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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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484 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Acceleration Processes in the Cusp: Observations by the FAST Satellite

The Fast Auroral Snapshot (FAST) spacecraft has encountered the Earth's cusp regions near its apogee of 4175 km on numerous occasions during its first two and half years of operations. The cusp encounters are identified by their signatures of keV dispersed ion injections of solar wind origin. The FAST instruments reveal a complex microphysics inherent to many, but not all, of the cusp regions encountered by the spacecraft, that often include upgoing ion beams within regions of downgoing electrons that may appear as series of inverted-V features with energies near a few hundred eV. In many instances, upgoing electron beams have also been observed. Intense (> 100 mV/m) spikey DC-coupled electric fields and plasma waves are common features of the cusp encounters which also provide evidence for the presence of such local acceleration processes. In some cases, the FAST data show clear modulation of the precipitating magnetosheath ions indicative that they are affected by local electric potentials, as evidenced by simultaneous electron acceleration within such intervals. Furthermore, the acceleration events are sometimes organized with an apparent cellular structure that suggest Alfv6n waves or other large scale phenomena are controlling the localized potentials. We examine several cusp encounters in detail in order to study the complex relation of the cusp energetic particle populations with the plasma waves and DC electric fields.

Pfaff, R. F.↗
NASA NTRS2010

Widely Tunable Mode-Hop-Free External-Cavity Quantum Cascade Laser

The external-cavity quantum cascade laser (EC-QCL) system is based on an optical configuration of the Littrow type. It is a room-temperature, continuous wave, widely tunable, mode-hop-free, mid-infrared, EC-QCL spectroscopic source. It has a single-mode tuning range of 155 cm(exp -1) (approximately equal to 8% of the center wavelength) with a maximum power of 11.1 mW and 182 cm(exp -1) (approximately equal to 15% of the center wavelength), and a maximum power of 50 mW as demonstrated for 5.3 micron and 8.4 micron EC-QCLs, respectively. This technology is particularly suitable for high-resolution spectroscopic applications, multi-species tracegas detection, and spectroscopic measurements of broadband absorbers. Wavelength tuning of EC-QCL spectroscopic source can be implemented by varying three independent parameters of the laser: (1) the optical length of the gain medium (which, in this case, is equivalent to QCL injection current modulation), (2) the length of the EC (which can be independently varied in the Rice EC-QCL setup), and (3) the angle of beam incidence at the diffraction grating (frequency tuning related directly to angular dispersion of the grating). All three mechanisms of frequency tuning have been demonstrated and are required to obtain a true mode-hop-free laser frequency tuning. The precise frequency tuning characteristics of the EC-QCL output have been characterized using a variety of diagnostic tools available at Rice University (e.g., a monochromator, FTIR spectrometer, and a Fabry-Perot spectrometer). Spectroscopic results were compared with available databases (such as HITRAN, PNNL, EPA, and NIST). These enable precision verification of complete spectral parameters of the EC-QCL, such as wavelength, tuning range, tuning characteristics, and line width. The output power of the EC-QCL is determined by the performance of the QC laser chip, its operating conditions, and parameters of the QC laser cavity such as mirror reflectivity or intracavity losses. In order to maximize the output power, an analysis and optimization of the EC laser parameters has been performed. The parameters of the beam emitted from the gain medium, such as divergence angle, beam profile, and astigmatism, have been investigated. The gain medium has been fully characterized before and after each stage of modification. The main modification steps are coating one facet of the gain chip with a high reflectivity mirror and the other facet with an anti-reflection layer. Then the chip is mounted in the EC-QCL. The optomechanical design has been reviewed and improved to provide for precise collimation of the strongly divergent beam of the QCL and the tuning diffraction grating.

Wysocki, Gerard↗
NASA NTRS1997

The Stability of Radiatively Cooling Jets I. Linear Analysis

The results of a spatial stability analysis of a two-dimensional slab jet, in which optically thin radiative cooling is dynamically important, are presented. We study both magnetized and unmagnetized jets at external Mach numbers of 5 and 20. We model the cooling rate by using two different cooling curves: one appropriate to interstellar gas, and the other to photoionized gas of reduced metallicity. Thus, our results will be applicable to both protostellar (Herbig-Haro) jets and optical jets from active galactic nuclei. We present analytical solutions to the dispersion relations in useful limits and solve the dispersion relations numerically over a broad range of perturbation frequencies. We find that the growth rates and wavelengths of the unstable Kelvin-Helmholtz (K-H) modes are significantly different from the adiabatic limit, and that the form of the cooling function strongly affects the results. In particular, if the cooling curve is a steep function of temperature in the neighborhood of the equilibrium state, then the growth of K-H modes is reduced relative to the adiabatic jet. On the other hand, if the cooling curve is a shallow function of temperature, then the growth of K-H modes can be enhanced relative to the adiabatic jet by the increase in cooling relative to heating in overdense regions. Inclusion of a dynamically important magnetic field does not strongly modify the important differences between an adiabatic jet and a cooling jet, provided the jet is highly supermagnetosonic and not magnetic pressure-dominated. In the latter case, the unstable modes behave more like the transmagnetosonic magnetic pressure-dominated adiabatic limit. We also plot fluid displacement surfaces associated with the various waves in a cooling jet in order to predict the structures that might arise in the nonlinear regime. This analysis predicts that low-frequency surface waves and the lowest order body modes will be the most effective at producing observable features in the jet.

Hardee, Philip E.↗
NASA NTRS1992

Non-relativistic solar electron events during December 1990 - Results from Ulysses

Several groups of impulsive flare accelerated nonrelativistic solar electron events occurred in November and December 1990. In a total of 18 separate events, most show the characteristic dispersion in arrival times at the Ulysses spacecraft corresponding to travel time for the various particle energy groups. After maximum development, the electron intensities generally decay smoothly with characteristic times of 10 to 15 hours. In a few cases there are marked departures from this 'classic' behavior. On 15 December 1990, these departures are associated with a structure in the interplanetary magnetic field having a width of about 4 x 10 exp 6 km at 1.37 AU. The particle intensities inside this structure varied greatly with spatial position. Some of the changes occurred over distances as small as 3 x 10 exp 4 km. It is believed that this interplanetary structure had its origin in the complex magnetic fields that overlay the solar active region in which the electron accelerating flares occurred, and that it is these fields near the sun that determine access of the flare accelerated electrons to interplanetary field lines. A solar electron event on 11 December 1990 is similar in many respects to the one on 15 December. Neither of these events is directly related to an interplanetary shock wave.

Anderson, K. A.↗
DOE OSTI2024

Interaction-enhanced nesting in spin-fermion and Fermi-Hubbard models

The spin-fermion (SF) model postulates that the dominant coupling between low-energy fermions in near critical metals is mediated by collective spin fluctuations (paramagnons) peaked at the Néel wave vector, Q N , connecting hot spots on opposite sides of the Fermi surface. It has been argued that strong correlations at hot spots lead to a Fermi surface deformation (FSD) featuring flat regions and increased nesting. This conjecture was confirmed in the perturbative self-consistent calculations when the paramagnon propagator dependence on momentum deviation from Q N is given by χ − 1 ∝ | Δ q | . Using diagrammatic Monte Carlo (diagMC) technique we show that such a dependence holds only at temperatures orders of magnitude smaller than any other energy scale in the problem, indicating that a different mechanism may be at play. Instead, we find that a χ − 1 ∝ | Δ q | 2 dependence yields a robust finite- T scenario for achieving FSD. To link phenomenological and microscopic descriptions, we applied the connected determinant diagMC method to the ( t − t ′ ) Hubbard model and found that at large U / t > 5.5 before the formation of electron and hole pockets (i) the FSD defined as a maximum of the spectral function is not very pronounced; instead, it is the lines of zeros of the renormalized dispersion relation that deforms toward nesting, and (ii) the static spin susceptibility is well described by χ − 1 ∝ | Δ q | 2 . Flat FS regions yield a nontrivial scenario for realizing a non-Fermi liquid state. Published by the American Physical Society 2024

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Resistive hose modes in tokamak runaway electron beams II

Resistive hose instabilities of runaway electron (RE) beams immersed in resistive background plasmas are examined with analytic and numerical calculations. The RE beam-plasma equilibria considered are characteristic of the situation observed post-thermal quench in a tokamak disruption. An analytic linear dispersion relation is presented for the case of a uniform RE current density profile with a sharp boundary in cylindrical geometry. Initial value linear calculations for a more general profile in toroidal geometry find that reducing aspect ratio increases the resistive hose mode growth rates with fixed safety factor profile. Nonlinear calculations in cylindrical and toroidal geometry find that the resistive hose instability-driven fluctuations relax the gradient of the current density profile. In toroidal geometry, changes to the magnetic topology are observed as a result of the resistive hose activity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Intermittency, bursty turbulence, and ion and electron phase-space holes formation in collisionless current-carrying plasmas

In the previous studies of nonlinear saturation of the Buneman instability caused by high electron drift velocity relative to ions, the phase-space holes and the plateau on the electron velocity distribution function were identified as features of the saturation stage of instability [notably in the paper by Omura et al., J. Geophys. Res. 108, 1197 (2003)]. We have performed a much longer simulation of the Buneman instability and observed a secondary instability. This secondary instability generates fast electron-acoustic waves. By analyzing the phase-space plot of ions and electrons, we show that the fast electron heating and the formation of the plateau of electron velocity distribution function are not due to the quasi-linear diffusion but due to the nonlinear interaction of ion- and electron-acoustic solitary waves (phase-space holes) by exchange of trapped electrons in each wave. We also report the details on the intermittent and bursty nature of turbulence driven by this instability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Resistive wall tearing mode disruptions in DIII-D and ITER tokamaks

Disruptions are a serious problem in tokamaks, in which thermal and magnetic energy confinement is lost. This paper uses data from the DIII-D experiment, theory, and simulations to demonstrate that resistive wall tearing modes (RWTMs) produce the thermal quench (TQ) in a typical locked mode shot. Analysis of the linear RWTM dispersion relation shows the parameter dependence of the growth rate, particularly on the resistive wall time. Linear simulations of the locked mode equilibrium show that it is unstable with a resistive wall and stable with an ideally conducting wall. Nonlinear simulations demonstrate that the RWTM grows to sufficient amplitude to cause a complete thermal quench. The RWTM growth time is proportional to the thermal quench time. Here, the nonlinearly saturated RWTM magnetic perturbation amplitude agrees with experimental measurements. The onset condition is that the q = 2 rational surface is sufficiently close to the resistive wall. Collectively, this identifies the RWTM as the cause of the TQ. In ITER, RWTMs will produce long TQ times compared to present-day experiments. ITER disruptions may be significantly more benign than previously predicted.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Generalized slab universal instability and its appearance in pair plasma

In this work, a generalized linear dispersion relation of electromagnetic slab universal modes is derived, taking into account arbitrary ion charge state, electron finite Larmor radius (FLR) effects, and Debye shielding effects. As a consequence, it provides more accurate predictions and is applicable to a wider range of plasmas. We find that electron FLR effects have a weakly stabilizing effect on the slab universal instability in electron–ion plasma, while Debye shielding strongly stabilizes this instability when λ D approaches ρ i (λ D is the Debye length and ρi is the ion gyroradius). In particular, we examine the stability criterion for this instability in electron–positron pair plasmas and find that the instability persists in this simplest plasma system as long as the pair plasma number density exceeds the critical value n c = B 2 /(8πm e c 2 ).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Saturation and decay of an induced scattering instability driven by static field asymmetries in a non-neutral plasma

Experimental data on the saturation and decay of a previously described induced scattering instability are presented. The instability is driven by static background field asymmetries and initially produces a single growing mode (ω 1 , k 1 ). As the instability develops, several harmonically related (ω n =nω 1 , k n =nk 1 ) eigenmodes of the plasma column grow up, resulting in a spatially localized moving potential perturbation with δϕ/T ≈ 20%. After a period of rapid growth, the mode amplitudes saturate and vary slowly for roughly 10 5 ω 1 −1 . This quasi-equilibrium ends with an unusual change in the eigenmode phases, wherein δϕ changes from positive to negative. Plasma heating during this period increases the damping of all modes and rapidly quenches the instability. This instability is of particular interest because the coupling with the field asymmetry produces an enhanced level of radial transport.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Weibel-like instability in magnetohydrodynamics

In magnetohydrodynamics (MHD), a density perturbation perpendicular to an electron temperature gradient generates a magnetic field around itself that acts to increase the perturbation, which can lead to instability. An MHD dispersion relation is obtained for perturbations perpendicular to a fixed electron temperature gradient with an initial in-plane magnetic field, including resistivity, viscosity, and the electrothermal coefficient. Instability occurs for sufficiently small electron temperature-gradient scale lengths determined by the ion collisionless skin depth. Both viscosity and resistivity are required to prevent growth at arbitrarily small spatial scales and to give a physical result for the fastest growing mode. The perpendicular electrothermal coefficient is only significant for a narrow range of low electron Hall parameters, causing a modest reduction in magnetic field growth and modifying the criteria for instability in the presence of viscosity. If the definition of the Weibel instabilityis extended to include all instabilities due to anisotropy in the electron velocity distribution, then this is a Weibel-like instability because an electron temperature gradient implies an anisotropic electron velocity distribution. Here, the implications for the formation of filaments in laser-produced plasmas and for the verification of MHD codes are considered.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2009

Relative Shock Effects in Mixed Powders of Calcite, Gypsum, and Quartz: A Calibration Scheme from Shock Experiments

The shock behavior of calcite and gypsum is important in understanding the Cretaceous/Tertiary event and other terrestrial impacts that contain evaporite sediments in their targets. Most interest focuses on issues of devolatilization to quantify the production of CO2 or SO2 to better understand their role in generating a temporary atmosphere and its effects on climate and biota [e.g., papers in 1,2,3,4]. Devolatilization of carbonate is also important because the dispersion and fragmentation of ejecta is strongly controlled by the expansion of large volumes of gas during the impact process as well [5,6]. Shock recovery experiments for calcite yield seemingly conflicting results: early experimental devolatilization studies [7,8,9] suggested that calcite was substantially outgassed at 30 GPa (> 50%). However, the recent petrographic work of [10,11,12] presented evidence that essentially intact calcite is recovered from 60 GPa experiments. [13] reported results of shock experiments on anhydrite, gypsum, and mixtures of those phases with silica. Their observations indicate little or no devolatilization of anhydrite shocked to 42 GPa and that the fraction of sulfur, by mass, that degassed is approx.10(exp -2) of theoretical prediction. In another (preliminary) report of shock experiments on calcite, anhydrite, and gypsum, [14] observe calcite recrystallization when shock loaded at 61 GPa, only intensive plastic deformation in anhydrite shock loaded at 63 GPa, and gypsum converted to anhydrite when shock loaded at 56 GPa. [15] shock loaded anhydrite and quartz to a peak pressure of 60 GPa. All of the quartz grains were trans-formed to glass and the platy anhydrite grains were completely pseudomorphed by small crystallized anhydrite grains. However, no evidence of interaction between the two phases could be observed and they suggest that recrystallization of anhydrite grains is the result of a solid state transformation. [16] reanalyzed the calcite and anhydrite shock wave experiments of [17] using improved equations of state of porous materials and vaporized products. They determined the pressures for incipient and complete vaporization to be 32.5 and 122 GPa for anhydrite and 17.8 and 54.1 GPa for calcite, respectively, a factor of 2 to 3 lower than reported earlier by [17].

Bell, Mary S.↗
DOE OSTI2023

Three-dimensional coupling of electron cyclotron drift instability and ion–ion two stream instability

Electron cyclotron drift instability (ECDI) and ion–ion two stream instability (IITSI) are both kinetic instabilities that can be present in low-temperature, partially magnetized plasmas. The coupling of instabilities in a three-dimensional configuration leads to the existence of more than one unstable roots to the kinetic dispersion relation. In this paper, a generalized method has been developed for numerically evaluating solutions to the three-dimensional dispersion relation for coupled ECDI and IITSI, assuming cold singly and doubly charged ions and a Maxwellian velocity distribution function for the electrons. The present study demonstrates the coupling between ECDI and IITSI that affects the most unstable mode as a function of the wavenumbers in three dimensions and various plasma properties, including the applied electric field, magnetic field, electron temperature, ion velocities, and plasma density. One of the most notable results is that, while the most unstable mode with the largest growth rate is in the direction of the E×B drift in the two-dimensional cases, the most unstable mode for the three-dimensional configuration occurs in the oblique direction between the applied electric field and the E×B drift. Here, this agrees with experimental observations in cross field plasma sources using coherent Thomson scattering.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Excitation of whistler and slow-X waves by runaway electrons in a collisional plasma

Runaway electrons are known to provide robust ideal or collisionless kinetic drive for plasma wave instabilities in both the whistler and slow-X branches, via the anomalous Doppler-shifted cyclotron resonances. In a cold and dense post-thermal-quench plasma, collisional damping of the plasma waves can compete with the collisionless drive. Previous studies have found that, due to their higher wavelength and frequency, slow-X waves suffer stronger collisional damping than the whistlers, while the ideal growth rate of slow-X modes is higher. Here, we study runaway avalanche distributions that maintain the same eigen distribution and increase only in magnitude over time. The distributions are computed from the relativistic Fokker–Planck–Boltzmann solver, upon which a linear dispersion analysis is performed to search for the most unstable or least damped slow-X and whistler modes. Taking into account the effect of plasma density, plasma temperature, and effective charge number, we find that the slow-X modes tend to be excited before the whistlers in a runaway current ramp-up. Furthermore, even when the runaway current density is sufficiently high that both branches are excited, the most unstable slow-X mode has a much higher growth rate than the most unstable whistler mode. The qualitative and quantitative trends uncovered in the current study indicate that even though past experiments and modeling efforts have concentrated on whistler modes, there is a compelling case that slow-X modes should also be a key area of focus in the runaway self-mediation through wave instabilities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2015

The Compositional Evolution of C/2012 S1 (ISON) from Ground-Based High-Resolution Infrared Spectroscopy as Part of a Worldwide Observing Campaign

Volatile production rates, relative abundances, rotational temperatures, and spatial distributions in the coma were measured in C/2012 S1 (ISON) using long-slit high-dispersion (lambda/delta lambda approximately 2.5 times 10 (sup 4)) infrared spectroscopy as part of a worldwide observing campaign. Spectra were obtained on Universal Time 2013 October 26 and 28 with NIRSPEC (Near Infrared Spectrometer) at the W.M. Keck Observatory, and Universal Time 2013 November 19 and 20 with CSHELL (Cryogenic Echelle Spectrograph) at the NASA IRTF (Infrared Telescope Facility). H2O was detected on all dates, with production rates increasing markedly from (8.7 plus or minus 1.5) times 10 (sup 27) molecules per second on October 26 (Heliocentric Distance = 1.12 Astronomical Units) to (3.7 plus or minus 0.4) times 10 (sup 29) molecules per second on November 20 (Heliocentric Distance = 0.43 Astronomical Units). Short-term variability of H2O production is also seen as observations on November 19 show an increase in H2O production rate of nearly a factor of two over a period of about 6 hours. C2H6, CH3OH and CH4 abundances in ISON (International Scientific Optical Network) are slightly depleted relative to H2O when compared to mean values for comets measured at infrared wavelengths. On the November dates, C2H2, HCN and OCS abundances relative to H2O appear to be within the range of mean values, whereas H2CO and NH3 were significantly enhanced. There is evidence that the abundances with respect to H2O increased for some species but not others between October 28 (Heliocentric Distance = 1.07 Astronomical Units) and November 19 (Heliocentric Distance = 0.46 Astronomical Units). The high mixing ratios of H2CO to CH3OH and C2H2 to C2H6 on November 19, and changes in the mixing ratios of some species with respect to H2O between October 28 to November 19, indicates compositional changes that may be the result of a transition from sampling radiation-processed outer layers in this dynamically new comet to sampling more pristine natal material as the outer processed layer was increasingly eroded and the thermal wave propagated into the nucleus as the comet approached perihelion for the first time. On November 19 and 20, the spatial distribution for dust appears asymmetric and enhanced in the antisolar direction, whereas spatial distributions for volatiles (excepting CN) appear symmetric with their peaks slightly offset in the sunward direction compared to the dust. Spatial distributions for H2O, HCN, C2H6, C2H2, and H2CO on November 19 show no definitive evidence for significant contributions from extended sources; however, broader spatial distributions for NH3 and OCS may be consistent with extended sources for these species. Abundances of HCN and C2H2 on November 19 and 20 are insufficient to account for reported abundances of CN and C2 in ISON near this time. Differences in HCN and CN spatial distributions are also consistent with HCN as only a minor source of CN in ISON on November 19 as the spatial distribution of CN in the coma suggests a dominant distributed source that is correlated with dust and not volatile release. The spatial distributions for NH3 and NH2 are similar, suggesting that NH3 is the primary source of NH2 with no evidence of a significant dust source of NH2; however, the higher production rates derived for NH3 compared to NH2 on November 19 and 20 remain unexplained. This suggests a more complete analysis that treats NH2 as a distributed source and accounts for its emission mechanism is needed for future work.

Russo, N. Dello↗
DOE OSTI2022

Less Common Topological Phenomena in Bulk Materials

"Prediction and subsequent discovery of topological insulators is considered to be one of the main results in condensed matter physics in the last decades. Not surprisingly, it has received major attention of both researchers and funding agencies. This attention is well-deserved; yet, one cannot but note that nearly all this research revolves about essentially the same concept: electronic excitations with linear dispersion, covering, of course, such diverse and intriguing phenomena as topological insulator, bulk Dirac states (or Weyl, if not spin degenerate), Mayorana fermions. In this project, we will address, mainly, other topological phenomena, such as topologically nontrivial magnetic patterns (as, for instance, topological Hall and related phenomena). Specifically, we propose three interrelated trusts: (1) Time-reversal symmetry breaking nonrelativistic antiferromagnets, called altermagnets. These are materials that break Kramers degeneracy of electronic bands, despite having zero net magnetization by symmetry and being fully collinear, and not necessarily non-centrosymmetric. The corresponding band structure is very similar to the band structure in non-centrosymmetric spin-orbital materials, but materials that we propose to study are distinctly different, first and foremost in the sense that despite sharing many aspects of their electronic properties with the latter, they break the time-reversal symmetry without either spin-orbit coupling or lack of inversion symmetry. (2) Topologically nontrivial magnetic spirals. The PI has been engaged with the experimental group of Dr. Ghimire at GMU investigating Dirac materials with helical magnetism, based on stacked magnetic Kagome layers, with a generic formula of RMn6Sn6. In particular, Y Mn6Sn6 demonstrates a component of the Hall effect that is naturally interpreted in terms of a topological spin texture, as well as linear magnetoresistance. Our calculation identify Dirac states that are robust with respect to the spiral formation, and let us derive an advance mean-field model explaining the observed phase diagram. This model predicted four distinct phases, with very distinct properties, which have now been seen in neutron experiments. The same compound is known to demonstrate topological Hall effect in a particular magnetic phase, and only at elevated temperature. Based on our understanding of the phase diagram, we have worked out a phenomenological theory of a chiral (skyrmionic) response to an external magnetic field, similar to the nematic response to external strain in Fe-based superconductors, which is possible in a centrosymmetric lattice and without interplanar Dzyaloshinskii-Moriya interaction. This phenomenological theory agrees quantitatively with the experiment. It is in our plans to research other similar materials for this effect. (3) Search for 3D analogues of Fe-based superconductors. We want to investigate materials that can be viewed as 3D analogues of FeSe. Specifically, we want materials that are good metals and host antiferromagnetism, which can be suppressed by pressure and generate an s-wave superconductivity, as in Fe-based superconductors. We have in mind some candidates already. This work will proceed in close collaboration with the experimental group of Prof. Nirmal Ghimire in the same department, whose expertise lies in sample making, magnetometry and transport measurements of materials with complex magnetic structures."

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗