Magnetic Measurement Data Research Articles

Modeling of Scalar Dependencies of Soft Magnetic Material Magnetization for Electrical Machine Finite-Element Simulation

The magnetization behavior and thus the form of the magnetization curve of electrical steel strongly depend on the direction of the magnetic field, frequency of excitation, external mechanical stress, and cut edge effect. These factors influence the performance of electrical machines and need to be considered in advanced machine design processes or numerical modeling. Most of the aforementioned effects occur locally in the machine and, therefore, need to be described locally. It is crucial to characterize the material under realistic conditions for adequate identification and quantification of the influences. In this article, modeling and simulation of soft magnetic material are performed based on a detailed magnetic characterization, considering magnetization amplitude, angle with respect to the rolling direction of magnetization, mechanical stress, and cut edge effect. The dependent soft magnetic material characteristics are derived from the magnetic measurement data and concluded into interpolation surfaces. Subsequently, these surfaces are used to simulate a synchronous machine designed for a traction drive of an electric vehicle by finite-element simulation. One of the main challenges is the correct determination of the local material properties, depending on the operating point, which influences global quantities such as losses and torque. This article provides a methodology to consider different local influences on the magnetization behavior of electrical steel in a finite-element simulation, thus offering the potential for improving electromagnetic circuit design.

V-doped ZnO diluted magnetic semiconductor prepared by chemical spray pyrolysis

Chemical spray pyrolysis is utilized to deposit ZnO thin films with varied vanadium (V) contents, offering a simple, low cost and large-scale production deposition process. The effect of introducing V on structural, morphological, optical, electrical and magnetic properties of ZnO thin films is studied. XRD measurements reveal single phase ZnO polycrystalline layers with hexagonal wurtzite structure and high texturing along {002} plane. The incorporation of V into the ZnO lattice is confirmed through the XRD peaks shift towards a higher angle. Further, the SEM micrographs indicate morphological transformation from hexagonal nanoplates to spherical particles when increasing the V content from 2% to 10% nominally. All films are optically transparent in VIS and NIR spectral regions and the optical transmittance is strongly decreasing with increasing the V percentage. The magnetic measurement data shows paramagnetic behavior for the ZnO layer doped with 2% V while ZnO layer doped with 10% V shows a small ferromagnetic behavior. Additionally, the magnetoresistance measurement at 1.6 T shows positive values at room temperature and increased from 6% to 12% when increasing V amount.

Boundary-Element Methods for Field Reconstruction in Accelerator Magnets

Magnetic fields in the aperture of particle accelerator magnets can be represented by boundary potentials, exploiting Kirchhoff's integral equation. Depending on the formulation, magnetic measurement data can be represented by the discrete approximations of Dirichlet or Neumann data at the domain boundary. The missing Cauchy data, which are related to the tangential-field components, can then be computed by the boundary-element method (BEM) in a numerical post-processing step. Evaluating the integral equation for field reconstruction inside the domain of interest will reduce measurement uncertainties and approximation errors due to the smoothing property of Green's kernel. Applications to the reconstruction of 2-D fields (integrated quantities from stretched-wire measurements) and 3-D fields (local quantities from measurements with moving induction-coil magnetometers) are presented.

Enhanced detection using stable isotope enriched 65Cu doped ferrite nanoparticles for tracing studies

65Copper stable isotope doped ferrite nanoparticles with two dopant concentrations were prepared by a co-precipitation method for conducting biomedical experiments at environmentally relevant concentrations. The synthesized (65CuxFe1-xFe2O4) nanoparticles were of 30 ± 7 nm in size and the VSM measurements showed a magnetic moment of 30 emu/g of un-doped ferrite particles at 310 K. The amount of 65Cu doped in the ferrite nanoparticles were calculated using ICP-MS. Cytocompatibility studies were performed through cellular toxicity assays on WRL68 liver cell line. MTT and ROS assay demonstrated cell viability in an order of Fe3O4>65Cu0.088Fe2.085O4>65Cu0.143Fe3.31O4. The cytocompatibility and magnetic measurement data set indicate that by doping a small amount of copper, the ferrite nanoparticles can retain their magnetic properties and the cytocompatibility is not severely compromised. 65Cu0.088Fe2.085O4 (d1-Fe3O4) and 65CuO nanoparticles were used for tracing experiments, wherein, even at a lower exposure concentration of 0.5 μg/mL, 65Cu can be detected in the media even when the copper background concentration is high. The results indicate the ability to perform biological studies at low exposure concentrations with enhanced detection ability. The proposed technique shows that isotope enriched copper doped ferrite can serve the purpose of quantifiable traceable nanocarriers.

Water current measurements using oceanographic bottom lander LoTUS

LoTUS is a bottom landing, Long Term Underwater Sensing node made for the observation of ocean water temperatures. LoTUS is moored to the seafloor and measures temperature according to a specified time schedule until, at the end of the mission, it surfaces to transmit the collected data to on-shore recipients using an Iridium link. The paper presents an extension of the sensing capability which includes water current velocity (speed and direction) using a robust, reliable and inexpensive Eulerian method. The method is based on the “tilting stick” principle where a combination of inertial and magnetic measurement data are used. The paper discusses the principal technique, modeling of the system, practical considerations, optimization of the setup for specific flow conditions, and the verification of experimental data.

Magnetic properties of the non-stoichiometric TbCo2Mnx and TbCo2Nix alloys

The crystal structure, magnetic and magnetothermal properties of non-stoichiometric TbCo2Mnx and TbCo2Nix alloys were studied. It was shown that single-phase compounds with the MgCu2-type structure exist up to a certain content of x (x < 0.4 for compounds with Mn and x ≤ 0.1 for compounds with Ni). The concentration changes of the lattice parameter, Curie temperature, magnetic moment of the 3d sublattice in TbCo2Mnx and TbCo2Nix alloys were compared. The magnetocaloric effect in alloys were estimated using data of magnetic and heat capacity measurements.

Magnetic properties of Cu2MnBO5 ludwigite in weak magnetic fields

The results of magnetization measurements in low and ultralow (0<|H|<10 Oe) magnetic fields are presented for single-crystal Cu2MnBO5 ludwigite. An own SQUID magnetometer and AC measurement system and vibrating sample magnetometer options of PPMS were used. Magnetic properties have been investigated at different cooling modes of the sample. The features of the magnetic moment behaviour are revealed. The dissimilarity of magnetic measurement data obtained using various types of magnetometers is observed. The reasons for this are discussed.

Thermodynamic and magnetic properties of compounds in the system MeO–Nd2O3–Mo(W)O3 (Me = Mg, Ca, Sr)

Using the sol-gel method we synthesized the samples of triple oxide compounds in equimolar ratios in the MeO–Nd2O3–MoO3 and MeO–Nd2O3–WO3 systems, where Me is alkaline-earth element (Mg, Ca, Sr, Ba). Structural research confirmed the formation of complex compounds in the samples of MgNdMo, CaNdMo, MgNdW, CaNdW, SrNdW. By adiabatic calorimetry we determined the thermodynamic functions of the samples and revealed low-temperature anomalies indicating magnetic interactions in their structure. The data of magnetic measurements in the compounds studied show the competitive ferro-antiferromagnetic interactions, which in the case of CaNdMo exert in a transition from the paramagnetic to antiferromagnetic state at T = 6 K.

Physical properties of double-doping Lanthanum manganite for bolometer applications

We have studied the structural, magnetic, critical behavior and electrical properties of La0.5Ag0.1Ca0.4MnO3 sample synthesized by traditional Solid State route. X-ray diffraction studies reveal that La0.5Ag0.1Ca0.4MnO3 crystallizes in the orthorhombic structure with Pnma space group. Vibrational study by means of infrared spectroscopy each give a part of the vibrational reality of the material explored. Studying the magnetic and electric properties of La0.5Ag0.1Ca0.4MnO3, it has been found the compound exhibits a second-order phase transition around the ferromagnetic-paramagnetic transition. The critical behavior of La0.5Ag0.1Ca0.4MnO3 compound is investigated based on the data of static magnetic measurements in the vicinity of its critical temperature TC. The estimated critical exponents derived from the magnetic data were estimated using modified Arrott plot (MAP) and critical isotherm technique (CI). The critical exponents find are comparable to the values theoretical predicted for the values corresponding to the 3D-Ising model and are confirmed by scaling equations of state. The investigated compound exhibits a semiconductor-metal transition at 380 K. For the important value of TCR at zero magnetic fields, we consider our sample is a good candidate infrared sensor for night vision bolometer applications.

Equilibrium Configuration Reconstruction of Multipole Galatea Magnetic Trap Based on Magnetic Measurement

Equilibrium reconstruction is an important basic work for the design and operation of a multipole Galatea magnetic trap device, and it is also a fundamental theoretical work for plasma equilibrium control. Based on the static equilibrium model of the multipole Galatea magnetic trap, an equilibrium reconstruction scheme based on solving the Grad–Shafranov equilibrium equation is proposed. In the proposed scheme, a plasma current density distribution model is established, and the combination of the Green function and the finite difference method is investigated to realize the fast solution to the Grad–Shafranov equilibrium equation. At the same time, the least-squares fitting method is employed, along with the magnetic probe measurement data, which realizes correction and iteration of the parameters of the plasma current density distribution model. Through simulation, the magnetic field distribution, plasma current density distribution, and plasma pressure distribution of multipole Galatea magnetic trap can be obtained, which confirms the effectiveness of the equilibrium reconstruction when compares with other experimental results. At the end of this paper, the influence of the magnetic field produced by the solenoid coil on the equilibrium configuration of plasma is studied.

The impact of Ag and Cu nanoparticles on optical and magnetic properties of new Tb2O3-PbO-TeO2 glass ceramic system

New lead tellurite glass ceramics doped with terbium (III) oxide and co-doped with AgNPs and CuNPs were obtained by melt quenching technique. The samples were analyzed by XRD, photoluminescence, UV–Vis spectroscopy and magnetic measurements. XRD data were used to estimate the nature of the obtained samples and also to determine the crystallites size. UV–Vis spectra reveal the presence of terbium ions in the batch and, for the samples co-doped with CuNPs, the presence of Cu2+ ions octahedrally surrounded by six oxygen atoms. Optical band gap energy values were calculated based on the UV–Vis data. The photoluminescence spectra exhibit the emission from terbium ions and also reveal the influence of the co-dopant nature on this emission. Magnetic measurements data show a complex behavior due the presence of Tb3+ ions, metal nanoparticles and to the microstructure of samples.

Enhanced perpendicular magnetocrystalline anisotropy energy in an artificial magnetic material with bulk spin-momentum coupling

We systematically investigate the perpendicular magnetocrystalline anisotropy (MCA) in Co$-$Pt/Pd-based multilayers. Our magnetic measurement data shows that the asymmetric Co/Pd/Pt multilayer has a significantly larger perpendicular magnetic anisotropy (PMA) energy compared to the symmetric Co/Pt and Co/Pd multilayer samples. We further support this experiment by first principles calculations on the CoPt$_2$, CoPd$_2$, and CoPtPd, which are composite bulk materials that consist of three atomic layers in a unit cell, Pt/Co/Pt, Pd/Co/Pd, Pt/Co/Pd, respectively. By estimating the contribution of bulk spin-momentum coupling to the MCA energy, we show that the CoPtPd multilayer with the symmetry breaking has a significantly larger perpendicular magnetic anisotropy (PMA) energy than the other multilayers that are otherwise similar but lack the symmetry breaking. This observation thus provides an evidence of the PMA enhancement due to the structural inversion symmetry breaking and highlights the asymmetric CoPtPd as the first artificial magnetic material with bulk spin-momentum coupling, which opens a new pathway toward the design of materials with strong PMA.

Hybridizable Discontinuous Galerkin Method Contrast Source Inversion of 2-D and 3-D Dielectric and Magnetic Targets

We present a microwave imaging algorithm capable of simultaneously reconstructing electric and magnetic targets from both electric and magnetic field measurement data, with support for arbitrary imaging system boundaries and inhomogeneous background media. A high-order time-harmonic discontinuous Galerkin method (DGM) forward solver is adopted within a contrast source inversion (CSI) algorithm formulated for electric and magnetic targets. Due to its high-order capabilities, the DGM forward solver effectively decouples the contrast and field discretizations without introducing a dual mesh. The drawback of standard DGM forward solvers, namely, their high computational cost, is addressed by a hybridizable DGM (HDGM) formulation. Synthetic and experimental results for both DGM-CSI and HDGM-CSI are presented for a variety of 2-D and 3-D measurement configurations and both dielectric and magnetic targets. HDGM-CSI is shown to have imaging performance comparable to FEM-CSI for dielectric targets, and significant additional flexibility that will enable future electromagnetic imaging applications and system design.

Formation of the magnetic subsystems in antiferromagnetic NiO nanoparticles using the data of magnetic measurements in fields up to 250 kOe

Abstract It is well-known that the fraction of surface atoms and the number of defects in an antiferromagnetic particle increase with a decrease in the particle size to tens of nanometers, which qualitatively changes the properties of the particle. Specifically, in antiferromagnetic nanoparticles, spins in the ferromagnetically ordered planes can partially decompensate; as a result, an antiferromagnetic particle acquires a magnetic moment. As a rule, uncompensated chemical bonds of the surface atoms significantly weaken the exchange coupling with the antiferromagnetic particle core, which can lead to the formation of an additional magnetic subsystem paramagnetic at high temperatures and spin-glass-like in the low-temperature region. The existence of several magnetic subsystems makes it difficult to interpret the magnetic properties of antiferromagnetic nanoparticles. It is shown by the example of NiO nanoparticles with an average size of 8 nm that the correct determination of the contributions of the magnetic subsystems forming in antiferromagnetic nanoparticles requires magnetic measurements in much stronger external magnetic fields than those commonly used in standard experiments (up to 60–90 kOe). An analysis of the magnetization curves obtained in pulsed magnetic fields up to 250 kOe allows one to establish the contributions of the uncompensated particle magnetic moment μun, paramagnetic subsystem, and antiferromagnetic particle core. The μun value obtained for the investigated NiO particles is consistent with the Neel model, in which μun ∼ N1/2 (N is the number of magnetically active atoms in a particle), and thereby points out the existence of defects on the surface and in the bulk of a particle. It is demonstrated that the anomalous behavior of the high-field susceptibility dM/dH of antiferromagnetic NiO nanoparticles, which was observed by many authors, is caused by the existence of a paramagnetic subsystem, rather than by the superantiferromagnetism effect.

In Ukrainian

in Ukrainian

Effect of Gd substitution on the critical scaling of the ferromagnetic transition of La0.6-x Gdx Sr0.4 MnO3(x=0, 0.05, 0.1) manganite

This paper presents a detailed study on the critical properties of perovskite manganite La0.6-x Gdx Sr0.4 MnO3(x = 0, 0.05, 0.1) synthesized by Sol-gel method. The critical exponents near the PM-FM phase transition are determined through various methods such as modified Arrot plot, Kouvel-Fisher methods, and critical isothermal analysis based on the data of magnetic measurements recorded around the Curie temperature. These specimens are in agreement with their corresponding values proved by Widom scaling law, as well as the scaling theory. According to the values of critical exponents, the presence of the phase transition is found to be not relevant to the common transition classes but they can be attributed to some abnormal variations. It is suggested that the induced lattice disordering and magnetic disordering, as a result of Gadolinium incorporation, to be potential reasons for the presence of a large magnetocaloric effect, in addition to an anomalous ferromagnetic phase transition in the studied material.

Study of plasma equilibrium reconstruction on HL-2A

An equilibrium reconstruction code is a basic tool for determining the plasma position, boundary, shape and current density profile in a tokamak discharge. The equilibrium reconstruction code CPF has been written to make these calculations. It uses a polynomial to describe the spatial distribution of current density. The coefficients of the polynomial are determined by the best least squares fit to the internal and external magnetic measurement data. A finite difference method is used to solve the Grad-Shafranov equation. The equilibrium magnetic surfaces satisfying the convergence criterion is obtained by Picard iteration. The CPF equilibrium reconstruction is also checked by comparing to results obtained by the equilibrium code SWEQU. The CPF code is stable and has been used for several years.

Unconventional critical behavior near the phase transition temperature and magnetocaloric effect in La0.5Ca0.4Ag0.1MnO3 compound

The critical behavior associated with the magnetic phase transition has been investigated by magnetization isotherms in La0.5Ca0.4 Ag0.1MnO3 (LCAMO) powder. The X-ray diffraction characterization has revealed that this sample crystallized in the orthorhombic symmetry with Pnma space group. While the experimental results revealed that this sample underwent a paramagnetic-ferromagnetic transition, the magnetic measurements data indicated that the compound exhibited a second-order phase transition. Furthermore, the critical exponents values were found as β = 0.79, γ = 0.71 and δ = 1.828 with TC = 189.87 K. The relative cooling power of the sample was determined as 14.70 J/kg under a magnetic field of 1 T making it a potential working material in magnetic refrigeration.

Erratum: “An MHD Simulation of Solar Active Region 11158 Driven with Time-dependent Electric Field Determined from HMI Vector Magnetic Field Measurement Data” (2018, ApJ, 855, 11)

Erratum: “An MHD Simulation of Solar Active Region 11158 Driven with Time-dependent Electric Field Determined from HMI Vector Magnetic Field Measurement Data” (2018, ApJ, 855, 11)

Numerical assessment of geometrical and magnetic parameters for dummy double pancake of ITER PF1 coil using optic and magnetic measurements

A measurement-based numerical reconstruction technique is proposed to control winding geometry of the poloidal coils manufactured for ITER. A detailed coil model is parameterized in terms of the magnetic characteristics. Deviations from the specified coil shape are evaluated in a comparison of reconstructed “ideal” field and data of magnetic measurements. The technique has been validated in the course of quality inspection of the dummy double pancake similar to the pancakes of the ITER PF1 coil. Experimental results are presented.