Towards a Compositional SPIN

NASA Technical Reports Server (NTRS)

Pasareanu, Corina S.; Giannakopoulou, Dimitra

2006-01-01

This paper discusses our initial experience with introducing automated assume-guarantee verification based on learning in the SPIN tool. We believe that compositional verification techniques such as assume-guarantee reasoning could complement the state-reduction techniques that SPIN already supports, thus increasing the size of systems that SPIN can handle. We present a "light-weight" approach to evaluating the benefits of learning-based assume-guarantee reasoning in the context of SPIN: we turn our previous implementation of learning for the LTSA tool into a main program that externally invokes SPIN to provide the model checking-related answers. Despite its performance overheads (which mandate a future implementation within SPIN itself), this approach provides accurate information about the savings in memory. We have experimented with several versions of learning-based assume guarantee reasoning, including a novel heuristic introduced here for generating component assumptions when their environment is unavailable. We illustrate the benefits of learning-based assume-guarantee reasoning in SPIN through the example of a resource arbiter for a spacecraft. Keywords: assume-guarantee reasoning, model checking, learning.

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

NASA Astrophysics Data System (ADS)

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

2015-05-01

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

A Spiral Spin-Echo MR Imaging Technique for Improved Flow Artifact Suppression in T1-Weighted Postcontrast Brain Imaging: A Comparison with Cartesian Turbo Spin-Echo.

PubMed

Li, Z; Hu, H H; Miller, J H; Karis, J P; Cornejo, P; Wang, D; Pipe, J G

2016-04-01

A challenge with the T1-weighted postcontrast Cartesian spin-echo and turbo spin-echo brain MR imaging is the presence of flow artifacts. Our aim was to develop a rapid 2D spiral spin-echo sequence for T1-weighted MR imaging with minimal flow artifacts and to compare it with a conventional Cartesian 2D turbo spin-echo sequence. T1-weighted brain imaging was performed in 24 pediatric patients. After the administration of intravenous gadolinium contrast agent, a reference Cartesian TSE sequence with a scanning time of 2 minutes 30 seconds was performed, followed by the proposed spiral spin-echo sequence with a scanning time of 1 minutes 18 seconds, with similar spatial resolution and volumetric coverage. The results were reviewed independently and blindly by 3 neuroradiologists. Scores from a 3-point scale were assigned in 3 categories: flow artifact reduction, subjective preference, and lesion conspicuity, if any. The Wilcoxon signed rank test was performed to evaluate the reviewer scores. The t test was used to evaluate the SNR. The Fleiss κ coefficient was calculated to examine interreader agreement. In 23 cases, spiral spin-echo was scored over Cartesian TSE in flow artifact reduction (P < .001). In 21 cases, spiral spin-echo was rated superior in subjective preference (P < .001). Ten patients were identified with lesions, and no statistically significant difference in lesion conspicuity was observed between the 2 sequences. There was no statistically significant difference in SNR between the 2 techniques. The Fleiss κ coefficient was 0.79 (95% confidence interval, 0.65-0.93). The proposed spiral spin-echo pulse sequence provides postcontrast images with minimal flow artifacts at a faster scanning time than its Cartesian TSE counterpart. © 2016 by American Journal of Neuroradiology.

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

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

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy

2015-05-07

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

Anisotropic interactions of a single spin and dark-spin spectroscopy in diamond

NASA Astrophysics Data System (ADS)

Epstein, R. J.; Mendoza, F. M.; Kato, Y. K.; Awschalom, D. D.

2005-11-01

Experiments on single nitrogen-vacancy (N-V) centres in diamond, which include electron spin resonance, Rabi oscillations, single-shot spin readout and two-qubit operations with a nearby13C nuclear spin, show the potential of this spin system for solid-state quantum information processing. Moreover, N-V centre ensembles can have spin-coherence times exceeding 50 μs at room temperature. We have developed an angle-resolved magneto-photoluminescence microscope apparatus to investigate the anisotropic electron-spin interactions of single N-V centres at room temperature. We observe negative peaks in the photoluminescence as a function of both magnetic-field magnitude and angle that are explained by coherent spin precession and anisotropic relaxation at spin-level anti-crossings. In addition, precise field alignment unmasks the resonant coupling to neighbouring `dark' nitrogen spins, otherwise undetected by photoluminescence. These results demonstrate the capability of our spectroscopic technique for measuring small numbers of dark spins by means of a single bright spin under ambient conditions.

Spin Hall effects in metallic antiferromagnets – perspectives for future spin-orbitronics

DOE PAGES

Sklenar, Joseph; Zhang, Wei; Jungfleisch, Matthias B.; ...

2016-03-07

In this paper, we investigate angular dependent spin-orbit torques from the spin Hall effect in a metallic antiferromagnet using the spin-torque ferromagnetic resonance technique. The large spin Hall effect exists in PtMn, a prototypical CuAu-I-type metallic antiferromagnet. By applying epitaxial growth, we previously reported an appreciable difference in spin-orbit torques for c- and a-axis orientated samples, implying anisotropic effects in magnetically ordered materials. In this work we demonstrate through bipolar-magnetic-field experiments a small but noticeable asymmetric behavior in the spin-transfer-torque that appears as a hysteresis effect. Finally, we also suggest that metallic antiferromagnets may be good candidates for the investigationmore » of various unidirectional effects related to novel spin-orbitronics phenomena.« less

Cross-correlation spin noise spectroscopy of heterogeneous interacting spin systems

DOE PAGES

Roy, Dibyendu; Yang, Luyi; Crooker, Scott A.; ...

2015-04-30

Interacting multi-component spin systems are ubiquitous in nature and in the laboratory. As such, investigations of inter-species spin interactions are of vital importance. Traditionally, they are studied by experimental methods that are necessarily perturbative: e.g., by intentionally polarizing or depolarizing one spin species while detecting the response of the other(s). Here, we describe and demonstrate an alternative approach based on multi-probe spin noise spectroscopy, which can reveal inter-species spin interactions - under conditions of strict thermal equilibrium - by detecting and cross-correlating the stochastic fluctuation signals exhibited by each of the constituent spin species. Specifically, we consider a two-component spinmore » ensemble that interacts via exchange coupling, and we determine cross-correlations between their intrinsic spin fluctuations. The model is experimentally confirmed using “two-color” optical spin noise spectroscopy on a mixture of interacting Rb and Cs vapors. Noise correlations directly reveal the presence of inter-species spin exchange, without ever perturbing the system away from thermal equilibrium. These non-invasive and noise-based techniques should be generally applicable to any heterogeneous spin system in which the fluctuations of the constituent components are detectable.« less

Technique to determine location of radio sources from measurements taken on spinning spacecraft

NASA Technical Reports Server (NTRS)

Fainberg, J.

1979-01-01

The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.

Electron Spin Relaxation: The Role of Spin-Orbit Coupling in Organic Semiconductors

NASA Astrophysics Data System (ADS)

Willis, M.; Nuccio, L.; Schulz, L.; Gillin, W.; Kreouzis, T.; Pratt, F.; Lord, J.; Heeney, M.; Fratini, S.; Bernhard, C.; Drew, A.

2012-02-01

Rapid development of organic materials has lead to their availability in commercial products. Until now, the spin degree of freedom has not generally been used in organic materials. As well as engineering difficulties, there are fundamental questions with respect to the electron spin relaxation (eSR) mechanisms in organic molecules. Muons used as a microscopic spin probe, localized to a single molecule, can access information needed to identify the relevant model for eSR. In this presentation I will introduce the ALC-MuSR technique describing how eSR can be extracted and the expected effects. I will show how the technique has been applied to small organic molecules such as the group III Quinolate series and functionalized molecules with a pentacene-like backbone. Lastly I will present the Z-number and temperature dependence in these organic molecules and show strong evidence for a spin-orbit based eSR mechanism.

Single-spin stochastic optical reconstruction microscopy

PubMed Central

Pfender, Matthias; Aslam, Nabeel; Waldherr, Gerald; Neumann, Philipp; Wrachtrup, Jörg

2014-01-01

We experimentally demonstrate precision addressing of single-quantum emitters by combined optical microscopy and spin resonance techniques. To this end, we use nitrogen vacancy (NV) color centers in diamond confined within a few ten nanometers as individually resolvable quantum systems. By developing a stochastic optical reconstruction microscopy (STORM) technique for NV centers, we are able to simultaneously perform sub–diffraction-limit imaging and optically detected spin resonance (ODMR) measurements on NV spins. This allows the assignment of spin resonance spectra to individual NV center locations with nanometer-scale resolution and thus further improves spatial discrimination. For example, we resolved formerly indistinguishable emitters by their spectra. Furthermore, ODMR spectra contain metrology information allowing for sub–diffraction-limit sensing of, for instance, magnetic or electric fields with inherently parallel data acquisition. As an example, we have detected nuclear spins with nanometer-scale precision. Finally, we give prospects of how this technique can evolve into a fully parallel quantum sensor for nanometer resolution imaging of delocalized quantum correlations. PMID:25267655

Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets

NASA Astrophysics Data System (ADS)

dos Santos, Flaviano José; dos Santos Dias, Manuel; Guimarães, Filipe Souza Mendes; Bouaziz, Juba; Lounis, Samir

2018-01-01

Topological noncollinear magnetic phases of matter are at the heart of many proposals for future information nanotechnology, with novel device concepts based on ultrathin films and nanowires. Their operation requires understanding and control of the underlying dynamics, including excitations such as spin waves. So far, no experimental technique has attempted to probe large wave-vector spin waves in noncollinear low-dimensional systems. In this paper, we explain how inelastic electron scattering, being suitable for investigations of surfaces and thin films, can detect the collective spin-excitation spectra of noncollinear magnets. To reveal the particularities of spin waves in such noncollinear samples, we propose the usage of spin-polarized electron-energy-loss spectroscopy augmented with a spin analyzer. With the spin analyzer detecting the polarization of the scattered electrons, four spin-dependent scattering channels are defined, which allow us to filter and select specific spin-wave modes. We take as examples a topological nontrivial skyrmion lattice, a spin-spiral phase, and the conventional ferromagnet. Then we demonstrate that, counterintuitively and in contrast to the ferromagnetic case, even non-spin-flip processes can generate spin waves in noncollinear substrates. The measured dispersion and lifetime of the excitation modes permit us to fingerprint the magnetic nature of the substrate.

Spin forming development

NASA Astrophysics Data System (ADS)

Gates, W. G.

1982-05-01

Bendix product applications require the capability of fabricating heavy gage, high strength materials. Five commercial sources have been identified that have the capability of spin forming metal thicknesses greater than 9.5 mm and four equipment manufacturers produce machines with this capability. Twelve assemblies selected as candidates for spin forming applications require spin forming of titanium, 250 maraging steel, 17-4 pH stainless steel, Nitronic 40 steel, 304 L stainless steel, and 6061 aluminum. Twelve parts have been cold spin formed from a 250 maraging steel 8.1 mm wall thickness machine preform, and six have been hot spin formed directly from 31.8-mm-thick flat plate. Thirty-three Ti-6Al-4V titanium alloy parts and 26 17-4 pH stainless steel parts have been hot spin formed directly from 31.8-mm-thick plate. Hot spin forming directly from plate has demonstrated the feasibility and favorable economics of this fabrication technique for Bendix applications.

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

NASA Astrophysics Data System (ADS)

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

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

Spin-transfer torque in spin filter tunnel junctions

NASA Astrophysics Data System (ADS)

Ortiz Pauyac, Christian; Kalitsov, Alan; Manchon, Aurelien; Chshiev, Mairbek

2014-12-01

Spin-transfer torque in a class of magnetic tunnel junctions with noncollinear magnetizations, referred to as spin filter tunnel junctions, is studied within the tight-binding model using the nonequilibrium Green's function technique within Keldysh formalism. These junctions consist of one ferromagnet (FM) adjacent to a magnetic insulator (MI) or two FM separated by a MI. We find that the presence of the magnetic insulator dramatically enhances the magnitude of the spin-torque components compared to conventional magnetic tunnel junctions. The fieldlike torque is driven by the spin-dependent reflection at the MI/FM interface, which results in a small reduction of its amplitude when an insulating spacer (S) is inserted to decouple MI and FM layers. Meanwhile, the dampinglike torque is dominated by the tunneling electrons that experience the lowest barrier height. We propose a device of the form FM/(S)/MI/(S)/FM that takes advantage of these characteristics and allows for tuning the spin-torque magnitudes over a wide range just by rotation of the magnetization of the insulating layer.

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

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

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

2015-05-07

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

Software Library for Bruker TopSpin NMR Data Files

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

A software library for parsing and manipulating frequency-domain data files that have been processed using the Bruker TopSpin NMR software package. In the context of NMR, the term "processed" indicates that the end-user of the Bruker TopSpin NMR software package has (a) Fourier transformed the raw, time-domain data (the Free Induction Decay) into the frequency-domain and (b) has extracted the list of NMR peaks.

Low-cost high-resolution fast spin-echo MR of acoustic schwannoma: an alternative to enhanced conventional spin-echo MR?

PubMed

Allen, R W; Harnsberger, H R; Shelton, C; King, B; Bell, D A; Miller, R; Parkin, J L; Apfelbaum, R I; Parker, D

1996-08-01

To determine whether unenhanced high-resolution T2-weighted fast spin-echo MR imaging provides an acceptable and less expensive alternative to contrast-enhanced conventional T1-weighted spin-echo MR techniques in the diagnosis of acoustic schwannoma. We reviewed in a blinded fashion the records of 25 patients with pathologically documented acoustic schwannoma and of 25 control subjects, all of whom had undergone both enhanced conventional spin-echo MR imaging and unenhanced fast spin-echo MR imaging of the cerebellopontine angle/internal auditory canal region. The patients were imaged with the use of a quadrature head receiver coil for the conventional spin-echo sequences and dual 3-inch phased-array receiver coils for the fast spin-echo sequences. The size of the acoustic schwannomas ranged from 2 to 40 mm in maximum dimension. The mean maximum diameter was 12 mm, and 12 neoplasms were less than 10 mm in diameter. Acoustic schwannoma was correctly diagnosed on 98% of the fast spin-echo images and on 100% of the enhanced conventional spin-echo images. Statistical analysis of the data using the kappa coefficient demonstrated agreement beyond chance between these two imaging techniques for the diagnosis of acoustic schwannoma. There is no statistically significant difference in the sensitivity and specificity of unenhanced high-resolution fast spin-echo imaging and enhance T1-weighted conventional spin-echo imaging in the detection of acoustic schwannoma. We believe that the unenhanced high-resolution fast spin-echo technique provides a cost-effective method for the diagnosis of acoustic schwannoma.

Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin-orbit coupling.

PubMed

Sun, Dali; van Schooten, Kipp J; Kavand, Marzieh; Malissa, Hans; Zhang, Chuang; Groesbeck, Matthew; Boehme, Christoph; Valy Vardeny, Z

2016-08-01

Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule's surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials.

Electron spin resonance and spin-valley physics in a silicon double quantum dot.

PubMed

Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen

2014-05-14

Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.

Magnetic tunnel spin injectors for spintronics

NASA Astrophysics Data System (ADS)

Wang, Roger

Research in spin-based electronics, or "spintronics", has a universal goal to develop applications for electron spin in a broad range of electronics and strives to produce low power nanoscale devices. Spin injection into semiconductors is an important initial step in the development of spintronic devices, with the goal to create a highly spin polarized population of electrons inside a semiconductor at room temperature for study, characterization, and manipulation. This dissertation investigates magnetic tunnel spin injectors that aim to meet the spin injection requirements needed for potential spintronic devices. Magnetism and spin are inherently related, and chapter 1 provides an introduction on magnetic tunneling and spintronics. Chapter 2 then describes the fabrication of the spin injector structures studied in this dissertation, and also illustrates the optical spin detection technique that correlates the measured electroluminescence polarization from quantum wells to the electron spin polarization inside the semiconductor. Chapter 3 reports the spin injection from the magnetic tunnel transistor (MTT) spin injector, which is capable of producing highly spin polarized tunneling currents by spin selective scattering in its multilayer structure. The MTT achieves ˜10% lower bound injected spin polarization in GaAs at 1.4 K. Chapter 4 reports the spin injection from CoFe-MgO(100) tunnel spin injectors, where spin dependent tunneling through MgO(100) produces highly spin polarized tunneling currents. These structures achieve lower bound spin polarizations exceeding 50% at 100 K and 30% in GaAs at 290 K. The CoFe-MgO spin injectors also demonstrate excellent thermal stability, maintaining high injection efficiencies even after exposure to temperatures of up to 400 C. Bias voltage and temperature dependent studies on these structures indicate a significant dependence of the electroluminescence polarization on the spin and carrier recombination lifetimes inside the

Dynamics of polymers in elongational flow studied by the neutron spin-echo technique

NASA Astrophysics Data System (ADS)

Rheinstädter, Maikel C.; Sattler, Rainer; Häußler, Wolfgang; Wagner, Christian

2010-09-01

The nanoscale fluctuation dynamics of semidilute high molecular weight polymer solutions of polyethylenoxide (PEO) in D 2O under non-equilibrium flow conditions were studied by the neutron spin-echo technique. The sample cell was in contraction flow geometry and provided a pressure driven flow with a high elongational component that stretched the polymers most efficiently. Neutron scattering experiments in dilute polymer solutions are challenging because of the low polymer concentration and corresponding small quasi-elastic signals. A relaxation process with relaxation times of about 10 ps was observed, which shows anisotropic dynamics with applied flow.

Fast Single-Shot Hold Spin Readout in Double Quantum Dots

NASA Astrophysics Data System (ADS)

Bogan, Alexander; Studenikin, Sergei; Korkusinski, Marek; Aers, Geof; Gaudreau, Louis; Zawadzki, Piotr; Sachrajda, Andy; Tracy, Lisa; Reno, John; Hargett, Terry

Solid state spin qubits in quantum dots hold promise as scalable, high-density qubits in quantum information processing architectures. While much of the experimental investigation of these devices and their physics has focused on confined electron spins, hole spins in III-V semiconductors are attractive alternatives to electrons due to the reduced hyperfine coupling between the spin and the incoherent nuclear environment. In this talk, we will discuss a measurement protocol of the hole spin relaxation time T1 in a gated lateral GaAs double quantum dot tuned to the one and two-hole regimes, as well as a new technique for single-shot projective measurement of a single spin in tens of nanoseconds or less. The technique makes use of fast non-spin-conserving inter-dot transitions permitted by strong spin-orbit interactions for holes, as well as the latching of the charge state of the second quantum dot for enhanced sensitivity. This technique allows a direct measurement of the single spin relaxation time on time-scales set by physical device rather than by limitations of the measurement circuit.

Spin formalism and applications to new physics searches

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

Haber, H.E.

1994-12-01

An introduction to spin techniques in particle physics is given. Among the topics covered are: helicity formalism and its applications to the decay and scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity amplitudes (including projection operator methods and the spinor helicity method), and density matrix techniques. The utility of polarization and spin correlations for untangling new physics beyond the Standard Model at future colliders such as the LHC and a high energy e{sup +}e{sup {minus}} linear collider is then considered. A number of detailed examples are explored including the search for low-energy supersymmetry, a non-minimal Higgs boson sector,more » and new gauge bosons beyond the W{sup {+-}} and Z.« less

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Episodic Spin-up and Spin-down Torque on Earth

NASA Astrophysics Data System (ADS)

Slabinski, Victor J.; Mendonca, Antonio A.

2018-04-01

Variations in Earth rotation angle are traditionally expressed by the time difference (ΔT=TT-UT1) between Terrestrial Time (TT) as told by atomic clocks and Universal Time UT1, the time variable used by the Earth-rotation formula. A plot of ΔT versus TT over the past 160 years shows a continuous curve with approximate straight-line segments with different spans of order ~20 years. Removing the tidal and seasonal variations from the data gives these line segments which represent the “decadal variations” in Earth rotation.The slope of a straight-line segment is proportional to the departure of Earth rotation rate from a reference value at the time. The change in slope over the relatively short time between segments indicates an episodic spin-up or spin-down in Earth rotation. The daily combination of VLBI, SLR, and other modern data available since 1973 gives us accurate, daily values of ΔT and the corresponding LOD (Length Of Day) values during these episodes. These allow us to determine the rotational acceleration occurring then.The three largest spin-speed changes found during the VLBI era have the following characteristics:Episode _____________ Duration__ ΔLOD__LOD Rate1983 Dec 30-1984 Jan 28 ... 29 d ...-0.65 ms ..-8.3 ms/y ..........spin-up1989 Mar 15-1989 May 23 ...69 d ....0.68 .......+3.6 ..............spin-down1994 Jan 21-2001 Apr 01 ... 6.5 y ...-2.2 .........-0.36 ..extended spin-upFor the first two episodes listed, we find the acceleration grows from zero (or at least a relatively small value) to its extreme value in ~1 day, stays approximately constant at this value for 29 or 69 days, and then decays back to zero over ~1 day. The acceleration, while it occurs, gives an LOD rate much greater than the 0.02 ms/y rate from tidal friction.The third episode shows that occasionally a several-year-long episode occurs. The acceleration magnitude is smaller but can make a larger total change in LOD (and spin rate). Tidal friction requires >100 y to equal

Application of a system modification technique to dynamic tuning of a spinning rotor blade

NASA Technical Reports Server (NTRS)

Spain, C. V.

1987-01-01

An important consideration in the development of modern helicopters is the vibratory response of the main rotor blade. One way to minimize vibration levels is to ensure that natural frequencies of the spinning main rotor blade are well removed from integer multiples of the rotor speed. A technique for dynamically tuning a finite-element model of a rotor blade to accomplish that end is demonstrated. A brief overview is given of the general purpose finite element system known as Engineering Analysis Language (EAL) which was used in this work. A description of the EAL System Modification (SM) processor is then given along with an explanation of special algorithms developed to be used in conjunction with SM. Finally, this technique is demonstrated by dynamically tuning a model of an advanced composite rotor blade.

Epitaxy of spin injectors and their application toward spin-polarized lasers

NASA Astrophysics Data System (ADS)

Holub, Michael A.

Spintronics is an emerging; multidisciplinary field which examines the role of electron and nuclear spin in solid-state physics. Recent experiments suggest that the spin degree of freedom may be exploited to enhance the functionality of conventional semi conductor devices. Such endeavors require methods for efficient spin injection; spin transport, and spin detection in semiconductor heterostructures. This dissertation investigates the molecular-beam epitaxial growth and properties of ferromagnetic materials for electrical spin injection. Spin-injecting contacts are incorporated into prototype spintronic devices and their performance is examined. Two classes of materials may be used for spin injection into semiconductors: dilute magnetic semiconductor and ferromagnetic metals. The low-temperature growth and properties of (Al)Gal4nAs and In(Ga)MnAs epilayers and nanostructures are investigated, and a technique for the self-organized growth of Mn-doped InAs quantum dots is developed. The epitaxial growth of (Fe,MnAs)/(Al)GaAs Schottky tunnel barriers for electron spin injection is also investigated. The spin-injection efficiency of these contacts is assessed using a spin-valve or spin-polarized light-emitting diode. Lateral MnAs/GaAs spin-valves where Schottky tunnel barriers enable all-electrical spin injection and detection are grown, fabricated, and characterized. The Rowell criteria confirm that tunneling is the dominant, transport mechanism for the Schottky tunnel contacts. A peak magnetoresistance of 3.6% at 10 K and 1.1% at 125 K are observed for a 0.5 pin channel length spin-valve. Measurements using non-local spin-valves and other control devices verify that spurious contributions from anisotropic magnetoresistance and local Hall effects are negligible. Spin-polarized lasers offer inherent polarization control, reduced chirp, and lower threshold currents and are expected to outperform their charge-based counterparts. Initial efforts to realize a spin

ExoMol line list - XXI. Nitric Oxide (NO)

NASA Astrophysics Data System (ADS)

Wong, Andy; Yurchenko, Sergei N.; Bernath, Peter; Müller, Holger S. P.; McConkey, Stephanie; Tennyson, Jonathan

2017-09-01

Line lists for the X 2Π electronic ground state for the parent isotopologue of nitric oxide (14N16O) and five other major isotopologues (14N17O, 14N18O, 15N16O, 15N17O and 15N18O) are presented. The line lists are constructed using empirical energy levels (and line positions) and high-level ab initio intensities. The energy levels were obtained using a combination of two approaches, from an effective Hamiltonian and from solving the rovibronic Schrödinger equation variationally. The effective Hamiltonian model was obtained through a fit to the experimental line positions of NO available in the literature for all six isotopologues using the programs spfit and spcat. The variational model was built through a least squares fit of the ab initio potential and spin-orbit curves to the experimentally derived energies and experimental line positions of the main isotopologue only using the duo program. The ab initio potential energy, spin-orbit and dipole moment curves (PEC, SOC and DMC) are computed using high-level ab initio methods and the marvel method is used to obtain energies of NO from experimental transition frequencies. The line lists are constructed for each isotopologue based on the use of the most accurate energy levels and the ab initio DMC. Each line list covers a wavenumber range from 0 to 40 000 cm-1 with approximately 22 000 rovibronic states and 2.3-2.6 million transitions extending to Jmax = 184.5 and vmax = 51. Partition functions are also calculated up to a temperature of 5000 K. The calculated absorption line intensities at 296 K using these line lists show excellent agreement with those included in the HITRAN and HITEMP data bases. The computed NO line lists are the most comprehensive to date, covering a wider wavenumber and temperature range compared to both the HITRAN and HITEMP data bases. These line lists are also more accurate than those used in HITEMP. The full line lists are available from the CDS http://cdsarc.u-strasbg.fr and ExoMol www

ExoMol molecular line lists - XXIII. Spectra of PO and PS

NASA Astrophysics Data System (ADS)

Prajapat, Laxmi; Jagoda, Pawel; Lodi, Lorenzo; Gorman, Maire N.; Yurchenko, Sergei N.; Tennyson, Jonathan

2017-12-01

Comprehensive line lists for phosphorus monoxide (31P16O) and phosphorus monosulphide (31P32S) in their X 2Π electronic ground state are presented. The line lists are based on new ab initio potential energy (PEC), spin-orbit (SOC) and dipole moment (DMC) curves computed using the MRCI+Q-r method with aug-cc-pwCV5Z and aug-cc-pV5Z basis sets. The nuclear motion equations (i.e. the rovibronic Schrödinger equations for each molecule) are solved using the program DUO. The PECs and SOCs are refined in least-squares fits to available experimental data. Partition functions, Q(T), are computed up to T = 5000 K, the range of validity of the line lists. These line lists are the most comprehensive available for either molecule. The characteristically sharp peak of the Q-branches from the spin-orbit split components gives useful diagnostics for both PO and PS in spectra at infrared wavelengths. These line lists should prove useful for analysing observations and setting up models of environments such as brown dwarfs, low-mass stars, O-rich circumstellar regions and potentially for exoplanetary retrievals. Since PS is yet to be detected in space, the role of the two lowest excited electronic states (a 4Π and B 2Π) are also considered. An approximate line list for the PS X-B electronic transition, which predicts a number of sharp vibrational bands in the near ultraviolet, is also presented. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.

Repetitive readout of a single electronic spin via quantum logic with nuclear spin ancillae.

PubMed

Jiang, L; Hodges, J S; Maze, J R; Maurer, P; Taylor, J M; Cory, D G; Hemmer, P R; Walsworth, R L; Yacoby, A; Zibrov, A S; Lukin, M D

2009-10-09

Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers.

ExoMol line lists XXIV: a new hot line list for silicon monohydride, SiH

NASA Astrophysics Data System (ADS)

Yurchenko, Sergei N.; Sinden, Frances; Lodi, Lorenzo; Hill, Christian; Gorman, Maire N.; Tennyson, Jonathan

2018-02-01

SiH has long been observed in the spectrum of our Sun and other cool stars. Computed line lists for the main isotopologues of silicon monohydride, 28SiH, 29SiH, 30SiH and 28SiD are presented. These line lists consider rotation-vibration transitions within the ground X 2Π electronic state as well as transitions to the low-lying A 2Δ and a 4Σ- states. Ab initio potential energy (PECs) and dipole moment curves along with spin-orbit and electronic angular momentum couplings between them are calculated using the multireference configuration interaction level of theory with the MOLPRO package. The PEC for the ground X 2Π state is refined to available experimental data with a typical accuracy of around 0.01 cm-1 or better. The 28SiH line list includes 11 785 rovibronic states and 1724 841 transitions with associated Einstein-A coefficients for angular momentum J up to 82.5 and covering wavenumbers up to 31 340 cm-1 (λ < 0.319 μm). Spectra are simulated using the new line list and comparisons made with various experimental spectra. These line lists are applicable up to temperatures of 5000 K, making them relevant to astrophysical objects such as exoplanetary atmospheres and cool stars and opening up the possibility of detection in the interstellar medium. These line lists, called SiGHTLY, are available at the ExoMol (www.exomol.com) and CDS data base websites.

SD-CAS: Spin Dynamics by Computer Algebra System.

PubMed

Filip, Xenia; Filip, Claudiu

2010-11-01

A computer algebra tool for describing the Liouville-space quantum evolution of nuclear 1/2-spins is introduced and implemented within a computational framework named Spin Dynamics by Computer Algebra System (SD-CAS). A distinctive feature compared with numerical and previous computer algebra approaches to solving spin dynamics problems results from the fact that no matrix representation for spin operators is used in SD-CAS, which determines a full symbolic character to the performed computations. Spin correlations are stored in SD-CAS as four-entry nested lists of which size increases linearly with the number of spins into the system and are easily mapped into analytical expressions in terms of spin operator products. For the so defined SD-CAS spin correlations a set of specialized functions and procedures is introduced that are essential for implementing basic spin algebra operations, such as the spin operator products, commutators, and scalar products. They provide results in an abstract algebraic form: specific procedures to quantitatively evaluate such symbolic expressions with respect to the involved spin interaction parameters and experimental conditions are also discussed. Although the main focus in the present work is on laying the foundation for spin dynamics symbolic computation in NMR based on a non-matrix formalism, practical aspects are also considered throughout the theoretical development process. In particular, specific SD-CAS routines have been implemented using the YACAS computer algebra package (http://yacas.sourceforge.net), and their functionality was demonstrated on a few illustrative examples. Copyright © 2010 Elsevier Inc. All rights reserved.

Spin-analyzed SANS for soft matter applications

NASA Astrophysics Data System (ADS)

Chen, W. C.; Barker, J. G.; Jones, R.; Krycka, K. L.; Watson, S. M.; Gagnon, C.; Perevozchivoka, T.; Butler, P.; Gentile, T. R.

2017-06-01

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

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

Kaushal, Nitin; Herbrych, Jacek W.; Nocera, Alberto

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t 2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ, at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase tomore » an excitonic insulator with increasing λ at intermediate U. In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum <(J eff) 2>≠0 near the excitonic phase, smoothly connected to the <(J eff) 2>=0 regime. In conclusion, we also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.« less

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

NASA Astrophysics Data System (ADS)

Kaushal, Nitin; Herbrych, Jacek; Nocera, Alberto; Alvarez, Gonzalo; Moreo, Adriana; Reboredo, F. A.; Dagotto, Elbio

2017-10-01

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ , at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase to an excitonic insulator with increasing λ at intermediate U . In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum 〈(Jeff)2〉≠0 near the excitonic phase, smoothly connected to the 〈(Jeff)2〉=0 regime. We also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

DOE PAGES

Kaushal, Nitin; Herbrych, Jacek W.; Nocera, Alberto; ...

2017-10-09

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t 2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ, at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase tomore » an excitonic insulator with increasing λ at intermediate U. In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum <(J eff) 2>≠0 near the excitonic phase, smoothly connected to the <(J eff) 2>=0 regime. In conclusion, we also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.« less

Getting the Most Out of Dual-Listed Courses: Involving Undergraduate Students in Discussion Through Active Learning Techniques

NASA Astrophysics Data System (ADS)

Tasich, C. M.; Duncan, L. L.; Duncan, B. R.; Burkhardt, B. L.; Benneyworth, L. M.

2015-12-01

Dual-listed courses will persist in higher education because of resource limitations. The pedagogical differences between undergraduate and graduate STEM student groups and the underlying distinction in intellectual development levels between the two student groups complicate the inclusion of undergraduates in these courses. Active learning techniques are a possible remedy to the hardships undergraduate students experience in graduate-level courses. Through an analysis of both undergraduate and graduate student experiences while enrolled in a dual-listed course, we implemented a variety of learning techniques used to complement the learning of both student groups and enhance deep discussion. Here, we provide details concerning the implementation of four active learning techniques - role play, game, debate, and small group - that were used to help undergraduate students critically discuss primary literature. Student perceptions were gauged through an anonymous, end-of-course evaluation that contained basic questions comparing the course to other courses at the university and other salient aspects of the course. These were given as a Likert scale on which students rated a variety of statements (1 = strongly disagree, 3 = no opinion, and 5 = strongly agree). Undergraduates found active learning techniques to be preferable to traditional techniques with small-group discussions being rated the highest in both enjoyment and enhanced learning. The graduate student discussion leaders also found active learning techniques to improve discussion. In hindsight, students of all cultures may be better able to take advantage of such approaches and to critically read and discuss primary literature when written assignments are used to guide their reading. Applications of active learning techniques can not only address the gap between differing levels of students, but also serve as a complement to student engagement in any science course design.

Large spin accumulation and crystallographic dependence of spin transport in single crystal gallium nitride nanowires

PubMed Central

Park, Tae-Eon; Park, Youn Ho; Lee, Jong-Min; Kim, Sung Wook; Park, Hee Gyum; Min, Byoung-Chul; Kim, Hyung-jun; Koo, Hyun Cheol; Choi, Heon-Jin; Han, Suk Hee; Johnson, Mark; Chang, Joonyeon

2017-01-01

Semiconductor spintronics is an alternative to conventional electronics that offers devices with high performance, low power and multiple functionality. Although a large number of devices with mesoscopic dimensions have been successfully demonstrated at low temperatures for decades, room-temperature operation still needs to go further. Here we study spin injection in single-crystal gallium nitride nanowires and report robust spin accumulation at room temperature with enhanced spin injection polarization of 9%. A large Overhauser coupling between the electron spin accumulation and the lattice nuclei is observed. Finally, our single-crystal gallium nitride samples have a trigonal cross-section defined by the (001), () and () planes. Using the Hanle effect, we show that the spin accumulation is significantly different for injection across the (001) and () (or ()) planes. This provides a technique for increasing room temperature spin injection in mesoscopic systems. PMID:28569767

Comparison of axial T1 spin-echo and T1 fat-saturation magnetic resonance imaging techniques in the diagnosis of chondromalacia patellae.

PubMed

Vanarthos, W J; Pope, T L; Monu, J U

1994-12-01

To test the diagnostic value of T1 spin-echo and T1 fat-saturated magnetic resonance images (MRIs), we reviewed axial T1-weighted images with and without fat saturation in 20 patients with clinically suspected chondromalacia of the patella. All scans were obtained on 1.5-MR units. The scans were randomly ordered and reviewed independently at different times by two radiologists without knowledge of the arthroscopy results. The sensitivity of the individual techniques for detecting grade 3 or 4 chondromalacia patellae was 92% for fat-saturated axial T1-weighted images alone, and 67% for axial T1-weighted images without fat saturation. The sensitivity of the combined techniques was 100% for grades 3 and 4 and 90% for all grades (0 to 4). Chondromalacia patellae is diagnosed more accurately by using T1 fat saturation than by using T1 spin-echo images. With a combination of the two techniques, accuracy is 90% to 100%.

A homonuclear spin-pair filter for solid-state NMR based on adiabatic-passage techniques

NASA Astrophysics Data System (ADS)

Verel, René; Baldus, Marc; Ernst, Matthias; Meier, Beat H.

1998-05-01

A filtering scheme for the selection of spin pairs (and larger spin clusters) under fast magic-angle spinning is proposed. The scheme exploits the avoided level crossing in spin pairs during an adiabatic amplitude sweep through the so-called HORROR recoupling condition. The advantages over presently used double-quantum filters are twofold. (i) The maximum theoretical filter efficiency is, due to the adiabatic variation, 100% instead of 73% as for transient methods. (ii) Since the filter does not rely on the phase-cycling properties of the double-quantum coherence, there is no need to obtain the full double-quantum intensity for all spins in the sample at one single point in time. The only important requirement is that all coupled spins pass through a two-spin state during the amplitude sweep. This makes the pulse scheme robust with respect to rf-amplitude missetting, rf-field inhomogeneity and chemical-shift offset.

Critical behavior of two- and three-dimensional ferromagnetic and antiferromagnetic spin-ice systems using the effective-field renormalization group technique

NASA Astrophysics Data System (ADS)

Garcia-Adeva, Angel J.; Huber, David L.

2001-07-01

In this work we generalize and subsequently apply the effective-field renormalization-group (EFRG) technique to the problem of ferro- and antiferromagnetically coupled Ising spins with local anisotropy axes in geometrically frustrated geometries (kagomé and pyrochlore lattices). In this framework, we calculate the various ground states of these systems and the corresponding critical points. Excellent agreement is found with exact and Monte Carlo results. The effects of frustration are discussed. As pointed out by other authors, it turns out that the spin-ice model can be exactly mapped to the standard Ising model, but with effective interactions of the opposite sign to those in the original Hamiltonian. Therefore, the ferromagnetic spin ice is frustrated and does not order. Antiferromagnetic spin ice (in both two and three dimensions) is found to undergo a transition to a long-range-ordered state. The thermal and magnetic critical exponents for this transition are calculated. It is found that the thermal exponent is that of the Ising universality class, whereas the magnetic critical exponent is different, as expected from the fact that the Zeeman term has a different symmetry in these systems. In addition, the recently introduced generalized constant coupling method is also applied to the calculation of the critical points and ground-state configurations. Again, a very good agreement is found with exact, Monte Carlo, and renormalization-group calculations for the critical points. Incidentally, we show that the generalized constant coupling approach can be regarded as the lowest-order limit of the EFRG technique, in which correlations outside a frustrated unit are neglected, and scaling is substituted by strict equality of the thermodynamic quantities.

75 FR 1069 - Agency Information Collection Activities: Passenger List/Crew List (Form I-418)

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-08

...: Extension (without change). Affected Public: Businesses. Estimated Number of Respondents: 95,000. Estimated.... CBP is proposing that this information collection be extended with no change to the burden hours. This... other technological techniques or other forms of information. Title: Passenger List/Crew List. OMB...

Room temperature electrical spin injection into GaAs by an oxide spin injector

PubMed Central

Bhat, Shwetha G.; Kumar, P. S. Anil

2014-01-01

Spin injection, manipulation and detection are the integral parts of spintronics devices and have attracted tremendous attention in the last decade. It is necessary to judiciously choose the right combination of materials to have compatibility with the existing semiconductor technology. Conventional metallic magnets were the first choice for injecting spins into semiconductors in the past. So far there is no success in using a magnetic oxide material for spin injection, which is very important for the development of oxide based spintronics devices. Here we demonstrate the electrical spin injection from an oxide magnetic material Fe3O4, into GaAs with the help of tunnel barrier MgO at room temperature using 3-terminal Hanle measurement technique. A spin relaxation time τ ~ 0.9 ns for n-GaAs at 300 K is observed along with expected temperature dependence of τ. Spin injection using Fe3O4/MgO system is further established by injecting spins into p-GaAs and a τ of ~0.32 ns is obtained at 300 K. Enhancement of spin injection efficiency is seen with barrier thickness. In the field of spin injection and detection, our work using an oxide magnetic material establishes a good platform for the development of room temperature oxide based spintronics devices. PMID:24998440

Recent trends in spin-resolved photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Okuda, Taichi

2017-12-01

Since the discovery of the Rashba effect on crystal surfaces and also the discovery of topological insulators, spin- and angle-resolved photoelectron spectroscopy (SARPES) has become more and more important, as the technique can measure directly the electronic band structure of materials with spin resolution. In the same way that the discovery of high-Tc superconductors promoted the development of high-resolution angle-resolved photoelectron spectroscopy, the discovery of this new class of materials has stimulated the development of new SARPES apparatus with new functions and higher resolution, such as spin vector analysis, ten times higher energy and angular resolution than conventional SARPES, multichannel spin detection, and so on. In addition, the utilization of vacuum ultra violet lasers also opens a pathway to the realization of novel SARPES measurements. In this review, such recent trends in SARPES techniques and measurements will be overviewed.

Electrically tunable spin filtering for electron tunneling between spin-resolved quantum Hall edge states and a quantum dot

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

Kiyama, H., E-mail: kiyama@meso.t.u-tokyo.ac.jp; Fujita, T.; Teraoka, S.

2014-06-30

Spin filtering with electrically tunable efficiency is achieved for electron tunneling between a quantum dot and spin-resolved quantum Hall edge states by locally gating the two-dimensional electron gas (2DEG) leads near the tunnel junction to the dot. The local gating can change the potential gradient in the 2DEG and consequently the edge state separation. We use this technique to electrically control the ratio of the dot–edge state tunnel coupling between opposite spins and finally increase spin filtering efficiency up to 91%, the highest ever reported, by optimizing the local gating.

Radical production from the interaction of ozone and PUFA as demonstrated by electron spin resonance spin-trapping techniques

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

Pryor, W.A.; Prier, D.G.; Church, D.F.

1981-02-01

There is considerable evidence that indicates that a fraction of the damage caused by ozone to cellular systems involves radical-mediated reactions. The most direct method for probing the mechanism by which ozone reacts with target molecules such as polyunsaturated fatty acids involves the use of electron spin resonance. In 1968, Goldstein et al. reported that ESR signals were observed when 40 ppM ozone in air is bubbled through linoleic acid. We have repeated this experiment and have performed several experiments modified from this design; in none of these do we observe ESR signals. We have studied the reaction of ozonemore » with PUFA at -78/sup 0/C using spin traps. Spin traps themselves react with ozone, but the following protocol avoids that reaction. (1) Ozone in air or oxygen-free ozone is allowed to bubble through the sample in Freon-11 in an ESR tube at -78/sup 0/C; no ESR absorption is observed. (2) Unreacted ozone is flushed out with argon or nitrogen. (3) The spin trap in Freon-11 is added to give a 0.1 M solution, still at -78/sup 0/C; no ESR signal is observed. (4) The tube is allowed to warm slowly. At about -45/sup 0/C, the ESR spectra of spin adducts appear. Using this method with methyl linoleate we observe spin adducts of alkoxy radicals and also a signal that is consistent with a carbon radical with one ..cap alpha..-H. We hypothesize that an intermediate is formed from the reaction of ozone with PUFA that is stable at -78/sup 0/Cbut decomposes to form radicals at about -45/sup 0/C. We tentatively identify the intermediate as a trioxide on the basis of analogies and its temperature profile for decomposition to radicals. It appears reasonable to suggest that the reaction(s) responsible for the production of radicals under these low-temperature conditions also occurs at room temperature. Although the low-temperature intermediate cannot be observed at ambient temperatures, radicals from it could be responsible for the effects on autoxidation that

Highly Efficient Room Temperature Spin Injection Using Spin Filtering in MgO

NASA Astrophysics Data System (ADS)

Jiang, Xin

2007-03-01

Efficient electrical spin injection into GaAs/AlGaAs quantum well structures was demonstrated using CoFe/MgO tunnel spin injectors at room temperature. The spin polarization of the injected electron current was inferred from the circular polarization of electroluminescence from the quantum well. Polarization values as high as 57% at 100 K and 47% at 290 K were obtained in a perpendicular magnetic field of 5 Tesla. The interface between the tunnel spin injector and the GaAs interface remained stable even after thermal annealing at 400 ^oC. The temperature dependence of the electron-hole recombination time and the electron spin relaxation time in the quantum well was measured using time-resolved optical techniques. By taking into account of these properties of the quantum well, the intrinsic spin injection efficiency can be deduced. We conclude that the efficiency of spin injection from a CoFe/MgO spin injector is nearly independent of temperature and, moreover, is highly efficient with an efficiency of ˜ 70% for the temperature range studied (10 K to room temperature). Tunnel spin injectors are thus highly promising components of future semiconductor spintronic devices. Collaborators: Roger Wang^1, 3, Gian Salis^2, Robert Shelby^1, Roger Macfarlane^1, Seth Bank^3, Glenn Solomon^3, James Harris^3, Stuart S. P. Parkin^1 ^1 IBM Almaden Research Center, San Jose, CA 95120 ^2 IBM Zurich Research Laboratory, S"aumerstrasse 4, 8803 R"uschlikon, Switzerland ^3 Solid States and Photonics Laboratory, Stanford University, Stanford, CA 94305

Direct observation of the alignment of ferromagnetic spins by antiferromagnetic spins

NASA Astrophysics Data System (ADS)

Nolting, F.; Scholl, A.; Stöhr, J.; Seo, J. W.; Fompeyrine, J.; Siegwart, H.; Locquet, J.-P.; Anders, S.; Lüning, J.; Fullerton, E. E.; Toney, M. F.; Scheinfein, M. R.; Padmore, H. A.

2000-06-01

The arrangement of spins at interfaces in a layered magnetic material often has an important effect on the properties of the material. One example of this is the directional coupling between the spins in an antiferromagnet and those in an adjacent ferromagnet, an effect first discovered in 1956 and referred to as exchange bias. Because of its technological importance for the development of advanced devices such as magnetic read heads and magnetic memory cells, this phenomenon has received much attention. Despite extensive studies, however, exchange bias is still poorly understood, largely due to the lack of techniques capable of providing detailed information about the arrangement of magnetic moments near interfaces. Here we present polarization-dependent X-ray magnetic dichroism spectro-microscopy that reveals the micromagnetic structure on both sides of a ferromagnetic-antiferromagnetic interface. Images of thin ferromagnetic Co films grown on antiferromagnetic LaFeO3 show a direct link between the arrangement of spins in each material. Remanent hysteresis loops, recorded for individual ferromagnetic domains, show a local exchange bias. Our results imply that the alignment of the ferromagnetic spins is determined, domain by domain, by the spin directions in the underlying antiferromagnetic layer.

Quasiparticle spin resonance and coherence in superconducting aluminium

NASA Astrophysics Data System (ADS)

Quay, C. H. L.; Weideneder, M.; Chiffaudel, Y.; Strunk, C.; Aprili, M.

2015-10-01

Conventional superconductors were long thought to be spin inert; however, there is now increasing interest in both (the manipulation of) the internal spin structure of the ground-state condensate, as well as recently observed long-lived, spin-polarized excitations (quasiparticles). We demonstrate spin resonance in the quasiparticle population of a mesoscopic superconductor (aluminium) using novel on-chip microwave detection techniques. The spin decoherence time obtained (~100 ps), and its dependence on the sample thickness are consistent with Elliott-Yafet spin-orbit scattering as the main decoherence mechanism. The striking divergence between the spin coherence time and the previously measured spin imbalance relaxation time (~10 ns) suggests that the latter is limited instead by inelastic processes. This work stakes out new ground for the nascent field of spin-based electronics with superconductors or superconducting spintronics.

'Spin' in published biomedical literature: A methodological systematic review.

PubMed

Chiu, Kellia; Grundy, Quinn; Bero, Lisa

2017-09-01

In the scientific literature, spin refers to reporting practices that distort the interpretation of results and mislead readers so that results are viewed in a more favourable light. The presence of spin in biomedical research can negatively impact the development of further studies, clinical practice, and health policies. This systematic review aims to explore the nature and prevalence of spin in the biomedical literature. We searched MEDLINE, PreMEDLINE, Embase, Scopus, and hand searched reference lists for all reports that included the measurement of spin in the biomedical literature for at least 1 outcome. Two independent coders extracted data on the characteristics of reports and their included studies and all spin-related outcomes. Results were grouped inductively into themes by spin-related outcome and are presented as a narrative synthesis. We used meta-analyses to analyse the association of spin with industry sponsorship of research. We included 35 reports, which investigated spin in clinical trials, observational studies, diagnostic accuracy studies, systematic reviews, and meta-analyses. The nature of spin varied according to study design. The highest (but also greatest) variability in the prevalence of spin was present in trials. Some of the common practices used to spin results included detracting from statistically nonsignificant results and inappropriately using causal language. Source of funding was hypothesised by a few authors to be a factor associated with spin; however, results were inconclusive, possibly due to the heterogeneity of the included papers. Further research is needed to assess the impact of spin on readers' decision-making. Editors and peer reviewers should be familiar with the prevalence and manifestations of spin in their area of research in order to ensure accurate interpretation and dissemination of research.

Thermal imaging of spin Peltier effect

NASA Astrophysics Data System (ADS)

Daimon, Shunsuke; Iguchi, Ryo; Hioki, Tomosato; Saitoh, Eiji; Uchida, Ken-Ichi

2016-12-01

The Peltier effect modulates the temperature of a junction comprising two different conductors in response to charge currents across the junction, which is used in solid-state heat pumps and temperature controllers in electronics. Recently, in spintronics, a spin counterpart of the Peltier effect was observed. The `spin Peltier effect' modulates the temperature of a magnetic junction in response to spin currents. Here we report thermal imaging of the spin Peltier effect; using active thermography technique, we visualize the temperature modulation induced by spin currents injected into a magnetic insulator from an adjacent metal. The thermal images reveal characteristic distribution of spin-current-induced heat sources, resulting in the temperature change confined only in the vicinity of the metal/insulator interface. This finding allows us to estimate the actual magnitude of the temperature modulation induced by the spin Peltier effect, which is more than one order of magnitude greater than previously believed.

Artificial tektites: an experimental technique for capturing the shapes of spinning drops

NASA Astrophysics Data System (ADS)

Baldwin, K. A.

2014-12-01

Tektites are small stones formed from rapidly cooling drops of molten rock ejected from high velocity asteroid impacts with the Earth, that freeze into a myriad of shapes during flight. Many splash-form tektites have an elongated or dumb-bell shape owing to their rotation prior to solidification[1]. Here we present a novel method for creating 'artificial tektites' from spinning drops of molten wax, using diamagnetic levitation to suspend the drops[2]. We find that the solid wax models produced this way are the stable equilibrium shapes of a spinning liquid droplet held together by surface tension. In addition to the geophysical interest in tektite formation, the stable equilibrium shapes of liquid drops have implications for many physical phenomena, covering a wide range of length scales, from nuclear physics (e.g. in studies of rapidly rotating atomic nuclei), to astrophysics (e.g. in studies of the shapes of astronomical bodies such as asteroids, rapidly rotating stars and event horizons of rotating black holes). For liquid drops bound by surface tension, analytical and numerical methods predict a series of stable equilibrium shapes with increasing angular momentum. Slowly spinning drops have an oblate-like shape. With increasing angular momentum these shapes become secularly unstable to a series of triaxial pseudo-ellipsoids that then evolve into a family of two-lobed 'dumb-bell' shapes as the angular momentum is increased still further. Our experimental method allows accurate measurements of the drops to be taken, which are useful to validate numerical models. This method has provided a means for observing tektite formation, and has additionally confirmed experimentally the stable equilibrium shapes of liquid drops, distinct from the equivalent shapes of rotating astronomical bodies. Potentially, this technique could be applied to observe the non-equilibrium dynamic processes that are also important in real tektite formation, involving, e.g. viscoelastic

Inverse engineering for fast transport and spin control of spin-orbit-coupled Bose-Einstein condensates in moving harmonic traps

NASA Astrophysics Data System (ADS)

Chen, Xi; Jiang, Ruan-Lei; Li, Jing; Ban, Yue; Sherman, E. Ya.

2018-01-01

We investigate fast transport and spin manipulation of tunable spin-orbit-coupled Bose-Einstein condensates in a moving harmonic trap. Motivated by the concept of shortcuts to adiabaticity, we design inversely the time-dependent trap position and spin-orbit-coupling strength. By choosing appropriate boundary conditions we obtain fast transport and spin flip simultaneously. The nonadiabatic transport and relevant spin dynamics are illustrated with numerical examples and compared with the adiabatic transport with constant spin-orbit-coupling strength and velocity. Moreover, the influence of nonlinearity induced by interatomic interaction is discussed in terms of the Gross-Pitaevskii approach, showing the robustness of the proposed protocols. With the state-of-the-art experiments, such an inverse engineering technique paves the way for coherent control of spin-orbit-coupled Bose-Einstein condensates in harmonic traps.

General theory of feedback control of a nuclear spin ensemble in quantum dots

NASA Astrophysics Data System (ADS)

Yang, Wen; Sham, L. J.

2013-12-01

We present a microscopic theory of the nonequilibrium nuclear spin dynamics driven by the electron and/or hole under continuous-wave pumping in a quantum dot. We show the correlated dynamics of the nuclear spin ensemble and the electron and/or hole under optical excitation as a quantum feedback loop and investigate the dynamics of the many nuclear spins as a nonlinear collective motion. This gives rise to three observable effects: (i) hysteresis, (ii) locking (avoidance) of the pump absorption strength to (from) the natural resonance, and (iii) suppression (amplification) of the fluctuation of weakly polarized nuclear spins, leading to prolonged (shortened) electron-spin coherence time. A single nonlinear feedback function is constructed which determines the different outcomes of the three effects listed above depending on the feedback being negative or positive. The general theory also helps to put in perspective the wide range of existing theories on the problem of a single electron spin in a nuclear spin bath.

Paramagnetic Spin Seebeck Effect

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

Wu, Stephen M.; Pearson, John E.; Bhattacharya, Anand

2015-05-01

We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (< 20 K), we resolve the paramagnetic spin Seebeck effect in the insulating paramagnets Gd3Ga5O12 (gadolinium gallium garnet) and DyScO3 (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which producesmore » a phenomenologically similar signal.« less

High efficiency spin-valve and spin-filter in a doped rhombic graphene quantum dot device

NASA Astrophysics Data System (ADS)

Silva, P. V.; Saraiva-Souza, A.; Maia, D. W.; Souza, F. M.; Filho, A. G. Souza; Meunier, V.; Girão, E. C.

2018-04-01

Spin-polarized transport through a rhombic graphene quantum dot (rGQD) attached to armchair graphene nanoribbon (AGNR) electrodes is investigated by means of the Green's function technique combined with single-band tight-binding (TB) approach including a Hubbard-like term. The Hubbard repulsion was included within the mean-field approximation. Compared to anti-ferromagnetic (AFM), we show that the ferromagnetic (FM) ordering of the rGQD corresponds to a smaller bandgap, thus resulting in an efficient spin injector. As a consequence, the electron transport spectrum reveals a spin valve effect, which is controlled by doping with B/N atoms creating a p-n-type junction. The calculations point out that such systems can be used as spin-filter devices with efficiency close to a 100 % .

Quasiparticle spin resonance and coherence in superconducting aluminium.

PubMed

Quay, C H L; Weideneder, M; Chiffaudel, Y; Strunk, C; Aprili, M

2015-10-26

Conventional superconductors were long thought to be spin inert; however, there is now increasing interest in both (the manipulation of) the internal spin structure of the ground-state condensate, as well as recently observed long-lived, spin-polarized excitations (quasiparticles). We demonstrate spin resonance in the quasiparticle population of a mesoscopic superconductor (aluminium) using novel on-chip microwave detection techniques. The spin decoherence time obtained (∼100 ps), and its dependence on the sample thickness are consistent with Elliott-Yafet spin-orbit scattering as the main decoherence mechanism. The striking divergence between the spin coherence time and the previously measured spin imbalance relaxation time (∼10 ns) suggests that the latter is limited instead by inelastic processes. This work stakes out new ground for the nascent field of spin-based electronics with superconductors or superconducting spintronics.

Spin-orbit scattering visualized in quasiparticle interference

NASA Astrophysics Data System (ADS)

Kohsaka, Y.; Machida, T.; Iwaya, K.; Kanou, M.; Hanaguri, T.; Sasagawa, T.

2017-03-01

In the presence of spin-orbit coupling, electron scattering off impurities depends on both spin and orbital angular momentum of electrons—spin-orbit scattering. Although some transport properties are subject to spin-orbit scattering, experimental techniques directly accessible to this effect are limited. Here we show that a signature of spin-orbit scattering manifests itself in quasiparticle interference (QPI) imaged by spectroscopic-imaging scanning tunneling microscopy. The experimental data of a polar semiconductor BiTeI are well reproduced by numerical simulations with the T -matrix formalism that include not only scalar scattering normally adopted but also spin-orbit scattering stronger than scalar scattering. To accelerate the simulations, we extend the standard efficient method of QPI calculation for momentum-independent scattering to be applicable even for spin-orbit scattering. We further identify a selection rule that makes spin-orbit scattering visible in the QPI pattern. These results demonstrate that spin-orbit scattering can exert predominant influence on QPI patterns and thus suggest that QPI measurement is available to detect spin-orbit scattering.

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

NASA Technical Reports Server (NTRS)

Patton, J. M., Jr.

1980-01-01

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

Identification of mitochondrial electron transport chain-mediated NADH radical formation by EPR spin-trapping techniques.

PubMed

Matsuzaki, Satoshi; Kotake, Yashige; Humphries, Kenneth M

2011-12-20

The mitochondrial electron transport chain (ETC) is a major source of free radical production. However, due to the highly reactive nature of radical species and their short lifetimes, accurate detection and identification of these molecules in biological systems is challenging. The aim of this investigation was to determine the free radical species produced from the mitochondrial ETC by utilizing EPR spin-trapping techniques and the recently commercialized spin-trap, 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO). We demonstrate that this spin-trap has the preferential quality of having minimal mitochondrial toxicity at concentrations required for radical detection. In rat heart mitochondria and submitochondrial particles supplied with NADH, the major species detected under physiological pH was a carbon-centered radical adduct, indicated by markedly large hyperfine coupling constant with hydrogen (a(H) > 2.0 mT). In the presence of the ETC inhibitors, the carbon-centered radical formation was increased and exhibited NADH concentration dependency. The same carbon-centered radical could also be produced with the NAD biosynthesis precursor, nicotinamide mononucleotide, in the presence of a catalytic amount of NADH. The results support the conclusion that the observed species is a complex I derived NADH radical. The formation of the NADH radical could be blocked by hydroxyl radical scavengers but not SOD. In vitro experiments confirmed that an NADH-radical is readily formed by hydroxyl radical but not superoxide anion, further implicating hydroxyl radical as an upstream mediator of NADH radical production. These findings demonstrate the identification of a novel mitochondrial radical species with potential physiological significance and highlight the diverse mechanisms and sites of production within the ETC.

Application of spin-exchange relaxation-free magnetometry to the Cosmic Axion Spin Precession Experiment

NASA Astrophysics Data System (ADS)

Wang, Tao; Kimball, Derek F. Jackson; Sushkov, Alexander O.; Aybas, Deniz; Blanchard, John W.; Centers, Gary; Kelley, Sean R. O.'; Wickenbrock, Arne; Fang, Jiancheng; Budker, Dmitry

2018-03-01

The Cosmic Axion Spin Precession Experiment (CASPEr) seeks to measure oscillating torques on nuclear spins caused by axion or axion-like-particle (ALP) dark matter via nuclear magnetic resonance (NMR) techniques. A sample spin-polarized along a leading magnetic field experiences a resonance when the Larmor frequency matches the axion/ALP Compton frequency, generating precessing transverse nuclear magnetization. Here we demonstrate a Spin-Exchange Relaxation-Free (SERF) magnetometer with sensitivity ≈ 1 fT /√{ Hz } and an effective sensing volume of 0.1 cm3 that may be useful for NMR detection in CASPEr. A potential drawback of SERF-magnetometer-based NMR detection is the SERF's limited dynamic range. Use of a magnetic flux transformer to suppress the leading magnetic field is considered as a potential method to expand the SERF's dynamic range in order to probe higher axion/ALP Compton frequencies.

Entangled spins and ghost-spins

NASA Astrophysics Data System (ADS)

Jatkar, Dileep P.; Narayan, K.

2017-09-01

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 [20] 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 ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

Spin Current Noise of the Spin Seebeck Effect and Spin Pumping

NASA Astrophysics Data System (ADS)

Matsuo, M.; Ohnuma, Y.; Kato, T.; Maekawa, S.

2018-01-01

We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.

Quasiparticle spin resonance and coherence in superconducting aluminium

PubMed Central

Quay, C. H. L.; Weideneder, M.; Chiffaudel, Y.; Strunk, C.; Aprili, M.

2015-01-01

Conventional superconductors were long thought to be spin inert; however, there is now increasing interest in both (the manipulation of) the internal spin structure of the ground-state condensate, as well as recently observed long-lived, spin-polarized excitations (quasiparticles). We demonstrate spin resonance in the quasiparticle population of a mesoscopic superconductor (aluminium) using novel on-chip microwave detection techniques. The spin decoherence time obtained (∼100 ps), and its dependence on the sample thickness are consistent with Elliott–Yafet spin–orbit scattering as the main decoherence mechanism. The striking divergence between the spin coherence time and the previously measured spin imbalance relaxation time (∼10 ns) suggests that the latter is limited instead by inelastic processes. This work stakes out new ground for the nascent field of spin-based electronics with superconductors or superconducting spintronics. PMID:26497744

3D GRASE PROPELLER: Improved Image Acquisition Technique for Arterial Spin Labeling Perfusion Imaging

PubMed Central

Tan, Huan; Hoge, W. Scott; Hamilton, Craig A.; Günther, Matthias; Kraft, Robert A.

2014-01-01

Arterial spin labeling (ASL) is a non-invasive technique that can quantitatively measure cerebral blood flow (CBF). While traditionally ASL employs 2D EPI or spiral acquisition trajectories, single-shot 3D GRASE is gaining popularity in ASL due to inherent SNR advantage and spatial coverage. However, a major limitation of 3D GRASE is through-plane blurring caused by T2 decay. A novel technique combining 3D GRASE and a PROPELLER trajectory (3DGP) is presented to minimize through-plane blurring without sacrificing perfusion sensitivity or increasing total scan time. Full brain perfusion images were acquired at a 3×3×5mm3 nominal voxel size with Q2TIPS-FAIR as the ASL preparation sequence. Data from 5 healthy subjects was acquired on a GE 1.5T scanner in less than 4 minutes per subject. While showing good agreement in CBF quantification with 3D GRASE, 3DGP demonstrated reduced through-plane blurring, improved anatomical details, high repeatability and robustness against motion, making it suitable for routine clinical use. PMID:21254211

New technique for excitation of bulk and surface spin waves in ferromagnets

NASA Astrophysics Data System (ADS)

Bogacz, S. A.; Ketterson, J. B.

1985-09-01

A meander-line magnetic transducer is discussed in the context of bulk and surface spin-wave generation in ferromagnets. The magnetic field created by the transducer was calculated in closed analytic form for this model. The linear response of the ferromagnet to the inhomogenous surface disturbance of arbitrary ω and k was obtained as a self-consistent solution to the Bloch equation of motion and the Maxwell equations, subject to appropriate boundary condition. In particular, the energy flux through the boundary displays a sharp resonantlike absorption maximum concentrated at the frequency of the magnetostatic Damon-Eshbach (DE) surface mode; furthermore, the energy transfer spectrum is cut off abruptly below the threshold frequency of the bulk spin waves. The application of the meander line to the spin diffusion problem in NMR is also discussed.

Entanglement entropy of critical spin liquids.

PubMed

Zhang, Yi; Grover, Tarun; Vishwanath, Ashvin

2011-08-05

Quantum spin liquids are phases of matter whose internal structure is not captured by a local order parameter. Particularly intriguing are critical spin liquids, where strongly interacting excitations control low energy properties. Here we calculate their bipartite entanglement entropy that characterizes their quantum structure. In particular we calculate the Renyi entropy S(2) on model wave functions obtained by Gutzwiller projection of a Fermi sea. Although the wave functions are not sign positive, S(2) can be calculated on relatively large systems (>324 spins) using the variational Monte Carlo technique. On the triangular lattice we find that entanglement entropy of the projected Fermi sea state violates the boundary law, with S(2) enhanced by a logarithmic factor. This is an unusual result for a bosonic wave function reflecting the presence of emergent fermions. These techniques can be extended to study a wide class of other phases.

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

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

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

2015-02-14

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

Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures.

PubMed

Vinante, A; Wijts, G; Usenko, O; Schinkelshoek, L; Oosterkamp, T H

2011-12-06

Magnetic resonance force microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed superconducting quantum interference device (SQUID)-based cantilever detection technique, which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centres on a silicon surface down to millikelvin temperatures. Fluctuations of such defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs, as well as in several superconducting and single spin qubits. We find evidence that spin diffusion has a key role in the low-temperature spin dynamics.

Effect of electron spin-spin interaction on level crossings and spin flips in a spin-triplet system

NASA Astrophysics Data System (ADS)

Jia, Wei; Hu, Fang-Qi; Wu, Ning; Zhao, Qing

2017-12-01

We study level crossings and spin flips in a system consisting of a spin-1 (an electron spin triplet) coupled to a nuclear spin of arbitrary size K , in the presence of a uniform magnetic field and the electron spin-spin interaction within the triplet. Through an analytical diagonalization based on the SU (3 ) Lie algebra, we find that the electron spin-spin interaction not only removes the curious degeneracy which appears in the absence of the interaction, but also produces some level anticrossings (LACs) for strong interactions. The real-time dynamics of the system shows that periodic spin flips occur at the LACs for arbitrary K , which might provide an option for nuclear or electron spin polarization.

Evaluation of the Chondromalacia Patella Using a Microscopy Coil: Comparison of the Two-Dimensional Fast Spin Echo Techniques and the Three-Dimensional Fast Field Echo Techniques

PubMed Central

Kim, Hyun-joo; Kang, Chang Ho; Ryu, Jeong Ah; Shin, Myung Jin; Cho, Kyung-Ja; Cho, Woo Shin

2011-01-01

Objective We wanted to compare the two-dimensional (2D) fast spin echo (FSE) techniques and the three-dimensional (3D) fast field echo techniques for the evaluation of the chondromalacia patella using a microscopy coil. Materials and Methods Twenty five patients who underwent total knee arthroplasty were included in this study. Preoperative MRI evaluation of the patella was performed using a microscopy coil (47 mm). The proton density-weighted fast spin echo images (PD), the fat-suppressed PD images (FS-PD), the intermediate weighted-fat suppressed fast spin echo images (iw-FS-FSE), the 3D balanced-fast field echo images (B-FFE), the 3D water selective cartilage scan (WATS-c) and the 3D water selective fluid scan (WATS-f) were obtained on a 1.5T MRI scanner. The patellar cartilage was evaluated in nine areas: the superior, middle and the inferior portions that were subdivided into the medial, central and lateral facets in a total of 215 areas. Employing the Noyes grading system, the MRI grade 0-I, II and III lesions were compared using the gross and microscopic findings. The sensitivity, specificity and accuracy were evaluated for each sequence. The significance of the differences for the individual sequences was calculated using the McNemar test. Results The gross and microscopic findings demonstrated 167 grade 0-I lesions, 40 grade II lesions and eight grade III lesions. Iw-FS-FSE had the highest accuracy (sensitivity/specificity/accuracy = 88%/98%/96%), followed by FS-PD (78%/98%/93%, respectively), PD (76%/98%/93%, respectively), B-FFE (71%/100%/93%, respectively), WATS-c (67%/100%/92%, respectively) and WATS-f (58%/99%/89%, respectively). There were statistically significant differences for the iw-FS-FSE and WATS-f and for the PD-FS and WATS-f (p < 0.01). Conclusion The iw-FS-FSE images obtained with a microscopy coil show best diagnostic performance among the 2D and 3D GRE images for evaluating the chondromalacia patella. PMID:21228943

Evaluation of the chondromalacia patella using a microscopy coil: comparison of the two-dimensional fast spin echo techniques and the three-dimensional fast field echo techniques.

PubMed

Kim, Hyun-joo; Lee, Sang Hoon; Kang, Chang Ho; Ryu, Jeong Ah; Shin, Myung Jin; Cho, Kyung-Ja; Cho, Woo Shin

2011-01-01

We wanted to compare the two-dimensional (2D) fast spin echo (FSE) techniques and the three-dimensional (3D) fast field echo techniques for the evaluation of the chondromalacia patella using a microscopy coil. Twenty five patients who underwent total knee arthroplasty were included in this study. Preoperative MRI evaluation of the patella was performed using a microscopy coil (47 mm). The proton density-weighted fast spin echo images (PD), the fat-suppressed PD images (FS-PD), the intermediate weighted-fat suppressed fast spin echo images (iw-FS-FSE), the 3D balanced-fast field echo images (B-FFE), the 3D water selective cartilage scan (WATS-c) and the 3D water selective fluid scan (WATS-f) were obtained on a 1.5T MRI scanner. The patellar cartilage was evaluated in nine areas: the superior, middle and the inferior portions that were subdivided into the medial, central and lateral facets in a total of 215 areas. Employing the Noyes grading system, the MRI grade 0-I, II and III lesions were compared using the gross and microscopic findings. The sensitivity, specificity and accuracy were evaluated for each sequence. The significance of the differences for the individual sequences was calculated using the McNemar test. The gross and microscopic findings demonstrated 167 grade 0-I lesions, 40 grade II lesions and eight grade III lesions. Iw-FS-FSE had the highest accuracy (sensitivity/specificity/accuracy = 88%/98%/96%), followed by FS-PD (78%/98%/93%, respectively), PD (76%/98%/93%, respectively), B-FFE (71%/100%/93%, respectively), WATS-c (67%/100%/92%, respectively) and WATS-f (58%/99%/89%, respectively). There were statistically significant differences for the iw-FS-FSE and WATS-f and for the PD-FS and WATS-f (p < 0.01). The iw-FS-FSE images obtained with a microscopy coil show best diagnostic performance among the 2D and 3D GRE images for evaluating the chondromalacia patella.

Spin-dependent excitation of plasma modes in non-neutral ion plasmas

NASA Astrophysics Data System (ADS)

Sawyer, Brian C.; Britton, Joe W.; Bollinger, John J.

2011-10-01

We report on a new technique for exciting and sensitively detecting plasma modes in small, cold non-neutral ion plasmas. The technique uses an optical dipole force generated from laser beams to excite plasma modes. By making the force spin- dependent (i.e. depend on the internal state of the atomic ion) very small mode excitations (<100 nm) can be detected through spin-motion entanglement. Even when the optical dipole force is homogeneous throughout the plasma, short wavelength modes on the order of the interparticle spacing can in principle be excited and detected through the spin dependence of the force. We use this technique to study the drumhead modes of single plane triangular arrays of a few hundred Be+ ions. Spin-dependent mode excitation is interesting in this system because it provides a means of engineering an Ising interaction on a 2-D triangular lattice. For the case of an anti-ferromagnetic interaction, this system exhibits spin frustration on a scale that is at present computationally intractable. Work supported by the DARPA OLE program and NIST.

Spin-dependent recombination probed through the dielectric polarizability

PubMed Central

Bayliss, Sam L.; Greenham, Neil C.; Friend, Richard H.; Bouchiat, Hélène; Chepelianskii, Alexei D

2015-01-01

Despite residing in an energetically and structurally disordered landscape, the spin degree of freedom remains a robust quantity in organic semiconductor materials due to the weak coupling of spin and orbital states. This enforces spin-selectivity in recombination processes which plays a crucial role in optoelectronic devices, for example, in the spin-dependent recombination of weakly bound electron-hole pairs, or charge-transfer states, which form in a photovoltaic blend. Here, we implement a detection scheme to probe the spin-selective recombination of these states through changes in their dielectric polarizability under magnetic resonance. Using this technique, we access a regime in which the usual mixing of spin-singlet and spin-triplet states due to hyperfine fields is suppressed by microwave driving. We present a quantitative model for this behaviour which allows us to estimate the spin-dependent recombination rate, and draw parallels with the Majorana–Brossel resonances observed in atomic physics experiments. PMID:26439933

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

NASA Astrophysics Data System (ADS)

Roy, Kuntal

2017-11-01

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

Spin currents and magnon dynamics in insulating magnets

NASA Astrophysics Data System (ADS)

Nakata, Kouki; Simon, Pascal; Loss, Daniel

2017-03-01

Nambu-Goldstone theorem provides gapless modes to both relativistic and nonrelativistic systems. The Nambu-Goldstone bosons in insulating magnets are called magnons or spin-waves and play a key role in magnetization transport. We review here our past works on magnetization transport in insulating magnets and also add new insights, with a particular focus on magnon transport. We summarize in detail the magnon counterparts of electron transport, such as the Wiedemann-Franz law, the Onsager reciprocal relation between the Seebeck and Peltier coefficients, the Hall effects, the superconducting state, the Josephson effects, and the persistent quantized current in a ring to list a few. Focusing on the electromagnetism of moving magnons, i.e. magnetic dipoles, we theoretically propose a way to directly measure magnon currents. As a consequence of the Mermin-Wagner-Hohenberg theorem, spin transport is drastically altered in one-dimensional antiferromagnetic (AF) spin-1/2 chains; where the Néel order is destroyed by quantum fluctuations and a quasiparticle magnon-like picture breaks down. Instead, the low-energy collective excitations of the AF spin chain are described by a Tomonaga-Luttinger liquid (TLL) which provides the spin transport properties in such antiferromagnets some universal features at low enough temperature. Finally, we enumerate open issues and provide a platform to discuss the future directions of magnonics.

Ultrafast spintronics roadmap: from femtosecond spin current pulses to terahertz non-uniform spin dynamics via nano-confined spin transfer torques (Conference Presentation)

NASA Astrophysics Data System (ADS)

Melnikov, Alexey; Razdolski, Ilya; Alekhin, Alexandr; Ilin, Nikita; Meyburg, Jan; Diesing, Detlef; Roddatis, Vladimir; Rungger, Ivan; Stamenova, Maria; Sanvito, Stefano; Bovensiepen, Uwe

2016-10-01

Further development of spintronics requires miniaturization and reduction of characteristic timescales of spin dynamics combining the nanometer spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the spin transfer torque (STT) exerted by ultrashort SC pulses on the FM open the time domain for studying STT fingerprint on spatially non-uniform magnetization dynamics. Using the sensitivity of magneto-induced second harmonic generation to SC, we develop technique for SC monitoring. With 20 fs resolution, we demonstrate the generation of 250 fs-long SC pulses in Fe/Au/Fe/MgO(001) structures. Their temporal profile indicates (i) nearly-ballistic hot electron transport in Au and (ii) that the pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Together with strongly spin-dependent Fe/Au interface transmission calculated for these carriers, this suggests the non-thermal spin-dependent Seebeck effect dominating the generation of ultrashort SC pulses. The analysis of SC transmission/reflection at the Au/Fe interface shows that hot electron spins orthogonal to the Fe magnetization rotate gaining huge parallel (anti-parallel) projection in transmitted (reflected) SC. This is accompanied by a STT-induced perturbation of the magnetization localized at the interface, which excites the inhomogeneous high-frequency spin dynamics in the FM. Time-resolved magneto-optical studies reveal the excitation of several standing spin wave modes in the Fe film with their spectrum extending up to 0.6 THz and indicating the STT spatial confinement to 2 nm.

Low Temperature Electrical Spin Injection from Highly Spin Polarized Co₂CrAl Heusler Alloy into p-Si.

PubMed

Kar, Uddipta; Panda, J; Nath, T K

2018-06-01

The low temperature spin accumulation in p-Si using Co2CrAl/SiO2 tunnel junction has been investigated in detail. The heterojunction has been fabricated using electron beam evaporation (EBE) technique. The 3-terminal contacts in Hanle geometry has been made for spin transport measurements. The electrical transport properties have been investigated at different isothermal conditions in the temperature range of 10-300 K. The current-voltage characteristics of the junction shows excellent rectifying magnetic diode like behaviour in lower temperature range (below 200 K). At higher temperature, the junction shows nonlinear behaviour without rectifying characteristics. We have observed spin accumulation signal in p-Si semiconductor using SiO2/Co2CrAl tunnel junction in the low temperature regime (30-100 K). Hence the highly spin polarized Full Heusler alloys compounds, like Co2CrAl etc., are very attractive and can act as efficient tunnel device for spin injection in the area of spintronics devices in near future. The estimated spin life time is τ = 54 pS and spin diffusion length inside p-Si is LSD = 289 nm at 30 K for this heterostructure.

Charge and Spin Dynamics of the Hubbard Chains

NASA Technical Reports Server (NTRS)

Park, Youngho; Liang, Shoudan

1999-01-01

We calculate the local correlation functions of charge and spin for the one-chain and two-chain Hubbard model using density matrix renormalization group method and the recursion technique. Keeping only finite number of states we get good accuracy for the low energy excitations. We study the charge and spin gaps, bandwidths and weights of the spectra for various values of the on-site Coulomb interaction U and the electron filling. In the low energy part, the local correlation functions are different for the charge and spin. The bandwidths are proportional to t for the charge and J for the spin respectively.

Spin current and spin transfer torque in ferromagnet/superconductor spin valves

NASA Astrophysics Data System (ADS)

Moen, Evan; Valls, Oriol T.

2018-05-01

Using fully self-consistent methods, we study spin transport in fabricable spin valve systems consisting of two magnetic layers, a superconducting layer, and a spacer normal layer between the ferromagnets. Our methods ensure that the proper relations between spin current gradients and spin transfer torques are satisfied. We present results as a function of geometrical parameters, interfacial barrier values, misalignment angle between the ferromagnets, and bias voltage. Our main results are for the spin current and spin accumulation as functions of position within the spin valve structure. We see precession of the spin current about the exchange fields within the ferromagnets, and penetration of the spin current into the superconductor for biases greater than the critical bias, defined in the text. The spin accumulation exhibits oscillating behavior in the normal metal, with a strong dependence on the physical parameters both as to the structure and formation of the peaks. We also study the bias dependence of the spatially averaged spin transfer torque and spin accumulation. We examine the critical-bias effect of these quantities, and their dependence on the physical parameters. Our results are predictive of the outcome of future experiments, as they take into account imperfect interfaces and a realistic geometry.

Spin polarization in Co-Pt alloys

NASA Astrophysics Data System (ADS)

Pulikkotil, J.; Antropov, V.; Faiz, M.; Panguluri, R.; Nadgorny, B.; Kaiser, C.; Parkin, S.

2007-03-01

The degree of spin polarization in the system of disordered Co-Pt alloys has been studied using density functional approach. The electronic structure of several ordered intermetallics have been analyzed in details. Our analysis is focussed on the difference between magnetization and the degree of spin polarization as a function of Pt concentration, measured by spin tunneling spectroscopy[1] and Andreev reflection spectroscopy[2]. Several factors influencing the deviation of these quantities from a linear behavior have been identified. We attempt to explain the dependence of spin polarization on magnetization observed experimentally by both techniques. We also discuss the effect of different tunnel barriers observed in Ref.[1]. In general, experimental tendencies have been confirmed using ab-intio methods, and we consider the possible origin of spin polarization in these alloys. [1] C. Kaiser, S. van Dijken, S.-H. Yang, H. Yang, and S. S. P. Parkin, Phys. Rev. Lett. 94, 247203 (2005) [2] R. P. Panguluri et al, unpublished

Recent research related to prediction of stall/spin characteristics of fighter aircraft

NASA Technical Reports Server (NTRS)

Nguyen, L. T.; Anglin, E. L.; Gilbert, W. P.

1976-01-01

The NASA Langley Research Center is currently engaged in a stall/spin research program to provide the fundamental information and design guidelines required to predict the stall/spin characteristics of fighter aircraft. The prediction methods under study include theoretical spin prediction techniques and piloted simulation studies. The paper discusses the overall status of theoretical techniques including: (1) input data requirements, (2) math model requirements, and (3) correlation between theoretical and experimental results. The Langley Differential Maneuvering Simulator (DMS) facility has been used to evaluate the spin susceptibility of several current fighters during typical air combat maneuvers and to develop and evaluate the effectiveness of automatic departure/spin prevention concepts. The evaluation procedure is described and some of the more significant results of the studies are presented.

Organic Spin-Valves and Beyond: Spin Injection and Transport in Organic Semiconductors and the Effect of Interfacial Engineering.

PubMed

Jang, Hyuk-Jae; Richter, Curt A

2017-01-01

Since the first observation of the spin-valve effect through organic semiconductors, efforts to realize novel spintronic technologies based on organic semiconductors have been rapidly growing. However, a complete understanding of spin-polarized carrier injection and transport in organic semiconductors is still lacking and under debate. For example, there is still no clear understanding of major spin-flip mechanisms in organic semiconductors and the role of hybrid metal-organic interfaces in spin injection. Recent findings suggest that organic single crystals can provide spin-transport media with much less structural disorder relative to organic thin films, thus reducing momentum scattering. Additionally, modification of the band energetics, morphology, and even spin magnetic moment at the metal-organic interface by interface engineering can greatly impact the efficiency of spin-polarized carrier injection. Here, progress on efficient spin-polarized carrier injection into organic semiconductors from ferromagnetic metals by using various interface engineering techniques is presented, such as inserting a metallic interlayer, a molecular self-assembled monolayer (SAM), and a ballistic carrier emitter. In addition, efforts to realize long spin transport in single-crystalline organic semiconductors are discussed. The focus here is on understanding and maximizing spin-polarized carrier injection and transport in organic semiconductors and insight is provided for the realization of emerging organic spintronics technologies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-fidelity spin entanglement using optimal control.

PubMed

Dolde, Florian; Bergholm, Ville; Wang, Ya; Jakobi, Ingmar; Naydenov, Boris; Pezzagna, Sébastien; Meijer, Jan; Jelezko, Fedor; Neumann, Philipp; Schulte-Herbrüggen, Thomas; Biamonte, Jacob; Wrachtrup, Jörg

2014-02-28

Precise control of quantum systems is of fundamental importance in quantum information processing, quantum metrology and high-resolution spectroscopy. When scaling up quantum registers, several challenges arise: individual addressing of qubits while suppressing cross-talk, entangling distant nodes and decoupling unwanted interactions. Here we experimentally demonstrate optimal control of a prototype spin qubit system consisting of two proximal nitrogen-vacancy centres in diamond. Using engineered microwave pulses, we demonstrate single electron spin operations with a fidelity F≈0.99. With additional dynamical decoupling techniques, we further realize high-quality, on-demand entangled states between two electron spins with F>0.82, mostly limited by the coherence time and imperfect initialization. Crosstalk in a crowded spectrum and unwanted dipolar couplings are simultaneously eliminated to a high extent. Finally, by high-fidelity entanglement swapping to nuclear spin quantum memory, we demonstrate nuclear spin entanglement over a length scale of 25 nm. This experiment underlines the importance of optimal control for scalable room temperature spin-based quantum information devices.

Spin-orbit beams for optical chirality measurement

NASA Astrophysics Data System (ADS)

Samlan, C. T.; Suna, Rashmi Ranjan; Naik, Dinesh N.; Viswanathan, Nirmal K.

2018-01-01

Accurate measurement of chirality is essential for the advancement of natural and pharmaceutical sciences. We report here a method to measure chirality using non-separable states of light with geometric phase-gradient in the circular polarization basis, which we refer to as spin-orbit beams. A modified polarization Sagnac interferometer is used to generate spin-orbit beams wherein the spin and orbital angular momentum of the input Gaussian beam are coupled. The out-of-phase interference between counter-propagating Gaussian beams with orthogonal spin states and lateral-shear or/and linear-phase difference between them results in spin-orbit beams with linear and azimuthal phase gradient. The spin-orbit beams interact efficiently with the chiral medium, inducing a measurable change in the center-of-mass of the beam, using the polarization rotation angle and hence the chirality of the medium are accurately calculated. Tunable dynamic range of measurement and flexibility to introduce large values of orbital angular momentum for the spin-orbit beam, to improve the measurement sensitivity, highlight the techniques' versatility.

The physics of spin polarized gases

NASA Astrophysics Data System (ADS)

Cates, Gordon D.

1995-01-01

Most of our research was connected either directly or indirectly to the study of spin polarized atoms and nuclei, and their applications. In most cases we used lasers to optically pump, and hence polarize, alkali-metal vapors. Spin-exchange collisions were used to transfer the angular momentum to other systems. Of particular interest was our continuing study of the polarization of noble gas nuclei, which are characterized by extremely long spin relaxation times of minutes to many days. During this past research period we have demonstrated several applications of polarized noble gas nuclei that may have important implications for such diverse areas as nondestructive testing and medical diagnostics, as well as many areas in fundamental research. Of particular note is the use of spin-exchange polarized He-3 and Xe-129 for magnetic resonance imaging. At present, our imaging work has focused on the lungs of small animals such as mice and guinea pigs. We believe, however, that our technique would also be useful for nondestructive testing. We have also continued our study of Xe that is polarized in the gaseous state, and subsequently frozen. This novel technique for producing a highly polarized solid has received considerable attention in the NMR community.

Omnidirectional spin-wave nanograting coupler

PubMed Central

Yu, Haiming; Duerr, G.; Huber, R.; Bahr, M.; Schwarze, T.; Brandl, F.; Grundler, D.

2013-01-01

Magnonics as an emerging nanotechnology offers functionalities beyond current semiconductor technology. Spin waves used in cellular nonlinear networks are expected to speed up technologically, demanding tasks such as image processing and speech recognition at low power consumption. However, efficient coupling to microelectronics poses a vital challenge. Previously developed techniques for spin-wave excitation (for example, by using parametric pumping in a cavity) may not allow for the relevant downscaling or provide only individual point-like sources. Here we demonstrate that a grating coupler of periodically nanostructured magnets provokes multidirectional emission of short-wavelength spin waves with giantly enhanced amplitude compared with a bare microwave antenna. Exploring the dependence on ferromagnetic materials, lattice constants and the applied magnetic field, we find the magnonic grating coupler to be more versatile compared with gratings in photonics and plasmonics. Our results allow one to convert, in particular, straight microwave antennas into omnidirectional emitters for short-wavelength spin waves, which are key to cellular nonlinear networks and integrated magnonics. PMID:24189978

Dynamics of hot random quantum spin chains: from anyons to Heisenberg spins

NASA Astrophysics Data System (ADS)

Parameswaran, Siddharth; Potter, Andrew; Vasseur, Romain

2015-03-01

We argue that the dynamics of the random-bond Heisenberg spin chain are ergodic at infinite temperature, in contrast to the many-body localized behavior seen in its random-field counterpart. First, we show that excited-state real-space renormalization group (RSRG-X) techniques suffer from a fatal breakdown of perturbation theory due to the proliferation of large effective spins that grow without bound. We repair this problem by deforming the SU (2) symmetry of the Heisenberg chain to its `anyonic' version, SU(2)k , where the growth of effective spins is truncated at spin S = k / 2 . This enables us to construct a self-consistent RSRG-X scheme that is particularly simple at infinite temperature. Solving the flow equations, we compute the excited-state entanglement and show that it crosses over from volume-law to logarithmic scaling at a length scale ξk ~eαk3 . This reveals that (a) anyon chains have random-singlet-like excited states for any finite k; and (b) ergodicity is restored in the Heisenberg limit k --> ∞ . We acknowledge support from the Quantum Materials program of LBNL (RV), the Gordon and Betty Moore Foundation (ACP), and UC Irvine startup funds (SAP).

Spin and Valley Noise in Two-Dimensional Dirac Materials

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Saxena, A.; Smith, D. L.; Sinitsyn, N. A.

2014-07-01

We develop a theory for optical Faraday rotation noise in two-dimensional Dirac materials. In contrast to spin noise in conventional semiconductors, we find that the Faraday rotation fluctuations are influenced not only by spins but also the valley degrees of freedom attributed to intervalley scattering processes. We illustrate our theory with two-dimensional transition-metal dichalcogenides and discuss signatures of spin and valley noise in the Faraday noise power spectrum. We propose optical Faraday noise spectroscopy as a technique for probing both spin and valley relaxation dynamics in two-dimensional Dirac materials.

The effect of spin in swing bowling in cricket: model trajectories for spin alone

NASA Astrophysics Data System (ADS)

Robinson, Garry; Robinson, Ian

2015-02-01

significant. For a given amount of spin the amount of side-ways movement increases as the bowler's delivery arm becomes more horizontal. This technique could also be exploited by normal spin bowlers as well as swing bowlers.

Coherent Spin Control at the Quantum Level in an Ensemble-Based Optical Memory.

PubMed

Jobez, Pierre; Laplane, Cyril; Timoney, Nuala; Gisin, Nicolas; Ferrier, Alban; Goldner, Philippe; Afzelius, Mikael

2015-06-12

Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, spin states are often subjected to different dephasing processes that limit the storage time, which in principle could be overcome using spin-echo techniques. Theoretical studies suggest this to be challenging due to unavoidable spontaneous emission noise in ensemble-based quantum memories. Here, we demonstrate spin-echo manipulation of a mean spin excitation of 1 in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read-out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.

Spin Transfer Torque in Spin Filter Tunnel Junctions

NASA Astrophysics Data System (ADS)

Ortiz Pauyac, Christian; Kalitsov, Alan; Manchon, Aurelien; Chshiev, Mair

2014-03-01

STT in MTJs is well known for its potential spin electronic applications. However, recently a new class of MTJs based on spin filtering across magnetic insulators (SFTJ) has been attracting much attention since in such MTJs electrons with a certain spin orientation tunnel much more efficiently. In this structure, STT remains to be addressed and clarified. Here we present a systematic study of its angular and voltage bias dependences consisting of one or two FM layers separated by a magnetic insulator (MI). The calculations were performed within the tight-binding model using NEGF technique in the framework of Keldysh formalism. We predict that STT is higher in magnitude compared to regular MTJs, which strongly depends in the relative directions of the magnetic states of the free layer (FM2) and MI. Namely, in case of parallel orientation of MI and FM2 moments in a FM1|MI|FM2 structure, the system behaves as a regular MTJ with a modest increase of STT magnitude. However, as the angle between MI and FM2 moments increases, the field-like torque becomes three orders of magnitude higher than the Slonczewski component and oscillates with bias as band-filling increases. This may have practical implications.

Spin Seebeck devices using local on-chip heating

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

Wu, Stephen M.; Fradin, Frank Y.; Hoffman, Jason

2015-05-07

A micro-patterned spin Seebeck device is fabricated using an on-chip heater. Current is driven through a Au heater layer electrically isolated from a bilayer consisting of Fe3O4 (insulating ferrimagnet) and a spin detector layer. It is shown that through this method it is possible to measure the longitudinal spin Seebeck effect (SSE) for small area magnetic devices, equivalent to traditional macroscopic SSE experiments. Using a lock-in detection technique, it is possible to more sensitively characterize both the SSE and the anomalous Nernst effect (ANE), as well as the inverse spin Hall effect in various spin detector materials. By using themore » spin detector layer as a thermometer, we can obtain a value for the temperature gradient across the device. These results are well matched to values obtained through electromagnetic/thermal modeling of the device structure and with large area spin Seebeck measurements.« less

Spin Seebeck devices using local on-chip heating

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

Wu, Stephen M., E-mail: swu@anl.gov; Fradin, Frank Y.; Hoffman, Jason

2015-05-07

A micro-patterned spin Seebeck device is fabricated using an on-chip heater. Current is driven through a Au heater layer electrically isolated from a bilayer consisting of Fe{sub 3}O{sub 4} (insulating ferrimagnet) and a spin detector layer. It is shown that through this method it is possible to measure the longitudinal spin Seebeck effect (SSE) for small area magnetic devices, equivalent to traditional macroscopic SSE experiments. Using a lock-in detection technique, it is possible to more sensitively characterize both the SSE and the anomalous Nernst effect (ANE), as well as the inverse spin Hall effect in various spin detector materials. Bymore » using the spin detector layer as a thermometer, we can obtain a value for the temperature gradient across the device. These results are well matched to values obtained through electromagnetic/thermal modeling of the device structure and with large area spin Seebeck measurements.« less

Preliminary Tests in the NACA Free-Spinning Wind Tunnel

NASA Technical Reports Server (NTRS)

Zimmerman, C H

1937-01-01

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

Quantum control and engineering of single spins in diamond

NASA Astrophysics Data System (ADS)

Toyli, David M.

The past two decades have seen intensive research efforts aimed at creating quantum technologies that leverage phenomena such as coherence and entanglement to achieve device functionalities surpassing those attainable with classical physics. While the range of applications for quantum devices is typically limited by their cryogenic operating temperatures, in recent years point defects in semiconductors have emerged as potential candidates for room temperature quantum technologies. In particular, the nitrogen vacancy (NV) center in diamond has gained prominence for the ability to measure and control its spin under ambient conditions and for its potential applications in magnetic sensing. Here we describe experiments that probe the thermal limits to the measurement and control of single NV centers to identify the origin of the system's unique temperature dependence and that define novel thermal sensing applications for single spins. We demonstrate the optical measurement and coherent control of the spin at temperatures exceeding 600 K and show that its addressability is eventually limited by thermal quenching of the optical spin readout. These measurements provide important information for the electronic structure responsible for the optical spin initialization and readout processes and, moreover, suggest that the coherence of the NV center's spin states could be harnessed for thermometry applications. To that end, we develop novel quantum control techniques that selectively probe thermally induced shifts in the spin resonance frequencies while minimizing the defect's interactions with nearby nuclear spins. We use these techniques to extend the NV center's spin coherence for thermometry by 45-fold to achieve thermal sensitivities approaching 10 mK Hz-1/2 . We show the versatility of these techniques by performing measurements in a range of magnetic environments and at temperatures as high as 500 K. Together with diamond's ideal thermal, mechanical, and chemical

Spin pumping and inverse spin Hall effects—Insights for future spin-orbitronics (invited)

DOE PAGES

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

2015-03-13

Quantification of spin-charge interconversion has become increasingly important in the fast-developing field of spin-orbitronics. Pure spin current generated by spin pumping acts a sensitive probe for many bulk and interface spin-orbit effects, which has been indispensable for the discovery of many promising new spin-orbit materials. Here, we apply spin pumping and inverse spin Hall effect experiments, as a useful metrology, and study spin-orbit effects in a variety of metals and metal interfaces. We also quantify the spin Hall effects in Ir and W using the conventional bilayer structures, and discuss the self-induced voltage in a single layer of ferromagnetic permalloy.more » Finally, we extend our discussions to multilayer structures and quantitatively reveal the spin current flow in two consecutive normal metal layers.« less

Quantitative analysis of the breath-holding half-Fourier acquisition single-shot turbo spin-echo technique in abdominal MRI

NASA Astrophysics Data System (ADS)

Dong, Kyung-Rae; Goo, Eun-Hoe; Lee, Jae-Seung; Chung, Woon-Kwan

2013-01-01

A consecutive series of 50 patients (28 males and 22 females) who underwent hepatic magnetic resonance imaging (MRI) from August to December 2011 were enrolled in this study. The appropriate parameters for abdominal MRI scans were determined by comparing the images (TE = 90 and 128 msec) produced using the half-Fourier acquisition single-shot turbo spin-echo (HASTE) technique at different signal acquisition times. The patients consisted of 15 normal patients, 25 patients with a hepatoma and 10 patients with a hemangioma. The TE in a single patient was set to either 90 msec or 128 msec. This was followed by measurements using the four normal rendering methods of the biliary tract system and the background signal intensity using the maximal signal intensity techniques in the liver, spleen, pancreas, gallbladder, fat, muscles and hemangioma. The signal-to-noise and the contrast-to-noise ratios were obtained. The image quality was assessed subjectively, and the results were compared. The signal-to-noise and the contrast-to-noise ratios were significantly higher at TE = 128 msec than at TE = 90 when diseases of the liver, spleen, pancreas, gallbladder, and fat and muscles, hepatocellular carcinomas and hemangiomas, and rendering the hepatobiliary tract system based on the maximum signal intensity technique were involved (p < 0.05). In addition, the presence of artifacts, the image clarity and the overall image quality were excellent at TE = 128 msec (p < 0.05). In abdominal MRI, the breath-hold half-Fourier acquisition single-shot turbo spin-echo (HASTE) was found to be effective in illustrating the abdominal organs for TE = 128 msec. Overall, the image quality at TE = 128 msec was better than that at TE = 90 msec due to the improved signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Overall, the HASTE technique for abdominal MRI based on a high-magnetic field (3.0 T) at a TE of 128 msec can provide useful data.

The motion and stability of a dual spin satellite during the momentum wheel spin-up maneuver

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Sen, S.

1972-01-01

The stability of a dual-spin satellite system during the momentum wheel spin-up maneuver is treated both analytically and numerically. The dual-spin system consists of: a slowly rotating or despun main-body; a momentum wheel (or rotor) which is accelerated by a torque motor to change its initial angular velocity relative to the main part to some high terminal value; and a nutation damper. A closed form solution for the case of a symmetrical satellite indicates that when the nutation damper is physically constrained for movement (i.e. by use of a mechanical clamp) the magnitude of the vector sum of the transverse angular velocity components remains bounded during the wheel spin-up under the influence of a constant motor torque. The analysis is extended to consider such effects as: the motion of the nutation damper during spin-up; a non-uniform motor torque; and the effect of a non-symmetrical mass distribution in the main spacecraft and the rotor. An approximate analytical solution using perturbation techniques is developed for the case of a slightly asymmetric main spacecraft.

A Multivariate Quality Loss Function Approach for Optimization of Spinning Processes

NASA Astrophysics Data System (ADS)

Chakraborty, Shankar; Mitra, Ankan

2018-05-01

Recent advancements in textile industry have given rise to several spinning techniques, such as ring spinning, rotor spinning etc., which can be used to produce a wide variety of textile apparels so as to fulfil the end requirements of the customers. To achieve the best out of these processes, they should be utilized at their optimal parametric settings. However, in presence of multiple yarn characteristics which are often conflicting in nature, it becomes a challenging task for the spinning industry personnel to identify the best parametric mix which would simultaneously optimize all the responses. Hence, in this paper, the applicability of a new systematic approach in the form of multivariate quality loss function technique is explored for optimizing multiple quality characteristics of yarns while identifying the ideal settings of two spinning processes. It is observed that this approach performs well against the other multi-objective optimization techniques, such as desirability function, distance function and mean squared error methods. With slight modifications in the upper and lower specification limits of the considered quality characteristics, and constraints of the non-linear optimization problem, it can be successfully applied to other processes in textile industry to determine their optimal parametric settings.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f>1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f >1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Finite-size scaling and integer-spin Heisenberg chains

NASA Astrophysics Data System (ADS)

Bonner, Jill C.; Müller, Gerhard

1984-03-01

Finite-size scaling (phenomenological renormalization) techniques are trusted and widely applied in low-dimensional magnetism and, particularly, in lattice gauge field theory. Recently, investigations have begun which subject the theoretical basis to systematic and intensive scrutiny to determine the validity of finite-size scaling in a variety of situations. The 2D ANNNI model is an example of a situation where finite-size scaling methods encounter difficulty, related to the occurrence of a disorder line (one-dimensional line). A second example concerns the behavior of the spin-1/2 antiferromagnetic XXZ model where the T=0 critical behavior is exactly known and features an essential singularity at the isotropic Heisenberg point. Standard finite-size scaling techniques do not convincingly reproduce the exact phase behavior and this is attributable to the essential singularity. The point is relevant in connection with a finite-size scaling analysis of a spin-one antiferromagnetic XXZ model, which claims to support a conjecture by Haldane that the T=0 phase behavior of integer-spin Heisenberg chains is significantly different from that of half-integer-spin Heisenberg chains.

Majorana spin in magnetic atomic chain systems

NASA Astrophysics Data System (ADS)

Li, Jian; Jeon, Sangjun; Xie, Yonglong; Yazdani, Ali; Bernevig, B. Andrei

2018-03-01

In this paper, we establish that Majorana zero modes emerging from a topological band structure of a chain of magnetic atoms embedded in a superconductor can be distinguished from trivial localized zero energy states that may accidentally form in this system using spin-resolved measurements. To demonstrate this key Majorana diagnostics, we study the spin composition of magnetic impurity induced in-gap Shiba states in a superconductor using a hybrid model. By examining the spin and spectral densities in the context of the Bogoliubov-de Gennes (BdG) particle-hole symmetry, we derive a sum rule that relates the spin densities of localized Shiba states with those in the normal state without superconductivity. Extending our investigations to a ferromagnetic chain of magnetic impurities, we identify key features of the spin properties of the extended Shiba state bands, as well as those associated with a localized Majorana end mode when the effect of spin-orbit interaction is included. We then formulate a phenomenological theory for the measurement of the local spin densities with spin-polarized scanning tunneling microscopy (STM) techniques. By combining the calculated spin densities and the measurement theory, we show that spin-polarized STM measurements can reveal a sharp contrast in spin polarization between an accidental-zero-energy trivial Shiba state and a Majorana zero mode in a topological superconducting phase in atomic chains. We further confirm our results with numerical simulations that address generic parameter settings.

Energy levels and exchange interactions of spin clusters

NASA Astrophysics Data System (ADS)

Belorizky, E.

1993-02-01

We first describe a simple method for diagonalizing the isotropic exchange Hamiltonian of a cluster of N spins in the most general case where all the exchange constants are different. The technique, based on the rotation invariance of the system, leads to a considerable reduction of the total matrix. Simple expressions of the magnetization and susceptibility are provided and an example of the determination of the exchange constants of a complex with five Cu^{2+} ions is given. It is also shown that for a large variety of spin configurations occuring in metal complexes, it is possible to diagonalize the dominant isotropic exchange spin hamiltonian in a straightforward way by using recoupling techniques. This allows to solve problems up to a nine spin cluster with spins having different g values. This survey is pursued by the theoretical approach of the magnetic properties of interacting spins on a finite ring with a detailed study of an oligonuclear metal nitroxide complex formed by six Mn^{2+}(S = 5/2) and six free radicals (s = 1/2). The temperature behaviour of the susceptibility is interpreted with a semi-classical model of a cyclic alternate finite chain. Finally we give a procedure for determining the three exchange constants of three spin 1/2 coupled by isotropic exchange constants in the unsolved case where these constants are all dilferent. Nous décrivons d'abord une méthode simple pour diagonaliser l'Hamiltonien d'échange isotrope d'un cluster de N spins dans le cas le plus général où toutes les constantes d'échange sont différentes. La technique, basée sur l'invariance rotationnelle du système, conduit à une réduction considérable de la matrice totale. On donne des expressions simples de l'aimantation et de la susceptibilité et la méthode est appliquée à la détermination des interactions d'échange d'un complexe comprenant cinq ions Cu^{2+}. On montre également que pour une assez grande variété de configurations de spins pr

Radiation reaction for spinning bodies in effective field theory. II. Spin-spin effects

NASA Astrophysics Data System (ADS)

Maia, Natália T.; Galley, Chad R.; Leibovich, Adam K.; Porto, Rafael A.

2017-10-01

We compute the leading post-Newtonian (PN) contributions at quadratic order in the spins to the radiation-reaction acceleration and spin evolution for binary systems, entering at four-and-a-half PN order. Our calculation includes the backreaction from finite-size spin effects, which is presented for the first time. The computation is carried out, from first principles, using the effective field theory framework for spinning extended objects. At this order, nonconservative effects in the spin-spin sector are independent of the spin supplementary conditions. A nontrivial consistency check is performed by showing that the energy loss induced by the resulting radiation-reaction force is equivalent to the total emitted power in the far zone. We find that, in contrast to the spin-orbit contributions (reported in a companion paper), the radiation reaction affects the evolution of the spin vectors once spin-spin effects are incorporated.

Scanning Probe Microscopy for Spin Mapping and Spin Manipulation on the Atomic Scale

NASA Astrophysics Data System (ADS)

Wiesendanger, Roland

2008-03-01

A fundamental understanding of magnetic and spin-dependent phenomena requires the determination of spin structures and spin excitations down to the atomic scale. The direct visualization of atomic-scale spin structures [1-4] has first been accomplished for magnetic metals by combining the atomic resolution capability of Scanning Tunnelling Microscopy (STM) with spin sensitivity, based on vacuum tunnelling of spin-polarized electrons [5]. The resulting technique, Spin-Polarized Scanning Tunnelling Microscopy (SP-STM), nowadays provides unprecedented insight into collinear and non-collinear spin structures at surfaces of magnetic nanostructures and has already led to the discovery of new types of magnetic order at the nanoscale [6,7]. More recently, the detection of spin-dependent exchange and correlation forces has allowed a first direct real-space observation of spin structures at surfaces of antiferromagnetic insulators [8]. This new type of scanning probe microscopy, called Magnetic Exchange Force Microscopy (MExFM), offers a powerful new tool to investigate different types of spin-spin interactions based on direct-, super-, or RKKY-type exchange down to the atomic level. By combining MExFM with high-precision measurements of damping forces, localized or confined spin excitations in magnetic systems of reduced dimensions now become experimentally accessible. Moreover, the combination of spin state read-out and spin state manipulation, based on spin-current induced switching across a vacuum gap by means of SP-STM [9], provides a fascinating novel type of approach towards ultra-high density magnetic recording without the use of magnetic stray fields. [1] R. Wiesendanger, I. V. Shvets, D. Bürgler, G. Tarrach, H.-J. Güntherodt, J. M. D. Coey, and S. Gräser, Science 255, 583 (1992) [2] S. Heinze, M. Bode, O. Pietzsch, A. Kubetzka, X. Nie, S. Blügel, and R. Wiesendanger, Science 288, 1805 (2000) [3] A. Kubetzka, P. Ferriani, M. Bode, S. Heinze, G. Bihlmayer, K. von

Neutron resonance spin echo with longitudinal DC fields

NASA Astrophysics Data System (ADS)

Krautloher, Maximilian; Kindervater, Jonas; Keller, Thomas; Häußler, Wolfgang

2016-12-01

We report on the design, construction, and performance of a neutron resonance spin echo (NRSE) instrument employing radio frequency (RF) spin flippers combining RF fields with DC fields, the latter oriented parallel (longitudinal) to the neutron propagation direction (longitudinal NRSE (LNRSE)). The advantage of the longitudinal configuration is the inherent homogeneity of the effective magnetic path integrals. In the center of the RF coils, the sign of the spin precession phase is inverted by a π flip of the neutron spins, such that non-uniform spin precession at the boundaries of the RF flippers is canceled. The residual inhomogeneity can be reduced by Fresnel- or Pythagoras-coils as in the case of conventional spin echo instruments (neutron spin echo (NSE)). Due to the good intrinsic homogeneity of the B0 coils, the current densities required for the correction coils are at least a factor of three less than in conventional NSE. As the precision and the current density of the correction coils are the limiting factors for the resolution of both NSE and LNRSE, the latter has the intrinsic potential to surpass the energy resolution of present NSE instruments. Our prototype LNRSE spectrometer described here was implemented at the resonance spin echo for diverse applications (RESEDA) beamline at the MLZ in Garching, Germany. The DC fields are generated by B0 coils, based on resistive split-pair solenoids with an active shielding for low stray fields along the beam path. One pair of RF flippers at a distance of 2 m generates a field integral of ˜0.5 Tm. The LNRSE technique is a future alternative for high-resolution spectroscopy of quasi-elastic excitations. In addition, it also incorporates the MIEZE technique, which allows to achieve spin echo resolution for spin depolarizing samples and sample environments. Here we present the results of numerical optimization of the coil geometry and first data from the prototype instrument.

Spin-transistor action in waveguides with periodically modulated strength of the spin-orbit interaction

NASA Astrophysics Data System (ADS)

Vasilopoulos, P.; Wang, X. F.

2004-03-01

Spin-polarized electron transport through waveguides, in which the strength a of the spin-orbit interaction is varied periodically, is studied using the transfer-matrix technique. It is shown that the transmission T exhibits a spin-transistor action, as a function of a or of the length of one of the two subunits of the unit cell if only one mode is allowed to propagate in the waveguide. A similar but not periodic behavior is shown by T as a function of the elec-tron energy E. In a waveguide with only one segment, of strength a2 and length l2, comprised between two segments of strength a1, the total transmission, obtained as T=1/[cos2(D2*l2)+r*sin2(D2*l2)], shows a sinusoidal dependence. The spin-up (T+) and spin-down (T-) transmissions are given by T+=T cos2x and T-=T sin2x, where x is a measure of the spin precession. The total phase acquired by electrons in different branches during propagation is x=2[d1*(L-l2)+ d2*l2] with di=2m*a1/h2 and L the waveguide length. The transmission through a superlattice, with alternating segments of lengths l1, l2, and strengths a1, a2, is also a periodic function of aj and lj, j=1,2. As the strength a can be controlled by applying gates, the structure considered is a good candidate for the establishment of a realistic spin transistor.

How well can we measure black hole spin?

NASA Astrophysics Data System (ADS)

Bonson, K.; Gallo, L.

2015-07-01

Being one of only two fundamental properties black holes possess, the spin of supermassive black holes (SMBHs) is of great interest for understanding accretion processes and galaxy evolution. However, in these early days of spin measurements, we often struggle to obtain consistent spin values for the same object because of different modeling approaches. Here we examine various techniques and observing conditions to determine which yield the most accurate spin measurements. We have created and fit over 6500 simulated Seyfert 1 spectra, using both XMM-Newton and NuStar responses, in an effort to uncover any systematic ``blind spots'' and determine how best to approach measuring spin in AGN. With the next generation of high-energy observatories like Astro-H and ATHENA, it is imperative that we understand just how well we are presently measuring spin and how we can maximize the potential of current and future missions.

Direct observation of spin-quadrupolar excitations in Sr2CoGe2O7 by high-field electron spin resonance

NASA Astrophysics Data System (ADS)

Akaki, Mitsuru; Yoshizawa, Daichi; Okutani, Akira; Kida, Takanori; Romhányi, Judit; Penc, Karlo; Hagiwara, Masayuki

2017-12-01

Exotic spin-multipolar ordering in spin transition metal insulators has so far eluded unambiguous experimental observation. A less studied, but perhaps more feasible fingerprint of multipole character emerges in the excitation spectrum in the form of quadrupolar transitions. Such multipolar excitations are desirable as they can be manipulated with the use of light or electric field and can be captured by means of conventional experimental techniques. Here we study single crystals of multiferroic Sr2CoGe2O7 and observe a two-magnon spin excitation appearing above the saturation magnetic field in electron spin resonance (ESR) spectra. Our analysis of the selection rules reveals that this spin excitation mode does not couple to the magnetic component of the light, but it is excited by the electric field only, in full agreement with the theoretical calculations. Due to the nearly isotropic nature of Sr2CoGe2O7 , we identify this excitation as a purely spin-quadrupolar two-magnon mode.

$$t\\bar{t}$$ Spin Correlations at D0

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

Peters, Yvonne

2013-01-01

The heaviest known elementary particle today, the top quark, has been discovered in 1995 by the CDF and D0 collaborations at the Tevatron collider at Fermilab. Its high mass and short lifetime, shorter than the timescale for hadronization, makes the top quark a special particle to study. Due to the short lifetime, the top quark's spin information is preserved in the decay products. In this article we discuss the studies of ttbar spin correlations at D0, testing the full chain from production to decay. In particular, we present a measurement using angular information and an analysis using a matrix-element basedmore » technique. The application of the matrix-element based technique to the ttbar dilepton and semileponic final state resulted in the first evidence for non-vanishing ttbar spin correlations.« less

Multi-scale modeling of spin transport in organic semiconductors

NASA Astrophysics Data System (ADS)

Hemmatiyan, Shayan; Souza, Amaury; Kordt, Pascal; McNellis, Erik; Andrienko, Denis; Sinova, Jairo

In this work, we present our theoretical framework to simulate simultaneously spin and charge transport in amorphous organic semiconductors. By combining several techniques e.g. molecular dynamics, density functional theory and kinetic Monte Carlo, we are be able to study spin transport in the presence of anisotropy, thermal effects, magnetic and electric field effects in a realistic morphologies of amorphous organic systems. We apply our multi-scale approach to investigate the spin transport in amorphous Alq3 (Tris(8-hydroxyquinolinato)aluminum) and address the underlying spin relaxation mechanism in this system as a function of temperature, bias voltage, magnetic field and sample thickness.

Re-polarization of nuclear spins using selective SABRE-INEPT

NASA Astrophysics Data System (ADS)

Knecht, Stephan; Kiryutin, Alexey S.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L.

2018-02-01

A method is proposed for significant improvement of NMR pulse sequences used in high-field SABRE (Signal Amplification By Reversible Exchange) experiments. SABRE makes use of spin order transfer from parahydrogen (pH2, the H2 molecule in its singlet spin state) to a substrate in a transient organometallic Ir-based complex. The technique proposed here utilizes "re-polarization", i.e., multiple application of an NMR pulse sequence used for spin order transfer. During re-polarization only the form of the substrate, which is bound to the complex, is excited by selective NMR pulses and the resulting polarization is transferred to the free substrate via chemical exchange. Owing to the fact that (i) only a small fraction of the substrate molecules is in the bound form and (ii) spin relaxation of the free substrate is slow, the re-polarization scheme provides greatly improved NMR signal enhancement, ε . For instance, when pyridine is used as a substrate, single use of the SABRE-INEPT sequence provides ε ≈ 260 for 15N nuclei, whereas SABRE-INEPT with re-polarization yields ε > 2000 . We anticipate that the proposed method is useful for achieving maximal NMR enhancement with spin hyperpolarization techniques.

Dynamic detection of spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance (Conference Presentation)

NASA Astrophysics Data System (ADS)

Crowell, Paul A.; Liu, Changjiang; Patel, Sahil; Peterson, Tim; Geppert, Chad C.; Christie, Kevin; Stecklein, Gordon; Palmstrøm, Chris J.

2016-10-01

A distinguishing feature of spin accumulation in ferromagnet-semiconductor devices is its precession in a magnetic field. This is the basis for detection techniques such as the Hanle effect, but these approaches become ineffective as the spin lifetime in the semiconductor decreases. For this reason, no electrical Hanle measurement has been demonstrated in GaAs at room temperature. We show here that by forcing the magnetization in the ferromagnet to precess at resonance instead of relying only on the Larmor precession of the spin accumulation in the semiconductor, an electrically generated spin accumulation can be detected up to 300 K. The injection bias and temperature dependence of the measured spin signal agree with those obtained using traditional methods. We further show that this new approach enables a measurement of short spin lifetimes (< 100 psec), a regime that is not accessible in semiconductors using traditional Hanle techniques. The measurements were carried out on epitaxial Heusler alloy (Co2FeSi or Co2MnSi)/n-GaAs heterostructures. Lateral spin valve devices were fabricated by electron beam and photolithography. We compare measurements carried out by the new FMR-based technique with traditional non-local and three-terminal Hanle measurements. A full model appropriate for the measurements will be introduced, and a broader discussion in the context of spin pumping experimenments will be included in the talk. The new technique provides a simple and powerful means for detecting spin accumulation at high temperatures. Reference: C. Liu, S. J. Patel, T. A. Peterson, C. C. Geppert, K. D. Christie, C. J. Palmstrøm, and P. A. Crowell, "Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance," Nature Communications 7, 10296 (2016). http://dx.doi.org/10.1038/ncomms10296

(3) He Spin Filter for Neutrons.

PubMed

Batz, M; Baeßler, S; Heil, W; Otten, E W; Rudersdorf, D; Schmiedeskamp, J; Sobolev, Y; Wolf, M

2005-01-01

The strongly spin-dependent absorption of neutrons in nuclear spin-polarized (3)He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable (3)He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts.

3He Spin Filter for Neutrons

PubMed Central

Batz, M.; Baeßler, S.; Heil, W.; Otten, E. W.; Rudersdorf, D.; Schmiedeskamp, J.; Sobolev, Y.; Wolf, M.

2005-01-01

The strongly spin-dependent absorption of neutrons in nuclear spin-polarized 3He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable 3He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts. PMID:27308139

Spin dynamics in the modulation frame: application to homonuclear recoupling in magic angle spinning solid-state NMR.

PubMed

De Paëpe, Gaël; Lewandowski, Józef R; Griffin, Robert G

2008-03-28

We introduce a family of solid-state NMR pulse sequences that generalizes the concept of second averaging in the modulation frame and therefore provides a new approach to perform magic angle spinning dipolar recoupling experiments. Here, we focus on two particular recoupling mechanisms-cosine modulated rotary resonance (CMpRR) and cosine modulated recoupling with isotropic chemical shift reintroduction (COMICS). The first technique, CMpRR, is based on a cosine modulation of the rf phase and yields broadband double-quantum (DQ) (13)C recoupling using >70 kHz omega(1,C)/2pi rf field for the spinning frequency omega(r)/2=10-30 kHz and (1)H Larmor frequency omega(0,H)/2pi up to 900 MHz. Importantly, for p>or=5, CMpRR recouples efficiently in the absence of (1)H decoupling. Extension to lower p values (3.5spinning frequencies is possible using low power (1)H irradiation (<0.25 omega(r)/2pi). This phenomenon is explained through higher order cross terms including a homonuclear third spin assisted recoupling mechanism among protons. CMpRR mitigates the heating effects of simultaneous high power (13)C recoupling and (1)H decoupling. The second technique, COMICS, involves low power (13)C irradiation that induces simultaneous recoupling of the (13)C DQ dipolar and isotropic chemical shift terms. In contrast to CMpRR, where the DQ bandwidth (approximately 30 kHz at omega(0,H)/2pi=750 MHz) covers the entire (13)C spectral width, COMICS recoupling, through the reintroduction of the isotropic chemical shift, is selective with respect to the carrier frequency, having a typical bandwidth of approximately 100 Hz. This approach is intended as a general frequency selective method circumventing dipolar truncation (supplementary to R(2) experiments). These new gamma-encoded sequences with attenuated rf requirements extend the applicability of homonuclear recoupling techniques to new regimes--high spinning and Larmor frequencies--and therefore should be of major

Polycrystalline BiFeO{sub 3} thin film synthesized via sol-gel assisted spin coating technique for photosensitive application

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

Bogle, K. A., E-mail: kashinath.bogle@gmail.com; Narwade, R. D.; Mahabole, M. P.

2016-05-06

We are reporting photosensitivity property of BiFeO{sub 3} thin film under optical illumination. The thin film used for photosensitivity work was fabricated via sol-gel assisted spin coating technique. I-V measurements on the Cu/BiFeO{sub 3}/Al structure under dark condition show a good rectifying property and show dramatic blue shit in threshold voltage under optical illumination. The microstructure, morphology and elemental analysis of the films were characterized by using XRD, UV-Vis, FTIR, SEM and EDS.

Investigation of Annealing Temperature on Copper Oxide Thin Films Using Sol-Gel Spin Coating Technique

NASA Astrophysics Data System (ADS)

Hashim, H.; Samat, S. F. A.; Shariffudin, S. S.; Saad, P. S. M.

2018-03-01

Copper (II) Oxide or cupric oxide (CuO) is one of the well-known materials studied for thin films applications. This paper was studied on the effect of annealing temperature to CuO thin films using sol-gel method and spin coating technique. The solution was prepared by sol-gel method and the thin films were synthesized at various temperatures from 500°C to 700°C that deposited onto the quartz substrates. After the annealing process, the thin films were uniform and brownish black in colour. The measurements were performed by atomic force microscopy (AFM), surface profiler (SP), two-point probe and Ultraviolet-visible (UV-Vis-NIR) spectrometer. From the optical measurement, the band gap was estimated to be 1.44eV for sample annealed at 550°C.

Adiabatic quantum computing with spin qubits hosted by molecules.

PubMed

Yamamoto, Satoru; Nakazawa, Shigeaki; Sugisaki, Kenji; Sato, Kazunobu; Toyota, Kazuo; Shiomi, Daisuke; Takui, Takeji

2015-01-28

A molecular spin quantum computer (MSQC) requires electron spin qubits, which pulse-based electron spin/magnetic resonance (ESR/MR) techniques can afford to manipulate for implementing quantum gate operations in open shell molecular entities. Importantly, nuclear spins, which are topologically connected, particularly in organic molecular spin systems, are client qubits, while electron spins play a role of bus qubits. Here, we introduce the implementation for an adiabatic quantum algorithm, suggesting the possible utilization of molecular spins with optimized spin structures for MSQCs. We exemplify the utilization of an adiabatic factorization problem of 21, compared with the corresponding nuclear magnetic resonance (NMR) case. Two molecular spins are selected: one is a molecular spin composed of three exchange-coupled electrons as electron-only qubits and the other an electron-bus qubit with two client nuclear spin qubits. Their electronic spin structures are well characterized in terms of the quantum mechanical behaviour in the spin Hamiltonian. The implementation of adiabatic quantum computing/computation (AQC) has, for the first time, been achieved by establishing ESR/MR pulse sequences for effective spin Hamiltonians in a fully controlled manner of spin manipulation. The conquered pulse sequences have been compared with the NMR experiments and shown much faster CPU times corresponding to the interaction strength between the spins. Significant differences are shown in rotational operations and pulse intervals for ESR/MR operations. As a result, we suggest the advantages and possible utilization of the time-evolution based AQC approach for molecular spin quantum computers and molecular spin quantum simulators underlain by sophisticated ESR/MR pulsed spin technology.

Applications of quantum measurement techniques: Counterfactual quantum computation, spin hall effect of light, and atomic-vapor-based photon detectors

NASA Astrophysics Data System (ADS)

Hosten, Onur

This dissertation investigates several physical phenomena in atomic and optical physics, and quantum information science, by utilizing various types and techniques of quantum measurements. It is the deeper concepts of these measurements, and the way they are integrated into the seemingly unrelated topics investigated, which binds together the research presented here. The research comprises three different topics: Counterfactual quantum computation, the spin Hall effect of light, and ultra-high-efficiency photon detectors based on atomic vapors. Counterfactual computation entails obtaining answers from a quantum computer without actually running it, and is accomplished by preparing the computer as a whole into a superposition of being activated and not activated. The first experimental demonstration is presented, including the best performing implementation of Grover's quantum search algorithm to date. In addition, we develop new counterfactual computation protocols that enable unconditional and completely deterministic operation. These methods stimulated a debate in the literature, on the meaning of counterfactuality in quantum processes, which we also discuss. The spin Hall effect of light entails tiny spin-dependent displacements, unsuspected until 2004, of a beam of light when it changes propagation direction. The first experimental demonstration of the effect during refraction at an air-glass interface is presented, together with a novel enabling metrological tool relying on the concepts of quantum weak measurements. Extensions of the effect to smoothly varying media are also presented, along with utilization of a time-varying version of the weak measurement techniques. Our approach to ultra-high-efficiency photon detection develops and extends a recent novel non-solid-state scheme for photo-detection based on atomic vapors. This approach is in principle capable of resolving the number of photons in a pulse, can be extended to non-destructive detection of

Imprints of spinning particles on primordial cosmological perturbations

NASA Astrophysics Data System (ADS)

Franciolini, Gabriele; Kehagias, Alex; Riotto, Antonio

2018-02-01

If there exist higher-spin particles during inflation which are light compared to the Hubble rate, they may leave distinct statistical anisotropic imprints on the correlators involving scalar and graviton fluctuations. We characterise such signatures using the dS/CFT3 correspondence and the operator product expansion techniques. In particular, we obtain generic results for the case of partially massless higher-spin states.

Spin state switching in iron coordination compounds

PubMed Central

Gaspar, Ana B; Garcia, Yann

2013-01-01

Summary The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices. The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST) and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property. PMID:23504535

Longitudinal and transverse spin dynamics of donor-bound electrons in fluorine-doped ZnSe: Spin inertia versus Hanle effect

NASA Astrophysics Data System (ADS)

Heisterkamp, F.; Zhukov, E. A.; Greilich, A.; Yakovlev, D. R.; Korenev, V. L.; Pawlis, A.; Bayer, M.

2015-06-01

The spin dynamics of strongly localized donor-bound electrons in fluorine-doped ZnSe epilayers is studied using pump-probe Kerr rotation techniques. A method exploiting the spin inertia is developed and used to measure the longitudinal spin relaxation time T1 in a wide range of magnetic fields, temperatures, and pump densities. The T1 time of the donor-bound electron spin of about 1.6 μ s remains nearly constant for external magnetic fields varied from zero up to 2.5 T (Faraday geometry) and in a temperature range 1.8-45 K. These findings impose severe restrictions on possible spin relaxation mechanisms. In our opinion they allow us to rule out scattering between free and donor-bound electrons, jumping of electrons between different donor centers, scattering between phonons and donor-bound electrons, and with less certainty charge fluctuations in the environment of the donors caused by the 1.5 ps pulsed laser excitation.

Calculation method of spin accumulations and spin signals in nanostructures using spin resistors

NASA Astrophysics Data System (ADS)

Torres, Williams Savero; Marty, Alain; Laczkowski, Piotr; Jamet, Matthieu; Vila, Laurent; Attané, Jean-Philippe

2018-02-01

Determination of spin accumulations and spin currents is essential for a deep understanding of spin transport in nanostructures and further optimization of spintronic devices. So far, they are easily obtained using different approaches in nanostructures composed of few elements; however their calculation becomes complicated as the number of elements increases. Here, we propose a 1-D spin resistor approach to calculate analytically spin accumulations, spin currents and magneto-resistances in heterostructures. Our method, particularly applied to multi-terminal metallic nanostructures, provides a fast and systematic mean to determine such spin properties in structures where conventional methods remain complex.

Observation of Spin Hall Effect in Photon Tunneling via Weak Measurements

PubMed Central

Zhou, Xinxing; Ling, Xiaohui; Zhang, Zhiyou; Luo, Hailu; Wen, Shuangchun

2014-01-01

Photonic spin Hall effect (SHE) manifesting itself as spin-dependent splitting escapes detection in previous photon tunneling experiments due to the fact that the induced beam centroid shift is restricted to a fraction of wavelength. In this work, we report on the first observation of this tiny effect in photon tunneling via weak measurements based on preselection and postselection technique on the spin states. We find that the spin-dependent splitting is even larger than the potential barrier thickness when spin-polarized photons tunneling through a potential barrier. This photonic SHE is attributed to spin-redirection Berry phase which can be described as a consequence of the spin-orbit coupling. These findings provide new insight into photon tunneling effect and thereby offer the possibility of developing spin-based nanophotonic applications. PMID:25487043

A quantum spin-probe molecular microscope

NASA Astrophysics Data System (ADS)

Perunicic, V. S.; Hill, C. D.; Hall, L. T.; Hollenberg, L. C. L.

2016-10-01

Imaging the atomic structure of a single biomolecule is an important challenge in the physical biosciences. Whilst existing techniques all rely on averaging over large ensembles of molecules, the single-molecule realm remains unsolved. Here we present a protocol for 3D magnetic resonance imaging of a single molecule using a quantum spin probe acting simultaneously as the magnetic resonance sensor and source of magnetic field gradient. Signals corresponding to specific regions of the molecule's nuclear spin density are encoded on the quantum state of the probe, which is used to produce a 3D image of the molecular structure. Quantum simulations of the protocol applied to the rapamycin molecule (C51H79NO13) show that the hydrogen and carbon substructure can be imaged at the angstrom level using current spin-probe technology. With prospects for scaling to large molecules and/or fast dynamic conformation mapping using spin labels, this method provides a realistic pathway for single-molecule microscopy.

An approach to attitude determination for a spin-stabilized spacecraft (IMP 1)

NASA Technical Reports Server (NTRS)

Fang, A. C.

1972-01-01

The analysis and the FORTRAN program are presented for the determination of attitude of a spin-stabilized spacecraft. The use of telemetry data that provide information about two reference vectors and their relation to the spin is outlined. A technique for the determination of the spin-axis orientation that employs only simple calculations is described.

Honeycomb artificial spin ice at low temperatures

NASA Astrophysics Data System (ADS)

Zeissler, Katharina; Chadha, Megha; Cohen, Lesley; Branford, Will

2015-03-01

Artificial spin ice is a macroscopic playground for magnetically frustrated systems. It consists of a geometrically ordered but magnetically frustrated arrangement of ferromagnetic macros spins, e.g. an arrangement of single domain ferromagnetic nanowires on a honeycomb lattice. Permalloy and cobalt which have critical temperature scales far above 290 K, are commonly used in the construction of such systems. Previous measurements have shown unusual features in the magnetotransport signature of cobalt honeycomb artificial spin ice at temperatures below 50 K which are due to changes in the artificial spin ice's magnetic reversal. In that case, the artificial spin ice bars were 1 micron long, 100 nm wide and 20 nm thick. Here we explore the low temperature magnetic behavior of honeycomb artificial spin ice structures with a variety of bar dimensions, indirectly via electrical transport, as well as, directly using low temperature magnetic imaging techniques. We discuss the extent to which this change in the magnetic reversal at low temperatures is generic to the honeycomb artificial spin ice geometry and whether the bar dimensions have an influence on its onset temperature. The EPSRC (Grant No. EP/G004765/1; Grant No. EP/L504786/1) and the Leverhulme Trust (Grant No. RPG 2012-692) funded this scientific work.

Experimental evidences of a large extrinsic spin Hall effect in AuW alloy

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

Laczkowski, P.; Rojas-Sánchez, J.-C.; INAC/SP2M, CEA-Université Joseph Fourier, F-38054 Grenoble

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.

Spin torque efficiency of Ta, W, and Pt in metallic bilayers evaluated by harmonic Hall and spin Hall magnetoresistance measurements

NASA Astrophysics Data System (ADS)

Lau, Yong-Chang; Hayashi, Masamitsu

2017-08-01

We investigate the efficiency of current-induced torque, i.e., the spin torque efficiency, in in-plane magnetized heavy metal/CoFeB/MgO heterostructures (heavy metals = Pt, W, and Ta) using the harmonic Hall technique and the spin Hall magnetoresistance. We find that the amplitude of the external magnetic field has a strong influence on the spin torque efficiency evaluation by the harmonic Hall measurements. This can be corrected by measuring the corresponding Hall resistance susceptibility. The sign and magnitude of the resulting Slonczewski-like spin torque efficiencies are in agreement with previous reports and the measurements utilizing the spin Hall magnetoresistance, except for the Pt underlayer films. The origin of the discrepancy for the Pt underlayer films is unclear. The field like torque efficiencies, upon subtracting the Oersted field contribution, are quite low or negligible. This is in significant contrast to what has been found for the field like torque in heterostructures with perpendicular magnetization. These results suggest that a more advanced model is required in order to describe accurately spin transport and momentum transfer at metallic interfaces.

The theory of spin noise spectroscopy: a review

DOE PAGES

Sinitsyn, Nikolai A.; Pershin, Yuriy V.

2016-09-12

Direct measurements of spin fluctuations are becoming the mainstream approach for studies of complex condensed matter, molecular, nuclear, and atomic systems. Our review covers recent progress in the field of optical spin noise spectroscopy (SNS) with an additional goal to establish an introduction into its theoretical foundations. Finally we used various theoretical techniques recently to interpret results of SNS measurements are explained alongside examples of their applications.

Re-polarization of nuclear spins using selective SABRE-INEPT.

PubMed

Knecht, Stephan; Kiryutin, Alexey S; Yurkovskaya, Alexandra V; Ivanov, Konstantin L

2018-02-01

A method is proposed for significant improvement of NMR pulse sequences used in high-field SABRE (Signal Amplification By Reversible Exchange) experiments. SABRE makes use of spin order transfer from parahydrogen (pH 2 , the H 2 molecule in its singlet spin state) to a substrate in a transient organometallic Ir-based complex. The technique proposed here utilizes "re-polarization", i.e., multiple application of an NMR pulse sequence used for spin order transfer. During re-polarization only the form of the substrate, which is bound to the complex, is excited by selective NMR pulses and the resulting polarization is transferred to the free substrate via chemical exchange. Owing to the fact that (i) only a small fraction of the substrate molecules is in the bound form and (ii) spin relaxation of the free substrate is slow, the re-polarization scheme provides greatly improved NMR signal enhancement, ε. For instance, when pyridine is used as a substrate, single use of the SABRE-INEPT sequence provides ε≈260 for 15 N nuclei, whereas SABRE-INEPT with re-polarization yields ε>2000. We anticipate that the proposed method is useful for achieving maximal NMR enhancement with spin hyperpolarization techniques. Copyright © 2017 Elsevier Inc. All rights reserved.

Spin decoherence of InAs surface electrons by transition metal ions

NASA Astrophysics Data System (ADS)

Zhang, Yao; Soghomonian, V.; Heremans, J. J.

2018-04-01

Spin interactions between a two-dimensional electron system at the InAs surface and transition metal ions, Fe3 +, Co2 +, and Ni2 +, deposited on the InAs surface, are probed by antilocalization measurements. The spin-dependent quantum interference phenomena underlying the quantum transport phenomenon of antilocalization render the technique sensitive to the spin states of the transition metal ions on the surface. The experiments yield data on the magnitude and temperature dependence of the electrons' inelastic scattering rates, spin-orbit scattering rates, and magnetic spin-flip rates as influenced by Fe3 +, Co2 +, and Ni2 +. A high magnetic spin-flip rate is shown to mask the effects of spin-orbit interaction, while the spin-flip rate is shown to scale with the effective magnetic moment of the surface species. The spin-flip rates and their dependence on temperature yield information about the spin states of the transition metal ions at the surface, and in the case of Co2 + suggest either a spin transition or formation of a spin-glass system.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Exchange-mediated spin-lattice relaxation of Fe3+ ions in borate glasses.

PubMed

Misra, Sushil K; Pilbrow, John R

2007-03-01

Spin-lattice relaxation times (T1) of two borate glasses doped with different concentrations of Fe2O3 were measured using the Electron Spin-Echo (ESE) technique at X-band (9.630 GHz) in the temperature range 2-6K. In comparison with a previous investigation of Fe3+-doped silicate glasses, the relaxation rates were comparable and differed by no more than a factor of two. The data presented here extend those previously reported for borate glasses in the 10-250K range but measured using the amplitude-modulation technique. The T1 values were found to depend on temperature (T) as T(n) with n approximately 1 for the 1% and 0.1% Fe2O3-doped glass samples. These results are consistent with spin-lattice relaxation as effected by exchange interaction of a Fe3+ spin exchange-coupled to another Fe3+ spin in an amorphous material.

Organic light-emitting devices using spin-dependent processes

DOEpatents

Vardeny, Z. Valy; Wohlgenannt, Markus

2010-03-23

The maximum luminous efficiency of organic light-emitting materials is increased through spin-dependent processing. The technique is applicable to all electro-luminescent processes in which light is produced by singlet exciton decay, and all devices which use such effects, including LEDs, super-radiant devices, amplified stimulated emission devices, lasers, other optical microcavity devices, electrically pumped optical amplifiers, and phosphorescence (Ph) based light emitting devices. In preferred embodiments, the emissive material is doped with an impurity, or otherwise modified, to increase the spin-lattice relaxation rate (i.e., decrease the spin-lattice time), and hence raise the efficiency of the device. The material may be a polymer, oligomer, small molecule, single crystal, molecular crystal, or fullerene. The impurity is preferably a magnetic or paramagnetic substance. The invention is applicable to IR, UV, and other electromagnetic radiation generation and is thus not limited to the visible region of the spectrum. The methods of the invention may also be combined with other techniques used to improve device performance.

Driving spin transition at interface: Role of adsorption configurations

NASA Astrophysics Data System (ADS)

Zhang, Yachao

2018-01-01

A clear insight into the electrical manipulation of molecular spins at interface is crucial to the design of molecule-based spintronic devices. Here we report on the electrically driven spin transition in manganocene physisorbed on a metallic surface in two different adsorption configurations predicted by ab initio techniques, including a Hubbard-U correction at the manganese site and accounting for the long-range van der Waals interactions. We show that the application of an electric field at the interface induces a high-spin to low-spin transition in the flat-lying manganocene, while it could hardly alter the high-spin ground state of the standing-up molecule. This phenomenon cannot be explained by either the molecule-metal charge transfer or the local electron correlation effects. We demonstrate a linear dependence of the intra-molecular spin-state splitting on the energy difference between crystal-field splitting and on-site Coulomb repulsion. After considering the molecule-surface binding energy shifts upon spin transition, we reproduce the obtained spin-state energetics. We find that the configuration-dependent responses of the spin-transition originate from the binding energy shifts instead of the variation of the local ligand field. Through these analyses, we obtain an intuitive understanding of the effects of molecule-surface contact on spin-crossover under electrical bias.

Spin Hall and Spin Swapping Torques in Diffusive Ferromagnets

NASA Astrophysics Data System (ADS)

Pauyac, Christian Ortiz; Chshiev, Mairbek; Manchon, Aurelien; Nikolaev, Sergey A.

2018-04-01

A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession, and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precession effects displays a complex spatial dependence that can be exploited to generate torques and nucleate or propagate domain walls in centrosymmetric geometries without the use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.

Axial-spin technique of endoscopic intracorporeal knot tying: comparison with the conventional technique and objective assessment of knot security, learning curves, and performance efficiency across training levels.

PubMed

Gopaldas, Raja R; Rohatgi, Chand

2009-04-01

A major limitation of conventional laparoscopic surgery is the placement of an intracorporeal (IC) knot, which requires a significant amount of training and practice. An easier technique of IC knot tying using 90-degree grasper is compared with the conventional technique (CLT). The new axial-spin technique (AST) uses the spin of the instrument shaft to tie IC knots. Fourteen participants stratified into 3 training levels were instructed to tie 50 reef IC knots using each technique on trainers in 3 sessions. The final 5 knots tied using each technique were deemed to be representative of maximal performance efficiency (PE) and randomly subject to tensile strength measurements using a tensiometer at 50 mm/s distraction. Mean knot execution time (mKET) measured in seconds (s), normalized KE time (nET=group mean/mKET), knot holding capacity, relative knot security (RKS), and PE (PE=RKS/nET) of the knots tied were computed and analyzed using paired t and analysis of variance. Variables included knot-tying session, technique and the training level. On completion of the study, junior residents (JR) averaged 51.72 seconds more, senior residents (SR) averaged 26.22 seconds more and attendings (ATT) averaged 19.17 seconds less to tie using CLT compared with the AST (F=40.52, P=0.0001). Across all levels, the CLT technique was taking 83.26 seconds on average to execute an IC knot compared with 59.08 seconds with AST method (t=2.784, P=0.015). Learning curves revealed that JR significantly improved mean KE times with the AST technique (first session vs. final session: 473.8 s vs. 55.9 s) compared with CLT (672.5 s vs. 107.6 s) across the sessions as compared with those in advanced levels of training. The RKS of knots executed by AST was significantly stronger (AST: 13.1 vs. 5.44 N, t=4.9, P=0.0001). The PE of knots executed using the CLT increased geometrically across training levels (JR: 1.35% SR: 5.58% ATT: 11.22%) whereas those of AST showed a linear trend (17.09%; 17

Observation of spinon spin currents in one-dimensional spin liquid

NASA Astrophysics Data System (ADS)

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

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

Advanced Tools and Techniques for Formal Techniques in Aerospace Systems

NASA Technical Reports Server (NTRS)

Knight, John C.

2005-01-01

This is the final technical report for grant number NAG-1-02101. The title of this grant was "Advanced Tools and Techniques for Formal Techniques In Aerospace Systems". The principal investigator on this grant was Dr. John C. Knight of the Computer Science Department, University of Virginia, Charlottesville, Virginia 22904-4740. This report summarizes activities under the grant during the period 7/01/2002 to 9/30/2004. This report is organized as follows. In section 2, the technical background of the grant is summarized. Section 3 lists accomplishments and section 4 lists students funded under the grant. In section 5, we present a list of presentations given at various academic and research institutions about the research conducted. Finally, a list of publications generated under this grant is included in section 6.

Electrical control of single hole spins in nanowire quantum dots.

PubMed

Pribiag, V S; Nadj-Perge, S; Frolov, S M; van den Berg, J W G; van Weperen, I; Plissard, S R; Bakkers, E P A M; Kouwenhoven, L P

2013-03-01

The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes.

Control of electron spin decoherence in nuclear spin baths

NASA Astrophysics Data System (ADS)

Liu, Ren-Bao

2011-03-01

Nuclear spin baths are a main mechanism of decoherence of spin qubits in solid-state systems, such as quantum dots and nitrogen-vacancy (NV) centers of diamond. The decoherence results from entanglement between the electron and nuclear spins, established by quantum evolution of the bath conditioned on the electron spin state. When the electron spin is flipped, the conditional bath evolution is manipulated. Such manipulation of bath through control of the electron spin not only leads to preservation of the center spin coherence but also demonstrates quantum nature of the bath. In an NV center system, the electron spin effectively interacts with hundreds of 13 C nuclear spins. Under repeated flip control (dynamical decoupling), the electron spin coherence can be preserved for a long time (> 1 ms) . Thereforesomecharacteristicoscillations , duetocouplingtoabonded 13 C nuclear spin pair (a dimer), are imprinted on the electron spin coherence profile, which are very sensitive to the position and orientation of the dimer. With such finger-print oscillations, a dimer can be uniquely identified. Thus, we propose magnetometry with single-nucleus sensitivity and atomic resolution, using NV center spin coherence to identify single molecules. Through the center spin coherence, we could also explore the many-body physics in an interacting spin bath. The information of elementary excitations and many-body correlations can be extracted from the center spin coherence under many-pulse dynamical decoupling control. Another application of the preserved spin coherence is identifying quantumness of a spin bath through the back-action of the electron spin to the bath. We show that the multiple transition of an NV center in a nuclear spin bath can have longer coherence time than the single transition does, when the classical noises due to inhomogeneous broadening is removed by spin echo. This counter-intuitive result unambiguously demonstrates the quantumness of the nuclear spin bath

Towards Polarised Antiprotons: Machine Developments for Spin-Filtering Studies

NASA Astrophysics Data System (ADS)

Lenisa, Paolo

2016-02-01

We address the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at the COSY ring in Jülich (Germany) at a beam kinetic energy of 49.3 MeV. The implementation of a low-beta insertion made it possible to achieve beam lifetimes of 8000 s in the presence of a dense polarized hydrogen storage cell target. The developed techniques can be directly applied to antiproton machines and allow for the determination of the spin-dependent pbar-p cross sections via spin-filtering.

Towards a phase diagram for spin foams

NASA Astrophysics Data System (ADS)

Delcamp, Clement; Dittrich, Bianca

2017-11-01

One of the most pressing issues for loop quantum gravity and spin foams is the construction of the continuum limit. In this paper, we propose a systematic coarse-graining scheme for three-dimensional lattice gauge models including spin foams. This scheme is based on the concept of decorated tensor networks, which have been introduced recently. Here we develop an algorithm applicable to gauge theories with non-Abelian groups, which for the first time allows for the application of tensor network coarse-graining techniques to proper spin foams. The procedure deals efficiently with the large redundancy of degrees of freedom resulting from gauge invariance. The algorithm is applied to 3D spin foams defined on a cubical lattice which, in contrast to a proper triangulation, allows for non-trivial simplicity constraints. This mimics the construction of spin foams for 4D gravity. For lattice gauge models based on a finite group we use the algorithm to obtain phase diagrams, encoding the continuum limit of a wide range of these models. We find phase transitions for various families of models carrying non-trivial simplicity constraints.

A bottom-up approach to assess verbal therapeutic techniques. Development of the Psychodynamic Interventions List (PIL)

PubMed Central

Gumz, Antje; Neubauer, Karolin; Horstkotte, Julia Katharina; Geyer, Michael; Löwe, Bernd; Murray, Alexandra M.; Kästner, Denise

2017-01-01

Objective Knowing which specific verbal techniques “good” therapists use in their daily work is important for training and evaluation purposes. In order to systematize what is being practiced in the field, our aim was to empirically identify verbal techniques applied in psychodynamic sessions and to differentiate them according to their basic semantic features using a bottom-up, qualitative approach. Method Mixed-Method-Design: In a comprehensive qualitative study, types of techniques were identified at the level of utterances based on transcribed psychodynamic therapy sessions using Qualitative Content Analysis (4211 utterances). The definitions of the identified categories were successively refined and modified until saturation was achieved. In a subsequent quantitative study, inter-rater reliability was assessed both at the level of utterances (n = 8717) and at the session level (n = 38). The convergent validity of the categories was investigated by analyzing associations with the Interpretive and Supportive Technique Scale (ISTS). Results The inductive approach resulted in a classification system with 37 categories (Psychodynamic Interventions List, PIL). According to their semantic content, the categories can be allocated to three dimensions: form (24 categories), thematic content (9) and temporal focus (4). Most categories showed good or excellent inter-rater reliability and expected associations with the ISTS were predominantly confirmed. The rare use of the residual category “Other” suggests that the identified categories might comprehensively describe the breadth of applied techniques. Conclusions The atheoretical orientation and the clear focus on overt linguistic features should enable the PIL to be used without intensive training or prior theoretical knowledge. The PIL can be used to investigate the links between verbal techniques derived from practice and micro-outcomes (at the session level) as well as the overall therapeutic outcomes. This

Neutron Resonance Spin Determination Using Multi-Segmented Detector DANCE

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

Baramsai, B.; Mitchell, G. E.; Chyzh, A.

2011-06-01

A sensitive method to determine the spin of neutron resonances is introduced based on the statistical pattern recognition technique. The new method was used to assign the spins of s-wave resonances in {sup 155}Gd. The experimental neutron capture data for these nuclei were measured with the DANCE (Detector for Advanced Neutron Capture Experiment) calorimeter at the Los Alamos Neutron Science Center. The highly segmented calorimeter provided detailed multiplicity distributions of the capture {gamma}-rays. Using this information, the spins of the neutron capture resonances were determined. With these new spin assignments, level spacings are determined separately for s-wave resonances with J{supmore » {pi}} = 1{sup -} and 2{sup -}.« less

Quantum model of a solid-state spin qubit: Ni cluster on a silicon surface by the generalized spin Hamiltonian and X-ray absorption spectroscopy investigations

NASA Astrophysics Data System (ADS)

Farberovich, Oleg V.; Mazalova, Victoria L.; Soldatov, Alexander V.

2015-11-01

We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals Jij of the nanosystem Ni7-Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni7-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy pattern with the

Nuclear spin circular dichroism.

PubMed

Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

2014-04-07

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.

Time Frequency Analysis of Spacecraft Propellant Tank Spinning Slosh

NASA Technical Reports Server (NTRS)

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

2010-01-01

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

Spin-current emission governed by nonlinear spin dynamics.

PubMed

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

2015-10-16

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

Spin-current emission governed by nonlinear spin dynamics

PubMed Central

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

2015-01-01

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

Spin Funneling for Enhanced Spin Injection into Ferromagnets

PubMed Central

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

2016-01-01

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

Spin Funneling for Enhanced Spin Injection into Ferromagnets

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

Stimulated Raman adiabatic control of a nuclear spin in diamond

NASA Astrophysics Data System (ADS)

Coto, Raul; Jacques, Vincent; Hétet, Gabriel; Maze, Jerónimo R.

2017-08-01

Coherent manipulation of nuclear spins is a highly desirable tool for both quantum metrology and quantum computation. However, most of the current techniques to control nuclear spins lack fast speed, impairing their robustness against decoherence. Here, based on stimulated Raman adiabatic passage, and its modification including shortcuts to adiabaticity, we present a fast protocol for the coherent manipulation of nuclear spins. Our proposed Λ scheme is implemented in the microwave domain and its excited-state relaxation can be optically controlled through an external laser excitation. These features allow for the initialization of a nuclear spin starting from a thermal state. Moreover we show how to implement Raman control for performing Ramsey spectroscopy to measure the dynamical and geometric phases acquired by nuclear spins.

Separated spin-up and spin-down quantum hydrodynamics of degenerated electrons: Spin-electron acoustic wave appearance.

PubMed

Andreev, Pavel A

2015-03-01

The quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains physical quantities defined for all particles of a species including particles with spin-up and with spin-down. Different populations of states with different spin directions are included in the spin density (the magnetization). In this paper I derive a QHD model, which separately describes spin-up electrons and spin-down electrons. Hence electrons with different projections of spins on the preferable direction are considered as two different species of particles. It is shown that the numbers of particles with different spin directions do not conserve. Hence the continuity equations contain sources of particles. These sources are caused by the interactions of the spins with the magnetic field. Terms of similar nature arise in the Euler equation. The z projection of the spin density is no longer an independent variable. It is proportional to the difference between the concentrations of the electrons with spin-up and the electrons with spin-down. The propagation of waves in the magnetized plasmas of degenerate electrons is considered. Two regimes for the ion dynamics, the motionless ions and the motion of the degenerate ions as the single species with no account of the spin dynamics, are considered. It is shown that this form of the QHD equations gives all solutions obtained from the traditional form of QHD equations with no distinction of spin-up and spin-down states. But it also reveals a soundlike solution called the spin-electron acoustic wave. Coincidence of most solutions is expected since this derivation was started with the same basic equation: the Pauli equation. Solutions arise due to the different Fermi pressures for the spin-up electrons and the spin-down electrons in the magnetic field. The results are applied to degenerate electron gas of paramagnetic and ferromagnetic metals in the external magnetic field. The dispersion of the spin-electron acoustic waves in the partially spin

Synthesis of ZnO thin film by sol-gel spin coating technique for H2S gas sensing application

NASA Astrophysics Data System (ADS)

Nimbalkar, Amol R.; Patil, Maruti G.

2017-12-01

In this present work, zinc oxide (ZnO) thin film synthesized by a simple sol-gel spin coating technique. The structural, morphology, compositional, microstructural, optical, electrical and gas sensing properties of the film were studied by using XRD, FESEM, EDS, XPS, HRTEM, Raman, FTIR and UV-vis techniques. The ZnO thin film shows hexagonal wurtzite structure with a porous structured morphology. Gas sensing performance of synthesized ZnO thin film was tested initially for H2S gas at different operating temperatures as well as concentrations. The maximum gas response is achieved towards H2S gas at 300 °C operating temperature, at 100 ppm gas concentration as compared to other gases like CH3OH, Cl2, NH3, LPG, CH3COCH3, and C2H5OH with a good stability.

Spin nematics next to spin singlets

NASA Astrophysics Data System (ADS)

Yokoyama, Yuto; Hotta, Chisa

2018-05-01

We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.

Computer studies of multiple-quantum spin dynamics

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

Murdoch, J.B.

The excitation and detection of multiple-quantum (MQ) transitions in Fourier transform NMR spectroscopy is an interesting problem in the quantum mechanical dynamics of spin systems as well as an important new technique for investigation of molecular structure. In particular, multiple-quantum spectroscopy can be used to simplify overly complex spectra or to separate the various interactions between a nucleus and its environment. The emphasis of this work is on computer simulation of spin-system evolution to better relate theory and experiment.

[The study and manufacture of spinning counter for experimental animals].

PubMed

Qi, X P; Zhou, C; Liu, F J; Chen, Z; Jiang, L; Yan, Z

1997-09-01

The single-chip microcomputer technique is used in the present study of spinning counter, which has 4 observation tunnels, the spinning behave of four experiment animals can be recorded at same time. The function of this instrument has four selections according to different experiment, and the recording data can be compute processed.

Asteroid shape and spin statistics from convex models

NASA Astrophysics Data System (ADS)

Torppa, J.; Hentunen, V.-P.; Pääkkönen, P.; Kehusmaa, P.; Muinonen, K.

2008-11-01

We introduce techniques for characterizing convex shape models of asteroids with a small number of parameters, and apply these techniques to a set of 87 models from convex inversion. We present three different approaches for determining the overall dimensions of an asteroid. With the first technique, we measured the dimensions of the shapes in the direction of the rotation axis and in the equatorial plane and with the two other techniques, we derived the best-fit ellipsoid. We also computed the inertia matrix of the model shape to test how well it represents the target asteroid, i.e., to find indications of possible non-convex features or albedo variegation, which the convex shape model cannot reproduce. We used shape models for 87 asteroids to perform statistical analyses and to study dependencies between shape and rotation period, size, and taxonomic type. We detected correlations, but more data are required, especially on small and large objects, as well as slow and fast rotators, to reach a more thorough understanding about the dependencies. Results show, e.g., that convex models of asteroids are not that far from ellipsoids in root-mean-square sense, even though clearly irregular features are present. We also present new spin and shape solutions for Asteroids (31) Euphrosyne, (54) Alexandra, (79) Eurynome, (93) Minerva, (130) Elektra, (376) Geometria, (471) Papagena, and (776) Berbericia. We used a so-called semi-statistical approach to obtain a set of possible spin state solutions. The number of solutions depends on the abundancy of the data, which for Eurynome, Elektra, and Geometria was extensive enough for determining an unambiguous spin and shape solution. Data of Euphrosyne, on the other hand, provided a wide distribution of possible spin solutions, whereas the rest of the targets have two or three possible solutions.

Design of spin-Seebeck diode with spin semiconductors.

PubMed

Zhang, Zhao-Qian; Yang, Yu-Rong; Fu, Hua-Hua; Wu, Ruqian

2016-12-16

We report a new design of spin-Seebeck diode using two-dimensional spin semiconductors such as sawtooth-like (ST) silicence nanoribbons (SiNRs), to generate unidirectional spin currents with a temperature gradient. ST SiNRs have subbands with opposite spins across the Fermi level and hence the flow of thermally excited carriers may produce a net spin current but not charge current. Moreover, we found that even-width ST SiNRs display a remarkable negative differential thermoelectric resistance due to a charge-current compensation mechanism. In contrast, odd-width ST SiNRs manifest features of a thermoelectric diode and can be used to produce both charge and spin currents with temperature gradient. These findings can be extended to other spin semiconductors and open the door for designs of new materials and spin caloritronic devices.

Single-shot readout of accumulation mode Si/SiGe spin qubits using RF reflectometry

NASA Astrophysics Data System (ADS)

Volk, Christian; Martins, Frederico; Malinowski, Filip; Marcus, Charles M.; Kuemmeth, Ferdinand

Spin qubits based on gate-defined quantum dots are promising systems for realizing quantum computation. Due to their low concentration of nuclear-spin-carrying isotopes, Si/SiGe heterostructures are of particular interest. While high fidelities have been reported for single-qubit and two-qubit gate operations, qubit initialization and measurement times are relatively slow. In order to develop fast read-out techniques compatible with the operation of spin qubits, we characterize double and triple quantum dots confined in undoped Si/Si0.7Ge0.3 heterostructures using accumulation and depletion gates and a nearby RF charge sensor dot. We implement a RF reflectometry technique that allows single-shot charge read-out at integration times on the order of a few μs. We show our recent advancement towards implementing spin qubits in these structures, including spin-selective single-shot read-out.

Spin-transfer torque induced spin waves in antiferromagnetic insulators

DOE PAGES

Daniels, Matthew W.; Guo, Wei; Stocks, George Malcolm; ...

2015-01-01

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.

Spin Currents and Ferromagnetic Resonance in Magnetic Thin Films

NASA Astrophysics Data System (ADS)

Ellsworth, David

Spin currents represent a new and exciting phenomenon. There is both a wealth of new physics to be discovered and understood, and many appealing devices which may result from this area of research. To fully realize the potential of this discipline it is necessary to develop new methods for realizing spin currents and explore new materials which may be suitable for spin current applications. Spin currents are an inherently dynamic phenomenon involving the transfer of angular momentum within and between different thin films. In order to understand and optimize such devices the dynamics of magnetization must be determined. This dissertation reports on novel approaches for spin current generation utilizing the magnetic insulators yttrium iron garnet (YIG) and M-type barium hexagonal ferrite (BaM). First, the light-induced spin Seebeck effect is reported for the first time in YIG. Additionally, the first measurement of the spin Seebeck effect without an external magnetic field is demonstrated. To accomplish this the self-biased BaM thin films are utilized. Second, a new method for the generation of spin currents is presented: the photo-spin-voltaic effect. In this new phenomenon, a spin current may be generated by photons in a non-magnetic metal that is in close proximity to a magnetic insulator. On exposure to light, there occurs a light induced, spin-dependent excitation of electrons in a few platinum layers near the metal/magnetic insulator interface. This excitation gives rise to a pure spin current which flows in the metal. This new effect is explored in detail and extensive measurements are carried out to confirm the photonic origin of the photo-spin-voltaic effect and exclude competing effects. In addition to the spin current measurements, magnetization dynamics were probed in thin films using ferromagnetic resonance (FMR). In order to determine the optimal material configuration for magnetic recording write heads, FMR measurements were used to perform damping

Electron spin dynamics and optical orientation of Mn2+ ions in GaAs

NASA Astrophysics Data System (ADS)

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

2013-04-01

We present an overview of spin-related phenomena in GaAs doped with low concentration of Mn-acceptors (below 1018 cm-3). We use the combination of different experimental techniques such as spin-flip Raman scattering and time-resolved photoluminescence. This allows to evaluate the time evolution of both electron and Mn spins. We show that optical orientation of Mn ions is possible under application of weak magnetic field, which is required to suppress the manganese spin relaxation. The optically oriented Mn2+ ions maintain the spin and return part of the polarization back to the electron spin system providing a long-lived electron spin memory. This leads to a bunch of spectacular effects such as non-exponential electron spin decay and spin precession in the effective exchange fields.

Detection of the spin injection into silicon by broadband ferromagnetic resonance spectroscopy

NASA Astrophysics Data System (ADS)

Ohshima, Ryo; Dushenko, Sergey; Ando, Yuichiro; Weiler, Mathias; Klingler, Stefan; Huebl, Hans; Shinjo, Teruya; Goennenwein, Sebastian; Shiraishi, Masashi

Silicon (Si) based spintronics was eagerly studied to realize spin metal-oxide-semiconductor field-effect-transistors (MOSFETs) since it has long spin lifetime and gate tunability. The operation of n-type Si spin MOSFET was successfully demonstrated, however, their resistivity is still too low for practical applications and a systematic study of spin injection properties (such as spin lifetime, spin injection efficiency and so on) from the ferromagnet into the Si with different resistivity is awaited for further progress in Si spintronics. In this study, we show the spin injection by spin pumping technique in the NiFe(Py)/Si system. Broadband FMR measurement was carried out to see the enhancement of the Gilbert damping parameter with different resistivity of the Si channel. Additional damping indicated the successful spin injection by spin pumping and observed even for the Si channel with high resistivity, which is necessary for the gate operation of the device.

Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

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

Yang, Luyi

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 demonstrationmore » 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

Correlation study of theoretical and experimental results for spin tests of a 1/10 scale radio control model

NASA Technical Reports Server (NTRS)

Bihrle, W., Jr.

1976-01-01

A correlation study was conducted to determine the ability of current analytical spin prediction techniques to predict the flight motions of a current fighter airplane configuration during the spin entry, the developed spin, and the spin recovery motions. The airplane math model used aerodynamics measured on an exact replica of the flight test model using conventional static and forced-oscillation wind-tunnel test techniques and a recently developed rotation-balance test apparatus capable of measuring aerodynamics under steady spinning conditions. An attempt was made to predict the flight motions measured during stall/spin flight testing of an unpowered, radio-controlled model designed to be a 1/10 scale, dynamically-scaled model of a current fighter configuration. Comparison of the predicted and measured flight motions show that while the post-stall and spin entry motions were not well-predicted, the developed spinning motion (a steady flat spin) and the initial phases of the spin recovery motion are reasonably well predicted.

Precessional Instability in Binary Black Holes with Aligned Spins.

PubMed

Gerosa, Davide; Kesden, Michael; O'Shaughnessy, Richard; Klein, Antoine; Berti, Emanuele; Sperhake, Ulrich; Trifirò, Daniele

2015-10-02

Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been test beds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is antialigned. Spins in these configurations are unstable to precession to large misalignment when the binary separation r is between the values r(ud±)=(√(χ(1))±√(qχ(2)))(4)(1-q)(-2)M, where M is the total mass, q≡m(2)/m(1) is the mass ratio, and χ(1) (χ(2)) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near the merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes.

Effective field renormalization group approach for Ising lattice spin systems

NASA Astrophysics Data System (ADS)

Fittipaldi, Ivon P.

1994-03-01

A new applicable real-space renormalization group framework (EFRG) for computing the critical properties of Ising lattice spin systems is presented. The method, which follows up the same strategy of the mean-field renormalization group scheme (MFRG), is based on rigorous Ising spin identities and utilizes a convenient differential operator expansion technique. Within this scheme, in contrast with the usual mean-field type of equation of state, all the relevant self-spin correlations are taken exactly into account. The results for the critical coupling and the critical exponent v, for the correlation length, are very satisfactory and it is shown that this technique leads to rather accurate results which represent a remarkable improvement on those obtained from the standard MFRG method. In particular, it is shown that the present EFRG approach correctly distinguishes the geometry of the lattice structure even when employing its simplest size-cluster version. Owing to its simplicity we also comment on the wide applicability of the present method to problems in crystalline and disordered Ising spin systems.

Physics and application of persistent spin helix state in semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Kohda, Makoto; Salis, Gian

2017-07-01

In order to utilize the spin degree of freedom in semiconductors, control of spin states and transfer of the spin information are fundamental requirements for future spintronic devices and quantum computing. Spin orbit (SO) interaction generates an effective magnetic field for moving electrons and enables spin generation, spin manipulation and spin detection without using external magnetic field and magnetic materials. However, spin relaxation also takes place due to a momentum dependent SO-induced effective magnetic field. As a result, SO interaction is considered to be a double-edged sword facilitating spin control but preventing spin transport over long distances. The persistent spin helix (PSH) state solves this problem since uniaxial alignment of the SO field with SU(2) symmetry enables the suppression of spin relaxation while spin precession can still be controlled. Consequently, understanding the PSH becomes an important step towards future spintronic technologies for classical and quantum applications. Here, we review recent progress of PSH in semiconductor heterostructures and its device application. Fundamental physics of SO interaction and the conditions of a PSH state in semiconductor heterostructures are discussed. We introduce experimental techniques to observe a PSH and explain both optical and electrical measurements for detecting a long spin relaxation time and the formation of a helical spin texture. After emphasizing the bulk Dresselhaus SO coefficient γ, the application of PSH states for spin transistors and logic circuits are discussed.

High Spin States in ^24Mg

NASA Astrophysics Data System (ADS)

Schwartz, J.; Lister, C. J.; Wuosmaa, A.; Betts, R. R.; Blumenthal, D.; Carpenter, M. P.; Davids, C. N.; Fischer, S. M.; Hackman, G.; Janssens, R. V. F.

1996-05-01

The ^12C(^16O,α)^24Mg reaction was used at 51.5MeV to populate high angular momentum states in ^24Mg. Gamma-rays de-exciting high spin states were detected in a 20 detector spectrometer (the AYE-ball) triggered by the ANL Fragment Mass Analyser (FMA). Channel selection, through detection of ^24Mg nuclei with the appropriate time of flight, was excellent. All the known decays from high spin states were seen in a few hours, with the exception of the 5.04 MeV γ-decay of the J^π=9^- state at 16.904 MeV footnote A.E.Smith et al., Phys. Lett. \\underlineB176, (1986)292. which could not be confirmed. The potential of the technique for studying the radiative decay of states with very high spin in light nuclei will be discussed.

Coherent manipulation of spin correlations in the Hubbard model

NASA Astrophysics Data System (ADS)

Wurz, N.; Chan, C. F.; Gall, M.; Drewes, J. H.; Cocchi, E.; Miller, L. A.; Pertot, D.; Brennecke, F.; Köhl, M.

2018-05-01

We coherently manipulate spin correlations in a two-component atomic Fermi gas loaded into an optical lattice using spatially and time-resolved Ramsey spectroscopy combined with high-resolution in situ imaging. This technique allows us not only to imprint spin patterns but also to probe the static magnetic structure factor at an arbitrary wave vector, in particular, the staggered structure factor. From a measurement along the diagonal of the first Brillouin zone of the optical lattice, we determine the magnetic correlation length and the individual spatial spin correlators. At half filling, the staggered magnetic structure factor serves as a sensitive thermometer, which we employ to study the equilibration in the spin and density sector during a slow quench of the lattice depth.

Quantum spin transistor with a Heisenberg spin chain.

PubMed

Marchukov, O V; Volosniev, A G; Valiente, M; Petrosyan, D; Zinner, N T

2016-10-10

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.

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

NASA Astrophysics Data System (ADS)

Avsar, Ahmet; Tan, Jun Y.; Kurpas, Marcin; Gmitra, Martin; Watanabe, Kenji; Taniguchi, Takashi; Fabian, Jaroslav; Özyilmaz, Barbaros

2017-09-01

Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron's spin. Although graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a bandgap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of two-dimensional semiconductors could help overcome this basic challenge. In this letter we report an important step towards making two-dimensional semiconductor spin devices. We have fabricated a spin valve based on ultrathin (~5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material, which supports all electrical spin injection, transport, precession and detection up to room temperature. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 μm. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that the Elliott-Yafet spin relaxation mechanism is dominant. We also show that spin transport in ultrathin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect.

Spin filter and spin valve in ferromagnetic graphene

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

Song, Yu, E-mail: kwungyusung@gmail.com; Dai, Gang; Research Center for Microsystems and Terahertz, China Academy of Engineering Physics, Mianyang 621999

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 spinmore » filter can operate at higher temperature than the spin valve.« less

Operating Spin Echo in the Quantum Regime for an Atomic-Ensemble Quantum Memory

NASA Astrophysics Data System (ADS)

Rui, Jun; Jiang, Yan; Yang, Sheng-Jun; Zhao, Bo; Bao, Xiao-Hui; Pan, Jian-Wei

2015-09-01

Spin echo is a powerful technique to extend atomic or nuclear coherence times by overcoming the dephasing due to inhomogeneous broadenings. However, there are disputes about the feasibility of applying this technique to an ensemble-based quantum memory at the single-quanta level. In this experimental study, we find that noise due to imperfections of the rephasing pulses has both intense superradiant and weak isotropic parts. By properly arranging the beam directions and optimizing the pulse fidelities, we successfully manage to operate the spin echo technique in the quantum regime by observing nonclassical photon-photon correlations as well as the quantum behavior of retrieved photons. Our work for the first time demonstrates the feasibility of harnessing the spin echo method to extend the lifetime of ensemble-based quantum memories at the single-quanta level.

Development and application of high-resolution solid- state NMR dipolar recovery techniques for spin-1/2 nuclei

NASA Astrophysics Data System (ADS)

Joers, James M.

The use of magic angle spinning to obtain high resolution solid state spectra has been well documented. This resolution occurs by coherently averaging the chemical shift anisotropy and dipolar interactions to zero over the period of a full rotation. While this allows for higher resolution, the structural information is seemingly lost to the spectrometer eye. Thus, high resolution spectra and structural information appear to be mutually exlusive. Recently, the push in solid state NMR is the development of recoupling techniques which afford both high resolution and structural information. The following dissertation demonstrates the feasibility of implementing such experiments in solving real world problems, and is centered on devising a method to recover homonuclear dipolar interactions in the high resolution regime.

Homogenization of Doppler broadening in spin-noise spectroscopy

NASA Astrophysics Data System (ADS)

Petrov, M. Yu.; Ryzhov, I. I.; Smirnov, D. S.; Belyaev, L. Yu.; Potekhin, R. A.; Glazov, M. M.; Kulyasov, V. N.; Kozlov, G. G.; Aleksandrov, E. B.; Zapasskii, V. S.

2018-03-01

The spin-noise spectroscopy, being a nonperturbative linear optics tool, is still reputed to reveal a number of capabilities specific to nonlinear optics techniques. The effect of the Doppler broadening homogenization discovered in this work essentially widens these unique properties of spin-noise spectroscopy. We investigate spin noise of a classical system—cesium atoms vapor with admixture of buffer gas—by measuring the spin-induced Faraday rotation fluctuations in the region of D 2 line. The line, under our experimental conditions, is strongly inhomogeneously broadened due to the Doppler effect. Despite that, optical spectrum of the spin-noise power has the shape typical for the homogeneously broadened line with a dip at the line center. This fact is in stark contrast with the results of previous studies of inhomogeneous quantum dot ensembles and Doppler broadened atomic systems. In addition, the two-color spin-noise measurements have shown, in a highly spectacular way, that fluctuations of the Faraday rotation within the line are either correlated or anticorrelated depending on whether the two wavelengths lie on the same side or on different sides of the resonance. The experimental data are interpreted in the frame of the developed theoretical model which takes into account both kinetics and spin dynamics of Cs atoms. It is shown that the unexpected behavior of the Faraday rotation noise spectra and effective homogenization of the optical transition in the spin-noise measurements are related to smallness of the momentum relaxation time of the atoms as compared with their spin-relaxation time. Our findings demonstrate abilities of spin-noise spectroscopy for studying dynamic properties of inhomogeneously broadened ensembles of randomly moving spins.

Giant Spin Hall Effect and Switching Induced by Spin-Transfer Torque in a W /Co40Fe40B20/MgO Structure with Perpendicular Magnetic Anisotropy

NASA Astrophysics Data System (ADS)

Hao, Qiang; Xiao, Gang

2015-03-01

We obtain robust perpendicular magnetic anisotropy in a β -W /Co40Fe40B20/MgO structure without the need of any insertion layer between W and Co40Fe40B20 . This is achieved within a broad range of W thicknesses (3.0-9.0 nm), using a simple fabrication technique. We determine the spin Hall angle (0.40) and spin-diffusion length for the bulk β form of tungsten with a large spin-orbit coupling. As a result of the giant spin Hall effect in β -W and careful magnetic annealing, we significantly reduce the critical current density for the spin-transfer-torque-induced magnetic switching in Co40Fe40B20 . The elemental β -W is a superior candidate for magnetic memory and spin-logic applications.

NMR in Pulsed Magnetic Fields on the Orthogonal Shastry-Sutherland spin system SrCu2 (BO3)2

NASA Astrophysics Data System (ADS)

Stern, Raivo; Kohlrautz, Jonas; Kühne, Hannes; Greene, Liz; Wosnitza, Jochen; Haase, Jügen

2015-03-01

SrCu2(BO3)2 is a quasi-two-dimensional spin system consisting of Cu2+ ions which form orthogonal spin singlet dimers, also known as the Shastry-Sutherland lattice, in the ground state. Though this system has been studied extensively using a variety of techniques to probe the spin triplet excitations, including recent magnetization measurements over 100 T, microscopic techniques, such as nuclear magnetic resonance (NMR), could provide further insight into the spin excitations and spin-coupling mechanisms. We demonstrate the feasibility of performing NMR on real physics system in pulsed magnets. We present 11B NMR spectra measured in pulsed magnetic fields up to 53 T, and compare those with prior results obtained in static magnetic fields. Herewith we prove the efficacy of this technique and then extend to higher fields to fully explore the spin structure of the 1/3 plateau. Support by EMFL, DFG, ETAg (EML+ & PUT210).

Electron spin resonance studies of Bi1-xScxFeO3 nanoparticulates: Observation of an enhanced spin canting over a large temperature range

NASA Astrophysics Data System (ADS)

Titus, S.; Balakumar, S.; Sakar, M.; Das, J.; Srinivasu, V. V.

2017-12-01

Bi1-xScxFeO3 (x = 0.0, 0.1, 0.15, 0.25) nano particles were synthesized by sol gel method. We then probed the spin system in these nano particles using electron spin resonance technique. Our ESR results strongly suggest the scenario of modified spin canted structures. Spin canting parameter Δg/g as a function of temperature for Scandium doped BFO is qualitatively different from undoped BFO. A broad peak is observed for all the Scandium doped BFO samples and an enhanced spin canting over a large temperature range (75-210 K) in the case of x = 0.15 doping. We also showed that the asymmetry parameter and thereby the magneto-crystalline anisotropy in these BSFO nanoparticles show peaks around 230 K for (x = 0.10 and 0.15) and beyond 300 K for x = 0.25 system. Thus, we established that the Sc doping significantly modifies the spin canting and magneto crystalline anisotropy in the BFO system.

Floquet spin states in graphene under ac-driven spin-orbit interaction

NASA Astrophysics Data System (ADS)

López, A.; Sun, Z. Z.; Schliemann, J.

2012-05-01

We study the role of periodically driven time-dependent Rashba spin-orbit coupling (RSOC) on a monolayer graphene sample. After recasting the originally 4×4 system of dynamical equations as two time-reversal related two-level problems, the quasienergy spectrum and the related dynamics are investigated via various techniques and approximations. In the static case, the system is gapped at the Dirac point. The rotating wave approximation (RWA) applied to the driven system unphysically preserves this feature, while the Magnus-Floquet approach as well as a numerically exact evaluation of the Floquet equation show that this gap is dynamically closed. In addition, a sizable oscillating pattern of the out-of-plane spin polarization is found in the driven case for states that are completely unpolarized in the static limit. Evaluation of the autocorrelation function shows that the original uniform interference pattern corresponding to time-independent RSOC gets distorted. The resulting structure can be qualitatively explained as a consequence of the transitions induced by the ac driving among the static eigenstates, i.e., these transitions modulate the relative phases that add up to give the quantum revivals of the autocorrelation function. Contrary to the static case, in the driven scenario, quantum revivals (suppressions) are correlated to spin-up (down) phases.

Epitaxial strain-mediated spin-state transitions: can we switch off magnetism?

NASA Astrophysics Data System (ADS)

Rondinelli, James; Spaldin, Nicola

2008-03-01

We use first-principles density functional theory calculations to explore spin-state transitions in epitaxially strained LaCoO3. While high-spin to low-spin state transitions in minerals are common in geophysics, where pressures can reach over 200 GPa, we explore whether heteroepitaxial strain can achieve similar transitions with moderate strain in thin films. LaCoO3 is known to undergo a low-spin (S=0, t2g^6eg^0) to intermediate-spin (S=1, t2g^5eg^1) or high-spin (S=2, t2g^4eg^2) state transition with increasing temperature, and thus makes it a promising candidate material for strain-mediated spin transitions. Here we discuss the physics of the low-spin transition and changes in the electronic structure of LaCoO3, most notably, the metal-insulator transition that accompanies the spin-state transitions with epitaxial strain. As thin film growth techniques continue to reach atomic-level precision, we suggest this is another approach for controlling magnetism in complex oxide heterostructures.

Brillouin-Mandelstam spectroscopy of standing spin waves in a ferrite waveguide

NASA Astrophysics Data System (ADS)

Balinskiy, Michael; Kargar, Fariborz; Chiang, Howard; Balandin, Alexander A.; Khitun, Alexander G.

2018-05-01

This article reports results of experimental investigation of the spin wave interference over large distances in the Y3Fe2(FeO4)3 waveguide using Brillouin-Mandelstam spectroscopy. Two coherent spin waves are excited by the micro-antennas fabricated at the edges of the waveguide. The amplitudes of the input spin waves are adjusted to provide approximately the same intensity in the central region of the waveguide. The relative phase between the excited spin waves is controlled by the phase shifter. The change of the local intensity distribution in the standing spin wave is monitored using Brillouin-Mandelstam light scattering spectroscopy. Experimental data demonstrate the oscillation of the scattered light intensity depending on the relative phase of the interfering spin waves. The oscillations of the intensity, tunable via the relative phase shift, are observed as far as 7.5 mm away from the spin-wave generating antennas at room temperature. The obtained results are important for developing techniques for remote control of spin currents, with potential applications in spin-based memory and logic devices.

Angular dependence of spin-orbit spin-transfer torques

NASA Astrophysics Data System (ADS)

Lee, Ki-Seung; Go, Dongwook; Manchon, Aurélien; Haney, Paul M.; Stiles, M. D.; Lee, Hyun-Woo; Lee, Kyung-Jin

2015-04-01

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.

Quantum spin transistor with a Heisenberg spin chain

PubMed Central

Marchukov, O. V.; Volosniev, A. G.; Valiente, M.; Petrosyan, D.; Zinner, N. T.

2016-01-01

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. PMID:27721438

Thermally Generated Spin Signals in a Nondegenerate Silicon Spin Valve

NASA Astrophysics Data System (ADS)

Yamashita, Naoto; Ando, Yuichiro; Koike, Hayato; Miwa, Shinji; Suzuki, Yoshishige; Shiraishi, Masashi

2018-05-01

Thermally generated spin signals are observed in a nondegenerate Si spin valve. The spin-dependent Seebeck effect is used for thermal spin-signal generation. A thermal gradient of about 200 mK at the interface of Fe and Si enables the generation of a spin voltage of 8 μ V at room temperature. A simple expansion of the conventional spin-drift-diffusion model that takes into account the spin-dependent Seebeck effect shows that semiconductor materials are more promising for thermal spin-signal generation comparing than metallic materials, and thus enable efficient heat recycling in semiconductor spin devices.

Spin resonance and spin fluctuations in a quantum wire

NASA Astrophysics Data System (ADS)

Pokrovsky, V. L.

2017-02-01

This is a review of theoretical works on spin resonance in a quantum wire associated with the spin-orbit interaction. We demonstrate that the spin-orbit induced internal "magnetic field" leads to a narrow spin-flip resonance at low temperatures in the absence of an applied magnetic field. An applied dc magnetic field perpendicular to and small compared with the spin-orbit field enhances the resonance absorption by several orders of magnitude. The component of applied field parallel to the spin-orbit field separates the resonance frequencies of right and left movers and enables a linearly polarized ac electric field to produce a dynamic magnetization as well as electric and spin currents. We start with a simple model of noninteracting electrons and then consider the interaction that is not weak in 1d electron system. We show that electron spin resonance in the spin-orbit field persists in the Luttinger liquid. The interaction produces an additional singularity (cusp) in the spin-flip channel associated with the plasma oscillation. As it was shown earlier by Starykh and his coworkers, the interacting 1d electron system in the external field with sufficiently large parallel component becomes unstable with respect to the appearance of a spin-density wave. This instability suppresses the spin resonance. The observation of the electron spin resonance in a thin wires requires low temperature and high intensity of electromagnetic field in the terahertz diapason. The experiment satisfying these two requirements is possible but rather difficult. An alternative approach that does not require strong ac field is to study two-time correlations of the total spin of the wire with an optical method developed by Crooker and coworkers. We developed theory of such correlations. We prove that the correlation of the total spin component parallel to the internal magnetic field is dominant in systems with the developed spin-density waves but it vanishes in Luttinger liquid. Thus, the

Improved Spin-Echo-Edited NMR Diffusion Measurements

NASA Astrophysics Data System (ADS)

Otto, William H.; Larive, Cynthia K.

2001-12-01

The need for simple and robust schemes for the analysis of ligand-protein binding has resulted in the development of diffusion-based NMR techniques that can be used to assay binding in protein solutions containing a mixture of several ligands. As a means of gaining spectral selectivity in NMR diffusion measurements, a simple experiment, the gradient modified spin-echo (GOSE), has been developed to reject the resonances of coupled spins and detect only the singlets in the 1H NMR spectrum. This is accomplished by first using a spin echo to null the resonances of the coupled spins. Following the spin echo, the singlet magnetization is flipped out of the transverse plane and a dephasing gradient is applied to reduce the spectral artifacts resulting from incomplete cancellation of the J-coupled resonances. The resulting modular sequence is combined here with the BPPSTE pulse sequence; however, it could be easily incorporated into any pulse sequence where additional spectral selectivity is desired. Results obtained with the GOSE-BPPSTE pulse sequence are compared with those obtained with the BPPSTE and CPMG-BPPSTE experiments for a mixture containing the ligands resorcinol and tryptophan in a solution of human serum albumin.

Noise in tunneling spin current across coupled quantum spin chains

NASA Astrophysics Data System (ADS)

Aftergood, Joshua; Takei, So

2018-01-01

We theoretically study the spin current and its dc noise generated between two spin-1 /2 spin chains weakly coupled at a single site in the presence of an over-population of spin excitations and a temperature elevation in one subsystem relative to the other, and we compare the corresponding transport quantities across two weakly coupled magnetic insulators hosting magnons. In the spin chain scenario, we find that applying a temperature bias exclusively leads to a vanishing spin current and a concomitant divergence in the spin Fano factor, defined as the spin current noise-to-signal ratio. This divergence is shown to have an exact analogy to the physics of electron scattering between fractional quantum Hall edge states and not to arise in the magnon scenario. We also reveal a suppression in the spin current noise that exclusively arises in the spin chain scenario due to the fermion nature of the spin-1/2 operators. We discuss how the spin Fano factor may be extracted experimentally via the inverse spin Hall effect used extensively in spintronics.

When measured spin polarization is not spin polarization

NASA Astrophysics Data System (ADS)

Dowben, P. A.; Wu, Ning; Binek, Christian

2011-05-01

Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO2 and Cr2O3 illustrate some of the complications which hinders comparisons of spin polarization values.

Preparation and Adsorption Property of Imido-acetic Acid Type Chelating Nano-fibers by Electro-spinning Technique

NASA Astrophysics Data System (ADS)

Yang, Jiali; Lu, Lansi; Zhang, Zhu; Liao, Minhui; He, Huirong; Li, Lingxing; Chen, Jida; Chen, Shijin

2017-12-01

A novel nano-fibrous adsorbent from imino-acetic acid (IDA) and polyvinyl alcohol (PVA) mixture solution was prepared by electro-spinning technique. The nano-fibrous adsorbents with imino-acetic acid functional groups were characterized and demonstrated by fourier transform infrared spectrometry (FT-IR) and the scanning electron microscopy (SEM). The effect of the adsorbents to remove heavy metals such as lead (Pb) and copper (Cu) ions from the aqueous solution was studied. The maximum adsorption percentage (SP) of the metal ions can reach 93.08% for Cu (II) and 96.69% for Pb(II), respectively. Furthermore, it shows that the adsorption procedure of the adsorbents is spontaneous and endothermic, and adsorption rate fits well with pseudo-second-order kinetic model. Most importantly, the reusability of the nanofibers for removal of metal ions was also demonstrated to be used at least five times.

Quantum memory operations in a flux qubit - spin ensemble hybrid system

NASA Astrophysics Data System (ADS)

Saito, S.; Zhu, X.; Amsuss, R.; Matsuzaki, Y.; Kakuyanagi, K.; Shimo-Oka, T.; Mizuochi, N.; Nemoto, K.; Munro, W. J.; Semba, K.

2014-03-01

Superconducting quantum bits (qubits) are one of the most promising candidates for a future large-scale quantum processor. However for larger scale realizations the currently reported coherence times of these macroscopic objects (superconducting qubits) has not yet reached those of microscopic systems (electron spins, nuclear spins, etc). In this context, a superconductor-spin ensemble hybrid system has attracted considerable attention. The spin ensemble could operate as a quantum memory for superconducting qubits. We have experimentally demonstrated quantum memory operations in a superconductor-diamond hybrid system. An excited state and a superposition state prepared in the flux qubit can be transferred to, stored in and retrieved from the NV spin ensemble in diamond. From these experiments, we have found the coherence time of the spin ensemble is limited by the inhomogeneous broadening of the electron spin (4.4 MHz) and by the hyperfine coupling to nitrogen nuclear spins (2.3 MHz). In the future, spin echo techniques could eliminate these effects and elongate the coherence time. Our results are a significant first step in utilizing the spin ensemble as long-lived quantum memory for superconducting flux qubits. This work was supported by the FIRST program and NICT.

Spin Relaxation and Manipulation in Spin-orbit Qubits

NASA Astrophysics Data System (ADS)

Borhani, Massoud; Hu, Xuedong

2012-02-01

We derive a generalized form of the Electric Dipole Spin Resonance (EDSR) Hamiltonian in the presence of the spin-orbit interaction for single spins in an elliptic quantum dot (QD) subject to an arbitrary (in both direction and magnitude) applied magnetic field. We predict a nonlinear behavior of the Rabi frequency as a function of the magnetic field for sufficiently large Zeeman energies, and present a microscopic expression for the anisotropic electron g-tensor. Similarly, an EDSR Hamiltonian is devised for two spins confined in a double quantum dot (DQD). Finally, we calculate two-electron-spin relaxation rates due to phonon emission, for both in-plane and perpendicular magnetic fields. Our results have immediate applications to current EDSR experiments on nanowire QDs, g-factor optimization of confined carriers, and spin decay measurements in DQD spin-orbit qubits.

Nonlinear spin current generation in noncentrosymmetric spin-orbit coupled systems

NASA Astrophysics Data System (ADS)

Hamamoto, Keita; Ezawa, Motohiko; Kim, Kun Woo; Morimoto, Takahiro; Nagaosa, Naoto

2017-06-01

Spin current plays a central role in spintronics. In particular, finding more efficient ways to generate spin current has been an important issue and has been studied actively. For example, representative methods of spin-current generation include spin-polarized current injections from ferromagnetic metals, the spin Hall effect, and the spin battery. Here, we theoretically propose a mechanism of spin-current generation based on nonlinear phenomena. By using Boltzmann transport theory, we show that a simple application of the electric field E induces spin current proportional to E2 in noncentrosymmetric spin-orbit coupled systems. We demonstrate that the nonlinear spin current of the proposed mechanism is supported in the surface state of three-dimensional topological insulators and two-dimensional semiconductors with the Rashba and/or Dresselhaus interaction. In the latter case, the angular dependence of the nonlinear spin current can be manipulated by the direction of the electric field and by the ratio of the Rashba and Dresselhaus interactions. We find that the magnitude of the spin current largely exceeds those in the previous methods for a reasonable magnitude of the electric field. Furthermore, we show that application of ac electric fields (e.g., terahertz light) leads to the rectifying effect of the spin current, where dc spin current is generated. These findings will pave a route to manipulate the spin current in noncentrosymmetric crystals.

Quantum Entanglement of Quantum Dot Spin Using Flying Qubits

DTIC Science & Technology

2015-05-01

QUANTUM ENTANGLEMENT OF QUANTUM DOT SPIN USING FLYING QUBITS UNIVERSITY OF MICHIGAN MAY 2015 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE...To) SEP 2012 – DEC 2014 4. TITLE AND SUBTITLE QUANTUM ENTANGLEMENT OF QUANTUM DOT SPIN USING FLYING QUBITS 5a. CONTRACT NUMBER FA8750-12-2-0333...been to advance the frontier of quantum entangled semiconductor electrons using ultrafast optical techniques. The approach is based on

Spin temperature concept verified by optical magnetometry of nuclear spins

NASA Astrophysics Data System (ADS)

Vladimirova, M.; Cronenberger, S.; Scalbert, D.; Ryzhov, I. I.; Zapasskii, V. S.; Kozlov, G. G.; Lemaître, A.; Kavokin, K. V.

2018-01-01

We develop a method of nonperturbative optical control over adiabatic remagnetization of the nuclear spin system and apply it to verify the spin temperature concept in GaAs microcavities. The nuclear spin system is shown to exactly follow the predictions of the spin temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalization. These findings open a way for the deep cooling of nuclear spins in semiconductor structures, with the prospect of realizing nuclear spin-ordered states for high-fidelity spin-photon interfaces.

A Comparison of Two Methods for Estimating Black Hole Spin in Active Galactic Nuclei

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

Capellupo, Daniel M.; Haggard, Daryl; Wafflard-Fernandez, Gaylor, E-mail: danielc@physics.mcgill.ca

Angular momentum, or spin, is a fundamental property of black holes (BHs), yet it is much more difficult to estimate than mass or accretion rate (for actively accreting systems). In recent years, high-quality X-ray observations have allowed for detailed measurements of the Fe K α emission line, where relativistic line broadening allows constraints on the spin parameter (the X-ray reflection method). Another technique uses accretion disk models to fit the AGN continuum emission (the continuum-fitting, or CF, method). Although each technique has model-dependent uncertainties, these are the best empirical tools currently available and should be vetted in systems where bothmore » techniques can be applied. A detailed comparison of the two methods is also useful because neither method can be applied to all AGN. The X-ray reflection technique targets mostly local ( z ≲ 0.1) systems, while the CF method can be applied at higher redshift, up to and beyond the peak of AGN activity and growth. Here, we apply the CF method to two AGN with X-ray reflection measurements. For both the high-mass AGN, H1821+643, and the Seyfert 1, NGC 3783, we find a range in spin parameter consistent with the X-ray reflection measurements. However, the near-maximal spin favored by the reflection method for NGC 3783 is more probable if we add a disk wind to the model. Refinement of these techniques, together with improved X-ray measurements and tighter BH mass constraints, will permit this comparison in a larger sample of AGN and increase our confidence in these spin estimation techniques.« less

Electronic spin transport in gate-tunable black phosphorus spin valves

NASA Astrophysics Data System (ADS)

Liu, Jiawei; Avsar, Ahmet; Tan, Jun You; Oezyilmaz, Barbaros

High charge mobility, the electric field effect and small spin-orbit coupling make semiconducting black phosphorus (BP) a promising material for spintronics device applications requiring long spin distance spin communication with all rectification and amplification actions. Towards this, we study the all electrical spin injection, transport and detection under non-local spin valve geometry in fully encapsulated ultra-thin BP devices. We observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 μm. These values are an order of magnitude higher than what have been measured in typical graphene spin valve devices. Moreover, the spin transport depends strongly on charge carrier concentration and can be manipulated in a spin transistor-like manner by controlling electric field. This behaviour persists even at room temperature. Finally, we will show that similar to its electrical and optical properties, spin transport property is also strongly anisotropic.

Spin-Mechatronics

NASA Astrophysics Data System (ADS)

Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

2017-01-01

We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.

Bulk electron spin polarization generated by the spin Hall current

NASA Astrophysics Data System (ADS)

Korenev, V. L.

2006-07-01

It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

Benchmarking GPU and CPU codes for Heisenberg spin glass over-relaxation

NASA Astrophysics Data System (ADS)

Bernaschi, M.; Parisi, G.; Parisi, L.

2011-06-01

We present a set of possible implementations for Graphics Processing Units (GPU) of the Over-relaxation technique applied to the 3D Heisenberg spin glass model. The results show that a carefully tuned code can achieve more than 100 GFlops/s of sustained performance and update a single spin in about 0.6 nanoseconds. A multi-hit technique that exploits the GPU shared memory further reduces this time. Such results are compared with those obtained by means of a highly-tuned vector-parallel code on latest generation multi-core CPUs.

Spin-dependent analysis of two-dimensional electron liquids

NASA Astrophysics Data System (ADS)

Bulutay, C.; Tanatar, B.

2002-05-01

Two-dimensional electron liquid (2D EL) at full Fermi degeneracy is revisited, giving special attention to the spin-polarization effects. First, we extend the recently proposed classical-map hypernetted-chain (CHNC) technique to the 2D EL, while preserving the simplicity of the original proposal. An efficient implementation of CHNC is given utilizing Lado's quadrature expressions for the isotropic Fourier transforms. Our results indicate that the paramagnetic phase stays to be the ground state until the Wigner crystallization density, even though the energy separation with the ferromagnetic and other partially polarized states become minute. We analyze compressibility and spin stiffness variations with respect to density and spin polarization, the latter being overlooked until now. Spin-dependent static structure factor and pair-distribution functions are computed; agreement with the available quantum Monte Carlo data persists even in the strong-coupling regime of the 2D EL.

Bias Dependent Spin Relaxation in a [110]-InAs/AlSb Two Dimensional Electron System

NASA Astrophysics Data System (ADS)

Hicks, J.; Holabird, K.

2005-03-01

Manipulation of electron spin is a critical component of many proposed semiconductor spintronic devices. One promising approach utilizes the Rashba effect by which an applied electric field can be used to reduce the spin lifetime or rotate spin orientation through spin-orbit interaction. The large spin-orbit interaction needed for this technique to be effective typically leads to fast spin relaxation through precessional decay, which may severely limit device architectures and functionalities. An exception arises in [110]-oriented heterostructures where the crystal magnetic field associated with bulk inversion asymmetry lies along the growth direction and in which case spins oriented along the growth direction do not precess. These considerations have led to a recent proposal of a spin-FET that incorporates a [110]-oriented, gate-controlled InAs quantum well channel [1]. We report measurements of the electron spin lifetime as a function of applied electric field in a [110]-InAs 2DES. Measurements made using an ultrafast, mid-IR pump-probe technique indicate that the spin lifetime can be reduced from its maximum to minimum value over a range of less than 0.2V per quantum well at room temperature. This work is supported by DARPA, NSERC and the NSF grant ECS - 0322021. [1] K. C. Hall, W. H. Lau, K. Gundogdu, M. E. Flatte, and T. F. Boggess, Appl. Phys. Lett. 83, 2937 (2003).

Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

NASA Astrophysics Data System (ADS)

Gopinath, T.; Veglia, Gianluigi

2013-05-01

We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

Toward polarized antiprotons: Machine development for spin-filtering experiments

NASA Astrophysics Data System (ADS)

Weidemann, C.; Rathmann, F.; Stein, H. J.; Lorentz, B.; Bagdasarian, Z.; Barion, L.; Barsov, S.; Bechstedt, U.; Bertelli, S.; Chiladze, D.; Ciullo, G.; Contalbrigo, M.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Goslawski, P.; Grigoriev, K.; Guidoboni, G.; Kacharava, A.; Kamerdzhiev, V.; Khoukaz, A.; Kulikov, A.; Lehrach, A.; Lenisa, P.; Lomidze, N.; Macharashvili, G.; Maier, R.; Martin, S.; Mchedlishvili, D.; Meyer, H. O.; Merzliakov, S.; Mielke, M.; Mikirtychiants, M.; Mikirtychiants, S.; Nass, A.; Nikolaev, N. N.; Oellers, D.; Papenbrock, M.; Pesce, A.; Prasuhn, D.; Retzlaff, M.; Schleichert, R.; Schröer, D.; Seyfarth, H.; Soltner, H.; Statera, M.; Steffens, E.; Stockhorst, H.; Ströher, H.; Tabidze, M.; Tagliente, G.; Engblom, P. Thörngren; Trusov, S.; Valdau, Yu.; Vasiliev, A.; Wüstner, P.

2015-02-01

The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of 49.3 MeV in COSY. The implementation of a low-β insertion made it possible to achieve beam lifetimes of τb=8000 s in the presence of a dense polarized hydrogen storage-cell target of areal density dt=(5.5 ±0.2 )×1 013 atoms /cm2 . The developed techniques can be directly applied to antiproton machines and allow the determination of the spin-dependent p ¯p cross sections via spin filtering.

Spin Hamiltonian Analysis of the SMM V15 Using High Field ESR

NASA Astrophysics Data System (ADS)

Martens, Mathew; van Tol, Hans; Bertaina, Sylvain; Barbara, Bernard; Muller, Achim; Chiorescu, Irinel

2014-03-01

We have studied molecular magnets using high field / high frequency Electron Spin Resonance. Such molecular structures contain many quantum spins linked by exchange interactions and consequently their energy structure is often complex and require a good understanding of the molecular spin Hamiltonian. In particular, we studied the V15 molecule, comprised of 15 spins 1/2 and a total spin 1/2, which is a system that recently showed quantum Rabi oscillations of its total quantum spin. This type of molecule is an essential system for advancing molecular structures into quantum computing. We used high frequency characterization techniques (of hundreds of GHz) to gain insight into the exchange anisotropy interactions, crystal field, and anti-symmetric interactions present in this system. We analyzed the data using a detailed numerical analysis of spin interactions and our findings regarding the V15 spin Hamiltonian will be discussed. Supported by the NSF Cooperative Agreement Grant No. DMR-0654118 and No. NHMFL UCGP 5059, NSF grant No. DMR-0645408.

Efficient creation of dipolar coupled nitrogen-vacancy spin qubits in diamond

NASA Astrophysics Data System (ADS)

Jakobi, I.; Momenzadeh, S. A.; Fávaro de Oliveira, F.; Michl, J.; Ziem, F.; Schreck, M.; Neumann, P.; Denisenko, A.; Wrachtrup, J.

2016-09-01

Coherently coupled pairs or multimers of nitrogen-vacancy defect electron spins in diamond have many promising applications especially in quantum information processing (QIP) but also in nanoscale sensing applications. Scalable registers of spin qubits are essential to the progress of QIP. Ion implantation is the only known technique able to produce defect pairs close enough to allow spin coupling via dipolar interaction. Although several competing methods have been proposed to increase the resulting resolution of ion implantation, the reliable creation of working registers is still to be demonstrated. The current limitation are residual radiation-induced defects, resulting in degraded qubit performance as trade-off for positioning accuracy. Here we present an optimized estimation of nanomask implantation parameters that are most likely to produce interacting qubits under standard conditions. We apply our findings to a well-established technique, namely masks written in electron-beam lithography, to create coupled defect pairs with a reasonable probability. Furthermore, we investigate the scaling behavior and necessary improvements to efficiently engineer interacting spin architectures.

Studies of superconducting materials with muon spin rotation

NASA Technical Reports Server (NTRS)

Davis, Michael R.; Stronach, Carey E.; Kossler, W. J.; Schone, H. E.; Yu, X. H.; Uemura, Y. J.; Sternlieb, B. J.; Kempton, J. R.; Oostens, J.; Lankford, W. F.

1989-01-01

The muon spin rotation/relaxation technique was found to be an exceptionally effective means of measuring the magnetic properties of superconductors, including the new high temperature superconductor materials, at the microscopic level. The technique directly measures the magnetic penetration depth (type II superconductors (SC's)) and detects the presence of magnetic ordering (antiferromagnetism or spin-glass ordering were observed in some high temperature superconductor (HTSC's) and in many closely related compounds). Extensive studies of HTSC materials were conducted by the Virginia State University - College of William and Mary - Columbia University collaboration at Brookhaven National Laboratory and TRIUMF (Vancouver). A survey of LaSrCuO and YBaCaCuO systems shows an essentially linear relationship between the transition temperature T(sub c) and the relaxation rate. This appears to be a manifestation of the proportionality between T(sub c) and the Fermi energy, which suggests a high energy scale for the SC coupling, and which is not consistent with the weak coupling of phonon-mediated SC. Studies of LaCuO and YBaCuO parent compounds show clear evidence of antiferromagnetism. YBa2Cu(3-x)CO(x)O7 shows the simultaneous presence of spin-glass magnetic ordering and superconductivity. Three-dimensional SC, (Ba, K) BiO3, unlike the layered CuO-based compounds, shows no suggestion of magnetic ordering. Experimental techniques and theoretical implications are discussed.

Spin manipulation and relaxation in spin-orbit qubits

NASA Astrophysics Data System (ADS)

Borhani, Massoud; Hu, Xuedong

2012-03-01

We derive a generalized form of the electric dipole spin resonance (EDSR) Hamiltonian in the presence of the spin-orbit interaction for single spins in an elliptic quantum dot (QD) subject to an arbitrary (in both direction and magnitude) applied magnetic field. We predict a nonlinear behavior of the Rabi frequency as a function of the magnetic field for sufficiently large Zeeman energies, and present a microscopic expression for the anisotropic electron g tensor. Similarly, an EDSR Hamiltonian is devised for two spins confined in a double quantum dot (DQD), where coherent Rabi oscillations between the singlet and triplet states are induced by jittering the inter-dot distance at the resonance frequency. Finally, we calculate two-electron-spin relaxation rates due to phonon emission, for both in-plane and perpendicular magnetic fields. Our results have immediate applications to current EDSR experiments on nanowire QDs, g-factor optimization of confined carriers, and spin decay measurements in DQD spin-orbit qubits.

ExoMol molecular line lists - XXVI: spectra of SH and NS

NASA Astrophysics Data System (ADS)

Yurchenko, Sergei N.; Bond, Wesley; Gorman, Maire N.; Lodi, Lorenzo; McKemmish, Laura K.; Nunn, William; Shah, Rohan; Tennyson, Jonathan

2018-04-01

Line lists for the sulphur-containing molecules SH (the mercapto radical) and NS are computed as part of the ExoMol project. These line lists consider transitions within the X 2Π ground state for 32SH, 33SH, 34SH and 32SD, and 14N32S, 14N33S, 14N34S, 14N36S and 15N32S. Ab initio potential energy (PEC) and spin-orbit coupling (SOC) curves are computed and then improved by fitting to experimentally observed transitions. Fully ab initio dipole moment curves (DMCs) computed at high level of theory are used to produce the final line lists. For SH, our fit gives a root-mean-square (rms) error of 0.03 cm-1 between the observed (vmax = 4, Jmax = 34.5) and calculated transitions wavenumbers; this is extrapolated such that all X 2Π rotational-vibrational-electronic (rovibronic) bound states are considered. For 32SH the resulting line list contains about 81 000 transitions and 2 300 rovibronic states, considering levels up to vmax = 14 and Jmax = 60.5. For NS the refinement used a combination of experimentally determined frequencies and energy levels and led to an rms fitting error of 0.002 cm-1. Each NS calculated line list includes around 2.8 million transitions and 31 000 rovibronic states with a vibrational range up to v = 53 and rotational range to J = 235.5, which covers up to 23 000 cm-1. Both line lists should be complete for temperatures up to 5000 K. Example spectra simulated using this line list are shown and comparisons made to the existing data in the CDMS database. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.

ExoMol molecular line lists - XXVI: spectra of SH and NS

NASA Astrophysics Data System (ADS)

Yurchenko, Sergei N.; Bond, Wesley; Gorman, Maire N.; Lodi, Lorenzo; McKemmish, Laura K.; Nunn, William; Shah, Rohan; Tennyson, Jonathan

2018-07-01

Line lists for the sulphur-containing molecules SH (the mercapto radical) and NS are computed as part of the ExoMol project. These line lists consider transitions within the X2Π ground state for 32SH, 33SH, 34SH,36SH and, 32SD, and 14N32S, 14N33S, 14N34S, 14N36S, and 15N32S. Ab initio potential energy (PEC) and spin-orbit coupling (SOC) curves are computed and then improved by fitting to experimentally observed transitions. Fully ab initio dipole moment curves (DMCs) computed at high level of theory are used to produce the final line lists. For SH, our fit gives a root-mean-square (rms) error of 0.03 cm-1 between the observed (vmax = 4, Jmax = 34.5) and calculated transitions wavenumbers; this is extrapolated such that all X2Π rotational-vibrational-electronic (rovibronic) bound states are considered. For 32SH the resulting line list contains about 81 000 transitions and 2300 rovibronic states, considering levels up to vmax = 14 and Jmax = 60.5. For NS the refinement used a combination of experimentally determined frequencies and energy levels and led to an rms-fitting error of 0.002 cm-1. Each NS-calculated line list includes around 2.8 million transitions and 31 000 rovibronic states with a vibrational range up to v = 53 and rotational range up to J = 235.5, which covers up to 23 000 cm-1. Both line lists should be complete for temperatures up to 5000 K. Example spectra simulated using this line list are shown and comparisons made to the existing data in the CDMS data base. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.

Investigation of the fluidity of biological fluids with a PDDTBN spin probe

NASA Astrophysics Data System (ADS)

Severcan, Feride; Acar, Berrin; Gökalp, Saadet

1997-06-01

The aim of this study is to ascertain whether the electron spin resonance technique using perdeutero-di- t-butyl nitroxide (PDDTBN) as a spin probe is able to monitor relative fluidity changes occurring in body fluids, such as blood and parotid saliva, according to different physiological conditions. The present study reveals that the spin probe PDDTBN is able to monitor the fluidity changes in parotid saliva related to habitual smoking, and in whole blood related to the estradiol level. The rotational correlation time of the spin probe and the local viscosity values of the parotid saliva and blood have been reported.

Determination of the spin and recovery characteristics of a typical low-wing general aviation design

NASA Technical Reports Server (NTRS)

Tischler, M. B.; Barlow, J. B.

1980-01-01

The equilibrium spin technique implemented in a graphical form for obtaining spin and recovery characteristics from rotary balance data is outlined. Results of its application to recent rotary balance tests of the NASA Low-Wing General Aviation Aircraft are discussed. The present results, which are an extension of previously published findings, indicate the ability of the equilibrium method to accurately evaluate spin modes and recovery control effectiveness. A comparison of the calculated results with available spin tunnel and full scale findings is presented. The technique is suitable for preliminary design applications as determined from the available results and data base requirements. A full discussion of implementation considerations and a summary of the results obtained from this method to date are presented.

Wurtzite spin lasers

NASA Astrophysics Data System (ADS)

Faria Junior, Paulo E.; Xu, Gaofeng; Chen, Yang-Fang; Sipahi, Guilherme M.; Žutić, Igor

2017-03-01

Semiconductor lasers are strongly altered by adding spin-polarized carriers. Such spin lasers could overcome many limitations of their conventional (spin-unpolarized) counterparts. While the vast majority of experiments in spin lasers employed zinc-blende semiconductors, the room-temperature electrical manipulation was first demonstrated in wurtzite GaN-based lasers. However, the underlying theoretical description of wurtzite spin lasers is still missing. To address this situation, focusing on (In,Ga)N-based wurtzite quantum wells, we develop a theoretical framework in which the calculated microscopic spin-dependent gain is combined with a simple rate equation model. A small spin-orbit coupling in these wurtzites supports simultaneous spin polarizations of electrons and holes, providing unexplored opportunities to control spin lasers. For example, the gain asymmetry, as one of the key figures of merit related to spin amplification, can change the sign by simply increasing the carrier density. The lasing threshold reduction has a nonmonotonic dependence on electron-spin polarization, even for a nonvanishing hole spin polarization.

Recovery of spinning satellites

NASA Technical Reports Server (NTRS)

Coppey, J. M.; Mahaffey, W. R.

1977-01-01

The behavior of a space tug and a spinning satellite in a coupled configuration was simulated and analyzed. A docking concept was developed to investigate the requirements pertaining to the design of a docking interface. Sensing techniques and control requirements for the chase vehicle were studied to assess the feasibility of an automatic docking. The effects of nutation dampers and liquid propellant slosh motion upon the docking transient were investigated.

Squeezed spin states: Squeezing the spin uncertainty relations

NASA Technical Reports Server (NTRS)

Kitagawa, Masahiro; Ueda, Masahito

1993-01-01

The notion of squeezing in spin systems is clarified, and the principle for spin squeezing is shown. Two twisting schemes are proposed as building blocks for spin squeezing and are shown to reduce the standard quantum noise, s/2, of the coherent S-spin state down to the order of S(sup 1/3) and 1/2. Applications to partition noise suppression are briefly discussed.

Manipulating Tabu List to Handle Machine Breakdowns in Job Shop Scheduling Problems

NASA Astrophysics Data System (ADS)

Nababan, Erna Budhiarti; SalimSitompul, Opim

2011-06-01

Machine breakdowns in a production schedule may occur on a random basis that make the well-known hard combinatorial problem of Job Shop Scheduling Problems (JSSP) becomes more complex. One of popular techniques used to solve the combinatorial problems is Tabu Search. In this technique, moves that will be not allowed to be revisited are retained in a tabu list in order to avoid in gaining solutions that have been obtained previously. In this paper, we propose an algorithm to employ a second tabu list to keep broken machines, in addition to the tabu list that keeps the moves. The period of how long the broken machines will be kept on the list is categorized using fuzzy membership function. Our technique are tested to the benchmark data of JSSP available on the OR library. From the experiment, we found that our algorithm is promising to help a decision maker to face the event of machine breakdowns.

High-fidelity projective read-out of a solid-state spin quantum register.

PubMed

Robledo, Lucio; Childress, Lilian; Bernien, Hannes; Hensen, Bas; Alkemade, Paul F A; Hanson, Ronald

2011-09-21

Initialization and read-out of coupled quantum systems are essential ingredients for the implementation of quantum algorithms. Single-shot read-out of the state of a multi-quantum-bit (multi-qubit) register would allow direct investigation of quantum correlations (entanglement), and would give access to further key resources such as quantum error correction and deterministic quantum teleportation. Although spins in solids are attractive candidates for scalable quantum information processing, their single-shot detection has been achieved only for isolated qubits. Here we demonstrate the preparation and measurement of a multi-spin quantum register in a low-temperature solid-state system by implementing resonant optical excitation techniques originally developed in atomic physics. We achieve high-fidelity read-out of the electronic spin associated with a single nitrogen-vacancy centre in diamond, and use this read-out to project up to three nearby nuclear spin qubits onto a well-defined state. Conversely, we can distinguish the state of the nuclear spins in a single shot by mapping it onto, and subsequently measuring, the electronic spin. Finally, we show compatibility with qubit control: we demonstrate initialization, coherent manipulation and single-shot read-out in a single experiment on a two-qubit register, using techniques suitable for extension to larger registers. These results pave the way for a test of Bell's inequalities on solid-state spins and the implementation of measurement-based quantum information protocols. © 2011 Macmillan Publishers Limited. All rights reserved

Lattice spin models for non-Abelian chiral spin liquids

DOE PAGES

Lecheminant, P.; Tsvelik, A. M.

2017-04-26

Here, we suggest a class of two-dimensional lattice spin Hamiltonians describing non-Abelian SU(2) chiral spin liquids—spin analogs of fractional non-Abelian quantum Hall states—with gapped bulk and gapless chiral edge excitations described by the SU(2) n Wess-Zumino-Novikov-Witten conformal field theory. The models are constructed from an array of generalized spin-n/2 ladders with multi-spin-exchange interactions which are coupled by isolated spins. Such models allow a controllable analytic treatment starting from the one-dimensional limit and are characterized by a bulk gap and non-Abelian SU(2) n gapless edge excitations.

Arterial spin labeled perfusion imaging using three-dimensional turbo spin echo with a distributed spiral-in/out trajectory.

PubMed

Li, Zhiqiang; Schär, Michael; Wang, Dinghui; Zwart, Nicholas R; Madhuranthakam, Ananth J; Karis, John P; Pipe, James G

2016-01-01

The three-dimensional (3D) spiral turbo spin echo (TSE) sequence is one of the preferred readout methods for arterial spin labeled (ASL) perfusion imaging. Conventional spiral TSE collects the data using a spiral-out readout on a stack of spirals trajectory. However, it may result in suboptimal image quality and is not flexible in protocol design. The goal of this study is to provide a more robust readout technique without such limitation. The proposed technique incorporates a spiral-in/out readout into 3D TSE, and collects the data on a distributed spirals trajectory. The data set is split into the spiral-in and -out subsets that are reconstructed separately and combined after image deblurring. The volunteer results acquired with the proposed technique show no geometric distortion or signal pileup, as is present with GRASE, and no signal loss, as is seen with conventional spiral TSE. Examples also demonstrate the flexibility in changing the imaging parameters to satisfy various criteria. The 3D TSE with a distributed spiral-in/out trajectory provides a robust readout technique and allows for easy protocol design, thus is a promising alternative to GRASE or conventional spiral TSE for ASL perfusion imaging. © 2015 Wiley Periodicals, Inc.

First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

PubMed

Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

2014-05-01

Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

An approach to spin-resolved molecular gas microscopy

NASA Astrophysics Data System (ADS)

Covey, Jacob P.; De Marco, Luigi; Acevedo, Óscar L.; Rey, Ana Maria; Ye, Jun

2018-04-01

Ultracold polar molecules are an ideal platform for studying many-body physics with long-range dipolar interactions. Experiments in this field have progressed enormously, and several groups are pursuing advanced apparatus for manipulation of molecules with electric fields as well as single-atom-resolved in situ detection. Such detection has become ubiquitous for atoms in optical lattices and tweezer arrays, but has yet to be demonstrated for ultracold polar molecules. Here we present a proposal for the implementation of site-resolved microscopy for polar molecules, and specifically discuss a technique for spin-resolved molecular detection. We use numerical simulation of spin dynamics of lattice-confined polar molecules to show how such a scheme would be of utility in a spin-diffusion experiment.

Effect of hyperfine-induced spin mixing on the defect-enabled spin blockade and spin filtering in GaNAs

NASA Astrophysics Data System (ADS)

Puttisong, Y.; Wang, X. J.; Buyanova, I. A.; Chen, W. M.

2013-03-01

The effect of hyperfine interaction (HFI) on the recently discovered room-temperature defect-enabled spin-filtering effect in GaNAs alloys is investigated both experimentally and theoretically based on a spin Hamiltonian analysis. We provide direct experimental evidence that the HFI between the electron and nuclear spin of the central Ga atom of the spin-filtering defect, namely, the Gai interstitials, causes strong mixing of the electron spin states of the defect, thereby degrading the efficiency of the spin-filtering effect. We also show that the HFI-induced spin mixing can be suppressed by an application of a longitudinal magnetic field such that the electronic Zeeman interaction overcomes the HFI, leading to well-defined electron spin states beneficial to the spin-filtering effect. The results provide a guideline for further optimization of the defect-engineered spin-filtering effect.

Spin transfer and spin pumping in disordered normal metal-antiferromagnetic insulator systems

NASA Astrophysics Data System (ADS)

Gulbrandsen, Sverre A.; Brataas, Arne

2018-02-01

We consider an antiferromagnetic insulator that is in contact with a metal. Spin accumulation in the metal can induce spin-transfer torques on the staggered field and on the magnetization in the antiferromagnet. These torques relate to spin pumping: the emission of spin currents into the metal by a precessing antiferromagnet. We investigate how the various components of the spin-transfer torque are affected by spin-independent disorder and spin-flip scattering in the metal. Spin-conserving disorder reduces the coupling between the spins in the antiferromagnet and the itinerant spins in the metal in a manner similar to Ohm's law. Spin-flip scattering leads to spin-memory loss with a reduced spin-transfer torque. We discuss the concept of a staggered spin current and argue that it is not a conserved quantity. Away from the interface, the staggered spin current varies around a 0 mean in an irregular manner. A network model explains the rapid decay of the staggered spin current.

Nonequilibrium Phase Transition in a Periodically Driven XY Spin Chain

NASA Astrophysics Data System (ADS)

Prosen, Tomaž; Ilievski, Enej

2011-08-01

We present a general formulation of Floquet states of periodically time-dependent open Markovian quasifree fermionic many-body systems in terms of a discrete Lyapunov equation. Illustrating the technique, we analyze periodically kicked XY spin-(1)/(2) chain which is coupled to a pair of Lindblad reservoirs at its ends. A complex phase diagram is reported with reentrant phases of long range and exponentially decaying spin-spin correlations as some of the system’s parameters are varied. The structure of phase diagram is reproduced in terms of counting nontrivial stationary points of Floquet quasiparticle dispersion relation.

Spin precession and spin Hall effect in monolayer graphene/Pt nanostructures

NASA Astrophysics Data System (ADS)

Savero Torres, W.; Sierra, J. F.; Benítez, L. A.; Bonell, F.; Costache, M. V.; Valenzuela, S. O.

2017-12-01

Spin Hall effects have surged as promising phenomena for spin logics operations without ferromagnets. However, the magnitude of the detected electric signals at room temperature in metallic systems has been so far underwhelming. Here, we demonstrate a two-order of magnitude enhancement of the signal in monolayer graphene/Pt devices when compared to their fully metallic counterparts. The enhancement stems in part from efficient spin injection and the large spin resistance of graphene but we also observe 100% spin absorption in Pt and find an unusually large effective spin Hall angle of up to 0.15. The large spin-to-charge conversion allows us to characterise spin precession in graphene under the presence of a magnetic field. Furthermore, by developing an analytical model based on the 1D diffusive spin-transport, we demonstrate that the effective spin-relaxation time in graphene can be accurately determined using the (inverse) spin Hall effect as a means of detection. This is a necessary step to gather full understanding of the consequences of spin absorption in spin Hall devices, which is known to suppress effective spin lifetimes in both metallic and graphene systems.

Suppression of Pauli Spin Blockade in Few Hole Laterally Gated Double Quantum Dots

NASA Astrophysics Data System (ADS)

Gaudreau, Louis; Bogan, Alex; Studenikin, Sergei; Korkusinski, Marek; Aers, Geof; Zawadzki, Piotr; Sachrajda, Andy; Tracy, Lisa; Reno, John; Hargett, Terry; National Research Council Team; Sandia Labs Team

Hole spins have attracted increasing attention as candidates for qubits in quantum information applications. The p-type character of their wavefunction leads to smaller hyperfine interaction with the nuclei resulting in longer coherence times. Additionally, strong spin-orbit interaction allows for enhanced all-electrical manipulation of spin qubit states. Single hole spins have been electrically studied in InSb and Si nanowire quantum dots, however, electrostatically confined hole spins in a 2D hole gas have thus far been limited to the many hole regime. In this talk we will present a full description of the two-hole spin spectrum in a lateral GaAs/AlGaAs double quantum. High-bias magneto-transport spectroscopy reveals all four states of the spectrum (singlet and triplets) in both the (1,1) and (2,0) configurations, essential for spin readout based on Pauli spin blockade. We show that spin-flip tunneling between dots is as strong as spin conserving tunneling, a consequence of the strong spin-orbit interaction. This suppresses the Pauli spin blockade. Our results suggest that alternate techniques for single hole spin qubit readout need to be explored.

Free-Spinning-Tunnel Investigation of a 1/20-Scale Model of the North American T2J-1 Airplane

NASA Technical Reports Server (NTRS)

Bowman, James S., Jr.; Healy, Frederick M.

1959-01-01

An investigation has been made in the Langley 20-foot free-spinning tunnel to determine the erect and inverted spin and recovery characteristics of a 1/20-scale dynamic model of the North American T2J-1 airplane. The model results indicate that the optimum technique for recovery from erect spins of the airplane will be dependent on the distribution of the disposable load. The recommended recovery procedure for spins encountered at the flight design gross weight is simultaneous rudder reversal to against the spin and aileron movement to with the spin. With full wingtip tanks plus rocket installation and full internal fuel load, rudder reversal should be followed by a downward movement of the elevator. For the flight design gross weight plus partially full wingtip tanks, recovery should be attempted by simultaneous rudder reversal to against the spin, movement of ailerons to with the spin, and ejection of the wing-tip tanks. The optimum recovery technique for airplane-inverted spins is rudder reversal to against the spin with the stick maintained longitudinally and laterally neutral.

Spin-lock imaging of exogenous exchange-based contrast agents to assess tissue pH.

PubMed

Zu, Zhongliang; Li, Hua; Jiang, Xiaoyu; Gore, John C

2018-01-01

Some X-ray contrast agents contain exchangeable protons that give rise to exchange-based effects on MRI, including chemical exchange saturation transfer (CEST). However, CEST has poor specificity to explicit exchange parameters. Spin-lock sequences at high field are also sensitive to chemical exchange. Here, we evaluate whether spin-locking techniques can detect the contrast agent iohexol in vivo after intravenous administration, and their potential for measuring changes in tissue pH. Two metrics of contrast based on R 1ρ , the spin lattice relaxation rate in the rotating frame, were derived from the behavior of R 1ρ at different locking fields. Solutions containing iohexol at different concentrations and pH were used to evaluate the ability of the two metrics to quantify exchange effects. Images were also acquired from rat brains bearing tumors before and after intravenous injections of iohexol to evaluate the potential of spin-lock techniques for detecting the agent and pH variations. The two metrics were found to depend separately on either agent concentration or pH. Spin-lock imaging may therefore provide specific quantification of iohexol concentration and the iohexol-water exchange rate, which reports on pH. Spin-lock techniques may be used to assess the dynamics of intravenous contrast agents and detect extracellular acidification. Magn Reson Med 79:298-305, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Tunable spin splitting and spin lifetime in polar WSTe monolayer

NASA Astrophysics Data System (ADS)

Adhib Ulil Absor, Moh.; Kotaka, Hiroki; Ishii, Fumiyuki; Saito, Mineo

2018-04-01

The established spin splitting with out-of-plane Zeeman spin polarizations in the monolayer (ML) of transition metal dichalcogenides (TMDs) is dictated by inversion symmetry breaking together with mirror symmetry in the surface plane. Here, by density functional theory calculations, we find that mirror symmetry breaking in the polar WSTe ML leads to large spin splitting exhibiting in-plane Rashba spin polarizations. We also find that the interplay between the out-of-plane Zeeman- and in-plane Rashba spin-polarized states sensitively affects the spin lifetime, which can be effectively controlled by in-plane strain. In addition, the tunability of spin splitting using an external electric field is also demonstrated. Our study clarifies that the use of in-plane strain and an external electric field is effective for tuning the spin splitting and spin lifetime of the polar WSTe ML; thus, it is useful for designing spintronic devices.

Nuclear spin noise in the central spin model

NASA Astrophysics Data System (ADS)

Fröhling, Nina; Anders, Frithjof B.; Glazov, Mikhail

2018-05-01

We study theoretically the fluctuations of the nuclear spins in quantum dots employing the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. These fluctuations are calculated both with an analytical approach using homogeneous hyperfine couplings (box model) and with a numerical simulation using a distribution of hyperfine coupling constants. The approaches are in good agreement. The box model serves as a benchmark with low computational cost that explains the basic features of the nuclear spin noise well. We also demonstrate that the nuclear spin noise spectra comprise a two-peak structure centered at the nuclear Zeeman frequency in high magnetic fields with the shape of the spectrum controlled by the distribution of the hyperfine constants. This allows for direct access to this distribution function through nuclear spin noise spectroscopy.

Competing Spin Liquids and Hidden Spin-Nematic Order in Spin Ice with Frustrated Transverse Exchange

NASA Astrophysics Data System (ADS)

Taillefumier, Mathieu; Benton, Owen; Yan, Han; Jaubert, L. D. C.; Shannon, Nic

2017-10-01

Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho2 Ti2 O7 and Dy2 Ti2 O7 exemplify this phenomenon, displaying a classical spin-liquid state, with fractionalized magnetic-monopole excitations. Recently, there has been great interest in closely related "quantum spin-ice" materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively entangled, quantum spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realize a still-richer scenario. Using a combination of classical Monte Carlo simulation, semiclassical molecular-dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three competing forms of spin liquid, as well as a phase with hidden, spin-nematic order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.

Spin transport study in a Rashba spin-orbit coupling system

PubMed Central

Mei, Fuhong; Zhang, Shan; Tang, Ning; Duan, Junxi; Xu, Fujun; Chen, Yonghai; Ge, Weikun; Shen, Bo

2014-01-01

One of the most important topics in spintronics is spin transport. In this work, spin transport properties of two-dimensional electron gas in AlxGa1-xN/GaN heterostructure were studied by helicity-dependent photocurrent measurements at room temperature. Spin-related photocurrent was detected under normal incidence of a circularly polarized laser with a Gaussian distribution. On one hand, spin polarized electrons excited by the laser generate a diffusive spin polarization current, which leads to a vortex charge current as a result of anomalous circular photogalvanic effect. On the other hand, photo-induced spin polarized electrons driven by a longitudinal electric field give rise to a transverse current via anomalous Hall Effect. Both of these effects originated from the Rashba spin-orbit coupling. By analyzing spin-related photocurrent varied with laser position, the contributions of the two effects were differentiated and the ratio of the spin diffusion coefficient to photo-induced anomalous spin Hall mobility Ds/μs = 0.08 V was extracted at room temperature. PMID:24504193

Separating inverse spin Hall voltage and spin rectification voltage by inverting spin injection direction

NASA Astrophysics Data System (ADS)

Zhang, Wenxu; Peng, Bin; Han, Fangbin; Wang, Qiuru; Soh, Wee Tee; Ong, Chong Kim; Zhang, Wanli

2016-03-01

We develop a method for universally resolving the important issue of separating the inverse spin Hall effect (ISHE) from the 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, the inversion of the spin injection direction changes the ISHE voltage signal, while the SRE voltage remains. It applies generally to analyzing the different voltage contributions without fitting them to special line shapes. This fast and simple method can be used in a wide frequency range and has the flexibility of sample preparation.

Quantum dynamics of nuclear spins and spin relaxation in organic semiconductors

NASA Astrophysics Data System (ADS)

Mkhitaryan, V. V.; Dobrovitski, V. V.

2017-06-01

We investigate the role of the nuclear-spin quantum dynamics in hyperfine-induced spin relaxation of hopping carriers in organic semiconductors. The fast-hopping regime, when the carrier spin does not rotate much between subsequent hops, is typical for organic semiconductors possessing long spin coherence times. We consider this regime and focus on a carrier random-walk diffusion in one dimension, where the effect of the nuclear-spin dynamics is expected to be the strongest. Exact numerical simulations of spin systems with up to 25 nuclear spins are performed using the Suzuki-Trotter decomposition of the evolution operator. Larger nuclear-spin systems are modeled utilizing the spin-coherent state P -representation approach developed earlier. We find that the nuclear-spin dynamics strongly influences the carrier spin relaxation at long times. If the random walk is restricted to a small area, it leads to the quenching of carrier spin polarization at a nonzero value at long times. If the random walk is unrestricted, the carrier spin polarization acquires a long-time tail, decaying as 1 /√{t } . Based on the numerical results, we devise a simple formula describing the effect quantitatively.

Generalized Elliott-Yafet spin-relaxation time for arbitrary spin mixing

NASA Astrophysics Data System (ADS)

Vollmar, Svenja; Hilton, David J.; Schneider, Hans Christian

2017-08-01

We extend our recent result for the spin-relaxation time due to acoustic electron-phonon scattering in degenerate bands with spin mixing [New J. Phys. 18, 023012 (2016), 10.1088/1367-2630/18/2/023012] to include interactions with optical phonons, and present a numerical evaluation of the spin-relaxation time for intraband hole-phonon scattering in the heavy-hole (HH) bands of bulk GaAs. Comparing our computed spin-relaxation times to the conventional Elliott-Yafet result quantitatively demonstrates that the latter underestimates the spin-relaxation time because it does not correctly describe how electron-phonon interactions change the (vector) spin expectation value of the single-particle states. We show that the conventional Elliott-Yafet spin relaxation time is a special case of our result for weak spin mixing.

Spin dynamics and Kondo physics in optical tweezers

NASA Astrophysics Data System (ADS)

Lin, Yiheng; Lester, Brian J.; Brown, Mark O.; Kaufman, Adam M.; Long, Junling; Ball, Randall J.; Isaev, Leonid; Wall, Michael L.; Rey, Ana Maria; Regal, Cindy A.

2016-05-01

We propose to use optical tweezers as a toolset for direct observation of the interplay between quantum statistics, kinetic energy and interactions, and thus implement minimum instances of the Kondo lattice model in systems with few bosonic rubidium atoms. By taking advantage of strong local exchange interactions, our ability to tune the spin-dependent potential shifts between the two wells and complete control over spin and motional degrees of freedom, we design an adiabatic tunneling scheme that efficiently creates a spin-singlet state in one well starting from two initially separated atoms (one atom per tweezer) in opposite spin state. For three atoms in a double-well, two localized in the lowest vibrational mode of each tweezer and one atom in an excited delocalized state, we plan to use similar techniques and observe resonant transfer of two-atom singlet-triplet states between the wells in the regime when the exchange coupling exceeds the mobile atom hopping. Moreover, we argue that such three-atom double-tweezers could potentially be used for quantum computation by encoding logical qubits in collective spin and motional degrees of freedom. Current address: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.

NMR Spin-Lock Induced Crossing (SLIC) Dispersion and Long-Lived Spin States of Gaseous Propane at Low Magnetic Field (0.05 T)

PubMed Central

Barskiy, Danila A.; Salnikov, Oleg G.; Romanov, Alexey S.; Feldman, Matthew A.; Coffey, Aaron M.; Kovtunov, Kirill V.; Koptyug, Igor V.; Chekmenev, Eduard Y.

2017-01-01

When parahydrogen reacts with propylene in low magnetic fields (e.g., 0.05 T), the reaction product propane develops an overpopulation of pseudo-singlet nuclear spin states. We studied how the spin-lock induced crossing (SLIC) technique can be used to convert these pseudo-singlet spin states of hyperpolarized gaseous propane into observable magnetization and to detect 1H NMR signal directly at 0.05 T. The theoretical simulation and experimental study of the NMR signal dependence on B1 power (SLIC amplitude) exhibits a well-resolved dispersion, which is induced by the spin-spin couplings in the eight-proton spin system of propane. We also measured the exponential decay time constants (TLLSS or TS) of these pseudo-singlet long-lived spin states (LLSS) by varying the time between hyperpolarized propane production and SLIC detection. We have found that, on average, TS is approximately 3 times longer than the corresponding T1 value under the same conditions in the range of pressures studied (up to 7.6 atm). Moreover, TS may exceed 13 seconds at pressures above 7 atm in the gas phase. These results are in agreement with the previous reports, and they corroborate a great potential of long-lived hyperpolarized propane as an inhalable gaseous contrast agent for lung imaging and as a molecular tracer to study porous media using low-field NMR and MRI. PMID:28152435

NMR Spin-Lock Induced Crossing (SLIC) dispersion and long-lived spin states of gaseous propane at low magnetic field (0.05 T)

NASA Astrophysics Data System (ADS)

Barskiy, Danila A.; Salnikov, Oleg G.; Romanov, Alexey S.; Feldman, Matthew A.; Coffey, Aaron M.; Kovtunov, Kirill V.; Koptyug, Igor V.; Chekmenev, Eduard Y.

2017-03-01

When parahydrogen reacts with propylene in low magnetic fields (e.g., 0.05 T), the reaction product propane develops an overpopulation of pseudo-singlet nuclear spin states. We studied how the Spin-Lock Induced Crossing (SLIC) technique can be used to convert these pseudo-singlet spin states of hyperpolarized gaseous propane into observable magnetization and to detect 1H NMR signal directly at 0.05 T. The theoretical simulation and experimental study of the NMR signal dependence on B1 power (SLIC amplitude) exhibits a well-resolved dispersion, which is induced by the spin-spin couplings in the eight-proton spin system of propane. We also measured the exponential decay time constants (TLLSS or TS) of these pseudo-singlet long-lived spin states (LLSS) by varying the time between hyperpolarized propane production and SLIC detection. We have found that, on average, TS is approximately 3 times longer than the corresponding T1 value under the same conditions in the range of pressures studied (up to 7.6 atm). Moreover, TS may exceed 13 s at pressures above 7 atm in the gas phase. These results are in agreement with the previous reports, and they corroborate a great potential of long-lived hyperpolarized propane as an inhalable gaseous contrast agent for lung imaging and as a molecular tracer to study porous media using low-field NMR and MRI.

Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures

NASA Astrophysics Data System (ADS)

Sapkota, Keshab R.

Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical

Delayed entanglement echo for individual control of a large number of nuclear spins

PubMed Central

Wang, Zhen-Yu; Casanova, Jorge; Plenio, Martin B.

2017-01-01

Methods to selectively detect and manipulate nuclear spins by single electrons of solid-state defects play a central role for quantum information processing and nanoscale nuclear magnetic resonance (NMR). However, with standard techniques, no more than eight nuclear spins have been resolved by a single defect centre. Here we develop a method that improves significantly the ability to detect, address and manipulate nuclear spins unambiguously and individually in a broad frequency band by using a nitrogen-vacancy (NV) centre as model system. On the basis of delayed entanglement control, a technique combining microwave and radio frequency fields, our method allows to selectively perform robust high-fidelity entangling gates between hardly resolved nuclear spins and the NV electron. Long-lived qubit memories can be naturally incorporated to our method for improved performance. The application of our ideas will increase the number of useful register qubits accessible to a defect centre and improve the signal of nanoscale NMR. PMID:28256508

Delayed entanglement echo for individual control of a large number of nuclear spins.

PubMed

Wang, Zhen-Yu; Casanova, Jorge; Plenio, Martin B

2017-03-03

Methods to selectively detect and manipulate nuclear spins by single electrons of solid-state defects play a central role for quantum information processing and nanoscale nuclear magnetic resonance (NMR). However, with standard techniques, no more than eight nuclear spins have been resolved by a single defect centre. Here we develop a method that improves significantly the ability to detect, address and manipulate nuclear spins unambiguously and individually in a broad frequency band by using a nitrogen-vacancy (NV) centre as model system. On the basis of delayed entanglement control, a technique combining microwave and radio frequency fields, our method allows to selectively perform robust high-fidelity entangling gates between hardly resolved nuclear spins and the NV electron. Long-lived qubit memories can be naturally incorporated to our method for improved performance. The application of our ideas will increase the number of useful register qubits accessible to a defect centre and improve the signal of nanoscale NMR.

Amplified Sensitivity of Nitrogen-Vacancy Spins in Nanodiamonds Using All-Optical Charge Readout.

PubMed

Hopper, David A; Grote, Richard R; Parks, Samuel M; Bassett, Lee C

2018-04-23

Nanodiamonds containing nitrogen-vacancy (NV) centers offer a versatile platform for sensing applications spanning from nanomagnetism to in vivo monitoring of cellular processes. In many cases, however, weak optical signals and poor contrast demand long acquisition times that prevent the measurement of environmental dynamics. Here, we demonstrate the ability to perform fast, high-contrast optical measurements of charge distributions in ensembles of NV centers in nanodiamonds and use the technique to improve the spin-readout signal-to-noise ratio through spin-to-charge conversion. A study of 38 nanodiamonds with sizes ranging between 20 and 70 nm, each hosting a small ensemble of NV centers, uncovers complex, multiple time scale dynamics due to radiative and nonradiative ionization and recombination processes. Nonetheless, the NV-containing nanodiamonds universally exhibit charge-dependent photoluminescence contrasts and the potential for enhanced spin readout using spin-to-charge conversion. We use the technique to speed up a T 1 relaxometry measurement by a factor of 5.

Listings.

PubMed

1990-11-07

Nursing Standard regrets that owing to unprecedented demand we are no longer able to take listings over the telephone. We would like to remind our readers that the listings section is for use by charitable organisations, unions, professional organisations and health authorities to publicise forthcoming events. Your listings should be sent to us on an official listings form and contain all relevant details. Listings forms can be obtained from Clare Ward at Nursing Standard, 17-19 Peterborough Road, Harrow, Middlesex HA1 2AX.

EPR spin trapping of oxygen radicals in plants: a methodological overview.

PubMed

Bacić, Goran; Mojović, Milos

2005-06-01

We present a brief account of the difficulties involved in detection of oxygen free radicals in plants and give a rationale for using the EPR spin trapping technique in such studies. Comparative analysis of characteristics of different spin traps is given, having in mind their suitability in trapping oxygen-centered free radicals. Certain technical aspects of EPR experiments related to successful trapping of free radicals are discussed. Previous studies of trapping of oxygen radicals in plants are reviewed in terms of how efficient the experimental approach employed has been in their detection and how this influences conclusions about the mechanisms of their production. In addition, we analyze the potential of spin labels in the analysis of free radical production in plants and demonstrate that the combination of EPR spin traps and spin labels is extremely efficient for this purpose.

Excitation of propagating spin waves by pure spin current

NASA Astrophysics Data System (ADS)

Demokritov, Sergej

Recently it was demonstrated that pure spin currents can be utilized to excite coherent magnetization dynamics, which enables development of novel magnetic nano-oscillators. Such oscillators do not require electric current flow through the active magnetic layer, which can help to reduce the Joule power dissipation and electromigration. In addition, this allows one to use insulating magnetic materials and provides an unprecedented geometric flexibility. The pure spin currents can be produced by using the spin-Hall effect (SHE). However, SHE devices have a number of shortcomings. In particular, efficient spin Hall materials exhibit a high resistivity, resulting in the shunting of the driving current through the active magnetic layer and a significant Joule heating. These shortcomings can be eliminated in devices that utilize spin current generated by the nonlocal spin-injection (NLSI) mechanism. Here we review our recent studies of excitation of magnetization dynamics and propagating spin waves by using NLSI. We show that NLSI devices exhibit highly-coherent dynamics resulting in the oscillation linewidth of a few MHz at room temperature. Thanks to the geometrical flexibility of the NLSI oscillators, one can utilize dipolar fields in magnetic nano-patterns to convert current-induced localized oscillations into propagating spin waves. The demonstrated systems exhibit efficient and controllable excitation and directional propagation of coherent spin waves characterized by a large decay length. The obtained results open new perspectives for the future-generation electronics using electron spin degree of freedom for transmission and processing of information on the nanoscale.

Imaging free radicals in organelles, cells, tissue, and in vivo with immuno-spin trapping.

PubMed

Mason, Ronald Paul

2016-08-01

The accurate and sensitive detection of biological free radicals in a reliable manner is required to define the mechanistic roles of such species in biochemistry, medicine and toxicology. Most of the techniques currently available are either not appropriate to detect free radicals in cells and tissues due to sensitivity limitations (electron spin resonance, ESR) or subject to artifacts that make the validity of the results questionable (fluorescent probe-based analysis). The development of the immuno-spin trapping technique overcomes all these difficulties. This technique is based on the reaction of amino acid- and DNA base-derived radicals with the spin trap 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) to form protein- and DNA-DMPO nitroxide radical adducts, respectively. These adducts have limited stability and decay to produce the very stable macromolecule-DMPO-nitrone product. This stable product can be detected by mass spectrometry, NMR or immunochemistry by the use of anti-DMPO nitrone antibodies. The formation of macromolecule-DMPO-nitrone adducts is based on the selective reaction of free radical addition to the spin trap and is thus not subject to artifacts frequently encountered with other methods for free radical detection. The selectivity of spin trapping for free radicals in biological systems has been proven by ESR. Immuno-spin trapping is proving to be a potent, sensitive (a million times higher sensitivity than ESR), and easy (not quantum mechanical) method to detect low levels of macromolecule-derived radicals produced in vitro and in vivo. Anti-DMPO antibodies have been used to determine the distribution of free radicals in cells and tissues and even in living animals. In summary, the invention of the immuno-spin trapping technique has had a major impact on the ability to accurately and sensitively detect biological free radicals and, subsequently, on our understanding of the role of free radicals in biochemistry, medicine and toxicology. Published by

Evaluation of thermal gradients in longitudinal spin Seebeck effect measurements

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

Sola, A., E-mail: a.sola@inrim.it; Kuepferling, M.; Basso, V.

2015-05-07

In the framework of the longitudinal spin Seebeck effect (LSSE), we developed an experimental setup for the characterization of LSSE devices. This class of device consists in a layered structure formed by a substrate, a ferrimagnetic insulator (YIG) where the spin current is thermally generated, and a paramagnetic metal (Pt) for the detection of the spin current via the inverse spin-Hall effect. In this kind of experiments, the evaluation of a thermal gradient through the thin YIG layer is a crucial point. In this work, we perform an indirect determination of the thermal gradient through the measurement of the heatmore » flux. We developed an experimental setup using Peltier cells that allow us to measure the heat flux through a given sample. In order to test the technique, a standard LSSE device produced at Tohoku University was measured. We find a spin Seebeck S{sub SSE} coefficient of 2.8×10{sup −7} V K{sup −1}.« less

A Probabilistic Model of Spin and Spin Measurements

NASA Astrophysics Data System (ADS)

Niehaus, Arend

2016-01-01

Several theoretical publications on the Dirac equation published during the last decades have shown that, an interpretation is possible, which ascribes the origin of electron spin and magnetic moment to an autonomous circular motion of the point-like charged particle around a fixed centre. In more recent publications an extension of the original so called "Zitterbewegung Interpretation" of quantum mechanics was suggested, in which the spin results from an average of instantaneous spin vectors over a Zitterbewegung period. We argue that, the corresponding autonomous motion of the electron should, if it is real, determine non-relativistic spin measurements. Such a direct connection with the established formal quantum mechanical description of spin measurements, into which spin is introduced as a "non-classical" quantity has, to our knowledge, not been reported. In the present work we show that, under certain "model assumptions" concerning the proposed autonomous motion, results of spin measurements, including measurements of angular correlations in singlet systems, can indeed be correctly described using classical probabilities. The success of the model is evidence for the "reality" of the assumed autonomous motion. The resulting model violates the Bell—inequalities to the same extent as quantum mechanics.

Pilot Human Factors in Stall/Spin Accidents of Supersonic Fighter Aircraft

NASA Technical Reports Server (NTRS)

Anderson, S. B.; Enevoldson, E. K.; Nguyen, L. T.

1983-01-01

A study has been made of pilot human factors related to stall/spin accidents of supersonic fighter aircraft. The military specifications for flight at high angles of attack are examined. Several pilot human factors problems related to stall/spin are discussed. These problems include (1) unsatisfactory nonvisual warning cues; (2) the inability of the pilot to quickly determine if the aircraft is spinning out of control, or to recognize the type of spin; (3) the inability of the pilot to decide on and implement the correct spin recovery technique; (4) the inability of the pilot to move, caused by high angular rotation; and (5) the tendency of pilots to wait too long in deciding to abandon the irrecoverable aircraft. Psycho-physiological phenomena influencing pilot's behavior in stall/spin situations include (1) channelization of sensory inputs, (2) limitations in precisely controlling several muscular inputs, (3) inaccurate judgment of elapsed time, and (4) disorientation of vestibulo-ocular inputs. Results are given of pilot responses to all these problems in the F14A, F16/AB, and F/A-18A aircraft. The use of departure spin resistance and automatic spin prevention systems incorporated on recent supersonic fighters are discussed. These systems should help to improve the stall/spin accident record with some compromise in maneuverability.

SU (N ) spin-wave theory: Application to spin-orbital Mott insulators

NASA Astrophysics Data System (ADS)

Dong, Zhao-Yang; Wang, Wei; Li, Jian-Xin

2018-05-01

We present the application of the SU (N ) spin-wave theory to spin-orbital Mott insulators whose ground states exhibit magnetic orders. When taking both spin and orbital degrees of freedom into account rather than projecting Hilbert space onto the Kramers doublet, which is the lowest spin-orbital locked energy levels, the SU (N ) spin-wave theory should take the place of the SU (2 ) one due to the inevitable spin-orbital multipole exchange interactions. To implement the application, we introduce an efficient general local mean-field method, which involves all local fluctuations, and develop the SU (N ) linear spin-wave theory. Our approach is tested firstly by calculating the multipolar spin-wave spectra of the SU (4 ) antiferromagnetic model. Then, we apply it to spin-orbital Mott insulators. It is revealed that the Hund's coupling would influence the effectiveness of the isospin-1 /2 picture when the spin-orbital coupling is not large enough. We further carry out the SU (N ) spin-wave calculations of two materials, α -RuCl3 and Sr2IrO4 , and find that the magnonic and spin-orbital excitations are consistent with experiments.

Spin-Triplet Pairing Induced by Spin-Singlet Interactions in Noncentrosymmetric Superconductors

NASA Astrophysics Data System (ADS)

Matsuzaki, Tomoaki; Shimahara, Hiroshi

2017-02-01

In noncentrosymmetric superconductors, we examine the effect of the difference between the intraband and interband interactions, which becomes more important when the band splitting increases. We define the difference ΔVμ between their coupling constants, i.e., that between the intraband and interband hopping energies of intraband Cooper pairs. Here, the subscript μ of ΔVμ indicates that the interactions scatter the spin-singlet and spin-triplet pairs when μ = 0 and μ = 1,2,3, respectively. It is shown that the strong antisymmetric spin-orbit interaction reverses the target spin parity of the interaction: it converts the spin-singlet and spin-triplet interactions represented by ΔV0 and ΔVμ>0 into effective spin-triplet and spin-singlet pairing interactions, respectively. Hence, for example, triplet pairing can be induced solely by the singlet interaction ΔV0. We name the pairing symmetry of the system after that of the intraband Cooper pair wave function, but with an odd-parity phase factor excluded. The pairing symmetry must then be even, even for the triplet component, and the following results are obtained. When ΔVμ is small, the spin-triplet p-wave interactions induce spin-triplet s-wave and spin-triplet d-wave pairings in the regions where the repulsive singlet s-wave interaction is weak and strong, respectively. When ΔV0 is large, a repulsive interband spin-singlet interaction can stabilize spin-triplet pairing. When the Rashba interaction is adopted for the spin-orbit interaction, the spin-triplet pairing interactions mediated by transverse magnetic fluctuations do not contribute to triplet pairing.

Use of spin traps to detect superoxide production in living cells by electron paramagnetic resonance (EPR) spectroscopy.

PubMed

Abbas, Kahina; Babić, Nikola; Peyrot, Fabienne

2016-10-15

Detection of superoxide produced by living cells has been an on-going challenge in biology for over forty years. Various methods have been proposed to address this issue, among which spin trapping with cyclic nitrones coupled to EPR spectroscopy, the gold standard for detection of radicals. This technique is based on the nucleophilic addition of superoxide to a diamagnetic cyclic nitrone, referred to as the spin trap, and the formation of a spin adduct, i.e. a persistent radical with a characteristic EPR spectrum. The first application of spin trapping to living cells dates back 1979. Since then, considerable improvements of the method have been achieved both in the structures of the spin traps, the EPR methodology, and the design of the experiments including appropriate controls. Here, we will concentrate on technical aspects of the spin trapping/EPR technique, delineating recent breakthroughs, inherent limitations, and potential artifacts. Copyright © 2016 Elsevier Inc. All rights reserved.

Dynamical spin accumulation in large-spin magnetic molecules

NASA Astrophysics Data System (ADS)

Płomińska, Anna; Weymann, Ireneusz; Misiorny, Maciej

2018-01-01

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

Hardy's argument and successive spin-s measurements

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

Ahanj, Ali

2010-07-15

We consider a hidden-variable theoretic description of successive measurements of noncommuting spin observables on an input spin-s state. In this scenario, the hidden-variable theory leads to a Hardy-type argument that quantum predictions violate it. We show that the maximum probability of success of Hardy's argument in quantum theory is ((1/2)){sup 4s}, which is more than in the spatial case.

Spin caloric effects in antiferromagnets assisted by an external spin current

NASA Astrophysics Data System (ADS)

Gomonay, O.; Yamamoto, Kei; Sinova, Jairo

2018-07-01

Searching for novel spin caloric effects in antiferromagnets, we study the properties of thermally activated magnons in the presence of an external spin current and temperature gradient. We predict the spin Peltier effect—generation of a heat flux by spin accumulation—in an antiferromagnetic insulator with cubic or uniaxial magnetic symmetry. This effect is related to the spin-current induced splitting of the relaxation times of the magnons with the opposite spin direction. We show that the Peltier effect can trigger antiferromagnetic domain wall motion with a force whose value grows with the temperature of a sample. At a temperature larger than the energy of the low-frequency magnons, this force is much larger than the force caused by direct spin transfer between the spin current and the domain wall. We also demonstrate that the external spin current can induce the magnon spin Seebeck effect. The corresponding Seebeck coefficient is controlled by the current density. These spin-current assisted caloric effects open new ways for the manipulation of the magnetic states in antiferromagnets.

Large spin current injection in nano-pillar-based lateral spin valve

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

Nomura, Tatsuya; Ohnishi, Kohei; Kimura, Takashi, E-mail: t-kimu@phys.kyushu-u.ac.jp

We have investigated the influence of the injection of a large pure spin current on a magnetization process of a non-locally located ferromagnetic dot in nano-pillar-based lateral spin valves. Here, we prepared two kinds of the nano-pillar-type lateral spin valve based on Py nanodots and CoFeAl nanodots fabricated on a Cu film. In the Py/Cu lateral spin valve, although any significant change of the magnetization process of the Py nanodot has not been observed at room temperature. The magnetization reversal process is found to be modified by injecting a large pure spin current at 77 K. Switching the magnetization bymore » the nonlocal spin injection has also been demonstrated at 77 K. In the CoFeAl/Cu lateral spin valve, a room temperature spin valve signal was strongly enhanced from the Py/Cu lateral spin valve because of the highly spin-polarized CoFeAl electrodes. The room temperature nonlocal switching has been demonstrated in the CoFeAl/Cu lateral spin valve.« less

Spin Hall effects

NASA Astrophysics Data System (ADS)

Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

2015-10-01

Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

Spin-dependent thermoelectric effect and spin battery mechanism in triple quantum dots with Rashba spin-orbital interaction

NASA Astrophysics Data System (ADS)

Xu, Wei-Ping; Zhang, Yu-Ying; Wang, Qiang; Nie, Yi-Hang

2016-11-01

We have studied spin-dependent thermoelectric transport through parallel triple quantum dots with Rashba spin-orbital interaction (RSOI) embedded in an Aharonov-Bohm interferometer connected symmetrically to leads using nonequilibrium Green’s function method in the linear response regime. Under the appropriate configuration of magnetic flux phase and RSOI phase, the spin figure of merit can be enhanced and is even larger than the charge figure of merit. In particular, the charge and spin thermopowers as functions of both the magnetic flux phase and the RSOI phase present quadruple-peak structures in the contour graphs. For some specific configuration of the two phases, the device can provide a mechanism that converts heat into a spin voltage when the charge thermopower vanishes while the spin thermopower is not zero, which is useful in realizing the thermal spin battery and inducing a pure spin current in the device. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274208 and 11447170).

Generation and detection of dissipationless spin current in a MgO/Si bilayer

NASA Astrophysics Data System (ADS)

Lou, Paul C.; Kumar, Sandeep

2018-04-01

Spintronics is an analogue to electronics where the spin of the electron rather than its charge is functionally controlled for devices. The generation and detection of spin current without ferromagnetic or exotic/scarce materials are two of the biggest challenges for spintronics devices. In this study, we report a solution to the two problems of spin current generation and detection in Si. Using non-local measurement, we experimentally demonstrate the generation of helical dissipationless spin current using the spin-Hall effect. Contrary to the theoretical prediction, we observe the spin-Hall effect in both n-doped and p-doped Si. The helical spin current is attributed to the site-inversion asymmetry of the diamond cubic lattice of Si and structure inversion asymmetry in a MgO/Si bilayer. The spin to charge conversion in Si is insignificant due to weak spin-orbit coupling. For the efficient detection of spin current, we report spin to charge conversion at the MgO (1 nm)/Si (2 µm) (p-doped and n-doped) thin film interface due to Rashba spin-orbit coupling. We detected the spin current at a distance of  >100 µm, which is an order of magnitude larger than the longest spin diffusion length measured using spin injection techniques. The existence of spin current in Si is verified from the coercivity reduction in a Co/Pd multilayer due to spin-orbit torque generated by spin current from Si.

Spin transport across antiferromagnets induced by the spin Seebeck effect

NASA Astrophysics Data System (ADS)

Cramer, Joel; Ritzmann, Ulrike; Dong, Bo-Wen; Jaiswal, Samridh; Qiu, Zhiyong; Saitoh, Eiji; Nowak, Ulrich; Kläui, Mathias

2018-04-01

For prospective spintronics devices based on the propagation of pure spin currents, antiferromagnets are an interesting class of materials that potentially entail a number of advantages as compared to ferromagnets. Here, we present a detailed theoretical study of magnonic spin current transport in ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics simulations. The relevant length scales of magnonic spin transport in antiferromagnets are determined. We demonstrate the transfer of angular momentum from a ferromagnet into an antiferromagnet due to the excitation of only one magnon branch in the antiferromagnet. As an experimental system, we ascertain the transport across an antiferromagnet in Y3Fe5O12 |Ir20Mn80|Pt heterostructures. We determine the spin transport signals for spin currents generated in the Y3Fe5O12 by the spin Seebeck effect and compare to measurements of the spin Hall magnetoresistance in the heterostructure stack. By means of temperature-dependent and thickness-dependent measurements, we deduce conclusions on the spin transport mechanism across Ir20Mn80 and furthermore correlate it to its paramagnetic-antiferromagnetic phase transition.

Spin-orbit induced electronic spin separation in semiconductor nanostructures.

PubMed

Kohda, Makoto; Nakamura, Shuji; Nishihara, Yoshitaka; Kobayashi, Kensuke; Ono, Teruo; Ohe, Jun-ichiro; Tokura, Yasuhiro; Mineno, Taiki; Nitta, Junsaku

2012-01-01

The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin-orbit interaction in an InGaAs-based heterostructure. Using a Stern-Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 10(8) T m(-1) resulting in a highly polarized spin current.

Demonstration of the spin solar cell and spin photodiode effect

PubMed Central

Endres, B.; Ciorga, M.; Schmid, M.; Utz, M.; Bougeard, D.; Weiss, D.; Bayreuther, G.; Back, C.H.

2013-01-01

Spin injection and extraction are at the core of semiconductor spintronics. Electrical injection is one method of choice for the creation of a sizeable spin polarization in a semiconductor, requiring especially tailored tunnel or Schottky barriers. Alternatively, optical orientation can be used to generate spins in semiconductors with significant spin-orbit interaction, if optical selection rules are obeyed, typically by using circularly polarized light at a well-defined wavelength. Here we introduce a novel concept for spin injection/extraction that combines the principle of a solar cell with the creation of spin accumulation. We demonstrate that efficient optical spin injection can be achieved with unpolarized light by illuminating a p-n junction where the p-type region consists of a ferromagnet. The discovered mechanism opens the window for the optical generation of a sizeable spin accumulation also in semiconductors without direct band gap such as Si or Ge. PMID:23820766

NMR spin-rotation relaxation and diffusion of methane

NASA Astrophysics Data System (ADS)

Singer, P. M.; Asthagiri, D.; Chapman, W. G.; Hirasaki, G. J.

2018-05-01

The translational diffusion-coefficient and the spin-rotation contribution to the 1H NMR relaxation rate for methane (CH4) are investigated using MD (molecular dynamics) simulations, over a wide range of densities and temperatures, spanning the liquid, supercritical, and gas phases. The simulated diffusion-coefficients agree well with measurements, without any adjustable parameters in the interpretation of the simulations. A minimization technique is developed to compute the angular velocity for non-rigid spherical molecules, which is used to simulate the autocorrelation function for spin-rotation interactions. With increasing diffusivity, the autocorrelation function shows increasing deviations from the single-exponential decay predicted by the Langevin theory for rigid spheres, and the deviations are quantified using inverse Laplace transforms. The 1H spin-rotation relaxation rate derived from the autocorrelation function using the "kinetic model" agrees well with measurements in the supercritical/gas phase, while the relaxation rate derived using the "diffusion model" agrees well with measurements in the liquid phase. 1H spin-rotation relaxation is shown to dominate over the MD-simulated 1H-1H dipole-dipole relaxation at high diffusivity, while the opposite is found at low diffusivity. At high diffusivity, the simulated spin-rotation correlation time agrees with the kinetic collision time for gases, which is used to derive a new expression for 1H spin-rotation relaxation, without any adjustable parameters.

Efficient Organometallic Spin Filter between Single-Wall Carbon Nanotube or Graphene Electrodes

NASA Astrophysics Data System (ADS)

Koleini, Mohammad; Paulsson, Magnus; Brandbyge, Mads

2007-05-01

We present a theoretical study of spin transport in a class of molecular systems consisting of an organometallic benzene-vanadium cluster placed in between graphene or single-wall carbon-nanotube-model contacts. Ab initio modeling is performed by combining spin density functional theory and nonequilibrium Green’s function techniques. We consider weak and strong cluster-contact bonds. Depending on the bonding we find from 73% (strong bonds) up to 99% (weak bonds) spin polarization of the electron transmission, and enhanced polarization with increased cluster length.

The Effects of Linguistic Context on Word Recognition in Noise by Elderly Listeners Using Spanish Sentence Lists (SSL)

ERIC Educational Resources Information Center

Cervera, Teresa; Rosell, Vicente

2015-01-01

This study evaluated the effects of the linguistic context on the recognition of words in noise in older listeners using the Spanish Sentence Lists. These sentences were developed based on the approach of the SPIN test for the English language, which contains high and low predictability (HP and LP) sentences. In addition, the relative contribution…

Improving the prediction of going concern of Taiwanese listed companies using a hybrid of LASSO with data mining techniques.

PubMed

Goo, Yeung-Ja James; Chi, Der-Jang; Shen, Zong-De

2016-01-01

The purpose of this study is to establish rigorous and reliable going concern doubt (GCD) prediction models. This study first uses the least absolute shrinkage and selection operator (LASSO) to select variables and then applies data mining techniques to establish prediction models, such as neural network (NN), classification and regression tree (CART), and support vector machine (SVM). The samples of this study include 48 GCD listed companies and 124 NGCD (non-GCD) listed companies from 2002 to 2013 in the TEJ database. We conduct fivefold cross validation in order to identify the prediction accuracy. According to the empirical results, the prediction accuracy of the LASSO-NN model is 88.96 % (Type I error rate is 12.22 %; Type II error rate is 7.50 %), the prediction accuracy of the LASSO-CART model is 88.75 % (Type I error rate is 13.61 %; Type II error rate is 14.17 %), and the prediction accuracy of the LASSO-SVM model is 89.79 % (Type I error rate is 10.00 %; Type II error rate is 15.83 %).

Rotational Invariance of the 2d Spin - Spin Correlation Function

NASA Astrophysics Data System (ADS)

Pinson, Haru

2012-09-01

At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).

Verification of Spin Magnetic Attitude Control System using air-bearing-based attitude control simulator

NASA Astrophysics Data System (ADS)

Ousaloo, H. S.; Nodeh, M. T.; Mehrabian, R.

2016-09-01

This paper accomplishes one goal and it was to verify and to validate a Spin Magnetic Attitude Control System (SMACS) program and to perform Hardware-In-the-Loop (HIL) air-bearing experiments. A study of a closed-loop magnetic spin controller is presented using only magnetic rods as actuators. The magnetic spin rate control approach is able to perform spin rate control and it is verified with an Attitude Control System (ACS) air-bearing MATLAB® SIMULINK® model and a hardware-embedded LABVIEW® algorithm that controls the spin rate of the test platform on a spherical air bearing table. The SIMULINK® model includes dynamic model of air-bearing, its disturbances, actuator emulation and the time delays caused by on-board calculations. The air-bearing simulator is employed to develop, improve, and carry out objective tests of magnetic torque rods and spin rate control algorithm in the experimental framework and to provide a more realistic demonstration of expected performance of attitude control as compared with software-based architectures. Six sets of two torque rods are used as actuators for the SMACS. It is implemented and simulated to fulfill mission requirement including spin the satellite up to 12 degs-1 around the z-axis. These techniques are documented for the full nonlinear equations of motion of the system and the performances of these techniques are compared in several simulations.

Selective Optical Addressing of Nuclear Spins through Superhyperfine Interaction in Rare-Earth Doped Solids.

PubMed

Car, B; Veissier, L; Louchet-Chauvet, A; Le Gouët, J-L; Chanelière, T

2018-05-11

In Er^{3+}:Y_{2}SiO_{5}, we demonstrate the selective optical addressing of the ^{89}Y^{3+} nuclear spins through their superhyperfine coupling with the Er^{3+} electronic spins possessing large Landé g factors. We experimentally probe the electron-nuclear spin mixing with photon echo techniques and validate our model. The site-selective optical addressing of the Y^{3+} nuclear spins is designed by adjusting the magnetic field strength and orientation. This constitutes an important step towards the realization of long-lived solid-state qubits optically addressed by telecom photons.

Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface

NASA Astrophysics Data System (ADS)

Hao, Runrun; Zhong, Hai; Kang, Yun; Tian, Yufei; Yan, Shishen; Liu, Guolei; Han, Guangbing; Yu, Shuyun; Mei, Liangmo; Kang, Shishou

2018-03-01

The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in Pt/YIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect (ISHE) in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents ({{\\boldsymbol{σ }}}sc}), the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electrochemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 (Py) than that of Ni is obtained from the nonlocal voltage measurements. Project supported by the National Basic Research Program of China (Grant No. 2015CB921502), the National Natural Science Foundation of China (Grant Nos. 11474184 and 11627805), the 111 Project, China (Grant No. B13029), and the Fundamental Research Funds of Shandong University, China.

Dynamics of a localized spin excitation close to the spin-helix regime

NASA Astrophysics Data System (ADS)

Salis, Gian; Walser, Matthias; Altmann, Patrick; Reichl, Christian; Wegscheider, Werner

2014-03-01

The time evolution of a local spin excitation in a (001)-confined two-dimensional electron gas subjected to Rashba and Dresselhaus spin-orbit interactions of similar strength is investigated theoretically and compared with experimental data. Specifically, the consequences of a finite spatial extension of the initial spin polarization are studied for non-balanced Rashba and Dresselhaus terms and for finite cubic Dresselhaus spin-orbit interaction. We show that the initial out-of-plane spin polarization evolves into a helical spin pattern with a wave number that gradually approaches the value q0 of the persistent spin helix mode. In addition to an exponential decay of the spin polarization that is proportional to both the spin-orbit imbalance and the cubic Dresselhaus term, the finite width w of the spin excitation reduces the spin polarization by a factor that approaches exp(-q02w2 / 2) at longer times. This result bridges the gap between the formation of a long-lived helical spin mode and a spatially homogeneous spin decay described by the Dyakonov-Perel mechanism. This work is financially supported by NCCR QSIT.

Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling

PubMed Central

Levy, Miguel; Karki, Dolendra

2017-01-01

We present a formulation of electromagnetic spin-orbit coupling in magneto-optic media, and propose an alternative source of spin-orbit coupling to non-paraxial optics vortices. Our treatment puts forth a formulation of nonreciprocal transverse-spin angular-momentum-density shifts for evanescent waves in magneto-optic waveguide media. It shows that magnetization-induced electromagnetic spin-orbit coupling is possible, and that it leads to unequal spin to orbital angular momentum conversion in magneto-optic media evanescent waves in opposite propagation-directions. Generation of free-space helicoidal beams based on this conversion is shown to be spin-helicity- and magnetization-dependent. We show that transverse-spin to orbital angular momentum coupling into magneto-optic waveguide media engenders spin-helicity-dependent unidirectional propagation. This unidirectional effect produces different orbital angular momenta in opposite directions upon excitation-spin-helicity reversals. PMID:28059120

Enhanced spin pumping into superconductors provides evidence for superconducting pure spin currents

NASA Astrophysics Data System (ADS)

Jeon, Kun-Rok; Ciccarelli, Chiara; Ferguson, Andrew J.; Kurebayashi, Hidekazu; Cohen, Lesley F.; Montiel, Xavier; Eschrig, Matthias; Robinson, Jason W. A.; Blamire, Mark G.

2018-06-01

Unlike conventional spin-singlet Cooper pairs, spin-triplet pairs can carry spin1,2. Triplet supercurrents were discovered in Josephson junctions with metallic ferromagnet spacers, where spin transport can occur only within the ferromagnet and in conjunction with a charge current. Ferromagnetic resonance injects a pure spin current from a precessing ferromagnet into adjacent non-magnetic materials3,4. For spin-singlet pairing, the ferromagnetic resonance spin pumping efficiency decreases below the critical temperature (Tc) of a coupled superconductor5,6. Here we present ferromagnetic resonance experiments in which spin sink layers with strong spin-orbit coupling are added to the superconductor. Our results show that the induced spin currents, rather than being suppressed, are substantially larger in the superconducting state compared with the normal state; although further work is required to establish the details of the spin transport process, we show that this cannot be mediated by quasiparticles and is most likely a triplet pure spin supercurrent.

Bending strain engineering in quantum spin hall system for controlling spin currents

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

Huang, Bing; Jin, Kyung-Hwan; Cui, Bin

Quantum spin Hall system can exhibit exotic spin transport phenomena, mediated by its topological edge states. The concept of bending strain engineering to tune the spin transport properties of a quantum spin Hall system is demonstrated. Here, we show that bending strain can be used to control the spin orientation of counter-propagating edge states of a quantum spin system to generate a non-zero spin current. This physics mechanism can be applied to effectively tune the spin current and pure spin current decoupled from charge current in a quantum spin Hall system by control of its bending curvature. Moreover, the curvedmore » quantum spin Hall system can be achieved by the concept of topological nanomechanical architecture in a controllable way, as demonstrated by the material example of Bi/Cl/Si(111) nanofilm. This concept of bending strain engineering of spins via topological nanomechanical architecture affords a promising route towards the realization of topological nano-mechanospintronics.« less

Bending strain engineering in quantum spin hall system for controlling spin currents

DOE PAGES

Huang, Bing; Jin, Kyung-Hwan; Cui, Bin; ...

2017-06-16

Quantum spin Hall system can exhibit exotic spin transport phenomena, mediated by its topological edge states. The concept of bending strain engineering to tune the spin transport properties of a quantum spin Hall system is demonstrated. Here, we show that bending strain can be used to control the spin orientation of counter-propagating edge states of a quantum spin system to generate a non-zero spin current. This physics mechanism can be applied to effectively tune the spin current and pure spin current decoupled from charge current in a quantum spin Hall system by control of its bending curvature. Moreover, the curvedmore » quantum spin Hall system can be achieved by the concept of topological nanomechanical architecture in a controllable way, as demonstrated by the material example of Bi/Cl/Si(111) nanofilm. This concept of bending strain engineering of spins via topological nanomechanical architecture affords a promising route towards the realization of topological nano-mechanospintronics.« less

Spin pumping and inverse spin Hall voltages from dynamical antiferromagnets

NASA Astrophysics Data System (ADS)

Johansen, Øyvind; Brataas, Arne

2017-06-01

Dynamical antiferromagnets can pump spins into adjacent conductors. The high antiferromagnetic resonance frequencies represent a challenge for experimental detection, but magnetic fields can reduce these resonance frequencies. We compute the ac and dc inverse spin Hall voltages resulting from dynamical spin excitations as a function of a magnetic field along the easy axis and the polarization of the driving ac magnetic field perpendicular to the easy axis. We consider the insulating antiferromagnets MnF2,FeF2, and NiO. Near the spin-flop transition, there is a significant enhancement of the dc spin pumping and inverse spin Hall voltage for the uniaxial antiferromagnets MnF2 and FeF2. In the uniaxial antiferromagnets it is also found that the ac spin pumping is independent of the external magnetic field when the driving field has the optimal circular polarization. In the biaxial NiO, the voltages are much weaker, and there is no spin-flop enhancement of the dc component.

Preparation, ferromagnetic and photocatalytic performance of NiO and hollow Co{sub 3}O{sub 4} fibers through centrifugal-spinning technique

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

Feng, Cong; Lin, Xuejun; Wang, Xinqiang, E-mail: xqwang@sdu.edu.cn

Highlights: • NiO and hollow Co{sub 3}O{sub 4} fibers with the diameter of about 10 μm were prepared through centrifugal-spinning technique. • The evolution mechanism from precursor to crystalline fibers was explored. • Both NiO and hollow Co{sub 3}O{sub 4} fibers show ferromagnetism. • The NiO fibers exhibit good photocatalytic performance. - Abstract: Both NiO and hollow Co{sub 3}O{sub 4} fibers with the diameter of about 10 μm have been successfully prepared through spinning high viscous sols into precursor fibers and followed calcination process. The evolution process from precursor to crystalline fibers and the microstructures of the obtained fibers weremore » characterized by TG-DSC, FT-IR, XRD, HRTEM, SEM and the like. The method is facile and cost-effective for mass production of fibers and the obtained fibers are pure phase with high crystallinity. Their magnetic properties were investigated, showing that both the fibers are ferromagnetic. Meanwhile, the NiO fibers exhibit good photocatalytic performance for the removal of Congo red from water under UV light irradiation.« less

Spin-lattice relaxation of individual solid-state spins

NASA Astrophysics Data System (ADS)

Norambuena, A.; Muñoz, E.; Dinani, H. T.; Jarmola, A.; Maletinsky, P.; Budker, D.; Maze, J. R.

2018-03-01

Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given to the dynamics of one-phonon processes below 1 K where our results agree with recent experimental findings and analytically describe the temperature and magnetic-field scaling. At higher temperatures, linear and second-order terms in the interaction Hamiltonian are considered and the temperature scaling is discussed for acoustic and quasilocalized phonons when appropriate. Our results, in addition to confirming a T5 temperature dependence of the longitudinal relaxation rate at higher temperatures, in agreement with experimental observations, provide a theoretical background for modeling the spin-lattice relaxation at a wide range of temperatures where different temperature scalings might be expected.

Efficient micromagnetic modelling of spin-transfer torque and spin-orbit torque

NASA Astrophysics Data System (ADS)

Abert, Claas; Bruckner, Florian; Vogler, Christoph; Suess, Dieter

2018-05-01

While the spin-diffusion model is considered one of the most complete and accurate tools for the description of spin transport and spin torque, its solution in the context of dynamical micromagnetic simulations is numerically expensive. We propose a procedure to retrieve the free parameters of a simple macro-spin like spin-torque model through the spin-diffusion model. In case of spin-transfer torque the simplified model complies with the model of Slonczewski. A similar model can be established for the description of spin-orbit torque. In both cases the spin-diffusion model enables the retrieval of free model parameters from the geometry and the material parameters of the system. Since these parameters usually have to be determined phenomenologically through experiments, the proposed method combines the strength of the diffusion model to resolve material parameters and geometry with the high performance of simple torque models.

Laser-muon spin spectroscopy in liquids - a technique to study the excited state chemistry of transients.

PubMed

Ghandi, Khashayar; Clark, Ian P; Lord, James S; Cottrell, Stephen P

2007-01-21

This study introduces laser-muon spin spectroscopy in the liquid phase, which extends muonium chemistry in liquids to the realm of excited states and enables the detection of muoniated molecules by their spin evolution after laser excitation. This leads to new opportunities to study the Kinetic Isotope Effects (KIEs) of muonium/atomic hydrogen reactions and to probe transient chemistry in radiolysis processes involved in muonium formation, as well as muoniated intermediates in excited states.

Magnetic Charge Organization and Screening in Thermalized Artificial Spin Ice

NASA Astrophysics Data System (ADS)

Gilbert, Ian

2014-03-01

Artificial spin ice is a material-by-design in which interacting single-domain ferromagnetic nanoislands are used to model Ising spins in frustrated spin systems. Artificial spin ice has proved a useful system in which to directly probe the physics of geometrical frustration, allowing us to better understand materials such as spin ice. Recently, several new experimental techniques have been developed that allow effective thermalization of artificial spin ice. Given the intense interest in magnetic monopole excitations in spin ice materials and artificial spin ice's success in modeling these materials, it should not come as a surprise that interesting monopole physics emerges here as well. The first experimental investigation of thermalized artificial square spin ice determined that the system's monopole-like excitations obeyed a Boltzmann distribution and also found evidence for monopole-antimonopole interactions. Further experiments have implicated these monopole excitations in the growth of ground state domains. Our recent study of artificial kagome spin ice, whose odd-coordinated vertices always possess a net magnetic charge, has revealed a theoretically-predicted magnetic charge ordering transition which has not been previously observed experimentally. We have also investigated the details of magnetic charge interactions in lattices of mixed coordination number. This work was done in collaboration with Sheng Zhang, Cristiano Nisoli, Gia-Wei Chern, Michael Erickson, Liam O'Brien, Chris Leighton, Paul Lammert, Vincent Crespi, and Peter Schiffer. This work was primarily funded by the US Department of Energy, Office of Basic Energy Sciences, Materials Science and Engineering Division, grant no. DE-SC0005313.

Moderate MAS enhances local (1)H spin exchange and spin diffusion.

PubMed

Roos, Matthias; Micke, Peter; Saalwächter, Kay; Hempel, Günter

2015-11-01

Proton NMR spin-diffusion experiments are often combined with magic-angle spinning (MAS) to achieve higher spectral resolution of solid samples. Here we show that local proton spin diffusion can indeed become faster at low (<10 kHz) spinning rates as compared to static conditions. Spin diffusion under static conditions can thus be slower than the often referred value of 0.8 nm(2)/ms, which was determined using slow MAS (Clauss et al., 1993). The enhancement of spin diffusion by slow MAS relies on the modulation of the orientation-dependent dipolar couplings during sample rotation and goes along with transient level crossings in combination with dipolar truncation. The experimental finding and its explanation is supported by density matrix simulations, and also emphasizes the sensitivity of spin diffusion to the local coupling topology. The amplification of spin diffusion by slow MAS cannot be explained by any model based on independent spin pairs; at least three spins have to be considered. Copyright © 2015 Elsevier Inc. All rights reserved.

Nonvolatile memory thin film transistors using CdSe/ZnS quantum dot-poly(methyl methacrylate) composite layer formed by a two-step spin coating technique

NASA Astrophysics Data System (ADS)

Chen, Ying-Chih; Huang, Chun-Yuan; Yu, Hsin-Chieh; Su, Yan-Kuin

2012-08-01

The nonvolatile memory thin film transistors (TFTs) using a core/shell CdSe/ZnS quantum dot (QD)-poly(methyl methacrylate) (PMMA) composite layer as the floating gate have been demonstrated, with the device configuration of n+-Si gate/SiO2 insulator/QD-PMMA composite layer/pentacene channel/Au source-drain being proposed. To achieve the QD-PMMA composite layer, a two-step spin coating technique was used to successively deposit QD-PMMA composite and PMMA on the insulator. After the processes, the variation of crystal quality and surface morphology of the subsequent pentacene films characterized by x-ray diffraction spectra and atomic force microscopy was correlated to the two-step spin coating. The crystalline size of pentacene was improved from 147.9 to 165.2 Å, while the degree of structural disorder was decreased from 4.5% to 3.1% after the adoption of this technique. In pentacene-based TFTs, the improvement of the performance was also significant, besides the appearances of strong memory characteristics. The memory behaviors were attributed to the charge storage/discharge effect in QD-PMMA composite layer. Under the programming and erasing operations, programmable memory devices with the memory window (Δ Vth) = 23 V and long retention time were obtained.

Spin Rotation of Formalism for Spin Tracking

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

Luccio,A.

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.

Spin valves with spin-engineered domain-biasing scheme

NASA Astrophysics Data System (ADS)

Lu, Z. Q.; Pan, G.

2003-06-01

Synthetic spin-filter spin valves with spin-engineered biasing scheme "sub/Ta/NiFe/IrMn/NiFe/NOL/Cu1/CoFe/Cu2/CoFe/Ru/CoFe/IrMn/Ta" were developed. In the structure, the orthogonal magnetic configuration for biasing and pinning field was obtained by one-step magnetic annealing process by means of spin flop, which eliminated the need for two antiferromagnetic materials with distinctively different blocking temperatures and two-step magnetic annealing as in conventional exchange biasing scheme. The longitudinal domain biasing of spin valves was achieved by using interlayer coupling field through Cu1 spacer. By adjusting the thickness of the Cu1 layer, the interlayer coupling biasing field can provide domain stabilization and was sufficiently strong to constrain the magnetization in coherent rotation. This can prevent Barkhausen noises associated with magnetization reversal. We report here a proof of concept study of such a domain-biasing scheme, which has its important technological applications in nanoscale spin valve and magnetic tunneling junction read heads and other spintronic devices.

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

NASA Technical Reports Server (NTRS)

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

1974-01-01

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

Lifting SU(2) spin networks to projected spin networks

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

Dupuis, Maiete; Livine, Etera R.

2010-09-15

Projected spin network states are the canonical basis of quantum states of geometry for the recent EPRL-FK spinfoam models for quantum gravity introduced by Engle-Pereira-Rovelli-Livine and Freidel-Krasnov. They are functionals of both the Lorentz connection and the time-normal field. We analyze in detail the map from these projected spin networks to the standard SU(2) spin networks of loop quantum gravity. We show that this map is not one to one and that the corresponding ambiguity is parameterized by the Immirzi parameter. We conclude with a comparison of the scalar products between projected spin networks and SU(2) spin network states.

Sensitivity optimization of Bell-Bloom magnetometers by manipulation of atomic spin synchronization

NASA Astrophysics Data System (ADS)

Ranjbaran, M.; Tehranchi, M. M.; Hamidi, S. M.; Khalkhali, S. M. H.

2018-05-01

Many efforts have been devoted to the developments of atomic magnetometers for achieving the high sensitivity required in biomagnetic applications. To reach the high sensitivity, many types of atomic magnetometers have been introduced for optimization of the creation and relaxation rates of atomic spin polarization. In this paper, regards to sensitivity optimization techniques in the Mx configuration, we have proposed a novelty approach for synchronization of the spin precession in the Bell-Bloom magnetometers. We have utilized the phenomenological Bloch equations to simulate the spin dynamics when modulation of pumping light and radio frequency magnetic field were both used for atomic spin synchronization. Our results showed that the synchronization process, improved the magnetometer sensitivity respect to the classical configurations.

Higher-order spin and charge dynamics in a quantum dot-lead hybrid system.

PubMed

Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R; Amaha, Shinichi; Yoneda, Jun; Takeda, Kenta; Allison, Giles; Stano, Peter; Noiri, Akito; Ito, Takumi; Loss, Daniel; Ludwig, Arne; Wieck, Andreas D; Tarucha, Seigo

2017-09-22

Understanding the dynamics of open quantum systems is important and challenging in basic physics and applications for quantum devices and quantum computing. Semiconductor quantum dots offer a good platform to explore the physics of open quantum systems because we can tune parameters including the coupling to the environment or leads. Here, we apply the fast single-shot measurement techniques from spin qubit experiments to explore the spin and charge dynamics due to tunnel coupling to a lead in a quantum dot-lead hybrid system. We experimentally observe both spin and charge time evolution via first- and second-order tunneling processes, and reveal the dynamics of the spin-flip through the intermediate state. These results enable and stimulate the exploration of spin dynamics in dot-lead hybrid systems, and may offer useful resources for spin manipulation and simulation of open quantum systems.

Many-body Quantum Control of a Spin-1 BEC

NASA Astrophysics Data System (ADS)

Hoang, Thai; Anquez, Martin; Robbins, Bryce; Yang, Xiaoyun; Land, Benjamin; Hamley, Christopher; Chapman, Michael

2014-05-01

Spin-1 condensates provide a useful platform for investigations of atom squeezing, generation of non-Gaussian states, and dynamical control. We demonstrate dynamic control of a quantum many-body spin-1 system that is enabled by strong collisional interactions. In contrast to the usual single-particle quantum control techniques, the method demonstrated here is intrinsically many-body, exploiting the strong collisional interactions. The experiment uses a spin-1 87Rb condensate initialized in the | F = 1 , mF = 0 > polar state at a high magnetic field above the quantum phase transition, and then prepared in a coherent state using a rf rotation. The many-body control is implemented by time-varying the relative strength of the Zeeman and spin interaction energies of the condensate at multiples of the natural coherent oscillation frequency of the system. This is a parametric excitation method relying on time varying changes to the Hamiltonian. We will present our experimental results, which compare well to theory, and will discuss future directions and applications.

The Scattering of Particles with Spin from Targets with Spin

ERIC Educational Resources Information Center

Stewart, Noel M.

1978-01-01

The density matrix is used to obtain an expression for the mean value of any spin operator in the scattering of particles with arbitrary spin. The example of spin-1/2-spin-1 scattering is developed and physical information obtained by establishing connections with the polarization tensor and Wolfenstein observables. (Author/GA)

High spin states of 141Pm

NASA Astrophysics Data System (ADS)

Bhattacharyya, Sarmishtha; Chanda, Somen; Bhattacharjee, Tumpa; Basu, Swapan Kumar; Bhowmik, R. K.; Muralithar, S.; Singh, R. P.; Ghugre, S. S.

2004-01-01

The high spin states in the N=80 odd- A141Pm nucleus have been investigated by in-beam γ-spectroscopic techniques following the reaction 133Cs( 12C, 4n) 141Pm at E=65 MeV using a modest γ detector array, consisting of seven Compton-suppressed high purity germanium detectors and a multiplicity ball of 14 bismuth germanate elements. Thirty new γ rays have been assigned to 141Pm on the basis of γ-ray singles and γγ-coincidence data. The level scheme of 141Pm has been extended upto an excitation energy of 5.2 MeV and spin {35}/{2}ℏ and 16 new levels have been proposed. Spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced directional correlation orientation ratios for strong transitions. The meanlives of a few excited states have been determined from the pulsed beam- γγ coincidence data using the generalised centroid-shift method. The level structure is discussed in the light of known systematics of neighbouring N=80 isotonic nuclei.

Spin Transport in Nondegenerate Si with a Spin MOSFET Structure at Room Temperature

NASA Astrophysics Data System (ADS)

Sasaki, Tomoyuki; Ando, Yuichiro; Kameno, Makoto; Tahara, Takayuki; Koike, Hayato; Oikawa, Tohru; Suzuki, Toshio; Shiraishi, Masashi

2014-09-01

Spin transport in nondegenerate semiconductors is expected to pave the way to the creation of spin transistors, spin logic devices, and reconfigurable logic circuits, because room-temperature (RT) spin transport in Si has already been achieved. However, RT spin transport has been limited to degenerate Si, which makes it difficult to produce spin-based signals because a gate electric field cannot be used to manipulate such signals. Here, we report the experimental demonstration of spin transport in nondegenerate Si with a spin metal-oxide-semiconductor field-effect transistor (MOSFET) structure. We successfully observe the modulation of the Hanle-type spin-precession signals, which is a characteristic spin dynamics in nondegenerate semiconductors. We obtain long spin transport of more than 20 μm and spin rotation greater than 4π at RT. We also observe gate-induced modulation of spin-transport signals at RT. The modulation of the spin diffusion length as a function of a gate voltage is successfully observed, which we attribute to the Elliott-Yafet spin relaxation mechanism. These achievements are expected to lead to the creation of practical Si-based spin MOSFETs.

Three-electron spin qubits

NASA Astrophysics Data System (ADS)

Russ, Maximilian; Burkard, Guido

2017-10-01

The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the exchange-only qubit (Bacon et al 2000 Phys. Rev. Lett. 85 1758-61, DiVincenzo et al 2000 Nature 408 339) and its derived versions, e.g. the resonant exchange (RX) qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the envisioned physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby completing the list of requirements for quantum computation for a viable candidate qubit implementation. We start by describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram, restricting ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states (Russ et al 2016 Phys. Rev. B 94 165411). Introducing the various qubit implementations, we begin with the exchange-only qubit (DiVincenzo et al 2000 Nature 408 339, Laird et al 2010 Phys. Rev. B 82 075403), followed by the RX qubit (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502), the spin-charge qubit (Kyriakidis and Burkard 2007 Phys. Rev. B 75 115324), and the hybrid qubit (Shi et al 2012 Phys. Rev. Lett. 108 140503, Koh et al 2012 Phys. Rev. Lett. 109 250503, Cao et al 2016 Phys. Rev. Lett. 116 086801, Thorgrimsson et al 2016 arXiv:1611.04945). The main focus will be on the exchange-only qubit and its modification, the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange

Polarisation in spin-echo experiments: Multi-point and lock-in measurements

NASA Astrophysics Data System (ADS)

Tamtögl, Anton; Davey, Benjamin; Ward, David J.; Jardine, Andrew P.; Ellis, John; Allison, William

2018-02-01

Spin-echo instruments are typically used to measure diffusive processes and the dynamics and motion in samples on ps and ns time scales. A key aspect of the spin-echo technique is to determine the polarisation of a particle beam. We present two methods for measuring the spin polarisation in spin-echo experiments. The current method in use is based on taking a number of discrete readings. The implementation of a new method involves continuously rotating the spin and measuring its polarisation after being scattered from the sample. A control system running on a microcontroller is used to perform the spin rotation and to calculate the polarisation of the scattered beam based on a lock-in amplifier. First experimental tests of the method on a helium spin-echo spectrometer show that it is clearly working and that it has advantages over the discrete approach, i.e., it can track changes of the beam properties throughout the experiment. Moreover, we show that real-time numerical simulations can perfectly describe a complex experiment and can be easily used to develop improved experimental methods prior to a first hardware implementation.

Polarized 3He Neutron Spin Filters

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

Sno, William Michael

The goal of this grant to Indiana University and subcontractors at Hamilton College and Wisconsin and the associated Interagency Agreement with NIST was to extend the technique of polarized neutron scattering by the development and application of polarized 3He-based neutron spin filters. This effort was blessed with long-term support from the DOE Office of Science, which started in 2003 and continued until the end of a final no-cost extension of the last 3-year period of support in 2013. The steady support from the DOE Office of Science for this long-term development project was essential to its eventual success. Further 3Hemore » neutron spin filter development is now sited at NIST and ORNL.« less

Spin-resolved electron waiting times in a quantum-dot spin valve

NASA Astrophysics Data System (ADS)

Tang, Gaomin; Xu, Fuming; Mi, Shuo; Wang, Jian

2018-04-01

We study the electronic waiting-time distributions (WTDs) in a noninteracting quantum-dot spin valve by varying spin polarization and the noncollinear angle between the magnetizations of the leads using the scattering matrix approach. Since the quantum-dot spin valve involves two channels (spin up and down) in both the incoming and outgoing channels, we study three different kinds of WTDs, which are two-channel WTD, spin-resolved single-channel WTD, and cross-channel WTD. We analyze the behaviors of WTDs in short times, correlated with the current behaviors for different spin polarizations and noncollinear angles. Cross-channel WTD reflects the correlation between two spin channels and can be used to characterize the spin-transfer torque process. We study the influence of the earlier detection on the subsequent detection from the perspective of cross-channel WTD, and define the influence degree quantity as the cumulative absolute difference between cross-channel WTDs and first-passage time distributions to quantitatively characterize the spin-flip process. We observe that influence degree versus spin-transfer torque for different noncollinear angles as well as different polarizations collapse into a single curve showing universal behaviors. This demonstrates that cross-channel WTDs can be a pathway to characterize spin correlation in spintronics system.

Microfabrication Techniques for Plastic Microelectromechanical Systems (MEMS)

DTIC Science & Technology

2003-07-01

micromachining techniques were investigated. Surface micromachining techniques include deposition of thin and thick polymer films using vacuum and spin ...1 2.0 Introduction ...100 4.3.1 Nozzle-diffuser pumps theory

Manipulating spins of magnetic molecules: Hysteretic behavior with respect to bias voltage

NASA Astrophysics Data System (ADS)

Płomińska, Anna; Misiorny, Maciej; Weymann, Ireneusz

2018-02-01

Formation of a magnetic hysteresis loop with respect to a bias voltage is investigated theoretically in a spin-valve device based on a single magnetic molecule. We consider a device consisting of two ferromagnetic electrodes bridged by a carbon nanotube, acting as a quantum dot, to which a spin-anisotropic molecule is exchange-coupled. Such a coupling allows for transfer of angular momentum between the molecule and a spin current flowing through the dot, and thus, for switching orientation of the molecular spin. We demonstrate that this current-induced switching process exhibits a hysteretic behavior with respect to a bias voltage applied to the device. The analysis is carried out with the use of the real-time diagrammatic technique in the lowest-order expansion of the tunnel coupling of the dot to electrodes. The influence of both the intrinsic properties of the spin-valve device (the spin polarization of electrodes and the coupling strength of the molecule to the dot) and those of the molecule itself (magnetic anisotropy and spin relaxation) on the size of the magnetic hysteresis loop is discussed.

Spin wave Feynman diagram vertex computation package

NASA Astrophysics Data System (ADS)

Price, Alexander; Javernick, Philip; Datta, Trinanjan

Spin wave theory is a well-established theoretical technique that can correctly predict the physical behavior of ordered magnetic states. However, computing the effects of an interacting spin wave theory incorporating magnons involve a laborious by hand derivation of Feynman diagram vertices. The process is tedious and time consuming. Hence, to improve productivity and have another means to check the analytical calculations, we have devised a Feynman Diagram Vertex Computation package. In this talk, we will describe our research group's effort to implement a Mathematica based symbolic Feynman diagram vertex computation package that computes spin wave vertices. Utilizing the non-commutative algebra package NCAlgebra as an add-on to Mathematica, symbolic expressions for the Feynman diagram vertices of a Heisenberg quantum antiferromagnet are obtained. Our existing code reproduces the well-known expressions of a nearest neighbor square lattice Heisenberg model. We also discuss the case of a triangular lattice Heisenberg model where non collinear terms contribute to the vertex interactions.

Spin injection and spin transport in paramagnetic insulators

DOE PAGES

Okamoto, Satoshi

2016-02-22

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

X-ray imaging of spin currents and magnetisation dynamics at the nanoscale

NASA Astrophysics Data System (ADS)

Bonetti, Stefano

2017-04-01

Understanding how spins move in time and space is the aim of both fundamental and applied research in modern magnetism. Over the past three decades, research in this field has led to technological advances that have had a major impact on our society, while improving the understanding of the fundamentals of spin physics. However, important questions still remain unanswered, because it is experimentally challenging to directly observe spins and their motion with a combined high spatial and temporal resolution. In this article, we present an overview of the recent advances in x-ray microscopy that allow researchers to directly watch spins move in time and space at the microscopically relevant scales. We discuss scanning x-ray transmission microscopy (STXM) at resonant soft x-ray edges, which is available at most modern synchrotron light sources. This technique measures magnetic contrast through the x-ray magnetic circular dichroism (XMCD) effect at the resonant absorption edges, while focusing the x-ray radiation at the nanometre scale, and using the intrinsic pulsed structure of synchrotron-generated x-rays to create time-resolved images of magnetism at the nanoscale. In particular, we discuss how the presence of spin currents can be detected by imaging spin accumulation, and how the magnetisation dynamics in thin ferromagnetic films can be directly imaged. We discuss how a direct look at the phenomena allows for a deeper understanding of the the physics at play, that is not accessible to other, more indirect techniques. Finally, we present an overview of the exciting opportunities that lie ahead to further understand the fundamentals of novel spin physics, opportunities offered by the appearance of diffraction limited storage rings and free electron lasers.

X-ray imaging of spin currents and magnetisation dynamics at the nanoscale.

PubMed

Bonetti, Stefano

2017-04-05

Understanding how spins move in time and space is the aim of both fundamental and applied research in modern magnetism. Over the past three decades, research in this field has led to technological advances that have had a major impact on our society, while improving the understanding of the fundamentals of spin physics. However, important questions still remain unanswered, because it is experimentally challenging to directly observe spins and their motion with a combined high spatial and temporal resolution. In this article, we present an overview of the recent advances in x-ray microscopy that allow researchers to directly watch spins move in time and space at the microscopically relevant scales. We discuss scanning x-ray transmission microscopy (STXM) at resonant soft x-ray edges, which is available at most modern synchrotron light sources. This technique measures magnetic contrast through the x-ray magnetic circular dichroism (XMCD) effect at the resonant absorption edges, while focusing the x-ray radiation at the nanometre scale, and using the intrinsic pulsed structure of synchrotron-generated x-rays to create time-resolved images of magnetism at the nanoscale. In particular, we discuss how the presence of spin currents can be detected by imaging spin accumulation, and how the magnetisation dynamics in thin ferromagnetic films can be directly imaged. We discuss how a direct look at the phenomena allows for a deeper understanding of the the physics at play, that is not accessible to other, more indirect techniques. Finally, we present an overview of the exciting opportunities that lie ahead to further understand the fundamentals of novel spin physics, opportunities offered by the appearance of diffraction limited storage rings and free electron lasers.

High-mobility ultrathin semiconducting films prepared by spin coating

NASA Astrophysics Data System (ADS)

Mitzi, David B.; Kosbar, Laura L.; Murray, Conal E.; Copel, Matthew; Afzali, Ali

2004-03-01

The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (~50Å), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS2-xSex films, which exhibit n-type transport, large current densities (>105Acm-2) and mobilities greater than 10cm2V-1s-1-an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

Spin-orbit-torque-induced skyrmion dynamics for different types of spin-orbit coupling

NASA Astrophysics Data System (ADS)

Lee, Seung-Jae; Kim, Kyoung-Whan; Lee, Hyun-Woo; Lee, Kyung-Jin

2018-06-01

We investigate current-induced skyrmion dynamics in the presence of Dzyaloshinskii-Moriya interaction and spin-orbit spin-transfer torque corresponding to various types of spin-orbit coupling. We determine the symmetries of Dzyaloshinskii-Moriya interaction and spin-orbit spin-transfer torque based on linear spin-orbit coupling model. We find that like interfacial Dzyaloshinskii-Moriya interaction (Rashba spin-orbit coupling) and bulk Dzyaloshinskii-Moriya interaction (Weyl spin-orbit coupling), Dresselhaus spin-orbit coupling also has a possibility for stabilizing skyrmion and current-induced skyrmion dynamics.

Note: Spin-exchange optical pumping in a van

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

Chauvin, C.; Liagre, L.; Boutin, C.

2016-01-15

The advent of spin-hyperpolarization techniques designed to overcome the sensitivity issue of nuclear magnetic resonance owing to polarization transfer from more ordered systems has recently raised great enthusiasm. However, the out-of-equilibrium character of the polarization requires a close proximity between the area of production and the site of use. We present here a mobile spin-exchange optical pumping setup that enables production of laser-polarized noble gases in a standalone mode, in close proximity to hospitals or research laboratories. Only compressed air and mains power need to be supplied by the host laboratory.

Decoupling a hole spin qubit from the nuclear spins.

PubMed

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 <1% of the longitudinal coupling. For unpolarized, randomly fluctuating nuclei, the ideal heavy-hole limit is achieved down to nanoelectronvolt 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.

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

PubMed

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

2018-02-22

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

Spin-orbit coupling manipulating composite topological spin textures in atomic-molecular Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Liu, Chao-Fei; Juzeliūnas, Gediminas; Liu, W. M.

2017-02-01

Atomic-molecular Bose-Einstein condensates (BECs) offer brand new opportunities to revolutionize quantum gases and probe the variation of fundamental constants with unprecedented sensitivity. The recent realization of spin-orbit coupling (SOC) in BECs provides a new platform for exploring completely new phenomena unrealizable elsewhere. In this study, we find a way of creating a Rashba-Dresselhaus SOC in atomic-molecular BECs by combining the spin-dependent photoassociation and Raman coupling, which can control the formation and distribution of a different type of topological excitation—carbon-dioxide-like skyrmion. This skyrmion is formed by two half-skyrmions of molecular BECs coupling with one skyrmion of atomic BECs, where the two half-skyrmions locate at both sides of one skyrmion. Carbon-dioxide-like skyrmion can be detected by measuring the vortices structures using the time-of-flight absorption imaging technique in real experiments. Furthermore, we find that SOC can effectively change the occurrence of the Chern number in k space, which causes the creation of topological spin textures from some separated carbon-dioxide-like monomers each with topological charge -2 to a polymer chain of the skyrmions. This work helps in creating dual SOC atomic-molecular BECs and opens avenues to manipulate topological excitations.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

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

NASA Astrophysics Data System (ADS)

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

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

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence

PubMed Central

Ma, Wen-Long; Wolfowicz, Gary; Zhao, Nan; Li, Shu-Shen; Morton, John J.L.; Liu, Ren-Bao

2014-01-01

Central spin decoherence caused by nuclear spin baths is often a critical issue in various quantum computing schemes, and it has also been used for sensing single-nuclear spins. Recent theoretical studies suggest that central spin decoherence can act as a probe of many-body physics in spin baths; however, identification and detection of many-body correlations of nuclear spins in nanoscale systems are highly challenging. Here, taking a phosphorus donor electron spin in a 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in decoherence of the central spin under multiple-pulse dynamical decoupling control. We demonstrate that under control by an odd or even number of pulses, the central spin decoherence is principally caused by second- or fourth-order nuclear spin correlations, respectively. This study marks an important step toward studying many-body physics using spin qubits. PMID:25205440

Temperature dependence of spin-orbit torques in Cu-Au alloys

NASA Astrophysics Data System (ADS)

Wen, Yan; Wu, Jun; Li, Peng; Zhang, Qiang; Zhao, Yuelei; Manchon, Aurelien; Xiao, John Q.; Zhang, Xixiang

2017-03-01

We investigated current driven spin-orbit torques in C u40A u60/N i80F e20/Ti layered structures with in-plane magnetization. We have demonstrated a reliable and convenient method to separate dampinglike torque and fieldlike torque by using the second harmonic technique. It is found that the dampinglike torque and fieldlike torque depend on temperature very differently. Dampinglike torque increases with temperature, while fieldlike torque decreases with temperature, which are different from results obtained previously in other material systems. We observed a nearly linear dependence between the spin Hall angle and longitudinal resistivity, suggesting that skew scattering may be the dominant mechanism of spin-orbit torques.

Instrumentation and control system for an F-15 stall/spin

NASA Technical Reports Server (NTRS)

Pitts, F. L.; Holmes, D. C. E.; Zaepfel, K. P.

1974-01-01

An instrumentation and control system is described that was used for radio-controlled F-15 airplane model stall/spin research at the NASA-Langley Research Center. This stall/spin research technique, using scale model aircraft, provides information on the post-stall and spin-entry characteristics of full-scale aircraft. The instrumentation described provides measurements of flight parameters such as angle of attack and sideslip, airspeed, control-surface position, and three-axis rotation rates; these data are recorded on an onboard magnetic tape recorder. The proportional radio control system, which utilizes analog potentiometric signals generated from ground-based pilot inputs, and the ground-based system used in the flight operation are also described.

Natural language processing and inference rules as strategies for updating problem list in an electronic health record.

PubMed

Plazzotta, Fernando; Otero, Carlos; Luna, Daniel; de Quiros, Fernan Gonzalez Bernaldo

2013-01-01

Physicians do not always keep the problem list accurate, complete and updated. To analyze natural language processing (NLP) techniques and inference rules as strategies to maintain completeness and accuracy of the problem list in EHRs. Non systematic literature review in PubMed, in the last 10 years. Strategies to maintain the EHRs problem list were analyzed in two ways: inputting and removing problems from the problem list. NLP and inference rules have acceptable performance for inputting problems into the problem list. No studies using these techniques for removing problems were published Conclusion: Both tools, NLP and inference rules have had acceptable results as tools for maintain the completeness and accuracy of the problem list.

Notch filtering the nuclear environment of a spin qubit.

PubMed

Malinowski, Filip K; Martins, Frederico; Nissen, Peter D; Barnes, Edwin; Cywiński, Łukasz; Rudner, Mark S; Fallahi, Saeed; Gardner, Geoffrey C; Manfra, Michael J; Marcus, Charles M; Kuemmeth, Ferdinand

2017-01-01

Electron spins in gate-defined quantum dots provide a promising platform for quantum computation. In particular, spin-based quantum computing in gallium arsenide takes advantage of the high quality of semiconducting materials, reliability in fabricating arrays of quantum dots and accurate qubit operations. However, the effective magnetic noise arising from the hyperfine interaction with uncontrolled nuclear spins in the host lattice constitutes a major source of decoherence. Low-frequency nuclear noise, responsible for fast (10 ns) inhomogeneous dephasing, can be removed by echo techniques. High-frequency nuclear noise, recently studied via echo revivals, occurs in narrow-frequency bands related to differences in Larmor precession of the three isotopes 69 Ga, 71 Ga and 75 As (refs 15,16,17). Here, we show that both low- and high-frequency nuclear noise can be filtered by appropriate dynamical decoupling sequences, resulting in a substantial enhancement of spin qubit coherence times. Using nuclear notch filtering, we demonstrate a spin coherence time (T 2 ) of 0.87 ms, five orders of magnitude longer than typical exchange gate times, and exceeding the longest coherence times reported to date in Si/SiGe gate-defined quantum dots.

Systematic construction of spin liquids on the square lattice from tensor networks with SU(2) symmetry

NASA Astrophysics Data System (ADS)

Mambrini, Matthieu; Orús, Román; Poilblanc, Didier

2016-11-01

We elaborate a simple classification scheme of all rank-5 SU(2) spin rotational symmetric tensors according to (i) the onsite physical spin S , (ii) the local Hilbert space V⊗4 of the four virtual (composite) spins attached to each site, and (iii) the irreducible representations of the C4 v point group of the square lattice. We apply our scheme to draw a complete list of all SU(2)-symmetric translationally and rotationally invariant projected entangled pair states (PEPS) with bond dimension D ≤6 . All known SU(2)-symmetric PEPS on the square lattice are recovered and simple generalizations are provided in some cases. More generally, to each of our symmetry class can be associated a (D -1 )-dimensional manifold of spin liquids (potentially) preserving lattice symmetries and defined in terms of D -independent tensors of a given bond dimension D . In addition, generic (low-dimensional) families of PEPS explicitly breaking either (i) particular point-group lattice symmetries (lattice nematics) or (ii) time-reversal symmetry (chiral spin liquids) or (iii) SU(2) spin rotation symmetry down to U(1 ) (spin nematics or Néel antiferromagnets) can also be constructed. We apply this framework to search for new topological chiral spin liquids characterized by well-defined chiral edge modes, as revealed by their entanglement spectrum. In particular, we show how the symmetrization of a double-layer PEPS leads to a chiral topological state with a gapless edge described by a SU (2) 2 Wess-Zumino-Witten model.

Quantum Spin Liquids in Frustrated Spin-1 Diamond Antiferromagnets

NASA Astrophysics Data System (ADS)

Buessen, Finn Lasse; Hering, Max; Reuther, Johannes; Trebst, Simon

2018-01-01

Motivated by the recent synthesis of the spin-1 A -site spinel NiRh2 O4 , we investigate the classical to quantum crossover of a frustrated J1-J2 Heisenberg model on the diamond lattice upon varying the spin length S . Applying a recently developed pseudospin functional renormalization group approach for arbitrary spin-S magnets, we find that systems with S ≥3 /2 reside in the classical regime, where the low-temperature physics is dominated by the formation of coplanar spirals and a thermal (order-by-disorder) transition. For smaller local moments S =1 or S =1 /2 , we find that the system evades a thermal ordering transition and forms a quantum spiral spin liquid where the fluctuations are restricted to characteristic momentum-space surfaces. For the tetragonal phase of NiRh2 O4 , a modified J1-J2--J2⊥ exchange model is found to favor a conventionally ordered Néel state (for arbitrary spin S ), even in the presence of a strong local single-ion spin anisotropy, and it requires additional sources of frustration to explain the experimentally observed absence of a thermal ordering transition.

Inverse spin Hall effect by spin injection

NASA Astrophysics Data System (ADS)

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.

Selective Optical Addressing of Nuclear Spins through Superhyperfine Interaction in Rare-Earth Doped Solids

NASA Astrophysics Data System (ADS)

Car, B.; Veissier, L.; Louchet-Chauvet, A.; Le Gouët, J.-L.; Chanelière, T.

2018-05-01

In Er3 +:Y2SiO5 , we demonstrate the selective optical addressing of the Y89 3 + nuclear spins through their superhyperfine coupling with the Er3 + electronic spins possessing large Landé g factors. We experimentally probe the electron-nuclear spin mixing with photon echo techniques and validate our model. The site-selective optical addressing of the Y3 + nuclear spins is designed by adjusting the magnetic field strength and orientation. This constitutes an important step towards the realization of long-lived solid-state qubits optically addressed by telecom photons.

Spin filter for arbitrary spins by substrate engineering

NASA Astrophysics Data System (ADS)

Pal, Biplab; Römer, Rudolf A.; Chakrabarti, Arunava

2016-08-01

We design spin filters for particles with potentially arbitrary spin S≤ft(=1/2,1,3/2,\\ldots \\right) using a one-dimensional periodic chain of magnetic atoms as a quantum device. Describing the system within a tight-binding formalism we present an analytical method to unravel the analogy between a one-dimensional magnetic chain and a multi-strand ladder network. This analogy is crucial, and is subsequently exploited to engineer gaps in the energy spectrum by an appropriate choice of the magnetic substrate. We obtain an exact correlation between the magnitude of the spin of the incoming beam of particles and the magnetic moment of the substrate atoms in the chain desired for opening up of a spectral gap. Results of spin polarized transport, calculated within a transfer matrix formalism, are presented for particles having half-integer as well as higher spin states. We find that the chain can be made to act as a quantum device which opens a transmission window only for selected spin components over certain ranges of the Fermi energy, blocking them in the remaining part of the spectrum. The results appear to be robust even when the choice of the substrate atoms deviates substantially from the ideal situation, as verified by extending the ideas to the case of a ‘spin spiral’. Interestingly, the spin spiral geometry, apart from exhibiting the filtering effect, is also seen to act as a device flipping spins—an effect that can be monitored by an interplay of the system size and the period of the spiral. Our scheme is applicable to ultracold quantum gases, and might inspire future experiments in this direction.

Correction of spin diffusion during iterative automated NOE assignment

NASA Astrophysics Data System (ADS)

Linge, Jens P.; Habeck, Michael; Rieping, Wolfgang; Nilges, Michael

2004-04-01

Indirect magnetization transfer increases the observed nuclear Overhauser enhancement (NOE) between two protons in many cases, leading to an underestimation of target distances. Wider distance bounds are necessary to account for this error. However, this leads to a loss of information and may reduce the quality of the structures generated from the inter-proton distances. Although several methods for spin diffusion correction have been published, they are often not employed to derive distance restraints. This prompted us to write a user-friendly and CPU-efficient method to correct for spin diffusion that is fully integrated in our program ambiguous restraints for iterative assignment (ARIA). ARIA thus allows automated iterative NOE assignment and structure calculation with spin diffusion corrected distances. The method relies on numerical integration of the coupled differential equations which govern relaxation by matrix squaring and sparse matrix techniques. We derive a correction factor for the distance restraints from calculated NOE volumes and inter-proton distances. To evaluate the impact of our spin diffusion correction, we tested the new calibration process extensively with data from the Pleckstrin homology (PH) domain of Mus musculus β-spectrin. By comparing structures refined with and without spin diffusion correction, we show that spin diffusion corrected distance restraints give rise to structures of higher quality (notably fewer NOE violations and a more regular Ramachandran map). Furthermore, spin diffusion correction permits the use of tighter error bounds which improves the distinction between signal and noise in an automated NOE assignment scheme.

Spin Ice

NASA Astrophysics Data System (ADS)

Bramwell, Steven T.; Gingras, Michel J. P.; Holdsworth, Peter C. W.

2013-03-01

Pauling's model of hydrogen disorder in water ice represents the prototype of a frustrated system. Over the years it has spawned several analogous models, including Anderson's model antiferromagnet and the statistical "vertex" models. Spin Ice is a sixteen vertex model of "ferromagnetic frustration" that is approximated by real materials, most notably the rare earth pyrochlores Ho2Ti2O7, Dy2Ti2O7 and Ho2Sn2O7. These "spin ice materials" have the Pauling zero point entropy and in all respects represent almost ideal realisations of Pauling's model. They provide experimentalists with unprecedented access to a wide variety of novel magnetic states and phase transitions that are located in different regions of the field-temperature phase diagram. They afford theoreticians the opportunity to explore many new features of the magnetic interactions and statistical mechanics of frustrated systems. This chapter is a comprehensive review of the physics -- both experimental and theoretical -- of spin ice. It starts with a discussion of the historic problem of water ice and its relation to spin ice and other frustrated magnets. The properties of spin ice are then discussed in three sections that deal with the zero field spin ice state, the numerous field-induced states (including the recently identified "kagomé ice") and the magnetic dynamics. Some materials related to spin ice are briefly described and the chapter is concluded with a short summary of spin ice physics.

Tuning spin-spin interactions in radical dendrimers.

PubMed

Vidal-Gancedo, José; Lloveras, Vega; Liko, Flonja; Pinto, Luiz F; Muñoz-Gómez, Jose L

2018-05-10

Two generations of phosphorous dendrimers were synthesized and fully functionalized with TEMPO radicals via acrylamido or imino group linkers to evaluate the impact of the linker substitution on the radical-radical interactions. A drastic change in the way that the radicals interacted among them was observed by EPR and CV studies: while radicals in Gn-imino-TEMPO dendrimers presented a strong spin-spin interaction, in the Gn-acrylamido-TEMPO ones they acted mainly as independent radicals. This shows that these interactions could be tuned by the solely substitution of the radical linker, opening the perspective of controlling and modulating the extension of these interactions depending on each application. The chemical properties of the linker strongly influence the spin-spin exchange between pendant radicals. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

NASA Astrophysics Data System (ADS)

Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst; Mahmoodian, Sahand; Löbl, Matthias Christian; Söllner, Immo; Schott, Rüdiger; Papon, Camille; Pregnolato, Tommaso; Stobbe, Søren; Midolo, Leonardo; Schröder, Tim; Wieck, Andreas Dirk; Ludwig, Arne; Warburton, Richard John; Lodahl, Peter

2018-05-01

The spin of an electron is a promising memory state and qubit. Connecting spin states that are spatially far apart will enable quantum nodes and quantum networks based on the electron spin. Towards this goal, an integrated spin-photon interface would be a major leap forward as it combines the memory capability of a single spin with the efficient transfer of information by photons. Here, we demonstrate such an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared in the ground state with a fidelity of up to 96%. Subsequently, the system is used to implement a single-spin photonic switch, in which the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may enable on-chip photon-photon gates, single-photon transistors and the efficient generation of a photonic cluster state.

Spin wave amplification using the spin Hall effect in permalloy/platinum bilayers

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

Gladii, O.; Henry, Y.; Bailleul, M.

2016-05-16

We investigate the effect of an electrical current on the attenuation length of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating spin-wave spectroscopy. The modification of the spin-wave relaxation rate is linear in current density, reaching up to 14% for a current density of 2.3 × 10{sup 11} A/m{sup 2} in Pt. This change is attributed to the spin transfer torque induced by the spin Hall effect and corresponds to an effective spin Hall angle of 0.13, which is among the highest values reported so far. The spin Hall effect thus appears as an efficient way of amplifying/attenuating propagating spin waves.

Spin injection into Pt-polymers with large spin-orbit coupling

NASA Astrophysics Data System (ADS)

Sun, Dali; McLaughlin, Ryan; Siegel, Gene; Tiwari, Ashutosh; Vardeny, Z. Valy

2014-03-01

Organic spintronics has entered a new era of devices that integrate organic light-emitting diodes (OLED) in organic spin valve (OSV) geometry (dubbed bipolar organic spin valve, or spin-OLED), for actively manipulating the device electroluminescence via the spin alignment of two ferromagnetic electrodes (Science 337, 204-209, 2012; Appl. Phys. Lett. 103, 042411, 2013). Organic semiconductors that contain heavy metal elements have been widely used as phosphorescent dopants in white-OLEDs. However such active materials are detrimental for OSV operation due to their large spin-orbit coupling (SOC) that may limit the spin diffusion length and thus spin-OLED based on organics with large SOC is a challenge. We report the successful fabrication of OSVs based on pi-conjugated polymers which contain intrachain Platinum atoms (dubbed Pt-polymers). Spin injection into the Pt-polymers is investigated by the giant magnetoresistance (GMR) effect as a function of bias voltage, temperature and polymer layer thickness. From the GMR bias voltage dependence we infer that the ``impendence mismatch'' between ferromagnetic electrodes and Pt-polymer may be suppressed due to the large SOC. Research sponsored by the NSF (Grant No. DMR-1104495) and NSF-MRSEC (DMR 1121252) at the University of Utah.

FMR-driven spin pumping in Y3Fe5O12-based structures

NASA Astrophysics Data System (ADS)

Yang, Fengyuan; Hammel, P. Chris

2018-06-01

Ferromagnetic resonance driven spin pumping, a topic of steadily increasing interest since its emergence over two decades ago, remains one of the most exciting research fields in condensed matter physics. Among the many materials that have been explored for spin pumping, yttrium iron garnet (YIG) is one of the most extensively studied because of its exceptionally low magnetic damping and insulating nature. There is a great amount of literature in the spin pumping and related research fields, too broad for this review to cover. In this Topical Review, we focus on the YIG-based spin pumping results carried out by our groups, including: the mechanism and technical details of our off-axis sputtering technique for the growth of single-crystalline YIG epitaxial films with a high degree ordering, experimental evidence for the high quality of the YIG films, spin pumping results from YIG into various transition metals and their heterostructures, dynamic spin transport in YIG/antiferromagnet hybrid structures, intralayer spin pumping by localized spin wave modes confined by a micromagnetic probe, dynamic spin coupling between YIG and nitrogen-vacancy centers in diamond, parametric spin pumping from high-wavevector spin waves in YIG, and localized spin wave mode behavior in broadly tunable spatially complex magnetic configurations. These results build on the power and versatility of YIG spin pumping to improve our understanding of spin dynamics, spin currents, spin Hall physics, spin–orbit coupling, dynamic magnetic coupling, and the relationship between these phenomena in a broad range of materials, geometries, and settings.

Beyond the Spin Model Approximation for Ramsey Spectroscopy

DTIC Science & Technology

2014-03-26

December 2013; revised manuscript received 31 January 2014; published 26 March 2014) Ramsey spectroscopy has become a powerful technique for probing...atomic systems without the need for ultralow temperatures. It is thus important to determine the parameter regime in which a pure interacting-spins picture

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

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

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

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

Resonant polarization transfer from electron spins to nuclear spins-or to muon spins-in semiconductors

NASA Astrophysics Data System (ADS)

Henstra, A.; Wenckebach, W. Th.

1991-02-01

A review is given of newly developed pulsed Electron Spin Resonance (ESR) methods for dynamic polarization of nuclear spins. The application of two of these methods, Nuclear Orientation Via Electron spin Locking (NOVEL) and the Integrated Solid Effect (ISE), for the polarization of nuclear spins in semiconductors is discussed in more detail. It is proposed to use these methods to study the ESR spectrum of unpaired electrons in the vicinity of muons that are bound in a solid. Thus, ESR would be observed with a sensitivity which is enhanced by about ten orders of magnitude compared to conventional ESR.

Spin-bowling in cricket re-visited: model trajectories for various spin-vector angles

NASA Astrophysics Data System (ADS)

Robinson, Garry; Robinson, Ian

2016-08-01

In this paper we investigate, via the calculation of model trajectories appropriate to slow bowling in cricket, the effects on the flight path of the ball before pitching due to changes in the angle of the spin-vector. This was accomplished by allowing the spin-vector to vary in three ways. Firstly, from off-spin, where the spin-vector points horizontally and directly down the pitch, to top-spin where it points horizontally towards the off-side of the pitch. Secondly, from off-spin to side-spin where, for side-spin, the spin-vector points vertically upwards. Thirdly, where the spin-vector points horizontally and at 45° to the pitch (in the general direction of ‘point’, as viewed by the bowler), and is varied towards the vertical, while maintaining the 45° angle in the horizontal plane. It is found that, as is well known, top-spin causes the ball to dip in flight, side-spin causes the ball to move side-ways in flight and, perhaps most importantly, off-spin can cause the ball to drift to the off-side of the pitch late in its flight as it begins to fall. At a more subtle level it is found that, if the total spin is kept constant and a small amount of top-spin is added to the ball at the expense of some off-spin, there is little change in the side-ways drift. However, a considerable reduction in the length at which the ball pitches occurs, ˜25 cm, an amount that batsmen can ignore at their peril. On the other hand, a small amount of side-spin introduced to a top-spin delivery does not alter the point of pitching significantly, but produces a considerable amount of side-ways drift, ˜10 cm or more. For pure side-spin the side-ways drift is up to ˜30 cm. When a side-spin component is added to the spin of a ball bowled with a mixture of off-spin and top-spin in equal proportions, significant movement occurs in both the side-ways direction and in the point of pitching, of the order of a few tens of centimetres.

Controllable spin polarization and spin filtering in a zigzag silicene nanoribbon

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

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

2015-05-07

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

Magnetic proximity control of spin currents and giant spin accumulation in graphene

NASA Astrophysics Data System (ADS)

Singh, Simranjeet

Two dimensional (2D) materials provide a unique platform to explore the full potential of magnetic proximity driven phenomena. We will present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to the ferromagnetic-insulator (FMI) magnetization in graphene/FMI heterostructures. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. We also discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the non-local spin signals in graphene, which is due to spin relaxation by thermally-induced transverse fluctuations of the FMI magnetization. Additionally, it has been a challenge to grow a smooth, robust and pin-hole free tunnel barriers on graphene, which can withstand large current densities for efficient electrical spin injection. We have experimentally demonstrated giant spin accumulation in graphene lateral spin valves employing SrO tunnel barriers. Nonlocal spin signals, as large as 2 mV, are observed in graphene lateral spin valves at room temperature. This high spin accumulations observed using SrO tunnel barriers puts graphene on the roadmap for exploring the possibility of achieving a non-local magnetization switching due to the spin torque from electrically injected spins. Financial support from ONR (No. N00014-14-1-0350), NSF (No. DMR-1310661), and C-SPIN, one of the six SRC STARnet Centers, sponsored by MARCO and DARPA.

Exact Mapping from Many-Spin Hamiltonians to Giant-Spin Hamiltonians.

PubMed

Ghassemi Tabrizi, Shadan; Arbuznikov, Alexei V; Kaupp, Martin

2018-03-26

Thermodynamic and spectroscopic data of exchange-coupled molecular spin clusters (e.g. single-molecule magnets) are routinely interpreted in terms of two different models: the many-spin Hamiltonian (MSH) explicitly considers couplings between individual spin centers, while the giant-spin Hamiltonian (GSH) treats the system as a single collective spin. When isotropic exchange coupling is weak, the physical compatibility between both spin Hamiltonian models becomes a serious concern, due to mixing of spin multiplets by local zero-field splitting (ZFS) interactions ('S-mixing'). Until now, this effect, which makes the mapping MSH→GSH ('spin projection') non-trivial, had only been treated perturbationally (up to third order), with obvious limitations. Here, based on exact diagonalization of the MSH, canonical effective Hamiltonian theory is applied to construct a GSH that exactly matches the energies of the relevant (2S+1) states comprising an effective spin multiplet. For comparison, a recently developed strategy for the unique derivation of effective ('pseudospin') Hamiltonians, now routinely employed in ab initio calculations of mononuclear systems, is adapted to the problem of spin projection. Expansion of the zero-field Hamiltonian and the magnetic moment in terms of irreducible tensor operators (or Stevens operators) yields terms of all ranks k (up to k=2S) in the effective spin. Calculations employing published MSH parameters illustrate exact spin projection for the well-investigated [Ni(hmp)(dmb)Cl] 4 ('Ni 4 ') single-molecule magnet, which displays weak isotropic exchange (dmb=3,3-dimethyl-1-butanol, hmp - is the anion of 2-hydroxymethylpyridine). The performance of the resulting GSH in finite field is assessed in terms of EPR resonances and diabolical points. The large tunnel splitting in the M=± 4 ground doublet of the S=4 multiplet, responsible for fast tunneling in Ni 4 , is attributed to a Stevens operator with eightfold rotational symmetry, marking

Giant magnetoresistance in ion beam deposited spin-valve films with specular enhancement

NASA Astrophysics Data System (ADS)

Sant, S.; Mao, M.; Kools, J.; Koi, K.; Iwasaki, H.; Sahashi, M.

2001-06-01

Three different techniques, natural oxidation, remote plasma oxidation and low energy ion beam oxidation, have been proved to be equally effective in forming nano-oxide layers (NOLs) in spin-valve films for specular enhancement of giant magnetoresistance (GMR) effect. GMR values over 12% have been routinely obtained in spin-valve films with NOL, corresponding to a 30% specular enhancement over those without NOL. The consistency and robustness of the oxidation processes has been demonstrated by a very large GMR value ˜19% in a dual spin-valve film with the NOLs formed in both pinned layers, the oscillatory dependence of the interlayer coupling field on Cu layer thickness in specular enhanced spin-valve films and the uniform and repeatable film performance over 5 in. substrates.

Template-grown NiFe/Cu/NiFe nanowires for spin transfer devices.

PubMed

Piraux, Luc; Renard, Krystel; Guillemet, Raphael; Matéfi-Tempfli, Stefan; Matéfi-Tempfli, Maria; Antohe, Vlad Andrei; Fusil, Stéphane; Bouzehouane, Karim; Cros, Vincent

2007-09-01

We have developed a new reliable method combining template synthesis and nanolithography-based contacting technique to elaborate current perpendicular-to-plane giant magnetoresistance spin valve nanowires, which are very promising for the exploration of electrical spin transfer phenomena. The method allows the electrical connection of one single nanowire in a large assembly of wires embedded in anodic porous alumina supported on Si substrate with diameters and periodicities to be controllable to a large extent. Both magnetic excitations and switching phenomena driven by a spin-polarized current were clearly demonstrated in our electrodeposited NiFe/Cu/ NiFe trilayer nanowires. This novel approach promises to be of strong interest for subsequent fabrication of phase-locked arrays of spin transfer nano-oscillators with increased output power for microwave applications.

High-fidelity readout and control of a nuclear spin qubit in silicon.

PubMed

Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Zwanenburg, Floris A; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2013-04-18

Detection of nuclear spin precession is critical for a wide range of scientific techniques that have applications in diverse fields including analytical chemistry, materials science, medicine and biology. Fundamentally, it is possible because of the extreme isolation of nuclear spins from their environment. This isolation also makes single nuclear spins desirable for quantum-information processing, as shown by pioneering studies on nitrogen-vacancy centres in diamond. The nuclear spin of a (31)P donor in silicon is very promising as a quantum bit: bulk measurements indicate that it has excellent coherence times and silicon is the dominant material in the microelectronics industry. Here we demonstrate electrical detection and coherent manipulation of a single (31)P nuclear spin qubit with sufficiently high fidelities for fault-tolerant quantum computing. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate quantum non-demolition and electrical single-shot readout of the nuclear spin with a readout fidelity higher than 99.8 percent-the highest so far reported for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radio-frequency pulses. For an ionized (31)P donor, we find a nuclear spin coherence time of 60 milliseconds and a one-qubit gate control fidelity exceeding 98 percent. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear-spin-based quantum-information processing.

Spin-Label Oximetry at Q- and W-Band

PubMed Central

Subczynski, W.K.; Mainali, L.; Camenisch, T.G.; Froncisz, W.; Hyde, J.S.

2011-01-01

Spin-lattice relaxation times (T1s) of both small water-soluble spin labels in the aqueous phase as well as lipid-type spin labels in membranes increase when the microwave frequency increases from 2 to 35 GHz (Hyde et al., J. Phys. Chem. B 108 [2004] 9524–9529). The T1 measured at W-band (94 GHz) for the water-soluble spin labels CTPO and TEMPONE (Froncisz et al., J. Magn. Reson. 193 [2008] 297–304) is, however, shorter than when measured at Q-band (35 GHz). In this paper, the decreasing trends at W-band have been confirmed for commonly used lipid-type spin labels in model membranes. It is concluded that the longest values of T1 will generally be found at Q-band, noting that long values are advantageous for measurement of bimolecular collisions with oxygen. The contribution of dissolved molecular oxygen to the relaxation rate was found to be independent of microwave frequency up to 94 GHz for lipid-type spin labels in membranes. This contribution is expressed in terms of the oxygen transport parameter W = T1−1(Air) − T1−1(N2), which is a function of both concentration and translational diffusion of oxygen in the local environment of a spin label. The new capabilities in measurement of the oxygen transport parameter using saturation-recovery (SR) EPR at Q- and W-band have been demonstrated in saturated (DMPC) and unsaturated (POPC) lipid bilayer membranes with the use of stearic acid (n-SASL) and phosphatidylcholine (n-PC) spin labels, and compared with results obtained earlier at X-band. SR EPR spin-label oximetry at Q- and W-band has the potential to be a powerful tool for studying samples of small volume, ~30 nL. These benefits, together with other factors such as a higher resonator efficiency parameter and a new technique for canceling free induction decay signals, are discussed. PMID:21277814

Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

PubMed

Marsh, Derek

2016-11-01

Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

Spin-coating: A new approach for improving dispersion of cellulose nanocrystals and mechanical properties of poly (lactic acid) composites.

PubMed

Shojaeiarani, Jamileh; Bajwa, Dilpreet S; Stark, Nicole M

2018-06-15

This study systematically evaluated the influence of masterbatch preparation techniques, solvent casting and spin-coating methods, on composite properties. Composites were manufactured by combining CNCs masterbatches and PLA resin using twin screw extruder followed by injection molding. Different microscopy techniques were used to investigate the dispersion of CNCs in masterbatches and composites. Thermal, thermomechanical, and mechanical properties of composites were evaluated. Scanning electron microscopy (SEM) images showed superior dispersion of CNCs in spin-coated masterbatches compared to solvent cast masterbatches. At lower CNCs concentrations, both SEM and optical microscope images confirmed more uniform CNCs dispersion in spin-coated composites than solvent cast samples. Degree of crystallinity of PLA exhibited a major enhancement by 147% and 380% in solvent cast and spin-coated composites, respectively. Spin-coated composites with lower CNCs concentration exhibited a noticeable improvement in mechanical properties. However, lower thermal characteristics in spin-coated composites were observed, which could be attributed to the residual solvents in masterbatches. Copyright © 2018 Elsevier Ltd. All rights reserved.

Spin injection and detection in lateral spin valves with hybrid interfaces

NASA Astrophysics Data System (ADS)

Wang, Le; Liu, Wenyu; Ying, Hao; Chen, Luchen; Lu, Zhanjie; Han, Shuo; Chen, Shanshan; Zhao, Bing; Xu, Xiaoguang; Jiang, Yong

2018-06-01

Spin injection and detection in lateral spin valves with hybrid interfaces comprising a Co/Ag transparent contact and a Co/MgO/Ag junction (III) are investigated at room temperature in comparison with pure Co/Ag transparent contacts (I) and Co/MgO/Ag junctions (II). The measured spin-accumulation signals of a type III device are five times higher than those for type I. The extracted spin diffusion length in Ag is 180 nm for all three types of devices. The enhancement of the spin signal of the hybrid structure is mainly attributed to the increase of the interfacial spin polarization from the Co/MgO/Ag junction.

Spin dependent transport and spin transfer in nanoconstrictions and current confined nanomagnets

NASA Astrophysics Data System (ADS)

Ozatay, Ozhan

In this thesis, I have employed point contact spectroscopy to determine the nature of electron transport across constrained domain walls in a ferromagnetic nanocontact and to uncover the relationship between ballisticity of electron transport and domain wall magnetoresistance. In the range of hole sizes studied (from 10 to 3 nm) the resulting magnetoresistance was found to be less than 0.5% and one that increases with decreasing contact size. I have used point contacts as local probes, to study the spin dependent transport across Ferromagnet/Normal Metal/Ferromagnet(FM/NM/FM) trilayers as well as the consequences of localized spin polarized current injection into a nano magnet on spin angular momentum transfer and high frequency magnetization dynamics. I have demonstrated that absolute values for spin transfer switching critical currents are reduced in this new geometry as compared to uniform current injection. I have also performed micromagnetic simulations to determine the evolution of magnetization under the application of magnetic fields and currents to gain more insights into experimental results. I have used Scanning Transmission Electron Microscopy (STEM), X-Ray Photoemission Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) techniques to characterize the interfacial mixing and oxygen diffusion in the metallic multilayers of interest. I have shown that the Ta/CuOx bilayer structure provides a smooth substrate by improving interfacial roughness due to grain boundary diffusion of oxygen and reaction with Ta that fills in the grain boundary gaps in Cu. Analysis of the Py/AlOx interface proved a strong oxidation passivation on the Py surface by Al coating accompanied by Fe segregation into the alumina. I have utilized the characterization results to design a new nanomagnet whose sidewalls are protected from adventitious sidewall oxide layers and yields improved device performance. The oxide layers that naturally develop at the sidewalls of Py

Creater-cizes: Creativity Exercises.

ERIC Educational Resources Information Center

Rule, Michael

1998-01-01

Creativity exercises, or creater-cizes, can help camp staff generate ideas and solve problems. Common techniques are brainstorming, story-boarding, analogies and metaphors, association and free association, spinning, and lists. Defines and gives examples of each technique. (SAS)

PREFACE: 13th International Conference on Muon Spin Rotation, Relaxation and Resonance

NASA Astrophysics Data System (ADS)

2014-12-01

The 13th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2014) organized by the Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute in collaboration with the University of Zurich and the University of Fribourg, was held in Grindelwald, Switzerland from 1st to 6th June 2014. The conference provided a forum for researchers from around the world with interests in the applications of μSR to study a wide range of topics including condensed matter physics, materials and molecular sciences, chemistry and biology. Polarized muons provide a unique and versatile probe of matter, enabling studies at the atomic level of electronic structure and dynamics in a wide range of systems. The conference was the thirteenth in a series, which began in Rorschach in 1978 and it took place for the third time in Switzerland. The previous conferences were held in Cancun, Mexico (2011), Tsukuba, Japan (2008), Oxford, UK (2005), Williamsburg, USA (2002), Les Diablerets, Switzerland (1999), Nikko, Japan (1996), Maui, USA (1993), Oxford, UK (1990), Uppsala, Sweden (1986), Shimoda, Japan (1983), Vancouver, Canada (1980), and Rorschach, Switzerland (1978). These conference proceedings contain 67 refereed publications from presentations covering magnetism, superconductivity, chemistry, semiconductors, biophysics and techniques. The conference logo, displayed in the front pages of these proceedings, represents both the location of μSR2014 in the Alps and the muon-spin rotation technique. The silhouette represents the famous local mountains Eiger, Mönch and Jungfrau as drawn by the Swiss painter Ferdinand Hodler and the apple with arrow is at the same time a citation of the Wilhelm Tell legend and a remembrance of the key role played by the muon spin and the asymmetric muon decay (which for the highest positron energy has an apple like shape). More than 160 participants (including 32 registered as students and 13 as accompanying persons) from 19 countries

Spin correlations and spin-wave excitations in Dirac-Weyl semimetals

NASA Astrophysics Data System (ADS)

Araki, Yasufumi; Nomura, Kentaro

We study correlations among magnetic dopants in three-dimensional Dirac and Weyl semimetals. Effective field theory for localized magnetic moments is derived by integrating out the itinerant electron degrees of freedom. We find that spin correlation in the spatial direction parallel to local magnetization is more rigid than that in the perpendicular direction, reflecting spin-momentum locking nature of the Dirac Hamiltonian. Such an anisotropy becomes stronger for Fermi level close to the Dirac points, due to Van Vleck paramagnetism triggered by spin-orbit coupling. One can expect topologically nontrivial spin textures under this anisotropy, such as a hedgehog around a single point, or a radial vortex around an axis, as well as a uniform ferromagnetic order. We further investigate the characteristics of spin waves in the ferromagnetic state. Spin-wave dispersion also shows a spatial anisotropy, which is less dispersed in the direction transverse to the magnetization than that in the longitudinal direction. The spin-wave dispersion anisotropy can be traced back to the rigidity and flexibility of spin correlations discussed above. This work was supported by Grant-in-Aid for Scientific Research (Grants No.15H05854, No.26107505, and No.26400308) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Electrical and optical properties of p-type codoped ZnO thin films prepared by spin coating technique

NASA Astrophysics Data System (ADS)

Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

2016-03-01

Undoped, doped and codoped ZnO thin films were synthesized on glass substrates using a spin coating technique. Zinc acetate dihydrate, ammonium acetate and aluminum nitrate were used as precursor for zinc, nitrogen and aluminum, respectively. X-ray diffraction shows that the thin films have a hexagonal wurtzite structure for the undoped, doped and co-doped ZnO. The transmittance of the films was above 80% and the band gap of the film varied from 3.20 eV to 3.24 eV for undoped and doped ZnO. An energy band diagram to describe the photoluminescence from the thin films was also constructed. This diagram includes the various defect levels and possible quasi-Fermi levels. A minimum resistivity of 0.0834 Ω-cm was obtained for the N and Al codoped ZnO thin films with p-type carrier conductivity. These ZnO films can be used as a window layer in solar cells and in UV lasers.

Gel spinning of silk tubes for tissue engineering

PubMed Central

Lovett, Michael; Cannizzaro, Christopher; Vunjak-Novakovic, Gordana; Kaplan, David L.

2011-01-01

Tubular vessels for tissue engineering are typically fabricated using a molding, dipping, or electrospinning technique. While these techniques provide some control over inner and outer diameters of the tube, they lack the ability to align the polymers or fibers of interest throughout the tube. This is an important aspect of biomaterial composite structure and function for mechanical and biological impact of tissue outcomes. We present a novel aqueous process system to spin tubes from biopolymers and proteins such as silk fibroin. Using silk as an example, this method of winding an aqueous solution around a reciprocating rotating mandrel offers substantial improvement in the control of the tube properties, specifically with regard to winding pattern, tube porosity, and composite features. Silk tube properties are further controlled via different post-spinning processing mechanisms such as methanol-treatment, air-drying, and lyophilization. This approach to tubular scaffold manufacture offers numerous tissue engineering applications such as complex composite biomaterial matrices, blood vessel grafts and nerve guides, among others. PMID:18801570

Electrically Driving Donor Spin Qubits in Silicon Using Photonic Bandgap Resonators

NASA Astrophysics Data System (ADS)

Sigillito, A. J.; Tyryshkin, A. M.; Lyon, S. A.

In conventional experiments, donor nuclear spin qubits in silicon are driven using radiofrequency (RF) magnetic fields. However, magnetic fields are difficult to confine at the nanoscale, which poses major issues for individually addressable qubits and device scalability. Ideally one could drive spin qubits using RF electric fields, which are easy to confine, but spins do not naturally have electric dipole transitions. In this talk, we present a new method for electrically controlling nuclear spin qubits in silicon by modulating the hyperfine interaction between the nuclear spin qubit and the donor-bound electron. By fabricating planar superconducting photonic bandgap resonators, we are able to use pulsed electron-nuclear double resonance (ENDOR) techniques to selectively probe both electrically and magnetically driven transitions for 31P and 75As nuclear spin qubits. The electrically driven spin resonance mechanism allows qubits to be driven at either their transition frequency, or at one-half their transition frequency, thus reducing bandwidth requirements for future quantum devices. Moreover, this form of control allows for higher qubit densities and lower power requirements compared to magnetically driven schemes. In our proof-of-principle experiments we demonstrate electrically driven Rabi frequencies of approximately 50 kHz for widely spaced (10 μm) gates which should be extendable to MHz for nanoscale devices.

Thermoelectric properties of Si/CoSi2 sub-micrometer composites prepared by melt-spinning technique

NASA Astrophysics Data System (ADS)

Xie, Jun; Ohishi, Yuji; Ichikawa, Satoshi; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke

2017-05-01

We here report on the influence of CoSi2 precipitates on the thermoelectric properties of heavily doped p-type Si. A simple self-assembly process using a melt-spinning technique followed by spark plasma sintering is introduced to prepare bulk Si/CoSi2 composites with a nominal composition of (Si0.99B0.01)95Co5. Scanning and transmission electron microscopy observations present clear evidence of a sub-micrometer CoSi2 phase with a size ranging from 50 to 500 nm. These sub-micrometer precipitates resulted in a retention of the high electrical performance of heavily doped Si, while simultaneously reducing thermal conductivity by over 20% compared to a coarse CoSi2 phase (1-10 μm) in a comparative sample prepared by arc melting and spark plasma sintering. As a result, a figure of merit ZT value of 0.21 at 1073 K was achieved in the sub-micrometer Si/CoSi2, an increase of 16% compared with the ZT value for homogeneous p-type Si with a similar carrier concentration. This suggests that the self-assembled sub-micrometer inclusions effectively enhanced the thermoelectric performance of Si-based thermoelectric materials.

Inverse spin-valve effect in nanoscale Si-based spin-valve devices

NASA Astrophysics Data System (ADS)

Hiep, Duong Dinh; Tanaka, Masaaki; Hai, Pham Nam

2017-12-01

We investigated the spin-valve effect in nano-scale silicon (Si)-based spin-valve devices using a Fe/MgO/Ge spin injector/detector deposited on Si by molecular beam epitaxy. For a device with a 20 nm Si channel, we observed clear magnetoresistance up to 3% at low temperature when a magnetic field was applied in the film plane along the Si channel transport direction. A large spin-dependent output voltage of 20 mV was observed at a bias voltage of 0.9 V at 15 K, which is among the highest values in lateral spin-valve devices reported so far. Furthermore, we observed that the sign of the spin-valve effect is reversed at low temperatures, suggesting the possibility of a spin-blockade effect of defect states in the MgO/Ge tunneling barrier.

High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature.

PubMed

Trifunovic, Luka; Pedrocchi, Fabio L; Hoffman, Silas; Maletinsky, Patrick; Yacoby, Amir; Loss, Daniel

2015-06-01

Magnetic resonance techniques not only provide powerful imaging tools that have revolutionized medicine, but they have a wide spectrum of applications in other fields of science such as biology, chemistry, neuroscience and physics. However, current state-of-the-art magnetometers are unable to detect a single nuclear spin unless the tip-to-sample separation is made sufficiently small. Here, we demonstrate theoretically that by placing a ferromagnetic particle between a nitrogen-vacancy magnetometer and a target spin, the magnetometer sensitivity is improved dramatically. Using materials and techniques that are already experimentally available, our proposed set-up is sensitive enough to detect a single nuclear spin within ten milliseconds of data acquisition at room temperature. The sensitivity is practically unchanged when the ferromagnet surface to the target spin separation is smaller than the ferromagnet lateral dimensions; typically about a tenth of a micrometre. This scheme further benefits when used for nitrogen-vacancy ensemble measurements, enhancing sensitivity by an additional three orders of magnitude.

Fictitious spin-12 operators and correlations in quadrupole nuclear spin system

NASA Astrophysics Data System (ADS)

Furman, G. B.; Goren, S. D.; Meerovich, V. M.; Sokolovsky, V. L.

The Hamiltonian and the spin operators for a spin 3/2 are represented in the basis formed by the Kronecker productions of the 2×2 Pauli matrices. This reformulation allows us to represent a spin 3/2 as a system of two coupled fictitious spins 1/2. Correlations between these fictitious spins are studied using well-developed methods. We investigate the temperature and field dependences of correlations, such as mutual information, classical correlations, entanglement, and geometric and quantum discords in the fictitious spin-1/2 system describing a nuclear spin 3/2 which is placed in magnetic and inhomogeneous electric fields. It is shown that the correlations between the fictitious spins demonstrate properties which differ from those of real two-spin systems. In contrast to real systems all the correlations between the fictitious spins do not vanish with increasing external magnetic field; at a high magnetic field the correlations tend to their limiting values. Classical correlations, quantum and geometric discords reveal a pronounced asymmetry relative to the measurements on subsystems (fictitious spins) even in a uniform magnetic field and at symmetrical EFG, η=0. The correlations depend also on the distribution of external charges, on the parameter of symmetry η. At η≠0 quantum and geometric discords have finite values in a zero magnetic field. The proposed approach may be useful in analysis of properties of particles with larger angular momentum, can provide the way to discover new physical phenomenon of quantum correlations, and can be a useful tool for similar definitions of other physical quantities of complex systems.

Realizing three-dimensional artificial spin ice by stacking planar nano-arrays

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

Chern, Gia-Wei; Reichhardt, Charles; Nisoli, Cristiano

2014-01-06

Artificial spin ice is a frustrated magnetic two-dimensional nano-material, recently employed to study variety of tailor-designed unusual collective behaviours. Recently proposed extensions to three dimensions are based on self-assembly techniques and allow little control over geometry and disorder. We present a viable design for the realization of a three-dimensional artificial spin ice with the same level of precision and control allowed by lithographic nano-fabrication of the popular two-dimensional case. Our geometry is based on layering already available two-dimensional artificial spin ice and leads to an arrangement of ice-rule-frustrated units, which is topologically equivalent to that of the tetrahedra in amore » pyrochlore lattice. Consequently, we show, it exhibits a genuine ice phase and its excitations are, as in natural spin ice materials, magnetic monopoles interacting via Coulomb law.« less

Realizing three-dimensional artificial spin ice by stacking planar nano-arrays

NASA Astrophysics Data System (ADS)

Chern, Gia-Wei; Reichhardt, Charles; Nisoli, Cristiano

2014-01-01

Artificial spin ice is a frustrated magnetic two-dimensional nano-material, recently employed to study variety of tailor-designed unusual collective behaviours. Recently proposed extensions to three dimensions are based on self-assembly techniques and allow little control over geometry and disorder. We present a viable design for the realization of a three-dimensional artificial spin ice with the same level of precision and control allowed by lithographic nano-fabrication of the popular two-dimensional case. Our geometry is based on layering already available two-dimensional artificial spin ice and leads to an arrangement of ice-rule-frustrated units, which is topologically equivalent to that of the tetrahedra in a pyrochlore lattice. Consequently, we show, it exhibits a genuine ice phase and its excitations are, as in natural spin ice materials, magnetic monopoles interacting via Coulomb law.

Thermal properties of spin-S Kitaev-Heisenberg model on a honeycomb lattice

NASA Astrophysics Data System (ADS)

Suzuki, Takafumi; Yamaji, Youhei

2018-05-01

Temperature (T) dependence of heat capacity C (T) in the S = 1 / 2 Kitaev honeycomb model shows a double-peak structure resulting from fractionalization of spins into two kinds of Majorana fermions. Recently it has been discussed that the double-peak structure in C (T) is also observed in magnetic ordered phases of the S = 1 / 2 Kitaev-Heisenberg (KH) model on a honeycomb lattice when the system is located in the vicinity of the Kitaev's spin liquid phase. In addition to the S = 1 / 2 spin case, similar double-peak structure has been confirmed in the KH honeycomb model for classical Heisenberg spins, where spin S is regarded as S → ∞ . We investigate spin-S dependence of C (T) for the KH honeycomb models by using thermal pure quantum state. We also perform classical Monte Carlo calculations to obtain C (T) for the classical KH model. From obtained results, we find that the origin of the high-temperature peak is different between the quantum spin case with small Ss and the classical Heisenberg spin case. Furthermore, the high-temperature peak in the quantum spin case, which is one of the clues for fractionalization of spins, disappears for S > 1 .

Direct Identification of Dilute Surface Spins on Al2 O3 : Origin of Flux Noise in Quantum Circuits

NASA Astrophysics Data System (ADS)

de Graaf, S. E.; Adamyan, A. A.; Lindström, T.; Erts, D.; Kubatkin, S. E.; Tzalenchuk, A. Ya.; Danilov, A. V.

2017-02-01

An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al2 O3 . We measure a spin density of 2.2 ×1 017 spins/m2 , attributed to physisorbed atomic hydrogen and S =1 /2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices.

N-tert-butylmethanimine N-oxide is an efficient spin-trapping probe for EPR analysis of glutathione thiyl radical

PubMed Central

Scott, Melanie J.; Billiar, Timothy R.; Stoyanovsky, Detcho A.

2016-01-01

The electron spin resonance (EPR) spin-trapping technique allows detection of radical species with nanosecond half-lives. This technique is based on the high rates of addition of radicals to nitrones or nitroso compounds (spin traps; STs). The paramagnetic nitroxides (spin-adducts) formed as a result of reactions between STs and radical species are relatively stable compounds whose EPR spectra represent “structural fingerprints” of the parent radical species. Herein we report a novel protocol for the synthesis of N-tert-butylmethanimine N-oxide (EBN), which is the simplest nitrone containing an α-H and a tertiary α′-C atom. We present EPR spin-trapping proof that: (i) EBN is an efficient probe for the analysis of glutathione thiyl radical (GS•); (ii) β-cyclodextrins increase the kinetic stability of the spin-adduct EBN/•SG; and (iii) in aqueous solutions, EBN does not react with superoxide anion radical (O2−•) to form EBN/•OOH to any significant extent. The data presented complement previous studies within the context of synthetic accessibility to EBN and efficient spin-trapping analysis of GS•. PMID:27941944

List based prefetch

DOEpatents

Boyle, Peter [Edinburgh, GB; Christ, Norman [Irvington, NY; Gara, Alan [Yorktown Heights, NY; Kim,; Changhoan, [San Jose, CA; Mawhinney, Robert [New York, NY; Ohmacht, Martin [Yorktown Heights, NY; Sugavanam, Krishnan [Yorktown Heights, NY

2012-08-28

A list prefetch engine improves a performance of a parallel computing system. The list prefetch engine receives a current cache miss address. The list prefetch engine evaluates whether the current cache miss address is valid. If the current cache miss address is valid, the list prefetch engine compares the current cache miss address and a list address. A list address represents an address in a list. A list describes an arbitrary sequence of prior cache miss addresses. The prefetch engine prefetches data according to the list, if there is a match between the current cache miss address and the list address.

Spin Currents and Spin Orbit Torques in Ferromagnets and Antiferromagnets

NASA Astrophysics Data System (ADS)

Hung, Yu-Ming

This thesis focuses on the interactions of spin currents and materials with magnetic order, e.g., ferromagnetic and antiferromagnetic thin films. The spin current is generated in two ways. First by spin-polarized conduction-electrons associated with the spin Hall effect in heavy metals (HMs) and, second, by exciting spin-waves in ferrimagnetic insulators using a microwave frequency magnetic field. A conduction-electron spin current can be generated by spin-orbit coupling in a heavy non-magnetic metal and transfer its spin angular momentum to a ferromagnet, providing a means of reversing the magnetization of perpendicularly magnetized ultrathin films with currents that flow in the plane of the layers. The torques on the magnetization are known as spin-orbit torques (SOT). In the first part of my thesis project I investigated and contrasted the quasistatic (slowly swept current) and pulsed current-induced switching characteristics of micrometer scale Hall crosses consisting of very thin (<1 nm) perpendicularly magnetized CoFeB layers on beta-Ta. While complete magnetization reversal occurs at a threshold current density in the quasistatic case, pulses with short duration (≤10 ns) and larger amplitude (≃10 times the quasistatic threshold current) lead to only partial magnetization reversal and domain formation. The partial reversal is associated with the limited time for reversed domain expansion during the pulse. The second part of my thesis project studies and considers applications of SOT-driven domain wall (DW) motion in a perpendicularly magnetized ultrathin ferromagnet sandwiched between a heavy metal and an oxide. My experiment results demonstrate that the DW motion can be explained by a combination of the spin Hall effect, which generates a SOT, and Dzyaloshinskii-Moriya interaction, which stabilizes chiral Neel-type DW. Based on SOT-driven DW motion and magnetic coupling between electrically isolated ferromagnetic elements, I proposed a new type of spin

Electrical detection of nuclear spin-echo signals in an electron spin injection system

NASA Astrophysics Data System (ADS)

Lin, Zhichao; Rasly, Mahmoud; Uemura, Tetsuya

2017-06-01

We demonstrated spin echoes of nuclear spins in a spin injection device with a highly polarized spin source by nuclear magnetic resonance (NMR). Efficient spin injection into GaAs from a half-metallic spin source of Co2MnSi enabled efficient dynamic nuclear polarization (DNP) and sensitive detection of NMR signals even at a low magnetic field of ˜0.1 T and a relatively high temperature of 4.2 K. The intrinsic coherence time T2 of 69Ga nuclear spins was evaluated from the spin-echo signals. The relation between T2 and the decay time of the Rabi oscillation suggests that the inhomogeneous effects in our system are not obvious. This study provides an all-electrical NMR system for nuclear-spin-based qubits.

Literature Review of Spin On Glass

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

Peterson, Reuben James

2016-03-02

Spin on glass (SOG) is a promising material that combines the planarization properties of a low-viscosity liquid with a dielectric constant lower than that of silicon dioxide. However, as this paper will show, this material comes with significant processing and material properties challenges that must be understood and overcome. Significant research has been accomplished through a variety of processing techniques that will be reviewed here.

Spin-Ice Thin Films: Large-N Theory and Monte Carlo Simulations

NASA Astrophysics Data System (ADS)

Lantagne-Hurtubise, Étienne; Rau, Jeffrey G.; Gingras, Michel J. P.

2018-04-01

We explore the physics of highly frustrated magnets in confined geometries, focusing on the Coulomb phase of pyrochlore spin ices. As a specific example, we investigate thin films of nearest-neighbor spin ice, using a combination of analytic large-N techniques and Monte Carlo simulations. In the simplest film geometry, with surfaces perpendicular to the [001] crystallographic direction, we observe pinch points in the spin-spin correlations characteristic of a two-dimensional Coulomb phase. We then consider the consequences of crystal symmetry breaking on the surfaces of the film through the inclusion of orphan bonds. We find that when these bonds are ferromagnetic, the Coulomb phase is destroyed by the presence of fluctuating surface magnetic charges, leading to a classical Z2 spin liquid. Building on this understanding, we discuss other film geometries with surfaces perpendicular to the [110] or the [111] direction. We generically predict the appearance of surface magnetic charges and discuss their implications for the physics of such films, including the possibility of an unusual Z3 classical spin liquid. Finally, we comment on open questions and promising avenues for future research.