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Sample records for efficient spin injection

  1. 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

  2. Spin injection into semiconductors

    NASA Astrophysics Data System (ADS)

    Oestreich, M.; Hübner, J.; Hägele, D.; Klar, P. J.; Heimbrodt, W.; Rühle, W. W.; Ashenford, D. E.; Lunn, B.

    1999-03-01

    The injection of spin-polarized electrons is presently one of the major challenges in semiconductor spin electronics. We propose and demonstrate a most efficient spin injection using diluted magnetic semiconductors as spin aligners. Time-resolved photoluminescence with a Cd0.98Mn0.02Te/CdTe structure proves the feasibility of the spin-alignment mechanism.

  3. Demonstration of efficient spin injection and detection in various systems using Fe3O4 based spin injectors

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Half-metal based spin injector devices for spin injection and detection application have proven to be efficient owing to their enhanced injection and detection efficiency. In this study, we extend the all-electrical spin injection and detection studies into different systems like Si and GaAs using half-metal Fe3O4 as a spin injector in the presence and absence of tunnel barrier MgO. Injection into GaAs is verified using conventional Fe/MgO/GaAs devices. Room temperature spin injection into both p-type and n-type Si is achieved and the spin injection could be observed down to 100K. Obtained spin relaxation time for these n-type and p-type Si at different temperatures agree well with the existing reports. Further, the temperature dependent spin injection and detection is also successfully achieved in Fe3O4/GaAs (n-type) Schottky devices, and a comparison study of the results with control experiment using Fe/MgO/GaAs (n-type) devices confirm the relaxation to be similar in the GaAs substrate, as expected. Hence, even Fe3O4 material can be effectively used as an efficient spin injector as well as detector, making it an attractive candidate for the room temperature spintronics device applications.

  4. Interdiffusion-controlled Kondo suppression of injection efficiency in metallic nonlocal spin valves

    NASA Astrophysics Data System (ADS)

    O'Brien, L.; Spivak, D.; Jeong, J. S.; Mkhoyan, K. A.; Crowell, P. A.; Leighton, C.

    2016-01-01

    Nonlocal spin valves (NLSVs) generate pure spin currents, providing unique insight into spin injection and relaxation at the nanoscale. Recently it was shown that the puzzling low temperature nonmonotonicity of the spin accumulation in all-metal NLSVs occurs due to a manifestation of the Kondo effect arising from dilute local-moment-forming impurities in the nonmagnetic material. Here it is demonstrated that precise control over interdiffusion in Fe/Cu NLSVs via thermal annealing can induce dramatic increases in this Kondo suppression of injection efficiency, observation of injector/detector separation-dependent Kondo effects in both charge and spin channels simultaneously, and, in the limit of large interdiffusion, complete breakdown of standard Valet-Fert-based models. The Kondo effect in the charge channel enables extraction of the exact interdiffusion profile, quantifying the influence of local moment density on the injection efficiency and presenting a well-posed challenge to theory.

  5. Enhancing spin injection efficiency through half-metallic miniband conduction in a spin-filter superlattice

    NASA Astrophysics Data System (ADS)

    Yang, Yi-Hang; Li, Lin; Liu, Fen; Gao, Zhi-Wei; Miao, Guo-Xing

    2016-02-01

    We theoretically and numerically studied the band structure and spin transport of electrons subject to a superlattice structure where magnetic semiconductor layers lie between normal semiconductor layers to form periodic spin-filter tunnel barriers. In this alternately deposited superlattice structure, due to the induced periodicity of the envelope wavefunctions, there are additional allowed and forbidden energy regions established, i.e. forming minibands that are far narrower than the conventional conduction bands. The number and thickness of the stacked potential profiles can finely tune these minibands. The spin dependent potential barriers also induce spin splitting at the bottom of each miniband, which generates strongly spin-dependent miniband conduction. Most strikingly, the lowest lying miniband is 100% spin-polarized mimicking a half-metallic behavior on this conduction channel. The total transmission electron current carries thus near-perfectly polarized spin currents when the superlattice falls into suitable miniband conduction regime. This half-metallic miniband enhanced spin-filtering capability paves the way to generate highly polarized spin current without incurring exponentially increased device impedance, as usually happens when only a single spin-filter barrier is applied.

  6. Enhancing spin injection efficiency through half-metallic miniband conduction in a spin-filter superlattice.

    PubMed

    Yang, Yi-Hang; Li, Lin; Liu, Fen; Gao, Zhi-Wei; Miao, Guo-Xing

    2016-02-10

    We theoretically and numerically studied the band structure and spin transport of electrons subject to a superlattice structure where magnetic semiconductor layers lie between normal semiconductor layers to form periodic spin-filter tunnel barriers. In this alternately deposited superlattice structure, due to the induced periodicity of the envelope wavefunctions, there are additional allowed and forbidden energy regions established, i.e. forming minibands that are far narrower than the conventional conduction bands. The number and thickness of the stacked potential profiles can finely tune these minibands. The spin dependent potential barriers also induce spin splitting at the bottom of each miniband, which generates strongly spin-dependent miniband conduction. Most strikingly, the lowest lying miniband is 100% spin-polarized mimicking a half-metallic behavior on this conduction channel. The total transmission electron current carries thus near-perfectly polarized spin currents when the superlattice falls into suitable miniband conduction regime. This half-metallic miniband enhanced spin-filtering capability paves the way to generate highly polarized spin current without incurring exponentially increased device impedance, as usually happens when only a single spin-filter barrier is applied. PMID:26761786

  7. Efficient spin injection into silicon and the role of the Schottky barrier.

    PubMed

    Dankert, André; Dulal, Ravi S; Dash, Saroj P

    2013-01-01

    Implementing spin functionalities in Si, and understanding the fundamental processes of spin injection and detection, are the main challenges in spintronics. Here we demonstrate large spin polarizations at room temperature, 34% in n-type and 10% in p-type degenerate Si bands, using a narrow Schottky and a SiO2 tunnel barrier in a direct tunneling regime. Furthermore, by increasing the width of the Schottky barrier in non-degenerate p-type Si, we observed a systematic sign reversal of the Hanle signal in the low bias regime. This dramatic change in the spin injection and detection processes with increased Schottky barrier resistance may be due to a decoupling of the spins in the interface states from the bulk band of Si, yielding a transition from a direct to a localized state assisted tunneling. Our study provides a deeper insight into the spin transport phenomenon, which should be considered for electrical spin injection into any semiconductor. PMID:24217343

  8. Efficient injection of spin-polarized electrons from manganese arsenide contacts into aluminum gallium arsenide/gallium arsenide spin LEDs

    NASA Astrophysics Data System (ADS)

    Schweidenback, Lars

    In this thesis we describe two spectroscopic projects project on semiconductor heterostructures, as well as putting together and testing a micro-photoluminescence/7 tesla magnet system for the study of micron size two-dimensional crystals. Below we discuss the three parts in more detail. i) MnAs-based spin light emitting diodes. We have studied the injection of spin-polarized electrons from a ferromagnetic MnAs contact into an AlGaAs(n)/GaAs(i)/AlGaAs(p) n-i-p light emitting diode. We have recorder the emitted electroluminescence as function of magnetic field applied at right angles to the device plane in the 7-300 K temperature range. It was found that at 7 Kelvin the emitted light is circularly polarized with a polarization that is proportional to the MnAs contact magnetization with a saturation value of 26% for B > 1.25 tesla. The polarization persists up to room temperature with a saturation value of 6%. ii) Optical Aharonov-Bohm effect in InGaAs quantum wells. The excitonic photoluminescence intensity from InGaAs quantum wells as function of magnetic field exhibits two local maxima superimposed on a decreasing background. The maxima are attributed to the optical Aharonov-Bohm effect of electrons orbiting around a hole localized at the center of an Indium rich InGaAs islands detected by cross sectional scanning tunneling microscopy. Analysis of the position of the maxima yields a value of the electron orbit radius. iii) Micro-Photoluminescence. We have put together a micro-photoluminescence /7 tesla system for the study of two dimensional crystals. The samples are placed inside a continuous flow cryostat whose tail is positioned in the bore of the 7 tesla magnet. A microscope objective is used to focus the exciting laser light and collect the emitted photoluminescence. The system was tested by recording the photoluminescence spectra of WS2 and WSe 2 monolayers at T = 77 K.

  9. Nonequilibrium spin injection in monolayer black phosphorus.

    PubMed

    Chen, Mingyan; Yu, Zhizhou; Wang, Yin; Xie, Yiqun; Wang, Jian; Guo, Hong

    2016-01-21

    Monolayer black phosphorus (MBP) is an interesting emerging electronic material with a direct band gap and relatively high carrier mobility. In this work we report a theoretical investigation of nonequilibrium spin injection and spin-polarized quantum transport in MBP from ferromagnetic Ni contacts, in two-dimensional magnetic tunneling structures. We investigate physical properties such as the spin injection efficiency, the tunnel magnetoresistance ratio, spin-polarized currents, charge currents and transmission coefficients as a function of external bias voltage, for two different device contact structures where MBP is contacted by Ni(111) and by Ni(100). While both structures are predicted to give respectable spin-polarized quantum transport, the Ni(100)/MBP/Ni(100) trilayer has the superior properties where the spin injection and magnetoresistance ratio maintains almost a constant value against the bias voltage. The nonequilibrium quantum transport phenomenon is understood by analyzing the transmission spectrum at nonequilibrium. PMID:26675820

  10. Nonequilibrium spin injection in monolayer black phosphorus

    NASA Astrophysics Data System (ADS)

    Chen, Mingyan; Yu, Zhizhou; Wang, Yin; Xie, Yiqun; Wang, Jian; Guo, Hong

    Monolayer black phosphorus (MBP) is an interesting emerging electronic material with a direct band gap and relatively high carrier mobility. In this work we report a theoretical investigation of nonequilibrium spin injection and spin-polarized quantum transport in MBP from ferromagnetic Ni contacts, in two-dimensional magnetic tunneling structures. We investigate physical properties such as the spin injection efficiency, the tunnel magnetoresistance ratio, spin-polarized currents, charge currents and transmission coefficients as a function of external bias voltage, for two different device contact structures where MBP is contacted by Ni(111) and by Ni(100). While both structures are predicted to give respectable spin-polarized quantum transport, the Ni(100)/MBP/Ni(100) trilayer has the superior properties where the spin injection and magnetoresistance ratio maintains almost a constant value against the bias voltage. The nonequilibrium quantum transport phenomenon is understood by analyzing the transmission spectrum at nonequilibrium.

  11. 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.

  12. MoO3 Films Spin-Coated from Nanoparticle Suspension for Efficient Hole-Injection in Organic Electronics

    SciTech Connect

    Meyer, Jens; Khalandovsky, Rebecca; Görrn, Patrick; Kahn, Antoine

    2010-10-26

    MoO3 films spin-coated from a suspension of nanoparticles, which offers energetic properties nearly identical to those of thermally evaporated MoO3 films, are reported. It is demonstrated that our solution-based MoO3 acts as a very efficient hole-injection layer for organic devices.

  13. Memory and Spin Injection Devices Involving Half Metals

    DOE PAGESBeta

    Shaughnessy, M.; Snow, Ryan; Damewood, L.; Fong, C. Y.

    2011-01-01

    We suggest memory and spin injection devices fabricated with half-metallic materials and based on the anomalous Hall effect. Schematic diagrams of the memory chips, in thin film and bulk crystal form, are presented. Spin injection devices made in thin film form are also suggested. These devices do not need any external magnetic field but make use of their own magnetization. Only a gate voltage is needed. The carriers are 100% spin polarized. Memory devices may potentially be smaller, faster, and less volatile than existing ones, and the injection devices may be much smaller and more efficient than existing spin injectionmore » devices.« less

  14. Influence of thermal annealing on the spin injection and spin detection through Fe/GaAs interfaces

    NASA Astrophysics Data System (ADS)

    Liefeith, Lennart-Knud; Tholapi, Rajkiran; Hänze, Max; Hartmann, Robert; Slobodskyy, Taras; Hansen, Wolfgang

    2016-05-01

    A strong bias asymmetry of the spin-injection efficiency through an epitaxial Fe/GaAs Schottky tunnel contact is observed. Low-temperature post-growth thermal annealing is shown to strongly affect the spin-injection efficiency. The annealing leads either to a reduction or an enhancement. The spin accumulation is addressed electrically in a lateral spin-valve geometry using a non-local spin-valve setup at liquid helium temperatures. A spin-injection efficiency of up to 5.5% is estimated from experimental results. The electrical properties of the Schottky tunnel diode do not reflect the bias asymmetry and the changes in the spin-injection efficiency during annealing. Formation of spin-polarized interface states (IS) close to the Fermi-level is a possible explanation. The IS will not only radically affect the spin-injection but also the spin-detection process.

  15. Effective nonlocal spin injection through low-resistance oxide junctions

    NASA Astrophysics Data System (ADS)

    Cai, Yunjiao; Luo, Yongming; Qin, Chuan; Chen, Shuhan; Wu, Yizheng; Ji, Yi

    2016-05-01

    Many (>40) nonlocal spin valves on the same substrate have been characterized at 6 K and 295 K by using a probe station. Low-resistance oxide junctions (0.2-0.8 Ω) are used to inject spin current into mesoscopic Cu channels. Spin signals exceeding 10 mΩ at 6 K have been consistently observed, indicating efficient spin injection and detection. However, complex switching behavior and possible variations between devices pose a challenge to using a standard fitting method to quantify the spin signals. Two methods are used for quantitative analysis. The range of the effective spin polarizations can be estimated by assuming a reasonable range for the Cu spin diffusion lengths. A nonlocal spin polarization is introduced to evaluate the spin current in the Cu channels.

  16. Optimization of spin injection and spin detection in lateral nanostructures by geometrical means

    NASA Astrophysics Data System (ADS)

    Stejskal, Ondřej; Hamrle, Jaroslav; Pištora, Jaromír; Otani, Yoshichika

    2016-09-01

    Lateral spin devices are an important concept in nowadays all-metallic spintronic devices. One of the key problems is to obtain large spin injection and detection efficiency. Several concepts has been envisaged, such as to use half-metallic ferromagnetic electrodes or spin-polarized interface barriers. Within this work, we address the optimization of spin devices (namely optimization of spin current density, spin current and spin accumulation) based on adjustment of the geometry (dimensions) of the lateral device, material selection of spin conductors, jointly with optimization of the interface resistance.

  17. Spin transport in non-magnetic nano-structures induced by non-local spin injection

    NASA Astrophysics Data System (ADS)

    Idzuchi, Hiroshi; Fukuma, Yasuhiro; Otani, YoshiChika

    2015-04-01

    We review our recent achievements on optimization of spin injection from ferromagnetic into non-magnetic metals and characterization of spin transport properties in the non-magnetic nano-structures. We have realized the efficient spin injection by solving spin resistance mismatch problem in spin diffusion process across the interface between ferromagnetic and nonmagnetic metals. We analyzed temperature dependent spin relaxation length and time in Ag within the framework of the Elliot-Yafet mechanism based on spin-orbit interaction and momentum relaxation. The spin relaxation length in a light metal Mg is found comparable to that of Ag due to its peculiar electronic band structure in which so called spin-hotspots dramatically enhance spin relaxation. Spin relaxation properties in various metals are also quantitatively discussed. We employed commonly used Hanle effect measurements to characterize spin relaxation of spin current and reexamined both theoretically and experimentally the effect of spin absorption at the interface. The affected spatial profile of chemical potential due to the longitudinal and transverse spin absorption results in the broadened Hanle curve. All the Hanle curves both in metallic and semi-conductive materials including graphene fall into the universal scaling plot. Anatomy of spin injection properties of the junction and spin transport properties in non-magnetic metal is shown in tables.

  18. 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

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

    PubMed

    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. 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 [corrected]. PMID:24998440

  20. Spin polarized current injection and transportation in a double T-shaped organic spintronic device

    NASA Astrophysics Data System (ADS)

    Ren, JunFeng; Song, RuiRong; Yuan, XiaoBo; Hu, GuiChao

    2015-03-01

    A double T-shaped device model is constructed to investigate the spin polarized current injection and transportation properties in organic semiconductors. Based on the spin diffusion theory and Ohm's law and considering the different charge-spin relationship of the special carriers in organic semiconductors, the current spin polarization has been obtained. Effects of the branch current ratio and the polaron proportion on the spin polarized current injection efficiency are studied. From the calculation, it is found that the improvement of the spin polarized current injection efficiency can be obtained by adjusting the branch current ratio; moreover, high polaron proportion in organic semiconductors is beneficial for obtaining high current spin polarization.

  1. Ultrafast and Gigantic Spin Injection in Semiconductors

    NASA Astrophysics Data System (ADS)

    Battiato, M.; Held, K.

    2016-05-01

    The injection of spin currents in semiconductors is one of the big challenges of spintronics. Motivated by the ultrafast demagnetization and spin injection into metals, we propose an alternative femtosecond route based on the laser excitation of superdiffusive spin currents in a ferromagnet such as Ni. Our calculations show that even though only a fraction of the current crosses the Ni-Si interface, the laser-induced creation of strong transient electrical fields at a ferromagnet-semiconductor interface allows for the injection of chargeless spin currents with record spin polarizations of 80%. Beyond that they are pulsed on the time scale of 100 fs which opens the door for new experiments and ultrafast spintronics.

  2. Ultrafast and Gigantic Spin Injection in Semiconductors.

    PubMed

    Battiato, M; Held, K

    2016-05-13

    The injection of spin currents in semiconductors is one of the big challenges of spintronics. Motivated by the ultrafast demagnetization and spin injection into metals, we propose an alternative femtosecond route based on the laser excitation of superdiffusive spin currents in a ferromagnet such as Ni. Our calculations show that even though only a fraction of the current crosses the Ni-Si interface, the laser-induced creation of strong transient electrical fields at a ferromagnet-semiconductor interface allows for the injection of chargeless spin currents with record spin polarizations of 80%. Beyond that they are pulsed on the time scale of 100 fs which opens the door for new experiments and ultrafast spintronics. PMID:27232029

  3. Spin injection and spin transport in paramagnetic insulators

    DOE PAGESBeta

    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

  4. Tunneling spin injection into single layer graphene.

    PubMed

    Han, Wei; Pi, K; McCreary, K M; Li, Yan; Wong, Jared J I; Swartz, A G; Kawakami, R K

    2010-10-15

    We achieve tunneling spin injection from Co into single layer graphene (SLG) using TiO₂ seeded MgO barriers. A nonlocal magnetoresistance (ΔR(NL)) of 130  Ω is observed at room temperature, which is the largest value observed in any material. Investigating ΔR(NL) vs SLG conductivity from the transparent to the tunneling contact regimes demonstrates the contrasting behaviors predicted by the drift-diffusion theory of spin transport. Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are therefore important for future investigations of spin relaxation in graphene. PMID:21231003

  5. Tunnel based spin injection devices for semiconductor spintronics

    NASA Astrophysics Data System (ADS)

    Jiang, Xin

    This dissertation summarizes the work on spin-dependent electron transport and spin injection in tunnel based spintronic devices. In particular, it focuses on a novel three terminal hot electron device combining ferromagnetic metals and semiconductors---the magnetic tunnel transistor (MTT). The MTT has extremely high magnetic field sensitivity and is a useful tool to explore spin-dependent electron transport in metals, semiconductors, and at their interfaces over a wide energy range. In Chap. 1, the basic concept and fabrication of the MTT are discussed. Two types of MTTs, with ferromagnetic single and spin-valve base layers, respectively, are introduced and compared. In the following chapters, the transport properties of the MTT are discussed in detail, including the spin-dependent hot electron attenuation lengths in CoFe and NiFe thin films on GaAs (Chap. 2), the bias voltage dependence of the magneto-current (Chap. 3), the giant magneto-current effect in MTTs with a spin-valve base (Chap. 4), and the influence of non-magnetic seed layers on magneto-electronic properties of MTTs with a Si collector (Chap. 5). Chap. 6 concentrates on electrical injection of spin-polarized electrons into semiconductors, which is an essential ingredient in semiconductor spintronics. Two types of spin injectors are discussed: an MTT injector and a CoFe/MgO tunnel injector. The spin polarization of the injected electron current is detected optically by measuring the circular polarization of electroluminescence from a quantum well light emitting diode. Using an MTT injector a spin polarization of ˜10% is found for injection electron energy of ˜2 eV at 1.4K. This moderate spin polarization is most likely limited by significant electron spin relaxation at high energy. Much higher spin injection efficiency is obtained by using a CoFe/MgO tunnel injector with spin polarization values of ˜50% at 100K. The temperature and bias dependence of the electroluminescence polarization provides

  6. 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

  7. Spin Funneling for Enhanced Spin Injection into Ferromagnets.

    PubMed

    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

  8. 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.

  9. 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.

  10. Dynamical spin injection at a quasi-one-dimensional ferromagnet-graphene interface

    SciTech Connect

    Singh, S.; Ahmadi, A.; Mucciolo, E. R.; Barco, E. del; Cherian, C. T.; Özyilmaz, B.

    2015-01-19

    We present a study of dynamical spin injection from a three-dimensional ferromagnet into two-dimensional single-layer graphene. Comparative ferromagnetic resonance (FMR) studies of ferromagnet/graphene strips buried underneath the central line of a coplanar waveguide show that the FMR linewidth broadening is the largest when the graphene layer protrudes laterally away from the ferromagnetic strip, indicating that the spin current is injected into the graphene areas away from the area directly underneath the ferromagnet being excited. Our results confirm that the observed damping is indeed a signature of dynamical spin injection, wherein a pure spin current is pumped into the single-layer graphene from the precessing magnetization of the ferromagnet. The observed spin pumping efficiency is difficult to reconcile with the expected backflow of spins according to the standard spin pumping theory and the characteristics of graphene, and constitutes an enigma for spin pumping in two-dimensional structures.

  11. Domain wall displacement by remote spin-current injection

    SciTech Connect

    Skirdkov, P. N.; Zvezdin, K. A.; Belanovsky, A. D.; Zvezdin, A. K.; Grollier, J.; Cros, V.

    2014-06-16

    We demonstrate numerically the ability to displace a magnetic domain wall (DW) by remote spin current injection. We consider a long and narrow magnetic nanostripe with a single DW. The spin-polarized current is injected perpendicularly to the film plane through a small nanocontact which is located at certain distance from the DW initial position. We show that the DW motion can be initiated not only by conventional spin-transfer torque but also by indirect spin-torque, created by remote spin-current injection and then transferred to the DW by the exchange-spring mechanism. An analytical description of this effect is proposed.

  12. Towards electrical spin injection into LaAlO3-SrTiO3.

    PubMed

    Bibes, M; Reyren, N; Lesne, E; George, J-M; Deranlot, C; Collin, S; Barthélémy, A; Jaffrès, H

    2012-10-28

    Future spintronics devices will be built from elemental blocks allowing the electrical injection, propagation, manipulation and detection of spin-based information. Owing to their remarkable multi-functional and strongly correlated character, oxide materials already provide such building blocks for charge-based devices such as ferroelectric field-effect transistors (FETs), as well as for spin-based two-terminal devices such as magnetic tunnel junctions, with giant responses in both cases. Until now, the lack of suitable channel materials and the uncertainty of spin-injection conditions in these compounds had however prevented the exploration of similar giant responses in oxide-based lateral spin transport structures. In this paper, we discuss the potential of oxide-based spin FETs and report magnetotransport data that suggest electrical spin injection into the LaAlO(3)-SrTiO(3) interface system. In a local, three-terminal measurement scheme, we analyse the voltage variation associated with the precession of the injected spin accumulation driven by perpendicular or longitudinal magnetic fields (Hanle and 'inverted' Hanle effects). The spin accumulation signal appears to be much larger than expected, probably owing to amplification effects by resonant tunnelling through localized states in the LaAlO(3). We give perspectives on how to achieve direct spin injection with increased detection efficiency, as well on the implementation of efficient top gating schemes for spin manipulation. PMID:22987038

  13. Spin injection in n-type resonant tunneling diodes

    NASA Astrophysics Data System (ADS)

    Orsi Gordo, Vanessa; Herval, Leonilson KS; Galeti, Helder VA; Gobato, Yara Galvão; Brasil, Maria JSP; Marques, Gilmar E.; Henini, Mohamed; Airey, Robert J.

    2012-10-01

    We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X-). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to -88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers.

  14. Fast electron spin resonance controlled manipulation of spin injection into quantum dots

    SciTech Connect

    Merz, Andreas Siller, Jan; Schittny, Robert; Krämmer, Christoph; Kalt, Heinz; Hetterich, Michael

    2014-06-23

    In our spin-injection light-emitting diodes, electrons are spin-polarized in a semimagnetic ZnMnSe spin aligner and then injected into InGaAs quantum dots. The resulting electron spin state can be read out by measuring the circular polarization state of the emitted light. Here, we resonantly excite the Mn 3d electron spin system with microwave pulses and perform time-resolved measurements of the spin dynamics. We find that we are able to control the spin polarization of the injected electrons on a microsecond timescale. This electron spin resonance induced spin control could be one of the ingredients required to utilize the quantum dot electrons or the Mn spins as qubits.

  15. Control of light polarization using optically spin-injected vertical external cavity surface emitting lasers

    SciTech Connect

    Frougier, J. Jaffrès, H.; Deranlot, C.; George, J.-M.; Baili, G.; Dolfi, D.; Alouini, M.; Sagnes, I.; Garnache, A.

    2013-12-16

    We fabricated and characterized an optically pumped (100)-oriented InGaAs/GaAsP multiple quantum well Vertical External Cavity Surface Emitting Laser (VECSEL). The structure is designed to allow the integration of a Metal-Tunnel-Junction ferromagnetic spin-injector for future electrical injection. We report here the control at room temperature of the electromagnetic field polarization using optical spin injection in the active medium of the VECSEL. The switching between two highly circular polarization states had been demonstrated using an M-shaped extended cavity in multi-modes lasing. This result witnesses an efficient spin-injection in the active medium of the LASER.

  16. Modification of Spin Wave Propagation by Current Injection

    NASA Astrophysics Data System (ADS)

    Ono, Teruo

    2010-03-01

    We studied the effect of an electric current on the spin wave propagation in magnetic wires, and found the following two effects. (i) Current injection changes the velocity of spin wave; the velocity is increased or decreased depending on the current polarity. (ii) Current injection modifies the attenuation length of spin wave; the attenuation length of spin wave can increase when the spin waves and electrons move in the same direction. The first finding can be interpreted as the time-domain observation of the spin-wave Doppler shift by current injection [1]. The second effect is thought to be affected by the nonadiabaticity of the spin transfer torque and thus can be used to estimate the nonadiabaticity [2]. [4pt] [1] V. Vlaminck and M. Bailleul, Science 322, (2008) 410. [0pt] [2] S. M. Seo, K. J. Lee, H. Yang, and T. Ono, Phys. Rev. Lett. 102, (2009) 147202.

  17. Highly efficient spin filtering of ballistic electrons

    NASA Astrophysics Data System (ADS)

    Steinmuller, S. J.; Trypiniotis, T.; Cho, W. S.; Hirohata, A.; Lew, W. S.; Vaz, C. A.; Bland, J. A.

    2004-04-01

    Spin dependent electron transport in hybrid Au/Co/Cu/NiFe/n-GaAs spin valve Schottky barrier structures was investigated using photoexcitation at various wavelengths. For excitation with the photon energy well above the Schottky barrier height we found a ˜2400% increase in helicity dependent photocurrent on switching the spin valve from parallel to antiparallel alignment. Our observations provide clear evidence for highly efficient spin filtering of spin polarized ballistic electrons.

  18. Spin-current nano-oscillator based on nonlocal spin injection

    PubMed Central

    Demidov, V. E.; Urazhdin, S.; Zholud, A.; Sadovnikov, A. V.; Slavin, A. N.; Demokritov, S. O.

    2015-01-01

    Nonlocal spin injection has been recognized as an efficient mechanism for creation of pure spin currents not tied to the electrical charge transfer. Here we demonstrate experimentally that it can induce coherent magnetization dynamics, which can be utilized for the implementation of novel microwave nano-sources for spintronic and magnonic applications. We show that such sources exhibit a small oscillation linewidth and are tunable over a wide frequency range by the static magnetic field. Spatially resolved measurements of the dynamical magnetization indicate a relatively large oscillation area, resulting in a high stability of the oscillation with respect to thermal fluctuations. We propose a simple quasilinear dynamical model that reproduces well the oscillation characteristics. PMID:25716118

  19. Spin-injection spectroscopy of a spin-orbit coupled Fermi gas.

    PubMed

    Cheuk, Lawrence W; Sommer, Ariel T; Hadzibabic, Zoran; Yefsah, Tarik; Bakr, Waseem S; Zwierlein, Martin W

    2012-08-31

    The coupling of the spin of electrons to their motional state lies at the heart of recently discovered topological phases of matter. Here we create and detect spin-orbit coupling in an atomic Fermi gas, a highly controllable form of quantum degenerate matter. We directly reveal the spin-orbit gap via spin-injection spectroscopy, which characterizes the energy-momentum dispersion and spin composition of the quantum states. For energies within the spin-orbit gap, the system acts as a spin diode. We also create a spin-orbit coupled lattice and probe its spinful band structure, which features additional spin gaps and a fully gapped spectrum. In the presence of s-wave interactions, such systems should display induced p-wave pairing, topological superfluidity, and Majorana edge states. PMID:23002844

  20. Triplet supercurrent in ferromagnetic Josephson junctions by spin injection

    NASA Astrophysics Data System (ADS)

    Mal'shukov, A. G.; Brataas, Arne

    2012-09-01

    We show that injecting nonequilibrium spins into the superconducting leads strongly enhances the stationary Josephson current through a superconductor-ferromagnet-superconductor junction. The resulting long-range supercurrent through a ferromagnet is carried by triplet Cooper pairs that are formed in s-wave superconductors by the combined effects of spin injection and exchange interaction. We quantify the exchange interaction in terms of Landau Fermi-liquid factors. The magnitude and direction of the long-range Josephson current can be manipulated by varying the angles of the injected polarizations with respect to the magnetization in the ferromagnet.

  1. Enhancement of Thermally Injected Spin Current through an Antiferromagnetic Insulator.

    PubMed

    Lin, Weiwei; Chen, Kai; Zhang, Shufeng; Chien, C L

    2016-05-01

    We report a large enhancement of thermally injected spin current in normal metal (NM)/antiferromagnet (AF)/yttrium iron garnet (YIG), where a thin AF insulating layer of NiO or CoO can enhance the spin current from YIG to a NM by up to a factor of 10. The spin current enhancement in NM/AF/YIG, with a pronounced maximum near the Néel temperature of the thin AF layer, has been found to scale linearly with the spin-mixing conductance at the NM/YIG interface for NM=3d, 4d, and 5d metals. Calculations of spin current enhancement and spin mixing conductance are qualitatively consistent with the experimental results. PMID:27203336

  2. Enhancement of Thermally Injected Spin Current through an Antiferromagnetic Insulator

    NASA Astrophysics Data System (ADS)

    Lin, Weiwei; Chen, Kai; Zhang, Shufeng; Chien, C. L.

    2016-05-01

    We report a large enhancement of thermally injected spin current in normal metal (NM)/antiferromagnet (AF)/yttrium iron garnet (YIG), where a thin AF insulating layer of NiO or CoO can enhance the spin current from YIG to a NM by up to a factor of 10. The spin current enhancement in NM /AF /YIG , with a pronounced maximum near the Néel temperature of the thin AF layer, has been found to scale linearly with the spin-mixing conductance at the NM /YIG interface for NM =3 d , 4 d , and 5 d metals. Calculations of spin current enhancement and spin mixing conductance are qualitatively consistent with the experimental results.

  3. Towards spin injection from silicon into topological insulators

    NASA Astrophysics Data System (ADS)

    Ojeda-Aristizabal, Claudia; Fuhrer, Michael S.; Appelbaum, Ian

    2012-02-01

    Attempts to uncover evidence of spin-momentum coupling in a topological insulator (TI) using transport measurements are hampered by many challenges. Most importantly, injection of a spin polarized current from a ferromagnet that is in contact or close proximity to a topological insulator can easily give rise to anisotropic magnetoresistance signals or planar Hall effect from stray fields, which have the same symmetry and hence are indistinguishable from any signal coming from the spin-momentum-locked surface states. Here we propose a scheme to remove this difficulty by injecting spin-polarized electrons from undoped silicon into the TI surface states. In addition to providing a long-distance transport region to separate the ferromagnetic spin source from the TI by several hundred microns or even millimeters, this approach will also allow spin precession measurements (necessary for unambiguous identification of spin signals) whereas direct injection does not. Detection is provided by differential measurement from two ballistic current contacts on the topological insulator. We will describe our progress in fabrication and measurement of devices with exfoliated crystals of TI Bi2Se3, including the determination of the silicon-Bi2Se3 Schottky barrier height of 0.34 eV

  4. Optical spin injection in MoS2 monolayers

    NASA Astrophysics Data System (ADS)

    Arzate, N.; Mendoza, Bernardo S.; Vázquez-Nava, R. A.; Ibarra-Borja, Z.; Álvarez-Núñez, M. I.

    2016-03-01

    Two-dimensional transition-metal dichalcogenide materials have recently attracted great attention from the scientific community due to their interesting properties such as the presence of an energy band gap and the support of spin-polarized states. In particular, monolayer molybdenum disulfide has a structure with no inversion symmetry and, thus, presents a large spin-splitting of the top valence bands. This latter fact makes it favorable for studies of optical spin injection, a phenomenon that, under incidence of circularly polarized light, creates spin-polarized electrons in the conduction bands. Here, we perform a theoretical study of the one-photon optical spin and current injection on transition-metal dichalcogenide monolayers of molybdenum disulfide. In particular, we present calculations for spectra of the degree of spin polarization, which are calculated in a full-band structure scheme employing density functional theory; besides the so-called quasiparticle GW approximation is applied for the calculation of the band gap energy correction. Our results show 100% of spin polarization of the electrons for the one monolayer structure at the K valley. The degree of spin polarization also presents a net maximum value at the direct energy band gap at K as the number of monolayers increases.

  5. Spin injection effects on exciton distributions in conjugated organic semiconductors

    NASA Astrophysics Data System (ADS)

    Yunus, Mohammad; Ruden, P. Paul; Smith, Darryl

    2008-03-01

    Conjugated organic semiconductors are under rapid development as the active material in organic light emitting diodes (OLEDs). Electrons and holes injected into the organic semiconductor form bound singlet or triplet excitons. Singlet excitons may recombine radiatively giving rise to light emission whereas triplet excitons do not recombine radiatively. Thus the quantum efficiency of OLEDs is limited by the fraction of singlet excitons, χS. In this work, we explore theoretically an approach to control χS through spin-polarized electron and hole injection from ferromagnetic contacts. Conventional ferromagnetic transition metals and half-metallic materials, such as LSMO, are considered as candidate electrode materials. Electron and hole transport in the organic semiconductor is treated through the conventional device equations with the formation of excitons described by a Langevin process. Once formed, the excitons may recombine or diffuse. Triplet excitons have a lower recombination probability and hence a longer diffusion length. The model calculations yield steady state spatial profiles for singlet and triplet exciton densities in the organic semiconductor.

  6. Electrical spin injection and detection in silicon nanowires through oxide tunnel barriers.

    PubMed

    Zhang, Shixiong; Dayeh, Shadi A; Li, Yan; Crooker, Scott A; Smith, Darryl L; Picraux, S T

    2013-02-13

    We demonstrate all-electrical spin injection, transport, and detection in heavily n-type-doped Si nanowires using ferromagnetic Co/Al(2)O(3) tunnel barrier contacts. Analysis of both local and nonlocal spin valve signals at 4 K on the same nanowire device using a standard spin-transport model suggests that high spin injection efficiency (up to ~30%) and long spin diffusion lengths (up to ~6 μm) are achieved. These values exceed those reported for spin transport devices based on comparably doped bulk Si. The spin valve signals are found to be strongly bias and temperature dependent and can invert sign with changes in the dc bias current. The influence of the nanowire morphology on field-dependent switching of the contacts is also discussed. Owing to their nanoscale geometry, ~5 orders of magnitude less current is required to achieve nonlocal spin valve voltages comparable to those attained in planar microscale spin transport devices, suggesting lower power consumption and the potential for applications of Si nanowires in nanospintronics. PMID:23324028

  7. Tailoring spin injection and magnetoresistance in ferromagnet/graphene junctions from first principles

    NASA Astrophysics Data System (ADS)

    Lazic, Predrag; Sipahi, Guilherme; Kawakami, Roland; Zutic, Igor

    2013-03-01

    Recent experimental advances in graphene suggest intriguing opportunities for novel spintronic applications which could significantly exceed the state-of-the art performance of their conventional charge-based counterparts. However, for reliable operation of such spintronic devices it is important to achieve an efficient spin injection and large magnetoresistive effects. We use the first principles calculations to guide the choice of a ferromagnetic region and its relative orientation to optimize the desired effects. We propose structures which could enable uniform spin injection, one of the key factors in implementing scalable spintronic circuits. Supported by NSF-NRI, SRC, ONR, Croatian Ministry of Science, Education, and Sports, and CCR at SUNY UB.

  8. Energy efficient hybrid computing systems using spin devices

    NASA Astrophysics Data System (ADS)

    Sharad, Mrigank

    Emerging spin-devices like magnetic tunnel junctions (MTJ's), spin-valves and domain wall magnets (DWM) have opened new avenues for spin-based logic design. This work explored potential computing applications which can exploit such devices for higher energy-efficiency and performance. The proposed applications involve hybrid design schemes, where charge-based devices supplement the spin-devices, to gain large benefits at the system level. As an example, lateral spin valves (LSV) involve switching of nanomagnets using spin-polarized current injection through a metallic channel such as Cu. Such spin-torque based devices possess several interesting properties that can be exploited for ultra-low power computation. Analog characteristic of spin current facilitate non-Boolean computation like majority evaluation that can be used to model a neuron. The magneto-metallic neurons can operate at ultra-low terminal voltage of ˜20mV, thereby resulting in small computation power. Moreover, since nano-magnets inherently act as memory elements, these devices can facilitate integration of logic and memory in interesting ways. The spin based neurons can be integrated with CMOS and other emerging devices leading to different classes of neuromorphic/non-Von-Neumann architectures. The spin-based designs involve `mixed-mode' processing and hence can provide very compact and ultra-low energy solutions for complex computation blocks, both digital as well as analog. Such low-power, hybrid designs can be suitable for various data processing applications like cognitive computing, associative memory, and currentmode on-chip global interconnects. Simulation results for these applications based on device-circuit co-simulation framework predict more than ˜100x improvement in computation energy as compared to state of the art CMOS design, for optimal spin-device parameters.

  9. Spin injection and detection in a graphene lateral spin valve using an yttrium-oxide tunneling barrier

    NASA Astrophysics Data System (ADS)

    Komatsu, Katsuyoshi; Kasai, Shinya; Li, Song-Lin; Nakaharai, Shu; Mitoma, Nobuhiko; Yamamoto, Mahito; Tsukagoshi, Kazuhito

    2014-08-01

    We demonstrate charge and spin current transport in a graphene-based lateral spin valve using yttrium oxide (Y-O) as a tunneling barrier between graphene and a ferromagnetic electrode. A Y-O layer grown on graphene is flat, with a root-mean-square roughness of 0.17 nm, which is much lower than that of conventional barrier materials. This flatness allows the utilization of a very thin but well-defined tunneling barrier, leading to a large spin signal of ˜20 Ω and a high spin injection efficiency of 15% with a low contact resistance of ˜1 kΩ. These findings represent important progress toward the realization of graphene-based spintronics applications.

  10. Spin injection and spin-charge conversion in LaAlO3/SrTiO3

    NASA Astrophysics Data System (ADS)

    Bibes, Manuel; Lesne, Edouard; Rojas Sanchez, Juan Carlos; Oyarzun, Simon; Fu, Yu; Reyren, Nicolas; Jamet, Mathieu; Jacquet, Eric; Barthelemy, Agnes; George, Jean-Marie; Fert, Albert; Jaffres, Henri; Vila, Laurent

    2015-03-01

    The perovskite oxides family provides materials to efficiently generate and control spin polarized currents using respectively half-metallic ferromagnets such as mixed-valence manganites or ferroelectrics and multiferroics. More recently channel materials to transport spin information have also emerged. These include the LaAlO3/SrTiO3 two-dimensional electron system (2DES) which, in addition, possesses a gate-tunable spin-orbit coupling. A limitation of this system is however the minimum LaAlO3 thickness of 4 uc required for 2DES formation. In this presentation we will show that this thickness can be reduced if the LaAlO3 is capped by appropriate metals. We will also present different approaches to inject spins in these engineered LaAlO3/SrTiO3 2DES and introduce detection schemes taking advantage of efficient spin-charge conversion via interfacial spin-orbit effects. Support by ERC Consolidator Grant MINT (No. 615759) is acknowledged.

  11. Effects of disorder on spin injection and extraction for organic semiconductor spin-valves

    SciTech Connect

    Shi, Sha Liu, Feilong; Smith, Darryl L.; Ruden, P. Paul

    2015-02-28

    A device model for tunnel injection and extraction of spin-polarized charge carriers between ferromagnetic contacts and organic semiconductors with disordered molecular states is presented. Transition rates for tunneling are calculated based on a transfer Hamiltonian. Transport in the bulk semiconductor is described by macroscopic device equations. Tunneling predominantly involves organic molecular levels near the metal Fermi energy, and therefore typically in the tail of the band that supports carrier transport in the semiconductor. Disorder-induced broadening of the relevant band plays a critical role for the injection and extraction of charge carriers and for the resulting magneto-resistance of an organic semiconductor spin valve.

  12. Spectral linewidth of spin-current nano-oscillators driven by nonlocal spin injection

    NASA Astrophysics Data System (ADS)

    Demidov, V. E.; Urazhdin, S.; Divinskiy, B.; Rinkevich, A. B.; Demokritov, S. O.

    2015-11-01

    We study experimentally the auto-oscillation characteristics of magnetic nano-oscillators driven by pure spin currents generated by nonlocal spin injection. By combining micro-focus Brillouin light scattering spectroscopy with electronic microwave spectroscopy, we are able to simultaneously perform both the spatial and the high-resolution spectral analyses of auto-oscillations induced by spin current. We find that the devices exhibit a highly coherent dynamics with the spectral linewidth of a few megahertz at room temperature. This narrow linewidth can be achieved over a wide range of operational frequencies, demonstrating a significant potential of nonlocal oscillators for applications.

  13. Spectral linewidth of spin-current nano-oscillators driven by nonlocal spin injection

    SciTech Connect

    Demidov, V. E. Divinskiy, B.; Urazhdin, S.; Rinkevich, A. B.; Demokritov, S. O.

    2015-11-16

    We study experimentally the auto-oscillation characteristics of magnetic nano-oscillators driven by pure spin currents generated by nonlocal spin injection. By combining micro-focus Brillouin light scattering spectroscopy with electronic microwave spectroscopy, we are able to simultaneously perform both the spatial and the high-resolution spectral analyses of auto-oscillations induced by spin current. We find that the devices exhibit a highly coherent dynamics with the spectral linewidth of a few megahertz at room temperature. This narrow linewidth can be achieved over a wide range of operational frequencies, demonstrating a significant potential of nonlocal oscillators for applications.

  14. Assistive Device for Efficient Intravitreal Injections.

    PubMed

    Ullrich, Franziska; Michels, Stephan; Lehmann, Daniel; Pieters, Roel S; Becker, Matthias; Nelson, Bradley J

    2016-08-01

    Intravitreal therapy is the most common treatment for many chronic ophthalmic diseases, such as age-related macular degeneration. Due to the increasing worldwide demand for intravitreal injections, there exists a need to render this medical procedure more time- and cost-efficient while increasing patient safety. The authors propose a medical assistive device that injects medication intravitreally. Compared to the manual intravitreal injection procedure, an automated device has the potential to increase safety for patients, decrease procedure times, allow for integrated data storage and documentation, and reduce costs for medical staff and expensive operating rooms. This work demonstrates the development of an assistive injection system that is coarsely positioned over the patient's head by the human operator, followed by automatic fine positioning and intravitreal injection through the pars plana. Several safety features, such as continuous eye tracking and iris recognition, have been implemented. The functioning system is demonstrated through ex vivo experiments with porcine eyes. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:752-762.]. PMID:27548453

  15. Electrical spin injection and detection in Si nanowires with axial doping gradient

    NASA Astrophysics Data System (ADS)

    Kountouriotis, Konstantinos; Barreda, Jorge; Keiper, Tim; Zhang, Mei; Xiong, Peng

    Due to the technological importance and potential long spin coherence time in silicon, there have been significant recent efforts to realize spin injection, coherent transport, and electrical spin detection in Si nanowires (NWs). The nature of the electronic transport at the interface and its resistance are crucial factors in realizing efficient spin injection/detection between a ferromagnet (FM) and a semiconductor (SC). In this work, we examine the effects on electrical spin injection and detection by FM/SC interfaces with well-defined Schottky barriers in Si NW devices. The Si NWs are synthesized via a vapor-liquid-solid method using silane and phosphine precursor gases for the growth and doping respectively, which results in a graded phosphorus doping profile along the length of the NW. The Si NWs are dispersed on a p+-Si/SiO2/SiNx substrate, and a series of CoFe electrodes are defined along a Si NW with electron beam lithography and magnetron sputtering after the removal of the native oxide by HF treatment. As a consequence of the doping gradient, the FM electrodes form Ohmic and Schottky barrier contacts of varying heights along the length of a single NW. Two-terminal local and four-terminal non-local spin-valve measurements are performed to probe spin accumulation and transport at different FM contacts, enabling a study of the dependence of the spin signals on the Schottky barrier height and interface resistance on a single device. Work supported by NSF Grant DMR-1308613.

  16. Time required to injection-lock spin torque nanoscale oscillators

    NASA Astrophysics Data System (ADS)

    Rippard, William; Pufall, Matthew; Kos, Anthony

    2013-10-01

    We have injection-locked a spin-transfer oscillator to a second-harmonic electrical input signal and measured the relative phase and amplitude of the device output as a function of DC current under steady-state conditions. The relative phase of the device varies quasi-linearly with DC bias, although the averaged amplitude decreases significantly outside of the spectrally determined locking range. By pulsing the injected microwaves, the time required for the device to phase-lock to the injected signal was measured as a function of microwave amplitude. The locking time varied quasi-linearly over the range of amplitudes studied, with the shortest locking times being a few nanoseconds.

  17. Nonlinear and Nonequilibrium Spin Injection in Magnetic Tunneling Junctions

    NASA Astrophysics Data System (ADS)

    Guo, Hong

    2007-03-01

    Quantitative analysis of charge and spin quantum transport in spintronic devices requires an atomistic first principles approach that can handle nonlinear and nonequilibrium transport conditions. We have developed an approach for this purpose based on real space density functional theory (DFT) carried out within the Keldysh nonequilibrium Green's function formalism (NEGF). We report theoretical analysis of nonlinear and nonequilibrium spin injection and quantum transport in Fe/MgO/Fe trilayer structures as a function of external bias voltage. Devices with well relaxed atomic structures and with FeO oxidization layers are investigated as a function of external bias voltage. We also report calculations of nonequilibrium spin injection into molecular layers and graphene. Comparisons to experimental data will be presented. Work in collaborations with: Derek Waldron, Vladimir Timochevski (McGill University); Ke Xia (Institute of Physics, Chinese Academy of Science, Beijing, China); Eric Zhu, Jian Wang (University of Hong Kong); Paul Haney, and Allan MacDonald (University of Texas at Austin).

  18. Non-local thermal spin injection to study spin diffusion in yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Giles, Brandon; Yang, Zihao; Jamison, John; Myers, Roberto

    Understanding the generation, detection, and manipulation of spin current is critical for the development of devices that depend on spin transport for information processing and storage. Recent studies have shown that spin transport over long distances is possible in the magnetic insulator yttrium iron garnet (YIG) through the diffusion of non-equilibrium magnons. Electrically excited magnons have been shown to diffuse up to 40um at room temperature, while thermally injected magnons were detected at ranges greater than 125um at 23K. However, much work is still required to fully understand the processes responsible for magnon diffusion. Here, we present an in-depth study of the diffusion of magnons in YIG. By using the non-local thermal spin detection method, we analyze spin transport as a function of temperature. Spin diffusion maps, which can be used to experimentally determine the spin diffusion length in YIG as a function of temperature, are presented Work supported by the Army Research Office MURI W911NF-14-1-0016.

  19. Electric-field control of electromagnon propagation and spin-wave injection in a spiral multiferroic/ferromagnet composite

    SciTech Connect

    Chen, Hong-Bo; Li, You-Quan; Berakdar, Jamal

    2015-01-28

    We consider theoretically a composite chain consisting of a multiferroic helimagnet coupled to a conventional ferromagnet and inspect the conversion of electromagnon excitation into spin waves and vice versa. We demonstrate an electric-field control of spin-wave injection realized by electrically exciting an electromagnon that propagates with an intrinsic frequency larger than the gap of the spin wave in the ferromagnet. The efficiency of the conversion of the electromagnon into spin waves depends strongly on the strength of the magnetoelectric coupling at the interface and the intrinsic frequency of the multiferroic helimagnets. The phenomena predicted here suggest that a multiferroic/ferromagnet composite offers new opportunities for spin-wave injection, conversion, and control using electric field.

  20. Ferromagnetic Resonance Spin Pumping and Electrical Spin Injection in Silicon-Based Metal-Oxide-Semiconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Pu, Y.; Odenthal, P. M.; Adur, R.; Beardsley, J.; Swartz, A. G.; Pelekhov, D. V.; Flatté, M. E.; Kawakami, R. K.; Pelz, J.; Hammel, P. C.; Johnston-Halperin, E.

    2015-12-01

    We present the measurement of ferromagnetic resonance (FMR-)driven spin pumping and three-terminal electrical spin injection within the same silicon-based device. Both effects manifest in a dc spin accumulation voltage Vs that is suppressed as an applied field is rotated to the out-of-plane direction, i.e., the oblique Hanle geometry. Comparison of Vs between these two spin injection mechanisms reveals an anomalously strong suppression of FMR-driven spin pumping with increasing out-of-plane field Happz . We propose that the presence of the large ac component to the spin current generated by the spin pumping approach, expected to exceed the dc value by 2 orders of magnitude, is the origin of this discrepancy through its influence on the spin dynamics at the oxide-silicon interface. This convolution, wherein the dynamics of both the injector and the interface play a significant role in the spin accumulation, represents a new regime for spin injection that is not well described by existing models of either FMR-driven spin pumping or electrical spin injection.

  1. Ferromagnetic Resonance Spin Pumping and Electrical Spin Injection in Silicon-Based Metal-Oxide-Semiconductor Heterostructures.

    PubMed

    Pu, Y; Odenthal, P M; Adur, R; Beardsley, J; Swartz, A G; Pelekhov, D V; Flatté, M E; Kawakami, R K; Pelz, J; Hammel, P C; Johnston-Halperin, E

    2015-12-11

    We present the measurement of ferromagnetic resonance (FMR-)driven spin pumping and three-terminal electrical spin injection within the same silicon-based device. Both effects manifest in a dc spin accumulation voltage V_{s} that is suppressed as an applied field is rotated to the out-of-plane direction, i.e., the oblique Hanle geometry. Comparison of V_{s} between these two spin injection mechanisms reveals an anomalously strong suppression of FMR-driven spin pumping with increasing out-of-plane field H_{app}^{z}. We propose that the presence of the large ac component to the spin current generated by the spin pumping approach, expected to exceed the dc value by 2 orders of magnitude, is the origin of this discrepancy through its influence on the spin dynamics at the oxide-silicon interface. This convolution, wherein the dynamics of both the injector and the interface play a significant role in the spin accumulation, represents a new regime for spin injection that is not well described by existing models of either FMR-driven spin pumping or electrical spin injection. PMID:26705647

  2. Spin injection into multilayer graphene from highly spin-polarized Co2FeSi Heusler alloy

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Takehiro; Moriya, Rai; Oki, Soichiro; Yamada, Shinya; Masubuchi, Satoru; Hamaya, Kohei; Machida, Tomoki

    2016-06-01

    We demonstrate electrical spin injection into multilayer graphene (MLG) in a lateral spin valve device from a highly spin-polarized Co2FeSi (CFS) Huesler electrode. Exfoliated MLG was transferred onto prepatterned epitaxial CFS wires grown on an Si(111) substrate by a polymer-based transfer method. This method enabled us to fabricate multiple single-crystal CFS electrodes in contact with MLG. Electrical spin injection from CFS to MLG was detected through nonlocal magnetoresistance (MR) measurement. A nonlocal spin signal of 430 Ω was observed; this is the largest value among all reported nonlocal MR values in graphene-based devices.

  3. Efficient room-temperature Spin Hall nano-oscillator

    NASA Astrophysics Data System (ADS)

    Zholud, Andrei; Urazhdin, Sergei

    2014-03-01

    Spin current injected into a ferromagnet exerts a spin torque on the magnetization, modifying its dynamical damping. Complete compensation of damping by spin current can result in magnetization auto-oscillations, as was demonstrated for in-plane point-contact spin Hall oscillator devices utilizing Pt spin Hall material as a source of spin current and permalloy (Py) as active magnetic layer. Electronic spectroscopy has demonstrated microwave generation by oscillations of magnetization at cryogenic temperatures, but this microwave generation decreases with increasing temperature and disappears at room temperature. We will describe a new device geometry that decouples spin transport from the magnetic configuration by separate patterning of the spin Hall Pt layer and the active Py layer. We demonstrate that this device geometry can operate at smaller driving dc currents for microwave generation that persists up to room temperature. We discuss the physical mechanisms that affect the temperature- and geometry-dependent performance of spin Hall nano-oscillators.

  4. Spin current injection by spin Seebeck and spin pumping effects in yttrium iron garnet/Pt structures

    NASA Astrophysics Data System (ADS)

    da Silva, G. L.; Vilela-Leão, L. H.; Rezende, S. M.; Azevedo, A.

    2012-04-01

    It is reported an investigation of pure spin current injection in Pt strips deposited on yttrium iron garnet (YIG) films by means of the spin pumping (SPE) and spin Seebeck (SSE) effects. Both effects were characterized by measuring the DC voltage created along the Pt strips by means of the inverse spin Hall effect (VISHE). SPE and SSE are simultaneously activated by exciting the ferromagnetic resonance (FMR) of the YIG film at the same time that a temperature gradient is created along the sample length. While the FMR signal is little affected by the temperature gradient, the voltage measured at the Pt strip placed at the lower temperature end exhibits a very challenging behavior. The voltage excited by the FMR uniform mode increases by six times as the temperature difference (ΔT) between the two ends of the YIG slab changes from 0 to 12 K. In contrast the VISHE generated by other magnetostatic spin-wave modes decreases to zero as ΔT varies from 0 to 12 K.

  5. Vertical Spin Current Injection induced Domain Wall Oscillations

    NASA Astrophysics Data System (ADS)

    Sharma, Sanchar; Muralidharan, Bhaskaran; Tulapurkar, Ashwin

    2015-03-01

    We present a novel oscillator based on domain wall motion using vertical spin current injection and an external magnetic field above the Walker breakdown. We numerically simulate 1D Landau-Lifshitz-Gilbert equation to extract the oscillation parameters such as the amplitude, the frequency and the Q-factor, as a function of the inputs. We also provide a theoretical analysis using rigid domain walls and find an approximate waveform for the oscillations. We find that the oscillation frequency is twice the resonant frequency of a magnet in an applied magnetic field; while the amplitude is approximately a linear function of the ratio of the demagnetization field and the applied magnetic field. Both of them are independent of input current and other material parameters to a very good degree of accuracy; and hence can be of great technological advantage for accurate oscillatory waveforms.

  6. Graphene-diamond interface: Gap opening and electronic spin injection

    NASA Astrophysics Data System (ADS)

    Ma, Yandong; Dai, Ying; Guo, Meng; Huang, Baibiao

    2012-06-01

    Creating a finite band gap, injecting electronic spin, and finding a suitable substrate are the three important challenges for building graphene-based devices. Here, first-principles calculations are performed to investigate the electronic and magnetic properties of graphene adsorbed on the (111) surface of diamond, which is synthesized experimentally [Nature10.1038/nature09979 472, 74 (2011); J. Appl. Phys.10.1063/1.3627370 110, 044324 (2011); Nano Lett.10.1021/nl204545q 12, 1603 (2012); ACS Nano10.1021/nn204362p 6, 1018 (2012)]. Our results reveal that the graphene adsorbed on the diamond surface is a semiconductor with a finite gap depending on the adsorption arrangements due to the variation of on-site energy induced by the diamond surface, with the extra advantage of maintaining main characters of the linear band dispersion of graphene. More interestingly, different from typical graphene/semiconductor hybrid systems, we find that electronic spin can arise ``intrinsically'' in graphene owing to the exchange proximity interaction between electrons in graphene and localized electrons in the diamond surface rather than the characteristic graphene states. These predications strongly revive this new synthesized system as a viable candidate to overcome all the aforementioned challenges, providing an ideal platform for future graphene-based electronics.

  7. Electrical spin injection using GaCrN in a GaN based spin light emitting diode

    SciTech Connect

    Banerjee, D.; Ganguly, S.; Saha, D.; Adari, R.; Sankaranarayan, S.; Kumar, A.; Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S.

    2013-12-09

    We have demonstrated electrical spin-injection from GaCrN dilute magnetic semiconductor (DMS) in a GaN-based spin light emitting diode (spin-LED). The remanent in-plane magnetization of the thin-film semiconducting ferromagnet has been used for introducing the spin polarized electrons into the non-magnetic InGaN quantum well. The output circular polarization obtained from the spin-LED closely follows the normalized in-plane magnetization curve of the DMS. A saturation circular polarization of ∼2.5% is obtained at 200 K.

  8. Microwave Manipulation of Electrically Injected Spin-Polarized Electrons in Silicon

    NASA Astrophysics Data System (ADS)

    Lo, C. C.; Li, J.; Appelbaum, I.; Morton, J. J. L.

    2014-02-01

    We demonstrate microwave manipulation of the spin states of electrically injected spin-polarized electrons in silicon. Although the silicon channel is bounded by ferromagnetic metal films, we show that moderate microwave power can be applied to the devices without altering the device operation significantly. Resonant microwave irradiation is used to induce spin rotation of spin-polarized electrons as they travel across a silicon channel, and the resultant spin polarization is subsequently detected by a ferromagnetic Schottky barrier spin detector. These results demonstrate the potential for combining advanced electron spin resonance techniques to complement the study of semiconductor spintronic devices beyond standard magnetotransport measurements.

  9. Enhanced efficiency of internal combustion engines by employing spinning gas

    NASA Astrophysics Data System (ADS)

    Geyko, V. I.; Fisch, N. J.

    2014-08-01

    The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency.

  10. Enhanced efficiency of internal combustion engines by employing spinning gas.

    PubMed

    Geyko, V I; Fisch, N J

    2014-08-01

    The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency. PMID:25215720

  11. Enhanced Efficiency of Internal Combustion Engines By Employing Spinning Gas

    SciTech Connect

    Geyko, Vasily; Fisch, Nathaniel

    2014-02-27

    The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A gain in fuel efficiency of several percent is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in the efficiency.

  12. Hot electron injection, vertical transport, and electrical spin detection in Silicon

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian; Huang, Biqin; Altfeder, Igor; Monsma, Douwe

    2007-03-01

    In our devices, spin-dependent hot electron transport through metallic ferromagnetic thin films is used to polarize a charge current injected into the conduction band of Si, and then to analyze the remaining polarization after vertical drift. Our measurements of a clear spin-valve signature indicate substantial electron spin polarization after transport through several microns of Si.

  13. Spin-injection optical pumping of molten cesium salt and its NMR diagnosis

    SciTech Connect

    Ishikawa, Kiyoshi

    2015-07-15

    Nuclear spin polarization of cesium ions in the salt was enhanced during optical pumping of cesium vapor at high magnetic field. Significant motional narrowing and frequency shift of NMR signals were observed by intense laser heating of the salt. When the hyperpolarized salt was cooled by blocking the heating laser, the signal width and frequency changed during cooling and presented the phase transition from liquid to solid. Hence, we find that the signal enhancement is mostly due to the molten salt and nuclear spin polarization is injected into the salt efficiently in the liquid phase. We also show that optical pumping similarly induces line narrowing in the solid phase. The use of powdered salt provided an increase in effective surface area and signal amplitude without glass wool in the glass cells.

  14. Spin-injection optical pumping of molten cesium salt and its NMR diagnosis

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kiyoshi

    2015-07-01

    Nuclear spin polarization of cesium ions in the salt was enhanced during optical pumping of cesium vapor at high magnetic field. Significant motional narrowing and frequency shift of NMR signals were observed by intense laser heating of the salt. When the hyperpolarized salt was cooled by blocking the heating laser, the signal width and frequency changed during cooling and presented the phase transition from liquid to solid. Hence, we find that the signal enhancement is mostly due to the molten salt and nuclear spin polarization is injected into the salt efficiently in the liquid phase. We also show that optical pumping similarly induces line narrowing in the solid phase. The use of powdered salt provided an increase in effective surface area and signal amplitude without glass wool in the glass cells.

  15. Electrical spin injection into GaAs based light emitting diodes using perpendicular magnetic tunnel junction-type spin injector

    NASA Astrophysics Data System (ADS)

    Tao, B. S.; Barate, P.; Frougier, J.; Renucci, P.; Xu, B.; Djeffal, A.; Jaffrès, H.; George, J.-M.; Marie, X.; Petit-Watelot, S.; Mangin, S.; Han, X. F.; Wang, Z. G.; Lu, Y.

    2016-04-01

    Remanent electrical spin injection into an InGaAs/GaAs based quantum well light emitting diode is realized by using a perpendicularly magnetized MgO/CoFeB/Ta/CoFeB/MgO spin injector. We demonstrate that the Ta interlayer plays an important role to establish the perpendicular magnetic anisotropy and the thickness of Ta interlayer determines the type of exchange coupling between the two adjacent CoFeB layers. They are ferromagnetically or antiferromagnetically coupled for a Ta thickness of 0.5 nm or 0.75 nm, respectively. A circular polarized electroluminescence (Pc) of about 10% is obtained at low temperature and at zero magnetic field. The direction of the electrically injected spins is determined only by the orientation of the magnetization of the bottom CoFeB layer which is adjacent to the MgO/GaAs interface. This work proves the critical role of the bottom CoFeB/MgO interface on the spin-injection and paves the way for the electrical control of spin injection via magnetic tunnel junction-type spin injector.

  16. Reduction of ammonia emission by shallow slurry injection: injection efficiency and additional energy demand.

    PubMed

    Hansen, Martin N; Sommer, Sven G; Madsen, Niels P

    2003-01-01

    Ammonia (NH3) emission from livestock production causes undesirable environmental effects and a loss of plant-available nitrogen. Much atmospheric NH3 is lost from livestock manure applied in the field. The NH3 emission may be reduced by slurry injection, but slurry injection in general, and especially on grassland, increases the energy demand and places heavy demands on the slurry injection techniques used. The reduction in NH3 emission, injection efficiency, and energy demand of six different shallow slurry-injection techniques was examined. The NH3 emission from cattle slurry applied to grassland was reduced by all the injectors tested in the study, but there were major differences in the NH3 reduction potential of the different types of injectors. Compared with the trailing hose spreading technique, the NH3 loss was reduced by 75% when cattle slurry was injected using the most efficient slurry injection technique, and by 20% when incorporated by the least efficient injection technique. The reduction in NH3 emission was correlated with injection depth and the volume of the slot created. The additional energy demand for reducing ammonia emissions by slurry injection was approximately 13 000 kJ ha(-1) for a 20% reduction and 34 000 kJ ha(-1) for a 75% reduction. The additional energy demand corresponds to additional emissions of, respectively, 5.6 and 14.5 kg CO2 per ha injected. PMID:12809311

  17. Optical spin- and current-injection study on Si(111)-In surfaces

    NASA Astrophysics Data System (ADS)

    Arzate, N.; Vázquez-Nava, R. A.; Mendoza, Bernardo S.

    2014-11-01

    We present a theoretical study of the optical generation of one-photon spin and current injection onto In-adsorbed Si(111) surfaces with 4 ×2 and 8 ×2 reconstructions. The spin injection, under incidence of circularly polarized light into nonmagnetic semiconductors, creates spin-polarized electrons in the conduction bands. The current injection is a nonlinear second-order effect that is allowed in materials without inversion symmetry. In bulk centrosymmetric crystals, the optical injection of current can only be observed at the surface wherein the inversion of symmetry might be broken. We report calculations for the degree of spin polarization and current-injection spectra which are calculated in a full electronic band structure scheme at the level of GW scissor-energy correction. Our results show an anisotropic behavior of the spin- and current-injection optical response. We obtain maximum percentages of the degree of spin polarization of 30% and 35% for the 4 ×2 and 8 ×2 surface reconstructions, respectively. It is also possible to optically generate injection current coming mainly from the first two top layers on both In-adsorbed surface reconstructions.

  18. Electrical spin injection and detection of spin precession in room temperature bulk GaN lateral spin valves

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Aniruddha; Baten, Md Zunaid; Bhattacharya, Pallab

    2016-01-01

    We report the measurement of diffusive electronic spin transport characteristics in an epitaxial wurtzite GaN lateral spin valve at room temperature. Hanle spin precession and non-local spin accumulation measurements have been performed with the spin valves fabricated with FeCo/MgO spin contacts. Electron spin relaxation length and spin-flip lifetime of 176 nm and 37 ps, respectively, are derived from analysis of results obtained from four-terminal Hanle spin precession measurements at 300 K. The role of dislocations and defects in bulk GaN has also been examined in the context of electronic spin relaxation dynamics.

  19. High spin-filter efficiency and Seebeck effect through spin-crossover iron-benzene complex

    NASA Astrophysics Data System (ADS)

    Yan, Qiang; Zhou, Liping; Cheng, Jue-Fei; Wen, Zhongqian; Han, Qin; Wang, Xue-Feng

    2016-04-01

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

  20. High spin-filter efficiency and Seebeck effect through spin-crossover iron-benzene complex.

    PubMed

    Yan, Qiang; Zhou, Liping; Cheng, Jue-Fei; Wen, Zhongqian; Han, Qin; Wang, Xue-Feng

    2016-04-21

    Electronic structures and coherent quantum transport properties are explored for spin-crossover molecule iron-benzene Fe(Bz)2 using density functional theory combined with non-equilibrium Green's function. High- and low-spin states are investigated for two different lead-molecule junctions. It is found that the asymmetrical T-shaped contact junction in the high-spin state behaves as an efficient spin filter while it has a smaller conductivity than that in the low-spin state. Large spin Seebeck effect is also observed in asymmetrical T-shaped junction. Spin-polarized properties are absent in the symmetrical H-shaped junction. These findings strongly suggest that both the electronic and contact configurations play significant roles in molecular devices and metal-benzene complexes are promising materials for spintronics and thermo-spintronics. PMID:27389217

  1. Effects of spin doping and spin injection in the luminescence and vibrational spectrum of C{sub 60}

    SciTech Connect

    Moorsom, Timothy; Wheeler, May; Taukeer Khan, Mohd; Al Ma'Mari, Fatma; Burnell, Gavin; Hickey, Bryan J.; Cespedes, Oscar; Lazarov, Vlado; Gilks, Daniel

    2014-07-14

    We have studied the Raman spectrum and photoemission of hybrid magneto-fullerene devices. For C{sub 60} layers on cobalt, the spin polarized electron transfer shifts the photoemission energy, reducing the zero phonon contribution. The total luminescence of hybrid devices can be controlled via spin injection from magnetic electrodes, with changes of the order of 10%–20% at room temperature. Spin polarised currents alter as well the Raman spectrum of the molecules, enhancing some modes by a factor 5 while shifting others by several wavenumbers due to a spin-dependent hopping time and/or enhanced intermolecular interactions. These results can be used to measure spin polarisation in molecules or to fabricate magneto-optic and magneto-vibrational devices.

  2. Electrical spin injection and detection in Fe/MgO/Si: influence of interface states

    NASA Astrophysics Data System (ADS)

    Pu, Yong; Beardsley, Jonas; Swartz, Adrain; Odenthal, Patrick; Berger, Andrew; Ko, Dongkyun; Bhallamudi, Vydia; Hammel, Chris; Kawakami, Roland; Johnston-Halperin, Ezekiel; Pelz, Jon

    2012-02-01

    We report electrical spin injection and detection in Fe/MgO/Si tunnel diodes using a 3-terminal (3T) geometry. Analysis of our Hanle curves yields an effective spin life-time of ˜0.1 ns and a spin-RA product ˜1 Mφ*μm^2, both of which are in rough agreement with previous 3T studies. However, according to our analysis the spin-RA is ˜ 6 orders of magnitude larger than expectations for bulk Si, and the 0.1 ns effective spin life-time is much smaller than reported value in Si by ESR or non-local methods. Here we provide a detailed analysis of electrical injection and detection in the 3T geometry. We present an alternative expression for the 3T spin signal than is usually used, and we propose that spin is accumulating in localized states (LS) at the MgO/Si interface rather than just in bulk Si. Incorporating a theory of spin accumulation in LS developed by M. Tran et al (PRL 102, 036601), we propose an energy distribution for the density of localized states, and introduce a model that agrees well with our anomalously large spin-RA and can explain the strong bias dependence of both spin and charge transport.

  3. Spin-current injection and detection in κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br

    SciTech Connect

    Qiu, Z. Hou, D.; Uruichi, M.; Uchida, K.; Yamamoto, H. M.; Saitoh, E.

    2015-05-15

    Spin-current injection into an organic semiconductor κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br film induced by the spin pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage signal was found to appear in the κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br film. Magnetic-field-angle dependence measurements indicate that the voltage signal is governed by the inverse spin Hall effect in κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br. We found that the voltage signal in the κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br/YIG system is critically suppressed around 80 K, around which magnetic and/or glass transitions occur, implying that the efficiency of the spin-current injection is suppressed by fluctuations which critically enhanced near the transitions.

  4. Self-Injection Locking of a Vortex Spin Torque Oscillator by Delayed Feedback

    PubMed Central

    Tsunegi, Sumito; Grimaldi, Eva; Lebrun, Romain; Kubota, Hitoshi; Jenkins, Alex S.; Yakushiji, Kay; Fukushima, Akio; Bortolotti, Paolo; Grollier, Julie; Yuasa, Shinji; Cros, Vincent

    2016-01-01

    The self-synchronization of spin torque oscillators is investigated experimentally by re-injecting its radiofrequency (rf) current after a certain delay time. We demonstrate that the integrated power and spectral linewidth are improved for optimal delays. Moreover by varying the phase difference between the emitted power and the re-injected one, we find a clear oscillatory dependence on the phase difference with a 2π periodicity of the frequency of the oscillator as well as its power and linewidth. Such periodical behavior within the self-injection regime is well described by the general model of nonlinear auto-oscillators including not only a delayed rf current but also all spin torque forces responsible for the self-synchronization. Our results reveal new approaches for controlling the non-autonomous dynamics of spin torque oscillators, a key issue for rf spintronics applications as well as for the development of neuro-inspired spin-torque oscillators based devices. PMID:27241747

  5. Self-Injection Locking of a Vortex Spin Torque Oscillator by Delayed Feedback.

    PubMed

    Tsunegi, Sumito; Grimaldi, Eva; Lebrun, Romain; Kubota, Hitoshi; Jenkins, Alex S; Yakushiji, Kay; Fukushima, Akio; Bortolotti, Paolo; Grollier, Julie; Yuasa, Shinji; Cros, Vincent

    2016-01-01

    The self-synchronization of spin torque oscillators is investigated experimentally by re-injecting its radiofrequency (rf) current after a certain delay time. We demonstrate that the integrated power and spectral linewidth are improved for optimal delays. Moreover by varying the phase difference between the emitted power and the re-injected one, we find a clear oscillatory dependence on the phase difference with a 2π periodicity of the frequency of the oscillator as well as its power and linewidth. Such periodical behavior within the self-injection regime is well described by the general model of nonlinear auto-oscillators including not only a delayed rf current but also all spin torque forces responsible for the self-synchronization. Our results reveal new approaches for controlling the non-autonomous dynamics of spin torque oscillators, a key issue for rf spintronics applications as well as for the development of neuro-inspired spin-torque oscillators based devices. PMID:27241747

  6. Self-Injection Locking of a Vortex Spin Torque Oscillator by Delayed Feedback

    NASA Astrophysics Data System (ADS)

    Tsunegi, Sumito; Grimaldi, Eva; Lebrun, Romain; Kubota, Hitoshi; Jenkins, Alex S.; Yakushiji, Kay; Fukushima, Akio; Bortolotti, Paolo; Grollier, Julie; Yuasa, Shinji; Cros, Vincent

    2016-05-01

    The self-synchronization of spin torque oscillators is investigated experimentally by re-injecting its radiofrequency (rf) current after a certain delay time. We demonstrate that the integrated power and spectral linewidth are improved for optimal delays. Moreover by varying the phase difference between the emitted power and the re-injected one, we find a clear oscillatory dependence on the phase difference with a 2π periodicity of the frequency of the oscillator as well as its power and linewidth. Such periodical behavior within the self-injection regime is well described by the general model of nonlinear auto-oscillators including not only a delayed rf current but also all spin torque forces responsible for the self-synchronization. Our results reveal new approaches for controlling the non-autonomous dynamics of spin torque oscillators, a key issue for rf spintronics applications as well as for the development of neuro-inspired spin-torque oscillators based devices.

  7. Ultrafast spin tunneling and injection in coupled nanostructures of InGaAs quantum dots and quantum well

    SciTech Connect

    Yang, Xiao-Jie Kiba, Takayuki; Yamamura, Takafumi; Takayama, Junichi; Subagyo, Agus; Sueoka, Kazuhisa; Murayama, Akihiro

    2014-01-06

    We investigate the electron-spin injection dynamics via tunneling from an In{sub 0.1}Ga{sub 0.9}As quantum well (QW) to In{sub 0.5}Ga{sub 0.5}As quantum dots (QDs) in coupled QW-QDs nanostructures. These coupled nanostructures demonstrate ultrafast (5 to 20 ps) spin injection into the QDs. The degree of spin polarization up to 45% is obtained in the QDs after the injection, essentially depending on the injection time. The spin injection and conservation are enhanced with thinner barriers due to the stronger electronic coupling between the QW and QDs.

  8. Spin injection from topological insulator into metal leads

    NASA Astrophysics Data System (ADS)

    Aseev, P. P.; Artemenko, S. N.

    2015-03-01

    We study theoretically helical edge and surface states of 2D and 3D topological insulators (TI) tunnel-coupled to metal leads and show that their transport properties are strongly affected by contacts as the latter play a role of a heat bath and induce damping and relaxation of electrons in the helical states of TI. A simple structure that produces a pure spin current in the external circuit is proposed. The current and the spin current delivered to the external circuit depend on the relation between characteristic lengths: decay length due to tunneling, contact length and, in case of 3D TI, mean free path and spin relaxation length caused by momentum scattering. If the decay length due to tunneling is the smallest one, then the electric and spin currents are of order of the conductance quantum in 2D TI, and of order of the conductance quantum multiplied by the ratio of the contact width to the Fermi wavelength in 3D TI. A role of electron-electron interaction is discussed in case of 2D TI, and it is shown that in contrast to the conventional Luttinger liquid picture the interaction can be treated perturbatively. The presence of interaction results in suppression of density of states at the Fermi level and hence in decrease of the electric and spin currents.

  9. Effect of CoFe insertion in Co{sub 2}MnSi/CoFe/n-GaAs junctions on spin injection properties

    SciTech Connect

    Ebina, Yuya; Akiho, Takafumi; Liu, Hong-xi; Yamamoto, Masafumi; Uemura, Tetsuya

    2014-04-28

    The CoFe thickness (t{sub CoFe}) dependence of spin injection efficiency was investigated for Co{sub 2}MnSi/CoFe/n-GaAs junctions. The ΔV{sub NL}/I value, which is a measure of spin injection efficiency, strongly depended on t{sub CoFe}, where ΔV{sub NL} is the amplitude of a nonlocal spin-valve signal, and I is an injection current. Importantly, the maximum value of ΔV{sub NL}/I for a Co{sub 2}MnSi/CoFe/n-GaAs junction was one order of magnitude higher than that for a CoFe/n-GaAs junction, indicating that a Co{sub 2}MnSi electrode works as a highly polarized spin source. No clear spin signal, on the other hand, was observed for a Co{sub 2}MnSi/n-GaAs junction due to diffusion of Mn atoms into the GaAs channel. Secondary ion mass spectrometry analysis indicated that the CoFe insertion effectively suppressed the diffusion of Mn into GaAs, resulting in improved spin injection properties compared with those for a Co{sub 2}MnSi/n-GaAs junction.

  10. Efficient Injection of Electron Beams into Magnetic Guide Fields

    SciTech Connect

    Chorny, V.; Cooperstein, G.; Dubyna, V.; Frolov, O.; Harper-Slaboszewicz, V.; Hinshelwood, D.; Schneider, R.; Solovyov, V.; Tsepilov, H.; Vitkovitsky, I.; Ware, K,

    1999-06-08

    Preliminary experimental and modeling study of injection and transport of high current electron beams in current-neutralized background gas has been performed. Initial analysis of the results indicates that high current triaxial ring diode operates very reproducibly in the pinch mode. High current density beam can be injected efficiently into the drift region, using azimuthal guide field with reduced intensity near the injection region. This was shown to improve the effectiveness of capturing the beam for the transport. The transport length was insufficient to measure losses, such as would arise from scattering with the background gas.

  11. Electrical Spin Injection and Detection in Silicon: Effect of Interface States

    NASA Astrophysics Data System (ADS)

    Bearsdley, Jonas; Pu, Yong; Swartz, Adrian; Odenthal, Pat; Berger, Andrew; Ko, Dongkyun; Bhallamudi, Vidya; Hammel, Peter Christopher; Kawakami, Roland; Johnston-Halperin, Ezekiel; Pelz, Jon

    2012-02-01

    We have observed (using the local Hanle method) electrical spin injection into n and p type Si through a Fe/MgO/Si tunnel, with an effective spin lifetime of ˜130ps and an extremely large spin RA product as high as ˜0.1 Mφ*μm^2 at low bias and temperature. Both the spin-RA and the differential resistance decrease exponentially with bias at temperatures below 150K. The effective spin lifetime weakly depends on temperature, decreasing by ˜30% from 10K to 300K. We observe the inverse Hanle effect when an external magnetic field is applied parallel to the magnetization, possibly indicating the presence of stray fields near the Si surface. These observations roughly agree with other local Hanle spin injection studies in Silicon and GaAs, but differ strongly from the results expected for injection into bulk Silicon. The two stage tunneling model through localized states (LS) developed by Tran et al (PRL 102; p. 036601) can explain the large magnitude of the observed spin RA, and we have developed an extended LS model which can explain the voltage dependence, which will be discussed in another talk.

  12. Efficient spin filter using multi-terminal quantum dot with spin-orbit interaction

    PubMed Central

    2011-01-01

    We propose a multi-terminal spin filter using a quantum dot with spin-orbit interaction. First, we formulate the spin Hall effect (SHE) in a quantum dot connected to three leads. We show that the SHE is significantly enhanced by the resonant tunneling if the level spacing in the quantum dot is smaller than the level broadening. We stress that the SHE is tunable by changing the tunnel coupling to the third lead. Next, we perform a numerical simulation for a multi-terminal spin filter using a quantum dot fabricated on semiconductor heterostructures. The spin filter shows an efficiency of more than 50% when the conditions for the enhanced SHE are satisfied. PACS numbers: 72.25.Dc,71.70.Ej,73.63.Kv,85.75.-d PMID:21711500

  13. Broadband injection and scattering of spin waves in lossy width-modulated magnonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Arikan, M.; Au, Y.; Vasile, G.; Ingvarsson, S.; Kruglyak, V. V.

    2013-04-01

    We have used the time-resolved scanning Kerr microscopy to study the spin-wave injection from the semi-infinite magnetic films (‘reservoirs’) into unmodulated (straight) and periodically modulated magnonic waveguides. The measurements reveal a broadband nature of the spin-wave injection in the frequency domain. The demonstrated tunability range of 0.8 GHz is determined by the linewidth of the reservoir's uniform resonance peak. In contrast to the unmodulated waveguide, we have observed a standing spin wave in the modulated waveguide that existed as a result of a direct coupling between the global microwave field and the finite wavelength spin waves mediated by the spatial periodicity of the waveguide. The measurements are discussed in terms of the important role played by magnetic damping in magnonics.

  14. Spin injection studies on thin film Fe/MgO/Si tunneling devices

    NASA Astrophysics Data System (ADS)

    Beardsley, Jonas; Pu, Yong; Swartz, Adrian; Bhallamudi, Vidya; Kawakami, Roland; Johnston-Halperin, Ezekiel; Hammel, Chris; Pelz, Jon

    2011-03-01

    We report progress on the injection of spin polarized electrons into 35 nm thick Si films, using Fe/MgO injector/tunnel barrier structures grown by molecular beam epitaxy on SIMOX silicon-on-insulator substrates. The device requires heavy top-surface n-type doping of the Si film to produce a suitable tunnel barrier, accomplished by diffusion from a spin-on phosphorous-doped glass. Measurements indicate a roughly exponential doping profile with 7E20 per cubic cm at the top surface and a 2 nm decay length. Three terminal measurements showed evidence of spin injection similar to reports of Jansen et al., while injection with a thinner MgO barrier shows more complicated behavior. On-going measurements and modeling will be discussed.

  15. Electric field effects on spin accumulation in Nb-doped SrTiO{sub 3} using tunable spin injection contacts at room temperature

    SciTech Connect

    Kamerbeek, A. M.; Vries, E. K. de; Wees, B. J. van; Banerjee, T.; Dankert, A.; Dash, S. P.

    2014-05-26

    We report on features in charge transport and spin injection in an oxide semiconductor, Nb-doped SrTiO{sub 3}. This is demonstrated using electrically tunable spin injection contacts which exploit the large electric field at the interface and its interplay with the relative permittivity of the semiconductor. We realize spin accumulation in Nb-doped SrTiO{sub 3} which displays a unique dependence of the spin lifetime with bias polarity. These findings suggest a strong influence of the interface electric field on the charge transport as well as on spin accumulation unlike in conventional semiconductors and opens up promising avenues in oxide spintronics.

  16. Reprint of : Transient dynamics of spin-polarized injection in helical Luttinger liquids

    NASA Astrophysics Data System (ADS)

    Calzona, A.; Carrega, M.; Dolcetto, G.; Sassetti, M.

    2016-08-01

    We analyze the time evolution of spin-polarized electron wave packets injected into the edge states of a two-dimensional topological insulator. In the presence of electron interactions, the system is described as a helical Luttinger liquid and injected electrons fractionalize. However, because of the presence of metallic detectors, no evidences of fractionalization are encoded in dc measurements, and in this regime the system does not show deviations from its non-interacting behavior. Nevertheless, we show that the helical Luttinger liquid nature emerges in the transient dynamics, where signatures of charge/spin fractionalization can be clearly identified.

  17. Long-range spin accumulation from heat injection in mesoscopic superconductors with Zeeman splitting.

    PubMed

    Silaev, M; Virtanen, P; Bergeret, F S; Heikkilä, T T

    2015-04-24

    We describe far-from-equilibrium nonlocal transport in a diffusive superconducting wire with a Zeeman splitting, taking into account different spin relaxation mechanisms. We demonstrate that due to the Zeeman splitting, an injection of current in a superconducting wire creates spin accumulation that can only relax via thermalization. This effect leads to a long-range spin accumulation detectable in the nonlocal signal. Our model gives a qualitative explanation and provides accurate fits of recent experimental results in terms of realistic parameters. PMID:25955071

  18. Highly efficient 6-stroke engine cycle with water injection

    SciTech Connect

    Szybist, James P; Conklin, James C

    2012-10-23

    A six-stroke engine cycle having improved efficiency. Heat is recovered from the engine combustion gases by using a 6-stroke engine cycle in which combustion gases are partially vented proximate the bottom-dead-center position of the fourth stroke cycle, and water is injected proximate the top-dead-center position of the fourth stroke cycle.

  19. The study of charge injection and spin polarization in ferromagnetic metal-polymer-ferromagnetic metal structure

    NASA Astrophysics Data System (ADS)

    Zhao, Hua; Liu, Zhong-Wang; Chen, Shao-Bo; Chang, Liu-An

    2014-10-01

    By using extended SSH Hamiltonian plus long-range electron correlation Hamiltonian model, we calculated charge injection and spin polarization in a ferromagnetic metal/polymer/ferromagnetic metal structure. We adjust relative chemical potential between the ferromagnetic materials and the polymer to control charge transfer. It is found that when spin orientations of two ferromagnetic materials are parallel to each other, spin-polarized single polaron can be formed in the polymer, but when the spin orientations of two ferromagnetic materials are antiparallel to each other, bipolaron is formed and that spin polarization is found to be zero inside the polymer. The influence of the long-range electronic correlation on these polarons in the polymer is discussed.

  20. Communication: An efficient algorithm for evaluating the Breit and spin-spin coupling integrals

    NASA Astrophysics Data System (ADS)

    Shiozaki, Toru

    2013-03-01

    We present an efficient algorithm for evaluating a class of two-electron integrals of the form {r}_{12}⊗ {r}_{12}/r_{12}^n over one-electron Gaussian basis functions. The full Breit interaction in four-component relativistic theories beyond the Gaunt term is such an operator with n = 3. Another example is the direct spin-spin coupling term in the quasi-relativistic Breit-Pauli Hamiltonian (n = 5). These integrals have been conventionally evaluated by expensive derivative techniques. Our algorithm is based on tailored Gaussian quadrature, similar to the Rys quadrature for electron repulsion integrals (ERIs), and can utilize the so-called horizontal recurrence relation to reduce the computational cost. The CPU time for computing all six Cartesian components of the Breit or spin-spin coupling integrals is found to be only 3 to 4 times that of the ERI evaluation.

  1. Communication: An efficient algorithm for evaluating the Breit and spin-spin coupling integrals.

    PubMed

    Shiozaki, Toru

    2013-03-21

    We present an efficient algorithm for evaluating a class of two-electron integrals of the form r12⊗r12/r12(n) over one-electron Gaussian basis functions. The full Breit interaction in four-component relativistic theories beyond the Gaunt term is such an operator with n = 3. Another example is the direct spin-spin coupling term in the quasi-relativistic Breit-Pauli Hamiltonian (n = 5). These integrals have been conventionally evaluated by expensive derivative techniques. Our algorithm is based on tailored Gaussian quadrature, similar to the Rys quadrature for electron repulsion integrals (ERIs), and can utilize the so-called horizontal recurrence relation to reduce the computational cost. The CPU time for computing all six Cartesian components of the Breit or spin-spin coupling integrals is found to be only 3 to 4 times that of the ERI evaluation. PMID:23534619

  2. Tunneling Spectroscopy Study of Spin-Polarized Quasiparticle Injection Effects in Cuparate/Manganite Heterostructures

    NASA Technical Reports Server (NTRS)

    Wei, J. Y. T.; Yeh, N. C.; Vasquez, R. P.

    1998-01-01

    Scanning tunneling spectroscopy was performed at 4.2K on epitaxial thin-film heterostructures comprising YBa2Cu3O7 and La0.7Ca0.3MnO3, to study the microscopic effects of spin-polarized quasiparticle injection from the half-metallic ferromagnetic manganite on the high-Tc cuprate superconductor.

  3. Efficient demagnetization protocol for the artificial triangular spin ice

    NASA Astrophysics Data System (ADS)

    Rodrigues, J. H.; Mól, L. A. S.; Moura-Melo, W. A.; Pereira, A. R.

    2013-08-01

    In this work, we study demagnetization protocols for an artificial spin ice in a triangular geometry. Our results show that a simple hysteresis-like process is very efficient in driving the system to its ground state, even for a relatively strong disorder in the system, confirming previous expectations. In addition, transitions between the magnetized state and the ground state were observed to be mediated by the creation and propagation of vertices that behave like magnetic monopoles pseudo-particles. This is an important step towards a more detailed experimental study of monopole-like excitations in artificial spin ice systems.

  4. High domain wall velocities via spin transfer torque using vertical current injection

    PubMed Central

    Metaxas, Peter J.; Sampaio, Joao; Chanthbouala, André; Matsumoto, Rie; Anane, Abdelmadjid; Fert, Albert; Zvezdin, Konstantin A.; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji; Cros, Vincent; Grollier, Julie

    2013-01-01

    Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm2. Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching. PMID:23670402

  5. High domain wall velocities via spin transfer torque using vertical current injection.

    PubMed

    Metaxas, Peter J; Sampaio, Joao; Chanthbouala, André; Matsumoto, Rie; Anane, Abdelmadjid; Fert, Albert; Zvezdin, Konstantin A; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji; Cros, Vincent; Grollier, Julie

    2013-01-01

    Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm(2). Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching. PMID:23670402

  6. High domain wall velocities via spin transfer torque using vertical current injection

    NASA Astrophysics Data System (ADS)

    Metaxas, Peter J.; Sampaio, Joao; Chanthbouala, André; Matsumoto, Rie; Anane, Abdelmadjid; Fert, Albert; Zvezdin, Konstantin A.; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji; Cros, Vincent; Grollier, Julie

    2013-05-01

    Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm2. Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching.

  7. Enhanced Tunnel Spin Injection into Graphene using Chemical Vapor Deposited Hexagonal Boron Nitride

    PubMed Central

    Kamalakar, M. Venkata; Dankert, André; Bergsten, Johan; Ive, Tommy; Dash, Saroj P.

    2014-01-01

    The van der Waals heterostructures of two-dimensional (2D) atomic crystals constitute a new paradigm in nanoscience. Hybrid devices of graphene with insulating 2D hexagonal boron nitride (h-BN) have emerged as promising nanoelectronic architectures through demonstrations of ultrahigh electron mobilities and charge-based tunnel transistors. Here, we expand the functional horizon of such 2D materials demonstrating the quantum tunneling of spin polarized electrons through atomic planes of CVD grown h-BN. We report excellent tunneling behavior of h-BN layers together with tunnel spin injection and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN tunnel contacts, we observe enhancements in both spin signal amplitude and lifetime by an order of magnitude. We demonstrate spin transport and precession over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our results and complementary magnetoresistance calculations illustrate that CVD h-BN tunnel barrier provides a reliable, reproducible and alternative approach to address the conductivity mismatch problem for spin injection into graphene. PMID:25156685

  8. Enhanced tunnel spin injection into graphene using chemical vapor deposited hexagonal boron nitride.

    PubMed

    Kamalakar, M Venkata; Dankert, André; Bergsten, Johan; Ive, Tommy; Dash, Saroj P

    2014-01-01

    The van der Waals heterostructures of two-dimensional (2D) atomic crystals constitute a new paradigm in nanoscience. Hybrid devices of graphene with insulating 2D hexagonal boron nitride (h-BN) have emerged as promising nanoelectronic architectures through demonstrations of ultrahigh electron mobilities and charge-based tunnel transistors. Here, we expand the functional horizon of such 2D materials demonstrating the quantum tunneling of spin polarized electrons through atomic planes of CVD grown h-BN. We report excellent tunneling behavior of h-BN layers together with tunnel spin injection and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN tunnel contacts, we observe enhancements in both spin signal amplitude and lifetime by an order of magnitude. We demonstrate spin transport and precession over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our results and complementary magnetoresistance calculations illustrate that CVD h-BN tunnel barrier provides a reliable, reproducible and alternative approach to address the conductivity mismatch problem for spin injection into graphene. PMID:25156685

  9. Low-resistance spin injection into silicon using graphene tunnel barriers

    NASA Astrophysics Data System (ADS)

    van't Erve, O. M. J.; Friedman, A. L.; Cobas, E.; Li, C. H.; Robinson, J. T.; Jonker, B. T.

    2012-12-01

    Spin manipulation in a semiconductor offers a new paradigm for device operation beyond Moore's law. Ferromagnetic metals are ideal contacts for spin injection and detection, but the intervening tunnel barrier required to accommodate the large difference in conductivity introduces defects, trapped charge and material interdiffusion, which severely compromise performance. Here, we show that single-layer graphene successfully circumvents the classic issue of conductivity mismatch between a metal and a semiconductor for electrical spin injection and detection, providing a highly uniform, chemically inert and thermally robust tunnel barrier. We demonstrate electrical generation and detection of spin accumulation in silicon above room temperature, and show that the contact resistance-area products are two to three orders of magnitude lower than those achieved with oxide tunnel barriers on silicon substrates with identical doping levels. Our results identify a new route to low resistance-area product spin-polarized contacts, a key requirement for semiconductor spintronic devices that rely on two-terminal magnetoresistance, including spin-based transistors, logic and memory.

  10. Controlling the spin-torque efficiency with ferroelectric barriers

    NASA Astrophysics Data System (ADS)

    Useinov, A.; Chshiev, M.; Manchon, A.

    2015-02-01

    Nonequilibrium spin-dependent transport in magnetic tunnel junctions comprising a ferroelectric barrier is theoretically investigated. The exact solutions of the free electron Schrödinger equation for electron tunneling in the presence of interfacial screening are obtained by combining Bessel and Airy functions. We demonstrate that the spin transfer torque efficiency, and more generally the bias dependence of tunneling magneto- and electroresistance, can be controlled by switching the ferroelectric polarization of the barrier. In particular, the critical voltage at which the in-plane torque changes sign can be strongly enhanced or reduced depending on the direction of the ferroelectric polarization of the barrier. This effect provides a supplementary way to electrically control the current-driven dynamic states of the magnetization and related magnetic noise in spin transfer devices.

  11. Spin Contrast Variation Study of Fuel-efficient Tire Rubber

    NASA Astrophysics Data System (ADS)

    Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Shamoto, Shin-ichi; Koizumi, Satoshi; Yuasa, Takeshi; Tominaga, Tetsuo; Sone, Takuo

    The scattering length of a proton against a polarized neutron depends strongly on the polarization of proton spins (PH). This dependence can be utilized for contrast variation in small angle neutron scattering (SANS). We applied this spin contrast variation technique to a silica-filled SBR rubber specimen, which is widely used for tread rubber of fuel-efficient tires. For realizing high PH, we used dynamic nuclear polarization (DNP) technique, in which large polarization of electron spin at low temperature and high magnetic field is transferred to proton spin by microwave irradiation with a tuned frequency. As this electron spin source, we doped stable radical TEMPO (2,2,6,6-tetramethyl piperidine 1-oxyl) into the rubber sample by use of a vapor sorption technique. For the TEMPO-doped rubber sample, SANS measurements were conducted at PH = -20%, 0%, and +13%, with almost fully polarized neutron beam %) with its wavelength of 6.5±0.6 Å. The SANS profile clearly changed as a function of PH, which can be explained by the PH dependence of the neutron scattering length densities of the main three components (SBR, silica and zinc oxide). By a linear transformation of the profiles obtained at the three different PH values, we successfully determined the partial scattering function of silica, which reflects the aggregation of silica particles.

  12. Growth-temperature dependence of optical spin-injection dynamics in self-assembled InGaAs quantum dots

    SciTech Connect

    Yamamura, Takafumi; Kiba, Takayuki; Yang, Xiaojie; Takayama, Junichi; Subagyo, Agus; Sueoka, Kazuhisa; Murayama, Akihiro

    2014-09-07

    The growth-temperature dependence of the optical spin-injection dynamics in self-assembled quantum dots (QDs) of In{sub 0.5}Ga{sub 0.5}As was studied by increasing the sheet density of the dots from 2 × 10{sup 10} to 7 × 10{sup 10} cm{sup −2} and reducing their size through a decrease in growth temperature from 500 to 470 °C. The circularly polarized transient photoluminescence (PL) of the resulting QD ensembles was analyzed after optical excitation of spin-polarized carriers in GaAs barriers by using rate equations that take into account spin-injection dynamics such as spin-injection time, spin relaxation during injection, spin-dependent state-filling, and subsequent spin relaxation. The excitation-power dependence of the transient circular polarization of PL in the QDs, which is sensitive to the state-filling effect, was also examined. It was found that a systematic increase occurs in the degree of circular polarization of PL with decreasing growth temperature, which reflects the transient polarization of exciton spin after spin injection. This is attributed to strong suppression of the filling effect for the majority-spin states as the dot-density of the QDs increases.

  13. Spin currents injected electrically and thermally from highly spin polarized Co{sub 2}MnSi

    SciTech Connect

    Pfeiffer, Alexander; Reeve, Robert M.; Kronenberg, Alexander; Jourdan, Martin; Kläui, Mathias; Hu, Shaojie; Kimura, Takashi

    2015-08-24

    We demonstrate the injection and detection of electrically and thermally generated spin currents probed in Co{sub 2}MnSi/Cu lateral spin valves. Devices with different electrode separations are patterned to measure the non-local signal as a function of the electrode spacing and we determine a relatively high effective spin polarization α of Co{sub 2}MnSi to be 0.63 and the spin diffusion length of Cu to be 500 nm at room temperature. The electrically generated non-local signal is measured as a function of temperature and a maximum signal is observed for a temperature of 80 K. The thermally generated non-local signal is measured as a function of current density and temperature in a second harmonic measurement detection scheme. We find different temperature dependences for the electrically and thermally generated non-local signals, which allows us to conclude that the temperature dependence of the signals is not just dominated by the transport in the Cu wire, but there is a crucial contribution from the different generation mechanisms, which has been largely disregarded till date.

  14. Engineering of spin injection and spin transport in organic spin valves using π-conjugated polymer brushes

    NASA Astrophysics Data System (ADS)

    Geng, Rugang; Roy, Anandi; Subedi, Ram; Locklin, Jason; Nguyen, Tho; Zhao, Wenbo; Li, Xiaoguang

    Charge transport in amorphous organic semiconductors is governed by carriers hopping between localized states with small spin diffusion length. Furthermore, the spin interfacial resistance of organic spin valves (OSVs) is poorly controlled resulting in controversial reports of the magnetoresistance response. Here, we used surface initiated Kumada transfer polycondensation to covalently graft π-conjugated poly(3-methylthiophene) brushes from the La0.67Sr0.33MnO3 (LSMO) bottom electrode. The covalent attachment along with the brush morphology allows for more control over the LSMO/brush interfacial resistance and large spacer mobility. Remarkably, with 15 nm brush spacer layer, we observed an optimum magnetoresistance (MR) effect of 70% at cryogenic temperatures and a MR of 2.7% at 280K. The temperature dependence of the MR is nearly an order of magnitude weaker than that found in control OSVs made from spin-coated poly(3-hexylthiophene). Using a variety of different brush layer thicknesses, the thickness dependent MR at 20K was investigated. A spin diffusion length of 20 nm at 5 mV junction voltage rapidly increases to 55 nm at -280 mV. We acknowledge NSF (CHE 1412714 and DMR 0953112) (J.L.), the UGA start-up funds and Faculty Research Grant (T.N.), NSFC and NBRPC (2012CB922003 and 2015CB921201, X.G.L.) for funding this work.

  15. Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire

    PubMed Central

    Zhang, S. F.; Gan, W. L.; Kwon, J.; Luo, F. L.; Lim, G. J.; Wang, J. B.; Lew, W. S.

    2016-01-01

    Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~1012 A/m2. Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 1011 A/m2. Micromagnetic simulations reveal the evolution of the domain nucleation – first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line. PMID:27098108

  16. Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire.

    PubMed

    Zhang, S F; Gan, W L; Kwon, J; Luo, F L; Lim, G J; Wang, J B; Lew, W S

    2016-01-01

    Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~10(12) A/m(2). Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 10(11) A/m(2). Micromagnetic simulations reveal the evolution of the domain nucleation - first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line. PMID:27098108

  17. Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire

    NASA Astrophysics Data System (ADS)

    Zhang, S. F.; Gan, W. L.; Kwon, J.; Luo, F. L.; Lim, G. J.; Wang, J. B.; Lew, W. S.

    2016-04-01

    Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~1012 A/m2. Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 1011 A/m2. Micromagnetic simulations reveal the evolution of the domain nucleation – first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line.

  18. Bias dependence of spin injection/transport properties of a perpendicularly magnetized FePt/MgO/GaAs structure

    NASA Astrophysics Data System (ADS)

    Ohsugi, Rento; Kunihashi, Yoji; Sanada, Haruki; Kohda, Makoto; Gotoh, Hideki; Sogawa, Tetsuomi; Nitta, Junsaku

    2016-04-01

    We demonstrate injection and transport of perpendicularly spin-polarized electrons in an FePt/MgO/n-GaAs structure. Spin-polarized electrons were injected from a perpendicularly magnetized FePt layer into an n-GaAs layer through a MgO barrier and detected by spatially resolved Kerr rotation microscopy. By measuring the Hanle effect, we reveal that the injected/extracted spin polarizations drastically vary with bias voltages. A spin lifetime of 3.5 ns is obtained that is consistent with the result from pump-probe measurements. This direct observation of perpendicularly polarized spin injection and lateral transport is one step toward realizing future spintronic devices.

  19. Analysis of the Injection Efficiency Saturation in Polyfluorene Copolymers

    NASA Astrophysics Data System (ADS)

    Dunlap, David; Lu, Tianjian; Fong, Hon Hang; Malliaras, George

    2007-03-01

    Recent experiments of the transport of holes across a 1 - 5 μm layers of the copolymer poly [9,9-dioctylfluorenyl-2,7-diyl)- co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) reveal an injection efficiency that saturates at high voltages, which is indicative of space-charge-limited current. The injection efficiency is on the order of 10-3, three orders of magnitude smaller than what would be expected if the current followed the Mott-Gurney law. It is difficult to explain this behavior as arising from trapping phenomena, for time of flight transients show clear plateaus, and the extracted mobility is only weakly dependent on temperature[1]. We propose that the behavior may be accounted for by an interface dipole at the metal/organic injecting contact which is dependent on the applied voltage. Quantitative support to for this mechanism is obtained through numerical simulations of the convection-diffusion equation. [1] H. H. Fong, A. Papadimitratos, and G. G. Malliaras, Appl. Phys. Lett. 89 (2006) 172116

  20. High Efficiency Spin Flipper for the n3He Experiment

    NASA Astrophysics Data System (ADS)

    Hayes, Christopher; n3He Collaboration

    2015-10-01

    The n3He experiment, constructed on the Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source, is designed to measure the parity violating (PV) proton asymmetry Ap in the capture reaction n +3 He -->3 H + p + 765 keV The asymmetry has an estimated value Ap ~ - 1 ×10-7 and is directly related to the weak isospin conserved couplings hρ0 and ωρ0 which are of fundamental interest in the verification of the meson exchange model of low energy NN intereactions. Data production for the n3He experiment began in February 2015 and is scheduled to continue thru December 2015 - reaching a statistical sensitivity δAp ~10-8 or better. I will discuss the spin flipper which is designed using the theory of double cosine-theta coils, and capable of flipping neutron spins with an efficiency approaching its maximum value ɛsf = 1 . I will also discuss the theory of Spin Magnetic Resonance (SMR) and how it is employed by the spin flipper to flip 60 Hz pulses of cold neutrons over a range of wavelengths.

  1. Injection efficiency of bound modes. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio Oliveira

    1990-01-01

    Previous work on efficiency of light injection into the core of a fiber from a thin film and a bulk distribution of sources in the cladding have used the fields of a weakly guiding fiber. This approximation simplifies the analysis of the power efficiency by introducing universal values for the eigenvalues of different fibers with the same V-number, but cannot predict accurately the behavior of the injected light into a fiber with arbitrary differences in indices of refraction. The exact field solution was used in the expressions of the power efficiency, p sub eff, and its behavior as a function of the fiber parameter was analyzed. Weakly guiding results obtained previously are confirmed. However, P sub eff does not always increase with the V-number but with the difference in the indices of refraction, eta sub core-eta sub clad. For the bulk distribution it was found that P sub eff increases with the wavelength, lambda, and decreases with the fiber core radius, a, i.e., it decreases with the V-number. However, for the thin film, the P sub eff remains almost constant with lambda and the fiber core radius.

  2. Tunnel spin injection into graphene through ALD-grown tunnel barrier

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Takehiro; Masubuchi, Satoru; Iguchi, Kazuyuki; Moriya, Rai; Machida, Tomoki

    2012-02-01

    Graphene is a promising material for spintronics devices because of its long spin relaxation time due to weak spin-orbit interaction and hyperfine interaction. For the spintronics, it is very essential to develop a reliable method to inject spin polarized electrons into graphene from ferromagnetic electrodes. In this study, between ferromagnetic electrodes and graphene we fabricated a new type of Al2O3 tunnel barrier grown by atomic layer deposition (ALD). Before ALD of Al2O3, we functionalized the surface of graphene with a self-assembled monolayer of 3, 4, 9, 10 perylene tetracarboxylic acid (PTCA) to improve adhesion and growth of Al2O3. Using ALD-Al2O3/PTCA composite barrier, large nonlocal magnetoresistance of 30 φ was observed at 45 K. Nonlocal magnetoresistance reached maximum around charge neutrality point, and I-V characteristics of the contacts are nonlinear. These results indicate the achievement of tunnel spin injection into graphene, revealing potentially high performance of ALD-Al2O3/PTCA tunnel barrier [1]. [1] T. Yamaguchi et al., J. Magn. Magn. Mater. (2011), doi: 10. 1016/j.jmmm. 2011. 09. 031

  3. Pseudocontinuous arterial spin labeling with optimized tagging efficiency.

    PubMed

    Shin, David D; Liu, Thomas T; Wong, Eric C; Shankaranarayanan, Ajit; Jung, Youngkyoo

    2012-10-01

    The adiabatic inversion of blood in pseudocontinuous arterial spin labeling (PCASL) is highly sensitive to off-resonance effects and gradient imperfections and this sensitivity can lead to tagging efficiency loss and unpredictable variations in cerebral blood flow estimates. This efficiency loss is caused by a phase tracking error between the RF pulses and the flowing spins. This article introduces a new method, referred to as Optimized PCASL (OptPCASL), that minimizes the phase tracking error by applying an additional compensation RF phase term and in-plane gradients to the PCASL pulse train. The optimal RF phase and gradient amplitudes are determined using a prescan procedure, which consists of a series of short scans interleaved with automated postprocessing routines integrated to the scanner console. The prescan procedure is shown to minimize the phase tracking error in a robust and time efficient manner. As an example of its application, the use of OptPCASL for the improved detection of functional activation in the visual cortex is demonstrated and temporal signal-to-noise ratio (SNR), image SNR, and baseline cerebral blood flow measures are compared to those acquired from conventional PCASL. PMID:22234782

  4. Electronic and magnetic properties of ferromagnetic interfaces for spin injection applications: metallic and semiconducting cases

    NASA Astrophysics Data System (ADS)

    Albanesi, E. A.; Makinistian, L.; Zandalazini, C. I.; Oszwaldowski, R. M.; Petukhov, A. G.

    Robust and reliable operation of spintronic devices is determined by the quality of interfaces between magnetic and nonmagnetic materials. In order to get insights in the tuning of the magnetic properties of such interfaces we present comparative studies of two important cases relevant to applications in spin injection devices. We performed ab-initio calculations of the electronic and magnetic properties, of the ferromagnetic metallic interface of Co2MnAl and gold, and of the interfaces of non-and of magnetic II-VI semiconductors and their quantum wells. In the case of the Heusler alloy Co2MnAl-Au, two structural models are implemented: one with the ferromagnet slab terminated in a pure cobalt plane (Co2-t), and the other with it terminated with a plane of MnAl (MnAl-t). The electric in-plane and averaged potential are resolved and analyzed layer by layer through the interface. We predict that both terminations are to be expected to display sensibly different spin injection performances. On the example of magnetic quantum wells of ZnSeZnxMn1-xTeZnSe, we study the variations in the spin resolved density of states, and the potential energy along the junctions. We acknowledge finantial support from SDSMT (USA), and CONICET, FIUNER, of Argentina.

  5. Efficient spin transfer phenomena in Fe/MgO/GaAs structure

    NASA Astrophysics Data System (ADS)

    Park, Y. J.; Hickey, M. C.; Van Veenhuizen, M. J.; Chang, J.; Heiman, D.; Perry, C. H.; Moodera, J. S.

    2011-03-01

    The efficiency of spin polarized charge transfer was investigated in an Fe/MgO tunnel barrier/GaAs based structure using spin dependent photocurrent measurements, whereby a spin imbalance in carrier population was generated in the GaAs by circularly polarized light. The dominance of tunneling transport processes over Schottky emission gave rise to a high spin transfer efficiency of 35% under the photovoltaic mode of device operation. A spin dependent tunneling conductance associated with spin polarized electron transport was identified by the observation of phase changes. This transport prevails over the unpolarized electron and hole conduction over the bias range which corresponds to flat band conditions.

  6. Efficient gate control of spin-valve signals and Hanle signals in GaAs channel with p-i-n junction-type back-gate structure

    NASA Astrophysics Data System (ADS)

    Miyakawa, Takumi; Akiho, Takafumi; Ebina, Yuya; Yamamoto, Masafumi; Uemura, Tetsuya

    2016-02-01

    Efficient gate control of spin-valve signals and Hanle signals was achieved in a GaAs channel with a p-i-n back-gate structure. Experiments showed that the amplitude of the spin-valve signal (ΔVNL) under constant-injection-current conditions increased for a cross nonlocal geometry when the channel was depleted by the gate voltage (VG). In contrast, the VG dependence of ΔVNL for a nonlocal geometry was complicated. The gate modulation efficiency of spin signals was approximately 50 times that with a graphene or Si channel.

  7. Electrical injection and detection of spin accumulation in silicon at 500 K with magnetic metal/silicon dioxide contacts.

    PubMed

    Li, C H; van 't Erve, O M J; Jonker, B T

    2011-01-01

    The International Technology Roadmap for Semiconductors has identified the electron's spin angular momentum as a new state variable that should be explored as an alternative to the electron's charge for use beyond the size scaling of Moore's Law. A major obstacle has been achieving control of the spin variable at temperatures required for practical applications. Here we demonstrate electrical injection, detection and precession of spin accumulation in silicon, the cornerstone material of device technology, at temperatures that easily exceed these requirements. We observe Hanle precession of electron spin accumulation in silicon for a wide range of bias, show that the magnitude of the Hanle signal agrees well with theory, and that the spin lifetime varies with silicon carrier density. These results confirm spin accumulation in the silicon transport channel to 500 K rather than trapping in localized interface states, and enable utilization of the spin variable in practical device applications. PMID:21427716

  8. Observation of the inverse spin Hall effect in ZnO thin films: An all-electrical approach to spin injection and detection

    SciTech Connect

    Prestgard, Megan C.; Tiwari, Ashutosh

    2014-03-24

    The inverse spin Hall effect (ISHE) is a newly discovered, quantum mechanical phenomenon where an applied spin current results in the generation of an electrical voltage in the transverse direction. It is anticipated that the ISHE can provide a more simple way of measuring spin currents in spintronic devices. The ISHE was first observed in noble metals that exhibit strong spin-orbit coupling. However, recently, the ISHE has been detected in conventional semiconductors (such as Si and Ge), which possess weak spin-orbit coupling. This suggests that large-spin orbit coupling is not a requirement for observing the ISHE. In this paper, we are reporting the observation of the ISHE in an alternative semiconductor material, zinc oxide (ZnO) using all-electrical means. In our study, we found that when a spin-polarized current is injected into the ZnO film from a NiFe ferromagnetic injector via an MgO tunnel barrier layer, a voltage transverse to both the direction of the current as well as its spin-polarization is generated in the ZnO layer. The polarity of this voltage signal was found to flip on reversing the direction of the injected current as well as on reversing the polarization of the current, consistent with the predictions of the ISHE process. Through careful analysis of the ISHE data, we determined a spin-Hall angle of approximately 1.651 × 10{sup −2} for ZnO, which is two orders of magnitude higher than that of silicon. Observation of a detectable room-temperature ISHE signal in ZnO via electrical injection and detection is a groundbreaking step that opens a path towards achieving transparent spin detectors for next-generation spintronic device technology.

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

    NASA Astrophysics Data System (ADS)

    van't Erve, Olaf

    2014-03-01

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

  10. Nanoscale Magnetic Materials for Energy-Efficient Spin Based Transistors

    NASA Astrophysics Data System (ADS)

    Incorvia, Jean Anne Currivan

    In this dissertation, I study the physical behavior of nanoscale magnetic materials and build spin-based transistors that encode information in magnetic domain walls. It can be argued that energy dissipation is the most serious problem in modern electronics, and one that has been resistant to a breakthrough. Wasted heat during computing both wastes energy and hinders further technology scaling. This is an opportunity for physicists and engineers to come up with creative solutions for more energy-efficient computing. I present the device we have designed, called domain wall logic (DW-Logic). Information is stored in the position of a magnetic domain wall in a ferromagnetic wire and read out using a magnetic tunnel junction. This hybrid design uses electrical current as the input and output, keeping the device compatible with charge- based transistors. I build an iterative model to predict both the micromagnetic and circuit behavior of DW- Logic, showing a single device can operate as a universal gate. The model shows we can build complex circuits including an 18-gate Full Adder, and allows us to predict the device switching energy compared to complementary metal-oxide semiconductor (CMOS) transistors. Comparing ?15 nm feature nodes, I find DW-Logic made with perpendicular magnetic anisotropy materials, and utilizing both spin torque transfer and the Spin Hall effect, could operate with 1000x reduced switching energy compared to CMOS. I fabricate DW-Logic device prototypes and show in experiment they can act as AND and NAND gates. I demonstrate that one device can drive two subsequent devices, showing gain, which is a necessary requirement for fanout. I also build a clocked ring oscillator circuit to demonstrate successful bit propagation in a DW-Logic circuit and show that properly scaled devices can have improved operation. Through building the devices, I develop a novel fabrication method for patterning sub-25 nm magnetic wires with very low (˜ 2 nm) average edge

  11. Hole spin injection from a GaMnAs layer into GaAs-AlAs-InGaAs resonant tunneling diodes

    NASA Astrophysics Data System (ADS)

    Rodrigues, D. H.; Brasil, M. J. S. P.; Orlita, M.; Kunc, J.; Galeti, H. V. A.; Henini, M.; Taylor, D.; Galvão Gobato, Y.

    2016-04-01

    We have investigated the polarization-resolved electroluminescence (EL) of a p-i-n GaAs/AlAs/InGaAs resonant tunneling diode (RTD) containing a GaMnAs (x  =  5%) spin injector under high magnetic fields. We demonstrate that under hole resonant tunneling condition, the GaMnAs contact acts as an efficient spin-polarized source for holes tunneling through the device. Polarization degrees up to 80% were observed in the device around the hole resonance at 2 K under 15 T. Our results could be valuable for improving the hole-spin injection in GaMnAs-based spintronic devices.

  12. Spin polarized current injection through HgBr{sub 2} intercalated Bi2212 intrinsic Josephson junctions.

    SciTech Connect

    Ozyuzer, L.; Kurter, C.; Ozdemir, M.; Zasadzinski, J. F.; Gray, K. E.; Hinks, D. G.

    2007-06-01

    To investigate the effect of polarized current on tunneling characteristics of intrinsic Josephson junctions (IJJs), spin-polarized and spin-degenerate current have been injected through the c-axis of HgBr{sub 2} intercalated Bi{sub 2.1}Sr{sub 1.5}Ca{sub 1.4}Cu{sub 2}O{sub 8+delta} (Bi2212) single crystals on which 10 times 10 mum{sup 2} mesas have been fabricated. These two spin conditions are achieved by depositing either Au (15 nm)/Co (80 nm)/Au (156 nm) multilayers or single Au film on HgBr{sub 2} intercalated Bi2212 with T{sub c} = 74 K followed by photolithography and Ar ion beam etching. The I-V characteristics have been measured with and without a magnetic field parallel to c-axis at 4.2 K. A fine, soft Au wire is used to make a gentle mechanical contact on the top of a particular mesa in the array. Tunneling conductance characteristics were obtained and the magnetic field dependence of sumgap voltage peaks was investigated. These peaks do not change in position with increasing magnetic field for both contact configurations. In addition, the temperature dependence of tunneling characteristics of the IJJs are obtained and existence of pseudogap feature is observed above T{sub c} for HgBr{sub 2} intercalated Bi2212.

  13. Accurate and efficient spin integration for particle accelerators

    NASA Astrophysics Data System (ADS)

    Abell, Dan T.; Meiser, Dominic; Ranjbar, Vahid H.; Barber, Desmond P.

    2015-02-01

    Accurate spin tracking is a valuable tool for understanding spin dynamics in particle accelerators and can help improve the performance of an accelerator. In this paper, we present a detailed discussion of the integrators in the spin tracking code gpuSpinTrack. We have implemented orbital integrators based on drift-kick, bend-kick, and matrix-kick splits. On top of the orbital integrators, we have implemented various integrators for the spin motion. These integrators use quaternions and Romberg quadratures to accelerate both the computation and the convergence of spin rotations. We evaluate their performance and accuracy in quantitative detail for individual elements as well as for the entire RHIC lattice. We exploit the inherently data-parallel nature of spin tracking to accelerate our algorithms on graphics processing units.

  14. Abnormal bias dependence of magnetoresistance in CoFeB/MgO/Si spin-injection tunnel contacts

    SciTech Connect

    Park, June-Young; Park, Byong-Guk; Baek, Seung-heon Chris; Park, Seung-Young; Jo, Younghun

    2015-11-02

    We report a strong bias voltage dependence of magnetoresistance (MR) in CoFeB/MgO/Si spin-injection tunnel contacts using the three-terminal Hanle geometry. When a bias voltage is relatively large, the MR is composed of two characteristic signals: a conventional Hanle signal observed at a low magnetic field, which is due to the precession of injected spins, and another signal originating from the rotation of the magnetization at a larger magnetic field. In contrast, for a small bias voltage, additional signals appear at a wide range of magnetic fields, which occasionally overwhelms the conventional Hanle signals. Because the additional signals are pronounced at a low bias and are significantly reduced by annealing at moderate temperatures, they can be attributed to multi-step tunneling via defect states at the interfaces or tunnel barrier. Our results demonstrate that the spin injection signal caused by the defect states can be evaluated by its bias voltage dependence.

  15. Efficient spin filter and spin valve in a single-molecule magnet Fe4 between two graphene electrodes

    NASA Astrophysics Data System (ADS)

    Zu, Feng-Xia; Gao, Guo-Ying; Fu, Hua-Hua; Xiong, Lun; Zhu, Si-Cong; Peng, Li; Yao, Kai-Lun

    2015-12-01

    We propose a magnetic molecular junction consisting of a single-molecule magnet Fe4 connected two graphene electrodes and investigate transport properties, using the nonequilibrium Green's function method in combination with spin-polarized density-functional theory. The results show that the device can be used as a nearly perfect spin filter with efficiency approaching 100%. Our calculations provide crucial microscopic information how the four iron cores of the chemical structure are responsible for the spin-resolved transmissions. Moreover, it is also found that the device behaves as a highly efficient spin valve, which is an excellent candidate for spintronics of molecular devices. The idea of combining single-molecule magnets with graphene provides a direction in designing a new class of molecular spintronic devices.

  16. Efficient spin filter and spin valve in a single-molecule magnet Fe{sub 4} between two graphene electrodes

    SciTech Connect

    Zu, Feng-Xia; Gao, Guo-Ying; Fu, Hua-Hua; Peng, Li; Yao, Kai-Lun; Xiong, Lun; Zhu, Si-Cong

    2015-12-21

    We propose a magnetic molecular junction consisting of a single-molecule magnet Fe{sub 4} connected two graphene electrodes and investigate transport properties, using the nonequilibrium Green's function method in combination with spin-polarized density-functional theory. The results show that the device can be used as a nearly perfect spin filter with efficiency approaching 100%. Our calculations provide crucial microscopic information how the four iron cores of the chemical structure are responsible for the spin-resolved transmissions. Moreover, it is also found that the device behaves as a highly efficient spin valve, which is an excellent candidate for spintronics of molecular devices. The idea of combining single-molecule magnets with graphene provides a direction in designing a new class of molecular spintronic devices.

  17. Electrical spin injection in modulation-doped GaAs from an in situ grown Fe/MgO layer

    SciTech Connect

    Shim, Seong Hoon; Kim, Hyung-jun; Koo, Hyun Cheol; Lee, Yun-Hi; Chang, Joonyeon

    2015-09-07

    We study spin accumulation in n-doped GaAs that were electrically injected from Fe via MgO using three-terminal Hanle measurement. The Fe/MgO/GaAs structures were prepared in a cluster molecular beam epitaxy that did not require the breaking of the vacuum. We found the crystal orientation relationship of epitaxial structures Fe[100]//MgO[110]//GaAs[110] without evident defects at the interface. Control of depletion width and interface resistance by means of modulation doping improves spin injection, leading to enhanced spin voltage (ΔV) of 6.3 mV at 10 K and 0.8 mV even at 400 K. The extracted spin lifetime and spin diffusion length of GaAs are 220 ps and 0.77 μm, respectively, at 200 K. MgO tunnel barrier grown in situ with modulation doping at the interface appears to be promising for spin injection into GaAs.

  18. Electrical injection and detection of spin-polarized currents in topological insulator Bi2Te2Se

    PubMed Central

    Tian, Jifa; Miotkowski, Ireneusz; Hong, Seokmin; Chen, Yong P.

    2015-01-01

    Topological insulators (TIs) are an unusual phase of quantum matter with nontrivial spin-momentum-locked topological surface states (TSS). The electrical detection of spin-momentum-locking of TSS has been lacking till very recently. Many of the results are from samples with significant bulk conduction, such as Bi2Se3, where it can be challenging to separate the surface and bulk contribution to the spin signal. Here, we report spin potentiometric measurements in flakes exfoliated from bulk insulating Bi2Te2Se crystals, using two outside nonmagnetic contacts for driving a DC spin helical current and a middle ferromagnetic (FM)-Al2O3 contact for detecting spin polarization. The voltage measured by the FM electrode exhibits a hysteretic step-like change when sweeping an in-plane magnetic field between opposite directions along the easy axis of the FM contact. Importantly, the direction of the voltage change can be reversed by reversing the direction of current, and the amplitude of the change as measured by the difference in the detector voltage between opposite FM magnetization increases linearly with increasing current, consistent with the current-induced spin polarization of spin-momentum-locked TSS. Our work directly demonstrates the electrical injection and detection of spin polarization in TI and may enable utilization of TSS for applications in nanoelectronics and spintronics. PMID:26391089

  19. Electrical injection and detection of spin-polarized currents in topological insulator Bi2Te2Se

    NASA Astrophysics Data System (ADS)

    Tian, Jifa; Miotkowski, Ireneusz; Hong, Seokmin; Chen, Yong P.

    2015-09-01

    Topological insulators (TIs) are an unusual phase of quantum matter with nontrivial spin-momentum-locked topological surface states (TSS). The electrical detection of spin-momentum-locking of TSS has been lacking till very recently. Many of the results are from samples with significant bulk conduction, such as Bi2Se3, where it can be challenging to separate the surface and bulk contribution to the spin signal. Here, we report spin potentiometric measurements in flakes exfoliated from bulk insulating Bi2Te2Se crystals, using two outside nonmagnetic contacts for driving a DC spin helical current and a middle ferromagnetic (FM)-Al2O3 contact for detecting spin polarization. The voltage measured by the FM electrode exhibits a hysteretic step-like change when sweeping an in-plane magnetic field between opposite directions along the easy axis of the FM contact. Importantly, the direction of the voltage change can be reversed by reversing the direction of current, and the amplitude of the change as measured by the difference in the detector voltage between opposite FM magnetization increases linearly with increasing current, consistent with the current-induced spin polarization of spin-momentum-locked TSS. Our work directly demonstrates the electrical injection and detection of spin polarization in TI and may enable utilization of TSS for applications in nanoelectronics and spintronics.

  20. Electrical injection and detection of spin-polarized currents in topological insulator Bi2Te2Se.

    PubMed

    Tian, Jifa; Miotkowski, Ireneusz; Hong, Seokmin; Chen, Yong P

    2015-01-01

    Topological insulators (TIs) are an unusual phase of quantum matter with nontrivial spin-momentum-locked topological surface states (TSS). The electrical detection of spin-momentum-locking of TSS has been lacking till very recently. Many of the results are from samples with significant bulk conduction, such as Bi2Se3, where it can be challenging to separate the surface and bulk contribution to the spin signal. Here, we report spin potentiometric measurements in flakes exfoliated from bulk insulating Bi2Te2Se crystals, using two outside nonmagnetic contacts for driving a DC spin helical current and a middle ferromagnetic (FM)-Al2O3 contact for detecting spin polarization. The voltage measured by the FM electrode exhibits a hysteretic step-like change when sweeping an in-plane magnetic field between opposite directions along the easy axis of the FM contact. Importantly, the direction of the voltage change can be reversed by reversing the direction of current, and the amplitude of the change as measured by the difference in the detector voltage between opposite FM magnetization increases linearly with increasing current, consistent with the current-induced spin polarization of spin-momentum-locked TSS. Our work directly demonstrates the electrical injection and detection of spin polarization in TI and may enable utilization of TSS for applications in nanoelectronics and spintronics. PMID:26391089

  1. Spin thermoelectric efficiency across a normal-metal/ferromagnetic-insulator interface

    NASA Astrophysics Data System (ADS)

    Yan, Yonghong; Wu, Haifei; Jiang, Feng

    2016-08-01

    We investigate the spin and heat transport across a normal-metal/ferromagnetic-insulator (NM/FI) interface based on the s-d exchange model. Under a certain temperature gradient, the heat current carried by magnons partly flows into the metal, and is partly converted to spin power corresponding to spin current. We find that when the magnon dispersion of the FI (such as yttrium iron garnet) is quadratic, the conversion efficiency of heat current to spin power is about ηs ∼ 0.2ηC with ηC being the Carnot efficiency. The corresponding spin thermopower is roughly Ss ∼ 110 μ V / K . The efficiency and the spin thermopower can be enhanced by opening a gap via, for example, introducing a magnetic field. Effects of temperature in the presence of a gap and dimensionality are also discussed briefly.

  2. Dynamic neutron scattering on incoherent systems using efficient resonance spin flip techniques

    SciTech Connect

    Häussler, Wolfgang; Kredler, Lukas

    2014-05-15

    We have performed numerical ray-tracing Monte-Carlo-simulations of incoherent dynamic neutron scattering experiments. We intend to optimize the efficiency of incoherent measurements depending on the fraction of neutrons scattered without and with spin flip at the sample. In addition to conventional spin echo, we have numerically and experimentally studied oscillating intensity techniques. The results point out the advantages of these different spin echo variants and are an important prerequisite for neutron resonance spin echo instruments like RESEDA (FRM II, Munich), to choose the most efficient technique depending on the scattering vector range and the properties of the sample system under study.

  3. Probing the Spin Transfer Efficiency at Topological Insulator/Ferromagnetic Insulator Interfaces

    NASA Astrophysics Data System (ADS)

    Wang, Hailong; Kally, James; Lee, Joon Sue; Richardella, Anthony; Kempinger, Susan; Pan, Yu; Kamp, Eric; Samarth, Nitin; Liu, Tao; Chang, Houcheng; Wu, Mingzhong; Reifsnyder-Hickey, Danielle; Mkhoyan, Andre

    The development of next-generation spintronics devices has driven extensive studies of spin-charge conversion through measurement of the inverse spin Hall effect (ISHE) and ferromagnetic resonance (FMR) driven spin pumping of pure spin currents in ferromagnet/non-magnet bilayers. Topological insulators (TIs) such as the Bi-chalcogenides are naturally relevant in this context because the inherent spin-momentum ``locking'' in their surface states promises very efficient spin-charge conversion, although the first experimental studies have involved ferromagnetic metals that provide a shunting current path [e.g. Nature, 511,449 (2014)]. To circumvent the current shunting problem, we are growing and characterizing bilayers of TIs and the ferrimagnetic insulator Y3Fe5O12 (YIG). Here, we report measurements of FMR-driven spin pumping in TI/YIG bilayers, showing robust spin pumping signals at room temperature. Analysis of the ISHE voltages and FMR linewidth broadening show that, as in other studies of spin pumping into TIs [Nano Lett., 15 (10) (2015)], the interface condition presents a critical challenge for enhancing the spin conversion efficiency in these devices. Funded by C-SPIN/SRC/DARPA and ONR.

  4. High-efficiency spin-resolved and spin-integrated electron detection: Parallel mounting on a hemispherical analyzer

    NASA Astrophysics Data System (ADS)

    Ghiringhelli, G.; Larsson, K.; Brookes, N. B.

    1999-11-01

    We have mounted a compact 25 kV mini-Mott spin polarimeter on a commercial high-throughput hemispherical electron analyzer with a double purpose: to maximize the polarization detection and to preserve the original efficiency of the spectrometer in the spin-integrated measurements. We have thus replaced the 16-anode microchannel-plate detector with a 12-anode microsphere-plate detector in parallel with a Rice University retarding Mott spin polarimeter. Passing from one detection mode to the other is quick and easy. The transfer optics from the analyzer exit slit to the scattering target of the polarimeter allows the full potential of both the electron analyzer and the spin detector to be exploited. The expected effective Sherman function (Seff=0.17) and figure of merit (η0≅1.4×10-4) are found in the spin-resolved mode, and only 25% of the original efficiency is lost in the spin-integrated acquisitions.

  5. CFD modeling could optimize sorbent injection system efficiency

    SciTech Connect

    Blankinship, S.

    2006-01-15

    Several technologies will probably be needed to remove mercury from coal-plant stack emissions as mandated by new mercury emission control legislation in the USA. One of the most promising mercury removal approaches is the injection of a sorbent, such as powdered activated carbon (PAC), to make it much more controllable. ADA-ES recently simulated field tests of sorbent injection at New England Power Company's Brayton Point Power Plant in Somerset, Mass., where activated carbon sorbent was injected using a set of eight lances upstream of the second of two electrostatic precipitators (ESPs). Consultants from Fluent created a computational model of the ductwork and injection lances. The simulation results showed that the flue gas flow was poorly distributed at the sorbent injection plane, and that a small region of reverse flow occurred, a result of the flow pattern at the exit of the first ESP. The results also illustrated that the flow was predominantly in the lower half of the duct, and affected by some upstream turning vanes. The simulations demonstrated the value of CFD as a diagnostic tool. They were performed in a fraction of the time and cost required for the physical tests yet provided far more diagnostic information, such as the distribution of mercury and sorbent at each point in the computational domain. 1 fig.

  6. Injection of nonequilibrium quasiparticles into Zeeman-split superconductors: A way to create long-range spin imbalance

    NASA Astrophysics Data System (ADS)

    Bobkova, I. V.; Bobkov, A. M.

    2016-01-01

    A theory of spin transport and spin detection in Zeeman-split superconducting films at low temperatures is developed. It is shown that an injection of spin-unpolarized quasiparticles into a Zeeman-split superconductor gives rise to a spin imbalance. The relaxation length of such a spin signal is determined by the energy relaxation length and can be extremely large as compared to the usual spin relaxation length. There can exist two types of signals: due to nonthermalized quasiparticle distribution and due to thermalized overheated electron distribution. They have different decay lengths and can be distinguished by their different dependencies on the applied voltage. The decay length of the nonthermalized signal is determined by the electron-electron scattering rate, renormalized due to superconductivity. The decay length of the thermalized signal is determined by the length on which energy leaves the electronic subsystem and can be very large under special conditions. Applications of the theory to recent experimental data on spin relaxation in Zeeman-split and exchange-split superconductors are discussed. In particular, it can explain the extremely high spin relaxation lengths, experimentally observed in Zeeman-split superconductors, and their growth with the magnetic field and with the applied voltage.

  7. Efficient Cluster Algorithm for Spin Glasses in Any Space Dimension.

    PubMed

    Zhu, Zheng; Ochoa, Andrew J; Katzgraber, Helmut G

    2015-08-14

    Spin systems with frustration and disorder are notoriously difficult to study, both analytically and numerically. While the simulation of ferromagnetic statistical mechanical models benefits greatly from cluster algorithms, these accelerated dynamics methods remain elusive for generic spin-glass-like systems. Here, we present a cluster algorithm for Ising spin glasses that works in any space dimension and speeds up thermalization by at least one order of magnitude at temperatures where thermalization is typically difficult. Our isoenergetic cluster moves are based on the Houdayer cluster algorithm for two-dimensional spin glasses and lead to a speedup over conventional state-of-the-art methods that increases with the system size. We illustrate the benefits of the isoenergetic cluster moves in two and three space dimensions, as well as the nonplanar chimera topology found in the D-Wave Inc. quantum annealing machine. PMID:26317743

  8. Efficient Cluster Algorithm for Spin Glasses in Any Space Dimension

    NASA Astrophysics Data System (ADS)

    Zhu, Zheng; Ochoa, Andrew J.; Katzgraber, Helmut G.

    2015-08-01

    Spin systems with frustration and disorder are notoriously difficult to study, both analytically and numerically. While the simulation of ferromagnetic statistical mechanical models benefits greatly from cluster algorithms, these accelerated dynamics methods remain elusive for generic spin-glass-like systems. Here, we present a cluster algorithm for Ising spin glasses that works in any space dimension and speeds up thermalization by at least one order of magnitude at temperatures where thermalization is typically difficult. Our isoenergetic cluster moves are based on the Houdayer cluster algorithm for two-dimensional spin glasses and lead to a speedup over conventional state-of-the-art methods that increases with the system size. We illustrate the benefits of the isoenergetic cluster moves in two and three space dimensions, as well as the nonplanar chimera topology found in the D-Wave Inc. quantum annealing machine.

  9. Dependence of the Spin Hall Torque Efficiency on the Transparency of Pt-Ferromagnetic Layer Interfaces

    NASA Astrophysics Data System (ADS)

    Pai, Chi-Feng; Ou, Yongxi; Ralph, Daniel C.; Buhrman, Robert A.

    2015-03-01

    We report that spin current transport across Pt-ferromagnet (FM) interfaces is strongly dependent on the type and the thickness of the FM layer and on post-deposition processing protocols. By employing both harmonic voltage response measurements and spin-torque ferromagnetic resonance measurements on various Pt-Co and Pt-CoFe magnetic heterostructures, we find that the efficiency of the Pt spin Hall effect in exerting a damping-like spin torque on the FM ranges from < 0.05 to > 0.10 under different interfacial conditions. We also show that the temperature dependence of the spin torque efficiencies for both the damping-like torque and field-like torque is dependent upon the details of the Pt-FM interface. The ``internal'' spin Hall angle of the Pt thin films used in this study, after taking the interfacial spin transmission factor that is derived from the spin mixing conductance into account, is estimated to be ~0.20. This suggests that a careful engineering of Pt-FM interfaces can improve the spin-Hall-torque efficiency of Pt-based spintronic devices. Now at Massachusetts Institute of Technology.

  10. Efficient rotational echo double resonance recoupling of a spin-1/2 and a quadrupolar spin at high spinning rates and weak irradiation fields

    NASA Astrophysics Data System (ADS)

    Nimerovsky, Evgeny; Goldbourt, Amir

    2010-09-01

    A modification of the rotational echo (adiabatic passage) double resonance experiments, which allows recoupling of the dipolar interaction between a spin-1/2 and a half integer quadrupolar spin is proposed. We demonstrate efficient and uniform recoupling at high spinning rates ( ν r), low radio-frequency (RF) irradiation fields ( ν1), and high values of the quadrupolar interaction ( ν q) that correspond to values of α=ν12/νqνr, the adiabaticity parameter, which are down to less than 10% of the traditional adiabaticity limit for a spin-5/2 (α = 0.55). The low-alpha rotational echo double resonance curve is obtained when the pulse on the quadrupolar nucleus is extended to full two rotor periods and beyond. For protons (spin-1/2) and aluminum (spin-5/2) species in the zeolite SAPO-42, a dephasing curve, which is significantly better than the regular REAPDOR experiment (pulse length of one-third of the rotor period) is obtained for a spinning rate of 13 kHz and RF fields down to 10 and even 6 kHz. Under these conditions, α is estimated to be approximately 0.05 based on an average quadrupolar coupling in zeolites. Extensive simulations support our observations suggesting the method to be robust under a large range of experimental values.

  11. 35% magnetocurrent with spin transport through Si

    NASA Astrophysics Data System (ADS)

    Huang, Biqin; Zhao, Lai; Monsma, Douwe J.; Appelbaum, Ian

    2007-07-01

    Efficient injection of spin-polarized electrons into the conduction band of silicon is limited by the formation of a silicide at the ferromagnetic metal (FM)/silicon interface. In the present work, this "magnetically dead" silicide (where strong spin scattering significantly reduces injected spin polarization) is eliminated by moving the FM in the spin injector from the tunnel junction base anode to the emitter cathode and away from the silicon surface. This results in over an order-of-magnitude increase in spin injection efficiency, from a previously reported magnetocurrent ratio of ≈2% to ≈35% and an estimated spin polarization in Si from ≈1% to at least ≈15%. The injector tunnel junction bias dependence of this spin transport signal is also measured, demonstrating the importance of low bias voltage to preserve high injected spin polarization.

  12. Bioresorbable microspheres by spinning disk atomization as injectable cell carrier: from preparation to in vitro evaluation.

    PubMed

    Senuma, Y; Franceschin, S; Hilborn, J G; Tissières, P; Bisson, I; Frey, P

    2000-06-01

    Vesico-ureteral reflux, a common pathology in children, can be treated cystoscopically by injection of a bulking material underneath the most distal, intramural ureter, which forces the latter to do a detour, increasing its submucosal path. This increase of the length of the submucosal path of the ureter within the bladder is directly responsible for the anti-reflux effect. So far Teflon and collagen paste have been commonly used as bulking materials. We suggest replacing these materials by living tissue consisting of bladder smooth muscle, normally present at this location. The aim of this work is to provide a long-term effective treatment by producing bioresorbable microspheres which can act as a support matrix and an entrapment substance for bladder smooth muscle cells, with the goal of an in vivo transfer of the in vitro cultured cells with a minimal surgical procedure. By the use of Spinning Disk Atomization, which has specifically been developed for this purpose, we have shown two methods for the preparation of porous poly(lactic acid) microspheres with tunable sizes from 160 to 320 microm. The controlled solvent burst method has shown the advantage over the crystal leaching method in the direct creation of microspheres with large closed pores, by atomizing the polymer solution in controlled temperature conditions. Microspheres with various closed pore structures have thus been prepared. The innovation of this work is in the direct and rapid formation of porous microspheres with a pore morphology which is designed to create cavities suitable for adherence and growth of cells by adapting the temperature conditions of atomization. Injection tests have shown promising results in using these cell-loaded microspheres for future non-invasive tissue engineering. PMID:10817266

  13. Critical current and linewidth reduction in spin-torque nano-oscillators by delayed self-injection

    SciTech Connect

    Khalsa, Guru Stiles, M. D.; Grollier, J.

    2015-06-15

    Based on theoretical models, the dynamics of spin-torque nano-oscillators can be substantially modified by re-injecting the emitted signal to the input of the oscillator after some delay. Numerical simulations for vortex magnetic tunnel junctions show that with reasonable parameters this approach can decrease critical currents as much as 25% and linewidths by a factor of 4. Analytical calculations, which agree well with simulations, demonstrate that these results can be generalized to any kind of spin-torque oscillator.

  14. [Techniques to enhance the accuracy and efficiency of injections of the face in aesthetic medicine].

    PubMed

    Manfrédi, P-R; Hersant, B; Bosc, R; Noel, W; Meningaud, J-P

    2016-02-01

    The common principle of injections in esthetic medicine is to treat and to prevent the signs of aging with minimal doses and with more precision and efficiency. This relies on functional, histological, ultrasound or electromyographic analysis of the soft tissues and of the mechanisms of facial skin aging (fine lines, wrinkles, hollows). These injections may be done with hyaluronic acid (HA) and botulinum toxin. The aim of this technical note was to present four delivery techniques allowing for more precision and low doses of product. The techniques of "vacuum", "interpores" and "blanching" will be addressed for HA injection and the concept of "Face Recurve" for botulinum toxin injection. PMID:26740201

  15. Spin injection and diffusion in silicon based devices from a space charge layer

    SciTech Connect

    Ghosh, Joydeep Sverdlov, Viktor; Windbacher, Thomas; Selberherr, Siegfried

    2014-05-07

    We have performed simulations on electron spin transport in an n-doped silicon bar with spin-dependent conductivity with or without the presence of an external electric field. We further consider three cases like charge neutrality, charge accumulation, and charge depletion at one boundary and found substantial differences in the spin transport behavior. The criteria determining the maximum spin current are investigated. The physical reason behind the transport behavior is explained.

  16. Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

    SciTech Connect

    Alharthi, S. S. Henning, I. D.; Adams, M. J.; Hurtado, A.; Korpijarvi, V.-M.; Guina, M.

    2015-01-12

    We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.

  17. Similar time restriction for intracytoplasmic sperm injection and round spermatid injection into activated oocytes for efficient offspring production.

    PubMed

    Kishigami, Satoshi; Wakayama, Sayaka; Nguyen, Van Thuan; Wakayama, Teruhiko

    2004-06-01

    The injection of male haploid germ cells, such as spermatozoa and round spermatids, into preactivated mouse oocytes can result in the development of viable embryos and offspring. However, it is not clear how the timing of intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI) affects the production of offspring. We carried out ICSI and ROSI every 20 min for up to 4 h after the activation of mouse oocytes by Sr(2+) and compared the late-stage development of ICSI- and ROSI- treated oocytes, including the formation of pronuclei, blastocyst formation, and offspring production. The rate of pronucleus formation (RPF) after carrying out ICSI started to decrease from >95% at 100 min following oocyte activation and declined to <20% by 180 min. In comparison, RPF by ROSI decreased gradually from >70% between 0 and 4 h after activation. The RPFs were closely correlated with blastocyst formation. Offspring production for both ICSI and ROSI decreased significantly when injections were conducted after 100 min, a time at which activated oocytes were in the early G1 stage of the cell cycle. These results suggest that spermatozoa and round spermatids have different potentials for inducing the formation of a male pronucleus in activated oocytes, but ICSI and ROSI are both subject to the same time constraint for the efficient production of offspring, which is determined by the cell cycle of the activated oocyte. PMID:14985245

  18. Carrier injection properties in spin-orbit coupling structure based on a correlated electronic ferromagnetic system

    NASA Astrophysics Data System (ADS)

    Ren, R.; Wang, Weiren; Li, Xuan; Ren, Yijing; Sun, Yuanjun; Zhao, Zhongxia

    2014-03-01

    Carrier injection effects on phase-field domain structures are displayed between BiFeO3 and La0.4Gd0.1Sr0.5CoO3 thin films prepared by pulsed laser deposition, epitaxially grown on LaAlO3 (100) substrates. The leakage current and magnetoresistance (MR) in the fabricated BiFeO3/La0.4Gd0.1Sr0.5CoO3/LaAlO3 heterostructure were measured under 0.2, 0.4 and 0.6 T at 80-300 K. The BiFeO3/LGSCO heterojunction exhibits the carrier transfer of the metal-insulator transition and a positive MR effect at 219-250 K. The electric-conductivity mechanism below the Curie temperature, TC, is dominated by Poole-Frenkel emission. The BiFeO3/LGSCO pn junction shows rectifying behavior between 80-300 K. The energy bands of the heterojunction were modified by the morphology of the interface, the magnetic domain, spin polarization and interface tensile strain due to external magnetic perturbations. The strain and magnetic field-modified domain wall and the carrier density at the BiFeO3/LGCO interface were characterized by atomic force microscopy. The domain and phase separation of LGSCO/BiFeO3 changed with strain, structural defects, grain size and boundary and the modified concentration of carriers. Additionally, the BiFeO3/La1-xGdxSrCoO3 heterostructure shows a positive colossal MR effect at 80-300 K and an metal-insulator phase transition was observed around TC 219.5 K for 0.6 T, 220 K for 0.4 T and 249.7 K for 0.2 T.

  19. Efficient Spin Injector Scheme Based on Heusler Materials

    NASA Astrophysics Data System (ADS)

    Chadov, Stanislav; Graf, Tanja; Chadova, Kristina; Dai, Xuefang; Casper, Frederick; Fecher, Gerhard H.; Felser, Claudia

    2011-07-01

    We present a rational design scheme intended to provide stable high spin polarization at the interfaces of the magnetoresistive junctions by fulfilling the criteria of structural and chemical compatibilities at the interface. This can be realized by joining the semiconducting and half-metallic Heusler materials with similar structures. The present first-principles calculations verify that the interface remains half-metallic if the nearest interface layers effectively form a stable Heusler material with the properties intermediately between the surrounding bulk parts. This leads to a simple rule for selecting the proper combinations.

  20. Temperature-dependent spin injection dynamics in InGaAs/GaAs quantum well-dot tunnel-coupled nanostructures

    NASA Astrophysics Data System (ADS)

    Chen, S. L.; Kiba, T.; Yang, X. J.; Takayama, J.; Murayama, A.

    2016-03-01

    Time-resolved optical spin orientation spectroscopy was employed to investigate the temperature-dependent electron spin injection in In0.1Ga0.9As quantum well (QW) and In0.5Ga0.5As quantum dots (QDs) tunnel-coupled nanostructures with 4, 6, and 8 nm-thick GaAs barriers. The fast picosecond-ranged spin injection from QW to QD excited states (ES) was observed to speed up with temperature, as induced by pronounced longitudinal-optical (LO)-phonon-involved multiple scattering process, which contributes to a thermally stable and almost fully spin-conserving injection within 5-180 K. The LO-phonon coupling was also found to cause accelerated electron spin relaxation of QD ES at elevated temperature, mainly via hyperfine interaction with random nuclear field.

  1. Efficient conversion of light to charge and spin in Hall-bar microdevices

    NASA Astrophysics Data System (ADS)

    Nádvorník, L.; Haigh, J. A.; Olejník, K.; Irvine, A. C.; Novák, V.; Jungwirth, T.; Wunderlich, J.

    2015-03-01

    We report an experimental study of the direct conversion of light into electrical signals in GaAs/AlGaAs Hall-bar microdevices. Our approach, based on different modulation frequencies of the intensity and polarization of the laser beam, allows us to disentangle the charge- and spin-dependent parts of the induced electrical signal and to link them to the incident light intensity and polarization, respectively. We demonstrate that the efficiency of the light to spin conversion in our electrical polarimeter is strongly enhanced by adding a drift component to the transport of the spin-polarized photocarriers, as compared to a purely diffusive transport regime of the device. For a micron-size focused laser beam, the experiments demonstrate that the light to charge and spin conversion efficiency depends on the precise position of the light spot, reflecting the spatially dependent response function of the Hall cross.

  2. Switching efficiency improvement in spin torque majority gates

    SciTech Connect

    Nikonov, Dmitri E. Manipatruni, Sasikanth; Young, Ian A.

    2014-05-07

    Spin torque majority gate (STMG) is one of the promising options for beyond complementary metal-oxide-semiconductor logic. Improvement of its performance—switching speed vs. required current—is critical for its competitiveness. In this paper, (a) we identify an optimized layout of the gate comprised of thin magnetic wires with in-plane magnetization; (b) we optimize geometries of perpendicular magnetization spin torque majority gates. Micromagnetic simulations demonstrate an improvement in switching current for in-plane magnetization (with less than 1 ns switching time) from 6 mA in the original scheme to 1.5 mA in the present one. Additionally, failures of switching caused by vortex formation are eliminated and desired output magnetization is achieved. Various geometries of STMG with perpendicular magnetization are explored. The scheme with a straight cross proves to be the most advantageous. It is predicted to operate with the switching current of 50 μA and less than 4 ns switching time.

  3. Switching efficiency improvement in spin torque majority gates

    NASA Astrophysics Data System (ADS)

    Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.

    2014-05-01

    Spin torque majority gate (STMG) is one of the promising options for beyond complementary metal-oxide-semiconductor logic. Improvement of its performance—switching speed vs. required current—is critical for its competitiveness. In this paper, (a) we identify an optimized layout of the gate comprised of thin magnetic wires with in-plane magnetization; (b) we optimize geometries of perpendicular magnetization spin torque majority gates. Micromagnetic simulations demonstrate an improvement in switching current for in-plane magnetization (with less than 1 ns switching time) from 6 mA in the original scheme to 1.5 mA in the present one. Additionally, failures of switching caused by vortex formation are eliminated and desired output magnetization is achieved. Various geometries of STMG with perpendicular magnetization are explored. The scheme with a straight cross proves to be the most advantageous. It is predicted to operate with the switching current of 50 μA and less than 4 ns switching time.

  4. Efficiency of spin-exchange optical pumping: theoretical limits and practical limitations

    NASA Astrophysics Data System (ADS)

    Erickson, Christopher; Romalis, Michael; Happer, William

    1998-05-01

    We address the issue of how many optical pumping photons are required to polarize the nucleus of a ^3He atom through spin exchange with an alkali vapor. The optimal efficiency is measured to be a factor of 10 greater for K than for Rb. Considerations of the effects associated with the optical pumping cycle suggest that practical attainable efficiencies may be substantially lower than optimal efficiencies.

  5. Spin-neurons: A possible path to energy-efficient neuromorphic computers

    SciTech Connect

    Sharad, Mrigank; Fan, Deliang; Roy, Kaushik

    2013-12-21

    Recent years have witnessed growing interest in the field of brain-inspired computing based on neural-network architectures. In order to translate the related algorithmic models into powerful, yet energy-efficient cognitive-computing hardware, computing-devices beyond CMOS may need to be explored. The suitability of such devices to this field of computing would strongly depend upon how closely their physical characteristics match with the essential computing primitives employed in such models. In this work, we discuss the rationale of applying emerging spin-torque devices for bio-inspired computing. Recent spin-torque experiments have shown the path to low-current, low-voltage, and high-speed magnetization switching in nano-scale magnetic devices. Such magneto-metallic, current-mode spin-torque switches can mimic the analog summing and “thresholding” operation of an artificial neuron with high energy-efficiency. Comparison with CMOS-based analog circuit-model of a neuron shows that “spin-neurons” (spin based circuit model of neurons) can achieve more than two orders of magnitude lower energy and beyond three orders of magnitude reduction in energy-delay product. The application of spin-neurons can therefore be an attractive option for neuromorphic computers of future.

  6. Spin-neurons: A possible path to energy-efficient neuromorphic computers

    NASA Astrophysics Data System (ADS)

    Sharad, Mrigank; Fan, Deliang; Roy, Kaushik

    2013-12-01

    Recent years have witnessed growing interest in the field of brain-inspired computing based on neural-network architectures. In order to translate the related algorithmic models into powerful, yet energy-efficient cognitive-computing hardware, computing-devices beyond CMOS may need to be explored. The suitability of such devices to this field of computing would strongly depend upon how closely their physical characteristics match with the essential computing primitives employed in such models. In this work, we discuss the rationale of applying emerging spin-torque devices for bio-inspired computing. Recent spin-torque experiments have shown the path to low-current, low-voltage, and high-speed magnetization switching in nano-scale magnetic devices. Such magneto-metallic, current-mode spin-torque switches can mimic the analog summing and "thresholding" operation of an artificial neuron with high energy-efficiency. Comparison with CMOS-based analog circuit-model of a neuron shows that "spin-neurons" (spin based circuit model of neurons) can achieve more than two orders of magnitude lower energy and beyond three orders of magnitude reduction in energy-delay product. The application of spin-neurons can therefore be an attractive option for neuromorphic computers of future.

  7. Efficient spin transfer torque in La{sub 2/3}Sr{sub 1/3}MnO{sub 3} nanostructures

    SciTech Connect

    Foerster, Michael; Peña, Luis; Finizio, Simone; Schulz, Tomek; Bisig, André; Vaz, C. A. F.; Heinen, Jan; Büttner, Felix; Eisebitt, Stefan; Méchin, Laurence; and others

    2014-02-17

    We carry out low temperature magnetotransport measurements on nanostructured La{sub 2/3}Sr{sub 1/3}MnO{sub 3} wires to study the interaction between spin-polarized current and magnetization in this half metallic material. We selectively position domain walls by applying external fields. The domain wall resistance is found to be positive, in contrast to conventional 3d metals. The depinning field is reduced when current pulses are injected into the wire. By comparing measurements for both current polarities, we can disentangle heating and spin transfer torque effects. The determined spin transfer torque efficiency is of the order of 4 × 10{sup −14} Tm{sup 2}/A, which is significantly higher than in permalloy.

  8. Towards spin injection from silicon into topological insulators: Schottky barrier between Si and Bi2Se3

    NASA Astrophysics Data System (ADS)

    Ojeda-Aristizabal, C.; Fuhrer, M. S.; Butch, N. P.; Paglione, J.; Appelbaum, I.

    2012-07-01

    A scheme is proposed to electrically measure the spin-momentum coupling in the topological insulator surface state by injection of spin polarized electrons from silicon. As an initial approach, devices were fabricated consisting of thin (<100 nm) exfoliated crystals of Bi2Se3 on n-type silicon with independent electrical contacts to silicon and Bi2Se3. Analysis of the temperature dependence of thermionic emission in reverse bias indicates a barrier height of 0.34 eV at the Si-Bi2Se3 interface. This robust Schottky barrier opens the possibility of original device designs based on sub-band gap internal photoemission from Bi2Se3 into Si.

  9. High efficiency of the spin-orbit torques induced domain wall motion in asymmetric interfacial multilayered Tb/Co wires

    SciTech Connect

    Bang, Do; Awano, Hiroyuki

    2015-05-07

    We investigated current-induced DW motion in asymmetric interfacial multilayered Tb/Co wires for various thicknesses of magnetic and Pt-capping layers. It is found that the driving mechanism for the DW motion changes from interfacial to bulk effects at much thick magnetic layer (up to 19.8 nm). In thin wires, linearly depinning field dependence of critical current density and in-plane field dependence of DW velocity suggest that the extrinsic pinning governs field-induced DW motion and injecting current can be regarded as an effective field. It is expected that the high efficiency of spin-orbit torques in thick magnetic multilayers would have important implication for future spintronic devices based on in-plane current induced-DW motion or switching.

  10. Higher efficiency of CO2 injection into seawater by a venturi than a conventional diffuser system.

    PubMed

    Du, Hong; Lin, Junda; Zuercher, Chris

    2012-03-01

    Mass production of microalgae generally requires the injection of CO(2) into open ponds or photo-bioreactors. The present study compares the CO(2) injection efficiency into seawater of a porous stone air diffuser and a venturi. CO(2) was injected at flow rates of 400, 700 and 1000 standard mL/min and 4, 7 and 10 standard L/min into a small and a large pond, respectively until the pH decreased from 7.8 to 6.8. No significant differences in CO(2) injection efficiency between the three CO(2) flow rates (p>0.05) were observed; however, CO(2) injection efficiency with venturi was about 100% (p<0.05) higher than that of the air diffuser. Therefore, it is possible to both reduce the cost and increase the effectiveness of CO(2) dissolution in seawater by using venturi operated at a lower flow rate, i.e. 400 standard mL/min in a small pond and 4 standard L/min in a large pond. PMID:22209441

  11. Minimizing electrode edge in organic transistors with ultrathin reduced graphene oxide for improving charge injection efficiency.

    PubMed

    Xu, Zeyang; Chen, Xiaosong; Zhang, Suna; Wu, Kunjie; Li, Hongwei; Meng, Yancheng; Li, Liqiang

    2016-05-11

    Electrode materials and geometry play a crucial role in the charge injection efficiency in organic transistors. Reduced graphene oxide (RGO) electrodes show good compatibility with an organic semiconductor from the standpoint of energy levels and ordered growth of the organic semiconductor, both of which are favourable for charge injection. However, the wide electrode edge (>10 nm) in commonly-used RGO electrodes is generally detrimental to charge injection. In this study, ultrathin (about 3 nm) RGO electrodes are fabricated via a covalency-based assembly strategy, which has advantages such as robustness against solvents, high conductivity, transparency, and easy scaling-up. More remarkably, the ultrathin electrode fabricated in this study has a narrow edge, which may facilitate the diffusion and assembly of organic semiconductors and thus form a uniform semiconductor film across the electrode/channel junction area. As a result, the minimized electrode edge may significantly improve the charge injection in organic transistors compared with thick electrodes. PMID:27062997

  12. Evolution in the charge injection efficiency of evaporated Au contacts on a molecularly doped polymer

    NASA Astrophysics Data System (ADS)

    Ioannidis, Andronique; Facci, John S.; Abkowitz, Martin A.

    1998-08-01

    Injection efficiency from evaporated Au contacts on a molecularly doped polymer (MDP) system has been previously observed to evolve from blocking to ohmic over time. In the present article this contact forming phenomenon is analyzed in detail. The initially blocking nature of the Au contact is in contrast with that expected from the relative workfunctions of Au and of the polymer which suggest Au should inject holes efficiently. It is also in apparent contrast to a differently prepared interface of the same materials. The phenomenon is not unique to this interface, having been confirmed also for evaporated Ag and mechanically made liquid Hg contacts on the same MDP. The MDP is a disordered solid state solution of electroactive triarylamine hole transporting TPD molecules in a polycarbonate matrix. The trap-free hole-transport MDP provides a model system for the study of metal/polymer interfaces by enabling the use of a recently developed technique that gives a quantitative measure of contact injection efficiency. The technique combines field-dependent steady state injection current measurements at a contact under test with time-of-flight (TOF) mobility measurements made on the same sample. In the present case, MDP films were prepared with two top vapor-deposited contacts, one of Au (test contact) and one of Al (for TOF), and a bottom carbon-loaded polymer electrode which is known to be ohmic for hole injection. The samples were aged at various temperatures below the glass transition of the MDP (85 °C) and the evolution of current versus field and capacitance versus frequency behaviors are followed in detail over time and analyzed. Control measurements ensure that the evolution of the electrical properties is due to the Au/polymer interface behavior and not the bulk. All evaporated Au contacts eventually achieved ohmic injection. The evaporated Au/MDP interface was also investigated by transmission electron microscopy as a function of time and showed no evidence of

  13. Efficient Synchronization of Dipolarly Coupled Vortex-Based Spin Transfer Nano-Oscillators

    PubMed Central

    Locatelli, Nicolas; Hamadeh, Abbass; Abreu Araujo, Flavio; Belanovsky, Anatoly D.; Skirdkov, Petr N.; Lebrun, Romain; Naletov, Vladimir V.; Zvezdin, Konstantin A.; Muñoz, Manuel; Grollier, Julie; Klein, Olivier; Cros, Vincent; de Loubens, Grégoire

    2015-01-01

    Due to their nonlinear properties, spin transfer nano-oscillators can easily adapt their frequency to external stimuli. This makes them interesting model systems to study the effects of synchronization and brings some opportunities to improve their microwave characteristics in view of their applications in information and communication technologies and/or to design innovative computing architectures. So far, mutual synchronization of spin transfer nano-oscillators through propagating spinwaves and exchange coupling in a common magnetic layer has been demonstrated. Here we show that the dipolar interaction is also an efficient mechanism to synchronize neighbouring oscillators. We experimentally study a pair of vortex-based spin transfer nano-oscillators, in which mutual synchronization can be achieved despite a significant frequency mismatch between oscillators. Importantly, the coupling efficiency is controlled by the magnetic configuration of the vortices, as confirmed by an analytical model and micromagnetic simulations highlighting the physics at play in the synchronization process. PMID:26608230

  14. Efficient Synchronization of Dipolarly Coupled Vortex-Based Spin Transfer Nano-Oscillators.

    PubMed

    Locatelli, Nicolas; Hamadeh, Abbass; Abreu Araujo, Flavio; Belanovsky, Anatoly D; Skirdkov, Petr N; Lebrun, Romain; Naletov, Vladimir V; Zvezdin, Konstantin A; Muñoz, Manuel; Grollier, Julie; Klein, Olivier; Cros, Vincent; de Loubens, Grégoire

    2015-01-01

    Due to their nonlinear properties, spin transfer nano-oscillators can easily adapt their frequency to external stimuli. This makes them interesting model systems to study the effects of synchronization and brings some opportunities to improve their microwave characteristics in view of their applications in information and communication technologies and/or to design innovative computing architectures. So far, mutual synchronization of spin transfer nano-oscillators through propagating spinwaves and exchange coupling in a common magnetic layer has been demonstrated. Here we show that the dipolar interaction is also an efficient mechanism to synchronize neighbouring oscillators. We experimentally study a pair of vortex-based spin transfer nano-oscillators, in which mutual synchronization can be achieved despite a significant frequency mismatch between oscillators. Importantly, the coupling efficiency is controlled by the magnetic configuration of the vortices, as confirmed by an analytical model and micromagnetic simulations highlighting the physics at play in the synchronization process. PMID:26608230

  15. Efficient Synchronization of Dipolarly Coupled Vortex-Based Spin Transfer Nano-Oscillators

    NASA Astrophysics Data System (ADS)

    Locatelli, Nicolas; Hamadeh, Abbass; Abreu Araujo, Flavio; Belanovsky, Anatoly D.; Skirdkov, Petr N.; Lebrun, Romain; Naletov, Vladimir V.; Zvezdin, Konstantin A.; Muñoz, Manuel; Grollier, Julie; Klein, Olivier; Cros, Vincent; de Loubens, Grégoire

    2015-11-01

    Due to their nonlinear properties, spin transfer nano-oscillators can easily adapt their frequency to external stimuli. This makes them interesting model systems to study the effects of synchronization and brings some opportunities to improve their microwave characteristics in view of their applications in information and communication technologies and/or to design innovative computing architectures. So far, mutual synchronization of spin transfer nano-oscillators through propagating spinwaves and exchange coupling in a common magnetic layer has been demonstrated. Here we show that the dipolar interaction is also an efficient mechanism to synchronize neighbouring oscillators. We experimentally study a pair of vortex-based spin transfer nano-oscillators, in which mutual synchronization can be achieved despite a significant frequency mismatch between oscillators. Importantly, the coupling efficiency is controlled by the magnetic configuration of the vortices, as confirmed by an analytical model and micromagnetic simulations highlighting the physics at play in the synchronization process.

  16. Reduction of critical current density for out-of-plane mode oscillation in a mag-flip spin torque oscillator using highly spin-polarized Co2Fe(Ga0.5Ge0.5) spin injection layer

    NASA Astrophysics Data System (ADS)

    Bosu, S.; Sepehri-Amin, H.; Sakuraba, Y.; Hayashi, M.; Abert, C.; Suess, D.; Schrefl, T.; Hono, K.

    2016-02-01

    We study spin torque oscillators comprised of a perpendicular spin injection layer (SIL) and a planar field generating layer to reveal the influence of the spin polarization of SIL material on the critical current density, JC, to induce microwave oscillation. Two systems with different SIL are compared: one with a highly spin-polarized Heusler alloy, Co2Fe(Ga0.5Ge0.5) (CFGG), and the other a prototypical Fe2Co alloy. Cross sectional scanning transmission electron microscopy observations show the B2-ordered structure in a 3-nm-thick CFGG SIL, a prerequisite for obtaining half-metallic transport properties. Current induced microwave oscillations are found at frequencies of ˜15 GHz for both systems. However, the current needed to cause the oscillations is ˜50% smaller for films with the CFGG SIL compared to those of the Fe2Co SIL. These results are in accordance with micromagnetic simulations that include spin accumulation at the SIL.

  17. Paramagnetic spin pumping.

    PubMed

    Shiomi, Y; Saitoh, E

    2014-12-31

    We have demonstrated spin pumping from a paramagnetic state of an insulator La2NiMnO6 into a Pt film. Single-crystalline films of La2NiMnO6 which exhibit a ferromagnetic order at TC≈270  K were grown by pulsed laser deposition. The inverse spin Hall voltage induced by spin-current injection has been observed in the Pt layer not only in the ferromagnetic phase of La2NiMnO6, but also in a wide temperature range above TC. The efficient spin pumping in the paramagnetic phase is ascribable to ferromagnetic correlation, not to ferromagnetic order. PMID:25615367

  18. Efficiency of quantum energy teleportation within spin-1/2 particle pairs

    NASA Astrophysics Data System (ADS)

    Frey, Michael R.

    2016-03-01

    A protocol for quantum energy teleportation (QET) is known for a so-called minimal spin-1/2 particle pair model. We extend this protocol to explicitly admit quantum weak measurements at its first stage. The extended protocol is applied beyond the minimal model to spin-1/2 particle pairs whose Hamiltonians are of a general class characterized by orthogonal pairs of entangled eigenstates. The energy transfer efficiency of the extended QET protocol is derived for this setting, and we show that weaker measurement yields greater efficiency. In the minimal particle pair model, for example, the efficiency can be doubled by this means. We also show that the QET protocol's transfer efficiency never exceeds 100 %, supporting the understanding that quantum energy teleportation is, indeed, an energy transfer protocol, rather than a protocol for remotely catalyzing local extraction of system energy already present.

  19. Efficient rotamer elimination applied to protein side-chains and related spin glasses.

    PubMed Central

    Goldstein, R F

    1994-01-01

    Folded proteins and spin glasses share various properties, such as seemingly random interactions between residues (spins), and one might presume that some generic behaviors of spin glasses would also be exhibited in a general way by proteins. But a comparison here shows that the side-chain conformation systems of apo-myoglobin and lysozyme are qualitatively different from specific closely related spin glass systems. This difference is manifest in the number of rotamers that can be identified as definitely not contributing to the global energy minimum. This identification is effected by using a significantly enhanced version of the Dead End Elimination theorem (Desmet, J., M. De Maeyer, B. Hazes, and I. Lasters. 1992. The dead-end elimination theorem and its use in protein side-chain positioning. Nature. 356:539-542), which is much more effective and efficient in eliminating rotamers. In several cases (for proteins, although not for spin glasses) this improved Dead End Elimination theorem succeeded in identifying the absolute global minimum of rotamer conformations, with no statistical uncertainty. The difference between protein and spin glass is due to correlations between the interactions of one residue pair with another pair, and probably will play an important role in the thermodynamic behavior of the protein system. PMID:8061189

  20. Spin-transfer torques in antiferromagnetic textures: Efficiency and quantification method

    NASA Astrophysics Data System (ADS)

    Yamane, Yuta; Ieda, Jun'ichi; Sinova, Jairo

    2016-08-01

    We formulate a theory of spin-transfer torques in textured antiferromagnets, which covers the small to large limits of the exchange coupling energy relative to the kinetic energy of the intersublattice electron dynamics. Our theory suggests a natural definition of the efficiency of spin-transfer torques in antiferromagnets in terms of well-defined material parameters, revealing that the charge current couples predominantly to the antiferromagnetic order parameter and the sublattice-canting moment in, respectively, the limits of large and small exchange coupling. The effects can be quantified by analyzing the antiferromagnetic spin-wave dispersions in the presence of charge current: in the limit of large exchange coupling the spin-wave Doppler shift always occurs, whereas, in the opposite limit, the only spin-wave modes to react to the charge current are ones that carry a pronounced sublattice-canting moment. The findings offer a framework for understanding and designing spin-transfer torques in antiferromagnets belonging to different classes of sublattice structures such as, e.g., bipartite and layered antiferromagnets.

  1. Validation and Diagnostic Efficiency of the Mini-SPIN in Spanish-Speaking Adolescents

    PubMed Central

    Garcia-Lopez, LuisJoaquín; Moore, Harry T. A.

    2015-01-01

    Objectives Social Anxiety Disorder (SAD) is one of the most common mental disorders in adolescence. Many validated psychometric tools are available to diagnose individuals with SAD efficaciously. However, there is a demand for shortened self-report instruments that identify adolescents at risk of developing SAD. We validate the Mini-SPIN and its diagnostic efficiency in overcoming this problem in Spanish-speaking adolescents in Spain. Methods The psychometric properties of the 3-item Mini-SPIN scale for adolescents were assessed in a community (study 1) and clinical sample (study 2). Results Study 1 consisted of 573 adolescents, and found the Mini-SPIN to have appropriate internal consistency and high construct validity. Study 2 consisted of 354 adolescents (147 participants diagnosed with SAD and 207 healthy controls). Data revealed that the Mini-SPIN has good internal consistency, high construct validity and adequate diagnostic efficiency. Conclusions Our findings suggest that the Mini-SPIN has good psychometric properties on clinical and healthy control adolescents and general population, which indicates that it can be used as a screening tool in Spanish-speaking adolescents. Cut-off scores are provided. PMID:26317695

  2. Electron-hole asymmetry of spin injection and transport in single-layer graphene.

    PubMed

    Han, Wei; Wang, W H; Pi, K; McCreary, K M; Bao, W; Li, Yan; Miao, F; Lau, C N; Kawakami, R K

    2009-04-01

    Spin-dependent properties of single-layer graphene (SLG) have been studied by nonlocal spin valve measurements at room temperature. Gate voltage dependence shows that the nonlocal magnetoresistance (MR) is proportional to the conductivity of the SLG, which is the predicted behavior for transparent ferromagnetic-nonmagnetic contacts. While the electron and hole bands in SLG are symmetric, gate voltage and bias dependence of the nonlocal MR reveal an electron-hole asymmetry in which the nonlocal MR is roughly independent of bias for electrons, but varies significantly with bias for holes. PMID:19392401

  3. Enhanced spin Hall torque efficiency in Pt100-xAlx and Pt100-xHfx alloys arising from the intrinsic spin Hall effect

    NASA Astrophysics Data System (ADS)

    Nguyen, Minh-Hai; Zhao, Mengnan; Ralph, D. C.; Buhrman, R. A.

    2016-06-01

    We report that the spin Hall torque generated by Pt can be enhanced substantially by alloying with Al or Hf. We observe damping-like spin torque efficiency per unit applied current density as high as ξDLj=0.23 ±0.02 , nearly twice the maximum value reported for pure Pt. To achieve this maximum efficiency, a very thin (0.5 nm) Pt spacer layer is inserted between the alloy and the ferromagnet being manipulated, to avoid a degraded spin transparency at the alloy/ferromagnet interface.

  4. Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

    SciTech Connect

    Li, J.; Hu, J.; Wang, H.; Wu, R. Q.

    2015-07-20

    Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

  5. Spin Hall voltages from a.c. and d.c. spin currents

    PubMed Central

    Wei, Dahai; Obstbaum, Martin; Ribow, Mirko; Back, Christian H.; Woltersdorf, Georg

    2014-01-01

    In spin electronics, the spin degree of freedom is used to transmit and store information. To this end the ability to create pure spin currents—that is, without net charge transfer—is essential. When the magnetization vector in a ferromagnet–normal metal junction is excited, the spin pumping effect leads to the injection of pure spin currents into the normal metal. The polarization of this spin current is time-dependent and contains a very small d.c. component. Here we show that the large a.c. component of the spin currents can be detected efficiently using the inverse spin Hall effect. The observed a.c.-inverse spin Hall voltages are one order of magnitude larger than the conventional d.c.-inverse spin Hall voltages measured on the same device. Our results demonstrate that ferromagnet–normal metal junctions are efficient sources of pure spin currents in the gigahertz frequency range. PMID:24780927

  6. Next Generation Hole Injection/Transport Nano-Composites for High Efficiency OLED Development

    SciTech Connect

    King Wang

    2009-07-31

    The objective of this program is to use a novel nano-composite material system for the OLED anode coating/hole transport layer. The novel anode coating is intended to significantly increase not only hole injection/transport efficiency, but the device energy efficiency as well. Another goal of the Core Technologies Program is the optimization and scale-up of air-stable and cross-linkable novel HTL nano-composite materials synthesis and the development of low-cost, large-scale mist deposition processes for polymer OLED fabrication. This proposed technology holds the promise to substantially improve OLED energy efficiency and lifetime.

  7. The Enhancement of spin Hall torque efficiency and Reduction of Gilbert damping in spin Hall metal/normal metal/ferromagnetic trilayers

    NASA Astrophysics Data System (ADS)

    Nguyen, Minh-Hai; Pai, Chi-Feng; Ralph, Daniel C.; Buhrman, Robert A.

    2015-03-01

    The spin Hall effect (SHE) in ferromagnet/heavy metal bilayer structures has been demonstrated to be a powerful means for producing pure spin currents and for exerting spin-orbit damping-like and field-like torques on the ferromagnetic layer. Large spin Hall (SH) angles have been reported for Pt, beta-Ta and beta-W films and have been utilized to achieve magnetic switching of in-plane and out-of-plane magnetized nanomagnets, spin torque auto-oscillators, and the control of high velocity domain wall motion. For many of the proposed applications of the SHE it is also important to achieve an effective Gilbert damping parameter that is as low as possible. In general the spin orbit torques and the effective damping are predicted to depend directly on the spin-mixing conductance of the SH metal/ferromagnet interface. This opens up the possibility of tuning these properties with the insertion of a very thin layer of another metal between the SH metal and the ferromagnet. Here we will report on experiments with such trilayer structures in which we have observed both a large enhancement of the spin Hall torque efficiency and a significant reduction in the effective Gilbert damping. Our results indicate that there is considerable opportunity to optimize the effectiveness and energy efficiency of the damping-like torque through engineering of such trilayer structures. Supported in part by NSF and Samsung Electronics Corporation.

  8. Control of emitted light polarization in a 1310 nm dilute nitride spin-vertical cavity surface emitting laser subject to circularly polarized optical injection

    SciTech Connect

    Alharthi, S. S. Hurtado, A.; Al Seyab, R. K.; Henning, I. D.; Adams, M. J.; Korpijarvi, V.-M.; Guina, M.

    2014-11-03

    We experimentally demonstrate the control of the light polarization emitted by a 1310 nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.

  9. Inverse spin-Hall effect voltage generation by nonlinear spin-wave excitation

    NASA Astrophysics Data System (ADS)

    Feiler, Laura; Sentker, Kathrin; Brinker, Manuel; Kuhlmann, Nils; Stein, Falk-Ulrich; Meier, Guido

    2016-02-01

    We investigate spin currents in microstructured permalloy/platinum bilayers that are excited via magnetic high-frequency fields. Due to this excitation spin pumping occurs at the permalloy/platinum interface and a spin current is injected into the platinum layer. The spin current is detected as a voltage via the inverse spin-Hall effect. We find two regimes reflected by a nonlinear, abrupt voltage surge, which is reproducibly observed at distinct excitation field strengths. Micromagnetic simulations suggest that the surge is caused by excitation of a spin-wave-like mode. The comparatively large voltages reveal a highly efficient spin-current generation method in a mesoscopic spintronic device.

  10. 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

  11. Development of High Efficiency and Low Emission Low Temperature Combustion Diesel Engine with Direct EGR Injection

    NASA Astrophysics Data System (ADS)

    Ho, R. J.; Kumaran, P.; Yusoff, M. Z.

    2016-03-01

    Focus on energy and environmental sustainability policy has put automotive research & development directed to developing high efficiency and low pollutant power train. Diffused flame controlled diesel combustion has reach its limitation and has driven R&D to explore other modes of combustions. Known effective mode of combustion to reduce emission are Low temperature combustion (LTC) and homogeneous charge combustion ignition by suppressing Nitrogen Oxide(NOx) and Particulate Matter (PM) formation. The key control to meet this requirement are chemical composition and distribution of fuel and gas during a combustion process. Most research to accomplish this goal is done by manipulating injected mass flow rate and varying indirect EGR through intake manifold. This research paper shows viable alternative direct combustion control via co-axial direct EGR injection with fuel injection process. A simulation study with OpenFOAM is conducted by varying EGR injection velocity and direct EGR injector diameter performed with under two conditions with non-combustion and combustion. n-heptane (C7H16) is used as surrogate fuel together with 57 species 290 semi-detailed chemical kinetic model developed by Chalmers University is used for combustion simulation. Simulation result indicates viability of co-axial EGR injection as a method for low temperature combustion control.

  12. Highly efficient and lowly toxic docetaxel nanoemulsions for intravenous injection to animals.

    PubMed

    Li, Xin; Du, Lina; Wang, Chenyun; Liu, Yan; Mei, Xingguo; Jin, Yiguang

    2011-07-01

    Hypersensitivity many occur with commercial docetaxel injections containing Tween 80 and ethanol. An alternative formulation of docetaxel, an oil-in-water nanoemulsion was prepared using the high-pressure homogenization method. It was composed of medium-chain triglyceride, oleic acid, egg lecithin, and poloxamer. These ingredients are known as safe agents for intravenous (i.v.) injection. The nanoemulsion had a small size of 169 nm, and a high surface charge with the zeta potential of -33.9 mV. It maintained well stable even under high centrifugation. Acute toxicity of i.v. injection, erythrocyte hemolysis experiment, and rabbit ear vein irritation test showed no toxicity for the docetaxel nanoemulsion. The docetaxel nanoemulsion led to a larger apparent distribution volume and area under curve than the docetaxel injection after i.v. administration to rats. The histopathological test of tumor further demonstrated the highly anticancer efficiency of the docetaxel nanoemulsion. Thus, the nanoemulsion is a promising delivery system for docetaxel with highly anticancer efficiency and low toxicity. PMID:21812321

  13. Modification to the accelerator of the NBI-1B ion source for improving the injection efficiency.

    PubMed

    Kim, T S; Jeong, S H; Chang, D H; In, S R; Park, M; Jung, B K; Lee, K W; Wang, S J; Bae, Y S; Park, H T; Kim, J S; Cho, W; Choi, D J

    2016-02-01

    Minimizing power loss of a neutral beam imposes modification of the accelerator of the ion source for further improvement of the beam optics. The beam optics can be improved by focusing beamlets. The injection efficiencies by the steering of ion beamlets are investigated numerically to find the optimum modification of the accelerator design of the NBI-1B ion source. The beam power loss was reduced by aperture displacement of three edge beamlets arrays considering power loadings on the beamline components. Successful testing and operation of the ion source at 60 keV/84% of injection efficiency led to the possibility of enhancing the system capability to a 2.4 MW power level at 100 keV/1.9 μP. PMID:26932045

  14. Modification to the accelerator of the NBI-1B ion source for improving the injection efficiency

    NASA Astrophysics Data System (ADS)

    Kim, T. S.; Jeong, S. H.; Chang, D. H.; In, S. R.; Park, M.; Jung, B. K.; Lee, K. W.; Wang, S. J.; Bae, Y. S.; Park, H. T.; Kim, J. S.; Cho, W.; Choi, D. J.

    2016-02-01

    Minimizing power loss of a neutral beam imposes modification of the accelerator of the ion source for further improvement of the beam optics. The beam optics can be improved by focusing beamlets. The injection efficiencies by the steering of ion beamlets are investigated numerically to find the optimum modification of the accelerator design of the NBI-1B ion source. The beam power loss was reduced by aperture displacement of three edge beamlets arrays considering power loadings on the beamline components. Successful testing and operation of the ion source at 60 keV/84% of injection efficiency led to the possibility of enhancing the system capability to a 2.4 MW power level at 100 keV/1.9 μP.

  15. INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS

    SciTech Connect

    David S. Schechter

    2004-04-26

    This report describes the work performed during the second year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on investigating the effect of CO{sub 2} injection rates in homogeneous and fractured cores on oil recovery and a strategy to mitigate CO{sub 2} bypassing in a fractured core.

  16. Spin power and efficiency in an Aharnov-Bohm ring with an embedded magnetic impurity quantum dot

    SciTech Connect

    Yang, Xi; Guo, Yong; Zheng, Jun; Chi, Feng

    2015-05-11

    Spin thermoelectric effects in an Aharnov-Bohm ring with a magnetic impurity quantum dot (QD) are theoretically investigated by using the nonequilibrium Green's function method. It is found that due to the exchange coupling between the impurity and the electrons in QD, spin output power, and efficiency can be significant and be further modulated by the gate voltage. The spin thermoelectric effect can be modulated effectively by adjusting the Rashba spin-orbit interaction (RSOI) and the magnetic flux. The spin power and efficiency show zigzag oscillations, and thus spin thermoelectric effect can be switched by adjusting the magnetic flux phase factor and RSOI ones. In addition, the spin efficiency can be significantly enhanced by the coexistence of the RSOI and the magnetic flux, and the maximal value of normalized spin efficiency η{sub max}/η{sub C} = 0.35 is obtained. Our results show that such a QD ring device may be used as a manipulative spin thermoelectric generator.

  17. Efficient spin sense determination of Flora-region asteroids via the epoch method

    NASA Astrophysics Data System (ADS)

    Dykhuis, Melissa J.; Molnar, Lawrence A.; Gates, Christopher J.; Gonzales, Joshua A.; Huffman, Jared J.; Maat, Aaron R.; Maat, Stacy L.; Marks, Matthew I.; Massey-Plantinga, Alyssa R.; McReynolds, Nathan D.; Schut, Jeremy A.; Stoep, Joshua P.; Stutzman, Andrew J.; Thomas, Brandon C.; Vander Tuig, George W.; Vriesema, Jess W.; Greenberg, Richard

    2016-03-01

    The Flora asteroid family's size and location on the inner edge of the main belt make it a likely source of NEOs and terrestrial planet impactors; however, reliable determination of Flora membership is inhibited by the family's age and the presence of a high density of background objects. Dykhuis et al. (Dykhuis et al. [2014]. Icarus 243, 111-128) identified the Flora family as the product of a 950-My-old collision dispersed in semimajor axis as a result of the Yarkovsky effect, and defined the family's membership and extent in orbital parameter space. The observed preponderance of prograde rotators at semimajor axes greater than that of (8) Flora is consistent with the predictions of the single-collision Yarkovsky dispersion model. Here we extend the available rotational property data for the Flora family via a survey of 21 Flora-region asteroids, using a time-efficient modification of the "epoch method" to determine prograde/retrograde spin sense. Five of the survey asteroids are shown to be prograde; five are shown to be retrograde; six are shown to have spin axes in or near their orbital planes; and five represent other cases for which spin axis information was not determined. The high-semimajor axis component of the Flora family is found to have only prograde and in-plane rotators, consistent with model predictions of Yarkovsky dispersion. Moreover, we confirm a wide range of ecliptic latitudes of the spin axes among these prograde rotators, consistent with models of family evolution in which a significant fraction of the members are captured in spin-orbit resonance. Near the "center" of the family (near the semimajor axis location of (8) Flora), the spin directions are mixed, with a slight preference for retrograde rotators, placing constraints on the efficiency of YORP-cycle spin reorientation for the family. In addition to our spin sense survey, we also report new measurements of the Sloan colors of a number of large inner main belt asteroids.

  18. Excitation of coherent propagating spin waves by pure spin currents

    NASA Astrophysics Data System (ADS)

    Demidov, Vladislav E.; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O.

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics.

  19. Excitation of coherent propagating spin waves by pure spin currents.

    PubMed

    Demidov, Vladislav E; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics. PMID:26818232

  20. Excitation of coherent propagating spin waves by pure spin currents

    PubMed Central

    Demidov, Vladislav E.; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O.

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics. PMID:26818232

  1. Vesicles Cytoplasmic Injection: An Efficient Technique to Produce Porcine Transgene-Expressing Embryos.

    PubMed

    Luchetti, C G; Bevacqua, R J; Lorenzo, M S; Tello, M F; Willis, M; Buemo, C P; Lombardo, D M; Salamone, D F

    2016-08-01

    The use of vesicles co-incubated with plasmids showed to improve the efficiency of cytoplasmic injection of transgenes in cattle. Here, this technique was tested as a simplified alternative for transgenes delivery in porcine zygotes. To this aim, cytoplasmic injection of the plasmid alone was compared to the injection with plasmids co-incubated with vesicles both in diploid parthenogenic and IVF zygotes. The plasmid pcx-egfp was injected circular (CP) at 3, 30 and 300 ng/μl and linear (LP) at 30 ng/μl. The experimental groups using parthenogenetic zygotes were as follows: CP naked at 3 ng/μl (N = 105), 30 ng/μl (N = 95) and 300 ng/μl (N = 65); Sham (N = 105); control not injected (N = 223); LP naked at 30 ng/μl (N = 78); LP vesicles (N = 115) and Sham vesicles (N = 59). For IVF zygotes: LP naked (N = 44) LP vesicles (N = 94), Sham (N = 59) and control (N = 79). Cleavage, blastocyst and GFP+ rates were analysed by Fisher's test (p < 0.05). The parthenogenic CP naked group showed lower cleavage respect to control (p < 0.05). The highest concentration of plasmids to allow development to blastocyst stage was 30 ng/μl. There were no differences in DNA fragmentation between groups. The parthenogenic LP naked group resulted in high GFP rates (46%) and also allowed the production of GFP blastocysts (33%). The cytoplasmic injection with LP vesicles into parthenogenic zygotes allowed 100% GFP blastocysts. Injected IVF showed higher cleavage rates than control (p < 0.05). In IVF zygotes, only the use of vesicles produced GFP blastocysts. The use of vesicles co-incubated with plasmids improves the transgene expression efficiency for cytoplasmic injection in porcine zygotes and constitutes a simple technique for easy delivery of plasmids. PMID:27260090

  2. Efficient dipolar double quantum filtering under magic angle spinning without a 1H decoupling field

    NASA Astrophysics Data System (ADS)

    Courtney, Joseph M.; Rienstra, Chad M.

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in 13C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n ⩾ 7, provided that the 13C nutation frequency is on the order of 100 kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between 13C and 1H fields. For 13C nutation frequencies greater than 75 kHz, optimal performance is observed without an applied 1H field. At spinning rates exceeding 20 kHz, symmetry conditions as low as n = 3 were found to perform adequately.

  3. Efficient dipolar double quantum filtering under magic angle spinning without a (1)H decoupling field.

    PubMed

    Courtney, Joseph M; Rienstra, Chad M

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in (13)C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n⩾7, provided that the (13)C nutation frequency is on the order of 100kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between (13)C and (1)H fields. For (13)C nutation frequencies greater than 75kHz, optimal performance is observed without an applied (1)H field. At spinning rates exceeding 20kHz, symmetry conditions as low as n=3 were found to perform adequately. PMID:27314744

  4. Ferromagnetic-organic interfacial states and their role on low voltage current injection in tris-8-hydroxyquinloline (Alq{sub 3}) organic spin valves

    SciTech Connect

    Zhang, H. T.; Drew, A. J.; Zhang, S. J. E-mail: t.kreouzis@qmul.ac.uk; Kreouzis, T. E-mail: t.kreouzis@qmul.ac.uk; Han, S.; Desai, P.; Scott, K.; Zhan, Y. Q.; Li, W.; Si, W.; Gillin, W. P.

    2014-11-17

    Organic Spin Valves (OSVs) operate at small bias (<100 mV) when carrier injection should not occur due to injection barriers and in built potentials. We explore the consequences of hybrid-interface states between a ferromagnetic electrode and an organic semiconductor in OSV carrier injection. By temperature-dependent Dark Injection measurements, we observe hole trapping due to these filled states and measure a low thermal activation energy (∼100 meV) of the carrier density within OSVs. The small injection barrier is consistent with a significant interfacial potential, due to hybrid-interface state filling, overcoming the injection barrier due to the electrode work function—transport level mismatch.

  5. Spin-transfer-torque efficiency enhanced by edge-damage of perpendicular magnetic random access memories

    SciTech Connect

    Song, Kyungmi; Lee, Kyung-Jin

    2015-08-07

    We numerically investigate the effect of magnetic and electrical damages at the edge of a perpendicular magnetic random access memory (MRAM) cell on the spin-transfer-torque (STT) efficiency that is defined by the ratio of thermal stability factor to switching current. We find that the switching mode of an edge-damaged cell is different from that of an undamaged cell, which results in a sizable reduction in the switching current. Together with a marginal reduction of the thermal stability factor of an edge-damaged cell, this feature makes the STT efficiency large. Our results suggest that a precise edge control is viable for the optimization of STT-MRAM.

  6. Chiral Tunneling of Topological States: Towards the Efficient Generation of Spin Current Using Spin-Momentum Locking

    NASA Astrophysics Data System (ADS)

    Habib, K. M. Masum; Sajjad, Redwan N.; Ghosh, Avik W.

    2015-05-01

    We show that the interplay between chiral tunneling and spin-momentum locking of helical surface states leads to spin amplification and filtering in a 3D topological insulator (TI). Our calculations show that the chiral tunneling across a TI p n junction allows normally incident electrons to transmit, while the rest are reflected with their spins flipped due to spin-momentum locking. The net result is that the spin current is enhanced while the dissipative charge current is simultaneously suppressed, leading to an extremely large, gate-tunable spin-to-charge current ratio (˜20 ) at the reflected end. At the transmitted end, the ratio stays close to 1 and the electrons are completely spin polarized.

  7. Interfacial Structure in Co2MnSi/GaAs(001) Spin Injection Heterostructures

    NASA Astrophysics Data System (ADS)

    Patel, Sahil; Christie, Kevin; Geppert, Chad; Stecklein, Gordon; Wienkes, Lee; Shi, Fengyuan; Rath, Ashutosh; Schultz, Brian; Mryasov, Oleg; Butler, William; Voyles, Paul; Crowell, Paul; Palmstrom, Christopher; Cspin Collaboration

    2015-03-01

    We report on the role of the interface formation and structure of molecular beam epitaxially grown Co2MnSi/GaAs(001) heterostructures with measured spin accumulations of approximately 60% at 30K in GaAs. In-situ scanning tunneling microscopy (STM) was used to study morphology and x-ray photoelectron spectroscopy (XPS) for the evolution of core level emission peaks as a function of film thickness for thin epitaxial Co2MnSi films. Alternate monolayers of Co and MnSi were deposited to form an epitaxial template layer upon which codeposition of Co, Mn, and Si was used to grow thicker single crystal films. By combining the in-situ XPS elemental layer-by-layer peak evolutions and STM results with ex-situ high angular dark field scanning transmission electron microscopy (HAADF-STEM), x-ray diffraction, SQUID magnetometry and first-principles calculations, consistent models of the growth and interface formation have been developed and will be presented. This work was supported by C-SPIN, one of the six centers of STARnet, a SRC program sponsored by MARCO and DARPA; and by the NSF MRSEC program.

  8. In situ injection of phenylboronic acid based low molecular weight gels for efficient chemotherapy.

    PubMed

    Gao, Wenxia; Liang, Yan; Peng, Xinyu; Hu, Yalong; Zhang, Longgui; Wu, Huayue; He, Bin

    2016-10-01

    Injectable low molecular weight gels (LMWGs) based on the derivatives of phenylboronic acid were prepared and used as substrates for efficient in situ chemotherapy. The gelators as well as LMWGs were characterized by (1)H NMR, UV-vis, FTIR, MS and SEM. Anticancer drug doxorubicin hydrochloride (DOX) was encapsulated in the gels. The rheological properties and rapid recovery capability of both blank and drug-loaded gels were tested. The LMWGs were non-toxic to both 3T3 fibroblasts and 4T1 breast cancer cells. The gels were formed rapidly after injected in vivo. The in vivo anticancer activities of DOX-loaded LMWGs were investigated in breast cancer bearing mice. The intratumoral injection of DOX loaded LMWGs with dose of 30 mg/kg revealed that the gels could coat around the tumor tissues to release DOX sustainingly and maintain effective DOX concentration for chemotherapy. The systemic toxicity of DOX was reduced significantly with the in situ administration of LMWGs formulations. The injectable LMWGs exhibited excellent therapeutic efficacy and low side effects in local chemotherapy. PMID:27497056

  9. The injection efficiency measurement and analysis for central region model cyclotron.

    PubMed

    Yao, Hongjuan; Li, Zhenguo; Ge, Tao; Wu, Longcheng; Guan, Fengping; Lv, Yinlong; Wang, Zhenhui; Liu, Gengshou; Zhang, Tianjue; Cai, Hongru

    2010-02-01

    At the China Institute of Atomic Energy, a central region model cyclotron has been constructed, which is dedicated for various experimental verifications to study beam properties. The design features of the ion source and injection line have already been described in other papers. We shall report here the results of the initial beam tests. A wire scanner is employed in the injection line to measure beam transverse sizes and these data can be used to fit the phase plane parameters after the ion source. Based on the beam tests results, the ion source built in 2003 has been improved recently. The improvement is mainly due to the repair of the multicusp field. From the ion source to the exit of the inflector, a transmission efficiency of 93% has been obtained for a continuous and low current input beam. It is also described here the experimental arrangement and the results. PMID:20192449

  10. Direct evaluation of contact injection efficiency into small molecule based transport layers: Influence of extrinsic factors

    NASA Astrophysics Data System (ADS)

    Abkowitz, M.; Facci, J. S.; Rehm, J.

    1998-03-01

    Studies of interface formation on conventional semiconductor materials are typically carried out under relatively pristine conditions. However, for devices based on the use of electronic polymers there is also compelling interest in exploring the variations in contact behavior that might result under realistic manufacturing conditions like multilayer device assembly based on solution coating technology. Small molecule doped polymers (MDPs) developed principally as large area coatings for electrophotographic use are now finding wider device applications. These polymers are insulators capable of transporting excess injected charge with a unipolar drift mobility which can be tuned over a wide range by varying the concentration of transport active species. Most significant in the present context, MDPs can be rendered trap free by molecular design. These unique characteristics of MDPs make it possible to analyze the relative injection efficiencies of their interfaces with various contacts simply by a direct comparison of current-voltage characteristics with time of flight drift mobility measurements carried out on the same film coatings. In this way, and apart from their intrinsic interest and practical value, MDPs and closely related polymeric media provide the ideal venue for the study of contact phenomena on molecular solids. Almost all the present measurements were carried out by measuring dark hole injection from various preformed metal substrates into the MDP film TPD/polycarbonate. Under these circumstances it was found that while injection efficiency nominally scaled with the estimated interfacial energy step there was significant variance that in some cases could be clearly associated with the specific details of interfacial chemistry. For one exceptional case where Au was evaporated on the free surface of an already cast film a time and temperature dependent contact forming process could be delineated in which the interface systematically evolved from emission

  11. Efficient signal processing for time-resolved fluorescence detection of nitrogen-vacancy spins in diamond

    NASA Astrophysics Data System (ADS)

    Gupta, A.; Hacquebard, L.; Childress, L.

    2016-03-01

    Room-temperature fluorescence detection of the nitrogen-vacancy center electronic spin typically has low signal to noise, requiring long experiments to reveal an averaged signal. Here, we present a simple approach to analysis of time-resolved fluorescence data that permits an improvement in measurement precision through signal processing alone. Applying our technique to experimental data reveals an improvement in signal to noise equivalent to a 14% increase in photon collection efficiency. We further explore the dependence of the signal to noise ratio on excitation power, and analyze our results using a rate equation model. Our results provide a rubric for optimizing fluorescence spin detection, which has direct implications for improving precision of nitrogen-vacancy-based sensors.

  12. An efficient numerical method for computing dynamics of spin F = 2 Bose-Einstein condensates

    SciTech Connect

    Wang Hanquan

    2011-07-01

    In this paper, we extend the efficient time-splitting Fourier pseudospectral method to solve the generalized Gross-Pitaevskii (GP) equations, which model the dynamics of spin F = 2 Bose-Einstein condensates at extremely low temperature. Using the time-splitting technique, we split the generalized GP equations into one linear part and two nonlinear parts: the linear part is solved with the Fourier pseudospectral method; one of nonlinear parts is solved analytically while the other one is reformulated into a matrix formulation and solved by diagonalization. We show that the method keeps well the conservation laws related to generalized GP equations in 1D and 2D. We also show that the method is of second-order in time and spectrally accurate in space through a one-dimensional numerical test. We apply the method to investigate the dynamics of spin F = 2 Bose-Einstein condensates confined in a uniform/nonuniform magnetic field.

  13. Perpendicular spin transfer torque magnetic random access memories with high spin torque efficiency and thermal stability for embedded applications (invited)

    NASA Astrophysics Data System (ADS)

    Thomas, Luc; Jan, Guenole; Zhu, Jian; Liu, Huanlong; Lee, Yuan-Jen; Le, Son; Tong, Ru-Ying; Pi, Keyu; Wang, Yu-Jen; Shen, Dongna; He, Renren; Haq, Jesmin; Teng, Jeffrey; Lam, Vinh; Huang, Kenlin; Zhong, Tom; Torng, Terry; Wang, Po-Kang

    2014-05-01

    Magnetic random access memories based on the spin transfer torque phenomenon (STT-MRAMs) have become one of the leading candidates for next generation memory applications. Among the many attractive features of this technology are its potential for high speed and endurance, read signal margin, low power consumption, scalability, and non-volatility. In this paper, we discuss our recent results on perpendicular STT-MRAM stack designs that show STT efficiency higher than 5 kBT/μA, energy barriers higher than 100 kBT at room temperature for sub-40 nm diameter devices, and tunnel magnetoresistance higher than 150%. We use both single device data and results from 8 Mb array to demonstrate data retention sufficient for automotive applications. Moreover, we also demonstrate for the first time thermal stability up to 400 °C exceeding the requirement of Si CMOS back-end processing, thus opening the realm of non-volatile embedded memory to STT-MRAM technology.

  14. Perpendicular spin transfer torque magnetic random access memories with high spin torque efficiency and thermal stability for embedded applications (invited)

    SciTech Connect

    Thomas, Luc Jan, Guenole; Zhu, Jian; Liu, Huanlong; Lee, Yuan-Jen; Le, Son; Tong, Ru-Ying; Pi, Keyu; Wang, Yu-Jen; Shen, Dongna; He, Renren; Haq, Jesmin; Teng, Jeffrey; Lam, Vinh; Huang, Kenlin; Zhong, Tom; Torng, Terry; Wang, Po-Kang

    2014-05-07

    Magnetic random access memories based on the spin transfer torque phenomenon (STT-MRAMs) have become one of the leading candidates for next generation memory applications. Among the many attractive features of this technology are its potential for high speed and endurance, read signal margin, low power consumption, scalability, and non-volatility. In this paper, we discuss our recent results on perpendicular STT-MRAM stack designs that show STT efficiency higher than 5 k{sub B}T/μA, energy barriers higher than 100 k{sub B}T at room temperature for sub-40 nm diameter devices, and tunnel magnetoresistance higher than 150%. We use both single device data and results from 8 Mb array to demonstrate data retention sufficient for automotive applications. Moreover, we also demonstrate for the first time thermal stability up to 400 °C exceeding the requirement of Si CMOS back-end processing, thus opening the realm of non-volatile embedded memory to STT-MRAM technology.

  15. Triarylamine Siloxane Anode Functionalization/Hole Injection Layers in High Efficiency/High Luminance Small-Molecule Green- and Blue-Emitting Organic Light-Emitting Diodes

    SciTech Connect

    Huang,Q.; Li, J.; Marks, T.; Evmenenko, G.; Dutta, P.

    2007-01-01

    High efficiency/high luminance small-molecule organic light-emitting diodes (OLEDs) are fabricated by combining thin, covalently bound triarylamine hole injection/adhesion interlayers with hole- and exciton-blocking/electron transport interlayers in tris(8-hydroxyquinolato)aluminum(III) (Alq) and tetrakis(2-methyl-8-hydroxyquinolinato)borate (BQ{sub 4}{sup -})-based OLEDs. Green-emitting OLEDs with maximum luminance {approx}85 000 cd/m{sup 2}, power and forward external quantum efficiencies as high as 15.2 lm/W and 4.4{+-}0.5%, respectively, and turn-on voltages {approx}4.5 V are achieved in devices of the structure, ITO/N,N(prime)-diphenyl-N,N(prime)-bis(p-trichlorosilylpropylphenyl)(1,1(prime)-biphenyl)-4,4(prime)-diamine (TPD-Si2)/1,4-bis(1-naphthylphenylamino)biphenyl (NPB)/Alq doped with N,N(prime)-di(3-heptyl)quinacridone (DIQA)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/Li/AgMg. Also, bright and efficient blue-emitting OLEDs with turn-on voltages {approx}5.0 V, maximum luminance {approx}30 000 cd/m2, and {approx}5.0 lm/W and 1.6{+-}0.2% power and external forward quantum efficiencies, respectively, are achieved in devices of the structure, ITO/TPD-Si2/NPB/BQ{sub 4}{sup -}/BCP/Li/Al. TPD-Si2 interlayers are fabricated by spin casting N,N(prime)-diphenyl-N,N(prime)-bis(p-trichlorosilylpropylphenyl)(1,1(prime)-biphenyl)-4,4(prime)-diamine onto the ITO surface, while BCP interlayers are introduced by thermal evaporation. The excellent OLED performance is attributed to the differing functions of the above two interlayers: (1) The TPD-Si2 layer has a direct impact on hole injection by reducing the injection barrier and improving interfacial cohesion, and an indirect but strong effect on electron injection by altering internal electric fields. (2) The BCP layer, doped with lithium, directly reduces the electron injection barrier. Incorporation of both interlayers in OLED structures affords synergistically enhanced hole/electron injection and recombination

  16. A differential spin current detection scheme

    NASA Astrophysics Data System (ADS)

    Hemingway, Bryan; Appelbaum, Ian

    2013-09-01

    We provide detailed calculations for modeling an alternative scheme to detect spin polarization of conduction electrons injected into a nonmagnetic metal or degeneratively doped semiconductor using transport to two oppositely polarized ferromagnetic metal contacts. We show that, as in the well-known spin injection problem, detection efficiency can be amplified by the addition of spin-selective tunneling barriers. Considering the appropriate geometry and achievable injection rates, we estimate that the differential current can be as high as 1-10 nA for reasonable design parameters.

  17. INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS

    SciTech Connect

    David S. Schechter

    2003-10-01

    This report describes the work performed during the second year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling the fluid flow in fracture surface, examining the fluid transfer mechanisms and describing the fracture aperture distribution under different overburden pressure using X-ray CT scanner.

  18. INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS

    SciTech Connect

    David S. Schechter

    2005-04-27

    This report describes the work performed during the fourth year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificially fractured cores (AFCs) and X-ray CT scanner to examine the physical mechanisms of bypassing in hydraulically fractured reservoirs (HFR) and naturally fractured reservoirs (NFR) that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. In Chapter 1, we worked with DOE-RMOTC to investigate fracture properties in the Tensleep Formation at Teapot Dome Naval Reserve as part of their CO{sub 2} sequestration project. In Chapter 2, we continue our investigation to determine the primary oil recovery mechanism in a short vertically fractured core. Finally in Chapter 3, we report our numerical modeling efforts to develop compositional simulator with irregular grid blocks.

  19. Photoacoustic imaging of intravenously injected photosensitizer in rat burn models for efficient antibacterial photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Tsunoi, Yasuyuki; Sato, Shunichi; Ashida, Hiroshi; Terakawa, Mitsuhiro

    2012-02-01

    For efficient photodynamic treatment of wound infection, a photosensitizer must be distributed in the whole infected tissue region. To ensure this, depth profiling of a photosensitizer is necessary in vivo. In this study, we applied photoacoustic (PA) imaging to visualize the depth profile of an intravenously injected photosensitizer in rat burn models. In burned tissue, pharmacokinetics is complicated; vascular occlusion takes place in the injured tissue, while vascular permeability increases due to thermal invasion. In this study, we first used Evans Blue (EB) as a test drug to examine the feasibility of photosensitizer dosimetry based on PA imaging. On the basis of the results, an actual photosensitizer, talaporfin sodium was used. An EB solution was intravenously injected into a rat deep dermal burn model. PA imaging was performed on the wound with 532 nm and 610 nm nanosecond light pulses for visualizing vasculatures (blood) and EB, respectively. Two hours after injection, the distribution of EB-originated signal spatially coincided well with that of blood-originated signal measured after injury, indicating that EB molecules leaked out from the blood vessels due to increased permeability. Afterwards, the distribution of EB signal was broadened in the depth direction due to diffusion. At 12 hours after injection, clear EB signals were observed even in the zone of stasis, demonstrating that the leaked EB molecules were delivered to the injured tissue layer. The level and time course of talaporfin sodium-originated signals were different compared with those of EB-originated signals, showing animal-dependent and/or drug-dependent permeabilization and diffusion in the tissue. Thus, photosensitizer dosimetry should be needed before every treatment to achieve desirable outcome of photodynamic treatment, for which PA imaging can be concluded to be valid and useful.

  20. Radical-Ion-Pair Spin Decoherence and the Quantum Efficiency of Photosynthetic Charge Separation

    NASA Astrophysics Data System (ADS)

    Kominis, Iannis; Dellis, A. T.

    2014-03-01

    We have pioneered the fundamental quantum dynamics of radical-ion-pair reactions, elucidating the basic spin-decoherence mechanism pertaining to these biochemical reactions. Radical-ion pair reactions appear in the avian magnetic compass, but more importantly, they participate in the cascade of electron-transfer reactions taking place in photosynthetic reaction centers. We will here present new insights on how the fundamental quantum dynamics of radical-ion pair reactions affect the quantum efficiency of charge separation in photosynthetic reaction centers.

  1. INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS

    SciTech Connect

    David S. Schechter

    2004-10-10

    This report describes the work performed during the third year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling fluid flow through rough fractures and investigating the grid orientation effect in rectangular grid blocks particularly at high mobility ratio as our precursor to use a compositional simulator. We are developing a robust simulator using Voronoi grids to accurately represent natural and induced fractures. We are also verifying the accuracy of the simulation using scaled laboratory experiments to provide a benchmark for our simulation technique. No such simulator currently exists so this capability will represent a major breakthrough in simulation of gas injection in fractured systems. The following sections outline the results that appear in this report.

  2. Test results of a steam injected gas turbine to increase power and thermal efficiency

    SciTech Connect

    Messerlie, R.L.; Tischler, A.O.

    1983-08-01

    The desire to increase both power and thermal efficiency of the gas turbine (Brayton cycle) engine has been pursued for a number of years and has involved many approaches. The use of steam in the cycle to improve performance has been proposed by various investigators. This was most recently proposed by International Power Technology, Inc. (IPT) and has been tested by Detroit Diesel Allison (DDA), Division of General Motors. This approach, identified as the Cheng dual-fluid cycle (Cheng/DFC), includes the generation of steam using heat from the exhaust, and injecting this steam into the engine combustion chamber. Test results on an Allison 501-KB engine have demonstrated that use of this concept will increase the thermal efficiency of the engine by 30% and the output power by 60% with no increase in turbine inlet temperature. These results will be discussed, as will the impact of steam rate, location of steam injection, turbine temperature, and engine operational characteristics on the performance of the Cheng/DFC.

  3. Cluster VS. Single-Spin ALGORITHMS—WHICH are More Efficient?

    NASA Astrophysics Data System (ADS)

    Ito, N.; Kohring, G. A.

    A comparison between single-cluster and single-spin algorithms is made for the Ising model in 2 and 3 dimensions. We compare the amount of computer time needed to achieve a given level of statistical accuracy, rather than the speed in terms of site updates per second or the dynamical critical exponents. Our main result is that the cluster algorithms become more efficient when the system size, Ld, exceeds, L~70-300 for d=2 and l~80-200 for d=3. The exact value of the crossover is dependent upon the computer being used. The lower end of the crossover range is typical of workstations while the higher end is typical of vector computers. Hence, even for workstations, the system sizes needed for efficient use of the cluster algorithm is relatively large.

  4. All-electric spin transistor using perpendicular spins

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hoon; Bae, Joohyung; Min, Byoung-Chul; Kim, Hyung-jun; Chang, Joonyeon; Koo, Hyun Cheol

    2016-04-01

    All-electric spin transistor is demonstrated using perpendicular spins in an InAs quantum well channel. For the injection and detection of perpendicular spins in the quantum well channel, we use Tb20Fe62Co18/Co40Fe40B20 electrodes, where the Tb20Fe62Co18 layer produces the perpendicular magnetization and the Co40Fe40B20 layer enhances the spin polarization. In this spin transistor device, a gate-controlled spin signal as large as 80 mΩ is observed at 10 K without an external magnetic field. In order to confirm the spin injection and relaxation independently, we measure the three-terminal Hanle effect with an in-plane magnetic field, and obtain a spin signal of 1.7 mΩ at 10 K. These results clearly present that the electric field is an efficient way to modulate spin orientation in a strong spin-orbit interaction system.

  5. Multiwell CO2 injectivity: impact of boundary conditions and brine extraction on geologic CO2 storage efficiency and pressure buildup.

    PubMed

    Heath, Jason E; McKenna, Sean A; Dewers, Thomas A; Roach, Jesse D; Kobos, Peter H

    2014-01-21

    CO2 storage efficiency is a metric that expresses the portion of the pore space of a subsurface geologic formation that is available to store CO2. Estimates of storage efficiency for large-scale geologic CO2 storage depend on a variety of factors including geologic properties and operational design. These factors govern estimates on CO2 storage resources, the longevity of storage sites, and potential pressure buildup in storage reservoirs. This study employs numerical modeling to quantify CO2 injection well numbers, well spacing, and storage efficiency as a function of geologic formation properties, open-versus-closed boundary conditions, and injection with or without brine extraction. The set of modeling runs is important as it allows the comparison of controlling factors on CO2 storage efficiency. Brine extraction in closed domains can result in storage efficiencies that are similar to those of injection in open-boundary domains. Geomechanical constraints on downhole pressure at both injection and extraction wells lower CO2 storage efficiency as compared to the idealized scenario in which the same volumes of CO2 and brine are injected and extracted, respectively. Geomechanical constraints should be taken into account to avoid potential damage to the storage site. PMID:23971876

  6. Efficient production of transgenic mice by intracytoplasmic injection of streptolysin-O-treated spermatozoa.

    PubMed

    Sim, Bo-Woong; Cha, Jae-Jin; Song, Bong-Seok; Kim, Ji-Su; Yoon, Seung-Bin; Choi, Seon-A; Jeong, Kang-Jin; Kim, Young-Hyun; Huh, Jae-Won; Lee, Sang-Rae; Kim, Sang-Hyun; Lee, Chul-Sang; Kim, Sun-Uk; Chang, Kyu-Tae

    2013-03-01

    Many methods for efficient production of transgenic animals for biomedical research have been developed. Despite great improvements in transgenesis rates resulting from the use of intracytoplasmic sperm injection (ICSI), the ICSI-based sperm-mediated gene-transfer (iSMGT) technique is still not optimal in terms of sperm permeabilization efficiency and subsequent development. Here, we demonstrate that streptolysin-O (SLO) can efficiently permeabilize mouse spermatozoa, leading to improved developmental competence and high transgenesis rates in iSMGT embryos and pups. In particular, the most efficient production of iSMGT-transgenic embryos resulted from pretreatment with 5 U/ml SLO for 30 min and co-incubation with 1.0 ng/µl of an EGFP expression vector. By incubating spermatozoa with Cy-3-labelled DNA, we found that fluorescence intensity was prominently detected in the head region of SLO-treated spermatozoa. In addition, blastocyst development rate and blastomere survival were greatly improved by iSMGT using SLO-treated spermatozoa (iSMGT-SLO) as compared to freeze-thawed spermatozoa. Consistent with this, a high proportion of transgenic offspring was obtained by iSMGT-SLO after transfer into foster mothers, reaching 10.6% of the number of oocytes used (42.3% among pups). Together with successful germline transmission of transgenes in all founders analyzed, our data strongly suggest that SLO makes spermatozoa amenable to exogenous DNA uptake, and that the iSMGT-SLO technique is an efficient method for production of transgenic animals for biomedical research. PMID:23359330

  7. Method and apparatus for efficient injection of CO2 in oceans

    DOEpatents

    West, Olivia R.; Tsouris, Constantinos; Liang, Liyuan

    2003-07-29

    A liquid CO.sub.2 injection system produces a negatively buoyant consolidated stream of liquid CO.sub.2, CO.sub.2 hydrate, and water that sinks upon release at ocean depths in the range of 700-1500 m. In this approach, seawater at a predetermined ocean depth is mixed with the liquid CO.sub.2 stream before release into the ocean. Because mixing is conducted at depths where pressures and temperatures are suitable for CO.sub.2 hydrate formation, the consolidated stream issuing from the injector is negatively buoyant, and comprises mixed CO.sub.2 -hydrate/CO.sub.2 -liquid/water phases. The "sinking" characteristic of the produced stream will prolong the metastability of CO.sub.2 ocean sequestration by reducing the CO.sub.2 dissolution rate into water. Furthermore, the deeper the CO.sub.2 hydrate stream sinks after injection, the more stable it becomes internally, the deeper it is dissolved, and the more dispersed is the resulting CO.sub.2 plume. These factors increase efficiency, increase the residence time of CO2 in the ocean, and decrease the cost of CO.sub.2 sequestration while reducing deleterious impacts of free CO.sub.2 gas in ocean water.

  8. Industrial Compositional Streamline Simulation for Efficient and Accurate Prediction of Gas Injection and WAG Processes

    SciTech Connect

    Margot Gerritsen

    2008-10-31

    Gas-injection processes are widely and increasingly used for enhanced oil recovery (EOR). In the United States, for example, EOR production by gas injection accounts for approximately 45% of total EOR production and has tripled since 1986. The understanding of the multiphase, multicomponent flow taking place in any displacement process is essential for successful design of gas-injection projects. Due to complex reservoir geometry, reservoir fluid properties and phase behavior, the design of accurate and efficient numerical simulations for the multiphase, multicomponent flow governing these processes is nontrivial. In this work, we developed, implemented and tested a streamline based solver for gas injection processes that is computationally very attractive: as compared to traditional Eulerian solvers in use by industry it computes solutions with a computational speed orders of magnitude higher and a comparable accuracy provided that cross-flow effects do not dominate. We contributed to the development of compositional streamline solvers in three significant ways: improvement of the overall framework allowing improved streamline coverage and partial streamline tracing, amongst others; parallelization of the streamline code, which significantly improves wall clock time; and development of new compositional solvers that can be implemented along streamlines as well as in existing Eulerian codes used by industry. We designed several novel ideas in the streamline framework. First, we developed an adaptive streamline coverage algorithm. Adding streamlines locally can reduce computational costs by concentrating computational efforts where needed, and reduce mapping errors. Adapting streamline coverage effectively controls mass balance errors that mostly result from the mapping from streamlines to pressure grid. We also introduced the concept of partial streamlines: streamlines that do not necessarily start and/or end at wells. This allows more efficient coverage and avoids

  9. Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion

    PubMed Central

    Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

    2016-01-01

    The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene’s unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics. PMID:27507171

  10. LETTER TO THE EDITOR: Efficient photocarrier injection in a transition metal oxide heterostructure

    NASA Astrophysics Data System (ADS)

    Muraoka, Y.; Yamauchi, T.; Ueda, Y.; Hiroi, Z.

    2002-12-01

    An efficient method for doping a transition metal oxide (TMO) with hole carriers is presented: photocarrier injection (PCI) in an oxide heterostructure. It is shown that an insulating vanadium dioxide (VO2) film is rendered metallic under light irradiation by PCI from an n-type titanium dioxide (TiO2) substrate doped with Nb. Consequently, a large photoconductivity, which is exceptional for TMOs, is found in the VO2/TiO2:Nb heterostructure. We propose an electronic band structure where photoinduced holes created in TiO2:Nb can be transferred into the filled V 3d band via the low-lying O 2p band of VO2.

  11. Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion.

    PubMed

    Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

    2016-01-01

    The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene's unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics. PMID:27507171

  12. Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion

    NASA Astrophysics Data System (ADS)

    Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

    2016-08-01

    The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene’s unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics.

  13. Coexistence of perfect spin filtering for entangled electron pairs and high magnetic storage efficiency in one setup.

    PubMed

    Ji, T T; Bu, N; Chen, F J; Tao, Y C; Wang, J

    2016-01-01

    For Entangled electron pairs superconducting spintronics, there exist two drawbacks in existing proposals of generating entangled electron pairs. One is that the two kinds of different spin entangled electron pairs mix with each other. And the other is a low efficiency of entanglement production. Herein, we report the spin entanglement state of the ferromagnetic insulator (FI)/s-wave superconductor/FI structure on a narrow quantum spin Hall insulator strip. It is shown that not only the high production of entangled electron pairs in wider energy range, but also the perfect spin filtering of entangled electron pairs in the context of no highly spin-polarized electrons, can be obtained. Moreover, the currents for the left and right leads in the antiferromagnetic alignment both can be zero, indicating 100% tunnelling magnetoresistance with highly magnetic storage efficiency. Therefore, the spin filtering for entangled electron pairs and magnetic storage with high efficiencies coexist in one setup. The results may be experimentally demonstrated by measuring the tunnelling conductance and the noise power. PMID:27074893

  14. Coexistence of perfect spin filtering for entangled electron pairs and high magnetic storage efficiency in one setup

    PubMed Central

    Ji, T. T.; Bu, N.; Chen, F. J.; Tao, Y. C.; Wang, J.

    2016-01-01

    For Entangled electron pairs superconducting spintronics, there exist two drawbacks in existing proposals of generating entangled electron pairs. One is that the two kinds of different spin entangled electron pairs mix with each other. And the other is a low efficiency of entanglement production. Herein, we report the spin entanglement state of the ferromagnetic insulator (FI)/s-wave superconductor/FI structure on a narrow quantum spin Hall insulator strip. It is shown that not only the high production of entangled electron pairs in wider energy range, but also the perfect spin filtering of entangled electron pairs in the context of no highly spin-polarized electrons, can be obtained. Moreover, the currents for the left and right leads in the antiferromagnetic alignment both can be zero, indicating 100% tunnelling magnetoresistance with highly magnetic storage efficiency. Therefore, the spin filtering for entangled electron pairs and magnetic storage with high efficiencies coexist in one setup. The results may be experimentally demonstrated by measuring the tunnelling conductance and the noise power. PMID:27074893

  15. Coexistence of perfect spin filtering for entangled electron pairs and high magnetic storage efficiency in one setup

    NASA Astrophysics Data System (ADS)

    Ji, T. T.; Bu, N.; Chen, F. J.; Tao, Y. C.; Wang, J.

    2016-04-01

    For Entangled electron pairs superconducting spintronics, there exist two drawbacks in existing proposals of generating entangled electron pairs. One is that the two kinds of different spin entangled electron pairs mix with each other. And the other is a low efficiency of entanglement production. Herein, we report the spin entanglement state of the ferromagnetic insulator (FI)/s-wave superconductor/FI structure on a narrow quantum spin Hall insulator strip. It is shown that not only the high production of entangled electron pairs in wider energy range, but also the perfect spin filtering of entangled electron pairs in the context of no highly spin-polarized electrons, can be obtained. Moreover, the currents for the left and right leads in the antiferromagnetic alignment both can be zero, indicating 100% tunnelling magnetoresistance with highly magnetic storage efficiency. Therefore, the spin filtering for entangled electron pairs and magnetic storage with high efficiencies coexist in one setup. The results may be experimentally demonstrated by measuring the tunnelling conductance and the noise power.

  16. Development of a high intensity laser for efficient spin exchange optical pumping in a spin maser measurement of the 129Xe EDM

    NASA Astrophysics Data System (ADS)

    Funayama, Chikako; Furukawa, Takeshi; Sato, Tomoya; Ichikawa, Yuichi; Ohtomo, Yuichi; Sakamoto, Yu; Kojima, Shuichiro; Suzuki, Takahiro; Chikamori, Masatoshi; Hikota, Eri; Tsuchiya, Masato; Yoshimi, Akihiro; Bidinosti, Christopher; Ino, Takashi; Ueno, Hideki; Matsuo, Yukari; Fukuyama, Takeshi; Asahi, Koichiro

    2014-09-01

    We aim to search for an atomic electric dipole moment (EDM) in 129Xe beyond the present upper limit at the level of 10-28 e cm. The enhancement of the spin polarization through the efficient spin-exchange optical pumping process is important for stable maser operation. Previously, a distributed feedback (DFB) laser and a spatially separated tapered amplifier (TA) were used for the optical pumping. The characteristics of the TA-DFB laser, such as its narrow line width and high frequency stability, enable us to produce a large spin polarization. However, the power of the TA-DFB laser was not sufficient for stable operation of the 3He spin-maser comagnetometer. Recently, we have been preparing a new laser system containing an external cavity laser diode (ECLD) and a more intense TA for more efficient pumping. In the presentation, we discuss the Rb and noble gases polarizations achieved with our new ECLD compared to that with the DFB laser, and evaluate the advantages gained by employing the ECLD.

  17. Photophysical Properties and Efficient, Stable, Electrogenerated Chemiluminescence of Donor-Acceptor Molecules Exhibiting Thermal Spin Upconversion.

    PubMed

    Ishimatsu, Ryoichi; Edura, Tomohiko; Adachi, Chihaya; Nakano, Koji; Imato, Toshihiko

    2016-03-24

    The photophysical properties and electrogenerated chemiluminescence (ECL) of three donor-acceptor molecules composed of dicyanobenzene and methyl-, tert-butyl-, and phenyl-substituted carbazolyl groups, 1,2,3,5-tetrakis(3,6-disubstituted-carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN-Me, 4CzIPN-tBu, and 4CzIPN-Ph, respectively) are described. These molecules show delayed fluorescence as a result of thermal spin upconversion from the lowest triplet state to the lowest singlet state at room temperature. The three molecules showed yellow to yellowish-red ECL. Remarkably, the ECL efficiencies of 4CzIPN-tBu in dichloromethane reached almost 40 %. Moreover, stable ECL was emitted from 4CzIPN-tBu and 4CzIPN-Ph. In case of 4CzIPN-Me, the ECL intensity decreased during voltage cycles because of polymerization. Quantum chemical calculations revealed that polymerization was inhibited by the steric hindrance of the bulky tert-butyl and phenyl groups on the carbazolyl moieties and lowered the spin density on the carbazolyl groups through electron conjugation for 4CzIPN-Ph. PMID:26916843

  18. Spin-Torque Sensors for Energy Efficient High-Speed Long Interconnects

    NASA Astrophysics Data System (ADS)

    Azim, Zubair Al; Sengupta, Abhronil; Sarwar, Syed Shakib; Roy, Kaushik

    2016-02-01

    In this paper, we propose a Spin-Torque (ST) based sensing scheme that can enable energy efficient multi-bit long distance interconnect architectures. Current-mode interconnects have recently been proposed to overcome the performance degradations associated with conventional voltage mode Copper (Cu) interconnects. However, the performance of current mode interconnects are limited by analog current sensing transceivers and equalization circuits. As a solution, we propose the use of ST based receivers that use Magnetic Tunnel Junctions (MTJ) and simple digital components for current-to-voltage conversion and do not require analog transceivers. We incorporate Spin-Hall Metal (SHM) in our design to achieve high speed sensing. We show both single and multi-bit operations that reveal major benefits at higher speeds. Our simulation results show that the proposed technique consumes only 3.93-4.72 fJ/bit/mm energy while operating at 1-2 Gbits/sec; which is considerably better than existing charge based interconnects. In addition, Voltage Controlled Magnetic Anisotropy (VCMA) can reduce the required current at the sensor. With the inclusion of VCMA, the energy consumption can be further reduced to 2.02-4.02 fJ/bit/mm

  19. Cathodes incorporating thin fluoride layers for efficient injection in blue polymer light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Brown, Thomas M.; Millard, Ian S.; Lacey, David; Burroughes, Jeremy H.; Friend, Richard H.; Cacialli, Franco

    2002-02-01

    Efficient blue Polymer Light-Emitting Diodes (PLEDs) were fabricated by evaporating thin LiF layers between Al or Ca cathodes. Electroabsorption measurements of the built-in potential across the diodes show that devices fabricated with LiF/Ca/Al cathodes exhibit the smallest average barrier height and operating voltage (compared to both Ca and LiF/Al currently amongst the most efficient electron injectors). The turn-on bias is essentially equivalent to the built-in potential (~2.7 V), indicating an effective minimisation of the barrier to electron injection. Results are also compared with devices incorporating CsF layers and are correlated with the electroluminescent characteristics of the LEDs. A very strong dependence (~ exponential) between the built-in potential and the current and luminance at a fixed electric field (0.5MV/cm) is observed and is explained with the reduction of the cathodic barrier height brought about by the different cathode multilayers.

  20. Modified chitosan thermosensitive hydrogel enables sustained and efficient anti-tumor therapy via intratumoral injection.

    PubMed

    Jiang, Yingchun; Meng, Xuanyu; Wu, Zhenghong; Qi, Xiaole

    2016-06-25

    Thermosensitive in situ hydrogels are potential candidates to achieve intratumoral administration, nevertheless their weak mechanical strength always lead to serious drug leakage and burst. Herein, we developed a chitosan based thermosensitive hydrogel of high mechanical strength, which was modified by glutaraldehyde (GA) and polyvinyl alcohol (PVA), for intratumoral delivery of paclitaxel (PTX). The modified hydrogel system could achieve sol-gel transition at 35.79±0.4°C and exhibit a 7.03-fold greater mechanical strength compared with simple chitosan hydrogel. Moreover, the drug release of PTX loaded modified hydrogel in PBS (pH 7.4) was found to be extended to 13 days. After intratumoral administration in mice bearing H22 tumors, PTX-loaded modified hydrogels exhibited a 3.72-fold greater antitumor activity compared with Taxol(®). Overall, these modified hydrogel systems demonstrated to be a promising way to achieve efficient sustained release and enhanced anti-tumor therapy efficiency of anticancer drugs through in situ tumor injectable administration. PMID:27083815

  1. Efficient Lie-Poisson Integrator for Secular Spin Dynamics of Rigid Bodies

    NASA Astrophysics Data System (ADS)

    Breiter, Sławomir; Nesvorný, David; Vokrouhlický, David

    2005-09-01

    A fast and efficient numerical integration algorithm is presented for the problem of the secular evolution of the spin axis. Under the assumption that a celestial body rotates around its maximum moment of inertia, the equations of motion are reduced to the Hamiltonian form with a Lie-Poisson bracket. The integration method is based on the splitting of the Hamiltonian function, and so it conserves the Lie-Poisson structure. Two alternative partitions of the Hamiltonian are investigated, and second-order leapfrog integrators are provided for both cases. Non-Hamiltonian torques can be incorporated into the integrators with a combination of Euler and Lie-Euler approximations. Numerical tests of the methods confirm their useful properties of short computation time and reliability on long integration intervals.

  2. Pure spin current in lateral structures

    NASA Astrophysics Data System (ADS)

    Chen, Shuhan

    Spintronics, a frontier academic research area, is advancing rapidly in recent years. It has been chosen as one of the promising candidates for overcoming the obstacles in continuing the "Moore's Law" of the electronics industry. Spintronics employs both spin and charge degrees of freedom of electrons to reduce energy consumption and increase the flexibility of IC design. To achieve this, it is extremely important to understand the generation, transport, and detection of the spin polarized current (spin current). In this work we use a mesoscopic metallic spintronic structure-nonlocal spin valve (NLSV)-for fundamental studies of spintronics. A nonlocal spin valve consists of two ferromagnetic electrodes (a spin injector and a spin detector) bridged by a non-magnetic spin channel. A thin aluminum oxide barrier (~ 2 - 3 nm) has been shown to effectively enhance the spin injection and detection polarizations. We have studied spin injection and detection in these nanoscale structures. Several topics will be discussed in this work. In Chapter 4 we explore spin transport in NLSVs with Ag channels. Substantial spin signals are observed. The temperature dependence of the spin signals indicates long spin diffusion lengths and low surface spin-flip rate in the mesoscopic Ag channels. Chapter 5 will focus on the asymmetric spin absorption across the low-resistance AlOx barriers in NLSVs. This effect allows for a more simplified and efficient detection scheme for the spin accumulation. Then in Chapter 6 we report a large spin signal owing to a highly resistive break-junction. We have also developed a model to describe the spin-charge coupling effect which enables the large spin signal. In the end, Spin Hall Effect (SHE) is investigated in Chapter 7. A mesoscopic Pt film is utilized to inject a spin accumulation into a mesoscopic Cu channel via the SHE. The spin accumulation in Cu can be detected by the nonlocal method. The reciprocal effect -- the inverse Spin Hall Effect - (i

  3. Efficient generation of gene-modified pigs via injection of zygote with Cas9/sgRNA.

    PubMed

    Wang, Yong; Du, Yinan; Shen, Bin; Zhou, Xiaoyang; Li, Jian; Liu, Yu; Wang, Jianying; Zhou, Jiankui; Hu, Bian; Kang, Nannan; Gao, Jimin; Yu, Liqing; Huang, Xingxu; Wei, Hong

    2015-01-01

    Co-injection of zygotes with Cas9 mRNA and sgRNA has been proven to be an efficient gene-editing strategy for genome modification of different species. Genetic engineering in pigs holds a great promise in biomedical research. By co-injection of one-cell stage embryos with Cas9 mRNA and Npc1l1 sgRNA, we achieved precise Npc1l1 targeting in Chinese Bama miniature pigs at the efficiency as high as 100%. Meanwhile, we carefully analyzed the Npc1l1 sgRNA:Cas9-mediated on- and off-target mutations in various somatic tissues and ovaries, and demonstrated that injection of zygotes with Cas9 mRNA and sgRNA is an efficient and reliable approach for generation of gene-modified pigs. PMID:25653176

  4. Efficient generation of gene-modified pigs via injection of zygote with Cas9/sgRNA

    PubMed Central

    Wang, Yong; Du, Yinan; Shen, Bin; Zhou, Xiaoyang; Li, Jian; Liu, Yu; Wang, Jianying; Zhou, Jiankui; Hu, Bian; Kang, Nannan; Gao, Jimin; Yu, Liqing; Huang, Xingxu; Wei, Hong

    2015-01-01

    Co-injection of zygotes with Cas9 mRNA and sgRNA has been proven to be an efficient gene-editing strategy for genome modification of different species. Genetic engineering in pigs holds a great promise in biomedical research. By co-injection of one-cell stage embryos with Cas9 mRNA and Npc1l1 sgRNA, we achieved precise Npc1l1 targeting in Chinese Bama miniature pigs at the efficiency as high as 100%. Meanwhile, we carefully analyzed the Npc1l1 sgRNA:Cas9-mediated on- and off-target mutations in various somatic tissues and ovaries, and demonstrated that injection of zygotes with Cas9 mRNA and sgRNA is an efficient and reliable approach for generation of gene-modified pigs. PMID:25653176

  5. Slope efficiency and spurious-free dynamic range of silicon Mach-Zehnder modulator upon carrier depletion and injection effects.

    PubMed

    Luo, Xianshu; Tu, Xiaoguang; Song, Junfeng; Ding, Lu; Fang, Qing; Liow, Tsung-Yang; Yu, Mingbin; Lo, Guo-Qiang

    2013-07-15

    We investigate the performances of a silicon PN-junction Mach-Zehnder modulator for analog application. The slope efficiency and spurious-free dynamic range (SFDR) of such a modulator upon carrier depletion and carrier injection effects are characterized and compared. Input RF frequency-dependence measurements show that the depletion-type modulator is usually with ~20 dB ∙ Hz(2/3) higher SFDR comparing to the injection-type modulator, yet with an order-of-magnitude lower slope efficiency. For the depletion-type and injection-type modulators, the measured maximum SFDRs are respectively ~95 dB ∙ Hz(2/3) and 75 dB∙Hz(2/3), with maximum slope efficiency of 0.3 V(-1) and 8 V(-1<). We numerically model the SFDR by using the experimentally extracted effective refractive index change, which shows good agreement with the measurements. PMID:23938508

  6. Exploiting level anti-crossings for efficient and selective transfer of hyperpolarization in coupled nuclear spin systems.

    PubMed

    Pravdivtsev, Andrey N; Yurkovskaya, Alexandra V; Kaptein, Robert; Miesel, Karsten; Vieth, Hans-Martin; Ivanov, Konstantin L

    2013-09-21

    Spin hyperpolarization can be coherently transferred to other nuclei in field-cycling NMR experiments. At low magnetic fields spin polarization is redistributed in a strongly coupled network of spins. Polarization transfer is most efficient at fields where level anti-crossings (LACs) occur for the nuclear spin-states. A further condition is that field switching to the LAC positions is non-adiabatic in order to convert the starting population differences into spin coherences that cause time-dependent mixing of states. The power of this method has been demonstrated by studying transfer of photo-Chemically Induced Dynamic Nuclear Polarization (photo-CIDNP) in N-acetyl-tryptophan. We have investigated the magnetic field dependence and time dependence of coherent CIDNP transfer and directly assessed nuclear spin LACs by studying polarization transfer at specific field positions. The proposed approach based on LACs is not limited to CIDNP but is advantageous for enhancing NMR signals by spin order transfer from any type of hyper-polarized nuclei. PMID:23893009

  7. A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry

    SciTech Connect

    Jozwiak, Chris M.; Graff, Jeff; Lebedev, Gennadi; Andresen, Nord; Schmid, Andreas; Fedorov, Alexei; El Gabaly, Farid; Wan, Weishi; Lanzara, Alessandra; Hussain, Zahid

    2010-04-13

    We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.

  8. Relativistic four-component calculations of indirect nuclear spin-spin couplings with efficient evaluation of the exchange-correlation response kernel

    SciTech Connect

    Křístková, Anežka; Malkin, Vladimir G.; Komorovsky, Stanislav; Repisky, Michal; Malkina, Olga L.

    2015-03-21

    In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method.

  9. Highly efficient, solution processed electrofluorescent small molecule white organic light-emitting diodes with a hybrid electron injection layer.

    PubMed

    Jiang, Zhixiong; Zhong, Zhiming; Xue, Shanfeng; Zhou, Yan; Meng, Yanhong; Hu, Zhanhao; Ai, Na; Wang, Jianbin; Wang, Lei; Peng, Junbiao; Ma, Yuguang; Pei, Jian; Wang, Jian; Cao, Yong

    2014-06-11

    Highly efficient, solution-processed, and all fluorescent white organic light-emitting diodes (WOLEDs) based on fluorescent small molecules have been achieved by incorporating a low-conductivity hole injection layer and an inorganic-organic hybrid electron injection layer. The light-emission layer is created by doping a fluorescent π-conjugated blue dendrimer host (the zeroth generation dendrimer, G0) with a yellow-emitting fluorescent dopant oligo(paraphenylenevinylene) derivative CN-DPASDB with a doping ratio of 100:0.15 (G0:CN-DPASDB) by weight. To suppress excessive holes, the high-conductivity hole injection layer (PEDOT:PSS AI 4083) is replaced by the low-conductivity PEDOT:PSS CH 8000. To facilitate the electron injection, a hybrid electron injection layer is introduced by doping a methanol/water-soluble conjugated polymer poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFNR2) with solution-processed cesium fluoride (CsF). The device achieves a maximum luminous efficiency of 17.0 cd A(-1) and a peak power efficiency of 15.6 lm W(-1) at (0.32, 0.37) with a color rendering index of 64. PMID:24840940

  10. Heterogeneous Spin States in Ultrathin Nanosheets Induce Subtle Lattice Distortion To Trigger Efficient Hydrogen Evolution.

    PubMed

    Liu, Youwen; Hua, Xuemin; Xiao, Chong; Zhou, Tengfei; Huang, Pengcheng; Guo, Zaiping; Pan, Bicai; Xie, Yi

    2016-04-20

    The exploration of efficient nonprecious metal eletrocatalysis of the hydrogen evolution reaction (HER) is an extraordinary challenge for future applications in sustainable energy conversion. The family of first-row-transition-metal dichalcogenides has received a small amount of research, including the active site and dynamics, relative to their extraordinary potential. In response, we developed a strategy to achieve synergistically active sites and dynamic regulation in first-row-transition-metal dichalcogenides by the heterogeneous spin states incorporated in this work. Specifically, taking the metallic Mn-doped pyrite CoSe2 as a self-adaptived, subtle atomic arrangement distortion to provide additional active edge sites for HER will occur in the CoSe2 atomic layers with Mn incorporated into the primitive lattice, which is visually verified by HRTEM. Synergistically, the density functional theory simulation results reveal that the Mn incorporation lowers the kinetic energy barrier by promoting H-H bond formation on two adjacently adsorbed H atoms, benefiting H2 gas evolution. As a result, the Mn-doped CoSe2 ultrathin nanosheets possess useful HER properties with a low overpotential of 174 mV, an unexpectedly small Tafel slope of 36 mV/dec, and a larger exchange current density of 68.3 μA cm(-2). Moreover, the original concept of coordinated regulation presented in this work can broaden horizons and provide new dimensions in the design of newly highly efficient catalysts for hydrogen evolution. PMID:27018462