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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Emerging magnetic materials for electric vehicle drive motors [Slides]

Increasing demand for electric vehicles (EVs) is increasing demand for the permanent magnets that drive their motors, as approximately 80% of modern EV drivetrains rely on high-performance permanent magnets to convert electricity into torque. In turn, these high-performance permanent magnets rely on rare earth elements for their magnetic properties. These elements are "critical" (i.e., at risk of limiting the growth of renewable energy technologies such as EVs), which motivates an exploration for alternative materials. In this article, we overview the relevant fundamentals of permanent magnets, describe commercialized and emerging materials, and add perspective on future areas of research. Currently, the leading magnetic material for EV motors is Nd 2 Fe 14 B, with samarium-cobalt compounds (SmCo 5 and Sm 2 Co 17 ) providing the only high-performing commercialized alternative. Emerging materials that address criticality concerns include Sm 2 Fe 17 N 3 , Fe 16 N 2 , and the L10 structure of FeNi, which use lower cost elements that produce similar magnetic properties. However, these temperature-sensitive materials are incompatible with current metallurgical processing techniques. We provide perspective on how advances in low-temperature synthesis and processing science could unlock new classes of high-performing magnetic materials for a paradigm shift beyond rare earth-based magnets. In doing so, we explore the question: What magnetic materials will drive future EVs?

42 ENGINEERING↗
DOE OSTI2016

Control of the third dimension in copper-based square-lattice antiferromagnets

Using a mixed-ligand synthetic scheme, we create a family of quasi-two-dimensional antiferromagnets, namely, [Cu(HF 2 )(pyz) 2 ]ClO 4 [pyz = pyrazine], [CuL 2 (pyz) 2 ](ClO 4 ) 2 [L = pyO = pyridine-N-oxide and 4-phpy-O = 4-phenylpyridine-N-oxide. These materials are shown to possess equivalent two-dimensional [Cu(pyz) 2 ] 2+ nearly square layers, but exhibit interlayer spacings that vary from 6.5713 to 16.777 Å, as dictated by the axial ligands. We present the structural and magnetic properties of this family as determined via x-ray diffraction, electron-spin resonance, pulsed- and quasistatic-field magnetometry and muon-spin rotation, and compare them to those of the prototypical two-dimensional magnetic polymer Cu(pyz) 2 (ClO 4 ) 2 . We find that, within the limits of the experimental error, the two-dimensional, intralayer exchange coupling in our family of materials remains largely unaffected by the axial ligand substitution, while the observed magnetic ordering temperature (1.91 K for the material with the HF 2 axial ligand, 1.70 K for the pyO and 1.63 K for the 4-phpy-O) decreases slowly with increasing layer separation. Despite the structural motifs common to this family and Cu(pyz) 2 (ClO 4 ) 2 , the latter has significantly stronger two-dimensional exchange interactions and hence a higher ordering temperature. Here, we discuss these results, as well as the mechanisms that might drive the long-range order in these materials, in terms of departures from the ideal S = 1/2 two-dimensional square-lattice Heisenberg antiferromagnet. In particular, we find that both spin-exchange anisotropy in the intralayer interaction and interlayer couplings (exchange, dipolar, or both) are needed to account for the observed ordering temperatures, with the intralayer anisotropy becoming more important as the layers are pulled further apart.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhanced Room-Temperature Ferromagnetism Observed in SiO{sub 2}-Coated CuO Nanostructures

In this paper, the magnetic properties of pure CuO and SiO{sub 2}-coated CuO nanocrystals were reported. Strongly enhanced room-temperature ferromagnetism was observed in SiO{sub 2}-coated CuO nanocrystals, whose saturation magnetization is two orders of magnitude enhanced compared to that of the uncoated CuO nanocrystals. The mechanism of this enhancement was investigated. It points out the main origin of ferromagnetism in these CuO nanocrystals is the uncompensated surface state, so that the coating of SiO{sub 2} can effectively protect the surface state to improve the ferromagnetism in these CuO nanocrystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Confinement of quasi-atomic structures in Ti 2 N and Ti 3 N 2 MXene electrides

Metal carbides, nitrides, or carbonitrides of early transition metals, better known as MXenes, possess notable structural, electrical, and magnetic properties. Analyzing electronic structures by calculating structural stability, band structure, density of states, Bader charge transfer, and work functions utilizing first principle calculations, we revealed that titanium nitride MXenes, namely Ti 2 N and Ti 3 N 2 , have excess anionic electrons in their lattice voids, making them MXene electrides. Bulk Ti 3 N 2 has competing antiferromagnetic (AFM) and ferromagnetic (FM) configurations with slightly more stable AFM configuration, while the Ti 2 N MXene is nonmagnetic. Although Ti 3 N 2 favors AFM configuration with hexagonal crystal systems having 6/ mmm point group symmetry, Ti 3 N 2 does not support altermagnetism. The monolayer of the Ti 3 N 2 MXene is a ferromagnetic electride. These unique properties of having non-nuclear interstitial anionic electrons in the electronic structure of titanium nitride MXene have not yet been reported in the literature. Density functional theory calculations show TiN is neither an electride, MXene, or magnetic.

Anionic electrons↗
DOE OSTI2025

Magnetic compressibility of layered ferromagnet under pressure

This study systematically investigates the magnetic properties of the layered ferromagnet MnPt 5 As under pressure through a combination of experimental measurements and theoretical simulations. MnPt 5 As exhibits a ferromagnetic transition at approximately 301 K. Neutron diffraction measurements under applied pressures up to ∼4.9 GPa were performed over a temperature range from 320 to 100 K to probe its magnetic behavior. The results confirm that the Mn atoms maintain a ferromagnetic order under applied pressures, consistent with the ambient-pressure findings. However, magnetic anisotropy is notably suppressed. To further elucidate the compressibility of magnetic anisotropy in MnPt 5 As, x-ray diffraction under pressure was conducted. The results reveal that the c-axis undergoes a greater and more rapid compression compared to the ab -plane, which may contribute to the observed suppression of Mn ferromagnetic ordering along the c -axis. Additionally, theoretical calculations indicate that magnetic ordering exhibits a similar pressure-induced trend under applied pressure, supporting the experimental observations. These findings offer insights into the pressure-dependent magnetic properties and anisotropy of MnPt 5 As, with potential implications for strain engineering in Mn-based magnetic devices.

Electronic band structure↗
DOE OSTI2024

Tuning the spontaneous exchange bias effect in La 1.5 Sr 0.5 CoMnO 6 with sintering temperature

Here, in this study, we present a study of the influence of microstructure on the magnetic properties of polycrystalline samples of the La 1.5 Sr 0.5 CoMnO 6 double perovskite, with primary attention to the spontaneous exchange bias effect, a fascinating recently discovered phenomena for which some materials exhibit unidirectional magnetic anisotropy after being cooled in zero magnetic fields. By sintering La 1.5 Sr 0.5 CoMnO 6 at different temperatures, we obtained samples with distinct average grain sizes, ranging from 1.54-6.65 μm. A detailed investigation of the material's structural, morphologic, electronic, and magnetic properties using x-ray powder diffraction, powder neutron diffraction, x-ray absorption near edge structure spectroscopy, scanning electron microscopy, and ac and dc magnetometry has revealed a systematic enhancement of the exchange bias effect with increasing the average grain size. This evolution is discussed in terms of changes in the material's porosity and grain morphology and its influence on the exchange couplings at the magnetic interfaces.

14 SOLAR ENERGY↗
DOE OSTI2021

Synthesis and anisotropic magnetism in quantum spin liquid candidates A YbSe 2 ( A = K and Rb)

The quantum spin liquid (QSL) state in rare-earth triangular lattices has attracted much attention recently due to its potential application in quantum computing and communication. Here, we report the single-crystal growth synthesis, crystal structure characterizations, and magnetic properties of AYbSe 2 (A = K and Rb) compounds. The x-ray diffraction analysis shows that AYbSe 2 (A = K and Rb) crystallizes in a trigonal space group, R-3m (No. 166) with Z = 3. AYbSe 2 possesses a two-dimensional (2D) Yb–Se–Yb layered structure formed by edged-shared YbSe 6 octahedra. The magnetic properties are highly anisotropic for both title compounds, and no long-range order is found down to 0.4 K, revealing the possible QSL ground state in these compounds. The isothermal magnetization exhibits a one-third magnetization plateau when the magnetic fields are applied in the ab-plane. Heat capacity is performed along both ab-plane and c axis and features the characteristic dome for triangular magnetic lattice compounds as a function of magnetic fields. Due to the change in the interlayer and intralayer distance of Yb 3+ , the dome shifts to low fields from KYbSe 2 to RbYbSe 2 . All these results indicate that the AYbSe 2 family presents unique frustrated magnetism close to the possible QSL and noncollinear spin states.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis and Characterization of Er-Doped Nano ZnO Samples

Pure and erbium-doped ZnO nanoparticles (Zn{sub 1−x}Er{sub x}O), (0.00 ≤ x ≤ 0.10), were synthesized by wet chemical co-precipitation method. The structural, optical, and magnetic properties of the prepared samples were investigated using x-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), M-H magnetic hysteresis, and electron paramagnetic resonance (EPR). XRD studies exhibit the presence of a single ZnO wurtzite hexagonal crystal structure for 0.00 ≤ x ≤ 0.06. A secondary phase of Er{sub 2}O{sub 3} appears for x > 0.06. This means that the solubility limit for doping Zn{sup 2+} ions by Er{sup 3+} ions is about x = 0.06 under our preparations condition. The lattice parameter a is not affected by the Erbium doping. On the other hand, the lattice parameter c and the unit cell volume V increase with the increase of x up to x = 0.06. This is attributed to the larger ionic size of Er{sup 3+} ions (0.88 Å) compared to Zn{sup 2+} ions (0.74 Å). Both c and V decrease for x > 0.06. TEM micrographs indicate that the shape and the size of the ZnO nanoparticles are modified by changing the doping level of Er. The UV measurements point out that band gap energy E{sub g} decreases with the increase of x up to x = 0.06. Then, it increases for both x = 0.08 and 0.10. FTIR spectra confirm the presence of O–H and Zn–O stretching modes at 3451.963 and 428.901 cm{sup − 1}, respectively, in pure and doped ZnO samples. The Zn–O stretching mode shifts toward a lower wavenumber for x = 0.06 and toward a higher wavenumber for x = 0.10. M-H hysteresis analysis, at room temperature, reveals that the pure ZnO has a ferromagnetic signal combined with diamagnetic and paramagnetic contributions. This ferromagnetism is reduced for the doped samples up to x = 0.02, and an antiferromagnetic alignment appears for 0.04 ≤ x ≤ 0.10. The saturation magnetization (M{sub s}), the coercivity (H{sub c}), the retentivity (M{sub r}), the anisotropy constant (K{sub a}), and the magnetic moment (μ{sub m}) were estimated and discussed in terms of erbium doping for the different samples. EPR spectra for Zn{sub 1−x}Er{sub x}O were measured at room temperature in order to study the effect of Er substitution on the g value, resonance field (H{sub r}), peak to peak line width (ΔH{sub pp}) and spin–spin relaxation time constant (T{sub 2}).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Direct Evidence of the Competing Nature between Electronic and Lattice Breathing Order in Rare-Earth Nickelates

Correlated electrons give rise to both exotic electronic and magnetic properties in rare-earth nickelates. IN this research, we introduce evidence of the interfacial coupling between two nickelate systems, EuNiO 3 (ENO) and LaNiO 3 (LNO), with different electronic and magnetic properties but with compatible structural registry giving rise to an electrostructural transition, unobserved in each constituent. Nominally, LNO remains in a paramagnetic-metallic R 3 ¯ c phase while orthorhombic ENO undergoes antiferromagnetic and insulating transitions. However, the ENO/LNO heterostructure displays a uniform rotational symmetry set by an entwined interface. This leads to an anomalous reduction of bond disproportionation in the ENO layer through the metal to insulator transition and concomitantly charge disproportionation opens the gap accompanied by antiferromagnetic ordering. Our findings resolve a long-standing question in the physics of rare-earth nickelates, herein demonstrating that charge and bond disproportionation are competing mechanisms for the charge localization process in the rare-earth nickelate system.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Methods for creating ligand induced paramagnetism in nanocrystalline structures

A method according to one general embodiment includes applying an organic surfactant to a nanoparticle having a d.sup.10 configuration for altering a magnetic property of the nanoparticle. A method according to another general embodiment includes applying an organic surfactant to a II-VI semiconductor nanoparticle having a d.sup.10 configuration for altering a magnetic property of the nanoparticle, wherein the nanoparticle has a mean radius of less than about 50 .ANG..

36 MATERIALS SCIENCE↗
DOE OSTI2018

161 Dy Time-Domain Synchrotron Mössbauer Spectroscopy for Investigating Single-Molecule Magnets Incorporating Dy Ions [ 161 Dy time-domain synchrotron Mössbauer spectroscopy as a new way forward for investigating single molecule magnets incorporating Dy ions]

Time–domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of 161 Dy has been used to investigate the magnetic properties of a Dy III –based single–molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy 3 PO) 2 (H 2 O) 5 ]Br 3 •2 (Cy 3 PO)•2 H 2 O•2 EtOH is with B 0 =582.3(5) T significantly larger than that of the free–ion Dy III with a 6 H 15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the Dy III ion. Furthermore this study demonstrates that 161 Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy–containing compounds.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Structural and magnetic phase transitions in CeCu 6 - x T x ( T = Ag , Pd )

The structural and the magnetic properties of CeCu6-xAgx (0≤x≤0.85) and CeCu6-xPdx (0≤x≤0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈0.1. The structural transition in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x≈0.2 and x≈0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ10 δ2), where δ1~0.62,δ2~0.25,x=0.125 for CeCu6-xPdx and δ1~0.64,δ2~0.3,x=0.3 for CeCu6-xAgx. The magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Magnetism and topological Hall effect in antiferromagnetic Ru 2 MnSn-based Heusler compounds

Heusler compounds and alloys based on them are of great recent interest because they exhibit a wide variety of spin structures, magnetic properties, and electron-transport phenomena. Their properties are tunable by alloying and we have investigated L2 1 -orderd compound Ru 2 MnSn and its alloys by varying the atomic Mn:Sn composition. While antiferromagnetic ordering with a Néel temperature of 361 K was observed in Ru 2 MnSn, the Mn-poor Ru 2 Mn 0.8 Sn 1.2 alloy exhibits properties of a diluted antiferromagnet in which there are localized regions of uncompensated Mn spins. Furthermore, a noncoplanar spin structure, evident from a topological Hall-effect contribution to the room-temperature Hall resistivity, is realized in Ru 2 Mn 0.8 Sn 1.2 . Finally, our combined experimental and theoretical analysis shows that in the Ru 2 Mn 0.8 Sn 1.2 alloy, the magnetic properties can be explained in terms of a noncoplanar antiferromagnetic scissor mode, which creates a small net magnetization in a magnetic field and subsequently yields a Berry curvature with a strong topological Hall effect.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis and Characterisation of Superparamagnetic MgFe{sub 2}O{sub 4} Nanoferrite

Nanocrystalline MgFe{sub 2}O{sub 4} with crystallite size of 10.4 nm was synthesised using combustion method and characterised for structural, electrical, and magnetic properties. The powder X-ray diffraction analysis reveals the single-phase nature of MgFe{sub 2}O{sub 4}. The field emission scanning electron microscopy image shows the nanosized grains. The magnetic study reveals the superparamagnetic behaviour of MgFe{sub 2}O{sub 4} with saturation magnetisation value of 14.57 emu/g. The blocking temperature is determined using low-temperature magnetic measurement which is equal to 139 K. Electrical study shows that the value of AC conductivity at 1 Hz is 1.12 × 10{sup − 8} S/cm at 303 K and increases with frequency as well as temperature. The complex impedance analysis shows the grain and grain boundary resistance equal to 6.23 × 10{sup 6} Ω and 1.27 × 10{sup 7} Ω, respectively. The complex electric modulus analysis confirms the presence of two relaxation processes in nanocrystalline MgFe{sub 2}O{sub 4}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Ferromagnetic resonances in single-crystal yttrium iron garnet nanofilms fabricated by metal-organic decomposition

Tunable microwave and millimeter wave oscillators and bandpass filters with ultra-low phase noise play a critical role in electronic devices, including wireless communication, microelectronics, and quantum computing. Magnetic materials, such as yttrium iron garnet (YIG), possess ultra-low phase noise and a ferromagnetic resonance tunable up to tens of gigahertz. Here, we report structural and magnetic properties of single-crystal 60 and 130 nm-thick YIG films prepared by metal-organic decomposition epitaxy. These films, consisting of multiple homoepitaxially grown monolayers, are atomically flat and possess magnetic properties similar to those grown with liquid-phase epitaxy, pulsed laser deposition, and sputtering. Our approach does not involve expensive high-vacuum deposition systems and is a true low-cost alternative to current commercial techniques that have the potential to transform the industry.

Wang, Szu-Fan (Paul)↗
DOE OSTI2017

Emitting heterostructures with a bilayer InGaAs/GaAsSb/GaAs quantum well and a GaMnAs ferromagnetic layer

The radiative and magnetic properties of novel heterostructures with a bilayer InGaAs/GaAsSb/GaAs quantum well and a GaMnAs ferromagnetic layer are studied. The circular polarization of electroluminescent radiation is observed at temperatures from 10 to 160 K. The magnetic field dependences of the degree of circular polarization are nonlinear with a hysteresis loop at temperatures from 10 to 50 K, and they become linear at higher temperatures. The magnitude of polarization at the saturation magnetization of GaMnAs in the 2000 Oe field remains at the level of ~0.2%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Oxygen Inhomogeneity and Reversibility in Single Crystal LaNiO{sub 3-{delta}}.

LaNiO 3− δ single crystals have been obtained via high pressure floating zone growth under 149 bar of oxygen pressure. We find a radial gradient in the magnetic properties of specimens extracted from the as-grown boule, which we correlate with the appearance of ordered oxygen vacancy structures. This radial oxygen inhomogeneity has been characterized systematically using a combination of magnetization and X-ray scattering measurements. We establish the presence of rhombohedral ( R 3 ¯ c ), oxygen stoichiometric specimens at the periphery of the boule and the presence of a dilute concentration of ordered oxygen-deficient orthorhombic La 2 Ni 2 O 5 in the center. Furthermore, we demonstrate that the as-grown, oxygen-deficient central regions of the crystal can be annealed under high oxygen pressure, without loss of crystallinity, into fully oxygenated LaNiO 3 , recovering magnetic properties that are characteristic of stoichiometric specimens from the exterior region of the crystal. Thus, single crystals of LaNiO 3− δ possess oxygen content that can be reversibly modified under oxidizing and reducing conditions.

crystal growth↗
DOE OSTI2017

A review: applications of the phase field method in predicting microstructure and property evolution of irradiated nuclear materials

Here, complex microstructure changes occur in nuclear fuel and structural materials due to the extreme environments of intense irradiation and high temperature. This paper evaluates the role of the phase field method in predicting the microstructure evolution of irradiated nuclear materials and the impact on their mechanical, thermal, and magnetic properties. The paper starts with an overview of the important physical mechanisms of defect evolution and the significant gaps in simulating microstructure evolution in irradiated nuclear materials. Then, the phase field method is introduced as a powerful and predictive tool and its applications to microstructure and property evolution in irradiated nuclear materials are reviewed. The review shows that (1) Phase field models can correctly describe important phenomena such as spatial-dependent generation, migration, and recombination of defects, radiation-induced dissolution, the Soret effect, strong interfacial energy anisotropy, and elastic interaction; (2) The phase field method can qualitatively and quantitatively simulate two-dimensional and three-dimensional microstructure evolution, including radiation-induced segregation, second phase nucleation, void migration, void and gas bubble superlattice formation, interstitial loop evolution, hydrate formation, and grain growth, and (3) The Phase field method correctly predicts the relationships between microstructures and properties. The final section is dedicated to a discussion of the strengths and limitations of the phase field method, as applied to irradiation effects in nuclear materials.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗