Terahertz Spectroscopy of Spin Waves in Multiferroic BiFeO 3 in High Magnetic Fields
Not Available
Nagel, U.↗
SEARCH · Engineering Papers
Results for “MAGNET”
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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X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu
Not Available
Kukreja, R.↗
Magnetic Interactions at the Nanoscale in Trilayer Titanates
We report on the phase diagram of competing magnetic interactions at the nanoscale in engineered ultrathin trilayer heterostructures of LaTiO3/SrTiO3/YTiO3, in which the interfacial inversion symmetry is explicitly broken. Combined atomic layer resolved scanning transmission electron microscopy with electron energy loss spectroscopy and electrical transport have confirmed the formation of a spatially separated two-dimensional electron liquid and high density two-dimensional localized magnetic moments at the LaTiO3/SrTiO3 and SrTiO3/YTiO3 interfaces, respectively. Resonant soft x-ray linear dichroism spectroscopy has demonstrated the presence of orbital polarization of the conductive LaTiO3/SrTiO3 and localized SrTiO3/YTiO3 electrons. Our results provide a route with prospects for exploring new magnetic interfaces, designing a tunable two-dimensional d-electron Kondo lattice, and potential spin Hall applications.
Cao, Yanwei↗
Structure of a magnetic flux annihilation layer formed by the collision of supersonic, magnetized plasma flows
We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and magnetized aluminum plasma flows. The anti parallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T i ~¯ZT e , with average ionization ¯Z=7). Lastly, analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the in-flowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.
42 ENGINEERING↗
Local Orthorhombicity in the Magnetic C 4 Phase of the Hole-Doped Iron-Arsenide Superconductor Sr 1 - x Na x Fe 2 As 2
We report on temperature-dependent pair distribution function measurements of Sr 1-x Na x Fe 2 As 2 , an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C 4 phase. Quantitative refinements indicate that the instantaneous local structure in the C 4 phase comprises fluctuating orthorhombic regions with a length scale of similar to 2 nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. Furthermore, these results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C 4 phase and the neighboring C 2 and superconducting phases.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Magnetic Damping Modulation in IrMn 3 / Ni 80 Fe 20 via the Magnetic Spin Hall Effect
Noncollinear antiferromagnets can have additional spin Hall effects due to the net chirality of their magnetic spin structure, which provides for more complex spin-transport phenomena compared to ordinary nonmagnetic materials. Here we investigated how ferromagnetic resonance of permalloy (Ni 80 Fe 20 ) is modulated by spin Hall effects in adjacent epitaxial IrMn 3 films. We observe a large dc modulation of the ferromagnetic resonance linewidth for currents applied along the [001] IrMn 3 direction. Furthermore, this very strong angular dependence of spin-orbit torques from dc currents through the bilayers can be explained by the magnetic spin Hall effect where IrMn 3 provides novel pathways for modulating magnetization dynamics electrically.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Disorder-Enriched Magnetic Excitations in a Heisenberg-Kitaev Quantum Magnet Na 2 Co 2 TeO 6
Using optical magnetospectroscopy, we investigate the magnetic excitations of Na 2 Co 2 TeO 6 in a broad magnetic field range (0 T ≤ B ≤ 17.5 T) at low temperature. Our measurements reveal rich spectra of in-plane magnetic excitations with a surprisingly large number of modes, even in the high-field spin-polarized state. Theoretical calculations find that the Na-occupation disorder in Na 2 Co 2 TeO 6 plays a crucial role in generating these modes. Our Letter demonstrates the necessity to consider disorder in the spin environment in the search for Kitaev quantum spin liquid states in practicable materials.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Magnetic and Mechanical Design of a 15-T Large Aperture Dipole Magnet for Cable Testing
© 2019 IEEE. A large aperture Nb 3 Sn dipole is proposed to replace the magnet assembly of EDIPO, which was irreversibly damaged in 2016. The goal is to generate a background field of 15 T at 4.2 K in a clear aperture of approximately 100×150 mm 2 and over a uniform length of 1000 mm in order to test superconducting cables for both fusion and high-energy physics applications. The magnet features a block-type coil design wound with wide Rutherford cable (two alternative coil cross sections are considered) and supported by a mechanical structure based on keys-and-bladders technology. In the end regions, the coils tilt up (flare) through a hard-way bend of the cables to provide room for the test well, following a layout already adopted in the LBNL HD2 and CERN-CEA FRESCA2 magnets. The two considered coil design alternatives aim at minimizing the mechanical stress in the coil windings. One coil pack design makes the use of two double pancake coils per pole, whereas the other alternative features three double pancakes per pole. Both design options are presented focusing on the results of numerical computations carried out with finite-element models to investigate peak stresses in the coils during room-temperature pre-loading, cool down, and powering.
Sarasola, Xabier (ORCID:0000000324306939)↗
Experimental characterization of magnetic materials for the magnetic shielding of cryomodules in particle accelerators
The magnetic properties of two important passive magnetic shielding materials (A4K and Amumetal) for accelerator applications, subjected to various processing and heat treatment conditions are studied comprehensively over a wide range of temperatures: from cryogenic to room temperature. Furthermore, we analyze the effect of processing on the extent of degradation of the magnetic properties of both materials and investigate the possibility of restoring these properties by re-annealing.
43 PARTICLE ACCELERATORS↗
Equal channel angular extrusion for bulk processing of Fe–Co–2V soft magnetic alloys, part II: Texture analysis and magnetic properties
In Part I, equal channel angular extrusion (ECAE) was demonstrated as a novel, simple-shear deformation process for producing bulk forms of the low ductility Fe–Co–2V (Hiperco 50A®) soft ferromagnetic alloy with refined grain sizes. Microstructures and mechanical properties were discussed. In this Part II contribution, the crystallographic textures and quasi-static magnetic properties of ECAE-processed Hiperco were characterized. The textures were of a simple-shear character defined by partial {110} and <111> fibers inclined relative to the extrusion direction, in agreement with the expectations for simple-shear deformation textures of BCC metals. These textures were observed throughout all processing conditions and only slightly reduced in intensity by subsequent recrystallization heat treatments. Characterization of the magnetic properties revealed a lower coercivity and higher permeability for ECAE-processed Hiperco specimens relative to the conventionally processed and annealed Hiperco bar. In conclusion, the effects of the resultant microstructure and texture on the coercivity and permeability magnetic properties are discussed.
36 MATERIALS SCIENCE↗
Magnetic Shielding with Soft Magnetic Alloys
Abnormal electrical environments receive a lot of attention from nuclear safety engineers, but less attention has been paid to the magnetic effects that accompany such environments. Engineers with backgrounds outside of physics or electrical engineering may not be as familiar with this topic; this report serves as a brief summary of the phenomena and proposes experiments to support practical engineering solutions. Lightning strikes, in particular, create an environment hazardous to electronics, especially to components that rely on magnetic coupling for normal function. The most direct method of mitigating unwanted magnetic effects caused by lightning is to shield the component of interest; several materials and configuration options are explained here. An experimental approach is recommended to validate numerical modeling.
42 ENGINEERING↗
The application of macroscopic flakes for Fe-6.5%Si bulk magnetics with superior magnetic properties
Silicon steel is the most popular crystalline soft magnetic material for motor and transformer applications. The material must be in thin thickness to reduce the eddy current loss. Conventional thin steel sheet manufacturing process starts with cast slab, followed by a series of hot/cold roll process. For transformer, thin sheet is wrapped to form the core; for motor, the sheet is stamped, coated, heat treated, and stacked to form stator/rotor. This process requires the steel to possess sufficient ductility. For Si steel, increasing Si content will improve its electrical and magnetic properties, but it will also lead to embrittlement with 3.5% Si as the limit for the conventional manufacturing processes. Despite poor mechanical properties, high Si steel, especially the one with 6.5% Si, is gaining more attention due to its lower iron loss, higher permeability, and near zero magnetostriction. To address the brittleness problem of the 6.5% Si steel, we developed a novel process, using rapid solidification to prepare thin flakes with high ductility, then using hot press to consolidate the flakes into near net shape bulk sample. The obtained Fe-6.5%Si sample with 0.2 mm thickness exhibits an iron loss of 7.2 W/kg at 400Hz and magnetic flux density of 1 Tesla, and a maximum permeability of 28,400. In addition, various coating materials and processes were investigated as inter-flake insulators for their effect on reducing the eddy current losses for thicker configuration.
Fe-6.5%Si Steel↗
Magnetic Field Sensing via Optically Detected Magnetic Resonance and Spin Relaxometry Using Nitrogen Vacancies in Nanodiamonds
Quantum sensing is broadly defined as the use of quantum materials, quantum coherence, and/or quantum entanglement to measure physical quantities and/or to enhance the sensitivity of classical analytical measurements. Certain materials exhibit interesting quantum properties that have the potential to be utilized in quantum sensing applications. One such quantum property is electronic spin, which is utilized in this work. Here, we built a custom apparatus capable of conducting both optically detected magnetic resonance (ODMR) and spin relaxometry. The quantum material investigated was an ensemble of nitrogen vacancies (NV) in nanodiamonds. We have characterized the system and measured ODMR spectra for different strengths of the applied DC magnetic field and clearly observed the expected splitting of the resonances due to Zeeman splitting. We also have measured the spin relaxation times for two different powers of the applied AC magnetic field. The lower power dataset exhibited expected exponential temporal dependence of the relaxation of a modified spin state, whereas the higher power dataset exhibited stretched exponential dependence of the evolution of the modified spin state, indicating the presence of high-power phenomena that emerge that retard the relaxation of the spin state.
Lander, Gary↗
Applied Magnetic Field Increases Magnetic Anisotropy in HDDR-Processed Nd-Fe-B Alloy
We investigate the effect of an applied magnetic field on the entire HDDR process using a customized reactor vessel and a warm-bore superconducting magnet. We analyzed the resulting properties produced at both a 0 applied field and a 2 Tesla applied field. We show that the application of a magnetic field throughout the HDDR process results in powders that exhibit a greater level of anisotropy compared to their ambient field counterparts.
36 MATERIALS SCIENCE↗
Progress on the experimental search for the chiral magnetic effect, the chiral vortical effect, and the chiral magnetic wave
In quantum chromodynamics, the interactions of quarks with the topological gluon field can lead to nonconservation of local parity (P) and conjugated parity (CP) , which provides a solution to the strong CP problem and a possibility to explain the asymmetry of matter-antimatter in the current universe. Under the action of a strong magnetic field, the nonconservation of P and CP can lead to the separation of particles according to their electric charges, which is called the chiral magnetic effect (CME). An observation of the CME-induced charge separation will confirm several fundamental properties of quantum chromodynamics (QCD), namely, approximate chiral symmetry restoration, topological charge fluctuation, and local parity violation. In relativistic heavy-ion collisions, there are other chiral anomalous effects similar to the CME, such as the chiral vortical effect (CVE) and the chiral magnetic wave (CMW). This review briefly summarizes the current progress of experimental research on the CME, CVE, and CMW in relativistic heavy-ion collisions.
Physics↗
System and method for magnetic current density imaging at ultra low magnetic fields
Preferred systems can include an electrical impedance tomography apparatus electrically connectable to an object; an ultra low field magnetic resonance imaging apparatus including a plurality of field directions and disposable about the object; a controller connected to the ultra low field magnetic resonance imaging apparatus and configured to implement a sequencing of one or more ultra low magnetic fields substantially along one or more of the plurality of field directions; and a display connected to the controller, and wherein the controller is further configured to reconstruct a displayable image of an electrical current density in the object. Preferred methods, apparatuses, and computer program products are also disclosed.
60 APPLIED LIFE SCIENCES↗