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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Progress on HL-LHC Nb 3 Sn Magnets

The high-luminosity Large Hadron Collider (HL-LHC) project aims at allowing to increase the collisions in the LHC by a factor of ten in the decade 2025-2035. One essential element is the superconducting magnet around the interaction region points, where the large aperture magnets will be installed to allow to further reduce the beam size in the interaction point. The core of this upgrade is the Nb 3 Sn triplet, made up of 150-mm aperture quadrupoles in the range of 7-8 m. The project is being shared between the European Organization for Nuclear Research and the US Accelerator Upgrade Program, based on the same design, and on the two strand technologies. The project is ending the short model phase, and entering the prototype construction. We will report on the main results of the short model program, including the quench performance and field quality. A second important element is the 11 T dipole that replaces a standard dipole making space for additional collimators. The magnet is also ending the model development and entering the prototype phase. A critical point in the design of this magnet is the large current density, allowing increase of the field from 8 to 11 T with the same coil cross section as in the LHC dipoles. This is also the first two-in-one Nb 3 Sn magnet developed so far. We will report the main results on the test and the critical aspects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic structure and excitation spectrum of the hyperhoneycomb Kitaev magnet β – Li 2 IrO 3

We present a theoretical study of the static and dynamical properties of the three-dimensional, hyperhoneycomb Kitaev magnet β–Li 2 IrO 3 . We argue that the observed incommensurate order can be understood in terms of a long-wavelength twisting of a nearby commensurate period-3 state, with the same key qualitatively features. The period-3 state shows very different structure when either the Kitaev interaction K or the off-diagonal exchange anisotropy Γ is dominant. A comparison of the associated static spin structure factors with reported scattering experiments in zero and finite fields gives strong evidence that β–Li 2 IrO 3 lies in the regime of dominant Kitaev coupling, and that the Heisenberg exchange J is much weaker than both K and Γ. Furthermore, our predictions for the magnon excitation spectra, the dynamical spin structure factors, and their polarization dependence provide additional distinctive fingerprints that can be checked experimentally.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Magnetization of the oceanic crust - Thermoremanent magnetization of chemical remanent magnetization?

A model was proposed in which chemical remanent magnetization (CRM) acquired within the first 20 Ma of crustal evolution may account for 80 percent of the bulk natural remanent magnetization (NRM) of older basalts. The CRM of the crust is acquired as the original thermoremanent magnetization (TRM) is lost through low temperature alteration. The CRM intensity and direction are controlled by the post-emplacement polarity history. This model explains several independent observations concerning the magnetization of the oceanic crust. The model accounts for amplitude and skewness dicrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern. It also explains the decay of magnetization away from the spreading axis, and the enhanced magnetization of the Cretaceous Quiet Zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust. The model also explains discrepancies in the anomaly skewness parameter observed for anomalies of Cretaceous age. Further studies indicate varying rates of TRM decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer.

Raymond, C. A.↗
DOE OSTI2018

Magnetic Domain Evolution in Sintered Nd–Fe–B Magnet during Magnetization Process

In the present study, the magnetic domains and their evolution during magnetization process have been investigated for sintered Nd–Fe–B permanent magnets with Kerr microscopy. Observation of the magnetic domain evolution process during magnetization process shows that some domain walls were pinned at the grain boundary area under magnetic field up to 5 kOe. It is suggested that magnetic interaction between individual Nd{sub 2}Fe{sub 14}B grains contacting to each other leads to appearance of small closed domains near the grain boundary area, which are responsible for the pinning effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

A High-Speed High-Power-Density Non-Heavy Rare-Earth Permanent Magnet Traction Motor

There has been a global push for higher torque density and lower cost traction motors. The use of non-heavy rare-earth (non-HRE) permanent magnet materials in traction motors are being investigated for the sustainability, profitability and affordability of electric vehicles and to broaden their adoption. A 20,000-rpm permanent magnet traction motor using non-HRE magnet materials is proposed. A dual three-phase winding configuration driven by a segmented dual three-phase drive is proposed to reduce the current ripple, and as a result, the DC Link capacitor, as well as to ease the voltage constraint at high speed and eliminate any risk of uncontrolled regeneration. Furthermore, the dual winding configuration enables a fault tolerant design which is useful for reliability. The paper presents comprehensive electromagnetic, thermal and mechanical designs and analyses using an integrated approach. The results have shown that the design is robust against demagnetization and confirmed its thermal and mechanical viability.

47 OTHER INSTRUMENTATION↗
NASA NTRS1976

Mass spectrometer with magnetic pole pieces providing the magnetic fields for both the magnetic sector and an ion-type vacuum pump

A mass spectrometer (MS) with unique magnetic pole pieces which provide a homogenous magnetic field across the gap of the MS magnetic sector as well as the magnetic field across an ion-type vacuum pump is disclosed. The pole pieces form the top and bottom sides of a housing. The housing is positioned so that portions of the pole pieces form part of the magnetic sector with the space between them defining the gap region of the magnetic sector, through which an ion beam passes. The pole pieces extend beyond the magnetic sector with the space between them being large enough to accommodate the electrical parts of an ion-type vacuum pump. The pole pieces which provide the magnetic field for the pump, together with the housing form the vacuum pump enclosure or housing.

Sieradski, L. M.↗
DOE OSTI2018

Insights into the magnetic dead layer in La 0.7 Sr 0.3 MnO 3 thin films from temperature, magnetic field and thickness dependence of their magnetization

Experimental investigations of the magnetic dead layer in 7.6 nm thick film of La 0.7 Sr 0.3 MnO 3 (LSMO) are reported. The dc magnetization ( M ) measurements for a sample cooled to T = 5 K in applied field H = 0 reveal the presence of negative remanent magnetization (NRM) in the M vs. H (magnetic field) measurements as well as in the M vs. T measurements in H = 50 Oe and 100 Oe. The M vs. T data in ZFC (zero-field-cooled) and FC (field-cooled) protocols are used to determine the blocking temperature T B in different H . Isothermal hysteresis loops at different T are used to determine the temperature dependence of saturation magnetization ( M S ), remanence (MR) and coercivity HC. The M S vs. T data are fit to the Bloch law, M S ( T ) = M 0 ( 1 – BT 3/2 ), showing a good fit for T < 100 K and yielding the nearest-neighbor exchange constant J/k B ≅ 18 K. The variations of T B vs. H and H C vs. T are well described by the model often used for randomly oriented magnetic nanoparticles with magnetic domain diameter ≈ 9 nm present in the dead-layer of thickness d =1.4 nm. Finally, the data available from literature on the thickness ( D ) variation of Curie temperature ( T C ) and M S of LSMO films grown under 200, 150, and 0.38 mTorr pressures of O 2 are analyzed in terms of the finite-size scaling, with M S vs. D data fit to M S ( D ) = M S (b)(1-d / D ) yielding the dead layer thickness d = 1.1 nm, 1.4 nm and 2.4 nm respectively. Brief discussion on the significance of these results is presented.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Direct visualization of magnetic domains and moiré magnetism in twisted 2D magnets

Moiré superlattices of twisted nonmagnetic two-dimensional (2D) materials are highly controllable platforms for the engineering of exotic correlated and topological states. In this work, we report emerging magnetic textures in small-angle twisted 2D magnet chromium triiodide (CrI 3 ). Using single-spin quantum magnetometry, we directly visualized nanoscale magnetic domains and periodic patterns, a signature of moiré magnetism, and measured domain size and magnetization. In twisted bilayer CrI 3 , we observed the coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) domains with disorder-like spatial patterns. In twisted double-trilayer CrI 3 , AFM and FM domains with periodic patterns appear, which is in good agreement with the calculated spatial magnetic structures that arise from the local stacking-dependent interlayer exchange interactions in CrI 3 moiré superlattices. Our results highlight magnetic moiré superlattices as a platform for exploring nanomagnetism.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2018

Comparison of Magnetic Fields from a New Satellite Magnetic Model of the Lithosphere with Magnetic Fields Predicted from Crust 1.0

Both magnetic and seismic techniques can provide information about the Moho (Mohorovicic discontinuity). We develop a new technique that provides a better estimate of the magnetic thickness of the crust, as compared with previous approaches. It uses prior knowledge from seismology (Crust 1.0), a new high-degree model from CHAMP (CHAllenging Mini-satellite Payload) and Swarm (LCS-1 - a model of Earth's lithospheric field) and a newly developed technique. The technique is appropriate for regions where induced magnetization dominates over remanent magnetization. We compare the predictions from LCS-1 with those from Crust 1.0, with some simple assumptions, and find that the correlations increase until about spherical harmonic degree 30, and then decrease globally. Spatially, the correlations between the seismic and magnetic techniques are strongest over North America and Australia, and weakest over South America and northern Africa. Strong correlations also exist between the two approaches over the Antarctic, northern Europe, and Greenland. While we might expect the seismic and magnetic approaches to correlate over well-characterized regions (i.e. North America), and show weaker correlations over poorly-characterized regions (i.e. South America and north Africa), the strong correlation in the Antarctic and Greenland is puzzling, because both of these regions are poorly-characterized. We discuss some possible explanations, and implications, of this attempt to correlate seismic and magnetic approaches to characterizing the lithosphere.

Seismic↗
DOE OSTI2018

Physical and electrical properties of melt-spun Fe-Si (3–8 wt.%) soft magnetic ribbons

Highlights: • Increasing processing wheel speed during melt spinning refined both the ribbon cross-sectional thickness and grain size. • Mössbauer studies indicated Si content influenced the number of Fe sites and the magnetic field/structural environments. • Vickers hardness and the elastic modulus were observed to increase in response to elevated Si content and wheel speed. • Increasing Si content diluted the magnetization. - Abstract: Fe-Si alloys ranging from 3 to 8 wt% Si were rapidly solidified using melt spinning. Wheel speeds of 30 m/s and 40 m/s were employed to vary cooling rates. Mössbauer spectroscopic studies indicated the Si content significantly influenced the number of Fe sites, relative abundance of various Fe species, and internal magnetic fields/structural environments. Wheel speed altered Fe speciation only in the 3 wt% sample. Scanning electron microscopy confirmed that increasing the wheel speed refined both the ribbon thickness and grain size. Electron backscatter diffraction results suggest tailoring melt spinning process parameters and alloy chemistry may offer the ability to manipulate {001} texture development. Electrical resistivity measurements were observed to increase in response to elevated Si content. Increased hardness was correlated to elevated Si content and wheel speed.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Design and Comparison of Surface Inset Permanent Magnet Machine and Surface Permanent Magnet Machine without Heavy Rare Earth Magnets for Traction Applications

This paper presents two machine designs: a surface inset permanent magnet (SIPM) machine and a surface permanent magnet (SPM) machine, both without heavy rare-earth magnets, that achieve 50 kW/L active power density and a constant-power speed ratio of 3 for EV traction applications. Compared to surface PM machines, SIPM machines do not require a special containment sleeve to hold the magnets in place at high speeds, provided that the rotor laminations are carefully designed together with the magnet mounting configuration to ensure the rotor’s structural integrity. Comparisons between the SPM and SIPM machines sharing the same stator, same current level, and same power speed envelope are presented. Both deliver very similar performance characteristics, but the SIPM machine’s simpler magnet containment configuration may give it an advantage in terms of reduced material and manufacturing costs.

42 ENGINEERING↗
DOE OSTI2019

Observation of a Large Magnetic Anisotropy and a Field-Induced Magnetic State in SrCo(VO 4 )(OH): A Structure with a Quasi One-Dimensional Magnetic Chain

A new member of the descloizite family, a cobalt vanadate, SrCo(VO 4 )(OH), has been synthesized as large single crystals using high-temperature and high-pressure hydrothermal methods. SrCo(VO 4 )(OH) crystallizes in the orthorhombic crystal system in space group P 2 1 2 1 2 1 with the following unit cell parameters: a = 6.0157(2) Å, b = 7.645(2) Å, c = 9.291(3) Å, V = 427.29(2) Å 3 , and Z = 4. It contains one-dimensional Co–O–Co chains of edge-sharing CoO 6 octahedra along the a -axis connected to each other via VO 4 tetrahedra along the b -axis forming a three-dimensional structure. The magnetic susceptibility of SrCo(VO 4 )(OH) indicates an antiferromagnetic transition at 10 K as well as unusually large spin orbit coupling. Single-crystal magnetic measurements in all three main crystallographic directions displayed a significant anisotropy in both temperature- and field-dependent data. Single-crystal neutron diffraction at 4 K was used to characterize the magnetically ordered state. The Co 2+ magnetic spins are arranged in a staggered configuration along the chain direction, with a canting angle that follows the tipping of the CoO 6 octahedra. The net magnetization along the chain direction, resulting in ferromagnetic coupling of the a -axis spin components in each chain, is compensated by an antiferromagnetic interaction between nearest neighbor chains. A metamagnetic transition appears in the isothermal magnetization data at 2 K along the chain direction, which seems to correspond to a co-alignment of the spin directions of the nearest neighbor chain. We propose a phenomenological spin Hamiltonian that describes the canted spin configuration of the ground state and the metamagnetic transition in SrCo(VO 4 )(OH).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Correlation between Epitaxial Strain and Magnetic Properties in La0.7Sr0.3CoO3/La0.7Sr0.3MnO3 bilayers

Magnetic properties arising at interfaces of perovskite oxides such as La0.7Sr0.3MnO3 (LSMO) and La0.7Sr0.3CoO3 (LSCO) depend sensitively on the fine details of their structural properties. In this work, we use high-resolution transmission electron microscopy and spectroscopy to examine the structural and electronic phenomena at the interfaces in two LSMO/LSCO bilayers with reversed growth order. Two different strain mechanisms are at work in these films; compressive or tensile epitaxial strain, and distortion of the octahedral tilt pattern to maintain the network of corner-sharing octahedra. While the epitaxial strain is constant, regardless of growth order, the modification of the octahedral tilt pattern depends on whether the film is grown directly on the substrate, or as the second sublayer. As a consequence, exchange spring behavior is observed only when the LSCO sublayer is grown first. The different mechanisms of strain accommodation within the oxygen octahedra network in each material prove to be of critical importance in determining the interfacial structure and thus magnetic and electronic properties of the bilayers.

perovskites, interfaces, microscopy, magnetism↗
DOE OSTI2025

Magnetic force microscopy revealing long-range room temperature stable molecule bridge-induced magnetic ordering on magnetic tunnel junction (MTJ) pillars

Magnetic tunnel junctions (MTJs) can integrate novel single molecular device elements to overcome long-standing fabrication challenges, thus unlocking their novel potential. This study employs magnetic force microscopy (MFM) to demonstrate that organometallic molecules, when placed between two ferromagnetic electrodes along cross-junction shaped MTJ edges, dramatically altered the magnetic properties of the electrodes, affecting areas several hundred microns in size around the molecular junction vicinity at room temperature. These findings are supported by magnetic resonance and magnetometer studies on ∼7000 MTJ pillars. MFM on the pillar sample showed an almost complete disappearance of the magnetic contrast. The spatial magnetic image suggests that molecular channels significantly impacted the spin density of states in the ferromagnetic electrodes. This advancement in MTJ-based molecular devices paves the way for a new generation of commercially viable logic and memory devices controlled by molecular quantum states at near-room temperatures.

Tyagi, Pawan (ORCID:0000000275411344)↗
DOE OSTI2023

Using an Analytic-Based Magnetic Charge Fourier Series Model to Study a Magnetic Lead Screw when Operating as a Magnetic Spring

A magnetic charge field analysis approach is presented that models an array of magnets by using a magnetic vector Fourier series representation. Using a Fourier series function enables the magnets' relative permeability to be accounted for and also reduces the computational burden. The accuracy of the presented modelling approach is validated by studying the fields and forces created by a magnetic lead screw when acting as a magnetic spring

Kouhshahi, Mojtaba Bahrami↗
DOE OSTI2021

Magnetic anisotropy and spin dynamics in the kagome magnet Fe 4 Si 2 Sn 7 O 16 : NMR and magnetic susceptibility study on oriented powder

Fe 4 Si 2 Sn 7 O 16 hosts an undistorted kagome lattice of Fe 2+ (3d 6 , S = 2) ions. We present results of bulk magnetization and Sn nuclear magnetic resonance (NMR) measurements on an oriented Fe 4 Si 2 Sn 7 O 16 powder sample oriented in geometries parallel (∥) and perpendicular (⊥) to the external applied magnetic field used for orienting the powder (Bori). The bulk susceptibility χ shows a broad peak at T N ~ 3 K associated with antiferromagnetic ordering. NMR spectra indicate the presence of planar anisotropy in the kagome planes. From an analysis of the static NMR shift (K) and dynamic spin-lattice relaxation rate (1/T 1 ) we conclude the presence of dominant magnetic fluctuations in the kagome planes. For the ∥ orientation, K scales linearly with the bulk susceptibility for temperatures down to ~ 4 K, while in the ⊥ orientation K starts to deviate strongly below T ~ 30 K. We associate this deviation with the onset of spin-tilting towards the kagome planes. These correlations are also reflected in the 1/T 1 data for the ∥ orientation, which starts to decrease below T ~ 30 K. Here, in this correlated regime, T N < T < ~ 30 K, we discuss the formation of positive chiral spin correlations in the kagome planes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗