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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Structural and Magnetic Properties of La{sub 1−x}(Ca,Sr){sub x}MnO{sub 3} Powders Produced by the Hydrothermal Method

La{sub 1−x}(Ca,Sr){sub x}MnO{sub 3} manganites have been produced using the hydrothermal method. The influence of the concentration of La, Ca, and Sr on the structural, morphological, and magnetic properties was studied and analyzed. The X-ray diffraction analysis showed that samples crystallized in rhombohedral or trigonal symmetries depending on the stoichiometry. The morphological analyses obtained by using scanning electron microscopy showed cauliflower-type microstructures in all samples. Energy-dispersive spectroscopy studies were also performed, evidencing not only the presence of the constituent elements but an oxygen deficiency and manganese-relative excess in all the samples. This fact is suggested as the cause of the unusual magnetic behavior where a low-temperature re-entrant phase was observed within the ferromagnetic matrix in some of the samples attributed to spin frustration. Furthermore, for some samples, a critical Curie temperature higher than the reported values is attributed to the relative excess of manganese ions, which can occupy other sites in the lattices as interstices or La, Ca, and Sr sites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Magnetic properties of (Mo 2/3 Dy 1/3 ) 2 AlC arc melted polycrystalline samples

Here, this study investigates the structural and magnetic properties of arc-melted (Mo 2/3 Dy 1/3 ) 2 AlC polycrystalline samples, a member of the i-MAX phase family. Temperature-dependent magnetization and specific heat measurements confirm the low-temperature antiferromagnetic transitions around 14 K and 17 K. Neutron diffraction data collected at 4 K reveal the emergence of magnetic Bragg peaks that are not allowed in the paramagnetic space group C2/c, further confirming the presence of antiferromagnetic ordering. The detection of a secondary phase, DyAl 2 , is complicated by overlapping Bragg peaks with the monoclinic phase of (Mo 2/3 Dy 1/3 ) 2 AlC in powder XRD patterns. However, magnetization and neutron diffraction data suggest the presence of DyAl 2 , evidenced by a ferromagnetic phase transition around 62 K.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Crystal structure and magnetic properties in semiconducting Eu 3-δ Zn x Sn y As 3 with Eu-Eu dimers

Magnetic structure and crystal symmetry, which primarily determine the time-reversal and inversion symmetry, may give rise to numerous exotic quantum phenomena in magnetic semiconductors and semimetals when arranged in different patterns. Here, a new layered magnetic semiconductor, Eu 3-δ Zn x Sn y As 3 , was discovered and high-quality single crystals were grown using the Sn flux. According to structural characterization by x-ray diffraction and atomic-resolution scanning transmission electron microscopy, Eu 3-δ Zn x Sn y As 3 is found to crystallize in a hexagonal symmetry with the space group P6 3 /mmc (No. 194). After examining different specimens, we conclude that their stoichiometry is fixed at ~Eu 2.6 Zn 0.65 Sn 0.85 As 3 , which meets the chemical charge balance. Eu 3-δ Zn x Sn y As 3 is composed of septuple (Eu 1-δ Sn y As 2 )-Eu-(Zn x As)-Eu sequences. The shortest Eu–Eu distance in the system is between two Eu layers separated by Zn x As along the c-axis. Magnetization measurement shows an antiferromagnetic ordering in Eu 3-δ Zn x Sn y As 3 at T N ~ 12 K, where the magnetic easy-axis is along the c-axis, and Mössbauer spectroscopy observes magnetic hyperfine splitting on Eu and Sn at 6 K. Magnetic anisotropy is significantly different from the ones along the ab-plane in other layered Eu-based magnetic semimetals. Heat capacity measurements confirm the magnetic transition around 12 K. Electrical resistivity measurement indicates semiconductor behavior with a band gap of ~0.86 eV. Finally, various Eu-based magnetic semiconductors could provide a tunable platform to study potential topological and magnetic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Magnetic Properties and Critical Current of Superconducting Nanocomposites (1 −x)YBa{sub 2}Cu{sub 3}O{sub 7−δ} + xCuO

The aim of this paper was to study the effect of nanoscale inclusions of CuO as the second ingredient of composites on transport properties of superconducting YBa{sub 2}Cu{sub 3}O{sub 7} polycrystals. The samples of YBa{sub 2}Cu{sub 3}O{sub 7−δ} with different content of CuO nanoparticles were synthesized. The analysis of the magnetic properties was carried out within the extended critical state model. It was found that the addition of 0.5 and 1% of CuO nanoparticles leads to an increase in the intragranular density of the critical current at T= 4.2 K. A further increase of x from 2 to 15% and more than 40% decreases the critical current density. The critical current density higher than in the reference sample was also found in the samples with x= 20% and x= 24%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic properties of the low-dimensional Ba M 2 Si 2 O 7 system ( M = Cu , Co , Mn )

Here, we explored the magnetic properties of the low-dimensional Ba M 2 Si 2 O 7 (M = Cu, Co, and Mn) system using both experimental measurements and theoretical calculations. Magnetization, specific heat, and single crystal neutron diffraction measurements have been performed on single crystal Ba M 2 Si 2 O 7 . The spin structure was determined and a magnetic phase diagram with applied field along the b axis was constructed, which contains a spin flop transition around 6 T. Magnetization and specific heat measurements confirmed the presence of weak ferromagnetism in Ba M 2 Si 2 O 7 . Furthermore, we performed local-spin density approximation with on-site Coulomb energy (LSDA+U) calculations for the Ba M 2 Si 2 O 7 (M = Cu, Co, and Mn) system. Due to the first-principles calculations, the origin of the magnetic differences of the three materials is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Magnetic properties of the frustrated spin-$\frac{1}{2}$ capped-kagome antiferromagnet (CsBr)Cu 5 V 2 O 10

Here, the structural and magnetic properties of a spin-$\frac{1}{2}$ averievite (CsBr)⁢Cu 5⁢ V 2 ⁢O 10 are investigated by means of temperature-dependent x-ray diffraction, magnetization, heat capacity, and 51 V nuclear magnetic resonance (NMR) measurements. The crystal structure (trigonal, $P\bar{3}$) features a frustrated capped-kagome lattice of the magnetic Cu 2+ ions. Magnetic susceptibility analysis indicates a large Curie-Weiss temperature of $\theta$ CW ≃ -175K. Heat capacity signals the onset of a magnetic long-range-order (LRO) at T N ≃21.5K at zero magnetic field due to the presence of significant inter-planer coupling in this system. The magnetic LRO below 27 K is further evident from the drastic change in the 51 V NMR signal intensity and rapid enhancement in the 51 V spin-lattice relaxation rate in a magnetic field of 6.3 T. The frustration index ƒ=|⁢$\theta$ CW ⁢|/⁢T N ≃ 8 ascertains strong magnetic frustration in this compound. From the high-temperature value of the 51 V NMR spin-lattice relaxation rate, the leading antiferromagnetic exchange interaction between the Cu 2+ ions is calculated to be J/k B ≃ 136K.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Preparation Structure and Magnetic Properties of Mn-Doped ZnO Nanoparticles Prepared by Hydrothermal Method

In this research, manganese-doped ZnO (Zn{sub 0.99-x}Mn{sub x}O) nanoparticles were synthesized by hydrothermal method using the chemicals. The samples were annealed at 500 and 600 °C to figure out the optimum annealing temperature characterized by differential thermal analysis (DTA) method. Simultaneously with DTA analysis, the possible weight loss was observed by thermal gravimetric (TG) method and categorized the lost chemicals with varying temperature regions. The crystal structure with lattice parameters and the phases were determined by X-ray diffraction method. Microstrain (ε), stress (σ), the dislocation density (δ), the locality of the atoms and their displacements (u), and the bond length (L) values were calculated by making use of lattice parameters. The particle morphologies were monitored by scanning electron microscope (SEM) technique and the elemental compositions of the samples were investigated and found that all peaks belong to Zn, Mn, and O elements. The magnetic properties of the samples were revealed using Quantum design PPMS measurement system and correlated with structural properties.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Magnetic properties of the double trillium lattice antiferromagnet KBaCr 2 ⁢(PO 4 ) 3

Trillium lattices formed by corner-shared triangular units are the platform for magnetic frustration in three dimensions. Herein, we report structural and magnetic properties of the Cr-based (S = 3/2) double trillium lattice material KBaCr 2 ⁢(PO 4 ) 3 studied by x-ray diffraction, dc and ac magnetization, heat capacity, thermal conductivity, and 31 P nuclear magnetic resonance (NMR) measurements complemented by density-functional band-structure calculations. Magnetization, heat capacity, and 31 P NMR measurements reveal the magnetic transition at T N⁢1 ≃ 12.5 K in zero field followed by another transition (T N⁢2 ) at low temperatures in weak applied fields. The 31 P spin-lattice relaxation rate in the ordered state follows the T 3 behavior indicative of the two-magnon Raman process. Finally, the spin lattice of KBaCr 2 ⁢(PO 4 ) 3 comprises two crystallographically nonequivalent ferromagnetic sublattices that are coupled antiferromagnetically, thus eliminating frustration in this trillium network and leading to weak ferromagnetism in the vicinity of T N⁢1 .

36 MATERIALS SCIENCE↗
DOE OSTI2019

Interface depended electronic and magnetic properties of vertical CrI 3 /WSe 2 heterostructures

Owing to the great potential applications in information processing and storage, two-dimensional (2D) magnetic materials have recently attracted significant attention. Here, using first-principles calculations, we investigate the electronic and magnetic properties of the van der Waals CrI 3 /WSe 2 heterostructures. We find that after forming heterostructures, monolayer CrI 3 undergoes a direct to indirect band gap transition and its gap size is greatly reduced. In particular, the out-plane spin quantization axis of monolayer CrI 3 is tuned into in-plane for most stacking configurations of CrI 3 /WSe 2 . We further reveal that the transition of the easy magnetization direction is mainly originated from the hybridization between Cr-d and Se-p orbitals. These theoretical results provide a useful picture for the electronic structure and magnetic anisotropy behaviors in vertical CrI 3 /WSe 2 heterostructures.

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

Microstructure and Hard Magnetic Properties of Sm 1-x Zr x (Fe,Co) 11.3-y Ti 0.7 By Ingots and Thick Melt-Spun Ribbons

Permanent magnets made from Sm(Fe,Co) 12 -based compounds are being actively pursued through nanostructuring and powder metallurgy. This study was aimed at the development of hard magnetic properties in bulk as-cast alloys and in melt-spun alloys for very low wheel speeds. Slower solidification rates and alloying with Zr promote the tetragonal ThMn 12 -type crystal structure, whereas higher solidification rates and alloying with B replace the ThMn 12 structure type with the TbCu 7 structure type. When introduced simultaneously, Zr and B dramatically reduce the alloy solidification rates required for both the refinement of the 1:12 crystallites and their replacement with the 1:7 phase. In bulk arc-melted alloys, this allowed for a microstructure of separated 1:12 crystallites 1–3 μm in size, although, because of the ferromagnetic nature of a minority phase, the coercivity of these fine-grained alloys reached only 0.73 kOe. A moderately accelerated solidification further refined the 1:12 crystallites and increased the coercivity; a Sm 0.7 Zr 0.4 (Fe,Co) 10.8 Ti 0.7 B 0.5 alloy exhibited a coercivity of 1.5 kOe and a maximum energy product of 3.4 MGOe when it was melt-spun into a 0.26-mm-thick ribbon. A more rapid solidification suppressed the 1:12 phase and after annealing at 800–850 °C, the alloys modified with Zr and B developed reasonably high coercivity and maximum energy product even when melt-spun at a wheel speed of 6 m/s. For the above-mentioned alloy, these values were 4.1 kOe and 7.8 MGOe, respectively. Further, a similarly processed very-Sm-lean Sm 0.5 Zr 0.6 (Fe,Co) 10.6 Ti 0.7 B 0.7 alloy exhibited a remanence of 8.8 kG and an energy product of 7.4 MGOe.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Crystal Field Effects on Magnetic Properties of a Mixed Ferrimagnetic Ising System: a Monte Carlo Study

The effects of two different single-ion anisotropies on the magnetization of the mixed (7/2, 5/2) Ising ferrimagnetic system on a square lattice are investigated by the use of Monte Carlo simulation. The ground-state phase diagram is obtained. Compensation points are detected for certain values of the crystal fields. Different types of magnetization curves are available.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Structural and magnetic properties of the CeCo 5 –CeZn 5 solid solution and potential improvements upon iron substitution

In an effort to create high-performance permanent magnets with reduced critical rare earth content, we explored the CeCo 5-x T x (T = transition metal or metalloid) family of compounds to investigate the effect of substitution on the material’s magnetic properties. In our exploration of the CeCo 5-x Zn x system, we discovered a continuous solid solution at 900 °C between the CeCo 5 and CeZn 5 binary phases with ferromagnetism existing from the CeCo 5 compound to the intermediate CeCo 2.75 Zn 2.25 compound. Single crystal studies were also conducted revealing a relatively large anisotropy field of 11.5 T at 300 K for Ce 0.96 Ta 0.04 Co 4.35 Zn 0.65 . Here, the addition of iron Ce 0.79 Ta 0.07 Co 3.77 Fe 0.89 Zn 0.47 yielded further increases in Curie temperature and saturation magnetization to 800 K and 85.5 emu/g, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The application of macroscopic flakes for Fe-6.5%Si bulk magnetics with superior magnetic properties

Inductors are used in power electronics to convert current to different frequency and voltage. They are used extensively from where power is generated all the way to electric vehicles and portable electronic devices. The soft magnetic materials used in the inductors is critical for the performance of the inductors. Currently, a majority of the inductor uses powder core. The use of powder is not ideal as the 3D granule powders generate large demagnetization field working against the applied field, resulting in reduced permeability and efficiency. In this paper, 2D flakes were used to replace the 3D granules as the feedstock for fabricating inductor core. The crystalline Fe-Si based crystalline soft magnetic material in the form of flakes approximately 0.1mm thick, 1mm long and 2mm wide were prepared via melt spinning. The flakes were then coated with insulating materials before compacted into a toroid. The effect of coating thickness and concentration on magnetic properties of the toroidal sample are studied. It was also found that the magnetic cores made by flakes surpass the cores made by same size powder with larger permeability and lower iron losses.

Fe-6.5%Si Steel↗
DOE OSTI2022

Static and dynamic magnetic properties of the spiin-$\frac{5}{2}$triangle lattice antiferromagnet Na 3 Fe(PO 4 ) 2 studied by 31 P NMR

We report 31 P nuclear magnetic resonance (NMR) measurements have been carried out to investigate the magnetic properties and spin dynamics of Fe 3+ (S = 5/2) spins in the two-dimensional triangular lattice (TL) compound Na 3 Fe(PO 4 ) 2 . The temperature (T) dependence of nuclear spin-lattice relaxation rates (1/T 1 ) shows a clear peak around Néel temperature, T N = 10.9 K, corresponding to an antiferromagnetic (AFM) transition. From the temperature dependence of NMR shift (K) above T N , an exchange coupling between Fe 3+ spins was estimated to be J/k B ≃ 1.9 K using the spin-5/2 Heisenberg isotropic-TL model. The temperature dependence of 1/T 1 T divided by the magnetic susceptibility (χ), 1/T 1 T χ , above T N proves the AFM nature of spin fluctuations below ~50 K in the paramagnetic state. In the magnetically ordered state below T N , the characteristic rectangular shape of the NMR spectra is observed, indicative of a commensurate AFM state in its ground state. The strong temperature dependence of 1/T 1 in the AFM state is well explained by the two-magnon (Raman) process of the spin waves in a 3D antiferromagnet with a spin-anisotropy energy gap of 5.7 K. The temperature dependence of sublattice magnetization is also well reproduced by the spin waves. Those results indicate that the magnetically ordered state of Na 3 Fe(PO 4 ) 2 is a conventional 3D AFM state, and no obvious spin frustration effects were detected in its ground state

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗