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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Adsorption Performance and Mechanisms of Methylene Blue Removal by Non-magnetic and Magnetic Particles Derived from the Vallisneria natans Waste

Vallisneria natans (V. natans) is a submerged aquatic plant, and its dried biomass waste was used to prepare magnetic particle biomass adsorbent by chemical co-precipitation via FeSO{sub 4}·7H{sub 2}O and FeCl{sub 3}·6H{sub 2}O as iron precursors. Brunauer–Emmett–Teller specific surface area, total pore volume, and average pore width were 7.434 m{sup 2} g{sup −1}, 0.013 cm{sup 3} g{sup −1}, and 6.992 nm for magnetic V. natans, correspondingly, and 3.575 m{sup 2} g{sup −1}, 0.004 cm{sup 3} g{sup −1}, and 4.476 nm for non-magnetic V. natans, respectively. The adsorption kinetics of methylene blue (MB) is a more appropriate fit for pseudo-second-order kinetic model than pseudo-first-order and intraparticle diffusion kinetic models. Isotherm results showed that the adsorption of MB onto the non-magnetic and magnetic adsorbents agrees well with Dubinin–Radushkevich isotherm model. Moreover, the thermodynamics study implied that the adsorption of MB onto both adsorbents is a spontaneous and exothermic process. The maximum adsorption capacities of MB on non-magnetic and magnetic V. natans were 657.90 and 473.93 mg g{sup −1} at 303 K, correspondingly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Investigation on Effect of Magnetic Field Dependency Coefficient of Critical Current Density on the AC Magnetizing Loss in HTS Tapes Exposed to External Field

High-temperature superconducting (HTS) technology is the most promising, advanced, and beneficial technological developments of the last two decades in terms of fabricating more efficient, compact, and reliable electrical power apparatus. The second-generation HTS wires are now quite competitive with traditional conductors from the cost point of view. In addition, they are of high interest in electrical machine manufacturing due to their unique merits such as high current density, high magnetic field, and low loss. The most significant issue for any superconducting devices which work with alternating current or magnetic field is the AC loss of the HTS tapes. Since HTS tapes are always exposed to an external magnetic field in electrical machine applications, it is vital to consider the effect of this external field on their AC magnetizing (ACMG) loss. It is well-known that external magnetic field decreases the current carrying capability of the wire. In real life, critical current density of HTS tapes is dependent to magnetic field but this dependency sometime was not considered in modeling stage in order to make it faster and simple. In this paper, the electromagnetic properties of HTS tapes for use in superconducting electric machines have been investigated with a particular focus on the ACMG loss of YBCO tapes. For this purpose, a two-dimensional finite element model has been implemented based on the H formulation in order to study the effect of dependency of critical current density to magnetic field on the variation of ACMG loss. The modeling results will be helpful for electrical machine designers to have a better understanding about this effect and have a more accurate estimate of ACMG loss in design stage.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Phase stability and magnetic and electronic properties of a spark plasma sintered CoFe – P soft magnetic alloy

More efficient power conversion devices are able to transmit greater electrical power across larger distances to satisfy growing global electrical needs. A critical requirement to achieve more efficient power conversion are the soft magnetic materials used as core materials in transformers, inductors, and motors. To that effect it is well known that the use of non-equilibrium microstructures, which are, for example, nanocrystalline or consist of single phase solid solutions, can yield high saturation magnetic polarization and high electrical resistivity necessary for more efficient soft magnetic materials. In this work, we synthesized CoFe – P soft magnetic alloys containing nanocrystalline, single phase solid solution microstructures and studied the effect of a secondary intermetallic phase on the saturation magnetic polarization and electrical resistivity of the consolidated alloy. Single phase solid solution CoFe – P alloys were prepared through mechanically alloying metal powders and phase decomposition was observed after subsequent consolidation via spark plasma sintering (SPS) at various temperatures. The secondary intermetallic phase was identified as the orthorhombic (Co x Fe 1-x ) 2 P phase and the magnetic properties of the (Co x Fe 1-x ) 2 P intermetallic phase were found to be detrimental to the soft magnetic properties of the targeted CoFe – P alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2019

3d-Metal Induced Magnetic Ordering on U(IV) Atoms as a Route toward U(IV) Magnetic Materials

Uranium(IV) 5f 2 magnetism is dominated by a transition from a triplet to a singlet ground state at low temperatures. For the first time, we achieved magnetic ordering of U(IV) atoms in a complex fluoride through the incorporation of 3d transition metal cations. This new route allowed us to obtain an unprecedented series of U(IV) ferrimagnetic materials of the new composition Cs 2 MU 3 F 16 (M = Mn 2+ , Co 2+ , and Ni 2+ ), which were comprehensively characterized with respect to their structural and magnetic properties. Magnetic susceptibility measurements revealed ferromagnetic-like phase transitions at temperatures of ~14.0, 3.5, and 4.8 K for M = Mn 2+ , Co 2+ , and Ni 2+ , respectively. The transition is not observed when the magnetic M cations are replaced by a diamagnetic cation, Zn 2+ . Neutron diffraction measurements revealed the magnetic moments of 0.91(6)–1.97(3) μ B on the U atoms, which are only partially compensated by antiparallel moments of 1.53(14)–3.26(5) μ B on the 3 d cations. This arrangement promotes suppression of the transition to a diamagnetic ground state characteristic of U(IV), and in doing so, induces magnetic ordering on uranium via 3 d –5 f exchange coupling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Complex magnetic properties associated with competing local and itinerant magnetism in \({\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}\)

Ternary intermetallic compound \({\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}\) has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ( \(\mu\) SR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below \(\sim\) 4 K. Neutron diffraction measurement further reveals that the magnetic ordering is antiferromagnetic in nature with an weak ordered moment. The high temperature magnetic phase has been attributed to glassy in nature consisting of ferromagnetic clusters of itinerant (3 d ) Co moments as evident by the development of internal field in zero-field \(\mu\) SR below 50 K. The density-functional theory (DFT) calculations suggest that the low temperature magnetic transition is associated with antiferromagnetic coupling between Pr 4 f and Co 3 d spins. Pr moments show spin fluctuation along with unconventional orbital moment quenching due to crystal field. The evolution of the symmetry and the crystalline electric field environment of Pr-ions are also studied and compared theoretically between the elemental Pr and when it is coupled with other elements such as Co. The localized moment of Pr 4 f and itinerant moment of Co 3 d compete with each other below \(\sim\) 20 K resulting in an unusual temperature dependence of magnetic coercivity in the system.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Low-temperature magnetic crossover in the topological kagome magnet TbMn 6 Sn 6

Magnetic topological phases of quantum matter are an emerging frontier in physics and materials science, of which kagome magnets appear as a highly promising platform. Here, we explore magnetic correlations in the recently identified topological kagome system TbMn6 S n 6 using muon spin rotation, combined with local field analysis and neutron diffraction. Our studies identify an out-of-plane ferrimagnetic structure with slow magnetic fluctuations which exhibit a critical slowing down below $T^{*}_{C1}$ ≃ 120 K and finally freeze into static patches with ideal out-of-plane order below T C1 ≃ 20 K. We further show that hydrostatic pressure of 2.1 GPa stabilises the static out-of-plane topological ferrimagnetic ground state in the whole volume of the sample. Therefore the exciting perspective arises of a magnetically-induced topological system whose magnetism can be controlled through external parameters. The present results will stimulate theoretical investigations to obtain a microscopic understanding of the relation between the low-temperature volume-wise magnetic evolution of the static c-axis ferrimagnetic patches and the topological electronic properties in TbMn 6 Sn 6 .

36 MATERIALS SCIENCE↗
DOE OSTI2016

Magnetic field sensor based on cascaded microfiber coupler with magnetic fluid

A kind of magnetic field sensor based on cascaded microfiber coupler with magnetic fluid is proposed and experimentally demonstrated. The magnetic fluid is utilized as the cladding of the fused regions of the cascaded microfiber coupler. As the interference valley wavelength of the sensing structure is sensitive to the ambient variation, considering the magnetic-field-dependent refractive index of magnetic fluid, the proposed structure is employed for magnetic field sensing. The effective coupling length for each coupling region of the as-fabricated cascaded microfiber coupler is 6031 μm. The achieved sensitivity is 125 pm/Oe, which is about three times larger than that of the previously similar structure based on the single microfiber coupler. Experimental results indicate that the sensing sensitivity can be easily improved by increasing the effective coupling length or cascading more microfiber couplers. The proposed magnetic field sensor is attractive due to its low cost, immunity to electromagnetic interference, as well as high sensitivity, which also has the potentials in other tunable all-fiber photonic devices, such as filter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Parallel magnetic field suppresses dissipation in superconducting nanostrips

The motion of Abrikosov vortices in type-II superconductors results in a finite resistance in the presence of an applied electric current. Elimination or reduction of the resistance via immobilization of vortices is the "holy grail" of superconductivity research. Common wisdom dictates that an increase in the magnetic field escalates the loss of energy since the number of vortices increases. Here we show that this is no longer true if the magnetic field and the current are applied parallel to each other. Our experimental studies on the resistive behavior of a superconducting Mo0.79Ge0.21 nanostrip reveal the emergence of a dissipative state with increasing magnetic field, followed by a pronounced resistance drop, signifying a reentrance to the superconducting state. Large-scale simulations of the 3D time-dependent Ginzburg-Landau model indicate that the intermediate resistive state is due to an unwinding of twisted vortices. When the magnetic field increases, this instability is suppressed due to a better accommodation of the vortex lattice to the pinning configuration. Our findings show that magnetic field and geometrical confinement can suppress the dissipation induced by vortex motion and thus radically improve the performance of superconducting materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Magnetic structure, excitations and short-range order in honeycomb Na 2 Ni 2 TeO 6

Na 2 Ni 2 TeO 6 has a layered hexagonal structure with a honeycomb lattice constituted by Ni 2+ and a chiral charge distribution of Na + that resides between the Ni layers. In the present work, the antiferromagnetic transition temperature of Na 2 Ni 2 TeO 6 is confirmed at TN˜ 27 K, and further, it is found to be robust up to 8 T magnetic field and 1.2 GPa external pressure; and, without any frequency-dependence. Slight deviations from nominal Na-content (up to 5%) does not seem to influence the magnetic transition temperature, TN. Isothermal magnetization curves remain almost linear up to 13 T. Our analysis of neutron diffraction data shows that the magnetic structure of Na 2 Ni 2 TeO 6 is faithfully described by a model consisting of two phases described by the commensurate wave vectors vec kc, (0.5 0 0) and (0.5 0 0.5), with an additional short-range order component incorporated in to the latter phase. Consequently, a zig-zag long-range ordered magnetic phase of Ni 2+ results in the compound, mixed with a short-range ordered phase, which is supported by our specific heat data. Theoretical computations based on density functional theory (DFT) predict predominantly in-plane magnetic exchange interactions that conform to a J1-J2-J3 model with a strong J3 term. The computationally predicted parameters lead to a reliable estimate for TN and the experimentally observed zig-zag magnetic structure. A spin wave excitation in Na 2 Ni 2 TeO 6 at E ˜ 5 meV at T = 5 K is mapped out through inelastic neutron scattering experiments, which is reproduced by linear spin wave theory calculations using the J values from our computations. Our specific heat data and inelastic neutron scattering data strongly indicate the presence of short-range spin correlations, at T > TN, stemming from incipient antiferromagnetic clusters.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet

Here, with the motivation to study how non-magnetic ion site disorder affects the quantum magnetism of Ba 3 CoSb 2 O 9 , a spin-1/2 equilateral triangular lattice antiferromagnet, we performed DC and AC susceptibility, specific heat, elastic and inelastic neutron scattering measurements on single crystalline samples of Ba 2.87 Sr 0.13 CoSb 2 O 9 with Sr doping on non-magnetic Ba 2+ ion sites. The results show that Ba 2.87 Sr 0.13 CoSb 2 O 9 exhibits (i) a two-step magnetic transition at 2.7 K and 3.3 K, respectively; (ii) a possible canted 120 degree spin structure at zero field with reduced ordered moment as 1.24 μ B /Co; (iii) a series of spin state transitions for both H∥ab-plane and H∥c-axis. For H∥ab-plane, the magnetization plateau feature related to the up–up–down phase is significantly suppressed; (iv) an inelastic neutron scattering spectrum with only one gapped mode at zero field, which splits to one gapless and one gapped mode at 9 T. All these features are distinctly different from those observed for the parent compound Ba 3 CoSb 2 O 9 , which demonstrates that the non-magnetic ion site disorder (the Sr doping) plays a complex role on the magnetic properties beyond the conventionally expected randomization of the exchange interactions. We propose the additional effects including the enhancement of quantum spin fluctuations and introduction of a possible spatial anisotropy through the local structural distortions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Magnetic phase diagram of (Mo 2/3 RE 1/3 ) 2 AlC, RE = Tb and Dy, studied by magnetization, specific heat, and neutron diffraction analysis

We report the results of magnetization, heat capacity, and neutron diffraction measurements on (Mo 2/3 RE 1/3 ) 2 AlC with RE = Dy and Tb. Temperature and field-dependent magnetization as well as heat capacity were measured on a powder sample and on a single crystal allowing the construction of the magnetic field-temperature phase diagram. To study the magnetic structure of each magnetic phase, we applied neutron diffraction in a magnetic field up to 6 T. For (Mo 2/3 Dy 1/3 ) 2 AlC in zero field, a spin density wave is stabilized at 16 K, with antiferromagnetic ordering at 13 K. Furthermore, we identify the coexistence of ferromagnetic and antiferromagnetic phases induced by magnetic fields for both RE = Tb and Dy. The origin of the field induced phases is resulting from the competing ferromagnetic and antiferromagnetic interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Planetary magnetic field control of ion escape from weakly magnetized planets

ABSTRACT Intrinsic magnetic fields have long been thought to shield planets from atmospheric erosion via stellar winds; however, the influence of the plasma environment on atmospheric escape is complex. Here we study the influence of a weak intrinsic dipolar planetary magnetic field on the plasma environment and subsequent ion escape from a Mars-sized planet in a global three-dimensional hybrid simulation. We find that increasing the strength of a planet’s magnetic field enhances ion escape until the magnetic dipole’s standoff distance reaches the induced magnetosphere boundary. After this point increasing the planetary magnetic field begins to inhibit ion escape. This reflects a balance between shielding of the Southern hemisphere from ‘misaligned’ ion pickup forces and trapping of escaping ions by an equatorial plasmasphere. Thus, the planetary magnetic field associated with the peak ion escape rate is critically dependent on the stellar wind pressure. Where possible we have fit power laws for the variation of fundamental parameters (escape rate, escape power, polar cap opening angle, and effective interaction area) with magnetic field, and assessed upper and lower limits for the relationships.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Manipulating magnetic moments by superconducting currents

Here, we show that the interaction between a superconducting order parameter and the magnetic moment of an atomic cluster in a two-dimensional s-wave superconductor with Rashba spin-orbit coupling generates magnetic anisotropy that can be stronger or comparable to the magnetic anisotropy due to the crystal field and the shape of the cluster. Transport current through the superconductor produces the effective magnetic field acting on the cluster’s magnetic moment. The direction of the effective field depends on the direction of the current, thus allowing one to manipulate the magnetic moment by the superconducting current. Due to the large density of the superconducting current this method of magnetization reversal can be more advantageous at low temperatures than the spin-transfer torque method that requires a large spin-polarized current through a normal metal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic field dependence of nonlinear magnetic response and tricritical point in the monoaxial chiral helimagnet Cr 1 / 3 Nb S 2

We present a comprehensive study of the magnetization dynamics and phase evolution in the chiral helimagnet Cr 1/3 NbS 2 , which realizes a chiral soliton lattice (CSL). The magnetic field dependence of the ac magnetic response is analyzed for the first five harmonic components, M nω (H ) (n = 1–5), using a phase sensitive measurement over a frequency range, f = 11–10 000 Hz. At a critical field, the modulated CSL continuously evolves from a helicity-rich to a ferromagnetic domain-rich structure, where the crossover is revealed by the onset of an anomalous nonlinear magnetic response that coincides with extremely slow dynamics. The behavior is indicative of the formation of a spatially coherent array of large ferromagnetic domains, which relax on macroscopic time scales. The frequency dependence of the ac magnetic loss displays an asymmetric distribution of relaxation times across the highly nonlinear CSL regime, which shift to shorter time scales with increasing temperature. We experimentally resolve the tricritical point at T TCP in a temperature regime above the ferromagnetic Curie temperature which separates the linear and nonlinear magnetic regimes of the CSL at the phase transition. A comprehensive phase diagram is constructed which summarizes the features of the field and temperature dependence of the magnetic crossovers and phase transitions in Cr 1/3 NbS 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2019

Spin dynamics and field-induced magnetic phase transition in the honeycomb Kitaev magnet α Li 2 IrO 3

The layered honeycomb iridate $α-Li_2IrO_3$ displays an incommensurate magnetic structure with counter-rotating moments on nearest-neighbor sites, proposed to be stabilized by strongly frustrated anisotropic Kitaev interactions between spin-orbit entangled $Ir^{4+}$ magnetic moments. Here we report powder inelastic neutron scattering measurements that observe sharply dispersive low-energy magnetic excitations centered at the magnetic ordering wave vector, attributed to Goldstone excitations of the incommensurate order, as well as an additional intense mode above a gap $Δ ≃ 2.3$ meV. Zero-field muon-spin relaxation measurements show clear oscillations in the muon polarization below the Néel temperature $T_N ≃ 15$ K with a time-dependent profile consistent with bulk incommensurate long-range magnetism. Pulsed-field magnetization measurements observe that only about half the saturation magnetization value is reached at the maximum field of 64 T. A clear anomaly near 25 T indicates a transition to a phase with reduced susceptibility. The transition field has a Zeeman energy comparable to the zero-field gapped mode, suggesting gap suppression as a possible mechanism for the field-induced transition.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Laminated Permanent Magnets Enable Compact Magnetic Components in Current Source Converters

Magnetic components play a key role in determining the size, cost, efficiency of a power converter. They are more significant in current source converters, where the dc-link energy is stored in an inductor/transformer. In such cases, the magnetics have a predominantly DC flux, superimposed by an AC flux at switching frequency. Previously, permanent magnets have been proposed to offset the DC flux and thereby reduce the size, cost, and losses of the inductors/transformers. This paper starts by analyzing the issue of eddy currents when using such standard permanent magnets, especially in medium frequency applications, making them practically unusable. Alternatively, the paper proposes the use of laminated permanent magnets to reduce these eddy currents and thereby realize the benefits of offsetting the DC flux to reduce the size, cost, and loss of inductors/transformers. Using a soft-switching solid-state transformer as an example, experimental results are presented to show the impact of eddy currents in standard permanent magnets when used with a medium frequency transformer. Here, experimental results showing the benefits of using laminated magnets in reducing the eddy currents are presented.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Vertical Magnetic Measurements of the First Full-Length Prototype MQXFAP2 Quadrupole for the LHC Hi-Lumi Accelerator Upgrade Project

This paper reports the commissioning of the vertical magnetic measurement system and the room temperature (warm) and cryogenic (cold) magnetic field measurements of the first full-length (4.2 m) quadrupole built by the U.S. Accelerator Upgrade Project (AUP) (formerly the LARP collaboration) for the high luminosity upgrade of the Large Hadron Collider at CERN. The magnet, designated MQXFAP2, is a prototype preceding production for the AUP which will provide ten sets of 8.4-m superconducting insertion region quadrupoles for the Hi-Lumi Upgrade. The quadrupoles will be built by assembling two 4.2-m magnets in a single cryostat. Agreement between Brookhaven National Laboratory's (BNL's) and Lawrence Berkeley National Laboratory's (LBNL's) warm measurement data has indicated that the upgraded vertical magnetic measurement system at Brookhaven National Laboratory is ready for MQXFA magnet production testing. Lastly, the cold magnetic measurement has been performed and preliminary data analysis has been conducted.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

An Initial Look at the Magnetic Design of a 150 mm Aperture High-Temperature Superconducting Magnet With a Dipole Field of 8 to 10 T

High-temperature superconducting REBa 2 Cu 3 O 7-$x$ (rebco) conductors have the potential to generate a high magnetic field over a broad temperature range. The corresponding accelerator magnet technology, still in its infancy, can be attractive for future energy-frontier particle colliders such as a multi-TeV muon collider. To help develop the technology, we explore the requirements and potential characteristics of a rebco magnet, operating at 4.2 or 20 K, with a dipole field of 8-10 T in a clear aperture of 150 mm. We use the canted cos $\theta$ magnet configuration to reduce the electromagnetic stresses on the conductors. We present the resulting dipole fields, field gradients for combined-function cases, conductor stresses, magnet dimensions and conductor lengths. We also discuss the conductor performance that is required to achieve the target dipole field at 4.2 and 20 K. In conclusion, the information can provide useful input to the development of rebco magnet and conductor technology for collider-ring magnets in a muon collider.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗