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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Electric-field tunable spin diode FMR in patterned PMN-PT/NiFe structures

Dynamic properties of NiFe thin films on PMN-PT piezoelectric substrate are investigated using the spin-diode method. Ferromagnetic resonance (FMR) spectra of microstrips with varying width are measured as a function of magnetic field and frequency. The FMR frequency is shown to depend on the electric field applied across the substrate, which induces strain in the NiFe layer. Electric field tunability of up to 100 MHz per 1 kV/cm is achieved. An analytical model based on total energy minimization and the Landau-Lifshitz-Gilbert equation, taking into account the magnetostriction effect, is used to explain the measured dynamics. Based on this model, conditions for optimal electric-field tunable spin diode FMR in patterned NiFe/PMN-PT structures are derived.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Magnetocaloric effect and the influence of pressure on magnetic properties of La-excess pseudo-binary alloys La{sub 1+δ}(Fe{sub 0.85}Si{sub 0.15}){sub 13}

The La-excess alloys La{sub 1+δ}(Fe{sub 0.85}Si{sub 0.15}){sub 13} (δ = 0.06 and 0.09) exhibit large magnetocaloric effect which has been attributed to the occurrence of itinerant-electron metamagnetic transition near the Curie temperature T{sub C}. The maximum entropy change −ΔS{sub m} was shown to be from 4.5 to 11.5 J/kg K for the applied field variation ΔH from 20 to 70 kOe, respectively. The estimated relative cooling power for ΔH = 70 kOe was 418 J/kg. The alloys show a typical NaZn{sub 13}-type cubic structure, featuring a doping-induced magnetovolume effect with the increase in T{sub C}. Under the applied pressure up to 2 GPa, the T{sub C} as deduced from resistance measurements decreased linearly, ΔT{sub C} = 113 (for δ = 0.06) and 111 K (for δ = 0.09), together with a corresponding decrease of resistivity, Δρ = 6.1 μΩ m at room temperature for both samples. At a low pressure, the effect of spontaneous magnetostriction on T{sub C} caused by applying the pressure appeared to have a similar magnitude to that of the negative magnetovolume effect caused by La-excess doping. In comparison with other stoichiometric La(Fe{sub 1−x}Si{sub x}){sub 13} compounds, the pressure in our case was shown to have a smaller influence on T{sub C}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

The influence of hydrostatic pressure on the magnetic and magnetocaloric properties of DyRu 2 Si 2

In this paper, we report the magnetic and magnetocaloric properties of the tetragonal rare-earth compound DyRu 2 Si 2 under applied hydrostatic pressure. The isothermal entropy change (ΔS) and the adiabatic temperature change (ΔT ad ) were calculated from magnetization data collected at different applied pressures and from heat capacity measurements conducted at atmospheric pressure, respectively. The application of hydrostatic pressure significantly modified the multi-step magnetization curve and the saturation magnetization. A suppression of the magnetization was observed for P = 0.588 GPa and P = 0.654 GPa whereas, at about P ≈1 GPa, the saturation magnetization increased and the magnetization isotherms again resembled the curves measured at atmospheric pressure. A small thermal hysteresis was observed between the heating and cooling M(T) curves at T t =3.4 K, with an applied magnetic field of H = 0.1 T. This thermal hysteresis indicates a first-order like transition which was also supported by the Arrott plot analysis. Finally, the volume magnetostriction was estimated from the pressure-dependent magnetization measurements using a Maxwell relation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2012

Supersensitive SQUID/magnetostrictor detecting system

It is shown that using the state-of-the-art quantum interferometer (SQUID) with the resolution 10{sup -6} {Phi}{sub 0} Hz{sup -1/2} = 2.07 Multiplication-Sign 10{sup -21} Wb Hz{sup -1/2}, coupled to a magnetostrictor, playing the role of tensomagnetic transducer, it is possible to construct a system for detecting pressure variations with the ultimate sensitivity of 10{sup -13} Pa Hz{sup -1/2} and for measuring specific elongation with the sensitivity of 10{sup -24} Hz{sup -1/2}. The analysis of physical grounds of the inverse magnetostriction effect demonstrates concrete ways to essentially higher efficiency of tensomagnetic conversion. The estimates performed demonstrate the possibility of using the SQUID/magnetostrictor system as a detector of gravitational waves. Other possibilities of using this system for solving both fundamental and applied problems are also considered. (experimental techniques)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Magnetic nanopantograph in the SrCu 2 (BO 3 ) 2 Shastry–Sutherland lattice

Magnetic materials having competing, i.e., frustrated, interactions can display magnetism prolific in intricate structures, discrete jumps, plateaus, and exotic spin states with increasing applied magnetic fields. When the associated elastic energy cost is not too expensive, this high potential can be enhanced by the existence of an omnipresent magnetoelastic coupling. Here in this work, we report experimental and theoretical evidence of a nonnegligible magnetoelastic coupling in one of these fascinating materials, SrCu 2 (BO 3 ) 2 (SCBO). First, using pulsed-field transversal and longitudinal magnetostriction measurements we show that its physical dimensions, indeed, mimic closely its unusually rich field-induced magnetism. Second, using density functional-based calculations we find that the driving force behind the magnetoelastic coupling is the CuOCuˆ superexchange angle that, due to the orthogonal Cu 2+ dimers acting as pantographs, can shrink significantly (0.44%) with minute (0.01%) variations in the lattice parameters. Lastly, with this original approach we also find a reduction of ~10% in the intradimer exchange integral J, enough to make predictions for the highly magnetized states and the effects of applied pressure on SCBO.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Metastable states in the frustrated triangular compounds Ca 3 Co 2 - x Mn x O 6 and Ca 3 Co 2 O 6

The observation of unusual metastable behavior in Ca 3 Co 2 O 6 remains an ongoing puzzle. When the magnetic field is increased at certain very slow rates, evenly spaced steps occur in the magnetization and other physical quantities as a function of magnetic field every 1.2 T. The ground state without steps is approached by slow relaxation processes over hours to days. It is a striking example of extremely slow dynamics arising from geometrical frustration in an otherwise clean and long-range ordered system, and its precise description remains controversial. Here we shed light on the mystery by reporting similar behavior in isostructural Ca 3 Co 2-x MnxO 6 , albeit at magnetic field sweep rates that are six orders of magnitude faster than that in Ca 3 Co 2 O 6 . We observe these steps not only in the magnetization, but also in the magnetostriction, electric polarization, and magnetocaloric effect. Here, we present a study of metastable behavior in both compounds across seven orders of magnitude of magnetic field sweep rates using unique magnets at the National High Magnetic Field Laboratory. The metastable steps occur for intermediate ranges of magnetic field sweep rates, vanishing or evolving for the fastest and slowest sweep rates. Our data support that these metastable steps are an intrinsic feature of the three-dimensionally frustrated geometry of Ising spins in this structural family and thus narrow the number of applicable models.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Evolution of noncollinear magnetism in magnetocaloric MnPtGa

MnPtGa crystallizes in the hexagonal Ni 2 In structure type in space group P6 3 /mmc and has been reported to display a ferromagnetic Curie temperature near 220K. Here we find a transition near T c = 236 K to a ferromagnetic state, albeit with a reduced moment from what is expected for collinear ordering. The peak magnetocaloric entropy change was determined to be ΔS M = –1.9 J kg –1 K –1 for an applied magnetic field of H = 5 T at the ferromagnetic ordering temperature. Magnetostructural coupling manifests as a change in the slope of the thermal expansion coefficients of the c lattice parameter near T c , with a negative spontaneous volume magnetostriction; ω = –300 ppm at 190K. In this work, neutron powder diffraction studies of the magnetic ground state reveal an evolution in complexity as temperature decreases: from a ferromagnet, to a canted antiferromagnet, to the eventual formation of a spin-density-wave state at low temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Spectroscopy of a Cavitating Liquid in the Optical and X-ray Spectral Ranges

Results of spectroscopic investigation of a multibubble sonoluminescence and a hydrodynamic luminescence of glycerol in the optical range between 400 and 700 nm and in the X-ray spectral interval between 1 and 70 keV are presented. Continuous spectrum the shape of which is sufficiently well described by the normal distribution with respect to photon energy was obtained for both sono- and hydroluminescence in the optical spectral range. Based on the identity of the spectra, a conclusion can be drawn that the effects of the sono- and hydroluminescence are of the same physical nature. The shape of the obtained spectra suggests that the observed glow of a liquid under mechanical action represents fluorescence of only one type of centers in a condensed medium. X-ray radiation is absent in the specified energy range. Although an X-ray spectrometer detects some a signal of some kind, in reality, this turns out to be noise created by the magnetostrictive transducer of an ultrasonic generator.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Crystalline and spin chiralities in multiferroics with langasite-type structure and Fe{sub 1–x}Co{sub x}Si crystals

It is shown that, when magnetic ordering occurs in layered iron-containing langasites (sp. gr. P321), one of the reasons for spin chiralities of different signs is the presence of structural chirality (the existence of inversion twins), which, in turn, is due to the nonsymmetricity of these crystals. Spin helicoids arise in these multiferroics at split sites of Fe{sup 3+} ions below the Néel point. The direction of electric polarization vectors coincides with the direction of the magnetic helicoid axes because of the piezoelectric properties of these materials. Due to the magnetostriction effects, structural chirality wave vector k{sub z} exceeds the magnetic helicoid wave vector by a factor of 2: k{sub z} = 2q{sub z}. The temperatures of transitions to the chiral structural and chiral magnetic states may differ. In particular, if the structural transition initial temperature exceeds the magnetic transition temperature (Τ{sub U}> Τ{sub M}), structural displacements may arise in the absence of magnetism at Τ{sub M} < Τ < Τ{sub U}. In noncentrosymmetric Fe{sub 1–x}Co{sub x}Si crystals (sp. gr. P2{sub 1}3), which are not multiferroics, magnetic chirality is due to the Dzyaloshinski–Moriya interaction. The dependence of the moduli of incommensurate wave number of the corresponding helicoid on the atomic composition of the crystals under consideration is nonmonotonic.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Magnetovolume effects and effect of pressure on the temperature dependence of sublattice magnetization in Ho(Co{sub 0.9}Ga{sub 0.1}){sub 2} compounds

The temperature dependence of the magnetic moments of cobalt and holmium ions in the temperature range of 5–300 K at pressures of P = 0 and 5 kbar was determined based on neutron diffraction data on Ho(Co{sub 0.9}Ga{sub 0.1}){sub 2} intermetallide. The temperature dependence of the lattice parameter was established, and the spontaneous bulk magnetostriction was determined. These quantities were calculated using the exchange striction model of a ferrimagnet, and good agreement with the experiment was obtained. The parameters of the exchange interaction between pairs of atoms of this compound and the magnetoelastic coupling constant were estimated. An original interpretation of the nature of the first-order magnetic phase transition in HoCo{sub 2} is proposed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T > T{sub C}) and ferromagnetic (T < T{sub C}) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B2‑clusters, regions with the D0{sub 3} short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Magnetoelectricity in CoFe 2 O 4 nanocrystal-P(VDF-HFP) thin films

Transition metal ferrites such as CoFe 2 O 4 , possessing a large magnetostriction coefficient and high Curie temperature (T c > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/ piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 μm. We describe the synthesis and structural characterization of the nanocrystals and composite films by XRD, TEM, HRTEM, STEM, and SEM, as well as dielectric and magnetic properties, in order to identify evidence of cooperative interactions between the two phases. The CoFe 2 O 4 polymer nanocomposite thin films exhibit composition-dependent effective permittivity, loss tangent, and specific saturation magnetization (Ms). An enhancement of the effective permittivity and saturation magnetization of the CoFe 2 O 4 -P(VDF-HFP) films was observed and directly compared with CoFe 2 O 4 -polyvinylpyrrolidone, a non-ferroelectric polymer-based nanocomposite prepared by the same method. The comparison provided evidence for the observation of a magnetoelectric effect in the case of CoFe 2 O 4 -P(VDF-HFP), attributed to a magnetostrictive/piezoelectric interaction. An enhancement of Ms up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe 2 O 4 -P(VDF-HFP) sample.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Monitoring microstructural evolution of alloy 617 with non-linear acoustics for remaining useful life prediction; multiaxial creep-fatigue and creep-ratcheting

The research built upon a prior investigation to develop a unified constitutive model for design-­by-­analysis of the intermediate heat exchanger (IHX) for a very high temperature reactor (VHTR) design of next generation nuclear plants (NGNPs). Model development requires a set of failure data from complex mechanical experiments to characterize the material behavior. Therefore uniaxial and multiaxial creep-­fatigue and creep-­ratcheting tests were conducted on the nickel-­base Alloy 617 at 850 and 950°C. The time dependence of material behavior, and the interaction of time dependent behavior (e.g., creep) with ratcheting, which is an increase in the cyclic mean strain under load-­controlled cycling, are major concerns for NGNP design. This research project aimed at characterizing the microstructure evolution mechanisms activated in Alloy 617 by mechanical loading and dwell times at elevated temperature. The acoustic harmonic generation method was researched for microstructural characterization. It is a nonlinear acoustics method with excellent potential for nondestructive evaluation, and even online continuous monitoring once high temperature sensors become available. It is unique because it has the ability to quantitatively characterize microstructural features well before macroscale defects (e.g., cracks) form. The nonlinear acoustics beta parameter was shown to correlate with microstructural evolution using a systematic approach to handle the complexity of multiaxial creep-­fatigue and creep-­ratcheting deformation. Mechanical testing was conducted to provide a full spectrum of data for: thermal aging, tensile creep, uniaxial fatigue, uniaxial creep-­fatigue, uniaxial creep-ratcheting, multiaxial creep-fatigue, and multiaxial creep-­ratcheting. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Optical Microscopy were conducted to correlate the beta parameter with individual microstructure mechanisms. We researched application of the harmonic generation method to tubular mechanical test specimens and pipes for nondestructive evaluation. Tubular specimens and pipes act as waveguides, thus we applied the acoustic harmonic generation method to guided waves in both plates and shells. Magnetostrictive transducers were used to generate and receive guided wave modes in the shell sample and the received signals were processed to show the sensitivity of higher harmonic generation to microstructure evolution. Modeling was initiated to correlate higher harmonic generation with the microstructure that will lead to development of a life prediction model that is informed by the nonlinear acoustics measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A Multiphysics Thermoelastoviscoplastic Damage Internal State Variable Constitutive Model including Magnetism

We present a macroscale constitutive model that couples magnetism with thermal, elastic, plastic, and damage effects in an Internal State Variable (ISV) theory. Previous constitutive models did not include an interdependence between the internal magnetic (magnetostriction and magnetic flux) and mechanical fields. Although constitutive models explaining the mechanisms behind mechanical deformations caused by magnetization changes have been presented in the literature, they mainly focus on nanoscale structure–property relations. A fully coupled multiphysics macroscale ISV model presented herein admits lower length scale information from the nanoscale and microscale descriptions of the multiphysics behavior, thus capturing the effects of magnetic field forces with isotropic and anisotropic magnetization terms and moments under thermomechanical deformations. For the first time, this ISV modeling framework internally coheres to the kinematic, thermodynamic, and kinetic relationships of deformation using the evolving ISV histories. For the kinematics, a multiplicative decomposition of deformation gradient is employed including a magnetization term; hence, the Jacobian represents the conservation of mass and conservation of momentum including magnetism. The first and second laws of thermodynamics are used to constrain the appropriate constitutive relations through the Clausius–Duhem inequality. The kinetic framework employs a stress–strain relationship with a flow rule that couples the thermal, mechanical, and magnetic terms. Experimental data from the literature for three different materials (iron, nickel, and cobalt) are used to compare with the model’s results showing good correlations.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Updated Results of Ultrasonic Transducer Irradiation Test

Ultrasonic technologies offer the potential for high accuracy and resolution in-pile measurement of a range of parameters, including geometry changes, temperature, crack initiation and growth, gas pressure and composition, and microstructural changes. Many Department of Energy-Office of Nuclear Energy (DOE-NE) programs are exploring the use of ultrasonic technologies to provide enhanced sensors for in-pile instrumentation during irradiation testing. For example, the ability of small diameter ultrasonic thermometers (UTs) to provide a temperature profile in candidate metallic and oxide fuel would provide much needed data for validating new fuel performance models. These efforts are limited by the lack of identified ultrasonic transducer materials capable of long term performance under irradiation test conditions. To address this need, the Pennsylvania State University (PSU) was awarded an Advanced Test Reactor National Scientific User Facility (ATR NSUF) project to evaluate the performance of promising magnetostrictive and piezoelectric transducers in the Massachusetts Institute of Technology Research Reactor (MITR) up to a fast fluence of at least 10{sup 21} n/cm{sup 2}. A multi-National Laboratory collaboration funded by the Nuclear Energy Enabling Technologies Advanced Sensors and Instrumentation (NEET-ASI) program also provided initial support for this effort. This irradiation, which started in February 2014, is an instrumented lead test and real-time transducer performance data are collected along with temperature and neutron and gamma flux data. The irradiation is ongoing and will continue to approximately mid-2015. To date, very encouraging results have been attained as several transducers continue to operate under irradiation. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Mechanical Resonant Sensing of Spin Texture Dynamics in a 2D Antiferromagnet

Abstract The coupling between the spin degrees of freedom and macroscopic mechanical motions, including striction, shearing, and rotation, has attracted wide interest with applications in actuation, transduction, and information processing. Experiments so far have established the mechanical responses to the long‐range ordered or isolated single spin states. However, it remains elusive whether mechanical motions can couple to a different type of magnetic structure, the non‐collinear spin textures, which exhibit nanoscale spatial variations of spin (domain walls, skyrmions,etc.) and are promising candidates to realize high‐speed computing devices. Here, collective spin texture dynamics is detected with nanoelectromechanical resonators fabricated from 2D antiferromagnetic (AFM) MnPS 3 with 10 −9 strain sensitivity. By examining radio frequency mechanical oscillations under magnetic fields, new magnetic transitions are identified with sharp dips in resonant frequency. They are attributed to collective AFM domain wall motions as supported by the analytical modeling of magnetostriction and large‐scale spin‐dynamics simulations. Additionally, an abnormally large modulation in the mechanical nonlinearity at the transition field infers a fluid‐like response due to ultrafast domain motion. The work establishes a strong coupling between spin texture and mechanical dynamics, laying the foundation for electromechanical manipulation of spin texture and developing quantum hybrid devices.

Chemistry↗
DOE OSTI2019

Competing Interface and Bulk Effect–Driven Magnetoelectric Coupling in Vertically Aligned Nanocomposites

Abstract Room‐temperature magnetoelectric (ME) coupling is developed in artificial multilayers and nanocomposites composed of magnetostrictive and electrostrictive materials. While the coupling mechanisms and strengths in multilayers are widely studied, they are largely unexplored in vertically aligned nanocomposites (VANs), even though theory has predicted that VANs exhibit much larger ME coupling coefficients than multilayer structures. Here, strong transverse and longitudinal ME coupling in epitaxial BaTiO 3 :CoFe 2 O 4 VANs measured by both optical second harmonic generation and piezoresponse force microscopy under magnetic fields is reported. Phase field simulations have shown that the ME coupling strength strongly depends on the vertical interfacial area which is ultimately controlled by pillar size. The ME coupling in VANs is determined by the competition between the vertical interface coupling effect and the bulk volume conservation effect. The revealed mechanisms shed light on the physical insights of vertical interface coupling in VANs in general, which can be applied to a variety of nanocomposites with different functionalities beyond the studied ME coupling effect.

36 MATERIALS SCIENCE↗