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Sample records for absolute seebeck coefficient

  1. Absolute Seebeck Coefficient Measurements of Thermoelectric Thin Films

    NASA Astrophysics Data System (ADS)

    Mason, Sarah; Avery, Azure; Basset, Dain; Zink, Barry

    2014-03-01

    Significant advancements in thermoelectric device efficiencies are possible through size reduction to the nanoscale. Quantities that determine a material's efficiency, such as thermopower, or Seebeck coefficient, S, are influenced by the measurement apparatus, so that measuring a thermally generated voltage gives, dV/dT =Ssample -Slead . If accurate values of, Slead, are available, simple subtraction provides Ssample. This is rarely the case in measurements using micromachined devices, with leads exclusively made from thin film materials that do not have well known bulk-like thermopower values. We have developed a technique to directly measure S as a function of T using a micromachined thermal isolation platform consisting of a suspended, patterned SiN membrane. By measuring a series of thicknesses of metallic films up to the infinitely thick thin film limit, in which the thermopower is no longer increasing with thickness, but still not at bulk values, we are able to show the contribution of the leads needed to measure this property. Having a thorough understanding of the background contribution we are able to determine the absolute thermopower of a wide variety of thin films, as well as their thermal and electrical conductivities, on the same sample.

  2. Nanoscale Thermoelectrics: A Study of the Absolute Seebeck Coefficient of Thin Films

    NASA Astrophysics Data System (ADS)

    Mason, Sarah J.

    measure, S, as a function of temperature using a micro-machined thermal isolation platform consisting of a suspended, patterned SiN membrane. By measuring a series of thicknesses of metallic films up to the infinitely thin film limit, in which the electrical resistivity is no longer decreasing with increasing film thickness, but still not at bulk values, along with the effective electron mean free path, we are able to show the contribution of the leads needed to measure this property. Having a comprehensive understanding of the background contribution we are able to determine the absolute Seebeck coefficient of a wide variety of thin films. The nature of the design of the SiN membrane also allows the ability to accurately and directly measure thermal and electrical transport of the thin films yielding a comprehensive measurement of the three quantities that characterize a material's efficiency. This can serve to further the development of thermoelectric materials through precise measurements of the material properties that dictate efficiency.

  3. Measuring Seebeck Coefficient

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor)

    2015-01-01

    A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.

  4. Seebeck coefficient of one electron

    SciTech Connect

    Durrani, Zahid A. K.

    2014-03-07

    The Seebeck coefficient of one electron, driven thermally into a semiconductor single-electron box, is investigated theoretically. With a finite temperature difference ΔT between the source and charging island, a single electron can charge the island in equilibrium, directly generating a Seebeck effect. Seebeck coefficients for small and finite ΔT are calculated and a thermally driven Coulomb staircase is predicted. Single-electron Seebeck oscillations occur with increasing ΔT, as one electron at a time charges the box. A method is proposed for experimental verification of these effects.

  5. High temperature Seebeck coefficient metrology

    SciTech Connect

    Martin, J.; Tritt, T.; Uher, C.

    2010-12-15

    We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.

  6. The Seebeck coefficient of superionic conductors

    SciTech Connect

    Mahan, G. D.

    2015-01-28

    We present a theory of the anomalous Seebeck coefficient found in the superionic conductor Cu{sub 2}Se. It has a phase transition at T = 400 K where the cations disorder but the anions do not. This disorder gives a temperature-dependent width to the electronic states in the conduction band. This width provides the anomalous Seebeck contribution.

  7. The Seebeck coefficient of superionic conductors

    NASA Astrophysics Data System (ADS)

    Mahan, G. D.

    2015-01-01

    We present a theory of the anomalous Seebeck coefficient found in the superionic conductor Cu2Se. It has a phase transition at T = 400 K where the cations disorder but the anions do not. This disorder gives a temperature-dependent width to the electronic states in the conduction band. This width provides the anomalous Seebeck contribution.

  8. Seebeck Coefficient Measured With Differential Heat Pulses

    NASA Technical Reports Server (NTRS)

    Zoltan, L.; Wood, C.; Stapfer, G.

    1986-01-01

    Common experimental errors reduced because pulse technique suppresses drifts in thermoelectric measurements. Differential-heat-pulse apparatus measures Seebeck coefficient in semiconductors at temperatures up to 1,900 K. Sample heated to measuring temperature in furnace. Ends of sample then differentially heated a few degrees more by lamps. Differential temperature rise and consequent Seebeck voltage measured via thermocouple leads. Because pulse technique used, errors that often arise from long-term drifts in thermoelectric measurements suppressed. Apparatus works with temperature differences of only few degrees, further increasing accuracy of coefficients obtained.

  9. Apparatus Measures Seebeck Coefficient And Resistivity

    NASA Technical Reports Server (NTRS)

    Zoltan, Leslie D.; Wood, Charles; Fleurial, Jean-Pierre; Liu, Yixin

    1993-01-01

    Electrical measurements made by four point probes, two of which double as temperature probes. Laboratory apparatus measures both Seebeck coefficients and electrical resistivities of candidate thermoelectric materials at temperatures from ambient to 1,300 K. Apparatus makes possible to take both measurements alternately and in rapid succession during same heating cycle, thereby reducing distortion.

  10. Seebeck Coefficient Metrology: Do Contemporary Protocols Measure Up?

    NASA Astrophysics Data System (ADS)

    Martin, Joshua; Wong-Ng, Winnie; Green, Martin L.

    2015-06-01

    Comparative measurements of the Seebeck coefficient are challenging due to the diversity of instrumentation and measurement protocols. With the implementation of standardized measurement protocols and the use of Standard Reference Materials (SRMs®), for example, the recently certified National Institute of Standards and Technology (NIST) SRM® 3451 ``Low Temperature Seebeck Coefficient Standard (10-390 K)'', researchers can reliably analyze and compare data, both intra- and inter-laboratory, thereby accelerating the development of more efficient thermoelectric materials and devices. We present a comparative overview of commonly adopted Seebeck coefficient measurement practices. First, we examine the influence of asynchronous temporal and spatial measurement of electric potential and temperature. Temporal asynchronicity introduces error in the absolute Seebeck coefficient of the order of ≈10%, whereas spatial asynchronicity introduces error of the order of a few percent. Second, we examine the influence of poor thermal contact between the measurement probes and the sample. This is especially critical at high temperature, wherein the prevalent mode of measuring surface temperature is facilitated by pressure contact. Each topic will include the comparison of data measured using different measurement techniques and using different probe arrangements. We demonstrate that the probe arrangement is the primary limit to high accuracy, wherein the Seebeck coefficients measured by the 2-probe arrangement and those measured by the 4-probe arrangement diverge with the increase in temperature, approaching ≈14% at 900 K. Using these analyses, we provide recommended measurement protocols to guide members of the thermoelectric materials community in performing more accurate measurements and in evaluating more comprehensive uncertainty limits.

  11. Scanning measurement of Seebeck coefficient of a heated sample

    DOEpatents

    Snyder, G. Jeffrey; Iwanaga, Shiho

    2016-04-19

    A novel scanning Seebeck coefficient measurement technique is disclosed utilizing a cold scanning thermocouple probe tip on heated bulk and thin film samples. The system measures variations in the Seebeck coefficient within the samples. The apparatus may be used for two dimensional mapping of the Seebeck coefficient on the bulk and thin film samples. This technique can be utilized for detection of defective regions, as well as phase separations in the sub-mm range of various thermoelectric materials.

  12. Measurement of Seebeck coefficient using a light pulse

    NASA Technical Reports Server (NTRS)

    Wood, C.; Zoltan, D.; Stapfer, G.

    1985-01-01

    A high-temperature (1900 K) Seebeck coefficient apparatus is described in which small thermal gradients are generated in a sample by light pulses transmitted via light pipes. By employing an analog subtraction circuit, the Seebeck coefficient is displayed directly on an X-Y recorder. This technique presents a convenient, accurate, and rapid method for measuring the Seebeck coefficient in highly doped semiconductors as a function of temperature. The nature of the resulting display (X-Y recording) is a valuable tool in determining validity of the data. A straight line results (i.e., a minimum of hysteresis) only if all potential experimental errors are minimized. Under these conditions, the error of measurements of the Seebeck coefficient is estimated to be less than + or - 1 percent.

  13. Magnetic-doped alloys with very large Seebeck coefficients

    NASA Technical Reports Server (NTRS)

    Sellmeyer, D. J.; Zagarins, J.

    1972-01-01

    Preliminary results of this study show that, based on selection of magnetic solute and nonmagnetic solvent from periodic table, alloys having Seebeck coefficients approaching 100 micron V/K can be obtained.

  14. System to Measure Thermal Conductivity and Seebeck Coefficient for Thermoelectrics

    NASA Technical Reports Server (NTRS)

    Kim, Hyun-Jung; Skuza, Jonathan R.; Park, Yeonjoon; King, Glen C.; Choi, Sang H.; Nagavalli, Anita

    2012-01-01

    The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.

  15. Enhancement of Seebeck Coefficient in Bi Nanowires by Electric Field Effect

    NASA Astrophysics Data System (ADS)

    Komine, Takashi; Aono, Tomosuke; Nabatame, Yuta; Murata, Masayuki; Hasegawa, Yasuhiro

    2016-03-01

    In this study, we investigated the electric field effect on the transport properties of a Bi nanowire. These effects were modeled by a surface potential. The electron states of Bi nanowires were numerically analyzed by effective mass equations at the T-point and L-point taking into account surface potential due to an external electric field. The Seebeck coefficients of Bi nanowires were calculated by using the Boltzmann equation with a constant relaxation time. It was found that the Seebeck coefficients increased when the sign of the surface potential parameter was negative. In particular, when the surface potential parameter was -1 eV and the skin depth was 10 nm in a 20-nm-diameter nanowire, the maximum absolute value of the Seebeck coefficient was larger than 1 mV/K, which was greatly improved compared to that without an external electric field.

  16. Identification of a positive-Seebeck-coefficient exohedral fullerene.

    PubMed

    Almutlaq, Nasser; Al-Galiby, Qusiy; Bailey, Steven; Lambert, Colin J

    2016-07-14

    If fullerene-based thermoelectricity is to become a viable technology, then fullerenes exhibiting both positive and negative Seebeck coefficients are needed. C60 is known to have a negative Seebeck coefficient and therefore in this paper we address the challenge of identifying a positive-Seebeck-coefficient fullerene. We investigated the thermoelectric properties of single-molecule junctions of the exohedral fullerene C50Cl10 connected to gold electrodes and found that it indeed possesses a positive Seebeck coefficient. Furthermore, in common with C60, the Seebeck coefficient can be increased by placing more than one C50Cl10 in series. For a single C50Cl10, we find S = +8 μV K(-1) and for two C50Cl10's in series we find S = +30 μV K(-1). We also find that the C50Cl10 monomer and dimer have power factors of 0.5 × 10(-5) W m(-1) K(-2) and 6.0 × 10(-5) W m(-1) K(-2) respectively. These results demonstrate that exohedral fullerenes provide a new class of thermoelectric materials with desirable properties, which complement those of all-carbon fullerenes, thereby enabling the boosting of the thermovoltage in all-fullerene tandem structures.

  17. Measurement of Seebeck coefficient using a large thermal gradient

    NASA Technical Reports Server (NTRS)

    Wood, C.; Chmielewski, A.; Zoltan, D.

    1988-01-01

    The integral method of measuring the Seebeck voltage, V(T), has been applied to short rod-shaped samples. In the present method, one end of the sample is held at a fixed temperature and the other end is automatically varied through a temperature T range of interest, up to a maximum temperature of 1000 C. The Seebeck coefficient is then obtained from the slope of the V(T) vs T curve. The method offers simplicity of sample handling and minimal operator involvement.

  18. A high temperature apparatus for measurement of the Seebeck coefficient

    SciTech Connect

    Iwanaga, Shiho; Toberer, Eric S.; LaLonde, Aaron; Snyder, G. Jeffrey

    2011-06-15

    A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes.

  19. Characterization of Lorenz number with Seebeck coefficient measurement

    SciTech Connect

    Kim, Hyun-Sik; Gibbs, Zachary M.; Tang, Yinglu; Wang, Heng; Snyder, G. Jeffrey

    2015-04-01

    In analyzing zT improvements due to lattice thermal conductivity (κ{sub L}) reduction, electrical conductivity (σ) and total thermal conductivity (κ{sub Total}) are often used to estimate the electronic component of the thermal conductivity (κ{sub E}) and in turn κ{sub L} from κ{sub L} = ∼ κ{sub Total} − LσT. The Wiedemann-Franz law, κ{sub E} = LσT, where L is Lorenz number, is widely used to estimate κ{sub E} from σ measurements. It is a common practice to treat L as a universal factor with 2.44 × 10{sup −8} WΩK{sup −2} (degenerate limit). However, significant deviations from the degenerate limit (approximately 40% or more for Kane bands) are known to occur for non-degenerate semiconductors where L converges to 1.5 × 10{sup −8} WΩK{sup −2} for acoustic phonon scattering. The decrease in L is correlated with an increase in thermopower (absolute value of Seebeck coefficient (S)). Thus, a first order correction to the degenerate limit of L can be based on the measured thermopower, |S|, independent of temperature or doping. We propose the equation: L=1.5+exp[−(|S|)/(116) ] (where L is in 10{sup −8} WΩK{sup −2} and S in μV/K) as a satisfactory approximation for L. This equation is accurate within 5% for single parabolic band/acoustic phonon scattering assumption and within 20% for PbSe, PbS, PbTe, Si{sub 0.8}Ge{sub 0.2} where more complexity is introduced, such as non-parabolic Kane bands, multiple bands, and/or alternate scattering mechanisms. The use of this equation for L rather than a constant value (when detailed band structure and scattering mechanism is not known) will significantly improve the estimation of lattice thermal conductivity.

  20. Seebeck coefficient in correlated low-dimensional organic metals

    NASA Astrophysics Data System (ADS)

    Shahbazi, M.; Bourbonnais, C.

    2016-11-01

    We study the influence of inelastic electron-electron scattering on the temperature variation of the Seebeck coefficient in the normal phase of quasi-one-dimensional organic superconductors. The theory is based on the numerical solution of the semiclassical Boltzmann equation for which the collision integral equation is solved with the aid of the renormalization-group method for the electronic umklapp scattering vertex. We show that the one-loop renormalization-group flow of momentum and temperature-dependent umklapp scattering, in the presence of nesting alterations of the Fermi surface, introduce electron-hole asymmetry in the energy dependence of the anisotropic scattering time. This is responsible for the enhancement of the Seebeck coefficient with respect to the band T -linear prediction and even its sign reversal around the quantum critical point of the phase diagram, namely, where the interplay between antiferromagnetism and superconductivity and also the strength of spin fluctuations are the strongest. A comparison of the results with available data on low-dimensional organic superconductors is presented and critically discussed.

  1. Field-effect-modulated Seebeck coefficient in organic semiconductors.

    PubMed

    Pernstich, K P; Rössner, B; Batlogg, B

    2008-04-01

    Central to the operation of organic electronic and optoelectronic devices is the transport of charge and energy in the organic semiconductor, and to understand the nature and dynamics of charge carriers is at the focus of intense research efforts. As a basic transport property of solids, the Seebeck coefficient S provides deep insight as it is given by the entropy transported by thermally excited charge carriers and involves in the simplest case only electronic contributions where the transported entropy is determined by details of the band structure and scattering events. We have succeeded for the first time to measure the temperature- and carrier-density-dependent thermopower in single crystals and thin films of two prototypical organic semiconductors by a controlled modulation of the chemical potential in a field-effect geometry. Surprisingly, we find the Seebeck coefficient to be well within the range of the electronic contribution in conventional inorganic semiconductors, highlighting the similarity of transport mechanisms in organic and inorganic semiconductors. Charge and entropy transport is best described as band-like transport of quasiparticles that are subjected to scattering, with exponentially distributed in-gap trap states, and without further contributions to S.

  2. Large Seebeck coefficient in frustrated doped Mott insulators

    NASA Astrophysics Data System (ADS)

    Arsenault, Louis-François; Shastry, B. Sriram; Sémon, Patrick; Tremblay, André-Marie

    2011-03-01

    Since calculations based on the standard Kubo formula have proven extremely difficult for electric and thermal transport, Shastry and co-workers suggested two novel approximate ways to obtain the thermopower (S) in interacting systems. One method is based on the high-frequency limit. The other, based on ideas of Kelvin, is purely thermodynamical. With these we study the Hubbard model on a 3d FCC lattice, a frustrated lattice. The high dimensionality of the problem justifies the use of dynamical mean field theory (DMFT). CTQMC in the hybridization expansion and the fast IPT are the impurity solver. The Seebeck coefficient is obtained as a function of doping and temperature for different U. Within DMFT, vertex corrections vanish for transports coefficients, hence the bubble suffices. This enables us to further assess how both approximate methods compare with each other and with the DC Kubo approach. At low T, results can be interpreted in terms of effective Fermi temperatures and carrier number.

  3. The effect of the band edges on the Seebeck coefficient.

    PubMed

    Sonntag, Joachim

    2010-06-16

    The classical thermopower formulae generally applied for the calculation of the Seebeck coefficient S are argued to be incomplete. S can be separated into two different contributions, a scattering term, S(0), and a thermodynamic term, ΔS, representing the additional change of the electrochemical potential μ with temperature T caused by 'non-scattering' effects, for instance, the band edge shift with T. On the basis of this separation into S(0) and ΔS, it is shown that shifts of the band edges with T lead to an additional contribution to the classical thermopower formulae. This separation provides the basis for an interpretation of positive thermopowers measured for many metals. Positive thermopower is expected if the energy of the conduction band edge increases with T and if this effect overcompensates for the influence of the energy dependent conductivity, σ(E). Using experimental thermopower data, the band edge shifts are determined for a series of liquid normal metals.

  4. Thermocyclic stability of candidate Seebeck coefficient standard reference materials at high temperature

    NASA Astrophysics Data System (ADS)

    Martin, Joshua; Wong-Ng, Winnie; Caillat, Thierry; Yonenaga, I.; Green, Martin L.

    2014-05-01

    The Seebeck coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs®) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck coefficient measurement equipment, NIST certified SRM® 3451 "Low Temperature Seebeck Coefficient Standard (10 K to 390 K)". Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM® is required for the high temperature regime (300 K to 900 K). The principal requirement of a SRM® for the Seebeck coefficient at high temperature is thermocyclic stability. We therefore characterized the thermocyclic behavior of the Seebeck coefficient for a series of candidate materials: constantan, p-type single crystal SiGe, and p-type polycrystalline SiGe, by measuring the temperature dependence of the Seebeck coefficient as a function of 10 sequential thermal cycles, between 300 K and 900 K. We employed multiple regression analysis to interpolate and analyze the thermocyclic variability in the measurement curves.

  5. Tailoring of Seebeck coefficient with surface roughness effects in silicon sub-50-nm films.

    PubMed

    Kumar, Manoj; Bagga, Anjana; Neeleshwar, S

    2012-01-01

    The effect of surface roughness on the Seebeck coefficient in the sub-50-nm scale silicon ultra thin films is investigated theoretically using nonequilibrium Green's function formalism. For systematic studies, the surface roughness is modelled by varying thickness periodically with square wave profile characterized by two parameters: amplitude (A 0) and wavelength (λ). Since high Seebeck coefficient is obtained if the temperature difference between the ends of device produces higher currents and higher induced voltages, we investigate how the generated current and induced voltage is affected with increasing A 0 and λ. The theoretical investigations show that pseudoperiodicity of the device structure gives rise to two effects: firstly the threshold energy at which the transmission of current starts is shifted towards higher energy sides and secondly transmission spectra of current possess pseudobands and pseudogaps. The width of the pseudobands and their occupancies determine the total generated current. It is found that current decreases with increasing A 0 but shows a complicated trend with λ. The trends of threshold energy determine the trends of Seebeck voltage with roughness parameters. The increase in threshold energy makes the current flow in higher energy levels. Thus, the Seebeck voltage, i.e. voltage required to nullify this current, increases. Increase in Seebeck voltage results in increase in Seebeck coefficient. We find that threshold energy increases with increasing A 0 and frequency (1/λ). Hence, Seebeck voltage and Seebeck coefficient increase vice versa. It is observed that Seebeck coefficient is tuneable with surface roughness parameters.

  6. Determining a hopping polaron's bandwidth from its Seebeck coefficient: Measuring the disorder energy of a non-crystalline semiconductor

    SciTech Connect

    Emin, David

    2016-01-28

    Charge carriers that execute multi-phonon hopping generally interact strongly enough with phonons to form polarons. A polaron's sluggish motion is linked to slowly shifting atomic displacements that severely reduce the intrinsic width of its transport band. Here a means to estimate hopping polarons' bandwidths from Seebeck-coefficient measurements is described. The magnitudes of semiconductors' Seebeck coefficients are usually quite large (>k/|q| = 86 μV/K) near room temperature. However, in accord with the third law of thermodynamics, Seebeck coefficients must vanish at absolute zero. Here, the transition of the Seebeck coefficient of hopping polarons to its low-temperature regime is investigated. The temperature and sharpness of this transition depend on the concentration of carriers and on the width of their transport band. This feature provides a means of estimating the width of a polaron's transport band. Since the intrinsic broadening of polaron bands is very small, less than the characteristic phonon energy, the net widths of polaron transport bands in disordered semiconductors approach the energetic disorder experienced by their hopping carriers, their disorder energy.

  7. Influence of Thomson effect on the resultant local Seebeck coefficient in thermoelectric composite materials

    NASA Astrophysics Data System (ADS)

    Yamashita, Osamu; Odahara, Hirotaka; Ochi, Takahiro; Satou, Kouji

    2009-01-01

    The resultant local Seebeck coefficient α R (= α S- α T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric efficiency, where α S is the local Seebeck coefficient and α T is the one caused by the Thomson effect. It is shown in this paper that α S, α T, and α R of the p- and n-type Cu/Bi Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of the composite on which the temperature difference Δ T is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position from the local experimental data of R,Δ I,Δ T, and V generated by applying an additional current of ± I to the composite, where R is the electrical resistance and Δ I is a current generated by the composite. As a result, it was found that the absolute values of α S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite, respectively, while those of α T are less than 8% of α S all over the composite and are so small that the relation α R≈ α S can be held. We thus succeeded in measuring α R at the interfaces of the composite.

  8. Studies on Seebeck Coefficient of Individual Bismuth Telluride Nanotube

    NASA Astrophysics Data System (ADS)

    Kim, Duksoo; Du, Renzhong; Yin, Yuewei; Dong, Sining; Li, Xiaoguang; Li, Qi; Tadigadapa, Srinivas

    2013-03-01

    We have studied on Seebeck coefficient (S) of freestanding individual Bismuth Telluride nanotubes using micro-fabricated thermoelectric workbench at the temperatures from 300 K to 25 K. The thermoelectric workbench is composed of three main elements: heater, thermocouple, and platinum pad. A polysilicon-gold thermocouple accurately measures the temperature, arising from the heat generated at the tips of the test sites from the polysilicon heater located 2 μm apart from the thermocouple. Platinum pads placed on top of the heater and thermocouple structures and electrically isolated from these constitute S measurement circuit. IPA solution containing Bi2Te3 nanotubes was drop-cast on the workbench and the Ebeam Induced Deposition of platinum was used to improve the electrical and thermal contacts between nanotube and platinum pads. The inner and outer diameter of nanotube is 50 nm and 70 nm, respectively. The sign of obtained S was positive which is indicating the nanotube is p-type. And the magnitude was increased compared to the bulk and nanowire types. The measured S (364 μV/K) of nanotube at T = 300 K is 1.65 times larger than that (220 μV/K) of bulk and 1.4 times larger than the previously reported value (260 μV/K) of nanowire. This work is supported by NSF MRSEC (Grant No. DMR-0820404)

  9. First principles explanation of the positive Seebeck coefficient of lithium.

    PubMed

    Xu, Bin; Verstraete, Matthieu J

    2014-05-16

    Lithium is one of the simplest metals, with negative charge carriers and a close reproduction of free-electron dispersion. Experimentally, however, Li is one of a handful of elemental solids (along with Cu, Ag, and Au) where the sign of the Seebeck coefficient (S) is opposite to that of the carrier. This counterintuitive behavior still lacks a satisfactory interpretation. We calculate S fully from first principles, within the framework of Allen's formulation of Boltzmann transport theory. Here it is crucial to avoid the constant relaxation time approximation, which gives a sign for S which is necessarily that of the carriers. Our calculated S are in excellent agreement with experimental data, up to the melting point. In comparison with another alkali metal, Na, we demonstrate that within the simplest nontrivial model for the energy dependency of the electron lifetimes, the rapidly increasing density of states (DOS) across the Fermi energy is related to the sign of S in Li. The exceptional energy dependence of the DOS is beyond the free-electron model, as the dispersion is distorted by the Brillouin zone edge; this has a stronger effect in Li than other alkali metals. The electron lifetime dependency on energy is central, but the details of the electron-phonon interaction are found to be less important, contrary to what has been believed for several decades. Band engineering combined with the mechanism exposed here may open the door to new "ambipolar" thermoelectric materials, with a tunable sign for the thermopower even if either n- or p-type doping is impossible.

  10. A new method for simultaneous measurement of Seebeck coefficient and resistivity

    NASA Astrophysics Data System (ADS)

    He, Xu; Yang, Junyou; Jiang, Qinghui; Luo, Yubo; Zhang, Dan; Zhou, Zhiwei; Ren, Yangyang; Li, Xin; Xin, Jiwu; Hou, Jingdi

    2016-12-01

    A new method has been proposed and verified to measure the Seebeck coefficient and electrical resistivity of a sample in the paper. Different from the conventional method for Seebeck coefficient and resistivity measurement, the new method adopts a four-point configuration to measure both the Seebeck coefficient and resistivity. It can well identify the inhomogeneity of the sample by simply comparing the four Seebeck coefficients of different probe combinations, and it is more accurate and appropriate to take the average value of the four Seebeck coefficients as the measured result of the Seebeck coefficient of the sample than that measured by the two-point method. Furthermore, the four-point configuration makes it also very convenient to measure the resistivity by using the Van der Pauw method. The validity of this method has been verified with both the constantan alloy and p-type Bi2Te3 semiconductor samples, and the measurement results are in good agreement with those obtained by commercial available equipment.

  11. A new method for simultaneous measurement of Seebeck coefficient and resistivity.

    PubMed

    He, Xu; Yang, Junyou; Jiang, Qinghui; Luo, Yubo; Zhang, Dan; Zhou, Zhiwei; Ren, Yangyang; Li, Xin; Xin, Jiwu; Hou, Jingdi

    2016-12-01

    A new method has been proposed and verified to measure the Seebeck coefficient and electrical resistivity of a sample in the paper. Different from the conventional method for Seebeck coefficient and resistivity measurement, the new method adopts a four-point configuration to measure both the Seebeck coefficient and resistivity. It can well identify the inhomogeneity of the sample by simply comparing the four Seebeck coefficients of different probe combinations, and it is more accurate and appropriate to take the average value of the four Seebeck coefficients as the measured result of the Seebeck coefficient of the sample than that measured by the two-point method. Furthermore, the four-point configuration makes it also very convenient to measure the resistivity by using the Van der Pauw method. The validity of this method has been verified with both the constantan alloy and p-type Bi2Te3 semiconductor samples, and the measurement results are in good agreement with those obtained by commercial available equipment.

  12. Multifunctional probes for high-throughput measurement of Seebeck coefficient and electrical conductivity at room temperature

    NASA Astrophysics Data System (ADS)

    García-Cañadas, Jorge; Min, Gao

    2014-04-01

    An apparatus capable of rapid measurement of the Seebeck coefficient and electrical resistivity at room temperature is reported. The novel aspect of this apparatus is the use of 4 multifunctional probes that comprise a junction of two conductors at the tip and serve as both thermocouples and electrical contacts. In addition, one of the probes has a built-in heater that can establish a temperature gradient in the sample for the Seebeck measurement. The technique does not require special sample geometries or preparation of contacts and is suitable for bulk and thin film materials. Together with automated sample stage and data acquisition, the equipment is able to measure both the Seebeck coefficient and electrical resistivity in less than 20 s with good accuracy. Less than 5% and 4% relative errors were found for the measurement of the Seebeck coefficient and electrical resistivity, respectively. This makes the apparatus especially useful for high throughput evaluation of thermoelectric materials.

  13. The Seebeck Coefficient and Phonon Drag in Silicon

    DOE PAGES

    Mahan, Gerald; Lindsay, Lucas R.; Broido, David

    2014-12-29

    We present a theory of the phonon-drag Seebeck coe cient in nondegenerate semiconductors, and apply it to silicon for temperatures 30 < T < 300K. Our calculation uses only parameters from the literature, and previous calculations of the phonon lifetime. We nd excellent agreement with the measurements of Geballe and Hull [Phys.Rev. 98, 940 (1955)]. The phonon-drag term dominates at low temperature, and shows an important dependence on the dimensions of the experimental sample.

  14. The Effect of Binding Groups on the Seebeck Coefficient of Phenyl Derivative Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Chang, William; Mai, Chengkang; Kotiuga, Michele; Urban, Jeffrey; Neaton, Jeffrey; Bazan, Gui; Segalman, Rachel

    2013-03-01

    Thermoelectrics currently suffer from low efficiencies due to inverse coupling of the Seebeck coefficient and electrical conductivity, limiting the power factor. Decoupling of these two physical properties has previously been demonstrated in molecular junctions. Using an STM break junction measurement technique, we demonstrate the effect that the direct binding group Au-C has on the Seebeck coefficient. Phenyl derivative molecules with an Au-C direct binding group show a significantly lower Seebeck coefficient than molecules with an Au-S binding group. This lower Seebeck coefficient is explained by theoretical calculations as a broadening in the transmission function due to the direct bonding group. This demonstrates the importance of the metal-molecule interface and binding group selection in tuning the transmission function, and the resultant conductance and Seebeck coefficient. This result will lend further insight in rational design for molecules with higher power factors. We would like to acknowledge support from Office of Naval Research - ONR/AFOSR BAA 10-026

  15. Combination of PVA with Graphene to Improve the Seebeck Coefficient for Thermoelectric Generator Applications

    NASA Astrophysics Data System (ADS)

    Mahmoud, L.; Abdul Samad, Y.; Alhawari, M.; Mohammad, B.; Liao, K.; Ismail, M.

    2015-01-01

    Ultrasensitive thermoelectric (TE) materials are essential for the next generation of self-powered electronic devices. In this work, a graphene-based TE generator was fabricated. For 50 to 1000 graphene layers the average Seebeck coefficient was 90 μV/K. We also report improvement of the Seebeck coefficient by use of a hybrid material containing 10% poly(vinyl alcohol) (PVA) and 90% graphene oxide prepared and tested under the same conditions. The results show that the Seebeck coefficient is improved by an average of 30% compared with graphene alone. Because the fabrication process is facile, scalable, and cost effective, it could also be applicable to other fields of science and engineering.

  16. Critical evaluation of the colossal Seebeck coefficient of nanostructured rutile MnO2

    NASA Astrophysics Data System (ADS)

    Music, Denis; Schneider, Jochen M.

    2015-03-01

    We have explored the correlation between the Seebeck coefficient and the electronic structure of nanostructured rutile MnO2 using density functional theory to critically appraise the three orders of magnitude scatter in literature data. Our hypothesis is that the microstructure and morphology on the nanoscale is causing this behaviour, which we have tested by comparing the Seebeck coefficient of bulk MnO2 with two low-energy surfaces: MnO2(1 1 0) and MnO2(0 0 1). From these data, it is evident that variations over two orders of magnitude in the Seebeck coefficient can be attained by affecting domain size and texture on the nanoscale. This may be understood by analysing the electronic structure. Surface hybridized Mn d-O p states fill the band gap of MnO2 and thus substantially alter the transport properties.

  17. First-principles calculations of Seebeck coefficients in a magnetic semiconductor CuFeS2

    NASA Astrophysics Data System (ADS)

    Takaki, Hirokazu; Kobayashi, Kazuaki; Shimono, Masato; Kobayashi, Nobuhiko; Hirose, Kenji; Tsujii, Naohito; Mori, Takao

    2017-02-01

    We analyze the Seebeck coefficients of a magnetic semiconductor CuFeS2 using first-principles calculation methods based on density functional theory. The calculated temperature dependence of the Seebeck coefficient in the antiferromagnetic phase reproduces a distinctive behavior in a bulk CuFeS2, such as a peak structure at a low temperature and weak temperature dependence around room temperature. In doped systems, almost linear temperature dependence appears. Despite not including any effect beyond the conventional spin density functional theory in our calculations, the calculated results agree qualitatively with the experimental results. These agreements indicate that the behavior of the Seebeck coefficients in CuFeS2 is mainly determined by its electronic structure.

  18. A Study of the Measurement of Seebeck Coefficient of SiGe

    NASA Technical Reports Server (NTRS)

    Heung, King Yi

    2005-01-01

    In 1821 German Physicist Thomas J. Seebeck discovered that heat could be converted into electricity when a temperature difference was applied across two points on a material. Theoretically, the generated voltage has a directly proportional relationship with the temperature difference. This relationship is the Seebeck coefficient that scientists always referred to when determining the efficiency of a thermoelectricity convention. In our experiments, however, hysteresis loops appeared when we plotted voltage against temperature difference, and the measured Seebeck appeared differently when the measurements were run under vacuum, air, and helium gas. Measurements were done by using a low-frequency AC measuring method. By simulating the experimental setup into a; thermal circuit, we found that the loop and inconsistency in measuring Seebeck coefficient could be explained by studying the behaviors of a RC circuit in a thermal sense. Under vacuum, the gap of the hysteresis loop can be largely eliminated if the time period of the temperature difference increased up to 4800s. The trend of the variations in measuring Seebeck coefficients in different environments can also be predicted by using different thermal circuit models.

  19. A hot probe setup for the measurement of Seebeck coefficient of thin wires and thin films using integral method.

    PubMed

    Kumar, S R Sarath; Kasiviswanathan, S

    2008-02-01

    An experimental setup is developed for the measurement of the Seebeck coefficient of thin wires and thin films in the temperature range of 300-650 K. The setup makes use of the integral method for measuring the Seebeck voltage across the sample. Two pointed copper rods with in-built thermocouples serve as hot and cold probes as well as leads for measuring the Seebeck voltage. The setup employs localized heating and enables easy sample loading using a spring loaded mounting system and is fully automated. Test measurements are made on a constantan wire and indium tin oxide (ITO) thin film for illustration. The Seebeck voltage obtained for constantan wire is in agreement with the NIST data for copper constantan couple with an error of 1%. The calculated carrier concentration of ITO film from the Seebeck coefficient measurement is comparable with that obtained by electrical transport measurements. The error in the Seebeck coefficient is estimated to be within 3%.

  20. A hot probe setup for the measurement of Seebeck coefficient of thin wires and thin films using integral method

    NASA Astrophysics Data System (ADS)

    Sarath Kumar, S. R.; Kasiviswanathan, S.

    2008-02-01

    An experimental setup is developed for the measurement of the Seebeck coefficient of thin wires and thin films in the temperature range of 300-650K. The setup makes use of the integral method for measuring the Seebeck voltage across the sample. Two pointed copper rods with in-built thermocouples serve as hot and cold probes as well as leads for measuring the Seebeck voltage. The setup employs localized heating and enables easy sample loading using a spring loaded mounting system and is fully automated. Test measurements are made on a constantan wire and indium tin oxide (ITO) thin film for illustration. The Seebeck voltage obtained for constantan wire is in agreement with the NIST data for copper constantan couple with an error of 1%. The calculated carrier concentration of ITO film from the Seebeck coefficient measurement is comparable with that obtained by electrical transport measurements. The error in the Seebeck coefficient is estimated to be within 3%.

  1. High Seebeck Coefficient of Porous Silicon: Study of the Porosity Dependence.

    PubMed

    Valalaki, Katerina; Benech, Philippe; Galiouna Nassiopoulou, Androula

    2016-12-01

    In-plane Seebeck coefficient of porous Si free-standing membranes of different porosities was accurately measured at room temperature. Quasi-steady-state differential Seebeck coefficient method was used for the measurements. A detailed description of our home-built setup is presented. The Seebeck coefficient was proved to increase with increasing porosity up to a maximum of ~1 mV/K for the ~50 % porosity membrane, which is more than a threefold increase compared to the starting highly doped bulk c-Si substrate. By further increasing porosity and after a maximum is reached, the Seebeck coefficient sharply decreases and stabilizes at ~600 μV/K. The possible mechanisms that determine this behaviour are discussed, supported by structural characterization and photoluminescence measurements. The decrease in nanostructure size and increase in carrier depletion with increasing porosity, together with the complex structure and morphology of porous Si, are at the origin of complex energy filtering and phonon drag effects. All the above contribute to the observed anomalous behaviour of thermopower as a function of porosity and will be discussed.

  2. Measurement system of the Seebeck coefficient or of the electrical resistivity at high temperature.

    PubMed

    Rouleau, O; Alleno, E

    2013-10-01

    A high temperature Seebeck coefficient or electrical resistivity apparatus has been designed and fabricated to measure sample with typical size ~10 × 1 × 1 mm(3). It can measure both transport properties from 300 K to 1000 K in argon atmosphere. The sample lies transversely on top of two metallic half-cylinders, which contain heating cartridges and allow temperature and thermal gradient control and reversal. The temperature gradient is measured by two type N thermocouples pressed against the upper surface of the sample. The key feature of this apparatus is the disk-shaped junction of each type N thermocouple which strongly improves the thermal contact with the sample. The Seebeck coefficient is obtained by averaging over two measured values with opposite thermal gradient directions (~±2 K). For the resistivity measurements, the temperature is stabilized and the temperature gradient is actively reduced below 0.2 K to make negligible any spurious thermal voltage. Uncertainties of ~3% for the Seebeck coefficient and 1% for the resistivity were obtained on Ni samples. The Seebeck coefficient and resistivity have also been measured on a skutterudite sample as small as ~7 × 1.5 × 0.5 mm(3) with very good agreement with literature.

  3. High Seebeck Coefficient of Porous Silicon: Study of the Porosity Dependence

    NASA Astrophysics Data System (ADS)

    Valalaki, Katerina; Benech, Philippe; Galiouna Nassiopoulou, Androula

    2016-04-01

    In-plane Seebeck coefficient of porous Si free-standing membranes of different porosities was accurately measured at room temperature. Quasi-steady-state differential Seebeck coefficient method was used for the measurements. A detailed description of our home-built setup is presented. The Seebeck coefficient was proved to increase with increasing porosity up to a maximum of ~1 mV/K for the ~50 % porosity membrane, which is more than a threefold increase compared to the starting highly doped bulk c-Si substrate. By further increasing porosity and after a maximum is reached, the Seebeck coefficient sharply decreases and stabilizes at ~600 μV/K. The possible mechanisms that determine this behaviour are discussed, supported by structural characterization and photoluminescence measurements. The decrease in nanostructure size and increase in carrier depletion with increasing porosity, together with the complex structure and morphology of porous Si, are at the origin of complex energy filtering and phonon drag effects. All the above contribute to the observed anomalous behaviour of thermopower as a function of porosity and will be discussed.

  4. Calculation of Phonon Conductivity and Seebeck Coefficient in Cu-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Konishi, Yusuke; Asai, Yoshihiro

    2015-03-01

    In recent years, thermoelectric materials have been attracting a lot of attention because they are expected to be applied for utilization of waste heat. Many kinds of materials are studied for this purpose; semiconductors, alloys, organic materials, etc. In 2010, a giant Peltier effect was observed in a Cu-Ni/Au junction. It is considered that this giant Peltier effect is caused by nano-scale phase separation formed in the sputtering process. Although this material is a great candidate for a thermoelectric material, we need to find the condition for a large thermoelectric coefficient that requires a large Seebeck coefficient, large electric conductivity, and small phonon conductivity. We calculated phonon conductivity in Cu-Ni alloy by using nonequilibrium molecular dynamics simulation and calculated Seebeck coefficients via ab-initio methods.

  5. Extracting the effective mass of electrons in transparent conductive oxide thin films using Seebeck coefficient

    SciTech Connect

    Wang, Yaqin; Zhu, Junhao; Tang, Wu

    2014-05-26

    A method is proposed that combines Seebeck coefficient and carrier concentration to determine the electron effective mass of transparent conductive oxide (TCO) thin films. Experiments were conducted to test the validity of this approach on the transparent conductive Ga-doped ZnO thin films deposited by magnetron sputtering. An evident agreement of the calculated electron effective mass of the films is observed between the proposed approach and the previous studies. Besides, the optical carrier concentration and mobility derived from the calculated electron effective mass and spectroscopic ellipsometry using a complex dielectric function are consistent with those from direct Hall-effect measurement. The agreements suggest that Seebeck coefficient can serve as an alternative tool for extracting the effective mass of electrons in TCO films.

  6. Electrical Conductivity, Thermal Behavior, and Seebeck Coefficient of Conductive Films for Printed Thermoelectric Energy Harvesting Systems

    NASA Astrophysics Data System (ADS)

    Ankireddy, Krishnamraju; Menon, Akanksha K.; Iezzi, Brian; Yee, Shannon K.; Losego, Mark D.; Jur, Jesse S.

    2016-11-01

    Printed electronics is being explored as a rapid, facile means for manufacturing thermoelectric generators (TEGs) that can recover useful electrical energy from waste heat. This work examines the relevant electrical conductivity, thermal resistance, thermovoltage, and Seebeck coefficient of printed films for use in such printed flexible TEGs. The thermoelectric performance of TEGs printed using commercially relevant nickel, silver, and carbon inks is evaluated. The microstructure of the printed films is investigated to better understand why the electrical conductivity and Seebeck coefficient are degraded. Thermal conduction is shown to be relatively insensitive to the type of metalized coating and nearly equivalent to that of an uncoated polymer substrate. Of the commercially available conductive ink materials examined, carbon-nickel TEGs are shown to exhibit the highest thermovoltage, with a value of 10.3 μV/K. However, silver-nickel TEGs produced the highest power generation of 14.6 μW [from 31 junctions with temperature difference (Δ T) of 113°C] due to their low electrical resistance. The voltage generated from the silver-nickel TEG was stable under continuous operation at 275°C for 3 h. We have also demonstrated that, after a year of storage in ambient conditions, these devices retain their performance. Notably, the electrical conductivity and Seebeck coefficient measured for individual materials were consistent with those measured from actual printed TEG device structures, validating the need for further fundamental materials characterization to accelerate flexible TEG device optimization.

  7. Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

    DOE PAGES

    Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

    2015-04-28

    The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibriummore » is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.« less

  8. Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

    SciTech Connect

    Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

    2015-04-28

    The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibrium is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.

  9. Low-Temperature Seebeck Coefficients for Polaron-Driven Thermoelectric Effect in Organic Polymers.

    PubMed

    de Oliveira Neto, Pedro Henrique; da Silva Filho, Demétrio A; Roncaratti, Luiz F; Acioli, Paulo H; E Silva, Geraldo Magela

    2016-07-14

    We report the results of electronic structure coupled to molecular dynamics simulations on organic polymers subject to a temperature gradient at low-temperature regimes. The temperature gradient is introduced using a Langevin-type dynamics corrected for quantum effects, which are very important in these systems. Under this condition we were able to determine that in these no-impurity systems the Seebeck coefficient is in the range of 1-3 μV/K. These results are in good agreement with reported experimental results under the same low-temperature conditions.

  10. Economical Route to Produce High Seebeck Coefficient Calcium Cobaltate for Bulk Thermoelectric Applications

    SciTech Connect

    Selig, Jiri; Lin, Sidney; Lin, Hua-Tay; Johnson, D Ray; Wang, Hsin

    2011-01-01

    Phase pure calcium cobaltate (Ca1.24Co1.62O3.86) was prepared by Self-propagating High-temperature Synthesis (SHS) followed by a short post heat treatment. Prepared powders were characterized by XRD for phase purity, and SEM for particle size and distribution. Temperature histories at the center and on the surface of reaction pellet during the SHS process were monitored and recorded. Particles size of synthesized powders was reduced using a planetary mill to increase its specific surface area. Electrical conductivity, thermal conductivity and Seebeck coefficient of the prepared power were measured and figure of merit was reported.

  11. Density functional theory of the Seebeck coefficient in the Coulomb blockade regime

    NASA Astrophysics Data System (ADS)

    Yang, Kaike; Perfetto, Enrico; Kurth, Stefan; Stefanucci, Gianluca; D'Agosta, Roberto

    2016-08-01

    The Seebeck coefficient plays a fundamental role in identifying the efficiency of a thermoelectric device. Its theoretical evaluation for atomistic models is routinely based on density functional theory calculations combined with the Landauer-Büttiker approach to quantum transport. This combination, however, suffers from serious drawbacks for devices in the Coulomb blockade regime. We show how to cure the theory through a simple correction in terms of the temperature derivative of the exchange correlation potential. Our results compare well with both rate equations and experimental findings on carbon nanotubes.

  12. Effect of silicide/silicon hetero-junction structure on thermal conductivity and Seebeck coefficient.

    PubMed

    Choi, Wonchul; Park, Young-Sam; Hyun, Younghoon; Zyung, Taehyoung; Kim, Jaehyeon; Kim, Soojung; Jeon, Hyojin; Shin, Mincheol; Jang, Moongyu

    2013-12-01

    We fabricated a thermoelectric device with a silicide/silicon laminated hetero-structure by using RF sputtering and rapid thermal annealing. The device was observed to have Ohmic characteristics by I-V measurement. The temperature differences and Seebeck coefficients of the proposed silicide/silicon laminated and bulk structure were measured. The laminated thermoelectric device shows suppression of heat flow from the hot to cold side. This is supported by the theory that the atomic mass difference between silicide and silicon creates a scattering center for phonons. The major impact of our work is that phonon transmission is suppressed at the interface between silicide and silicon without degrading electrical conductivity. The estimated thermal conductivity of the 3-layer laminated device is 126.2 +/- 3.7 W/m. K. Thus, by using the 3-layer laminated structure, thermal conductivity is reduced by around 16% compared to bulk silicon. However, the Seebeck coefficient of the thermoelectric device is degraded compared to that of bulk silicon. It is understood that electrical conductivity is improved by using silicide as a scattering center.

  13. Anomalous enhancement of Seebeck coefficients of the graphene/hexagonal boron nitride composites

    NASA Astrophysics Data System (ADS)

    Nakamura, Jun; Akaishi, Akira

    2016-11-01

    Thermoelectric devices convert heat energy to electric power. The dimensionless thermoelectric figure of merit, ZT, is used as a standard criterion for efficiency of thermoelectric conversion. This criterion requires a high Seebeck coefficient, a high electric conductivity, and a low thermal conductivity. In this regard, PbTe, BiTe, and their alloys consisting of relatively heavier elements have been found to show higher values of ZT. In this paper, we focus on the potential of graphene-based composites as thermoelectric materials. Graphene was considered to be a disadvantageous material because of its extremely high thermal conductance and relatively low Seebeck coefficient. However, it has been reported recently that a structural modulation is an effective way of raising the thermoelectric ability of graphene. We introduce the recent progress in the design of graphene-based materials for thermoelectric devices. In particular, we provide a focused investigation of our recent progress regarding the thermopower enhancement in nanoarchitectonics, superlattices, and composites consisting of graphene and hexagonal BN nanoribbons. It has been shown that low-dimensional modulations are effective ways of obtaining a high thermoelectric performance of graphene-based materials.

  14. An instrument for the high temperature measurement of the Seebeck coefficient and electrical resistivity

    NASA Astrophysics Data System (ADS)

    Gunes, Murat; Parlak, Mehmet; Ozenbas, Macit

    2014-05-01

    A system for the simultaneous measurement of thermoelectric power and resistivity of one and/or two samples over a temperature range of 300-1000 K in a vacuum chamber is designed and implemented. A sample probe is developed to provide its easy mounting and usage. In addition, two samples can be measured at the same time. Measurement accuracy has been enhanced by beadless thermocouples and micro-heaters that are specifically designed in order to minimize the ‘cold-finger effect’ and to eliminate some possible source of contact, design and measurement errors. A broad range of physical types and shapes of samples, such as bulk, bar or disc, can be measured by a software controlled system. A differential steady-state method has been applied for Seebeck coefficient measurement. Resistivity measurement is conducted with the axial technique of the four-point probe method. Platinum wire and a niobium rod are chosen as the standard samples. The total data error for the Seebeck coefficient and resistivity measurements is estimated to be less than 2.6% and 1%, respectively.

  15. Spectroscopy of electronic thermal noise as a direct probe of absolute thermoelectric coefficients

    NASA Astrophysics Data System (ADS)

    Garrity, Patrick L.

    2011-04-01

    The utilization of thermal fluctuations or Johnson/Nyquist noise as a generalized spectroscopic technique to experimentally measure transport properties is applied to Pt and W metal films. Through cross-correlation and autocorrelation functions obtained from voltage power spectral density measurements, multiple transport coefficients are obtained through the Green-Kubo formalism. Supported rigorously by the underlying fluctuation-dissipation theorem and Green-Kubo transport theory, this novel experimental technique provides a direct measurement of absolute Seebeck and Peltier coefficients in addition to the electrical resistivity, electronic contribution to thermal conductivity, and Lorenz number. This work reports the validation results of the experiment accomplished through the use of materials with thermoelectric properties widely accepted by the thermoelectric community, Pt and W. Further validation of the data was accomplished by comparing the resistivity results to standard collinear four-probe resistivity measurements. Spectroscopic results for resistivity at 300 K resulted in 5.3% and 2.5% agreement with four-probe resistivity measurements for Pt and W, respectively. The Seebeck coefficient measurements at 300 K showed agreement with published values within 3.8% and 7.5% for Pt and W, respectively. The electronic thermal conductivity measured 66% and 75% of the total thermal conductivity for Pt and W, respectively, at 300 K.

  16. Exploration of thermal conductivity, Seebeck coefficient, and Lorenz number deviations in Ni-Fe alloy films

    NASA Astrophysics Data System (ADS)

    Zink, B. L.; Avery, A. D.; Sultan, R.; Bassett, D.; Cotteril, G.

    2011-03-01

    As electronic and spintronic systems continue to shrink, exploration of the fundamental physics affecting thermal transport in prospective materials becomes increasingly essential. For example, the potential use of spin-torque driven domain wall motion in ferromagnetic nanowires as a memory element requires application of large current densities to these tiny structures. The resulting heating could have both helpful and harmful effects, and is in general not yet well-understood. This is partly due to a gap in the fundamental knowledge of thermal properties of nanoscale systems that is due to the challenging nature of the necessary measurements. We have recently developed a micromachined thermal isolation platform that allows measurement of thermal conductivity, electrical conductivity, and thermopower (or Seebeck effect) in thin film systems. In this talk we present our recent data on thermal conductivity, resistivity, and Seebeck coefficient, for Ni-Fe alloy films with thicknesses varying from 25-100 nm. We compare our results to the predictions of the Wiedemann-Franz law and discuss variations represented by deviations from the Sommerfeld value of the Lorenz number, and conclude with our plans to extend the technique to yet smaller structures. We thank the NRI-WIN and the NSF CAREER program for support.

  17. Thermal Conductivity and Seebeck Coefficients of Icosahedral Boron Arsenide Films on Silicon Carbide

    SciTech Connect

    Y Gong; Y Zhang; M Dudley; Y Zhang; J Edgar; P Heard; M Kuball

    2011-12-31

    The thermal conductivity of icosahedral boron arsenide (B{sub 12}As{sub 2}) films grown on (0001) 6H-SiC substrates by chemical vapor deposition was studied by the 3{omega} technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway's theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 {micro}V/K and 136 {micro}V/K for samples grown at 1350 C with AsH{sub 3}/B{sub 2}H{sub 6} flow ratio equals to 1:1 and 3:5, respectively.

  18. Field-effect modulation of Seebeck coefficient in single PbSe nanowires.

    PubMed

    Liang, Wenjie; Hochbaum, Allon I; Fardy, Melissa; Rabin, Oded; Zhang, Minjuan; Yang, Peidong

    2009-04-01

    In this Letter, we present a novel strategy to control the thermoelectric properties of individual PbSe nanowires. Using a field-effect gated device, we were able to tune the Seebeck coefficient of single PbSe nanowires from 64 to 193 microV x K(-1). This direct electrical field control of sigma and S suggests a powerful strategy for optimizing ZT in thermoelectric devices. These results represent the first demonstration of field-effect modulation of the thermoelectric figure of merit in a single semiconductor nanowire. This novel strategy for thermoelectric property modulation could prove especially important in optimizing the thermoelectric properties of semiconductors where reproducible doping is difficult to achieve.

  19. Record Seebeck coefficient and extremely low thermal conductivity in nanostructured SnSe

    SciTech Connect

    Serrano-Sánchez, F.; Gharsallah, M.; Nemes, N. M.; Mompean, F. J.; Martínez, J. L.; Alonso, J. A.

    2015-02-23

    SnSe has been prepared by arc-melting, as mechanically robust pellets, consisting of highly oriented polycrystals. This material has been characterized by neutron powder diffraction (NPD), scanning electron microscopy, and transport measurements. A microscopic analysis from NPD data demonstrates a quite perfect stoichiometry SnSe{sub 0.98(2)} and a fair amount of anharmonicity of the chemical bonds. The Seebeck coefficient reaches a record maximum value of 668 μV K{sup −1} at 380 K; simultaneously, this highly oriented sample exhibits an extremely low thermal conductivity lower than 0.1 W m{sup −1} K{sup −1} around room temperature, which are two of the main ingredients of good thermoelectric materials. These excellent features exceed the reported values for this semiconducting compound in single crystalline form in the moderate-temperatures region and highlight its possibilities as a potential thermoelectric material.

  20. Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor

    NASA Astrophysics Data System (ADS)

    Jaafar, W. M. N. Wan; Snyder, J. E.; Min, Gao

    2013-05-01

    An apparatus for measuring the Seebeck coefficient (α) and electrical resistivity (ρ) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring α and ρ of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for "simultaneous" measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 °C-100 °C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ±4.9% for Seebeck coefficient and ±5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is -2.43 μVK-1 (-12.5%) for the Seebeck coefficient and -0.4 μΩ cm (-4.6%) for the electrical resistivity, respectively.

  1. Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor.

    PubMed

    Jaafar, W M N Wan; Snyder, J E; Min, Gao

    2013-05-01

    An apparatus for measuring the Seebeck coefficient (α) and electrical resistivity (ρ) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring α and ρ of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for "simultaneous" measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 °C-100 °C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ±4.9% for Seebeck coefficient and ±5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is -2.43 μVK(-1) (-12.5%) for the Seebeck coefficient and -0.4 μΩ cm (-4.6%) for the electrical resistivity, respectively.

  2. Measurement of the high-temperature Seebeck coefficient of thin films by means of an epitaxially regrown thermometric reference material

    NASA Astrophysics Data System (ADS)

    Ramu, Ashok T.; Mages, Phillip; Zhang, Chong; Imamura, Jeffrey T.; Bowers, John E.

    2012-09-01

    The Seebeck coefficient of a typical thermoelectric material, silicon-doped InGaAs lattice-matched to InP, is measured over a temperature range from 300 K to 550 K. By depositing and patterning a thermometric reference bar of silicon-doped InP adjacent to a bar of the material under test, temperature differences are measured directly. This is in contrast to conventional two-thermocouple techniques that subtract two large temperatures to yield a small temperature difference, a procedure prone to errors. The proposed technique retains the simple instrumentation of two-thermocouple techniques while eliminating the critical dependence of the latter on good thermal contact. The repeatability of the proposed technique is demonstrated to be ±2.6% over three temperature sweeps, while the repeatability of two-thermocouple measurements is about ±5%. The improved repeatability is significant for reliable reporting of the ZT figure of merit, which is proportional to the square of the Seebeck coefficient. The accuracy of the proposed technique depends on the accuracy with which the high-temperature Seebeck coefficient of the reference material may be computed or measured. In this work, the Seebeck coefficient of the reference material, n+ InP, is computed by rigorous solution of the Boltzmann transport equation. The accuracy and repeatability of the proposed technique can be systematically improved by scaling, and the method is easily extensible to other material systems currently being investigated for high thermoelectric energy conversion efficiency.

  3. Determination of absolute internal conversion coefficients using the SAGE spectrometer

    NASA Astrophysics Data System (ADS)

    Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.

    2016-03-01

    A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.

  4. Iron Disilicide as High-Temperature Reference Material for Traceable Measurements of Seebeck Coefficient Between 300 K and 800 K

    NASA Astrophysics Data System (ADS)

    Ziolkowski, Pawel; Stiewe, Christian; de Boor, Johannes; Druschke, Ines; Zabrocki, Knud; Edler, Frank; Haupt, Sebastian; König, Jan; Mueller, Eckhard

    2017-01-01

    Thermoelectric generators (TEGs) convert heat to electrical energy by means of the Seebeck effect. The Seebeck coefficient is a central thermoelectric material property, measuring the magnitude of the thermovoltage generated in response to a temperature difference across a thermoelectric material. Precise determination of the Seebeck coefficient provides the basis for reliable performance assessment in materials development in the field of thermoelectrics. For several reasons, measurement uncertainties of up to 14% can often be observed in interlaboratory comparisons of temperature-dependent Seebeck coefficient or in error analyses on currently employed instruments. This is still too high for an industrial benchmark and insufficient for many scientific investigations and technological developments. The TESt (thermoelectric standardization) project was launched in 2011, funded by the German Federal Ministry of Education and Research (BMBF), to reduce measurement uncertainties, engineer traceable and precise thermoelectric measurement techniques for materials and TEGs, and develop reference materials (RMs) for temperature-dependent determination of the Seebeck coefficient. We report herein the successful development and qualification of cobalt-doped β-iron disilicide ( β-Fe0.95Co0.05Si2) as a RM for high-temperature thermoelectric metrology. A brief survey on technological processes for manufacturing and machining of samples is presented. Focus is placed on metrological qualification of the iron disilicide, results of an international round-robin test, and final certification as a reference material in accordance with ISO-Guide 35 and the "Guide to the expression of uncertainty in measurement" by the Physikalisch-Technische Bundesanstalt, the national metrology institute of Germany.

  5. Optoelectronic properties and Seebeck coefficient in SnSe thin films

    NASA Astrophysics Data System (ADS)

    Urmila, K. S.; Namitha, T. A.; Rajani, J.; Philip, R. R.; Pradeep, B.

    2016-09-01

    SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523 ± 5 K and pressure of 10-5 mbar. The as-prepared SnSe thin films are characterized for their structural, optical and electrical properties by various experimental techniques. The p-type conductivity, near-optimum direct band gap, high absorption coefficient and good photosensitivity of the SnSe thin film indicate its suitability for photovoltaic applications. The optical constants, loss factor, quality factor and optical conductivity of the films are evaluated. The results of Hall and thermoelectric power measurements are correlated to determine the density of states, Fermi energy and effective mass of carriers and are obtained as 2.8 × 1017 cm-3, 0.03 eV and 0.05m 0 respectively. The high Seebeck coefficient ≈ 7863 μV/K, reasonably good power factor ≈ 7.2 × 10-4 W/(m·K2) and thermoelectric figure of merit ≈ 1.2 observed at 42 K suggests that, on further work, the prepared SnSe thin films can also be considered as a possible candidate for cryogenic thermoelectric applications.

  6. Quantifying the Local Seebeck Coefficient using Scanning Thermoelectric Microscopy (SThEM)

    NASA Astrophysics Data System (ADS)

    Walrath, Jenna; Lin, Yen-Hsiang; Pipe, Kevin; Goldman, Rachel

    2013-03-01

    Thermoelectric (TE) devices allow reliable solid-state conversion of heat to electricity. The efficiency of a TE device is determined by the figure of merit, ZT, which is sensitive to the Seebeck coefficient, S. A promising alternative to traditional macroscale measurements of S is scanning thermoelectric microscopy (SThEM), which can profile S with nm resolution. In SThEM, an unheated scanning tunneling microscopy tip acts as a high-resolution voltmeter probe to measure the thermally-induced voltage, V, in a heated sample. However, the temperature (T) gradient is not localized to the sample, and the measured V is a convolution of voltages within the region of non-zero temperature gradient. Therefore we have developed a 1D Fourier heat conduction model to predict the T gradient in the tip and to deconvolute the measured V within the sample. This approach enables direct conversion between the measured V and the local S. This material is based upon work supported by the Department of Energy under Award Number DE-PI0000012. Y.H. Lin and R.S. Goldman are supported in part by the DOE under contract No. DE-FG02-06ER46339.

  7. Seebeck Coefficient Measurements on Micron-Size Single-Crystal Zinc Germanium Nitride Rods

    NASA Astrophysics Data System (ADS)

    Dyck, J. S.; Colvin, J. R.; Quayle, P. C.; Peshek, T. J.; Kash, K.

    2016-06-01

    II-IV-nitride compounds are tetrahedrally bonded, heterovalent ternary semiconductors that have recently garnered attention for their potential technological applications. These materials are derived from the parent III-nitride compounds; ZnGeN2 is the II-IV-nitride analogue to the III-nitride GaN. Very little is known about the transport properties of ZnGeN2. In this work, we present Seebeck coefficient ( S) data on 3-micron-diameter, 70-micron-long, single-crystal ZnGeN2 rods, employing a novel measurement approach. The measurements of S show that the majority free carriers are electrons, and imply that the carrier gas is degenerate. Within a single-band model for the conduction band, a carrier concentration of order 1019 cm-3 was estimated for a measured S = -90 μV/K. Together with electrical transport measurements, a lower limit for the electron mobility is estimated to be ˜20 cm2/V-s. A discussion of this material as a thermoelectric is presented. The background level of free electrons in this unintentionally doped ZnGeN2 is very near the predicted optimum value for maximum thermoelectric performance.

  8. Thermal conductivity and Seebeck coefficients of icosahedral boron arsenide films on silicon carbide

    SciTech Connect

    Gong, Y.; Kuball, M.; Zhang, Y.; Dudley, M.; Zhang, Y.; Edgar, J. H.; Heard, P. J.

    2010-10-15

    The thermal conductivity of icosahedral boron arsenide (B{sub 12}As{sub 2}) films grown on (0001) 6H-SiC substrates by chemical vapor deposition was studied by the 3{omega} technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 deg. C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway's theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 {mu}V/K and 136 {mu}V/K for samples grown at 1350 deg. C with AsH{sub 3}/B{sub 2}H{sub 6} flow ratio equals to 1:1 and 3:5, respectively.

  9. The Seebeck Coefficient in Oxygen Enriched La2NiO4

    NASA Astrophysics Data System (ADS)

    Bach, Paul; Leboran, Victor; Rivadulla, Francisco

    2013-03-01

    Oxide-based devices show promise for themoelectric applications due to their chemical stability and straightforward fabrication. The La2NiO4+δ system has been predicted to show an increased thermopower coupled with an increased electrical conductivity around δ = 0 . 05 [Pardo et al. PRB 86, 165114 (2012)] that could lead to a large thermoelectric figure of merit (ZT). We investigate the suitability of lanthanum nickelate as a candidate material for high-ZT devices through a systematic study of oxygenated thin films grown by pulsed laser deposition. We report the electrical conductivity, Seebeck coefficient, and structural morphology of La2NiO4 grown in a range of oxidizing atmospheres and discuss their implications for controlled engineering of thermoelectric properties. We have explored the possibility of gate-tuning these systems in order to fabricate single-oxide based devices. This work was supported by the Ministerio de Ciencia e Innovación (Spain), grant MAT2010-16157, and the European Research Council, grant ERC-2010-StG 259082 2D THERMS.

  10. Strain-induced electronic band convergence: effect on the Seebeck coefficient of Mg2Si for thermoelectric applications.

    PubMed

    Balout, H; Boulet, P; Record, M-C

    2017-04-01

    The present theoretical study, performed using density-functional theory and Boltzmann transport theory formalisms, shows that under 2.246 % isotropic tensile strain, the two energy-lowest conduction bands of Mg2Si overlap. The two, threefold-degenerated orbitals become a unique, sixfold-degenerated orbital. It is demonstrated that such degeneracy implies an increase of the Seebeck coefficient, of the electrical conductivity, of the power factor, and in fine of the figure of merit.

  11. Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides

    DOE PAGES

    Levin, E. M.

    2016-06-27

    Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S, depends on the free (mobile) carrier concentration, n, and effective mass, m*, as S ~ m*/n2/3. The carrier concentration in tellurides can be derived from 125Te nuclear magnetic resonance (NMR) spin-lattice relaxation measurements. The NMR spin-lattice relaxation rate, 1/T1, depends on both n and m* as 1/T1~(m*)3/2n (within classical Maxwell-Boltzmann statistics) or as 1/T1~(m*)2n2/3 (within quantum Fermi-Dirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficientmore » and 125Te NMR spin-lattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study AgxSbxGe50–2xTe50, well-known GeTe-based high-efficiency tellurium-antimony-germanium-silver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Thus, values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.« less

  12. High temperature setup for measurements of Seebeck coefficient and electrical resistivity of thin films using inductive heating

    NASA Astrophysics Data System (ADS)

    Adnane, L.; Williams, N.; Silva, H.; Gokirmak, A.

    2015-10-01

    We have developed an automated setup for simultaneous measurement of Seebeck coefficient S(T) and electrical resistivity ρ(T) of thin film samples from room temperature to ˜650 °C. S and ρ are extracted from current-voltage (I-V) measurements obtained using a semiconductor parameter analyzer and temperature measurements obtained using commercial thermocouples. The slope and the x-axis intercept of the I-V characteristics represent the sample conductance G and the Seebeck voltage, respectively. The measured G(T) can be scaled to ρ(T) by the geometry factor obtained from the room temperature resistivity measurement of the film. The setup uses resistive or inductive heating to control the temperature and temperature gradient on the sample. Inductive heating is achieved with steel plates that surround the test area and a water cooled copper pipe coil underneath that generates an AC magnetic field. The measurements can be performed using resistive heating only or inductive heating only, or a combination of both depending on the desired heating ranges. Inductive heating provides a more uniform heating of the test area, does not require contacts to the sample holder, can be used up to the Curie temperature of the particular magnetic material, and the temperature gradients can be adjusted by the relative positions of the coil and sample. Example results obtained for low doped single-crystal silicon with inductive heating only and with resistive heating only are presented.

  13. Reliable measurement of the Seebeck coefficient of organic and inorganic materials between 260 K and 460 K

    SciTech Connect

    Beretta, D.; Lanzani, G.; Bruno, P.; Caironi, M.

    2015-07-15

    A new experimental setup for reliable measurement of the in-plane Seebeck coefficient of organic and inorganic thin films and bulk materials is reported. The system is based on the “Quasi-Static” approach and can measure the thermopower in the range of temperature between 260 K and 460 K. The system has been tested on a pure nickel bulk sample and on a thin film of commercially available PEDOT:PSS deposited by spin coating on glass. Repeatability within 1.5% for the nickel sample is demonstrated, while accuracy in the measurement of both organic and inorganic samples is guaranteed by time interpolation of data and by operating with a temperature difference over the sample of less than 1 K.

  14. Statistical Analysis of a Round-Robin Measurement Survey of Two Candidate Materials for a Seebeck Coefficient Standard Reference Material.

    PubMed

    Lu, Z Q J; Lowhorn, N D; Wong-Ng, W; Zhang, W; Thomas, E L; Otani, M; Green, M L; Tran, T N; Caylor, C; Dilley, N R; Downey, A; Edwards, B; Elsner, N; Ghamaty, S; Hogan, T; Jie, Q; Li, Q; Martin, J; Nolas, G; Obara, H; Sharp, J; Venkatasubramanian, R; Willigan, R; Yang, J; Tritt, T

    2009-01-01

    In an effort to develop a Standard Reference Material (SRM™) for Seebeck coefficient, we have conducted a round-robin measurement survey of two candidate materials-undoped Bi2Te3 and Constantan (55 % Cu and 45 % Ni alloy). Measurements were performed in two rounds by twelve laboratories involved in active thermoelectric research using a number of different commercial and custom-built measurement systems and techniques. In this paper we report the detailed statistical analyses on the interlaboratory measurement results and the statistical methodology for analysis of irregularly sampled measurement curves in the interlaboratory study setting. Based on these results, we have selected Bi2Te3 as the prototype standard material. Once available, this SRM will be useful for future interlaboratory data comparison and instrument calibrations.

  15. High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell

    SciTech Connect

    Baker, Jason; Kumar, Ravhi S.; Park, Changyong; Kenney-Benson, Curtis; Cornelius, Andrew L.; Velisavljevic, Nenad

    2016-01-01

    A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid–solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric material PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. Furthermore, this new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.

  16. High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell

    DOE PAGES

    Baker, Jason; Kumar, Ravhi S.; Park, Changyong; ...

    2016-01-01

    A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid–solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric materialmore » PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. Furthermore, this new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.« less

  17. Cross-Plane Seebeck Coefficient Measurement of Misfit Layered Compounds (SnSe)n(TiSe2)n (n = 1,3,4,5).

    PubMed

    Li, Zhen; Bauers, Sage R; Poudel, Nirakar; Hamann, Danielle; Wang, Xiaoming; Choi, David S; Esfarjani, Keivan; Shi, Li; Johnson, David C; Cronin, Stephen B

    2017-03-08

    We report cross-plane thermoelectric measurements of misfit layered compounds (SnSe)n(TiSe2)n (n = 1,3,4,5), approximately 50 nm thick. Metal resistance thermometers are fabricated on the top and bottom of the (SnSe)n(TiSe2)n material to measure the temperature difference and heat transport through the material directly. By varying the number of layers in a supercell, n, we vary the interface density while maintaining a constant global stoichiometry. The Seebeck coefficient measured across the (SnSe)n(TiSe2)n samples was found to depend strongly on the number of layers in the supercell (n). When n decreases from 5 to 1, the cross-plane Seebeck coefficient decreases from -31 to -2.5 μV/K, while the cross-plane effective thermal conductivity decreases by a factor of 2, due to increased interfacial phonon scattering. The cross-plane Seebeck coefficients of the (SnSe)n(TiSe2)n are very different from the in-plane Seebeck coefficients, which are higher in magnitude and less sensitive to the number of layers in a supercell, n. We believe this difference is due to the different carrier types in the n-SnSe and p-TiSe2 layers and the effect of tunneling on the cross-plane transport.

  18. Thermal conductivity and Seebeck coefficient of Fe and Fe-Si alloys: Implications for variable Lorenz number

    NASA Astrophysics Data System (ADS)

    Secco, Richard A.

    2017-04-01

    The Wiedemann-Franz Law is often used to calculate the thermal conductivity of Fe from experimental measurements of the electrical conductivity. It is shown by measurements of the Seebeck coefficient (S) of solid and liquid Fe at pressures up to 6 GPa and temperatures up to 2100 K that the Sommerfeld value (L0 = 2.445 × 10-8 W Ω K-2) of the Lorenz number (L) represents more than 99% of the electronic component of the thermal conductivity of Fe. Using experimental values of electrical resistivity and thermal conductivity of Fe, L/L0 is shown to vary by as much as 1.22 in the solid state and 1.32 in the liquid state, signifying a non-negligible phonon component. An expression for the pressure dependence of L at the melting boundary up to 5 GPa is derived for electron-phonon scattering. For Fe-Si alloys, L/L0 varies more than for pure Fe and generally increases with increasing Si and state of disorder. New values for the conductive heat flow in a pure Fe core of Mercury are presented.

  19. Transport Properties of Bulk Thermoelectrics An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity

    SciTech Connect

    Wang, Hsin; Porter, Wallace D; Bottner, Harold; Konig, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolett, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Partricia; Sharp, Jeff; Lo, Jason; Keinke, Holger; Kiss, Laszlo I.

    2013-01-01

    Recent research and development of high temperature thermoelectric materials has demonstrated great potential of converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as an important area for improving energy efficiency. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is Part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main focuses in Part I are on two electronic transport properties: Seebeck coefficient and electrical resistivity.

  20. Transport Properties of Bulk Thermoelectrics—An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity

    NASA Astrophysics Data System (ADS)

    Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff W.; Lo, Jason; Kleinke, Holger; Kiss, Laszlo

    2013-04-01

    Recent research and development of high-temperature thermoelectric materials has demonstrated great potential for converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air-conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The dimensionless figure of merit, ZT, still needs to be improved from the current value of 1.0 to 1.5 to above 2.0 to be competitive with other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods, and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as a key component for improving energy efficiency. The International Energy Agency (IEA) group under the Implementing Agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main foci in part I are the measurement of two electronic transport properties: Seebeck coefficient and electrical resistivity.

  1. The fabrication of thermoelectric La0.95Sr0.05CoO3 nanofibers and Seebeck coefficient measurement.

    PubMed

    Xu, Weihe; Shi, Yong; Hadim, Hamid

    2010-10-01

    The P-type perovskite oxides La(1-x)Sr(x)CoO(3) are a promising group of complex oxide thermoelectric (TE) materials. The thermoelectric properties of these oxides are expected to be significantly improved when their critical dimensions are reduced to the nanoscale. In this paper, the La(0.95)Sr(0.05)CoO(3) nanofibers, with diameters in the range of approximately 35 nm, were successfully prepared by the electrospinning process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize these thermoelectric nanofibers. A micro-electromechanical (MEMS) tester was designed and fabricated to measure the Seebeck coefficient of the nanofibers. The measured voltage output was as large as 1.7 mV and the obtained Seebeck coefficient of the nanofibers reached 650 microV K(-1).

  2. Effects of Ge replacement in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration modified by local electron imbalance

    NASA Astrophysics Data System (ADS)

    Levin, E. M.; Howard, A.; Straszheim, W. E.

    2015-03-01

    XRD, SEM, EDS, 125Te NMR, Seebeck coefficient, and electrical resistivity of AgxGe50-xTe50 and SbxGe50-xTe50 alloys have been studied. Replacement of Ge in GeTe by Sb significantly increases the Seebeck coefficient, while replacement by Ag decreases it. These effects can be attributed to a change in carrier concentration observed via 125Te NMR spin-lattice relaxation measurements and NMR signal position, which mostly depends on the Knight shift. Variation in carrier concentration in AgxGe50-xTe50 and SbxGe50-xTe50 can be attributed to different electron configurations of valence electrons of Ag (4d105s1) and Sb (5s25p3) compared to that of Ge (4s24p2) resulting in local electron imbalances and changing the concentration of charge carrier (holes) generated by Ge vacancies. In contrast, our 125Te NMR and Seebeck coefficient data for Ag2Sb2Ge46Te50 are similar to those observed for GeTe. This shows that effects from Ag and Sb compensate each other and indicates the existence of [Ag +Sb] pairs. The effects of Ge replacement in GeTe by Ag, Sb, or [Ag +Sb] on rhombohedral lattice distortion also have been analyzed. Interplay between the Seebeck coefficient and electrical resistivity in these alloys results in variation of power factor; the value of 45 mW/cm K2, the highest among known tellurides, was found for Sb2Ge48Te50.

  3. Influence of surface states and size effects on the Seebeck coefficient and electrical resistance of Bi1-xSbx nanowire arrays.

    PubMed

    Cassinelli, M; Müller, S; Voss, K-O; Trautmann, C; Völklein, F; Gooth, J; Nielsch, K; Toimil-Molares, M E

    2017-03-02

    The Seebeck coefficient and electrical resistance of Bi1-xSbx nanowire arrays electrodeposited in etched ion-track membranes have been investigated as a function of wire diameter (40-750 nm) and composition (0 ≤ x ≤ 1). The experimental data reveal a non-monotonic dependence between thermopower and wire diameter for three different compositions. Thus, the thermopower values decrease with decreasing wire diameter, exhibiting a minimum around ∼60 nm. This non-monotonic dependence of the Seebeck coefficient is attributed to the interplay of surface and bulk states. On the one hand, the metallic properties of the surface states can contribute to decreasing the thermopower of the nanostructure with increasing surface-to-volume ratio. On the other hand, for wires thinner than ∼60 nm, the relative increase of the thermopower can be tentatively attributed to the presence of quantum-size effects on both surface and bulk states. These measurements contribute to a better understanding of the interplay between bulk and surface states in nanostructures, and indicate that the decrease of Seebeck coefficient with decreasing diameter caused by the presence of surfaces states can possibly be overcome for even thinner nanowires.

  4. Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and 125Te NMR measurements in complex tellurides

    NASA Astrophysics Data System (ADS)

    Levin, E. M.

    2016-06-01

    Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S , depends on the free (mobile) carrier concentration, n , and effective mass, m*, as S ˜m*/n2 /3 . The carrier concentration in tellurides can be derived from 125Te nuclear magnetic resonance (NMR) spin-lattice relaxation measurements. The NMR spin-lattice relaxation rate, 1 /T1 , depends on both n and m* as 1 /T1˜(m*)3/2n (within classical Maxwell-Boltzmann statistics) or as 1 /T1˜(m*)2n2 /3 (within quantum Fermi-Dirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficient and 125Te NMR spin-lattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study A gxS bxG e50-2xT e50 , well-known GeTe-based high-efficiency tellurium-antimony-germanium-silver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.

  5. The Seebeck coefficient of monocrystalline α-SiC and polycrystalline β-SiC measured at 300-533 K

    NASA Astrophysics Data System (ADS)

    Abu-Ageel, N.; Aslam, M.; Ager, R.; Rimai, L.

    2000-01-01

    The temperature dependence of the Seebeck coefficient of polycrystalline icons/Journals/Common/beta" ALT="beta" ALIGN="TOP"/> -SiC films deposited on quartz substrates by laser ablation and of commercially available icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> -SiC wafers is reported in a temperature range of 300-533 K for the first time. The Seebeck emf of icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> -SiC substrates and icons/Journals/Common/beta" ALT="beta" ALIGN="TOP"/> -SiC samples ranges between -9 µV °C-1 and -108 µV °C-1 which is higher than that of commercial Pt thermocouples.

  6. Effect of Synthesis Conditions on Formation, Electrical Properties, and Seebeck Coefficient of p-Type Ca3Co4O9±δ Thermoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Radhika, T.; Raghu, N.; Powrnami, N.; Jothi Ramalingam, R.; Al-Lohedan, Hamad A.

    2017-01-01

    Ca3Co4O9±δ ceramic powders have been prepared by a solid-state method. The calcination and sintering temperatures and reaction conditions were varied to achieve highly dense materials for thermoelectric applications. The optimized calcination temperature and reaction conditions were derived. X-ray diffraction patterns showed formation of secondary phases for longer calcination duration. The density of the ceramics ranged from 3.2 g cm-3 to 3.4 g cm-3, not varying greatly with the calcination/sintering conditions. The electrical properties and Seebeck coefficient reveal that the density and nonstoichiometry greatly influenced the achievement of good thermoelectric properties. Transmission electron microscopy (TEM) images showed fine particles with nanosize, strongly bound together to form metal-rich particle aggregates. Tubular morphology below 50 nm to 100 nm scale was observed in TEM images of as-prepared solid-state Ca3Co4O9±δ . As-prepared samples showed improved electrical conductivity and Seebeck coefficient, suitable for thermoelectric applications.

  7. Apparatus for the measurement of electrical resistivity, Seebeck coefficient, and thermal conductivity of thermoelectric materials between 300 K and 12 K.

    PubMed

    Martin, Joshua; Nolas, George S

    2016-01-01

    We have developed a custom apparatus for the consecutive measurement of the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of materials between 300 K and 12 K. These three transport properties provide for a basic understanding of the thermal and electrical properties of materials. They are of fundamental importance in identifying and optimizing new materials for thermoelectric applications. Thermoelectric applications include waste heat recovery for automobile engines and industrial power generators, solid-state refrigeration, and remote power generation for sensors and space probes. The electrical resistivity is measured using a four-probe bipolar technique, the Seebeck coefficient is measured using the quasi-steady-state condition of the differential method in a 2-probe arrangement, and the thermal conductivity is measured using a longitudinal, multiple gradient steady-state technique. We describe the instrumentation and the measurement uncertainty associated with each transport property, each of which is presented with representative measurement comparisons using round robin samples and/or certified reference materials. Transport properties data from this apparatus have supported the identification, development, and phenomenological understanding of novel thermoelectric materials.

  8. Apparatus for the measurement of electrical resistivity, Seebeck coefficient, and thermal conductivity of thermoelectric materials between 300 K and 12 K

    NASA Astrophysics Data System (ADS)

    Martin, Joshua; Nolas, George S.

    2016-01-01

    We have developed a custom apparatus for the consecutive measurement of the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of materials between 300 K and 12 K. These three transport properties provide for a basic understanding of the thermal and electrical properties of materials. They are of fundamental importance in identifying and optimizing new materials for thermoelectric applications. Thermoelectric applications include waste heat recovery for automobile engines and industrial power generators, solid-state refrigeration, and remote power generation for sensors and space probes. The electrical resistivity is measured using a four-probe bipolar technique, the Seebeck coefficient is measured using the quasi-steady-state condition of the differential method in a 2-probe arrangement, and the thermal conductivity is measured using a longitudinal, multiple gradient steady-state technique. We describe the instrumentation and the measurement uncertainty associated with each transport property, each of which is presented with representative measurement comparisons using round robin samples and/or certified reference materials. Transport properties data from this apparatus have supported the identification, development, and phenomenological understanding of novel thermoelectric materials.

  9. Effect of Synthesis Conditions on Formation, Electrical Properties, and Seebeck Coefficient of p-Type Ca3Co4O9± δ Thermoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Radhika, T.; Raghu, N.; Powrnami, N.; Jothi Ramalingam, R.; Al-Lohedan, Hamad A.

    2017-03-01

    Ca3Co4O9± δ ceramic powders have been prepared by a solid-state method. The calcination and sintering temperatures and reaction conditions were varied to achieve highly dense materials for thermoelectric applications. The optimized calcination temperature and reaction conditions were derived. X-ray diffraction patterns showed formation of secondary phases for longer calcination duration. The density of the ceramics ranged from 3.2 g cm-3 to 3.4 g cm-3, not varying greatly with the calcination/sintering conditions. The electrical properties and Seebeck coefficient reveal that the density and nonstoichiometry greatly influenced the achievement of good thermoelectric properties. Transmission electron microscopy (TEM) images showed fine particles with nanosize, strongly bound together to form metal-rich particle aggregates. Tubular morphology below 50 nm to 100 nm scale was observed in TEM images of as-prepared solid-state Ca3Co4O9± δ . As-prepared samples showed improved electrical conductivity and Seebeck coefficient, suitable for thermoelectric applications.

  10. Seebeck effect in electrolytes.

    PubMed

    Chikina, I; Shikin, V; Varlamov, A A

    2012-07-01

    We study Seebeck effect in liquid electrolytes, starting from its simple neutral analog--thermodiffusion (so-called Ludwig-Soret or Soret effect). It is observed that when two or more subsystems of mobile particles are subjected to the temperature gradient, various types of them respond to it differently. In the case when these fractions, with different mobility parameters (Soret coefficients), are oppositely charged (a case typical for electrolytes), the nonhomogeneous internal electric field is generated. The latter field prevents these fractions from space separation and determines the intensity of the appearing Seebeck effect.

  11. Picosecond Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T.; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G.

    2017-02-01

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal /Y3Fe5 O12 bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal /Y3Fe5 O12 interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 108 A m-2 K-1 .

  12. Nernst and Seebeck effects in HgTe/CdTe topological insulator

    NASA Astrophysics Data System (ADS)

    Zhang, Yuan; Song, Juntao; Li, Yu-Xian

    2015-03-01

    The Seebeck and Nernst effects in HgTe/CdTe quantum wells are studied using the tight-binding Hamiltonian and the nonequilibrium Green's function method. The Seebeck coefficient, Sc, and the Nernst coefficient, Nc, oscillate as a function of EF, where EF is the Fermi energy. The Seebeck coefficient shows peaks when the Fermi energy crosses the discrete transverse channels, and the height of the nth peak of the Sc is [ln2 /(1/2 +|n |)] for EF > 0. For the case EF < 0, the values of the peaks are negative, but the absolute values of the first five peaks are the same as those for EF > 0. The 6th peak of Sc reaches the value [ln2 /1.35 ] due to a higher density of states. When a magnetic field is applied, the Nernst coefficient appears. However, the values of the peaks for Nc are all positive. For a weak magnetic field, the temperature suppresses the oscillation of the Seebeck and Nernst coefficients but increases their magnitude. For a large magnetic field, because of the highly degenerate Landau levels, the peaks of the Seebeck coefficient at position EF=-12 , 10 , 28 meV , and Nernst coefficient at EF=-7 , 10 meV are robust against the temperature.

  13. Absolute rate coefficients for the recombination of open f-shell tungsten ions

    NASA Astrophysics Data System (ADS)

    Krantz, C.; Spruck, K.; Badnell, N. R.; Becker, A.; Bernhardt, D.; Grieser, M.; Hahn, M.; Novotný, O.; Repnow, R.; Savin, D. W.; Wolf, A.; Müller, A.; Schippers, S.

    2014-04-01

    We have carried out direct measurements of the absolute recombination rate coefficients of four charge states of tungsten in the range from W18+ to W21+ in a heavy ion storage ring. We find that the rich atomic fine structure of the open f-shell leads to very high resonant enhancement of the recombination rate at energies below ~50 eV. Even in the higher energy domain relevant to fusion plasma this leads to a recombination rate coefficient that is more than four times higher than predicted by the commonly used ADAS database of recombination rates. In addition to the experimental measurements we have carried out theoretical calculations using Autostructure. For W20+ these predict a plasma recombination rate coefficient that agrees much better with the measurement than the ADAS model but still fail to reproduce the experimental data in detail.

  14. Spin-dependent Seebeck effects in a graphene nanoribbon coupled to two square lattice ferromagnetic leads

    NASA Astrophysics Data System (ADS)

    Zhou, Benhu; Zhou, Benliang; Zeng, Yangsu; Zhou, Guanghui; Ouyang, Tao

    2015-03-01

    We theoretically investigate spin-dependent Seebeck effects for a system consisting of a narrow graphene nanoribbon (GNR) contacted to square lattice ferromagnetic (FM) electrodes with noncollinear magnetic moments. Both zigzag-edge graphene nanoribbons (ZGNRs) and armchair-edge graphene nanoribbons (AGNRs) were considered. Compared with our previous work with two-dimensional honeycomb-lattice FM leads, a more realistic model of two-dimensional square-lattice FM electrodes is adopted here. Using the nonequilibrium Green's function method combining with the tight-binding Hamiltonian, it is demonstrated that both the charge Seebeck coefficient SC and the spin-dependent Seebeck coefficient SS strongly depend on the geometrical contact between the GNR and the leads. In our previous work, SC for a semiconducting 15-AGNR system near the Dirac point is two orders of magnitude larger than that of a metallic 17-AGNR system. However, SC is the same order of magnitude for both metallic 17-AGNR and semiconducting 15-AGNR systems in the present paper because of the lack of a transmission energy gap for the 15-AGNR system. Furthermore, the spin-dependent Seebeck coefficient SS for the systems with 20-ZGNR, 17-AGNR, and 15-AGNR is of the same order of magnitude and its maximum absolute value can reach 8 μV/K. The spin-dependent Seebeck effects are not very pronounced because the transmission coefficient weakly depends on spin orientation. Moreover, the spin-dependent Seebeck coefficient is further suppressed with increasing angle between the relative alignments of magnetization directions of the two leads. Additionally, the spin-dependent Seebeck coefficient can be strongly suppressed for larger disorder strength. The results obtained here may provide valuable theoretical guidance in the experimental design of heat spintronic devices.

  15. Spin-dependent Seebeck effects in a graphene nanoribbon coupled to two square lattice ferromagnetic leads

    SciTech Connect

    Zhou, Benhu Zeng, Yangsu; Zhou, Benliang; Zhou, Guanghui; Ouyang, Tao

    2015-03-14

    We theoretically investigate spin-dependent Seebeck effects for a system consisting of a narrow graphene nanoribbon (GNR) contacted to square lattice ferromagnetic (FM) electrodes with noncollinear magnetic moments. Both zigzag-edge graphene nanoribbons (ZGNRs) and armchair-edge graphene nanoribbons (AGNRs) were considered. Compared with our previous work with two-dimensional honeycomb-lattice FM leads, a more realistic model of two-dimensional square-lattice FM electrodes is adopted here. Using the nonequilibrium Green's function method combining with the tight-binding Hamiltonian, it is demonstrated that both the charge Seebeck coefficient S{sub C} and the spin-dependent Seebeck coefficient S{sub S} strongly depend on the geometrical contact between the GNR and the leads. In our previous work, S{sub C} for a semiconducting 15-AGNR system near the Dirac point is two orders of magnitude larger than that of a metallic 17-AGNR system. However, S{sub C} is the same order of magnitude for both metallic 17-AGNR and semiconducting 15-AGNR systems in the present paper because of the lack of a transmission energy gap for the 15-AGNR system. Furthermore, the spin-dependent Seebeck coefficient S{sub S} for the systems with 20-ZGNR, 17-AGNR, and 15-AGNR is of the same order of magnitude and its maximum absolute value can reach 8 μV/K. The spin-dependent Seebeck effects are not very pronounced because the transmission coefficient weakly depends on spin orientation. Moreover, the spin-dependent Seebeck coefficient is further suppressed with increasing angle between the relative alignments of magnetization directions of the two leads. Additionally, the spin-dependent Seebeck coefficient can be strongly suppressed for larger disorder strength. The results obtained here may provide valuable theoretical guidance in the experimental design of heat spintronic devices.

  16. Nernst and Seebeck coefficients of the cuprate superconductor YBa2Cu3O6.67: a study of Fermi surface reconstruction.

    PubMed

    Chang, J; Daou, R; Proust, Cyril; Leboeuf, David; Doiron-Leyraud, Nicolas; Laliberté, Francis; Pingault, B; Ramshaw, B J; Liang, Ruixing; Bonn, D A; Hardy, W N; Takagi, H; Antunes, A B; Sheikin, I; Behnia, K; Taillefer, Louis

    2010-02-05

    The Seebeck and Nernst coefficients S and nu of the cuprate superconductor YBa{2}Cu{3}O{y} (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28 T. Down to T=9 K, nu becomes independent of field by H approximately 30 T, showing that superconducting fluctuations have become negligible. In this field-induced normal state, S/T and nu/T are both large and negative in the T-->0 limit, with the magnitude and sign of S/T consistent with the small electronlike Fermi surface pocket detected previously by quantum oscillations and the Hall effect. The change of sign in S(T) at T approximately 50 K is remarkably similar to that observed in La2-xBaxCuO4, La{2-x-y}Nd{y}Sr_{x}CuO{4}, and La{2-x-y}Eu{y}Sr{x}CuO{4}, where it is clearly associated with the onset of stripe order. We propose that a similar density-wave mechanism causes the Fermi surface reconstruction in YBCO.

  17. Picosecond Spin Seebeck Effect.

    PubMed

    Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G

    2017-02-03

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal/Y_{3}Fe_{5}O_{12} bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal/Y_{3}Fe_{5}O_{12} interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 10^{8}  A m^{-2} K^{-1}.

  18. Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides

    SciTech Connect

    Levin, E. M.

    2016-06-27

    Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S, depends on the free (mobile) carrier concentration, n, and effective mass, m*, as S ~ m*/n2/3. The carrier concentration in tellurides can be derived from 125Te nuclear magnetic resonance (NMR) spin-lattice relaxation measurements. The NMR spin-lattice relaxation rate, 1/T1, depends on both n and m* as 1/T1~(m*)3/2n (within classical Maxwell-Boltzmann statistics) or as 1/T1~(m*)2n2/3 (within quantum Fermi-Dirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficient and 125Te NMR spin-lattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study AgxSbxGe50–2xTe50, well-known GeTe-based high-efficiency tellurium-antimony-germanium-silver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Thus, values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.

  19. Seebeck effect in magnetic tunnel junctions.

    PubMed

    Walter, Marvin; Walowski, Jakob; Zbarsky, Vladyslav; Münzenberg, Markus; Schäfers, Markus; Ebke, Daniel; Reiss, Günter; Thomas, Andy; Peretzki, Patrick; Seibt, Michael; Moodera, Jagadeesh S; Czerner, Michael; Bachmann, Michael; Heiliger, Christian

    2011-10-01

    Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, that is, the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge-based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In this respect, it is the analogue to the tunnelling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configurations are of the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. The geometric centre of the electronic density of states relative to the Fermi level determines the size of the Seebeck effect. Experimentally, we realized 8.8% magneto-Seebeck effect, which results from a voltage change of about -8.7 μV K⁻¹ from the antiparallel to the parallel direction close to the predicted value of -12.1 μV K⁻¹. In contrast to the spin-Seebeck effect, it can be measured as a voltage change directly without conversion of a spin current.

  20. Effects of Ge substitution in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration derived from 125Te NMR

    NASA Astrophysics Data System (ADS)

    Levin, E. M.

    2016-01-01

    GeTe, a self-doping p -type semiconductor where the high free hole concentration is determined by Ge vacancies is a well-known base for high-efficiency A gxS bxG e50 -2 xT e50 (a tellurium-antimony-germanium-silver series) thermoelectric materials. Here it is shown that the replacement of Ge by Ag in GeTe (a A gxG e50 -xT e50 system) significantly decreases the Seebeck coefficient, whereas the replacement by Sb (S bxG e50 -xT e50 ) increases it. These effects can be attributed to a change in carrier concentration and consistent with 125Te NMR spin-lattice relaxation measurements and NMR signal position, which is mostly dependent on the Knight shift. Opposite changes in carrier concentration in A gxG e50 -xT e50 and S bxG e50 -xT e50 can be explained by different valence electron configurations of Ag and Sb compared to that of Ge, which results in a different local electron imbalance and/or in a change in Ge vacancy formation energy and affects the total carrier concentration. Comparison of our data for GeTe, A g2G e48T e50 , and S b2G e48T e50 with those for A g2S b2G e46T e50 shows that the effects from Ag and Sb compensate for each other and supports the formation of [Ag +Sb ] atomic pairs suggested earlier based on theoretical calculations.

  1. Nernst and Seebeck effects in HgTe/CdTe topological insulator

    SciTech Connect

    Zhang, Yuan; Song, Juntao; Li, Yu-Xian

    2015-03-28

    The Seebeck and Nernst effects in HgTe/CdTe quantum wells are studied using the tight-binding Hamiltonian and the nonequilibrium Green's function method. The Seebeck coefficient, S{sub c}, and the Nernst coefficient, N{sub c}, oscillate as a function of E{sub F}, where E{sub F} is the Fermi energy. The Seebeck coefficient shows peaks when the Fermi energy crosses the discrete transverse channels, and the height of the nth peak of the S{sub c} is [ln2/(1/2 +|n|)] for E{sub F} > 0. For the case E{sub F} < 0, the values of the peaks are negative, but the absolute values of the first five peaks are the same as those for E{sub F} > 0. The 6th peak of S{sub c} reaches the value [ln2/1.35] due to a higher density of states. When a magnetic field is applied, the Nernst coefficient appears. However, the values of the peaks for N{sub c} are all positive. For a weak magnetic field, the temperature suppresses the oscillation of the Seebeck and Nernst coefficients but increases their magnitude. For a large magnetic field, because of the highly degenerate Landau levels, the peaks of the Seebeck coefficient at position E{sub F}=−12, 10, 28meV, and Nernst coefficient at E{sub F}=−7, 10meV are robust against the temperature.

  2. Spatially resolved absolute diffuse reflectance measurements for noninvasive determination of the optical scattering and absorption coefficients of biological tissue

    NASA Astrophysics Data System (ADS)

    Kienle, Alwin; Lilge, Lothar; Patterson, Michael S.; Hibst, Raimund; Steiner, Rudolf; Wilson, Brian C.

    1996-05-01

    The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm-1 and absorption coefficients between 0.002 and 0.1 mm -1 showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle (breast), were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam. Carlo, neural network.

  3. Tomographic imaging of absolute optical absorption coefficient in turbid media using combined photoacoustic and diffusing light measurements.

    PubMed

    Yin, Lu; Wang, Qiang; Zhang, Qizhi; Jiang, Huabei

    2007-09-01

    We present a new method that can provide high resolution images of absolute optical absorption coefficient in heterogeneous turbid media. In this method, acoustic measurements in conventional photoacoustic tomography are combined with diffusing light measurements to separate the product of absorption coefficient and optical fluence or photon density. We validate this method using a series of tissuelike phantom experiments. The experimental results show that targets as small as 0.5 mm in diameter with optical absorption contrasts as low as 1.5 relative to a 50 mm diameter scattering background medium can be clearly detected.

  4. Observation of the spin Seebeck effect.

    PubMed

    Uchida, K; Takahashi, S; Harii, K; Ieda, J; Koshibae, W; Ando, K; Maekawa, S; Saitoh, E

    2008-10-09

    The generation of electric voltage by placing a conductor in a temperature gradient is called the Seebeck effect. Its efficiency is represented by the Seebeck coefficient, S, which is defined as the ratio of the generated electric voltage to the temperature difference, and is determined by the scattering rate and the density of the conduction electrons. The effect can be exploited, for example, in thermal electric-power generators and for temperature sensing, by connecting two conductors with different Seebeck coefficients, a device called a thermocouple. Here we report the observation of the thermal generation of driving power, or voltage, for electron spin: the spin Seebeck effect. Using a recently developed spin-detection technique that involves the spin Hall effect, we measure the spin voltage generated from a temperature gradient in a metallic magnet. This thermally induced spin voltage persists even at distances far from the sample ends, and spins can be extracted from every position on the magnet simply by attaching a metal. The spin Seebeck effect observed here is directly applicable to the production of spin-voltage generators, which are crucial for driving spintronic devices. The spin Seebeck effect allows us to pass a pure spin current, a flow of electron spins without electric currents, over a long distance. These innovative capabilities will invigorate spintronics research.

  5. Absolute rate coefficients for photorecombination of beryllium-like and boron-like silicon ions

    NASA Astrophysics Data System (ADS)

    Bernhardt, D.; Becker, A.; Brandau, C.; Grieser, M.; Hahn, M.; Krantz, C.; Lestinsky, M.; Novotný, O.; Repnow, R.; Savin, D. W.; Spruck, K.; Wolf, A.; Müller, A.; Schippers, S.

    2016-04-01

    We report measured rate coefficients for electron-ion recombination of Si10+ forming Si9+ and of Si9+ forming Si8+, respectively. The measurements were performed using the electron-ion merged-beams technique at a heavy-ion storage ring. Electron-ion collision energies ranged from 0 to 50 eV for Si9+ and from 0 to 2000 eV for Si10+, thus, extending previous measurements for Si10+ (Orban et al 2010 Astrophys. J. 721 1603) to much higher energies. Experimentally derived rate coefficients for the recombination of Si9+ and Si10+ ions in a plasma are presented along with simple parameterizations. These rate coefficients are useful for the modeling of the charge balance of silicon in photoionized plasmas (Si9+ and Si10+) and in collisionally ionized plasmas (Si10+ only). In the corresponding temperature ranges, the experimentally derived rate coefficients agree with the latest corresponding theoretical results within the experimental uncertainties.

  6. Nonequilibrium thermodynamics of the spin Seebeck and spin Peltier effects

    NASA Astrophysics Data System (ADS)

    Basso, Vittorio; Ferraro, Elena; Magni, Alessandro; Sola, Alessandro; Kuepferling, Michaela; Pasquale, Massimo

    2016-05-01

    We study the problem of magnetization and heat currents and their associated thermodynamic forces in a magnetic system by focusing on the magnetization transport in ferromagnetic insulators like YIG. The resulting theory is applied to the longitudinal spin Seebeck and spin Peltier effects. By focusing on the specific geometry with one Y3Fe5O12 (YIG) layer and one Pt layer, we obtain the optimal conditions for generating large magnetization currents into Pt or large temperature effects in YIG. The theoretical predictions are compared with experiments from the literature permitting to derive the values of the thermomagnetic coefficients of YIG: the magnetization diffusion length lM˜0.4 μ m and the absolute thermomagnetic power coefficient ɛM˜10-2TK-1 .

  7. Photo-Seebeck effect in polycrystalline ZnO

    NASA Astrophysics Data System (ADS)

    Horikawa, Ayaka; Igarashi, Taichi; Terasaki, Ichiro; Okazaki, Ryuji

    2015-09-01

    We have measured the Seebeck coefficient and the resistance under light illumination of 365 nm in a ceramic sample of ZnO at 100, 150, and 200 K, and have analyzed the photo-Seebeck coefficient and the photoconductivity using a two-layer model. We have evaluated the photo-doped carrier concentration from the magnitude of the photo-Seebeck coefficient to be of the order of 1019 cm-3, as is similar to the case of thin-film and single-crystal samples. The photo-doping effects are compared among ceramic, single crystal, and thin-film samples.

  8. Large Seebeck effect by charge-mobility engineering

    NASA Astrophysics Data System (ADS)

    Sun, Peijie; Wei, Beipei; Zhang, Jiahao; Tomczak, Jan M.; Strydom, A. M.; Søndergaard, M.; Iversen, Bo B.; Steglich, Frank

    2015-06-01

    The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts towards superior thermoelectrics through the engineering of electronic structure. Here we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: a charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a marked mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials.

  9. Large Seebeck effect by charge-mobility engineering.

    PubMed

    Sun, Peijie; Wei, Beipei; Zhang, Jiahao; Tomczak, Jan M; Strydom, A M; Søndergaard, M; Iversen, Bo B; Steglich, Frank

    2015-06-25

    The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts towards superior thermoelectrics through the engineering of electronic structure. Here we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: a charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a marked mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials.

  10. Large Seebeck effect by charge-mobility engineering

    PubMed Central

    Sun, Peijie; Wei, Beipei; Zhang, Jiahao; Tomczak, Jan M.; Strydom, A.M.; Søndergaard, M.; Iversen, Bo B.; Steglich, Frank

    2015-01-01

    The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts towards superior thermoelectrics through the engineering of electronic structure. Here we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: a charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a marked mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials. PMID:26108283

  11. Experimental investigation of factors affecting the absolute recovery coefficients in iodine-124 PET lesion imaging.

    PubMed

    Jentzen, Walter

    2010-04-21

    The use of recovery coefficients (RCs) in (124)I PET lesion imaging is a simple method to correct the imaged activity concentration (AC) primarily for the partial-volume effect and, to a minor extent, for the prompt gamma coincidence effect. The aim of this phantom study was to experimentally investigate a number of various factors affecting the (124)I RCs. Three RC-based correction approaches were considered. These approaches differ with respect to the volume of interest (VOI) drawn, which determines the imaged AC and the RCs: a single voxel VOI containing the maximum value (maximum RC), a spherical VOI with a diameter of the scanner resolution (resolution RC) and a VOI equaling the physical object volume (isovolume RC). Measurements were performed using mainly a stand-alone PET scanner (EXACT HR(+)) and a latest-generation PET/CT scanner (BIOGRAPH mCT). The RCs were determined using a cylindrical phantom containing spheres or rotational ellipsoids and were derived from images acquired with a reference acquisition protocol. For each type of RC, the influence of the following factors on the RC was assessed: object shape, background activity spill in and iterative image reconstruction parameters. To evaluate the robustness of the RC-based correction approaches, the percentage deviation between RC-corrected and true ACs was determined from images acquired with a clinical acquisition protocol of different AC regimes. The observed results of the shape and spill-in effects were compared with simulation data derived from a convolution-based model. The study demonstrated that the shape effect was negligible and, therefore, was in agreement with theoretical expectations. In contradiction to the simulation results, the observed spill-in effect was unexpectedly small. To avoid variations in the determination of RCs due to reconstruction parameter changes, image reconstruction with a pixel length of about one-third or less of the scanner resolution and an OSEM 1 x 32

  12. Experimental investigation of factors affecting the absolute recovery coefficients in iodine-124 PET lesion imaging

    NASA Astrophysics Data System (ADS)

    Jentzen, Walter

    2010-04-01

    The use of recovery coefficients (RCs) in 124I PET lesion imaging is a simple method to correct the imaged activity concentration (AC) primarily for the partial-volume effect and, to a minor extent, for the prompt gamma coincidence effect. The aim of this phantom study was to experimentally investigate a number of various factors affecting the 124I RCs. Three RC-based correction approaches were considered. These approaches differ with respect to the volume of interest (VOI) drawn, which determines the imaged AC and the RCs: a single voxel VOI containing the maximum value (maximum RC), a spherical VOI with a diameter of the scanner resolution (resolution RC) and a VOI equaling the physical object volume (isovolume RC). Measurements were performed using mainly a stand-alone PET scanner (EXACT HR+) and a latest-generation PET/CT scanner (BIOGRAPH mCT). The RCs were determined using a cylindrical phantom containing spheres or rotational ellipsoids and were derived from images acquired with a reference acquisition protocol. For each type of RC, the influence of the following factors on the RC was assessed: object shape, background activity spill in and iterative image reconstruction parameters. To evaluate the robustness of the RC-based correction approaches, the percentage deviation between RC-corrected and true ACs was determined from images acquired with a clinical acquisition protocol of different AC regimes. The observed results of the shape and spill-in effects were compared with simulation data derived from a convolution-based model. The study demonstrated that the shape effect was negligible and, therefore, was in agreement with theoretical expectations. In contradiction to the simulation results, the observed spill-in effect was unexpectedly small. To avoid variations in the determination of RCs due to reconstruction parameter changes, image reconstruction with a pixel length of about one-third or less of the scanner resolution and an OSEM 1 × 32 algorithm or

  13. 1-Octanol/Water Partition Coefficients of n-Alkanes from Molecular Simulations of Absolute Solvation Free Energies.

    PubMed

    Garrido, Nuno M; Queimada, António J; Jorge, Miguel; Macedo, Eugénia A; Economou, Ioannis G

    2009-09-08

    The 1-octanol/water partition coefficient is an important thermodynamic variable usually employed to understand and quantify the partitioning of solutes between aqueous and organic phases. It finds widespread use in many empirical correlations to evaluate the environmental fate of pollutants as well as in the design of pharmaceuticals. The experimental evaluation of 1-octanol/water partition coefficients is an expensive and time-consuming procedure, and thus, theoretical estimation methods are needed, particularly when a physical sample of the solute may not yet be available, such as in pharmaceutical screening. 1-Octanol/water partition coefficients can be obtained from Gibbs free energies of solvation of the solute in both the aqueous and the octanol phases. The accurate evaluation of free energy differences remains today a challenging problem in computational chemistry. In order to study the absolute solvation Gibbs free energies in 1-octanol, a solvent that can mimic many properties of important biological systems, free energy calculations for n-alkanes in the range C1-C8 were performed using molecular simulation techniques, following the thermodynamic integration approach. In the first part of this paper, we test different force fields by evaluating their performance in reproducing pure 1-octanol properties. It is concluded that all-atom force fields can provide good accuracy but at the cost of a higher computational time compared to that of the united-atom force fields. Recent versions of united-atom force fields, such as Gromos and TraPPE, provide satisfactory results and are, thus, useful alternatives to the more expensive all-atom models. In the second part of the paper, the Gibbs free energy of solvation in 1-octanol is calculated for several n-alkanes using three force fields to describe the solutes, namely Gromos, TraPPE, and OPLS-AA. Generally, the results obtained are in excellent agreement with the available experimental data and are of similar

  14. Giant Seebeck effect in pure fullerene thin films

    NASA Astrophysics Data System (ADS)

    Kojima, Hirotaka; Abe, Ryo; Ito, Mitsuhiro; Tomatsu, Yasuyuki; Fujiwara, Fumiya; Matsubara, Ryosuke; Yoshimoto, Noriyuki; Nakamura, Masakazu

    2015-12-01

    The small thermal conductivity of molecular solids is beneficial for their thermoelectric applications. If Seebeck coefficients were sufficiently large to compensate for the relatively small electrical conductivity, these materials would be promising candidates for thermoelectric devices. In this work, the thermoelectric properties of C60 were studied by in situ measurements under ultrahigh vacuum after the deposition of a pure C60 thin film. An exceptionally large Seebeck coefficient of more than 150 mV/K was observed as a steady-state thermoelectromotive force. Even considering several extreme but realistic conditions, conventional semiclassical thermoelectric theories cannot explain this giant Seebeck effect.

  15. Domain wall magneto-Seebeck effect

    NASA Astrophysics Data System (ADS)

    Krzysteczko, Patryk; Hu, Xiukun; Liebing, Niklas; Sievers, Sibylle; Schumacher, Hans W.

    2015-10-01

    The interplay between charge, spin, and heat currents in magnetic nanostructures subjected to a temperature gradient has led to a variety of novel effects and promising applications studied in the fast-growing field of spin caloritronics. Here, we explore the magnetothermoelectrical properties of an individual magnetic domain wall in a permalloy nanowire. In thermal gradients of the order of few K /μ m along the long wire axis, we find a clear magneto-Seebeck signature due to the presence of a single domain wall. The observed domain wall magneto-Seebeck effect can be explained by the magnetization-dependent Seebeck coefficient of permalloy in combination with the local spin configuration of the domain wall.

  16. Photo-Seebeck Effect in ZnO

    NASA Astrophysics Data System (ADS)

    Okazaki, Ryuji; Horikawa, Ayaka; Yasui, Yukio; Terasaki, Ichiro

    2012-11-01

    We examine how the photo-induced carriers contribute the thermoelectric transport, i.e., the nature of the photo-Seebeck effect, in the wide-gap oxide semiconductor ZnO for the first time. We measure the electrical conductivity and the Seebeck coefficient with illuminating light. The light illumination considerably changes the Seebeck coefficient as well as the conductivity, which is sensitive to the photon energy of the illuminated light. By using a simple parallel-circuit model, we evaluate the contributions of the photo-induced carriers to the conductivity and the Seebeck coefficient, whose relationship shows a remarkable resemblance to that in doped semiconductors. Our results also demonstrate that the light illumination increases both the carrier concentration and the mobility, which can be compared with impurity-doping case for ZnO. Future prospects for thermoelectrics using light are discussed.

  17. Dynamical Correction of Thermoelectric Coefficients for Strongly Interacting Electrons in the Coulomb Blockade Regime

    NASA Astrophysics Data System (ADS)

    Yang, Kaike

    FOR MOLECULES WEAKLY COUPLED TO LEADS THE EXACT ZERO-BIAS KOHN-SHAM CONDUCTANCE CAN BE ORDERS OF MAGNITUDE LARGER THAN THE TRUE CONDUCTANCE DUE TO THE LACK OF DYNAMICAL EXCHANGE-CORRELATION (XC) EFFECTS. RECENTLY, IT HAS BEEN SHOWN HOW THESE DYNAMICAL XC CORRECTIONS CAN BE CALCULATED USING ONLY QUANTITIES OBTAINED FROM STATIC DENSITY FUNCTIONAL THEORY. HERE, WE INVESTIGATE THE THERMOELECTRIC TRANSPORT AND DERIVE THE XC CORRECTION TO THE SEEBECK COEFFICIENT. WE FIND THAT THE DYNAMICAL CORRECTION TO THE SEEBECK COEFFICIENT IS DETERMINANT IN EVALUATING THE THERMOPOWER: THE ABSOLUTE VALUE OF THE DYNAMICAL CORRECTION FOR THE SEEBECK COEFFICIENT IS, FOR CERTAIN VALUES OF GATE VOLTAGE, MUCH LARGER THAN THAT OF THE KOHN-SHAM TERM. FINALLY, WE COMPARE OUR DENSITY FUNCTIONAL CALCULATIONS TO THE RATE EQUATION AND THE EXPERIMENTAL RESULTS

  18. Thermal conductivities, electrical resistivities, and Seebeck coefficients of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductors from 80 to 300 K

    SciTech Connect

    Yarbrough, D.W.; Williams, R.K.; Shockley, D.R.

    1993-12-31

    Thermal conductivities, electrical resistivities, and Seebeck coefficients of three polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} specimens have been measured over the temperature range 80 to 300 K in a longitudinal-heat-flow apparatus. Smoothed values for thermal conductivity, and electrical resistivity have been obtained for temperatures above the superconducting transition temperature of 90 K. The thermal conductivity values decreased as the temperature was increased, a trend which is inconsistent with the results of some other investigators. The thermal conductivities were less than previously published values and it is suggested that these differences are due to radiative heat loss in the published values. This effect is especially important for linear heat flow measurements on low thermal conductivity materials. The electrical and thermal conductivities of the specimens varied with Ba content and this variation was used to separate the thermal conductivity into lattice and electronic components are significant. The phonon component exhibits the expected temperature variation and an analysis indicates that the electron-phonon interaction is unusually strong.

  19. Seebeck effect at the atomic scale.

    PubMed

    Lee, Eui-Sup; Cho, Sanghee; Lyeo, Ho-Ki; Kim, Yong-Hyun

    2014-04-04

    The atomic variations of electronic wave functions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nat. Mater. 12, 913 (2013)]. Because thermoelectricity, or the Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wave functions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a pointlike contact produces an atomic Seebeck effect, which is described by the mesoscopic Seebeck coefficient multiplied by an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a subangstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging.

  20. Seebeck Effect at the Atomic Scale

    NASA Astrophysics Data System (ADS)

    Lee, Eui-Sup; Cho, Sanghee; Lyeo, Ho-Ki; Kim, Yong-Hyun

    2014-04-01

    The atomic variations of electronic wave functions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nat. Mater. 12, 913 (2013)]. Because thermoelectricity, or the Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wave functions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a pointlike contact produces an atomic Seebeck effect, which is described by the mesoscopic Seebeck coefficient multiplied by an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a subangstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging.

  1. Spin-dependent Seebeck effect in Aharonov-Bohm rings with Rashba and Dresselhaus spin-orbit interactions

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Li, Yunyun; Zhou, Jun; Nakayama, Tsuneyoshi; Li, Baowen

    2016-06-01

    We theoretically investigate the spin-dependent Seebeck effect in an Aharonov-Bohm mesoscopic ring in the presence of both Rashba and Dresselhaus spin-orbit interactions under magnetic flux perpendicular to the ring. We apply the Green's function method to calculate the spin Seebeck coefficient employing the tight-binding Hamiltonian. It is found that the spin Seebeck coefficient is proportional to the slope of the energy-dependent transmission coefficients. We study the strong dependence of spin Seebeck coefficient on the Fermi energy, magnetic flux, strength of spin-orbit coupling, and temperature. Maximum spin Seebeck coefficients can be obtained when the strengths of Rashba and Dresselhaus spin-orbit couplings are slightly different. The spin Seebeck coefficient can be reduced by increasing temperature and disorder.

  2. Paramagnetic spin seebeck effect.

    PubMed

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

    2015-05-08

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

  3. Paramagnetic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  4. Calibration-free absolute quantification of optical absorption coefficients using acoustic spectra in 3D photoacoustic microscopy of biological tissue.

    PubMed

    Guo, Zijian; Hu, Song; Wang, Lihong V

    2010-06-15

    Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of nonfluorescent molecules. We propose a method to use acoustic spectra of photoacoustic signals to quantify the absolute optical absorption. This method is self-calibrating and thus insensitive to variations in the optical fluence. Factors such as system bandwidth and acoustic attenuation can affect the quantification but can be canceled by dividing the acoustic spectra measured at two optical wavelengths. Using optical-resolution photoacoustic microscopy, we quantified the absolute optical absorption of black ink samples with various concentrations. We also quantified both the concentration and oxygen saturation of hemoglobin in a live mouse in absolute units.

  5. Uncertainty analysis for common Seebeck and electrical resistivity measurement systems.

    PubMed

    Mackey, Jon; Dynys, Frederick; Sehirlioglu, Alp

    2014-08-01

    This work establishes the level of uncertainty for electrical measurements commonly made on thermoelectric samples. The analysis targets measurement systems based on the four probe method. Sources of uncertainty for both electrical resistivity and Seebeck coefficient were identified and evaluated. Included are reasonable estimates on the magnitude of each source, and cumulative propagation of error. Uncertainty for the Seebeck coefficient includes the cold-finger effect which has been quantified with thermal finite element analysis. The cold-finger effect, which is a result of parasitic heat transfer down the thermocouple probes, leads to an asymmetric over-estimation of the Seebeck coefficient. A silicon germanium thermoelectric sample has been characterized to provide an understanding of the total measurement uncertainty. The electrical resistivity was determined to contain uncertainty of ±7.0% across any measurement temperature. The Seebeck coefficient of the system is +1.0%/-13.1% at high temperature and ±1.0% near room temperature. The power factor has a combined uncertainty of +7.3%/-27.0% at high temperature and ±7.5% near room temperature. These ranges are calculated to be typical values for a general four probe Seebeck and resistivity measurement configuration.

  6. Photo-Seebeck effect in ZnS

    NASA Astrophysics Data System (ADS)

    Shiraishi, Yuuka; Okazaki, Ryuji; Taniguchi, Hiroki; Terasaki, Ichiro

    2015-03-01

    To explore the thermoelectric transport nature of photo-excited carriers, the electrical conductivity and the Seebeck coefficient are measured under ultraviolet illumination in the wide-gap semiconductor ZnS near room temperature. The conductivity increases linearly as against the photon flux density with little dependence on temperature, indicating the conduction under illumination is mostly governed by the photo-doped carriers. We have found that, in high contrast to the temperature-insensitive photoconductivity, the temperature dependence of the Seebeck coefficient is dramatically varied by illumination, which is unexplained from a simple photo-doping effect for one majority carrier. Such a distinct difference in the transport quantities is rather understood within a two-carrier model, in which only the Seebeck coefficient is strongly affected by photo-excited minority carriers. The present result is also compared with earlier reports of the photo-Hall experiments to discuss the underlying photo-transport mechanism.

  7. Spin Seebeck power generators

    SciTech Connect

    Cahaya, Adam B.; Tretiakov, O. A.; Bauer, Gerrit E. W.

    2014-01-27

    We derive expressions for the efficiency and figure of merit of two spin caloritronic devices based on the spin Seebeck effect (SSE), i.e., the generation of spin currents by a temperature gradient. The inverse spin Hall effect is conventionally used to detect the SSE and offers advantages for large area applications. We also propose a device that converts spin current into electric one by means of a spin-valve detector, which scales favorably to small sizes and approaches a figure of merit of 0.5 at room temperature.

  8. Antiferromagnetic spin Seebeck effect.

    SciTech Connect

    Wu, Stephen M.; Zhang, Wei; KC, Amit; Borisov, Pavel; Pearson, John E.; Jiang, J. Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-03

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF2. A device scale on-chip heater is deposited on a bilayer of MnF2 (110) (30nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF2(110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF2 through the inverse spin Hall effect. The low temperature (2–80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9T) are applied parallel to the easy axis of the MnF2 thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.

  9. Antiferromagnetic Spin Seebeck Effect.

    PubMed

    Wu, Stephen M; Zhang, Wei; Kc, Amit; Borisov, Pavel; Pearson, John E; Jiang, J Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-04

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF_{2}. A device scale on-chip heater is deposited on a bilayer of MnF_{2} (110) (30  nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF_{2} (110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF_{2} through the inverse spin Hall effect. The low temperature (2-80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9  T) are applied parallel to the easy axis of the MnF_{2} thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.

  10. Antiferromagnetic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Wu, Stephen M.; Zhang, Wei; KC, Amit; Borisov, Pavel; Pearson, John E.; Jiang, J. Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-01

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF2 . A device scale on-chip heater is deposited on a bilayer of MnF2 (110) (30 nm )/Pt (4 nm) grown by molecular beam epitaxy on a MgF2 (110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF2 through the inverse spin Hall effect. The low temperature (2-80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9 T ) are applied parallel to the easy axis of the MnF2 thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.

  11. Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy.

    PubMed

    Hallacoglu, Bertan; Sassaroli, Angelo; Wysocki, Michael; Guerrero-Berroa, Elizabeth; Schnaider Beeri, Michal; Haroutunian, Vahram; Shaul, Merav; Rosenberg, Irwin H; Troen, Aron M; Fantini, Sergio

    2012-08-01

    We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially available multi-distance frequency-domain system and analyzed using a diffusion theory model for a semi-infinite, homogeneous medium with semi-infinite boundary conditions. Our study included repeat measurements, taken five months apart, on 16 elderly volunteers that demonstrate intra-subject reproducibility of the absolute measurements with cross-correlation coefficients of 0.9 for absorption coefficient (μa), oxy-hemoglobin concentration ([HbO2]), and total hemoglobin concentration ([HbT]), 0.7 for deoxy-hemoglobin concentration ([Hb]), 0.8 for hemoglobin oxygen saturation (StO2), and 0.7 for reduced scattering coefficient (μ's). We found significant differences between the two age groups. Compared to young subjects, elderly subjects had lower cerebral [HbO2], [Hb], [HbT], and StO2 by 10 ± 4 μM, 4 ± 3 μM, 14 ± 5 μM, and 6%±5%, respectively. Our results demonstrate the reliability and robustness of multi-distance near-infrared spectroscopy measurements based on a homogeneous model in the human forehead on a large sample of human subjects. Absolute, non-invasive optical measurements on the brain, such as those presented here, can significantly advance the development of NIRS technology as a tool for monitoring resting/basal cerebral perfusion, hemodynamics, oxygenation, and metabolism.

  12. Seebeck effects in two-dimensional spin transistors

    NASA Astrophysics Data System (ADS)

    Alomar, M. I.; Serra, Llorenç; Sánchez, David

    2015-02-01

    We consider a spin-orbit-coupled two-dimensional electron system under the influence of a thermal gradient externally applied to two attached reservoirs. We discuss the generated voltage bias (charge Seebeck effect), spin bias (spin Seebeck effect), and magnetization-dependent thermopower (magneto-Seebeck effect) in the ballistic regime of transport at linear response. We find that the charge thermopower is an oscillating function of both the spin-orbit strength and the quantum well width. We also observe that it is always negative for normal leads. We carefully compare the exact results for the linear response coefficients and a Sommerfeld approximation. When the contacts are ferromagnetic, we calculate the spin-resolved Seebeck coefficient for parallel and antiparallel magnetization configuration. Remarkably, the thermopower can change its sign by tuning the Fermi energy. This effect disappears when the Rashba coupling is absent. Additionally, we determine the magneto-Seebeck ratio, which shows dramatic changes in the presence of a the Rashba potential.

  13. Spin Seebeck insulator.

    PubMed

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

    2010-11-01

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

  14. Intrinsic absolute bioavailability prediction in rats based on in situ absorption rate constants and/or in vitro partition coefficients: 6-fluoroquinolones.

    PubMed

    Sánchez-Castaño, G; Ruíz-García, A; Bañón, N; Bermejo, M; Merino, V; Freixas, J; Garriguesx, T M; Plá-Delfina, J M

    2000-11-01

    A preliminary study attempting to predict the intrinsic absolute bioavailability of a group of antibacterial 6-fluoroquinolones-including true and imperfect homologues as well as heterologues-was carried out. The intrinsic absolute bioavailability of the test compounds, F, was assessed on permanently cannulated conscious rats by comparing the trapezoidal normalized areas under the plasma concentration-time curves obtained by intravenous and oral routes (n = 8-12). The high-performance liquid chromatography analytical methods used for plasma samples are described. Prediction of the absolute bioavailability of the compounds was based on their intrinsic rat gut in situ absorption rate constant, k(a). The working equation was: where T represents the mean absorbing time. A T value of 0.93 (+/-0.06) h provides the best correlation between predicted and experimentally obtained bioavailabilities (F' and F, respectively) when k(a) values are used (slope a = 1.10; intercept b = -0.05; r = 0.991). The k(a) values can also be expressed in function of the in vitro partition coefficients, P, between n-octanol and a phosphate buffer. In this case, theoretical k(a) values can be determined with the parameters of a standard k(a)/P correlation previously established for a group of model compounds. When P values are taken instead of k(a) values, reliable bioavailability predictions can also be made. These and other relevant features of the method are discussed.

  15. Absolute absorption coefficient of C6H2 in the mid-UV range at low temperature; implications for the interpretation of Titan atmospheric spectra.

    PubMed

    Bénilan, Y; Bruston, P; Raulin, F; Courtin, R; Guillemin, J C

    1995-01-01

    The interpretation of mid-UV albedo spectra of planetary atmospheres, especially that of Titan, is the main goal of the SIPAT (Spectroscopie uv d'Interet Prebiologique dans l'Atmosphere de Titan) research program. This laboratory experiment has been developed in order to systematically determine the absorption coefficients of molecular compounds which are potential absorbers of scattered sunlight in planetary atmospheres, with high spectral resolution, and at various temperatures below room temperature. From photochemical modelling and experimental simulations, we may expect triacetylene (C6H2) to be present in the atmosphere of Titan, even though it has not yet been detected. We present here the first determination of the absolute absorption coefficient of that compound in the 200-300 nm range and at two temperatures (296 K and 233 K). The temperature dependence of the C6H2 absorption coefficient in that wavelength range is compared to that previously observed in the case of cyanoacetylene (HC3N). We then discuss the implications of the present results for the interpretation of Titan UV spectra, where it appears that large uncertainities can be introduced either by the presence of trace impurities in laboratory samples or by the variations of absorption coefficients with temperature.

  16. A potential for overestimating the absolute magnitudes of second virial coefficients by small-angle X-ray scattering.

    PubMed

    Scott, David J; Patel, Trushar R; Winzor, Donald J

    2013-04-15

    Theoretical consideration is given to the effect of cosolutes (including buffer and electrolyte components) on the determination of second virial coefficients for proteins by small-angle X-ray scattering (SAXS)-a factor overlooked in current analyses in terms of expressions for a two-component system. A potential deficiency of existing practices is illustrated by reassessment of published results on the effect of polyethylene glycol concentration on the second virial coefficient for urate oxidase. This error reflects the substitution of I(0,c3,0), the scattering intensity in the limit of zero scattering angle and solute concentration, for I(0,0,0), the corresponding parameter in the limit of zero cosolute concentration (c3) as well. Published static light scattering results on the dependence of the apparent molecular weight of ovalbumin on buffer concentration are extrapolated to zero concentration to obtain the true value (M2) and thereby establish the feasibility of obtaining the analogous SAXS parameter, I(0,0,0), experimentally.

  17. Magneto-Seebeck effect in magnetic tunnel junctions with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Ning, Keyu; Liu, Houfang; Ju, Zhenyi; Fang, Chi; Wan, Caihua; Cheng, Jinglei; Liu, Xiao; Li, Linsen; Feng, Jiafeng; Wei, Hongxiang; Han, Xiufeng; Yang, Yi; Ren, Tian-Ling

    2017-01-01

    As one invigorated filed of spin caloritronics combining with spin, charge and heat current, the magneto-Seebeck effect has been experimentally and theoretically studied in spin tunneling thin films and nanostructures. Here we analyze the tunnel magneto-Seebeck effect in magnetic tunnel junctions with perpendicular anisotropy (p-MTJs) under various measurement temperatures. The large tunnel magneto-Seebeck (TMS) ratio up to -838.8% for p-MTJs at 200 K is achieved, with Seebeck coefficient S in parallel and antiparallel states of 6.7 mV/K and 62.9 mV/K, respectively. The temperature dependence of the tunnel magneto-Seebeck can be attributed to the contributing transmission function and electron states at the interface between CoFeB electrode and MgO barrier.

  18. Seebeck effect in molecular junctions.

    PubMed

    Zimbovskaya, Natalya A

    2016-05-11

    Advances in the fabrication and characterization of nanoscale systems presently allow for a better understanding of their thermoelectric properties. As is known, the building blocks of thermoelectricity are the Peltier and Seebeck effects. In the present work we review results of theoretical studies of the Seebeck effect in single-molecule junctions and similar systems. The behavior of thermovoltage and thermopower in these systems is controlled by several factors including the geometry of molecular bridges, the characteristics of contacts between the bridge and the electrodes, the strength of the Coulomb interactions between electrons on the bridge, and of electron-phonon interactions. We describe the impact of these factors on the thermopower. Also, we discuss a nonlinear Seebeck effect in molecular junctions.

  19. Seebeck effect in molecular junctions

    NASA Astrophysics Data System (ADS)

    Zimbovskaya, Natalya A.

    2016-05-01

    Advances in the fabrication and characterization of nanoscale systems presently allow for a better understanding of their thermoelectric properties. As is known, the building blocks of thermoelectricity are the Peltier and Seebeck effects. In the present work we review results of theoretical studies of the Seebeck effect in single-molecule junctions and similar systems. The behavior of thermovoltage and thermopower in these systems is controlled by several factors including the geometry of molecular bridges, the characteristics of contacts between the bridge and the electrodes, the strength of the Coulomb interactions between electrons on the bridge, and of electron-phonon interactions. We describe the impact of these factors on the thermopower. Also, we discuss a nonlinear Seebeck effect in molecular junctions.

  20. Interplay of Peltier and Seebeck Effects in Nanoscale Nonlocal Spin Valves

    NASA Astrophysics Data System (ADS)

    Bakker, F. L.; Slachter, A.; Adam, J.-P.; van Wees, B. J.

    2010-09-01

    We have experimentally studied the role of thermoelectric effects in nanoscale nonlocal spin valve devices. A finite element thermoelectric model is developed to calculate the generated Seebeck voltages due to Peltier and Joule heating in the devices. By measuring the first, second, and third harmonic voltage response nonlocally, the model is experimentally examined. The results indicate that the combination of Peltier and Seebeck effects contributes significantly to the nonlocal baseline resistance. Moreover, we found that the second and third harmonic response signals can be attributed to Joule heating and temperature dependencies of both the Seebeck coefficient and resistivity.

  1. Interplay of Peltier and Seebeck effects in nanoscale nonlocal spin valves.

    PubMed

    Bakker, F L; Slachter, A; Adam, J-P; van Wees, B J

    2010-09-24

    We have experimentally studied the role of thermoelectric effects in nanoscale nonlocal spin valve devices. A finite element thermoelectric model is developed to calculate the generated Seebeck voltages due to Peltier and Joule heating in the devices. By measuring the first, second, and third harmonic voltage response nonlocally, the model is experimentally examined. The results indicate that the combination of Peltier and Seebeck effects contributes significantly to the nonlocal baseline resistance. Moreover, we found that the second and third harmonic response signals can be attributed to Joule heating and temperature dependencies of both the Seebeck coefficient and resistivity.

  2. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  3. Theory of the spin Seebeck effect.

    PubMed

    Adachi, Hiroto; Uchida, Ken-ichi; Saitoh, Eiji; Maekawa, Sadamichi

    2013-03-01

    The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects.

  4. Non-equilibrium Thermodynamics of the Longitudinal Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Basso, Vittorio; Ferraro, Elena; Sola, Alessandro; Magni, Alessandro; Kuepferling, Michaela; Pasquale, Massimo

    In this paper we employ non equilibrium thermodynamics of fluxes and forces to describe magnetization and heat transport. By the theory we are able to identify the thermodynamic driving force of the magnetization current as the gradient of the effective field ▿H*. This definition permits to define the spin Seebeck coefficient ɛM which relates ▿H* and the temperature gradient ▿T. By applying the theory to the geometry of the longitudinal spin Seebeck effect we are able to obtain the optimal conditions for generating large magnetization currents. Furthermore, by using the results of recent experiments, we obtain an order of magnitude for the value of ɛM ∼ 10-2 TK-1 for yttrium iron garnet (Y3Fe5O12).

  5. Evaluation of thermal gradients in longitudinal spin Seebeck effect measurements

    NASA Astrophysics Data System (ADS)

    Sola, A.; Kuepferling, M.; Basso, V.; Pasquale, M.; Kikkawa, T.; Uchida, K.; Saitoh, E.

    2015-05-01

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

  6. Absolute refractive indices and thermal coefficients of CaF2, SrF2, BaF2, and LiF near 157 nm.

    PubMed

    Burnett, John H; Gupta, Rajeev; Griesmann, Ulf

    2002-05-01

    We present high-accuracy measurements for wavelengths near 157 nm of the absolute index of refraction, the index dispersion, and the temperature dependence of the index for the ultraviolet optical materials with cubic symmetry: CaF2, SrF2, BaF2, and LiF. Accurate values of these quantities for these materials are needed for designs of the lens systems for F2 excimer-laser-based exposure tools for 157-nm photolithography. These tools are expected to use CaF2 as the primary optical material and possibly one of the others to correct for chromatic aberrations. These optical properties were measured by the minimum deviation method. Absolute refractive indices were obtained with an absolute accuracy of 5 x 10(-6) to 6 x 10(-6).

  7. Seebeck effect in a battery-type thermocell

    NASA Astrophysics Data System (ADS)

    Kobayashi, Wataru; Kinoshita, Akemi; Moritomo, Yutaka

    2015-08-01

    We demonstrated that battery-type thermocells, which consist of two paste-type electrodes with the same active material and electrolyte, show the Seebeck effect. The magnitudes of electrochemical Seebeck coefficient (S) of the thermocells with several layered oxides were evaluated: -12.7 μV/K for Na0.99CoO2, -29.7 μV/K for Na0.52MnO2, -22.4 μV/K for Na0.51Mn0.5Fe0.5O2, and -6.8 μV/K for LiCoO2. In the thermocell with Na0.99CoO2, time-dependence of the electromotive force (ΔV) at a constant temperature difference (ΔT) was well reproduced by a mean-field approach of the chemical potential ( ϕ)—Na+ concentration (x) relationship, indicating that the Na+ intercalation/deintercalation plays an intrinsic role in the electrochemical Seebeck effect.

  8. Spin-current Seebeck effect in quantum dot systems.

    PubMed

    Yang, Zhi-Cheng; Sun, Qing-Feng; Xie, X C

    2014-01-29

    We first bring up the concept of the spin-current Seebeck effect based on a recent experiment (Vera-Marun et al 2012 Nature Phys. 8 313), and investigate the spin-current Seebeck effect in quantum dot (QD) systems. Our results show that the spin-current Seebeck coefficient S is sensitive to different polarization states of the QD, and therefore can be used to detect the polarization state of the QD and monitor the transitions between different polarization states of the QD. The intradot Coulomb interaction can greatly enhance S due to the stronger polarization of the QD. By using the parameters for a typical QD whose intradot Coulomb interaction U is one order of magnitude larger than the linewidth Γ, we demonstrate that the maximum value of S can be enhanced by a factor of 80. On the other hand, for a QD whose Coulomb interaction is negligible, we show that one can still obtain a large S by applying an external magnetic field.

  9. Photo-Seebeck effect in tetragonal PbO single crystals

    SciTech Connect

    Mondal, P. S.; Okazaki, R.; Taniguchi, H.; Terasaki, I.

    2013-11-07

    We report the observation of photo-Seebeck effect in tetragonal PbO crystals. The photo-induced carriers contribute to the transport phenomena, and consequently the electrical conductivity increases and the Seebeck coefficient decreases with increasing photon flux density. A parallel-circuit model is used to evaluate the actual contributions of photo-excited carriers from the measured transport data. The photo-induced carrier concentration estimated from the Seebeck coefficient increases almost linearly with increasing photon flux density, indicating a successful photo-doping effect on the thermoelectric property. The mobility decreases by illumination but the reduction rate strongly depends on the illuminated photon energy. Possible mechanisms of such photon-energy-dependent mobility are discussed.

  10. Photo-Seebeck effect in tetragonal PbO single crystals

    NASA Astrophysics Data System (ADS)

    Mondal, P. S.; Okazaki, R.; Taniguchi, H.; Terasaki, I.

    2013-11-01

    We report the observation of photo-Seebeck effect in tetragonal PbO crystals. The photo-induced carriers contribute to the transport phenomena, and consequently the electrical conductivity increases and the Seebeck coefficient decreases with increasing photon flux density. A parallel-circuit model is used to evaluate the actual contributions of photo-excited carriers from the measured transport data. The photo-induced carrier concentration estimated from the Seebeck coefficient increases almost linearly with increasing photon flux density, indicating a successful photo-doping effect on the thermoelectric property. The mobility decreases by illumination but the reduction rate strongly depends on the illuminated photon energy. Possible mechanisms of such photon-energy-dependent mobility are discussed.

  11. Thermal Conductance and Seebeck Effect in Mesoscopic Systems

    NASA Astrophysics Data System (ADS)

    Aly, Arafa H.; El-Gawaad, N. S. Abd

    2015-11-01

    In this work, thermoelectric transport through a saddle-point potential is discussed with an emphasis on the effects of the chemical potential and temperature. In particular, the thermal conductance and the Seebeck coefficient are calculated for two-dimensional systems of a constriction defined by a saddle-point potential. The solution as a function of temperature and chemical potential has been investigated. The Peltier coefficient and thermal transport in a quantum point contact (QPC), under the influence of external fields and different temperatures, are presented. Also, the oscillations of the Peltier coefficient in external fields are obtained. Numerical calculations of the Peltier coefficient are performed at different applied voltages, amplitudes, and temperatures. Moreover, a method is proposed for measuring the sub-band energies and spin-splitting energies in a bottle-neck of the constriction. For weak non-linearities, the charge and entropy currents across a QPC are expanded as a series in powers of the applied bias voltage and the temperature difference. Expansions of the Seebeck voltage in terms of the temperature difference and the Peltier heat in terms of the current are obtained.

  12. Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially a...

  13. Current heating induced spin Seebeck effect

    SciTech Connect

    Schreier, Michael Roschewsky, Niklas; Dobler, Erich; Meyer, Sibylle; Huebl, Hans; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2013-12-09

    A measurement technique for the spin Seebeck effect is presented, wherein the normal metal layer used for its detection is exploited simultaneously as a resistive heater and thermometer. We show how the various contributions to the measured total signal can be disentangled, allowing to extract the voltage signal solely caused by the spin Seebeck effect. To this end, we performed measurements as a function of the external magnetic field strength and its orientation. We find that the effect scales linearly with the induced rise in temperature, as expected for the spin Seebeck effect.

  14. Nonlinear Seebeck and Peltier effects in quantum point contacts

    NASA Astrophysics Data System (ADS)

    Çipilolu, M. A.; Turgut, S.; Tomak, M.

    2004-09-01

    The charge and entropy currents across a quantum point contact are expanded as a series in powers of the applied bias voltage and the temperature difference. After that, the expansions of the Seebeck voltage in temperature difference and the Peltier heat in current are obtained. With a suitable choice of the average temperature and chemical potential, the lowest order nonlinear term in both cases appear to be of third order. The behavior of the third-order coefficients in both cases are then investigated for different contact parameters.

  15. Apparatus Tests Thermocouples For Seebeck Inhomogeneity

    NASA Technical Reports Server (NTRS)

    Burkett, Cecil G., Jr.; Bauserman, Willard A., Jr.; West, James W.

    1995-01-01

    Automated apparatus reveals sources of error not revealed in calibration. Computer-controlled apparatus detects and measures Seebeck inhomogeneities in sheathed thermocouples. Measures thermocouple output voltage as function of position of probe along sharp gradient of temperature. Abnormal variations in voltage-versus-position data indicative of Seebeck inhomogeneities. Prototype for development of standard method and equipment for routine acceptance/rejection testing of sheathed thermocouples in industrial and research laboratories.

  16. Evidence for a magnetic Seebeck effect.

    PubMed

    Brechet, Sylvain D; Vetro, Francesco A; Papa, Elisa; Barnes, Stewart E; Ansermet, Jean-Philippe

    2013-08-23

    The irreversible thermodynamics of a continuous medium with magnetic dipoles predicts that a temperature gradient in the presence of magnetization waves induces a magnetic induction field, which is the magnetic analog of the Seebeck effect. This thermal gradient modulates the precession and relaxation. The magnetic Seebeck effect implies that magnetization waves propagating in the direction of the temperature gradient and the external magnetic induction field are less attenuated, while magnetization waves propagating in the opposite direction are more attenuated.

  17. Magneto-Seebeck effect in an ITO/PEDOT:PSS/Au thin-film device

    NASA Astrophysics Data System (ADS)

    Wang, Hongfeng; Liu, Qing; Tisdale, Jeremy; Xu, Ling; Liu, Yuchun; Hu, Bin

    2016-04-01

    This article reports giant magnetic field effects on the Seebeck coefficient by exerting a Lorentz force on charge diffusion based on vertical multi-layer ITO/PEDOT:PSS/Au thin-film devices. The Lorentz force, induced by an external magnetic field, changes the charge transport and consequently generates angular dependent magnetoresistance. The proposed mechanism of the magneto-Seebeck effect is proved by measuring the magnetoresistance at a parallel, 45o and perpendicular angle to the temperature gradient. The gradual change of the magnetoresistance from a parallel to perpendicular angle indicates that the Lorentz force is a key driving force to develop the magneto-Seebeck effect. Therefore, our experimental results demonstrate a magnetic approach to control the thermoelectric properties in organic materials.

  18. Absolute Rovibrational Intensities, Self-Broadening and Self-Shift Coefficients for the X(sup 1) Sigma(+) V=3 (left arrow) V=0 Band (C-12)(O-16)

    NASA Technical Reports Server (NTRS)

    Chackerian, Charles, Jr.; Freedman, R.; Giver, L. P.; Brown, L. R.

    2001-01-01

    The rotationless transition moment squared for the x(sup 1) sigma (sup +) v=3 (left arrow) v=0 band of CO is measured to be the absolute value of R (sub 3-0) squared = 1.7127(25)x 10(exp -7) Debye squared. This value is about 8.6 percent smaller than the value assumed for HITRAN 2000. The Herman-Wallis intensity factor of this band is F=1+0.01168(11)m+0.0001065(79)m squared. The determination of self-broadening coefficients is improved with the inclusion of line narrowing; self-shifts are also reported.

  19. Uncertainty Analysis of Seebeck Coefficient and Electrical Resistivity Characterization

    NASA Technical Reports Server (NTRS)

    Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

    2014-01-01

    In order to provide a complete description of a materials thermoelectric power factor, in addition to the measured nominal value, an uncertainty interval is required. The uncertainty may contain sources of measurement error including systematic bias error and precision error of a statistical nature. The work focuses specifically on the popular ZEM-3 (Ulvac Technologies) measurement system, but the methods apply to any measurement system. The analysis accounts for sources of systematic error including sample preparation tolerance, measurement probe placement, thermocouple cold-finger effect, and measurement parameters; in addition to including uncertainty of a statistical nature. Complete uncertainty analysis of a measurement system allows for more reliable comparison of measurement data between laboratories.

  20. Paramagnetic and Antiferromagnetic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Wu, Stephen

    We report on the observation of the longitudinal spin Seebeck effect in both antiferromagnetic and paramagnetic insulators. By using a microscale on-chip local heater, it is possible to generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. This technique allows us to easily access low temperatures (200 mK) and high magnetic fields (14 T) through conventional dilution refrigeration and superconducting magnet setups. By exploring this regime, we detect the spin Seebeck effect through the spin-flop transition in antiferromagnetic MnF2 when a large magnetic field (>9 T) is applied along the easy axis direction. Using the same technique, we are also able to resolve a spin Seebeck effect from the paramagnetic phase of geometrically frustrated antiferromagnet Gd3Ga5O12 (gadolinium gallium garnet) and antiferromagnetic DyScO3 (DSO). Since these measurements occur above the ordering temperatures of these two materials, short-range magnetic order is implicated as the cause of the spin Seebeck effect in these systems. The discovery of the spin Seebeck effect in these two materials classes suggest that both antiferromagnetic spin waves and spin excitations from short range magnetic order may be used to generate spin current from insulators and that the spin wave spectra of individual materials are highly important to the specifics of the longitudinal spin Seebeck effect. Since insulating antiferromagnets and paramagnets are far more common than the typical insulating ferrimagnetic materials used in spin Seebeck experiments, this discovery opens up a large new class of materials for use in spin caloritronic devices. All authors acknowledge support of the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. The use of facilities at the Center for Nanoscale Materials, was supported by the U.S. DOE, BES under Contract No. DE-AC02-06CH11357.

  1. First experimental determination of the absolute gas-phase rate coefficient for the reaction of OH with 4-hydroxy-2-butanone (4H2B) at 294 K by vapor pressure measurements of 4H2B.

    PubMed

    El Dib, Gisèle; Sleiman, Chantal; Canosa, André; Travers, Daniel; Courbe, Jonathan; Sawaya, Terufat; Mokbel, Ilham; Chakir, Abdelkhaleq

    2013-01-10

    The reaction of the OH radicals with 4-hydroxy-2-butanone was investigated in the gas phase using an absolute rate method at room temperature and over the pressure range 10-330 Torr in He and air as diluent gases. The rate coefficients were measured using pulsed laser photolysis (PLP) of H(2)O(2) to produce OH and laser induced fluorescence (LIF) to measure the OH temporal profile. An average value of (4.8 ± 1.2) × 10(-12) cm(3) molecule(-1) s(-1) was obtained. The OH quantum yield following the 266 nm pulsed laser photolysis of 4-hydroxy-2-butanone was measured for the first time and found to be about 0.3%. The investigated kinetic study required accurate measurements of the vapor pressure of 4-hydroxy-2-butanone, which was measured using a static apparatus. The vapor pressure was found to range from 0.056 to 7.11 Torr between 254 and 323 K. This work provides the first absolute rate coefficients for the reaction of 4-hydroxy-2-butanone with OH and the first experimental saturated vapor pressures of the studied compound below 311 K. The obtained results are compared to those of the literature and the effects of the experimental conditions on the reactivity are examined. The calculated tropospheric lifetime obtained in this work suggests that once emitted into the atmosphere, 4H2B may contribute to the photochemical pollution in a local or regional scale.

  2. MODELING MULTI-WAVELENGTH STELLAR ASTROMETRY. II. DETERMINING ABSOLUTE INCLINATIONS, GRAVITY-DARKENING COEFFICIENTS, AND SPOT PARAMETERS OF SINGLE STARS WITH SIM LITE

    SciTech Connect

    Coughlin, Jeffrey L.; Harrison, Thomas E.; Gelino, Dawn M.

    2010-11-10

    We present a novel technique to determine the absolute inclination of single stars using multi-wavelength submilliarcsecond astrometry. The technique exploits the effect of gravity darkening, which causes a wavelength-dependent astrometric displacement parallel to a star's projected rotation axis. We find that this effect is clearly detectable using SIM Lite for various giant stars and rapid rotators, and present detailed models for multiple systems using the REFLUX code. We also explore the multi-wavelength astrometric reflex motion induced by spots on single stars. We find that it should be possible to determine spot size, relative temperature, and some positional information for both giant and nearby main-sequence stars utilizing multi-wavelength SIM Lite data. These data will be extremely useful in stellar and exoplanet astrophysics, as well as supporting the primary SIM Lite mission through proper multi-wavelength calibration of the giant star astrometric reference frame, and reduction of noise introduced by starspots when searching for extrasolar planets.

  3. Length Scale of the Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Kehlberger, Andreas; Ritzmann, Ulrike; Hinzke, Denise; Guo, Er-Jia; Cramer, Joel; Jakob, Gerhard; Onbasli, Mehmet C.; Kim, Dong Hun; Ross, Caroline A.; Jungfleisch, Matthias B.; Hillebrands, Burkard; Nowak, Ulrich; Kläui, Mathias

    2015-08-01

    We investigate the origin of the spin Seebeck effect in yttrium iron garnet (YIG) samples for film thicknesses from 20 nm to 50 μ m at room temperature and 50 K. Our results reveal a characteristic increase of the longitudinal spin Seebeck effect amplitude with the thickness of the insulating ferrimagnetic YIG, which levels off at a critical thickness that increases with decreasing temperature. The observed behavior cannot be explained as an interface effect or by variations of the material parameters. Comparison to numerical simulations of thermal magnonic spin currents yields qualitative agreement for the thickness dependence resulting from the finite magnon propagation length. This allows us to trace the origin of the observed signals to genuine bulk magnonic spin currents due to the spin Seebeck effect ruling out an interface origin and allowing us to gauge the reach of thermally excited magnons in this system for different temperatures. At low temperature, even quantitative agreement with the simulations is found.

  4. Length Scale of the Spin Seebeck Effect.

    PubMed

    Kehlberger, Andreas; Ritzmann, Ulrike; Hinzke, Denise; Guo, Er-Jia; Cramer, Joel; Jakob, Gerhard; Onbasli, Mehmet C; Kim, Dong Hun; Ross, Caroline A; Jungfleisch, Matthias B; Hillebrands, Burkard; Nowak, Ulrich; Kläui, Mathias

    2015-08-28

    We investigate the origin of the spin Seebeck effect in yttrium iron garnet (YIG) samples for film thicknesses from 20 nm to 50  μm at room temperature and 50 K. Our results reveal a characteristic increase of the longitudinal spin Seebeck effect amplitude with the thickness of the insulating ferrimagnetic YIG, which levels off at a critical thickness that increases with decreasing temperature. The observed behavior cannot be explained as an interface effect or by variations of the material parameters. Comparison to numerical simulations of thermal magnonic spin currents yields qualitative agreement for the thickness dependence resulting from the finite magnon propagation length. This allows us to trace the origin of the observed signals to genuine bulk magnonic spin currents due to the spin Seebeck effect ruling out an interface origin and allowing us to gauge the reach of thermally excited magnons in this system for different temperatures. At low temperature, even quantitative agreement with the simulations is found.

  5. Exciton Seebeck effect in molecular systems.

    PubMed

    Yan, Yun-An; Cai, Shaohong

    2014-08-07

    We investigate the exciton dynamics under temperature difference with the hierarchical equations of motion. Through a nonperturbative simulation of the transient absorption of a heterogeneous trimer model, we show that the temperature difference causes exciton population redistribution and affects the exciton transfer time. It is found that one can reproduce not only the exciton population redistribution but also the change of the exciton transfer time induced by the temperature difference with a proper tuning of the site energies of the aggregate. In this sense, there exists a site energy shift equivalence for any temperature difference in a broad range. This phenomenon is similar to the Seebeck effect as well as spin Seebeck effect and can be named as exciton Seebeck effect.

  6. Exciton Seebeck effect in molecular systems

    SciTech Connect

    Yan, Yun-An; Cai, Shaohong

    2014-08-07

    We investigate the exciton dynamics under temperature difference with the hierarchical equations of motion. Through a nonperturbative simulation of the transient absorption of a heterogeneous trimer model, we show that the temperature difference causes exciton population redistribution and affects the exciton transfer time. It is found that one can reproduce not only the exciton population redistribution but also the change of the exciton transfer time induced by the temperature difference with a proper tuning of the site energies of the aggregate. In this sense, there exists a site energy shift equivalence for any temperature difference in a broad range. This phenomenon is similar to the Seebeck effect as well as spin Seebeck effect and can be named as exciton Seebeck effect.

  7. Spin pumping and spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Saitoh, Eiji

    2012-02-01

    Utilization of a spin current, a flow of electrons' spins in a solid, is the key technology in spintronics that will allow the achievement of efficient magnetic memories and computing devices. In this technology, generation and detection of spin currents are necessary. Here, we review inverse spin-Hall effect and spin-current-generation phenomena recently discovered both in metals and insulators: inverse spin-Hall effect, spin pumping, and spin Seebeck effect. (1)Spin pumping and spin torque in a Mott insulator system We found that spin pumping and spin torque effects appear also at an interface between Pt and an insulator YIG.. This means that we can connect a spin current carried by conduction electrons and a spin-wave spin current flowing in insulators. We demonstrate electric signal transmission by using these effects and interconversion of the spin currents [1]. (2) Spin Seebeck effect We have observed, by using the inverse spin-Hall effect [2], spin voltage generation from a heat current in a NiFe, named the spin-Seebeck effect [3]. Surprisingly, spin-Seebeck effect was found to appear even in insulators [4], a situation completely different from conventional charge Seebeck effect. The result implies an important role of elementary excitation in solids beside charge in the spin Seebeck effect. In the talk, we review the recent progress of the research on this effect. This research is collaboration with K. Ando, K. Uchida, Y. Kajiwara, S. Maekawa, G. E. W. Bauer, S. Takahashi, and J. Ieda. [4pt] [1] Y. Kajiwara and E. Saitoh et al. Nature 464 (2010) 262. [0pt] [2] E. Saitoh et al., Appl. Phys. Lett. 88 (2006) 182509. [0pt] [3] K. Uchida and E. Saitoh et al., Nature 455 (2008)778. [0pt] [4] K. Uchida and E. Saitoh et al.,Nature materials 9 (2010) 894 - 897.

  8. Time resolved spin Seebeck effect experiments

    SciTech Connect

    Roschewsky, Niklas Schreier, Michael; Schade, Felix; Ganzhorn, Kathrin; Meyer, Sibylle; Geprägs, Stephan; Kamra, Akashdeep; Huebl, Hans; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2014-05-19

    In this Letter, we present the results of transient thermopower experiments, performed at room temperature on yttrium iron garnet/platinum bilayers. Upon application of a time-varying thermal gradient, we observe a characteristic low-pass frequency response of the ensuing thermopower voltage with cutoff frequencies of up to 37 MHz. We interpret our results in terms of the spin Seebeck effect, and argue that small wavevector magnons are of minor importance for the spin Seebeck effect in our thin film hybrid structures.

  9. Evaluation of thermal gradients in longitudinal spin Seebeck effect measurements

    SciTech Connect

    Sola, A. Kuepferling, M.; Basso, V.; Pasquale, M.; Kikkawa, T.; Uchida, K.; Saitoh, E.

    2015-05-07

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

  10. Transverse Spin Seebeck Effect on YIG/Pt

    NASA Astrophysics Data System (ADS)

    Prakash, Arati; Boona, Stephen; Jin, Hyungyu; Heremans, Joseph

    2015-03-01

    The existence of the longitudinal spin-Seebeck effect (LSSE) is well established and supported by theory. Much more controversial is the nature of the signals observed in the transverse spin-Seebeck (TSSE) geometry, where the heat current (x) is orthogonal to the direction of spin current propagation (y). TSSE has been described as simply non-local thermal spin-injection, but questions remain about the fact that the effect is observed at macroscopic length scales. To explore possible explanations for the observed TSSE signals, we report data from new TSSE measurements on the YIG/Pt system. The system studied has multiple Pt strips deposited in series upon bulk single crystals of YIG. We investigate the TSSE coefficient as a function of four variables: (1) sample temperature; (2) magnitude of the temperature gradient; (3) position of Pt strips along x; and (4) width of Pt strips along x. We consider nonlinear effects and the role of magnon density in the interpretation of our results. Work supported by the ARO- MURI Grant W911NF-14-1-0016 and NSF MRSEC program, Grant No. DMR 1420451.

  11. Kinetics of O(1D) + H2O and O(1D) + H2: absolute rate coefficients and O(3P) yields between 227 and 453 K.

    PubMed

    Vranckx, Stijn; Peeters, Jozef; Carl, Shaun

    2010-08-28

    The rate coefficients for the crucial atmospheric reactions of O((1)D) with H(2)O and H(2), k(1) and k(2), were measured over a wide temperature range using O((1)D) detection based on the chemiluminescence reaction of O((1)D) with C(2)H. Analyzing the decays of the chemiluminescence intensities yielded a value for k(1)(T) of (1.70 x 10(-10)exp[36 K/T]) cm(3) s(-1). Multiplying or dividing k(1)(T) by a factor f(T) = 1.04 exp(5.59(|1 K/T- 1/287|)), gives the 95% confidence limits; our new determination, in good agreement with previous studies, further reduces the uncertainty in k(1). An extended study of k(2) yielded a temperature independent rate constant of (1.35 +/- 0.05) x 10(-10) cm(3) s(-1). This precise value, based on an extended set of determinations with very low scatter, is significantly larger than the current recommendations, as were two other recent k(2) determinations. Secondly, the fractions of O((1)D) quenched to O((3)P) by H(2)O and H(2), k(1b)/k(1) and k(2b)/k(2), were precisely determined from fits to chemiluminescence decays. A temperature-independent value for k(1b)/k(1) of 0.010 +/- 0.003 was found. For the quenching fraction k(2b)/k(2) a value of 0.007 +/- 0.007 was obtained at room temperature. Both determinations are significantly smaller than values and upper limits from previous studies.

  12. High Seebeck effects from conducting polymer: Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) based thin-film device with hybrid metal/polymer/metal architecture

    SciTech Connect

    Stanford, Michael G; Wang, Hsin; Ivanov, Ilia N; Hu, Bin

    2012-01-01

    Conductive polymers are of particular interest for thermoelectric applications due to their low thermal conductivity and relatively high electrical conductivity. In this study, commercially available conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used in a hybrid metal/polymer/metal thin film design in order to achieve a high Seebeck coefficient with the value of 252lV/k on a relatively low temperature scale. Polymer film thickness was varied in order to investigate its influence on the Seebeck effect. The high Seebeck coefficient indicates that the metal/polymer/metal design can develop a large entropy difference in internal energy of charge carriers between high and low-temperature metal electrodes to develop electrical potential due to charge transport in conducting polymer film through metal/polymer interface. Therefore, the metal/polymer/metal structure presents a new design to combine inorganic metals and organic polymers in thin-film form to develop Seebeck devices

  13. Simple Demonstration of the Seebeck Effect

    ERIC Educational Resources Information Center

    Molki, Arman

    2010-01-01

    In this article we propose a simple and low-cost experimental set-up through which science educators can demonstrate the Seebeck effect using a thermocouple and an instrumentation amplifier. The experiment can be set up and conducted during a 1-hour laboratory session. (Contains 3 tables and 3 figures.)

  14. Spin Seebeck effect in a weak ferromagnet

    NASA Astrophysics Data System (ADS)

    Arboleda, Juan David; Arnache Olmos, Oscar; Aguirre, Myriam Haydee; Ramos, Rafael; Anadon, Alberto; Ibarra, Manuel Ricardo

    2016-06-01

    We report the observation of room temperature spin Seebeck effect (SSE) in a weak ferromagnetic normal spinel Zinc Ferrite (ZFO). Despite the weak ferromagnetic behavior, the measurements of the SSE in ZFO show a thermoelectric voltage response comparable with the reported values for other ferromagnetic materials. Our results suggest that SSE might possibly originate from the surface magnetization of the ZFO.

  15. Absolute and relative nonlinear optical coefficients of KDP, KD(asterisk)P, BaB2O4, LiIO3, MgO:LiNbO3, and KTP measured by phase-matched second-harmonic generation

    NASA Technical Reports Server (NTRS)

    Eckardt, Robert C.; Byer, Robert L.; Masuda, Hisashi; Fan, Yuan Xuan

    1990-01-01

    Both absolute and relative nonlinear optical coefficients of six nonlinear materials measured by second-harmonic generation are discussed. A single-mode, injection-seeded, Q-switched Nd:YAG laser with spatially filtered output was used to generate the 1.064-micron fundamental radiation. The following results were obtained: d36(KDP) = 0.38 pm/V, d36(KD/asterisk/P) = 0.37 pm/V, (parallel)d22(BaB2O4)(parallel) = 2.2 pm/V, d31(LiIO3) = -4.1 pm/V, d31(5 percentMgO:MgO LiNbO3) = -4.7 pm/V, and d(eff)(KTP) = 3.2 pm/V. The accuracy of these measurements is estimated to be better than 10 percent.

  16. Seebeck Enhancement Through Miniband Conduction in III-V Semiconductor Superlattices at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Bahk, Je-Hyeong; Sadeghian, Ramin Banan; Bian, Zhixi; Shakouri, Ali

    2012-06-01

    We present theoretically that the cross-plane Seebeck coefficient of InGaAs/InGaAlAs III-V semiconductor superlattices can be significantly enhanced through miniband transport at low temperatures. The miniband dispersion curves are calculated by self-consistently solving the Schrödinger equation with the periodic potential, and the Poisson equation taking into account the charge transfer between the two layers. Boltzmann transport in the relaxation-time approximation is used to calculate the thermoelectric transport properties in the cross-plane direction based on the modified density of states and group velocity. It is found that the cross-plane Seebeck coefficient can be enhanced more than 60% over the bulk values at an equivalent doping level at 80 K when the Fermi level is aligned at an edge of the minibands. Other thermoelectric transport properties are also calculated and discussed to further enhance the thermoelectric power factor.

  17. Enhanced Seebeck effect in graphene devices by strain and doping engineering

    NASA Astrophysics Data System (ADS)

    Nguyen, M. Chung; Nguyen, V. Hung; Nguyen, Huy-Viet; Saint-Martin, J.; Dollfus, P.

    2015-09-01

    In this work, we investigate the possibility of enhancing the thermoelectric power (Seebeck coefficient) in graphene devices by strain and doping engineering. While a local strain can result in the misalignment of Dirac cones of different graphene sections in the k-space, doping engineering leads to their displacement in energy. By combining these two effects, we demonstrate that a conduction gap as large as a few hundred meV can be achieved and hence the enhanced Seebeck coefficient can reach a value higher than 1.4 mV/K in graphene doped heterojunctions with a locally strained area. Such hetero-channels appear to be very promising for enlarging the applications of graphene devices as in strain and thermal sensors.

  18. Giant Seebeck effect in Ge-doped SnSe

    PubMed Central

    Gharsallah, M.; Serrano-Sánchez, F.; Nemes, N. M.; Mompeán, F. J.; Martínez, J. L.; Fernández-Díaz, M. T.; Elhalouani, F.; Alonso, J. A.

    2016-01-01

    Thermoelectric materials may contribute in the near future as new alternative sources of sustainable energy. Unprecedented thermoelectric properties in p-type SnSe single crystals have been recently reported, accompanied by extremely low thermal conductivity in polycrystalline samples. In order to enhance thermoelectric efficiency through proper tuning of this material we report a full structural characterization and evaluation of the thermoelectric properties of novel Ge-doped SnSe prepared by a straightforward arc-melting method, which yields nanostructured polycrystalline samples. Ge does not dope the system in the sense of donating carriers, yet the electrical properties show a semiconductor behavior with resistivity values higher than that of the parent compound, as a consequence of nanostructuration, whereas the Seebeck coefficient is higher and thermal conductivity lower, favorable to a better ZT figure of merit. PMID:27251233

  19. Giant Seebeck effect in Ge-doped SnSe.

    PubMed

    Gharsallah, M; Serrano-Sánchez, F; Nemes, N M; Mompeán, F J; Martínez, J L; Fernández-Díaz, M T; Elhalouani, F; Alonso, J A

    2016-06-02

    Thermoelectric materials may contribute in the near future as new alternative sources of sustainable energy. Unprecedented thermoelectric properties in p-type SnSe single crystals have been recently reported, accompanied by extremely low thermal conductivity in polycrystalline samples. In order to enhance thermoelectric efficiency through proper tuning of this material we report a full structural characterization and evaluation of the thermoelectric properties of novel Ge-doped SnSe prepared by a straightforward arc-melting method, which yields nanostructured polycrystalline samples. Ge does not dope the system in the sense of donating carriers, yet the electrical properties show a semiconductor behavior with resistivity values higher than that of the parent compound, as a consequence of nanostructuration, whereas the Seebeck coefficient is higher and thermal conductivity lower, favorable to a better ZT figure of merit.

  20. Giant Seebeck effect in Ge-doped SnSe

    NASA Astrophysics Data System (ADS)

    Gharsallah, M.; Serrano-Sánchez, F.; Nemes, N. M.; Mompeán, F. J.; Martínez, J. L.; Fernández-Díaz, M. T.; Elhalouani, F.; Alonso, J. A.

    2016-06-01

    Thermoelectric materials may contribute in the near future as new alternative sources of sustainable energy. Unprecedented thermoelectric properties in p-type SnSe single crystals have been recently reported, accompanied by extremely low thermal conductivity in polycrystalline samples. In order to enhance thermoelectric efficiency through proper tuning of this material we report a full structural characterization and evaluation of the thermoelectric properties of novel Ge-doped SnSe prepared by a straightforward arc-melting method, which yields nanostructured polycrystalline samples. Ge does not dope the system in the sense of donating carriers, yet the electrical properties show a semiconductor behavior with resistivity values higher than that of the parent compound, as a consequence of nanostructuration, whereas the Seebeck coefficient is higher and thermal conductivity lower, favorable to a better ZT figure of merit.

  1. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  2. Magnon Polarons in the Spin Seebeck Effect.

    PubMed

    Kikkawa, Takashi; Shen, Ka; Flebus, Benedetta; Duine, Rembert A; Uchida, Ken-Ichi; Qiu, Zhiyong; Bauer, Gerrit E W; Saitoh, Eiji

    2016-11-11

    Sharp structures in the magnetic field-dependent spin Seebeck effect (SSE) voltages of Pt/Y_{3}Fe_{5}O_{12} at low temperatures are attributed to the magnon-phonon interaction. Experimental results are well reproduced by a Boltzmann theory that includes magnetoelastic coupling. The SSE anomalies coincide with magnetic fields tuned to the threshold of magnon-polaron formation. The effect gives insight into the relative quality of the lattice and magnetization dynamics.

  3. Magnon Polarons in the Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takashi; Shen, Ka; Flebus, Benedetta; Duine, Rembert A.; Uchida, Ken-ichi; Qiu, Zhiyong; Bauer, Gerrit E. W.; Saitoh, Eiji

    2016-11-01

    Sharp structures in the magnetic field-dependent spin Seebeck effect (SSE) voltages of Pt /Y3Fe5 O12 at low temperatures are attributed to the magnon-phonon interaction. Experimental results are well reproduced by a Boltzmann theory that includes magnetoelastic coupling. The SSE anomalies coincide with magnetic fields tuned to the threshold of magnon-polaron formation. The effect gives insight into the relative quality of the lattice and magnetization dynamics.

  4. Magnons, Spin Current and Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Maekawa, Sadamichi

    2012-02-01

    When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

  5. Magnetic equivalent of the Seebeck effect

    NASA Astrophysics Data System (ADS)

    Brechet, Sylvain

    Spin caloritonics seeks to investigate the effect of a thermal gradient on the electronic charge and spin degrees of freedom. In a conductor, a thermal gradient leads a transport of the conduction electrons that in turn generate an electric field along the temperature gradient, which is the well-known Seebeck effect. In an insulator, there are no conduction electrons. Thus no electronic charge transport takes place. However, the electronic spins can reorient themselves in the presence of a temperature gradient as they precess around an external field oriented along the temperature gradient. In fact, the temperature gradient generates a magnetic induction field in the plane orthogonal to the temperature gradient. The effect is the magnetic analog of the Seebeck effect and is thus refered to as the magnetic Seebeck effect. It has been observed for the propagation of spin waves along and against a temperature gradient in a YIG slab. The propagation of spin waves against the temperature gradient lead to a positive thermal damping and the propagation along the temperature gradient leads to the opposite effect, namely a negative thermal damping. Thus, the magnetic Seebeck effect generate of heat driven spin torque that can generate a positive or a negative thermal damping. The magnetic Seebeck effect has been recently established using a fundamental variational approach. In many experimental situations, the system can be treated as a classical continuum with magnetisation on the scale of interest where the quantum fluctuations average out and the underlying microscopic structure is smoothed out. For the propagation of magnetisation waves in a stationary state, the system is slightly out of equilibrium but the magnetic kinetic energy is constant. In such a case, the action of the system is a functional of the magnetisation and the magnetisation current. Since the magnetisation is a function of the temperature, the action variation yields an explicit expression for the

  6. Absence of the Thermal Hall Effect in Anomalous Nernst and Spin Seebeck Effects.

    PubMed

    Chen, Yi-Jia; Huang, Ssu-Yen

    2016-12-09

    The anomalous Nernst effect (ANE) and the spin Seebeck effect (SSE) in spin caloritronics are two of the most important mechanisms to manipulate the spin-polarized current and pure spin current by thermal excitation. While the ANE in ferromagnetic metals and the SSE in magnetic insulators have been extensively studied, a recent theoretical work suggests that the signals from the thermal Hall effect (THE) have field dependences indistinguishable from, and may even overwhelm, those of the ANE and SSE. Therefore, it is vital to investigate the contribution of the THE in the ANE and SSE. In this work, we systematically study the THE in a ferromagnetic metal, Permalloy (Py), and magnetic insulator, an yttrium iron garnet (YIG), by using different Seebeck coefficients between electrodes and contact wires. Our results demonstrate that the contribution of the THE by the thermal couple effect in the Py and YIG is negligibly small if one includes the thickness dependence of the Seebeck coefficient. Thus, the spin-polarized current in the ANE and the pure spin current in the SSE remain indispensable for exploring spin caloritronics phenomena.

  7. Comparison of the magneto-Peltier and magneto-Seebeck effects in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Shan, J.; Dejene, F. K.; Leutenantsmeyer, J. C.; Flipse, J.; Münzenberg, M.; van Wees, B. J.

    2015-07-01

    Understanding heat generation and transport processes in a magnetic tunnel junction (MTJ) is a significant step towards improving its application in current memory devices. Recent work has experimentally demonstrated the magneto-Seebeck effect in MTJs, where the Seebeck coefficient of the junction varies as the magnetic configuration changes from a parallel (P) to an antiparallel (AP) configuration. Here we report a study on its reciprocal effect, the magneto-Peltier effect, where the heat flow carried by the tunneling electrons is altered by changing the magnetic configuration of the MTJ. The magneto-Peltier signal that reflects the change in the temperature difference across the junction between the P and AP configurations scales linearly with the applied current in the small bias but is greatly enhanced in the large-bias regime, due to higher-order Joule heating mechanisms. By carefully extracting the linear response which reflects the magneto-Peltier effect, and comparing it with the magneto-Seebeck measurements performed on the same device, we observe results consistent with Onsager reciprocity. We estimate a magneto-Peltier coefficient of 13.4 mV in the linear regime using a three-dimensional thermoelectric model. Our result opens up the possibility of programmable thermoelectric devices based on the Peltier effect in MTJs.

  8. Absence of the Thermal Hall Effect in Anomalous Nernst and Spin Seebeck Effects

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Jia; Huang, Ssu-Yen

    2016-12-01

    The anomalous Nernst effect (ANE) and the spin Seebeck effect (SSE) in spin caloritronics are two of the most important mechanisms to manipulate the spin-polarized current and pure spin current by thermal excitation. While the ANE in ferromagnetic metals and the SSE in magnetic insulators have been extensively studied, a recent theoretical work suggests that the signals from the thermal Hall effect (THE) have field dependences indistinguishable from, and may even overwhelm, those of the ANE and SSE. Therefore, it is vital to investigate the contribution of the THE in the ANE and SSE. In this work, we systematically study the THE in a ferromagnetic metal, Permalloy (Py), and magnetic insulator, an yttrium iron garnet (YIG), by using different Seebeck coefficients between electrodes and contact wires. Our results demonstrate that the contribution of the THE by the thermal couple effect in the Py and YIG is negligibly small if one includes the thickness dependence of the Seebeck coefficient. Thus, the spin-polarized current in the ANE and the pure spin current in the SSE remain indispensable for exploring spin caloritronics phenomena.

  9. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  10. Spin Seebeck effect in quantum dot side-coupled to topological superconductor

    NASA Astrophysics Data System (ADS)

    Weymann, Ireneusz

    2017-03-01

    The spin-resolved thermoelectric transport properties of a quantum dot coupled to ferromagnetic leads and side-coupled to a topological superconductor wire hosting Majorana zero-energy modes are studied theoretically. The calculations are performed in the linear response regime by using the numerical renormalization group method. It is shown that transport characteristics are determined by the interplay of Kondo correlations, exchange field due to the presence of ferromagnets and the strength of coupling to Majorana wire. These different energy scales are revealed in the behavior of the Seebeck and spin Seebeck coefficients, which exhibit an enhancement for temperatures of the order of the coupling strength to topological wire. Moreover, it is demonstrated that additional sign changes of the thermopower can occur due to the presence of Majorana zero-energy modes. These findings may provide additional fingerprints of the presence of Majorana fermions.

  11. Spin Seebeck effect in quantum dot side-coupled to topological superconductor.

    PubMed

    Weymann, Ireneusz

    2017-03-08

    The spin-resolved thermoelectric transport properties of a quantum dot coupled to ferromagnetic leads and side-coupled to a topological superconductor wire hosting Majorana zero-energy modes are studied theoretically. The calculations are performed in the linear response regime by using the numerical renormalization group method. It is shown that transport characteristics are determined by the interplay of Kondo correlations, exchange field due to the presence of ferromagnets and the strength of coupling to Majorana wire. These different energy scales are revealed in the behavior of the Seebeck and spin Seebeck coefficients, which exhibit an enhancement for temperatures of the order of the coupling strength to topological wire. Moreover, it is demonstrated that additional sign changes of the thermopower can occur due to the presence of Majorana zero-energy modes. These findings may provide additional fingerprints of the presence of Majorana fermions.

  12. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  13. Cryogenic, Absolute, High Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

    2001-01-01

    A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

  14. Spin Seebeck effect at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Schreier, Michael; Kramer, Franz; Huebl, Hans; Geprägs, Stephan; Gross, Rudolf; Goennenwein, Sebastian T. B.; Noack, Timo; Langner, Thomas; Serga, Alexander A.; Hillebrands, Burkard; Vasyuchka, Vitaliy I.

    2016-06-01

    We experimentally study the transient voltage response of yttrium iron garnet/platinum bilayer samples subject to periodic heating up to gigahertz frequencies. We observe an intrinsic cutoff frequency of the induced thermopower voltage, which characteristically depends on the thickness of the yttrium iron garnet film. The cutoff frequency reaches values of up to 350 MHz in a 50-nm-thick yttrium iron garnet film, but drops to below 1 MHz for several-micrometer-thick films. These data corroborate the notion that the magnon spectrum responsible for the spin current emission in the spin Seebeck effect can be shaped by tuning the thickness of the ferromagnetic layer.

  15. Spin Seebeck Effect in a Compensated Ferrimagnet

    NASA Astrophysics Data System (ADS)

    Goennenwein, Sebastian T. B.; Geprägs, S.; Kehlberger, A.; Schulz, T.; Mix, C.; Della Coletta, F.; Meyer, S.; Kamra, A.; Jakob, G.; Althammer, M.; Huebl, H.; Gross, R.; Kläui, M.

    2015-03-01

    Thermal gradients allow for driving pure spin currents in electrically insulating magnetic materials. In magnetic insulator/normal metal heterostructures, such thermally driven spin currents can be electrically detected via the inverse spin Hall effect in the normal metal, in so-called spin Seebeck effect (SSE) experiments. We have fabricated Gadolinium Iron Garnet/Platinum (GdIG/Pt) thin film heterostructures, and measured the spin Seebeck effect in these samples as a function of temperature. We observe two sign changes as a function of T in the SSE signal. The first sign change occurs around the GdIG magnetic compensation temperature, and can be straightforwardly understood in terms of the reorientation of the iron sublattice magnetizations at this temperature. The second, more gradual SSE sign change takes place around the ordering temperature of the Gd magnetic sublattice, suggesting that the thermally driven spin current is mainly determined by the Gd sublattice at low T. Our results thus show that the SSE spin currents do not simply replicate the effective magnetization of the magnetic insulator, but rather reflect a complex interplay of magnetic sublattice properties.

  16. Gamma radiation resistance of spin Seebeck devices

    NASA Astrophysics Data System (ADS)

    Yagmur, A.; Uchida, K.; Ihara, K.; Ioka, I.; Kikkawa, T.; Ono, M.; Endo, J.; Kashiwagi, K.; Nakashima, T.; Kirihara, A.; Ishida, M.; Saitoh, E.

    2016-12-01

    Thermoelectric devices based on the spin Seebeck effect (SSE) were irradiated with gamma (γ) rays with the total dose of around 3 × 105 Gy in order to investigate the γ-radiation resistance of the devices. To demonstrate this, Pt/Ni0.2Zn0.3Fe2.5O4/Glass and Pt/Bi0.1Y2.9Fe5O12/Gd3Ga5O12 SSE devices were used. We confirmed that the thermoelectric, magnetic, and structural properties of the SSE devices are not affected by the γ-ray irradiation. This result demonstrates that SSE devices are applicable to thermoelectric generation even in high radiation environments.

  17. All-oxide spin Seebeck effects

    NASA Astrophysics Data System (ADS)

    Qiu, Zhiyong; Hou, Dazhi; Kikkawa, Takashi; Uchida, Ken-ichi; Saitoh, Eiji

    2015-08-01

    We report the observation of longitudinal spin Seebeck effects (LSSEs) in an all-oxide bilayer system comprising an IrO2 film and an Y3Fe5O12 film. Spin currents, which are generated by a temperature gradient across the IrO2/Y3Fe5O12 interface, were detected as a voltage via the inverse spin Hall effect in the conductive IrO2 layer. This voltage is proportional to the magnitude of the temperature gradient; its magnetic field dependence is consistent with the characteristics of LSSEs. This demonstration may lead to the realization of low-cost, stable, transparent spin-current-driven thermoelectric devices.

  18. Surface sensitivity of the spin Seebeck effect

    SciTech Connect

    Aqeel, A.; Vera-Marun, I. J.; Wees, B. J. van; Palstra, T. T. M.

    2014-10-21

    We have investigated the influence of the interface quality on the spin Seebeck effect (SSE) of the bilayer system yttrium iron garnet (YIG)–platinum (Pt). The magnitude and shape of the SSE is strongly influenced by mechanical treatment of the YIG single crystal surface. We observe that the saturation magnetic field (H{sub sat}{sup SSE}) for the SSE signal increases from 55.3 mT to 72.8 mT with mechanical treatment. The change in the magnitude of H{sub sat}{sup SSE} can be attributed to the presence of a perpendicular magnetic anisotropy due to the treatment induced surface strain or shape anisotropy in the Pt/YIG system. Our results show that the SSE is a powerful tool to investigate magnetic anisotropy at the interface.

  19. Spin Seebeck effect in insulating epitaxial γ-Fe2O3 thin films

    NASA Astrophysics Data System (ADS)

    Jiménez-Cavero, P.; Lucas, I.; Anadón, A.; Ramos, R.; Niizeki, T.; Aguirre, M. H.; Algarabel, P. A.; Uchida, K.; Ibarra, M. R.; Saitoh, E.; Morellón, L.

    2017-02-01

    We report the fabrication of high crystal quality epitaxial thin films of maghemite (γ-Fe2O3), a classic ferrimagnetic insulating iron oxide. Spin Seebeck effect (SSE) measurements in γ-Fe2O3/Pt bilayers as a function of sample preparation conditions and temperature yield a SSE coefficient of 0.5(1) μV/K at room temperature. Dependence on temperature allows us to estimate the magnon diffusion length in maghemite to be in the range of tens of nanometers, in good agreement with that of conducting iron oxide magnetite (Fe3O4), establishing the relevance of spin currents of magnonic origin in magnetic iron oxides.

  20. Multifold Seebeck increase in RuO2 films by quantum-guided lanthanide dilute alloying

    NASA Astrophysics Data System (ADS)

    Music, Denis; Basse, Felix H.-U.; Han, Liang; Devender; Borca-Tasciuc, Theo; Gengler, Jamie J.; Voevodin, Andrey A.; Ramanath, Ganpati; Schneider, Jochen M.

    2014-02-01

    Ab initio predictions indicating that alloying RuO2 with La, Eu, or Lu can increase the Seebeck coefficient α manifold due to quantum confinement effects are validated in sputter-deposited La-alloyed RuO2 films showing fourfold α increase. Combinatorial screening reveals that α enhancement correlates with La-induced lattice distortion, which also decreases the thermal conductivity twentyfold, conducive for high thermoelectric figures of merit. These insights should facilitate the rational design of high efficiency oxide-based thermoelectrics through quantum-guided alloying.

  1. New experimental methodology, setup and LabView program for accurate absolute thermoelectric power and electrical resistivity measurements between 25 and 1600 K: Application to pure copper, platinum, tungsten, and nickel at very high temperatures

    NASA Astrophysics Data System (ADS)

    Abadlia, L.; Gasser, F.; Khalouk, K.; Mayoufi, M.; Gasser, J. G.

    2014-09-01

    In this paper we describe an experimental setup designed to measure simultaneously and very accurately the resistivity and the absolute thermoelectric power, also called absolute thermopower or absolute Seebeck coefficient, of solid and liquid conductors/semiconductors over a wide range of temperatures (room temperature to 1600 K in present work). A careful analysis of the existing experimental data allowed us to extend the absolute thermoelectric power scale of platinum to the range 0-1800 K with two new polynomial expressions. The experimental device is controlled by a LabView program. A detailed description of the accurate dynamic measurement methodology is given in this paper. We measure the absolute thermoelectric power and the electrical resistivity and deduce with a good accuracy the thermal conductivity using the relations between the three electronic transport coefficients, going beyond the classical Wiedemann-Franz law. We use this experimental setup and methodology to give new very accurate results for pure copper, platinum, and nickel especially at very high temperatures. But resistivity and absolute thermopower measurement can be more than an objective in itself. Resistivity characterizes the bulk of a material while absolute thermoelectric power characterizes the material at the point where the electrical contact is established with a couple of metallic elements (forming a thermocouple). In a forthcoming paper we will show that the measurement of resistivity and absolute thermoelectric power characterizes advantageously the (change of) phase, probably as well as DSC (if not better), since the change of phases can be easily followed during several hours/days at constant temperature.

  2. New experimental methodology, setup and LabView program for accurate absolute thermoelectric power and electrical resistivity measurements between 25 and 1600 K: application to pure copper, platinum, tungsten, and nickel at very high temperatures.

    PubMed

    Abadlia, L; Gasser, F; Khalouk, K; Mayoufi, M; Gasser, J G

    2014-09-01

    In this paper we describe an experimental setup designed to measure simultaneously and very accurately the resistivity and the absolute thermoelectric power, also called absolute thermopower or absolute Seebeck coefficient, of solid and liquid conductors/semiconductors over a wide range of temperatures (room temperature to 1600 K in present work). A careful analysis of the existing experimental data allowed us to extend the absolute thermoelectric power scale of platinum to the range 0-1800 K with two new polynomial expressions. The experimental device is controlled by a LabView program. A detailed description of the accurate dynamic measurement methodology is given in this paper. We measure the absolute thermoelectric power and the electrical resistivity and deduce with a good accuracy the thermal conductivity using the relations between the three electronic transport coefficients, going beyond the classical Wiedemann-Franz law. We use this experimental setup and methodology to give new very accurate results for pure copper, platinum, and nickel especially at very high temperatures. But resistivity and absolute thermopower measurement can be more than an objective in itself. Resistivity characterizes the bulk of a material while absolute thermoelectric power characterizes the material at the point where the electrical contact is established with a couple of metallic elements (forming a thermocouple). In a forthcoming paper we will show that the measurement of resistivity and absolute thermoelectric power characterizes advantageously the (change of) phase, probably as well as DSC (if not better), since the change of phases can be easily followed during several hours/days at constant temperature.

  3. New experimental methodology, setup and LabView program for accurate absolute thermoelectric power and electrical resistivity measurements between 25 and 1600 K: Application to pure copper, platinum, tungsten, and nickel at very high temperatures

    SciTech Connect

    Abadlia, L.; Mayoufi, M.; Gasser, F.; Khalouk, K.; Gasser, J. G.

    2014-09-15

    In this paper we describe an experimental setup designed to measure simultaneously and very accurately the resistivity and the absolute thermoelectric power, also called absolute thermopower or absolute Seebeck coefficient, of solid and liquid conductors/semiconductors over a wide range of temperatures (room temperature to 1600 K in present work). A careful analysis of the existing experimental data allowed us to extend the absolute thermoelectric power scale of platinum to the range 0-1800 K with two new polynomial expressions. The experimental device is controlled by a LabView program. A detailed description of the accurate dynamic measurement methodology is given in this paper. We measure the absolute thermoelectric power and the electrical resistivity and deduce with a good accuracy the thermal conductivity using the relations between the three electronic transport coefficients, going beyond the classical Wiedemann-Franz law. We use this experimental setup and methodology to give new very accurate results for pure copper, platinum, and nickel especially at very high temperatures. But resistivity and absolute thermopower measurement can be more than an objective in itself. Resistivity characterizes the bulk of a material while absolute thermoelectric power characterizes the material at the point where the electrical contact is established with a couple of metallic elements (forming a thermocouple). In a forthcoming paper we will show that the measurement of resistivity and absolute thermoelectric power characterizes advantageously the (change of) phase, probably as well as DSC (if not better), since the change of phases can be easily followed during several hours/days at constant temperature.

  4. Theory of phonon-driven spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroto; Ohe, Jun-Ichiro; Takahashi, Saburo; Maekawa, Sadamichi

    2012-02-01

    Spin Seebeck effect refers to a thermal spin injection occurring over millimeter scales from a ferromagnet into an attached nonmagnetic metal [Uchida et al., Nature 455, 778 (2008)]. We discuss the importance of the phonon-drag process in the spin Seebeck effect. Our theory of phonon-drag spin Seebeck effect [Adachi et al., Appl. Phys. Lett. 97, 252506 (2010)] explains simultaneously the local nature of the spin Seebeck effect [Jaworski et al., Nature Materials 9, 898 (2010); Uchida et al., Nature Materials 10, 737 (2011)] and the signal enhancement at low temperatures [Jaworski et al., Phys. Rev. Lett. 106, 186601 (2011)]. We also discuss the difference between our approach and that developed in Xiao et al., Phys. Rev. B 81, 214418 (2010).

  5. Absolute intensities and foreign gas broadening coefficients of the 11(sub 1,10) from 11(sub 2,10) and 18(sub 0,18) from 18(sub 1,18) lines in the nu(sub 7) band of C2H4

    NASA Technical Reports Server (NTRS)

    Reuter, Dennis C.; Sirota, J. Marcos

    1993-01-01

    Absolute intensities and foreign gas broadening coefficients of the 18(sub 0,18) from 18(sub 1,18) and 11(sub 1,10) from 11(sub 2,10) transitions in the nu(sub 7) band of C2H4 near 948/cm have been measured at a spectral resolution of approximately 5 x 10(exp -4)/cm using tunable diode laser spectrometry. Ar, He, N2, O2 were used as the broadening gases. In order to determine the temperature dependence of the broadening coefficient, data were obtained at temperatures ranging from 150 to 296 K. The absolute intensity of the 5(sub 0,5) from 5(sub 1,5) transition was also found at 296 K. A band strength of 330 +/- 10/sq cm/atm was obtained from weighted averages of the individual line intensities and a rigid asymmetric top calculation.

  6. Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFO

    PubMed Central

    Meier, Daniel; Reinhardt, Daniel; van Straaten, Michael; Klewe, Christoph; Althammer, Matthias; Schreier, Michael; Goennenwein, Sebastian T. B.; Gupta, Arunava; Schmid, Maximilian; Back, Christian H.; Schmalhorst, Jan-Michael; Kuschel, Timo; Reiss, Günter

    2015-01-01

    The spin Seebeck effect, the generation of a spin current by a temperature gradient, has attracted great attention, but the interplay over a millimetre range along a thin ferromagnetic film as well as unintended side effects which hinder an unambiguous detection have evoked controversial discussions. Here, we investigate the inverse spin Hall voltage of a 10 nm thin Pt strip deposited on the magnetic insulators Y3Fe5O12 and NiFe2O4 with a temperature gradient in the film plane. We show characteristics typical of the spin Seebeck effect, although we do not observe the most striking features of the transverse spin Seebeck effect. Instead, we attribute the observed voltages to the longitudinal spin Seebeck effect generated by a contact tip induced parasitic out-of-plane temperature gradient, which depends on material, diameter and temperature of the tip. PMID:26394541

  7. Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFO

    NASA Astrophysics Data System (ADS)

    Meier, Daniel; Reinhardt, Daniel; van Straaten, Michael; Klewe, Christoph; Althammer, Matthias; Schreier, Michael; Goennenwein, Sebastian T. B.; Gupta, Arunava; Schmid, Maximilian; Back, Christian H.; Schmalhorst, Jan-Michael; Kuschel, Timo; Reiss, Günter

    2015-09-01

    The spin Seebeck effect, the generation of a spin current by a temperature gradient, has attracted great attention, but the interplay over a millimetre range along a thin ferromagnetic film as well as unintended side effects which hinder an unambiguous detection have evoked controversial discussions. Here, we investigate the inverse spin Hall voltage of a 10 nm thin Pt strip deposited on the magnetic insulators Y3Fe5O12 and NiFe2O4 with a temperature gradient in the film plane. We show characteristics typical of the spin Seebeck effect, although we do not observe the most striking features of the transverse spin Seebeck effect. Instead, we attribute the observed voltages to the longitudinal spin Seebeck effect generated by a contact tip induced parasitic out-of-plane temperature gradient, which depends on material, diameter and temperature of the tip.

  8. Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFO.

    PubMed

    Meier, Daniel; Reinhardt, Daniel; van Straaten, Michael; Klewe, Christoph; Althammer, Matthias; Schreier, Michael; Goennenwein, Sebastian T B; Gupta, Arunava; Schmid, Maximilian; Back, Christian H; Schmalhorst, Jan-Michael; Kuschel, Timo; Reiss, Günter

    2015-09-23

    The spin Seebeck effect, the generation of a spin current by a temperature gradient, has attracted great attention, but the interplay over a millimetre range along a thin ferromagnetic film as well as unintended side effects which hinder an unambiguous detection have evoked controversial discussions. Here, we investigate the inverse spin Hall voltage of a 10 nm thin Pt strip deposited on the magnetic insulators Y3Fe5O12 and NiFe2O4 with a temperature gradient in the film plane. We show characteristics typical of the spin Seebeck effect, although we do not observe the most striking features of the transverse spin Seebeck effect. Instead, we attribute the observed voltages to the longitudinal spin Seebeck effect generated by a contact tip induced parasitic out-of-plane temperature gradient, which depends on material, diameter and temperature of the tip.

  9. Spin Seebeck Effect Signals from Antiferromagnets

    NASA Astrophysics Data System (ADS)

    Prakash, Arati; Brangham, Jack; Yang, Fengyuan; Heremans, Joseph

    The Longitudinal Spin Seebeck Effect (LSSE), in which a heat current stimulates spin propagation across an interface between a magnetic material and a normal metal, is well established and observed in ferromagnetic systems. Data have been presented indicating that antiferromagnetic systems could also give rise to LSSE signals. We report here on LSSE signal measured on the Pt/NiO/YIG structure, where NiO is an antiferromagnet. This system is reported to exhibit antiferromagnonic transport. We explore the dependence of the signal on the thickness of the NiO and YIG layers. We also report its temperature dependence, which was not explored before. The results are interpreted in terms of the temperature dependence of the magnon density of states. It appears that magnon modes with energies below about 40 K are most involved in the process, as was the case to the LSSE on YIG itself. Preliminary results using other antiferromagnets and other inverse spin-Hall layers look promising and will also be reported Work supported by ARO- MURI W911NF-14-1-0016.

  10. 125Te NMR and Seebeck Effect in Bi2Te3 Synthesized from Stoichiometric and Te-Rich Melts

    DOE PAGES

    Levin, E. M.; Riedemann, T. M.; Howard, A.; ...

    2016-10-14

    Bi2Te3 is a well-known thermoelectric material and, as a new form of quantum matter, a topological insulator. Variation of local chemical composition in Bi2Te3 results in formation of several types of atomic defects, including Bi and Te vacancies and Bi and Te antisite defects; these defects can strongly affect material functionality via generation of free electrons and/or holes. Nonuniform distribution of atomic defects produces electronic inhomogeneity, which can be detected by 125Te nuclear magnetic resonance (NMR). Here we report on 125Te NMR and Seebeck effect (heat to electrical energy conversion) for two single crystalline samples: (#1) grown from stoichiometric compositionmore » by Bridgman technique and (#2) grown out of Te-rich, high temperature flux. The Seebeck coefficients of these samples show p- and n-type conductivity, respectively, arising from different atomic defects. 125Te NMR spectra and spin–lattice relaxation measurements demonstrate that both Bi2Te3 samples are electronically inhomogeneous at the atomic scale, which can be attributed to a different Te environment due to spatial variation of the Bi/Te ratio and formation of atomic defects. In conclusion, correlations between 125Te NMR spectra, spin–lattice relaxation times, the Seebeck coefficients, carrier concentrations, and atomic defects are discussed. Our data demonstrate that 125Te NMR is an effective probe to study antisite defects in Bi2Te3.« less

  11. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  12. Spin Seebeck effect and thermoelectric phenomena in superconducting hybrids with magnetic textures or spin-orbit coupling.

    PubMed

    Bathen, Marianne Etzelmüller; Linder, Jacob

    2017-01-31

    We theoretically consider the spin Seebeck effect, the charge Seebeck coefficient, and the thermoelectric figure of merit in superconducting hybrid structures including either magnetic textures or intrinsic spin-orbit coupling. We demonstrate that large magnitudes for all these quantities are obtainable in Josephson-based systems with either zero or a small externally applied magnetic field. This provides an alternative to the thermoelectric effects generated in high-field (~1 T) superconducting hybrid systems, which were recently experimentally demonstrated. The systems studied contain either conical ferromagnets, spin-active interfaces, or spin-orbit coupling. We present a framework for calculating the linear thermoelectric response for both spin and charge of a system upon applying temperature and voltage gradients based on quasiclassical theory which allows for arbitrary spin-dependent textures and fields to be conveniently incorporated.

  13. Spin Seebeck effect in an (In,Ga)As quantum well with equal Rashba and Dresselhaus spin-orbit couplings

    NASA Astrophysics Data System (ADS)

    Capps, Jeremy; Marinescu, D. C.; Manolescu, Andrei

    2016-02-01

    We demonstrate that a spin-dependent Seebeck effect can be detected in quantum wells with zinc-blend structure with equal Rashba-Dresselhaus spin-orbit couplings. This theory is based on the establishment of an itinerant antiferromagnetic state, a low total-energy configuration realized in the presence of the Coulomb interaction enabled by the k =0 degeneracy of the opposite-spin single-particle energy spectra. Transport in this state is modeled by using the solutions of a Boltzmann equation obtained within the relaxation time approximation. Numerical estimates performed for realistic GaAs samples indicate that at low temperatures, the amplitude of the spin Seebeck coefficient can be increased by scattering on magnetic impurities.

  14. Spin-dependent Seebeck effect in asymmetric four-terminal systems with Rashba spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Wang, Biao; Li, Mengjie; Nakayama, Tsuneyoshi; Li, Baowen

    2015-05-01

    We propose a new type of spin-dependent Seebeck effect (SDSE) emerging from the Rashba spin-orbit coupling in asymmetric four-terminal electron systems. This system generates spin currents or spin voltages along the longitudinal direction parallel to the temperature gradient in the absence of magnetic fields. The remarkable result arises from the breaking of the reflection symmetry along the transverse direction. In the meantime, the SDSE along the transverse direction, the so-called the spin Nernst effect, with spin currents or spin voltages perpendicular to the temperature gradient, can be simultaneously realized in our system. We further find that it is possible to use the temperature differences between four leads to tune the spin-dependent Seebeck coefficients.

  15. Spin Seebeck effect and thermoelectric phenomena in superconducting hybrids with magnetic textures or spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Bathen, Marianne Etzelmüller; Linder, Jacob

    2017-01-01

    We theoretically consider the spin Seebeck effect, the charge Seebeck coefficient, and the thermoelectric figure of merit in superconducting hybrid structures including either magnetic textures or intrinsic spin-orbit coupling. We demonstrate that large magnitudes for all these quantities are obtainable in Josephson-based systems with either zero or a small externally applied magnetic field. This provides an alternative to the thermoelectric effects generated in high-field (~1 T) superconducting hybrid systems, which were recently experimentally demonstrated. The systems studied contain either conical ferromagnets, spin-active interfaces, or spin-orbit coupling. We present a framework for calculating the linear thermoelectric response for both spin and charge of a system upon applying temperature and voltage gradients based on quasiclassical theory which allows for arbitrary spin-dependent textures and fields to be conveniently incorporated.

  16. Spin Seebeck effect and thermoelectric phenomena in superconducting hybrids with magnetic textures or spin-orbit coupling

    PubMed Central

    Bathen, Marianne Etzelmüller; Linder, Jacob

    2017-01-01

    We theoretically consider the spin Seebeck effect, the charge Seebeck coefficient, and the thermoelectric figure of merit in superconducting hybrid structures including either magnetic textures or intrinsic spin-orbit coupling. We demonstrate that large magnitudes for all these quantities are obtainable in Josephson-based systems with either zero or a small externally applied magnetic field. This provides an alternative to the thermoelectric effects generated in high-field (~1 T) superconducting hybrid systems, which were recently experimentally demonstrated. The systems studied contain either conical ferromagnets, spin-active interfaces, or spin-orbit coupling. We present a framework for calculating the linear thermoelectric response for both spin and charge of a system upon applying temperature and voltage gradients based on quasiclassical theory which allows for arbitrary spin-dependent textures and fields to be conveniently incorporated. PMID:28139667

  17. Giant spin Seebeck effect in a non-magnetic material.

    PubMed

    Jaworski, C M; Myers, R C; Johnston-Halperin, E; Heremans, J P

    2012-07-11

    The spin Seebeck effect is observed when a thermal gradient applied to a spin-polarized material leads to a spatially varying transverse spin current in an adjacent non-spin-polarized material, where it gets converted into a measurable voltage. It has been previously observed with a magnitude of microvolts per kelvin in magnetically ordered materials, ferromagnetic metals, semiconductors and insulators. Here we describe a signal in a non-magnetic semiconductor (InSb) that has the hallmarks of being produced by the spin Seebeck effect, but is three orders of magnitude larger (millivolts per kelvin). We refer to the phenomenon that produces it as the giant spin Seebeck effect. Quantizing magnetic fields spin-polarize conduction electrons in semiconductors by means of Zeeman splitting, which spin-orbit coupling amplifies by a factor of ∼25 in InSb. We propose that the giant spin Seebeck effect is mediated by phonon-electron drag, which changes the electrons' momentum and directly modifies the spin-splitting energy through spin-orbit interactions. Owing to the simultaneously strong phonon-electron drag and spin-orbit coupling in InSb, the magnitude of the giant spin Seebeck voltage is comparable to the largest known classical thermopower values.

  18. Gigantic enhancement of spin Seebeck effect by phonon drag

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroto; Uchida, Ken-Ichi; Saitoh, Eiji; Ohe, Jun-Ichiro; Takahashi, Saburo; Maekawa, Sadamichi

    2011-03-01

    We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect [K. Uchida et al., Nature 455, 778 (2008); C. M. Jaworski et al., Nature Mater. 9, 898 (2010); K. Uchida et al., Nature Mater. 9, 894 (2010)] in a prototypical magnet La Y2 Fe 5 O12 at low temperatures. Our theoretical analysis sheds light on the important role of phonons; the spin Seebeck effect is enormously enhanced by nonequilibrium phonons that drag the low-lying spin excitations. We further argue that this scenario gives a clue to understand the observation of the spin Seebeck effect that is unaccompanied by a global spin current, and predict that the substrate condition affects the observed signal.

  19. Spin-Seebeck Effect in III-V Based Semiconductors

    NASA Astrophysics Data System (ADS)

    Jaworski, Christopher M.; Myers, Roberto C.; Heremans, Joseph P.

    2012-02-01

    The spin-Seebeck effect has now been observed in metals^1 (NiFe), semiconductors^2 (GaMnAs), and insulators^3 (YIG). It consists of a thermally generated spin distribution that is phonon driven. Here we extend our measurements of the spin-Seebeck effect to other group III-V based magnetic semiconductors and present measurements of conventional thermomagnetic and galvanomagnetic properties as well as the spin-Seebeck effect. Work supported by the National Science Foundation, NSF-CBET-1133589 1. K. Uchida, et al., Nature 455 778 (2008) 2. C.M. Jaworski et al., Nature Materials 8 898 (2010), Phys. Rev. Lett. 106 186601 (2011) 3. K. Uchida, et al., Nature Materials 8 893 (2010)

  20. Spin Seebeck devices using local on-chip heating

    SciTech Connect

    Wu, Stephen M. Fradin, Frank Y.; Hoffman, Jason; Hoffmann, Axel; Bhattacharya, Anand

    2015-05-07

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

  1. Spin-seebeck effect: a phonon driven spin distribution.

    PubMed

    Jaworski, C M; Yang, J; Mack, S; Awschalom, D D; Myers, R C; Heremans, J P

    2011-05-06

    Here we report on measurements of the spin-Seebeck effect in GaMnAs over an extended temperature range alongside the thermal conductivity, specific heat, magnetization, and thermoelectric power. The amplitude of the spin-Seebeck effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and the phonon-drag contribution to the thermoelectric power of the GaMnAs, demonstrating that phonons drive the spin redistribution. A phenomenological model involving phonon-magnon drag explains the spatial and temperature dependence of the measured spin distribution.

  2. Strong spin Seebeck effect in Kondo T-shaped double quantum dots.

    PubMed

    Wójcik, K P; Weymann, I

    2017-02-08

    We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads' spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.

  3. Spin-dependent Seebeck effect and spin caloritronics in magnetic graphene

    NASA Astrophysics Data System (ADS)

    Rameshti, Babak Zare; Moghaddam, Ali G.

    2015-04-01

    We investigate the spin-dependent thermoelectric effects in magnetic graphene in both diffusive and ballistic regimes. Employing the Boltzmann and Landauer formalisms we calculate the spin and charge Seebeck coefficients (thermopower) in magnetic graphene varying the spin splitting, temperature, and doping of the junction. It is found that while in normal graphene the temperature gradient drives a charge current, in the case of magnetic graphene a significant spin current is also established. In particular we show that in the undoped magnetic graphene in which different spin carriers belong to conduction and valence bands, a pure spin current is driven by the temperature gradient. In addition it is revealed that profound thermoelectric effects can be achieved at intermediate easily accessible temperatures when the thermal energy is comparable with Fermi energy kBT ≲μ . By further investigation of the spin-dependent Seebeck effect and a significantly large figure of merit for spin thermopower ZspT , we suggest magnetic graphene as a promising material for spin-caloritronics studies and applications.

  4. Strong spin Seebeck effect in Kondo T-shaped double quantum dots

    NASA Astrophysics Data System (ADS)

    Wójcik, K. P.; Weymann, I.

    2017-02-01

    We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads’ spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.

  5. A computer-controlled apparatus for Seebeck inhomogeneity testing of sheathed thermocouples

    NASA Technical Reports Server (NTRS)

    Burkett, Cecil G., Jr.; Bauserman, Willard A., Jr.

    1993-01-01

    Mineral-insulated metal-sheathed (MIMS) thermocouple assemblies are used throughout industry and research facilities as a method of temperature measurement where requirements for either harsh environmental conditions exist, or where rigidity of the measurement probe is required. Seebeck inhomogeneity is the abnormal variation of the Seebeck coefficient from point to point in a material. It is not disclosed in conventional calibration. A standardized method of measuring thermoelectric inhomogeneity along the thermocouple probe length is not available. Therefore, calibration for sheathed probes normally does not include testing of probe inhomogeneity. The measurement accuracy would be severely impacted if significant inhomogeneity and a temperature gradient were present in the same region of the probe. A computer-controlled system for determining inhomogeneities was designed, fabricated, and tested. This system provides an accurate method for the identification of the location of inhomogeneity along the length of a sheathed thermocouple and for the quantification of the inhomogeneity. This paper will discuss the apparatus and procedure used to perform these tests and will present data showing tests performed on sheathed thermocouple probes.

  6. Determination of the amount of Peroxy in granite rock using the Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Tregloan-Reed, J. J.; Tarnas, J.; Plante, Z.; Freund, F. T.

    2015-12-01

    We present a series of laboratory experiments which provide evidence for peroxy defects in granite, coupled with a determination of the peroxy defect concentration. When peroxy defects are activated they become defect electrons (positive holes) in the oxygen anion sub-lattice. This in essence converts the granite sample to a p-type semiconductor. Our preliminary results of the thermoelectric (Seebeck) effect for granite show that positive charge carriers are being generated (positive gradient: see Figure) in the granite sample and that the concentration of peroxy defects in the granite sample is 1137 ± 20 ppm. The Seebeck coefficient (α) is the gradient between the voltage (V) and the temperature (T), such that α = V /T . One end of the granite sample was placed in a furnace and heated. At 300ºC the peroxy defect spins decouple, while at 430ºC the peroxy defects dissociate, producing positive holes. When the positive holes are activated their mobility increases and they move towards the cool end of the granite sample through diffusion. This induces a potential difference linked to a thermal gradient between the two ends of the sample. We then fitted the coefficients of two first order polynomials and a point of inflection using a Markov Chain Monte Carlo algorithm. This was done to statistically estimate the uncertainties in the coefficients from a Bayesian statistical analysis. The best fit and corresponding standarderror of the reflection point was found to be 426 ± 5ºC. This is in excellent agreement to values, around 430ºC, found in the literature. We then find α = 18.50 ± 0.18 μV K-1 above 426 ± 5ºC, which equates to a carrier concentration of 1.16 × 1020 cm-3 compared to the carrier concentrations of heavily doped semiconductors, which are on the order of 1021 cm-3. This then gives a peroxy defect concentration of 1137 ± 20 ppm.

  7. Absolutely classical spin states

    NASA Astrophysics Data System (ADS)

    Bohnet-Waldraff, F.; Giraud, O.; Braun, D.

    2017-01-01

    We introduce the concept of "absolutely classical" spin states, in analogy to absolutely separable states of bipartite quantum systems. Absolutely classical states are states that remain classical (i.e., a convex sum of projectors on coherent states of a spin j ) under any unitary transformation applied to them. We investigate the maximal size of the ball of absolutely classical states centered on the maximally mixed state and derive a lower bound for its radius as a function of the total spin quantum number. We also obtain a numerical estimate of this maximal radius and compare it to the case of absolutely separable states.

  8. Longitudinal spin Seebeck effect: from fundamentals to applications.

    PubMed

    Uchida, K; Ishida, M; Kikkawa, T; Kirihara, A; Murakami, T; Saitoh, E

    2014-08-27

    The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This 'longitudinal spin Seebeck effect' (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations.

  9. Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons.

    PubMed

    Yang, Xi-Feng; Zhou, Wen-Qian; Hong, Xue-Kun; Liu, Yu-Shen; Wang, Xue-Feng; Feng, Jin-Fu

    2015-01-14

    Ab initio calculations combining density-functional theory and nonequilibrium Green's function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.

  10. Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons

    SciTech Connect

    Yang, Xi-Feng; Zhou, Wen-Qian; Hong, Xue-Kun; Liu, Yu-Shen Feng, Jin-Fu; Wang, Xue-Feng

    2015-01-14

    Ab initio calculations combining density-functional theory and nonequilibrium Green’s function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.

  11. Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Yang, Xi-Feng; Zhou, Wen-Qian; Hong, Xue-Kun; Liu, Yu-Shen; Wang, Xue-Feng; Feng, Jin-Fu

    2015-01-01

    Ab initio calculations combining density-functional theory and nonequilibrium Green's function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.

  12. Multifold Seebeck increase in RuO{sub 2} films by quantum-guided lanthanide dilute alloying

    SciTech Connect

    Music, Denis Basse, Felix H.-U.; Schneider, Jochen M.; Han, Liang; Borca-Tasciuc, Theo; Devender; Gengler, Jamie J.; Voevodin, Andrey A.; Ramanath, Ganpati

    2014-02-03

    Ab initio predictions indicating that alloying RuO{sub 2} with La, Eu, or Lu can increase the Seebeck coefficient α manifold due to quantum confinement effects are validated in sputter-deposited La-alloyed RuO{sub 2} films showing fourfold α increase. Combinatorial screening reveals that α enhancement correlates with La-induced lattice distortion, which also decreases the thermal conductivity twentyfold, conducive for high thermoelectric figures of merit. These insights should facilitate the rational design of high efficiency oxide-based thermoelectrics through quantum-guided alloying.

  13. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  14. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  15. Optimum design of a nanoscale spin-Seebeck power device.

    PubMed

    Liao, Tianjun; Lin, Jian; Su, Guozhen; Lin, Bihong; Chen, Jincan

    2015-05-07

    A theoretical model of a nanoscale spin-Seebeck power device (SSPD) is proposed based on the longitudinal spin-Seebeck effect in bilayers made of a ferromagnetic insulator and a normal metal. Expressions for the power output and thermal efficiency of the SSPD are derived analytically. The performance characteristics of the nanoscale SSPD are analyzed using numerical simulation. The maximum power output density and efficiency are calculated numerically. The effect of the spin Hall angle on the performance characteristics of the SSPD is analyzed. The choice of materials and the structure of the device are discussed. The optimum criteria of some key parameters of the SSPD, such as the power output density, efficiency, thickness of the normal metal, and the load resistance, are given. The results obtained here could provide a theoretical basis for the optimal design and operation of nanoscale SSPDs.

  16. Magnetic field control of the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Ritzmann, Ulrike; Hinzke, Denise; Kehlberger, Andreas; Guo, Er-Jia; Kläui, Mathias; Nowak, Ulrich

    2015-11-01

    The origin of the suppression of the longitudinal spin Seebeck effect by applied magnetic fields is studied. We perform numerical simulations of the stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin model and calculate the magnon accumulation in linear temperature gradients for different strengths of applied magnetic fields and different length scales of the temperature gradient. We observe a decrease of the magnon accumulation with increasing magnetic field and we reveal that the origin of this effect is a field dependent change of the frequency distribution of the propagating magnons. With increasing field the magnonic spin currents are reduced due to a suppression of parts of the frequency spectrum. By comparison with measurements of the magnetic field dependent longitudinal spin Seebeck effect in YIG thin films with various thicknesses, we find qualitative agreement between our model and the experimental data, demonstrating the importance of this effect for experimental systems.

  17. Intrinsic spin Seebeck effect in Au/YIG.

    PubMed

    Qu, D; Huang, S Y; Hu, Jun; Wu, Ruqian; Chien, C L

    2013-02-08

    The acute magnetic proximity effects in Pt/YIG compromise the suitability of Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall effect and a negligible magnetoresistance, allows the measurements of the intrinsic spin Seebeck effect with a magnitude much smaller than that in Pt/YIG. The experiment results are consistent with the spin polarized density functional calculations for Pt with a sizable and Au with a negligible magnetic moment near the interface with YIG.

  18. Influence of interface condition on spin-Seebeck effects

    NASA Astrophysics Data System (ADS)

    Qiu, Z.; Hou, D.; Uchida, K.; Saitoh, E.

    2015-04-01

    The longitudinal spin-Seebeck effect (LSSE) has been investigated for Pt/yttrium iron garnet (YIG) bilayer systems. The magnitude of the voltage induced by the LSSE is found to be sensitive to the Pt/YIG interface condition. We observed a large LSSE voltage in a Pt/YIG system with a better crystalline interface, while the voltage decays steeply when an amorphous layer is introduced at the interface artificially.

  19. Seebeck Effects in N-Type and P-Type Polymers Driven Simultaneously by Surface Polarization and Entropy Differences Based on Conductor/Polymer/Conductor Thin-Film Devices

    SciTech Connect

    Hu, Dehua; Liu, Qing; Tisdale, Jeremy; Lei, Ting; Pei, Jian; Wang, Hsin; Urbas, Augustine; Hu, Bin

    2015-04-15

    This paper reports Seebeck effects driven by both surface polarization difference and entropy difference by using intramolecular charge-transfer states in n-type and p-type conjugated polymers, namely IIDT and IIDDT, based on vertical conductor/polymer/conductor thin-film devices. Large Seebeck coefficients of -898 V/K and 1300 V/K from are observed from n-type IIDT p-type IIDDT, respectively, when the charge-transfer states are generated by a white light illumination of 100 mW/cm2. Simultaneously, electrical conductivities are increased from almost insulating states in dark condition to conducting states under photoexcitation in both n-type IIDT and p-type IIDDT devices. We find that the intramolecular charge-transfer states can largely enhance Seebeck effects in the n-type IIDT and p-type IIDDT devices driven by both surface polarization difference and entropy difference. Furthermore, the Seebeck effects can be shifted between polarization and entropy regimes when electrical conductivities are changed. This reveals a new concept to develop Seebeck effects by controlling polarization and entropy regimes based on charge-transfer states in vertical conductor/polymer/conductor thin-film devices.

  20. Seebeck Effects in N-Type and P-Type Polymers Driven Simultaneously by Surface Polarization and Entropy Differences Based on Conductor/Polymer/Conductor Thin-Film Devices

    DOE PAGES

    Hu, Dehua; Liu, Qing; Tisdale, Jeremy; ...

    2015-04-15

    This paper reports Seebeck effects driven by both surface polarization difference and entropy difference by using intramolecular charge-transfer states in n-type and p-type conjugated polymers, namely IIDT and IIDDT, based on vertical conductor/polymer/conductor thin-film devices. Large Seebeck coefficients of -898 V/K and 1300 V/K from are observed from n-type IIDT p-type IIDDT, respectively, when the charge-transfer states are generated by a white light illumination of 100 mW/cm2. Simultaneously, electrical conductivities are increased from almost insulating states in dark condition to conducting states under photoexcitation in both n-type IIDT and p-type IIDDT devices. We find that the intramolecular charge-transfer states canmore » largely enhance Seebeck effects in the n-type IIDT and p-type IIDDT devices driven by both surface polarization difference and entropy difference. Furthermore, the Seebeck effects can be shifted between polarization and entropy regimes when electrical conductivities are changed. This reveals a new concept to develop Seebeck effects by controlling polarization and entropy regimes based on charge-transfer states in vertical conductor/polymer/conductor thin-film devices.« less

  1. Hall and Seebeck measurements estimate the thickness of a (buried) carrier system: Identifying interface electrons in In-doped SnO{sub 2} films

    SciTech Connect

    Papadogianni, Alexandra; Bierwagen, Oliver; White, Mark E.; Speck, James S.; Galazka, Zbigniew

    2015-12-21

    We propose a simple method based on the combination of Hall and Seebeck measurements to estimate the thickness of a carrier system within a semiconductor film. As an example, this method can distinguish “bulk” carriers, with homogeneous depth distribution, from “sheet” carriers, that are accumulated within a thin layer. The thickness of the carrier system is calculated as the ratio of the integral sheet carrier concentration, extracted from Hall measurements, to the volume carrier concentration, derived from the measured Seebeck coefficient of the same sample. For rutile SnO{sub 2}, the necessary relation of Seebeck coefficient to volume electron concentration in the range of 3 × 10{sup 17} to 3 × 10{sup 20 }cm{sup −3} has been experimentally obtained from a set of single crystalline thin films doped with varying Sb-doping concentrations and unintentionally doped bulk samples, and is given as a “calibration curve.” Using this calibration curve, our method demonstrates the presence of interface electrons in homogeneously deep-acceptor (In) doped SnO{sub 2} films on sapphire substrates.

  2. Apparatus and method for measuring the Seebeck coefficient and resistivity of materials

    NASA Technical Reports Server (NTRS)

    Hadek, V. (Inventor)

    1973-01-01

    An apparatus for measuring the thermoelectric properties of materials under high pressure is described that includes a pair of force transmitting assemblies constructed of thermally and electrically conductive material positioned between the ram and anvil of a press. Each force transmitting assembly has a small diameter pressing portion for contacting a face of the sample so that the sample can be squeezed between them. Each assembly also includes a heat exchanger to maintain the sample face at a controlled temperature, and an electrical conductor to carry current generated by the sample. A sleeve of thermally and electrically insulative material closely surrounds the pressing portions of the two assemblies.

  3. Geometric Shape Induced Small Change of Seebeck Coefficient in Bulky Metallic Wires.

    PubMed

    Li, Gang; Su, Xiaohui; Yang, Fan; Huo, Xiaoye; Zhang, Gengmin; Xu, Shengyong

    2017-02-10

    In this paper, we report the results of slight changes in the thermopower of long W, Mo, Zn, Cu, brass, and Ti wires, that resulted from changes in the wire's diameter or cross-sectional area. The samples used in the tests had a round shape with a diameter that ranged from tens of micron to 2 mm, which was much larger than the corresponding mean free paths of these materials. Nevertheless, a small change in thermopower, at the order of 1-10 nV/K, was repeatedly observed when the wire diameter was changed, or when the cross-sectional area of the wire was altered by mechanical methods, such as grinding or splitting. The results are consistent with previous observations showing that the thermopower in metallic thin film stripes changes with their width, from 100 μm to as little as 70 nm, implying a universal, geometric-boundary-related size effect of thermopower in metal materials, that occurs at the nanometer scale and continuously decreases all the way to the millimeter scale. This effect could be applied in the manufacturing of high-temperature sensors with simple structures.

  4. Geometric Shape Induced Small Change of Seebeck Coefficient in Bulky Metallic Wires

    PubMed Central

    Li, Gang; Su, Xiaohui; Yang, Fan; Huo, Xiaoye; Zhang, Gengmin; Xu, Shengyong

    2017-01-01

    In this paper, we report the results of slight changes in the thermopower of long W, Mo, Zn, Cu, brass, and Ti wires, that resulted from changes in the wire’s diameter or cross-sectional area. The samples used in the tests had a round shape with a diameter that ranged from tens of micron to 2 mm, which was much larger than the corresponding mean free paths of these materials. Nevertheless, a small change in thermopower, at the order of 1–10 nV/K, was repeatedly observed when the wire diameter was changed, or when the cross-sectional area of the wire was altered by mechanical methods, such as grinding or splitting. The results are consistent with previous observations showing that the thermopower in metallic thin film stripes changes with their width, from 100 μm to as little as 70 nm, implying a universal, geometric-boundary-related size effect of thermopower in metal materials, that occurs at the nanometer scale and continuously decreases all the way to the millimeter scale. This effect could be applied in the manufacturing of high-temperature sensors with simple structures. PMID:28208585

  5. The central role of the Peltier coefficient in thermoelectric cooling

    NASA Astrophysics Data System (ADS)

    Garrido, J.; Casanovas, A.

    2014-03-01

    This paper discusses the special role that the Peltier effect plays in thermoelectric cooling. From a particular energy balance for a thermocouple, we can conclude that the Peltier component pumps out the energy of all other terms: Joule, Fourier, Seebeck, and thermoelectric cooling. We emphasize also that in this energy balance, there is a need to include a new contribution, named after Seebeck that usually is not considered in the literature. We discuss a new method to evaluate the Peltier coefficient using measurements of the two temperature gradients at the junction of a thermocouple. An arrangement has been built to explore this method. A precise value for the Peltier coefficient of a thermocouple has been obtained but which deviates from the Kelvin relation. A better design of the experimental device is needed.

  6. Absolute Value Boundedness, Operator Decomposition, and Stochastic Media and Equations

    NASA Technical Reports Server (NTRS)

    Adomian, G.; Miao, C. C.

    1973-01-01

    The research accomplished during this period is reported. Published abstracts and technical reports are listed. Articles presented include: boundedness of absolute values of generalized Fourier coefficients, propagation in stochastic media, and stationary conditions for stochastic differential equations.

  7. Absolute and relative blindsight.

    PubMed

    Balsdon, Tarryn; Azzopardi, Paul

    2015-03-01

    The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight.

  8. Theory of magnon-driven spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Xiao, Jiang; Bauer, Gerrit E. W.; Uchida, Ken-Chi; Saitoh, Eiji; Maekawa, Sadamichi

    2010-06-01

    The spin Seebeck effect is a spin-motive force generated by a temperature gradient in a ferromagnet that can be detected via normal metal contacts through the inverse spin Hall effect [K. Uchida , Nature (London) 455, 778 (2008)]. We explain this effect by spin pumping at the contact that is proportional to the spin-mixing conductance of the interface, the inverse of a temperature-dependent magnetic coherence volume, and the difference between the magnon temperature in the ferromagnet and the electron temperature in the normal metal [D. J. Sanders and D. Walton, Phys. Rev. B 15, 1489 (1977)].

  9. Enhanced thermoelectric performance and anomalous seebeck effects in topological insulators.

    PubMed

    Xu, Yong; Gan, Zhongxue; Zhang, Shou-Cheng

    2014-06-06

    Improving the thermoelectric figure of merit zT is one of the greatest challenges in material science. The recent discovery of topological insulators (TIs) offers new promise in this prospect. In this work, we demonstrate theoretically that zT is strongly size dependent in TIs, and the size parameter can be tuned to enhance zT to be significantly greater than 1. Furthermore, we show that the lifetime of the edge states in TIs is strongly energy dependent, leading to large and anomalous Seebeck effects with an opposite sign to the Hall effect. These striking properties make TIs a promising material for thermoelectric science and technology.

  10. Domain Wall Motion by the Magnonic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Hinzke, D.; Nowak, U.

    2011-07-01

    The recently discovered spin Seebeck effect refers to a spin current induced by a temperature gradient in a ferromagnetic material. It combines spin degrees of freedom with caloric properties, opening the door for the invention of new, spin caloritronic devices. Using spin model simulations as well as an innovative, multiscale micromagnetic framework we show that magnonic spin currents caused by temperature gradients lead to spin transfer torque effects, which can drag a domain wall in a ferromagnetic nanostructure towards the hotter part of the wire. This effect opens new perspectives for the control and manipulation of domain structures.

  11. Charging of heated colloidal particles using the electrolyte Seebeck effect.

    PubMed

    Majee, Arghya; Würger, Alois

    2012-03-16

    We propose a novel actuation mechanism for colloids, which is based on the Seebeck effect of the electrolyte solution: Laser heating of a nonionic particle accumulates in its vicinity a net charge Q, which is proportional to the excess temperature at the particle surface. The corresponding long-range thermoelectric field E is proportional to 1/r(2) provides a tool for controlled interactions with nearby beads or with additional molecular solutes. An external field E(ext) drags the thermocharged particle at a velocity that depends on its size and absorption properties; the latter point could be particularly relevant for separating carbon nanotubes according to their electronic band structure.

  12. Longitudinal spin Seebeck effect free from the proximity Nernst effect.

    PubMed

    Kikkawa, T; Uchida, K; Shiomi, Y; Qiu, Z; Hou, D; Tian, D; Nakayama, H; Jin, X-F; Saitoh, E

    2013-02-08

    This Letter provides evidence for intrinsic longitudinal spin Seebeck effects (LSSEs) that are free from the anomalous Nernst effect (ANE) caused by an extrinsic proximity effect. We report the observation of LSSEs in Au/Y(3)Fe(5)O(12) (YIG) and Pt/Cu/YIG systems, showing that the LSSE appears even when the mechanism of the proximity ANE is clearly removed. In the conventional Pt/YIG structure, furthermore, we separate the LSSE from the ANE by comparing the voltages in different magnetization and temperature-gradient configurations; the ANE contamination was found to be negligibly small even in the Pt/YIG structure.

  13. Domain wall motion by the magnonic spin Seebeck effect.

    PubMed

    Hinzke, D; Nowak, U

    2011-07-08

    The recently discovered spin Seebeck effect refers to a spin current induced by a temperature gradient in a ferromagnetic material. It combines spin degrees of freedom with caloric properties, opening the door for the invention of new, spin caloritronic devices. Using spin model simulations as well as an innovative, multiscale micromagnetic framework we show that magnonic spin currents caused by temperature gradients lead to spin transfer torque effects, which can drag a domain wall in a ferromagnetic nanostructure towards the hotter part of the wire. This effect opens new perspectives for the control and manipulation of domain structures.

  14. A Focker-Planck description of the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Reyes, Guillermo; Reyes, Juan Adrian

    Thermally driven spin-wave spin current in a ferromagnetic material FM and the resulting electric signal in a metal probe placed on the FM are theoretically investigated by considering a thermally fluctuating spin at the interface of a FM-metal junction. We develop an analytical formulation to establish a Focker Plank equation for the probability distribution as a function of magnetization components of the material, for calculating the spin Seebeck signal detected by the metal probe, which converts spin current to charge current by the inverse spin Hall effect. The spin current is induced in the metal probe via an exchange interaction when the metal senses the temperature gradient.

  15. Skyrmionic spin Seebeck effect via dissipative thermomagnonic torques

    NASA Astrophysics Data System (ADS)

    Kovalev, Alexey A.

    2014-06-01

    We derive thermomagnonic torque and its "β-type" dissipative correction from the stochastic Landau-Lifshitz-Gilbert equation. The β-type dissipative correction describes viscous coupling between magnetic dynamics and magnonic current and it stems from spin mistracking of the magnetic order. We show that thermomagnonic torque is important for describing temperature gradient induced motion of skyrmions in helical magnets while dissipative correction plays an essential role in generating transverse Magnus force. We propose to detect such skyrmionic motion by employing the transverse spin Seebeck effect geometry.

  16. Absolute neutrino mass scale

    NASA Astrophysics Data System (ADS)

    Capelli, Silvia; Di Bari, Pasquale

    2013-04-01

    Neutrino oscillation experiments firmly established non-vanishing neutrino masses, a result that can be regarded as a strong motivation to extend the Standard Model. In spite of being the lightest massive particles, neutrinos likely represent an important bridge to new physics at very high energies and offer new opportunities to address some of the current cosmological puzzles, such as the matter-antimatter asymmetry of the Universe and Dark Matter. In this context, the determination of the absolute neutrino mass scale is a key issue within modern High Energy Physics. The talks in this parallel session well describe the current exciting experimental activity aiming to determining the absolute neutrino mass scale and offer an overview of a few models beyond the Standard Model that have been proposed in order to explain the neutrino masses giving a prediction for the absolute neutrino mass scale and solving the cosmological puzzles.

  17. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  18. Spin-current Seebeck effect in an interacting quantum dot: Atomic approximation for the Anderson impurity model

    NASA Astrophysics Data System (ADS)

    Ramos, E.; Silva-Valencia, J.; Franco, R.; Siqueira, E. C.; Figueira, M. S.

    2015-11-01

    We study the spin-current Seebeck effect through an immersed gate defined quantum dot, employing the U-finite atomic method for the single impurity Anderson model. Our description qualitatively confirms some of the results obtained by an earlier Hartree-Fock work, but as our calculation includes the Kondo effect, some new features will appear in the spin-current Seebeck effect S, which as a function of the gate voltage present an oscillatory shape. At intermediate temperatures, our results show a three zero structure and at low temperatures, our results are governed by the emergence of the Kondo peak in the transmittance, which defines the behavior of the shape of the S coefficient as a function of the parameters of the model. The oscillatory behavior obtained by the Hartree-Fock approximation reproduces the shape obtained by us in a non-interacting system (U=0). The S sign is sensitive to different polarization of the quantum dot, and as a consequence the device could be employed to experimentally detect the polarization states of the system. Our results also confirm that the large increase of S upon increasing U, obtained by the mean field approximation, is correct only for low temperatures. We also discuss the role of the Kondo peak in defining the behavior of the spin thermopower at low temperatures.

  19. Extreme Seebeck anisotropy in the quasi-one-dimensional metal, Li0.9Mo6O17

    NASA Astrophysics Data System (ADS)

    Cohn, Joshua; Moshfeghyeganeh, Saeed; Dos Santos, Carlos A. M.; Neumeier, John J.

    2014-03-01

    We present resistivity and thermopower measurements in the range 300 K <= T <= 500 K on single crystals of the quasi-one-dimensional (q1D) metal, Li0.9Mo6O17 (LiPB) transverse to the q1D metallic chains. Direct electron transfer between the chains of this material is sufficiently weak that inter-chain transport above 400 K is predominated by thermal activation of valence-band states (~ 0 . 14 eV below EF), yielding a large, p-type inter-chain Seebeck coefficient that coexists with n-type metallic behavior confined along the q1D chains. A significant Seebeck anisotropy, ΔS ~= 200 μ V/K, along mutually perpendicular directions gives LiPB potential as a transverse thermoelectric. This anisotropy along with a relatively low inter-chain thermal conductivity (κ ~= 2 W/mK) results in a substantial transverse Peltier effect. Work supported by the U.S. Department of Energy Office of Basic Energy Sciences (DE-FG02-12ER46888, Univ. Miami), the National Science Foundation (DMR-0907036, Mont. St. Univ.), and in Lorena by the CNPq (301334/2007-2) and FAPESP (2009/14524-6).

  20. Spin Seebeck effect through antiferromagnetic NiO

    NASA Astrophysics Data System (ADS)

    Prakash, Arati; Brangham, Jack; Yang, Fengyuan; Heremans, Joseph P.

    2016-07-01

    We report temperature-dependent spin Seebeck measurements on Pt/YIG bilayers and Pt/NiO/YIG trilayers, where YIG (yttrium iron garnet, Y3F e5O12 ) is an insulating ferrimagnet and NiO is an antiferromagnet at low temperatures. The thickness of the NiO layer is varied from 0 to 10 nm. In the Pt/YIG bilayers, the temperature gradient applied to the YIG stimulates dynamic spin injection into the Pt, which generates an inverse spin Hall voltage in the Pt. The presence of a NiO layer dampens the spin injection exponentially with a decay length of 2 ± 0.6 nm at 180 K. The decay length increases with temperature and shows a maximum of 5.5 ± 0.8 nm at 360 K. The temperature dependence of the amplitude of the spin Seebeck signal without NiO shows a broad maximum of 6.5 ± 0.5 μV/K at 20 K. In the presence of NiO, the maximum shifts sharply to higher temperatures, likely correlated to the increase in decay length. This implies that NiO is most transparent to magnon propagation near the paramagnet-antiferromagnet transition. We do not see the enhancement in spin current driven into Pt reported in other papers when 1-2 nm NiO layers are sandwiched between Pt and YIG.

  1. Spin Seebeck effect in YIG-based systems

    NASA Astrophysics Data System (ADS)

    Siegel, Gene; Prestgard, Megan; Teng, Shiang; Tiwari, Ashutosh

    2015-03-01

    Recently, the use of magnetic insulators (yttrium iron garnet, YIG) in conjunction with platinum has sparked interest in spintronics research. This is due to the existence of the spin Seebeck effect which could potentially be a source of pure spin current for spintronic devices. Furthermore, these coatings could potentially show the versatility of spintronics by acting as a spin-based thermoelectric generator, thereby providing a new method of transforming heat into power. However, there remain questions regarding the origins and legitimacy of the spin Seebeck effect. Moreover, recent publications claim that the observed effects are a manifestation of magnetic proximity effects in platinum and not a true SSE signal. Because of these concerns, we are providing supporting evidence that the voltages observed in the YIG/Pt films are truly SSE voltages. We are reaffirming claims that magnon transport theory provides an accurate basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed laser deposition, as these YIG films possess a large SSE voltage compared to those films grown using liquid phase deposition techniques.

  2. Design of spin-Seebeck diode with spin semiconductors

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  3. Design of spin-Seebeck diode with spin semiconductors.

    PubMed

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

    2016-12-16

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

  4. Thermoelectric Seebeck effect in oxide-based resistive switching memory.

    PubMed

    Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming

    2014-08-20

    Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor-metal transition around 150 K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour.

  5. Origin of the spin Seebeck effect in compensated ferrimagnets.

    PubMed

    Geprägs, Stephan; Kehlberger, Andreas; Della Coletta, Francesco; Qiu, Zhiyong; Guo, Er-Jia; Schulz, Tomek; Mix, Christian; Meyer, Sibylle; Kamra, Akashdeep; Althammer, Matthias; Huebl, Hans; Jakob, Gerhard; Ohnuma, Yuichi; Adachi, Hiroto; Barker, Joseph; Maekawa, Sadamichi; Bauer, Gerrit E W; Saitoh, Eiji; Gross, Rudolf; Goennenwein, Sebastian T B; Kläui, Mathias

    2016-02-04

    Magnons are the elementary excitations of a magnetically ordered system. In ferromagnets, only a single band of low-energy magnons needs to be considered, but in ferrimagnets the situation is more complex owing to different magnetic sublattices involved. In this case, low lying optical modes exist that can affect the dynamical response. Here we show that the spin Seebeck effect (SSE) is sensitive to the complexities of the magnon spectrum. The SSE is caused by thermally excited spin dynamics that are converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the SSE in the ferrimagnet gadolinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that higher-energy exchange magnons play a key role in the SSE.

  6. Critical suppression of spin Seebeck effect by magnetic fields

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takashi; Uchida, Ken-ichi; Daimon, Shunsuke; Qiu, Zhiyong; Shiomi, Yuki; Saitoh, Eiji

    2015-08-01

    The longitudinal spin Seebeck effect (LSSE) in Pt /Y3Fe5O12(YIG ) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low temperatures. The field-induced suppression of the LSSE in the Pt/YIG-slab system is too large at around room temperature to be explained simply by considering the effect of the Zeeman gap in magnon excitation. This result requires us to introduce a magnon-frequency-dependent mechanism into the scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The magnetic field dependence of the LSSE voltage was observed to change by changing the thickness of YIG, suggesting that the thermospin conversion by the low-frequency magnons is suppressed in thin YIG films due to the long characteristic lengths of such magnons.

  7. Thermoelectric Seebeck effect in oxide-based resistive switching memory

    PubMed Central

    Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming

    2014-01-01

    Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor–metal transition around 150 K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour. PMID:25141267

  8. Origin of the spin Seebeck effect in compensated ferrimagnets

    NASA Astrophysics Data System (ADS)

    Geprägs, Stephan; Kehlberger, Andreas; Coletta, Francesco Della; Qiu, Zhiyong; Guo, Er-Jia; Schulz, Tomek; Mix, Christian; Meyer, Sibylle; Kamra, Akashdeep; Althammer, Matthias; Huebl, Hans; Jakob, Gerhard; Ohnuma, Yuichi; Adachi, Hiroto; Barker, Joseph; Maekawa, Sadamichi; Bauer, Gerrit E. W.; Saitoh, Eiji; Gross, Rudolf; Goennenwein, Sebastian T. B.; Kläui, Mathias

    2016-02-01

    Magnons are the elementary excitations of a magnetically ordered system. In ferromagnets, only a single band of low-energy magnons needs to be considered, but in ferrimagnets the situation is more complex owing to different magnetic sublattices involved. In this case, low lying optical modes exist that can affect the dynamical response. Here we show that the spin Seebeck effect (SSE) is sensitive to the complexities of the magnon spectrum. The SSE is caused by thermally excited spin dynamics that are converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the SSE in the ferrimagnet gadolinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that higher-energy exchange magnons play a key role in the SSE.

  9. Origin of the spin Seebeck effect in compensated ferrimagnets

    PubMed Central

    Geprägs, Stephan; Kehlberger, Andreas; Coletta, Francesco Della; Qiu, Zhiyong; Guo, Er-Jia; Schulz, Tomek; Mix, Christian; Meyer, Sibylle; Kamra, Akashdeep; Althammer, Matthias; Huebl, Hans; Jakob, Gerhard; Ohnuma, Yuichi; Adachi, Hiroto; Barker, Joseph; Maekawa, Sadamichi; Bauer, Gerrit E. W.; Saitoh, Eiji; Gross, Rudolf; Goennenwein, Sebastian T. B.; Kläui, Mathias

    2016-01-01

    Magnons are the elementary excitations of a magnetically ordered system. In ferromagnets, only a single band of low-energy magnons needs to be considered, but in ferrimagnets the situation is more complex owing to different magnetic sublattices involved. In this case, low lying optical modes exist that can affect the dynamical response. Here we show that the spin Seebeck effect (SSE) is sensitive to the complexities of the magnon spectrum. The SSE is caused by thermally excited spin dynamics that are converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the SSE in the ferrimagnet gadolinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that higher-energy exchange magnons play a key role in the SSE. PMID:26842873

  10. Nonlinear thermokinetic phenomena due to the Seebeck effect.

    PubMed

    Sugioka, Hideyuki

    2014-07-22

    We propose a novel mechanism to produce nonlinear thermokinetic vortex flows around a circular cylinder with ideally high thermal conductivity in an electrolyte. That is, the nonlinear thermokinetic slip velocity, which is proportional to the square of the temperature gradient [∇(T)0(2)], is derived based on the electrolyte Seebeck effect, heat conduction equation, and Helmholtz–Smoluchowski formula. Different from conventional linear thermokinetic theory, our theory predicts that the inversion of the temperature gradient does not change the direction of the thermokinetic flows and thus a Janus particle using this phenomenon can move to the both hotter and colder regions in a temperature gradient field by changing the direction of its dielectric end. Our findings bridge the gap between the electro- and thermo-kinetic phenomena and provide an integrated physical viewpoint for the interface science.

  11. Spectral characteristics of time resolved magnonic spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Etesami, S. R.; Chotorlishvili, L.; Berakdar, J.

    2015-09-01

    Spin Seebeck effect (SSE) holds promise for new spintronic devices with low-energy consumption. The underlying physics, essential for a further progress, is yet to be fully clarified. This study of the time resolved longitudinal SSE in the magnetic insulator yttrium iron garnet concludes that a substantial contribution to the spin current stems from small wave-vector subthermal exchange magnons. Our finding is in line with the recent experiment by S. R. Boona and J. P. Heremans [Phys. Rev. B 90, 064421 (2014)]. Technically, the spin-current dynamics is treated based on the Landau-Lifshitz-Gilbert equation also including magnons back-action on thermal bath, while the formation of the time dependent thermal gradient is described self-consistently via the heat equation coupled to the magnetization dynamics.

  12. Microscopic origin of subthermal magnons and the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Diniz, I.; Costa, A. T.

    2016-05-01

    Recent experimental evidence points to low-energy magnons as the primary contributors to the spin Seebeck effect. This spectral dependence is puzzling since it is not observed on other thermocurrents in the same material. Here, we argue that the physical origin of this behavior is the magnon-magnon scattering mediated by phonons, in a process which conserves the number of magnons. To assess the importance and features of this kind of scattering, we derive the effective magnon-phonon interaction from a microscopic model, including band energy, a screened electron-electron interaction and the electron-phonon interaction. Unlike higher order magnon-only scattering, we find that the coupling with phonons induce a scattering which is very small for low-energy (or subthermal) magnons but increases sharply above a certain energy—rendering magnons above this energy poor spin-current transporters.

  13. Spectral characteristics of time resolved magnonic spin Seebeck effect

    SciTech Connect

    Etesami, S. R.; Chotorlishvili, L.; Berakdar, J.

    2015-09-28

    Spin Seebeck effect (SSE) holds promise for new spintronic devices with low-energy consumption. The underlying physics, essential for a further progress, is yet to be fully clarified. This study of the time resolved longitudinal SSE in the magnetic insulator yttrium iron garnet concludes that a substantial contribution to the spin current stems from small wave-vector subthermal exchange magnons. Our finding is in line with the recent experiment by S. R. Boona and J. P. Heremans [Phys. Rev. B 90, 064421 (2014)]. Technically, the spin-current dynamics is treated based on the Landau-Lifshitz-Gilbert equation also including magnons back-action on thermal bath, while the formation of the time dependent thermal gradient is described self-consistently via the heat equation coupled to the magnetization dynamics.

  14. Mechanism of the two sign changes in the spin Seebeck effect of a compensated ferrimagnet

    NASA Astrophysics Data System (ADS)

    Ohnuma, Yuichi; Adachi, Hiroto; Saitoh, Eiji; Maekawa, Sadamichi

    Spin Seebeck effect is the mechanism of thermal spin injection from a precessing ferromagnet into an attached paramagnetic metal [Uchida et al., Nature 455, 778 (2008)]. We have theoretically investigated the spin Seebeck effect in compensated ferrimagnets [Ohnuma et al., Phys. Rev. B 87, 014423 (2013)] and predicted that the sign of the spin Seebeck signal changes at the compensation temperature, which is recently confirmed by an experiment [Geprägs et al., arXiv:1405.4971 (2014)]. Interestingly, the experiment found another sign change at a lower temperature. Here we explain its origin by taking account of sublattice dependence of the exchange coupling at the ferrimagnet/paramagnet interface.

  15. Seebeck and thermal conductivity analysis in amorphous/crystalline {beta}-K{<_2}Bi{<_8}Se{<_13} nanocomposite materials.

    SciTech Connect

    Kyratsi, Th.; Hatzikraniotis, E.; Ioannou, M.; Chung, D. Y.; Tsiaoussis, I.

    2011-01-01

    In this work, ball milling is applied on {beta}-K{sub 2}Bi{sub 8}Se{sub 13} compounds in order to explore the potential of the process for the fabrication of nano-based material. Polycrystalline {beta}-K{sub 2}Bi{sub 8}Se{sub 13}, synthesized from melt, was ball milled under inert atmosphere. Powder x-ray diffraction showed a significantly increased disorder with ball milling time. TEM studies confirmed the presence of nanocrystalline material in an amorphous matrix, suggesting the development of crystalline/amorphous {beta}-K{sub 2}Bi{sub 8}Se{sub 13} nanocomposite material via ball milling process. Seebeck coefficient and thermal conductivity were analyzed based on the effective medium theory and show a significant contribution of a nanocrystalline phase.

  16. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  17. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  18. Absolute-structure reports.

    PubMed

    Flack, Howard D

    2013-08-01

    All the 139 noncentrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. Defining A and D as the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2AD and selected-D plots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstat is shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.

  19. Magneto-Seebeck effect in spin-valve with in-plane thermal gradient

    SciTech Connect

    Jain, S. Bose, A. Palkar, V. R. Tulapurkar, A. A.; Lam, D. D. Suzuki, Y.; Sharma, H. Tomy, C. V.

    2014-12-15

    We present measurements of magneto-Seebeck effect on a spin valve with in-plane thermal gradient. We measured open circuit voltage and short circuit current by applying a temperature gradient across a spin valve stack, where one of the ferromagnetic layers is pinned. We found a clear hysteresis in these two quantities as a function of magnetic field. From these measurements, the magneto-Seebeck effect was found to be same as magneto-resistance effect.

  20. 125Te NMR and Seebeck Effect in Bi2Te3 Synthesized from Stoichiometric and Te-Rich Melts

    SciTech Connect

    Levin, E. M.; Riedemann, T. M.; Howard, A.; Jo, N. H.; Bud’ko, S. L.; Canfield, P. C.; Lograsso, T. A.

    2016-10-14

    Bi2Te3 is a well-known thermoelectric material and, as a new form of quantum matter, a topological insulator. Variation of local chemical composition in Bi2Te3 results in formation of several types of atomic defects, including Bi and Te vacancies and Bi and Te antisite defects; these defects can strongly affect material functionality via generation of free electrons and/or holes. Nonuniform distribution of atomic defects produces electronic inhomogeneity, which can be detected by 125Te nuclear magnetic resonance (NMR). Here we report on 125Te NMR and Seebeck effect (heat to electrical energy conversion) for two single crystalline samples: (#1) grown from stoichiometric composition by Bridgman technique and (#2) grown out of Te-rich, high temperature flux. The Seebeck coefficients of these samples show p- and n-type conductivity, respectively, arising from different atomic defects. 125Te NMR spectra and spin–lattice relaxation measurements demonstrate that both Bi2Te3 samples are electronically inhomogeneous at the atomic scale, which can be attributed to a different Te environment due to spatial variation of the Bi/Te ratio and formation of atomic defects. In conclusion, correlations between 125Te NMR spectra, spin–lattice relaxation times, the Seebeck coefficients, carrier concentrations, and atomic defects are discussed. Our data demonstrate that 125Te NMR is an effective probe to study antisite defects in Bi2Te3.

  1. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  2. Absolute multilateration between spheres

    NASA Astrophysics Data System (ADS)

    Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin

    2017-04-01

    Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m‑1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.

  3. Seebeck effects in n-type and p-type polymers driven simultaneously by surface polarization and entropy differences based on conductor/polymer/conductor thin-film devices.

    PubMed

    Hu, Dehua; Liu, Qing; Tisdale, Jeremy; Lei, Ting; Pei, Jian; Wang, Hsin; Urbas, Augustine; Hu, Bin

    2015-05-26

    This paper reports Seebeck effects driven by both surface polarization difference and entropy difference by using photoinduced intramolecular charge-transfer states in n-type and p-type conjugated polymers, namely IIDT and IIDDT, respectively, based on vertical conductor/polymer/conductor thin-film devices. We obtain large Seebeck coefficients of -898 μV/K from n-type IIDT and 1300 μV/K from p-type IIDDT when the charge-transfer states are generated by a white light illumination of 100 mW/cm(2), compared with the values of 380 and 470 μV/K in dark condition, respectively. Simultaneously, the electrical conductivities are increased from almost insulating state in dark condition to conducting state under photoexcitation in both n-type IIDT and p-type IIDDT based devices. The large Seebeck effects can be attributed to the following two mechanisms. First, the intramolecular charge-transfer states exhibit strong electron-phonon coupling, which leads to a polarization difference between high and low temperature surfaces. This polarization difference essentially forms a temperature-dependent electric field, functioning as a new driving force additional to entropy difference, to drive the energetic carriers for the development of Seebeck effects under a temperature difference. Second, the intramolecular charge-transfer states generate negative or positive majority carriers (electrons or holes) in the n-type IIDT or p-type IIDDT, ready to be driven between high and low temperature surfaces for developing Seebeck effects. On the basis of coexisted polarization difference and entropy difference, the intramolecular charge-transfer states can largely enhance the Seebeck effects in both n-type IIDT and p-type IIDDT devices. Furthermore, we find that changing electrical conductivity can switch the Seebeck effects between polarization and entropy regimes when the charge-transfer states are generated upon applying photoexcitation. Therefore, using intramolecular charge

  4. Spin Seebeck measurements of current-induced switching in YIG

    NASA Astrophysics Data System (ADS)

    Bartell, Jason; Jermain, Colin; Aradhya, Sriharsha; Wang, Hailong; Buhrman, Robert; Yang, Fengyuan; Ralph, Daniel; Fuchs, Gregory

    Quantifying spin torques generated at the interface between a normal metal (NM) and a ferromagnetic insulator (FI) is an important step in understanding the spin hall effect without charge transport. Measuring magnetization in NM/FI devices is challenging, however, because both magnetoresistive and magneto-optical signals are tiny in thin-film bilayers. We show that a promising alternative measurement approach is the use of picosecond thermal gradients to study spin torques in Pt/Yttrium Iron Garnet (YIG) bilayers. Recently, we demonstrated the application of heat to stroboscopically transduce a local magnetic moment into an electrical signal via the time resolved anomalous Nernst effect (TRANE) in ferromagnetic metals. Using a similar geometry the spin Seebeck effect of YIG combined with the inverse spin Hall effect of Pt enables measurement of local magnetization. Here we describe our study using this technique to study current-induced switching in Pt/YIG with sub-10 nm thick YIG films We acknowledge support from AFOSR.

  5. Thermoelectric coating based on the spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Kirihara, Akihiro; Uchida, Ken-Ichi; Kajiwara, Yosuke; Ishida, Masahiko; Nakamura, Yasunobu; Manako, Takashi; Kohmoto, Shigeru; Saitoh, Eiji; Yorozu, Shinichi

    2012-02-01

    Thermoelectric (TE) technologies have been drawing great interest, since they can directly generate electricity from thermal energy that is available in various places. However, their complicated module structure, which is based on a number of thermocouples, still makes it difficult to fabricate large-area TE devices at low cost. In this work, we show a novel concept based on the spin Seebeck effect (SSE) called TE coating, which is characterized by a simple film structure, convenient scaling capability, and easy fabrication. We fabricated a TE-coating film with a bismuth-substituted yttrium iron garnet (Bi:YIG) by a highly productive spin-coating-based process on a nonmagnetic substrate, and demonstrated the SSE-induced TE conversion. The TE-coating layer amounts to only 0.01 % of the total sample thickness, suggesting that such an ultrathin magnetic film can work as a useful thermal-energy collector. This new concept may enable us to implement low-cost and large-area TE functions on various objects, opening opportunities for innovative energy harvesting applications.

  6. Long-range spin Seebeck effect and acoustic spin pumping.

    PubMed

    Uchida, K; Adachi, H; An, T; Ota, T; Toda, M; Hillebrands, B; Maekawa, S; Saitoh, E

    2011-10-01

    Imagine that a metallic wire is attached to a part of a large insulator, which itself exhibits no magnetization. It seems impossible for electrons in the wire to register where the wire is positioned on the insulator. Here we found that, using a Ni₈₁Fe₁₉/Pt bilayer wire on an insulating sapphire plate, electrons in the wire recognize their position on the sapphire. Under a temperature gradient in the sapphire, surprisingly, the voltage generated in the Pt layer is shown to reflect the wire position, although the wire is isolated both electrically and magnetically. This non-local voltage is due to the coupling of spins and phonons: the only possible carrier of information in this system. We demonstrate this coupling by directly injecting sound waves, which realizes the acoustic spin pumping. Our finding provides a persuasive answer to the long-range nature of the spin Seebeck effect, and it opens the door to 'acoustic spintronics' in which sound waves are exploited for constructing spin-based devices.

  7. Theory of the spin Seebeck effect in antiferromagnets

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; Rodríguez-Suárez, R. L.; Azevedo, A.

    2016-01-01

    The spin Seebeck effect (SSE) consists in the generation of a spin current by a temperature gradient applied in a magnetic film. The SSE is usually detected by an electric voltage generated in a metallic layer in contact with the magnetic film resulting from the conversion of the spin current into charge current by means of the inverse spin Hall effect. The SSE has been widely studied in bilayers made of the insulating ferrimagnet yttrium iron garnet (YIG) and metals with large spin-orbit coupling such as platinum. Recently the SSE has been observed in bilayers made of the antiferromagnet Mn F2 and Pt, revealing dependences of the SSE voltage on temperature and field very different from the ones observed in YIG/Pt. Here we present a theory for the SSE in structures with an antiferromagnetic insulator (AFI) in contact with a normal metal (NM) that relies on the bulk magnon spin current created by the temperature gradient across the thickness of the AFI/NM bilayer. The theory explains quite well the measured dependences of the SSE voltage on the sample temperature and on the applied magnetic field in Mn F2/Pt .

  8. Temperature dependence of the Soret coefficient of ionic colloids

    NASA Astrophysics Data System (ADS)

    Sehnem, A. L.; Figueiredo Neto, A. M.; Aquino, R.; Campos, A. F. C.; Tourinho, F. A.; Depeyrot, J.

    2015-10-01

    The temperature dependence of the Soret coefficient ST(T ) in electrostatically charged magnetic colloids is investigated. Two different ferrofluids, with different particles' mean dimensions, are studied. In both cases we obtain a thermophilic behavior of the Soret effect. The temperature dependence of the Soret coefficient is described assuming that the nanoparticles migrate along the ionic thermoelectric field created by the thermal gradient. A model based on the contributions from the thermoelectrophoresis and variation of the double-layer energy, without fitting parameters, is used to describe the experimental results of the colloid with the bigger particles. To do so, independent measurements of the ζ potential, mass diffusion coefficient, and Seebeck coefficient are performed. The agreement of the theory and the experimental results is rather good. In the case of the ferrofluid with smaller particles, it is not possible to get experimentally reliable values of the ζ potential and the model described is used to evaluate this parameter and its temperature dependence.

  9. Estimating Absolute Site Effects

    SciTech Connect

    Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

    2004-07-15

    The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from

  10. Acupuncture needles and the Seebeck effect: do temperature gradients produce electrostimulation?

    PubMed

    Cohen, M; Kwok, G; Cosic, I

    1997-01-01

    Acupuncture may act through modifying bioelectric events and this may occur through different mechanisms including the application of external currents. According to the Seebeck effect which produces a potential difference when a temperature gradient is placed across a conductor, the physical properties of acupuncture needles may produce internal currents due to the temperature gradient across the needle when placed insitu. Such currents were detected when needles were differentially heated and these currents were found to be in the range capable of producing biological effects. The traditional design of acupuncture needles and traditional needle manipulations seem to maintain a temperature gradient across the needle and thus enhance the Seebeck effect.

  11. How to control spin-Seebeck current in a metal-quantum dot-magnetic insulator junction

    NASA Astrophysics Data System (ADS)

    Gu, Lei; Fu, Hua-Hua; Wu, Ruqian

    2016-09-01

    The control of the spin-Seebeck current is still a challenging task for the development of spin caloritronic devices. Here, we construct a spin-Seebeck device by inserting a quantum dot (QD) between the metal lead and magnetic insulator. Using the slave-particle approach and noncrossing approximation, we find that the spin-Seebeck effect increases significantly when the energy level of the QD locates near the Fermi level of the metal lead due to the enhancement of spin flipping and occurrences of quantum resonance. Since this can be easily realized by applying a gate voltage in experiments, the spin-Seebeck device proposed here can also work as a thermovoltaic transistor. Moreover, the optimal correlation strength and the energy level position of the QD are discussed to maximize the spin-Seebeck current as required for applications in controllable spin caloritronic devices.

  12. Thermoelectric performance of spin Seebeck effect in Fe3O4/Pt-based thin film heterostructures

    NASA Astrophysics Data System (ADS)

    Ramos, R.; Anadón, A.; Lucas, I.; Uchida, K.; Algarabel, P. A.; Morellón, L.; Aguirre, M. H.; Saitoh, E.; Ibarra, M. R.

    2016-10-01

    We report a systematic study on the thermoelectric performance of spin Seebeck devices based on Fe3O4/Pt junction systems. We explore two types of device geometries: a spin Hall thermopile and spin Seebeck multilayer structures. The spin Hall thermopile increases the sensitivity of the spin Seebeck effect, while the increase in the sample internal resistance has a detrimental effect on the output power. We found that the spin Seebeck multilayers can overcome this limitation since the multilayers exhibit the enhancement of the thermoelectric voltage and the reduction of the internal resistance simultaneously, therefore resulting in significant power enhancement. This result demonstrates that the multilayer structures are useful for improving the thermoelectric performance of the spin Seebeck effect.

  13. Thermoelectric properties of the unfilled skutterudite FeSb3 from first principles and Seebeck local probes

    DOE PAGES

    Lemal, Sébastien; Nguyen, Ngoc; de Boor, Johannes; ...

    2015-11-16

    In this paper, using a combination of first-principles calculations and experimental transport measurements, we study the electronic and magnetic structure of the unfilled skutterudite FeSb3. We employ the hybrid functional approach for exchange correlation. The ground state is determined to be antiferromagnetic with an atomic magnetic moment of 1.6μB/Fe. The Néel temperature TN is estimated at 6 K, in agreement with experiments which found a paramagnetic state down to 10 K. The ground state is semiconducting, with a small electronic gap of 33meV, also consistent with previous experiments on films. Charge carrier concentrations are estimated from Hall resistance measurements. Themore » Seebeck coefficient is measured and mapped using a scanning probe at room temperature that yields an average value of 38.6μVK-1, slightly lower than the theoretical result. Finally, the theoretical conductivity is analyzed as a function of temperature and concentration of charge carriers.« less

  14. Thermoelectric properties of the unfilled skutterudite FeSb3 from first principles and Seebeck local probes

    SciTech Connect

    Lemal, Sébastien; Nguyen, Ngoc; de Boor, Johannes; Ghosez, Philippe; Varignon, Julien; Klobes, Benedikt; Hermann, Raphaël P.; Verstraete, Matthieu J.

    2015-11-16

    In this paper, using a combination of first-principles calculations and experimental transport measurements, we study the electronic and magnetic structure of the unfilled skutterudite FeSb3. We employ the hybrid functional approach for exchange correlation. The ground state is determined to be antiferromagnetic with an atomic magnetic moment of 1.6μB/Fe. The Néel temperature TN is estimated at 6 K, in agreement with experiments which found a paramagnetic state down to 10 K. The ground state is semiconducting, with a small electronic gap of 33meV, also consistent with previous experiments on films. Charge carrier concentrations are estimated from Hall resistance measurements. The Seebeck coefficient is measured and mapped using a scanning probe at room temperature that yields an average value of 38.6μVK-1, slightly lower than the theoretical result. Finally, the theoretical conductivity is analyzed as a function of temperature and concentration of charge carriers.

  15. Colossal Seebeck effect enhanced by quasi-ballistic phonons dragging massive electrons in FeSb2.

    PubMed

    Takahashi, H; Okazaki, R; Ishiwata, S; Taniguchi, H; Okutani, A; Hagiwara, M; Terasaki, I

    2016-09-06

    Phonon transport is an essential property of thermoelectric materials. Although the phonon carries heat, which reduces the thermoelectric efficiency, it contributes positively to the Seebeck coefficient S through the phonon-drag effect, as typified by the high-purity semiconductors, which show fairly large S at cryogenic temperatures. Although such a large S is attractive in terms of Peltier cooling, a clear guiding principle for designing thermoelectric materials enriched by the phonon-drag effect remains to be established. Here we demonstrate that a correlated semiconductor, FeSb2, is a promising thermoelectric material featuring quasi-ballistic phonons dragging d electrons with large effective mass. By changing the sample size within the sub-millimetre order for high-purity single crystals, we succeed in substantially increasing S to as much as -27 mV K(-1) at low temperatures. Our results exemplify a strategy for exploring phonon-drag-based thermoelectric materials, the performance of which can be maximized by combining heavy electrons with ballistic phonons.

  16. Colossal Seebeck effect enhanced by quasi-ballistic phonons dragging massive electrons in FeSb2

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Okazaki, R.; Ishiwata, S.; Taniguchi, H.; Okutani, A.; Hagiwara, M.; Terasaki, I.

    2016-09-01

    Phonon transport is an essential property of thermoelectric materials. Although the phonon carries heat, which reduces the thermoelectric efficiency, it contributes positively to the Seebeck coefficient S through the phonon-drag effect, as typified by the high-purity semiconductors, which show fairly large S at cryogenic temperatures. Although such a large S is attractive in terms of Peltier cooling, a clear guiding principle for designing thermoelectric materials enriched by the phonon-drag effect remains to be established. Here we demonstrate that a correlated semiconductor, FeSb2, is a promising thermoelectric material featuring quasi-ballistic phonons dragging d electrons with large effective mass. By changing the sample size within the sub-millimetre order for high-purity single crystals, we succeed in substantially increasing S to as much as -27 mV K-1 at low temperatures. Our results exemplify a strategy for exploring phonon-drag-based thermoelectric materials, the performance of which can be maximized by combining heavy electrons with ballistic phonons.

  17. Colossal Seebeck effect enhanced by quasi-ballistic phonons dragging massive electrons in FeSb2

    PubMed Central

    Takahashi, H.; Okazaki, R.; Ishiwata, S.; Taniguchi, H.; Okutani, A.; Hagiwara, M.; Terasaki, I.

    2016-01-01

    Phonon transport is an essential property of thermoelectric materials. Although the phonon carries heat, which reduces the thermoelectric efficiency, it contributes positively to the Seebeck coefficient S through the phonon-drag effect, as typified by the high-purity semiconductors, which show fairly large S at cryogenic temperatures. Although such a large S is attractive in terms of Peltier cooling, a clear guiding principle for designing thermoelectric materials enriched by the phonon-drag effect remains to be established. Here we demonstrate that a correlated semiconductor, FeSb2, is a promising thermoelectric material featuring quasi-ballistic phonons dragging d electrons with large effective mass. By changing the sample size within the sub-millimetre order for high-purity single crystals, we succeed in substantially increasing S to as much as −27 mV K−1 at low temperatures. Our results exemplify a strategy for exploring phonon-drag-based thermoelectric materials, the performance of which can be maximized by combining heavy electrons with ballistic phonons. PMID:27597055

  18. On the emission coefficient of uranium plasmas.

    NASA Technical Reports Server (NTRS)

    Schneider, R. T.; Campbell, H. D.; Mack, J. M.

    1973-01-01

    The emission coefficient for uranium plasmas (temperature: 8000 K) was measured for the wavelength range from 1200 to 6000 A. The results were compared to theoretical calculations and other measurements. Reasonable agreement between theoretical predictions and our measurements was found in the region from 1200 to 2000 A. Although it was difficult to make absolute comparisons among the different reported measurements, considerable disagreement was found for the higher wavelength region. A short discussion regarding the overall comparisons is given, and final suggestions are made as to the most appropriate emission coefficient values to be used in future design calculations. The absorption coefficient for the same wavelength interval is also reported.

  19. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  20. Thin Film Thermoelectric Metal-Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity. Supporting Information

    DTIC Science & Technology

    2015-04-28

    0188 3. DATES COVERED (From - To) - UU UU UU UU Approved for public release; distribution is unlimited. Thin Film Thermoelectric Metal -Organic...is demonstrated based on an electrically conducting metal –organic framework (MOF) using the guest@MOF concept. This demonstration opens a new...thermoelectric response, metal organic framework REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S ACRONYM(S

  1. Absolute classification with unsupervised clustering

    NASA Technical Reports Server (NTRS)

    Jeon, Byeungwoo; Landgrebe, D. A.

    1992-01-01

    An absolute classification algorithm is proposed in which the class definition through training samples or otherwise is required only for a particular class of interest. The absolute classification is considered as a problem of unsupervised clustering when one cluster is known initially. The definitions and statistics of the other classes are automatically developed through the weighted unsupervised clustering procedure, which is developed to keep the cluster corresponding to the class of interest from losing its identity as the class of interest. Once all the classes are developed, a conventional relative classifier such as the maximum-likelihood classifier is used in the classification.

  2. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  3. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  4. Absolute Standards for Climate Measurements

    NASA Astrophysics Data System (ADS)

    Leckey, J.

    2016-10-01

    In a world of changing climate, political uncertainty, and ever-changing budgets, the benefit of measurements traceable to SI standards increases by the day. To truly resolve climate change trends on a decadal time scale, on-orbit measurements need to be referenced to something that is both absolute and unchanging. One such mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) that will measure a variety of climate variables with an unprecedented accuracy to definitively quantify climate change. In the CLARREO mission, we will utilize phase change cells in which a material is melted to calibrate the temperature of a blackbody that can then be observed by a spectrometer. A material's melting point is an unchanging physical constant that, through a series of transfers, can ultimately calibrate a spectrometer on an absolute scale. CLARREO consists of two primary instruments: an infrared (IR) spectrometer and a reflected solar (RS) spectrometer. The mission will contain orbiting radiometers with sufficient accuracy to calibrate other space-based instrumentation and thus transferring the absolute traceability. The status of various mission options will be presented.

  5. An agreement coefficient for image comparison

    USGS Publications Warehouse

    Ji, L.; Gallo, K.

    2006-01-01

    Combination of datasets acquired from different sensor systems is necessary to construct a long time-series dataset for remotely sensed land-surface variables. Assessment of the agreement of the data derived from various sources is an important issue in understanding the data continuity through the time-series. Some traditional measures, including correlation coefficient, coefficient of determination, mean absolute error, and root mean square error, are not always optimal for evaluating the data agreement. For this reason, we developed a new agreement coefficient for comparing two different images. The agreement coefficient has the following properties: non-dimensional, bounded, symmetric, and distinguishable between systematic and unsystematic differences. The paper provides examples of agreement analyses for hypothetical data and actual remotely sensed data. The results demonstrate that the agreement coefficient does include the above properties, and therefore is a useful tool for image comparison. ?? 2006 American Society for Photogrammetry and Remote Sensing.

  6. New Method for Evaluating the Peltier Coefficient Based on Temperature Measurements in a Thermoelectric Module

    NASA Astrophysics Data System (ADS)

    Garrido, J.; Casanovas, A.

    2012-07-01

    A new method for determining the Peltier coefficient of thermoelectric devices has been developed. The Peltier coefficient has been evaluated by measuring the temperature distribution along the junction of two dissimilar materials X and Y. The energy balance has been used to link the Peltier coefficient with the hot and cold temperatures of the metallic blocks of a thermoelectric module (TEM), thus enabling the evaluation of this coefficient. Data on the thermal conductance of the pellets are also needed. The experimental device used in this paper is a TEM composed of N = 71 couples of bismuth telluride, suitably doped to provide individual n and p elements. Using nominal values given by the manufacturer for the Seebeck coefficient of the TEM, the Onsager reciprocal relation has been confirmed.

  7. Separation of spin Seebeck effect and anomalous Nernst effect in Co/Cu/YIG

    NASA Astrophysics Data System (ADS)

    Tian, Dai; Li, Yufan; Qu, D.; Jin, Xiaofeng; Chien, C. L.

    2015-05-01

    The spin Seebeck effect (SSE) and Anomalous Nernst effect (ANE) have been observed in Co/Cu/YIG (yttrium iron garnet) multi-layer structure, where the ferromagnetic insulator YIG acts as the pure spin injector and the ferromagnetic metal Co layer acts as the spin current detector. With the insertion of 5 nm Cu layer, the two ferromagnetic layers are decoupled, thus allowing unambiguous separation of the SSE and ANE contributions under the same experimental conditions in the same sample.

  8. Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers

    NASA Astrophysics Data System (ADS)

    Ramos, R.; Kikkawa, T.; Aguirre, M. H.; Lucas, I.; Anadón, A.; Oyake, T.; Uchida, K.; Adachi, H.; Shiomi, J.; Algarabel, P. A.; Morellón, L.; Maekawa, S.; Saitoh, E.; Ibarra, M. R.

    2015-12-01

    Spin Seebeck effects (SSEs) have been investigated in highly crystalline magnetic multilayer [Fe3O4/Pt] n films. Voltage as well as power generated by the SSE were found to be significantly enhanced with increasing the number of layers n . This voltage enhancement defies the simple understanding of the SSE and suggests that spin current flowing between the magnetic layers in the thickness direction plays an important role in multilayer SSE systems and the observed voltage enhancement.

  9. Separation of spin Seebeck effect and anomalous Nernst effect in Co/Cu/YIG

    SciTech Connect

    Tian, Dai; Li, Yufan; Qu, D.; Chien, C. L.; Jin, Xiaofeng

    2015-05-25

    The spin Seebeck effect (SSE) and Anomalous Nernst effect (ANE) have been observed in Co/Cu/YIG (yttrium iron garnet) multi-layer structure, where the ferromagnetic insulator YIG acts as the pure spin injector and the ferromagnetic metal Co layer acts as the spin current detector. With the insertion of 5 nm Cu layer, the two ferromagnetic layers are decoupled, thus allowing unambiguous separation of the SSE and ANE contributions under the same experimental conditions in the same sample.

  10. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  11. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  12. Physics of negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Abraham, Eitan; Penrose, Oliver

    2017-01-01

    Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins; nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the "volume entropy") due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments. We also examine the principal arguments that have been advanced against the negative temperature concept; we find that these arguments are not logically compelling, and moreover that the underlying "volume" entropy formula leads to predictions inconsistent with existing experimental results on nuclear spins. We conclude that, despite the counterarguments, negative absolute temperatures make good theoretical sense and did occur in the experiments designed to produce them.

  13. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  14. A spin-Seebeck diode with a negative differential spin-Seebeck effect in a hydrogen-terminated zigzag silicene nanoribbon heterojunction.

    PubMed

    Fu, Hua-Hua; Gu, Lei; Wu, Dan-Dan

    2016-05-14

    The spin-Seebeck effect (SSE), the central topic of spin caloritronics, provides a new direction for future low power consumption technology. To realize device applications of SSE, a spin-Seebeck diode (SSD) with a negative differential SSE is very desirable. To this end, we constructed a spin caloritronics device that was composed of a ferromagnetic double-single-hydrogen-terminated zigzag silicene nanoribbon (ZSiNR-H2-H) and an antiferromagnetic double-double-hydrogen-terminated zigzag silicene nanoribbon (ZSiNR-H2-H2). By using ab initio calculations combined with nonequilibrium Green's function technique, we found that thermally driven spin current through the heterojunction featured the SSD effect and negative differential SSE. The former originates from the asymmetrical thermal-driven conducting electrons and holes, and the latter ascribes to the thermal spin compensation effect. Their physical mechanisms are much different from the previous ones mainly relying on the spin-wave excitations in the interface between metals and magnetic insulators, supporting our study that puts forward a new route to realize the SSD with a negative differential SSE.

  15. On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect

    PubMed Central

    Boehnke, Alexander; Milnikel, Marius; von der Ehe, Marvin; Franz, Christian; Zbarsky, Vladyslav; Czerner, Michael; Rott, Karsten; Thomas, Andy; Heiliger, Christian; Reiss, Günter; Münzenberg, Markus

    2015-01-01

    Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a ”green” information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic “1” state and off to “0” by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions. PMID:25755010

  16. Thermal spin current from a ferromagnet to silicon by Seebeck spin tunnelling.

    PubMed

    Le Breton, Jean-Christophe; Sharma, Sandeep; Saito, Hidekazu; Yuasa, Shinji; Jansen, Ron

    2011-06-29

    Heat generation by electric current, which is ubiquitous in electronic devices and circuits, raises energy consumption and will become increasingly problematic in future generations of high-density electronics. The control and re-use of heat are therefore important topics for existing and emerging technologies, including spintronics. Recently it was reported that heat flow within a ferromagnet can produce a flow of spin angular momentum-a spin current-and an associated voltage. This spin Seebeck effect has been observed in metallic, insulating and semiconductor ferromagnets with temperature gradients across them. Here we describe and report the demonstration of Seebeck spin tunnelling-a distinctly different thermal spin flow, of purely interfacial nature-generated in a tunnel contact between electrodes of different temperatures when at least one of the electrodes is a ferromagnet. The Seebeck spin current is governed by the energy derivative of the tunnel spin polarization. By exploiting this in ferromagnet-oxide-silicon tunnel junctions, we observe thermal transfer of spins from the ferromagnet to the silicon without a net tunnel charge current. The induced spin accumulation scales linearly with heating power and changes sign when the temperature differential is reversed. This thermal spin current can be used by itself, or in combination with electrical spin injection, to increase device efficiency. The results highlight the engineering of heat transport in spintronic devices and facilitate the functional use of heat.

  17. Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions

    SciTech Connect

    Liu, Yu-Shen; Zhang, Xue; Feng, Jin-Fu; Wang, Xue-Feng

    2014-06-16

    We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T = 25 K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.

  18. Thermal spin current from a ferromagnet to silicon by Seebeck spin tunnelling

    NASA Astrophysics Data System (ADS)

    Le Breton, Jean-Christophe; Sharma, Sandeep; Saito, Hidekazu; Yuasa, Shinji; Jansen, Ron

    2011-07-01

    Heat generation by electric current, which is ubiquitous in electronic devices and circuits, raises energy consumption and will become increasingly problematic in future generations of high-density electronics. The control and re-use of heat are therefore important topics for existing and emerging technologies, including spintronics. Recently it was reported that heat flow within a ferromagnet can produce a flow of spin angular momentum--a spin current--and an associated voltage. This spin Seebeck effect has been observed in metallic, insulating and semiconductor ferromagnets with temperature gradients across them. Here we describe and report the demonstration of Seebeck spin tunnelling--a distinctly different thermal spin flow, of purely interfacial nature--generated in a tunnel contact between electrodes of different temperatures when at least one of the electrodes is a ferromagnet. The Seebeck spin current is governed by the energy derivative of the tunnel spin polarization. By exploiting this in ferromagnet-oxide-silicon tunnel junctions, we observe thermal transfer of spins from the ferromagnet to the silicon without a net tunnel charge current. The induced spin accumulation scales linearly with heating power and changes sign when the temperature differential is reversed. This thermal spin current can be used by itself, or in combination with electrical spin injection, to increase device efficiency. The results highlight the engineering of heat transport in spintronic devices and facilitate the functional use of heat.

  19. Quasianalytical treatment of the spin Seebeck effect on the Na2 molecule

    NASA Astrophysics Data System (ADS)

    Lefkidis, G.; Reyes, S. A.

    2016-10-01

    We present a method to calculate from first principles the spin Seebeck effect on finite systems. Our method, which is suited for all ab initio, quantum-chemistry-based results, is demonstrated quasianalytically on the Na2 dimer. To this end we start from the analytical solutions of the many-body wave function for the minimal Na2 molecule and propagate it numerically in time using the Liouville-von Neumann equation of motion. The system is coupled to two baths with different temperatures, described with a Lindblad superoperator. We mainly focus on the concept of how to divide any operator into several spatially localized contributions and show that the spatial localization of the virtual excitations (i.e., splitting of the ladder operators into two sets of localized operators with different eigenbases) is the underlying reason for the spin Seebeck effect. Last but not least, we analyze the entanglement of the system and find that the maxima of the Laplacian of the negativity coincide with the change of the direction of the spin Seebeck effect.

  20. On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect

    NASA Astrophysics Data System (ADS)

    Boehnke, Alexander; Milnikel, Marius; von der Ehe, Marvin; Franz, Christian; Zbarsky, Vladyslav; Czerner, Michael; Rott, Karsten; Thomas, Andy; Heiliger, Christian; Reiss, Günter; Münzenberg, Markus

    2015-03-01

    Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a ''green'' information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic ``1'' state and off to ``0'' by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions.

  1. On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect.

    PubMed

    Boehnke, Alexander; Milnikel, Marius; von der Ehe, Marvin; Franz, Christian; Zbarsky, Vladyslav; Czerner, Michael; Rott, Karsten; Thomas, Andy; Heiliger, Christian; Reiss, Günter; Münzenberg, Markus

    2015-03-10

    Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a "green" information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic "1" state and off to "0" by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions.

  2. The Third Way of Thermal-Electric Conversion beyond Seebeck and Pyroelectric Effects

    SciTech Connect

    Ren, Jie

    2014-02-14

    Thermal-electric conversion is crucial for smart energy control and harvesting, such as thermal sensing and waste heat recovering. So far, people are aware of only two ways of direct thermal-electric conversion, Seebeck and pyroelectric effects, each with distinct working conditions and limitations. Here, we report the third way of thermal-electric conversion beyond Seebeck and pyroelectric effects. In contrast to Seebeck effect that requires spatial temperature difference, the-third-way converts the time-dependent ambient temperature fluctuation into electricity, similar to the behavior of pyroelectricity. However, the-third-way is also distinct from pyroelectric effect in the sense that it does not require polar materials but applies to general conducting systems. We demonstrate that the-third-way results from the temperature-fluctuation-induced dynamical charge redistribution. It is a consequence of the fundamental nonequilibrium thermodynamics and has a deep connection to the topological phase in quantum mechanics. Our findings expand our knowledge and provide new means of thermal-electric energy harvesting.

  3. Factor Scores, Structure Coefficients, and Communality Coefficients

    ERIC Educational Resources Information Center

    Goodwyn, Fara

    2012-01-01

    This paper presents heuristic explanations of factor scores, structure coefficients, and communality coefficients. Common misconceptions regarding these topics are clarified. In addition, (a) the regression (b) Bartlett, (c) Anderson-Rubin, and (d) Thompson methods for calculating factor scores are reviewed. Syntax necessary to execute all four…

  4. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  5. Absolute flux measurements for swift atoms

    NASA Technical Reports Server (NTRS)

    Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

    1987-01-01

    While a torsion balance in vacuum can easily measure the momentum transfer from a gas beam impinging on a surface attached to the balance, this measurement depends on the accommodation coefficients of the atoms with the surface and the distribution of the recoil. A torsion balance is described for making absolute flux measurements independent of recoil effects. The torsion balance is a conventional taut suspension wire design and the Young modulus of the wire determines the relationship between the displacement and the applied torque. A compensating magnetic field is applied to maintain zero displacement and provide critical damping. The unique feature is to couple the impinging gas beam to the torsion balance via a Wood's horn, i.e., a thin wall tube with a gradual 90 deg bend. Just as light is trapped in a Wood's horn by specular reflection from the curved surfaces, the gas beam diffuses through the tube. Instead of trapping the beam, the end of the tube is open so that the atoms exit the tube at 90 deg to their original direction. Therefore, all of the forward momentum of the gas beam is transferred to the torsion balance independent of the angle of reflection from the surfaces inside the tube.

  6. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < -1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  7. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    SciTech Connect

    Miao, B. F.; Huang, S. Y.; Qu, D.; Chien, C. L.

    2016-01-15

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  8. Transverse spin Seebeck effect versus anomalous and planar Nernst effects in Permalloy thin films.

    PubMed

    Schmid, M; Srichandan, S; Meier, D; Kuschel, T; Schmalhorst, J-M; Vogel, M; Reiss, G; Strunk, C; Back, C H

    2013-11-01

    Transverse magnetothermoelectric effects are studied in Permalloy thin films grown on MgO and GaAs substrates and compared to those grown on suspended SiN(x) membranes. The transverse voltage along platinum strips patterned on top of the Permalloy films is measured versus the external magnetic field as a function of the angle and temperature gradients. After the identification of the contribution of the planar and anomalous Nernst effects, we find an upper limit for the transverse spin Seebeck effect, which is several orders of magnitude smaller than previously reported.

  9. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    NASA Astrophysics Data System (ADS)

    Miao, B. F.; Huang, S. Y.; Qu, D.; Chien, C. L.

    2016-01-01

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  10. Enhanced spin Seebeck effect in a germanene p-n junction

    SciTech Connect

    Zheng, Jun; Chi, Feng; Guo, Yong

    2014-12-28

    Spin Seebeck effect in a germanene p-n junction is studied by using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian. We find that the thermal bias ΔT can generate spin thermopower when a local exchange field is applied on one edge of the germanene nano-ribbon. The magnitude of the spin thermopower can be modulated by the potential drop across the two terminals of the p-n junction. When the value of the potential drop is smaller than the spin-orbit interaction strength, the spin thermopower is enhanced by two orders of magnitude larger as compared to the case of zero p-n voltage. Optimal temperature corresponding to maximum spin thermopower is insensitive to the potential drop. In the p-n region, maximum spin thermopower can be obtained at relatively higher temperatures. When the value of the potential drop is larger than that of the spin-orbit interaction, however, the spin Seebeck effect decays rapidly with increasing potential drop or temperature. By optimizing the structure parameters, the magnitude of the spin thermopower can be remarkably enhanced due to the coexistence of the exchange field and the potential drop.

  11. Observation of the spin-Seebeck effect in a ferromagnetic semiconductor.

    PubMed

    Jaworski, C M; Yang, J; Mack, S; Awschalom, D D; Heremans, J P; Myers, R C

    2010-11-01

    Reducing the heat generated in traditional electronics is a chief motivation for the development of spin-based electronics, called spintronics. Spin-based transistors that do not strictly rely on the raising or lowering of electrostatic barriers can overcome scaling limits in charge-based transistors. Spin transport in semiconductors might also lead to dissipation-less information transfer with pure spin currents. Despite these thermodynamic advantages, little experimental literature exists on the thermal aspects of spin transport in solids. A recent and surprising exception was the discovery of the spin-Seebeck effect, reported as a measurement of a redistribution of spins along the length of a sample of permalloy (NiFe) induced by a temperature gradient. This macroscopic spatial distribution of spins is, surprisingly, many orders of magnitude larger than the spin diffusion length, which has generated strong interest in the thermal aspects of spin transport. Here, the spin-Seebeck effect is observed in a ferromagnetic semiconductor, GaMnAs, which allows flexible design of the magnetization directions, a larger spin polarization, and measurements across the magnetic phase transition. This effect is observed even in the absence of longitudinal charge transport. The spatial distribution of spin currents is maintained across electrical breaks, highlighting the local nature of this thermally driven effect.

  12. Asymmetric and Negative Differential Thermal Spin Effect at Magnetic Interfaces: Towards Spin Seebeck Diodes and Transistors

    NASA Astrophysics Data System (ADS)

    Ren, Jie; Zhu, Jian-Xin

    2014-03-01

    We study the nonequilibrium thermal-spin transport across metal-magnetic insulator interfaces. The transport is assisted by the exchange interaction between conduction electrons in the metal and localized spins in the magnetic insulator. We predict the rectification and negative differential spin Seebeck effect (SSE), that is, reversing the temperature bias is able to give asymmetric spin currents and increasing temperature bias could give an anomalously decreasing spin current. We resolve their microscopic mechanism as a consequence of the energy-dependent electronic DOS in the metal. The rectification of spin Peltier effect is also discussed. We then study the asymmetric and negative differential magnon tunneling driven by temperature bias. We show that the many-body magnon interaction that makes the magnonic spectrum temperature-dependent is the crucial factor for the emergence of rectification and negative differential SSEs in magnon tunneling junctions. We show that these asymmetric and negative differential SSEs are relevant for building magnon and spin Seebeck diodes and transistors, which could play important roles in controlling information and energy in functional devices. Supported by the National Nuclear Security Administration of the US DOE at LANL under Contract No. DE-AC52-06NA25396.

  13. Modified Biserial Correlation Coefficients.

    ERIC Educational Resources Information Center

    Kraemer, Helena Chmura

    1981-01-01

    Asymptotic distribution theory of Brogden's form of biserial correlation coefficient is derived and large sample estimates of its standard error obtained. Its relative efficiency to the biserial correlation coefficient is examined. Recommendations for choice of estimator of biserial correlation are presented. (Author/JKS)

  14. Absolute Radiometric Calibration of KOMPSAT-3A

    NASA Astrophysics Data System (ADS)

    Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.

    2016-06-01

    This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.

  15. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  16. ON A SUFFICIENT CONDITION FOR ABSOLUTE CONTINUITY.

    DTIC Science & Technology

    The formulation of a condition which yields absolute continuity when combined with continuity and bounded variation is the problem considered in the...Briefly, the formulation is achieved through a discussion which develops a proof by contradiction of a sufficiently theorem for absolute continuity which uses in its hypothesis the condition of continuity and bounded variation .

  17. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  18. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  19. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  20. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

    Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

  1. Band gap estimation from temperature dependent Seebeck measurement—Deviations from the 2e|S|{sub max}T{sub max} relation

    SciTech Connect

    Gibbs, Zachary M.; Kim, Hyun-Sik; Wang, Heng; Snyder, G. Jeffrey

    2015-01-12

    In characterizing thermoelectric materials, electrical and thermal transport measurements are often used to estimate electronic band structure properties such as the effective mass and band gap. The Goldsmid-Sharp band gap, E{sub g} = 2e|S|{sub max}T{sub max}, is a tool widely employed to estimate the band gap from temperature dependent Seebeck coefficient measurements. However, significant deviations of more than a factor of two are now known to occur. We find that this is when either the majority-to-minority weighted mobility ratio (A) becomes very different from 1.0 or as the band gap (E{sub g}) becomes significantly smaller than 10 k{sub B}T. For narrow gaps (E{sub g} ≲ 6 k{sub B}T), the Maxwell-Boltzmann statistics applied by Goldsmid-Sharp break down and Fermi-Dirac statistics are required. We generate a chart that can be used to quickly estimate the expected correction to the Goldsmid-Sharp band gap depending on A and S{sub max}; however, additional errors can occur for S < 150 μV/K due to degenerate behavior.

  2. Piezo-optic coefficients of CaWO4 crystals

    NASA Astrophysics Data System (ADS)

    Mytsyk, B. G.; Kost', Ya. P.; Demyanyshyn, N. M.; Andrushchak, A. S.; Solskii, I. M.

    2015-01-01

    All components of the piezo-optic coefficient matrix of calcium tungstate crystals, belonging to the 4/ m symmetry class, are determined. The reliability of the piezo-optic effect measurements in CaWO4 crystals is achieved by determining each piezo-optic coefficient from several experimental geometries and is also based on the correlation of the absolute piezo-electric coefficients and the path-difference coefficients. The rotation-shear diagonal coefficients π44 and π66 and three principal piezo-optic coefficients π11, π13, and π31 are refined by the polarization-optical method. It is confirmed that both the interferometric and polarization-optical methods should be used to study the piezo-optic effect with high accuracy. The results show that calcium tungstate is a promising material for acousto-optical and photoelastic modulation.

  3. Investigation of the magnetic properties of insulating thin films using the longitudinal spin Seebeck effect

    SciTech Connect

    Kehlberger, A. Jakob, G.; Kläui, M.; Onbasli, M. C.; Kim, D. H.; Ross, C. A.

    2014-05-07

    The longitudinal spin Seebeck effect is used as a detector for the magnetic properties and switching characteristics of magnetic thin insulating films. We use a 300 nm and a 20 nm thick Yttrium Iron Garnet (YIG, Y{sub 3}Fe{sub 5}O{sub 12}) film prepared by pulsed laser deposition and afterwards coated by platinum for the detection of the thermally excited magnons by the inverse spin Hall effect. The inverse spin Hall signals reveal a magnetic uniaxial anisotropy along the direction of the platinum stripe in the thicker film. For the thin film we find a more isotropic behavior, which is complementarily observed using the magnetoresistance occurring at the platinum/YIG interface. We explain our results on the basis of x-ray diffraction data, which reveal a miscut of the substrate and film surface and an expansion of the YIG lattice. Both findings favor a growth-induced magnetic anisotropy that we observe.

  4. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    SciTech Connect

    Seki, Takeshi Takanashi, Koki; Uchida, Ken-ichi; Kikkawa, Takashi; Qiu, Zhiyong; Saitoh, Eiji

    2015-08-31

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (J{sub s}) in the FePt|Y{sub 3}Fe{sub 5}O{sub 12} (YIG) structure, and J{sub s} was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  5. Enhancement of spin-Seebeck effect by inserting ultra-thin Fe70Cu30 interlayer

    NASA Astrophysics Data System (ADS)

    Kikuchi, D.; Ishida, M.; Uchida, K.; Qiu, Z.; Murakami, T.; Saitoh, E.

    2015-02-01

    We report the longitudinal spin-Seebeck effects (LSSEs) for Pt/Fe70Cu30/BiY2Fe5O12 (BiYIG) and Pt/BiYIG devices. The LSSE voltage was found to be enhanced by inserting an ultra-thin Fe70Cu30 interlayer. This enhancement decays sharply with increasing the Fe70Cu30 thickness, suggesting that it is not due to bulk phenomena, such as a superposition of conventional thermoelectric effects, but due to interface effects related to the Fe70Cu30 interlayer. Combined with control experiments using Pt/Fe70Cu30 devices, we conclude that the enhancement of the LSSE voltage in the Pt/Fe70Cu30/BiYIG devices is attributed to the improvement of the spin-mixing conductance at the Pt/BiYIG interfaces.

  6. 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.

  7. Seebeck effect influence on joule heat evolution in electrically conductive silicate materials

    NASA Astrophysics Data System (ADS)

    Fiala, Lukáš; Medved, Igor; Maděra, Jiří; Černý, Robert

    2016-07-01

    In general, silicate building materials are non-conductive matters that are not able to evolve heat when they are subjected to an external voltage. However, the electrical conductivity can be increased by addition of electrically conductive admixtures in appropriate amount which leads to generation of conductive paths in materials matrix. Such enhanced materials can evolve Joule heat and are utilizable as a core of self-heating or snow-melting systems. In this paper, Joule heat evolution together with Seebeck effect in electrically conductive silicate materials was taken into consideration and the model based on heat equation with included influence of DC electric field was proposed. Besides, a modeling example of heating element was carried out on FEM basis and time development of temperature in chosen surface points was expressed in order to declare ability of such system to be applicable.

  8. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Seki, Takeshi; Uchida, Ken-ichi; Kikkawa, Takashi; Qiu, Zhiyong; Saitoh, Eiji; Takanashi, Koki

    2015-08-01

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (Js) in the FePt|Y3Fe5O12 (YIG) structure, and Js was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  9. Electric gating induced bandgaps and enhanced Seebeck effect in zigzag bilayer graphene ribbons

    NASA Astrophysics Data System (ADS)

    Vu, Thanh-Tra; Tran, Van-Truong

    2016-08-01

    We theoretically investigate the effect of a transverse electric field generated by side gates and a vertical electric field generated by top/back gates on energy bands and transport properties of zigzag bilayer graphene ribbons (Bernal stacking). Using atomistic tight binding calculations and Green’s function formalism we demonstrate that a bandgap is opened when either field is applied and even enlarged under simultaneous influence of the two fields. Interestingly, although vertical electric fields are widely used to control the bandgap in bilayer graphene, here we show that transverse fields exhibit a more positive effect in terms of modulating a larger range of bandgap and retaining good electrical conductance. The Seebeck effect is also demonstrated to be enhanced strongly—by about 13 times for a zigzag bilayer graphene ribbon with 16 chain lines. These results may motivate new designs of devices made of bilayer graphene ribbons using electric gates.

  10. 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.

  11. Hot-Carrier Seebeck Effect: Diffusion and Remote Detection of Hot Carriers in Graphene

    NASA Astrophysics Data System (ADS)

    Sierra, Juan F.; Neumann, Ingmar; Costache, Marius V.; Valenzuela, Sergio O.

    2015-06-01

    We investigate hot carrier propagation across graphene using an electrical nonlocal injection/detection method. The device consists of a monolayer graphene flake contacted by multiple metal leads. Using two remote leads for electrical heating, we generate a carrier temperature gradient that results in a measurable thermoelectric voltage VNL across the remaining (detector) leads. Due to the nonlocal character of the measurement, VNL is exclusively due to the Seebeck effect. Remarkably, a departure from the ordinary relationship between Joule power P and VNL, VNL ~ P, becomes readily apparent at low temperatures, representing a fingerprint of hot-carrier dominated thermoelectricity. By studying VNL as a function of bias, we directly determine the carrier temperature and the characteristic cooling length for hot-carrier propagation, which are key parameters for a variety of new applications that rely on hot-carrier transport.

  12. Hot-Carrier Seebeck Effect: Diffusion and Remote Detection of Hot Carriers in Graphene.

    PubMed

    Sierra, Juan F; Neumann, Ingmar; Costache, Marius V; Valenzuela, Sergio O

    2015-06-10

    We investigate hot carrier propagation across graphene using an electrical nonlocal injection/detection method. The device consists of a monolayer graphene flake contacted by multiple metal leads. Using two remote leads for electrical heating, we generate a carrier temperature gradient that results in a measurable thermoelectric voltage V(NL) across the remaining (detector) leads. Due to the nonlocal character of the measurement, V(NL) is exclusively due to the Seebeck effect. Remarkably, a departure from the ordinary relationship between Joule power P and V(NL), V(NL) ∼ P, becomes readily apparent at low temperatures, representing a fingerprint of hot-carrier dominated thermoelectricity. By studying V(NL) as a function of bias, we directly determine the carrier temperature and the characteristic cooling length for hot-carrier propagation, which are key parameters for a variety of new applications that rely on hot-carrier transport.

  13. Seebeck rectification enabled by intrinsic thermoelectrical coupling in magnetic tunneling junctions.

    PubMed

    Zhang, Z H; Gui, Y S; Fu, L; Fan, X L; Cao, J W; Xue, D S; Freitas, P P; Houssameddine, D; Hemour, S; Wu, K; Hu, C-M

    2012-07-20

    An intrinsic thermoelectric coupling effect in the linear response regime of magnetic tunneling junctions (MTJ) is reported. In the dc response, it leads to a nonlinear correction to Ohm's law. Dynamically, it enables a novel Seebeck rectification and second harmonic generation, which apply for a broad frequency range and can be magnetically controlled. A phenomenological model on the footing of the Onsager reciprocal relation and the principle of energy conservation explains very well the experimental results obtained from both dc and frequency-dependent transport measurements performed up to GHz frequencies. Our work refines previous understanding of magnetotransport and microwave rectification in MTJs. It forms a new foundation for utilizing spin caloritronics in high-frequency applications.

  14. Bose-Einstein condensation of magnons pumped by the bulk spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Tserkovnyak, Yaroslav; Bender, Scott A.; Duine, Rembert A.; Flebus, Benedetta

    2016-03-01

    We propose inducing Bose-Einstein condensation of magnons in a magnetic insulator by a heat flow oriented toward its boundary. At a critical heat flux, the oversaturated thermal gas of magnons accumulated at the boundary precipitates the condensate, which then grows gradually as the thermal bias is dialed up further. The thermal magnons thus pumped by the magnonic bulk (spin) Seebeck effect must generally overcome both the local Gilbert damping associated with the coherent magnetic dynamics as well as the radiative spin-wave losses toward the magnetic bulk, in order to achieve the threshold of condensation. We quantitatively estimate the requisite bias in the case of the ferrimagnetic yttrium iron garnet, discuss different physical regimes of condensation, and contrast it with the competing (so-called Doppler-shift) bulk instability.

  15. Reconstruction of an effective magnon mean free path distribution from spin Seebeck measurements in thin films

    NASA Astrophysics Data System (ADS)

    Chavez-Angel, E.; Zarate, R. A.; Fuentes, S.; Guo, E. J.; Kläui, M.; Jakob, G.

    2017-01-01

    A thorough understanding of the mean-free-path (MFP) distribution of the energy carriers is crucial to engineer and tune the transport properties of materials. In this context, a significant body of work has investigated the phonon and electron MFP distribution, however, similar studies of the magnon MFP distribution have not been carried out so far. In this work, we used thickness-dependence measurements of the longitudinal spin Seebeck (LSSE) effect of yttrium iron garnet films to reconstruct the cumulative distribution of a SSE related effective magnon MFP. By using the experimental data reported by (Guo et al 2016 Phys. Rev. X 6 031012), we adapted the phonon MFP reconstruction algorithm proposed by (Minnich 2012 Phys. Rev. Lett. 109 205901) and apply it to magnons. The reconstruction showed that magnons with different MFP contribute in different manner to the total LSSE and the effective magnon MFP distribution spreads far beyond their typical averaged values.

  16. Spin rectification in thermally driven XXZ spin chain via the spin-Seebeck effect

    NASA Astrophysics Data System (ADS)

    Thingna, Juzar; Wang, Jian-Sheng

    2013-11-01

    We study the phenomenon of spin-current rectification in a one-dimensional XXZ spin chain in the presence of a thermal drive. In our model a pure spin current is generated by a temperature difference between two harmonic heat baths which in turn creates a spin voltage via the spin-Seebeck effect. Along with a local spin-current operator definition and the nonequilibrium modified Redfield solution we study the spin-rectification ratio as a function of system size and external magnetic field. Intriguing effects are observed at low temperatures such as oscillations with system size and high range of tunability with external magnetic field making magnetic insulators, which are well described by the XXZ model, ideal candidates to build spin devices based on rectification.

  17. Absolute quantitation of protein posttranslational modification isoform.

    PubMed

    Yang, Zhu; Li, Ning

    2015-01-01

    Mass spectrometry has been widely applied in characterization and quantification of proteins from complex biological samples. Because the numbers of absolute amounts of proteins are needed in construction of mathematical models for molecular systems of various biological phenotypes and phenomena, a number of quantitative proteomic methods have been adopted to measure absolute quantities of proteins using mass spectrometry. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with internal peptide standards, i.e., the stable isotope-coded peptide dilution series, which was originated from the field of analytical chemistry, becomes a widely applied method in absolute quantitative proteomics research. This approach provides more and more absolute protein quantitation results of high confidence. As quantitative study of posttranslational modification (PTM) that modulates the biological activity of proteins is crucial for biological science and each isoform may contribute a unique biological function, degradation, and/or subcellular location, the absolute quantitation of protein PTM isoforms has become more relevant to its biological significance. In order to obtain the absolute cellular amount of a PTM isoform of a protein accurately, impacts of protein fractionation, protein enrichment, and proteolytic digestion yield should be taken into consideration and those effects before differentially stable isotope-coded PTM peptide standards are spiked into sample peptides have to be corrected. Assisted with stable isotope-labeled peptide standards, the absolute quantitation of isoforms of posttranslationally modified protein (AQUIP) method takes all these factors into account and determines the absolute amount of a protein PTM isoform from the absolute amount of the protein of interest and the PTM occupancy at the site of the protein. The absolute amount of the protein of interest is inferred by quantifying both the absolute amounts of a few PTM

  18. Absolute realization of low BRDF value

    NASA Astrophysics Data System (ADS)

    Liu, Zilong; Liao, Ningfang; Li, Ping; Wang, Yu

    2010-10-01

    Low BRDF value is widespread used in many critical domains such as space and military fairs. These values below 0.1 Sr-1 . So the Absolute realization of these value is the most critical issue in the absolute measurement of BRDF. To develop the Absolute value realization theory of BRDF , defining an arithmetic operators of BRDF , achieving an absolute measurement Eq. of BRDF based on radiance. This is a new theory method to solve the realization problem of low BRDF value. This theory method is realized on a self-designed common double orientation structure in space. By designing an adding structure to extend the range of the measurement system and a control and processing software, Absolute realization of low BRDF value is achieved. A material of low BRDF value is measured in this measurement system and the spectral BRDF value are showed within different angles allover the space. All these values are below 0.4 Sr-1 . This process is a representative procedure about the measurement of low BRDF value. A corresponding uncertainty analysis of this measurement data is given depend on the new theory of absolute realization and the performance of the measurement system. The relative expand uncertainty of the measurement data is 0.078. This uncertainty analysis is suitable for all measurements using the new theory of absolute realization and the corresponding measurement system.

  19. Absolute Rate Coefficients for F + H(2) and F + D(2) at T = 295 - 765K.

    DTIC Science & Technology

    1982-05-05

    2 at T 295 -765K R. F. HEIDNER III, J. F. BOTT. C. E. GARDNER, and J. E. MELZER Laboratory Operations The Aerospace Corporation El Segundo, CaliL... Corporation , El Segundo, CA 90245, under Contract No. F04701-81-C-0082 with the Space Division, Deputy for Technology, P.O. Box 92960, orldvay Postal...Center, Los Angeles, CA 90009. It was reviewed and approved for The Aerospace Corporation by V. P. Thompson, Director, Aerophysics Laboratory. Lt E

  20. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  1. Magnifying absolute instruments for optically homogeneous regions

    SciTech Connect

    Tyc, Tomas

    2011-09-15

    We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

  2. The Simplicity Argument and Absolute Morality

    ERIC Educational Resources Information Center

    Mijuskovic, Ben

    1975-01-01

    In this paper the author has maintained that there is a similarity of thought to be found in the writings of Cudworth, Emerson, and Husserl in his investigation of an absolute system of morality. (Author/RK)

  3. JKTLD: Limb darkening coefficients

    NASA Astrophysics Data System (ADS)

    Southworth, John

    2015-11-01

    JKTLD outputs theoretically-calculated limb darkening (LD) strengths for equations (LD laws) which predict the amount of LD as a function of the part of the star being observed. The coefficients of these laws are obtained by bilinear interpolation (in effective temperature and surface gravity) in published tables of coefficients calculated from stellar model atmospheres by several researchers. Many observations of stars require the strength of limb darkening (LD) to be estimated, which can be done using theoretical models of stellar atmospheres; JKTLD can help in these circumstances.

  4. Absolute cross sections of compound nucleus reactions

    NASA Astrophysics Data System (ADS)

    Capurro, O. A.

    1993-11-01

    The program SEEF is a Fortran IV computer code for the extraction of absolute cross sections of compound nucleus reactions. When the evaporation residue is fed by its parents, only cumulative cross sections will be obtained from off-line gamma ray measurements. But, if one has the parent excitation function (experimental or calculated), this code will make it possible to determine absolute cross sections of any exit channel.

  5. Kelvin and the absolute temperature scale

    NASA Astrophysics Data System (ADS)

    Erlichson, Herman

    2001-07-01

    This paper describes the absolute temperature scale of Kelvin (William Thomson). Kelvin found that Carnot's axiom about heat being a conserved quantity had to be abandoned. Nevertheless, he found that Carnot's fundamental work on heat engines was correct. Using the concept of a Carnot engine Kelvin found that Q1/Q2 = T1/T2. Thermometers are not used to obtain absolute temperatures since they are calculated temperatures.

  6. Complete Suppression of Longitudinal Spin Seebeck Effect by Frozen Magnetization Dynamics in Y3Fe5O12

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takashi; Uchida, Ken-ichi; Daimon, Shunsuke; Saitoh, Eiji

    2016-06-01

    The spin Seebeck effect (SSE) in a Pt-film/Y3Fe5O12 (YIG)-slab junction system has been investigated at low temperatures and under various magnetic fields in the longitudinal configuration. We found that, by increasing applied magnetic fields, the SSE signal gradually decreases and converges to zero without showing sign reversal. The complete field-induced suppression of the SSE is interpreted in terms of the effect of the Zeeman gap in magnon excitation.

  7. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed.

  8. Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites.

    PubMed

    Boona, Stephen R; Vandaele, Koen; Boona, Isabel N; McComb, David W; Heremans, Joseph P

    2016-12-12

    Transverse thermoelectric devices produce electric fields perpendicular to an incident heat flux. Classically, this process is driven by the Nernst effect in bulk solids, wherein a magnetic field generates a Lorentz force on thermally excited electrons. The spin Seebeck effect also produces magnetization-dependent transverse electric fields. It is traditionally observed in thin metallic films deposited on electrically insulating ferromagnets, but the films' high resistance limits thermoelectric conversion efficiency. Combining Nernst and spin Seebeck effect in bulk materials would enable devices with simultaneously large transverse thermopower and low electrical resistance. Here we demonstrate experimentally that this is possible in composites of conducting ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong spin-orbit interactions (Pt or Au). These materials display positive shifts in transverse thermopower attributable to inverse spin Hall electric fields in the nanoparticles. This more than doubles the power output of the Ni-Pt materials, establishing proof of principle that the spin Seebeck effect persists in bulk nanocomposites.

  9. Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites

    NASA Astrophysics Data System (ADS)

    Boona, Stephen R.; Vandaele, Koen; Boona, Isabel N.; McComb, David W.; Heremans, Joseph P.

    2016-12-01

    Transverse thermoelectric devices produce electric fields perpendicular to an incident heat flux. Classically, this process is driven by the Nernst effect in bulk solids, wherein a magnetic field generates a Lorentz force on thermally excited electrons. The spin Seebeck effect also produces magnetization-dependent transverse electric fields. It is traditionally observed in thin metallic films deposited on electrically insulating ferromagnets, but the films' high resistance limits thermoelectric conversion efficiency. Combining Nernst and spin Seebeck effect in bulk materials would enable devices with simultaneously large transverse thermopower and low electrical resistance. Here we demonstrate experimentally that this is possible in composites of conducting ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong spin-orbit interactions (Pt or Au). These materials display positive shifts in transverse thermopower attributable to inverse spin Hall electric fields in the nanoparticles. This more than doubles the power output of the Ni-Pt materials, establishing proof of principle that the spin Seebeck effect persists in bulk nanocomposites.

  10. Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites

    PubMed Central

    Boona, Stephen R.; Vandaele, Koen; Boona, Isabel N.; McComb, David W.; Heremans, Joseph P.

    2016-01-01

    Transverse thermoelectric devices produce electric fields perpendicular to an incident heat flux. Classically, this process is driven by the Nernst effect in bulk solids, wherein a magnetic field generates a Lorentz force on thermally excited electrons. The spin Seebeck effect also produces magnetization-dependent transverse electric fields. It is traditionally observed in thin metallic films deposited on electrically insulating ferromagnets, but the films' high resistance limits thermoelectric conversion efficiency. Combining Nernst and spin Seebeck effect in bulk materials would enable devices with simultaneously large transverse thermopower and low electrical resistance. Here we demonstrate experimentally that this is possible in composites of conducting ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong spin–orbit interactions (Pt or Au). These materials display positive shifts in transverse thermopower attributable to inverse spin Hall electric fields in the nanoparticles. This more than doubles the power output of the Ni-Pt materials, establishing proof of principle that the spin Seebeck effect persists in bulk nanocomposites. PMID:27941927

  11. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  12. A three-axis SQUID-based absolute vector magnetometer.

    PubMed

    Schönau, T; Zakosarenko, V; Schmelz, M; Stolz, R; Anders, S; Linzen, S; Meyer, M; Meyer, H-G

    2015-10-01

    We report on the development of a three-axis absolute vector magnetometer suited for mobile operation in the Earth's magnetic field. It is based on low critical temperature dc superconducting quantum interference devices (LTS dc SQUIDs) with sub-micrometer sized cross-type Josephson junctions and exhibits a white noise level of about 10 fT/Hz(1/2). The width of superconducting strip lines is restricted to less than 6 μm in order to avoid flux trapping during cool-down in magnetically unshielded environment. The long-term stability of the flux-to-voltage transfer coefficients of the SQUID electronics is investigated in detail and a method is presented to significantly increase their reproducibility. We further demonstrate the long-term operation of the setup in a magnetic field varying by about 200 μT amplitude without the need for recalibration.

  13. A three-axis SQUID-based absolute vector magnetometer

    SciTech Connect

    Schönau, T.; Schmelz, M.; Stolz, R.; Anders, S.; Linzen, S.; Meyer, H.-G.; Zakosarenko, V.; Meyer, M.

    2015-10-15

    We report on the development of a three-axis absolute vector magnetometer suited for mobile operation in the Earth’s magnetic field. It is based on low critical temperature dc superconducting quantum interference devices (LTS dc SQUIDs) with sub-micrometer sized cross-type Josephson junctions and exhibits a white noise level of about 10 fT/Hz{sup 1/2}. The width of superconducting strip lines is restricted to less than 6 μm in order to avoid flux trapping during cool-down in magnetically unshielded environment. The long-term stability of the flux-to-voltage transfer coefficients of the SQUID electronics is investigated in detail and a method is presented to significantly increase their reproducibility. We further demonstrate the long-term operation of the setup in a magnetic field varying by about 200 μT amplitude without the need for recalibration.

  14. Quantitative standards for absolute linguistic universals.

    PubMed

    Piantadosi, Steven T; Gibson, Edward

    2014-01-01

    Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification.

  15. Robust longitudinal spin-Seebeck effect in Bi-YIG thin films

    PubMed Central

    Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

    2014-01-01

    In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods. PMID:24651124

  16. Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films

    SciTech Connect

    Niizeki, Tomohiko; Kikkawa, Takashi; Uchida, Ken-ichi; Oka, Mineto; Suzuki, Kazuya Z.; Yanagihara, Hideto; Kita, Eiji; Saitoh, Eiji

    2015-05-15

    The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. External-magnetic-field (H) dependence of the LSSE voltage (V{sub LSSE}) in the Pt/CFO(110) sample with H ∥ [001] was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with H∥[11{sup -}0] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of V{sub LSSE} has a linear relationship with the temperature difference (ΔT), giving the relatively large V{sub LSSE} /ΔT of about 3 μV/K for CFO(110) which was kept even at zero external field.

  17. Thermal Modeling and Analysis of a Sub-Compact Seebeck Furnace

    NASA Technical Reports Server (NTRS)

    Wang, Francis C.; Peters, Palmer; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    The Sub-Compact Seebeck Furnace (SCSF) is a third generation furnace designed as an experimental facility to study the phenomena of undercooling associated with directional solidification. It is intended to provide a double peak temperature profile along the axial direction with gradient zones at each end. By keeping the temperature in the central portion above the melting point of the sample, and cooling the ends of the furnace, a solid/liquid (S/L) interface can be maintained in each one of the gradient zones. A motorized motion control provides a motion to one-half of the furnace. The undercooling associated with the interface being directionally solidified can thus be studied. Modeling of the temperature profile is important to help assure that the furnace design provides the correct thermal characteristics. The furnace is designed with two halves that telescope. Results of thermal analysis based on an analytical solution using simple assumptions will be presented. The resulting temperature profile will show the salient features of the desired thermal profile and provide the general directions for thermal design. Experimental results will be used to compare with the analytical profile. Approach for numerical modeling to provide more detailed information such as two-dimensional effects will be discussed.

  18. Subthermal-magnon-driven longitudinal spin Seebeck effect in yttrium iron garnets (YIG)

    NASA Astrophysics Data System (ADS)

    Jin, Hyungyu; Boona, Stephen; Yang, Zihao; Myers, Roberto; Heremans, Joseph

    2015-03-01

    Since its discovery in 2008, the spin Seebeck effect (SSE) has intrigued many interesting research all around the world, which has led to the birth of a new field of research, called ``spin-caloritronics''. Of the two different experimental configurations used for detecting SSE, the longitudinal geometry (LSSE) seems to be generally accepted. The yttrium iron garnet (YIG) / Pt bilayer structure has been most commonly used for LSSE experiments because absence of electrons in YIG excludes contaminations from other thermomagnetic effects. The dependence of the LSSE on YIG film thickness and on temperature have been reported, but not yet both together. Here we present experimental data on the temperature dependence of LSSE in Pt/YIG below room temperature in systems in which the thickness of YIG varies. Detailed discussion is given on the experimental results, with emphasis on the role of subthermal-magnons in the temperature dependence of LSSE in the YIG/Pt system. Work supported by the AFOSR-MURI #FA9550-10-1-0533 and the ARO-MURI #W911NF-14-1-0016.

  19. Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect.

    PubMed

    Tikhonov, Konstantin S; Sinova, Jairo; Finkel'stein, Alexander M

    2013-01-01

    Recently discovered spin-dependent thermoelectric effects have merged spin, charge, and thermal physics, known as spin caloritronics, of which the spin Seebeck effect is its most puzzling. Here we present a theory of this effect driven by subthermal non-local phonon heat transfer and spectral non-uniform temperature. The theory explains its non-local behaviour from the fact that phonons that store the energy (thermal) and the phonons that transfer it (subthermal) are located in different parts of the spectrum and have different kinetics. This gives rise to a spectral phonon distribution that deviates from local equilibrium along the substrate and is sensitive to boundary conditions. The theory also predicts a non-magnon origin of the effect in ferromagnetic metals in agreement with observations in recent experiments. Equilibration of the heat flow from the substrate to the Pt probe and backwards leads to a vertical spin current produced by the spin-polarized electrons dragged by the thermal phonons.

  20. Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states

    NASA Astrophysics Data System (ADS)

    Jiang, Zilong; Chang, Cui-Zu; Masir, Massoud Ramezani; Tang, Chi; Xu, Yadong; Moodera, Jagadeesh S.; MacDonald, Allan H.; Shi, Jing

    2016-05-01

    Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect (SSE), that is, measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (BixSb1-x)2Te3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (BixSb1-x)2Te3 into a bulk insulator, a large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. The enhanced, tunable SSE which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual SSE in metals and therefore opens up exciting possibilities in spintronics.

  1. Surface sensitivity of the spin Seebeck effect in the Pt/YIG system

    NASA Astrophysics Data System (ADS)

    Aqeel, Aisha; Vera-Marun, Ivan J.; van Wees, Bart J.; Palstra, Thomas T. M.

    2015-03-01

    It is well-known that the surface plays an important role in the spin Seebeck effect (SSE). However the effect of mechanical treatment on the SSE has not been systematically studied yet. Here, we have investigated the influence of the interface quality on the SSE in a bilayer system of platinum and yttrium iron garnet (Pt/YIG). The surfaces of the YIG crystals are modified by different types of mechanical polishing before Pt deposition for different samples. We observed that the magnitude and magnetic field dependence of the SSE is strongly influenced by mechanical treatment of the YIG surface. No definite relation has been found between the SSE response and the sample roughness. However, we observe a direct correlation between the saturation magnetic field (Hsat) of the SSE and the roughness of sample, as the former increases by moving from soft toward coarse particle polishing. The change in the magnitude of Hsat can be attributed to the presence of a perpendicular magnetic anisotropy due to the treatment induced surface strain or shape anisotropy in the Pt/YIG system.

  2. Effect of the magnon dispersion on the longitudinal spin Seebeck effect in yttrium iron garnets

    NASA Astrophysics Data System (ADS)

    Jin, Hyungyu; Boona, Stephen R.; Yang, Zihao; Myers, Roberto C.; Heremans, Joseph P.

    2015-08-01

    We study the temperature dependence of the longitudinal spin Seebeck effect (LSSE) in an yttrium iron garnet Y3F e5O12 (YIG)/Pt system for samples of different thicknesses. In this system, the thermal spin torque is magnon driven. The LSSE signal peaks at a specific temperature that depends on the YIG sample thickness. We also observe freeze-out of the LSSE signal at high magnetic fields, which we attribute to the opening of an energy gap in the magnon dispersion. We observe partial freeze-out of the LSSE signal even at room temperature, where kBT is much larger than the gap. This suggests that a subset of the magnon population with an energy below kBTC (TC˜40 K ) contributes disproportionately to the LSSE; at temperatures above TC, we label these magnons subthermal magnons. The T dependence of the LSSE at temperatures below the maximum is interpreted in terms of an empirical model that ascribes most of the temperature dependence to that of the thermally driven magnon flux, which is related to the details of the magnon dispersion.

  3. Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states

    PubMed Central

    Jiang, Zilong; Chang, Cui-Zu; Masir, Massoud Ramezani; Tang, Chi; Xu, Yadong; Moodera, Jagadeesh S.; MacDonald, Allan H.; Shi, Jing

    2016-01-01

    Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect (SSE), that is, measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (BixSb1−x)2Te3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (BixSb1−x)2Te3 into a bulk insulator, a large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. The enhanced, tunable SSE which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual SSE in metals and therefore opens up exciting possibilities in spintronics. PMID:27142594

  4. Robust longitudinal spin-Seebeck effect in Bi-YIG thin films.

    PubMed

    Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

    2014-03-21

    In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods.

  5. Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Niizeki, Tomohiko; Kikkawa, Takashi; Uchida, Ken-ichi; Oka, Mineto; Suzuki, Kazuya Z.; Yanagihara, Hideto; Kita, Eiji; Saitoh, Eiji

    2015-05-01

    The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. External-magnetic-field (H) dependence of the LSSE voltage (VLSSE) in the Pt/CFO(110) sample with H ∥ [001] was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with H ∥ [ 1 1 ¯ 0 ] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of VLSSE has a linear relationship with the temperature difference (ΔT), giving the relatively large VLSSE /ΔT of about 3 μV/K for CFO(110) which was kept even at zero external field.

  6. Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states.

    PubMed

    Jiang, Zilong; Chang, Cui-Zu; Masir, Massoud Ramezani; Tang, Chi; Xu, Yadong; Moodera, Jagadeesh S; MacDonald, Allan H; Shi, Jing

    2016-05-04

    Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect (SSE), that is, measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (BixSb1-x)2Te3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (BixSb1-x)2Te3 into a bulk insulator, a large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. The enhanced, tunable SSE which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual SSE in metals and therefore opens up exciting possibilities in spintronics.

  7. Bulk magnon spin current theory for the longitudinal spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; Rodríguez-Suárez, R. L.; Cunha, R. O.; López Ortiz, J. C.; Azevedo, A.

    2016-02-01

    The longitudinal spin Seebeck effect (LSSE) consists in the generation of a spin current parallel to a temperature gradient applied across the thickness of a bilayer made of a ferromagnetic insulator (FMI), such as yttrium iron garnet (YIG), and a metallic layer (ML) with strong spin orbit coupling, such as platinum. The LSSE is usually detected by a DC voltage generated along the ML due to the conversion of the spin current into a charge current perpendicular to the static magnetic field by means of the inverse spin Hall effect. Here we present a model for the LSSE that relies on the bulk magnon spin current created by the temperature gradient across the thickness of the FMI. We show that the spin current pumped into the metallic layer by the magnon accumulation in the FMI provides continuity of the spin current at the FMI/ML interface and is essential for the existence of the LSSE. The results of the theory are in good agreement with experimental LSSE data in YIG/Pt bilayers on the variation of the DC voltage with the sample temperature, with the FMI layer thickness and with the intensity of high magnetic fields.

  8. Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states

    SciTech Connect

    Jiang, Zilong; Chang, Cui -Zu; Masir, Massoud Ramezani; Tang, Chi; Xu, Yadong; Moodera, Jagadeesh S.; MacDonald, Allan H.; Shi, Jing

    2016-05-04

    Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect (SSE), that is, measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (BixSb1–x)2Te3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (BixSb1–x)2Te3 into a bulk insulator, a large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. Lastly, the enhanced, tunable SSE which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual SSE in metals and therefore opens up exciting possibilities in spintronics.

  9. Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states

    DOE PAGES

    Jiang, Zilong; Chang, Cui -Zu; Masir, Massoud Ramezani; ...

    2016-05-04

    Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect (SSE), that is, measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (BixSb1–x)2Te3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (BixSb1–x)2Te3 into a bulk insulator, amore » large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. Lastly, the enhanced, tunable SSE which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual SSE in metals and therefore opens up exciting possibilities in spintronics.« less

  10. Error analysis in newborn screening: can quotients support the absolute values?

    PubMed

    Arneth, Borros; Hintz, Martin

    2017-03-01

    Newborn screening is performed using modern tandem mass spectrometry, which can simultaneously detect a variety of analytes, including several amino acids and fatty acids. Tandem mass spectrometry measures the diagnostic parameters as absolute concentrations and produces fragments which are used as markers of specific substances. Several prominent quotients can also be derived, which are quotients of two absolute measured concentrations. In this study, we determined the precision of both the absolute concentrations and the derived quotients. First, the measurement error of the absolute concentrations and the measurement error of the ratios were practically determined. Then, the Gaussian theory of error calculation was used. Finally, these errors were compared with one another. The practical analytical accuracies of the quotients were significantly higher (e.g., coefficient of variation (CV) = 5.1% for the phenylalanine to tyrosine (Phe/Tyr) quotient and CV = 5.6% for the Fisher quotient) than the accuracies of the absolute measured concentrations (mean CVs = 12%). According to our results, the ratios are analytically correct and, from an analytical point of view, can support the absolute values in finding the correct diagnosis.

  11. Absolute Distance Measurement with the MSTAR Sensor

    NASA Technical Reports Server (NTRS)

    Lay, Oliver P.; Dubovitsky, Serge; Peters, Robert; Burger, Johan; Ahn, Seh-Won; Steier, William H.; Fetterman, Harrold R.; Chang, Yian

    2003-01-01

    The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beamlaunching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances.

  12. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed.

  13. Comparative vs. Absolute Judgments of Trait Desirability

    ERIC Educational Resources Information Center

    Hofstee, Willem K. B.

    1970-01-01

    Reversals of trait desirability are studied. Terms indicating conservativw behavior appeared to be judged relatively desirable in comparative judgement, while traits indicating dynamic and expansive behavior benefited from absolute judgement. The reversal effect was shown to be a general one, i.e. reversals were not dependent upon the specific…

  14. New Techniques for Absolute Gravity Measurements.

    DTIC Science & Technology

    1983-01-07

    Hammond, J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J. A., and Iliff, R. L. (1979) The AFGL absolute gravity system...International Gravimetric Bureau, No. L:I-43. 7. Hammond. J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J.A., and

  15. An Absolute Electrometer for the Physics Laboratory

    ERIC Educational Resources Information Center

    Straulino, S.; Cartacci, A.

    2009-01-01

    A low-cost, easy-to-use absolute electrometer is presented: two thin metallic plates and an electronic balance, usually available in a laboratory, are used. We report on the very good performance of the device that allows precise measurements of the force acting between two charged plates. (Contains 5 footnotes, 2 tables, and 6 figures.)

  16. Stimulus Probability Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Kent, Christopher; Lamberts, Koen

    2016-01-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…

  17. Absolute Positioning Using the Global Positioning System

    DTIC Science & Technology

    1994-04-01

    Global Positioning System ( GPS ) has becom a useful tool In providing relativ survey...Includes the development of a low cost navigator for wheeled vehicles. ABSTRACT The Global Positioning System ( GPS ) has become a useful tool In providing...technique of absolute or point positioning involves the use of a single Global Positioning System ( GPS ) receiver to determine the three-dimenslonal

  18. Absolute Radiation Thermometry in the NIR

    NASA Astrophysics Data System (ADS)

    Bünger, L.; Taubert, R. D.; Gutschwager, B.; Anhalt, K.; Briaudeau, S.; Sadli, M.

    2017-04-01

    A near infrared (NIR) radiation thermometer (RT) for temperature measurements in the range from 773 K up to 1235 K was characterized and calibrated in terms of the "Mise en Pratique for the definition of the Kelvin" (MeP-K) by measuring its absolute spectral radiance responsivity. Using Planck's law of thermal radiation allows the direct measurement of the thermodynamic temperature independently of any ITS-90 fixed-point. To determine the absolute spectral radiance responsivity of the radiation thermometer in the NIR spectral region, an existing PTB monochromator-based calibration setup was upgraded with a supercontinuum laser system (0.45 μm to 2.4 μm) resulting in a significantly improved signal-to-noise ratio. The RT was characterized with respect to its nonlinearity, size-of-source effect, distance effect, and the consistency of its individual temperature measuring ranges. To further improve the calibration setup, a new tool for the aperture alignment and distance measurement was developed. Furthermore, the diffraction correction as well as the impedance correction of the current-to-voltage converter is considered. The calibration scheme and the corresponding uncertainty budget of the absolute spectral responsivity are presented. A relative standard uncertainty of 0.1 % (k=1) for the absolute spectral radiance responsivity was achieved. The absolute radiometric calibration was validated at four temperature values with respect to the ITS-90 via a variable temperature heatpipe blackbody (773 K ...1235 K) and at a gold fixed-point blackbody radiator (1337.33 K).

  19. Determination of optical absorption coefficient with focusing photoacoustic imaging.

    PubMed

    Li, Zhifang; Li, Hui; Zeng, Zhiping; Xie, Wenming; Chen, Wei R

    2012-06-01

    Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Grüneisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement.

  20. Vacancy filling effect in thermoelectric NbO.

    PubMed

    Music, Denis; Geyer, Richard W; Bliem, Pascal; Hans, Marcus; Primetzhofer, Daniel

    2015-03-25

    Using density functional theory, we have systematically explored the 1a and 1b vacancy filling in NbO (space group Pm-3m) with Nb and N, respectively, to design compounds with large Seebeck coefficients. The most dominating effect was identified for filling of 1b Wyckoff sites with N giving rise to a fivefold increase in the Seebeck coefficient. This may be understood based on the electronic structure. Nb d-nonmetal p hybridization induces quantum confinement and hence enables the enhancement of the Seebeck coefficient. This was validated by measuring the Seebeck coefficient of reactively sputtered thin films. At 800 °C these electrically conductive oxynitrides exhibit the Seebeck coefficient of -70 µV K(-1), which is the largest absolute value ever reported for these compounds.

  1. Weighted Wilcoxon-type Smoothly Clipped Absolute Deviation Method

    PubMed Central

    Wang, Lan; Li, Runze

    2009-01-01

    Summary Shrinkage-type variable selection procedures have recently seen increasing applications in biomedical research. However, their performance can be adversely influenced by outliers in either the response or the covariate space. This paper proposes a weighted Wilcoxon-type smoothly clipped absolute deviation (WW-SCAD) method, which deals with robust variable selection and robust estimation simultaneously. The new procedure can be conveniently implemented with the statistical software R. We establish that the WW-SCAD correctly identifies the set of zero coefficients with probability approaching one and estimates the nonzero coefficients with the rate n−1/2. Moreover, with appropriately chosen weights the WW-SCAD is robust with respect to outliers in both the x and y directions. The important special case with constant weights yields an oracle-type estimator with high efficiency at the presence of heavier-tailed random errors. The robustness of the WW-SCAD is partly justified by its asymptotic performance under local shrinking contamination. We propose a BIC-type tuning parameter selector for the WW-SCAD. The performance of the WW-SCAD is demonstrated via simulations and by an application to a study that investigates the effects of personal characteristics and dietary factors on plasma beta-carotene level. PMID:18647294

  2. Optical absorption coefficients of pure water

    NASA Astrophysics Data System (ADS)

    Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.

    2002-10-01

    The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.

  3. High Accuracy, Absolute, Cryogenic Refractive Index Measurements of Infrared Lens Materials for JWST NIRCam using CHARMS

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas; Frey, Bradley

    2005-01-01

    The current refractive optical design of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) uses three infrared materials in its lenses: LiF, BaF2, and ZnSe. In order to provide the instrument s optical designers with accurate, heretofore unavailable data for absolute refractive index based on actual cryogenic measurements, two prismatic samples of each material were measured using the cryogenic, high accuracy, refraction measuring system (CHARMS) at NASA GSFC, densely covering the temperature range from 15 to 320 K and wavelength range from 0.4 to 5.6 microns. Measurement methods are discussed and graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient for these three materials are presented along with estimates of uncertainty. Coefficients for second order polynomial fits of measured index to temperature are provided for many wavelengths to allow accurate interpolation of index to other wavelengths and temperatures.

  4. Quantifying colocalization by correlation: the Pearson correlation coefficient is superior to the Mander's overlap coefficient.

    PubMed

    Adler, Jeremy; Parmryd, Ingela

    2010-08-01

    The Pearson correlation coefficient (PCC) and the Mander's overlap coefficient (MOC) are used to quantify the degree of colocalization between fluorophores. The MOC was introduced to overcome perceived problems with the PCC. The two coefficients are mathematically similar, differing in the use of either the absolute intensities (MOC) or of the deviation from the mean (PCC). A range of correlated datasets, which extend to the limits of the PCC, only evoked a limited response from the MOC. The PCC is unaffected by changes to the offset while the MOC increases when the offset is positive. Both coefficients are independent of gain. The MOC is a confusing hybrid measurement, that combines correlation with a heavily weighted form of co-occurrence, favors high intensity combinations, downplays combinations in which either or both intensities are low and ignores blank pixels. The PCC only measures correlation. A surprising finding was that the addition of a second uncorrelated population can substantially increase the measured correlation, demonstrating the importance of excluding background pixels. Overall, since the MOC is unresponsive to substantial changes in the data and is hard to interpret, it is neither an alternative to nor a useful substitute for the PCC. The MOC is not suitable for making measurements of colocalization either by correlation or co-occurrence.

  5. The dynamic control ratio at the equilibrium point (DCRe): introducing relative and absolute reliability scores.

    PubMed

    Alt, Tobias; Knicker, Axel J; Strüder, Heiko K

    2017-04-01

    Analytical methods to assess thigh muscle balance need to provide reliable data to allow meaningful interpretation. However, reproducibility of the dynamic control ratio at the equilibrium point has not been evaluated yet. Therefore, the aim of this study was to compare relative and absolute reliability indices of its angle and moment values with conventional and functional hamstring-quadriceps ratios. Furthermore, effects of familiarisation and angular velocity on reproducibility were analysed. A number of 33 male volunteers participated in 3 identical test sessions. Peak moments (PMs) were determined unilaterally during maximum concentric and eccentric knee flexion (prone) and extension (supine position) at 0.53, 1.57 and 2.62 rad · s(-1). A repeated measure, ANOVA, confirmed systematic bias. Intra-class correlation coefficients and standard errors of measurement indicated relative and absolute reliability. Correlation coefficients were averaged over respective factors and tested for significant differences. All balance scores showed comparable low-to-moderate relative (<0.8-0.9) and good absolute reliability (<10%). Relative reproducibility of dynamic control equilibrium parameters augmented with increasing angular velocity, but not with familiarisation. At 2.62 rad · s(-1), high (moment: 0.906) to moderate (angle: 0.833) relative reliability scores with accordingly high absolute indices (4.9% and 6.4%) became apparent. Thus, the dynamic control equilibrium is an equivalent method for the reliable assessment of thigh muscle balance.

  6. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  7. Consistent thermostatistics forbids negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Dunkel, Jörn; Hilbert, Stefan

    2014-01-01

    Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to speculation that ultracold gases may be dark-energy analogues and also suggests the feasibility of heat engines with efficiencies larger than one. Here, we prove that all previous negative temperature claims and their implications are invalid as they arise from the use of an entropy definition that is inconsistent both mathematically and thermodynamically. We show that the underlying conceptual deficiencies can be overcome if one adopts a microcanonical entropy functional originally derived by Gibbs. The resulting thermodynamic framework is self-consistent and implies that absolute temperature remains positive even for systems with a bounded spectrum. In addition, we propose a minimal quantum thermometer that can be implemented with available experimental techniques.

  8. Absolute measurement of length with nanometric resolution

    NASA Astrophysics Data System (ADS)

    Apostol, D.; Garoi, F.; Timcu, A.; Damian, V.; Logofatu, P. C.; Nascov, V.

    2005-08-01

    Laser interferometer displacement measuring transducers have a well-defined traceability route to the definition of the meter. The laser interferometer is de-facto length scale for applications in micro and nano technologies. However their physical unit -half lambda is too large for nanometric resolution. Fringe interpolation-usual technique to improve the resolution-lack of reproducibility could be avoided using the principles of absolute distance measurement. Absolute distance refers to the use of interferometric techniques for determining the position of an object without the necessity of measuring continuous displacements between points. The interference pattern as produced by the interference of two point-like coherent sources is fitted to a geometric model so as to determine the longitudinal location of the target by minimizing least square errors. The longitudinal coordinate of the target was measured with accuracy better than 1 nm, for a target position range of 0.4μm.

  9. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  10. Computer processing of spectrograms for absolute intensities.

    PubMed

    Guttman, A; Golden, J; Galbraith, H J

    1967-09-01

    A computer program was developed to process photographically recorded spectra for absolute intensity. Test and calibration films are subjected to densitometric scans that provide digitally recorded densities on magnetic tapes. The nonlinear calibration data are fitted by least-squares cubic polynomials to yield a good approximation to the monochromatic H&D curves for commonly used emulsions (2475 recording film, Royal-X, Tri-X, 4-X). Several test cases were made. Results of these cases show that the machine processed absolute intensities are accurate to within 15%o. Arbitrarily raising the sensitivity threshold by 0.1 density units above gross fog yields cubic polynomial fits to the H&D curves that are radiometrically accurate within 10%. In addition, curves of gamma vs wavelength for 2475, Tri-X, and 4-X emulsions were made. These data show slight evidence of the photographic Purkinje effect in the 2475 emulsion.

  11. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  12. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum.

  13. Absolute and relative dosimetry for ELIMED

    NASA Astrophysics Data System (ADS)

    Cirrone, G. A. P.; Cuttone, G.; Candiano, G.; Carpinelli, M.; Leonora, E.; Lo Presti, D.; Musumarra, A.; Pisciotta, P.; Raffaele, L.; Randazzo, N.; Romano, F.; Schillaci, F.; Scuderi, V.; Tramontana, A.; Cirio, R.; Marchetto, F.; Sacchi, R.; Giordanengo, S.; Monaco, V.

    2013-07-01

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  14. Silicon Absolute X-Ray Detectors

    SciTech Connect

    Seely, John F.; Korde, Raj; Sprunck, Jacob; Medjoubi, Kadda; Hustache, Stephanie

    2010-06-23

    The responsivity of silicon photodiodes having no loss in the entrance window, measured using synchrotron radiation in the 1.75 to 60 keV range, was compared to the responsivity calculated using the silicon thickness measured using near-infrared light. The measured and calculated responsivities agree with an average difference of 1.3%. This enables their use as absolute x-ray detectors.

  15. Study of Thermocurrents in ILC cavities via measurements of the Seebeck Effect in niobium, titanium, and stainless steel thermocouples

    SciTech Connect

    Cooley, Victoria

    2014-01-01

    The goals of Fermilab’s Superconductivity and Radio Frequency Development Department are to engineer, fabricate, and improve superconducting radio frequency (SCRF) cavities in the interest of advancing accelerator technology. Improvement includes exploring possible limitations on cavity performance and mitigating such impediments. This report focuses on investigating and measuring the Seebeck Effect observed in cavity constituents titanium, niobium, and stainless steel arranged in thermocouples. These junctions exist between cavities, helium jackets, and bellows, and their connection can produce a loop of electrical current and magnetic flux spontaneously during cooling. The experimental procedure and results are described and analyzed. Implications relating the results to cavity performance are discussed.

  16. Spin Seebeck effect and spin Hall magnetoresistance at high temperatures for a Pt/yttrium iron garnet hybrid structure

    NASA Astrophysics Data System (ADS)

    Wang, Shuanhu; Zou, Lvkuan; Zhang, Xu; Cai, Jianwang; Wang, Shufang; Shen, Baogen; Sun, Jirong

    2015-10-01

    Based on unique experimental setups, the temperature dependences of the longitudinal spin Seebeck effect (LSSE) and spin Hall magnetoresistance (SMR) of the Pt/yttrium iron garnet (Pt/YIG) hybrid structure are determined in a wide temperature range up to the Curie temperature of YIG. From a theoretical analysis of the experimental relationship between the SMR and temperature, the spin mixing conductance of the Pt/YIG interface is deduced as a function of temperature. Adopting the deduced spin mixing conductance, the temperature dependence of the LSSE is well reproduced based on the magnon spin current theory. Our research sheds new light on the controversy about the theoretical models for the LSSE.

  17. Spin Seebeck effect and spin Hall magnetoresistance at high temperatures for a Pt/yttrium iron garnet hybrid structure.

    PubMed

    Wang, Shuanhu; Zou, Lvkuan; Zhang, Xu; Cai, Jianwang; Wang, Shufang; Shen, Baogen; Sun, Jirong

    2015-11-14

    Based on unique experimental setups, the temperature dependences of the longitudinal spin Seebeck effect (LSSE) and spin Hall magnetoresistance (SMR) of the Pt/yttrium iron garnet (Pt/YIG) hybrid structure are determined in a wide temperature range up to the Curie temperature of YIG. From a theoretical analysis of the experimental relationship between the SMR and temperature, the spin mixing conductance of the Pt/YIG interface is deduced as a function of temperature. Adopting the deduced spin mixing conductance, the temperature dependence of the LSSE is well reproduced based on the magnon spin current theory. Our research sheds new light on the controversy about the theoretical models for the LSSE.

  18. Investigation of the off-diagonal Seebeck effect and Peltier effect on textured YBa 2Cu 3O 7-δ

    NASA Astrophysics Data System (ADS)

    He, Z. H.; Zhong, F. Q.; Luo, Y. Y.; Wu, M.; Gavalek, W.; Liang, K. F.; Fung, P. C. W.

    1997-08-01

    Both of the off-diagonal Seebeck effect and the off-diagonal Peltier effect were investigated with the use of the same textured sample YBa 2Cu 3O 7-δ (Y-123) and the same experimental setup. The reliability of the measurement is studied by applying different heat-conductive mediums. The flatness of both of the sample and the heat-conducting block, and the matching between them are found very important for the reduction of the heat resistance. The annealing effect on the Sxz is also studied and found in accordance with that studied by the thermoelectric power.

  19. Negative absolute temperature for mobile particles

    NASA Astrophysics Data System (ADS)

    Braun, Simon; Ronzheimer, Philipp; Schreiber, Michael; Hodgman, Sean; Bloch, Immanuel; Schneider, Ulrich

    2013-05-01

    Absolute temperature is usually bound to be strictly positive. However, negative absolute temperature states, where the occupation probability of states increases with their energy, are possible in systems with an upper energy bound. So far, such states have only been demonstrated in localized spin systems with finite, discrete spectra. We realized a negative absolute temperature state for motional degrees of freedom with ultracold bosonic 39K atoms in an optical lattice, by implementing the attractive Bose-Hubbard Hamiltonian. This new state strikingly revealed itself by a quasimomentum distribution that is peaked at maximum kinetic energy. The measured kinetic energy distribution and the extracted negative temperature indicate that the ensemble is close to degeneracy, with coherence over several lattice sites. The state is as stable as a corresponding positive temperature state: The negative temperature stabilizes the system against mean-field collapse driven by negative pressure. Negative temperatures open up new parameter regimes for cold atoms, enabling fundamentally new many-body states. Additionally, they give rise to several counterintuitive effects such as heat engines with above unity efficiency.

  20. Measurement of absolute gravity acceleration in Firenze

    NASA Astrophysics Data System (ADS)

    de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.

    2011-01-01

    This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0) μGal and (980 492 048.3 ± 3.0) μGal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.

  1. System for absolute measurements by interferometric sensors

    NASA Astrophysics Data System (ADS)

    Norton, Douglas A.

    1993-03-01

    The most common problem of interferometric sensors is their inability to measure absolute path imbalance. Presented in this paper is a signal processing system that gives absolute, unambiguous reading of optical path difference for almost any style of interferometric sensor. Key components are a wide band (incoherent) optical source, a polychromator, and FFT electronics. Advantages include no moving parts in the signal processor, no active components at the sensor location, and the use of standard single mode fiber for sensor illumination and signal transmission. Actual absolute path imbalance of the interferometer is determined without using fringe counting or other inferential techniques. The polychromator extracts the interference information that occurs at each discrete wavelength within the spectral band of the optical source. The signal processing consists of analog and digital filtering, Fast Fourier analysis, and a peak detection and interpolation algorithm. This system was originally designed for use in a remote pressure sensing application that employed a totally passive fiber optic interferometer. A performance qualification was made using a Fabry-Perot interferometer and a commercially available laser interferometer to measure the reference displacement.

  2. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.

  3. Constrained Least Absolute Deviation Neural Networks

    PubMed Central

    Wang, Zhishun; Peterson, Bradley S.

    2008-01-01

    It is well known that least absolute deviation (LAD) criterion or L1-norm used for estimation of parameters is characterized by robustness, i.e., the estimated parameters are totally resistant (insensitive) to large changes in the sampled data. This is an extremely useful feature, especially, when the sampled data are known to be contaminated by occasionally occurring outliers or by spiky noise. In our previous works, we have proposed the least absolute deviation neural network (LADNN) to solve unconstrained LAD problems. The theoretical proofs and numerical simulations have shown that the LADNN is Lyapunov-stable and it can globally converge to the exact solution to a given unconstrained LAD problem. We have also demonstrated its excellent application value in time-delay estimation. More generally, a practical LAD application problem may contain some linear constraints, such as a set of equalities and/or inequalities, which is called constrained LAD problem, whereas the unconstrained LAD can be considered as a special form of the constrained LAD. In this paper, we present a new neural network called constrained least absolute deviation neural network (CLADNN) to solve general constrained LAD problems. Theoretical proofs and numerical simulations demonstrate that the proposed CLADNN is Lyapunov stable and globally converges to the exact solution to a given constrained LAD problem, independent of initial values. The numerical simulations have also illustrated that the proposed CLADNN can be used to robustly estimate parameters for nonlinear curve fitting, which is extensively used in signal and image processing. PMID:18269958

  4. Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor

    PubMed Central

    Ponzoni, Flávio Jorge; Albuquerque, Bráulio Fonseca Carneiro

    2008-01-01

    Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community. PMID:27873886

  5. Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor.

    PubMed

    Ponzoni, Flávio Jorge; Albuquerque, Bráulio Fonseca Carneiro

    2008-10-23

    Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community.

  6. Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Frey, Bradley J.

    2006-01-01

    Using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have measured the absolute refractive index of five specimens taken from a very large boule of Corning 7980 fused silica from temperatures ranging from 30 to 310 K at wavelengths from 0.4 to 2.6 microns with an absolute uncertainty of plus or minus 1 x 10 (exp -5). Statistical variations in derived values of the thermo-optic coefficient (dn/dT) are at the plus or minus 2 x 10 (exp -8)/K level. Graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient are presented for selected wavelengths and temperatures along with estimates of uncertainty in index. Coefficients for temperature-dependent Sellmeier fits of measured refractive index are also presented to allow accurate interpolation of index to other wavelengths and temperatures. We compare our results to those from an independent investigation (which used an interferometric technique for measuring index changes as a function of temperature) whose samples were prepared from the same slugs of material from which our prisms were prepared in support of the Kepler mission. We also compare our results with sparse cryogenic index data from measurements of this material from the literature.

  7. Absolute bioavailability and absorption characteristics of divalproex sodium extended-release tablets in healthy volunteers.

    PubMed

    Dutta, Sandeep; Reed, Ronald C; Cavanaugh, John H

    2004-07-01

    Conventional delayed-release, enteric-coated divalproex sodium tablet has an absolute bioavailability of approximately 100%. Divalproex sodium extended-release (ER) tablet is a novel formulation of valproic acid (VPA) designed to release the drug slowly at a constant zero-order rate. The purpose of this study was to evaluate the absolute bioavailability and absorption characteristics of divalproex ER. Healthy adult volunteers (n = 16) received divalproex ER and intravenous VPA in crossover fashion. Absolute bioavailability was calculated as the divalproex ER/intravenous VPA ratio of area under the curve extrapolated to infinity. The duration and rate of absorption of VPA from divalproex ER tablets were determined by deconvolution analysis. The geometric mean absolute bioavailability of divalproex ER was 0.896. The mean (coefficient of variation) duration of drug absorption from divalproex ER was 21.8 (17%) hours, and the zero-order absorption rate was 21.6 (24%) mg/h for a 500-mg tablet. Divalproex ER has a lower absolute bioavailability than conventional divalproex tablets but exhibits good extended-release characteristics without any dose dumping.

  8. Zonal and tesseral harmonic coefficients for the geopotential function, from zero to 18th order

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, J. C.

    1976-01-01

    Zonal and tesseral harmonic coefficients for the geopotential function are usually tabulated in normalized form to provide immediate information as to the relative significance of the coefficients in the gravity model. The normalized form of the geopotential coefficients cannot be used for computational purposes unless the gravity model has been modified to receive them. This modification is usually not done because the absolute or unnormalized form of the coefficients can be obtained from the simple mathematical relationship that relates the two forms. This computation can be quite tedious for hand calculation, especially for the higher order terms, and can be costly in terms of storage and execution time for machine computation. In this report, zonal and tesseral harmonic coefficients for the geopotential function are tabulated in absolute or unnormalized form. The report is designed to be used as a ready reference for both hand and machine calculation to save the user time and effort.

  9. Maximum entropy analytic continuation for frequency-dependent transport coefficients with nonpositive spectral weight

    NASA Astrophysics Data System (ADS)

    Reymbaut, A.; Gagnon, A.-M.; Bergeron, D.; Tremblay, A.-M. S.

    2017-03-01

    The computation of transport coefficients, even in linear response, is a major challenge for theoretical methods that rely on analytic continuation of correlation functions obtained numerically in Matsubara space. While maximum entropy methods can be used for certain correlation functions, this is not possible in general, important examples being the Seebeck, Hall, Nernst, and Reggi-Leduc coefficients. Indeed, positivity of the spectral weight on the positive real-frequency axis is not guaranteed in these cases. The spectral weight can even be complex in the presence of broken time-reversal symmetry. Various workarounds, such as the neglect of vertex corrections or the study of the infinite frequency or Kelvin limits, have been proposed. Here, we show that one can define auxiliary response functions that allow one to extract the desired real-frequency susceptibilities from maximum entropy methods in the most general multiorbital cases with no particular symmetry. As a benchmark case, we study the longitudinal thermoelectric response and corresponding Onsager coefficient in the single-band two-dimensional Hubbard model treated with dynamical mean-field theory and continuous-time quantum Monte Carlo. We thereby extend the maximum entropy analytic continuation with auxiliary functions (MaxEntAux method), developed for the study of the superconducting pairing dynamics of correlated materials, to transport coefficients.

  10. Absolute calibration of the EnviSat-1 radar altimeter

    NASA Astrophysics Data System (ADS)

    Roca, Monica; Francis, Richard

    1998-12-01

    The EnviSat-1 satellite will embark an innovative radar altimeter. The calibration of the measurements of range from this instrument will be performed using novel techniques. The range measurement will be calibrated absolutely by establishing the actual geocentric sea-level along the sub- satellite tracks. These tracks are located in a limited and well-controlled region in the western Mediterranean and will include a number of fully-equipped individual sites which will provide higher confidence in the overall analysis, combined with data from the whole area at lower weight. The determination of the geocentric sea-level is performed using tide gauges and geodetic means such as leveling and floating GPS receivers. The altimeter sea-level is derived from the altimeter range corrected for propagation effects and sea- state bias, and a precise restitution of the trajectory of the satellite. These measurements comprise three vectors: range, orbital height and sea-surface height. The difference between orbital-height minus range, and sea-surface height provides the bias. The backscatter coefficient measured by previous altimeters has not been absolutely calibrated. An emerging application of the RA-2 in investigation of surface properties has identified the need to perform this calibration. A number of techniques are under study to determine the feasibility of meeting this need, including the use of well-controlled natural targets, the use of the altimeter receiver as a passive radiometer in order to determine its gain and the use of a transponder to return a precisely known return echo power to the radar.

  11. Unambiguous separation of the inverse spin Hall and anomalous Nernst effects within a ferromagnetic metal using the spin Seebeck effect

    SciTech Connect

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

    2014-09-01

    The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe{sub 3}O{sub 4} with the ferromagnetic metal Co{sub 0.2}Fe{sub 0.6}B{sub 0.2} (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), it is possible to decouple the two ferromagnetic materials and directly observe pure spin flow from Fe{sub 3}O{sub 4} into CoFeB. It is shown that in a single ferromagnetic metal, the inverse spin Hall effect (ISHE) and anomalous Nernst effect (ANE) can occur simultaneously with opposite polarity. Using this and the large difference in the coercive fields between the two magnets, it is possible to unambiguously separate the contributions of the spin Seebeck effect from the ANE and observe the degree to which each effect contributes to the total response. These experiments show conclusively that the ISHE and ANE in CoFeB are separate phenomena with different origins and can coexist in the same material with opposite response to a thermal gradient.

  12. Investigation of the timescale of the spin-Seebeck effect in yttrium iron garnet from pico to nanoseconds

    NASA Astrophysics Data System (ADS)

    Jamison, John; Yang, Zihao; Myers, Roberto

    We investigate the timescale of the spin-Seebeck effect (SSE) in yttrium iron garnet (YIG) by exciting transient thermal gradients with 150-fs laser heating pulses. The transient thermal gradient generates a spin current which is measured by a Pt top contact via the inverse spin Hall-effect (ISHE). A pulse selection system is used to lower the repetition rate of the laser to low frequencies (e.g. 10 kHz) such that the transient thermal gradient decays completely before the arrival of the next pulse. Lock-in detection, referenced at the laser repetition rate, is used to measure ISHE as a function of magnetic field, verifying that SSE is generated from the individual ultrafast laser pulses. Next, utilizing an optical delay line we vary the time delay between two equal fluence pulses. The correlated ISHE signal is measured with lock-in detection as a function of delay time with 0.1 ps resolution out to 1 ns to examine the characteristic decay times of the ultrafast laser pulse induced spin-Seebeck effect. Work supported by ARO MURI W911NF-14-1-0016.

  13. Temperature dependences of magnetic anisotropy and longitudinal spin Seebeck effect in Y3Fe5O12

    NASA Astrophysics Data System (ADS)

    Kalappattil, Vijaysankar; Das, Raja; Phan, Manh-Huong; Srikanth, Hariharan

    Spin caloritronics is an emerging, exciting research area in condensed matter owing to its potential use in advanced spintronics devices. Pure spin current without having charge current has been achieved though spin Seebeck effect (SSE). Over the last 7 years SSE has been observed in ferromagnetic metals, insulators, and semiconductors using longitudinal and transverse SSE measurement configurations. In this work, we have carried out an experimental study to understand the effect of magnetic anisotropy on the temperature evolution of longitudinal spin Seebeck effect (LSSE) in a single crystalline yttrium iron garnet (YIG). The effective anisotropy field (HK) and inverse spin Hall (ISH) voltage (VISH) were measured using the radio-frequency transverse susceptibility (TS) and LSSE configuration, respectively. The VISH of a 15 nm Pt strip on (6*2*1 mm) YIG slab with a temperature gradient of 3 K was measured in the temperature range of 120 to 300 K. The observed values of VISH vary from 1 microV for 120 K to 0.5 microV for 300 K, These values fall into the previously reported theoretical and experimental results. The temperature evolution of HKhas been compared with that of VISH to gain better fundamental understanding. Work is supported by ARO through Grant No. W911NF-15-1-0626.

  14. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  15. Absolute Radiometric Calibration of EUNIS-06

    NASA Technical Reports Server (NTRS)

    Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

    2007-01-01

    The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

  16. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  17. Brownian motion: Absolute negative particle mobility

    NASA Astrophysics Data System (ADS)

    Ros, Alexandra; Eichhorn, Ralf; Regtmeier, Jan; Duong, Thanh Tu; Reimann, Peter; Anselmetti, Dario

    2005-08-01

    Noise effects in technological applications, far from being a nuisance, can be exploited with advantage - for example, unavoidable thermal fluctuations have found application in the transport and sorting of colloidal particles and biomolecules. Here we use a microfluidic system to demonstrate a paradoxical migration mechanism in which particles always move in a direction opposite to the net acting force (`absolute negative mobility') as a result of an interplay between thermal noise, a periodic and symmetric microstructure, and a biased alternating-current electric field. This counterintuitive phenomenon could be used for bioanalytical purposes, for example in the separation and fractionation of colloids, biological molecules and cells.

  18. Arbitrary segments of absolute negative mobility

    NASA Astrophysics Data System (ADS)

    Chen, Ruyin; Nie, Linru; Chen, Chongyang; Wang, Chaojie

    2017-01-01

    In previous research work, investigators have reported only one or two segments of absolute negative mobility (ANM) in a periodic potential. In fact, many segments of ANM also occur in the system considered here. We investigate transport of an inertial particle in a gating ratchet periodic potential subjected to a constant bias force. Our numerical results show that its mean velocity can decrease with the bias force increasing, i.e. ANM phenomenon. Furthermore, the ANM can take place arbitrary segments, even up to more than thirty. Intrinsic physical mechanism and conditions for arbitrary segments of ANM to occur are discussed in detail.

  19. Absolute quantification of myocardial blood flow.

    PubMed

    Yoshinaga, Keiichiro; Manabe, Osamu; Tamaki, Nagara

    2016-07-21

    With the increasing availability of positron emission tomography (PET) myocardial perfusion imaging, the absolute quantification of myocardial blood flow (MBF) has become popular in clinical settings. Quantitative MBF provides an important additional diagnostic or prognostic information over conventional visual assessment. The success of MBF quantification using PET/computed tomography (CT) has increased the demand for this quantitative diagnostic approach to be more accessible. In this regard, MBF quantification approaches have been developed using several other diagnostic imaging modalities including single-photon emission computed tomography, CT, and cardiac magnetic resonance. This review will address the clinical aspects of PET MBF quantification and the new approaches to MBF quantification.

  20. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  1. Absolute Rate Theories of Epigenetic Stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, Jose N.; Wolynes, Peter G.

    2006-03-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape, and the transmission factor, depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic and strictly adiabatic regimes, characterized by the relative values of those input rates.

  2. Absolute rate theories of epigenetic stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, José N.; Wolynes, Peter G.

    2005-12-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic, and strictly adiabatic regimes, characterized by the relative values of those input rates. rate theory | stochastic gene expression | gene switches

  3. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  4. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  5. Ozone absorption coefficients' role in Dobson instrument ozone measurement accuracy

    NASA Astrophysics Data System (ADS)

    Basher, R. E.

    1982-11-01

    The differences of 10% or more between the laboratory measurements of UV absorption coefficients by different investigators indicate accuracies that are quite inadequate for current needs in the measurement of atmospheric ozone. The standard band-integrated set of coefficients now used with the Dobson instrument are mutually consistent to about 2%, but their absolute accuracy is still in question. The accurate calculation of band-integrated coefficients must take account of their dependence on source spectral irradiance, atmospheric spectral transmittance, mean ozone temperature, and instrument spectral transmittance. A careful examination shows that Komhyr's (1980) case for an error of about +5% in the standard Dobson AD ozone estimation is subject to large uncertainties and certain lacks of independence. The obvious solution to this accuracy problem lies in better laboratory measurements of ozone absorption.

  6. On determination of sign of the piezo-optic coefficients using torsion method.

    PubMed

    Vasylkiv, Yurij; Savaryn, Viktoriya; Smaga, Ihor; Skab, Ihor; Vlokh, Rostyslav

    2011-06-10

    We have shown that a high-accuracy torsion method recently developed by the authors for measuring piezo-optic coefficients allows determining not only the absolute value of the coefficients but also their sign. The techniques and experimental procedures used for determination of the sign are described in detail and proven based on studies of α-BaB2O4 and LiNbO3 crystals. The piezo-optic coefficients are determined for both crystals, and a combination of the corresponding photoelastic coefficients is determined for the case of α-BaB2O4 crystals.

  7. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  8. Linear ultrasonic motor for absolute gravimeter.

    PubMed

    Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

    2017-02-01

    Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters.

  9. Why to compare absolute numbers of mitochondria.

    PubMed

    Schmitt, Sabine; Schulz, Sabine; Schropp, Eva-Maria; Eberhagen, Carola; Simmons, Alisha; Beisker, Wolfgang; Aichler, Michaela; Zischka, Hans

    2014-11-01

    Prompted by pronounced structural differences between rat liver and rat hepatocellular carcinoma mitochondria, we suspected these mitochondrial populations to differ massively in their molecular composition. Aiming to reveal these mitochondrial differences, we came across the issue on how to normalize such comparisons and decided to focus on the absolute number of mitochondria. To this end, fluorescently stained mitochondria were quantified by flow cytometry. For rat liver mitochondria, this approach resulted in mitochondrial protein contents comparable to earlier reports using alternative methods. We determined similar protein contents for rat liver, heart and kidney mitochondria. In contrast, however, lower protein contents were determined for rat brain mitochondria and for mitochondria from the rat hepatocellular carcinoma cell line McA 7777. This result challenges mitochondrial comparisons that rely on equal protein amounts as a typical normalization method. Exemplarily, we therefore compared the activity and susceptibility toward inhibition of complex II of rat liver and hepatocellular carcinoma mitochondria and obtained significant discrepancies by either normalizing to protein amount or to absolute mitochondrial number. Importantly, the latter normalization, in contrast to the former, demonstrated a lower complex II activity and higher susceptibility toward inhibition in hepatocellular carcinoma mitochondria compared to liver mitochondria. These findings demonstrate that solely normalizing to protein amount may obscure essential molecular differences between mitochondrial populations.

  10. The absolute threshold of cone vision

    PubMed Central

    Koeing, Darran; Hofer, Heidi

    2013-01-01

    We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1′ fwhm), brief (34 msec), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 ± 38 photons at the cornea, ∼0.47 log units lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

  11. [Estimation of absolute risk for fracture].

    PubMed

    Fujiwara, Saeko

    2009-03-01

    Osteoporosis treatment aims to prevent fractures and maintain the QOL of the elderly. However, persons at high risk of future fracture cannot be effectively identified on the basis of bone density (BMD) alone, although BMD is used as an diagnostic criterion. Therefore, the WHO recommended that absolute risk for fracture (10-year probability of fracture) for each individual be evaluated and used as an index for intervention threshold. The 10-year probability of fracture is calculated based on age, sex, BMD at the femoral neck (body mass index if BMD is not available), history of previous fractures, parental hip fracture history, smoking, steroid use, rheumatoid arthritis, secondary osteoporosis and alcohol consumption. The WHO has just announced the development of a calculation tool (FRAX: WHO Fracture Risk Assessment Tool) in February this year. Fractures could be prevented more effectively if, based on each country's medical circumstances, an absolute risk value for fracture to determine when to start medical treatment is established and persons at high risk of fracture are identified and treated accordingly.

  12. Absolute stereochemistry of altersolanol A and alterporriols.

    PubMed

    Kanamaru, Saki; Honma, Miho; Murakami, Takanori; Tsushima, Taro; Kudo, Shinji; Tanaka, Kazuaki; Nihei, Ken-Ichi; Nehira, Tatsuo; Hashimoto, Masaru

    2012-02-01

    The absolute stereochemistry of altersolanol A (1) was established by observing a positive exciton couplet in the circular dichroism (CD) spectrum of the C3,C4-O-bis(2-naphthoyl) derivative 10 and by chemical correlations with known compound 8. Before the discussion, the relative stereochemistry of 1 was confirmed by X-ray crystallographic analysis. The shielding effect at C7'-OMe group by C1-O-benzoylation established the relative stereochemical relationship between the C8-C8' axial bonding and the C1-C4/C1'-C4' polyol moieties of alterporriols E (3), an atropisomer of the C8-C8' dimer of 1. As 3 could be obtained by dimerization of 1 in vitro, the absolute configuration of its central chirality elements (C1-C4) must be identical to those of 1. Spectral comparison between the experimental and theoretical CD spectra supported the above conclusion. Axial stereochemistry of novel C4-O-deoxy dimeric derivatives, alterporriols F (4) and G (5), were also revealed by comparison of their CD spectra to those of 2 and 3.

  13. Absolute Electron Extraction Efficiency of Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter

    2016-03-01

    Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.

  14. Standardization of the cumulative absolute velocity

    SciTech Connect

    O'Hara, T.F.; Jacobson, J.P. )

    1991-12-01

    EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

  15. Swarm's Absolute Scalar Magnetometers Burst Mode Results

    NASA Astrophysics Data System (ADS)

    Coisson, P.; Vigneron, P.; Hulot, G.; Crespo Grau, R.; Brocco, L.; Lalanne, X.; Sirol, O.; Leger, J. M.; Jager, T.; Bertrand, F.; Boness, A.; Fratter, I.

    2014-12-01

    Each of the three Swarm satellites embarks an Absolute Scalar Magnetometer (ASM) to provide absolute scalar measurements of the magnetic field with high accuracy and stability. Nominal data acquisition of these ASMs is 1 Hz. But they can also run in a so-called "burst mode" and provide data at 250 Hz. During the commissioning phase of the mission, seven burst mode acquisition campaigns have been run simultaneously for all satellites, obtaining a total of ten days of burs-mode data. These campaigns allowed the identification of issues related to the operations of the piezo-electric motor and the heaters connected to the ASM, that do not impact the nominal 1 Hz scalar data. We analyze the burst mode data to identify high frequency geomagnetic signals, focusing the analysis in two regions: the low latitudes, where we seek signatures of ionospheric irregularities, and the high latitudes, to identify high frequency signals related to polar region currents. Since these campaigns have been conducted during the initial months of the mission, the three satellites where still close to each other, allowing to analyze the spatial coherency of the signals. Wavelet analysis have revealed 31 Hz signals appearing in the night-side in the equatorial region.

  16. Coefficient Alpha: A Reliability Coefficient for the 21st Century?

    ERIC Educational Resources Information Center

    Yang, Yanyun; Green, Samuel B.

    2011-01-01

    Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…

  17. Extracting infrared absolute reflectance from relative reflectance measurements.

    PubMed

    Berets, Susan L; Milosevic, Milan

    2012-06-01

    Absolute reflectance measurements are valuable to the optics industry for development of new materials and optical coatings. Yet, absolute reflectance measurements are notoriously difficult to make. In this paper, we investigate the feasibility of extracting the absolute reflectance from a relative reflectance measurement using a reference material with known refractive index.

  18. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  19. Noninvasive absolute cerebral oximetry with frequency-domain near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hallacoglu, Bertan

    Near-infrared spectroscopy (NIRS) measurements of absolute concentrations of oxy-hemoglobin and deoxy-hemoglobin in the human brain can provide critical information about cerebral physiology in terms of cerebral blood volume, blood flow, oxygen delivery, and metabolic rate of oxygen. We developed several frequency domain NIRS data acquisition and analysis methods aimed at absolute measurements of hemoglobin concentration and saturation in cerebral tissue of adult human subjects. Extensive experimental investigations were carried out in various homogenous and two-layered tissue-mimicking phantoms, and biological tissues. The advantages and limitations of commonly used homogenous models and inversion strategies were thoroughly investigated. Prior to human subjects, extensive studies were carried out in in vivo animal models. In rabbits, absolute hemoglobin oxygen desaturation was shown to depend strongly on surgically induced testicular torsion. Methods developed in this study were then adapted for measurements in the rat brain. Absolute values were demonstrated to discern cerebrovascular impairment in a rat model of diet-induced vascular cognitive impairment. These results facilitated the development of clinically useful optical measures of cerebrovascular health. In a large group of human subjects, employing a homogeneous model for absolute measurements was shown to be reliable and robust. However, it was also shown to be limited due to the relatively thick extracerebral tissue. The procedure we develop in this work and the thesis thereof performs a nonlinear inversion procedure with six unknown parameters with no other prior knowledge for the retrieval of the optical coefficients and top layer thickness with high accuracy on two-layered media. Our absolute measurements of cerebral hemoglobin concentration and saturation are based on the discrimination of extracerebral and cerebral tissue layers, and they can enhance the impact of NIRS for cerebral hemodynamics and

  20. Using absolute gravimeter data to determine vertical gravity gradients

    USGS Publications Warehouse

    Robertson, D.S.

    2001-01-01

    The position versus time data from a free-fall absolute gravimeter can be used to estimate the vertical gravity gradient in addition to the gravity value itself. Hipkin has reported success in estimating the vertical gradient value using a data set of unusually good quality. This paper explores techniques that may be applicable to a broader class of data that may be contaminated with "system response" errors of larger magnitude than were evident in the data used by Hipkin. This system response function is usually modelled as a sum of exponentially decaying sinusoidal components. The technique employed here involves combining the x0, v0 and g parameters from all the drops made during a site occupation into a single least-squares solution, and including the value of the vertical gradient and the coefficients of system response function in the same solution. The resulting non-linear equations must be solved iteratively and convergence presents some difficulties. Sparse matrix techniques are used to make the least-squares problem computationally tractable.

  1. Use of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions

    ERIC Educational Resources Information Center

    Moore, Don A.; Klein, William M. P.

    2008-01-01

    Which matters more--beliefs about absolute ability or ability relative to others? This study set out to compare the effects of such beliefs on satisfaction with performance, self-evaluations, and bets on future performance. In Experiment 1, undergraduate participants were told they had answered 20% correct, 80% correct, or were not given their…

  2. THE ABSOLUTE MAGNITUDES OF RED HORIZONTAL BRANCH STARS IN THE ugriz SYSTEM

    SciTech Connect

    Chen, Y. Q.; Zhao, G.; Zhao, J. K.

    2009-09-10

    Based on photometric data of the central parts of eight globular clusters and one open cluster presented by An and his collaborators, we select red horizontal branch (RHB) stars in the (g - r){sub 0}-g {sub 0} diagram and make a statistical study of the distributions of their colors and absolute magnitudes in the SDSS ugriz system. Meanwhile, absolute magnitudes in the Johnson VRI system are calculated through the translation formulae between gri and VRI in the literature. The calibrations of absolute magnitude as functions of metallicity and age are established by linear regressions of the data. It is found that metallicity coefficients in these calibrations decrease, while age coefficients increase, from the blue u filter to the red z filter. The calibration of M{sub i} = 0.06[Fe/H] + 0.040t + 0.03 has the smallest scatter of 0.04 mag, and thus i is the best filter in the ugriz system when RHB stars are used for distance indicators. The comparison of the M{sub I} calibration from our data with that from red clump stars indicates that the previous suggestion that the I filter is better than the V filter in distance determination may not be true because of its significant dependence on age.

  3. Absolute nonlocality via distributed computing without communication

    NASA Astrophysics Data System (ADS)

    Czekaj, Ł.; Pawłowski, M.; Vértesi, T.; Grudka, A.; Horodecki, M.; Horodecki, R.

    2015-09-01

    Understanding the role that quantum entanglement plays as a resource in various information processing tasks is one of the crucial goals of quantum information theory. Here we propose an alternative perspective for studying quantum entanglement: distributed computation of functions without communication between nodes. To formalize this approach, we propose identity games. Surprisingly, despite no signaling, we obtain that nonlocal quantum strategies beat classical ones in terms of winning probability for identity games originating from certain bipartite and multipartite functions. Moreover we show that, for a majority of functions, access to general nonsignaling resources boosts success probability two times in comparison to classical ones for a number of large enough outputs. Because there are no constraints on the inputs and no processing of the outputs in the identity games, they detect very strong types of correlations: absolute nonlocality.

  4. In vivo absorption spectroscopy for absolute measurement.

    PubMed

    Furukawa, Hiromitsu; Fukuda, Takashi

    2012-10-01

    In in vivo spectroscopy, there are differences between individual subjects in parameters such as tissue scattering and sample concentration. We propose a method that can provide the absolute value of a particular substance concentration, independent of these individual differences. Thus, it is not necessary to use the typical statistical calibration curve, which assumes an average level of scattering and an averaged concentration over individual subjects. This method is expected to greatly reduce the difficulties encountered during in vivo measurements. As an example, for in vivo absorption spectroscopy, the method was applied to the reflectance measurement in retinal vessels to monitor their oxygen saturation levels. This method was then validated by applying it to the tissue phantom under a variety of absorbance values and scattering efficiencies.

  5. Determining Absolute Zero Using a Tuning Fork

    NASA Astrophysics Data System (ADS)

    Goldader, Jeffrey D.

    2008-04-01

    The Celsius and Kelvin temperature scales, we tell our students, are related. We explain that a change in temperature of 1°C corresponds to a change of 1 Kelvin and that atoms and molecules have zero kinetic energy at zero Kelvin, -273°C. In this paper, we will show how students can derive the relationship between the Celsius and Kelvin temperature scales using a simple, well-known physics experiment. By making multiple measurements of the speed of sound at different temperatures, using the classic physics experiment of determining the speed of sound with a tuning fork and variable-length tube, they can determine the temperature at which the speed of sound is zero—absolute zero.

  6. MAGSAT: Vector magnetometer absolute sensor alignment determination

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.

    1981-01-01

    A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.

  7. An estimate of global absolute dynamic topography

    NASA Technical Reports Server (NTRS)

    Tai, C.-K.; Wunsch, C.

    1984-01-01

    The absolute dynamic topography of the world ocean is estimated from the largest scales to a short-wavelength cutoff of about 6700 km for the period July through September, 1978. The data base consisted of the time-averaged sea-surface topography determined by Seasat and geoid estimates made at the Goddard Space Flight Center. The issues are those of accuracy and resolution. Use of the altimetric surface as a geoid estimate beyond the short-wavelength cutoff reduces the spectral leakage in the estimated dynamic topography from erroneous small-scale geoid estimates without contaminating the low wavenumbers. Comparison of the result with a similarly filtered version of Levitus' (1982) historical average dynamic topography shows good qualitative agreement. There is quantitative disagreement, but it is within the estimated errors of both methods of calculation.

  8. Micron Accurate Absolute Ranging System: Range Extension

    NASA Technical Reports Server (NTRS)

    Smalley, Larry L.; Smith, Kely L.

    1999-01-01

    The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.

  9. Absolute measurements of fast neutrons using yttrium.

    PubMed

    Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

    2010-08-01

    Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge.

  10. Measured and modelled absolute gravity in Greenland

    NASA Astrophysics Data System (ADS)

    Nielsen, E.; Forsberg, R.; Strykowski, G.

    2012-12-01

    Present day changes in the ice volume in glaciated areas like Greenland will change the load on the Earth and to this change the lithosphere will respond elastically. The Earth also responds to changes in the ice volume over a millennial time scale. This response is due to the viscous properties of the mantle and is known as Glaical Isostatic Adjustment (GIA). Both signals are present in GPS and absolute gravity (AG) measurements and they will give an uncertainty in mass balance estimates calculated from these data types. It is possible to separate the two signals if both gravity and Global Positioning System (GPS) time series are available. DTU Space acquired an A10 absolute gravimeter in 2008. One purpose of this instrument is to establish AG time series in Greenland and the first measurements were conducted in 2009. Since then are 18 different Greenland GPS Network (GNET) stations visited and six of these are visited more then once. The gravity signal consists of three signals; the elastic signal, the viscous signal and the direct attraction from the ice masses. All of these signals can be modelled using various techniques. The viscous signal is modelled by solving the Sea Level Equation with an appropriate ice history and Earth model. The free code SELEN is used for this. The elastic signal is modelled as a convolution of the elastic Greens function for gravity and a model of present day ice mass changes. The direct attraction is the same as the Newtonian attraction and is calculated as this. Here we will present the preliminary results of the AG measurements in Greenland. We will also present modelled estimates of the direct attraction, the elastic and the viscous signals.

  11. Absolute bioavailability of quinine formulations in Nigeria.

    PubMed

    Babalola, C P; Bolaji, O O; Ogunbona, F A; Ezeomah, E

    2004-09-01

    This study compared the absolute bioavailability of quinine sulphate as capsule and as tablet against the intravenous (i.v.) infusion of the drug in twelve male volunteers. Six of the volunteers received intravenous infusion over 4 h as well as the capsule formulation of the drug in a cross-over manner, while the other six received the tablet formulation. Blood samples were taken at predetermined time intervals and plasma analysed for quinine (QN) using reversed-phase HPLC method. QN was rapidly absorbed after the two oral formulations with average t(max) of 2.67 h for both capsule and tablet. The mean elimination half-life of QN from the i.v. and oral dosage forms varied between 10 and 13.5 hr and were not statistically different (P > 0.05). On the contrary, the maximum plasma concentration (C(max)) and area under the curve (AUC) from capsule were comparable to those from i.v. (P > 0.05), while these values were markedly higher than values from tablet formulation (P < 0.05). The therapeutic QN plasma levels were not achieved with the tablet formulation. The absolute bioavailability (F) were 73% (C.l., 53.3 - 92.4%) and 39 % (C.I., 21.7 - 56.6%) for the capsule and tablet respectively and the difference was significant (P < 0.05). The subtherapeutic levels obtained from the tablet form used in this study may cause treatment failure during malaria and caution should be taken when predictions are made from results obtained from different formulations of QN.

  12. Absolute GPS Positioning Using Genetic Algorithms

    NASA Astrophysics Data System (ADS)

    Ramillien, G.

    A new inverse approach for restoring the absolute coordinates of a ground -based station from three or four observed GPS pseudo-ranges is proposed. This stochastic method is based on simulations of natural evolution named genetic algorithms (GA). These iterative procedures provide fairly good and robust estimates of the absolute positions in the Earth's geocentric reference system. For comparison/validation, GA results are compared to the ones obtained using the classical linearized least-square scheme for the determination of the XYZ location proposed by Bancroft (1985) which is strongly limited by the number of available observations (i.e. here, the number of input pseudo-ranges must be four). The r.m.s. accuracy of the non -linear cost function reached by this latter method is typically ~10-4 m2 corresponding to ~300-500-m accuracies for each geocentric coordinate. However, GA can provide more acceptable solutions (r.m.s. errors < 10-5 m2), even when only three instantaneous pseudo-ranges are used, such as a lost of lock during a GPS survey. Tuned GA parameters used in different simulations are N=1000 starting individuals, as well as Pc=60-70% and Pm=30-40% for the crossover probability and mutation rate, respectively. Statistical tests on the ability of GA to recover acceptable coordinates in presence of important levels of noise are made simulating nearly 3000 random samples of erroneous pseudo-ranges. Here, two main sources of measurement errors are considered in the inversion: (1) typical satellite-clock errors and/or 300-metre variance atmospheric delays, and (2) Geometrical Dilution of Precision (GDOP) due to the particular GPS satellite configuration at the time of acquisition. Extracting valuable information and even from low-quality starting range observations, GA offer an interesting alternative for high -precision GPS positioning.

  13. Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers

    PubMed Central

    Lee, Kyeong-Dong; Kim, Dong-Jun; Yeon Lee, Hae; Kim, Seung-Hyun; Lee, Jong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Lee, Ki-Suk; Song, Hyon-Seok; Sohn, Jeong-Woo; Shin, Sung-Chul; Park, Byong-Guk

    2015-01-01

    The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices. PMID:26020492

  14. Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers.

    PubMed

    Lee, Kyeong-Dong; Kim, Dong-Jun; Yeon Lee, Hae; Kim, Seung-Hyun; Lee, Jong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Lee, Ki-Suk; Song, Hyon-Seok; Sohn, Jeong-Woo; Shin, Sung-Chul; Park, Byong-Guk

    2015-05-28

    The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices.

  15. Temperature-controlled colossal magnetoresistance and perfect spin Seebeck effect in hybrid graphene/boron nitride nanoribbons.

    PubMed

    Zhu, Lin; Li, Ruimin; Yao, Kailun

    2017-02-01

    Thermal spin transport properties of graphene and hexagonal boron nitride nanoribbon heterojunctions have been investigated using density functional theory calculations combined with the Keldysh nonequilibrium Green's function approach. The results showed that the perfect spin Seebeck effect and analogy negative differential thermoelectric resistance occurred in the device under a temperature difference without a gate or bias voltage. An intriguing thermally induced colossal magnetoresistance without gate regulation was also observed, which can be switched between a positive and negative value with temperature control. It was also found that the unit number of zigzag graphene nanoribbons and boron nitride nanoribbons can tune the electronic band structure and the energy gap of the heterostructure, and then modulate the thermal spin transport properties. The results suggest that graphene and hexagonal boron nitride nanoribbon heterostructures may have potential applications in graphene-based nanodevices.

  16. Thermal spin-transfer torque driven by the spin-dependent Seebeck effect in metallic spin-valves

    NASA Astrophysics Data System (ADS)

    Choi, Gyung-Min; Moon, Chul-Hyun; Min, Byoung-Chul; Lee, Kyung-Jin; Cahill, David G.

    2015-07-01

    The coupling of spin and heat gives rise to new physical phenomena in nanoscale spin devices. In particular, spin-transfer torque (STT) driven by thermal transport provides a new way to manipulate local magnetization. We quantify thermal STT in metallic spin-valve structures using an intense and ultrafast heat current created by picosecond pulses of laser light. Our result shows that thermal STT consists of demagnetization-driven and spin-dependent Seebeck effect (SDSE)-driven components; the SDSE-driven STT becomes dominant after 3 ps. The sign and magnitude of the SDSE-driven STT can be controlled by the composition of a ferromagnetic layer and the thickness of a heat sink layer.

  17. Longitudinal Spin Seebeck Effect in Bi-substituted Neodymium Iron Garnet on Gadolinium Gallium Garnet Substrate Prepared by MOD Method

    NASA Astrophysics Data System (ADS)

    Asada, H.; Kuwahara, A.; Sueyasu, K.; Ishibashi, T.; Liu, Q.; Lou, G.; Kishimoto, K.; Koyanagi, T.

    Bi-substituted Neodymium Iron Garnet (Nd3-xBixFe5O12, Bi:NIG) thin films with the Bi composition x=0-1.0 are prepared on both the (001) and (111) oriented gadolinium gallium garnet (GGG) substrates by a metal organic decomposition method. Crystalline qualities and magnetic properties of these films are examined by X-ray diffraction, atomic force microscopy and vibrating sample magnetometer. Longitudinal spin Seebeck effects (LSSEs) are investigated by means of the inverse spin Hall effect in a Pt film. The increase of LSSE voltage in Bi:NIG(x=0-1.0)/Pt bilayers on GGG(001) is observed with the increase of Bi composition. In the case of GGG(111), the LSSE voltage for Bi:NIG(x=1.0) is also larger than that for NIG.

  18. Generation of pure spin currents via spin Seebeck effect in self-biased hexagonal ferrite thin films

    SciTech Connect

    Li, Peng; Ellsworth, David; Chang, Houchen; Janantha, Praveen; Richardson, Daniel; Phillips, Preston; Vijayasarathy, Tarah; Wu, Mingzhong; Shah, Faisal

    2014-12-15

    Light-induced generation of pure spin currents in a Pt(2.5 nm)/BaFe{sub 12}O{sub 19}(1.2 μm)/sapphire(0.5 mm) structure is reported. The BaFe{sub 12}O{sub 19} film had strong in-plane uniaxial anisotropy and was therefore self-biased. Upon exposure to light, a temperature difference (ΔT) was established across the BaFe{sub 12}O{sub 19} thickness that gave rise to a pure spin current in the Pt via the spin Seebeck effect. Via the inverse spin Hall effect, the spin current produced an electric voltage across one of the Pt lateral dimensions. The voltage varied with time in the same manner as ΔT and flipped its sign when the magnetization in BaFe{sub 12}O{sub 19} was reversed.

  19. Cytoplasmic hydrogen ion diffusion coefficient.

    PubMed Central

    al-Baldawi, N F; Abercrombie, R F

    1992-01-01

    The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 x 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantitatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient. PMID:1617134

  20. Effets Seebeck et Nernst dans les cuprates: Etude de la reconstruction de la surface de Fermi sous champ magnetique intense

    NASA Astrophysics Data System (ADS)

    Laliberte, Francis

    2010-06-01

    Ce memoire presente des mesures de transport thermoelectrique, les effets Seebeck et Nernst, dans une serie d'echantillons de supraconducteurs a haute temperature critique. Des resultats obtenus recemment au Laboratoire National des Champs Magnetiques Intenses a Grenoble sur La1.7Eu0.2Sr0.1 CuO4, La1.675Eu0.2Sr0.125CuO 4, La1.64Eu0.2Sr0.16CuO4, La1.74Eu0.1Sr0.16CuO4 et La 1.4Nd0.4Sr0.2CuO4 sont analyses. Une attention particuliere est accordee aux equations de la theorie semi-classique du transport et leur validite est verifiee. La procedure experimentale et les materiaux utilises pour concevoir les montages de mesures sont expliques en detail. Enfin, un chapitre est dedie a l'explication et l'interpretation des resultats de transport thermoelectrique sur YBa2Cu3O6+delta publies au cours de l'hiver 2010 dans les revues Nature et Physical Review Letters. Les donnees d'effet Seebeck dans les echantillons de La 1.8-x,Eu0.2SrxCuO 4, ou un changement de signe est observe, permettent de conclure a la presence d'une poche d'electrons dans la surface de Fermi qui domine le transport a basse temperature dans la region sous-dopee du diagramme de phase. Cette conclusion est similaire a celle obtenue par des mesures d'effet Hall dans YBa 2Cu3O6+delta et elle cadre bien dans un scenario de reconstruction de la surface de Fermi. Les donnees d'effet Nernst recueillies indiquent que la contribution des fluctuations supraconductrices est limitee a un modeste intervalle de temperature au-dessus de la temperature critique.

  1. A novel absolute measurement for the low-frequency figure correction of aspheric surfaces

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Cheng; Chang, Shenq-Tsong; Ho, Cheng-Fang; Kuo, Ching-Hsiang; Chung, Chien-Kai; Hsu, Wei-Yao; Tseng, Shih-Feng; Sung, Cheng-Kuo

    2015-07-01

    This study proposes an absolute measurement method with a computer-generated hologram (CGHs) to assist the identification of manufacturing form error, and gravity and mounting resulted distortions for a 300 mm aspherical mirror. This method adopts the frequency of peaks and valleys of each Zernike coefficient grabbed by the measurement with various orientations of the mirror in horizontal optical-axis configuration. In addition, the rotational-symmetric aberration (spherical aberration) is calibrated with random ball test method. According to the measured absolute surface figure, a high accuracy aspherical surface with peak to valley (P-V) value of 1/8 wave @ 632.8 nm was fabricated after surface figure correction with the reconstructed error map.

  2. Reliability and validity of quantifying absolute muscle hardness using ultrasound elastography.

    PubMed

    Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki

    2012-01-01

    Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young's moduli of seven tissue-mimicking materials (in vitro; Young's modulus range, 20-80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young's modulus ratio of two reference materials, one hard and one soft (Young's moduli of 7 and 30 kPa, respectively), the Young's moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (≤6.9%) and substantially high intraclass correlation coefficients (≥0.77) obtained from all measurements. The correlation coefficient between the Young's moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young's moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified.

  3. Vicarious absolute radiometric calibration of GF-2 PMS2 sensor using permanent artificial targets in China

    NASA Astrophysics Data System (ADS)

    Liu, Yaokai; Li, Chuanrong; Ma, Lingling; Wang, Ning; Qian, Yonggang; Tang, Lingli

    2016-10-01

    GF-2, launched on August 19 2014, is one of the high-resolution land resource observing satellite of the China GF series satellites plan. The radiometric performance evaluation of the onboard optical pan and multispectral (PMS2) sensor of GF-2 satellite is very important for the further application of the data. And, the vicarious absolute radiometric calibration approach is one of the most useful way to monitor the radiometric performance of the onboard optical sensors. In this study, the traditional reflectance-based method is used to vicarious radiometrically calibrate the onboard PMS2 sensor of GF-2 satellite using three black, gray and white reflected permanent artificial targets located in the AOE Baotou site in China. Vicarious field calibration campaign were carried out in the AOE-Baotou calibration site on 22 April 2016. And, the absolute radiometric calibration coefficients were determined with in situ measured atmospheric parameters and surface reflectance of the permanent artificial calibration targets. The predicted TOA radiance of a selected desert area with our determined calibrated coefficients were compared with the official distributed calibration coefficients. Comparison results show a good consistent and the mean relative difference of the multispectral channels is less than 5%. Uncertainty analysis was also carried out and a total uncertainty with 3.87% is determined of the TOA radiance.

  4. Functional constraints on phenomenological coefficients

    NASA Astrophysics Data System (ADS)

    Klika, Václav; Pavelka, Michal; Benziger, Jay B.

    2017-02-01

    Thermodynamic fluxes (diffusion fluxes, heat flux, etc.) are often proportional to thermodynamic forces (gradients of chemical potentials, temperature, etc.) via the matrix of phenomenological coefficients. Onsager's relations imply that the matrix is symmetric, which reduces the number of unknown coefficients is reduced. In this article we demonstrate that for a class of nonequilibrium thermodynamic models in addition to Onsager's relations the phenomenological coefficients must share the same functional dependence on the local thermodynamic state variables. Thermodynamic models and experimental data should be validated through consistency with the functional constraint. We present examples of coupled heat and mass transport (thermodiffusion) and coupled charge and mass transport (electro-osmotic drag). Additionally, these newly identified constraints further reduce the number of experiments needed to describe the phenomenological coefficient.

  5. Wrong Signs in Regression Coefficients

    NASA Technical Reports Server (NTRS)

    McGee, Holly

    1999-01-01

    When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.

  6. A new method on recycling coefficient measurement using impurity pellet injection in a large helical device

    SciTech Connect

    Nozato, Hideaki; Morita, Shigeru; Goto, Motoshi

    2005-07-15

    Recycling coefficients of carbon, aluminum, and titanium were evaluated using a new technique combining impurity pellet injection with high-spatial resolution bremsstrahlung measurement in hydrogen and helium plasmas on the large helical device. The recycling coefficient of impurities was investigated by measuring absolute intensities with the visible bremsstrahlung array. The time evolution of the bremsstrahlung signals was modeled by an impurity transport code adjusting the diffusion coefficient, convective velocity, and recycling coefficient. As a result, a finite value of the recycling coefficient was required in the case of carbon, whereas aluminum and titanium were explained as nonrecycled particles. It was also clarified that the recycling coefficient of carbon had a larger value in hydrogen plasmas (R=0.5-0.65) than in helium plasmas (R=0-0.2), suggesting the formation of hydrogen molecules.

  7. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  8. Elevation correction factor for absolute pressure measurements

    NASA Technical Reports Server (NTRS)

    Panek, Joseph W.; Sorrells, Mark R.

    1996-01-01

    With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

  9. What is Needed for Absolute Paleointensity?

    NASA Astrophysics Data System (ADS)

    Valet, J. P.

    2015-12-01

    Many alternative approaches to the Thellier and Thellier technique for absolute paleointensity have been proposed during the past twenty years. One reason is the time consuming aspect of the experiments. Another reason is to avoid uncertainties in determinations of the paleofield which are mostly linked to the presence of multidomain grains. Despite great care taken by these new techniques, there is no indication that they always provide the right answer and in fact sometimes fail. We are convinced that the most valid approach remains the original double heating Thellier protocol provided that natural remanence is controlled by pure magnetite with a narrow distribution of small grain sizes, mostly single domains. The presence of titanium, even in small amount generates biases which yield incorrect field values. Single domain grains frequently dominate the magnetization of glass samples, which explains the success of this selective approach. They are also present in volcanic lava flows but much less frequently, and therefore contribute to the low success rate of most experiments. However the loss of at least 70% of the magnetization at very high temperatures prior to the Curie point appears to be an essential prerequisite that increases the success rate to almost 100% and has been validated from historical flows and from recent studies. This requirement can easily be tested by thermal demagnetization while low temperature experiments can document the detection of single domain magnetite using the δFC/δZFC parameter as suggested (Moskowitz et al, 1993) for biogenic magnetite.

  10. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  11. Climate Absolute Radiance and Refractivity Observatory (CLARREO)

    NASA Technical Reports Server (NTRS)

    Leckey, John P.

    2015-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.

  12. Absolute quantification of proteins by LCMSE: a virtue of parallel MS acquisition.

    PubMed

    Silva, Jeffrey C; Gorenstein, Marc V; Li, Guo-Zhong; Vissers, Johannes P C; Geromanos, Scott J

    2006-01-01

    Relative quantification methods have dominated the quantitative proteomics field. There is a need, however, to conduct absolute quantification studies to accurately model and understand the complex molecular biology that results in proteome variability among biological samples. A new method of absolute quantification of proteins is described. This method is based on the discovery of an unexpected relationship between MS signal response and protein concentration: the average MS signal response for the three most intense tryptic peptides per mole of protein is constant within a coefficient of variation of less than +/-10%. Given an internal standard, this relationship is used to calculate a universal signal response factor. The universal signal response factor (counts/mol) was shown to be the same for all proteins tested in this study. A controlled set of six exogenous proteins of varying concentrations was studied in the absence and presence of human serum. The absolute quantity of the standard proteins was determined with a relative error of less than +/-15%. The average MS signal responses of the three most intense peptides from each protein were plotted against their calculated protein concentrations, and this plot resulted in a linear relationship with an R(2) value of 0.9939. The analyses were applied to determine the absolute concentration of 11 common serum proteins, and these concentrations were then compared with known values available in the literature. Additionally within an unfractionated Escherichia coli lysate, a subset of identified proteins known to exist as functional complexes was studied. The calculated absolute quantities were used to accurately determine their stoichiometry.

  13. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

    2015-12-01

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  14. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-06-05

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  15. Positioning, alignment and absolute pointing of the ANTARES neutrino telescope

    NASA Astrophysics Data System (ADS)

    Fehr, F.; Distefano, C.; Antares Collaboration

    2010-01-01

    A precise detector alignment and absolute pointing is crucial for point-source searches. The ANTARES neutrino telescope utilises an array of hydrophones, tiltmeters and compasses for the relative positioning of the optical sensors. The absolute calibration is accomplished by long-baseline low-frequency triangulation of the acoustic reference devices in the deep-sea with a differential GPS system at the sea surface. The absolute pointing can be independently verified by detecting the shadow of the Moon in cosmic rays.

  16. Position error correction in absolute surface measurement based on a multi-angle averaging method

    NASA Astrophysics Data System (ADS)

    Wang, Weibo; Wu, Biwei; Liu, Pengfei; Liu, Jian; Tan, Jiubin

    2017-04-01

    We present a method for position error correction in absolute surface measurement based on a multi-angle averaging method. Differences in shear rotation measurements at overlapping areas can be used to estimate the unknown relative position errors of the measurements. The model and the solving of the estimation algorithm have been discussed in detail. The estimation algorithm adopts a least-squares technique to eliminate azimuthal errors caused by rotation inaccuracy. The cost functions can be minimized to determine the true values of the unknowns of Zernike polynomial coefficients and rotation angle. Experimental results show the validity of the method proposed.

  17. Absolute quantification by droplet digital PCR versus analog real-time PCR

    PubMed Central

    Hindson, Christopher M; Chevillet, John R; Briggs, Hilary A; Gallichotte, Emily N; Ruf, Ingrid K; Hindson, Benjamin J; Vessella, Robert L; Tewari, Muneesh

    2014-01-01

    Nanoliter-sized droplet technology paired with digital PCR (ddPCR) holds promise for highly precise, absolute nucleic acid quantification. Our comparison of microRNA quantification by ddPCR and real-time PCR revealed greater precision (coefficients of variation decreased by 37–86%) and improved day-to-day reproducibility (by a factor of seven) of ddPCR but with comparable sensitivity. When we applied ddPCR to serum microRNA biomarker analysis, this translated to superior diagnostic performance for identifying individuals with cancer. PMID:23995387

  18. Absolute and Convective Instability of a Liquid Jet

    NASA Technical Reports Server (NTRS)

    Lin, S. P.; Hudman, M.; Chen, J. N.

    1999-01-01

    The existence of absolute instability in a liquid jet has been predicted for some time. The disturbance grows in time and propagates both upstream and downstream in an absolutely unstable liquid jet. The image of absolute instability is captured in the NASA 2.2 sec drop tower and reported here. The transition from convective to absolute instability is observed experimentally. The experimental results are compared with the theoretical predictions on the transition Weber number as functions of the Reynolds number. The role of interfacial shear relative to all other relevant forces which cause the onset of jet breakup is explained.

  19. Thermoelectricity at the molecular scale: a large Seebeck effect in endohedral metallofullerenes

    NASA Astrophysics Data System (ADS)

    Lee, See Kei; Buerkle, Marius; Yamada, Ryo; Asai, Yoshihiro; Tada, Hirokazu

    2015-12-01

    Single molecule devices provide a unique system to study the thermoelectric energy conversion at an atomistic level and can provide valuable information for the design of organic thermoelectric materials. Here we present a comprehensive study of the thermoelectric transport properties of molecular junctions based on C82, Gd@C82, and Ce@C82. We combine precise scanning tunneling microscope break-junction measurements of the thermopower and conductance with quantitatively accurate self-energy-corrected first-principles transport calculations. We find that all three fullerene derivatives give rise to a negative thermopower (n-conducting). The absolute value, however, is much larger for the Gd@C82 and Ce@C82 junctions. The conductance, on the other hand, remains comparable for all three systems. The power factor determined for the Gd@C82 based junction is so far the highest obtained for a single-molecule device. Although the encapsulated metal atom does not directly contribute to the transport, we show that the observed enhancement of the thermopower for Gd@C82 and Ce@C82 is elucidated by the substantial changes in the electronic- and geometrical structure of the fullerene molecule induced by the encapsulated metal atom.Single molecule devices provide a unique system to study the thermoelectric energy conversion at an atomistic level and can provide valuable information for the design of organic thermoelectric materials. Here we present a comprehensive study of the thermoelectric transport properties of molecular junctions based on C82, Gd@C82, and Ce@C82. We combine precise scanning tunneling microscope break-junction measurements of the thermopower and conductance with quantitatively accurate self-energy-corrected first-principles transport calculations. We find that all three fullerene derivatives give rise to a negative thermopower (n-conducting). The absolute value, however, is much larger for the Gd@C82 and Ce@C82 junctions. The conductance, on the other hand

  20. Accurate van der Waals coefficients from density functional theory

    PubMed Central

    Tao, Jianmin; Perdew, John P.; Ruzsinszky, Adrienn

    2012-01-01

    The van der Waals interaction is a weak, long-range correlation, arising from quantum electronic charge fluctuations. This interaction affects many properties of materials. A simple and yet accurate estimate of this effect will facilitate computer simulation of complex molecular materials and drug design. Here we develop a fast approach for accurate evaluation of dynamic multipole polarizabilities and van der Waals (vdW) coefficients of all orders from the electron density and static multipole polarizabilities of each atom or other spherical object, without empirical fitting. Our dynamic polarizabilities (dipole, quadrupole, octupole, etc.) are exact in the zero- and high-frequency limits, and exact at all frequencies for a metallic sphere of uniform density. Our theory predicts dynamic multipole polarizabilities in excellent agreement with more expensive many-body methods, and yields therefrom vdW coefficients C6, C8, C10 for atom pairs with a mean absolute relative error of only 3%. PMID:22205765