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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
DOE OSTI2022

Emergent magnetic properties of biphase iron oxide nanorods

We report on the magnetic properties of biphase iron oxide nanorods (NRs) consisting of ferrimagnetic Fe 3 O 4 and antiferromagnetic α-Fe 2 O 3 phases. Annealing as-prepared NRs at 250 °C for 5h, significantly improved the crystallinity of the Fe 3 O 4 phase and enhanced the volume fraction of the α-Fe 2 O 3 phase. Magnetometry data consistently reveal these two magnetically distinct phases, which are not in proximity to each other but separated by a region of disordered spins giving rise to enhanced magnetization at low temperatures when the sample was cooled down from 300 K in the presence of a 1T field to 10 K. This phenomenon which is also known as the pinning effect is much more pronounced in the annealed sample, resulting from the increased volume fraction of the α-Fe 2 O 3 phase which could strengthen the interfacial spin frustration between these two phases and enhance the density of disordered spins at the interface.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structural, vibrational, thermal, and magnetic properties of mullite-type NdMnTiO 5 ceramic

Mullite-type $R$Mn 2 O 5 ($R$ = Y, rare-earth element) ceramics are of ongoing research attention because of their interesting crystal-chemical and magnetic properties. We report nuclear and magnetic structures of NdMnTiO 5 together with its spectroscopic, thermogravimetric, and magnetic properties. The polycrystalline sample is prepared by solid-state synthesis and characterized from neutron and X-ray powder diffraction data Rietveld refinements. NdMnTiO 5 crystallizes in the orthorhombic space group $Pbam$ with metric parameter $a$ = 755.20(1) pm, $b$ = 869.91(1) pm, $c$ = 582.42(1) pm, and $V$ = 382.62(1) 10 6 pm 3 . The Mn 3+ and Ti 4+ cations are observed to be located in the octahedral and pyramidal sites, respectively. The vibrational features in these polyhedral sites are characterized by Raman and Fourier transform infrared spectroscopes. The higher decomposition temperature of NdMnTiO 5 , compared to other $R$Mn 2 O 5 phases, is explained in terms of the higher bond strength of Ti-O bonds than those of Mn-O bonds. Temperature-dependent DC magnetic susceptibility suggests a paramagnetic to antiferromagnetic phase transition at 43(1) K. Inverse susceptibility in the paramagnetic region above 120 K follows the Curie-Weiss law, resulting in a magnetic moment of 6.33(1) μ B per formula unit. Neutron diffraction data collected at 7.5 K reveal that the magnetic moments of Nd 3+ and Mn 3+ in NdMnTiO 5 are incommensurately ordered with a propagation vector $k$ = (0, 0.238, 0.117).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of Annealing on Microstructure, Electrochemical, and Magnetic Properties of Co-Doped SrTiO{sub 3} Nanocubes

Effect of annealing on microstructure, electrochemical, and magnetic properties of Co-doped SrTiO{sub 3} nanocubes obtained by the hydrothermal method was studied. X-ray diffraction (XRD) results of all as-prepared and annealed Co-doped SrTiO{sub 3} samples revealed a cubic perovskite structure with the second phases of SrCO{sub 3} and Co{sub 3}O{sub 4}in as-prepared and annealed SrTi{sub 0.90}Co{sub 0.10}O{sub 3} samples, respectively. Agglomerated nanocubes could be clearly observed in all as-prepared and annealed Co-doped samples by scanning electron microscope (SEM) and transmission electron microscope (TEM). X-ray absorption near edge spectroscopy (XANES) results suggested the presence of Co{sup 2+} cations in as-prepared Co-doped SrTiO{sub 3} samples, while both of Co{sup 2+} and Co{sup 3+} cations were found in annealed Co-doped SrTiO{sub 3} samples. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) results of as-prepared and annealed SrTi{sub 1-x}Co{sub x}O{sub 3} (x = 0.05, 0.075 and 0.10) electrodes revealed pseudocapacitor behavior of the Faradaic redox reaction type. The specific capacitance (Csc) was affected by the increase of Co content in all as-prepared and annealed Co-doped SrTiO{sub 3} samples with an excellent cycling stability after 200 cycle test of 97.24% and the highest value of 75.28 F g{sup −1} at 1 A g{sup −1} in an annealed SrTi{sub 0.925}Co{sub 0.075}O{sub 3} electrode. Magnetization measurements at room temperature using vibrating sample magnetometer (VSM) revealed diamagnetic behavior of as-prepared SrTiO{sub 3} sample, whereas paramagnetic behavior was observed in all as-prepared Co-doped SrTiO{sub 3} samples. After annealing, undoped sample exhibited paramagnetic behavior, whereas ferromagnetic behavior was observed in all Co-doped SrTiO{sub 3} samples with the increase of saturation magnetization (M{sub s}) at 10 kOe from 0.58 to 1.63 emu/g and the coercive field (H{sub c}) from 43.71 to 123.87 Oe, suggested to originate from the face-center exchange (FCE) mechanism.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Effects of Fe Ion Vacancy on Magnetic Properties of NiFe{sub 2}O{sub 4} Ferrite Nanoparticles

The effects of Fe ion vacancy on structural and magnetic properties of NiFeO{sub 4} nanoparticles are investigated using X-ray diffraction, Fourier transform infrared, morphological, and magnetic measurements. The introduction of Fe ion vacancy leads to the increase of the lattice parameter and decrease of the particle size. Moreover, vibrating sample magnetometer measurement results revealed that the values of the magnetization decreased and that coercivity had no regular behavior with increasing Fe ion vacancy content. These behaviors could be explained by considering cation distribution in the spinel structure. The estimated cation distribution results show that the Fe ion vacancy mostly occurred at the B sites which is in good agreement with the theoretical calculations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Comparative Characterization of Magnetic Properties of Textured Ni–5 at.%W Alloy Substrates

The hysteresis loss of Ni–5 at.%W (Ni5W) substrate contributes considerably to the alternating current (AC) loss of coated conductors (CCs) working at low transporting current or low-frequency field. In the present work, the evolution of texture and magnetic properties in Ni5W substrates is analyzed and also the relationship between magnetic properties and the extrinsic characteristics (evolved due to the processing techniques) is determined. By making the comparison, we discovered the magnetic domain structures of Ni5W substrates for the first time, achieving a strip/branched domain structures in the recrystallized substrates. The hysteresis loss has been decreased dramatically for the recrystallized substrates. Interestingly, we also observed that this loss is also related to the annealing temperature in the fully recrystallized substrates. The reduced loss can be mainly attributed toward the decrease of grain boundary, which proves the contribution of grain size toward the reduction of hysteresis loss. This result provides a new insight to tailor the hysteresis loss of Ni5W substrates used for coated conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Study of Structural, Electronic, and Magnetic Properties of Cubic Lanthanide Based on Oxide Perovskite-Type NdGaO{sub 3}

Based on the density functional theory (DFT), the full-potential linearized augmented plane wave with local orbital (FP-L/APW+lo) technique is now employed in this approach to understand the structural, electronic, and magnetic properties of simple cubic oxide perovskite NdGaO{sub 3} compound. In all this investigation, the exchange-correlation (XC) energy is selected in the framework of spin-polarized generalized gradient approximation (spin-GGA). The structural analysis unveils that the ferromagnetic (FM) phase is the stable ground state of the cubic NdGaO{sub 3} compound, where the equilibrium lattice parameters (lattice constant (a{sub 0}), bulk modulus (B{sub 0}), and its first pressure derivative (B′)) are determined in both FM and paramagnetic (PM) phases. The spin-polarized electronic properties (band structure and density of states) of the cubic NdGaO{sub 3} oxide perovskite are studied under the platform of equilibrium lattice parameters; this investigation demonstrates the half-metallic behavior of the studied cubic NdGaO{sub 3} compound because the spin-up case displays the metallic nature, whereas the semiconducting character is observed in spin-down case. The magnetic properties reveal that the total magnetic moment of the cubic NdGaO{sub 3} compound is equal to 3 μ{sub B} and its contribution is mostly generated by Nd atoms, whereas feeble local magnetic moments are installed in non-magnetic Ga and O sites. Through the electronic and magnetic results, we conclude that the cubic perovskite NdGaO{sub 3} compound is classified as a half-metallic ferromagnetic material.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Structural and magnetic properties of Pt/Co/Mn-based multilayers

Magnetic multilayers are a rich class of material systems with numerous highly tunable physical parameters that determine both their magnetic and electronic properties. Here, we present a comprehensive experimental study of the system Pt/Co/Mn, which extends the group of Pt / Co / X ( X = metal) multilayers that have been investigated thus far. We demonstrate that an increasing Co layer thickness changes the magnetic anisotropy from out of plane to in plane, whereas the deposition of thicker Mn layers leads to a decrease in the saturation magnetization. Temperature-dependent magnetometry measurements reinforce the hypothesis of antiferromagnetic coupling at the Co/Mn interfaces being responsible for the observed Mn thickness dependence of the magnetization reversal. Moreover, magneto-optical imaging experiments indicate systematic changes in magnetic domain patterns as a function of the Co and Mn layer thickness, suggesting the existence of bubblelike domains—potentially even magnetic skyrmions—in the case of sufficiently thick Mn layers, which are expected to contribute to a sizable Dzyaloshinskii-Moriya interaction in the multilayer stacks. As a result, we identify Pt/Co/Mn as a highly complex multilayer system with strong potential for further fundamental studies and possible applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nonequivalent Spin Exchanges of the Hexagonal Spin Lattice Affecting the Low-Temperature Magnetic Properties of RInO 3 (R = Gd, Tb, Dy): Importance of Spin–Orbit Coupling for Spin Exchanges between Rare-Earth Cations with Nonzero Orbital Moments

Here, rare-earth indium oxides RInO 3 (R = Gd, Tb, Dy) consist of spin-frustrated hexagonal spin lattices made up of rare-earth ions R 3+ , where R 3+ = Gd 3+ (f 7 , L = 0), Tb 3+ (f 8 , L = 3), and Dy 3+ (f 9 , L = 5). We carried out DFT calculations for RInO 3 , including on-site repulsion U with/without spin–orbit coupling (SOC), to explore if their low-temperature magnetic properties are related to the two nonequivalent nearest-neighbor (NN) spin exchanges of their hexagonal spin lattices. Our DFT + U + SOC calculations predict that the orbital moments of the Tb 3+ and Dy 3+ ions are smaller than their free-ion values by ~2μ B while the Tb 3+ spins have an inplane magnetic anisotropy, in agreement with the experiments. This suggests that the f orbitals of each R 3+ (R = Tb, Dy) ion are engaged, though weakly, in bonding with the surrounding ligand atoms. The magnetic properties of GdInO 3 with the zero orbital moment are adequately described by the spin exchanges extracted by DFT + U calculations. In describing the magnetic properties of TbInO 3 and DyInO 3 with nonzero orbital moments, however, the spin exchanges extracted by DFT + U + SOC calculations are necessary.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Review on crystal structures and magnetic properties of RTX 3 materials

The structural and compositional diversity of the RTX 3 family of materials offers various magnetic and thermodynamic properties such as complex magnetic structure, vibronic bound states, heavy-fermions, valence fluctuations, metamagnetism, spin glass behavior, quantum criticality, and unconventional superconductivity. In this study we present an overview of the crystal structures, crystal growth and magnetic properties of RTX 3 compounds as well as a discussion of the relevant physics. The magnetic properties of several compounds of the RTX 3 family still remain unexplored. The compounds with a complex magnetic structure could potentially host exotic topological phases. This review article may help explore exotic magnetic properties such as the vibron state and topological spin textures.

quantum materials↗
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↗
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 OSTI2018

Non-isothermal Crystallization Kinetics and Magnetic Properties of FeCoNiCrZr Metallic Glass

In the present paper, the non-isothermal crystallization kinetics, crystallization process, and magnetic properties of (Fe{sub 0.52}Co{sub 0.30}Ni{sub 0.18}){sub 73}Cr{sub 17}Zr{sub 10} metallic glass were studied by means of differential scanning calorimetry (DSC), Kissinger equation, Ozawa equation, Kempen model, and vibrating sample magnetometer (VSM), respectively. According to the classical nucleation theory, the value of Avrami exponent (n), initially being larger than 4 which implies that phase transformation mechanism is typical for interface-controlled three-dimensional (3-D) growth with increasing nucleation rates, along with the development of crystallization, decreases to 1.5 ∼ 2, which implies that the growth mechanism changes to diffusion-controlled 3-D growth with decreasing nucleation rates; finally, the nucleation rates decrease to zero. Through proper annealing conditions, the saturation magnetization(M{sub s}) values of the annealed sample can reach up to 106.8A m{sup 2} kg{sup − 1}, the crystallization process of this alloy is amorphous → α-Fe(Co) + amorphous′ → α-Fe(Co) + Cr{sub 2}Ni{sub 3} + Fe{sub 3}Ni{sub 2} + Cr{sub 2}Zr + unidentified phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
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↗