-q structure on the face-centered cubic lattice. Quantitative analysis of our neutron-scattering data reveals that these 3-q states are stabilized by biquadratic interactions. Our study identifies double perovskites as a highly promising class of materials to realize topological magnetism, elucidates the stabilization mechanism of the 3-q state in these materials, and establishes neutron spectroscopy on powder samples as a valuable technique to distinguish multi-q from single-q states, facilitating the discovery of topologically-nontrivial magnetic materials. [ABSTRACT FROM AUTHOR]

The work is devoted to the theoretical investigation of the quasi-static magnetoelectric interaction in three-layer structures consisting of a piezoelectric and two magnetic layers with positive and negative magnetostriction. Using the system of elasto- and electrostatics equations for the piezoelectric and magnetostrictive phases, expressions for the electrical response of the structure in a magnetic field are obtained. The contributions from longitudinal and bending deformations are taken into account in value of ME interactions. It is shown that the use of an asymmetric three-layer asymmetric structure leads to an increase in the magnitude of the ME interaction by almost an order of magnitude compared to a two-layer structure. The dependences of the effect magnitude on the thickness of the third layer for the nickel/lead zirconate titanate/metglas structure are presented. [ABSTRACT FROM AUTHOR]

Galactic cosmic rays (GCRs) interact with the Earth's atmosphere to produce energetic neutrons and cosmogenic radionuclides, such as 14C. The atmosphere is partially shielded from the interstellar GCR spectrum by both the geomagnetic and solar magnetic fields. Solar shielding is often expressed as the heliospheric modulation potential ϕ , which consolidates information about the strength and structure of the solar magnetic field into a single parameter. For the period 1951 to today, ϕ can be estimated from ground-based neutron monitor data. Prior to 1950, 14C in tree rings can be used to estimate ϕ and hence the solar magnetic field, back centuries or millennia. Bridging the gap in the ϕ record is therefore of vital importance for long-term solar reconstructions. One method is to model ϕ using the sunspot number (SN) record. However, the SN record is only an indirect measure of the Sun's magnetic field, introducing uncertainty, and the record suffers from calibration issues. Here we present a new reconstruction of ϕ based on geomagnetic data, which spans both the entire duration of the neutron monitor record and stretches back to 1845, providing a significant overlap with the 14C data. We first modify and test the existing model of ϕ based on a number of heliospheric parameters, namely the open solar flux F S , the heliospheric current sheet tilt angle α , and the global heliospheric magnetic polarity p . This modified model is applied to recently updated geomagnetic estimates of F S and cyclic variations of α and p . This approach is shown to produce an annual estimate of ϕ in excellent agreement with that obtained from neutron monitors over 1951 – 2023. It also suggests that ionisation chamber estimates of ϕ – which have previously been used to extend the instrumental estimate back from 1951 to 1933 – are not well calibrated. Comparison of the new geomagnetic ϕ with 14C estimates of ϕ suggests that the long-term trend is overestimated in the most recent 14C data, possibly due to hemispheric differences in the Suess effect, related to the release of carbon by the burning of fossil fuels. We suggest that the new geomagnetic estimate of ϕ will provide an improved basis for future calibration of long-term solar activity reconstructions. [ABSTRACT FROM AUTHOR]

Thermal heating process has been used, under a pressure of 10−7 mbar, to deposit thin films of cobalt onto monocrystalline silicon substrate. The incident beam strikes the substrates under normal incidence. The thickness ranges from 50 to 400 nm. To investigate the static magnetic properties, the hysteresis loops are performed by means of alternating gradient field magnetometer device. The zero-field magnetic structure has been investigated by magnetic force microscopy (MFM) technique, using a Veeco 3100 apparatus. MFM images reveal well-defined stripe patterns, mainly for the thickest films, which infer the dominance of the magnetocrystalline anisotropy. The easy magnetization axis lies within the plane of the film with a small component out-of-the plane for the thicker films. Coercivity evolution versus thickness follows a t−n Néel law, characteristic of Bloch domain wall motion. In addition, it was found that coercivity depends plainly on the surface roughness of the films. [ABSTRACT FROM AUTHOR]

We proposed the numerical studies and machine learning prediction for the multilayered Borophene-GST-silica-Ag-based refractive index sensor for the 1.3–1.5 µm wavelength range. The top layers of the proposed sensor incorporate Ag gratings. The proposed structure utilizes a mode based on surface plasmonic resonance, which has been created using a finite element model through computational analysis. Resonance is observed across a range of refractive index values from 1 to 2.5, which primarily aligns with the refractive indices of key biomolecules such as haemoglobin, saliva, urine, and cancerous cells. The proposed structure has also been investigated for the different physical parameters such as material height, grating space, the incident wave's wide incident angle, and the GST material's phase. We demonstrate the modulation of reflectance values in response to varying phases of the GST material (amorphous and crystalline), which can be controlled through external temperature changes. The distribution of the electric and magnetic fields of the structure is also provided in order to examine the field distribution across the grating and other layers of material. This sensor offers a wide angle of stability (0 to 80°) for the respective resonating points. An artificial neural network is employed to analyze the simulated data and make predictions regarding the behaviour of the structure. We have found the R2 = 0.97 for the proposed artificial neural network (ANN) model. The ANN model of this structure also presented the values of mean square error (MSE), mean absolute error (MAE), and root mean square error (RMSE) for different epoch values. Results shown in this research can help to sense the wide range of biomolecule samples whose refractive index ranges from 1 to 2.5. The wide wavelength range makes this device applicable for developing wideband infrared biosensors. [ABSTRACT FROM AUTHOR]

During orthodontic treatments, orthodontists want to simultaneously measure different kinds of intraoral pressure of a patient to determine a suitable orthodontic treatment plan for the patient. To achieve this, an intraoral pressure sensors-array with a specific arrangement in the oral cavity is needed. Hence, in this paper, we design a smart magnetic thin-sheet structure based wireless sensors-array arrangement for intraoral-pressure sensing for orthodontics to determine the above suitable treatment plan. In general, the sensors-array consists of multiple sensing modules. Each module consists of two parts: the first part is a transmitting/receiving electromagnet which is connected to a reference electromagnet in a balanced inductance bridge configuration while the second part is a smart magnetic thin-sheet structure based high-permeable sensing diaphragm. A voltage input is applied to the reference electromagnet and transmitting/receiving electromagnet, while the voltage output is measured from the transmitting/receiving electromagnet, respectively (the transmitting/receiving electromagnet can transmit the magnetic flux as well as receive or sense the change of magnetic flux). When the sensing diaphragm (which is placed in proximity to the transmitting/receiving electromagnet) undergoes a displacement, the gap between the sensing diaphragm and transmitting/receiving electromagnet changes. This subsequently changes surrounding magnetic flux, and consequently results in a change in magnetic reluctance between the sensing diaphragm and transmitting/receiving electromagnet. Thus, the voltage output of the transmitting/receiving electromagnet is changed accordingly. Based on this operation principle, furthermore, we use multiple transmitting/receiving electromagnets to form a compact (specifically arranged) sensors-array. The results show that specifically arranged sensors-array can provide measurement results in multiple points in the oral cavity to the orthodontists, as a simplified decision-making reference for the orthodontists to determine the clinical treatment plan for patients. [ABSTRACT FROM AUTHOR]

With help of ab-initio density functional theory calculation, DFT+U, and hybrid functional HSE06, we revisit the layer-dependent electronic structure and magnetic properties of pristine and 3d transition metal Cr doped MoS2 monolayer and multi-layers. Our results show that the dopant Cr atoms prefer to stay at nearest neighbor distances. In the multilayers, they prefer to remain in the outermost surface layers. Matching with the experimental band gap, the optimized U parameter we report is 4 eV. The band gap of the Cr-doped monolayer is indirect, confirming the experimental observation from photoluminescence experiments. The HSE06 calculation for Cr doped monolayer shows that the band gap of doped Cr MoS2 monolayer is indirect and no magnetism is observed. From the DFT studies, the band gap for the multilayers is indirect, and doping with Cr does not induce magnetic moments in MoS2 layers. The band gap is observed to decrease with the multilayer thickness. The strain induced by substitutional Cr doping at the Mo site transforms the band gap in monolayer MoS2 from direct to indirect; the defect states are produced within the band gap region close to the conduction band minimum. [ABSTRACT FROM AUTHOR]

The permanent magnet claw pole machine (PMCPM) with soft magnetic composite (SMC) cores has shown better performance than the traditional transverse flux machine, and its performance can be improved by developing its stator with hybrid silicon sheet and SMC cores, and this kind of PMCPM is named as HPMCPM. Due to its complex 3D magnetic structure, analyzing its performance by using the traditional finite element method (FEM) is time-consuming. To overcome this constraint, this paper proposes a magneto-electric-thermal coupling network (METCN) model with bidirectional data transmission to calculate the electromagnetic performance and temperature distribution and the calculation results are verified by the FEM method and experimental measurement results. Compared with the 3D FEM, the proposed METCN method has the advantage of fast calculation speed and similar accuracy. [ABSTRACT FROM AUTHOR]

Anisotropic aerogel possesses structure which exhibits a strong influence over the composition and orientation of the order parameter of imbibed superfluid 3 He. Computational studies have identified stretched aerogel with plane-like structures and compressed aerogel with nematic-like structures. Studies of the B phase of superfluid 3 He in stretched aerogel display an enhanced nuclear magnetic susceptibility likely caused by Andreev bound states near plane-like impurity sites. We report further details on the influence of these planar structures on both magnetic and orbital orientation transitions. The orbital orientation transitions appear in both the B and A phases of stretched and compressed aerogels. These transitions result from a crossover of the superfluid coherence length with long and short length scale structure with the coherence length and are consequently magnetic field independent. Additionally, the apparent temperature-independence of the susceptibility of the B phase, equal to that of the A phase in stretched aerogel and indicative of a near-isentropic transition, is in marked contrast with the field dependence of the superfluid A to B phase transition. [ABSTRACT FROM AUTHOR]

The dispersion stability of carbonyl iron particle (CIP)-based magnetorheological fluid (MRF) is improved by CIP, which particle is etched with hydrochloric acid (HCl) to form porous structure with many hydroxyl groups and subsequently coated with silane coupling agents that have varying chain lengths. The microstructures, coating effect and magnetism of the CIPs were examined using the Scanning Electron Microscopy, Automatic Surface and Porosity Analyzer (BET), Fourier-Transform Infrared Spectroscopy, Thermogravimetric Analysis and Vibrating Sample Magnetometer. Furthermore, the rheological properties and dispersion stability of the MRFs were assessed using a Rotating Rheometer and Turbiscan-lab. The results revealed that the nanoporous structure appeared on the CIPs and the specific surface area increased remarkably after being etched by hydrochloric acid. Additionally, as the chain length of the silane coupling agent increases, the coated mass on the particles increases, the the density and the saturation magnetization of particles decreased, and the coated particles with different shell thicknesses were obtained; without a magnetic field, the viscosity of MRF prepared by coated particles increase slightly, due to the enhancement of special three-dimensional network structure; under a magnetic field, the viscosity of the MRF decreased distinctly; the sedimentation rate of MRF decreased from 58 to 3.5% after 100 days of sedimentation, and the migration distances of the MRFs were 22.4, 3.7, 2.4, and 0 mm, with particle sedimentation rates of 0.149, 0.019, 0.017, and 0 mm/h, respectively. The MRF with high dispersion stability was obtained, and the etching of CIP by HCl and the proper chain length of the coating of silane coupling agent were proved effective manners to improve the dispersion stability of MRF. [ABSTRACT FROM AUTHOR]

A generalized Thiele equation, which includes a given set of low-energy excitations of an equilibrium magnetic structure, has been derived to describe the dynamics of chiral topological systems. A "breathing" mode of magnetic skyrmions corresponding to a change in their size is included. The relaxation of the magnetic structure under the variation of a magnetic field has been studied. The importance of keeping the Hamiltonian form of the equations of motion has been demonstrated. The radius and helicity of a skyrmion are canonically conjugate variables, and only their simultaneous inclusion allows the reproduction of the main features of the magnetic relaxation after the magnetic field is switched-on/off, which is accompanied by oscillations of the radius. [ABSTRACT FROM AUTHOR]

In this work, the electronic structure and magnetic properties of GdNiSi have been investigated within the framework of theoretical DFT + U method. The antiferromagnetic ordering of the Gd moments was obtained as the ground state, whereas Ni and Si have negligible magnetic moments. An antiferromagnetic-to-ferromagnetic transition was found when GdNiSi is doped with Al in our theoretical calculations. The antiferromagnetic-to-ferromagnetic transition takes place in the Gd sublattice, the magnetic moments at the Gd ions remain the same but the type of magnetic ordering changes. It was found that even at concentrations as low as , the ferromagnetic ordering in the Gd sublattice is more favorable in total energy as the ground state which can be ascribed to the shortening of Gd–Gd distances and the oscillating behavior of the Ruderman–Kittel–Kasuya–Yosida interaction in the Al-doped compositions. The electronic structure demonstrates significant changes in the vicinity of the localized Gd 4f states that confirms the presence of the antiferromagnetic-to-ferromagnetic transition using our theoretical results for Al in good agreement with the previous experimental magnetic results. [ABSTRACT FROM AUTHOR]

Spatial topology endows topological solitons, such as skyrmions and hopfions, with fascinating dynamics. However, the temporal dimension has so far provided a passive stage on which topological solitons evolve. Here we construct spacetime magnetic hopfions: magnetic textures in two spatial dimensions that when excited by a time-periodic drive develop spacetime topology. We uncover two complementary construction routes using skyrmions by braiding their center of mass position and by controlling their internal low-energy excitations. Spacetime magnetic hopfions can be realized in nanopatterned grids to braid skyrmions and in frustrated magnets under an applied AC electric field. Their topological invariant, the spacetime Hopf index, can be tuned by the applied electric field as demonstrated by our collective coordinate modeling and micromagnetic simulations. The principles we have introduced to actively control spacetime topology are not limited to magnetic solitons, opening avenues to explore spacetime topology of general order parameters and fields. Topological solitons are localized structures whose stability emerges from the topology of their spatial structure, hence they are usually independent of the temporal dimension. The authors construct topological magnetic solitons in space-time from periodically driven magnetic structures that can be externally controlled. [ABSTRACT FROM AUTHOR]

The potential for amplifying tunnel magnetoresistance and magnetoimpedance in island nanofilms without energy consumption or the use of amplifying devices was studied. Such amplification was observed for the films deposited on a Gd2O3 layer instead of a glass substrate. The enhancement is due to the f–d exchange interaction established between atoms with unfilled f- and d-electron shells, present in both Fe and Gd2O3. The f–d exchange interaction enhances the ordering of the magnetic structure within the Fe ferromagnetic layer, increases its magnetization, and subsequently improves the properties that depend on this magnetization. Iron and Gd2O3 were selected because the magnetic moments of Fe in the iron group and Gd in the lanthanide series are among the highest effective ones: μFe = 7.13 μB and μGd = 7.95 μB. This, according to theory, determines the high energy of the f–d exchange interaction. The island morphology of Fe films deposited on a Gd2O3 layer enabled electron tunneling under the influence of the f–d exchange interaction. This allowed the study of tunnel magnetoresistance under direct current and magnetoimpedance under alternating current influenced by the f–d exchange interaction. The frequency dependence of the active component Z', the reactive component Z'', and the total impedance Z of Fe films on glass and Gd2O3 substrates, without and under a constant magnetic field of 7500 Oe, was analyzed. These characteristics are used to determine the frequency dependence of tunnel magnetoimpedance and estimate tunnel magnetoresistance for Fe island films on glass and Gd2O3 substrates. These characteristics were found to be 55 % higher, on average, for Fe deposited on Gd2O3 than for Fe on glass, both at a low frequency of 0.1 Hz for tunnel magnetoresistance and at higher frequencies of 1–105 Hz for tunnel magnetoimpedance. This results from the influence of f–d exchange interaction on electron tunneling between the iron islands. [ABSTRACT FROM AUTHOR]

The electronic structure and magnetic properties of a YFeO3 thin film deposited on a SrTiO3 substrate are studied using the GGA+U method. It is shown that the epitaxial strain in the YFeO3/SrTiO3 thin film significantly changes the crystal structure and displaces iron atoms located at the film surface from the plane formed by the nearest oxygen atoms. These distortions lead to a change in the type of long-range magnetic ordering from the G-type antiferromagnetic ordering observed in stoichiometric YFeO3 to ferrimagnetic ordering close to the A-type antiferromagnetism and to the transition from the insulating state to metallic one. The complete relaxation of atomic positions gives rise to a "breathing mode" distortion in the film bulk, which is accompanied by the electric polarization of 15.1 μC/cm2. The latter is in agreement with the experiment. The distortion of oxygen octahedra surrounding iron atoms leads to the transition from the high-spin state to the intermediate-spin state and to a stepwise decrease in local magnetic moments. [ABSTRACT FROM AUTHOR]