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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 OSTI2016

Transient enhancement of magnetization damping in CoFeB film via pulsed laser excitation

Laser-induced spin dynamics of in-plane magnetized CoFeB films has been studied by using time-resolved magneto-optical Kerr effect measurements. While the effective demagnetization field shows little dependence on the pump laser fluence, the intrinsic damping constant has been found to be increased from 0.008 to 0.076 with the increase in the pump fluence from 2 mJ/cm{sup 2} to 20 mJ/cm{sup 2}. This sharp enhancement has been shown to be transient and ascribed to the heating effect induced by the pump laser excitation, as the damping constant is almost unchanged when the pump-probe measurements are performed at a fixed pump fluence of 5 mJ/cm{sup 2} after irradiation by high power pump pulses.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Magnetic cooling close to a quantum phase transition—The case of Er{sub 2}Ti{sub 2}O{sub 7}

Magnetic cooling, first introduced in the late twenties of last century, has regained considerable interest recently as a cost-efficient and easy-to-handle alternative to {sup 3}He-based refrigeration techniques. Especially, adiabatic demagnetization of paramagnets—the standard materials for magnetic refrigeration—has become indispensable for the present space applications. To match the growing demand for increasing the efficiency in these applications, a new concept for magnetic cooling based on many-body effects around a quantum-critical-point has been introduced and successfully tested [B. Wolf et al., Proc. Natl. Acad. Sci. U.S.A. 108, 6862 (2011)]. By extending this concept to three-dimensional magnetic systems, we present here the magnetothermal response of the cubic pyrochlore material Er{sub 2}Ti{sub 2}O{sub 7} in the vicinity of its B-induced quantum-critical point which is located around 1.5 T. We discuss performance characteristics such as the range of operation, the efficiency, and the hold time. These figures are compared with those of state-of-the-art paramagnetic coolants and with other quantum-critical systems which differ by the dimensionality of the magnetic interactions and the degree of frustration.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

A Novel $In-Situ$ Radiation Damage Diagnostic System for Undulators

Radiation damage has been a known problem at many synchrotron radiations and free-electron lasers facilities, especially those that use hybrid or pure permanent magnet undulators to produce high brightness light. Field strength loss due to demagnetization makes it necessary to remove the insertion device from the tunnel for inspection and repair, which brings several inconveniences. We aimed to develop an in situ radiation damage detection system for undulators capable of diagnosing relative field changes of 10 -4 (100 ppm) or smaller. The system measures the flux change in a flexible printed circuit board coil attached to the undulator magnet array by periodically measuring the integral flux change during the opening and closing of the undulator gap. If the magnet block damage occurs, the signal from the coil will decrease proportionally to the damage. First tests performed on variable gap hybrid undulators for the Linac Coherent Light Source II (LCLS-II) at SLAC National Accelerator Laboratory showed that the system is capable of measuring flux changes with a relative precision of approximately 0.7 × 10 -4 over several days. Relative field changes smaller than 10 -4 were detected in short-term measurements. Here, the novel system that we propose here opens the possibility of detecting radiation damage in undulators during operation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Unusual Behavior of the Coercive Field in a (CoFeB){sub x}(LiNbO{sub y}){sub 100 –x} Nanocomposite with a High Content of Magnetic Ions in an Insulating Matrix

The temperature behavior of the coercive field H{sub c}(T) and the magnetic anisotropy in (CoFeB){sub x}(LiNbO{sub y}){sub 100 –x} nanocomposite films with a ferromagnetic alloy content x = 33–48 at % near the metal–insulator transition (x{sub c} ≈ 42 at %) have been studied by the magnetometry and ferromagnetic resonance methods. The films were ensembles of CoFe granules with lateral sizes of 2–4 nm, which are highly elongated (up to 10–15 nm) in the nanocomposite growth direction and embedded in a LiNbO{sub y} matrix with a high content of magnetic Fe{sup 2+} and Co{sup 2+} ions (up to 3 × 10{sup 22} cm{sup –3}). A nonmonotonic behavior of H{sub c}(T), viz., a sharp minimum at a temperature T{sub F} ≈ 50 K close to the blocking temperature (T{sub b}{sup ∗} ≈ 70 K) of the granule magnetic moment, has been detected in samples with x < 42 at %. The effective field of the perpendicular growth anisotropy (0.4–0.8 kOe) turns out to be an order of magnitude lower than the field of the granule shape anisotropy (about 7 kOe) and increases with x. The revealed peculiarities are explained by the fact that, apart from the ferromagnetic intergranular exchange interaction in an infinite cluster, the surface anisotropy effects involving magnetic ions in a thin layer adjacent to the cluster and responsible for the surface interaction fluctuations play a big role in the investigated percolation nanocomposites, enhancing the nanocomposite demagnetization at T ≈ T{sub F} ~ T{sub b}{sup ∗}.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Formation of gapless Z{sub 2} spin liquid phase manganites in the (Sm{sub 1–y}Gd{sub y}){sub 0.55}Sr{sub 0.45}MnO{sub 3} system in zero magnetic field: Topological phase transitions to states with low and high density of 2D-vortex pairs induced by the magnetic field

The evolution of the ground state of the manganese spin ensemble in the (Sm{sub 1–y}Gd{sub y}){sub 0.55}Sr{sub 0.45}MnO{sub 3} in the case of isovalent substitution of rare-earth samarium ions with large radii with gadolinium ions with significantly smaller radii is studied. The measured temperature dependences of the ac magnetic susceptibility and the field dependences of the dc magnetizations are analyzed using the Heisenberg–Kitaev model describing the transition from the ordered spin state with classical isotropic AFM exchange to the frustrated spin state with quantum highly anisotropic FM exchange. A continuous transition from the 3D ferromagnetic state of manganese spins in the initial sample with y = 0 to zigzag AFM ordering of CE-type spins in ab planes for y = 0.5, coexisting in samples with y = 0.5, 0.6, and 0.7 at temperatures below T{sub N} ≅ 48.5 K with a disordered phase such as a quantum Griffiths phase is identified. As the gadolinium concentration further increases, the CE-type zigzag AFM structure is molten, which leads to the appearance of an unusual phase in Gd{sub 0.55}Sr{sub 0.45}MnO{sub 3} in the temperature range close to the absolute zero. This phase has characteristic features of a gapless Z{sub 2} quantum spin liquid in zero external magnetic field. The step changes in the magnetization isotherms measured at 4.2 K in the field range of ±75 kOe are explained by quantum phase transitions of the Z{sub 2} spin liquid to a phase with topological order in weak magnetic fields and a polarized phase in strong fields. The significant difference between critical fields and magnetization jumps in isotherms indicates the existence of hysteretic phenomena in quantum spin liquid magnetization–demagnetization processes caused by the difference between localization–delocalization of 2D vortex pairs induced by a magnetic field in a quantum spin liquid with disorder.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Temporal Stability of Magnetization of ε-In{sub 0.24}Fe{sub 1.76}O{sub 3} Nanoparticles

The kinetics of spontaneous demagnetization in nanoparticles of the exotic epsilon-phase of indium-doped iron(III) oxide (ε-In{sub 0.24}Fe{sub 1.76}O{sub 3}) has been studied using the method of accelerated testing of magnets for temporal stability in a magnetization-reversal field. Time dependences of the magnetization of nanoparticles measured in a wide range of magnetic fields exhibited rectification in semilogarithmic coordinates. The dependence of the magnetic viscosity on the magnetic field has been measured and used for determining the fluctuation field and activation volume. A relationship between the magnetic viscosity and magnetic noise caused by random thermoinduced magnetization reversal in separate nanoparticles is established.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Final Report for DOE Grant # DE-FG02-01ER45893

During the period July 1, 2001 to June 30, 2016, the DOE-supported research project covered a significant number of research topics, all of them related to the study of magnetic materials. Part of this work was experimental but the main focus was on theoretical analyses of magnetic materials characterization approaches, such as Lorentz transmission electron microscopy (LTEM) using phase reconstructions; vector field electron tomography (VFET); and in-depth analyses of the demagnetization tensor field for uniformly magnetized particles of arbitrary shape. A total of 39 papers were published in peer-reviewed journals over the 16 years of this research program. In the following sub-sections, we list the abstracts for all 33 journal papers; the interested reader may find more details in the actual publications. Conference papers are also listed in the list of publications at the end of this report, but are not covered in the following sections due to the fact that these papers typically do not have an abstract.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A Novel In-situ Radiation Damage Diagnostic System for Undulators

Radiation damage has been a known problem at many synchrotron radiation and free-electron lasers facilities, especially those that use hybrid or pure permanent magnet undulators to produce high brightness light. Field strength loss due to demagnetization makes it necessary to remove the insertion device from the tunnel for inspection and repair, which brings several inconveniences. Here, we aimed to develop an in-situ radiation damage detection system for undulators capable of diagnosing relative field changes of 10 -4 (100 ppm) or smaller.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

The eruptibility of magmas at Tharsis and Syrtis Major on Mars

Magnetic and geologic data indicate that the ratio of intrusive to extrusive magmatism (the I/E ratio) is higher in the Tharsis and Syrtis Major volcanic provinces on Mars relative to most volcanic centers on Earth. The fraction of magmas that erupt helps to determine the effects of magmatism on crustal structure and the flux of magmatic gases to the atmosphere and also influences estimates of melt production inferred from the history of surface volcanism. We consider several possible controls on the prevalence of intrusive magmatism at Tharsis and Syrtis Major, including melt production rates, lithospheric properties, regional stresses and strain rates, and magmatic volatile budgets. The Curie temperature is the minimum crustal temperature required for thermal demagnetization, implying that if the primary magnetic mineral is magnetite or hematite, the crust was warm during the intrusive magmatism reflected in Tharsis and Syrtis Major I/E ratios. When wall rocks are warm, thermally activated creep relaxes stresses from magma replenishment and regional tectonics, and eruptibility depends on buoyancy overpressure. We develop a new one-dimensional model for the development of buoyancy in a viscous regime that accounts for cooling, crystallization, volatile exsolution, bubble coalescence and rise, fluid egress, and compaction of country rock. Under these conditions, we find that initial water and CO 2 contents typically < 1.5 wt % can explain the observed range of intrusive/extrusive ratios. Furthermore, our results support the hypothesis that warm crust and a relatively sparse volatile budget encouraged the development of large intrusive complexes beneath Tharsis and Syrtis Major.

58 GEOSCIENCES↗
DOE OSTI2017

Electron diffusion region during magnetopause reconnection with an intermediate guide field: Magnetospheric multiscale observations

An electron diffusion region (EDR) in magnetic reconnection with a guide magnetic field approximately 0.2 times the reconnecting component is encountered by the four Magnetospheric Multiscale spacecraft at the Earth's magnetopause. The distinct substructures in the EDR on both sides of the reconnecting current sheet are visualized with electron distribution functions that are 2 orders of magnitude higher cadence than ever achieved to enable the following new findings: (1) Motion of the demagnetized electrons plays an important role to sustain the reconnection current and contributes to the dissipation due to the nonideal electric field, (2) the finite guide field dominates over the Hall magnetic field in an electron–scale region in the exhaust and modifies the electron flow dynamics in the EDR, (3) the reconnection current is in part carried by inflowing field–aligned electrons in the magnetosphere part of the EDR, and (4) the reconnection electric field measured by multiple spacecraft is uniform over at least eight electron skin depths and corresponds to a reconnection rate of approximately 0.1. Here, the observations establish the first look at the structure of the EDR under a weak but not negligible guide field.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Large Exchange Coupling Between Localized Spins and Topological Bands in MnBi 2 Te 4

Magnetism in topological materials creates phases exhibiting quantized transport phenomena with potential technological applications. The emergence of such phases relies on strong interaction between localized spins and the topological bands, and the consequent formation of an exchange gap. However, this remains experimentally unquantified in intrinsic magnetic topological materials. Here, this interaction is quantified in MnBi 2 Te 4 , a topological insulator with intrinsic antiferromagnetism. This is achieved by optically exciting Bi-Te p states comprising the bulk topological bands and interrogating the consequent Mn 3d spin dynamics, using a multimodal ultrafast approach. Ultrafast electron scattering and magneto-optic measurements show that the p states demagnetize via electron-phonon scattering at picosecond timescales. Despite being energetically decoupled from the optical excitation, the Mn 3d spins, probed by resonant X-ray scattering, are observed to disorder concurrently with the p spins. Together with atomistic simulations, this reveals that the exchange coupling between localized spins and the topological bands is at least 100 times larger than the superexchange interaction, implying an optimal exchange gap of at least 25 meV in the surface states. Here, by quantifying this exchange coupling, this study validates the materials-by-design strategy of utilizing localized magnetic order to manipulate topological phases, spanning static to ultrafast timescales.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Ultrafast Terahertz Field Control of the Emergent Magnetic and Electronic Interactions at Oxide Interfaces

Ultrafast electric-field control of emergent electronic and magnetic states at oxide interfaces offers exciting prospects for the development of the next generation of energy-efficient devices. Here, it is demonstrated that the electronic structure and emergent ferromagnetic interfacial state in epitaxial LaNiO3/CaMnO3 superlattices can be effectively controlled using intense, single-cycle THz electric-field pulses. A suite of advanced X-ray spectroscopic techniques is employed to measure a detailed magneto-optical profile and the thickness of the ferromagnetic interfacial layer. Then, a combination of time-resolved and temperature-dependent optical measurements is used to disentangle several correlated electronic and magnetic processes driven by ultrafast, high-field THz pulses. Sub-picosecond non-equilibrium Joule heating of the electronic system is observed, ultrafast demagnetization of the ferromagnetic interfacial layer, and slower dynamics indicative of a change in the magnetic state of the superlattice due to the transfer of spin-angular momentum to the lattice. These findings suggest a promising avenue for the efficient control of 2D ferromagnetic states at oxide interfaces using ultrafast electric-field pulses.

X-ray spectroscopy and scattering↗
DOE OSTI2026

Design and optimization of processes for recovering rare earth elements from end‐of‐life permanent magnets

Recovery of rare earth elements (REEs) from end-of-life (EOL) products represents a strategic opportunity to strengthen the domestic supply chain for rare earth elements. This work presents a superstructure-based optimization framework for finding the most economical processing pathway for different EOL rare earth permanent magnets (REPMs). The framework evaluates state-of-the-art technologies across four processing stages—disassembly, demagnetization, leaching and extraction, and precipitation and calcination—using net present value (NPV) maximization and cost of recovery (COR) minimization objectives. A novel bottom-up costing framework for hydrogen decrepitation is also introduced. Two feedstocks were considered: REPMs from EOL hard disk drives (HDDs), and electric and hybrid electric vehicles (EVs and HEVs). While HDD recycling proved unprofitable due to limited feedstock availability, EVs/HEVs were profitable across a range of parameters and cost estimates. Therefore, our findings suggest that the proposed EOL EV/HEV recycling process may be economical and is worthy of further investigation.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Algorithm advances and applications of time‐dependent first‐principles simulations for ultrafast dynamics

Abstract Far from equilibrium phenomenon is a central theme of contemporary material research. Such phenomenon can exhibit itself in atomic structure and dynamics, but very often it also happens as non‐equilibrium phenomenon in the electronic structure. In ab initio material simulation, density functional theory (DFT) has played an essential role in studying electronic ground state problems. For excited states, besides many‐body perturbation theory, another powerful tool is the time dependent DFT (TDDFT) method. In particular, the real‐time TDDFT (rt‐TDDFT) method can be used to simulate many non‐equilibrium phenomena directly. Here we introduce our works on some algorithm advances based on our recently rt‐TDDFT method. This method uses the plane‐wave basis set, and significantly accelerates its efficiency by increasing the time step from 0.1–1 as in traditional methods to 0.2–0.5 fs. The noncollinear magnetic moments and spin–orbit coupling have also been included in our rt‐TDDFT method. Furthermore, a Boltzmann‐TDDFT algorithm has been developed to solve the hot carrier overheating problem in Ehrenfest dynamics, and a natural orbital branching algorithm has been developed to overcome the mean‐field approximation in Ehrenfest dynamics nuclear trajectory, thus allows stochastic multiple paths in chemical reactions. Utilizing these methods, we have studied the photoinduced ultrafast demagnetization, ultrafast phase transition, energy transfer between plasmon and hot carriers, as well as the high‐energy ion implantation and low‐energy atomic diffusion in semiconductors. We believe the tools as the ones introduced here can enable us to study a wide range of phenomena which are of great interest in modern day material research. This article is categorized under: Structure and Mechanism > Computational Materials Science Electronic Structure Theory > Ab Initio Electronic Structure Methods Electronic Structure Theory > Density Functional Theory

Liu, Wen‐Hao↗
DOE OSTI2025

The X-ray Integral Field Unit at the end of the Athena reformulation phase

The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4’ field of view (compared to 5’ before). Here, in this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027.

Peille, Philippe [Centre National d’Etudes Spatial↗
DOE OSTI2018

The LiteBIRD Satellite Mission: Sub-Kelvin Instrument

Inflation is the leading theory of the first instant of the universe. Inflation, which postulates that the universe underwent a period of rapid expansion an instant after its birth, provides convincing explanation for cosmological observations. Recent advancements in detector technology have opened opportunities to explore primordial gravitational waves generated by the inflation through “B-mode” (divergent-free) polarization pattern embedded in the cosmic microwave background anisotropies. If detected, these signals would provide strong evidence for inflation, point to the correct model for inflation, and open a window to physics at ultra-high energies. LiteBIRD is a satellite mission with a goal of detecting degree-and-larger-angular-scale B-mode polarization. LiteBIRD will observe at the second Lagrange point with a 400 mm diameter telescope and 2622 detectors. It will survey the entire sky with 15 frequency bands from 40 to 400 GHz to measure and subtract foregrounds. The US LiteBIRD team is proposing to deliver sub-Kelvin instruments that include detectors and readout electronics. A lenslet-coupled sinuous antenna array will cover low-frequency bands (40–235 GHz) with four frequency arrangements of trichroic pixels. An orthomode-transducer-coupled corrugated horn array will cover high-frequency bands (280–402 GHz) with three types of single frequency detectors. The detectors will be made with transition edge sensor (TES) bolometers cooled to a 100 milli-Kelvin base temperature by an adiabatic demagnetization refrigerator. The TES bolometers will be read out using digital frequency multiplexing with Superconducting QUantum Interference Device (SQUID) amplifiers. Up to 78 bolometers will be multiplexed with a single SQUID amplifier. Lastly, we report on the sub-Kelvin instrument design and ongoing developments for the LiteBIRD mission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Updated design of the CMB polarization experiment satellite LiteBIRD

Recent developments of transition-edge sensors (TESs), based on extensive experience in ground-based experiments, have been making the sensor techniques mature enough for their application on future satellite CMB polarization experiments. LiteBIRD is in the most advanced phase among such future satellites, targeting its launch in Japanese Fiscal Year 2027 (2027FY) with JAXA's H3 rocket. It will accommodate more than 4000 TESs in focal planes of reflective low-frequency and refractive medium-and-high-frequency telescopes in order to detect a signature imprinted on the cosmic microwave background (CMB) by the primordial gravitational waves predicted in cosmic inflation. The total wide frequency coverage between 34GHz and 448GHz enables us to extract such weak spiral polarization patterns through the precise subtraction of our Galaxy's foreground emission by using spectral differences among CMB and foreground signals. Telescopes are cooled down to 5Kelvin for suppressing thermal noise and contain polarization modulators with transmissive half-wave plates at individual apertures for separating sky polarization signals from artificial polarization and for mitigating from instrumental 1/f noise. Passive cooling by using V-grooves supports active cooling with mechanical coolers as well as adiabatic demagnetization refrigerators. Sky observations from the second Sun-Earth Lagrangian point, L2, are planned for three years. An international collaboration between Japan, USA, Canada, and Europe is sharing various roles. In May 2019, the Institute of Space and Astronautical Science (ISAS), JAXA selected LiteBIRD as the strategic large mission No. 2.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Switching of Coercivity Process in MnBi Alloys

MnBi-based alloys represent an interesting choice for developing rare earth-free permanent magnets due to the high magnetocrystalline anisotropy of their characteristic low-temperature intermetallic phase (LTIP) with hexagonal structure. In this work, we discuss the switching of coercivity mechanism in MnBi alloys by modulation of their phase distribution and microstructure. As-cast MnBi alloys obtained by suction-casting technique exhibited LTIP interspersed within Bi- and Mn-rich areas. A noticeable coercivity field of 282 kA/m was observed. The coercivity mechanism for this alloy was explained in terms of the nucleation of reverse domains after saturation, by means of the Kronmüller equation, which incorporates the detrimental effect of microstructure defects through fitting parameters associated to reduced intrinsic magnetic properties at grain size boundaries, interfaces, and local demagnetizing fields. Subsequent annealing at 583 K for 24 h produced a marked reduction of coercivity (down to 16 kA/m), reflecting a switching of coercivity process from nucleation to pinning of domain walls. The key microstructural feature determining this variation is the formation/suppression of Bi-rich areas, which promotes the nucleation and growth of the initial MnBi intermetallic phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗