Model Of Magnetic Structure Research Articles

Determining magnetic structures in GSAS-II using the Bilbao Crystallographic Server tool k-SUBGROUPSMAG.

The embedded call to a special version of the web-based Bilbao Crystallographic Server tool k-SUBGROUPSMAG from within GSAS-II to form a list of all possible commensurate magnetic subgroups of a parent magnetic grey group is described. It facilitates the selection and refinement of the best commensurate magnetic structure model by having all the analysis tools including Rietveld refinement in one place as part of GSAS-II. It also provides the chosen magnetic space group as one of the 1421 possible standard Belov-Neronova-Smirnova forms or equivalent non-standard versions.

Unique magnetic structure of the vdW antiferromagnet VBr3

VBr3 is a van der Waals antiferromagnet below the Néel temperature of 26.5 K with a saturation moment of 1.2 µB/f.u. above the metamagnetic transitions detected in the in-plane and out-of-plane directions. To reveal the AFM structure of VBr3 experimentally, we performed a single-crystal neutron diffraction study on a large high-quality crystal. The collected data confirmed a slight monoclinic distortion of the high-temperature rhombohedral structure below 90 K. The magnetic structure was, nevertheless, investigated within the R-3 model. The antiferromagnetic structure propagation vector k = (1, 0, ½) was revealed. In an attempt to determine the magnetic structure, 72 non-equivalent magnetic reflections were recorded. The experimental data were confronted with the magnetic space groups dictated by the R-3 lattice symmetry and propagation vector. The best agreement between the experimental data and the magnetic structure model was obtained for the space group P-1.1′_c. The magnetic unit cell of the proposed unique antiferromagnetic structure with periodicity 6c is built from two identical triple layers antiferromagnetically coupled along the c axis. Each triple layer comprises a Néel antiferromagnetic monolayer sandwiched between two antiferromagnetically coupled ferromagnetic monolayers.

Abell 0399–Abell 0401 radio bridge spectral index: First multi-frequency detection

Aims. Recent low-frequency radio observations at 140 MHz discovered a bridge of diffuse emission with a length of 3 Mpc that connects the galaxy clusters Abell 0399 and Abell 0401. We present follow-up observations at 60 MHz to constrain the spectral index of the bridge, which has only been detected at 140 and 144 MHz so far. Methods. We analysed deep (∼18 h) LOw Frequency ARray (LOFAR) Low Band Antenna (LBA) data at 60 MHz to detect the bridge at very low frequencies. We then conducted a multi-frequency study with LOFAR HBA data at 144 MHz and uGMRT data at 400 MHz. Assuming second-order Fermi mechanisms for the re-acceleration of relativistic electrons driven by turbulence in the radio bridge regions, we compared the observed radio spectrum with theoretical synchrotron models. Results. The bridge is detected in the 75″ resolution LOFAR image at 60 MHz, and its emission fully connects the region between the two galaxy clusters. Between 60 MHz and 144 MHz, we found an integrated spectral index value of α60144 = −1.44 ± 0.16 for the bridge emission. For the first time, we produced spectral index and related uncertainties maps for a radio bridge. We produce a radio spectrum that shows a significant steepening between 144 and 400 MHz. Conclusions. This detection at low frequencies provides important information for models of particle acceleration and magnetic field structure on very extended scales. The spectral index gives important clues about the origin of inter-cluster diffuse emission. The steepening of the spectrum above 144 MHz can be explained in a turbulent re-acceleration framework, assuming that the acceleration timescales are longer than ∼200 Myr.

Design and optimization of H-type asymmetric magnetic suspension vibration absorber for ships

The active–passive hybrid vibration isolation technology emerges with the advancement of the requirements for ship vibration and noise reduction. Among these, the magnetic suspension damper based on magnetic suspension technology has received more attention. In this paper, the effects of magnetic pole area and control current on the magnetic flux density and suspension force are verified by establishing a magnetic suspension structure model and comparing and verifying the results carried out by combining the theoretical formulas and finite element simulation. By exploring the effect of the structure on the magnetic flux density and suspension force, a new H-type asymmetric magnetic suspension structure is proposed and simulated. The results show that the H-type asymmetric magnetic suspension structure is more successful at improving the suspension force while also widening the suspension force response interval and improving the performance of the magnetic suspension damper. In addition to offering a new design concept for the construction of ship vibration and noise reduction structures, this structural solution serves as a reference for the development of magnetic suspension dampers.

Magnetization State and Magnetic Structure of Wiegand Wire Evaluated by External Magnetic Field Measurement

Wiegand wires exhibit unique and fast magnetization reversal features, termed as large Barkhausen jumps, in externally applied alternating magnetic fields. However, the mechanisms and magnetization states yielding these large Barkhausen jumps are yet to be sufficiently elucidated. Thus, in this study, we analyzed the magnetization state and magnetic structure of a Wiegand wire by measuring the magnetic field of the wire. Moreover, we defined a four-layer magnetic structure model of the Wiegand wire and analyzed the magnetization states and processes of these layers in an applied alternating magnetic field. Additionally, we determined the switching field of each layer and specified the magnetization states resulting in the large Barkhausen jump.

On the magnetic structures of 1:1:1 stoichiometric topological phases LnSbTe (Ln = Pr, Nd, Dy and Er)

LnSbTe (Ln – lanthanide) group of materials, belonging to ZrSiS/PbFCl (P4/nmm) structure type, is a platform to study the phenomena originating from the interplay between the electronic correlations, magnetism, structural instabilities and topological electronic structure. Here we report a systematic study of magnetic properties and magnetic structures of LnSbTe materials. The studied materials undergo antiferromagnetic ordering at TN = 2.1 K (Ln = Er), 6.7 K (Ln = Dy), 3.1 K (Ln = Nd). Neutron powder diffraction reveals ordering with k1 = (½ + δ 0 0) in ErSbTe, k2 = (½ 0 ¼) in NdSbTe. DySbTe features two propagation vectors k2 and k4 = (0 0 ½). No long-range magnetic order is observed in PrSbTe down to 1.8 K. We propose the most probable models of magnetic structures, discuss their symmetry and possible relation between the electronic structure and magnetic ordering.

Synthesis of (Ca, Sr)-based W-type hexagonal ferrite

This investigation has examined the synthesis conditions and magnetic properties of (Ca, Sr)-based W-type hexagonal ferrite. Substituting Ca for Sr in CaxSr1−xZn2Fe16O27 (where 0≤x≤1) resulted in the formation of the W-type structure at x≤0.7 sintered at TS = 1250 and 1300°C. However, these W-type samples were accompanied by secondary spinel and hematite phases, making it necessary to modify the initial composition to form a single W-type phase. Eliminating the potential compositions of these secondary phases resulted in the optimal single-phase-forming condition of Ca: Sr: Zn: Fe = 0.55: 0.45: 0.88: 11.6 and TS = 1200°C. The magnetization of this sample at 5 K was 130.7 A m2/kg at 7 T, consistent with a model of a collinear magnetic structure. The Curie temperature of this sample was found to be 350°C.

Diffpy.mpdf: open-source software for magnetic pair distribution function analysis

The open-source Python package diffpy.mpdf, part of the DiffPy suite for diffraction and pair distribution function analysis, provides a user-friendly approach for performing magnetic pair distribution function (mPDF) analysis. The package builds on existing libraries in the DiffPy suite to allow users to create models of magnetic structures and calculate corresponding one- and three-dimensional mPDF patterns. diffpy.mpdf can be used to perform fits to mPDF data either in isolation or in combination with atomic pair distribution function data for joint refinement of the atomic and magnetic structure. Examples are given using MnO and MnTe as representative antiferromagnetic compounds and MnSb as a representative ferromagnet.

Competing Magnetic Phases in LnSbTe (Ln = Ho and Tb)

The interplay between a topological electronic structure and magnetism may result in intricate physics. In this work, we describe a case of rather peculiar coexistence or competition of several magnetic phases below seemingly single antiferromagnetic transition in LnSbTe (Ln = Ho and Tb) topological semimetals, the magnetic members of the ZrSiS/PbFCl structure type (space group P4/nmm). Neutron diffraction experiments reveal a complex multi-step order below TN = 3.8 K (Ln = Ho) and TN = 6.4 K (Ln = Tb). Magnetic phases can be described using four propagation vectors k1 = (1/2 0 0) and k2 = (1/2 0 1/4) at a base temperature of 1.7 K, which transform into incommensurate vectors k1' = (1/2 - δ 0 0) and k3 = (1/2 - δ 0 1/2) at elevated temperatures in both compounds. Together with the refined models of magnetic structures, we present the group theoretical analysis of magnetic symmetry of the proposed solutions. These results prompt further investigations of the relation between the electronic structure of those semimetals and the determined antiferromagnetic ordering existing therein.

The JCMT BISTRO Survey: Evidence for Pinched Magnetic Fields in Quiescent Filaments of NGC 1333

Abstract We investigate the internal 3D magnetic structure of dense interstellar filaments within NGC 1333 using polarization data at 850 μm from the B-fields In STar-forming Region Observations survey at the James Clerk Maxwell Telescope. Theoretical models predict that the magnetic field lines in a filament will tend to be dragged radially inward (i.e., pinched) toward the central axis due to the filament’s self-gravity. We study the cross-sectional profiles of the total intensity (I) and polarized intensity (PI) of dust emission in four segments of filaments unaffected by local star formation that are expected to retain a pristine magnetic field structure. We find that the filaments’ FWHMs in PI are not the same as those in I, with two segments being appreciably narrower in PI (FWHM ratio ≃0.7–0.8) and one segment being wider (FWHM ratio ≃1.3). The filament profiles of the polarization fraction (P) do not show a minimum at the spine of the filament, which is not in line with an anticorrelation between P and I normally seen in molecular clouds and protostellar cores. Dust grain alignment variation with density cannot reproduce the observed P distribution. We demonstrate numerically that the I and PI cross-sectional profiles of filaments in magnetohydrostatic equilibrium will have differing relative widths depending on the viewing angle. The observed variations of FWHM ratios in NGC 1333 are therefore consistent with models of pinched magnetic field structures inside filaments, especially if they are magnetically near-critical or supercritical.

Magnetic Structure of Short-Range Ordering in Intermetallic Antiferromagnet Mn3RhSi

Magnetic pair distribution function (mPDF) of intermetallic antiferromagnet Mn3RhSi is estimated from the powder neutron diffraction data. The mPDF exhibits negative peak at about r = 2.7 Å corresponding to the nearest neighbor Mn–Mn distance above the antiferromagnetic transition temperature TN. Below TN, the mPDF is a superposition of the mPDF with the negative peak at about r = 2.7 Å and the mPDF calculated from the antiferromagnetic structure which is determined by the previous neutron diffraction study, indicating the coexistence of the short range ordering and the antiferromagnetic long range ordering. The mPDF of the short range ordering is not reproduced by the magnetic structure model with the symmetry consistent with that of the crystal structure. The possible magnetic structure which can reproduce the observed mPDF of the short range ordering is proposed.

Simulation of conducted emission voltage method for DCDC converter in electric vehicle

In order to quickly predict the conducted emission (CE) of electric vehicle (EV) DC/DC converter, a co-simulation analysis method based on HFSS-simplorer is introduced. The detailed 3D models of magnetic devices, PCB board and metal structure, and the active device nonlinear models are added to the co-simulation circuit. The method is used to simulate and analysis the EMC performance of the conducted emission of the actual electric vehicle DC/DC converter, the simulation results are in good agreement with the test results in magnitude, trend and peak values, which shows that the method is feasible and practical.

Magnetodielectric effect in an organic-inorganic hybrid layered perovskite (CH3NH3)2MnCl4 with canted antiferromagnetism

Herein, we report the magnetodielectric effect in a single crystal of (CH3NH3)2MnCl4, an organic–inorganic hybrid layered perovskite having a composition of A2MX4 (A = organic anion, M = metal divalent ion, X = halogen cation). Magnetic property measurements reveal that a magnetic phase transition to antiferromagnetism appears at 47 K and a spin-flop transition occurs at 3.5 T in the magnetization (M) curve. We observed a considerable maximum magnetodielectric (MD) effect of 0.4% at 8 K. Furthermore, it was found that the MD effect is proportional to M2 in low magnetic fields and the MD effect starts to saturate at the spin-flop transition field. We proposed a magnetic structure model to explain the mechanism of the peculiar step-like MD effect induced by the spin reorientation.

Magnetization distribution in Cu0.6Mn2.4Ge2 ferromagnet from polarized and non-polarized neutron powder diffraction aided by density-functional theory calculations

The crystal structure and magnetic properties of Cu0.6Mn2.4Ge2 have been re-investigated by a combination of extensive magnetic measurements and neutron scattering experiments, aided by electronic structure calculations. The material is found to be a soft ferromagnet with the ordering temperature TC = 316 K. The magnetocaloric effect evaluated from field-dependent magnetization isotherms is equal to 1.2 J/(kg·K) and 2.5 J/(kg·K) under the maximum applied magnetic field of 2 T and 5 T, respectively. The compound crystallizes in the hexagonal space group P63/mmc. A complex structural disorder necessitated testing of several disorder models against the results of non-polarized and polarized neutron scattering experiments and magnetization measurements. Simulations at the density-functional theory level were also performed to identify the most robust solution that properly described the data observed. The final magnetic structure model reveals non-equal magnetic moments on the Mn1 and Mn2 atoms (2.29(9) µB and 2.7(1) µB, respectively) and the presence of vacancies and minor Cu substitution defects in both Mn sites. The work demonstrates how the non-polarized and polarized neutron scattering methods can be combined with electronic structure calculations to establish the microscopic structure of magnetic materials with complex crystallographic disorder.

A Novel Compensation Method of Probe Gesture for Magnetic Flux Leakage Testing

For in-line inspection of ferromagnetic materials, magnetic flux leakage (MFL) detection is one of the most common nondestructive testing methods. In practical applications of conventional MFL inspection, random mechanical vibration can cause the detection gesture of the probe, in particular, the lift-off and tilt detection angle, to continuously fluctuate throughout the inspection process, which introduces measurement errors to MFL signals. To address the problem and realize ultra-high-definition MFL detection, this paper proposed a new type of probe with dual diagonal distributed magnetic sensors for MFL detection. Based on the dual magnetic sensor probe structure and magnetic dipole model, this paper further developed analytical solutions of the real-time sensor lift-off, tilt detection angle, and defect depth. Additionally, this paper presented a compensation algorithm for MFL measurement errors caused by random lift-off and tilt detection angles. A practical implementation for the dual magnetic sensor probe in the actual MFL testing tool was given. The finite element simulation and physical experiments were designed to verify the feasibility of probe gesture compensation algorithm. Even under abnormal probe detection gesture case, MFL signals measured and compensated by the dual magnetic sensor probe were also in line with the engineering application, and measurement errors of MFL signals were reduced from more than 30 % to less than 10 %, which is conducive to the realization of ultra-high-definition MFL testing.

Relevance of jet magnetic field structure for blazar axionlike particle searches

Many theories beyond the Standard Model of particle physics predict the existence of axionlike particles (ALPs) that mix with photons in the presence of a magnetic field. One prominent indirect method of searching for ALPs is to look for irregularities in blazar gamma-ray spectra caused by ALP-photon mixing in astrophysical magnetic fields. This requires the modeling of magnetic fields between Earth and the blazar. So far, only very simple models for the magnetic field in the blazar jet have been used. Here, we investigate the effects of more complicated jet magnetic field configurations on these spectral irregularities by imposing a magnetic field structure model onto the jet model proposed by Potter Cotter. We simulate gamma-ray spectra of Mrk 501 with ALPs and fit them to ALP-less spectra, scanning the ALP and B-field configuration parameter space, and show that the jet can be an important mixing region, able to probe new ALP parameter space around ${m}_{a}\ensuremath{\sim}1--1000\text{ }\text{ }\mathrm{neV}$ and ${g}_{a\ensuremath{\gamma}}\ensuremath{\gtrsim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$. However, reasonable (i.e., consistent with observation) changes of the magnetic field structure can have a large effect on the mixing. For jets in highly magnetized clusters, mixing in the cluster can overpower mixing in the jet. This means that the current constraints using mixing in the Perseus cluster are still valid.

Evidence of two dimensional dilute antiferromagnet mediated exchange bias field and vertical shift in LaFeO3-NiO nanocomposite

Low dimensional antiferromagnetic systems, such as nanoparticles, are known to exhibit weak ferromagnetic behavior due to the uncompensated surface spins. In this report, we present a detailed magnetic study of LaFeO3/NiO nanocomposite, synthesized by propylene glycol gel method. The X-ray diffraction (XRD) based analyses, in combination with transmission electron microscopy (TEM), confirms 50:50 ratio composite with ~35–40 nm size particles. Owing to the high Néel temperatures (TN) of LaFeO3 and NiO, significant exchange bias (EB) and vertical magnetization shift (VMS) have been observed in the nanocomposite at room temperature. These features are attributed to the exchange interaction at the interface between the core and shell of the nanoparticles that are homogeneously dispersed in the nanocomposite. In our studies, the EB field and the VMS attains a value as high as 2050 Oe & 1.8 × 10-1 emu/g at 5 K and 75 Oe & 1.7 × 10-2 emu/g at 300 K, respectively. The thermoremanent magnetization (TRM) and isothermoremanent magnetization (IRM) analyses are done to identify the two-dimensional (2D) diluted antiferromagnet (DAFF) behavior of the surface shell of nanoparticles. We propose a phenomenological antiferromagnetic-(2D-DAFF)-antiferromagnetic magnetic structure model, to explain all the rich features and the observed magnetic properties of this nanocomposite.

Complicated magnetic structure and its strong correlation with the anomalous Hall effect in Mn3Sn

The large anomalous Hall effect (AHE) has recently been found in noncollinear antiferromagnet $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$. However, the complex magnetic structure and its correlation with the AHE remain unclear. Here we investigate the magnetic structure of $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$ completely by means of both the temperature and magnetic field dependence of neutron power diffraction. This study establishes the possible incommensurate magnetic structure models and extracts the temperature evolution of the magnetic moment of the Mn atom over the whole temperature range for $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$. The large AHE of polycrystalline bulk $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$ is measured in detail. By comparing the temperature dependence of the spontaneous component of the AHE and the magnetic moment, direct experimental evidence reveals that the triangular antiferromagnetic ordered moment of the Mn atom controls the change in the AHE of $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$. This study provides the possibility to control the AHE of functional materials via changing the magnetic structure.

Complex magnetic order in the decorated spin-chain system Rb2Mn3(MoO4)3(OH)2

Macroscopic magnetic properties and microscopic magnetic structure of Rb$_2$Mn$_3$(MoO$_4$)$_3$(OH)$_2$ (space group $Pnma$) are investigated by magnetization, heat capacity and single-crystal neutron diffraction measurements. The compound's crystal structure contains bond-alternating [Mn$_3$O$_{11}$]$^{\infty}$ chains along the $b$-axis, formed by isosceles triangles of Mn ions occupying two crystallographically nonequivalent sites (Mn1 site on the base and Mn2 site on the vertex). These chains are only weakly linked to each other by nonmagnetic oxyanions. Both SQUID magnetometry and neutron diffraction experiments show two successive magnetic transitions as a function of temperature. On cooling, it transitions from a paramagnetic phase into an incommensurate phase below 4.5~K with a magnetic wavevector near ${\bf k}_{1} = (0,~0.46,~0)$. An additional commensurate antiferromagnetically ordered component arises with ${\bf k}_{2} = (0,~0,~0)$, forming a complex magnetic structure below 3.5~K with two different propagation vectors of different stars. On further cooling, the incommensurate wavevector undergoes a lock-in transition below 2.3~K. The experimental results suggest that the magnetic superspace group is $Pnma.1'(0b0)s0ss$ for the single-${\bf k}$ incommensurate phase and is $Pn'ma(0b0)00s$ for the 2-${\bf k}$ magnetic phase. We propose a simplified magnetic structure model taking into account the major ordered contributions, where the commensurate ${\bf k}_{2}$ defines the ordering of the $c$-axis component of Mn1 magnetic moment, while the incommensurate ${\bf k}_{1}$ describes the ordering of the $ab$-plane components of both Mn1 and Mn2 moments into elliptical cycloids

A Structure Parameter Design Method of DD Coils to Optimize Coupling Performance and Misalignment-tolerant Ability

Aiming at the problems of weak coupling performance and poor misalignment-tolerant ability of the magnetic coupling structure of electric vehicle wireless charging system, this paper proposes a coil structure parameter design method. This paper analyzes the relationship between the system characteristics and the coupling coefficient of the wireless charging system based on the dual LCC resonant compensation network. Then, based on the analysis of the structure parameters of DD coils, a structure parameter design method to optimize coupling performance and misalignment-tolerant ability is proposed. Finally, the ANSYS MAXWELL 3-D finite element model of the DD magnetic coupling structure is built, and the validity and feasibility of the proposed design method are verified by simulation. Under the design method of coil structure parameter in this paper, the magnetic coupling structure can achieve excellent coupling performance and misalignment-tolerant ability.