WorldWideScience

Sample records for angular dependent magnetoresistance

  1. Angular dependence of anisotropic magnetoresistance in magnetic systems

    Science.gov (United States)

    Zhang, Steven S.-L.; Zhang, Shufeng

    2014-05-01

    Anisotropic magnetoresistance (AMR), whose physical origin is attributed to the combination of spin dependent scattering and spin orbital coupling (SOC), usually displays simple angular dependence for polycrystalline ferromagnetic metals. By including generic spin dependent scattering and spin Hall (SH) terms in the Ohm's law, we explicitly show that various magneto-transport phenomena such as anomalous Hall (AH), SH, planar Hall (PH) and AMR could be quantitatively related for bulk polycrystalline ferromagnetic metals. We also discuss how AMR angular dependence is affected by the presence of interfacial SOC in magnetic layered structure.

  2. Correlation of the angular dependence of spin-transfer torque and giant magnetoresistance in the limit of diffusive transport in spin valves

    OpenAIRE

    Gmitra, M.; Barnas, J.

    2009-01-01

    Angular variation of giant magnetoresistance and spin-transfer torque in metallic spin-valve heterostructures is analyzed theoretically in the limit of diffusive transport. It is shown that the spin-transfer torque in asymmetric spin valves can vanish in non-collinear magnetic configurations, and such a non-standard behavior of the torque is generally associated with a non-monotonic angular dependence of the giant magnetoresistance, with a global minimum at a non-collinear magnetic configurat...

  3. Angular dependence of critical current density and magnetoresistance of sputtered high-T{sub c}-films

    Energy Technology Data Exchange (ETDEWEB)

    Geerkens, A.; Frenck, H.J.; Ewert, S. [Technical Univ. of Cottbus (Germany)] [and others

    1994-12-31

    The angular dependence of the critical current density and the magnetoresistance of high-T{sub c}-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle {Theta} between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the {Theta}-rotation plane is discussed.

  4. Shubnikov-de Haas Effect and Angular-Dependent Magnetoresistance in Layered Organic Conductor β''-(ET)(TCNQ)

    Science.gov (United States)

    Yasuzuka, Syuma; Uji, Shinya; Konoike, Takako; Terashima, Taichi; Graf, David; Choi, Eun Sang; Brooks, James S.; Yamamoto, Hiroshi M.; Kato, Reizo

    2016-08-01

    This paper reports the experimental results of the Shubnikov-de Haas (SdH) effect and angular-dependent magnetoresistance oscillation (AMRO) for the organic conductor β''-(ET)(TCNQ). We observed several two dimensional (2D) SdH frequencies, whose cross-sectional areas of the Fermi surfaces (FSs) correspond to only a few percent of the first Brillouin zone. Such small 2D FSs are not predicted by band-structure calculations, suggesting that these FS pockets are created by an imperfect nesting of FSs at low temperatures. It is found that the AMRO consists of a long-period oscillation and a short-period one. The long-period oscillation is associated with the Yamaji oscillation corresponding to the α orbit, whose shape and area are consistent with previous magneto-optical measurement. The short-period oscillation is not caused by peaks instead but dips. The dip structure is discussed in terms of the AMRO of a quasi-2D electron system with a periodic potential caused by the possible density-wave related to the ET layers or the 4kF charge-density-wave associated with the TCNQ layers.

  5. Theory of Angular Magnetoresistance in CPP spin valves

    OpenAIRE

    Huertas-Hernando, Daniel; Bauer, Gerrit E. W.; Nazarov, Yu. V.

    2001-01-01

    The resistance of CPP spin valve is a continuous function of the angle $\\theta $ between the magnetizations of both ferromagnets. We use the cicuit theory for non-collinear magnetoelectronics to compute the angular magnetoresistance of CPP spin valves taking the spin accumulation in the ferromagnetic layers into account.

  6. Angular magnetoresistance in semiconducting undoped amorphous carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sagar, Rizwan Ur Rehman; Saleemi, Awais Siddique; Zhang, Xiaozhong, E-mail: xzzhang@tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People' s Republic of China and Beijing National Center for Electron Microscopy, Beijing 100084 (China)

    2015-05-07

    Thin films of undoped amorphous carbon thin film were fabricated by using Chemical Vapor Deposition and their structure was investigated by using High Resolution Transmission Electron Microscopy and Raman Spectroscopy. Angular magnetoresistance (MR) has been observed for the first time in these undoped amorphous carbon thin films in temperature range of 2 ∼ 40 K. The maximum magnitude of angular MR was in the range of 9.5% ∼ 1.5% in 2 ∼ 40 K. The origin of this angular MR was also discussed.

  7. Asymmetric angular dependence of domain wall motion in magnetic nanowires.

    Science.gov (United States)

    Nam, Chunghee

    2013-03-01

    An angular dependence of domain wall (DW) motion is studied in a magnetic wire consisting of a giant-magnetoresistance spin-valve. A DW pinning site is formed by a single notch, where a conventional linear one and a specially designed tilted one are compared. The asymmetric angular dependence was found in the DW depinning behavior with the tilted notch. The geometry control of the pinning site can be useful for DW diode devices using a rotating magnetic field. PMID:23755619

  8. Systematic Angular Study of Magnetoresistance in Permalloy Connected Kagome Artificial Spin Ice

    Science.gov (United States)

    Park, Jungsik; Le, Brian; Watts, Justin; Leighton, Chris; Samarth, Nitin; Schiffer, Peter

    Artificial spin ices are nanostructured two-dimensional arrays of ferromagnetic elements, where frustrated interactions lead to unusual collective magnetic behavior. Here we report a room-temperature magnetoresistance study of connected permalloy (Ni81Fe19) kagome artificial spin ice networks, wherein the direction of the applied in-plane magnetic field is systematically varied. We measure both the longitudinal and transverse magnetoresistance in these structures, and we find certain transport geometries of the network show strong angular sensitivity - even small variations in the applied field angle lead to dramatic changes of the magnetoresistance response. We also investigate the magnetization reversal of the networks using magnetic force microscopy (MFM), demonstrating avalanche behavior in the magnetization reversal. The magnetoresistance features are analyzed using an anisotropic magnetoresistance (AMR) model. Supported by the US Department of Energy. Work at the University of Minnesota was supported by Seagate Technology, NSF MRSEC, and a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme.

  9. Multidimensional Nature of Molecular Organic Conductors Revealed by Angular Magnetoresistance Oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Pashupati Dhakal, Harukazu Yoshino, Jeong-Il Oh, Koichi Kikuchi, Michael J. Naughton

    2012-09-01

    Angle-dependent magnetoresistance experiments on organic conductors exhibit a wide range of angular oscillations associated with the dimensionality and symmetry of the crystal structure and electron energy dispersion. In particular, characteristics associated with 1, 2, and 3-dimensional electronic motion are separately revealed when a sample is rotated through different crystal planes in a magnetic field. Originally discovered in the TMTSF-based conductors, these effects are particularly pronounced in the related system (DMET){sub 2}I{sub 3}. Here, experimental and computational results for magnetoresistance oscillations in this material, over a wide range of magnetic field orientations, are presented in such a manner as to uniquely highlight this multidimensional behavior. The calculations employ the Boltzmann transport equation that incorporates the system's triclinic crystal structure, which allows for accurate estimates of the transfer integrals along the crystallographic axes, verifying the 1D, 2D and 3D nature of (DMET){sub 2}I{sub 3}, as well as crossovers between dimensions in the electronic behavior.

  10. Systematic study of doping dependence on linear magnetoresistance in p-PbTe

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, J. M.; Chitta, V. A.; Oliveira, N. F. [Instituto de Física, Universidade de São Paulo, São Paulo, PB 66318, São Paulo CEP 05315-970 (Brazil); Peres, M. L., E-mail: marcelos@unifei.edu.br; Castro, S. de; Soares, D. A. W. [Departamento de Física e Química, Universidade Federal de Itajubá, Itajubá, PB 50, Minas Gerais CEP 37500-903 (Brazil); Wiedmann, S.; Zeitler, U. [Radboud University Nijmegen, Institute for Molecules and Materials, High Field Magnet Laboratory, Toernooiveld 7, 6525 ED Nijmegen (Netherlands); Abramof, E.; Rappl, P. H. O.; Mengui, U. A. [Laboratório Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, PB 515, São Paulo CEP 12201-970 (Brazil)

    2014-10-20

    We report on a large linear magnetoresistance effect observed in doped p-PbTe films. While undoped p-PbTe reveals a sublinear magnetoresistance, p-PbTe films doped with BaF{sub 2} exhibit a transition to a nearly perfect linear magnetoresistance behaviour that is persistent up to 30 T. The linear magnetoresistance slope ΔR/ΔB is to a good approximation, independent of temperature. This is in agreement with the theory of Quantum Linear Magnetoresistance. We also performed magnetoresistance simulations using a classical model of linear magnetoresistance. We found that this model fails to explain the experimental data. A systematic study of the doping dependence reveals that the linear magnetoresistance response has a maximum for small BaF{sub 2} doping levels and diminishes rapidly for increasing doping levels. Exploiting the huge impact of doping on the linear magnetoresistance signal could lead to new classes of devices with giant magnetoresistance behavior.

  11. Magnetization reversal signatures in the magnetoresistance of magnetic multilayers

    OpenAIRE

    Prieto Martin, Jose Luis; Romera Rabasa, Miguel; Akerman, Johanna; Perna, Paolo; Rodrigo, C.; Muñoz, Manuel; Bollero, Alberto; Maccariello, Davide; Fernández Cuñado, José Luis; E. Jiménez; Mikuszeit, Nikolai; Cros, Vincent; Camarero, Julio; Miranda, Rodolfo

    2012-01-01

    The simultaneous determination of magnetoresistance and vectorial-resolved magnetization hysteresis curves in a spin valve structure reveals distinct magnetoresistive features for different magnetic field orientations, which are directly related to the magnetization reversal processes. Measurements performed in the whole angular range demonstrate that the magnetoresistive response originates from the intrinsic anisotropic angular dependence of the magnetization orientation between the two fer...

  12. Dependency injection with AngularJS

    CERN Document Server

    Knol, Alex

    2013-01-01

    This book is a practical, hands-on approach to using dependency injection and implementing test-driven development using AngularJS. Dependency Injection with AngularJS is aimed at developers who are aware of AngularJS but need to get started with using it in real life applications. Also, developers who want to get into test-driven development with AngularJS can use this book as practical guide. Even if you know about dependency injection, it can serve as a good reference on how it is used within AngularJS. Readers are expected to have some experience with JavaScript.

  13. Development of a Magneto-Resistive Angular Position Sensor for Space Mechanisms

    Science.gov (United States)

    Hahn, Robert; Schmidt, Tilo; Seifart, Klaus; Olberts, Bastian; Romera, Fernando

    2016-01-01

    Magnetic microsystems in the form of magneto-resistive (MR) sensors are firmly established in automobiles and industrial applications. They are used to measure travel, angle, electrical current, or magnetic fields. MR technology opens up new sensor possibilities in space applications and can be an enabling technology for optimal performance, high robustness and long lifetime at reasonable costs. In some science missions, the technology is already applied, however, the designs are proprietary and case specific, for instance in case of the angular sensors used for JPL/NASA's Mars rover Curiosity [1]. Since 2013 HTS GmbH and Sensitec GmbH have teamed up to develop and qualify a standardized yet flexible to use MR angular sensor for space mechanisms. Starting with a first assessment study and market survey performed under ESA contract, a very strong industry interest in novel, contactless position measurement means was found. Currently a detailed and comprehensive development program is being performed by HTS and Sensitec. The objective of this program is to advance the sensor design up to Engineering Qualification Model level and to perform qualification testing for a representative space application. The paper briefly reviews the basics of magneto-resistive effects and possible sensor applications and describes the key benefits of MR angular sensors with reference to currently operational industrial and space applications. The key applications and specification are presented and the preliminary baseline mechanical and electrical design will be discussed. An outlook on the upcoming development and test stages as well as the qualification program will be provided.

  14. Probabilistic calculation for angular dependence collision

    International Nuclear Information System (INIS)

    This collision probabilistic method is broadly used in cylindrical geometry (in one- or two-dimensions). It constitutes a powerful tool for the heterogeneous Response Method where, the coupling current is of the cosine type, that is, without angular dependence at azimuthal angle θ and proportional to μ (cosine of the θ polar angle). (Author)

  15. Time-dependent angularly averaged inverse transport

    OpenAIRE

    Bal, Guillaume; Jollivet, Alexandre

    2009-01-01

    This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured al...

  16. Time-dependent angularly averaged inverse transport

    International Nuclear Information System (INIS)

    This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. Such measurement settings find applications in medical and geophysical imaging. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain

  17. Time-dependent angularly averaged inverse transport

    CERN Document Server

    Bal, Guillaume

    2009-01-01

    This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain.

  18. Giant Magnetoresistance in Multilayers with Noncollinear Magnetizations

    OpenAIRE

    Urazhdin, S.; Loloee, R.; Pratt Jr, W. P.

    2004-01-01

    We study the dependence of perpendicular-current magnetoresistance in magnetic multilayers on the angle between the magnetizations of the layers. This dependence varies with the thickness of one of the layers, and is different for multilayers with two and three magnetic layers. We derive a system of equations representing an extension of the two-current series resistor model, and show that the angular dependence of magnetoresistance gives information about the noncollinear spin-transport in f...

  19. Crossover of angular dependent magnetoresistance with the metal-insulator transition in colossal magnetoresistive manganite films

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Sun, J.R.; Zhao, T.Y.;

    2009-01-01

    directions was observed with the appearance of magnetic-field-induced metal-insulator transition, which further led to a sign crossover in the AMR effect. The AMR crossover may give a direct evidence of the drastic modification of electronic structure or possible orbital reconstruction with the magnetic...

  20. Orbital angular momentum is dependent on polarization

    OpenAIRE

    Li, Chun-Fang

    2009-01-01

    It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that originates from the former part is spin, and the angular momentum that originates from the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and or...

  1. Tunneling magnetoresistance dependence on the temperature in a ferromagnetic Zener diode

    Energy Technology Data Exchange (ETDEWEB)

    Comesana, E; Aldegunde, M; GarcIa-Loureiro, A, E-mail: enrique.comesana@usc.e [Departamento de Electronica e Computacion, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2009-11-15

    In the present work we focus on the study of the temperature dependence of the tunnelling current in a ferromagnetic Zener diode. We predict the tunneling magnetoresistance dependence on the temperature. Large doping concentrations lead to magnetic semiconductors with Curie temperature T{sub C} near or over room temperature and this will facilitate the introduction of new devices that make use of the ferromagnetism effects. According to our calculations the tunneling magnetoresistance has the form TMR {proportional_to} (T{sup n}{sub C}-T{sup n}).

  2. Electric field dependence of junction magnetoresistance in magnetite/semiconductor heterostructure at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Aireddy, H.; Bhaumik, S.; Das, A. K., E-mail: amal@phy.iitkgp.ernet.in [Department of Physics, Indian Institute of Technology, Kharagpur 721 302 (India)

    2015-12-07

    We have fabricated Fe{sub 3}O{sub 4}/p-Si heterojunction using pulsed laser deposition technique and explored its electro-magnetic transport properties. The heterojunction exhibits backward rectifying property at all temperatures, and appraisal of giant junction magnetoresistance (JMR) is observed at room temperature (RT). Conspicuously, the variation and sign change of JMR as a function of electric field is observed at RT. The backward rectifying behavior of the device is ascribed to the highly doped p-type (p{sup ++}) semiconducting nature of Fe{sub 3}O{sub 4}, and the origin of electric field (voltage) dependence of magnetoresistance is explained proposing electronic band diagram of Fe{sub 3}O{sub 4}/SiO{sub 2}/p-Si heterojunction. This interesting result may have importance to integrate Si-based magnetoresistance sources in multifunctional spintronic devices.

  3. Angular dependent light emission from planar waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Peter, Jaison, E-mail: jaison.peter@gmail.com [International School of Photonics, Cochin University of Science and Technology, Cochin 682022 (India); CRE" +E, IDEAS Research Institute, Robert Gordon University, Aberdeen AB10 7GJ (United Kingdom); Prabhu, Radhakrishna [CRE" +E, IDEAS Research Institute, Robert Gordon University, Aberdeen AB10 7GJ (United Kingdom); Radhakrishnan, P.; Vallabhan, C. P. G.; Nampoori, V. P. N.; Kailasnath, M. [International School of Photonics, Cochin University of Science and Technology, Cochin 682022 (India)

    2015-01-07

    We have investigated the angular dependence of amplified spontaneous emission (ASE) and laser emission from an asymmetric and free-standing polymer thin films doped with rhodamine 6G, which is transversely pumped by a pulsed Nd:YAG laser. A semi-leaky waveguide or quasi-waveguide structure has been developed by spin coating technique. In these waveguides, the light was confined by the film/air-film/glass substrate interfaces. At the film/substrate interface, a portion of light will reflect back into the film (guided mode) and the remaining refracted to the substrate resulting in cutoff modes. A blue-shift in ASE has been observed when the pump power was increased from 8 to 20 mW allowing a limited range of tuning of emission wavelength. To study the directionality of the ASE from the waveguide, we have measured the output intensity and FWHM of emission spectra as a function of viewing angle (θ) from the plane parallel to film. From the detailed examination of the output emission spectra, as +θ increases from 0° there has been an initial decrease in output intensity, but at a particular angle ≈10° an increase in output intensity was observed. This additional peak in output intensity as +θ is a clear indication of coexistence of the cutoff mode. We also present a compact solid-state laser based on leaky mode propagation from the dye-doped polymer free-standing film (∼50 μm thickness) waveguide. The partial reflections from the broad lateral surfaces of the free-standing films provided the optical feedback for the laser emission with high directionality. For a pump power of 22 mW, an intense line with FWHM <0.2 nm was observed at 578 nm.

  4. Correlation between the Magnetoresistance, IR Magnetoreflectance, and Spin-Dependent Characteristics of Multilayer Magnetic Films

    Directory of Open Access Journals (Sweden)

    V. G. Kravets

    2012-01-01

    Full Text Available We present the experimental results on magnetorefractive effect (MRE in ferromagnetic metal-metal and metal-insulator multilayer films of different composition and different type of magnetoresistive effects. The shape and magnitude of the MRE dependences are found to be very sensitive to the spin-dependent scattering parameters and the effective polarization of the electron density of state around the Fermi level. A study of an MRE in multilayered films is shown to be sufficient for direct extracting of the spin-dependent relaxation times of electron (for GMR-like samples and energy dependence of the tunnel spin-polarization density of states near the Fermi level for layered TMR films. It is proposed to use the magnetorefractive effect as a noncontact probe of magnetoresistive effects in thin magnetic films through investigations of the field-dependent reflection behaviors of multilayered films in the IR region.

  5. Domain wall magnetoresistance in nanowires: Dependence on geometrical factors and material parameters

    Energy Technology Data Exchange (ETDEWEB)

    Allende, S.; Retamal, J.C. [Departamento de Física, CEDENNA, Universidad de Santiago de Chile, USACH, Avenida Ecuador 3493, 917-0124 Santiago (Chile); Altbir, D., E-mail: dora.altbir@usach.cl [Departamento de Física, CEDENNA, Universidad de Santiago de Chile, USACH, Avenida Ecuador 3493, 917-0124 Santiago (Chile); D' Albuquerque e Castro, J. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro 21941-972 (Brazil)

    2014-04-15

    The magnetoresistance associated with the presence of domain walls in metallic nanowires is investigated as a function of geometrical parameters, corresponding to the wall thickness and the nanowire width, as well as of material parameters, such as the band filling and the exchange interaction. Transport across the structure is described within Landauer formalism. Both cases of saturated and non-saturated ferromagnets are considered, and in all of them the contributions from spin-flip and non-spin-flip are separately analyzed. It has been found that for certain range of parameters deviations in the normalized magnetoresistance as high as 20% may be achieved. In addition, it has been shown that the spin-flip process is dependent on the wall thickness. - Highlights: • We identify thickness regions within which transport across the wall is dominated by either spin-flip or non-spin-flip process. • We analyze the dependence of the magnetoresistance on both the material's band filling and strength of the exchange interaction. • We identify parameter ranges within which magnetoresistance ratios as high as 20% or even more might be achieved.

  6. Relativistic calculations of angular dependent photoemission time delay

    CERN Document Server

    Kheifets, A S; Deshmukh, P C; Dolmatov, V K; Manson, S T

    2016-01-01

    Angular dependence of photoemission time delay for the valence $np_{3/2}$ and $np_{1/2}$ subshells of Ar, Kr and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.

  7. Bias voltage dependence of tunneling anisotropic magnetoresistance in magnetic tunnel junctions with MgO and Al2O3 tunnel barriers.

    Science.gov (United States)

    Gao, Li; Jiang, Xin; Yang, See-Hun; Burton, J D; Tsymbal, Evgeny Y; Parkin, Stuart S P

    2007-11-30

    Tunneling anisotropic magnetoresistance (TAMR) is observed in tunnel junctions with transition metal electrodes as the moments are rotated from in-plane to out-of-plane in sufficiently large magnetic fields that the moments are nearly parallel to one another. A complex angular dependence of the tunneling resistance is found with twofold and fourfold components that vary strongly with bias voltage. Distinctly different TAMR behaviors are obtained for devices formed with highly textured crystalline MgO(001) and amorphous Al2O3 tunnel barriers. A tight-binding model shows that a fourfold angular dependence can be explained by the presence of an interface resonant state that affects the transmission of the contributing tunneling states through a spin-orbit interaction. PMID:18233308

  8. Temperature dependence of spin Hall magnetoresistance in W/CoFeB bilayer

    Science.gov (United States)

    Okuno, Takaya; Taniguchi, Takuya; Kim, Sanghoon; Baek, Seung-heon Chris; Park, Byong-Guk; Moriyama, Takahiro; Kim, Kab-Jin; Ono, Teruo

    2016-08-01

    We investigate the temperature dependence of the spin Hall magnetoresistance (SMR) in a W/CoFeB bilayer. The SMR is found to increase with decreasing temperature. An analysis based on the SMR theory suggests that the spin Hall angle of W and/or the spin polarization of CoFeB can be the origin of the temperature dependence of the SMR. We also find that the spin diffusion length and the resistivity of W do not significantly vary with temperature, which indicates the necessity of further study on the electron transport mechanism in W films to reveal the origin of the spin Hall effect in W.

  9. Large anisotropic normal-state magnetoresistance in clean MgB2 thin films.

    Science.gov (United States)

    Li, Qi; Liu, B T; Hu, Y F; Chen, J; Gao, H; Shan, L; Wen, H H; Pogrebnyakov, A V; Redwing, J M; Xi, X X

    2006-04-28

    We report a large normal-state magnetoresistance with temperature-dependent anisotropy in very clean epitaxial MgB2 thin films (residual resistivity much smaller than 1 microOmega cm) grown by hybrid physical-chemical vapor deposition. The magnetoresistance shows a complex dependence on the orientation of the applied magnetic field, with a large magnetoresistance (Delta(rho)/(rho)0=136%) observed for the field H perpendicular ab plane. The angular dependence changes dramatically as the temperature is increased, and at high temperatures the magnetoresistance maximum changes to H||ab. We attribute the large magnetoresistance and the evolution of its angular dependence with temperature to the multiple bands with different Fermi surface topology in MgB2 and the relative scattering rates of the sigma and pi bands, which vary with temperature due to stronger electron-phonon coupling for the sigma bands.

  10. Strong temperature dependence of extraordinary magnetoresistance correlated to mobility in a two-contact device

    KAUST Repository

    Sun, Jian

    2012-02-21

    A two-contact extraordinary magnetoresistance (EMR) device has been fabricated and characterized at various temperatures under magnetic fields applied in different directions. Large performance variations across the temperature range have been found, which are due to the strong dependence of the EMR effect on the mobility. The device shows the highest sensitivity of 562ω/T at 75 K with the field applied perpendicularly. Due to the overlap between the semiconductor and the metal shunt, the device is also sensitive to planar fields but with a lower sensitivity of about 20 to 25% of the one to perpendicular fields. © 2012 The Japan Society of Applied Physics.

  11. Strong spin-orbit coupling and Zeeman spin splitting in angle dependent magnetoresistance of Bi2Te3

    International Nuclear Information System (INIS)

    We have studied angle dependent magnetoresistance of Bi2Te3 thin film with field up to 9 T over 2–20 K temperatures. The perpendicular field magnetoresistance has been explained by the Hikami-Larkin-Nagaoka theory alone in a system with strong spin-orbit coupling, from which we have estimated the mean free path, the phase coherence length, and the spin-orbit relaxation time. We have obtained the out-of-plane spin-orbit relaxation time to be small and the in-plane spin-orbit relaxation time to be comparable to the momentum relaxation time. The estimation of these charge and spin transport parameters are useful for spintronics applications. For parallel field magnetoresistance, we have confirmed the presence of Zeeman effect which is otherwise suppressed in perpendicular field magnetoresistance due to strong spin-orbit coupling. The parallel field data have been explained using both the contributions from the Maekawa-Fukuyama localization theory for non-interacting electrons and Lee-Ramakrishnan theory of electron-electron interactions. The estimated Zeeman g-factor and the strength of Coulomb screening parameter agree well with the theory. Finally, the anisotropy in magnetoresistance with respect to angle has been described by the Hikami-Larkin-Nagaoka theory. This anisotropy can be used in anisotropic magnetic sensor applications.

  12. Angular dependence of spin-orbit spin-transfer torques

    KAUST Repository

    Lee, Ki-Seung

    2015-04-06

    In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.

  13. Angular-dependent magnetization reversal processes in artificial spin ice

    Science.gov (United States)

    Burn, D. M.; Chadha, M.; Branford, W. R.

    2015-12-01

    The angular dependence of the magnetization reversal in interconnected kagome artificial spin ice structures has been studied through experimental MOKE measurements and micromagnetic simulations. This reversal is mediated by the propagation of magnetic domain walls along the interconnecting bars, which either nucleate at the vertex or arrive following an interaction in a neighboring vertex. The physical differences in these processes show a distinct angular dependence allowing the different contributions to be identified. The configuration of the initial magnetization state, either locally or on a full sublattice of the system, controls the reversal characteristics of the array within a certain field window. This shows how the available magnetization reversal routes can be manipulated and the system can be trained.

  14. Time and "angular" dependent backgrounds from stationary axisymmetric solutions

    CERN Document Server

    Obregón, O; Ryan, M P; Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.

    2004-01-01

    Backgrounds depending on time and on "angular" variable, namely polarized and unpolarized $S^1 \\times S^2$ Gowdy models, are generated as the sector inside the horizons of the manifold corresponding to axisymmetric solutions. As is known, an analytical continuation of ordinary $D$-branes, $iD$-branes allows one to find $S$-brane solutions. Simple models have been constructed by means of analytic continuation of the Schwarzchild and the Kerr metrics. The possibility of studying the $i$-Gowdy models obtained here is outlined with an eye toward seeing if they could represent some kind of generalized $S$-branes depending not only on time but also on an ``angular'' variable.

  15. Temperature dependence of angular momentum transport across interfaces

    Science.gov (United States)

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

    2016-08-01

    Angular momentum transport in magnetic multilayered structures plays a central role in spintronic physics and devices. The angular momentum currents or spin currents are carried by either quasiparticles such as electrons and magnons, or by macroscopic order parameters such as local magnetization of ferromagnets. Based on the generic interface exchange interaction, we develop a microscopic theory that describes interfacial spin conductance for various interfaces among nonmagnetic metals, ferromagnetic insulators, and antiferromagnetic insulators. Spin conductance and its temperature dependence are obtained for different spin batteries including spin pumping, temperature gradient, and spin Hall effect. As an application of our theory, we calculate the spin current in a trilayer made of a ferromagnetic insulator, an antiferromagnetic insulator, and a nonmagnetic heavy metal. The calculated results on the temperature dependence of spin conductance quantitatively agree with the existing experiments.

  16. Angular dependence of primordial trispectra and CMB spectral distortions

    Science.gov (United States)

    Shiraishi, Maresuke; Bartolo, Nicola; Liguori, Michele

    2016-10-01

    Under the presence of anisotropic sources in the inflationary era, the trispectrum of the primordial curvature perturbation has a very specific angular dependence between each wavevector that is distinguishable from the one encountered when only scalar fields are present, characterized by an angular dependence described by Legendre polynomials. We examine the imprints left by curvature trispectra on the TTμ bispectrum, generated by the correlation between temperature anisotropies (T) and chemical potential spectral distortions (μ) of the Cosmic Microwave Background (CMB). Due to the angular dependence of the primordial signal, the corresponding TTμ bispectrum strongly differs in shape from TTμ sourced by the usual gNL or τNL local trispectra, enabling us to obtain an unbiased estimation. From a Fisher matrix analysis, we find that, in a cosmic-variance-limited (CVL) survey of TTμ, a minimum detectable value of the quadrupolar Legendre coefficient is d2 ~ 0.01, which is 4 orders of magnitude better than the best value attainable from the TTTT CMB trispectrum. In the case of an anisotropic inflationary model with a f(phi)F2 interaction (coupling the inflaton field phi with a vector kinetic term F2), the size of the curvature trispectrum is related to that of quadrupolar power spectrum asymmetry, g*. In this case, a CVL measurement of TTμ makes it possible to measure g* down to 10‑3.

  17. Quantized magnetoresistance in atomic-size contacts.

    Science.gov (United States)

    Sokolov, Andrei; Zhang, Chunjuan; Tsymbal, Evgeny Y; Redepenning, Jody; Doudin, Bernard

    2007-03-01

    When the dimensions of a metallic conductor are reduced so that they become comparable to the de Broglie wavelengths of the conduction electrons, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In ferromagnetic metals, the spin angular momentum of the electrons results in spin-dependent conductance quantization and various unusual magnetoresistive phenomena. Theorists have predicted a related phenomenon known as ballistic anisotropic magnetoresistance (BAMR). Here we report the first experimental evidence for BAMR by observing a stepwise variation in the ballistic conductance of cobalt nanocontacts as the direction of an applied magnetic field is varied. Our results show that BAMR can be positive and negative, and exhibits symmetric and asymmetric angular dependences, consistent with theoretical predictions. PMID:18654248

  18. Angular momentum of non-paraxial light beam: Dependence of orbital angular momentum on polarization

    OpenAIRE

    Li, Chun-Fang

    2009-01-01

    It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that is associated with the former part is spin, and the angular momentum that is associated with the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin ...

  19. An Explicit Function Expression for dc Bias and Temperature Dependence of Magnetoresistances in Magnetic Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An explicit function expression for the bias voltage or/and temperature dependences of tunnel magnetoresistance ratio and resistances were obtained with a unique set of intrinsic parameters. Two of these intrinsic parameters are the Curie temperature TC and the density of state (DOS) for itinerant majority and minority electrons ξ(ρM/ρm),which are the eigen parameters of ferromagnetic electrodes. Others are the spin-dependent matrix-element ratio (i.e.,|Td|2/|TJ|2 ) and the anisotropic-wavelength-cutoff energy EγC of spin-wave spectrum in magnetic tunnel junction (MT J), which are the structure parameters of an MTJ. These intrinsic parameters can be predetermined using the experimental measurement or, in principle, using the first-principle calculation method for an MTJ with the three key layers of FM/I/FM. Furthermore, a series of experimental data for an MTJ, for example, a spin-valve-type MTJ of Ta (5 nm)/Ni79Fe21(25 nm)/Ir22Mn78(12 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide/Co75Fe25(4 nm)/Ni79Fe21(20 nm)/Ta (5 nm) in this work, can be self-consistently evaluated and explained using such concise explicit function formulations.

  20. Angular dependence of primordial trispectra and CMB spectral distortions

    CERN Document Server

    Shiraishi, Maresuke; Liguori, Michele

    2016-01-01

    Under the presence of anisotropic sources in the inflationary era, the trispectrum of the primordial curvature perturbation is sensitive to the angles between each wave vector. We examine the imprints left by curvature trispectra, in which the angular dependence is described by Legendre polynomials, on the $TT\\mu$ bispectrum, generated by the correlation between temperature anisotropies (T) and chemical potential spectral distortions ($\\mu$) of the Cosmic Microwave Background (CMB). Due to the angular dependence of the primordial signal, the corresponding $TT\\mu$ bispectrum strongly differs in shape from $TT\\mu$ sourced by the usual $g_{\\rm NL}$ or $\\tau_{\\rm NL}$ local trispectra, enabling us to obtain an unbiased estimation. From a Fisher matrix analysis, we find that, in a cosmic-variance-limited (CVL) survey of $TT\\mu$, a minimum detectable value of the quadrupolar Legendre coefficient is $d_2 \\sim 0.01$, which is 4 orders of magnitude better than the best value attainable from the $TTTT$ CMB trispectrum....

  1. Combined study of microwave-power/linear-polarization dependence of the microwave-radiation-induced magnetoresistance oscillations in GaAs/AlGaAs devices

    OpenAIRE

    Ye, Tianyu; Liu, Han-Chun; Wegscheider, W.; Mani, R G

    2014-01-01

    We report the results of a combined microwave polarization-dependence and power-dependence study of the microwave-radiation-induced magnetoresistance oscillations in high mobility GaAs/AlGaAs heterostructure devices at liquid helium temperatures. The diagonal resistance was measured with the magnetic field fixed at the extrema of the radiation-induced magnetoresistance oscillations, as the microwave power was varied at a number of microwave polarization angles. The results indicate a nonlinea...

  2. Magnetoresistance effect in (La, Sr)MnO{sub 3} bicrystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Alejandro, G; Pastoriza, H; Granada, M; Rojas Sanchez, J C; Sirena, M; Alascio, B [Centro Atomico Bariloche (CNEA), Av. Bustillo 9500, 8400 San Carlos de Bariloche, Pcia. de Rio Negro (Argentina); Steren, L B; Vega, D, E-mail: galejand@cab.cnea.gov.a [Centro Atomico Constituyentes (CNEA), 1650 San MartIn, Pcia. de Buenos Aires (Argentina)

    2010-09-01

    The angular dependence of the magnetoresistance effect has been measured on bicrystalline La{sub 0.75}Sr{sub 0.25}MnO{sub 3} films. The measurements have been performed on an electronically lithographed Wheatstone bridge. The study of the angular dependence of both the magnetoresistance and the resistance of single-crystalline and grain-boundary regions of the samples allowed us to isolate two contributions of low-field magnetoresistance in manganites. One of them is associated with the spin-orbit effect, i.e. the anisotropic magnetoresistance of ferromagnetic compounds, and the other one is related to spin-disorder regions at the grain boundary. Complementary x-ray diffraction, ferromagnetic resonance and low temperature magnetization experiments contribute to the characterization of the magnetic anisotropy of the samples and the general comprehension of the problem.

  3. Magnetoresistance effect in (La, Sr)MnO3 bicrystalline films.

    Science.gov (United States)

    Alejandro, G; Steren, L B; Pastoriza, H; Vega, D; Granada, M; Sánchez, J C Rojas; Sirena, M; Alascio, B

    2010-09-01

    The angular dependence of the magnetoresistance effect has been measured on bicrystalline La(0.75)Sr(0.25)MnO(3) films. The measurements have been performed on an electronically lithographed Wheatstone bridge. The study of the angular dependence of both the magnetoresistance and the resistance of single-crystalline and grain-boundary regions of the samples allowed us to isolate two contributions of low-field magnetoresistance in manganites. One of them is associated with the spin-orbit effect, i.e. the anisotropic magnetoresistance of ferromagnetic compounds, and the other one is related to spin-disorder regions at the grain boundary. Complementary x-ray diffraction, ferromagnetic resonance and low temperature magnetization experiments contribute to the characterization of the magnetic anisotropy of the samples and the general comprehension of the problem.

  4. Angular dependence of interactions in polycrystalline Co nanowire arrays

    International Nuclear Information System (INIS)

    Ordered Co nanowire arrays with a constant geometry (∼40 nm diameter, ∼10 μm length and ∼100 nm interwire distance) were ac pulse electrodeposited into anodic aluminum oxide template under different deposition current densities (5.31, 7.08 and 8.85 mA/cm2). Microstructure and magnetic properties of the samples were studied using X-ray diffraction (XRD) pattern, selected area diffraction (SAED) pattern and first-order reversal curve (FORC) diagrams. SAED patterns showed inhomogeneous polycrystalline structure along the length of a nanowire. FORC diagrams revealed two-phase magnetic behavior in which soft and hard magnetic phases related to triplet cobalt crystalline directions. Despite the fact that angular dependence of hysteresis loops provides information about magnetization reversal, angular FORC offers additional information on the magnetostatic and interphase interactions depending on angle between the field and nanowires axis (α). Different magnetic behaviors were seen by change in α; interacting two-phase behavior in α = 0° which reduced to a non-interacting behavior for α > 60° may be attributed to reduce delay in magnetization reversal of two phases. Increasing the reversible portion of the major hysteresis loop in α = 90° is a possible source of difference between the hard to soft ratio obtained from FORC diagrams and XRD patterns. - Highlights: • Increasing α cause to reduce demagnetizing interaction and remove additional feature in 90°. • Magnetic behavior of Co-hcp(002) change from hard to soft phase as α increased from 0 to 90°. • Increasing reversible portion in 90° is source of different hard-soft ratio obtained from FORC and XRD

  5. Anisotropic Magnetotransport and Exotic Longitudinal Linear Magnetoresistance in WTe2 Crystals

    OpenAIRE

    Zhao, Yanfei; Liu, Haiwen; Yan, Jiaqiang; An, Wei; Liu, Jun; Zhang, Xi; Jiang, Hua; Li, Qing; Wang, Yong; Li, Xin-Zheng; Mandrus, David; Xie, X. C.; Pan, Minghu; Wang, Jian

    2015-01-01

    WTe2 semimetal, as a typical layered transition-metal dichalcogenide, has recently attracted much attention due to the extremely large, non-saturating parabolic magnetoresistance in perpendicular field. Here, we report a systematic study of the angular dependence of the magnetoresistance in WTe2 single crystal. The violation of the Kohler rule and a significant anisotropic magnetotransport behavior in different magnetic field directions are observed. Surprisingly, when the applied field is pa...

  6. Temperature and thickness dependence of tunneling anisotropic magnetoresistance in exchange-biased Py/IrMn/MgO/Ta stacks

    Science.gov (United States)

    Reichlová, H.; Novák, V.; Kurosaki, Y.; Yamada, M.; Yamamoto, H.; Nishide, A.; Hayakawa, J.; Takahashi, H.; Maryško, M.; Wunderlich, J.; Marti, X.; Jungwirth, T.

    2016-07-01

    We investigate the thickness and temperature dependence of a series of Ni{}0.8Fe{}0.2/Ir{}0.2Mn{}0.8 bilayer samples with varying thickness ratio of the ferromagnet/antiferromagnet ({{t}}{{FM}}/{{t}}{{AFM}}) in order to explore the exchange coupling strengths in tunneling anisotropic magnetoresistance (TAMR) devices. Specific values of {{t}}{{FM}}/{{t}}{{AFM}} lead to four distinct scenarios with specific electric responses to moderate magnetic fields. The characteristic dependence of the measured TAMR signal on applied voltage allows us to confirm its persistence up to room temperature despite an overlapped contribution by a thermal magnetic noise.

  7. Infinite magnetoresistance from the spin dependent proximity effect in symmetry driven bcc-Fe/V/Fe heteroepitaxial superconducting spin valves.

    Science.gov (United States)

    Miao, Guo-Xing; Ramos, Ana V; Moodera, Jagadeesh S

    2008-09-26

    Superconductivity in fully epitaxial bcc-Fe/V/Fe hybrid spin valve structures is influenced by the spin currents and supercurrents as well as band symmetry. The transition temperature is spin dependent in the presence of the proximity effect. A unique feature in this system is the band symmetry filtering taking place at the Fe/V interface. The absence of Delta2 Bloch states at the Fermi level in the Fe spin majority channel leads to spin selectivity and reduced transparency at the interface. Infinite magnetoresistance with clear remanence states is obtained, and implies the potential for spintronic applications. PMID:18851482

  8. Temperature dependent three-dimensional anisotropy of the magnetoresistance in WTe$_2$

    OpenAIRE

    Thoutam, L. R.; Wang, Y.L.; Xiao, Z. L.; S. Das; Luican-Mayer, A.; Divan, R.; Crabtree, G.W.; Kwok, W. K.

    2015-01-01

    Extremely large magnetoresistance (XMR) was recently discovered in WTe$_2$, triggering extensive research on this material regarding the XMR origin. Since WTe$_2$ is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe$_2$: (1) WTe$_2$ is electronically 3D with a mass anisotropy as low as $2$, as revealed by the 3D scaling behavior of ...

  9. Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe2

    Science.gov (United States)

    Thoutam, L. R.; Wang, Y. L.; Xiao, Z. L.; Das, S.; Luican-Mayer, A.; Divan, R.; Crabtree, G. W.; Kwok, W. K.

    2015-07-01

    Extremely large magnetoresistance (XMR) was recently discovered in WTe2 , triggering extensive research on this material regarding the XMR origin. Since WTe2 is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe2 : (1) WTe2 is electronically 3D with a mass anisotropy as low as 2, as revealed by the 3D scaling behavior of the resistance R (H ,θ )=R (ɛθH ) with ɛθ=(cos2θ +γ-2sin2θ )1 /2 , θ being the magnetic field angle with respect to the c axis of the crystal and γ being the mass anisotropy and (2) the mass anisotropy γ varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state. Our results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe2 , including the origin of the remarkable "turn-on" behavior in the resistance versus temperature curve, which has been widely observed in many materials and assumed to be a metal-insulator transition.

  10. Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe_{2}.

    Science.gov (United States)

    Thoutam, L R; Wang, Y L; Xiao, Z L; Das, S; Luican-Mayer, A; Divan, R; Crabtree, G W; Kwok, W K

    2015-07-24

    Extremely large magnetoresistance (XMR) was recently discovered in WTe_{2}, triggering extensive research on this material regarding the XMR origin. Since WTe_{2} is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe_{2}: (1) WTe_{2} is electronically 3D with a mass anisotropy as low as 2, as revealed by the 3D scaling behavior of the resistance R(H,θ)=R(ϵ_{θ}H) with ϵ_{θ}=(cos^{2}θ+γ^{-2}sin^{2}θ)^{1/2}, θ being the magnetic field angle with respect to the c axis of the crystal and γ being the mass anisotropy and (2) the mass anisotropy γ varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state. Our results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe_{2}, including the origin of the remarkable "turn-on" behavior in the resistance versus temperature curve, which has been widely observed in many materials and assumed to be a metal-insulator transition. PMID:26252701

  11. Effects of angular dependent terms in the interatomic potential on defect properties in TiAl

    Energy Technology Data Exchange (ETDEWEB)

    Panova, J.; Farkas, D. [Virginia Polytechnic Inst., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1995-08-01

    Interatomic potentials of the Embedded Atom and Embedded Defect types were used to study the effect of the angular dependent term in the Embedded Defect potential on the properties of defects in TiAl. The defect properties were computed with interatomic potentials developed with and without angular dependent terms. It was found that the inclusion of the angular dependent terms tends to increase the energies of the APB`s and lower the energies of stacking faults. The effects of the angular term on the relaxation around vacancies and antisites in TiAl was also studied, as well as the core structure of several dislocations in this compound.

  12. Angular dependence to the threshold intensity of scattered radiation for passing ionic-sound waves

    International Nuclear Information System (INIS)

    Present article is devoted to angular dependence to the threshold intensity of scattered radiation for passing ionic-sound waves. The angular dependence of intensity of scattered radiation in two-dimensional field of localization of a wave of a rating of passing ionic-sound waves at any scattering angles was considered. (author)

  13. CURRENT-DEPENDENT POSITIVE MAGNETORESISTANCE IN Ga-DOPED a0.5Ca0.5MnO3

    Institute of Scientific and Technical Information of China (English)

    CHEN XIN; WANG ZHI-HONG; LI RUN-WEI; SHEN BAO-GEN; ZHAO HONG-WU; ZHAN WEN-SHAN; CHEN JIN-SONG; ZHANG XI-XIANG

    2001-01-01

    The magnetic and transport properties of the Ga-doped charge-ordering state Lao.5Cao.5MnO3 have been studied.A current-dependent large positive magnetoresistance (1080%) at 5 K was observed. These observations are interpreted in terms of the spin-dependent tunnelling process between ferromagnetic clusters embedded in an antiferromagnetic matrix.

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

    Energy Technology Data Exchange (ETDEWEB)

    Park, June-Young; Park, Byong-Guk, E-mail: bgpark@kaist.ac.kr [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Baek, Seung-heon Chris [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Department of Electrical Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Park, Seung-Young; Jo, Younghun [Spin Engineering Physics Team, Division of Scientific Instrument, KBSI, Daejeon 305-806 (Korea, Republic of)

    2015-11-02

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

  15. Spin rectification induced by spin Hall magnetoresistance at room temperature

    Science.gov (United States)

    Wang, P.; Jiang, S. W.; Luan, Z. Z.; Zhou, L. F.; Ding, H. F.; Zhou, Y.; Tao, X. D.; Wu, D.

    2016-09-01

    We have experimentally and theoretically investigated the dc voltage generation in the heterostructure of Pt and yttrium iron garnet under the ferromagnetic resonance. Besides a symmetric Lorenz line shape dc voltage, an antisymmetric Lorenz line shape dc voltage is observed in field scan, which can solely originate from the spin rectification effect due to the spin Hall magnetoresistance. The angular dependence of the dc voltage is theoretically analyzed by taking into account both the spin pumping and the spin rectification effects. We find that the experimental results are in excellent agreement with the theoretical model, further identifying the spin Hall magnetoresistance origin of the spin rectification effect. Moreover, the spin pumping and the spin rectification effects are quantitatively separated by their different angular dependence at particular experimental geometry.

  16. Strong spin-orbit coupling and Zeeman spin splitting in angle dependent magnetoresistance of Bi{sub 2}Te{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Dey, Rik, E-mail: rikdey@utexas.edu; Pramanik, Tanmoy; Roy, Anupam; Rai, Amritesh; Guchhait, Samaresh; Sonde, Sushant; Movva, Hema C. P.; Register, Leonard F.; Banerjee, Sanjay K. [Microelectronics Research Center, University of Texas at Austin, Austin, Texas 78758 (United States); Colombo, Luigi [Texas Instruments, Dallas, Texas 75243 (United States)

    2014-06-02

    We have studied angle dependent magnetoresistance of Bi{sub 2}Te{sub 3} thin film with field up to 9 T over 2–20 K temperatures. The perpendicular field magnetoresistance has been explained by the Hikami-Larkin-Nagaoka theory alone in a system with strong spin-orbit coupling, from which we have estimated the mean free path, the phase coherence length, and the spin-orbit relaxation time. We have obtained the out-of-plane spin-orbit relaxation time to be small and the in-plane spin-orbit relaxation time to be comparable to the momentum relaxation time. The estimation of these charge and spin transport parameters are useful for spintronics applications. For parallel field magnetoresistance, we have confirmed the presence of Zeeman effect which is otherwise suppressed in perpendicular field magnetoresistance due to strong spin-orbit coupling. The parallel field data have been explained using both the contributions from the Maekawa-Fukuyama localization theory for non-interacting electrons and Lee-Ramakrishnan theory of electron-electron interactions. The estimated Zeeman g-factor and the strength of Coulomb screening parameter agree well with the theory. Finally, the anisotropy in magnetoresistance with respect to angle has been described by the Hikami-Larkin-Nagaoka theory. This anisotropy can be used in anisotropic magnetic sensor applications.

  17. Raman scattering investigation of large positive magnetoresistance material WTe$_2$

    OpenAIRE

    Kong, W. -D.; Wu, S. -F.; Richard, P.; Lian, C. -S.; Wang, J. -T.; Yang, C. -L.; Shi, Y. -G.; H. Ding

    2015-01-01

    We have performed polarized Raman scattering measurements on WTe$_2$, for which an extremely large positive magnetoresistance has been reported recently. We observe 5 A$_1$ phonon modes and 2 A$_2$ phonon modes out of 33 Raman active modes, with frequencies in good accordance with first-principles calculations. The angular dependence of the intensity of the peaks observed is consistent with the Raman tensors of the $C_{2v}$ point group symmetry attributed to WTe$_2$. Although the phonon spect...

  18. Depth and latitude dependence of the solar internal angular velocity

    Energy Technology Data Exchange (ETDEWEB)

    Rhodes, E.J. Jr.; Cacciani, A.; Korzennik, S.; Tomczyk, S.; Ulrich, R.K.; Woodard, M.F. (Southern California Univ., Los Angeles, CA (USA) JPL, Pasadena, CA (USA) Roma I Universita (Italy) California Univ., Los Angeles (USA))

    1990-03-01

    One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone. 43 refs.

  19. Depth and latitude dependence of the solar internal angular velocity

    Science.gov (United States)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

    1990-01-01

    One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone.

  20. Vortex domain structures and dc current dependence of magneto-resistances in magnetic tunnel junctions

    Institute of Scientific and Technical Information of China (English)

    Wei Hong-Xiang; Lu Qing-Feng; Zhao Su-Fen; Zhang Xie-Qun; Feng Jia-Feng; Han Xiu-Feng

    2004-01-01

    Microfabrication and the magneto-transport characteristics of the magnetic tunnel junctions (MTJs) with a spin-valve-type structure of Ta (5nm)/Ni7gFe21 (25nm)/Ir22Mn78 (12nm)/Co75Fe25 (4nm)/Al(0.8nm) oxide/Co75Fe25(4nm)/Ni7gFe21 (20nm)/Ta(5nm) were investigated in this paper. A series of experimental data measured with a MTJ was used to verify a magnon-assisted tunnelling model and theory. Furthermore, a micromagnetics simulation shows that the butterfly-like vortex domain structures can be formed under a current-induced Oersted field, which decreases the net magnetization values of the ferromagnetic electrodes under a large dc current (i.e., in high voltage regimes). It is one of the main reasons for the tunnel magnetoresistance ratios to decrease significantly at high voltage biasing.

  1. Array calibration of angularly dependent gain and phase uncertainties with carry-on instrumental sensors

    Institute of Scientific and Technical Information of China (English)

    WANG Buhong; WANG Yongliang; CHEN Hui; GUO Ying

    2004-01-01

    Array calibration with angularly dependent gain and phase uncertainties has long been a difficult problem. Although many array calibration methods have been reported extensively in the literature, they almost all assumed an angularly independent model for array uncertainties. Few calibration methods have been developed for the angularly dependent array uncertainties. A novel and efficient auto-calibration method for angularly dependent gain and phase uncertainties is proposed in this paper, which is called ISM (Instrumental Sensors Method). With the help of a few well-calibrated instrumental sensors, the ISM is able to achieve favorable and unambiguous direction-of-arrivals (DOAs) estimate and the corresponding angularly dependent gain and phase estimate simultaneously, even in the case of multiple non-disjoint sources. Since the mutual coupling and sensor position errors can all be described as angularly dependent gain/phase uncertainties, the ISM proposed still works in the presence of a combination of all these array perturbations. The ISM can be applied to arbitrary array geometries including linear arrays. The ISM is computationally efficient and requires only one-dimensional search, with no high-dimensional nonlinear search and convergence burden involved. Besides, no small error assumption is made, which is always an essential prerequisite for many existing array calibration techniques. The estimation performance of the ISM is analyzed theoretically and simulation results are provided to demonstrate the effectiveness and behavior of the proposed ISM.

  2. Sensitivity in frequency dependent angular rotation of optical vortices.

    Science.gov (United States)

    Rumala, Yisa S

    2016-03-10

    This paper presents robust strategies to enhance the rotation sensitivity (and resolution) of a coherent superposition of optical vortices emerging from a single spiral phase plate (SPP) device when light's optical frequency (or wavelength) going into the SPP device is varied. The paper discusses the generation and measurement of ultrasmall rotation. Factors that affect the ability to perform precision rotation measurements include the linewidth and stability of the input light source, the number of photon counts making position rotation measurements on the CCD detector, SPP reflectivity, the length of SPP device, and the angular modulation frequency of the intensity pattern due to a coherent superposition of optical vortices in a single SPP device. This paper also discusses parameters to obtain a high-sensitivity single shot measurement and multiple measurements. Furthermore, it presents what I believe is a new scaling showing the enhancement in sensitivity (and resolution) in the standard quantum limit and Heisenberg limit. With experimentally realizable parameters, there is an enhancement of rotation sensitivity by at least one order of magnitude compared to previous rotation measurements with optical vortices. Understanding robust strategies to enhance the rotation sensitivity in an SPP device is important to metrology in general and for building compact SPP sensors such as gyroscopes, molecular sensors, and thermal sensors. PMID:26974798

  3. ANGULAR VELOCITY AND CORIOLIS EFFECT IN TIME-DEPENDENT QUANTUM MECHANICAL SU2 ROTATION

    Institute of Scientific and Technical Information of China (English)

    FAN HONG-YI; SUN MING-ZHAI

    2001-01-01

    Starting from a time-dependent rotation U (t) in SU2 group element space, we derive its corresponding quantum mechanical dynamic Coriolis term and the relationship between U (t) and rotational angular velocity. Throughout our discussion, the technique of integration within an ordered product of operators is fully used, which has the advantage that the correspondence between the classical rotation and the quantum rotation is in a transparent fashion. A new angular-velocity formula is also derived.

  4. Angular dependence of surfactant-mediated forces between carbon nanotubes.

    Science.gov (United States)

    Müter, Dirk; Angelikopoulos, Panagiotis; Bock, Henry

    2012-12-27

    We employ dissipative particle dynamics to examine surfactant-mediated forces between two carbon nanotubes. Calculations are performed varying both the distance and the angle between the nanotubes. For small distances, a repulsive region is observed, followed by an overall attractive interval with strong oscillations in the force. Decreasing the angle between the tubes leads to a steady increase in the force, but the relative dependence on the separation distance is preserved. We find that the force scales linearly with the size of the overlap area between the tubes. This allows us to express the angle dependence by a simple equation, whereas the distance dependence is represented by a master curve. For the parallel case, the behavior is significantly different. PMID:23116052

  5. Angular dependences in electroweak semi-inclusive leptoproduction

    NARCIS (Netherlands)

    Boer, D; Jakob, R; Mulders, PJ

    2000-01-01

    We present the leading order unpolarized and polarized cross sections in electroweak semi-inclusive deep inelastic leptoproduction, The azimuthal dependences in the cross section differential in the transverse momentum of the vector boson arise due to intrinsic transverse momenta of the quarks. Howe

  6. Angular dependent transport properties of MgB2 films with columnar grains

    International Nuclear Information System (INIS)

    We studied the angular dependence of the transport properties of MgB2 films with columnar grains grown by hybrid physical chemical vapor deposition method, one sample with unreacted boron in the volume and the other sample with no traceable impurity phase. The angular dependence of resistivity and critical current density in applied magnetic fields for both samples showed a flux pinning effect by the grain boundaries between columnar grains. The temperature dependence of the upper critical fields was analyzed by using the dirty-limit two-gap model. We found that the unreacted boron in the body of the film had negative effect on flux pinning and intraband electron diffusivities

  7. A study of angular dependence in the ablation rate of polymers by nanosecond pulses

    Science.gov (United States)

    Pedder, James E. A.; Holmes, Andrew S.

    2006-02-01

    Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

  8. Temperature dependence of tunneling magnetoresistance in epitaxial magnetic tunnel junctions using a Co2FeAl Heusler alloy electrode

    Science.gov (United States)

    Wang, Wenhong; Sukegawa, Hiroaki; Inomata, Koichiro

    2010-09-01

    Spin-valve-type epitaxial magnetic tunnel junctions (MTJs) consisting of a full-Heusler alloy Co2FeAl (CFA) and a MgO tunnel barrier were fabricated on a single-crystal MgO(001) substrate using sputtering method for all the layers. Experimental temperature-dependent tunnel magnetoresistance in the MTJs was revealed to be fitted well using spin wave excitation model for tunneling spin polarization, P(T)=P0(1-αT3/2) up to room temperature, where P0 is the spin polarization at 0 K and α is a fitting parameter. The determined P and α are shown to be significantly different between bottom and top CFA electrodes facing a MgO barrier. It is demonstrated that the bottom CFA deposited on a Cr buffer has a low α and behaves as a half-metal with P˜1 in terms of the Δ1 symmetry due to the coherent tunneling through a MgO barrier.

  9. Investigation of organic magnetoresistance dependence on spin-orbit coupling using 8-hydroxyquinolinate rare-earth based complexes

    Science.gov (United States)

    Carvalho, R. S.; Costa, D. G.; Ávila, H. C.; Paolini, T. B.; Brito, H. F.; Capaz, Rodrigo B.; Cremona, M.

    2016-05-01

    The recently discovered organic magnetoresistance effect (OMAR) reveals the spin-dependent behavior of the charge transport in organic semiconductors. So far, it is known that hyperfine interactions play an important role in this phenomenon and also that spin-orbit coupling is negligible for light-atom based compounds. However, in the presence of heavy atoms, spin-orbit interactions should play an important role in OMAR. It is known that these interactions are responsible for singlet and triplet states mixing via intersystem crossing and the change of spin-charge relaxation time in the charge mobility process. In this work, we report a dramatic change in the OMAR effect caused by the presence of strong intramolecular spin-orbit coupling in a series of rare-earth quinolate organic complex-based devices. Our data show a different OMAR lineshape compared with the OMAR lineshape of tris(8-hydroxyquinolinate) aluminum-based devices, which are well described in the literature. In addition, electronic structure calculations based on density functional theory help to establish the connection between this results and the presence of heavy central ions in the different complexes.

  10. Temperature and angular momentum dependence of the quadrupole deformation in sd-shell

    Indian Academy of Sciences (India)

    P A Ganai; J A Sheikh; I Maqbool; R P Singh

    2009-11-01

    Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard universal sd-shell (USD) interaction and the canonical partition function constructed from the calculated eigensolutions. It is shown that the extracted average quadrupole moments show a transitional behaviour as a function of temperature and the infered transitional temperature is shown to vary with angular momentum. The quadrupole deformation of the individual eigenstate is also analysed.

  11. Temperature and angular momentum dependence of the quadrupole deformation in sd-shell

    CERN Document Server

    Ganai, P A; Maqbool, I; Singh, R P

    2009-01-01

    Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard USD interaction and the canonical partition function constructed from the calculated eigen-solutions. It is shown that the extracted average quadrupole moments show a transitional behavior as a function of temperature and the inferred transitional temperature is shown to vary with angular-momentum. The quadrupole deformation of the individual eigen-states is also analyzed.

  12. Subatomic mechanism of the oscillatory magnetoresistance in superconductors

    CERN Document Server

    Ivlev, Boris I

    2016-01-01

    In the recent experiments the unusual oscillatory magnetoresistance in superconductors was discovered with a periodicity that is essentially independent on magnetic field direction and even material parameters. The nearly universal period points to a subatomic mechanism of the phenomenon. This mechanism is related to formation inside samples of small rings of a subatomic (Compton) size. Electron states inside rings are hybridized with conduction electrons which carry the same spin imbalance in energy as rings. The imbalance occurs due to spin interaction with the orbital momentum of the ring. The conductivity near $T_c$ is determined by fluctuating Cooper pairs consisting of electrons with shifted energies. Due to different angular momenta of rings these energies periodically depend on magnetic field resulting in the observed oscillatory magnetoresistance. Calculated universal positions of peaks $(n+1/2)\\Delta H$ ($n=0,1,2...$) on the $R(H)$ curve are in a very good agreement with experiments.

  13. Angular dependence of coercivity with temperature in Co-based nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Bran, C., E-mail: cristina.bran@icmm.csic.es [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Espejo, A.P. [Departamento de Física, Universidad de Santiago de Chile (USACH) and Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avenida Ecuador 3493, 9170124 Santiago (Chile); Palmero, E.M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH) and Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avenida Ecuador 3493, 9170124 Santiago (Chile); Vázquez, M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain)

    2015-12-15

    The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300 K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations. That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure. Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays.

  14. Angular-dependent Raman study of a- and s-plane InN

    Energy Technology Data Exchange (ETDEWEB)

    Filintoglou, K.; Katsikini, M., E-mail: katsiki@auth.gr; Arvanitidis, J.; Lotsari, A.; Dimitrakopulos, G. P.; Vouroutzis, N.; Ves, S. [School of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Christofilos, D.; Kourouklis, G. A. [Chemical Engineering Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Ajagunna, A. O.; Georgakilas, A. [Microelectronics Research Group, Department of Physics, University of Crete, P.O. Box 2208, GR 71003 Heraklion, Greece and IESL, FORTH, P.O. Box 1385, GR 71110 Heraklion (Greece); Zoumakis, N. [Department of Food Technology, Technological Educational Institute of Thessaloniki, 57400 Sindos (Greece)

    2015-02-21

    Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar a-plane (11{sup ¯}20) and semipolar s-plane (101{sup ¯}1) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A{sub 1}(TO), E{sub 1}(TO), and E{sub 2}{sup h} on the angle ψ that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and a-plane InN epilayers grown on nitridated r-plane sapphire (Al{sub 2}O{sub 3}) exhibit good crystalline quality as deduced from the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E{sub 1}(TO) and E{sub 2}{sup h} Raman peaks was used for the estimation of the strain state of the samples.

  15. Angular dependence of hysteresis shift in oblique deposited ferromagnetic/antiferromagnetic coupled bilayers

    Science.gov (United States)

    Oliveira, A. B.; Rodriguez-Suarez, R. L.; Michea, S.; Vega, H.; Azevedo, A.; Rezende, S. M.; Aliaga, C.; Denardin, J.

    2014-07-01

    The angular dependence of the hysteresis shift has been investigated in ferromagnetic/antiferromagnetic (NiFe/IrMn) bilayers grown by oblique deposition under the influence of a static magnetic field applied perpendicular to the uniaxial anisotropy direction induced during the growth process. It was found that at low oblique deposition angles, the unidirectional anisotropy field is much greater than the uniaxial anisotropy field and the corresponding anisotropies directions are noncollinear. In these conditions, the angular dependence of the hysteresis loop shift exhibits the well know cosine like shape but demanding a phase shift. Contrary to this, at high oblique deposition angle (70°), the uniaxial anisotropy plays the fundamental role and the anisotropies directions are collinear. In this case, the exchange bias displays a jump phenomenon. The numerical calculations are consistent with the experimental data obtained from magneto-optical Kerr effect and ferromagnetic resonance.

  16. An Extended Greuling-Goertzel Approximation with a Pn-Approximation in the Angular Dependence

    International Nuclear Information System (INIS)

    The slowing-down spectrum has been calculated for different media. It is given in slab geometry as a function of space at the beginning of the epithermal region (10 eV). The angular dependence is also shown. The basic method is that given by E. Greuling, F. Clark and G. Goertzel in a NDA report, but in this report it is permissible to include more terms in the legendre expansion

  17. WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER

    OpenAIRE

    YONGHO LEE

    2013-01-01

    Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying th...

  18. A versatile variable field module for field and angular dependent scanning probe microscopy measurements

    CERN Document Server

    Liu, Hongxue; Lu, Jiwei; Wolf, Stuart; Hodgson, Jim; Rutgers, Maarten

    2013-01-01

    We demonstrate a versatile variable field module (VFM) with capability of both field and angular dependent measurements up to 1800 Oe for scanning probe system. The magnetic field strength is changed by adjusting the distance between a rare earth magnet and the probe tip and is monitored in-situ by a built-in Hall sensor. Rotating the magnet allows the field vector to change from the horizontal to vertical direction and makes it possible to do angular dependent measurements. The capability of the VFM system is demonstrated by degaussing a floppy disk media with increasing magnetic field. Angular dependent measurements clearly show the evolution of magnetic domain structures, with a completely reversible magnetic force microscopy phase contrast observed when the magnetic field is rotated by 180{\\deg}. A further demonstration of out-of-plane and in-plane magnetic switching of CoFe2O4 pillars in CoFe2O4-BiFeO3 nanocomposites was presented and discussed.

  19. Microscopic origin of magnetoresistance

    Directory of Open Access Journals (Sweden)

    Christian Heiliger

    2006-11-01

    Full Text Available Tunneling magnetoresistance is one of the basic effects of spintronics with the potential for applications in sensors and IT, where the spin degree of freedom of electrons is exploited. Successful application requires control of the materials and processes involved on the atomic scale. To support experimental developments, predict new materials, and optimize the effect, first-principle electronic structure calculations based on density functional theory are the most powerful tool. The method gives an insight into the microscopic origin of spin-dependent tunneling. The main components of a planar tunnel junction – barrier, leads, and their interface – and their specific role for tunneling magnetoresistance are discussed for one of the standard systems, Fe/MgO/Fe.

  20. WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER

    Directory of Open Access Journals (Sweden)

    YONGHO LEE

    2013-02-01

    Full Text Available Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying the angular velocity of the turbine a priori, but by calculating the actual time-dependent angular velocity and aerodynamic torque along with other properties in the course of simulation. In the present work, successful results obtained by an efficient computational fluid dynamics technique are shown, as a demonstration, for a vertical-axis wind turbine with a two-dimensionalSavonius rotor, and the cycle-averaged output powers are compared with experimental power curves and a theory developed on the basis of experimental observations.

  1. Study of angular dependences of ion component parameters in CO2-laser-produced plasma

    International Nuclear Information System (INIS)

    CO2-laser-produced plasma ion component parameters were studied for aluminium and lead targets at laser intensity of P = 4x1013 W cm-2 and pulse duration of τ = 15 ns experimentally and numerically. Angular dependences of ion number density for different charge states, average velocity and its spread were measured by time-of-flight method. Ion charge state distribution shows high-charge and low-charge state groups at normal expansion direction. Ions in these groups have different average expansion velocity and longitudinal velocity spread. Angular distribution of high-charge states is narrower than that of the low-charge state ion group, maximum yield of low-charge states occur at some angle from normal. For Al target results show similar trends as for Pb target, but simulations have indicated that the effect of laser ponderomotive force is more pronounced in this case

  2. ENERGY AND ANGULAR DEPENDENCE OF RADIOPHOTOLUMINESCENT GLASS DOSEMETERS FOR EYE LENS DOSIMETRY.

    Science.gov (United States)

    Silva, E H; Knežević, Ž; Struelens, L; Covens, P; Ueno, S; Vanhavere, F; Buls, N

    2016-09-01

    Recent studies demonstrated that lens opacities can occur at lower radiation doses than previously accepted. In view of these studies, the International Commission of Radiological Protection recommended in 2011 to reduce the eye lens dose limit from 150 mSv/y to 20 mSv/y. This implies in the need of monitoring doses received by the eye lenses. In this study, small rod radiophotoluminescent glass dosemeters (GD-300 series; AGC, Japan) were characterized in terms of their energy (ISO 4037 X-rays narrow spectrum series, S-Cs and S-Co) and angular dependence (0  up to 90 degrees, with 2 ISO energies: N-60 and S-Cs). All acquisitions were performed at SCK•CEN-Belgium, using the ORAMED proposed cylindrical phantom. For selected energies (N-60, N-80, N-100, N-120 and N-250), the response of dosemeters irradiated on the ISO water slab phantom, at the Ruđer Bošković Institute-Croatia, was compared to those irradiated on the cylindrical phantom. GD-300 series showed good energy dependence, relative to S-Cs, on the cylindrical phantom. From 0 up to 45 degrees, the dosemeters showed no significant angular dependence, regardless whether they were tested when placed vertically or horizontally on the cylindrical phantom. However, at higher angles, some angular dependence was observed, mainly when the dosemeters were irradiated with low-energy photons (N-60). Results showed that GD-300 series have good properties related to Hp(3), although some improvements may be necessary.

  3. On the angular dependence of the photoemission time delay in helium

    CERN Document Server

    Ivanov, I A; Lindroth, E; Kheifets, A S

    2016-01-01

    We investigate an angular dependence of the photoemission time delay in helium as measured by the RABBITT (Reconstruction of Attosecond Beating By Interference of Two-photon Transitions) technique. The measured time delay $ \\tau_a=\\tau_W+\\tau_{cc} $ contains two distinct components: the Wigner time delay $\\tau_W$ and the continuum-continuum CC) correction $\\tau_{cc}$. In the case of helium with only one $1s\\to Ep$ photoemission channel, the Wigner time delay $\\tau_W$ does not depend on the photoelectron detection angle relative to the polarization vector. However, the CC correction $\\tau_{cc}$ shows a noticeable angular dependence. We illustrate these findings by performing two sets of calculations. In the first set, we solve the time-dependent Schr\\"odinger equation for the helium atom ionized by an attosecond pulse train and probed by an IR pulse. In the second approach, we employ the lowest order perturbation theory which describes absorption of the XUV and IR photons. Both calculations produce close resul...

  4. Measuring the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Albert, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pollock, B. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shaw, J. L. [Univ. of California, Los Angeles, CA (United States); Marsh, K. A. [Univ. of California, Los Angeles, CA (United States); Ralph, J. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chen, Y. -H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Alessi, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pak, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Clayton, C. E. [Univ. of California, Los Angeles, CA (United States); Glenzer, S. H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Joshi, C. [Univ. of California, Los Angeles, CA (United States)

    2014-07-22

    This paper presents a new technique to measure the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator. Measurements are performed with a stacked image plates spectrometer, capable of detecting broadband x-ray radiation up to 1 MeV. It can provide measurements of the betatron x-ray spectrum at any angle of observation (within a 40 mrad cone) and of the beam profile. A detailed description of our data analysis is given, along with comparison for several shots. As a result, these measurements provide useful information on the dynamics of the electrons are they are accelerated and wiggled by the wakefield.

  5. Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances

    Directory of Open Access Journals (Sweden)

    Amir R. Ali

    2014-04-01

    Full Text Available We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle.

  6. Effect of angular velocity on sensors based on morphology dependent resonances.

    Science.gov (United States)

    Ali, Amir R; Ioppolo, Tindaro

    2014-01-01

    We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle. PMID:24759108

  7. Angular dependence of the spin textures in two-dimensional chiral magnets

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Dan [Institute of Materials Physics and Chemistry, Northeastern University, Shenyang 110004 (China); Institute of Applied Physics and Technology, Liaoning Technical University, Huludao 125105 (China); Qi, Yang, E-mail: qiyang@imp.neu.edu.cn [Institute of Materials Physics and Chemistry, Northeastern University, Shenyang 110004 (China)

    2015-05-28

    The angular dependence of spin textures in thin helimagnetic films is investigated by a Monte Carlo simulation. When an external field is applied at an angle relative to the film normal, we find that the skyrmion states with broken axis-symmetric structure are able to persist over a wide range of angles by changing the spin orientation. In addition, the uniaxial anisotropy is able to stabilize the distorted skyrmions. This behavior reflects the robust topological stability of skyrmion states in helimagnets and favors their application in spintronic devices.

  8. Angular dependence of the coercivity and remanence of ordered arrays of Co nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Lavin, R. [Departamento de Fisica, Universidad de Santiago de Chile, USACH, Av. Ecuador 3493, Santiago (Chile); Facultad de Ingenieria, Universidad Diego Portales, UDP, Ejercito 441, Santiago (Chile); Gallardo, C.; Palma, J.L. [Departamento de Fisica, Universidad de Santiago de Chile, USACH, Av. Ecuador 3493, Santiago (Chile); Escrig, J. [Departamento de Fisica, Universidad de Santiago de Chile, USACH, Av. Ecuador 3493, Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology, CEDENNA, Av. Ecuador 3493, Santiago (Chile); Denardin, J.C., E-mail: jcdenardin@gmail.com [Departamento de Fisica, Universidad de Santiago de Chile, USACH, Av. Ecuador 3493, Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology, CEDENNA, Av. Ecuador 3493, Santiago (Chile)

    2012-08-15

    The angular dependence of the coercivity and remanence of ordered hexagonal arrays of Co nanowires prepared using anodic aluminum oxide templates was investigated. The experimental evolution of coercivity as a function of the angle, in which the external field is applied, is interpreted considering micromagnetic simulations. Depending on the angle between the axis of the wire and the applied magnetic field direction our results show that the magnetization reversal mode changes from vortex to a transverse domain wall. Besides, we observed that the dipolar interactions cause a reduction in coercive fields, mainly in the direction of easy magnetization of the nanowires. Good agreement between numerical and experimental data is obtained. - Highlights: Black-Right-Pointing-Pointer Angular dependence of the coercivity and remanence of Co nanowire arrays. Black-Right-Pointing-Pointer Results show that the magnetization reversal mode changes from vortex to a transverse domain wall. Black-Right-Pointing-Pointer Dipolar interactions cause a reduction in coercive fields, which is the strongest in the direction of easy magnetization of the nanowire.

  9. Equivalence between deep energy-dependent and shallow angular momentum dependent potentials

    International Nuclear Information System (INIS)

    Recently Baye showed that supersymmetry can be applied to determine a shallow l-dependent potential phase equivalent to a deep potential, assumed to be energy-independent and have Panli forbidden states (PFS), for α-α scattering. The PFS are eliminated by this procedure. Such deep potentials are generated as equivalent local potentials (ELP) to the Resonating Group Model (RGM) and are generally energy-dependent. To eliminate this E-dependence as required for the application of Baye's method, l-dependent, but E-independent, deep local potentials were generated by the exact inversion method of Marchenko. Subsequently, the supersymmetric method was used to eliminate the PFS, ensuring that the generalized Levinson theorem is satisfied. As an example, the method was applied to the simple model of two dineutrons scattering in the RGM, where the deep ELP of Horiuchi has a substantial energy-dependence and one PFS only for l=O. 16 refs., 5 figs

  10. Angular dependence of the FMR linewidth and the anisotropy of the relaxation time in iron garnets

    Science.gov (United States)

    Kobelev, A. V.; Shvachko, Yu. N.; Ustinov, V. V.

    2016-01-01

    This work is devoted to the problem of extracting the contribution of the anisotropy of relaxation to the angular dependence of the FMR linewidth and to the opportunity of determining the values of the parameters of relaxation. The results of the FMR study of films based on the yttrium iron garnet prepared by the method of liquid-phase epitaxy are given. The orientational dependence of the linewidth has been calculated using the traditional method of measuring an FMR spectrum and a method based on scanning at an angle to the resonance field for obtaining the minimum linewidth. A model for calculating the linewidth has been proposed that takes into account the anisotropy of the relaxation term in the equation of motion of the magnetic moment. The model leads to a dependence that agrees well with the experimental data, which makes it possible to state that the anisotropy of relaxation most likely takes place in the samples under consideration at the temperatures employed.

  11. Study on the angular dependence of personal exposure dosimeter - Focus on thermoluminescent dosimeter and photoluminescent dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Kyung-Rae [Department of Radiological Technology, Gwangju Health College University (Korea, Republic of); Department of Nuclear Engineering, Chosun University (Korea, Republic of); Kweon, Dae Cheol [Department of Radiologic Science, Shin Heung College University (Korea, Republic of); Chung, Woon-Kwan, E-mail: wkchung@chosun.ac.kr [Department of Nuclear Engineering, Chosun University (Korea, Republic of); Goo, Eun-Hoe [Department of Diagnostic Radiology, Seoul National University Hospital (Korea, Republic of); Department of Physics, Soonchunhyang University (Korea, Republic of); Dieter, Kevin [Department of Physical Therapy, Gwangju Health College University (Korea, Republic of); Choe, Chong-Hwan [Department of White Memorial Medical Center (United States)

    2011-02-15

    Radiation management departments place more emphasis on the accuracy of measurements than on the increase in the average dose and personal exposure dose from the use of radiation equipment and radioactive isotopes. Although current measurements are taken using devices, such as film badge dosimeters, pocket dosimeters and thermoluminescent dosimeters (TLDs), this study compared the angular dependence between the widely used TLDs and photoluminescent dosimeter (PLDs) in order to present primary data and evaluate the utility of PLD as a new dosimeter device. For X-ray fluoroscopy, a whole body phantom was placed on a table with a setting for the G-I technical factors fixed at a range of approximately 40 cm with a range of {+-}90{sup o} at an interval scale of 15{sup o} from the center location of an average radiological worker for PLDs (GD-450) and TLDs (Carot). This process was repeated 10 times, and at each time, the cumulative dosage was interpreted from 130 dosimeters using TLDs (UD-710R, Panasonic) and PLDs (FGD-650). The TLD and PLD showed a 52% and 23% decrease in the depth dosage from 0{sup o} to -90{sup o}, respectively. Therefore, PLDs have a lower angular dependence than TLDs.

  12. Relation between the alignment dependence of coercive force decrease ratio and the angular dependence of coercive force of ferrite magnets

    Science.gov (United States)

    Matsuura, Yutaka; Kitai, Nobuyuki; Hosokawa, Seiichi; Hoshijima, Jun

    2016-08-01

    The relation of the coercive force decrease ratio (CFDR) and the angular dependence of the coercive force (ADCF) of ferrite magnets and their temperature properties were investigated. When we compared that against the angle of the magnetization reverse area obtained from these calculation results, which was obtained from the Gaussian distribution of the grain alignment and the postulation that every grain follows the Kondorskii law or the 1/cos θ law, and against the angle of the reverse magnetization area calculated from the experiment CFDR data of these magnets, it was found that this latter expanded at room temperature, to 36° from the calculated angle, for magnet with α=0.96. It was also found that, as temperature increased from room temperature to 413 K, the angle of the reverse magnetization area of ferrite magnets obtained from the experiment data expanded from 36° to 41°. When we apply these results to the temperature properties of ADCF, it seems that the calculated ADCF could qualitatively and reasonably explain these temperature properties, even though the difference between the calculated angular dependence and the experimental data still exists in the high angle range. These results strongly suggest that the coercive force of these magnets is determined by the magnetic domain wall motion. The magnetic domain walls are strongly pinned at tilted grains, and when the domain walls are de-pinned from their pinning sites, the coercive force is determined.

  13. The horizontal angular vestibulo-ocular reflex: a nonlinear mechanism for context-dependent responses.

    Science.gov (United States)

    Ranjbaran, Mina; Galiana, Henrietta L

    2013-11-01

    Studies of the vestibulo-ocular reflex (VOR) have revealed that this type of involuntary eye movement is influenced by viewing distance. This paper presents a bilateral model for the horizontal angular VOR in the dark based on realistic physiological mechanisms. It is shown that by assigning proper nonlinear neural computations at the premotor level, the model is capable of replicating target-distance-dependent VOR responses that are in agreement with geometrical requirements. Central premotor responses in the model are also shown to be consistent with experimental observations. Moreover, the model performance after simulated unilateral canal plugging also reproduces experimental observations, an emerging property. Such local nonlinear computations could similarly generate context-dependent behaviors in other more complex motor systems.

  14. Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber.

    Science.gov (United States)

    Hršak, Hrvoje; Majer, Marija; Grego, Timor; Bibić, Juraj; Heinrich, Zdravko

    2014-12-01

    Dosimetry for Gamma-Knife requires detectors with high spatial resolution and minimal angular dependence of response. Angular dependence and end effect time for p-type silicon detectors (PTW Diode P and Diode E) and PTW PinPoint ionization chamber were measured with Gamma-Knife beams. Weighted angular dependence correction factors were calculated for each detector. The Gamma-Knife output factors were corrected for angular dependence and end effect time. For Gamma-Knife beams angle range of 84°-54°. Diode P shows considerable angular dependence of 9% and 8% for the 18 mm and 14, 8, 4 mm collimator, respectively. For Diode E this dependence is about 4% for all collimators. PinPoint ionization chamber shows angular dependence of less than 3% for 18, 14 and 8 mm helmet and 10% for 4 mm collimator due to volumetric averaging effect in a small photon beam. Corrected output factors for 14 mm helmet are in very good agreement (within ±0.3%) with published data and values recommended by vendor (Elekta AB, Stockholm, Sweden). For the 8 mm collimator diodes are still in good agreement with recommended values (within ±0.6%), while PinPoint gives 3% less value. For the 4 mm helmet Diodes P and E show over-response of 2.8% and 1.8%, respectively. For PinPoint chamber output factor of 4 mm collimator is 25% lower than Elekta value which is generally not consequence of angular dependence, but of volumetric averaging effect and lack of lateral electronic equilibrium. Diodes P and E represent good choice for Gamma-Knife dosimetry.

  15. Tailoring Rydberg interactions via F\\"orster resonances: state combinations, hopping and angular dependence

    CERN Document Server

    Paris-Mandoki, Asaf; Tresp, Christoph; Mirgorodskiy, Ivan; Hofferberth, Sebastian

    2016-01-01

    F\\"orster resonances provide a highly flexible tool to tune both the strength and the angular shape of interactions between two Rydberg atoms. We give a detailed explanation about how F\\"orster resonances can be found by searching through a large range of possible quantum number combinations. We apply our search method to $SS$, $SD$ and $DD$ pair states of $^{87}$Rb with principal quantum numbers from 30 to 100, taking into account the fine structure splitting of the Rydberg states. We find various strong resonances between atoms with a large difference in principal quantum numbers. We quantify the strength of these resonances by introducing a figure of merit $\\tilde C_3$ which is independent of the magnetic quantum number and geometry to classify the resonances by interaction strength. We further predict to what extent interaction exchange is possible on different resonances and point out limitations of the coherent hopping process. Finally, we discuss the angular dependence of the dipole-dipole interaction ...

  16. Tailoring Rydberg interactions via Förster resonances: state combinations, hopping and angular dependence

    Science.gov (United States)

    Paris-Mandoki, Asaf; Gorniaczyk, Hannes; Tresp, Christoph; Mirgorodskiy, Ivan; Hofferberth, Sebastian

    2016-08-01

    Förster resonances provide a highly flexible tool to tune both the strength and the angular shape of interactions between two Rydberg atoms. We give a detailed explanation about how Förster resonances can be found by searching through a large range of possible quantum number combinations. We apply our search method to SS, SD and DD pair states of 87Rb with principal quantum numbers from 30 to 100, taking into account the fine structure splitting of the Rydberg states. We find various strong resonances between atoms with a large difference in principal quantum numbers. We quantify the strength of these resonances by introducing a figure of merit {\\tilde{C}}3 which is independent of the magnetic quantum numbers and geometry to classify the resonances by interaction strength. We further predict to what extent excitation exchange is possible on different resonances and point out limitations of the coherent hopping process. Finally, we discuss the angular dependence of the dipole–dipole interaction and its tunability near resonances.

  17. The dependence of nano-contact magnetoresistance on the bulk scattering spin asymmetry in CoFe alloys with oxidation impurities

    Science.gov (United States)

    Shiokawa, Yohei; Jung, JinWon; Otsuka, Takahiko; Sahashi, Masashi

    2015-08-01

    Nano-contact magnetoresistance (NCMR) spin-valves (SVs) using an AlOx nano-oxide-layer (NOL) have numerous nanocontacts in the thin AlOx oxide layer. The NCMR theoretically depends on the bulk scattering spin asymmetry ( β) of the ferromagnetic material in the nanocontacts. To determine the relationship between NCMR and β, we investigated the dependence of NCMR on the composition of the ferromagnetic material Co1-xFex. The samples were annealed at 270 °C and 380 °C to enhance the MR ratio. For both annealing temperatures, the magnetorsistance ratio in the low-resistance area product region at less than 1 Ω μm2 was maximized for Co0.5Fe0.5. To evaluate β exactly, we fabricated current-perpendicular-to-plane giant magnetoresistance SVs with Co1-xFex/Cu/Co1-xFex layers and used Valet and Fert's theory to solve the diffusion equation of the spin accumulation for a ferromagnetic layer/non-ferromagnetic layer of five layers with a finite diffusion length. The evaluated β for Co1-xFex was also maximized for Co0.5Fe0.5. Additionally, to determine the difference between the experimental MR ratio of NCMR SVs and the theoretical MR ratio, we fabricated Co0.5Fe0.5 with oxygen impurities and estimated the decrease in β with increasing oxygen impurity concentration. Our Co0.5Fe0.5 nano-contacts fabricated using ion-assisted oxidation may contain oxygen impurities, and the oxygen impurities might cause a decrease in β and the MR ratio.

  18. Dependence of the roll angular vestibuloocular reflex (aVOR) on gravity.

    Science.gov (United States)

    Yakushin, Sergei B; Xiang, Yongqing; Cohen, Bernard; Raphan, Theodore

    2009-11-01

    Little is known about the dependence of the roll angular vestibuloocular reflex (aVOR) on gravity or its gravity-dependent adaptive properties. To study gravity-dependent characteristics of the roll aVOR, monkeys were oscillated about a naso-occipital axis in darkness while upright or tilted. Roll aVOR gains were largest in the upright position and decreased by 7-15% as animals were tilted from the upright. Thus the unadapted roll aVOR gain has substantial gravitational dependence. Roll gains were also decreased or increased by 0.25 Hz, in- or out-of-phase rotation of the head and the visual surround while animals were prone, supine, upright, or in side-down positions. Gain changes, determined as a function of head tilt, were fit with a sinusoid; the amplitudes represented the amount of the gravity-dependent gain change, and the bias, the gravity-independent gain change. Gravity-dependent gain changes were absent or substantially smaller in roll (approximately 5%) than in yaw (25%) or pitch (17%), whereas gravity-independent gain changes were similar for roll, pitch, and yaw (approximately 20%). Thus the high-frequency roll aVOR gain has an inherent dependence on head orientation re gravity in the unadapted state, which is different from the yaw/pitch aVORs. This inherent gravitational dependence may explain why the adaptive circuits are not active when the head is tilted re gravity during roll aVOR adaptation. These behavioral differences support the idea that there is a fundamental difference in the central organization of canal-otolith convergence of the roll and yaw/pitch aVORs.

  19. Secondary-electron-emission spectroscopy of tungsten: Angular dependence and phenomenology

    DEFF Research Database (Denmark)

    Willis, Roy F.; Christensen, Niels Egede

    1978-01-01

    -vacuum interface. In addition, transmission-induced spectral features are observed (transmission resonances), which are not related to the density-of-states fine structure, but are due to a quantum-mechanical enhancement in the escape probability arising from wave-function matching at the emitter-vacuum interface....... Bulk and surface band-structure effects are concurrently manifest in the SEE spectra via the wave-matching conditions imposed at the solid-vacuum interface. The results are discussed within the general conceptual framework provided by "the (time-reversed) incoming final-state wave-function" approach......Angle-resolved energy-distribution measurements of secondary-electron emission (SEE) from metals reveal spectral fine structure that relates directly to the density distribution of the one-electron states throughout E-K→ space located above the vacuum level Ev. The angular dependence of the SEE...

  20. Light scattering by fractal dust aggregates: I. Angular dependence of scattering

    CERN Document Server

    Tazaki, Ryo; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko

    2016-01-01

    In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh-Gans-Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates, ballistic cluster-cluster agglomerates (BCCAs) and ballistic particle-cluster agglomerates (BPCAs). First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scatteri...

  1. Angular radiation temperature simulation for time-dependent capsule drive prediction in inertial confinement fusion

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Longfei; Yang, Dong; Li, Hang; Zhang, Lu; Lin, Zhiwei; Li, Liling; Kuang, Longyu [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Jiang, Shaoen, E-mail: jiangshn@vip.sina.com; Ding, Yongkun [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Huang, Yunbao, E-mail: huangyblhy@gmail.com [Mechatronics School of Guangdong University of Technology, Guangzhou 510080 (China)

    2015-02-15

    The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was then used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from “U20W112” (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented.

  2. Magnetoresistance of Rippled Graphene in a Parallel Magnetic Field

    Science.gov (United States)

    Wakabayashi, Junichi; Sano, Tomoya

    2011-12-01

    The magnetoresistance of a monolayer graphene in a random magnetic field(RMF) with zero mean has been investigated. The RMF was produced by applying a magnetic field parallel to the graphene plane utilizing ripples. The magnetoresistance has shown the same magnetic field dependence and, unexpectedly, the same carrier density dependence as the conventional two-dimensional electron systems in random magnetic fields. The relation between the characteristic length of ripples and the magnitude of the magnetoresistance is discussed.

  3. Characterization of a new ionization chamber in radiotherapy beams: angular dependence and variation of response with distance.

    Science.gov (United States)

    Silva, Jonas O; Linda V E, Caldas

    2012-10-01

    A new double faced ionization chamber was constructed at the Calibration Laboratory of IPEN. It has different collecting electrode materials: aluminum and graphite. It was irradiated in standard radiotherapy beams ((60)Co and X-rays). The response variation with distance and the angular dependence of this ionization chamber were evaluated. It was verified that the chamber response follows the inverse square law within a maximum variation of 11.2% in relation to the reference value. For the angular dependence it showed good agreement with international standards.

  4. Measurement of energy dependence of fission fragment angular anisotropy for resonance neutron induced fission of 235U aligned target

    International Nuclear Information System (INIS)

    The results of the experiment on measuring the energy dependence of fission fragment angular anisotropy in resonance neutron induced fission of 235U aligned target in energy region up to 42 eV are presented. The agreement with the data of Pattenden and Postma in resonances is good enough, while the theoretical curve, calculated using the R-matrix multilevel two fission channel approach, does not seem to describe the energy dependence of fission fragment angular anisotropy property. The necessity of taking into account the interference between levels with different spins is discussed. 11 refs., 2 figs

  5. Modeling angular-dependent spectral emissivity of snow and ice in the thermal infrared atmospheric window.

    Science.gov (United States)

    Hori, Masahiro; Aoki, Teruo; Tanikawa, Tomonori; Hachikubo, Akihiro; Sugiura, Konosuke; Kuchiki, Katsuyuki; Niwano, Masashi

    2013-10-20

    A model of angular-dependent emissivity spectra of snow and ice in the 8-14 μm atmospheric window is constructed. Past field research revealed that snow emissivity varies depending on snow grain size and the exitance angle. Thermography images acquired in this study further revealed that not only welded snow particles such as sun crust, but also disaggregated particles such as granular snow and dendrite crystals exhibit high reflectivity on their crystal facets, even when the bulk snow surface exhibits blackbody-like behavior as a whole. The observed thermal emissive behaviors of snow particles suggest that emissivity of the bulk snow surface can be expressed by a weighted sum of two emissivity components: those of the specular and blackbody surfaces. Based on this assumption, a semi-empirical emissivity model was constructed; it is expressed by a linear combination of specular and blackbody surfaces' emissivities with a weighting parameter characterizing the specularity of the bulk surface. Emissivity spectra calculated using the model succeeded in reproducing the past in situ measured directional spectra of various snow types by employing a specific weighting parameter for each snow type.

  6. Modeling angular-dependent spectral emissivity of snow and ice in the thermal infrared atmospheric window.

    Science.gov (United States)

    Hori, Masahiro; Aoki, Teruo; Tanikawa, Tomonori; Hachikubo, Akihiro; Sugiura, Konosuke; Kuchiki, Katsuyuki; Niwano, Masashi

    2013-10-20

    A model of angular-dependent emissivity spectra of snow and ice in the 8-14 μm atmospheric window is constructed. Past field research revealed that snow emissivity varies depending on snow grain size and the exitance angle. Thermography images acquired in this study further revealed that not only welded snow particles such as sun crust, but also disaggregated particles such as granular snow and dendrite crystals exhibit high reflectivity on their crystal facets, even when the bulk snow surface exhibits blackbody-like behavior as a whole. The observed thermal emissive behaviors of snow particles suggest that emissivity of the bulk snow surface can be expressed by a weighted sum of two emissivity components: those of the specular and blackbody surfaces. Based on this assumption, a semi-empirical emissivity model was constructed; it is expressed by a linear combination of specular and blackbody surfaces' emissivities with a weighting parameter characterizing the specularity of the bulk surface. Emissivity spectra calculated using the model succeeded in reproducing the past in situ measured directional spectra of various snow types by employing a specific weighting parameter for each snow type. PMID:24216578

  7. Angular dependence of dose sensitivity of nanoDot optically stimulated luminescent dosimeters in different radiation geometries

    Energy Technology Data Exchange (ETDEWEB)

    Jursinic, Paul A., E-mail: pjursinic@wmcc.org [West Michigan Cancer Center, 200 North Park Street, Kalamazoo, Michigan 49007 (United States)

    2015-10-15

    Purpose: A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. Methods: The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. Results: No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.433–0.633. A group of nanoDots had sensitive layers with mass density of 2.42–2.58 g/cm{sup 3} and relative sensitivity of 0.92–1.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. Conclusions: When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90°. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.92–1.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al{sub 2}O{sub 3}:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm{sup 3}. The angular dependence is not related to Al{sub 2}O{sub 3}:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber.

  8. Angular Dependence of the Sharply Directed Emission in Organic Light Emitting Diodes with a Microcavity Structure

    Science.gov (United States)

    Juang, Fuh-Shyang; Laih, Li-Hong; Lin, Chia-Ju; Hsu, Yu-Jen

    2002-04-01

    An optical microcavity structure was used in organic light emitting diodes. We succeeded in fabricating a device with sharply directed emission vertical to an emission surface. The device shows green emission (bright green) at normal position which turns red (bright red) at the 30° position. The angular dependences of the electroluminescence and the emission patterns versus viewing angle in the microcavity OLED were studied. The resonance wavelength λ decreases with viewing angle. The emission peak at 490 nm is directed vertically to the device surface more sharply than that at 632 nm. The microcavity structure shows non-Lambertian emission. The spectra appear more blue off-axis and the intensity of the green-like emission decreases rapidly with increasing viewing angle. A significantly narrow linewidth of 7.4 nm in the 0° direction for the 490 nm peak was observed. The full-widths at half maximum (FWHM) of the green-like spectra are much smaller than those of the red-like ones, indicating better cavity quality.

  9. Angular Dependence of Lateral and Levitation Forces in Asymmetric Small Magnet/Superconducting Systems

    Institute of Scientific and Technical Information of China (English)

    H. M. Al-Khateeb; M. K. Alqadi; F. Y. Alzoubi; N. Y. Ayoub

    2007-01-01

    The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally offthe symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.

  10. Tomographic imaging of the angular-dependent coherent-scatter cross section.

    Science.gov (United States)

    Westmore, M S; Fenster, A; Cunningham, I A

    1997-01-01

    A new special-purpose computed tomographic (CT) imaging system is described which produces images based on measurements of the low-angle (0-10 degrees) x-ray diffraction properties of an object. Low-angle scatter in the diagnostic x-ray energy range is dominated by coherent scatter, and the system uses first-generation CT geometry to acquire a diffraction pattern for each pencil beam. The patterns are used to reconstruct a series of images which represent the coherent-scatter intensity at a series of scatter angles. To demonstrate the potential of coherent-scatter CT (CSCT), the scanner has been built and used to image a phantom consisting of a water-filled Lucite cylinder containing rods of polyethylene, Lucite, polycarbonate, and nylon. In this paper, the system is described and a sequence of CSCT images of this phantom is shown. Coherent-scatter cross sections of these materials are generated for each pixel from this sequence of images and compared with cross sections measured separately. The resulting excellent agreement shows that the angular-dependent coherent-scatter cross section can be accurately imaged in a tomographic slice through an object. These cross sections give material-specific information about the object. The long-term goal of this research is to make measurements of bone-mineral content for every pixel in a tomographic slice. PMID:9029536

  11. Angular Dependence of the Facular-Sunspot Coverage Relation as Derived by MDI Magnetograms

    Science.gov (United States)

    Criscuoli, S.

    2016-07-01

    Previous studies have shown that the variation over the solar magnetic activity cycle of the area of facular/network features identified from broad-band and narrow-band imagery is positively correlated with the sunspot area and number, the relation being described as either linear or quadratic. On the other hand, the temporal variation of the spatial distributions of faculae, network and sunspots follows patterns that are less obviously correlated, so that we expect the relation that describes variation of the area coverage of different types of magnetic features to vary with the position over the disk. In this work we employ Michelson Doppler Interferometer (MDI) full-disk magnetograms acquired during solar cycle 23 and at the beginning of cycle 24 to investigate the relation between the coverage of magnetic elements characterized by different amounts of magnetic flux and located at different angular distances from disk center with the sunspot number. In agreement with some previous studies we find that daily data are best described by a quadratic function while data averaged over six months are best described by a linear function. In both cases the coefficients of the fits show large dependence on the position over the disk and the magnetic flux. We also find that toward disk center six-month averaged data show asymmetries between the ascending and the descending phases. The implications for solar irradiance modeling are discussed.

  12. Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence

    CERN Document Server

    Gallet, Florian

    2015-01-01

    We developed angular momentum evolution models for 0.5 and 0.8 $M_{\\odot}$ stars. The parametric models include a new wind braking law based on recent numerical simulations of magnetised stellar winds, specific dynamo and mass-loss rate prescriptions, as well as core/envelope decoupling. We compare model predictions to the distributions of rotational periods measured for low mass stars belonging to star forming regions and young open clusters. Furthermore, we explore the mass dependence of model parameters by comparing these new models to the solar-mass models we developed earlier. Rotational evolution models are computed for slow, median, and fast rotators at each stellar mass. The models reproduce reasonably well the rotational behaviour of low-mass stars between 1~Myr and 8-10~Gyr, including pre-main sequence to zero-age main sequence spin up, prompt zero-age main sequence spin down, and early-main sequence convergence of the surface rotation rates. Fast rotators are found to have systematically shorter di...

  13. Angular Dependence of the Facular-Sunspot Coverage Relation as Derived by MDI Magnetograms

    Science.gov (United States)

    Criscuoli, S.

    2016-08-01

    Previous studies have shown that the variation over the solar magnetic activity cycle of the area of facular/network features identified from broad-band and narrow-band imagery is positively correlated with the sunspot area and number, the relation being described as either linear or quadratic. On the other hand, the temporal variation of the spatial distributions of faculae, network and sunspots follows patterns that are less obviously correlated, so that we expect the relation that describes variation of the area coverage of different types of magnetic features to vary with the position over the disk. In this work we employ Michelson Doppler Interferometer (MDI) full-disk magnetograms acquired during solar cycle 23 and at the beginning of cycle 24 to investigate the relation between the coverage of magnetic elements characterized by different amounts of magnetic flux and located at different angular distances from disk center with the sunspot number. In agreement with some previous studies we find that daily data are best described by a quadratic function while data averaged over six months are best described by a linear function. In both cases the coefficients of the fits show large dependence on the position over the disk and the magnetic flux. We also find that toward disk center six-month averaged data show asymmetries between the ascending and the descending phases. The implications for solar irradiance modeling are discussed.

  14. Light Scattering by Fractal Dust Aggregates. I. Angular Dependence of Scattering

    Science.gov (United States)

    Tazaki, Ryo; Tanaka, Hidekazu; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko

    2016-06-01

    In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh–Gans–Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates—ballistic cluster–cluster agglomerates (BCCAs) and ballistic particle–cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.

  15. Impact of surface-polish on the angular and wavelength dependence of fiber focal ratio degradation

    CERN Document Server

    Eigenbrot, Arthur D; Wood, Corey M

    2012-01-01

    We present measurements of how multimode fiber focal-ratio degradation (FRD) and throughput vary with levels of fiber surface polish from 60 to 0.5 micron grit. Measurements used full-beam and laser injection methods at wavelengths between 0.4 and 0.8 microns on 17 meter lengths of Polymicro FBP 300 and 400 micron core fiber. Full-beam injection probed input focal-ratios between f/3 and f/13.5, while laser injection allowed us to isolate FRD at discrete injection angles up to 17 degrees (f/1.6 marginal ray). We find (1) FRD effects decrease as grit size decreases, with the largest gains in beam quality occurring at grit sizes above 5 microns; (2) total throughput increases as grit size decreases, reaching 90% at 790 nm with the finest polishing levels; (3) total throughput is higher at redder wavelengths for coarser polishing grit, indicating surface-scattering as the primary source of loss. We also quantify the angular dependence of FRD as a function of polishing level. Our results indicate that a commonly a...

  16. The horizontal angular vestibulo-ocular reflex: a non-linear mechanism for context-dependent responses.

    Science.gov (United States)

    Ranjbaran, Mina; Galiana, Henrietta L

    2012-01-01

    A bilateral model for the horizontal angular vestibulo-ocular reflex (AVOR) is presented in this paper. It is shown that by assigning proper non-linear neural computations at the premotor level, the model is capable of replicating target-distance dependent VOR responses. Moreover, the model behavior in case of sensory plugging is also consistent with reported experimental observations.

  17. Spectral dependence of angular distribution halfwidths of Vavilov-Cherenkov radiation

    International Nuclear Information System (INIS)

    Angular distributions of Vavilov-Cherenkov radiation have been measured. This radiaiton is excited during 210 keV electron propagation in a mica 2.5 mm thick target in a spectral range from 2500 up to 5000 A. A formula for diffraction halfwidth of angular distribution has been derived, its applicability limits are pointed out. Experimental halfwidth agrees with the calculated ones. The deviation of angular distribution maximum from Vavilov-Cherenkov radiation angle is analyzed. This deviation is due to radiator boundaries and multiple scattering of electrons

  18. Velocity dependence of angular distributions in gas/solid--surface collisions: Relationship to the interaction potential

    Energy Technology Data Exchange (ETDEWEB)

    Brady, J.W. Jr.; Doll, J.D.; Thompson, D.L.

    1978-10-15

    The angular and velocity distributions for gas/solid-surface collisions are examined. It is shown that the envelope of the scattered phase-space distribution is quite sensitive to the gas/surface interaction potential.

  19. Angular dependence of the MOSFET dosimeter and its impact on in vivo surface dose measurement in breast cancer treatment.

    Science.gov (United States)

    Qin, S; Chen, T; Wang, L; Tu, Y; Yue, N; Zhou, J

    2014-08-01

    The focus of this study is the angular dependence of two types of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeters (MOSFET20 and OneDose/OneDosePlus) when used for surface dose measurements. External beam radiationat different gantry angles were delivered to a cubic solid water phantom with a MOSFET placed on the top surface at CAX. The long axis of the MOSFET was oriented along the gantry axis of rotation, with the dosimeter (bubble side) facing the radiation source. MOSFET-measured surface doses were compared against calibrated radiochromic film readings. It was found that both types of MOSFET dosimeters exhibited larger than previously reported angular dependence when measuring surface dose in beams at large oblique angles. For the MOSFET20 dosimeter the measured surface dose deviation against film readings was as high as 17% when the incident angle was 72 degrees to the norm of the phantom surface. It is concluded that some MOSFET dosimeters may have a strong angular dependence when placed on the surface of water-equivalent material, even though they may have an isotropic angular response when surrounded by uniform medium. Extra on-surface calibration maybe necessary before using MOSFET dosimeters for skin dose measurement in tangential fields. PMID:24206205

  20. Angular Dependence of the Nuclear Enhancement of Drell-Yan Pairs

    CERN Document Server

    Fries, R J; Schäfer, A; Stein, E

    1999-01-01

    We calculate the nuclear enhancement in the angular distribution of Drell-Yan pairs produced in proton-nucleus reactions. Nuclear effects are encoded in universal twist-4 parton correlation functions. We find that the Lam-Tung relation for the angular coefficients of the lepton-pair distribution holds for the double-hard, but not for the soft-hard contribution. We also predict that nuclear enhancement effects at RHIC energies can be large.

  1. Giant tunneling magnetoresistance in silicene

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu, E-mail: ywang@semi.ac.cn [Department of Physics, Faculty of Science, Kunming University of Science and Technology, Kunming, 650500 Yunnan (China); Lou, Yiyi [Yiyuan Student Community, Center of Student Community Education and Management, Kunming University of Science and Technology, Kunming, 650500 Yunnan (China)

    2013-11-14

    We have theoretically studied ballistic electron transport in silicene under the manipulation of a pair of ferromagnetic gate. Transport properties like transmission and conductance have been calculated by the standard transfer matrix method for parallel and antiparallel magnetization configurations. It is demonstrated here that, due to the stray field-induced wave-vector filtering effect, remarkable difference in configuration-dependent transport gives rise to a giant tunneling magnetoresistance. In combination with the peculiar buckled structure of silicene and its electric tunable energy gap, the receiving magnetoresistance can be efficiently modulated by the externally-tunable stray field, electrostatic potential, and staggered sublattice potential, providing some flexible strategies to construct silicene-based nanoelectronic device.

  2. Angular Dependency of Hyperspectral Measurements over Wheat Characterized by a Novel UAV Based Goniometer

    Directory of Open Access Journals (Sweden)

    Andreas Burkart

    2015-01-01

    Full Text Available In this study we present a hyperspectral flying goniometer system, based on a rotary-wing unmanned aerial vehicle (UAV equipped with a spectrometer mounted on an active gimbal. We show that this approach may be used to collect multiangular hyperspectral data over vegetated environments. The pointing and positioning accuracy are assessed using structure from motion and vary from σ = 1° to 8° in pointing and σ = 0.7 to 0.8 m in positioning. We use a wheat dataset to investigate the influence of angular effects on the NDVI, TCARI and REIP vegetation indices. Angular effects caused significant variations on the indices: NDVI = 0.83–0.95; TCARI = 0.04–0.116; REIP = 729–735 nm. Our analysis highlights the necessity to consider angular effects in optical sensors when observing vegetation. We compare the measurements of the UAV goniometer to the angular modules of the SCOPE radiative transfer model. Model and measurements are in high accordance (r2 = 0.88 in the infrared region at angles close to nadir; in contrast the comparison show discrepancies at low tilt angles (r2 = 0.25. This study demonstrates that the UAV goniometer is a promising approach for the fast and flexible assessment of angular effects.

  3. Monte Carlo calculations of the magnetoresistance in magnetic multilayer structures with giant magnetoresistance effects

    Science.gov (United States)

    Prudnikov, V. V.; Prudnikov, P. V.; Romanovskiy, D. E.

    2016-06-01

    A Monte Carlo study of trilayer and spin-valve magnetic structures with giant magnetoresistance effects is carried out. The anisotropic Heisenberg model is used for description of magnetic properties of ultrathin ferromagnetic films forming these structures. The temperature and magnetic field dependences of magnetic characteristics are considered for ferromagnetic and antiferromagnetic configurations of these multilayer structures. The methodology for determination of the magnetoresistance by the Monte Carlo method is introduced; this permits us to calculate the magnetoresistance of multilayer structures for different thicknesses of the ferromagnetic films. The calculated temperature dependence of the magnetoresistance agrees very well with the experimental results measured for the Fe(0 0 1)–Cr(0 0 1) multilayer structure and CFAS–Ag–CFAS–IrMn spin-valve structure based on the half-metallic Heusler alloy Co2FeAl0.5Si0.5.

  4. Raman scattering investigation of large positive magnetoresistance material WTe2

    Science.gov (United States)

    Kong, W.-D.; Wu, S.-F.; Richard, P.; Lian, C.-S.; Wang, J.-T.; Yang, C.-L.; Shi, Y.-G.; Ding, H.

    2015-02-01

    We have performed polarized Raman scattering measurements on WTe2, for which an extremely large positive magnetoresistance has been reported recently. We observe 5 A1 phonon modes and 2 A2 phonon modes out of 33 Raman active modes, with frequencies in good accordance with first-principles calculations. The angular dependence of the intensity of the peaks observed is consistent with the Raman tensors of the C2v point group symmetry attributed to WTe2. Although the phonon spectra suggest neither strong electron-phonon nor spin-phonon coupling, the intensity of the A1 phonon mode at 160.6 cm-1 shows an unconventional decrease with temperature decreasing, for which the origin remains unclear.

  5. Raman scattering investigation of large positive magnetoresistance material WTe2

    International Nuclear Information System (INIS)

    We have performed polarized Raman scattering measurements on WTe2, for which an extremely large positive magnetoresistance has been reported recently. We observe 5 A1 phonon modes and 2 A2 phonon modes out of 33 Raman active modes, with frequencies in good accordance with first-principles calculations. The angular dependence of the intensity of the peaks observed is consistent with the Raman tensors of the C2v point group symmetry attributed to WTe2. Although the phonon spectra suggest neither strong electron-phonon nor spin-phonon coupling, the intensity of the A1 phonon mode at 160.6 cm−1 shows an unconventional decrease with temperature decreasing, for which the origin remains unclear

  6. Large magnetoresistance in non-magnetic silver chalcogenides and new class of magnetoresistive compounds

    Science.gov (United States)

    Saboungi, Marie-Louis; Price, David C. L.; Rosenbaum, Thomas F.; Xu, Rong; Husmann, Anke

    2001-01-01

    The heavily-doped silver chalcogenides, Ag.sub.2+.delta. Se and Ag.sub.2+.delta. Te, show magnetoresistance effects on a scale comparable to the "colossal" magnetoresistance (CMR) compounds. Hall coefficient, magnetoconductivity, and hydrostatic pressure experiments establish that elements of narrow-gap semiconductor physics apply, but both the size of the effects at room temperature and the linear field dependence down to fields of a few Oersteds are surprising new features.

  7. Scaling Behavior of Angular Dependent Resistivity in CeCoIn$_5$: Possible Evidence for d-Wave Density Waves

    OpenAIRE

    Hu, T.; Xiao, H; Sayles, T. A.; M.B. Maple; Maki, Kazumi; Dora, B.; Almasan, C. C.

    2006-01-01

    In-plane angular dependent resistivity ADR was measured in the non-Fermi liquid regime of CeCoIn$_5$ single crystals at temperatures $T \\le 20$ K and in magnetic fields $H$ up to 14 T. Two scaling behaviors were identified in low field region where resistivity shows T-linear dependence, separated by a critical angle $\\theta_{c}$ which is determined by the anisotropy of CeCoIn$_5$; i.e., ADR depends only on the perpendicular (parallel) field component below (above) $\\theta_c$. These scaling be...

  8. A phenomenological Landauer-type theory on colossal magnetoresistance

    Science.gov (United States)

    Ding, M.; Tian, G.-S.; Lin, T.-H.

    1996-12-01

    A two-dimensional interacting magnetic domains model is examined to explain the colossal magnetoresistance (CMR) recently observed in manganese-oxides. Electrons transport properties were studied by using Landauer's multichannel transport theory and recursive Green's function technique. Colossal magnetoresistance shows up in this system. The temperature dependence of system's MR is also studied.

  9. Spin Hall magnetoresistance at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, Ken-ichi, E-mail: kuchida@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); Qiu, Zhiyong [Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Kikkawa, Takashi; Iguchi, Ryo [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); Saitoh, Eiji [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); CREST, Japan Science and Technology Agency, Tokyo 102-0076 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195 (Japan)

    2015-02-02

    The temperature dependence of spin Hall magnetoresistance (SMR) in Pt/Y{sub 3}Fe{sub 5}O{sub 12} (YIG) bilayer films has been investigated in a high temperature range from room temperature to near the Curie temperature of YIG. The experimental results show that the magnitude of the magnetoresistance ratio induced by the SMR monotonically decreases with increasing the temperature and almost disappears near the Curie temperature. We found that, near the Curie temperature, the temperature dependence of the SMR in the Pt/YIG film is steeper than that of a magnetization curve of the YIG; the critical exponent of the magnetoresistance ratio is estimated to be 0.9. This critical behavior of the SMR is attributed mainly to the temperature dependence of the spin-mixing conductance at the Pt/YIG interface.

  10. Evaluation of linearity of response and angular dependence of an ionization chamber for dosimetry in computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana P.; Neves, Lucio P.; Xavier, Marcos; Caldas, Linda V.E., E-mail: mxavier@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear

    2011-07-01

    In this paper a pencil-type ionization chamber designed and manufactured at Instituto de Pesquisas Energeticas e Nucleares was evaluated for dosimetric applications in computed tomography beams. To evaluate the performance of this chamber two tests were undertaken: linearity of response and angular dependence. The results obtained in these tests showed good results, within the international recommendations. Moreover, this homemade ionization chamber is easy to manufacture, of low cost and efficient. (author)

  11. Temperature dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La1-xSrxMnO3

    Energy Technology Data Exchange (ETDEWEB)

    Arenholz, Elke; Mannella, N.; Booth, C.H.; Rosenhahn, A.; Sell, B.C.; Nambu, A.; Marchesini, S.; Mun, B. S.; Yang, S.-H.; Watanabe, M.; Ibrahim, K.; Arenholz, E.; Young, A.; Guo, J.; Tomioka, Y.; Fadley, C.S.

    2007-12-06

    We have studied the temperature-dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La{sub 1-x}Sr{sub x}MnO{sub 3} (x= 0.3-0.4) with core and valence level photoemission (PE), x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS), extended x-ray absorption fine structure (EXAFS) spectroscopy and magnetometry. As the temperature is varied across the Curie temperature T{sub c}, our PE experiments reveal a dramatic change of the electronic structure involving an increase in the Mn spin moment from {approx} 3 {micro}B to {approx} 4 {micro}B, and a modification of the local chemical environment of the other constituent atoms indicative of electron localization on the Mn atom. These effects are reversible and exhibit a slow-timescale {approx}200 K-wide hysteresis centered at T{sub c}. Based upon the probing depths accessed in our PE measurements, these effects seem to survive for at least 35-50 {angstrom} inward from the surface, while other consistent signatures for this modification of the electronic structure are revealed by more bulk sensitive spectroscopies like XAS and XES/RIXS. We interpret these effects as spectroscopic fingerprints for polaron formation, consistent with the presence of local Jahn-Teller distortions of the MnO{sub 6} octahedra around the Mn atom, as revealed by the EXAFS data. Magnetic susceptibility measurements in addition show typical signatures of ferro-magnetic clusters formation well above the Curie temperature.

  12. Magnetoresistive waves in plasmas

    International Nuclear Information System (INIS)

    The self-generated magnetic field of a current diffusing into a plasma between conductors can magnetically insulate the plasma. Propagation of magnetoresistive waves in plasmas is analyzed. Applications to plasma opening switches are discussed

  13. Probing giant magnetoresistance with THz spectroscopy

    DEFF Research Database (Denmark)

    Jin, Zuanming; Tkach, Alexander; Casper, Frederick;

    2014-01-01

    We observe a giant magnetoresistance effect in CoFe/Cu-based multistack using THz time-domain spectroscopy. The magnetic field-dependent dc conductivity, electron scattering time, as well as spin-asymmetry parameter of the structure are successfully determined. © 2014 OSA.......We observe a giant magnetoresistance effect in CoFe/Cu-based multistack using THz time-domain spectroscopy. The magnetic field-dependent dc conductivity, electron scattering time, as well as spin-asymmetry parameter of the structure are successfully determined. © 2014 OSA....

  14. Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions

    CERN Document Server

    Dasgupta, Basudeb; Sen, Manibrata

    2016-01-01

    It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, and find that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries. Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres. If these fast flavor conversions indeed take place, they would have important implications for the supernova explosion mechanism and nucleosynthesis.

  15. Analysis of dependence of the moment of inertia on the angular velocity squared in phenomenological collective nuclear theory

    Energy Technology Data Exchange (ETDEWEB)

    Seregin, A.A.

    1976-03-01

    In framework of a phenomenological collective nuclear theory the dependence of the moment of inertia on the angular velocity squared is studied. It is shown that this theory may explain the S shape of dependence of J on ..omega../sup 2/ if the collective motion potential V(..beta..) has two points of inflection. Anomalies in the low-lying part of the energy spectrum of the nuclei /sup 184/Hg and /sup 186/Hg are related to inflection points of the potential.

  16. Transport methods: general. 3. An Additive Angular-Dependent Re-balance Acceleration Method for Neutron Transport Equations

    International Nuclear Information System (INIS)

    An additive angular-dependent re-balance (AADR) factor acceleration method is described to accelerate the source iteration of discrete ordinates transport calculation. The formulation of the AADR method follows that of the angular-dependent re-balance (ADR) method in that the re-balance factor is defined only on the cell interface and in that the low-order equation is derived by integrating the transport equation (high-order equation) over angular subspaces. But, the re-balance factor is applied additively. While the AADR method is similar to the boundary projection acceleration and the alpha-weighted linear acceleration, it is more general and does have distinct features. The method is easily extendible to DPN and low-order SN re-balancing, and it does not require consistent discretizations between the high- and low-order equations as in diffusion synthetic acceleration. We find by Fourier analysis and numerical results that the AADR method with a chosen form of weighting functions is unconditionally stable and very effective. There also exists an optimal weighting parameter that leads to the smallest spectral radius. The AADR acceleration method described in this paper is simple to implement, unconditionally stable, and very effective. It uses a physically based weighting function with an optimal parameter, leading to the best spectral radius of ρ<0.1865, compared to ρ<0.2247 of DSA. The application of the AADR acceleration method with the LMB scheme on a test problem shows encouraging results

  17. Spin and temperature dependence of nuclear deformation using alpha-gamma angular correlations

    International Nuclear Information System (INIS)

    Alpha-particle angular distributions with respect to the spin direction of residual nuclei have been measured in heavy-ion fusion reactions. The spin direction was determined by measuring the γ-ray angular distributions, for each event, using the spin spectrometer. α-particle anisotropies have been extracted for the compound nuclear systems: 110Sn*(94 MeV), 114Sn*(80 MeV), 138Nd*(82 MeV), 164Yb*(67 MeV) and 170Yb*(135 MeV) as a function of the α-particle energy and γ-ray multiplicity. The results are compared with statistical model calculations using transmission coefficients from a spherically symmetric optical model potential. The trend of the anisotropy coefficients below the evaporation Coulomb barrier is consistent with spherical emitting shapes in the case of the Sn* isotopes. Small deformation effects are suggested by the 138Nd* and 164Yb* data. The 170Yb* data indicate a large deformation which increases considerably with increasing spin. These results are in agreement with findings for similar systems in which the decay of the giant resonances built on excited states have been studied. 16 refs., 5 figs

  18. Current-perpendicular-to-the-plane magnetoresistance from large interfacial spin-dependent scattering between Co50Fe50 magnetic layer and In-Zn-O conductive oxide spacer layer

    Science.gov (United States)

    Nakatani, T. M.; Childress, J. R.

    2015-06-01

    We have investigated electrically conductive indium-zinc-oxide (IZO) deposited by magnetron sputtering as spacer layer for current-perpendicular-to-the-plane giant magnetoresistance sensor devices. Spin-valves with a Co50Fe50/IZO/Co50Fe50 trilayer showed resistance-area product (RA) ranging from 110 to 250 mΩ μm2, significantly larger than all-metal structures with Ag or Cu spacers (˜40 mΩ μm2). Magnetoresistance ratios (ΔR/R) of 2.5% to 5.5% depending on the IZO spacer thickness (1.5-6.0 nm), corresponding to ΔRA values from 3 to 13 mΩ μm2, were obtained. The values of ΔRA with the IZO spacers and Co50Fe50 magnetic layers were significantly larger than those with conventional metal spacers and Co50Fe50 magnetic layers (˜1-2 mΩ μm2). The dependence of ΔRA on the magnetic layer thickness suggests that the larger ΔRA obtained with IZO spacer is due to a large interfacial spin-dependent scattering caused by the large specific resistance at the Co50Fe50/IZO interface. From structural characterization by TEM and the observed dependence of the RA dispersion on device size, the electric current flowing through the IZO spacer is thought to be laterally uniform, similar to normal metal spacers.

  19. Tunneling magnetoresistive heads for magnetic data storage.

    Science.gov (United States)

    Mao, Sining

    2007-01-01

    Spintronics is emerging to be a new form of nanotechnologies, which utilizes not only the charge but also spin degree of freedom of electrons. Spin-dependent tunneling transport is one of the many kinds of physical phenomena involving spintronics, which has already found industrial applications. In this paper, we first provide a brief review on the basic physics and materials for magnetic tunnel junctions, followed more importantly by a detailed coverage on the application of magnetic tunneling devices in magnetic data storage. The use of tunneling magnetoresistive reading heads has helped to maintain a fast growth of areal density, which is one of the key advantages of hard disk drives as compared to solid-state memories. This review is focused on the first commercial tunneling magnetoresistive heads in the industry at an areal density of 80 approximately 100 Gbit/in2 for both laptop and desktop Seagate hard disk drive products using longitudinal media. The first generation tunneling magnetoresistive products utilized a bottom stack of tunnel junctions and an abutted hard bias design. The output signal amplitude of these heads was 3 times larger than that of comparable giant magnetoresistive devices, resulting in a 0.6 decade bit error rate gain over the latter. This has enabled high component and drive yields. Due to the improved thermal dissipation of vertical geometry, the tunneling magnetoresistive head runs cooler with a better lifetime performance, and has demonstrated similar electrical-static-discharge robustness as the giant magnetoresistive devices. It has also demonstrated equivalent or better process and wafer yields compared to the latter. The tunneling magnetoresistive heads are proven to be a mature and capable reader technology. Using the same head design in conjunction with perpendicular recording media, an areal density of 274 Gbit/in2 has been demonstrated, and advanced tunneling magnetoresistive heads can reach 311 Gbit/in2. Today, the

  20. Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals

    Science.gov (United States)

    Lv, Yang-Yang; Zhang, Bin-Bin; Li, Xiao; Pang, Bin; Zhang, Fan; Lin, Da-Jun; Zhou, Jian; Yao, Shu-Hua; Chen, Y. B.; Zhang, Shan-Tao; Lu, Minghui; Liu, Zhongkai; Chen, Yulin; Chen, Yan-Feng

    2016-05-01

    Recently, the layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~105%), which can be useful for magnetic memory and spintronic devices. However, the underlying mechanisms of the giant magnetoresistance are still under hot debate. Herein, we grew the stoichiometric and non-stoichiometric WTe2 crystals to test the robustness of giant magnetoresistance. The stoichiometric WTe2 crystals have magnetoresistance as large as 3100% at 2 K and 9-Tesla magnetic field. However, only 71% and 13% magnetoresistance in the most non-stoichiometry (WTe1.80) and the highest Mo isovalent substitution samples (W0.7Mo0.3Te2) are observed, respectively. Analysis of the magnetic-field dependent magnetoresistance of non-stoichiometric WTe2 crystals substantiates that both the large electron-hole concentration asymmetry and decreased carrier mobility, induced by non-stoichiometry, synergistically lead to the decreased magnetoresistance. This work sheds more light on the origin of giant magnetoresistance observed in WTe2.

  1. Field dependence of magnetoresistance in epitaxial single-crystal La2/3Ca1/3MnO3-δ thin film

    Institute of Scientific and Technical Information of China (English)

    李可斌; 程荣胜; 王守国; 陈志祥; 方军; 王智河; 曹效文; 许小军; 朱警生; 张裕恒

    1999-01-01

    Epitaxial La2/3Ca1/3MnO3 thin films were prepared on NdGaO3 (110) substrates by d.c. magnetron sputtering method. The measurements of magnetoresistance ρ(H) upon magnetic field at different temperatures were carried out in the field range of 0—8 T. It is found that ρ(H) obeys the following relations: when the temperature (T) is higher than the Curie temperature TC, ρ(H)=1/(α(T)+β(T)H2); below TC, ρ(H)=ρ0(T)+1/(A(T)+B(T)exp(H/c(T)), and ρ(H)=(1/(σ(T)+γ(T)H)) when T is far below TC. It is suggested that the negative magnetoresistive effect is mainly due to enhancement of the magnetoconductanee.

  2. Training Effect and Hysteretic Behaviour of Angular Dependence of Exchange Bias in Co/IrMn Bilayers

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jing; DU Jun; BAI Xiao-Jun; YOU Biao; ZHANG Wei; HU An

    2009-01-01

    @@ The training effect and the hysteresis behaviour of the angular dependence of exchange bias are extensively investigated upon the variation of the IrMn layer thickness tIrMn in a series of Co/IrMn bilayers. When tIrMn is very small, both of them are negligible. Then they increase very sharply with increasing tIrMn and then reach maxima at almost the same value of tIrMn. Finally they both decrease when tIrMn is further increased. The similar variation trends suggest that these phenomena arise from irreversible change of antiferromagnet spin orientations, according to the thermal activation model.

  3. Carrier-Envelop Phase-Dependent Effect on Photoelectron Angular Distribution in Single-Cycle Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jie; ZHANG Jing-Tao; SUN Zhen-Rong; XU Zhi-Zhan

    2004-01-01

    @@ Using a nonperturbative scattering theory, we study the photoelectron angular distributions (PADs) of Kr atoms irradiated by an infinite sequence of intense single-cycle pulses of circular polarization. We demonstrate the inversion asymmetry of PADs and the dependence of PADs on the carrier-envelop phase of the single-cycle pulses. The inversion asymmetry is caused by the interference between transition channels where the different channels are characterized by different combinations of absorbed-photon numbers in the ionization process. Our results provide a possible method to determine the value of carrier-envelop phase by the detected PADs.

  4. Study on Angular Dependence in Micro-cavity OLED%微腔OLED的视角特性研究

    Institute of Scientific and Technical Information of China (English)

    袁桃利; 张方辉; 牟强; 马颖; 张思璐

    2012-01-01

    The angular dependence of QLED is studied and it showed that the brightness and current efficiency gradually decreased with increased view angle, the intensity and current efficiency at 50 degrees dropped to 1/3 and 40% respectively with respect to the normal direction. And Color coordinates produce drift at a certain extent with increased view angle, but spectral peak and FWHM didn't change depend on the angle. Reasons for the occurrence of angular dependence were discussed.%文章研究了微腔OLED的视角特性,结果表明,亮度和发光效率随着视角的增加逐渐减小,当视角增加到50°时,其亮度降为正面输出的1/3;发光效率下降了约40%左右;色坐标随着视角的增加产生漂移,而光谱峰值和半高宽基本不随视角的变化而变化。同时分析并讨论了视角特性产生的原因。

  5. Angular dependent torque measurements on CaFe0.88Co0.12AsF

    Science.gov (United States)

    Xiao, H.; Gao, B.; Ma, Y. H.; Li, X. J.; Mu, G.; Hu, T.

    2016-08-01

    Out-of-plane angular dependent torque measurements were performed on CaFe0.88Co0.12AsF (Ca1 1 1 1) single crystals. In the normal state, the torque data shows \\sin 2θ angular dependence and H 2 magnetic field dependence, as a result of paramagnetism. In the mixed state, the torque signal is a combination of the vortex torque and paramagnetic torque, and the former allows the determination of the anisotropy parameter γ. At T   =  11.5 K, γ (11.5 K ≃ 0.5 T c)  =  19.1, which is similar to the result of SmFeAsO0.8F0.2, γ ≃ 23 at T≃ 0.4{{T}\\text{c}} . So the 11 1 1 is more anisotropic compared to 11 and 122 families of iron-based superconductors. This may suggest that the electronic coupling between layers in 1 1 1 1 is less effective than in 11 and 122 families.

  6. The energy dependence of $p_t$ angular correlations inferred from mean-$p_{t}$ fluctuation scale dependence in heavy ion collisions at the SPS and RHIC

    CERN Document Server

    Adams, J; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Bai, Y; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellingeri-Laurikainen, A; Bellwied, R; Bezverkhny, B I; Bhardwaj, S; Bhasin, A; Bhati, A K; Bichsel, H; Bielcik, J; Bielcikova, J; Bland, L C; Blyth, C O; Blyth, S L; Bonner, B E; Botje, M; Bouchet, J; Brandin, A V; Bravar, A; Bystersky, M; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca-Sanchez, M; Castillo, J; Catu, O; Cebra, D; Chajecki, Z; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, J H; Chen, Y; Cheng, J; Cherney, M; Chikanian, A; Choi, H A; Christie, W; Coffin, J P; Cormier, T M; Cosentino, M R; Cramer, J G; Crawford, H J; Das, D; Das, S; Daugherity, M; De Moura, M M; Dedovich, T G; De Phillips, M; Derevshchikov, A A; Didenko, L; Dietel, T; Djawotho, P; Dogra, S M; Dong, W J; Dong, X; Draper, J E; Du, F; Dunin, V B; Dunlop, J C; Dutta-Majumdar, M R; Eckardt, V; Edwards, W R; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Estienne, M; Fachini, P; Fatemi, R; Fedorisin, J; Filimonov, K; Filip, P; Finch, E; Fine, V; Fisyak, Yu; Fu, J; Gagliardi, C A; Gaillard, L; Gans, J; Ganti, M S; Ghazikhanian, V; Ghosh, P; González, J E; Gorbunov, Y G; Gos, H; Grebenyuk, O; Grosnick, D P; Guertin, S M; Guimaraes, K S F F; Guo, Y; Gupta, N; Gutíerrez, T D; Haag, B; Hallman, T J; Hamed, A; Harris, J W; He, W; Heinz, M; Henry, T W; Hepplemann, S; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horner, M J; Huang, H Z; Huang, S L; Hughes, E W; Humanic, T J; Igo, G; Jacobs, P; Jacobs, W W; Jakl, P; Jia, F; Jiang, H; Jones, P G; Judd, E G; Kabana, S; Kang, K; Kapitan, J; Kaplan, M; Keane, D; Kechechyan, A; Khodyrev, V Yu; Kim, B C; Kiryluk, J; Kisiel, A; Kislov, E M; Koetke, D D; Kollegger, T; Kopytine, M; Kotchenda, L; Kouchpil, V; Kowalik, K L; Krämer, M; Kravtsov, P; Kravtsov, V I; Krüger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; La Pointe, S; Laue, F; Lauret, J; Lebedev, A; Lednicky, R; Lee, C H; Lehocka, S; Le Vine, M J; Li, C; Li, Q; Li, Y; Lin, G; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, H; Liu, J; Liu, L; Liu, Z; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; López-Noriega, M; Love, W A; Lu, Y; Ludlam, T; Lynn, D; Ma, G L; Ma, J G; Ma, Y G; Magestro, D; Mahapatra, D P; Majka, R; Mangotra, L K; Manweiler, R; Margetis, S; Markert, C; Martin, L; Matis, H S; Matulenko, Yu A; McClain, C J; McShane, T S; Melnik, Yu M; Meschanin, A; Miller, M L; Minaev, N G; Mioduszewski, S; Mironov, C; Mischke, A; Mishra, D K; Mitchell, J; Mohanty, B; Molnár, L; Moore, C F; Morozov, D A; Munhoz, M G; Nandi, B K; Nattrass, C; Nayak, T K; Nelson, J M; Netrakanti, P K; Nikitin, V A; Nogach, L V; Nurushev, S B; Odyniec, Grazyna Janina; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Pachr, M; Pal, S K; Panebratsev, Yu A; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Peitzmann, T; Perevozchikov, V; Perkins, C; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Poljak, N; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M V; Potrebenikova, E V; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rakness, G; Raniwala, R; Raniwala, S; Ray, R L; Razin, S V; Reinnarth, J; Relyea, D; Retière, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L; Russcher, M J; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Sarsour, M; Sazhin, P S; Schambach, J; Scharenberg, R P; Schmitz, N; Schweda, K; Seger, J; Selyuzhenkov, I; Seyboth, P; Shabetai, A; Shahaliev, E; Shao, M; Sharma, M; Shen, W Q; Shimansky, S S; ESichtermann; Simon, F; Singaraju, R N; Smirnov, N; Snellings, R; Sood, G; Sørensen, P; Sowinski, J; Speltz, J; Spinka, H M; Srivastava, B; Stadnik, A; Stanislaus, T D S; Stock, R; Stolpovsky, A; Strikhanov, M N; Stringfellow, B C; Suaide, A A P; Sugarbaker, E R; Sumbera, M; Sun, Z; Surrow, B; Swanger, M; Symons, T J M; Szanto, A; de Toledo; Tai, A; Takahashi, J; Tang, A H; Tarnowsky, T J; Thein, D; Thomas, J H; Timmins, A R; Timoshenko, S; Tokarev, M; Trainor, T A; Trentalange, S; Tribble, R E; Tsai, O D; Ulery, J; Ullrich, T; Underwood, D G; Van Buren, G; Van der Kolk, N; Van Leeuwen, M; Van der Molen, A M; Varma, R; Vasilevski, I M; Vasilev, A N; Vernet, R; Vigdor, S E; Viyogi, Y P; Vokal, S; Waggoner, W T; Wang, F; Wang, G; Wang, J S; Wang, X L; Wang, Y; Watson, J W; Webb, J C; Westfall, G D; Wetzler, A; Whitten, C; Wieman, H; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Q H; Xu, Z; Yepes, P; Yoo, I K; Yurevich, V I; Zhan, W; Zhang, H; Zhang, W M; Zhang, Y; Zhang, Z P; Zhao, Y; Zhong, C; Zoulkarneev, R; Zoulkarneeva, Y; Zubarev, A N; Zuo, J X

    2006-01-01

    We present the first study of the energy dependence of $p_t$ angular correlations inferred from event-wise mean transverse momentum $$ fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies $\\sqrt{s_{NN}} =$ 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. $p_t$ angular correlation structure suggests that the principal source of $p_t$ correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with $\\ln \\sqrt{s_{NN}}$ from the onset of observable jet-related $$ fluctuations near 10 GeV.

  7. Temperature-dependence of current-perpendicular-to-the-plane giant magnetoresistance spin-valves using Co2(Mn1-xFex)Ge Heusler alloys

    Science.gov (United States)

    Page, M. R.; Nakatani, T. M.; Stewart, D. A.; York, B. R.; Read, J. C.; Choi, Y.-S.; Childress, J. R.

    2016-04-01

    The properties of Co2(Mn1-xFex)Ge (CMFG) (x = 0-0.4) Heusler alloy magnetic layers within polycrystalline current-perpendicular-to-the plane giant magnetoresistance (CPP-GMR) spin-valves are investigated. CMFG films annealed at 220-320 °C exhibit partly ordered B2 structure with an order parameter SB2 = 0.3-0.4, and a lower SB2 was found for a higher Fe content. Nevertheless, CPP-GMR spin-valve devices exhibit a relatively high magnetoresistance ratio of ˜13% and a magnetoresistance-area product (ΔRA) of ˜6 mΩ μm2 at room temperature, which is almost independent of the Fe content in the CMFG films. By contrast, at low temperatures, ΔRA clearly increases with higher Fe content, despite the lower B2 ordering for increasing the Fe content. Indeed, first-principles calculations reveal that the CMFG alloy with a partially disordered B2 structure has a greater density of d-state at the Fermi level in the minority band compared to the Fe-free (Co2MnGe) alloy. This could explain the larger ΔRA measured on CMFG at low temperatures by assuming that s-d scattering mainly determines the spin asymmetry of resistivity as described in Mott's theory.

  8. Angular dependence of electron emission induced by grazing-ion surface collisions

    Science.gov (United States)

    Gravielle, M. S.; Miraglia, J. E.; Otero, G. G.; Sánchez, E. A.; Grizzi, O.

    2004-04-01

    In this work, electron emission spectra produced by impact of fast protons on Al(111) surfaces are theoretically and experimentally studied. Contributions coming from the different electronic sources of the metal—atomic inner shells and valence band—are analyzed as a function of the angle of electron emission. In the forward direction, the inner-shell ionization process is the dominant mechanism. The valence emission, instead, becomes important when the ejection angle is separated from the specular-reflection direction. In both angular regions, theoretical and experimental values are in reasonable agreement. The energy shift and broadening of the convoy electron peak at glancing observation angles are well described by the present model, which takes into account the influence of the induced surface field on the ionized electron.

  9. Negative magnetoresistivity in holography

    CERN Document Server

    Sun, Ya-Wen

    2016-01-01

    Negative magnetoresistivity is a special magnetotransport property associated with chiral anomaly in four dimensional chiral anomalous systems, which refers to the transport behavior that the DC longitudinal magnetoresistivity decreases with increasing magnetic field. We calculate the longitudinal magnetoconductivity in the presence of backreactions of the magnetic field to gravity in holographic zero charge and axial charge density systems with and without axial charge dissipation. In the absence of axial charge dissipation, we find that the quantum critical conductivity grows with increasing magnetic field when the backreaction strength is larger than a critical value, in contrast to the monotonically decreasing behavior of quantum critical conductivity in the probe limit. With axial charge dissipation, we find the negative magnetoresistivity behavior. The DC longitudinal magnetoconductivity scales as $B$ in the large magnetic field limit, which deviates from the exact $B^2$ scaling of the probe limit resul...

  10. Molecular anisotropic magnetoresistance

    Science.gov (United States)

    Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy

    2015-12-01

    Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.

  11. Angular dependence of the facular-sunspot coverage relation as derived by MDI magnetograms

    CERN Document Server

    Criscuoli, Serena

    2016-01-01

    Previous studies have shown that the variation over the solar magnetic activity cycle of the area of facular/network features identified on broad band and narrow band imagery is positively correlated with the sunspot area and number, the relation between the area coverages being described as either linear or quadratic. On the other hand, the temporal variation of the spatial distributions of faculae, network and sunspots follows patterns that are less obviously correlated, so that we expect the relation that describes variation of the area coverage of different types of magnetic features to vary with the position over the disk. In this work we employ MDI full-disk magnetograms acquired during Cycle 23 and at the beginning of Cycle 24 to investigate the relation between the coverage of magnetic elements characterized by different amounts of magnetic flux and located at different angular distances from disk center with the sunspot number. In agreement with some previous studies we find that daily data are best ...

  12. On solving the orientation gradient dependency of high angular resolution EBSD

    Energy Technology Data Exchange (ETDEWEB)

    Maurice, Claire, E-mail: maurice@emse.fr [Ecole des Mines de Saint-Etienne, UMR CNRS 5146 LCG, 158 cours Fauriel, F-42023 Saint-Etienne (France); Driver, Julian H. [Ecole des Mines de Saint-Etienne, UMR CNRS 5146 LCG, 158 cours Fauriel, F-42023 Saint-Etienne (France); Fortunier, Roland [Universite de Lyon, ENISE, UMR CNRS 5513 LTDS, 58 rue Jean Parot, F-42100 Saint-Etienne (France)

    2012-02-15

    Current high angular resolution electron backscatter diffraction (HR-EBSD) methods are successful at measuring pure elastic strains but have difficulties with plastically deformed metals containing orientation gradients. The strong influences of these rotations have been systematically studied using simulated patterns based on the many-beam dynamic theory of EBSP formation; a rotation of only 1 Degree-Sign can lead to apparent elastic strains of several hundred microstrains. A new method is proposed to correct for orientation gradient effects using a two-step procedure integrating finite strain theory: (i) reference pattern rotation and (ii) cross-correlation; it reduces the strain errors on the simulated patterns to tens of microstrains. An application to plastically deformed ferritic steel to generates elastic strain maps with significantly reduced values of both strains and residual errors in regions of rotations exceeding 1 Degree-Sign . -- Highlights: Black-Right-Pointing-Pointer Many-beam theory simulations show that HR-EBSD is sensitive to orientation gradients. Black-Right-Pointing-Pointer Finite strain theory and rotation processing the reference EBSP solves the problem. Black-Right-Pointing-Pointer New method succesfully applied to plastically strained IF steel.

  13. Signature of Strong Spin-Orbital Coupling in the Large Nonsaturating Magnetoresistance Material WTe2

    Science.gov (United States)

    Jiang, J.; Tang, F.; Pan, X. C.; Liu, H. M.; Niu, X. H.; Wang, Y. X.; Xu, D. F.; Yang, H. F.; Xie, B. P.; Song, F. Q.; Dudin, P.; Kim, T. K.; Hoesch, M.; Das, P. Kumar; Vobornik, I.; Wan, X. G.; Feng, D. L.

    2015-10-01

    We report the detailed electronic structure of WTe2 by high resolution angle-resolved photoemission spectroscopy. We resolved a rather complicated Fermi surface of WTe2. Specifically, there are in total nine Fermi pockets, including one hole pocket at the Brillouin zone center Γ , and two hole pockets and two electron pockets on each side of Γ along the Γ -X direction. Remarkably, we have observed circular dichroism in our photoemission spectra, which suggests that the orbital angular momentum exhibits a rich texture at various sections of the Fermi surface. This is further confirmed by our density-functional-theory calculations, where the spin texture is qualitatively reproduced as the conjugate consequence of spin-orbital coupling. Since the spin texture would forbid backscatterings that are directly involved in the resistivity, our data suggest that the spin-orbit coupling and the related spin and orbital angular momentum textures may play an important role in the anomalously large magnetoresistance of WTe2. Furthermore, the large differences among spin textures calculated for magnetic fields along the in-plane and out-of-plane directions also provide a natural explanation of the large field-direction dependence on the magnetoresistance.

  14. Determination of the angular dependence of the detector matrix Matrix X-evolution of IBA; Determinacion de la dependencia angular del detector matricicial Matrix-X-evolution de IBA

    Energy Technology Data Exchange (ETDEWEB)

    Mateos, J. C.; Luis, F. J.; Sanchez, G.; Herrados, M.

    2011-07-01

    The objective of this work consists in determining the correction for the angular dependence of the detector-Evolution Matrix x matrix (IBA, Germany), when used in the multi cube dummy (IBA, Germany), verification of treatment VMAT IMRT, using the software OP'IMRT (IBA, Germany).

  15. Angular dependence of the redeposition rates during SiO2 etching in a CF4 plasma

    International Nuclear Information System (INIS)

    The angular dependence of the redeposition rates during SiO2 etching in a CF4 plasma was studied using three types of Faraday cages located in a transformer coupled plasma etcher. The SiO2 substrates were fixed on sample holder slopes that have different angles to the cathode. The substrate was subjected to one of three processes depending on the design of the Faraday cage, i.e., redeposition of sputtered particles from the SiO2 bottom surface (case I), substrate etching by incident ions (case II), or simultaneous etching and redeposition (case III). Both the redeposition and the etch rates were measured by changing the substrate-surface angle and the self-bias voltage in the range of -100 to -800 V. The redeposition-only rates (case I) at -450 and -800 V closely followed the quadratic curve of the angle whereas the rates at -100 V followed the cubic curve, indicating different mechanisms of the bottom SiO2 etching depending on the energy regimes. The steep increase of the redeposition rate with the angle was attributed to three factors: the substrate-bottom distance, the angular distribution of emitted particles from the bottom surface, and the particle incident angle on the substrate surface. The etch-only rate curves (case II) closely followed the cosine of the surface angle. The etch-rate curve changed into a reverse-S shape when the substrate was subjected to simultaneous etching and redeposition (case III). The net etch rate for case III decreased drastically above 60 deg. , showing a negative value, i.e., a net redeposition, beyond 75 deg. . The drastic decrease in the net etch rate coincided with the steep increase in the redeposition rate, implying the significant effect of redeposition

  16. Angular dependent study on spin transport in magnetic semiconductor heterostructures with Dresselhaus spin-orbit interaction

    Science.gov (United States)

    Mirzanian, S. M.; Shokri, A. A.; Mikaili Agah, K.; Elahi, S. M.

    2015-09-01

    We investigate theoretically the effects of Dresselhaus spin-orbit coupling (DSOC) on the spin-dependent current and shot noise through II-VI diluted magnetic semiconductor/nonmagnetic semiconductor (DMS/NMS) barrier structures. The calculation of transmission probability is based on an effective mass quantum-mechanical approach in the presence of an external magnetic field applied along the growth direction of the junction and also applied voltage. We also study the dependence of spin-dependent properties on external magnetic field and relative angle between the magnetizations of two DMS layers in CdTe/CdMnTe heterostructures by including the DSOC effect. The results show that the DSOC has great different influence on transport properties of electrons with spin up and spin down in the considered system and this aspect may be utilized in designing new spintronics devices.

  17. Magnetoresistance Anisotropy in WTe2

    Science.gov (United States)

    Thoutam, Laxman Raju; Wang, Yonglei; Xiao, Zhili; Das, Saptarshi; Luican Mayer, Adina; Divan, Ralu; Crabtree, George W.; Kwok, Wai Kwong

    We report the angle dependence of the magnetoresistance in WTe2. Being a layered material, WTe2 is considered to be electronically two-dimensional (2D). Our results demonstrate that it is in fact 3D with an anisotropy of effective mass as small as 2. We measured the magnetic field dependence of the sample resistance R(H) at various angles between the applied magnetic field with respect to the c-axis of the crystal and found that they can be scaled based on the mass anisotropy, which changes from ~2 to ~5 with decreasing temperature in the Fermi liquid state. We will also discuss the origin of the turn-on temperature behavior in this material.

  18. Non-local magnetoresistance in YIG/Pt nanostructures

    International Nuclear Information System (INIS)

    We study the local and non-local magnetoresistance of thin Pt strips deposited onto yttrium iron garnet. The local magnetoresistive response, inferred from the voltage drop measured along one given Pt strip upon current-biasing it, shows the characteristic magnetization orientation dependence of the spin Hall magnetoresistance. We simultaneously also record the non-local voltage appearing along a second, electrically isolated, Pt strip, separated from the current carrying one by a gap of a few 100 nm. The corresponding non-local magnetoresistance exhibits the symmetry expected for a magnon spin accumulation-driven process, confirming the results recently put forward by Cornelissen et al. [“Long-distance transport of magnon spin information in a magnetic insulator at room temperature,” Nat. Phys. (published online 14 September 2015)]. Our magnetotransport data, taken at a series of different temperatures as a function of magnetic field orientation, rotating the externally applied field in three mutually orthogonal planes, show that the mechanisms behind the spin Hall and the non-local magnetoresistance are qualitatively different. In particular, the non-local magnetoresistance vanishes at liquid Helium temperatures, while the spin Hall magnetoresistance prevails

  19. Energy-dependent photoelectron angular distributions of two-color two-photon above threshold ionization of atomic helium

    International Nuclear Information System (INIS)

    Energy-dependent photoelectron angular distributions from two-color two-photon above threshold ionizations are investigated to determine the partial-wave characteristics of free-free electronic transitions in helium. Sideband photoelectron energies ranging from 0.18 to 13.0 eV are measured with different wavelengths of the perturbative infrared dressing field as well as different individually selected high-order harmonics. Using the experimentally measured cross-section ratios and anisotropy parameters together with analytical expressions derived from second-order perturbation theory, the partial-wave branching fractions going to the S and D waves in the positive and negative sidebands are determined as a function of photoelectron kinetic energy. The results provide a sensitive test for theoretical models of two-color two-photon above threshold ionization in atoms and molecules.

  20. Angular dependence of L X-rays emission for Ag by 10 keV electron-impact

    Science.gov (United States)

    Wang, Xing; Xu, Zhongfeng; Zhang, Ying; Ma, Chao; Zhu, Chengwei

    2016-08-01

    The characteristic X-ray intensities of Ag-Lα, Lβ1, Lβ2 and Lγ1 are measured in electron-impact ionization at energy of 10 keV. The emission angle in this work ranges from 0° to 20° at interval of 5°. The angular dependence of L X-ray intensity ratios has been investigated for Lα / Lβ1, Lβ2 / Lβ1 and Lγ1 / Lβ1. It is found from the experimental results that the emissions of Lβ1, Lβ2 and Lγ1 X-rays are spatially isotropic, while the Lα X-rays exhibit anisotropic emission. Consequently, the alignment behavior of vacancy states is discussed with thorough analysis of vacancy transfer process.

  1. Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances

    OpenAIRE

    Ali, Amir R.; Tindaro Ioppolo

    2014-01-01

    We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning senso...

  2. Current-perpendicular-to-the-plane magnetoresistance from large interfacial spin-dependent scattering between Co{sub 50}Fe{sub 50} magnetic layer and In-Zn-O conductive oxide spacer layer

    Energy Technology Data Exchange (ETDEWEB)

    Nakatani, T. M., E-mail: Tomoya.Nakatani@hgst.com; Childress, J. R. [San Jose Research Center, HGST, a Western Digital company, 3403 Yerba Buena Road, San Jose, California 95135 (United States)

    2015-06-28

    We have investigated electrically conductive indium-zinc-oxide (IZO) deposited by magnetron sputtering as spacer layer for current-perpendicular-to-the-plane giant magnetoresistance sensor devices. Spin-valves with a Co{sub 50}Fe{sub 50}/IZO/Co{sub 50}Fe{sub 50} trilayer showed resistance-area product (RA) ranging from 110 to 250 mΩ μm{sup 2}, significantly larger than all-metal structures with Ag or Cu spacers (∼40 mΩ μm{sup 2}). Magnetoresistance ratios (ΔR/R) of 2.5% to 5.5% depending on the IZO spacer thickness (1.5–6.0 nm), corresponding to ΔRA values from 3 to 13 mΩ μm{sup 2}, were obtained. The values of ΔRA with the IZO spacers and Co{sub 50}Fe{sub 50} magnetic layers were significantly larger than those with conventional metal spacers and Co{sub 50}Fe{sub 50} magnetic layers (∼1–2 mΩ μm{sup 2}). The dependence of ΔRA on the magnetic layer thickness suggests that the larger ΔRA obtained with IZO spacer is due to a large interfacial spin-dependent scattering caused by the large specific resistance at the Co{sub 50}Fe{sub 50}/IZO interface. From structural characterization by TEM and the observed dependence of the RA dispersion on device size, the electric current flowing through the IZO spacer is thought to be laterally uniform, similar to normal metal spacers.

  3. Anomalous magnetoresistance in NiMnGa thin films

    Science.gov (United States)

    Golub, Vladimir O.; Vovk, Andriy Ya.; Malkinski, Leszek; O'Connor, Charles J.; Wang, Zhenjun; Tang, Jinke

    2004-10-01

    The origin of anomalous negative magnetoresistance and its temperature dependence in polycrystalline Ni -Mn-Ga films prepared by pulse laser deposition was studied. The investigation of structural, transports, magnetic, and ferromagnetic resonance properties of the films suggests contributions of different mechanisms in magnetotransport. At low magnetic fields the main contribution to magnetoresistance is due to the transport between the areas with different orientation of magnetic moments, while at high fields it is an electron scattering of in spin-disordered areas.

  4. Angular confinement and direction-dependent transmission in graphene nanostructures with magnetic barriers

    Science.gov (United States)

    Masir, M. Ramezani; Vasilopoulos, P.; Matulis, A.; Peeters, F. M.

    2010-01-01

    We evaluate the transmission through magnetic barriers in graphene-based nanostructures. Several particular cases are considered: a magnetic step, single and double barriers, δ -function barriers as well as barrier structures with inhomogeneous magnetic field profiles but with average magnetic field equal to zero. The transmission exhibits a strong dependence on the direction of the incident wave vector. In general the resonant structure of the transmission is significantly more pronounced for (Dirac) electrons with linear spectrum compared to that for electrons with a parabolic one.

  5. Molecular anisotropic magnetoresistance

    OpenAIRE

    Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy

    2015-01-01

    Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by $3d$ transition-metal wires. We show that the gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symm...

  6. Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures

    KAUST Repository

    Ortiz Pauyac, Christian

    2013-06-26

    In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.

  7. Simulations of the angular dependence of the dipole–dipole interaction among Rydberg atoms

    Science.gov (United States)

    Bigelow, Jacob L.; Paul, Jacob T.; Peleg, Matan; Sanford, Veronica L.; Carroll, Thomas J.; Noel, Michael W.

    2016-08-01

    The dipole–dipole interaction between two Rydberg atoms depends on the relative orientation of the atoms and on the change in the magnetic quantum number. We simulate the effect of this anisotropy on the energy transport in an amorphous many atom system subject to a homogeneous applied electric field. We consider two experimentally feasible geometries and find that the effects should be measurable in current generation imaging experiments. In both geometries atoms of p character are localized to a small region of space which is immersed in a larger region that is filled with atoms of s character. Energy transfer due to the dipole–dipole interaction can lead to a spread of p character into the region initially occupied by s atoms. Over long timescales the energy transport is confined to the volume near the border of the p region which suggests Anderson localization. We calculate a correlation length of 6.3 μm for one particular geometry.

  8. Angular and Frequency-Dependent Wave Velocity and Attenuation in Fractured Porous Media

    Science.gov (United States)

    Carcione, José M.; Gurevich, Boris; Santos, Juan E.; Picotti, Stefano

    2013-11-01

    Wave-induced fluid flow generates a dominant attenuation mechanism in porous media. It consists of energy loss due to P-wave conversion to Biot (diffusive) modes at mesoscopic-scale inhomogeneities. Fractured poroelastic media show significant attenuation and velocity dispersion due to this mechanism. The theory has first been developed for the symmetry axis of the equivalent transversely isotropic (TI) medium corresponding to a poroelastic medium containing planar fractures. In this work, we consider the theory for all propagation angles by obtaining the five complex and frequency-dependent stiffnesses of the equivalent TI medium as a function of frequency. We assume that the flow direction is perpendicular to the layering plane and is independent of the loading direction. As a consequence, the behaviour of the medium can be described by a single relaxation function. We first consider the limiting case of an open (highly permeable) fracture of negligible thickness. We then compute the associated wave velocities and quality factors as a function of the propagation direction (phase and ray angles) and frequency. The location of the relaxation peak depends on the distance between fractures (the mesoscopic distance), viscosity, permeability and fractures compliances. The flow induced by wave propagation affects the quasi-shear (qS) wave with levels of attenuation similar to those of the quasi-compressional (qP) wave. On the other hand, a general fracture can be modeled as a sequence of poroelastic layers, where one of the layers is very thin. Modeling fractures of different thickness filled with CO2 embedded in a background medium saturated with a stiffer fluid also shows considerable attenuation and velocity dispersion. If the fracture and background frames are the same, the equivalent medium is isotropic, but strong wave anisotropy occurs in the case of a frameless and highly permeable fracture material, for instance a suspension of solid particles in the fluid.

  9. Angular dependence of optical modes in metal-insulator-metal coupled quantum well infrared photodetector

    Directory of Open Access Journals (Sweden)

    YouLiang Jing

    2016-04-01

    Full Text Available We report the dependence of the near-field optical modes in metal-insulator-metal quantum well infrared photodetector (MIM-QWIP on the incident angles. Three optical modes are observed and attributed to the 2nd- and the 3rd-order surface plasmon polariton (SPP modes and the localized surface polariton (LSP mode. In addition to the observation of a responsivity enhancement of 14 times by the LSP mode, the varying pattern of the three modes against the incident angle are revealed, in which the LSP mode is fixed while the 2nd SPP mode splits into two branches and the 3rd SPP mode red-shifts. The detailed mechanisms are analyzed and numerically simulated. The results fit the experiments very well, demonstrating the wavevector coupling effect between the incident light and the metal gratings on the SPP modes. Our work will pave the way to fully understanding the influence of incident angles on a detector’s response for applying the MIM-QWIP to focal plane arrays.

  10. Magnetoresistive properties of nanostructured magnetic metals, manganites, and magnetic semiconductors

    Science.gov (United States)

    Solin, N. I.; Romashev, L. N.; Naumov, S. V.; Saranin, A. A.; Zotov, A. V.; Olyanich, D. A.; Kotlyar, V. G.; Utas, O. A.

    2016-02-01

    We consider methods for controlling magnetoresistive parameters of magnetic metal superlattices, manganites, and magnetic semiconductors. By reducing the thickness of ferromagnetic layers in superlattices (e.g., Fe layers in Fe/Cr superlattices), it is possible to form superparamagnetic clustered-layered nanostructures with a magnetoresistance weakly depending on the direction of the external magnetic field, which is very important for applications of such type of materials. Producing Mn vacancies and additionally annealing lanthanum manganites in the oxygen atmosphere, it is possible to increase their magnetoresistance by more than four orders of magnitude. By changing the thickness of p- n junction in the structure of ferromagnetic semiconductors, their magnetoresistance can be increased by 2-3 orders of magnitude.

  11. The suppression of the large magnetoresistance in thin WTe2

    Science.gov (United States)

    Shen, Jie; Woods, John; Cha, Judy

    The layered nature of WTe2 suggests the possibility of making a single layer WTe2 memory device that exploits the recently observed large magnetoresistance. Presently, the origin of the magnetoresistance is attributed to the charge balance between the electron and hole carriers, yet the exact underlying physical mechanism is unclear. Here we show a systematic suppression of the large magnetoresistance, as well as turn-on temperature, with decreasing thickness of WTe2. We attribute the thickness-dependent transport properties to undesirable parasitic effects that become dominant in thin films of WTe2. Our results highlight the increasing importance of characterizing the parasitic effects for 2D layered materials in a single- to a few-layer thick limit. Finally, our observations support the hypothesis that the origin of the large magnetoresistance may be due to the charge balance between the electron and the hole carriers.

  12. Development of a standard method for nanoparticle sizing by using the angular dependence of dynamic light scattering.

    Science.gov (United States)

    Takahashi, Kayori; Kato, Haruhisa; Kinugasa, Shinichi

    2011-01-01

    A standard method for nanoparticle sizing based on the angular dependence of dynamic light scattering was developed. The dependences of the diffusion coefficients for aqueous suspensions of polystyrene latex on the concentration and scattering angle were accurately measured by using a high-resolution dynamic light-scattering instrument. Precise measurements of the short-time correlation function at seven scattering angles and five concentrations were made for suspensions of polystyrene latex particles with diameters from 30 to 100 nm. The apparent diffusion coefficients obtained at various angles and concentrations showed properties characteristic of polystyrene latex particles with electrostatic interactions. A simulation was used to calculate a dynamic structure factor representing the long-range interactions between particles. Extrapolations to infinite dilution and to low angles gave accurate particle sizes by eliminating the effects of long-range interactions. The resulting particle sizes were consistent with those measured by using a differential mobility analyzer and those obtained by pulsed-field gradient nuclear magnetic resonance measurements. PMID:21747185

  13. Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation.

    Science.gov (United States)

    Yakushin, Sergei B

    2012-06-01

    The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.

  14. Giant negative magneto-resistance in non-magnetic quantum dot arrays in the nearest-neighbor hopping conduction

    CERN Document Server

    Wang, X R

    1999-01-01

    We propose a new mechanism of negative magnetoresistance in non-magnetic quantum dot arrays or granular materials in which electron transport in dominated by hopping between two nearest-neighbor clusters. We study the dependence of magnetoresistance on temperature and separation between neighboring clusters. At a small separation we find a negative magnetoresistance at low temperatures and it changes over to a positive value as temperature increases. For a fixed temperature, magnetoresistance changes from negative to positive when the cluster separation increases. The change of magnetoresistance DELTA R/R can be more than 80 % at low temperatures.

  15. Angular dependence of ferromagnetic resonance in Tb-doped Ni{sub 80}Fe{sub 20} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chen [Physics Department, Southeast University, Nanjing 211189 (China); Zhang, Dong [Physics Department, Southeast University, Nanjing 211189 (China); School of Physics Science and Information Engineering, Liaocheng University, Liaocheng 252059 (China); Wang, Yukun [Physics Department, Southeast University, Nanjing 211189 (China); Huang, Haibo [College of Material Science and Engineering, Southeast University, Nanjing 211189 (China); Zhai, Ya, E-mail: yazhai@seu.edu.cn [Physics Department, Southeast University, Nanjing 211189 (China); Zhai, Hongru [National Laboratory of Solid Microstructures, Nanjing University, Nanjing 210093 (China)

    2014-06-15

    Highlights: • The soft magnetic properties of Ni{sub 80}Fe{sub 20} films with Tb dopants up to 8.4% are kept. • The different mechanisms of FMR linewidth are separated and studied. • Magnetic anisotropy constants, Lande g factor, etc. are discussed quantitatively. • The Gilbert damping is increased by more than 50 times with 8.4% of Tb dopants. - Abstract: The mechanisms of angular dependence of ferromagnetic resonance (FMR) linewidth of dilute Tb doping in Ni{sub 80}Fe{sub 20} thin films are investigated by experimental approach and the theoretical fitting by considering the contributions from intrinsic spin–orbit coupling, two-magnon scattering and inhomogeneous broadening. It is shown that the damping coefficient α, by intrinsic contribution extracted from FMR linewidth, is increased by more than 50 times as the Tb concentration increases to 8.4%, indicating that the spin–orbit coupling of this system increases with the introduction of Tb impurities. The magnetic anisotropy constants K{sub 1} and K{sub 2} are obtained and show an increasing trend from negative to positive, which implies that the Tb dopants could enhance the perpendicular anisotropy.

  16. Large linear magnetoresistance in topological crystalline insulator Pb0.6Sn0.4Te

    Science.gov (United States)

    Roychowdhury, Subhajit; Ghara, Somnath; Guin, Satya N.; Sundaresan, A.; Biswas, Kanishka

    2016-01-01

    Classical magnetoresistance generally follows the quadratic dependence of the magnetic field at lower field and finally saturates when field is larger. Here, we report the large positive non-saturating linear magnetoresistance in topological crystalline insulator, Pb0.6Sn0.4Te, at different temperatures between 3 K and 300 K in magnetic field up to 9 T. Magnetoresistance value as high as ∼200% was achieved at 3 K at magnetic field of 9 T. Linear magnetoresistance observed in Pb0.6Sn0.4Te is mainly governed by the spatial fluctuation carrier mobility due to distortions in the current paths in inhomogeneous conductor.

  17. Dependence of deep-inelastic processes on entrance channel asymmetry and excitation energy. [506 to 732 MeV, angular distribution

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, R.P.

    1978-05-01

    The dependence of deep-inelastic processes on entrance channel asymmetry and on excitation energy was investigated. Thin targets of /sup nat/At, /sup 159/Tb, /sup 181/Ta and /sup 197/Au were bombarded with 620 MeV /sup 86/Kr ions. Additional measurements were performed on the reactions /sup nat/Ag + /sup 86/Kr and /sup 197/Au + /sup 86/Kr at 506 and 732 MeV incident energy. The energy spectra, the charge distributions and the angular distributions of these fragments were measured. At 620 MeV the energy spectra show that the distinction between quasi-elastic and deep-inelastic processes diminishes as the target mass is increased. The charge distributions, which are peaked at symmetry for /sup nat/Ag, tend to become increasingly asymmetric for the heavier systems. Likewise, the angular distributions exhibit a strong dependence on the entrance channel asymmetry. For the lightest system, /sup nat/Ag + /sup 86/Kr, the angular distributions are essentially forward peaked, aside from a separable quasi-elastic component. For the heaviest system, /sup 197/Au + /sup 86/Kr, the angular distributions are side-peaked. The transition between these two regimes occurs smoothly with increasing target mass. The results at 506 and 732 MeV show that the widths of the charge distributions are strongly dependent on the excitation energy. The angular distributions for the reaction /sup nat/Ag + /sup 86/Kr become increasingly more forward peaked at higher bombarding energies. The angular distributions for /sup 197/Au + /sup 86/Kr, which are strongly focused at 506 MeV, also tend to be more forward peaked at the highest incident energy. The results are interpreted by assuming that the projectile and target form an intermediate complex and that they exchange mass via a diffusion process. Because of the systematic nature of this study, the data should serve as a guide in the development of models of deep-inelastic processes.

  18. Giant magnetoresistance in organic spin-valves.

    Science.gov (United States)

    Xiong, Z H; Wu, Di; Vardeny, Z Valy; Shi, Jing

    2004-02-26

    A spin valve is a layered structure of magnetic and non-magnetic (spacer) materials whose electrical resistance depends on the spin state of electrons passing through the device and so can be controlled by an external magnetic field. The discoveries of giant magnetoresistance and tunnelling magnetoresistance in metallic spin valves have revolutionized applications such as magnetic recording and memory, and launched the new field of spin electronics--'spintronics'. Intense research efforts are now devoted to extending these spin-dependent effects to semiconductor materials. But while there have been noteworthy advances in spin injection and detection using inorganic semiconductors, spin-valve devices with semiconducting spacers have not yet been demonstrated. pi-conjugated organic semiconductors may offer a promising alternative approach to semiconductor spintronics, by virtue of their relatively strong electron-phonon coupling and large spin coherence. Here we report the injection, transport and detection of spin-polarized carriers using an organic semiconductor as the spacer layer in a spin-valve structure, yielding low-temperature giant magnetoresistance effects as large as 40 per cent. PMID:14985756

  19. Time-Dependent and Time-Integrated Angular Analysis of B -> phi Ks pi0 and B -> phi K+ pi-

    Energy Technology Data Exchange (ETDEWEB)

    Aubert, B; Bona, M; Karyotakis, Y; Lees, J P; Poireau, V

    2008-08-04

    We perform a time-dependent and time-integrated angular analysis of the B{sup 0} {yields} {psi}K*(892){sup 0}, {psi}K*{sub 2}(1430{sup 0}), and {psi}(K{pi}){sub S-wave}{sup 0} decays with the final sample of about 465 million B{bar B} pairs recorded with the BABAR detector. Overall, twelve parameters are measured for the vector-vector decay, nine parameters for the vector-tensor decay, and three parameters for the vector-scalar decay, including the branching fractions, CP-violation parameters, and parameters sensitive to final state interaction. We use the dependence on the K{pi} invariant mass of the interference between the scalar and vector or tensor components to resolve discrete ambiguities of the strong and weak phases. We use the time-evolution of the B {yields} {psi}K{sub S}{sup 0}{pi}{sup 0} channel to extract the CP-violation phase difference {Delta}{phi}{sub 00} = 0.28 {+-} 0.42 {+-} 0.04 between the B and {bar B} decay amplitudes. When the B {yields} {psi}K{sup {+-}}{pi}{sup {-+}} channel is included, the fractions of longitudinal polarization f{sub L} of the vector-vector and vector-tensor decay modes are measured to be 0.494 {+-} 0.034 {+-} 0.013 and 0.901{sub -0.058}{sup +0.046} {+-} 0.037, respectively. This polarization pattern requires the presence of a helicity-plus amplitude in the vector-vector decay from a presently unknown source.

  20. Raman scattering investigation of large positive magnetoresistance material WTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kong, W.-D.; Wu, S.-F.; Lian, C.-S.; Wang, J.-T.; Yang, C.-L.; Shi, Y.-G. [Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Richard, P., E-mail: p.richard@iphy.ac.cn; Ding, H., E-mail: dingh@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2015-02-23

    We have performed polarized Raman scattering measurements on WTe{sub 2}, for which an extremely large positive magnetoresistance has been reported recently. We observe 5 A{sub 1} phonon modes and 2 A{sub 2} phonon modes out of 33 Raman active modes, with frequencies in good accordance with first-principles calculations. The angular dependence of the intensity of the peaks observed is consistent with the Raman tensors of the C{sub 2v} point group symmetry attributed to WTe{sub 2}. Although the phonon spectra suggest neither strong electron-phonon nor spin-phonon coupling, the intensity of the A{sub 1} phonon mode at 160.6 cm{sup −1} shows an unconventional decrease with temperature decreasing, for which the origin remains unclear.

  1. From spin-polarized interfaces to giant magnetoresistance in organic spin valves

    NARCIS (Netherlands)

    Cakir, D.; Otalvaro Gutierrez, D.M.; Brocks, G.

    2014-01-01

    We calculate the spin-polarized electronic transport through a molecular bilayer spin valve from first principles, and establish the link between the magnetoresistance and the spin-dependent interactions at the metal-molecule interfaces. The magnetoresistance of a Fe| bilayer-C 70 | Fe spin valve at

  2. Measurement of angularly dependent spectra of betatron gamma-rays from a laser plasma accelerator with quadrant-sectored range filters

    Science.gov (United States)

    Jeon, Jong Ho; Nakajima, Kazuhisa; Kim, Hyung Taek; Rhee, Yong Joo; Pathak, Vishwa Bandhu; Cho, Myung Hoon; Shin, Jung Hun; Yoo, Byung Ju; Jo, Sung Ha; Shin, Kang Woo; Hojbota, Calin; Bae, Lee Jin; Jung, Jaehyung; Cho, Min Sang; Sung, Jae Hee; Lee, Seong Ku; Cho, Byoung Ick; Choi, Il Woo; Nam, Chang Hee

    2016-07-01

    Measurement of angularly dependent spectra of betatron gamma-rays radiated by GeV electron beams from laser wakefield accelerators (LWFAs) are presented. The angle-resolved spectrum of betatron radiation was deconvolved from the position dependent data measured for a single laser shot with a broadband gamma-ray spectrometer comprising four-quadrant sectored range filters and an unfolding algorithm, based on the Monte Carlo code GEANT4. The unfolded gamma-ray spectra in the photon energy range of 0.1-10 MeV revealed an approximately isotropic angular dependence of the peak photon energy and photon energy-integrated fluence. As expected by the analysis of betatron radiation from LWFAs, the results indicate that unpolarized gamma-rays are emitted by electrons undergoing betatron motion in isotropically distributed orbit planes.

  3. Characterization of MOSFET dosimeter angular dependence in three rotational axes measured free-in-air and in soft-tissue equivalent material.

    Science.gov (United States)

    Koivisto, Juha; Kiljunen, Timo; Wolff, Jan; Kortesniemi, Mika

    2013-09-01

    When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5º angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure. PMID:23520268

  4. Anomalous magnetoresistance on the topological surface

    International Nuclear Information System (INIS)

    We report theoretical study of charge transport in two-dimensional ferromag-net/ferromagnet junction on a topological insulator. The conductance across the interface shows anomalous dependence on the directions of the magnetizations of the two ferromagnets. This stems from the way how the wavefunctions connect between both sides. It is found that the conductance depends strongly on the in-plane direction of the magnetization. Moreover, in stark contrast to the conventional magnetoresistance effect, the conductance at the parallel configuration can be much smaller than that at the antiparallel configuration.

  5. Magnetization and magnetoresistance of a spin valve

    Science.gov (United States)

    Bebenin, N. G.; Ustinov, V. V.

    2015-02-01

    Hysteresis of magnetization and magnetoresistance caused by a change in the orientation of the free layer of a spin valve has been investigated theoretically. It has been shown that the width of the hysteresis loop determined from the data on the dependence of the magnetic moment of the valve on the magnetic field can be less than the width of the loop determined from the resistive data. Formulas have been obtained that describe the dependence of the width of the hysteresis loop on the magnetic field at various values of the exchange field acting on the free layer.

  6. Anomalous magnetoresistance in Fibonacci multilayers.

    Energy Technology Data Exchange (ETDEWEB)

    Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A. (Materials Science Division); (Universidade Federal do Rio Grande do Norte)

    2012-01-01

    We theoretically investigated magnetoresistance curves in quasiperiodic magnetic multilayers for two different growth directions, namely, [110] and [100]. We considered identical ferromagnetic layers separated by nonmagnetic layers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were included in our description of the magnetic energy: Zeeman, cubic anisotropy, bilinear coupling, and biquadratic coupling. The minimum energy was determined by the gradient method and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. By choosing spacers with a thickness such that biquadratic coupling is stronger than bilinear coupling, unusual behaviors for the magnetoresistance were observed: (i) for the [110] case, there is a different behavior for structures based on even and odd Fibonacci generations, and, more interesting, (ii) for the [100] case, we found magnetic field ranges for which the magnetoresistance increases with magnetic field.

  7. Magnetization reversal in permalloy ferromagnetic nanowires investigated with magnetoresistance measurements

    Science.gov (United States)

    Oliveira, A. B.; Rezende, S. M.; Azevedo, A.

    2008-07-01

    The magnetization reversal process in single Permalloy (Ni81Fe19) nanowires has been investigated by magnetoresistance measurements as a function of the angle between the applied field and the wire direction. The Permalloy nanostructures fabricated on an ultrathin film by atomic force microscopy consist of two large rectangular pads connected by a nanowire with the shape of a long thin narrow tape. For each field direction in the plane of the film the dependence of the magnetoresistance on the field value exhibits two main contributions: one from the pads and one from the nanowire. The contribution from the pads is due to a usual anisotropic magnetoresistance characteristic of coherent magnetization rotation, whereas the contribution from the nanowire is an abrupt transition at the switching field. The dependence of the switching field on the in-plane field angle is quantitatively described by a model of nucleation field with the buckling magnetization rotation mode.

  8. The dependence of stellar mass and angular momentum losses on latitude and on active region and dipolar magnetic fields

    CERN Document Server

    Garraffo, Cecilia; Cohen, Ofer

    2015-01-01

    Rotation evolution of late-type stars is dominated by magnetic braking and the underlying factors that control this angular momentum loss are important for the study of stellar spin-down. In this work, we study angular momentum loss as a function of two different aspects of magnetic activity using a calibrated Alfv\\'en wave-driven magnetohydrodynamic wind model: the strengths of magnetic spots and their distribution in latitude. By driving the model using solar and modified solar surface magnetograms, we show that the topology of the field arising from the net interaction of both small-scale and large-scale field is important for spin-down rates and that angular momentum loss is not a simple function of large scale magnetic field strength. We find that changing the latitude of magnetic spots can modify mass and angular momentum loss rates by a factor of two. The general effect that causes these differences is the closing down of large-scale open field at mid- and high-latitudes by the addition of the small-sc...

  9. The Hall effect and magnetoresistance of the high-temperature cuprate superconductors

    International Nuclear Information System (INIS)

    We show that underlying the unusual temperature dependence of RH is a Hall angle damping rate which varies as T2, in contrast with the linear-T dependence in the transport scattering rate. The effect of impurities on this rate is discussed. The dephasing rate for carriers in Bi 2201 is measured by low temperature magnetoresistance, and found to vary as the cube root of T from 0.4 to 20 K. Spin dependent effects in the magnetoresistance are discussed. (orig.)

  10. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent x-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Okabayashi, J. [Research Center for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Koo, J. W.; Mitani, S. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577 (Japan); Sukegawa, H. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Takagi, Y.; Yokoyama, T. [Institute of Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2014-09-22

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3d{sub z}{sup 2} and O 2p{sub z} states.

  11. Vibration-dependent angular anisotropy in the photodetachment of O{sub 2}{sup -}, viewed with velocity-map imaging

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, S T; Cavanagh, S J; Lewis, B R [Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Gascooke, J R [School of Chemistry, Physics and Earth Sciences, Flinders University, SA 5001 (Australia); Mabbs, R [Department of Chemistry, Washington University, St Louis MO 63930-4899 (United States); Sanov, A, E-mail: Stephen.Gibson@anu.edu.a, E-mail: Steven.Cavanagh@anu.edu.a [Department of Chemistry, University of Arizona, Tucson AZ 85721-0041 (United States)

    2009-11-01

    The photodetachment spectrum of O{sub 2}{sup -} has been measured at a number of wavelengths using velocity-map imaging. The electron kinetic-energy resolution (< 5 meV) is sufficient to resolve the anion fine-structure splitting, vibrational and electronic structure. The electron angular distribution varies with the electron kinetic-energy, with a different behaviour for each vibronic band.

  12. Active control of magnetoresistance of organic spin valves using ferroelectricity

    Science.gov (United States)

    Shen, Jian

    Organic spintronic devices have been appealing because of the long spin lifetime of the charge carriers in the organic materials and their low cost, flexibility and chemical diversity. In previous studies, the control of resistance of organic spin valves is generally achieved by the alignment of the magnetization directions of the two ferromagnetic electrodes, generating magnetoresistance. Here we employ a new knob to tune the resistance of organic spin valves by adding a thin ferroelectric interfacial layer between the ferromagnetic electrode and the organic spacer: the magnetoresistance of the spin valve depends strongly on the history of the bias voltage, which is correlated with the polarization of the ferroelectric layer; the magnetoresistance even changes sign when the electric polarization of the ferroelectric layer is reversed. These findings enable active control of resistance using both electric and magnetic fields, opening up possibility for multi-state organic spin valves.

  13. Nonlocal ordinary magnetoresistance in indium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Pan [School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021 (China); Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yuan, Zhonghui; Wu, Hao; Ali, S.S. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wan, Caihua, E-mail: wancaihua@iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Ban, Shiliang, E-mail: slban@imu.edu.cn [School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021 (China)

    2015-07-01

    Deflection of carriers by Lorentz force results in an ordinary magnetoresistance (OMR) of (μB){sup 2} at low field. Here we demonstrate that the OMR in high mobility semiconductor InAs could be enhanced by measurement geometry where two probes of voltmeter were both placed on one outer side of two probes of current source. The nonlocal OMR was 3.6 times as large as the local one, reaching 1.8×10{sup 4}% at 5 T. The slope of the linear field dependence of the nonlocal OMR was improved from 12.6 T{sup −1} to 45.3 T{sup −1}. The improvement was ascribed to polarity-conserved charges accumulating on boundaries in nonlocal region due to Hall effect. This InAs device with nonlocal geometry could be competitive in B-sensors due to its high OMR ratio, linear field dependence and simple structure. - Highlights: • Ordinary magnetoresistance could be enhanced by nonlocal geometry by 3.6 times. • Linear field dependence at high field could be realized in nonlocal geometry. • Nonlocal MR was realized by polarity-conserved accumulating charges on boundaries • Nonlocal MR in InAs reached 1.8×10{sup 4}% at 5 T. • Nonlocal MR devices could be used in high-field sensing applications.

  14. Nonlocal ordinary magnetoresistance in indium arsenide

    International Nuclear Information System (INIS)

    Deflection of carriers by Lorentz force results in an ordinary magnetoresistance (OMR) of (μB)2 at low field. Here we demonstrate that the OMR in high mobility semiconductor InAs could be enhanced by measurement geometry where two probes of voltmeter were both placed on one outer side of two probes of current source. The nonlocal OMR was 3.6 times as large as the local one, reaching 1.8×104% at 5 T. The slope of the linear field dependence of the nonlocal OMR was improved from 12.6 T−1 to 45.3 T−1. The improvement was ascribed to polarity-conserved charges accumulating on boundaries in nonlocal region due to Hall effect. This InAs device with nonlocal geometry could be competitive in B-sensors due to its high OMR ratio, linear field dependence and simple structure. - Highlights: • Ordinary magnetoresistance could be enhanced by nonlocal geometry by 3.6 times. • Linear field dependence at high field could be realized in nonlocal geometry. • Nonlocal MR was realized by polarity-conserved accumulating charges on boundaries • Nonlocal MR in InAs reached 1.8×104% at 5 T. • Nonlocal MR devices could be used in high-field sensing applications

  15. Experimental results and theoretical model to describe angular dependence of light scattering by monolayer of nematic droplets

    Science.gov (United States)

    Loiko, V. A.; Krakhalev, M. N.; Konkolovich, A. V.; Prishchepa, O. O.; Miskevich, A. A.; Zyryanov, V. Ya.

    2016-07-01

    Light scattering by a monolayer of bipolar nematic droplets encapsulated in polymer film is examined both experimentally and theoretically. A method for the simulation of the angular distribution of scattered light is based on the anomalous diffraction and interference approximations taking into account the director configuration within liquid crystal droplets and their bipolar axes orientation. The director configuration in nematic droplets is calculated using the relaxation method of the free energy minimization. The characteristics of the sample, including distribution of droplet sizes and shape anisometry, are measured in details. The experimental results and theoretical data agree closely with each other.

  16. Magnetoresistance stories of double perovskites

    Indian Academy of Sciences (India)

    Abhishek Nag; Sugata Ray

    2015-06-01

    Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain magnetic antiphase boundaries (APB) as well as magnetically frustrated grain surfaces have also been proposed to act as tunnel barriers in Sr2FeMoO6. In this review, the present state of the debate has been discussed briefly and how the physical state of the material can affect the magnetoresistance signal of double perovskites in many different ways has been pointed out.

  17. Observation of a Change in Bend of an RNA Kissing Complex Using the Angular Dependence of Fluorescence Resonance Energy Transfer

    CERN Document Server

    Rahmanseresht, Sheema; Gamari, Ben D; Goldner, Lori S

    2014-01-01

    We report on the observation of a change in the bend angle of an RNA kissing complex upon Rop binding using single-molecular-pair FRET. The angular relationship between the dyes, rather than the distance between them, is shown to be responsible for the observed change in energy transfer. It has long been thought that Rop increases the bend angle of the R1inv-R2inv complex upon binding, but this has never been directly observed. In contrast, we find an increase in FRET upon the addition of Rop that is shown via modeling to be consistent with a decrease in the bend angle of the complex of $-15^{\\circ}\\pm7^{\\circ}$. The model predicts FRET from dye trajectories generated using molecular dynamics simulations of Cy3 and Cy5 attached to $5'$ terminal cytosine or guanosine on RNA. While FRET is commonly used to observe global changes in molecular structure attributed to changes in the distance between dyes, it is rarely, if ever, used to elucidate angular changes. Subtle global changes in molecular structure upon bi...

  18. Angular Cheilitis

    Science.gov (United States)

    ... A This image displays a frequent location for candida infection (angular cheilitis), the corners of the mouth. Overview ... infection, those affected may also have thrush (oral candidiasis). The areas are generally slightly painful. The condition ...

  19. First-order chiral to non-chiral transition in the angular dependence of the upper critical induction of the Scharnberg-Klemm $p$-wave pair state

    OpenAIRE

    Zhang, Jingchuan; Lörscher, Christopher; Gu, Qiang; Klemm, Richard A.

    2014-01-01

    We calculate the temperature $T$ and angular $(\\theta,\\phi)$ dependence of the upper critical induction $B_{c2}(\\theta,\\phi,T)$ for parallel-spin superconductors with an axially symmetric $p$-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). For all FS anisotropies, the chiral Scharnberg-Klemm state $B_{c2}(\\theta,\\phi,T)$ exceeds that of the chiral Anderson-Brinkman-Morel state, and exhibits a kink at $\\theta=\\theta^{*}(T,\\phi)$, indicative of a fi...

  20. Flavour-tagged time-dependent angular analysis of the $B_s^0 \\rightarrow J/\\psi(\\mu^+\\mu^-)\\Phi(K^+K^-)$ decay with the ATLAS detector

    CERN Document Server

    Jakoubek, Tomas; The ATLAS collaboration

    2015-01-01

    We present a flavour tagged time dependent angular analysis of the $B_s \\rightarrow J/\\psi\\phi$ decay, using 4.9 fb$^{−1}$ of integrated luminosity collected by the ATLAS detector from 7 TeV proton-proton collisions recorded in 2011. CP violation in this channel is described by a weak phase $\\phi_s$, which is sensitive to new physics contributions. The measured value is $\\phi_s$ = 0.12 $\\pm$ 0.25 (stat.) $\\pm$ 0.05 (syst.) rad, which is in good agreement with Standard Model expectations. Also other measured parameters are consistent with the world average.

  1. Large magnetoresistance and electronic anisotropy in NbAs2

    Science.gov (United States)

    Shen, Bing; Jiang, Shan; Ni, Ni

    Recently, extremely large magnetoresistance (XMR) was discovered in semimetal such as WTe2 LaSb and so on, triggering extensive reseach on these materials and the origin of XMR. In this talk, we will report the transport properties of non-magnetic layered pnictide material NbAs2. Large transverse magnetoresistance is observed. At 10 K, the magnetoresistance is around 13000 % in the field of 9 T and shows no saturation behavior. The temperature dependent resistivity at various fields exhibits metal-to-semiconductor transition behavior around 100 K, which is coincident with the sudden increase of the Hall signal in the same temperature region. The angle dependent magnetoresistance at various temperatures follows the 3D scaling behavior with the mass anisotropy around 1.3-1.4, indicative of its 3D electron structure. Quantum oscillation data reveal the existence of at least three Fermi pockets in this material. Work at UCLA was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES) under Award Number DE-SC0011978.

  2. Effect of thermal-annealing on the magnetoresistance of manganite-based junctions

    Institute of Scientific and Technical Information of China (English)

    Xie Yan-Wu; Shen Bao-Gen; Sun Ji-Rong

    2008-01-01

    Thermal-annealing has been widely used in modulating the oxygen content of manganites. In this work, we have studied the effect of annealing on the transport properties and magnetoresistance of junctions composed of a La0.9Ca0.1MnO3+δ film and a Nb-doped SrTiO3 substrate. We have demonstrated that the magnetoresistance of junctions is strongly dependent on the annealing conditions: From the junction annealed-in-air to the junction annealed-in-vacuum, the magnetoresistance near 0-V bias can vary from ~-60% to~0. A possible mechanism accounting for this phenomenon is discussed.

  3. Tunneling anisotropic magnetoresistance in La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions

    Directory of Open Access Journals (Sweden)

    R. Galceran

    2016-04-01

    Full Text Available The magnetotransport properties of La2/3Sr1/3MnO3(LSMO/ LaAlO3(LAO/Pt tunneling junctions have been analyzed as a function of temperature and magnetic field. The junctions exhibit magnetoresistance (MR values of about 37%, at H=90 kOe at low temperature. However, the temperature dependence of MR indicates a clear distinct origin than that of conventional colossal MR. In addition, tunneling anisotropic MR (TAMR values around 4% are found at low temperature and its angular dependence reflects the expected uniaxial anisotropy. The use of TAMR response could be an alternative of much easier technological implementation than conventional MTJs since only one magnetic electrode is required, thus opening the door to the implementation of more versatile devices. However, further studies are required in order to improve the strong temperature dependence at the present stage.

  4. Theory of magnetoresistance due to lattice dislocations in face-centred cubic metals

    Science.gov (United States)

    Bian, Q.; Niewczas, M.

    2016-06-01

    A theoretical model to describe the low temperature magneto-resistivity of high purity copper single and polycrystals containing different density and distribution of dislocations has been developed. In the model, magnetoresistivity tensor is evaluated numerically using the effective medium approximation. The anisotropy of dislocation-induced relaxation time is considered by incorporating two independent energy bands with different relaxation times and the spherical and cylindrical Fermi surfaces representing open, extended and closed electron orbits. The effect of dislocation microstructure is introduced by means of two adjustable parameters corresponding to the length and direction of electron orbits in the momentum space, which permits prediction of magnetoresistance of FCC metals containing different density and distribution of dislocations. The results reveal that dislocation microstructure influences the character of the field-dependent magnetoresistivity. In the orientation of the open orbits, the quadratic variation in magnetoresistivity changes to quasi-linear as the density of dislocations increases. In the closed orbit orientation, dislocations delay the onset of magnetoresistivity saturation. The results indicate that in the open orbit orientations of the crystals, the anisotropic relaxation time due to small-angle dislocation scattering induces the upward deviation from Kohler's rule. In the closed orbit orientations Kohler's rule holds, independent of the density of dislocations. The results obtained with the model show good agreement with the experimental measurements of transverse magnetoresistivity in deformed single and polycrystal samples of copper at 2 K.

  5. Monte Carlo simulation of multilayer magnetic structures and calculation of the magnetoresistance coefficient

    Science.gov (United States)

    Prudnikov, V. V.; Prudnikov, P. V.; Romanovskii, D. E.

    2015-11-01

    The Monte Carlo study of three-layer and spin-valve magnetic structures with giant magnetoresistance effects has been performed with the application of the Heisenberg anisotropic model to the description of the magnetic properties of thin ferromagnetic films. The dependences of the magnetic characteristics on the temperature and external magnetic field have been obtained for the ferromagnetic and antiferromagnetic configurations of these structures. A Monte Carlo method for determining the magnetoresistance coefficient has been developed. The magnetoresistance coefficient has been calculated for three-layer and spin-valve magnetic structures at various thicknesses of ferromagnetic films. It has been shown that the calculated temperature dependence of the magnetoresistance coefficient is in good agreement with experimental data obtained for the Fe(001)/Cr(001) multilayer structure and the CFAS/Ag/CFAS/IrMn spin valve based on the Co2FeAl0.5Si0.5 (CFAS) Heusler alloy.

  6. Angular Momentum

    Science.gov (United States)

    Shakur, Asif; Sinatra, Taylor

    2013-01-01

    The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

  7. Electron-beam transmission through a micrometer-sized tapered-glass capillary: Dependence on incident energy and angular tilt angle

    Science.gov (United States)

    Wickramarachchi, S. J.; Ikeda, T.; Dassanayake, B. S.; Keerthisinghe, D.; Tanis, J. A.

    2016-08-01

    An experimental study of 500- and 1000-eV incident electrons transmitted through a micrometer-sized funnel-shaped (tapered) glass capillary with inlet diameter 0.80 mm, outlet diameter 0.10 mm, and a length of 35 mm is reported. The properties of the electron beam transmitted were measured as a function of the emerging angle and the incident energy dependence. The angular profiles were found to be comprised of up to three peaks for both 500 and 1000 eV showing evidence for transmission going straight through the capillary without interacting with the walls (direct), as well as transmission resulting from Coulomb deflection of the electrons from a negative charge patch or by scattering from nuclei close to the surface of the capillary (indirect). The energy spectra show that elastically transmitted electrons dominate at 500 eV for increasing sample tilt angles up to ˜5.0°, while inelastic processes dominate for 1000 eV already at tilt angles of ˜1.0°. The angular width of the emitted electrons was found to constitute a narrow beam for direct (˜0.4°) and indirect (<0.6° for 500 eV and <1.0° for 1000 eV) transmission for both energies with the widths decreasing for the largest tilt angles measured and approaching the inherent resolution (˜0.3°) of the electron analyzer.

  8. Titanic Magnetoresistance in WTe2

    OpenAIRE

    Ali, Mazhar N.; Xiong, Jun; Flynn, Steven; Gibson, Quinn; Schoop, Leslie; Haldolaarachchige, Neel; Ong, N. P.; Tao, Jing; Cava, R. J.

    2014-01-01

    Magnetoresistance is the change of a material's electrical resistance in response to an applied magnetic field. In addition to its intrinsic scientific interest, it is a technologically important property, placing it in "Pasteur's quadrant" of research value: materials with large magnetorsistance have found use as magnetic sensors 1, in magnetic memory 2, hard drives 3, transistors 4, and are the subject of frequent study in the field of spintronics 5, 6. Here we report the observation of an ...

  9. SU-E-T-644: Evaluation of Angular Dependence Correction for 2D Array Detector Using for Quality Assurance of Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Purpose: To evaluate the angular dependence correction for Matrix Evolution 2D array detector in quality assurance of volumetric modulated arc therapy(VMAT). Methods: Total ten patients comprising of different sites were planned for VMAT and taken for the study. Each plan was exposed on Matrix Evolution 2D array detector with Omnipro IMRT software based on the following three different methods using 6MV photon beams from Elekta Synergy linear accelerator. First method, VMAT plan was delivered on Matrix Evolution detector as it gantry mounted with dedicated holder with build-up of 2.3cm. Second, the VMAT plan was delivered with the static gantry angle on to the table mounted setup. Third, the VMAT plan was delivered with actual gantry angle on Matrix Evolution detector fixed in Multicube phantom with gantry angle sensor and angular dependence correction were applied to quantify the plan quality. For all these methods, the corresponding QA plans were generated in TPS and the dose verification was done for both point and 2D fluence analysis with pass criteria of 3% dose difference and 3mm distance to agreement. Results: The measured point dose variation for the first method was observed as 1.58±0.6% of mean and SD with TPS calculated. For second and third method, the mean and standard deviation(SD) was observed as 1.67±0.7% and 1.85±0.8% respectively. The 2D fluence analysis of measured and TPS calculated has the mean and SD of 97.9±1.1%, 97.88±1.2% and 97.55±1.3% for first, second and third methods respectively. The calculated two-tailed Pvalue for point dose and 2D fluence analysis shows the insignificance with values of 0.9316 and 0.9015 respectively, among the different methods of QA. Conclusion: The qualitative evaluation of angular dependence correction for Matrix Evolution 2D array detector shows its competency in accuracy of quality assurance measurement of composite dose distribution of volumetric modulated arc therapy

  10. SU-E-J-206: A Comparison of Different Hardware Design Approaches for Feature-Supported Optical Head-Tracking with Respect to Angular Dependencies

    Energy Technology Data Exchange (ETDEWEB)

    Stueber, P; Wissel, T; Wagner, B [Institute for Robotics and Cognitive Systems, University of Luebeck, Luebeck (Germany); Graduate School for Computing in Life Science, University of Luebeck, Luebeck (Germany); Bruder, R; Schweikard, A; Ernst, F [Institute for Robotics and Cognitive Systems, University of Luebeck, Luebeck (Germany)

    2014-06-01

    Purpose: Recent research has shown that optical features significantly improve marker-less optical head-tracking for cranial radiotherapy. Simulations, however, showed that these optical features, which are used to derive tissue thickness, depend on the incident angle of the IR scanning laser beam and the perspective of the camera analyzing the reflective patterns. We present an experimental analysis determining which is the most robust optical setup concerning angular influences. Methods: In three consecutive experiments, the incident angle of the laser (1), the perspective of the camera (2) or both simultaneously (3, ‘inBeam’-perspective) were changed with respect to the target. We analyzed how this affects feature intensity. These intensities were determined from seven concentric regions of interest (ROIs) around the laser spot. Two targets were used: a tissue-like silicone phantom and a human's forehead. Results: For each experiment, the feature intensity generally decreases with increasing angle. We found that the optical properties of the silicone phantom do not fit the properties of human skin. Furthermore, the angular influence of the laser on the features is significantly higher than the perspective of the camera. With the ‘inBeam’- perspective, the smoothest decays of feature intensity were found. We suppose that this is because of a fixed relationship between both devices. This smoothness, suggesting a predictable functional relationship, may simplify angle compensation for machine learning algorithms. This is particularly prominent for the medial ROIs. The inner ROIs highly depend on the angle and power of the laser. The outer ROIs show less angular dependency but the signal strength is critically low and prone to artifacts. Therefore and because of the smooth decays, medial ROIs are a suitable tradeoff between susceptibility, signal-noise-ratio and distance to the center of the laser spot. Conclusion: For tissue thickness correlated

  11. Characterization and Application of Large Magnetoresistance in Organic Semiconductors

    Science.gov (United States)

    Wohlgenannt, Markus

    2007-03-01

    Recent years have seen a surge in interest in magnetoresistive and spintronic properties of organic semiconductors, whereas this field was previously almost exclusively concerned with their electrooptical properties. We report on the extensive experimental characterization of a recently discovered large and intriguing magnetoresistive effect in organic light- emitting diodes that reaches up to 10% at room temperature for magnetic fields, B = 10mT. This magnetoresistive effect is therefore amongst the largest of any bulk material. The study includes a range of materials that show greatly different chemical structure, mobility, hyperfine and spin-orbit coupling strength. We show that the applied magnetic field affects the carrier transport inside the bulk semiconductor. By demonstrating that the effect is critically altered by the presence of strong spin- orbit coupling and that it does not occur in fullerene devices, we prove that the transport in organics sensitively depends on spin-dynamics induced by hyperfine interaction with the hydrogen protons. We discuss a possible relation between organic magnetoresistance and other magnetic field effects in organics that were known long before its discovery. As a possible mechanism we describe how Pauli's principle restricts carrier hopping between singly occupied sites near the Fermi level. However, spin-mixing by the hyperfine interaction may partially lift this restriction. Since the devices we describe can be manufactured cheaply they hold promise for applications where large numbers of magnetoresistive devices are needed, such as magnetic random- access-memory (MRAM); and applications related to organic light- emitting diode displays such as touch screens where the position of a magnetic stylus is detected (patent pending). We will show a video of a simple demonstrator device.

  12. Evolution and sign control of square-wave-like anisotropic magneto-resistance in spatially confined La0.3Pr0.4Ca0.3MnO3/LaAlO3(001) manganite thin films

    Science.gov (United States)

    Alagoz, H. S.; Jeon, J.; Keating, S.; Chow, K. H.; Jung, J.

    2016-04-01

    We investigated magneto-transport properties of a compressively strained spatially confined La0.3Pr0.4Ca0.3MnO3 (LPCMO) thin film micro-bridge deposited on LaAlO3. Angular dependence of the magneto-resistance R(θ) of this bridge, where θ is the angle between the magnetic field and the current directions in the film plane, exhibits sharp positive and negative percolation jumps near TMIT. The sign and the magnitude of these jumps can be tuned using the magnetic field. Such behavior has not been observed in LPCMO micro-bridges subjected to tensile strain, indicating a correlation between the type of the lattice strain, the distribution of electronic domains, and the anisotropic magneto-resistance in spatially confined manganite systems.

  13. On the relation between angular momentum and angular velocity

    Science.gov (United States)

    Silva, J. P.; Tavares, J. M.

    2007-01-01

    Students of mechanics usually have difficulties when they learn about the rotation of a rigid body. These difficulties are rooted in the relation between angular momentum and angular velocity, because these vectors are not parallel, and we need in general to utilize a rotating frame of reference or a time dependent inertia tensor. We discuss a series of problems that introduce both difficulties.

  14. Modelling Angular Dependencies in Land Surface Temperatures From the SEVIRI Instrument onboard the Geostationary Meteosat Second Generation Satellites

    DEFF Research Database (Denmark)

    Rasmussen, Mads Olander; Pinheiro, AC; Proud, Simon Richard;

    2010-01-01

    Satellite-based estimates of land surface temperature (LST) are widely applied as an input to models. A model output is often very sensitive to error in the input data, and high-quality inputs are therefore essential. One of the main sources of errors in LST estimates is the dependence on vegetat...

  15. First-order chiral to non-chiral transition in the angular dependence of the upper critical induction of the Scharnberg–Klemm p-wave pair state

    International Nuclear Information System (INIS)

    We calculate the temperature T and angular (θ, ϕ) dependencies of the upper critical induction Bc2(θ, ϕ, T) for parallel-spin superconductors with an axially symmetric p-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). For all FS anisotropies, the chiral Scharnberg–Klemm (SK) state Bc2(θ, ϕ, T) exceeds that of the chiral Anderson–Brinkman–Morel (ABM) state and exhibits a kink at θ = θ*(T, ϕ), indicative of a first-order transition from its chiral, nodal-direction behavior to its non-chiral, antinodal-direction behavior. Applicabilities to Sr2RuO4, UCoGe and the candidate topological superconductor CuxBi2Se3 are discussed. (fast track communication)

  16. Large anisotropic Fe orbital moments in perpendicularly magnetized Co2FeAl Heusler alloy thin films revealed by angular-dependent x-ray magnetic circular dichroism

    Science.gov (United States)

    Okabayashi, Jun; Sukegawa, Hiroaki; Wen, Zhenchao; Inomata, Koichiro; Mitani, Seiji

    2013-09-01

    Perpendicular magnetic anisotropy (PMA) in Heusler alloy Co2FeAl thin films sharing an interface with a MgO layer is investigated by angular-dependent x-ray magnetic circular dichroism. Orbital and spin magnetic moments are deduced separately for Fe and Co 3d electrons. In addition, the PMA energies are estimated using the orbital magnetic moments parallel and perpendicular to the film surfaces. We found that PMA in Co2FeAl is determined mainly by the contribution of Fe atoms with large orbital magnetic moments, which are enhanced at the interface between Co2FeAl and MgO. Furthermore, element specific magnetization curves of Fe and Co are found to be similar, suggesting the existence of ferromagnetic coupling between Fe and Co PMA directions.

  17. On the angular dependence of photoprotons from nuclei irradiated by γ-quanta with maximum energy 4.5 GeV

    International Nuclear Information System (INIS)

    The angular dependences of proton photoproduction on the C12, Cu63 and Pb208 nuclei by bremsstrahlung γ-quanta with the maximum energy 4.5 GeV both in cumulattive region (i.e. in kinematical region in which the production of protons at collision of γ-quanta of the given energy with the quasi-free nuclear nucleon is forbidden) and in non-cumulative region are investigated. Invariant cross sections on the photonuclear reactions are presented. The obtained experimental data are compared with the results of theoretical calculations of cumulative proton photoproduction according to the following models: quasi-two-body scaling model, low-nucleon correlation model fluctuon model and cluster model. The best agreement has been obtained for the cluster model

  18. Magnetoresistance in Parent Pnictide AFe2As2(A = Sr, Ba)

    International Nuclear Information System (INIS)

    Magnetoresistances of SrFe2As2 and BaFe2As2 in the magnetic ordered state are studied. Positive magnetoresistance is observed in the magnetic fields H applied in the azimuthes of θ = 0° and 30° with respect to the c-axis. The magnetoresistance can reach 20% for SrFe2As2 and 12% for BaFe2As2 at H = 9 T with θ = 0° (H || c). Above the magnetic transition temperature, the magnetoresistance becomes negligible. The data in the magnetic ordered state could be described by a modified two-band galvanomagnetic model including the enhancement effect of the applied magnetic field on the spin-density-wave gap. The field enhanced spin-density-wave gaps for different types of carriers are different. Temperature dependencies of the fitting parameters are discussed

  19. Magnetoresistance in Parent Pnictide AFe_2As_2(A=Sr, Ba)

    Institute of Scientific and Technical Information of China (English)

    ZHENG Ping; CHEN Gen-Fu; LI Zheng; HU Wan-Zheng; DONG Jing; LI Gang; WANG Nan-Lin; LUO Jian-Lin

    2009-01-01

    Magnetoresistances of SrFe_2 As_2 and BaFe_2 As_2 in the magnetic ordered state are studied.Positive magnetoresis-tance is observed in the magnetic fields H applied in the azimuthes foθ = 0°and 30°with respect to the c-axis.The magnetoresistance can reach 20% for SrFe_2 As_2 and 12% for BaFe_2As_2 at H = 9 T with θ= 0°(H||c).Above the magnetic transition temperature, the magnetoresistance becomes negligible.The data in the magnetic ordered state could be described by a modified two-band galvanomagnetic model including the enhancement effect of the applied magnetic field on the spin-density-wave gap.The field enhanced spin-density-wave gaps for different types of carriers are different.Temperature dependencies of the fitting parameters are discussed.

  20. Spectral and angular dependences of the efficiency of relief-phase diffractive lenses with two- and three-layer microstructures

    Science.gov (United States)

    Greisukh, G. I.; Danilov, V. A.; Ezhov, E. G.; Stepanov, S. A.; Usievich, B. A.

    2015-06-01

    The efficiency of diffractive lenses with two-layer single-relief and three-layer double-relief microstructures is studied. Studies are carried out using the scalar and electromagnetic diffraction theories. Depending on the requirements for the diffractive lens, the theories permit one to justifiably choose the configuration, optical materials, and constructive parameters of the microstructure, as well as to determine the real maximum allowable angle of radiation incidence on the diffractive lens with the microstructure of a particular type.

  1. Giant positive magnetoresistance in metallic VOx thin films

    OpenAIRE

    Rata, A. D.; Kataev, V.; Khomskii, D.; Hibma, T.

    2003-01-01

    We report on giant positive magnetoresistance effect observed in VOx thin films, epitaxially grown on SrTiO3 substrate. The MR effect depends strongly on temperature and oxygen content and is anisotropic. At low temperatures its magnitude reaches 70% in a magnetic field of 5 T. Strong electron-electron interactions in the presence of strong disorder may qualitatively explain the results. An alternative explanation, related to a possible magnetic instability, is also discussed.

  2. Giant positive magnetoresistance in metallic VOx thin films

    Science.gov (United States)

    Rata, A. D.; Kataev, V.; Khomskii, D.; Hibma, T.

    2003-12-01

    We report on giant positive magnetoresistance (MR) effect observed in VOx thin films, epitaxially grown on SrTiO3 substrate. The MR effect depends strongly on temperature and oxygen content and is anisotropic. At low temperatures its magnitude reaches 70% in a magnetic field of 5 T. Strong electron-electron interactions in the presence of strong disorder may qualitatively explain the results. An alternative explanation, related to a possible magnetic instability, is also discussed.

  3. Hall effect in the extremely large magnetoresistance semimetal WTe$_2$

    OpenAIRE

    Luo, Yongkang; Li, H.; Dai, Y. M.; Miao, H; Shi, Y. G.; H. Ding; Taylor, A. J.; Yarotski, D. A.; Prasankumar, R. P.; Thompson, J. D.

    2015-01-01

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe$_2$. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase of the hole density below $\\sim$160~K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a mor...

  4. Angular Momentum Transport by MHD Turbulence in Accretion Disks: Gas Pressure Dependence of the Saturation Level of the Magnetorotational Instability

    CERN Document Server

    Sano, T; Turner, N J; Stone, J M; Sano, Takayoshi; Inutsuka, Shu-ichiro; Turner, Neal J.; Stone, James M.

    2004-01-01

    The saturation level of the magnetorotational instability (MRI) is investigated using three-dimensional MHD simulations. The shearing box approximation is adopted and the vertical component of gravity is ignored, so that the evolution of the MRI is followed in a small local part of the disk. We focus on the dependence of the saturation level of the stress on the gas pressure, which is a key assumption in the standard alpha disk model. From our numerical experiments it is found that there is a weak power-law relation between the saturation level of the Maxwell stress and the gas pressure in the nonlinear regime; the higher the gas pressure, the larger the stress. Although the power-law index depends slightly on the initial field geometry, the relationship between stress and gas pressure is independent of the initial field strength, and is unaffected by Ohmic dissipation if the magnetic Reynolds number is at least 10. The relationship is the same in adiabatic calculations, where pressure increases over time, an...

  5. Magnetoresistance in organic spintronic devices: the role of nonlinear effects

    Science.gov (United States)

    Shumilin, A. V.; Kabanov, V. V.; Dediu, V. A.

    2015-02-01

    We derive kinetic equations describing injection and transport of spin-polarized carriers in organic semiconductors with hopping conductivity via an impurity level. The model predicts a strongly voltage dependent magnetoresistance, defined as resistance variation between devices with parallel and antiparallel electrode magnetizations (spin-valve effect). The voltage dependence of the magnetoresistance splits into three distinct regimes. The first regime matches well-known inorganic spintronic regimes, corresponding to barrier-controlled spin injection or the well-known conductivity mismatch case. The second regime at intermediate voltages corresponds to strongly suppressed magnetoresistance. The third regime develops at higher voltages and accounts for a novel paradigm. It is promoted by the strong nonlinearity in the charge transport whose strength is characterized by the dimensionless parameter eU/kBT. This nonlinearity, depending on device conditions, can lead to both significant enhancement or to exponential suppression of the spin-valve effect in organic devices. We believe that these predictions are valid beyond the case of organic semiconductors and should be considered for any material characterized by strongly nonlinear charge transport.

  6. Quantum Criticality and DBI Magneto-resistance

    CERN Document Server

    Kiritsis, Elias

    2016-01-01

    We use the DBI action from string theory and holography to study the magneto-resistance at quantum criticality with hyperscaling violation. We find and analyze a rich class of scaling behaviors for the magneto-resistance. A special case describes the scaling results found in pnictides by Hayers et al. in~\\cite{analytis}.

  7. Demonstrating the angular, wavelength and polarization dependence of surface plasmon resonance on thin gold films—An undergraduate experiment

    Science.gov (United States)

    Connolly, Peter W. R.; Kaplan, Andrey

    2016-10-01

    This paper describes the design of a simple and compact optical system capable of examining fundamental properties of light coupling to surface plasmon resonance (SPR) on a thin gold film. The setup, involving a rotatable Attenuated Total Reflection device, from which the reflected light is focused by means of a parabolic mirror, allows for the investigation of the dependence of the reflected intensity on the angle of incidence without moving the detector. It additionally makes provision for a convenient exchange of light sources or the possibility to incorporate a broadband source suitable to investigate SPR at different wavelengths. Theoretical simulation of the experimental data is provided, as well as straightforward calculations for exploring the physics of light excited waves propagating on a surface.

  8. SU-E-T-44: Angular Dependence of Surface Dose Enhancement Measured On Several Inhomogeneities Using Radiochromic EBT3 Films

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, A; Schoenfeld, A; Poppinga, D; Chofor, N; Poppe, B [University of Oldenburg, Oldenburg (Germany); Pius Hospital Oldenburg, Oldenburg (Germany)

    2014-06-01

    Purpose: The quantification of the relative surface dose enhancement in dependence on the angle of incidence and the atomic number Z of the surface material. Methods: Experiments were performed with slabs made of aluminum, titanium, copper, silver, dental gold and lead. The metal slabs with equal sizes of 1.0×8.0×8.8mm{sup 3} were embedded in an Octavius 4D phantom (PTW Freiburg, Germany). Radiochromic EBT3 films were used to measure the surface dose for angles of incidence ranging from 0° to 90°. The setup with the metals slabs at the isocenter was irradiated with acceleration voltages of 6MV and 10MV. Water reference measurements were taken under equal conditions. Results: The surface dose enhancement is highest for angles of incidence below 30° and drops significantly for higher. The surface dose enhancement produced by lead and dental gold at 6MV showed a peak of 65%. At 90°, the surface dose enhancement dropped to 15% for both materials. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 32%, 22% and 12% at 0°, respectively. At an angle of incidence of 80°, the values dropped to 22%, 18%, 12% und 6%. The values for 10MV were very similar. Lead and dental gold showed peaks of 65% und 60%. Their values dropped to 18% at an angle of 90°. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 30%, 20% and 8% at 0°. At 80° the values dropped to 30%, 20%, 12% and 5%. A dependence of the magnitude of the surface dose enhancement on the atomic number of the surface material can be seen, which is in consistence with literature. Conclusion: The results show that the surface dose enhancements near implant materials with high Z-values should be taken into consideration in radio therapy, even when the angle of incidence is flat.

  9. SU-E-T-44: Angular Dependence of Surface Dose Enhancement Measured On Several Inhomogeneities Using Radiochromic EBT3 Films

    International Nuclear Information System (INIS)

    Purpose: The quantification of the relative surface dose enhancement in dependence on the angle of incidence and the atomic number Z of the surface material. Methods: Experiments were performed with slabs made of aluminum, titanium, copper, silver, dental gold and lead. The metal slabs with equal sizes of 1.0×8.0×8.8mm3 were embedded in an Octavius 4D phantom (PTW Freiburg, Germany). Radiochromic EBT3 films were used to measure the surface dose for angles of incidence ranging from 0° to 90°. The setup with the metals slabs at the isocenter was irradiated with acceleration voltages of 6MV and 10MV. Water reference measurements were taken under equal conditions. Results: The surface dose enhancement is highest for angles of incidence below 30° and drops significantly for higher. The surface dose enhancement produced by lead and dental gold at 6MV showed a peak of 65%. At 90°, the surface dose enhancement dropped to 15% for both materials. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 32%, 22% and 12% at 0°, respectively. At an angle of incidence of 80°, the values dropped to 22%, 18%, 12% und 6%. The values for 10MV were very similar. Lead and dental gold showed peaks of 65% und 60%. Their values dropped to 18% at an angle of 90°. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 30%, 20% and 8% at 0°. At 80° the values dropped to 30%, 20%, 12% and 5%. A dependence of the magnitude of the surface dose enhancement on the atomic number of the surface material can be seen, which is in consistence with literature. Conclusion: The results show that the surface dose enhancements near implant materials with high Z-values should be taken into consideration in radio therapy, even when the angle of incidence is flat

  10. Rashba-Edelstein Magnetoresistance in Metallic Heterostructures

    Science.gov (United States)

    Nakayama, Hiroyasu; Kanno, Yusuke; An, Hongyu; Tashiro, Takaharu; Haku, Satoshi; Nomura, Akiyo; Ando, Kazuya

    2016-09-01

    We report the observation of magnetoresistance originating from Rashba spin-orbit coupling (SOC) in a metallic heterostructure: the Rashba-Edelstein (RE) magnetoresistance. We show that the simultaneous action of the direct and inverse RE effects in a Bi /Ag /CoFeB trilayer couples current-induced spin accumulation to the electric resistance. The electric resistance changes with the magnetic-field angle, reminiscent of the spin Hall magnetoresistance, despite the fact that bulk SOC is not responsible for the magnetoresistance. We further found that, even when the magnetization is saturated, the resistance increases with increasing the magnetic-field strength, which is attributed to the Hanle magnetoresistance in this system.

  11. Giant magneto-resistance devices

    CERN Document Server

    Hirota, Eiichi; Inomata, Koichiro

    2002-01-01

    This book deals with the application of giant magneto-resistance (GMR) effects to electronic devices. It will appeal to engineers and graduate students in the fields of electronic devices and materials. The main subjects are magnetic sensors with high resolution and magnetic read heads with high sensitivity, required for hard-disk drives with recording densities of several gigabytes. Another important subject is novel magnetic random-access memories (MRAM) with non-volatile non-destructive and radiation-resistant characteristics. Other topics include future GMR devices based on bipolar spin transistors, spin field-effect transistors (FETs) and double-tunnel junctions.

  12. LHCb: Tagged time-dependent angular analysis of $B^0_s \\to J/\\psi K^+ K^-$ at LHCb

    CERN Multimedia

    Syropoulos, V

    2013-01-01

    The time-dependent CP-violating asymmetry in $B^0_s\\to J/\\psi K^{+}K^{-}$ decays is measured using $1.0^{-1}$ of $pp$ of collisions at $\\sqrt{s}=7$ TeV collected with the LHCb detector. The decay time distribution of $B^0_s\\to J/\\psi K^{+}K^{-}$ is characterized by the decay widths $\\Gamma_{\\mathrm{H}}$ and $\\Gamma_{\\mathrm{L}}$ of the heavy and light mass eigenstates of the $B^0_s - \\bar{B^0_s}$ system and by a CP-violating phase $\\phi_s$. In a sample of approximately 27600 $B^0_s\\to J/\\psi K^{+}K^{-}$ events we measure $\\phi_s \\: = \\: 0.068 \\: \\pm \\: 0.091 \\: \\text{(stat)} \\: \\pm \\: 0.011 \\: \\text{(syst)} \\: \\text{rad}$. We also find an average $B^0_s$ decay width $\\Gamma_s \\equiv (\\Gamma_{\\mathrm{L}}+\\Gamma_{\\mathrm{H}})/2 \\: = \\: 0.671 \\: \\pm \\: 0.005 \\: \\text{(stat)} \\: \\pm \\: 0.006 \\: \\text{(syst)} \\: ps^{-1}$ and a decay width difference $\\Delta \\Gamma_s \\equiv \\Gamma_{\\mathrm{L}} - \\Gamma_{\\mathrm{H}} \\: = \\: 0.100 \\: \\pm \\: 0.016 \\: \\text{(stat)} \\: \\pm \\: 0.003 \\: \\text{(syst)} \\: ps^...

  13. Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) Heusler alloy and NiAl spacer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiamin; Hono, K., E-mail: kazuhiro.hono@nims.go.jp [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-2-1, Sengen, Tsukuba 305-0047 (Japan); Furubayashi, T.; Takahashi, Y. K.; Sasaki, T. T. [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba 305-0047 (Japan)

    2015-05-07

    We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (112{sup ¯}0) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation, which made it a good candidate for CPP-GMR device.

  14. Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co2Fe(Ge0.5Ga0.5) Heusler alloy and NiAl spacer

    Science.gov (United States)

    Chen, Jiamin; Furubayashi, T.; Takahashi, Y. K.; Sasaki, T. T.; Hono, K.

    2015-05-01

    We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co2Fe(Ge0.5Ga0.5) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (11 2 ¯ 0 ) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation, which made it a good candidate for CPP-GMR device.

  15. Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co2Fe(Ge0.5Ga0.5) Heusler alloy and NiAl spacer

    International Nuclear Information System (INIS)

    We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co2Fe(Ge0.5Ga0.5) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (112¯0) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation, which made it a good candidate for CPP-GMR device

  16. Maximum non-saturating magnetoresistance in MoTe2

    Science.gov (United States)

    Abdel-Hafiez, Mahmoud; Gu, Zhehao; Chen, Xiao-Jia; Center for High Pressure Science; Technology Advanced Research, Shanghai, 201203, China Team

    The search for exotic materials with a linear magnetoresistance (MR) is one of the most challenging tasks of the condensed matter community and materials science. Here, we investigated the magnetoresistance behavior of high-quality single crystals MoTe2. A large linear non-staturated MR in a magnetic field of 60 T, was observed with a maximum at a temperature of T = 45 K. The detailed field and temperature dependencies will be presented. Our results not only provide a general scaling approach for the anisotropic MR but also are crucial for correctly understanding the mechanism of the linear MR, including the origin of the remarkable ``turn-on'' behavior in the resistance versus temperature curve.

  17. Hall effect in the extremely large magnetoresistance semimetal WTe2

    Science.gov (United States)

    Luo, Yongkang; Li, H.; Dai, Y. M.; Miao, H.; Shi, Y. G.; Ding, H.; Taylor, A. J.; Yarotski, D. A.; Prasankumar, R. P.; Thompson, J. D.

    2015-11-01

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe2. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase in the hole density below ˜160 K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a more pronounced reduction in electron density occurs below 50 K, giving rise to comparable electron and hole densities at low temperature. Our observations indicate a possible electronic structure change below 50 K, which might be the direct driving force of the electron-hole "compensation" and the extremely large magnetoresistance as well. Numerical simulations imply that this material is unlikely to be a perfectly compensated system.

  18. Hall effect in the extremely large magnetoresistance semimetal WTe2

    International Nuclear Information System (INIS)

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe2. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase in the hole density below ∼160 K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a more pronounced reduction in electron density occurs below 50 K, giving rise to comparable electron and hole densities at low temperature. Our observations indicate a possible electronic structure change below 50 K, which might be the direct driving force of the electron-hole “compensation” and the extremely large magnetoresistance as well. Numerical simulations imply that this material is unlikely to be a perfectly compensated system

  19. Phase and ellipticity dependence of the photoelectron angular distribution in non-resonant two-photon ionization of atomic hydrogen. I

    Energy Technology Data Exchange (ETDEWEB)

    Faye, M; Wane, S T, E-mail: mamadou.faye@ucad.edu.sn [Departement de Physique, Faculte des Sciences et Techniques, Universite Cheikh Anta Diop, Boulevard Martin Luther King, (Corniche Ouest) BP 5005-Dakar Fann (Senegal)

    2011-03-14

    We study the ellipticity and the dependence on the phase lag (lead) (between the semimajor and the semiminor axes of the field components) of the photoelectron angular distribution (PAD) in the non-resonant two-photon ionization of atomic hydrogen. We establish exact analytical expressions for azimuthal PAD for 3s, 3p and 3d excited initial states, marked by the occurrence of an asymmetric term. This term gives rise to elliptic dichroism (ED), which can be obtained in two ways: either with the left (versus right) ellipticity, or with the phase lag (versus lead); for 3s and 3p initial states, it is shown that the quantum phase of continua is directly related to the phase lag, one-photon below-threshold ionization, and indirectly one photon above. Another important result is that the magnetic sublevels, m = 0, for 3p and m = {+-}1, for 3d, do not contribute to the azimuthal PAD. Our numerical results show, for 3s and 3d, and near-threshold ionization, that the PAD has maxima either along the semimajor or the semiminor axis, while for above-threshold ionization, they are always shifted from these axes. However, the maxima of the corresponding ED coincide with the PAD maxima, while for 3p, they are shifted from the PAD minima. A strong dependence of the ED sign is noted, regardless of the state or the process. However, strong ED signals are obtained for the 3s initial state and below-threshold ionization.

  20. Bilayer splitting versus Fermi-surface warping as an origin of slow oscillations of in-plane magnetoresistance in rare-earth tritellurides

    Science.gov (United States)

    Grigoriev, Pavel D.; Sinchenko, Alexander A.; Lejay, Pascal; Hadj-Azzem, Abdellali; Balay, Joël; Leynaud, Olivier; Zverev, Vladimir N.; Monceau, Pierre

    2016-06-01

    Slow oscillations (SlO) of the in-plane magnetoresistance with a frequency less than 4 T are observed in the rare-earth tritellurides and proposed as an effective tool to explore the electronic structure in various strongly anisotropic quasi-two-dimensional compounds. Contrary to the usual Shubnikov-de-Haas oscillations, SlO originate not from small Fermi-surface pockets, but from the entanglement of close frequencies due to a finite interlayer transfer integral, either between the two Te planes forming a bilayer or between two adjacent bilayers. From the observed angular dependence of the frequency and the phase of SlO we argue that they originate from the bilayer splitting rather than from the Fermi-surface warping. The SlO frequency gives the value of the interlayer transfer integral ≈1 meV for TbTe3 and GdTe3.

  1. Study of CP Symmetry Violation in the Charmonium-K*(892) Channel By a Complete Time Dependent Angular Analysis (BaBar Experiment)

    Energy Technology Data Exchange (ETDEWEB)

    T' Jampens, Stephane; /Orsay

    2006-09-18

    This thesis presents the full-angular time-dependent analysis of the vector-vector channel B{sub d}{sup 0} {yields} J/{psi}(K{sub S}{sup 0}{pi}{sup 0})*{sup 0}. After a review of the CP violation in the B meson system, the phenomenology of the charmonium-K*(892) channels is exposed. The method for the measurement of the transversity amplitudes of the B {yields} J/{psi}K*(892), based on a pseudo-likelihood method, is then exposed. The results from a 81.9 fb{sup -1} of collected data by the BABAR detector at the {Upsilon}(4S) resonance peak are |A{sub 0}|{sup 2} = 0.565 {+-} 0.011 {+-} 0.004, |A{sub {parallel}}|{sup 2} = 0.206 {+-} 0.016 {+-} 0.007, |A{sub {perpendicular}}|{sup 2} = 0.228 {+-} 0.016 {+-} 0.007, {delta}{sub {parallel}} = -2.766 {+-} 0.105 {+-} 0.040 and {delta}{sub {perpendicular}} = 2.935 {+-} 0.067 {+-} 0.040. Note that ({delta}{sub {parallel}}, {delta}{sub {perpendicular}}) {yields} (-{delta}{sub {parallel}}, {pi} - {delta}{sub {perpendicular}}) is also a solution. The strong phases {delta}{sub {parallel}} and {delta}{sub {perpendicular}} are at {approx}> 3{sigma} from {+-}{pi}, signing the presence of final state interactions and the breakdown of the factorization hypothesis. The forward-backward analysis of the K{pi} mass spectrum revealed the presence of a coherent S-wave interfering with the K*(892). It is the first evidence of this wave in the K{pi} system coming from a B meson. The particularity of the B{sub d}{sup 0} {yields} J/{psi}(K{sub S}{sup 0}{pi}{sup 0})*{sup 0} channel is to have a time-dependent but also an angular distribution which allows to measure sin 2{beta} but also cos2{beta}. The results from an unbinned maximum likelihood fit are sin 2{beta} = -0.10 {+-} 0.57 {+-} 0.14 and cos 2{beta} = 3.32{sub -0.96}{sup +0.76} {+-} 0.27 with the transversity amplitudes fixed to the values given above. The other solution for the strong phases flips the sign of cos 2{beta}. Theoretical considerations based on the s-quark helicity

  2. Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe

    Science.gov (United States)

    Kriegner, D.; Výborný, K.; Olejník, K.; Reichlová, H.; Novák, V.; Marti, X.; Gazquez, J.; Saidl, V.; Němec, P.; Volobuev, V. V.; Springholz, G.; Holý, V.; Jungwirth, T.

    2016-06-01

    Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II-VI semiconductors. Favourable micromagnetic characteristics of MnTe allow us to demonstrate a smoothly varying zero-field antiferromagnetic anisotropic magnetoresistance (AMR) with a harmonic angular dependence on the writing magnetic field angle, analogous to ferromagnets. The continuously varying AMR provides means for the electrical read-out of multiple-stable antiferromagnetic memory states, which we set by heat-assisted magneto-recording and by changing the writing field direction. The multiple stability in our memory is ascribed to different distributions of domains with the Néel vector aligned along one of the three magnetic easy axes. The robustness against strong magnetic field perturbations combined with the multiple stability of the magnetic memory states are unique properties of antiferromagnets.

  3. High field magnetoresistance and de Haas-van Alphen effect in antiferromagnetic PrB/sub 6/ and NdB/sub 6/

    Energy Technology Data Exchange (ETDEWEB)

    Onuki, Y.; Umezawa, A.; Kwok, W.K.; Crabtree, G.W.; Nishihara, M.; Yamazaki, T.; Omi, T.; Komatsubara, T.

    1987-08-01

    The transport properties and the de Haas-van Alphen (dHvA) effect have been measured for antiferromagnetic PrB/sub 6/ and NdB/sub 6/. The number of conduction electrons is approximately one per unit cell. The magnetoresistance shows the existence of open orbits implying a multiply connected Fermi surface. The angular dependence of the magnetoresistance is roughly similar to that of the reference material, LaB/sub 6/. The dHvA data in PrB/sub 6/ shows both paramagnetic and antiferromagnetic Fermi surfaces. The antiferromagnetic Fermi surface arises from new magnetic Brillouin zone boundaries and antiferromagnetic gaps introduced by the magnetic order, and the paramagnetic Fermi surface from magnetic breakdown through the small antiferromagnetic gaps in high field. Hybridization between the conduction electrons and the f electrons has been observed through the cyclotron masses, which in PrB/sub 6/ are three times larger than the corresponding masses of LaB/sub 6/. In NdB/sub 6/ only the antiferromagnetic Fermi surface, quite different from those of LaB/sub 6/ and PrB/sub 6/, has been observed. 26 refs., 10 figs., 3 tabs.

  4. Magnetoresistance of Multiwalled Carbon Nanotube Yarns

    Institute of Scientific and Technical Information of China (English)

    SHENG Lei-Mei; GAO Wei; CAO Shi-Xun; ZHANG Jin-Cang

    2008-01-01

    We measure zero-field resistivity and magnetoresistance of multiwalled carbon nanotube yarns (CNTYs). The CNTYs are drawn from superaligned multiwalled carbon nanotube arrays synthesized by the low-pressure chemical vapour deposition method. The zero-field resistivity shows a logarithmic decrease from 2 K to 300 K. In the presence of a magnetic field applied perpendicular to the yarn axis, a pronounced negative magnetoresistance is observed. A magnetoresistance ratio of 22% is obtained. These behaviours can be explained by the weak localization effect.

  5. Magnetoresistive multilayers deposited on the AAO membranes

    Energy Technology Data Exchange (ETDEWEB)

    Malkinski, Leszek M. [Advanced Materials Research Institute, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148 (United States)]. E-mail: lmalkins@uno.edu; Chalastaras, Athanasios [Advanced Materials Research Institute, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148 (United States); Vovk, Andriy [Advanced Materials Research Institute, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148 (United States); Jung, Jin-Seung [Department of Chemistry, Kangnung National University, Kangnung 210702 (Korea, Republic of) ; Kim, Eun-Mee [Department of Chemistry, Kangnung National University, Kangnung 210702 (Korea, Republic of) ; Jun, Jong-Ho [Department of Applied Chemistry, Kunkuk University, Chungju 151747 (Korea, Republic of) ; Ventrice, Carl A. [Advanced Materials Research Institute, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148 (United States)

    2005-02-01

    Silicon and GaAs wafers are the most commonly used substrates for deposition of giant magnetoresistive (GMR) multilayers. We explored a new type of a substrate, prepared electrochemically by anodization of aluminum sheets, for deposition of GMR multilayers. The surface of this AAO substrate consists of nanosized hemispheres organized in a regular hexagonal array. The current applied along the substrate surface intersects many magnetic layers in the multilayered structure, which results in enhancement of giant magnetoresistance effect. The GMR effect in uncoupled Co/Cu multilayers was significantly larger than the magnetoresistance of similar structures deposited on Si.

  6. Theory of spin Hall magnetoresistance (SMR) and related phenomena

    International Nuclear Information System (INIS)

    We review the so-called spin Hall magnetoresistance (SMR) in bilayers of a magnetic insulator and a metal, in which spin currents are generated in the normal metal by the spin Hall effect. The associated angular momentum transfer to the ferromagnetic layer and thereby the electrical resistance is modulated by the angle between the applied current and the magnetization direction. The SMR provides a convenient tool to non-invasively measure the magnetization direction and spin-transfer torque to an insulator. We introduce the minimal theoretical instruments to calculate the SMR, i.e. spin diffusion theory and quantum mechanical boundary conditions. This leads to a small set of parameters that can be fitted to experiments. We discuss the limitations of the theory as well as alternative mechanisms such as the ferromagnetic proximity effect and Rashba spin–orbit torques, and point out new developments. (topical review)

  7. Theory of spin Hall magnetoresistance (SMR) and related phenomena.

    Science.gov (United States)

    Chen, Yan-Ting; Takahashi, Saburo; Nakayama, Hiroyasu; Althammer, Matthias; Goennenwein, Sebastian T B; Saitoh, Eiji; Bauer, Gerrit E W

    2016-03-16

    We review the so-called spin Hall magnetoresistance (SMR) in bilayers of a magnetic insulator and a metal, in which spin currents are generated in the normal metal by the spin Hall effect. The associated angular momentum transfer to the ferromagnetic layer and thereby the electrical resistance is modulated by the angle between the applied current and the magnetization direction. The SMR provides a convenient tool to non-invasively measure the magnetization direction and spin-transfer torque to an insulator. We introduce the minimal theoretical instruments to calculate the SMR, i.e. spin diffusion theory and quantum mechanical boundary conditions. This leads to a small set of parameters that can be fitted to experiments. We discuss the limitations of the theory as well as alternative mechanisms such as the ferromagnetic proximity effect and Rashba spin-orbit torques, and point out new developments.

  8. Ambiguity-Free Measurement of cos2beta: Time-Integrated and Time-Dependent Angular Analyses of B->J/Psi K pi

    CERN Document Server

    Aubert, B; Boutigny, D; Couderc, F; Gaillard, J M; Hicheur, A; Karyotakis, Yu; Lees, J P; Tisserand, V; Zghiche, A; Palano, A; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Ronan, Michael T; Shelkov, V G; Wenzel, W A; Barrett, M; Ford, K E; Harrison, T J; Hart, A J; Hawkes, C M; Morgan, S E; Watson, A T; Fritsch, M; Goetzen, K; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Steinke, M; Boyd, J T; Chevalier, N; Cottingham, W N; Kelly, M P; Latham, T E; Wilson, F F; Çuhadar-Dönszelmann, T; Hearty, C; Knecht, N S; Mattison, T S; McKenna, J A; Thiessen, D; Khan, A; Kyberd, P; Teodorescu, L; Blinov, A E; Blinov, V E; Druzhinin, V P; Golubev, V B; Ivanchenko, V N; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bruinsma, M; Chao, M; Eschrich, I; Kirkby, D; Lankford, A J; Mandelkern, M A; Mommsen, R K; Röthel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Foulkes, S D; Gary, J W; Shen, B C; Wang, K; Del Re, D; Hadavand, H K; Hill, E J; MacFarlane, D B; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Dahmes, B; Levy, S L; Long, O; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Eisner, A M; Heusch, C A; Lockman, W S; Nesom, G; Schalk, T; Schmitz, R E; Schumm, B A; Seiden, A; Spradlin, P; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Ryd, A; Samuel, A; Yang, S; Jayatilleke, S M; Mancinelli, G; Meadows, B T; Sokoloff, M D; Abe, T; Blanc, F; Bloom, P; Chen, S; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Smith, J G; Zhang, J; Zhang, L; Chen, A; Harton, J L; Soffer, A; Toki, W H; Wilson, R J; Zeng, Q L; Altenburg, D; Brandt, T; Brose, J; Dickopp, M; Feltresi, E; Hauke, A; Lacker, H M; Müller-Pfefferkorn, R; Nogowski, R; Otto, S; Petzold, A; Schubert, J; Schubert, Klaus R; Schwierz, R; Spaan, B; Sundermann, J E; Bernard, D; Bonneaud, G R; Brochard, F; Grenier, P; Schrenk, S; Thiebaux, C; Vasileiadis, G; Verderi, M; Bard, D J; Clark, P J; Lavin, D; Muheim, F; Playfer, S; Xie, Y; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Sarti, A; Treadwell, E; Baldini-Ferroli, R; Calcaterra, A; De Sangro, R; Finocchiaro, G; Patteri, P; Piccolo, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Crosetti, G; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Brandenburg, G; Morii, M; Won, E; Dubitzky, R S; Langenegger, U; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Gaillard, J R; Morton, G W; Nash, J A; Nikolich, M B; Taylor, G P; Charles, M J; Grenier, G J; Mallik, U; Cochran, J; Crawley, H B; Lamsa, J; Meyer, W T; Prell, S; Rosenberg, E I; Yi, J; Davier, M; Grosdidier, G; Höcker, A; Laplace, S; Le Diberder, F R; Lepeltier, V; Lutz, A M; Petersen, T C; Plaszczynski, S; Schune, M H; Tantot, L; Wormser, G; Cheng, C H; Lange, D J; Simani, M C; Wright, D M; Bevan, A J; Chavez, C A; Coleman, J P; Forster, I J; Fry, J R; Gabathuler, Erwin; Gamet, R; Parry, R J; Payne, D J; Sloane, R J; Touramanis, C; Back, J J; Harrison, P F; Mohanty, G B; Cowan, G; Flack, R L; Flächer, H U; Green, M G; Jackson, P S; McMahon, T R; Ricciardi, S; Salvatore, F; Winter, M A; Brown, D; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Hodgkinson, M C; Lafferty, G D; Lyon, A J; Williams, J C; Farbin, A; Hulsbergen, W D; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Blaylock, G; Dallapiccola, C; Flood, K T; Hertzbach, S S; Kofler, R; Koptchev, V B; Moore, T B; Saremi, S; Stängle, H; Willocq, S; Cowan, R; Sciolla, G; Taylor, F; Yamamoto, R K; Mangeol, D J J; Patel, P M; Robertson, S H; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L M; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Taras, P; Nicholson, H; Fabozzi, F; Lista, L; Monorchio, D; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M; Bulten, H; Raven, G; Snoek, H L; Wilden, L; Jessop, C P; LoSecco, J M; Gabriel, T A; Allmendinger, T; Brau, B; Gan, K K; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pulliam, T; Rahimi, A M; Ter-Antonian, R; Wong, Q K; Brau, J E; Frey, R; Igonkina, O; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Tiozzo, G; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; La Vaissière, C de; Del Buono, L; Hamon, O; John, M J J; Leruste, P; Malcles, J; Ocariz, J; Pivk, M; Roos, L; T'Jampens, S; Therin, G; Manfredi, P F; Re, V; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Anulli, F; Biasini, M; Peruzzi, I M; Pioppi, M; Angelini, C; Batignani, G; Bettarini, S; Bondioli, M; Bucci, F; Calderini, G; Carpinelli, M; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Martínez-Vidal, F; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Sandrelli, F; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Danielson, N; Elmer, P; Lau, Y P; Lü, C; Miftakov, V; Olsen, J; Smith, A J S; Telnov, A V; Bellini, F; Cavoto, G; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Mazzoni, M A; Morganti, S; Pierini, M; Piredda, G; Safai-Tehrani, F; Voena, C; Christ, S; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B J; Geddes, N I; Gopal, G P; Olaiya, E O; Aleksan, Roy; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P F; Hamel de Monchenault, G; Kozanecki, Witold; Langer, M; Legendre, M; London, G W; Mayer, B; Schott, G; Vasseur, G; Yéche, C; Zito, M; Purohit, M V; Weidemann, A W; Wilson, J R; Yumiceva, F X; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmüller, O L; Claus, R; Convery, M R; Cristinziani, M; De Nardo, Gallieno; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W M; Elsen, E E; Fan, S; Field, R C; Glanzman, T; Gowdy, S J; Hadig, T; Halyo, V; Hast, C; Hrynóva, T; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Libby, J; Luitz, S; Lüth, V; Lynch, H L; Marsiske, H; Messner, R; Müller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Petrak, S; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Simi, G; Snyder, A; Soha, A; Stelzer, J; Su, D; Sullivan, M K; Vavra, J; Wagner, S R; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Young, C C; Burchat, Patricia R; Edwards, A J; Meyer, T I; Petersen, B A; Roat, C; Ahmed, S; Alam, M S; Ernst, J A; Saeed, M A; Saleem, M; Wappler, F R; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Kim, H; Ritchie, J L; Satpathy, A; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bóna, M; Gallo, F; Gamba, D; Borean, C; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vuagnin, G; Panvini, R S; Banerjee, Sw; Brown, C M; Fortin, D; Jackson, P D; Kowalewski, R V; Roney, J M; Sobie, R J; Band, H R; Dasu, S; Datta, M; Eichenbaum, A M; Graham, M; Hollar, J J; Johnson, J R; Kutter, P E; Li, H; Liu, R; Mihályi, A; Mohapatra, A K; Pan, Y; Prepost, R; Rubin, A E; Sekula, S J; Tan, P; Von Wimmersperg-Töller, J H; Wu, J; Wu, S L; Yu, Z; Greene, M G; Neal, H

    2004-01-01

    We present results on $B\\to J/\\psi\\xspace K\\pi$ decays using $e^+e^-$ annihilation data collected with the BABAR detector at the $\\Upsilon(4S)$ resonance. The detector is located at the PEP-II asymmetric-energy storage ring facility at the Stanford Linear Accelerator Center. Using approximately 88 million $B\\bar{B}$ pairs, we measure the decay amplitudes for the flavor eigenmodes and observe strong-phase differences indicative of final-state interactions with a significance of 7.6 standard deviations. We use the interference between the $K\\pi$ $S$-wave and $P$-wave amplitudes in the region of the $K^*(892)$ to resolve the ambiguity in the determination of these strong phases. We then perform an ambiguity-free measurement of $\\cos2\\beta$ using the angular and time-dependent asymmetry in $B\\to J/\\psi\\xspace K^{*0}(K_S^0\\pi^0$) dec With $\\sin 2 \\beta$ fixed at its measured value and $\\cos 2 \\beta$ treated as an in we find $\\cos 2\\beta=2.72_{-0.79}^{+0.50}\\mathrm{(stat)} \\pm 0.27\\mathrm{(syst)}$, de sign of $\\cos...

  9. Mapping of focused Laguerre-Gauss beams: The interplay between spin and orbital angular momentum and its dependence on detector characteristics

    CERN Document Server

    Klimov, Vasily V; Ducloy, Martial; Leite, Jose Roberto Rios

    2012-01-01

    We show that propagating optical fields bearing an axial symmetry are not truly hollow in spite of a null electric field on-axis. The result, obtained by general arguments based upon the vectorial nature of electromagnetic fields, is of particular significance in the situation of an extreme focusing, when the paraxial approximation no longer holds. The rapid spatial variations of fields with a "complicated" spatial structure are extensively analyzed in the general case and for a Laguerre-Gauss beam 2 as well, notably for beams bearing a |l| = 2 orbital angular momentum for which a magnetic field and a gradient of the electric field are present on-axis. We thus analyze the behavior of a atomic size light-detector, sensitive as well to quadrupole electric transitions and to magnetic dipole transitions, and apply it to the case of Laguerre-Gauss beam. We detail how the mapping of such a beam depends on the nature and on the specific orientation of the detector. We show also that the interplay of mixing of polari...

  10. Angular momentum in subbarrier fusion

    International Nuclear Information System (INIS)

    We have measured the ratio of the isomer to ground-state yields of 137Ce produced in the fusion reactions 128Te(12C,3n), 133Cs(7Li,3n), 136Ba(3He,2n), 136Ba(4He,3n), and 137Ba(3He,3n), from energies above the Coulomb barrier to energies typically 20--30% below the barrier by observing the delayed x- and γ-ray emission. We deduce the average angular momentum, , from the measured isomer ratios with a statistical model. In the first three reactions we observe that the values of exhibit the behavior predicted for low energies and the expected variation with the reduced mass of the entrance channel. We analyze these data and the associated cross sections with a barrier penetration model that includes the coupling of inelastic channels. Measurements of average angular momenta and cross sections made on other systems using the γ-multiplicity and fission-fragment angular correlation techniques are then analyzed in a similar way with this model. The discrepancies with theory for the γ-multiplicity data show correlations in cross section and angular momentum that suggest a valid model can be found. The measurements of angular momentum using the fission fragment angular correlation technique, however, do not appear reconcilable with the energy dependence of the cross sections. This systematic overview suggests, in particular, that our current understanding of the relationship of angular momentum and anisotropy in fission fragment angular correlations is incomplete. 26 refs

  11. Magnetoresistance in the ferromagnet/insulator/ferromagnet tunnel junction

    Institute of Scientific and Technical Information of China (English)

    Lu Hong-Xia; Dong Zheng-Chao; Fu Hao

    2008-01-01

    Recently experiments and theories show that the tunnel magnetoresistance (TMR) does not only depend on the ferromagnetic metal electrodes but also on the insulator.Considering the rough-scattering effect and spin-flip effect in the insulator,this paper investigates the TMR ratio in a ferromagnet/insulator/ferromagnet (FM/I/FM) tunnelling junction by using Slonczewsik's model.A more general expression of TMR ratio as a function of barrier height,interface roughness and spin-flip effect is obtained.In lower barrier case,it shows that the TMR ratio depends on the roughscattering effect and spin-flip effect.

  12. Interface of magnetoresistive converter of active power

    Directory of Open Access Journals (Sweden)

    A. I. Vytiaganets

    2009-10-01

    Full Text Available The vehicle and programmatic interfaces of magnetoresistive converter of active power are considered, the results of statistical treatment of the multiple measuring of active-power are analysed.

  13. Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions.

    Science.gov (United States)

    Zhang, Kun; Li, Huan-Huan; Grünberg, Peter; Li, Qiang; Ye, Sheng-Tao; Tian, Yu-Feng; Yan, Shi-Shen; Lin, Zhao-Jun; Kang, Shi-Shou; Chen, Yan-Xue; Liu, Guo-Lei; Mei, Liang-Mo

    2015-09-21

    Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can generate a significant direct-current voltage, and this rectification voltage strongly varies with the external magnetic field. We find that the rectification magnetoresistance in Al/Ge Schottky heterojunctions is as large as 250% at room temperature, which is greatly enhanced as compared with the conventional magnetoresistance of 70%. The findings of rectification magnetoresistance open the way to the new nonmagnetic Ge-based spintronics devices of large rectification magnetoresistance at ambient temperature under the alternating-current due to the simultaneous implementation of the rectification and magnetoresistance in the same devices.

  14. Tunneling anisotropic magnetoresistance in organic spin valves

    OpenAIRE

    Grünewald, M; M. Wahler; Schumann, F; Michelfeit, M.; Gould, C.; Schmidt, R.; Würthner, F.; Schmidt, G.; Molenkamp, L. W.

    2011-01-01

    We report the observation of tunneling anisotropic magnetoresistance (TAMR) in an organic spin-valve-like structure with only one ferromagnetic electrode. The device is based on a new high mobility perylene diimide-based n-type organic semiconductor. The effect originates from the tunneling injection from the LSMO contact and can thus occur even for organic layers which are too thick to support the assumption of tunneling through the layer. Magnetoresistance measurements show a clear spin-val...

  15. Angle resolved photoemission spectroscopy study on the non-saturate magnetoresistance material WTe2

    Science.gov (United States)

    Jiang, Juan; Niu, Xiaohai; Xie, Binping; Zhang, Tong; Feng, Donglai

    2015-03-01

    By performing high resolution angle-resolved photoemission spectroscopy, we obtain the detailed electronic structure of WTe2, which has an extremely large non-saturated magnetoresistance. Unlike the simple one electron and one hole pocket as expected, we resolved a rather complicated Fermi surface in WTe2. There is a hole pocket around the Brillouin zone center Γ, two hole pockets and two electron pockets along the tungsten chain direction. Thus the large magnetoresistance cannot be simply attributed to the electron-hole compensation, since this is based on a two carrier assumption model, the real case in WTe2 should be more complicated. Surprisingly, the circular dichroism ARPES result shows a strong intensity inversion between the data under the right-circular polarized light and the left-circular polarized light. This, indicates a proper different orbital angular momentum along the tungsten chain direction, which might also related to the different spin angular momentum since there're coupled with each other. Therefore, we propose that to fully understand the large magnetoresistance in WTe2, spin channel should also be involved where backscattering are forbidden under zero field.

  16. Impact of Tunnel-Barrier Strength on Magnetoresistance in Carbon Nanotubes

    Science.gov (United States)

    Morgan, Caitlin; Misiorny, Maciej; Metten, Dominik; Heedt, Sebastian; Schäpers, Thomas; Schneider, Claus M.; Meyer, Carola

    2016-05-01

    We investigate magnetoresistance in spin valves involving CoPd-contacted carbon nanotubes. Both the temperature and bias-voltage dependence clearly indicate tunneling magnetoresistance as the origin. We show that this effect is significantly affected by the tunnel-barrier strength, which appears to be one reason for the variation between devices previously detected in similar structures. Modeling the data by means of the scattering matrix approach, we find a nontrivial dependence of the magnetoresistance on the barrier strength. Furthermore, an analysis of the spin precession observed in a nonlocal Hanle measurement yields a spin lifetime of τs=1.1 ns , a value comparable with those found in silicon- or graphene-based spin-valve devices.

  17. Angular momentum projected semiclassics

    Science.gov (United States)

    Hasse, Rainer W.

    1987-06-01

    By using angular momentum projected plane waves as wave functions, we derive semiclassical expressions for the single-particle propagator, the partition function, the nonlocal density matrix, the single-particle density and the one particle-one hole level density for fixed angular momentum and fixed z-component or summed over the z-components. Other quantities can be deduced from the propagator. In coordinate space ( r, r') the relevant quantities depend on |r-r'| instead of | r- r'| and in Wigner space ( R, P) they become proportional to the angular momentum constraints δ(| R × P|/ h̵-l) and δ( R × P) z/ h̵-m) . As applications we calculate the single-particle and one-particle-one hole level densities for harmonic oscillator and Hill-Wheeler box potentials and the imaginary part of the optical potential and its volume integral with an underlying harmonic oscillator potential and a zero range two-body interaction.

  18. Enhanced Transverse Magnetoresistive Effect in Semiconducting Diamond Films

    Institute of Scientific and Technical Information of China (English)

    WANG Wan-Lu; LIAO Ke-Jun; WANG Bi-Ben

    2000-01-01

    A very large magnetoresistive effect in both homoepitaxial and heteroepitaxial semiconducting diamond films by chemical vapor deposition has been observed. The changes in the resistance of the films strongly depend on both magnetic field intensity and geometric form of the samples. The effect of disk structure is greater than that of stripe type samples, also variation in the resistance of homoepitaxial diamond films is greater than that of eteroepitaxial diamond films. The resistance of homoepitaxial diamond films with the disk structure is increased y a factor of 2.1 at room temperature under magnetic field intensity of 5 T, but only 0.80 for heteroepitaxial diamond films.

  19. Single nucleotide polymorphism (SNP) detection on a magnetoresistive sensor

    DEFF Research Database (Denmark)

    Rizzi, Giovanni; Østerberg, Frederik Westergaard; Dufva, Martin;

    2013-01-01

    We present a magnetoresistive sensor platform for hybridization assays and demonstrate its applicability on single nucleotide polymorphism (SNP) genotyping. The sensor relies on anisotropic magnetoresistance in a new geometry with a local negative reference and uses the magnetic field from...

  20. Magnetoresistance and upper critical magnetic field of UBe13 under pressure

    International Nuclear Information System (INIS)

    We have investigated the effects of pressure on the magnetoresistance and the upper critical magnetic field of the heavy electron compound UBe13. Both the superconducting transition temperature and the upper critical field decrease under hydrostatic pressure. The low-temperature magnetoresistance remains large and negative under pressure. The temperature region over which the resistivity has a T2 temperature dependence increases with both magnetic field and with pressure. At a fixed magnetic field, the coefficient of the T2 term in the resistivity decreases strongly with pressure. UBe13 is found to have a pressure independent intrinsic residual resistivity of 18 μΩ-cm

  1. Magnetoresistance in an Asymmetric GaMnAs Resonant Tunneling Diode

    OpenAIRE

    Likovich, Edward Michael; Russell, Kasey Joe; Yi, Wei; Narayanamurti, Venkatesh; Ku, Keh-Chiang; Zhu, Meng; Samarth, Nitin

    2009-01-01

    In a GaMnAs/AlGaAs resonant tunneling diode (RTD) structure, we observe that both the magnitude and polarity of magnetoresistance are bias dependent when tunneling from a three-dimensional GaMnAs layer through a two-dimensional GaMnAs quantum well. This magnetoresistance behavior results from a shift of negative differential resistance features to higher bias as the relative alignment of the GaMnAs layer magnetizations is changed from parallel to antiparallel. Our observations agree with rece...

  2. Crystalline Structure, Electrophysical and Magnetoresistive Properties of High Entropy Film Alloys

    Directory of Open Access Journals (Sweden)

    S.I. Vorobiov

    2016-10-01

    Full Text Available The results of research the phase composition and electrophysical (resistivity, thermal coefficient of resistance, strain coefficient and magnetoresistive properties (anisotropic magnetoresistance of thin films (to 40 nm high entropy alloys (HEA based on Al, Cu, Ni, Cr, Fe, Co and Ti. It is established that after forming the layered samples by electron condensation on diffraction pattern fixed lines from the two phases of the fcc lattice and actually tracks the bcc phase. After homogenization by annealing the samples is one of the fcc phase s.s. HEA and traces bcc phase (likely s.s. (-Fe, Cr, that samples are single phase. The study electrical properties allowed watching the first double-stage plastic deformation of a large value of the coefficient gauge (300 units, watch probably, is typical for НЕА. The character dependences MR from induction indicates to realization of anisotropic magnetoresistance.

  3. Tunnel anisotropic magnetoresistance in CoFeB|MgO|Ta junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hatanaka, S.; Miwa, S., E-mail: miwa@mp.es.osaka-u.ac.jp; Matsuda, K.; Nawaoka, K.; Tanaka, K.; Morishita, H.; Goto, M.; Mizuochi, N.; Shinjo, T.; Suzuki, Y. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2015-08-24

    We found that CoFeB|MgO|Ta tunnel junctions exhibit tunnel anisotropic magnetoresistance (TAMR) at room temperature. The tunnel junctions exhibit positive magnetoresistance with the application of a magnetic field normal to the film plane. The dependencies on the applied magnetic field angle and MgO thickness reveal that the magnetoresistance originates from the TAMR, caused by the spin polarization and the spin-orbit interaction at the CoFeB|MgO interface. We also found that the TAMR can be used to detect ferromagnetic resonance in the CoFeB. This detection method could be useful for the characterization of nanomagnets that are free from the spin-transfer effect and the stray field of a reference layer, unlike conventional magnetic tunnel junctions.

  4. Room Temperature Giant and Linear Magnetoresistance in Topological Insulator Bi2Te3 Nanosheets

    Science.gov (United States)

    Wang, Xiaolin; Du, Yi; Dou, Shixue; Zhang, Chao

    2012-06-01

    Topological insulators, a new class of condensed matter having bulk insulating states and gapless metallic surface states, have demonstrated fascinating quantum effects. However, the potential practical applications of the topological insulators are still under exploration worldwide. We demonstrate that nanosheets of a Bi2Te3 topological insulator several quintuple layers thick display giant and linear magnetoresistance. The giant and linear magnetoresistance achieved is as high as over 600% at room temperature, with a trend towards further increase at higher temperatures, as well as being weakly temperature-dependent and linear with the field, without any sign of saturation at measured fields up to 13 T. Furthermore, we observed a magnetic field induced gap below 10 K. The observation of giant and linear magnetoresistance paves the way for 3D topological insulators to be useful for practical applications in magnetoelectronic sensors such as disk reading heads, mechatronics, and other multifunctional electromagnetic applications.

  5. Giant amplification of tunnel magnetoresistance in a molecular junction: Molecular spin-valve transistor

    Energy Technology Data Exchange (ETDEWEB)

    Dhungana, Kamal B.; Pati, Ranjit, E-mail: patir@mtu.edu [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States)

    2014-04-21

    Amplification of tunnel magnetoresistance by gate field in a molecular junction is the most important requirement for the development of a molecular spin valve transistor. Herein, we predict a giant amplification of tunnel magnetoresistance in a single molecular spin valve junction, which consists of Ru-bis-terpyridine molecule as a spacer between two ferromagnetic nickel contacts. Based on the first-principles quantum transport approach, we show that a modest change in the gate field that is experimentally accessible can lead to a substantial amplification (320%) of tunnel magnetoresistance. The origin of such large amplification is attributed to the spin dependent modification of orbitals at the molecule-lead interface and the resultant Stark effect induced shift in channel position with respect to the Fermi energy.

  6. Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals

    OpenAIRE

    Yang-Yang Lv; Bin-Bin Zhang; Xiao Li; Bin Pang; Fan Zhang; Da-Jun Lin; Jian Zhou; Shu-Hua Yao; Chen, Y. B.; Shan-Tao Zhang; Minghui Lu; Zhongkai Liu; Yulin Chen; Yan-Feng Chen

    2016-01-01

    Recently, the layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~105%), which can be useful for magnetic memory and spintronic devices. However, the underlying mechanisms of the giant magnetoresistance are still under hot debate. Herein, we grew the stoichiometric and non-stoichiometric WTe2 crystals to test the robustness of giant magnetoresistance. The stoichiometric WTe2 crystals have magnetoresistance a...

  7. The dependency of tunnel magnetoresistance ratio on nanoscale thicknesses of Co2Fe6B2 free and pinned layers for Co2Fe6B2/MgO-based perpendicular-magnetic-tunnel-junctions

    Science.gov (United States)

    Jeon, Min-Su; Chae, Kyo-Suk; Lee, Du-Yeong; Takemura, Yasutaka; Lee, Seung-Eun; Shim, Tae-Hun; Park, Jea-Gun

    2015-04-01

    The tunnel magnetoresistance (TMR) ratio of a cobalt-iron-boron (CoFeB)-based perpendicular-magnetic-tunnel-junction (p-MTJ) spin valve is extremely sensitive to both nanoscale Co2Fe6B2 free- and pinned-layer thicknesses. The TMR ratio peaks at a Co2Fe6B2 free-layer thickness of 1.05 nm, while it peaks at a Co2Fe6B2 pinned-layer thickness of 1.59 nm, achieving 104%. The amount of tantalum diffused into the MgO tunneling barrier (originated from a tantalum seed) decreases with increasing Co2Fe6B2 free-layer thickness, while the amount of palladium diffused from a [Co/Pd]n SyAF layer decreases with increasing Co2Fe6B2 pinned-layer thickness, determining the crystallinity of the MgO tunneling barrier and the TMR ratio. In addition, the TMR ratio tended to decrease when the Co2Fe6B2 free layer and the Co2Fe6B2 pinned layer switched characteristics from interface-perpendicular anisotropic to in-plane anisotropic.

  8. Crossed Andreev reflection-induced magnetoresistance.

    Science.gov (United States)

    Giazotto, Francesco; Taddei, Fabio; Beltram, Fabio; Fazio, Rosario

    2006-08-25

    We show that very large negative magnetoresistance can be obtained in magnetic trilayers in a current-in-plane geometry owing to the existence of crossed Andreev reflection. This spin valve consists of a thin superconducting film sandwiched between two ferromagnetic layers whose magnetization is allowed to be either parallelly or antiparallelly aligned. For a suitable choice of structure parameters and nearly fully spin-polarized ferromagnets, the magnetoresistance can exceed -80%. Our results are relevant for the design and implementation of spintronic devices exploiting ferromagnet-superconductor structures. PMID:17026324

  9. Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers

    Science.gov (United States)

    Avci, Can Onur; Garello, Kevin; Ghosh, Abhijit; Gabureac, Mihai; Alvarado, Santos F.; Gambardella, Pietro

    2015-07-01

    Magnetoresistive effects are usually invariant on inversion of the magnetization direction. In non-centrosymmetric conductors, however, nonlinear resistive terms can give rise to a current dependence that is quadratic in the applied voltage and linear in the magnetization. Here we demonstrate that such conditions are realized in simple bilayer metal films where the spin-orbit interaction and spin-dependent scattering couple the current-induced spin accumulation to the electrical conductivity. We show that the longitudinal resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of the current or the sign of the magnetization. This unidirectional magnetoresistance scales linearly with current density and has opposite sign in Ta and Pt, which we associate with the modification of the interface scattering potential induced by the spin Hall effect in these materials. Our results suggest a route to control the resistance and detect magnetization switching in spintronic devices using a two-terminal geometry, which applies also to heterostructures including topological insulators.

  10. Orbital angular momentum and the parton model

    Energy Technology Data Exchange (ETDEWEB)

    Ratcliffe, P.G.

    1987-06-25

    The role of orbital angular momentum is discussed within the framework of the parton model. It is shown that a consistent interpretation of the Altarelli-Parisi equations governing the Q/sup 2/-evolution of helicity-weighted parton distributions necessitates the assumption that partons carry a large orbital angular momentum, contrary to popular belief. In developing the arguments presented, the Altarelli-Parisi formalism is extended to include orbital angular momentum dependence.

  11. Transverse target-spin asymmetry associated with deeply virtual Compton scattering on the proton and a resulting model-dependent constraint on the total angular momentum of quarks in the nucleon

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Zhenyu

    2007-02-15

    In this thesis we report on the rst results on the transverse target-spin asymmetry associated with deeply virtual Compton scattering on the proton. It is shown that this asymmetry can provide one of the rare possibilities to access the Generalized Parton Distribution (GPD) E of the nucleon, and thus, through models for E, also to the total angular momentum of u and d quarks in the nucleon. The measurement was performed using the 27.6 GeV positron beam of the HERA storage ring and the transversely polarized hydrogen target of the HERMES experiment at DESY. The two leading azimuthal amplitudes of the asymmetry are extracted from the HERMES 2002-2004 data, corresponding to an integrated luminosity of 65.3 pb.1. By comparing the results obtained at HERMES and theoretical predictions based on a phenomenological model of GPDs, we obtain a model-dependent constraint on the total angular momentum of quarks in the nucleon. (orig.)

  12. Optical studies of colossal magnetoresistance

    International Nuclear Information System (INIS)

    Full text: Colossal-magnetoresistance (CMR) materials are so named because they exhibit a large change in their electrical resistance in a magnetic field. This immediately suggests their application in magnetic memory, recording, sensing and switching devices. This intrinsic technological interest has also generated much fundamental research in CMR materials, with the goal of accounting for their fascinating behaviour. CMR occurs in perovskite manganese oxides, such as the lanthanum manganites (LaMnO3) doped with divalent ions substituting for La. The CMR mechanism is known to be related to the double exchange mechanism and to lattice distortion, but the details still generate intense debate. Millis (1998) summarised: 'Although a suggestive qualitative agreement between theory and experiment exists, much more needs to be done'. The main line of research has centred on the metalinsulator (Ml) transition during the phase change from paramagnetic-insulator (PMI) to ferromagnetic metal (FMM) that occurs at the Curie temperature, Tc, typically 200-250 K, but the phase diagram, usually represented as a function of doping fraction and temperature, is extremely rich. In this respect the CMR materials are similar, on the one hand, to organic conductors, and to a lesser extent, to high-temperature superconductors (HTS). Relatively little optical work on CMR materials has been reported in the literature. This is in spite of the recognition that an additional mechanism, proposed to be an electron-phonon interaction, is necessary as well as the earlier established double-exchange to account for the CMR effect, and that optical methods are sensitive to phonon modes, as well as to charge carrier dynamics. In particular, experimental evidence (De Teresa et al. 1997) indicates the existence of magnetic polarons above Tc, consistent with a 'small polaron' model. Jahn-Teller coupling is also important in explaining CMR (Popovic and Satpathy 2000). Our reflectivity measurements (Lewis

  13. Robust giant magnetoresistive effect type multilayer sensor

    NARCIS (Netherlands)

    Lenssen, K.M.H.; Kuiper, A.E.T.; Roozeboom, F.

    2002-01-01

    A robust Giant Magneto Resistive effect type multilayer sensor comprising a free and a pinned ferromagnetic layer, which can withstand high temperatures and strong magnetic fields as required in automotive applications. The GMR multi-layer has an asymmetric magneto-resistive curve and enables sensor

  14. Thin-film magnetoresistive absolute position detector

    NARCIS (Netherlands)

    Groenland, Johannes Petrus Jacobus

    1990-01-01

    The subject of this thesis is the investigation of a digital absolute posi- tion-detection system, which is based on a position-information carrier (i.e. a magnetic tape) with one single code track on the one hand, and an array of magnetoresistive sensors for the detection of the informatio

  15. Magnetoresistance in multilayer fullerene spin valves: A first-principles study

    Science.gov (United States)

    ćakır, Deniz; Otálvaro, Diana M.; Brocks, Geert

    2014-12-01

    Carbon-based molecular semiconductors are explored for application in spintronics because their small spin-orbit coupling promises long spin lifetimes. We calculate the electronic transport from first principles through spin valves comprising bi- and tri-layers of the fullerene molecules C60 and C70, sandwiched between two Fe electrodes. The spin polarization of the current, and the magnetoresistance depend sensitively on the interactions at the interfaces between the molecules and the metal surfaces. They are much less affected by the thickness of the molecular layers. A high current polarization (CP >90 %) and magnetoresistance (MR >100 %) at small bias can be attained using C70 layers. In contrast, the current polarization and the magnetoresistance at small bias are vanishingly small for C60 layers. Exploiting a generalized Jullière model we can trace the differences in spin-dependent transport between C60 and C70 layers to differences between the molecule-metal interface states. These states also allow one to interpret the current polarization and the magnetoresistance as a function of the applied bias voltage.

  16. Theory of the negative magnetoresistance in magnetic metallic multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Hood, R.Q.; Falicov, L.M. [California Univ., Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley Lab., CA (United States)

    1993-04-01

    The Boltzman equation is solved for a system consisting of alternating ferromagnetic normal metallic layers. The in-plane conductance of the film is calculated for two configurations: successive ferromagnetic layers aligned parallel and antiparallel to each other. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by application of an extemal magnetic field. The calculation depends on geometric parameters (the thicknesses of the layers); intrinsic metal parameters (number of conduction electrons, magnetization and effective masses in the layers); bulk sample properties (conductivity relaxation times); and interface scattering properties (diffuse scattering versus potential scattering at the interfaces). It is found that a large negative magnetoresistance requires, in general, considerable asymmetry in the interface scattering for the two spin orienmtions. All qualitative features of the experiments are reproduced. Quantitative agreement can be achieved with sensible values of the parameters. The effect can be conceptually explained based on considerations of phase-space availability for an electron of a given spin orientation as it travels through the multilayer sample in the various configurations and traverses the interfaces.

  17. Angular Momentum Distribution in the Transverse Plane

    CERN Document Server

    Adhikari, Lekha

    2016-01-01

    Several possibilities to relate the $t$-dependence of Generalized Parton Distributions (GPDs) to the distribution of angular momentum in the transverse plane are discussed. Using a simple spectator model we demonstrate that non of them correctly describes the orbital angular momentum distribution that for a longitudinally polarized nucleon obtained directly from light-front wavefunctions.

  18. Angular and energy dependences of emission probability for light particles in 22Ne-induced reactions at 8 MeV/nucleon

    International Nuclear Information System (INIS)

    Inclusive energy spectra and angular distributions have been measured for light charged particles with Z=1-4 emitted in the interaction of 22Ne ions with a 181Ta target. The reaction products were analysed and detected by means of a system of ΔE-E telescopes placed in the focal plane of a magnetic spectrometer. Energy spectra of light particles (p, d, t and He, Li, Be isotopes) correspond to the calculated kinematic limits taking into account the rotational energy of the residual nucleus. The angular distributions of the high-energy particles are strongly forward directed. The data obtained are analysed on the basis of the moving source, rotating hot spot, massive transfer and breakup-fusion models. The relative yields of the different isotopes and their most probable energies are described by the massive transfer model. The qualitative behaviour of the spectra in the vicinity of the kinematic limits can be explained in terms of the breakup-fusion model

  19. Resonant tunnel magnetoresistance in a double magnetic tunnel junction

    KAUST Repository

    Useinov, Arthur

    2011-08-09

    We present quasi-classical approach to calculate a spin-dependent current and tunnel magnetoresistance (TMR) in double magnetic tunnel junctions (DMTJ) FML/I/FMW/I/FMR, where the magnetization of the middle ferromagnetic metal layer FMW can be aligned parallel or antiparallel with respect to the fixed magnetizations of the left FML and right FMR ferromagnetic electrodes. The transmission coefficients for components of the spin-dependent current, and TMR are calculated as a function of the applied voltage. As a result, we found a high resonant TMR. Thus, DMTJ can serve as highly effective magnetic nanosensor for biological applications, or as magnetic memory cells by switching the magnetization of the inner ferromagnetic layer FMW.© Springer Science+Business Media, LLC 2011.

  20. Professional AngularJS

    CERN Document Server

    Karpov, Valeri

    2015-01-01

    A comprehensive guide to AngularJS, Google's open-source client-side framework for app development. Most of the existing guides to AngularJS struggle to provide simple and understandable explanations for more advanced concepts. As a result, some developers who understand all the basic concepts of AngularJS struggle when it comes to building more complex real-world applications. Professional AngularJS provides a thorough understanding of AngularJS, covering everything from basic concepts, such as directives and data binding, to more advanced concepts like transclusion, build systems, and auto

  1. Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors

    Directory of Open Access Journals (Sweden)

    Sergio Iván Ravelo Arias

    2013-12-01

    Full Text Available Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function  is obtained considering it as the relationship between sensor output voltage and input sensing current,[PLEASE CHECK FORMULA IN THE PDF]. The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR, giant magnetoresistance (GMR, spin-valve (GMR-SV and tunnel magnetoresistance (TMR. The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications.

  2. Fractional modeling of the AC large-signal frequency response in magnetoresistive current sensors.

    Science.gov (United States)

    Ravelo Arias, Sergio Iván; Ramírez Muñoz, Diego; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; de Freitas, Paulo Jorge Peixeiro

    2013-01-01

    Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Z(t)(JF) is obtained considering it as the relationship between sensor output voltage and input sensing current, Z(t)(jf)= V(o, sensor)(jf)/I(sensor)(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. PMID:24351648

  3. Mobility controlled linear magnetoresistance with 3D anisotropy in a layered graphene pallet

    Science.gov (United States)

    Zhang, Qiang; Li, Peng; He, Xin; Li, Jun; Wen, Yan; Ren, Wencai; Cheng, Hui-ming; Yang, Yang; Al-Hadeethi, Yas F.; Zhang, Xixiang

    2016-10-01

    A bulk sample of pressed graphene sheets was prepared under hydraulic pressure (~150 MPa). The cross-section of the sample demonstrates a layered structure, which leads to 3D electrical transport properties with anisotropic mobility. The electrical transport properties of the sample were measured over a wide temperature (2-400 K) and magnetic field (-140 ~\\text{kOe}≤slant H≤slant 140 ~\\text{kOe} ) range. The magnetoresistance measured at a fixed temperature can be described by R≤ft(H,θ \\right)=R≤ft({{\\varepsilon}θ}H,0\\right) with {{\\varepsilon}θ}={≤ft({{\\cos}2}θ +{{γ-2}{{\\sin}2}θ \\right)}1/2} , where γ is the mobility anisotropy constant and θ is the angle between the normal of the sample plane and the magnetic field. The large linear magnetoresistance (up to 36.9% at 400 K and 140 kOe) observed at high fields is ascribed to a classical magnetoresistance caused by mobility fluctuation ( Δ μ ). The magnetoresistance value at 140 kOe was related to the average mobility ≤ft( \\right) because of the condition Δ μ . The carrier concentration remained constant and the temperature-dependent resistivity was proportional to the average mobility, as verified by Kohler’s rule. Anisotropic dephasing length was deduced from weak localization observed at low temperatures.

  4. Magnetic properties,magnetoresistivity and magnetocaloric effect in GdxLa1-x-MnSi alloys

    Institute of Scientific and Technical Information of China (English)

    T.I.Ivanova; S.A.Nikitin; W.Suski; GA.Tskhadadze; I.A.Ovtchenkova; D.Badurski

    2009-01-01

    The results of magnetization,magnetoresistivity and magnetocaloric effect (MCE) studies performed on polycrystalline samples of the GdxLa1-xMnSi (x=0.5,0.6,0.7,0.8,0.9,1.0) compounds were presented.Complex measurements were carried out on the GdxLa1-xMnSi compounds to determine the influence of substitution in the rare earth (R) sublattice on the magnetic and related properties of these compounds.The compounds with x≤0.6 demonstrated two magnetic phase transitions (ferromagnetic to paramagnetic and antiferromagnetic to ferromagnetic) both of which were first order.Anomalies in the magnetocaloric effect,electroresistivity and magnetoresistivity were observed in the temperature ranges of the magnetic phase transitions.The temperature dependences of MCE and magnetoresistivity for these compounds correlated with the temperature dependence of magnetization.

  5. Angular momentum and topological dependence of Kepler's Third Law in the Broucke-Hadjidemetriou-H\\'enon family of periodic three-body orbits

    CERN Document Server

    Janković, Marija R

    2016-01-01

    We use 57 recently found topological satellites of Broucke-Hadjidemetriou-Henon's periodic orbits with values of the topological exponent $k$ ranging from $k$ = 3 to $k$ = 58 to plot the angular momentum $L$ as a function of the period $T$, with both $L$ and $T$ rescaled to energy $E=-\\frac12$. Upon plotting $L(T/k)$ we find that all our solutions fall on a curve that is virtually indiscernible by naked eye from the $L(T)$ curve for non-satellite solutions. The standard deviation of the satellite data from the sixth-order polynomial fit to the progenitor data is $\\sigma = 0.13$. This regularity supports Henon's 1976 conjecture that the linearly stable Broucke-Hadjidemetriou-Henon orbits are also perpetually, or Kolmogorov-Arnold-Moser stable.

  6. Angular Momentum and Topological Dependence of Kepler's Third Law in the Broucke-Hadjidemetriou-Hénon Family of Periodic Three-Body Orbits

    Science.gov (United States)

    Janković, Marija R.; Dmitrašinović, V.

    2016-02-01

    We use 57 recently found topological satellites of Broucke-Hadjidemetriou-Hénon's periodic orbits with values of the topological exponent k ranging from k =3 to k =58 to plot the angular momentum L as a function of the period T , with both L and T rescaled to energy E =-0.5 . Upon plotting L (T /k ) we find that all our solutions fall on a curve that is virtually indiscernible by the naked eye from the L (T ) curve for nonsatellite solutions. The standard deviation of the satellite data from the sixth-order polynomial fit to the progenitor data is σ =0.13 . This regularity supports Hénon's 1976 conjecture that the linearly stable Broucke-Hadjidemetriou-Hénon orbits are also perpetually, or Kol'mogorov-Arnol'd-Moser, stable.

  7. Magnetoresistive system with concentric ferromagnetic asymmetric nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Avila, J. I., E-mail: javila@ulg.ac.be; Tumelero, M. A.; Pasa, A. A.; Viegas, A. D. C. [Laboratório de Filmes Finos e Superfícies (LFFS), Departamento de Física, Universidade Federal de Santa Catarina, CP 476 Florianópolis (Brazil)

    2015-03-14

    A structure consisting of two concentric asymmetric nanorings, each displaying vortex remanent states, is studied with micromagnetic calculations. By orienting in suitable directions, both the asymmetry of the rings and a uniform magnetic field, the vortices chiralities can be switched from parallel to antiparallel, obtaining in this way the analogue of the ferromagnetic and antiferromagnetic configurations found in bar magnets pairs. Conditions on the thickness of single rings to obtain vortex states, as well as formulas for their remanent magnetization are given. The concentric ring structure enables the creation of magnetoresistive systems comprising the qualities of magnetic nanorings, such as low stray fields and high stability. A possible application is as contacts in spin injection in semiconductors, and estimations obtained here of magnetoresistance change for a cylindrical spin injection based device show significant variations comparable to linear geometries.

  8. Anomalous anisotropic magnetoresistance effects in graphene

    Directory of Open Access Journals (Sweden)

    Yiwei Liu

    2014-09-01

    Full Text Available We investigate the effect of external stimulus (temperature, magnetic field, and gases adsorptions on anisotropic magnetoresistance (AMR in multilayer graphene. The graphene sample shows superlinear magnetoresistance when magnetic field is perpendicular to the plane of graphene. A non-saturated AMR with a value of −33% is found at 10 K under a magnetic field of 7 T. It is surprisingly to observe that a two-fold symmetric AMR at high temperature is changed into a one-fold one at low temperature for a sample with an irregular shape. The anomalous AMR behaviors may be understood by considering the anisotropic scattering of carriers from two asymmetric edges and the boundaries of V+(V- electrodes which serve as active adsorption sites for gas molecules at low temperature. Our results indicate that AMR in graphene can be optimized by tuning the adsorptions, sample shape and electrode distribution in the future application.

  9. Superconductivity emerging from suppressed large magnetoresistant state in WTe2

    OpenAIRE

    Kang, Defen; Zhou, Yazhou; Yi, Wei; Yang, Chongli; Guo, Jing; Shi, Youguo; Zhang, Shan; Wang, Zhe; Zhang, Chao; Jiang, Sheng; Li, Aiguo; Yang, Ke; Wu, Qi; Zhang, Guangming; Sun, Liling

    2015-01-01

    The recent discovery of large and non-saturating magnetoresistance (LMR) in WTe2 provides a unique playground to find new phenomena and significant perspective for potential applications. Here we report the first observation of superconductivity near the proximity of suppressed LMR state in pressurized WTe2 through high-pressure synchrotron X-ray diffraction, electrical resistance, magnetoresistance, and ac magnetic susceptibility measurements. It is found that the positive magnetoresistance ...

  10. The Effect of Dopants on the Magnetoresistance of WTe2

    OpenAIRE

    Flynn, Steven; Ali, Mazhar; Cava, R. J.

    2015-01-01

    Elucidating the nature of the large, non-saturating magnetoresistance in WTe2 is a significant step in functionalizing this phenomenon for applications. Here, Mo, Re, and Ta doped WTe2 are compared to determine whether isovalent and aliovalent substitutions have different effects on the large magnetoresistance. By 1% substitution, isoelectronic doping reduces the magnetoresistance by a factor of 1.2 with an apparent linear trend, whereas aliovalent doping reduces the effect by over an order o...

  11. Robust linear magnetoresistance in WTe2

    OpenAIRE

    Pan, Xing-Chen; Pan, Yiming; Jiang, Juan; Zuo, Huakun; Liu, Huimei; Chen, Xuliang; Wei, Zhongxia; Zhang, Shuai; Wang, Zhihe; Wan, Xiangang; Yang, Zhaorong; Feng, Donglai; Xia, Zhengcai; Li, Liang; Song, Fengqi

    2015-01-01

    Unsaturated magnetoresistance (MR) has been reported in WTe2, and remains irrepressible up to very high field. Intense optimization of the crystalline quality causes a squarely-increasing MR, as interpreted by perfect compensation of opposite carriers. Herein we report our observation of linear MR (LMR) in WTe2 crystals, the onset of which is first identified by constructing the mobility spectra of the MR at low fields. The LMR further intensifies and predominates at fields higher than 20 Tes...

  12. Magnetoresistance of electrodeposited NiFeCu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Esmaili, S., E-mail: esmaili@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Bahrololoom, M.E. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Peter, L. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest (Hungary)

    2012-01-01

    NiFeCu alloy films were electrodeposited from baths containing nickel sulfate and/or nickel sulfamate. All samples were pulse plated in the potentiostatic mode. The room temperature magnetoresistances of the films were measured showing anisotropic magnetoresistances up to 1.5%. The anisotropic magnetoresistances increased with the addition of sulfamic acid to the sulfate bath. Samples deposited from the bath with high sulfamate concentration showed a giant magnetoresistance behavior. To characterize the films, scanning electron microscopy and X-ray diffraction were used.

  13. Giant magnetoresistance of electrodeposited Cu–Co–Ni alloy films

    Indian Academy of Sciences (India)

    İ H Karahan; Ö F Bakkaloğlu; M Bedir

    2007-01-01

    Electrodeposition of CuCoNi alloys was performed in an acid–citrate medium. Nickel density parameter was varied in order to analyse its influence on the magnetoresistance. The structure and giant magneto- resistance (GMR) effect of CuCoNi alloys have been investigated. The maximum value for GMR ratio, at room temperature is 1% at a field of 12 kOe, and at 20 K is 2.1% at a field of 8.5 kOe for 3.1 Ni. The MR ratio of Cu100−−CoNi alloys first increases and then decreases monotonically with increasing Ni content. The GMR and its dependence on magnetic field and temperature were discussed.

  14. Tunneling magnetoresistance in ferromagnetic planar hetero-nanojunctions

    KAUST Repository

    Useinov, Arthur

    2010-05-03

    We present a theoretical study of the tunneling magnetoresistance (TMR) in nanojunctions between non-identical ferromagnetic metals in the framework of the quasiclassical approach. The lateral size of a dielectric oxide layer, which is considered as a tunneling barrier between the metallic electrodes, is comparable with the mean-free path of electrons. The dependence of the TMR on the bias voltage, physical parameters of the dielectric barrier, and spin polarization of the electrodes is studied. It is demonstrated that a simple enough theory can give high TMR magnitudes of several hundred percent at bias voltages below 0.5 V. A qualitative comparison with the available experimental data is given. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. On Angular Momentum

    Science.gov (United States)

    Schwinger, J.

    1952-01-26

    The commutation relations of an arbitrary angular momentum vector can be reduced to those of the harmonic oscillator. This provides a powerful method for constructing and developing the properties of angular momentum eigenvectors. In this paper many known theorems are derived in this way, and some new results obtained. Among the topics treated are the properties of the rotation matrices; the addition of two, three, and four angular momenta; and the theory of tensor operators.

  16. Partonic orbital angular momentum

    Science.gov (United States)

    Arash, Firooz; Taghavi-Shahri, Fatemeh; Shahveh, Abolfazl

    2013-04-01

    Ji's decomposition of nucleon spin is used and the orbital angular momentum of quarks and gluon are calculated. We have utilized the so called valon model description of the nucleon in the next to leading order. It is found that the average orbital angular momentum of quarks is positive, but small, whereas that of gluon is negative and large. Individual quark flavor contributions are also calculated. Some regularities on the total angular momentum of the quarks and gluon are observed.

  17. Quark Orbital Angular Momentum

    OpenAIRE

    Burkardt Matthias

    2015-01-01

    Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asy...

  18. Large linear magnetoresistance in a new Dirac material BaMnBi2

    Science.gov (United States)

    Wang, Yi-Yan; Yu, Qiao-He; Xia, Tian-Long

    2016-10-01

    Dirac semimetal is a class of materials that host Dirac fermions as emergent quasi-particles. Dirac cone-type band structure can bring interesting properties such as quantum linear magnetoresistance and large mobility in the materials. In this paper, we report the synthesis of high quality single crystals of BaMnBi2 and investigate the transport properties of the samples. BaMnBi2 is a metal with an antiferromagnetic transition at T N = 288 K. The temperature dependence of magnetization displays different behavior from CaMnBi2 and SrMnBi2, which suggests the possible different magnetic structure of BaMnBi2. The Hall data reveals electron-type carriers and a mobility μ(5 K) = 1500 cm2/V·s. Angle-dependent magnetoresistance reveals the quasi-two-dimensional (2D) Fermi surface in BaMnBi2. A crossover from semiclassical MR ˜ H 2 dependence in low field to MR ˜ H dependence in high field, which is attributed to the quantum limit of Dirac fermions, has been observed in magnetoresistance. Our results indicate the existence of Dirac fermions in BaMnBi2. Project supported by the National Natural Science Foundation of China (Grant No. 11574391), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (Grant No. 14XNLQ07).

  19. Study of temperature dependence and angular distribution of poly(9,9-dioctylfluorene) polymer films deposited by matrix-assisted pulsed laser evaporation (MAPLE)

    International Nuclear Information System (INIS)

    Poly(9,9-dioctylfluorene) (PFO) polymer films were deposited by matrix-assisted pulsed laser evaporation (MAPLE) technique. The polymer was diluted (0.5 wt%) in tetrahydrofuran and, once cooled to liquid nitrogen temperature, it was irradiated with a KrF excimer laser. 10,000 laser pulses were used to deposit PFO films on Si substrates at different temperatures (-16, 30, 50 and 70 deg. C). One PFO film was deposited with 16,000 laser pulses at a substrate temperature of 50 deg. C. The morphology, optical and structural properties of the films were investigated by SEM, AFM, PL and FTIR spectroscopy. SEM inspection showed different characteristic features on the film surface, like deflated balloons, droplets and entangled polymer filaments. The roughness of the films was, at least partially, controlled by substrate heating, which however had the effect to reduce the deposition rate. The increase of the laser pulse number modified the target composition and increased the surface roughness. The angular distribution of the material ejected from the target confirmed the forward ejection of the target material. PFO films presented negligible modification of the chemical structure respect to the bulk material.

  20. Giant Magnetoresistance in La0.67Ca0.33MnO3/Alq3/Co Sandwiched-Structure Organic Spin Valves

    Institute of Scientific and Technical Information of China (English)

    PANG Zhi-Yong; CHEN Yan-xue; LIU Tian-Tian; ZHANG Yun-Pang; XIE Shi-Jie; YAN Shi-Shen; HAN Sheng-Hao

    2006-01-01

    La0/67Ca0.33Mn03/Alq3/Co sandwiched-structure organic spin valves are fabricated by vacuum thermal evaporation method.A giant magnetoresistance (GMR) of 14% is observed at low temperature 1OOK.At 30K,the magnetoresistance can increase to 50%.The large GMR of the device is attributed to the high spin polarization and low conductivity of the La0.67Ca0.33MnO3 contact.The magnetoresistance △R/R and the coercive field of the Co electrode depend strongly on temperature.The large high-field magnetoresistance reported on La0.67Sr0.33MnO3/Alq3/Co organic spin valves [Nature 427 (2004) 821] is not observed in our La0.67Ca0.33MnO3/Alq3/Co organic spin valves.

  1. Possible Origins for Paramagnetic-ferromagnetic and Insulator-metal Transitions as well as Colossal Magnetoresistance in Manganites

    Institute of Scientific and Technical Information of China (English)

    LI Jianqing; YUAN Songliu; TIAN Zaoming

    2009-01-01

    Systematical investigations of zero-field resistivity,magnetoresistance and mag-netization were performed for a typical manganese compound La_(2/3)Ca_(1/3)MnO_3.It is argued that the common origin for insulator-metal and paramagenetic ferromagnetic-transitions as well as colossal magnetoresistance is due to the formation of ferromagnetic clusters in the paramagnetic background.The transition to metallic state is resulted from percolation of ferromagnetic metallic clusters,while the colossal magnetoresistance is due to the application of magnetic field,which accelerates the growth of ferromagnetic metallic clusters and causes the shift of the onset temperature for the metallic percolation to higher temperature.Based on the random resistor network model,the zero-field resistivity versus temperature dependence is simulated by using experimental parameters,and experimental data well agree with those in whole temperature range,giving a strong support to our approach.

  2. Extraordinary Magnetoresistance Effect in Semiconductor/Metal Hybrid Structure

    KAUST Repository

    Sun, Jian

    2013-06-27

    In this dissertation, the extraordinary magnetoresistance (EMR) effect in semiconductor/metal hybrid structures is studied to improve the performance in sensing applications. Using two-dimensional finite element simulations, the geometric dependence of the output sensitivity, which is a more relevant parameter for EMR sensors than the magnetoresistance (MR), is studied. The results show that the optimal geometry in this case is different from the geometry reported before, where the MR ratio was optimized. A device consisting of a semiconductor bar with length/width ratio of 5~10 and having only 2 contacts is found to exhibit the highest sensitivity. A newly developed three-dimensional finite element model is employed to investigate parameters that have been neglected with the two dimensional simulations utilized so far, i.e., thickness of metal shunt and arbitrary semiconductor/metal interface. The simulations show the influence of those parameters on the sensitivity is up to 10 %. The model also enables exploring the EMR effect in planar magnetic fields. In case of a bar device, the sensitivity to planar fields is about 15 % to 20 % of the one to perpendicular fields. 5 A “top-contacted” structure is proposed to reduce the complexity of fabrication, where neither patterning of the semiconductor nor precise alignment is required. A comparison of the new structure with a conventionally fabricated device shows that a similar magnetic field resolution of 24 nT/√Hz is obtained. A new 3-contact device is developed improving the poor low-field sensitivity observed in conventional EMR devices, resulting from its parabolic magnetoresistance response. The 3-contact device provides a considerable boost of the low field response by combining the Hall effect with the EMR effect, resulting in an increase of the output sensitivity by 5 times at 0.01 T compared to a 2-contact device. The results of this dissertation provide new insights into the optimization of EMR devices

  3. Charge-multiplicity dependence of single-particle transverse-rapidity yt and pseudorapidity η densities and 2D angular correlations from 200 GeV p -p collisions

    Science.gov (United States)

    Trainor, Thomas A.; Prindle, Duncan J.

    2016-01-01

    An established phenomenology and theoretical interpretation of p -p collision data at lower collision energies should provide a reference for p -p and other collision systems at higher energies, against which claims of novel physics may be tested. The description of p -p collisions at the relativistic heavy ion collider has remained incomplete even as claims for collectivity and other novelties in data from smaller systems at the large hadron collider have emerged recently. In this study we report the charge-multiplicity dependence of two-dimensional angular correlations and of single-particle (SP) densities on transverse rapidity yt and pseudorapidity η from 200 GeV p -p collisions. We define a comprehensive and self-consistent two-component (soft+hard ) model for hadron production and report a significant p -p nonjet quadrupole component as a third (angular-correlation) component. Our results have implications for p -p centrality, the underlying event, collectivity in small systems and the existence of flows in high-energy nuclear collisions.

  4. CCharge-multiplicity dependence of single-particle transverse-rapidity $\\bf y_t$ and pseudorapidity $\\bf \\eta$ densities and 2D angular correlations from 200 GeV $p$-$p$ collisions

    CERN Document Server

    Trainor, Thomas A

    2015-01-01

    An established phenomenology and theoretical interpretation of $p$-$p$ collision data at lower collision energies should provide a reference for $p$-$p$ and other collision systems at higher energies, against which claims of novel physics may be tested. The description of $p$-$p$ collisions at the relativistic heavy ion collider (RHIC) has remained incomplete even as claims for collectivity and other novelties in data from smaller systems at the large hadron collider (LHC) have emerged recently. In this study we report the charge-multiplicity dependence of two-dimensional (2D) angular correlations and of single-particle (SP) densities on transverse rapidity $y_t$ and pseudorapidity $\\eta$ from 200 GeV $p$-$p$ collisions. We define a comprehensive and self-consistent two-component (soft + hard) model (TCM) for hadron production and report a significant $p$-$p$ nonjet (NJ) quadrupole component as a third (angular-correlation) component. Our results have implications for $p$-$p$ centrality, the underlying event ...

  5. Sign control of magnetoresistance through chemically engineered interfaces.

    Science.gov (United States)

    Ciudad, David; Gobbi, Marco; Kinane, Christy J; Eich, Marius; Moodera, Jagadeesh S; Hueso, Luis E

    2014-12-01

    Chemically engineered interfaces are shown to produce inversions of the magnetoresistance in spintronic devices including lithium fluoride interlayers. This behavior is explained by the formation of anti-ferromagnetic difluoride layers. By changing the order of deposition of the different materials, the sign of the magnetoresistance can be deterministically controlled both in organic spin valves and in inorganic magnetic tunnel junctions.

  6. Magnetoresistance in molybdenite (MoS2) crystals

    International Nuclear Information System (INIS)

    The principal magnetoresistance ratios of molybdenite (MoS2), the naturally occurring semiconducting crystal, have been investigated at magnetic fields ranging from 4.5 KOe and within the temperature range 3000K to 7000K. Unlike some previous observations, magnetoresistance has been found to be negative. (author)

  7. Magnetoresistive transducer for absolute position detection

    NARCIS (Netherlands)

    Groenland, J.P.J.

    1984-01-01

    In this paper a new method is presented for the measurement of absolute linear or angular position. The digital position information is recorded serially into one track of a suitable hard-magnetic medium. The stray field of this information layer determines the angular magnetisation distribution in

  8. Giant magnetoresistance in bilayer graphene nanoflakes

    Science.gov (United States)

    Farghadan, Rouhollah; Farekiyan, Marzieh

    2016-09-01

    Coherent spin transport through bilayer graphene (BLG) nanoflakes sandwiched between two electrodes made of single-layer zigzag graphene nanoribbon was investigated by means of Landauer-Buttiker formalism. Application of a magnetic field only on BLG structure as a channel produces a perfect spin polarization in a large energy region. Moreover, the conductance could be strongly modulated by magnetization of the zigzag edge of AB-stacked BLG, and the junction, entirely made of carbon, produces a giant magnetoresistance (GMR) up to 100%. Intestinally, GMR and spin polarization could be tuned by varying BLG width and length. Generally, MR in a AB-stacked BLG strongly increases (decreases) with length (width).

  9. Determination of g-tensors of low-symmetry Nd{sup 3+} centers in LiNbO{sub 3} by rectification of angular dependence of electron paramagnetic resonance spectra

    Energy Technology Data Exchange (ETDEWEB)

    Grachev, V., E-mail: grachev@physics.montana.edu; Malovichko, G. [Physics Department, Montana State University, Bozeman, Montana 59717 (United States); Munro, M. [Quantel Laser, Bozeman, Montana 59715 (United States); Kokanyan, E. [Institute of Physical Researches, Ashtarak (Armenia)

    2015-07-28

    Two procedures for facilitation of line tracing and deciphering of complicated spectra of electron paramagnetic resonance (EPR) were developed: a correction of microwave frequencies for every orientation of external magnetic field on the base of known values of g-tensor components for a reference paramagnetic center and followed rectification of measured angular dependences using plots of effective deviation of g{sup 2}-factors of observed lines from effective g{sup 2}-factors of the reference center versus angles or squared cosines of angles describing magnetic field orientations. Their application to EPR spectra of nearly stoichiometric lithium niobate crystals doped with neodymium allowed identifying two axial and six different low-symmetry Nd{sup 3+} centers, to determine all components of their g-tensors, and to propose common divacancy models for a whole family of Nd{sup 3+} centers.

  10. An automatic measuring system for mapping of spectral and angular dependence of direct and diffuse solar radiation; Et automatisk maalesystem for kartlegging av vinkel- og spektralfordeling av direkte og diffus solstraaling

    Energy Technology Data Exchange (ETDEWEB)

    Grandum, Oddbjoern

    1997-12-31

    In optimizing solar systems, it is necessary to know the spectral and angular dependence of the radiation. The general nonlinear character of most solar energy systems accentuates this. This thesis describes a spectroradiometer that will measure both the direct component of the solar radiation and the angular dependence of the diffuse component. Radiation from a selected part of the sky is transported through a movable set of tube sections on to a stationary set of three monochromators with detectors. The beam transport system may effectively be looked upon as a single long tube aimed at a particular spot in the sky. The half value of the effective opening angle is 1.3{sup o} for diffuse radiation and 2.8{sup o} for direct radiation. The whole measurement process is controlled and operated by a PC and normally runs without manual attention. The instrument is built into a caravan. The thesis describes in detail the experimental apparatus, calibration and measurement accuracies. To map the diffuse radiation, one divides the sky into 26 sectors of equal solid angle. A complete measurement cycle is then made at a random point within each sector. These measurements are modelled by fitting to spherical harmonics, enforcing symmetry around the solar direction and the horizontal plane. The direct radiation is measured separately. Also the circumsolar sector is given special treatment. The measurements are routinely checked against global radiation measured in parallel by a standard pyranometer, and direct solar radiation by a pyrheliometer. An extensive improvement programme is being planned for the instrument, including the use of a photomultiplier tube to measure the UV part of the spectrum, a diode array for the 400-1100 nm range, and use of a Ge diode for the 1000-1900 nm range. 78 refs., 90 figs., 31 tabs.

  11. Hall effect in the extremely large magnetoresistance semimetal WTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yongkang, E-mail: ykluo@lanl.gov; Dai, Y. M.; Taylor, A. J.; Yarotski, D. A.; Prasankumar, R. P.; Thompson, J. D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Li, H.; Miao, H.; Shi, Y. G. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190 (China); Ding, H. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100084 (China)

    2015-11-02

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe{sub 2}. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase in the hole density below ∼160 K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a more pronounced reduction in electron density occurs below 50 K, giving rise to comparable electron and hole densities at low temperature. Our observations indicate a possible electronic structure change below 50 K, which might be the direct driving force of the electron-hole “compensation” and the extremely large magnetoresistance as well. Numerical simulations imply that this material is unlikely to be a perfectly compensated system.

  12. Pure spin-Hall magnetoresistance in Rh/Y3Fe5O12 hybrid

    Science.gov (United States)

    Shang, T.; Zhan, Q. F.; Ma, L.; Yang, H. L.; Zuo, Z. H.; Xie, Y. L.; Li, H. H.; Liu, L. P.; Wang, B. M.; Wu, Y. H.; Zhang, S.; Li, Run-Wei

    2015-12-01

    We report an investigation of anisotropic magnetoresistance (AMR) and anomalous Hall resistance (AHR) of Rh and Pt thin films sputtered on epitaxial Y3Fe5O12 (YIG) ferromagnetic insulator films. For the Pt/YIG hybrid, large spin-Hall magne toresistance (SMR) along with a sizable conventional anisotropic magnetoresistance (CAMR) and a nontrivial temperature dependence of AHR were observed in the temperature range of 5-300 K. In contrast, a reduced SMR with negligible CAMR and AHR was found in Rh/YIG hybrid. Since CAMR and AHR are characteristics for all ferromagnetic metals, our results suggest that the Pt is likely magnetized by YIG due to the magnetic proximity effect (MPE) while Rh remains free of MPE. Thus the Rh/YIG hybrid could be an ideal model system to explore physics and devices associated with pure spin current.

  13. Pretzelosity TMD and Quark Orbital Angular Momentum

    OpenAIRE

    Lorce, Cédric; Pasquini, B.

    2015-01-01

    We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation can not be interpreted as the intrinsic contributions, but...

  14. DVL Angular Velocity Recorder

    Science.gov (United States)

    Liebe, Wolfgang

    1944-01-01

    In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.

  15. Quark Orbital Angular Momentum

    Directory of Open Access Journals (Sweden)

    Burkardt Matthias

    2015-01-01

    Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.

  16. Linearization strategies for high sensitivity magnetoresistive sensors

    Science.gov (United States)

    Silva, Ana V.; Leitao, Diana C.; Valadeiro, João; Amaral, José; Freitas, Paulo P.; Cardoso, Susana

    2015-10-01

    Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ˜40 pT/√Hz at 30 Hz, representing a step forward the low field detection at room temperature.

  17. Quantitative current measurements using scanning magnetoresistance microscopy.

    Science.gov (United States)

    Takezaki, Taiichi; Sueoka, Kazuhisa

    2008-08-01

    We have demonstrated the capability of scanning magnetoresistance microscope (SMRM) to be used for quantitative current measurements. The SMRM is a magnetic microscope that is based on an atomic force microscope (AFM) and simultaneously measures the localized surface magnetic field distribution and surface topography. The proposed SMRM employs an in-house built AFM cantilever equipped with a miniaturized magnetoresistive (MR) sensor as a magnetic field sensor. In this study, a spin-valve type MR sensor with a width of 1 microm was used to measure the magnetic field distribution induced by a current carrying wire with a width of 5 microm and a spacing of 1.6 microm at room temperature and under ambient conditions. Simultaneous imaging of the magnetic field distribution and the topography was successfully performed in the DC current ranging from 500 microA to 8 mA. The characterized SV sensor, which has a linear response to magnetic fields, offers the quantitative analysis of a magnetic field and current. The measured magnetic field strength was in good agreement with the result simulated using Biot-Savart's law. PMID:18599218

  18. Dependency of tunneling magneto-resistance on Fe insertion-layer thickness in Co{sub 2}Fe{sub 6}B{sub 2}/MgO-based magnetic tunneling junctions

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Kyo-Suk [MRAM Center, Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Electronics Co., Ltd., San #16 Banwol-dong, Hwasung-City, Gyeonggi-Do 445-701 (Korea, Republic of); Park, Jea-Gun, E-mail: parkjgL@hanyang.ac.kr [MRAM Center, Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2015-04-21

    For Co{sub 2}Fe{sub 6}B{sub 2}/MgO-based perpendicular magnetic tunneling junctions spin valves with [Co/Pd]{sub n}-synthetic-antiferromagnetic (SyAF) layers, the tunneling-magneto-resistance (TMR) ratio strongly depends on the nanoscale Fe insertion-layer thickness (t{sub Fe}) between the Co{sub 2}Fe{sub 6}B{sub 2} pinned layer and MgO tunneling barrier. The TMR ratio rapidly increased as t{sub Fe} increased up to 0.4 nm by improving the crystalline linearity of a MgO tunneling barrier and by suppressing the diffusion of Pd atoms from a [Co/Pd]{sub n}-SyAF. However, it abruptly decreased by further increasing t{sub Fe} in transferring interfacial-perpendicular magnetic anisotropy into the IMA characteristic of the Co{sub 2}Fe{sub 6}B{sub 2} pinned layer. Thus, the TMR ratio peaked at t{sub Fe} = 0.4 nm: i.e., 120% at 29 Ωμm{sup 2}.

  19. Electronic quenching of O({sup 1}D) by Xe: Oscillations in the product angular distribution and their dependence on collision energy

    Energy Technology Data Exchange (ETDEWEB)

    Garofalo, Lauren A.; Smith, Mica C. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Dagdigian, Paul J., E-mail: pjdagdigian@jhu.edu [Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218-2685 (United States); Kłos, Jacek [Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021 (United States); Alexander, Millard H., E-mail: mha@umd.edu [Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021 (United States); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2021 (United States); Boering, Kristie A., E-mail: boering@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States); Lin, Jim Jr-Min, E-mail: jimlin@gate.sinica.edu.tw [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China); Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan (China); Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

    2015-08-07

    The dynamics of the O({sup 1}D) + Xe electronic quenching reaction was investigated in a crossed beam experiment at four collision energies. Marked large-scale oscillations in the differential cross sections were observed for the inelastic scattering products, O({sup 3}P) and Xe. The shape and relative phases of the oscillatory structure depend strongly on collision energy. Comparison of the experimental results with time-independent scattering calculations shows qualitatively that this behavior is caused by Stueckelberg interferences, for which the quantum phases of the multiple reaction pathways accessible during electronic quenching constructively and destructively interfere.

  20. Optical Angular Momentum

    International Nuclear Information System (INIS)

    For many years the Institute of Physics has published books on hot topics based on a collection of reprints from different journals, including some remarks by the editors of each volume. The book on Optical Angular Momentum, edited by L Allen, S M Barnett and M J Padgett, is a recent addition to the series. It reproduces forty four papers originally published in different journals and in a few cases it provides direct access to works not easily accessible to a web navigator. The collection covers nearly a hundred years of progress in physics, starting from an historic 1909 paper by Poynting, and ending with a 2002 paper by Padgett, Barnett and coworkers on the measurement of the orbital angular momentum of a single photon. The field of optical angular momentum has expanded greatly, creating an interdisciplinary attraction for researchers operating in quantum optics, atomic physics, solid state physics, biophysics and quantum information theory. The development of laser optics, especially the control of single mode sources, has made possible the specific design of optical radiation modes with a high degree of control on the light angular momentum. The editors of this book are important figures in the field of angular momentum, having contributed to key progress in the area. L Allen published an historical paper in 1999, he and M J Padgett (together with M Babiker) produced few years ago a long review article which is today still the most complete basic introduction to the angular momentum of light, while S M Barnett has contributed several high quality papers to the progress of this area of physics. The editors' choice provides an excellent overview to all readers, with papers classified into eight different topics, covering the basic principles of the light and spin and orbital angular momentum, the laboratory tools for creating laser beams carrying orbital angular momentum, the optical forces and torques created by laser beams carrying angular momentum on

  1. Average Angular Velocity

    OpenAIRE

    Van Essen, H.

    2004-01-01

    This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to th...

  2. Angular velocity discrimination

    Science.gov (United States)

    Kaiser, Mary K.

    1990-01-01

    Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

  3. Magnetoresistance of Electrons Channelled by Microscopic Magnetic Field Modulation

    Institute of Scientific and Technical Information of China (English)

    DAI Bo; LIU Xiao-Xia; LEI Yong; Alain Nogaret

    2009-01-01

    We report the magnetoresistance of two-dimensional electron gas,which is made of GaAs based epitaxial multilayers and laterally subjected to a periodic magnetic field.The modulation field is produced by an array of submicrometre ferromagnets fabricated at the surface of the heterostructure.The magnetoresistance of about 20% is found at low temperature 80K.The measurement is in quantitative agreement with semiclassical simulations,which reveal that the magnetoresistance is due to electrons trapped in snake orbits along lines of zero magnetic field.

  4. Anisotropic magnetoresistance dominant in a three terminal Hanle measurement

    Science.gov (United States)

    Malec, Christopher; Miller, Michael M.; Johnson, Mark

    2016-02-01

    Experiments are performed on mesoscopic nonlocal lateral spin valves with aluminum channels and Permalloy electrodes. Four-terminal magnetoresistance and Hanle measurements characterize the spin accumulation with results that compare well with published work. Three-terminal Hanle measurements of the Permalloy/aluminum (Py/Al) interfaces show bell-shaped curves that can be fit to Lorentzians. These curves are three orders of magnitude larger than the spin accumulation. Using anisotropic magnetoresistance measurements of individual Permalloy electrodes, we demonstrate that the three-terminal measurements are dominated by anisotropic magnetoresistance effects unrelated to spin accumulation.

  5. Large Magnetoresistance Based on Double Spin Filter Tunnel Barriers

    Institute of Scientific and Technical Information of China (English)

    TANG Xiao-Li; ZHANG Huai-Wu; SU Hua; JING Yu-Lan

    2008-01-01

    We propose and theoretically analyse a double magnetic tunnel device that takes advantages of the spin filter effect. Two magnetic tunnel barriers are formed by different spin filters which have different barrier heights. The magnetoresistance of the device is low (high) when the magnetic moments of the two spin filters are parallel(antiparallel). We present a theoretical calculation of the magnetoresistance based on electric tunnel effect.In addition, the effect of the difference barrier heights and exchange splitting energies between the two spin filters are also analysed in detail. The numerical results show that the spin filter in this configuration gives a magnetoresistance larger than that with standard magnetic tunnel junctions.

  6. Electronic Structure Basis for the Extraordinary Magnetoresistance in WTe2

    Science.gov (United States)

    Pletikosić, I.; Ali, Mazhar N.; Fedorov, A. V.; Cava, R. J.; Valla, T.

    2014-11-01

    The electronic structure basis of the extremely large magnetoresistance in layered nonmagnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at low temperatures, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. A change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior of the magnetoresistance in WTe2 was identified.

  7. Magnetoresistance hysteresis in granular HTSCs as a manifestation of the magnetic flux trapped by superconducting grains in YBCO + CuO composites

    International Nuclear Information System (INIS)

    Hysterestic behavior of the magnetoresistance of granular HTSCs and its interaction with the magnetic hysteresis are studied by measuring magnetoresistance R(H) and critical current Ic(H) of composites formed by HTSC Y0.75Lu0.25Ba2Cu3O7 and CuO. A network of Josephson junctions is formed in such composites, in which the nonsuperconducting component plays the role of barriers between HTSC grains. Hysteretic dependences R(H) of magnetoresistance are studied in a wide range of transport current density j and are analyzed in the framework of the two-level model of a granular superconductor, in which dissipation takes place in the Josephson medium and the magnetic flux can be pinned both in grains and in the Josephson medium. The interrelation between the hysteresis of critical current Ic(H) and the evolution of the hysterestic dependence R(H) of the magnetoresistance upon transport current variation is demonstrated experimentally. The effect of the magnetic past history on the hysteretic behavior of R(H) and the emergence of a segment with a negative magnetoresistance are analyzed. It is shown for the first time that the R(H) dependences are characterized by a parameter that is independent of the transport current, viz., the width of the R(H) hysteresis loop

  8. Angular dependence of critical current density and n-values in BaZrO3/YBa2Cu3Oy quasi-multilayered films with columnar defects

    International Nuclear Information System (INIS)

    Highlights: •BZO/YBCO multilayered films were irradiated using 200 MeV Xe ions along c-axis. •Size and spatial distribution of particles were tuned by the growth temperature. •The difference in growth temperatures stand out on the Jc(θ), especially for high B. •A shoulder behaviour occurs on the Jc(θ) in the multilayered films with CDs. •The inverse correlation between Jc and n-value emerges around B||c at high T. -- Abstract: BaZrO3/YBa2Cu3Oy quasi-multilayered films, in which the size and the spatial distribution of BaZrO3 nano-particles were controlled, were irradiated using 200 MeV Xe ions along the c-axis direction. When the BaZrO3 nano-particles were larger in size, the flux lines not captured by CDs, such as interstitial flux lines between CDs and double kinks of flux lines, can be pinned more effectively by the BaZrO3 nano-particles, so that the Jc enhances for high magnetic fields and high temperature. In addition, the inverse correlation between Jc and n-value appears at high temperature in increasing magnetic field for the film with correlated rows of the nano-particles which might be curved off the c-axis. These suggest that the hybrid flux pinning depends not only on the combination of one-dimensional (1D) and three-dimensional pinning centers (3D-PCs) but also on the size and the spatial distribution of the 3D-PCs

  9. Anomalous magnetoresistance in magnetized topological insulator cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Siu, Zhuo Bin, E-mail: a0018876@nus.edu.sg [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, Singapore 117608 (Singapore); Jalil, Mansoor B. A. [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 (Singapore)

    2015-05-07

    The close coupling between the spin and momentum degrees of freedom in topological insulators (TIs) presents the opportunity for the control of one to manipulate the other. The momentum can, for example, be confined on a curved surface and the spin influenced by applying a magnetic field. In this work, we study the surface states of a cylindrical TI magnetized in the x direction perpendicular to the cylindrical axis lying along the z direction. We show that a large magnetization leads to an upwards bending of the energy bands at small |k{sub z}|. The bending leads to an anomalous magnetoresistance where the transmission between two cylinders magnetized in opposite directions is higher than when the cylinders are magnetized at intermediate angles with respect to each other.

  10. Magnetoresistive sensors for surveillance and remote sensing

    Science.gov (United States)

    Dalichaouch, Yacine; Perry, Alexander R.; Whitecotton, Brian W.; Moeller, Charles R.; Czipott, Peter V.

    2001-02-01

    Quantum Magnetics (QM) has developed a sensing array using small and lightweight magnetoresistive (MR) sensors. These sensors, which operate at room temperature with high sensitivity and wide bandwidth, provide new operational performance capabilities. The wide bandwidth makes them ideal for both passive and active detection techniques. Using a DSP-based electronics developed by QM, we have been able to operate these sensors with an unprecedented noise performance at low frequencies. Recent tests using an MR room temperature gradiometer show that its resolution equals that of a fluxgate room-temperature gradiometer we have previously developed. These results represent an important development for both attended and unattended ground sensor applications since MR sensors cost about ten times less than fluxgate sensors.

  11. Evaluation of Magnetoresistive RAM for Space Applications

    Science.gov (United States)

    Heidecker, Jason

    2014-01-01

    Magnetoresistive random-access memory (MRAM) is a non-volatile memory that exploits electronic spin, rather than charge, to store data. Instead of moving charge on and off a floating gate to alter the threshold voltage of a CMOS transistor (creating different bit states), MRAM uses magnetic fields to flip the polarization of a ferromagnetic material thus switching its resistance and bit state. These polarized states are immune to radiation-induced upset, thus making MRAM very attractive for space application. These magnetic memory elements also have infinite data retention and erase/program endurance. Presented here are results of reliability testing of two space-qualified MRAM products from Aeroflex and Honeywell.

  12. Grain Size Effect on Electrical Conductivity and Giant Magnetoresistance of Bulk Magnetic Polycrystals

    Institute of Scientific and Technical Information of China (English)

    LUO Wei; ZHU Lin-Li; ZHENG Xiao-Jing

    2009-01-01

    By solving the Boltzmann transport equation and considering the spin-dependent grain boundary scattering, the distribution of electrons in grains and the electrical transport properties in the applied magnetic field are studied. With regard to the dominant influence of grain boundary scattering which is taken as a boundary condi-tion for the electrical transport, the grain size-dependent electrical conductivity is investigated. In addition, the reorientation of the relative magnetization between grains brings the change of the electron spin when the magne-tonanocrystalline material is subjected to the magnetic field, resulting in the remarkable giant magnetoresistance effect.

  13. Recent Developments of Magnetoresistive Sensors for Industrial Applications.

    Science.gov (United States)

    Jogschies, Lisa; Klaas, Daniel; Kruppe, Rahel; Rittinger, Johannes; Taptimthong, Piriya; Wienecke, Anja; Rissing, Lutz; Wurz, Marc Christopher

    2015-11-12

    The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling).

  14. Facilities of management magnetoresistive transformer of active power

    Directory of Open Access Journals (Sweden)

    Val. S. Vuntesmeri

    2009-03-01

    Full Text Available Management facilities are considered, spectral composition is certain and the form of коммутируемого signal of magnetoresistive transformer of active power is rotined.

  15. Metamaterial Broadband Angular Selectivity

    CERN Document Server

    Shen, Yichen; Wang, Zhiyu; Wang, Li; Celanovic, Ivan; Ran, Lixin; Joannopoulos, John D; Soljacic, Marin

    2014-01-01

    We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each effective anisotropic layer is constructed from a multilayered metamaterial. We show that by simply changing the structure of the metamaterials, the selective angle can be tuned to a broad range of angles; and, by increasing the number of stacks, the angular transmission window can be made as narrow as desired. As a proof of principle, we realize the idea experimentally in the microwave regime. The angular selectivity and tunability we report here can have various applications such as in directional control of electromagnetic emitters and detectors.

  16. Fluidic angular velocity sensor

    Science.gov (United States)

    Berdahl, C. M. (Inventor)

    1986-01-01

    A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.

  17. Quantum conductance in electrodeposited nanocontacts and magnetoresistance measurements

    DEFF Research Database (Denmark)

    Elhoussine, F.; Encinas, A.; Mátéfi-Tempfli, Stefan;

    2003-01-01

    The conductance and magnetoresistance measurements in magnetic Ni-Ni and Co-Ni nanocontacts prepared by electrodeposition within the pores of a track of track-etched polymer membrane were discussed. At room temperature, Ni-Ni constrictions were found to show broad quantization plateaus...... of conductance during their dissolution in units of e/h, as expected for ferromagnetic ballistic nanocontacts. The measurement of the positive and negative magnetoresistance in Co-Ni nanocontacts was also elaborated....

  18. Angular Scaling In Jets

    Energy Technology Data Exchange (ETDEWEB)

    Jankowiak, Martin; Larkoski, Andrew J.; /SLAC

    2012-02-17

    We introduce a jet shape observable defined for an ensemble of jets in terms of two-particle angular correlations and a resolution parameter R. This quantity is infrared and collinear safe and can be interpreted as a scaling exponent for the angular distribution of mass inside the jet. For small R it is close to the value 2 as a consequence of the approximately scale invariant QCD dynamics. For large R it is sensitive to non-perturbative effects. We describe the use of this correlation function for tests of QCD, for studying underlying event and pile-up effects, and for tuning Monte Carlo event generators.

  19. Average Angular Velocity

    CERN Document Server

    Essén, H

    2003-01-01

    This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to three parts: center of mass, rotational, plus the remaining internal energy relative to an optimally translating and rotating frame.

  20. Dirac Green function for angular projection potentials

    Science.gov (United States)

    Zeller, Rudolf

    2015-11-01

    The aim of this paper is twofold: first, it is shown that the angular dependence of the Dirac Green function can be described analytically for potentials with non-local dependence on the angular variables if they are chosen as projection potentials in angular momentum space. Because the local dependence on the radial variable can be treated to any precision with present computing capabilities, this means that the Green function can be calculated practically exactly. Second, it is shown that a result of this kind not only holds for a single angular projection potential but also more generally, for instance if space is divided into non-overlapping cells and a separate angular projection potential is used in each cell. This opens the way for relativistic density-functional calculations within a different perspective than the conventional one. Instead of trying to obtain the density for a given potential approximately as well as possible, the density is determined exactly for non-local potentials which can approximate arbitrary local potentials as well as desired.

  1. Large, non-saturating magnetoresistance in WTe2

    Science.gov (United States)

    Ali, Mazhar N.; Xiong, Jun; Flynn, Steven; Tao, Jing; Gibson, Quinn D.; Schoop, Leslie M.; Liang, Tian; Haldolaarachchige, Neel; Hirschberger, Max; Ong, N. P.; Cava, R. J.

    2014-10-01

    Magnetoresistance is the change in a material's electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors, in magnetic memory, and in hard drives at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity.

  2. Induced Angular Momentum

    Science.gov (United States)

    Parker, G. W.

    1978-01-01

    Discusses, classically and quantum mechanically, the angular momentum induced in the bound motion of an electron by an external magnetic field. Calculates the current density and its magnetic moment, and then uses two methods to solve the first-order perturbation theory equation for the required eigenfunction. (Author/GA)

  3. A new theory of doped manganites exhibiting colossal magnetoresistance

    Indian Academy of Sciences (India)

    H R Krishnamurthy

    2005-06-01

    Rare earth manganites doped with alkaline earths, namely Re1-AMnO3, exhibit colossal magnetoresistance, metal insulator transitions, competing magnetic, orbital and charge ordering, and many other interesting but poorly understood phenomena. In this article I outline our recent theory based on the idea that in the presence of strong Jahn–Teller, Coulomb and Hund’s couplings present in these materials, the low-energy electronic states dynamically reorganize themselves into two sets: one set (ℓ) which are polaronic, i.e., localized and accompanied by large local lattice distortion, and another (b) which are non-polaronic and band-like. The coexistence of the radically different ℓ and states, and the sensitive dependence of their relative energies and occupation upon doping , temperature , magnetic field , etc., underlies the unique effects seen in manganites. I present results from strong correlation calculations using dynamical mean-field theory and simulations on a new 2-fluid model which accord with a variety of observations.

  4. Gilbert damping and anisotropic magnetoresistance in iron-based alloys

    Science.gov (United States)

    Berger, L.

    2016-07-01

    We use the two-current model of Campbell and Fert to understand the compositional dependence of the Gilbert damping parameter in certain iron alloys. In that model, spin-up and spin-down carriers have different resistivities ρ↑ and ρ↓. We emphasize the part of the Gilbert parameter, called Gsf, generated by spin-flip interband processes. Both Gsf and the anisotropic magnetoresistance Δρ are proportional to the square of the spin-orbit parameter, and also proportional to ρ↑. In bcc alloys of iron with V, Cr, Mo, etc. solutes on the left of iron in the periodic table, ρ↑ is increased by a scattering resonance (Gomes and Campbell, 1966, 1968). Then ρ↑, Δρ, and Gsf all exhibit a peak at the same moderate concentration of the solute. We find the best fit between this theory and existing experimental data of Gilbert damping for Fe-V epitaxial films at room temperature (Cheng, 2006; Scheck et al., 2007). At room temperature, the predicted Gsf peak is masked by a background arising from non-flip intraband processes. At elevated temperatures, the peak is expected to become more prominent, and less hidden in the background.

  5. Tunnel magnetoresistance in Self-Assembled Monolayers Based Tunnel Junctions

    Science.gov (United States)

    Mattana, Richard; Barraud, Clément; Tatay, Sergio; Galbiati, Marta; Seneor, Pierre; Bouzehouane, Karim; Jacquet, Eric; Deranlot, Cyrile; Fert, Albert; Petroff, Frédéric

    2012-02-01

    Organic/molecular spintronics is a rising research field at the frontier between spintronics and organic chemistry. Organic molecule and semiconductors were first seen as promising for spintronics devices due to their expected long spin lifetime. But an exciting challenge has also been to find opportunities arising from chemistry to develop new spintronics functionalities. It was shown that the molecular structure and the ferromagnetic metal/molecule hybridization can strongly influence interfacial spin properties going from spin polarization enhancement to its sign control in spintronics devices. In this scenario, while scarcely studied, self-assembled monolayers (SAMs) are expected to become perfect toy barriers to further test these tailoring properties in molecular magnetic tunnel junctions (MTJs). Due to its very high spin polarization and air stability LSMO has positioned itself as the electrode of choice in most of the organic spintronics devices. We will present a missing building block for molecular spintronics tailoring: the grafting and film characterization of organic monofunctionalized long alkane chains over LSMO. We have obtained 35% of magnetoresistance in LSMO/SAMs/Co MTJs. We will discuss the unusual behaviour of the bias voltage dependence of the TMR.

  6. Three-dimensional Anisotropy and Kohler's Rule Scaling of the Magnetoresistance in WTe2

    Science.gov (United States)

    Wang, Yong-Lei

    Tungsten ditelluride (WTe2) was recently discovered to have extremely large magnetoresistance (XMR) at low temperatures and exhibits a transformative 'turn-on' temperature behavior: when the applied magnetic field H is above a certain value, the resistivity versus temperature ρ (T) curve shows a minimum at a field dependent temperature T* (H) . Since WTe2 is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, it is typically considered to be a two dimensional (2D) material, whereby the anisotropic magnetoresistance is attributed only to the perpendicular component of the magnetic field. Moreover, the 'turn-on' temperature behavior has been interpreted as a magnetic-field-driven metal-insulator transition or attributed to an electronic structure change. In this talk I will report on two scaling behaviors of the magnetoresistance in WTe2. The first shows that the angle dependence of the magnetoresistance follows a conventional 3D anisotropy scaling and hence reveals the electrical 3D nature of WTe2. The second demonstrates that the ρ (T , H) curves, including those with 'turn-on' temperature behavior, can be scaled with Kohler's rule. The observed Kohler's rule scaling excludes the possible existence of a magnetic-field-driven metal-insulator transition or significant contribution of an electronic structure change to the low-temperature XMR in WTe2. It indicates that both the XMR and the 'turn-on' behavior originate from the high mobilities of the charge carriers, which are strongly temperature dependent in WTe2. We also derived quantitative expressions for the magnetic field dependence of the 'turn-on' temperature T* (H) and for the temperature dependence of the resistivity ρ (T* , H) at the onset of the XMR behavior. In collaboration with L. R. Thoutam, Z. L. Xiao, J. Hu, S. Das, Z. Q. Mao, J. Wei, R. Divan, A. Luican-Mayer, G. W. Crabtree, and W. K. Kwok This work was supported by the U.S. DOE, Office of Science, BES

  7. Anisotropic Magnetoresistance and Anisotropic Tunneling Magnetoresistance due to Quantum Interference in Ferromagnetic Metal Break Junctions

    DEFF Research Database (Denmark)

    Bolotin, Kirill; Kuemmeth, Ferdinand; Ralph, D

    2006-01-01

    We measure the low-temperature resistance of permalloy break junctions as a function of contact size and the magnetic field angle in applied fields large enough to saturate the magnetization. For both nanometer-scale metallic contacts and tunneling devices we observe large changes in resistance...... with the angle, as large as 25% in the tunneling regime. The pattern of magnetoresistance is sensitive to changes in bias on a scale of a few mV. We interpret the effect as a consequence of conductance fluctuations due to quantum interference....

  8. Magnetic behavior of Eu(3)Ni(4)Ga(4): antiferromagnetic order and large magnetoresistance.

    Science.gov (United States)

    Anupam; Geibel, C; Hossain, Z

    2012-08-15

    The results of the magnetic susceptibility, isothermal magnetization, heat capacity, electrical resistivity and magnetoresistance measurements on polycrystalline Eu(3)Ni(4)Ga(4) are presented. Eu(3)Ni(4)Ga(4) forms in Na(3)Pt(4)Ge(4)-type cubic crystal structure (space group [Formula: see text]). The temperature dependence of the magnetic susceptibility of Eu(3)Ni(4)Ga(4) confirms the divalent state (Eu(2+)) of Eu ions with an effective magnetic moment μ(eff) = 7.98 μ(B). At low fields, e.g. at 0.01 T, a magnetic phase transition to an antiferromagnetically ordered state occurs at T(N) = 10.9 K, which is further confirmed by the temperature dependence of the heat capacity and electrical resistivity. The field dependence of isothermal magnetization at 2 K reveals the presence of two field induced metamagnetic transitions at H(c1) and H(c2) = 0.55 and 1.2 T, respectively and a polarized phase above H(PO) = 1.7 T. The reduced jump in the heat capacity at the transition temperature, ΔC|(T(N)) = 13.48 J/mol-Eu K would indicate an amplitude modulated (AM) antiferromagnetic structure. An interesting feature is that a large negative magnetoresistance, MR = [ρ(H) - ρ(0)]/ρ(0), is observed in the vicinity of magnetic transition even up to 2T(N). Similar large magnetoresistance has been observed in the paramagnetic state in some Gd and Eu based alloys and has been attributed to the magneto-polaronic effect. PMID:22785157

  9. Magnetic behavior of Eu3Ni4Ga4: antiferromagnetic order and large magnetoresistance

    International Nuclear Information System (INIS)

    The results of the magnetic susceptibility, isothermal magnetization, heat capacity, electrical resistivity and magnetoresistance measurements on polycrystalline Eu3Ni4Ga4 are presented. Eu3Ni4Ga4 forms in Na3Pt4Ge4-type cubic crystal structure (space group I 4-bar 3 m). The temperature dependence of the magnetic susceptibility of Eu3Ni4Ga4 confirms the divalent state (Eu2+) of Eu ions with an effective magnetic moment μeff = 7.98 μB. At low fields, e.g. at 0.01 T, a magnetic phase transition to an antiferromagnetically ordered state occurs at TN 10.9 K, which is further confirmed by the temperature dependence of the heat capacity and electrical resistivity. The field dependence of isothermal magnetization at 2 K reveals the presence of two field induced metamagnetic transitions at Hc1 and Hc2 = 0.55 and 1.2 T, respectively and a polarized phase above HPO = 1.7 T. The reduced jump in the heat capacity at the transition temperature, ΔC|TN = 13.48 J/mol-Eu K would indicate an amplitude modulated (AM) antiferromagnetic structure. An interesting feature is that a large negative magnetoresistance, MR = [ρ(H) - ρ(0)]/ρ(0), is observed in the vicinity of magnetic transition even up to 2TN. Similar large magnetoresistance has been observed in the paramagnetic state in some Gd and Eu based alloys and has been attributed to the magneto-polaronic effect. (paper)

  10. Wigner Functions and Quark Orbital Angular Momentum

    Directory of Open Access Journals (Sweden)

    Mukherjee Asmita

    2015-01-01

    Full Text Available Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs and transverse momentum dependent parton distributions (TMDs. We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.

  11. Wigner Functions and Quark Orbital Angular Momentum

    OpenAIRE

    Mukherjee Asmita; Nair Sreeraj; Ojha Vikash Kumar

    2014-01-01

    Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.

  12. The effect of door states on the magnetoresistance of a single-molecule electric revolving door-based spintronic device

    Science.gov (United States)

    Zeng, Jing; Fan, Zhi-Qiang

    2015-08-01

    By applying nonequilibrium Green’s functions in combination with density-function theory, the spin-dependent transport properties of a single-molecule electric revolving door-based spintronic device are investigated. The computational results show that magnetoresistance ratios are strongly dependent on the door states of the single-molecule electric revolving door. Under the application of a gate electric field, the single-molecule electric revolving door can be changed from the closed-door state to the open-door state, and thus the maximum magnetoresistance ratio of the corresponding spintronic device at finite bias can be improved from about 77% to about 4 × 104%. Therefore, the single-molecule electric revolving door will provide the possibilities for designing the high-performance single-molecule spin-valve device.

  13. Sources of negative tunneling magnetoresistance in multilevel quantum dots with ferromagnetic contacts

    DEFF Research Database (Denmark)

    Koller, Sonja; Grifoni, Milena; Paaske, Jens

    2012-01-01

    a diagrammatic representation of our transport theory. The theory is valid for multilevel quantum dot systems and we exemplarily apply it to carbon nanotube quantum dots, where we show that the presence of many levels, among them of excited states, can qualitatively influence the TMR effect.......We analyze distinct sources of spin-dependent energy level shifts and their impact on the tunneling magnetoresistance (TMR) of interacting quantum dots coupled to collinearly polarized ferromagnetic leads. Level shifts due to virtual charge fluctuations can be quantitatively evaluated within...

  14. Magnetoresistance of a spin MOSFET with ferromagnetic MnAs source and drain contacts

    OpenAIRE

    Nakane, Ryosho; Harada, Tomoyuki; Sugiura, Kuniaki; Sugahara, Satoshi; Tanaka, Masaaki

    2010-01-01

    Spin-dependent transport was investigated in a spin metal-oxide-semiconductor field-effect transistors (spin MOSFET) with ferromagnetic MnAs source and drain (S/D) contacts. The spin MOSFET of bottom-gate type was fabricated by photolithography using an epitaxial MnAs film grown on a silicon-on-insulator (SOI) substrate. In-plane magnetoresistance showed spin-valve-type hysteretic behavior, when the measurements were performed with constant source-drain and source-gate biases. By comparing wi...

  15. Tunneling Anisotropic Magnetoresistance in Co/AlOx/Au Tunnel Junctions

    CERN Document Server

    Liu, R S; Canali, C M; Samuelson, L; Pettersson, H

    2008-01-01

    We observe spin-valve-like effects in nano-scaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer.

  16. Tunneling anisotropic magnetoresistance in Co/AlOx/Au tunnel junctions.

    Science.gov (United States)

    Liu, R S; Michalak, L; Canali, C M; Samuelson, L; Pettersson, H

    2008-03-01

    We observe spin-valve-like effects in nanoscaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer. PMID:18254603

  17. Voltage polarity manipulation of the magnetoresistance sign in organic spin valve devices

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, S. W.; Chen, B. B.; Wang, P.; Zhou, Y.; Shi, Y. J.; Yue, F. J.; Ding, H. F.; Wu, D., E-mail: dwu@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)

    2014-06-30

    The spin transport in organic spin valve (OSV) devices has been systematically investigated by inserting a low work function material Al between ferromagnetic electrode and organic layer. The resistance and current-voltage curve symmetry are dramatically altered as increasing Al thickness, indicating that an electron-unipolar OSV is obtained. Moreover, the magnetoresistance sign depends on the voltage polarity for certain Al thickness. We attribute this phenomenon to the Fermi and the lowest unoccupied molecular orbits energies of the two electrodes responding to the spin injection and detection, respectively. These findings provide a simple approach to control both the carrier type and the spin direction simultaneously.

  18. Magnetoresistance of ZnO:Co Thin Films at Low Temperatures

    Science.gov (United States)

    Kytin, V. G.; Maximova, O. V.; Kulbachinskii, V. A.; Muftieva, D. A.; Burova, L. I.; Kaul, A. R.

    2016-03-01

    Large positive magnetoresistance was observed in Co-doped thin ZnO films at low temperatures and analyzed in the frame of the model based on the exchange interaction between the conduction electrons and the electrons of a magnetic impurity for the films with temperature dependence of resistivity described by Mott's law. Estimates of the localization length of electronic states participating in hopping conduction were obtained. The obtained values of the localization length are close to the effective Bohr radii of shallow donors in ZnO.

  19. Quantum Heuristics of Angular Momentum

    Science.gov (United States)

    Levy-Leblond, Jean-Marc

    1976-01-01

    Discusses the quantization of angular momentum components, Heisenberg-type inequalities for their spectral dispersions, and the quantization of the angular momentum modulus, without using operators or commutation relations. (MLH)

  20. Transport properties of colossal magnetoresistive materials

    CERN Document Server

    Yates, K A

    2002-01-01

    A microwave technique was developed in order to test the validity of the hypothesis that the microwave transport of polycrystalline, optimally doped, colossal magnetoresistive materials was dominated by intragranular material. The microwave surface resistance at 9GHz was compared with dc resistivity and magnetisation to study the influence of yttrium doping on the grain boundary regions of bulk polycrystalline samples of La sub 0 sub . sub 7 sub - sub x Y sub x Ca sub 0 sub . sub 3 MnO sub 3. It was found that, within the grains, the addition of yttrium causes the activation energy above T sub p to increase. A phenomenological model was introduced to explain the data in terms of the difference in structure between the grain and grain boundary regions. The technique was also used to study the influence of deoxygenation on the grain boundary regions of bulk, polycrystalline, La sub 0 sub . sub 6 sub 7 Ca sub 0 sub . sub 3 sub 3 MnO sub 3. For samples interconnected porosity, low temperature (600 deg C), short a...

  1. Noncontact vibration measurements using magnetoresistive sensing elements

    Science.gov (United States)

    Tomassini, R.; Rossi, G.

    2016-06-01

    Contactless instrumentations is more and more used in turbomachinery testing thanks to the non-intrusive character and the possibility to monitor all the components of the machine at the same time. Performances of blade tip timing (BTT) measurement systems, used for noncontact turbine blade vibration measurements, in terms of uncertainty and resolution are strongly affected by sensor characteristics and processing methods. The sensors used for BTT generate pulses, used for precise measurements of turbine blades time of arrival. Nowadays proximity sensors used in this application are based on optical, capacitive, eddy current and microwave measuring principle. Pressure sensors has been also tried. This paper summarizes the results achieved using a novel instrumentation based on the magnetoresistive sensing elements. The characterization of the novel probe has been already published. The measurement system was validated in test benches and in a real jet-engine comparing different sensor technologies. The whole instrumentation was improved. The work presented in this paper focuses on the current developments. In particular, attention is given to the data processing software and new sensor configurations.

  2. Lateral flow immunoassay using magnetoresistive sensors

    Science.gov (United States)

    Taton, Kristin; Johnson, Diane; Guire, Patrick; Lange, Erik; Tondra, Mark

    2009-05-01

    Magnetic particles have been adapted for use as labels in biochemical lateral flow strip tests. Standard gold particle lateral flow assays are generally qualitative; however, with magnetic particles, quantitative results can be obtained by using electronic detection systems with giant magnetoresistive (GMR) sensors. As described here, these small integrated sensor chips can detect the presence of magnetic labels in capture spots whose volume is approximately 150 μm×150 μm×150 μm. The range of linear detection is better than two orders of magnitude; the total range is up to four orders of magnitude. The system was demonstrated with both indirect and sandwich enzyme-linked immunosorbent assays (ELISAs) for protein detection of rabbit IgG and interferon-γ, respectively, achieving detection of 12 pg/ml protein. Ultimately, the goal is for the detector to be fully integrated into the lateral flow strip backing to form a single consumable item that is interrogated by a handheld electronic reader.

  3. Tunneling magnetoresistance phenomenon utilizing graphene magnet electrode

    International Nuclear Information System (INIS)

    Using magnetic rare-metals for spintronic devices is facing serious problems for the environmental contamination and the limited material-resource. In contrast, by fabricating ferromagnetic graphene nanopore arrays (FGNPAs) consisting of honeycomb-like array of hexagonal nanopores with hydrogen-terminated zigzag-type atomic structure edges, we reported observation of polarized electron spins spontaneously driven from the pore edge states, resulting in rare-metal-free flat-energy-band ferromagnetism. Here, we demonstrate observation of tunneling magnetoresistance (TMR) behaviors on the junction of cobalt/SiO2/FGNPA electrode, serving as a prototype structure for future rare-metal free TMR devices using magnetic graphene electrodes. Gradual change in TMR ratios is observed across zero-magnetic field, arising from specified alignment between pore-edge- and cobalt-spins. The TMR ratios can be controlled by applying back-gate voltage and by modulating interpore distance. Annealing the SiO2/FGNPA junction also drastically enhances TMR ratios up to ∼100%

  4. Tunneling magnetoresistance phenomenon utilizing graphene magnet electrode

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, T.; Kamikawa, S.; Haruyama, J., E-mail: J-haru@ee.aoyama.ac.jp [Faculty of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258 (Japan); Soriano, D. [Institut Català de Nanociència i Nanotecnologia (ICN2), Campus de la UAB, Edifici ICN2, 08193 Bellaterra, Barcelona (Spain); Pedersen, J. G. [Institut Català de Nanociència i Nanotecnologia (ICN2), Campus de la UAB, Edifici ICN2, 08193 Bellaterra, Barcelona (Spain); Department of Micro-and Nanotechnology, DTU Nanotech, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Roche, S. [Institut Català de Nanociència i Nanotecnologia (ICN2), Campus de la UAB, Edifici ICN2, 08193 Bellaterra, Barcelona (Spain); ICREA - Institucio Catalana de Recerca i Estudis Avancats, 08010 Barcelona (Spain)

    2014-11-03

    Using magnetic rare-metals for spintronic devices is facing serious problems for the environmental contamination and the limited material-resource. In contrast, by fabricating ferromagnetic graphene nanopore arrays (FGNPAs) consisting of honeycomb-like array of hexagonal nanopores with hydrogen-terminated zigzag-type atomic structure edges, we reported observation of polarized electron spins spontaneously driven from the pore edge states, resulting in rare-metal-free flat-energy-band ferromagnetism. Here, we demonstrate observation of tunneling magnetoresistance (TMR) behaviors on the junction of cobalt/SiO{sub 2}/FGNPA electrode, serving as a prototype structure for future rare-metal free TMR devices using magnetic graphene electrodes. Gradual change in TMR ratios is observed across zero-magnetic field, arising from specified alignment between pore-edge- and cobalt-spins. The TMR ratios can be controlled by applying back-gate voltage and by modulating interpore distance. Annealing the SiO{sub 2}/FGNPA junction also drastically enhances TMR ratios up to ∼100%.

  5. The influence of interlayer exchange coupling in giant-magnetoresistive devices on spin diode effect in wide frequency range

    International Nuclear Information System (INIS)

    Spin diode effect in a giant magnetoresistive strip is measured in a broad frequency range, including resonance and off-resonance frequencies. The off-resonance dc signal is relatively strong and also significantly dependent on the exchange coupling between magnetic films through the spacer layer. The measured dc signal is described theoretically by taking into account magnetic dynamics induced by Oersted field created by an ac current flowing through the system

  6. On angular momentum transport in convection-dominated accretion flows

    CERN Document Server

    Igumenshchev, I V

    2002-01-01

    Convection-dominated accretion flow (CDAF) is a promising model to explain underluminous accreting black holes in X-ray binaries and galactic nuclei. I discuss effects of angular momentum transport in viscous hydrodynamical and MHD CDAFs. In hydrodynamical CDAFs, convection transports angular momentum inward, and this together with outward convection transport of thermal energy determine the radial structure of the flow. In MHD CDAFs, convection can transport angular momentum either inward or outward, depending on properties of turbulence in rotating magnetized plasma, which are not fully understood yet. Direction of convection angular momentum transport can affect the law of rotation of MHD CDAFs.

  7. Evolution equations for higher moments of angular momentum distributions

    CERN Document Server

    Hägler, P

    1998-01-01

    Based on a sumrule for the nucleon spin we expand quark and gluon orbital angular momentum operators and derive an evolution matrix for higher moments of the corresponding distributions. In combination with the spin-dependent DGLAP-matrix we find a complete set of spin and orbital angular momentum evolution equations.

  8. Superconducting magnetoresistance in ferromagnet/superconductor/ferromagnet trilayers

    Science.gov (United States)

    Stamopoulos, D.; Aristomenopoulou, E.

    2015-08-01

    Magnetoresistance is a multifaceted effect reflecting the diverse transport mechanisms exhibited by different kinds of plain materials and hybrid nanostructures; among other, giant, colossal, and extraordinary magnetoresistance versions exist, with the notation indicative of the intensity. Here we report on the superconducting magnetoresistance observed in ferromagnet/superconductor/ferromagnet trilayers, namely Co/Nb/Co trilayers, subjected to a parallel external magnetic field equal to the coercive field. By manipulating the transverse stray dipolar fields that originate from the out-of-plane magnetic domains of the outer layers that develop at coercivity, we can suppress the supercurrent of the interlayer. We experimentally demonstrate a scaling of the magnetoresistance magnitude that we reproduce with a closed-form phenomenological formula that incorporates relevant macroscopic parameters and microscopic length scales of the superconducting and ferromagnetic structural units. The generic approach introduced here can be used to design novel cryogenic devices that completely switch the supercurrent ‘on’ and ‘off’, thus exhibiting the ultimate magnetoresistance magnitude 100% on a regular basis.

  9. Superconducting magnetoresistance in ferromagnet/superconductor/ferromagnet trilayers.

    Science.gov (United States)

    Stamopoulos, D; Aristomenopoulou, E

    2015-01-01

    Magnetoresistance is a multifaceted effect reflecting the diverse transport mechanisms exhibited by different kinds of plain materials and hybrid nanostructures; among other, giant, colossal, and extraordinary magnetoresistance versions exist, with the notation indicative of the intensity. Here we report on the superconducting magnetoresistance observed in ferromagnet/superconductor/ferromagnet trilayers, namely Co/Nb/Co trilayers, subjected to a parallel external magnetic field equal to the coercive field. By manipulating the transverse stray dipolar fields that originate from the out-of-plane magnetic domains of the outer layers that develop at coercivity, we can suppress the supercurrent of the interlayer. We experimentally demonstrate a scaling of the magnetoresistance magnitude that we reproduce with a closed-form phenomenological formula that incorporates relevant macroscopic parameters and microscopic length scales of the superconducting and ferromagnetic structural units. The generic approach introduced here can be used to design novel cryogenic devices that completely switch the supercurrent 'on' and 'off', thus exhibiting the ultimate magnetoresistance magnitude 100% on a regular basis.

  10. Creating high-harmonic beams with controlled orbital angular momentum.

    Science.gov (United States)

    Gariepy, Genevieve; Leach, Jonathan; Kim, Kyung Taec; Hammond, T J; Frumker, E; Boyd, Robert W; Corkum, P B

    2014-10-10

    A beam with an angular-dependant phase Φ = ℓϕ about the beam axis carries an orbital angular momentum of ℓℏ per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |ℓ| = 1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.

  11. Enhanced magnetoresistance in half-metallic CrO2–TiO2 composites

    International Nuclear Information System (INIS)

    CrO2–TiO2 composites were synthesized by a high temperature and high pressure method (HTHP). The CrO2–TiO2 composites are composed of large rod-like CrO2 crystals separated by TiO2 nanoparticles. The saturation magnetization of the CrO2 in the composites is very close to the theoretical value. The CrO2–TiO2 composites show greatly enhanced magnetoresistance than that of pure CrO2. This is mainly attributed to spin-dependent tunneling between adjacent CrO2 grains enhanced by the addition of TiO2. The tunneling mechanism in the composites can be best described by the fluctuation-induced tunneling model as convinced by the temperature dependence of the conductivity of the CrO2–TiO2 composites at low temperature. - Highlights: ► CrO2–TiO2 composites consist of large rod-like CrO2 crystals and TiO2 nanoparticles. ► The composites show enhanced magnetoresistance than that of pure CrO2. ► TiO2 in composites acts as grain boundary barrier for spin-dependent tunneling. ► The tunneling mechanism is best described by fluctuation-induced tunneling model

  12. Angular Distribution and Angular Dispersion in Collision of 19F+27A1 at 114 MeV

    Institute of Scientific and Technical Information of China (English)

    WANG Qi; Li Zhi-Chang; LU Xiu-Qin; ZHAO Kui; LIU Jian-Cheng; SERGEY Yu-Kun; DONG Yu-Chuan; LI Song-Lin; DUAN Li-Min; XU Hu-Shan; XU Hua-Gen; CHEN Ruo-Fu; WU He-Yu; HAN Jian-Long

    2004-01-01

    Angular distributions of fragments B, C, N, O, F, Ne, Na, Mg and Al induced by the collision of 19F+27 A1 at 114MeV have been measured. Angular dispersion parameters are extracted from the experimental data and compared with the theoretical ones. The dynamic dispersions for dissipative products depend strongly on the charge number Z of the fragments.

  13. An orbital angular momentum spectrometer for electrons

    Science.gov (United States)

    Harvey, Tyler; Grillo, Vincenzo; McMorran, Benjamin

    2016-05-01

    With the advent of techniques for preparation of free-electron and neutron orbital angular momentum (OAM) states, a basic follow-up question emerges: how do we measure the orbital angular momentum state distribution in matter waves? Control of both the energy and helicity of light has produced a range of spectroscopic applications, including molecular fingerprinting and magnetization mapping. Realization of an analogous dual energy-OAM spectroscopy with matter waves demands control of both initial and final energy and orbital angular momentum states: unlike for photons, final state post-selection is necessary for particles that cannot be annihilated. We propose a magnetic field-based mechanism for quantum non-demolition measurement of electron OAM. We show that OAM-dependent lensing is produced by an operator of form U =exp iLzρ2/ℏb2 where ρ =√{x2 +y2 } is the radial position operator, Lz is the orbital angular momentum operator along z, and b is the OAM dispersion length. We can physically realize this operator as a term in the time evolution of an electron in magnetic round lens. We discuss prospects and practical challenges for implementation of a lensing orbital angular momentum measurement. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under the Early Career Research Program Award # DE-SC0010466.

  14. Anomalous electronic structure and magnetoresistance in TaAs2.

    Science.gov (United States)

    Luo, Yongkang; McDonald, R D; Rosa, P F S; Scott, B; Wakeham, N; Ghimire, N J; Bauer, E D; Thompson, J D; Ronning, F

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  15. Quark Orbital Angular Momentum

    Science.gov (United States)

    Burkardt, Matthias

    2016-06-01

    Generalized parton distributions provide information on the distribution of quarks in impact parameter space. For transversely polarized nucleons, these impact parameter distributions are transversely distorted and this deviation from axial symmetry leads on average to a net transverse force from the spectators on the active quark in a DIS experiment. This force when acting along the whole trajectory of the active quark leads to transverse single-spin asymmetries. For a longitudinally polarized nucleon target, the transverse force implies a torque acting on the quark orbital angular momentum (OAM). The resulting change in OAM as the quark leaves the target equals the difference between the Jaffe-Manohar and Ji OAMs.

  16. AngularJS directives

    CERN Document Server

    Vanston, Alex

    2013-01-01

    This book uses a practical, step-by-step approach, starting with how to build directives from the ground up before moving on to creating web applications comprised of multiple modules all working together to provide the best user experience possible.This book is intended for intermediate JavaScript developers who are looking to enhance their understanding of single-page web application development with a focus on AngularJS and the JavaScript MVC frameworks.It is expected that readers will understand basic JavaScript patterns and idioms and can recognize JSON formatted data.

  17. Magnetoresistance of Mn-decorated topological line defects in graphene

    KAUST Repository

    Obodo, Tobechukwu Joshua

    2015-01-13

    We study the spin polarized transport through Mn-decorated 8-5-5-8 topological line defects in graphene using the nonequilibrium Green\\'s function formalism. Strong preferential bonding overcomes the high mobility of transition metal atoms on graphene and results in stable structures. Despite a large distance between the magnetic centers, we find a high magnetoresistance and attribute this unexpected property to very strong induced π magnetism, in particular for full coverage of all octagonal hollow sites by Mn atoms. In contrast to the magnetoresistance of graphene nanoribbon edges, the proposed system is well controlled and therefore suitable for applications.

  18. Magnetoresistance of nanosized magnetic configurations in single nanowires

    Science.gov (United States)

    Wegrowe, J.-E.; Gilbert, S.; Doudin, B.; Ansermet, J.-Ph.

    1998-03-01

    The problem of studying spin configurations at nanoscopic level is that magnetic measurements at this scale cannot be performed using usual magnetometers. We have shown that anisotropic magnetoresistance (AMR) measured with micro-contacts allows spin configurations of a single nanowire to be studied in details. The nanowires are diameter 50 nm and length 6000 nm and are produced by a combination of electrodeposition in track-etched membrane templates and sputtering technics. Magnetoresistance of well-defined spin configurations in single nanowires, like Curling magnetization reversal modes or domain wall, are measured.

  19. Negative and nonlinear magnetoresistance effect in silicon strip

    CERN Document Server

    Wang, Fangcong; Guo, Hui; Fan, Xiaolong; Li, Zhankui

    2016-01-01

    Both negative magnetoresistance and nonlinear magnetoresisitance were observed in silicon strip nuclear radiation detector in room temperature if we applied high magnetic field intensity in different direction. This result is different with former report. We believe this is the result of coaction of high electric field (Gunn effect) and high magnetic field, or because of the variation of number of carriers and the carriers mobility. The weak localization and Landau energy levels also affect the magnetoresistance. Different crystal orientations have different energy band structures. Complex band structures lead complex carriers mobility plus Landau energy levels. So the magnetoresisitance effect is anisotropy.

  20. High Magnetic Field Study on Giant Negative Magnetoresistance in the Molecular Conductor TPP[Cr(Pc)(CN)2]2

    Science.gov (United States)

    Ikeda, Mitsuo; Kida, Takanori; Tahara, Time; Murakawa, Hiroshi; Nishi, Miki; Matsuda, Masaki; Hagiwara, Masayuki; Inabe, Tamotsu; Hanasaki, Noriaki

    2016-06-01

    We investigated the magnetic and transport properties of the phthalocyanine molecular conductor TPP[Cr(Pc)(CN)2]2 in magnetic fields of up to 54 T. We observed giant negative magnetoresistance which hardly depends on the magnetic field direction owing to the isotropic nature confirmed by electron spin resonance measurements. The magnitude of magnetoresistance [|ρ(μ0H)/ρ(0 T) - 1|] is proportional to the square of magnetization as observed in the case of the spin scattering process, while the proportionality coefficient increases with decreasing the temperature. The magnetization does not saturate even at 53 T, indicating the existence of the large antiferromagnetic exchange interactions between the localized spins. In spite of this antiferromagnetic exchange interaction and low dimensionality, a convex magnetization curve was observed in the low temperature and high magnetic field range. To reproduce this magnetization curve, we proposed a model taking into account the antiferromagnetic exchange interaction between the neighboring π-electron spins.

  1. Fully band-resolved scattering rate in MgB2 revealed by the nonlinear hall effect and magnetoresistance measurements.

    Science.gov (United States)

    Yang, Huan; Liu, Yi; Zhuang, Chenggang; Shi, Junren; Yao, Yugui; Massidda, Sandro; Monni, Marco; Jia, Ying; Xi, Xiaoxing; Li, Qi; Liu, Zi-Kui; Feng, Qingrong; Wen, Hai-Hu

    2008-08-01

    We have measured the normal state temperature dependence of the Hall effect and magnetoresistance in epitaxial MgB2 thin films with variable disorders characterized by the residual resistance ratio RRR ranging from 4.0 to 33.3. A strong nonlinearity of the Hall effect and magnetoresistance have been found in clean samples, and they decrease gradually with the increase of disorders or temperature. By fitting the data to the theoretical model based on the Boltzmann equation and ab initio calculations for a four-band system, for the first time, we derived the scattering rates of these four bands at different temperatures and magnitude of disorders. Our method provides a unique way to derive these important parameters in multiband systems.

  2. Local magnetoresistance in Fe/MgO/Si lateral spin valve at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Tomoyuki, E-mail: tomosasa@jp.tdk.com; Koike, Hayato; Oikawa, Tohru [Advanced Technology Development Center, TDK Corporation, Chiba (Japan); Suzuki, Toshio [AIT, Akita Industrial Technology Center, Akita (Japan); Ando, Yuichiro; Suzuki, Yoshishige [Graduate School of Engineering Science, Osaka University, Toyonaka (Japan); Shiraishi, Masashi [Graduate School of Engineering Science, Osaka University, Toyonaka (Japan); Department of Electronic Science and Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8530 (Japan)

    2014-02-03

    Room temperature local magnetoresistance in two-terminal scheme is reported. By employing 1.6 nm-thick MgO tunnel barrier, spin injection efficiency is increased, resulting in large non-local magnetoresistance. The magnitude of the non-local magnetoresistance is estimated to be 0.0057 Ω at room temperature. As a result, a clear rectangle signal is observed in local magnetoresistance measurement even at room temperature. We also investigate the origin of local magnetoresistance by measuring the spin accumulation voltage of each contact separately.

  3. Current-Perpendicular-to-Plane Magnetoresistance in Chemical Vapor Deposition-Grown Multilayer Graphene

    Directory of Open Access Journals (Sweden)

    Sandipan Pramanik

    2013-09-01

    Full Text Available Current-perpendicular-to-plane (CPP magnetoresistance (MR effects are often exploited in various state-of-the-art magnetic field sensing and data storage technologies. Most of the CPP-MR devices are artificial layered structures of ferromagnets and non-magnets, and in these devices, MR manifests, due to spin-dependent carrier transmission through the constituent layers. In this work, we explore another class of artificial layered structure in which multilayer graphene (MLG is grown on a metallic substrate by chemical vapor deposition (CVD. We show that depending on the nature of the graphene-metal interaction, these devices can also exhibit large CPP-MR. Magnetoresistance ratios (>100% are at least two orders of magnitude higher than “transferred” graphene and graphitic samples reported in the literature, for a comparable temperature and magnetic field range. This effect is unrelated to spin injection and transport and is not adequately described by any of the MR mechanisms known to date. The simple fabrication process, large magnitude of the MR and its persistence at room temperature make this system an attractive candidate for magnetic field sensing and data storage applications and, also, underscore the need for further fundamental investigations on graphene-metal interactions.

  4. Resistivity plateau and extreme magnetoresistance in LaSb

    Science.gov (United States)

    Tafti, F. F.; Gibson, Q. D.; Kushwaha, S. K.; Haldolaarachchige, N.; Cava, R. J.

    2016-03-01

    Time reversal symmetry (TRS) protects the metallic surface modes of topological insulators (TIs). The transport signature of such surface states is a plateau that arrests the exponential divergence of the insulating bulk with decreasing temperature. This universal behaviour is observed in all TI candidates ranging from Bi2Te2Se to SmB6. Recently, extreme magnetoresistance (XMR) has been reported in several topological semimetals which exhibit TI universal resistivity behaviour only when breaking time reversal symmetry, a regime where TIs theoretically cease to exist. Among these materials, TaAs and NbP are nominated as Weyl semimetals owing to their lack of inversion symmetry, Cd3As2 is known as a Dirac semimetal owing to its linear band crossing at the Fermi level, and WTe2 is termed a resonant compensated semimetal owing to its perfect electron-hole symmetry. Here we introduce LaSb, a simple rock-salt structure material that lacks broken inversion symmetry, perfect linear band crossing, and perfect electron-hole symmetry yet exhibits all the exotic field-induced behaviours of these more complex semimetals. It shows a field-induced universal TI resistivity with a plateau at roughly 15 K, ultrahigh mobility of carriers in the plateau region, quantum oscillations with the angle dependence of a two-dimensional Fermi surface, and XMR of about one million percent at 9 T. Owing to its structural simplicity, LaSb represents an ideal model system to formulate a theoretical understanding of the exotic consequences of breaking time reversal symmetry in topological semimetals.

  5. Asymmetry in the angular distributions of spectator-nucleons

    International Nuclear Information System (INIS)

    The asymmetry in the angular distributions of spectator-nucleons has been studied in dp interactions, and it has been found that the sign of the asymmetry depends on the reaction channel. It is shown that in the momentum interval 0-200 MeV/c of spectators basic features of the angular distributions can be reproduced in the framework of the spectator model taking into account the energy dependence of the NN cross section and the flux-factor

  6. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.

    2011-08-24

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  7. Linear magneto-resistance in Bi2SeTe2 topological insulator

    Science.gov (United States)

    Amaladass, E. P.; Sharma, Shilpam; Devidas, T. R.; Mani, Awadhesh

    2016-05-01

    Magnetic field and temperature dependent electronic transport measurements have been carried out on Bi2SeTe2 topological insulator single crystals. The measurements reveal an insulating behavior and the carriers were found to be electrons (n-type) from Hall measurement. Magneto-resistance (MR) measurements in the field range (B) of 15 T to -15 T carried out at 4.2 K showed a cusp like weak anti-localization behavior for lower fields (-5T 5T. Upon increasing temperature, MR transforms to linear dependence of B at 40, 50 and 100 K. On further increasing temperatures (> 200K), a parabolic MR is observed. Temperature dependent Hall data also showed a transition from a nonlinear to linear behavior upon increasing temperatures. Disorder induced changes in the electronic transport characteristics of bulk and surface electrons are believed to cause such changes in the magneto-transport behavior of this system.

  8. Modelling the sensitivity of infrared emissivity of magnetic thin films to giant magnetoresistance

    Energy Technology Data Exchange (ETDEWEB)

    Stirk, S.M. [Department of Physics, University of York, York YO10 5DD (United Kingdom)], E-mail: stewart.stirk@awe.co.uk; Thompson, S.M.; Matthew, J.A.D. [Department of Physics, University of York, York YO10 5DD (United Kingdom)

    2009-03-15

    The correlation between emissivity and giant magnetoresistance (GMR) in magnetic thin films is investigated at infrared (IR) wavelengths using a thin-film model of emissivity. The sensitivity of emissivity to GMR is shown to depend upon film thickness, and agrees excellently with bulk-material results for films thicker than the material skin depth. However, for films thinner than the skin depth the sensitivity to GMR is shown to weaken. In addition, at mid-to-far IR wavelengths the spectral dependence of the correlation is investigated using a modified Drude-type expression for the refractive index combined with the thin-film model. This is applied to a multilayered GMR material, and the sensitivity of emissivity to GMR is shown to have a similar spectral dependence to that of the magnetorefractive effect. An analytical interpretation in terms of skin depth is also developed at long wavelengths, and shown to agree excellently with thin-film simulations.

  9. Large magnetoresistance in compensated semimetals TaAs2 and NbAs2

    Science.gov (United States)

    Yuan, Zhujun; Lu, Hong; Liu, Yongjie; Wang, Junfeng; Jia, Shuang

    2016-05-01

    We report large magnetoresistance (MR) at low temperatures in single-crystalline nonmagnetic compounds TaAs2 and NbAs2. Both compounds exhibit parabolic-field-dependent MR larger than 5 ×103 in a magnetic field of 9 Tesla at 2 K. The MR starts to deviate from parabolic dependence above 10 T and intends to be saturated in 45 T for TaAs2 at 4.2 K. The Hall resistance measurements and band structure calculations reveal their compensated semimetal characteristics. Their large MR at low temperatures is ascribed to an effect for compensation of electrons and holes with large mobilities. After discussing the MR for different samples of TaAs2 and other semimetals, we found that the magnitudes of MR are strongly dependent on the samples' quality for different compounds.

  10. Magnetoresistive sensor for real-time single nucleotide polymorphism genotyping

    DEFF Research Database (Denmark)

    Rizzi, Giovanni; Østerberg, Frederik Westergaard; Dufva, Martin;

    2014-01-01

    We demonstrate a magnetoresistive sensor platform that allows for the real-time detection of point mutations in DNA targets. Specifically, we detect point mutations at two sites in the human beta globin gene. For DNA detection, the present sensor technology has a detection limit of about 160pM an...

  11. Tuning magnetic nanostructures and flux concentrators for magnetoresistive sensors

    Science.gov (United States)

    Yin, Xiaolu; Liu, Yen-Fu; Ewing, Dan; Ruder, Carmen K.; De Rego, Paul J.; Edelstein, A. S.; Liou, Sy-Hwang

    2015-09-01

    The methods for the optimization of the magnetoresistive (MR) sensors are to reduce sources of noises, to increase the signal, and to understand the involved fundamental limitations. The high-performance MR sensors result from important magnetic tunnel junction (MTJ) properties, such as tunneling magnetoresistance ratio (TMR), coercivity (Hc), exchange coupling field (He), domain structures, and noise properties as well as the external magnetic flux concentrators. All these parameters are sensitively controlled by the magnetic nanostructures, which can be tuned by varying junction free layer nanostructures, geometry, and magnetic annealing process etc. In this paper, we discuss some of efforts that an optimized magnetic sensor with a sensitivity as high as 5,146 %/mT. This sensitivity is currently the highest among all MR-type sensors that have been reported. The estimated noise of our magnetoresistive sensor is 47 pT/Hz1/2 at 1 Hz. This magnetoresistance sensor dissipates only 100 μW of power while operating under an applied voltage of 1 V at room temperature.

  12. Deposition temperature influence on sputtered nanogranular magnetoresistive composites

    Energy Technology Data Exchange (ETDEWEB)

    Mujika, M. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 San Sebastian (Spain)]. E-mail: mmujika@ceit.es; Arana, S. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 San Sebastian (Spain); Castano, E. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 San Sebastian (Spain)

    2007-09-15

    Among different physical principles magnetic sensors for low magnetic field detection can be based on, granular giant magnetoresistances have been studied due to their high sensitivity to small field changes and gradual magnetoresistance change at low fields. Following this aim, nanogranular Ag-Co thin films, deposited by DC co-sputtering from Ag and Co targets at different deposition temperatures have been tested. Samples have been grown at room temperature, 100 and 200 deg. C and annealed in a mixture of N{sub 2} and H{sub 2} at 200 and 300 deg. C for 45 min. The samples that have shown the best performance have been subjected to two sets of measurements where an external field has been applied in-plane and perpendicular to the film plane. The best performance has been shown by the samples deposited at room temperature and annealed at 300 deg. C, reporting a maximum value of magnetoresistance of 16.7% at 1.4 T and a linear sensitivity of 63%/T between 0.04 and 0.07 T within a magnetoresistance range varying from 1.5% to 3% when subjected to an in-plane external field.

  13. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications

    Directory of Open Access Journals (Sweden)

    Inga Ennen

    2016-06-01

    Full Text Available The giant magnetoresistance (GMR effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors.

  14. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications.

    Science.gov (United States)

    Ennen, Inga; Kappe, Daniel; Rempel, Thomas; Glenske, Claudia; Hütten, Andreas

    2016-01-01

    The giant magnetoresistance (GMR) effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors. PMID:27322277

  15. Orbital angular momentum microlaser

    Science.gov (United States)

    Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M.; Feng, Liang

    2016-07-01

    Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.

  16. Orbital angular momentum microlaser.

    Science.gov (United States)

    Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M; Feng, Liang

    2016-07-29

    Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes. PMID:27471299

  17. Angular Momentum Sharing in Dissipative Collisions

    Science.gov (United States)

    Casini, G.; Poggi, G.; Bini, M.; Calamai, S.; Maurenzig, P. R.; Olmi, A.; Pasquali, G.; Stefanini, A. A.; Taccetti, N.; Steckmeyer, J. C.; Laforest, R.; Saint-Laurent, F.

    1999-09-01

    Light charged particles emitted by the projectilelike fragment were measured in the direct and reverse collision of 93Nb and 116Sn at 25A MeV. The experimental multiplicities of hydrogen and helium particles as a function of the primary mass of the emitting fragment show evidence for a correlation with net mass transfer. The ratio of hydrogen and helium multiplicities points to a dependence of the angular momentum sharing on the net mass transfer.

  18. Angular momentum sharing in dissipative collisions

    CERN Document Server

    Casini, G; Bini, M; Calamai, S; Maurenzig, P R; Olmi, A; Pasquali, G; Stefanini, A A; Taccetti, N; Steckmeyer, J C; Laforest, R; Saint-Laurent, F

    1999-01-01

    Light charged particles emitted by the projectile-like fragment were measured in the direct and reverse collision of $^{93}$Nb and $^{116}$Sn at 25 AMeV. The experimental multiplicities of Hydrogen and Helium particles as a function of the primary mass of the emitting fragment show evidence for a correlation with net mass transfer. The ratio of Hydrogen and Helium multiplicities points to a dependence of the angular momentum sharing on the net mass transfer.

  19. Wigner distributions and quark orbital angular momentum

    OpenAIRE

    Cedric LorceOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)

    2015-01-01

    We discuss the quark phase-space or Wigner distributions of the nucleon which combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-front constituent quark model. We show how the quark orbital angular momentum can be extracted from the Wigner distributions a...

  20. Angular Diameter Distances in Clumpy Friedmann Universes

    OpenAIRE

    Tomita, Kenji

    1998-01-01

    Solving null-geodesic equations, behavior of angular diameter distances is studied in inhomogeneous cosmological models, which are given by performing N-body simulations with the CDM spectrum. The distances depend on the separation angle of ray pairs, the mass and the radius of particles cosisting of galaxies and dark matter balls, and cosmological model parameters. The calculated distances are compared with the Dyer- Roeder distance, and after many ray-shooting, the average, dispersion and d...

  1. Long phase coherence length and anisotropic magnetoresistance in MgZnO thin film

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Meng; Xu, Yonggang; Yu, Guolin, E-mail: yug@mail.sitp.ac.cn; Lin, Tie; Hu, Gujin; Chu, Junhao [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083 (China); Wang, Hao; Zhang, Huahan, E-mail: huahan@xmu.edu.cn [Department of Physics, Xiamen University, Xiamen 361005 (China); Dai, Ning [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China); Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou 213164 (China)

    2015-04-21

    We comprehensively investigate magnetotransport properties of MgZnO thin film grown on ZnO substrate by molecular-beam epitaxy. We measure the weak localization effect and extract the electron phase coherence length by fitting to a three-dimensional weak localization theory and by analyzing the different changing rate of the magnetoresistance, results of which are in good agreement with each other. The phase coherence length ranges from 38.4±1    nm at 50 K to 99.8±3.6 nm at 1.4  K, almost the same as that of ZnO nanoplates and In-doped ZnO nanowires, and its temperature dependence is found to scale as T{sup −3/4}. Meanwhile, we study the anisotropic magnetoresistance resulting from the geometric effect as well as the Lorentz force induced path-length effect, which will be enhanced in higher magnetic fields.

  2. Electrical Transport and Magnetoresistance in Single-Wall Carbon Nanotubes Films

    Directory of Open Access Journals (Sweden)

    Vitaly KSENEVICH

    2014-06-01

    Full Text Available Electrical transport properties and magnetoresistance of single-wall carbon nanotubes (SWCNT films were investigated within temperature range (2 – 300 K and in magnetic fields up to 8 T. A crossover between metallic (dR/dT > 0 and non-metallic (dR/dT < 0 temperature dependence of the resistance as well as low-temperature saturation of the resistance in high bias regime indicated on the diminishing of role of the contact barriers between individual nanotubes essential for the charge transport in SWCNT arrays. The magnetoresistance (MR data demonstrated influence of weak localization and electron-electron interactions on charge transport properties in SWCNT films. The low-field negative MR with positive upturn was observed at low temperatures. At T > 10 K only negative MR was observed in the whole range of available magnetic fields. The negative MR can be approximated using 1D weak localization (WL model. The low temperature positive MR is induced by contribution from electron-electron interactions. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6311

  3. Effect of cobalt on the magnetoresistance characteristics of rare-earth doped manganites

    Institute of Scientific and Technical Information of China (English)

    Jiang Kuo; Gong Sheng-Kai

    2009-01-01

    The effect of cobalt-doping on the magnetic, transport and magnetoresistance characteristics of La1-xSrxMnO3 was investigated. The results show that the magnetoelectric property of rare-earth doped manganites is greatly affected by substitution of Co for Mn sites. The Curie temperature as well as the magnetic moment decreases with the increase of doping concentration, and the samples exhibit obvious characteristics of the spin glass state. Moreover,the magnetoresistance is evidently modulated by doping concentration, and the relevant temperature dependence is also suppressed. In addition, low-temperature magnetorcsistance is significantly promoted as doping concentration increases, which renders a value of approximately 50% in the temperature range of 5-200 K and varies within 12.5%. It can be attributed to the effect of spin scattering, induced by cobalt doping, on the itinerant electrons of Mn ions, thus introducing a spin-disorder region into the ferromagnetic region of double-exchange interaction between neighbouring Mn3+ and Mn 4+ ions.

  4. On-chip magnetic bead-based DNA melting curve analysis using a magnetoresistive sensor

    Energy Technology Data Exchange (ETDEWEB)

    Rizzi, Giovanni, E-mail: giori@nanotech.dtu.dk; Østerberg, Frederik W.; Henriksen, Anders D.; Dufva, Martin; Hansen, Mikkel F., E-mail: mikkel.hansen@nanotech.dtu.dk

    2015-04-15

    We present real-time measurements of DNA melting curves in a chip-based system that detects the amount of surface-bound magnetic beads using magnetoresistive magnetic field sensors. The sensors detect the difference between the amount of beads bound to the top and bottom sensor branches of the differential sensor geometry. The sensor surfaces are functionalized with wild type (WT) and mutant type (MT) capture probes, differing by a single base insertion (a single nucleotide polymorphism, SNP). Complementary biotinylated targets in suspension couple streptavidin magnetic beads to the sensor surface. The beads are magnetized by the field arising from the bias current passed through the sensors. We demonstrate the first on-chip measurements of the melting of DNA hybrids upon a ramping of the temperature. This overcomes the limitation of using a single washing condition at constant temperature. Moreover, we demonstrate that a single sensor bridge can be used to genotype a SNP. - Highlights: • We apply magnetoresistive sensors to study solid-surface hybridization kinetics of DNA. • We measure DNA melting profiles for perfectly matching DNA duplexes and for a single base mismatch. • We present a procedure to correct for temperature dependencies of the sensor output. • We reliably extract melting temperatures for the DNA hybrids. • We demonstrate direct measurement of differential binding signal for two probes on a single sensor.

  5. High sensitivity detection of molecular recognition using magnetically labelled biomolecules and magnetoresistive sensors.

    Science.gov (United States)

    Graham, D L; Ferreira, H A; Freitas, P P; Cabral, J M S

    2003-04-01

    Small magnetoresistive spin valve sensors (2 x 6 microm(2)) were used to detect the binding of single streptavidin functionalized 2 microm magnetic microspheres to a biotinylated sensor surface. The sensor signals, using 8 mA sense current, were in the order of 150-400 microV for a single microsphere depending on sensor sensitivity and the thickness of the passivation layer over the sensor surface. Sensor saturation signals were 1-2 mV representing an estimated 6-20 microspheres, with a noise level of approximately 10 microV. The detection of biomolecular recognition for the streptavidin-biotin model was shown using both single and differential sensor architectures. The signal data compares favourably with previously reported signals for high numbers of magnetic microspheres detected using larger multilayered giant magnetoresistance sensors. A wide range of applications is foreseen for this system in the development of biochips, high sensitivity biosensors and the detection of single molecules and single molecule interactions. PMID:12604266

  6. Multiple photoexcitation of two-dimensional electron systems: Bichromatic magnetoresistance oscillations

    Science.gov (United States)

    Iñarrea, Jesús

    2011-04-01

    We analyze theoretically magnetoresistance of high-mobility two-dimensional electron systems being illuminated by multiple radiation sources. In particular, we study the influence on the striking effect of microwave-induced resistance oscillations. We consider moderate radiation intensities without reaching the zero-resistance states regime. We use the model of radiation-driven Larmor orbits extended to several light sources. First, we study the case of two different radiations polarized in the same direction with different or equal frequencies. For both cases, we find a regime of superposition or interference of harmonic motions. When the frequencies are different, we obtain a modulated magnetoresistance response with pulses and beats. On the other hand, when the frequencies are the same, we find that the final result will depend on the phase difference between both radiation fields going from an enhanced response to a total collapse of oscillations, reaching an outcome similar to darkness. Finally, we consider a multiple photoexcitation case (three different frequencies) in which we propose the two-dimensional electron system as a potential nanoantenna device for microwaves.

  7. Nuclear Level Density with Non-zero Angular Momentum

    Institute of Scientific and Technical Information of China (English)

    A.N. Behkami; M. Gholami; M. Kildir; M. Soltani

    2006-01-01

    The statistical properties of interacting fermions have been studied for various angular momentum with the inclusion of pairing interaction. The dependence of the critical temperature on angular momentum for several nuclei,have been studied. The yrast energy as a function of angular momentum for 28 Si and 24Mg nuclei have been calculated up to 60.0 MeV of excitation energy. The computed limiting angular momenta are compared with the experimental results for 26Al produced by 12C + 14N reaction. The relevant nuclear level densities for non-zero angular momentum have been computed for 44Ti and l36Ba nuclei. The results are compared with their corresponding values obtained from the approximateformulas.

  8. Magnetoresistance of p-type semiconducting diamond films%P型半导体金刚石膜的磁阻

    Institute of Scientific and Technical Information of China (English)

    孔春阳; 王万录; 廖克俊; 王蜀霞; 方亮; 马勇

    2001-01-01

    研究了p-型异质外延和同质外延金刚石膜的在不同温度和磁场下的磁阻,磁阻器件的结 构为条形和圆盘形。实验结果表明磁阻强烈依赖于磁场、温度和样品的几何形状,圆盘结构的磁 阻大于条形结构,条形结构的磁阻还取决于不同的长-宽比。利用F-S薄膜理论,计算磁场为 5T时条形和圆盘结构的磁阻分别为0.38和0.74,讨论了霍耳效应对磁阻的影响,给出了形状 效应的可能机制。%The magnetoresistive effects were investigated at different temperature and magnetic filed B in both homoepitaxial and heteroepitaxial p-type semiconducting diamond thin films. There are two kinds of device structure used i.e. strip and Corbino disk. Experimental results show that the changes of resistance in the film strongly depend on the magnetic field B, temperature and the geometric form of samples. The magnetoresistance of disk structure is greater than that of strip sample, and the effects of strip sample increase with the ratio of width-to-length. Based on the Fuchs and Sondheimer thin film theory (F-S theory), the magnetoresistances of strip and disk are calculated at magnetic field of 5 T. It is 0.38 for strip and 0.74 for disk. The influence of Hall effect on the magnetoresistance is discussed and a possible mechanism of geometric form effect is described.

  9. Novel Method to Evaluate Angular Stiffness of Prosthetic Feet From Linear Compression Tests

    OpenAIRE

    Adamczyk, Peter G.; Roland, Michelle; Hahn, Michael E.

    2013-01-01

    Lower limb amputee gait during stance phase is related to the angular stiffness of the prosthetic foot, which describes the dependence of ankle torque on angular progression of the shank. However, there is little data on angular stiffness of prosthetic feet, and no method to directly measure it has been described. The objective of this study was to derive and evaluate a method to estimate the angular stiffness of prosthetic feet using a simple linear compression test. Linear vertical compress...

  10. Intrinsic Angular Momentum of Light.

    Science.gov (United States)

    Santarelli, Vincent

    1979-01-01

    Derives a familiar torque-angular momentum theorem for the electromagnetic field, and includes the intrinsic torques exerted by the fields on the polarized medium. This inclusion leads to the expressions for the intrinsic angular momentum carried by the radiation traveling through a charge-free medium. (Author/MA)

  11. Enhancement of Magnetoresistance in Granular CrO2/Polystyrene Composites

    Institute of Scientific and Technical Information of China (English)

    陈亚杰; 张晓渝; 李振亚

    2003-01-01

    We present a study of magnetotransport in CrO2/polystyrene (PS) composites over a range of polystyrene concentration (0-30wt.%). In the experiment, an obvious enhancement in magnetoresistance (MR) is observed at 77K and at room temperature as the half-metallic CrO2 particles are encapsulated with a thin layer of insulating polystyrene. The enhanced MR can be interpreted in terms of spin-dependent intergranular tunnelling with 4-nm-thick PS barrier. Moreover, it is found that the novel PS barrier contributes to room-temperature MR more significantly than that at 77K. Temperature dependence of resistance is good agreement with ~ T-1/4 in the temperature range from 77 to 298 K.

  12. Extrinsic and intrinsic magnetoresistance contributions of CrO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Rudiger, U.; Rabe, M.; Samm, K.; Ozyilmaz, B.; Pommer, J.; Fraune, M.; Guntherodt, G.; Senz, St.; Hesse, D.

    2001-06-01

    The growth of (010)-oriented CrO{sub 2} thin films on Al{sub 2}O{sub 3}(0001) substrates leads to a higher grain boundary density than the growth of (100)-oriented CrO{sub 2} thin films on isostructural TiO{sub 2}(100) substrates. For both types of films an intrinsic linear contribution to the high field magnetoresistance (MR) due to spin disorder has been determined at T=300K. This contribution does not depend on the crystalline quality of the films and supports the suggested intrinsic double exchange mechanism for CrO{sub 2}. At low temperature (T=10K) intergrain tunneling MR and Lorentz MR appear, which strongly depend on the crystalline properties of the CrO{sub 2} films. {copyright} 2001 American Institute of Physics.

  13. Investigation of the magnetoresistivity in compositional superlattices under the influence of an intense electromagnetic wave

    Science.gov (United States)

    Hoi, Bui Dinh; Bau, Nguyen Quang; Nam, Nguyen Dinh

    2016-01-01

    The magnetoresistivity (MR) is theoretically calculated in a compositional semiconductor superlattice (CSSL), subjected to a crossed DC electric field and magnetic field, in the presence of an intense electromagnetic wave (EMW). The magnetic field is oriented along the growth direction of the CSSL and the electron-acoustic phonon interaction is taken into account at low temperature. Numerical results for the GaN/AlGaN CSSL show the Shubnikov-de Haas (SdH) oscillations in the MR whose period does not depend on the temperature and amplitude decreases with increasing temperature. The temperature dependence of the relative amplitude of these oscillations is in good agreement with other theories and experiments in some two-dimensional (2D) electron systems. The influence of the EMW as well as superlattice structure on the MR is discussed and compared with available theoretical and experimental results.

  14. Enhanced magnetoresistance in half-metallic CrO2-TiO2 composites

    Science.gov (United States)

    Fan, Yinbo; Zhang, Caiping; Du, Xiaobo; Wen, Gehui; Ma, Hongan; Jia, Xiaopeng

    2013-06-01

    CrO2-TiO2 composites were synthesized by a high temperature and high pressure method (HTHP). The CrO2-TiO2 composites are composed of large rod-like CrO2 crystals separated by TiO2 nanoparticles. The saturation magnetization of the CrO2 in the composites is very close to the theoretical value. The CrO2-TiO2 composites show greatly enhanced magnetoresistance than that of pure CrO2. This is mainly attributed to spin-dependent tunneling between adjacent CrO2 grains enhanced by the addition of TiO2. The tunneling mechanism in the composites can be best described by the fluctuation-induced tunneling model as convinced by the temperature dependence of the conductivity of the CrO2-TiO2 composites at low temperature.

  15. The effect of dimerization on the magnetoresistance in organic spin valves

    Institute of Scientific and Technical Information of China (English)

    Wang Hui; Hu Gui-Chao; Ren Jun-Feng

    2013-01-01

    The effect of lattice dimerization on the magnetoresistance (MR) in organic spin valves is investigated based on the Su-Schrieffer-Heeger (SSH) model and the Green's function method.By comparing with the results for a uniform chain,we find that the dimerization of the molecular chain modifies the monotonic dependence of the MR on the bias to an oscillatory one.A sign inversion of the MR is observed when the amplitude of the dimerization is adjusted.The results also show that at a low bias,the MR through a dimerized chain decreases with the increasing bias as well as the increasing chain length,which is consistent with the experimental reports.A further understanding can be achieved by analyzing the electronic states and the spin-dependent transmission spectrum with the parallel and antiparallel magnetization orientations of the two ferromagnetic electrodes.

  16. Large Magnetoresistance at High Bias Voltage in Double-layer Organic Spin Valves

    Science.gov (United States)

    Subedi, R. C.; Liang, S. H.; Geng, R.; Zhang, Q. T.; Lou, L.; Wang, J.; Han, X. F.; Nguyen, T. D.

    We report studies of magnetoresistance (MR) in double-layer organic spin valves (DOSV) using tris (8-hydroxyquinolinato) aluminum (Alq3) spacers. The device exhibits three distinct resistance levels depending on the relative magnetizations of the ferromagnetic electrodes. We observed a much weaker bias voltage dependence of MR in the device compared to that in the conventional organic spin valve (OSV). The MR magnitude reduces by the factor of two at 0.7 V bias voltage in the DOSV compared to 0.02 V in the conventional OSV. Remarkably, the MR magnitude reaches 0.3% at 6 V bias in the DOSVs, the largest MR response ever reported in OSVs at this bias. Our finding may have a significant impact on achieving high efficient bipolar OSVs strictly performed at high voltages. University of Georgia start-up fund, Ministry of Education, Singapore, National Natural Science Foundation of China.

  17. Multi-state magnetoresistance in ferromagnet/organic-ferromagnet/ferromagnet junctions

    Science.gov (United States)

    Hu, Guichao; Xie, Shijie

    Organic ferromagnets (OFs) are fascinating in the field of organic spintronics, since they combine both the ferromagnetic and organic properties. The utilization of OFs in the design of organic spintronic is promising to generate some novel effects. Here, we designed an organic spin valve by sandwiching the OF between two ferromagnets. By calculating the spin-dependent transport property, we found that the current through the device strongly depends on the alignment of the magnetization orientation of the electrodes and the OF. The spin-related electron tunneling between the ferromagnetic electrodes suffers a further spin selection from the spin-polarized states of the central OF. This work indicates a realization of four-state magnetoresistance based on OFs, which may be manipulated by a magnetic field to control the magnetization orientations of the ferromagnets and the OF. Support from the NSF of China is acknowledged.

  18. In-plane magnetoresistance obeys Kohler's rule in the pseudogap phase of cuprate superconductors.

    Science.gov (United States)

    Chan, M K; Veit, M J; Dorow, C J; Ge, Y; Li, Y; Tabis, W; Tang, Y; Zhao, X; Barišić, N; Greven, M

    2014-10-24

    We report in-plane resistivity (ρ) and transverse magnetoresistance (MR) measurements for underdoped HgBa(2)CuO(4+δ) (Hg1201). Contrary to the long-standing view that Kohler's rule is strongly violated in underdoped cuprates, we find that it is in fact satisfied in the pseudogap phase of Hg1201. The transverse MR shows a quadratic field dependence, δρ/ρ(0)=aH(2), with a(T)∝T(-4). In combination with the observed ρ∝T(2) dependence, this is consistent with a single Fermi-liquid quasiparticle scattering rate. We show that this behavior is typically masked in cuprates with lower structural symmetry or strong disorder effects. PMID:25379934

  19. Spin Seebeck effect and spin Hall magnetoresistance at high temperatures for a Pt/yttrium iron garnet hybrid structure.

    Science.gov (United States)

    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.

  20. Angular signal radiography.

    Science.gov (United States)

    Li, Panyun; Zhang, Kai; Bao, Yuan; Ren, Yuqi; Ju, Zaiqiang; Wang, Yan; He, Qili; Zhu, Zhongzhu; Huang, Wanxia; Yuan, Qingxi; Zhu, Peiping

    2016-03-21

    Microscopy techniques using visible photons, x-rays, neutrons, and electrons have made remarkable impact in many scientific disciplines. The microscopic data can often be expressed as the convolution of the spatial distribution of certain properties of the specimens and the inherent response function of the imaging system. The x-ray grating interferometer (XGI), which is sensitive to the deviation angle of the incoming x-rays, has attracted significant attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the comprehensive and analytical theoretical framework is yet to be presented. Herein, we propose a theoretical framework termed angular signal radiography (ASR) to describe the imaging process of the XGI system in a classical, comprehensive and analytical manner. We demonstrated, by means of theoretical deduction and synchrotron based experiments, that the spatial distribution of specimens' physical properties, including absorption, refraction and scattering, can be extracted by ASR in XGI. Implementation of ASR in XGI offers advantages such as simplified phase retrieval algorithm, reduced overall radiation dose, and improved image acquisition speed. These advantages, as well as the limitations of the proposed method, are systematically investigated in this paper. PMID:27136780

  1. Quasi-linear magnetoresistance and the violation of Kohler's rule in the quasi-one-dimensional Ta₄Pd₃Te₁₆ superconductor.

    Science.gov (United States)

    Xu, Xiaofeng; Jiao, W H; Zhou, N; Guo, Y; Li, Y K; Dai, Jianhui; Lin, Z Q; Liu, Y J; Zhu, Zengwei; Lu, Xin; Yuan, H Q; Cao, Guanghan

    2015-08-26

    We report on the quasi-linear in field intrachain magnetoresistance in the normal state of a quasi-one-dimensional superconductor Ta4Pd3Te16 (Tc ~ 4.6 K). Both the longitudinal and transverse in-chain magnetoresistance shows a power-law dependence, Δρ∝B(α) with the exponent α close to 1 over a wide temperature and field range. The magnetoresistance shows no sign of saturation up to 50 T studied. The linear magnetoresistance observed in Ta4Pd3Te16 is found to be overall inconsistent with the interpretations based on the Dirac fermions in the quantum limit, charge conductivity fluctuations as well as quantum electron-electron interference. Moreover, it is observed that the Kohler's rule, regardless of the field orientations, is violated in its normal state. This result suggests the loss of charge carriers in the normal state of this chain-containing compound, due presumably to the charge-density-wave fluctuations. PMID:26222182

  2. Quasi-linear magnetoresistance and the violation of Kohler's rule in the quasi-one-dimensional Ta₄Pd₃Te₁₆ superconductor.

    Science.gov (United States)

    Xu, Xiaofeng; Jiao, W H; Zhou, N; Guo, Y; Li, Y K; Dai, Jianhui; Lin, Z Q; Liu, Y J; Zhu, Zengwei; Lu, Xin; Yuan, H Q; Cao, Guanghan

    2015-08-26

    We report on the quasi-linear in field intrachain magnetoresistance in the normal state of a quasi-one-dimensional superconductor Ta4Pd3Te16 (Tc ~ 4.6 K). Both the longitudinal and transverse in-chain magnetoresistance shows a power-law dependence, Δρ∝B(α) with the exponent α close to 1 over a wide temperature and field range. The magnetoresistance shows no sign of saturation up to 50 T studied. The linear magnetoresistance observed in Ta4Pd3Te16 is found to be overall inconsistent with the interpretations based on the Dirac fermions in the quantum limit, charge conductivity fluctuations as well as quantum electron-electron interference. Moreover, it is observed that the Kohler's rule, regardless of the field orientations, is violated in its normal state. This result suggests the loss of charge carriers in the normal state of this chain-containing compound, due presumably to the charge-density-wave fluctuations.

  3. Spin heat accumulation and spin-dependent temperatures in nanopillar spin valves

    NARCIS (Netherlands)

    Dejene, F. K.; Flipse, J.; Bauer, G. E. W.; van Wees, B. J.

    2013-01-01

    Since the discovery of the giant magnetoresistance effect(1,2) the intrinsic angular momentum of the electron has opened up new spin-based device concepts. Our present understanding of the coupled transport of charge, spin and heat relies on the two-channel model for spin-up and spin-down electrons

  4. Control of Angular Intervals for Angle-Multiplexed Holographic Memory

    Science.gov (United States)

    Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

    2009-03-01

    In angle-multiplexed holographic memory, the full width at half maximum of the Bragg selectivity curves is dependent on the angle formed between the medium and incident laser beams. This indicates the possibility of high density and high multiplexing number by varying the angular intervals between adjacent holograms. We propose an angular interval scheduling for closely stacking holograms into medium even when the angle range is limited. We obtained bit error rates of the order of 10-4 under the following conditions: medium thickness of 1 mm, laser beam wavelength of 532 nm, and angular multiplexing number of 300.

  5. The pretzelosity TMD and quark orbital angular momentum

    Energy Technology Data Exchange (ETDEWEB)

    Lorce, C. [IPNO, Universite Paris-Sud, CNRS/IN2P3, 91406 Orsay (France); LPT, Universite Paris-Sud, CNRS, 91406 Orsay (France); Pasquini, B., E-mail: pasquini@pv.infn.it [Dipartimento di Fisica, Universita degli Studi di Pavia, Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy)

    2012-04-12

    We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation cannot be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum.

  6. Effect of angular momentum conservation on hydrodynamic simulations of colloids.

    Science.gov (United States)

    Yang, Mingcheng; Theers, Mario; Hu, Jinglei; Gompper, Gerhard; Winkler, Roland G; Ripoll, Marisol

    2015-07-01

    In contrast to most real fluids, angular momentum is not a locally conserved quantity in some mesoscopic simulation methods. Here we quantify the importance of this conservation in the flow fields associated with different colloidal systems. The flow field is analytically calculated with and without angular momentum conservation for the multiparticle collision dynamics (MPC) method, and simulations are performed to verify the predictions. The flow field generated around a colloidal particle moving under an external force with slip boundary conditions depends on the conservation of angular momentum, and the amplitude of the friction force is substantially affected. Interestingly, no dependence on the angular momentum conservation is found for the flow fields generated around colloids under the influence of phoretic forces. Moreover, circular Couette flow between a no-slip and a slip cylinder is investigated, which allows us to validate one of the two existing expressions for the MPC stress tensor.

  7. Theoretical study of disorder induced magnetoresistance in graphene

    Science.gov (United States)

    Adam, Shaffique; Ping, Jinglei; Yudhistira, Indra; Ramakrishnan, Navneeth; Cho, Sungjae; Fuhrer, Michael S.

    2014-03-01

    In this work we predict theoretically that carrier density inhomogeneity provides a new mechanism for classical magnetoresistance. For concreteness, we study the case of graphene where density inhomogeneity and carrier scattering is dominated by charged impurities, although the mechanism itself is quite general and applies to other systems in which there are large spatial fluctuations of the carrier density. Calculations using an effective medium approximation show that low-field magnetoresistance becomes a universal function of the ratio between the average carrier density and the fluctuations of the carrier density, and scales as a power-law when this ratio is large. Our finding is in excellent agreement with recent experimental results. This work is supported by the Singapore National Research Foundation NRF-NRFF2012-01.

  8. Enhancing magnetoresistance in tetrathiafulvalene carboxylate modified iron oxide nanoparticle assemblies

    Science.gov (United States)

    Lv, Zhong-Peng; Luan, Zhong-Zhi; Cai, Pei-Yu; Wang, Tao; Li, Cheng-Hui; Wu, Di; Zuo, Jing-Lin; Sun, Shouheng

    2016-06-01

    We report a facile approach to stabilize Fe3O4 nanoparticles (NPs) by using tetrathiafulvalene carboxylate (TTF-COO-) and to control electron transport with an enhanced magnetoresistance (MR) effect in TTF-COO-Fe3O4 NP assemblies. This TTF-COO-coating is advantageous over other conventional organic coatings, making it possible to develop stable Fe3O4 NP arrays for sensitive spintronics applications.We report a facile approach to stabilize Fe3O4 nanoparticles (NPs) by using tetrathiafulvalene carboxylate (TTF-COO-) and to control electron transport with an enhanced magnetoresistance (MR) effect in TTF-COO-Fe3O4 NP assemblies. This TTF-COO-coating is advantageous over other conventional organic coatings, making it possible to develop stable Fe3O4 NP arrays for sensitive spintronics applications. Electronic supplementary information (ESI) available: Experimental details; supplementary figures and tables. See DOI: 10.1039/c6nr03311c

  9. Structure and magnetoresistive properties in La endash manganite thin films

    International Nuclear Information System (INIS)

    This study investigates the structure of perovskite thin films and its influence on their colossal magnetoresistance (CMR) properties. Epitaxial thin films of perovskite manganites La1-xBxMnO3-δ (B=Ca,Sr) were prepared on SrTiO3 (100) substrates using on- and off-axis pulsed laser deposition (PLD) techniques. X-ray diffraction, resistance and magnetoresistance measurements, as well as high-resolution transmission electron microscopy (HRTEM) investigations were carried out. HRTEM observations reveal epitaxial growth for the first few layers of all prepared samples. Thicker on-axis prepared films grow with a large number of defects, whereas off-axis prepared samples grow in a columnar structure. Since the magnetic properties in systems with double-exchange interaction are very sensitive to the local structure it has great influence on the electronic properties. copyright 1997 American Institute of Physics

  10. A Magnetoresistive Tactile Sensor for Harsh Environment Applications

    KAUST Repository

    Alfadhel, Ahmed

    2016-05-07

    A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature.

  11. Low coercivity giant magnetoresistance with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong-Seop; Yoon, Jungbum; Kang, Mool-Bit; You, Chun-Yeol, E-mail: cyyou@inha.ac.kr

    2014-05-01

    We find the perpendicular magnetic anisotropy giant magnetoresistance structure, whose coercivity is less than 10 Oe. We reveal that the coercivity of free layer can be smaller than 5 Oe in Co/Pd/Cu/[Co/Pd]{sub 4} multilayer structure with a TiO{sub 2} seed layer. The TiO{sub 2} seed layer plays a critical role in the small coercivity of free layer. The GMR ratio is around 1–1.8% for the out-of-plane magnetic fields, and the maximum MR sensitivity of 0.12%/Oe is achieved. - Highlights: • We find an extremely small coercivity giant magnetoresistance (GMR) structure for the out-of-plane magnetic field. • The key ingredient of small coercivity is a TiO{sub 2} seed layer. • Such a small coercivity GMR structure will be useful for automotive applications such as wheel speed, rotation, and position sensors.

  12. Anisotropic Magnetoresistance of Cobalt Films Prepared by Thermal Evaporation

    Directory of Open Access Journals (Sweden)

    Yuttanun PANSONG

    2005-01-01

    Full Text Available Cobalt films on silicon substrates were prepared by thermal evaporation. By evaporating 0.05 g of cobalt for 80-240 s, a thickness from 21.1 to 67.7 nm was obtained with a deposition rate about 0.26-0.32 nm per second. The 29 nm-thick cobalt film exhibited magnetoresistance (MR ranging from -0.0793% (field perpendicular to the current to +0.0134% (field parallel to the current with saturation in a 220 mT magnetic field. This MR was attributed to anisotropic magnetoresistance (AMR since changing the angle between the field and the current (θ gave rise to a change in the electrical resistance (Rθ. The results agreed with the theory since the plot between Rθ and cos2θ could be linearly fitted. AMR was not observed in non-ferromagnetic gold films whose resistance was insensitive to the angle between the current and magnetic field.

  13. A Magnetoresistive Tactile Sensor for Harsh Environment Applications

    Directory of Open Access Journals (Sweden)

    Ahmed Alfadhel

    2016-05-01

    Full Text Available A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS, is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature.

  14. A Magnetoresistive Tactile Sensor for Harsh Environment Applications.

    Science.gov (United States)

    Alfadhel, Ahmed; Khan, Mohammed Asadullah; Cardoso, Susana; Leitao, Diana; Kosel, Jürgen

    2016-01-01

    A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature. PMID:27164113

  15. Wheatstone bridge giant-magnetoresistance based cell counter.

    Science.gov (United States)

    Lee, Chiun-Peng; Lai, Mei-Feng; Huang, Hao-Ting; Lin, Chi-Wen; Wei, Zung-Hang

    2014-07-15

    A Wheatstone bridge giant magnetoresistance (GMR) biosensor was proposed here for the detection and counting of magnetic cells. The biosensor was made of a top-pinned spin-valve layer structure, and it was integrated with a microchannel possessing the function of hydrodynamic focusing that allowed the cells to flow in series one by one and ensured the accuracy of detection. Through measuring the magnetoresistance variation caused by the stray field of the magnetic cells that flowed through the microchannel above the GMR biosensor, we can not only detect and count the cells but we can also recognize cells with different magnetic moments. In addition, a magnetic field gradient was applied for the separation of different cells into different channels. PMID:24534580

  16. Drastic pressure effect on the extremely large magnetoresistance in WTe2: quantum oscillation study

    OpenAIRE

    Cai, P. L.; Hu, J.; He, L. P.; Pan, J.; Hong, X. C.; Zhang, Z; Zhang, J.; J. Wei; Mao, Z. Q.; Li, S. Y.

    2014-01-01

    The quantum oscillations of the magnetoresistance under ambient and high pressure have been studied for WTe$_2$ single crystals, in which extremely large magnetoresistance was discovered recently. By analyzing the Shubnikov-de Haas oscillations, four Fermi surfaces are identified, and two of them are found to persist to high pressure. The sizes of these two pockets are comparable, but show increasing difference with pressure. At 0.3 K and in 14.5 T, the magnetoresistance decreases drastically...

  17. Angular momentum evolution for galaxies

    CERN Document Server

    Pedrosa, Susana

    2015-01-01

    Using cosmological hydrodynamics simulations we study the angular momentum content of the simulated galaxies in relation with their morphological type. We found that not only the angular momentum of the disk component follow the expected theoretical relation, Mo, Mao & Whiye (1998), but also the spheroidal one, with a gap due to its lost of angular momentum, in agreement with Fall & Romanowsky (2013),. We also found that the galaxy size can plot in one general relation, despite the morphological type, as found by Kravtsov (2013).

  18. AngularJS testing cookbook

    CERN Document Server

    Bailey, Simon

    2015-01-01

    This book is intended for developers who have an understanding of the basic principles behind both AngularJS and test-driven development. You, as a developer, are interested in eliminating the fear related to either introducing tests to an existing codebase or starting out testing on a fresh AngularJS application. If you're a team leader or part of a QA team with the responsibility of ensuring full test coverage of an application, then this book is ideal for you to comprehend the full testing scope required by your developers. Whether you're new to or are well versed with AngularJS, this book

  19. Handheld, giant magnetoresistive-sensor-based eddy current probes

    Science.gov (United States)

    Brady, S. K.; Palmer, D. D.

    2012-05-01

    The minimum crack length detectable with conventional eddy current probes increases dramatically as the thickness of metal through which the inspection is performed increases. The skin depth phenomenon is unavoidable, and demands low frequency inspection, hindering sensitivity. However, one time derivative introduced by Faraday's Law can be avoided by using giant magnetoresistive sensors to detect eddy currents instead of conventional coils, improving sensitivity. The theory will be explained, along with some probe designs and the observed benefits in sensitivity.

  20. Tuning spin transport properties and molecular magnetoresistance through contact geometry

    Energy Technology Data Exchange (ETDEWEB)

    Ulman, Kanchan [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Narasimhan, Shobhana [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Sheikh Saqr Laboratory, ICMS, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Delin, Anna [Department of Materials and Nanophysics, School of Information and Communication Technology, Electrum 229, Royal Institute of Technology (KTH), SE-16440 Kista (Sweden); Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); SeRC (Swedish e-Science Research Center), KTH, SE-10044 Stockholm (Sweden)

    2014-01-28

    Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its “closed” and “open” conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ∼5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ∼400%.

  1. Correlation of Crystal Quality and Extreme Magnetoresistance of WTe$_2$

    OpenAIRE

    Ali, Mazhar N.; Schoop, Leslie; Xiong, Jun; Flynn, Steven; Gibson, Quinn; Hirschberger, Max; Ong, N. P.; Cava, R. J.

    2015-01-01

    High quality single crystals of WTe$_2$ were grown using a Te flux followed by a cleaning step involving self-vapor transport. The method is reproducible and yields consistently higher quality single crystals than are typically obtained via halide assisted vapor transport methods. Magnetoresistance (MR)values at 9 Tesla and 2 Kelvin as high as 1.75 million \\%, nearly an order of magnitude higher than previously reported for this material, were obtained on crystals with residual resistivity ra...

  2. Ultrafast Carrier Dynamics in the Large Magnetoresistance Material WTe$_{2}$

    OpenAIRE

    Dai, Y. M.; Bowlan, J.; Li, H.; Miao, H; Wu, S. F.; Kong, W. D.; Shi, Y. G.; Trugman, S. A.; Zhu, J. -X.; H. Ding; Taylor, A. J.; Yarotski, D. A.; Prasankumar, R. P.

    2015-01-01

    Ultrafast optical pump-probe spectroscopy is used to track carrier dynamics in the large magnetoresistance material WTe$_{2}$. Our experiments reveal a fast relaxation process occurring on a sub-picosecond time scale that is caused by electron-phonon thermalization, allowing us to extract the electron-phonon coupling constant. An additional slower relaxation process, occurring on a time scale of $\\sim$5-15 picoseconds, is attributed to phonon-assisted electron-hole recombination. As the tempe...

  3. Electronic structure basis for the titanic magnetoresistance in WTe$_2$

    OpenAIRE

    Pletikosić, I.; Ali, Mazhar N.; Fedorov, A; Cava, R. J.; Valla, T.

    2014-01-01

    The electronic structure basis of the extremely large magnetoresistance in layered non-magnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at the Fermi level, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic, quasi one-dimensional Fermi surface from which the pronounced anisotropy of the magnetor...

  4. Anisotropic magnetoresistivity in structured elastomer composites: modelling and experiments.

    Science.gov (United States)

    Mietta, José Luis; Tamborenea, Pablo I; Martin Negri, R

    2016-08-14

    A constitutive model for the anisotropic magnetoresistivity in structured elastomer composites (SECs) is proposed. The SECs considered here are oriented pseudo-chains of conductive-magnetic inorganic materials inside an elastomer organic matrix. The pseudo-chains are formed by fillers which are simultaneously conductive and magnetic dispersed in the polymer before curing or solvent evaporation. The SEC is then prepared in the presence of a uniform magnetic field, referred to as Hcuring. This procedure generates the pseudo-chains, which are preferentially aligned in the direction of Hcuring. Electrical conduction is present in that direction only. The constitutive model for the magnetoresistance considers the magnetic pressure, Pmag, induced on the pseudo-chains by an external magnetic field, H, applied in the direction of the pseudo-chains. The relative changes in conductivity as a function of H are calculated by evaluating the relative increase of the electron tunnelling probability with Pmag, a magneto-elastic coupling which produces an increase of conductivity with magnetization. The model is used to adjust experimental results of magnetoresistance in a specific SEC where the polymer is polydimethylsiloxane, PDMS, and fillers are microparticles of magnetite-silver (referred to as Fe3O4[Ag]). Simulations of the expected response for other materials in both superparamagnetic and blocked magnetic states are presented, showing the influence of the Young's modulus of the matrix and filler's saturation magnetization. PMID:27418417

  5. Magnetoresistance near a quantum critical point

    OpenAIRE

    Hayes, I. M.; Breznay, Nicholas P.; Helm, Toni; Moll, Philip; Wartenbe, Mark; McDonald, Ross D.; Shekhter, Arkady; Analytis, James G.

    2014-01-01

    In metals near a quantum critical point, the electrical resistance is thought to be determined by the lifetime of the carriers of current, rather than the scattering from defects. The observation of $T$-linear resistivity suggests that the lifetime only depends on temperature, implying the vanishing of an intrinsic energy scale and the presence of a quantum critical point. Our data suggest that this concept extends to the magnetic field dependence of the resistivity in the unconventional supe...

  6. The integration of angular velocity

    OpenAIRE

    Boyle, Michael

    2016-01-01

    A common problem in physics and engineering is determination of the orientation of an object given its angular velocity. When the direction of the angular velocity changes in time, this is a nontrivial problem involving coupled differential equations. Several possible approaches are examined, along with various improvements over previous efforts. These are then evaluated numerically by comparison to a complicated but analytically known rotation that is motivated by the important astrophysical...

  7. Achromatic orbital angular momentum generator

    OpenAIRE

    Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W

    2014-01-01

    We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \\textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming be...

  8. Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

    Energy Technology Data Exchange (ETDEWEB)

    Yamanoi, K.; Yokotani, Y. [Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan); Cui, X. [Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Yakata, S. [Department of Information Electronics, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka 811-0295 (Japan); Kimura, T., E-mail: t-kimu@phys.kyushu-u.ac.jp [Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan); Research Center for Quantum Nano-Spin Sciences, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan)

    2015-12-21

    We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of the standing spin wave is an important advantage for the high power operation of the spin-wave device.

  9. Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

    Science.gov (United States)

    Yamanoi, K.; Yokotani, Y.; Cui, X.; Yakata, S.; Kimura, T.

    2015-12-01

    We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of the standing spin wave is an important advantage for the high power operation of the spin-wave device.

  10. Spin-valve magnetoresistance in Co/Si/(Co/Cu/Co) multilayers

    Institute of Scientific and Technical Information of China (English)

    SHEN Hong-lie; LI Guan-xiong

    2005-01-01

    A series of Co/Si/(Co/Cu/Co) multilayers and Co/Si/Co sandwiches were prepared by high vacuum electron-beam evaporation. It was found that a Si spacer (≥0.9nm) could greatly decrease the interlayer coupling in Co/Si/Co sandwiches and there was no magnetoresistance(MR) or spin-valve MR in them due to the high resistivity of Si spacer. While in Co/Si/(Co/Cu/Co) multilayers, we observed a spin-valve MR of about 0.5% through a nominal 2.7nm Si spacer at room temperature. The spin-valve MR in Co/Si/(Co/Cu/Co) multilayers was attributed to the enhanced spin polarization of conduction electrons caused by the top Co/Cu/Co sandwich with GMR mechanism and high spin-dependent scattering at Co/Cu interface.

  11. Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films

    KAUST Repository

    Mi, W. B.

    2013-06-07

    Polycrystalline ferromagnetic GdN x films were fabricated at different N2 flow rates ( fN2 ) to modify N-vacancy concentration so as to study its influence on electrotransport. Metal-semiconductor transition appears at Curie temperature (TC ) of ∼40 K. Temperature-dependent magnetoresistance (MR) shows a peak at T C. The films at fN2  = 5, 10, 15, and 20 sccm show MR of −38%, −42%, −46%, and −86% at 5 K and 50 kOe, respectively. Above 15 K, MR is from colossal MR and from both colossal and tunneling MR below 15 K. The enhanced MR at fN2  = 20 sccm is attributed to large spin polarization of half-metallicity in GdN x with low N vacancies.

  12. Effects of Rapid Recurrent Thermal Annealing on Giant Magnetoresistance NiFe/Ag Multilayers

    Institute of Scientific and Technical Information of China (English)

    文岐业; 张怀武; 蒋向东; 唐晓莉; 张万里

    2003-01-01

    NiFe/Ag multilayers were prepared by dc sputtering onto glass-ceramic substrates directly at room temperature.The samples were thermally processed by rapid recurrent thermal anneal (RRTA). We studied the effects of RRTA on giant magnetoresistance (GMR) NiFe/Ag multilayer by controlling the anneal temperature as well as the rapid anneal cycle. The samples after three RRTA cycles have a similar annealing temperature dependence of GMR responses to the ordinary annealed samples. With the increasing anneal cycle, the GMR response improved at first and then reached an unexpected high value of 9% before descent rapidly. Microstructure study shows that this effect is ascribed to the transformation of continuous NiFe layer into discontinuous one, and then into a granular like film in a step-by-step way.

  13. Low frequency noise and complex AC magnetoresistance in superconducting Pb/Ge with square antidot lattice

    International Nuclear Information System (INIS)

    The low frequency voltage noise and complex AC voltage response to weakly modulated magnetic fields have been studied in a superconducting Pb film with a square lattice of antidots. The temperature was close to Tc and the DC magnetic field was changed between ±1.5 H1 with H1=9.2 Oe corresponding to one vortex per antidot. A narrow band noise near f∼0.55 Hz has been observed which shows different dependences on the magnetic field in 4- and 5-point probe configurations. In the latter configuration one probes the correlation between the noise voltages in the two parts of the sample. We also measured the resistance when, in addition to the DC field, a small AC field with frequency f<177 Hz was applied. The data showed that the complex magnetoresistance response becomes nonlinear below 1/3 of the first matching field

  14. Giant magnetoresistance in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes

    Institute of Scientific and Technical Information of China (English)

    Lu Jianduo; Xu Bin

    2012-01-01

    In this paper,by using the transfer matrix method,we theoretically investigate the magnetoresistance (MR) effect in a two-dimensional electron gas (2DEG) modulatcd by two Schottky metal (SM) stripes and two ferromagnetic (FM) stripes on the top and bottom of the 2DEG.From the numerical results,we find that a considerable MR effect can be achieved in this device due to the significant difference between electron transmissions through the parallel and antiparallel magnetization configurations.We also find that the MR ratio obviously depends on the magnetic strength and the electric-barrier height as well as the distance between the FM and SM stripes.These characters are very helpful for making the new type of MR devices according to thcir practical applications.

  15. Bilayer splitting and c-axis coupling in bilayer manganites showing colossal magnetoresistance.

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, C.; Graf, J.; Zhou, S. Y.; Bostwick, A.; Rotenberg, E.; Zheng, H.; Mitchell, J. F.; Lanzara, A.; Materials Science Division; Univ. of California at Berkeley; LBNL

    2009-12-07

    By performing angle-resolved photoemission spectroscopy of the bilayer colossal magnetoresistive (CMR) manganite, La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}, we provide the complete mapping of the Fermi-level spectral weight topology. Clear and unambiguous bilayer splitting of the in-plane 3d{sub x{sup 2}-y{sup 2}} band, mapped throughout the Brillouin zone, and the full mapping of the 3d{sub 3z{sup 2}-r{sup 2}} band are reported. Peculiar doping and temperature dependencies of these bands imply that as transition from the ferromagnetic metallic phase approaches, either as a function of doping or temperature, coherence along the c-axis between planes within the bilayer is lost, resulting in reduced interplane coupling. These results suggest that interplane coupling plays a large role in the CMR transition.

  16. Influence of Si buffer layer on the giant magnetoresistance effect in Co/Cu/Co sandwiches

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Co/Cu/Co sandwiches with a semiconductor Si buffer layer were prepared by high vacuum electron-beam evaporation. The influence of the Si buffer layer with different thickness on the giant magnetoresistance (GMR) effect in the Co/Cu/Co sandwiches was investigated. It was found that the GMR showed an obvious anisotropy when the thickness of Si buffer layer was larger than or equal to 0.9 nm, and that the GMR was basically isotropic with an Si buffer layer thinner than 0.9 nm. The anisotropic behavior of GMR can be ascribed to the in-plane magnetic anisotropy in the sandwiches. Due to the interdiffusion at the Si buffer/Co interface, a Co2Si interface layer with a good (301) texture formed and induced the in-plane magnetic anisotropy in the sandwiches. The dependence of the crystalline texture of the sandwiches on the thickness of Si buffer layer was also studied.

  17. Magnetoresistance of One-Dimensional Subbands in Tunnel-Coupled Double Quantum Wires

    International Nuclear Information System (INIS)

    We study the low-temperature in-plane magnetoresistance of tunnel-coupled quasi-one-dimensional quantum wires. The wires are defined by two pairs of mutually aligned split gates on opposite sides of a < 1 micron thick AlGaAs/GaAs double quantum well heterostructure, allowing independent control of their widths. In the ballistic regime, when both wires are defined and the field is perpendicular to the current, a large resistance peak at 6 Tesla is observed with a strong gate voltage dependence. The data is consistent with a counting model whereby the number of subbands crossing the Fermi level changes with field due to the formation of an anticrossing in each pair of 1D subbands

  18. Tunneling Conductance and Magnetoresistance in Ferromagnet/Ferromagnet/d-Wave Superconductor Double Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    DONG Zheng-Chao

    2004-01-01

    The tunneling conductance and tunneling magnetoresistance (TMR) are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor (FM/I/FM/I/d-wave SC) structures by applying an extended Blonder-Tinkham-Klapwijk (BTK) approach. We study the effects of the exchange splitting in the FM,the magnetic impurity scattering in the thin insulator interface of FM/I/FM, and noncollinear magnetizations in adjacent magnetic layers on the TMR. It is shown (1) that the tunneling conductance and TMR exhibit amplitude-varying oscillating behavior with exchange splitting, (2) that with the presence of spin-flip scattering in insulator interface of FM/I/FM, the TMR can be dramatically enhanced, and (3) that the TMR depends strongly on the angle between the magnetization of two FMs.

  19. Low temperature magnetoresistance and magnetization studies of iron encapsulated multiwall carbon nanotube/polyvinyl chloride composites

    Science.gov (United States)

    Vasanthkumar, M. S.; Sameera, I.; Bhatia, Ravi; Prasad, V.; Jayanna, H. S.

    2015-01-01

    We present the experimental results of temperature dependent magnetoresistance (MR) and the magnetization studies of iron encapsulated multiwall carbon nanotube (MWCNT)/polyvinyl chloride (PVC) composites with different wt% of MWCNTs. Transmission electron microscopy characterization shows that MWCNTs are encapsulated with rod-shaped iron nanoparticles of aspect ratio of ~3. The MR behavior of 1.9 wt% MWCNT/PVC sample shows dominance of forward scattering and wave function shrinkage whereas, weak localization and electron-electron interactions explain the MR data of higher wt% samples (9.1, 16.6 and 44.4 wt%). The composites of 4.7 and 9.1 wt% exhibit ferromagnetic behavior at all temperatures with room temperature coercivities of ~1036 and 628 Oe, respectively.

  20. Hall effect within the colossal magnetoresistive semimetallic state of MoTe2

    Science.gov (United States)

    Zhou, Qiong; Rhodes, D.; Zhang, Q. R.; Tang, S.; Schönemann, R.; Balicas, L.

    2016-09-01

    Here, we report a systematic study on the Hall effect of the semimetallic state of bulk MoTe2, which was recently claimed to be a candidate for a novel type of Weyl semimetallic state. The temperature (T ) dependence of the carrier densities and of their mobilities, as estimated from a numerical analysis based on the isotropic two-carrier model, indicates that its exceedingly large and nonsaturating magnetoresistance may be attributed to a near perfect compensation between the densities of electrons and holes at low temperatures. A sudden increase in hole density, with a concomitant rapid increase in the electron mobility below T ˜40 K, leads to comparable densities of electrons and holes at low temperatures suggesting a possible electronic phase transition around this temperature.

  1. Orbital angular momentum of the laser beam and the second order intensity moments

    Institute of Scientific and Technical Information of China (English)

    高春清[1; 魏光辉[2; HorstWeber[3

    2000-01-01

    From the wave equation of a generalized beam the orbital angular momentum is studied. It is shown that the orbital angular momentum exists not only in the Laguerre-Gaussian beam, but in any beam with an angular-dependent structure. By calculating the second order intensity moments of the beam the relation between the orbital angular momentum and the second order moments 〈xθy〉, 〈yθx〉 is given. As an example the orbital angular momentum of the general astigmatic Gaussian beam is studied.

  2. Orbital angular momentum of the laser beam and the second order intensity moments

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    From the wave equation of a generalized beam the orbital angular momentum is studied. It is shown that the orbital angular momentum exists not only in the Laguerre_Gaussian beam,but in any beam with an angular_dependent structure. By calculating the second order intensity moments of the beam the relation between the orbital angular momentum and the second order moments 〈xθy〉, 〈yθx〉 is given. As an example the orbital angular momentum of the general astigmatic Gaussian beam is studied.

  3. An efficient biosensor made of an electromagnetic trap and a magneto-resistive sensor

    KAUST Repository

    Li, Fuquan

    2014-09-01

    Magneto-resistive biosensors have been found to be useful because of their high sensitivity, low cost, small size, and direct electrical output. They use super-paramagnetic beads to label a biological target and detect it via sensing the stray field. In this paper, we report a new setup for magnetic biosensors, replacing the conventional "sandwich" concept with an electromagnetic trap. We demonstrate the capability of the biosensor in the detection of E. coli. The trap is formed by a current-carrying microwire that attracts the magnetic beads into a sensing space on top of a tunnel magneto-resistive sensor. The sensor signal depends on the number of beads in the sensing space, which depends on the size of the beads. This enables the detection of biological targets, because such targets increase the volume of the beads. Experiments were carried out with a 6. μm wide microwire, which attracted the magnetic beads from a distance of 60. μm, when a current of 30. mA was applied. A sensing space of 30. μm in length and 6. μm in width was defined by the magnetic sensor. The results showed that individual E. coli bacterium inside the sensing space could be detected using super-paramagnetic beads that are 2.8. μm in diameter. The electromagnetic trap setup greatly simplifies the device and reduces the detection process to two steps: (i) mixing the bacteria with magnetic beads and (ii) applying the sample solution to the sensor for measurement, which can be accomplished within about 30. min with a sample volume in the μl range. This setup also ensures that the biosensor can be cleaned easily and re-used immediately. The presented setup is readily integrated on chips via standard microfabrication techniques. © 2014 Elsevier B.V.

  4. Tunneling anisotropic magnetoresistance driven by resonant surface states: first-principles calculations on an Fe(001) surface.

    Science.gov (United States)

    Chantis, Athanasios N; Belashchenko, Kirill D; Tsymbal, Evgeny Y; van Schilfgaarde, Mark

    2007-01-26

    Fully relativistic first-principles calculations of the Fe(001) surface demonstrate that resonant surface (interface) states may produce sizable tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a single magnetic electrode. The effect is driven by the spin-orbit coupling. It shifts the resonant surface band via the Rashba effect when the magnetization direction changes. We find that spin-flip scattering at the interface is controlled not only by the strength of the spin-orbit coupling, but depends strongly on the intrinsic width of the resonant surface states. PMID:17358794

  5. Large magnetic entropy change in the colossal magnetoresistance material La 2/3Ca 1/3MnO 3

    Science.gov (United States)

    Sun, Young; Xu, Xiaojun; Zhang, Yuheng

    2000-09-01

    In this paper, we present a study of magnetocaloric effect in the colossal magnetoresistance material La 2/3Ca 1/3MnO 3. From the measurements of temperature dependence of magnetization under various magnetic fields, we have discovered a large magnetic entropy change associated with the ferromagnetic-paramagnetic transition. This result suggests that perovskite manganites are suitable candidates as working substances in magnetic refrigeration technology.

  6. Stellar Diameters and Temperatures IV. Predicting Stellar Angular Diameters

    CERN Document Server

    Boyajian, Tabetha; von Braun, Kaspar

    2013-01-01

    The number of stellar angular diameter measurements has greatly increased over the past few years due to innovations and developments in the field of long baseline optical interferometry (LBOI). We use a collection of high-precision angular diameter measurements for nearby, main-sequence stars to develop empirical relations that allow the prediction of stellar angular sizes as a function of observed photometric color. These relations are presented for a combination of 48 broad-band color indices. We empirically show for the first time a dependence on metallicity to these relations using Johnson $(B-V)$ and Sloan $(g-r)$ colors. Our relations are capable of predicting diameters with a random error of less than 5% and represent the most robust and empirical determinations to stellar angular sizes to date.

  7. Quantum optimal control of photoelectron spectra and angular distributions

    CERN Document Server

    Goetz, R Esteban; Santra, Robin; Koch, Christiane P

    2016-01-01

    Photoelectron spectra and photoelectron angular distributions obtained in photoionization reveal important information on e.g. charge transfer or hole coherence in the parent ion. Here we show that optimal control of the underlying quantum dynamics can be used to enhance desired features in the photoelectron spectra and angular distributions. To this end, we combine Krotov's method for optimal control theory with the time-dependent configuration interaction singles formalism and a splitting approach to calculate photoelectron spectra and angular distributions. The optimization target can account for specific desired properties in the photoelectron angular distribution alone, in the photoelectron spectrum, or in both. We demonstrate the method for hydrogen and then apply it to argon under strong XUV radiation, maximizing the difference of emission into the upper and lower hemispheres, in order to realize directed electron emission in the XUV regime.

  8. Quantum optimal control of photoelectron spectra and angular distributions

    Science.gov (United States)

    Goetz, R. Esteban; Karamatskou, Antonia; Santra, Robin; Koch, Christiane P.

    2016-01-01

    Photoelectron spectra and photoelectron angular distributions obtained in photoionization reveal important information on, e.g., charge transfer or hole coherence in the parent ion. Here we show that optimal control of the underlying quantum dynamics can be used to enhance desired features in the photoelectron spectra and angular distributions. To this end, we combine Krotov's method for optimal control theory with the time-dependent configuration interaction singles formalism and a splitting approach to calculate photoelectron spectra and angular distributions. The optimization target can account for specific desired properties in the photoelectron angular distribution alone, in the photoelectron spectrum, or in both. We demonstrate the method for hydrogen and then apply it to argon under strong XUV radiation, maximizing the difference of emission into the upper and lower hemispheres, in order to realize directed electron emission in the XUV regime.

  9. All joint moments significantly contribute to trunk angular acceleration.

    Science.gov (United States)

    Nott, Cameron R; Zajac, Felix E; Neptune, Richard R; Kautz, Steven A

    2010-09-17

    Computationally advanced biomechanical analyses of gait demonstrate the often counter-intuitive roles of joint moments on various aspects of gait such as propulsion, swing initiation, and balance. Each joint moment can produce linear and angular acceleration of all body segments (including those on which the moment does not directly act) due to the dynamic coupling inherent in the interconnected musculoskeletal system. This study presents quantitative relationships between individual joint moments and trunk control with respect to balance during gait to show that the ankle, knee, and hip joint moments all affect the angular acceleration of the trunk. We show that trunk angular acceleration is affected by all joints in the leg with varying degrees of dependence during the gait cycle. Furthermore, it is shown that inter-planar coupling exists and a two-dimensional analysis of trunk balance neglects important out-of-plane joint moments that affect trunk angular acceleration.

  10. Correlation between vacancies and magnetoresistance changes in FM manganites using the Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Agudelo-Giraldo, J.D. [PCM Computational Applications, Universidad Nacional de Colombia-Sede Manizales, Km. 9 vía al aeropuerto, Manizales (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [PCM Computational Applications, Universidad Nacional de Colombia-Sede Manizales, Km. 9 vía al aeropuerto, Manizales (Colombia); Restrepo, J. [Grupo de Magnetismo y Simulación, Instituto de Física, Universidad de Antioquia, A.A. 1226, Medellín (Colombia)

    2015-10-01

    The Metropolis algorithm and the classical Heisenberg approximation were implemented by the Monte Carlo method to design a computational approach to the magnetization and resistivity of La{sub 2/3}Ca{sub 1/3}MnO{sub 3}, which depends on the Mn ion vacancies as the external magnetic field increases. This compound is ferromagnetic, and it exhibits the colossal magnetoresistance (CMR) effect. The monolayer was built with L×L×d dimensions, and it had L=30 umc (units of magnetic cells) for its dimension in the x–y plane and was d=12 umc in thickness. The Hamiltonian that was used contains interactions between first neighbors, the magnetocrystalline anisotropy effect and the external applied magnetic field response. The system that was considered contains mixed-valence bonds: Mn{sup 3+eg’}–O–Mn{sup 3+eg}, Mn{sup 3+eg}–O–Mn{sup 4+d3} and Mn{sup 3+eg’}–O–Mn{sup 4+d3}. The vacancies were placed randomly in the sample, replacing any type of Mn ion. The main result shows that without vacancies, the transitions T{sub C} (Curie temperature) and T{sub MI} (metal–insulator temperature) are similar, whereas with the increase in the vacancy percentage, T{sub MI} presented lower values than T{sub C}. This situation is caused by the competition between the external magnetic field, the vacancy percentage and the magnetocrystalline anisotropy, which favors the magnetoresistive effect at temperatures below T{sub MI}. Resistivity loops were also observed, which shows a direct correlation with the hysteresis loops of magnetization at temperatures below T{sub C}. - Highlights: • Changes in the resistivity of FM materials as a function of the temperature and external magnetic field can be obtained by the Monte Carlo method, Metropolis algorithm, classical Heisenberg and Kronig–Penney approximation for magnetic clusters. • Increases in the magnetoresistive effect were observed at temperatures below T{sub MI} by the vacancies effect. • The resistive hysteresis

  11. Angular Distributions of Discrete Mesoscale Mapping Functions

    Directory of Open Access Journals (Sweden)

    Kroszczyński Krzysztof

    2015-08-01

    Full Text Available The paper presents the results of analyses of numerical experiments concerning GPS signal propagation delays in the atmosphere and the discrete mapping functions defined on their basis. The delays were determined using data from the mesoscale non-hydrostatic weather model operated in the Centre of Applied Geomatics, Military University of Technology. A special attention was paid to investigating angular characteristics of GPS slant delays for low angles of elevation. The investigation proved that the temporal and spatial variability of the slant delays depends to a large extent on current weather conditions

  12. Angular Diameter Distances in Clumpy Friedmann Universes

    CERN Document Server

    Tomita, K

    1998-01-01

    Solving null-geodesic equations, behavior of angular diameter distances is studied in inhomogeneous cosmological models, which are given by performing N-body simulations with the CDM spectrum. The distances depend on the separation angle of ray pairs, the mass and the radius of particles cosisting of galaxies and dark matter balls, and cosmological model parameters. The calculated distances are compared with the Dyer- Roeder distance, and after many ray-shooting, the average, dispersion and distribution of the clumpiness parameter are derived.

  13. CPP magnetoresistance of magnetic multilayers: A critical review

    Science.gov (United States)

    Bass, Jack

    2016-06-01

    We present a comprehensive, critical review of data and analysis of Giant (G) Magnetoresistance (MR) with Current-flow Perpendicular-to-the-layer-Planes (CPP-MR) of magnetic multilayers [F/N]n (n=number of repeats) composed of alternating nanoscale layers of ferromagnetic (F) and non-magnetic (N) metals, or of spin-valves that allow control of anti-parallel (AP) and parallel (P) orientations of the magnetic moments of adjacent F-layers. GMR, a large change in resistance when an applied magnetic field changes the moment ordering of adjacent F-layers from AP to P, was discovered in 1988 in the geometry with Current flow in the layer-Planes (CIP). The CPP-MR has two advantages over the CIP-MR: (1) relatively simple two-current series-resistor (2CSR) and more general Valet-Fert (VF) models allow more direct access to the underlying physics; and (2) it is usually larger, which should be advantageous for devices. When the first CPP-MR data were published in 1991, it was not clear whether electronic transport in GMR multilayers is completely diffusive or at least partly ballistic. It was not known whether the properties of layers and interfaces would vary with layer thickness or number. It was not known whether the CPP-MR would be dominated by scattering within the F-metals or at the F/N interfaces. Nothing was known about: (1) spin-flipping within F-metals, characterized by a spin-diffusion length, lsfF; (2) interface specific resistances (AR=area A times resistance R) for N1/N2 interfaces; (3) interface specific resistances and interface spin-dependent scattering asymmetry at F/N and F1/F2 interfaces; and (4) spin-flipping at F/N, F1/F2 and N1/N2 interfaces. Knowledge of spin-dependent scattering asymmetries in F-metals and F-alloys, and of spin-flipping in N-metals and N-alloys, was limited. Since 1991, CPP-MR measurements have quantified the scattering and spin-flipping parameters that determine GMR for a wide range of F- and N-metals and alloys and of F/N pairs. This

  14. Magnetoresistance scaling in MBE-grown La0.7Ca0.3MnO3 thin films

    International Nuclear Information System (INIS)

    We present a detailed analysis of magnetoresistance in tetragonal thin films of ferromagnetic La0.7Ca0.3MnOδ grown by atomic layer-by-layer molecular-beam epitaxy. The field and temperature dependence of the resistivity ρ show an explicit dependence only on the fractional magnetization M/Msat and are consistent with a single approximate form ρ≅ρ(0)exp[-C(M/Msat)2] for small and intermediate magnetization both above and below the Curie temperature (TC). The microscopic magnetization and susceptibility (χ) have been inferred from the low-field magnetoresistance above TC with χ following a Curie-Weiss form. We observe a sharp transition in the low-field (H) dependence of ρ from quadratic (∝H2) above TC to linear (∝H) below, consistent with a temperature-independent ρ(M). Finally we show that within a simple model this temperature-independent form for ρ reproduces the behavior of the measured low-field sensitivity below TC. copyright 1996 The American Physical Society

  15. Factors influencing perceived angular velocity

    Science.gov (United States)

    Kaiser, Mary K.; Calderone, Jack B.

    1991-01-01

    Angular velocity perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear velocities and 2D image velocities of texture elements for a given angular velocity. Results of experiments show that edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities had an impact on perceived angular velocity; this bias was associated with 2D image velocity rather than 3D tangential velocity. Despite these biases judgements were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).

  16. Giant magnetoresistance, structural and magnetic properties of glass-coated Fe-Ni-Cu microwires

    International Nuclear Information System (INIS)

    Glass-coated Fe-Ni-Cu microwires prepared by Taylor's technique exhibit negative magnetoresistance (MR) of 8.15% at 77 K and 6.35% at 300 K in a magnetic field of 9.0 T. The MR is of the same origin found in the granular giant magnetoresistance (GMR) materials and is distinguishable from the giant magnetoimpedance (MI) commonly seen in soft magnetic microwires. MI displays a peak at zero field for RF currents with frequencies less than 20 MHz and it crosses over to a sharp dip at higher frequencies. This crossover is ascribed to the skin-depth-limited response primarily governed by the field dependence of the permeability. Micro-X-ray absorption near edge structure (micro-XANES) spectroscopy data were collected at the K edges of Cu, Ni and Fe and revealed that the Fe atoms in the as-cast sample are in FCC configuration and they remain in the FCC phase throughout the annealing processes. The MR decreases to ∼2.5% as the annealing temperature increases to 500 deg. C. The loss of GMR upon annealing is attributed to the growth of FCC Fe-Ni-rich magnetic particles. The increase in the Fe-Ni particle size also results in higher room temperature coercivity. When the annealing temperature is increased to 500 deg. C, a wasp-waisted hysteresis loop is observed which arises from the locking-in of the domain walls by the directional order of atoms due to diffusion under the influence of the local magnetic field. A magnetically hard glass-coated microwire with coercivity of 600 Oe is obtained after annealing at 700 deg. C for 1 h

  17. Achromatic orbital angular momentum generator

    CERN Document Server

    Bouchard, Frédéric; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W

    2014-01-01

    We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \\textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarisation, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of $95\\%$ for these three different wavelengths is observed. %, which confirms its wavelen...

  18. A Stern-Gerlach-like approach to electron orbital angular momentum measurement

    CERN Document Server

    Harvey, Tyler R

    2016-01-01

    Many methods now exist to prepare free electrons into orbital angular momentum states, and the predicted applications of these electron states as probes of materials and scattering processes are numerous. The development of electron orbital angular momentum measurement techniques has lagged behind. We show that coupling between electron orbital angular momentum and a spatially varying magnetic field produces an angular momentum-dependent focusing effect. We propose a design for an orbital angular momentum measurement device built on this principle. As the method of measurement is non-interferometric, the device works equally well for mixed, superposed and pure final orbital angular momentum states. The energy and orbital angular momentum distributions of inelastically scattered electrons may be simultaneously measurable with this technique.

  19. Angular momentum in human walking.

    Science.gov (United States)

    Herr, Hugh; Popovic, Marko

    2008-02-01

    Angular momentum is a conserved physical quantity for isolated systems where no external moments act about a body's center of mass (CM). However, in the case of legged locomotion, where the body interacts with the environment (ground reaction forces), there is no a priori reason for this relationship to hold. A key hypothesis in this paper is that angular momentum is highly regulated throughout the walking cycle about all three spatial directions [|Lt| approximately 0], and therefore horizontal ground reaction forces and the center of pressure trajectory can be explained predominantly through an analysis that assumes zero net moment about the body's CM. Using a 16-segment human model and gait data for 10 study participants, we found that calculated zero-moment forces closely match experimental values (Rx2=0.91; Ry2=0.90). Additionally, the centroidal moment pivot (point where a line parallel to the ground reaction force, passing through the CM, intersects the ground) never leaves the ground support base, highlighting how closely the body regulates angular momentum. Principal component analysis was used to examine segmental contributions to whole-body angular momentum. We found that whole-body angular momentum is small, despite substantial segmental momenta, indicating large segment-to-segment cancellations ( approximately 95% medio-lateral, approximately 70% anterior-posterior and approximately 80% vertical). Specifically, we show that adjacent leg-segment momenta are balanced in the medio-lateral direction (left foot momentum cancels right foot momentum, etc.). Further, pelvis and abdomen momenta are balanced by leg, chest and head momenta in the anterior-posterior direction, and leg momentum is balanced by upper-body momentum in the vertical direction. Finally, we discuss the determinants of gait in the context of these segment-to-segment cancellations of angular momentum.

  20. Non-Colinearity of Angular Velocity and Angular Momentum

    Science.gov (United States)

    Burr, A. F.

    1974-01-01

    Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)

  1. Tailoring magnetoresistance at the atomic level: An ab initio study

    KAUST Repository

    Tao, Kun

    2012-01-05

    The possibility of manipulating the tunneling magnetoresistance (TMR) of antiferromagnetic nanostructures is predicted in the framework of ab initio calculations. By the example of a junction composed of an antiferromagnetic dimer and a spin-polarized scanning tunneling microscopy tip we show that the TMR can be tuned and even reversed in sign by lateral and vertical movements of the tip. Moreover, our finite-bias calculations demonstrate that the magnitude and the sign of the TMR can also be tuned by an external voltage. © 2012 American Physical Society.

  2. Micromagnetic Simulation of Transfer Curve in Giant-Magnetoresistive Head

    Institute of Scientific and Technical Information of China (English)

    SHE Sheng-Xian; WEI Dan; ZHENG Yang; Qu Bing-Jun; REN Tian-Ling; LIU Xi; WEI Fu-Lin

    2009-01-01

    The transfer curve of the giant-magnetoresistive(GMR)magnetic head represents its most important property in applications,and it is calculated by the micromagnetic modeling of the free layer and the pinned layer in the heart of the GMR head.Affections of the bias hard magnetic layer and the anti-ferromagnetic pinning layer are modeled by effective magnetic Selds.The simulated transfer curve agrees with experiment quite well,therefore the values of these effective magnetic fields can be determined by the model.A synthetic antiferromagnetic spin valve structure GMR head is also analyzed for comparison.

  3. Magneto-resistive and spin valve heads fundamentals and applications

    CERN Document Server

    Mallinson, John C

    2002-01-01

    This book is aims to be a comprehensive source on the physics and engineering of magneto-resistive heads. Most of the material is presented in a nonmathematical manner to make it more digestible for researchers, students, developers, and engineers.In addition to revising and updating material available in the first edition, Mallinson has added nine new chapters dealing with various aspects concerning spin valves, the electron spin tunneling effect, the electrostatic discharge effects, read amplifiers, and signal-to-noise ratios, making this a completely up-to-date reference.Th

  4. Magnetic giant magnetoresistance commercial off the shelf for space applications

    DEFF Research Database (Denmark)

    Michelena, M.D.; Oelschlägel, Wulf; Arruego, I.;

    2008-01-01

    The increase of complexity and miniaturizing level of Aerospace platforms make use of commercial off the shelf (COTS) components constitute a plausible alternative to the use of military or rad-tolerant components. In this work, giant magnetoresistance commercial sensors are studied to be used...... as COTS, the next missions to be launched in the framework of the Spanish National Space Program: OPTOS and SEOSAT. This technology of magnetic sensors is interesting due to their high operating range up to 2 mT and the high temperature dynamic range from -50 up to 150 degrees C. However, in contrast...

  5. High signal output in current-perpendicular-to-the-plane giant magnetoresistance sensors using In-Zn-O-based spacer layers

    Science.gov (United States)

    Nakatani, Tomoya; Mihajlović, Goran; Read, John C.; Choi, Young-suk; Childress, Jeffrey R.

    2015-09-01

    We report current-perpendicular-to-the-plane giant magnetoresistance (CPP-GMR) sensors with a conductive Ag/In-Zn-O (IZO)/Zn trilayer as the spacer layer. Magnetoresistance ratios as high as 26% at resistance-area product (RA) = 60-120 mΩ µm2 were obtained in thin, polycrystalline spin valves suitable for modern read sensors of hard disk drives (HDDs). The large CPP-GMR values are attributed to the large spin-dependent scattering at the interfaces of the ferromagnet/IZO-based spacer junctions. The maximum voltage output of sensors with Ag/IZO/Zn spacers was ΔVmax = 11.3 mV, significantly larger than that observed for metallic AgSn spacers (2.3 mV). Such improved properties are important for HDD read heads with recording densities larger than 1 Tbit/in.2.

  6. Magnetic Properties and Low-Field Magnetoresistance of Pr0.7Pb0.3MnO3 Single Crystals

    Institute of Scientific and Technical Information of China (English)

    GU Ben-Xi; ZHANG Shi-Yuan; DU You-Wei

    2001-01-01

    The magnetic properties and magnetoresistance of Pr0.7Pb0.sMnOs single crystals have been studied. At lowtemperature, the temperature dependence of magnetization can be represented as M(T) = M(0)(1 - BT3/2).A large B value was observed. The spontaneous magnetic moment is slightly larger than the spin-only valuefor Mns+ and Mn4+ ions. Above the Curie temperature, the susceptibility obeys the Curie-Weiss Law and the resistivity R can fit well with Ro exp(To/T)1/4. It is found that the effective paramagnetic moment obtained from the Curie constant is larger than the theoretical value. The large effective paramagnetic moment may originatefrom the magnetic clusters. A large low-field magnetoresistance of A R/ R(0) = -50% is observed at 230K in 1 T.

  7. Voltage-controlled ferromagnetism and magnetoresistance in LaCoO3/SrTiO3 heterostructures

    Science.gov (United States)

    Hu, Chengqing; Park, Keun Woo; Posadas, Agham; Jordan-Sweet, Jean L.; Demkov, Alexander A.; Yu, Edward T.

    2013-11-01

    A LaCoO3/SrTiO3 heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO3, leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO3 layer on strain. Below the Curie temperature of the LaCoO3 layer, this effect leads to modulation of resistance in LaCoO3 as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO3. Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO3 layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO3 grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device.

  8. Large negative magnetoresistance induced by interplay between smooth disorder and antidots in AlGaN/GaN HEMT structures

    Science.gov (United States)

    Mishra, M. K.; Sharma, R. K.; Tyagi, R.; Manchanda, R.; Pandey, A. K.; Thakur, O. P.; Muralidharan, R.

    2016-04-01

    Large low temperature negative magnetoresistance (NMR) experimentally observed in AlGaN/GaN high electron mobility transistors (HEMT) structures grown by metalorganic chemical vapour deposition on sapphire substrate has been reported. A linear B -1 ln B dependence of magnetoresistance observed in our samples indicates the presence of random antidot array together with smooth disorder. It is proposed that the antidots are linked with high bandgap AlN rich regions formed due to possible Al-Ga segregation at the interface during growth and the smooth random disorder is due to interface roughness. The antidot density is estimated to be of ˜7 to 8 × 1010 cm-2 in our samples. The magnitude of NMR is also correlated with the extent of interface roughness indicated by x-ray reflectivity. It is also proposed that the formation of antidots is related with the lattice mismatch between substrate and epitaxial heterostructures. The NMR in AlGaN/GaN HEMT structures grown on SiC substrates having relatively lower lattice mismatch has been shown to have a usual B 2 and ln T dependences indicating only electron-electron interaction and absence of antidot-like scatterers.

  9. Magnetization, magnetoresistance, and x-ray diffraction measurements of discontinuous [Ni80Fe20/Ag] multilayers (abstract)

    Science.gov (United States)

    Lorenz, T.; Moske, M.; Käufler, A.; Geisler, H.; Samwer, K.

    1996-04-01

    Thin films for magnetic sensor application require a high sensitivity at low magnetic fields, for example, realized by Permalloy films. Promising candidates for a further improvement are discontinuous multilayers, first reported by Hylton et al. In our study, we report on [2.5 nm Ni80Fe20/y nm Ag] multilayers with the spacer layer thickness y ranging from 1.2 nm to 6.0 nm. The multilayers were electron beam deposited in UHV at different temperatures. The substrates used are thermally oxidized silicon wafers. The magnetization is obtained using a vibrating sample magnetometer (VSM), the magnetoresistance is measured at room temperature with the Montgomery method. Low and high angle x-ray diffraction measurements are performed in a Siemens D-5000 diffractometer. The samples are annealed ex situ between room temperature and 340 °C. The magnetoresistance is maximal after annealing the samples at a specific temperature, which decreases with increasing Ag-spacer thickness y. Moreover, the GMR decreases if the multilayers are deposited at elevated temperatures (100-200 °C). We also report on the dependence of the GMR on the interface roughness (σ≊0.5 nm rms) which we deduce from the small angle x-ray diffraction measurements. For a characterization of the reliability, we also investigated the dependence of the GMR on aging at 100 °C for several hours.

  10. Olympic Wrestling and Angular Momentum.

    Science.gov (United States)

    Carle, Mark

    1988-01-01

    Reported is the use of a wrestling photograph in a noncalculus introductory physics course. The photograph presents a maneuver that could serve as an example for a discussion on equilibrium, forces, torque, and angular motion. Provided are some qualitative thoughts as well as quantitative calculations. (YP)

  11. Turbodrill rod angular velocity indicator

    Energy Technology Data Exchange (ETDEWEB)

    Rogachev, O.K.; Belozerova, L.P.; Konenkov, A.K.

    1984-01-01

    This paper outlines shortcomings of existing types of telemetry systems which resulted in production of the IChT-1 unit. Unit is intended for control of angular velocity of serially produced turbodrill rods, during drilling of wells up to 5000 m deep, and bottomhole temperatures to 100C. The paper provides a detailed description and diagrams for installing this unit.

  12. Angular trapping of anisometric nano-objects in a fluid.

    Science.gov (United States)

    Celebrano, Michele; Rosman, Christina; Sönnichsen, Carsten; Krishnan, Madhavi

    2012-11-14

    We demonstrate the ability to trap, levitate, and orient single anisometric nanoscale objects with high angular precision in a fluid. An electrostatic fluidic trap confines a spherical object at a spatial location defined by the minimum of the electrostatic system free energy. For an anisometric object and a potential well lacking angular symmetry, the system free energy can further strongly depend on the object's orientation in the trap. Engineering the morphology of the trap thus enables precise spatial and angular confinement of a single levitating nano-object, and the process can be massively parallelized. Since the physics of the trap depends strongly on the surface charge of the object, the method is insensitive to the object's dielectric function. Furthermore, levitation of the assembled objects renders them amenable to individual manipulation using externally applied optical, electrical, or hydrodynamic fields, raising prospects for reconfigurable chip-based nano-object assemblies. PMID:23016893

  13. Angular distributions for two-photon double ionization of lithium

    Science.gov (United States)

    Armstrong, G. S. J.; Colgan, J.

    2012-08-01

    We present angular distributions for two-photon double ionization of lithium at photon energies of 50 eV (λ = 25 nm) and 59 eV (λ = 21 nm). The results are obtained from full-dimensional solution of the two-active-electron time-dependent Schrödinger equation using the time-dependent close-coupling method. We investigate two different double ionization mechanisms. First, we consider direct double ionization of the Li ground state following the absorption of two photons. Secondly, we consider an initial photoexcitation of the 1s2s2p doubly excited state, followed by photoionization of the 2s and 2p electrons. We find significant differences between the angular distributions obtained for these two distinct processes. We also compare the characteristics of the angular distributions for Li with those of other two-electron atoms.

  14. Imaging Ferromagnetic Tracers with a Magnetoresistive Sensors Array

    Science.gov (United States)

    Leyva, Juan A.; Carneiro, Antonio A. O.; Murta, Luís O.; Baffa, O.

    2006-09-01

    The aim of this work was to study the feasibility to obtain images from a distribution of ferromagnetic tracers using a magnetoresistive multichannel sensor array (MRA). A magnetic imaging system formed by a linear array composed of 12 magnetoresistive sensors (Honeywell HMC 1001) was constructed covering a scanning area of (16×18) cm2. The signal was pre-processed for off-set correction and interpolation to generate a matrix of (256×256). The point spread function of the MRA was evaluated and the sensors were spaced accordingly. The magnetic images were generated by mapping the response of the MRA at short distances from the presence of a magnetite powder dispersed in planar phantoms with different shapes. The phantoms were magnetized by a pulse field of approximately 80 mT produced by a Helmholtz coil. Using the Wiener filtering, the magnetic source images were obtained. We conclude that this biomagnetic method can be successfully used to generate planar functional images of the gastrointestinal tract using magnetic markers in the near field.

  15. Tunable magnetoresistance in an asymmetrically coupled single-molecule junction

    Science.gov (United States)

    Warner, Ben; El Hallak, Fadi; Prüser, Henning; Sharp, John; Persson, Mats; Fisher, Andrew J.; Hirjibehedin, Cyrus F.

    2015-03-01

    Phenomena that are highly sensitive to magnetic fields can be exploited in sensors and non-volatile memories. The scaling of such phenomena down to the single-molecule level may enable novel spintronic devices. Here, we report magnetoresistance in a single-molecule junction arising from negative differential resistance that shifts in a magnetic field at a rate two orders of magnitude larger than Zeeman shifts. This sensitivity to the magnetic field produces two voltage-tunable forms of magnetoresistance, which can be selected via the applied bias. The negative differential resistance is caused by transient charging of an iron phthalocyanine (FePc) molecule on a single layer of copper nitride (Cu2N) on a Cu(001) surface, and occurs at voltages corresponding to the alignment of sharp resonances in the filled and empty molecular states with the Cu(001) Fermi energy. An asymmetric voltage-divider effect enhances the apparent voltage shift of the negative differential resistance with magnetic field, which inherently is on the scale of the Zeeman energy. These results illustrate the impact that asymmetric coupling to metallic electrodes can have on transport through molecules, and highlight how this coupling can be used to develop molecular spintronic applications.

  16. Angular Momentum Transfer in Catastrophic Asteroid Impacts

    Science.gov (United States)

    Love, S. G.; Ahrens, T. J.

    1996-09-01

    Incomplete knowledge of angular momentum transfer in asteroid impacts has hampered efforts to deduce asteroid collisional histories from their rotation rates. This problem traditionally has been investigated using impact experiments on cm-scale, strength-dominated targets. Recent evidence, however, indicates that impacts on asteroids of km size and larger may be controlled by gravity rather than strength, and that the analogy to laboratory impacts may not hold. Accordingly, we have modelled catastrophic impacts on gravitating asteroids to better understand angular momentum transfer in such events. We employ a 3--D, strengthless, gravitating SPH computer code. Target bodies are 10 to 1000 km in diameter and do not initially rotate. Impact speeds are 3--7 km/s; impact angles are 15--75(deg) . Each target is composed of 1791 mass elements: spatial resolution is coarse but acceptable for large scale energy transfer. We simulate the hydrodynamic phase of each impact, after which particle motions are ballistic and treated analytically. Escaping particles have kinetic energy greater than the gravitational energy binding them to the rest of the system; the others reaccrete to form a ``rubble pile'' which is assumed spherical. The rubble pile's size, mass, and angular momentum define its rotation rate. Spin rates for ejected fragments cannot be determined. The target's final spin period depends on the impact angle and the fraction of target mass ejected, but not on impact speed or target size in the ranges tested. The lack of size dependence cannot explain the observed excess of slowly rotating asteroids of ~ 100 km diameter. The fraction of projectile angular momentum retained by the target varies dramatically with impact speed and angle and with target size and fraction of mass removed, complicating its use in models where collision geometry varies. The final spin period of an asteroid losing 50% of its mass is 6--10 hours, comparable to the asteroidal mean of 8 hours

  17. Observation of large low-field magnetoresistance in spinel cobaltite: A new half-metal

    KAUST Repository

    Li, Peng

    2015-12-10

    Low-field magnetoresistance is an effective and energy-saving way to use half-metallic materials in magnetic reading heads and magnetic random access memory. Common spin-polarized materials with low field magnetoresistance effect are perovskite-type manganese, cobalt, and molybdenum oxides. In this study, we report a new type of spinel cobaltite materials, self-assembled nanocrystalline NiCo2O4, which shows large low field magnetoresistance as large as –19.1% at 0.5 T and –50% at 9 T (2 K). The large low field magnetoresistance is attributed to the fast magnetization rotation of the core nanocrystals. The surface spin-glass is responsible for the observed weak saturation of magnetoresistance under high fields. Our calculation demonstrates that the half-metallicity of NiCo2O4 comes from the hopping eg electrons within the tetrahedral Co-atoms and the octahedral Ni-atoms. The discovery of large low-field magnetoresistance in simple spinel oxide NiCo2O4, a non-perovskite oxide, leads to an extended family of low-field magnetoresistance materials. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

  18. Studies of magnetoresistance and structure in Co-Ni-Cu thin wires

    Energy Technology Data Exchange (ETDEWEB)

    Zhukov, A. [Dpto. Fisica de Materiales, Fac. Quimicas, Universidad del Pais Vasco, 20009 San Sebastian (Spain); TAMAG Iberica S.L., Parque Tecnologico de Miramon, San Sebastian (Spain); Martin y Marero, D. [Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble, France and Instituto de Ciencia de Materiales de Aragon, CSIC, Zaragoza (Spain); Batallan, F.; Martinez, J.L.; Luna, C.; Vazquez, M. [Instituto de Ciencia de Materiales, CSIC, 28049, Cantoblanco, Madrid (Spain); Val, J.J. del [Dpto. de Fisica de Materiales, Facultad de Quimica, UPV, Centro Mixto CSIC-UPV/EHU, 1072, 20080 San Sebastian (Spain); Zhukova, V. [TAMAG Iberica S.L., Parque Tecnologico de Miramon, San Sebastian (Spain); Instituto de Ciencia de Materiales, CSIC, 28049, Cantoblanco, Madrid (Spain); Gonzalez, J. [Dpto. Fisica de Materiales, Fac. Quimicas, Universidad del Pais Vasco, 20009 San Sebastian (Spain); Kaloshkin, S. [Moscow Steel and Alloys Institute, Leninsky Av.4, 119991 Moscow (Russian Federation)

    2004-12-01

    We report on studies of magneto-transport properties and structure (by neutron and X-ray diffraction techniques) at 5-300 K in glass coated Co{sub 29}Ni{sub 25}Mn{sub 1}Cu{sub 45} microwires prepared by the Taylor-Ulitovsky technique. Annealing of the sample (973 K during 1 hour) results in an increasing of room temperature coercivity (H{sub c}) from 65 Oe up to 800 Oe. Considerable magneto-resistance, MR, is found in both in as-prepared and annealed microwires increasing up to about 4% in the annealed samples. Magnetic field dependence of MR in as-prepared and annealed samples is quite different. Roughly monotonic decay is observed in as-prepared microwires. Annealed sample exhibits a maximum and considerable hysteresis on magnetic field dependence of MR. Neutron diffraction allows to distinguish two peaks in the as-prepared sample and 3 peaks in annealed samples. Observed changes in temperature dependence of magnetic properties and of MR are correlated to the structure changes with temperature. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. The magnetoresistive effect induced by stress in spin-valve structures

    Institute of Scientific and Technical Information of China (English)

    Qian Li-Jie; Xu Xiao-Yong; Hu Jing-Guo

    2009-01-01

    Using a method of free energy minimization, this paper investigates the magnetization properties of a ferromagnetic (FM) monolayer and an FM/antiferromagnetic (AFM) bilayer under a stress field, respectively. It then investigates the magnetoresistance (MR) of the spin-valve structure, which is built by an FM monolayer and an FM/AFM bilayer, and its dependence upon the applied stress field. The results show that under the stress field, the magnetization properties of the FM monolayer is obviously different from that of the FM/AFM bilayer, since the coupled AFM layer can obviously block the magnetization of the FM layer. This phenomenon makes the MR of the spin-valve structure become obvious.In detail, there are two behaviors for the MR of the spin-valve structure dependence upon the stress field distinguished by the coupling (FM coupling or AFM coupling) between the FM layer and the FM/AFM bilayer. Either behavior of the MR of the spin-valve structure depends on the stress field including its value and orientation. Based on these investigations, a perfect mechanical sensor at the nano-scale is suggested to be devised experimentally.

  20. Role of spin polarized tunneling in magnetoresistance and low temperature minimum of polycrystalline La1–KMnO3 ( = 0.05, 0.1, 0.15) prepared by pyrophoric method

    Indian Academy of Sciences (India)

    Soma Das; T K Dey

    2006-11-01

    The low temperature resistivity and magnetoresistance of bulk samples of La1–KMnO3 has been investigated between 10 K and 300 K with and without the magnetic field ( = 0.8 T). All the samples show metal–insulator transitions with Curie temperature (C) ranging between 260 K and 309 K. At temperature below 60 K, the K-doped manganites exhibit a shallow minimum, which disappears under an applied field of 0.8 T. This field dependent minimum in resistivity, observed in K-doped lanthanum manganites is explained in the light of intergrain tunneling of the charge carriers between anti-ferromagnetically coupled grains of the polycrystalline samples. The field variation of magnetoresistance below C follows a phenomenological model which considers spin polarized tunneling at the grain boundaries. The intergranular contribution to the magnetoresistance is separated out from that due to spin polarized tunneling part at the grain boundaries. The temperature dependence of intrinsic contribution to the magnetoresistance follows the prediction of the double exchange model for all values of field at < C.