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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Hopf Solitons in Helical and Conical Backgrounds of Chiral Magnetic Solids

Three-dimensional topological solitons attract a great deal of interest in fields ranging from particle physics to cosmology, but remain experimentally elusive in solid-state magnets. Here we numerically predict magnetic heliknotons, an embodiment of such nonzero-Hopf-index solitons localized in all spatial dimensions while embedded in a helical or conical background of chiral magnets. In this work we describe conditions under which heliknotons emerge as metastable or ground-state localized nonsingular structures with fascinating knots of magnetization field in widely studied materials. We demonstrate magnetic control of three-dimensional spatial positions of such solitons, as well as show how they interact to form moleculelike clusters and possibly even crystalline phases comprising three-dimensional lattices of such solitons with both orientational and positional order. Finally, we discuss both fundamental importance and potential technological utility of magnetic heliknotons.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1979

Low dimensional magnetic solids and single crystal elpasolites: Need for improved crystal growing techniques

The need for extensive crystal growing experiments to develop techniques for preparing crystals suitable for magnetic anisotropy measurements and detailed X-ray and neutron diffraction studies is rationalized on the basis of the unique magnetic properties of the materials and their hydrogen bonded structures which have many features in common with metalloenzyme and metalloprotein active sites. Single crystals of the single and mixed lanthanide species are prepared by the Bridgeman technique of gradient solidification of molten samples. The effects of crystal imperfections on the optical properties of these materials are an important part of the projected research. A series of a-amido acid complexes of first row transition metals were prepared which crystallize as infinite linear chains and exhibit low dimensional magnetic ordering (one or two) at temperature below 40 K.

Good, M. L.↗
DOE OSTI2024

Quantum simulation of an extended Dicke model with a magnetic solid

Abstract The Dicke model describes the cooperative interaction of an ensemble of two-level atoms with a single-mode photonic field and exhibits a quantum phase transition as a function of light–matter coupling strength. Extending this model by incorporating short-range atom–atom interactions makes the problem intractable but is expected to produce new physical phenomena and phases. Here, we simulate such an extended Dicke model using a crystal of ErFeO 3 , where the role of atoms (photons) is played by Er 3+ spins (Fe 3+ magnons). Through terahertz spectroscopy and magnetocaloric effect measurements as a function of temperature and magnetic field, we demonstrated the existence of a novel atomically ordered phase in addition to the superradiant and normal phases that are expected from the standard Dicke model. Further, we elucidated the nature of the phase boundaries in the temperature–magnetic-field phase diagram, identifying both first-order and second-order phase transitions. These results lay the foundation for studying multiatomic quantum optics models using well-characterized many-body solid-state systems.

Marquez Peraca, Nicolas↗
DOE OSTI2024

Numerical study of implosion instability mitigation in magnetically driven solid liner dynamic screw pinches

Magnetized liner inertial fusion experiments on the Z accelerator suffer from magneto-Rayleigh–Taylor instabilities (MRTI) that compromise integrity of the imploding cylindrical liner, limiting achievable fusion fuel conditions and ultimately reducing magneto-inertial fusion target performance. Dynamic screw pinches (DSP) provide a method to reduce MRTI in-flight via application of magnetic field line tension to the imploding liner outer surface. In contrast with z-pinches that drive implosions with an azimuthal magnetic field, dynamic screw pinches enforce an additional axial drive magnetic field component, making the overall drive magnetic field helical. As the liner implodes, cumulative MRTI development is reduced by dynamically shifting the orientation of the fastest growing instability modes. Three-dimensional magnetohydrodynamic simulations show that the DSP mechanism effectively stabilizes initially solid cylindrical liner implosions driven by Z-scale current pulses, indicating that MRTI mitigation increases with the ratio of axial to azimuthal drive magnetic field components (i.e., the drive field ratio). We also performed a spectral analysis of the simulated imploding density distributions, extracting wavelength and pitch angle of the simulated MRTI structures to study their dynamics during the implosion. Simulations of liners initially perturbed with drive-field-aligned sinusoidal structures indicate that MRTI mitigation in DSP implosions decreases with perturbation wavelength, once again suggestive of magnetic field line tension effects.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1993

A Magnetic Solid-State Storage Technology: Vertical Bloch Line Storage

No storage technology is known to exist today which simultaneously offers high-storage density, nonvolatility, and a solid-state form factor. For example, common random access memories are solid-state, but are volatile and typically offer modest density. Alternatively, mainstream magnetic disk and magnetic tape systems offer high storage density and nonvolatility, but are fundamentally not solid-state. A number of applications exist which would be suited well with high performance solid- state technology. NASA, for example, is beginning baseline solid-state recorders for upcoming space missions, such as the Cassini mission to Saturn.

Katti, R. R.↗
NASA NTRS1983

The theory of an active magnetic regenerative refrigerator

The adiabatic temperature change with field which is limited to about 2 K/Tesla for ferromagnets near their Curie temperatures by the change of magnetization with temperature and the lattice heat capacity is discussed. Practical magnetic refrigerators operate on a regenerative cycle such as the Brayton cycle. This cycle can be executed through the use of an active magnetic regenerator, i.e., a regenerator composed of magnetic material that is cycled in an out of a magnetic field with appropriate fluid flows. The theory of these devices is predicted by solving the partial differential equations that describe fluid and the magnetic solid. The active magnetic regenerator is described along with the method of calculation. Temperature profiles for a normal regenerator and a magnetic regenerative refrigerator are shown.

Barclay, J. A.↗
DOE OSTI2021

Structural insights into Lewis acid- and F4TCNQ-doped conjugated polymers by solid-state magnetic resonance spectroscopy

Molecular doping strategies facilitate orders of magnitude enhancement in the charge carrier mobility of organic semiconductors (OSCs). Understanding the different doping mechanisms and molecular-level constraints on doping efficiency related to the material energy levels is crucial to develop versatile dopants for OSCs. Given the compositional and structural heterogeneities associated with OSC thin films, insight into dopant–polymer interactions by long-range techniques such as X-ray scattering and electron microscopy is exceedingly challenging to obtain. This study employs short-range probes, solid-state (ss)NMR and EPR spectroscopy, to resolve local structures and intermolecular interactions between dopants such as F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), Lewis acid BCF (tris[pentafluorophenyl] borane) and Lewis base conjugated polymer, PCPDTBT (P4) (poly[2,6-(4,4-bis(2-hexadecyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]). Analysis of 1 H and 13 C ssNMR spectra of P4, P4 : F4TCNQ and P4 : BCF blends indicates that the addition of dopants induces local structural changes in the P4 polymer, and causes paramagnetism-induced signal broadening and intensity losses. The hyperfine interactions in P4 : BCF and P4 : F4TCNQ are characterized by two-dimensional pulsed EPR spectroscopy. For P4 : F4TCNQ, 19 F ssNMR analysis indicates that the F4TCNQ molecules are distributed and aggregated into different local chemical environments. By comparison, BCF molecules are intermixed with the P4 polymer and interact with traces of water molecules to form BCF–water complexes that serve as Brønsted acid sites, as revealed by 11 B ssNMR spectroscopy. These results indicate that the P4–dopant blends exhibit complex morphology with different distributions of dopants, whereby the combined use of ssNMR and EPR provides essential insights into how higher doping efficiency is observed with BCF and a mediocre efficiency is associated with F4TCNQ molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Measurements of extended magnetic fields in laser-solid interaction

Magnetic fields generated from a laser-foil interaction are measured with high fidelity using a proton radiography scheme with x-ray fiducials. In contrast to prior findings under similar experimental conditions, this technique reveals the self-generated, Biermann-battery fields extend beyond the edge of the expanding plasma plume to a radius of over 3.5 mm by t = + 1.4 ns. An analysis of two monoenergetic proton populations confirms that proton deflection is dominated by magnetic fields far from the interaction ( > 2 mm) and electric fields are insignificant. The results are not captured in state-of-the-art magnetohydrodynamics simulations and suggest the need to consider additional physics mechanisms for the magnetic field generation and transport in laser-solid interactions. Published by the American Physical Society 2024

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1996

Velocity-Controlled Magnetic Bearings with Solid Cores

A methodology for designing velocity-controlled magnetic bearings with laminated cores has been extended to those with solid cores. The eddy-current effect of the solid cores is modeled as an opposing magnetomotive force. The bearing control dynamics is formulated in a dimensionless fashion which can be readily reviewed on a root-locus plot for stability. This facilitates the controller design and tuning process for solid core magnetic bearings using no displacement sensors.

Chen, H. Ming↗
NASA NTRS1973

Recovery of nonferrous metals from scrap automobiles by magnetic fluid levitation.

Ferrofluids are colloidal dispersions of subdomain magnetic solids in carrier liquids. In the presence of a non-homogeneous magnetic field, ferrofluids exert a pressure on immersed nonmagnetic objects in the opposite sense of the field gradient. This pressure force can, when opposite to gravity, levitate objects of higher density than the ferrofluid. This levitation technique can be used to separate solids according to density. Its application to the separation of nonferrous metals from shredded automobiles has been demonstrated on a prototype of a full-scale separator. Its use to recover nonferrous metals from municipal solid wastes also seems practical.

Mir, L.↗
NASA NTRS1985

Magnetic refrigeration for low-temperature applications

The application of refrigeration at low temperatures ranging from production of liquid helium for medical imaging systems to cooling of infrared sensors on surveillance satellites is discussed. Cooling below about 15 K with regenerative refrigerators is difficult because of the decreasing thermal mass of the regenerator compared to that of the working material. In order to overcome this difficulty with helium gas as the working material, a heat exchanger plus a Joule-Thomson or other exponder is used. Regenerative magnetic refrigerators with magnetic solids as the working material have the same regenerator problem as gas refrigerators. This problem provides motivation for the development of nonregenerative magnetic refrigerators that span approximately 1 K to approximately 0 K. Particular emphasis is placed on high reliability and high efficiency. Calculations indicate considerable promise in this area. The principles, the potential, the problems, and the progress towards development of successful 4 to 20 K magnetic refrigerators are discussed.

Barclay, J. A.↗
NASA NTRS1974

Technique for direct measurement of magnetic entropy of solids: Results for dysprosium titanium oxide

A measurement technique was devised which permits direct observation of the magnetic entropy of solids as a function of applied magnetic field. Measurements were made of the magnetic entropy, in the temperature range 2 to 20 K, of polycrystalline samples of dysprosium titanium oxide (Dy2Ti2O7) to determine its suitability for use as the working substance of a magnetic refrigerator. Magnetization measurements were also made at 4.2 K and below to provide additional information on the nature of the compound. The measurements indicated that crystalline electric fields perturbed the ground state of the dysprosium ions, removed the 16-fold degeneracy predicted by Hund's rules, and left only a twofold degeneracy in its place. A positive, temperature independent contribution to the magnetization was observed in the saturation region, which indicated that the doublet ground-state wave function was perturbed by a nearby unpopulated upper energy level.

Flood, D. J.↗
DOE OSTI2023

Nonlinear multi-magnon scattering in artificial spin ice

Abstract Magnons, the quantum-mechanical fundamental excitations of magnetic solids, are bosons whose number does not need to be conserved in scattering processes. Microwave-induced parametric magnon processes, often called Suhl instabilities, have been believed to occur in magnetic thin films only, where quasi-continuous magnon bands exist. Here, we reveal the existence of such nonlinear magnon-magnon scattering processes and their coherence in ensembles of magnetic nanostructures known as artificial spin ice. We find that these systems exhibit effective scattering processes akin to those observed in continuous magnetic thin films. We utilize a combined microwave and microfocused Brillouin light scattering measurement approach to investigate the evolution of their modes. Scattering events occur between resonance frequencies that are determined by each nanomagnet’s mode volume and profile. Comparison with numerical simulations reveals that frequency doubling is enabled by exciting a subset of nanomagnets that, in turn, act as nanosized antennas, an effect that is akin to scattering in continuous films. Moreover, our results suggest that tunable directional scattering is possible in these structures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2012

Solid State Multinuclear Magnetic Resonance Investigation of Electrolyte Decomposition Products on Lithium Ion Electrodes

Solid electrolyte interphase (SEI) formation in lithium ion cells prepared with advanced electrolytes is investigated by solid state multinuclear (7Li, 19F, 31P) magnetic resonance (NMR) measurements of electrode materials harvested from cycled cells subjected to an accelerated aging protocol. The electrolyte composition is varied to include the addition of fluorinated carbonates and triphenyl phosphate (TPP, a flame retardant). In addition to species associated with LiPF6 decomposition, cathode NMR spectra are characterized by the presence of compounds originating from the TPP additive. Substantial amounts of LiF are observed in the anodes as well as compounds originating from the fluorinated carbonates.

Li-ion battery electrolytes↗