Standard Magnetic Measurements Research Articles

Using NMR linewidth broadening for magnetic characterization of micrometer-size particles in silicone matrix

Standard magnetization measurements on samples of small magnetic particles may generate conflicting results. We compare the mass magnetization of MgZn ferrite particles in a compressed bulk material and in dry powder and find that at low fields the values can differ by as much as 50%. We show here that embedding the particles in a silicone matrix and measuring the NMR linewidth in combination with simulations establishes a new method to evaluate the magnetization of the particles at different fields and temperatures. The NMR results agree with the direct magnetization measurements of the powder samples and the magnetization measurements of the particles embedded in silicone. This work is motivated, in part, by studies on using small magnetic particles as MRI temperature indicators, and we compare the effectiveness of these particles for low-field and high-field MRI thermometry.

Assessment of measurement performance for a low field side IDTT plasma position reflectometry system

The Italian Divertor Test Tokamak (IDTT) facility will study advanced exhaust solutions applicable to DEMO. This new machine also opens the possibility to test and validate relevant non-magnetic control diagnostics in support of a DEMO design implementation. Reflectometry, compatible with a full grade reactor implementation, has been proposed as a source of real-time (RT) plasma position and shape measurements for control purposes, in replacement or complement of standard magnetic measurements, to ensure reliability and safety on the machine. Additionally, such a system can be useful to obtain the characteristics of edge turbulence, useful for Neoclassical Tearing Mode (NTM) control or to improve the efficiency of other diagnostics as Collective Thomson Scattering (CTS). This new control technique based on multiple, poloidally distributed, non-magnetic measurements, must be tested, in all of its aspects, before it can be fully implemented in future fusion reactors. IDTT will be one of the best candidates to implement and build a knowledge database of nonstandard reflectometry (away from the equatorial plane) that will be needed on DEMO and is currently unavailable. The performance of three Ordinary mode (O-mode) Plasma Position Reflectometers (PPR) at the Lower Field Side (LFS) on IDTT is assessed using the two-dimensional (2D) full-wave Finite-Difference Time-Domain (FDTD) code, REFMULF, in two of the foreseen IDTT plasma scenarios: 5MA Single Null (SN) and Double Null (DN) configurations.

Thickness dependences of structural and magnetic properties of Ni(Co)MnSn/MgO(001) thin films

The influence of film thickness on the formation of twinning structure, martensitic transformation and magnetoelastic properties of epitaxial films of Ni(Co)MnSn magnetic shape memory alloy is investigated by means of ferromagnetic resonance spectroscopy, synchrotron X-ray diffraction and standard magnetic measurements. It is found that constraints from the film/substrate interface block the martensitic transformation in the 20 nm thick film. The increase of the film thickness results in a progressive stress relaxation and, as a result, the martensitic transformation becomes possible starting from 50 nm. Twinning of the films is required to conserve the films surface area. The elastic energy balance between the film/substrate interface and the twin boundaries leads to the formation of a submicron wide, stripe like, periodical structure of twins, which is of interest for spintronic or magnonic applications. The width of the twin variants increases with the film thickness growth, resulting in the dramatic modification of magnetic properties.

Decomposing magnetic field measurements into internally and externally sourced components in toroidal plasma devices

The magnetic field on any closed surface can be separated into the component produced by currents in the volume enclosed by the surface and the component produced by currents external to the surface. This decomposition was first discovered by Gauss in 1839, and “Gauss' Algorithm” was used to show that the terrestrial field is sourced from inside the Earth. This magnetic source-decomposition can be used in magnetic confinement fusion to distinguish plasma fields from the fields of external sources using standard magnetic measurements, when no conductors reside in the region between the plasma and the magnetic sensors (otherwise, the internal source is not the plasma alone). Here, Gauss' Algorithm is extended from spherical geometry to cylindrical geometry to decompose fields in the cylindrical tokamak. Demonstrations of the decomposition on DIII-D discharges include the measurement of a rotating tearing mode separate from the induced wall eddy currents and the recovery of a vacuum measurement in the presence of an externally applied 3D field. Anticipated axisymmetric and non-axisymmetric applications, and the requisite diagnostics, are discussed. It is concluded that the ITER magnetic diagnostic design is well suited for many important axisymmetric and non-axisymmetric applications. Future work will extend this decomposition to include fields from halo currents and to generalize it to arbitrary toroidal geometries.

Ultrasonic fat fraction quantification using in vivo adaptive sound speed estimation

The non-invasive quantification of human tissue fat fraction using easily scalable and accessible imaging technologies is crucial for the diagnosis of many diseases including liver steatosis. Here, we propose a non-invasive quantification of fat content using a highly accessible ultrasonic imaging technology. Ultrasonic echoes backscattered from human liver tissues are recombined to synthetize echoes of a virtual point-like reflector within the organs. This virtual point-like reflector is an ultrasonic analogue of artificial stars generated by laser beams in the field of astronomy, which are used to estimate the aberrations induced in the propagation medium. Here, the ultrasonic echoes from the point-like reflector provide an estimate of the Green’s function relating the ultrasonic array and the reflector location and consequently represent a measurement of the aberrations induced along the ultrasonic beam travel path. Maximizing the spatial coherence of echoes backscattered from this targeted region provides an estimate of the acoustic sound speed while iteratively making the reflector more echogenic. The acoustic sound speed is dependent of the organ fat content, and we derive and cross-validate a theoretical equation relating acoustic sound speed and fat content both in phantom experiments and humans. An ultrasound-based fat fraction was found to be highly correlated with the oil paraffin concentration (R2 = 0.985) in phantoms and well correlated with the gold standard magnetic resonance imaging proton density fat fraction measurements (R2 = 0.73) in patients.

Representation of microstructural features and magnetic anisotropy of electrical steels in an energy-based vector hysteresis model

This paper demonstrates how the statistical distribution of pinning fields in a ferromagnetic material can be identified systematically from standard magnetic measurements, Epstein frame or Single Sheet Tester (SST). The correlation between the pinning field distribution and microstructural parameters of the material is then analyzed.

MnO nanoparticles as the cause of ferromagnetism in bulk dilute Mn-doped ZnO

We show that the observed ferromagnetic behavior of ZnO lightly doped with Mn coincides with the presence of MnO nanoparticles, whereas cluster-free Mn doped ZnO behaves paramagnetically. This conclusion is reached by a study of the structural and magnetic properties of powdered samples of (Mnx,Zn1–x)O with x ≤ 0.033 using polarized neutron scattering. Two types of samples were synthesized via, respectively, a solid state method and the decomposition of hydrozincite. Further characterization has been performed using standard X-ray diffraction and magnetization measurements. The results show evidence for the formation of MnO nanoparticles in the highest doped samples for both synthesis methods, with a ferromagnetic behavior attributed to uncompensated Mn2+ in the MnO nanoparticles. The lower Mn-doped samples showed no evidence for structural segregation or magnetic correlations and showed only a paramagnetic behaviour.

Estimated levator ani subtended volume: a novel assay for predicting surgical failure after uterosacral ligament suspension

Levator ani muscle complex plays an important role in pelvic support and defects or laxity in this muscle complex contributes to pelvic organ prolapse and recurrence after surgical repair. The purpose of this study was to determine whether estimated levator ani subtended volume can predict surgical outcomes for laparoscopic bilateral uterosacral ligament suspension. A retrospective cohort study was performed in patients who underwent laparoscopic uterosacral ligament suspension from 2010-2012. Only patients with a preoperative pelvic magnetic resonance image were included. Surgical failure was defined as a composite score that included the presence of anatomic bulge beyond the hymen with sensation of vaginal bulge or repeat treatment for prolapse via pessary or surgery by 1-year follow-up evaluation. Standard protocol pelvic magnetic resonance imaging measurements pubococcygeal line, H-line, and M-line were collected along with the calculation of the width of the levator ani hiatus. Estimated levator ani subtended volume was calculated for each subject. An optimal cutoff point was calculated and compared against categoric values of surgical success/failure. A Fisher exact test, an area under receiver operating characteristics curve, and logistic regression analysis were performed. A probability value of <.05 was considered statistically significant. Ninety-three women underwent laparoscopic bilateral uterosacral ligament suspension during study period. Of these, 66 women had a standardized preoperative pelvic magnetic resonance image per institutional protocol. Thirteen patients (19.6%) met the criteria for surgical failure by 1 year. An optimal cutoff point of 38.5 was calculated by Liu's method for optimization. Among the patients with defined surgical failures, 84.6% (11/13) had an estimated levator ani subtended volume above cutoff point of 38.5. Among the patients with defined surgical success, 39.6% (21/53) had an estimated levator ani subtended volume above the cutoff point (84.6% vs 39.6%; P= .0048) with a significant odds ratio of 8.38 (95% confidence interval, 1.69-41.68; P= .009). An area under receiver operating characteristics curve of 0.725 (95% confidence interval, 0.603-0.847), sensitivity of 84.6% (95% confidence interval, 54.6%-98.1%), and specificity of 60.4% (95% confidence interval, 46%-73.5%) at 38.5 were predictors of surgical success/failure by 1 year. Logistic regression analysis demonstrated no significant confounders among age, body mass index, stage, or parity. Estimated levator ani subtended volume may predict surgical failure for laparoscopic bilateral uterosacral ligament suspension. Patients with a calculated estimated levator ani subtended volume above 38.5 on a preoperative pelvic magnetic resonance imaging were associated with an increased risk for surgical failure by 1 year, regardless of age, body mass index, stage, or parity. Future investigation that will include repeatability, reliability analysis, and a prospective study is warranted.

ベクトル磁気特性制御材の開発

There is rotational iron loss under the V-junction in the yoke in an actual transformer because not only alternating magnetic field but also rotational and elliptical magnetic field are generated. The rotational iron loss can not be grasped in the standard magnetic measurements because it is assumed that the vectors of magnetic flux density B and magnetic field strength H are scalar quantity in them. We have proposed a two-dimensional vector magnetic measurement technique which can measure the B-vector and H-vector that are in the different directions，additionally，which can grasp the rotational iron loss. There is also phase difference θBH between the B-vector and the H-vector. The iron loss is calculated by the inner product between the B-vector and the H-vector. Therefore，the iron loss increases depending on the θBH. We controlled the θBH by fining the magnetic domain，and developed a new electrical steel sheet，and named “a vector magnetic characteristic controlled electrical steel sheet” which can reduce the iron loss. This paper presents the detail measured results from a vector magnetic characteristic controlled electrical steel sheet.

Sensitivity Analysis and Modeling of Symmetric Minor Hysteresis Loops Using the GRUCAD Description

This paper presents a predictive and easily implementable hysteresis model for ferromagnetic laminations subjected to various quasi-static magnetic loads. In this model, the description of magnetic hysteresis is based on the decoupling of the magnetic field strength in a reversible and irreversible part, unlike in the Jiles-Atherton model. Thereby, the source of problems originating in the assumption that total magnetization could be split into the reversible and the irreversible component is bypassed. It should be stressed that models based on field separation principles are consistent with the laws of thermodynamics. The presented model allows for a systematic parameter identification based on standard magnetic measurements. In this paper, the variation of model parameters on the shape of the modeled hysteresis loop is presented. Furthermore, parameter identified from the major loop are applied to model symmetric minor loops that are evaluated by comparison with measurements. The structure of the model enables an inclusion of eddy-current effects, and is ready for a further exploitation in the FE modeling of macroscopic devices.

Temperature and composition dependence of magnetic properties of cobalt–chromium co-substituted magnesium ferrite nanomaterials

The temperature and composition dependence of magnetic properties of Co–Cr co-substituted magnesium ferrite, Mg1−xCoxCrxFe2−xO4 (x=0.0–0.5), prepared by novel polyethylene glycol assisted microemulsion method, are studied. The synthesized materials are characterized by the Mössbauer spectrometer and standard magnetic measurements. Major hysteresis loops are measured up to the magnetic field of 50kOe at 300, 200 and 100K. The high field regimes of these loops are modeled using the Law of Approach to saturation to determine the first-order cubic anisotropy coefficient and saturation magnetization. Both the saturation magnetization and the anisotropy coefficient are observed to increase with the decrease in temperature for all Co–Cr co-substitution levels. Also, both the saturation magnetization and the anisotropy coefficient achieved maximum value at x=0.3 and x=0.2, respectively. Explanation of the observed behavior is proposed in terms of the site occupancy of the co-substituent, Co2+ and Cr3+ in the cubic spinel lattice.

Measurement of electromagnetic properties of heat exchanger tubes

Electromagnetic properties of heat exchanger tubes made of SAF 2205, Type 439 and Sea-Cure stainless steels were determined with magnetic and electrical techniques. The standard magnetic measurements were conducted at direct (DC) and alternate (AC – 200Hz) current excitation. The magnetic permeability, coercivity, retentivity, and other magnetic parameters were measured in tube axial and circumferential direction, in open and closed magnetic circuits and in wide range of magnetic field strengths from 10A/m to 82kA/m. The electrical conductivity was determined with custom-designed fixture in axial direction only at DC and AC (50 – 200Hz). The unique set of results revealed that a certain anisotropy of properties existed between the two geometric directions. The agreement between the measurements from the different techniques was good where comparison was possible.

Fabrication of the New Y3Ba5Cu8O y Superconductor Using Melt–Powder–Melt–Growth Method and Comparison with YBa2Cu3O7−x

YBaCuO superconducting sample with nominal composition in the stoichiometric ratio of 3:5:8 was fabricated by using the Melt–Powder–Melt–Growth (MPMG) process. Microstructural property of the sample was examined by X-rays diffraction (XRD) pattern and also observed at micrographs taken by both a polarized optical microscope and a scanning electron microscope (SEM) with energy dispersion analysis of X-rays (EDAX). Identification of chemical composition of the sample was investigated by the SEM-EDAX. Electric and magnetic properties were performed with a standard four-probe dc technique and magnetic levitation force measurements, respectively. In addition, all of these properties were compared with a standard MPMG YBa2Cu3O7−x (Y123) superconductor. According to the obtained results, it was determined that empirical resulting formula of the sample was Y3Ba4.89Cu8.17Oy (Y358) and also the magnetic levitation force of the Y358 was 169.8 mN under zero-field-cooled (ZFC) regime at 77 K while that of the Y123 was 99.3 mN.

CuSn(OH) 6 submicrospheres: Room-temperature synthesis, growth mechanism, and weak antiferromagnetic behavior

CuSn(OH) 6 submicrospheres with diameters of 400–900 nm have been successfully fabricated using a simple aqueous solution method at room temperature. Influencing factors such as the dosage of reactants and reaction time on the preparation were systematically investigated. The products were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and differential thermal analysis (DTA). Results reveal that the CuSn(OH) 6 spheres are built from numerous nanoparticles. It is found that the diameter of CuSn(OH) 6 spheres can be readily tuned by adjusting the molar ratio of Sn O 3 2 − to Cu 2+. A possible growth mechanism for the CuSn(OH) 6 submicrospheres has been proposed. Amorphous CuSnO 3 submicrospheres were obtained after thermal treatment of the CuSn(OH) 6 submicrospheres at 300 °C for 4 h. Standard magnetization measurements demonstrate that the CuSn(OH) 6 submicrospheres are antiferromagnetic and have a weak spin-Peierls transition at about 78 K.

On the determination of vortex creep parameters in superconductors using standardmagnetization relaxation data

The relaxation of the irreversible magnetic momentm(t) inYBa2Cu3O7 (YBCO) films was investigated as a function of temperatureT and the externalmagnetic field H along the c axis applied in zero-field cooling conditions, for the determination ofvortex creep parameters. The data analysis was performed using theT and current density dependence of the normalized vortex creep activation energy, or by the fit of them(t) data with the well known interpolation formula in the framework of the generalvortex creep equation. It was found that (i) even for specimens with strongstatic pinning the characteristic pinning energy remains small in the low-T range, where the vortex creep appearing in standard magnetizationmeasurements is elastic, (ii) the observed strong increase of the timescale for creep and the decrease of the creep exponent with increasingH beyond the theoretical predictions can be attributed to the crossoverelastic-creep–plastic-creep generated by the macroscopic currents inducedin the specimen during magnetization measurements, and (iii) the creepparameters extracted with the interpolation formula are highly affected by them(t) data registeredat short t, which may lead to unphysical creep parameter values.

Interpretation of 31P NMR saturation transfer experiments: what you can't see might confuse you. Focus on “Standard magnetic resonance-based measurements of the Pi→ATP rate do not index the rate of oxidative phosphorylation in cardiac and skeletal muscles”

the measurement of unidirectional rates of reaction, in vivo, using magnetization transfer techniques is a unique capability of nuclear magnetic resonance spectroscopy (NMRS). However, the complicated network of cytosolic reactions as well as the potential existence of small exchanging metabolic

Phase coexistence and magnetic anisotropy in polycrystalline and nanocrystalline LaMnO3+δ

We report on the phase coexistence and magnetic anisotropy in polycrystalline (bulk) and nanocrystalline (∼15 nm) LaMnO3+δ materials, which were prepared by solid state reaction and sol-gel methods, respectively. In addition to standard magnetization measurements, radio-frequency transverse susceptibility (TS) based on a very sensitive, self-resonant tunnel diode oscillator method was used to probe magnetic anisotropy and switching fields in the samples. The results revealed a coexistence of the ferromagnetic (FM) and antiferromagnetic (AFM) phases in both samples. For the bulk sample, the AFM phase significantly changed in volume fraction at ∼30 K and completely vanished around 120 K. Size reduction to the nanometer scale (∼15 nm) significantly suppressed the AFM phase while inducing surface spin disorder in the material. The large magnetic anisotropies were probed by TS experiments in both samples. Our studies showed that the magnetic properties of bulk LaMnO3+δ were strongly modified by size reduction.

Standard magnetic resonance-based measurements of the Pi→ATP rate do not index the rate of oxidative phosphorylation in cardiac and skeletal muscles

Magnetic resonance spectroscopy-based magnetization transfer techniques (MT) are commonly used to assess the rate of oxidative (i.e., mitochondrial) ATP synthesis in intact tissues. Physiologically appropriate interpretation of MT rate data depends on accurate appraisal of the biochemical events that contribute to a specific MT rate measurement. The relative contributions of the specific enzymatic reactions that can contribute to a MT P(i)→ATP rate measurement are tissue dependent; nonrecognition of this fact can bias the interpretation of MT P(i)→ATP rate data. The complexities of MT-based measurements of mitochondrial ATP synthesis rates made in striated muscle and other tissues are reviewed, following which, the adverse impacts of erroneous P(i)→ATP rate data analyses on the physiological inferences presented in selected published studies of cardiac and skeletal muscle are considered.

CuSn(OH) 6 submicrospheres: Room-temperature synthesis and weak antiferromagnetic behavior

CuSn(OH) 6 submicrospheres with a diameter of 400–900 nm, which are composed of nanoparticles with a size of about 27.8 nm, have been successfully synthesized for the first time via a simple liquid approach at room temperature in 15 min. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the products. Standard magnetization measurements at low temperature reveal that the as-obtained CuSn(OH) 6 submicrospheres are antiferromagnetic and have a weak spin-Peierls transition at about 78 K.

Cardiac function in growth hormone deficient patients before and after 1 year with replacement therapy: a magnetic resonance imaging study

Assessed by conventional echocardiography the influence of growth hormone deficiency (GHD) and effects of replacement therapy on left ventricle (LV) function and mass (LVM) have shown inconsistent results. We aimed to evaluate cardiac function before and during replacement therapy employing the gold standard method cardiac magnetic resonance imaging (CMRI) and measurements of circulating levels of B-type natriuretic peptides. Sixteen patients (8 males and 8 females, mean age 49 years (range 18-75)) with severe GHD and 16 matched control subjects were included. CMRI was performed at baseline and after 1 year of GH replacement therapy. IGF-I, B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) were measured after 0, 1, 2, 3, 6 and 12 months of treatment. IGF-I Z-score increased from (median (IQR)) -2.3 (-3.8 to -1.4) to 0.5 (-0.3 to 1.7). LVM index (LVMI), ejection fraction (range 63-80%), cardiac output index and levels of BNP and NT-proBNP were similar at baseline in patients compared to controls (P-values from 0.09 to 0.37). The patients had significantly smaller LV end-diastolic volume index (P = 0.032) and end-systolic volume index (P = 0.038). No significant change in LV systolic function or LVM occurred during 1 year of GH treatment. BNP levels were unchanged (P = 0.88), whereas NT-proBNP tended to decrease (P = 0.052). Assessed by the highly sensitive and precise CMRI method, untreated GHD was not associated with impaired systolic function or reduced LVMI and 1 year of GH replacement using physiological doses did not influence cardiac mass or function.