Magnetic Property Measurement System Research Articles

Control of Rotating Magnetic Flux Distribution in a Transformer Model Core by Laser Irradiation

To reduce power loss of transformers further from now on and to raise efficiency, we have measured magnetic property distributions in a three-phase tripod V-connection transformer model core. For the measurement, we have developed a localized vector magnetic property measurement system consisting of a three-axis positioning system, a vector magnetic sensor (V-H sensor), and PC. The measured results showed that rotational magnetic fluxes with a large axis ratio were generated in the V-junction parts of the transformer model core, and large iron loss was observed. To reduce the iron loss near the V-junction parts, we have tried to change local magnetic characteristics of the electrical steel sheet near the V-junction parts by using laser irradiation. The effect of the laser irradiation on the local magnetic properties is evaluated by measuring distributions of the local magnetic properties.

Effects of neutron irradiation on superconducting critical temperatures of in situ processed MgB2superconductors

Effects of neutron irradiation on the superconducting properties of the undoped <TEX>$MgB_2$</TEX> and the carbon(C)-doped <TEX>$MgB_2$</TEX> bulk superconductors, prepared by an in situ reaction process using Mg and B powder, were investigated. The prepared <TEX>$MgB_2$</TEX> samples were neutron-irradiated at the neutron fluence of <TEX>$10^{16}-10^{18}n/cm^2$</TEX> in a Hanaro nuclear reactor of KAERI involving both fast and thermal neutron. The magnetic moment-temperature (M-T) and magnetization-magnetic field (M-H) curves before/after irradiation were obtained using magnetic property measurement system (MPMS). The superconducting critical temperature (<TEX>$T_c$</TEX>) and transition width were estimated from the M-T curves and critical current density (<TEX>$J_c$</TEX>) was estimated from the M-H curves using a Bean's critical model. The <TEX>$T_cs$</TEX> of the undoped <TEX>$MgB_2$</TEX> and C-doped <TEX>$MgB_2$</TEX> before irradiation were 36.9-37.0 K and 36.6-36.8 K, respectively. The <TEX>$T_cs$</TEX> decreased to 33.2 K and 31.6 K, respectively after irradiation at neutron fluence of <TEX>$7.16{\times}10^{17}n/cm^2$</TEX>, and decreased to 22.6 K and 24.0 K, respectively, at <TEX>$3.13{\times}10^{18}n/cm^2$</TEX>. The <TEX>$J_c$</TEX> cross-over was observed at the high magnetic field of 5.2 T for the undoped <TEX>$MgB_2$</TEX> irradiated at <TEX>$7.16{\times}10^{17}n/cm^2$</TEX>. The <TEX>$T_c$</TEX> and <TEX>$J_c$</TEX> variation after the neutron irradiation at various neutron fluences were explained in terms of the defect formation in the superconducting matrix by neutron irradiation.

A Complex-Valued Rotating Magnetic Property Model and Its Application to Iron Core Loss Calculation

This paper presents a complex-valued model when considering rotational magnetic properties of an electrical steel sheet from the viewpoint of improving the computation efficiency. The effective magnetic reluctivity and magnetic hysteresis coefficients in this model were interpolated from measured data based on a 2-D rotational magnetic property measurement system, in which the effect of higher harmonic terms of magnetic field intensity after saturation was considered. To reduce the computation error to some extent resulted from complex approximation of magnetic field quantities, the effective magnetic coefficients were expressed as the function of magnitude and direction of magnetic flux density. Considering transformer and three-phase induction motor core models as examples, the magnetic field distribution and core loss were calculated and the effectiveness of the proposed model was verified with the experimental results.

Size dependent structural and magnetic properties of Al substituted Co–Mg ferrites synthesized by the sol–gel auto-combustion method

Single phased nanocrystalline Co0.7Mg0.3FeAlO4 ferrites having low coercivity were synthesized by the sol–gel auto-combustion route. The subsequent powder materials were sintered in a temperature range of 800–1200°C for 2h. The effects of sintering temperatures on the structure, morphology and magnetic properties of the prepared soft magnetic material were studied. X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and magnetic property measurement system (MPMS) were used to characterize the samples. X-ray diffraction analysis confirmed a single-phase cubic spinel structure and ruled out the presence of impurities like hematite. The higher sintering temperatures have caused in enhanced mark of crystallinity and bigger average grain size of the nanocrystals. A slight decrease in lattice parameters was noticed with a rise of grain size. Magnetic measurements revealed that grain size increase led to a decrease in the coercivity and, in difference, an increase in the saturation magnetization.

Structural and magnetic properties of erbium doped nanocrystalline Li–Ni ferrites

A series of nanocrystalline Li0.25Ni0.5Fe2.25−xErxO4 (x=0.00, 0.02, 0.06, 0.08, and 0.10) ferrite powders, having a cubic spinel crystal structure and a low value of coercivity, was synthesized by the sol–gel auto-combustion route. The structure, morphology and magnetic properties of the prepared nanoferrites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the magnetic property measurement system (MPMS). A well-defined single phase spinel structure is confirmed in all the samples by X-ray diffraction analysis. The lattice parameters of the samples increase slightly with increasing the erbium content. The crystallite size of the Er-doped samples is smaller than that of pure Li–Ni ferrite, and decrease regularly in the range of 36.0–14.5nm. It has been observed that the magnetic properties of these ferrites are strongly influenced by the added erbium content. The magnetic measurements indicate that saturation magnetization (Ms) and coercivity (Hc) decrease gradually with the increase of Er content in the lattice.

Template-free synthesis and magnetic properties of hollow Cu/Fe3O4 heterodimer sub-microcactus

Hollow Cu/Fe3O4 heterodimer sub-microcactus has been successfully fabricated by a facile one-pot solvothermal method without any templates, which was confirmed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and a magnetic property measurement system. Batch experiments showed that the morphology is strongly influenced by the content of Cu in the Cu/Fe3O4 samples. A mechanism for the formation of the hollow heterodimer sub-microcactus by a cooperation of oriented attachment and localized Ostwald ripening processes has been proposed based on the observations of time-dependent experiments. Magnetic measurements illustrated that the prepared hollow heterodimer sub-microcactus are superparamagnetic magnets with a saturation magnetization of 65.2 emu g−1. The synthesized hollow Cu/Fe3O4 heterodimer sub-microcactus may have important applications in catalysis, energy storage and biomedical applications.

Effect of superconducting magnet remanence on the soft magnetic material measurements

The superconducting magnet is used to provide magnetic field in a magnetic property measurement system (SQUID-VSM, Quantum Design), since it can provide high magnetic field up to 7 T. Due to the pinned magnetic flux, there is residual magnetic field as the magnetic field is set to be 0 from high field. There appears an error between the reported filed and the real filed. Sometimes, the residual magnetic field can be more than 30 Oe. It is so large that it may provide incorrect experiment data, such as Hc, Mr and inverted hysteresis loops. The effect of residual magnetic field on the soft magnetic material measurements should not be neglected. The residual magnetic field is dependent on initial magnetic field. The experimental data must be corrected by measuring the standard sample. In the paper we investigate the origin and the regular pattern of the residual magnetic field. The effects on the measurement results and the correction method are presented.

AMP/IO-PAN 복합체를 이용한 방사성 핵종(코발트, 스트론튬, 세슘)의 흡착 제거

Applicability of ammonium molybdophosphate/iron oxides-polyacrylonitrile (AMP/IO-PAN) composites on the removal of radionuclides in the radioactive wastewater generated from nuclear power plants was investigated. The composites were characterized using the following analytical techniques: X-ray diffraction (XRD), Fourior transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), particle size analyzer (PSA), nitrogen adsorption-desorption and magnetic property measurement system (MPMS). 10wt% of AMP/IO-PAN composite has a saturation magnetization of 2.038 emu/g. Single-solute sorptions of Co, Sr and Cs onto 10wt% of AMP/ IO-PAN composite were investigated. The maximum sorption capacities (Q) predicted by the Langmuir model on 10wt% of AMP/IO-PAN composite were 0.097, 0.086 and 0.66 mmol/g for Co, Sr and Cs, respectively. The maximum sorption capacities (Q) of Cs predicted by Langmuir model on 0, 10, 20 and 30wt% of AMP/IO-PAN composites were 0.702, 0.655, 0.602 and 0.559 mmol/g, respectively. The maximum sorption capacities (Q) of Cs decreased with increasing the iron oxide content in the AMP/IO-PAN composites.

Simplified analysis of iron loss in three-phase transformer considering rotating loss

Purpose – A simplified method for calculating iron loss of three-phase transformer is proposed in this paper. The rotating iron loss measured from 2-D vector magnetic property measurement system of gain-oriented silicon steel sheet can be taken into account in this method. The paper aims to discuss these issues. Design/methodology/approach – The finite element analysis formulation is combined with the magnetic reluctivity model expressed by diagonal tensor for 2-D nonlinear and anisotropic magnetic problem, while the iron loss is computed in terms of the interpolation of rotational loss curves measured under various loci of controlled magnetic flux density B. Findings – The iron loss of three-phase transformer is obtained by the proposed method. And the calculating iron loss is verified with experimental results. Originality/value – The method presented in this paper enables the iron loss of three-phase transformer to be more accurately calculated and more easily applied, considering the rotational iron loss.

Hydrothermal synthesis and magnetic properties of multiferroic rare-earth orthoferrites

• Orthoferrites RFeO 3 were prepared via hydrothermal synthesis in low temperatures. • The factors affecting the formation and growth of RFeO 3 were investigated. • A dissolution–precipitation mechanism was proposed. • R 3+ ionic radius affects the synthesis and magnetic properties. • The spin reorientation temperatures show some difference compared with literatures. Rare-earth orthoferrites RFeO 3 are gifted with fantastic magnetic properties. They have become a research focus for developing multiferroics in recent years. However, it is difficult to obtain pure-phase RFeO 3 from the high-temperature synthesis methods. In this work, we report hydrothermal synthesis of well-crystallized pure-phase orthoferrites RFeO 3 (R = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in low temperatures. Structures, morphologies and magnetic properties of the products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), magnetic property measurement system (MPMS), vibrating sample magnetometer (VSM), etc. The expected products were determined to be orthorhombic crystals of perovskite structure. The influences of alkalinity, reaction temperature and time on the formation and growth of RFeO 3 crystals were investigated in details, and a dissolution–precipitation mechanism was proposed for describing the formation and growth. Optimum hydrothermal conditions for synthesizing orthoferrites RFeO 3 were concluded. The magnetic properties were systematically characterized and studied, including antiferromagnetic transition of Fe ( T N1 ), spin reorientation ( T SR ), compensation effect ( T comp ), ordering of R ( T N2 ), etc. The relation between the magnetic properties of RFeO 3 and the ionic radii of R was investigated and discussed. The experimental results in this work may provide fundamental support to the research and development of multiferroic materials.

STRUCTURE AND MAGNETIC PROPERTIES OF NANOCRYSTALLINE (Fe50Co50)73.5Cu1Nb3Si13.5B9 ALLOYS

( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 amorphous ribbons, a type of Co doped Finemet alloy, were prepared by melt-spinning and annealed at 440–560°C for 30 min. Influences of heat treatment and Co content on the crystallization were analyzed through differential scanning calorimetric (DSC) and X-ray diffractometry (XRD). The microstructure was analyzed by atomic force microscopy (AFM). The magnetic properties of ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 and Finemet ribbons were tested by an alternating current soft magnetic properties measurement system. A comparative study of frequency dispersion properties between ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 and Finemet was conducted. Results indicate that the optimal magnetic property has been achieved when ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 ribbons were annealed at the temperature range of 480°C–520°C, after which the grain size became between 10 nm and 20 nm. Although the permeability of ( Fe 50 Co 50)73.5 Cu 1 Nb 3 Si 13.5 B 9 is not as high as that of Finemet, this Co -doped Finemet amorphous alloy presents better high frequency properties, and therefore is a promising candidate for the high frequency field applications.

Transition-Metal Salt-Containing Silica Nanocapsules Elaborated via Salt-Induced Interfacial Deposition in Inverse Miniemulsions as Precursor to Functional Hollow Silica Particles

Aqueous core-silica shell nanocapsules were successfully prepared using liquid droplets containing transition-metal salt as templates in inverse miniemulsions. The formation of the silica shell was attributed to the interfacial deposition of silica species induced by the presence of the transition-metal salt. In addition to the control of the particle morphology, the incorporated transition-metal salts could be used to derivatize the particles and confer additional functionalities to the hollow silica particles. To demonstrate the derivatization, the magnetic hollow silica particles were prepared by converting iron salts to magnetic iron oxides by heat treatment. The particle morphology, size, and size distribution were characterized by transmission electron microscopy and scanning electron microscopy. The results show that the particle properties strongly depend on the type and the amount of salts, the amount of tetraethoxysilane (TEOS), the pH of the droplets, and the ratios of 2-hydroxyethyl methacrylate to aqueous HCl solution. The specific surface area and pore properties were characterized by N2 sorption measurements. The pore properties and specific surface area could be tuned by varying the amount of salt. Levels of elements and of iron oxides in the magnetic hollow particles were measured by energy-dispersive X-ray spectroscopy. Iron was distributed homogenously with silicon and oxygen in the sample. The magnetization measured by a magnetic property measurement system confirmed the successful conversion of the iron salts to magnetic iron oxides.

Synthesis of various magnetite nanoparticles through simple phase transformation and their shape-dependent magnetic properties

Shape-controlled synthesis of magnetite nanoparticles has been successfully carried out through simple phase transformation via a modified polyol process using akaganeite (β-FeOOH) as the precursor. Different shapes of magnetite nanoparticles, including solid nanospheres and solid and hollow nanoellipsoids, could be obtained by either adding the appropriate amount of sodium acetate (NaOAc) or using the anion exchange of β-FeOOH. NaOAc makes it possible to retain the rod-like shape of the precursor material during the phase transformation by coordinating the surface and controlling the basic pH to slow down dissolution–recrystallization mechanism. It is also proposed that chloride ions in the β-FeOOH structure play a key role in the formation of hollow structure. The shape-dependent magnetic properties were investigated using a magnetic property measurement system at 300 K. All magnetite nanoparticles exhibited ferromagnetic behaviour with different values of saturation magnetization (Ms) and coercivity (Hc), and these values were highly depend on the shape of the nanoparticles due to their different grain size, spin disorder, shape, and surface anisotropy.

Polyvinyl alcohol functionalized cobalt ferrite nanoparticles for biomedical applications

In the present work, cobalt ferrite nanoparticles (CoFe2O4 NPs) have been synthesized by combustion method. The surface of the CoFe2O4 NPs was modified with biocompatible polyvinyl alcohol (PVA). To investigate effect and nature of coating on the surface of CoFe2O4 NPs, the NPs were characterized X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The transmission electron microscopy (TEM) and dynamic light scattering (DLS) results demonstrate the monodispersed characteristics of CoFe2O4 NPs after surface modification with PVA. The decrease in contact angle from 162° to 50° with PVA coating on NPs indicates the transition from hydrophobic nature to hydrophilic. The Magnetic properties measurement system (MPMS) results show that the NPs have ferromagnetic behavior with high magnetization of 75.04 and 71.02emu/g of uncoated and coated CoFe2O4 NPs respectively. These PVA coated NPs exhibit less toxicity over uncoated CoFe2O4 NPs up to 1.8mgmL−1 when tested with mouse fibroblast L929 cell line.

Magnetic Co3O4 nanowires, preparation and properties

Abstract The Co 3 O 4 nanowires have been successfully synthesized via modified template method. The as-prepared products have been characterized by EDS, TEM and HRTEM analysis. The magnetic behavior of it is investigated by a magnetic property measurement system. The nanowires exhibit some novel magnetic properties, which are different from its bulk material. The temperature dependence curves of magnetization in zero-field-cooling and field-cooling exhibit two peaks of antiferromagnetic at blocking temperature of ∼23 K and ∼31 K, respectively. The field dependent M ( H ) curves of the Co 3 O 4 nanowires at T = 5 and 300 K both exhibit PM properties. Moreover, the diameter of nanowires is hence determined according to the finite size effect as approximately 7–11 nm, in consistent with the characterizations by HRTEM.

Development of Miniature Transducer-Type Magnetic Property Measurement for Motor Stator Core

In this paper, we present a new magnetic property measurement system. We developed a miniature transducer, with a 16-mm2 footprint, for measuring the local magnetic properties of a motor stator core. The construction of the transducer and measurement system is proposed, and experimental results show the validity of the measurements.

Note: A sample holder design for sensitive magnetic measurements at high temperatures in a magnetic properties measurement system

A sample holder design for high temperature measurements in a commercial MPMS SQUID magnetometer from Quantum Design is presented. It fulfills the requirements for the simultaneous use of the oven and reciprocating sample option (RSO) options, thus allowing sensitive magnetic measurements up to 800 K. Alternating current susceptibility can also be measured, since the holder does not induce any phase shift relative to the ac driven field. It is easily fabricated by twisting Constantan© wires into a braid nesting the sample inside. This design ensures that the sample be placed tightly into a tough holder with its orientation fixed, and prevents any sample displacement during the fast movements of the RSO transport, up to high temperatures.

Martensitic transformation in Fe–Ni nanoparticles prepared by a sol–gel process

The Fe–29.5wt.%Ni, Fe–33.0wt.%Ni, Fe–35.9wt.%Ni nanoparticles with narrow size distribution were prepared via a sol–gel process followed by a reduction treatment. The MT (martensitic transformation) of Fe–Ni nanoparticles was studied by Magnetic Property Measurement System (MPMS) and X-ray Diffraction (XRD). It was found that a considerable amount of low temperature martensite in Fe–29.5wt.%Ni and a small amount of martensite in Fe–33.0wt.%Ni nanoparticles were detected by XRD at room temperature, while martensite was not detected in the Fe–35.9wt.%Ni nanoparticles, showing apparently compositional dependence of MT in Fe–Ni nanoparticles. Moreover, the Ms (defined as turning point of the increasing rate of magnetic susceptibility [1]) of Fe–33wt.%Ni nanoparticles with an average particle size of 19.4nm was tested as high as 246K by both MPMS and XRD, which was nearly 100K higher than the Ms of counterpart Fe–33wt.%Ni bulk specimen. The possible reasons for high Ms of nanoparticles were discussed.

Three‐dimensional magnetostriction and vector magnetic properties under alternating magnetic flux conditions in arbitrary direction

AbstractThis paper presents the measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two‐dimensional vector magnetic property measurement system, and a three‐axial strain gauge. In order to know the magnetostriction in an arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in the thickness direction. In this paper, the three‐dimensional magnetostriction in nonoriented and grain‐oriented silicon steel sheets are compared. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 1–9, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21257

Thermal Plasma Synthesis of Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles were synthesized by injecting ferrocene vapor and oxygen into an argon/helium DC thermal plasma. Size distributions of particles in the reactor exhaust were measured online using an aerosol extraction probe interfaced to a scanning mobility particle sizer, and particles were collected on transmission electron microscopy (TEM) grids and glass fiber filters for off-line characterization. The morphology, chemical and phase composition of the nanoparticles were characterized using TEM and X-ray diffraction, and the magnetic properties of the particles were analyzed with a vibrating sample magnetometer and a magnetic property measurement system. Aerosol at the reactor exhaust consisted of both single nanocrystals and small agglomerates, with a modal mobility diameter of 8–9 nm. Powder synthesized with optimum oxygen flow rate consisted primarily of magnetite (Fe3O4), and had a room-temperature saturation magnetization of 40.15 emu/g, with a coercivity and remanence of 26 Oe and 1.5 emu/g, respectively.