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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Lossless Currents at High Temperatures

Is superconductivity necessary for zero-resistance currents? We investigate the possibility of designing wires with non-superconducting, but nevertheless dissipation-free current flow at room temperature. Guided by a set of constraints for states carrying currents in thermodynamic equilibrium, we suggest using quantum mechanical interference and collapse processes to produce devices that yield the desired function. Two proposals for such devices are presented as examples and their function is discussed also with respect to the second law of thermodynamics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Ce-Doping and Reduction Annealing Effects on Magnetic Properties of Pr{sub 2-x}Ce{sub x}CuO{sub 4} Nanoparticles

Magnetic properties of reduced T’-Pr{sub 2-x}Ce{sub x}CuO{sub 4} (T’-PCCO) nanoparticles with x = 0, 0.10, and 0.15 have been investigated. The T’-PCCO samples were synthesized by the chemically dissolved method with HNO{sub 3} as dissolving agents and by the succeeding calcination at 1000 °C for 15 h in air. The reduced T’-PCCO samples were obtained by the reduction annealing at 700 °C for 10 h in Argon atmosphere and at 700 °C for 12 h in vacuum. Rietveld analyses of the X-ray diffraction (XRD) patterns for all the samples have revealed dependences of the c-axis length and the crystal size on the Ce doping and the reduction annealing. XRD analyses and transmission electron microscopy (TEM) images have confirmed T’-PCCO nanoparticles with the size of around 40–100 nm. Magnetic properties of all the T’-PCCO nanoparticles were studied by a superconducting quantum interference device (SQUID) showing a dominant paramagnetic feature with very weak ferromagnetism in the as-synthesized samples at room temperature. It has changed to a pure paramagnetic feature after the reduction annealing in argon atmosphere and an enhanced ferromagnetism through vacuum annealing. This is probably due to the change in the number of oxygen vacancies through the defect recovery and the removal of excess oxygen after both reduction annealing processes, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Magnetism and Conductivity Along Structural Domain Walls of SrTiO3

Abstract The interface between the oxide insulators LaAlO 3 and SrTiO 3 (LAO/STO) hosts a two-dimensional electron gas. The combination of interfacial conductivity and superconductivity at ultra-low temperatures with the physical phenomena of the oxide parent materials has fueled extensive research in the field since its discovery in 2004. Scanning superconducting quantum interference device (SQUID) measurements have shown that structural domain walls, formed below 105 K, modulate the current flow at the interface and recently revealed weak magnetic signals along the same domain structure. Here we use scanning SQUID to investigate the temperature dependence of different electronic properties of the LAO/STO interface. We find correlation between magnetism and conductivity, which are both spatially modulated on the domain structure. This data suggests a possible relation between the populations of electrons participating in each order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Improvement of the Superconducting Properties of GdBa{sub 2}Cu{sub 3}O{sub 7-δ} with Nano-Sized Ferrite Addition

We have been investigating the effect of (CoFe{sub 2}O{sub 4}){sub x} and (ZnFe{sub 2}O{sub 4}){sub x} (x is the wt%) nano-sized ferrites on the superconducting (SC) properties of the high-T{sub c} SC compound GdBa{sub 2}Cu{sub 3}O{sub 7-δ} (Gd123) prepared by the conventional solid-state reaction technique. In this work, the magnetic hysteresis for pure Gd123 samples and samples added with nano-sized ferrites was measured using a superconducting quantum interference device (SQUID) magnetometer using a dc field up to 30,000 Oe. The magnetic J{sub c} was estimated using the extended Bean model. While a clear increase in J{sub c} values with the addition of (CoFe{sub 2}O{sub 4}){sub x} nano-sized ferrites is observed, a less clear positive effect on the J{sub c} values is observed with the addition of (ZnFe{sub 2}O{sub 4}){sub x} nano-sized ferrites. These results indicate an improvement of grain connectivity, decrease of voids between the grains, and decrease of porosity in Gd123 compound resulting from CoFe{sub 2}O{sub 4} addition consistent with the mechanical properties measured before. (CoFe{sub 2}O{sub 4}){sub x} nano-sized ferrite addition has thus resulted in an improvement in the SC properties of Gd123 high-T{sub c} SC compound making it more convenient for applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Fabrication and Magnetic Characterization of CFO/NiO and CFO/NiS Heterostructures

Magnetic analysis of different magnetic bilayers and multilayers is an important step for designing next-generation multiferroic heterostructures. In this study, we have investigated the magnetic interaction at the interface in CFO/NiO hetero-structures grown by pulsed laser deposition on sapphire substrates. The thin film heterostructure samples were characterized by means of X-ray diffraction, scanning electron microscopy (SEM), energy disruptive X-ray spectroscopy (EDS), and superconducting quantum interference device (SQUID) for magnetic measurements. The XRD analysis on different samples shows the crystalline growth of the thin films. The SEM-EDS analysis provides information about structural and elemental compositions of the heterostructure films. A SQUID magnetometer was used to investigate the temperature and field-dependent magnetic properties. To better understand the magnetic properties of the thin film heterostructure samples, zero field cool (ZFC) and field cool (FC) magnetization data were analyzed. At low temperature, ferromagnetic hysteresis loop was observed. A shift in the M-H hysteresis curve was observed for the FC data from the ZFC data, which indicates the presence of exchange bias effect. In addition, we have examined the effect of antiferromagnetic NiS thin films on ferromagnetism of CFO. This study on the magnetic interaction between a ferromagnetic layer and an antiferromagnetic layer can advance the frontier for applications in spin valves, magnetic sensors, and magnetic random access memory.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Preparation of RE(DBM){sub 3}·Phen (RE=Eu{sup 3+},Tb{sup 3+}) Plate-Loading Fe{sub 3}O{sub 4} Nanospheres and their Magnetic-Optic Bifunctional Property

A facile wet chemical method has been used to synthesize bifunctional core-shell nanoparticles of Fe{sub 3}O{sub 4}@RE(DBM){sub 3}·Phen (RE=Eu{sup 3+},Tb{sup 3+}) showing an interesting combination of magnetic and luminescent properties. This method is convenient, cheap, and efficient. The morphology, structure, luminescent, and magnetic properties of the nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption, fluorescence emission, and superconducting quantum interference device magnetometer (SQUID-VSM). The maximum emission peaks of novel Eu{sup 3+} and Tb{sup 3+} nanocomposites are at 618 nm and at 514 nm, respectively. And their corresponding special saturation magnetization Ms. are 25.853 emu/g and 24.015 emu/g, respectively. For the nanoparticles, it is shown that there have better magnetic behavior and they may act as red- and green-emitting material with potential application for fluorescent magnetic particle testing. Moreover, this chemical route could be used to obtain the development of several bifunctional systems of other rare earth ions for practical application.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Josephson Junctions and Cosmic Microwave Background

The implementation of utilizing superconducting quantum interference device (SQUID) readout for constant voltage biased transition edge sensors (TES) has enabled the detection of the infinitesimal fluctuation in cosmic microwave background (CMB). The properties of the fluctuations will provide us the information of the universe at the time that this light was first emitted. In short, by measuring the CMB today, we learn about the distant, ancient universe—how the universe began, what it is made of, and how it evolved to its current state. Over the past 20 years, we have achieved many successful CMB measurements with Josephson junctions. Brian, I extend my congratulations on your eight decades of life—Happy 80th birthday!

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

The exceedingly strong two-dimensional ferromagnetism in bi-atomic layer SrRuO 3 with a critical conduction transition

In recent years, few-layer or even monolayer ferromagnetic materials have drawn a great deal of attention due to the promising integration of two-dimensional (2D) magnets into next-generation spintronic devices. The SrRuO 3 monolayer is a rare example of stable 2D magnetism under ambient conditions, but only weak ferromagnetism or antiferromagnetism has been found. The bi-atomic layer SrRuO3 as another environmentally inert 2D magnetic system has been paid less attention heretofore. Here we study both the bi-atomic layer and monolayer SrRuO 3 in (SrRuO 3 ) n /(SrTiO 3 ) m (n = 1, 2) superlattices in which the SrTiO 3 serves as a non-magnetic and insulating space layer. Although the monolayer exhibits arguably weak ferromagnetism, we find that the bi-atomic layer exhibits exceedingly strong ferromagnetism with a T c of 125 K and a saturation magnetization of 1.2 μ B /Ru, demonstrated by both superconducting quantum interference device (SQUID) magnetometry and element-specific X-ray circular dichroism. Moreover, in the bi-atomic layer SrRuO 3 , we demonstrate that random fluctuations and orbital reconstructions inevitably occurring in the 2D limit are critical to the electrical transport, but are much less critical to the ferromagnetism. Our study demonstrates that the bi-atomic layer SrRuO 3 is an exceedingly strong 2D ferromagnetic oxide which has great potentials for applications of ultracompact spintronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

pyTDGL: Time-dependent Ginzburg-Landau in Python

Time-dependent Ginzburg-Landau (TDGL) theory is a phenomenological model for the dynamics of superconducting systems. Due to its simplicity in comparison to microscopic theories and its effectiveness in describing the observed properties of the superconducting state, TDGL is widely used to interpret or explain measurements of superconducting devices. Here, we introduce pyTDGL, a Python package that solves a generalized TDGL model for superconducting thin films of arbitrary geometry, enabling simulations of vortex and phase dynamics in mesoscopic superconducting devices. pyTDGL can model the nonlinear magnetic response and dynamics of multiply connected films, films with multiple current bias terminals, and films with a spatially inhomogeneous critical temperature. We demonstrate these capabilities by modeling quasi-equilibrium vortex distributions in irregularly shaped films, and the dynamics and current-voltage-field characteristics of nanoscale superconducting quantum interference devices (nanoSQUIDs).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

magneto caloric↗
DOE OSTI2017

Contribution from Ising domains overlapping out-of-plane to perpendicular magnetic anisotropy in Mn 4 N thin films on MgO(001)

Single phase ε-Mn4N thin and ultrathin films are grown on MgO(001) using molecular beam epitaxy. Reflection high-energy electron diffraction and outof-plane x-ray diffraction measurements are taken for each sample in order to determine the in- and out-of-plane strain for each sample. Vibrating sample magnetometry and superconducting quantum interference device measurements, which are performed on the thin and ultrathin films respectively, are used to plot the magnetization of each sample versus both in- and out-of-plane $\vec H$-fields and to determine the magnitude of perpendicular magnetic anisotropy in these films. Three significant components of perpendicular magnetic anisotropy are observed in these films and are attributed to sample strain (1 component) and shape (2 components). Among these components, the most significant component (0.8 to 4.9 $\frac{Merg}{cm^3}$) is identified as a second term of shape anisotropy, which possesses a negative linear relationship with sample thickness over the range from 9 nm to 310 nm. Atomic (magnetic) force microscopy measurements show the presence of a surface localized magnetic polarization (22% to 82%), which increases with decreasing thickness, when the net magnetization of the films is zero. The second term of shape anisotropy as well as the surface localized polarization, which each depend on sample thickness, are each regarded as a consequence of Ising domains overlapping out-of-plane in these films.

Materials Science↗
DOE OSTI2025

Geometric control of magnetic domain morphology in electrodeposited Ni rich NiPt mesoscopic wires

In this paper, we study the electrodeposited Ni—Pt magnetic wires, exploring the mechanisms by which changes in geometry and composition influence the local magnetic structure. The samples were prepared by electrodeposition, their elemental composition was analyzed by energy dispersive X-ray spectroscopy, and phase analysis was carried out by an X-ray diffraction measurement. Magnetic force microscopy measurements, and magnetic force microscopy measurements in magnetic field were carried out to study the domain morphology of the prepared samples. Magnetization characteristics were measured via vibrating sample magnetometry mode of a superconducting quantum interference device. Here, the results were analyzed and compared with micromagnetic simulations. It is shown that a strong perpendicular magnetic anisotropy is responsible for the characteristic checkerboard-like surface magnetization patterns, which can be tuned by geometrical constriction and Ni content. Understanding these relationships provides insights into the design of magnetic materials with tailored properties for advanced applications, like magnetic sensors.

Binary alloy↗
DOE OSTI2013

Effect of organic solvents on particle size of Mn{sub 3}O{sub 4} nanoparticles synthesized by a solvothermal method

In this paper, a modified simple solvothermal method is employed to synthesize Mn{sub 3}O{sub 4} nanocrystals using four different solvents: acetone, ethanol, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). Mn{sub 3}O{sub 4} nanoparticles with a tetragonal hausmannite nano-structure are characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), as well as superconducting quantum interference device magnetometer (SQUID). The Mn{sub 3}O{sub 4} particle size is found to have a strong dependency on the solvent used. A reaction scheme is proposed to understand this dependency, suggesting that the solvent coordinating capability has a critical effect on Mn{sub 3}O{sub 4} particle size. The stronger the coordinating capability of the solvent is, the smaller the Mn{sub 3}O{sub 4} particle size is. In addition, magnetic properties of the nano-structured Mn{sub 3}O{sub 4} are also tested and discussed. - Graphical abstract: The comparison of the particle size of Mn{sub 3}O{sub 4} nanoparticles synthesized using different solvents and HRTEM image of Mn{sub 3}O{sub 4} individual nanoparticle revealed its single-crystal nature. - Highlights: • Mn{sub 3}O{sub 4} nanocrystals were synthesized using different solvents by a solvothermal method. • The particle size of Mn{sub 3}O{sub 4} nanocrystal is found to have a strong dependency on the solvent used. • A reaction mechanism is proposed to explain the difference of particle size of Mn{sub 3}O{sub 4} nanocrystals. • Magnetic properties of Mn{sub 3}O{sub 4} nanocrystals with different particle size are tested and compared.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

The stress, surface spin and dipolar interaction in the diluted NiFe{sub 2}O{sub 4} nanoparticles by the SiO{sub 2} matrix: Characterization and analyses

Well-dispersed uniform NiFe{sub 2}O{sub 4} nanoparticles (NPs) with an average particle size of 15.4 nm were synthesized by thermal decomposition of a metal–organic salt, and then were diluted in a SiO{sub 2} matrix via a sol–gel method with different concentration. The magnetization (M) dependence of NiFe{sub 2}O{sub 4}/SiO{sub 2} on the temperature (T) and on the applied magnetic field (H) was systematically characterized by the Quantum Design superconducting quantum interference device (SQUID) PPMS system. The results of M ~ H/T divide the magnetic properties between 10 K and 300 K into two regions: the low temperature blocked-particle regime below the blocking temperature T{sub B} and the interacting superparamagnetic (ISP) regime above T{sub B}. In the ISP regime, all samples deviate from the ideal Langevin superparamagnetic behavior due to the effective anisotropy induced by the stress, surface spins and interparticle dipolar interaction. The Raman spectra indicate that the stress in all samples exhibits the vibration behavior, which leads to the effective anisotropy and hence coercivity vibration. - Graphical abstract: Display Omitted - Highlights: • Increase of NiFe{sub 2}O{sub 4} NPs' concentration elevates T{sub B} and broadens ZFC peak. • NiFe{sub 2}O{sub 4}/SiO{sub 2} samples do not exhibit the ideal superparamagnetism above T{sub B}. • Stress leads to the effective anisotropy and hence H{sub c} vibration. • Stress vibration was characterized in detail by the Raman spectra.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Hydrothermal synthesis and magnetic properties of CuO hollow microspheres

Graphical abstract: - Highlights: • CuO hollow microspheres were synthesized through hydrothermal route. • The possible growth mechanism was proposed according to the experimental results. • CuO hollow microspheres show an anomalous ferromagnetic behavior at 5 K and 300 K. - Abstract: In the present work, CuO hollow microspheres with the diameter about 2 μm were successfully synthesized through a facile hydrothermal method. The phase purity, morphologies and structure features of the as obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy, respectively. It was found that reaction temperature, reaction time and different volume ratios of ethanol and distilled water played important roles on the morphologies of the obtained CuO hollow microspheres. The possible formation mechanism was also proposed according to the corresponding experimental results. The magnetic properties were investigated by superconducting quantum interference device, revealing that the CuO hollow microspheres exhibited an anomalous ferromagnetic behavior at 5 K and 300 K. At the same time, the origin of the ferromagnetism in CuO hollow microspheres was also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Defect-induced ferromagnetism in undoped In{sub 2}O{sub 3} nanowires

Highlights: • Undoped In{sub 2}O{sub 3} nanowires were synthesized by a thermal evaporation method. • In{sub 2}O{sub 3} nanowires show d{sup 0} ferromagnetism at room temperature. • Large amount of defects were confirmed by PL, UV/vis, and XPS. • Oxygen deficient surfaces and size effect mediating ferromagnetic ordering. - Abstract: We report the observation of intrinsic room-temperature ferromagnetism in undoped In{sub 2}O{sub 3} nanowires synthesized by a thermal evaporation method. The as-grown sample was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), temperature-dependent photoluminescence (PL), Ultraviolet–visible spectroscopy (UV/vis), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). Structural characterizations show that the as-grown sample is single crystal cubic bixbyite structure with 80–100 nm in diameter and 2–4 μm long. Both PL and UV/vis results reveal that the sample exhibits large amount of oxygen vacancies and indium vacancies (V{sub O} and V{sub In}). XPS results indicate that the In{sub 2}O{sub 3} nanowires are significantly oxygen deficient and non-stoichiometric at surface. Experimentally measured magnetic hysteresis curves for undoped In{sub 2}O{sub 3} nanowires clearly display ferromagnetic behavior at room temperature. We believe the ferromagnetism of undoped In{sub 2}O{sub 3} nanowires is ascribed to the large surface area and intrinsic defects mediating the ferromagnetic ordering.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Amorphous RE–Fe–B–Na colloidal nanoparticles: High temperature solution synthesis and magnetic properties

Graphical abstract: RE–Fe–B–Na (RE = Nd–Er) colloidal nanoparticles by high-temperature solution synthesis are ultra-small monodisperse and air-stable amorphous, whose size and magnetic dependence are studied. - Highlights: • RE–Fe–B–Na nanoparticles are obtained by high-temperature solution synthesis. • These colloidal nanoparticles are monodisperse and size controlled. • The magnetism dependence and possible magnetic coupling mechanism are studied. - Abstract: RE–Fe–B–Na (RE = Nd–Er) colloidal nanoparticles are prepared by high-temperature solution synthesis. These nanoparticles are ultra-small monodisperse, air-stable and amorphous, whose particle size and magnetic property are characterized by transmission electron microscope and superconducting quantum interference device. Taking Nd–Fe–B–Na nanoparticle as an example, it is found that the particle size can be controlled in less than 7 nm. Besides, the magnetic properties of RE–Fe–B–Na colloidal nanoparticles can be compared for different rare earth elements. Based on the bulk ferromagnetic coupling, other possible magnetic coupling mechanism is discussed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Effect of surface potential and charge transfer mechanism in reduced graphene oxide and magnetic nanocomposites

Highlights: • Cobalt oxide/reduced graphene oxide nanocomposites were prepared by hydrothermal method. • The of cobalt oxide nanoparticles on graphene oxide sheets leads modification of surface potential of graphene oxide sheets. • Modification of surface potential causes shifting of Fermi energy level of graphene oxide sheets due to charge transfer process. • The occurrence function of graphene oxide sheets modified from 4.5 eV to 5.8 eV by decoration of cobalt oxide nanoparticles on it. • The work of charge transfer between cobalt oxide nanoparticles and graphene oxide sheets also envisaged from Raman spectra. - Abstract: In this paper, the charge transfer mechanism in hydrothermally synthesized cobalt oxide/reduced graphene oxide (Co{sub 3}O{sub 4}/RGO) nanocomposites has been established. Scanning and transmission electron microscopy results expose the decoration of Co{sub 3}O{sub 4} nanoparticles on GO sheets. Magnetic response of nanocomposites was confirmed from superconducting quantum interference device magnetometer measurement. Raman spectroscopy investigated optical properties of these nanocomposites. The Raman spectra of Co{sub 3}O{sub 4}/RGO nanocomposites shows the enhancement of D and G bands which are associated with GO due to the Surface-enhanced Raman spectroscopy effect and blue shift. Increase in the full-width half-maximum value as well as upshift in D and G peaks are strong signals of association of charge transfer process between GO sheets and decorated Co{sub 3}O{sub 4} nanoparticles. The effect of charge transfer process is measured in the expression of shifting of Fermi energy level of Co{sub 3}O{sub 4}/RGO nanocomposites. Charge transfer is correlated with observed Raman shift and scanning Kelvin probe microscopy. XRD spectra of Co{sub 3}O{sub 4}/RGO confirm the polycrystalline nature of Co{sub 3}O{sub 4} nanoparticles.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗