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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Magnetic properties of Martian surface material

The hypothesis that the magnetic properties of the Martian surface material are due to the production of a magnetic phase in the clay mineral nontronite by transient shock heating is examined. In the course of the investigation a magnetic material is produced with rather unusual properties. Heating from 900 C to 1000 C, of natural samples of nontronite leads first to the production of what appears to be Si doped maghemite gamma (-Fe2O3). Although apparently metastable, the growth of gamma -Fe2O3 at these temprtures is unexpected, and its relative persistence of several hours at 1000 C is most surprising. Continued annealing of this material for longer periods promote the crystallization of alpha Fe2O3 and cristobalite (high temperature polymorph of SiO2). All available data correlate this new magnetic material with the cristobalite hence our naming it magnetic ferri cristobalite. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.

Hargraves, R. B.↗
DOE OSTI2019

Mössbauer Studies and Magnetic Properties of Cubic CuFe{sub 2}O{sub 4} Nanoparticles

This study reports the preparation and characterization of nanocrystalline spinel powder of cubic copper ferrite nanoparticles (NPs) which have been fabricated via a cost-effective citrate sol–gel approach. The structural and morphological properties of the nanoparticles are analyzed by X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR), and scanning electron microscopy (SEM) whereas magnetic properties and Mössbauer analysis were performed using vibrating sample magnetometer (VSM) and Mössbauer spectra, respectively, and were characterized in detail. The empirical aim of this study is to perceive the transition phase of CuFe{sub 2}O{sub 4} as cubic symmetry which was confirmed by SEM images, and a couple of studies reported on the cubic structure of copper ferrite and discussed the magnetic properties. However, the present study gives the detailed information of the formation of cubic structure and magnetic behavior of the CuFe{sub 2}O{sub 4} cubic structure. X-ray diffraction measurements of resulting NPs show that the grain size of the particles is about 42.08 nm while SEM analysis showed that the particles have cubic nanostructured shapes with non-homogeneous sizes in around 80–100 nm. From {sup 57}Fe, Mössbauer parameters consist of one superparamagnetic doublet and superposition of four sextets. VSM result shows the enhanced superparamagnetic nature of the CuFe{sub 2}O{sub 4} NPs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS2004

Preliminary Results of the Magnetic Properties Experiments on the Mars Exploration Rovers, Spirit and Opportunity

The Mars Exploration Rovers each carry a set of Magnetic Properties Experiments designed to investigate the properties of the air-borne dust in the Martian atmosphere. It is a preferred interpretation of previous experiments (Viking 1 & 2, 1976 and Mars Pathfinder, 1997) that the airborne dust in the Martian atmosphere is primarily composed by composite silicate particles containing one or more highly magnetic minerals as a minor constituent, this minor constituent probably being dominated by the mineral maghemite (gamma-Fe2O3). The ultimate goal of the magnetic properties experiments on the Mars Exploration Rover mission is to provide some information/constraints on whether the dust is formed by volcanic, meteoritic, aqueous, or other processes. In detail, the objectives are: a) To identify the magnetic mineral(s) in the dust, soil and rocks on Mars. b) To establish if the magnetic material is present in the form of nanosized (d < 10 nm) superparamagnetic crystallites embedded in the micrometer sized airborne dust part icles. c) To establish if the magnets are culling a subset of strongly magnetic particles or if essentially all particles of the airborne dust are sufficiently magnetic to be attracted by the magnets. d) Detect compositional differences between the airborne dust and the soil and rock sites which are investigated at two landing sites. To accomplish these goals the Mars Exploration Rovers each carry a set of permanent magnets of several different strengths and sizes. Each magnet has its own specific objective.

Hviid, S. F.↗
DOE OSTI2019

Synthesis, particle shape characterization, magnetic properties and surface modification of superparamagnetic iron oxide nanochains

We report monodisperse, chain-like particles (nanochains) consisted of silica-coated maghemite (γ-Fe2O3) nanoparticle clusters prepared by colloidal chemistry and magnetic field-induced self-assembly of nanoparticle clusters. In order to quantify the shapes of chain-like particles, we have used the measure for shape convexity which is also called solidity. We functionalize the surface of the nanochains with amino (–NH2) and carboxyl groups (–COOH) in order to modify surface charge. These surfaces of nanochains provide better colloidal stability and their potential for practical applications in biomedicine. The enhanced colloidal stability of the surface modified nanochains is confirmed by Zeta potential (ζ-potential) analysis. Magnetic properties of the nanochains show superparamagnetic state at room temperature since the nanochains are composed of tiny nanoparticles as their building blocks. The measured M(H) data at room temperature have been successfully fitted by the Langevin function and magnetic moment μp = 20,526 μB for sphere-like nanoparticle clusters and μp = 20,767 μB for nanochains are determined. The determined magnetic parameters have revealed that the nanochains show a magnetic moment of the nanoparticles higher than the one of individual nanoparticle clusters. These differences can be attributed to the collective magnetic properties of superparamagnetic iron oxide nanoparticles (SPION) assembled in different morphologies (isotropic and anisotropic morphology). © 2018.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Magnetic properties of the Ising-like rare earth pyrosilicate: D-Er 2 Si 2 O 7

Ising-like spin-1/2 magnetic materials are of interest for their ready connection to theory, particularly in the context of quantum critical behavior. In this work we report detailed studies of the magnetic properties of a member of the rare earth pyrosilicate family, D-Er 2 Si 2 O 7 , which is known to display a highly anisotropic Ising-like g-tensor and effective spin-1/2 magnetic moments. We used powder neutron diffraction, powder inelastic neutron spectroscopy (INS), and single crystal AC susceptibility to characterize its magnetic properties. Neutron diffraction enabled us to determine the magnetic structure below the known transition temperature (T N = 1.9 K) in zero field, confirming that the magnetic state is a four-sublattice antiferromagnetic structure with two non-collinear Ising axes, as was previously hypothesized. Our powder INS data revealed a gapped excitation at zero field, consistent with anisotropic (possibly Ising) exchange. An applied field of 1 T produces a mode softening, which is consistent with a field-induced second order phase transition. To assess the relevance of D-Er 2 Si 2 O 7 to the transverse field Ising model, we performed AC susceptibility measurements on a single crystal with the magnetic field oriented in the direction transverse to the Ising axes. This revealed a transition at 2.65 T at 0.1 K, a field significantly higher than the mode-softening field observed by powder INS, showing that the field-induced phase transitions are highly field-direction dependent as expected. Furthermore, these measurements suggest that D-Er 2 Si 2 O 7 may be a candidate for further exploration related to the transverse field Ising model.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Crafting Multifunctional Materials with Tailored Mechanical and Magnetic Properties by Solid-State Non-equilibrium Processing

Aluminum matrix composites hold promise for creating lightweight structural components with multifunctional properties. Nonetheless, achieving desired magnetic or electrical characteristics without compromising their fundamental mechanical properties presents a significant challenge. Here, in this study, we explore mechanical stir-based extrusion as a solid-state metalworking technique to develop fine-grained microstructures and highly refined metallic composites. Our study focuses on creating a SmCo 5 -reinforced aluminum matrix composite using solid stir extrusion (SSE) and assessing its microstructure, mechanical, and magnetic properties through a comprehensive suite of characterization tools, including x-ray diffraction, electron microscopy, and magnetometry. Our findings reveal that incorporating a small amount (3.76 wt.%) of SmCo 5 phase in a non-heat-treatable, non-magnetic aluminum alloy via SSE yields a composite that exhibits good hard magnetic characteristics with a large coercivity (H ci = 13.5 kOe) and improved mechanical properties. This study underscores non-equilibrium processing via solid-state high-speed stirring as a compelling method for crafting multifunctional materials with tailored mechanical and magnetic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigation of Electrical and Magnetic Properties of La{sup 3+} Substituted M-Type Ba–Ni Nano-Ferrites

In this paper, La{sup 3+} substituted M-type Ba–Ni hexaferrite nanoparticles having composition Ba{sub 0.8}Ni{sub 0.2}Fe{sub 12-x}La{sub x}O{sub 19} (x = 0, 0.2, 0.4, 0.6, and 0.8) were prepared by co-precipitation route. The phase of the grown NPs was confirmed using X-ray diffraction analysis and results reveal the growth of M-type hexaferrite NPs as a major phase. The energy dispersive X-ray spectroscopy (EDX) was employed to determine the elemental composition of prepared samples. The FTIR spectra of synthesized samples confirm the bond formation of M-type hexaferrites. The optical bandgap was determined by UV-Vis spectroscopy and the results exhibit an increase in optical bandgap with decreasing crystallite size. The vibrating sample magnetometry (VSM) technique was used to analyze the effect of dopant on the magnetic properties like coercivity, saturation magnetization, and remanence of the synthesized samples. The electrical resistivity was measured by two probe method and it was observed that the activation energy shows a decreasing trend with increase in La content. The highly resistive nature of prepared nano ferrites indicates the potential to use these ferrites for high-frequency applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

A Quantum Monte Carlo Study of the Structural, Energetic, and Magnetic Properties of Two-Dimensional H and T Phase VSe 2

Previous works have controversially claimed near-room-temperature ferromagnetism in two-dimensional (2D) VSe 2 , with conflicting results throughout the literature. These discrepancies in magnetic properties between both phases (T and H) of 2D VSe 2 are most likely due to the structural parameters being coupled to the magnetic properties. Specifically, both phases have a close lattice match and similar total energies, which makes it difficult to determine which phase is being observed experimentally. Here, in this study, we used a combination of density functional theory, highly accurate diffusion Monte Carlo (DMC), and a surrogate Hessian line-search optimization technique to resolve the previously reported discrepancy in structural parameters and relative phase stability. With DMC accuracy, we determined the free-standing geometry of both phases and constructed a phase diagram. Our findings demonstrate the successes of the DMC method coupled with the surrogate Hessian structural optimization technique when applied to a 2D magnetic system.

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

Structural and Magnetic Properties of Co{sub 100−x}Pd{sub x} Thin Films Evaporated on Si (100) Substrate

The structural and magnetic properties of Co{sub 100−x}Pd{sub x} thin films grown under vacuum by physical vapor deposition (PVD) on Si (100) are reported. The thicknesses of the samples were measured with a DEKTAK 150 profilometer; chemical composition was analyzed by energy dispersive X-ray analyses (EDX). Microscopic characterizations of the films were done with X-ray diffraction (XRD) and we conclude that all the samples were polycristalline with an hcp structure. The hysteresis loops are performed by means of vibrating sample magnetometer (VSM) and we point up that all the samples present a planar ferromagnetic anisotropy. The saturation magnetization decreases as the palladium content increases and high values of the squareness up to 0.62 were measured. All these results are analyzed and correlated.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Pressure dependent magnetic properties on bulk CrBr 3 single crystals

The van der Waals class of materials offer an approach to two-dimensional magnetism as their spin fluctuations can be tuned upon exfoliation of layers. Moreover, it has recently been shown that spin-lattice coupling and long-range magnetic ordering can be modified with pressure in van der Waals materials. In this work, the magnetic properties of quasi two-dimensional CrBr 3 are reported applying hydrostatic pressure. The application of pressure up to 0.844 GPa shows a 1.77% decrease in saturation magnetization with a decrease in the Curie temperature from 33.05 to 30.41 K. Density functional theory calculations with pressure up to 1 GPa show a reduction in volume and interplanar distance as pressure increases. To further understand the magnetic properties with applied pressure, the magnetocrystalline anisotropy energy (MAE) and exchange coupling parameter (J) are calculated. There is small decrease in MAE and the first nearest neighbor interaction (J 1 ) (U = 2.7 eV and J = 0.7 eV) is increasing with respect to increasing pressure. Overall, CrBr 3 displays ferromagnetic interlayer coupling and the calculated exchange coupling and MAE parameters match well with the observations from the experimental work.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Doping Effect of Fe Ions on the Structural, Electrical, and Magnetic Properties of SrTiO{sub 3} Nanoceramic Matrix

In the present investigation, strontium titanate nanoceramic was synthesized by incorporating iron (Fe) ion with general formula SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0.0, 0.1, 0.2, and 0.4) using sol-gel autocombustion method. The effect of Fe ions on the structural, morphological, electrical, dielectric, and magnetic properties of the prepared matrix has been investigated by various characterization techniques with the appropriate formulation. The structural properties such as phase space, crystallite size (D), and lattice parameter (a) of prepared matrix are calculated by X-ray diffraction (XRD) technique. The functional groups were analyzed by Fourier transform infrared spectroscopy (FT-IR). The surface morphology of the prepared nanoceramic matrix has been determined by using field emission scanning electron microscopy (FE-SEM) analysis. Calculation of average particle size and diffraction patterns was confirmed by using images from transmission electron microscopy (TEM) and selected area electron diffraction pattern (SAED), respectively. An energy dispersive spectrum analysis (EDS) confirmed the compositional stoichiometry in the investigated matrix. Electrical conductivity increased the prepared sample due to the increasing in the Fe concentration and temperature. The dielectric parameters in the frequency range of 30 Hz to 1 MHz were found higher at lower frequencies. The pure SrTiO{sub 3} matrix shows a paramagnetic nature at room temperature, but for a higher concentration of Fe doping was used to observe the weak ferromagnetic nature. Therefore, due to Fe ion concentration, the properties of the prepared matrix have been completely varied and enhancement in the magnetic properties was observed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Magnetic Properties of Hydrides of RNi{sub 1 –} {sub x}Si{sub x} Compounds (R = Dy, Gd, x = 0.05, 0.02)

The magnetic properties of intermetallic compounds GdNi{sub 0.98}Si{sub 0.02} and DyNi{sub 0.95}Si{sub 0.05} and hydrides based on them have been studied. It is found that a partial substitution of Si atoms for Ni atoms does not cause significant changes in the magnetic characteristics such as the Curie temperature. At the same time, incorporation of hydrogen into the crystal lattice of the GdNi{sub 0.98}Si{sub 0.02} and DyNi{sub 0.95}Si{sub 0.05} compounds leads to significant decrease in the Curie temperature, attenuation of exchange interactions due to significant increase in the unit cell volume (more than 20%), and an increase in the distances between magnetoactive ions. The magnetism of the initial and also hydrogenated compositions are mainly determined by the contribution from the subsystem of the rare-earth ions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Effect of atom substitutions on the magnetic properties in Ce 2 Fe 17 : Toward permanent magnet applications

Due to the rapidly developing technologies and huge market demand, there has been increasing interest internationally in exploring permanent magnet formulations in addition to the well-known Nd 2 Fe 14 B and SmCo 5 /Sm 2 Co 17 . Given Fe's low materials cost and generally high magnetization, Fe-rich rare earth binaries such as Ce 2 Fe 17 comprise a rich “hunting ground” for such new materials. While this compound suffers from a low ordering point and is a heli magnet, these difficulties are easily remedied by the substitution of appropriate amounts of cobalt for Fe, with room-temperature saturation magnetization as high as 1.5 T. In this work, we try to switch the all-important magnetic anisotropy from planar to uniaxial behavior in Ce 2 Fe 17 via 18 h - and 6 c -type atom substitutions with Si, Ir, and numerous other atoms. The uniaxial magnetocrystalline anisotropy is successfully achieved in the 6 c -site-substituted Ce 2 Fe 15 Ir 2 systems, along with large magnetization. We find that iridium substitution, in particular, induces a substantial uniaxial anisotropy of 11.25 MJ/m 3 , which is comparable to most of the current rare earth permanent magnets. Although the iridium substitution is costly, the finding of Ir-triggered uniaxial magnetic anisotropy indicates the potential of Ce–Fe-based alloys for permanent magnets.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Chondrule magnetic properties

The topics discussed include the following: chondrule magnetic properties; chondrules from the same meteorite; and REM values (the ratio for remanence initially measured to saturation remanence in 1 Tesla field). The preliminary field estimates for chondrules magnetizing environments range from minimal to a least several mT. These estimates are based on REM values and the characteristics of the remanence initially measured (natural remanence) thermal demagnetization compared to the saturation remanence in 1 Tesla field demagnetization.

Wasilewski, P. J.↗
DOE OSTI2024

Site Occupancy Preference and Magnetic Properties in Nd 2 (Fe,Co) 14 B

Partial replacement of Fe by Co is an effective method to increase Curie temperature (T C ) , which improves the thermal stability of magnetic properties in Nd 2 Fe 14 B-based permanent magnets. The correlation between Fe substitution and magnetic properties has been studied in Nd 2 (Fe,Co) 14 B via a first-principles calculation. The calculated Fe substitution energies indicate that the Co atoms avoid the 8 j 2 site, which agrees with the experiments. The Co atoms are ferromagnetically coupled with Fe sublattice and show magnetic moments of about 1.2 to 1.7 μ B at different crystallographic sites, less than that of Fe (2.1–2.7 μ B ), resulting in the decrease in total magnetization at ground state (0 K) with increasing Co content. The effective exchange interaction parameter, derived from the energy difference between varied magnetic structures, increases from 7.8 meV to 17.0 meV with increasing Co content from x = 0 to x = 14 in Nd 2 Fe 14–x Co x B. This change in the effective exchange interaction parameter is responsible for the enhancement of T C in Nd 2 (Fe,Co) 14 B. The total magnetization at 300 K, derived from mean-field theory, shows a peak maximum value at x = 1 in Nd 2 Fe 14–x Co x B. The phenomenon results from the interplay between the reduction of the magnetic moment in the Fe(Co) sublattice and the enhancement of T C with increasing Co content.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electronic and magnetic properties of quasi-one-dimensional osmium halide OsCl 4

Using ab initio density functional theory, we study the electronic and magnetic properties of the van der Waals chain material OsCl 4 . In the nonmagnetic state, a strongly anisotropic band structure was observed, in agreement with its anticipated one-dimensional crystal geometry. Based on Wannier functions, we found that the four electrons of the 5d Os atom form a low-spin S = 1 state, with a large crystal field between the d xz/yz and d xy orbitals, corresponding to a strong Jahn–Teller distortion (Q 3 < 0). As a consequence, the magnetic properties are mainly contributed by the d xz/yz states. Furthermore, when a Mott gap develops after the introduction of the Hubbard U and Hund coupling J, we found that the staggered spin order is the most likely magnetic state, namely, spins arranged as (↑-↓-↑-↓) with π wavevector along the chain. In addition, the energy differences between various spin states are small, suggesting a weak magnetic exchange coupling along the chain. Overall, our results provide guidance to experimentalists and theorists working on quasi-one-dimensional osmium halides chain materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tuning structural, transport, and magnetic properties of epitaxial SrRu O 3 through Ba substitution

The perovskite ruthenates (A RuO 3 , A=Ca, Ba, or Sr) exhibit unique properties owing to a subtle interplay of crystal structure and electronic-spin degrees of freedom. Here, in this study, we demonstrate an intriguing continuous tuning of crystal symmetry from orthorhombic to tetragonal (no octahedral rotations) phases in epitaxial SrRuO 3 achieved via Ba substitution (Sr 1-x Ba x RuO 3 with 0 ≤ x ≤ 0.7 ). An initial Ba substitution to SrRuO 3 not only changes the ferromagnetic properties, but also tunes the perpendicular magnetic anisotropy via flattening the Ru–O–Ru bond angle (to 180°), resulting in the maximum Curie temperature and an extinction of RuO 6 rotational distortions at x≈0.20. For x ≤ 0.2, the reduction of RuO 6 octahedral rotational distortion dominantly enhances the ferromagnetism in the system, though competing with the effect of the RuO 6 tetragonal distortion. Further increasing Ba substitution (x > 0.2) gradually enhances the tetragonal-type distortion, resulting in the tuning of Ru-4d orbital occupancy and suppression of ferromagnetism. Our results demonstrate that isovalent substitution of the A-site cations significantly and controllably impacts both electronic and magnetic properties of perovskite oxides.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Structure and Magnetic Properties of Homoleptic Trivalent Tris(alkyl)lanthanides

Six new solvent-free, homoleptic paramagnetic tris(alkyl)lanthanides Ln{C(SiHMe 2 ) 3 } 3 (1Ln) and Ln{C(SiHMe 2 ) 2 Ph} 3 (2Ln) (Ln = Gd, Dy, and Er) were synthesized to investigate the magnetic properties of 4f organometallic compounds stabilized by secondary Ln←H–Si and benzylic interactions. The unit cell of 1Gd contains one independent molecule (Z = 2), while 1Dy and 1Er crystallize with four independent isostructural molecules per unit cell (Z = 16). In all molecules, as in other 1Ln compounds, the three tris(dimethylsilyl)methyl ligands form a trigonal planar LnC 3 core, and six secondary interactions involving Ln←H–Si bonding in Ln{C(SiHMe 2 ) 3 } 3 form above and below the equatorial plane. Two and five crystallographically independent molecules of each 2Ln (2Gd, Z = 8; 2Dy, Z = 20) form with three π-coordinated phenyl groups in addition to either one or two secondary Ln←H–Si interactions per molecule. The packing of these midseries organolanthanide compounds contrasts the single crystallographically unique molecules in previously reported La{C(SiHMe 2 ) 3 } 3 (1La, Z = 2, Z' = 1) and La{C(SiHMe 2 ) 2 Ph} 3 (2La, Z = 2, Z' = 1/3). 2La doped with 2Dy can adopt the crystallographic structure of 2La, which promotes magnetic properties, namely a higher χ m T value at low temperatures as well as stronger magnetic anisotropy. The ac susceptibility data for 10% 2Dy doped into 2La suggests slow relaxation at low temperatures with a relaxation barrier of ~45 K. The computed saturated magnetization of 1Er (M ≈ 4.5 μ B ) and 1Dy (M ≈ 6 μ B ) matches the experimental values, while the computed value for 2Dy better matches the value measured for 2Dy diluted in 2La (M ≈ 5 μ B ). Gas-phase calculations predict that the ground-state and first excited-state multiplet separations are larger for 1Er than 2Er, while the ordering for dysprosium is 1Dy > 2Dy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗