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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Origins of Marslike spectral and magnetic properties of a Hawaiian palagonitic soil

Results are presented on spectral, Moessbauer, static magnetic, petrographic, and compositional data for a Hawaiian palagonitic soil from Mauna Kea (HWMK1). It was found that reflectivity spectra of size separates smaller than 20 microns resemble spectra for Martian bright regions, while spectra of larger size separates show characteristics in common with spectra for Martian dark regions. Data on the HWMK1 soil are consistent with the partitioning of iron among the following minerals: olivine, titanomagnetite, hematite, and a superparamagnetic colored ferric oxide. These mineralogies are heterogeneously distributed within the soil with respect to both particle type and soil-particle diameter. The strongly magnetic titanomagnetite is associated with black particles and is responsible for the magnetic nature of the soil, while the colored weakly magnetic superparamagnetic ferric oxide and minor hematite are associated with orange particles.

Morris, Richard V.↗
DOE OSTI2025

Effects of carbon substitution on magnetic properties and magnetocaloric effects in Mn 65-x Ga 17 C 18+x compounds

This study involved the tuning of the magnetic, magnetocaloric, and room-temperature structural properties of Mn 65-x Ga 17 C 18+x (0 ≤ x ≤ 4) compounds prepared using a high-energy ball milling (HEBM) technique. This study indicates that the crystal structure of all the compounds can be described as an anti-perovskite cubic structure with the Pm-3m space group and the crystal cell volume decreases with increasing carbon concentration. The system shows a first-order structural phase transition at a temperature T=T M between two cubic phases having different magnetic structures. The phases are characterized by antiferromagnetic (AFM) and ferromagnetic (FM) -like behavior at low (T < T M ) and high (T M > T) temperature regions, respectively. A suppression of the AFM phase was observed with increasing C concentration. The temperature-induced first-order transitions (FOTs) were found to possess a small thermal hysteresis in the magnetization (~2-3 K) in an applied magnetic field of H = 50 kOe. Magnetic entropy changes estimated from isothermal magnetization curves indicate that the largest value of the magnetic entropy change of |ΔS M | = 2.1 J kg -1 K -1 for x = 4 with ΔH = 50 kOe, with a relative cooling power (RCP) of ~190 J kg -1 . Furthermore, high-energy ball milling (HEBM), a scalable technique, has been demonstrated as a viable method to synthesize magnetocaloric materials with substantial RCP values.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reinvestigation of the intrinsic magnetic properties of (Fe 1–$x$ Co $x$ ) 2 B alloys and crystallization behavior of ribbons

In this paper, new determination of the magnetic anisotropy from single crystals of ( Fe 1 - x Co x ) 2 B alloys are presented. The anomalous temperature dependence of the anisotropy constant is discussed using the standard Callen-Callen theory, which is shown to be insufficient to explain the experimental results. A more material specific study using first-principles calculations with disordered moments approach gives a much more consistent interpretation of the experimental data. Since the intrinsic properties of the alloys with x = 0.3 - 0.35 are promising for permanent magnets applications, initial investigation of the extrinsic properties are described, in particular the crystallization of melt spun ribbons with Cu, Al, and Ti additions. Previous attempts at developing a significant hysteresis have been unsuccessful in this system. Our melt-spinning experiment indicates that this system shows rapid crystallization.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Alloying effect of rare-earth tritellurides on the charge density wave and magnetic properties

Among many van der Waals materials rare-earth tritellurides (RTe3) allow studying several phenomena like magnetic, superconducting, and charge density wave (CDW). These studies show the effect of cationic alloying of antiferromagnetic RTe3 for fully tunable near room-temperature CDW properties. DyxGd1−xTe3 and DyxTb1−xTe3 alloys were synthesized through a chemical vapor transport technique, and the rare-earth element composition was controlled by changing the ratio of rare-earth metal reagents. The results show that the lattice parameters can be continuously tuned with the composition of the rare-earth cations leading to the variation of the internal chemical pressure. Temperature-dependent Raman spectroscopy and electric transport measurement show that the CDW transition temperature (TCDW) of RTe3 alloys varies with lattice parameters/chemical pressure spanning across 300–380 K. Additional magnetism studies offer the first insights into the magnetic ordering in RTe3 alloys. The emergence of multiple magnetic transitions implies complex magnetic interactions that arise from interactions between different rare-earth elements. Overall findings introduce ways to control the CDW behavior and provide valuable insights into the magnetic ordering in RTe3 alloys, contributing to further investigation and a better understanding of their properties.

Physics↗
DOE OSTI2021

Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

Nanostructured functional oxides play an important role in enabling clean energy technologies and novel memory and processor devices. Using thin-film La 0.6 Sr 0.4 FeO 3 (LSF) as a model system, the novel utility of exsolution in fabricating self-assembled metal oxide nanocomposites with tunable functionalities is shown. Exsolution triggers the formation of metallic iron (Fe 0 ) nanoparticles, Ruddlesden–Popper domains, and nm-scale percolated Fe-deficient channels in LSF. Combining multimodal characterization with numerical modeling, the chemical, magnetic, and electrical properties of the exsolution-synthesized nanocomposite at different stages of Fe 0 exsolution as well as during redox cycling are assessed. After exsolution, the electronic conductivity of the nanocomposite LSF increased by more than two orders of magnitude. Based on numerical analysis representing all the constituents, it is expected that this increase in conductivity originates mainly from the Fe-deficient percolating channels formed during exsolution. Moreover, the exsolved nanocomposite is redox-active even at moderate temperatures. Such redox capabilities can enable dynamic control of the nanocomposite functionality by tailoring the oxygen non-stoichiometry. This concept is demonstrated with a continuous modulation of magnetization between 0 and 110 emu cm -3 . These findings point out that exsolution may serve as a platform for scalable fabrication of complex metal oxide nanocomposites for electrochemical and electronic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Crystal structure and magnetic properties of Gd 8 Mn 3 Sb 19

Here, in this study, a novel magnetic semimetal compound, Gd 8 Mn 3 Sb 19 , was synthesized successfully via high-temperature solid-state reaction. The crystal structure of Gd 8 Mn 3 Sb 19 was determined using both single crystal and powder X-ray diffraction techniques, revealing a non-centrosymmetric orthorhombic space group, Pmn2 1 (No. 31). The Sb atoms in Gd 8 Mn 3 Sb 19 form five-atom-wide Sb 5 7− ribbons, narrower three-atom-wide Sb 3 5− ribbons, and single Sb 3− anions. On the other hand, both Gd 3+ and Mn 2+ ions form the distorted Gd 3 and Mn 3 triangular lattices, respectively. The magnetic measurements suggest the complex magnetic interactions contributed by both Gd 3+ and Mn 2+ ions. A sharp peak observed in the magnetic susceptibility plot at approximately 25 K corresponds to the antiferromagnetic-type transition in Gd 8 Mn 3 Sb 19 . Furthermore, the magnetic measurements along different directions indicate the strong magnetic anisotropy present in Gd 8 Mn 3 Sb 19 , which is likely due to the complex magnetic interactions arising from the existence of Gd and Mn ions. Finally, the electrical resistivity measurements of Gd 8 Mn 3 Sb 19 indicate semimetallic behavior with a positive magnetoresistance.

Chemistry↗
DOE OSTI2021

Magnetic properties and signatures of moment ordering in the triangular lattice antiferromagnet KCeO 2

The magnetic ground state and the crystalline electric field level scheme of the triangular lattice antiferromagnet KCeO 2 are investigated here. Below $T_N$ = 300 mK, KCeO 2 develops signatures of magnetic order in specific heat measurements and low energy inelastic neutron scattering data. Trivalent Ce 3+ ions in the $D_{3d}$ local environment of this compound exhibit large splittings among the lowest three 4$f^1$ Kramers doublets defining for the free ion the $\textit{J}$ = 5/2 sextet and a ground state doublet with dipole character, consistent with recent theoretical predictions by Eldeeb et al. [Phys. Rev. Materials 4, 124001 (2020)]. An unexplained, additional local mode appears, and potential origins of this anomalous mode are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Synthesis, Stability, and Magnetic Properties of Antiperovskite Co 3 PdN

Experimental synthesis and characterization of theoretically predicted compounds are important steps in the materials discovery pipeline. Here, we report on the synthesis of Co 3 PdN, which was recently predicted to be a stable magnetic antiperovskite. The Co 3 PdN thin films were grown by reactive sputtering and were confirmed to form in an antiperovskite crystal structure. The thermal stability of the compound is demonstrated up to 600 K by in situ X-ray diffraction, though the phase persists at slightly higher temperatures (700 K) in an air-free magnetometer. Both ab initio calculations and magnetization measurements find Co 3 PdN to be ferromagnetic with an experimentally determined Curie temperature of T C = 560 ± 5 K. The saturation magnetization of 1.2 μ B /Co found in the experiment is slightly lower than the 1.7 μ B /Co value expected by theory. A narrow magnetic hysteresis loop with a coercive field of 100 Oe at low temperature suggests that Co 3 PdN might be useful in electronic applications requiring fast switching of the magnetization vector. While prior prediction of Co 3 PdN showed a gapped electronic band structure for each spin channel, we show that this was due to incomplete sampling of Brillouin zone paths and that band crossings exist along R-X|M and X|M-R paths. The metallic nature of Co 3 PdN is further confirmed by temperature-dependent transport measurements, which also show a considerable anomalous Hall effect. Altogether, this work represents an appreciable step toward understanding the synthesis, structure, stability, and properties of a new magnetic material.

14 SOLAR ENERGY↗
NASA NTRS1987

Selected spectroscopic and magnetic properties of lanthanide complexes in polyimide XU-218

Polyimide XU-218 films containing approximately 5 wt pct of Eu(III), Gd(III), Tb(III), and Er(III) were prepared, and the effects of complexing each of the metals with the following four ligands were investigated: N-phenylphthalamate (NPPA), 2,4-pentanedionate (AcAc), 1,3-diphenyl 1,3-propanedionate (DBM), and a new hexa-aza-macrocyclic (MAC) ligand. The tris-chelated complexes of the mononegative ligands NPPA, AcAc, and DBM produced transparent, flexible films, which had magnetic and spectral properties very similar to those of the parent lanthanide complexes, while complexes of MAC showed problems due to the presence of lattice water and yielded dark brittle films. AcAc caused little or no effect on the glass transition temperature (Tg), while NPPA and DBM complexes lowered Tg to 269-290 C, and MAC indicated moisture by inflexion at 95-100 C with a true Tg at 320 C. All lanthanide-containing films were paramagnetic.

Stoakley, D. M.↗
NASA NTRS1974

Magnetic properties of lunar samples returned by Luna 16 automatic station

Results of measuring the specific magnetic susceptibility of regolith are presented. The data indicate that regolith samples from the Sea of Tranquillity and the Sea of Fertility are similar in order of magnitude of the specific magnetic susceptibility. Several stony meteorites of subgroup L have a similar value of this quantity. After comparison with artificial analogs, it can be concluded that the bulk content of ferromagnetic minerals in regolith samples is 3 to 4 percent.

Gorshkov, E. S.↗
DOE OSTI2022

Single crystal synthesis and magnetic properties of a Shastry-Sutherland lattice compound BaNd 2 ZnS 5

In this study, single crystals of a Shastry-Sutherland magnetic semiconductor, BaNd 2 ZnS 5 , were synthesized through a high-temperature solution growth technique. Physical properties were characterized by powder and single crystal x-ray diffraction, temperature- and field-dependent magnetization, and temperature-dependent specific heat measurements. BaNd 2 ZnS 5 orders antiferromagnetically at 2.9 K, with magnetic moments primarily aligned within the $ab$ -plane. Magnetic isothermal measurements show metamagnetic transitions at ~ 15 kOe for the [110] direction and ~ 21 kOe for the [100] direction. Estimated magnetic entropy suggests a double ground state for each neodymium ion.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electronic and magnetic properties of the topological semimetal SmMg 2 Bi 2

Dirac semimetals show nontrivial physical properties and can host exotic quantum states like Weyl semimetals and topological insulators under suitable external conditions. Here, by combining angle-resolved photoemission spectroscopy measurements (ARPES) and first-principle calculations, we demonstrate that the Zintl-phase compound SmMg 2 Bi 2 is in close proximity to a topological Dirac semimetallic state. ARPES results show a Dirac-like band crossing at the zone center near the Fermi level (E F ), which is further confirmed by first-principle calculations. Theoretical studies also reveal that SmMg 2 Bi 2 belongs to a Z 2 topological class and hosts spin-polarized states around the E F . Zintl's theory predicts that the valence state of Sm in this material should be Sm 2+ , however, we detect many Sm-4f multiplet states (flat-bands) whose energy positions and relative intensities suggest the presence of both dominant Sm 2+ and minor Sm 3+ . The small concentration (2.5%) of Sm 3+ in the bulk of a crystal is inferred to arise from Sm vacancies in the crystal. It is also evident that these flat bands and other dispersive states are strongly hybridized when they cross each other. Due to the presence of Sm 3+ ions, the temperature dependence of the magnetic susceptibility χ (T) shows a Curie-Weiss-like contribution in the low-temperature region, in addition to the Van Vleck-like behavior expected for the Sm 2+ ions. The present study will help to better understand the electronic structure, magnetism, and transport properties of related materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1981

Permanent magnet properties of Mn-Al-C between -50 C and +150 C

Anisotropic Mn-Al-C (Ni) magnets are potential substitutes for Alnico 5 and 8. The limited machinability of the alloy and the fact that it is cobalt-free made it particularly interesting. The low Curie point and the costly warm extrusion process needed for grain orientation are drawbacks. The objective of this study was a detailed magnetic characterization of the material for possible use in electric machinery. The principal subjects of the study were the largest extruded bars presently available, of 31 mm diameter. Easy and hard axis magnetization curves and second-quadrant recoil loop fields were measured at various temperatures ranging from -50 C to +150 C. Property variations over the cross section of a bar were also studied.

Abdelnour, Z. A.↗
DOE OSTI2021

Static and dynamic magnetic properties of honeycomb lattice antiferromagnets Na 2 M 2 TeO 6 , M = Co and Ni

The magnetic structures and spin dynamics of Na 2 CO 2 TeO 6 and Na 2 Ni 2 TeO 6 are investigated by means of elastic and inelastic neutron scattering measurements and the results are discussed in the context of a generalized Kitaev-Heisenberg model on a honeycomb lattice with strong spin-orbit coupling. The large number of parameters involved in the Hamiltonian model is evaluated by using an iterative optimization algorithm capable of extracting model solutions and simultaneously estimating their uncertainty. The analyses indicate that both Co 2+ (d 7 ) and Ni 2+ (d 8 ) antiferromagnets realize bond-dependent anisotropic nearest-neighbor interactions and support the theoretical predictions for the realization of Kitaev physics in 3 d electron systems with effective spins S = 1/2 and 1. By studying the Na-doped system Na 2.4 Ni 2 TeO 6 , we show that the control of Na content can provide an effective route for fine-tuning the magnetic lattice dimensionality, as well as to controlling the bond-dependent anisotropic interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1993

Magnetic properties and Moessbauer analyses of glass from the K-T boundary, Beloc, Haiti

The experimental magnetic susceptibility, the temperature-independent component of the magnetic susceptibility, the magnetization, and the Curie constant have been measured for a number of specimens of glass from the K-T boundary found at Beloc, Haiti, and the results are compared with those of similar measurements of tektites. Because the Fe(3+)/Fe(2+) ratio is needed to calculate the magnetic parameters, Moessbauer spectroscopic measurements were also made. The data were consistent with the classification of the Beloc glasses as tektites.

Senftle, F. E.↗
DOE OSTI2020

Electronic structure, magnetic properties, and exchange splitting of gadolinium intermetallics

Here, we report here the electronic structure calculations of the magnetic moment, magneto-crystalline anisotropy energy (MAE), and density of states (DOS) of Gd-metal, GdAl 2 , GdAl 3 , GdCo 2 , GdCo 3 , and GdCo 5 . From the DOS, the exchange splitting energy is derived to map ferrimagnetic to paramagnetic phase transition (Curie temperature, T C ). The employed theoretical method here is based on advanced density functional theory, specifically the linearized augmented plane wave method (LAPW) within the local spin density approximation (LSDA), including spin–orbit coupling (SOC) and Hubbard model parameter (U). DOS analysis of both Gd-Al and Gd-Co systems reveals a strong correlation between exchange splitting energy and T C . The Gd-Co system exhibits an enormous exchange splitting energy among Co-3d electrons, vastly overwhelming the vanishing Gd 5d exchange splitting. Finally, these findings suggest that exchange splitting of Co-3d electrons plays a key role in the ground state magnetism and magnetic transition temperatures in these materials.

36 MATERIALS SCIENCE↗