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Results for “MAGNETS”

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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Passive magnetic bearing systems stabilizer/bearing utilizing time-averaging of a periodic magnetic field

A high-stiffness stabilizer/bearings for passive magnetic bearing systems is provide where the key to its operation resides in the fact that when the frequency of variation of the repelling forces of the periodic magnet array is large compared to the reciprocal of the growth time of the unstable motion, the rotating system will feel only the time-averaged value of the force. When the time-averaged value of the force is radially repelling by the choice of the geometry of the periodic magnet array, the Earnshaw-related unstable hit motion that would occur at zero rotational speed is suppressed when the system is rotating at operating speeds.

42 ENGINEERING↗
DOE OSTI2018

Iron nitride permanent magnet and technique for forming iron nitride permanent magnet

A permanent magnet may include a Fe 16 N 2 phase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a <001> crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a Fe 16 N 2 phase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Small bore magnetic measurement system, method for measuring small bore magnets

The invention provides a system for measuring magnets, the system comprising a guide tube removably received by a beam chamber tunnel, wherein said guide tube has a first end terminating at a first end of the tunnel and a second end terminating at a second end of the tunnel; a flexible substrate removably and slidably received by the tube, wherein the flexible substrate has a first end and a second end; a first rotary stage removably attached to the first end of said flexible substrate and a second rotary stage removably attached to the second end of said flexible substrate wherein the first rotary stage and the second rotary stage effects movement of the substrate through the tube; and a Hall probe supported by the flexible substrate. Also provided is a method for measuring magnetic fields, the method comprising extending a measuring probe into a magnetic core while maintaining the probe at ambient temperature and pressure.

Kasa, Matthew T.↗
DOE OSTI2022

Methods and systems for low to ultra-low magnetic field nuclear magnetic resonance for detecting chemical nerve agents

A nuclear magnetic resonance (NMR) system is configured to detect chemical threat material. The system comprises a magnet configured to generate a magnetic field of about 300 millitesla or less; and a probe configured to detect nuclear relaxation of at least two nuclei selected from the group consisting of 1H, 19F, 31P and 14N, and detect the spin density of nuclei selected from the group consisting of 1H, 19F, 31P and 14N, following excitation.

Williams, Robert F.↗
DOE OSTI2023

Iron nitride permanent magnet and technique for forming iron nitride permanent magnet

A permanent magnet may include a Fe 16 N 2 phase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a <001> crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a Fe 16 N 2 phase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

Wang, Jian-Ping↗
DOE OSTI2024

Magnetic Field Sensing via Optically Detected Magnetic Resonance and Spin Relaxometry Using Nitrogen Vacancies in Nanodiamonds

Quantum sensing is broadly defined as the use of quantum materials, quantum coherence, and/or quantum entanglement to measure physical quantities and/or to enhance the sensitivity of classical analytical measurements. Certain materials exhibit interesting quantum properties that have the potential to be utilized in quantum sensing applications. One such quantum property is electronic spin, which is utilized in this work. Here, we built a custom apparatus capable of conducting both optically detected magnetic resonance (ODMR) and spin relaxometry. The quantum material investigated was an ensemble of nitrogen vacancies (NV) in nanodiamonds. We have characterized the system and measured ODMR spectra for different strengths of the applied DC magnetic field and clearly observed the expected splitting of the resonances due to Zeeman splitting. We also have measured the spin relaxation times for two different powers of the applied AC magnetic field. The lower power dataset exhibited expected exponential temporal dependence of the relaxation of a modified spin state, whereas the higher power dataset exhibited stretched exponential dependence of the modified spin state, indicating the presence of high-power phenomena that emerge that retard the relaxation of the spin state.

Lander, Gary↗
DOE OSTI2018

Effects of Fe and Co Co-doping on Structural, Magnetic, and Optical Properties of Ti{sub 0.9}Fe{sub 0.1−x}Co{sub x}O{sub 2} Magnetic Semiconductors

A series of six samples with a general formula Ti{sub 0.9}Fe{sub 0.1−x}Co{sub x}O{sub 2} (x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.1) has been synthesized by solid-state reaction method at annealing temperature of 1150 {sup ∘}C for 2 hours. The synthesized samples have been characterized by X-ray diffractometer, Raman spectroscopy, scanning electron microscopy, EDX, vibrating sample magnetometer, and ultraviolet-visible spectroscopy to investigate structural, defective, morphological, elemental, magnetic, and optical properties. Structural analysis revealed dominant structure of rutile with a minor peak of hematite and anatase. An intensity loss and peak broadening of TiO{sub 2} (rutile) vibration lines has been observed from Raman analysis. Magnetic characterization showed ferromagnetic behavior at room temperature. Optical characterization revealed blue shift in band gap energy with increasing amount of Co concentration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Wave-Vector Filtering Effect in a Novel Magnetic Nanostructure with Zero Average Magnetic Field

We report a theoretical investigation on wave-vector filtering (WVF) effect in a magnetic nanostructure, which can be experimentally realized by depositing ferromagnetic (FM) stripes on the surface of GaAs/Al{sub x}Ga{sub 1-x}As heterostructure. An appreciable WVF effect appears in this nanosystem. The WVF efficiency is associated with structural parameters of magnetic nanostructure. Therefore, such a device can be employed as a momentum filter for nanoelectronics device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Synthesis and Characterization of Hydrophobic Fe{sub 3}O{sub 4} Magnetic Nanoparticles with High Saturation Magnetization

A simple one-step solvothermal method is proposed to prepare hydrophobic Fe{sub 3}O{sub 4} nanoparticles (MNPs) using iron acetylacetonate (Fe(acac){sub 3}), oleylamine (OAm), and ethylene glycol (EG). X-ray powder diffraction, scanning electron microscope, infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectrometry, and vibrating sample magnetometer are used to characterize the structure, morphology, and properties of products. The testing results indicate that the as-synthesized products are spherical-like hydrophobic MNPs, superparamagnetic at room temperature, with a saturation magnetization up to 76.8 emu/g. The good hydrophobic property of MNPs is attributed to the coverage of oleylamine, without causing a remarkable loss of magnetic property. In addition, the influences of material ratio, aging time, oleic acid, and stearic acid used as additives are studied in our research.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Magnetized ICF implosions: non-axial magnetic field topologies

This paper explores four different magnetic field topologies for application to spherical inertial confinement fusion implosions: axial, mirror, cusp and closed field lines. A mirror field is found to enhance the impact of magnetization over an axial field; this is because the mirror field more closely follows the hot-spot surface. A cusp field, while simple to generate, is not found to have any benefits over the tried-and-tested axial field. Closed field lines are found to be of the greatest benefit to hot-spot performance, with the simulated design undergoing a 2× increase in ion temperature before α-heating is considered. The plasma properties of the simulation with closed field lines are radically different from the unmagnetized counterpart, with electron temperatures in excess of 100 keV, suggesting that a fundamental redesign of the capsule implosion is possible if this method is pursued.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Development of Turbulent Magnetic Reconnection in a Magnetic Island

In this paper, with two-dimensional particle-in-cell simulations, we report that the electron Kelvin–Helmholtz instability is unstable in the current layer associated with a large-scale magnetic island, which is formed in multiple X-line guide field reconnections. The current sheet is fragmented into many small current sheets with widths down to the order of the electron inertial length. Secondary magnetic reconnection then occurs in these fragmented current sheets, which leads to a turbulent state. The electrons are highly energized in such a process.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Current and Future Constraints on Primordial Magnetic Fields

We present new limits on the amplitude of potential primordial magnetic fields (PMFs) using temperature and polarization measurements of the cosmic microwave background (CMB) from Planck, the BICEP2/Keck Array, Polarbear, and SPTpol. We reduce twofold the 95% confidence upper limit on the CMB anisotropy power due to a nearly scale-invariant PMF, with an allowed B-mode power at ℓ = 1500 of D{sub ℓ=1500}{sup BB}<0.071 μK{sup 2} for Planck versus D{sub ℓ=1500}{sup BB}<0.034 μK{sup 2} for the combined data set. We also forecast the expected limits from soon-to-deploy CMB experiments (like SPT-3G, Adv. ACTpol, or the Simons Array) and the proposed CMB-S4 experiment. Future CMB experiments should dramatically reduce the current uncertainties by one order of magnitude for the near-term experiments and two orders of magnitude for the CMB-S4 experiment. The constraints from CMB-S4 have the potential to rule out much of the parameter space for PMFs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

H-Mediated Magnetic Interactions between Layers in a 2D Mn II -Dicyanamide Polymer: Neutron Diffraction, DFT, and Quantum Monte Carlo Calculations: H-Mediated Magnetic Interactions between Layers in a 2D Mn II -Dicyanamide Polymer: Neutron Diffraction, DFT, and Quantum Monte Carlo Calculations

We report neutron-diffraction investigations of the quasi-2D Mn-II(dca)(2)(pym)(H2O) (pym = N2C4H4) compound, where high-spin Mn-II ions are bridged by dicyanamide anions, [N(CN)(2)](-) (herein abbreviated dca). Inside the layers, Mn2+ ions are connected by single or double dca bridges. The magnetic phase diagram was established by neutron diffraction on a single crystal. In the low-field phase, the Mn-II ions are antiferro-magnetically ordered in the layers, with moments nearly parallel to the c axis, and the layers are antiferromagnetically coupled. The spin-flop phase corresponds to ferromagnetic coupling between the antiferromagnetic layers, in which the Mn-II moments are nearly perpendicular to the c axis. The induced spin-density distribution in the paramagnetic phase, determined by polarized neutron diffraction, visualizes the super-exchange pathways through the dca ligands within the layers and through H bonding between neighboring layers. The theoretical spin density obtained by bidimensional periodic DFT calculations is compared with the experimental results. Furthermore, quantum Monte Carlo simulations have been performed to compare the DFT results with experimental susceptibility measurements.

density functional calculations↗
DOE OSTI2018

Integrated SQUID/Sensor Metallic Magnetic Microcalorimeter for Gamma-Ray Spectroscopy

Metallic magnetic microcalorimeters (MMCs) achieve energy resolution comparable to transition-edge sensors (TESs) but rely on different measurement physics that may allow MMCs to surpass TESs in some future applications. We have recently completed fabrication of new MMC γ-ray detector arrays using several exploratory sensor designs. All designs integrate the SQUID and sensor on the same chip and use a superconducting cap layer on the paramagnet, but explore different combinations of combined/separate sensing and magnetization coils and direct/flux transformer coupling to the input SQUIDs. This report describes the design and initial testing of one of these devices, which has so far demonstrated an energy resolution of 38 eV at 60 keV near 10 mK using natural-abundance silver–erbium paramagnet.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗