Experimental Searches for Exotic Short-Range Forces Using Mechanical Oscillators

NASA Astrophysics Data System (ADS)

Weisman, Evan

Experimental searches for forces beyond gravity and electromagnetism at short range have attracted a great deal of attention over the last decade. In this thesis I describe the test mass development for two new experiments searching for forces below 1 mm. Both modify a previous experiment that used 1 kHz mechanical oscillators as test masses with a stiff conducting shield between them to suppress backgrounds, a promising technique for probing exceptionally small distances at the limit of instrumental thermal noise. To further reduce thermal noise, one experiment will use plated silicon test masses at cryogenic temperatures. The other experiment, which searches for spin-dependent interactions, will apply the spin-polarizable material Dy3Fe5O 12 to the test mass surfaces. This material exhibits orbital compensation of the magnetism associated with its intrinsic electron spin, minimizing magnetic backgrounds. Several plated silicon test mass prototypes were fabricated using photolithography (useful in both experiments), and spin-dependent materials were synthesized with a simple chemical recipe. Both silicon and spin-dependent test masses demonstrate the mechanical and magnetic properties necessary for sensitive experiments. I also describe sensitivity calculations of another proposed spin-dependent experiment, based on a modified search for the electron electric dipole moment, which show unprecedented sensitivity to exotic monopole-dipole forces. Inspired by a finite element model, a study attempting to maximize detector quality factor versus geometry is also presented, with experimental results so far not explained by the model.

Free-Spinning-Tunnel Investigation of a 1/25-Scale Model of the McDonnell F3H-1N Airplane, TED No. NACA AD 3100

NASA Technical Reports Server (NTRS)

Lee, Henry A.; Wilkes, L. Faye

1954-01-01

An investigation was conducted in the Langley 20-foot free-spinning tunnel on a 1/23-scale model of the McDonnell F3H-1N airplane. The effects of control settings and movements upon the erect and inverted spin and recovery characteristics of the model were determined for the clean condition. Spin-recovery parachute tests were also performed. The results indicated that erect spins obtained on the airplane for the take-off or combat loadings should be satisfactorily terminated if full rudder reversal is accompanied by moving the ailerons to full with the spin (stick full right in a right spin). The spins obtained should be oscillatory in pitch, roll, and yaw. Recoveries from inverted spins should be satisfactory by full reversal of the rudder. A 16.7-foot- diameter tail parachute with a towline length of 30 feet and a drag coefficient of 0.734 should be adequate for emergency recovery from demonstration spins.

Research on the F/A-18E/F Using a 22%-Dynamically-Scaled Drop Model

NASA Technical Reports Server (NTRS)

Croom, M.; Kenney, H.; Murri, D.; Lawson, K.

2000-01-01

Research on the F/A-18E/F configuration was conducted using a 22%-dynamically-scaled drop model to study flight dynamics in the subsonic regime. Several topics were investigated including longitudinal response, departure/spin resistance, developed spins and recoveries, and the failing leaf mode. Comparisons to full-scale flight test results were made and show the drop model strongly correlates to the airplane even under very dynamic conditions. The capability to use the drop model to expand on the information gained from full-scale flight testing is also discussed. Finally, a preliminary analysis of an unusual inclined spinning motion, dubbed the "cartwheel", is presented here for the first time.

Turbine Rotor Disk Health Monitoring Assessment Based on Sensor Technology and Spin Tests Data

PubMed Central

2013-01-01

The paper focuses on presenting data obtained from spin test experiments of a turbine engine like rotor disk and assessing their correlation to the development of a structural health monitoring and fault detection system. The data were obtained under various operating conditions such as the rotor disk being artificially induced with and without a notch and rotated at a rotational speed of up to 10,000 rpm under balanced and imbalanced state. The data collected included blade tip clearance, blade tip timing measurements, and shaft displacements. Two different sensor technologies were employed in the testing: microwave and capacitive sensors, respectively. The experimental tests were conducted at the NASA Glenn Research Center's Rotordynamics Laboratory using a high precision spin system. Disk flaw observations and related assessments from the collected data for both sensors are reported and discussed. PMID:23844396

Friction losses in a lubricated thrust-loaded cageless angular-contract bearing

NASA Technical Reports Server (NTRS)

Townsend, D. P.; Allen, C. W.; Zaretsky, E. V.

1973-01-01

The NASA spinning torque apparatus was modified to measure the spinning torque on a cageless ball thrust bearing. Friction torque was measured for thrust loads varying from 44.5 to 403 newtons (10 to 90 lb) at speeds of 1000, 2000, and 3000 rpm. Tests were conducted with di-2-ethylhexyl sebacate and a synthetic paraffinic oil. These tests were run with either oil jet lubrication or with a thin surface film of lubricant only. An analytical model which included rolling resistance was developed and extended from previous models for spinning torque and lubricant rheology. The model was extended by the inclusion of rolling resistance. The computed values were in fair agreement with the experimental results and confirmed previous hypotheses that a thin lubricant film gives minimum bearing torque and an oil jet flow of a viscous lubricant will result in considerable rolling torque in addition to the torque due to ball spin.

Spin-Controlled Conductivity in a Thiophene-Functionalized Iron-Bis(dicarbollide)

NASA Astrophysics Data System (ADS)

Beach, Benjamin; Sauriol, Dustin; Derosa, Pedro

2016-04-01

The relationship between spin state and conductivity is studied for a thiophene-functionalized iron(III)-bis(dicarbollide) with one or two thiophenes at each end of the cage. Iron has a high ground state spin that can be adjusted by external electromagnetic fields to produce different magnetic states. The hypothesis explored here is that changes in the spin state of these Fe-containing molecules can lead to significant changes in molecular conductivity. Two examples of the possible application of such spin-dependent conductivity are its use as a molecular switch, the basic building block in digital logic, or as a memory bit. The molecules were first optimized using the Becke-3 Lee-Yang-Parr functional (B3LYP) with the 6-31G(d) basis set. A relaxed molecular geometry at each spin state was then placed between gold electrodes to conduct spin-polarized electron transport calculations with the density functional theory/non-equilibrium Green's functions formalism. The revised Perdew-Burke-Ernzerhf solids exchange-correlation functional (PBES) with double zeta polarized basis set was used. The result of these calculations show that the conductivity increases with the spin state. The cage structure is shown to exhibit fully delocalized molecular orbitals (MOs) appropriate for high conductivity and thus, in this system, the conductivity depends on the position of the MOs relative to the Fermi level. Minority spins are responsible for the conductivity of the doublet spin state while majority spins dominate for the quartet and sextet spin states as they are found closer to the Fermi level when they are occupied. Energy calculations predict a difference in energy between the more and the less conductive spin states (sextet and doublet respectively) that is 15-20 times greater than the thermal energy, which would imply stability at room temperature; however, the energy difference is sufficiently small that transitions between spin states can be induced.

NASA Lewis and Ohio Company Hit Hole in One

NASA Technical Reports Server (NTRS)

1998-01-01

Ben Hogan Company's Golf Ball Division, which is based in Elyria, Ohio, had developed concepts and prototypes for new golf balls but was unable to determine exact performance characteristics. Specifically, the company's R&D department wanted to measure the spin rates of experimental golf balls. After the Golf Ball Division requested assistance, researchers and technicians from the NASA Lewis Research Center went to Elyria and conducted several days worth of tests. Ben Hogan is using the test results to improve the spin characteristics of a new ball it plans to introduce to the market.

Spin-orbit assisted transmission at 3d/5d metallic interfaces

NASA Astrophysics Data System (ADS)

Jaffres, Henri; Barbedienne, Quentin; Jouy, Augustin; Reyren, Nicolas; George, Jean-Marie; Laboratoire de Physique Et Des Plasmas, Ecole Polytechnique, Palaiseau, France Team; Unite Mixte de Physique Cnrs-Thales, Palaiseau, France Team

We will describe the anatomy of spin-transport and spin-orbit torques (SOT) at spin-orbit active interfaces involving 5d transition metals (TM) as heavy metals spin-Hall effect (SHE) materials and 3d TM in [Co,Ni]/Pt, NiFe. NiFe/Au:W and Co/Pt/Au;W systems. In the case of Pt, recent studies have put forward the major role played by the spin-memory loss (SML), the electronic transparency at 3d/5d interfaces and the inhomogeneity of the conductivity in the CIP-geometry. Ingredients to consider for spin-transport and spin-Hall Magnetoresistance (SMR) are the conductivity, the spin-current profiles across the multilayers and the spin-transmission. We will present SMR measurements observed on these systems possibly involving interfacial Anisotropy of Magnetoresistance (AIMR) contributions. We analyze in large details our SMR signals in the series of samples owing: i) the exact conductivity profile across the multilayers via the Camley-Barnas approach and the spin current profile generated by SHE. We will discuss the role of the generalized spin-mixing conductance on the spin-transport properties and spin-orbit torques.

Acoustic imaging of a duct spinning mode by the use of an in-duct circular microphone array.

PubMed

Wei, Qingkai; Huang, Xun; Peers, Edward

2013-06-01

An imaging method of acoustic spinning modes propagating within a circular duct simply with surface pressure information is introduced in this paper. The proposed method is developed in a theoretical way and is demonstrated by a numerical simulation case. Nowadays, the measurements within a duct have to be conducted using in-duct microphone array, which is unable to provide information of complete acoustic solutions across the test section. The proposed method can estimate immeasurable information by forming a so-called observer. The fundamental idea behind the testing method was originally developed in control theory for ordinary differential equations. Spinning mode propagation, however, is formulated in partial differential equations. A finite difference technique is used to reduce the associated partial differential equations to a classical form in control. The observer method can thereafter be applied straightforwardly. The algorithm is recursive and, thus, could be operated in real-time. A numerical simulation for a straight circular duct is conducted. The acoustic solutions on the test section can be reconstructed with good agreement to analytical solutions. The results suggest the potential and applications of the proposed method.

Influence of Dzyaloshinskii-Moriya interaction and ballistic spin transport in the two and three-dimensional Heisenberg model

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-06-01

We study the effect of Dzyaloshisnkii-Moriya interaction on spin transport in the two and three-dimensional Heisenberg antiferromagnetic models in the square lattice and cubic lattice respectively. For the three-dimensional model, we obtain a large peak for the spin conductivity and therefore a finite AC conductivity. For the two-dimensional model, we have gotten the AC spin conductivity tending to the infinity at ω → 0 limit and a suave decreasing in the spin conductivity with increase of ω. We obtain a small influence of the Dzyaloshinskii-Moriya interaction on the spin conductivity in all cases analyzed.

Meissner mechanism for the spin supercurrent and interplay between quantum phase transition and spin transport in the frustrated Heisenberg model

NASA Astrophysics Data System (ADS)

Lima, Leonardo S.

2018-04-01

We have propose the Meissner mechanism for the spin supercurrent in quantum spin systems. Besides, we study the behavior of the AC spin conductivity in neighborhood of quantum phase transition in a frustrated spin model such as the antiferromagnet in the union jack lattice with single ion anisotropy at T = 0 . We investigate the spin conductivity for this model that presents exchange interactions J1 and J2 . Our results show a single peak for the conductivity with the height varying with the behavior of critical anisotropy Dc with J2 . We obtain the conductivity tending to zero in the limit ω → 0 .

Interplay between the Dzyaloshinskii-Moriya term and external fields on spin transport in the spin-1/2 one-dimensional antiferromagnet

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-05-01

We study the effect of the uniform Dzyaloshinskii-Moriya interaction (symmetric exchange anisotropy) and arbitrary oriented external magnetic fields on spin conductivity in the spin-1/2 one-dimensional Heisenberg antiferromagnet. The spin conductivity is calculated employing abelian bosonization and the Kubo formalism of transport. We investigate the influence of three competing phases at zero-temperature, (Néel phase, dimerized phase and gapless Luttinger liquid phase) on the AC spin conductivity.

Spin Transport in Electric-Barrier-Modulated Ferromagnetic/Normal/Ferromagnetic Monolayer Zigzag MoS2 Nanoribbon Junction

NASA Astrophysics Data System (ADS)

Xia, Y.-Y.; Yuan, R.-Y.; Yang, Q.-J.; Sun, Q.; Zheng, J.; Guo, Y.

In this paper, with the three-band tight-binding model and non-equilibrium Green’s function technique, we investigate spin transport in electric-barrier-modulated Ferromagnetic/Normal/Ferromagnetic (F/N/F) monolayer (ML) zigzag MoS2 nanoribbon junction. The results demonstrate that once the double electric barriers structure emerges, the oscillations of spin conductances become violent, especially for spin-down conductance, the numbers of resonant peaks increase obviously, thus we can obtain 100% spin polarization in the low energy region. It is also found that with the intensity of the exchange field enhancement, the resonant peaks of spin-up and spin-down conductances move in the opposite direction in a certain energy region. As a consequence, the spin-down conductance can be filtered out completely. The findings here indicate that the present structure may be considered as a good candidate for spin filter.

Evaluation of fluid behavior in spinning toroidal tanks

NASA Technical Reports Server (NTRS)

Anderson, J. E.; Fester, D. A.; Dugan, D. W.

1976-01-01

An experimental study was conducted to evaluate propellant behavior in spinning toroidal tanks that could be used in a retro-propulsion system of an advanced outer-planet Pioneer orbiter. Information on propellant slosh and settling and on ullage orientation and stability was obtained. The effects of axial acceleration, spin rate, spin rate change, and spacecraft wobble, both singly and in combination, were evaluated using a 1/8-scale transparent tank in one-g and low-g environments. Liquid loadings ranged from 5% to 96% full. The impact of a surface tension acquisition device was assessed. Testing simulated the behavior of F2/N2H4 and N2O4/MMH propellants. Results are presented which indicate no major fluid behavior problems would be encountered with any of the four propellants in the toroidal tanks of a spin-stabilized orbiter spacecraft.

Fluid interaction with spinning toroidal tanks

NASA Technical Reports Server (NTRS)

Fester, D. A.; Anderson, J. E.

1977-01-01

An experimental study was conducted to evaluate propellant behavior in spinning torroidal tanks that could be used in a retropropulsion system of an advanced outer-planet Pioneer orbiter. Information on propellant slosh and settling and on ullage orientation and stability was obtained. The effects of axial acceleration, spin rate, spin-rate change, and spacecraft wobble, both singly and in combination, were evaluated using a one-eighth scale transparent tank in one-g and low-g environments. Liquid loadings ranged from 5% to 96% full. The impact of a surface tension acquisition device was assessed by comparison with bare-tank results. The testing simulated the behavior of the fluorine/hydrazine and nitrogen textroxide/monomethylhydrazine propellants. Results are presented that indicate that no major fluid behavior problems would be encountered with any of the four propellants in the toroidal tanks of a spin-stabilized orbiter spacecraft.

Enhanced Spin Conductance of a Thin-Film Insulating Antiferromagnet

NASA Astrophysics Data System (ADS)

Bender, Scott A.; Skarsvâg, Hans; Brataas, Arne; Duine, Rembert A.

2017-08-01

We investigate spin transport by thermally excited spin waves in an antiferromagnetic insulator. Starting from a stochastic Landau-Lifshitz-Gilbert phenomenology, we obtain the out-of-equilibrium spin-wave properties. In linear response to spin biasing and a temperature gradient, we compute the spin transport through a normal-metal-antiferromagnet-normal-metal heterostructure. We show that the spin conductance diverges as one approaches the spin-flop transition; this enhancement of the conductance should be readily observable by sweeping the magnetic field across the spin-flop transition. The results from such experiments may, on the one hand, enhance our understanding of spin transport near a phase transition, and on the other be useful for applications that require a large degree of tunability of spin currents. In contrast, the spin Seebeck coefficient does not diverge at the spin-flop transition. Furthermore, the spin Seebeck coefficient is finite even at zero magnetic field, provided that the normal metal contacts break the symmetry between the antiferromagnetic sublattices.

Testing of a Loop Heat Pipe Subjective to Variable Accelerations. Part 1; Start-up

NASA Technical Reports Server (NTRS)

Ku, Jentung; Rogers, Paul; Hoff, Craig

2000-01-01

The effect of accelerating forces on the performance of loop heat pipes (LHP) is of interest and importance to terrestrial and space applications. They are being considered for cooling of military combat vehicles and for spinning spacecraft. In order to investigate the effect of an accelerating force on LHP operation, a miniature LHP was installed on a spin table. Variable accelerating forces were imposed on the LHP by spinning the table at different angular speeds. Several patterns of accelerating forces were applied, i.e. continuous spin at different speeds and periodic spin at different speeds and frequencies. The resulting accelerations ranged from 1.17 g's to 4.7 g's. This paper presents the first part of the experimental study, i.e. the effects of a centrifugal force on the LHP start-up. Tests were conducted by varying the heat load to the evaporator, sink temperature, magnitude and frequency of centrifugal force, and LHP orientation relative to the direction of the accelerating force. The accelerating force seems to have little effect on the loop start-up in terms of temperature overshoot and superheat at boiling incipience. Changes in these parameters seem to be stochastic with or without centrifugal accelerating forces. The LHP started successfully in all tests.

Investigation of the Spin and Recovery Characteristics of a 0.057-Scale Model of the Modified Chance Vought XF7U-1 Airplane. TED No. NACA DE 311

NASA Technical Reports Server (NTRS)

Berman, Theodore; Pumphrey, Norman E.

1950-01-01

An investigation has been conducted in the Langley 20-foot free-spinning tunnel to determine the spin and recovery characteristics of a 0.057-scale model of the modified Chance Vought XF7U-1 airplane. The primary change in the design from that previously tested was a revision of the twin vertical tails. Tests were also made to determine the effect of installation of external wing tanks. The results indicated that the revision in the vertical tails did not greatly alter the spin and recovery characteristics of the model and recovery by normal use of controls (fill rapid rudder reversal followed approximately one-half turn later by movement of the stick forward of neutral) was satisfactory. Adding the external wing tanks to cause the recovery characteristics to become critical and border on an unsatisfactory condition; however, it was shown that satisfactory recovery could be obtained by jettisoning the tanks, followed by normal recovery technique.

Strong Intrinsic Spin Hall Effect in the TaAs Family of Weyl Semimetals

NASA Astrophysics Data System (ADS)

Sun, Yan; Zhang, Yang; Felser, Claudia; Yan, Binghai

2016-09-01

Since their discovery, topological insulators are expected to be ideal spintronic materials owing to the spin currents carried by surface states with spin-momentum locking. However, the bulk doping problem remains an obstacle that hinders such an application. In this work, we predict that a newly discovered family of topological materials, the Weyl semimetals, exhibits a large intrinsic spin Hall effect that can be utilized to generate and detect spin currents. Our ab initio calculations reveal a large spin Hall conductivity in the TaAs family of Weyl materials. Considering the low charge conductivity of semimetals, Weyl semimetals are believed to present a larger spin Hall angle (the ratio of the spin Hall conductivity over the charge conductivity) than that of conventional spin Hall systems such as the 4 d and 5 d transition metals. The spin Hall effect originates intrinsically from the bulk band structure of Weyl semimetals, which exhibit a large Berry curvature and spin-orbit coupling, so the bulk carrier problem in the topological insulators is naturally avoided. Our work not only paves the way for employing Weyl semimetals in spintronics, but also proposes a new guideline for searching for the spin Hall effect in various topological materials.

Propulsion Health Monitoring of a Turbine Engine Disk Using Spin Test Data

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Woike, Mark R.; Oza, Nikunj; Matthews, Bryan; Baaklini, George Y.

2010-01-01

This paper considers data collected from an experimental study using high frequency capacitive sensor technology to capture blade tip clearance and tip timing measurements in a rotating turbine engine-like-disk-to predict the disk faults and assess its structural integrity. The experimental results collected at a range of rotational speeds from tests conducted at the NASA Glenn Research Center s Rotordynamics Laboratory are evaluated using multiple data-driven anomaly detection techniques to identify abnormalities in the disk. Further, this study presents a select evaluation of an online health monitoring scheme of a rotating disk using high caliber sensors and test the capability of the in-house spin system.

Photo-modulation of the spin Hall conductivity of mono-layer transition metal dichalcogenides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengupta, Parijat; Bellotti, Enrico

2016-05-23

We report on a possible optical tuning of the spin Hall conductivity in mono-layer transition metal dichalcogenides. Light beams of frequencies much higher than the energy scale of the system (the off-resonant condition) do not excite electrons but rearrange the band structure. The rearrangement is quantitatively established using the Floquet formalism. For such a system of mono-layer transition metal dichalcogenides, the spin Hall conductivity (calculated with the Kubo expression in presence of disorder) exhibits a drop at higher frequencies and lower intensities. Finally, we compare the spin Hall conductivity of the higher spin-orbit coupled WSe{sub 2} to MoS{sub 2}; themore » spin Hall conductivity of WSe{sub 2} was found to be larger.« less

Characteristics of the spin-trapping reaction of a free radical derived from AAPH: further development of the ORAC-ESR assay.

PubMed

Nakajima, A; Matsuda, E; Masuda, Y; Sameshima, H; Ikenoue, T

2012-06-01

The characteristics of the spin-trapping reaction in the oxygen radical absorbance capacity (ORAC)-electron spin resonance (ESR) assay were examined, focusing on the kind of spin traps. 2,2-Azobis(2-amidinopropane) dihydrochloride (AAPH) was used as a free radical initiator. The spin adducts of the AAPH-derived free radical were assigned as those of the alkoxyl radical, RO· (R=H(2)N(HN)C-C(CH(3))(2)). Among the spin traps tested, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 5,5-dimethyl-4-phenyl-1-pyrroline N-oxide (4PDMPO), 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO), and 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) were applicable to the ORAC-ESR assay. Optimal formation of spin-trapped radical adduct was observed with 1 mM AAPH, 10 mM spin trap, and 5 s UV irradiation. The calibration curve (the Stern-Volmer's plot) for each spin trap showed good linearity, and their slopes, k (SB)/k (ST), were estimated to be 87.7±2.3, 267±15, 228±9, and 213±16 for DMPO, 4PDMPO, CYPMPO, and DEPMPO, respectively. Though the k (SB)/k (ST) values for selected biosubstances varied with various spin traps, their ratios to Trolox (the relative ORAC values) were almost the same for all spin traps tested. The ORAC-ESR assay also had a very good reproducibility. The ORAC-ESR assay was conducted under stoichiometric experimental conditions. The present results demonstrate the superiority of the ORAC-ESR assay.

Conduct and Results of YF-16 RPRV Stall/Spin Drop Model Tests

DTIC Science & Technology

1977-04-01

Bomb Recovery System Tests Iron Bird Recovery System Tests Captive Flights Typical Flight Operations Flight Planning and Pilot Training...helicopter tow qualification test, one model tow qualification test, three Iron Bird parachute recovery system verification tests, three captive tests...Corresponding Full-Scale YF-16 Altitude -Reference 1: Woodcock , Robert J., Some Notes on Free-Flight Model Seal- ing, AFFDL-TM-73-123-FCC, Air Force Flight

Estimating the spin diffusion length and the spin Hall angle from spin pumping induced inverse spin Hall voltages

NASA Astrophysics Data System (ADS)

Roy, Kuntal

2017-11-01

There exists considerable confusion in estimating the spin diffusion length of materials with high spin-orbit coupling from spin pumping experiments. For designing functional devices, it is important to determine the spin diffusion length with sufficient accuracy from experimental results. An inaccurate estimation of spin diffusion length also affects the estimation of other parameters (e.g., spin mixing conductance, spin Hall angle) concomitantly. The spin diffusion length for platinum (Pt) has been reported in the literature in a wide range of 0.5-14 nm, and in particular it is a constant value independent of Pt's thickness. Here, the key reasonings behind such a wide range of reported values of spin diffusion length have been identified comprehensively. In particular, it is shown here that a thickness-dependent conductivity and spin diffusion length is necessary to simultaneously match the experimental results of effective spin mixing conductance and inverse spin Hall voltage due to spin pumping. Such a thickness-dependent spin diffusion length is tantamount to the Elliott-Yafet spin relaxation mechanism, which bodes well for transitional metals. This conclusion is not altered even when there is significant interfacial spin memory loss. Furthermore, the variations in the estimated parameters are also studied, which is important for technological applications.

Investigation of Spinning and Tumbling Characteristics of a 1/20-Scale Model of the Consolidated Vultee XFY-1 Airplane in the Free-Spinning Tunnel, TED No. NACA DE 370

NASA Technical Reports Server (NTRS)

Lee, Henry A.

1952-01-01

An investigation has been conducted in the Langley 20-foot free-spinning tunnel on a l/20-scale model of the Consolidated Vultee XFY-1 airplane with a windmilling propeller simulated to determine the effects of control setting and movements upon the erect spin and recovery characteristics for a range of airplane-loading conditions. The effects on the model's spin-recovery characteristics of removing the lower vertical tail, removing the gun pods, and fixing the rudders at neutral were also investigated briefly. The investigation included determination of the size parachute required for emergency recovery from demonstration spins. The tumbling tendencies of the model were also investigated. Brief static force tests were made to determine the aerodynamic characteristics in pitch at high angles of attack. The investigation indicated that the spin and recovery characteristics of the airplane with propeller windmilling will be satisfactory for all loading conditions if recovery is attempted by full rudder reversal accompanied by simultaneous movement of the stick laterally to full with the spin (stick right in a right spin) and longitudinally to neutral. Inverted spins should be satisfactorily terminated by fully reversing the rudder followed immediately by moving the stick laterally towards the forward rudder pedal and longitudinally to neutral. Removal of the gun pods or fixing the rudders at neutral will not adversely affect the airplane's spin-recovery characteristics, but removal of the lower vertical tail will result in unsatisfactory spin-recovery characteristics. The model-test results showed that a 13.3-foot wing-tip conventional parachute (drag coefficient approximately 0.7) should be effective as an emergency spin-recovery device during demonstration spins of the airplane. It was indicated that the airplane should not tumble and that no unusual longitudinal-trim characteristics should be obtained for the center-of-gravity positions investigated.

The influence of wing, fuselage and tail design on rotational flow aerodynamics data obtained beyond maximum lift with general aviation configurations

NASA Technical Reports Server (NTRS)

Bihrle, W., Jr.; Bowman, J. S., Jr.

1980-01-01

The NASA Langley Research Center has initiated a broad general aviation stall/spin research program. A rotary balance system was developed to support this effort. Located in the Langley spin tunnel, this system makes it possible to identify an airplane's aerodynamic characteristics in a rotational flow environment, and thereby permits prediction of spins. This paper presents a brief description of the experimental set-up, testing technique, five model programs conducted to date, and an overview of the rotary balance results and their correlation with spin tunnel free-spinning model results. It is shown, for example, that there is a large, nonlinear dependency of the aerodynamic moments on rotational rate and that these moments are pronouncedly configuration-dependent. Fuselage shape, horizontal tail and, in some instances, wing location are shown to appreciably influence the yawing moment characteristics above an angle of attack of 45 deg.

Magnetic modulation of inverse spin Hall effect in lateral spin-valves

NASA Astrophysics Data System (ADS)

Andrianov, T.; Vedyaev, A.; Dieny, B.

2018-05-01

We analytically investigated the spin-dependent transport properties in a lateral spin-valve device comprising pinned ferromagnetic electrodes allowing the injection of a spin current in a spin conducting channel where spin orbit scattering takes place. This produces an inverse spin Hall (ISHE) voltage across the thickness of the spin conducting channel. It is shown that by adding an extra soft ferromagnetic electrode with rotatable magnetization along the spin conducting channel, the ISHE generated voltage can be magnetically modulated by changing the magnetization orientation of this additional electrode. The dependence of the ISHE voltage on the direction of magnetization of the ferromagnetic electrode with rotatable magnetization was calculated in various configurations. Our results suggest that such structures could be considered as magnetic field sensors in situations where the total thickness of the sensor is constrained such as in hard disk drive readers.

Electrical spin injection from an n-type ferromagnetic semiconductor into a III-V device heterostructure

NASA Astrophysics Data System (ADS)

Kioseoglou, George; Hanbicki, Aubrey T.; Sullivan, James M.; van't Erve, Olaf M. J.; Li, Connie H.; Erwin, Steven C.; Mallory, Robert; Yasar, Mesut; Petrou, Athos; Jonker, Berend T.

2004-11-01

The use of carrier spin in semiconductors is a promising route towards new device functionality and performance. Ferromagnetic semiconductors (FMSs) are promising materials in this effort. An n-type FMS that can be epitaxially grown on a common device substrate is especially attractive. Here, we report electrical injection of spin-polarized electrons from an n-type FMS, CdCr2Se4, into an AlGaAs/GaAs-based light-emitting diode structure. An analysis of the electroluminescence polarization based on quantum selection rules provides a direct measure of the sign and magnitude of the injected electron spin polarization. The sign reflects minority rather than majority spin injection, consistent with our density-functional-theory calculations of the CdCr2Se4 conduction-band edge. This approach confirms the exchange-split band structure and spin-polarized carrier population of an FMS, and demonstrates a litmus test for these FMS hallmarks that discriminates against spurious contributions from magnetic precipitates.

Nonlinear spin conductance of yttrium iron garnet thin films driven by large spin-orbit torque

NASA Astrophysics Data System (ADS)

Thiery, N.; Draveny, A.; Naletov, V. V.; Vila, L.; Attané, J. P.; Beigné, C.; de Loubens, G.; Viret, M.; Beaulieu, N.; Ben Youssef, J.; Demidov, V. E.; Demokritov, S. O.; Slavin, A. N.; Tiberkevich, V. S.; Anane, A.; Bortolotti, P.; Cros, V.; Klein, O.

2018-02-01

We report high power spin transfer studies in open magnetic geometries by measuring the spin conductance between two nearby Pt wires deposited on top of an epitaxial yttrium iron garnet thin film. Spin transport is provided by propagating spin waves that are generated and detected by direct and inverse spin Hall effects. We observe a crossover in spin conductance from a linear transport dominated by exchange magnons (low current regime) to a nonlinear transport dominated by magnetostatic magnons (high current regime). The latter are low-damping magnetic excitations, located near the spectral bottom of the magnon manifold, with a sensitivity to the applied magnetic field. This picture is supported by microfocus Brillouin light-scattering spectroscopy. Our findings could be used for the development of controllable spin conductors by variation of relatively weak magnetic fields.

Reentry Motion and Aerodynamics of the MUSES-C Sample Return Capsule

NASA Astrophysics Data System (ADS)

Ishii, Nobuaki; Yamada, Tetsuya; Hiraki, Koju; Inatani, Yoshifumi

The Hayabusa spacecraft (MUSES-C) carries a small capsule for bringing asteroid samples back to the earth. The initial spin rate of the reentry capsule together with the flight path angle of the reentry trajectory is a key parameter for the aerodynamic motion during the reentry flight. The initial spin rate is given by the spin-release mechanism attached between the capsule and the mother spacecraft, and the flight path angle can be modified by adjusting the earth approach orbit. To determine the desired values of both parameters, the attitude motion during atmospheric flight must be clarified, and angles of attack at the maximum dynamic pressure and the parachute deployment must be assessed. In previous studies, to characterize the aerodynamic effects of the reentry capsule, several wind-tunnel tests were conducted using the ISAS high-speed flow test facilities. In addition to the ground test data, the aerodynamic properties in hypersonic flows were analyzed numerically. Moreover, these data were made more accurate using the results of balloon drop tests. This paper summarized the aerodynamic properties of the reentry capsule and simulates the attitude motion of the full-configuration capsule during atmospheric flight in three dimensions with six degrees of freedom. The results show the best conditions for the initial spin rates and flight path angles of the reentry trajectory.

Thermal transport in topological-insulator-based superconducting hybrid structures with mixed singlet and triplet pairing states.

PubMed

Li, Hai; Zhao, Yuan Yuan

2017-11-22

In the framework of the Bogoliubov-de Gennes equation, we investigate the thermal transport properties in topological-insulator-based superconducting hybrid structures with mixed spin-singlet and spin-triplet pairing states, and emphasize the different manifestations of the spin-singlet and spin-triplet pairing states in the thermal transport signatures. It is revealed that the temperature-dependent differential thermal conductance strongly depends on the components of the pairing state, and the negative differential thermal conductance only occurs in the spin-singlet pairing state dominated regime. It is also found that the thermal conductance is profoundly sensitive to the components of the pairing state. In the spin-singlet pairing state controlled regime, the thermal conductance obviously oscillates with the phase difference and junction length. With increasing the proportion of the spin-triplet pairing state, the oscillating characteristic of the thermal conductance fades out distinctly. These results suggest an alternative route for distinguishing the components of pairing states in topological-insulator-based superconducting hybrid structures.

Entanglement in the Anisotropic Kondo Necklace Model

NASA Astrophysics Data System (ADS)

Mendoza-Arenas, J. J.; Franco, R.; Silva-Valencia, J.

We study the entanglement in the one-dimensional Kondo necklace model with exact diagonalization, calculating the concurrence as a function of the Kondo coupling J and an anisotropy η in the interaction between conduction spins, and we review some results previously obtained in the limiting cases η = 0 and 1. We observe that as J increases, localized and conduction spins get more entangled, while neighboring conduction spins diminish their concurrence; localized spins require a minimum concurrence between conduction spins to be entangled. The anisotropy η diminishes the entanglement for neighboring spins when it increases, driving the system to the Ising limit η = 1 where conduction spins are not entangled. We observe that the concurrence does not give information about the quantum phase transition in the anisotropic Kondo necklace model (between a Kondo singlet and an antiferromagnetic state), but calculating the von Neumann block entropy with the density matrix renormalization group in a chain of 100 sites for the Ising limit indicates that this quantity is useful for locating the quantum critical point.

Conductance of two-dimensional waveguide in presence of the Rashba spin-orbit interaction

NASA Astrophysics Data System (ADS)

Liu, Duan-Yang; Xia, Jian-Bai

2018-04-01

By using the transfer matrix method, we investigated spin transport in some straight structures in presence of the Rashba spin-orbit interaction. It is proved that the interference of two spin states is the same as that in one-dimensional Datta-Das spin field-effect transistor. The conductance of these structures has been calculated. Conductance quantization is common in these waveguides when we change the Fermi energy and the width of the waveguide. Using a periodic system of quadrate stubs and changing the Fermi energy, a nearly square-wave conductance can be obtained in some regions of the Fermi energy.

The spin-Hall effect and spin-orbit torques in epitaxial Co2FeAl/platinum bilayers

NASA Astrophysics Data System (ADS)

Peterson, T. A.; Liu, C.; McFadden, T.; Palmstrøm, C. J.; Crowell, P. A.

We have performed magnetoresistance measurements on epitaxially grown Co2FeAl/platinum (CFA/Pt) ultrathin ferromagnet/heavy metal bilayers to study the spin-Hall effect in Pt and the accompanying spin-orbit torque (SOT) exerted on the magnetic CFA layer. Specifically, we measure the spin-Hall magnetoresistance in the Pt layer by changing the orientation of the CFA magnetization with respect to the spin current orientation created in the Pt, and we determine the SOT efficiency using a second-harmonic detection technique. Because the latter of the two measurements is proportional to the spin-Hall ratio θSHE while the former is proportional to θSHE2, we are able to extract the bare Pt spin-Hall ratio with no assumptions about the CFA/Pt interface spin mixing conductance. Furthermore, by varying the Pt thickness we show that the results are consistent with resistivity-independent spin-Hall conductivity. Finally, the two measurements in combination allow us to infer a spin-mixing conductance at the CFA/Pt interface of 2 +/- 1 ×1015Ω-1m-2 . The combination of spin-Hall magnetoresistance and SOT measurements allows for a determination of the spin-mixing conductance using only low-frequency transport techniques. This work was supported by STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

Psychometric Properties of the Mini-Social Phobia Inventory

PubMed Central

Seeley-Wait, Elizabeth; Rapee, Ronald M.

2009-01-01

Objective: Although a potentially useful measure, to date, there has been only one published test of the psychometric properties of the Mini-Social Phobia Inventory (Mini-SPIN). Therefore, the psychometric properties of the Mini-SPIN, a brief 3-item screen for social anxiety disorder, were examined. Method: Participants were 186 patients diagnosed with social anxiety disorder (DSM-IV criteria) attending a specialized anxiety disorders clinic for treatment, and 56 nonclinical participants were recruited to serve as comparisons. Participants were diagnosed using the Anxiety Disorders Interview Schedule for DSM-IV, and they also completed the Mini-SPIN, the Social Interaction Anxiety Scale (SIAS), and the Social Phobia Scale (SPS). Construct validity for the Mini-SPIN was assessed by its correlations with the SIAS and the SPS. Reliability, internal consistency, discriminant validity, and sensitivity to change were also examined, and receiver operating characteristic curve analysis was conducted to determine guidelines regarding cutoff scores for the Mini-SPIN. The study was conducted between April 1999 and December 2001. Results: Supporting findings from a previous study, strong support was found for the Mini-SPIN's ability to discriminate individuals with social anxiety disorder from those without the disorder. Receiver operating characteristic analysis revealed that using a cutoff score of 6 or greater (P < .001), the Mini-SPIN demonstrates excellent sensitivity, specificity, and positive and negative predictive values. Conclusions: Findings suggest that the Mini-SPIN is a reliable and valid instrument for screening social anxiety disorder in adults. Importantly, the use of the Mini-SPIN in primary care may be one way to address the underrecognition of social anxiety disorder in such settings. Due to the ease and brevity of the measure, it also shows potential for use in epidemiology. Given that this study has revealed the ability of the Mini-SPIN to reflect treatment change, the Mini-SPIN may also be considered for use in treatment outcome studies that specifically require minimal assessment. PMID:19956461

Y{sub 3}Fe{sub 5}O{sub 12} spin pumping for quantitative understanding of pure spin transport and spin Hall effect in a broad range of materials (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Chunhui; Wang, Hailong; Hammel, P. Chris

2015-05-07

Using Y{sub 3}Fe{sub 5}O{sub 12} (YIG) thin films grown by our sputtering technique, we study dynamic spin transport in nonmagnetic, ferromagnetic, and antiferromagnetic (AF) materials by ferromagnetic resonance spin pumping. From both inverse spin Hall effect and damping enhancement, we determine the spin mixing conductance and spin Hall angle in many metals. Surprisingly, we observe robust spin conduction in AF insulators excited by an adjacent YIG at resonance. This demonstrates that YIG spin pumping is a powerful and versatile tool for understanding spin Hall physics, spin-orbit coupling, and magnetization dynamics in a broad range of materials.

Universal Behavior of Quantum Spin Liquid and Optical Conductivity in the Insulator Herbertsmithite

NASA Astrophysics Data System (ADS)

Shaginyan, V. R.; Msezane, A. Z.; Stephanovich, V. A.; Popov, K. G.; Japaridze, G. S.

2018-04-01

We analyze optical conductivity with the goal to demonstrate experimental manifestation of a new state of matter, the so-called fermion condensate. Fermion condensates are realized in quantum spin liquids, exhibiting typical behavior of heavy-fermion metals. Measurements of the low-frequency optical conductivity collected on the geometrically frustrated insulator herbertsmithite provide important experimental evidence of the nature of its quantum spin liquid composed of spinons. To analyze recent measurements of the herbertsmithite optical conductivity at different temperatures, we employ a model of strongly correlated quantum spin liquid located near the fermion condensation phase transition. Our theoretical analysis of the optical conductivity allows us to expose the physical mechanism of its temperature dependence. We also predict a dependence of the optical conductivity on a magnetic field. We consider an experimental manifestation (optical conductivity) of a new state of matter (so-called fermion condensate) realized in quantum spin liquids, for, in many ways, they exhibit typical behavior of heavy-fermion metals. Measurements of the low-frequency optical conductivity collected on the geometrically frustrated insulator herbertsmithite produce important experimental evidence of the nature of its quantum spin liquid composed of spinons. To analyze recent measurements of the herbertsmithite optical conductivity at different temperatures, we employ a model of a strongly correlated quantum spin liquid located near the fermion condensation phase transition. Our theoretical analysis of the optical conductivity allows us to reveal the physical mechanism of its temperature dependence. We also predict a dependence of the optical conductivity on a magnetic field.

Spin-pumping and spin-Hall magnetoresistance (SMR) at transition metal interfaces: case of (Co/Pt) (Conference Presentation)

NASA Astrophysics Data System (ADS)

Jaffres, Henri; George, Jean-Marie; Laczowski, Piotr; Reyren, Nicolas; Vila, Laurent

2016-10-01

Spintronic phenomena are made possible via the diffusion of spin-currents or the generation of spin-accumulation. Spinorbitronics uses the electronic spin-orbit coupling (SOC) and emerges as a new route to create spin-currents in the transverse direction of the charge flow. This is made possible via the intrinsic spin Hall conduction (SHE) of heavy metals or extrinsic spin-Hall effect of metallic alloys. SHE borrows its concept from the anomalous Hall effect (AHE) where the relativistic spin-orbit coupling (SOC) promotes an asymmetric deflection of the spin-current. SHE is now at the base of magnetization commutation and domain wall moving via spin-orbit torque (SOT) and spin-transfer torque operations in the FMR regime. However, the exact anatomy of SOT at spin-orbit active interfaces like Co/Pt is still missing. In the case of Pt, recent studies have put forward the major role played by i) the spin-memory loss (SML) and the electronic transparency at 3d/5d interfaces and ii) the inhomogeneity of the conductivity in the current-in-plane (CIP) geometry to explain the discrepancy in the SHE. Ingredients to consider then are the profiles of both the conductivity and spin-current across the multilayers and spin-transmission. In this talk, we will present robust SMR measurements observed on NiCo/Pt multilayer stacks characterized by a perpendicular magnetic anisotropy (PMA). The SMR occurs for both in-plane magnetization rotation or from nominal out-of-plane to the in-plane direction transverse to the current flow. This clearly departs from standard AMR or pure interfacial anisotropic-AMR symmetries. We analyze in large details our SMR signals for the whole series of samples owing to two main guidelines: i) we consider the exact conductivity profile across the multilayers, in particular near the Co/Pt interface, via the Camley-Barnas approach and ii) we derive the spin current profile generated by SHE along the perpendicular direction responsible for SMR. We consider pure interfacial spin dissipation by SML (decoherence, interfacial enhanced scattering) and give out a general analytical expression for SMR. Our conclusions go towards a robust value of the spin-Hall conductivity and SML like previously published. The CIP spin-Hall angle, of the order of 0.10 is larger than the one found in spin-pumping experiments (CPP geometry) owing to the smaller conductivity at the Co/Pt interface, in agreement with the results of STT-FMR experiments.

Free-Spinning-Tunnel Investigation of a 0.034-Scale Model of the Production Version of the Chance Vought F7U-3 Airplane, TED No. NACA AD 3103

NASA Technical Reports Server (NTRS)

Klinar, Walter J.; Healy, Frederick M.

1955-01-01

An investigation of a 0.034-scale model of the production version of the Chance Vought F7U-3 airplane has been conducted in the Langley 20-foot free-spinning tunnel. The inverted and erect spin and recovery characteristics of the model were determined for the combat loading with the model in the clean condition and the effect of extending slats was investigated. A brief investigation of pilot ejection was also performed. The results indicate that the inverted spin-recovery characteristics of the airplane will be satisfactory by full rudder reversal. If the rudders can only be neutralized because of high pedal forces in the inverted spins, satisfactory recovery will be obtained if the auxiliary rudders can be moved to neutral or against the spin provided the stick is held full forward. Optimum control technique for satisfactory recovery from erect spins will be full rudder reversal in conjunction with aileron movement to full with the spin (stick right in a right spin). Extension of the slats will have a slightly adverse effect on recoveries from (1 inverted spins but will have a favorable effect on recoveries from erect spins. The results of brief tests indicate that if a pilot is ejected during a spin while a spin-recovery parachute is extended and fully inflated, he will probably clear the tail parachute.

Spin supercurrent and effect of quantum phase transition in the two-dimensional XY model

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-04-01

We have verified the influence of quantum phase transition on spin transport in the spin-1 two-dimensional XY model on the square lattice, with easy plane, single ion and exchange anisotropy. We analyze the effect of the phase transition from the Néel phase to the paramagnetic phase on the AC spin conductivity. Our results show a bit influence of the quantum phase transition on the conductivity. We also obtain a conventional spin transport for ω > 0 and an ideal spin transport in the limit of DC conductivity and therefore, a superfluid spin transport for the DC current in this limit. We have made the diagrammatic expansion for the Green-function with objective to include the effect exciton-exciton scattering on the results.

Dynamic generation of spin-wave currents in hybrid structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyapilin, I. I.; Okorokov, M. S., E-mail: Okorokovmike@gmail.com

2016-11-15

Spin transport through the interface in a semiconductor/ferromagnetic insulator hybrid structure is studied by the nonequilibrium statistical operator method under conditions of the spin Seebeck effect. The effective parameter approach in which each examined subsystem (conduction electrons, magnons, phonons) is characterized by its specific effective temperature is considered. The effect of the resonant (electric dipole) excitation of the spin electronic subsystem of conduction electrons on spin-wave current excitation in a ferromagnetic insulator is considered. The macroscopic equations describing the spin-wave current caused by both resonant excitation of the spin system of conduction electrons and the presence of a nonuniform temperaturemore » field in the ferromagnetic insulator are derived taking into account both the resonance-diffusion propagation of magnons and their relaxation processes. It is shown that spin-wave current excitation is also of resonant nature under the given conditions.« less

Conductance of a quantum wire at low electron density

NASA Astrophysics Data System (ADS)

Matveev, Konstantin

2006-03-01

We study the transport of electrons through a long quantum wire connecting two bulk leads. As the electron density in the wire is lowered, the Coulomb interactions lead to short-range crystalline ordering of electrons. In this Wigner crystal state the spins of electrons form an antiferromagnetic Heisenberg spin chain with exponentially small exchange coupling J. Inhomogeneity of the electron density due to the coupling of the wire to the leads results in violation of spin-charge separation in the device. As a result the spins affect the conductance of the wire. At zero temperature the low-energy spin excitations propagate freely through the wire, and its conductance remains 2e^2/h. At finite temperature some of the spin excitations are reflected by the wire and contribute to its resistance. Since the energy of the elementary excitations in the spin chain (spinons) cannot exceed πJ/2, the conductance of the wire acquires an exponentially small negative correction δG - (-πJ/2T) at low temperatures T J. At higher temperatures, T J, most of the spin excitations in the leads are reflected by the wire, and the conductance levels off at a new universal value e^2/h. This result is consistent with experimental observations of a mini-plateau of conductance at e^2/h in quantum wires in the absence of magnetic field.

Discovery of Emergent Photon and Monopoles in a Quantum Spin Liquid

NASA Astrophysics Data System (ADS)

Tokiwa, Yoshifumi; Yamashita, Takuya; Terazawa, Daiki; Kimura, Kenta; Kasahara, Yuichi; Onishi, Takafumi; Kato, Yasuyuki; Halim, Mario; Gegenwart, Philipp; Shibauchi, Takasada; Nakatsuji, Satoru; Moon, Eun-Gook; Matsuda, Yuji

2018-06-01

Quantum spin liquid (QSL) is an exotic quantum phase of matter whose ground state is quantum-mechanically entangled without any magnetic ordering. A central issue concerns emergent excitations that characterize QSLs, which are hypothetically associated with quasiparticle fractionalization and topological order. Here we report highly unusual heat conduction generated by the spin degrees of freedom in a QSL state of the pyrochlore magnet Pr2Zr2O7, which hosts spin-ice correlations with strong quantum fluctuations. The thermal conductivity in high temperature regime exhibits a two-gap behavior, which is consistent with the gapped excitations of magnetic (M-) and electric monopoles (E-particles). At very low temperatures below 200 mK, the thermal conductivity unexpectedly shows a dramatic enhancement, which well exceeds purely phononic conductivity, demonstrating the presence of highly mobile spin excitations. This new type of excitations can be attributed to emergent photons (ν-particle), coherent gapless spin excitations in a spin-ice manifold.

A graphene solution to conductivity mismatch: spin injection from ferromagnetic metal/graphene tunnel contacts into silicon

NASA Astrophysics Data System (ADS)

van't Erve, Olaf

2014-03-01

New paradigms for spin-based devices, such as spin-FETs and reconfigurable logic, have been proposed and modeled. These devices rely on electron spin being injected, transported, manipulated and detected in a semiconductor channel. This work is the first demonstration on how a single layer of graphene can be used as a low resistance tunnel barrier solution for electrical spin injection into Silicon at room temperature. We will show that a FM metal / monolayer graphene contact serves as a spin-polarized tunnel barrier which successfully circumvents the classic metal / semiconductor conductivity mismatch issue for electrical spin injection. We demonstrate electrical injection and detection of spin accumulation in Si above room temperature, and show that the corresponding spin lifetimes correlate with the Si carrier concentration, confirming that the spin accumulation measured occurs in the Si and not in interface trap states. An ideal tunnel barrier should exhibit several key material characteristics: a uniform and planar habit with well-controlled thickness, minimal defect / trapped charge density, a low resistance-area product for minimal power consumption, and compatibility with both the FM metal and semiconductor, insuring minimal diffusion to/from the surrounding materials at temperatures required for device processing. Graphene, offers all of the above, while preserving spin injection properties, making it a compelling solution to the conductivity mismatch for spin injection into Si. Although Graphene is very conductive in plane, it exhibits poor conductivity perpendicular to the plane. Its sp2 bonding results in a highly uniform, defect free layer, which is chemically inert, thermally robust, and essentially impervious to diffusion. The use of a single monolayer of graphene at the Si interface provides a much lower RA product than any film of an oxide thick enough to prevent pinholes (1 nm). Our results identify a new route to low resistance-area product spin-polarized contacts, a crucial requirement enabling future semiconductor spintronic devices, which rely upon two-terminal magnetoresistance, including spin-based transistors, logic and memory.

Slurry spin coating of thin film yttria stabilized zirconia/gadolinia doped ceria bi-layer electrolytes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Kim, Hyun Joong; Kim, Manjin; Neoh, Ke Chean; Han, Gwon Deok; Bae, Kiho; Shin, Jong Mok; Kim, Gyu-Tae; Shim, Joon Hyung

2016-09-01

Thin ceramic bi-layered membrane comprising yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is fabricated by the cost-effective slurry spin coating technique, and it is evaluated as an electrolyte of solid oxide fuel cells (SOFCs). It is demonstrated that the slurry spin coating method is capable of fabricating porous ceramic films by adjusting the content of ethyl-cellulose binders in the source slurry. The porous GDC layer deposited by spin coating under an optimal condition functions satisfactorily as a cathode-electrolyte interlayer in the test SOFC stack. A 2-μm-thick electrolyte membrane of the spin-coated YSZ/GDC bi-layer is successfully deposited as a dense and stable film directly on a porous NiO-YSZ anode support without any interlayers, and the SOFC produces power output over 200 mW cm-2 at 600 °C, with an open circuit voltage close to 1 V. Electrochemical impedance spectra analysis is conducted to evaluate the performance of the fuel cell components in relation with the microstructure of the spin-coated layers.

Effects of Zeeman splitting on spin transportation in a three-terminal Rashba ring under a weak magnetic field

NASA Astrophysics Data System (ADS)

Zhai, Li-Xue; Wang, Yan; An, Zhong

2018-05-01

Spin-dependent transport in one-dimensional (1D) three-terminal Rashba rings is investigated under a weak magnetic field, and we focus on the Zeeman splitting (ZS) effect. For this purpose, the interaction between the electron spin and the weak magnetic field has been treated by perturbation theory. ZS removes the spin degeneracy, and breaks both the time reversal symmetry and the spin reversal symmetry of the ring system. Consequently, all conductance zeros are lifted and turned into conductance dips. Aharonov-Bohm (AB) oscillations can be found in both branch conductances and the total conductance as a function of the magnetic field. In a relatively high magnetic field, the decoherence caused by ZS decreases the amplitude of the branch conductance and increases that of the total conductance. The results have been compared with those reported in the published literature, and a reasonable agreement is obtained. The conductance as a function of the Rashba spin-orbit coupling (RSOC) strength has also been investigated. As the RSOC strength increases, the role of ZS becomes weaker and weaker; ZS can even be neglected when B ≤ 0.1 T.

Spin-valleytronics of silicene based nanodevices (SBNs)

NASA Astrophysics Data System (ADS)

Ahmed, Ibrahim Sayed; Asham, Mina Danial; Phillips, Adel Helmy

2018-06-01

The quantum spin and valley characteristics in normal silicene/ferromagnetic silicene/normal silicene junction are investigated under the effects of both electric field and the exchange field of the ferromagnetic silicene. The spin resolved conductance and valley resolved conductance are deduced by solving the Dirac equation. Results show resonant oscillations of both spin and valley conductance. These oscillations might be due to confined states of ferromagnetic silicene. The spin and valley polarizations are also computed. Their trends of figures show that they might be tuned and modulated by the electric field and the exchange field of the ferromagnetic silicene. The present investigated silicene nanodevice might be good for spin-valleytronics applications which are needed for quantum information processing and quantum logic circuits.

Roles of nonlocal conductivity on spin Hall angle measurement

NASA Astrophysics Data System (ADS)

Chen, Kai; Zhang, Shufeng

2017-10-01

Spin Hall angle characterizes the rate of spin-charge current conversion and it has become one of the most important material parameters for spintronics physics and device application. A long-standing controversy is that the spin Hall angles for a given material measured by spin pumping and by spin Hall torque experiments are inconsistent and they could differ by as much as an order of magnitude. By using the linear response spin transport theory, we explicitly formulate the relation between the spin Hall angle and measured variables in different experiments. We find that the nonlocal conductivity inherited in the layered structure plays a key role to resolve conflicting values of the spin Hall angle. We provide a generalized scheme for extracting spin transport coefficients from experimental data.

Effect of spin fluctuations on the electronic structure in iron-based superconductors

NASA Astrophysics Data System (ADS)

Heimes, Andreas; Grein, Roland; Eschrig, Matthias

2012-08-01

Magnetic inelastic neutron scattering studies of iron-based superconductors reveal a strongly temperature-dependent spin-fluctuation spectrum in the normal conducting state, which develops a prominent low-energy resonance feature when entering the superconducting state. Angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS) allow us to study the fingerprints of fluctuation modes via their interactions with electronic quasiparticles. We calculate such fingerprints in 122 iron pnictides using an experimentally motivated spin-fluctuation spectrum and make a number of predictions that can be tested in ARPES and STS experiments. This includes discussions of the quasiparticle scattering rate and the superconducting order parameter. In quantitative agreement with experiment we reproduce the quasiparticle dispersions obtained from momentum distribution curves as well as energy distribution curves. We discuss the relevance of the coupling between spin fluctuations and electronic excitations for the superconducting mechanism.

Tunable strength saddle-point contacts impact on quantum rings transmission

NASA Astrophysics Data System (ADS)

González, J. J.; Diago-Cisneros, L.

2016-09-01

A particular subject of investigation is the role of several sadle-point contact (QPC) parameters on the scattering properties of an Aharonov-Bohm-Aharonov-Casher quantum ring (QR) under Rashba-type spin orbit interaction. We discuss the interplay of the conductance with the confinement strengths and height of the QPC, which yields new and tunable harmonic and non-harmonics patterns, while one manipulates these constriction parameters. This phenomenology may be of utility to implement a novel way to modulate spin interference effects in semiconducting QRs, providing an appealing test-platform for spintronics applications.

Drude weight and optical conductivity of a two-dimensional heavy-hole gas with k-cubic spin-orbit interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mawrie, Alestin; Ghosh, Tarun Kanti

We present a detailed theoretical study on zero-frequency Drude weight and optical conductivity of a two-dimensional heavy-hole gas (2DHG) with k-cubic Rashba and Dresselhaus spin-orbit interactions. The presence of k-cubic spin-orbit couplings strongly modifies the Drude weight in comparison to the electron gas with k-linear spin-orbit couplings. For large hole density and strong k-cubic spin-orbit couplings, the density dependence of Drude weight deviates from the linear behavior. We establish a relation between optical conductivity and the Berry connection. Unlike two-dimensional electron gas with k-linear spin-orbit couplings, we explicitly show that the optical conductivity does not vanish even for equal strengthmore » of the two spin-orbit couplings. We attribute this fact to the non-zero Berry phase for equal strength of k-cubic spin-orbit couplings. The least photon energy needed to set in the optical transition in hole gas is one order of magnitude smaller than that of electron gas. Types of two van Hove singularities appear in the optical spectrum are also discussed.« less

A spin-recovery parachute system for light general-aviation airplanes

NASA Technical Reports Server (NTRS)

Bradshaw, C.

1980-01-01

A tail mounted spin recovery parachute system was designed and developed for use on light general aviation airplanes. The system was designed for use on typical airplane configurations, including low wing, high wing, single engine and twin engine designs. A mechanically triggered pyrotechnic slug gun is used to forcibly deploy a pilot parachute which extracts a bag that deploys a ring slot spin recovery parachute. The total system weighs 8.2 kg. System design factors included airplane wake effects on parachute deployment, prevention of premature parachute deployment, positive parachute jettison, compact size, low weight, system reliability, and pilot and ground crew safety. Extensive ground tests were conducted to qualify the system. The recovery parachute was used successfully in flight 17 times.

Recent NASA Research on Aerodynamic Modeling of Post-Stall and Spin Dynamics of Large Transport Airplanes

NASA Technical Reports Server (NTRS)

Murch, Austin M.; Foster, John V.

2007-01-01

A simulation study was conducted to investigate aerodynamic modeling methods for prediction of post-stall flight dynamics of large transport airplanes. The research approach involved integrating dynamic wind tunnel data from rotary balance and forced oscillation testing with static wind tunnel data to predict aerodynamic forces and moments during highly dynamic departure and spin motions. Several state-of-the-art aerodynamic modeling methods were evaluated and predicted flight dynamics using these various approaches were compared. Results showed the different modeling methods had varying effects on the predicted flight dynamics and the differences were most significant during uncoordinated maneuvers. Preliminary wind tunnel validation data indicated the potential of the various methods for predicting steady spin motions.

Design, manufacture and spin test of high contact ratio helicopter transmission utilizing Self-Aligning Bearingless Planetary (SABP)

NASA Technical Reports Server (NTRS)

Folenta, Dezi; Lebo, William

1988-01-01

A 450 hp high ratio Self-Aligning Bearingless Planetary (SABP) for a helicopter application was designed, manufactured, and spin tested under NASA contract NAS3-24539. The objective of the program was to conduct research and development work on a high contact ratio helical gear SABP to reduce weight and noise and to improve efficiency. The results accomplished include the design, manufacturing, and no-load spin testing of two prototype helicopter transmissions, rated at 450 hp with an input speed of 35,000 rpm and an output speed of 350 rpm. The weight power density ratio of these gear units is 0.33 lb hp. The measured airborne noise at 35,000 rpm input speed and light load is 94 dB at 5 ft. The high speed, high contact ratio SABP transmission appears to be significantly lighter and quieter than comtemporary helicopter transmissions. The concept of the SABP is applicable not only to high ratio helicopter type transmissions but also to other rotorcraft and aircraft propulsion systems.

Solution-processed organic spin-charge converter.

PubMed

Ando, Kazuya; Watanabe, Shun; Mooser, Sebastian; Saitoh, Eiji; Sirringhaus, Henning

2013-07-01

Conjugated polymers and small organic molecules are enabling new, flexible, large-area, low-cost optoelectronic devices, such as organic light-emitting diodes, transistors and solar cells. Owing to their exceptionally long spin lifetimes, these carbon-based materials could also have an important impact on spintronics, where carrier spins play a key role in transmitting, processing and storing information. However, to exploit this potential, a method for direct conversion of spin information into an electric signal is indispensable. Here we show that a pure spin current can be produced in a solution-processed conducting polymer by pumping spins through a ferromagnetic resonance in an adjacent magnetic insulator, and that this generates an electric voltage across the polymer film. We demonstrate that the experimental characteristics of the generated voltage are consistent with it being generated through an inverse spin Hall effect in the conducting polymer. In contrast with inorganic materials, the conducting polymer exhibits coexistence of high spin-current to charge-current conversion efficiency and long spin lifetimes. Our discovery opens a route for a new generation of molecular-structure-engineered spintronic devices, which could lead to important advances in plastic spintronics.

Magnetoanisotropic spin-triplet Andreev reflection in ferromagnet-Ising superconductor junctions

NASA Astrophysics Data System (ADS)

Lv, Peng; Zhou, Yan-Feng; Yang, Ning-Xuan; Sun, Qing-Feng

2018-04-01

We theoretically study the electronic transport through a ferromagnet-Ising superconductor junction. A tight-binding Hamiltonian describing the Ising superconductor is presented. Then by combining the nonequilibrium Green's function method, the expressions of Andreev reflection coefficient and conductance are obtained. A strong magnetoanisotropic spin-triplet Andreev reflection is shown, and the magnetoanisotropic period is π instead of 2 π as in the conventional magnetoanisotropic system. We demonstrate a significant increase of the spin-triplet Andreev reflection for the single-band Ising superconductor. Furthermore, the dependence of the Andreev reflection on the incident energy and incident angle are also investigated. A complete Andreev reflection can occur when the incident energy is equal to the superconducting gap, regardless of the Fermi energy (spin polarization) of the ferromagnet. For the suitable oblique incidence, the spin-triplet Andreev reflection can be strongly enhanced. In addition, the conductance spectroscopies of both zero bias and finite bias are studied, and the influence of gate voltage, exchange energy, and spin-orbit coupling on the conductance spectroscopy are discussed in detail. The conductance exhibits a strong magnetoanisotropy with period π as the Andreev reflection coefficient. When the magnetization direction is parallel to the junction plane, a large conductance peak always emerges at the superconducting gap. This work offers a comprehensive and systematic study of the spin-triplet Andreev reflection and has an underlying application of π -periodic spin valve in spintronics.

Spin-dependent transport through an interacting quantum dot.

PubMed

Zhang, Ping; Xue, Qi-Kun; Wang, Yupeng; Xie, X C

2002-12-31

We study the nonequilibrium spin transport through a quantum dot coupled to the magnetic electrodes. A formula for the spin-dependent current is obtained and is applied to discuss the linear conductance and magnetoresistance in the interacting regime. We show that the Kondo resonance and the correlation-induced spin splitting of the dot levels may be systematically controlled by internal magnetization in the electrodes. As a result, when the electrodes are in parallel magnetic configuration, the linear conductance is characterized by two spin-resolved peaks. Furthermore, the presence of the spin-flip process in the dot splits the Kondo resonance into three peaks.

Innermost stable circular orbit of spinning particle in charged spinning black hole background

NASA Astrophysics Data System (ADS)

Zhang, Yu-Peng; Wei, Shao-Wen; Guo, Wen-Di; Sui, Tao-Tao; Liu, Yu-Xiao

2018-04-01

In this paper we investigate the innermost stable circular orbit (ISCO) (spin-aligned or anti-aligned orbit) for a classical spinning test particle with the pole-dipole approximation in the background of Kerr-Newman black hole in the equatorial plane. It is shown that the orbit of the spinning particle is related to the spin of the test particle. The motion of the spinning test particle will be superluminal if its spin is too large. We give an additional condition by considering the superluminal constraint for the ISCO in the black hole backgrounds. We obtain numerically the relations between the ISCO and the properties of the black holes and the test particle. It is found that the radius of the ISCO for a spinning test particle is smaller than that of a nonspinning test particle in the black hole backgrounds.

Signatures of spin-orbital states of t2g 2 system in optical conductivity: R VO3 (R =Y and La)

NASA Astrophysics Data System (ADS)

Kim, Minjae

2018-04-01

We investigate signatures of the spin and orbital states of R VO3 (R =Y and La) in optical conductivity using density functional theory plus dynamical mean-field theory (DFT+DMFT). From the assignment of multiplet state configurations to optical transitions, the DFT+DMFT reproduces experimental temperature-dependent evolutions of optical conductivity for both YVO3 and LaVO3. We also show that the optical conductivity is a useful quantity to probe the evolution of the orbital state even in the absence of spin order. The result provides a reference to investigate the spin and orbital states of t2g 2 vanadate systems, which is an important issue for both fundamental physics on spin and orbital states and applications of vanadates by means of orbital state control.

Strength evaluation test of pressureless-sintered silicon nitride at room temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Takahara, K.; Hashimoto, R.

1984-01-01

In order to study strength characteristics at room temperature and the strength evaluating method of ceramic materials, the following tests were conducted on pressureless sintered silicon nitride specimens: bending tests, the three tensile tests of rectangular plates, holed plates, and notched plates, and spin tests of centrally holed disks. The relationship between the mean strength of specimens and the effective volume of specimens are examined using Weibull's theory. The effect of surface grinding on the strength of specimens is discussed.

Additives influence on spinning solution and nano web properties

NASA Astrophysics Data System (ADS)

Kukle, S.; Jegina, S.; Sutka, A.; Makovska, R.

2017-10-01

Needleless electrospinning operated as a one-stage process producing nanofibres webs from spinning solutions with the corresponding to the final use properties seems has a good future prospects. Complicated spinning solution designing started with the selection of composition and components proportion, pre-processing sequence and parameters establishing for every component and for their mixing. Spinning solution viscosity and electro conductivity together with the spinning distance and intensity of electromagnetic field are main parameters determined spin ability and properties of obtained nanofibers. Influence of some pre-processing parameters of components, combinations of organic and non-organic components and their concentration influence on spinning solution viscosity and conductivity, as well on fibres diameters are under discussion.

Adatoms in graphene nanoribbons: spintronic properties and the quantum spin Hall phase

NASA Astrophysics Data System (ADS)

Ganguly, Sudin; Basu, Saurabh

2017-11-01

We study the charge and spin transport in a two terminal graphene nanoribbon (GNR) decorated with random distribution of Gold (Au) adatoms using a Kane-Mele model. The presence of the quantum spin Hall (QSH) phase is found to crucially depend on the strength of the intrinsic spin-orbit term, while the plateau in the longitudinal conductance at a 2e^2/h value is not the smoking gun for the QSH phase. Thus the Au adatoms which manage to induce only a small intrinsic spin-orbit coupling cannot guarantee a QSH phase, albeit yielding a 2e^2/h plateau in the longitudinal conductance around the zero of the Fermi energy. If other adatoms can induce larger spin-orbit strengths (we call them hypothetical adatoms), they would ensure both the plateau and the QSH phase as is evident from the presence of the conducting edge states. Motivated by these results, the spintronic applications are explored via computing the spin polarized conductance for both Au and hypothetical adatoms. The y-component of the spin polarized conductance renders the dominant contribution owing to the finite width of the GNR in the y-direction and is found to possess strikingly similar features with that of the longitudinal conductance. The other two components, namely x and z are small but finite and hence have relevance in spintronic applications. Moreover, via computing the local current distribution, we show the clear emergence of edge states in the case of hypothetical adatoms, which are conspicuously absent for Au decorated GNRs.

Detecting topological phases in silicene by anomalous Nernst effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Yafang; Zhou, Xingfei; Jin, Guojun, E-mail: gjin@nju.edu.cn

2016-05-16

Silicene undergoes various topological phases under the interplay of intrinsic spin-orbit coupling, perpendicular electric field, and off-resonant light. We propose that the abundant topological phases can be distinguished by measuring the Nernst conductivity even at room temperature, and their phase boundaries can be determined by differentiating the charge and spin Nernst conductivities. By modulating the electric and light fields, pure spin polarized, valley polarized, and even spin-valley polarized Nernst currents can be generated. As Nernst conductivity is zero for linear polarized light, silicene can act as an optically controlled spin and valley field-effect transistor. Similar investigations can be extended frommore » silicene to germanene and stanene, and a comparison is made for the anomalous thermomagnetic figure of merits between them. These results will facilitate potential applications in spin and valley caloritronics.« less

All-electrical production of spin-polarized currents in carbon nanotubes: Rashba spin-orbit interaction

NASA Astrophysics Data System (ADS)

Santos, Hernán; Latgé, A.; Alvarellos, J. E.; Chico, Leonor

2016-04-01

We study the effect of the Rashba spin-orbit interaction in the quantum transport of carbon nanotubes with arbitrary chiralities. For certain spin directions, we find a strong spin-polarized electrical current that depends on the diameter of the tube, the length of the Rashba region, and on the tube chirality. Predictions for the spin-dependent conductances are presented for different families of achiral and chiral tubes. We have found that different symmetries acting on spatial and spin variables have to be considered in order to explain the relations between spin-resolved conductances in carbon nanotubes. These symmetries are more general than those employed in planar graphene systems. Our results indicate the possibility of having stable spin-polarized electrical currents in absence of external magnetic fields or magnetic impurities in carbon nanotubes.

Magnetic adatoms in two and four terminal graphene nanoribbons: A comparison between their spin polarized transport

NASA Astrophysics Data System (ADS)

Ganguly, Sudin; Basu, Saurabh

2018-04-01

We study the charge and spin transport in two and four terminal graphene nanoribbons (GNR) decorated with random distribution of magnetic adatoms. The inclusion of the magnetic adatoms generates only the z-component of the spin polarized conductance via an exchange bias in the absence of Rashba spin-orbit interaction (SOI), while in presence of Rashba SOI, one is able to create all the three (x, y and z) components. This has important consequences for possible spintronic applications. The charge conductance shows interesting behaviour near the zero of the Fermi energy. Where in presence of magnetic adatoms the familiar plateau at 2e2 / h vanishes, thereby transforming a quantum spin Hall insulating phase to an ordinary insulator. The local charge current and the local spin current provide an intuitive idea on the conductance features of the system. We found that, the local charge current is independent of Rashba SOI, while the three components of the local spin currents are sensitive to Rashba SOI. Moreover the fluctuations of the spin polarized conductance are found to be useful quantities as they show specific trends, that is, they enhance with increasing adatom densities. A two terminal GNR device seems to be better suited for possible spintronic applications.

Improving Data Collection and Analysis Interface for the Data Acquisition Software of the Spin Laboratory at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Curatolo, Ben S.; Woike, Mark R.

2011-01-01

In jet engines, turbines spin at high rotational speeds. The forces generated from these high speeds make the rotating components of the turbines susceptible to developing cracks that can lead to major engine failures. The current inspection technologies only allow periodic examinations to check for cracks and other anomalies due to the requirements involved, which often necessitate entire engine disassembly. Also, many of these technologies cannot detect cracks that are below the surface or closed when the crack is at rest. Therefore, to overcome these limitations, efforts at NASA Glenn Research Center are underway to develop techniques and algorithms to detect cracks in rotating engine components. As a part of these activities, a high-precision spin laboratory is being utilized to expand and conduct highly specialized tests to develop methodologies that can assist in detecting predetermined cracks in a rotating turbine engine rotor. This paper discusses the various features involved in the ongoing testing at the spin laboratory and elaborates on its functionality and on the supporting data system tools needed to enable successfully running optimal tests and collecting accurate results. The data acquisition system and the associated software were updated and customized to adapt to the changes implemented on the test rig system and to accommodate the data produced by various sensor technologies. Discussion and presentation of these updates and the new attributes implemented are herein reported

A new approach to correct yaw misalignment in the spinning ultrasonic anemometer

NASA Astrophysics Data System (ADS)

Ghaemi-Nasab, M.; Davari, Ali R.; Franchini, S.

2018-01-01

Single-axis ultrasonic anemometers are the modern instruments for accurate wind speed measurements. Despite their widespread and ever increasing applications, little attention has been paid up to now to spinning ultrasonic anemometers that can accurately measure both the wind speed and its direction in a single and robust apparatus. In this study, intensive wind-tunnel tests were conducted on a spinning single-axis ultrasonic anemometer to investigate the yaw misalignment in ultrasonic wind speed measurements during the yaw rotation. The anemometer was rotating inside the test section with various angular velocities, and the experiments were performed at several combinations of wind speed and anemometer angular velocity. The instantaneous angular position of the ultrasonic signal path with wind direction was measured using an angular position sensor. For a spinning anemometer, the circulatory wake and the associated flow distortion, along with the Doppler effect, impart a phase shift in the signals measured by the anemometer, which should be added to the position data for correcting the yaw misalignment. In this paper, the experimental data are used to construct a theoretical model, based on a response surface method, to correct the phase shift for various wind speeds and anemometer rotational velocities. This model is shown to successfully correct the velocity indicated by the spinning anemometer for the phase shift due to the rotation, and can easily be used in the calibration process for such anemometers.

Probing temperature-driven flow lines in a gated two-dimensional electron gas with tunable spin-splitting.

PubMed

Wang, Yi-Ting; Kim, Gil-Ho; Huang, C F; Lo, Shun-Tsung; Chen, Wei-Jen; Nicholls, J T; Lin, Li-Hung; Ritchie, D A; Chang, Y H; Liang, C-T; Dolan, B P

2012-10-10

We study the temperature flow of conductivities in a gated GaAs two-dimensional electron gas (2DEG) containing self-assembled InAs dots and compare the results with recent theoretical predictions. By changing the gate voltage, we are able to tune the 2DEG density and thus vary disorder and spin-splitting. Data for both the spin-resolved and spin-degenerate phase transitions are presented, the former collapsing to the latter with decreasing gate voltage and/or decreasing spin-splitting. The experimental results support a recent theory, based on modular symmetry, which predicts how the critical Hall conductivity varies with spin-splitting.

Anisotropy of magnetic interactions and spin filter behavior in hexagonal (Ga,Mn)As nanoribbons

NASA Astrophysics Data System (ADS)

Nie, Ya; Lan, Mu; Zhang, Xi; Xiang, Gang

2017-09-01

The electronic and magnetic properties of Mn doped hexagonal GaAs nanoribbons ((Ga,Mn)As NRs) have been investigated using spin-polarized density functional theory (DFT), and the spin-resolved transport behaviors of (Ga,Mn)As NRs have also been studied with non-equilibrium Green function theory. The calculations show that every Mn dopant brings 4 Bohr magneton (μB) magnetic moment and the ground states of (Ga,Mn)As NRs are ferromagnetic (FM). The investigation of magnetic anisotropies shows that magnetic interactions are dependent on both the distribution directions of Mn atoms and the edge effect of the NRs. The studies of electronic structures and transport properties show that incorporation of Mn atom turns GaAs NR from semiconducting to half-metallic, which significantly enhances the spin-up conductivity and strongly weakens the spin-down conductivity, resulting in non-monatomic variations of spin-dependent conductivities. The nearly 100% spin polarization shown in (Ga,Mn)As NR may be used for low dimensional spin filters, even with as large a bias as 0.9 V. Also, (Ga,Mn)As NR can be used to generate a relatively stable spin-polarized current in a wide bias interval.

Spin-polarized light-emitting diodes based on organic bipolar spin valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vardeny, Zeev Valentine; Nguyen, Tho Duc; Ehrenfreund, Eitan Avraham

Spin-polarized organic light-emitting diodes are provided. Such spin-polarized organic light-emitting diodes incorporate ferromagnetic electrodes and show considerable spin-valve magneto-electroluminescence and magneto-conductivity responses, with voltage and temperature dependencies that originate from the bipolar spin-polarized space charge limited current.

Spin and Wind Directions I: Identifying Entanglement in Nature and Cognition.

PubMed

Aerts, Diederik; Arguëlles, Jonito Aerts; Beltran, Lester; Geriente, Suzette; Sassoli de Bianchi, Massimiliano; Sozzo, Sandro; Veloz, Tomas

2018-01-01

We present a cognitive psychology experiment where participants were asked to select pairs of spatial directions that they considered to be the best example of Two different wind directions . Data are shown to violate the CHSH version of Bell's inequality with the same magnitude as in typical Bell-test experiments with entangled spins. Wind directions thus appear to be conceptual entities connected through meaning, in human cognition, in a similar way as spins appear to be entangled in experiments conducted in physics laboratories. This is the first part of a two-part article. In the second part (Aerts et al. in Found Sci, 2017) we present a symmetrized version of the same experiment for which we provide a quantum modeling of the collected data in Hilbert space.

Thermal conductivity of magnetic insulators with strong spin-orbit coupling

NASA Astrophysics Data System (ADS)

Stamokostas, Georgios; Lapas, Panteleimon; Fiete, Gregory A.

We study the influence of spin-orbit coupling on the thermal conductivity of various types of magnetic insulators. In the absence of spin-orbit coupling and orbital-degeneracy, the strong-coupling limit of Hubbard interactions at half filling can often be adequately described in terms of a pure spin Hamiltonian of the Heisenberg form. However, in the presence of spin-orbit coupling the resulting exchange interaction can become highly anisotropic. The effect of the atomic spin-orbit coupling, taken into account through the effect of magnon-phonon interactions and the magnetic order and excitations, on the lattice thermal conductivity of various insulating magnetic systems is studied. We focus on the regime of low temperatures where the dominant source of scattering is two-magnon scattering to one-phonon processes. The thermal current is calculated within the Boltzmann transport theory. We are grateful for financial support from NSF Grant DMR-0955778.

Thermal conductivity of magnetic insulators with strong spin-orbit coupling

NASA Astrophysics Data System (ADS)

Lapas, Panteleimon; Stamokostas, Georgios; Fiete, Gregory

2015-03-01

We study the influence of spin-orbit coupling on the thermal conductivity of various types of magnetic insulators. In the absence of spin-orbit coupling and orbital-degeneracy, the strong-coupling limit of Hubbard interactions at half filling can often be adequately described in terms of a pure spin Hamiltonian of the Heisenberg form. However, in the presence of spin-orbit coupling the resulting exchange interaction can become highly anisotropic. The effect of the atomic spin-orbit coupling, taken into account through the effect of magnon-phonon interactions and the magnetic order and excitations, on the lattice thermal conductivity of various insulating magnetic systems is studied. We focus on the regime of low temperatures where the dominant source of scattering is two-magnon scattering to one-phonon processes. The thermal current is calculated within the Boltzmann transport theory. We are grateful for financial support from NSF Grant DMR-0955778.

Compilation of Test Data on 111 Free-Spinning Airplane Models Tested in the Langley 15-Foot and 20-Foot Free-Spinning Tunnels

NASA Technical Reports Server (NTRS)

Malvestuto, Frank S.; Gale, Lawrence J.; Wood, John H.

1947-01-01

A compilation of free-spinning-airplane model data on the spin and recovery characteristics of 111 airplanes is presented. These data were previously published in separate memorandum reports and were obtained from free-spinning tests in the Langley 15-foot and the Langley 20-foot free-spinning tunnels. The model test data presented include the steady-spin and recovery characteristics of each model for various combinations of aileron and elevator deflections and for various loadings and dimensional configurations. Dimensional data, mass data, and a three-view drawing of the corresponding free-spinning tunnel model are also presented for each airplane. The data presented should be of value to designers and should facilitate the design of airplanes incorporating satisfactory spin-recovery characteristics.

Magneto-Seebeck effect in spin valves

NASA Astrophysics Data System (ADS)

Zhang, X. M.; Wan, C. H.; Wu, H.; Tang, P.; Yuan, Z. H.; Zhang, Q. T.; Zhang, X.; Tao, B. S.; Fang, C.; Han, X. F.

2017-10-01

The magneto-Seebeck (MS) effect, which is also called magneto-thermo-power, was observed in Co/Cu/Co and NiFe/Cu/Co spin valves. Their Seebeck coefficients in the parallel state were larger than those in the antiparallel state, and the MS ratio defined as (SAP -SP)/SP could reach -9% in our case. The MS effect originated not only from trivial giant magnetoresistance but also from spin current generated due to spin-polarized thermoelectric conductivity of ferromagnetic materials and subsequent modulation of the spin current by different spin configurations in spin valves. A simple Mott two-channel model reproduced a -11% MS effect for the Co/Cu/Co spin valves, qualitatively consistent with our observations. The MS effect could be applied for simultaneously sensing the temperature gradient and the magnetic field and also be possibly applied to determine spin polarization of thermoelectric conductivity and the Seebeck coefficient of ferromagnetic thin films.

Rotary balance data for a single-engine trainer design for an angle-of-attack range of 8 deg to 90 deg. [conducted in langely spin tunnel

NASA Technical Reports Server (NTRS)

Pantason, P.; Dickens, W.

1979-01-01

Aerodynamic characteristics obtained in a rotational flow environment utilizing a rotary balance located in the Langley spin tunnel are presented in plotted form for a 1/6 scale, single engine trainer airplane model. The configurations tested included the basic airplane, various wing leading edge devices, elevator, aileron and rudder control settings as well as airplane components. Data are presented without analysis for an angle of attack range of 8 to 90 degrees and clockwise and counter-clockwise rotations.

Quantum-ring spin interference device tuned by quantum point contacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diago-Cisneros, Leo; Mireles, Francisco

2013-11-21

We introduce a spin-interference device that comprises a quantum ring (QR) with three embedded quantum point contacts (QPCs) and study theoretically its spin transport properties in the presence of Rashba spin-orbit interaction. Two of the QPCs conform the lead-to-ring junctions while a third one is placed symmetrically in the upper arm of the QR. Using an appropriate scattering model for the QPCs and the S-matrix scattering approach, we analyze the role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations of the QR-device. Exact formulas are obtained for the spin-resolved conductances of the QR-device as a functionmore » of the confinement of the QPCs and the AB/AC phases. Conditions for the appearance of resonances and anti-resonances in the spin-conductance are derived and discussed. We predict very distinctive variations of the QR-conductance oscillations not seen in previous QR proposals. In particular, we find that the interference pattern in the QR can be manipulated to a large extend by varying electrically the lead-to-ring topological parameters. The latter can be used to modulate the AB and AC phases by applying gate voltage only. We have shown also that the conductance oscillations exhibits a crossover to well-defined resonances as the lateral QPC confinement strength is increased, mapping the eigenenergies of the QR. In addition, unique features of the conductance arise by varying the aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results may be of relevance for promising spin-orbitronics devices based on quantum interference mechanisms.« less

Rotating rake design for unique measurement of fan-generated spinning acoustic modes

NASA Technical Reports Server (NTRS)

Konno, Kevin E.; Hausmann, Clifford R.

1993-01-01

In light of the current emphasis on noise reduction in subsonic aircraft design, NASA has been actively studying the source of and propagation of noise generated by subsonic fan engines. NASA/LeRC has developed and tested a unique method of accurately measuring these spinning acoustic modes generated by an experimental fan. This mode measuring method is based on the use of a rotating microphone rake. Testing was conducted in the 9 x 15 Low-speed Wind Tunnel. The rotating rake was tested with the Advanced Ducted Propeller (ADP) model. This memorandum discusses the design and performance of the motor/drive system for the fan-synchronized rotating acoustic rake. This novel motor/drive design approach is now being adapted for additional acoustic mode studies in new test rigs as baseline data for the future design of active noise control for subsonic fan engines. Included in this memorandum are the research requirements, motor/drive specifications, test performance results, and a description of the controls and software involved.

The Kubo-Greenwood spin-dependent electrical conductivity of 2D transition-metal dichalcogenides and group-IV materials: A Green's function study

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Yarmohammadi, Mohsen

2018-04-01

The spin-dependent electrical conductivity of counterparts of graphene, transition-metal dichalcogenides (TMDs) and group-IV nanosheets, have investigated by a magnetic exchange field (MEF)-induction to gain the electronic transport properties of charge carriers. We have implemented a k.p Hamiltonian model through the Kubo-Greenwood formalism in order to address the dynamical behavior of correlated Dirac fermions. Tuning the MEF enables one to control the effective mass of carriers in group-IV and TMDs, differently. We have found the Dirac-like points in a new quantum anomalous Hall (QAH) state at strong MEFs for both structures. For both cases, a broad peak in electrical conductivity originated from the scattering rate and entropy is observed. Spin degeneracy at some critical MEFs is another remarkable point. We have found that in the limit of zero or uniform MEFs with respect to the spin-orbit interaction, the large resulting electrical conductivity depends on the spin sub-bands in group-IV and MLDs. Featuring spin-dependent electronic transport properties, one can provide a new scenario for future possible applications.

π Spin Berry Phase in a Quantum-Spin-Hall-Insulator-Based Interferometer: Evidence for the Helical Spin Texture of the Edge States

NASA Astrophysics Data System (ADS)

Chen, Wei; Deng, Wei-Yin; Hou, Jing-Min; Shi, D. N.; Sheng, L.; Xing, D. Y.

2016-08-01

The quantum spin Hall insulator is characterized by helical edge states, with the spin polarization of the electron being locked to its direction of motion. Although the edge-state conduction has been observed, unambiguous evidence of the helical spin texture is still lacking. Here, we investigate the coherent edge-state transport in an interference loop pinched by two point contacts. Because of the helical character, the forward interedge scattering enforces a π spin rotation. Two successive processes can only produce a nontrivial 2 π or trivial 0 spin rotation, which can be controlled by the Rashba spin-orbit coupling. The nontrivial spin rotation results in a geometric π Berry phase, which can be detected by a π phase shift of the conductance oscillation relative to the trivial case. Our results provide smoking gun evidence for the helical spin texture of the edge states. Moreover, it also provides the opportunity to all electrically explore the trajectory-dependent spin Berry phase in condensed matter.

Direct evidence of hidden local spin polarization in a centrosymmetric superconductor LaO0.55 F0.45BiS2.

PubMed

Wu, Shi-Long; Sumida, Kazuki; Miyamoto, Koji; Taguchi, Kazuaki; Yoshikawa, Tomoki; Kimura, Akio; Ueda, Yoshifumi; Arita, Masashi; Nagao, Masanori; Watauchi, Satoshi; Tanaka, Isao; Okuda, Taichi

2017-12-04

Conventional Rashba spin polarization is caused by the combination of strong spin-orbit interaction and spatial inversion asymmetry. However, Rashba-Dresselhaus-type spin-split states are predicted in the centrosymmetric LaOBiS 2 system by recent theory, which stem from the local inversion asymmetry of active BiS 2 layer. By performing high-resolution spin- and angle-resolved photoemission spectroscopy, we have investigated the electronic band structure and spin texture of superconductor LaO 0.55 F 0.45 BiS 2 . Here we present direct spectroscopic evidence for the local spin polarization of both the valence band and the conduction band. In particular, the coexistence of Rashba-like and Dresselhaus-like spin textures has been observed in the conduction band. The finding is of key importance for fabrication of proposed dual-gated spin-field effect transistor. Moreover, the spin-split band leads to a spin-momentum locking Fermi surface from which superconductivity emerges. Our demonstration not only expands the scope of spintronic materials but also enhances the understanding of spin-orbit interaction-related superconductivity.

Hot Electron Injection into Uniaxially Strained Silicon

NASA Astrophysics Data System (ADS)

Kim, Hyun Soo

In semiconductor spintronics, silicon attracts great attention due to the long electron spin lifetime. Silicon is also one of the most commonly used semiconductor in microelectronics industry. The spin relaxation process of diamond crystal structure such as silicon is dominant by Elliot-Yafet mechanism. Yafet shows that intravalley scattering process is dominant. The conduction electron spin lifetime measured by electron spin resonance measurement and electronic measurement using ballistic hot electron method well agrees with Yafet's theory. However, the recent theory predicts a strong contribution of intervalley scattering process such as f-process in silicon. The conduction band minimum is close the Brillouin zone edge, X point which causes strong spin mixing at the conduction band. A recent experiment of electric field-induced hot electron spin relaxation also shows the strong effect of f-process in silicon. In uniaxially strained silicon along crystal axis [100], the suppression of f-process is predicted which leads to enhance electron spin lifetime. By inducing a change in crystal structure due to uniaxial strain, the six fold degeneracy becomes two fold degeneracy, which is valley splitting. As the valley splitting increases, intervalley scattering is reduced. A recent theory predicts 4 times longer electron spin lifetime in 0.5% uniaxially strained silicon. In this thesis, we demonstrate ballistic hot electron injection into silicon under various uniaxial strain. Spin polarized hot electron injection under strain is experimentally one of the most challenging part to measure conduction electron spin lifetime in silicon. Hot electron injection adopts tunnel junction which is a thin oxide layer between two conducting materials. Tunnel barrier, which is an oxide layer, is only 4 ˜ 5 nm thick. Also, two conducting materials are only tens of nanometer. Therefore, under high pressure to apply 0.5% strain on silicon, thin films on silicon substrate can be easily destroyed. In order to confirm the performance of tunnel junction, we use tunnel magnetoresistance(TMR). TMR consists of two kinds of ferromagnetic materials and an oxide layer as tunnel barrier in order to measure spin valve effect. Using silicon as a collector with Schottky barrier interface between metal and silicon, ballistic hot spin polarized electron injection into silicon is demonstrated. We also observed change of coercive field and magnetoresistance due to modification of local states in ferromagnetic materials and surface states at the interface between metal and silicon due to strain.

Turbine engine rotor health monitoring evaluation by means of finite element analyses and spin tests data

NASA Astrophysics Data System (ADS)

Abdul-Aziz, Ali; Woike, Mark R.; Clem, Michelle; Baaklini, George Y.

2014-04-01

Generally, rotating engine components undergo high centrifugal loading environment which subject them to various types of failure initiation mechanisms. Health monitoring of these components is a necessity and is often challenging to implement. This is primarily due to numerous factors including the presence of scattered loading conditions, flaw sizes, component geometry and materials properties, all which hinder the simplicity of applying health monitoring applications. This paper represents a summary work of combined experimental and analytical modeling that included data collection from a spin test experiment of a rotor disk addressing the aforementioned durability issues. It further covers presentation of results obtained from a finite element modeling study to characterize the structural durability of a cracked rotor as it relates to the experimental findings. The experimental data include blade tip clearance, blade tip timing and shaft displacement measurements. The tests were conducted at the NASA Glenn Research Center's Rotordynamics Laboratory, a high precision spin rig. The results are evaluated and examined to determine their significance on the development of a health monitoring system to pre-predict cracks and other anomalies and to assist in initiating a supplemental physics based fault prediction analytical model.

Spin-Transfer Studies in Magnetic Multilayer Nanostructures

NASA Astrophysics Data System (ADS)

Emley, N. C.; Albert, F. J.; Ryan, E. M.; Krivorotov, I. N.; Ralph, D. C.; Buhrman, R. A.

2003-03-01

Numerous experiments have demonstrated current-induced magnetization reversal in ferromagnet/paramagnet/ferromagnet nanostructures with the current in the CPP geometry. The primary mechanism for this reversal is the transfer of angular momentum from the spin-polarized conduction electrons to the nanomagnet moment the spin transfer effect. This phenomenon has potential application in nanoscale, current-controlled non-volatile memory elements, but several challenges must be overcome for realistic device implementation. Typical Co/Cu/Co nanopillar devices, although effective for fundamental studies, are not advantageous for technological applications because of their large switching currents Ic ( 3-10 mA) and small R·A (< 1 mΩ·µm^2). Here we report initial results testing some possible approaches for enhancing spin-transfer device performance which involve the addition of more layers, and hence, more complexity, to the simple Co/Cu/Co trilayer structure. These additions include synthetic antiferromagnet layers (SAF), exchange biased layers, nano-oxide layers (NOL), and additional magnetic layers. Research supported by NSF and DARPA

Spinning Characteristics of the XN2Y-1 Airplane Obtained from the Spinning Balance and Compared with Results from the Spinning Tunnel and from Flight Tests

NASA Technical Reports Server (NTRS)

Bamber, M J; House, R O

1937-01-01

Report presents the results of tests of a 1/10-scale model of the XN2Y-1 airplane tested in the NACA 5-foot vertical wind tunnel in which the six components of forces and moments were measured. The model was tested in 17 attitudes in which the full-scale airplane had been observed to spin, in order to determine the effects of scale, tunnel, and interference. In addition, a series of tests was made to cover the range of angles of attack, angles of sideslip, rates of rotation, and control setting likely to be encountered by a spinning airplane. The data were used to estimate the probable attitudes in steady spins of an airplane in flight and of a model in the free-spinning tunnel. The estimated attitudes of steady spin were compared with attitudes measured in flight and in the spinning tunnel. The results indicate that corrections for certain scale and tunnel effects are necessary to estimate full-scale spinning attitudes from model results.

A status report on NASA general aviation stall/spin flight testing

NASA Technical Reports Server (NTRS)

Patton, J. M., Jr.

1980-01-01

The NASA Langley Research Center has undertaken a comprehensive program involving spin tunnel, static and rotary balance wind tunnel, full-scale wind tunnel, free flight radio control model, flight simulation, and full-scale testing. Work underway includes aerodynamic definition of various configurations at high angles of attack, testing of stall and spin prevention concepts, definition of spin and spin recovery characteristics, and development of test techniques and emergency spin recovery systems. This paper presents some interesting results to date for the first aircraft (low-wing, single-engine) in the program, in the areas of tail design, wing leading edge design, mass distribution, center of gravity location, and small airframe changes, with associated pilot observations. The design philosophy of the spin recovery parachute system is discussed in addition to test techniques.

Tunable Intrinsic Spin Hall Conductivities in Bi2(Se,Te)3 Topological Insulators

NASA Astrophysics Data System (ADS)

Şahin, Cüneyt; Flatté, Michael E.

2015-03-01

It has been recently shown by spin-transfer torque measurements that Bi2Se3 exhibits a very large spin Hall conductivity (SHC). It is expected that Bi2Te3, a topological insulator with similar crystal and band structures as well as large spin-orbit coupling, would also exhibit a giant SHC. In this study we have calculated intrinsic spin Hall conductivities of Bi2Se3andBi2Te3 topological insulators from a tight-binding Hamiltonian including two nearest-neighbor interactions. We have calculated the Berry curvature, used the Kubo formula in the static, clean limit and shown that both materials exhibit giant spin Hall conductivities, consistent with the results of Ref. 1 and larger than previously reported Bi1-xSbx alloys. The density of Berry curvature has also been computed from the full Brillouin zone in order to compute the dependence of the SHC in these materials on the Fermi energy. Finally we report the intrinsic SHC for Bi2(Se,Te)3 topological insulators, which changes dramatically with doping or gate voltage. This work was supported in part by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

Gate control of spin-polarized conductance in alloyed transitional metal nanocontacts

NASA Astrophysics Data System (ADS)

Sivkov, Ilia N.; Brovko, Oleg O.; Rungger, Ivan; Stepanyuk, Valeri S.

2017-03-01

To date, endeavors in nanoscale spintronics are dominated by the use of single-electron or single-spin transistors having at their heart a semiconductor, metallic, or molecular quantum dot whose localized states are non-spin-degenerate and can be controlled by an external bias applied via a gate electrode. Adjusting the bias of the gate one can realign those states with respect to the chemical potentials of the leads and thus tailor the spin-polarized transmission properties of the device. Here we show that similar functionality can be achieved in a purely metallic junction comprised of a metallic magnetic chain attached to metallic paramagnetic leads and biased by a gate electrode. Our ab initio calculations of electron transport through mixed Pt-Fe (Fe-Pd and Fe-Rh) atomic chains suspended between Pt (Pd and Rh) electrodes show that spin-polarized confined states of the chain can be shifted by the gate bias causing a change in the relative contributions of majority and minority channels to the nanocontact's conductance. As a result, we observe strong dependence of conductance spin polarization on the applied gate potential. In some cases the spin polarization of conductance can even be reversed in sign upon gate potential application, which is a remarkable and promising trait for spintronic applications.

Free-Spinning and Recovery Characteristics of a 1/19-Scale Model of the North American T-28C Airplane, TED No. NACA AD 3127

NASA Technical Reports Server (NTRS)

Bowman, James S., Jr.

1956-01-01

An investigation has been conducted in the Langley 20-foot free-spinning tunnel on a l/19-scale model of the North American T-28C airplane to determine the spin and recovery characteristics. The T-28C airplane is similar to the T-28B airplane except for slight modifications for the arresting hook. The lower rear section of the fuselage was cut out and, consequently, the lower part of the rudder was removed to make a smooth fairing with the fuselage. The T-28B airplane had good recovery characteristics; but these modifications, along with the addition of gun packages on the wings, led to poor and unsatisfactory spin-recovery characteristics during demonstration spins of the T-28C airplane. Model test results indicated that without the gun packages installed, satisfactory recoveries could be obtained if the elevators were held full back while the rudder was fully reversed and the ailerons were held neutral. However, with the addition of gun packages to the wings and the corresponding change in loading, recoveries were considered unsatisfactory. Recoveries attempted by using a larger chord or larger span rudder were improved very slightly, but were still considered marginal or unsatisfactory. Strakes placed on the nose of the model were effective in slowing the spin rotation slightly and, in most instances, decreased the turns for recovery slightly. Recovery characteristics were slightly marginal for the full fuel loading when strakes and the extended-chord rudder were installed; but with the wing fuel partly used, recovery characteristics were again considered unsatisfactory or, at least, definitely on the marginal side. The optimum control technique for recovery is movement of the rudder to full against the spin with the stick held full back (elevators full up) and the ailerons held neutral, followed by forward movement of the stick only after the spin rotation ceases. Inverted-spin test results indicate that the airplane will spin steep and fast and that recovery by full rudder reversal will be satisfactory if the ailerons are held neutral.

Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elyasi, Mehrdad; Bhatia, Charanjit S.; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg

2015-02-14

We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets.

Measurements of decreasing lattice thermal conductivity of ferropericlase across the high-spin to mixed-spin state.

NASA Astrophysics Data System (ADS)

Merkel, S.; Langrand, C.; Hilairet, N.; Konopkova, Z.; Andrault, D.

2016-12-01

The thermal conductivity of lower mantle minerals depends on crystal structure and phase, with important implications for the style of convection in the mantle and the heat flow across the core-mantle boundary. In this study, we demonstrate how measurements of temperature in the laser-heated diamond anvil cell (LHDAC) can be used to determine relative changes in thermal conductivity across a pressure-induced phase change. A finite-element 3D heat flow model of the LHDAC is used to simulate experimental conditions. Results from modeling show that the peak temperature in the cell is primarily controlled by the geometry, sample thermal conductivity and heat input due to laser heating. Controlling for geometry, the model can output expected temperature versus laser-power curves for an increase or decrease in thermal conductivity with pressure. The modeled temperature differences indicate that we can experimentally distinguish the sign and magnitude of a thermal conductivity change due to a pressure-induced phase change. We perform a series of experiments to test our models. In one set of experiments, we measure temperature versus laser-power as a function of pressure for the NaCl B1-B2 phase transition, over the pressure range 18 to 54 GPa. A decrease in thermal conductivity across the NaCl B1-B2 phase transition (dκ/dP = -1.6 +/- 0.2 W/(mK GPa)) is needed to explain our measurements. This result is consistent with thermal conductivity measurements of other ionic salts, which undergo the B1-B2 phase transition at much lower pressure. We apply this experiment design to investigate the effect of spin transition on an iron-bearing magnesium oxide sample. In a series of experiments, we measure temperature vs. laser power for (Mg,Fe)O with 24 mol% Fe, loaded in Ne, over a pressure range from 22 to 60 GPa. We observe an increase in thermal conductivity between 22 and 42 GPa. But between 42 and 60 GPa, a pressure range consistent with previously reported mixed-spin state phase of (Mg,Fe)O, we observe a decrease in thermal conductivity. This result suggests that there may be a broad zone, in the depth range of 1000 - 1500 km, of reduced thermal transport properties in the mantle.

Measurements of decreasing lattice thermal conductivity of ferropericlase across the high-spin to mixed-spin state.

NASA Astrophysics Data System (ADS)

McGuire, C. P.; Sawchuk, K. L. S.; Kavner, A.

2017-12-01

The thermal conductivity of lower mantle minerals depends on crystal structure and phase, with important implications for the style of convection in the mantle and the heat flow across the core-mantle boundary. In this study, we demonstrate how measurements of temperature in the laser-heated diamond anvil cell (LHDAC) can be used to determine relative changes in thermal conductivity across a pressure-induced phase change. A finite-element 3D heat flow model of the LHDAC is used to simulate experimental conditions. Results from modeling show that the peak temperature in the cell is primarily controlled by the geometry, sample thermal conductivity and heat input due to laser heating. Controlling for geometry, the model can output expected temperature versus laser-power curves for an increase or decrease in thermal conductivity with pressure. The modeled temperature differences indicate that we can experimentally distinguish the sign and magnitude of a thermal conductivity change due to a pressure-induced phase change. We perform a series of experiments to test our models. In one set of experiments, we measure temperature versus laser-power as a function of pressure for the NaCl B1-B2 phase transition, over the pressure range 18 to 54 GPa. A decrease in thermal conductivity across the NaCl B1-B2 phase transition (dκ/dP = -1.6 +/- 0.2 W/(mK GPa)) is needed to explain our measurements. This result is consistent with thermal conductivity measurements of other ionic salts, which undergo the B1-B2 phase transition at much lower pressure. We apply this experiment design to investigate the effect of spin transition on an iron-bearing magnesium oxide sample. In a series of experiments, we measure temperature vs. laser power for (Mg,Fe)O with 24 mol% Fe, loaded in Ne, over a pressure range from 22 to 60 GPa. We observe an increase in thermal conductivity between 22 and 42 GPa. But between 42 and 60 GPa, a pressure range consistent with previously reported mixed-spin state phase of (Mg,Fe)O, we observe a decrease in thermal conductivity. This result suggests that there may be a broad zone, in the depth range of 1000 - 1500 km, of reduced thermal transport properties in the mantle.

Electric measurement and magnetic control of spin transport in InSb-based lateral spin devices

NASA Astrophysics Data System (ADS)

Viglin, N. A.; Ustinov, V. V.; Demokritov, S. O.; Shorikov, A. O.; Bebenin, N. G.; Tsvelikhovskaya, V. M.; Pavlov, T. N.; Patrakov, E. I.

2017-12-01

Electric injection and detection of spin-polarized electrons in InSb semiconductors have been realized in nonlocal experimental geometry using an InSb-based "lateral spin valve." The valve of the InSb /MgO /C o0.9F e0.1 composition has semiconductor/insulator/ferromagnet nanoheterojunctions in which the thickness of the InSb layer considerably exceeded the spin diffusion length of conduction electrons. The spin direction in spin diffusion current has been manipulated by a magnetic field under the Hanle effect conditions. The spin polarization of the electron gas has been registered using ferromagnetic C o0.9F e0.1 probes by measuring electrical potentials arising in the probes in accordance with the Johnson-Silsbee concept of the spin-charge coupling. The developed theory is valid at any degree of degeneracy of electron gas in a semiconductor. The spin relaxation time and spin diffusion length of conduction electrons in InSb have been determined, and the electron-spin polarization in InSb has been evaluated for electrons injected from C o0.9F e0.1 through an MgO tunnel barrier.

Spin injection and spin transport in paramagnetic insulators

DOE PAGES

Okamoto, Satoshi

2016-02-22

We investigate the spin injection and the spin transport in paramagnetic insulators described by simple Heisenberg interactions using auxiliary particle methods. Some of these methods allow access to both paramagnetic states above magnetic transition temperatures and magnetic states at low temperatures. It is predicted that the spin injection at an interface with a normal metal is rather insensitive to temperatures above the magnetic transition temperature. On the other hand below the transition temperature, it decreases monotonically and disappears at zero temperature. We also analyze the bulk spin conductance. We show that the conductance becomes zero at zero temperature as predictedmore » by linear spin wave theory but increases with temperature and is maximized around the magnetic transition temperature. These findings suggest that the compromise between the two effects determines the optimal temperature for spintronics applications utilizing magnetic insulators.« less

Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry

DOE PAGES

Ma, Eric Yue; Calvo, M. Reyes; Wang, Jing; ...

2015-05-26

The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy,more » and compare our findings to a non-inverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. Finally, this indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.« less

Taking Engineering Design out for a Spin

ERIC Educational Resources Information Center

Crismond, David; Soobyiah, Mark; Cain, Ryan

2013-01-01

This article highlights what inquiry and design have in common, and what makes engineering design uniquely different from inquiry. A case study is presented that gives students practice in conducting fair-test experiments, in troubleshooting to learn how to make designs better, and in building science-based explanations for how things work. The…

Mott transition between a spin-liquid insulator and a metal in three dimensions.

PubMed

Podolsky, Daniel; Paramekanti, Arun; Kim, Yong Baek; Senthil, T

2009-05-08

We study a bandwidth controlled Mott metal-insulator transition (MIT) from a Fermi-liquid metal to a quantum spin-liquid insulator in three dimensions. Using a slave rotor approach including gauge fluctuations, we obtain a continuous MIT and discuss finite temperature crossovers in its vicinity. We show that the specific heat C approximately Tlnln(1/T) at the MIT and that the metallic state near the MIT should exhibit a "conductivity minimum" as a function of temperature. We suggest Na4Ir3O8 as a candidate to test our predictions and compute its electron spectral function at the MIT.

Temperature Dependence of the Spin-Hall Conductivity of a Two-Dimensional Impure Rashba Electron Gas in the Presence of Electron-Phonon and Electron-Electron Interactions

NASA Astrophysics Data System (ADS)

Yavari, H.; Mokhtari, M.; Bayervand, A.

2015-03-01

Based on Kubo's linear response formalism, temperature dependence of the spin-Hall conductivity of a two-dimensional impure (magnetic and nonmagnetic impurities) Rashba electron gas in the presence of electron-electron and electron-phonon interactions is analyzed theoretically. We will show that the temperature dependence of the spin-Hall conductivity is determined by the relaxation rates due to these interactions. At low temperature, the elastic lifetimes ( and are determined by magnetic and nonmagnetic impurity concentrations which are independent of the temperature, while the inelastic lifetimes ( and related to the electron-electron and electron-phonon interactions, decrease when the temperature increases. We will also show that since the spin-Hall conductivity is sensitive to temperature, we can distinguish the intrinsic and extrinsic contributions.

Photo-conductance of a single Quantum Dot

NASA Astrophysics Data System (ADS)

Zimmers, Alexandre; Wang, Hongyue; Lhuillier, Emmanuel; Yu, Qian; Dubertret, Benoit; Aubin, Herve; Ulysse, Christian; LPEM Collaboration

One promising strategy for the development of nanoscale resonant spin sensors is to measure the spin-dependent photo-current in Quantum Dots (QDots) containing spin-dependent recombination centers. To reach single spin sensitivity will require measurements of the photo-conductance of single QDots. We present here an experimental study of the conductance and photo-conductance of single HgSe QDots as function of drain and gate voltage. The evolution of the differential conductance dI/dV spectrum with the gate voltage demonstrates that single HgSe QDots are forming the junction. The amplitude of the gap measured in the differential conductance spectrum changes with the occupation level. A large inter-band gap, 0,85eV, is observed for the empty QDot, a smaller intra-band gap 0,25eV is observed for the doubly occupied QDot. These gap energies are consistent with the values extracted from the optical absorption spectrum. Upon illuminating the QDot junction, we show that the photo-conductive signal produced by this single QDot can be measured with a simple demodulation method. ANR Grant ''QUANTICON'' 10-0409-01 / DIM Nano-K / Chinese Scholarship Council.

Spin Hall effect and Landau spectrum of Dirac electrons in bismuth

NASA Astrophysics Data System (ADS)

Fuseya, Yuki

2015-03-01

Bismuth has played an important role in solid-state physics. Many key phenomena were first discovered in bismuth, such as diamagnetism, Seebeck, Nernst, Shubnikov-de Haas, and de Haas-van Alphen effects. These phenomena result from particular electronic states of bismuth. The strong spin-orbit interaction (~ 1.5eV) causes strong spin-dependent interband couplings resulting in an anomalous spin magnetic moment. We investigate the spin Hall effect and the angular dependent Landau spectrum of bismuth paying special attention to the effect of the anomalous spin magnetic moment. It is shown that the spin Hall insulator is possible and there is a fundamental relationship between the spin Hall conductivity and orbital diamagnetism in the insulating state of the Dirac electrons. Based on this theoretical finding, the magnitude of spin Hall conductivity is estimated for bismuth by that of orbital susceptibility. The magnitude of spin Hall conductivity turns out to be as large as 104Ω-1 cm-1, which is about 100 times larger than that of Pt. It is also shown that the ratio of the Zeeman splitting to the cyclotron energy, which reflects the effect of crystalline spin-orbit interaction, for holes at the T-point can be larger than 1.0 (the maximum of previous theories) and exhibit strong angular dependence, which gives a possible solution to the long-standing mystery of holes at the T-point. In collaboration with Masao Ogata, Hidetoshi Fukuyama, Zengwei Zhu, Benoît Fauqué, Woun Kang, and Kamran Behnia. Supported by JSPS (KAKENHI 24244053, 25870231, and 13428660).

Gauge Physics of Spin Hall Effect

PubMed Central

Tan, Seng Ghee; Jalil, Mansoor B. A.; Ho, Cong Son; Siu, Zhuobin; Murakami, Shuichi

2015-01-01

Spin Hall effect (SHE) has been discussed in the context of Kubo formulation, geometric physics, spin orbit force, and numerous semi-classical treatments. It can be confusing if the different pictures have partial or overlapping claims of contribution to the SHE. In this article, we present a gauge-theoretic, time-momentum elucidation, which provides a general SHE equation of motion, that unifies under one theoretical framework, all contributions of SHE conductivity due to the kinetic, the spin orbit force (Yang-Mills), and the geometric (Murakami-Fujita) effects. Our work puts right an ambiguity surrounding previously partial treatments involving the Kubo, semiclassical, Berry curvatures, or the spin orbit force. Our full treatment shows the Rashba 2DEG SHE conductivity to be instead of −, and Rashba heavy hole instead of −. This renewed treatment suggests a need to re-derive and re-calculate previously studied SHE conductivity. PMID:26689260

Electron transport through magnetic quantum point contacts

NASA Astrophysics Data System (ADS)

Day, Timothy Ellis

Spin-based electronics, or spintronics, has generated a great deal of interest as a possible next-generation integrated circuit technology. Recent experimental and theoretical work has shown that these devices could exhibit increased processing speed, decreased power consumption, and increased integration densities as compared with conventional semiconductor devices. The spintronic device that was designed, fabricated, and tested throughout the course of this work aimed to study the generation of spin-polarized currents in semiconductors using magnetic fringe fields. The device scheme relied on the Zeeman effect in combination with a quantum mechanical barrier to generate spin-polarized currents. The Zeeman effect was used to break the degeneracy of spin-up and spin-down electrons and the quantum mechanical potential to transmit one while rejecting the other. The design was dictated by the drive to maximize the strength of the magnetic fringe field and in turn maximize the energy separation of the two spin species. The device was fabricated using advanced techniques in semiconductor processing including electron beam lithography and DC magnetron sputtering. Measurements were performed in a 3He cryostat equipped with a superconducting magnet at temperatures below 300 mK. Preliminary characterization of the device revealed magnetoconductance oscillations produced by the effect of the transverse confining potential on the density of states and the mobility. Evidence of the effect of the magnetic fringe fields on the transport properties of electrons in the device were observed in multiple device measurements. An abrupt washout of the quantized conductance steps was observed over a minute range of the applied magnetic field. The washout was again observed as electrons were shifted closer to the magnetic gates. In addition, bias spectroscopy demonstrated that the washout occurred despite stronger electron confinement, as compared to a non-magnetic split-gate. Thus, the measurements indicated that conductance quantization breaks down in a non-uniform magnetic field, possibly due to changes to the stationary Landau states. It was also demonstrated that non-integer conductance plateaus at high source-drain bias are not caused by a macroscopic asymmetry in the potential drop.

Spin current and second harmonic generation in non-collinear magnetic systems: the hydrodynamic model

NASA Astrophysics Data System (ADS)

Karashtin, E. A.; Fraerman, A. A.

2018-04-01

We report a theoretical study of the second harmonic generation in a noncollinearly magnetized conductive medium with equilibrium spin current. The hydrodynamic model is used to unravel the mechanism of a novel effect of the double frequency signal generation that is attributed to the spin current. According to our calculations, this second harmonic response appears due to the ‘non-adiabatic’ spin polarization of the conduction electrons induced by the oscillations in the non-uniform magnetization forced by the electric field of the electromagnetic wave. Together with the linear velocity response this leads to the generation of the double frequency spin current. This spin current is converted to the electric current via the inverse spin Hall effect, and the double-frequency electric current emits the second harmonic radiation. Possible experiment for detection of the new second harmonic effect is proposed.

Tunneling Anomalous and Spin Hall Effects.

PubMed

Matos-Abiague, A; Fabian, J

2015-07-31

We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems.

Temperature dependence of pure spin current and spin-mixing conductance in the ferromagnetic—normal metal structure

NASA Astrophysics Data System (ADS)

Atsarkin, V. A.; Borisenko, I. V.; Demidov, V. V.; Shaikhulov, T. A.

2018-06-01

Temperature evolution of pure spin current has been studied in an epitaxial thin-film bilayer La2/3Sr1/3MnO3/Pt deposited on a NdGaO3 substrate. The spin current was generated by microwave pumping under conditions of ferromagnetic resonance in the ferromagnetic La2/3Sr1/3MnO3 layer and detected in the Pt layer due to the inverse spin Hall effect. A considerable increase in the spin current magnitude has been observed upon cooling from the Curie point (350 K) down to 100 K. Using the obtained data, the temperature evolution of the mixed spin conductance g mix (T) has been extracted. It was found that the g mix (T) dependence correlates with magnetization in a thin area adjacent to the ferromagnetic-normal metal interface.

Design and Experimental Study on Spinning Solid Rocket Motor

NASA Astrophysics Data System (ADS)

Xue, Heng; Jiang, Chunlan; Wang, Zaicheng

The study on spinning solid rocket motor (SRM) which used as power plant of twice throwing structure of aerial submunition was introduced. This kind of SRM which with the structure of tangential multi-nozzle consists of a combustion chamber, propellant charge, 4 tangential nozzles, ignition device, etc. Grain design, structure design and prediction of interior ballistic performance were described, and problem which need mainly considered in design were analyzed comprehensively. Finally, in order to research working performance of the SRM, measure pressure-time curve and its speed, static test and dynamic test were conducted respectively. And then calculated values and experimental data were compared and analyzed. The results indicate that the designed motor operates normally, and the stable performance of interior ballistic meet demands. And experimental results have the guidance meaning for the pre-research design of SRM.

Supplementary Investigation to Determine the Effects of Center-of-Gravity Position on the Spin, Longitudinal-Trim, and Tumbling Characteristics of a 1/20-Scale Model of the Consolidated Vultee 7002 Airplane (Flying Mock-up of XF-92)

NASA Technical Reports Server (NTRS)

Klinar, Walter J.; Jones, Ira P., Jr.

1948-01-01

A supplementary wind-tunnel investigation has been conducted to determine the effect of rearward positions of the center of gravity on the spin, longitudinal-trim, and tumbling characteristics of the 1/20-scale model of the Consolidated Vultee 7002 airplane equipped with the single vertical tail. A few tests were also made with dual vertical tails added to the model. The model was ballasted to represent, the airplane in its approximate design gross weight for two center-of-gravity positions, 3O and 35 percent of the mean aerodynamic chord. The original tests previously reported were for a center-of-gravity position of 24 percent of the mean aerodynamic chord.

Impact of hole doping on spin transition in perovskite-type cobalt oxides.

PubMed

Che, Xiangli; Li, Liping; Hu, Wanbiao; Li, Guangshe

2016-06-28

Series of perovskite PrCo1-xNixO3-δ (x = 0-0.4) were prepared and carefully investigated to understand the spin state transition driven by hole doping and further to reveal the effect of spin state transition on electronic conduction. It is shown that with increasing doping level, the transition temperature Ts for Co(3+) ions from low-spin (LS) to intermediate-spin (IS) reduces from 211.9 K for x = 0 to 190.5 K for x = 0.4. XPS and FT-IR spectra demonstrate that hole doping promoted this transition due to a larger Jahn-Teller distortion. Moreover, a thermal activation of spin disorder caused by thermal population of the spin states for Co ions has a great impact on the electrical transport of these perovskite samples. This work may shed light on the comprehension of spin transition in cobalt oxides through hole doping, which is promising for finding new strategies of enhancing electronic conduction, especially for energy and catalysis applications.

Chemical disorder as an engineering tool for spin polarization in Mn3Ga -based Heusler systems

NASA Astrophysics Data System (ADS)

Chadov, S.; D'Souza, S. W.; Wollmann, L.; Kiss, J.; Fecher, G. H.; Felser, C.

2015-03-01

Our study highlights spin-polarization mechanisms in metals by focusing on the mobilities of conducting electrons with different spins instead of their quantities. Here, we engineer electron mobility by applying chemical disorder induced by nonstoichiometric variations. As a practical example, we discuss the scheme that establishes such variations in tetragonal Mn3Ga Heusler material. We justify this approach using first-principles calculations of the spin-projected conductivity components based on the Kubo-Greenwood formalism. It follows that, in the majority of cases, even a small substitution of some other transition element instead of Mn may lead to a substantial increase in spin polarization along the tetragonal axis.

Electric field controlled spin interference in a system with Rashba spin-orbit coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciftja, Orion, E-mail: ogciftja@pvamu.edu

There have been intense research efforts over the last years focused on understanding the Rashba spin-orbit coupling effect from the perspective of possible spintronics applications. An important component of this line of research is aimed at control and manipulation of electron’s spin degrees of freedom in semiconductor quantum dot devices. A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction in a two-dimensional electron system embedded in a host semiconducting material that lacks inversion-symmetry. This way, the Rashba spin-orbit coupling effect may potentially lead to fabrication of amore » new generation of spintronic devices where control of spin, thus magnetic properties, is achieved via an electric field and not a magnetic field. In this work we investigate theoretically the electron’s spin interference and accumulation process in a Rashba spin-orbit coupled system consisting of a pair of two-dimensional semiconductor quantum dots connected to each other via two conducting semi-circular channels. The strength of the confinement energy on the quantum dots is tuned by gate potentials that allow “leakage” of electrons from one dot to another. While going through the conducting channels, the electrons are spin-orbit coupled to a microscopically generated electric field applied perpendicular to the two-dimensional system. We show that interference of spin wave functions of electrons travelling through the two channels gives rise to interference/conductance patterns that lead to the observation of the geometric Berry’s phase. Achieving a predictable and measurable observation of Berry’s phase allows one to control the spin dynamics of the electrons. It is demonstrated that this system allows use of a microscopically generated electric field to control Berry’s phase, thus, enables one to tune the spin-dependent interference pattern and spintronic properties with no need for injection of spin-polarized electrons.« less

Nonlocal magnon spin transport in yttrium iron garnet with tantalum and platinum spin injection/detection electrodes

NASA Astrophysics Data System (ADS)

Liu, J.; Cornelissen, L. J.; Shan, J.; van Wees, B. J.; Kuschel, T.

2018-06-01

We study the magnon spin transport in the magnetic insulator yttrium iron garnet (YIG) in a nonlocal experiment and compare the magnon spin excitation and detection for the heavy metal paramagnetic electrodes platinum (Pt|YIG|Pt) and tantalum (Ta|YIG|Ta). The electrical injection and detection processes rely on the (inverse) spin Hall effect in the heavy metals and the conversion between the electron spin and magnon spin at the heavy metal|YIG interface. Pt and Ta possess opposite signs of the spin Hall angle. Furthermore, their heterostructures with YIG have different interface properties, i.e. spin mixing conductances. By varying the distance between injector and detector, the magnon spin transport is studied. Using a circuit model based on the diffusion-relaxation transport theory, a similar magnon relaxation length of  ∼10 μm was extracted from both Pt and Ta devices. By changing the injector and detector material from Pt to Ta, the influence of interface properties on the magnon spin transport has been observed. For Ta devices on YIG the spin mixing conductance is reduced compared with Pt devices, which is quantitatively consistent when comparing the dependence of the nonlocal signal on the injector-detector distance with the prediction from the circuit model.

Spin-dependent electrical conduction in a pentacene Schottky diode explored by electrically detected magnetic resonance

NASA Astrophysics Data System (ADS)

Fukuda, Kunito; Asakawa, Naoki

2017-02-01

Reported is the observation of dark spin-dependent electrical conduction in a Schottky barrier diode with pentacene (PSBD) using electrically detected magnetic resonance at room temperature. It is suggested that spin-dependent conduction exists in pentacene thin films, which is explored by examining the anisotropic linewidth of the EDMR signal and current density-voltage (J-V) measurements. The EDMR spectrum can be decomposed to Gaussian and Lorentzian components. The dependency of the two signals on the applied voltage was consistent with the current density-voltage (J-V) of the PSBD rather than that of the electron-only device of Al/pentacene/Al, indicating that the spin-dependent conduction is due to bipolaron formation associated with hole polaronic hopping processes. The applied-voltage dependence of the ratio of intensity of the Gaussian line to the Lorentzian may infer that increasing current density should make conducting paths more dispersive, thereby resulting in an increased fraction of the Gaussian line due to the higher dispersive g-factor.

Spin transport in oxygen adsorbed graphene nanoribbon

NASA Astrophysics Data System (ADS)

Kumar, Vipin

2018-04-01

The spin transport properties of pristine graphene nanoribbons (GNRs) have been most widely studied using theoretical and experimental tools. The possibilities of oxidation of fabricated graphene based nano electronic devices may change the device characteristics, which motivates to further explore the properties of graphene oxide nanoribbons (GONRs). Therefore, we present a systematic computational study on the spin polarized transport in surface oxidized GNR in antiferromagnetic (AFM) spin configuration using density functional theory combined with non-equilibrium Green's function (NEGF) method. It is found that the conductance in oxidized GNRs is significantly suppressed in the valance band and the conduction band. A further reduction in the conductance profile is seen in presence of two oxygen atoms on the ribbon plane. This change in the conductance may be attributed to change in the surface topology of the ribbon basal plane due to presence of the oxygen adatoms, where the charge transfer take place between the ribbon basal plane and the oxygen atoms.

Hydrogen-Fuel Engine Component Tests Near Completion

NASA Technical Reports Server (NTRS)

2003-01-01

Gaseous hydrogen is burned off at the E1 Test Stand the night of Oct. 7 during a cold-flow test of the fuel turbopump of the Integrated Powerhead Demonstrator (IPD) at NASA Stennis Space Center (SSC). The gaseous hydrogen spins the pump's turbine during the test, which was conducted to verify the pump's performance. Engineers plan one more test before sending the pump to The Boeing Co. for inspection. It will then be returned to SSC for engine system assembly. The IPD is the first reusable hydrogen-fueled advanced engine in development since the Space Shuttle Main Engine.

Hydrogen-Fuel Engine Component Tests Near Completion

NASA Image and Video Library

2003-11-05

Gaseous hydrogen is burned off at the E1 Test Stand the night of Oct. 7 during a cold-flow test of the fuel turbopump of the Integrated Powerhead Demonstrator (IPD) at NASA Stennis Space Center (SSC). The gaseous hydrogen spins the pump's turbine during the test, which was conducted to verify the pump's performance. Engineers plan one more test before sending the pump to The Boeing Co. for inspection. It will then be returned to SSC for engine system assembly. The IPD is the first reusable hydrogen-fueled advanced engine in development since the Space Shuttle Main Engine.

Magnon Valve Effect between Two Magnetic Insulators.

PubMed

Wu, H; Huang, L; Fang, C; Yang, B S; Wan, C H; Yu, G Q; Feng, J F; Wei, H X; Han, X F

2018-03-02

The key physics of the spin valve involves spin-polarized conduction electrons propagating between two magnetic layers such that the device conductance is controlled by the relative magnetization orientation of two magnetic layers. Here, we report the effect of a magnon valve which is made of two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer (Au). When a thermal gradient is applied perpendicular to the layers, the inverse spin Hall voltage output detected by a Pt bar placed on top of the magnon valve depends on the relative orientation of the magnetization of two YIG layers, indicating the magnon current induced by the spin Seebeck effect at one layer affects the magnon current in the other layer separated by Au. We interpret the magnon valve effect by the angular momentum conversion and propagation between magnons in two YIG layers and conduction electrons in the Au layer. The temperature dependence of the magnon valve ratio shows approximately a power law, supporting the above magnon-electron spin conversion mechanism. This work opens a new class of valve structures beyond the conventional spin valves.

Magnon Valve Effect between Two Magnetic Insulators

NASA Astrophysics Data System (ADS)

Wu, H.; Huang, L.; Fang, C.; Yang, B. S.; Wan, C. H.; Yu, G. Q.; Feng, J. F.; Wei, H. X.; Han, X. F.

2018-03-01

The key physics of the spin valve involves spin-polarized conduction electrons propagating between two magnetic layers such that the device conductance is controlled by the relative magnetization orientation of two magnetic layers. Here, we report the effect of a magnon valve which is made of two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer (Au). When a thermal gradient is applied perpendicular to the layers, the inverse spin Hall voltage output detected by a Pt bar placed on top of the magnon valve depends on the relative orientation of the magnetization of two YIG layers, indicating the magnon current induced by the spin Seebeck effect at one layer affects the magnon current in the other layer separated by Au. We interpret the magnon valve effect by the angular momentum conversion and propagation between magnons in two YIG layers and conduction electrons in the Au layer. The temperature dependence of the magnon valve ratio shows approximately a power law, supporting the above magnon-electron spin conversion mechanism. This work opens a new class of valve structures beyond the conventional spin valves.

Spin transport properties of n-polyacene molecules (n = 1–15) connected to Ni surface electrodes: Theoretical analysis

PubMed Central

Caliskan, S.; Laref, A.

2014-01-01

Using non-equilibrium Green function formalism in conjunction with density functional theory, we explore the spin-polarized transport characteristics of several planar n-acene molecules suspended between two semi-infinite Ni electrodes via the thiol group. We examine the spin-dependence transport on Ni-n-acenes-Ni junctions, while the number of fused benzene rings varies between 1 and 15. Intriguingly, the induced magnetic moments of small acene molecules are higher than that of longer acene rings. The augmentation of fused benzene rings affects both the magnetic and transport features, such as the transmission function and conductance owing to their coupling to the Ni surface contacts via the anchoring group. The interplay between the spin-polarized transport properties, structural configuration and molecular electronic is a fortiori essential in these attractive molecular devices. Thus, this can conduct to the engineering of the electron spin transport in atomistic and molecular junctions. These prominent molecules convincingly infer that the molecular spin valves can conduct to thriving molecular devices. PMID:25482076

Spin transport in normal metal/insulator/topological insulator coupled to ferromagnetic insulator structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kondo, Kenji, E-mail: kkondo@es.hokudai.ac.jp

In this study, we investigate the spin transport in normal metal (NM)/insulator (I)/topological insulator (TI) coupled to ferromagnetic insulator (FI) structures. In particular, we focus on the barrier thickness dependence of the spin transport inside the bulk gap of the TI with FI. The TI with FI is described by two-dimensional (2D) Dirac Hamiltonian. The energy profile of the insulator is assumed to be a square with barrier height V and thickness d along the transport-direction. This structure behaves as a tunnel device for 2D Dirac electrons. The calculation is performed for the spin conductance with changing the barrier thicknessmore » and the components of magnetization of FI layer. It is found that the spin conductance decreases with increasing the barrier thickness. Also, the spin conductance is strongly dependent on the polar angle θ, which is defined as the angle between the axis normal to the FI and the magnetization of FI layer. These results indicate that the structures are promising candidates for novel tunneling magnetoresistance devices.« less

Development of fiber shields for engine containment. [mathematical models

NASA Technical Reports Server (NTRS)

Bristow, R. J.; Davidson, C. D.

1977-01-01

Tests were conducted in translational launchers and spin pits to generate empirical data used in the design of a Kevlar shield for containing engine burst debris. Methods are given for modeling the relationship of fragment characteristics to shielding requirements. The change in relative importance of shield mounting provisions as fragment energy is increased is discussed.

Extrinsic Rashba spin-orbit coupling effect on silicene spin polarized field effect transistors

NASA Astrophysics Data System (ADS)

Pournaghavi, Nezhat; Esmaeilzadeh, Mahdi; Abrishamifar, Adib; Ahmadi, Somaieh

2017-04-01

Regarding the spin field effect transistor (spin FET) challenges such as mismatch effect in spin injection and insufficient spin life time, we propose a silicene based device which can be a promising candidate to overcome some of those problems. Using non-equilibrium Green’s function method, we investigate the spin-dependent conductance in a zigzag silicene nanoribbon connected to two magnetized leads which are supposed to be either in parallel or anti-parallel configurations. For both configurations, a controllable spin current can be obtained when the Rashba effect is present; thus, we can have a spin filter device. In addition, for anti-parallel configuration, in the absence of Rashba effect, there is an intrinsic energy gap in the system (OFF-state); while, in the presence of Rashba effect, electrons with flipped spin can pass through the channel and make the ON-state. The current voltage (I-V) characteristics which can be tuned by changing the gate voltage or Rashba strength, are studied. More importantly, reducing the mismatch conductivity as well as energy consumption make the silicene based spin FET more efficient relative to the spin FET based on two-dimensional electron gas proposed by Datta and Das. Also, we show that, at the same conditions, the current and {{I}\\text{on}}/{{I}\\text{off}} ratio of silicene based spin FET are significantly greater than that of the graphene based one.

Dwell time, Hartman effect and transport properties in a ferromagnetic phosphorene monolayer

NASA Astrophysics Data System (ADS)

Hedayati Kh, Hamed; Faizabadi, Edris

2018-02-01

In this paper, spin-dependent dwell time, spin Hartman effect and spin-dependent conductance were theoretically investigated through a rectangular barrier in the presence of an exchange field by depositing a ferromagnetic insulator on the phosphorene layer in the barrier region. The existence of the spin Hartman effect was shown for all energies (energies lower than barrier height) and all incident angles in phosphorene. We also compared our results of the dwell time in the phosphorene structure with similar research performed on graphene. We reported a significant difference between the tunneling time values of incident quasiparticles with spin-up and spin-down. We found that the barrier was almost transparent for incident quasiparticles with a wide range of incident angles and energies higher than the barrier height in phosphorene. We also found that the maximum spin-dependent transmission probability for energies higher than barrier height does not necessarily occur in the zero incident angle. In addition, we showed that the spin conductance for energies higher (lower) than barrier height fluctuates (decays) in terms of barrier thickness. We discovered that, in contrast to graphene, the Klein paradox does not occur in the normal incident in the phosphorene structure. Furthermore, the results demonstrated the achievement of good total conductance at certain thicknesses of the barrier for energies higher than the barrier height. This study could serve as a basis for investigations of the basic physics of tunneling mechanisms and also for using phosphorene as a spin polarizer in designing nanoelectronic devices.

Dwell time, Hartman effect and transport properties in a ferromagnetic phosphorene monolayer.

PubMed

Hedayati Kh, Hamed; Faizabadi, Edris

2018-02-28

In this paper, spin-dependent dwell time, spin Hartman effect and spin-dependent conductance were theoretically investigated through a rectangular barrier in the presence of an exchange field by depositing a ferromagnetic insulator on the phosphorene layer in the barrier region. The existence of the spin Hartman effect was shown for all energies (energies lower than barrier height) and all incident angles in phosphorene. We also compared our results of the dwell time in the phosphorene structure with similar research performed on graphene. We reported a significant difference between the tunneling time values of incident quasiparticles with spin-up and spin-down. We found that the barrier was almost transparent for incident quasiparticles with a wide range of incident angles and energies higher than the barrier height in phosphorene. We also found that the maximum spin-dependent transmission probability for energies higher than barrier height does not necessarily occur in the zero incident angle. In addition, we showed that the spin conductance for energies higher (lower) than barrier height fluctuates (decays) in terms of barrier thickness. We discovered that, in contrast to graphene, the Klein paradox does not occur in the normal incident in the phosphorene structure. Furthermore, the results demonstrated the achievement of good total conductance at certain thicknesses of the barrier for energies higher than the barrier height. This study could serve as a basis for investigations of the basic physics of tunneling mechanisms and also for using phosphorene as a spin polarizer in designing nanoelectronic devices.

Flight investigation of the effect of tail configuration on stall, spin, and recovery characteristics of a low-wing general aviation research airplane

NASA Technical Reports Server (NTRS)

Stough, H. Paul, III; Patton, James M., Jr.; Sliwa, Steven M.

1987-01-01

Flight tests were performed to investigate the stall, spin, and recovery characteristics of a low-wing, single-engine, light airplane with four interchangeable tail configurations. The four tail configurations were evaluated for effects of varying mass distribution, center-of-gravity position, and control inputs. The airplane tended to roll-off at the stall. Variations in tail configuration produced spins ranging from 40 deg to 60 deg angle of attack and turn rates of about 145 to 208 deg/sec. Some unrecoverable flat spins were encountered which required use of the airplane spin chute for recovery. For recoverable spins, antispin rudder followed by forward wheel with ailerons centered provided the quickest spin recovery. The moderate spin modes agreed very well with those predicted from spin-tunnel model tests, however, the flat spin was at a lower angle of attack and a slower rotation rate than indicated by the model tests.

Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

NASA Technical Reports Server (NTRS)

Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

2010-01-01

Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

Conductance dips and spin precession in a nonuniform waveguide with spin–orbit coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malyshev, A. I., E-mail: malyshev@phys.unn.ru; Kozulin, A. S.

An infinite waveguide with a nonuniformity, a segment of finite length with spin–orbit coupling, is considered in the case when the Rashba and Dresselhaus parameters are identical. Analytical expressions have been derived in the single-mode approximation for the conductance of the system for an arbitrary initial spin state. Based on numerical calculations with several size quantization modes, we have detected and described the conductance dips arising when the waves are localized in the nonuniformity due to the formation of an effective potential well in it. We show that allowance for the evanescent modes under carrier spin precession in an effectivemore » magnetic field does not lead to a change in the direction of the average spin vector at the output of the system.« less

Spin-Current-Controlled Modulation of the Magnon Spin Conductance in a Three-Terminal Magnon Transistor

NASA Astrophysics Data System (ADS)

Cornelissen, L. J.; Liu, J.; van Wees, B. J.; Duine, R. A.

2018-03-01

Efficient manipulation of magnon spin transport is crucial for developing magnon-based spintronic devices. In this Letter, we provide proof of principle of a method for modulating the diffusive transport of thermal magnons in an yttrium iron garnet channel between injector and detector contacts. The magnon spin conductance of the channel is altered by increasing or decreasing the magnon chemical potential via spin Hall injection of magnons by a third modulator electrode. We obtain a modulation efficiency of 1.6 %/mA at T =250 K . Finite element modeling shows that this could be increased to well above 10 %/mA by reducing the thickness of the channel, providing interesting prospects for the development of thermal-magnon-based logic circuits.

Influence of quantum phase transition on spin transport in the quantum antiferromagnet in the honeycomb lattice

NASA Astrophysics Data System (ADS)

Lima, L. S.

2017-06-01

We use the SU(3) Schwinger boson theory to study the spin transport properties of the two-dimensional anisotropic frustrated Heisenberg model in a honeycomb lattice at T = 0 with single ion anisotropy and third neighbor interactions. We have investigated the behavior of the spin conductivity for this model that presents exchange interactions J1 , J2 and J3 . We study the spin transport in the Bose-Einstein condensation regime where the bosons tz are condensed. Our results show an influence of the quantum phase transition point on the spin conductivity behavior. We also have made a diagrammatic expansion for the Green-function and did not obtain any significant change of the results.

External electric field driven modification of the anomalous and spin Hall conductivities in Fe thin films on MgO(001)

NASA Astrophysics Data System (ADS)

Pradipto, Abdul-Muizz; Akiyama, Toru; Ito, Tomonori; Nakamura, Kohji

2018-01-01

The effects of applying external electric fields to the anomalous and spin Hall conductivities in Fe thin-film models with different layer thicknesses on MgO(001) are investigated by using first-principles calculations. We observe that, for the considered systems, the application of positive electric field associated with the accumulation of negative charges on the Fe side generally decreases (increases) the anomalous (spin) Hall conductivities. The mapping of the Hall conductivities within the two-dimensional Brillouin zone shows that the electric-field-induced modifications are related to the modification of the band structures of the atoms at the interface with the MgO substrate. In particular, the external electric field affects the Hall conductivities via the modifications of the dx z,dy z orbitals, in which the application of positive electric field pushes the minority-spin states of the dx z,dy z bands closer to the Fermi level. Better agreement with the anomalous Hall conductivity for bulk Fe and a more realistic scenario for the electric field modification of Hall conductivities are obtained by using the thicker layers of Fe on MgO (Fe3/MgO and Fe5/MgO).

High Temperature Burst Testing of a Superalloy Disk With a Dual Grain Structure

NASA Technical Reports Server (NTRS)

Gayda, J.; Kantzos, P.

2004-01-01

Elevated temperature burst testing of a disk with a dual grain structure made from an advanced nickel-base superalloy, LSHR, was conducted. The disk had a fine grain bore and coarse grain rim, produced using NASA's low cost DMHT technology. The results of the spin testing showed the disk burst at 42 530 rpm in line with predictions based on a 2-D finite element analysis. Further, significant growth of the disk was observed before failure which was also in line with predictions.

Planetary explorer liquid propulsion study

NASA Technical Reports Server (NTRS)

Mckevitt, F. X.; Eggers, R. F.; Bolz, C. W.

1971-01-01

An analytical evaluation of several candidate monopropellant hydrazine propulsion system approaches is conducted in order to define the most suitable configuration for the combined velocity and attitude control system for the Planetary Explorer spacecraft. Both orbiter and probe-type missions to the planet Venus are considered. The spacecraft concept is that of a Delta launched spin-stabilized vehicle. Velocity control is obtained through preprogrammed pulse-mode firing of the thrusters in synchronism with the spacecraft spin rate. Configuration selection is found to be strongly influenced by the possible error torques induced by uncertainties in thruster operation and installation. The propulsion systems defined are based on maximum use of existing, qualified components. Ground support equipment requirements are defined and system development testing outlined.

Probing the magnetic field dependence of the light hole transition in GaAs/AlGaAs quantum wells using optically pumped NMR

NASA Astrophysics Data System (ADS)

Willmering, Matthew M.; Sesti, Erika L.; Hayes, Sophia E.; Wood, Ryan M.; Bowers, Clifford R.; Thapa, Sunil K.; Stanton, Christopher J.; Reyes, Arneil P.; Kuhns, Philip; McGill, Stephen

2018-02-01

Optically pumped NMR (OPNMR) of the NMR-active Ga/7169 species has been shown to be a unique method to probe electronic energy bands in GaAs, with sensitivity to the light hole-to-conduction band transition. This transition is often obscured in other optical measurements such as magnetoabsorption. Using OPNMR, we exploit the hyperfine interaction between conduction band electrons (and their spin states) and nuclear spins, which are detected through phase-sensitive radio-frequency (NMR) spectroscopy. Measurements were made over a range of external magnetic fields (B0) in two different labs with separate experimental setups to obtain the magnetic field dependence of the light hole-to-conduction band transition energy. In addition, k .p theory was used to interpret the experimental results, mapping out this specific transition's magnetic field dependence in an AlGaAs/GaAs quantum well. The combination of theory and experiment point to a mixing of valence bands at a field of approximately B0=4.7 T, swapping the dominant character of the absorption transition and, thus, explaining the magnetic field dependence. Lastly, the experimental dependence of the light hole-to-conduction band transition energy on B0 is found to be less steep compared to the calculated trend, indicating that inclusion of additional effects may be necessary to accurately model the spin-split band structure. The additional insight gained by Ga/7169 OPNMR about the light hole states will facilitate future testing of more complex band structure models.

Effect of asymmetric interface on charge and spin transport across two dimensional electron gas with Dresselhaus spin-orbit coupling/ferromagnet junction

NASA Astrophysics Data System (ADS)

Srisongmuang, B.; Pasanai, K.

2018-04-01

We theoretically studied the effect of interfacial scattering on the transport of charge and spin across the junction of a two-dimensional electron gas with Dresselhaus spin-orbit coupling and ferromagnetic material junction, via the conductance (G) and the spin-polarization of the conductance spectra (P) using the scattering method. At the interface, not only were the effects of spin-conserving (Z0) and spin-flip scattering (Zf) considered, but also the interfacial Rashba spin-orbit coupling scattering (ZRSOC) , which was caused by the asymmetry of the interface, was taken into account, and all of them were modeled by the delta potential. It was found that G was suppressed with increasing Z0 , as expected. Interestingly, a particular value of Zf can cause G and P to reach a maximum value. In particular, ZRSOC plays a crucial role to reduce G and P in the metallic limit, but its influence on the tunneling limit was quite weak. On the other hand, the effect of ZRSOC was diminished in the tunneling limit of the magnetic junction.

Spin heat capacity of monolayer and AB-stacked bilayer MoS2 in the presence of exchange magnetic field

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Yarmohammadi, Mohsen; Mirabbaszadeh, Kavoos

2017-04-01

Dirac theory and Green's function technique are carried out to compute the spin dependent band structures and corresponding electronic heat capacity (EHC) of monolayer (ML) and AB-stacked bilayer (BL) molybdenum disulfide (MoS2) two-dimensional (2D) crystals. We report the influence of induced exchange magnetic field (EMF) by magnetic insulator substrates on these quantities for both structures. The spin-up (down) subband gaps are shifted with EMF from conduction (valence) band to valence (conduction) band at both Dirac points in the ML because of the spin-orbit coupling (SOC) which leads to a critical EMF in the K point and EHC returns to its initial states for both spins. In the BL case, EMF results split states and the decrease (increase) behavior of spin-up (down) subband gaps has been observed at both K and K‧ valleys which is due to the combined effect of SOC and interlayer coupling. For low and high EMFs, EHC of BL MoS2 does not change for spin-up subbands while increases for spin-down subbands.

Onset of Spin Polarization in Four-Gate Quantum Point Contacts

NASA Astrophysics Data System (ADS)

Jones, Alex

A series of simulations which utilize a Non-equilibrium Green's function (NEGF) formalism is suggested which can provide indirect evidence of the fine and non-local electrostatic tuning of the onset of spin polarization in two closely spaced quantum point contacts (QPCs) that experience a phenomenon known as lateral spin-orbit coupling (LSOC). Each of the QPCs that create the device also has its own pair of side gates (SGs) which are in-plane with the device channel. Numerical simulations of the conductance of the two closely spaced QPCs or four-gate QPC are carried out for different biasing conditions applied to two leftmost and rightmost SGs. Conductance plots are then calculated as a function of the variable, Vsweep, which is the common sweep voltage applied to the QPC. When Vsweep is only applied to two of the four side gates, the plots show several conductance anomalies, i.e., below G0 = 2e2/h, characterized by intrinsic bistability, i.e., hysteresis loops due to a difference in the conductance curves for forward and reverse common voltage sweep simulations. The appearance of hysteresis loops is attributed to the co-existence of multistable spin textures in the narrow channel of the four-gate QPC. The shape, location, and number of hysteresis loops are very sensitive to the biasing conditions on the four SGs. The shape and size of the conductance anomalies and hysteresis loops are shown to change when the biasing conditions on the leftmost and rightmost SGs are swapped, a rectifying behavior providing an additional indirect evidence for the onset of spontaneous spin polarization in nanoscale devices made of QPCs. The results of the simulations reveal that the occurrence and fine tuning of conductance anomalies in QPC structures are highly sensitive to the non-local action of closely spaced SGs. It is therefore imperative to take into account this proximity effect in the design of all electrical spin valves making use of middle gates to fine tune the spin precession between QPC based spin injector and detector contacts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tani, Yasuo; Shikoh, Eiji, E-mail: shikoh@elec.eng.osaka-cu.ac.jp; Teki, Yoshio

We report the spin-pump-induced spin transport properties of a pentacene film prepared by thermal evaporation. In a palladium(Pd)/pentacene/Ni{sub 80}Fe{sub 20} tri-layer sample, a pure spin-current is generated in the pentacene layer by the spin-pumping of Ni{sub 80}Fe{sub 20}, which is independent of the conductance mismatch problem in spin injection. The spin current is absorbed into the Pd layer, converted into a charge current with the inverse spin-Hall effect in Pd, and detected as an electromotive force. This is clear evidence for the pure spin current at room temperature in pentacene films prepared by thermal evaporation.

Spin Seebeck insulator.

PubMed

Uchida, K; Xiao, J; Adachi, H; Ohe, J; Takahashi, S; Ieda, J; Ota, T; Kajiwara, Y; Umezawa, H; Kawai, H; Bauer, G E W; Maekawa, S; Saitoh, E

2010-11-01

Thermoelectric generation is an essential function in future energy-saving technologies. However, it has so far been an exclusive feature of electric conductors, a situation which limits its application; conduction electrons are often problematic in the thermal design of devices. Here we report electric voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, the magnetic insulator LaY(2)Fe(5)O(12) can convert a heat flow into a spin voltage. Attached Pt films can then transform this spin voltage into an electric voltage as a result of the inverse spin Hall effect. The experimental results require us to introduce a thermally activated interface spin exchange between LaY(2)Fe(5)O(12) and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect.

Quantum spin circulator in Y junctions of Heisenberg chains

NASA Astrophysics Data System (ADS)

Buccheri, Francesco; Egger, Reinhold; Pereira, Rodrigo G.; Ramos, Flávia B.

2018-06-01

We show that a quantum spin circulator, a nonreciprocal device that routes spin currents without any charge transport, can be achieved in Y junctions of identical spin-1 /2 Heisenberg chains coupled by a chiral three-spin interaction. Using bosonization, boundary conformal field theory, and density matrix renormalization group simulations, we find that a chiral fixed point with maximally asymmetric spin conductance arises at a critical point separating a regime of disconnected chains from a spin-only version of the three-channel Kondo effect. We argue that networks of spin-chain Y junctions provide a controllable approach to construct long-sought chiral spin-liquid phases.

Full-scale semi-span tests of an advanced NLF business jet wing

NASA Technical Reports Server (NTRS)

Hahne, David E.; Jordan, Frank L., Jr.; Davis, Patrick J.; Muchmore, C. Byram

1987-01-01

An investigation has been conducted in the NASA Langley Research Center's 30- by 60-Foot Wind Tunnel on a full-scale semispan model to evaluate and document the low-speed, high-lift characteristics of a business-jet class wing utilizing the HSNLF(1)-0213 airfoil section and a single slotted flap system. In addition to the high-lift studies, evaluations of boundary layer transition effects, the effectiveness of a segmented leading-edge droop for improved stall/spin resistance, and roll control effectiveness with and without flap deflection were made. The wind-tunnel investigation showed that deployment of a single-slotted trailing-edge flap provided substantial increments in lift. Fixed transition studies indicated no adverse effects on lift and pitching-moment characteristics for either the cruise or landing configuration. Subscale roll damping tests also indicated that stall/spin resistance could be enhanced through the use of a properly designed leading-edge droop.

Wind-tunnel investigation of effects of wing-leading-edge modifications on the high angle-of-attack characteristics of a T-tail low-wing general-aviation aircraft

NASA Technical Reports Server (NTRS)

White, E. R.

1982-01-01

Exploratory tests have been conducted in the NASA-Langley Research Center's 12-Foot Low-Speed wind Tunnel to evaluate the application of wing-leading-edge devices on the stall-departure and spin resistance characteristics of a 1/6-scale model of a T-tail general-aviation aircraft. The model was force tested with an internal strain-gauge balance to obtain aerodynamic data on the complete configuration and with a separate wing balance to obtain aerodynamic data on the outer portion of the wing. The addition of the outboard leading-edge droop eliminated the abrupt stall of the windtip and maintained or increased the resultant-force coefficient up to about alpha = 32 degrees. This change in slope of the resultant-force coefficient curve with angle of attack has been shown to be important for eliminating autorotation and for providing spin resistance.

Topological states of matter in two-dimensional fermionic systems

NASA Astrophysics Data System (ADS)

Beugeling, W.

2012-09-01

Topological states of matter in two-dimensional systems are characterised by the different properties of the edges and the bulk of the system: The edges conduct electrical current while the bulk is insulating. The first well-known example is the quantum Hall effect, which is induced by a perpendicular magnetic field that generates chiral edge channels along which the current propagates. Each channel contributes one quantum to the Hall conductivity. Due to the chirality, i.e., all currents propagate in the same direction, backscattering due to impurities is absent, and the Hall conductivity carried by the edge states is therefore protected from perturbations. Another example is the quantum spin Hall effect, induced by intrinsic spin-orbit coupling in absence of a magnetic field. There the edge states are helical, i.e., spin up and down currents propagate oppositely. In this case, the spin Hall conductivity is quantized, and it is protected by time-reversal symmetry from backscattering due to impurities. In Chapter 2 of the thesis, I discuss the combined effect of the magnetic field and intrinsic spin-orbit coupling. In addition, I discuss the influence of the Rashba spin-orbit coupling and of the Zeeman effect. In particular, I show that in absence of magnetic impurities, a weaker form of the quantum spin Hall state persists in the presence of a magnetic field. In addition, I show that the intrinsic spin-orbit coupling and the Zeeman effect act similarly in the low-flux limit. I furthermore analyse the phase transitions induced by intrinsic spin-orbit coupling at a fixed magnetic field, thereby explaining the change of the Hall and spin Hall conductivities at the transition. I also study the subtle interplay between the effects of the different terms in the Hamiltonian. In Chapter 3, I investigate an effective model for HgTe quantum wells doped with Mn ions. Without doping, HgTe quantum wells may exhibit the quantum spin Hall effect, depending on the thickness of the well. The doping with Mn ions modifies the behaviour of the system in two ways: First, the quantum spin Hall gap is reduced in size, and secondly, the system becomes paramagnetic. The latter effect causes a bending of the Landau levels, which is responsible for reentrant behaviour of the (spin) Hall conductivity. I investigate the different types of reentrant behaviour, and I estimate the experimental resolvability of this effect. In Chapter 4, I present a framework to describe the fractional quantum Hall effect in systems with multiple internal degrees of freedom, e.g., spin or pseudospin. This framework describes the so-called flux attachment in terms of a Chern-Simons theory in Hamiltonian form, proposed earlier for systems without internal degrees of freedom. Here, I show a generalization of these results, by replacing the number of attached flux quanta by a matrix. In particular, the plasma analogy proposed by Laughlin still applies, and Kohn’s theorem remains valid. I also show that the results remain valid when the flux-attachment matrix is singular.

Switching effects and spin-valley Andreev resonant peak shifting in silicene superconductor

NASA Astrophysics Data System (ADS)

Soodchomshom, Bumned; Niyomsoot, Kittipong; Pattrawutthiwong, Eakkarat

2018-03-01

The magnetoresistance and spin-valley transport properties in a silicene-based NM/FB/SC junction are investigated, where NM, FB and SC are normal, ferromagnetic and s-wave superconducting silicene, respectively. In the FB region, perpendicular electric and staggered exchange fields are applied. The quasiparticles may be described by Dirac Bogoliubov-de Gennes equation due to Cooper pairs formed by spin-valley massive fermions. The spin-valley conductances are calculated based on the modified Blonder-Tinkham-Klapwijk formalism. We find the spin-valley dependent Andreev resonant peaks in the junction shifted by applying exchange field. Perfect conductance switch generated by interplay of intrinsic spin orbit interaction and superconducting gap has been predicted. Spin and valley polarizations are almost linearly dependent on biased voltage near zero bias and then turn into perfect switch at biased voltage approaching the superconducting gap. The perfect switching of large magnetoresistance has been also predicted at biased energy near the superconducting gap. These switching effects may be due to the presence of spin-valley Andreev resonant peak near the superconducting gap. Our work reveals potential of silicene as applications of electronic switching devices and linear control of spin and valley polarizations.

Deformations of the spin currents by topological screw dislocation and cosmic dispiration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jianhua; Ma, Kai, E-mail: makainca@gmail.com; Li, Kang

2015-11-15

We study the spin currents induced by topological screw dislocation and cosmic dispiration. By using the extended Drude model, we find that the spin dependent forces are modified by the nontrivial geometry. For the topological screw dislocation, only the direction of spin current is bent by deforming the spin polarization vector. In contrast, the force induced by cosmic dispiration could affect both the direction and magnitude of the spin current. As a consequence, the spin-Hall conductivity does not receive corrections from screw dislocation.

Equations of motion of test particles for solving the spin-dependent Boltzmann–Vlasov equation

DOE PAGES

Xia, Yin; Xu, Jun; Li, Bao-An; ...

2016-06-16

A consistent derivation of the equations of motion (EOMs) of test particles for solving the spin-dependent Boltzmann–Vlasov equation is presented. The resulting EOMs in phase space are similar to the canonical equations in Hamiltonian dynamics, and the EOM of spin is the same as that in the Heisenburg picture of quantum mechanics. Considering further the quantum nature of spin and choosing the direction of total angular momentum in heavy-ion reactions as a reference of measuring nucleon spin, the EOMs of spin-up and spin-down nucleons are given separately. The key elements affecting the spin dynamics in heavy-ion collisions are identified. Themore » resulting EOMs provide a solid foundation for using the test-particle approach in studying spin dynamics in heavy-ion collisions at intermediate energies. Future comparisons of model simulations with experimental data will help to constrain the poorly known in-medium nucleon spin–orbit coupling relevant for understanding properties of rare isotopes and their astrophysical impacts.« less

Process optimization electrospinning fibrous material based on polyhydroxybutyrate

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Tyubaeva, P. M.; Staroverova, O. V.; Mastalygina, E. E.; Popov, A. A.; Ischenko, A. A.; Iordanskii, A. L.

2016-05-01

The article analyzes the influence of the main technological parameters of electrostatic spinning on the morphology and properties of ultrathin fibers on the basis of polyhydroxybutyrate. It is found that the electric conductivity and viscosity of the spinning solution affects the process of forming fibers macrostructure. The fiber-based materials PHB lets control geometry and optimize the viscosity and conductivity of a spinning solution. The resulting fibers have found use in medicine, particularly in the construction elements musculoskeletal.

Free-Spinning-Tunnel Tests of a 1/20-Scale Model of the Northrop N-9M Airplane

NASA Technical Reports Server (NTRS)

MacDougall, George F., Jr.; Lichtenstein, Jacob H.

1946-01-01

Spin tests of a 1/20-scale model of the Northrop N-9M airplane have been performed in the Langley 20-foot free-spinning tunnel. The erect and inverted spin and recovery characteristics were determined for various loading conditions and the effect of deflecting the flaps and of extending the landing gear was investigated. The investigation also included tests to determine the size parachute required for satisfactory spin recovery by parachute action alone. The tests were performed at an equivalent spin altitude of 15,000 feet. A specialized recovery technique consisting of rapid full reversal of the rudder pedals against the spin combined with turning the wheel against the spin and movement of the stick forward is recommended for all loadings and configurations of the airplane. The results also indicated that a 7-foot-diameter spin-recovery parachute having a drag coefficient of 0.7 attached to the outboard wing tip with a towline of 10 to 30 feet or an 8.8-foot-diameter parachute attached to the fixed portion of the wing between the elevons and the pitch flaps with a 30-foot towline would provide satisfactory recovery from demonstration spins by parachute action alone. It appears possible that the first N-9M airplane may have crashed because of failure to recover from a spin.

Preliminary Tests in the NACA Free-Spinning Wind Tunnel

NASA Technical Reports Server (NTRS)

Zimmerman, C H

1937-01-01

Typical models and the testing technique used in the NACA free-spinning wind tunnel are described in detail. The results of tests on two models afford a comparison between the spinning characteristics of scale models in the tunnel and of the airplanes that they represent.

Line patterning of anisotropic spin chains by polarized laser for application in micro-thermal management

NASA Astrophysics Data System (ADS)

Terakado, Nobuaki; Takahashi, Ryosuke; Takahashi, Yoshihiro; Fujiwara, Takumi

2017-05-01

The control of heat flow has become increasingly important in energy saving and harvesting. Among various thermal management materials, spinon thermal conductivity materials are promising for heat flow control at microscales because they exhibit high, anisotropic thermal conductivity resulting from spin chains. However, there has been only little development of the materials for controlling heat flow. Here, we present the line patterning of the spin chain structure on a SrCuO2 nanocrystalline film by laser scanning. When the polarization direction of laser light was orthogonal to the scanning direction, we found that the spin-chain structure anisotropically grew on the patterned line.

Finger-gate manipulated quantum transport in Dirac materials

NASA Astrophysics Data System (ADS)

Kleftogiannis, Ioannis; Tang, Chi-Shung; Cheng, Shun-Jen

2015-05-01

We investigate the quantum transport properties of multichannel nanoribbons made of materials described by the Dirac equation, under an in-plane magnetic field. In the low energy regime, positive and negative finger-gate potentials allow the electrons to make intra-subband transitions via hole-like or electron-like quasibound states (QBS), respectively, resulting in dips in the conductance. In the high energy regime, double dip structures in the conductance are found, attributed to spin-flip or spin-nonflip inter-subband transitions through the QBSs. Inverting the finger-gate polarity offers the possibility to manipulate the spin polarized electronic transport to achieve a controlled spin-switch.

Spin Hall Effect in Doped Semiconductor Structures

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Das Sarma, Sankar

2006-03-01

We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

Spin-Current-Controlled Modulation of the Magnon Spin Conductance in a Three-Terminal Magnon Transistor.

PubMed

Cornelissen, L J; Liu, J; van Wees, B J; Duine, R A

2018-03-02

Efficient manipulation of magnon spin transport is crucial for developing magnon-based spintronic devices. In this Letter, we provide proof of principle of a method for modulating the diffusive transport of thermal magnons in an yttrium iron garnet channel between injector and detector contacts. The magnon spin conductance of the channel is altered by increasing or decreasing the magnon chemical potential via spin Hall injection of magnons by a third modulator electrode. We obtain a modulation efficiency of 1.6%/mA at T=250  K. Finite element modeling shows that this could be increased to well above 10%/mA by reducing the thickness of the channel, providing interesting prospects for the development of thermal-magnon-based logic circuits.

Doping-induced spin-orbit splitting in Bi-doped ZnO nanowires

NASA Astrophysics Data System (ADS)

Aras, Mehmet; Güler-Kılıç, Sümeyra; Kılıç, ćetin

2017-04-01

Our predictions, based on density-functional calculations, reveal that surface doping of ZnO nanowires with Bi leads to a linear-in-k splitting of the conduction-band states, through spin-orbit interaction, due to the lowering of the symmetry in the presence of the dopant. This finding implies that spin polarization of the conduction electrons in Bi-doped ZnO nanowires could be controlled with applied electric (as opposed to magnetic) fields, making them candidate materials for spin-orbitronic applications. Our findings also show that the degree of spin splitting could be tuned by adjusting the dopant concentration. Defect calculations and ab initio molecular dynamics simulations indicate that stable doping configurations exhibiting the foregoing linear-in-k splitting could be realized under reasonable thermodynamic conditions.

Universality classes of order parameters composed of many-body bound states

DOE PAGES

Tsvelik, A. M.

2016-11-28

This theoretical paper discusses microscopic models giving rise to special types of order in which conduction electrons are bound together with localized spins to create composite order parameters. It is shown that composite order is related to the formation of a spin liquid with gapped excitations carrying quantum numbers which are a fraction of those of electron. These spin liquids are special in the sense that their formation necessarily involves spin degrees of freedom of both the conduction and the localized electrons and can be characterized by nonlocal order parameters. A detailed description of such spin liquid states is presentedmore » with a special care given to a demonstration of their robustness against local perturbations preserving the Lie group symmetry and the translational invariance.« less

Spin Lifetimes in III-V Semiconductor Heterostructures Originating from Zincblende Symmetry

NASA Astrophysics Data System (ADS)

Lau, Wayne; Olesberg, Jon; Flatté, Michael

2000-03-01

Electron spin relaxation in zincblende type semiconductors at room temperature is dominated by the D'yakonov-Perel' mechanism (DP), which is a direct result of the spin splitting of the conduction band due to the bulk inversion asymmetry (BIA) of zincblende materials. To accurately describe the DP spin relaxation mechanism in quantum wells we employ a heterostructure model based on a fourteen bulk band basis, which accounts for the zincblende symmetry of the heterostructure constituents. Electron spin lifetimes are calculated for 75Å n-doped GaAs/Al_0.4Ga_0.6As quantum wells at room temperature. Excellent agreement between theory and experiments is found. In contrast, the calculated spin lifetimes based on the D'yakonov-Kachorovskii theory are an order magnitude shorter than the experimental values. The spin splitting and spin lifetime in no common atom In_0.53Ga_0.47As/InP quantum wells are also investigated. The contribution to the conduction subband spin splitting is dominated by the native interface asymmetry (NIA) mechanism for thin quantum wells; while the spin splitting is governed by the BIA mechanism for thick quantum wells. We find that BIA provides a satisfactory explanation for the spin lifetime measured in an In_0.53Ga_0.47As/InP quantum well with a 97Å barrier and a 70Å well at room temperature.

Subsonic Dynamic Stability Tests of a Sample Return Entry Vehicle

NASA Technical Reports Server (NTRS)

Fremaux, C. Michael; Johnson, R. Keith

2006-01-01

An investigation has been conducted in the NASA Langley 20-Foot Vertical Spin Tunnel (VST) to determine the subsonic dynamic stability characteristics of a proposed atmospheric entry vehicle for sample return missions. In particular, the effects of changes in aft-body geometry on stability were examined. Freeflying tests of a dynamically scaled model with various geometric features were conducted, including cases in which the model was perturbed to measure dynamic response. Both perturbed and non-perturbed runs were recorded as motion time histories using the VST optical data acquisition system and reduced for post-test analysis. In addition, preliminary results from a static force and moment test of a similar model in the Langley 12-Foot Low Speed Tunnel are presented. Results indicate that the configuration is dynamically stable for the baseline geometry, but exhibits degraded dynamic behavior for the geometry modifications tested.

Observation of spinon spin currents in one-dimensional spin liquid

NASA Astrophysics Data System (ADS)

Hirobe, Daichi; Sato, Masahiro; Kawamata, Takayuki; Shiomi, Yuki; Uchida, Ken-Ichi; Iguchi, Ryo; Koike, Yoji; Maekawa, Sadamichi; Saitoh, Eiji

To date, two types of spin current have been explored experimentally: conduction-electron spin current and spin-wave spin current. Here, we newly present spinon spin current in quantum spin liquid. An archetype of quantum spin liquid is realized in one-dimensional spin-1/2 chains with the spins coupled via antiferromagnetic interaction. Elementary excitation in such a system is known as a spinon. Theories have predicted that the correlation of spinons reaches over a long distance. This suggests that spin current may propagate via one-dimensional spinons even in spin liquid states. In this talk, we report the experimental observation that a spin liquid in a spin-1/2 quantum chain generates and conveys spin current, which is attributed to spinon spin current. This is demonstrated by observing an anisotropic negative spin Seebeck effect along the spin chains in Sr2CuO3. The results show that spin current can flow via quantum fluctuation in spite of the absence of magnetic order, suggesting that a variety of quantum spin systems can be applied to spintronics. Spin Quantum Rectification Project, ERATO, JST, Japan; PRESTO, JST, Japan.

Microgravity

NASA Image and Video Library

2002-08-07

Brad McLain for the Space Biology Museum Network spins a volunteer in a rotating chair to illustrate how dependent the human vestibular system is on visual cues. The volunteer's thumbs indicate which way she thinks she is turning. Similar tests are conducted on astronauts to study how they adapt to space and readapt to Earth. The activity was part of the Space Research and You education event held by NASA's Office of Biological and Physical Research on June 25, 2002, in Arlington, VA, to highlight the research that will be conducted on STS-107.

Volunteer Interacting with a Rotating Chair Demonstration

NASA Technical Reports Server (NTRS)

2002-01-01

Brad McLain for the Space Biology Museum Network spins a volunteer in a rotating chair to illustrate how dependent the human vestibular system is on visual cues. The volunteer's thumbs indicate which way she thinks she is turning. Similar tests are conducted on astronauts to study how they adapt to space and readapt to Earth. The activity was part of the Space Research and You education event held by NASA's Office of Biological and Physical Research on June 25, 2002, in Arlington, VA, to highlight the research that will be conducted on STS-107.

Turbine Engine Disk Rotor Health Monitoring Assessment Using Spin Tests Data

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Woike, Mark; Baalini, George; Bodis, James R.

2012-01-01

Detecting rotating engine component malfunctions and structural anomalies is increasingly becoming a crucial key feature that will help boost safety and lower maintenance cost. However, achievement of such technology, which can be referred to as a health monitoring remains somewhat challenging to implement. This is mostly due to presence of scattered loading conditions, crack sizes, component geometry and material properties that hinders the simplicity of imposing such application. Different approaches are being considered to assist in developing other means of health monitoring or nondestructive techniques to detect hidden flaws and mini cracks before any catastrophic events occur. These methods extend further to assess material discontinuities and other defects that have matured to the level where a failure is very likely. This paper is focused on presenting data obtained from spin test experiments of a turbine engine like rotor disk and their correlation to the development of a structural health monitoring and fault detection system. The data collected includes blade tip clearance, blade tip timing measurements and shaft displacements. The experimental results are collected at rotational speeds up to 10,000 Rpm and tests are conducted at the NASA Glenn Research Center s Rotordynamics Laboratory via a high precision spin system. Additionally, this study offers a closer glance at a selective online evaluation of a rotating disk using advanced capacitive, microwave and eddy current sensor technology.

Turbine engine disk rotor health monitoring assessment using spin tests data

NASA Astrophysics Data System (ADS)

Abdul-Aziz, Ali; Woike, Mark; Baaklini, George; Bodis, James R.

2012-04-01

Detecting rotating engine component malfunctions and structural anomalies is increasingly becoming a crucial key feature that will help boost safety and lower maintenance cost. However, achievement of such technology, which can be referred to as a health monitoring remains somewhat challenging to implement. This is mostly due to presence of scattered loading conditions, crack sizes, component geometry and material properties that hinders the simplicity of imposing such application. Different approaches are being considered to assist in developing other means of health monitoring or nondestructive techniques to detect hidden flaws and mini cracks before any catastrophic events occur. These methods extend further to assess material discontinuities and other defects that have matured to the level where a failure is very likely. This paper is focused on presenting data obtained from spin test experiments of a turbine engine like rotor disk and their correlation to the development of a structural health monitoring and fault detection system. The data collected includes blade tip clearance, blade tip timing measurements and shaft displacements. The experimental results are collected at rotational speeds up to 10,000 Rpm and tests are conducted at the NASA Glenn Research Center's Rotordynamics Laboratory via a high precision spin system. Additionally, this study offers a closer glance at a selective online evaluation of a rotating disk using advanced capacitive, microwave and eddy current sensor technology.

Conductivity and Ambient Stability of Halogen-Doped Carbon Nanotube Fibers

NASA Technical Reports Server (NTRS)

Gaier, J. R.; Chirino, C. M.; Chen, M.; Waters, D. L.; Tran, Mai Kim; Headrick, R.; Young, C. C.; Tsentalovich, D.; Whiting, B.; Pasquali, M.;

Spin-controlled negative magnetoresistance resulting from exchange interactions

NASA Astrophysics Data System (ADS)

Agrinskaya, N. V.; Kozub, V. I.; Mikhailin, N. Yu.; Shamshur, D. V.

2017-04-01

We studied conductivity of AlGaAs-GaAs quantum well structures (where centers of the wells were doped by Be) at temperatures higher than 4 K in magnetic fields up 10 T. Throughout all the temperature region considered the conductivity demonstrated activated behavior. At moderate magnetic fields 0.1 T < H < 1 T, we observed negative isotropic magnetoresistance, which was linear in magnetic field while for magnetic field normal with respect to the plane of the wells the magnetoresistance was positive at H > 2T. To the best of our knowledge, it was the first observation of linear negative magnetoresistance, which would be isotropic with respect to the direction of magnetic field. While the isotropic character of magnetoresistance apparently evidences role of spins, the existing theoretical considerations concerning spin effects in conductance fail to explain our experimental results. We believe that such a behavior can be attributed to spin effects supported by exchange interactions between localized states.

Gilbert Damping Parameter in MgO-Based Magnetic Tunnel Junctions from First Principles

NASA Astrophysics Data System (ADS)

Tang, Hui-Min; Xia, Ke

2017-03-01

We perform a first-principles study of the Gilbert damping parameter (α ) in normal-metal/MgO-cap/ferromagnet/MgO-barrier/ferromagnetic magnetic tunnel junctions. The damping is enhanced by interface spin pumping, which can be parametrized by the spin-mixing conductance (G↑↓ ). The calculated dependence of Gilbert damping on the thickness of the MgO capping layer is consistent with experiment and indicates that the decreases in α with increasing thickness of the MgO capping layer is caused by suppression of spin pumping. Smaller α can be achieved by using a clean interface and alloys. For a thick MgO capping layer, the imaginary part of the spin-mixing conductance nearly equals the real part, and the large imaginary mixing conductance implies that the change in the frequency of ferromagnetic resonance can be observed experimentally. The normal-metal cap significantly affects the Gilbert damping.

Free-Spinning-Tunnel Tests of a 1/27-Scale Model of the Douglas XF3D-1 Airplane, TED No. NACA DE 312

NASA Technical Reports Server (NTRS)

Scher, Stanley H.

1947-01-01

Free-spinning-tunnel tests have been made on a 1/27-scale model of the Douglas XF3D-1 airplane to confirm a preliminary evaluation made of the airplane spin and recovery characteristics and previously reported. Recovery characteristics were satisfactory for erect and inverted spins when the model was in the clean condition. When the slow-down brakes were open, recoveries were slow. The pedal force necessary to reverse the airplane rudder during a spin will be within the physical capabilities of the pilot. A 10-foot-diameter parachute attached to the tail of the airplane (laid-out-flat diameter, drag coefficient 0.7) or a 4.5-foot-diameter parachute attached to the outboard wing tip will be satisfactory for emergency spin recovery from demonstration spins. If it becomes necessary for the crew to abandon the airplane during a spin, they should leave from the outboard side of the cockpit. The test results indicated spin and recovery characteristics generally similar to those indicated in the preliminary evaluation.

Electron-nuclear coherent spin oscillations probed by spin-dependent recombination

NASA Astrophysics Data System (ADS)

Azaizia, S.; Carrère, H.; Sandoval-Santana, J. C.; Ibarra-Sierra, V. G.; Kalevich, V. K.; Ivchenko, E. L.; Bakaleinikov, L. A.; Marie, X.; Amand, T.; Kunold, A.; Balocchi, A.

2018-04-01

We demonstrate the triggering and detection of coherent electron-nuclear spin oscillations related to the hyperfine interaction in Ga deep paramagnetic centers in GaAsN by band-to-band photoluminescence without an external magnetic field. In contrast to other point defects such as Cr4 + in SiC, Ce3 + in yttrium aluminum garnet crystals, nitrogen-vacancy centers in diamond, and P atoms in silicon, the bound-electron spin in Ga centers is not directly coupled to the electromagnetic field via the spin-orbit interaction. However, this apparent drawback can be turned into an advantage by exploiting the spin-selective capture of conduction band electrons to the Ga centers. On the basis of a pump-probe photoluminescence experiment we measure directly in the temporal domain the hyperfine constant of an electron coupled to a gallium defect in GaAsN by tracing the dynamical behavior of the conduction electron spin-dependent recombination to the defect site. The hyperfine constants and the relative abundance of the nuclei isotopes involved can be determined without the need of an electron spin resonance technique and in the absence of any magnetic field. Information on the nuclear and electron spin relaxation damping parameters can also be estimated from the oscillation amplitude decay and the long-time-delay behavior.

Theoretical study of spin Hall effect in conjugated Organic semiconductors

NASA Astrophysics Data System (ADS)

Mahani, M. R.; Delin, A.

The spin Hall effect (SHE), a direct conversion between electronic and spin currents, is a rapidly growing branch of spintronics. The study of SHE in conjugated polymers has gained momentum recently due to the weak spin-orbit couplings and hyperfine interactions in these materials. Our calculations of SHE based on the recent work, are the result of the misalignment of pi-orbitals in triads consisting of three molecules. In disordered organics, where the electronic conduction is through hopping of the electrons among randomly oriented molecules, instead of identifying a hopping triad to represent the entire system, we numerically solve the master equations for electrical and spin hall conductivities by summing the contributions from all triads in a sufficiently large system. The interference between the direct and indirect hoppings in these triads leads to SHE proportional to the orientation vector of molecule at the first order of spin-orbit coupling. Hence, our results show, the degree of molecular alignment as well as the strength of the spin-orbit coupling can be used to control the SHE in organics.

Investigation of the annealing temperature dependence of the spin pumping in Co20Fe60B20/Pt systems

NASA Astrophysics Data System (ADS)

Belmeguenai, M.; Aitoukaci, K.; Zighem, F.; Gabor, M. S.; Petrisor, T.; Mos, R. B.; Tiusan, C.

2018-03-01

Co20Fe60B20/Pt systems with variable thicknesses of Co20Fe60B20 and of Pt have been sputtered and then annealed at various temperatures (Ta) up to 300 °C. Microstrip line ferromagnetic resonance (MS-FMR) has been used to investigate Co20Fe60B20 and Pt thickness dependencies of the magnetic damping enhancement due to the spin pumping. Using diffusion and ballistic models for spin pumping, the spin mixing conductance and the spin diffusion length have been deduced from the Co20Fe60B20 and the Pt thickness dependencies of the Gilbert damping parameter α of the Co20Fe60B20/Pt heterostructures, respectively. Within the ballistic simple model, both the spin mixing conductance at the CoFeB/Pt interface and the spin-diffusion length of Pt increase with the increasing annealing temperature and show a strong enhancement at 300 °C annealing temperature. In contrast, the spin mixing conductance, which increases with Ta, shows a different trend to the spin diffusion length when using the diffusion model. Moreover, MS-FMR measurements revealed that the effective magnetization varies linearly with the Co20Fe60B20 inverse thickness due to the perpendicular interface anisotropy, which is found to decrease as the annealing temperature increases. It also revealed that the angular dependence of the resonance field is governed by small uniaxial anisotropy which is found to vary linearly with the Co20Fe60B20 inverse thickness of the annealed films, in contrast to that of the as grown ones.

Chirality-induced magnon transport in AA-stacked bilayer honeycomb chiral magnets.

PubMed

Owerre, S A

2016-11-30

In this Letter, we study the magnetic transport in AA-stacked bilayer honeycomb chiral magnets coupled either ferromagnetically or antiferromagnetically. For both couplings, we observe chirality-induced gaps, chiral protected edge states, magnon Hall and magnon spin Nernst effects of magnetic spin excitations. For ferromagnetically coupled layers, thermal Hall and spin Nernst conductivities do not change sign as function of magnetic field or temperature similar to single-layer honeycomb ferromagnetic insulator. In contrast, for antiferromagnetically coupled layers, we observe a sign change in the thermal Hall and spin Nernst conductivities as the magnetic field is reversed. We discuss possible experimental accessible honeycomb bilayer quantum materials in which these effects can be observed.

Theory of Tunneling Spectroscopy in a Mn12 Single-Electron Transistor by Density-Functional Theory Methods

NASA Astrophysics Data System (ADS)

Michalak, Ł.; Canali, C. M.; Pederson, M. R.; Paulsson, M.; Benza, V. G.

2010-01-01

We consider tunneling transport through a Mn12 molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wave functions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.

Theory of tunneling spectroscopy in a Mn12 single-electron transistor by density-functional theory methods.

PubMed

Michalak, Ł; Canali, C M; Pederson, M R; Paulsson, M; Benza, V G

2010-01-08

We consider tunneling transport through a Mn12 molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wave functions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.

Scaling Behavior of the Spin Pumping Effect in Ferromagnet-Platinum Bilayers

NASA Astrophysics Data System (ADS)

Czeschka, F. D.; Dreher, L.; Brandt, M. S.; Weiler, M.; Althammer, M.; Imort, I.-M.; Reiss, G.; Thomas, A.; Schoch, W.; Limmer, W.; Huebl, H.; Gross, R.; Goennenwein, S. T. B.

2011-07-01

We systematically measured the dc voltage VISH induced by spin pumping together with the inverse spin Hall effect in ferromagnet-platinum bilayer films. In all our samples, comprising ferromagnetic 3d transition metals, Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, VISH invariably has the same polarity, and scales with the magnetization precession cone angle. These findings, together with the spin mixing conductance derived from the experimental data, quantitatively corroborate the present theoretical understanding of spin pumping in combination with the inverse spin Hall effect.

Gate-driven pure spin current in graphene

NASA Astrophysics Data System (ADS)

Lin, Xiaoyang; Su, Li; Zhang, Youguang; Bournel, Arnaud; Zhang, Yue; Klein, Jacques-Olivier; Zhao, Weisheng; Fert, Albert

An important challenge of spin current based devices is to realize long-distance transport and efficient manipulation of pure spin current without frequent spin-charge conversions. Here, the mechanism of gate-driven pure spin current in graphene is presented. Such a mechanism relies on the electrical gating of conductivity and spin diffusion length in graphene. The gate-driven feature is adopted to realize the pure spin current demultiplexing operation, which enables gate-controllable distribution of the pure spin current into graphene branches. Compared with Elliot-Yafet spin relaxation mechanism, D'yakonov-Perel spin relaxation mechanism results in more appreciable demultiplexing performance, which also implies a feasible strategy to characterize the spin relaxation mechanisms. The unique feature of the pure spin current demultiplexing operation would pave a way for ultra-low power spin logic beyond CMOS. Supported by the NSFC (61627813, 51602013) and the 111 project (B16001).

Non-local detection of spin dynamics via spin rectification effect in yttrium iron garnet/SiO{sub 2}/NiFe trilayers near simultaneous ferromagnetic resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soh, Wee Tee, E-mail: a0046479@u.nus.edu; Ong, C. K.; Peng, Bin

2015-08-15

The spin rectification effect (SRE), a phenomenon that generates dc voltages from ac microwave fields incident onto a conducting ferromagnet, has attracted widespread attention due to its high sensitivity to ferromagnetic resonance (FMR) as well as its relevance to spintronics. Here, we report the non-local detection of yttrium iron garnet (YIG) spin dynamics by measuring SRE voltages from an adjacent conducting NiFe layer up to 200 nm thick. In particular, we detect, within the NiFe layer, SRE voltages stemming from magnetostatic surface spin waves (MSSWs) of the adjacent bulk YIG which are excited by a shorted coaxial probe. These non-localmore » SRE voltages within the NiFe layer that originates from YIG MSSWs are present even in 200 nm-thick NiFe films with a 50 nm thick SiO{sub 2} spacer between NiFe and YIG, thus strongly ruling out the mechanism of spin-pumping induced inverse spin Hall effect in NiFe as the source of these voltages. This long-range influence of YIG dynamics is suggested to be mediated by dynamic fields generated from YIG spin precession near YIG/NiFe interface, which interacts with NiFe spins near the simultaneous resonance of both spins, to generate a non-local SRE voltage within the NiFe layer.« less

Rover and Telerobotics Technology Program

NASA Technical Reports Server (NTRS)

Weisbin, Charles R.

1998-01-01

The Jet Propulsion Laboratory's (JPL's) Rover and Telerobotics Technology Program, sponsored by the National Aeronautics and Space Administration (NASA), responds to opportunities presented by NASA space missions and systems, and seeds commerical applications of the emerging robotics technology. The scope of the JPL Rover and Telerobotics Technology Program comprises three major segments of activity: NASA robotic systems for planetary exploration, robotic technology and terrestrial spin-offs, and technology for non-NASA sponsors. Significant technical achievements have been reached in each of these areas, including complete telerobotic system prototypes that have built and tested in realistic scenarios relevant to prospective users. In addition, the program has conducted complementary basic research and created innovative technology and terrestrial applications, as well as enabled a variety of commercial spin-offs.

Microscopic signature of insulator-to-metal transition in highly doped semicrystalline conducting polymers in ionic-liquid-gated transistors

NASA Astrophysics Data System (ADS)

Tanaka, Hisaaki; Nishio, Satoshi; Ito, Hiroshi; Kuroda, Shin-ichi

2015-12-01

Electronic state of charge carriers, in particular, in highly doped regions, in thin-film transistors of a semicrystalline conducting polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), has been studied by using field-induced electron spin resonance (ESR) spectroscopy. By adopting an ionic-liquid gate insulator, a gate-controlled reversible electrochemical hole-doping of the polymer backbone is achieved, as confirmed from the change of the optical absorption spectra. The edge-on molecular orientation in the pristine film is maintained even after the electrochemical doping, which is clarified from the angular dependence of the g value. As the doping level increases, spin 1/2 polarons transform into spinless bipolarons, which is demonstrated from the spin-charge relation showing a spin concentration peak around 1%, contrasting to the monotonic increase in the charge concentration. At high doping levels, a drastic change in the linewidth anisotropy due to the generation of conduction electrons is observed, indicating the onset of metallic state, which is also supported by the temperature dependence of the spin susceptibility and the ESR linewidth. Our results suggest that semicrystalline conducting polymers become metallic with retaining their molecular orientational order, when appropriate doping methods are chosen.

Spin coating of electrolytes

DOEpatents

Stetter, Joseph R.; Maclay, G. Jordan

1989-01-01

Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

Magnetic brightening and control of dark excitons in monolayer WSe2.

PubMed

Zhang, Xiao-Xiao; Cao, Ting; Lu, Zhengguang; Lin, Yu-Chuan; Zhang, Fan; Wang, Ying; Li, Zhiqiang; Hone, James C; Robinson, Joshua A; Smirnov, Dmitry; Louie, Steven G; Heinz, Tony F

2017-09-01

Monolayer transition metal dichalcogenide crystals, as direct-gap materials with strong light-matter interactions, have attracted much recent attention. Because of their spin-polarized valence bands and a predicted spin splitting at the conduction band edges, the lowest-lying excitons in WX 2 (X = S, Se) are expected to be spin-forbidden and optically dark. To date, however, there has been no direct experimental probe of these dark excitons. Here, we show how an in-plane magnetic field can brighten the dark excitons in monolayer WSe 2 and permit their properties to be observed experimentally. Precise energy levels for both the neutral and charged dark excitons are obtained and compared with ab initio calculations using the GW-BSE approach. As a result of their spin configuration, the brightened dark excitons exhibit much-increased emission and valley lifetimes. These studies directly probe the excitonic spin manifold and reveal the fine spin-splitting at the conduction band edges.

Magnetic brightening and control of dark excitons in monolayer WSe 2

DOE PAGES

Zhang, Xiao -Xiao; Cao, Ting; Lu, Zhengguang; ...

2017-06-26

Monolayer transition metal dichalcogenide crystals, as direct-gap materials with strong light–matter interactions, have attracted much recent attention. Because of their spin-polarized valence bands and a predicted spin splitting at the conduction band edges, the lowest-lying excitons in WX 2 (X = S, Se) are expected to be spin-forbidden and optically dark. To date, however, there has been no direct experimental probe of these dark excitons. Here, we show how an in-plane magnetic field can brighten the dark excitons in monolayer WSe2 and permit their properties to be observed experimentally. Precise energy levels for both the neutral and charged dark excitonsmore » are obtained and compared with ab initio calculations using the GW-BSE approach. As a result of their spin configuration, the brightened dark excitons exhibit much-increased emission and valley lifetimes. Furthermore, these studies directly probe the excitonic spin manifold and reveal the fine spin-splitting at the conduction band edges.« less

Magnon and phonon dispersion, lifetime, and thermal conductivity of iron from spin-lattice dynamics simulations

NASA Astrophysics Data System (ADS)

Wu, Xufei; Liu, Zeyu; Luo, Tengfei

2018-02-01

In recent years, the fundamental physics of spin-lattice (e.g., magnon-phonon) interaction has attracted significant experimental and theoretical interests given its potential paradigm-shifting impacts in areas like spin-thermoelectrics, spin-caloritronics, and spintronics. Modelling studies of the transport of magnons and phonons in magnetic crystals are very rare. In this paper, we use spin-lattice dynamics (SLD) simulations to model ferromagnetic crystalline iron, where the spin and lattice systems are coupled through the atomic position-dependent exchange function, and thus the interaction between magnons and phonons is naturally considered. We then present a method combining SLD simulations with spectral energy analysis to calculate the magnon and phonon harmonic (e.g., dispersion, specific heat, and group velocity) and anharmonic (e.g., scattering rate) properties, based on which their thermal conductivity values are calculated. This work represents an example of using SLD simulations to understand the transport properties involving coupled magnon and phonon dynamics.

Summary of spin technology as related to light general-aviation airplanes

NASA Technical Reports Server (NTRS)

Bowman, J. S., Jr.

1971-01-01

A summary was made of all NASA (and NACA) research and experience related to the spin and recovery characteristics of light personal-owner-type general-aviation airplanes. Very little of the research deals with light general-aviation airplanes as such, but many of the airplanes and models tested before and during World War II were similar to present-day light general-aviation airplanes with regard to the factors that are important in spinning. The material is based mainly on the results of spin-tunnel tests of free-spinning dynamically scaled models of about 100 different airplane designs and, whenever possible, includes correlation with full-scale spin tests. The research results are discussed in terms of airplane design considerations and the proper use of controls for recovery.

Development of a spinning wave heat engine

NASA Technical Reports Server (NTRS)

Zinn, B. T.; Powell, E. A.; Hubbartt, J. E.

1982-01-01

A theoretical analysis and an experimental investigation were conducted to assess the feasibility of developing a spinning wave heat engine. Such as engine would utilize a large amplitude traveling acoustic wave rotating around a cylindrica chamber, and it should not suffer from the inefficiency, noise, and intermittent thrust which characterizes pulse jet engines. The objective of this investigation was to determine whether an artificially driven large amplitude spinning transverse wave could induce a steady flow of air through the combustion chamber under cold flow conditions. In the theoretical analysis the Maslen and Moore perturbation technique was extended to study flat cylinders (pancake geometry) with completely open side walls and a central opening. In the parallel experimental study, a test moel was used to determine resonant frequencies and radial pressure distributions, as well as oscillatory and steady flow velocities at the inner and outer peripheries. The experimental frequency was nearly the same as the theoretical acoustic value for a model of the same outer diameter but without a central hole. Although the theoretical analysis did not predict a steady velocity component, simulaneous measurements of hotwire and microphone responses have shown that the spinning wave pumps a mean flow radially outward through the cavity.

Field-induced negative differential spin lifetime in silicon.

PubMed

Li, Jing; Qing, Lan; Dery, Hanan; Appelbaum, Ian

2012-04-13

We show that the electric-field-induced thermal asymmetry between the electron and lattice systems in pure silicon substantially impacts the identity of the dominant spin relaxation mechanism. Comparison of empirical results from long-distance spin transport devices with detailed Monte Carlo simulations confirms a strong spin depolarization beyond what is expected from the standard Elliott-Yafet theory even at low temperatures. The enhanced spin-flip mechanism is attributed to phonon emission processes during which electrons are scattered between conduction band valleys that reside on different crystal axes. This leads to anomalous behavior, where (beyond a critical field) reduction of the transit time between spin-injector and spin-detector is accompanied by a counterintuitive reduction in spin polarization and an apparent negative spin lifetime.

Gate tunable spin transport in graphene with Rashba spin-orbit coupling

NASA Astrophysics Data System (ADS)

Tan, Xiao-Dong; Liao, Xiao-Ping; Sun, Litao

2016-10-01

Recently, it attracts much attention to study spin-resolved transport properties in graphene with Rashba spin-orbit coupling (RSOC). One remarkable finding is that Klein tunneling in single layer graphene (SLG) with RSOC (SLG + R for short below) behaves as in bi-layer graphene (BLG). Based on the effective Dirac theory, we reconsider this tunneling problem and derive the analytical solution for the transmission coefficients. Our result shows that Klein tunneling in SLG + R and BLG exhibits completely different behaviors. More importantly, we find two new transmission selection rules in SLG + R, i.e., the single band to single band (S → S) and the single band to multiple bands (S → M) transmission regimes, which strongly depend on the relative height among Fermi level, RSOC, and potential barrier. Interestingly, in the S → S transmission regime, only normally incident electrons have capacity to pass through the barrier, while in the S → M transmission regime the angle-dependent tunneling becomes very prominent. Using the transmission coefficients, we also derive spin-resolved conductance analytically, and conductance oscillation with the increasing barrier height and zero conductance gap are found in SLG + R. The present study offers new insights and opportunities for developing graphene-based spin devices.

Reduced Spin Hall Effects from Magnetic Proximity.

DOE PAGES

Zhang, Wei; Jungfleisch, Matthias B.; Jiang, Wanjun; ...

2015-03-26

We investigate temperature-dependent spin pumping and inverse spin Hall effects in thin Pt and Pd in contact with Permalloy. Our experiments show a decrease of the spin Hall effect with decreasing temperature, which is attributed to a temperature-dependent proximity effect. The spin Hall angle decreases from 0.086 at room temperature to 0.042 at 10 K for Pt and is nearly negligible at 10 K for Pd. By first-principle calculations, we show that the spin Hall conductivity indeed reduces by increasing the proximity-induced spin magnetic moments for both Pt and Pd. This work highlights the important role of proximity-induced magnetic orderingmore » to spin Hall phenomena in Pt and Pd.« less

Modulation of pure spin currents with a ferromagnetic insulator

NASA Astrophysics Data System (ADS)

Villamor, Estitxu; Isasa, Miren; Vélez, Saül; Bedoya-Pinto, Amilcar; Vavassori, Paolo; Hueso, Luis E.; Bergeret, F. Sebastián; Casanova, Fèlix

2015-01-01

We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y3F e5O12 (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the nonlocal resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation. These results open a path towards the development of spin logics.

In-Situ Observation of Nano-Oxide Formation in Magnetic Thin Films

NASA Astrophysics Data System (ADS)

McCallum, Andrew; Russek, Stephen

2004-03-01

Exposure of a metal surface in a spin valve structure to oxygen creates a nano-oxide layer, or NOL, on that surface. Inclusion of NOLs into spin valve structures has been shown by many researchers to lower the resistance and increase the giant magnetoresistance effect. Four point in-situ conductance measurements were made during the deposition and oxidation of Co layers. These measurements show an initial decrease in conductance followed by an increase in conductance, due to a specularity increase of at least 0.10. RHEED measurements taken simultaneously with conductance measurements show the formation an amorphous oxide while the specularity increases. With further exposure of oxygen to the surface a CoO structure with a (111) texture forms. Magnetoconductance measurements during the oxidation of the free layer of bottom pinned spin valves show increases in the GMR of the spin valves. Estimates of the change in specularity and Co layer thickness were determined from the change in conductance and the change in magnetoconductance. Also determined from the magnetoconductance measurements was an increase in the coercivity of the free layer with oxidation. Adding Co onto the oxide had a strong effect on the coercivity and coupling between free and pinned layers.

Spin- and valley-dependent electrical conductivity of ferromagnetic group-IV 2D sheets in the topological insulator phase

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Yarmohammadi, Mohsen; Mirabbaszadeh, Kavoos; Habibiyan, Hamidreza

2018-03-01

In this work, based on the Kubo-Greenwood formalism and the k . p Hamiltonian model, the impact of Rashba spin-orbit coupling on electronic band structure and electrical conductivity of spin-up and spin-down subbands in counterparts of graphene, including silicene, stanene, and germanene nanosheets has been studied. When Rashba coupling is considered, the effective mass of Dirac fermions decreases significantly and no significant change is caused by this coupling for the subband gaps. All these nanosheets are found to be in topological insulator quantum phase at low staggered on-site potentials due to the applied perpendicular external electric field. We point out that the electrical conductivity of germanene increases gradually with Rashab coupling, while silicene and stanene have some fluctuations due to their smaller Fermi velocity. Furthermore, some critical temperatures with the same electrical conductivity values for jumping to the higher energy levels are observed at various Rashba coupling strengths. For all structures, a broad peak appears at low temperatures in electrical conductivity curves corresponding to the large entropy of systems when the thermal energy reaches to the difference between the energy states. Finally, we have reported that silicene has the larger has the larger electrical conductivity than two others.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshizumi, K.; Sasaki, A.; Kohda, M.

We demonstrate gate-controlled switching between persistent spin helix (PSH) state and inverse PSH state, which are detected by quantum interference effect on magneto-conductance. These special symmetric spin states showing weak localization effect give rise to a long spin coherence when the strength of Rashba spin-orbit interaction (SOI) is close to that of Dresselhaus SOI. Furthermore, in the middle of two persistent spin helix states, where the Rashba SOI can be negligible, the bulk Dresselhaus SOI parameter in a modulation doped InGaAs/InAlAs quantum well is determined.

Gate-Driven Pure Spin Current in Graphene

NASA Astrophysics Data System (ADS)

Lin, Xiaoyang; Su, Li; Si, Zhizhong; Zhang, Youguang; Bournel, Arnaud; Zhang, Yue; Klein, Jacques-Olivier; Fert, Albert; Zhao, Weisheng

2017-09-01

The manipulation of spin current is a promising solution for low-power devices beyond CMOS. However, conventional methods, such as spin-transfer torque or spin-orbit torque for magnetic tunnel junctions, suffer from large power consumption due to frequent spin-charge conversions. An important challenge is, thus, to realize long-distance transport of pure spin current, together with efficient manipulation. Here, the mechanism of gate-driven pure spin current in graphene is presented. Such a mechanism relies on the electrical gating of carrier-density-dependent conductivity and spin-diffusion length in graphene. The gate-driven feature is adopted to realize the pure spin-current demultiplexing operation, which enables gate-controllable distribution of the pure spin current into graphene branches. Compared with the Elliott-Yafet spin-relaxation mechanism, the D'yakonov-Perel spin-relaxation mechanism results in more appreciable demultiplexing performance. The feature of the pure spin-current demultiplexing operation will allow a number of logic functions to be cascaded without spin-charge conversions and open a route for future ultra-low-power devices.

TMC Behavior Modeling and Life Prediction Under Multiaxial Stresses

NASA Technical Reports Server (NTRS)

Merrick, H. F.; Aksoy, S. Z.; Costen, M.; Ahmad, J.

1998-01-01

The goal of this program was to manufacture and burst test small diameter SCS-6/Ti-6Al-4V composite rings for use in the design of an advanced titanium matrix composite (TMC) impeller. The Textron Specialty Metals grooved foil-fiber process was successfully used to make high quality TMC rings. A novel spin test arbor with "soft touch" fingers to retain the TMC ring was designed and manufactured. The design of the arbor took into account its use for cyclic experiments as well as ring burst tests. Spin testing of the instrumented ring was performed at ambient, 149C (300F), and 316C (600F) temperatures. Assembly vibration was encountered during spin testing but this was overcome through simple modification of the arbor. A spin-to-burst test was successfully completed at 316C (600F). The rotational speed of the TMC ring at burst was close to that predicted. In addition to the spin test program, a number of SCS-6/Ti-6Al-4V test panels were made. Neat Ti-6Al-4V panels also were made.

Mechanical design of a rotary balance system for NASA. Langley Research Center's vertical spin tunnel

NASA Technical Reports Server (NTRS)

Allred, J. W.; Fleck, V. J.

1992-01-01

A new lightweight Rotary Balance System is presently being fabricated and installed as part of a major upgrade to the existing 20 Foot Vertical Spin Tunnel. This upgrade to improve model testing productivity of the only free spinning vertical wind tunnel includes a modern fan/drive and tunnel control system, an updated video recording system, and the new rotary balance system. The rotary balance is a mechanical apparatus which enables the measurement of aerodynamic force and moment data under spinning conditions (100 rpm). This data is used in spin analysis and is vital to the implementation of large amplitude maneuvering simulations required for all new high performance aircraft. The new rotary balance system described in this report will permit greater test efficiency and improved data accuracy. Rotary Balance testing with the model enclosed in a tare bag can also be performed to obtain resulting model forces from the spinning operation. The rotary balance system will be stored against the tunnel sidewall during free flight model testing.

Spin-polarized two-dimensional t2 g electron gas: Ab initio study of EuO interface with oxygen-deficient SrTi O3

NASA Astrophysics Data System (ADS)

Gao, Lingyuan; Demkov, Alexander A.

2018-03-01

Using first-principles calculations we predict the existence of a spin-polarized two-dimensional electron gas (2DEG) at the interface of a ferromagnetic insulator EuO and oxygen-deficient SrTi O3 . The carriers are generated by oxygen vacancies in SrTi O3 near the interface and have predominantly Ti-t2 g orbital character. At the interface, the split-off dx y-derived conduction band of SrTi O3 is fully spin-polarized and the in-gap vacancy-induced state, found below the conduction-band edge, is aligned ferromagnetically with EuO. The calculations suggest a possible mechanism for generating spin-polarized 2DEG for spintronic applications.

Thermal transport through a spin-phonon interacting junction: A nonequilibrium Green's function method study

NASA Astrophysics Data System (ADS)

Zhang, Zu-Quan; Lü, Jing-Tao

2017-09-01

Using the nonequilibrium Green's function method, we consider heat transport in an insulating ferromagnetic spin chain model with spin-phonon interaction under an external magnetic field. Employing the Holstein-Primakoff transformation to the spin system, we treat the resulted magnon-phonon interaction within the self-consistent Born approximation. We find the magnon-phonon coupling can change qualitatively the magnon thermal conductance in the high-temperature regime. At a spectral mismatched ferromagnetic-normal insulator interface, we also find thermal rectification and negative differential thermal conductance due to the magnon-phonon interaction. We show that these effects can be effectively tuned by the external applied magnetic field, a convenient advantage absent in anharmonic phonon and electron-phonon systems studied before.

Flight test of a spin parachute for use with a Super Arcas sounding rocket

NASA Technical Reports Server (NTRS)

Silbert, M. N.

1975-01-01

The development and flight testing of a specially configured 16.6 ft Disc Band Gap (DBG) Spin Parachute is discussed. The parachute is integrated with a modified Super Arcas launch vehicle. Total payload weight was 17.6 lbs including the Spin Parachute and a scientific payload, and lift-off weight was 100.3 lbs. The Super Arcas vehicle was despun from 18.4 cps. After payload separation at 244,170 ft the Spin Parachute and its payload attained a maximum spin rate of 2.4 cps. Total suspended weight of the Spin Parachute and its payload was 14.64 lbs.

Spin relaxation in quantum dots due to electron exchange with leads.

PubMed

Vorontsov, A B; Vavilov, M G

2008-11-28

We calculate spin relaxation rates in lateral quantum dot systems due to electron exchange between dots and leads. Using rate equations, we develop a theoretical description of the experimentally observed electric current in the spin blockade regime of double quantum dots. A single expression fits the entire current profile and describes the structure of both the conduction peaks and the suppressed ("valley") region. Extrinsic rates calculated here have to be taken into account for accurate extraction of intrinsic relaxation rates due to the spin-orbit and hyperfine spin scattering mechanisms from spin blockade measurements.

Organic-inorganic proximity effect in the magneto-conductance of vertical organic field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khachatryan, B.; Devir-Wolfman, A. H.; Ehrenfreund, E., E-mail: eitane@technion.ac.il

Vertical organic field effect transistors having a patterned source electrode and an a-SiO{sub 2} insulation layer show high performance as a switching element with high transfer characteristics. By measuring the low field magneto-conductance under ambient conditions at room temperature, we show here that the proximity of the inorganic a-SiO{sub 2} insulation to the organic conducting channel affects considerably the magnetic response. We propose that in n-type devices, electrons in the organic conducting channel and spin bearing charged defects in the inorganic a-SiO{sub 2} insulation layer (e.g., O{sub 2} = Si{sup +·}) form oppositely charged spin pairs whose singlet-triplet spin configurations are mixedmore » through the relatively strong hyperfine field of {sup 29}Si. By increasing the contact area between the insulation layer and the conducting channel, the ∼2% magneto-conductance response may be considerably enhanced.« less

Spin-current emission governed by nonlinear spin dynamics.

PubMed

Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

2015-10-16

Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators.

Spin-current emission governed by nonlinear spin dynamics

PubMed Central

Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

2015-01-01

Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators. PMID:26472712

Thermally driven spin-Seebeck transport in chiral dsDNA-based molecular devices

NASA Astrophysics Data System (ADS)

Nian, L. L.; Zhang, Rong; Tang, F. R.; Tang, Jun; Bai, Long

2018-03-01

By employing the nonequilibrium Green's function technique, we study the thermal-induced spin-Seebeck transport through a chiral double-stranded DNA (dsDNA) connected to a normal-metal and a ferromagnetic lead. How the main parameters of the dsDNA-based system influence the spin-Seebeck transport is analyzed at length, and the thermally created charge (spin-related) current displays the rectification effect and the negative differential thermal conductance feature. More importantly, the spin current exhibits the rectification behavior of the spin-Seebeck effect; even the perfect spin-Seebeck effect can be obtained with the null charge current. Thus, the chiral dsDNA-based system can act as a spin(charge)-Seebeck diode, spin(charge)-Seebeck switch, and spin(charge)-Seebeck transistor. Our results provide new ways to design spin caloritronic devices based on dsDNA or other organic molecules.

Electron spin resonance in YbRh2Si2: local-moment, unlike-spin and quasiparticle descriptions.

PubMed

Huber, D L

2012-06-06

Electron spin resonance (ESR) in the Kondo lattice compound YbRh(2)Si(2) has stimulated discussion as to whether the low-field resonance outside the Fermi liquid regime in this material is more appropriately characterized as a local-moment phenomenon or one that requires a Landau quasiparticle interpretation. In earlier work, we outlined a collective mode approach to the ESR that involves only the local 4f moments. In this paper, we extend the collective mode approach to a situation where there are two subsystems of unlike spins: the pseudospins of the ground multiplet of the Yb ions and the spins of the itinerant conduction electrons. We assume a weakly anisotropic exchange interaction between the two subsystems. With suitable approximations our expression for the g-factor also reproduces that found in recent unlike-spin quasiparticle calculations. It is pointed out that the success of the local-moment approach in describing the resonance is due to the fact that the susceptibility of the Yb subsystem dominates that of the conduction electrons with the consequence that the relative shift in the resonance frequency predicted by the unlike-spin models (and absent in the local-moment models) is ≪ 1. The connection with theoretical studies of a two-component model with like spins is also discussed.

Coherent spin transport through a 350 micron thick silicon wafer.

PubMed

Huang, Biqin; Monsma, Douwe J; Appelbaum, Ian

2007-10-26

We use all-electrical methods to inject, transport, and detect spin-polarized electrons vertically through a 350-micron-thick undoped single-crystal silicon wafer. Spin precession measurements in a perpendicular magnetic field at different accelerating electric fields reveal high spin coherence with at least 13pi precession angles. The magnetic-field spacing of precession extrema are used to determine the injector-to-detector electron transit time. These transit time values are associated with output magnetocurrent changes (from in-plane spin-valve measurements), which are proportional to final spin polarization. Fitting the results to a simple exponential spin-decay model yields a conduction electron spin lifetime (T1) lower bound in silicon of over 500 ns at 60 K.

Large anomalous Nernst and spin Nernst effects in the noncollinear antiferromagnets Mn3X (X =Sn ,Ge ,Ga )

NASA Astrophysics Data System (ADS)

Guo, Guang-Yu; Wang, Tzu-Cheng

2017-12-01

Noncollinear antiferromagnets have recently been attracting considerable interest partly due to recent surprising discoveries of the anomalous Hall effect (AHE) in them and partly because they have promising applications in antiferromagnetic spintronics. Here we study the anomalous Nernst effect (ANE), a phenomenon having the same origin as the AHE, and also the spin Nernst effect (SNE) as well as AHE and the spin Hall effect (SHE) in noncollinear antiferromagnetic Mn3X (X =Sn , Ge, Ga) within the Berry phase formalism based on ab initio relativistic band structure calculations. For comparison, we also calculate the anomalous Nernst conductivity (ANC) and anomalous Hall conductivity (AHC) of ferromagnetic iron as well as the spin Nernst conductivity (SNC) of platinum metal. Remarkably, the calculated ANC at room temperature (300 K) for all three alloys is huge, being 10-40 times larger than that of iron. Moreover, the calculated SNC for Mn3Sn and Mn3Ga is also larger, being about five times larger than that of platinum. This suggests that these antiferromagnets would be useful materials for thermoelectronic devices and spin caloritronic devices. The calculated ANC of Mn3Sn and iron are in reasonably good agreement with the very recent experiments. The calculated SNC of platinum also agrees with the very recent experiments in both sign and magnitude. The calculated thermoelectric and thermomagnetic properties are analyzed in terms of the band structures as well as the energy-dependent AHC, ANC, SNC, and spin Hall conductivity via the Mott relations.

Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film.

PubMed

Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

2016-06-07

Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.

Vertical Spin Tunnel Testing and Stability Analysis of Multi-Mission Earth Entry Vehicles

NASA Technical Reports Server (NTRS)

Glaab, Louis J.; Morelli, Eugene A.; Fremaux, C. Michael; Bean, Jacob

2014-01-01

Multi-Mission Earth Entry Vehicles (MMEEVs) are blunt-body vehicles designed with the purpose of transporting payloads from space to the surface of the Earth. To achieve high reliability and minimum weight, MMEEVs avoid using limited-reliability systems, such as parachutes, retro-rockets, and reaction control systems and rely on the natural aerodynamic stability of the vehicle throughout the Entry, Descent, and Landing phases of flight. Testing in NASA Langley's 20-FT Vertical Spin Tunnel (20-FT VST), dynamically-scaled MMEEV models was conducted to improve subsonic aerodynamic models and validate stability criteria for this class of vehicle. This report documents the resulting data from VST testing for an array of 60-deg sphere-cone MMEEVs. Model configurations included were 1.2 meter, and 1.8 meter designs. The addition of a backshell extender, which provided a 150% increase in backshell diameter for the 1.2 meter design, provided a third test configuration. Center of Gravity limits were established for all MMEEV configurations. An application of System Identification (SID) techniques was performed to determine the aerodynamic coefficients in order to provide databases for subsequent 6-degree-of-freedom simulations.

Controllable spin-charge transport in strained graphene nanoribbon devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diniz, Ginetom S., E-mail: ginetom@gmail.com; Guassi, Marcos R.; Qu, Fanyao

2014-09-21

We theoretically investigate the spin-charge transport in two-terminal device of graphene nanoribbons in the presence of a uniform uniaxial strain, spin-orbit coupling, exchange field, and smooth staggered potential. We show that the direction of applied strain can efficiently tune strain-strength induced oscillation of band-gap of armchair graphene nanoribbon (AGNR). It is also found that electronic conductance in both AGNR and zigzag graphene nanoribbon (ZGNR) oscillates with Rashba spin-orbit coupling akin to the Datta-Das field effect transistor. Two distinct strain response regimes of electronic conductance as function of spin-orbit couplings magnitude are found. In the regime of small strain, conductance ofmore » ZGNR presents stronger strain dependence along the longitudinal direction of strain. Whereas for high values of strain shows larger effect for the transversal direction. Furthermore, the local density of states shows that depending on the smoothness of the staggered potential, the edge states of AGNR can either emerge or be suppressed. These emerging states can be determined experimentally by either spatially scanning tunneling microscope or by scanning tunneling spectroscopy. Our findings open up new paradigms of manipulation and control of strained graphene based nanostructure for application on novel topological quantum devices.« less

Electrical and optical transport properties of single layer WSe2

NASA Astrophysics Data System (ADS)

Tahir, M.

2018-03-01

The electronic properties of single layer WSe2 are distinct from the famous graphene due to strong spin orbit coupling, a huge band gap and an anisotropic lifting of the degeneracy of the valley degree of freedom under Zeeman field. In this work, band structure of the monolayer WSe2 is evaluated in the presence of spin and valley Zeeman fields to study the electrical and optical transport properties. Using Kubo formalism, an explicit expression for the electrical Hall conductivity is examined at finite temperatures. The electrical longitudinal conductivity is also evaluated. Further, the longitudinal and Hall optical conductivities are analyzed. It is observed that the contributions of the spin-up and spin-down states to the power absorption spectrum depend on the valley index. The numerical results exhibit absorption peaks as a function of photon energy, ℏ ω, in the range ∼ 1.5 -2 eV. Also, the optical response lies in the visible frequency range in contrast to the conventional two-dimensional electron gas or graphene where the response is limited to terahertz regime. This ability to isolate carriers in spin-valley coupled structures may make WSe2 a promising candidate for future spintronics, valleytronics and optical devices.

Role of motive forces for the spin torque transfer for nano-structures

NASA Astrophysics Data System (ADS)

Barnes, Stewart

2009-03-01

Despite an announced imminent commercial realization of spin transfer random access memory (SPRAM) the current theory evolved from that of Slonczewski [1,2] does not conserve energy. Barnes and Maekawa [3] have shown, in order correct this defect, forces which originate from the spin rather than the charge of an electron must be accounted for, this leading to the concept of spin-motive-forces (smf) which must appear in Faraday's law and which significantly modifies the theory for spin-valves and domain wall devices [4]. A multi-channel theory in which these smf's redirect the spin currents will be described. In nano-structures it is now well known that the Kondo effect is reflected by conductance peaks. In essence, the spin degrees of freedom are used to enhance conduction. In a system with nano-magnets and a Coulomb blockade [5] the similar spin channels can be the only means of effective conduction. This results in a smf which lasts for minutes and an enormous magneto-resistance [5]. This implies the possibility of ``single electron memory'' in which the magnetic state is switched by a single electron. [4pt] [1] J. C. Slonczewski, Current-Driven Excitation of Magnetic Multilayers J. Magn. Magn. Mater. 159, L1 (1996). [0pt] [2] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, and B. I. Halperin, Nonlocal magnetization dynamics in ferromagnetic heterostructures, Rev. Mod. Phys. 77, 1375 (2005). [0pt] [3] S. E. Barnes and S. Maekawa, Generalization of Faraday's Law to Include Nonconservative Spin Forces Phys. Rev. Lett. 98, 246601 (2007); S. E. Barnes and S. Maekawa, Currents induced by domain wall motion in thin ferromagnetic wires. arXiv:cond-mat/ 0410021v1 (2004). [0pt] [4] S. E., Barnes, Spin motive forces, measurement, and spin-valves. J. Magn. Magn. Mat. 310, 2035-2037 (2007); S. E. Barnes, J. Ieda. J and S. Maekawa, Magnetic memory and current amplification devices using moving domain walls. Appl. Phys. Lett. 89, 122507 (2006). [0pt] [5] Pham-Nam Hai, Byung-Ho Yu, Shinobu Ohya, Masaaki Tanaka, Stewart E. Barnes and Sadamichi Maekawa, Electromotive force and huge magnetoresistance in magnetic tunnel junctions. Submitted Nature, August, (2008).

Effects of Structural and Electronic Disorder in Topological Insulator Sb2Te3 Thin Films

NASA Astrophysics Data System (ADS)

Korzhovska, Inna

Topological quantum matter is a unique and potentially transformative protectorate against disorder-induced backscattering. The ultimate disorder limits to the topological state, however, are still not known - understanding these limits is critical to potential applications in the fields of spintronics and information processing. In topological insulators spin-orbit interaction and time-reversal-symmetry invariance guarantees - at least up to a certain disorder strength - that charge transport through 2D gapless Dirac surface states is robust against backscattering by non-magnetic disorder. Strong disorder may destroy topological protection and gap out Dirac surface states, although recent theories predict that under severe electronic disorder a quantized topological conductance might yet reemerge. Very strong electronic disorder, however, is not trivial to install and quantify, and topological matter under such conditions thus far has not been experimentally tested. This thesis addresses the behavior of three-dimensional (3D) topological insulator (TI) films in a wide range of structural and electronic disorder. We establish strong positional disorder in thin (20-50 nm) Sb2Te 3 films, free of extrinsic magnetic dopants. Sb 2Te3 is a known 2nd generation topological insulator in the low-disorder crystalline state. It is also a known phase-change material that undergoes insulator-to-metal transition with the concurrent orders of magnitude resistive drop, where a huge range of disorder could be controllably explored. In this work we show that even in the absence of magnetic dopants, disorder may induce spin correlations detrimental to the topological state. Chapter 1 contains a brief introduction to the topological matter and describes the role played by disorder. This is followed by theory considerations and a survey of prior experimental work. Next we describe the motivation for our experiments and explain the choice of the material. Chapter 2 describes deposition techniques used for material growth, including the parameters significance and effects on the material properties. Chapter 3 describes structural and electrical characterization techniques employed in the work. In Chapter 4-5 we discuss the experimental results. Sb2Te 3 films at extreme disorder, where spin correlations dominate the transport of charge, are discussed in Chapter 4. We employ transport measurements as our main tool to explore disorder-induced changes in the Sb2Te 3. In addition we directly detect disorder-induced spin response in thin Sb2Te3 films free of extrinsic magnetic dopants; it onsets at a surprisingly high temperature ( 200 K) and vanishes when disorder is reduced. Localized spins control the hopping (tunneling) transport through spin memory induced by the non-equilibrium charge currents. The observed spin-memory phenomenon emerges as negative magnetoresistance distinct from orbital quantum interference effects. The hopping mechanism and spin correlations dominate transport over an extensive disorder range. Spin correlations are eventually suppressed by the restoration of positional order in the (bulk) crystalline state, implying a disorder threshold to the topological state. As disorder is reduced the material undergoes structural and electronic transitions, which are discussed in Chapter 5. We obtain a number of characteristic attributes that change sharply at the structural and electronic transitions: localization length, dimensionality, and the nature of conductance. Structural transition is clearly seen in the changes in lattice vibrations tracked by Raman spectroscopy, which we use here as a metric of disorder. The significance of the disorder-induced localization transition is discussed. Next we investigate the effects of structural and electronic disorder on the bulk and surfaces in the crystalline state of Sb2Te3. The nontrivial topology of this strongly spin-orbit coupled material comes from the band inversion in the bulk. One of the key transport signatures of topological surfaces is weak antilocalization (WAL) correction to conductivity; it is associated with the topological pi Berry phase and should display a two-dimensional (2D) character. In our work, we establish the disorder level at which 2D WAL appears. The conduction at this threshold is one conduction quantum G0; it corresponds to the topological quantum channel. Finally, we summarize our key findings and discuss open questions and next steps toward the understanding of disorder-induced correlations in the spin and charge channels that can alter the emergent behaviors of the topological states.

Conduction-band valley spin splitting in single-layer H-T l2O

NASA Astrophysics Data System (ADS)

Ma, Yandong; Kou, Liangzhi; Du, Aijun; Huang, Baibiao; Dai, Ying; Heine, Thomas

2018-02-01

Despite numerous studies, coupled spin and valley physics is currently limited to two-dimensional (2D) transition-metal dichalcogenides (TMDCs). Here, we predict an exceptional 2D valleytronic material associated with the spin-valley coupling phenomena beyond 2D TMDCs—single-layer (SL) H-T l2O . It displays large valley spin splitting (VSS), significantly larger than that of 2D TMDCs, and a finite band gap, which are both critically attractive for the integration of valleytronics and spintronics. More importantly, in sharp contrast to all the experimentally confirmed 2D valleytronic materials, where the strong valence-band VSS (0.15-0.46 eV) supports the spin-valley coupling, the VSS in SL H-T l2O is pronounced in its conduction band (0.61 eV), but negligibly small in its valence band (21 meV), thus opening a way for manipulating the coupled spin and valley physics. Moreover, SL H-T l2O possesses extremely high carrier mobility, as large as 9.8 ×103c m2V-1s-1 .

The DEEP-South: Preliminary Photometric Results from the KMTNet-CTIO

NASA Astrophysics Data System (ADS)

Kim, Myung-Jin; Moon, Hong-Kyu; Choi, Young-Jun; Yim, Hong-Suh; Bae, Youngho; Roh, Dong-Goo; the DEEP-South Team

2015-08-01

The DEep Ecliptic Patrol of the Southern sky (DEEP-South) will not only conduct characterization of targeted asteroids and blind survey at the sweet spots, but also utilize data mining of small Solar System bodies in the whole KMTNet archive. As round-the-clock observation with the KMTNet is optimized for spin characterization of tumbling and slow-rotating bodies as it facilitates debiasing previously reported lightcurve observations. It is also most suitable for detection and rapid follow-up of Atens and Atiras, the “difficult objects” that are being discovered at lower solar elongations.For the sake of efficiency, we implemented an observation scheduler, SMART (Scheduler for Measuring Asteroids RoTation), designed to conduct follow-up observations in a timely manner. It automatically updates catalogs, generates ephemerides, checks priorities, prepares target lists, and sends a suite of scripts to site operators. We also developed photometric analysis software called ASAP (Asteroid Spin Analysis Package) that aids to find a set of appropriate comparison stars in an image, to derive spin parameters and reconstruct lightcurve simultaneously in a semi-automatic manner. In this presentation, we will show our preliminary results of time series analyses of a number of km-sized Potentially Hazardous Asteroids (PHAs), 5189 (1990 UQ), 12923 (1999 GK4), 53426 (1999 SL5), 136614 (1993 VA6), 385186 (1994 AW1), and 2000 OH from test runs in February and March 2015 at the KMTNet-CTIO.

Room-temperature electron spin amplifier based on Ga(In)NAs alloys.

PubMed

Puttisong, Yuttapoom; Buyanova, Irina A; Ptak, Aaron J; Tu, Charles W; Geelhaar, Lutz; Riechert, Henning; Chen, Weimin M

2013-02-06

The first experimental demonstration of a spin amplifier at room temperature is presented. An efficient, defect-enabled spin amplifier based on a non-magnetic semiconductor, Ga(In)NAs, is proposed and demonstrated, with a large spin gain (up to 2700% at zero field) for conduction electrons and a high cut-off frequency of up to 1 GHz. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin Funneling for Enhanced Spin Injection into Ferromagnets

PubMed Central

Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

2016-01-01

It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory. PMID:27374496

Spin Funneling for Enhanced Spin Injection into Ferromagnets

NASA Astrophysics Data System (ADS)

Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

2016-07-01

It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.

Temperature Ddependence of Anomalous Hall Conductivity in Rashba-type Ferromagnets

NASA Astrophysics Data System (ADS)

Sakuma, Akimasa

2018-03-01

We theoretically investigated the anomalous Hall conductivity (AHC) of Rashba-type ferromagnets at a finite temperature, taking into account spin fluctuation. We observed that the intrinsic AHC increases with increasing temperature. This can be understood from the characteristic nature of the spin chirality in the k-space, which increases with decreasing exchange splitting (EXS) when the spin-orbit interaction is much smaller than the EXS. The extrinsic part of the AHC also increases with temperature owing to the enhancement of the scattering strength of electrons due to the thermal fluctuation of the exchange field.

Free-Spinning Wind-Tunnel Tests of a Low-Wing Monoplane with Systematic Changes in Wings and Tails V : Effect of Airplane Relative Density

NASA Technical Reports Server (NTRS)

Seidman, Oscar; Neihouse, A I

1940-01-01

The reported tests are a continuation of an NACA investigation being made in the free-spinning wind tunnel to determine the effects of independent variations in load distribution, wing and tail arrangement, and control disposition on the spin characteristics of airplanes. The standard series of tests was repeated to determine the effect of airplane relative density. Tests were made at values of the relative-density parameter of 6.8, 8.4 (basic), and 12.0; and the results were analyzed. The tested variations in the relative-density parameter may be considered either as variations in the wing loading of an airplane spun at a given altitude, with the radii of gyration kept constant, or as a variation of the altitude at which the spin takes place for a given airplane. The lower values of the relative-density parameter correspond to the lower wing loadings or to the lower altitudes of the spin.

Spin Hall Effect in Doped Semiconductor Structures

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Das Sarma, S.

2006-02-01

In this Letter we present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump and skew-scattering contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show that their effects scale as σxySJ/σxySS˜(ℏ/τ)/ɛF, with τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n- and p-doped 3D and 2D GaAs structures, obtaining σs/σc˜10-3-10-4, where σs(c) is the spin Hall (charge) conductivity, which is in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)]SCIEAS0036-807510.1126/science.1105514 in n-doped 3D GaAs system.

Spin pumping and inverse spin Hall effects in heavy metal/antiferromagnet/Permalloy trilayers

NASA Astrophysics Data System (ADS)

Saglam, Hilal; Zhang, Wei; Jungfleisch, M. Benjamin; Jiang, Wanjun; Pearson, John E.; Hoffmann, Axel

Recent work shows efficient spin transfer via spin waves in insulating antiferromagnets (AFMs), suggesting that AFMs can play a more active role in the manipulation of ferromagnets. We use spin pumping and inverse spin Hall effect experiments on heavy metal (Pt and W)/AFMs/Py (Ni80Fe20) trilayer structures, to examine the possible spin transfer phenomenon in metallic AFMs, i . e . , FeMn and PdMn. Previous work has studied electronic effects of the spin transport in these materials, yielding short spin diffusion length on the order of 1 nm. However, the work did not examine whether besides diffusive spin transport by the conduction electrons, there are additional spin transport contributions from spin wave excitations. We clearly observe spin transport from the Py spin reservoir to the heavy metal layer through the sandwiched AFMs with thicknesses well above the previously measured spin diffusion lengths, indicating that spin transport by spin waves may lead to non-negligible contributions This work was supported by US DOE, OS, Materials Sciences and Engineering Division. Lithographic patterning was carried out at the CNM, which is supported by DOE, OS under Contract No. DE-AC02-06CH11357.

Analytical theory and possible detection of the ac quantum spin Hall effect

DOE PAGES

Deng, W. Y.; Ren, Y. J.; Lin, Z. X.; ...

2017-07-11

Here, we develop an analytical theory of the low-frequency ac quantum spin Hall (QSH) effect based upon the scattering matrix formalism. It is shown that the ac QSH effect can be interpreted as a bulk quantum pumping effect. When the electron spin is conserved, the integer-quantized ac spin Hall conductivity can be linked to the winding numbers of the reflection matrices in the electrodes, which also equal to the bulk spin Chern numbers of the QSH material. Furthermore, a possible experimental scheme by using ferromagnetic metals as electrodes is proposed to detect the topological ac spin current by electrical means.

Effects of symmetry and spin configuration on spin-dependent transport properties of iron-phthalocyanine-based devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Li-Ling; School of Science, Hunan University of Technology, Zhuzhou 412007; Yang, Bing-Chu, E-mail: bingchuyang@csu.edu.cn

2014-07-21

Spin-dependent transport properties of nanodevices constructed by iron-phthalocyanine (FePc) molecule sandwiched between two zigzag graphene nanoribbon electrodes are studied using first-principles quantum transport calculations. The effects of the symmetry and spin configuration of electrodes have been taken into account. It is found that large magnetoresistance, large spin polarization, dual spin-filtering, and negative differential resistance (NDR) can coexist in these devices. Our results show that 5Z-FePc system presents well conductive ability in both parallel (P) and anti-parallel (AP) configurations. For 6Z-FePc-P system, spin filtering effect and large spin polarization can be found. A dual spin filtering and NDR can also bemore » shown in 6Z-FePc-AP. Our studies indicate that the dual spin filtering effect depends on the orbitals symmetry of the energy bands and spin mismatching of the electrodes. And all the effects would open up possibilities for their applications in spin-valve, spin-filter as well as effective spin diode devices.« less

Reduced radiative conductivity of low spin FeO6-octahedra in FeCO3 at high pressure and temperature

NASA Astrophysics Data System (ADS)

Lobanov, Sergey S.; Holtgrewe, Nicholas; Goncharov, Alexander F.

2016-09-01

The ability of Earth's mantle to conduct heat by radiation is determined by optical properties of mantle phases. Optical properties of mantle minerals at high pressure are accessible through diamond anvil cell experiments, but because of the intense thermal radiation at T > 1000 K such studies are limited to lower temperatures. Accordingly, radiative thermal conductivity at mantle conditions has been evaluated with the assumption of the temperature-independent optical properties. Particularly uncertain is the temperature-dependence of optical properties of lower mantle minerals across the spin transition, as the spin state itself is a strong function of temperature. Here we use laser-heated diamond anvil cells combined with a pulsed ultra-bright supercontinuum laser probe and a synchronized time-gated detector to examine optical properties of high and low spin ferrous iron at 45-73 GPa up to 1600 K in an octahedral crystallographic unit (FeO6), one of the most abundant building blocks in the mantle. Siderite (FeCO3) is used as a model for FeO6-octahedra as it contains no ferric iron and exhibits a sharp optically apparent pressure-induced spin transition at 44 GPa, simplifying data interpretation. We find that the optical absorbance of low spin FeO6 increases with temperature due to the partially lifted Laporte selection rule. The temperature-induced low-to-high spin transition, however, results in a dramatic drop in absorbance of the FeO6 unit in siderite. The absorption edge (Fe-O charge transfer) red-shifts (∼1 cm-1/K) with increasing temperature and at T > 1600 K and P > 70 GPa becomes the dominant absorption mechanism in the visible range, suggesting its superior role in reducing the ability of mantle minerals to conduct heat by radiation. This implies that the radiative thermal conductivity of analogous FeO6-bearing minerals such as ferropericlase, the second most abundant mineral in the Earth's lower mantle, is substantially reduced approaching the core-mantle boundary conditions.

Free-Spinning Tunnel Tests of a 1/24-Scale Model of the Grumman XTB3F-1 Airplane, TED No. NACA DE304

NASA Technical Reports Server (NTRS)

Berman, Theodore

1947-01-01

In accordance with a request of the Bureau of Aeronautics, Navy Department, tests were performed in the Langley 20-foot free-spinning tunnel to determine the spin and recovery characteristics of a 1/24 scale model of the Grumman XTB3F-1 airplane. The airplane is a two-place, midwing torpedo bomber equipped with a tractor propeller and an auxiliary jet engine. The effect of control setting and movement on the erect and inverted spin and recovery characteristics of the model were determined for the normal loading. Brief tests with mass extended slightly along the fuselage were also made, however, in order to determine the effect of such a mass variation on elevator effectiveness. Tests were performed to determine the size of emergency spin-recovery tail and wing-tip parachutes required for satisfactory recovery by parachute action alone. The investigation also included emergency pilot-escape tests and tests to determine the rudder pedal and elevator stick forces necessary to move the rudder and elevator for recovery.

Spin-up simulation behaviors in a climate model to build a basement of long-time simulation

NASA Astrophysics Data System (ADS)

Lee, J.; Xue, Y.; De Sales, F.

2015-12-01

It is essential to develop start-up information when conducting long-time climate simulation. In case that the initial condition is already available from the previous simulation of same type model this does not necessary; however, if not, model needs spin-up simulation to have adjusted and balanced initial condition with the model climatology. Otherwise, a severe spin may take several years. Some of model variables such as deep soil temperature fields and temperature in ocean deep layers in initial fields would affect model's further long-time simulation due to their long residual memories. To investigate the important factor for spin-up simulation in producing an atmospheric initial condition, we had conducted two different spin-up simulations when no atmospheric condition is available from exist datasets. One simulation employed atmospheric global circulation model (AGCM), namely Global Forecast System (GFS) of National Center for Environmental Prediction (NCEP), while the other employed atmosphere-ocean coupled global circulation model (CGCM), namely Climate Forecast System (CFS) of NCEP. Both models share the atmospheric modeling part and only difference is in applying of ocean model coupling, which is conducted by Modular Ocean Model version 4 (MOM4) of Geophysical Fluid Dynamics Laboratory (GFDL) in CFS. During a decade of spin-up simulation, prescribed sea-surface temperature (SST) fields of target year is forced to the GFS daily basis, while CFS digested only first time step ocean condition and freely iterated for the rest of the period. Both models were forced by CO2 condition and solar constant given from the target year. Our analyses of spin-up simulation results indicate that freely conducted interaction between the ocean and the atmosphere is more helpful to produce the initial condition for the target year rather than produced by fixed SST forcing. Since the GFS used prescribed forcing exactly given from the target year, this result is unexpected. The detail analysis will be discussed in this presentation.

Resonant spin Hall effect in two dimensional electron gas

NASA Astrophysics Data System (ADS)

Shen, Shun-Qing

2005-03-01

Remarkable phenomena have been observed in 2DEG over last two decades, most notably, the discovery of integer and fractional quantum Hall effect. The study of spin transport provides a good opportunity to explore spin physics in two-dimensional electron gas (2DEG) with spin-orbit coupling and other interaction. It is already known that the spin-orbit coupling leads to a zero-field spin splitting, and competes with the Zeeman spin splitting if the system is subjected to a magnetic field perpendicular to the plane of 2DEG. The result can be detected as beating of the Shubnikov-de Haas oscillation. Very recently the speaker and his collaborators studied transport properties of a two-dimensional electron system with Rashba spin-orbit coupling in a perpendicular magnetic field. The spin-orbit coupling competes with the Zeeman splitting to generate additional degeneracies between different Landau levels at certain magnetic fields. It is predicted theoretically that this degeneracy, if occurring at the Fermi level, gives rise to a resonant spin Hall conductance, whose height is divergent as 1/T and whose weight is divergent as -lnT at low temperatures. The charge Hall conductance changes by 2e^2/h instead of e^2/h as the magnetic field changes through the resonant point. The speaker will address the resonance condition, symmetries in the spin-orbit coupling, the singularity of magnetic susceptibility, nonlinear electric field effect, the edge effect and the disorder effect due to impurities. This work was supported by the Research Grants Council of Hong Kong under Grant No.: HKU 7088/01P. *S. Q. Shen, M. Ma, X. C. Xie, and F. C. Zhang, Phys. Rev. Lett. 92, 256603 (2004) *S. Q. Shen, Y. J. Bao, M. Ma, X. C. Xie, and F. C. Zhang, cond-mat/0410169

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Qiang; Zhou, Liping, E-mail: zhoulp@suda.edu.cn; Cheng, Jue-Fei

Electronic structures and coherent quantum transport properties are explored for spin-crossover molecule iron-benzene Fe(Bz){sub 2} using density functional theory combined with non-equilibrium Green’s function. High- and low-spin states are investigated for two different lead-molecule junctions. It is found that the asymmetrical T-shaped contact junction in the high-spin state behaves as an efficient spin filter while it has a smaller conductivity than that in the low-spin state. Large spin Seebeck effect is also observed in asymmetrical T-shaped junction. Spin-polarized properties are absent in the symmetrical H-shaped junction. These findings strongly suggest that both the electronic and contact configurations play significant rolesmore » in molecular devices and metal-benzene complexes are promising materials for spintronics and thermo-spintronics.« less

Extraordinary Spin-Wave Thermal Conductivity in Low-Dimensional Copper Oxides

DTIC Science & Technology

2015-01-23

excitations of spin degrees of freedom. We measmed for the first time the magnon -phonon coupling parameter of a spin-ladder compound over a wide temperatme...the first time the magnon -phonon coupling parameter of a spin-ladder compound over a wide temperature range. We developed advances in the analysis of...Scientific Instruments, (10 2014): 104903. doi: 10.1063/1.4897622 Gregory T. Hohensee, R. B. Wilson, Joseph P. Feser, David G. Cahill. Magnon -phonon

Spin properties of black phosphorus and phosphorene, and their prospects for spincalorics

NASA Astrophysics Data System (ADS)

Kurpas, Marcin; Gmitra, Martin; Fabian, Jaroslav

2018-05-01

Semiconducting black phosphorus attracts a lot of attention due to its extraordinary electronic properties. Its application to spincalorics requires the knowledge about the spin and thermal properties. Here, we describe first principles calculations of the spin–orbit coupling and spin scattering in phosphorene and bulk black phosphorus. We find that the intrinsic spin–orbit coupling is of the order of 20 meV for the valence and conduction band, both for phosphorene and bulk black phosphorus, and induces spin mixing with the probability b2 ≈ 10-5 –10‑4. A strong anisotropy of b 2 is observed. The calculated Elliott–Yafet spin relaxation times reach nanoseconds for realistic values of the momentum relaxation times. The extrinsic spin–orbit coupling, enabling the D’yakonov–Perel’ spin relaxation mechanism, is studied for phosphorene by application of a transverse electric field. We observe a strong anisotropy of the extrinsic effects for the valence band and much weaker for the conduction band. It is shown, that for small enough electric fields the spin relaxation is dominated by the Elliott–Yafet mechanism, while the D’yakonov–Perel’ matters for higher electric fields. Our theoretical results stay in a good agreement with the experimental findings, and indicates that long spin lifetimes in black phosphorus and phosphorene makes them prospective materials for spincalorics and spintronics.

Spin generation by strong inhomogeneous electric fields

NASA Astrophysics Data System (ADS)

Finkler, Ilya; Engel, Hans-Andreas; Rashba, Emmanuel; Halperin, Bertrand

2007-03-01

Motivated by recent experiments [1], we propose a model with extrinsic spin-orbit interaction, where an inhomogeneous electric field E in the x-y plane can give rise, through nonlinear effects, to a spin polarization with non-zero sz, away from the sample boundaries. The field E induces a spin current js^z= z x(αjc+βE), where jc=σE is the charge current, and the two terms represent,respectively, the skew scattering and side-jump contributions. [2]. The coefficients α and β are assumed to be E- independent, but conductivity σ is field dependent. We find the spin density sz by solving the equation for spin diffusion and relaxation with a source term ∇.js^z. For sufficiently low fields, jc is linear in E, and the source term vanishes, implying that sz=0 away from the edges. However, for large fields, σ varies with E. Solving the diffusion equation in a T-shaped geometry, where the electric current propagates along the main channel, we find spin accumulation near the entrance of the side channel, similar to experimental findings [1]. Also, we present a toy model where spin accumulation away from the boundary results from a nonlinear and anisotropic conductivity. [1] V. Sih, et al, Phys. Rev. Lett. 97, 096605 (2006). [2] H.-A. Engel, B.I. Halperin, E.I.Rashba, Phys. Rev. Lett. 95, 166605 (2005).

Free-Spinning-Tunnel Tests of a 1/16-Scale Model of the Chance Vought XF5U-1 Airplane, TED No. NACA 2349

NASA Technical Reports Server (NTRS)

White, Richard P.

1947-01-01

Spin tests of a 1/16-scale model of the Chance Vought XF5U-1 airplane have been performed in the Langley 20-foot free-spinning tunnel. The effect of control position and movement upon the erect and inverted spin and recovery characteristics ae well as the effects of propellers, of stability flaps, and of various revisions to the design configuration have been determined for the normal fighter loading. The investigation also included spin recovery parachute, tumbling, and pilot-escape tests. For the original design configuration, with or without windmilling propellers, the recovery characteristics of the model were considered unsatisfactory. Increasing the maximum upward deflection of the ailavators from 45 deg to 65 deg resulted in greatly improved recovery characteristics. Dimensional revisions to the original airplane configuration, which satisfactorily improved the general spin and recovery characteristics of the model, consisted of: (1) a supplementary vertical tail 34 inches by 59 inches (full-scale) attached to a boom 80 inches aft of the trailing edge of the airplane in the plane of symmetry, (2) a large semispan undersurface spoiler placed along the airplane quarter-chord line and opened on the outboard side in a spin, or (3) two additional vertical tails 64 inches by 52 inches (full-scale) located at the tips of the ailavators. A satisfactory parachute arrangement for emergency spin recovery from demonstration spins was found to be an arrangement consisting of a 13.3-foot parachute attached by a 30-foot towline to the arresting gear mast on the airplane and opened simultaneously with an 8-foot parachute on the outboard end of the wing attached by a 3-foot towline. Tests indicated that pilot escape from a spin would be extremely hazardous unless the pilot is mechanically ejected from the cockpit. Model tumbling tests indicated that the airplane would not tumble.

Valley- and spin-switch effects in molybdenum disulfide superconducting spin valve

NASA Astrophysics Data System (ADS)

Majidi, Leyla; Asgari, Reza

2014-10-01

We propose a hole-doped molybdenum disulfide (MoS2) superconducting spin valve (F/S/F) hybrid structure in which the Andreev reflection process is suppressed for all incoming waves with a determined range of the chemical potential in ferromagnetic (F) region and the cross-conductance in the right F region depends crucially on the configuration of magnetizations in the two F regions. Using the scattering formalism, we find that the transport is mediated purely by elastic electron cotunneling (CT) process in a parallel configuration and changes to the pure crossed Andreev reflection (CAR) process in the low-energy regime, without fixing of a unique parameter, by reversing the direction of magnetization in the right F region. This suggests both valley- and spin-switch effects between the perfect elastic CT and perfect CAR processes and makes the nonlocal charge current to be fully valley- and spin-polarized inside the right F region where the type of the polarizations can be changed by reversing the magnetization direction in the right F region. We further demonstrate that the presence of the strong spin-orbit interaction λ and an additional topological term (β ) in the Hamiltonian of MoS2 result in an enhancement of the charge conductance of the CT and CAR processes and make them to be present for long lengths of the superconducting region. Besides, we find that the thermal conductance of the structure with a small length of the highly doped superconducting region exhibits linear dependence on the temperature at low temperatures, whereas it enhances exponentially at higher temperatures. In particular, we demonstrate that the thermal conductance versus the strength of the exchange field (h ) in F region displays a maximum value at h <λ , which moves towards larger exchange fields by increasing the temperature.

Coherent ultrafast spin-dynamics probed in three dimensional topological insulators

PubMed Central

Boschini, F.; Mansurova, M.; Mussler, G.; Kampmeier, J.; Grützmacher, D.; Braun, L.; Katmis, F.; Moodera, J. S.; Dallera, C.; Carpene, E.; Franz, C.; Czerner, M.; Heiliger, C.; Kampfrath, T.; Münzenberg, M.

2015-01-01

Topological insulators are candidates to open up a novel route in spin based electronics. Different to traditional ferromagnetic materials, where the carrier spin-polarization and magnetization are based on the exchange interaction, the spin properties in topological insulators are based on the coupling of spin- and orbit interaction connected to its momentum. Specific ways to control the spin-polarization with light have been demonstrated: the energy momentum landscape of the Dirac cone provides spin-momentum locking of the charge current and its spin. We investigate a spin-related signal present only during the laser excitation studying real and imaginary part of the complex Kerr angle by disentangling spin and lattice contributions. This coherent signal is only present at the time of the pump-pulses’ light field and can be described in terms of a Raman coherence time. The Raman transition involves states at the bottom edge of the conduction band. We demonstrate a coherent femtosecond control of spin-polarization for electronic states at around the Dirac cone. PMID:26510509

Generalized GW+Boltzmann Approach for the Description of Ultrafast Electron Dynamics in Topological Insulators.

PubMed

Battiato, Marco; Aguilera, Irene; Sánchez-Barriga, Jaime

2017-07-17

Quantum-phase transitions between trivial insulators and topological insulators differ from ordinary metal-insulator transitions in that they arise from the inversion of the bulk band structure due to strong spin-orbit coupling. Such topological phase transitions are unique in nature as they lead to the emergence of topological surface states which are characterized by a peculiar spin texture that is believed to play a central role in the generation and manipulation of dissipationless surface spin currents on ultrafast timescales. Here, we provide a generalized G W +Boltzmann approach for the description of ultrafast dynamics in topological insulators driven by electron-electron and electron-phonon scatterings. Taking the prototypical insulator Bi 2 Te 3 as an example, we test the robustness of our approach by comparing the theoretical prediction to results of time- and angle-resolved photoemission experiments. From this comparison, we are able to demonstrate the crucial role of the excited spin texture in the subpicosecond relaxation of transient electrons, as well as to accurately obtain the magnitude and strength of electron-electron and electron-phonon couplings. Our approach could be used as a generalized theory for three-dimensional topological insulators in the bulk-conducting transport regime, paving the way for the realization of a unified theory of ultrafast dynamics in topological materials.

CW and pulsed electrically detected magnetic resonance spectroscopy at 263 GHz/12 T on operating amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Akhtar, W.; Schnegg, A.; Veber, S.; Meier, C.; Fehr, M.; Lips, K.

2015-08-01

Here we describe a new high frequency/high field continuous wave and pulsed electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating at 263 GHz and resonance fields between 0 and 12 T. Spin dependent transport in illuminated hydrogenated amorphous silicon p-i-n solar cells at 5 K and 90 K was studied by in operando 263 GHz CW and pEDMR alongside complementary X-band CW EDMR. Benefiting from the superior resolution at 263 GHz, we were able to better resolve EDMR signals originating from spin dependent hopping and recombination processes. 5 K EDMR spectra were found to be dominated by conduction and valence band tail states involved in spin dependent hopping, with additional contributions from triplet exciton states. 90 K EDMR spectra could be assigned to spin pair recombination involving conduction band tail states and dangling bonds as the dominating spin dependent transport process, with additional contributions from valence band tail and triplet exciton states.

Optimization of the AGS superconducting helical partial snake strength.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin,F.; Huang, H.; Luccio, A.U.

2008-06-23

Two helical partial snakes, one super-conducting (a.k.a cold snake) and one normal conducting (a.k.a warm snake), have preserved the polarization of proton beam up to 65% in the Brookhaven Alternating Gradient Synchrotron (AGS) at the extraction energy from 85% at injection. In order to overcome spin resonances, stronger partial snakes would be required. However, the stronger the partial snake, the more the stable spin direction tilted producing a stronger horizontal intrinsic resonance. The balance between increasing the spin tune gap generated by the snakes and reducing the tilted stable spin direction has to be considered to maintain the polarization. Becausemore » the magnetic field of the warm snake has to be a constant, only the cold snake with a maximum 3T magnetic field can be varied to find out the optimum snake strength. This paper presents simulation results by spin tracking with different cold snake magnetic fields. Some experimental data are also analyzed.« less

Observation of spontaneous spin-splitting in the band structure of an n-type zinc-blende ferromagnetic semiconductor

PubMed Central

Anh, Le Duc; Hai, Pham Nam; Tanaka, Masaaki

2016-01-01

Large spin-splitting in the conduction band and valence band of ferromagnetic semiconductors, predicted by the influential mean-field Zener model and assumed in many spintronic device proposals, has never been observed in the mainstream p-type Mn-doped ferromagnetic semiconductors. Here, using tunnelling spectroscopy in Esaki-diode structures, we report the observation of such a large spontaneous spin-splitting energy (31.7–50 meV) in the conduction band bottom of n-type ferromagnetic semiconductor (In,Fe)As, which is surprising considering the very weak s-d exchange interaction reported in several zinc-blende type semiconductors. The mean-field Zener model also fails to explain consistently the ferromagnetism and the spin-splitting energy of (In,Fe)As, because we found that the Curie temperature values calculated using the observed spin-splitting energies are much lower than the experimental ones by a factor of 400. These results urge the need for a more sophisticated theory of ferromagnetic semiconductors. PMID:27991502

Wind-Tunnel Investigation of the Opening Characteristics, Drag, and Stability of Several Hemispherical Parachutes

NASA Technical Reports Server (NTRS)

Scher, Stanley E.; Gale, Lawrence J.

1948-01-01

An investigation has been conducted to determine the opening characteristics of several hemispherical parachutes and to study the influence of the parachute design variables on these opening characteristics. The effects of design variables on the drag and stability characteristics of the parachutes were also evaluated. The tests were made in the Langley 20-foot free-spinning tunnel and in the Langley 300 MPH 7 by 10-foot tunnel.

Current-induced switching in a magnetic insulator

NASA Astrophysics Data System (ADS)

Avci, Can Onur; Quindeau, Andy; Pai, Chi-Feng; Mann, Maxwell; Caretta, Lucas; Tang, Astera S.; Onbasli, Mehmet C.; Ross, Caroline A.; Beach, Geoffrey S. D.

2017-03-01

The spin Hall effect in heavy metals converts charge current into pure spin current, which can be injected into an adjacent ferromagnet to exert a torque. This spin-orbit torque (SOT) has been widely used to manipulate the magnetization in metallic ferromagnets. In the case of magnetic insulators (MIs), although charge currents cannot flow, spin currents can propagate, but current-induced control of the magnetization in a MI has so far remained elusive. Here we demonstrate spin-current-induced switching of a perpendicularly magnetized thulium iron garnet film driven by charge current in a Pt overlayer. We estimate a relatively large spin-mixing conductance and damping-like SOT through spin Hall magnetoresistance and harmonic Hall measurements, respectively, indicating considerable spin transparency at the Pt/MI interface. We show that spin currents injected across this interface lead to deterministic magnetization reversal at low current densities, paving the road towards ultralow-dissipation spintronic devices based on MIs.

Crossover to the anomalous quantum regime in the extrinsic spin Hall effect of graphene

NASA Astrophysics Data System (ADS)

Ferreira, Aires; Milletari, Mirco

Recent reports of spin-orbit coupling enhancement in chemically modified graphene have opened doors to studies of the spin Hall effect with massless chiral fermions. Here, we theoretically investigate the interaction and impurity density dependence of the extrinsic spin Hall effect in spin-orbit coupled graphene. We present a nonperturbative quantum diagrammatic calculation of the spin Hall response function in the strong-coupling regime that incorporates skew scattering and anomalous impurity density-independent contributions on equal footing. The spin Hall conductivity dependence on Fermi energy and electron-impurity interaction strength reveals the existence of experimentally accessible regions where anomalous quantum processes dominate. Our findings suggest that spin-orbit-coupled graphene is an ideal model system for probing the competition between semiclassical and bona fide quantum scattering mechanisms underlying the spin Hall effect. A.F. gratefully acknowledges the financial support of the Royal Society (U.K.).

Experimental Flights for Testing of a Reactor as an Expedient for the Termination of Dangerous Spins

NASA Technical Reports Server (NTRS)

Hoehler, P.; Koeppen, I. v.

1949-01-01

In the Institute for Flight Mechanics of the DVL a reactor arrangement with a maximum output of 100 kg was investigated as an expedient for the termination of dangerous spins on an airplane of the FW 56 type. reproduce the influence of a disturbance of the steady spin condition by a pitching or yawing moment. The tests were meant to reproduce the influence of a disturbance of the steady spin condition by a pitching and yawing moment.

Quantum entanglement for systems of identical bosons: II. Spin squeezing and other entanglement tests

NASA Astrophysics Data System (ADS)

Dalton, B. J.; Goold, J.; Garraway, B. M.; Reid, M. D.

2017-02-01

These two accompanying papers are concerned with entanglement for systems of identical massive bosons and the relationship to spin squeezing and other quantum correlation effects. The main focus is on two mode entanglement, but multi-mode entanglement is also considered. The bosons may be atoms or molecules as in cold quantum gases. The previous paper I dealt with the general features of quantum entanglement and its specific definition in the case of systems of identical bosons. Entanglement is a property shared between two (or more) quantum sub-systems. In defining entanglement for systems of identical massive particles, it was concluded that the single particle states or modes are the most appropriate choice for sub-systems that are distinguishable, that the general quantum states must comply both with the symmetrization principle and the super-selection rules (SSR) that forbid quantum superpositions of states with differing total particle number (global SSR compliance). Further, it was concluded that (in the separable states) quantum superpositions of sub-system states with differing sub-system particle number (local SSR compliance) also do not occur. The present paper II determines possible tests for entanglement based on the treatment of entanglement set out in paper I. Several inequalities involving variances and mean values of operators have been previously proposed as tests for entanglement between two sub-systems. These inequalities generally involve mode annihilation and creation operators and include the inequalities that define spin squeezing. In this paper, spin squeezing criteria for two mode systems are examined, and spin squeezing is also considered for principle spin operator components where the covariance matrix is diagonal. The proof, which is based on our SSR compliant approach shows that the presence of spin squeezing in any one of the spin components requires entanglement of the relevant pair of modes. A simple Bloch vector test for entanglement is also derived. Thus we show that spin squeezing becomes a rigorous test for entanglement in a system of massive bosons, when viewed as a test for entanglement between two modes. In addition, other previously proposed tests for entanglement involving spin operators are considered, including those based on the sum of the variances for two spin components. All of the tests are still valid when the present concept of entanglement based on the symmetrization and SSR criteria is applied. These tests also apply in cases of multi-mode entanglement, though with restrictions in the case of sub-systems each consisting of pairs of modes. Tests involving quantum correlation functions are also considered and for global SSR compliant states these are shown to be equivalent to tests involving spin operators. A new weak correlation test is derived for entanglement based on local SSR compliance for separable states, complementing the stronger correlation test obtained previously when this is ignored. The Bloch vector test is equivalent to one case of this weak correlation test. Quadrature squeezing for single modes is also examined but not found to yield a useful entanglement test, whereas two mode quadrature squeezing proves to be a valid entanglement test, though not as useful as the Bloch vector test. The various entanglement tests are considered for well-known entangled states, such as binomial states, relative phase eigenstates and NOON states—sometimes the new tests are satisfied while than those obtained in other papers are not. The present paper II then outlines the theory for a simple two mode interferometer showing that such an interferometer can be used to measure the mean values and covariance matrix for the spin operators involved in entanglement tests for the two mode bosonic system. The treatment is also generalized to cover multi-mode interferometry. The interferometer involves a pulsed classical field characterized by a phase variable and an area variable defined by the time integral of the field amplitude, and leads to a coupling between the two modes. For simplicity the center frequency was chosen to be resonant with the inter-mode transition frequency. Measuring the mean and variance of the population difference between the two modes for the output state of the interferometer for various choices of interferometer variables is shown to enable the mean values and covariance matrix for the spin operators for the input quantum state of the two mode system to be determined. The paper concludes with a discussion of several key experimental papers on spin squeezing.

SPIN-COSY: Spin-Manipulating Polarized Deuterons and Protons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leonova, M. A.; Chao, A. W.; Krisch, A. D.

2009-08-04

We studied spin manipulation of 1.85 GeV/c polarized deuteron beam stored in COSY obtaining a spin-flip efficiency of 97{+-}1%. We first discovered experimentally and then explained theoretically interesting behavior of the deuteron tensor polarization. We, for the first time, studied systematically spin resonance strengths induced by rf dipoles and solenoids. We found huge disagreements between the strengths measured in controlled Froissart-Stora sweeps and the theoretical values calculated using the well-known formulae. These data instigated re-examination of these formulae. We tested Chao's proposed new matrix formalism for describing the spin dynamics due to a single spin resonance, which may be themore » first fundamental improvement of the Froissart-Stora equation in that it allows analytic calculation of the beam polarization's behavior inside a resonance. Our measurements of the deuteron's polarization near and inside the resonance agreed precisely with the Chao formalism's predicted oscillations. We tested Kondratenko's proposal to overcome depolarizing resonances by ramping through them with a crossing pattern, which should force the depolarizing contributions to cancel themselves. Our first test of this idea with 2.1 GeV/c protons was not conclusive but a later test with 1.85 GeV/c deuterons demonstrated a rather substantial reduction in the depolarization compared to the tune jump at the same rate.« less

Spin-Tunnel Investigation of a 1/20-Scale Model of the Northrop F-5E Airplane

NASA Technical Reports Server (NTRS)

Scher, Stanley H.; White, William L.

1977-01-01

An investigation has been conducted in the Langley spin tunnel to determine the spin and recovery characteristics of a 1/20-scale model of the Northrop F-5E airplane. The investigation included erect and inverted spins, a range of center-of- gravity locations and moments of inertia, symmetric and asymmetric store loadings, and a determination of the parachute size required for emergency spin recovery. The effects of increased elevator trailing-edge-up deflections, of leading-edge and trailing-edge flap deflections, and of simulating the geometry of large external stores were also determined.

Data on kilometer scale production of stretchable conductive multifilaments enables knitting wearable strain sensing textiles.

PubMed

Seyedin, Shayan; Moradi, Sepehr; Singh, Charanpreet; Razal, Joselito M

2018-06-01

This data article contains analyzed data for the article "Continuous Production of Stretchable Conductive Multifilaments in Kilometer Scale Enables Facile Knitting of Wearable Strain Sensing Textiles" (Seyedin et al., 2018) [1]. Details of wet-spinning conditions to achieve scaled-up production of stretchable and conducting polyurethane/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PU/PEDOT:PSS) multifilaments are provided. The stress-strain curves for tensile and stretch-relaxation tests on the multifilament and different knitted textile structures (plain-knit, co-knit, co-knit-alternate, co-knit with conductive stitch, and plain with non-conductive stitch) are presented. It is shown that the PU/PEDOT:PSS multifilaments can also be knitted into fabrics that when worn on various body parts, such as knee, elbow, and finger, can monitor their various movements.

Asymmetric Andreev resonant state with a magnetic exchange field in spin-triplet superconducting monolayer MoS2

NASA Astrophysics Data System (ADS)

Goudarzi, H.; Khezerlou, M.; Ebadzadeh, S. F.

2018-03-01

We study the influence of magnetic exchange field (MEF) on the chirality of Andreev resonant state (ARS) appearing at the relating monolayer MoS2 ferromagnet/superconductor interface, in which the induced pairing order parameter is chiral p-wave symmetry. Transmission of low-energy Dirac-like electron (hole) quasiparticles through a ferromagnet/superconductor (F/S) interface is considered based on Dirac-Bogoliubov-de Gennes Hamiltonian and, of course, Andreev reflection process. The magnetic exchange field of a ferromagnetic section on top of ML-MDS may affect the electron (hole) excitations for spin-up and spin-down electrons, differently. We find the chirality symmetry of ARS to be conserved in the absence of MEF, whereas it is broken in the presence of MEF. Tuning the MEF enables one to control either electrical properties (such as band gap, SOC and etc.) or spin-polarized transport. The resulting normal conductance is found to be more sensitive to the magnitude of MEF and doping regime of F region. Unconventional spin-triplet p-wave symmetry features the zero-bias conductance, which strongly depends on p-doping level of F region in the relating NFS junction. A sharp conductance switching in zero is achieved in the absence of SOC.

Anisotropic in-plane spin splitting in an asymmetric (001) GaAs/AlGaAs quantum well

PubMed Central

2011-01-01

The in-plane spin splitting of conduction-band electron has been investigated in an asymmetric (001) GaAs/AlxGa1-xAs quantum well by time-resolved Kerr rotation technique under a transverse magnetic field. The distinctive anisotropy of the spin splitting was observed while the temperature is below approximately 200 K. This anisotropy emerges from the combined effect of Dresselhaus spin-orbit coupling plus asymmetric potential gradients. We also exploit the temperature dependence of spin-splitting energy. Both the anisotropy of spin splitting and the in-plane effective g-factor decrease with increasing temperature. PACS: 78.47.jm, 71.70.Ej, 75.75.+a, 72.25.Fe, PMID:21888636

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

NASA Astrophysics Data System (ADS)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

2015-05-01

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy

2015-05-07

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this usingmore » inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.« less

Nonequilibrium spintronic transport through an artificial Kondo impurity: conductance, magnetoresistance, and shot noise.

PubMed

López, Rosa; Sánchez, David

2003-03-21

We investigate the nonequilibrium transport properties of a quantum dot when spin flip processes compete with the formation of a Kondo resonance in the presence of ferromagnetic leads. Based upon the Anderson Hamiltonian in the strongly interacting limit, we predict a splitting of the differential conductance when the spin flip scattering amplitude is of the order of the Kondo temperature. We discuss how the relative orientation of the lead magnetizations strongly influences the electronic current and the shot noise in a nontrivial way. Furthermore, we find that the zero-bias tunneling magnetoresistance becomes negative with increasing spin flip scattering amplitude.

Optical Orientation of Mn2+ Ions in GaAs in Weak Longitudinal Magnetic Fields

NASA Astrophysics Data System (ADS)

Akimov, I. A.; Dzhioev, R. I.; Korenev, V. L.; Kusrayev, Yu. G.; Sapega, V. F.; Yakovlev, D. R.; Bayer, M.

2011-04-01

We report on optical orientation of Mn2+ ions in bulk GaAs subject to weak longitudinal magnetic fields (B≤100mT). A manganese spin polarization of 25% is directly evaluated by using spin-flip Raman scattering. The dynamical Mn2+ polarization occurs due to the s-d exchange interaction with optically oriented conduction band electrons. Time-resolved photoluminescence reveals a nontrivial electron spin dynamics, where the oriented Mn2+ ions tend to stabilize the electron spins.

Optical orientation of Mn2+ ions in GaAs in weak longitudinal magnetic fields.

PubMed

Akimov, I A; Dzhioev, R I; Korenev, V L; Kusrayev, Yu G; Sapega, V F; Yakovlev, D R; Bayer, M

2011-04-08

We report on optical orientation of Mn2+ ions in bulk GaAs subject to weak longitudinal magnetic fields (B≤100  mT). A manganese spin polarization of 25% is directly evaluated by using spin-flip Raman scattering. The dynamical Mn2+ polarization occurs due to the s-d exchange interaction with optically oriented conduction band electrons. Time-resolved photoluminescence reveals a nontrivial electron spin dynamics, where the oriented Mn2+ ions tend to stabilize the electron spins.

Influences of the coordinate dependent noncommutative space on charged and spin currents

NASA Astrophysics Data System (ADS)

Ren, Ya-Jie; Ma, Kai

2018-06-01

We study the charged and spin currents on a coordinate dependent noncommutative space. Starting from the noncommutative extended relativistic equation of motion, the nonrelativistic approximation is obtained by using the Foldy-Wouthuysen transformation, and then the charged and spin currents are derived by using the extended Drude model. We find that the charged current is twisted by modifying the off-diagonal elements of the Hall conductivity, however, the spin current is not affected up to leading order of the noncommutative parameter.

An experimental study of the effect of tail configuration on the spinning characteristics of general aviation aircraft. M.S. Thesis; [static wind tunnel force measurements

NASA Technical Reports Server (NTRS)

Ballin, M. G.

1982-01-01

The feasibility of using static wind tunnel tests to obtain information about spin damping characteristics of an isolated general aviation aircraft tail was investigated. A representative tail section was oriented to the tunnel free streamline at angles simulating an equilibrium spin. A full range of normally encountered spin conditions was employed. Results of parametric studies performed to determine the effect of spin damping on several tail design parameters show satisfactory agreement with NASA rotary balance tests. Wing and body interference effects are present in the NASA studies at steep spin attitudes, but agreement improves with increasing pitch angle and spin rate, suggesting that rotational flow effects are minimal. Vertical position of the horizontal stabilizer is found to be a primary parameter affecting yaw damping, and horizontal tail chordwise position induces a substantial effect on pitching moment.

Time Frequency Analysis of Spacecraft Propellant Tank Spinning Slosh

NASA Technical Reports Server (NTRS)

Green, Steven T.; Burkey, Russell C.; Sudermann, James

2010-01-01

Many spacecraft are designed to spin about an axis along the flight path as a means of stabilizing the attitude of the spacecraft via gyroscopic stiffness. Because of the assembly requirements of the spacecraft and the launch vehicle, these spacecraft often spin about an axis corresponding to a minor moment of inertia. In such a case, any perturbation of the spin axis will cause sloshing motions in the liquid propellant tanks that will eventually dissipate enough kinetic energy to cause the spin axis nutation (wobble) to grow further. This spinning slosh and resultant nutation growth is a primary design problem of spinning spacecraft and one that is not easily solved by analysis or simulation only. Testing remains the surest way to address spacecraft nutation growth. This paper describes a test method and data analysis technique that reveal the resonant frequency and damping behavior of liquid motions in a spinning tank. Slosh resonant frequency and damping characteristics are necessary inputs to any accurate numerical dynamic simulation of the spacecraft.

Strong Enhancement of the Spin Hall Effect by Spin Fluctuations near the Curie Point of FexPt1 -x Alloys

NASA Astrophysics Data System (ADS)

Ou, Yongxi; Ralph, D. C.; Buhrman, R. A.

2018-03-01

Robust spin Hall effects (SHE) have recently been observed in nonmagnetic heavy metal systems with strong spin-orbit interactions. These SHE are either attributed to an intrinsic band-structure effect or to extrinsic spin-dependent scattering from impurities, namely, side jump or skew scattering. Here we report on an extraordinarily strong spin Hall effect, attributable to spin fluctuations, in ferromagnetic FexPt1 -x alloys near their Curie point, tunable with x . This results in a dampinglike spin-orbit torque being exerted on an adjacent ferromagnetic layer that is strongly temperature dependent in this transition region, with a peak value that indicates a lower bound 0.34 ±0.02 for the peak spin Hall ratio within the FePt. We also observe a pronounced peak in the effective spin-mixing conductance of the FM /FePt interface, and determine the spin diffusion length in these FexPt1 -x alloys. These results establish new opportunities for fundamental studies of spin dynamics and transport in ferromagnetic systems with strong spin fluctuations, and a new pathway for efficiently generating strong spin currents for applications.

Equal-Spin Andreev Reflection on Junctions of Spin-Resolved Quantum Hall Bulk State and Spin-Singlet Superconductor.

PubMed

Matsuo, Sadashige; Ueda, Kento; Baba, Shoji; Kamata, Hiroshi; Tateno, Mizuki; Shabani, Javad; Palmstrøm, Christopher J; Tarucha, Seigo

2018-02-22

The recent development of superconducting spintronics has revealed the spin-triplet superconducting proximity effect from a spin-singlet superconductor into a spin-polarized normal metal. In addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity. Here we report experimental observation of Andreev reflection in junctions of spin-resolved quantum Hall (QH) states in an InAs quantum well and the spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap feature and two peaks on the outer side of the sub-gap feature in the QH plateau-transition regime increases. The observed structures can be explained by considering transport with Andreev reflection from two channels, one originating from equal-spin Andreev reflection intermediated by spin-flip processes and second arising from normal Andreev reflection. This result indicates the possibility to induce the superconducting proximity gap in the the QH bulk state, and the possibility for the development of superconducting spintronics in semiconductor devices.

Controlled enhancement of spin-current emission by three-magnon splitting.

PubMed

Kurebayashi, Hidekazu; Dzyapko, Oleksandr; Demidov, Vladislav E; Fang, Dong; Ferguson, A J; Demokritov, Sergej O

2011-07-03

Spin currents--the flow of angular momentum without the simultaneous transfer of electrical charge--play an enabling role in the field of spintronics. Unlike the charge current, the spin current is not a conservative quantity within the conduction carrier system. This is due to the presence of the spin-orbit interaction that couples the spin of the carriers to angular momentum in the lattice. This spin-lattice coupling acts also as the source of damping in magnetic materials, where the precessing magnetic moment experiences a torque towards its equilibrium orientation; the excess angular momentum in the magnetic subsystem flows into the lattice. Here we show that this flow can be reversed by the three-magnon splitting process and experimentally achieve the enhancement of the spin current emitted by the interacting spin waves. This mechanism triggers angular momentum transfer from the lattice to the magnetic subsystem and modifies the spin-current emission. The finding illustrates the importance of magnon-magnon interactions for developing spin-current based electronics.

Rashba-Zeeman-effect-induced spin filtering energy windows in a quantum wire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Xianbo, E-mail: xxb-11@hotmail.com; Nie, Wenjie; Chen, Zhaoxia

2014-06-14

We perform a numerical study on the spin-resolved transport in a quantum wire (QW) under the modulation of both Rashba spin-orbit coupling (SOC) and a perpendicular magnetic field by using the developed Usuki transfer-matrix method in combination with the Landauer-Büttiker formalism. Wide spin filtering energy windows can be achieved in this system for unpolarized spin injection. In addition, both the width of energy window and the magnitude of spin conductance within these energy windows can be tuned by varying Rashba SOC strength, which can be apprehended by analyzing the energy dispersions and spin-polarized density distributions inside the QW, respectively. Furthermore » study also demonstrates that these Rashba-SOC-controlled spin filtering energy windows show a strong robustness against disorders. These findings may not only benefit to further understand the spin-dependent transport properties of a QW in the presence of external fields but also provide a theoretical instruction to design a spin filter device.« less

Determination of the spin Hall angle in single-crystalline Pt films from spin pumping experiments

NASA Astrophysics Data System (ADS)

Keller, Sascha; Mihalceanu, Laura; Schweizer, Matthias R.; Lang, Philipp; Heinz, Björn; Geilen, Moritz; Brächer, Thomas; Pirro, Philipp; Meyer, Thomas; Conca, Andres; Karfaridis, Dimitrios; Vourlias, George; Kehagias, Thomas; Hillebrands, Burkard; Papaioannou, Evangelos Th

2018-05-01

We report on the determination of the spin Hall angle in ultra-clean, defect-reduced epitaxial Pt films. By applying vector network analyzer ferromagnetic resonance spectroscopy to a series of single crystalline Fe (12 nm) /Pt (t Pt) bilayers we determine the real part of the spin mixing conductance (4.4 ± 0.2) × 1019 m‑2 and reveal a very small spin diffusion length in the epitaxial Pt (1.1 ± 0.1) nm film. We investigate the spin pumping and ISHE in a stripe microstucture excited by a microwave coplanar waveguide antenna. By using their different angular dependencies, we distinguish between spin rectification effects and the inverse spin Hall effect. The relatively large value of the spin Hall angle (5.7 ± 1.4)% shows that ultra-clean e-beam evaporated non-magnetic materials can also have a comparable spin-to-charge current conversion efficiency as sputtered high resistivity layers.

Composition-dependent magnetic response properties of Mn1 -xFexGe alloys

NASA Astrophysics Data System (ADS)

Mankovsky, S.; Wimmer, S.; Polesya, S.; Ebert, H.

2018-01-01

The composition-dependent behavior of the Dzyaloshinskii-Moriya interaction (DMI), the spin-orbit torque (SOT), as well as anomalous and spin Hall conductivities of Mn1 -xFexGe alloys have been investigated by first-principles calculations using the relativistic multiple scattering Korringa-Kohn-Rostoker (KKR) formalism. The Dxx component of the DMI exhibits a strong dependence on the Fe concentration, changing sign at x ≈0.85 in line with previous theoretical calculations as well as with experimental results demonstrating the change of spin helicity at x ≈0.8 . A corresponding behavior with a sign change at x ≈0.5 is predicted also for the Fermi-sea contribution to the SOT, because this is closely related to the DMI. In the case of anomalous and spin Hall effects it is shown that the calculated Fermi-sea contributions are rather small and the composition-dependent behavior of these effects are determined mainly by the electronic states at the Fermi level. The spin-orbit-induced scattering mechanisms responsible for both these effects suggest a common origin of the minimum of the anomalous Hall effect and the sign change of the spin Hall effect conductivities.

Twofold spin-triplet pairing states and tunneling conductance in ferromagnet/ferromagnet/iron pnictide superconductor heterojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, X.; Tao, Y.C., E-mail: yctao88@163.com; Dong, Z.C.

By applying an extended eight-component Bogoliubov–de Gennes equation, we study theoretically the tunneling conductance in clean ferromagnet/ferromagnet/iron pnictide superconductor (FM/FM/iron-based SC) heterojunctions. Under the condition of noncollinear magnetizations, twofold novel Andreev reflections exist due to the existence of two bands in the SC, in which the incident electron and the two Andreev-reflected holes, belonging to the same spin subband, form twofold spin-triplet pairing states near the FM/iron-based SC interface. It is shown that the conversions of the conductance not only between the zero-bias peak and valley at zero energy but also between the peaks and dips at two gap energiesmore » are strongly dependent on both the interband coupling strength in the SC and the spin polarization in the FM. The qualitative differences from tunneling into a conventional s-wave SC are also presented, which may help with experimentally probing and identifying the antiphase s-wave pairing symmetry in the iron-based SC. -- Highlights: •An eight-component Bogoliubov–de Gennes (BDG) equation. •Twofold novel ARs and twofold usual ARs. •Conversions of conductance between the zero-bias peak and valley at zero energy. •Conversions of conductance between peaks and dips at two gap energies. •The importance of the interband coupling strength in the SC.« less

HOPPING CONDUCTIVITY AND MAGNETIC TRANSITIONS OF THE Cu2+ SPINS IN SINGLE-CRYSTAL La2CuO4+y

NASA Astrophysics Data System (ADS)

Thio, Tineke; Birgeneau, R. J.; Chen, C. Y.; Freer, B. S.; Gabbe, D. R.; Jenssen, H. P.; Kastner, M. A.; Picone, P. J.; Preyer, N. W.

Measurements are reported of the magnetoresistance (MR) for fields up to 23T in La2CuO4+y single crystals in which the Cu2+ spins order antiferromagnetically at TN˜240K, and in which the conductivity at low temperature is characterised by hopping between localised states. Using the MR, we map out the phase diagram of the spin flop transition, observed when the magnetic field is applied parallel to the zero-field staggered magnetisation, and that of the weak-ferromagnetic transition, observed with the field perpendicular to the CuO planes. In both transitions the antiferromagnetic propagation vector changes from the ěca direction at zero field to the ěcc direction at the highest fields. This rather subtle change of the Cu spin ordering is accompanied by a large increase in the interlayer hopping conductivity: up to a factor 2. We show that the magnetoconductance is proportional to the three-dimensional staggered moment with propagation vector in the orthorhombic ěcc direction. The origin of this unusual behaviour is an important unsolved problem.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling.

PubMed

Mawrie, Alestin; Verma, Sonu; Ghosh, Tarun Kanti

2017-10-25

We investigate the effect of k-cubic spin-orbit interaction on the electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions [Formula: see text] with [Formula: see text]. We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of k-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of a quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in the low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant.

Health Monitoring of a Rotating Disk Using a Combined Analytical-Experimental Approach

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Woike, Mark R.; Lekki, John D.; Baaklini, George Y.

2009-01-01

Rotating disks undergo rigorous mechanical loading conditions that make them subject to a variety of failure mechanisms leading to structural deformities and cracking. During operation, periodic loading fluctuations and other related factors cause fractures and hidden internal cracks that can only be detected via noninvasive types of health monitoring and/or nondestructive evaluation. These evaluations go further to inspect material discontinuities and other irregularities that have grown to become critical defects that can lead to failure. Hence, the objectives of this work is to conduct a collective analytical and experimental study to present a well-rounded structural assessment of a rotating disk by means of a health monitoring approach and to appraise the capabilities of an in-house rotor spin system. The analyses utilized the finite element method to analyze the disk with and without an induced crack at different loading levels, such as rotational speeds starting at 3000 up to 10 000 rpm. A parallel experiment was conducted to spin the disk at the desired speeds in an attempt to correlate the experimental findings with the analytical results. The testing involved conducting spin experiments which, covered the rotor in both damaged and undamaged (i.e., notched and unnotched) states. Damaged disks had artificially induced through-thickness flaws represented in the web region ranging from 2.54 to 5.08 cm (1 to 2 in.) in length. This study aims to identify defects that are greater than 1.27 cm (0.5 in.), applying available means of structural health monitoring and nondestructive evaluation, and documenting failure mechanisms experienced by the rotor system under typical turbine engine operating conditions.

Transport Studies of Quantum Magnetism: Physics and Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Minhyea

The main goal of this project was to understand novel ground states of spin systems probed by thermal and electrical transport measurements. They are well-suited to characterize the nature of low-energy excitations as unique property of the ground state. More specifically, it was aimed to study the transverse electrical conductivity in the presence of non-collinear and non-coplanar spin ordering and the effects of gauge field as well as novel spin excitations as a coherent heat transport channel in insulating quantum magnets. Most of works done during the grant period focused on these topics. As a natural extension of the project'smore » initial goals, the scope was broadened to include transport studies on the spin systems with strong spin-orbit coupling. One particular focus was an exploration of systems with strong magnetic anisotropy combined with non-trivial spin configuration. Magnetic anisotropy is directly related to implement the non-collinear spin ordering to the existing common geometry of planar devices and thus poses a significant potential. Work in this direction includes the comparison of the topological Hall signal under hydrostatic pressure and chemical doping, as well as the angular dependence dependence of the non-collinear spin ordered phase and their evolution up on temperature and field strength. Another focus was centered around the experimental identification of spin-originated heat carrying excitation in quasi two dimensional honeycomb lattice, where Kitaev type of quantum spin liquid phase is expected to emerge. In fact, when its long range magnetic order is destroyed by the applied field, we discovered anomalously large enhancement of thermal conductivity, for which proximate Kitaev excitations in field-induced spin liquid state are responsible for. This work, combined with further investigations in materials in the similar class may help establish the experimental characterization of new quantum spin liquid and their unique low energy excitation, e.g. Majorana fermions.« less

Vertigo-related cerebral blood flow changes on magnetic resonance imaging.

PubMed

Chang, Feiyan; Li, Zhongshi; Xie, Sheng; Liu, Hui; Wang, Wu

2014-11-01

A prospective study using magnetic resonance imaging on a consecutive cohort of patients with cervical vertigo. To quantitatively investigate the cerebral blood flow (CBF) changes associated with cervical vertigo by using 3-dimensional pseudocontinuous arterial spin labeling. Previous studies reported blood flow velocity reduction in posterior circulation during vertigo. However, the detailed information of CBF related to cervical vertigo has not been provided. A total of 33 patients with cervical vertigo and 14 healthy volunteers were recruited in this study. Three-dimensional pseudocontinuous arterial spin labeling was performed on each subject to evaluate the CBF before and after the cervical hyperextension-hyperflexion movement tests, which was used to induce cervical vertigo. Repeated-measures analysis of variance was conducted to assess the effect of subjects and tests. There were time effects of CBF in the territory of bilateral superior cerebellar artery, bilateral posterior cerebral artery, bilateral middle cerebral artery, and right anterior cerebral artery, but no group effect was observed. The analysis of CBF revealed a significant main effect of tests (P=0.024) and participants (P=0.038) in the dorsal pons. Cervical vertigo onset may be related to CBF reduction in the dorsal pons, which sequentially evokes the vestibular nuclei. 2.

Dynamical spin accumulation in large-spin magnetic molecules

NASA Astrophysics Data System (ADS)

Płomińska, Anna; Weymann, Ireneusz; Misiorny, Maciej

2018-01-01

The frequency-dependent transport through a nanodevice containing a large-spin magnetic molecule is studied theoretically in the Kondo regime. Specifically, the effect of magnetic anisotropy on dynamical spin accumulation is of primary interest. Such accumulation arises due to finite components of frequency-dependent conductance that are off diagonal in spin. Here, employing the Kubo formalism and the numerical renormalization group method, we demonstrate that the dynamical transport properties strongly depend on the relative orientation of spin moments in electrodes of the device, as well as on intrinsic parameters of the molecule. In particular, the effect of dynamical spin accumulation is found to be greatly affected by the type of magnetic anisotropy exhibited by the molecule, and it develops for frequencies corresponding to the Kondo temperature. For the parallel magnetic configuration of the device, the presence of dynamical spin accumulation is conditioned by the interplay of ferromagnetic-lead-induced exchange field and the Kondo correlations.

Effect of cubic Dresselhaus interaction on the longitudinal optical conductivity of a spin-orbit coupled system

NASA Astrophysics Data System (ADS)

Cruz, Elmer; López-Bastidas, Catalina; Maytorena, Jesús A.

2018-03-01

We investigate the effect of the oft-neglected cubic terms of the Dresselhaus spin-orbit coupling on the longitudinal current response of a two-dimensional electron gas with both Rashba and linear Dresselhaus interactions. For a quantum well grown in the [001] direction, the changes caused by these nonlinear-in-momentum terms on the absorption spectrum become more notable under SU(2) symmetry conditions, when the Rashba and linear Dresselhaus coupling strengths are tuned to be equal. The longitudinal optical response no longer vanishes then and shows a strong dependence on the direction of the externally applied electric field, giving a signature of the relative size of several spin-orbit contributions. This anisotropic response arises from the nonisotropic splitting of the spin states induced by the interplay of Rashba and Dresselhaus couplings. However, the presence of cubic terms introduces characteristic spectral features and can modify the overall shape of the spectra for some values of the relative sizes of the spin-orbit parameters. We compare this behavior to the case of a sample with [110] crystal orientation which, under conditions of spin-preserving symmetry, has a collinear spin-orbit vector field that leads to vanishing conductivity, even in the presence of cubic terms. In addition to the control through the driven frequency or electrical gating, such a directional aspect of the current response suggests new ways of manipulation and supports the use of interband optics as a sensitive probe of spin-orbit mechanisms in semiconductor spintronics.

Spin-scattering rates in metallic thin films measured by ferromagnetic resonance damping enhanced by spin-pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boone, C. T.; Shaw, J. M.; Nembach, H. T.

2015-06-14

We determined the spin-transport properties of Pd and Pt thin films by measuring the increase in ferromagnetic resonance damping due to spin-pumping in ferromagnetic (FM)-nonferromagnetic metal (NM) multilayers with varying NM thicknesses. The increase in damping with NM thickness depends strongly on both the spin- and charge-transport properties of the NM, as modeled by diffusion equations that include both momentum- and spin-scattering parameters. We use the analytical solution to the spin-diffusion equations to obtain spin-diffusion lengths for Pt and Pd. By measuring the dependence of conductivity on NM thickness, we correlate the charge- and spin-transport parameters, and validate the applicabilitymore » of various models for momentum-scattering and spin-scattering rates in these systems: constant, inverse-proportional (Dyakanov-Perel), and linear-proportional (Elliot-Yafet). We confirm previous reports that the spin-scattering time appears to be shorter than the momentum scattering time in Pt, and the Dyakanov-Perel-like model is the best fit to the data.« less

Ballistic Spin Field Effect Transistor Based on Silicon Nanowires

NASA Astrophysics Data System (ADS)

Osintsev, Dmitri; Sverdlov, Viktor; Stanojevic, Zlatan; Selberherr, Siegfried

2011-03-01

We investigate the properties of ballistic spin field-effect transistors build on silicon nanowires. An accurate description of the conduction band based on the k . p} model is necessary in thin and narrow silicon nanostructures. The subband effective mass and subband splitting dependence on the nanowire dimensions is analyzed and used in the transport calculations. The spin transistor is formed by sandwiching the nanowire between two ferromagnetic metallic contacts. Delta-function barriers at the interfaces between the contacts and the silicon channel are introduced. The major contribution to the electric field-dependent spin-orbit interaction in confined silicon systems is due to the interface-induced inversion asymmetry which is of the Dresselhaus type. We study the current and conductance through the system for the contacts being in parallel and anti-parallel configurations. Differences between the [100] and [110] orientated structures are investigated in details. This work is supported by the European Research Council through the grant #247056 MOSILSPIN.

Transition metal doped (X = V, Cr) CdS monolayer: A DFT study

NASA Astrophysics Data System (ADS)

Deb, Jyotirmoy; Paul, Debolina; Sarkar, Utpal

2018-05-01

In this work based on density functional theory approach with generalized gradient approximation we have investigated the effect doping and co-doping of transition metal atoms in CdS monolayer sheet. On the basis cohesive energy, we have determined the stability of all the transition metal doped systems. CdS monolayer is of nonmagnetic character but the insertion of transition metal atoms introduces the spontaneous spin polarization which results in a significant value of magnetic moment. The band structure analysis reveals that three different types of conducting nature such as spin-select-half-semiconductor, half metallic and metallic nature with total spin polarization has also been observed. The versatile conducting nature of the transition metal doped CdS monolayer predicts the possibility of using these systems in spintronics mainly as a spin filter and also to form metal-semiconductor interface etc. at nanoscale level.

Nonreciprocal dispersion of spin waves in ferromagnetic thin films covered with a finite-conductivity metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mruczkiewicz, M.; Krawczyk, M.

2014-03-21

We study the effect of one-side metallization of a uniform ferromagnetic thin film on its spin-wave dispersion relation in the Damon–Eshbach geometry. Due to the finite conductivity of the metallic cover layer on the ferromagnetic film, the spin-wave dispersion relation may be nonreciprocal only in a limited wave-vector range. We provide an approximate analytical solution for the spin-wave frequency, discuss its validity, and compare it with numerical results. The dispersion is analyzed systematically by varying the parameters of the ferromagnetic film, the metal cover layer and the value of the external magnetic field. The conclusions drawn from this analysis allowmore » us to define a structure based on a 30 nm thick CoFeB film with an experimentally accessible nonreciprocal dispersion relation in a relatively wide wave-vector range.« less

Theoretical study of optical conductivity of graphene with magnetic and nonmagnetic adatoms

NASA Astrophysics Data System (ADS)

Majidi, Muhammad Aziz; Siregar, Syahril; Rusydi, Andrivo

2014-11-01

We present a theoretical study of the optical conductivity of graphene with magnetic and nonmagnetic adatoms. First, by introducing an alternating potential in a pure graphene, we demonstrate a gap formation in the density of states and the corresponding optical conductivity. We highlight the distinction between such a gap formation and the so-called Pauli blocking effect. Next, we apply this idea to graphene with adatoms by introducing magnetic interactions between the carrier spins and the spins of the adatoms. Exploring various possible ground-state spin configurations of the adatoms, we find that the antiferromagnetic configuration yields the lowest total electronic energy and is the only configuration that forms a gap. Furthermore, we analyze four different circumstances leading to similar gaplike structures and propose a means to interpret the magneticity and the possible orderings of the adatoms on graphene solely from the optical conductivity data. We apply this analysis to the recently reported experimental data of oxygenated graphene.

Spin related transport in two pyrene and Triphenylene graphene nanodisks using NEGF method

NASA Astrophysics Data System (ADS)

Taghilou, Hamed; Fathi, Davood

2018-07-01

The present study is conducted to evaluate the spin polarization in two pyrene and Triphenylene graphene nanoflakes. All calculations are performed using non-equilibrium Green's function (NEGF) method. The obtained results show that, graphene has no magnetic property and using Pyrene nanoflake results in a better spin switching at extreme magnetic fields. On the contrary, when applying magnetized electrodes, depending on the direction of magnetization of the two electrodes (either parallel or anti-parallel), different spin polarization diagrams are obtained. In this situation, it is observed that, in the case of electrodes magnetization in Triphenylene nanoflake a better spin switching is reached.

Nutation control during precession of a spin-stabilized spacecraft

NASA Technical Reports Server (NTRS)

1974-01-01

Precession maneuver control laws for single-spin spacecraft are investigated so that nutation is concurrently controlled. Analysis has led to the development of two types of control laws employing precession modulation for concurrent nutation control. Results were verified through digital simulation of a Synchronous Meteorological Satellite (SMS) configuration. An addition research effort was undertaken to investigate the cause and elimination of nutation anomalies in dual-spin spacecraft. A literature search was conducted and a dual-spin configuration was simulated to verify that nutational anomalies are not predicted by the existing nonlinear model. No conclusions were drawn as to the cause of the observed nutational anomalies in dual-spin spacecraft.

Room-temperature coupling between electrical current and nuclear spins in OLEDs

NASA Astrophysics Data System (ADS)

Malissa, H.; Kavand, M.; Waters, D. P.; van Schooten, K. J.; Burn, P. L.; Vardeny, Z. V.; Saam, B.; Lupton, J. M.; Boehme, C.

2014-09-01

The effects of external magnetic fields on the electrical conductivity of organic semiconductors have been attributed to hyperfine coupling of the spins of the charge carriers and hydrogen nuclei. We studied this coupling directly by implementation of pulsed electrically detected nuclear magnetic resonance spectroscopy in organic light-emitting diodes (OLEDs). The data revealed a fingerprint of the isotope (protium or deuterium) involved in the coherent spin precession observed in spin-echo envelope modulation. Furthermore, resonant control of the electric current by nuclear spin orientation was achieved with radiofrequency pulses in a double-resonance scheme, implying current control on energy scales one-millionth the magnitude of the thermal energy.

Manipulation of spin transfer torque using light

NASA Astrophysics Data System (ADS)

Rontani, Massimo; Vendelbjerg, Karsten; Sham, Lu

We show that the spin transfer torque induced by a spin-polarized current on a nanomagnet as the current flows through a semiconductor-nanomagnet-semiconductor junction is externally controlled by shining the junction off-resonantly with a strong laser beam. The excitonic coherence driven by the laser dresses the virtual electron-hole pairs coupling conduction and valence bands and inducing an evanescent state in the proximity of the nanomagnet. The Fano-like quantum interference between this localized state and the continuum spectrum is different in the two spin channels and hence it dramatically alters the spin transport, leading to the coherent control of the spin transfer torque. This work is supported by EU-FP7 Marie Curie Initial Training Network INDEX.

All-electric spin modulator based on a two-dimensional topological insulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Xianbo; Ai, Guoping; Liu, Ying

2016-01-18

We propose and investigate a spin modulator device consisting of two ferromagnetic leads connected by a two-dimensional topological insulator as the channel material. It exploits the unique features of the topological spin-helical edge states, such that the injected carriers with a non-collinear spin-polarization direction would travel through both edges and show interference effect. The conductance of the device can be controlled in a simple and all-electric manner by a side-gate voltage, which effectively rotates the spin-polarization of the carrier. At low voltages, the rotation angle is linear in the gate voltage, and the device can function as a good spin-polarizationmore » rotator by replacing the drain electrode with a non-magnetic material.« less

Non-Abelian S =1 chiral spin liquid on the kagome lattice

NASA Astrophysics Data System (ADS)

Liu, Zheng-Xin; Tu, Hong-Hao; Wu, Ying-Hai; He, Rong-Qiang; Liu, Xiong-Jun; Zhou, Yi; Ng, Tai-Kai

2018-05-01

We study S =1 spin liquid states on the kagome lattice constructed by Gutzwiller-projected px+i py superconductors. We show that the obtained spin liquids are either non-Abelian or Abelian topological phases, depending on the topology of the fermionic mean-field state. By calculating the modular matrices S and T , we confirm that projected topological superconductors are non-Abelian chiral spin liquid (NACSL). The chiral central charge and the spin Hall conductance we obtained agree very well with the S O (3) 1 (or, equivalently, S U (2) 2 ) field-theory predictions. We propose a local Hamiltonian which may stabilize the NACSL. From a variational study, we observe a topological phase transition from the NACSL to the Z2 Abelian spin liquid.

A Novel Attitude Determination Algorithm for Spinning Spacecraft

NASA Technical Reports Server (NTRS)

Bar-Itzhack, Itzhack Y.; Harman, Richard R.

2007-01-01

This paper presents a single frame algorithm for the spin-axis orientation-determination of spinning spacecraft that encounters no ambiguity problems, as well as a simple Kalman filter for continuously estimating the full attitude of a spinning spacecraft. The later algorithm is comprised of two low order decoupled Kalman filters; one estimates the spin axis orientation, and the other estimates the spin rate and the spin (phase) angle. The filters are ambiguity free and do not rely on the spacecraft dynamics. They were successfully tested using data obtained from one of the ST5 satellites.

A T-shaped double quantum dot system as a Fano interferometer: Interplay of coherence and correlation upon spin currents

NASA Astrophysics Data System (ADS)

Fernandes, I. L.; Cabrera, G. G.

2018-05-01

Based on Keldysh non-equilibrium Green function method, we have investigated spin current production in a hybrid T-shaped device, consisting of a central quantum dot connected to the leads and a side dot which only couples to the central dot. The topology of this structure allows for quantum interference of the different paths that go across the device, yielding Fano resonances in the spin dependent transport properties. Correlation effects are taken into account at the central dot and handled within a mean field approximation. Its interplay with the Fano effect is analyzed in the strong coupling regime. Non-vanishing spin currents are only obtained when the leads are ferromagnetic, the current being strongly dependent on the relative orientation of the lead polarizations. We calculate the conductance (spin and charge) by numerically differentiating the current, and a rich structure is obtained as a manifestation of quantum coherence and correlation effects. Increase of the Coulomb interaction produces localization of states at the side dot, largely suppressing Fano resonances. The interaction is also responsible for the negative values of the spin conductance in some regions of the voltage near resonances, effect which is the spin analog of the Esaki tunnel diode. We also analyze control of the currents via gate voltages applied to the dots, possibility which is interesting for practical operations.

Liquid Motion in a Rotating Tank Experiment (LME)

NASA Technical Reports Server (NTRS)

Deffenbaugh, D. M.; Dodge, F. T.; Green, S. T.

1998-01-01

The Liquid Motion Experiment (LME), which flew on STS 84 in May 1997, was an investigation of liquid motions in spinning, nutating tanks. LME was designed to quantify the effects of such liquid motions on the stability of spinning spacecraft, which are known to be adversely affected by the energy dissipated by the liquid motions. The LME hardware was essentially a spin table which could be forced to nutate at specified frequencies at a constant cone angle, independently of the spin rate. Cylindrical and spherical test tanks, partially filled with liquids of different viscosities, were located at the periphery of the spin table to simulate a spacecraft with off-axis propellant tanks; one set of tanks contained generic propellant management devices (PMDs). The primary quantitative data from the flight tests were the liquid-induced torques exerted on the tanks about radial and tangential axes through the center of the tank. Visual recordings of the liquid oscillations also provided qualitative information. The flight program incorporated two types of tests: sine sweep tests, in which the spin rate was held constant and the nutation frequency varied over a wide range; and sine dwell test, in which both the spin rate and the nutation frequency were held constant. The sine sweep tests were meant to investigate all the prominent liquid resonant oscillations and the damping of the resonances, and the sine dwell tests were meant to quantify the viscous energy dissipation rate of the liquid oscillations for steady state conditions. The LME flight data were compared to analytical results obtained from two companion IR&D programs at Southwest Research Institute. The comparisons indicated that the models predicted the observed liquid resonances, damping, and energy dissipation rates for many test conditions but not for all. It was concluded that improved models and CFD simulations are needed to resolve the differences. This work is ongoing under a current IR&D program.

Spin- and Valley-Dependent Electronic Structure in Silicene Under Periodic Potentials

NASA Astrophysics Data System (ADS)

Lu, Wei-Tao; Li, Yun-Fang; Tian, Hong-Yu

2018-03-01

We study the spin- and valley-dependent energy band and transport property of silicene under a periodic potential, where both spin and valley degeneracies are lifted. It is found that the Dirac point, miniband, band gap, anisotropic velocity, and conductance strongly depend on the spin and valley indices. The extra Dirac points appear as the voltage potential increases, the critical values of which are different for electron with different spins and valleys. Interestingly, the velocity is greatly suppressed due to the electric field and exchange field, other than the gapless graphene. It is possible to achieve an excellent collimation effect for a specific spin near a specific valley. The spin- and valley-dependent band structure can be used to adjust the transport, and perfect transmissions are observed at Dirac points. Therefore, a remarkable spin and valley polarization is achieved which can be switched effectively by the structural parameters. Importantly, the spin and valley polarizations are greatly enhanced by the disorder of the periodic potential.

Electrical control of a confined electron spin in a silicene quantum dot

NASA Astrophysics Data System (ADS)

Szafran, Bartłomiej; Mreńca-Kolasińska, Alina; Rzeszotarski, Bartłomiej; Żebrowski, Dariusz

2018-04-01

We study spin control for an electron confined in a flake of silicene. We find that the lowest-energy conduction-band levels are split by the diagonal intrinsic spin-orbit coupling into Kramers doublets with a definite projection of the spin on the orbital magnetic moment. We study the spin control by AC electric fields using the nondiagonal Rashba component of the spin-orbit interactions with the time-dependent atomistic tight-binding approach. The Rashba interactions in AC electric fields produce Rabi spin-flip times of the order of a nanosecond. These times can be reduced to tens of picoseconds provided that the vertical electric field is tuned to an avoided crossing opened by the Rashba spin-orbit interaction. We demonstrate that the speedup of the spin transitions is possible due to the intervalley coupling induced by the armchair edge of the flake. The study is confronted with the results for circular quantum dots decoupled from the edge with well defined angular momentum and valley index.

Supplementary Investigation in the Free-Spinning Tunnel of a 1/24-Scale Model of the Grumman F9F-6 Airplane Incorporating only Flaperons for Lateral Control, TED No. NACA DE 364

NASA Technical Reports Server (NTRS)

Klinar, Walter J.; Lee, Henry A.

1954-01-01

A supplementary investigation was conducted in the Langley 20-foot free-spinning tunnel on a 1/24-scale model of the Grumman F9F-6 airplane. The primary purpose of the investigation was to reevaluate the spin-recovery characteristics of the airplane in view of the fact that the ailerons had been eliminated from the flaperon-aileron lateral control system of the airplane. A spin-tunnel investigation on a model of the earlier version of the F9F-6 airplane had indicated that use of ailerons with the spin (stick right in a right spin) was essential to insure recovery. The results indicate that with.ailerons eliminated, it may be difficult to obtain an erect developed spin but if a fully developed spin is obtained on the airplane, recovery therefrom may be difficult or impossible. Flaperon deflection should have little effect on spins or recoveries.

Velocity barrier-controlled of spin-valley polarized transport in monolayer WSe2 junction

NASA Astrophysics Data System (ADS)

Qiu, Xuejun; Lv, Qiang; Cao, Zhenzhou

2018-05-01

In this work, we have theoretically investigated the influence of velocity barrier on the spin-valley polarized transport in monolayer (ML) WSe2 junction with a large spin-orbit coupling (SOC). Both the spin-valley resolved transmission probabilities and conductance are strong dependent on the velocity barrier, as the velocity barrier decreases to 0.06, a spin-valley polarization of exceeding 90% is observed, which is distinct from the ML MoS2 owing to incommensurable SOC. In addition, the spin-valley polarization is further increased above 95% in a ML WSe2 superlattice, in particular, it's found many extraordinary velocity barrier-dependent transport gaps for multiple barrier due to evanescent tunneling. Our results may open an avenue for the velocity barrier-controlled high-efficiency spin and valley polarizations in ML WSe2-based electronic devices.

Study of blended conductive graft copolymer with graphite oxide thin films deposited using spin coating method for gas sensing and photovoltaic applications

NASA Astrophysics Data System (ADS)

KałuŻyński, P.; Procek, M.; Stolarczyk, Agnieszka; Maciak, E.

2017-08-01

This work presents an investigation on conductive graft comb copolymer like SILPEG CH9 with carbon materials like graphite oxide or reduced graphite oxide. Morphology and optical properties like sample roughness, graphite oxide particles distribution, optical transmittance were measured of obtained thin films deposited on glass substrate using spin coating method. The study showed that obtained thin films are repeatable, convenient to process, and their parameters can be easy changed by the spin rate regulation during the deposition. Given results shows the possibility of using such polymer blend in the implementation of organic photovoltaic cells and different optoelectronics applications.

Similarity between the superconductivity in the graphene with the spin transport in the two-dimensional antiferromagnet in the honeycomb lattice

NASA Astrophysics Data System (ADS)

Lima, L. S.

2017-02-01

We have used the Dirac's massless quasi-particles together with the Kubo's formula to study the spin transport by electrons in the graphene monolayer. We have calculated the electric conductivity and verified the behavior of the AC and DC currents of this system, that is a relativistic electron plasma. Our results show that the AC conductivity tends to infinity in the limit ω → 0 , similar to the behavior obtained for the spin transport in the two-dimensional frustrated antiferromagnet in the honeycomb lattice. We have made a diagrammatic expansion for the Green's function and we have not gotten significative change in the results.

The anisotropic tunneling behavior of spin transport in graphene-based magnetic tunneling junction

NASA Astrophysics Data System (ADS)

Pan, Mengchun; Li, Peisen; Qiu, Weicheng; Zhao, Jianqiang; Peng, Junping; Hu, Jiafei; Hu, Jinghua; Tian, Wugang; Hu, Yueguo; Chen, Dixiang; Wu, Xuezhong; Xu, Zhongjie; Yuan, Xuefeng

2018-05-01

Due to the theoretical prediction of large tunneling magnetoresistance (TMR), graphene-based magnetic tunneling junction (MTJ) has become an important branch of high-performance spintronics device. In this paper, the non-collinear spin filtering and transport properties of MTJ with the Ni/tri-layer graphene/Ni structure were studied in detail by utilizing the non-equilibrium Green's formalism combined with spin polarized density functional theory. The band structure of Ni-C bonding interface shows that Ni-C atomic hybridization facilitates the electronic structure consistency of graphene and nickel, which results in a perfect spin filtering effect for tri-layer graphene-based MTJ. Furthermore, our theoretical results show that the value of tunneling resistance changes with the relative magnetization angle of two ferromagnetic layers, displaying the anisotropic tunneling behavior of graphene-based MTJ. This originates from the resonant conduction states which are strongly adjusted by the relative magnetization angles. In addition, the perfect spin filtering effect is demonstrated by fitting the anisotropic conductance with the Julliere's model. Our work may serve as guidance for researches and applications of graphene-based spintronics device.

Unusual negative permeability of single magnetic nanowire excited by the spin transfer torque effect

NASA Astrophysics Data System (ADS)

Han, Mangui; Zhou, Wu

2018-07-01

Due to the effect of spin transfer torque, negative imaginary parts of permeability (μ″ < 0) are reported in a ferromagnetic nanowire. It is found that negative μ″ values are resulted from the interaction of spin polarized conduction electrons with the spatially non-uniform distributed magnetic moments at both ends of nanowires. The results are well explained from the effect of spin transfer torque on the precession of magnetization under the excitation of both the pulsed magnetic field and static electric field.

Spin-Driven Emergent Antiferromagnetism and Metal-Insulator Transition in Nanoscale p-Si

NASA Astrophysics Data System (ADS)

Lou, Paul C.; Kumar, Sandeep

2018-04-01

The entanglement of the charge, spin and orbital degrees of freedom can give rise to emergent behavior especially in thin films, surfaces and interfaces. Often, materials that exhibit those properties require large spin orbit coupling. We hypothesize that the emergent behavior can also occur due to spin, electron and phonon interactions in widely studied simple materials such as Si. That is, large intrinsic spin-orbit coupling is not an essential requirement for emergent behavior. The central hypothesis is that when one of the specimen dimensions is of the same order (or smaller) as the spin diffusion length, then non-equilibrium spin accumulation due to spin injection or spin-Hall effect (SHE) will lead to emergent phase transformations in the non-ferromagnetic semiconductors. In this experimental work, we report spin mediated emergent antiferromagnetism and metal insulator transition in a Pd (1 nm)/Ni81Fe19 (25 nm)/MgO (1 nm)/p-Si (~400 nm) thin film specimen. The spin-Hall effect in p-Si, observed through Rashba spin-orbit coupling mediated spin-Hall magnetoresistance behavior, is proposed to cause the spin accumulation and resulting emergent behavior. The phase transition is discovered from the diverging behavior in longitudinal third harmonic voltage, which is related to the thermal conductivity and heat capacity.

Controllable spin polarization and spin filtering in a zigzag silicene nanoribbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farokhnezhad, Mohsen, E-mail: Mohsen-farokhnezhad@physics.iust.ac.ir; Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir; Pournaghavi, Nezhat

2015-05-07

Using non-equilibrium Green's function, we study the spin-dependent electron transport properties in a zigzag silicene nanoribbon. To produce and control spin polarization, it is assumed that two ferromagnetic strips are deposited on the both edges of the silicene nanoribbon and an electric field is perpendicularly applied to the nanoribbon plane. The spin polarization is studied for both parallel and anti-parallel configurations of exchange magnetic fields induced by the ferromagnetic strips. We find that complete spin polarization can take place in the presence of perpendicular electric field for anti-parallel configuration and the nanoribbon can work as a perfect spin filter. Themore » spin direction of transmitted electrons can be easily changed from up to down and vice versa by reversing the electric field direction. For parallel configuration, perfect spin filtering can occur even in the absence of electric field. In this case, the spin direction can be changed by changing the electron energy. Finally, we investigate the effects of nonmagnetic Anderson disorder on spin dependent conductance and find that the perfect spin filtering properties of nanoribbon are destroyed by strong disorder, but the nanoribbon retains these properties in the presence of weak disorder.« less

Ab initio study of gold-doped zigzag graphene nanoribbons

NASA Astrophysics Data System (ADS)

Srivastava, Pankaj; Dhar, Subhra; Jaiswal, Neeraj K.

2014-12-01

The electronic transport properties of zigzag graphene nanoribbons (ZGNRs) through covalent functionalization of gold (Au) atoms is investigated by using non-equilibrium Green's function combined with density functional theory. It is revealed that the electronic properties of Au-doped ZGNRs vary significantly due to spin and its non-inclusion. We find that the DOS profiles of Au-adsorbed ZGNR due to spin reveal very less number of states available for conduction, whereas non-inclusion of spin results in higher DOS across the Fermi level. Edge Au-doped ribbons exhibit stable structure and are energetically more favorable than the center Au-doped ZGNRs. Though the chemical interaction at the ZGNR-Au interface modifies the Fermi level, Au-adsorbed ZGNR reveals semimetallic properties. A prominent qualitative change of the I-V curve from linear to nonlinear is observed as the Au atom shifts from center toward the edges of the ribbon. Number of peaks present near the Fermi level ensures conductance channels available for charge transport in case of Au-center-substituted ZGNR. We predict semimetallic nature of the Au-adsorbed ZGNR with a high DOS peak distributed over a narrow energy region at the Fermi level and fewer conductance channels. Our calculations for the magnetic properties predict that Au functionalization leads to semiconducting nature with different band gaps for spin up and spin down. The outcomes are compared with the experimental and theoretical results available for other materials.

A flight investigation of the effect of mass distribution and control setting on the spinning of the XN2Y-1 airplane

NASA Technical Reports Server (NTRS)

Scudder, N F

1935-01-01

The investigation of the effect of mass distribution on the spinning of airplanes initiated with tests on the NY-1 airplane has been continued by tests on another airplane in order to increase the scope of the information and to observe particularly the behavior of an airplane that shows considerable change in sideslip angle for its various conditions of spinning. The XN2Y-1 naval training biplane was used for the present tests in which changes of ballast along the longitudinal and lateral axes and changes of aileron, stabilizer, and elevator settings were made. The effects of these changes on the steady spin were measured in flight.

A test for correction made to spin systematics for coupled band in doubly-odd nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Vinod, E-mail: vinod2.k2@gmail.com

2015-12-15

Systematic Spin Assignments were generally made by using the argument that the energy of levels is a function of neutron number. In the present systematics, the excitation energy of the levels incorporated the effect of nuclear deformation and signature splitting. The nuclear deformation changes toward the mid-shell, therefore a smooth variation in the excitation energy of the levels is observed towards the mid-shell, that intended to make systematics as a function of neutron number towards the mid-shell. Another term “signature splitting” that push the energy of levels for odd- and even-spin sequences up and down, caused the different energy variationmore » pattern for odd- and even-spin sequences. The corrections made in the spin systematics were tested for the known spins of various isotopic chain. In addition, the inconsistency in spin assignments made by the spin systematics and other methods of the configuration πh{sub 11/2} ⊗ νh{sub 11/2} band belonging to {sup 112,114,116}Cs, {sup 126}Pr, and {sup 138}Pr, as an example, was resolved by the correctionmade in the present spin systematics.« less

Quantum spin liquids and the metal-insulator transition in doped semiconductors.

PubMed

Potter, Andrew C; Barkeshli, Maissam; McGreevy, John; Senthil, T

2012-08-17

We describe a new possible route to the metal-insulator transition in doped semiconductors such as Si:P or Si:B. We explore the possibility that the loss of metallic transport occurs through Mott localization of electrons into a quantum spin liquid state with diffusive charge neutral "spinon" excitations. Such a quantum spin liquid state can appear as an intermediate phase between the metal and the Anderson-Mott insulator. An immediate testable consequence is the presence of metallic thermal conductivity at low temperature in the electrical insulator near the metal-insulator transition. Further, we show that though the transition is second order, the zero temperature residual electrical conductivity will jump as the transition is approached from the metallic side. However, the electrical conductivity will have a nonmonotonic temperature dependence that may complicate the extrapolation to zero temperature. Signatures in other experiments and some comparisons with existing data are made.

A comment on the thermal conductivity of (U,Pu)O 2 and (U,Th)O 2 by molecular dynamics with adjustment for phonon-spin scattering

DOE PAGES

Cooper, Michael William D.; Liu, Xiang -Yang; Stanek, Christopher Richard; ...

2016-07-15

In this study, a new approach for adjusting molecular dynamics results on UO 2 thermal conductivity to include phonon-spin scattering has been used to improve calculations on U x Pu 1–x O 2 and U xTh 1xO 2. We demonstrate that by including spin scattering a strong asymmetry as a function of uranium actinide fraction, x, is obtained. Greater degradation is shown for U xTh 1–xO 2 than U xPu 1-xO 2. Minimum thermal conductivities are predicted at U 0.97Pu 0.03O 2 and U 0.58Th 0.42O 2, although the degradation in U xPu 1–xO 2 is negligible relative to puremore » UO 2.« less

Incipient- and Developed-Spin and Recovery Characteristics of a Modern High-Speed Fighter Design with Low Aspect Ratio as Determined from Dynamic-Model Tests

NASA Technical Reports Server (NTRS)

Lee, Henry A.; Libbey, Charles E.

1961-01-01

Incipient- and developed-spin and recovery characteristics of a modern high-speed fighter design with low aspect ratio have been investigated by means of dynamic model tests. A 1/7-scale radio-controlled model was tested by means of drop tests from a helicopter. Several 1/25-scale models with various configuration changes were tested in the Langley 20-foot free-spinning tunnel. Model results indicated that generally it would be difficult to obtain a developed spin with a corresponding airplane and that either the airplane would recover of its own accord from any poststall motion or the poststall motion could be readily terminated by proper control technique. On occasion, however, the results indicated that if a post-stall motion were allowed to continue, a fully developed spin might be obtainable from which recovery could range from rapid to no recovery at all, even when optimum control technique was used. Satisfactory recoveries could be obtained with a proper-size tail parachute or strake, application of pitching-, rolling-, or yawing-moment rockets, or sufficient differential deflection of the horizontal tail.

Stability of Mixed Preparations Consisting of Commercial Moisturizing Creams with an Ointment Base Investigated by Magnetic Resonance Imaging.

PubMed

Onuki, Yoshinori; Funatani, Chiaki; Yamamoto, Yoshihisa; Fukami, Toshiro; Koide, Tatsuo; Hayashi, Yoshihiro; Takayama, Kozo

2017-01-01

A moisturizing cream mixed with a steroid ointment is frequently prescribed to patients suffering from atopic dermatitis. However, there is a concern that the mixing operation causes destabilization. The present study was performed to investigate the stability of such preparations closely using magnetic resonance imaging (MRI). As sample preparations, five commercial moisturizing creams that are popular in Japan were mixed with an ointment base, a white petrolatum, at a volume ratio of 1 : 1. The mixed preparations were stored at 60°C to accelerate the destabilization processes. Subsequently, the phase separations induced by the storage test were monitored using MRI. Using advanced MR technologies including spin-spin relaxation time (T 2 ) mapping and MR spectroscopy, we successfully characterized the phase-separation behavior of the test samples. For most samples, phase separations developed by the bleeding of liquid oil components. From a sample consisting of an oil-in-water-type cream, Urepearl Cream 10%, a distinct phase-separation mode was observed, which was initiated by the aqueous component separating from the bottom part of the sample. The resultant phase separation was the most distinct among the test samples. To investigate the phase separation quantitatively and objectively, we conducted a histogram analysis on the acquired T 2 maps. The water-in-oil type creams were found to be much more stable after mixing with ointment base than those of oil-in-water type creams. This finding strongly supported the validity of the mixing operation traditionally conducted in pharmacies.

ECN-22193

NASA Image and Video Library

1982-12-22

A close-up photo of the spin chute mounted on the rear fuselage of the AFTI F-16, a safety device designed to prevent the loss of aircraft in spin conditions. Under some circumstances, pilots cannot recover from spins using normal controls. It these instances, the spin chute is deployed, thus "breaking" the spin and enabling the pilot to recover. The spin chute is held in a metal cylinder attached to the AFTI F-16 by four tubes, a structure strong enough to withstand the shock of the spin chute opening. Unlike the air probe in the last photo, spin chutes are not standard equipment on research or prototype aircraft but are commonly attached expressly for actual spin tests.

A general explanation on the correlation of dark matter halo spin with the large-scale environment

NASA Astrophysics Data System (ADS)

Wang, Peng; Kang, Xi

2017-06-01

Both simulations and observations have found that the spin of halo/galaxy is correlated with the large-scale environment, and particularly the spin of halo flips in filament. A consistent picture of halo spin evolution in different environments is still lacked. Using N-body simulation, we find that halo spin with its environment evolves continuously from sheet to cluster, and the flip of halo spin happens both in filament and nodes. The flip in filament can be explained by halo formation time and migrating time when its environment changes from sheet to filament. For low-mass haloes, they form first in sheets and migrate into filaments later, so their mass and spin growth inside filament are lower, and the original spin is still parallel to filament. For high-mass haloes, they migrate into filaments first, and most of their mass and spin growth are obtained in filaments, so the resulted spin is perpendicular to filament. Our results well explain the overall evolution of cosmic web in the cold dark matter model and can be tested using high-redshift data. The scenario can also be tested against alternative models of dark matter, such as warm/hot dark matter, where the structure formation will proceed in a different way.

Spin pumping and inverse Rashba-Edelstein effect in NiFe/Ag/Bi and NiFe/Ag/Sb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wei, E-mail: zwei@anl.gov; Jungfleisch, Matthias B.; Jiang, Wanjun

2015-05-07

The Rashba effect is an interaction between the spin and the momentum of electrons induced by the spin-orbit coupling in surface or interface states. We measured the inverse Rashba-Edelstein effect via spin pumping in Ag/Bi and Ag/Sb interfaces. The spin current is injected from the ferromagnetic resonance of a NiFe layer towards the Rashba interfaces, where it is further converted into a charge current. Using spin pumping theory, we quantify the conversion parameter of spin to charge current to be 0.11 ± 0.02 nm for Ag/Bi and a factor of ten smaller for Ag/Sb. The relative strength of the effect is in agreementmore » with spectroscopic measurements and first principles calculations. We also vary the interlayer materials to study the voltage output in relation to the change of the effective spin mixing conductance. The spin pumping experiment offers a straight-forward approach of using spin current as an efficient probe for detecting interface Rashba splitting.« less

Spin-to-charge conversion for hot photoexcited electrons in germanium

NASA Astrophysics Data System (ADS)

Zucchetti, C.; Bottegoni, F.; Isella, G.; Finazzi, M.; Rortais, F.; Vergnaud, C.; Widiez, J.; Jamet, M.; Ciccacci, F.

2018-03-01

We investigate the spin-to-charge conversion in highly doped germanium as a function of the kinetic energy of the carriers. Spin-polarized electrons are optically generated in the Ge conduction band, and their kinetic energy is varied by changing the photon energy in the 0.7-2.2 eV range. The spin detection scheme relies on spin-dependent scattering inside Ge, which yields an inverse spin-Hall electromotive force. The detected signal shows a sign inversion for h ν ≈1 eV which can be related to an interplay between the spin relaxation of high-energy electrons photoexcited from the heavy-hole and light-hole bands and that of low-energy electrons promoted from the split-off band. The inferred spin-Hall angle increases by about 3 orders of magnitude within the analyzed photon energy range. Since, for increasing photon energies, the phonon contribution to spin scattering exceeds that of impurities, our result indicates that the spin-to-charge conversion mediated by phonons is much more efficient than the one mediated by impurities.

Enhanced spin Hall ratios by Al and Hf impurities in Pt thin films

NASA Astrophysics Data System (ADS)

Nguyen, Minh-Hai; Zhao, Mengnan; Ralph, Daniel C.; Buhrman, Robert A.

The spin Hall effect (SHE) in Pt has been reported to be strong and hence promising for spintronic applications. In the intrinsic SHE mechanism, which has been shown to be dominant in Pt, the spin Hall conductivity σSH is constant, dependent only on the band structure of the spin Hall material. The spin Hall ratio θSH =σSH . ρ , on the other hand, should be proportional to the electrical resistivity ρ of the spin Hall layer. This suggests the possibility of enhancing the spin Hall ratio by introducing additional diffusive scattering to increase the electrical resistivity of the spin Hall layer. Our previous work has shown that this could be done by increasing the surface scattering by growing thinner Pt films in contact with higher resistivity materials such as Ta. In this talk, we discuss another approach: to introduce impurities of metals with negligible spin orbit torque into the Pt film. Our PtAl and PtHf alloy samples exhibit strong enhancement of the spin Hall torque efficiency with impurity concentration due to increased electrical resistivity. Supported in part by Samsung Electronics.

Measurements of the Double-Spin Asymmetry A 1 on Helium-3: Toward a Precise Measurement of the Neutron A 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parno, Diana Seymour

2011-04-01

The spin structure of protons and neutrons has been an open question for nearly twenty-five years, after surprising experimental results disproved the simple model in which valence quarks were responsible for nearly 100% of the nucleon spin. Diverse theoretical approaches have been brought to bear on the problem, but a shortage of precise data - especially on neutron spin structure - has prevented a thorough understanding. Experiment E06-014, conducted in Hall A of Jefferson Laboratory in 2009, presented an opportunity to add to the world data set for the neutron in the poorly covered valence-quark region. Jefferson Laboratory's highly polarizedmore » electron beam, combined with Hall A's facilities for a high-density, highly polarized 3He target, allowed a high-luminosity double-polarized experiment, while the large acceptance of the BigBite spectrometer gave coverage over a wide kinematic range: 0.15 < x < 0.95. In this work, we present the analysis of a portion of the E06-014 data, measured with an incident beam energy of 4.74 GeV and spanning 1.5 < Q 2 < 5.5 (GeV/c) 2. From these data, we extract the longitudinal asymmetry in virtual photon-nucleon scattering, A 1, on the 3He nucleus. Combined with the remaining E06-014 data, this will form the basis of a measurement of the neutron asymmetry A η 1 that will extend the kinematic range of the data available to test models of spin-dependent parton distributions in the nucleon.« less

Spin order in FeV2O4 determined by single crystal Mössbauer spectroscopy in applied magnetic field

NASA Astrophysics Data System (ADS)

Nakamura, Shin; Kobayashi, Yasuhiro; Kitao, Shinji; Seto, Makoto

2018-05-01

In order to clarify the spin order of FeV2O4, 57Fe Mössbauer spectroscopy has been conducted by using a single crystal specimen. A measurement in applied magnetic field has been also conducted. By applying a slight compression in the sample plane, almost single domain state was achieved in the low temperature phases. The spectra consist of Fe2+ spectra ( 85%) and Fe2.5+ spectra ( 15%), corresponding to the A- and B-site Fe ions, respectively. The B-site spectrum well represents the local structure and the magnetic structure of V3+ ion on the B-site. Notable changes in the Mössbauer parameters are recognized at 140, 110, and 65 K, where the successive phase transitions take place. The feature well represents the orbital and spin order. In the orthorhombic phase below 110 K, Fe2+ and V3+ spins form a collinear ferrimagnetic order along the a-axis. Below 65 K in the low temperature tetragonal phase, however, both spins incline from the c-axis to form a canted ferrimagnetic structure. The canting angles are about 17° and 52° at 4.2 K for Fe2+ and V3+ spins, respectively.

Nonequilibrium Kondo effect by the equilibrium numerical renormalization group method: The hybrid Anderson model subject to a finite spin bias

NASA Astrophysics Data System (ADS)

Fang, Tie-Feng; Guo, Ai-Min; Sun, Qing-Feng

2018-06-01

We investigate Kondo correlations in a quantum dot with normal and superconducting electrodes, where a spin bias voltage is applied across the device and the local interaction U is either attractive or repulsive. When the spin current is blockaded in the large-gap regime, this nonequilibrium strongly correlated problem maps into an equilibrium model solvable by the numerical renormalization group method. The Kondo spectra with characteristic splitting due to the nonequilibrium spin accumulation are thus obtained at high precision. It is shown that while the bias-induced decoherence of the spin Kondo effect is partially compensated by the superconductivity, the charge Kondo effect is enhanced out of equilibrium and undergoes an additional splitting by the superconducting proximity effect, yielding four Kondo peaks in the local spectral density. In the charge Kondo regime, we find a universal scaling of charge conductance in this hybrid device under different spin biases. The universal conductance as a function of the coupling to the superconducting lead is peaked at and hence directly measures the Kondo temperature. Our results are of direct relevance to recent experiments realizing a negative-U charge Kondo effect in hybrid oxide quantum dots [Nat. Commun. 8, 395 (2017), 10.1038/s41467-017-00495-7].

Transmission through a potential barrier in Luttinger liquids with a topological spin gap

NASA Astrophysics Data System (ADS)

Kainaris, Nikolaos; Carr, Sam T.; Mirlin, Alexander D.

2018-03-01

We study theoretically the transport of the one-dimensional single-channel interacting electron gas through a strong potential barrier in the parameter regime where the spin sector of the low-energy theory is gapped by interaction (Luther-Emery liquid). There are two distinct phases of this nature, of which one is of particular interest as it exhibits nontrivial interaction-induced topological properties. Focusing on this phase and using bosonization and an expansion in the tunneling strength we calculate the conductance through the barrier as a function of the temperature as well as the local density of states (LDOS) at the barrier. Our main result concerns the mechanism of bound-state-mediated tunneling. The characteristic feature of the topological phase is the emergence of protected zero-energy bound states with fractional spin located at the impurity position. By flipping this fractional spin, single electrons can tunnel across the impurity even though the bulk spectrum for spin excitations is gapped. This results in a finite LDOS below the bulk gap and in a nonmonotonic behavior of the conductance. The system represents an important physical example of an interacting symmetry-protected topological phase, which combines features of a topological spin insulator and a topological charge metal, in which the topology can be probed by measuring transport properties.

Enhancement of the anti-damping spin torque efficacy of platinum by interface modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Minh-Hai; Pai, Chi-Feng; Nguyen, Kayla X.

2015-06-01

We report a strong enhancement of the efficacy of the spin Hall effect (SHE) of Pt for exerting anti-damping spin torque on an adjacent ferromagnetic layer by the insertion of ≈0.5 nm layer of Hf between a Pt film and a thin, ≤2 nm, Fe{sub 60}Co{sub 20}B{sub 20} ferromagnetic layer. This enhancement is quantified by measurement of the switching current density when the ferromagnetic layer is the free electrode in a magnetic tunnel junction. The results are explained as the suppression of spin pumping through a substantial decrease in the effective spin-mixing conductance of the interface, but without a concomitant reduction ofmore » the ferromagnet's absorption of the SHE generated spin current.« less

Summary of flight tests to determine the spin and controllability characteristics of a remotely piloted, large-scale (3/8) fighter airplane model

NASA Technical Reports Server (NTRS)

Holleman, E. C.

1976-01-01

An unpowered, large, dynamically scaled airplane model was test flown by remote pilot to investigate the stability and controllability of the configuration at high angles of attack. The configuration proved to be departure/spin resistant; however, spins were obtained by using techniques developed on a flight support simulator. Spin modes at high and medium high angles of attack were identified, and recovery techniques were investigated. A flight support simulation of the airplane model mechanized with low speed wind tunnel data over an angle of attack range of + or - 90 deg. and an angle of sideslip range of + or - 40 deg. provided insight into the effects of altitude, stability, aerodynamic damping, and the operation of the augmented flight control system on spins. Aerodynamic derivatives determined from flight maneuvers were used to correlate model controllability with two proposed departure/spin design criteria.

Periastron shift for a spinning test particle around naked singularities

NASA Astrophysics Data System (ADS)

Mukherjee, Sajal

2018-06-01

In the present article, we investigate the Periastron precession for a spinning test particle moving in nearly circular orbits around naked singularities. We consider two well-known solutions that can produce a spacetime with naked singularity—(a) first, the Reissner-Nordström metric, which is a static charged solution with spherical symmetry, and (b) second, the stationary, axisymmetric Kerr metric. For simplicity, we only consider the motion confined on the equatorial plane in both these cases and solve exactly the Mathisson-Papapetrou equations. In addition, we analytically compute the Periastron precession within the framework of linear spin approximation. The inclusion of the spin parameter modifies the results with nonspinning particles and also reflects some interesting properties of the naked geometries. Furthermore, we carried out a numerical approach without any assumptions to probe the large order spin values. The implication of the spin-curvature coupling in connection with the naked geometries is also discussed.

Multifunctional Composites with Applications to Energy Performance and Efficiency

DTIC Science & Technology

2011-08-01

surface for comparing the effects of processing. Parylene/ Teflon AF adhesion was measured using a modified tape test. Samples were razor cut (3-6...lines, 2 mm spacing ) at 0 and 90 degrees to the tape -pull direction. SEMicro CHT tape (synthetic rubber adhesive, 12 to 25 mm wide x 75 mm long) was...surface, a thin layer of Teflon AF (~200 nm) is spin- coated for hydrophobicity. Small drops of ionic liquids in contact with a conductive probe are

Evaluating the effect of spinning systems on thermal comfort properties of modal fabrics

NASA Astrophysics Data System (ADS)

Seçil Aydın, İ.; Kertmen, M.; Marmarali, A.

2017-10-01

In recent years the importance of clothing comfort became one of the most important feature of the fabrics. The aim of this study is to characterize thermal comfort properties of single jersey fabrics were knitted using 100% modal yarns which were spun in various types of yarn spinning methods such as ring spinning, compact spinning, rotor spinning and airjet spinning. Thermal comfort properties like air permeability, thermal resistance, thermal absorptivity and water vapour permeability of fabrics were tested. The results indicate that compact spinning technology will be appropriate for the summer climate casual wear.

Dynamics and stability of spinning flexible space tether systems

NASA Astrophysics Data System (ADS)

Tyc, George

This dissertation focuses on a detailed dynamical investigation of a previously unexplored tether configuration that involves a spinning two-body tethered system with flexible appendages on each end-body where the spin axis is nominally aligned along the tether. The original motivation for this work came after the flight of the first Canadian sub-orbital tether mission OEDIPUS-A in 1989 which employed this spinning tethered configuration. To everyone's surprise, one of the end-bodies was observed to exhibit a rapid divergence of its nutation angle. It was clear after this flight that there were some fundamental mechanisms associated with the interaction between the tether and the end-body that were not fully understood at that time. Hence, a Tether Dynamics Experiment (TDE) was formed and became a formal part of the scientific agenda for the follow-on mission OEDIPUS-C which flew in 1995. This dissertation describes the work that was conducted as part of the TDE and involves: theoretical investigations into the dynamics of this spinning tethered flexible body system; ground testing to validate the models and establish the tether properties; application of the models to develop a stabilization approach for OEDIPUS-C, and comparisons between theory and flight data from both OEDIPUS-A and OEDIPUS-C. Nonlinear equations of motion are developed for a spinning tethered system where the tether could be either spinning with the end-bodies or attached to small de-spun platforms on the end-bodies. Since the tether used for the OEDIPUS missions is not a string, as is often assumed, but rather a wire that has some bending stiffness, albeit small, the tether bending was also taken into account in the formulation. Two sets of ground tests are described that were used to validate the stability conditions and gain confidence in the mathematical models. One set involved hanging a body by a tether and spinning at different speeds to investigate the end-body stability. The other set used a tethered spinning end-body suspended on a set of gimbals and had a means to measure the end-body attitude in real-time. The mathematical models were then applied to investigate suitable stabilization approaches for OEDIPUS-C. In general, very good agreement was found between the theory and both the ground experiments and flight data. One of the surprising results from this work is the significance of the tether root bending effects. It is shown that it is this subtle effect that caused the rapid divergence in one of the end-bodies in the OEDIPUS-A mission which was unstable. For OEDIPUS-C, the situation was rectified by adding the booms to ensure "short term" stability and also by not spinning as rapidly. The OEDIPUS-C was very successful as all systems worked as planned and hence a superb set of flight dynamics data was collected. (Abstract shortened by UMI.)

The structural, electronic and magnetic properties of CoS2 under pressure

NASA Astrophysics Data System (ADS)

Feng, Zhong-Ying; Yang, Yan; Zhang, Jian-Min

2018-05-01

The structural, electronic and magnetic properties of CoS2 under pressure have been investigated by the first-principles calculations. The lattice constant and volume decrease with increasing pressure. The CoS2 is stable and behaves a brittle characteristic under the pressures of 0-5 GPa. The CoS2 presents metallic characteristic under the pressures of 1-5 GPa although it is nearly half-metal (HM) under the pressure of 0 GPa. The lowest conduction bands for spin-up and spin-down channels shift towards higher and lower energy region, respectively, with the pressure increasing from 0 to 5 GPa. In spin-up channel the conduction band minimum (CBM) is mainly contributed by Co-3d(eg) orbitals at R point but the valence band maximum (VBM) is contributed by Co-3d(t2g) orbitals near M point. While in spin-down channel the CBM is contributed by S-3p orbitals at Γ point but the VBM is contributed by Co-3d(t2g) orbitals near X point. The CoS2 is still suitable to be used in the supercapacitor under the environmental pressures of 0-5 GPa due to the high conductivity.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling.

PubMed

Mawrie, Alestin; Verma, Sonu; Ghosh, Tarun Kanti

2017-09-01

We investigate effect of <i>k</i>-cubic spin-orbit interaction on electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions θ = (2n+1)π/3 with n=1,2,3. We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of <i>k</i>-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant. © 2017 IOP Publishing Ltd.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling

NASA Astrophysics Data System (ADS)

Mawrie, Alestin; Verma, Sonu; Kanti Ghosh, Tarun

2017-11-01

We investigate the effect of k-cubic spin-orbit interaction on the electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions θ^\\prime = (2n+1)π/3 with n=1, 2, 3 . We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of k-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of a quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in the low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant.

Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO4

NASA Astrophysics Data System (ADS)

Ma, Zhen; Wang, Jinghui; Dong, Zhao-Yang; Zhang, Jun; Li, Shichao; Zheng, Shu-Han; Yu, Yunjie; Wang, Wei; Che, Liqiang; Ran, Kejing; Bao, Song; Cai, Zhengwei; Čermák, P.; Schneidewind, A.; Yano, S.; Gardner, J. S.; Lu, Xin; Yu, Shun-Li; Liu, Jun-Ming; Li, Shiyan; Li, Jian-Xin; Wen, Jinsheng

2018-02-01

We report on comprehensive results identifying the ground state of a triangular-lattice structured YbZnGaO4 as a spin glass, including no long-range magnetic order, prominent broad excitation continua, and the absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature ac susceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K, indicating the spin-glass ground state. We suggest this conclusion holds also for its sister compound YbMgGaO4 , which is confirmed by the observation of spin freezing at low temperatures. We consider disorder and frustration to be the main driving force for the spin-glass phase.

Entanglement manipulation by a magnetic pulse in Gd3N@C80 endohedral metallofullerenes on a Cu(0 0 1) surface

NASA Astrophysics Data System (ADS)

Farberovich, Oleg V.; Gritzaenko, Vyacheslav S.

2018-04-01

In this paper we present the results of theoretical calculation of entanglement within a spin structure of Gd3N@C80 under the influence of rectangular impulses. Research is conducted using general spin Hamiltonian within SSNQ (spin system of N-qubits). The calculations of entanglement with various impulses are performed using the time-dependent Landau-Lifshitz-Gilbert equation with spin-spin correlation function. We show that long rectangular impulse (t = 850 ps) can be used for sustaining entanglement value. This allows us to offer a new algorithm which can be used to solve the problem of decoherence in the logical scheme optimization.

Robustness of topological Hall effect of nontrivial spin textures

NASA Astrophysics Data System (ADS)

Jalil, Mansoor B. A.; Tan, Seng Ghee

2014-05-01

We analyze the topological Hall conductivity (THC) of topologically nontrivial spin textures like magnetic vortices and skyrmions and investigate its possible application in the readback for magnetic memory based on those spin textures. Under adiabatic conditions, such spin textures would theoretically yield quantized THC values, which are related to topological invariants such as the winding number and polarity, and as such are insensitive to fluctuations and smooth deformations. However, in a practical setting, the finite size of spin texture elements and the influence of edges may cause them to deviate from their ideal configurations. We calculate the degree of robustness of the THC output in practical magnetic memories in the presence of edge and finite size effects.

Cobalt spin states and hyperfine interactions in LaCoO3 investigated by LDA+U calculations

NASA Astrophysics Data System (ADS)

Hsu, Han; Blaha, Peter; Wentzcovitch, Renata M.; Leighton, C.

2010-09-01

With a series of local-density approximation plus Hubbard U calculations, we have demonstrated that for lanthanum cobaltite (LaCoO3) , the electric field gradient at the cobalt nucleus can be used as a fingerprint to identify the spin state of the cobalt ion. Therefore, in principle, the spin state of the cobalt ion can be unambiguously determined from nuclear magnetic resonance spectra. Our calculations also suggest that a crossover from the low-spin to intermediate-spin state in the temperature range of 0-90 K is unlikely, based on the half-metallic band structure associated with isolated IS Co ions, which is incompatible with the measured conductivity.

Chemical potential of quasi-equilibrium magnon gas driven by pure spin current.

PubMed

Demidov, V E; Urazhdin, S; Divinskiy, B; Bessonov, V D; Rinkevich, A B; Ustinov, V V; Demokritov, S O

2017-11-17

Pure spin currents provide the possibility to control the magnetization state of conducting and insulating magnetic materials. They allow one to increase or reduce the density of magnons, and achieve coherent dynamic states of magnetization reminiscent of the Bose-Einstein condensation. However, until now there was no direct evidence that the state of the magnon gas subjected to spin current can be treated thermodynamically. Here, we show experimentally that the spin current generated by the spin-Hall effect drives the magnon gas into a quasi-equilibrium state that can be described by the Bose-Einstein statistics. The magnon population function is characterized either by an increased effective chemical potential or by a reduced effective temperature, depending on the spin current polarization. In the former case, the chemical potential can closely approach, at large driving currents, the lowest-energy magnon state, indicating the possibility of spin current-driven Bose-Einstein condensation.

Mass-number and excitation-energy dependence of the spin cutoff parameter

DOE PAGES

Grimes, S. M.; Voinov, A. V.; Massey, T. N.

2016-07-12

Here, the spin cutoff parameter determining the nuclear level density spin distribution ρ(J) is defined through the spin projection as < J 2 z > 1/2 or equivalently for spherical nuclei, (< J(J+1) >/3) 1/2. It is needed to divide the total level density into levels as a function of J. To obtain the total level density at the neutron binding energy from the s-wave resonance count, the spin cutoff parameter is also needed. The spin cutoff parameter has been calculated as a function of excitation energy and mass with a super-conducting Hamiltonian. Calculations have been compared with two commonlymore » used semiempirical formulas. A need for further measurements is also observed. Some complications for deformed nuclei are discussed. The quality of spin cut off parameter data derived from isomeric ratio measurement is examined.« less

Evidence for a gapped spin-liquid ground state in a kagome Heisenberg antiferromagnet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Mingxuan; Imai, Takahashi; Han, Tian -Heng

2015-11-06

Here, the kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu 3(OH) 6Cl 2], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χkagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction.more » Combined with the magnetic field dependence of χ kagome that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.« less

Spin-filtering and giant magnetoresistance effects in polyacetylene-based molecular devices

NASA Astrophysics Data System (ADS)

Chen, Tong; Yan, Shenlang; Xu, Liang; Liu, Desheng; Li, Quan; Wang, Lingling; Long, Mengqiu

2017-07-01

Using the non-equilibrium Green's function formalism in combination with density functional theory, we performed ab initio calculations of spin-dependent electron transport in molecular devices consisting of a polyacetylene (CnHn+1) chain vertically attached to a carbon chain sandwiched between two semi-infinite zigzag-edged graphene nanoribbon electrodes. Spin-charge transport in the device could be modulated to different magnetic configurations by an external magnetic field. The results showed that single spin conduction could be obtained. Specifically, the proposed CnHn+1 devices exhibited several interesting effects, including (dual) spin filtering, spin negative differential resistance, odd-even oscillation, and magnetoresistance (MR). Marked spin polarization with a filtering efficiency of up to 100% over a large bias range was found, and the highest MR ratio for the CnHn+1 junctions reached 4.6 × 104. In addition, the physical mechanisms for these phenomena were also revealed.

Spin Testing of Superalloy Disks With Dual Grain Structure

NASA Technical Reports Server (NTRS)

Hefferman, Tab M.

2006-01-01

This 24-month program was a joint effort between Allison Advanced Development Company (AADC), General Electric Aircraft (GEAE), and NASA Glenn Research Center (GRC). AADC led the disk and spin hardware design and analysis utilizing existing Rolls-Royce turbine disk forging tooling. Testing focused on spin testing four disks: two supplied by GEAE and two by AADC. The two AADC disks were made of Alloy 10, and each was subjected to a different heat treat process: one producing dual microstructure with coarse grain size at the rim and fine grain size at the bore and the other produced single fine grain structure throughout. The purpose of the spin tests was to provide data for evaluation of the impact of dual grain structure on disk overspeed integrity (yielding) and rotor burst criteria. The program culminated with analysis and correlation of the data to current rotor overspeed criteria and advanced criteria required for dual structure disks.

Effect of stabilizer location upon pitching and yawing moments in spins as shown by tests with the spinning balance

NASA Technical Reports Server (NTRS)

Bamber, M J; Zimmerman, C H

1933-01-01

Tests were made with the spinning balance in a 5-foot wind tunnel to study the effect of stabilizer location upon the pitching and yawing moments given by the tail surfaces in spinning attitudes. The tests revealed that the horizontal surfaces, when in a normal location, seriously reduced the effectiveness of the fin and rudder, particularly at angles of attack of 50 degrees or more. The tests also revealed that a more forward or more rearward location gave no consistent or decided improvement; that a lower location greatly increased the shielding so that the yawing moment from the combination was in general less than that given by the bare fuselage; and that a higher location decreased the shielding and gave a favorable interference effect, particularly at the high angles of attack. Additional results regarding the stabilizer and the elevator are given.

Morphology effects on spin-dependent transport and recombination in polyfluorene thin films

NASA Astrophysics Data System (ADS)

Miller, Richards; van Schooten, K. J.; Malissa, H.; Joshi, G.; Jamali, S.; Lupton, J. M.; Boehme, C.

2016-12-01

We have studied the role of spin-dependent processes on conductivity in polyfluorene (PFO) thin films by preforming continuous wave (cw) electrically detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K and room temperature using microwave frequencies between about 1 GHz and 20 GHz, as well as pulsed EDMR at the X band (10 GHz). Variable frequency EDMR allows us to establish the role of spin-orbit coupling in spin-dependent processes whereas pulsed EDMR allows for the observation of coherent spin motion effects. We used PFO for this study in order to allow for the investigation of the effects of microscopic morphological ordering since this material can adopt two distinct intrachain morphologies: an amorphous (glassy) phase, in which monomer units are twisted with respect to each other, and an ordered (β) phase, where all monomers lie within one plane. In thin films of organic light-emitting diodes, the appearance of a particular phase can be controlled by deposition parameters and solvent vapor annealing, and is verified by electroluminescence spectroscopy. Under bipolar charge-carrier injection conditions, we conducted multifrequency cw EDMR, electrically detected Rabi spin-beat experiments, and Hahn echo and inversion-recovery measurements. Coherent echo spectroscopy reveals electrically detected electron-spin-echo envelope modulation due to the coupling of the carrier spins to nearby nuclear spins. Our results demonstrate that, while conformational disorder can influence the observed EDMR signals, including the sign of the current changes on resonance as well as the magnitudes of local hyperfine fields and charge-carrier spin-orbit interactions, it does not qualitatively affect the nature of spin-dependent transitions in this material. In both morphologies, we observe the presence of at least two different spin-dependent recombination processes. At room temperature and 10 K, polaron-pair recombination through weakly spin-spin coupled intermediate charge-carrier pair states is dominant, while at low temperatures, additional signatures of spin-dependent charge transport through the interaction of polarons with triplet excitons are seen in the half-field resonance of a triplet spin-1 species. This additional contribution arises since triplet lifetimes are increased at lower temperatures. We tentatively conclude that spectral broadening induced by hyperfine coupling is slightly weaker in the more ordered β-phase than in the glassy phase since protons are more evenly spaced, whereas broadening effects due to spin-orbit coupling, which impacts the distribution of g -factors, appear to be somewhat more significant in the β-phase.

Effects of several factors on theoretical predictions of airplane spin characteristics. [dynamic models

NASA Technical Reports Server (NTRS)

Bihrle, W., Jr.; Barnhart, B.

1974-01-01

The influence of different mathematical and aerodynamic models on computed spin motion was investigated along with the importance of some of the aerodynamic and nonaerodynamic quantities defined in these models. An analytical technique was used which included the aerodynamic forces and moments acting on a spinning aircraft due to steady rotational flow and the contribution of the rotary derivatives to the oscillatory component of the total angular rates. It was shown that (1) during experimental-analytical correlation studies, the flight-recorded control time histories must be faithfully duplicated since the spinning motion can be sensitive to a small change in the application of the spin entry controls; (2) an error in the assumed inertias, yawing moments at high angle of attack, and initial spin entry bank angle do not influence the developed spin significantly; (3) damping in pitch derivatives and the center of gravity location play a role in the spinning motion; and (4) the experimental spin investigations conducted in a constant atmospheric density environment duplicate the Froude number only at the initial full-scale spin altitude (since the full-scale airplane at high altitudes experiences large density changes during the spin.)

Anomalies in the thermomechanical behavior of Ba0.5Sr0.5Co0.8Fe0.2O3-δ ceramic oxygen conductive membranes at intermediate temperatures

NASA Astrophysics Data System (ADS)

Huang, B. X.; Malzbender, J.; Steinbrech, R. W.; Grychtol, P.; Schneider, C. M.; Singheiser, L.

2009-08-01

The thermomechanical properties of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) were measured using ring-on-ring tests and depth-sensitive microindentation. The cubic BSCF material exhibits an anomaly in mechanical properties between 200 and 400 °C. The observed anomaly is attributed to the transition of Co3+ spin states which is experimentally confirmed by susceptibility measurements. Furthermore, slip lines were observed around the impression when indentation tests were carried out above 260 °C.

Spin-State Transition in La1-xSrxCoO3 Single Crystals

NASA Astrophysics Data System (ADS)

Bhardwaj, S.; Prabhakaran, D.; Awasthi, A. M.

2011-07-01

We present a study of the thermal conductivity (κ), specific heat (Cp) and Raman spectra of La1-xSrxCoO3 (x = 0,0.1) single crystals. Both the specimens have low thermal conductivity and board Raman peaks, arising from strong scattering of phonons by lattice disorder, produced by (and doping-enhanced) spin-states admixture of the Co3+ ions. The thermal conductivity anomalously deviates from ˜1/T behaviour at high (room) temperatures, expected of an insulator. High-temperature specific heat reveals large decrease in the metal-insulator (M-I) transition temperature with Sr-doping.

Detecting Kondo Entanglement by Electron Conductance

NASA Astrophysics Data System (ADS)

Yoo, Gwangsu; Lee, S.-S. B.; Sim, H.-S.

2018-04-01

Quantum entanglement between an impurity spin and electrons nearby is a key property of the single-channel Kondo effects. We show that the entanglement can be detected by measuring electron conductance through a double quantum dot in an orbital Kondo regime. We derive a relation between the entanglement and the conductance, when the SU(2) spin symmetry of the regime is weakly broken. The relation reflects the universal form of many-body states near the Kondo fixed point. Using it, the spatial distribution of the entanglement—hence, the Kondo cloud—can be detected, with breaking of the symmetry spatially nonuniformly by electrical means.

Spin injection and inverse Edelstein effect in the surface states of topological Kondo insulator SmB6

PubMed Central

Song, Qi; Mi, Jian; Zhao, Dan; Su, Tang; Yuan, Wei; Xing, Wenyu; Chen, Yangyang; Wang, Tianyu; Wu, Tao; Chen, Xian Hui; Xie, X. C.; Zhang, Chi; Shi, Jing; Han, Wei

2016-01-01

There has been considerable interest in exploiting the spin degrees of freedom of electrons for potential information storage and computing technologies. Topological insulators (TIs), a class of quantum materials, have special gapless edge/surface states, where the spin polarization of the Dirac fermions is locked to the momentum direction. This spin–momentum locking property gives rise to very interesting spin-dependent physical phenomena such as the Edelstein and inverse Edelstein effects. However, the spin injection in pure surface states of TI is very challenging because of the coexistence of the highly conducting bulk states. Here, we experimentally demonstrate the spin injection and observe the inverse Edelstein effect in the surface states of a topological Kondo insulator, SmB6. At low temperatures when only surface carriers are present, a clear spin signal is observed. Furthermore, the magnetic field angle dependence of the spin signal is consistent with spin–momentum locking property of surface states of SmB6. PMID:27834378

Spin injection and inverse Edelstein effect in the surface states of topological Kondo insulator SmB 6

DOE PAGES

Song, Qi; Mi, Jian; Zhao, Dan; ...

2016-11-11

There has been considerable interest in exploiting the spin degrees of freedom of electrons for potential information storage and computing technologies. Topological insulators (TIs), a class of quantum materials, have special gapless edge/surface states, where the spin polarization of the Dirac fermions is locked to the momentum direction. This spin–momentum locking property gives rise to very interesting spin-dependent physical phenomena such as the Edelstein and inverse Edelstein effects. However, the spin injection in pure surface states of TI is very challenging because of the coexistence of the highly conducting bulk states. Here, we experimentally demonstrate the spin injection and observemore » the inverse Edelstein effect in the surface states of a topological Kondo insulator, SmB 6. At low temperatures when only surface carriers are present, a clear spin signal is observed. Moreover, the magnetic field angle dependence of the spin signal is consistent with spin–momentum locking property of surface states of SmB6.« less

Electrical spin injection and detection in molybdenum disulfide multilayer channel

PubMed Central

Liang, Shiheng; Yang, Huaiwen; Renucci, Pierre; Tao, Bingshan; Laczkowski, Piotr; Mc-Murtry, Stefan; Wang, Gang; Marie, Xavier; George, Jean-Marie; Petit-Watelot, Sébastien; Djeffal, Abdelhak; Mangin, Stéphane; Jaffrès, Henri; Lu, Yuan

2017-01-01

Molybdenum disulfide has recently emerged as a promising two-dimensional semiconducting material for nano-electronic, opto-electronic and spintronic applications. However, the demonstration of an electron spin transport through a semiconducting MoS2 channel remains challenging. Here we show the evidence of the electrical spin injection and detection in the conduction band of a multilayer MoS2 semiconducting channel using a two-terminal spin-valve configuration geometry. A magnetoresistance around 1% has been observed through a 450 nm long, 6 monolayer thick MoS2 channel with a Co/MgO tunnelling spin injector and detector. It is found that keeping a good balance between the interface resistance and channel resistance is mandatory for the observation of the two-terminal magnetoresistance. Moreover, the electron spin-relaxation is found to be greatly suppressed in the multilayer MoS2 channel with an in-plane spin polarization. The long spin diffusion length (approximately ∼235 nm) could open a new avenue for spintronic applications using multilayer transition metal dichalcogenides. PMID:28387252

Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon

PubMed Central

Averyanov, Dmitry V.; Karateeva, Christina G.; Karateev, Igor A.; Tokmachev, Andrey M.; Vasiliev, Alexander L.; Zolotarev, Sergey I.; Likhachev, Igor A.; Storchak, Vyacheslav G.

2016-01-01

Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics. PMID:26957146

Synthesis of low-moment CrVTiAl: a potential room temperature spin filter

NASA Astrophysics Data System (ADS)

Stephen, Gregory; Wolfsberg, Jacob; McDonald, Ian; Lejeune, Brian; Lewis, Laura; Heiman, Don

The efficient production of spin-polarized currents at room temperature is fundamental to the advancement of spintronics. Spin-filter materials - semiconductors with unequal band gaps for each spin channel - can generate spin-polarized current without the need for spin-polarizing electrodes. In addition, a spin-filter material with zero magnetic moment would have the advantage of not producing fringing fields to interfere with neighboring components. Several quaternary Heusler compounds have recently been predicted to have spin-filter properties and Curie temperatures TC >1000 K. In this work, CrVTiAl has been synthesized in the Y-type Heusler structure, as confirmed by X-ray diffractometry. Magnetization measurements exhibit an exceptionally small temperature-independent moment of 10-3μB /f.u. up to 400 K, a result that is consistent with zero-moment ferrimagnetism. In addition, temperature dependent resistivity measurements reveal the existence of a semiconducting conduction channel. These results suggest that CrVTiAl is a promising candidate for future spintronic devices.

Control of single-spin magnetic anisotropy by exchange coupling

NASA Astrophysics Data System (ADS)

Oberg, Jenny C.; Calvo, M. Reyes; Delgado, Fernando; Moro-Lagares, María; Serrate, David; Jacob, David; Fernández-Rossier, Joaquín; Hirjibehedin, Cyrus F.

2014-01-01

The properties of quantum systems interacting with their environment, commonly called open quantum systems, can be affected strongly by this interaction. Although this can lead to unwanted consequences, such as causing decoherence in qubits used for quantum computation, it can also be exploited as a probe of the environment. For example, magnetic resonance imaging is based on the dependence of the spin relaxation times of protons in water molecules in a host's tissue. Here we show that the excitation energy of a single spin, which is determined by magnetocrystalline anisotropy and controls its stability and suitability for use in magnetic data-storage devices, can be modified by varying the exchange coupling of the spin to a nearby conductive electrode. Using scanning tunnelling microscopy and spectroscopy, we observe variations up to a factor of two of the spin excitation energies of individual atoms as the strength of the spin's coupling to the surrounding electronic bath changes. These observations, combined with calculations, show that exchange coupling can strongly modify the magnetic anisotropy. This system is thus one of the few open quantum systems in which the energy levels, and not just the excited-state lifetimes, can be renormalized controllably. Furthermore, we demonstrate that the magnetocrystalline anisotropy, a property normally determined by the local structure around a spin, can be tuned electronically. These effects may play a significant role in the development of spintronic devices in which an individual magnetic atom or molecule is coupled to conducting leads.

Development and standardization of Arabic words in noise test in Egyptian children.

PubMed

Abdel Rahman, Tayseer Taha

2018-05-01

To develop and establish norms of Arabic Words in Noise test in Egyptian children. Total number of participants was 152 with normal hearing and ranging in age from 5 to 12 years. They are subdivided into two main groups (standardization group) which comprised 120 children with normal scholastic achievement and (application group) which comprised 32 children with different types of central auditory processing disorders. Arabic version of both Speech perception in noise (SPIN) and Words in Noise (WIN) tests were presented in each ear at zero signal to-noise ratio (SNR) using ipsilateral Cafeteria noise fixed at 50 dB sensation level (dBSL). The least performance in WIN test occurred between 5 and 7 years and highest scores from 9 to 12 years. However, no statistically significant difference was found among the three standardization age groups. Moreover, no statistically significant difference was found between the right and left ears scores or among the three lists. When the WIN test was compared to SPIN test in children with and without abnormal SPIN scores it showed highly consistent results except in children suffering from memory deficit reflecting that WIN test is more accurate than SPIN in this group of children. The Arabic WIN test can be used in children as young as 5 years. Also, it can be a good cross check test with SPIN test or used to follow up children after rehabilitation program in hearing impaired children or follow up after central auditory remediation of children with selective auditory attention deficit. Copyright © 2017. Published by Elsevier B.V.

Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices

NASA Astrophysics Data System (ADS)

Jha, Pankaj

Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.

Superconductivity from a non-Fermi-liquid metal: Kondo fluctuation mechanism in slave-fermion theory

NASA Astrophysics Data System (ADS)

Kim, Ki-Seok

2010-03-01

We propose Kondo fluctuation mechanism of superconductivity, differentiated from the spin-fluctuation theory as the standard model for unconventional superconductivity in the weak-coupling approach. Based on the U(1) slave-fermion representation of an effective Anderson lattice model, where localized spins are described by the Schwinger boson theory and hybridization or Kondo fluctuations weaken antiferromagnetic correlations of localized spins, we found an antiferromagnetic quantum critical point from an antiferromagnetic metal to a heavy-fermion metal in our recent study. The Kondo-induced antiferromagnetic quantum critical point was shown to be described by both conduction electrons and fermionic holons interacting with critical spin fluctuations given by deconfined bosonic spinons with a spin quantum number 1/2. Surprisingly, such critical modes turned out to be described by the dynamical exponent z=3 , giving rise to the well-known non-Fermi-liquid physics such as the divergent Grüneisen ratio with an exponent 2/3 and temperature-linear resistivity in three dimensions. We find that the z=3 antiferromagnetic quantum critical point becomes unstable against superconductivity, where critical spinon excitations give rise to pairing correlations between conduction electrons and between fermionic holons, respectively, via hybridization fluctuations. Such two kinds of pairing correlations result in multigap unconventional superconductivity around the antiferromagnetic quantum critical point of the slave-fermion theory, where s -wave pairing is not favored generically due to strong correlations. We show that the ratio between each superconducting gap for conduction electrons Δc and holons Δf and the transition temperature Tc is 2Δc/Tc˜9 and 2Δf/Tc˜O(10-1) , remarkably consistent with CeCoIn5 . A fingerprint of the Kondo mechanism is emergence of two kinds of resonance modes in not only spin but also charge fluctuations, where the charge resonance mode at an antiferromagnetic wave vector originates from d -wave pairing of spinless holons. We discuss how the Kondo fluctuation theory differs from the spin-fluctuation approach.

Microwave-induced direct spin-flip transitions in mesoscopic Pd/Co heterojunctions

NASA Astrophysics Data System (ADS)

Pietsch, Torsten; Egle, Stefan; Keller, Martin; Fridtjof-Pernau, Hans; Strigl, Florian; Scheer, Elke

2016-09-01

We experimentally investigate the effect of resonant microwave absorption on the magneto-conductance of tunable Co/Pd point contacts. At the interface a non-equilibrium spin accumulation is created via microwave absorption and can be probed via point contact spectroscopy. We interpret the results as a signature of direct spin-flip excitations in Zeeman-split spin-subbands within the Pd normal metal part of the junction. The inverse effect, which is associated with the emission of a microwave photon in a ferromagnet/normal metal point contact, can also be detected via its unique signature in transport spectroscopy.

Testing of Selective Laser Melting Turbomachinery Applicable to Exploration Upper Stage

NASA Technical Reports Server (NTRS)

Calvert, Marty; Turpin, Jason; Nettles, Mindy

2015-01-01

This task is to design, fabricate, and spin test to failure a Ti6-4 hydrogen turbopump impeller that was built using the selective laser melting (SLM) fabrication process (fig. 1). The impeller is sized around upper stage engine requirements. In addition to the spin burst test, material testing will be performed on coupons that are built with the impeller.

Superconductivity switch from spin-singlet to -triplet pairing in a topological superconducting junction.

PubMed

Tao, Ze; Chen, F J; Zhou, L Y; Li, Bin; Tao, Y C; Wang, J

2018-06-06

The interedge coupling is the cardinal characteristic of the narrow quantum spin Hall (QSH) insulator, and thus could bring about exotic transport phenomena. Herein, we present a theoretical investigation of the spin-resolved Andreev reflection (AR) in a QSH insulator strip touching on two neighbouring ferromagnetic insulators and one s-wave superconductor. It is demonstrated that, due to the interplay of the interedge coupling and ferromagnetic configuration, there could be not only usual local ARs leading to the spin-singlet pairing with the incident electron and Andreev-reflected hole from different spin subbands, but also novel local ARs giving rise to the spin-triplet pairing from the same spin subband. However, only the latter exists in the absence of the interedge coupling, and therefore the two pairings in turn testify the helical spin texture of the edge states. By proper tuning of the band structures of the ferromagnetic layers, under the resonance bias voltage, the usual and novel local ARs of [Formula: see text] can be all exhibited, resulting in fully spin-polarized pure spin-singlet superconductivity and pure spin-triplet superconductivity, respectively, which suggests a superconductivity switch from spin-singlet to -triplet pairing by electrical control. The results can be experimentally confirmed by the tunneling conductance and the noise power.

Superconductivity switch from spin-singlet to -triplet pairing in a topological superconducting junction

NASA Astrophysics Data System (ADS)

Tao, Ze; Chen, F. J.; Zhou, L. Y.; Li, Bin; Tao, Y. C.; Wang, J.

2018-06-01

The interedge coupling is the cardinal characteristic of the narrow quantum spin Hall (QSH) insulator, and thus could bring about exotic transport phenomena. Herein, we present a theoretical investigation of the spin-resolved Andreev reflection (AR) in a QSH insulator strip touching on two neighbouring ferromagnetic insulators and one s-wave superconductor. It is demonstrated that, due to the interplay of the interedge coupling and ferromagnetic configuration, there could be not only usual local ARs leading to the spin-singlet pairing with the incident electron and Andreev-reflected hole from different spin subbands, but also novel local ARs giving rise to the spin-triplet pairing from the same spin subband. However, only the latter exists in the absence of the interedge coupling, and therefore the two pairings in turn testify the helical spin texture of the edge states. By proper tuning of the band structures of the ferromagnetic layers, under the resonance bias voltage, the usual and novel local ARs of can be all exhibited, resulting in fully spin-polarized pure spin-singlet superconductivity and pure spin-triplet superconductivity, respectively, which suggests a superconductivity switch from spin-singlet to -triplet pairing by electrical control. The results can be experimentally confirmed by the tunneling conductance and the noise power.

Spin-tunnel investigation of a 1/15-scale model of an Australian trainer airplane

NASA Technical Reports Server (NTRS)

Bowman, James S., Jr.; Whipple, Raymond D.; White, William L.

1987-01-01

An investigation was conducted in the Langley Spin Tunnel of the spin and spin-recovery characteristics of a 1/15-scale model of an Australian trainer airplane. The invesigation included erect and inverted spins; configuration variables such as a long tail, fuselage strakes, 20 deg. elevator cutouts, and rudder modifications; and determination of the parachute size for emergency spin recovery. Also included in the investigation were wing leading-edge modifications to evaluate Reynolds number effects. Results indicate that the basic configuration will spin erect at an angle of attack of about 63 deg. at about 2 to 2.3 seconds per turn. Recovery from this spin was unsatisfactory by rudder reversal or by rudder reversal and ailerons deflected to full with the spin. The elevators had a pronounced effect on the recovery characteristics. The elevators-down position was very adverse to recoveries, whereas the elevators-up position provided favorable recovery effects. Moving the vertical tail aft (producing a long tail configuration) improved the spin characteristics, but the recoveries were still considered marginal. An extension to the basic rudder chord and length made a significant improvement in the spin and recovery characteristics. Satisfactory recoveries were obtained by deflecting the rudder to full against the spin and the elevators and ailerons to neutral.

Spin-polarized scanning tunneling microscopy with quantitative insights into magnetic probes

NASA Astrophysics Data System (ADS)

Phark, Soo-hyon; Sander, Dirk

2017-04-01

Spin-polarized scanning tunneling microscopy and spectroscopy (spin-STM/S) have been successfully applied to magnetic characterizations of individual nanostructures. Spin-STM/S is often performed in magnetic fields of up to some Tesla, which may strongly influence the tip state. In spite of the pivotal role of the tip in spin-STM/S, the contribution of the tip to the differential conductance d I/d V signal in an external field has rarely been investigated in detail. In this review, an advanced analysis of spin-STM/S data measured on magnetic nanoislands, which relies on a quantitative magnetic characterization of tips, is discussed. Taking advantage of the uniaxial out-of-plane magnetic anisotropy of Co bilayer nanoisland on Cu(111), in-field spin-STM on this system has enabled a quantitative determination, and thereby, a categorization of the magnetic states of the tips. The resulting in-depth and conclusive analysis of magnetic characterization of the tip opens new venues for a clear-cut sub-nanometer scale spin ordering and spin-dependent electronic structure of the non-collinear magnetic state in bilayer high Fe nanoislands on Cu(111).

Reexamination of Spin Transport Through a DOUBLE-δ Magnetic Barrier with Spin-Orbit Interactions

NASA Astrophysics Data System (ADS)

Bi, Caihua; Zhai, Feng

We revisit the properties of spin transport through a semiconductor 2DEG system subjected to the modulation of both a ferromagnetic metal (FM) stripe on top and the Rashba and Dresselhaus spin-orbit interactions (SOIs). The FM stripe has a magnetization along the transporting direction and generates an inhomogeneous magnetic field in the 2DEG plane which is taken as a double-δ shape. It is found that the spin polarization of this system generated from a spin-unpolarized injection can be remarkable only within a low Fermi energy region and is not more than 30% for the parameters available in current experiments. In this energy region, both the magnitude and the orientation of the spin polarization can be tuned by the Rashba strength, the Dresselhaus strength, and the magnetic field strength. The magnetization reversal of the FM stripe cannot result in a change of the conductance, but can rotate the orientation of the spin polarization. The results are in contrast to those in [ J. Phys.: Condens. Matter 15 (2003) L31] where a pure spin state for incident electrons is artificially assumed.

Testing the Binary Black Hole Nature of a Compact Binary Coalescence

NASA Astrophysics Data System (ADS)

Krishnendu, N. V.; Arun, K. G.; Mishra, Chandra Kant

2017-09-01

We propose a novel method to test the binary black hole nature of compact binaries detectable by gravitational wave (GW) interferometers and, hence, constrain the parameter space of other exotic compact objects. The spirit of the test lies in the "no-hair" conjecture for black holes where all properties of a Kerr black hole are characterized by its mass and spin. The method relies on observationally measuring the quadrupole moments of the compact binary constituents induced due to their spins. If the compact object is a Kerr black hole (BH), its quadrupole moment is expressible solely in terms of its mass and spin. Otherwise, the quadrupole moment can depend on additional parameters (such as the equation of state of the object). The higher order spin effects in phase and amplitude of a gravitational waveform, which explicitly contains the spin-induced quadrupole moments of compact objects, hence, uniquely encode the nature of the compact binary. Thus, we argue that an independent measurement of the spin-induced quadrupole moment of the compact binaries from GW observations can provide a unique way to distinguish binary BH systems from binaries consisting of exotic compact objects.

Testing the Binary Black Hole Nature of a Compact Binary Coalescence.

PubMed

Krishnendu, N V; Arun, K G; Mishra, Chandra Kant

2017-09-01

We propose a novel method to test the binary black hole nature of compact binaries detectable by gravitational wave (GW) interferometers and, hence, constrain the parameter space of other exotic compact objects. The spirit of the test lies in the "no-hair" conjecture for black holes where all properties of a Kerr black hole are characterized by its mass and spin. The method relies on observationally measuring the quadrupole moments of the compact binary constituents induced due to their spins. If the compact object is a Kerr black hole (BH), its quadrupole moment is expressible solely in terms of its mass and spin. Otherwise, the quadrupole moment can depend on additional parameters (such as the equation of state of the object). The higher order spin effects in phase and amplitude of a gravitational waveform, which explicitly contains the spin-induced quadrupole moments of compact objects, hence, uniquely encode the nature of the compact binary. Thus, we argue that an independent measurement of the spin-induced quadrupole moment of the compact binaries from GW observations can provide a unique way to distinguish binary BH systems from binaries consisting of exotic compact objects.

Polarized lepton-nucleon scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, E.

1994-12-01

The author provides a summary of the proposed and published statistical (systematic) uncertainties from the world experiments on nucleon spin structure function integrals. By the time these programs are complete, there will be a vast resource of data on nucleon spin structure functions. Each program has quite different experimental approaches regarding the beams, targets, and spectrometers thus ensuring systematically independent tests of the spin structure function measurements. Since the field of spin structure function measurements began, there has been a result appearing approximately every five years. With advances in polarized target technology and high polarization in virtually all of themore » lepton beams, results are now coming out each year; this is a true signature of the growth in the field. Hopefully, the experiments will provide a consistent picture of nucleon spin structure at their completion. In summary, there are still many open questions regarding the internal spin structure of the nucleon. Tests of QCD via the investigation of the Bjorken sum rule is a prime motivator for the field, and will continue with the next round of precision experiments. The question of the origin of spin is still a fundamental problem. Researchers hope is that high-energy probes using spin will shed light on this intriguing mystery, in addition to characterizing the spin structure of the nucleon.« less

A spin labelling study of immunomodulating peptidoglycan monomer and adamantyltripeptides entrapped into liposomes.

PubMed

Frkanec, Ruza; Noethig-Laslo, Vesna; Vranesić, Branka; Mirosavljević, Krunoslav; Tomasić, Jelka

2003-04-01

The interaction of immunostimulating compounds, the peptidoglycan monomer (PGM) and structurally related adamantyltripeptides (AdTP1 and AdTP2), respectively, with phospholipids in liposomal bilayers were investigated by electron paramagnetic resonance spectroscopy. (1). The fatty acids bearing the nitroxide spin label at different positions along the acyl chain were used to investigate the interaction of tested compounds with negatively charged multilamellar liposomes. Electron spin resonance (ESR) spectra were studied at 290 and 310 K. The entrapment of the adamantyltripeptides affected the motional properties of all spin labelled lipids, while the entrapment of PGM had no effect. (2). Spin labelled PGM was prepared and the novel compound bearing the spin label attached via the amino group of diaminopimelic acid was chromatographically purified and chemically characterized. The rotational correlation time of the spin labelled molecule dissolved in buffer at pH 7.4 was studied as a function of temperature. The conformational change was observed above 300 K. The same effect was observed with the spin labelled PGM incorporated into liposomes. Such effect was not observed when the spin labelled PGM was studied at alkaline pH, probably due to the hydrolysis of PGM molecule. The study of possible interaction with liposomal membrane is relevant to the use of tested compounds incorporated into liposomes, as adjuvants in vivo.

Highly conductive and anticorrosion Ag/CNTs/NDs hybrid films on molecular-grafted PET substrate for flexible electrodes

NASA Astrophysics Data System (ADS)

Zhang, Yang; Kang, Zhixin

2018-01-01

We reported an approach of preparing highly conductive, anticorrosion, flexible Ag hybrid films enhanced by multi-walled carbon nanotubes (CNTs) and nanodaimonds (NDs) on molecular-grafted PET substrate by spin-spray for flexible electronics. we studied in this paper and found that even an outstanding enhancement on conductivity of Ag films, CNTs have a negative effect on anticorrosion property. Meanwhile, NDs decreased the conductivity of Ag/CNTs hybrids, but it remained a relatively high conductivity property and even was affirmed a distinctly boost improvement on anticorrosion, microhardness and tensile strength, which meant a better mechanical chemical stabilization and practicability in real flexible electronics. To obtain the strong adhesive strength of films/substrate, molecular-grafting technology was applied, which was affirmed by XPS and cross-cut test. What's more, we evaluated anticorrosion property by electrochemistry test, including Tafel measurements and electrochemical impedance spectroscopy measurements, proving the positive effect of NDs on Ag/CNTs hybrid films. For practical application, a flexible light-emitting diode (LED) circuit was successfully structured and remained steady under bending, folding and twisting. Besides, after 1000000 cycles inner/outer bending deformation, the hybrid films showed a mechanical compliance, fatigue stability and practicability in real flexible electronics.

Origin and evolution of surface spin current in topological insulators

NASA Astrophysics Data System (ADS)

Dankert, André; Bhaskar, Priyamvada; Khokhriakov, Dmitrii; Rodrigues, Isabel H.; Karpiak, Bogdan; Kamalakar, M. Venkata; Charpentier, Sophie; Garate, Ion; Dash, Saroj P.

2018-03-01

The Dirac surface states of topological insulators offer a unique possibility for creating spin polarized charge currents due to the spin-momentum locking. Here we demonstrate that the control over the bulk and surface contribution is crucial to maximize the charge-to-spin conversion efficiency. We observe an enhancement of the spin signal due to surface-dominated spin polarization while freezing out the bulk conductivity in semiconducting Bi1.5Sb0.5Te1.7Se1.3 below 100 K . Detailed measurements up to room temperature exhibit a strong reduction of the magnetoresistance signal between 2 and100 K , which we attribute to the thermal excitation of bulk carriers and to the electron-phonon coupling in the surface states. The presence and dominance of this effect up to room temperature is promising for spintronic science and technology.

Mass Property Measurements of the Mars Science Laboratory Rover

NASA Technical Reports Server (NTRS)

Fields, Keith

2012-01-01

The NASA/JPL Mars Science Laboratory (MSL) spacecraft mass properties were measured on a spin balance table prior to launch. This paper discusses the requirements and issues encountered with the setup, qualification, and testing using the spin balance table, and the idiosyncrasies encountered with the test system. The final mass measurements were made in the Payload Hazardous Servicing Facility (PHSF) at Kennedy Space Center on the fully assembled and fueled spacecraft. This set of environmental tests required that the control system for the spin balance machine be at a remote location, which posed additional challenges to the operation of the machine

Effects of external magnetic fields and Rashba spin-orbit coupling on spin conductance in graphene

NASA Astrophysics Data System (ADS)

Shirkani, H.; Amiri, F.; Golshan, M. M.

2013-12-01

The present article is concerned with spin conductance in graphene (SCG) when both the application of an external magnetic field and Rashba spin-orbit coupling (RSOC) are taken into account. Introducing a Casimir operator, we analyze the structure of total Hamiltonian and demonstrate how the matrix elements along with the summations involved in the suitably adopted Kubo’s formula, may be analytically calculated. From the results so-obtained one finds that, in addition to discrete and symmetric behavior of SCG against the external field, it exhibits large peaks as high as six times that in ordinary two dimensional electron gases. Moreover, it is shown that for any Fermi energy the SCG asymptotically approaches a value three times larger than the standard unit of (e/4π), for large magnetic fields. Effects of the magnetic field, RSOC and Fermi energy on the characteristics of SCG are also discussed. The material presented in this article thus provides novel means of controlling the SCG by external agents.

Freestanding films of crosslinked gold nanoparticles prepared via layer-by-layer spin-coating.

PubMed

Schlicke, Hendrik; Schröder, Jan H; Trebbin, Martin; Petrov, Alexey; Ijeh, Michael; Weller, Horst; Vossmeyer, Tobias

2011-07-29

A new, extremely efficient method for the fabrication of films comprised of gold nanoparticles (GNPs) crosslinked by organic dithiols is presented in this paper. The method is based on layer-by-layer spin-coating of both components, GNPs and crosslinker, and enables the deposition of films several tens of nanometers in thickness within a few minutes. X-ray diffraction and conductance measurements reveal the proper adjustment concentration of the crosslinker solution of the critical is in order to prevent the destabilization and coalescence of particles. UV/vis spectroscopy, atomic force microscopy, and conductivity measurements indicate that films prepared via layer-by-layer spin-coating are of comparable quality to coatings prepared via laborious layer-by-layer self-assembly using immersion baths. Because spin-coated films are not bound chemically to the substrate, they can be lifted-off by alkaline underetching and transferred onto 3d-electrodes to produce electrically addressable, freely suspended films. Comparative measurements of the sheet resistances indicate that the transfer process does not compromise the film quality.

Freestanding films of crosslinked gold nanoparticles prepared via layer-by-layer spin-coating

NASA Astrophysics Data System (ADS)

Schlicke, Hendrik; Schröder, Jan H.; Trebbin, Martin; Petrov, Alexey; Ijeh, Michael; Weller, Horst; Vossmeyer, Tobias

2011-07-01

A new, extremely efficient method for the fabrication of films comprised of gold nanoparticles (GNPs) crosslinked by organic dithiols is presented in this paper. The method is based on layer-by-layer spin-coating of both components, GNPs and crosslinker, and enables the deposition of films several tens of nanometers in thickness within a few minutes. X-ray diffraction and conductance measurements reveal the proper adjustment concentration of the crosslinker solution of the critical is in order to prevent the destabilization and coalescence of particles. UV/vis spectroscopy, atomic force microscopy, and conductivity measurements indicate that films prepared via layer-by-layer spin-coating are of comparable quality to coatings prepared via laborious layer-by-layer self-assembly using immersion baths. Because spin-coated films are not bound chemically to the substrate, they can be lifted-off by alkaline underetching and transferred onto 3d-electrodes to produce electrically addressable, freely suspended films. Comparative measurements of the sheet resistances indicate that the transfer process does not compromise the film quality.

The influence of interface on spin pumping effect in Ni{sub 80}Fe{sub 20} /Tb bilayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Jinjin; Jiang, Sheng; Zhang, Dong

2016-05-15

Focusing on the interface effect of the Ni{sub 80}Fe{sub 20} (Py)/terbium (Tb) bilayer, the influence of interface on the magnetization dynamic damping is investigated systematically. Two series of Py (12 nm)/Tb (d nm) films with and without copper (Cu) (1 nm) interlayer are deposited on silicon (Si) substrates by DC magnetron sputtering at room temperature. From vibrating sample magnetometer (VSM) measurements, the saturation magnetization (M{sub s}) decreases with increasing Tb thickness in Py/Tb bilayer while the decrease of M{sub s} is suppressed efficiently by inserting a Cu layer with even 1 nm of thickness. From the frequency dependence of ferromagneticmore » resonance (FMR) linewidth, we can obtain the Gilbert damping coefficient (α), α is found to exhibit an extreme enhancement in comparison to the single Py layer and shows an increasing trend with increasing Tb thickness. By inserting the Cu layer, α decreases significantly. From theoretical fitting, the spin diffusion length (λ{sub SD}) and spin mixing conductance (g{sup ↑↓}) are determined. It shows that the interface structure influences the spin mixing conductance but not the spin diffusion length.« less

Spin transistor based on pure nonlocal Andreev reflection in EuO-graphene/superconductor/EuO-graphene nanostructure

NASA Astrophysics Data System (ADS)

Ang, Yee Sin; Ang, Lay Kee; Zhang, Chao; Ma, Zhongshui

In graphene-magnetic-insulator hybrid structure such as graphene-Europium-oxide, proximity induced exchange interaction opens up a spin-dependent bandgap and spin splitting in the Dirac band. We show that such band topology allows pure crossed Andreev reflection to be generated exclusively without the parasitic local Andreev reflection and elastic cotunnelling over a wide range of bias and Fermi levels. We model the charge transport in an EuO-graphene/superconductor/EuO-graphene three-terminal device and found that the pure non-local conductance exhibits rapid on/off switching characteristic with a minimal subthreshold swing of ~ 20 mV. Non-local conductance oscillation is observed when the Fermi levels in the superconducting lead is varied. The oscillatory behavior is directly related to the quasiparticle propagation in the superconducting lead and hence can be used as a tool to probe the subgap quasiparticle mode in superconducting graphene. The non-local current is 100% spin-polarized and is highly tunable in our proposed device. This opens up the possibility of highly tunable graphene-based spin transistor that operates purely in the non-local transport regime.

Tunnel magnetoresistance for coherent spin-flip processes on an interacting quantum dot.

PubMed

Rudziński, W

2009-01-28

Spin-polarized electronic tunneling through a quantum dot coupled to ferromagnetic electrodes is investigated within a nonequilibrium Green function approach. An interplay between coherent intradot spin-flip transitions, tunneling processes and Coulomb correlations on the dot is studied for current-voltage characteristics of the tunneling junction in parallel and antiparallel magnetic configurations of the leads. It is found that due to the spin-flip processes electric current in the antiparallel configuration tends to the current characteristics in the parallel configuration, thus giving rise to suppression of the tunnel magnetoresistance (TMR) between the threshold bias voltages at which the dot energy level becomes active in tunneling. Also, the effect of a negative differential conductance in symmetrical junctions, splitting of the conductance peaks, significant modulation of TMR peaks around the threshold bias voltages as well as suppression of the diode-like behavior in asymmetrical junctions is discussed in the context of coherent intradot spin-flip transitions. It is also shown that TMR may be inverted at selected gate voltages, which qualitatively reproduces the TMR behavior predicted recently for temperatures in the Kondo regime, and observed experimentally beyond the Kondo regime for a semiconductor InAs quantum dot coupled to nickel electrodes.

Model of biological quantum logic in DNA.

PubMed

Mihelic, F Matthew

2013-08-02

The DNA molecule has properties that allow it to act as a quantum logic processor. It has been demonstrated that there is coherent conduction of electrons longitudinally along the DNA molecule through pi stacking interactions of the aromatic nucleotide bases, and it has also been demonstrated that electrons moving longitudinally along the DNA molecule are subject to a very efficient electron spin filtering effect as the helicity of the DNA molecule interacts with the spin of the electron. This means that, in DNA, electrons are coherently conducted along a very efficient spin filter. Coherent electron spin is held in a logically and thermodynamically reversible chiral symmetry between the C2-endo and C3-endo enantiomers of the deoxyribose moiety in each nucleotide, which enables each nucleotide to function as a quantum gate. The symmetry break that provides for quantum decision in the system is determined by the spin direction of an electron that has an orbital angular momentum that is sufficient to overcome the energy barrier of the double well potential separating the C2-endo and C3-endo enantiomers, and that enantiomeric energy barrier is appropriate to the Landauer limit of the energy necessary to randomize one bit of information.

GMI Instrument Spin Balance Method, Optimization, Calibration, and Test

NASA Technical Reports Server (NTRS)

Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

2014-01-01

The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3 year mission life. Therefore, GMI must be very precisely balanced about the spin axis and CG to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

GMI Instrument Spin Balance Method, Optimization, Calibration and Test

NASA Technical Reports Server (NTRS)

Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

2014-01-01

The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3-year mission life. Therefore, GMI must be very precisely balanced about the spin axis and center of gravity (CG) to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

Dyakonov-Perel Effect on Spin Dephasing in n-Type GaAs

NASA Technical Reports Server (NTRS)

Ning, C. Z.; Wu, M. W.

2003-01-01

A paper presents a study of the contribution of the Dyakonov-Perel (DP) effect to spin dephasing in electron-donor-doped bulk GaAs in the presence of an applied steady, moderate magnetic field perpendicular to the growth axis of the GaAs crystal. (The DP effect is an electron-wave-vector-dependent spin-state splitting of the conduction band, caused by a spin/orbit interaction in a crystal without an inversion center.) The applicable Bloch equations of kinetics were constructed to include terms accounting for longitudinal optical and acoustic phonon scattering as well as impurity scattering. The contributions of the aforementioned scattering mechanisms to spin-dephasing time in the presence of DP effect were examined by solving the equations numerically. Spin-dephasing time was obtained from the temporal evolution of the incoherently summed spin coherence. Effects of temperature, impurity level, magnetic field, and electron density on spin-dephasing time were investigated. Spin-dephasing time was found to increase with increasing magnetic field. Contrary to predictions of previous simplified treatments of the DP effect, spin-dephasing time was found to increase with temperature in the presence of impurity scattering. These results were found to agree qualitatively with results of recent experiments.

Artificial Gravity as a Multi-System Countermeasure to Bed Rest Deconditioning: Preliminary Results

NASA Technical Reports Server (NTRS)

Warren, L. E.; Paloski, William H.; Young, L. R.

2006-01-01

Artificial gravity paradigms may offer effective, efficient, multi-system protection from the untoward effects of adaptation to the microgravity of space or the hypogravity of planetary surfaces. Intermittent artificial gravity (AG) produced by a horizontal short-radius centrifuge (SRC) has recently been utilized on human test subjects deconditioned by bed rest. This presentation will review preliminary results of a 41 day study conducted at the University of Texas Medical Branch, Galveston, TX bed rest facility. During the first eleven days of the protocol, subjects were ambulatory, but confined to the facility. They began a carefully controlled diet, and participated in multiple baseline tests of bone, muscle, cardiovascular, sensory-motor, immunological, and psychological function. On the twelfth day, subjects entered the bed rest phase of the study, during which they were confined to strict 6deg head down tilt bed rest for 21 days. Beginning 24 hrs into this period, treatment subjects received one hour daily exposures to artificial gravity which was produced by spinning the subjects on a 3.0 m radius SRC. They were oriented radially in the supine position so that the centrifugal force was aligned with their long body axis, and while spinning, they "stood" on a force plate, supporting the centrifugal loading (2.5 g at the feet, 1.0 g at the heart). The subject station allowed free translation over approximately 10 cm to ensure full loading of the lower extremities and to allow for anti-orthostatic muscle contractions. Control subjects were positioned on the centrifuge but did not spin. Following the bed rest phase, subjects were allowed to ambulate again, but remained within the facility for an additional 9 days and participated in multiple follow-up tests of physiological function.

Spin and Recovery Characteristics of the Curtiss-Wright XP-87 Airplane

NASA Technical Reports Server (NTRS)

Berman, Theodore

1947-01-01

The spin and recovery characteristics of the Curtiss-Wright XP-87 airplane, as well as the spin-recovery parachute requirements, the control forces that would be encountered in the spin, and the best method for the crew to attempt an emergency escape, are presented in this report. The characteristics were estimated rather than determined by model tests because the XP-87 dimensional and mass characteristics were considered to be noncritical and because data were available from model tests of several similar airplanes. The study indicated that the recovery characteristics of the airplane will be satisfactory for all loadings if the controls are reversed fully and rapidly. The control forces, however, will probably be beyond the capabilities of the pilot unless some additional balance or a booster is used. A 6-foot tail parachute or a 3.5-foot wing-tip parachute with a drag coefficient of 0.7 will be a satisfactory, emergency spin-recovery device for spin demonstrations. If it is necessary for the crew to abandon the spinning airplane, they should leave from the outboard side of the cockpit.

Spin-split fermi surfaces in CexLa1-xB6 and PrxLa1-xB6

NASA Astrophysics Data System (ADS)

Isshiki, T.; Endo, M.; Sugi, M.; Kimura, N.; Nakamura, S.; Nojima, T.; Aoki, H.; Kunii, S.

2006-05-01

We have performed the dHvA measurements on CexLa1-xB6 and PrxLa1-xB6 compounds to study spin splitting of the Fermi surfaces. In PrB 6 we have found new frequency branches to confirm that the Fermi surface splits into up and down spin Fermi surfaces, whereas no spin splitting has been found for x=0.25,0.5,0.75. We have also found several new frequency branches in CeB6. The new frequency branches imply that the Fermi surfaces of up and down spin conduction electrons are significantly different in CeB6 as well as in PrB6.

Spin-up studies of the Space Shuttle Orbiter main gear tire

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Stubbs, Sandy M.

1988-01-01

One of the factors needed to describe the wear behavior of the Space Shuttle Orbiter main gear tires is their behavior during the spin-up process. An experimental investigation of tire spin-up processes was conducted at the NASA Langley Research Center's Aircraft Landing Dynamics Facility. During the investigation, the influence of various parameters such as forward speed and sink speed on tire spin-up forces were evaluated. A mathematical model was developed to estimate drag forces and spin-up times and is presented. The effect of prerotation was explored and is discussed. Also included is a means of determining the sink speed of the orbiter at touchdown based upon the appearance of the rubber deposits left on the runway during spinup.

Spin-Polarization Control in a Two-Dimensional Semiconductor

NASA Astrophysics Data System (ADS)

Appelbaum, Ian; Li, Pengke

2016-05-01

Long carrier spin lifetimes are a double-edged sword for the prospect of constructing "spintronic" logic devices: Preservation of the logic variable within the transport channel or interconnect is essential to successful completion of the logic operation, but any spins remaining past this event will pollute the environment for subsequent clock cycles. Electric fields can be used to manipulate these spins on a fast time scale by careful interplay of spin-orbit effects, but efficient controlled depolarization can only be completely achieved with amenable materials properties. Taking III-VI monochalcogenide monolayers as an example 2D semiconductor, we use symmetry analysis, perturbation theory, and ensemble calculation to show how this longstanding problem can be solved by suitable manipulation of conduction electrons.

Spin-tunnel investigation of the spinning characteristics of typical single-engine general aviation airplane designs. 2: Low-wing model A; tail parachute diameter and canopy distance for emergency spin recovery

NASA Technical Reports Server (NTRS)

Burk, S. M., Jr.; Bowman, J. S., Jr.; White, W. L.

1977-01-01

A spin tunnel study is reported on a scale model of a research airplane typical of low-wing, single-engine, light general aviation airplanes to determine the tail parachute diameter and canopy distance (riser length plus suspension-line length) required for energency spin recovery. Nine tail configurations were tested, resulting in a wide range of developed spin conditions, including steep spins and flat spins. The results indicate that the full-scale parachute diameter required for satisfactory recovery from the most critical conditions investigated is about 3.2 m and that the canopy distance, which was found to be critical for flat spins, should be between 4.6 and 6.1 m.

Parachute Swivel Mechanism for planetary entry

NASA Technical Reports Server (NTRS)

Birner, R.; Kaese, J.; Koller, F.; Muehlner, E.; Luhmann, H.-J.

1993-01-01

A parachute swivel mechanism (PSM) for planetary entry missions such as a Mars probe (MARSNET) or return of cometary material samples (ROSETTA mission) has been developed. The purpose of the PSM is to decouple the spin of the probe from the parachute, with low friction torque, during both the deployment and descent phases. Critical requirements are high shock loads, low friction, low temperatures, and several years of storage in the deep space environment (during the cruise phase of the probe, prior to operation). The design uses a main thrust ball bearing to cope with the load requirement and a smaller thrust ball bearing for guiding of the shaft. Except for use on the Viking and Galileo swivels, it appears that this type of bearing has very rarely been employed in space mechanisms, so that little is known of its friction behavior with dry lubrication. A slip ring assembly allows the transfer of electrical power for post-reefing of the parachute. A test program has been conducted covering the environmental conditions of Mars entry and Earth reentry. This paper describes requirement constraints, model missions of planetary entries, a bearing trade-off, analyses performed, design details, the lubrication system, and test results (friction torque versus load/spin rate). In addition, the design of the test rig is addressed.

Spin-glass behaviors in carrier polarity controlled Fe{sub 3−x}Ti{sub x}O{sub 4} semiconductor thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamahara, H., E-mail: yamahara@bioxide.t.u-tokyo.ac.jp; Seki, M.; Adachi, M.

2015-08-14

Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe{sub 3−x}Ti{sub x}O{sub 4} thin films have been obtained on spinel MgAl{sub 2}O{sub 4} substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x = 0.8) show p-type conduction, while Ti-poor films (x = 0.6–0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmedmore » by the X-ray absorption spectra. All of the Fe{sub 3−x}Ti{sub x}O{sub 4} films (x = 0.6–0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe{sub 2.2}Ti{sub 0.8}O{sub 4} film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe{sub 2.2}Ti{sub 0.8}O{sub 4} film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state.« less

(1) Majorana fermions in pinned vortices; (2) Manipulating and probing Majorana fermions using superconducting circuits; and (3) Controlling a nanowire spin-orbit qubit via electric-dipole spin resonance

NASA Astrophysics Data System (ADS)

Nori, Franco

2014-03-01

We study a heterostructure which consists of a topological insulator and a superconductor with a hole. This system supports a robust Majorana fermion state bound to the vortex core. We study the possibility of using scanning tunneling spectroscopy (i) to detect the Majorana fermion in this setup and (ii) to study excited states bound to the vortex core. The Majorana fermion manifests itself as an H-dependent zero-bias anomaly of the tunneling conductance. The excited states spectrum differs from the spectrum of a typical Abrikosov vortex, providing additional indirect confirmation of the Majorana state observation. We also study how to manipulate and probe Majorana fermions using super-conducting circuits. In we consider a semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC), which can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the spin-orbit qubit can respond to an external ac electric field, i.e., electric-dipole spin resonance. We develop a theory that can apply in the strong SOC regime. We find that there is an optimal SOC strength ηopt = √ 2/2, where the Rabi frequency induced by the ac electric field becomes maximal. Also, we show that both the level spacing and the Rabi frequency of the spin-orbit qubit have periodic responses to the direction of the external static magnetic field. These responses can be used to determine the SOC in the nanowire. FN is partly supported by the RIKEN CEMS, iTHES Project, MURI Center for Dynamic Magneto-Optics, JSPS-RFBR Contract No. 12-02-92100, Grant-in-Aid for Scientific Research (S), MEXT Kakenhi on Quantum Cybernetics, and the JSPS via its FIRST program.

Cobalt spin states and hyperfine interactions in LaCoO3 investigated by LDA+U calculations

NASA Astrophysics Data System (ADS)

Leighton, C.; Hsu, H.; Blaha, P.; Wentzcovitch, R. M.

2010-12-01

The spin states of cobalt ions in the bulk and epitaxial-thin-film lanthanum cobaltite (LaCoO3) have been controversial for years. The controversial point is mainly the presence of intermediate-spin (IS) Co in the temperature range of 0-85 K. In this region, bulk LaCoO3 experiences a crossover from a diamagnetic to a paramagnetic phase, and the thin-film LaCoO3 is ferromagnetic and insulator. An approach to probe the Co spin state is thus of interest. With a series of LDA+U calculations, we have demonstrated that the electric field gradient (EFG) at the Co nucleus can be used as a fingerprint to identify the spin state of the Co ion in each case. Therefore, in principle, the spin state of the Co ion can be unambiguously determined from nuclear magnetic resonance (NMR) spectra. Our calculations also suggest that the presence of IS Co in this temperature range is unlikely, based not only on its relatively higher energy, but also on its associated conducting band structure incompatible with the measured insulating conductivity. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The computations were performed mainly at the Minnesota Supercomputing Institute (MSI).

Soil Moisture Active and Passive (SMAP) White-Painted Expanded Polystyrene (EPS) Radome Survivability Test

NASA Technical Reports Server (NTRS)

Mikhaylov, Rebecca; Kwack, Eug; Stegman, Matthew; Dawson, Douglas; Hoffman, Pamela

2015-01-01

NASA's SMAP Mission launched in January 2015 into a 685 km near-polar, sun-synchronous orbit. The SMAP instrument architecture incorporates an L-band radar and radiometer which share a common feedhorn and mesh reflector. The instrument rotates about the nadir axis at approximately 15 rpm, thereby providing a conically scanning wide swath antenna beam that is capable of achieving global coverage within three days. The radiometer and its associated electronics have tight thermal stability requirements in order to meet the required surface emittance measurement precision from space. Maintaining the thermal stabilities is quite challenging because the radiometer is located on a spinning platform that can either be in full sunlight or eclipse, and thus exposed to a highly transient environment. Stability requirements were met by integrating a light-weight Expanded Polystyrene (EPS) radome into the design to prevent solar illumination of the feed horn interior. The radome was painted white since the thermo-optical properties of bare sunlit EPS degrade rapidly over the three-year mission. Milling of the EPS and solvent within the white paint created cavities on the EPS surface which may introduce localized hot spots possibly violating the EPS glass transition temperature of 96degC and leading to structural integrity concerns. A three-day thermal test was conducted in a vacuum chamber to verify survivability of the radome during a simulated non-spin fault condition at end of mission. A portable solar simulator illuminated the test article and the beam irradiance was kept nearly constant during the entire 50 hour test, except during the first hour which simulated the expected 79degC on-orbit surface temperature of the radome. The test article survived based on the established pass criteria for three separate metrics: dimensional, optical property, and color. If any hot spots exist locally, they did not cause any observable permanent deformation when compared to pre- and post-test images. The test results increase confidence that there is a high probability that the radome will survive the worst-case scenario of a no-spin fault condition at the end of mission.

Spinning angle optical calibration apparatus

DOEpatents

Beer, Stephen K.; Pratt, II, Harold R.

1991-01-01

An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.

Passive Thermal Control for the Low Density Supersonic Decelerator (LDSD) Test Vehicle Spin Motors Sub-System

NASA Technical Reports Server (NTRS)

Redmond, Matthew; Mastropietro, A. J.; Pauken, Michael; Mobley, Brandon

2014-01-01

Future missions to Mars will require improved entry, descent, and landing (EDL) technology over the Viking-heritage systems which recently landed the largest payload to date, the 900 kg Mars Science Laboratory. As a result, NASA's Low Density Supersonic Decelerator (LDSD) project is working to advance the state of the art in Mars EDL systems by developing and testing three key technologies which will enable heavier payloads and higher altitude landing sites on the red planet. These technologies consist of a large 33.5 m diameter Supersonic Disk Sail (SSDS) parachute and two different Supersonic Inflatable Aerodynamic Decelerator (SIAD) devices - a robotic class that inflates to a 6 m diameter torus (SIAD-R), and an exploration class that inflates to an 8 m diameter isotensoid (SIADE). All three technologies will be demonstrated on test vehicles at high earth altitudes in order to simulate the Mars EDL environment. Each vehicle will be carried to altitude by a large helium balloon, released, spun up using spin motors to stabilize the vehicle's trajectory, and accelerated to supersonic speeds using a large solid rocket motor. The vehicle will then be spun down using another set of spin motors, and will deploy either the SIAD-R or SIAD-E, followed by the SSDS parachute until the vehicle lands in the ocean. Component level testing and bounding analysis are used to ensure the survival of system components in extreme thermal environments and predict temperatures throughout the flight. This paper presents a general description of the thermal testing, model correlation, and analysis of the spin motor passive thermal control sub-system to maintain spin motor performance, prescribed vehicle trajectory, and structural integrity of the test vehicle. The spin motor subsystem is predicted to meet its requirements with margin.

Experiments Result in Safer, Spin-Resistant Aircraft

NASA Technical Reports Server (NTRS)

2014-01-01

The General Aviation Spin Program at Langley Research Center devised the first-of-their-kind guidelines for designing more spin-resistant aircraft. Thanks to NASA's contributions, the Federal Aviation Administration introduced the Part 23 spin-resistance standard in 1991. Los Angeles-based ICON Aircraft has now manufactured a new plane for consumer recreational flying that meets the complete set of criteria specified for Part 23 testing.

Free Flight Ground Testing of ADEPT in Advance of the Sounding Rocket One Flight Experiment

NASA Technical Reports Server (NTRS)

Smith, B. P.; Dutta, S.

2017-01-01

The Adaptable Deployable Entry and Placement Technology (ADEPT) project will be conducting the first flight test of ADEPT, titled Sounding Rocket One (SR-1), in just two months. The need for this flight test stems from the fact that ADEPT's supersonic dynamic stability has not yet been characterized. The SR-1 flight test will provide critical data describing the flight mechanics of ADEPT in ballistic flight. These data will feed decision making on future ADEPT mission designs. This presentation will describe the SR-1 scientific data products, possible flight test outcomes, and the implications of those outcomes on future ADEPT development. In addition, this presentation will describe free-flight ground testing performed in advance of the flight test. A subsonic flight dynamics test conducted at the Vertical Spin Tunnel located at NASA Langley Research Center provided subsonic flight dynamics data at high and low altitudes for multiple center of mass (CoM) locations. A ballistic range test at the Hypervelocity Free Flight Aerodynamics Facility (HFFAF) located at NASA Ames Research Center provided supersonic flight dynamics data at low supersonic Mach numbers. Execution and outcomes of these tests will be discussed. Finally, a hypothesized trajectory estimate for the SR-1 flight will be presented.

Magnetism and local symmetry breaking in a Mott insulator with strong spin orbit interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, L.; Song, M.; Liu, W.

2017-02-09

Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence of SOC implies that the spin is not a good quantum number. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local point symmetry breaking or local spin expectation values, even in materials with simple cubic crystal structure such as Ba 2NaOsO 6. Experimental tests of these theories by local probes are highly sought for. Our local measurements designed to concurrently probemore » spin and orbital/lattice degrees of freedom of Ba 2NaOsO 6 provide such tests. As a result, we show that a canted ferromagnetic phase which is preceded by local point symmetry breaking is stabilized at low temperatures, as predicted by quantum theories involving multipolar spin interactions.« less

Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes.

PubMed

Nishizawa, Nozomi; Nishibayashi, Kazuhiro; Munekata, Hiro

2017-02-21

We report the room-temperature electroluminescence (EL) with nearly pure circular polarization (CP) from GaAs-based spin-polarized light-emitting diodes (spin-LEDs). External magnetic fields are not used during device operation. There are two small schemes in the tested spin-LEDs: first, the stripe-laser-like structure that helps intensify the EL light at the cleaved side walls below the spin injector Fe slab, and second, the crystalline AlO x spin-tunnel barrier that ensures electrically stable device operation. The purity of CP is depressively low in the low current density ( J ) region, whereas it increases steeply and reaches close to the pure CP when J > 100 A/cm 2 There, either right- or left-handed CP component is significantly suppressed depending on the direction of magnetization of the spin injector. Spin-dependent reabsorption, spin-induced birefringence, and optical spin-axis conversion are suggested to account for the observed experimental results.

Quantized magnetoresistance in atomic-size contacts.

PubMed

Sokolov, Andrei; Zhang, Chunjuan; Tsymbal, Evgeny Y; Redepenning, Jody; Doudin, Bernard

2007-03-01

When the dimensions of a metallic conductor are reduced so that they become comparable to the de Broglie wavelengths of the conduction electrons, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In ferromagnetic metals, the spin angular momentum of the electrons results in spin-dependent conductance quantization and various unusual magnetoresistive phenomena. Theorists have predicted a related phenomenon known as ballistic anisotropic magnetoresistance (BAMR). Here we report the first experimental evidence for BAMR by observing a stepwise variation in the ballistic conductance of cobalt nanocontacts as the direction of an applied magnetic field is varied. Our results show that BAMR can be positive and negative, and exhibits symmetric and asymmetric angular dependences, consistent with theoretical predictions.

Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

PubMed Central

Giorgioni, Anna; Paleari, Stefano; Cecchi, Stefano; Vitiello, Elisa; Grilli, Emanuele; Isella, Giovanni; Jantsch, Wolfgang; Fanciulli, Marco; Pezzoli, Fabio

2016-01-01

Control of electron spin coherence via external fields is fundamental in spintronics. Its implementation demands a host material that accommodates the desirable but contrasting requirements of spin robustness against relaxation mechanisms and sizeable coupling between spin and orbital motion of the carriers. Here, we focus on Ge, which is a prominent candidate for shuttling spin quantum bits into the mainstream Si electronics. So far, however, the intrinsic spin-dependent phenomena of free electrons in conventional Ge/Si heterojunctions have proved to be elusive because of epitaxy constraints and an unfavourable band alignment. We overcome these fundamental limitations by investigating a two-dimensional electron gas in quantum wells of pure Ge grown on Si. These epitaxial systems demonstrate exceptionally long spin lifetimes. In particular, by fine-tuning quantum confinement we demonstrate that the electron Landé g factor can be engineered in our CMOS-compatible architecture over a range previously inaccessible for Si spintronics. PMID:28000670

Magnetic nano-oscillator driven by pure spin current.

PubMed

Demidov, Vladislav E; Urazhdin, Sergei; Ulrichs, Henning; Tiberkevich, Vasyl; Slavin, Andrei; Baither, Dietmar; Schmitz, Guido; Demokritov, Sergej O

2012-12-01

With the advent of pure-spin-current sources, spin-based electronic (spintronic) devices no longer require electrical charge transfer, opening new possibilities for both conducting and insulating spintronic systems. Pure spin currents have been used to suppress noise caused by thermal fluctuations in magnetic nanodevices, amplify propagating magnetization waves, and to reduce the dynamic damping in magnetic films. However, generation of coherent auto-oscillations by pure spin currents has not been achieved so far. Here we demonstrate the generation of single-mode coherent auto-oscillations in a device that combines local injection of a pure spin current with enhanced spin-wave radiation losses. Counterintuitively, radiation losses enable excitation of auto-oscillation, suppressing the nonlinear processes that prevent auto-oscillation by redistributing the energy between different modes. Our devices exhibit auto-oscillations at moderate current densities, at a microwave frequency tunable over a wide range. These findings suggest a new route for the implementation of nanoscale microwave sources for next-generation integrated electronics.

Material Targets for Scaling All-Spin Logic

NASA Astrophysics Data System (ADS)

Manipatruni, Sasikanth; Nikonov, Dmitri E.; Young, Ian A.

2016-01-01

All-spin-logic devices are promising candidates to augment and complement beyond-CMOS integrated circuit computing due to nonvolatility, ultralow operating voltages, higher logical efficiency, and high density integration. However, the path to reach lower energy-delay product performance compared to CMOS transistors currently is not clear. We show that scaling and engineering the nanoscale magnetic materials and interfaces is the key to realizing spin-logic devices that can surpass the energy-delay performance of CMOS transistors. With validated stochastic nanomagnetic and vector spin-transport numerical models, we derive the target material and interface properties for the nanomagnets and channels. We identify promising directions for material engineering and discovery focusing on the systematic scaling of magnetic anisotropy (Hk ) and saturation magnetization (Ms ), the use of perpendicular magnetic anisotropy, and the interface spin-mixing conductance of the ferromagnet-spin-channel interface (Gmix ). We provide systematic targets for scaling a spin-logic energy-delay product toward 2 aJ ns, comprehending the stochastic noise for nanomagnets.

Disorder induced spin coherence in polyfluorene thin film semiconductors

NASA Astrophysics Data System (ADS)

Miller, Richard G.; van Schooten, Kipp; Malissa, Hans; Waters, David P.; Lupton, John M.; Boehme, Christoph

2014-03-01

Charge carrier spins in polymeric organic semiconductors significantly influence magneto-optoelectronic properties of these materials. In particular, spin relaxation times influence magnetoresistance and electroluminescence. We have studied the role of structural and electronic disorder in polaron spin-relaxation times. As a model polymer, we used polyfluorene, which can exist in two distinct morphologies: an amorphous (glassy) and an ordered (beta) phase. The phases can be controlled in thin films by preparation parameters and verified by photoluminescence spectroscopy. We conducted pulsed electrically detected magnetic resonance (pEDMR) measurements to determine spin-dephasing times by transient current measurements under bipolar charge carrier injection conditions and a forward bias. The measurements showed that, contrary to intuition, spin-dephasing times increase with material disorder. We attribute this behavior to a reduction in hyperfine field strength for carriers in the glassy phase due to increased structural disorder in the hydrogenated side chains, leading to longer spin coherence times. We acknowledge support by the Department of Energy, Office of Basic Energy Sciences under Award #DE-SC0000909.

Tuning Interfacial States Using Organic Molecules as Spin Filters

NASA Astrophysics Data System (ADS)

Deloach, Andrew; Wang, Jingying; Papa, Christopher M.; Myahkostupov, Mykhaylo; Castellano, Felix N.; Dougherty, Daniel B.; Jiang, Wei; Liu, Feng

Organic semiconductors are known to have long spin relaxation times which makes them a good candidate for spintronics. However, an issue with these materials is that at metal-organic interfaces there is a conductivity mismatch problem that suppresses spin injection. To overcome this, orbital mixing at the interface can be tuned with an organic spacer layer to promote the formation of spin polarized interface states. These states act as a ``spin filters'' and have been proposed as an explanation for the large tunneling magnetoresistance seen in devices using tris-(8-hydroxyquinolate)-aluminum(Alq3). Here, we show that the spin polarized interface states can be tuned from metallic to resistive by subtle changes in molecular orbitals. This is done using spin polarized scanning tunneling microscopy with three different tris-(8-hydroxyquinolate) compounds: aluminum, chromium, and iron. Differences in d-orbital mixing results in different mechanisms of interfacial coupling, giving rise to metallic or resistive interface states. Supported by the U.S. DoE award No. DE-SC0010324.

Spin resolved electronic transport through N@C20 fullerene molecule between Au electrodes: A first principles study

NASA Astrophysics Data System (ADS)

Caliskan, Serkan

2018-05-01

Using first principles study, through Density Functional Theory combined with Non Equilibrium Green's Function Formalism, electronic properties of endohedral N@C20 fullerene molecule joining Au electrodes (Au-N@C20) was addressed in the presence of spin property. The electronic transport behavior across the Au-N@C20 molecular junction was investigated by spin resolved transmission, density of states, molecular orbitals, differential conductance and current-voltage (I-V) characteristics. Spin asymmetric variation was clearly observed in the results due to single N atom encapsulated in the C20 fullerene cage, where the N atom played an essential role in the electronic behavior of Au-N@C20. This N@C20 based molecular bridge, exhibiting a spin dependent I-V variation, revealed a metallic behavior within the bias range from -1 V to 1 V. The induced magnetic moment, spin polarization and other relevant quantities associated with the spin resolved transport were elucidated.

Enhanced Tunnel Spin Injection into Graphene using Chemical Vapor Deposited Hexagonal Boron Nitride

PubMed Central

Kamalakar, M. Venkata; Dankert, André; Bergsten, Johan; Ive, Tommy; Dash, Saroj P.

2014-01-01

The van der Waals heterostructures of two-dimensional (2D) atomic crystals constitute a new paradigm in nanoscience. Hybrid devices of graphene with insulating 2D hexagonal boron nitride (h-BN) have emerged as promising nanoelectronic architectures through demonstrations of ultrahigh electron mobilities and charge-based tunnel transistors. Here, we expand the functional horizon of such 2D materials demonstrating the quantum tunneling of spin polarized electrons through atomic planes of CVD grown h-BN. We report excellent tunneling behavior of h-BN layers together with tunnel spin injection and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN tunnel contacts, we observe enhancements in both spin signal amplitude and lifetime by an order of magnitude. We demonstrate spin transport and precession over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our results and complementary magnetoresistance calculations illustrate that CVD h-BN tunnel barrier provides a reliable, reproducible and alternative approach to address the conductivity mismatch problem for spin injection into graphene. PMID:25156685

Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect

DOE PAGES

Sklenar, Joseph; Zhang, Wei; Jungfleisch, Matthias B.; ...

2015-11-06

We demonstrate the generation and detection of spin-torque ferromagnetic resonance in Pt/Y 3Fe 5O 12 (YIG) bilayers. A unique attribute of this system is that the spin Hall effect lies at the heart of both the generation and detection processes and no charge current is passing through the insulating magnetic layer. When the YIG undergoes resonance, a dc voltage is detected longitudinally along the Pt that can be described by two components. One is the mixing of the spin Hall magnetoresistance with the microwave current. The other results from spin pumping into the Pt being converted to a dc currentmore » through the inverse spin Hall effect. The voltage is measured with applied magnetic field directions that range in-plane to nearly perpendicular. In conclusion, we find that for magnetic fields that are mostly out-of-plane, an imaginary component of the spin mixing conductance is required to model our data.« less

Electronic and optical properties of double perovskite Ba2VMoO6: FP-LAPW study

NASA Astrophysics Data System (ADS)

Hnamte, Lalhriatpuia; Sandeep, Joshi, Himanshu; Thapa, R. K.

2018-05-01

The calculation is carried out using the FPLAPW method in the DFT framework within mBJ and LDA using the WIEN2k code. The investigation of electronic properties showed Ba2VMoO6 to be semi-metal in spin-up and insulation in spin down. In both spin up and spin down channel, direct band gap along with indirect band gap in ΓX direction was observed. For investigation of the optical transitions in this compound, the real and imaginary parts of the dielectric function, reflectivity, refractive index and optical conductivity of real and imaginary parts are calculated and analysed.

Antiferromagnetic resonance excited by oscillating electric currents

NASA Astrophysics Data System (ADS)

Sluka, Volker

2017-12-01

In antiferromagnetic materials the order parameter exhibits resonant modes at frequencies that can be in the terahertz range, making them interesting components for spintronic devices. Here, it is shown that antiferromagnetic resonance can be excited using the inverse spin-Hall effect in a system consisting of an antiferromagnetic insulator coupled to a normal-metal waveguide. The time-dependent interplay between spin torque, ac spin accumulation, and magnetic degrees of freedom is studied. It is found that the dynamics of the antiferromagnet affects the frequency-dependent conductivity of the normal metal. Further, a comparison is made between spin-current-induced and Oersted-field-induced excitation under the condition of constant power injection.

Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

NASA Technical Reports Server (NTRS)

Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

2015-01-01

The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163 (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The Orion MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a single-piece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment were the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

NASA Technical Reports Server (NTRS)

Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

2015-01-01

The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163, (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a singlepiece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment are the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

Spin-splitting calculation for zincblende semiconductors using an atomic bond-orbital model.

PubMed

Kao, Hsiu-Fen; Lo, Ikai; Chiang, Jih-Chen; Chen, Chun-Nan; Wang, Wan-Tsang; Hsu, Yu-Chi; Ren, Chung-Yuan; Lee, Meng-En; Wu, Chieh-Lung; Gau, Ming-Hong

2012-10-17

We develop a 16-band atomic bond-orbital model (16ABOM) to compute the spin splitting induced by bulk inversion asymmetry in zincblende materials. This model is derived from the linear combination of atomic-orbital (LCAO) scheme such that the characteristics of the real atomic orbitals can be preserved to calculate the spin splitting. The Hamiltonian of 16ABOM is based on a similarity transformation performed on the nearest-neighbor LCAO Hamiltonian with a second-order Taylor expansion k at the Γ point. The spin-splitting energies in bulk zincblende semiconductors, GaAs and InSb, are calculated, and the results agree with the LCAO and first-principles calculations. However, we find that the spin-orbit coupling between bonding and antibonding p-like states, evaluated by the 16ABOM, dominates the spin splitting of the lowest conduction bands in the zincblende materials.

Control of exciton spin statistics through spin polarization in organic optoelectronic devices

PubMed Central

Wang, Jianpu; Chepelianskii, Alexei; Gao, Feng; Greenham, Neil C.

2012-01-01

Spintronics based on organic semiconductor materials is attractive because of its rich fundamental physics and potential for device applications. Manipulating spins is obviously important for spintronics, and is usually achieved by using magnetic electrodes. Here we show a new approach where spin populations can be controlled primarily by energetics rather than kinetics. We find that exciton spin statistics can be substantially controlled by spin-polarizing carriers after injection using high magnetic fields and low temperatures, where the Zeeman energy is comparable with the thermal energy. By using this method, we demonstrate that singlet exciton formation can be suppressed by up to 53% in organic light-emitting diodes, and the dark conductance of organic photovoltaic devices can be increased by up to 45% due to enhanced formation of triplet charge-transfer states, leading to less recombination to the ground state. PMID:23149736

A feasibility study of developing toroidal tanks for a spinning spacecraft. Part 2: Evaluation of fluid behavior in spinning toroidal tanks

NASA Technical Reports Server (NTRS)

Anderson, J. E.

1974-01-01

An experimental program was conducted for the purpose of evaluating propellant behavior characteristics in spinning toroidal tanks. The effects of typical mission requirements, and related phenomena upon propellant slosh and settling, and orientation and stability of the ullage were investigated in a subscale model tank under both one-g and low-g acceleration environments. Specific conditions included were axial acceleration, spin rate, spinrate change, and spacecraft wobble, both singly and in combination. Methanol and water in combination with appropriate spin-rates and accelerations of the scale model system were used to simulate the behavior of fluorine, nitrogen tetroxide, monomethylhydrazine, and hydrazine. The experimental results indicate that no major fluid behavior problems would be encountered with the use of toroidal tanks containing any of the four propellants in a proposed spin-stabilized orbiter spacecraft.

Scanning nuclear resonance imaging of a hyperfine-coupled quantum Hall system.

PubMed

Hashimoto, Katsushi; Tomimatsu, Toru; Sato, Ken; Hirayama, Yoshiro

2018-06-07

Nuclear resonance (NR) is widely used to detect and characterise nuclear spin polarisation and conduction electron spin polarisation coupled by a hyperfine interaction. While the macroscopic aspects of such hyperfine-coupled systems have been addressed in most relevant studies, the essential role of local variation in both types of spin polarisation has been indicated in 2D semiconductor systems. In this study, we apply a recently developed local and highly sensitive NR based on a scanning probe to a hyperfine-coupled quantum Hall (QH) system in a 2D electron gas subject to a strong magnetic field. We succeed in imaging the NR intensity and Knight shift, uncovering the spatial distribution of both the nuclear and electron spin polarisation. The results reveal the microscopic origin of the nonequilibrium QH phenomena, and highlight the potential use of our technique in microscopic studies on various electron spin systems as well as their correlations with nuclear spins.

Selective equal spin Andreev reflection at vortex core center in magnetic semiconductor-superconductor heterostructure.

PubMed

Li, Chuang; Hu, Lun-Hui; Zhou, Yi; Zhang, Fu-Chun

2018-05-18

Sau, Lutchyn, Tewari and Das Sarma (SLTD) proposed a heterostructure consisting of a semiconducting thin film sandwiched between an s-wave superconductor and a magnetic insulator and showed possible Majorana zero mode. Here we study spin polarization of the vortex core states and spin selective Andreev reflection at the vortex center of the SLTD model. In the topological phase, the differential conductance at the vortex center contributed from the Andreev reflection, is spin selective and has a quantized value [Formula: see text] at zero bias. In the topological trivial phase, [Formula: see text] at the lowest quasiparticle energy of the vortex core is spin selective due to the spin-orbit coupling (SOC). Unlike in the topological phase, [Formula: see text] is suppressed in the Giaever limit and vanishes exactly at zero bias due to the quantum destruction interference.

Role of spin polarization in FM/Al/FM trilayer film at low temperature

NASA Astrophysics Data System (ADS)

Lu, Ning; Webb, Richard

2014-03-01

Measurements of electronic transport in diffusive FM/normal metal/FM trilayer film are performed at temperature ranging from 2K to 300K to determine the behavior of the spin polarized current in normal metal under the influence of quantum phase coherence and spin-orbital interaction. Ten samples of Hall bar with length of 200 micron and width of 20 micron are fabricated through e-beam lithography followed by e-gun evaporation of Ni0.8Fe0.2, aluminum and Ni0.8Fe0.2 with different thickness (5nm to 45nm) in vacuum. At low temperature of 4.2K, coherent backscattering, Rashba spin-orbital interaction and spin flip scattering of conduction electrons contribute to magnetoresistance at low field. Quantitative analysis of magnetoresistance shows transition between weak localization and weak anti-localization for samples with different thickness ratio, which indicates the spin polarization actually affects the phase coherence length and spin-orbital scattering length. However, at temperature between 50K and 300K, only the spin polarization dominates the magnetoresistance.

Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions

NASA Astrophysics Data System (ADS)

Anwar, M. S.; Lee, S. R.; Ishiguro, R.; Sugimoto, Y.; Tano, Y.; Kang, S. J.; Shin, Y. J.; Yonezawa, S.; Manske, D.; Takayanagi, H.; Noh, T. W.; Maeno, Y.

2016-10-01

Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics.

Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions

PubMed Central

Anwar, M. S.; Lee, S. R.; Ishiguro, R.; Sugimoto, Y.; Tano, Y.; Kang, S. J.; Shin, Y. J.; Yonezawa, S.; Manske, D.; Takayanagi, H.; Noh, T. W.; Maeno, Y.

2016-01-01

Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics. PMID:27782151

Iron spin transitions in the lower mantle

NASA Astrophysics Data System (ADS)

McCammon, C.; Dubrovinsky, L.; Potapkin, V.; Glazyrin, K.; Kantor, A.; Kupenko, I.; Prescher, C.; Sinmyo, R.; Smirnov, G.; Chumakov, A.; Rüffer, R.

2012-04-01

Iron has the ability to adopt different electronic configurations (spin states), which can significantly influence mantle properties and dynamics. It is now generally accepted as a result of studies over the past decade that ferrous iron in (Mg,Fe)O undergoes a high-spin to low-spin transition in the mid-part of the lower mantle; however results on (Mg,Fe)(Si,Al)O3 perovskite, the dominant phase of the lower mantle, remain controversial. Identifying spin transitions in (Mg,Fe)(Si,Al)O3 perovskite presents a significant challenge. X-ray emission spectroscopy provides information on the bulk spin number, but cannot separate individual contributions. Nuclear forward scattering measures hyperfine interactions, but is not well suited to complex materials due to the non-uniqueness of fitting models. Energy-domain Mössbauer spectroscopy generally enables an unambiguous resolution of all hyperfine parameters which can be used to infer spin states; however high pressure measurements using conventional radioactive point sources require extremely long counting times. To solve this problem, we have developed an energy-domain synchrotron Mössbauer source that enables rapid measurement of spectra under extreme conditions (both high pressure and high temperature) with a quality generally sufficient to unambiguously deconvolute even highly complex spectra. We have used the newly developed method to measure high quality Mössbauer spectra of different compositions of (Mg,Fe)O and (Mg,Fe)(Si,Al)O3 perovskite at pressures up to 122 GPa and temperatures up to 2400 K. Experiments were carried out at the European Synchrotron Radiation Facility on the nuclear resonance beamline ID18 equipped with a portable laser heating system for diamond anvil cells. Our results confirm previous observations for (Mg,Fe)O that show a broad spin crossover region at high pressures and high temperatures, and show unambiguously that ferric iron in (Mg,Fe)(Si,Al)O3 perovskite remains in the high-spin state at conditions throughout the lower mantle. Electrical conductivity data of (Mg,Fe)(Si,Al)O3 perovskite are known to show a drop in conductivity above 50 GPa, which combined with our new results suggests that the currently controversial high-pressure transition of ferrous iron is indeed due to a high-spin to intermediate-spin transition at conditions near the top of the lower mantle. Our current picture of iron in the lower mantle is therefore of a relatively homogeneous spin state in (Mg,Fe)(Si,Al)O3 perovskite throughout most of the lower mantle: intermediate-spin ferrous iron and high-spin ferric iron. Different spin states are expected in ferrous iron in (Mg,Fe)(Si,Al)O3 perovskite only at the very top of the lower mantle (high spin) and at the very bottom (low spin). There is a broad transition from high-spin to low-spin ferrous iron in (Mg,Fe)O in the mid part of the lower mantle. Implications of these results for mantle properties and dynamics will be presented.

Thermoelectric effects in superconductor-ferromagnet tunnel junctions on europium sulfide

NASA Astrophysics Data System (ADS)

Kolenda, S.; Sürgers, C.; Fischer, G.; Beckmann, D.

2017-06-01

We report on large thermoelectric effects in superconductor-ferromagnet tunnel junctions in proximity contact with the ferromagnetic insulator europium sulfide. The combination of a spin-splitting field and spin-polarized tunnel conductance in these systems breaks the electron-hole symmetry and leads to spin-dependent thermoelectric currents. We show that the exchange splitting induced by europium sulfide boosts the thermoelectric effect in small applied fields and can therefore eliminate the need to apply large magnetic fields, which might otherwise impede applications in thermometry or cooling.

Antiferromagnetic domain wall as spin wave polarizer and retarder.

PubMed

Lan, Jin; Yu, Weichao; Xiao, Jiang

2017-08-02

As a collective quasiparticle excitation of the magnetic order in magnetic materials, spin wave, or magnon when quantized, can propagate in both conducting and insulating materials. Like the manipulation of its optical counterpart, the ability to manipulate spin wave polarization is not only important but also fundamental for magnonics. With only one type of magnetic lattice, ferromagnets can only accommodate the right-handed circularly polarized spin wave modes, which leaves no freedom for polarization manipulation. In contrast, antiferromagnets, with two opposite magnetic sublattices, have both left and right-circular polarizations, and all linear and elliptical polarizations. Here we demonstrate theoretically and confirm by micromagnetic simulations that, in the presence of Dzyaloshinskii-Moriya interaction, an antiferromagnetic domain wall acts naturally as a spin wave polarizer or a spin wave retarder (waveplate). Our findings provide extremely simple yet flexible routes toward magnonic information processing by harnessing the polarization degree of freedom of spin wave.Spin waves are promising candidates as carriers for energy-efficient information processing, but they have not yet been fully explored application wise. Here the authors theoretically demonstrate that antiferromagnetic domain walls are naturally spin wave polarizers and retarders, two key components of magnonic devices.

To perform a gyro test of general relativity in a satellite and develop associated control technology

NASA Technical Reports Server (NTRS)

Fairbank, W. M.; Everitt, C. W. F.; Debra, D. B.

1974-01-01

Performance tests of gyroscope operations and gyroscope readout equipment are discussed. The gyroscope was tested for 400 hours at liquid helium temperatures with spin speeds up to 30 Hz. Readout by observing trapped magnetic flux in the spinning rotor with a sensitive magnetometer was accomplished. Application of the gyroscope to space probes and shuttle vehicles.

Enhancement of the thermoelectric figure of merit in a ferromagnet-quantum dot-superconductor device due to intradot spin-flip scattering and ac field

NASA Astrophysics Data System (ADS)

Xu, Wei-Ping; Zhang, Yu-Ying; Li, Zhi-Jian; Nie, Yi-Hang

2017-08-01

We investigate the thermoelectric properties of a ferromagnet-quantum dot-superconductor hybrid system with the intradot spin-flip scattering and the external microwave field. The results indicate that the increase of figure of merit in the gap is very slight when the spin-flip scattering strength increases, but outside the gap it significantly increases with enhancing spin-flip scattering strength. The presence of microwave field results in photon-assisted Andreev reflection and induces the satellite peaks in conductance spectrum. The appropriate match of spin-flip scattering strength, microwave field strength and frequency can significantly enhances the figure of merit of thermoelectric conversion of the device, which can be used as a scheme improving thermoelectric efficiency using microwave frequency.

Antigravity: Spin-gravity coupling in action

NASA Astrophysics Data System (ADS)

Plyatsko, Roman; Fenyk, Mykola

2016-08-01

The typical motions of a spinning test particle in Schwarzschild's background which show the strong repulsive action of the highly relativistic spin-gravity coupling are considered using the exact Mathisson-Papapetrou equations. An approximated approach to choice solutions of these equations which describe motions of the particle's proper center of mass is developed.

Fabricating continuous electroconductive polyacrylonitrile fibers with thermosensitive property via wet-spinning

NASA Astrophysics Data System (ADS)

Liu, Wanwan; Jin, Yang; Wang, Yangyi; Ge, Mingqiao; Gao, Qiang

2017-12-01

In this work, conductive polyacrylonitrile (PAN) composite fiber with thermosensitive property was successfully prepared via wet-spinning. Thermochromic pigment (TCP) microsphere capsules were applied to manufacture color-changing fibers. Meanwhile, light-colored conductive whiskers (ATO@TiO2) were employed to endow polyacrylonitrile fibers with conductivity without prejudicing their thermosensitive property. Interestingly, unlike other conductive fibers in dark color, this kind of conductive composite fiber can be dyed by thermosensitive pigment. The obtained composite fiber containing 20 vol% ATO@TiO2 whiskers shows a resistivity of 105 Ω · cm and could generate heat by Joule heating when being applied under a certain voltage. The composite fiber shows a red color at room temperature, while the color of the composite fiber fades gradually and finally becomes white as temperature rise. This simple and cost-effective approach is expected to inspire more research into the applications of multifunctional conductive fibers.

Design and fabrication of prototype system for early warning of impending bearing failure

NASA Technical Reports Server (NTRS)

Meacher, J.; Chen, H. M.

1974-01-01

A test program was conducted with the objective of developing a method and equipment for on-line monitoring of installed ball bearings to detect deterioration or impending failure of the bearings. The program was directed at the spin-axis bearings of a control moment gyro. The bearings were tested at speeds of 6000 and 8000 rpm, thrust loads from 50 to 1000 pounds, with a wide range of lubrication conditions, with and without a simulated fatigue spall implanted in the inner race ball track. It was concluded that a bearing monitor system based on detection and analysis of modulations of a fault indicating bearing resonance frequency can provide a low threshold of sensitivity.

Commander Lousma with Bubble Separation Experiment

NASA Image and Video Library

1982-03-31

S82-28914 (26 March 1982) --- Astronaut Jack R. Lousma, STS-3 commander, spins a package of colored liquid in zero-gravity aboard the Earth-orbiting space shuttle Columbia. He was actually creating a centrifuge to conduct a test involving the separation of bubbles from the liquid rehydrated strawberry powder for visible clarity. The gas from liquid experiment is a test devised by scientist-astronaut William E. Thornton. The gun-like device at center of left edge is a water-dispenser which the astronauts use in rehydrating food packets, many of which can be seen in the background of this middeck area of the Columbia. Astronaut C. Gordon Fullerton, pilot, exposed this frame with a 35mm camera. Photo credit: NASA

Spinning angle optical calibration apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beer, S.K.; Pratt, H.R. II.

1989-09-12

An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting and accurate reproducing of spinning magic angles in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the magic angle of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation ormore » graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning magic angle of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position. 2 figs.« less

Using high pressure to study thermal transport and phonon scattering mechanisms

NASA Astrophysics Data System (ADS)

Hohensee, Gregory Thomas

The aerospace industry studies nanocomposites for heat dissipation and moderation of thermal expansion, and the semiconductor industry faces a Joule heating barrier in devices with high power density. My primary experimental tools are the diamond anvil cell (DAC) coupled with time-domain thermoreflectance (TDTR). TDTR is a precise optical method well-suited to measuring thermal conductivities and conductances at the nanoscale and across interfaces. The DAC-TDTR method yields thermal property data as a function of pressure, rather than temperature. This relatively unexplored independent variable can separate the components of thermal conductance and serve as an independent test for phonon-defect scattering models. I studied the effect of non-equilibrium thermal transport at the aluminum-coated surface of an exotic cuprate material Ca9La5Cu 24O41, which boasts a tenfold enhanced thermal conductivity along one crystalline axis where two-leg copper-oxygen spin-ladder structures carry heat in the form of thermalized magnetic excitations. Highly anisotropic materials are of interest for controlled thermal management applications, and the spin-ladder magnetic heat carriers ("magnons") are not well understood. I found that below room temperature, the apparent thermal conductivity of Ca9La5Cu24O41 depends on the frequency of the applied surface heating in TDTR. This occurs because the thermal penetration depth in the TDTR experiment is comparable to the length-scale for the equilibration of the magnons that are the dominant channel for heat conduction and the phonons that dominate the heat capacity. I applied a two-temperature model to analyze the TDTR data and extracted an effective volumetric magnon-phonon coupling parameter g for Ca9La5Cu24O 41 at temperatures from 75 K to 300 K; g varies by approximately two orders of magnitude over this range of temperature and has the value g = 1015 W m-3 K-1 near the peak of the thermal conductivity at T ≈ 180 K. To examine intrinsic phonon-mediated interface conductance between dissimilar materials, I applied DAC-TDTR to measure the thermal conductance of a series of metal-diamond interfaces as a function of pressure up to 50 GPa. The thermal conductance of interfaces between metals and diamond, which has a comparatively high Debye temperature, is often greater than can be accounted for by two phonon-processes, and the nature of heat transport between such dissimilar materials is central to the thermal design of composite materials. The high pressures achievable in a diamond anvil cell can significantly extend the metal phonon density of states to higher frequencies, and can also suppress extrinsic effects by greatly stiffening interface bonding. I measured the interface thermal conductances of Pb, Au0.95Pd0.05, Pt, and Al films deposited on Type 1A natural [100] and Type 2A synthetic [110] diamond anvils, from ambient pressure to 50 GPa. In all cases, the thermal conductances increase weakly or saturate to similar values at high pressure. My results suggest that anharmonic conductance at metal-diamond interfaces is controlled by partial transmission processes, where a diamond phonon that inelastically scatters at the interface absorbs or emits a metal phonon. The thermal conductivity and absolute electrical resistivity of metallic silicon have not been measured previously. I performed regular and beam-offset TDTR to establish the thermal conductivities of Si and Si0.991Ge 0.009 across the semiconductor-metal phase transition and up to 45 GPa. The thermal conductivities of metallic Si and Si(Ge) are comparable to aluminum and indicative of predominantly electronic heat carriers. Metallic Si and Si(Ge) have a transport anisotropy of approximately 1.4, similar to that of beryllium, due to the primitive hexagonal crystal structure. I used the Wiedemann-Franz law to derive the associated electrical resistivity, and found it consistent with the Bloch-Gruneisen model. Not all crystalline point defects are alike in how they scatter phonons and reduce the thermal conductivity of mixed crystals. Heat-carrying phonons in iron (Fe) doped MgO, or [Mg,Fe]O ferropericlase, are known to be resonantly scattered by interaction with a 3.3 THz electronic transition in the high-spin state of the Fe impurities. At sufficiently high pressures, the Fe atoms transition from a high-spin to a low-spin state, which eliminates the resonant interaction and reduces the Fe atoms to simpler point defect phonon scatterers. To study the behavior of phonon-defect scattering with and without this resonant scattering process, I measured the thermal conductivity of Mg0.92Fe0.08 O ferropericlase up to and above the 40--60 GPa spin transition. Fe-doped MgO (ferropericlase) is also a model system relevant to geophysical modeling of the Earth's core-mantle boundary, so data on its thermal transport under pressure is valuable in itself. (Abstract shortened by UMI.).

Spin relaxation in semiconductor quantum rings and dots--a comparative study.

PubMed

Zipper, Elżbieta; Kurpas, Marcin; Sadowski, Janusz; Maśka, Maciej M

2011-03-23

We calculate spin relaxation times due to spin-orbit-mediated electron-phonon interactions for experimentally accessible semiconductor quantum ring and dot architectures. We elucidate the differences between the two systems due to different confinement. The estimated relaxation times (at B = 1 T) are in the range between a few milliseconds to a few seconds. This high stability of spin in a quantum ring allows us to test it as a spin qubit. A brief discussion of quantum state manipulations with such a qubit is presented.

Spin contribution to the ponderomotive force in a plasma.

PubMed

Brodin, G; Misra, A P; Marklund, M

2010-09-03

The concept of a ponderomotive force due to the intrinsic spin of electrons is developed. An expression containing both the classical as well as the spin-induced ponderomotive force is derived. The results are used to demonstrate that an electromagnetic pulse can induce a spin-polarized plasma. Furthermore, it is shown that, for certain parameters, the nonlinear backreaction on the electromagnetic pulse from the spin magnetization current can be larger than that from the classical free current. Suitable parameter values for a direct test of this effect are presented.

Lieb-Robinson bounds for spin-boson lattice models and trapped ions.

PubMed

Jünemann, J; Cadarso, A; Pérez-García, D; Bermudez, A; García-Ripoll, J J

2013-12-06

We derive a Lieb-Robinson bound for the propagation of spin correlations in a model of spins interacting through a bosonic lattice field, which satisfies a Lieb-Robinson bound in the absence of spin-boson couplings. We apply these bounds to a system of trapped ions and find that the propagation of spin correlations, as mediated by the phonons of the ion crystal, can be faster than the regimes currently explored in experiments. We propose a scheme to test the bounds by measuring retarded correlation functions via the crystal fluorescence.

A proposed experimental diagnosing of specular Andreev reflection using the spin orbit interaction

PubMed Central

Yang, Yanling; Zhao, Bing; Zhang, Ziyu; Bai, Chunxu; Xu, Xiaoguang; Jiang, Yong

2016-01-01

Based on the Dirac-Bogoliubov-de Gennes equation, we theoretically investigate the chirality-resolved transport properties through a superconducting heterojunction in the presence of both the Rashba spin orbit interaction (RSOI) and the Dresselhaus spin orbit interaction (DSOI). Our results show that, if only the RSOI is present, the chirality-resolved Andreev tunneling conductance can be enhanced in the superconducting gap, while it always shows a suppression effect for the case of the DSOI alone. In contrast to the similar dependence of the specular Andreev zero bias tunneling conductance on the SOI, the retro-Andreev zero bias tunneling conductance exhibit the distinct dependence on the RSOI and the DSOI. Moreover, the zero-bias tunneling conductances for the retro-Andreev reflection (RAR) and the specular Andreev reflection (SAR) also show a qualitative difference with respect to the barrier parameters. When the RSOI and the DSOI are finite, three orders of magnitude enhancement of specular Andreev tunneling conductance is revealed. Furthermore, by analyzing the balanced SOI case, we find that the RAR is in favor of a parabolic dispersion, but a linear dispersion is highly desired for the SAR. These results shed light on the diagnosing of the SAR in graphene when subjected to both kinds of SOI. PMID:27388426

Spin Currents and Spin Orbit Torques in Ferromagnets and Antiferromagnets

NASA Astrophysics Data System (ADS)

Hung, Yu-Ming

This thesis focuses on the interactions of spin currents and materials with magnetic order, e.g., ferromagnetic and antiferromagnetic thin films. The spin current is generated in two ways. First by spin-polarized conduction-electrons associated with the spin Hall effect in heavy metals (HMs) and, second, by exciting spin-waves in ferrimagnetic insulators using a microwave frequency magnetic field. A conduction-electron spin current can be generated by spin-orbit coupling in a heavy non-magnetic metal and transfer its spin angular momentum to a ferromagnet, providing a means of reversing the magnetization of perpendicularly magnetized ultrathin films with currents that flow in the plane of the layers. The torques on the magnetization are known as spin-orbit torques (SOT). In the first part of my thesis project I investigated and contrasted the quasistatic (slowly swept current) and pulsed current-induced switching characteristics of micrometer scale Hall crosses consisting of very thin (<1 nm) perpendicularly magnetized CoFeB layers on beta-Ta. While complete magnetization reversal occurs at a threshold current density in the quasistatic case, pulses with short duration (≤10 ns) and larger amplitude (≃10 times the quasistatic threshold current) lead to only partial magnetization reversal and domain formation. The partial reversal is associated with the limited time for reversed domain expansion during the pulse. The second part of my thesis project studies and considers applications of SOT-driven domain wall (DW) motion in a perpendicularly magnetized ultrathin ferromagnet sandwiched between a heavy metal and an oxide. My experiment results demonstrate that the DW motion can be explained by a combination of the spin Hall effect, which generates a SOT, and Dzyaloshinskii-Moriya interaction, which stabilizes chiral Neel-type DW. Based on SOT-driven DW motion and magnetic coupling between electrically isolated ferromagnetic elements, I proposed a new type of spin logic devices. I then demonstrate the device operation by using micromagnetic modeling which involves studying the magnetic coupling induced by fringe fields from chiral DWs in perpendicularly magnetized nanowires. The last part of my thesis project reports spin transport and spin-Hall magnetoresistance (SMR) in yttrium iron garnet Y3Fe5O 12 (YIG)/NiO/Pt trilayers with varied NiO thickness. To characterize the spin transport through NiO we excite ferromagnetic resonance in YIG with a microwave frequency magnetic field and detect the voltage associated with the inverse spin-Hall effect (ISHE) in the Pt layer. The ISHE signal is found to decay exponentially with the NiO thickness with a characteristic decay length of 3.9 nm. However, in contrast to the ISHE response, as the NiO thickness increases the SMR signal goes towards zero abruptly at a NiO thickness of 4 nm, highlighting the different length scales associated with the spin-transport in NiO and SMR in such trilayers.

Asteroid spin and shape modelling using two lightcurve inversion methods

NASA Astrophysics Data System (ADS)

Marciniak, Anna; Bartczak, Przemyslaw; Konstanciak, Izabella; Dudzinski, Grzegorz; Mueller, Thomas G.; Duffard, Rene

2016-10-01

We are conducting an observing campaign to counteract strong selection effects in photometric studies of asteroids. Our targets are long-period (P>12 hours) and low-amplitude (a_max<0.25 mag) asteroids, that although numerous, have poor lightcurve datasets (Marciniak et al. 2015, PSS 118, 256). As a result such asteroids are very poorly studied in terms of their spins and shapes. Our campaign targets a sample of around 100 bright (H<11 mag) main belt asteroids sharing both of these features, resulting in a few tens of new composite lightcurves each year. At present the data gathered so far allowed to construct detailed models for the shape and spin for about ten targets.In this study we perform spin and shape modelling using two lightcurve inversion methods: convex inversion (Kaasalainen et al. 2001, Icarus, 153, 37) and nonconvex SAGE modelling algorithm (Shaping Asteroids with Genetic Evolution, Bartczak et al. 2014, MNRAS, 443, 1802). These two methods are independent from each other, and are based on different assumptions for the shape.Thus, the results obtained on the same datasets provide a cross-check of both the methods and the resulting spin and shape models. The results for the spin solutions are highly consistent, and the shape models are similar, though the ones from SAGE algorithm provide more details of the surface features. Nonconvex shape produced by SAGE have been compared with direct images from spacecrafts and the first results for targets like Eros or Lutetia (Batczak et al. 2014, ACM conf. 29B) provide a high level of agreement.Another way of validation is the shape model comparison with the asteroid shape contours obtained using different techniques (like the stellar occultation timings or adaptive optics imaging) or against data in thermal infrared range gathered by ground and space-bound observatories. The thermal data could provide assignment of size and albedo, but also can help to resolve spin-pole ambiguities. In special cases, the thermal data from Spitzer and Wise/NEOWise might even help in testing specific shape features via thermal infrared lightcurves.

Probing Nuclear Spin Effects on Electronic Spin Coherence via EPR Measurements of Vanadium(IV) Complexes.

PubMed

Graham, Michael J; Krzyaniak, Matthew D; Wasielewski, Michael R; Freedman, Danna E

2017-07-17

Quantum information processing (QIP) has the potential to transform numerous fields from cryptography, to finance, to the simulation of quantum systems. A promising implementation of QIP employs unpaired electronic spins as qubits, the fundamental units of information. Though molecular electronic spins offer many advantages, including chemical tunability and facile addressability, the development of design principles for the synthesis of complexes that exhibit long qubit superposition lifetimes (also known as coherence times, or T 2 ) remains a challenge. As nuclear spins in the local qubit environment are a primary cause of shortened superposition lifetimes, we recently conducted a study which employed a modular spin-free ligand scaffold to place a spin-laden propyl moiety at a series of fixed distances from an S = 1 / 2 vanadium(IV) ion in a series of vanadyl complexes. We found that, within a radius of 4.0(4)-6.6(6) Å from the metal center, nuclei did not contribute to decoherence. To assess the generality of this important design principle and test its efficacy in a different coordination geometry, we synthesized and investigated three vanadium tris(dithiolene) complexes with the same ligand set employed in our previous study: K 2 [V(C 5 H 6 S 4 ) 3 ] (1), K 2 [V(C 7 H 6 S 6 ) 3 ] (2), and K 2 [V(C 9 H 6 S 8 ) 3 ] (3). We specifically interrogated solutions of these complexes in DMF-d 7 /toluene-d 8 with pulsed electron paramagnetic resonance spectroscopy and electron nuclear double resonance spectroscopy and found that the distance dependence present in the previously synthesized vanadyl complexes holds true in this series. We further examined the coherence properties of the series in a different solvent, MeCN-d 3 /toluene-d 8 , and found that an additional property, the charge density of the complex, also affects decoherence across the series. These results highlight a previously unknown design principle for augmenting T 2 and open new pathways for the rational synthesis of complexes with long coherence times.

Flight test experience with high-alpha control system techniques on the F-14 airplane

NASA Technical Reports Server (NTRS)

Gera, J.; Wilson, R. J.; Enevoldson, E. K.; Nguyen, L. T.

1981-01-01

Improved handling qualities of fighter aircraft at high angles of attack can be provided by various stability and control augmentation techniques. NASA and the U.S. Navy are conducting a joint flight demonstration of these techniques on an F-14 airplane. This paper reports on the flight test experience with a newly designed lateral-directional control system which suppresses such high angle of attack handling qualities problems as roll reversal, wing rock, and directional divergence while simultaneously improving departure/spin resistance. The technique of integrating a piloted simulation into the flight program was used extensively in this program. This technique had not been applied previously to high angle of attack testing and required the development of a valid model to simulate the test airplane at extremely high angles of attack.

Factorization and resummation: A new paradigm to improve gravitational wave amplitudes. II. The higher multipolar modes

NASA Astrophysics Data System (ADS)

Messina, Francesco; Maldarella, Alberto; Nagar, Alessandro

2018-04-01

The factorization and resummation approach of Nagar and Shah [Phys. Rev. D 94, 104017 (2016), 10.1103/PhysRevD.94.104017], designed to improve the strong-field behavior of the post-Newtonian (PN) residual waveform amplitudes fℓm's entering the effective-one-body, circularized, gravitational waveform for spinning coalescing binaries, is improved and generalized here to all multipoles up to ℓ=6 . For a test particle orbiting a Kerr black hole, each multipolar amplitude is truncated at relative 6 PN order, both for the orbital (nonspinning) and spin factors. By taking a certain Padé approximant (typically the P24 one) of the orbital factor in conjunction with the inverse Taylor (iResum) representation of the spin factor, it is possible to push the analytical/numerical agreement of the energy flux at the level of 5% at the last-stable orbit for a quasimaximally spinning black hole with dimensionless spin parameter +0.99 . When the procedure is generalized to comparable-mass binaries, each orbital factor is kept at relative 3+3 PN order; i.e., the globally 3 PN-accurate comparable-mass terms are hybridized with higher-PN test-particle terms up to 6 PN relative order in each mode. The same Padé resummation is used for continuity. By contrast, the spin factor is only kept at the highest comparable-mass PN order currently available. We illustrate that the consistency between different truncations in the spin content of the waveform amplitudes is more marked in the resummed case than when using the standard Taylor-expanded form of Pan et al. [Phys. Rev. D 83, 064003 (2011), 10.1103/PhysRevD.83.064003]. We finally introduce a method to consistently hybridize comparable-mass and test-particle information also in the presence of spin (including the spin of the particle), discussing it explicitly for the ℓ=m =2 spin-orbit and spin-square terms. The improved, factorized and resummed, multipolar waveform amplitudes presented here are expected to set a new standard for effective one body-based gravitational waveform models.

SU (N ) spin-wave theory: Application to spin-orbital Mott insulators

NASA Astrophysics Data System (ADS)

Dong, Zhao-Yang; Wang, Wei; Li, Jian-Xin

2018-05-01

We present the application of the SU (N ) spin-wave theory to spin-orbital Mott insulators whose ground states exhibit magnetic orders. When taking both spin and orbital degrees of freedom into account rather than projecting Hilbert space onto the Kramers doublet, which is the lowest spin-orbital locked energy levels, the SU (N ) spin-wave theory should take the place of the SU (2 ) one due to the inevitable spin-orbital multipole exchange interactions. To implement the application, we introduce an efficient general local mean-field method, which involves all local fluctuations, and develop the SU (N ) linear spin-wave theory. Our approach is tested firstly by calculating the multipolar spin-wave spectra of the SU (4 ) antiferromagnetic model. Then, we apply it to spin-orbital Mott insulators. It is revealed that the Hund's coupling would influence the effectiveness of the isospin-1 /2 picture when the spin-orbital coupling is not large enough. We further carry out the SU (N ) spin-wave calculations of two materials, α -RuCl3 and Sr2IrO4 , and find that the magnonic and spin-orbital excitations are consistent with experiments.

Spin of Planetary Probes in Atmospheric Flight

NASA Astrophysics Data System (ADS)

Lorenz, R. D.

Probes that enter planetary atmospheres are often spun during entry or descent for a variety of reasons. Their spin rate histories are influenced by often subtle effects. The spin requirements, control methods and flight experience from planetary and earth entry missions are reviewed. An interaction of the probe aerodynamic wake with a drogue parachute, observed in Gemini wind tunnel tests, is discussed in connection with the anomalous spin behaviour of the Huygens probe.

Testing of a Loop Heat Pipe Subjective to Variable Accelerations. Part 2; Temperature Stability

NASA Technical Reports Server (NTRS)

Ku, Jentung; Ottenstein, Laura; Kaya, Taril; Rogers, Paul; Hoff, Craig

2000-01-01

The effect of accelerating forces on the performance of loop heat pipes (LHP) is of interest and importance to terrestrial and space applications. LHP's are being considered for cooling of military combat vehicles and for spinning spacecraft. In order to investigate the effect of an accelerating force on LHP operation, a miniature LHP was installed on a spin table. Variable accelerating forces were imposed on the LHP by spinning the table at different angular speeds. Several patterns of accelerating forces were applied, i.e. continuous spin at different speeds and periodic spin at different speeds and frequencies. The resulting accelerations ranged from 1.17 g's to 4.7 g's. This paper presents the second part of the experimental study, i.e. the effect of an accelerating force on the LHP operating temperature. It has been known that in stationary tests the LHP operating temperature is a function of the evaporator power and the condenser sink temperature when the compensation temperature is not actively controlled. Results of this test program indicate that any change in the accelerating force will result in a chance in the LHP operating temperature through its influence on the fluid distribution in the evaporator, condenser and compensation chamber. However, the effect is not universal, rather it is a function of other test conditions. A steady, constant acceleration may result in an increase or decrease of the operating temperature, while a periodic spin will lead to a quasi-steady operating temperature over a sufficient time interval. In addition, an accelerating force may lead to temperature hysteresis and changes in the temperature oscillation. In spite of all these effects, the LHP continued to operate without any problems in all tests.

Advanced radial inflow turbine rotor program: Design and dynamic testing

NASA Technical Reports Server (NTRS)

Rodgers, C.

1976-01-01

The advancement of small, cooled, radial inflow turbine technology in the area of operation at higher turbine inlet temperature is discussed. The first step was accomplished by designing, fabricating, and subjecting to limited mechanical testing an advanced gas generator rotating assembly comprising a radial inflow turbine and two-stage centrifugal compressor. The radial inflow turbine and second-stage compressor were designed as an integrally machined monorotor with turbine cooling taking place basically by conduction to the compressor. Design turbine inlet rotor gas temperature, rotational speed, and overall gas generator compressor pressure ratio were 1422 K (2560 R), 71,222 rpm, and 10/1 respectively. Mechanical testing on a fabricated rotating assembly and bearing system covered 1,000 cold start/stop cycles and three spins to 120 percent design speed (85,466 rpm).

Magnetic Suspension for Dynamic Spin Rig

NASA Technical Reports Server (NTRS)

Johnson, Dexter

1998-01-01

NASA Lewis Research Center's Dynamic Spin Rig, located in Building 5, Test Cell CW-18, is used to test turbomachinery blades and components by rotating them in a vacuum chamber. A team from Lewis' Machine Dynamics Branch successfully integrated a magnetic bearing and control system into the Dynamic Spin Rig. The magnetic bearing worked very well both to support and shake the shaft. It was demonstrated that the magnetic bearing can transmit more vibrational energy into the shaft and excite some blade modes to larger amplitudes than the existing electromagnetic shakers can.

Payload spin assembly for the commercial Titan launch vehicle

NASA Technical Reports Server (NTRS)

Robinson, Wilf; Pech, Greg

1991-01-01

A contract was completed to design, build, and test a Payload Spin Assembly (PSA) for installation onto the Martin Marietta Titan 3 Commercial launch vehicle. This assembly provides launch support for satellite payloads up to 5783 kilograms (6.37 tons) and controls release, spin-up, and final separation of the satellite from the second stage. Once separated, the satellite's Perigee Kick Motor (PKM) boosts the satellite into its transfer orbit. The first successful flight occurred December 31, 1989. Requirements, design, test, and problems associated with this mechanical assembly are discussed.

Thrust and torque vector characteristics of axially-symmetric E-sail

NASA Astrophysics Data System (ADS)

Bassetto, Marco; Mengali, Giovanni; Quarta, Alessandro A.

2018-05-01

The Electric Solar Wind Sail is an innovative propulsion system concept that gains propulsive acceleration from the interaction with charged particles released by the Sun. The aim of this paper is to obtain analytical expressions for the thrust and torque vectors of a spinning sail of given shape. Under the only assumption that each tether belongs to a plane containing the spacecraft spin axis, a general analytical relation is found for the thrust and torque vectors as a function of the spacecraft attitude relative to an orbital reference frame. The results are then applied to the noteworthy situation of a Sun-facing sail, that is, when the spacecraft spin axis is aligned with the Sun-spacecraft line, which approximatively coincides with the solar wind direction. In that case, the paper discusses the equilibrium shape of the generic conducting tether as a function of the sail geometry and the spin rate, using both a numerical and an analytical (approximate) approach. As a result, the structural characteristics of the conducting tether are related to the spacecraft geometric parameters.

Valence and spin states of iron are invisible in Earth’s lower mantle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiachao; Dorfman, Susannah M.; Zhu, Feng

Heterogeneity in Earth’s mantle is a record of chemical and dynamic processes over Earth’s history. The geophysical signatures of heterogeneity can only be interpreted with quantitative constraints on effects of major elements such as iron on physical properties including density, compressibility, and electrical conductivity. However, deconvolution of the effects of multiple valence and spin states of iron in bridgmanite (Bdg), the most abundant mineral in the lower mantle, has been challenging. Here we show through a study of a ferric-iron-only (Mg 0.46Fe 3+0.53)(Si 0.49Fe 3+ 0.51)O 3 Bdg that Fe 3+ in the octahedral site undergoes a spin transition betweenmore » 43 and 53 GPa at 300 K. The resolved effects of the spin transition on density, bulk sound velocity, and electrical conductivity are smaller than previous estimations, consistent with the smooth depth profiles from geophysical observations. For likely mantle compositions, the valence state of iron has minor effects on density and sound velocities relative to major cation composition.« less

Valence and spin states of iron are invisible in Earth’s lower mantle

DOE PAGES

Liu, Jiachao; Dorfman, Susannah M.; Zhu, Feng; ...

2018-03-29

Heterogeneity in Earth’s mantle is a record of chemical and dynamic processes over Earth’s history. The geophysical signatures of heterogeneity can only be interpreted with quantitative constraints on effects of major elements such as iron on physical properties including density, compressibility, and electrical conductivity. However, deconvolution of the effects of multiple valence and spin states of iron in bridgmanite (Bdg), the most abundant mineral in the lower mantle, has been challenging. Here we show through a study of a ferric-iron-only (Mg 0.46Fe 3+0.53)(Si 0.49Fe 3+ 0.51)O 3 Bdg that Fe 3+ in the octahedral site undergoes a spin transition betweenmore » 43 and 53 GPa at 300 K. The resolved effects of the spin transition on density, bulk sound velocity, and electrical conductivity are smaller than previous estimations, consistent with the smooth depth profiles from geophysical observations. For likely mantle compositions, the valence state of iron has minor effects on density and sound velocities relative to major cation composition.« less

Is perpendicular magnetic anisotropy essential to all-optical ultrafast spin reversal in ferromagnets?

NASA Astrophysics Data System (ADS)

Zhang, G. P.; Bai, Y. H.; George, Thomas F.

2017-10-01

All-optical spin reversal presents a new opportunity for spin manipulations, free of a magnetic field. Most of all-optical-spin-reversal ferromagnets are found to have a perpendicular magnetic anisotropy (PMA), but it has been unknown whether PMA is necessary for spin reversal. Here we theoretically investigate magnetic thin films with either PMA or in-plane magnetic anisotropy (IMA). Our results show that spin reversal in IMA systems is possible, but only with a longer laser pulse and within a narrow laser parameter region. Spin reversal does not show a strong helicity dependence where the left- and right-circularly polarized light lead to the identical results. By contrast, the spin reversal in PMA systems is robust, provided both the spin angular momentum and laser field are strong enough while the magnetic anisotropy itself is not too strong. This explains why experimentally the majority of all-optical spin-reversal samples are found to have strong PMA and why spins in Fe nanoparticles only cant out of plane. It is the laser-induced spin-orbit torque that plays a key role in the spin reversal. Surprisingly, the same spin-orbit torque results in laser-induced spin rectification in spin-mixed configuration, a prediction that can be tested experimentally. Our results clearly point out that PMA is essential to spin reversal, though there is an opportunity for in-plane spin reversal.

The effect of inertia on the Dirac electron, the spin Hall current and the momentum space Berry curvature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhury, Debashree, E-mail: debashreephys@gmail.com; Basu, B., E-mail: sribbasu@gmail.com

2013-02-15

We have studied the spin dependent force and the associated momentum space Berry curvature in an accelerating system. The results are derived by taking into consideration the non-relativistic limit of a generally covariant Dirac equation with an electromagnetic field present, where the methodology of the Foldy-Wouthuysen transformation is applied to achieve the non-relativistic limit. Spin currents appear due to the combined action of the external electric field, the crystal field and the induced inertial electric field via the total effective spin-orbit interaction. In an accelerating frame, the crucial role of momentum space Berry curvature in the spin dynamics has alsomore » been addressed from the perspective of spin Hall conductivity. For time dependent acceleration, the expression for the spin polarization has been derived. - Highlights: Black-Right-Pointing-Pointer We study the effect of acceleration on the Dirac electron in the presence of an electromagnetic field, where the acceleration induces an electric field. Black-Right-Pointing-Pointer Spin currents appear due to the total effective electric field via the total spin-orbit interaction. Black-Right-Pointing-Pointer We derive the expression for the spin dependent force and the spin Hall current, which is zero for a particular acceleration. Black-Right-Pointing-Pointer The role of the momentum space Berry curvature in an accelerating system is discussed. Black-Right-Pointing-Pointer An expression for the spin polarization for time dependent acceleration is derived.« less

Automated Method for Estimating Nutation Time Constant Model Parameters for Spacecraft Spinning on Axis

NASA Technical Reports Server (NTRS)

2008-01-01

Calculating an accurate nutation time constant (NTC), or nutation rate of growth, for a spinning upper stage is important for ensuring mission success. Spacecraft nutation, or wobble, is caused by energy dissipation anywhere in the system. Propellant slosh in the spacecraft fuel tanks is the primary source for this dissipation and, if it is in a state of resonance, the NTC can become short enough to violate mission constraints. The Spinning Slosh Test Rig (SSTR) is a forced-motion spin table where fluid dynamic effects in full-scale fuel tanks can be tested in order to obtain key parameters used to calculate the NTC. We accomplish this by independently varying nutation frequency versus the spin rate and measuring force and torque responses on the tank. This method was used to predict parameters for the Genesis, Contour, and Stereo missions, whose tanks were mounted outboard from the spin axis. These parameters are incorporated into a mathematical model that uses mechanical analogs, such as pendulums and rotors, to simulate the force and torque resonances associated with fluid slosh.

Study of the spin and parity of the Higgs boson in diboson decays with the ATLAS detector.

PubMed

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Anghinolfi, F; Anisenkov, A V; Anjos, N; Annovi, A; Antonelli, M; Antonov, A; Antos, J; Anulli, F; Aoki, M; Aperio Bella, L; Arabidze, G; Arai, Y; Araque, J P; Arce, A T H; Arduh, F A; Arguin, J-F; Argyropoulos, S; Arik, M; Armbruster, A J; Arnaez, O; Arnal, V; Arnold, H; Arratia, M; Arslan, O; Artamonov, A; Artoni, G; Asai, S; Asbah, N; Ashkenazi, A; Åsman, B; Asquith, L; Assamagan, K; Astalos, R; Atkinson, M; Atlay, N B; Auerbach, B; Augsten, K; Aurousseau, M; Avolio, G; Axen, B; Ayoub, M K; Azuelos, G; Baak, M A; Baas, A E; Bacci, C; Bachacou, H; Bachas, K; Backes, M; Backhaus, M; Bagiacchi, P; Bagnaia, P; Bai, Y; Bain, T; Baines, J T; Baker, O K; Baldin, E M; Balek, P; Balestri, T; Balli, F; Banas, E; Banerjee, Sw; Bannoura, A A E; Bansil, H S; Barak, L; Barberio, E L; Barberis, D; Barbero, M; Barillari, T; Barisonzi, M; Barklow, T; Barlow, N; Barnes, S L; Barnett, B M; Barnett, R M; Barnovska, Z; Baroncelli, A; Barone, G; Barr, A J; Barreiro, F; Barreiro Guimarães da Costa, J; Bartoldus, R; Barton, A E; Bartos, P; Basalaev, A; Bassalat, A; Basye, A; Bates, R L; Batista, S J; Batley, J R; Battaglia, M; Bauce, M; Bauer, F; Bawa, H S; Beacham, J B; Beattie, M D; Beau, T; Beauchemin, P H; Beccherle, R; Bechtle, P; Beck, H P; Becker, K; Becker, M; Becker, S; Beckingham, M; Becot, C; Beddall, A J; Beddall, A; Bednyakov, V A; Bee, C P; Beemster, L J; Beermann, T A; Begel, M; Behr, J K; Belanger-Champagne, C; Bell, W H; Bella, G; Bellagamba, L; Bellerive, A; Bellomo, M; Belotskiy, K; Beltramello, O; Benary, O; Benchekroun, D; Bender, M; Bendtz, K; Benekos, N; Benhammou, Y; Benhar Noccioli, E; Benitez Garcia, J A; Benjamin, D P; Bensinger, J R; Bentvelsen, S; Beresford, L; Beretta, M; Berge, D; Bergeaas Kuutmann, E; Berger, N; Berghaus, F; Beringer, J; Bernard, C; Bernard, N R; Bernius, C; Bernlochner, F U; Berry, T; Berta, P; Bertella, C; Bertoli, G; Bertolucci, F; Bertsche, C; Bertsche, D; Besana, M I; Besjes, G J; Bessidskaia Bylund, O; Bessner, M; Besson, N; Betancourt, C; Bethke, S; 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Christodoulou, V; Chromek-Burckhart, D; Chudoba, J; Chuinard, A J; Chwastowski, J J; Chytka, L; Ciapetti, G; Ciftci, A K; Cinca, D; Cindro, V; Cioara, I A; Ciocio, A; Cirotto, F; Citron, Z H; Ciubancan, M; Clark, A; Clark, B L; Clark, P J; Clarke, R N; Cleland, W; Clement, C; Coadou, Y; Cobal, M; Coccaro, A; Cochran, J; Coffey, L; Cogan, J G; Cole, B; Cole, S; Colijn, A P; Collot, J; Colombo, T; Compostella, G; Conde Muiño, P; Coniavitis, E; Connell, S H; Connelly, I A; Consonni, S M; Consorti, V; Constantinescu, S; Conta, C; Conti, G; Conventi, F; Cooke, M; Cooper, B D; Cooper-Sarkar, A M; Cornelissen, T; Corradi, M; Corriveau, F; Corso-Radu, A; Cortes-Gonzalez, A; Cortiana, G; Costa, G; Costa, M J; Costanzo, D; Côté, D; Cottin, G; Cowan, G; Cox, B E; Cranmer, K; Cree, G; Crépé-Renaudin, S; Crescioli, F; Cribbs, W A; Crispin Ortuzar, M; Cristinziani, M; Croft, V; Crosetti, G; Cuhadar Donszelmann, T; Cummings, J; Curatolo, M; Cuthbert, C; Czirr, H; Czodrowski, P; D'Auria, S; D'Onofrio, M; Da Cunha Sargedas De Sousa, M J; Da Via, C; Dabrowski, W; Dafinca, A; Dai, T; Dale, O; Dallaire, F; Dallapiccola, C; Dam, M; Dandoy, J R; Dang, N P; Daniells, A C; Danninger, M; Dano Hoffmann, M; Dao, V; Darbo, G; Darmora, S; Dassoulas, J; Dattagupta, A; Davey, W; David, C; Davidek, T; Davies, E; Davies, M; Davison, P; Davygora, Y; Dawe, E; Dawson, I; Daya-Ishmukhametova, R K; De, K; de Asmundis, R; De Castro, S; De Cecco, S; De Groot, N; de Jong, P; De la Torre, H; De Lorenzi, F; De Nooij, L; De Pedis, D; De Salvo, A; De Sanctis, U; De Santo, A; De Vivie De Regie, J B; Dearnaley, W J; Debbe, R; Debenedetti, C; Dedovich, D V; Deigaard, I; Del Peso, J; Del Prete, T; Delgove, D; Deliot, F; Delitzsch, C M; Deliyergiyev, M; Dell'Acqua, A; Dell'Asta, L; Dell'Orso, M; Della Pietra, M; Della Volpe, D; Delmastro, M; Delsart, P A; Deluca, C; DeMarco, D A; Demers, S; Demichev, M; Demilly, A; Denisov, S P; Derendarz, D; Derkaoui, J E; Derue, F; Dervan, P; Desch, K; Deterre, C; Deviveiros, P O; Dewhurst, A; 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Pommès, K; Pontecorvo, L; Pope, B G; Popeneciu, G A; Popovic, D S; Poppleton, A; Pospisil, S; Potamianos, K; Potrap, I N; Potter, C J; Potter, C T; Poulard, G; Poveda, J; Pozdnyakov, V; Pralavorio, P; Pranko, A; Prasad, S; Prell, S; Price, D; Price, L E; Primavera, M; Prince, S; Proissl, M; Prokofiev, K; Prokoshin, F; Protopapadaki, E; Protopopescu, S; Proudfoot, J; Przybycien, M; Ptacek, E; Puddu, D; Pueschel, E; Puldon, D; Purohit, M; Puzo, P; Qian, J; Qin, G; Qin, Y; Quadt, A; Quarrie, D R; Quayle, W B; Queitsch-Maitland, M; Quilty, D; Raddum, S; Radeka, V; Radescu, V; Radhakrishnan, S K; Radloff, P; Rados, P; Ragusa, F; Rahal, G; Rajagopalan, S; Rammensee, M; Rangel-Smith, C; Rauscher, F; Rave, S; Ravenscroft, T; Raymond, M; Read, A L; Readioff, N P; Rebuzzi, D M; Redelbach, A; Redlinger, G; Reece, R; Reeves, K; Rehnisch, L; Reisin, H; Relich, M; Rembser, C; Ren, H; Renaud, A; Rescigno, M; Resconi, S; Rezanova, O L; Reznicek, P; Rezvani, R; Richter, R; Richter, S; Richter-Was, E; Ricken, O; Ridel, M; Rieck, P; Riegel, C J; Rieger, J; Rijssenbeek, M; Rimoldi, A; Rinaldi, L; Ristić, B; Ritsch, E; Riu, I; Rizatdinova, F; Rizvi, E; Robertson, S H; Robichaud-Veronneau, A; Robinson, D; Robinson, J E M; Robson, A; Roda, C; Roe, S; Røhne, O; Rolli, S; Romaniouk, A; Romano, M; Romano Saez, S M; Romero Adam, E; Rompotis, N; Ronzani, M; Roos, L; Ros, E; Rosati, S; Rosbach, K; Rose, P; Rosendahl, P L; Rosenthal, O; Rossetti, V; Rossi, E; Rossi, L P; Rosten, R; Rotaru, M; Roth, I; Rothberg, J; Rousseau, D; Royon, C R; Rozanov, A; Rozen, Y; Ruan, X; Rubbo, F; Rubinskiy, I; Rud, V I; Rudolph, C; Rudolph, M S; Rühr, F; Ruiz-Martinez, A; Rurikova, Z; Rusakovich, N A; Ruschke, A; Russell, H L; Rutherfoord, J P; Ruthmann, N; Ryabov, Y F; Rybar, M; Rybkin, G; Ryder, N C; Saavedra, A F; Sabato, G; Sacerdoti, S; Saddique, A; Sadrozinski, H F-W; Sadykov, R; Safai Tehrani, F; Saimpert, M; Sakamoto, H; Sakurai, Y; Salamanna, G; Salamon, A; Saleem, M; Salek, D; Sales De Bruin, P H; Salihagic, D; Salnikov, A; 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Schouten, D; Schovancova, J; Schramm, S; Schreyer, M; Schroeder, C; Schuh, N; Schultens, M J; Schultz-Coulon, H-C; Schulz, H; Schumacher, M; Schumm, B A; Schune, Ph; Schwanenberger, C; Schwartzman, A; Schwarz, T A; Schwegler, Ph; Schweiger, H; Schwemling, Ph; Schwienhorst, R; Schwindling, J; Schwindt, T; Sciacca, F G; Scifo, E; Sciolla, G; Scuri, F; Scutti, F; Searcy, J; Sedov, G; Sedykh, E; Seema, P; Seidel, S C; Seiden, A; Seifert, F; Seixas, J M; Sekhniaidze, G; Sekhon, K; Sekula, S J; Seliverstov, D M; Semprini-Cesari, N; Serfon, C; Serin, L; Serkin, L; Serre, T; Sessa, M; Seuster, R; Severini, H; Sfiligoj, T; Sforza, F; Sfyrla, A; Shabalina, E; Shamim, M; Shan, L Y; Shang, R; Shank, J T; Shapiro, M; Shatalov, P B; Shaw, K; Shaw, S M; Shcherbakova, A; Shehu, C Y; Sherwood, P; Shi, L; Shimizu, S; Shimmin, C O; Shimojima, M; Shiyakova, M; Shmeleva, A; Shoaleh Saadi, D; Shochet, M J; Shojaii, S; Shrestha, S; Shulga, E; Shupe, M A; Shushkevich, S; Sicho, P; Sidebo, P E; Sidiropoulou, O; Sidorov, D; Sidoti, A; Siegert, F; Sijacki, Dj; Silva, J; Silver, Y; Silverstein, S B; Simak, V; Simard, O; Simic, Lj; Simion, S; Simioni, E; Simmons, B; Simon, D; Simoniello, R; Sinervo, P; Sinev, N B; Sioli, M; Siragusa, G; Sisakyan, A N; Sivoklokov, S Yu; Sjölin, J; Sjursen, T B; Skinner, M B; Skottowe, H P; Skubic, P; Slater, M; Slavicek, T; Slawinska, M; Sliwa, K; Smakhtin, V; Smart, B H; Smestad, L; Smirnov, S Yu; Smirnov, Y; Smirnova, L N; Smirnova, O; Smith, M N K; Smith, R W; Smizanska, M; Smolek, K; Snesarev, A A; Snidero, G; Snyder, S; Sobie, R; Socher, F; Soffer, A; Soh, D A; Solans, C A; Solar, M; Solc, J; Soldatov, E Yu; Soldevila, U; Solodkov, A A; Soloshenko, A; Solovyanov, O V; Solovyev, V; Sommer, P; Song, H Y; Soni, N; Sood, A; Sopczak, A; Sopko, B; Sopko, V; Sorin, V; Sosa, D; Sosebee, M; Sotiropoulou, C L; Soualah, R; Soukharev, A M; South, D; Sowden, B C; Spagnolo, S; Spalla, M; Spanò, F; Spearman, W R; Sperlich, D; Spettel, F; Spighi, R; Spigo, G; Spiller, L A; Spousta, M; Spreitzer, T; St Denis, R D; Staerz, S; Stahlman, J; Stamen, R; Stamm, S; Stanecka, E; Stanescu, C; Stanescu-Bellu, M; Stanitzki, M M; Stapnes, S; Starchenko, E A; Stark, J; Staroba, P; Starovoitov, P; Staszewski, R; Stavina, P; Steinberg, P; Stelzer, B; Stelzer, H J; Stelzer-Chilton, O; Stenzel, H; Stewart, G A; Stillings, J A; Stockton, M C; Stoebe, M; Stoicea, G; Stolte, P; Stonjek, S; Stradling, A R; Straessner, A; Stramaglia, M E; Strandberg, J; Strandberg, S; Strandlie, A; Strauss, E; Strauss, M; Strizenec, P; Ströhmer, R; Strom, D M; Stroynowski, R; Strubig, A; Stucci, S A; Stugu, B; Styles, N A; Su, D; Su, J; Subramaniam, R; Succurro, A; Sugaya, Y; Suhr, C; Suk, M; Sulin, V V; Sultansoy, S; Sumida, T; Sun, S; Sun, X; Sundermann, J E; Suruliz, K; Susinno, G; Sutton, M R; Suzuki, S; Svatos, M; Swedish, S; Swiatlowski, M; Sykora, I; Sykora, T; Ta, D; Taccini, C; Tackmann, K; Taenzer, J; Taffard, A; Tafirout, R; Taiblum, N; Takai, H; Takashima, R; Takeda, H; Takeshita, T; Takubo, Y; Talby, M; Talyshev, A A; Tam, J Y C; Tan, K G; Tanaka, J; Tanaka, R; Tanaka, S; Tannenwald, B B; Tannoury, N; Tapprogge, S; Tarem, S; Tarrade, F; Tartarelli, G F; Tas, P; Tasevsky, M; Tashiro, T; Tassi, E; Tavares Delgado, A; Tayalati, Y; Taylor, F E; Taylor, G N; Taylor, W; Teischinger, F A; Teixeira Dias Castanheira, M; Teixeira-Dias, P; Temming, K K; Ten Kate, H; Teng, P K; Teoh, J J; Tepel, F; Terada, S; Terashi, K; Terron, J; Terzo, S; Testa, M; Teuscher, R J; Theveneaux-Pelzer, T; Thomas, J P; Thomas-Wilsker, J; Thompson, E N; Thompson, P D; Thompson, R J; Thompson, A S; Thomsen, L A; Thomson, E; Thomson, M; Thun, R P; Tibbetts, M J; Ticse Torres, R E; Tikhomirov, V O; Tikhonov, Yu A; Timoshenko, S; Tiouchichine, E; Tipton, P; Tisserant, S; Todome, K; Todorov, T; Todorova-Nova, S; Tojo, J; Tokár, S; Tokushuku, K; Tollefson, K; Tolley, E; Tomlinson, L; Tomoto, M; Tompkins, L; Toms, K; Torrence, E; Torres, H; Torró Pastor, E; Toth, J; Touchard, F; Tovey, D R; Trefzger, T; Tremblet, L; 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Zwalinski, L

Studies of the spin, parity and tensor couplings of the Higgs boson in the [Formula: see text], [Formula: see text] and [Formula: see text] decay processes at the LHC are presented. The investigations are based on [Formula: see text] of pp collision data collected by the ATLAS experiment at [Formula: see text] TeV and [Formula: see text] TeV. The Standard Model (SM) Higgs boson hypothesis, corresponding to the quantum numbers [Formula: see text], is tested against several alternative spin scenarios, including non-SM spin-0 and spin-2 models with universal and non-universal couplings to fermions and vector bosons. All tested alternative models are excluded in favour of the SM Higgs boson hypothesis at more than 99.9 % confidence level. Using the [Formula: see text] and [Formula: see text] decays, the tensor structure of the interaction between the spin-0 boson and the SM vector bosons is also investigated. The observed distributions of variables sensitive to the non-SM tensor couplings are compatible with the SM predictions and constraints on the non-SM couplings are derived.

Performance of wave function and density functional methods for water hydrogen bond spin-spin coupling constants.

PubMed

García de la Vega, J M; Omar, S; San Fabián, J

2017-04-01

Spin-spin coupling constants in water monomer and dimer have been calculated using several wave function and density functional-based methods. CCSD, MCSCF, and SOPPA wave functions methods yield similar results, specially when an additive approach is used with the MCSCF. Several functionals have been used to analyze their performance with the Jacob's ladder and a set of functionals with different HF exchange were tested. Functionals with large HF exchange appropriately predict 1 J O H , 2 J H H and 2h J O O couplings, while 1h J O H is better calculated with functionals that include a reduced fraction of HF exchange. Accurate functionals for 1 J O H and 2 J H H have been tested in a tetramer water model. The hydrogen bond effects on these intramolecular couplings are additive when they are calculated by SOPPA(CCSD) wave function and DFT methods. Graphical Abstract Evaluation of the additive effect of the hydrogen bond on spin-spin coupling constants of water using WF and DFT methods.

A flight investigation of the ultra-deep-stall descent and spin recovery characteristics of a 1/6 scale radiocontrolled model of the Piper PA38 Tomahawk

NASA Technical Reports Server (NTRS)

Blanchard, W. S., Jr.

1981-01-01

Ultradeep stall descent and spin recovery characteristics of a 1/6 scale radio controlled model of the Piper PA38 Tomahawk aircraft was investigated. It was shown that the full scale PA38 is a suitable aircraft for conducting ultradeep stall research. Spin recovery was accomplished satisfactorily by entry to the ultradeep stall mode, followed by the exit from the ultradeep stall mode. It is concluded that since the PA38 has excellent spin recovery characteristics using normal recovery techniques (opposite rudder and forward control colum pressure), recovery using ultradeep stall would be beneficial only if the pilot suffered from disorientation.

Antiferromagnetic d-Electron Exchange via a Spin-Singlet π-Electron Ground State in an Organic Conductor

NASA Astrophysics Data System (ADS)

Tokumoto, T.; Brooks, J. S.; Oshima, Y.; Choi, E. S.; Brunel, L. C.; Akutsu, H.; Kaihatsu, T.; Yamada, J.; van Tol, J.

2008-04-01

Electron spin resonance reveals the spin behavior of conduction (π) and localized (d) electrons in β-(BDA-TTP)2MCl4 (M=Fe, Ga). Both the Ga3+(S=0) and Fe3+(S=5/2) compounds exhibit a metal-insulator transition at 113 K with the simultaneous formation of a spin-singlet ground state in the π electron system of the donor molecules. The behavior is consistent with charge ordering in β-(BDA-TTP)2MCl4 at the metal-insulator transition. At 5 K, the Fe3+ compound orders antiferromagnetically, even though the π electrons, which normally would facilitate magnetic exchange, are localized nonmagnetic singlets.

Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes

PubMed Central

Nishibayashi, Kazuhiro

2017-01-01

We report the room-temperature electroluminescence (EL) with nearly pure circular polarization (CP) from GaAs-based spin-polarized light-emitting diodes (spin-LEDs). External magnetic fields are not used during device operation. There are two small schemes in the tested spin-LEDs: first, the stripe-laser-like structure that helps intensify the EL light at the cleaved side walls below the spin injector Fe slab, and second, the crystalline AlOx spin-tunnel barrier that ensures electrically stable device operation. The purity of CP is depressively low in the low current density (J) region, whereas it increases steeply and reaches close to the pure CP when J > 100 A/cm2. There, either right- or left-handed CP component is significantly suppressed depending on the direction of magnetization of the spin injector. Spin-dependent reabsorption, spin-induced birefringence, and optical spin-axis conversion are suggested to account for the observed experimental results. PMID:28174272

Zirconia-based mixed potential sensor with Pt electrode prepared by spin-coating of polymeric precursor

NASA Astrophysics Data System (ADS)

Chrzan, A.; Woźniak, Ł.; Szymczewska, D.; Jasiński, P.

2016-11-01

Many types of yttria-stabilized zirconia (YSZ) based gas sensors have been explored extensively in recent years. Great attention have been directed to mixed-potential-type gas sensors. It is due to growing concerns with environmental issues. Not without a significance is the fact of very attractive performance of this type of sensor allowing to detect low concentration of pollutant gases. In this paper two types of YSZ based mixed-potential planar sensors were investigated, with platinum electrode painted using commercial paste and with spin coated platinum layer. Both types had second electrode in the form of porous gold. Measurements were performed at 400 °C in synthetic air and different concentrations of SO2. Gas flow was set to 100 cm3min-1 and the concentration of 50 ppm SO2 was tested. During this measurements the sensor was sintered in-situ at increasing temperatures. Sensor with 100 nm spin-coated platinum layer sintered at 700 °C was shown to exhibit two times smaller response than sensor with 5 μm porous electrode, while consisting of over 20 times smaller amount of Pt. The influence of sintering temperature on electrical conductivity of platinum films was also examined. Moreover, the platinum microstructure was investigated using SEM microscopy.

Generalized GW+Boltzmann Approach for the Description of Ultrafast Electron Dynamics in Topological Insulators

PubMed Central

Battiato, Marco; Sánchez-Barriga, Jaime

2017-01-01

Quantum-phase transitions between trivial insulators and topological insulators differ from ordinary metal-insulator transitions in that they arise from the inversion of the bulk band structure due to strong spin–orbit coupling. Such topological phase transitions are unique in nature as they lead to the emergence of topological surface states which are characterized by a peculiar spin texture that is believed to play a central role in the generation and manipulation of dissipationless surface spin currents on ultrafast timescales. Here, we provide a generalized GW+Boltzmann approach for the description of ultrafast dynamics in topological insulators driven by electron–electron and electron–phonon scatterings. Taking the prototypical insulator Bi2Te3 as an example, we test the robustness of our approach by comparing the theoretical prediction to results of time- and angle-resolved photoemission experiments. From this comparison, we are able to demonstrate the crucial role of the excited spin texture in the subpicosecond relaxation of transient electrons, as well as to accurately obtain the magnitude and strength of electron–electron and electron–phonon couplings. Our approach could be used as a generalized theory for three-dimensional topological insulators in the bulk-conducting transport regime, paving the way for the realization of a unified theory of ultrafast dynamics in topological materials. PMID:28773171

Spinning Characteristics of Wings III : a Rectangular and Tapered Clark Y Monoplane Wing with Rounded Tips

NASA Technical Reports Server (NTRS)

Bamber, M J; House, R O

1937-01-01

An investigation was made to determine the spinning characteristics of Clark Y monoplane wings with different plan forms. A rectangular wing and a wing tapered 5:2, both with rounded tips, were tested on the N.A.C.A. spinning balance in the 5-foot vertical wind tunnel. The aerodynamic characteristics of the models and a prediction of the angles of sideslip for steady spins are given. Also included is an estimate of the yawning moment that must be furnished by the parts of the airplane to balance the inertia couples and wing yawing moment for spinning equilibrium. The effects on the spin of changes in plan form and of variations of some of the important parameters are discussed and the results are compared with those for a rectangular wing with square tips. It is concluded that for a conventional monoplane using Clark Y wing the sideslip will be algebraically larger for the wing with the rounded tip than for the wing with the square tip and will be largest for the tapered wing. The effect of plan form on the spin will vary with the type of airplane; and the provision of a yawing-moment coefficient of -0.025 (i.e., opposing the spin) by the tail, fuselage, and interference effects will insure against the attainment of equilibrium on a steady spin for any of the plan forms tested and for any of the parameters used in the analysis.

Scattering of two spinning black holes in post-Minkowskian gravity, to all orders in spin, and effective-one-body mappings

NASA Astrophysics Data System (ADS)

Vines, Justin

2018-04-01

We demonstrate equivalences, under simple mappings, between the dynamics of three distinct systems—(i) an arbitrary-mass-ratio two-spinning-black-hole system, (ii) a spinning test black hole in a background Kerr spacetime, and (iii) geodesic motion in Kerr—when each is considered in the first post-Minkowskian (1PM) approximation to general relativity, i.e. to linear order G but to all orders in 1/c, and to all orders in the black holes’ spins, with all orders in the multipole expansions of their linearized gravitational fields. This is accomplished via computations of the net results of weak gravitational scattering encounters between two spinning black holes, namely the net O(G) changes in the holes’ momenta and spins as functions of the incoming state. The results are given in remarkably simple closed forms, found by solving effective Mathisson–Papapetrou–Dixon-type equations of motion for a spinning black hole in conjunction with the linearized Einstein equation, with appropriate matching to the Kerr solution. The scattering results fully encode the gauge-invariant content of a canonical Hamiltonian governing binary-black-hole dynamics at 1PM order, for generic (unbound and bound) orbits and spin orientations. We deduce one such Hamiltonian, which reproduces and resums the 1PM parts of all such previous post-Newtonian results, and which directly manifests the equivalences with the test-body limits via simple effective-one-body mappings.

Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics

NASA Astrophysics Data System (ADS)

Wang, Yifei; Sahin-Tiras, Kevser; Harmon, Nicholas J.; Wohlgenannt, Markus; Flatté, Michael E.

2016-01-01

As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFEs) ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFEs if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in coevaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex). Here, we show that exciplex recombination in blends exhibiting thermally activated delayed fluorescence produces MFEs in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device's current-voltage response curve by device conditioning. Both of these immense MFEs are the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFEs in materials emitting light from excitons by affecting the precursor pairs. Demonstration of immense MFEs in common organic blends provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices without patterning the constituent materials on the nanoscale. Magnetic fields increase the power efficiency of unconditioned devices by 30% at room temperature, also showing that magnetic fields may increase the efficiency of the thermally activated delayed fluorescence process.

Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics

DOE PAGES

Wang, Yifei; Sahin-Tiras, Kevser; Harmon, Nicholas J.; ...

2016-02-05

As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFEs) ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFEs if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in coevaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex). Here, we show that exciplex recombination in blendsmore » exhibiting thermally activated delayed fluorescence produces MFEs in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device’s current-voltage response curve by device conditioning. Both of these immense MFEs are the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFEs in materials emitting light from excitons by affecting the precursor pairs. Demonstration of immense MFEs in common organic blends provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices without patterning the constituent materials on the nanoscale. In conclusion, magnetic fields increase the power efficiency of unconditioned devices by 30% at room temperature, also showing that magnetic fields may increase the efficiency of the thermally activated delayed fluorescence process.« less

Charge and spin diffusion on the metallic side of the metal-insulator transition: A self-consistent approach

NASA Astrophysics Data System (ADS)

Wellens, Thomas; Jalabert, Rodolfo A.

2016-10-01

We develop a self-consistent theory describing the spin and spatial electron diffusion in the impurity band of doped semiconductors under the effect of a weak spin-orbit coupling. The resulting low-temperature spin-relaxation time and diffusion coefficient are calculated within different schemes of the self-consistent framework. The simplest of these schemes qualitatively reproduces previous phenomenological developments, while more elaborate calculations provide corrections that approach the values obtained in numerical simulations. The results are universal for zinc-blende semiconductors with electron conductance in the impurity band, and thus they are able to account for the measured spin-relaxation times of materials with very different physical parameters. From a general point of view, our theory opens a new perspective for describing the hopping dynamics in random quantum networks.

Dependence of spin pumping and spin transfer torque upon Ni81Fe19 thickness in Ta/Ag /Ni 81Fe19/Ag/Co 2MnGe /Ag /Ta spin-valve structures

NASA Astrophysics Data System (ADS)

Durrant, C. J.; Shelford, L. R.; Valkass, R. A. J.; Hicken, R. J.; Figueroa, A. I.; Baker, A. A.; van der Laan, G.; Duffy, L. B.; Shafer, P.; Klewe, C.; Arenholz, E.; Cavill, S. A.; Childress, J. R.; Katine, J. A.

2017-10-01

Spin pumping has been studied within Ta / Ag / Ni81Fe19 (0-5 nm) / Ag (6 nm) / Co2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni81Fe19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfer torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. This study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.

Verification of Spin Magnetic Attitude Control System using air-bearing-based attitude control simulator

NASA Astrophysics Data System (ADS)

Ousaloo, H. S.; Nodeh, M. T.; Mehrabian, R.

2016-09-01

This paper accomplishes one goal and it was to verify and to validate a Spin Magnetic Attitude Control System (SMACS) program and to perform Hardware-In-the-Loop (HIL) air-bearing experiments. A study of a closed-loop magnetic spin controller is presented using only magnetic rods as actuators. The magnetic spin rate control approach is able to perform spin rate control and it is verified with an Attitude Control System (ACS) air-bearing MATLAB® SIMULINK® model and a hardware-embedded LABVIEW® algorithm that controls the spin rate of the test platform on a spherical air bearing table. The SIMULINK® model includes dynamic model of air-bearing, its disturbances, actuator emulation and the time delays caused by on-board calculations. The air-bearing simulator is employed to develop, improve, and carry out objective tests of magnetic torque rods and spin rate control algorithm in the experimental framework and to provide a more realistic demonstration of expected performance of attitude control as compared with software-based architectures. Six sets of two torque rods are used as actuators for the SMACS. It is implemented and simulated to fulfill mission requirement including spin the satellite up to 12 degs-1 around the z-axis. These techniques are documented for the full nonlinear equations of motion of the system and the performances of these techniques are compared in several simulations.

The Effect of Thickness of ZnO Thin Films on Hydrophobic Self-Cleaning Properties

NASA Astrophysics Data System (ADS)

Mufti, N.; Arista, D.; Diantoro, M.; Fuad, A.; Taufiq, A.; Sunaryono

2017-05-01

Glass coating can be conducted by using ZnO-photocatalyst based semiconductor material since it is preeminent in decomposing organics compound and dangerous bacteria which often contaminates the environment. If there are dirt containing organics compound on the glass, the ZnO photocatalyst coat can be applied as self-cleaning, usually called self-cleaning glass. It depends on the coating thickness which can be controlled by setting the speed of spin coating. In this research, the various rotating speeds of spin coating were conducted at 2000 rpm, 3000 rpm, and 4000 rpm to control the thickness. The raw materials used in this research were Zn(CH3COOH)2.2H2O (PA 99,5%), Ethylene glycol, Diethanolamine (PA 99%), Isopropanol Alkohol, Glycerol, and Ashton. Synthesis methods used were sol-gel prior to spin coating technic were applied. The results of the film were characterized by using SEM, XRD, and UV-Spectrophotometer. The crystal structure was analyzed by using Highscore plus and GSAS software, the size crystal was calculated by using Scherrer equation, a contact angle with ImageJ software. It was shown that ZnO thin film had been successfully synthesized with the crystal size around 21 nm up to 26 nm. The absorption value is higher due to the increasing of coat thickness with bandgap ± 3.2 eV. The test result of hydrophobic and hydrophilic characteristics show that all samples of ZnO thin film with the thickness ± 1.050 μm, ± 0.450 μm, ± 0.250 μm can be applied as self-cleaning glass. The best result was gained with the thickness of thin film ± 1.050 μm.

Asymmetrical penetration of microwave in a conducting media and determination of microwave conductivity for very thin samples using electron spin resonance

NASA Astrophysics Data System (ADS)

Seridonio, A. C.; Walmsley, L.

2001-04-01

Dyson's theory of conduction electron spin resonance (CESR) has been used in the limit d≤δ (d being the thickness of the sample and δ the skin depth of the microwave field) to obtain the microwave conductivity from the (A/B) ratio of the CESR absorbed power derivative. In this work we calculate the CESR absorbed power derivative using Kaplan's approach and show that the (A/B) ratio can be enhanced if asymmetrical penetration of microwave is used, which means that the microwave field enters into the sample from one of the faces. Therefore, the determination of the microwave conductivity from the (A/B) ratio of the CESR line can be performed for thinner samples. Experimentally, asymmetrical penetration can be obtained if one of the sample's faces is covered with a thin gold layer. The determination of microwave conductivity in conducting polymers films is among the possible applications of this method.

Deployment Mechanism for the Space Technology 5 Micro Satellite

NASA Technical Reports Server (NTRS)

Rossoni, Peter; Cooperrider, Caner; Durback, Gerard

2004-01-01

Space Technology 5 (ST5) is a technology mission that will send three spin-stabilized, 25-kg satellites into a highly elliptical Earth orbit. Each of these satellites must be deployed separately from the same launch vehicle with a spin rate of 3.4 rads (32.4 rpm). Because of the satellite's small size and the requirement to achieve its mission spin rate on deploy, typical spin table, pyrotechnic deployment devices or spin up thrusters could not be used. Instead, this new mechanism design employs a "Frisbee" spin up strategy with a shape memory alloy actuated Pinpuller to deploy each satellite. The mechanism has undergone several design and test iterations and has been successfully qualified for flight.

Deployment Mechanism for the Space Technology 5 Micro Satellite

NASA Technical Reports Server (NTRS)

Rossoni, Peter; Cooperrider, Caner; Durback, Gerard

2004-01-01

Space Technology 5 (ST5) is a technology mission that will send three spin-stabilized, 25-kg satellites into a highly elliptical Earth orbit. Each of these satellites must be deployed separately from the same launch vehicle with a spin rate of 3.4 rad/s (32.4 rpm). Because of the satellite's small size and the requirement to achieve its mission spin rate on deploy, typical spin table, pyrotechnic deployment devices or spin up thrusters could not be used. Instead, this new mechanism design employs a 'Frisbee' spin up strategy with a shape memory alloy actuated Pinpuller to deploy each satellite. The mechanism has undergone several design and test iterations and has been successfully qualified for flight.

First-principles study on half-metallic ferromagnetic properties of Zn1- x V x Se ternary alloys

NASA Astrophysics Data System (ADS)

Khatta, Swati; Tripathi, S. K.; Prakash, Satya

2017-09-01

The spin-polarised density functional theory along with self-consistent plane-wave pseudopotential is used to investigate the half-metallic ferromagnetic properties of ternary alloys Zn1- x V x Se. The generalized gradient approximation is used for exchange-correlation potential. The equilibrium lattice constants, bulk modulus, and its derivatives are calculated. The calculated spin-polarised energy-band structures reveal that these alloys are half-metallic for x = 0.375 and 0.50 and nearly half-metallic for other values of x. The estimated direct and indirect bandgaps may be useful for the magneto-optical absorption experiments. It is found that there is strong Zn 4s, Se 4p, and V 3d orbital hybridization in the conduction bands of both the spins, while Se 4p and V 3d orbital hybridization predominates in the valence bands of both the spins. The s, p-d, and p-d orbital hybridization reduces the local magnetic moment of V atoms and small local magnetic moments are produced on Zn and Se atoms which get coupled with V atoms in ferromagnetic and antiferromagnetic phases, respectively. The conduction and valence-band-edge splittings and exchange constants predict the ferromagnetism in these alloys. The conduction band-impurity (s and p-d) exchange interaction is more significant for ferromagnetism in these alloys than the valence band-impurity (p-d) exchange interaction.

Spin-dependent electron many-body effects in GaAs

NASA Astrophysics Data System (ADS)

Nemec, P.; Kerachian, Y.; van Driel, H. M.; Smirl, Arthur L.

2005-12-01

Time- and polarization-resolved differential transmission measurements employing same and oppositely circularly polarized 150fs optical pulses are used to investigate spin characteristics of conduction band electrons in bulk GaAs at 295K . Electrons and holes with densities in the 2×1016cm-3-1018cm-3 range are generated and probed with pulses whose center wavelength is between 865 and 775nm . The transmissivity results can be explained in terms of the spin sensitivity of both phase-space filling and many-body effects (band-gap renormalization and screening of the Coulomb enhancement factor). For excitation and probing at 865nm , just above the band-gap edge, the transmissivity changes mainly reflect spin-dependent phase-space filling which is dominated by the electron Fermi factors. However, for 775nm probing, the influence of many-body effects on the induced transmission change are comparable with those from reduced phase space filling, exposing the spin dependence of the many-body effects. If one does not take account of these spin-dependent effects one can misinterpret both the magnitude and time evolution of the electron spin polarization. For suitable measurements we find that the electron spin relaxation time is 130ps .

Anisotropic optical absorption induced by Rashba spin-orbit coupling in monolayer phosphorene

NASA Astrophysics Data System (ADS)

Li, Yuan; Li, Xin; Wan, Qi; Bai, R.; Wen, Z. C.

2018-04-01

We obtain the effective Hamiltonian of the phosphorene including the effect of Rashba spin-orbit coupling in the frame work of the low-energy theory. The spin-splitting energy bands show an anisotropy feature for the wave vectors along kx and ky directions, where kx orients to ΓX direction in the k space. We numerically study the optical absorption of the electrons for different wave vectors with Rashba spin-orbit coupling. We find that the spin-flip transition from the valence band to the conduction band induced by the circular polarized light closes to zero with increasing the x-component wave vector when ky equals to zero, while it can be significantly increased to a large value when ky gets a small value. When the wave vector varies along the ky direction, the spin-flip transition can also increase to a large value, however, which shows an anisotropy feature for the optical absorption. Especially, the spin-conserved transitions keep unchanged and have similar varying trends for different wave vectors. This phenomenon provides a novel route for the manipulation of the spin-dependent property of the fermions in the monolayer phosphorene.

A spin-modulated telescope for measurement of cosmic microwave background anisotropy

NASA Astrophysics Data System (ADS)

Staren, John William

The measurement of anisotropy in the Cosmic Microwave Background (CMB) advances our knowledge of the early Universe from which the radiation originated. The angular power spectrum of CMB anisotropy at sub-degree scales depends heavily on comsological parameters such as Ob, O 0 and H0. In pursuit of critical power spectrum measurements over a range of angular scales, a spin-modulated telescope with a single cryogenic amplifier used in a total power radiometer is designed, built and tested. The new technique of spin-modulation with a spinning flat mirror canted 2.5° relative to its spin axis modulates the beam in a 10° oval pattern on the sky at 2.5 Hz. This rapid two-dimensional modulation of the beam is tested at balloon altitudes to minimize the atmospheric offset and determine the efficacy of the scan and telescope design. Maps of over 600 and 400 square degrees are made of regions observed using the spin-modulation and a 20° azimuth scan. These maps yield a 95% confidence level flat band power upper limit of DeltaTℓ = Tcmb(ℓ(ℓ + 1)Cℓ/2pi)0.5 < 77 muK at ℓ = 38 and are free of systematics effects and striping due to long-term drifts in our amplifier to the levels tested here. Planning for the next telescope, with multiple amplifiers, is performed to ensure its success.

Theory of unidirectional magnetoresistance in magnetic heterostructures

NASA Astrophysics Data System (ADS)

Zhang, Steven S.-L.; Vignale, Giovanni

2017-09-01

We present a general drift-diffusion theory beyond linear response to explain the unidirectional magnetoresistance (UMR) observed in recent experiments in various magnetic heterostructures. In general, such nonlinear magnetoresistance may originate from the concerted action of current-induced spin accumulation and spin asymmetry in electron mobility. As a case study, we calculate the UMR in a bilayer system consisting of a heavy-metal (HM) and a ferromagnetic metal (FM), where the spin accumulation is induced via the spin Hall effect in the bulk of the HM layer. Our previous formulation [cf. PRB 94, 140411(R) (2016)] is generalized to include the interface resistance and spin memory loss, which allows us to analyze in details their effects on the UMR. We found that the UMR turns out to be independent of the spin asymmetry of the interfacial resistance, at variance with the linear giant-magnetoresistance (GMR) effect. A linear relation between the UMR and the conductivity-spin asymmetry is revealed, which provides an alternative way to control the sign and magnitude of the UMR and hence may serve as an experimental signature of our proposed mechanism.

IR Studies of the Spin-Nuclear Conversion in the Vicinity of alpha α - beta β - Transition in Cryodeposited Methane Films

NASA Astrophysics Data System (ADS)

Drobyshev, A.; Aldiyarov, A.; Sokolov, D.; Shinbayeva, A.

2017-06-01

Solid methane belongs to a group of crystals containing hydrogen atoms, whose macroscopic properties are greatly influenced by the spin interaction of hydrogen nuclei. In particular, the methane molecule, which has four protons with spin I=1/2, has three total spin modifications: para-, ortho- and meta-states with three values of the total spin moments of 0, 1 and 2, respectively. Equilibrium concentrations of these modifications and relaxation times are dependent on the temperature, affecting the observed thermal properties of solid methane, such as thermal conductivity, specific heat, thermal expansion. In this paper, we attempt to explain the peculiarities of thin film growth of methane at cryogenic temperatures from the viewpoint of spin-nuclear transformations. Our observations of absorption intensity at a frequency corresponding to 1/2 of the absorption band amplitude of deformation vibrations record a step-like change in the position of the absorption band during the sample deposition process. The observed phenomenon, in our opinion, is the demonstration of spin transformations during deposition.

Theory of Intrinsic Spin Torque Due to Interface Spin-Orbit Coupling

NASA Astrophysics Data System (ADS)

Kalitsov, Alan; Chshiev, Mairbek; Butler, William; Mryasov, Oleg

2014-03-01

The effect of intrinsic spin torque due to spin-orbit coupling (SOC) at the interface between thin ferromagnetic film and non-magnetic metal has attracted significant fundamental and applied research interest. We report quantum theory of SOC driven spin torque (SOT) within the Rashba model of SOC and two-band tight binding (TB) Hamiltonian including s-d exchange interactions (J). We employ the non-equilibrium Green Function formalism and find that SOT to the first order in SOC has symmetry consistent with the earlier quasi-classical diffusive theory. An obvious benefit of the proposed approach is the expression for the SOT given in terms of TB parameters which enables a physically transparent analysis of the dependencies of SOT on material specific parameters such as Rashba SOC constant, hopping integral, Fermi level and J. On the basis of analytical and numerical results we discuss trends in strength of SOT and its correlation with the Spin Hall conductivity. This work was supported in part by C-SPIN, STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor Sb2Se3

NASA Astrophysics Data System (ADS)

Das, Shekhar; Sirohi, Anshu; Kumar Gupta, Gaurav; Kamboj, Suman; Vasdev, Aastha; Gayen, Sirshendu; Guptasarma, Prasenjit; Das, Tanmoy; Sheet, Goutam

2018-06-01

Majority of the A2B3 -type chalcogenide systems with strong spin-orbit coupling (SOC), such as Bi2Se3,Bi2Te3 , and Sb2Te3 , etc., are topological insulators. One important exception is Sb2Se3 where a topological nontrivial phase was argued to be possible under ambient conditions, but such a phase could be detected to exist only under pressure. In this paper, we show that Sb2Se3 like Bi2Se3 displays a generation of highly spin-polarized current under mesoscopic superconducting point contacts as measured by point-contact Andreev reflection spectroscopy. In addition, we observe a large negative and anisotropic magnetoresistance of the mesoscopic metallic point contacts formed on Sb2Se3 . Our band-structure calculations confirm the trivial nature of Sb2Se3 crystals and reveal two trivial surface states one of which shows large spin splitting due to Rashba-type SOC. The observed high spin polarization and related phenomena in Sb2Se3 can be attributed to this spin splitting.

Coexistence of perfect spin filtering for entangled electron pairs and high magnetic storage efficiency in one setup.

PubMed

Ji, T T; Bu, N; Chen, F J; Tao, Y C; Wang, J

2016-04-14

For Entangled electron pairs superconducting spintronics, there exist two drawbacks in existing proposals of generating entangled electron pairs. One is that the two kinds of different spin entangled electron pairs mix with each other. And the other is a low efficiency of entanglement production. Herein, we report the spin entanglement state of the ferromagnetic insulator (FI)/s-wave superconductor/FI structure on a narrow quantum spin Hall insulator strip. It is shown that not only the high production of entangled electron pairs in wider energy range, but also the perfect spin filtering of entangled electron pairs in the context of no highly spin-polarized electrons, can be obtained. Moreover, the currents for the left and right leads in the antiferromagnetic alignment both can be zero, indicating 100% tunnelling magnetoresistance with highly magnetic storage efficiency. Therefore, the spin filtering for entangled electron pairs and magnetic storage with high efficiencies coexist in one setup. The results may be experimentally demonstrated by measuring the tunnelling conductance and the noise power.

Rockets for spin recovery

NASA Technical Reports Server (NTRS)

Whipple, R. D.

1980-01-01

The potential effectiveness of rockets as an auxiliary means for an aircraft to effect recovery from spins was investigated. The advances in rocket technology produced by the space effort suggested that currently available systems might obviate many of the problems encountered in earlier rocket systems. A modern fighter configuration known to exhibit a flat spin mode was selected. An analytical study was made of the thrust requirements for a rocket spin recovery system for the subject configuration. These results were then applied to a preliminary systems study of rocket components appropriate to the problem. Subsequent spin tunnel tests were run to evaluate the analytical results.

Investigation of the difference between spin Hall magnetoresistance rectification and spin pumping from the viewpoint of magnetization dynamics

NASA Astrophysics Data System (ADS)

Zhang, Qihan; Fan, Xiaolong; Zhou, Hengan; Kong, Wenwen; Zhou, Shiming; Gui, Y. S.; Hu, C.-M.; Xue, Desheng

2018-02-01

Spin pumping (SP) and spin rectification due to spin Hall magnetoresistance (SMR) can result in a dc resonant voltage signal, when magnetization in ferromagnetic insulator/nonmagnetic structures experiences ferromagnetic resonance. Since the two effects are often interrelated, quantitative identification of them is important for studying the dynamic nonlocal spin transport through an interface. In this letter, the key difference between SP and SMR rectification was investigated from the viewpoint of spin dynamics. The phase-dependent nature of SMR rectification, which is the fundamental characteristic distinguishing it from SP, was tested by a well-designed experiment. In this experiment, two identical yttrium iron garnet/Pt strips with a π phase difference in dynamic magnetization show the same SP signals and inverse SMR signals.

Spacer type mediated tunable spin crossover (SCO) characteristics of pyrene decorated 2,6-bis(pyrazol-1-yl)pyridine (bpp) based Fe(ii) molecular spintronic modules.

PubMed

Kumar, Kuppusamy Senthil; Šalitroš, Ivan; Moreno-Pineda, Eufemio; Ruben, Mario

2017-08-14

A simple "isomer-like" variation of the spacer group in a set of Fe(ii) spin crossover (SCO) complexes designed to probe spin state dependence of electrical conductivity in graphene-based molecular spintronic junctions led to the observation of remarkable variations in the thermal- and light-induced magnetic characteristics, paving a simple route for the design of functional SCO complexes with different temperature switching regimes based on a 2,6-bis(pyrazol-1-yl)pyridine ligand skeleton.

A high-efficiency spin polarizer based on edge and surface disordered silicene nanoribbons

NASA Astrophysics Data System (ADS)

Xu, Ning; Zhang, Haiyang; Wu, Xiuqiang; Chen, Qiao; Ding, Jianwen

2018-07-01

Using the tight-binding formalism, we explore the effect of weak disorder upon the conductance of zigzag edge silicene nanoribbons (SiNRs), in the limit of phase-coherent transport. We find that the fashion of the conductance varies with disorder, and depends strongly on the type of disorder. Conductance dips are observed at the Van Hove singularities, owing to quasilocalized states existing in surface disordered SiNRs. A conductance gap is observed around the Fermi energy for both edge and surface disordered SiNRs, because edge states are localized. The average conductance of the disordered SiNRs decreases exponentially with the increase of disorder, and finally tends to disappear. The near-perfect spin polarization can be realized in SiNRs with a weak edge or surface disorder, and also can be attained by both the local electric field and the exchange field.

Angular-dependent EDMR linewidth for spin-dependent space charge limited conduction in a polycrystalline pentacene

NASA Astrophysics Data System (ADS)

Fukuda, Kunito; Asakawa, Naoki

2017-08-01

Spin-dependent space charge limited carrier conduction in a Schottky barrier diode using polycrystalline p-type π-conjugated molecular pentacene is explored using multiple-frequency electrically detected magnetic resonance (EDMR) spectroscopy with a variable-angle configuration. The measured EDMR spectra are decomposed into two components derived respectively from mobile and trapped positive polarons. The linewidth of the EDMR signal for the trapped polarons increases with increasing resonance magnetic field for an in-plane configuration where the normal vector of the device substrate is perpendicular to the resonance magnetic field, while it is independent of the field for an out-of-plane configuration. This difference is consistent with the pentacene arrangement on the device substrate, where pentacene molecules exhibit a uniaxial orientation on the out-of-substrate plane. By contrast, the mobile polarons do not show anisotropic behavior with respect to the resonance magnetic field, indicating that the anisotropic effect is averaged out owing to carrier motion. These results suggest that the orientational arrangements of polycrystalline pentacene molecules in a nano thin film play a crucial role in spin-dependent electrical conduction.

First Test of Fan Active Noise Control (ANC) Completed

NASA Technical Reports Server (NTRS)

2005-01-01

With the advent of ultrahigh-bypass engines, the space available for passive acoustic treatment is becoming more limited, whereas noise regulations are becoming more stringent. Active noise control (ANC) holds promise as a solution to this problem. It uses secondary (added) noise sources to reduce or eliminate the offending noise radiation. The first active noise control test on the low-speed fan test bed was a General Electric Company system designed to control either the exhaust or inlet fan tone. This system consists of a "ring source," an induct array of error microphones, and a control computer. Fan tone noise propagates in a duct in the form of spinning waves. These waves are detected by the microphone array, and the computer identifies their spinning structure. The computer then controls the "ring source" to generate waves that have the same spinning structure and amplitude, but 180 out of phase with the fan noise. This computer generated tone cancels the fan tone before it radiates from the duct and is heard in the far field. The "ring source" used in these tests is a cylindrical array of 16 flat-plate acoustic radiators that are driven by thin piezoceramic sheets bonded to their back surfaces. The resulting source can produce spinning waves up to mode 7 at levels high enough to cancel the fan tone. The control software is flexible enough to work on spinning mode orders from -6 to 6. In this test, the fan was configured to produce a tone of order 6. The complete modal (spinning and radial) structure of the tones was measured with two builtin sets of rotating microphone rakes. These rakes provide a measurement of the system performance independent from the control system error microphones. In addition, the far-field noise was measured with a semicircular array of 28 microphones. This test represents the first in a series of tests that demonstrate different active noise control concepts, each on a progressively more complicated modal structure. The tests are in preparation for a demonstration on a flight-type engine.

Spin pumping in ion-beam sputtered C o2FeAl /Mo bilayers: Interfacial Gilbert damping

NASA Astrophysics Data System (ADS)

Husain, Sajid; Kumar, Ankit; Barwal, Vineet; Behera, Nilamani; Akansel, Serkan; Svedlindh, Peter; Chaudhary, Sujeet

2018-02-01

The spin-pumping mechanism and associated interfacial Gilbert damping are demonstrated in ion-beam sputtered C o2FeAl (CFA)/Mo bilayer thin films employing ferromagnetic resonance spectroscopy. The dependence of the net spin-current transportation on Mo layer thickness, 0 to 10 nm, and the enhancement of the net effective Gilbert damping are reported. The experimental data have been analyzed using spin-pumping theory in terms of spin current pumped through the ferromagnet/nonmagnetic metal interface to deduce the real spin-mixing conductance and the spin-diffusion length, which are estimated to be 1.56 (±0.30 ) ×1019m-2 and 2.61 (±0.15 )nm , respectively. The damping constant is found to be 8.8 (±0.2 ) ×10-3 in the Mo(3.5 nm)-capped CFA(8 nm) sample corresponding to an ˜69 % enhancement of the original Gilbert damping 5.2 (±0.6 ) ×10-3 in the Al-capped CFA thin film. This is further confirmed by inserting the Cu dusting layer which reduces the spin transport across the CFA/Mo interface. The Mo layer thickness-dependent net spin-current density is found to lie in the range of 1 -4 MA m-2 , which also provides additional quantitative evidence of spin pumping in this bilayer thin-film system.

Scattering of charge and spin excitations and equilibration of a one-dimensional Wigner crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matveev, K. A.; Andreev, A. V.; Klironomos, A. D.

2014-07-01

We study scattering of charge and spin excitations in a system of interacting electrons in one dimension. At low densities, electrons form a one-dimensional Wigner crystal. To a first approximation, the charge excitations are the phonons in the Wigner crystal, and the spin excitations are described by the Heisenberg model with nearest-neighbor exchange coupling. This model is integrable and thus incapable of describing some important phenomena, such as scattering of excitations off each other and the resulting equilibration of the system. We obtain the leading corrections to this model, including charge-spin coupling and the next-nearest-neighbor exchange in the spin subsystem.more » We apply the results to the problem of equilibration of the one-dimensional Wigner crystal and find that the leading contribution to the equilibration rate arises from scattering of spin excitations off each other. We discuss the implications of our results for the conductance of quantum wires at low electron densities« less

SU(4) Kondo effect in double quantum dots with ferromagnetic leads

NASA Astrophysics Data System (ADS)

Weymann, Ireneusz; Chirla, Razvan; Trocha, Piotr; Moca, Cǎtǎlin Paşcu

2018-02-01

We investigate the spin-resolved transport properties, such as the linear conductance and the tunnel magnetoresistance, of a double quantum dot device attached to ferromagnetic leads and look for signatures of the SU (4 ) symmetry in the Kondo regime. We show that the transport behavior greatly depends on the magnetic configuration of the device, and the spin-SU(2) as well as the orbital and spin-SU(4) Kondo effects become generally suppressed when the magnetic configuration of the leads varies from the antiparallel to the parallel one. Furthermore, a finite spin polarization of the leads lifts the spin degeneracy and drives the system from the SU(4) to an orbital-SU(2) Kondo state. We analyze in detail the crossover and show that the Kondo temperature between the two fixed points has a nonmonotonic dependence on the degree of spin polarization of the leads. In terms of methods used, we characterize transport by using a combination of analytical and numerical renormalization group approaches.

Probing ultrafast spin dynamics through a magnon resonance in the antiferromagnetic multiferroic HoMnO 3

DOE PAGES

Bowlan, P.; Trugman, S. A.; Bowlan, J.; ...

2016-09-26

Here, we demonstrate an approach for directly tracking antiferromagnetic (AFM) spin dynamics by measuring ultrafast changes in a magnon resonance. We also test this idea on the multiferroic HoMnO 3 by optically photoexciting electrons, after which changes in the spin order are probed with a THz pulse tuned to a magnon resonance. This reveals a photoinduced change in the magnon line shape that builds up over 5–12 picoseconds, which we show to be the spin-lattice thermalization time, indicating that electrons heat the spins via phonons. We compare our results to previous studies of spin-lattice thermalization in ferromagnetic manganites, giving insightmore » into fundamental differences between the two systems. Finally, our work sheds light on the microscopic mechanism governing spin-phonon interactions in AFMs and demonstrates a powerful approach for directly monitoring ultrafast spin dynamics.« less

Rotatable spin-polarized electron source for inverse-photoemission experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stolwijk, S. D., E-mail: Sebastian.Stolwijk@wwu.de; Wortelen, H.; Schmidt, A. B.

2014-01-15

We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111)more » highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces.« less

Probing ultrafast spin dynamics through a magnon resonance in the antiferromagnetic multiferroic HoMnO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowlan, P.; Trugman, S. A.; Bowlan, J.

Here, we demonstrate an approach for directly tracking antiferromagnetic (AFM) spin dynamics by measuring ultrafast changes in a magnon resonance. We also test this idea on the multiferroic HoMnO 3 by optically photoexciting electrons, after which changes in the spin order are probed with a THz pulse tuned to a magnon resonance. This reveals a photoinduced change in the magnon line shape that builds up over 5–12 picoseconds, which we show to be the spin-lattice thermalization time, indicating that electrons heat the spins via phonons. We compare our results to previous studies of spin-lattice thermalization in ferromagnetic manganites, giving insightmore » into fundamental differences between the two systems. Finally, our work sheds light on the microscopic mechanism governing spin-phonon interactions in AFMs and demonstrates a powerful approach for directly monitoring ultrafast spin dynamics.« less

Prescription Drug Use among College Students: A Test of Criminal Spin Theory

ERIC Educational Resources Information Center

Lin, Wan-Chun

2017-01-01

Criminal spin theory developed by Ronel intends to provide a more comprehensive explanation of criminal behavior. It includes wide-ranging factors that impact human behavior at an individual, group, and cultural level. According to criminal spin theory, an event or a set of events can impact human emotions, thoughts, and behaviors. With the…

Defect-Rich Dopant-Free ZrO2 Nanostructures with Superior Dilute Ferromagnetic Semiconductor Properties.

PubMed

Rahman, Md Anisur; Rout, S; Thomas, Joseph P; McGillivray, Donald; Leung, Kam Tong

2016-09-14

Control of the spin degree of freedom of an electron has brought about a new era in spin-based applications, particularly spin-based electronics, with the potential to outperform the traditional charge-based semiconductor technology for data storage and information processing. However, the realization of functional spin-based devices for information processing remains elusive due to several fundamental challenges such as the low Curie temperature of group III-V and II-VI semiconductors (<200 K), and the low spin-injection efficiencies of existing III-V, II-VI, and transparent conductive oxide semiconductors in a multilayer device structure, which are caused by precipitation and migration of dopants from the host layer to the adjacent layers. Here, we use catalyst-assisted pulsed laser deposition to grow, for the first time, oxygen vacancy defect-rich, dopant-free ZrO2 nanostructures with high TC (700 K) and high magnetization (5.9 emu/g). The observed magnetization is significantly greater than both doped and defect-rich transparent conductive oxide nanomaterials reported to date. We also provide the first experimental evidence that it is the amounts and types of oxygen vacancy defects in, and not the phase of ZrO2 that control the ferromagnetic order in undoped ZrO2 nanostructures. To explain the origin of ferromagnetism in these ZrO2 nanostructures, we hypothesize a new defect-induced bound polaron model, which is generally applicable to other defect-rich, dopant-free transparent conductive oxide nanostructures. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and contribute to the design of exotic magnetic and novel multifunctional materials.

F-15 RPRV Spin Research Vehicle (SRV) attached to B-52 pylon

NASA Technical Reports Server (NTRS)

1975-01-01

In this ground photo, one of the F-15 RPRV/SRVs is shown on the same pylon used for the X-15 and lifting body flights. The vehicle was a 3/8 scale model of the F-15 aircraft, and was designed for stall and spin research. The cost was $250,000 for each RPRV versus $6.8 million for an actual F-15. After being released from the B-52, the unpowered vehicle was flown by pilots on the ground, including Einar K. Envoldson, William H. Dana, Thomas C. McMurtry, John A. Manke, and Michael C. Swann. During the descent, the F-15 RPRV underwent tests of its stability and control, departure characteristics, spin evaluation at high and low altitude, upright and inverted spins, and different spin modes. On its first 16 flights, the F-15 RPRV was to be recovered in midair by a helicopter. The F-15 RPRV's parachute would be caught by ropes strung between two poles below the helicopter. Of the 16 attempts, 13 were successful, while the three other flights ended with parachute landings and varying amounts of damage. The F-15 RPRVs were then fitted with three retractable skids, which allowed the ground pilot to land the aircraft on the lakebed. Of the next 10 flights, nine were successful lakebed landings, while the other came down by parachute. After 26 flights, the aircraft was renamed the Spin Research Vehicle (SRV) and was used to test different nose configurations. The tests made on flights 27 through 52 were spin mode determination, auto-spin recovery, airflow visualization, the effects of strakes on vortex flow, aft pressure measurements, and a nose-mounted anti-spin parachute. The latter was unusual, as anti-spin parachutes are commonly mounted on the tail. During flight 36, on February 18, 1981, the nose-mounted parachute fouled the pitot tube after deployment. This forced a parachute landing, which was the only one in the SRV flights. The last RPRV/SRV flight was made on July 15, 1981. One of the vehicles has been restored and is on display at the Dryden Flight Research Center.

Sharp peaks in the conductance of a double quantum dot and a quantum-dot spin valve at high temperatures: A hierarchical quantum master equation approach

NASA Astrophysics Data System (ADS)

Wenderoth, S.; Bätge, J.; Härtle, R.

2016-09-01

We study sharp peaks in the conductance-voltage characteristics of a double quantum dot and a quantum dot spin valve that are located around zero bias. The peaks share similarities with a Kondo peak but can be clearly distinguished, in particular as they occur at high temperatures. The underlying physical mechanism is a strong current suppression that is quenched in bias-voltage dependent ways by exchange interactions. Our theoretical results are based on the quantum master equation methodology, including the Born-Markov approximation and a numerically exact, hierarchical scheme, which we extend here to the spin-valve case. The comparison of exact and approximate results allows us to reveal the underlying physical mechanisms, the role of first-, second- and beyond-second-order processes and the robustness of the effect.

Conductance Change Induced by the Rashba Effect in the LaAlO3/SrTiO3 Interface.

PubMed

Kim, Taeyueb; Kim, Shin-Ik; Baek, Seung-Hyub; Hong, Jinki; Koo, Hyun Cheol

2015-11-01

The LaAlO3/SrTiO3 (LAO/STO) heterostructure has an inherent space inversion asymmetry causing an internal electric field near the interface. The Rashba spin-orbit coupling arising from this structural characteristic has a considerable influence on spin transport. With application of an external magnetic field, we observed conductance change in the LAO/STO interface which depends on the sign and magnitude of the field. Our systematic study revealed that these results come from spin dependent transport, by which we obtained quantitative strength of the Rashba effect. The Rashba strength in this system depends on the temperature: it varies from 2.6 x 10(-12) eVm to negligible value in the temperature range of 1.8 K-12 K. This method for detecting Rashba effect covers a wider temperature range in comparison with those obtained from Shubnikov-de Haas oscillation or weak antilocalization measurements.

Experimental Spin Testing of Integrally Damped Composite Plates

NASA Technical Reports Server (NTRS)

Kosmatka, John

1998-01-01

The experimental behavior of spinning laminated composite pretwisted plates (turbo-fan blade-like) with small (less than 10% by volume) integral viscoelastic damping patches was investigated at NASA-Lewis Research Center. Ten different plate sets were experimentally spin tested and the resulting data was analyzed. The first-four plate sets investigated tailoring patch locations and definitions to damp specific modes on spinning flat graphite/epoxy plates as a function of rotational speed. The remaining six plate sets investigated damping patch size and location on specific modes of pretwisted (30 degrees) graphite/epoxy plates. The results reveal that: (1) significant amount of damping can be added using a small amount of damping material, (2) the damped plates experienced no failures up to the tested 28,000 g's and 750,000 cycles, (3) centrifugal loads caused an increase in bending frequencies and corresponding reductions in bending damping levels that are proportional to the bending stiffness increase, and (4) the centrifugal loads caused a decrease in torsion natural frequency and increase in damping levels of pretwisted composite plates.

Atomic "bomb testing": the Elitzur-Vaidman experiment violates the Leggett-Garg inequality

NASA Astrophysics Data System (ADS)

Robens, Carsten; Alt, Wolfgang; Emary, Clive; Meschede, Dieter; Alberti, Andrea

2017-01-01

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the "bomb test" with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett-Garg inequality.

Transitional millisecond pulsars in the low-level accretion state

NASA Astrophysics Data System (ADS)

Jaodard, Amruta D.; Hessels, Jason W. T.; Archibald, Anne; Bogdanov, Slavko; Deller, Adam; Hernandez Santisteban, Juan; Patruno, Alessandro; D'Angelo, Caroline; Bassa, Cees; Amruta Jaodand

2018-01-01

In the canonical pulsar recycling scenario, a slowly spinning neutron star can be rejuvenated to rapid spin rates by the transfer of angular momentum and mass from a binary companion star. Over the last decade, the discovery of three transitional millisecond pulsars (tMSPs) has allowed us to study recycling in detail. These systems transition between accretion-powered (X-ray) and rotation-powered (radio) pulsar states within just a few days, raising questions such as: what triggers the state transition, when does the recycling process truly end, and what will the radio pulsar’s final spin rate be? Systematic multi-wavelength campaigns over the last decade have provided critical insights: multi-year-long, low-level accretion states showing coherent X-ray pulsations; extremely stable, bi-modal X-ray light curves; outflows probed by radio continuum emission; a surprising gamma-ray brightening during accretion, etc. In my thesis I am trying to bring these clues together to understand the low-level accretion process that recycles a pulsar. For example, recently we timed PSR J1023+0038 in the accretion state and found it to be spinning down ~26% faster compared to the non-accreting radio pulsar state. We are currently conducting simultaneous multi-wavelength campaigns (XMM, HST, Kepler and VLA) to understand the global variability of the accretion flow, as well as high-energy Fermi-LAT observations to probe the gamma-ray emission mechanism. I will highlight these recent developments, while also presenting a broad overview of tMSPs as exciting new laboratories to test low-level accretion onto magnetized neutron stars.