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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Spin Glasses: Old and New Complexity

Spin glasses are disordered magnetic systems that exhibit a variety of properties that are characteristic of 'complex systems'. After a brief review of the systems themselves, I will discuss how spin glass concepts have found use in and, in some cases, further advanced areas such as computer science, biology, and other fields: what one might term 'old complexity'. I will then turn to a discussion of more recent concepts and ideas that have flowed from studies of spin glasses, and using these introduce a proposal for a kind of 'new complexity'.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Phase diagram of CeSb 2 from magnetostriction and magnetization measurements: Evidence for ferrimagnetic and antiferromagnetic states

Cerium diantimonide (CeSb 2 ) is one of a family of rare-earth-based magnetic materials that exhibit metamagnetism, enabling control of the magnetic ground state through an applied magnetic field. At low temperatures, CeSb 2 hosts a rich phase diagram with multiple magnetically ordered phases for many of which the order parameter is only poorly understood. In this work, we report a study of its metamagnetic properties by scanning tunneling microscopy (STM) and magnetization measurements. We use STM measurements to characterize the sample magnetostriction with subpicometer resolution from magnetic field and temperature sweeps. This allows us to directly assess the bulk phase diagram as a function of field and temperature and relate spectroscopic features from tunneling spectroscopy to bulk phases. Our magnetostriction and magnetization measurements indicate that the low-temperature ground state at zero field is ferrimagnetic. Quasiparticle interference mapping shows evidence for a reconstruction of the electronic structure close to the Fermi energy upon entering the magnetically ordered phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Demagnetization of Nd 2 Fe 14 B, Pr 2 Fe 14 B, and Sm 2 Co 17 Permanent Magnets in Spallation Irradiation Fields

Prompted by the need for radiation-resistant permanent magnets for insertion devices (IDs) of high-brilliance next-generation synchrotrons such as the National Synchrotron Light Source II, the demagnetization of Nd 2 Fe 14 B and Pr 2 Fe 14 B was studied after exposure to a mixed irradiating field. Degradation and damage of the permanent magnetic material by components of electromagnetic showers induced in magnets by intense high-energy electron beams will alter the magnetic field structure of the IDs. Plate-like Nd 2 Fe 14 B magnets were irradiated to 1.8 Grad dose and were evaluated against Pr 2 Fe 14 B magnets irradiated to a lower dose of 20 Mrad. In addition, annular Sm 2 Co 17 and Nd 2 Fe 14 B magnets integrated within a ferrofluidic feedthrough (FFFT) rotary seal were also irradiated to dose levels of 2 Grad for Sm 2 Co 17 and 20 Mrad for Nd 2 Fe 14 B. Post-irradiation measurements of the magnetic intensity revealed that severe demagnetization exceeding 85% occurs in Nd 2 Fe 14 B magnets after only 50 Mrad dose and over 87% for Pr 2 Fe 14 B after 10 Mrad dose. The annular-shaped Sm 2 Co 17 magnets of the FFFTs were almost insensitive to irradiation up to a dose of 2 Grad. Annular-shaped Nd 2 Fe 14 B magnets also showed resistance to demagnetization, a direct consequence of the annular shape which is characterized by the removal of the stronger demagnetizing field present at the center of a disk-like magnet. As a result, the sensitivity of boron-based permanent magnets to neutron energy (thermal versus fast) was also assessed via specifically designed experiments and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

High Temperature 300°C Measurement While Drilling System

Many countries around the world, including the USA, have untapped geothermal energy potential. Enhanced Geothermal Systems (EGS) technology is needed to economically utilize this resource. Temperatures in some EGS reservoirs can exceed 300°C. To effectively utilize EGS resources, an array of injection and production wells must be accurately placed in the formation fracture network. Therefore, EGS can greatly benefit from a high temperature directional drilling system. Most commercial services for directional drilling systems are rated for 175°C while geothermal wells require operation at much higher temperatures. Two U.S. Department of Energy (DOE) Geothermal Technologies Office (GTO) projects have been initiated to develop a 300°C capable directional drilling system, the first developing a drill bit, directional motor, and drilling fluid (award number DE-EE0002782), and the second adding navigation and telemetry systems. This report is for the second project, “High Temperature 300°C Measurement While Drilling System”, award number DE-EE0005505. The “High Temperature 300°C Measurement While Drilling (MWD)” system complements the already developed drilling system with real time navigation capability. It is comprised of 175°C directional measurement electronics including the required sensors for measuring inclination and azimuth in 3 axes. It is embedded in a cooling and temperature isolation system to protect the electronics and sensors from the higher temperature outside the system, which can reach 300°C. Building the cooling and isolation system from non-magnetic materials and keeping a required distance to any magnetic component, such as alternator parts, ensures a high quality measurement of the earth’s magnetic field. This is required to achieve the specified navigation accuracy. The MWD system has a turbine driven alternator that is capable of delivering the required electrical energy to the electronic system at a 300°C borehole temperature. Measured data will be communicated to the surface by mud-pulse-telemetry. For this purpose the tool has a mud-pulse-valve that is controlled by the measurement electronics to establish a serial data communication via the mud stream. The mud-pulse-valve is also built to operate under 300°C borehole conditions. Three prototypes of the 300°C MWD were built and tested. These systems are available for a joint application with the previously developed 300°C drilling system, in a geothermal well.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

2021 Annual Progress Report: Vertical GaN Device Development

This project is part of a multi-lab consortium that leverages U.S. research expertise and facilities at national labs and universities to significantly advance electric drive power density and reliability, while simultaneously reducing cost. The final objective of the consortium is to develop a 100 kW traction drive system that achieves 33 kW/L, has an operational life of 300,000 miles, and a cost of less than 6 dollars/kW. One element of the system is a 100 kW inverter with a power density of 100 kW/L and a cost of 2.7 dollars/kW. New materials such as wide-bandgap semiconductors, soft magnetic materials, and ceramic dielectrics, integrated using multi-objective co-optimization design techniques, will be utilized to achieve these program goals. This project focuses on a subset of the power electronics work within the consortium, specifically the design, fabrication, and evaluation of vertical GaN power devices suitable for automotive applications.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Epitaxial Electrodeposition of Wide Bandgap Semiconductors for Energy Conversion and Storage

The focus of this project was to electrodeposit epitaxial films and nanostructures of inorganic materials. Although electrodeposition is normally associated with the electroplating of metals, the emphasis in this work was the deposition of compound materials such as metal oxides, semiconductors, catalysts, and magnetic materials. An electrochemical/chemical approach was used, in which an electrochemical redox reaction was followed by a chemical reaction to produce the product. The materials were deposited as epitaxial thin films or nanostructures onto a single-crystal substrate that determined their in-plane and out-of-plane orientation. Epitaxial films can have enhanced properties due to the lack of grain boundaries. They can also produce catalytic materials which have enhanced reactivity due to the exposure of the most catalytically active surface. A method was developed to produce inexpensive single-crystal-like metal foils that could be used as the substrate to deposit materials for applications such as flexible electronics. It was also demonstrated that epitaxial films of inorganic materials could be produced by a simple spin-coating technique.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Fabrication and test of a space power boiler feed electromagnetic pump. Part 1: Design and manufacture of pump

A three-phase helical induction electromagnetic (EM) pump has been designed and built. This pump was designed for use as the boiler-feed pump of a potassium Rankine-cycle space electric power system. The pump is constructed of high temperature materials including a T-111 duct, Hiperco 27 magnetic material, nickel clad silver conductor wire, and a completely inorganic insulation system. The pump is designed to deliver 3.25 lb/sec potassium at 1000 F with a developed head of 240 psi while being cooled by 800 F NaK. At these conditions, the overall pump efficiency is expected to be 18%.

Gahan, J. W.↗
NASA NTRS1988

Tool For Tinning Integrated-Circuit Leads

As many as eight flatpacks held. Tool made of fiberglass boards. Clamps row of flatpacks by their leads so leads on opposite side of packages dipped. After dipping, nuts on boards loosened, flatpacks turned around, nuts retightened, and untinned leads dipped. Strips of magnetic material grip leads of flatpacks (made of Kovar, magnetic iron/nickel/cobalt alloy) while boards repositioned. Micrometerlike screw used to adjust exposed width of magnetic strip to suit dimensions of flatpacks. Holds flatpack integrated circuits so leads tinned. Accommodates several flatpacks for simultaneous dipping of leads in molten solder. Adjusts to accept flatpacks in range of sizes.

Prosser, Gregory N.↗
NASA NTRS1990

Magnetic suspension and balance system advanced study, phase 2

The design improvements for the system encompass 14 or 18 external superconductive coils mounted on a 8 x 8 foot wind tunnel, a superconductive model core magnet on a holmium mandrel to fit an F-16 model, model wings of permanent magnet material Nd2Fe14B, and fiber glass epoxy structure. The Magnetic Suspension and Balance System (MSBS) advanced design is confirmed by the successful construction and test of a full size superconductive model core solenoid with holmium mandrel. The solenoid is 75 cm long and 12.6 cm in diameter and produces 6.1 tesla for a hold time of 47 minutes. An integrated coil system design of a new compact configuration without specific coils for roll or pitch shows promise of simplicity; magnet reductions of 30 percent compared to the most recent 1985 design are possible.

Boom, R. W.↗
NASA NTRS1993

Magnetic bearing turbomachinery case histories and applications for space related equipment

The concept of magnetic levitation is not a new one and can be easily traced back to the 1800's. It is only recently, however, that the congruous technologies of electronic control systems, power electronics, and magnetic materials have begun to merge to make the magnetic suspension device a viable product. A brief overview of an active magnetic bearing technology is provided. Case histories of various turbomachinery in North America presently operating on magnetic bearings are reviewed. Finally, projections are made as to the space related machinery that may be benefited by incorporating magnetic bearings into the equipment design.

Weise, David A.↗
NASA NTRS2004

Cryogenic Characterization and Testing of Magnetically-Actuated Microshutter Arrays for the James Webb Space Telescope

Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (approximately 35 K) spectrographic astronomy measurements in the near-infrared region. Functioning as a focal plane object selection device, the MSA is a 2-D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA are close- packed silicon nitride shutters (cell size of 100 x 200 microns) patterned with a torsion flexure to allow opening to 90 degrees. A layer of magnetic material is deposited onto each shutter to permit magnetic actuation. Two electrodes are deposited, one onto each shutter and another onto the support structure side-wall, permitting electrostatic latching and 2-D addressing. New techniques were developed to test MSA under mission-similar conditions (8 K less than or equal to T less than 300K). The magnetic rotisserie has proven to be an excellent tool for rapid characterization of MSA. Tests conducted with the magnetic rotisserie method include accelerated cryogenic lifetesting of unpackaged 128 x 64 MSA and parallel measurement of the magneto-mechanical stiffness of shutters in pathfinder test samples containing multiple MSA designs. Lifetest results indicate a logarithmic failure rate out to approximately 10(exp 6) shutter actuations. These results have increased our understanding of failure mechanisms and provide a means to predict the overall reliability of MSA devices.

King, T. T.↗
NASA NTRS2007

Resonant Tunneling Spin Pump

The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

Ting, David Z.↗
DOE OSTI2015

Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na 2 IrO 3

We show that heisenberg interactions are ubiquitous in magnetic materials and play a central role in modelling and designing quantum magnets. Bond-directional interactions offer a novel alternative to Heisenberg exchange and provide the building blocks of the Kitaev model, which has a quantum spin liquid as its exact ground state. Honeycomb iridates, A 2 IrO 3 (A = Na, Li), offer potential realizations of the Kitaev magnetic exchange coupling, and their reported magnetic behaviour may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-directional interactions has so far been indirect. Here we present direct evidence for dominant bond-directional interactions in antiferromagnetic Na 2 IrO 3 and show that they lead to strong magnetic frustration. Diffuse magnetic X-ray scattering reveals broken spin-rotational symmetry even above the Néel temperature, with the three spin components exhibiting short-range correlations along distinct crystallographic directions. Lastly, this spin- and real-space entanglement directly uncovers the bond-directional nature of these interactions, thus providing a direct connection between honeycomb iridates and Kitaev physics.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Magneto-Dielectric Effects Induced by Optically-Generated Intermolecular Charge-Transfer States in Organic Semiconducting Materials

Traditionally, magneto-dielectric effects have been developed by combining ferroelectric and magnetic materials. Here, we show a magneto-dielectric effect from optically-generated intermolecular charge-transfer states in an organic semiconducting donor:acceptor (PVK:TCNB) system. We observe in magnetic field effects of photoluminescence that a magnetic field can change singlet/triplet population ratio in intermolecular charge-transfer states. Furthermore, our theoretical analysis and experimental evidence indicate that the singlets and triplets in charge-transfer states have stronger and weaker electrical polarizations, respectively. Therefore, the observed magneto-dielectric effect can be attributed to magnetically-dependent singlet/triplet ratio in intermolecular charge-transfer states. In principle, a magneto-dielectric effect can be generated through two different channels based on magneto-polarization and magneto-current effects when the singlet/triplet ratio in intermolecular charge-transfer states is changed by a magnetic field. We find, from the simulation of dielectric effects, that magneto-polarization and magneto-current effects play primary and secondary roles in the generation of magneto-dielectric effect.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Liquid-like spin dynamics in a hybrid Heisenberg-Ising antiferromagnet

Two-dimensional (2D) materials and their heterostructures enable unconventional electronic properties and functionalities not accessible in their bulk counterparts. This approach is now being extended to magnetic materials to engineer their spin structures and magnetic fields produced by them. However, spin dynamics of 2D magnetic heterostructures remain largely unexplored. Here, we demonstrate that heterointerfacing Heisenberg square-lattice antiferromagnet (AF) Sr 2 IrO 4 with its bilayer variant Ising AF Sr 3 Ir 2 O 7 in a superlattice leads to liquid-like spin dynamics in the former, characterized by slow recovery of the AF order after its transient suppression by an optical pump, and complete absence of spin waves except in an immediate vicinity of the ordering wavevector. Instead, the spin excitation spectra are dominated by isotropic continua, which in previous works have been interpreted as fractional spin excitations, or spinons, that extends to unprecedentedly low energies. Thus, our results provide a pathway to frustrated magnetism in square lattices by heterointerfacing two distinct types of AFs.

RIXS↗
DOE OSTI2018

Stochastic nature of magnetic processes studied by full-field soft X-ray microscopy

In nanomagnetism, one of the crucial scientific questions is whether magnetic behaviors are deterministic or stochastic on a nanoscale. Apart from the exciting physical issue, this question is also of paramount highest relevance for using magnetic materials in a wealth of technological applications such as magnetic storage and sensor devices. In the past, the research on the stochasticity of a magnetic process has been mainly done by macroscopic measurements, which only offer ensemble-averaged information. To give more accurate answer for the question and to fully understand related underlying physics, the direct observation of statistical behaviors in magnetic structures and magnetic phenomena utilizing advanced characterization techniques is highly required. One of the ideal tools for such study is a full-field soft X-ray microscope since it enables imaging of magnetic structures on the large field of view within a few seconds. Here in this paper, we review the stochastic behaviors of various magnetic processes including magnetization reversal process in thin films, magnetic domain wall motions in nanowires, and magnetic vortex formations in nanodisks studied by full-field soft X-ray microscopy. The origin triggering the stochastic nature witnessed in each magnetic process and the way to control the intrinsic nature are also discussed.

36 MATERIALS SCIENCE↗