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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

SrNi(VO 4 )(OH): The High-Temperature Hydrothermal Synthesis and Magnetic Properties of an Adelite-Descloizite-Type Structure

Single crystals of a new transition metal adelite-descloizite-type structure were synthesized using a high temperature (580 °C) high-pressure hydrothermal technique. Single crystal X-ray diffraction and energy dispersive X-ray analysis (EDX) were used to investigate the structure and elemental composition, respectively. SrNi(VO 4 )(OH) crystallizes in an acentric orthorhombic crystal system in the space group P2 1 2 1 2 1 (no. 19); Z = 4, a = 5.9952(4) Å, b = 7.5844(4) Å, c = 9.2240(5) Å. The structure is comprised of a Ni–O–V framework where Sr 2+ ions reside inside the channels. Single-crystal magnetic measurements display a significant anisotropy in both temperature- and field-dependent data. The temperature dependent magnetic measurement shows antiferromagnetic behavior at T N ~8 K. Overall, the magnetic properties indicate the presence of competing antiferromagnetic and ferromagnetic interactions of SrNi(VO 4 )(OH).

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

Template Synthesis, Structure, and Magnetic Properties of Layered Nanowires

Nanowires (NWs) consisting of Ni/Cu and Co/Cu alternating layers with a diameter of 100 nm and layer thicknesses varying between 10 and 500 nm are prepared by template synthesis in pores of polymer track-etched membranes. Bath compositions and different regimes for pulsed electrodeposition of NWs are explored. A procedure for electrodeposition of NWs using pulses of equal charge is developed. By diminishing the amount of charge per pulse, initially we manage to lower the layer thickness to 10–15 nm, but further diminishing of charge in pulses leads to the blending of elemental composition of adjacent layers and/or formation of rod–shell nanostructures within the NWs. The coercive force (15–30 mT) and residual magnetization of our layered NWs are determined from magnetization measurements. For NWs with a layer thickness of 50–100 nm, the magnetization curves recorded in the out-of-plane and in-plane geometries are similar in shape and have similar parameters. For NWs with thicker layers (250 and 500 nm), magnetization curves are markedly different due to magnetic anisotropy (an easy magnetization axis emerges longitudinally to NWs) and interference between neighboring NWs. Magnetic force microscopy of isolated NWs identifies that the NWs comprise magnetic regions extending over ~100–150 nm. The NW can be partially remagnetized by applying an external magnetic field (+16 mT) longitudinally.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Effects of Nd, Er Doping on the Structure and Magnetic Properties of YFeO{sub 3}

Nd, Er co-doped YFeO{sub 3} compounds were synthesized by sol-gel method. The prepared compounds were characterized by powder x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), and vibrating sample magnetometer (VSM) integrated in a physical property measurement system (PPMS-9), respectively. The results show that the compounds possess orthorhombic perovskite structure. The Y{sub 0.5}Er{sub 0.1}Nd{sub 0.4}FeO{sub 3} compound mainly consists of five elements (Er, Nd, Y, Fe, and O) and atom ratio matched well with the formula. With the increase of Nd{sup 3+} doping content in Y{sub 0.5}Er{sub 0.5−x}Nd{sub x}FeO{sub 3} (x = 0, 0.1, 0.2, 0.3, and 0.4), the coercivity increases gradually while the saturation magnetization and remanent magnetization decrease at the same time. Introducing Nd{sup 3+} and Er{sup 3+} ions into YFeO{sub 3} will make a change on a structure distortion, resulting in the decrease of the Fe–O–Fe angle and the consequent reduction of superexchange effect. From our research results, the relationship between the r (R{sup 3+}) and the superexchange bond angle is different from pure-phase orthoferrites R FeO{sub 3}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic Properties of MFeCrO{sub 4} (M = Co/Ni) Prepared by Solution Combustion Method

Single phase MFeCrO{sub 4} (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO{sub 4} and NiCrFeO{sub 4} samples are 8.374 and 8.325 Å and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm{sup −1}, indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO{sub 4} having a higher value of saturation magnetisation. Mössbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe{sup 3+} cations is higher in NiCrFeO{sub 4}.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structural, Optical and Magnetic Properties of PANI/Se{sub 0.95}Fe{sub 0.05} Nanocomposites

Polyaniline (PANI) coupled with Se{sub 0.95}Fe{sub 0.05} in various weight percentage (5 and 10 wt%) were formed by in situ polymerization method of PANI in the presence of Se{sub 0.95}Fe{sub 0.05}. The functionality of the investigated nanocomposites was investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), vibrating sample magnetometer (VSM), and photoluminescence (PL) analyses. The structural characteristics of PANI and the existence of Se{sub 0.95}Fe{sub 0.05} together with PANI were confirmed using XRD. The different functional groups of nanocomposite were studied using FTIR. PANI/Se{sub 0.95}Fe{sub 0.05} nanocomposites exhibited a weak ferromagnetic behavior. Law of Approach to saturation was used to determine the saturation magnetization of nanocomposites samples. The PL of PANI and nanocomposites emitted five emissions in violet and blue ranges. The PL intensity of the emission peaks is significantly reduced when Se{sub 0.95}Fe{sub 0.05} is introduced to PANI matrix.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Solvothermal Synthesis of Mesoporous Fe{sub 3}O{sub 4} Nanoparticles in Mixed Solvent of Ethylene Glycol and Water: Structure and Magnetic Properties

Mesoporous Fe{sub 3}O{sub 4} nanoparticles were synthesized by a solvothermal method, via a mixed solvent of ethylene glycol (EG) and deionized water, using iron chloride and urea as the precursors. The phase, morphology, and pore structure are investigated by the characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), and N{sub 2} isotherm adsorption–desorption. The results show that the amount of water in the mixed solvent plays vital role in controlling the size of Fe{sub 3}O{sub 4} nanoparticles, specific surface area, and pore size. Additionally, solid Fe{sub 3}O{sub 4} nanospheres were prepared using only EG as solvent, while α-Fe{sub 2}O{sub 3} nanosized polyhedrals were obtained with only water as solvent. The mesoporous Fe{sub 3}O{sub 4} nanoparticles show a ferromagnetic behavior, with saturation magnetizations (Ms) of 78–82 emu g{sup − 1} and coercivities (Hc) ranging from 13–58 Oe. The α-Fe{sub 2}O{sub 3} nanoparticles also exhibit a weak-ferrimagnetic character, with a remanent magnetization (Mr) of 0.24 emu g{sup − 1}, and Hc of 558 Oe.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of Sb substitution on crystal structure, texture and hard magnetic properties of melt-spun MnBi alloys

Melt-spun Mn 50 Bi 50-x Sb x alloys with x ≤ 5 were prepared at different solidification rates and characterized both in the as-spun state and after annealing. In the as-spun alloys, the Sb substitution leads to the formation of a metastable phase, similar to the binary "quenched high-temperature phase" but without the superstructure of the latter and exhibiting a different – increasing – temperature dependence of coercivity. The new nanocrystalline metastable phase is not only itself characterized by a high room-temperature coercivity (in excess of 20 kOe), but upon annealing it transforms into a high-coercivity (up to 13.5 kOe) "low-temperature" α phase. However, the advantage of obtaining a high coercivity without the otherwise required milling made possible by the Sb substitution is undermined by the absence of a local crystallographic texture in the melt-spun alloys. The best combination of the isotropic hard magnetic properties realized for the Mn 55 Bi 43.5 Sb 1.5 composition is a remanence of 35.5 emu/g and a coercivity of 8.1 kOe. The annealed Sb-free Mn 50 Bi 50 alloys did possess a local crystallographic alignment and, for high solidification rates, a moderate coercivity up to 5.6 kOe; however, they had an inadequate "rectangularity" in the demagnetization curve. The orthorhombic compound known as MnBi 0.9 Sb 0.1 and described earlier as antiferromagnetic was obtained in the annealed ribbons with x ≈ 5. The compound was found to order ferromagnetically between 200 K and ≈250 K and to exhibit a significant coercivity, 14.3 kOe at 50 K. Here, it is suggested that the MnBi 0.9 Sb 0.1 may actually be a Sb-stabilized "new phase" observed earlier as metastable in the Bi–MnBi eutectic alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Chemical, Morphological, Structural, Optical, and Magnetic Properties of Transition Metal Titanium (Ti)-Doped LaFeO{sub 3} Nanoparticles

In the present work, pure and transition metal titanium (Ti)-doped LaFe{sub 1−x}Ti{sub x}O{sub 3}(x = 0.0, 0.2, 0.4, and 0.6) nanoparticles have been successfully synthesized by hydrothermal synthesis technique for various molar ratios of 0.2, 0.4, and 0.6. The prepared samples were grinned and annealed in furnace at 600 {sup ∘}C/4 h. The X-ray diffraction (XRD) analysis confirms the phase orthorhombic formation of LaFeO{sub 3} and Ti-doped LaFeO{sub 3}. The stoichiometric analysis was performed through energy-dispersive X-ray studies (EDX). The micro-structural features of surface morphology were examined by field emission scanning electron microscopy (FESEM). Further, surface nanocrystalline of the titanium (Ti)-doped LaFe{sub 1−x}Ti{sub x}O{sub 3} was also investigated through high-resolution transmission electron microscopic (TEM) analysis. The enhancement of room temperature magnetization value has been observed from the M–H curve which is measured using vibrating sample magnetometer (VSM).The weak ferromagnetic behavior was observed from hysteresis loop. From hysteresis loop, saturation takes place when the applied magnetic field intensity is 15 kO{sub e}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Tuning the magnetic properties of the spin-split antiferromagnet MnTe through pressure

The hexagonal antiferromagnet MnTe has attracted enormous interest as a prototypical example of a spin-compensated magnet in which the combination of crystal and spin symmetries lifts the spin degeneracy of the electron bands without the need for spin-orbit coupling, a phenomenon called nonrelativistic spin splitting (NRSS). Subgroups of NRSS are determined by the specific spin-interconverting symmetry that connects the two opposite-spin sublattices. In MnTe, this symmetry is rotation, leading to the subgroup with spin splitting away from the Brillouin zone center, often called altermagnetism. MnTe also has the largest spontaneous magnetovolume effect of any known antiferromagnet, implying strong coupling between the magnetic moment and volume. This magnetostructural coupling offers a potential knob for tuning the spin-splitting properties of MnTe. Here, we use neutron diffraction with in situ applied pressure to determine the effects of pressure on the magnetic properties of MnTe and further explore this magnetostructural coupling. We find that applying pressure significantly increases the Néel temperature, but decreases the ordered magnetic moment. We explain this as a consequence of strengthened magnetic exchange interactions under pressure, resulting in higher 𝑇 N , with a simultaneous reduction of the local moment of individual Mn atoms, described here via density functional theory. This reflects the increased orbital hybridization and electron delocalization with pressure. In conclusion, these results shed light on the competition between magnetic exchange interactions and the strength of individual magnetic moments and show that the magnetic properties of MnTe can be controlled by pressure, opening the door to improved properties for spintronic applications through tuning via physical or chemical pressure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Structural and magnetic properties of La2Ni1−xCoxMnO6 compounds

Highlights: • Monoclinic La2Ni1−xCoxMnO6 samples have been prepared using Sol-gel technique. • Rietveld analysis shows an octahedrally distorted double perovskite structure. • The nature of FM interaction and TC depend on the B-site ions. • The short range FM ordering above TC is induced by antisite disorders. • The existence of any spin glass like phase in such system is discarded. - Abstract: Single phase monoclinic La{sub 2}Ni{sub 1−x}Co{sub x}MnO{sub 6} (x = 0.2, 0.4, 0.8) compounds, henceforth, referred as LNC{sub x}MO (x = 0.2, 0.4, 0.8) have been prepared by Sol–gel technique. The structural study and redox titration suggest that the samples are both La and O deficient. The generated atomic models using Rietveld refined structural parameters show octahedral distortion in the double perovskite structure. X-ray photoelectron spectroscopy (XPS) study has been used to determine the predominant valence states of Ni, Mn and Co ions. LNC{sub x}MO (x = 0.2, 0.4) are found to be Heisenberg ferromagnets whereas LNC{sub 0.8}MO is a phase segregated system. In LNC{sub 0.4}MO and LNC{sub 0.8}MO, at temperatures above T{sub C}, χ{sup −1}(T) curve shows the characteristics of Griffiths phase. The study of ac susceptibility and isothermal remanent magnetization (IRM) discard the possibility of any glassy state at low temperatures. The antiphase boundaries (APBs), antisite disorders (ASDs) and oxygen vacancies play important roles in this system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Abnormal Transport and Magnetic Properties Induced by Change of the Phase Volume Ratio for YBa{sub 2}Cu{sub 3}O{sub 7-δ}/La{sub 0.67}Sr{sub 0.33}MnO{sub 3} Hybrids

Two elaborately designed hybrids consisting of superconducting YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) and ferromagnetic La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO), namely 20 × (YBCO(m)/LSMO(100 − m)) are prepared on single crystal SrTiO{sub 3} (STO) by pulsed laser deposition (PLD) with 20 being repetition periods and m = 90 and 10, respectively, which represents YBCO pulse number in a period. The films show highly c-oriented and epitaxial quality, suggested by XRD 𝜃–2𝜃 scans and pole figures. The 20 × (YBCO90/LSMO10) sample with a large YBCO volume fraction exhibits the typical character of a metal superconductor at about 90 K, while its transition width reaches 9.1 K, which is nearly eight times of that of the pure YBCO film. Above the superconducting transition temperature, a superparamagnetic signal rather than ferromagnetic behavior is observed, which may be associated with a diluted system consisting of the ferromagnetic nanoparticles embedded in the superconducting films. For the hybrid with a small YBCO volume fraction, i.e., the 20 × (YBCO10/LSMO90) sample, its transport behavior at normal state is insulating, and it is found that the Mott variable range hopping conduction dominates in this insulating phase in the temperature range 70–310 K. Obviously distinguishable insulator to superconductor (IS) transition occurs at 52 K, but the superconducting diamagnetic signals are very weak in the magnetic measurements below the IS temperature. For this sample, the magnetization loop at 100 K is ferromagnetic, yet manifested by a reduced coercive field and residual magnetization as compared with a pure LSMO film. In fact, both hybrids represent two kinds of nanocomposites, i.e., superconducting nanoparticles in a ferromagnetic matrix and ferromagnetic nanoparticles in a superconducting matrix, which benefits to study interfacial interactions due to an increased interface to value ratio and reduced size effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Quantum Magnetic Properties and Metal‐to‐Insulator Transition in Chemically Doped Calcium Ruthenate Perovskite

Ruthenates provide a comprehensive platform to study a plethora of novel properties, such as quantum magnetism, superconductivity, and magnetic fluctuation mediated metal–insulator transition (MIT). Herein, an overview of quantum mechanical phenomenology in calcium ruthenium oxide with varying compositions is provided. While the stoichiometric composition of exhibits non‐fermi liquid (FL) behavior with quasi‐criticality, chemically doped compounds depict prominent signatures of quantum magnetic fluctuations at low temperature that in some cases are argued to mediate in metal–insulator transition. In the case of cobalt‐doped , an unusual continuum fluctuation is found to persist deep inside the glassy phase of the material. These observations reflect the richness of the ruthenate research platform in the study of quantum magnetic phenomena of fundamental importance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Magnetic properties of Lu and Y doped Ce-Fe-B magnets

The growing demand for Nd2Fe14B magnets is exacerbating the current critical materials shortage. To reduce the amount of critical material in Nd2Fe14B magnets, chemical substitutions have been used and shown to improve the magnetic behavior, such as the Curie Temperature TC, anisotropy field Ha, and saturation magnetization MS.

Bretana, Alex↗
DOE OSTI2019

Stability, Electronic and Magnetic Properties of Rare Earth (Eu, Tm) Implanted InGaN

The electronic structure and magnetic behavior of InGaN:RE (RE = Eu, Tm) have been studied by using scalar relativistic full-potential linear augmented-plane-wave plus local orbital (FPLAPW + lo) calculations with LSDA+U approximation. Band structure and density of states are analyzed. It appears that the In-site is the preferred site for doping InGaN alloy with rares earth (Eu, Tm) from the formation energy. Our study reveals that these materials are semiconductors with a direct band gap of 1.2345 eV and 1.3657 eV for InGaN:Eu and InGaN:Tm respectively. The total energy of the FM phase is lower than the AFM total energy; this confirms the fact that the ground state at zero temperature is ferromagnetic. A small-induced magnetic moment on other nonmagnetic atoms (Ga, In, and N) and the total magnetic moment of these compounds is mainly due to RE-4f states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Double transition metal MXenes with wide band gaps and novel magnetic properties

Novel wide band gaps and magnetism in ordered titanium–vanadium, titanium–chromium, and titanium–manganese carbide and nitride based MXenes are predicted using density functional theory. Based on the recent synthesis of Ti centred double transition metal MXenes, we study MXenes with a central Ti layer and different surface early 3d metals, and various terminations, TiM 2 X 2 T (M = V, Cr, Mn; X = C, N; T = H, F, O, OH). While previously studied MXenes are strongly metallic, we predict surface metal and termination dependent metal–insulator transitions in the Cr–N and Mn–N series. A uniquely wide band gap over 1 eV is predicted for TiMn 2 N 2 F 2 using the HSE06 density functional while the unterminated TiMn 2 N 2 remains metallic. The entire TiCr 2 C 2 T series is predicted to be semiconducting. Distinct from the more common Ti–C MXenes, not all combinations of metals and terminations are predicted to be stable. Within the examined sets of materials, anti-ferromagnetic orders are generally most favorable. In conclusion, the new MXenes further extend the range of properties accessible in this family of two-dimensional nanomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Unusual electrical and magnetic properties in layered EuZn 2 As 2

Eu-based compounds often exhibit unusual magnetism, which is critical for nontrivial topological properties seen in materials such as EuCd 2 As 2 . The authors investigate the structure and physical properties of EuZn 2 As 2 through measurements of the electrical resistivity, Hall effect, magnetization, and neutron diffraction. Their data show that EuZn 2 As 2 orders antiferromagnetically with an A-type spin configuration below T N = 19 K. Surprisingly, there is strong evidence for dominant ferromagnetic fluctuations above T N , as reflected by positive Curie–Weiss temperature and extremely large negative magnetoresistance (MR) between T N and T fl ≈200 K. Furthermore, the angle dependence of the MRab indicates field-induced spin reorientation from the ab-plane to a direction ≈45° from the ab plane. Compared to EuCd 2 As 2 , the doubled T N and T fl make EuZn 2 As 2 a better platform for exploring nontrivial magnetic and electronic properties in both magnetic fluctuation (T N < T < T fl ) and ordered (T < T N ) regimes.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Magnetic properties of Lutetium and Yttrium doped Ce 2 Fe 14 B magnets

The increasing demand for Nd-Dy and Sm-Co based permanent magnets is exacerbating the current critical materials shortage, therefore improving and optimizing current candidate critical element free permanent magnets is necessary to develop future clean energy technologies. In this work, we aim to increase the thermal stability and magnetic performance of Ce 2 Fe 14 B based permanent magnets through the substitution of Ce ions with noncritical rare earth elements Lu and Y. The substitution of Lu (x=0; 0.05; 0.1; 0.15) for Ce ions in (LuxCe 2-x )Fe 14 B was unsuccessful, likely due to disparities in ionic size and valencies, and failed to exhibit improved thermal stability or magnetic performance. In contrast, Y substitution for Ce ions in (Y x Ce 2-x )Fe14B (x= 0.1; 0.2; 0.3; 0.4; 0.5) alloys was successful. Notably, these alloys demonstrated enhanced thermal stability, as evidenced by an increase in the Curie temperature, reaching a peak of 443 K at x= 0.5. Y substitution also helped to suppress the CeFe2 Laves phase. Without loss of the anisotropy field Y substitution increased the saturation magnetization, MS, peaking at MS = 125 emu/g for a Y concentration of x= 0:4, demonstrating (Y 0.4 Ce 1.6 )Fe 14 B as a potential critical element free permanent magnet with an energy product as high as 29 MGOe. This work is advantageous in developing low cost high performance permanent magnets with reduced or little to no critical rare earth elements.

Rai, Binod K.↗