Staphylococcus aureus Peptidoglycan Tertiary Structure from Carbon-13 Spin Diffusion
Sharif, Shasad; Singh, Manmilan; Kim, Sung Joon; Schaefer,Jacob
2009-01-01
The cell-wall peptidoglycan of Staphylococcus aureus is a heterogeneous, highly cross-linked polymer of unknown tertiary structure. We have partially characterized this structure by measuring spin diffusion from 13C labels in pentaglycyl cross-linking segments to natural-abundance 13C in the surrounding intact cell walls. The measurements were performed using a version of centerband-only detection of exchange (CODEX). The cell walls were isolated from S. aureus grown in media containing [1-13...
DEFF Research Database (Denmark)
Bruun, Georg
2011-01-01
We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures......, strong correlation effects are included through the Landau parameters which we extract from Monte Carlo results. We show that the spin diffusion coefficient has a minimum for a temperature somewhat below the Fermi temperature with a value that approaches the quantum limit ~/m in the unitarity regime...
Acceleration of carbon-13 spin-lattice relaxation times in amino acids by electrolytes
Institute of Scientific and Technical Information of China (English)
Tian Jinping; Yin Yingwu
2004-01-01
A series of amino acids and carboxylic acids were determined by 13C NMR spectroscopy.The results showed that addition of 3M MgCl2 led to the 13C NMR integral area of samples being well proportional to number of carbon atoms that produce the particular signal with reliability over 95%. Measurements of 13C spin-lattice relaxation times (T1's) are reported for a number of amino acids. T1's of all the carbons in amino acids generally tend to decrease with the increase of the concentration of electrolytes, and the presence of magnesium slats is of significant. Carboxylic carbons in amino acids are the most sensitive "acceptor" of the 13C spin-lattice relaxation accelerating effects in electrolytes, and the 13C spin-lattice relaxation accelerating ability of electrolytes is Mg(ClO4)2 ＞MgCl2 ＞CaCl2 ＞NaCl ＞KCl ＞LiClO4 ＞NaOH. In general, T1's of C1 carbons in nonpolar a-amino acids are higher than those in polar and basic a-amino acids both in aqueous and 3M MgCl2 medium. In aliphatic straight-chain amino acids, a-, a-, a-, ai- and a- amino acids, T1's of C1 carbons tend to reduce with the increase of inserted carbon numbers between amino and carboxylic groups compared with Gly. T1's can be decreased even more when amino acids are mixed in 3M MgCl2, but T1's of carbons in amino acids decrease slightly with increase of the concentration of amino acids in 3M MgCl2. The mechanisms of the observed phenomena are discussed in terms of intermolecular interaction and paramagnetic impurity in electrolytes, large contributions of intermolecular interaction which is enhanced in electrolytes concentrate on the incoming "unsaturation" of the primary solvation shell of cations with the increase of electrolytes concentration and complexes formation of amino acids with metal ions. In electrolytes, amino acids are "anchored" to cations and molecule tumbling is slowed down, molecular rigidity is increased and molecular size is "enlarged", all of these are helpful to accelerate
Spin drift and spin diffusion currents in semiconductors
Directory of Open Access Journals (Sweden)
M Idrish Miah
2008-01-01
Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.
Spin transfer torque with spin diffusion in magnetic tunnel junctions
Manchon, Aurelien
2012-08-09
Spin transport in magnetic tunnel junctions in the presence of spin diffusion is considered theoretically. Combining ballistic tunneling across the barrier and diffusive transport in the electrodes, we solve the spin dynamics equation in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque, as well as a nonconventional thickness dependence of both spin torque components.
Baldo, M.; Grassi, A.; Guidoni, L.; Nicolini, M.; Pappalardo, G. C.; Viti, V.
The spin-lattice relaxation times ( T1) of carbon-13 resonances of the drug 2-oxopyrrolidin- 1-ylacetamide ( 2OPYAC) were determined in CDCl 3 + DMSO and H 2O solutions to investigate the internal conformational flexibility. The measured T1s for the hydrogen-bearing carbon atoms of the 2-pyrrolidone ring fragment were diagnostic of a rigid conformation with respect to the acetamide linked moiety. The model of anisotropic reorientation of a rigid body was used to analyse the measured relaxation data in terms of a single conformation. Owing to the small number of T1 data available the fitting procedure for each of the possible conformations failed. The structure corresponding to the rigid conformation was therefore considered to be the one that is strongly stabilized by internal hydrogen bonding as predicted on the basis of theoretical MO ab initio quantum chemical calculations.
Diffusive magnonic spin transport in antiferromagnetic insulators
Rezende, S. M.; Rodríguez-Suárez, R. L.; Azevedo, A.
2016-02-01
It has been shown recently that a layer of the antiferromagnetic insulator (AFI) NiO can be used to transport spin current between a ferromagnet (FM) and a nonmagnetic metal (NM). In the experiments one uses the microwave-driven ferromagnetic resonance in a FM layer to produce a spin pumped spin current that flows through an AFI layer and reaches a NM layer where it is converted into a charge current by means of the inverse spin Hall effect. Here we present a theory for the spin transport in an AFI that relies on the spin current carried by the diffusion of thermal antiferromagnetic magnons. The theory explains quite well the measured dependence of the voltage in the NM layer on the thickness of the NiO layer.
Spin diffusion in doped semiconductors: the role of Coulomb interactions
D'Amico, Irene; Vignale, Giovanni
2000-01-01
We examine the effect of the Coulomb interaction on the mobility and diffusion of spin packets in doped semiconductors. We find that the diffusion constant is reduced, relative to its non-interacting value, by the combined effect of Coulomb-enhanced spin susceptibility and spin Coulomb drag. In ferromagnetic semiconductors, the spin diffusion constant vanishes at the ferromagnetic transition temperature.
Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect
Energy Technology Data Exchange (ETDEWEB)
Zhang, Wei; Pearson, John E.; Hoffmann, Axel [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Vlaminck, Vincent [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Colegio de Ciencias e Ingenería, Universidad San Fransciso de Quito, Quito (Ecuador); Divan, Ralu [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States); Bader, Samuel D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)
2013-12-09
The spin diffusion length of Pt at room temperature and at 8 K is experimentally determined via spin pumping and spin Hall effect in permalloy/Pt bilayers. Voltages generated during excitation of ferromagnetic resonance from the inverse spin Hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Varying the Pt layer thickness gives rise to an evolution of the voltage line shape due to the superposition of the above two effects. By studying the ratio of the two voltage components with the Pt layer thickness, the spin diffusion length of Pt can be directly extracted. We obtain a spin diffusion length of ∼1.2 nm at room temperature and ∼1.6 nm at 8 K.
Effect of spin diffusion on spin torque in magnetic nanopillars
Urazhdin, Sergei; Button, Scott
2008-01-01
We present systematic magnetoelectronic measurements of magnetic nanopillars with different structures of polarizing magnetic layers. The magnetic reversal at small magnetic field, the onset of magnetic dynamics at larger field, and the magnetoresistance exhibit a significant dependence on the type of the polarizing layer. We performed detailed quantitative modeling showing that the differences can be explained by the effects of spin-dependent electron diffusion.
Topological spin drag driven by skyrmion diffusion
Ochoa, Hector; Kim, Se Kwon; Tserkovnyak, Yaroslav
2016-01-01
We study the spin drag mediated by the Brownian motion of skyrmions. We consider a two-terminal geometry in which a thin film of a magnetic insulator is placed in between two metallic contacts. An electric current in one of the terminals pumps topological charge into the magnet via a spin-transfer torque. The charge diffuses over the bulk of the system as stable skyrmion textures. By Onsager's reciprocity, the topological charge leaving the magnet produces an electromotive force in the second...
Spin Hall effect, Hall effect and spin precession in diffusive normal metals
Shchelushkin, R. V.; Brataas, Arne
2005-01-01
We study transport in normal metals in an external magnetic field. This system exhibits an interplay between a transverse spin imbalance (spin Hall effect) caused by the spin-orbit interaction, a Hall effect via the Lorentz force, and spin precession due to the Zeeman effect. Diffusion equations for spin and charge flow are derived. The spin and charge accumulations are computed numerically in experimentally relevant thin film geometries. The out-of-plane spin Hall potential is suppressed whe...
Spin diffusion in trapped clouds of strongly interacting cold atoms
Bruun, G. M.; Pethick, C.J.
2011-01-01
We show that puzzling recent experimental results on spin diffusion in a strongly interacting atomic gas may be understood in terms of the predicted spin diffusion coefficient for a generic strongly interacting system. Three important features play a central role: a) Fick's law for diffusion must be modified to allow for the trapping potential, b) the diffusion coefficient is inhomogeneous, due to the density variations in the cloud and c) the diffusion approximation fails in the outer parts ...
A novel method to evaluate spin diffusion length of Pt
Zhang, Yan-qing; Sun, Niu-yi; Che, Wen-ru; Shan, Rong; Zhu, Zhen-gang
2016-05-01
Spin diffusion length of Pt is evaluated via proximity effect of spin orbit coupling (SOC) and anomalous Hall effect (AHE) in Pt/Co2FeAl bilayers. By varying the thicknesses of Pt and Co2FeAl layer, the thickness dependences of AHE parameters can be obtained, which are theoretically predicted to be proportional to the square of the SOC strength. According to the physical image of the SOC proximity effect, the spin diffusion length of Pt can easily be identified from these thickness dependences. This work provides a novel method to evaluate spin diffusion length in a material with a small value.
Diffusion equation and spin drag in spin-polarized transport
DEFF Research Database (Denmark)
Flensberg, Karsten; Jensen, Thomas Stibius; Mortensen, Asger
2001-01-01
We study the role of electron-electron interactions for spin-polarized transport using the Boltzmann equation, and derive a set of coupled transport equations. For spin-polarized transport the electron-electron interactions are important, because they tend to equilibrate the momentum of the two-spin...... species. This "spin drag" effect enhances the resistivity of the system. The enhancement is stronger the lower the dimension is, and should be measurable in, for example, a two-dimensional electron gas with ferromagnetic contacts. We also include spin-flip scattering, which has two effects......: it equilibrates the spin density imbalance and, provided it has a non-s-wave component, also a current imbalance....
Lorenz, Klaus; Preston, Caroline M
2002-01-01
Condensed tannins can be found in various parts of many plants. Unlike lignin there has been little study of their fate as they enter the soil organic matter pool and their influence on nutrient cycling, especially through their protein-binding properties. We extracted and characterized tannin-rich fractions from humus collected in 1998 from a black spruce [Picea mariana (Mill.) Britton et al.] forest in Canada where a previous study (1995) showed high levels (3.8% by weight) of condensed tannins. A reference tannin purified from black spruce needles was characterized by solution 13C nuclear magnetic resonance (NMR) as a pure procyanidin with mainly cis stereochemistry and an average chain length of four to five units. The colorimetric proanthocyanidin (PA) assay, standardized against the black spruce tannin, showed that both extracted humus fractions had higher tannin contents than the original humus (2.84% and 11.17% vs. 0.08%), and accounted for 32% of humus tannin content. Consistent with the results from the chemical assay, the aqueous fraction showed higher tannin signals in the 13C cross-polarization and magic-angle spinning (CPMAS) NMR spectrum than the emulsified one. As both tannin-rich humus fractions were depleted in N and high in structures derived from lignin and cutin, they did not have properties consistent with recaldtrant tannin-protein complexes proposed as a mechanism for N sequestration in humus. Further studies are needed to establish if tannin-protein structures in humus can be detected or isolated, or if tannins contribute to forest management problems observed in these ecosystems by binding to and slowing down the activity of soil enzymes.
Spin Echo Attenuation of Restricted Diffusion as a Discord of Spin Phase Structure
Stepisnik
1998-04-01
By using the particle probability density we analyze the spin echo attenuation of particles, diffusing in a bounded region. It provides a means to expand a nonuniform spin phase distribution into a series of waves that characterize the geometry and boundary conditions of confinement. Random motion disrupts the initial phase structure created by applied gradients and consequently discords its structure waves. By assuming the spin phase fluctuation and/or the randomness of spin phase distribution in the subensemble as a Gaussian stochastic process, we derive a new analytical expression for the echo attenuation related to the particle velocity correlation. For a diffusion in porous structure we get the expression featuring the same "diffusive diffraction" patterns as those being found and explained by P. T. Callaghan and A. Coy ("Principles of Nuclear Magnetic Resonance Microscopy," Oxford Univ. Press, Oxford (1991); J. Chem. Phys. 101, 4599-4609 (1994)) with the use of propagator theory. With the new approach we cast a new light on the phenomena and derive analitically how the diffusive diffractions appear when the sequence of finite or even modulated gradients are applied. The method takes into account the non-Markovian character of restricted diffusion, and therefore the echo dependence on the diffusion lengths and on the strength of applied gradient differs from the results of authors assuming the Markovian diffusion either by dealing with the diffusion propagators or by the computer simulation of Fick's diffusion. Copyright 1998 Academic Press. PMID:9571110
Diffuse Galactic Emission from Spinning Dust Grains
Draine, B. T.; Lazarian, A.
1997-01-01
Spinning interstellar dust grains produce detectable rotational emission in the 10-100 GHz frequency range. We calculate the emission spectrum, and show that this emission can account for the ``anomalous'' Galactic background component which correlates with 100um thermal emission from dust. Implications for cosmic background studies are discussed.
Spin diffusion in an inhomogeneous internal field (non equidistant energy spectrum)
Furman, Gregory B.; Goren, Shaul D.
2004-01-01
The theory of spin diffusion is extended to the case of spin lattice relaxation and spin diffusion in an inhomogeneous field in spin systems with non-equidistant energy spectrum. Two coupled equations describing the mutual relaxation and the spin diffusion of the nuclear magnetization and dipolar energy were obtained by using the method of nonequilibrium state operator. The equations were solved for short and long times approximation corresponding to the direct and diffusion relaxation regimes.
Spin diffusion in bulk GaN measured with MnAs spin injector
Jahangir, Shafat
2012-07-16
Spin injection and precession in bulk wurtzite n-GaN with different doping densities are demonstrated with a ferromagnetic MnAs contact using the three-terminal Hanle measurement technique. Theoretical analysis using minimum fitting parameters indicates that the spin accumulation is primarily in the n-GaN channel rather than at the ferromagnet (FM)/semiconductor (SC) interface states. Spin relaxation in GaN is interpreted in terms of the D’yakonov-Perel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Our results indicate that epitaxial ferromagnetic MnAs is a suitable high-temperature spin injector for GaN.
Magnetization and spin diffusion of liquid 3He in aerogel
International Nuclear Information System (INIS)
We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of 3He in aerogel, including both elastic and inelastic scattering of 3He quasiparticles, and compare these results with data for 3He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the 'dirty' B phase of 3He in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density
Sayed, Shehrin; Hong, Seokmin; Datta, Supriyo
We will present a general semiclassical theory for an arbitrary channel with spin-orbit coupling (SOC), that uses four electrochemical potential (U + , D + , U - , and D -) depending on the sign of z-component of the spin (up (U) , down (D)) and the sign of the x-component of the group velocity (+ , -) . This can be considered as an extension of the standard spin diffusion equation that uses two electrochemical potentials for up and down spin states, allowing us to take into account the unique coupling between charge and spin degrees of freedom in channels with SOC. We will describe applications of this model to answer a number of interesting questions in this field such as: (1) whether topological insulators can switch magnets, (2) how the charge to spin conversion is influenced by the channel resistivity, and (3) how device structures can be designed to enhance spin injection. This work was supported by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.
Spin diffusive modes and thermal transport in neutron star crusts
Sedrakian, Armen
2015-01-01
In this contribution we first review a method for obtaining the collective modes of pair-correlated neutron matter as found in a neutron star inner crust. We discuss two classes of modes corresponding to density and spin perturbations with energy spectra $\\omega = \\omega_0 + \\alpha q^2$, where $\\omega_0 = 2\\Delta$ is the threshold frequency and $\\Delta$ is the gap in the neutron fluid spectrum. For characteristic values of Landau parameters in neutron star crusts the exitonic density modes have $\\alpha 0$ and they exist above $\\omega_0$ which implies that these modes are damped. As an application of these findings we compute the thermal conductivity due to spin diffusive modes and show that it scales as $T^{1/2} \\exp(-2\\omega_0/T)$ in the case where their two-by-two scattering cross-section is weakly dependent on temperature.
High dynamic orientation of protons, deuterons and carbon-13 nuclei
International Nuclear Information System (INIS)
The behaviour of hydrogen, deuterium, and carbon-13 nuclear spin systems have been studied in partially deuterated diols, doped with paramagnetic Crsup(V) complexes, between 0.1 and 0.5 K. Experimental evidence is given that the dynamic polarization in such samples comes from a cooling of the electron spin-spin interaction reservoir by off-resonance microwave irradiation; a strong thermal coupling between this reservoir and the nuclear Zeeman reservoirs cools these too, thus changing the polarizations. In a 25 kG magnetic field at a lattice temperature of 0.37 K we reached a common spin temperature for the nuclear Zeeman reservoirs of 1.1 mK in 1,2-propanediol-D6, which corresponds to a proton polarization of 98%, a deuteron polarization of 44%, and a carbon-13 polarization of 52%. A new way of dynamic orientation of the deuteron spin system was found. It allows one to vary the deuteron tensor polarization or alignment independently of its vector polarization. This can be done by slightly off-resonance RF irradiation of the polarized proton system, which cools the proton spin-spin interaction reservoir. It appeared that at the same time the RF field provides a thermal contract between this reservoir and the deuteron quadrupole interaction reservoir, which caused the observed alignment. Values around 60% were reached for some parts of the deuteron spin system, corresponding to a deuteron quadrupole spin temperature of 7 uK. The dependence of the alignment on RF frequency and initial proton polarization as well as thermal mixing rates are in good agreement with quantitative estimates from spin temperature theory. (author)
Li, Lijun; Lee, Inyeal; Lim, Dongsuk; Rathi, Servin; Kang, Moonshik; Uemura, Tetsuya; Kim, Gil-Ho
2016-08-01
We fabricated a non-local spin valve with a thin layer of graphite with Co transparent electrodes. The spin-valve effect and spin precession were observed at room temperature. The magnitude of the mangetoresistance increases when temperature decreases. The spin-relaxation time, {τ }s, obtained from the fitting of the Hanle curves increases with decreasing temperature with a weak dependence ∼ {T}-0.065 while the spin-diffusion constant D decreases. At room temperature, {τ }s exceeds 100 ps and the spin-diffusion length, {λ }s, is ∼2 μm. The temperature dependence of {λ }s is not monotonic, and it has the largest value at room temperature. Our results show that multilayer graphene is a suitable material for spintronic devices.
Yue, Z.; Prestgard, M. C.; Tiwari, A.; Raikh, M. E.
2016-01-01
We study theoretically the effective spin Hall properties of a composite consisting of two materials with and without spin-orbit (SO) coupling. In particular, we assume that SO material represents a system of grains in a matrix with no SO. We calculate the effective spin Hall angle and the effective spin diffusion length of the mixture. Our main qualitative finding is that, when the bare spin diffusion length is much smaller than the radius of the grain, the effective spin diffusion length is strongly enhanced, well beyond the "geometrical" factor. The physical origin of this additional enhancement is that, with small diffusion length, the spin current mostly flows around the grain without suffering much loss. We also demonstrate that the voltage, created by a spin current, is sensitive to a very weak magnetic field directed along the spin current, and even reverses sign in a certain domain of fields. The origin of this sensitivity is that the spin precession, caused by magnetic field, takes place outside the grains where SO is absent.
Zheng, W; Liu, J -G; Zhang, Y; Ye, Q; Swank, C; 10.1103/PhysRevA.84.053411
2012-01-01
We develop an approach, by calculating the autocorrelation function of spins, to derive the magnetic field gradient induced transverse ($T_2$) relaxation of spins undergoing restricted diffusion. This approach is an extension to the method adopted by McGregor. McGregor's approach solves the problem only in the fast diffusion limit; however, our approach yields a single analytical solution suitable in all diffusion regimes, including the intermediate regime. This establishes a direct connection between the well-known Torrey's slow diffusion result and the fast diffusion result. We also perform free induction decay measurements on spin-exchange optically polarized $^3$He gas with different diffusion constants. The transverse relaxation profiles are compared with the theory and satisfactory agreement has been found throughout all diffusion regimes. In addition to the transverse relaxation, this approach is also applicable to solving the longitudinal relaxation ($T_1$) regardless of the diffusion limits. It turns...
Spin Diffusion in Trapped Clouds of Cold Atoms with Resonant Interactions
DEFF Research Database (Denmark)
Bruun, Georg Morten; Pethick, C. J.
2011-01-01
We show that puzzling recent experimental results on spin diffusion in a strongly interacting atomic gas may be understood in terms of the predicted spin diffusion coefficient for a generic strongly interacting system. Three important features play a central role: (a) Fick’s law for diffusion mus...... be modified to allow for the trapping potential; (b) the diffusion coefficient is inhomogeneous, due to the density variations in the cloud; and (c) the diffusion approximation fails in the outer parts of the cloud, where the mean free path is long....
Drew, A J; Hoppler, J; Schulz, L; Pratt, F L; Desai, P; Shakya, P; Kreouzis, T; Gillin, W P; Suter, A; Morley, N A; Malik, V K; Dubroka, A; Kim, K W; Bouyanfif, H; Bourqui, F; Bernhard, C; Scheuermann, R; Nieuwenhuys, G J; Prokscha, T; Morenzoni, E
2009-02-01
Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance. PMID:19029892
Shot noise in a diffusive F-N-F spin valve
Mishchenko, E. G.
2003-01-01
Fluctuations of electric current in a spin valve consisting of a diffusive conductor connected to ferromagnetic leads and operated in the giant magnetoresistance regime are studied. It is shown that a new source of fluctuations due to spin-flip scattering enhances strongly shot noise up to a point where the Fano factor approaches the full Poissonian value.
Silicon spin diffusion transistor: materials, physics and device characteristics
Dennis, C L; Tiusan, C.; Gregg, J.F.; Ensell, G.; Thompson, S M
2005-01-01
The realisation that eaveryday electronics has ignored the spin of the carrier in favour of its charge is the foundation of the field of spintronics. Starting with simple two-terminal devices based on GMR and tunnel magnetoresistance, the technology has advanced to consider three-terminal devices that aim to combine spin sensitivity with a high current gain and a large current output. These devices require both efficient spin injection and semiconductor fabrication. In this paper, a discussio...
Gill, Michelle L.; Palmer, Arthur G.
2014-01-01
The present work demonstrates that NMR spin relaxation rate constants for molecules interconverting between states with different diffusion tensors can be modeled theoretically by combining orientational correlation functions for exchanging spherical molecules with locally isotropic approximations for the diffusion anisotropic tensors. The resulting expressions are validated by comparison with correlation functions obtained by Monte Carlo simulations and are accurate for moderate degrees of d...
Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets
Akosa, Collins Ashu
2015-03-12
Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spin-conserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ∼∇2[m×(u⋅∇)m]+ξ∇2[(u⋅∇)m], where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dynamics (precession, dephasing, and spin-flip). This torque, which scales as the inverse square of the domain wall width, only weakly enhances the longitudinal velocity of a transverse domain wall but significantly enhances the transverse velocity of vortex walls. The spatial-dependent spin transfer torque uncovered in this study is expected to have significant impact on the current-driven motion of abrupt two-dimensional textures such as vortices, skyrmions, and merons.
Imaging Drift and Diffusion of Accumulation from the Spin Hall Effect
Stern, N. P.; Steuerman, D. W.; Mack, S.; Gossard, A. C.; Awschalom, D. D.
2008-03-01
The spontaneous generation of spin polarization near sample edges by the spin Hall effect when electron currents flow in a metal or semiconductor with spin-orbit coupling has attracted recent attention due to the elegant and complex spin-orbit physics as well as the potential for all-electrical spin generation in spintronics devices. Optical techniques in semiconductors allow for spatial resolution of the electrically generated spin accumulation, a feature not present in all-electrical measurements. We use Kerr rotation microscopy to image the spatial and temporal evolution of spin accumulation produced by the extrinsic spin Hall effect in n-GaAs devices. Measurements in a variety of device geometries, including arms transverse to a channel, reveal the unambiguous contribution of longitudinal spin drift in accumulation profilesootnotetextN. P. Stern, D. W. Steuerman, S. Mack, A.C. Gossard, and D. D. Awschalom, Appl. Phys. Rev. Lett. 91, 062109 (2007). We develop one- and two- dimensional drift-diffusion modeling to explain the observed features, providing a more complete understanding of observations of spin accumulation and the spin Hall effect.
Institute of Scientific and Technical Information of China (English)
YANG Yanwu; WANG Dehua; QIU Jianqing; QIAN Baogong; WANG Hongzuo
1992-01-01
The carbon-13 spin-spin relaxation times of fluorine-containing ionomers are measured and motional correlation times τ0 and τd are calculated by using VJGM model. The results show that the motions of polymer main chain in ionomers become more difficult with increasing of ionization degree and contents of functional group, and depend on the fine structures and stability of ionic microdomains.
Analysis of a coupled spin drift-diffusion Maxwell-Landau-Lifshitz system
Zamponi, Nicola; Jüngel, Ansgar
2016-05-01
The existence of global weak solutions to a coupled spin drift-diffusion and Maxwell-Landau-Lifshitz system is proved. The equations are considered in a two-dimensional magnetic layer structure and are supplemented with Dirichlet-Neumann boundary conditions. The spin drift-diffusion model for the charge density and spin density vector is the diffusion limit of a spinorial Boltzmann equation for a vanishing spin polarization constant. The Maxwell-Landau-Lifshitz system consists of the time-dependent Maxwell equations for the electric and magnetic fields and of the Landau-Lifshitz-Gilbert equation for the local magnetization, involving the interaction between magnetization and spin density vector. The existence proof is based on a regularization procedure, L2-type estimates, and Moser-type iterations which yield the boundedness of the charge and spin densities. Furthermore, the free energy is shown to be nonincreasing in time if the magnetization-spin interaction constant in the Landau-Lifshitz equation is sufficiently small.
Elyasi, Mehrdad; Yang, Hyunsoo
2016-07-01
We have considered the effect of different spin-orbit interaction mechanisms on the process of demagnetization under the influence of short-pulse lasers. All-optical magnetization reversal of perpendicularly magnetized thin films can occur if there are sufficient strong spin-Hall, skew scattering, and Rashba interactions. In the presence of spin-orbit interactions, the transient charge currents provide the generation of transverse-spin currents and accumulations, which eventually exert spin-transfer torque on the magnetization. By combining the optically excited spin-dependent diffusive transport with the spin and charge currents due to skew scattering, spin-Hall, inverse spin-Hall, and Rashba interactions into a numerical model, we demonstrate a possibility of ultrafast all-optical magnetization reversal. This understanding provokes intriguing, more in-depth experimental studies on the role of spin-orbit interaction mechanisms in optimizing structures for all-optical magnetization reversal.
Diffusive Spin Dynamics in Ferromagnetic Thin Films with a Rashba Interaction
Wang, Xuhui
2012-03-13
In a ferromagnetic metal layer, the coupled charge and spin diffusion equations are obtained in the presence of both Rashba spin-orbit interaction and magnetism. The misalignment between the magnetization and the nonequilibrium spin density induced by the Rashba field gives rise to Rashba spin torque acting on the ferromagnetic order parameter. In a general form, we find that the Rashba torque consists of both in-plane and out-of-plane components, i.e., T=T Sy×m+T Sm×(y×m). Numerical simulations on a two-dimensional nanowire consider the impact of diffusion on the Rashba torque and reveal a large enhancement to the ratio T/T S for thin wires. Our theory provides an explanation for the mechanism driving the magnetization switching in a single ferromagnet as observed in the recent experiments. © 2012 American Physical Society.
Gill, Michelle L; Palmer, Arthur G
2014-09-25
The present work demonstrates that NMR spin relaxation rate constants for molecules interconverting between states with different diffusion tensors can be modeled theoretically by combining orientational correlation functions for exchanging spherical molecules with locally isotropic approximations for the diffusion anisotropic tensors. The resulting expressions are validated by comparison with correlation functions obtained by Monte Carlo simulations and are accurate for moderate degrees of diffusion anisotropy typically encountered in investigations of globular proteins. The results are complementary to an elegant, but more complex, formalism that is accurate for all degrees of diffusion anisotropy [Ryabov, Y.; Clore, G. M.; Schwieters, C. D. J. Chem. Phys. 2012, 136, 034108]. PMID:25167331
Gmitra, M.; Barnas, J.
2009-01-01
Angular variation of giant magnetoresistance and spin-transfer torque in metallic spin-valve heterostructures is analyzed theoretically in the limit of diffusive transport. It is shown that the spin-transfer torque in asymmetric spin valves can vanish in non-collinear magnetic configurations, and such a non-standard behavior of the torque is generally associated with a non-monotonic angular dependence of the giant magnetoresistance, with a global minimum at a non-collinear magnetic configurat...
Electron interaction effect on the spin diffusion and transport in half metallic magnets
Energy Technology Data Exchange (ETDEWEB)
Chui, S.T., E-mail: chui@bartol.udel.edu
2015-11-01
For half metallic magnets, spin fluctuation is the same as charge fluctuation. The length scale is controlled by electron–electron interaction and is of the order of the screening length, typically of the order of an Angstrom whereas the ordinary spin diffusion length is of the order of 100 Å or more. We examine the eigenstates for charge and spin transport for systems close to half-metallicity. Due to the electron–electron interaction, the decay length of the eigenstate that corresponds to the longitudinal spin diffusion length is much reduced, consistent with recent experimental results. We explore the consequence of this. We find that there are two parameters that characterize half-metallicity and illustrate our results numerically with a simple model. - Highlights: • We show that in half metallic magnets such as the Heusler alloys electron–electron interaction need to be included. • In this class of material the length scale for the transport eigenstates that corresponds to spin diffusion is much reduced. • There are two quantities, the diffusion constant and the density of states, that control the magneto-resistance ratio.
Energy Technology Data Exchange (ETDEWEB)
Kohda, M. [IBM Research–Zürich, Säumerstrasse 4, CH-8803 Rüschlikon (Switzerland); Department of Materials Science, Tohoku University, 980-8579 Sendai (Japan); Altmann, P.; Salis, G. [IBM Research–Zürich, Säumerstrasse 4, CH-8803 Rüschlikon (Switzerland); Schuh, D.; Ganichev, S. D. [Institute of Experimental and Applied Physics, University of Regensburg, D-93040 Regensburg (Germany); Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich (Switzerland)
2015-10-26
A method is presented that enables the measurement of spin-orbit coefficients in a diffusive two-dimensional electron gas without the need for processing the sample structure, applying electrical currents or resolving the spatial pattern of the spin mode. It is based on the dependence of the average electron velocity on the spatial distance between local excitation and detection of spin polarization, resulting in a variation of spin precession frequency that in an external magnetic field is linear in the spatial separation. By scanning the relative positions of the exciting and probing spots in a time-resolved Kerr rotation microscope, frequency gradients along the [100] and [010] crystal axes of GaAs/AlGaAs QWs are measured to obtain the Rashba and Dresselhaus spin-orbit coefficients, α and β. This simple method can be applied in a variety of materials with electron diffusion for evaluating spin-orbit coefficients.
Diffusion-mediated nuclear spin phase decoherence in cylindrically porous materials
Knight, Michael J.; Kauppinen, Risto A.
2016-08-01
In NMR or MRI of complex materials, including biological tissues and porous materials, magnetic susceptibility differences within the material result in local magnetic field inhomogeneities, even if the applied magnetic field is homogeneous. Mobile nuclear spins move though the inhomogeneous field, by translational diffusion and other mechanisms, resulting in decoherence of nuclear spin phase more rapidly than transverse relaxation alone. The objective of this paper is to simulate this diffusion-mediated decoherence and demonstrate that it may substantially reduce coherence lifetimes of nuclear spin phase, in an anisotropic fashion. We do so using a model of cylindrical pores within an otherwise homogeneous material, and calculate the resulting magnetic field inhomogeneities. Our simulations show that diffusion-mediated decoherence in a system of parallel cylindrical pores is anisotropic, with coherence lifetime minimised when the array of cylindrical pores is perpendicular to B0. We also show that this anisotropy of coherence lifetime is reduced if the orientations of cylindrical pores are disordered within the system. In addition we characterise the dependence on B0, the magnetic susceptibility of the cylindrical pores relative to the surroundings, the diffusion coefficient and cylinder wall thickness. Our findings may aid in the interpretation of NMR and MRI relaxation data.
Magnetization and Spin-Diffusion of Liquid 3He in Aerogel
Sauls, J. A.; Bunkov, Yu. M.; Collin, E.; Godfrin, H.; Sharma, P
2004-01-01
We report theoretical calculations of the normal-state spin diffusion coefficient of 3He in aerogel, including both elastic and inelastic scattering of 3He quasiparticles, and compare these results with experimental data for 3He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase provide a test of the theory of pairbreaking and magnetic response of low-energy excitation...
Lupulescu, Adonis; Frydman, Lucio
2011-10-01
Recent years have witnessed efforts geared at increasing the sensitivity of NMR experiments, by relying on the suitable tailoring and exploitation of relaxation phenomena. These efforts have included the use of paramagnetic agents, enhanced (1)H-(1)H incoherent and coherent transfers processes in 2D liquid state spectroscopy, and homonuclear (13)C-(13)C spin diffusion effects in labeled solids. The present study examines some of the opportunities that could open when exploiting spontaneous (1)H-(1)H spin-diffusion processes, to enhance relaxation and to improve the sensitivity of dilute nuclei in solid state NMR measurements. It is shown that polarization transfer experiments executed under sufficiently fast magic-angle-spinning conditions, enable a selective polarization of the dilute low-γ spins by their immediate neighboring protons. Repolarization of the latter can then occur during the time involved in monitoring the signal emitted by the low-γ nuclei. The basic features involved in the resulting approach, and its potential to improve the effective sensitivity of solid state NMR measurements on dilute nuclei, are analyzed. Experimental tests witness the advantages that could reside from utilizing this kind of approach over conventional cross-polarization processes. These measurements also highlight a number of limitations that will have to be overcome for transforming selective polarization transfers of this kind into analytical methods of choice.
Romero-Borja, Fernando; Grabiec, Piotr B.; Zagozdzon-Wasik, Wanda; Wood, Lowell L.
1994-01-01
A new rapid thermal diffusion (proximity RTD) method, utilizing spin-on dopant (SOD) layers, was reported recently. This technique is based on an evaporation-gas phase diffusion- adsorption-surface reaction-diffusion in Si scheme. In this paper we use FTIR spectroscopy to investigate a relationship between the SOD layer structure/composition and its doping efficiency, as determined by sheet resistance (RS) measurements, for a phosphorus diffusion case.
Energy Technology Data Exchange (ETDEWEB)
Meenakumari, V.; Benial, A. Milton Franklin, E-mail: miltonfranklin@yahoo.com [Department of Physics, NMSSVN College, Nagamalai, Madurai-625019, Tamilnadu (India); Utsumi, Hideo; Ichikawa, Kazuhiro; Yamada, Ken-ichi [Department of Bio-functional Science, Kyushu University, Fukuoka (Japan); Hyodo, Fuminori [Innovation Center for Medical Redox Navigation, Kyushu University, Fukuoka (Japan); Jawahar, A. [Department of Chemistry, NMSSVN College, Nagamalai, Madurai-625019, Tamilnadu (India)
2015-06-24
Electron spin resonance (ESR) studies were carried out for permeable 2mM {sup 14}N-labeled deutrated 3 Methoxy carbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (MC-PROXYL) in pure water and 1mM, 2mM, 3mM, 4mM concentration of 14N-labeled deutrated MC-PROXYL in 400mM concentration of liposomal solution by using a 300 MHz ESR spectrometer. The ESR parameters such as linewidth, hyperfine coupling constant, g-factor, partition parameter and permeability were reported for these samples. The line broadening was observed for the nitroxyl spin probe in the liposomal solution. The line broadening indicates that the high viscous nature of the liposomal solution. The partition parameter and permeability values indicate the maximum diffusion of nitroxyl spin probes in the bilayer lipid membranes at 2 mM concentration of nitroxyl radical. This study illustrates that ESR can be used to differentiate between the intra and extra- membrane water by loading the liposome vesicles with a lipid-permeable nitroxyl spin probe. From the ESR results, the spin probe concentration was optimized as 2mM in liposomal solution for ESR phantom studies/imaging, invivo and invitro experiments.
Energy Technology Data Exchange (ETDEWEB)
Weber, Christopher Phillip [Univ. of California, Berkeley, CA (United States)
2005-01-01
Spin diffusion in n-GaAs quantum wells, as measured by our optical transient-grating technique, is strongly suppressed relative to that of charge. Over a broad range of temperatures and dopings, the suppression of Ds relative to Dc agrees quantitatively with the prediction of ''spin Coulomb dra'' theory, which takes into account the exchange of spin in electron-electron collisions. Moreover, the spin-diffusion length, Ls, is a nearly constant 1 micrometer over the same range of T and n, despite Ds's varying by nearly two orders of magnitude. This constancy supports the D'yakonov-Perel'-Kachorovskii model of spin relaxation through interrupted precessional dephasing in the spin-orbit field.
Spin--echo diffusion coefficients of water to 2380 bar and -20degreeC
International Nuclear Information System (INIS)
The self-diffusion coefficient of water has been measured by the steady-gradient spin-echo method at pressures up to 2380 bar and temperatures between 2 and -200C in the stable liquid range using both strengthened glass and beryllium--copper pressure vessels. At low temperatures and high pressures the diffusion coefficient becomes almost independent of pressure. However, a rapid increase in D/sub H/2/sub O/ with the first kilobar of applied pressure is inferred for the supercooled liquid from the relation of the new data to the 1 atm pressure diffusivity of supercooled water. The observations may be correlated with the high pressure low temperature thermodynamic properties of water in a manner consistent with the Adam--Gibbs entropy theory of liquid transport processes
Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo
2014-01-01
The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.
Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas
DEFF Research Database (Denmark)
Bruun, Georg
2012-01-01
Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components....... It is demonstrated that the minimum value of the viscosity decreases with the mass ratio, since Fermi blocking becomes less efficient. We furthermore analyze recent experimental results for the quadrupole mode of a two-dimensional gas in terms of viscous damping, obtaining a qualitative agreement using no fitting...
Spin-polarized lithium diffusion in a glass hot-vapor cell
Ishikawa, Kiyoshi
2016-08-01
We report diffusion coefficients of optically pumped lithium atoms in helium buffer gas. The free-induction decay and the spin-echo signals of ground-state atoms were optically detected in an external magnetic field with the addition of field gradient. Lithium hot vapor was produced in a borosilicate-glass cell at a temperature between 290 and 360°C. The simple setup using the glass cells enabled lithium atomic spectroscopy in a similar way to other alkali-metal atoms and study of the collisional properties of lithium atoms in a hot-vapor phase.
Carbon-13 NMR studies of liquid crystals
International Nuclear Information System (INIS)
High resolution, proton decoupled 13C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = less than P2(costheta) greater than are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so, with temperature in the smectic-A phase. In the nematic series studied, the ordering exhibits an even-odd alternation along the series and qualitative agreement with a recent theory due to Marcelja is found. In both phases, the spectra show that the molecule rotates rapidly about its long axis. Tentative conclusions about molecular conformational motion and 14N spin relaxation are presented for both nematic and smectic-A phases. In the smectic-A phase, the sample is rotated about an axis perpendicular to H0 and the resulting spectra are dicusssed. The theory of observed chemical shifts in liquid crystals is discussed and equations are derived which relate the nmr spectra of liquid-crystals to the order parameters. A model for the smectic-C phase due to Luz and Meiboom and Doane is described and lineshapes are determined on the basis of this model for special cases. The dependence of the order parameters on the molecular potential which give rise to the various degrees of order in the different liquid crystalline phases is examined. To a good approximation the functional dependence of the order parameters on the molecular potential is shown to be a simple one in the limit of small tilt angle in the smectic-C phase
Wenrich, Broc R; Sonstrom, Reilly E; Gupta, Riju A; Rovnyak, David
2015-11-01
Routes to carbon-13 enrichment of bacterially expressed proteins include achieving uniform or positionally selective (e.g. ILV-Me, or (13)C', etc.) enrichment. We consider the potential for biosynthetically directed fractional enrichment (e.g. carbon-13 incorporation in the protein less than 100%) for performing routine n-(D)dimensional NMR spectroscopy of proteins. First, we demonstrate an approach to fractional isotope addition where the initial growth media containing natural abundance glucose is replenished at induction with a small amount (e.g. 10%(w/w)u-(13)C-glucose) of enriched nutrient. The approach considered here is to add 10% (e.g. 200mg for a 2g/L culture) u-(13)C-glucose at the induction time (OD600=0.8), resulting in a protein with enhanced (13)C incorporation that gives almost the same NMR signal levels as an exact 20% (13)C sample. Second, whereas fractional enrichment is used for obtaining stereospecific methyl assignments, we find that (13)C incorporation levels no greater than 20%(w/w) yield (13)C and (13)C-(13)C spin pair incorporation sufficient to conduct typical 3D-bioNMR backbone experiments on moderate instrumentation (600 MHz, RT probe). Typical 3D-bioNMR experiments of a fractionally enriched protein yield expected backbone connectivities, and did not show amino acid biases in this work, with one exception. When adding 10% u-(13)C glucose to expression media at induction, there is poor preservation of (13)Cα-(13)Cβ spin pairs in the amino acids ILV, leading to the absence of Cβ signals in HNCACB spectra for ILV, a potentially useful editing effect. Enhanced fractional carbon-13 enrichment provides lower-cost routes to high throughput protein NMR studies, and makes modern protein NMR more cost-accessible.
Combined Diffusion Tensor Imaging and Arterial Spin Labeling as Markers of Early Parkinson’s disease
Wei, Xiaobo; Yan, Ronghua; Chen, Zhaoyu; Weng, Ruihui; Liu, Xu; Gao, Huimin; Xu, Xiaofeng; Kang, Zhuang; Liu, Zhexing; Guo, Yan; Liu, Zhenhua; Larsen, Jan Petter; Wang, Jin; Tang, Beisha; Hallett, Mark; Wang, Qing
2016-01-01
This study aimed to identify a PD-specific MRI pattern using combined diffusion tensor imaging (DTI) and arterial spin labeling (ASL) to discriminate patients with early PD from healthy subjects and evaluate disease status. Twenty-one early and 22 mid-late PD patients, and 22 healthy, age/gender-matched controls underwent 3-T MRI with apparent diffusion coefficient (ADC), fractional anisotropy (FA), fiber number (FN) and cerebral blood flow (CBF) measurements. We found that compared with healthy subjects, there was a profound reduction in FN passing through the SN in PD. FA in the SN and CBF in the caudate nucleus were inversely correlated with motor dysfunction. A negative correlation was observed between FA in the hippocampus (Hip) and the NMSS-Mood score, whereas CBF in the Hip and the prefrontal cortex(PFC) correlated with declined cognition. Stratified five-fold cross-validation identified FA in the SN(FA-SNAv), CBF in the PFC(CBF-PFCAv) and FA in the parietal white matter(FA-PWMAv), and the combination of these measurements offered relatively high accuracy (AUC 0.975, 90% sensitivity and 100% specificity) in distinguishing those with early PD from healthy subjects. We demonstrate that the decreased FNs through SN in combination with changes in FA-SNAv, CBF-PFCAv and FA-PWMAv values might serve as potential markers of early-stage PD. PMID:27646647
Wei, Xiaobo; Yan, Ronghua; Chen, Zhaoyu; Weng, Ruihui; Liu, Xu; Gao, Huimin; Xu, Xiaofeng; Kang, Zhuang; Liu, Zhexing; Guo, Yan; Liu, Zhenhua; Larsen, Jan Petter; Wang, Jin; Tang, Beisha; Hallett, Mark; Wang, Qing
2016-09-20
This study aimed to identify a PD-specific MRI pattern using combined diffusion tensor imaging (DTI) and arterial spin labeling (ASL) to discriminate patients with early PD from healthy subjects and evaluate disease status. Twenty-one early and 22 mid-late PD patients, and 22 healthy, age/gender-matched controls underwent 3-T MRI with apparent diffusion coefficient (ADC), fractional anisotropy (FA), fiber number (FN) and cerebral blood flow (CBF) measurements. We found that compared with healthy subjects, there was a profound reduction in FN passing through the SN in PD. FA in the SN and CBF in the caudate nucleus were inversely correlated with motor dysfunction. A negative correlation was observed between FA in the hippocampus (Hip) and the NMSS-Mood score, whereas CBF in the Hip and the prefrontal cortex(PFC) correlated with declined cognition. Stratified five-fold cross-validation identified FA in the SN(FA-SNAv), CBF in the PFC(CBF-PFCAv) and FA in the parietal white matter(FA-PWMAv), and the combination of these measurements offered relatively high accuracy (AUC 0.975, 90% sensitivity and 100% specificity) in distinguishing those with early PD from healthy subjects. We demonstrate that the decreased FNs through SN in combination with changes in FA-SNAv, CBF-PFCAv and FA-PWMAv values might serve as potential markers of early-stage PD.
Ultra-diffuse galaxies: the high-spin tail of the abundant dwarf galaxy population
Amorisco, N C
2016-01-01
Recent observations have revealed the existence of an abundant population of faint, low surface brightness (SB) galaxies, which appear to be numerous and ubiquitous in nearby galaxy clusters, including the Virgo, Coma and Fornax clusters. With median stellar masses of dwarf galaxies, these ultra-diffuse galaxies (UDGs) have unexpectedly large sizes, corresponding to a mean SB of $24\\lesssim\\langle\\mu_e\\rangle_r\\ {\\rm mag}^{-1} {\\rm arcsec}^2\\lesssim27$ within the effective radius. We show that the UDG population represents the tail of galaxies formed in dwarf-sized haloes with higher-than-average angular momentum at collapse. By adopting the standard model of disk formation -- in which the size of galaxies is set by the spin of the halo -- we recover both the abundance of UDGs as a function of the host cluster mass and the distribution of sizes within the UDG population. According to this model, UDGs are not failed $L_*$ galaxies, but genuine dwarfs, and their low SB is not uniquely connected to the harsh clu...
International Nuclear Information System (INIS)
We investigate phase diffusion of a two-component Bose–Einstein condensates prepared initially in arbitrary coherent spin state |θ0, φ0). Analytical expression of the phase-diffusion time is presented for θ0 ≠ π/2 case. In comparison with the symmetrical case (i.e., θ0 = π/2), we find that the diffusion process becomes slow due to the reduced atom number variance. (general)
Ivanov, Konstantin L.; Sadovsky, Vladimir M.; Lukzen, Nikita N.
2015-08-01
In this work, we treat spin-selective recombination of a geminate radical pair (RP) in a spherical "microreactor," i.e., of a RP confined in a micelle, vesicle, or liposome. We consider the microreactor model proposed earlier, in which one of the radicals is located at the center of the micelle and the other one undergoes three-dimensional diffusion inside the micelle. In addition, we suggest a two-dimensional model, in which one of the radicals is located at the "pole" of the sphere, while the other one diffuses on the spherical surface. For this model, we have obtained a general analytical expression for the RP recombination yield in terms of the free Green function of two-dimensional diffusion motion. In turn, this Green function is expressed via the Legendre functions and thus takes account of diffusion over a restricted spherical surface and its curvature. The obtained expression allows one to calculate the RP recombination efficiency at an arbitrary magnetic field strength. We performed a comparison of the two models taking the same geometric parameters (i.e., the microreactor radius and the closest approach distance of the radicals), chemical reactivity, magnetic interactions in the RP and diffusion coefficient. Significant difference between the predictions of the two models is found, which is thus originating solely from the dimensionality effect: for different dimensionality of space, the statistics of diffusional contacts of radicals becomes different altering the reaction yield. We have calculated the magnetic field dependence of the RP reaction yield and chemically induced dynamic nuclear polarization of the reaction products at different sizes of the microreactor, exchange interaction, and spin relaxation rates. Interestingly, due to the intricate interplay of diffusional contacts of reactants and spin dynamics, the dependence of the reaction yield on the microreactor radius is non-monotonous. Our results are of importance for (i) interpreting
Energy Technology Data Exchange (ETDEWEB)
Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru; Lukzen, Nikita N. [International Tomography Center, Siberian Branch, Russian Academy of Sciences, Institutskaya St. 3a, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090 (Russian Federation); Sadovsky, Vladimir M. [Institute of Computational Modeling, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50/44, Krasnoyarsk 660036 (Russian Federation)
2015-08-28
In this work, we treat spin-selective recombination of a geminate radical pair (RP) in a spherical “microreactor,” i.e., of a RP confined in a micelle, vesicle, or liposome. We consider the microreactor model proposed earlier, in which one of the radicals is located at the center of the micelle and the other one undergoes three-dimensional diffusion inside the micelle. In addition, we suggest a two-dimensional model, in which one of the radicals is located at the “pole” of the sphere, while the other one diffuses on the spherical surface. For this model, we have obtained a general analytical expression for the RP recombination yield in terms of the free Green function of two-dimensional diffusion motion. In turn, this Green function is expressed via the Legendre functions and thus takes account of diffusion over a restricted spherical surface and its curvature. The obtained expression allows one to calculate the RP recombination efficiency at an arbitrary magnetic field strength. We performed a comparison of the two models taking the same geometric parameters (i.e., the microreactor radius and the closest approach distance of the radicals), chemical reactivity, magnetic interactions in the RP and diffusion coefficient. Significant difference between the predictions of the two models is found, which is thus originating solely from the dimensionality effect: for different dimensionality of space, the statistics of diffusional contacts of radicals becomes different altering the reaction yield. We have calculated the magnetic field dependence of the RP reaction yield and chemically induced dynamic nuclear polarization of the reaction products at different sizes of the microreactor, exchange interaction, and spin relaxation rates. Interestingly, due to the intricate interplay of diffusional contacts of reactants and spin dynamics, the dependence of the reaction yield on the microreactor radius is non-monotonous. Our results are of importance for (i) interpreting
International Nuclear Information System (INIS)
Although carbon 13 nuclear magnetic resonance spectroscopy (13C-NMR) is widely used in lignin structural studies, serious difficulties are encountered in the assignments of 13C signals because of their extensive overlaps resulting from the complex structure of lignin and of delicate detection of minor structures. To overcome these difficulties, specifically 13C-enriched precursors of lignin biosynthesis, coniferin-[side chain-β-13C] and coniferin-[side chain-γ-13C], were administered to growing stems of ginkgo (Ginkgo biloba). The NMR analysis of the milled wood lignins isolated from the newly formed xylem showed that selective enrichment of specific carbons of protolignin in the cell wall was achieved without seriously disturbing the lignin biosynthesis. The presence of saturated methylene side chains in the protolignin was shown for the first time by this selective enrichment technique in combination with NMR analysis. (authors). 23 refs., 3 figs., 1 tab
Energy Technology Data Exchange (ETDEWEB)
Xie, Y. (Nagoya Univ. (Japan). Faculty of Agriculture); Robert, D.R. (CEA Centre d' Etudes de Grenoble, 38 (France). Dept. de Recherche Fondamentale sur la Matiere Condensee); Terashima, N. (Forest Products Lab., Madison, WI (United States))
Although carbon 13 nuclear magnetic resonance spectroscopy ([sup 13]C-NMR) is widely used in lignin structural studies, serious difficulties are encountered in the assignments of [sup 13]C signals because of their extensive overlaps resulting from the complex structure of lignin and of delicate detection of minor structures. To overcome these difficulties, specifically [sup 13]C-enriched precursors of lignin biosynthesis, coniferin-[side chain-[beta]-[sup 13]C] and coniferin-[side chain-[gamma]-[sup 13]C], were administered to growing stems of ginkgo (Ginkgo biloba). The NMR analysis of the milled wood lignins isolated from the newly formed xylem showed that selective enrichment of specific carbons of protolignin in the cell wall was achieved without seriously disturbing the lignin biosynthesis. The presence of saturated methylene side chains in the protolignin was shown for the first time by this selective enrichment technique in combination with NMR analysis. (authors). 23 refs., 3 figs., 1 tab.
A Model of Charge Transfer Excitons: Diffusion, Spin Dynamics, and Magnetic Field Effects
Lee, Chee Kong; Willard, Adam P
2016-01-01
In this letter we explore how the microscopic dynamics of charge transfer (CT) excitons are influenced by the presence of an external magnetic field in disordered molecular semiconductors. This influence is driven by the dynamic interplay between the spin and spatial degrees of freedom of the electron-hole pair. To account for this interplay we have developed a numerical framework that combines a traditional model of quantum spin dynamics with a coarse-grained model of stochastic charge transport. This combination provides a general and efficient methodology for simulating the effects of magnetic field on CT state dynamics, therefore providing a basis for revealing the microscopic origin of experimentally observed magnetic field effects. We demonstrate that simulations carried out on our model are capable of reproducing experimental results as well as generating theoretical predictions related to the efficiency of organic electronic materials.
Diffusion studies on permeable nitroxyl spin probe through lipid bilayer membrane
Energy Technology Data Exchange (ETDEWEB)
Benial, A. Milton Franklin; Meenakumari, V. [Department of Physics, NMSSVN College, Nagamalai, Madurai-625019 (India); Ichikawa, Kazuhiro; Yamada, Ken-ichi; Utsumi, Hideo, E-mail: hideo.utsumi.278@m.kyushu-u.ac.jp [Department of Bio-functional Science, Kyushu University, Fukuoka (Japan); Hyodo, Fuminori [Innovation Center for Medical Redox Navigation, Kyushu University, Fukuoka (Japan); Jawahar, A. [Department of Chemistry, NMSSVN College, Nagamalai, Madurai-625 019 (India)
2014-04-24
Electron spin resonance (ESR) studies were carried out for 2mM {sup 14}N labeled deutrated permeable 3- methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (MC-PROXYL) in pure water, 1 mM, 2 mM, 3 mM and 4 mM concentration of MC-PROXYL in 300 mM concentration of liposomal solution by using a L-band ESR spectrometer. The ESR parameters such as linewidth, hyperfine coupling constant, g-factor, partition parameter and permeability were reported. The partition parameter and permeability values indicate the maximum spin distribution in the lipid phase at 2 mM concentration. This study illustrates that ESR can be used to differentiate between the intra and extra-membrane water by loading the liposome vesicles with a lipid-permeable nitroxyl spin probe. From the ESR results, the radical concentration was optimized as 2 mM in liposomal solution for ESR phantom studies and experiments.
Carbon-13 magnetic resonance of hydrocarbons. Annual report
Energy Technology Data Exchange (ETDEWEB)
Grant, D.M.; Pugmire, R.J.
1979-01-01
Several tetralins, tetrahydrophenanthrenes, and dihydroanthracenes were synthesized, /sup 13/C spin-lattice relaxation measurements were carried out on aromatic and hydroaromatic compounds. /sup 13/C chemical shift studies were also conducted on methylated 1,2,3,4-tetrahydronaphthalenes, 1,2,3,4-tetrahydrophenanthrenes, and 9,10-dihydroanthracenes. (DLC)
Proposal to realize a cost breakthrough in carbon-13 production by photochemical separation
International Nuclear Information System (INIS)
A cost breakthrough can now be made in photochemical production of the rare stable isotope carbon-13. This cost breakthrough is achieved by CO2 laser infrared multiple-photon dissociation of any of several halocarbons (Freon derivatives) such as CF3Cl, CF3Br, or CF2Cl2. The single-step carbon-13 enrichment factor for this process is approximately 50, yielding 30% pure C-13 in one step, or up to 97% pure C-13 in two steps. A three-fold carbon-13 cost reduction to below $20/gram is expected to be achieved in a small laboratory-scale demonstration facility capable of producing 4 to 8 kg/year of carbon-13, using presently available pulsed CO2 TEA lasers at an average power level of 50 watts. Personnel costs dominate the attainable C-13 production costs in a small photochemical enrichment facility. A price reduction to $2/gm carbon-13 is feasible at carbon-13 production levels of 100 to 1000 kg/year, dominated by the Freon raw material costs
Directory of Open Access Journals (Sweden)
Abdullah Ahmed Ali Ahmed
2013-01-01
Full Text Available The coprecipitation method was used to prepare Zn–Al layered double hydroxide (Zn–Al–NO3-LDH at pH 7.5 and different Zn2+/Al3+ molar ratios of 2, 3, 4, 5, and 6. The elemental, structural, and textural properties of prepared samples were studied. The crystallinity of prepared LDH nanostructure decreases as Zn2+/Al3+ molar ratio increases. The electron spin resonance (ESR spectroscopy of different LDH samples showed new ESR spectra. These spectra were produced due to the presence of different phases with formed LDH such as ZnO phase and ZnAl2O4 spinel. At low Zn2+/Al3+ molar ratio, the ESR signals were produced from the presence of free nitrate anions in the LDH interlayer. Above Zn2+/Al3+ = 2, the ESR signals were attributed to the existence of ZnO phase and ZnAl2O4 spinel in the samples. Because the nuclear magnetic moment of 67Zn is lower than 27Al, the increasing in Zn2+/Al3+ molar ratio causes a reduction of the magnetic activity of ZnAl2O4 spinel. Thermal diffusivity versus in situ temperature showed nonlinear relation for different samples due to the changing in the water content of LDH as temperature increases. The dc conductivity of samples decreased as Zn2+/Al3+ molar ratio.
Energy Technology Data Exchange (ETDEWEB)
Chapelet-Letourneux, G. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1967-07-01
N-t-butyl-N-phenyl nitroxide is obtained by: a) action of t-butyl-magnesium chloride on nitrobenzene, or of phenyl-magnesium bromide on nitro-t-butane, b) oxidation of N-t-butyl-N-phenylhydroxylamine, c) oxidation of N-t-butylaniline. In these latter two cases, it has been possible to isolate the pure radical and to study it using UV, IR and EPR. It decomposes to give N-t-butylaniline and the N-oxide of N-t-butyl-p-quinon-imine. The action of peracids such as p-nitro-perbenzoic or m-chloro-perbenzoic acids on amines or hydroxylamines leads to the formation of stable or unstable nitroxide radicals easily observable by EPR. Finally, with a view to obtaining definite values for the coupling between the free electron of a nitroxide and carbon 13, the preparation of such radicals marked with {sup 13}C in the {alpha} or {beta} position of the nitroxide function has been carried out. The coupling with an {alpha} carbon 13 is negative and does not appear to vary with the spin density on the nitrogen. The interaction with the p nuclei of the nitrogen depends on the nature of the substituents: the two benzyl protons have a hyperfine splitting a{sub H} which is always less than that of the ethyl. On the other hand, the {sup 13}C coupling is greater in the first case. The usually adopted conformations for the compounds having the carbonyl group cannot account for the observed values of the {beta} couplings. (author) [French] Le N-t-butyl-N-phenyl nitroxyde est obtenu par: a) action du chlorure de t-butylmagnesium sur le nitrobenzene, ou du bromure de phenylmagnesium sur le nitro-t-butane, b) oxydation de la N-t-butyl-N-phenylhydroxylamine, c) oxydation de la N-t-butylaniline. Dans ces deux derniers cas, le radical a pu etre isole pur et etudie par UV, IR et RPE. Il se decompose en N-t-butylaniline et N-oxyde de N-t-butyl-p-quinonimine. L'action de peracides (p-nitroperbenzoique ou m-chloroperbenzoique) sur des amines ou des hydroxylamines conduit a des radicaux nitroxydes
Institute of Scientific and Technical Information of China (English)
余华梁; 陈曦矅; 狄俊安
2013-01-01
为研究空穴对自旋极化电子扩散的影响，提出用自旋密度光栅方法来观察电子自旋扩散过程。由飞秒激光在本征GaAs多量子阱中激发产生瞬态自旋光栅和瞬态自旋密度光栅，并用于研究电子自旋扩散和电子自旋双极扩散。实验测得自旋双极扩散系数Das ＝25.4 cm 2/s，低于自旋扩散系数Ds ＝113.0 cm 2/s，表明自旋密度光栅中电子自旋扩散受到空穴的显著影响。%In order to research the effect of holes on the spin electron diffusion , a method of resonant spin am-plication called“Spin Concentration Grating(SCG)” is adopt to observe the process of electron spin diffusion . Transient spin grating and spin concentration grating excited by femtosecond laser beams are used to investigate electron spin diffusion and “electron spin ambipolar diffusion” in intrinsic GaAs multiple quantum wells .The measured coefficient of “electron spin ambipolar diffusion” Das =25.4 cm 2? s-1 is lower than that of electron spin diffusion Ds=113.0 cm 2? s-1 , which indicates that the influence of holes on electron spin diffusion in spin concentration grating is notable .
Energy Technology Data Exchange (ETDEWEB)
Tsuchiya, K.; Katase, S.; Fujikawa, A.; Hachiya, J. [Department of Radiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, 181-8611, Tokyo (Japan); Kanazawa, H. [Toshiba Corporation, 1-1-1 Shibaura, Minato-ku, 105-8001, Tokyo (Japan); Yodo, K. [Toshiba Medical Systems, 3-26-5 Hongo, Bunkyo-ku, 113-8456, Tokyo (Japan)
2003-02-01
We have implemented a new diffusion-weighted MRI (DWI) sequence based on the single-shot fast spin-echo technique. We hypothesised that this would add information to conventional MRI for diagnosis of lesions of the cervical spinal cord. DWI was performed using a technique in which echo collection after the application of motion-probing gradients was done in the same manner as in the single-shot fast spin-echo technique. We first imaged six healthy volunteers to demonstrate the cervical spinal cord using the sequence. Then we applied the sequence to 12 patients with cervical myelomalacia due to chronic cord compression. The spinal cord was well seen in all subjects without the distortion associated with echo-planar DWI. In the patients, lesions appeared as areas of low- or isointense signal on DWI. Calculated apparent diffusion coefficients of the lesions (3.30{+-}0.38 x 10{sup -3} mm{sup 2}/s) were significantly higher than those of normal volunteers (2.26{+-}0.08 x 10{sup -3} mm{sup 2}/s). Increased diffusion in areas of cervical myelomalacia, suggesting irreversible damage, can be detected using this technique. (orig.)
Spin accumulation in the extrinsic spin Hall effect
Tse, Wang-Kong; Fabian, J.; Žutić, I.; Das Sarma, S.
2005-12-01
The drift-diffusion formalism for spin-polarized carrier transport in semiconductors is generalized to include spin-orbit coupling. The theory is applied to treat the extrinsic spin Hall effect using realistic boundary conditions. It is shown that carrier and spin-diffusion lengths are modified by the presence of spin-orbit coupling and that spin accumulation due to the extrinsic spin Hall effect is strongly and qualitatively influenced by boundary conditions. Analytical formulas for the spin-dependent carrier recombination rates and inhomogeneous spin densities and currents are presented.
Studying biosphere-atmosphere exchange of CO2 through Carbon-13 stable isotopes
Velde, van der I.R.
2015-01-01
Summary Thesis ‘Studying biosphere-atmosphere exchange of CO2 through carbon-13 stable isotopes’ Ivar van der Velde Making predictions of future climate is difficult, mainly due to large uncertainties in the carbon cycle. The rate at which carbon is stored in the oceans and terrestrial b
International Nuclear Information System (INIS)
The natural abundance carbon-13 nuclear magnetic resonance spectra of various clinically used furocoumarins and furochromones have been studied. The assignments of carbon chemical shift values were based on the theory of chemical shift, additivity rules, SFORD spectra and model compounds. (author)
International Nuclear Information System (INIS)
In the production of n-type crystalline silicon solar cells with boron diffused emitters, the formation of a boron rich layer (BRL) is a common phenomenon and is largely responsible for bulk lifetime degradation. The phenomenon of BRL formation during diffusion of boron spin-on dopant and its impact on bulk lifetime degradation are investigated in this work. The BRL formed beneath the borosilicate glass layer has thicknesses varying from 10 nm–150 nm depending on the diffusion conditions. The effective and bulk minority carrier lifetimes, measured with Al2O3 deposited layers and a quinhydron–methanol solution, show that carrier lifetime degradation is proportional to the BRL thicknesses and their surface recombination velocities. The controlled diffusion processes and different oxidation techniques used in this work can partially reduce the BRL thickness and improve carrier lifetime by more than 10%. But for BRL thicknesses higher than 50 nm, different etching techniques further lower the carrier lifetime and the degradation in the device cannot be recovered. (paper)
Arjoranta, Juho; Heikkilä, Tero T.
2016-01-01
We study the effect of the intrinsic (Rashba or Dresselhaus) spin-orbit interaction in superconductor-nanowire-superconductor (SNS) weak links in the presence of a spin-splitting field that can result either from an intrinsic exchange field or the Zeeman effect of an applied field. We solve the full nonlinear Usadel equations numerically [The code used for calculating the results in this paper is available in https://github.com/wompo/Usadel-for-nanowires] and analyze the resulting supercurrent through the weak link and the behavior of the density of states in the center of the wire. We point out how the presence of the spin-orbit interaction gives rise to a long-range spin triplet supercurrent, which remains finite even in the limit of very large exchange fields. In particular, we show how rotating the field leads to a sequence of transitions between the 0 and π states as a function of the angle between the exchange field and the spin-orbit field. Simultaneously, the triplet pairing leads to a zero-energy peak in the density of states. We proceed by solving the linearized Usadel equations, showing the correspondence to the solutions of the full equations and detail the emergence of the long-range supercurrent components. Our studies are relevant for ongoing investigations of supercurrent in semiconductor nanowires in the limit of several channels and in the presence of disorder.
Scheenen, T.W.J.; Vergeldt, F.J.; Windt, C.W.; Jager, de P.A.; As, van H.
2001-01-01
In this paper we present a pulse sequence that combines a displacement-encoded stimulated echo with rapid sampling of k-space by means of turbo spin echo imaging. The stimulated echo enables the use of long observation times between the two pulsed field gradients that sample q-space completely. Prop
JONGMAN, [No Value; BACELAR, JCS; BALANDA, A; NOORMAN, RF; STEENBERGEN, T; DEVOIGT, MJA; NYBERG, J; SLETTEN, G; DIONISIO, J; VIEU, C; LAGRANGE, JM; PAUTRAT, M; Urban, W
1995-01-01
High-spin states in the odd-odd nucleus Eu-148, populated by a carbon-13 induced reaction on a lanthanum target, were investigated with several different tools of in-beam nuclear spectroscopy. The low-energy levels show collective excitations, interpreted as 3- octupole-phonon couplings to multi-par
Probing spin-charge separation using spin transport
Si, Qimiao
2000-01-01
Pedagogical discussions are given on what constitutes a signature of spin-charge separation. A proposal is outlined to probe spin-charge separation in the normal state of the high $T_c$ cuprates using spin transport. Specifically, the proposal is to compare the temperature dependences of the spin resistivity and electrical resistivity: Spin-charge separation will be manifested in the different temperature dependences of these two resistivities. We also estimate the spin diffusion length and s...
Miyauchi, Yuhei; Maruyama, Shigeo
2005-01-01
We have studied photoluminescence (PL) and resonant Raman scatterings of single-walled carbon nanotubes (SWNTs) consisting of carbon-13 (SW13CNTs) synthesized from a small amount of isotopically modified ethanol. There was almost no change in the Raman spectra shape for SW13CNTs except for a downshift of the Raman shift frequency by the square-root of the mass ratio 12/13. By comparing photoluminescence excitation (PLE) spectra of SW13CNTs and normal SWNTs, the excitonic phonon sideband due t...
Schimmelmann, Arndt; Tegner, Mia J.
1991-01-01
A 1844-1987 time-series of carbon stable isotope ratios from dated sedimentary total organic carbon from the center of the Santa Barbara basin is compared with historical climate and oceanographic records. Carbon derived from carbon-13-depleted phytoplankton and carbon-13-enriched kelp appear responsible for a large part of the isotopic variance in sedimentary total organic carbon. El Niño/Southern Oscillation events are recorded by the isotopic response of marine organic carbon in sediments.
International Nuclear Information System (INIS)
The purpose of the present study was to prospectively evaluate the diagnostic ability of diffusion-weighted magnetic resonance imaging (DWI) using single-shot fast spin echo (SSFSE) technique to discriminate pituitary adenomas from Rathke's cleft cysts. DWIs were obtained from 40 patients with pathologically proven pituitary macroadenomas and 15 patients with proven Rathke's cleft cysts. Pituitary adenomas were divided into 27 cases with solid components alone, five with non-hemorrhagic large cysts, and eight with intratumoral hemorrhage. On SSFSE DWI, solid components of pituitary adenomas revealed iso or slightly increased intensity and intratumoral hemorrhage showed higher intensity than normal brain parenchyma, whereas Rathke's cleft cysts and intratumoral cysts demonstrated very low intensity. SSFSE DWI did not display the susceptibility artifacts that are seen close to the skull base and sinonasal cavities on echo planar diffusion imaging. On the basis of our preliminary findings, DWI may enable us to differentiate pituitary adenomas with only solid components and hemorrhagic pituitary adenomas appearing hyperintense on T1-weighted images from Rathke's cleft cysts without administration of gadolinium-DTPA. SSFSE DWI appears to be a useful technique for characterizing pituitary diseases without the susceptibility artifacts. Our study is the first report to demonstrate the identification of pituitary disorders on SSFSE DWI. (author)
Energy Technology Data Exchange (ETDEWEB)
Park, Seo Young; Lee, Ghi Jai; Kim, Jeong Seok; Shim, Jae Chan; Kim, Ho Kyun [Inje Univ. College of Medicine, Seoul (Korea, Republic of)
1998-10-01
To compare T2-weighted images with spin-echo T1- and turbo spin-echo (TSE) T2-weighted images in patients with diffuse axonal injury(DAI). Using a 1.0T MR unit, SE T1-, TSE T2-, and and FLASH T2-weighted images were obtained from 69 patients with a history of head trauma. In 18MR images of 17 patients with imaging findings of DAI, T2-weighted images were retrospectively compared with SE T1- and TSE T2-weighted images. The interval between trauma and MR scan varied from 5 days to 24(mean, 11) months. Focusing on the number of lesions, and their location and signal intensity, as weel as associated findings, three images were simultaueously evaluated. In 18 MR images of 17 patients with MR imaging findings of DAI, 21 lesions were detected on T1-weighted images, 28 on TSE T2-weighted images, and 70 on T2-weighted images;the last of these revealed all lesions detected on the other two. Most lesions were hypointense on T1-weighted images(17/21), hyperintense on TSE T2-weighted (21/28), and hypointense on T2-weighted (63/70). Common locations for DAI were the frontal lobe (n=3D35) and corpus callosum (n=3D22). Associated brain injuries were cortical contusion (n=3D5), brainstem injury (n=3D3), deep gray matter injury (n=3D2), and subdural hematoma(n=3D1). In patients with DAI. T2-weighted images can detect more lesions and associated petechial hemorrhage than can TSE T2-weighted images. This modality is thus useful for the evaluation of patients with head trauma.=20.
Energy Technology Data Exchange (ETDEWEB)
Lu, Xingyu, E-mail: luxingyu@udel.edu; Guo, Changmiao, E-mail: cmguo@udel.edu; Hou, Guangjin, E-mail: hou@udel.edu; Polenova, Tatyana, E-mail: tpolenov@udel.edu [University of Delaware, Department of Chemistry and Biochemistry (United States)
2015-01-15
Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35–40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD–RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD–RFDR sequences experimentally on a U-{sup 13}C,{sup 15}N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD–RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD–RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD–RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD–RFDR experiment is beneficial in a
Toward microtesla MRI of hyperpolarized carbon-13 for real-time metabolic imaging
Zotev, V S; Savukov, I M; Matlashov, A N; Gómez, J J; Espy, M A
2009-01-01
Hyperpolarization of carbon-13 is a promising technique that has enabled MR angiography, perfusion mapping, and real-time metabolic imaging of C-13 labeled organic substances with unprecedented signal-to-noise levels. Because the hyperpolarization is performed outside an MRI scanner (using a special NMR-style hyperpolarizer), high magnetic fields of conventional MRI systems offer little advantage in terms of achievable C-13 polarization. Here we propose an ultimate low-field MRI scanner for imaging hyperpolarized C-13. It uses only microtesla-range magnetic fields and employs SQUID (superconducting quantum interference device) sensors for broadband reception of MRI signals. We present the first images acquired by SQUID-based microtesla MRI with dynamic nuclear polarization (Overhauser enhancement). We also report the first NMR spectra of C-13 at microtesla fields, including spectra of metabolically relevant sodium pyruvate, bicarbonate, and alanine. Our results demonstrate feasibility and potential of the pro...
Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material
Friedman, I.; O'Neil, J.R.; Adami, L.H.; Gleason, J.D.; Hardcastle, K.
1970-01-01
The water content of the breccia is 150 to 455 ppm, with a ??D from -580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a ??D of -830 to -970 per mil. The CO2 is 290 to 418 ppm with S 13C = + 2.3 to + 5.1 per mil and ??18O = 14.2 to 19.1 per mil. Non-CO2 carbon is 22 to 100 ppm, ??18C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H2O (D = 80 ppm) and 188 ppm total carbon (??13C = -17.6 per mil). The 18O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100?? to 1300??C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.
Synthesis of colchicine and isocolchicine labelled with carbon-11 or carbon-13
Energy Technology Data Exchange (ETDEWEB)
Kothari, P.J.; Finn, R.D.; Larson, S.M. [Memorial Sloan-Kettering Cancer Center, New York, NY (United States)
1995-06-01
The syntheses of isotopically labelled (-)-10-[{sup 11}C/{sup 13}C]-colchicine and (-)-9-[{sup 11}C/{sup 13}C]-isocolchicine have been achieved from the reaction of (-)desmethylcolchicine with [{sup 11}C/{sup 13}C]-iodomethane. The radiolabelled compounds, (-)-10-[{sup 11}C]-colchicine ({sup 11}C-n-colchicine) and (-)-9-[{sup 11}C]-isocolchicine ({sup 11}C-i-colchicine), were isolated by reversed phase HPLC. The total synthesis time was approximately 60 minutes for both radiolabelled compounds with an average specific activity of 240 mCi/{mu}mol calculated to EOB. Utilizing a similar synthetic strategy, we also reported the synthesis of milligram quantities of the carbon-13 enriched compounds and the magnetic resonance signal assignment for (-)-9-[{sup 13}C] isocolchicine. (Author).
Isotopic composition of carbon-13 and oxygen-18 from authigenic carbonates, Black Sea region
Logvina, E.; Mazurenko, L.; Prasolov, E.
2004-05-01
Several types of authigenic carbonates related to the fluid discharge zones were sampled during the international expeditions onboard R/V "Professor Vodyanitskiy" (56th cruise) and R/V "Professor Logachev" (11th cruise of UNESCO-TTR) in the northwest part of the Black sea. These carbonates are represented as mounds, build-ups and chimney-like structures, cemented sediments, crusts and concretions. The isotope analyses of carbonates were conducted using mass-spectrometer MS-20 in the Laboratory of Isotope Geology (St.Petersburg State University). The obtained values of oxygen-18 varied from +0,6 to -1,9 per mille (up to C0.8 per mille on average). This value is corresponding to normal seawater oxygen-18 value (about 0 per mille); we suspect, that the source of oxygen for carbonate formation is the seawater. The carbonates are characterized by low carbon-13 (from -35,4 to -42,6 per mille) in comparison with normal marine carbonates (about 0 per mille). We have reason to suppose that carbonates associated with fluid venting were formed by light isotopic composition of carbon dioxide (carbon-13 -45 to -52 per mille), which forming under methane microbiologic oxidation with such isotopic composition. This is because of crossing fluid process of carbon dioxide to carbonate with 8~10 degrees temperature carbon became heaver to 10- 11 per mille. The isotopic composition study of carbonate build-ups is of interest because its association with the gas hydrate accumulations is quite often in the gas seeps. This work is financially supported by Russian Foundation for Basic Research, grant 02-05-64346.
Energy Technology Data Exchange (ETDEWEB)
Xiao, Hua-Feng [302 Hospital of Chinese People' s Liberation Army, Department of Radiology, Beijing (China); Chen, Zhi-Ye; Wang, Yu-Lin; Wang, Yan; Ma, Lin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); Lou, Xin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); University of California, Department of Neurology, Los Angeles, CA (United States); Gui, Qiu-Ping [People' s Liberation Army General Hospital, Department of Pathology, Beijing (China); Shi, Kai-Ning; Zhou, Zhen-Yu; Zheng, Dan-Dan [General Electric Healthcare (China) Co., Ltd., Beijing; Wang, Danny J.J. [University of California, Department of Neurology, Los Angeles, CA (United States)
2015-12-15
We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 x 10{sup -3} mm{sup 2}/s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. (orig.)
International Nuclear Information System (INIS)
We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 x 10-3 mm2/s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Bhattacharya, Aniruddha; Baten, Md Zunaid; Bhattacharya, Pallab, E-mail: pkb@umich.edu [Center for Photonic and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States)
2016-01-25
We report the measurement of diffusive electronic spin transport characteristics in an epitaxial wurtzite GaN lateral spin valve at room temperature. Hanle spin precession and non-local spin accumulation measurements have been performed with the spin valves fabricated with FeCo/MgO spin contacts. Electron spin relaxation length and spin-flip lifetime of 176 nm and 37 ps, respectively, are derived from analysis of results obtained from four-terminal Hanle spin precession measurements at 300 K. The role of dislocations and defects in bulk GaN has also been examined in the context of electronic spin relaxation dynamics.
Energy Technology Data Exchange (ETDEWEB)
Wang, Tuo; Williams, Jonathan K. [Massachusetts Institute of Technology, Department of Chemistry (United States); Schmidt-Rohr, Klaus [Brandeis University, Department of Chemistry (United States); Hong, Mei, E-mail: meihong@mit.edu [Massachusetts Institute of Technology, Department of Chemistry (United States)
2015-02-15
The measurement of long-range distances remains a challenge in solid-state NMR structure determination of biological macromolecules. In 2D and 3D correlation spectra of uniformly {sup 13}C-labeled biomolecules, inter-residue, inter-segmental, and intermolecular {sup 13}C–{sup 13}C cross peaks that provide important long-range distance constraints for three-dimensional structures often overlap with short-range cross peaks that only reflect the covalent structure of the molecule. It is therefore desirable to develop new approaches to obtain spectra containing only long-range cross peaks. Here we show that a relaxation-compensated modification of the commonly used 2D {sup 1}H-driven spin diffusion (PDSD) experiment allows the clean detection of such long-range cross peaks. By adding a z-filter to keep the total z-period of the experiment constant, we compensate for {sup 13}C T{sub 1} relaxation. As a result, the difference spectrum between a long- and a scaled short-mixing time spectrum show only long-range correlation signals. We show that one- and two-bond cross peaks equalize within a few tens of milliseconds. Within ∼200 ms, the intensity equilibrates within an amino acid residue and a monosaccharide to a value that reflects the number of spins in the local network. With T{sub 1} relaxation compensation, at longer mixing times, inter-residue and inter-segmental cross peaks increase in intensity whereas intra-segmental cross-peak intensities remain unchanged relative to each other and can all be subtracted out. Without relaxation compensation, the difference 2D spectra exhibit both negative and positive intensities due to heterogeneous T{sub 1} relaxation in most biomolecules, which can cause peak cancellation. We demonstrate this relaxation-compensated difference PDSD approach on amino acids, monosaccharides, a crystalline model peptide, a membrane-bound peptide and a plant cell wall sample. The resulting difference spectra yield clean multi-bond, inter
Monitoring of liver glycogen synthesis in diabetic patients using carbon-13 MR spectroscopy
International Nuclear Information System (INIS)
To investigate the relationship between liver glucose, glycogen, and plasma glucose in diabetic patients, in vivo liver carbon-13 magnetic resonance spectroscopy (13C MRS) with a clinical 3.0 T MR system was performed. Subjects were healthy male volunteers (n = 5) and male type-2 diabetic patients (n = 5). Pre- and during oral glucose tolerance tests (OGTT), 13C MR spectra without proton decoupling were acquired in a monitoring period of over 6 h, and in total seven spectra were obtained from each subject. For OGTT, 75 g of glucose, including 5 g of [1-13C]glucose, was administered. The MR signals of liver [1-13C]glucose and glycogen were detected and their time-course changes were assessed in comparison with the plasma data obtained at screening. The correlations between the fasting plasma glucose level and liver glycogen/glucose rate (Spearman: ρ = -0.68, p 13C MRS can perform noninvasive measurement of glycogen storage/degradation ability in the liver individually and can assist in tailor-made therapy for diabetes. In conclusion, 13C MRS has a potential to become a powerful tool in diagnosing diabetes multilaterally.
Spin-Hall interface resistance in terms of Landauer type spin dipoles
Mal'shukov, A. G.; L. Y. Wang; Chu, C. S.
2006-01-01
We considered the nonequlibrium spin dipoles induced around spin independent elastic scatterers by the intrinsic spin-Hall effect associated with the Rashba spin-orbit coupling. The normal to 2DEG spin polarization has been calculated in the diffusion range around the scatterer. We found that although around each impurity this polarization is finite, the corresponding macroscopic spin density, obtained via averaging of individual spin dipole distributions over impurity positions is zero in th...
Composition of Carbon-13 and Nitrogen-15 in Sediments of the Ha Long Bay
International Nuclear Information System (INIS)
The Ha Long Bay with beautiful landscape and rich ecosystems is being used by human to develop the economy. The Ha Long Bay is currently affected by human activities causing the sedimentary environment to be much changed. The change of the environment in the Bay was studied using the composition of carbon-13, nitrogen-15 (δ13C, δ15N) and the C/N ratio in sediment of seven cores collected within the Ha Long Bay. In the Ha Long Bay, sedimentary environment receives many source sediment supplies. The north-east of Ha Long bay receives sources from sea, it is characterized by δ13C in sediment from -8.79 to -18.01‰, value δ15N in sediment from 4.36 to 4.73 ‰ and ratio of C/N from 13 to 41, the source organic matter in sediment shows that affected by C4 plant. The centre of Ha Long Bay receives organic source from sea, it is characterized by δ13C in sediment from -16.72 to -21.58 ‰, value δ15N in sediment ranges 4.15 - 5.20 ‰, ratio of C/N in sediment from 7 to 23. The north-west of Ha Long Bay is affected by rivers, it is characterized by δ13C in sediment range from -13.64 to -25.77 ‰, value δ15N in sediment from 2.50 to 4.38 ‰, and ratio C/N from 9 to 19. (author)
International Nuclear Information System (INIS)
Carbon-13 kinetic isotope effects in the decarboxylation of phenylpropiolic acid (carboxyl-13C) in formic acid medium and in the decarbonylation of liquid formic acid assisted with phenylpropiolic acid (PPA) and acetophenone (AP) have been studied in the 70-100oC temperature interval. The carboxyl-13C KIEs are in the range 1.0034 at 71.6oC and 1.0047 at 101.2oC respectively. The C-13C KIE, k-12/k-13, in the decarbonylation of liquid formic acid assisted with PPA were found to be of 1.0419 at 71.6oC and 1.0383 at 101.2oC. The C-13 KIE in the decarbonylation of pure formic acid are 1.0464 at 70.2oC and 1.0411 at 98oC respectively. The above experimental results have been discussed and interpreted as indicating that the formation of Cα-H bond preceded by the protonation of triple acetylenic bond of PPA is the rate determining step followed by carbon dioxide splitting. The 13-CO-KIE in the carbon monooxide generation assisted with PPA is much larger than the 13-CO-KIE generated in the presence of phenylacetylene. This shows that the decarboxylation of PPA and decarboxylation of FA are interrelated processes proceeding in the reaction cage. The formic acid involved in the formation of TS is decarbonylating directly avoiding probably largely the formic acid anhydride intermediate formation. (author)
Carbon-13 variations in fluids from the Cerro Prieto geothermal system
Energy Technology Data Exchange (ETDEWEB)
Janik, C.J.; Nehring, N.L.; Huebner, M.A.; Truesdell, A.H.
1982-08-10
The carbon isotope compositions of CO/sub 2/ in steam from Cerro Prieto production well have been measured for 1977, 1979, and 1982. Variations in the delta/sup 13/C values are caused by production-related changes in the chemical and physical parameters of the geothermal system. In 1977, most CO/sub 2/ in the reservoir was isotopically light (delta/sup 13/C = -6.4 +/- 0.4). Heavier CO/sub 2/ was produced from wells in the center of the field (M5,M26,M27) due to deposition of isotopically light calcite caused by near-well boiling. In 1979 nearly all well showed relatively heavy CO/sub 2/, probably due to expansion of aquifer boiling and calcite precipitation. In 1982, many wells in the central part of the field were shut in. The amount of drawndown decreased and as temperatures and pressures near the wells increased, the boiling zones collapsed. The CO/sub 2/ in the fluid then exchanged with the precipitated calcite and became isotopically lighter. The sensitivity of carbon isotopes to calcite precipitations caused by aquifer boiling and to reequilibration with this deposited calcite upon decrease of boiling suggests use as an indicator of these aquifer processes. Surficial CO/sub 2/ of thermal origin was collected in 1981. Generally, the carbon-13 contents were close to CO/sub 2/ from production wells except for high-temperature mud pots and fumaroles containing isotopically light CO/sub 2/ derived from near surface alteration of organic matter.
Energy Technology Data Exchange (ETDEWEB)
Koziet, J. [Centre de Recherche Pernod-Ricard, 94 - Creteil (France)
1994-12-31
The coupled gaseous chromatography and isotope ratio mass spectrometry approach was first validated on beet and maize glucose and glycerol aqueous solutions containing variable carbon 13 content. Then human plasma was used to prepare samples where glucose and glycerol were labelled with small amounts of (1.3-{sup 13}C{sub 2})-glycerol and D-(U{sup 13}-C{sub 6})-glucose. The samples are then de-proteinized with acetone before lyophilization and acetylation in order to be able to measure them in the form of acetates. Carbon 13 content evaluation should then take into account the exogenous carbons from the acetyl radicals. This method appears well adapted to the simultaneous metabolic monitoring of glycerol and glucose in the blood plasma. 1 fig., 3 tabs., 5 refs.
Knols Bart GJ; Mayr Leo; Hood-Nowotny Rebecca
2006-01-01
Abstract Background Monitoring of sterile to wild insect ratios in field populations can be useful to follow the progress in genetic control programmes such as the Sterile Insect Technique (SIT). Of the numerous methods for marking insects most are not suitable for use in mass rearing and mass release. Suitable ones include dye marking, genetic marking and chemical marking. Methods The feasibility of using the stable isotope of carbon, 13C, as a potential chemical marker for Anopheles arabien...
Meissen, John K; Pirman, David A; Wan, Min; Miller, Emily; Jatkar, Aditi; Miller, Russell; Steenwyk, Rick C; Blatnik, Matthew
2016-09-01
Metabolite stable isotope tracing is a powerful bioanalytical strategy that has the potential to unravel phenotypic markers of early pharmaceutical efficacy by monitoring enzymatic incorporation of carbon-13 atoms into targeted pathways over time. The practice of probing biological systems with carbon-13 labeled molecules using broad MS-based screens has been utilized for many years in academic laboratories but has had limited application in the pharmaceutical R&D environment. The goal of this work was to establish a LCMS analytical workflow that was capable of monitoring carbon-13 isotope changes in glycolysis, the TCA and urea cycles, and non-essential amino acid metabolism. This work applies a standardized protein precipitation with 80% cold methanol and two distinct reverse-phase ion-pair liquid chromatography methods coupled to either a positive- or negative-ion mode high-resolution accurate mass spectrometry screening method. The data herein combines thousands of single-point peak integrations into a novel metabolite network map as a visualization aid to probe and monitor stable isotope incorporation in murine hepatocytes using uniformly labeled (13)C6 glucose, (13)C3 lactate, and (13)C5 glutamine. This work also demonstrates that nitrogen metabolism may have a large influence on the TCA cycle and gluconeogenic carbon fluxes in hepatocyte cell culture. PMID:27343766
Hnybida, Jeff
2016-10-01
We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. In doing so the sums over spins have been carried out. The boundary data of each n-valent node is explicitly reduced with respect to the local gauge invariance and has a manifest geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions.
De Leo, Stefano
2010-01-01
We present the results of the planar diffusion of a Dirac particle by step and barrier potentials, when the incoming wave impinges at an arbitrary angle with the potential. Except for right-angle incidence this process is characterized by the appearance of spin flip terms. For the step potential, spin flip occurs for both transmitted and reflected waves. However, we find no spin flip in the transmitted barrier result. This is surprising because the barrier result may be derived directly from a two-step calculation. We demonstrate that the spin flip cancellation indeed occurs for each particle (wave packet) contribution.
Spin Funneling for Enhanced Spin Injection into Ferromagnets.
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
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.
Rojas-Sánchez, J. -C.; Reyren, N.; Laczkowski, P.; Savero, W.; Attané, J. -P.; Deranlot, C.; Jamet, M.; George, J.-M.; Vila, L.; Jaffrès, H.
2013-01-01
Through combined ferromagnetic resonance, spin-pumping and inverse spin Hall effect experiments in Co|Pt bilayers and Co|Cu|Pt trilayers, we demonstrate consistent values of spin diffusion length $\\ell_{\\rm sf}^{\\rm Pt}=3.4\\pm0.4$ nm and of spin Hall angle $\\theta_{\\rm SHE}^{\\rm Pt}=0.051\\pm0.004$ for Pt. Our data and model emphasize on the partial depolarization of the spin current at each interface due to spin-memory loss. Our model reconciles the previously published spin Hall angle values...
Spin Hall and Spin Nernst effect from first principles
Mertig, Ingrid
2013-03-01
Spintronics without magnetic materials is an interesting alternative to the existing spintronics applications. The spin Hall effect creates spin currents in nonmagnetic materials and avoids the problem of spin injection. Future applications of the spin Hall effect require two properties of the materials, a large spin Hall angle and a long spin diffusion length. Ab intio calculations based on density functional theory are a powerful tool to design the desired materials and to get insight into the underlying microscopic processes. We investigated the spin Hall effect in dilute alloys, in particular the intrinsic effect based on the Berry curvature as well as side-jump and the skew-scattering contributions. The results demonstrate that a large extrinsic spin Hall effect is determined by the differences between host and impurity concerning the spin-orbit interaction. It can be caused by light p scatterers as C and N in Au. A comparable large effect is observed for heavy p scatterers as Bi in Cu. An alternative way is to deposit impurities in the adatom position. Furthermore, we predict a spin current perpendicular to a temperature gradient. The phenomenon is called spin Nernst effect. The predicted spin currents can be comparably large as in the case of the spin Hall effect.
Pure spin current transport in Alq3 by spin pumping
Jiang, Shengwei; Wang, Peng; Luan, Zhongzhi; Tao, Xinde; Ding, Haifeng; Wu, Di
2015-03-01
The use of organic semiconductors (OSCs) in spintronics has aroused considerable interests, owing to their much longer spin-relaxation times of OSCs than those of inorganic counterparts. The most studied example is the organic spin valve (OSV), in which magnetoresistance (MR) effect is frequently reported. However, studies on pure spin current injection and transport in OSCs are scarce. Recently, the pioneering work by Watanabe et al. demonstrated that pure spin current can be pumped into and propagates in semiconducting polymers. In the present work we extend the study to small molecule OSCs, and demonstrate that pure spin current can be injected into Alq3 from the adjacent magnetic insulator Y3Fe5O12 (YIG) by spin pumping. The pure spin current is detected by inverse spin Hall effect (ISHE) in Pd after propagation through Alq3. From the ISHE voltage VISHE as a function of the Alq3 thickness, the spin diffusion length is determined to be ~ 50 nm and does not depend on temperature. This result indicates the MR decrease as increasing temperature in OSVs is not due to the reduced spin diffusion length.
Spin current swapping and spin hall effect in disordered metals
Saidaoui, Hamed; Pauyac, Christian; Manchon, Aurelien
2015-03-01
The conversion of charge currents into spin currents via the spin Hall effect has attracted intense experimental and theoretical efforts lately, providing an efficient means to generate electric signals and manipulate the magnetization of single layers. More recently, it was proposed that spin-dependent scattering induced by spin-orbit coupled impurities also produces a so-called spin swapping, i.e. an exchange between the spin angular momentum and linear momentum of itinerant electrons. In this work, we investigate the nature of spin swapping and its interplay with extrinsic spin Hall effect and spin relaxation in finite size normal metals. We use two complementary methods based on non-equilibrium Green's function technique. The first method consists in rigorously deriving the drift-diffusion equation of the spin accumulation in the presence of spin-orbit coupled impurities from quantum kinetics using Wigner expansion. The second method is the real-space tight binding modeling of a finite system in the presence of spin-orbit coupled disorder.
Energy Technology Data Exchange (ETDEWEB)
Herve, M.; Wietzerbin, J.; Tran-Dinh, S. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Biologie Cellulaire et Moleculaire
1994-12-31
A new approach for studying the effects of two drugs, amphotericine B (AMB), an anti-fungal antibiotic, and 2-deoxy-D-glucose (DG), on the glucose metabolism in brewer yeast cells (Saccharomyces cerevisiae), is presented; AMB interacts with the membrane sterols, inducing formation of pores through which ions and small molecules can pass. DG may enter in the cytosol, where it is phosphoryled by hexokinase into deoxy-D-glucose 6-phosphate (DG6P) which disappears very slowly. DG slows down the glycolysis process and induces the formation of new substances. This paper shows the advantages of utilizing carbon 13-labelled substrates combined to the NMR-13C and NMR-1H techniques. 6 figs., 5 refs.
A generalized Theory of Diffusion based on Kinetic Theory
Schaefer, Thomas
2016-01-01
We propose to use spin hydrodynamics, a two-fluid model of spin propagation, as a generalization of the diffusion equation. We show that in the dense limit spin hydrodynamics reduces to Fick's law and the diffusion equation. In the opposite limit spin hydrodynamics is equivalent to a collisionless Boltzmann treatment of spin propagation. Spin hydrodynamics avoids unphysical effects that arise when the diffusion equation is used to describe to a strongly interacting gas with a dilute corona. We apply spin hydrodynamics to the problem of spin diffusion in a trapped atomic gas. We find that the observed spin relaxation rate in the high temperature limit [Sommer et al., Nature 472, 201 (2011)] is consistent with the diffusion constant predicted by kinetic theory.
Spin-orbit-coupled transport and spin torque in a ferromagnetic heterostructure
Wang, Xuhui
2014-02-07
Ferromagnetic heterostructures provide an ideal platform to explore the nature of spin-orbit torques arising from the interplay mediated by itinerant electrons between a Rashba-type spin-orbit coupling and a ferromagnetic exchange interaction. For such a prototypic system, we develop a set of coupled diffusion equations to describe the diffusive spin dynamics and spin-orbit torques. We characterize the spin torque and its two prominent—out-of-plane and in-plane—components for a wide range of relative strength between the Rashba coupling and ferromagnetic exchange. The symmetry and angular dependence of the spin torque emerging from our simple Rashba model is in an agreement with experiments. The spin diffusion equation can be generalized to incorporate dynamic effects such as spin pumping and magnetic damping.
Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi
2012-01-01
In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.
Ellsworth, David; Lu, Lei; Lan, Jin; Chang, Houchen; Li, Peng; Wang, Zhe; Hu, Jun; Johnson, Bryan; Bian, Yuqi; Xiao, Jiang; Wu, Ruqian; Wu, Mingzhong
2016-09-01
The photo-voltaic effect typically occurs in semiconductors and involves photon-driven excitation of electrons from a valence band to a conduction band. In a region such as a p-n junction that has a built-in electric field, the excited electrons and holes diffuse in opposite directions, resulting in an electric voltage. This letter reports that a spin voltage can be created by photons in a non-magnetic metal that is in close proximity to a magnetic insulator: a photo-spin-voltaic effect. The experiments use platinum/magnetic insulator bilayer structures. On exposure to light, there occurs photon-driven, spin-dependent excitation of electrons in several platinum atomic layers near the platinum/magnetic insulator interface. The excited electrons and holes diffuse in different manners, and this gives rise to an effective spin voltage at the interface and a corresponding pure spin current that flows across the platinum.
International Nuclear Information System (INIS)
Purpose: To compare lesion conspicuity and image quality between single-shot spin echo echo planar imaging (SS SE-EPI) before, immediately and 5 min after intravenous (IV) injection of superparamagnetic iron oxide (SPIO) for detecting and characterizing focal liver lesions (FLLs). Materials and methods: Twenty-five patients suspected for colorectal liver metastases were prospectively included. Lesion detection and characterization were compared between all SS SE-EPI and T2-weighted turbo spin echo (T2w TSE) sets (two-sided Fisher's exact test). Image quality and lesion conspicuity were compared for SS SE-EPI sets using rank order statistic (RIDIT). Reference standard comprised of surgery, biopsy and/or follow-up. Results: Reference standard demonstrated 18 benign and 43 malignant FLLs. Best lesion detection (p < 0.05) was achieved with non-contrast-enhanced SS SE-EPI. Lesion characterization was best using all T2w TSE sequences. Best image quality and lesion conspicuity (p < 0.05) was achieved with non-contrast-enhanced SS SE-EPI. Conclusion: Non-contrast-enhanced SS SE-EPI was best for lesion detection. SS SE-EPI sequences were not useful for lesion characterization (differentiation between benign and malignant lesions). Unenhanced SS SE-EPI did not allow differentiation especially as many benign FLLs were hyperintense on the highest b-value images. Combining unenhanced and SPIO-enhanced SS SE-EPI performed better but still was not clinically useful due to variable degree of uptake and vascular pooling of SPIO for (especially) benign FLLs. T2w TSE with SPIO-enhancement was needed for characterization.
Newman, Ezra T.; Silva-Ortigoza, Gilberto
2005-01-01
We show how to define and go from the spin-s spherical harmonics to the tensorial spin-s harmonics. These quantities, which are functions on the sphere taking values as Euclidean tensors, turn out to be extremely useful for many calculations in General Relativity. In the calculations, products of these functions, with their needed decompositions which are given here, often arise naturally.
Josephson current through a diffusive half metal
Asano, Y.; Tanaka, Y.; Golubov, A.A.
2007-01-01
This paper discusses the Josephson effect in superconductor/diffusive half metal/superconductor junctions. The spin-flip scattering at the junction interfaces opens a Josephson channel between the two spin-singlet superconductors. The odd-frequency equal-spin-triplet Cooper pairs carry the Josephson
Slachter, Abraham; Bakker, Frank Lennart; van Wees, Bart Jan
2011-01-01
In this article we extend the currently established diffusion theory of spin-dependent electrical conduction by including spin-dependent thermoelectricity and thermal transport. Using this theory, we propose experiments aimed at demonstrating novel effects such as the spin-Peltier effect, the recipr
Tahara, Takayuki; Ando, Yuichiro; Kameno, Makoto; Koike, Hayato; Tanaka, Kazuhito; Miwa, Shinji; Suzuki, Yoshishige; Sasaki, Tomoyuki; Oikawa, Tohru; Shiraishi, Masashi
2016-06-01
A large spin accumulation voltage of more than 1.5 mV at 1 mA, i.e., a magnetoresistance of 1.5 Ω, was measured by means of the local three-terminal magnetoresistance in nondegenerate Si-based lateral spin valves (LSVs) at room temperature. This is the largest spin accumulation voltage measured in semiconductor-based LSVs. The modified spin drift-diffusion model, which successfully accounts for the spin drift effect, explains the large spin accumulation voltage and significant bias-current-polarity dependence. The model also shows that the spin drift effect enhances the spin-dependent magnetoresistance in the electric two-terminal scheme. This finding provides a useful guiding principle for spin metal-oxide-semiconductor field-effect transistor operations.
Kalivianakis, M; Elstrodt, J; Havinga, R; Kuipers, F; Stellaard, F; Sauer, PJJ; Vonk, RJ; Verkade, HJ
1999-01-01
Objective: To determine, in a rat model of fat malabsorption, the potency of the carbon 13-labeled mixed triglyceride (C-13-MTG) breath test as a noninvasive, patient-friendly replacement for classic fat balance studies, Study design: Comparison of the percentage of Fat absorption, detected by fat b
International Nuclear Information System (INIS)
To prospectively assess the efficacy of 3-T magnetic resonance (MR) imaging using the three-dimensional turbo spin-echo T2-weighted and diffusion-weighted technique (3D-TSE/DW) compared with that of conventional imaging using the two-dimensional turbo spin-echo T2-weighted and dynamic contrast-enhanced technique (2D-TSE/DCE) for the preoperative staging of endometrial cancer, with pathological analysis as the reference standard. Seventy-one women with endometrial cancer underwent MR imaging using 3D-TSE/DW (b = 1,000 s/mm2) and 2D-TSE/DCE. Two radiologists independently assessed the two imaging sets. Accuracy, sensitivity, and specificity for staging were analysed with the McNemar test; the areas under the receiver operating characteristic curve (Az) were compared with a univariate z-score test. The results for assessing deep myometrial invasion, accuracy, sensitivity, specificity and Az, respectively, were as follows: 3D-TSE/DW - observer 1, 87 %, 95 %, 85 % and 0.96; observer 2, 92 %, 84 %, 94 % and 0.95; 2D-TSE/DCE - observer 1, 80 %, 79 %, 81 % and 0.89; observer 2, 86 %, 84 %, 87 % and 0.86. Most of the values were higher with 3D-TSE/DW without significant differences (P > 0.12). For assessing cervical stromal invasion, there were no significant differences in those values for both observers (P > 0.6). Accuracy of 3D-TSE/DW was at least equivalent to that of the conventional technique for the preoperative assessment of endometrial cancer. (orig.)
de Carvalho, Erika Martins; Velloso, Marcia Helena Rodrigues; Tinoco, Luzineide Wanderley; Figueroa-Villar, José Daniel
2003-10-01
A study of the nature of the anthelmintic p-cresol:piperazine complex in chloroform solution has been conducted using different NMR techniques: self-diffusion coefficients using DOSY; NOE, NULL, and double-selective T1 measurements to determine inter-molecular distances; and selective and non-selective T1 measurements to determine correlation times. The experimental results in solution and CP-MAS were compared to literature X-ray diffraction data using molecular modeling. It was shown that the p-cresol:piperazine complex exists in solution in a very similar manner as it does in the solid state, with one p-cresol molecule hydrogen bonded through the hydroxyl hydrogen to each nitrogen atom of piperazine. The close correspondence between the X-ray diffraction data and the inter-proton distances obtained by NULL and double selective excitation techniques indicate that those methodologies can be used to determine inter-molecular distances in solution.
Sun, Feng M; Shi, Guang Y; Wang, Hui W
2016-07-01
Consumers prefer natural and healthy food, but artificial pigments are often abused in egg products. The study aimed at differentiating the origin of pigments in eggs by applying the technique of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope analysis. Five hundred sixty laying hens were randomly distributed into 14 treatments, which were divided into four groups: maize, carophyll red pigment, carophyll yellow pigment, and a mixture of carophyll red and yellow pigments. Eggs were collected and pretreated to determe the values of the Roche Yolk Color Fan (RCF), δ(13)C, and δ(15)N. With increasing maize content, the RCF and δ(13)C values of yolks increased. Moreover, the RCF values in the three pigment groups were significantly influenced by the artificial colors, but δ(13)C values were not significantly different, regardless of the existence of pigment. The δ(15)N values in all treatments did not vary as regularly as the carbon stable isotope. A strong positive correlation was found between RCF and δ(13)C in the maize group, but no such correlation was be observed in the pigment groups. It is concluded that carbon stable isotope ratio analysis (δ(13)C) of the yolk can be used to differentiate the origin of the pigment added to eggs.
Sun, Feng M; Shi, Guang Y; Wang, Hui W
2016-07-01
Consumers prefer natural and healthy food, but artificial pigments are often abused in egg products. The study aimed at differentiating the origin of pigments in eggs by applying the technique of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope analysis. Five hundred sixty laying hens were randomly distributed into 14 treatments, which were divided into four groups: maize, carophyll red pigment, carophyll yellow pigment, and a mixture of carophyll red and yellow pigments. Eggs were collected and pretreated to determe the values of the Roche Yolk Color Fan (RCF), δ(13)C, and δ(15)N. With increasing maize content, the RCF and δ(13)C values of yolks increased. Moreover, the RCF values in the three pigment groups were significantly influenced by the artificial colors, but δ(13)C values were not significantly different, regardless of the existence of pigment. The δ(15)N values in all treatments did not vary as regularly as the carbon stable isotope. A strong positive correlation was found between RCF and δ(13)C in the maize group, but no such correlation was be observed in the pigment groups. It is concluded that carbon stable isotope ratio analysis (δ(13)C) of the yolk can be used to differentiate the origin of the pigment added to eggs. PMID:27302905
Towards spin injection into silicon
Energy Technology Data Exchange (ETDEWEB)
Dash, S.P.
2007-08-15
Si has been studied for the purpose of spin injection extensively in this thesis. Three different concepts for spin injection into Si have been addressed: (1) spin injection through a ferromagnet-Si Schottky contact, (2) spin injection using MgO tunnel barriers in between the ferromagnet and Si, and (3) spin injection from Mn-doped Si (DMS) as spin aligner. (1) FM-Si Schottky contact for spin injection: To be able to improve the interface qualities one needs to understand the atomic processes involved in the formation of silicide phases. In order to obtain more detailed insight into the formation of such phases the initial stages of growth of Co and Fe were studied in situ by HRBS with monolayer depth resolution.(2) MgO tunnel barrier for spin injection into Si: The fabrication and characterization of ultra-thin crystalline MgO tunnel barriers on Si (100) was presented. (3) Mn doped Si for spin injection: Si-based diluted magnetic semiconductor samples were prepared by doping Si with Mn by two different methods i) by Mn ion implantation and ii) by in-diffusion of Mn atoms (solid state growth). (orig.)
Directory of Open Access Journals (Sweden)
Knols Bart GJ
2006-01-01
Full Text Available Abstract Background Monitoring of sterile to wild insect ratios in field populations can be useful to follow the progress in genetic control programmes such as the Sterile Insect Technique (SIT. Of the numerous methods for marking insects most are not suitable for use in mass rearing and mass release. Suitable ones include dye marking, genetic marking and chemical marking. Methods The feasibility of using the stable isotope of carbon, 13C, as a potential chemical marker for Anopheles arabiensis was evaluated in the laboratory. Labeled-13C glucose was incorporated into the larval diet in a powder or liquid form. The contribution of adult sugar feeding to the total mosquito carbon pool and the metabolically active carbon pool was determined by tracing the decline of the enrichment of the adult male mosquito as it switched from a labeled larval diet to an unlabeled adult diet. This decline in the adult was monitored by destructive sampling of the whole mosquito and analyzed using isotope ratio mass spectrometry. Results A two-pool model was used to describe the decline of the 13C-enrichment of adult mosquitoes. The proportion of the total adult carbon pool derived from the adult sugar diet over the life span of mosquitoes was determined and the ratio of structural carbon, with a low turnover rate to metabolically active non-structural carbon was assessed. The uptake and turnover of sugar in the metabolically active fraction suggests that after 3 days >70% of the active fraction carbon is derived from sugar feeding (increasing to >90% by day 7, indicating the high resource demand of male mosquitoes. Conclusion It was possible to "fix" the isotopic label in adult An. arabiensis and to detect the label at an appropriate concentration up to 21 days post-emergence. The optimum labeling treatment would cost around 250 US$ per million mosquitoes. Stable isotope marking may thus aid research on the fate of released insects besides other population
Spin currents in metallic nanostructures
Energy Technology Data Exchange (ETDEWEB)
Czeschka, Franz Dominik
2011-09-05
A pure spin current, i.e., a flow of angular momentum without accompanying net charge current, is a key ingredient in the field of spintronics. In this thesis, we experimentally investigated two different concepts for pure spin current sources suggested by theory. The first is based on a time-dependent magnetization precession which ''pumps'' a pure spin current into an adjacent non-magnetic conductor. Our experiments quantitatively corroborated important predictions expected theoretically for this approach, including the dependence of the spin current on the sample geometry and the microwave power. Even more important, we could show for the first time that the spin pumping concept is viable in a large variety of ferromagnetic materials and that it only depends on the magnetization damping. Therefore, our experiments established spin pumping as generic phenomenon and demonstrated that it is a powerful way to generate pure spin currents. The second theoretical concept is based on the conversion of charge currents into spin currents in non-magnetic nanostructures via the spin Hall effect. We experimentally investigated this approach in H-shaped, metallic nanodevices, and found that the predictions are linked to requirements not realizable with the present experimental techniques, neither in sample fabrication nor in measurement technique. Indeed, our experimental data could be consistently understood by a spin-independent transport model describing the transition from diffusive to ballistic transport. In addition, the implementation of advanced fabrication and measurement techniques allowed to discover a new non-local phenomenon, the non-local anisotropic magnetoresistance. Finally, we also studied spin-polarized supercurrents carried by spin-triplet Cooper pairs. We found that low resistance interfaces are a key requirement for further experiments in this direction. (orig.)
Effects of thermal magnetic fluctuations on spin transport in Pt
Freeman, Ryan; Zholud, Andrei; Cao, Rongxing; Urazhdin, Sergei
Despite extensive studies and applications of Pt as a spin Hall material in spintronic devices, its spin-dependent transport properties are still debated. We present a comprehensive experimental study of spin transport in Pt, utilizing measurements of giant magnetoresistance (GMR) in nanoscale Permalloy (Py)-based spin valves with Pt inserted in the nonmagnetic spacer. The spin diffusion length and the interfacial spin flipping coefficients are extracted from the dependence of MR on the Pt thickness. For samples with Pt separated from Py by Cu spacers, the spin diffusion length is 6 nm at 7K, and decreases to 3 nm at room temperature. The interfacial spin flipping decreases with increasing temperature, resulting in nonmonotonic temperature dependence of MR in samples with thin Pt. In contrast, in samples with Pt in direct contact with Py, we do not observe such a nonmonotonic dependence, and the spin diffusion length is significantly larger than in samples with Pt surrounded by Cu spacers. Our results indicate a large effect of the giant paramagnetic fluctuations in the nearly ferromagnetic Pt. These fluctuations are suppressed due to the proximity magnetism when Pt is in contact with Py, resulting in enhanced spin diffusion length and reduced spin flipping at the Pt interfaces. These observations indicate the need for a critical revision of spin transport and spin Hall-related properties of Pt-based structures. Supported by NSF ECCS-1305586.
Dynamic Feedback in Ferromagnet-Spin Hall Metal Heterostructures.
Cheng, Ran; Zhu, Jian-Gang; Xiao, Di
2016-08-26
In ferromagnet-normal-metal heterostructures, spin pumping and spin-transfer torques are two reciprocal processes that occur concomitantly. Their interplay introduces a dynamic feedback effect interconnecting energy dissipation channels of both magnetization and current. By solving the spin diffusion process in the presence of the spin Hall effect in the normal metal, we show that the dynamic feedback gives rise to (i) a nonlinear magnetic damping that is crucial to sustain uniform steady-state oscillations of a spin Hall oscillator at large angles and (ii) a frequency-dependent spin Hall magnetoimpedance that reduces to the spin Hall magnetoresistance in the dc limit. PMID:27610880
Dynamic Feedback in Ferromagnet-Spin Hall Metal Heterostructures
Cheng, Ran; Zhu, Jian-Gang; Xiao, Di
2016-08-01
In ferromagnet-normal-metal heterostructures, spin pumping and spin-transfer torques are two reciprocal processes that occur concomitantly. Their interplay introduces a dynamic feedback effect interconnecting energy dissipation channels of both magnetization and current. By solving the spin diffusion process in the presence of the spin Hall effect in the normal metal, we show that the dynamic feedback gives rise to (i) a nonlinear magnetic damping that is crucial to sustain uniform steady-state oscillations of a spin Hall oscillator at large angles and (ii) a frequency-dependent spin Hall magnetoimpedance that reduces to the spin Hall magnetoresistance in the dc limit.
Tagliabue, A.; L. Bopp; Roche, D. M.; N. Bouttes; J.-C. Dutay; Alkama, R.; Kageyama, M.; Michel, E.; Paillard, D.
2009-01-01
We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO_{2} at the last glacial maximum (LGM). We examine 5 different realisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton ph...
Institute of Scientific and Technical Information of China (English)
GAO Song; WANG Xiaoying; BAO Shanglian
2006-01-01
Diffusion time and diffusion gradient strength are two important parameters of pulsed gradient spin echo (PGSE) that is the most commonly used method in diffusion-weighted magnetic resonance imaging. However, the effects of the diffusion time on the mean diffusivity (MD) in previous studies are controversial. In this study, a new experimental protocol was designed to evaluate the effects of the two parameters on the results of PGSE. It was found that MD decreased significantly with the increased diffusion time or increased diffusion gradient strength, which cannot be explained by the previous theories. Through theoretical analysis, we found the flaw in the pulsed gradient spin echo (PGSE) method, which is the explanation for the controversial results of diffusion time obtained by others.
Hu, H; Hu, Huping; Wu, Maoxin
2002-01-01
We postulate that consciousness is connected to quantum mechanical spin since said spin is embedded in the microscopic structure of spacetime and may be more fundamental than spacetime itself. Thus, we theorize that consciousness is connected with the fabric of spacetime through spin. That is, spin is the "pixel" and "antenna" of mind. The unity of mind is achieved by non-local means within the pre-spacetime domain interfaced with spacetime. Human mind is possible because of the particular structures and dynamics of our brain postulated working as follows: The unpaired electronic spins of highly lipid-soluble and rapidly diffusing oxygen molecules extract information from the dynamical neural membranes and communicate said information through strong spin-spin couplings to the nuclear spin ensemble in the membranes for consciousness-related quantum statistical processing which survives decoherence. In turn, the dynamics of the nuclear spin ensemble has effects through spin chemistry on the classical neural act...
Pure spin current in lateral structures
Chen, Shuhan
Spintronics, a frontier academic research area, is advancing rapidly in recent years. It has been chosen as one of the promising candidates for overcoming the obstacles in continuing the "Moore's Law" of the electronics industry. Spintronics employs both spin and charge degrees of freedom of electrons to reduce energy consumption and increase the flexibility of IC design. To achieve this, it is extremely important to understand the generation, transport, and detection of the spin polarized current (spin current). In this work we use a mesoscopic metallic spintronic structure-nonlocal spin valve (NLSV)-for fundamental studies of spintronics. A nonlocal spin valve consists of two ferromagnetic electrodes (a spin injector and a spin detector) bridged by a non-magnetic spin channel. A thin aluminum oxide barrier (~ 2 - 3 nm) has been shown to effectively enhance the spin injection and detection polarizations. We have studied spin injection and detection in these nanoscale structures. Several topics will be discussed in this work. In Chapter 4 we explore spin transport in NLSVs with Ag channels. Substantial spin signals are observed. The temperature dependence of the spin signals indicates long spin diffusion lengths and low surface spin-flip rate in the mesoscopic Ag channels. Chapter 5 will focus on the asymmetric spin absorption across the low-resistance AlOx barriers in NLSVs. This effect allows for a more simplified and efficient detection scheme for the spin accumulation. Then in Chapter 6 we report a large spin signal owing to a highly resistive break-junction. We have also developed a model to describe the spin-charge coupling effect which enables the large spin signal. In the end, Spin Hall Effect (SHE) is investigated in Chapter 7. A mesoscopic Pt film is utilized to inject a spin accumulation into a mesoscopic Cu channel via the SHE. The spin accumulation in Cu can be detected by the nonlocal method. The reciprocal effect -- the inverse Spin Hall Effect - (i
Bovier, Anton
2007-01-01
Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.
Yoon, Haesung; Yoon, Dahye; Yun, Mijin; Choi, Ji Soo; Park, Vivian Youngjean; Kim, Eun-Kyung; Jeong, Joon; Koo, Ja Seung; Yoon, Jung Hyun; Moon, Hee Jung; Kim, Suhkmann; Kim, Min Jung
2016-01-01
Purpose Our goal in this study was to find correlations between breast cancer metabolites and conventional quantitative imaging parameters using high-resolution magic angle spinning (HR-MAS) magnetic resonance spectroscopy (MRS) and to find breast cancer subgroups that show high correlations between metabolites and imaging parameters. Materials and methods Between August 2010 and December 2013, we included 53 female patients (mean age 49.6 years; age range 32–75 years) with a total of 53 breast lesions assessed by the Breast Imaging Reporting and Data System. They were enrolled under the following criteria: breast lesions larger than 1 cm in diameter which 1) were suspicious for malignancy on mammography or ultrasound (US), 2) were pathologically confirmed to be breast cancer with US-guided core-needle biopsy (CNB) 3) underwent 3 Tesla MRI with dynamic contrast-enhanced (DCE) and diffusion-weighted imaging (DWI) and positron emission tomography-computed tomography (PET-CT), and 4) had an attainable immunohistochemistry profile from CNB. We acquired spectral data by HR-MAS MRS with CNB specimens and expressed the data as relative metabolite concentrations. We compared the metabolites with the signal enhancement ratio (SER), maximum standardized FDG uptake value (SUV max), apparent diffusion coefficient (ADC), and histopathologic prognostic factors for correlation. We calculated Spearman correlations and performed a partial least squares-discriminant analysis (PLS-DA) to further classify patient groups into subgroups to find correlation differences between HR-MAS spectroscopic values and conventional imaging parameters. Results In a multivariate analysis, the PLS-DA models built with HR-MAS MRS metabolic profiles showed visible discrimination between high and low SER, SUV, and ADC. In luminal subtype breast cancer, compared to all cases, high SER, ADV, and SUV were more closely clustered by visual assessment. Multiple metabolites were correlated with SER and SUV in
Jain, Abhinav; Rojas-Sanchez, Juan-Carlos; Cubukcu, Murat; Peiro, Julian; Le Breton, Jean-Christophe; Vergnaud, Céline; Augendre, Emmanuel; Vila, Laurent; Attané, Jean-Philippe; Gambarelli, Serge; Jaffrès, Henri; George, Jean-Marie; Jamet, Matthieu
2013-04-01
Electrical spin injection into semiconductors paves the way for exploring new phenomena in the area of spin physics and new generations of spintronic devices. However the exact role of interface states in the electrical spin injection mechanism from a magnetic tunnel junction into a semiconductor is still under debate. Here we demonstrate a clear transition from spin accumulation into interface states to spin injection in the conduction band of n-Si and n-Ge using a CoFeB/MgO tunnel contact. We observe spin signal amplification at low temperature due to spin accumulation into interface states followed by a clear transition towards spin injection in the conduction band from approximately 150 K up to room temperature. In this regime, the spin signal is reduced down to a value compatible with the standard spin diffusion model. More interestingly, in the case of germanium, we demonstrate a significant modulation of the spin signal by applying a back-gate voltage to the conduction channel. We also observe the inverse spin Hall effect in Ge by spin pumping from the CoFeB electrode. Both observations are consistent with spin accumulation in the Ge conduction band.
International Nuclear Information System (INIS)
Spin-lattice relaxation rates (R1) from naturally occuring C-13 F.T. N.M.R. spectra of some catecholamines and parent compounds with Iron(III) at pD = 4 were determined in order to elucidate the molecular mechanism underlying their association in aqueous solutions. Complexation was observed only for catecholic ligands. The R1 values were used to calculate iron-carbon scaled distances, and two complexation models were proposed where the catecholic function binds Fe(III) in the first and second coordination spheres respectively. The latter case was shown to be the consistent with the molecular geometries. (orig.)
Theory of the ac spin-valve effect
Kochan, Denis; Gmitra, Martin; Fabian, Jaroslav
2011-01-01
The spin-valve complex magnetoimpedance of symmetric ferromagnet/normal metal/ferromagnet junctions is investigated within the drift-diffusion (standard) model of spin injection. The ac magnetoresistance---the real part difference of the impedances of the parallel and antiparallel magnetization configurations---exhibits an overall damped oscillatory behavior, as an interplay of the diffusion and spin relaxation times. In wide junctions the ac magnetoresistance oscillates between positive and ...
NMR IMAGING OF ACETONE DIFFUSION PROCESS IN POLYCARBONATE
Institute of Scientific and Technical Information of China (English)
QIN Wei; SHEN Yimin; FEI Lun
1993-01-01
SAcetone diffusion in polycarbonate was investigated by spin-echo 1H NMR imaging method at room temperature. The result shows that the diffusion process satisfies Case Ⅱ diffusion. The velocity of diffusion front is 13.8nm sec-1(0.05mm/h).
Hanle effect near boundaries: Diffusion-induced lineshape inhomogeneity
Engel, Hans-Andreas
2008-03-01
The Hanle effect describes suppression of spin polarization due to precession in a magnetic field. This is a standard spintronics tool and it gives access to the spin lifetime of samples in which spins are generated homogeneously. We examine the Hanle effect when spins are generated at a boundary of a diffusive sample by the extrinsic spin Hall effect. We show that the Hanle curve is spatially dependent and that the “apparent” spin lifetime, given by its inverse half-width, is shorter near the boundary even if the spin relaxation rate is homogeneous.
Spin-Swapping Transport and Torques in Ultrathin Magnetic Bilayers
Saidaoui, Hamed Ben Mohamed
2016-07-12
Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness d and the mean free path λ. While the spin Hall effect dominates in the diffusive limit (d≫λ), spin swapping dominates in the Knudsen regime (d≲λ). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.
Spin-Swapping Transport and Torques in Ultrathin Magnetic Bilayers
Saidaoui, Hamed Ben Mohamed; Manchon, A.
2016-07-01
Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness d and the mean free path λ . While the spin Hall effect dominates in the diffusive limit (d ≫λ ), spin swapping dominates in the Knudsen regime (d ≲λ ). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.
Buhrman, Robert; Daughton, James; Molnár, Stephan; Roukes, Michael
2004-01-01
This report is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magnetoelectronics and devices. The panel's conclusions are based on a literature review and a series of site visits to leading spin electronics research centers in Japan and Western Europe. The panel found that Japan is clearly the world leader in new material synthesis and characterization; it is also a leader in magneto-optical properties of semiconductor devices. Europe is strong in theory pertaining to spin electronics, including injection device structures such as tunneling devices, and band structure predictions of materials properties, and in development of magnetic semiconductors and semiconductor heterost...
Long-range spin transport in superconductors
Energy Technology Data Exchange (ETDEWEB)
Beckmann, Detlef; Wolf, Michael J. [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Huebler, Florian [Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Loehneysen, Hilbert von [Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany)
2012-07-01
Recently, there has been some controversy about spin-polarized quasiparticle transport and relaxation in superconductors, with reports of both anomalously short or anomalously long relaxation times as compared to the normal state. Here, we report on non-local transport in multiterminal superconductor-ferromagnet structures. We find signatures of spin transport over distances much larger than the normal-state spin-diffusion length in the presence of a large Zeeman splitting of the quasiparticle states. The relaxation length shows a nearly linear increase with magnetic field, hinting at a freeze-out of spin relaxation by the Zeeman splitting.
Zhu, Laipan; Liu, Yu; Huang, Wei; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai
2016-12-01
The spin diffusion and drift at different excitation wavelengths and different temperatures have been studied in undoped InGaAs/AlGaAs multiple quantum well (MQW). The spin polarization was created by optical spin orientation using circularly polarized light, and the reciprocal spin Hall effect was employed to measure the spin polarization current. We measured the ratio of the spin diffusion coefficient to the mobility of spin-polarized carriers. From the wavelength dependence of the ratio, we found that the spin diffusion and drift of holes became as important as electrons in this undoped MQW, and the ratio for light holes was much smaller than that for heavy holes at room temperature. From the temperature dependence of the ratio, the correction factors for the common Einstein relationship for spin-polarized electrons and heavy holes were firstly obtained to be 93 and 286, respectively. PMID:26744148
Hydrodynamic approach to coherent nuclear spin transport
Greenbaum, D.; Kindermann, M.; Ramanathan, C.; Cory, D. G.
2004-01-01
We develop a linear response formalism for nuclear spin diffusion in a dipolar coupled solid. The theory applies to the high-temperature, long-wavelength regime studied in the recent experiments of Boutis et al. [Phys. Rev. Lett. 92, 137201 (2004)], which provided direct measurement of interspin energy diffusion in such a system. A systematic expansion of Kubo's formula in the flip-flop term of the Hamiltonian is used to calculate the diffusion coefficients. We show that this approach is equi...
Structure determination of a 2''-O(α-D-glucopyranose) isomaltotriose by proton and carbon-13 NMR
International Nuclear Information System (INIS)
The glucosyltransferases from Leuconostoc mesenteroides are known to catalyze the transfer of the D-glucosyl group of sucrose onto sugars, commonly named acceptors. We investigated in the present work the transfer of the glucose moiety of sucrose onto isomaltose acceptor catalyzed by the glucosyltransferases from Leuconostoc mesenteroides. Several oligosaccharides were produced, isolated, fractionated by HPLC and characterized. The primary structure of the tetrasaccharide has been determined as that of 2'' -O-(α-D-glucopyranose) isomaltotriose by n.m.r. spectroscopy, using homo-and heteronuclear, shift correlated, two dimensional and n.o.e. difference experiments. This chemical structure was corrobored by 13C spin lattice relaxation time measurements (T1) indicating that internal units B and C are notably less flexible than A and D termini units, C being the less mobile. (authors). 18 refs., 3 figs., 3 tabs
Effect of Electric Field on Spin Polarized Current in Ferromagnetic/ Organic Semiconductor Systems
Institute of Scientific and Technical Information of China (English)
MA Yan-Ni; REN Jun-Feng; ZHANG Yu-Bin; LIU De-Sheng; XIE Shi-Jie
2007-01-01
Considering the special carriers in organic semiconductors, the spin polarized current under electric field in a ferromagnetic/organic semiconductor system is theoretically studied. Based on the spin-diffusion theory, the current spin polarization under the electric field is obtained. It is found that electric field can enhance the current spin polarization.
Serés Roig, Eulalia; Magill, Arthur W.; Donati, Guillaume; Meyerspeer, Martin; Xin, Lijing; Ipek, Ozlem; Gruetter, Rolf
2015-01-01
Purpose Carbon-13 magnetic resonance spectroscopy (13C-MRS) is challenging because of the inherent low sensitivity of 13C detection and the need for radiofrequency transmission at the 1H frequency while receiving the 13C signal, the latter requiring electrical decoupling of the 13C and 1H radiofrequency channels. In this study, we added traps to the 13C coil to construct a quadrature-13C/quadrature-1H surface coil, with sufficient isolation between channels to allow simultaneous operation at...
El Toukhy, Ahmed [احمد الطوخي; Al-Kubaisi, Abdulla H.; Kenawy, Ibrahim
1991-01-01
The proton and carbon-13 NMR spectra of some 4-amino-3-alkyl(aryl)-5-thio-1,2,4-triazolines, some 3-alkyl-5-thio- 1,2,4-triazolines and some 4-amino-3-aryl-5-thio-l,2,4-triazoles were measured in DMSO-d6 as solvent. The chemical shift for each proton and carbon in these compounds were assigned. The 'H, chemical shift of N-H protons of the thioamide group and the "C chemical shift of C(3) in the triazolines were found to be sensitive to the substituent R (alkyi or aryl) at C(3), and correlated...
2015-01-01
Diffusion Fundamentals is a peer-reviewed interdisciplinary open-access online journal published as a part of the website Diffusion-Fundamentals.org. It publishes original research articles in the field of diffusion and transport. Main research areas include theory, experiments applications, methods and diffusion-like phenomena. The readers of Diffusion Fundamentals are academic or industrial scientists in all research disciplines. The journal aims at providing a broad forum for their c...
Spin-Orbit induced semiconductor spin guides
Valin-Rodriguez, Manuel; Puente, Antonio; Serra, Llorens
2002-01-01
The tunability of the Rashba spin-orbit coupling allows to build semiconductor heterostructures with space modulated coupling intensities. We show that a wire-shaped spin-orbit modulation in a quantum well can support propagating electronic states inside the wire only for a certain spin orientation and, therefore, it acts as an effective spin transmission guide for this particular spin orientation.
Theory of the ac spin-valve effect.
Kochan, Denis; Gmitra, Martin; Fabian, Jaroslav
2011-10-21
The spin-valve complex magnetoimpedance of symmetric ferromagnet-normal-metal-ferromagnet junctions is investigated within the drift-diffusion (standard) model of spin injection. The ac magnetoresistance-the real part difference of the impedances of the parallel and antiparallel magnetization configurations-exhibits an overall damped oscillatory behavior, as an interplay of the diffusion and spin relaxation times. In wide junctions the ac magnetoresistance oscillates between positive and negative values, reflecting resonant amplification and depletion of the spin accumulation, while the line shape for thin tunnel junctions is predicted to be purely Lorentzian. The ac spin-valve effect could be a technique to extract spin transport and spin relaxation parameters in the absence of a magnetic field and for a fixed sample size. PMID:22107552
Gate-Tunable Spin-Charge Conversion and the Role of Spin-Orbit Interaction in Graphene
Dushenko, S.; Ago, H.; Kawahara, K.; Tsuda, T.; Kuwabata, S.; Takenobu, T.; Shinjo, T.; Ando, Y.; Shiraishi, M.
2016-04-01
The small spin-orbit interaction of carbon atoms in graphene promises a long spin diffusion length and the potential to create a spin field-effect transistor. However, for this reason, graphene was largely overlooked as a possible spin-charge conversion material. We report electric gate tuning of the spin-charge conversion voltage signal in single-layer graphene. Using spin pumping from an yttrium iron garnet ferrimagnetic insulator and ionic liquid top gate, we determined that the inverse spin Hall effect is the dominant spin-charge conversion mechanism in single-layer graphene. From the gate dependence of the electromotive force we showed the dominance of the intrinsic over Rashba spin-orbit interaction, a long-standing question in graphene research.
Effect of Carrier Differences on Spin Polarized Injection into Organic and Inorganic Semiconductors
Institute of Scientific and Technical Information of China (English)
REN Jun-Feng; XIU Ming-Xia
2008-01-01
Spin polarized injection into organic and inorganic semiconductors are studied theoretically from the spin diffusion theory and Ohm's law, and the emphases are placed on the effect of the carrier differences on the current spin polarization. The mobility and the spin-Rip time of carriers in organic and inorganic semiconductors are different. From the calculation, it is found that current spin polarization at a ferromagnetic/organic interface is higher than that at a ferromagnetic/inorganic interface because of different carriers in them. Effects of the conductivity matching, the spin dependent interfacial resistances, and the balk spin polarization of the ferromagnetic layer on the spin polarized injection are also discussed.
International Nuclear Information System (INIS)
13CO chemisorbed on platinum particles in L-zeolite has been investigated by static and magic angles spinning NMR spectroscopy. The representative spectra ate composed of a broad asymmetric peak with a center of gravity at 230±30 ppm and a sharp symmetric peak at 124±2 ppm which is tentatively assigned to physisorbed CO2 on inner walls of L-zeolite. Overall, the broad resonance component is similar to our previous results of highly dispersed (80-96%) CO/Pt/silica or CO/Pt/alumina samples, still showing metallic characters. The principal difference is in the first moment value. The broad peak in the spectra is assigned to CO linearly bound to Pt particles in the L-zeolites, and indicates a distribution of isotropic shifts from bonding site to bonding site. The NMR results reported here manifest that the Pt particles inside of the L-zeolites channels are not collectively the same with the ones supported on silica or alumina with similar dispersion in terms of Pt particle shape and/or ordering of Pt atoms in a particle. As a result, Pt particles of CO/Pt/L-zeolite were agglomerated accompanying CO desorption upon annealing. There were no definite changes in the NMR spectra due to differences of exchanged cations. Comparison of our observation on CO/Pt/L-zeolite with Sharma et al.'s reveals that even when the first moment, the linewidth, and the relaxation times of the static spectra and the dispersion measured by chemisorption are similar, the properties of Pt particles can be dramatically different. Therefore, it is essential to take advantage of the strengths of several techniques together in order to interpret data reliably, especially for the highly dispersed samples
Fukuyama, Hidenao
Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.
WESSELINGH, JA
1993-01-01
In this paper I first briefly look at diffusion in several controlled release devices. I have found that these exploit complicated diffusional mechanisms. These cannot be understood using the conventional description of diffusion. So, a general theory of multicomponent diffusion which can describe t
Brahms, N
2010-01-01
The dynamics of a large quantum spin coupled parametrically to an optical resonator is treated in analogy with the motion of a cantilever in cavity optomechanics. New spin optodynamic phenonmena are predicted, such as cavity-spin bistability, optodynamic spin-precession frequency shifts, coherent amplification and damping of spin, and the spin optodynamic squeezing of light.
Generation of a three-qudit GHZ state with diamond defect spins
Hebbache, M.
2016-07-01
Diamond defect spins have emerged as potential qudits (d-dimensional quantum bit) in quantum information and quantum computing. A new scheme is proposed for realizing entangled states of GHZ (Greenberger-Horne-Zeilinger) class in a 3-qudit solid-state register. The qudits are the electron spin-1 carried by the negatively charged nitrogen-vacancy color center (NV‑1) in diamond and the nuclear spin-\\frac{1}{2} of two carbon-13 impurities in the first neighbour shell. Multipartite entanglements between qudits are obtained by bringing the spin system in the vicinity of a level anticrossing. The degree of entanglement between all three qudits is quantified rigorously. GHZ and GHZ-like entangled states have applications in quantum communication and computation protocols.
Quantum Monte Carlo with Variable Spins
Melton, Cody A; Mitas, Lubos
2016-01-01
We investigate the inclusion of variable spins in electronic structure quantum Monte Carlo, with a focus on diffusion Monte Carlo with Hamiltonians that include spin-orbit interactions. Following our previous introduction of fixed-phase spin-orbit diffusion Monte Carlo (FPSODMC), we thoroughly discuss the details of the method and elaborate upon its technicalities. We present a proof for an upper-bound property for complex nonlocal operators, which allows for the implementation of T-moves to ensure the variational property. We discuss the time step biases associated with our particular choice of spin representation. Applications of the method are also presented for atomic and molecular systems. We calculate the binding energies and geometry of the PbH and Sn$_2$ molecules, as well as the electron affinities of the 6$p$ row elements in close agreement with experiments.
Spin transport in graphene nanostructures
International Nuclear Information System (INIS)
Full text: Graphene, a monolayer of carbon atoms packed into a two-dimensional honeycomb lattice, is an exciting and promising material for spintronic applications. Due to its high mobility it has a long spin diffusion length l up to 2 μm. However, l is currently limited by the strong interaction between graphene and the substrate and by the corrugation in the graphene sheet, respectively. This can be overcome by using more robust turbostratic graphene (TG), a multilayer graphene stack without the usual Bernal stacking. Therefore, enhancements in the mobility and the spin lifetime in TG are expected. Our recent results on spin-injection experiments using graphene as well as TG will be presented. (author)
Directory of Open Access Journals (Sweden)
Andréa Carvalho da Silva
2011-06-01
Full Text Available O objetivo do trabalho foi determinar a taxa de renova��ão do carbono-13 ("turnover", dos diferentes órgãos da figueira 'Roxo de Valinhos'. O experimento foi conduzido no pomar da Faculdade de Ciências Agronômicas, FCA/UNESP, Câmpus de Botucatu-SP. Determinou-se previamente, através das trocas gasosas com um medidor aberto portátil de fotossíntese, IRGA, a principal folha fotossinteticamente ativa. Essa folha foi colocada em uma câmara onde ocorreu a injeção do gás enriquecido. O tempo de enriquecimento da folha foi de 30 minutos. Os tratamentos foram constituídos por sete plantas de figueira, que foram retiradas do solo após: 6; 24; 48; 72; 120; 168 e 360 horas do enriquecimento com 13C, e suas partes seccionadas em: gema apical, folha jovem, folhas adultas (fotossinteticamente ativas, brotações laterais, frutos e ramo. Os resultados obtidos permitiram o estabelecimento da sequência de metabolização do carbono-13 nas partições estudadas: Folhas novas > Frutos > Brotações > Folhas Adultas > Gema Apical > Ramo > Folha marcada. Plantas de figueira 'Roxo de Valinhos' apresentam reciclagem do 13C de 24 horas e um tempo de meia-vida de duração do carbono-13 inferior a 11 horas.The aim of this study was to assess carbon-13 turnover in different organs of the fig tree cultivar 'Roxo de Valinhos'. The experiment was carried out in an orchard at School of Agronomical Sciences, FCA/UNESP, Botucatu Campus, São Paulo State, Brazil. The main photosynthetically active leaf was previously determined based on gas exchanges by means of an open portable photosynthesis system, IRGA. That leaf was placed in a chamber where the enriched gas injection occurred. The leaf enrichment time was 30 minutes. Treatments were constituted of seven fig trees harvested of soil after: 6; 24; 48; 72; 120; 168 and 360 hours of enrichment using 13C, and their parts were sectioned into: apical bud, young leaves, adult leaves (photosynthetically active
Universal control and error correction in multi-qubit spin registers in diamond.
Taminiau, T H; Cramer, J; van der Sar, T; Dobrovitski, V V; Hanson, R
2014-03-01
Quantum registers of nuclear spins coupled to electron spins of individual solid-state defects are a promising platform for quantum information processing. Pioneering experiments selected defects with favourably located nuclear spins with particularly strong hyperfine couplings. To progress towards large-scale applications, larger and deterministically available nuclear registers are highly desirable. Here, we realize universal control over multi-qubit spin registers by harnessing abundant weakly coupled nuclear spins. We use the electron spin of a nitrogen-vacancy centre in diamond to selectively initialize, control and read out carbon-13 spins in the surrounding spin bath and construct high-fidelity single- and two-qubit gates. We exploit these new capabilities to implement a three-qubit quantum-error-correction protocol and demonstrate the robustness of the encoded state against applied errors. These results transform weakly coupled nuclear spins from a source of decoherence into a reliable resource, paving the way towards extended quantum networks and surface-code quantum computing based on multi-qubit nodes. PMID:24487650
Circuit model for spin-bottleneck resistance in magnetic-tunnel-junction devices
Jungwirth, T.; MacDonald, A. H.
1998-01-01
Spin-bottlenecks are created in magnetic-tunnel-junction devices by spatial inhomogeneity in the relative resistances for up and down spins. We propose a simple electrical circuit model for these devices which incorporates spin-bottleneck effects and can be used to calculate their overall resistance and magnetoresistance. The model permits a simple understanding of the dependence of device magnetoresistance on spin diffusion lengths, tunneling magnetoresistance, and majority and minority spin...
Mabit, Lionel; Gibbs, Max; Meusburger, Katrin; Toloza, Arsenio; Resch, Christian; Klik, Andreas; Swales, Andrew; Alewell, Christine
2016-04-01
- Several recently published information from scientific research have highlighted that compound-specific stable isotope (CSSI) signatures of fatty acids (FAs) based on the measurement of carbon-13 natural abundance signatures showed great promises to identify sediment origin. The authors have used this innovative isotopic approach to investigate the sources of sediment in a three hectares Austrian sub-watershed (i.e. Mistelbach). Through a previous study using the Cs-137 technique, Mabit et al. (Geoderma, 2009) reported a local maximum sedimentation rate reaching 20 to 50 t/ha/yr in the lowest part of this watershed. However, this study did not identify the sources. Subsequently, the deposited sediment at its outlet (i.e. the sediment mixture) and representative soil samples from the four main agricultural fields - expected to be the source soils - of the site were investigated. The bulk delta carbon-13 of the samples and two long-chain FAs (i.e. C22:0 and C24:0) allowed the best statistical discrimination. Using two different mixing models (i.e. IsoSource and CSSIAR v1.00) and the organic carbon content of the soil sources and sediment mixture, the contribution of each source has been established. Results suggested that the grassed waterway contributed to at least 50% of the sediment deposited at the watershed outlet. This study, that will require further validation, highlights that CSSI and Cs-137 techniques are complementary as fingerprints and tracers for establishing land sediment redistribution and could provide meaningful information for optimized decision-making by land managers.
Spin Echo Studies on Cellular Water
Chang, D C; Nichols, B L; Rorschach, H E
2014-01-01
Previous studies indicated that the physical state of cellular water could be significantly different from pure liquid water. To experimentally investigate this possibility, we conducted a series of spin-echo NMR measurements on water protons in rat skeletal muscle. Our result indicated that the spin-lattice relaxation time and the spin-spin relaxation time of cellular water protons are both significantly shorter than that of pure water (by 4.3-fold and 34-fold, respectively). Furthermore, the spin diffusion coefficient of water proton is almost 1/2 of that of pure water. These data suggest that cellular water is in a more ordered state in comparison to pure water.
Spin generation by strong inhomogeneous electric fields
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).
Macroscopic diffusive transport in a microscopically integrable Hamiltonian system.
Prosen, Tomaž; Zunkovič, Bojan
2013-07-26
We demonstrate that a completely integrable classical mechanical model, namely the lattice Landau-Lifshitz classical spin chain, supports diffusive spin transport with a finite diffusion constant in the easy-axis regime, while in the easy-plane regime, it displays ballistic transport in the absence of any known relevant local or quasilocal constant of motion in the symmetry sector of the spin current. This surprising finding should open the way towards analytical computation of diffusion constants for integrable interacting systems and hints on the existence of new quasilocal classical conservation laws beyond the standard soliton theory.
Spin injection into semiconductors
Oestreich, M.; Hübner, J.; Hägele, D.; Klar, P. J.; Heimbrodt, W.; Rühle, W. W.; Ashenford, D. E.; Lunn, B.
1999-03-01
The injection of spin-polarized electrons is presently one of the major challenges in semiconductor spin electronics. We propose and demonstrate a most efficient spin injection using diluted magnetic semiconductors as spin aligners. Time-resolved photoluminescence with a Cd0.98Mn0.02Te/CdTe structure proves the feasibility of the spin-alignment mechanism.
Experimental evidences of a large extrinsic spin Hall effect in AuW alloy
Energy Technology Data Exchange (ETDEWEB)
Laczkowski, P.; Rojas-Sánchez, J.-C. [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 91767 Palaiseau (France); INAC/SP2M, CEA-Université Joseph Fourier, F-38054 Grenoble (France); Savero-Torres, W.; Notin, L.; Beigné, C.; Marty, A.; Attané, J.-P.; Vila, L. [INAC/SP2M, CEA-Université Joseph Fourier, F-38054 Grenoble (France); Jaffrès, H.; Reyren, N.; Deranlot, C.; George, J.-M.; Fert, A. [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 91767 Palaiseau (France)
2014-04-07
We report an experimental study of a gold-tungsten alloy (7 at. % W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity, and small induced damping, this AuW alloy may find applications in the nearest future.
Experimental evidences of a large extrinsic spin Hall effect in AuW alloy
Laczkowski, P.; Rojas-Sánchez, J.-C.; Savero-Torres, W.; Jaffrès, H.; Reyren, N.; Deranlot, C.; Notin, L.; Beigné, C.; Marty, A.; Attané, J.-P.; Vila, L.; George, J.-M.; Fert, A.
2014-04-01
We report an experimental study of a gold-tungsten alloy (7 at. % W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity, and small induced damping, this AuW alloy may find applications in the nearest future.
Direct detection of spin waves in gaseous 3He↑
Tastevin, G.; Nacher, P.J.; Leduc, M.; Laloë, F.
1985-01-01
In gaseous spin-polarized 3He at low temperature, spin-diffusion becomes oscillatory and gives rise to spin waves; these waves have a quality factor μM, where M is the (relative) nuclear magnetization and μ a dimensionless coefficient characteristic of the importance of exchange effects in binary collisions. We describe here an NMR technique where these oscillatory modes are directly excited and detected, with the use of two sets of radiofrequency coils (for induction and detection), each con...
Tuning the spin Hall effect of Pt from the moderately dirty to the superclean regime
Sagasta, Edurne; Omori, Yasutomo; Isasa, Miren; Gradhand, Martin; Hueso, Luis E.; Niimi, Yasuhiro; Otani, YoshiChika; Casanova, Fèlix
2016-08-01
We systematically measure and analyze the spin diffusion length and the spin Hall effect in Pt with a wide range of conductivities using the spin absorption method in lateral spin valve devices. We observe a linear relation between the spin diffusion length and the conductivity, evidencing that the spin relaxation in Pt is governed by the Elliott-Yafet mechanism. We find a single intrinsic spin Hall conductivity (σSHint=1600 ±150 Ω-1c m-1) for Pt in the full range studied which is in good agreement with theory. We have obtained the crossover between the moderately dirty and the superclean scaling regimes of the spin Hall effect by tuning the conductivity. This is equivalent to that obtained for the anomalous Hall effect. Our results explain the spread of the spin Hall angle values in the literature and find a route to maximize this important parameter.
Energy relaxation in the spin-polarized disordered electron liquid
Chtchelkatchev, N. M.; Burmistrov, I. S.
2007-01-01
The energy relaxation in the spin-polarized disordered electron systems is studied in the diffusive regime. We derived the quantum kinetic equation in which the kernel of electron-electron collision integral explicitly depends on the electron magnetization. As the consequence, the inelastic scattering rate is found to have non-monotonic dependence on the spin polarization of the electron system.
Current-Induced Spin-Torque Resonance of Magnetic Insulators
Chiba, T.; Bauer, G.E.W.; Takahashi, S.
2014-01-01
We formulate a theory of the ac spin Hall magnetoresistance in a bilayer system consisting of a magnetic insulator such as yttrium iron garnet and a heavy metal such as platinum. We derive expressions for the dc voltage generation based on the drift-diffusion spin model and quantum mechanical bounda
Spin noise in mixed Spin Systems
Bauch, Erik; Junghyun, Paul; Singh, Swati; Devakul, Trithep; Feguin, Adrian; Hart, Connor; Walsworth, Ronald
2016-05-01
The spin noise due to interaction of multiple spin species in mixed spin systems provides a fundamental limit to ultra-sensitive ensemble sensing and quantum information applications. In our work, we investigate the interaction of dense nuclear 13C spins with electronic nitrogen spins using Nitrogen-Vacancy centers in diamond. Our work shows experimentally and theoretically, that under certain conditions, spin noise is greatly suppressed and the coherence time of NV centers improved by order of magnitudes, providing a pathway to engineering high density ensemble samples with long coherence times at room temperature.
Institute of Scientific and Technical Information of China (English)
ZHANG Peng-Fei; RUAN Tu-Nan
2001-01-01
A systematic theory on the appropriate spin operators for the relativistic states is developed. For a massive relativistic particle with arbitrary nonzero spin, the spin operator should be replaced with the relativistic one, which is called in this paper as moving spin. Further the concept of moving spin is discussed in the quantum field theory. A new is constructed. It is shown that, in virtue of the two operators, problems in quantum field concerned spin can be neatly settled.
Senoo, Y.
The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser inlet does not decay easily. In large specific speed compressors, flow out of the impeller is distorted axially. Pressure recovery of diffusers at distorted inlet flow is considerably improved by half guide vanes. The best height of the vanes is a little 1/2 diffuser width. In small specific speed compressors, flow out of the impeller is not much distorted and pressure recovery can be predicted with one-dimensional flow analysis. Wall friction loss is significant in narrow diffusers. The large pressure drop at a small flow rate can cause the positive gradient of the pressure-flow rate characteristic curve, which may cause surging.
Dynamic-angle spinning and double rotation of quadrupolar nuclei
International Nuclear Information System (INIS)
Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei is complicated by the coupling of the electric quadrupole moment of the nucleus to local variations in the electric field. The quadrupolar interaction is a useful source of information about local molecular structure in solids, but it tends to broaden resonance lines causing crowding and overlap in NMR spectra. Magic- angle spinning, which is routinely used to produce high resolution spectra of spin-1/2 nuclei like carbon-13 and silicon-29, is incapable of fully narrowing resonances from quadrupolar nuclei when anisotropic second-order quadrupolar interactions are present. Two new sample-spinning techniques are introduced here that completely average the second-order quadrupolar coupling. Narrow resonance lines are obtained and individual resonances from distinct nuclear sites are identified. In dynamic-angle spinning (DAS) a rotor containing a powdered sample is reoriented between discrete angles with respect to high magnetic field. Evolution under anisotropic interactions at the different angles cancels, leaving only the isotropic evolution of the spin system. In the second technique, double rotation (DOR), a small rotor spins within a larger rotor so that the sample traces out a complicated trajectory in space. The relative orientation of the rotors and the orientation of the larger rotor within the magnetic field are selected to average both first- and second-order anisotropic broadening. The theory of quadrupolar interactions, coherent averaging theory, and motional narrowing by sample reorientation are reviewed with emphasis on the chemical shift anisotropy and second-order quadrupolar interactions experienced by half-odd integer spin quadrupolar nuclei. The DAS and DOR techniques are introduced and illustrated with application to common quadrupolar systems such as sodium-23 and oxygen-17 nuclei in solids
Spin-Up/Spin-Down models for Type Ia Supernovae
Di Stefano, R; Claeys, J S W
2011-01-01
In the single degenerate scenario for Type Ia supernova (SNeIa), a white dwarf (WD) must gain a significant amount of matter from a companion star. Because the accreted mass carries angular momentum, the WD is likely to achieve fast spin periods, which can increase the critical mass, $M_{crit}$, needed for explosion. When $M_{crit}$ is higher than the maximum mass achieved by the WD, the WD must spin down before it can explode. This introduces a delay between the time at which the WD has completed its epoch of mass gain and the time of the explosion. Matter ejected from the binary during mass transfer therefore has a chance to become diffuse, and the explosion occurs in a medium with a density similar to that of typical regions of the interstellar medium. Also, either by the end of the WD's mass increase or else by the time of explosion, the donor may exhaust its stellar envelope and become a WD. This alters, generally diminishing, explosion signatures related to the donor star. Nevertheless, the spin-up/spin...
Geometrical dependence of spin current absorption into a ferromagnetic nanodot
Nomura, Tatsuya; Ohnishi, Kohei; Kimura, Takashi
2016-10-01
We have investigated the absorption property of the diffusive pure spin current due to a ferromagnetic nanodot in a laterally configured ferromagnetic/nonmagnetic hybrid nanostructure. The spin absorption in a nano-pillar-based lateral-spin-valve structure was confirmed to increase with increasing the lateral dimension of the ferromagnetic dot. However, the absorption efficiency was smaller than that in a conventional lateral spin valve based on nanowire junctions because the large effective cross section of the two dimensional nonmagnetic film reduces the spin absorption selectivity. We also found that the absorption efficiency of the spin current is significantly enhanced by using a thick ferromagnetic nanodot. This can be understood by taking into account the spin absorption through the side surface of the ferromagnetic dot quantitatively.
Nonequilibrium thermodynamics of the spin Seebeck and spin Peltier effects
Basso, Vittorio; Ferraro, Elena; Magni, Alessandro; Sola, Alessandro; Kuepferling, Michaela; Pasquale, Massimo
2016-05-01
We study the problem of magnetization and heat currents and their associated thermodynamic forces in a magnetic system by focusing on the magnetization transport in ferromagnetic insulators like YIG. The resulting theory is applied to the longitudinal spin Seebeck and spin Peltier effects. By focusing on the specific geometry with one Y3Fe5O12 (YIG) layer and one Pt layer, we obtain the optimal conditions for generating large magnetization currents into Pt or large temperature effects in YIG. The theoretical predictions are compared with experiments from the literature permitting to derive the values of the thermomagnetic coefficients of YIG: the magnetization diffusion length lM˜0.4 μ m and the absolute thermomagnetic power coefficient ɛM˜10-2TK-1 .
Spin Lifetimes Exceeding 12 ns in Graphene Nonlocal Spin Valve Devices.
Drögeler, Marc; Franzen, Christopher; Volmer, Frank; Pohlmann, Tobias; Banszerus, Luca; Wolter, Maik; Watanabe, Kenji; Taniguchi, Takashi; Stampfer, Christoph; Beschoten, Bernd
2016-06-01
We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5 μm in single layer graphene nonlocal spin transport devices at room temperature. This is accomplished by the fabrication of Co/MgO-electrodes on a Si/SiO2 substrate and the subsequent dry transfer of a graphene-hBN-stack on top of this electrode structure where a large hBN flake is needed in order to diminish the ingress of solvents along the hBN-to-substrate interface. Interestingly, long spin lifetimes are observed despite the fact that both conductive scanning force microscopy and contact resistance measurements reveal the existence of conducting pinholes throughout the MgO spin injection/detection barriers. Compared to previous devices, we observe an enhancement of the spin lifetime in single layer graphene by a factor of 6. We demonstrate that the spin lifetime does not depend on the contact resistance area products when comparing all bottom-up devices indicating that spin absorption at the contacts is not the predominant source for spin dephasing. PMID:27210240
Horst, Axel; Mahlknecht, Jürgen; Merkel, Broder J
2007-12-01
Stable Isotopes (strontium-87, deuterium and oxygen-18, carbon-13) have been used to reveal different sources of groundwater and mixing processes in the aquifer of the Silao-Romita Valley in the state of Guanajuato, Mexico. Calcite dissolution appeared to be the main process of strontium release leading to relatively equal (87)Sr/(86)Sr ratios of 0.7042-0.7062 throughout the study area which could be confirmed by samples of carbonate rocks having similar Sr ratios (0.7041-0.7073). delta(13)C values (-11.91- -6.87 per thousand VPDB) of groundwaters confirmed the solution of carbonates but indicated furthermore influences of soil-CO(2). Deuterium and (18)O contents showed a relatively narrow range of-80.1- -70.0 per thousand VSMOW and -10.2- -8.8 per thousand, VSMOW, respectively but are affected by evaporation and mixing processes. The use of delta(13)C together with (87)Sr/(86)Sr revealed three possible sources: (i) carbonate-controlled waters showing generally higher Sr-concentrations, (ii) fissure waters with low-strontium contents and (iii) infiltrating water which is characterized by low delta(13)C and (87)Sr/(86)Sr ratios. The third component is affected by evaporation processes taking place before and during infiltration which might be increased by extraction and reinfiltration (irrigation return flow). PMID:18041622
International Nuclear Information System (INIS)
Stable carbon isotope ratios (13C/12C) at natural abundance levels have been determined for individual carbon atoms in each of the major phospholipid fatty acids of Escherichia coli grown on glucose as the sole carbon source. Two models were constructed for the isotope effects and carbon flow pathways which must be responsible for the observed isotopic fractionations. Both models incorporate a branch in the carbon flow at which fatty acyl-acyl carrier protein (acyl-ACP) is utilized either for complex lipid synthesis or for elongation by fatty acid synthetase. Depletion of carbon 13 in the carboxyl groups of myristic and palmitoleic acids (relative to carbonyl groups in precursor acyl-ACP's) was observed to occur at this branching site. Only one of the models was consistent both with this observation and with the observation that exogenous fatty acids are incorporated into phospholipids but are not elongated. The successful model has free fatty acid as the intermediate product coupling fatty acid biosynthesis to phospholipid synthesis. Essential to this pathway are those reactions catalyzed by thioesterases I and II as well as acyl-ACP synthetase, enzymes whose roles have previously been unknown in vivo
Directory of Open Access Journals (Sweden)
C Móri
2007-12-01
Full Text Available Consistent information on meat products consumed by the public is essential. The technique of stable isotopes is a powerful tool to recover consumers' confidence, as it allows the detection of animal byproduct residues in poultry meat, particularly in quail meat. This study aimed at checking the presence of poultry byproduct mixtures in quail diets by applying the technique of carbon (13C/12C and nitrogen (15N/14N stable isotopes in quail breast muscle, keel, and tibia. Sixty four one-day-old male quails were obtained from a commercial farm. Birds were housed in an experimental house from one to 42 days of age, and were randomly distributed into 8 experimental treatments, and fed diets containing poultry offal meal (POM, bovine meat and bone meal (MBM or poultry feather meal (PFM, or their mixtures. Four birds per treatment were slaughtered at 42 days of age, and breast (Pectoralis major, keel, and tibia were collected for analyses. The inclusion of animal byproducts in quail diets was detected by 13C e 15N analyses in the tissues of the birds; however, it was not possible to specify which byproducts were used. It was concluded that quail meat can be certified by the technique of stable isotopes.
Latli, Bachir; Hrapchak, Matt; Chevliakov, Maxim; Li, Guisheng; Campbell, Scot; Busacca, Carl A; Senanayake, Chris H
2015-05-30
Deleobuvir, (2E)-3-(2-{1-[2-(5-bromopyrimidin-2-yl)-3-cyclopentyl-1-methyl-1H-indole-6-carboxamido]cyclobutyl}-1-methyl-1H-benzimidazol-6-yl)prop-2-enoic acid (1), is a non-nucleoside, potent, and selective inhibitor of hepatitis C virus NS5B polymerase. Herein, we describe the detailed synthesis of this compound labeled with carbon-13 and carbon-14. The synthesis of its three major metabolites, namely, the reduced double bond metabolite (2) and the acyl glucuronide derivatives of (1) and (2), is also reported. Aniline-(13) C6 was the starting material to prepare butyl (E)-3-(3-methylamino-4-nitrophenyl-(13) C6 )acrylate [(13) C6 ]-(11) in six steps. This intermediate was then used to obtain [(13) C6 ]-(1) and [(13) C6 ]-(2) in five and four more steps, respectively. For the radioactive synthesis, potassium cyanide-(14) C was used to prepare 1-cylobutylaminoacid [(14) C]-(23) via Buchrer-Bergs reaction. The carbonyl chloride of this acid was then used to access both [(14) C]-(1) and [(14) C]-(2) in four steps. The acyl glucuronide derivatives [(13) C6 ]-(3), [(13) C6 ]-(4) and [(14) C]-(3) were synthesized in three steps from the acids [(13) C6 ]-(1), [(13) C6 ]-(2) and [(14) C]-(1) using known procedures. PMID:25964148
Energy Technology Data Exchange (ETDEWEB)
Saito, Moyoko [Biomedical Imaging Group, Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)]. E-mail: moyoko-saitou@aist.go.jp; Matsuda, Tsuyoshi [Imaging Application Tech. Center, GE Yokogawa Medical Systems Ltd., Tokyo (Japan); Tropp, James [General Electric Company, CA (United States); Inubushi, Toshiro [Molecular Neuroscience Research Center, Shiga University of Medical Science, Shiga (Japan); Nakai, Toshiharu [Biomedical Imaging Group, Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan) and Institute of Biomedical Research and Innovation, Kobe (Japan)]. E-mail: t-nakai@aist.go.jp
2005-08-01
A strategy for proton decoupled carbon-13 MR spectroscopy ({l_brace}{sup 1}H{r_brace}-{sup 13}C MRS) with a strong static magnetic field (3.0 T) in vivo was investigated. The proton decoupling improves the signal-to-noise ratio, however, the effect of the decoupling power on the human body, especially in strong magnetic fields, should be considered. In order to establish a technique for monitoring the metabolism of glucose in the liver using {l_brace}{sup 1}H{r_brace}-{sup 13}C MRS at 3.0 T, two phantom experiments were performed. To assess whether the decoupling energy conformed to SAR limits defined by the IEC, temperature rises inside an agar gel phantom were monitored during a {l_brace}{sup 1}H{r_brace}-{sup 13}C MRS experiment. Then, the decoupling conditions of a glucose solution phantom were systematically optimized with combinations of decoupling bandwidth and power. The reliability of this procedure was discussed in conjunction with IEC guidelines.
Magnetic Nanostructures Spin Dynamics and Spin Transport
Farle, Michael
2013-01-01
Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.
Circuit Simulation of All-Spin Logic
Alawein, Meshal
2016-05-01
With the aggressive scaling of complementary metal-oxide semiconductor (CMOS) nearing an inevitable physical limit and its well-known power crisis, the quest for an alternative/augmenting technology that surpasses the current semiconductor electronics is needed for further technological progress. Spintronic devices emerge as prime candidates for Beyond CMOS era by utilizing the electron spin as an extra degree of freedom to decrease the power consumption and overcome the velocity limit connected with the charge. By using the nonvolatility nature of magnetization along with its direction to represent a bit of information and then manipulating it by spin-polarized currents, routes are opened for combined memory and logic. This would not have been possible without the recent discoveries in the physics of nanomagnetism such as spin-transfer torque (STT) whereby a spin-polarized current can excite magnetization dynamics through the transfer of spin angular momentum. STT have expanded the available means of switching the magnetization of magnetic layers beyond old classical techniques, promising to fulfill the need for a new generation of dense, fast, and nonvolatile logic and storage devices. All-spin logic (ASL) is among the most promising spintronic logic switches due to its low power consumption, logic-in-memory structure, and operation on pure spin currents. The device is based on a lateral nonlocal spin valve and STT switching. It utilizes two nanomagnets (whereby information is stored) that communicate with pure spin currents through a spin-coherent nonmagnetic channel. By using the well-known spin physics and the recently proposed four-component spin circuit formalism, ASL can be thoroughly studied and simulated. Previous attempts to model ASL in the linear and diffusive regime either neglect the dynamic characteristics of transport or do not provide a scalable and robust platform for full micromagnetic simulations and inclusion of other effects like spin Hall
Energy Technology Data Exchange (ETDEWEB)
BAI,M.; ROSER, T.
2007-06-25
This paper proposes a new design of spin flipper for RHIC to obtain full spin flip with the spin tune staying at half integer. The traditional technique of using an rf dipole or solenoid as spin flipper to achieve full spin flip in the presence of full Siberian snake requires one to change the snake configuration to move the spin tune away from half integer. This is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. The design of the new spin flipper as well as numerical simulations are presented.
Decoherence dynamics of a single spin versus spin ensemble
Dobrovitski, V.V.; Feiguin, A.E.; Awschalom, D.D.; Hanson, R.
2008-01-01
We study decoherence of central spins by a spin bath, focusing on the difference between measurement of a single central spin and measurement of a large number of central spins (as found in typical spin-resonance experiments). For a dilute spin bath, the single spin demonstrates Gaussian free-induct
Yin, Gen; Liu, Yizhou; Barlas, Yafis; Zang, Jiadong; Lake, Roger K.
2015-01-01
The intrinsic spin Hall effect (SHE) originates from the topology of the Bloch bands in momentum space. The duality between real space and momentum space calls for a spin Hall effect induced from a real space topology in analogy to the topological Hall effect (THE) of skyrmions. We theoretically demonstrate the topological spin Hall effect (TSHE) in which a pure transverse spin current is generated from a skyrmion spin texture.
Murakami, Shuichi
2005-01-01
A brief review is given on the spin Hall effect, where an external electric field induces a transverse spin current. It has been recognized over 30 years that such effect occurs due to impurities in the presence of spin-orbit coupling. Meanwhile, it was proposed recently that there is also an intrinsic contribution for this effect. We explain the mechanism for this intrinsic spin Hall effect. We also discuss recent experimental observations of the spin Hall effect.
Cahaya, Adam B.; Tretiakov, Oleg A.; Bauer, G. E. W.
2015-01-01
Spin caloritronics is the science and technology to control spin, charge, and heat currents in magnetic nanostructures. The spin degree of freedom provides new strategies for thermolelectric power generation that have not yet been fully explored. After an elementary introduction into conventional thermoelectrics and spintronics, we give a brief review of the physics of spin caloritronics. We discuss spin-dependent thermoelectrics based on the the two-current model in metallic magnets as well ...
Spin projection chromatography
Danieli, Ernesto P.; Pastawski, Horacio M.; Levstein, Patricia R.
2003-01-01
We formulate the many-body spin dynamics at high temperature within the non-equilibrium Keldysh formalism. For the simplest XY interaction, analytical expressions in terms of the one particle solutions are obtained for linear and ring configurations. For small rings of even spin number, the group velocities of excitations depend on the parity of the total spin projection. This should enable a dynamical filtering of spin projections with a given parity i.e. a Spin projection chromatography.
Spin projection chromatography
Danieli, E. P.; Pastawski, H. M.; Levstein, P. R.
2004-01-01
We formulate the many-body spin dynamics at high temperature within the non-equilibrium Keldysh formalism. For the simplest XY interaction, analytical expressions in terms of the one particle solutions are obtained for linear and ring configurations. For small rings of even spin number, the group velocities of excitations depend on the parity of the total spin projection. This should enable a dynamical filtering of spin projections with a given parity i.e., a spin projection chromatography.
O'Brien, L.; Spivak, D.; Krueger, N.; Peterson, T. A.; Erickson, M. J.; Bolon, B.; Geppert, C. C.; Leighton, C.; Crowell, P. A.
2016-09-01
In the nonlocal spin valve (NLSV) geometry, four-terminal electrical Hanle effect measurements have the potential to provide a particularly simple determination of the lifetime (τs) and diffusion length (λN) of spins injected into nonmagnetic (N) materials. Recent papers, however, have demonstrated that traditional models typically used to fit such data provide an inaccurate measurement of τs in ferromagnet (FM)/N metal devices with low interface resistance, particularly when the separation of the source and detector contacts is small. In the transparent limit, this shortcoming is due to the back diffusion and subsequent relaxation of spins within the FM contacts, which is not properly accounted for in standard models of the Hanle effect. Here we have used the separation dependence of the spin accumulation signal in NLSVs with multiple FM/N combinations, and interfaces in the diffusive limit, to determine λN in traditional spin valve measurements. We then compare these results to Hanle measurements as analyzed using models that either include or exclude spin sinking. We demonstrate that differences between the spin valve and Hanle measurements of λN can be quantitatively modelled provided that both the FM contact-induced isotropic spin sinking and the full three-dimensional geometry of the devices, which is particularly important at small contact separations, are accounted for. We find, however, that considerable difficulties persist, in particular due to the sensitivity of fitting to the contact interface resistance and the FM contact magnetization rotation, in precisely determining λN with the Hanle technique alone, particularly at small contact separations.
Hybrid Spin Noise Spectroscopy and the Spin Hall Effect
Slipko, V. A.; Sinitsyn, N. A.; Pershin, Y. V.
2013-01-01
Here we suggest a novel hybrid spin noise spectroscopy technique, which is sensitive to the spin Hall effect. It is shown that, while the standard spin-spin correlation function is not sensitive to the spin Hall effect, spin-transverse voltage and transverse voltage-voltage correlation functions provide the missing sensitivity being linear and quadratic in the spin Hall coefficient, respectively. The correlation between transverse voltage and spin fluctuations appears as a result of spin-char...
Magnons, Spin Current and Spin Seebeck Effect
Maekawa, Sadamichi
2012-02-01
When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).
Spin-polarized spin excitation spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J, E-mail: lothseb@us.ibm.com, E-mail: heinrich@almaden.ibm.com [IBM Research Division, Almaden Research Center, San Jose, CA 95120 (United States)
2010-12-15
We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu{sub 2}N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.
Entangled spins and ghost-spins
Jatkar, Dileep P
2016-01-01
We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in arXiv:1602.06505 [hep-th] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves), the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the gho...
Geng, Rugang; Roy, Anandi; Subedi, Ram; Locklin, Jason; Nguyen, Tho; Zhao, Wenbo; Li, Xiaoguang
Charge transport in amorphous organic semiconductors is governed by carriers hopping between localized states with small spin diffusion length. Furthermore, the spin interfacial resistance of organic spin valves (OSVs) is poorly controlled resulting in controversial reports of the magnetoresistance response. Here, we used surface initiated Kumada transfer polycondensation to covalently graft π-conjugated poly(3-methylthiophene) brushes from the La0.67Sr0.33MnO3 (LSMO) bottom electrode. The covalent attachment along with the brush morphology allows for more control over the LSMO/brush interfacial resistance and large spacer mobility. Remarkably, with 15 nm brush spacer layer, we observed an optimum magnetoresistance (MR) effect of 70% at cryogenic temperatures and a MR of 2.7% at 280K. The temperature dependence of the MR is nearly an order of magnitude weaker than that found in control OSVs made from spin-coated poly(3-hexylthiophene). Using a variety of different brush layer thicknesses, the thickness dependent MR at 20K was investigated. A spin diffusion length of 20 nm at 5 mV junction voltage rapidly increases to 55 nm at -280 mV. We acknowledge NSF (CHE 1412714 and DMR 0953112) (J.L.), the UGA start-up funds and Faculty Research Grant (T.N.), NSFC and NBRPC (2012CB922003 and 2015CB921201, X.G.L.) for funding this work.
International Nuclear Information System (INIS)
While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs
Energy Technology Data Exchange (ETDEWEB)
Kostorz, G. [Eidgenoessische Technische Hochschule, Angewandte Physik, Zurich (Switzerland)
1996-12-31
While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs.
Institute of Scientific and Technical Information of China (English)
Wen Wu
2007-01-01
Spin polarizer is one of the most important devices for the newly developing field of spintronics, which may revolute the popular information techniques. Here we present a phenomenal model for a novel spin polarizer, which utilizes two back to back ferromagnetic metal/semiconductor Schottky barriers to define a semiconductor transport channel whose length is less than the spin decoherence length of the host semiconductor. Along this channel, conducting electrons move diffusively in momentum space while they keep ballistic motion in spin space. Across the channel, electrons suffer a spin dependent tunneling, which establishes spin polarization along the channel.
Spin-torque generation in topological insulator based heterostructures
Fischer, Mark H.
2016-03-11
Heterostructures utilizing topological insulators exhibit a remarkable spin-torque efficiency. However, the exact origin of the strong torque, in particular whether it stems from the spin-momentum locking of the topological surface states or rather from spin-Hall physics of the topological-insulator bulk, remains unclear. Here, we explore a mechanism of spin-torque generation purely based on the topological surface states. We consider topological-insulator-based bilayers involving ferromagnetic metal (TI/FM) and magnetically doped topological insulators (TI/mdTI), respectively. By ascribing the key theoretical differences between the two setups to location and number of active surface states, we describe both setups within the same framework of spin diffusion of the nonequilibrium spin density of the topological surface states. For the TI/FM bilayer, we find large spin-torque efficiencies of roughly equal magnitude for both in-plane and out-of-plane spin torques. For the TI/mdTI bilayer, we elucidate the dominance of the spin-transfer-like torque. However, we cannot explain the orders of magnitude enhancement reported. Nevertheless, our model gives an intuitive picture of spin-torque generation in topological-insulator-based bilayers and provides theoretical constraints on spin-torque generation due to topological surface states.
Haba, Z
2009-02-01
We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.
Gomes, M; da Silva, A J
2010-01-01
Using the Berezin-Marinov pseudoclassical formulation of spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spacial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external e.m. field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, $\\Delta x\\Delta y\\geq\\theta^{2}/2$, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.
Gomes, M.; Kupriyanov, V. G.; da Silva, A. J.
2010-04-01
Using the Berezin-Marinov pseudoclassical formulation of the spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spatial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external electromagnetic field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, ΔxΔy≥θ2/2, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.
International Nuclear Information System (INIS)
Using the Berezin-Marinov pseudoclassical formulation of the spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spatial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external electromagnetic field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, ΔxΔy≥θ2/2, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.
Spin Rotation of Formalism for Spin Tracking
Energy Technology Data Exchange (ETDEWEB)
Luccio,A.
2008-02-01
The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.
Energy Technology Data Exchange (ETDEWEB)
Brunel, V
1999-06-29
This thesis presents three studies that are respectively the spin-1 disordered chain, the non magnetic impurities in the spin-1/2 chain and the reaction-diffusion process. The spin-1 chain of weak disorder is performed by the Abelian bosonization and the renormalization group. This allows to take into account the competition between the disorder and the interactions and predicts the effects of various spin-1 anisotropy chain phases under many different disorders. A second work uses the non magnetic impurities as local probes of the correlations in the spin-1/2 chain. When the impurities are connected to the chain boundary, the author predicts a temperature dependence of the relaxation rate (1/T) of the nuclear spin impurities, different from the case of these impurities connected to the whole chain. The last work deals with one dimensional reaction-diffusion problem. The Jordan-Wigner transformation allows to consider a fermionic field theory that critical exponents follow from the renormalization group. (A.L.B.)
Excellent spin transport in spin valves based on the conjugated polymer with high carrier mobility
Li, Feng; Li, Tian; Chen, Feng; Zhang, Fapei
2015-03-01
Organic semiconductors (OSCs) are characteristic of long spin-relaxation lifetime due to weak spin-orbit interaction and hyperfine interaction. However, short spin diffusion length and weak magnetoresistance (MR) effect at room temperature (RT) was commonly found on spin valves (SVs) using an organic spacer, which should be correlated with low carrier mobility of the OSCs. Here, N-type semiconducting polymer P(NDI2OD-T2) with high carrier mobility is employed as the spacer in the SV devices. Exceedingly high MR ratio of 90.0% at 4.2 K and of 6.8% at RT are achieved, respectively, via improving the interface structure between the polymer interlayer and top cobalt electrode as well as optimal annealing of manganite bottom electrode. Furthermore, we observe spin dependent transport through the polymeric interlayer and a large spin diffusion length with a weak temperature dependence. The results indicate that this polymer material can be used as a good medium for spintronic devices.
Optimisation of geometrical ratchets for spin-current amplification
Energy Technology Data Exchange (ETDEWEB)
Abdullah, Ranjdar M. [Department of Electronics, University of York, Heslington, York YO10 5DD (United Kingdom); Vick, Andrew J. [Department of Electronics, University of York, Heslington, York YO10 5DD (United Kingdom); Department of Physics, University of York, York YO10 5DD (United Kingdom); Murphy, Benedict A. [Department of Physics, University of York, York YO10 5DD (United Kingdom); Hirohata, Atsufumi, E-mail: atsufumi.hirohata@york.ac.uk [Department of Electronics, University of York, Heslington, York YO10 5DD (United Kingdom); PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012 (Japan)
2015-05-07
A two-dimensional model is used to study the geometrical effects of a nonmagnetic (NM) nanowire upon a spin-polarised electron current in a lateral spin-valve structure. We found that the implemented ratchet shapes at the centre of the NM have a crucial effect on the diffusive rate for up- and down-spin electrons along the wire, which leads to the amplification of non-local spin-current signals. By using our simple model, the geometries have been optimised. The calculated spin-current signals are in good qualitative agreement with our recent experimental results [Abdullah et al., J. Phys. D: Appl. Phys. 47, 482001(FTC) (2014)]. Our model may be very useful to evaluate such a geometrical effect on spin-polarised electron transport.
Phenomenological Spin Transport Theory Driven by Anomalous Nernst Effect
Taniguchi, Tomohiro
2016-07-01
Several experimental efforts such as material investigation and structure improvement have been made recently to find a large anomalous Nernst effect in ferromagnetic metals. Here, we develop a theory of spin transport driven by the anomalous Nernst effect in a diffusive ferromagnetic/nonmagnetic multilayer. Starting from a phenomenological formula of a spin-dependent electric current, the theoretical formulas of electric voltage and spin torque generated by the anomalous Nernst effect are derived. The magnitude of the electric voltage generated from the spin current via the inverse spin Hall effect is on the order of 0.1 µV for currently available experimental parameter values. The temperature gradient necessary to switch the magnetization is quite larger than the typical experimental value. The separation of the contributions of the Seebeck and transverse spin Seebeck effects is also discussed.
Theory of spin Hall magnetoresistance (SMR) and related phenomena.
Chen, Yan-Ting; Takahashi, Saburo; Nakayama, Hiroyasu; Althammer, Matthias; Goennenwein, Sebastian T B; Saitoh, Eiji; Bauer, Gerrit E W
2016-03-16
We review the so-called spin Hall magnetoresistance (SMR) in bilayers of a magnetic insulator and a metal, in which spin currents are generated in the normal metal by the spin Hall effect. The associated angular momentum transfer to the ferromagnetic layer and thereby the electrical resistance is modulated by the angle between the applied current and the magnetization direction. The SMR provides a convenient tool to non-invasively measure the magnetization direction and spin-transfer torque to an insulator. We introduce the minimal theoretical instruments to calculate the SMR, i.e. spin diffusion theory and quantum mechanical boundary conditions. This leads to a small set of parameters that can be fitted to experiments. We discuss the limitations of the theory as well as alternative mechanisms such as the ferromagnetic proximity effect and Rashba spin-orbit torques, and point out new developments.
Anderson, Robert C.
1976-06-22
1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.
International Nuclear Information System (INIS)
The spin-torque ferromagnetic resonance (ST-FMR) in a bilayer system consisting of a magnetic insulator such as Y3Fe5O12 and a normal metal with spin-orbit interaction such as Pt is addressed theoretically. We model the ST-FMR for all magnetization directions and in the presence of field-like spin-orbit torques based on the drift-diffusion spin model and quantum mechanical boundary conditions. ST-FMR experiments may expose crucial information about the spin-orbit coupling between currents and magnetization in the bilayers
Spin Transport by Collective Spin Excitations
Hammel, P. Chris
We report studies of angular momentum transport in insulating materials. Our measurements reveal efficient spin pumping from high wavevector k spin waves in thin film Y3Fe5O12 (YIG): spin pumping is independent of wavevector up to k ~ 20 μm-1. Optical detection of YIG FMR by NV centers in diamond reveals a role for spin waves in this insulator-to-insulator spin transfer process. Spin transport is typically suppressed by insulating barriers, but we find that fluctuating antiferromagnetic correlations enable efficient spin transport at nm-scale thicknesses in insulating antiferromagnets, even in the absence of long-range order, and that the spin decay length increases with the strength of the antiferromagnetic correlations. This research is supported by the U.S. DOE through Grants DE-FG02-03ER46054 and DE-SC0001304, by the NSF MRSEC program through Grant No. 1420451 and by the Army Research Office through Grant W911NF0910147.
Dynamic nuclear spin polarization
Energy Technology Data Exchange (ETDEWEB)
Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)
1996-11-01
Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.
Arbitrary Spin Galilean Oscillator
Hagen, C R
2014-01-01
The so-called Dirac oscillator was proposed as a modification of the free Dirac equation which reproduces many of the properties of the simple harmonic oscillator but accompanied by a strong spin-orbit coupling term. It has yet to be extended successfully to the arbitrary spin S case primarily because of the unwieldiness of general spin Lorentz invariant wave equations. It is shown here using the formalism of totally symmetric multispinors that the Dirac oscillator can, however, be made to accommodate spin by incorporating it into the framework of Galilean relativity. This is done explicitly for spin zero and spin one as special cases of the arbitrary spin result. For the general case it is shown that the coefficient of the spin-orbit term has a 1/S behavior by techniques which are virtually identical to those employed in the derivation of the g-factor carried out over four decades ago.
Theory of electron spin echoes in solids
Energy Technology Data Exchange (ETDEWEB)
Asadullina, N.Ya.; Asadullin, T.Ya.; Asadullin, Ya.Ya. [Kazan State Technical University, Department of General Physics, Karl Marx Street 10, Kazan (Russian Federation)
2002-11-04
We propose modified Bloch equations (MBEs) with specific power-dependent relaxation and dispersion parameters characteristic for two-pulse excitation and when the magnetic dipole-dipole interactions in the electron spin system control the dephasing. We discriminate between the 'active' (excited by both pulses) and 'passive' (excited by the second pulse only) spins: it is shown that the 'active' spins participate in a new effect, an active spin frequency modulation effect giving rise to the power-dependent dispersion and multiple electron spin echoes (ESEs); the 'passive' spins contribute to the power-dependent relaxation. The MBEs are solved and a general expression for the two-pulse ESEs is obtained. Detailed numerical analysis of this expression gives results in good quantitative agreement with the recent experiments on the two-pulse ESEs at conventional low applied fields. The developed theory is applied also to high field ESEs, which are promising for future investigations. On the basis of published results it is deduced that the instantaneous diffusion mechanism is ineffective.
Schliemann, John
2006-01-01
It is proposed that when a charge current circulates in a paramagnetic metal a transverse spin imbalance will be generated, giving rise to a 'spin Hall voltage'. Similarly, that when a spin current circulates a transverse charge imbalance will be generated, hence a Hall voltage, in the absence of charge current and magnetic field. Based on these principles we propose an experiment to generate and detect a spin current in a paramagnetic metal.
International Nuclear Information System (INIS)
Spin is a beautiful concept that plays an ever important role in modern physics. In this talk, I start with a discussion of the origin of spin, and then turn to three themes in which spin has been crucial in subatomic physics: a lab to explore physics beyond the standard model, a tool to measure physical observables that are hard to obtain otherwise, a probe to unravel nonperturbative QCD. I conclude with some remarks on a world without spin
Cross, Rod
2013-01-01
Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…
Meißner, Ulf-G.
2010-01-01
I review recent developments in theoretical spin physics. Topics include pion production in nucleon-nucleon collisions, the implications of heavy quark spin symmetry for heavy hadron molecules, the nucleon electric dipole form factors and ab initio calculations of the width of hadron resonances. A few spin physics high-lights from experiments at the COSY accelerator are also discussed.
Bauer, G.E.W.; Brataas, A.; Tserkovnyak, Y.; Van Wees, B.J.
2003-01-01
A magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain. The working principle is the modulation of the soure–drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spin-torque created by a control spin
Inverse spin Hall effect by spin injection
Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.
2007-09-01
Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.
Spin supplementary conditions for spinning compact binaries
Mikóczi, Balázs
2016-01-01
We consider the different spin supplementary conditions (SSC) for a spinning compact binary with the leading-order spin-orbit (SO) interaction. The Lagrangian of the binary system can be constructed but it is acceleration-dependent in two cases of SSC. We rewrite the generalized Hamiltonian formalism proposed by Ostrogradsky and compute the conservative quantities and the dissipative part of relative motion during the gravitational radiation of each SSCs. We give the orbital elements and observed quantities of the SO dynamics, for instance the energy and the orbital angular momentum losses and waveforms and discuss their SSC dependence.
Quantum Monte Carlo study of spin-polarized deuterium
Beslic, I.; Markic, L. Vranjes; Casulleras, J.; Boronat, J.
2012-01-01
The ground state properties of spin-polarized deuterium (D$\\downarrow$) at zero temperature are obtained by means of the diffusion Monte Carlo calculations within the fixed-node approximation. Three D$\\downarrow$ species have been investigated (D$\\downarrow_1$, D$\\downarrow_2$, D$\\downarrow_3$), corresponding respectively to one, two and three equally occupied nuclear spin states. Influence of the backflow correlations on the ground state energy of the systems is explored. The equilibrium den...
Mellado, Paula
Spin ice in magnetic pyrochlore oxides is a peculiar magnetic state. Like ordinary water ice, these materials are in apparent violation with the third law of thermodynamics, which dictates that the entropy of a system in thermal equilibrium vanishes as its temperature approaches absolute zero. In ice, a "zero-point" entropy is retained down to low temperatures thanks to a high number of low-energy positions of hydrogen ions associated with the Bernal-Fowler ice-rules. Spins in pyrochlore oxides Ho2Ti 2O7 and Dy2Ti2O7 exhibit a similar degeneracy of ground states and thus also have a sizable zero-point entropy. A recent discovery of excitations carrying magnetic charges in pyrochlore spin ice adds another interesting dimension to these magnets. This thesis is devoted to a theoretical study of a two-dimensional version of spin ice whose spins reside on kagome, a lattice of corner-sharing triangles. It covers two aspects of this frustrated classical spin system: the dynamics of artificial spin ice in a network of magnetic nanowires and the thermodynamics of crystalline spin ice. Magnetization dynamics in artificial spin ice is mediated by the emission, propagation and absorption of domain walls in magnetic nanowires. The dynamics shows signs of self-organized behavior such as avalanches. The theoretical model compares favorably to recent experiments. The thermodynamics of the microscopic version of spin ice on kagome is examined through analytical calculations and numerical simulations. The results show that, in addition to the high-temperature paramagnetic phase and the low-temperature phase with magnetic order, spin ice on kagome may have an intermediate phase with fluctuating spins and ordered magnetic charges. This work is concluded with a calculation of the entropy of kagome spin ice at zero temperature when one of the sublattices is pinned by an applied magnetic field and the system breaks up into independent spin chains, a case of dimensional reduction.
Shumilin, A. V.
2016-10-01
We discuss the spin excitations in systems with hopping electron conduction and strong position disorder. We focus on the problem in a strong magnetic field when the spin Hamiltonian can be reduced to the effective single-particle Hamiltonian and treated with conventional numerical technics. It is shown that in a 3D system with Heisenberg exchange interaction the spin excitations have a delocalized part of the spectrum even in the limit of strong disorder, thus leading to the possibility of the coherent spin transport. The spin transport provided by the delocalized excitations can be described by a diffusion coefficient. Non-homogenous magnetic fields lead to the Anderson localization of spin excitations while anisotropy of the exchange interaction results in the Lifshitz localization of excitations. We discuss the possible effect of the additional exchange-driven spin diffusion on the organic spin-valve devices.
Diffusion coefficient in photon diffusion theory
Graaff, R; Ten Bosch, JJ
2000-01-01
The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to
Temperature dependence of spin Hall magnetoresistance in W/CoFeB bilayer
Okuno, Takaya; Taniguchi, Takuya; Kim, Sanghoon; Baek, Seung-heon Chris; Park, Byong-Guk; Moriyama, Takahiro; Kim, Kab-Jin; Ono, Teruo
2016-08-01
We investigate the temperature dependence of the spin Hall magnetoresistance (SMR) in a W/CoFeB bilayer. The SMR is found to increase with decreasing temperature. An analysis based on the SMR theory suggests that the spin Hall angle of W and/or the spin polarization of CoFeB can be the origin of the temperature dependence of the SMR. We also find that the spin diffusion length and the resistivity of W do not significantly vary with temperature, which indicates the necessity of further study on the electron transport mechanism in W films to reveal the origin of the spin Hall effect in W.
Muon spin relaxation in random spin systems
International Nuclear Information System (INIS)
The longitudinal relaxation function Gsub(z)(t) of the positive muon can reflect dynamical characters of local field in a unique way even when the correlation time is longer than the Larmor period of local field. This method has been applied to studies of spin dynamics in spin glass systems, revealing sharp but continuous temperature dependence of the correlation time. Its principle and applications are reviewed. (author)
Magnetization damping in noncollinear spin valves with antiferromagnetic interlayer couplings
Chiba, Takahiro; Bauer, Gerrit E. W.; Takahashi, Saburo
2015-08-01
We study the magnetic damping in the simplest of synthetic antiferromagnets, i.e., antiferromagnetically exchange-coupled spin valves, in the presence of applied magnetic fields that enforce noncolliear magnetic configurations. We formulate the dynamic exchange of spin currents in a noncollinear texture based on the spin-diffusion theory with quantum mechanical boundary conditions at the ferrromagnet/normal-metal interfaces and derive the Landau-Lifshitz-Gilbert equations coupled by the interlayer static and dynamic exchange interactions. We predict noncollinearity-induced additional damping that is modulated by an applied magnetic field. We compare theoretical results with published experiments.
Theory of spin Hall magnetoresistance (SMR) and related phenomena
International Nuclear Information System (INIS)
We review the so-called spin Hall magnetoresistance (SMR) in bilayers of a magnetic insulator and a metal, in which spin currents are generated in the normal metal by the spin Hall effect. The associated angular momentum transfer to the ferromagnetic layer and thereby the electrical resistance is modulated by the angle between the applied current and the magnetization direction. The SMR provides a convenient tool to non-invasively measure the magnetization direction and spin-transfer torque to an insulator. We introduce the minimal theoretical instruments to calculate the SMR, i.e. spin diffusion theory and quantum mechanical boundary conditions. This leads to a small set of parameters that can be fitted to experiments. We discuss the limitations of the theory as well as alternative mechanisms such as the ferromagnetic proximity effect and Rashba spin–orbit torques, and point out new developments. (topical review)
Zhang, Hongjun; Yamamoto, Shunya; Fukaya, Yuki; Maekawa, Masaki; Li, Hui; Kawasuso, Atsuo; Seki, Takeshi; Saitoh, Eiji; Takanashi, Koki; JAEA Team; Tohoku Team
2015-03-01
Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W films were studied by spin-polarized positron beam (SPPB). The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3 ~ 15% per charge current of 105 A/cm2) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The outermost spin poalrization of Bi/Ag/Al2O3andAg/Bi/Al2O3 (charge currents directly connected to Ag layers) were probed by SPPB. The opposite outermost spin polarization of Bi/Ag/Al2O3andAg/Bi/Al2O3 clarified the charge-to-spin conversion in Bi/Ag bilayers. Nevertheless, the magnitudes of the outermost spin polarization of Bi(0.3 ~5)/Ag(25)/Al2O3 (numbers in parentheses denote thickness in nm) and Ag(25 ~500)/Bi(8)/Al2O3 decrease exponentially with increasing Bi thickness and Ag thickness, respectively. This provides probably the first direct evidence for spin diffusion mechanism. Financial support from JSPS Kakenhi Grant 24310072.
Spin caloritronics in graphene
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Angsula; Frota, H. O. [Department of Physics, Federal University of Amazonas, Av. Rodrigo Octavio 3000-Japiim, 69077-000 Manaus, AM (Brazil)
2015-06-14
Spin caloritronics, the combination of spintronics with thermoelectrics, exploiting both the intrinsic spin of the electron and its associated magnetic moment in addition to its fundamental electronic charge and temperature, is an emerging technology mainly in the development of low-power-consumption technology. In this work, we study the thermoelectric properties of a Rashba dot attached to two single layer/bilayer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current, which depends on the temperature and chemical potential. We demonstrate that the Rashba dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature, and also the Rashba term have been observed.
Müller, Norbert; Jerschow, Alexej
2006-01-01
NMR images were obtained from the proton spin noise signals of a water-containing phantom, which was placed in the highly tuned, low-noise resonant circuit of a cryogenically cooled NMR probe in the presence of systematically varied magnetic field gradients. The spatially resolved proton spin density was obtained from the raw signal by a modified projection–reconstruction protocol. Although spin noise imaging is inherently less sensitive than conventional magnetic resonance imaging, it afford...
Nonequilibrium spin noise spectroscopy
Li, Fuxiang; Pershin, Yuriy V.; Slipko, Valeriy A.; Sinitsyn, Nikolai A.
2013-01-01
Spin Noise Spectroscopy (SNS) is an experimental approach to obtain correlators of mesoscopic spin fluctuations in time by purely optical means. We explore the information that this technique can provide when it is applied to a weakly non-equilibrium regime when an electric current is driven through a sample by an electric field. We find that the noise power spectrum of conducting electrons experiences a shift, which is proportional to the strength of the spin-orbit coupling for electrons mov...
Kamra, A.; Witek, F.P.; Meyer, S.; Huebl, H.; Geprägs, S.; Gross, R.; Bauer, G. E. W.; Goennenwein, S. T. B.
2014-01-01
We measure the low-frequency thermal fluctuations of pure spin current in a Platinum film deposited on yttrium iron garnet via the inverse spin Hall effect (ISHE)-mediated voltage noise as a function of the angle $\\alpha$ between the magnetization and the transport direction. The results are consistent with the fluctuation dissipation theorem in terms of the recently discovered spin Hall magnetoresistance (SMR). We present a microscopic description of the $\\alpha$ dependence of the voltage no...
Torczynski, John R.
2000-01-01
A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.
Curvature-enhanced Spin-orbit Coupling and Spinterface Effect in Fullerene-based Spin Valves
Liang, Shiheng; Geng, Rugang; Yang, Baishun; Zhao, Wenbo; Chandra Subedi, Ram; Li, Xiaoguang; Han, Xiufeng; Nguyen, Tho Duc
2016-01-01
We investigated curvature-enhanced spin-orbit coupling (SOC) and spinterface effect in carbon-based organic spin valves (OSVs) using buckyball C60 and C70 molecules. Since the naturally abundant 12C has spinless nuclear, the materials have negligible hyperfine interaction (HFI) and the same intrinsic SOC, but different curvature SOC due to their distinct curvatures. We fitted the thickness dependence of magnetoresistance (MR) in OSVs at various temperatures using the modified Jullière equation. We found that the spin diffusion length in the C70 film is above 120 nm, clearly longer than that in C60 film at all temperatures. The effective SOC ratio of the C70 film to the C60 film was estimated to be about 0.8. This was confirmed by the magneto-electroluminescence (MEL) measurement in fullerene-based light emitting diodes (LED). Next, the effective spin polarization in C70-based OSVs is smaller than that in C60-based OSVs implying that they have different spinterface effect. First principle calculation study shows that the spin polarization of the dz2 orbital electrons of Co atoms contacted with C60 is larger causing better effective spin polarization at the interface.
Biswas, Ayan K.; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo
2015-01-01
In artificial neural networks, neurons are usually implemented with highly dissipative CMOS-based operational amplifiers. A more energy-efficient implementation is a 'spin-neuron' realized with a magneto-tunneling junction (MTJ) that is switched with a spin-polarized current (representing weighted sum of input currents) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the MTJ. Here, we propose and analyze a different type of spin-neuron in which t...
Spin transport in tantalum studied using magnetic single and double layers
Montoya, Eric; Omelchenko, Pavlo; Coutts, Chris; Lee-Hone, Nicholas R.; Hübner, René; Broun, David; Heinrich, Bret; Girt, Erol
2016-08-01
We report on spin transport in sputter-grown Ta films measured by ferromagnetic resonance. Spin diffusion length and spin mixing conductance are determined from magnetic damping measurements for a varying thickness of Ta layer 0 ≤dTa≤10 nm. The different boundary conditions of single- and double-magnetic-layer heterostructures Py |Ta and Py |Ta | [Py |Fe ] allow us to significantly narrow down the parameter space and test various models. We show that a common approach of using bulk resistivity value in the analysis yields inconsistent spin diffusion length and spin mixing conductance values for magnetic single- and double-layer structures. X-ray diffraction shows that bulk Ta is a combination of β -Ta and bcc-Ta . However, in the region of significant spin transport, ≲2 nm, there is an intermediate region of growth where the Ta lacks long-range structural order, as observed by transmission electron microscopy. Thickness-dependent resistivity measurements confirm that the bulk and intermediate regions have significantly different resistivity values. We find that the data can be well represented if the intermediate region resistivity value is used in the analysis. Additionally, the data can be fit if resistivity has the measured thickness dependence and spin diffusion length is restricted to be inversely proportional to resistivity. Finally, we rule out a model in which spin diffusion length is a constant, while the resistivity has the measured thickness dependence.
Response of a spin valve to a spin battery
Pham, Khuôn-Viêt
2016-01-01
It is shown that spin valves under suitable symmetry conditions exhibit an ON-OFF response to a spin battery, and are therefore perfect spin transistors. While a spin valve driven by a charge battery displays the usual GMR (Giant Magneto-Resistance), this means that a pure spin current or pure spin accumulation can generate an infinite magnetoresistance (IMR). Magnetic tunnel junctions as well as CPP (current perpendicular to plane) or CIP (current in plane) metallic trilayers are discussed.
Quantum theory of spin waves in finite chiral spin chains
Roldán-Molina, A.; Santander, M. J.; Núñez, A.S.; Fernández Rossier, Joaquín
2013-01-01
We calculate the effect of spin waves on the properties of finite-size spin chains with a chiral spin ground state observed on biatomic Fe chains deposited on iridium(001). The system is described with a Heisenberg model supplemented with a Dzyaloshinskii-Moriya coupling and a uniaxial single ion anisotropy that presents a chiral spin ground state. Spin waves are studied using the Holstein-Primakoff boson representation of spin operators. Both the renormalized ground state and the elementary ...
Large extrinsic spin Hall effect in Au-Cu alloys by extensive atomic disorder scattering
Zou, L. K.; Wang, S. H.; Zhang, Y.; Sun, J. R.; Cai, J. W.; Kang, S. S.
2016-01-01
Spin Hall angle, which denotes the conversion efficiency between spin and charge current, is a key parameter in the pure spin current phenomenon. The search for materials with large spin Hall angle is indeed important for scientific interest and potential application in spintronics. Here the large enhanced spin Hall effect (SHE) of Au-Cu alloy is reported by investigating the spin Seebeck effect, spin Hall anomalous Hall effect, and spin Hall magnetoresistance of the Y3F e5O12 (YIG)/A uxC u1 -x hybrid structure over the full composition. At the near equiatomic Au-Cu composition with maximum atomic disorder scattering, the spin Hall angle of the Au-Cu alloy increases by two to three times together with a moderate spin diffusion length in comparison with Au. The longitudinal spin Seebeck voltage and the spin Hall magnetoresistance ratio also increase by two to three times. More importantly, no evidence of anomalous Hall effect is observed in all YIG/Au-Cu samples, in contrast to the cases of other giant SHE materials Pt(Pd), Ta, and W. This behavior makes Au-Cu free from any suspicion of the magnetic proximity effect involved in the hybrid structure, and thus the Au-Cu alloy can be an ideal material for pure spin current study.
Electron spin dynamics and spin-lattice relaxation of trityl radicals in frozen solutions.
Chen, Hanjiao; Maryasov, Alexander G; Rogozhnikova, Olga Yu; Trukhin, Dmitry V; Tormyshev, Victor M; Bowman, Michael K
2016-09-28
Electron spin-lattice relaxation of two trityl radicals, d24-OX063 and Finland trityl, were studied under conditions relevant to their use in dissolution dynamic nuclear polarization (DNP). The dependence of relaxation kinetics on temperature up to 100 K and on concentration up to 60 mM was obtained at X- and W-bands (0.35 and 3.5 Tesla, respectively). The relaxation is quite similar at both bands and for both trityl radicals. At concentrations typical for DNP, relaxation is mediated by excitation transfer and spin-diffusion to fast-relaxing centers identified as triads of trityl radicals that spontaneously form in the frozen samples. These centers relax by an Orbach-Aminov mechanism and determine the relaxation, saturation and electron spin dynamics during DNP. PMID:27560644
Bahr, Benjamin; Kamiński, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy
2010-01-01
The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as the main tool. An equivalence relation we impose in the set of the operator spin foams allows to split the faces and the edges of the foams. The consistency with that relation requires introduction of the (familiar for the BF theory) face amplitude. The operator spin foam models are defined quite generally. Imposing a maximal symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with demanding consistency with splitting the edges, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on Spin(4) BF spin foam model is exactly the way we tend to view 4d quantum gravity, starting with the BC model and continuing with the EPRL or FK models. That makes...
Antiferromagnetic spin Seebeck effect.
Energy Technology Data Exchange (ETDEWEB)
Wu, Stephen M.; Zhang, Wei; KC, Amit; Borisov, Pavel; Pearson, John E.; Jiang, J. Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand
2016-03-03
We report on the observation of the spin Seebeck effect in antiferromagnetic MnF2. A device scale on-chip heater is deposited on a bilayer of MnF2 (110) (30nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF2(110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF2 through the inverse spin Hall effect. The low temperature (2–80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9T) are applied parallel to the easy axis of the MnF2 thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.
Kamra, A.; Witek, F.P.; Meyer, S.; Huebl, H.; Geprägs, S.; Gross, R.; Bauer, G.E.W.; Goennenwein, S.T.B.
2014-01-01
We measure the low-frequency thermal fluctuations of pure spin current in a platinum film deposited on yttrium iron garnet via the inverse spin Hall effect (ISHE)-mediated voltage noise as a function of the angle α between the magnetization and the transport direction. The results are consistent wit
Kleiner, Alex
2002-01-01
It is shown here that electrons on the surface of a nanotube in a perpendicular magnetic field undergo spin-chirality separation along the circumference. Stripes of spin-polarization propagate along the tube, with a spatial pattern that can be modulated by the electron filling.
Single spin magnetic resonance
Wrachtrup, Jörg; Finkler, Amit
2016-08-01
Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.
Spin torque transistor revisited
Chiba, T.; Bauer, G.E.W.; Takahashi, S.
2013-01-01
We theoretically study the operation of a 4-terminal device consisting of two lateral thin-film spin valves that are coupled by a magnetic insulator such as yttrium iron garnet via the spin transfer torque. By magnetoelectronic circuit theory we calculate the current voltage characteristics and find
Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas
Energy Technology Data Exchange (ETDEWEB)
Yang, Luyi [Univ. of California, Berkeley, CA (United States)
2013-05-17
Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly
International Nuclear Information System (INIS)
In Athabasca oil sands there is a fraction of non-crystalline solids tightly bound to humic matter. It is believed, that the presence of this fraction, which resists subsequent wetting by water, introduces serious problems in bitumen recovery when using water based processes. In the present work, 29Si and 13C solid state magic angle spinning (MAS) NMR techniques were applied to characterize these solids which were isolated from Athabasca oil sands of estuarine and marine origin. On the basis of 29Si results it is suggested that there is a short-range disorder in these samples. It is also shown that aluminum is present in the nearest-neighbor environment of the silicon atoms, thus demonstrating that these solids are comprised of disordered alumino-silicates (allophanes). 13C CP/MAS NMR spectra of demineralized inorganic matter-humic complexes derived from both estuarine and marine oil sands indicate that the distribution of carbon types in each region of the spectra is similar, with aromatic carbon being the predominant type of carbon
International Nuclear Information System (INIS)
Paroxetine, BRL 29060A has been labelled with both carbon-14 and carbon-13. Hydroxymethylation of 4-(4-fluorophenyl)-1-methyl-1,2,5,6-tetrahydropyridine, using [14C]formaldehyde, produced an enantiomeric mixture of products which was taken without separation through a multistage sequence. Resolution of the mixture of stereoisomers at the penultimate step gave [14C]BRL 29060A with the required configuration. The overall radiochemical yield was 8%. At some stage in this process, as shown by C-13 labelling studies, scrambling of the label took place to give BRL 29060A with the majority of the label in the C-2 position of the piperidine ring and the remainder at the expected 7-methylene position. Further investigations of this route using carbon-13 as the label are described. When sesamol, (3,4-methylenedioxyphenol) was reacted with the O-benzene sulphonate of -cis-4-(4-fluorophenyl)-3-(hydroxy[13C]methyl-l-methylpiperidine, an inversion of configuration resulted via the previously described 1-aza[3.1.1]bicycloheptane ring system. It is also shown that the corresponding -trans-substituted piperidine, under similar conditions, does not undergo this inversion. (Author)
Energy Technology Data Exchange (ETDEWEB)
Willcocks, K.; Rustidge, D.C.; Tidy, D.J.D. (SmithKline Beecham Pharmaceuticals Research Div., Harlow (United Kingdom)); Barnes, R.D. (SmithKline Beecham Pharmaceuticals Div., Betchworth (United Kingdom). Chemotherapeutic Research Centre)
1993-01-01
Paroxetine, BRL 29060A has been labelled with both carbon-14 and carbon-13. Hydroxymethylation of 4-(4-fluorophenyl)-1-methyl-1,2,5,6-tetrahydropyridine, using [[sup 14]C]formaldehyde, produced an enantiomeric mixture of products which was taken without separation through a multistage sequence. Resolution of the mixture of stereoisomers at the penultimate step gave [[sup 14]C]BRL 29060A with the required configuration. The overall radiochemical yield was 8%. At some stage in this process, as shown by C-13 labelling studies, scrambling of the label took place to give BRL 29060A with the majority of the label in the C-2 position of the piperidine ring and the remainder at the expected 7-methylene position. Further investigations of this route using carbon-13 as the label are described. When sesamol, (3,4-methylenedioxyphenol) was reacted with the O-benzene sulphonate of -cis-4-(4-fluorophenyl)-3-(hydroxy[[sup 13]C]methyl-l-methylpiperidine), an inversion of configuration resulted via the previously described 1-aza[3.1.1]bicycloheptane ring system. It is also shown that the corresponding -trans-substituted piperidine, under similar conditions, does not undergo this inversion. (Author).
DEFF Research Database (Denmark)
Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans
1975-01-01
The energies of spin waves propagating in the c direction of Tb have been studied by inelastic neutron scattering, as a function of a magnetic field applied along the easy and hard directions in the basal plane, and as a function of temperature. From a general spin Hamiltonian, consistent...... with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results...... with increasing temperatures implies that the two-ion coupling is effectively isotropic above ∼ 150 K. We present arguments for concluding that, among the mechanisms which may introduce anisotropic two-ion couplings in the rare-earth metals, the modification of the indirect exchange interaction by the spin...
Lan, Jin; Yu, Weichao; Wu, Ruqian; Xiao, Jiang
2015-10-01
A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound states in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. Our findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.
Fractionalized spin-wave continuum in kagome spin liquids
Mei, Jia-Wei; Wen, Xiao-Gang
Motivated by spin-wave continuum (SWC) observed in recent neutron scattering experiments in Herbertsmithite, we use Gutzwiller-projected wave functions to study dynamic spin structure factor S (q , ω) of spin liquid states on the kagome lattice. Spin-1 excited states in spin liquids are represented by Gutzwiller-projected two-spinon excited wave functions. We investigate three different spin liquid candidates, spinon Fermi-surface spin liquid (FSL), Dirac spin liquid (DSL) and random-flux spin liquid (RSL). FSL and RSL have low energy peaks in S (q , ω) at K points in the extended magnetic Brillouin zone, in contrast to experiments where low energy peaks are found at M points. There is no obviuos contradiction between DSL and neutron scattering measurements. Besides a fractionalized spin (i.e. spin-1/2), spinons in DSL carry a fractionalized crystal momentum which is potentially detectable in SWC in the neutron scattering measurements.
International Nuclear Information System (INIS)
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
Spin Hall and spin Nernst effects in graphene with intrinsic and Rashba spin-orbit interactions
Institute of Scientific and Technical Information of China (English)
Zhu Guo-Bao
2012-01-01
The spin Hall and spin Nernst effects in graphene are studied based on Green's function formalism.We calculate intrinsic contributions to spin Hall and spin Nernst conductivities in the Kane-Mele model with various structures.When both intrinsic and Rashba spin-orbit interactions are present,their interplay leads to some characteristics of the dependence of spin Hall and spin Nernst conductivities on the Fermi level.When the Rashba spin-orbit interaction is smaller than intrinsic spin-orbit coupling,a weak kink in the conductance appears.The kink disappears and a divergence appears when the Rashba spin-orbit interaction enhances.When the Rashba spin-orbit interaction approaches and is stronger than intrinsic spin-orbit coupling,the divergence becomes more obvious.
Institute of Scientific and Technical Information of China (English)
Tina Boikos
2008-01-01
@@ The alarm has just gone off. Do I really have to get up? I wonder. Originally, signing up for an early-morning spinning class seemed like a good idea; it jump-starts the day with some well-needed exercise.
Gluon Spin Contribution to The Nucleon Spin
Energy Technology Data Exchange (ETDEWEB)
Arash, Firooz, E-mail: farash@cic.aut.ac.i [Physics Department, Tafresh University, Tafresh (Iran, Islamic Republic of); Shahveh, Abolfazl [Physics Department, Tafresh University, Tafresh (Iran, Islamic Republic of); Taghavi-Shahri, Fateme [School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM) P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)
2010-10-15
We have calculated {delta}g/g in the nucleon at all measured kinematics. The smallness of {delta}g/g in the measured kinematics should not be interpreted as the the gluon contribution to the nucleon spin is small. In fact the first moment of gluon polarization in the nucleon, {Delta}g(Q{sup 2}) can be sizable.
Gluon Spin Contribution to The Nucleon Spin
Arash, Firooz; Shahveh, Abolfazl; Taghavi-Shahri, Fateme
2010-10-01
We have calculated δg/ g in the nucleon at all measured kinematics. The smallness of δg/ g in the measured kinematics should not be interpreted as the the gluon contribution to the nucleon spin is small. In fact the first moment of gluon polarization in the nucleon, Δ g( Q2) can be sizable.
Gluon Spin Contribution to The Nucleon Spin
International Nuclear Information System (INIS)
We have calculated δg/g in the nucleon at all measured kinematics. The smallness of δg/g in the measured kinematics should not be interpreted as the the gluon contribution to the nucleon spin is small. In fact the first moment of gluon polarization in the nucleon, Δg(Q2) can be sizable.
Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs
Botzem, Tim; McNeil, Robert P. G.; Mol, Jan-Michael; Schuh, Dieter; Bougeard, Dominique; Bluhm, Hendrik
2016-04-01
Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III-V nanowires.
Representation of Spin Group Spin(p, q)
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The representation (&)(p, q) of spin group Spin(p, q) in any dimensional space is given by induction, and the relation between two representations, which are obtained in two kinds of inductions from Spin(p, q) to Spin(p + 1, q + 1)are studied.
Electron spin decoherence in nuclear spin baths and dynamical decoupling
International Nuclear Information System (INIS)
We introduce the quantum theory of the electron spin decoherence in a nuclear spin bath and the dynamical decoupling approach for protecting the electron spin coherence. These theories are applied to various solid-state systems, such as radical spins in molecular crystals and NV centers in diamond.
Quantifying Spin Hall Angles from Spin Pumping: Experiments and Theory
Mosendz, O.; Pearson, J.E.; Fradin, F.Y.; Bauer, G.E.W.; Bader, S.D.; Hoffmann, A.
2010-01-01
Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating Ni80Fe20|normal metal (N) bilayers into a coplanar wavegu
SPIN Tutorial: How to Become a SPIN Doctor
Ruys, T.C.; Bosnacki, D.; Leue, S.
2002-01-01
SPIN is a model checker for the verification of software systems. SPIN uses a high level language called PROMELA to specify systems descriptions. The goal of this tutorial is to introduce novice users to both PROMELA and SPIN. The tutorial itself is divided into two parts. The BASIC SPIN part is tar
K. Coenegrachts; J. Delanote; L. ter Beek; M. Haspeslagh; S. Bipat; J. Stoker; L. Steyaert; H. Rigauts
2009-01-01
PURPOSE: To assess the added value of true diffusion (D), perfusion factor (f) and apparent diffusion coefficient at low b-values (ADC(low)) for differentiation between liver metastases and hemangiomas based on respiratory-triggered high-resolution Black-Blood Single-Shot SpinEcho Echo Planar Imagin
Zero-temperature spin-wave damping in a spin-polarized Fermi liquid
International Nuclear Information System (INIS)
We have measured the temperature and polarization dependence of the spin-wave damping and spin diffusion coefficient in a saturated 3He-4He mixture with a concentration of 9.4% at a pressure of 8 bars. A Leiden dilution refrigerator has been used to enhance the nuclear polarization and to cool the mixture to temperatures in the range 10-15 mK. The maximum polarization is 3.4 times higher than the equilibrium value of 2.7% in an external magnetic field of 11.36 T. The effects of the dipolar interactions and the radiation damping have been taken into account in the analysis of the spin-wave spectra. We observe that the polarization dependence of the spin-wave damping is proportional to T2+A2Ta02 where T is the temperature, A is the polarization enhancement factor, and Ta0 is the anisotropy temperature for the mixture at equilibrium in the external field. Our result Ta0=3.66±0.14 mK is 30% higher than the theoretical prediction for very dilute mixtures and is evidence for the existence of polarization-induced relaxation of transverse spin currents
Theory of Intrinsic Spin Torque Due to Interface Spin-Orbit Coupling
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.
Krishnan, Chethan; Raju, Avinash; Roy, Shubho; Thakur, Somyadip
2014-02-01
We construct cosmological solutions of higher spin gravity in 2+1 dimensional de Sitter space. We show that a consistent thermodynamics can be obtained for their horizons by demanding appropriate holonomy conditions. This is equivalent to demanding the integrability of the Euclidean boundary conformal field theory partition function, and it reduces to Gibbons-Hawking thermodynamics in the spin-2 case. By using the prescription of Maldacena, we relate the thermodynamics of these solutions to those of higher spin black holes in AdS3.
Energy Technology Data Exchange (ETDEWEB)
Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-01-15
The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.
McWeeny, Roy
2004-01-01
Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp
2013-01-01
This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated
Antiferromagnetic phase transition and spin correlations in NiO
DEFF Research Database (Denmark)
Chatterji, Tapan; McIntyre, G.J.; Lindgård, Per-Anker
2009-01-01
We have investigated the antiferromagnetic (AF) phase transition and spin correlations in NiO by high-temperature neutron diffraction below and above TN. We show that AF phase transition is a continuous second-order transition within our experimental resolution. The spin correlations manifested...... by the strong diffuse magnetic scattering persist well above TN530 K and could still be observed at T=800 K which is about 1.5TN. We argue that the strong spin correlations above TN are due to the topological frustration of the spins on a fcc lattice. The Néel temperature is substantially reduced...... by this process. We determined the critical exponents =0.328±0.002 and =0.64±0.03 and the Néel temperature TN=530±1 K. These critical exponents suggest that NiO should be regarded as a 3dXY system...
Ozarslan, Evren; Mareci, Thomas H
2003-11-01
A new method for mapping diffusivity profiles in tissue is presented. The Bloch-Torrey equation is modified to include a diffusion term with an arbitrary rank Cartesian tensor. This equation is solved to give the expression for the generalized Stejskal-Tanner formula quantifying diffusive attenuation in complicated geometries. This makes it possible to calculate the components of higher-rank tensors without using the computationally-difficult spherical harmonic transform. General theoretical relations between the diffusion tensor (DT) components measured by traditional (rank-2) DT imaging (DTI) and 3D distribution of diffusivities, as measured by high angular resolution diffusion imaging (HARDI) methods, are derived. Also, the spherical tensor components from HARDI are related to the rank-2 DT. The relationships between higher- and lower-rank Cartesian DTs are also presented. The inadequacy of the traditional rank-2 tensor model is demonstrated with simulations, and the method is applied to excised rat brain data collected in a spin-echo HARDI experiment. PMID:14587006
ANALYSIS ON THE SPINNING FORCES IN FLEXIBLE SPINNING OF CONES
Institute of Scientific and Technical Information of China (English)
Xia Qinxiang; Susumu Shima
2003-01-01
Flexible spinning is a new type of spinning process where spin-forming is performed without using a mandrel. Combining shearing and rolling processes, the calculation formulas of thespinning forces in flexible spinning of cones is presented. The effects of the main processing parameters, such as gripping force G applied to the blank by the inner roller, the feed rate of rollersfand the roundness radius of outer roller ro, on the spinning forces are analyzed experimentally and theoretically.
Spin transfer torques in the nonlocal lateral spin valve.
Xu, Yuan; Xia, Ke; Ma, Zhongshui
2008-06-11
We report a theoretical study on the spin and electron transport in the nonlocal lateral spin valve with a non-collinear magnetic configuration. The nonlocal magnetoresistance, defined as the voltage difference on the detection lead over the injected current, is derived analytically. The spin transfer torques on the detection lead are calculated. It is found that spin transfer torques are symmetrical for parallel and antiparallel magnetic configurations, in contrast to that in a conventional sandwiched spin valve. PMID:21825793
Proposal for a spin MOSFET based on spin gapless semiconductors
Graziosi, Patrizio
2016-01-01
We propose a spintronic metal oxide semiconductor field effect transistor (spin MOSFET) where a spin gapless semiconductor (SGS) constitutes the channel and the drain is a ferromagnetic metal. SGS exhibit a non-zero band gap in only one of the spin sub-bands and feature complete spin polarization at finite temperature. We present an analytical model of the device and comment the properties relevant for devices applications. Our results boost SGS as a new paradigm for the spin MOSFET concept.
Diffusion imaging with stimulated echoes: signal models and experiment design
Alexander, Daniel C
2013-01-01
Purpose: Stimulated echo acquisition mode (STEAM) diffusion MRI can be advantageous over pulsed-gradient spin-echo (PGSE) for diffusion times that are long compared to $\\ttwo$. It is important therefore for biomedical diffusion imaging applications at 7T and above where $\\ttwo$ is short. However, imaging gradients in the STEAM sequence contribute much greater diffusion weighting than in PGSE, but are often ignored during post-processing. We demonstrate here that this can severely bias parameter estimates. Method: We present models for the STEAM signal for free and restricted diffusion that account for crusher and slice-select (butterfly) gradients to avoid such bias. The butterfly gradients also disrupt experiment design, typically by skewing gradient-vectors towards the slice direction. We propose a simple compensation to the diffusion gradient vector specified to the scanner that counterbalances the butterfly gradients to preserve the intended experiment design. Results: High-field data fixed monkey brain e...
International Spin Physics 2014 Summary
Milner, Richard G
2015-01-01
The Stern-Gerlach experiment and the origin of electron spin are described in historical context. SPIN 2014 occurs on the fortieth anniversary of the first International High Energy Spin Physics Symposium at Argonne in 1974. A brief history of the international spin conference series is presented.
On Nonlinear Higher Spin Curvature
Manvelyan, Ruben(Yerevan Physics Institute, Alikhanian Br. St. 2, Yerevan, 0036, Armenia); Mkrtchyan, Karapet; Rühl, Werner; Tovmasyan, Murad
2011-01-01
We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider in detail the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the deWit-Freedman curvature.
On nonlinear higher spin curvature
Energy Technology Data Exchange (ETDEWEB)
Manvelyan, Ruben, E-mail: manvel@physik.uni-kl.d [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia); Mkrtchyan, Karapet, E-mail: karapet@yerphi.a [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia); Ruehl, Werner, E-mail: ruehl@physik.uni-kl.d [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Tovmasyan, Murad, E-mail: mtovmasyan@ysu.a [Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia)
2011-05-09
We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the de Wit-Freedman curvature.
Anisotropic spin relaxation in graphene
Tombros, N.; Tanabe, S.; Veligura, A.; Jozsa, C.; Popinciuc, M.; Jonkman, H. T.; van Wees, B. J.
2008-01-01
Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular
Microscopic studies of nonlocal spin dynamics and spin transport (invited)
Energy Technology Data Exchange (ETDEWEB)
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, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)
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 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.
Yamaguchi, A.; Ishimoto, H.; Kojima, H.
2009-03-01
The superfluid component of ^3He A1 phase is spin-polarized. The process of forcing the superfluid component through a spin filtering structure, in a manner of mechano-magnetic effect, can be used to increase the spin polarization beyond the equilibrium under a given applied magnetic field. We have constructed a test cell in which a glass capillary array acts as the spin (and entropy) filter and an electrostatically actuated diaphragm forces the superfluid flow through it. Preliminary results show that a maximum relative increase of polarization by 50 % could be achieved. The maximum increase in polarization appears to be limited by the critical superfluid flow through the channels in the glass capillary array. The dependence of the observed effects on temperature, pressure and magnetic field will be presented.
Spin-Electromagnetic Hydrodynamics
Koide, T
2013-01-01
The hydrodynamic model including the spin degree of freedom and the electromagnetic field was discussed. In this derivation, we applied electromagnetism for macroscopic medium proposed by Minkowski. For the equation of motion of spin, we assumed that the hydrodynamic equation of the Pauli equation is reproduced when the many-body effect is neglected. The fluid and spin stress tensors induced by the many-body effect were obtained by employing the algebraic positivity of the entropy production in the framework of linear irreversible thermodynamics. In our model, the effect of the spin-magnetic interaction is absorbed into the magnetic polarization so as to satisfy the momentum and angular momentum conservations. We further compared our result with other existing models.
Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas
Schwab, Peter; Raimondi, Roberto; Gorini, Cosimo
2010-01-01
We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas in the transport diffusive regime. For systems with inversion symmetry there are established relations between the spin Hall effect, the anomalous Hall effect and the inverse spin Hall effect. However, in two-dimensional electron gases of semiconductors like GaAs, inversion symmetry is broken so that the standard arguments do not apply. We demonstrate that in the presence of a Rashba type of spin-orbit...
Zhu, Lei; Yu, Edward T.
2011-04-01
Ballistic electron transport at nanoscale dimensions is investigated and exploited in a nanoscale three-terminal, all-electrical spintronic semiconductor device. Charge current cancellation under appropriate device biasing yields a large, spin-dependent current signal even with modest spin injection efficiency into the semiconductor, while reliance on ballistic, rather than diffusive, carrier transport is expected to enable robust scalability to smaller dimensions. Magnetocurrent in excess of 200% is measured with spin injection efficiency of 5%, and a spin-dependent ballistic carrier transport model is shown to yield accurate, quantitative predictions of current-voltage behavior.
Alexandrov, Victor; Coleman, Piers
2012-01-01
In this paper we discuss two-dimensional holographic metals from a condensed matter physics perspective. We examine the spin structure of the Green's function of the holographic metal, demonstrating that the excitations of the holographic metal are "chiral", lacking the inversion symmetry of a conventional Fermi surface, with only one spin orientation for each point on the Fermi surface, aligned parallel to the momentum. While the presence of a Kramer's degeneracy across the Fermi surface per...
Spin polarizability of hyperons
Indian Academy of Sciences (India)
K B Vijaya Kumar
2014-11-01
We review the recent progress of the theoretical understanding of spin polarizabilities of the hyperon in the framework of (3) heavy baryon chiral perturbation theory (HBChPT). We present the results of a systematic leading-order calculation of hyperon Compton scattering and extract the forward spin polarizability (0) of hyperons. The results obtained for $_0$ in the case of nucleons agree with the known results of (2) HBChPT when kaon loops are not considered.
Nuclear spin effect in metallic spin valve
Danon, J.; Nazarov, Yu.V.
2006-01-01
We study electronic transport through a ferromagnet normal-metal ferromagnet system and we investigate the effect of hyperfine interaction between electrons and nuclei in the normal-metal part. A switching of the magnetization directions of the ferromagnets causes nuclear spins to precess. We show that the effect of this precession on the current through the system is large enough to be observed in experiment.
A Generalized Kawasaki-Type Dynamics with Spin-Pair Redistribution Mechanism
Institute of Scientific and Technical Information of China (English)
朱建阳; 朱涵
2002-01-01
We generalize Kawasaki's dynamics, spin-pair exchange mechanism, to a spin-pair redistribution mechanism,and we present a normalized redistribution probability. As an application, we treat the one-dimensional kinetic Gaussian model and obtain the exact diffusion equation and the temperature-dependent diffusion coefficient. We find that the diffusion process can slow down infinitely near the critical point and obtain the critical dynamic exponent z = 2 that is independent of the assumed mechanism, either Glauber-type or Kawasaki-type.
Spin transport in nanoscale spin valves and magnetic tunnel junctions
Patibandla, Sridhar
Spintronics or electronics that utilizes the spin degree of freedom of a single charge carrier (or an ensemble of charge carriers) to store, process, sense or communicate data and information is a rapidly burgeoning field in electronics. In spintronic devices, information is encoded in the spin polarization of a single carrier (or multiple carriers) and the spin(s) of these carrier(s) are manipulated for device operation. This strategy could lead to devices with low power consumption. This dissertation investigates spin transport in one dimensional and two dimensional semiconductors, with a view to applications in spintronic devices. This dissertation is arranged as follows: Chapter 1 gives a detailed introduction and necessary background to understand aspects of spin injection into a semiconductor from a spin polarized source such as a ferromagnet, and spin polarized electron transport in the semiconductor. Chapter 2 discusses the nanoporous alumina technique that is employed to fabricate nanowires and nanowire spin valves for the investigation of spin transport in 1D semiconductors. Chapter 3 investigates the spin transport in quasi one-dimensional spin valves with germanium spacer layer. These spin valves with 50nm in diameter and 1 mum length were fabricated using the porous alumina technique. Spin transport in nanoscale germanium spin valves was demonstrated and the spin relaxation lengths and the spin relaxation times were calculated. Chapter 4 discusses spin transport studies conducted in bulk high purity germanium with a view to comparing spin relaxation mechanisms in low mobility nanowires and high mobility bulk structures. Lateral spin valve with tunnel injectors were employed in this study and the spin transport measurements were conducted at various temperatures. The spin relaxation rates were measured as a function of temperature which allowed us to distinguish between two different mechanisms---D'yakonov-Perel' and Elliott-Yafet---that dominate spin
Spin Hall effects in mesoscopic Pt films with high resistivity
Qin, Chuan; Luo, Yongming; Zhou, Chao; Cai, Yunjiao; Jia, Mengwen; Chen, Shuhan; Wu, Yizheng; Ji, Yi
2016-10-01
The energy efficiency of the spin Hall effects (SHE) can be enhanced if the electrical conductivity is decreased without sacrificing the spin Hall conductivity. The resistivity of Pt films can be increased to 150-300 µΩ · cm by mesoscopic lateral confinement, thereby decreasing the conductivity. The SHE and inverse spin Hall effects (ISHE) in these mesoscopic Pt films are explored at 10 K by using the nonlocal spin injection/detection method. All relevant physical quantities are determined in situ on the same substrate, and a quantitative approach is developed to characterize all processes effectively. Extensive measurements with various Pt thickness values reveal an upper limit for the Pt spin diffusion length: {λ\\text{pt}} ⩽ 0.8 nm. The average product of {λ\\text{pt}} and the Pt spin Hall angle {α\\text{H}} is substantial: {α\\text{H}}{λ\\text{pt}} = (0.142 ± 0.040) nm for 4 nm thick Pt, though a gradual decrease is observed at larger Pt thickness. The results suggest enhanced spin Hall effects in resistive mesoscopic Pt films.
Effects of off-resonance spins on the performance of the modulated gradient spin echo sequence
Serša, Igor; Bajd, Franci; Mohorič, Aleš
2016-09-01
Translational molecular dynamics in various materials can also be studied by diffusion spectra. These can be measured by a constant gradient variant of the modulated gradient spin echo (MGSE) sequence which is composed of a CPMG RF pulse train superimposed to a constant magnetic field gradient. The application of the RF train makes the effective gradient oscillating thus enabling measurements of diffusion spectra in a wide range of frequencies. However, seemingly straightforward implementation of the MGSE sequence proved to be complicated and can give overestimated results for diffusion if not interpreted correctly. In this study, unrestricted diffusion in water and other characteristic materials was analyzed by the MGSE sequence in the frequency range 50-3000 Hz using a 6 T/m diffusion probe. First, it was shown that the MGSE echo train acquired from the entire sample decays faster than the train acquired only from a narrow band at zero frequency of the sample. Then, it was shown that the decay rate is dependent on the band's off-resonance characterized by the ratio Δω0 /ω1 and that with higher off-resonances the decay is faster. The faster decay therefore corresponds to a higher diffusion coefficient if the diffusion is calculated using standard Stejskal-Tanner formula. The result can be explained by complex coherence pathways contributing to the MGSE echo signals when | Δω0 | /ω1 > 0 . In a magnetic field gradient, all the pathways are more diffusion attenuated than the direct coherence pathway and therefore decay faster, which leads to an overestimation of the diffusion coefficient. A solution to this problem was found in an efficient off-resonance signal reduction by using only zero frequency filtered MGSE echo train signals.
Chudnovsky, Eugene M.
2007-01-01
An extension of Drude model is proposed that accounts for spin and spin-orbit interaction of charge carriers. Spin currents appear due to combined action of the external electric field, crystal field and scattering of charge carriers. The expression for spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, spin Hall conductivity $\\sigma_s$ and charge conductivity $\\sigma_c$ are related through $\\sigma_s = [2 \\pi \\hbar...
Resolving and measuring diffusion in complex interfaces: Exploring new capabilities
Energy Technology Data Exchange (ETDEWEB)
Alam, Todd M. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2015-09-01
This exploratory LDRD targeted the use of a new high resolution spectroscopic diffusion capabilities developed at Sandia to resolve transport processes at interfaces in heterogeneous polymer materials. In particular, the combination of high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy with pulsed field gradient (PFG) diffusion experiments were used to directly explore interface diffusion within heterogeneous polymer composites, including measuring diffusion for individual chemical species in multi-component mixtures. Several different types of heterogeneous polymer systems were studied using these HRMAS NMR diffusion capabilities to probe the resolution limitations, determine the spatial length scales involved, and explore the general applicability to specific heterogeneous systems. The investigations pursued included a) the direct measurement of the diffusion for poly(dimethyl siloxane) polymer (PDMS) on nano-porous materials, b) measurement of penetrant diffusion in additive manufactures (3D printed) processed PDMS composites, and c) the measurement of diffusion in swollen polymers/penetrant mixtures within nano-confined aluminum oxide membranes. The NMR diffusion results obtained were encouraging and allowed for an improved understanding of diffusion and transport processes at the molecular level, while at the same time demonstrating that the spatial heterogeneity that can be resolved using HRMAS NMR PFG diffusion experiment must be larger than ~μm length scales, expect for polymer transport within nanoporous carbons where additional chemical resolution improves the resolvable heterogeneous length scale to hundreds of nm.
Lopes, Thiago I B; Ribeiro, Marilene D M M; Ming, Chiu C; Grimaldi, Renato; Gonçalves, Lireny A G; Marsaioli, Anita J
2016-12-01
The nutritional and organoleptic attributes of oils can proceed via interesterification of oils blends catalyzed by enzymes or chemicals. Enzymatic interesterification processes are preferred due the regiospecific outcome. Traditionally, monitoring of distribution of fatty acids (FA) in glycerol backbone is performed by enzymatic and chromatographic methods that are time-consuming, involving a series of chemical manipulations employing large volumes of organic solvents. Alternatively, carbon-13 nuclear magnetic resonance ((13)C NMR) is a fast and reliable technique that could be applied to determine the saturated and unsaturated FA distribution of the triacylglycerols (TAGs) present in high oleic sunflower oil (SO) and fully hydrogenated high oleic sunflower oil (HSO) blends and their interesterification products. The enzymatic interesterification was conducted employing the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM), the results show that the process was not completely regiospecific at sn-1,3 positions, due to the spontaneous acyl migration from position sn-2 to sn-1,3.
Lopes, Thiago I B; Ribeiro, Marilene D M M; Ming, Chiu C; Grimaldi, Renato; Gonçalves, Lireny A G; Marsaioli, Anita J
2016-12-01
The nutritional and organoleptic attributes of oils can proceed via interesterification of oils blends catalyzed by enzymes or chemicals. Enzymatic interesterification processes are preferred due the regiospecific outcome. Traditionally, monitoring of distribution of fatty acids (FA) in glycerol backbone is performed by enzymatic and chromatographic methods that are time-consuming, involving a series of chemical manipulations employing large volumes of organic solvents. Alternatively, carbon-13 nuclear magnetic resonance ((13)C NMR) is a fast and reliable technique that could be applied to determine the saturated and unsaturated FA distribution of the triacylglycerols (TAGs) present in high oleic sunflower oil (SO) and fully hydrogenated high oleic sunflower oil (HSO) blends and their interesterification products. The enzymatic interesterification was conducted employing the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM), the results show that the process was not completely regiospecific at sn-1,3 positions, due to the spontaneous acyl migration from position sn-2 to sn-1,3. PMID:27374579
Jedema, F.J.; Costache, M.V.; Heersche, H.B.; Baselmans, J.J.A.; Wees, B.J. van
2002-01-01
We have fabricated a multiterminal lateral mesoscopic metallic spin valve demonstrating spin precession at room temperature (RT), using tunnel barriers in combination with metallic ferromagnetic electrodes as a spin injector and detector. The observed modulation of the output signal due to the spin
Spin heat accumulation and spin-dependent temperatures in nanopillar spin valves
Dejene, F. K.; Flipse, J.; Bauer, G. E. W.; van Wees, B. J.
2013-01-01
Since the discovery of the giant magnetoresistance effect(1,2) the intrinsic angular momentum of the electron has opened up new spin-based device concepts. Our present understanding of the coupled transport of charge, spin and heat relies on the two-channel model for spin-up and spin-down electrons
The Diffusive Shock Acceleration Myth
Gloeckler, G.; Fisk, L. A.
2012-12-01
It is generally accepted that diffusive shock acceleration (DSA) is the dominant mechanism for particle acceleration at shocks. This is despite the overwhelming observational evidence that is contrary to predictions of DSA models. For example, our most recent survey of hourly-averaged, spin-averaged proton distribution functions around 61 locally observed shocks in 2001 at 1 AU found that in 21 cases no particles were accelerated. Spectral indices (γ ) of suprathermal tails on the velocity distributions around the 40 shocks that did accelerate particles, showed none of the DSA-predicted correlations of γ with the shock compression ratio and the shock normal to magnetic field angle. Here we will present ACE/SWICS observations of three sets of 72 consecutive one-hour averaged velocity distributions (in each of 8 SWICS spin sectors). Each set includes passage of one or more shocks or strong compression regions. All spectra were properly transformed to the solar wind frame using the detailed, updated SWICS forward model, taking into account the hourly-averaged directions of the solar wind flow, the magnetic field and the ACE spin axis (http://www.srl.caltech.edu/ACE/ASC/). The suprathermal tails are observed to be a combination of locally accelerated and remote tails. The local tails are power laws. The remote tails are also power laws with rollovers at higher energies. When local tails are weak (as is the case especially upstream of strong shocks or compression regions) the remote tails also have a rollover at low energies due to modulation (transport effects). Among our main findings are that (1) the spectral indices of both the local and remote tails are -5 within the uncertainties of the measurements, as predicted by our pump acceleration mechanism, and (2) the velocity distributions are anisotropic with the perpendicular (to the magnetic field) pressure greater than the parallel pressure.
Spin photonics and spin-photonic devices with dielectric metasurfaces
Liu, Yachao; Ke, Yougang; Zhou, Xinxing; Luo, Hailu; Wen, Shuangchun
2015-01-01
Dielectric metasurfaces with spatially varying birefringence and high transmission efficiency can exhibit exceptional abilities for controlling the photonic spin states. We present here some of our works on spin photonics and spin-photonic devices with metasurfaces. We develop a hybrid-order Poincare sphere to describe the evolution of spin states of wave propagation in the metasurface. Both the Berry curvature and the Pancharatnam-Berry phase on the hybrid-order Poincare sphere are demonstrated to be proportional to the variation of total angular momentum. Based on the spin-dependent property of Pancharatnam-Berry phase, we find that the photonic spin Hall effect can be observed when breaking the rotational symmetry of metasurfaces. Moreover, we show that the dielectric metasurfaces can provide great flexibility in the design of novel spin-photonic devices such as spin filter and spin-dependent beam splitter.
Developing a temperature sensitive tool for studying spin dissipation
Wickey, Kurtis Jon
Measuring the thermodynamic properties of nanoscale structures is becoming increasingly important as heterostructures and devices shrink in size. For example, recent discoveries of spin thermal effects such as spin Seebeck and spin Peltier show that thermal gradients can manipulate spin systems and vice versa. However, the relevant interactions occur within a spin diffusion length of a spin active interface, making study of these spin thermal effects challenging. In addition, recent ferromagnetic resonance studies of spatially confined nanomagnets have shown unique magnon modes in arrays and lines which may give rise to unique magnon-phonon interactions. In this case, the small volume of magnetic material presents a challenge to measurement and as a result the bulk of the work is done on arrays with measurements of the magnetization of individual particles possible through various microscopies but limited access to thermal properties. As a result, tools capable of measuring the thermal properties of nanoscale structures are required to fully explore this emerging science. One approach to addressing this challenge is the use of microscale suspended platforms that maximize their sensitivity to these spin thermal interactions through thermal isolation from their surroundings. Combining this thermal decoupling with sensitive thermometry allows for the measurement of nanojoule heat accumulations, such as those resulting from the small heat flows associated with spin transport and spin relaxation. As these heat flows may manifest themselves in a variety of spin-thermal effects, the development of measurement platforms that can be tailored to optimize their sensitivity to specific thermal measurements is essential. To address these needs, I have fabricated thermally isolated platforms using a unique focused ion beam (FIB) machining that allow for flexible geometries as well as a wide choice of material systems. The thermal characteristics of these platforms were
Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling.
Caetano, R A
2016-01-01
The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices. PMID:27009836
Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction
ortiz pauyac, christian
2016-06-19
In the present thesis we introduce the reader to the ﬁeld of spintronics and explore new phenomena, such as spin transfer torques, spin ﬁltering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin ﬁltering. In Chap. 3 we discuss the Rashba torque in ferromagnetic ﬁlms, and in Chap. 4 we study spin Hall eﬀect and spin swapping in ferromagnetic ﬁlms, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.
Electrical detection of spin transport in Si two-dimensional electron gas systems
Chang, Li-Te; Fischer, Inga Anita; Tang, Jianshi; Wang, Chiu-Yen; Yu, Guoqiang; Fan, Yabin; Murata, Koichi; Nie, Tianxiao; Oehme, Michael; Schulze, Jörg; Wang, Kang L.
2016-09-01
Spin transport in a semiconductor-based two-dimensional electron gas (2DEG) system has been attractive in spintronics for more than ten years. The inherent advantages of high-mobility channel and enhanced spin-orbital interaction promise a long spin diffusion length and efficient spin manipulation, which are essential for the application of spintronics devices. However, the difficulty of making high-quality ferromagnetic (FM) contacts to the buried 2DEG channel in the heterostructure systems limits the potential developments in functional devices. In this paper, we experimentally demonstrate electrical detection of spin transport in a high-mobility 2DEG system using FM Mn-germanosilicide (Mn(Si0.7Ge0.3)x) end contacts, which is the first report of spin injection and detection in a 2DEG confined in a Si/SiGe modulation doped quantum well structure (MODQW). The extracted spin diffusion length and lifetime are l sf = 4.5 μm and {τ }{{s}}=16 {{ns}} at 1.9 K respectively. Our results provide a promising approach for spin injection into 2DEG system in the Si-based MODQW, which may lead to innovative spintronic applications such as spin-based transistor, logic, and memory devices.
Effect of the Pauli principle on photoelectron spin transport in p+ GaAs
Cadiz, F.; Paget, D.; Rowe, A. C. H.; Amand, T.; Barate, P.; Arscott, S.
2015-04-01
In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly focused light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about 2 μ m from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photoelectron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and band-gap renormalization are negligible due to electrostatic screening by the hole gas.
Energy Technology Data Exchange (ETDEWEB)
Adelnia, Fatemeh; Lascialfari, Alessandro [Dipartimento di Fisica, Università degli Studi di Milano and INSTM, Milano (Italy); Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, Pavia (Italy); Mariani, Manuel [Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna (Italy); Ammannato, Luca; Caneschi, Andrea; Rovai, Donella [Dipartimento di Chimica, Università degli Studi di Firenze and INSTM, Firenze (Italy); Winpenny, Richard; Timco, Grigore [School of Chemistry, The University of Manchester, Manchester (United Kingdom); Corti, Maurizio, E-mail: maurizio.corti@unipv.it; Borsa, Ferdinando [Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, Pavia (Italy)
2015-05-07
We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.
Diffusion Weighted and Trace Images
Directory of Open Access Journals (Sweden)
Helen Nayeri
2009-01-01
Full Text Available "nThe signal intensity in MRI depends on the proton density, T1, T2, and T2* relaxation processes of any ensemble of the spins within each imaging element. Another important contrast mechanism in MRI is signal loss caused by proton dephasing in the presence of coherent and incoherent flow. Diffusion refers to the dispersion of molecules from a region of high concentration to one of low concentration by random molecular or “Brownian” motion. "nDWI is based on the microscopic movement (Brownian motion of water molecules. The motion of water molecules, under the influence of diffusion-sensitizing gradient pulses, causes irreversible signal attenuation (hypointensity on DWI. In restricted diffusion (like acute infarction the signal attenuation is decreased (hyperintensity on DWI. "nIn biological tissues, water diffusion is not truly random. Structural barriers such as membranes and cellular elements, as well as chemical interactions, restrict Brownian motion in 3-D space. Additionally, disturbances associated with tissue perfusion and respiration can alter the biological environment. So it is termed “apparent” because the measured value does not indicate pure diffusion, but reflects capillary perfusion and other processes. ADC (Apparent Diffusion Coefficient maps are typically created by combining at least two DWIs that are differently sensitized to diffusion (different b-values but which remain identical with respect to the other imaging parameters (TR and TE. Diffusion-weighted images are a combination of diffusion information and T2 signal intensity. In order to avoid the hyperintensity effect of T2 signal intensity (T2 shine-through, DW images should be compared with ADC images. ADC maps demonstrate contrast based purely on diffusion differences. "nThe apparent diffusion in tissue is slowed if the protons are “hindered” or slowed in their random motion by the presence of cell membranes, walls, and macromolecules but are not
Zhang, Wenxu; Peng, Bin; Han, Fangbin; Wang, Qiuru; Soh, Wee Tee; Ong, C. K.; Zhang, WanLi
2015-01-01
We develop a method for universally resolving the important issue of separating the inverse spin Hall effect (ISHE) from spin rectification effect (SRE) signal. This method is based on the consideration that the two effects depend on the spin injection direction: The ISHE is an odd function of the spin injection direction while the SRE is independent on it. Thus, inversion of the spin injection direction changes the ISHE voltage signal, while SRE voltage remains. It applies generally to analy...
Direct X-Ray Imaging of Transient Spin Accumulation near a Ferromagnet/Nonmagnet Interface
Chen, Zhao; Kukreja, Roopali; Bonetti, Stefano; Backes, Dirk; Kent, Andrew; Katine, Jordan; Durr, Hermann; Ohldag, Hendrik; Stohr, Joachim
2015-03-01
The physics of spin transport across a ferromagnet/nonmagnet interface is not well understood, even though such interfaces are common in spintronic devices. We use time-resolved x-ray spectro-microscopy to directly image transient spin accumulation in a Cu film caused by an injected spin current from an adjacent Co film. The measurement uses element-specific, circularly polarized x-rays detected via a scanning transmission x-ray microscope (STXM) in conjunction with 1.28MHz temporal modulation for remarkably increased x-ray sensitivity to spin signals. The transient moments per atom within the spin diffusion length from the interface were measured to be 8 x 10-5μB per Cu atom and 1.5 x 10-4μB per Co atom. The transient spin signal in Cu is found to be confined to states at the Fermi level, as expected, but we also observe a second peak of the same spin polarization in the spin accumulation signal that is 0.7eV higher than Fermi. The transient moments in the 28nm thick Cu layer exhibit the same spin sign as both the hybridization-induced static spins in Cu at the Cu/Co interface and the spins in the Co film. In contrast, the transient moments in the Co layer have the opposite sign, consistent with magnetization depleting from the Co polarizing layer.
H I spin temperature in the Fermi-LAT era
Johannesson, Gudlaugur; Digel, Seth
2010-01-01
The diffuse high-energy gamma-ray emission of the Milky Way arises from interactions of cosmic-rays (CRs) with interstellar gas and radiation field in the Galaxy. The neutral hydrogen (H I) gas component is by far the most massive and broadly distributed component of the interstellar medium. Using the 21-cm emission line from the hyperfine structure transition of atomic hydrogen it is possible to determine the column density of H I if the spin temperature (Ts) of the emitting gas is known. Studies of diffuse gamma-ray emission have generally relied on the assumption of a fixed, constant spin temperature for all H I in the Milky Way. Unfortunately, observations of H I in absorption against bright background sources has shown it to vary greatly with location in the Milky Way. We will discuss methods for better handling of spin temperatures for Galactic diffuse emission modeling using the Fermi-LAT data and direct observation of the spin temperature using H I absorption.
Measurements of nuclear spin dynamics by spin-noise spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); Kavokin, K. V.; Glazov, M. M. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); Ioffe Institute, Russian Academy of Sciences, 26 Polytechnicheskaya, St.-Petersburg 194021 (Russian Federation); Vladimirova, M.; Scalbert, D.; Cronenberger, S. [Laboratoire Charles Coulomb UMR 5221 CNRS/Université de Montpellier, Place Eugene Bataillon, 34095 Montpellier Cedex 05 (France); Kavokin, A. V. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); School of Physics and Astronomy, University of Southampton, SO17 1NJ Southampton (United Kingdom); Lemaître, A.; Bloch, J. [Laboratoire de Photonique et de Nanostructures, UPR CNRS, Route de Nozay, 91460 Marcoussis (France)
2015-06-15
We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.
Amplification of Spin Waves by Thermal Spin-Transfer Torque
Padrón-Hernández, E.; Azevedo, A.; Rezende, S. M.
2011-11-01
We observe amplification of spin-wave packets propagating along a film of single-crystal yttrium iron garnet subject to a transverse temperature gradient. The spin waves are excited and detected with standard techniques used in magnetostatic microwave delay lines in the 1-2 GHz frequency range. The amplification is attributed to the action of a thermal spin-transfer torque acting on the magnetization that opposes the relaxation and which is created by spin currents generated through the spin-Seebeck effect. The experimental data are interpreted with a spin-wave model that gives an amplification gain in very good agreement with the data.
Spin transport with dispersive traps: Narrowing of the Hanle curve
Roundy, R. C.; Raikh, M. E.
2014-12-01
We study theoretically the spin transport in a device in which the active layer is an organic film with numerous deep and widely dispersed in energy in-gap levels serving as traps. A carrier, diffusing between a magnetized injector and detector, spends a considerable portion of time on the traps. This feature of transport does not affect the giant magnetoresistance, which is sensitive only to the mutual orientation of magnetizations of the injector and detector. By contrast, the presence of traps strongly affects the sensitivity of the spin transport to an external magnetic field perpendicular to the magnetizations of the electrodes (the Hanle effect). Namely, the Hanle curve narrows dramatically and develops a flat background. The origin of such a narrowing is that the spin precession takes place during the entire time of the carrier motion between the electrodes, while the spin relaxation takes place only during diffusive motion between the subsequent traps. If the resulting width of the Hanle curve is smaller than the measurement resolution, observation of the Hanle peak becomes impossible. This would explain why the Hanle effect is missing in experiments on organic spin valves, where the giant magnetoresistance is unambiguously detected.
International Nuclear Information System (INIS)
We review recent studies of the shot noise of spin-polarized charge currents and pure spin currents in multiterminal semiconductor nanostructures, while focusing on the effects brought by the intrinsic Rashba spin–orbit (SO) coupling and/or extrinsic SO scattering off impurities in two-dimensional electron gas (2DEG) based devices. By generalizing the scattering theory of quantum shot noise to include the full spin-density matrix of electrons injected from a spin-filtering electrode, we show how decoherence and dephasing in the course of spin precession can lead to the substantial enhancement of the Fano factor (noise-to-current ratio) of spin-polarized charge currents. These processes are suppressed by decreasing the width of the diffusive Rashba wire, so that purely electrical measurement of the shot noise in a ferromagnet|SO-coupled-diffusive-wire|paramagnet setup can quantify the degree of quantum coherence of transported spin through a remarkable one-to-one correspondence between the purity of the spin state and the Fano factor. In four-terminal SO-coupled nanostructures, injection of unpolarized charge current through the longitudinal leads is responsible not only for the pure spin Hall current in the transverse leads, but also for nonequilibrium random time-dependent current fluctuations. The analysis of the shot noise of transverse pure spin Hall current and zero charge current, or transverse spin current and non-zero charge Hall current, driven by unpolarized or spin-polarized injected longitudinal charge current, respectively, reveals a unique experimental tool to differentiate between the intrinsic Rashba and extrinsic SO mechanisms underlying the spin Hall effect in 2DEG devices. When the intrinsic mechanisms responsible for spin precession start to dominate the spin Hall effect, they also enhance the shot noise of transverse spin and charge transport in multiterminal geometries. Finally, we discuss the shot noise of transverse spin and zero charge
Salberger, Olof
2016-01-01
We introduce a new model of interacting spin 1/2. It describes interaction of three nearest neighbors. The Hamiltonian can be expressed in terms of Fredkin gates. The Fredkin gate (also known as the CSWAP gate) is a computational circuit suitable for reversible computing. Our construction generalizes the work of Ramis Movassagh and Peter Shor. Our model can be solved by means of Catalan combinatorics in the form of random walks on the upper half of a square lattice [Dyck walks]. Each Dyck path can be mapped to a wave function of the spins. The ground state is an equally weighted superposition of Dyck walks [instead of Motzkin walks]. We can also express it as a matrix product state. We further construct the model of interacting spins 3/2 and greater half-integer spins. The models with higher spins require coloring of Dyck walks. We construct SU(k) symmetric model [here k is the number of colors]. The leading term of the entanglement entropy is then proportional to the square root of the length of the lattice ...
Takahashi, R.; Matsuo, M.; Ono, M.; Harii, K.; Chudo, H.; Okayasu, S.; Ieda, J.; Takahashi, S.; Maekawa, S.; Saitoh, E.
2016-01-01
Magnetohydrodynamic generation is the conversion of fluid kinetic energy into electricity. Such conversion, which has been applied to various types of electric power generation, is driven by the Lorentz force acting on charged particles and thus a magnetic field is necessary. On the other hand, recent studies of spintronics have revealed the similarity between the function of a magnetic field and that of spin-orbit interactions in condensed matter. This suggests the existence of an undiscovered route to realize the conversion of fluid dynamics into electricity without using magnetic fields. Here we show electric voltage generation from fluid dynamics free from magnetic fields; we excited liquid-metal flows in a narrow channel and observed longitudinal voltage generation in the liquid. This voltage has nothing to do with electrification or thermoelectric effects, but turned out to follow a universal scaling rule based on a spin-mediated scenario. The result shows that the observed voltage is caused by spin-current generation from a fluid motion: spin hydrodynamic generation. The observed phenomenon allows us to make mechanical spin-current and electric generators, opening a door to fluid spintronics.
Hui, Zi; Tang, Xiaoyue; Li, Wei; Greneche, Jean-Marc; Wang, Qiuping A.
2015-04-01
In this work, we study the problem of diffusing a product (idea, opinion, disease etc.) among agents on spatial network. The network is constructed by random addition of nodes on the planar. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power of α. The diffusion rate between two connected nodes is inversely proportional to their spatial distance to the power of β as well. Inspired from the Fick's first law, we introduce the diffusion coefficient to measure the diffusion ability of the spatial network. Using both theoretical analysis and Monte Carlo simulation, we get the fact that the diffusion coefficient always decreases with the increasing of parameter α and β, and the diffusion sub-coefficient follows the power-law of the spatial distance with exponent equals to -α-β+2. Since both short-range diffusion and long-range diffusion exist, we use anomalous diffusion method in diffusion process. We get the fact that the slope index δ in anomalous diffusion is always smaller that 1. The diffusion process in our model is sub-diffusion.
Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures
Ortiz Pauyac, Christian
2013-06-26
In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.
Spin- and valley-polarized transport in a monolayer of MoS2
Krstajić, P. M.; Vasilopoulos, P.; Tahir, M.
2016-08-01
We investigate dc and ac transport in a monolayer of MoS2 in the presence of an effective mass asymmetry, a momentum-dependent term, and an out-of plane or in-plane Zeeman term. Analytical results are presented for both dc and ac conductivities in the framework of linear response theory. We show that the spin-Hall conductivity exhibits a strong dependence on the strength of the spin-orbit interaction while both spin- and valley-Hall conductivities show a very weak dependence on the temperature. The sum of the well separated spin-up and spin-down components of the diffusive dc longitudinal conductivity is linear in the electron concentration though the Fermi level is a nonmonotonic function of it. Further, we evaluate the power absorption spectrum and assess its dependence on the spin and valley degrees of freedom as well as on the scattering which is essential at low frequencies.
Tuning carrier mobility without spin transport degrading in copper-phthalocyanine
Energy Technology Data Exchange (ETDEWEB)
Jiang, S. W.; Wang, P.; Chen, B. B.; Zhou, Y. [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing 210093 (China); Ding, H. F., E-mail: hfding@nju.edu.cn, E-mail: dwu@nju.edu.cn; Wu, D., E-mail: hfding@nju.edu.cn, E-mail: dwu@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)
2015-07-27
We demonstrate more than one order of magnitude of carrier mobility tuning for the copper-phthalocyanine (CuPc) without spin transport degrading in organic spin valve devices. Depending on the preparation conditions, organic spin valves with the CuPc film mobility of 5.78 × 10{sup −3} and 1.11 × 10{sup −4} cm{sup 2}/V s are obtained for polycrystalline and amorphous CuPc, respectively. Strikingly, the spin diffusion lengths are almost the same regardless of their mobilities that are ∼50 times different, which is in sharp contrast with previous prediction. These findings directly support that the spin relaxation in CuPc is dominated by the spin-orbit coupling.
Spin Structures in Magnetic Nanoparticles
DEFF Research Database (Denmark)
Mørup, Steen; Brok, Erik; Frandsen, Cathrine
2013-01-01
Spin structures in nanoparticles of ferrimagnetic materials may deviate locally in a nontrivial way from ideal collinear spin structures. For instance, magnetic frustration due to the reduced numbers of magnetic neighbors at the particle surface or around defects in the interior can lead to spin...... canting and hence a reduced magnetization. Moreover, relaxation between almost degenerate canted spin states can lead to anomalous temperature dependences of the magnetization at low temperatures. In ensembles of nanoparticles, interparticle exchange interactions can also result in spin reorientation....... Here, we give a short review of anomalous spin structures in nanoparticles....
The evolution of misaligned accretion discs and spinning black holes
LODATO G; Pringle, J. E.
2006-01-01
In this paper we consider the process of alignment of a spinning black hole and a surrounding misaligned accretion disc. We use a simplified set of equations, that describe the evolution of the system in the case where the propagation of warping disturbances in the accretion disc occurs diffusively, a situation likely to be common in the thin discs in Active Galactic Nuclei (AGN). We also allow the direction of the hole spin to move under the action of the disc torques. In such a way, the evo...
Spin Response and Neutrino Emissivity of Dense Neutron Matter
Shen, G.; Gandolfi, S.; S. Reddy; Carlson, J.
2012-01-01
We study the spin response of cold dense neutron matter in the limit of zero momentum transfer, and show that the frequency dependence of the long-wavelength spin response is well constrained by sum-rules and the asymptotic behavior of the two-particle response at high frequency. The sum-rules are calculated using Auxiliary Field Diffusion Monte Carlo technique and the high frequency two-particle response is calculated for several nucleon-nucleon potentials. At nuclear saturation density, the...
Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization.
Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva
2015-09-01
study also shows the complexity of the MAS-DNP process and therefore the necessity to rely on numerical simulations for understanding parametric dependencies of the enhancements. Finally an extension of the spin system up to five spins allowed us to probe the first steps of the transfer of polarization from the nuclei coupled to the electrons to further away nuclei, demonstrating a decrease in the spin-diffusion barrier under MAS conditions. PMID:26232770
... this page: //medlineplus.gov/ency/article/003854.htm Lung diffusion testing To use the sharing features on this page, please enable JavaScript. Lung diffusion testing measures how well the lungs exchange ...
Fermi spin current contribution in spin wave spectrum of spin-1/2 fermions
Andreev, Pavel; Kuzmenkov, Leonid
2016-05-01
General theory predicts the presence of the thermal part of the spin current in the spin evolution equation for bosons and fermions. For bosons in Bose-Einstein condensate state, it is equal to zero. However, for degenerate fermions it is non zero and it can give a considerable contribution since it describes the Pauli blocking. In this work, we consider spin-1/2 partially polarized fermions. We derive an equation of state for the thermal part of the spin current of degenerate fermions and call it Fermi spin current. We present the spin evolution equation with the Fermi spin current as a part of applied hydrodynamic model. We consider spectrum of collective excitation and describe contribution of the Fermi spin current in the spin wave spectrum. The work of P.A. was supported by the Russian Foundation for Basic Research (Grant No. 16-32-00886) and the Dynasty foundation.
Spin filter and spin valve in ferromagnetic graphene
Song, Yu; Dai, Gang
2015-06-01
We propose and demonstrate that a EuO-induced and top-gated graphene ferromagnetic junction can be simultaneously operated as a spin filter and a spin valve. We attribute such a remarkable result to a coexistence of a half-metal band and a common energy gap for opposite spins in ferromagnetic graphene. We show that both the spin filter and the spin valve can be effectively controlled by a back gate voltage, and they survive for practical metal contacts and finite temperature. Specifically, larger single spin currents and on-state currents can be reached with contacts with work functions similar to graphene, and the spin filter can operate at higher temperature than the spin valve.
Spin rectification induced by spin Hall magnetoresistance at room temperature
Wang, P.; Jiang, S. W.; Luan, Z. Z.; Zhou, L. F.; Ding, H. F.; Zhou, Y.; Tao, X. D.; Wu, D.
2016-09-01
We have experimentally and theoretically investigated the dc voltage generation in the heterostructure of Pt and yttrium iron garnet under the ferromagnetic resonance. Besides a symmetric Lorenz line shape dc voltage, an antisymmetric Lorenz line shape dc voltage is observed in field scan, which can solely originate from the spin rectification effect due to the spin Hall magnetoresistance. The angular dependence of the dc voltage is theoretically analyzed by taking into account both the spin pumping and the spin rectification effects. We find that the experimental results are in excellent agreement with the theoretical model, further identifying the spin Hall magnetoresistance origin of the spin rectification effect. Moreover, the spin pumping and the spin rectification effects are quantitatively separated by their different angular dependence at particular experimental geometry.
Quantum spin transistor with a Heisenberg spin chain
Marchukov, O. V.; Volosniev, A. G.; Valiente, M.; Petrosyan, D.; Zinner, N. T.
2016-10-01
Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements.
Rackham, Neil
1995-01-01
True or false? In selling high-value products or services: "closing" increases your chance of success; it is essential to describe the benefits of your product or service to the customer; objection handling is an important skill; and open questions are more effective than closed questions. All false, says Neil Rackham. He and his team studied more than 35,000 sales calls made by 10,000 sales people in 23 countries over 12 years. Their findings revealed that many of the methods developed for selling low-value goods just don't work for major sales. Rackham went on to introduce his SPIN-selling method, where SPIN describes the whole selling process - Situation questions, Problem questions, Implication questions, Need-payoff questions. SPIN-selling provides you with a set of simple and practical techniques which have been tried in many of today's leading companies with dramatic improvements to their sales performance.
Miller, Jan D; Hupka, Jan; Aranowski, Robert
2012-11-20
A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.
Contucci, Pierluigi
2013-01-01
Presenting and developing the theory of spin glasses as a prototype for complex systems, this book is a rigorous and up-to-date introduction to their properties. The book combines a mathematical description with a physical insight of spin glass models. Topics covered include the physical origins of those models and their treatment with replica theory; mathematical properties like correlation inequalities and their use in the thermodynamic limit theory; main exact solutions of the mean field models and their probabilistic structures; and the theory of the structural properties of the spin glass phase such as stochastic stability and the overlap identities. Finally, a detailed account is given of the recent numerical simulation results and properties, including overlap equivalence, ultrametricity and decay of correlations. The book is ideal for mathematical physicists and probabilists working in disordered systems.
Alday, Luis F
2013-01-01
We analyze the properly normalized three-point correlator of two protected scalar operators and one higher spin twist-two operator in N=4 super Yang-Mills, in the limit of large spin j. The relevant structure constant can be extracted from the OPE of the four-point correlator of protected scalar operators. We show that crossing symmetry of the four point correlator plus a judicious guess for the perturbative structure of the three-point correlator, allow to make a prediction for the structure constant at all loops in perturbation theory, up to terms that remain finite as the spin becomes large. Furthermore, the expression for the structure constant allows to propose an expression for the all loops four-point correlator G(u,v), in the limit u,v -> 0. Our predictions are in perfect agreement with the large j expansion of results available in the literature.
Brzoska, A. M.; Lenz, F.; Negele, J. W.; Thies, M.
2004-01-01
A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops i...
Ganichev, Sergey D.; Bel'Kov, Vasily V.; Tarasenko, Sergey A.; Danilov, Sergey N.; Giglberger, Stephan; Hoffmann, Christoph; Ivchenko, Eougenious L.; Weiss, Dieter; Wegscheider, Werner; Gerl, Christian; Schuh, Dieter; Stahl, Joachim; de Boeck, Jo; Borghs, Gustaaf; Prettl, Wilhelm
2006-09-01
The generation, manipulation and detection of spin-polarized electrons in low-dimensional semiconductors are at the heart of spintronics. Pure spin currents, that is, fluxes of magnetization without charge current, are quite attractive in this respect. A paradigmatic example is the spin Hall effect, where an electrical current drives a transverse spin current and causes a non-equilibrium spin accumulation observed near the sample boundary. Here we provide evidence for an another effect causing spin currents which is fundamentally different from the spin Hall effect. In contrast to the spin Hall effect, it does not require an electric current to flow: without bias the spin separation is achieved by spin-dependent scattering of electrons in media with suitable symmetry. We show, by free-carrier absorption of terahertz (THz) radiation, that spin currents flow in a wide range of temperatures. Moreover, the experimental results provide evidence that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy-relaxation processes.
Spin polarization of the quantum spin Hall edge states
Brüne, Christoph; Roth, Andreas; Buhmann, Hartmut; Hankiewicz, Ewelina M.; Molenkamp, Laurens W.; Maciejko, Joseph; Qi, Xiao-Liang; Zhang, Shou-Cheng
2011-01-01
While the helical character of the edge channels responsible for charge transport in the quantum spin Hall regime of a two-dimensional topological insulator is by now well established, an experimental confirmation that the transport in the edge channels is spin-polarized is still outstanding. We report experiments on nanostructures fabricated from HgTe quantum wells with an inverted band structure, in which a split gate technique allows us to combine both quantum spin Hall and metallic spin H...
Spin Charge Separation in the Quantum Spin Hall State
Qi, Xiao-Liang; Zhang, Shou-Cheng
2007-01-01
The quantum spin Hall state is a topologically non-trivial insulator state protected by the time reversal symmetry. We show that such a state always leads to spin-charge separation in the presence of a $\\pi$ flux. Our result is generally valid for any interacting system. We present a proposal to experimentally observe the phenomenon of spin-charge separation in the recently discovered quantum spin Hall system.
Spin Charge Separation in the Quantum Spin Hall State
Energy Technology Data Exchange (ETDEWEB)
Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-19
The quantum spin Hall state is a topologically non-trivial insulator state protected by the time reversal symmetry. We show that such a state always leads to spin-charge separation in the presence of a {pi} flux. Our result is generally valid for any interacting system. We present a proposal to experimentally observe the phenomenon of spin-charge separation in the recently discovered quantum spin Hall system.
Spin transfer torques in nonlocal lateral spin valve
Xu, Yuan; Xia, Ke; Ma, Zhongshui
2008-01-01
We report a theoretical study on the spin and electron transport in the nonlocal lateral spin valve with non-collinear magnetic configuration. The nonlocal magnetoresistance, defined as the voltage difference on the detection lead over the injected current, is derived analytically. The spin transfer torques on the detection lead are calculated. It is found that spin transfer torques are symmetrical for parallel and antiparallel magnetic configurations, which is different from that in conventi...
Electron-spin dynamics induced by photon spins
Ahrens, S.; Bauke, H.; Keitel, C.; Grobe, R.
2014-01-01
Strong rotating magnetic fields may cause a precession of the electron's spin around the rotation axis of the magnetic field. The superposition of two counterpropagating laser beams with circular polarization and opposite helicity features such a rotating magnetic field component but also carries spin. The laser's spin density, that can be expressed in terms of the lase's electromagnetic fields and potentials, couples to the electron's spin via a relativistic correction to the Pauli equation....
Energy Technology Data Exchange (ETDEWEB)
Chao, Alexander W.; /SLAC; Courant, Ernest D.; /Brookhaven
2006-12-01
As a polarized beam is accelerated through a depolarization resonance, its polarization is reduced by a well-defined calculable reduction factor. When the beam subsequently crosses a second resonance, the final beam polarization is considered to be reduced by the product of the two reduction factors corresponding to the two crossings, each calculated independently of the other. This is a good approximation when the spread of spin precession frequency {Delta}{nu}{sub spin} of the beam (particularly due to its energy spread) is sufficiently large that the spin precession phases of individual particles smear out completely during the time {tau} between the two crossings. This approximate picture, however, ignores two spin dynamics effects: an interference effect and a spin echo effect. This paper is to address these two effects. The interference effect occurs when {Delta}{nu}{sub spin} is too small, or when {tau} is too short, to complete the smearing process. In this case, the two resonance crossings interfere with each other, and the final polarization exhibits constructive or destructive patterns depending on the exact value of {tau}. Typically, the beam's energy spread is large and this interference effect does not occur. To study this effect, therefore, it is necessary to reduce the beam energy spread and to consider two resonance crossings very close to each other. The other mechanism, also due to the interplay between two resonance crossings, is spin echo. It turns out that even when the precession phases appear to be completely smeared between the two crossings, there will still be a sudden and short-lived echo signal of beam polarization at a time {tau} after the second crossing; the magnitude of which can be as large as 57%. This echo signal exists even when the beam has a sizable energy spread and when {tau} is very large, and could be a sensitive (albeit challenging) way to experimentally test the intricate spin dynamics in a synchrotron. After giving
2008-01-01
This book presents recent scientific achievements in the investigation of magnetization dynamics in confined magnetic systems. Introduced by Bloch as plane waves of magnetization in unconfined ferromagnets, spin waves currently play an important role in the description of very small magnetic systems ranging from microelements, which form the basis of magnetic sensors, to magnetic nano-contacts. The spin wave confinement effect was experimentally discovered in the 1990s in permalloy microstripes. The diversity of systems where this effect is observed has been steadily growing since then, and
Diffusion of uranium hexafluoride
Winkelmann, J.
This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of uranium hexafluoride
Coherent spin mixing dynamics in thermal $^{87}$Rb spin-1 and spin-2 gases
He, Xiaodong; Li, Xiaoke; Wang, Fudong; Xu, Zhifang; Wang, Dajun
2015-01-01
We study the non-equilibrium coherent spin mixing dynamics in ferromagnetic spin-1 and antiferromagnetic spin-2 thermal gases of ultracold $^{87}$Rb atoms. Long lasting spin population oscillations with magnetic field dependent resonances are observed in both cases. Our observations are well reproduced by Boltzmann equations of the Wigner distribution function. Compared to the equation of motion of spinor Bose-Einstein condensates, the only difference here is a factor of two increase in the spin-dependent interaction, which is confirmed directly in the spin-2 case by measuring the relation between the oscillation amplitude and the sample's density.
Attenuation characteristics of spin pumping signal due to travelling spin waves
Mukherjee, Sankha Subhra; Deorani, Praveen; Kwon, Jae Hyun; Yang, Hyunsoo
2012-01-01
The authors have investigated the contribution of the surface spin waves to spin pumping. A Pt/NiFe bilayer has been used for measuring spin waves and spin pumping signals simultaneously. The theoretical framework of spin pumping resulting from ferromagnetic resonance has been extended to incorporate spin pumping due to spin waves. Equations for the effective area of spin pumping due to spin waves have been derived. The amplitude of the spin pumping signal resulting from travelling waves is s...
Transverse Spin Physics: Recent Developments
Yuan, Feng
2009-01-01
Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics.
Polariton condensates: Electrical spin switching
Liew, T. C. H.
2016-10-01
Ultra-low-power electronic switching of stable exciton-polariton spin states has now been achieved in a semiconductor microcavity. This opens a new route to the integration of spin-based photonics and electronics.
RESPECT: Neutron Resonance Spin-Echo Spectrometer for Extreme Studies
Georgii, Robert; Pfleiderer, Christian; Böni, Peter
2016-01-01
We propose the design of a Resonance SPin-echo spECtrometer for exTreme studies, RESPECT, that is ideally suited for the exploration of non-dispersive processes such as diffusion, crystallization, slow dynamics, tunneling processes, crystal electric field excitations, and spin fluctuations. It is a variant of the conventional neutron spin-echo technique (NSE) by i) replacing the long precession coils by pairs of longitudinal neutron spin-echo coils combined with RF-spin flippers and ii) by stabilizing the neutron polarization with small longitudinal guide fields that can in addition be used as field subtraction coils thus allowing to adjust the field integrals over a range of 8 orders of magnitude. Therefore, the dynamic range of RESPECT can in principle be varied over 8 orders of magnitude in time, if neutrons with the required energy are made available. Similarly as for existing NSE-spectrometers, spin echo times of up to approximately 1 microsecond can be reached if the divergence and the correction elemen...
Spin dynamics of polarons and polaron pairs in a random hyperfine field
Roundy, Robert C.
Spin-dependent recombination of polaron pairs and spin relaxation of a single polaron are the most fundamental processes are responsible for the performance of organic spintronics-based devices such as light-emitting diodes and organic spin valves. In organic materials, with no spin-orbit coupling, both processes are due to random hyperfine fields created by protons neighboring the polaron sites. The essence of spin-dependent recombination is that in order to recombine the pair must be in the singlet state. Hyperfine fields acting on the electron and hole govern the spin-dynamics of localized pairs during the waiting time for recombination. We demonstrate that for certain domain of trapping configurations of hyperfine fields, crossover to the singlet state is quenched. This leads to the blocking of current. The phenomenon of organic magnetoresistance (OMAR) is described by counting the weights of trapping configurations as a function of magnetic field. This explains the universality of the lineshapes of the OMAR curves. In finite samples incomplete averaging over the hyperfine fields gives rise to mesoscopic fluctuations of the current response. We also demonstrate that under the condition of magnetic resonance, new trapping configurations emerge. This leads to nontrivial evolution of current through the sample with microwave power. When discussing spin-relaxation two questions can be asked: (a) How does the local spin polarization decay as a function of distance from the spin-polarized injector? (b) How does the injected spin decay as a function of time after spatial averaging? With regard to (a), we demonstrate that, while decaying exponentially on average, local spin-polarization exhibits giant fluctuations from point to point. Concerning (b), we find that for a spin-carrier which moves diffusively in low dimensions the decay is faster than a simple exponent. The underlying physics for both findings is that in describing spin evolution it is necessary to add up
Proposal for a graphene-based all-spin logic gate
International Nuclear Information System (INIS)
In this work, we present a graphene-based all-spin logic gate (G-ASLG) that integrates the functionalities of perpendicular anisotropy magnetic tunnel junctions (p-MTJs) with spin transport in graphene-channel. It provides an ideal integration of logic and memory. The input and output states are defined as the relative magnetization between free layer and fixed layer of p-MTJs. They can be probed by the tunnel magnetoresistance and controlled by spin transfer torque effect. Using lateral non-local spin valve, the spin information is transmitted by the spin-current interaction through graphene channels. By using a physics-based spin current compact model, the operation of G-ASLG is demonstrated and its performance is analyzed. It allows us to evaluate the influence of parameters, such as spin injection efficiency, spin diffusion length, contact area, the device length, and their interdependence, and to optimize the energy and dynamic performance. Compared to other beyond-CMOS solutions, longer spin information transport length (∼μm), higher data throughput, faster computing speed (∼ns), and lower power consumption (∼μA) can be expected from the G-ASLG
Proposal for a graphene-based all-spin logic gate
Energy Technology Data Exchange (ETDEWEB)
Su, Li; Zhao, Weisheng, E-mail: weisheng.zhao@u-psud.fr [Department of Electrical Engineering, Spintronics Interdisciplinary Center, Beihang University, Beijing 100191 (China); Institut d' Electronique Fondamentale, Univ. Paris-Sud, F-91405 Orsay (France); UMR 8622, CNRS, F-91405 Orsay (France); Zhang, Yue; Querlioz, Damien; Klein, Jacques-Olivier; Dollfus, Philippe; Bournel, Arnaud [Institut d' Electronique Fondamentale, Univ. Paris-Sud, F-91405 Orsay (France); UMR 8622, CNRS, F-91405 Orsay (France); Zhang, Youguang [Department of Electrical Engineering, Spintronics Interdisciplinary Center, Beihang University, Beijing 100191 (China)
2015-02-16
In this work, we present a graphene-based all-spin logic gate (G-ASLG) that integrates the functionalities of perpendicular anisotropy magnetic tunnel junctions (p-MTJs) with spin transport in graphene-channel. It provides an ideal integration of logic and memory. The input and output states are defined as the relative magnetization between free layer and fixed layer of p-MTJs. They can be probed by the tunnel magnetoresistance and controlled by spin transfer torque effect. Using lateral non-local spin valve, the spin information is transmitted by the spin-current interaction through graphene channels. By using a physics-based spin current compact model, the operation of G-ASLG is demonstrated and its performance is analyzed. It allows us to evaluate the influence of parameters, such as spin injection efficiency, spin diffusion length, contact area, the device length, and their interdependence, and to optimize the energy and dynamic performance. Compared to other beyond-CMOS solutions, longer spin information transport length (∼μm), higher data throughput, faster computing speed (∼ns), and lower power consumption (∼μA) can be expected from the G-ASLG.
Proposal for a graphene-based all-spin logic gate
Su, Li; Zhao, Weisheng; Zhang, Yue; Querlioz, Damien; Zhang, Youguang; Klein, Jacques-Olivier; Dollfus, Philippe; Bournel, Arnaud
2015-02-01
In this work, we present a graphene-based all-spin logic gate (G-ASLG) that integrates the functionalities of perpendicular anisotropy magnetic tunnel junctions (p-MTJs) with spin transport in graphene-channel. It provides an ideal integration of logic and memory. The input and output states are defined as the relative magnetization between free layer and fixed layer of p-MTJs. They can be probed by the tunnel magnetoresistance and controlled by spin transfer torque effect. Using lateral non-local spin valve, the spin information is transmitted by the spin-current interaction through graphene channels. By using a physics-based spin current compact model, the operation of G-ASLG is demonstrated and its performance is analyzed. It allows us to evaluate the influence of parameters, such as spin injection efficiency, spin diffusion length, contact area, the device length, and their interdependence, and to optimize the energy and dynamic performance. Compared to other beyond-CMOS solutions, longer spin information transport length (˜μm), higher data throughput, faster computing speed (˜ns), and lower power consumption (˜μA) can be expected from the G-ASLG.
Hamp, James; Dutton, Sian; Mourigal, Martin; Mukherjee, Paromita; Paddison, Joseph; Ong, Harapan; Castelnovo, Claudio
Spin ice materials provide a rare instance of emergent gauge symmetry and fractionalisation in three dimensions: the effective degrees of freedom of the system are emergent magnetic monopoles, and the extensively many `ice rule' ground states are those devoid of monopole excitations. Two-dimensional (kagome) analogues of spin ice have also been shown to display a similarly rich behaviour. In kagome ice however the ground-state `ice rule' condition implies the presence everywhere of magnetic charges. As temperature is lowered, an Ising transition occurs to a charge-ordered state, which can be mapped to a dimer covering of the dual honeycomb lattice. A second transition, of Kosterlitz-Thouless or three-state Potts type, occurs to a spin-ordered state at yet lower temperatures, due to small residual energy differences between charge-ordered states. Inspired by recent experimental capabilities in growing spin ice samples with selective (layered) substitution of non-magnetic ions, in this work we investigate the fate of the two ordering transitions when individual kagome layers are brought together to form a three-dimensional pyrochlore structure coupled by long range dipolar interactions. We also consider the response to substitutional disorder and applied magnetic fields.
Brookhaven: Spin result underlined
International Nuclear Information System (INIS)
A recent experiment looking at violent proton-proton elastic scattering confirms, with high precision, earlier data which puzzled many theorists. Most pictures of strong interactions based on perturbative quark-gluon field theory (Quantum Chromodynamics, QCD) suggested that spin effects should disappear with energy and as the collisions become more violent
Antiferromagnetic spin-orbitronics
Manchon, Aurelien
2015-05-01
Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.
TRANSVERSITY SINGLE SPIN ASYMMETRIES.
Energy Technology Data Exchange (ETDEWEB)
BOER,D.
2001-04-27
The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.
Collins, Robert; Simpson, Frances
2007-01-01
In this article, the authors explore the question, "Does the Moon spin?", and show how the question is investigated. They emphasise the importance of the process by which people work out what they know, by "learning from the inside out." They stress that those involved in science education have to challenge current conceptions and ideas, making…
Nguyen, V.Y.; Ruys, T.C.; Havelund, K.; Majumdar, R.; Palsberg, J.
2008-01-01
This paper discusses a generalised incremental hashing scheme for explicit state model checkers. The hashing scheme has been implemented into the model checker Spin. The incremental hashing scheme works for Spin’s exhaustive and both approximate verification modes: bitstate hashing and hash compacti
Urdampilleta, M; Klyatskaya, S; Cleuziou, J-P; Ruben, M; Wernsdorfer, W
2011-07-01
Magnetic molecules are potential building blocks for the design of spintronic devices. Moreover, molecular materials enable the combination of bottom-up processing techniques, for example with conventional top-down nanofabrication. The development of solid-state spintronic devices based on the giant magnetoresistance, tunnel magnetoresistance and spin-valve effects has revolutionized magnetic memory applications. Recently, a significant improvement of the spin-relaxation time has been observed in organic semiconductor tunnel junctions, single non-magnetic molecules coupled to magnetic electrodes have shown giant magnetoresistance and hybrid devices exploiting the quantum tunnelling properties of single-molecule magnets have been proposed. Herein, we present an original spin-valve device in which a non-magnetic molecular quantum dot, made of a single-walled carbon nanotube contacted with non-magnetic electrodes, is laterally coupled through supramolecular interactions to TbPc(2) single-molecule magnets (Pc=phthalocyanine). Their localized magnetic moments lead to a magnetic field dependence of the electrical transport through the single-walled carbon nanotube, resulting in magnetoresistance ratios up to 300% at temperatures less than 1 K. We thus demonstrate the functionality of a supramolecular spin valve without magnetic leads. Our results open up prospects of new spintronic devices with quantum properties. PMID:21685902
Spin Injection in Indium Arsenide
Directory of Open Access Journals (Sweden)
Mark eJohnson
2015-08-01
Full Text Available In a two dimensional electron system (2DES, coherent spin precession of a ballistic spin polarized current, controlled by the Rashba spin orbit interaction, is a remarkable phenomenon that’s been observed only recently. Datta and Das predicted this precession would manifest as an oscillation in the source-drain conductance of the channel in a spin-injected field effect transistor (Spin FET. The indium arsenide single quantum well materials system has proven to be ideal for experimental confirmation. The 2DES carriers have high mobility, low sheet resistance, and high spin orbit interaction. Techniques for electrical injection and detection of spin polarized carriers were developed over the last two decades. Adapting the proposed Spin FET to the Johnson-Silsbee nonlocal geometry was a key to the first experimental demonstration of gate voltage controlled coherent spin precession. More recently, a new technique measured the oscillation as a function of channel length. This article gives an overview of the experimental phenomenology of the spin injection technique. We then review details of the application of the technique to InAs single quantum well (SQW devices. The effective magnetic field associated with Rashba spin-orbit coupling is described, and a heuristic model of coherent spin precession is presented. The two successful empirical demonstrations of the Datta Das conductance oscillation are then described and discussed.
Spin Transport in Semiconductor heterostructures
Energy Technology Data Exchange (ETDEWEB)
Domnita Catalina Marinescu
2011-02-22
The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.
Mechanical generation of spin current
Directory of Open Access Journals (Sweden)
Mamoru eMatsuo
2015-07-01
Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.
Spin transport in graphene nanostructures
Guimaraes, M. H. D.; van den Berg, J. J.; Vera-Marun, I. J.; Zomer, P. J.; van Wees, B. J.
2014-01-01
Graphene is an interesting material for spintronics, showing long spin relaxation lengths even at room temperature. For future spintronic devices it is important to understand the behavior of the spins and the limitations for spin transport in structures where the dimensions are smaller than the spi
Algebraic spin liquid in an exactly solvable spin model
Energy Technology Data Exchange (ETDEWEB)
Yao, Hong; Zhang, Shou-Cheng; Kivelson, Steven A.; /Stanford U., Phys. Dept.
2010-03-25
We have proposed an exactly solvable quantum spin-3/2 model on a square lattice. Its ground state is a quantum spin liquid with a half integer spin per unit cell. The fermionic excitations are gapless with a linear dispersion, while the topological 'vison' excitations are gapped. Moreover, the massless Dirac fermions are stable. Thus, this model is, to the best of our knowledge, the first exactly solvable model of half-integer spins whose ground state is an 'algebraic spin liquid.'
Inverse Spin Hall Effect Driven by Spin Motive Force
Shibata, Junya; Kohno, Hiroshi
2008-01-01
The spin Hall effect is a phenomenon that an electric field induces a spin Hall current. In this Letter, we examine the inverse effect that, in a ferromagnetic conductor, a charge Hall current is induced by a spin motive force, or a spin-dependent effective ` electric' field ${\\bm E}_{\\rm s}$, arising from the time variation of magnetization texture. By considering skew-scattering and side-jump processes due to spin-orbit interaction at impurities, we obtain the Hall current density as $\\sigm...
International Nuclear Information System (INIS)
The author presents first the theoretical frame of the nucleon spin structure study carried out through the deep inelastic scattering of polarised leptons on a polarised target. The interest of the lepton scattering reaction to study the hadronic structure is discussed and the formalism of the inclusive inelastic scattering presented. If the target and the beam are both polarised, the formalism enables to connect the experimentally measured asymmetries to the contribution of quarks to the spin of nucleon. The recent knowledge about the nucleon spin structure is also presented. The Bjorken sum rule is then discussed: it correlates the difference of spin structure between proton and neutron to the neutron lifetime. Then, the author mentions the experimental results of SMC (CERN) and E142, E143 (SLAC). The transition from rough asymmetry to the g sub 1 structure function integral is discussed as well as the main causes of uncertainty. Compared to theoretical data, the measurements confirm the reliability of the Bjorken sum rule. They also confirm the deficit of the quark contribution with respect to the naive unpolarized strange sea model. The possible origins of this discrepancy and the contributions of the current and planned experiments are also discussed. Finally, the author brings up the next major step for nucleon spin studies: the estimation of the gluon contribution. He discusses the experimental knowledge about the polarised gluon distribution function with regard to the multiple existing parameter set. Concerning the experimental determination of this distribution function, outlooks are proposed with respect to feasibility on current experimental facilities. (N.T.)
Thermal creation of a spin current by Seebeck spin tunneling
Jansen, R.; Le Breton, J. C.; Deac, A. M.; Saito, H.; Yuasa, S.
2013-09-01
The thermoelectric analog of spin-polarized tunneling, namely Seebeck spin tunneling, is a recently discovered phenomenon that arises from the spin-dependent Seebeck coefficient of a magnetic tunnel contact. In a tunnel junction with one ferromagnetic electrode and one non-magnetic electrode, a temperature difference between the two electrodes creates a spin current across the contact. Here, the basic principle and the observation of Seebeck spin tunneling are described. It is shown how it can be used to create a spin accumulation in silicon driven by a heat flow across a magnetic tunnel contact, without a charge tunnel current. The sign of the spin current depends on the direction of the heat flow, whereas its magnitude is anisotropic, i.e., dependent on the absolute orientation of the magnetization of the ferromagnet. The connection between Seebeck spin tunneling and the tunnel magneto-Seebeck effect, observed in metal magnetic tunnel junctions, is also clarified. Seebeck spin tunneling may be used to convert waste heat into useful thermal spin currents that aid or replace electrical spin current, and thereby improve the energy efficiency of spintronic devices and technologies.
Spin-Currents and Spin-Pumping Forces for Spintronics
Directory of Open Access Journals (Sweden)
Henri-Jean Drouhin
2011-01-01
Full Text Available A general definition of the Spintronics concept of spin-pumping is proposed as generalized forces conjugated to the spin degrees of freedom in the framework of the theory of mesoscopic non-equilibrium thermodynamics. It is shown that at least three different kinds of spin-pumping forces and associated spin-currents can be defined in the most simple spintronics system: the Ferromagnetic/Non-Ferromagnetic metal interface. Furthermore, the generalized force associated with the ferromagnetic collective variable is also introduced on an equal footing to describe the coexistence of the spin of the conduction electrons (paramagnetic spins attached to s-band electrons and the ferromagnetic-order parameter. The dynamical coupling between these two kinds of magnetic degrees of freedom is presented and interpreted in terms of spin-transfer effects.
Electron-spin dynamics induced by photon spins
Ahrens, Sven; Keitel, Christoph H; Grobe, Rainer
2014-01-01
Strong rotating magnetic fields may cause a precession of the electron's spin around the rotation axis of the magnetic field. The superposition of two counterpropagating laser beams with circular polarization and opposite helicity features such a rotating magnetic field component but also carries spin. The laser's spin density, which can be expressed in terms of the laser's electromagnetic fields and potentials, couples to the electron's spin via a relativistic correction to the Pauli equation. We show that the quantum mechanical interaction of the electron's spin with the laser's rotating magnetic field and with the laser's spin density counteract each other in such a way that a net spin rotation remains with a precession frequency that is much smaller than the frequency one would expect from the rotating magnetic field alone. In particular, the frequency scales differently with the laser's electric field strength depending on if relativistic corrections are taken into account or not. Thus, the relativistic ...
Spin-transfer torque induced spin waves in antiferromagnetic insulators
Daniels, Matthew; Guo, Wei; Stocks, G. Malcolm; Xiao, Di; Xiao, Jiang
2015-03-01
We explore the possibility of exciting spin waves in insulating antiferromagnetic films by injecting spin current at the surface. We analyze both magnetically compensated and uncompensated interfaces. We find that the spin current induced spin-transfer torque can excite spin waves in insulating antiferromagnetic materials and that the chirality of the excited spin wave is determined by the polarization of the injected spin current. Furthermore, the presence of magnetic surface anisotropy can greatly increase the accessibility of these excitations. Supported by NSF EFRI-1433496 (M.W.D), U.S. DOE Office of Basic Energy Sciences, Materials Sciences and Engineering (D.X. & G.M.S.), Major State Basic Research Project of China and National Natural Science Foundation of China (W.G. and J.X.).
State diagram of an orthogonal spin transfer spin valve device
Energy Technology Data Exchange (ETDEWEB)
Ye, Li; Wolf, Georg; Pinna, Daniele; Chaves-O' Flynn, Gabriel D.; Kent, Andrew D. [Department of Physics, New York University, New York, New York 10003 (United States)
2015-05-21
We present the switching characteristics of a spin-transfer device that incorporates a perpendicularly magnetized spin-polarizing layer with an in-plane magnetized free and fixed magnetic layer, known as an orthogonal spin transfer spin valve device. This device shows clear switching between parallel (P) and antiparallel (AP) resistance states and the reverse transition (AP → P) for both current polarities. Further, hysteretic transitions are shown to occur into a state with a resistance intermediate between that of the P and AP states, again for both current polarities. These unusual spin-transfer switching characteristics can be explained within a simple macrospin model that incorporates thermal fluctuations and considers a spin-polarized current that is tilted with respect to the free layer's plane, due to the presence of the spin-transfer torque from the polarizing layer.
Magnon spin transport driven by the magnon chemical potential in a magnetic insulator
Cornelissen, L. J.; Peters, K. J. H.; Bauer, G. E. W.; Duine, R. A.; van Wees, B. J.
2016-07-01
We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position-dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation lengths. Proceeding from a linearized Boltzmann equation, we derive expressions for length scales and transport coefficients. For yttrium iron garnet (YIG) at room temperature we find that long-range transport is dominated by the magnon chemical potential. We compare the model's results with recent experiments on YIG with Pt contacts [L. J. Cornelissen et al., Nat. Phys. 11, 1022 (2015), 10.1038/nphys3465] and extract a magnon spin conductivity of σm=5 ×105 S/m. Our results for the spin Seebeck coefficient in YIG agree with published experiments. We conclude that the magnon chemical potential is an essential ingredient for energy and spin transport in magnetic insulators.
Estimation of bounded and unbounded trajectories in diffusion MRI
Directory of Open Access Journals (Sweden)
Lipeng eNing
2016-03-01
Full Text Available Disentangling the tissue microstructural information from the diffusion magnetic resonance imaging (dMRI measurements is quite important for extracting brain tissue specific measures. The autocorrelation function of diffusing spins is key for understanding the relation between dMRI signals and the acquisition gradient sequences. In this paper, we demonstrate that the autocorrelation of diffusion in restricted or bounded spaces can be well approximated by exponential functions. To this end, we propose to use the multivariate Ornstein-Uhlenbeck (OU process to model the matrix-valued exponential autocorrelation function of three-dimensional diffusion processes with bounded trajectories. We present detailed analysis on the relation between the model parameters and the time-dependent apparent axon radius and provide a general model for dMRI signals from the frequency domain perspective. For our experimental setup, we model the diffusion signal as a mixture of two compartments that correspond to diffusing spins with bounded and unbounded trajectories, and analyze the corpus-callosum in an ex-vivo data set of a monkey brain.
Microporosity of Bicontinuous Polymer Composites: Diffusion of Water and Surfactant
Kuta, K.; Challa, V.; Cheung, M.; Lopina, S.; von Meerwall, E.
2000-10-01
We have used the proton NMR pulsed-gradient spin-echo method to study the self-diffusion of water and surfactant in bicontinuous microcomposites formed with methyl methacrylate and hydroxy ethyl methacrylate, crosslinked with ethylene glycol dimethacrylate, in the presence of water containing 10 wt. percent sodium dodecyl sulfate as surfactant. Measurements were made over the full bicontinuous range of water content, (30 to 96 wt. percent) at 50 deg. C at a diffusion time of 12-15 ms. At spin-echo times greater than a few ms the echo of the glassy open-cell network phase was unobservable. The diffusivity spectrum of the mobile fraction is cleanly separable into two components differing by a factor of at least 30, attributable to water and surfactant. We find that the diffusivity of water increases with increasing water content, but that of the surfactant decreases. Measurements of restricted diffusion (non-adherence to Fick's second law) can reveal the size of the diffusionally accessible pores and its distribution, and their degree of interconnection. Corresponding measurements of time-resolved apparent diffusion are in progress.
Spin injection and spin accumulation in all-metal mesoscopic spin valves
Jedema, FJ; Nijboer, MS; Filip, AT; van Wees, BJ
2003-01-01
We study the electrical injection and detection of spin accumulation in lateral ferromagnetic-metal-nonmagnetic-metal-ferromagnetic-metal (F/N/F) spin valve devices with transparent interfaces. Different ferromagnetic metals, Permalloy (Py), cobalt (Co), and nickel (Ni), are used as electrical spin
RHIC spin flipper commissioning results
Energy Technology Data Exchange (ETDEWEB)
Bai M.; Roser, T.; Dawson, C.; Kewisch, J.; Makdisi, Y.; Oddo, P.; Pai, C.; Pile, P.
2012-05-20
The five AC dipole RHIC spin flipper design in the RHIC Blue ring was first tested during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper. The closure of each ac dipole vertical bump was measured with orbital response as well as spin. The effect of the rotating field on the spin motion by the spin flipper was also confirmed by measuring the suppressed resonance at Q{sub s} = 1 - Q{sub osc}.
Learning networks of academic spin-offs - A spatial perspective
Taheri, Mozhdeh; Geenhuizen, Marina van
2010-01-01
Abstract-The importance of new knowledge in innovative activities of firms and the impact of these activities on economic development of regions have been acknowledged in many studies. In particular, universities and firms that are established on university knowledge, spin-off firms, function as nodes and channels through which new knowledge is diffused into the wider (regional) economy. New knowledge is a strategic resource of competitive advantage for young high-tech firms. Of course, many ...
Spin Physics and Transverse Structure
Mulders, P J
2015-01-01
Spin is a welcome complication in the study of partonic structure that has led to new insights, even if theoretically and experimentally not all dust has settled, in particular on quark flavor dependence and gluon spin. At the same time it opened new questions on angular momentum and effects of transverse structure. In this talk the focus is on the role of the transverse momenta of partons. Like for collinear parton distribution functions (PDFs), we are also in the case of transverse momentum dependent (TMD) PDFs, talking about forward matrix elements. TMD PDFs (or in short TMDs) extend collinear PDFs with only spin-spin correlations to PDFs that include spin-momentum correlations, including also time-reversal-odd (T-odd) correlations, relevant for the description of single spin asymmetries. In this way TMDs open up new ways of studying the spin structure. Their operator structure within QCD, however, is more complex leading to various ways of breaking of universality.
Magnetic correlation, excitation and slow dynamics in concentrated spin-glass alloys
Indian Academy of Sciences (India)
Kiyoichiro Motoya
2004-07-01
Three kinds of neutron scattering experiments have been performed to clarify the role of magnetic clusters on the various properties of re-entrant spin-glasses. The presence of two kinds of spin-wave excitations, the limitations of magnetic phase diagrams and the mechanism of slow dynamics have been discussed based on the results of in-elastic scattering, diffuse scattering and time-resolved small-angle scattering experiments, respectively.
Continuity, the Bloch-Torrey equation, and Diffusion MRI
Hall, Matt G
2016-01-01
The Bloch equation describes the evolution of classical particles tagged with a magnetisation vector in a strong magnetic field and is fundamental to many NMR and MRI contrast methods. The equation can be generalised to include the effects of spin motion by including a spin flux, which typically contains a Fickian diffusive term and/or a coherent velocity term. This form is known as the Bloch-Torrey equation, and is fundamental to MR modalities which are sensitive to spin dynamics such as diffusion MRI. Such modalities have received a great deal of interest in the research literature over the last few years, resulting in a huge range of models and methods. In this work we make make use of a more general Bloch-Torrey equation with a generalised flux term. We show that many commonly employed approaches in Diffusion MRI may be viewed as different choices for the flux terms in this equation. This viewpoint, although obvious theoretically, is not usually emphasised in the diffusion MR literature and points to inte...
Synthesis of carbon-13-labeled tetradecanoic acids.
Sparrow, J T; Patel, K M; Morrisett, J D
1983-07-01
The synthesis of tetradecanoic acid enriched with 13C at carbons 1, 3, or 6 is described. The label at the carbonyl carbon was introduced by treating 1-bromotridecane with K13CN (90% enriched) to form the 13C-labeled nitrile, which upon hydrolysis yielded the desired acid. The [3-13C]tetradecanoic acid was synthesized by alkylation of diethyl sodio-malonate with [1-13C]1-bromododecane; the acid was obtained upon saponification and decarboxylation. The label at the 6 position was introduced by coupling the appropriately labeled alkylcadmium chloride with the half acid chloride methyl ester of the appropriate dioic acid, giving the corresponding oxo fatty acid ester. Formation of the tosylhydrazone of the oxo-ester followed by reduction with sodium cyanoborohydride gave the labeled methyl tetradecanoate which, upon hydrolysis, yielded the desired tetradecanoic acid. All tetradecanoic acids were identical to unlabeled analogs as evaluated by gas-liquid chromatography and infrared or NMR spectroscopy. These labeled fatty acids were used subsequently to prepare the correspondingly labeled diacyl phosphatidylcholines. PMID:6631228
Carbon-13 NMR spectroscopy of biological systems
Beckmann, Nicolau
1995-01-01
This book is intended to provide an in-depth understanding of 13C NMR as a tool in biological research. 13C NMR has provided unique information concerning complex biological systems, from proteins and nucleic acids to animals and humans. The subjects addressed include multidimensional heteronuclear techniques for structural studies of molecules in the liquid and solid states, the investigation of interactions in model membranes, the elucidation of metabolic pathwaysin vitro and in vivo on animals, and noninvasive metabolic studies performed on humans. The book is a unique mix of NMR methods and biological applications which makes it a convenient reference for those interested in research in this interdisciplinary area of physics, chemistry, biology, and medicine.Key Features* An interdisciplinary text with emphasis on both 13C NMR methodology and the relevant biological and biomedical issues* State-of-the-art 13C NMR techniques are described; Whenever possible, their advantages over other approaches are empha...
Kruk, D.; Korpała, A.; Kubica, A.; Meier, R.; Rössler, E. A.; Moscicki, J.
2013-01-01
For nitroxide radicals in solution one can identify three frequency regimes in which 1H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the 1H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854 with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for 14N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to 15N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)], 10.1021/jp980397h). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of 1H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data—1H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of 14N and 15N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in 1H resonance frequency, 10 kHz-20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.
Electron-spin dynamics induced by photon spins
Bauke, Heiko; Ahrens, Sven; Keitel, Christoph H.; Grobe, Rainer
2014-10-01
Strong rotating magnetic fields may cause a precession of the electron's spin around the rotation axis of the magnetic field. The superposition of two counterpropagating laser beams with circular polarization and opposite helicity features such a rotating magnetic field component but also carries spin. The laser's spin density, which can be expressed in terms of the laser's electromagnetic fields and potentials, couples to the electron's spin via a relativistic correction to the Pauli equation. We show that the quantum mechanical interaction of the electron's spin with the laser's rotating magnetic field and with the laser's spin density counteract each other in such a way that a net spin rotation remains with a precession frequency that is much smaller than the frequency one would expect from the rotating magnetic field alone. In particular, the frequency scales differently with the laser's electric field strength depending on whether relativistic corrections are taken into account or not. Thus, the relativistic coupling of the electron's spin to the laser's spin density changes the dynamics not only quantitatively but also qualitatively as compared to the nonrelativistic theory. The electron's spin dynamics are a genuine quantum mechanical relativistic effect.
Spin coating of an evaporating polymer solution
Münch, Andreas
2011-01-01
We consider a mathematical model of spin coating of a single polymer blended in a solvent. The model describes the one-dimensional development of a thin layer of the mixture as the layer thins due to flow created by a balance of viscous forces and centrifugal forces and evaporation of the solvent. In the model both the diffusivity of the solvent in the polymer and the viscosity of the mixture are very rapidly varying functions of the solvent mass fraction. Guided by numerical solutions an asymptotic analysis reveals a number of different possible behaviours of the thinning layer dependent on the nondimensional parameters describing the system. The main practical interest is in controlling the appearance and development of a "skin" on the polymer where the solvent concentration reduces rapidly on the outer surface leaving the bulk of the layer still with high concentrations of solvent. In practice, a fast and uniform drying of the film is required. The critical parameters controlling this behaviour are found to be the ratio of the diffusion to advection time scales ε, the ratio of the evaporation to advection time scales δ and the ratio of the diffusivity of the pure polymer and the initial mixture exp(-1/γ). In particular, our analysis shows that for very small evaporation with δ
Relativistic diffusive transport
Haba, Z.
2009-01-01
We discuss transport equations resulting from relativistic diffusions in the proper time. We show that a solution of the transport equation can be obtained from the solution of the diffusion equation by means of an integration over the proper time. We study the stochastic processes solving the relativistic diffusion equation and the relativistic transport equation. We show that the relativistic transport equation for massive particles in the light cone coordinates and for massless particles i...
Diffusers for holographic stereography
Helseth, L.E.; Singstad, I.
2001-01-01
Holographic diffusers have long been recognized as versatile components with a broad number of applications. In this work we discuss holographic diffusers for projection of laser light from a Liquid Crystal Display(LCD) onto a holographic recording medium. In holographic stereography, projection of the information from a LCD onto a holographic recording medium has traditionally been done by a lens or a ground glass. It is suggested that the holographic diffusers can replace these elements and...
Diffusion of Classical Solitons
Dziarmaga, J.; Zakrzewski, W.
1998-01-01
We study the diffusion and deformation of classical solitons coupled to thermal noise. The diffusion coefficient for kinks in the $\\phi^4$ theory is predicted up to the second order in $kT$. The prediction is verified by numerical simulations. Multiskyrmions in the vector O(3) sigma model are studied within the same formalism. Thermal noise results in a diffusion on the multisoliton collective coordinate space (moduli space). There are entropic forces which tend, for example, to bind pairs of...
Large Spin Perturbation Theory
Alday, Luis F
2016-01-01
We consider conformal field theories around points of large twist degeneracy. Examples of this are theories with weakly broken higher spin symmetry and perturbations around generalised free fields. At the degenerate point we introduce twist conformal blocks. These are eigenfunctions of certain quartic operators and encode the contribution, to a given four-point correlator, of the whole tower of intermediate operators with a given twist. As we perturb around the degenerate point, the twist degeneracy is lifted. In many situations this breaking is controlled by inverse powers of the spin. In such cases the twist conformal blocks can be decomposed into a sequence of functions which we systematically construct. Decomposing the four-point correlator in this basis turns crossing symmetry into an algebraic problem. Our method can be applied to a wide spectrum of conformal field theories in any number of dimensions and at any order in the breaking parameter. As an example, we compute the spectrum of various theories ...
Piegsa, Florian M; Schanzer, Christian
2016-01-01
A novel neutron spin resonance technique is presented based on the well-know neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of $4 \\times 10^{-7}$ can be resolved, corresponding to an energy resolution of better than 3~neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing for energy resolutions in the 10~peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.
Florakis, Ioannis; Tsulaia, Mirian
2014-01-01
We consider the Sp(2n) invariant formulation of higher spin fields on flat and curved backgrounds of constant curvature.In this formulation an infinite number of higher spin fields are packed into single scalar and spinor master fields (hyperfields) propagating on extended spaces, to be called hyperspaces, parametrized by tensorial coordinates.We show that the free field equations on flat and AdS-like hyperspaces are related to each other by a generalized conformal transformation of the scalar and spinor master fields. We compute the four--point functions on a flat hyperspace for both scalar and spinor master fields, thus extending the two-- and three--point function results of arXiv:hep-th/0312244. Then using the generalized conformal transformation we derive two--, three-- and four--point functions on AdS--like hyperspace from the corresponding correlators on the flat hyperspace.
Friedrich, Jan Michael
2006-01-01
Results for the spin structure of the nucleon from the COMPASS data taking periods 2002 to 2004 are presented. The quark contribution to the nucleon spin, following from a QCD fit to the new data, turns out to be significantly larger than it was derived from the previous world data. The new data favour, on the other side, a comparatively small gluon polarisation in the range $x_{g} \\approx$ 0.1. In the data taken with the deuteron target polarised transversely, the related asymmetries are found to be small on the level of accuracy reached so far, indicating a cancellation of the proton and neutron contributions. This is in agreement, for both the Collins and the Sivers asymmetry, with recent theoretical calculations. Also, a step towards the understanding of angular momentum contributions with COMPASS is taken by the evaluation of asymmetries in exclusive vector meson production.
Modeling of the magnetic free energy of self-diffusion in bcc Fe
Sandberg, N.; Chang, Z.; Messina, L.; Olsson, P.; Korzhavyi, P.
2015-11-01
A first-principles based approach to calculating self-diffusion rates in bcc Fe is discussed with particular focus on the magnetic free energy associated with diffusion activation. First, the enthalpies and entropies of vacancy formation and migration in ferromagnetic bcc Fe are calculated from standard density functional theory methods in combination with transition state theory. Next, the shift in diffusion activation energy when going from the ferromagnetic to the paramagnetic state is estimated by averaging over random spin states. Classical and quantum mechanical Monte Carlo simulations within the Heisenberg model are used to study the effect of spin disordering on the vacancy formation and migration free energy. Finally, a quasiempirical model of the magnetic contribution to the diffusion activation free energy is applied in order to connect the current first-principles results to experimental data. The importance of the zero-point magnon energy in modeling of diffusion in bcc Fe is stressed.
Diffusion formalism and applications
Dattagupta, Sushanta
2013-01-01
Within a unifying framework, Diffusion: Formalism and Applications covers both classical and quantum domains, along with numerous applications. The author explores the more than two centuries-old history of diffusion, expertly weaving together a variety of topics from physics, mathematics, chemistry, and biology. The book examines the two distinct paradigms of diffusion-physical and stochastic-introduced by Fourier and Laplace and later unified by Einstein in his groundbreaking work on Brownian motion. The author describes the role of diffusion in probability theory and stochastic calculus and
Immirzi, Giorgio
2016-01-01
I discuss how to impose causality on spin-foam models, separating forward and backward propagation, turning a given triangulation to a 'causal set', and giving asymptotically the exponential of the Regge action, not a cosine. I show the equivalence of the prescriptions which have been proposed to achieve this. Essential to the argument is the closure condition for the 4-simplices, all made of space-like tetrahedra.
Hatton, Peter; Murray, Val; Pilling, Lynn
2010-01-01
Spinning a Yarn is a major outcome of an on going ten-year research project in Manchester. Through the production of a series of site-specific multimedia exhibitions and performances this research focussed on the ecology and evolution of the city of Manchester and its inhabitants. This work innovated new forms of social engagement and encounters for the public, taking narratives of site, work and identity as a central part of the research process as means to generate new experiential and...
Ray, J. R.
1982-01-01
The fundamental variational principle for a perfect fluid in general relativity is extended so that it applies to the metric-torsion Einstein-Cartan theory. Field equations for a perfect fluid in the Einstein-Cartan theory are deduced. In addition, the equations of motion for a fluid with intrinsic spin in general relativity are deduced from a special relativistic variational principle. The theory is a direct extension of the theory of nonspinning fluids in special relativity.
Obukhov, Yuri N.
1993-11-01
Following recent studies of Ford, we suggest - in the framework of general relativity - an inflationary cosmological model with self-interacting spinning matter. A generalization of the standard fluid model is discussed and estimates of the physical parameters of the evolution are given. I would like to thank Professor Friedrich W. Hehl for the careful reading of the manuscript and useful advice. This research was supported by the Alexander von Humboldt Foundation (Bonn).
Myocardial arterial spin labeling
Kober, Frank; Jao, Terrence; Troalen, Thomas; Nayak, Krishna S.
2016-01-01
Arterial spin labeling (ASL) is a cardiovascular magnetic resonance (CMR) technique for mapping regional myocardial blood flow. It does not require any contrast agents, is compatible with stress testing, and can be performed repeatedly or even continuously. ASL-CMR has been performed with great success in small-animals, but sensitivity to date has been poor in large animals and humans and remains an active area of research. This review paper summarizes the development of ASL-CMR techniques, c...
Experimental study of vortex diffusers
Energy Technology Data Exchange (ETDEWEB)
Shakerin, S.; Miller, P.L. [National Renewable Energy Lab., Golden, CO (United States)
1995-11-01
This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.
Napsuciale, M; Ferro-Hernández, Rodolfo; Gómez-Ávila, Selim
2015-01-01
Spin one matter fields are relevant both for the description of hadronic states and as potential extensions of the Standard Model. In this work we present a formalism for the description of massive spin one fields transforming in the $(1,0)\\oplus(0,1)$ representation of the Lorentz group, based on the covariant projection onto parity eigenspaces and Poincar\\'e orbits. The formalism yields a constrained dynamics. We solve the constraints and perform the canonical quantization accordingly. This formulation uses the recent construction of a parity-based covariant basis for matrix operators acting on the $(j,0)\\oplus(0,j) $ representations. The algebraic properties of the covariant basis play an important role in solving the constraints and allowing the canonical quantization of the theory. We study the chiral structure and possible interactions of the spin one matter fields, and conclude that the theory is not chirally symmetric in the massless limit, hence it is not possible to have chiral gauge interactions. H...
International Nuclear Information System (INIS)
The physics potential of colliding beams of protons, polarized either longitudinally or transversely, at RHIC is remarkable. A luminosity of L = 2 x 1032 cm-2 sec-1 with 70% polarized beams will be available with up to 250 GeV energy in each beam. The proposal to collide polarized protons in RHIC was submitted in August 1992 and approved in October 1993, just after this workshop. The collaboration has been encouraged to complete R ampersand D on Siberian Snakes, so that RHIC will be able to accelerate polarized protons early in its program. The expected date of the first heavy ion collisions is 1999. The spin physics program includes measurement of gluon and sea quark polarization in the longitudinally polarized proton, measurement and then application of parity violation in W and Z production, measurement of hard scattering parton-parton asymmetries, and quark polarization or transversity in transversely polarized protons. Single spin asymmetries allow sensitive searches for parity violation (longitudinal polarization), and correlations between quark spin and gluons (transverse). Probes include direct photons (to pT = 20 GeV/c), jets (to pT > 50 GeV/c), Drell-Yan pairs (to mll = 9 GeV), W+/-, Z. Here, the collaboration emphasizes the new information included in the Update, given to the Brookhaven PAC this September
Nonergodic dynamics of nuclear spin 1/2 with equal constants of spin-spin interaction
Rudavets, M G
2002-01-01
The exact solution of the nuclear spins polarization evolution in the system with the similar q-constant spin-spin interaction (SSI) between all spin pairs is obtained in the case when only one (the first) spin was polarized at the initial time moment. It is shown that polarization of the first spin P sub 1 (t) has the form of periodical pulsations in the time with the 4 pi/g period. The P sub 1 (t) function changes in each period from the initial value P(0) = 1 up to 1/3 value during the time period of the t approx = 4 pi/Ng order, when the spins number is N >= 1 and remains in the P sub 1 (t) 1/3 state practically during the whole period. The simple classical model within the frames of the average field theory explains the physical cause of the nonergodic dynamics of the considered system
Spinning particle approach to higher spin field theory
International Nuclear Information System (INIS)
We shortly review on the connection between higher-spin gauge field theories and supersymmetric spinning particle models. In such approach the higher spin equations of motion are linked to the first-class constraint algebra associated with the quantization of particle models. Here we consider a class of spinning particle models characterized by local O(N)-extended supersymmetry since these models are known to provide an alternative approach to the geometric formulation of higher spin field theory. We describe the canonical quantization of the models in curved target space and discuss the obstructions that appear in presence of an arbitrarily curved background. We then point out the special role that conformally flat spaces appear to have in such models and present a derivation of the higher-spin curvatures for maximally symmetric spaces.
Spinning particle approach to higher spin field theory
Energy Technology Data Exchange (ETDEWEB)
Corradini, Olindo, E-mail: Olindo.Corradini@bo.infn.it [Centro de Estudios en Fisica y Matematicas Basicas y Aplicadas Universidad Autonoma de Chiapas, Tuxtla Gutierrez, Chiapas (Mexico); Dipartimento di Fisica, Universita di Bologna via Irnerio 46, I-40126 Bologna (Italy); INFN, Sezione di Bologna via Irnerio 46, I-40126 Bologna (Italy)
2011-04-01
We shortly review on the connection between higher-spin gauge field theories and supersymmetric spinning particle models. In such approach the higher spin equations of motion are linked to the first-class constraint algebra associated with the quantization of particle models. Here we consider a class of spinning particle models characterized by local O(N)-extended supersymmetry since these models are known to provide an alternative approach to the geometric formulation of higher spin field theory. We describe the canonical quantization of the models in curved target space and discuss the obstructions that appear in presence of an arbitrarily curved background. We then point out the special role that conformally flat spaces appear to have in such models and present a derivation of the higher-spin curvatures for maximally symmetric spaces.
Amplification of spin waves by the spin Seebeck effect
Padrón-Hernández, E.; Azevedo, A.; Rezende, S. M.
2012-04-01
We observe amplification of spin-wave packets propagating along a film of single-crystal yttrium iron garnet (YIG) subject to a transverse temperature gradient. The spin waves are excited and detected with standard techniques used to study volume or surface magnetostatic waves in the 1-2 GHz frequency range. Amplification gains larger than 20 are observed in a YIG film heated by a current of 20 mA in a Pt layer in a simple YIG/Pt bilayer. The amplification is attributed to the action of a spin-transfer thermal torque acting on the magnetization that opposes the relaxation and which is created by spin currents generated through the spin Seebeck effect. The experimental data are interpreted with a spin-wave model.
Charged spinning black holes as accelerators of spinning particles
Zhang, Yu-Peng; Wei, Shao-Wen; Yang, Jie; Liu, Yu-Xiao
2016-01-01
It is well known that some black holes can act as accelerators for particles without spin. Recently, there are some works considering collision of two spinning particles in the background of Schwarzschild and Kerr black holes and it was shown that the spin of the test particles is related to the center-of-mass energy. In this paper we extend the results to some more general cases. We consider Kerr-Newman black holes as accelerators for spinning particles. We derive the center-of-mass energy of the spinning particles and use numerical method to investigate how the center-of-mass energy is affected by the properties of the black holes and spinning particles.
Towards Long Range Spin-Spin Interactions via Mechanical Resonators
Kabcenell, Aaron; Gieseler, Jan; Safira, Arthur; Kolkowitz, Shimon; Zibrov, Alexander; Harris, Jack; Lukin, Mikhail
2016-05-01
Nitrogen vacancy centers (NVs) are promising candidates for quantum computation, with room temperature optical spin read-out and initialization, microwave manipulability, and weak coupling to the environment resulting in long spin coherence times. The major outstanding challenge involves engineering coherent interactions between the spin states of spatially separated NV centers. To address this challenge, we are working towards the experimental realization of mechanical spin transducers. We have successfully fabricated magnetized high quality factor (Q> 105) , doubly-clamped silicon nitride mechanical resonators integrated close to a diamond surface, and report on experimental progress towards achieving the coherent coupling of the motion of these resonators with the electronic spin states of individual NV centers under cryogenic conditions. Such a system is expected to provide a scalable platform for mediating effective interactions between isolated spin qubits.
Low-spin models for higher-spin Lagrangians
Francia, Dario
2011-01-01
Higher-spin theories are most commonly modelled on the example of spin 2. While this is appropriate for the description of free irreducible spin-s particles, alternative options could be equally interesting. In particular Maxwell's equations provide the effective model for maximally reducible theories of higher spins inspired by the tensionless limit of the open string. For both options, as well as for their fermionic counterparts, one can extend the analogy beyond the equations for the gauge potentials, formulating the corresponding Lagrangians in terms of higher-spin curvatures. The associated non-localities are effectively due to the elimination of auxiliary fields and do not modify the spectrum. Massive deformations of these theories are also possible, and in particular in this contribution we propose a generalisation of the Proca Lagrangian for the Maxwell-inspired geometric theories.
Enhanced spin Hall ratios by Al and Hf impurities in Pt thin films
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.
Probing dynamics of a spin ensemble of P1 centers in diamond using a superconducting resonator
de Lange, Gijs; Ranjan, Vishal; Schutjens, Ron; Debelhoir, Thibault; Groen, Joost; Szombati, Daniel; Thoen, David; Klapwijk, Teun; Hanson, Ronald; Dicarlo, Leonardo
2013-03-01
Solid-state spin ensembles are promising candidates for realizing a quantum memory for superconducting circuits. Understanding the dynamics of such ensembles is a necessary step towards achieving this goal. Here, we investigate the dynamics of an ensemble of nitrogen impurities (P1 centers) in diamond using magnetic-field controlled coupling to the first two modes of a superconducting (NbTiN) coplanar waveguide resonator. Three hyperfine-split spin sub-ensembles are clearly resolved in the 0.25-1.2 K temperature range, with a collective coupling strength extrapolating to 23 MHz at full polarization. The coupling to multiple modes allows us to distinguish the contributions of dipolar broadening and magnetic field inhomogeneity to the spin linewidth. We find the spin polarization recovery rate to be temperature independent below 1 K and conclude that spin out-diffusion across the resonator mode volume provides the mechanism for spin relaxation of the ensemble. Furthermore, by pumping spins in one sub-ensemble and probing the spins in the other sub-ensembles, we observe fast steady-state cross-relaxation (compared to spin repolarization) across the hyperfine transitions. These observations have important implications for using the three sub-ensembles as independent quantum memories. Research supported by NWO, FOM, and EU Project SOLID
Spin transistor action from Onsager reciprocity and SU(2) gauge theory
Adagideli, Inanc
2012-02-01
We construct a local gauge transformation to show how a generic, nonhomogeneous SU(2) spin-orbit Hamiltonian reduces to two U(1) Hamiltonians for spinless fermions at opposite magnetic fields, to leading order in the spin-orbit strength. Using an Onsager reciprocity relation, we show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry by applied magnetic fields or opening additional transport terminals. We numerically illustrate our theory for diffusive conductors, ballistic mesoscopic cavities as well as Aharonov-Bohm rings.
Spin-flip noise in a multiterminal spin valve
Belzig, Wolfgang; Zareyan, Malek
2004-01-01
We study shot noise and cross-correlations in a four terminal spin-valve geometry using a Boltzmann-Langevin approach. The Fano factor (shot noise to current ratio) depends on the magnetic configuration of the leads and the spin-flip processes in the normal metal. In a four-terminal geometry, spin-flip processes are particularly prominent in the cross-correlations between terminals with opposite magnetization.
Field-controlled spin current in frustrated spin chains
Directory of Open Access Journals (Sweden)
A.K. Kolezhuk
2009-01-01
Full Text Available We study states with spontaneous spin current, emerging in frustrated antiferromagnetic spin-S chains subject to a strong external magnetic field. As a numerical tool, we use a non-Abelian symmetry realization of the density matrix renormalization group. The field dependence of the order parameter and the critical exponents are presented for zigzag chains with S=1/2, 1, 3/2, and 2.
Diffusion-weighted MRI of maple syrup urine disease encephalopathy
Energy Technology Data Exchange (ETDEWEB)
Cavalleri, F.; Mavilla, L. [Servizio di Neuroradiologia, Azienda Ospedaliera Policlinico, Modena (Italy); Berardi, A.; Ferrari, F. [Servizio di Neonatologia, Azienda Ospedaliera Policlinico, Modena (Italy); Burlina, A.B. [Dipartimento di Pediatria, Azienda Ospedaliera, Universita di Padova, Padua (Italy)
2002-06-01
We report the case of a newborn child with maple syrup urine disease (MSUD), diagnosed at 10 days of life. Diffusion-weighted echoplanar MRI showed marked hyperintensity of the cerebellar white matter, the brainstem, the cerebral peduncles, the thalami, the dorsal limb of the internal capsule and the centrum semiovale, while conventional dual-echo sequence evidenced only a weak diffuse T2 hyperintensity in the cerebellar white matter and in the dorsal brainstem. The apparent diffusion coefficient (ADC) of these regions was markedly (>80%) decreased. Therefore, in agreement with current hypotheses on MSUD pathogenesis, MSUD oedema proves to be a cytotoxic oedema. Diffusion-weighted MRI may be a valuable tool, more sensitive than conventional spin-echo techniques, to assess the extent and progression of cytotoxicity in MSUD, as well as the effectiveness of the therapeutic interventions. (orig.)
Direct observation of atomic diffusion in warm rubidium ensembles
Parniak, Michal
2013-01-01
We present a robust method for measuring the diffusion coefficients of warm atoms in buffer gases. Using optical pumping, we manipulate the atomic spin in a thin cylinder inside the cell. Then we observe the spatial spread of optically pumped atoms in time using a camera, which allows us to determine the diffusion coefficient. As an example, we demonstrate measurements of diffusion coefficients of rubidium in neon, krypton and xenon acting as buffer gases. We have determined the normalized (273 K, 760 Torr) diffusion coefficients to be 0.18\\pm0.03 cm^2/s for neon, 0.07\\pm0.01 cm^2/s for krypton, and 0.052\\pm0.006 cm^2/s for xenon.
Diffusion weighted imaging with circularly polarized oscillating gradients
DEFF Research Database (Denmark)
Lundell, Henrik; Sønderby, Casper Kaae; Dyrby, Tim B
2015-01-01
PURPOSE: The short diffusion time regime provides an interesting probe for tissue microstructure and can be investigated with oscillating gradient spin echo (OGSE) experiments. Several studies report new contrasts in preclinical settings and the first in vivo human experiments have recently been...... in diffusion weighting with encoding in a plane rather than in one direction. CP-OGSE can be used for rotationally invariant acquisitions on anisotropic tissues. METHODS: Experiments with a 4.7 T preclinical scanner on a postmortem monkey brain as well as simulations were performed using conventional OGSE...... presented. One major hurdle in practical implementation is the low effective diffusion weighting provided at high frequency with limited gradient strength. THEORY: As a solution to the low diffusion weighting of OGSE, circularly polarized OGSE (CP-OGSE) is introduced. CP-OGSE gives a twofold increase...
Dynamic Nuclear Polarization as Kinetically Constrained Diffusion
Karabanov, A.; Wiśniewski, D.; Lesanovsky, I.; Köckenberger, W.
2015-07-01
Dynamic nuclear polarization (DNP) is a promising strategy for generating a significantly increased nonthermal spin polarization in nuclear magnetic resonance (NMR) and its applications that range from medicine diagnostics to material science. Being a genuine nonequilibrium effect, DNP circumvents the need for strong magnetic fields. However, despite intense research, a detailed theoretical understanding of the precise mechanism behind DNP is currently lacking. We address this issue by focusing on a simple instance of DNP—so-called solid effect DNP—which is formulated in terms of a quantum central spin model where a single electron is coupled to an ensemble of interacting nuclei. We show analytically that the nonequilibrium buildup of polarization heavily relies on a mechanism which can be interpreted as kinetically constrained diffusion. Beyond revealing this insight, our approach furthermore permits numerical studies of ensembles containing thousands of spins that are typically intractable when formulated in terms of a quantum master equation. We believe that this represents an important step forward in the quest of harnessing nonequilibrium many-body quantum physics for technological applications.
Dynamic Nuclear Polarization as Kinetically Constrained Diffusion.
Karabanov, A; Wiśniewski, D; Lesanovsky, I; Köckenberger, W
2015-07-10
Dynamic nuclear polarization (DNP) is a promising strategy for generating a significantly increased nonthermal spin polarization in nuclear magnetic resonance (NMR) and its applications that range from medicine diagnostics to material science. Being a genuine nonequilibrium effect, DNP circumvents the need for strong magnetic fields. However, despite intense research, a detailed theoretical understanding of the precise mechanism behind DNP is currently lacking. We address this issue by focusing on a simple instance of DNP-so-called solid effect DNP-which is formulated in terms of a quantum central spin model where a single electron is coupled to an ensemble of interacting nuclei. We show analytically that the nonequilibrium buildup of polarization heavily relies on a mechanism which can be interpreted as kinetically constrained diffusion. Beyond revealing this insight, our approach furthermore permits numerical studies of ensembles containing thousands of spins that are typically intractable when formulated in terms of a quantum master equation. We believe that this represents an important step forward in the quest of harnessing nonequilibrium many-body quantum physics for technological applications. PMID:26207453
Spin-orbit mediated control of spin qubits
DEFF Research Database (Denmark)
Flindt, Christian; Sørensen, A.S; Flensberg, Karsten
2006-01-01
We propose to use the spin-orbit interaction as a means to control electron spins in quantum dots, enabling both single-qubit and two-qubit operations. Very fast single-qubit operations may be achieved by temporarily displacing the electrons. For two-qubit operations the coupling mechanism is based...... on a combination of the spin-orbit coupling and the mutual long-ranged Coulomb interaction. Compared to existing schemes using the exchange coupling, the spin-orbit induced coupling is less sensitive to random electrical fluctuations in the electrodes defining the quantum dots....
High-field spin dynamics of antiferromagnetic quantum spin chains
DEFF Research Database (Denmark)
Enderle, M.; Regnault, L.P.; Broholm, C.;
2000-01-01
The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quantum phase transitions are expected. We...... present recent work on the high-field spin dynamics of the S = I antiferromagnetic Heisenberg chains NENP (Haldane ground state) and CsNiCl3 (quasi-1D HAF close to the quantum critical point), the uniform S = 1/2 chain CTS, and the spin-Peierls system CuGeO3. (C) 2000 Elsevier Science B,V. All rights...
Decoupling a hole spin qubit from the nuclear spins
Prechtel, Jonathan H.; Kuhlmann, Andreas V.; Houel, Julien; Ludwig, Arne; Valentin, Sascha R.; Wieck, Andreas D.; Warburton, Richard J.
2016-09-01
A huge effort is underway to develop semiconductor nanostructures as low-noise hosts for qubits. The main source of dephasing of an electron spin qubit in a GaAs-based system is the nuclear spin bath. A hole spin may circumvent the nuclear spin noise. In principle, the nuclear spins can be switched off for a pure heavy-hole spin. In practice, it is unknown to what extent this ideal limit can be achieved. A major hindrance is that p-type devices are often far too noisy. We investigate here a single hole spin in an InGaAs quantum dot embedded in a new generation of low-noise p-type device. We measure the hole Zeeman energy in a transverse magnetic field with 10 neV resolution by dark-state spectroscopy as we create a large transverse nuclear spin polarization. The hole hyperfine interaction is highly anisotropic: the transverse coupling is energies; equivalently dephasing times up to a microsecond. The combination of large and strong optical dipole makes the single hole spin in a GaAs-based device an attractive quantum platform.
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Fogh Olsen, Ole; Sporring, Jon
2007-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Earabino, Gerard J.; Heyl, G. Christopher; Percorini, Thomas J.
1987-01-01
New ideas encounter obstacles on way to becoming products. Report examines process by which new ideas become products, processes, or accepted standards. Sequence of events called "the diffusion of innovation." Focuses on development of material processing in low gravity as case study in diffusion of innovation.
Discrimination of thermal diffusivity
Bergmann Tiest, W.M.; Kappers, A.M.L.
2009-01-01
Materials such as wood or metal which are at equal temperatures are perceived to be of different ‘coldness’ due to differences in thermal properties, such as the thermal diffusivity. The thermal diffusivity of a material is a parameter that controls the rate with which heat is extracted from the han
Mekkaoui, Imen; Moulin, Kevin; Croisille, Pierre; Pousin, Jerome; Viallon, Magalie
2016-08-01
Cardiac motion presents a major challenge in diffusion weighted MRI, often leading to large signal losses that necessitate repeated measurements. The diffusion process in the myocardium is difficult to investigate because of the unqualified sensitivity of diffusion measurements to cardiac motion. A rigorous mathematical formalism is introduced to quantify the effect of tissue motion in diffusion imaging. The presented mathematical model, based on the Bloch-Torrey equations, takes into account deformations according to the laws of continuum mechanics. Approximating this mathematical model by using finite elements method, numerical simulations can predict the sensitivity of the diffusion signal to cardiac motion. Different diffusion encoding schemes are considered and the diffusion weighted MR signals, computed numerically, are compared to available results in literature. Our numerical model can identify the existence of two time points in the cardiac cycle, at which the diffusion is unaffected by myocardial strain and cardiac motion. Of course, these time points depend on the type of diffusion encoding scheme. Our numerical results also show that the motion sensitivity of the diffusion sequence can be reduced by using either spin echo technique with acceleration motion compensation diffusion gradients or stimulated echo acquisition mode with unipolar and bipolar diffusion gradients.
Mekkaoui, Imen; Moulin, Kevin; Croisille, Pierre; Pousin, Jerome; Viallon, Magalie
2016-08-01
Cardiac motion presents a major challenge in diffusion weighted MRI, often leading to large signal losses that necessitate repeated measurements. The diffusion process in the myocardium is difficult to investigate because of the unqualified sensitivity of diffusion measurements to cardiac motion. A rigorous mathematical formalism is introduced to quantify the effect of tissue motion in diffusion imaging. The presented mathematical model, based on the Bloch-Torrey equations, takes into account deformations according to the laws of continuum mechanics. Approximating this mathematical model by using finite elements method, numerical simulations can predict the sensitivity of the diffusion signal to cardiac motion. Different diffusion encoding schemes are considered and the diffusion weighted MR signals, computed numerically, are compared to available results in literature. Our numerical model can identify the existence of two time points in the cardiac cycle, at which the diffusion is unaffected by myocardial strain and cardiac motion. Of course, these time points depend on the type of diffusion encoding scheme. Our numerical results also show that the motion sensitivity of the diffusion sequence can be reduced by using either spin echo technique with acceleration motion compensation diffusion gradients or stimulated echo acquisition mode with unipolar and bipolar diffusion gradients. PMID:27385441
Quantum Cryptography in Spin Networks
Institute of Scientific and Technical Information of China (English)
DENG Hong-Liang; FANG Xi-Ming
2007-01-01
In this paper we propose a new scheme of long-distance quantum cryptography based on spin networks with qubits stored in electron spins of quantum dots. By conditional Faraday rotation, single photon polarization measurement, and quantum state transfer, maximal-entangled Bell states for quantum cryptography between two long-distance parties are created. Meanwhile, efficient quantum state transfer over arbitrary distances is obtained in a spin chain by a proper choice of coupling strengths and using spin memory technique improved. We also analyse the security of the scheme against the cloning-based attack which can be also implemented in spin network and discover that this spin network cloning coincides with the optimal fidelity achieved by an eavesdropper for entanglement-based cryptography.
Multifrequency spin resonance in diamond
Childress, Lilian
2010-01-01
Magnetic resonance techniques provide a powerful tool for controlling spin systems, with applications ranging from quantum information processing to medical imaging. Nevertheless, the behavior of a spin system under strong excitation remains a rich dynamical problem. In this paper, we examine spin resonance of the nitrogen-vacancy center in diamond under conditions outside the regime where the usual rotating wave approximation applies, focusing on effects of multifrequency excitation and excitation with orientation parallel to the spin quantization axis. Strong-field phenomena such as multiphoton transitions and coherent destruction of tunneling are observed in the spectra and analyzed via numerical and analytic theory. In addition to illustrating the response of a spin system to strong multifrequency excitation, these observations may inform techniques for manipulating electron-nuclear spin quantum registers.
Semicircular Rashba arc spin polarizer
Energy Technology Data Exchange (ETDEWEB)
Bin Siu, Zhuo, E-mail: a0018876@nus.edu.sg [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 (Singapore); Advanced Concepts and Nanotechnology, Data Storage Institute, DSI Building, 5 Engineering Drive 1 (Off Kent Ridge Crescent, NUS), Singapore 117608 (Singapore); Jalil, Mansoor B. A. [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 (Singapore); Ghee Tan, Seng [Advanced Concepts and Nanotechnology, Data Storage Institute, DSI Building, 5 Engineering Drive 1 (Off Kent Ridge Crescent, NUS), Singapore 117608 (Singapore)
2014-05-07
In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions.
Accurate ab initio spin densities
Boguslawski, Katharina; Legeza, Örs; Reiher, Markus
2012-01-01
We present an approach for the calculation of spin density distributions for molecules that require very large active spaces for a qualitatively correct description of their electronic structure. Our approach is based on the density-matrix renormalization group (DMRG) algorithm to calculate the spin density matrix elements as basic quantity for the spatially resolved spin density distribution. The spin density matrix elements are directly determined from the second-quantized elementary operators optimized by the DMRG algorithm. As an analytic convergence criterion for the spin density distribution, we employ our recently developed sampling-reconstruction scheme [J. Chem. Phys. 2011, 134, 224101] to build an accurate complete-active-space configuration-interaction (CASCI) wave function from the optimized matrix product states. The spin density matrix elements can then also be determined as an expectation value employing the reconstructed wave function expansion. Furthermore, the explicit reconstruction of a CA...
BRST Theory for Continuous Spin
Bengtsson, Anders K H
2013-01-01
Some puzzling aspects of higher spin field theory in Minkowski space-time, such as the tracelessness constraints and the search for an underlying physical principle, are discussed. A connecting idea might be provided by the recently much researched continuous spin representations of the Poincar\\'e group. The Wigner equations, treated as first class constraints, yields to a four-constraint BRST formulation. The resulting field theory, generalizing free higher spin field theory, is one among a set of higher spin theories that can be related to previous work on unconstrained formulations. In particular, it is conjectured that the unconstrained higher spin theory of Francia and Sagnotti is a limit of a continuous spin theory. Furthermore, a simple analysis of the constraint structure reveals a hint of a physical rationale behind the trace constraints.
BRST theory for continuous spin
Bengtsson, Anders K. H.
2013-10-01
Some puzzling aspects of higher spin field theory in Minkowski space-time, such as the tracelessness constraints and the search for an underlying physical principle, are discussed. A connecting idea might be provided by the recently much researched continuous spin representations of the Poincaré group. The Wigner equations, treated as first class constraints, yields to a four-constraint BRST formulation. The resulting field theory, generalizing free higher spin field theory, is one among a set of higher spin theories that can be related to previous work on unconstrained formulations. In particular, it is conjectured that the unconstrained higher spin theory of Francia and Sagnotti is a limit of a continuous spin theory. Furthermore, a simple analysis of the constraint structure reveals a hint of a physical rationale behind the trace constraints.
Michaud, Georges; Richer, Jacques
2015-01-01
This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling. In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...
Di Rago, Matthew; Chu, Mark; Rodda, Luke N; Jenkins, Elizabeth; Kotsos, Alex; Gerostamoulos, Dimitri
2016-05-01
The number of oral fluid samples collected by the road policing authority in Victoria, Australia, requiring confirmatory laboratory analysis for drugs proscribed under Victorian legislation (methamphetamine, MDMA and Δ9-tetrahydrocannabinol) has greatly increased in recent years, driving the need for improved analysis techniques to enable expedient results. The aim of this study was to develop an LC-MS/MS-based targeted oral fluid screening technique that covers a broad range of basic and neutral drugs of abuse that can satisfy increased caseload while monitoring other compounds of interest for epidemiological purposes. By combining small sample volume, simple extraction procedure, rapid LC-MS/MS analysis and automated data processing, 40 drugs of abuse including amphetamines, benzodiazepines, cocaine and major metabolites, opioids, cannabinoids and some designer stimulants were separated over 5 min (with an additional 0.5 min re-equilibration time). The analytes were detected using a Sciex® API 4500 Q-Trap LC-MS/MS system with positive ESI in MRM mode monitoring three transitions per analyte. The method was fully validated in accordance with international guidelines and also monitored carbon-13 isotopes of MDMA and MA to reduce detector saturation effects, allowing for confirmation of large concentrations of these compounds without the need for dilution or re-analysis. The described assay has been successfully used for analysis of oral fluid collected as part of law enforcement procedures at the roadside in Victoria, providing forensic results as well as epidemiological prevalence in the population tested. The fast and reliable detection of a broad range of drugs and subsequent automated data processing gives the opportunity for high throughput and fast turnaround times for forensic toxicology.
Di Rago, Matthew; Chu, Mark; Rodda, Luke N; Jenkins, Elizabeth; Kotsos, Alex; Gerostamoulos, Dimitri
2016-05-01
The number of oral fluid samples collected by the road policing authority in Victoria, Australia, requiring confirmatory laboratory analysis for drugs proscribed under Victorian legislation (methamphetamine, MDMA and Δ9-tetrahydrocannabinol) has greatly increased in recent years, driving the need for improved analysis techniques to enable expedient results. The aim of this study was to develop an LC-MS/MS-based targeted oral fluid screening technique that covers a broad range of basic and neutral drugs of abuse that can satisfy increased caseload while monitoring other compounds of interest for epidemiological purposes. By combining small sample volume, simple extraction procedure, rapid LC-MS/MS analysis and automated data processing, 40 drugs of abuse including amphetamines, benzodiazepines, cocaine and major metabolites, opioids, cannabinoids and some designer stimulants were separated over 5 min (with an additional 0.5 min re-equilibration time). The analytes were detected using a Sciex® API 4500 Q-Trap LC-MS/MS system with positive ESI in MRM mode monitoring three transitions per analyte. The method was fully validated in accordance with international guidelines and also monitored carbon-13 isotopes of MDMA and MA to reduce detector saturation effects, allowing for confirmation of large concentrations of these compounds without the need for dilution or re-analysis. The described assay has been successfully used for analysis of oral fluid collected as part of law enforcement procedures at the roadside in Victoria, providing forensic results as well as epidemiological prevalence in the population tested. The fast and reliable detection of a broad range of drugs and subsequent automated data processing gives the opportunity for high throughput and fast turnaround times for forensic toxicology. PMID:26993306
Enhancing profitability of a spinning
MARSAL Feliu
2011-01-01
Systematic control of the rheological behavior of the ravings in an installation facility dynamometer constant elongation gradient is proposed in this paper. It is an application for all types of spinning both shortfibers as long fibers. Industrial experiments conducted show that this control drawing of the spinning frame is optimized, getting more regular yarns mass with greater industrial profitability. This work is applied to a spinning worsted manufactures fine yarns with high quality ...
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Spinning. 23.221 Section 23.221 Aeronautics... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Flight Spinning § 23.221 Spinning. (a...-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn...
Biswas, Ayan K; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo
2015-07-17
In artificial neural networks, neurons are usually implemented with highly dissipative CMOS-based operational amplifiers. A more energy-efficient implementation is a 'spin-neuron' realized with a magneto-tunneling junction (MTJ) that is switched with a spin-polarized current (representing weighted sum of input currents) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the MTJ to mimic neuron firing. Here, we propose and analyze a different type of spin-neuron in which the soft layer of the MTJ is switched with mechanical strain generated by a voltage (representing weighted sum of input voltages) and term it straintronic spin-neuron. It dissipates orders of magnitude less energy in threshold operations than the traditional current-driven spin neuron at 0 K temperature and may even be faster. We have also studied the room-temperature firing behaviors of both types of spin neurons and find that thermal noise degrades the performance of both types, but the current-driven type is degraded much more than the straintronic type if both are optimized for maximum energy-efficiency. On the other hand, if both are designed to have the same level of thermal degradation, then the current-driven version will dissipate orders of magnitude more energy than the straintronic version. Thus, the straintronic spin-neuron is superior to current-driven spin neurons.
DEFF Research Database (Denmark)
Flindt, Christian; Sørensen, A. S.; Lukin, M. D.;
2007-01-01
We propose a semiconductor device that can electrically generate entangled electron spin-photon states, providing a building block for entanglement of distant spins. The device consists of a p-i-n diode structure that incorporates a coupled double quantum dot. We show that electronic control...... of the diode bias and local gating allow for the generation of single photons that are entangled with a robust quantum memory based on the electron spins. Practical performance of this approach to controlled spin-photon entanglement is analyzed....
Isoscalar spin transition in nuclei
Energy Technology Data Exchange (ETDEWEB)
Tomasi-Gustafsson, E. [CEA Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France); Morlet, M.; Willis, A.; Marty, N. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Baker, F.T. [Georgia Univ., Athens, GA (United States); Beatty, D.; Edwards, G.W.R.; Glashausser, C. [Rutgers--the State Univ., Piscataway, NJ (United States); Djalali, C. [South Carolina Univ., Columbia, SC (United States). Dept. of Physics and Astronomy; Duchazeaubeneix, J.C. [Laboratoire National Saturne - Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)
1992-12-31
The study of the nuclear spin response gives a very deep insight in the magnetic properties of a nucleus. The spin-flip probability measured in inelastic scattering is a robust variable rich of information on the spin response. A study of the inelastic deuteron scattering is presented, where the isoscalar spin component of the nuclear response has been isolated for the first time. This has been possible with the 400 MeV polarized deuteron beam of Saturne and the measurement of the polarization of the outgoing deuteron with the polarimeter POMME. (author) 6 refs.; 7 figs.
Spin manipulation in nanoscale superconductors
Beckmann, D.
2016-04-01
The interplay of superconductivity and magnetism in nanoscale structures has attracted considerable attention in recent years due to the exciting new physics created by the competition of these antagonistic ordering phenomena, and the prospect of exploiting this competition for superconducting spintronics devices. While much of the attention is focused on spin-polarized supercurrents created by the triplet proximity effect, the recent discovery of long range quasiparticle spin transport in high-field superconductors has rekindled interest in spin-dependent nonequilibrium properties of superconductors. In this review, the experimental situation on nonequilibrium spin injection into superconductors is discussed, and open questions and possible future directions of the field are outlined.
International Nuclear Information System (INIS)
The present talk has three parts: first, a discussion of current ideas about the physics of very high spin states; second, some comments about noncollective behavior up to the highest spins where it is known, approx. 40 h; and finally, a presentation of the newest method for studying collective behavior up to spins of 60 to 70 h. The intention is that the overview presented in the first part will be sufficiently broad to indicate the relationship of the noncollective and collective behavior discussed in the other parts, and to provide some understanding of the compromise in behavior that seems to occur at the very highest spins. 13 figures
Spinning particles coupled to gravity
Hojman, Sergio A
2016-01-01
Recent experimental work has determined that free falling $^{87}$Rb atoms on Earth, with vertically aligned spins, follow geodesics, thus apparently ruling out spin--gravitation interactions. It is showed that while some spinning matter models coupled to gravitation referenced to in that work seem to be ruled out by the experiment, those same experimental results confirm theoretical results derived from a Lagrangian description of spinning particles coupled to gravity constructed over forty years ago. A proposal to carry out (similar but) different experiments which will help to test the validity of the Universality of Free Fall as opposed to the correctness of the aforementioned Lagrangian theory, is presented.
International Nuclear Information System (INIS)
Colliding beams of high energy polarized protons at RHIC is an excellent way to probe the polarization of gluons, u and d quarks in a polarized proton. RHIC is the Relativistic Heavy Ion Collider being built now at Brookhaven in the ISABELLE tunnel. It is designed to collide gold ions on gold ions at 100 GeV/nucleon. Its goal is to discover the quark-gluon plasma, and the first collisions are expected in March, 1999. RHIC will also make an ideal polarized proton collider with high luminosity and 250 GeV x 250 GeV collisions. The RHIC spin physics program is: (1) Use well-understood perturbative QCD probes to study non-perturbative confining dynamics in QCD. We will measure - gluon and sea quark polarization in a polarized proton, polarization of quarks in a transversely polarized proton. (2) Look for additional surprises using the first high energy polarized proton collider. We will - look for the expected maximal parity violation in W and Z boson production, - search for parity violation in other processes, - test parton models with spin. This lecture is organized around a few of the key ideas: Siberian Snakes--What are they? High energy proton-proton collisions are scatters of quarks and leptons, at high x, a polarized proton beam is a beam of polarized u quarks, quark and gluon collisions are very sensitive to spin. We will discuss two reactions: how direct photon production measures gluon polarization, and how W+ boson production measures u and d quark polarization
Spin-Hall effect and spin-Coulomb drag in doped semiconductors
Energy Technology Data Exchange (ETDEWEB)
Hankiewicz, E M [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg, D-97074 Wuerzburg (Germany); Vignale, G [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States)
2009-06-24
In this review, we describe in detail two important spin-transport phenomena: the extrinsic spin-Hall effect (coming from spin-orbit interactions between electrons and impurities) and the spin-Coulomb drag. The interplay of these two phenomena is analyzed. In particular, we discuss the influence of scattering between electrons with opposite spins on the spin current and the spin accumulation produced by the spin-Hall effect. Future challenges and open questions are briefly discussed. (topical review)
Electrical Measurements of the Extrinsic Spin Hall Effect in Fe/ In x Ga 1-xAs Heterostructures
Geppert, Chad; Garlid, Eric; Chan, Mun; Crowell, Paul; Hu, Qi; Palmstrøm, Chris
2011-03-01
We report on all-electrical measurements of the extrinsic spin Hall effect in Fe/ In x Ga 1-x As heterostructures with n -type channel doping (Si) and highly doped Schottky tunnel barriers. The spin Hall effect refers to the transverse spin current generated by application of a longitudinal unpolarized charge current. Complementary spin accumulation at opposing edges of the channel is detected via a Hanle effect in the voltage measured by pairs of ferromagnetic Hall contacts. The spin Hall conductivity is extracted by fitting the data to a drift-diffusion model incorporating spin precession and relaxation. Tuning the channel conductivity with applied bias allows the skew and side-jump contributions to be determined independently. The resulting magnitude is in agreement with models based on ionized impurity scattering. Further quantitative comparison to theoretical models is achieved by increasing the In concentration beyond previously reported values. Supported by ONR and NSF.
Cherniak, D. J.; Van Orman, J. A.
2014-03-01
Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.
Spin-rotation coupling in compound spin objects
Energy Technology Data Exchange (ETDEWEB)
Lambiase, Gaetano, E-mail: lambiase@sa.infn.it [Dipartimento di Fisica “E.R. Caianiello”, Università di Salerno, 84084 Fisciano (Italy); INFN, Sezione di Napoli (Italy); International Institute for Advanced Scientific Studies, 89019 Vietri sul Mare (Italy); Papini, Giorgio [International Institute for Advanced Scientific Studies, 89019 Vietri sul Mare (Italy); Department of Physics, University of Regina, Regina, SK, S4S 0A2 (Canada); Prairie Particle Physics Institute, Regina, SK, S4S 0A2 (Canada)
2013-06-03
We generalize spin-rotation coupling to compound spin systems. In the case of muons bound to nuclei in a storage ring the decay process acquires a modulation. Typical frequencies for Z/A∼1/2 are ∼3×10{sup 6} Hz, a factor 10 higher than the modulation observed in g−2 experiments.
Spin-rotation coupling in compound spin objects
Lambiase, G
2013-01-01
We generalize spin-rotation coupling to compound spin systems. In the case of muons bound to nuclei in a storage ring the decay process acquires a modulation. Typical frequencies for $Z/A\\sim 1/2$ are $\\sim 3\\times 10^6$Hz, a factor 10 higher than the modulation observed in $g-2$ experiments.
Angular dependence of spin-orbit spin-transfer torques
Lee, Ki-Seung
2015-04-06
In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.
Spin-SILC: CMB polarisation component separation with spin wavelets
Rogers, Keir K.; Peiris, Hiranya V.; Leistedt, Boris; McEwen, Jason D.; Pontzen, Andrew
2016-08-01
We present Spin-SILC, a new foreground component separation method that accurately extracts the cosmic microwave background (CMB) polarisation E and B modes from raw multifrequency Stokes Q and U measurements of the microwave sky. Spin-SILC is an internal linear combination method that uses spin wavelets to analyse the spin-2 polarisation signal P = Q + iU. The wavelets are additionally directional (non-axisymmetric). This allows different morphologies of signals to be separated and therefore the cleaning algorithm is localised using an additional domain of information. The advantage of spin wavelets over standard scalar wavelets is to simultaneously and self-consistently probe scales and directions in the polarisation signal P = Q + iU and in the underlying E and B modes, therefore providing the ability to perform component separation and E-B decomposition concurrently for the first time. We test Spin-SILC on full-mission Planck simulations and data and show the capacity to correctly recover the underlying cosmological E and B modes. We also demonstrate a strong consistency of our CMB maps with those derived from existing component separation methods. Spin-SILC can be combined with the pseudo- and pure E-B spin wavelet estimators presented in a companion paper to reliably extract the cosmological signal in the presence of complicated sky cuts and noise. Therefore, it will provide a computationally-efficient method to accurately extract the CMB E and B modes for future polarisation experiments.
Takahashi, Fumiaki; Katta, Viswanath R.
2007-01-01
Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (Fig. 1, left). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated (Fig. 1, right). A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.
Unconventional spin texture in a noncentrosymmetric quantum spin Hall insulator
Mera Acosta, C.; Babilonia, O.; Abdalla, L.; Fazzio, A.
2016-07-01
We propose that the simultaneous presence of both Rashba and band inversion can lead to a Rashba-like spin splitting formed by two bands with the same in-plane helical spin texture. Because of this unconventional spin texture, the backscattering is forbidden in edge and bulk conductivity channels. We propose a noncentrosymmetric honeycomb-lattice quantum spin Hall (QSH) insulator family formed by the IV, V, and VII elements with this property. The system formed by Bi, Pb, and I atoms is mechanically stable and has both a large Rashba spin splitting of 60 meV and a large nontrivial band gap of 0.14 eV. Since the edge and the bulk states are protected by the time-reversal (TR) symmetry, contrary to what happens in most doped QSH insulators, the bulk states do not contribute to the backscattering in the electronic transport, allowing the construction of a spintronic device with less energy loss.
Harding; Contopoulos; Kazanas
1999-11-10
We examine the effects of a relativistic wind on the spin-down of a neutron star and apply our results to the study of soft gamma repeaters (SGRs), which are thought to be neutron stars with magnetic fields greater than 1014 G. We derive a spin-down formula that includes torques from both dipole radiation and episodic or continuous particle winds. We find that if SGR 1806-20 puts out a continuous particle wind of 1037 ergs s-1, then the pulsar age is consistent with that of the supernova remnant, but the derived surface dipole magnetic field is only 3x1013 G, in the range of normal radio pulsars. If instead the particle wind flows are episodic with small duty cycle, then the observed period derivatives imply magnetar-strength fields, while still allowing characteristic ages within a factor of 2 of the estimated supernova remnant age. Close monitoring of the periods of SGRs will allow us to establish or place limits on the wind duty cycle and thus the magnetic field and age of the neutron star.
Spin-Dependent Transport Phenomena in Ferromagnet/Semiconductor Heterostructures
Geppert, Chad Christopher
This dissertation examines several aspects of spin-dependent transport phenomena in epitaxially grown ferromagnet/n-GaAs heterostructures. Further maturation of the field of semiconductor-based spintronics is hindered by difficulties in evaluating device performance across materials systems. Using Fe/n-GaAs and Co2MnSi/n-GaAs heterostructures as a test case, the main goal of this work is to demonstrate how such difficulties may be overcome by (1) specifying a more quantitative framework for evaluating transport parameters and (2) the introduction of a new spin-to-charge conversion phenomenon which may be parameterized by bulk semiconductor parameters. In the introductory chapter, this work is placed in the broader context of developing improved methods for the generation, modulation, and detection of spins. The lateral spin-valve geometry is presented as a concrete example of the typical measurement procedures employed. Chapter 2 presents the charge-based transport properties of these samples and establishes the notation and calculation techniques to be employed in subsequent chapters. In particular, we examine in detail the calculation of the electrochemical potential for a given carrier concentration. Chapter 3 provides a full derivation of the equations governing spin-dependent transport in the large polarization regime. This is applied to the case of extracting spin lifetimes and diffusion rates, demonstrating how quantitative agreement with theoretical predictions may be obtained upon properly accounting for both device geometry and material parameters. Further examination of the boundary conditions applicable to the heterojunctions of these samples demonstrates to what extent device performance may be parameterized across materials systems. Chapter 4 presents experimental observations of a new spin-to-charge conversion phenomenon using a non-magnetic probe. In the presence of a large non-equilibrium spin accumulation, the combination of a non-constant density
Theories on diffusion of technology
DEFF Research Database (Denmark)
Munch, Birgitte
Tracing the body of the diffusion proces by analysing the diffusion process from historical, sociological, economic and technical approaches. Discussing central characteristics of the proces of diffusion og CAD/CAM in Denmark....
International Nuclear Information System (INIS)
Molecular exchange properties and diffusion of n-hexane embedded in a bimodal pore structure with characteristic length scales in the order of nano and micrometres, respectively, formed by packing of zeolite particles, are studied. Two-dimensional (2D) nuclear magnetic resonance (NMR) diffusion correlation experiments together with relaxation-diffusion correlation experiments are performed at low magnetic field using a single-sided NMR scanner. The exchange time covers a range from 10-3 to 10-1 s. The molecular exchange properties are modulated by transport inside the zeolite particles. Different exchange regimes are observed for molecules starting from different positions inside the porous sample. The influence of the spin-lattice relaxation properties of the fluid molecules inside the zeolite particles on the signal intensity is also studied. A Monte Carlo simulation of the exchange process is performed and is used to support the analysis of the experimental data.
Spin transport in p-type germanium.
Rortais, F; Oyarzún, S; Bottegoni, F; Rojas-Sánchez, J-C; Laczkowski, P; Ferrari, A; Vergnaud, C; Ducruet, C; Beigné, C; Reyren, N; Marty, A; Attané, J-P; Vila, L; Gambarelli, S; Widiez, J; Ciccacci, F; Jaffrès, H; George, J-M; Jamet, M
2016-04-27
We report on the spin transport properties in p-doped germanium (Ge-p) using low temperature magnetoresistance measurements, electrical spin injection from a ferromagnetic metal and the spin pumping-inverse spin Hall effect method. Electrical spin injection is carried out using three-terminal measurements and the Hanle effect. In the 2-20 K temperature range, weak antilocalization and the Hanle effect provide the same spin lifetime in the germanium valence band (≈1 ps) in agreement with predicted values and previous optical measurements. These results, combined with dynamical spin injection by spin pumping and the inverse spin Hall effect, demonstrate successful spin accumulation in Ge. We also estimate the spin Hall angle θ(SHE) in Ge-p (6-7 x 10(-4) at room temperature, pointing out the essential role of ionized impurities in spin dependent scattering.
IV. Workshop on High Energy Spin Physics
International Nuclear Information System (INIS)
In this proceedings the results on high energy spin physics are summarized. The theory of spin phenomenon and the experimental results at intermediate energy and at high energy spin physics and new technical developments in polarization experiments are presented
DEFF Research Database (Denmark)
Pries-Heje, Jan; Baskerville, Richard
2014-01-01
Both the practice and the research literature on information systems attach great value to the identification and dissemination of information on “best practices”. In the philosophy of science, this type of knowledge is regarded as technological knowledge because it becomes manifest...... in the successful techniques in one context. While the value for other contexts is unproven, knowledge of best practices circulates under an assumption that the practices will usefully self-diffuse through innovation and adoption in other contexts. We study diffusion of best practices using a design science...... approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...
Hereditary diffuse gastric cancer
DEFF Research Database (Denmark)
van der Post, Rachel S; Vogelaar, Ingrid P; Carneiro, Fátima;
2015-01-01
Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects...
Diffusion Adaptation over Networks
Sayed, Ali H
2012-01-01
Adaptive networks are well-suited to perform decentralized information processing and optimization tasks and to model various types of self organized and complex behavior encountered in nature. Adaptive networks consist of a collection of agents with processing and learning abilities. The agents are linked together through a connection topology, and they cooperate with each other through local interactions to solve distributed inference problems in real-time. The continuous diffusion of information across the network enables agents to adapt their performance in relation to changing data and network conditions; it also results in improved adaptation and learning performance relative to non-cooperative networks. This article provides an overview of diffusion strategies for adaptation and learning over networks. The article is divided into several sections: 1. Motivation; 2. Mean-Square-Error Estimation; 3. Distributed Optimization via Diffusion Strategies; 4. Adaptive Diffusion Strategies; 5. Performance of Ste...
Peppin, Stephen S. L.
2009-01-01
Diffusion and permeation are discussed within the context of irreversible thermodynamics. A new expression for the generalized Stokes-Einstein equation is obtained which links the permeability to the diffusivity of a two-component solution and contains the poroelastic Biot-Willis coefficient. The theory is illustrated by predicting the concentration and pressure profiles during the filtration of a protein solution. At low concentrations the proteins diffuse independently while at higher concentrations they form a nearly rigid porous glass through which the fluid permeates. The theoretically determined pressure drop is nonlinear in the diffusion regime and linear in the permeation regime, in quantitative agreement with experimental measurements. © 2009 Walter de Gruyter, Berlin, New York.
Tomographic characteristics of spin states
Chernega, VN; Man'ko, OV; Man'ko, [No Value; Pilyavets, OV; Zborovskii, VG
2006-01-01
Spin states are studied in the tomographic-probability representation. The standard probability distribution of spin projection onto a direction in space is used instead of the spinor or the density matrix to identify the quantum state. The Shannon entropy and information are associated with the spi
Ultrafast spin-transfer torque driven by femtosecond pulsed-laser excitation
Koopmans, Bert
A hot topic in the field of ultrafast laser-induced manipulation of the magnetic state is that of the role and exploitation of laser-induced spin currents. Intense debate has been triggered by claims that such a spin-transfer, e.g. in the form of super-diffusive spin currents over tens of nanometers, might be a main contributor to the demagnetization process in ferromagnetic thin films after femtosecond laser excitation. In this presentation the underlying concepts will be introduced and recent developments reviewed. Particularly we demonstrate the possibility to apply a laser-induced spin transfer torque on a free magnetic layer, using a non-collinear multilayer configuration consisting of a free in-plane layer on top of a perpendicularly magnetized injection layer, as separated by a nonmagnetic spacer. Interestingly, this approach allows for a quantitative measurement of the amount of spin transfer. Moreover, it might provide access to novel device architectures in which the magnetic state is controlled by fs laser pulses. Careful analysis of the resulting precession of the free layer allows us to quantify the applied torque, and distinguish between driving mechanisms based on laser-induced transfer of hot electrons versus a spin Seebeck effect due to the large thermal gradients. Further engineering of the layered structures in order to gain fundamental understanding and optimize efficiencies will be reported. A simple model that treats local non-equilibrium magnetization dynamics to spin transport effects via a spin-dependent chemical potential will be introduced.
Some recent developments in spin glasses
Indian Academy of Sciences (India)
A P Young
2005-06-01
I give some experimental and theoretical background to spin glasses, and then discuss the nature of the phase transition in spin glasses with vector spins. Results of Monte Carlo simulations of the Heisenberg spin glass model in three dimensions are presented. A finite-size scaling analysis of the correlation length of the spins and chiralities shows that there is a single, finite-temperature transition at which both spins and chiralities order.
Directory of Open Access Journals (Sweden)
K. Banoo
1998-01-01
equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.
Energy Technology Data Exchange (ETDEWEB)
Mielke, U.
1979-01-01
We measured in 287 persons the pulmonary CO diffusion capacity with the steady-state and the single breath methods, applying apnoeic periods of 4 and 10 seconds duration. The aspects methodical significance, polyclinical applicability and pathognostic relevance with respect to other approved pulmonary functional tests are discussed. Differing pulmonary diffusion capacity values found in normal persons or in patients suffering from silicosis, pulmonary fibrosis, Boeck's disease or rheumatoid arthritis, were investigated and critically evaluated.
Transverse spin with coupled plasmons
Mukherjee, Samyobrata
2016-01-01
We study theoretically the transverse spin associated with the eigenmodes of a thin metal film embedded in a dielectric. We show that the transverse spin has a direct dependence on the nature and strength of the coupling leading to two distinct branches for the long- and short- range modes. We show that the short-range mode exhibits larger extraordinary spin because of its more 'structured' nature due to higher decay in propagation. In contrast to some of the earlier studies, calculations are performed retaining the full lossy character of the metal. In the limit of vanishing losses we present analytical results for the extraordinary spin for both the coupled modes. The results can have direct implications for enhancing the elusive transverse spin exploiting the coupled plasmon structures.
Spinning bodies in curved spacetime
d'Ambrosi, G.; Satish Kumar, S.; van de Vis, J.; van Holten, J. W.
2016-02-01
We study the motion of neutral and charged spinning bodies in curved spacetime in the test-particle limit. We construct equations of motion using a closed covariant Poisson-Dirac bracket formulation that allows for different choices of the Hamiltonian. We derive conditions for the existence of constants of motion and apply the formalism to the case of spherically symmetric spacetimes. We show that the periastron of a spinning body in a stable orbit in a Schwarzschild or Reissner-Nordstrøm background not only precesses but also varies radially. By analyzing the stability conditions for circular motion we find the innermost stable circular orbit (ISCO) as a function of spin. It turns out that there is an absolute lower limit on the ISCOs for increasing prograde spin. Finally we establish that the equations of motion can also be derived from the Einstein equations using an appropriate energy-momentum tensor for spinning particles.
Advanced manufacturing: Technology diffusion
Energy Technology Data Exchange (ETDEWEB)
Tesar, A.
1995-12-01
In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.
Stern-Gerlach Experiment with Higher Spins
Tekin, Bayram
2015-01-01
We analyze idealized sequential Stern-Gerlach experiments with higher spin particles. This analysis serves at least two purposes: The widely discussed spin-1/2 case leads to some misunderstandings which hopefully is removed by the higher spin discussion. Secondly, Wigner rotation matrices for generic spins become conceptually more transparent with this physical example. We also give compact formulas for the probabilities in terms of the angle between the sequential SG apparatuses for generic spins. We work out the spin-$1/2$, spin-$1$ and spin-$2$ cases explicitly. Since there are some confusing issues regarding the actual experiment, we also compile a "facts and fiction" section on the SG experiments.
Theory of the spin Seebeck effect.
Adachi, Hiroto; Uchida, Ken-ichi; Saitoh, Eiji; Maekawa, Sadamichi
2013-03-01
The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects.
Energy Technology Data Exchange (ETDEWEB)
Okuda, Taichi, E-mail: okudat@hiroshima-u.ac.jp [Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Miyamoto, Koji [Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Kimura, Akio [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan); Namatame, Hirofumi [Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Taniguchi, Masaki [Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan)
2015-05-15
Newly developed double spin-detectors system utilizing high-efficient very low energy electron diffraction type spin detector for three dimensional spin vectorial analysis is presented. The high efficiency of the spin detector and the state of the art hemispherical electron analyzer enables us to measure all the spin vector components in high energy- and angular-resolution. The detection of orthogonal three spin components (P{sub x}, P{sub y} and P{sub z}) are important to observe real spin structure of the Rashba systems or topological insulators that are deviating from the ideal in-plane tangential helical spin structure. In addition three dimensional spin analysis is important for the determination of the degree of spin polarization of such systems since the spin quantization axis of the systems is not obvious unlike the ferromagnetic materials.
International Nuclear Information System (INIS)
Newly developed double spin-detectors system utilizing high-efficient very low energy electron diffraction type spin detector for three dimensional spin vectorial analysis is presented. The high efficiency of the spin detector and the state of the art hemispherical electron analyzer enables us to measure all the spin vector components in high energy- and angular-resolution. The detection of orthogonal three spin components (Px, Py and Pz) are important to observe real spin structure of the Rashba systems or topological insulators that are deviating from the ideal in-plane tangential helical spin structure. In addition three dimensional spin analysis is important for the determination of the degree of spin polarization of such systems since the spin quantization axis of the systems is not obvious unlike the ferromagnetic materials
Spinning-Down of Moving Magnetars in the Propeller Regime
Toropina, O D; Lovelace, R V
2006-01-01
We use axisymmetric magnetohydrodynamic simulations to investigate the spinning-down of magnetars rotating in the propeller regime and moving supersonically through the interstellar medium. The simulations indicate that magnetars spin-down rapidly due to this interaction, faster than for the case of a non-moving star. From many simulation runs we have derived an approximate scaling laws for the angular momentum loss rate, \\dot{L} \\propto \\~\\eta_m^{0.3}\\mu^{0.6}\\rho^{0.8}{\\cal M}^{-0.4} \\Omega_*^{1.5}, where \\rho is the density of the interstellar medium, \\cal M is Mach number, \\mu is the star's magnetic moment, \\Omega_* is its angular velocity, and \\eta_m is magnetic diffusivity. A magnetar with a surface magnetic field of 10^{13} - 10^{15} G is found to spin-down to a period P > 10^5-10^6 s in \\sim 10^4 - 10^5 years. There is however uncertainty about the value of the magnetic diffusivity so that the time-scale may be longer. We discuss this model in respect of Soft Gamma Repeaters (SGRs) and the isolated ne...
Negative g-Force Ocular Trauma Caused by a Rapidly Spinning Carousel
Directory of Open Access Journals (Sweden)
Elad Moisseiev
2013-10-01
Full Text Available We present a case of a 10-year-old boy who presented with bilateral diffuse subconjunctival hemorrhages after spinning rapidly on a carousel attached to an electrical scooter. We present his clinical course and discuss the physics and pathophysiology of this unique mechanism of ocular trauma.
Energy Technology Data Exchange (ETDEWEB)
Bensafa, I.K
2006-05-15
The first part of this work presents the analysis and results of the VCS-SSA (virtual Compton scattering - single spin asymmetry) experiment at MAMI (Mainz). It was carried out with beam energy 883 MeV and longitudinal polarization (about 80%), at virtual photon four-momentum transfer squared (Q{sup 2} = 0.35 GeV{sup 2}) to measure the beam asymmetry in the ep {yields} ep{gamma} and ep {yields} ep{pi}{sup 0} reactions. The asymmetry obtained in photon (resp. pion) electro-production is between 0-15% (resp. 0-2%). The dispersion relation model for virtual Compton scattering and MAID model (for {pi}{sup 0}) reproduce the amplitude globally but not completely the shape of the asymmetry. Perhaps this discrepancy is due to an imperfect parameterization of some pion production multipoles ({gamma}{sup *}N {yields} {pi}N). The second part is dedicated to the study of the nucleon energy spectrum in ground-state L=0 and excited-state L=1 in the quark model, using the Coulomb + linear potential type (CL) and a relativistic correction. The hyperfine correction is applied to discriminate the nucleon masses. The values of the mass found for the proton and the {delta}(1232) are respectively equal to (968 MeV, 1168 MeV), and the masses of the excited states are between 1564 - 1607 MeV. This part is completed by an application of the CL model to an approximate calculation of generalized polarizabilities of the proton. (author)
Spin Orbit Interaction Engineering for beyond Spin Transfer Torque memory
Wang, Kang L.
Spin transfer torque memory uses electron current to transfer the spin torque of electrons to switch a magnetic free layer. This talk will address an alternative approach to energy efficient non-volatile spintronics through engineering of spin orbit interaction (SOC) and the use of spin orbit torque (SOT) by the use of electric field to improve further the energy efficiency of switching. I will first discuss the engineering of interface SOC, which results in the electric field control of magnetic moment or magneto-electric (ME) effect. Magnetic memory bits based on this ME effect, referred to as magnetoelectric RAM (MeRAM), is shown to have orders of magnitude lower energy dissipation compared with spin transfer torque memory (STTRAM). Likewise, interests in spin Hall as a result of SOC have led to many advances. Recent demonstrations of magnetization switching induced by in-plane current in heavy metal/ferromagnetic heterostructures have been shown to arise from the large SOC. The large SOC is also shown to give rise to the large SOT. Due to the presence of an intrinsic extraordinarily strong SOC and spin-momentum lock, topological insulators (TIs) are expected to be promising candidates for exploring spin-orbit torque (SOT)-related physics. In particular, we will show the magnetization switching in a chromium-doped magnetic TI bilayer heterostructure by charge current. A giant SOT of more than three orders of magnitude larger than those reported in heavy metals is also obtained. This large SOT is shown to come from the spin-momentum locked surface states of TI, which may further lead to innovative low power applications. I will also describe other related physics of SOC at the interface of anti-ferromagnetism/ferromagnetic structure and show the control exchange bias by electric field for high speed memory switching. The work was in part supported by ERFC-SHINES, NSF, ARO, TANMS, and FAME.
RESPECT: Neutron resonance spin-echo spectrometer for extreme studies
Georgii, R.; Kindervater, J.; Pfleiderer, C.; Böni, P.
2016-11-01
We propose the design of a REsonance SPin-echo spECtrometer for exTreme studies, RESPECT, that is ideally suited for the exploration of non-dispersive processes such as diffusion, crystallization, slow dynamics, tunneling processes, crystal electric field excitations, and spin fluctuations. It is a variant of the conventional neutron spin-echo technique (NSE) by (i) replacing the long precession coils by pairs of longitudinal neutron spin-echo coils combined with RF-spin flippers and (ii) by stabilizing the neutron polarization with small longitudinal guide fields that can in addition be used as field subtraction coils thus allowing to adjust the field integrals over a range of 8 orders of magnitude. Therefore, the dynamic range of RESPECT can in principle be varied over 8 orders of magnitude in time, if neutrons with the required energy are made available. Similarly as for existing NSE-spectrometers, spin echo times of up to approximately 1 μs can be reached if the divergence and the correction elements are properly adjusted. Thanks to the optional use of neutron guides and the fact that the currents for the correction coils are much smaller than in standard NSE, intensity gains of at least one order of magnitude are expected, making the concept of RESPECT also competitive for operation at medium flux neutron sources. RESPECT can also be operated in a MIEZE configuration allowing the investigation of relaxation processes in depolarizing environments as they occur when magnetic fields are applied at the sample position, i.e. for the investigation of the dynamics of flux lines in superconductors, magnetic fluctuations in ferromagnetic materials, and samples containing hydrogen.
Spin Backflow and ac Voltage Generation by Spin Pumping and the Inverse Spin Hall Effect
Jiao, H.; Bauer, G.E.W.
2013-01-01
The spin current pumped by a precessing ferromagnet into an adjacent normal metal has a constant polarization component parallel to the precession axis and a rotating one normal to the magnetization. The former is now routinely detected as a dc voltage induced by the inverse spin Hall effect (ISHE).
Spin Injection and Spin Accumulation in Permalloy–Copper Mesoscopic Spin Valves
Jedema, F.J.; Filip, A.T.; Wees, B.J. van
2002-01-01
We study the electrical injection and detection of spin currents in a lateral spin valve device, using permalloy (Py) as ferromagnetic injecting and detecting electrodes and copper (Cu) as nonmagnetic metal. Our multiterminal geometry allows us to experimentally distinguish different magnetoresistan
Directory of Open Access Journals (Sweden)
V.M. Loktev
2008-09-01
Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.
Prets, A
1998-01-01
In the present Ph. D. thesis we are considering a special form of scaling limits, namely the hydrodynamic limit. Such limits are considered to explain macroscopic behavior of matter by means of microscopic dynamic laws. In this procedure a rescaling of space and time plays a central role. The limit will be formulated in a quantum mechanical way. Within this framework we study derivations of the Landau Lifshitz equation for ferromagnets. This equation is a macroscopic equation of motion for the magnetization vector and results into the theory of spin waves. Since we have no exact knowledge of the Heisenberg operator's time evolution no definitive statement an how to regain the Landau Lifshitz equation from the microscopic dynamics can be given. In contrast to the Heisenberg operator, for an Ising type interaction inside a ferromagnet one is able to recover macroscopically a solution of a linearized Landau Lifschitz equation.
Energy Technology Data Exchange (ETDEWEB)
Prosen, Tomaz [Physics Department, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana (Slovenia)]. E-mail: prosen@fiz.uni-lj.si; Seligman, Thomas H. [Centro de Ciencias Fisicas, University of Mexico (UNAM), Cuernavaca (Mexico)]. E-mail: seligman@fis.unam.mx
2002-06-07
We define a quantity, the so-called purity fidelity, which measures the rate of dynamical irreversibility due to decoherence, observed e.g. in echo experiments, in the presence of an arbitrary small perturbation of the total (system + environment) Hamiltonian. We derive a linear response formula for the purity fidelity in terms of integrated time correlation functions of the perturbation. Our relation predicts, similar to the case of fidelity decay, that the faster the decay of purity fidelity the slower is the decay of time correlations. In particular, we find exponential decay in quantum mixing regime and faster, initially quadratic and later typically Gaussian decay in the regime of non-ergodic, e.g. integrable quantum dynamics. We illustrate our approach by an analytical calculation and numerical experiments in the Ising spin 1/2 chain kicked with tilted homogeneous magnetic field where part of the chain is interpreted as a system under observation and part as an environment. (author)
Spin-Thermodynamics of Ultra-Cold Spin-1 Atoms
Li, Z. B.; Yao, D. X.; Bao, C. G.
2015-08-01
The spin-thermodynamics of a -body spin-1 condensate containing only the spin-degrees of freedom is studied via a theory in which , the total spin and its Z-component are exactly conserved. The magnetic field is considered as zero at first. Then the effect of a residual is evaluated. A temperature is defined as below that all the spatial degrees of freedom can be considered as being frozen and, accordingly, a pure spin-system will emerge. Effort is made to evaluate . When goes up from zero, the internal energy and the entropy experience sharp changes in two narrow domains of surrounding two turning temperatures and , the latter is higher. When or , and remain unchanged. Whereas when , and . It was found that and originate from the gap (the energy difference between the ground state (g.s.) and the first excited state) and the width (the energy difference between the g.s. and the highest state without spatial excitation) of the spectra, respectively. Thus their appearance is a common feature in spin-thermodynamics. In fact, marks the lowest excitation of the spin-modes, while marks the maximization of the entropy in the spin-space. In particular, the T-dependent population density is defined so that the theory can be checked by experimental data. Two kinds of condensates are notable: (i) the strongly trapped systems with a very small , they can work as pure spin-systems at relatively higher temperature; (ii) the systems with a high magnetization (say, ), the dimensions of their spin-spaces are very low. Furthermore, a larger together with a large N (for Rb) or a large (for Na) will lead to a sufficiently large so that a real g.s. can be experimentally created at a higher temperature. The spin-thermodynamics would remain valid whenever the spatial modes decouple from the spin-modes. This can occur at a higher temperature as demonstrated in Pechkis et al. (Phys Rev Lett 111:025301, 2013).
Topologically Massive Spin-1 Particles and Spin-Dependent Potentials
Ferreira, F A Gomes; Ospedal, L P R; Helayël-Neto, J A
2014-01-01
We investigate the role played by particular representations of an intermediate massive spin-1 boson in the context of spin-dependent potentials between fermionic sources in the limit of low momentum transfer. A comparison between the well-known Proca case and that of a rank-2 tensor gauge potential coupled to a 4-vector gauge field is investigated in order to extract spin- as well as velocity-dependent profiles of the interparticle potentials. Bounds on some of the coupling parameters are derived and we discuss possible applications.