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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Ab Initio Quantum Information Processor Design with Single-Molecule Magnets: A Multiscale Modeling Approach (Final Report)

This final report summarizes the team's efforts to develop a multiscale modeling approach that ranges from different levels of ab-initio quantum chemistry simulations to effective models and time-dependent external control, and to use this approach to systematically design quantum information processors with TbPc 2 single-molecule magnets. The impact of the work is two-fold: (i) New quantum chemistry simulation techniques capable of treating complex, multiscale problems such as the TbPc 2 molecule were developed, and (ii) the prospects for building quantum processors based on single-molecule magnets coupled by superconducting transmission line resonators were analyzed. The outcomes of this project revealed that current technology is at the cusp of being able to realize the main components of such a processor, and they highlighted the need to achieve stronger molecule-resonator interactions to enhance the viability of this approach. The multiscale modeling techniques developed during this project are general and transferable to other molecules and will thus have a broad impact on the field of quantum chemistry. Methods for controlling and simulating many coupled qubits developed here will also impact other quantum information technologies.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Investigating the impact of donor atoms of single-source precursors on f-element nanomaterial formation and mechanisms of initial bond cleavage

Nanotechnology is advancing exponentially, with novel discoveries and applications emerging every day across various fields, including environmental remediation, biomedicine, electronics, and textiles. Nanoparticles (NPs) are defined as particles with sizes ranging from 1 to 100 nm, and their properties are influenced by factors such as composition, phase, size, and shape. Single-source precursors (SSPs) offer a promising method for controlling the synthesis of phase-pure nanoparticles with the desired stoichiometry and have been successfully applied to prepare transition metal and lanthanide NPs. SSPs are molecular compounds that contain all the necessary components to form the final nanomaterial and decompose under mild conditions, such as heating, to create the solid-state product. The objective of this work was to garner a mechanistic understanding of cerium oxide NP formation from cerium SSPs. To achieve these goals, first, ligands with oxygen and sulfur donor atoms were synthesized; among the array of ligands synthesized, some were novel. These ligands were then chelated to cerium ions to synthesize cerium precursors. Initially, known cerium alkoxide precursors were synthesized. Subsequently, these basic cerium complexes were further manipulated through acid-base protonolysis reactions to install a diverse set of ligands. Within this body of work, 10 novel cerium precursors were successfully synthesized. The ligands and the SSPs were analyzed using nuclear magnetic resonance (NMR) and thermogravimetric analysis coupled with differential scanning calorimetry (TGA-DSC). These SSPs were then introduced to a collision-induced dissociation mass spectrometer (CID-MS), and their dissociation pathways were studied.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2024

Synthesis of cerium precursors with alkoxide ligands for degradation to cerium oxide nanoparticles

Lanthanide oxide and sulfide nanoparticles present intriguing theoretical questions regarding their electronic structures, alongside numerous potential applications in material science and catalysis. Although these materials can be formed through hydrolysis, their synthesis via thermolysis is crucial for nanoscale materials and practical applications. This research aims to enhance our understanding of the decomposition mechanisms by focusing on cerium compounds, which are analogous to those studied previously. Currently, our knowledge of the decomposition mechanisms of cerium alkoxide precursors is limited. The objective of this project is to develop a mechanistic understanding of the formation of cerium oxide nanoparticles from cerium alkoxide precursors, employing a variety of techniques. These techniques include collision-induced dissociation in an ion-trap mass spectrometer, nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis coupled with differential scanning calorimetry (TGA-DSC), and gas chromatography-mass spectrometry (GC-MS) to investigate the decomposition mechanisms of the synthesized precursors.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2014

Low temperature magnetic phase transition and interlayer coupling in double-wall carbon nanotubes

The magnetic properties of double wall carbon nanotubes (DWCNTs) were investigated using electron spin resonance (ESR) spectroscopy. An asymmetric resonance line of low intensity was identified and analyzed by the superimposition of a narrow and a broad metallic lineshape, attributed to the distinct contributions of defect spins located on the inner and outer DWCNTs shells. The spin susceptibilities of both ESR components revealed a ferromagnetic phase transition at low temperatures (T < 10 K) with small variation in the corresponding Curie-Weiss temperatures, approaching closely that of metallic single wall carbon nanotubes. Interlayer coupling between the DWCNT layers is suggested to effectively reduce the difference between the transition temperatures for the inner and outer shells and enhance spin-spin interactions between defect spins via the RKKY-type interaction of localized spins with conduction electrons.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Static and dynamic properties of vortex pairs in asymmetric nanomagnets

Stacked spin-vortex pairs in magnetic multilayered nanopillars, with vertical separation between the vortices small compared to the vortex core size and pure magnetostatic coupling, exhibit spin dynamics absent in individual vortices. This dynamics is nonlinear and is due to the strong direct core-core coupling in the system, dominating energetically for small-signal excitation. We observe and explain the appearance of spin resonance modes, forbidden within linear dynamics, and discuss how they depend on the magnetic and morphological asymmetries in the samples.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Tuning the reactivity of carbon surfaces with oxygen-containing functional groups

Oxygen-containing carbons are promising supports and metal-free catalysts for many reactions. However, distinguishing the role of various oxygen functional groups and quantifying and tuning each functionality is still difficult. Here we investigate the role of Brønsted acidic oxygen-containing functional groups by synthesizing a diverse library of materials. By combining acid-catalyzed elimination probe chemistry, comprehensive surface characterizations, 15N isotopically labeled acetonitrile adsorption coupled with magic-angle spinning nuclear magnetic resonance, machine learning, and density-functional theory calculations, we demonstrate that phenolic is the main acid site in gas-phase chemistries and unexpectedly carboxylic groups are much less acidic than phenolic groups in the graphitized mesoporous carbon due to electron density delocalization induced by the aromatic rings of graphitic carbon. The methodology can identify acidic sites in oxygenated carbon materials in solid acid catalyst-driven chemistry.

Zhou, Jiahua↗
DOE OSTI2014

Micro-coil detection of nuclear magnetic resonance for nanofluidic samples

We have developed a novel dc SQUID system with a micro-coil input circuit to act as a local probe of quantum matter and nanosystems. The planar niobium micro-coil pickup loop is located remotely from the SQUID, coupled through a superconducting twisted pair. A high degree of coupling between the coil and the region of interest of similar dimensions (up to ∼ 100 microns) can be achieved. We report nuclear magnetic resonance (NMR) measurements to characterise the sensitivity of these coils to {sup 3}He in the gas phase at 4.2 K in a 30 mT magnetic field.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Combinatorial split-ring and spiral metaresonator for efficient magnon-photon coupling

Developing hybrid materials and structures for electromagnetic wave engineering has been a promising route towards novel functionalities and tunabilities in many modern applications. Despite its established success in engineering optical light and terahertz waves, the implementation of metaresonators operating in the microwave band is still emerging, especially the implementation of metaresonators that allow on-chip integration and size miniaturization, which is crucial for developing hybrid quantum systems in the microwave band. In this work, we present a microwave metaresonator consisting of split-ring and spiral resonators, and implement it for the investigation of photon-magnon coupling for hybrid magnonic applications. We observe broadened bandwidth of the split-ring modes augmented by the additional spiral resonator, and, by coupling the modes to a magnetic sample, the resultant photon-magnon coupling can be significantly enhanced by more than tenfold. Furthermore, our work suggests that combinatorial, hybrid microwave resonators may be a promising approach towards future development and implementation of photon-magnon coupling in hybrid magnonic systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Coupling of microwave magnetic dynamics in thin ferromagnetic films to stripline transducers in the geometry of the broadband stripline ferromagnetic resonance

We constructed a quasi-analytical self-consistent model of the stripline-based broadband ferromagnetic resonance (FMR) measurements of ferromagnetic films. Exchange-free description of magnetization dynamics in the films allowed us to obtain simple analytical expressions. They enable quick and efficient numerical simulations of the dynamics. With this model, we studied the contribution of radiation losses to the ferromagnetic resonance linewidth, as measured with the stripline FMR. We found that for films with large conductivity of metals the radiation losses are significantly smaller than for magneto-insulating films. Excitation of microwave eddy currents in these materials contributes to the total microwave impedance of the system. This leads to impedance mismatch with the film environment resulting in decoupling of the film from the environment and, ultimately, to smaller radiation losses. We also show that the radiation losses drop with an increase in the stripline width and when the sample is lifted up from the stripline surface. Hence, in order to eliminate this measurement artefact, one needs to use wide striplines and introduce a spacer between the film and the sample surface. The radiation losses contribution is larger for thicker films.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Low-symmetry vacancy-related spin qubit in hexagonal boron nitride

Abstract Point defect qubits in semiconductors have demonstrated their outstanding capabilities for high spatial resolution sensing generating broad multidisciplinary interest. Hexagonal boron nitride (hBN) hosting point defect qubits have recently opened up new horizons for quantum sensing by implementing sensing foils. The sensitivity of point defect sensors in hBN is currently limited by the linewidth of the magnetic resonance signal, which is broadened due to strong hyperfine couplings. Here, we report on a vacancy-related spin qubit with an inherently low symmetry configuration, the VB2 center, giving rise to a reduced magnetic resonance linewidth at zero magnetic fields. The VB2 center is also equipped with a classical memory that can be utilized for storing population information. Using scanning transmission electron microscopy imaging, we confirm the existence of the VB2 configuration in free-standing monolayer hBN.

Chemistry↗
DOE OSTI2014

Interaction between magnetic vortex cores in a pair of nonidentical nanodisks

The coupling of two nonidentical magnetic nanodisks, i.e., with different vortex gyrotropic frequencies, is studied. From the analytical approach, the interactions between the nanodisks along x and y directions (the coupling integrals) were obtained as a function of distance. From the numerical solution of Thiele's equation, we derived the eigenfrequencies of the vortex cores as a function of distance. The motion of the two vortex cores and, consequently, the time dependence of the total magnetization M(t) were derived both using Thiele's equation and by micromagnetic simulation. From M(t), a recently developed method, the magnetic vortex echoes, analogous to the Nuclear Magnetic Resonance spin echoes, was used to compute the distance dependence of the magnetic coupling strength. The results of the two approaches differ by approximately 10%; using one single term, a dependence with distance found is broadly in agreement with studies employing other techniques.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

A comparison of numerical simulations and analytical theory of the dynamics of interacting magnetic vortices

Magnetostatic interactions between vortices in closely spaced planar structures are important for applications including vortex-based magnonic crystals and spin torque oscillator networks. Analytical theories that include magnetostatic interaction effects have been proposed but have not yet been rigorously tested. Here, we compare micromagnetic simulations of the dynamics of magnetic vortices confined in three disks in an equilateral triangle configuration to analytical theories that include coupling. Micromagnetic simulations show that the magnetostatic coupling between the disks leads to splitting of the gyrotropic resonance into three modes and that the frequency splitting increases with decreasing separation. The temporal profiles of the magnetization depend on the vortex polarities and chiralities; however, the frequencies depend only on the polarity combinations and will fall into one of two categories: all polarities equal or one polarity opposite to the others, where the latter leads to a larger frequency splitting. Although the magnitude of the splitting observed in the simulations is larger than what is expected based on purely dipolar interactions, a simple analytical model that assumes dipole-dipole coupling captures the functional form of the frequency splitting and the motion patterns just as well as more complex models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Coherent Magnon–Photon Coupling in the Magnetic Semiconductor CrSBr

Magnon-based hybrid quantum systems are promising candidates for quantum interconnects and quantum sensors, and they offer a rich platform for exploring nonlinear magnonics and cavity–photon interactions. Two-dimensional (2D) van der Waals magnets provide a compact, atomically flat geometry that can be easily integrated into existing quantum circuits, such as superconducting resonators and qubits. Among various 2D magnets, the magnetic semiconductor CrSBr is particularly unique due to its strong spin–exciton, spin–lattice, and magnon–exciton interactions. In this work, we demonstrate coherent coupling between antiferromagnetic (AFM) magnons in CrSBr and microwave photons in a niobium-(Nb)-based-on-chip resonator. We tuned the magnon–photon coupling strength by changing the number of CrSBr flakes integrated into the Nb microwave photon resonators. Furthermore, this work demonstrates the first step toward integrating layered van der Waals 2D magnets into superconducting microwave circuits, with full access for microwave and optical probing.

Electromagnetic radiation↗
DOE OSTI2016

Synthesis and characterization of amorphous mesoporous silica using TEMPO-functionalized amphiphilic templates

Inorganic–organic hybrid materials based on amorphous mesoporous silica containing organized nitroxide radicals within its mesopores have been prepared using the micellar self-assembly of TEOS solutions containing the nitroxide functionalized amphiphile (4-(N,N-dimethyl-N-hexadecylammonium)-2,2,6, 6-tetramethyl-piperidin-N-oxyl-iodide) (CAT-16). This template has been used both in its pure form and in various mixtures with cetyl trimethylammonium bromide (CTAB). The samples have been characterized by chemical analysis, N{sub 2} sorption studies, magnetic susceptibility measurements, and various spectroscopic methods. While electron paramagnetic resonance (EPR) spectra indicate that the strength of the intermolecular spin–spin interactions can be controlled via the CAT-16/CTAB ratio, nuclear magnetic resonance (NMR) data suggest that these interactions are too weak to facilitate cooperative magnetism. - Graphical abstract: The amphiphilic radical CAT-16 is used as a template for the synthesis of amorphous mesoporous silica. The resulting paramagnetic hybrid materials are characterized by BET, FTIR, NMR, EPR and magnetic susceptibility studies. - Highlights: • Amphiphilic CAT-16 as a template for mesoporous silica. • Comprehensive structural characterization by BET, FTIR; EPR and NMR. • Strength of radical-radical interactions tuable within CAT-16/CTAB mixtures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Hemicellulose Modulates Nanoscale Lignin Architecture in Synthetic Plant Cell Walls

Cellulose, hemicellulose, and lignin─the most abundant biopolymers on Earth─compose the structural matrix of plant biomass, providing renewable resources critical to bioenergy and sustainable materials. Despite their importance, the nanoscale mechanochemical processes underlying lignocellulose assembly during plant secondary cell wall formation remain poorly understood, hindering advancements in biomass conversion technologies. Here, in this study, we synthesize a biomimetic model system comprising cellulose–hemicellulose nanofibrils (CHN) to examine guaiacyl lignin polymerization in a physiologically relevant context. Using advanced nanocharacterization─scattering-type scanning near-field optical microscopy (s-SNOM) with infrared nanospectroscopy coupled to solid-state nuclear magnetic resonance (NMR)─we reveal that hemicellulose presence considerably modulates lignin deposition and alters its interunit bond distribution. Specifically, hemicellulose-rich environments dramatically reduce lignin deposition by approximately 50% and yield highly condensed lignin structures characterized by severely reduced β–O–4′ linkages (<2%) and suppressed β–β′ linkages. Conversely, cellulose-alone scaffolds support notably higher β–O–4′ content (∼10%), resulting in a more uniform nanoscale lignin coating. Our work helps explain how accessible hemicellulose sites, both sterically and chemically, direct radical coupling during lignification, fundamentally reshaping lignin’s nanoscale architecture. These findings deepen our mechanistic understanding of plant cell wall biosynthesis and inform strategies aimed at enhancing biomass deconstruction efficiency for sustainable bioenergy applications.

NMR↗
DOE OSTI2014

Spin counting in electrically detected magnetic resonance via low-field defect state mixing

The work herein describes a method that allows one to measure paramagnetic defect densities in semiconductor and insulator based devices with electrically detected magnetic resonance (EDMR). The method is based upon the mixing of defect states which results from the dipolar coupling of paramagnetic sites at low magnetic fields. We demonstrate the measurement method with spin dependent tunneling in thin film dielectrics; however, the method should be equally applicable to paramagnetic defect density measurements in semiconductors via the more commonly utilized EDMR technique called spin dependent recombination.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Ferromagnetic resonance in a single crystal of iron borate and magnetic field tuning of hybrid oscillations in a composite structure with a dielectric: Experiment and theory

The high-frequency properties of a composite resonator comprised single crystal iron borate (FeBO{sub 3}), a canted antiferromagnet with a weak ferromagnetic moment, and a polycrystalline dielectric were investigated at 9–10 GHz. Ferromagnetic resonance in this frequency range was observed in FeBO{sub 3} for bias magnetic fields of ∼250 Oe. In the composite resonator, the magnetic mode in iron borate and dielectric mode are found to hybridize strongly. It is shown that the hybrid mode can be tuned with a static magnetic field. Our studies indicate that coupling between the magnetic mode and the dielectric resonance can be altered from maximum hybridization to a minimum by adjusting the position of resonator inside the waveguide. Magnetic field tuning of the resonance frequency by a maximum of 145 MHz and a change in the transmitted microwave power by as much as 16 dB have been observed for a bias field of 250 Oe. A model is discussed for the magnetic field tuning of the composite resonator and theoretical estimates are in reasonable agreement with the data. The composite resonator with a weak ferromagnet and a dielectric is of interest for application in frequency agile devices with electronically tunable electrodynamic characteristics for the mm and sub-mm wave bands.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗