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Sample records for spin ti multidecker

  1. The spin filter effect of iron-cyclopentadienyl multidecker clusters: the role of the electrode band structure and the coupling strength

    International Nuclear Information System (INIS)

    Shen Xin; Yi Zelong; Shen Ziyong; Zhao Xingyu; Wu Jinlei; Hou Shimin; Sanvito, Stefano

    2009-01-01

    We present a theoretical study of spin transport in a series of organometallic iron-cyclopentadienyl, Fe n Cp n+1 , multidecker clusters sandwiched between either gold or platinum electrodes. Ab initio modeling is performed by combining the non-equilibrium Green's function formalism with spin density functional theory. Due to the intrinsic bonding nature, the low-bias conductance of the Fe n Cp n+1 clusters contacted to gold electrodes is relatively small even for strong cluster-electrode coupling. However, a nearly 100% spin polarization of the transmitted electrons can be achieved for the Fe n Cp n+1 (n>2) clusters. In contrast, the Fe n Cp n+1 (n>2) clusters attached to platinum electrodes through Pt adatoms not only can act as nearly perfect spin filters but also show a much larger transmission around the Fermi level, demonstrating their promising applications in future molecular spintronics.

  2. Spin correlations in Ho2Ti2O7: A dipolar spin ice system

    DEFF Research Database (Denmark)

    Bramwell, S.T.; Harris, M.J.; Hertog, B.C. den

    2001-01-01

    described by a nearest neighbor spin ice model and very accurately described by a dipolar spin ice model. The heat capacity is well accounted for by the sum of a dipolar spin ice contribution and an expected nuclear spin contribution, known to exist in other Ho(3+) salts. These results settle the question......The pyrochlore material Ho(2)Ti(2)O(7) has been suggested to show "spin ice" behavior. We present neutron scattering and specific heat results that establish unambiguously that Ho(2)Ti(2)O(7) exhibits spin ice correlations at low temperature. Diffuse magnetic neutron scattering is quite well...

  3. Possible spin frustration in Nd2Ti2O7 probed by muon spin relaxation.

    Science.gov (United States)

    Guo, Hanjie; Xing, Hui; Tong, Jun; Tao, Qian; Watanabe, Isao; Xu, Zhu-an

    2014-10-29

    Muon spin relaxation on Nd2Ti2O7 (NTO) and NdLaTi2O7 (NLTO) compounds are presented. The time spectra for both compounds are as expected for the paramagnetic state at high temperatures, but deviate from the exponential function below around 100 K. Firstly, the muon spin relaxation rate increases with decreasing temperature and then levels off below around 10 K, which is reminiscent of the frustrated systems. An enhancement of the relaxation rate by a longitudinal field in the paramagnetic state is observed for NTO and eliminated by a magnetic dilution for the NLTO sample. This suggests that the spectral density is modified by a magnetic dilution and thus indicates that the spins behave cooperatively rather than individually. The zero-field measurement at 0.3 K indicates that the magnetic ground state for NTO is ferromagnetic.

  4. Magnetostriction of the spin-ice system Yb2Ti2O7

    Science.gov (United States)

    Doerr, M.; Stöter, T.; Rotter, M.; Zvyagin, A. A.

    2018-03-01

    Low temperature magnetostriction effects have been studied at Yb2Ti2O7 which is characterized by a geometric magnetic frustration. The experimental finding and the developed theory suggest that Yb2Ti2O7 is a quantum spin ice. Most of the magnetoelastic effects can be explained by an exchange striction model. The external magnetic field together with the temperature govern the transition between the collective paramagnetic behavior of the classical spin ice and the magnetically ordered state.

  5. Valence and Spin fluctuations in Mn-doped ferroelectric BaTiO3

    OpenAIRE

    Mandal, Subhasish; Cohen, R. E.; Haule, K.

    2018-01-01

    We study Mn substitution for Ti in BaTiO$_3$ with and without compensating oxygen vacancies using density functional theory (DFT) in combination with dynamical mean field theory (DMFT). We find strong charge and spin fluctuations. Without compensating oxygen vacancies, the ground state is found to be a quantum superposition of two distinct atomic valences, 3{\\it d}$^4$ and 3{\\it d}$^5$. Introducing a compensating oxygen vacancy at a neighboring site reduces both charge and spin fluctuations d...

  6. Crystallization and Martensitic Transformation Behavior of Ti-Ni-Si Alloy Ribbons Prepared via Melt Spinning.

    Science.gov (United States)

    Park, Ju-Wan; Kim, Yeon-Wook; Nam, Tae-Hyun

    2018-09-01

    Ti-(50-x)Ni-xSi (at%) (x = 0.5, 1.0, 3.0, 5.0) alloy ribbons were prepared via melt spinning and their crystallization procedure and transformation behavior were investigated using differential scanning calorimtry, X-ray diffraction, and transmission electron microscopy. Ti-Ni-Si alloy ribbons with Si content less than 1.0 at% were crystalline, whereas those with Si content more than 3.0 at% were amorphous. Crystallization occurred in the sequence of amorphous →B2 → B2 → Ti5Si4 + TiNi3 → B2 + Ti5Si4 + TiNi3 + TiSi in the Ti-47.0Ni-3.0Si alloy and amorphous →R → R + Ti5Si4 + TiNi3 → R + Ti5Si4 + TiNi3 + TiSi in the Ti-45.0Ni-5.0Si alloy. The activation energy for crystallization was 189 ±8.6 kJ/mol for the Ti-47Ni-3Si alloy and 212±8.6 kJ/mol for the Ti-45Ni-5Si alloy. One-stage B2-R transformation behavior was observed in Ti-49.5Ni-0.5Si, Ti-49.0Ni-1.0Si, and Ti-47.0Ni- 3.0Si alloy ribbons after heating to various temperatures in the range of 873 K to 1073 K. In the Ti-45.0Ni-5.0Si alloy, one-stage B2-R transformation occurred after heating to 893 K, two-stage B2-R-B19' occurred after heating to 973 K, and two-stage B2-R-B19' occurred on cooling and one-stage B19'-B2 occurred on heating, after heating to 1073 K.

  7. Spin singlet formation in MgTi2O4: evidence of a helical dimerization pattern.

    Science.gov (United States)

    Schmidt, M; Ratcliff, W; Radaelli, P G; Refson, K; Harrison, N M; Cheong, S W

    2004-02-06

    The transition-metal spinel MgTi2O4 undergoes a metal-insulator (M-I) transition on cooling below T(M-I)=260 K. A sharp reduction of the magnetic susceptibility below T(M-I) suggests the onset of a magnetic singlet state. Using high-resolution synchrotron and neutron powder diffraction, we have solved the low-temperature crystal structure of MgTi2O4, which is found to contain dimers with short Ti-Ti distances (the locations of the spin singlets) alternating with long bonds to form helices. Band structure calculations based on hybrid exchange density functional theory show that, at low temperatures, MgTi2O4 is an orbitally ordered band insulator.

  8. Spin waves and phonons in a paraelectric antiferromagnet EuTiO3

    Science.gov (United States)

    Cao, Huibo; Hong, Jiawang; Delaire, Olivier; Hahn, Steven; Ehlers, Georg; Chi, Songxue; Garlea, Vasile; Fernandez-Baca, Jaime; Chakoumakos, Bryan; Yan, Jiaqiang; Sales, Brian

    2015-03-01

    Perovskite titanates ATiO3 (A=Ba,Pb,Sr,Ca,Cd,or Eu) are widely studied for their interesting instabilities and broad applications. A ferroelectric (FE) transition occurs in Ba, Pb, and Cd titanates, but not in SrTiO3 (STO) or EuTiO3 (ETO). In the case of STO, fluctuations yield a quantum paraelectric state, but whether ETO is quantum paraelectric remains an open question. Despite a number of similarities with well-studied STO, ETO is also unique owing to the magnetic Eu ions. By applying a tuning parameter, such as bi-axial tension, ETO can be turned into a FE ferromagnet, the ideal multiferroic. [J. H. Lee, et al., Nature 466, 954 (2010)] Studies of spin-spin and spin-lattice couplings in ETO are of great interest not only from a fundamental standpoint, but also for technological applications. We successfully grew a large, high-quality isotopically-enriched ETO crystal for neutron scattering. The crystal and magnetic structures were characterized with single crystal diffraction at HB-3A at HFIR at ORNL. The spin waves and phonons were measured in the temperature range of 1.5-400 K with CNCS at SNS and HB-3 at HFIR at ORNL. In this presentation, we will discuss structural instabilities, spin-spin interactions, and spin-phonon couplings in ETO. This work was supported by Office of Basic Energy Sciences, U.S. Department of Energy.

  9. Spin and orbital Ti magnetism at LaMnO3/SrTiO3 interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Garcial-Barriocanal, J [Universidad Complutense, Spain; Cezar, J. C. [European Synchrotron Radiation Facility (ESRF); Bruno, F. Y. [Universidad Complutense, Spain; Thakur, P. [European Synchrotron Radiation Facility (ESRF); Brookes, N. B. [European Synchrotron Radiation Facility (ESRF); Utfeld, C. [University of Bristol, UK; Riviera-Calzada, A. [Universidad Complutense, Spain; Giblin, S. R. [ISIS Facility, Rutherford Appleton Laboratory; Taylor, J. W. [ISIS Facility, Rutherford Appleton Laboratory; Duffy, J. A. [University of Warwick, UK; Dugdale, S. B. [University of Bristol, UK; Nakamura, T. [Japan Synchrotron Radiation Research Institute, SPring-8; Kodama, K. [Japan Synchrotron Radiation Research Institute, SPring-8; Leon, C. [Universidad Complutense, Spain; Okamoto, Satoshi [ORNL; Santamaria, J. [Universidad Complutense, Spain

    2010-01-01

    In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, what causes a null expectation value of the orbital moment. Magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment. Accordingly, novel forms of ferromagnetic superexchange interaction unique to t2g electrons systems have been theoretically predicted, although their experimental observation has remained elusive. Here we report a new kind of Ti3+ ferromagnetism at LaMnO3/SrTiO3 epitaxial interfaces. It results from charge transfer to the empty conduction band of the titanate and has spin and orbital contributions evidencing the role played by orbital degeneracy. The possibility of tuning magnetic alignment (ferromagnetic or antiferromagnetic) of Ti and Mn moments by structural parameters is demonstrated. This result will provide important clues for the understanding of the effects of orbital degeneracy in superexchange coupling.

  10. Spin-Peierls transition in TiOCl

    Czech Academy of Sciences Publication Activity Database

    Shaz, M.; van Smaalen, S.; Palatinus, Lukáš; Hoinkis, M.; Klemm, M.; Horn, S.; Classen, R.

    2005-01-01

    Roč. 71, č. 10 (2005), 100405/1-100405/4 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : spin-Peierls state * quantum magnet * cation-cation interaction Subject RIV: BM - Solid Matter Physics ; Magnet ism Impact factor: 3.185, year: 2005

  11. PENUMBUHAN DAN KARAKTERISASI LAPISAN TIPIS PbTiO3 YANG DISIAPKAN DENGAN TEKNIK SPIN COATING

    Directory of Open Access Journals (Sweden)

    Bilalodin

    2008-05-01

    Full Text Available The growth of PbTiO3 ferroelectric thin films have successfully done. Thin films were made from bulk (powder PbTiO3 dissolved in methanol solution. The condensation was mixed during 1 hour to get homogeneous condensation. Thin films were grown above corning substrates by spin coating method. Optimation was done by various of annealing temperature. The physical properties of thin films were characterized by Energi Dispersive X-Ray Spectroscopy (EDS, X-Ray Diffraction (XRD, Scanning and Electron Microscopy (SEM. EDS measurement showed that the stoichiometry composition ratio of Pb/Ti is 1/1.26 at annealing temperature 600oC and 1/1.29 at annealing temperature 700oC. The result of XRD pattern showed that crystal structure of PbTiO3 thin films are tetragonal. The calculated lattice parameters ontained from Chohen Method are

  12. Spin-polarized electron gas in Co2MSi/SrTiO3(M= Ti, V, Cr, Mn, and Fe) heterostructures

    KAUST Repository

    Nazir, S.

    2016-06-08

    Spin-polarized density functional theory is used to study the TiO2 terminated interfaces between the magnetic Heusler alloys Co2Si (M = Ti, V, Cr, Mn, and Fe) and the non-polar band insulator SrTiO3. The structural relaxation at the interface turns out to depend systematically on the lattice mis- match. Charge transfer from the Heusler alloys (mainly the M 3d orbitals) to the Ti dxy orbitals of the TiO2 interface layer is found to gradually grow from M = Ti to Fe, resulting in an electron gas with increasing density of spin-polarized charge carriers. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  13. Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study

    Directory of Open Access Journals (Sweden)

    Dana Dvoranová

    2014-10-01

    Full Text Available The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent. The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen- and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.

  14. Study polymeric membranes PVDF/TiO2 photocatalytic applications with synthesized by solution blow spinning

    International Nuclear Information System (INIS)

    Gimenes, T.C.; Pereira, E.A.; Montanhera, M.A.; Paula, F.R. de; Spada, E.R.

    2016-01-01

    In this study we obtained nanofibers titanium dioxide (TiO2) incorporated into the poly (vinylidene fluoride) - PVDF in different concentrations, using a new technique denominated Solution Blow Spinning. This technique has the merits of simplicity, low cost and high efficiency in the production of nanofibers, compared with the technique of Electrospinning, using pressurized gas instead of high voltage, is not limited to the dielectric constant of the material and provides a processing period of at least 100 times faster. The obtained nanofibers exhibit little account and a very smooth morphology, with diameters ranging from 400 to 700 nm and with presence of crystalline anatase phase. The tests showed photocatalytic degradation of Rhodamine B dye, being more degradation shown by the PVDF nanofibers containing 0,7 g of TiO 2 , approximately 75 % of degraded dye. However nanofibers obtained the PVDF/TiO2 applications of this material are numerous, as filters, conductive nanofibers, photocatalysis and sensors. (author)

  15. Dimensional evolution of spin correlations in the magnetic pyrochlore Yb2Ti2O7

    DEFF Research Database (Denmark)

    Ross, K.A.; Yaraskavitch, L.R.; Laver, Mark

    2011-01-01

    The pyrochlore material Yb2Ti2O7 displays unexpected quasi-two-dimensional (2D) magnetic correlations within a cubic lattice environment at low temperatures, before entering an exotic disordered ground state below T=265 mK. We report neutron scattering measurements of the thermal evolution of the 2......D spin correlations in space and time. Short-range three-dimensional (3D) spin correlations develop below 400 mK, accompanied by a suppression in the quasielastic (QE) scattering below ∼0.2 meV. These show a slowly fluctuating ground state with spins correlated over short distances within a kagome...... analysis. ©2011 American Physical Society...

  16. Not so accidental degeneracies: origin of dimensional-reduction in the Quantum Spin Ice Yb2Ti2O7

    Science.gov (United States)

    Jaubert, Ludovic; Yan, Han; Benton, Owen; Shannon, Nic

    2013-03-01

    Despite being the best-characterised example of a ``quantum spin ice'', Yb2Ti2O7 remains an enigma. One of its most striking, and puzzling, features are the diffuse, rod-like structures seen in quasi-elastic neutron scattering. These suggest that spin fluctuations in Yb2Ti2O7 decouple into independent Kagome planes, even though magnetic ions occupy a fully three-dimensional pyrochlore lattice. Here, we use a combination of lattice gauge theory, spin-wave calculations and Monte Carlo simulation, to show how the dimensional-reduction seen in Yb2Ti2O7 follows from a two-dimensional branch of excitations ``inherited'' from a nearby phase transition. This analysis sheds new light on ground state selection in a wide range of rare-earth pyrochlore oxides, including the model ``order-by-disorder'' system Er2Ti2O7.

  17. Spin Speed and Duration Dependence of TiO2 Thin Films pH Sensing Behavior

    Directory of Open Access Journals (Sweden)

    Muhammad AlHadi Zulkefle

    2016-01-01

    Full Text Available Titanium dioxide (TiO2 thin films were applied as the sensing membrane of an extended-gate field-effect transistor (EGFET pH sensor. TiO2 thin films were deposited by spin coating method and the influences of the spin speed and spin duration on the pH sensing behavior of TiO2 thin films were investigated. The spin coated TiO2 thin films were connected to commercial metal-oxide-semiconductor field-effect transistor (MOSFET to form the extended gates and the MOSFET was integrated in a readout interfacing circuit to complete the EGFET pH sensor system. For the spin speed parameter investigation, the highest sensitivity was obtained for the sample spun at 3000 rpm at a fixed spinning time of 60 s, which was 60.3 mV/pH. The sensitivity was further improved to achieve 68 mV/pH with good linearity of 0.9943 when the spin time was 75 s at the speed of 3000 rpm.

  18. Large positive spin polarization and giant inverse tunneling magnetoresistance in Fe/PbTiO3/Fe multiferroic tunnel junction

    International Nuclear Information System (INIS)

    Dai, Jian-Qing; Zhang, Hu; Song, Yu-Min

    2014-01-01

    We perform first-principles electronic structure and spin-dependent transport calculations of a multiferroic tunnel junction (MFTJ) with an epitaxial Fe/PbTiO 3 /Fe heterostructure. We predict a large positive spin-polarization (SP) and an intriguing giant inverse tunneling magnetoresistance (TMR) ratio in this tunnel junction. We demonstrate that the tunneling properties are determined by ferroelectric (FE) polarization screening and electronic reconstruction at the interface with lower electrostatic potential. The intricate complex band structure of PbTiO 3 , in particular the lowest decay rates concerning Pb 6p z and Ti 3d z2 states near the Γ ¯ point, gives rise to the large positive SP of the tunneling current in the parallel magnetic configuration. However, the giant inverse TMR ratio is attributed to the minority-spin electrons of the interfacial Ti 3d xz +3d yz orbitals which have considerably weight in the extended area around the Γ ¯ point at the Fermi energy and causes remarkable contributions to the conductance in the antiparallel magnetic configuration. - Highlights: • We study spin-dependent tunneling in Fe/PbTiO 3 /Fe multiferroic tunnel junction. • We find a large positive spin polarization in the parallel magnetic configuration. • An intriguing giant inverse TMR ratio (about −2000%) is predicted. • Complex band structure of PbTiO 3 causes the large positive spin polarization. • Negative TMR is due to minority-spin electrons of interfacial Ti d xz +d yz orbitals

  19. Spin distribution in preequilibrium reactions for 48Ti + n.

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, Dugersuren [North Carolina State Univ., Raleigh, NC (United States)

    2005-04-12

    Cross section measurements were made of prompt γ-ray production as a function of incident neutron energy on a 48Ti sample. Partial γ-ray cross sections for transitions in 45-48Ti, 44-48Sc, and 42-45Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction γ rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The γ-ray excitation functions were converted to partial γ-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). The data are presented for neutron energies En between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for En up to 20 MeV and the GNASH reaction code for En up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). The multistep direct (MSD) part of the FKK theory was calculated for a one-step process. The contribution from higher steps is estimated to be small. The spin distribution of the multistep compound (MSC) part of FKK theory is assumed to be the same as in the compound nucleus. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the γ-ray production cross sections were calculated and compared with experimental data. The difference in the partial γ-ray cross sections using spin distributions with and without

  20. Theoretical models of Rashba spin splitting in asymmetric SrTiO3-based heterostructures

    Science.gov (United States)

    van Heeringen, L. W.; McCollam, A.; de Wijs, G. A.; Fasolino, A.

    2017-04-01

    Rashba spin splitting in two-dimensional (2D) semiconductor systems is generally calculated in a k .p Luttinger-Kohn approach where the spin splitting due to asymmetry emerges naturally from the bulk band structure. In recent years, several new classes of 2D systems have been discovered where electronic correlations are believed to have an important role. In these correlated systems, the effects of asymmetry leading to Rashba splitting have typically been treated phenomenologically. We compare these two approaches for the case of 2D electron systems in SrTiO3-based heterostructures, and find that the two models produce fundamentally different behavior in regions of the Brillouin zone that are particularly relevant for magnetotransport. Our results demonstrate the importance of identifying the correct approach in the quantitative interpretation of experimental data, and are likely to be relevant to a range of 2D systems in correlated materials.

  1. Synthesis of dense TiO2 nanoparticle multilayers using spin coating technique

    Science.gov (United States)

    DeSilva, L. Ajith; Thakurdesai, Madhavi; Bandara, T. M. W. J.; Preston, Joshua; Johnson, Wyatt; Gaquere-Parker, Anne; Survase, Smita

    2018-04-01

    A stack of nine layers is prepared by sequential spun casting of commercially available colloidal TiO2 nanoparticles of average size of 10-15 nm. Scanning electron microscopy (SEM) is employed to investigate the surface morphology of the multilayers. SEM micrographs exhibit formation of highly uniform and dense TiO2 nanoparticle layers. The uniformity and density is found to be increasing with layer thickness. Structural characterization is carried out using X-ray diffraction (XRD) technique. XRD spectra indicate improvement in crystalline quality of all the layers with increasing layer thickness. All the layers are having mainly the anatase phase of TiO2. Optical characterization is carried out by UV-visible spectroscopy. The value of bandgap estimated on the basis of absorption coefficient is found to be 3.26 eV and approximately remains the same for the layers. The electrical characterization suggests that multilayer resistivity increases with increasing layer thickness. The good quality spin coated thin dense TiO2 layers have many applications in optoelectronics.

  2. Investigation of spin-gapless semiconductivity and half-metallicity in Ti2MnAl-based compounds

    International Nuclear Information System (INIS)

    Lukashev, P.; Staten, B.; Hurley, N.; Kharel, P.; Gilbert, S.; Fuglsby, R.; Huh, Y.; Valloppilly, S.; Zhang, W.; Skomski, R.; Sellmyer, D. J.; Yang, K.

    2016-01-01

    The increasing interest in spin-based electronics has led to a vigorous search for new materials that can provide a high degree of spin polarization in electron transport. An ideal candidate would act as an insulator for one spin channel and a conductor or semiconductor for the opposite spin channel, corresponding to the respective cases of half-metallicity and spin-gapless semiconductivity. Our first-principle electronic-structure calculations indicate that the metallic Heusler compound Ti 2 MnAl becomes half-metallic and spin-gapless semiconducting if half of the Al atoms are replaced by Sn and In, respectively. These electronic structures are associated with structural transitions from the regular cubic Heusler structure to the inverted cubic Heusler structure.

  3. Dy2Ti2O7 spin ice: a test case for emergent clusters in a frustrated magnet.

    Science.gov (United States)

    Yavors'kii, Taras; Fennell, Tom; Gingras, Michel J P; Bramwell, Steven T

    2008-07-18

    Dy2Ti2O7 is a geometrically frustrated magnetic material with a strongly correlated spin ice regime that extends from 1 K down to as low as 60 mK. The diffuse elastic neutron scattering intensities in the spin ice regime can be remarkably well described by a phenomenological model of weakly interacting hexagonal spin clusters, as invoked in other geometrically frustrated magnets. We present a highly refined microscopic theory of Dy2Ti2O7 that includes long-range dipolar and exchange interactions to third nearest neighbors and which demonstrates that the clusters are purely fictitious in this material. The seeming emergence of composite spin clusters and their associated scattering pattern is instead an indicator of fine-tuning of ancillary correlations within a strongly correlated state.

  4. Neutron scattering study of heisenberg-like spin glass NixMn1-xTiO3

    International Nuclear Information System (INIS)

    Kawano, Hazuki; Yoshizawa, Hideki; Ito, Atsuko.

    1993-01-01

    A mixed compound Ni x Mn 1-x TiO 3 with two competitions of exchange interactions and of weak anisotropies was studied by neutron scattering experiments, and its x-T phase diagram was established. In addition to the spin-glass (SG) and re-entrant spin-glass (RSG) behaviors, two types of a spin axis rotation were observed. One is a spin axis rotation due to the competition of anisotropies, the other is a new type of the spin axis rotation in which spins rotate from the spin easy axis against the anisotropy. We interpret that the latter rotation occurs by the competition of the subtle energy balance between the exchange frustration, the single-ion anisotropy and the dipole interaction. From the magnetization measurement, we find that a weak single-ion anisotropy causes the successive SG transitions in the Ni x Mn 1-x TiO 3 system. By the profile analysis of quasi-elastic scattering, we find that there appears the diffuse scattering which cannot be explained by single Lorentzian below the lower SG transition temperature. (author)

  5. A measure of monopole inertia in the quantum spin ice Yb2Ti2O7

    Science.gov (United States)

    Pan, Lidong; Laurita, N. J.; Ross, Kate A.; Gaulin, Bruce D.; Armitage, N. P.

    2016-04-01

    An important and continuing theme of modern solid state physics is the realization of exotic excitations in materials, known as quasiparticles, that have no analogy in the actual physical vacuum of free space. Although they are not fundamental, such quasiparticles do constitute the most basic description of the excited states of the `vacuum' in which they reside. In this regard the magnetic textures of the excited states of spin ices, magnetic pyrochlore oxides with dominant Ising interactions, have been proposed to behave as effective magnetic charge monopoles. Inelastic neutron scattering experiments have established the pyrochlore material Yb2Ti2O7 (YbTO) as a quantum spin ice, where, in addition to the Ising interactions, there are substantial transverse terms that may induce quantum dynamics and--in principle--coherent monopole motion. Here we report a combined time-domain terahertz spectroscopy (TDTS) and microwave cavity study of YbTO to probe its complex dynamic magnetic susceptibility. We find that the form of the susceptibility is consistent with that of a monopole gas, and a magnetic monopole conductivity can be defined and measured. Using the phase sensitive capabilities of these techniques, we observe a sign change in the reactive part of the magnetic response. In generic models of magnetic excitations this is possible only by introducing inertial effects, such as a mass-dependent term, to the equations of motion. Analogous to conventional electric charge systems, measurement of the conductivity's spectral weight allows us to derive a value for the magnetic monopole mass. Our results support the idea of magnetic monopoles of quantum spin ice as the true coherently propagating quasiparticles of this system.

  6. Magnetic order, magnetic correlations, and spin dynamics in the pyrochlore antiferromagnet Er2Ti2O7

    Science.gov (United States)

    Dalmas de Réotier, P.; Yaouanc, A.; Chapuis, Y.; Curnoe, S. H.; Grenier, B.; Ressouche, E.; Marin, C.; Lago, J.; Baines, C.; Giblin, S. R.

    2012-09-01

    Er2Ti2O7 is believed to be a realization of an XY antiferromagnet on a frustrated lattice of corner-sharing regular tetrahedra. It is presented as an example of the order-by-disorder mechanism in which fluctuations lift the degeneracy of the ground state, leading to an ordered state. Here we report detailed measurements of the low-temperature magnetic properties of Er2Ti2O7, which displays a second-order phase transition at TN≃1.2 K with coexisting short- and long-range orders. Magnetic susceptibility studies show that there is no spin-glass-like irreversible effect. Heat capacity measurements reveal that the paramagnetic critical exponent is typical of a 3-dimensional XY magnet while the low-temperature specific heat sets an upper limit on the possible spin-gap value and provides an estimate for the spin-wave velocity. Muon spin relaxation measurements show the presence of spin dynamics in the nanosecond time scale down to 21 mK. This time range is intermediate between the shorter time characterizing the spin dynamics in Tb2Sn2O7, which also displays long- and short-range magnetic order, and the time scale typical of conventional magnets. Hence the ground state is characterized by exotic spin dynamics. We determine the parameters of a symmetry-dictated Hamiltonian restricted to the spins in a tetrahedron, by fitting the paramagnetic diffuse neutron scattering intensity for two reciprocal lattice planes. These data are recorded in a temperature region where the assumption that the correlations are limited to nearest neighbors is fair.

  7. Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique

    KAUST Repository

    Han, Wei

    2013-07-08

    There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ∼100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti 3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. © 2013 Macmillan Publishers Limited. All rights reserved.

  8. Improving the Grading Accuracy of Astrocytic Neoplasms Noninvasively by Combining Timing Information with Cerebral Blood Flow: A Multi-TI Arterial Spin-Labeling MR Imaging Study.

    Science.gov (United States)

    Yang, S; Zhao, B; Wang, G; Xiang, J; Xu, S; Liu, Y; Zhao, P; Pfeuffer, J; Qian, T

    2016-12-01

    Systematic and accurate glioma grading has clinical significance. We present the utility of multi-TI arterial spin-labeling imaging and provide the bolus arrival time maps for grading astrocytomas. Forty-three patients with astrocytomas (21 men; mean age, 51 years) were recruited. The classification abilities of conventional MR imaging features, normalized CBF value derived from multi-TI arterial spin-labeling imaging, normalized bolus arrival time, and normalized CBF derived from single-TI arterial spin-labeling were compared in patients with World Health Organization (WHO) grade II, III, and IV astrocytomas. The normalized CBF value derived from multi-TI arterial spin-labeling imaging was higher in patients with higher grade astrocytoma malignancies compared with patients with lower grade astrocytomas, while the normalized bolus arrival time showed the opposite tendency. The normalized CBF value derived from the multi-TI arterial spin-labeling imaging showed excellent performance with areas under the receiver operating characteristic curve of 0.813 (WHO II versus III), 0.964 (WHO II versus IV), 0.872 (WHO III versus IV), and 0.883 (low-grade-versus-high-grade gliomas). The normalized CBF value derived from single-TI arterial spin-labeling imaging could statistically differentiate the WHO II and IV groups (area under the receiver operating characteristic curve = 0.826). The normalized bolus arrival time effectively identified the WHO grades II and III with an area under the receiver operating characteristic curve of 0.836. Combining the normalized CBF value derived from multi-TI arterial spin-labeling imaging and normalized bolus arrival time improved the diagnostic accuracy from 65.10% to 72.10% compared with the normalized CBF value derived from multi-TI arterial spin-labeling imaging being applied independently. The combination of multi-TI arterial spin-labeling imaging and conventional MR imaging had the best performance, with a diagnostic accuracy of 81

  9. Magnetism, Spin Texture, and In-Gap States: Atomic Specialization at the Surface of Oxygen-Deficient SrTiO_{3}.

    Science.gov (United States)

    Altmeyer, Michaela; Jeschke, Harald O; Hijano-Cubelos, Oliver; Martins, Cyril; Lechermann, Frank; Koepernik, Klaus; Santander-Syro, Andrés F; Rozenberg, Marcelo J; Valentí, Roser; Gabay, Marc

    2016-04-15

    Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near the (001) surface of oxygen-deficient SrTiO_{3}, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ∼100  meV at the Γ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t_{2g} itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.

  10. Thermal relaxation and heat transport in spin ice Dy{sub 2}Ti{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Klemke, Bastian; Meissner, M.; Tennant, D.A. [Helmholtz-Zentrum Berlin (Germany); Technische Universitaet Berlin (Germany); Strehlow, P. [Technische Universitaet Berlin (Germany); Physikalisch Technische Bundesanstalt, Institut Berlin (Germany); Kiefer, K. [Helmholtz-Zentrum Berlin (Germany); Grigera, S.A. [School of Physics and Astronomy, St. Andrews (United Kingdom); Instituto de Fisica de Liquidos y Sistemas Biologicos, CONICET, UNLP, La Plata (Argentina)

    2011-07-01

    The thermal properties of single crystalline Dy{sub 2}Ti{sub 2}O{sub 7} have been studied at temperature below 30 K and magnetic fields applied along [110] direction up to 1.5 T. Based on a thermodynamic field theory (TFT) various heat relaxation and thermal transport measurements were analysed. So we were able to present not only the heat capacity of Dy{sub 2}Ti{sub 2}O{sub 7}, but also for the first time the different contributions of the magnetic excitations and their corresponding relaxation times in the spin ice phase. In addition, the thermal conductivity and the shortest relaxation time were determined by thermodynamic analysis of steady state heat transport measurements. Finally, we were able to reproduce the temperature profiles recorded in heat pulse experiments on the basis of TFT using the previously determined heat capacity and thermal conductivity data without additional parameters. Thus, TFT has been proved to be thermodynamically consistent in describing three thermal transport experiments on different time scales. The observed temperature and field dependencies of heat capacity contributions and relaxation times indicate the magnetic excitations in the spin ice Dy{sub 2}Ti{sub 2}O{sub 7} as thermally activated monopole-antimonopole defects.

  11. Electric field triggering the spin reorientation and controlling the absorption and release of heat in the induced multiferroic compound EuTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ranke, P. J. von, E-mail: von.ranke@uol.com.br; Ribeiro, P. O.; Alho, B. P.; Alvarenga, T. S. T.; Nobrega, E. P.; Caldas, A.; Sousa, V. S. R. de; Lopes, P. H. O.; Oliveira, N. A. de [Instituto de Física, Universidade do Estado do Rio de Janeiro–UERJ, Rua São, Francisco Xavier, 524, 20550-013 Rio de Janeiro, Rio de Janerio (Brazil); Gama, S. [Departamento de Ciências Exatas e da Terra-UNIFESP, Diadema, 09971-270 Sao Paulo (Brazil); Carvalho, A. Magnus G. [Laboratório Nacional de Luz Síncrotron, CNPEM, 13083-970 Campinas, Sao Paulo (Brazil)

    2015-12-28

    We report remarkable results due to the coupling between the magnetization and the electric field induced polarization in EuTiO{sub 3}. Using a microscopic model Hamiltonian to describe the three coupled sublattices, Eu-(spin-up), Eu-(spin-down), and Ti-(moment), the spin flop and spin reorientation phase transitions were described with and without the electric-magnetic coupling interaction. The external electric field can be used to tune the temperature of the spin reorientation phase transition T{sub SR} = T{sub SR}(E). When the T{sub SR} is tuned around the EuTiO{sub 3}—Néel temperature (T{sub N} = 5.5 K), an outstanding effect emerges in which EuTiO{sub 3} releases heat under magnetic field change. The electric field controlling the spin reorientation transition and the endo-exothermic processes are discussed through the microscopic interactions model parameters.

  12. Surface dependent structural phase transition in SrTiO 3 observed with spin relaxation of 8Li

    Science.gov (United States)

    Smadella, M.; Salman, Z.; Chow, K. H.; Egilmez, M.; Fan, I.; Hossain, M. D.; Kiefl, R. F.; Kreitzman, S. R.; Levy, C. D. P.; MacFarlane, W. A.; Mansour, A. I.; Morris, G. D.; Parolin, T. J.; Pearson, M.; Saadaoui, H.; Song, Q.; Wang, D.

    2009-04-01

    We investigate the 105 K structural phase transition in SrTiO 3 using depth controlled measurements of the spin relaxation of 8Li. The measurements were performed in zero external magnetic field and rely on the local electric field gradient (EFG) at the crystalline implantation site of the 8Li ( I=2) to hold the nuclear polarization. The tetragonal distortion accompanying the phase transition modifies the EFG in some 8Li implantation sites, resulting in an observable loss of 8Li polarization. This loss of polarization begins at a temperature T*=150 K, indicating there is some loss of cubic symmetry well above the bulk transition. We find that the value of T* is unaffected by the range of implantation depths available (10-150 nm); however, the temperature dependence of the polarization depends on the surface preparation of the SrTiO 3 sample.

  13. Surface dependent structural phase transition in SrTiO{sub 3} observed with spin relaxation of {sup 8}Li

    Energy Technology Data Exchange (ETDEWEB)

    Smadella, M. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Salman, Z. [Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom); ISIS Facility, Rutherford-Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Chow, K.H.; Egilmez, M.; Fan, I. [Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7 (Canada); Hossain, M.D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Kiefl, R.F., E-mail: kiefl@triumf.c [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Canadian Institute for Advanced Research (Canada); Kreitzman, S.R.; Levy, C.D.P. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); MacFarlane, W.A. [Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z3 (Canada); Mansour, A.I. [Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7 (Canada); Morris, G.D. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Parolin, T.J. [Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z3 (Canada); Pearson, M. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Saadaoui, H.; Song, Q.; Wang, D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)

    2009-04-15

    We investigate the 105 K structural phase transition in SrTiO{sub 3} using depth controlled measurements of the spin relaxation of {sup 8}Li. The measurements were performed in zero external magnetic field and rely on the local electric field gradient (EFG) at the crystalline implantation site of the {sup 8}Li (I=2) to hold the nuclear polarization. The tetragonal distortion accompanying the phase transition modifies the EFG in some {sup 8}Li implantation sites, resulting in an observable loss of {sup 8}Li polarization. This loss of polarization begins at a temperature T{sup *}=150K, indicating there is some loss of cubic symmetry well above the bulk transition. We find that the value of T{sup *} is unaffected by the range of implantation depths available (10-150 nm); however, the temperature dependence of the polarization depends on the surface preparation of the SrTiO{sub 3} sample.

  14. Origin of the decoherence of the extended electron spin state in Ti-doped β-Ga2O3

    Science.gov (United States)

    Mentink-Vigier, F.; Binet, L.; Gourier, D.; Vezin, H.

    2013-08-01

    The mechanism of decoherence of the electron spin of Ti3+ in β-Ga2O3 was investigated by pulsed electron paramagnetic resonance. At 4.2 K, both instantaneous and spectral diffusion contribute to the decoherence. For electron spin concentrations ≈1025 m-3 in the studied samples, calculations indicate that electron-electron couplings and electron couplings with 69Ga and 71Ga nuclei yield similar contributions to the spectral diffusion, but that electron-nuclei interactions could become the dominant cause of spectral diffusion for only slightly lower spin concentrations. Above 20 K, an additional contribution to the decoherence as well as to the spin-lattice relaxation arises from a two-optical-phonon Raman process, which becomes the leading decoherence mechanism for T > 39 K. Rabi oscillations with a damping time of about 79 ns at 4.2 K could also be observed. The damping of the Rabi oscillations, independent of the oscillation frequency, is suspected to arise from electron-nuclei interactions.

  15. Hydrogen absorption study of Ti-based alloys performed by melt-spinning

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, R.M.; Lemus, L.F.; Santos, D.S. dos, E-mail: rafaella@metalmat.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (PEMM/COPPEP/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Metalurgica e de Materiais

    2013-11-01

    The hydrogen absorption and desorption of Ti{sub 53}Zr{sub 27}Ni{sub 20} icosahedral quasicrystal (ICQ) and Ti{sub 50}Ni{sub 50} shape memory alloy (SMA) melt-spun ribbons was studied. Samples were exposed to hydrogen gas at 623 K and 4 MPa for 1000 minutes. The total capacity of hydrogen obtained for Ti{sub 53}Zr{sub 27}Ni{sub 20} and Ti{sub 50}Ni{sub 50} was 3.2 and 2.4 wt. % respectively. The Thermal Desorption Spectrometry (TDS) of the hydrogenated alloys shows that both alloys start to desorb hydrogen around 750 K. X-ray diffraction (XRD) patterns, performed after hydrogenation, indicate a complete amorphization of the Ti{sub 53}Zr{sub 27}Ni{sub 20} i-phase alloy, while the Ti{sub 50}Ni{sub 50} alloy remained crystalline after hydride formation. (author)

  16. Room temperature relaxor ferroelectricity and spin glass behavior in Sr2FeTiO6 double perovskite

    International Nuclear Information System (INIS)

    Neenu Lekshmi, P.; Savitha Pillai, S.; Suresh, K.G.; Santhosh, P.N.; Varma, Manoj Raama

    2012-01-01

    Highlights: ► Studied the structure, dielectric and magnetic properties of Sr 2 FeTiO 6 complex double perovskite. ► The thermal evolution of the lattice parameter and volume shows no structural phase transition. ► Dielectric data analysis shows a diffuse phase transition characteristics. ► The diffusion-assisted small-polaron hopping conduction evidences an intermediate-valence state and semiconductor like behaviour. ► The magnetic characterisation exhibits a non-metallic spin-glass-like state below 16 K. - Abstract: The structure, dielectric and magnetic properties of complex Sr 2 FeTiO 6 double perovskite have been investigated. Reitveld analysis of X-ray powder diffraction pattern reveals that the material is stabilized in a cubic perovskite phase with Pm3 ¯ m space group without the B-site cations ordering. The temperature evolution of crystal structural studies indicates the absence of structural changes with temperature. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1–7.5 μm. The bond valence sum calculations and diffusion-assisted small-polaron hopping conduction mechanism confirm the mixed valence state of Fe/Ti ions. Dielectric spectra show a broad dielectric anomaly coupled with a shift in dielectric maxima towards higher temperature with frequency, exhibiting a typical relaxor ferroelectric behavior. The relaxor behavior has been quantitatively characterized based on the phenomenological parameters (T m , T B , γ, ΔT relax ). The agreement of dielectric relaxation with non-linear Vogel Fulcher relation indicates that the system is indeed a relaxor exhibiting glassy characteristics. The transport studies show a semiconductor like behavior and a negligible magnetoresistance. Furthermore, the magnetic characterisation exhibits a non-metallic spin-glass-like state below 16 K, driven by competing interactions between the antiferromagnetic and the ferromagnetic states.

  17. The effect of the melting spinning cooling rate on transformation temperatures in ribbons Ti-Ni-Cu shape memory

    International Nuclear Information System (INIS)

    Ramos, A.P.; Castro, W.B.; Anselmo, G.C. dos S.

    2014-01-01

    Ti-Ni-Cu alloys have been attracting attention by their high performance of shape memory effect and decrease of thermal and stress hysteresis in comparison with Ti-Ni binary alloys. One important challenge of microsystems design is the implementation of miniaturized actuation principles efficient at the micro-scale. Shape memory alloys (SMAs) have early on been considered as a potential solution to this problem as these materials offer attractive properties like a high-power to weight ratio, large deformation and the capability to be processed at the micro-scale. Shape memory characteristics of Ti-37,8Cu-18,7Ni alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change of the velocity of cooling wheel from 21 to 63 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on austenitic and martensitic transformations behaviors is discussed. (author)

  18. Quasi-2D J1-J2 antiferromagnet Zn2VO(PO4)2 and its Ti-substituted derivative: A spin-wave analysis

    Science.gov (United States)

    Kar, Satyaki; Saha-Dasgupta, Tanusri

    2014-01-01

    In this study, we present non-linear spin wave analysis of a quasi-2D spin-{1}/{2}J1-J2 antiferromagnet at the parameter regime relevant for the recently studied compound Zn2VO(PO4)2. We obtain the temperature dependence of the spin wave energy, susceptibility and magnetization using Green's function technique and Tyablikov's decoupling or Hartree-Fock factorization. The comparison of our numerical results with the experimental findings is discussed. Magnetic structure factor is calculated and compared with powder neutron diffraction data. We also study the spin wave behavior of the compound Zn2Ti0.25V0.75O(PO4)2 obtained by partial chemical substitution of Ti at V sites of the compound Zn2VO(PO4)2 [Kanungo, et al., Phys. Rev. B 87 (2013) 054431]. Due to the superlattice structure of the spin lattice, the substituted compound possesses multiple spin wave modes. The spin wave analysis confirms the quasi-1D nature of the substituted system.

  19. Double-decker phthalocyanine complex: Scanning tunneling microscopy study of film formation and spin properties

    Science.gov (United States)

    Komeda, Tadahiro; Katoh, Keiichi; Yamashita, Masahiro

    2014-05-01

    We review recent studies of double-decker and triple-decker phthalocyanine (Pc) molecules adsorbed on surfaces in terms of the bonding configuration, electronic structure and spin state. The Pc molecule has been studied extensively in surface science. A Pc molecule can contain various metal atoms at the center, and the class of the molecule is called as metal phthalocyanine (MPc). If the center metal has a large radius, like as lanthanoid metals, it becomes difficult to incorporate the metal atom inside of the Pc ring. Pc ligands are placed so as to sandwich the metal atom, where the metal atom is placed out of the Pc plane. The molecule in this configuration is called as a multilayer-decker Pc molecule. After the finding that the double-decker Pc lanthanoid complex shows single-molecule magnet (SMM) behavior, it has attracted a large attention. This is partly due to a rising interest for the ‘molecular spintronics’, in which the freedoms of spin and charge of an electron are applied to the quantum process of information. SMMs represent a class of compounds in which a single molecule behaves as a magnet. The reported blocking temperature, below which a single SMM molecule works as an quantum magnet, has been increasing with the development in the molecular design and synthesis techniques of multiple-decker Pc complex. However, even the bulk properties of these molecules are promising for the use of electronic materials, the films of multi-decker Pc molecules is less studied than those for the MPc molecules. An intriguing structural property is expected for the multi-decker Pc molecules since the Pc planes are linked by metal atoms. This gives an additional degree of freedom to the rotational angle between the two Pc ligands, and they can make a wheel-like symmetric rotation. Due to a simple and well-defined structure of a multi-decker Pc complex, the molecule can be a model molecule for molecular machine studies. The multi-decker Pc molecules can provide

  20. Studies of diluted antiferromagnets MnxMg1-xTiO3 with x=0.55 and 0.70 by muon spin relaxation method

    International Nuclear Information System (INIS)

    Fukaya, A.; Ito, A.; Torikai, E.; Nishiyama, K.; Nagamine, K.

    1997-01-01

    Longitudinal fields μSR measurements have been performed in order to probe the spin dynamics in the diluted antiferromagnets Mn x Mg 1-x TiO 3 with x=0.70 and 0.55. In the x=0.70 sample which forms the antiferromagnetic long-range order, the static and fluctuating fields coexist at the muon stopping site below T N . On the other hand, in the x=0.55 sample which shows the spin-glass behavior, the local fields fluctuate rather fast even below T SG . We infer that this drastic change occurs when Mn x Mg 1-x TiO 3 transforms from an antiferromagnetic system to a spin-glass system by dilution

  1. Preparation of nanocrystalline Ce1-xSmx(Fe,Co)11Ti by melt spinning and mechanical alloying

    Science.gov (United States)

    Wuest, H.; Bommer, L.; Huber, A. M.; Goll, D.; Weissgaerber, T.; Kieback, B.

    2017-04-01

    Permanent magnetic materials based on Ce(Fe, Co)12-xTix with the ThMn12 structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd2Fe14B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce1-xSmxFe11-yCoyTi (x=0-1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 Hc,J values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm.

  2. Silver Doped TiO2 Nanostructure Composite Photocatalyst Film Synthesized by Sol-Gel Spin and Dip Coating Technique on Glass

    Directory of Open Access Journals (Sweden)

    Mojtaba Nasr-Esfahani

    2008-01-01

    Full Text Available New composite films (P25SGF-MC-Ag, MPC500SGF-MC-Ag, and ANPSGF-MC-Ag have been synthesized by a modified sol-gel method using different particle sizes of TiO2 powder and silver addition. Nanostructure TiO2/Ag composite thin films were prepared by a sol-gel spin and dip coating technique. while, by introducing methyl cellulose (MC porous, TiO2/Ag films were obtained after calcining at a temperature of 500°C. The as-prepared TiO2 and TiO2/Ag films were characterized by X-ray diffractometry, and scanning electron microscopy to reveal the structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methyl orange (MO under UV irradiation. After 500°C calcination, the microstructure of MC-TiO2 film without Ag addition exhibited a microstructure, while significant sintering effect was noticed with Ag additions and the films exhibited a porous microstructure. Nanostructure anatase-phase TiO2 can be observed with respect to the sharpening of XRD diffraction peaks. The photodegradation of porous TiO2 deposited with 5×10−4 mol Ag exhibited the best photocatalytic efficiency, where 69% methyl orange can be decomposed after UV exposure for 1 hour.

  3. Quasiparticle Breakdown and Spin Hamiltonian of the Frustrated Quantum Pyrochlore Yb2 Ti2 O7 in a Magnetic Field

    Science.gov (United States)

    Thompson, J. D.; McClarty, P. A.; Prabhakaran, D.; Cabrera, I.; Guidi, T.; Coldea, R.

    2017-08-01

    The frustrated pyrochlore magnet Yb2 Ti2 O7 has the remarkable property that it orders magnetically but has no propagating magnons over wide regions of the Brillouin zone. Here we use inelastic neutron scattering to follow how the spectrum evolves in cubic-axis magnetic fields. At high fields we observe, in addition to dispersive magnons, a two-magnon continuum, which grows in intensity upon reducing the field and overlaps with the one-magnon states at intermediate fields leading to strong renormalization of the dispersion relations, and magnon decays. Using heat capacity measurements we find that the low- and high-field regions are smoothly connected with no sharp phase transition, with the spin gap increasing monotonically in field. Through fits to an extensive data set of dispersion relations combined with magnetization measurements, we reevaluate the spin Hamiltonian, finding dominant quantum exchange terms, which we propose are responsible for the anomalously strong fluctuations and quasiparticle breakdown effects observed at low fields.

  4. Incommensurate interactions and nonconventional spin-Peierls transition in TiOBr

    Czech Academy of Sciences Publication Activity Database

    van Smaalen, S.; Palatinus, Lukáš; Schönleber, A.

    2005-01-01

    Roč. 72, č. 2 (2005), 020105/1-020105/4 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : spin-Peierls transition * quantum magnet * incommensurate structure Subject RIV: BM - Solid Matter Physics ; Magnet ism Impact factor: 3.185, year: 2005

  5. Strain effects on the spin polarized electron gas in ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures

    KAUST Repository

    Nazir, Safdar

    2013-04-11

    The spin polarized two dimensional electron gas in the correlated ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures is investigated by ab-initio calculations using density functional theory. Structural relaxation shows a strong buckling at and near the TiO2 terminated n-type interface (IFs) due to significant TiO6 octahedral distortions. We find in all cases, metallic states in a very narrow region of the SrTiO3, in agreement with experimental results. We demonstrate that the interface magnetism strongly reacts to the magnitude of the lattice strain. The orbital occupations and, hence, the charge carrier density change systematically as a function of the lattice mismatch between the component materials.

  6. Low-temperature muon spin rotation studies of the monopole charges and currents in Y doped Ho2Ti2O7.

    Science.gov (United States)

    Chang, L J; Lees, M R; Balakrishnan, G; Kao, Y-J; Hillier, A D

    2013-01-01

    In the ground state of Ho2Ti2O7 spin ice, the disorder of the magnetic moments follows the same rules as the proton disorder in water ice. Excitations take the form of magnetic monopoles that interact via a magnetic Coulomb interaction. Muon spin rotation has been used to probe the low-temperature magnetic behaviour in single crystal Ho2-xYxTi2O7 (x = 0, 0.1, 1, 1.6 and 2). At very low temperatures, a linear field dependence for the relaxation rate of the muon precession λ(B), that in some previous experiments on Dy2Ti2O7 spin ice has been associated with monopole currents, is observed in samples with x = 0, and 0.1. A signal from the magnetic fields penetrating into the silver sample plate due to the magnetization of the crystals is observed for all the samples containing Ho allowing us to study the unusual magnetic dynamics of Y doped spin ice.

  7. Effect of iron doping on structural and optical properties of TiO2 thin film by sol–gel routed spin coating technique

    Directory of Open Access Journals (Sweden)

    Stephen Lourduraj

    2017-08-01

    Full Text Available Thin films of iron (Fe-doped titanium dioxide (Fe:TiO2 were prepared by sol–gel spin coating technique and further calcined at 450∘C. The structural and optical properties of Fe-doped TiO2 thin films were investigated by X-ray diffraction (XRD, scanning electron microscopy (SEM, ultraviolet–visible spectroscopy (UV–vis and atomic force microscopic (AFM techniques. The XRD results confirm the nanostructured TiO2 thin films having crystalline nature with anatase phase. The characterization results show that the calcined thin films having high crystallinity and the effect of iron substitution lead to decreased crystallinity. The SEM investigations of Fe-doped TiO2 films also gave evidence that the films were continuous spherical shaped particles with a nanometric range of grain size and film was porous in nature. AFM analysis establishes that the uniformity of the TiO2 thin film with average roughness values. The optical measurements show that the films having high transparency in the visible region and the optical band gap energy of Fe-doped TiO2 film with iron (Fe decrease with increase in iron content. These important requirements for the Fe:TiO2 films are to be used as window layers in solar cells.

  8. Near-Surface Structural Phase Transition of SrTiO3 Studied with Zero-Field β-Detected Nuclear Spin Relaxation and Resonance

    Science.gov (United States)

    Salman, Z.; Kiefl, R. F.; Chow, K. H.; Hossain, M. D.; Keeler, T. A.; Kreitzman, S. R.; Levy, C. D. P.; Miller, R. I.; Parolin, T. J.; Pearson, M. R.; Saadaoui, H.; Schultz, J. D.; Smadella, M.; Wang, D.; Macfarlane, W. A.

    2006-04-01

    We demonstrate that zero-field β-detected nuclear quadrupole resonance and spin relaxation of low energy Li8 can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO3 single crystal occurs at Tc˜150K, i.e., ˜45K higher than Tcbulk, and that the tetragonal domains formed below Tc are randomly oriented.

  9. Photocatalytic Graphene-TiO2 Thin Films Fabricated by Low-Temperature Ultrasonic Vibration-Assisted Spin and Spray Coating in a Sol-Gel Process

    Directory of Open Access Journals (Sweden)

    Fatemeh Zabihi

    2017-05-01

    Full Text Available In this work, we communicate a facile and low temperature synthesis process for the fabrication of graphene-TiO2 photocatalytic composite thin films. A sol-gel chemical route is used to synthesize TiO2 from the precursor solutions and spin and spray coating are used to deposit the films. Excitation of the wet films during the casting process by ultrasonic vibration favorably influences both the sol-gel route and the deposition process, through the following mechanisms. The ultrasound energy imparted to the wet film breaks down the physical bonds of the gel phase. As a result, only a low-temperature post annealing process is required to eliminate the residues to complete the conversion of precursors to TiO2. In addition, ultrasonic vibration creates a nanoscale agitating motion or microstreaming in the liquid film that facilitates mixing of TiO2 and graphene nanosheets. The films made based on the above-mentioned ultrasonic vibration-assisted method and annealed at 150 °C contain both rutile and anatase phases of TiO2, which is the most favorable configuration for photocatalytic applications. The photoinduced and photocatalytic experiments demonstrate effective photocurrent generation and elimination of pollutants by graphene-TiO2 composite thin films fabricated via scalable spray coating and mild temperature processing, the results of which are comparable with those made using lab-scale and energy-intensive processes.

  10. Spin-Orbit Interaction and Kondo Scattering at the PrAlO3/SrTiO3 Interface

    Science.gov (United States)

    Mozaffari, Shirin; Guchhait, Samaresh; Markert, John

    We have investigated the effect of oxygen content, in the PO2 range of 6 ×10-6 - 1 ×10-3 torr, on the spin-orbit (SO) interaction at PrAlO3/SrTiO3 interface. The most-conducting 2-D-like PrAlO3 interfaces were not as conducting as comparable LaAlO3 samples, indicating either a steric or mixed-valent effect. The least-conducting, most oxygenated PrAlO3 interface exhibits hole conductivity, a departure from the typical electron-doped behavior. For 10-5 and 10-4 torr samples, high-temperature metallic behavior is accompanied by an upturn in resistivity at low temperatures, consistent with Kondo scattering theory; analysis gives a Kondo temperature 17 K. The magnetoresistance (MR) for the low PO2-grown samples was modeled with a positive part due to weak anti-localization (WAL) from a strong SO interaction, and a negative part due to the Kondo effect. The variation of MR suggests a strong SO interaction for the 10-5 torr sample with HSO = 1.25 T in both field orientations. The WAL effect is smaller for higher PO2-grown samples, where the high-field MR is dominated by the Kondo effect.

  11. Anisotropic magnetoresistance and spin polarization of La0.7Sr0.3MnO3/SrTiO3 superlattices

    International Nuclear Information System (INIS)

    Wang, L.M.; Guo, C.-C.

    2005-01-01

    The crystalline structure, anisotropic magnetoresistance (AMR), and magnetization of La 0.7 Sr 0.3 MnO 3 /SrTiO 3 (LSMO/STO) superlattices grown by a rf sputtering system are systematically analyzed to study the spin polarization of manganite at interfaces. The presence of positive low-temperature AMR in LSMO/STO superlattices implies that two bands of majority and minority character contribute to the transport properties, leading to a reduced spin polarization. Furthermore, the magnetization of superlattices follows the T 3/2 law and decays more quickly as the thickness ratio d STO /d LSMO increases, corresponding to a reduced exchange coupling. The results clearly show that the spin polarization is strongly correlated with the influence of interface-induced strain on the structure

  12. Preparation of nanocrystalline Ce{sub 1−x}Sm{sub x}(Fe,Co){sub 11}Ti by melt spinning and mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Huber, A.M., E-mail: arne.huber@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Goll, D., E-mail: dagmar.goll@htw-aalen.de [Aalen University, Materials Research Institute, Beethovenstr. 1, 73430 Aalen (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)

    2017-04-15

    Permanent magnetic materials based on Ce(Fe, Co){sub 12−x}Ti{sub x} with the ThMn{sub 12} structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd{sub 2}Fe{sub 14}B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce{sub 1−x}Sm{sub x}Fe{sub 11−y}Co{sub y}Ti (x=0−1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 H{sub c,J} values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm. - Highlights: • CeFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 77 kA/m. • SmFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 392 kA/m. • Dependence of H{sub c,J} on x in Ce{sub 1−x}Sm{sub x(}Fe, Co){sub 11}Ti obeys non-linear dependence. • Optimum annealing shifts to from 800 °C for CeFe{sub 11}Ti to 900 °C for SmFe{sub 11}Ti.

  13. Structural and photodegradation behaviors of Fe{sup 3+}-doping TiO{sub 2} thin films prepared by a sol–gel spin coating

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Huey-Jiuan; Yang, Tien-Syh [Department of Materials Science and Engineering, National United University, 1 Lien-Da, Kung-Ching Li, Miao-Li 36003, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80782, Taiwan (China); Hsi, Chi-Shiung, E-mail: chsi@nuu.edu.tw [Department of Materials Science and Engineering, National United University, 1 Lien-Da, Kung-Ching Li, Miao-Li 36003, Taiwan (China)

    2014-10-15

    Highlights: • Pure and various Fe{sup 3+}-doped TiO{sub 2} thin films have been successfully fabricated. • The phase of all thin films was single phase of anatase TiO{sub 2} when calcined at 823 K. • The crystallinity of TiO{sub 2} thin films decreased as Fe{sup 3+}-doping increased. • The photodegradation of each sample increased as the irradiation time increased. • The photodegradation increased as Fe{sup 3+}-doping increased at a fixed irradiation time. - Abstract: Pure and various Fe{sup 3+}-doping TiO{sub 2} thin films have been successfully fabricated on glass substrate prepared by a sol–gel spin coating route. The structural and photodegradation behavior of these films after calcined at various temperatures for 1 h were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectrum and degradation of 1.0 × 10{sup −5} M methylene blue solution. When all thin films after calcined at 823 K for 1 h, the crystalline phase are comprised only contained single phase of anatase TiO{sub 2}. The crystallinity of various Fe{sup 3+}-doping TiO{sub 2} thin films decreases with Fe{sup 3+}-doping concentration increased. The PL intensity of all thin films also decreases with Fe{sup 3+}-doping concentration increased. When all various Fe{sup 3+}-doping TiO{sub 2} thin films after calcined at 823 K for 1 h, the photodegradation of each sample increases with irradiation time increased. Moreover, the photodegradation also increases with Fe{sup 3+}-doping concentration increased when fixed at constant irradiation time.

  14. Sequential Dip-spin Coating Method: Fully Infiltration of MAPbI 3-x Cl x into Mesoporous TiO 2 for Stable Hybrid Perovskite Solar Cells

    KAUST Repository

    Kim, Woochul

    2017-05-31

    Organic-inorganic hybrid perovskite solar cells (PSCs) have reached a power conversion efficiency of 22.1% in a short period (∼7 years), which has been obtainable in silicon-based solar cells for decades. The high power conversion efficiency and simple fabrication process render perovskite solar cells as potential future power generators, after overcoming the lack of long-term stability, for which the deposition of void-free and pore-filled perovskite films on mesoporous TiO2 layers is the key pursuit. In this research, we developed a sequential dip-spin coating method in which the perovskite solution can easily infiltrate the pores within the TiO2 nanoparticulate layer, and the resultant film has large crystalline grains without voids between them. As a result, a higher short circuit current is achieved owing to the large interfacial area of TiO2/perovskite, along with enhanced power conversion efficiency, compared to the conventional spin coating method. The as-made pore-filled and void-free perovskite film avoids intrinsic moisture and air and can effectively protect the diffusion of degradation factors into the perovskite film, which is advantageous for the long-term stability of PSCs.

  15. Spin-Coating and Characterization of Multiferroic MFe{sub 2}O{sub 4} (M=Co, Ni) / BaTiO{sub 3} Bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Quandt, Norman [Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 2, 06120 Halle (Germany); Roth, Robert [Institute of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Germany); Syrowatka, Frank [Interdisciplinary Center of Materials Science, Martin Luther University Halle-Wittenberg, Heinrich-Damerow-Straße 4, 06120 Halle (Germany); Steimecke, Matthias [Institute of Chemistry, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Germany); Ebbinghaus, Stefan G., E-mail: stefan.ebbinghaus@chemie.uni-halle.de [Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 2, 06120 Halle (Germany)

    2016-01-15

    Bilayer films of MFe{sub 2}O{sub 4} (M=Co, Ni) and BaTiO{sub 3} were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO{sub 3}. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm{sup −3} for the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} and 188 emu cm{sup −3} for the NiFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer, respectively were found. For the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems. - Graphical abstract: The SEM image of the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer on Pt–Si-substrate (left), magnetization as a function of the magnetic field perpendicular and parallel to the film plane (right top) and P–E and I–V hysteresis loops of the bilayer at room temperature. - Highlights: • Ferrite and perovskite oxides grown on platinum using spin coating technique. • Columnar growth of cobalt ferrite particle on the substrate. • Surface investigation showed a homogenous and smooth surface. • Perpendicular and parallel applied magnetic field revealed a magnetic anisotropy. • Switching peaks and saturated P–E hysteresis loops show ferroelectricity.

  16. NMR spin-lattice relaxation study of 7Li and 93Nb nuclei in Ti- or Fe-doped LiNbO3:Mg single crystals

    Directory of Open Access Journals (Sweden)

    Tae Ho Yeom

    2016-04-01

    Full Text Available In this study, to understand the effects of paramagnetic impurities, we investigated the temperature dependent of the spin-lattice relaxation times of pure LiNbO3, LiNbO3:Mg, LiNbO3:Mg/Ti, LiNbO3:Mg/Fe, and LiNbO3:Mg/Fe (thermally treated at 500°C single crystals. The results for the LiNbO3:Mg single crystals doped with Fe3+ or Ti3+ are discussed with respect to the site distribution and atomic mobility of Li and Nb. In addition, the effects of a thermal treatment on LiNbO3:Mg/Fe single crystals were examined based on the T1 analysis of 7Li and 93Nb. It was found that the presence of impurities in the crystals induced systematic changes of activation energies concerning atomic mobility.

  17. Pressure and field induced magnetic order in the spin liquid Tb2Ti2O7 as studied by single crystal neutron diffraction.

    Science.gov (United States)

    Mirebeau, I; Goncharenko, I N; Dhalenne, G; Revcolevschi, A

    2004-10-29

    We have studied the spin liquid Tb2Ti2O7 by single crystal neutron diffraction under high pressure up to 2.8 GPa, together with uniaxial stress, down to 0.1 K, in zero and high magnetic fields up to 7 T. In zero magnetic field, a long-range ordered antiferromagnetic structure is induced by pressure. The Néel temperature and ordered magnetic moment can be tuned by the anisotropic pressure component. Under magnetic field, the antiferromagnetic structure transforms into a canted ferromagnetic one at 0.6 T. Spin canting persists even at 7 T. The magnetic phase diagram under pressure shows a strong increase of the Néel temperature with the field.

  18. Pressure and field induced magnetic order in the spin liquid Tb2Ti2O7 as studied by single crystal neutron diffraction

    International Nuclear Information System (INIS)

    Mirebeau, I.; Goncharenko, I. N.; Dhalenne, G.; Revcolevschi, A.

    2004-01-01

    We have studied the spin liquid Tb 2 Ti 2 O 7 by single crystal neutron diffraction under high pressure up to 2.8 GPa, together with uniaxial stress, down to 0.1 K, in zero and high magnetic fields up to 7 T. In zero magnetic field, a long-range ordered antiferromagnetic structure is induced by pressure. The Neel temperature and ordered magnetic moment can be tuned by the anisotropic pressure component. Under magnetic field, the antiferromagnetic structure transforms into a canted ferromagnetic one at 0.6 T. Spin canting persists even at 7 T. The magnetic phase diagram under pressure shows a strong increase of the Neel temperature with the field

  19. Near-surface structural phase transition of SrTiO3 studied with zero-field beta-detected nuclear spin relaxation and resonance.

    Science.gov (United States)

    Salman, Z; Kiefl, R F; Chow, K H; Hossain, M D; Keeler, T A; Kreitzman, S R; Levy, C D P; Miller, R I; Parolin, T J; Pearson, M R; Saadaoui, H; Schultz, J D; Smadella, M; Wang, D; MacFarlane, W A

    2006-04-14

    We demonstrate that zero-field beta-detected nuclear quadrupole resonance and spin relaxation of low energy (8)Li can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO(3) single crystal occurs at T(c) approximately 150K, i.e., approximately 45K higher than T(c)bulk, and that the tetragonal domains formed below T(c) are randomly oriented.

  20. Muon spin relaxation study on itinerant ferromagnet CeCrGe₃ and the effect of Ti substitution on magnetism of CeCrGe₃.

    Science.gov (United States)

    Das, Debarchan; Bhattacharyya, A; Anand, V K; Hillier, A D; Taylor, J W; Gruner, T; Geibel, C; Adroja, D T; Hossain, Z

    2015-01-14

    A Muon spin relaxation (µSR) study has been performed on the Kondo lattice heavy fermion itinerant ferromagnet CeCrGe3. Recent investigations of bulk properties have revealed a long-range ordering of Cr moments at Tc = 70 K in this compound. Our µSR investigation between 1.2 K and 125 K confirm the bulk magnetic order which is marked by a loss in initial asymmetry below 70 K accompanied with a sharp increase in the muon depolarization rate. Field dependent µSR spectra show that the internal field at the muon site is higher than 0.25 T apparently due to the ferromagnetic nature of ordering. The effect of Ti substitution on the magnetism in CeCrGe3 is presented. A systematic study has been made on polycrystalline CeCr(1-x)Ti(x)Ge3 (0 ⩽ x ⩽ 1) using magnetic susceptibility χ(T), isothermal magnetization M(H), specific heat C(T) and electrical resistivity ρ(T) measurements which clearly reveal that the substitution of Ti for Cr in CeCrGe3 strongly influences the exchange interaction and ferromagnetic ordering of Cr moments. The Cr moment ordering temperature is suppressed gradually with increasing Ti concentration up to x = 0.50 showing Tc = 7 K beyond which Ce moment ordering starts to dominate and a crossover between Cr and Ce moment ordering is observed with a Ce moment ordering Tc = 14 K for x = 1.0. The Kondo lattice behavior is evident from temperature dependence of ρ(T) in all CeCr(1-x)Ti(x)Ge3 samples.

  1. Magnetoelectric coupling and spin-dependent tunneling in Fe/PbTiO3/Fe multiferroic heterostructure with a Ni monolayer inserted at one interface

    International Nuclear Information System (INIS)

    Dai, Jian-Qing; Zhang, Hu; Song, Yu-Min

    2015-01-01

    We report on first-principles calculations of a Ni monolayer inserted at one interface in the epitaxial Fe/PbTiO 3 /Fe multiferroic heterostructure, focusing on the magnetoelectric coupling and the spin-dependent transport properties. The results of magnetoelectric coupling calculations reveal an attractive approach to realize cumulative magnetoelectric effects in the ferromagnetic/ferroelectric/ferromagnetic superlattices. The underlying physics is attributed to the combinations of several different magnetoelectric coupling mechanisms such as interface bonding, spin-dependent screening, and different types of magnetic interactions. We also demonstrate that inserting a Ni monolayer at one interface in the Fe/PbTiO 3 /Fe multiferroic tunnel junction is an efficient method to produce considerable tunneling electroresistance effect by modifying the tunnel potential barrier and the interfacial electronic structure. Furthermore, coexistence of tunneling magnetoresistance and tunneling electroresistance leads to the emergence of four distinct resistance states, which can be served as a multistate-storage device. The complicated influencing factors including bulk properties of the ferromagnetic electrodes, decay rates of the evanescent states in the tunnel barrier, and the specific interfacial electronic structure provide us promising opportunities to design novel multiferroic tunnel junctions with excellent performances

  2. Magnetoelectric coupling and spin-dependent tunneling in Fe/PbTiO{sub 3}/Fe multiferroic heterostructure with a Ni monolayer inserted at one interface

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jian-Qing, E-mail: djqkust@sina.com; Zhang, Hu; Song, Yu-Min [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

    2015-08-07

    We report on first-principles calculations of a Ni monolayer inserted at one interface in the epitaxial Fe/PbTiO{sub 3}/Fe multiferroic heterostructure, focusing on the magnetoelectric coupling and the spin-dependent transport properties. The results of magnetoelectric coupling calculations reveal an attractive approach to realize cumulative magnetoelectric effects in the ferromagnetic/ferroelectric/ferromagnetic superlattices. The underlying physics is attributed to the combinations of several different magnetoelectric coupling mechanisms such as interface bonding, spin-dependent screening, and different types of magnetic interactions. We also demonstrate that inserting a Ni monolayer at one interface in the Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction is an efficient method to produce considerable tunneling electroresistance effect by modifying the tunnel potential barrier and the interfacial electronic structure. Furthermore, coexistence of tunneling magnetoresistance and tunneling electroresistance leads to the emergence of four distinct resistance states, which can be served as a multistate-storage device. The complicated influencing factors including bulk properties of the ferromagnetic electrodes, decay rates of the evanescent states in the tunnel barrier, and the specific interfacial electronic structure provide us promising opportunities to design novel multiferroic tunnel junctions with excellent performances.

  3. Ferromagnetic ordered phase of quantum spin ice system Yb{sub 2}Ti{sub 2}O{sub 7} under [001] magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Hamachi, Noriaki, E-mail: ce46414@meiji.ac.jp; Yasui, Yukio [Department of Physics, School of Science and Technology, Meiji University, Kawasaki, 214-8571 (Japan); Araki, Koji [Institute for Solid State Physics, The University of Tokyo, Kashiwa, 277-8581 (Japan); Department of Applied Physics, National Defense Academy, Yokosuka, 239-8686 (Japan); Kittaka, Shunichiro; Sakakibara, Toshiro [Institute for Solid State Physics, The University of Tokyo, Kashiwa, 277-8581 (Japan)

    2016-05-15

    Measurements of magnetization (M) and specific heat (C) under a [001] magnetic field were carried out on a single crystal of a quantum spin ice system Yb{sub 2}Ti{sub 2}O{sub 7} in order to investigate a feature of the transition occurred at T{sub C} ∼ 0.2 K. As a result of applying the magnetic field μ{sub 0}H < 0.1 T, the C/T − T curve structure and transition temperature barely changed. On the other hand, applying the more than 0.1 T magnetic field, the C/T − T curve structure drastically change from sharp peak structure to broad peak one, and the broad peak temperature of C/T − T curves linearly increases with increasing magnetic field (H). In the magnetic field μ{sub 0}H < 0.1 T, the magnetization drastically increases around T{sub C} ∼ 0.2 K with decreasing T, and a thermal hysteresis loop of the M − T curve is observed. With increasing H, the thermal hysteresis loop of the M − T curves disappears above μ{sub 0}H{sub C} = 0.1 T. We can understand these results, where Yb{sub 2}Ti{sub 2}O{sub 7} exhibits a first-order ferromagnetic transition associated with the latent heat corresponding to the energy of μ{sub 0}H{sub C} = 0.1 T. Basis of the H − T phase diagram along [001] magnetic field, the feature of the transition occurred at T{sub C} ∼ 0.2 K in quantum spin ice system Yb{sub 2}Ti{sub 2}O{sub 7} is discussed.

  4. DLTS analysis of amphoteric interface defects in high-TiO2 MOS structures prepared by sol-gel spin-coating

    Directory of Open Access Journals (Sweden)

    Arvind Kumar

    2015-11-01

    Full Text Available High-κ TiO2 thin films have been fabricated from a facile, combined sol – gel spin – coating technique on p and n type silicon substrate. XRD and Raman studies headed the existence of anatase phase of TiO2 with a small grain size of 18 nm. The refractive index ‘n’ quantified from ellipsometry is 2.41. AFM studies suggest a high quality, pore free films with a fairly small surface roughness of 6 Å. The presence of Ti in its tetravalent state is confirmed by XPS analysis. The defect parameters observed at the interface of Si/TiO2 were studied by capacitance – voltage (C – V and deep level transient spectroscopy (DLTS. The flat – band voltage (VFB and the density of slow interface states estimated are – 0.9, – 0.44 V and 5.24×1010, 1.03×1011 cm−2; for the NMOS and PMOS capacitors, respectively. The activation energies, interface state densities and capture cross – sections measured by DLTS are EV + 0.30, EC – 0.21 eV; 8.73×1011, 6.41×1011 eV−1 cm−2 and 5.8×10−23, 8.11×10−23 cm2 for the NMOS and PMOS structures, respectively. A low value of interface state density in both P- and N-MOS structures makes it a suitable alternate dielectric layer for CMOS applications. And also very low value of capture cross section for both the carriers due to the amphoteric nature of defect indicates that the traps are not aggressive recombination centers and possibly can not contribute to the device operation to a large extent.

  5. Ferromagnetic insulating and spin glass properties of La{sub 0.7}Sr{sub 0.3}MnO{sub 3}-TiO{sub 2} composites

    Energy Technology Data Exchange (ETDEWEB)

    Phong, P.T., E-mail: ptphong.nh@khanhhoa.edu.vn [Department of Advanced Materials Chemistry, Dongguk University, 707 Suckjang-dong, Gyeongju-Si, Gyeonbuk 780-714 (Korea, Republic of); Nha Trang Pedagogic College, 01 Nguyen Chanh Street, Nha Trang City, Khanh Hoa Province (Viet Nam); Manh, D.H.; Phuc, N.X. [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Ha Noi (Viet Nam); Lee, I.-J. [Department of Advanced Materials Chemistry, Dongguk University, 707 Suckjang-dong, Gyeongju-Si, Gyeonbuk 780-714 (Korea, Republic of)

    2013-01-01

    In this study, the effect of TiO{sub 2} doping on the electro-magnetic properties of (1-x)La{sub 0.7}Sr{sub 0.3}MnO{sub 3}+xTiO{sub 2} (with 0%{<=}x{<=}6%, in wt%) composites has been investigated. X-ray diffraction observations show the evidence of reaction between the La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and TiO{sub 2} grains. Also the results show that by increasing TiO{sub 2} doping levels, the metal insulator transition temperatures decrease and the system becomes an insulator. Furthermore, the paramagnetic-ferromagnetic transition temperature also decreases as TiO{sub 2} content increases. The spin glass state exists in the composites with x=5% and 6%. The dynamic properties of the magnetic properties are investigated by temperature dependence of dc magnetization and frequency dependence of ac susceptibilities. A dynamic scaling analysis of ac susceptibility data using conventional critical slowing down indicates that a finite spin-glass phase-transition temperature (T{sub g}) and a dynamic exponent (zv) change from 103 K and 9.30 correspondingly for 0.95La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/0.05TiO{sub 2} to 133 K and 9.10, for 0.94La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/0.06TiO{sub 2}. In addition, MR in low temperature of these samples decline simultaneously with occur spin-glass behavior. These results are interpreted as the dilution of Mn{sup 3+}/Mn{sup 4+} interactions by the random Ti substitution on the Mn site considerably reduces the ferromagnetic double exchange interaction within the manganese lattice.

  6. 2D Electron Gas with 100% Spin-Polarization in the (LaMnO3)2/(SrTiO3)2 Superlattice under Uniaxial Strain

    KAUST Repository

    Cossu, Fabrizio

    2014-07-28

    By first-principles calculations we investigate the structural, electronic, and magnetic properties of the (LaMnO3)2/(SrTiO3)2 superlattice. We find that a monoclinic C2h symmetry is energetically favorable and that the spins order ferromagnetically. Under both compressive and tensile uniaxial strain the electronic structure of the superlattice shows a half-metallic character. In particular, a fully spin-polarized two-dimensional electron gas, which traces back to the Ti 3dxy orbitals, is achieved under compressive uniaxial strain. The (LaMnO3)2/(SrTiO3)2 superlattice is analysed with respect to its structure, magnetism, and electronic properties. Our results demonstrate that uniaxial strain in an experimentally accessible range, both tensile and compressive, can be used to induce half-metallicity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Synthesis and characterization of Ba0.5Pb0.5TiO3 perovskite - type thin films deposited by spin coating at low temperatures

    International Nuclear Information System (INIS)

    Wermuth, T.B.; Wiederkehr, N.A.; Alves, A.K.; Bergmann, C.P.

    2014-01-01

    In this paper we present a non-aqueous sol-gel route for the obtention of solid compounds and thin films of oxide type- perovskite ABO 3 , such as Ba 0.5 Pb 0.5 TiO 3 , synthesized by sol - gel route with subsequent heat treatment. The solid compounds were characterized by X-ray diffraction (XRD) techniques and thermal analysis (TGA / DTA). The thin film was obtained by using spin-coating techniques at low temperatures onto commercial substrates of polymethylmethacrylate (PMMA) and characterized by contact angle, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results show that the films present microstructures and roughness directly related to annealing temperatures, characterized by the formation of crystalline nanostructures with surface regularity and transparency. (author)

  8. Giant Negative Magnetoresistance Driven by Spin-Orbit Coupling at the LaAlO3/SrTiO3 Interface.

    Science.gov (United States)

    Diez, M; Monteiro, A M R V L; Mattoni, G; Cobanera, E; Hyart, T; Mulazimoglu, E; Bovenzi, N; Beenakker, C W J; Caviglia, A D

    2015-07-03

    The LaAlO3/SrTiO3 interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with Kondo-screened magnetic impurities. Here we report on experiments over a broad temperature range, showing the persistence of the magnetoresistance up to the 20 K range--indicative of a single-particle mechanism. Motivated by a striking correspondence between the temperature and carrier density dependence of our magnetoresistance measurements we propose an alternative explanation. Working in the framework of semiclassical Boltzmann transport theory we demonstrate that the combination of spin-orbit coupling and scattering from finite-range impurities can explain the observed magnitude of the negative magnetoresistance, as well as the temperature and electron density dependence.

  9. Spin-strain effects in the frustrated magnet Tb{sub 2}Ti{sub 2}O{sub 7} at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Gritsenko, Y.; Wosnitza, J. [HZDR/HLD, Dresden (Germany); TUD/IFP, Dresden (Germany); Zherlitsyn, S. [HZDR/HLD, Dresden (Germany); Ruminy, M.; Fennell, T. [PSI/LNS, 5232 Villigen PSI (Switzerland); Kenzelmann, M. [PSI/LDM, 5232 Villigen PSI (Switzerland)

    2016-07-01

    Geometrically frustrated magnets have attracted much attention, due to their tendency to build unconventional ground states with exotic excitations. Tb{sub 2}Ti{sub 2}O{sub 7} possesses a pyrochlore lattice as building block of the crystallographic structure, providing a basis for geometric frustration. This cubic material features Curie-Weiss temperature of Θ{sub CW} = -19 K, but no long-range magnetic order has been detected down to 50 mK indicating a large frustration. The existence of a spin-liquid state has been suggested for Tb{sub 2}Ti{sub 2}O{sub 7}. Here, we present results of ultrasonic investigations of this material. The magnetic field was applied along the [110] direction at temperatures of 20, 150 and 300 mK. Clear anomalies were found for different acoustic modes. The temperature dependence of the sound velocity shows a softening at about 500 mK and step-like features at about 150 mK suggesting a low-temperature phase transformation. This investigation sheds new light on the role of lattice degrees of freedom and magneto-elastic interactions in this material.

  10. Spin-orbit interaction and Kondo scattering at the PrAlO3/SrTiO3 interface: effects of oxygen content

    Science.gov (United States)

    Mozaffari, Shirin; Guchhait, Samaresh; Markert, John T.

    2017-10-01

    We report the effects of oxygen pressure during growth (PO2 ) on the electronic and magnetic properties of PrAlO3 films grown on TiO2 -terminated SrTiO3 substrates. Resistivity measurements show an increase in the sheet resistance as PO2 is increased. The saturation of the sheet resistance down to 0.3 K is consistent with Kondo theory for PO2 ≥slant 10-5 torr. Resistivity data fits indicate Kondo temperatures of 16-18 K. For the 10-4 sample, we measured a moderate positive magnetoresistance (MR) due to a strong spin-orbit (SO) interaction at low magnetic fields that evolves into a larger negative MR at high fields due to the Kondo effect. Analysis of the MR data permitted the extraction of the SO interaction critical field for the PO2=10-5 torr interface ( H_SO=1.25 T). We observed high positive MR for the least oxygenated sample, where a fraction of the n-type carriers are derived from oxygen vacancies and possible cation interdiffusion; for this 6×10-6 torr sample, Hall effect data indicate a thick conducting layer. Its extremely high MR (˜400% ) is attributed to classical behavior due to a distribution of mobilities.

  11. DLTS analysis of amphoteric interface defects in high-TiO{sub 2} MOS structures prepared by sol-gel spin-coating

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara, E-mail: ksrkrao@physics.iisc.ernet.in, E-mail: raoksrk@gmail.com [Department of Physics, Indian Institute of Science, Bangalore, 560012 (India)

    2015-11-15

    High-κ TiO{sub 2} thin films have been fabricated from a facile, combined sol – gel spin – coating technique on p and n type silicon substrate. XRD and Raman studies headed the existence of anatase phase of TiO{sub 2} with a small grain size of 18 nm. The refractive index ‘n’ quantified from ellipsometry is 2.41. AFM studies suggest a high quality, pore free films with a fairly small surface roughness of 6 Å. The presence of Ti in its tetravalent state is confirmed by XPS analysis. The defect parameters observed at the interface of Si/TiO{sub 2} were studied by capacitance – voltage (C – V) and deep level transient spectroscopy (DLTS). The flat – band voltage (V{sub FB}) and the density of slow interface states estimated are – 0.9, – 0.44 V and 5.24×10{sup 10}, 1.03×10{sup 11} cm{sup −2}; for the NMOS and PMOS capacitors, respectively. The activation energies, interface state densities and capture cross – sections measured by DLTS are E{sub V} + 0.30, E{sub C} – 0.21 eV; 8.73×10{sup 11}, 6.41×10{sup 11} eV{sup −1} cm{sup −2} and 5.8×10{sup −23}, 8.11×10{sup −23} cm{sup 2} for the NMOS and PMOS structures, respectively. A low value of interface state density in both P- and N-MOS structures makes it a suitable alternate dielectric layer for CMOS applications. And also very low value of capture cross section for both the carriers due to the amphoteric nature of defect indicates that the traps are not aggressive recombination centers and possibly can not contribute to the device operation to a large extent.

  12. Preparation, characterization, emission (Eu3+), and electron spin resonance (Gd3+) studies of Y2-xLnxTi2O7 (Ln=Eu and Gd, x=0.0,0.05)

    Science.gov (United States)

    Kumar, B. Vijaya; Velchuri, Radha; Devi, V. Rama; Prasad, G.; Sreedhar, B.; Bansal, C.; Vithal, M.

    2010-08-01

    Bulk and nanopyrochlore materials of composition Y2-xLnxTi2O7 (Ln=Eu and Gd, x=0.0,0.05) have been prepared by sol-gel method via peroxo titanium complex precursor. All the samples were characterized by powder x-ray diffraction (XRD), Raman spectra, and transmission electron microscopy (TEM). The unit cell parameters were obtained from Rietveld analysis of XRD patterns. The influence of particle size on the emission of Eu3+ (in Y2-xEuxTi2O7), the electron spin resonance (ESR) of Gd3+ (in Y2-xGdxTi2O7) and optical absorption spectra have been studied. The band gap energy of Y1.95Ln0.05Ti2O7 (Ln=Eu and Gd) was determined and compared with parent Y2Ti2O7. The variation in the emission intensity of Eu3+ is accounted with the particle size and short range order. The spin-Hamiltonian parameters of Gd3+ were obtained from the powder ESR spectra. The single-ion anisotropy was taken in to account in the analysis of powder ESR spectra. The crystallite size was obtained from powder XRD and TEM images.

  13. Magnetoelastic properties of the quantum-spin-ice candidate Yb{sub 2}Ti{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Stoeter, T.; Wang, Z.S.; Wosnitza, J. [SFB 1143 (Germany); TUD/IFP, Dresden (Germany); HZDR, Dresden (Germany); Doerr, M.; Granovsky, S. [SFB 1143 (Germany); TUD/IFP, Dresden (Germany); Erfanifam, S.; Green, E. [HZDR, Dresden (Germany); Zherlitsyn, S. [SFB 1143 (Germany); HZDR, Dresden (Germany); Maljuk, A.; Wurmehl, S. [SFB 1143 (Germany); IFW, Dresden (Germany)

    2016-07-01

    Intriguing phenomena such as the occurrence of magnetic monopoles and a wide variety of ground states are associated to magnetic frustration. In a number of cases, elastic effects, e.g. lattice distortions, may result in the lifting of degeneracies or the appearance of new magnetic states. The rare-earth titanate Yb{sub 2}Ti{sub 2}O{sub 7}, where the magnetic Yb{sup 3+} ions form a pyrochlore spin network, is a prime example of a geometrically frustrated material, with numerous field-induced phases and strong ferromagnetic correlations below 170 mK. In order to characterize the magneto-elastic coupling in this material, we have investigated the thermal expansion, magnetostriction, and sound propagation in different dilution refrigerators between 60 mK and 1.5 K and large applied magnetic fields. At around 170 mK we find distinct anomalies in the expansion coefficient, acoustic properties, as well as the specific heat. Lattice anomalies in field hint to additional low temperature phases.

  14. Magnetic and spin-dependent transport properties of reactive sputtered epitaxial Ti 1-xCr xN films

    KAUST Repository

    Duan, Xiaofei

    2012-05-01

    Reactive-sputtered epitaxial Ti 1-xCr xN films are ferromagnetic in the range of 0.17 ≤ x ≤ 0.51 due to the Cr-N-Cr double-exchange interaction below the Curie temperature (T C). The T C first increases, then decreases as x increases, and a maximum of 120 K appears at x = 0.47. All of the films are metallic with a transition near T C. A resistivity minimum ρ min is observed below 60 K in the films with 0.10 ≤ x ≤ 0.51 due to the effects of the weak localization and electron-electron interaction. The negative magnetoresistance (MR) is caused by the double-exchange interaction below T C and the weak localization can also contribute to MR below T min where ρ min appears. The x-dependent electron carrier densities reveal that the ferromagnetism is not from the carrier-mediated mechanism. The anomalous Hall resistivity follows the relation of ρxyA∝ρxx2, which is from the side-jump mechanism. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  15. Influences of the iron ion (Fe{sup 3+})-doping on structural and optical properties of nanocrystalline TiO{sub 2} thin films prepared by sol-gel spin coating

    Energy Technology Data Exchange (ETDEWEB)

    Ben Naceur, J. [Laboratoire de Photovoltaique de Semi-conducteurs et de Nanostructures, Centre de Recherche des Sciences et Technologies de l' Energie, BP.95, Hammam-Lif 2050 (Tunisia); Mechiakh, R., E-mail: raouf_mechiakh@yahoo.fr [Laboratoire de Photovoltaique de Semi-conducteurs et de Nanostructures, Centre de Recherche des Sciences et Technologies de l' Energie, BP.95, Hammam-Lif 2050 (Tunisia); Departement de Medecine, Faculte de Medecine, Universite Hadj Lakhdar, Batna (Algeria); Bousbih, F.; Chtourou, R. [Laboratoire de Photovoltaique de Semi-conducteurs et de Nanostructures, Centre de Recherche des Sciences et Technologies de l' Energie, BP.95, Hammam-Lif 2050 (Tunisia)

    2011-10-01

    Titanium dioxide (TiO{sub 2}) thin films doping of various iron ion (Fe{sup 3+}) concentrations were deposited on silicon (Si) (100) and quartz substrates by sol-gel Spin Coating technique followed by a thermal treatment at 600 deg. C. The structure, surface morphology and optical properties, as a function of the doping, have been studied by X-ray diffractometer (XRD), Raman, ultraviolet-visible (UV-vis) and Spectroscopic Ellipsometry (SE). XRD and Raman analyzes of our thin films show that the crystalline phase of TiO{sub 2} thin films comprised only the anatase TiO{sub 2}, but the crystallinity decreased when the Fe{sup 3+} content increased from 0% to 20%. During the Fe{sup 3+} addition to 20%, the phase of TiO{sub 2} thin film still maintained the amorphous state. The grain size calculated from XRD patterns varies from 29.3 to 22.6 nm. The complex index and the optical band gap (E{sub g}) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreased with an increasing Fe{sup 3+} content.

  16. Dirac strings and magnetic monopoles in the spin ice, Dy{sub 2}Ti{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Morris, David Jonathan Pryce; Czternasty, Clemens; Meissner, Michael; Rule, Kirrily; Hoffmann, Jens-Uwe; Kiefer, Klaus [Helmholtz Center for Materials and Energy, Berlin (Germany); Tennant, Alan; Klemke, Bastian [Helmholtz Center for Materials and Energy, Berlin (Germany); Technische Universitaet, Berlin (Germany); Grigera, Santiago [Instituto de Fisica de Liquidos y Sistemas Biologicos, La Plata (Argentina); Castelnovo, Claudio [University of Oxford (United Kingdom); Moessner, Roderich [Max-Planck-Institut fuer Physik komplexer Systeme, Dresden (Germany); Slobinsky, Damien [St. Andrews University (United Kingdom); Perry, Robin [University of Edinburgh (United Kingdom)

    2010-07-01

    Recent proposals in condensed matter physics that magnetic monopoles can appear as emergent quasiparticles have attracted wide levels of interest. Dirac's original picture of magnetic monopoles had them connected to strings through which magnetic flux flowed. Here we report studies into a system called Spin Ice, where spins obey ''ice rules'' of 2 spins into and 2 spins out of their tetrahedron. In these materials it has been predicted that strings of spins form via a 3D Kasteleyn transition. The geometry of spin-ice allows for net magnetic charge (magnetic monopoles) to form where ''ice rules'' are broken at the tips of the strings. Here we present three experimental pieces of evidence for these strings and magnetic monopoles.

  17. The effect of the melting spinning cooling rate on transformation temperatures in ribbons Ti-Ni-Cu shape memory; Efeito da taxa de resfriamento nas temperaturas de transformacao de uma liga Ni-Cu-Ti com efeito de memoria de forma solidificadas rapidamente

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, A.P.; Castro, W.B.; Anselmo, G.C. dos S., E-mail: walman@dem.ufcg.edu.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

    2014-07-01

    Ti-Ni-Cu alloys have been attracting attention by their high performance of shape memory effect and decrease of thermal and stress hysteresis in comparison with Ti-Ni binary alloys. One important challenge of microsystems design is the implementation of miniaturized actuation principles efficient at the micro-scale. Shape memory alloys (SMAs) have early on been considered as a potential solution to this problem as these materials offer attractive properties like a high-power to weight ratio, large deformation and the capability to be processed at the micro-scale. Shape memory characteristics of Ti-37,8Cu-18,7Ni alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change of the velocity of cooling wheel from 21 to 63 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on austenitic and martensitic transformations behaviors is discussed. (author)

  18. Magnetic behaviour governed by Co spin transitions in LaCo{sub 1-x}Ti{sub x}O{sub 3} (0 {<=} x {<=} 0.5) perovskite oxides

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Serrano, I; Lopez, M L; Pico, C; RodrIguez, E; Veiga, M L [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense, 28040 Madrid (Spain); Cuello, G J [Institut Max von Laue-Paul Langevin (ILL), 38042 Grenoble Cedex 9 (France); Jimenez-Lopez, A; RodrIguez-Castellon, E [Departamento de Quimica Inorganica, CristalografIa y MineralogIa, Facultad de Ciencias, Universidad de Malaga, 29071 Malaga (Spain)], E-mail: marisal@quim.ucm.es

    2008-10-07

    Perovskite-type cobaltites LaCo{sub 1-x}Ti{sub x}O{sub 3} (0 {<=} x {<=} 0.5) synthesized by the liquid mix technique were characterized by x-ray diffraction, neutron diffraction, XPS, magnetic susceptibility and magnetization versus magnetic field measurements. Structural symmetry changes from rhombohedral (S.G. R 3-bar c) for 0.05 {<=} x {<=} 0.20 to orthorhombic (S.G. Pbnm) for 0.25 {<=} x {<=} 0.40. The bond distances dependence on the composition, x, has been analysed from x-ray and neutron diffraction data. Both the structural and the spectroscopic (from XPS) results suggest that Ti{sup 4+} substitution implies the stabilization of low-spin Co{sup III} ions and the evolution of magnetic moments in the paramagnetic zone is also coherent with this assumption. For small values of x both FM responses and the absence of saturation in the M versus H curves at 2 K are interpreted in terms of a magnetic frustration. For x > 0.25 the cobalt cations seem to stabilize as Co{sup III} (rather than Co{sup 3+}) coexisting with Co{sup 2+}. In these more substituted perovskites, AFM Co{sup 2+}-O-Co{sup 2+} interactions become predominant, leading to a well established AFM ordering for x = 0.4 and 0.5.

  19. Spin-torque generation in topological insulator based heterostructures

    KAUST Repository

    Fischer, Mark H.

    2016-03-11

    Heterostructures utilizing topological insulators exhibit a remarkable spin-torque efficiency. However, the exact origin of the strong torque, in particular whether it stems from the spin-momentum locking of the topological surface states or rather from spin-Hall physics of the topological-insulator bulk, remains unclear. Here, we explore a mechanism of spin-torque generation purely based on the topological surface states. We consider topological-insulator-based bilayers involving ferromagnetic metal (TI/FM) and magnetically doped topological insulators (TI/mdTI), respectively. By ascribing the key theoretical differences between the two setups to location and number of active surface states, we describe both setups within the same framework of spin diffusion of the nonequilibrium spin density of the topological surface states. For the TI/FM bilayer, we find large spin-torque efficiencies of roughly equal magnitude for both in-plane and out-of-plane spin torques. For the TI/mdTI bilayer, we elucidate the dominance of the spin-transfer-like torque. However, we cannot explain the orders of magnitude enhancement reported. Nevertheless, our model gives an intuitive picture of spin-torque generation in topological-insulator-based bilayers and provides theoretical constraints on spin-torque generation due to topological surface states.

  20. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2012-01-01

    In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

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

    Directory of Open Access Journals (Sweden)

    Mathieu Taillefumier

    2017-12-01

    Full Text Available Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho_{2}Ti_{2}O_{7} and Dy_{2}Ti_{2}O_{7} exemplify this phenomenon, displaying a classical spin-liquid state, with fractionalized magnetic-monopole excitations. Recently, there has been great interest in closely related “quantum spin-ice” materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively entangled, quantum spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realize a still-richer scenario. Using a combination of classical Monte Carlo simulation, semiclassical molecular-dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three competing forms of spin liquid, as well as a phase with hidden, spin-nematic order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.

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

    Science.gov (United States)

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

    2017-10-01

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

  3. Electron paramagnetic resonance studies of manganese centers in SrTiO.sub.3./sub.: Non-Kramers Mn.sup.3+./sup. ions and spin-spin coupled Mn.sup.4+./sup. dimers

    Czech Academy of Sciences Publication Activity Database

    Azamat, Dmitry; Dejneka, Alexandr; Lančok, Ján; Trepakov, Vladimír; Jastrabík, Lubomír; Badalyan, A. G.

    2012-01-01

    Roč. 111, č. 10 (2012), "104119-1"-"104119-6" ISSN 0021-8979. [International Symposium on Integrated Functionalities (ISIF) /22./. San Juan, Puerto Rico , 13.06.2010-16.06.2010] R&D Projects: GA TA ČR TA01010517; GA MŠk(CZ) LM2011029; GA ČR GAP108/12/1941 Grant - others:SAFMAT(CZ) CZ.2.16/3.1.00/22132 Institutional research plan: CEZ:AV0Z10100522 Keywords : electron paramagnetic resonance * X- and Q-band * SrTiO 3 doped with Mn Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.210, year: 2012

  4. Electroactive β-crystalline phase inclusion and photoluminescence response of a heat-controlled spin-coated PVDF/TiO2 free-standing nanocomposite film for a nanogenerator and an active nanosensor

    Science.gov (United States)

    Mehebub Alam, Md; Sultana, Ayesha; Sarkar, Debabrata; Mandal, Dipankar

    2017-09-01

    The electroactive β-phase is most desirable due to its highest piezo-, pyro- and ferroelectric properties in poly(vinylidene fluoride) (PVDF). Induction of the β-phase is successfully accomplished in titanium dioxide (TiO2) nanoparticles (NPs) doped spin-coated PVDF nanocomposite (PNC) films. The optimized yields of β-phase and homogeneous ultra-smooth free-standing PNC film is utilized in a mechanical-energy harvesting application by fabricating a nanogenerator (NG) where the typical electrical poling step is not undertaken. Under a repeated human finger touch and release process, it delivers an open-circuit voltage of 5 V. Moreover, the physical sensing capabilities of the NG are examined through harvesting mechanical energy from mouse clicking of a laptop and wrist pulse detection, which indicates that it can also be used as a nanosensor. The blue photoluminescence centred at 444 nm, which was also observed in PNC films, makes us anticipate a new type of photonic application where the design feasibility of hybrid sensors, i.e. electromechanical and photonic combination, is also possible.

  5. Spin Orbit Interaction Engineering for beyond Spin Transfer Torque memory

    Science.gov (United States)

    Wang, Kang L.

    Spin transfer torque memory uses electron current to transfer the spin torque of electrons to switch a magnetic free layer. This talk will address an alternative approach to energy efficient non-volatile spintronics through engineering of spin orbit interaction (SOC) and the use of spin orbit torque (SOT) by the use of electric field to improve further the energy efficiency of switching. I will first discuss the engineering of interface SOC, which results in the electric field control of magnetic moment or magneto-electric (ME) effect. Magnetic memory bits based on this ME effect, referred to as magnetoelectric RAM (MeRAM), is shown to have orders of magnitude lower energy dissipation compared with spin transfer torque memory (STTRAM). Likewise, interests in spin Hall as a result of SOC have led to many advances. Recent demonstrations of magnetization switching induced by in-plane current in heavy metal/ferromagnetic heterostructures have been shown to arise from the large SOC. The large SOC is also shown to give rise to the large SOT. Due to the presence of an intrinsic extraordinarily strong SOC and spin-momentum lock, topological insulators (TIs) are expected to be promising candidates for exploring spin-orbit torque (SOT)-related physics. In particular, we will show the magnetization switching in a chromium-doped magnetic TI bilayer heterostructure by charge current. A giant SOT of more than three orders of magnitude larger than those reported in heavy metals is also obtained. This large SOT is shown to come from the spin-momentum locked surface states of TI, which may further lead to innovative low power applications. I will also describe other related physics of SOC at the interface of anti-ferromagnetism/ferromagnetic structure and show the control exchange bias by electric field for high speed memory switching. The work was in part supported by ERFC-SHINES, NSF, ARO, TANMS, and FAME.

  6. Tunneling spin injection into single layer graphene.

    Science.gov (United States)

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

    2010-10-15

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

  7. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2017-01-01

    Since the discovery of the giant magnetoresistance effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called “spin current,” are manipulated and controlled together. The physics of magnetism and the application of spin current have progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book aims to provide an introduction and guide to the new physics and applications of spin current, with an emphasis on the interaction between spin and charge currents in magnetic nanostructures.

  8. Cerebral Hemodynamic and White Matter Changes of Type 2 Diabetes Revealed by Multi-TI Arterial Spin Labeling and Double Inversion Recovery Sequence

    Directory of Open Access Journals (Sweden)

    Yelong Shen

    2017-12-01

    Full Text Available Diabetes has been reported to affect the microvasculature and lead to cerebral small vessel disease (SVD. Past studies using arterial spin labeling (ASL at single post-labeling delay reported reduced cerebral blood flow (CBF in patients with type 2 diabetes. The purpose of this study was to characterize cerebral hemodynamic changes of type 2 diabetes using a multi-inversion-time 3D GRASE pulsed ASL (PASL sequence to simultaneously measure CBF and bolus arrival time (BAT. Thirty-six patients with type 2 diabetes (43–71 years, 17 male and 36 gender- and age-matched control subjects underwent MRI scans at 3 T. Mean CBF/BAT values were computed for gray and white matter (GM and WM of each subject, while a voxel-wise analysis was performed for comparison of regional CBF and BAT between the two groups. In addition, white matter hyperintensities (WMHs were detected by a double inversion recovery (DIR sequence with relatively high sensitivity and spatial resolution. Mean CBF of the WM, but not GM, of the diabetes group was significantly lower than that of the control group (p < 0.0001. Regional CBF decreases were detected in the left middle occipital gyrus (p = 0.0075, but failed to reach significance after correction of partial volume effects. BAT increases were observed in the right calcarine fissure (p < 0.0001, left middle occipital gyrus (p < 0.0001, and right middle occipital gyrus (p = 0.0011. Within the group of diabetic patients, BAT in the right middle occipital gyrus was positively correlated with the disease duration (r = 0.501, p = 0.002, BAT in the left middle occipital gyrus was negatively correlated with the binocular visual acuity (r = −0.408, p = 0.014. Diabetic patients also had more WMHs than the control group (p = 0.0039. Significant differences in CBF, BAT, and more WMHs were observed in patients with diabetes, which may be related to impaired vision and risk of SVD of type 2 diabetes.

  9. Spin Electronics

    Science.gov (United States)

    2003-08-01

    applications, a ferromagnetic metal may be used as a source of spin-polarized electronics to be injected into a semiconductor, a superconductor or a...physical phenomena in II-VI and III-V semiconductors. In II-VI systems, the Mn2+ ions act to boost the electron spin precession up to terahertz ...conductors, proximity effect between ferromagnets and superconductors , and the effects of spin injection on the physical properties of the

  10. Spin doctoring

    OpenAIRE

    Vozková, Markéta

    2011-01-01

    1 ABSTRACT The aim of this text is to provide an analysis of the phenomenon of spin doctoring in the Euro-Atlantic area. Spin doctors are educated people in the fields of semiotics, cultural studies, public relations, political communication and especially familiar with the infrastructure and the functioning of the media industry. Critical reflection of manipulative communication techniques puts spin phenomenon in historical perspective and traces its practical use in today's social communica...

  11. Spin glasses

    CERN Document Server

    Bovier, Anton

    2007-01-01

    Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.

  12. Chiral tunneling of topological states: towards the efficient generation of spin current using spin-momentum locking.

    Science.gov (United States)

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

    2015-05-01

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

  13. TOPICAL REVIEW: Spin current, spin accumulation and spin Hall effect

    Directory of Open Access Journals (Sweden)

    Saburo Takahashi and Sadamichi Maekawa

    2008-01-01

    Full Text Available Nonlocal spin transport in nanostructured devices with ferromagnetic injector (F1 and detector (F2 electrodes connected to a normal conductor (N is studied. We reveal how the spin transport depends on interface resistance, electrode resistance, spin polarization and spin diffusion length, and obtain the conditions for efficient spin injection, spin accumulation and spin current in the device. It is demonstrated that the spin Hall effect is caused by spin–orbit scattering in nonmagnetic conductors and gives rise to the conversion between spin and charge currents in a nonlocal device. A method of evaluating spin–orbit coupling in nonmagnetic metals is proposed.

  14. Spin electronics

    CERN Document Server

    Buhrman, Robert; Daughton, James; Molnár, Stephan; Roukes, Michael

    2004-01-01

    This report is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magnetoelectronics and devices. The panel's conclusions are based on a literature review and a series of site visits to leading spin electronics research centers in Japan and Western Europe. The panel found that Japan is clearly the world leader in new material synthesis and characterization; it is also a leader in magneto-optical properties of semiconductor devices. Europe is strong in theory pertaining to spin electronics, including injection device structures such as tunneling devices, and band structure predictions of materials properties, and in development of magnetic semiconductors and semiconductor heterost...

  15. Spin glasses

    International Nuclear Information System (INIS)

    Fischer, K.H.; Hertz, J.A.

    1993-01-01

    Spin glasses, simply defined by the authors as a collection of spins (i.e., magnetic moments) whose low-temperature state is a frozen disordered one, represent one of the fascinating new fields of study in condensed matter physics, and this book is the first to offer a comprehensive account of the subject. Included are discussions of the most important developments in theory, experimental work, and computer modeling of spin glasses, all of which have taken place essentially within the last two decades. The first part of the book gives a general introduction to the basic concepts and a discussion of mean field theory, while the second half concentrates on experimental results, scaling theory, and computer simulation of the structure of spin glasses

  16. Electrical Detection of Spin-to-Charge Conversion in a Topological Insulator Bi2Te3

    Science.gov (United States)

    Li, Connie H.; van't Erve, Olaf M. J.; Li, Yaoyi; Li, Lian; Jonker, Berry T.

    Spin-momentum locking in topological insulators (TIs) dictates that an unpolarized charge current creates a net spin polarization. We recently demonstrated the first electrical detection of this spontaneous polarization in a transport geometry, using a ferromagnetic (FM) / tunnel barrier contact, where the projection of the TI surface state spin on the magnetization of detector is measured as a voltage [1]. Alternatively, if spins are injected into the TI surface state system, it is distinctively associated with a unique carrier momentum, and hence should generated a charge accumulation, similar to that of inverse spin Hall effect. Here we experimentally demonstrate both effects in the same device fabricated in Bi2Te3: the electrical detection of the spin accumulation generated by an unpolarized current flowing through the surface states, and that of the charge accumulation generated by spins injected into the surface states system. This reverse measurement is an independent confirmation of spin-momentum locking in the TI surface states, and offers additional avenue for spin manipulation. It further demonstrates the robustness and versatility of electrical access to the TI surface state spin system, an important step towards its utilization in TI-based spintronics devices. C.H. Li et al., Nat. Nanotech. 9, 218 (2014). Supported by NRL core funds and Nanoscience Institute.

  17. Interference Spins

    DEFF Research Database (Denmark)

    Popovski, Petar; Simeone, Osvaldo; Nielsen, Jimmy Jessen

    2015-01-01

    on traffic load and interference condition leads to performance gains. In this letter, a general network of multiple interfering two-way links is studied under the assumption of a balanced load in the two directions for each link. Using the notion of interference spin, we introduce an algebraic framework...

  18. Spinning worlds

    NARCIS (Netherlands)

    Schwarz, H.

    2017-01-01

    The thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants, with orbital periods as long as thousands of years. The thesis is based on near-infrared observations of 1

  19. First-principles study of ferromagnetism in N doped TiO{sub 2} and TiO

    Energy Technology Data Exchange (ETDEWEB)

    Wang Hongxia; Zong Zhaocun [College of Mathematics, Physics and Information Science, Zhejiang Ocean University, Zhoushan 316000 (China); Yan Yu, E-mail: kingslaywhx@yahoo.com [State Key Laboratory of Superhard Materials and Department of Physics, Jilin University, Changchun 130012 (China); Qi Shengwen [College of Mathematics, Physics and Information Science, Zhejiang Ocean University, Zhoushan 316000 (China)

    2012-09-15

    N doped TiO is nonmagnetic, in which spin-split impurity states are not induced near the Fermi energy (E{sub F}) by N dopant. N doped TiO{sub 2} along with transition-metal (TM) doped TiO is magnetic, in which spin-split impurity states are induced across E{sub F}. The magnetic moment is determined by the 3d4s electron configurations and the valence states of TM-dopant ions when they substitute Ti. Hence, the origin of ferromagnetism of N doped TiO{sub 2} and TiO is not closely related to the width of the band gaps of host oxides, but would be crucially related to that if the dopant can induce spin-split impurity states near E{sub F}. - Highlights: Black-Right-Pointing-Pointer N doped TiO{sub 2} is magnetic with 1 {mu}{sub B} per N dopant while N doped TiO is nonmagnetic. Black-Right-Pointing-Pointer The band gaps of host oxides are not the key of ferromagnetism of N doped TiO{sub 2} and TiO. Black-Right-Pointing-Pointer Impurity states across E{sub F} deduced by dopants are the key of ferromagnetism.

  20. Devitrification of rapidly quenched Al–Cu–Ti amorphous alloys

    Indian Academy of Sciences (India)

    Unknown

    spinning, the entire apparatus was ... The crystallization behaviour of these amorphous alloys has been studied using DSC 2910 (TA ... Thus the change in the structure of amorphous Al50Cu45Ti5 and Al45Cu45Ti10 alloys may be summarized as ...

  1. Ti, Al

    Indian Academy of Sciences (India)

    In the present study, authors report on the effect that substrate bias voltage has on the microstructure and mechanical properties of (Ti, Al)N hard coatings deposited with cathodic arc evaporation (CAE) technique. The coatings were deposited from a Ti0.5Al0.5 powder metallurgical target in a reactive nitrogen atmosphere at ...

  2. In a spin at Brookhaven spin physics

    CERN Document Server

    Makdisi, Y I

    2003-01-01

    The mysterious quantity that is spin took centre stage at Brookhaven for the SPIN2002 meeting last September. The 15th biennial International Spin Physics Symposium (SPIN2002) was held at Brookhaven National Laboratory on 9-14 September 2002. Some 250 spin enthusiasts attended, including experimenters and theorists in both nuclear and high-energy physics, as well as accelerator physicists and polarized target and polarized source experts. The six-day symposium included 23 plenary talks and 150 parallel talks. SPIN2002 was preceded by a one-day spin physics tutorial for students, postdocs, and anyone else who felt the need for a refresher course. (2 refs).

  3. Spin-Circuit Representation of Spin Pumping

    Science.gov (United States)

    Roy, Kuntal

    2017-07-01

    Circuit theory has been tremendously successful in translating physical equations into circuit elements in an organized form for further analysis and proposing creative designs for applications. With the advent of new materials and phenomena in the field of spintronics and nanomagnetics, it is imperative to construct the spin-circuit representations for different materials and phenomena. Spin pumping is a phenomenon by which a pure spin current can be injected into the adjacent layers. If the adjacent layer is a material with a high spin-orbit coupling, a considerable amount of charge voltage can be generated via the inverse spin Hall effect allowing spin detection. Here we develop the spin-circuit representation of spin pumping. We then combine it with the spin-circuit representation for the materials having spin Hall effect to show that it reproduces the standard results as in the literature. We further show how complex multilayers can be analyzed by simply writing a netlist.

  4. Spin Coherence in Semiconductor Nanostructures

    National Research Council Canada - National Science Library

    Flatte, Michael E

    2006-01-01

    ... dots, tuning of spin coherence times for electron spin, tuning of dipolar magnetic fields for nuclear spin, spontaneous spin polarization generation and new designs for spin-based teleportation and spin transistors...

  5. Spin-forming Project Report

    Energy Technology Data Exchange (ETDEWEB)

    Switzner, Nathan; Henry, Dick

    2009-03-20

    In a second development order, spin-forming equipment was again evaluated using the test shape, a hemispherical shell. In this second development order, pure vanadium and alloy titanium (Ti-6Al-4V) were spin-formed, as well as additional copper and 21-6-9 stainless. In the first development order the following materials had been spin-formed: copper (alloy C11000 ETP), 6061 aluminum, 304L stainless steel, 21-6-9 stainless steel, and tantalum-2.5% tungsten. Significant challenges included properly adjusting the rotations-per-minute (RPM), cracking at un-beveled edges and laser marks, redressing of notches, surface cracking, non-uniform temperature evolution in the titanium, and cracking of the tailstock. Lessons learned were that 300 RPM worked better than 600 RPM for most materials (at the feed rate of 800 mm/min); beveling the edges to lower the stress reduces edge cracking; notches, laser marks, or edge defects in the preform doom the process to cracking and failure; coolant is required for vanadium spin-forming; increasing the number of passes to nine or more eliminates surface cracking for vanadium; titanium develops a hot zone in front of the rollers; and the tailstock should be redesigned to eliminate the cylindrical stress concentrator in the center.

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

    Science.gov (United States)

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

    2018-02-22

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

  7. Valence and spin states in perovskites LaCo.sub.0.95./sub.M.sub.0.05./sub.O.sub.3./sub. (M = Mg, Ga, Ti)

    Czech Academy of Sciences Publication Activity Database

    Hejtmánek, Jiří; Jirák, Zdeněk; Knížek, Karel; Maryško, Miroslav; Veverka, Miroslav; Autret, C.

    2008-01-01

    Roč. 320, č. 14 (2008), s. 92-95 ISSN 0304-8853 R&D Projects: GA AV ČR IAA100100611 Institutional research plan: CEZ:AV0Z10100521 Keywords : transition metal oxide * spin-state transition * electrical resistivity * thermopower Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.283, year: 2008

  8. Heat and spin interconversion

    International Nuclear Information System (INIS)

    Ohnuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi; Saitoh, Eeiji

    2017-01-01

    Spin Seebeck and spin Peltier effects, which are mutual conversion phenomena of heat and spin, are discussed on the basis of the microscopic theory. First, the spin Seebeck effect, which is the spin-current generation due to heat current, is discussed. The recent progress in research on the spin Seebeck effect are introduced. We explain the origin of the observed sign changes of the spin Seebeck effect in compensated ferromagnets. Next, the spin Peltier effect, which is the heat-current generation due to spin current, is discussed. Finally, we show that the spin Seebeck and spin Peltier effects are summarized by Onsager's reciprocal relation and derive Kelvin's relation for the spin and heat transports. (author)

  9. Magnetic tunnel junctions with Co:TiO2 magnetic semiconductor electrodes

    NARCIS (Netherlands)

    Lee, Y.J.; Abhishek Kumar, A.K.; Kumar, A.; Vera Marun, I.J.; de Jong, Machiel Pieter; Jansen, R.

    2010-01-01

    Spin-polarized tunneling is investigated in magnetic tunnel junctions containing an ultrathin interfacial layer of Co:TiO2 magnetic semiconductor. The Co:TiO2 layers (0 to 1 nm thick) are inserted at the SrTiO3/Co interface in La0.67Sr0.33MnO3/SrTiO3/Co tunnel junctions. For all junctions we find a

  10. Magnetization switching of a metallic nanomagnet via current-induced surface spin-polarization of an underlying topological insulator

    International Nuclear Information System (INIS)

    Roy, Urmimala; Dey, Rik; Pramanik, Tanmoy; Ghosh, Bahniman; Register, Leonard F.; Banerjee, Sanjay K.

    2015-01-01

    We consider a thermally stable, metallic nanoscale ferromagnet (FM) subject to spin-polarized current injection and exchange coupling from the spin-helically locked surface states of a topological insulator (TI) to evaluate possible non-volatile memory applications. We consider parallel transport in the TI and the metallic FM, and focus on the efficiency of magnetization switching as a function of transport between the TI and the FM. Transport is modeled as diffusive in the TI beneath the FM, consistent with the mobility in the TI at room temperature, and in the FM, which essentially serves as a constant potential region albeit spin-dependent except in the low conductivity, diffusive limit. Thus, it can be captured by drift-diffusion simulation, which allows for ready interpretation of the results. We calculate switching time and energy consumed per write operation using self-consistent transport, spin-transfer-torque (STT), and magnetization dynamics calculations. Calculated switching energies and times compare favorably to conventional spin-torque memory schemes for substantial interlayer conductivity. Nevertheless, we find that shunting of current from the TI to a metallic nanomagnet can substantially limit efficiency. Exacerbating the problem, STT from the TI effectively increases the TI resistivity. We show that for optimum performance, the sheet resistivity of the FM layer should be comparable to or larger than that of the TI surface layer. Thus, the effective conductivity of the FM layer becomes a critical design consideration for TI-based non-volatile memory

  11. Nuclear spin pumping and electron spin susceptibilities

    NARCIS (Netherlands)

    Danon, J.; Nazarov, Y.V.

    2011-01-01

    In this work we present a new formalism to evaluate the nuclear spin dynamics driven by hyperfine interaction with nonequilibrium electron spins. To describe the dynamics up to second order in the hyperfine coupling it suffices to evaluate the susceptibility and fluctuations of the electron spin.

  12. Theory of the Spin Galvanic Effect at Oxide Interfaces

    Science.gov (United States)

    Seibold, Götz; Caprara, Sergio; Grilli, Marco; Raimondi, Roberto

    2017-12-01

    The spin galvanic effect (SGE) describes the conversion of a nonequilibrium spin polarization into a transverse charge current. Recent experiments have demonstrated a large conversion efficiency for the two-dimensional electron gas formed at the interface between two insulating oxides, LaAlO3 and SrTiO3 . Here, we analyze the SGE for oxide interfaces within a three-band model for the Ti t2 g orbitals which displays an interesting variety of effective spin-orbit couplings in the individual bands that contribute differently to the spin-charge conversion. Our analytical approach is supplemented by a numerical treatment where we also investigate the influence of disorder and temperature, which turns out to be crucial to providing an appropriate description of the experimental data.

  13. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael

    2013-01-01

    Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.

  14. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

    Dobrovitski, V.V.; Feiguin, A.E.; Awschalom, D.D.; Hanson, R.

    2008-01-01

    We study decoherence of central spins by a spin bath, focusing on the difference between measurement of a single central spin and measurement of a large number of central spins (as found in typical spin-resonance experiments). For a dilute spin bath, the single spin demonstrates Gaussian

  15. Spin-polarized spin excitation spectroscopy

    International Nuclear Information System (INIS)

    Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J

    2010-01-01

    We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.

  16. Magnons, Spin Current and Spin Seebeck Effect

    Science.gov (United States)

    Maekawa, Sadamichi

    2012-02-01

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

  17. Sol-Gel Synthesis and Characterization of Ba1-xGdxTiO3+δ Thin Films on SiO2/Si Substrates Using Spin-Coating Technique

    Directory of Open Access Journals (Sweden)

    Yen Chin TEH

    2017-02-01

    Full Text Available Ba1-xGdxTiO3+δ, at x = 0, 0.05, 0.1, 0.15, 0.2, (BGT thin films have been fabricated on SiO2/Si substrate using Sol-Gel method. The microstructure and surface morphology of the fabricated films have been investigated using X-ray diffraction (XRD and atomic force microscopy (AFM. The XRD results show that the fabricated films are crystalline with perovskite structure. There is a shifting of the preferred peak at 31.5o to a higher angle as the doping ratio increases suggesting a distortion lattice exists in the films, which could be due to the substitution of Gd3+ ions into Ba-site. The decreasing of lattice constants confirms the substitution of Gd3+ in BaTiO3 lattice structure. The microstrain and dislocation density are found to be increased with the increase of Gd3+ doping, which attributed to the reduction of lattice volume that due to the ionic size mismatch effect. The AFM results show decreasing trend in both average grain size and roughness parameters. Therefore, the microstructure and surface morphology of BGT samples is strongly dependent on the Gd3+ doping concentration that mainly due to the difference ionic radius substitution.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.13954

  18. Effects of oxygen concentration in Co/CoO exchange-coupled spin valves

    International Nuclear Information System (INIS)

    Eckert, J.C.; Stern, N.P.; Snowden, D.S.; Checkelsky, J.G.; Sparks, P.D.; Carey, M.J.

    2004-01-01

    The properties of Co/CoO x exchange-coupled spin valves are explored at temperatures to 5 K. The spin valve structure is: 100 A CoO x /30 A Co/30 A Cu/10 A Co/50 A NiFe/50 A Ti. Our discovery is the considerable differences between the properties of the spin valves for which the CoO x layer is prepared in different O 2 concentrations

  19. Spin-Mechatronics

    Science.gov (United States)

    Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

    2017-01-01

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

  20. Two-dimensional spin diffusion in multiterminal lateral spin valves

    Science.gov (United States)

    Saha, D.; Basu, D.; Holub, M.; Bhattacharya, P.

    2008-01-01

    The effects of two-dimensional spin diffusion on spin extraction in lateral semiconductor spin valves have been investigated experimentally and theoretically. A ferromagnetic collector terminal of variable size is placed between the ferromagnetic electron spin injector and detector of a conventional lateral spin valve for spin extraction. It is observed that transverse spin diffusion beneath the collector terminal plays an important role along with the conventional longitudinal spin diffusion in describing the overall transport of spin carriers. Two-dimensional spin diffusion reduces the perturbation of the channel electrochemical potentials and improves spin extraction.

  1. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  2. Trends in (LaMnO3)n/(SrTiO3)m superlattices with varying layer thicknesses

    KAUST Repository

    Jilili, J.

    2015-09-01

    We investigate the thickness dependence of the structural, electronic, and magnetic properties of (LaMnO3)n/(SrTiO3)m (n, m = 2, 4, 6, 8) superlattices using density functional theory. The electronic structure turns out to be highly sensitive to the onsite Coulomb interaction. In contrast to bulk SrTiO3, strongly distorted O octahedra are observed in the SrTiO3 layers with a systematic off centering of the Ti atoms. The systems favour ferromagnetic spin ordering rather than the antiferromagnetic spin ordering of bulk LaMnO3 and all show half-metallicity, while a systematic reduction of the minority spin band gaps as a function of the LaMnO3 and SrTiO3 layer thicknesses originates from modifications of the Ti dxy states.

  3. Spin at Lausanne

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    From 25 September to 1 October, some 150 spin enthusiasts gathered in Lausanne for the 1980 International Symposium on High Energy Physics with Polarized Beams and Polarized Targets. The programme was densely packed, covering physics interests with spin as well as the accelerator and target techniques which make spin physics possible

  4. Spin-torque transistor

    NARCIS (Netherlands)

    Bauer, G.E.W.; Brataas, A.; Tserkovnyak, Y.; Van Wees, B.J.

    2003-01-01

    A magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain. The working principle is the modulation of the soure–drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spin-torque created by a control spin

  5. Spin physics in semiconductors

    CERN Document Server

    2017-01-01

    This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.

  6. Spin pumping through a topological insulator probed by x-ray detected ferromagnetic resonance

    Science.gov (United States)

    Figueroa, A. I.; Baker, A. A.; Collins-McIntyre, L. J.; Hesjedal, T.; van der Laan, G.

    2016-02-01

    In the field of spintronics, the generation of a pure spin current (without macroscopic charge flow) through spin pumping of a ferromagnetic (FM) layer opens up the perspective of a new generation of dissipation-less devices. Microwave driven ferromagnetic resonance (FMR) can generate a pure spin current that enters adjacent layers, allowing for both magnetization reversal (through spin-transfer torque) and to probe spin coherence in non-magnetic materials. However, standard FMR is unable to probe multilayer dynamics directly, since the measurement averages over the contributions from the whole system. The synchrotron radiation-based technique of x-ray detected FMR (XFMR) offers an elegant solution to this drawback, giving access to element-, site-, and layer-specific dynamical measurements in heterostructures. In this work, we show how XFMR has provided unique information to understand spin pumping and spin transfer torque effects through a topological insulator (TI) layer in a pseudo-spin valve heterostructure. We demonstrate that TIs function as efficient spin sinks, while also allowing a limited dynamic coupling between ferromagnetic layers. These results shed new light on the spin dynamics of this novel class of materials, and suggest future directions for the development of room temperature TI-based spintronics.

  7. Muon spin relaxation in random spin systems

    International Nuclear Information System (INIS)

    Toshimitsu Yamazaki

    1981-01-01

    The longitudinal relaxation function Gsub(z)(t) of the positive muon can reflect dynamical characters of local field in a unique way even when the correlation time is longer than the Larmor period of local field. This method has been applied to studies of spin dynamics in spin glass systems, revealing sharp but continuous temperature dependence of the correlation time. Its principle and applications are reviewed. (author)

  8. Spin pumping through a topological insulator probed by x-ray detected ferromagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa, A.I., E-mail: aifigueg@gmail.com [Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE (United Kingdom); Baker, A.A. [Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE (United Kingdom); Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Collins-McIntyre, L.J.; Hesjedal, T. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Laan, G. van der [Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE (United Kingdom)

    2016-02-15

    In the field of spintronics, the generation of a pure spin current (without macroscopic charge flow) through spin pumping of a ferromagnetic (FM) layer opens up the perspective of a new generation of dissipation-less devices. Microwave driven ferromagnetic resonance (FMR) can generate a pure spin current that enters adjacent layers, allowing for both magnetization reversal (through spin-transfer torque) and to probe spin coherence in non-magnetic materials. However, standard FMR is unable to probe multilayer dynamics directly, since the measurement averages over the contributions from the whole system. The synchrotron radiation-based technique of x-ray detected FMR (XFMR) offers an elegant solution to this drawback, giving access to element-, site-, and layer-specific dynamical measurements in heterostructures. In this work, we show how XFMR has provided unique information to understand spin pumping and spin transfer torque effects through a topological insulator (TI) layer in a pseudo-spin valve heterostructure. We demonstrate that TIs function as efficient spin sinks, while also allowing a limited dynamic coupling between ferromagnetic layers. These results shed new light on the spin dynamics of this novel class of materials, and suggest future directions for the development of room temperature TI-based spintronics. - Highlights: • X-ray detected ferromagnetic resonance is used to study the spin pumping phenomenon. • We show a powerful way to get information of spin transfer between magnetic layers. • We observe spin pumping through a topological insulators at room temperature. • Topological insulators function as efficient spin sinks.

  9. Spin pumping through a topological insulator probed by x-ray detected ferromagnetic resonance

    International Nuclear Information System (INIS)

    Figueroa, A.I.; Baker, A.A.; Collins-McIntyre, L.J.; Hesjedal, T.; Laan, G. van der

    2016-01-01

    In the field of spintronics, the generation of a pure spin current (without macroscopic charge flow) through spin pumping of a ferromagnetic (FM) layer opens up the perspective of a new generation of dissipation-less devices. Microwave driven ferromagnetic resonance (FMR) can generate a pure spin current that enters adjacent layers, allowing for both magnetization reversal (through spin-transfer torque) and to probe spin coherence in non-magnetic materials. However, standard FMR is unable to probe multilayer dynamics directly, since the measurement averages over the contributions from the whole system. The synchrotron radiation-based technique of x-ray detected FMR (XFMR) offers an elegant solution to this drawback, giving access to element-, site-, and layer-specific dynamical measurements in heterostructures. In this work, we show how XFMR has provided unique information to understand spin pumping and spin transfer torque effects through a topological insulator (TI) layer in a pseudo-spin valve heterostructure. We demonstrate that TIs function as efficient spin sinks, while also allowing a limited dynamic coupling between ferromagnetic layers. These results shed new light on the spin dynamics of this novel class of materials, and suggest future directions for the development of room temperature TI-based spintronics. - Highlights: • X-ray detected ferromagnetic resonance is used to study the spin pumping phenomenon. • We show a powerful way to get information of spin transfer between magnetic layers. • We observe spin pumping through a topological insulators at room temperature. • Topological insulators function as efficient spin sinks.

  10. Spin orientation in solid solution hematite-ilmenite

    DEFF Research Database (Denmark)

    Brok, Erik; Frandsen, Cathrine; Lefmann, Kim

    2017-01-01

    temperature range below the Néel temperature and does not depend systematically on Ti-content. The results indicate that the out-of-plane spin component is an intrinsic feature of hematite itself, with an origin not yet fully understood, but consistent with group theory. This represents a major shift...... spectroscopy. The usually assumed magnetic structure of hematite within this temperature range is antiferromagnetic with the spins confined to the basal plane of the hexagonal structure; however, an out-of-plane spin component is allowed by the symmetry of the system and has been observed in recent studies......The spin orientation in synthetic hematite-ilmenite samples and in a sample of natural hematite was studied from room temperature to above the antiferromagnetic-paramagnetic phase transition (the Néel temperature; TN ≈ 600–950 K) by neutron powder diffraction and at room temperature by Mössbauer...

  11. The susceptibilities in the spin-S Ising model

    International Nuclear Information System (INIS)

    Ainane, A.; Saber, M.

    1995-08-01

    The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs

  12. Higher spin gauge theories

    CERN Document Server

    Henneaux, Marc; Vasiliev, Mikhail A

    2017-01-01

    Symmetries play a fundamental role in physics. Non-Abelian gauge symmetries are the symmetries behind theories for massless spin-1 particles, while the reparametrization symmetry is behind Einstein's gravity theory for massless spin-2 particles. In supersymmetric theories these particles can be connected also to massless fermionic particles. Does Nature stop at spin-2 or can there also be massless higher spin theories. In the past strong indications have been given that such theories do not exist. However, in recent times ways to evade those constraints have been found and higher spin gauge theories have been constructed. With the advent of the AdS/CFT duality correspondence even stronger indications have been given that higher spin gauge theories play an important role in fundamental physics. All these issues were discussed at an international workshop in Singapore in November 2015 where the leading scientists in the field participated. This volume presents an up-to-date, detailed overview of the theories i...

  13. Spin caloritronics in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Angsula; Frota, H. O. [Department of Physics, Federal University of Amazonas, Av. Rodrigo Octavio 3000-Japiim, 69077-000 Manaus, AM (Brazil)

    2015-06-14

    Spin caloritronics, the combination of spintronics with thermoelectrics, exploiting both the intrinsic spin of the electron and its associated magnetic moment in addition to its fundamental electronic charge and temperature, is an emerging technology mainly in the development of low-power-consumption technology. In this work, we study the thermoelectric properties of a Rashba dot attached to two single layer/bilayer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current, which depends on the temperature and chemical potential. We demonstrate that the Rashba dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature, and also the Rashba term have been observed.

  14. Spin caloritronics in graphene

    Science.gov (United States)

    Frota, H. O.; Ghosh, Angsula

    2014-08-01

    Spin caloritronics, the combination of spintronics with thermoelectrics, based on spin and heat transport has attracted a great attention mainly in the development of low-power-consumption technology. In this work we study the thermoelectric properties of a quantum dot attached to two single layer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current which depends on the temperature and chemical potential. We demonstrate that the quantum dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature and also the Coulomb repulsion due to the double occupancy of an energy level have been observed.

  15. Strain engineered magnetic tunnel junctions and spin-orbit torque switching (Conference Presentation)

    Science.gov (United States)

    Wu, Yang; Narayanapillai, Kulothungasagaran; Elyasi, Mehrdad; Qiu, Xuepeng; Yang, Hyunsoo

    2016-10-01

    The efficient generation of pure spin currents and manipulation of the magnetization dynamics of magnetic structures is of central importance in the field of spintronics. The spin-orbit effect is one of the promising ways to generate spin currents, in which a charge current can be converted to a transverse spin current due to the spin-orbit interaction. We investigate the spin dynamics in the presence of strong spin-orbit coupling materials such as LaAlO3/SrTiO3 oxide heterostructures. Angle dependent magnetoresistance measurements are employed to detect and understand the current-induced spin-orbit torques, and an effective field of 2.35 T is observed for a dc-current of 200 uA. In order to understand the interaction between light and spin currents, we use a femtosecond laser to excite an ultrafast transient spin current and subsequent terahertz (THz) emission in nonmagnet (NM)/ferromagnet (FM)/oxide heterostructures. The THz emission strongly relies on spin-orbit interaction, and is tailored by the magnitude and sign of the effective spin Hall angle of the NM. Our results can be utilized for ultrafast spintronic devices and tunable THz sources.

  16. Optimized spin-injection efficiency and spin MOSFET operation based on low-barrier ferromagnet/insulator/n-Si tunnel contact

    Science.gov (United States)

    Yang, Yang; Wu, Zhenhua; Yang, Wen; Li, Jun; Chen, Songyan; Li, Cheng

    2017-06-01

    We theoretically investigate the spin injection in different ferromagnet/insulator/n-Si tunnel contacts by using the lattice non-equilibrium Green’s function method. We find that the tunnel contacts with low-barrier materials such as TiO2 and Ta2O5 have far lower resistances than the conventional-barrier materials, resulting in a wider and attainable optimum parameters window for improving the spin-injection efficiency and magnetoresistance ratio of a vertical-spin metal-oxide-semiconductor field-effect transistor. Additionally, we find that the spin-asymmetry coefficient of the TiO2 tunnel contact has a negative value, while that of the Ta2O5 contact can be tuned between positive and negative values by changing the parameters.

  17. Spin and Maximal Acceleration

    Directory of Open Access Journals (Sweden)

    Giorgio Papini

    2017-12-01

    Full Text Available We study the spin current tensor of a Dirac particle at accelerations close to the upper limit introduced by Caianiello. Continual interchange between particle spin and angular momentum is possible only when the acceleration is time-dependent. This represents a stringent limit on the effect that maximal acceleration may have on spin physics in astrophysical applications. We also investigate some dynamical consequences of maximal acceleration.

  18. Spin Hall effect devices

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; Wunderlich, Joerg; Olejník, Kamil

    2012-01-01

    Roč. 11, č. 5 (2012), s. 382-390 ISSN 1476-1122 EU Projects: European Commission(XE) 268066 - 0MSPIN; European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronics * spin transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 35.749, year: 2012

  19. Spin coating apparatus

    Science.gov (United States)

    Torczynski, John R.

    2000-01-01

    A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.

  20. A controllable spin prism

    International Nuclear Information System (INIS)

    Hakioglu, T

    2009-01-01

    Based on Khodas et al (2004 Phys. Rev. Lett. 92 086602), we propose a device acting like a controllable prism for an incident spin. The device is a large quantum well where Rashba and Dresselhaus spin-orbit interactions are present and controlled by the plunger gate potential, the electric field and the barrier height. A totally destructive interference can be manipulated externally between the Rashba and Dresselhaus couplings. The spin-dependent transmission/reflection amplitudes are calculated as the control parameters are changed. The device operates as a spin prism/converter/filter in different regimes and may stimulate research in promising directions in spintronics in analogy with linear optics.

  1. Quantum spin Hall phases

    International Nuclear Information System (INIS)

    Murakami, Shuichi

    2009-01-01

    We review our recent theoretical works on the quantum spin Hall effect. First we compare edge states in various 2D systems, and see whether they are robust or fragile against perturbations. Through the comparisons we see the robust nature of edge states in 2D quantum spin Hall phases. We see how it is protected by the Z 2 topological number, and reveal the nature of the Z 2 topological number by studying the phase transition between the quantum spin Hall and insulator phases. We also review our theoretical proposal of the ultrathin bismuth film as a candidate to the 2D quantum spin Hall system. (author)

  2. PREFACE: Spin Electronics

    Science.gov (United States)

    Dieny, B.; Sousa, R.; Prejbeanu, L.

    2007-04-01

    Conventional electronics has in the past ignored the spin on the electron, however things began to change in 1988 with the discovery of giant magnetoresistance in metallic thin film stacks which led to the development of a new research area, so called spin-electronics. In the last 10 years, spin-electronics has achieved a number of breakthroughs from the point of view of both basic science and application. Materials research has led to several major discoveries: very large tunnel magnetoresistance effects in tunnel junctions with crystalline barriers due to a new spin-filtering mechanism associated with the spin-dependent symmetry of the electron wave functions new magnetic tunnelling barriers leading to spin-dependent tunnelling barrier heights and acting as spin-filters magnetic semiconductors with increasingly high ordering temperature. New phenomena have been predicted and observed: the possibility of acting on the magnetization of a magnetic nanostructure with a spin-polarized current. This effect, due to a transfer of angular momentum between the spin polarized conduction electrons and the local magnetization, can be viewed as the reciprocal of giant or tunnel magnetoresistance. It can be used to switch the magnetization of a magnetic nanostructure or to generate steady magnetic excitations in the system. the possibility of generating and manipulating spin current without charge current by creating non-equilibrium local accumulation of spin up or spin down electrons. The range of applications of spin electronics materials and phenomena is expanding: the first devices based on giant magnetoresistance were the magnetoresistive read-heads for computer disk drives. These heads, introduced in 1998 with current-in plane spin-valves, have evolved towards low resistance tunnel magnetoresistice heads in 2005. Besides magnetic recording technology, these very sensitive magnetoresistive sensors are finding applications in other areas, in particular in biology. magnetic

  3. Local Noncollinear Spin Analysis.

    Science.gov (United States)

    Abate, Bayileyegn A; Joshi, Rajendra P; Peralta, Juan E

    2017-12-12

    In this work, we generalize the local spin analysis of Clark and Davidson [J. Chem. Phys. 2001 115 (16), 7382] for the partitioning of the expectation value of the molecular spin square operator, ⟨Ŝ 2 ⟩, into atomic contributions, ⟨Ŝ A ·Ŝ B ⟩, to the noncollinear spin case in the framework of density functional theory (DFT). We derive the working equations, and we show applications to the analysis of the noncollinear spin solutions of typical spin-frustrated systems and to the calculation of magnetic exchange couplings. In the former case, we employ the triangular H 3 He 3 test molecule and a Mn 3 complex to show that the local spin analysis provides additional information that complements the standard one-particle spin population analysis. For the calculation of magnetic exchange couplings, J AB , we employ the local spin partitioning to extract ⟨Ŝ A ·Ŝ B ⟩ as a function of the interatomic spin orientation given by the angle θ. This, combined with the dependence of the electronic energy with θ, provides a methodology to extract J AB from DFT calculations that, in contrast to conventional energy differences based methods, does not require the use of ad hoc S A and S B values.

  4. Spin glasses (II)

    International Nuclear Information System (INIS)

    Fischer, K.H.

    1985-01-01

    Experimental results of spin glass studies are reviewed and related to existing theories. Investigations of spin glasses are concentrated on atomic structure, metallurgical treatment, and high-temperature susceptibility of alloys, on magnetic properties at low temperature and near the freezing temperature, on anisotropy behaviour measured by ESR, NMR and torque, on specific heat, Moessbauer effect, neutron scattering and muon-spin depolarization experiments, ultrasound and transport properties. Some new theories of spin glasses are discussed which have been developed since Part I appeared

  5. Noise in tunneling spin current across coupled quantum spin chains

    OpenAIRE

    Aftergood, Joshua; Takei, So

    2017-01-01

    We theoretically study the spin current and its dc noise generated between two spin-1/2 spin chains weakly coupled at a single site in the presence of an over-population of spin excitations and a temperature elevation in one subsystem relative to the other, and compare the corresponding transport quantities across two weakly coupled magnetic insulators hosting magnons. In the spin chain scenario, we find that applying a temperature bias exclusively leads to a vanishing spin current and a conc...

  6. Effect of spin rotation coupling on spin transport

    International Nuclear Information System (INIS)

    Chowdhury, Debashree; Basu, B.

    2013-01-01

    We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k → ⋅p → perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k → ⋅p → framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied

  7. Microstructures and electrochemical properties of Si-Ni-xTi alloys for anode materials.

    Science.gov (United States)

    Song, Jong Jin; Kwon, Hye Jin; Ahn, Deuk Kyu; Chu, Yeon Yi; Cho, Jong Soo; Moon, Jeong Tak; Park, Won-Wook; Sohn, Keun Yong

    2013-05-01

    The phase change due to varying content of titanium in Si-Ni-xTi alloys and its effect on the electrochemical behavior has been investigated. Specimens were prepared by melt-spinning to reduce the microstructure scale. Results showed that silicon particles of 50-100 nm diameter and dendrites of somewhat larger scale were formed in the Si-Ni-Ti alloys ribbons. The microstructure of Si70Ni15Ti15 alloy ribbons was composed of silicon particles finely dispersed in Si7Ni4Ti4 phase. The cycle performance was improved by the formation of TiSi2 or NiSi2 phase at the presence of Si7Ni4Ti4 phase, either of which combined with Si7Ni4Ti4 phase effectively accommodated the volume change of silicon particles during cycling. The reduced scale of silicon particles contributed to the enhanced cycle efficiency as well.

  8. Low temperature fabrication of perovskite solar cells with TiO{sub 2} nanoparticle layers

    Energy Technology Data Exchange (ETDEWEB)

    Kanayama, Masato; Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Suzuki, Atsushi [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga 522-8533 (Japan); Yamada, Masahiro; Sakamoto, Hiroki [Energy Technology Laboratories, Osaka Gas Co., Ltd., Osaka 554-0051 (Japan); Minami, Satoshi; Kohno, Kazufumi [Frontier Materials Laboratories, Osaka Gas Chemicals Co., Ltd., Osaka 554-0051 (Japan)

    2016-02-01

    TiO{sub 2}/CH{sub 3}NH{sub 3}PbI{sub 3}-based photovoltaic devices were fabricated by a spin-coating method using a mixture solution. TiO{sub 2} require high-temperature processing to achieve suitably high carrier mobility. TiO{sub 2} electron transport layers and TiO{sub 2} scaffold layers for the perovskite were fabricated from TiO{sub 2} nanoparticles with different grain sizes. The photovoltaic properties and microstructures of solar cells were characterized. Nanoparticle sizes of these TiO{sub 2} were 23 nm and 3 nm and the performance of solar cells was improved by combination of two TiO{sub 2} nanoparticles.

  9. Variable range hopping in TiO2 insulating layers for oxide electronic devices

    Directory of Open Access Journals (Sweden)

    Y. L. Zhao

    2012-03-01

    Full Text Available TiO2 thin films are of importance in oxide electronics, e.g., Pt/TiO2/Pt for memristors and Co-TiO2/TiO2/Co-TiO2 for spin tunneling devices. When such structures are deposited at a variety of oxygen pressures, how does TiO2 behave as an insulator? We report the discovery of an anomalous resistivity minimum in a TiO2 film at low pressure (not strongly dependent on deposition temperature. Hall measurements rule out band transport and in most of the pressure range the transport is variable range hopping (VRH though below 20 K it was difficult to differentiate between Mott and Efros-Shklovskii's (ES mechanism. Magnetoresistance (MR of the sample with lowest resistivity was positive at low temperature (for VRH but negative above 10 K indicating quantum interference effects.

  10. Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator: α-Sn Films.

    Science.gov (United States)

    Rojas-Sánchez, J-C; Oyarzún, S; Fu, Y; Marty, A; Vergnaud, C; Gambarelli, S; Vila, L; Jamet, M; Ohtsubo, Y; Taleb-Ibrahimi, A; Le Fèvre, P; Bertran, F; Reyren, N; George, J-M; Fert, A

    2016-03-04

    We present results on spin to charge current conversion in experiments of resonant spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) α-Sn. By angle-resolved photoelectron spectroscopy (ARPES), we first check that the Dirac cone (DC) at the α-Sn (0 0 1) surface subsists after covering Sn with Ag. Then we show that resonant spin pumping at room temperature from Fe through Ag into α-Sn layers induces a lateral charge current that can be ascribed to the inverse Edelstein effect by the DC states. Our observation of an inverse Edelstein effect length much longer than those generally found for Rashba interfaces demonstrates the potential of TIs for the conversion between spin and charge in spintronic devices. By comparing our results with data on the relaxation time of TI free surface states from time-resolved ARPES, we can anticipate the ultimate potential of the TI for spin to charge conversion and the conditions to reach it.

  11. Spin labels. Applications in biology

    International Nuclear Information System (INIS)

    Frangopol, T.P.; Frangopol, M.; Ionescu, S.M.; Pop, I.V.; Benga, G.

    1980-11-01

    The main applications of spin labels in the study of biomembranes, enzymes, nucleic acids, in pharmacology, spin immunoassay are reviewed along with the fundamentals of the spin label method. 137 references. (author)

  12. Spin Switching via Quantum Dot Spin Valves

    Science.gov (United States)

    Gergs, N. M.; Bender, S. A.; Duine, R. A.; Schuricht, D.

    2018-01-01

    We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state. Our model may be realized by a number of experimental systems, including magnetic scanning-tunneling microscope tips and artificial quantum dot systems.

  13. Spin, mass, and symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E. [Stanford Univ., CA (United States)

    1994-12-01

    When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics.

  14. Physics lab in spin

    CERN Multimedia

    Hawkes, N

    1999-01-01

    RAL is fostering commerical exploitation of its research and facilities in two main ways : spin-out companies exploit work done at the lab, spin-in companies work on site taking advantage of the facilities and the expertise available (1/2 page).

  15. More spinoff from spin

    International Nuclear Information System (INIS)

    Masaike, Akira

    1993-01-01

    Despite playing a major role in today's Standard Model, spin - the intrinsic angular momentum carried by particles - is sometimes dismissed as an inessential complication. However several major spin questions with important implications for the Standard Model remain unanswered, and recent results and new technological developments made the 10th International Symposium on High Energy Spin Physics, held in Nagoya, Japan, in November, highly topical. The symposium covered a wide range of physics, reflecting the diversity of spin effects, however four main themes were - the spin content of the nucleon, tests of symmetries and physics beyond standard models, intermediate energy physics, and spin technologies. Opening the meeting, T. Kinoshita reviewed the status of measurements of the anomalous magnetic moment (g-2) of the electron and the muon. The forthcoming experiment at Brookhaven (September 1991, page 23) will probe beyond the energy ranges open to existing electronpositron colliders. For example muon substructure will be opened up to 5 TeV and Ws to 2 TeV. R.L. Jaffe classified quark-parton distributions in terms of their spin dependence, pointing out their leftright attributes, and emphasized the importance of measuring transverse spin distributions through lepton pair production

  16. Spin Hall noise

    NARCIS (Netherlands)

    Kamra, A.; Witek, F.P.; Meyer, S.; Huebl, H.; Geprägs, S.; Gross, R.; Bauer, G.E.W.; Goennenwein, S.T.B.

    2014-01-01

    We measure the low-frequency thermal fluctuations of pure spin current in a platinum film deposited on yttrium iron garnet via the inverse spin Hall effect (ISHE)-mediated voltage noise as a function of the angle ? between the magnetization and the transport direction. The results are consistent

  17. Antiferromagnetic spin Seebeck effect.

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-03

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

  18. Spin, mass, and symmetry

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1994-01-01

    When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics

  19. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans

    1975-01-01

    with increasing temperatures implies that the two-ion coupling is effectively isotropic above ∼ 150 K. We present arguments for concluding that, among the mechanisms which may introduce anisotropic two-ion couplings in the rare-earth metals, the modification of the indirect exchange interaction by the spin......The energies of spin waves propagating in the c direction of Tb have been studied by inelastic neutron scattering, as a function of a magnetic field applied along the easy and hard directions in the basal plane, and as a function of temperature. From a general spin Hamiltonian, consistent...... with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results...

  20. Spin Hall and spin swapping torques in diffusive ferromagnets

    KAUST Repository

    Pauyac, C. O.

    2017-12-08

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

  1. Effects of TiO{sub 2} buffer layer on the photoelectrochemical properties of TiO{sub 2} Nano rods grown by modified chemical bath deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tae-hyun; Ha, Jin-wook; Ryu, Hyukhyun [Inje University, Gimhae (Korea, Republic of); Lee, Won-Jae [Dong-Eui University, Busan (Korea, Republic of)

    2015-08-15

    In this study, we grew TiO{sub 2} nano rods on TiO{sub 2}-film buffered FTO substrate using modified chemical bath deposition (M-CBD). The TiO{sub 2} buffer layer was grown by spin coating method with different RPM (revolutions per minute) values and deposition cycles. We investigated the effects of the RPM values and the deposition cycles on the morphological, structural and photoelectrochemical properties of TiO{sub 2} nano rods. In this work, we have also found that the morphological and structural properties of TiO{sub 2} nano rods affected the photoelectrochemical properties of TiO{sub 2} nano rods. And the maximum photocurrent density of 0.34 mA/cm{sup 2} at 0.6V (vs.SCE) was obtained from the buffer layer deposition process condition of 4,000 RPM and two-times buffer layer depositions.

  2. Resonant Tunneling Spin Pump

    Science.gov (United States)

    Ting, David Z.

    2007-01-01

    The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

  3. Nuclear spins in nanostructures

    International Nuclear Information System (INIS)

    Coish, W.A.; Baugh, J.

    2009-01-01

    We review recent theoretical and experimental advances toward understanding the effects of nuclear spins in confined nanostructures. These systems, which include quantum dots, defect centers, and molecular magnets, are particularly interesting for their importance in quantum information processing devices, which aim to coherently manipulate single electron spins with high precision. On one hand, interactions between confined electron spins and a nuclear-spin environment provide a decoherence source for the electron, and on the other, a strong effective magnetic field that can be used to execute local coherent rotations. A great deal of effort has been directed toward understanding the details of the relevant decoherence processes and to find new methods to manipulate the coupled electron-nuclear system. A sequence of spectacular new results have provided understanding of spin-bath decoherence, nuclear spin diffusion, and preparation of the nuclear state through dynamic polarization and more general manipulation of the nuclear-spin density matrix through ''state narrowing.'' These results demonstrate the richness of this physical system and promise many new mysteries for the future. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  4. Spin drift and spin diffusion currents in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Idrish Miah, M [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au

    2008-09-15

    On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  5. Spin drift and spin diffusion currents in semiconductors

    Directory of Open Access Journals (Sweden)

    M Idrish Miah

    2008-01-01

    Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  6. Spin drift and spin diffusion currents in semiconductors

    International Nuclear Information System (INIS)

    Idrish Miah, M

    2008-01-01

    On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  7. Higher spins and holography

    Science.gov (United States)

    Kraus, Per; Ross, Simon F.

    2013-05-01

    The principles of quantum mechanics and relativity impose rigid constraints on theories of massless particles with nonzero spin. Indeed, Yang-Mills theory and General Relativity are the unique solution in the case of spin-1 and spin-2. In asymptotically flat spacetime, there are fundamental obstacles to formulating fully consistent interacting theories of particles of spin greater than 2. However, indications are that such theories are just barely possible in asymptotically anti-de Sitter or de Sitter spacetimes, where the non-existence of an S-matrix provides an escape from the theorems restricting theories in Minkowski spacetime. These higher spin gravity theories are therefore of great intrinsic interest, since they, along with supergravity, provide the only known field theories generalizing the local invariance principles of Yang-Mills theory and General Relativity. While work on higher spin gravity goes back several decades, the subject has gained broader appeal in recent years due to its appearance in the AdS/CFT correspondence. In three and four spacetime dimensions, there exist duality proposals linking higher spin gravity theories to specific conformal field theories living in two and three dimensions respectively. The enlarged symmetry algebra of the conformal field theories renders them exactly soluble, which makes them excellent laboratories for understanding in detail the holographic mechanism behind AdS/CFT duality. Steady progress is also being made on better understanding the space of possible higher spin gravity theories and their physical content. This work includes classifying the possible field multiplets and their interactions, constructing exact solutions of the nonlinear field equations, and relating higher spin theories to string theory. A full understanding of these theories will involve coming to grips with the novel symmetry principles that enlarge those of General Relativity and Yang-Mills theory, and one can hope that this will provide

  8. Spin manipulation at the interface of a topological insulator/GaAs heterostructure

    Science.gov (United States)

    Qu, Dongxia; Che, Xiaoyu; Kou, Xufeng; Lang, Murong; Crowhurst, Jonathan; Armstrong, Michael R.; Zaug, Joseph; Wang, Kang L.; Chapline, George F.; Lawrence Livermore National Laboratory Team; University of California, Los Angeles Team

    One primary goal of spintronics is to discover materials and devices, which enable efficient electrical control of spins. The emerging field of topological insulator (TI) provides intriguing opportunities for spin generation and manipulation, owing to its strong spin-orbit character. Here we report that spins can be driven from a topological insulator thin film (Bi0.5Sb0.5)2 Te3 into an adjacent semiconductor GaAs at room temperature. In a TI/GaAs heterostructure, a photo-induced spin current flows across the interface and induces an electrical current via the inverse spin Hall effect, which converts the spin current into a charge current. We find that the magnitude and direction of the helicity-dependent photocurrent can be controlled by gate-voltage, indicative of electric tuning of the spin configuration. This work is supported by Grants 15-LW-018 and 16-SI-004 from the Department of Energy, Laboratory Directed Research and Development (LDRD) funding.

  9. Island of high-spin isomers near N = 82

    International Nuclear Information System (INIS)

    Pedersen, J.; Back, B.B.; Bernthal, F.M.; Bjornholm, S.; Borggreen, J.; Christensen, O.; Folkmann, F.; Herskind, B.; Khoo, T.L.; Neiman, M.; Puehlhofer, F.; Sletten, G.

    1977-01-01

    Experiments aimed at testing for the existence of yrast traps are reported. A search for delayed γ radiation of lifetimes longer than approx. 10 ns and of high multiplicity has been performed by producing more than 100 compound nuclei between Ba and Pb in bombardments with 40 Ar, 50 Ti, and 65 Cu projectiles. An island of high-spin isomers is found to exist in the region 64 or approx. = 71 and N < or approx. = 82

  10. Rapidly solidified prealloyed powders by laser spin atomization

    Science.gov (United States)

    Konitzer, D. G.; Walters, K. W.; Heiser, E. L.; Fraser, H. L.

    1984-01-01

    A new technique, termed laser spin atomization, for the production of rapidly solidified prealloyed powders is described. The results of experiments involving the production of powders of two alloys, one based on Ni, the other on Ti, are presented. The powders have been characterized using light optical metallography, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Auger elec-tron spectroscopy, and these various observations are described.

  11. Current-driven spin dynamics in spin-orbit coupled superconductors

    Science.gov (United States)

    Vignale, Giovanni

    2012-02-01

    The study of the interplay between spin-orbit coupling (SOC) and superconductivity in two-dimensional electron gases (2DEG) has recently gained impetus following the discovery of i) 2DEGs in InAs or GaAs semiconductor heterostructures that are proximized by ordinary s-wave superconducting leads -- a class of systems which plays a key role in the quest for Majorana fermions -- and ii) 2DEGs that form at interfaces between complex oxides such as LaAlO3 and SrTiO3, which display tunable SOC and, under appropriate conditions, superconductivity. Motivated by this body of experimental and theoretical literature, we investigate the collective spin dynamics of an archetypical 2DEG model Hamiltonian with Rashba SOC in the presence of repulsive electron-electron (e-e) interactions. In the absence of superconductivity a Rashba 2DEG exhibits spin oscillations, which, at long wavelength and for weak repulsive interactions, have a frequency 2 αkF, α being the strength of SOC and kF the usual 2D Fermi wavenumber in the absence of SOC. These oscillations, however, are damped and quickly decay due to the emission of (double) electron-hole pairs, which, in the normal phase, are present at arbitrary low energies. In the presence of superconductivity, collective spin oscillations continue to exist in a wide range of parameters, because the Cooper pairs are mixtures of singlet and triplet components. Further, these excitations are undamped because they lie inside the superconducting gap where no other excitation exists. These spin oscillations can be excited by the application of a magnetic field or a supercurrent and can be used to realize persistent spin oscillators operating in the frequency range of 10 GHz - 1 THz.[4pt] Work supported by EU FP7 Programme Grant No. 215368-SEMISPINNET, No. 234970- NANOCTM and No. 248629-SOLID, and by NSF DMR-0705460.

  12. Spin transfer torque with spin diffusion in magnetic tunnel junctions

    KAUST Repository

    Manchon, Aurelien

    2012-08-09

    Spin transport in magnetic tunnel junctions in the presence of spin diffusion is considered theoretically. Combining ballistic tunneling across the barrier and diffusive transport in the electrodes, we solve the spin dynamics equation in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque, as well as a nonconventional thickness dependence of both spin torque components.

  13. Electron spin and nuclear spin manipulation in semiconductor nanosystems

    International Nuclear Information System (INIS)

    Hirayama, Yoshiro; Yusa, Go; Sasaki, Satoshi

    2006-01-01

    Manipulations of electron spin and nuclear spin have been studied in AlGaAs/GaAs semiconductor nanosystems. Non-local manipulation of electron spins has been realized by using the correlation effect between localized and mobile electron spins in a quantum dot- quantum wire coupled system. Interaction between electron and nuclear spins was exploited to achieve a coherent control of nuclear spins in a semiconductor point contact device. Using this device, we have demonstrated a fully coherent manipulation of any two states among the four spin levels of Ga and As nuclei. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Untersuchung der magnetischen und strukturellen Eigenschaften der beiden niedrigdimensionalen Antiferromagnete TiPO4 und CrOCl

    OpenAIRE

    Reuvekamp, Patrick Gerald

    2014-01-01

    Titanium (III) phosphate TiPO4 (3d1 electronic configuration with S = 1/2) is a one-dimensional quantum antiferromagnet exhibiting non-conventional spin-Peierls behaviour at low temperatures. Chromium oxychloride CrOCl (3d3 electronic configuration with S = 3/2) is a two-dimensional antiferromagnet consisting of ferromagnetic spin chains interconnected by competing anti and ferromagnetic spin exchanges interactions. The magnetic and the structural properties of these compounds are intimately ...

  15. Spins in chemistry

    CERN Document Server

    McWeeny, Roy

    2004-01-01

    Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp

  16. Frustrated spin systems

    CERN Document Server

    2013-01-01

    This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated

  17. Spin Hall effect transistor

    Czech Academy of Sciences Publication Activity Database

    Wunderlich, Joerg; Park, B.G.; Irvine, A.C.; Zarbo, Liviu; Rozkotová, E.; Němec, P.; Novák, Vít; Sinova, Jairo; Jungwirth, Tomáš

    2010-01-01

    Roč. 330, č. 6012 (2010), s. 1801-1804 ISSN 0036-8075 R&D Projects: GA AV ČR KAN400100652; GA MŠk LC510 EU Projects: European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronics * spin transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 31.364, year: 2010

  18. Spin tracking in RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Luccio, A.U. [Brookhaven National Lab., Upton, NY (United States); Katayama, T. [Univ. of Tokyo (Japan); Wu, H. [Riken Inst., Tokyo (Japan)

    1997-07-01

    In the acceleration of polarized protons in RHIC many spin depolarizing resonances are encountered. Helical Siberian snakes will be used to overcome depolarizing effects. The behavior of polarization can be studied by numerical tracking in a model accelerator. That allows one to check the strength of the resonances, to study the effect of snakes, to find safe lattice tune regions, and finally to study the operation of special devices like spin flippers. In this paper the authors describe numerical spin tracking. Results show that, for the design corrected distorted orbit and the design beam emittance, the polarization of the beam will be preserved in the whole range of proton energies in RHIC.

  19. SPINning parallel systems software

    International Nuclear Information System (INIS)

    Matlin, O.S.; Lusk, E.; McCune, W.

    2002-01-01

    We describe our experiences in using Spin to verify parts of the Multi Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of processes connected by Unix network sockets. MPD is dynamic processes and connections among them are created and destroyed as MPD is initialized, runs user processes, recovers from faults, and terminates. This dynamic nature is easily expressible in the Spin/Promela framework but poses performance and scalability challenges. We present here the results of expressing some of the parallel algorithms of MPD and executing both simulation and verification runs with Spin

  20. PIIID-formed (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti coatings on NiTi shape memory alloy for medical applications

    International Nuclear Information System (INIS)

    Sun Tao; Wang Langping; Wang Min; Tong Howang; Lu, William W.

    2012-01-01

    (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti composite coatings were fabricated on NiTi shape memory alloy via plasma immersion ion implantation and deposition (PIIID). Surface morphology of samples was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross-sectional morphology indicated that the PIIID-formed coatings were dense and uniform. X-ray diffraction (XRD) was used to characterize the phase composition of samples. X-ray photoelectron spectroscopy (XPS) results showed that the surface of coated NiTi SMA samples was Ni-free. Nanoindentation measurements and pin-on-disc tests were carried out to evaluate mechanical properties and wear resistance of coated NiTi SMA, respectively. For the in vitro biological assessment of the composite coatings in terms of cell morphology and cell viability, osteoblast-like SaOS-2 cells and breast cancer MCF-7 cells were cultured on NiTi SMA samples, respectively. SaOS-2 cells attached and spread better on coated NiTi SMA. Viability of MCF-7 cells showed that the PIIID-formed composite coatings were noncytotoxic and coated samples were more biocompatible than uncoated samples. - Highlights: ► PIIID-formed coatings were fabricated on NiTi SMA to improve its biocompatibility. ► Microstructure, mechanical properties and biocompatibility of coatings were investigated. ► All PIIID-formed composite coatings were noncytotoxic and cytocompatible.

  1. Spin dynamics in highly frustrated pyrochlore magnets

    International Nuclear Information System (INIS)

    Petit, S.; Guitteny, S.; Robert, J.; Mirebeau, I.; Bonville, P.; Decorse, C.; Ollivier, J.; Mutka, H.

    2015-01-01

    This paper aims at showing the complementarity between time-of-flight and triple-axis neutron scattering experiments, on the basis of two topical examples in the field of geometrical magnetic frustration. Rare earth pyrochlore magnets R 2 Ti 2 O 7 (R is a rare earth) play a prominent role in this field, as they form model systems showing a rich variety of ground states, depending on the balance between dipolar, exchange interactions and crystal field. We first review the case of the XY antiferromagnet Er 2 Ti 2 O 7 . Here a transition towards a Neel state is observed, possibly induced by an order-by-disorder mechanism. Effective exchange parameters can be extracted from S(Q, ω). We then examine the case of the spin liquid Tb 2 Ti 2 O 7 . Recent experiments reveal a complex ground state characterized by 'pinch points' and supporting a low energy excitation. These studies demonstrate the existence of a coupling between crystal field transitions and a transverse acoustic phonon mode. (authors)

  2. Magnetocrystalline anisotropy and magnetic domain structure of ErFe11Ti and HoFe11Ti compounds

    International Nuclear Information System (INIS)

    Pastushenkov, Yury G.; Skokov, Konstantin P.; Skourski, Yury; Lebedeva, Ludmila; Ivanova, Tatyana; Grushichev, Anton; Mueller, Karl-Hartmut

    2006-01-01

    Tetragonal ThMn 12 -type single crystalline ErFe 11 Ti and HoFe 11 Ti samples have been investigated by magnetization measurements and by observations of the magnetic domain structure at various temperatures between 10 and 300K. The magnetic structure of ErFe 11 Ti changes from room temperature 'easy axis' (c-axis) type to conical at spin-reorientation temperature T SR =50K. The HoFe 11 Ti has a metastable anisotropy energy minimum in the a-direction at T<40K. It leads to a first-order magnetization process detected by magnetization measurements along the a-axis in this temperature region

  3. Spin squeezing and quantum correlations

    Indian Academy of Sciences (India)

    2 states. A coherent spin-s state. (CSS) θ φ can then be thought of as having no quantum correlations as the constituent. 2s elementary spins point in the same direction ˆn(θ φ) which is the mean spin direction. 2. State classification and squeezing. In order to discuss squeezing, we begin with the squeezing condition itself.

  4. Geometry of spin coherent states

    Science.gov (United States)

    Chryssomalakos, C.; Guzmán-González, E.; Serrano-Ensástiga, E.

    2018-04-01

    Spin states of maximal projection along some direction in space are called (spin) coherent, and are, in many respects, the ‘most classical’ available. For any spin s, the spin coherent states form a 2-sphere in the projective Hilbert space \

  5. Spin Hall effect and spin swapping in diffusive superconductors

    Science.gov (United States)

    Espedal, Camilla; Lange, Peter; Sadjina, Severin; Mal'shukov, A. G.; Brataas, Arne

    2017-02-01

    We consider the spin-orbit-induced spin Hall effect and spin swapping in diffusive superconductors. By employing the nonequilibrium Keldysh Green's function technique in the quasiclassical approximation, we derive coupled transport equations for the spectral spin and particle distributions and for the energy density in the elastic scattering regime. We compute four contributions to the spin Hall conductivity, namely, skew scattering, side jump, anomalous velocity, and the Yafet contribution. The reduced density of states in the superconductor causes a renormalization of the spin Hall angle. We demonstrate that all four of these contributions to the spin Hall conductivity are renormalized in the same way in the superconducting state. In its simplest manifestation, spin swapping transforms a primary spin current into a secondary spin current with swapped current and polarization directions. We find that the spin-swapping coefficient is not explicitly but only implicitly affected by the superconducting gap through the renormalized diffusion coefficients. We discuss experimental consequences for measurements of the (inverse) spin Hall effect and spin swapping in four-terminal geometries. In our geometry, below the superconducting transition temperature, the spin-swapping signal is increased an order of magnitude while changes in the (inverse) spin Hall signal are moderate.

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

    Energy Technology Data Exchange (ETDEWEB)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-05-07

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

  7. First-principles study on the thermodynamic stability, magnetism, and half-metallicity of full-Heusler alloy Ti{sub 2}FeGe (001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yan; Zhang, Jian-Min, E-mail: jmzhang@snnu.edu.cn

    2017-05-10

    For the Ti{sub 2}FeGe Heusler alloy, the surface stability, electronic and magnetic properties of the various (001) surfaces have been studied by using first-principles calculations. The TiGe termination is the most stable one while the GeGe* termination is the most unstable one. Both the density of states (DOS) and atomic magnetic moments (AMMs) of the central layers are similar to the corresponding bulk characters due to no influence of surface effect as we expected. The TiGe termination has the highest spin polarization 96.67%, followed by the TiFe (67.17%), GeGe* (66.51%) and FeFe* terminations (62.02%). The TiTi* terminations has the lowest spin polarization 61.31%. The magnetic moments for atoms on the surfaces and subsurfaces of these terminations are different from the bulk case. - Highlights: • TiGe termination is the most stable while GeGe* termination is the most unstable. • TiGe termination has the highest spin polarization followed by TiFe, GeGe*, FeFe* and TiTi*. • Atomic magnetic moments at the (001) surfaces are greatly different from the bulk values.

  8. Higher Spins & Strings

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal field theories is reviewed. I shall then outline the evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall explain how this relation fits into the framework of the familiar stringy AdS/CFT correspondence.

  9. Quantum spin quadrumer

    Science.gov (United States)

    Khatua, Subhankar; Shankar, R.; Ganesh, R.

    2018-02-01

    A fundamental motif in frustrated magnetism is the fully mutually coupled cluster of N spins, with each spin coupled to every other spin. Clusters with N =2 and 3 have been extensively studied as building blocks of square and triangular lattice antiferromagnets. In both cases, large-S semiclassical descriptions have been fruitfully constructed, providing insights into the physics of macroscopic magnetic systems. Here, we develop a semiclassical theory for the N =4 cluster. This problem has rich mathematical structure with a ground-state space that has nontrivial topology. We show that ground states are appropriately parametrized by a unit vector order parameter and a rotation matrix. Remarkably, in the low-energy description, the physics of the cluster reduces to that of an emergent free spin-S spin and a rigid rotor. This successfully explains the spectrum of the quadrumer and its associated degeneracies. However, this mapping does not hold in the vicinity of collinear ground states due to a subtle effect that arises from the nonmanifold nature of the ground-state space. We demonstrate this by an analysis of soft fluctuations, showing that collinear states have a larger number of soft modes. Nevertheless, as these singularities only occur on a subset of measure zero, the mapping to a spin and a rotor provides a good description of the quadrumer. We interpret thermodynamic properties of the quadrumer that are accessible in molecular magnets, in terms of the rotor and spin degrees of freedom. Our study paves the way for field theoretic descriptions of systems such as pyrochlore magnets.

  10. Spider Spinning for Dummies

    Science.gov (United States)

    Bird, Richard S.

    Spider spinning is a snappy name for the problem of listing the ideals of a totally acyclic poset in such a way that each ideal is computed from its predecessor in constant time. Such an algorithm is said to be loopless. Our aim in these lectures is to show how to calculate a loopless algorithm for spider spinning. The calculation makes use of the fundamental laws of functional programming and the real purpose of the exercise is to show these laws in action.

  11. Ti år med formidlingspligt

    DEFF Research Database (Denmark)

    Meyer, Gitte

    2014-01-01

    Jubilæet blev markeret ved et symposium - men hvor var journalisterne, og hvor var forskerne? For få uger siden lagde TV 2 hus til et symposium om videnskab, formidling, journalistik og spin. Danske Videnskabsjournalister og Akademiet for de Tekniske Videnskaber tog med arrangementet et behjertet...... initiativ. De ville gøre status efter ti år med lovfæstet formidlingspligt på universiteterne. Samtidig lagde de op til et kritisk blik på universitetsverdenens kommunikationsafdelinger...

  12. Spin-engineered quantum dots

    OpenAIRE

    Fleurov, V.; Ivanov, V. A.; Peeters, F. M.; Vagner, I. D.

    2001-01-01

    Spatially nonhomogeneously spin polarized nuclei are proposed as a new mechanism to monitor electron states in a nanostructure, or as a means to createn and, if necessary, reshape such nanostructures in the course of the experiment. We found that a polarization of nulear spins may lift the spin polarization of the electron states in a nanostructure and, if sufficiently strong, leads to a polarization of the electron spins. Polarized nuclear spins may form an energy landscape capable of bindin...

  13. Theory of spin Hall effect

    OpenAIRE

    Chudnovsky, Eugene M.

    2007-01-01

    An extension of Drude model is proposed that accounts for spin and spin-orbit interaction of charge carriers. Spin currents appear due to combined action of the external electric field, crystal field and scattering of charge carriers. The expression for spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, spin Hall conductivity $\\sigma_s$ and charge conductivity $\\sigma_c$ are related through $\\sigma_s = [2 \\pi \\hbar...

  14. PIIID-formed (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti coatings on NiTi shape memory alloy for medical applications.

    Science.gov (United States)

    Sun, Tao; Wang, Lang-Ping; Wang, Min; Tong, Ho-Wang; Lu, William W

    2012-08-01

    (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti composite coatings were fabricated on NiTi shape memory alloy via plasma immersion ion implantation and deposition (PIIID). Surface morphology of samples was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross-sectional morphology indicated that the PIIID-formed coatings were dense and uniform. X-ray diffraction (XRD) was used to characterize the phase composition of samples. X-ray photoelectron spectroscopy (XPS) results showed that the surface of coated NiTi SMA samples was Ni-free. Nanoindentation measurements and pin-on-disc tests were carried out to evaluate mechanical properties and wear resistance of coated NiTi SMA, respectively. For the in vitro biological assessment of the composite coatings in terms of cell morphology and cell viability, osteoblast-like SaOS-2 cells and breast cancer MCF-7 cells were cultured on NiTi SMA samples, respectively. SaOS-2 cells attached and spread better on coated NiTi SMA. Viability of MCF-7 cells showed that the PIIID-formed composite coatings were noncytotoxic and coated samples were more biocompatible than uncoated samples. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Electrical detection of spin-momentum locking in Bi2Se3(Conference Presentation)

    Science.gov (United States)

    Jonker, Berend T.; Li, Connie H.; van't Erve, Olaf M.; Liu, Y.; Li, Y. Y.; Li, Lian

    2016-10-01

    Topological insulators (TIs) exhibit topologically protected metallic surface states populated by massless Dirac fermions with spin-momentum locking - the carrier spin lies in-plane, locked at right angle to the carrier momentum. An unpolarized charge current should thus create a net spin polarization. Here we show direct electrical detection of this bias current induced spin polarization as a voltage measured on a ferromagnetic (FM) metal tunnel barrier surface contact [1]. The voltage measured at this contact is proportional to the projection of the TI spin polarization onto this axis, and similar data are obtained for two different FM contact structures, Fe/Al2O3 and Co/MgO/graphene. From measurements of the carrier type and sign of the spin voltage for n-Bi2Se3 and p-Sb2Te3, we show that transport measurements can be used to determine the chirality of the spin texture [2]. The chirality inverts as one crosses the Dirac point, so that the carrier spin-momentum locking follows a left-hand rule (clockwise chirality) when the Fermi level is above the Dirac point, and right-hand rule below (counter-clockwise chirality). These results demonstrate simple and direct electrical access to the TI Dirac surface state spin system, provide clear evidence for the spin-momentum locking and bias current-induced spin polarization, and enable utilization of these remarkable properties for future technological applications. [1] C. H. Li, O. M. J. van `t Erve, J. T. Robinson, Y. Liu, L. Li , and B. T. Jonker, Nature Nanotech. 9, 218 (2014). [2] C. H. Li, O. M. J. van `t Erve, Y. Y. Li, L. Li and B. T. Jonker, under review.

  16. Anomalous magnetoresistance in the spinel superconductor LiTi2O4.

    Science.gov (United States)

    Jin, K; He, G; Zhang, X; Maruyama, S; Yasui, S; Suchoski, R; Shin, J; Jiang, Y; Yu, H S; Yuan, J; Shan, L; Kusmartsev, F V; Greene, R L; Takeuchi, I

    2015-05-20

    LiTi2O4 is a unique compound in that it is the only known spinel oxide superconductor. The lack of high quality single crystals has thus far prevented systematic investigations of its transport properties. Here we report a careful study of transport and tunnelling spectroscopy in epitaxial LiTi2O4 thin films. An unusual magnetoresistance is observed which changes from nearly isotropic negative to prominently anisotropic positive as the temperature is decreased. We present evidence that shows that the negative magnetoresistance likely stems from the suppression of local spin fluctuations or spin-orbit scattering centres. The positive magnetoresistance suggests the presence of an orbital-related state, also supported by the fact that the superconducting energy gap decreases as a quadratic function of magnetic field. These observations indicate that the spin-orbital fluctuations play an important role in LiTi2O4 in a manner similar to high-temperature superconductors.

  17. Reflectance spectroscopy from TiO2 particles embedded in polyurethane

    DEFF Research Database (Denmark)

    Gudla, Visweswara Chakravarthy; Canulescu, Stela; Johansen, Villads Egede

    2013-01-01

    This paper presents the results of a physical simulation carried out using TiO2-Polyurethane composite coating on bright aluminium surface to understand the light scattering effect for designing white surfaces. Polyurethane matrix is selected due to the matching refractive index (1.7) with Al2O3...... layer on anodized aluminium surfaces. Three different TiO2 particle distributions were dispersed in polyurethane and spin coated onto high gloss and caustic etched aluminium substrates. Reflectance spectra of TiO2-polyurethane films of various concentrations were analysed using an integrating sphere....... The results show that the TiO2-polyurethane coatings have a high diffuse reflectance as a result of multiple scattering from TiO2 particles. Diffuse reflectance spectra of TiO2 containing films vary weakly with particle concentration and reach a steady state value at a concentration of 0.75 wt.%. Using...

  18. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling

    Science.gov (United States)

    Caetano, R. A.

    2016-03-01

    The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices.

  19. Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction

    KAUST Repository

    Ortiz Pauyac, Christian

    2016-06-19

    In the present thesis we introduce the reader to the field of spintronics and explore new phenomena, such as spin transfer torques, spin filtering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin filtering. In Chap. 3 we discuss the Rashba torque in ferromagnetic films, and in Chap. 4 we study spin Hall effect and spin swapping in ferromagnetic films, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.

  20. First-principles calculation of the structure and electronic properties of Fe-substituted Bi2Ti2O7

    Science.gov (United States)

    Huang, Jin-Dou; Zhang, Zhenyi; Lin, Feng; Dong, Bin

    2017-12-01

    We performed first-principles calculations to investigate the formation energy, geometry structure, and electronic property of Fe-doped Bi2Ti2O7 systems with different Fe doping content. The calculated formation energies indicate that the substitutional configurations of Fe-doping Bi2Ti2O7 are easy to obtain under O-rich growth condition, but their thermodynamic stability decreases with the increase of Fe content. The calculated spin-resolved density of states and band structures indicate that the introduction of Fe into Bi2Ti2O7 brings high spin polarization. The spin-down impurity levels in Fe x Bi2-x Ti2O7 and spin-up impurity levels in Fe x Bi2Ti2-x O7 systems locate in the bottom of conduction band and narrow the band gap significantly, thus leading to the absorption of visible light. Interestingly, the impurity states in Fe x Bi2-x Ti2O7 are the efficient separation center of photogenerated electron and hole, and less affected by Fe doping content, in comparison, the levels of impurity band in Fe x Bi2Ti2-x O7 systems are largely effected by the Fe doping content, and high Fe doping content is the key factor to improve the separating rate of photogenerated electron and hole.

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

    KAUST Repository

    Wen, Yan

    2017-03-07

    We investigated current driven spin-orbit torques in Cu40Au60/Ni80Fe20/Ti layered structures with in-plane magnetization. We have demonstrated a reliable and convenient method to separate dampinglike torque and fieldlike torque by using the second harmonic technique. It is found that the dampinglike torque and fieldlike torque depend on temperature very differently. Dampinglike torque increases with temperature, while fieldlike torque decreases with temperature, which are different from results obtained previously in other material systems. We observed a nearly linear dependence between the spin Hall angle and longitudinal resistivity, suggesting that skew scattering may be the dominant mechanism of spin-orbit torques.

  2. Optical spin generation/detection and spin transport lifetimes

    International Nuclear Information System (INIS)

    Miah, M. Idrish

    2011-01-01

    We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.

  3. Optical spin generation/detection and spin transport lifetimes

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

    2011-02-25

    We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.

  4. Thermoelectric spin voltage in graphene.

    Science.gov (United States)

    Sierra, Juan F; Neumann, Ingmar; Cuppens, Jo; Raes, Bart; Costache, Marius V; Valenzuela, Sergio O

    2018-02-01

    In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents 1,2 . Amongst the most intriguing phenomena is the spin Seebeck effect 3-5 , in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect 6-8 . Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport 9-11 , energy-dependent carrier mobility and unique density of states 12,13 . Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current 14-17 . These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias.

  5. Noise in tunneling spin current across coupled quantum spin chains

    Science.gov (United States)

    Aftergood, Joshua; Takei, So

    2018-01-01

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

  6. Overview of spin physics

    Energy Technology Data Exchange (ETDEWEB)

    Yokosawa, A.

    1992-12-23

    Spin physics activities at medium and high energies became significantly active when polarized targets and polarized beams became accessible for hadron-hadron scattering experiments. My overview of spin physics will be inclined to the study of strong interaction using facilities at Argonne ZGS, Brookhaven AGS (including RHIC), CERN, Fermilab, LAMPF, an SATURNE. In 1960 accelerator physicists had already been convinced that the ZGS could be unique in accelerating a polarized beam; polarized beams were being accelerated through linear accelerators elsewhere at that time. However, there was much concern about going ahead with the construction of a polarized beam because (i) the source intensity was not high enough to accelerate in the accelerator, (ii) the use of the accelerator would be limited to only polarized-beam physics, that is, proton-proton interaction, and (iii) p-p elastic scattering was not the most popular topic in high-energy physics. In fact, within spin physics, [pi]-nucleon physics looked attractive, since the determination of spin and parity of possible [pi]p resonances attracted much attention. To proceed we needed more data beside total cross sections and elastic differential cross sections; measurements of polarization and other parameters were urgently needed. Polarization measurements had traditionally been performed by analyzing the spin of recoil protons. The drawbacks of this technique are: (i) it involves double scattering, resulting in poor accuracy of the data, and (ii) a carbon analyzer can only be used for a limited region of energy.

  7. cis-Thioindigo (TI) - a new ligand with accessible radical anion and dianion states. Strong magnetic coupling in the {[TI-(μ2-O),(μ-O)]Cp*Cr}2 dimers.

    Science.gov (United States)

    Konarev, Dmitri V; Khasanov, Salavat S; Shestakov, Alexander F; Fatalov, Alexey M; Batov, Mikhail S; Otsuka, Akihiro; Yamochi, Hideki; Kitagawa, Hiroshi; Lyubovskaya, Rimma N

    2017-10-24

    Reaction of decamethylchromocene (Cp* 2 Cr) with thioindigo (TI) yields a coordination complex {[TI-(μ 2 -O), (μ-O)]Cp*Cr} 2 ·C 6 H 14 (1) in which one Cp* ligand in Cp* 2 Cr is substituted by TI. TI adopts cis-conformation in 1 allowing the coordination of both carbonyl groups to chromium. Additionally, one oxygen atom of TI becomes a μ 2 -bridge for two chromium atoms to form {[TI-(μ 2 -O), (μ-O)]Cp*Cr} 2 dimers with a CrCr distance of 3.12 Å. According to magnetic data, diamagnetic TI 2- dianions and two Cr 3+ atoms with a high S = 3/2 spin state are present in a dimer allowing strong antiferromagnetic coupling between two Cr 3+ spins with an exchange interaction of -35.4 K and the decrease of molar magnetic susceptibility below 140 K. Paramagnetic TI˙ - radical anions with the S = 1/2 spin state have also been obtained and studied in crystalline {cryptand[2,2,2](Na + )}(TI˙ - ) (2) salt showing that both radical anion and dianion states are accessible for TI.

  8. Half-metallic magnetism in Ti3Co5-xFexB2

    Directory of Open Access Journals (Sweden)

    Rohit Pathak

    2017-05-01

    Full Text Available Bulk alloys and thin films of Fe-substituted Ti3Co5B2 have been investigated by first-principle density-functional calculations. The series, which is of interest in the context of alnico magnetism and spin electronics, has been experimentally realized in nanostructures but not in the bulk. Our bulk calculations predict paramagnetism for Ti3Co5B2, Ti3Co4FeB2 and Ti3CoFe4B2, whereas Ti3Fe5B2 is predicted to be ferromagnetic. The thin films are all ferromagnetic, indicating that moment formation may be facilitated at nanostructural grain boundaries. One member of the thin-film series, namely Ti3CoFe4B2, is half-metallic and exhibits perpendicular easy-axis magnetic anisotropy. The half-metallicity reflects the hybridization of the Ti, Fe and Co 3d orbitals, which causes a band gap in minority spin channel, and the limited equilibrium solubility of Fe in bulk Ti3Co5B2 may be linked to the emerging half-metallicity due to Fe substitution.

  9. A spin-liquid with pinch-line singularities on the pyrochlore lattice.

    Science.gov (United States)

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

    2016-05-26

    The mathematics of gauge theories lies behind many of the most profound advances in physics in the past 200 years, from Maxwell's theory of electromagnetism to Einstein's theory of general relativity. More recently it has become clear that gauge theories also emerge in condensed matter, a prime example being the spin-ice materials which host an emergent electromagnetic gauge field. In spin-ice, the underlying gauge structure is revealed by the presence of pinch-point singularities in neutron-scattering measurements. Here we report the discovery of a spin-liquid where the low-temperature physics is naturally described by the fluctuations of a tensor field with a continuous gauge freedom. This gauge structure underpins an unusual form of spin correlations, giving rise to pinch-line singularities: line-like analogues of the pinch points observed in spin-ice. Remarkably, these features may already have been observed in the pyrochlore material Tb2Ti2O7.

  10. Lithium diffusion in spinel Li4Ti5O12 and LiTi2O4 films detected with 8Liβ -NMR

    Science.gov (United States)

    Sugiyama, Jun; Umegaki, Izumi; Uyama, Takeshi; McFadden, Ryan M. L.; Shiraki, Susumu; Hitosugi, Taro; Salman, Zaher; Saadaoui, Hassan; Morris, Gerald D.; MacFarlane, W. Andrew; Kiefl, Robert F.

    2017-09-01

    Diffusion of Li+ in (111) oriented thin films of the spinels Li4Ti5O12 and LiTi2O4 has been studied with 8Liβ -detected NMR in the temperature range between 5 and 310 K. In Li4Ti5O12 , the spin-lattice relaxation rate (1 /T1 ) versus temperature shows a clear maximum around 100 K (=Tmax ) which we attribute to magnetic freezing of dilute Ti3 + local magnetic moments, consistent with the results of magnetization and muon spin relaxation (μ+SR ) measurements. The decrease in 1 /T1 with temperature above Tmax indicates that Li+ starts to diffuse with a thermal activation energy (Ea) of 0.11(1) eV. In LiTi2O4 , on the contrary, as temperature increases from 200 K, 1 /T1 increases monotonically up to 310 K. This suggests that Li also starts to diffuse above 200 K with Ea=0.16 (2 ) eV in LiTi2O4 . Comparison with conventional Li-NMR on Li4Ti5O12 implies that both β -NMR and μ+SR sense short-range Li motion, i.e., a jump diffusion of Li+ to the nearest neighboring sites.

  11. Relationship between Photocatalytic Activity and Ti{sup 3+} Defects in Acid-Leached Titanium Dioxide / Hydroxyapatite Composite

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Y; Rachi, T; Okuda, T; Yokouchi, M; Kamimoto, Y [Mechanical and Material Engineering Division, Kanagawa Industrial Technology Center, 705-1 Shimo-imaizumi, Ebina, Kanagawa 243-0435 (Japan); Nakajima, A [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Okada, K, E-mail: ono-y@kanagawa-iri.go.jp [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 226-8503 (Japan)

    2011-10-29

    Effect of Ti{sup 3+} defect density on the photocatalytic activity was investigated using electron spin resonance (ESR) spectroscopy under UV irradiation at 103K. The Ti{sup 3+} signal intensity decreased with increasing heating temperature for the TiO{sub 2} powders prepared by hydroxyapatite (HAp) precipitation, heating and acid leaching process. The Ti{sup 3+} defect density of the TiO{sub 2} powder heat-treated at 700 deg. C was found to be about half that of the starting material, P25, without anatase-to-rutile phase transformation based on the results of X-ray diffraction. The photocatalytic activity of the TiO{sub 2} powder determined from the change of methylene blue concentration under UV irradiation became higher with decreasing of the Ti{sup 3+} defects without a significant change in the anatase ratio and specific surface area during the heat treatment.

  12. Quantum spin transistor with a Heisenberg spin chain

    Science.gov (United States)

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

    2016-01-01

    Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements. PMID:27721438

  13. Spinning fluids reactor

    Science.gov (United States)

    Miller, Jan D; Hupka, Jan; Aranowski, Robert

    2012-11-20

    A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.

  14. Spin gating electrical current

    Science.gov (United States)

    Ciccarelli, C.; Zârbo, L. P.; Irvine, A. C.; Campion, R. P.; Gallagher, B. L.; Wunderlich, J.; Jungwirth, T.; Ferguson, A. J.

    2012-09-01

    The level of the chemical potential is a fundamental parameter of the electronic structure of a physical system, which consequently plays an important role in defining the properties of active electrical devices. We directly measure the chemical potential shift in the relativistic band structure of the ferromagnetic semiconductor (Ga,Mn)As, controlled by changes in its magnetic order parameter. Our device comprises a non-magnetic aluminum single electron channel capacitively coupled to the (Ga,Mn)As gate electrode. The chemical potential shifts of the gate are directly read out from the shifts in the Coulomb blockade oscillations of the single electron transistor. The experiments introduce a concept of spin gating electrical current. In our spin transistor spin manipulation is completely removed from the electrical current carrying channel.

  15. SPIN-selling

    CERN Document Server

    Rackham, Neil

    1995-01-01

    True or false? In selling high-value products or services: "closing" increases your chance of success; it is essential to describe the benefits of your product or service to the customer; objection handling is an important skill; and open questions are more effective than closed questions. All false, says Neil Rackham. He and his team studied more than 35,000 sales calls made by 10,000 sales people in 23 countries over 12 years. Their findings revealed that many of the methods developed for selling low-value goods just don't work for major sales. Rackham went on to introduce his SPIN-selling method, where SPIN describes the whole selling process - Situation questions, Problem questions, Implication questions, Need-payoff questions. SPIN-selling provides you with a set of simple and practical techniques which have been tried in many of today's leading companies with dramatic improvements to their sales performance.

  16. Chiral higher spin gravity

    Science.gov (United States)

    Krishnan, Chethan; Raju, Avinash

    2017-06-01

    We construct a candidate for the most general chiral higher spin theory with AdS3 boundary conditions. In the Chern-Simons language, on the left it has the Drinfeld-Sokolov reduced form, but on the right all charges and chemical potentials are turned on. Altogether (for the spin-3 case) these are 19 functions. Despite this, we show that the resulting metric has the form of the "most general" AdS3 boundary conditions discussed by Grumiller and Riegler. The asymptotic symmetry algebra is a product of a W3 algebra on the left and an affine s l (3 )k current algebra on the right, as desired. The metric and higher spin fields depend on all the 19 functions. We compare our work with previous results in the literature.

  17. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden

    1975-01-01

    The selection rules for the linear couplings between magnons and phonons propagating in the c direction of a simple basal-plane hcp ferromagnet are determined by general symmetry considerations. The acoustic-optical magnon-phonon interactions observed in the heavy-rare-earth metals have been...... explained by Liu as originating from the mixing of the spin states of the conduction electrons due to the spin-orbit coupling. We find that this coupling mechanism introduces interactions which violate the selection rules for a simple ferromagnet. The interactions between the magnons and phonons propagating...... in the c direction of Tb have been studied experimentally by means of inelastic neutron scattering. The magnons are coupled to both the acoustic- and optical-transverse phonons. By studying the behavior of the acoustic-optical coupling, we conclude that it is a spin-mixed-induced coupling as proposed...

  18. Theory for Spin Selective Andreev Re ection in Vortex Core of Topological Superconductor: Majorana Zero Modes on Spherical Surface and Application to Spin Polarized Scanning Tunneling Microscope Probe

    Science.gov (United States)

    Zhang, Fu-Chun; Hu, Lun-Hui; Li, Chuang; Xu, Dong-Hui; Zhou, Yi

    Majorana zero modes (MZMs) have been predicted to exist in the topological insulator (TI)/superconductor (SC) heterostructure. Recent spin polarized scanning tunneling microscope(STM) experiment has observed spin-polarization dependence of the zero bias differential tunneling conductance at the center of vortex core. Here we consider a helical electron system described by a Rashba spin orbit coupling Hamiltonian on a spherical surface with a s-wave superconducting pairing due to proximity effect. We examine in-gap excitations of a pair of vortices with one at the north pole and the other at the south pole. While the MZM is not a spin eigenstate, the spin wavefunction of the MZM at the center of the vortex core, r = 0, is parallel to the magnetic field, and the local Andreev reflection of the MZM is spin selective, namely occurs only when the STM tip has the spin polarization parallel to the magnetic field, similar to the case in 1-dimensional nanowire. The total local differential tunneling conductance consists of the normal term proportional to the local density of states and an additional term arising from the Andreev reflection. We apply our theory to examine the recently reported spin-polarized STM experiments and show good agreement with the experiments

  19. Magnetic two-dimensional electron gas at the manganite-buffered LaAlO3/SrTiO3 interface

    DEFF Research Database (Denmark)

    R. Zhang, H.; Zhang, Y.; Zhang, H.

    2017-01-01

    Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions with the mediat......Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions...... with the mediation of itinerant electrons. Herein, we report a magnetic 2DEG at a La7/8Sr1/8MnO3-buffered LaAlO3/SrTiO3 interface, which simultaneously shows electrically tunable anomalous Hall effect and high conductivity. The spin-polarized temperature for the 2DEG is promoted to 30 K while the mobility remains...... high. The magnetism likely results from a gradient manganese interdiffusion into SrTiO3. The present work demonstrates the great potential of manganite-buffered LaAlO3/SrTiO3 interfaces for spintronic applications....

  20. Spin flexoelectricity and chiral spin structures in magnetic films

    OpenAIRE

    Pyatakov, A. P.; Sergeev, A. S.; Mikailzade, F. A.; Zvezdin, A. K.

    2015-01-01

    In this short review a broad range of chiral phenomena observed in magnetic films (spin cycloid and skyrmion structures formation as well as chirality dependent domain wall motion) is considered under the perspective of spin flexoelectricity, i.e. the relation between bending of magnetization pattern and electric polarization. The similarity and the difference between the spin flexoelectricity and the newly emerged notion of spin flexomagnetism is discussed. The phenomenological arguments bas...

  1. Bias dependence of tunnel magnetoresistance in spin filtering tunnel junctions: Experiment and theory

    Science.gov (United States)

    Lüders, U.; Bibes, M.; Fusil, S.; Bouzehouane, K.; Jacquet, E.; Sommers, C. B.; Contour, J.-P.; Bobo, J.-F.; Barthélémy, A.; Fert, A.; Levy, P. M.

    2007-10-01

    A spin filter is a type of magnetic tunnel junction in which only one of the electrodes is magnetic and the insulating barrier is ferro- or ferrimagnetic. We report on spin-dependent transport measurements and their theoretical analysis in epitaxial spin filters integrating a tunnel barrier of the high-Curie-temperature ferrimagnetic spinel NiFe2O4 , with half-metallic La2/3Sr1/3MnO3 and Au electrodes. A positive tunnel magnetoresonance of up to ˜50% is obtained at low temperature, which we find decreases with bias voltage. In view of these experimental results, we propose a theoretical treatment of the transport properties of spin filters with epitaxial magnetic barriers, based on an elliptical variation of the decay rates within the spin-dependent gaps in analogy with what was calculated for nonmagnetic barrier materials such as MgO or SrTiO3 . Whereas the spin filtering efficiency for zero bias is of one sign, we show that this can easily change with bias; the degree of change hinges on the energy variation of the majority and minority spin decay rates of the transmission across the barrier. We point out some shortcomings of approaches based on models in which the transmission is related to spin-dependent barrier heights, and some implications for future experimental and theoretical research on spin filters.

  2. Spinning geodesic Witten diagrams

    International Nuclear Information System (INIS)

    Dyer, Ethan; Freedman, Daniel Z.; Massachusetts Institute of Technology; Massachusetts Institute of Technology; Sully, James; McGill University, Montreal, QC

    2017-01-01

    We present an expression for the four-point conformal blocks of symmetric traceless operators of arbitrary spin as an integral over a pair of geodesics in Anti-de Sitter space, generalizing the geodesic Witten diagram formalism of Hijano et al. to arbitrary spin. As an intermediate step in the derivation, we identify a convenient basis of bulk threepoint interaction vertices which give rise to all possible boundary three point structures. Lastly, we highlight a direct connection between the representation of the conformal block as geodesic Witten diagram and the shadow operator formalism.

  3. Spin gating electrical current

    Czech Academy of Sciences Publication Activity Database

    Ciccarelli, C.; Zarbo, Liviu; Irvine, A.C.; Campion, R. P.; Gallagher, B. L.; Wunderlich, Joerg; Jungwirth, Tomáš; Ferguson, A.J.

    2012-01-01

    Roč. 101, č. 12 (2012), , , "122411-1"-"122411-4" ISSN 0003-6951 R&D Projects: GA AV ČR KJB100100802; GA AV ČR KAN400100652 EU Projects: European Commission(XE) 268066 - 0MSPIN; European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : ferromagnetic resonance * spin-orbit coupling * nanodevices Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.794, year: 2012 http://arxiv.org/abs/1203.2439

  4. Spin echo in synchrotrons

    Directory of Open Access Journals (Sweden)

    Alexander W. Chao

    2007-01-01

    Full Text Available As a polarized beam is accelerated through a depolarization resonance, its polarization is reduced by a well-defined calculable reduction factor. When the beam subsequently crosses a second resonance, the final beam polarization is considered to be reduced by the product of the two reduction factors corresponding to the two crossings, each calculated independently of the other. This is a good approximation when the spread of spin precession frequency Δν_{spin} of the beam (particularly due to its energy spread is sufficiently large that the spin precession phases of individual particles smear out completely during the time τ between the two crossings. This approximate picture, however, ignores two spin dynamics effects: an interference-overlap effect and a spin echo effect. This paper is to address these two effects. The interference-overlap effect occurs when Δν_{spin} is too small, or when τ is too short, to complete the smearing process. In this case, the two resonance crossings overlap each other, and the final polarization exhibits constructive or destructive interference patterns depending on the exact value of τ. Typically, the beam’s energy spread is large and this interference-overlap effect does not occur. To study this effect, therefore, it is necessary to reduce the beam energy spread and to consider two resonance crossings very close to each other. The other mechanism, also due to the interplay between two resonance crossings, is spin echo. It turns out that even when the precession phases appear to be completely smeared between the two crossings, there will still be a sudden and short-lived echo signal of beam polarization at a time τ after the second crossing; the magnitude of which can be as large as 57%. This echo signal exists even when the beam has a sizable energy spread and when τ is very large, and could be a sensitive (albeit challenging way to experimentally test the intricate spin dynamics in a synchrotron

  5. Spin, gravity, and inertia.

    Science.gov (United States)

    Obukhov, Y N

    2001-01-08

    The gravitational effects in the relativistic quantum mechanics are investigated. The exact Foldy-Wouthuysen transformation is constructed for the Dirac particle coupled to the static spacetime metric. As a direct application, we analyze the nonrelativistic limit of the theory. The new term describing the specific spin (gravitational moment) interaction effect is recovered in the Hamiltonian. The comparison of the true gravitational coupling with the purely inertial case demonstrates that the spin relativistic effects do not violate the equivalence principle for the Dirac fermions.

  6. Hybrid magnon-phonons in the paraelectric antiferromagnet EuTiO3

    Science.gov (United States)

    Cao, Huibo; Delaire, Olivier; Hong, Jiawang; Hahn, Steven; Chi, Songxue; Ehlers, George; Abernathy, Douglas; Christianson, Andrew; Fernandez-Baca, Jaime; Chakoumakos, Bryan; Yan, Jiaqiang; Sales, Brian

    Magnetic perovskite titanate EuTiO3 has attracted a lot of attentions for its large spin-lattice coupling. It has a number of similarities with the well-studied quantum paraelectric SrTiO3 but a much higher cubic-tetragonal lattice transition at 290 K and an extra magnetic order at 5.5 K. The large difference between EuTiO3 and SrTiO3 has been attributed to the magnetic ion Eu2+, that couples with the structural properties. However the spin-lattice coupling mechanism has not been fully understood yet although many theoretical models have been proposed. We grew a large, high-quality isotopically-enriched EuTiO3 crystal for neutron scattering. The crystal and magnetic structures were calibrated with neutron diffraction at HB-3A at HFIR at ORNL at temperatures from 1.5 K to 450 K. The spin waves and phonons were measured in the temperature range of 1.5-400 K with HB-3 at HFIR, CNCS and ARCS at SNS at ORNL. I will report our new discovery of interaction between the soft ferroelectric phonon mode and likely (para)magnon mode, that is responsible for a giant magnetoelectric coupling in EuTiO3. The magnetic excitation and atomic displacements will be discussed. This work was supported by Office of Basic Energy Sciences, U.S. Department of Energy.

  7. Effect of TiO{sub 2} thickness on nanocomposited aligned ZnO nanorod/TiO{sub 2} for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Saurdi, I., E-mail: saurdy788@gmail.com; Ishak, A. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); UiTM Sarawak Kampus Kota Samarahan Jalan Meranek, Sarawak (Malaysia); Shafura, A. K.; Azhar, N. E. A.; Mamat, M. H. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); Malek, M. F.; Rusop, M. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), (Centre for Nano-Science and Nano-Technology), Institute of Science - IOS, Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Alrokayan, A. H. Salman; Khan, Haseeb A. [Department of Biochemistry, College of Science, Bldg. 5, King Saud University (KSU) P.O: 2455 Riyadh 1145 (Saudi Arabia)

    2016-07-06

    The TiO{sub 2} films were deposited on glass substrate at different thicknesses with different deposition frequencies (1, 2, 3 and 4 times) using spin coating technique and their structural properties were investigated. Subsequently, the nanocomposited aligned ZnO nanorods and TiO{sub 2} were formed by deposited the TiO{sub 2} on top of aligned ZnO Nanorod on ITO-coated glass at different thicknesses using the same method of TiO{sub 2} deposited on glass substrate. The nanocomposited aligned ZnO nanorod/TiO{sub 2} were coated with different thicknesses of 900µm, 1815µm, 2710µm, 3620µm and ZnO without TiO{sub 2}. The dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO{sub 2} with thickness of 900µm, 1815µm, 2710µm and 3620µm and ZnO without TiO{sub 2} and their photovoltaic properties of the DSSCs were investigated. From the solar simulator measurement the solar energy conversion efficiency (η) of 2.543% under AM 1.5 was obtained for the ZnO nanorod/TiO{sub 2} photoanode-2710µm Dye-Sensitized solar cell.

  8. Solidification Rate Dependence of Microstructures and Transformation Behavior of Ti-Ni-Hf Alloys.

    Science.gov (United States)

    Kim, Dong-Jo; Kim, Yeon-Wook; Nam, Tae-Hyun

    2018-09-01

    The microstructures and transformation behavior of Ti-49Ni-20Hf, Ti-49.5Ni-20Hf and Ti-50.3Ni- 20Hf alloys, when prepared by conventional casting, were investigated and compared with the properties of the alloys prepared by melt spinning. The area fraction of (Ti,Hf)2Ni in Ti-Ni-Hf alloys decreased to 3.9% from 9.4% as Ni content rose to 50.3 at% from 49 at%. Several cracks were observed in the hot-rolled Ti-49Ni-20Hf alloy sheet but none were found in the Ti-50.3Ni-20Hf alloy sheet. The B2-B19' transformation start temperature (Ms) decreased to 476 K from 580 K as Ni content increased to 50.3 at% from 49 at%. All the as-spun ribbons were amorphous, and the activation energy for crystallization ranged from 167.8 kJ/mol to 182.7 kJ/mol based on Ni content. When annealing temperature ranged from 810 K to 873 K, crystalline Ti-Ni-Hf alloys without (Ti,Hf)2Ni particles were obtained. At annealing temperatures higher than 873 K, very fine (Ti,Hf)2Ni particles, less than 20 nm in size, were found embedded in a crystalline matrix.

  9. Epoxidation of limonene over Ti MCM 41 and Ti BETA

    International Nuclear Information System (INIS)

    Cubillos Lobo, Jairo Antonio; Gonzalez Rodriguez, Lina Maria; Montes de Correa, Consuelo

    2002-01-01

    Ti MCM 41 were synthesized and evaluated in the epoxidation of limonene, using peroxide of hydrogen (H 2 O) as agent oxidizer. The characteristic hexagonal phase of Ti MCM 41 was obtained by heating the precursor gel during three days at 100 centigrade degrees. Further heating up to ten days leads to a decrease of this phase. The increase (Ti) in the synthesis gel also decreases that phase. The increase of Ti in the synthesis gel also decreases that phase UV VIS and FTIR spectroscopy indicates that Ti was incorporated in the lattice of Ti MCM 41 as well as, in Ti BETA. SEM micrographs of Ti MCM 41 show that the morphology changes with the Ti loading. Ti MCM 41 was most active than Ti BETA for limonene epoxidation even though both show high selectivity to epoxides

  10. A stochastic picture of spin

    International Nuclear Information System (INIS)

    Faris, W.G.

    1981-01-01

    Dankel has shown how to incorporate spin into stochastic mechanics. The resulting non-local hidden variable theory gives an appealing picture of spin correlation experiments in which Bell's inequality is violated. (orig.)

  11. Optical Properties and Surface Morphology of Nano-composite PMMA: TiO2 Thin Films

    International Nuclear Information System (INIS)

    Lyly Nyl Ismail; Ahmad Fairoz Aziz; Habibah Zulkefle

    2011-01-01

    There are two nano-composite PMMA: TiO 2 solutions were prepared in this research. First solution is nano-composite PMMA commercially available TiO 2 nanopowder and the second solution is nano-composite PMMA with self-prepared TiO 2 powder. The self-prepared TiO 2 powder is obtained by preparing the TiO 2 sol-gel. Solvo thermal method were used to dry the TiO 2 sol-gel and obtained TiO 2 crystal. Ball millers were used to grind the TiO 2 crystal in order to obtained nano sized powder. Triton-X was used as surfactant to stabilizer the composite between PMMA: TiO 2 . Besides comparing the nano-composite solution, we also studied the effect of the thin films thickness on the optical properties and surface morphology of the thin films. The thin films were deposited by sol-gel spin coating method on glass substrates. The optical properties and surface characterization were measured with UV-VIS spectrometer equipment and atomic force microscopy (AFM). The result showed that nano-composite PMMA with self prepared TiO 2 give high optical transparency than nano-composite PMMA with commercially available TiO 2 nano powder. The results also indicate as the thickness is increased the optical transparency are decreased. Both AFM images showed that the agglomerations of TiO 2 particles are occurred on the thin films and the surface roughness is increased when the thickness is increased. High agglomeration particles exist in the AFM images for nano-composite PMMA: TiO 2 with TiO 2 nano powder compare to the other nano-composite solution. (author)

  12. Low-temperature processed ultrathin TiO_2 for efficient planar heterojunction perovskite solar cells

    International Nuclear Information System (INIS)

    Huang, Xiaokun; Hu, Ziyang; Xu, Jie; Wang, Peng; Zhang, Jing; Zhu, Yuejin

    2017-01-01

    Highlights: • An ultrathin and discrete TiO_2 (u-TiO_2) was fabricated at low temperature. • High-performance perovskite solar cells based u-TiO_2was realized. • u-TiO_2 between perovskite and FTO functions as a bridge for electron transport. • u-TiO_2 accelerates electron transfer and alleviates charge recombination. - Abstract: A compact TiO_2 (c-TiO_2) layer fabricated by spin coating or spray pyrolysis following a high-temperature sintering is a routine in high-performance planar heterojunction perovskite solar cells. Here, we demonstrate an effective low-temperature approach to fabricate an ultrathin and discrete TiO_2 (u-TiO_2) for enhancing photovoltaic performance of perovskite solar cells. Via hydrolysis of low-concentration TiCl_4 solution at 70 °C, u-TiO_2 was grown on a fluorine doped tin oxide (FTO) substrate, forming the electron selective contact with the photoactive CH_3NH_3PbI_3 film. The perovskite solar cell using u-TiO_2 achieves an efficiency of 13.42%, which is compared to 13.56% of the device using c-TiO_2 prepared by high-temperature sintering. Cyclic voltammetry, steady-state photoluminescence spectroscopy and electrical impedance spectroscopy were conducted to study interface engineering and charge carrier dynamics. Our results suggest that u-TiO_2 functions as a bridge for electron transport between perovskite and FTO, which accelerates electron transfer and alleviates charge recombination.

  13. Characterization of TiO2 films obtained by a wet chemical process

    Science.gov (United States)

    Sedik, Asma; Ferraria, Ana M.; Carapeto, Ana P.; Bellal, Bouzid; Trari, Mohamed; Outemzabet, Ratiba

    2017-12-01

    TiO2 has an easily tunable bandgap and a great absorption dye ability being widely used in many fields and in a number of fascinating applications. In this study, a wet chemical route, particularly a sol gel method using spin-coating is adopted to deposit TiO2 thin films onto soda lime glass and silicon substrates. TiO2 films were prepared by using an alcoholic solution of analytical reagent grade TiCl4 as titanium precursor at various experimental conditions. The accent was put on the conditions of preparation (spin time, spin speed, precursor concentration, number of coating layers etc), doping and on the post-deposit treatment namely the drying and the crystallization. The results showed a strong dependence on the drying temperature and on the temperature and duration of the crystallization. We found that the solution preparation and its color are important for getting a reproducible final product. The Raman spectra recorded at room temperature, showed the characteristic peaks of anatase which appear at 143 and around 396 cm-1. These peaks confirm the presence of TiO2. The X-ray diffraction (XRD) was used to identify the crystalline characteristic of TiO2 while the chemical states and relative amounts of the main elements existing in the samples were investigated by X-ray Photoelectron Spectroscopy (XPS). The morphology of the samples was visualized by AFM. We show by this work the feasibility to obtain different nanostructured TiO2 by changing the concentration of the solution. Photocatalytic activity of TiO2 films was evaluated. Rhodamine B is a recalcitrant dye and TiO2 was successfully tested for its oxidation. An abatement of 60% was obtained under sunlight for an initial concentration of 10 mg/l.

  14. Dirac cone with helical spin polarization in ultrathin α-Sn(001) films.

    Science.gov (United States)

    Ohtsubo, Yoshiyuki; Le Fèvre, Patrick; Bertran, François; Taleb-Ibrahimi, Amina

    2013-11-22

    Spin-split two-dimensional electronic states have been observed on ultrathin Sn(001) films grown on InSb(001) substrates. Angle-resolved photoelectron spectroscopy (ARPES) performed on these films revealed Dirac-cone-like linear dispersion around the Γ¯ point of the surface Brillouin zone, suggesting nearly massless electrons belonging to 2D surface states. The states disperse across a band gap between bulklike quantum well states in the films. Moreover, both circular dichroism of ARPES and spin-resolved ARPES studies show helical spin polarization of the Dirac-cone-like surface states, suggesting a topologically protected character as in a bulk topological insulator (TI). These results indicate that a quasi-3D TI phase can be realized in ultrathin films of zero-gap semiconductors.

  15. Metal propionate synthesis of TiO{sub 2} nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Suciu, R.-C., E-mail: Ramona.Suciu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, Donath Street, No. 73-105, RO-400293 Cluj-Napoca (Romania); Marian, I., E-mail: marianionut78@yahoo.com [Technical University of Cluj-Napoca, Memorandumului Street, No. 28, RO-400114 Cluj-Napoca (Romania); Bratu, I. [National Institute for Research and Development of Isotopic and Molecular Technologies, Donath Street, No. 73-105, RO-400293 Cluj-Napoca (Romania)

    2014-01-25

    Highlights: • TiO{sub 2} based nanomaterials were prepared using sol–gel process. • Nucleophilic addition is possible giving rise to the intermediate: Ti(OBun){sub 4}(PrOH). • The samples were characterized using thermal (DTA–TG–DTG) analysis. • Optical spectroscopy, XRD and SEM were employed for material characterization. • Materials have uniformly distribution even at low temperatures. -- Abstract: In this paper, we report the preparation and characterization of TiO{sub 2} films prepared using the sol–gel process, using titanium (IV) n-butoxide and propionic acid as precursors and deposited onto ITO glass substrates by spin coating technique. The thermal analysis, FT–IR, UV–VIS, Raman spectroscopy and X-ray diffraction techniques have been used to investigate the characteristics of the TiO{sub 2} powder precursor the chemical and the physical changes produced during the process. The morphology of the film was studied by Scanning Electron Microscopy. The band gap energy values of the TiO{sub 2}/ITO (ITO – Indium Tin Oxide) films are determined. The unit cell parameters of the TiO{sub 2} anatase phase, the effective crystallite mean size, D{sub eff} (nm), and the root mean square (rms) of the microstrains, 〈ε{sup 2}〉{sub hkl}{sup 1/2}, were calculated by Rietveld refinement analysis.

  16. Antiferromagnetic spin-orbitronics

    KAUST Repository

    Manchon, Aurelien

    2015-05-01

    Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.

  17. " The Story of Spin

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 3; Issue 11. The Story of Spin - From Spectroscopy to Relativistic Quantum Mechanics. N Mukunda. Book Review Volume 3 Issue 11 November 1998 pp 89-90. Fulltext. Click here to view fulltext PDF. Permanent link:

  18. Spin and isospin modes

    International Nuclear Information System (INIS)

    Suzuki, T.; Sagawa, H.

    2000-01-01

    Complete text of publication follows. Spin and isospin modes in nuclei are investigated. We discuss some of the following topics. 1. Spin-dipole excitations in 12 C and 16 O are studied (1). Effects of tensor and spin-orbit interactions on the distribution of the strengths are investigated, and neutral current neutrino scattering cross sections in 16 O are obtained for heavy-flavor neutrinos from the supernovae. 2. Gamow-Teller (GT) and spin-dipole (SD) modes in 208 Bi are investigated. Quenching and fragmentation of the GT strength are discussed (2). SD excitations and electric dipole (E1) transitions between the GT and SD states are studied (3). Calculated E1 strengths are compared with the sum rule values obtained within the 1p-1h and 1p-1h + 2p-2h configuration spaces. 3. Coulomb displacement energy (CDE) of the IAS of 14 Be is calculated, and the effects of the halo on the CDE and the configuration of the halo state are investigated. 4. Spreading width of IAS and isospin dependence of the width are investigated (4). Our formula for the width explains very well the observed isospin dependence (5). (author)

  19. On "spinning" membrane models

    NARCIS (Netherlands)

    Bergshoeff, E.; Sezgin, E.; Townsend, P.K.

    1988-01-01

    Several alternative actions for a bosonic membrane have recently been proposed. We show that a linearly realized locally world-volume-supersymmetric (spinning membrane) extension of any of these actions implies an analogous extension of the standard Dirac membrane action. We further show that a

  20. Nuclear spin-off

    International Nuclear Information System (INIS)

    1981-11-01

    This booklet gives examples of 'nuclear spin off', from research programmes carried out for the UKAEA, under the following headings; non destructive testing; tribology; environmental protection; flow measurement; material sciences; mechanical engineering; marine services; biochemical technology; electronic instrumentation. (U.K.)

  1. The invariance of spin

    International Nuclear Information System (INIS)

    Bramson, B.D.

    1978-01-01

    An isolated system in general relativity makes a transition between stationary states. It is shown that the spin vectors of the system, long before and long after the emission of radiation, are supertranslation invariant and, hence, independent of the choice of Minkowski observation space. (author)

  2. Spin Injection in Indium Arsenide

    Directory of Open Access Journals (Sweden)

    Mark eJohnson

    2015-08-01

    Full Text Available In a two dimensional electron system (2DES, coherent spin precession of a ballistic spin polarized current, controlled by the Rashba spin orbit interaction, is a remarkable phenomenon that’s been observed only recently. Datta and Das predicted this precession would manifest as an oscillation in the source-drain conductance of the channel in a spin-injected field effect transistor (Spin FET. The indium arsenide single quantum well materials system has proven to be ideal for experimental confirmation. The 2DES carriers have high mobility, low sheet resistance, and high spin orbit interaction. Techniques for electrical injection and detection of spin polarized carriers were developed over the last two decades. Adapting the proposed Spin FET to the Johnson-Silsbee nonlocal geometry was a key to the first experimental demonstration of gate voltage controlled coherent spin precession. More recently, a new technique measured the oscillation as a function of channel length. This article gives an overview of the experimental phenomenology of the spin injection technique. We then review details of the application of the technique to InAs single quantum well (SQW devices. The effective magnetic field associated with Rashba spin-orbit coupling is described, and a heuristic model of coherent spin precession is presented. The two successful empirical demonstrations of the Datta Das conductance oscillation are then described and discussed.

  3. Spin tunnelling in mesoscopic systems

    Indian Academy of Sciences (India)

    Spin tunnelling; spin path integrals; discrete phase integral method; diabolical points. ... technologies. Our purpose in this article is rather different. The molecular systems have total spin of the order of 10, and magnetocrystalline anisotropies of few tens of Kelvin ...... The point С' is of this new type, and here it may be said to.

  4. Spin transport in graphene nanostructures

    NARCIS (Netherlands)

    Guimaraes, M. H. D.; van den Berg, J. J.; Vera-Marun, I. J.; Zomer, P. J.; van Wees, B. J.

    2014-01-01

    Graphene is an interesting material for spintronics, showing long spin relaxation lengths even at room temperature. For future spintronic devices it is important to understand the behavior of the spins and the limitations for spin transport in structures where the dimensions are smaller than the

  5. Spin Transport in Bose Gases

    NARCIS (Netherlands)

    van Driel, H.J.

    2012-01-01

    In this Thesis, we show that in a rotating two-component Bose mixture, the spin drag between the two different spin species shows a Hall effect. This spin drag Hall effect can be observed experimentally by studying the out-of-phase dipole mode of the mixture. We determine the damping of this mode

  6. Spin Transport in Semiconductor heterostructures

    International Nuclear Information System (INIS)

    Marinescu, Domnita Catalina

    2011-01-01

    The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.

  7. Spinning Them Off: Entrepreneuring Practices in Corporate Spin-Offs

    Directory of Open Access Journals (Sweden)

    Katja Maria Hydle

    2016-01-01

    Full Text Available This paper focuses on the practices between parent and child firms in corporate spinoffs. We uncover the enacted aspects of knowledge, called knowing, through theories from seven cases of incumbent-backed spin-offs and find that the management of the parent firms are highly involved in the spin-offs. The practices associated with spinning off are solving problems, involving multidisciplinary expertise and entrepreneuring management at the parent firm. We contribute to the spin-off literature by discussing the knowledge required for successfully spinning off child firms and to practice theory by empirically uncovering the practical understanding involved in the origin and perpetuation of an organization.

  8. Spin flexoelectricity and chiral spin structures in magnetic films

    Science.gov (United States)

    Pyatakov, A. P.; Sergeev, A. S.; Mikailzade, F. A.; Zvezdin, A. K.

    2015-06-01

    In this short review a broad range of chiral phenomena observed in magnetic films (spin cycloid and skyrmion structures formation as well as chirality dependent domain wall motion) is considered under the perspective of spin flexoelectricity, i.e. the relation between bending of magnetization pattern and electric polarization. The similarity and the difference between the spin flexoelectricity and the newly emerged notion of spin flexomagnetism are discussed. The phenomenological arguments based on the geometrical idea of curvature-induced effects are supported by analysis of the microscopic mechanisms of spin flexoelectricity based on three-site ion indirect exchange and twisted RKKY interaction models.

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

    Science.gov (United States)

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

    2016-01-28

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

  10. Spin-wave-induced spin torque in Rashba ferromagnets

    Science.gov (United States)

    Umetsu, Nobuyuki; Miura, Daisuke; Sakuma, Akimasa

    2015-05-01

    We study the effects of Rashba spin-orbit coupling on the spin torque induced by spin waves, which are the plane-wave dynamics of magnetization. The spin torque is derived from linear-response theory, and we calculate the dynamic spin torque by considering the impurity-ladder-sum vertex corrections. This dynamic spin torque is divided into three terms: a damping term, a distortion term, and a correction term for the equation of motion. The distorting torque describes a phenomenon unique to the Rashba spin-orbit coupling system, where the distorted motion of magnetization precession is subjected to the anisotropic force from the Rashba coupling. The oscillation mode of the precession exhibits an elliptical trajectory, and the ellipticity depends on the strength of the nesting effects, which could be reduced by decreasing the electron lifetime.

  11. Paramagnetic centers in nanocrystalline TiC/C system

    International Nuclear Information System (INIS)

    Guskos, N.; Bodziony, T.; Maryniak, M.; Typek, J.; Biedunkiewicz, A.

    2008-01-01

    Electron paramagnetic resonance is applied to study the defect centers in nanocrystalline titanium carbide dispersed in carbon matrix (TiC x /C) synthesized by the non-hydrolytic sol-gel process. The presence of Ti 3+ paramagnetic centers is identified below 120 K along with a minor contribution from localized defect spins coupled with the conduction electron system in the carbon matrix. The temperature dependence of the resonance intensity of the latter signal indicates weak antiferromagnetic interactions. The presence of paramagnetic centers connected with trivalent titanium is suggested to be the result of chemical disorder, which can be further related to the observed anomalous behavior of conductivity, hardness, and corrosion resistance of nanocrystalline TiC x /C

  12. Structure of 49Ti and 49Cr

    International Nuclear Information System (INIS)

    Dhar, A.K.; Bhatt, K.H.

    1976-01-01

    Deformed configuration mixing calculations based on projected Hartree-Fock theory have been performed to study the structure of the low-lying states of 49 Ti and 49 Cr. For 49 Ti the spectrum of the low-lying states upto 3.5 MeV agrees very well with the observed spectrum. Positions of low-lying high spin states have been predicted. For 49 Cr the ground state band of states upto J = 17/2 is in excellent agreement with the experiment. A well defined low-lying collective K=1/2 band of states is predicted to exist in the spectrum of 49 Cr. The first few members of this band, however, appear to be about 500 KeV lower than the observed states. The mixing ratios B(E2), B(M1),(E2/M1) and branching ratios for the transitions between the low-lying states of these nuclei have alsi been calculated. The agreement with the observed values is good. The calculated ground state magnetic moments of -1.03 and -0.52 (n,m) for the nuclei 49 Ti and 49 Cr respectively agree very well with the observed values of -1.10 and 0.48 (n.m). (author)

  13. Sprayed and Spin-Coated Multilayer Antireflection Coating Films for Nonvacuum Processed Crystalline Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Abdullah Uzum

    2017-01-01

    Full Text Available Using the simple and cost-effective methods, spin-coated ZrO2-polymer composite/spray-deposited TiO2-compact multilayer antireflection coating film was introduced. With a single TiO2-compact film on the surface of a crystalline silicon wafer, 5.3% average reflectance (the reflectance average between the wavelengths of 300 nm and 1100 nm was observed. Reflectance decreased further down to 3.3% after forming spin-coated ZrO2 on the spray-deposited TiO2-compact film. Silicon solar cells were fabricated using CZ-Si p-type wafers in three sets: (1 without antireflection coating (ARC layer, (2 with TiO2-compact ARC film, and (3 with ZrO2-polymer composite/TiO2-compact multilayer ARC film. Conversion efficiency of the cells improved by a factor of 0.8% (from 15.19% to 15.88% owing to the multilayer ARC. Jsc was improved further by 2 mA cm−2 (from 35.3 mA cm−2 to 37.2 mA cm−2 when compared with a single TiO2-compact ARC.

  14. Spin Structures in Magnetic Nanoparticles

    DEFF Research Database (Denmark)

    Mørup, Steen; Brok, Erik; Frandsen, Cathrine

    2013-01-01

    Spin structures in nanoparticles of ferrimagnetic materials may deviate locally in a nontrivial way from ideal collinear spin structures. For instance, magnetic frustration due to the reduced numbers of magnetic neighbors at the particle surface or around defects in the interior can lead to spin...... canting and hence a reduced magnetization. Moreover, relaxation between almost degenerate canted spin states can lead to anomalous temperature dependences of the magnetization at low temperatures. In ensembles of nanoparticles, interparticle exchange interactions can also result in spin reorientation...

  15. Determination of the spin diffusion length in germanium by spin optical orientation and electrical spin injection

    Science.gov (United States)

    Rinaldi, C.; Bertoli, S.; Asa, M.; Baldrati, L.; Manzoni, C.; Marangoni, M.; Cerullo, G.; Bianchi, M.; Sordan, R.; Bertacco, R.; Cantoni, M.

    2016-10-01

    The measurement of the spin diffusion length and/or lifetime in semiconductors is a key issue for the realisation of spintronic devices, exploiting the spin degree of freedom of carriers for storing and manipulating information. In this paper, we address such parameters in germanium (0 0 1) at room temperature (RT) by three different measurement methods. Exploiting optical spin orientation in the semiconductor and spin filtering across an insulating MgO barrier, the dependence of the resistivity on the spin of photo-excited carriers in Fe/MgO/Ge spin photodiodes (spin-PDs) was electrically detected. A spin diffusion length of 0.9  ±  0.2 µm was obtained by fitting the photon energy dependence of the spin signal by a mathematical model. Electrical techniques, comprising non-local four-terminal and Hanle measurements performed on CoFeB/MgO/Ge lateral devices, led to spin diffusion lengths of 1.3  ±  0.2 µm and 1.3  ±  0.08 µm, respectively. Despite minor differences due to experimental details, the order of magnitude of the spin diffusion length is the same for the three techniques. Although standard electrical methods are the most employed in semiconductor spintronics for spin diffusion length measurements, here we demonstrate optical spin orientation as a viable alternative for the determination of the spin diffusion length in semiconductors allowing for optical spin orientation.

  16. Diffuse neutron scattering of interesting phases in Dy2Ti2O7

    Energy Technology Data Exchange (ETDEWEB)

    Morris, Jonathan; Rule, Kirrily; Klemke, Bastian [Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany); Tennant, Alan [Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany); Institut fur Festkoerperphysik, Technische Universitaet Berlin (Germany); Grigera, Santiago [St. Andrew' s University, St. Andrews (United Kingdom); Instituto de Fisica de Liquidos y Sistemas Biologicos, La Plata (Argentina)

    2009-07-01

    The prospect of observing emergent magnetic monopoles in spin-ice has recently increased the interest in these systems. Dy{sub 2}Ti{sub 2}O{sub 7} is a effective spin-1/2 pyrochlore which is a clean model frustrated system where interesting physics may be observed and compared with theory. Here we present new neutron measurements from E2 at the Helmholtz-Zentrum Berlin which show an agreement with spin-ice correlation functions at 0.7 K and 0 T, and a complex Q-dependent diffuse scattering at fields below the saturation field along[100]. These are being understood in the context of spin-strings, or spin-random-walks, which are the prerequisite for monopoles. The scattering allows us to follow the development of these strings with field and provides new insight into the Kastelyn physics within this pyrochlore.

  17. Spin diffusion length of Permalloy using spin absorption in lateral spin valves

    Science.gov (United States)

    Sagasta, Edurne; Omori, Yasutomo; Isasa, Miren; Otani, YoshiChika; Hueso, Luis E.; Casanova, Fèlix

    2017-08-01

    We employ the spin absorption technique in lateral spin valves to extract the spin diffusion length of Permalloy (Py) as a function of temperature and resistivity. A linear dependence of the spin diffusion length with the conductivity of Py is observed, evidencing that the Elliott-Yafet mechanism is the dominant spin relaxation mechanism in Permalloy. Completing the dataset with additional data found in the literature, we obtain λPy = (0.91 ± 0.04) (fΩm2)/ρPy.

  18. Muon spin rotation studies

    Science.gov (United States)

    1984-01-01

    The bulk of the muon spin rotation research work centered around the development of the muon spin rotation facility at the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory (BNL). The collimation system was both designed and fabricated at Virginia State University. This improved collimation system, plus improvements in detectors and electronics enabled the acquisition of spectra free of background out to 15 microseconds. There were two runs at Brookhaven in 1984, one run was devoted primarily to beam development and the other run allowed several successful experiments to be performed. The effect of uniaxial strain on an Fe(Si) crystal at elevated temperature (360K) was measured and the results are incorporated herein. A complete analysis of Fe pulling data taken earlier is included.

  19. Spin and Madelung fluid

    International Nuclear Information System (INIS)

    Salesi, G.

    1995-07-01

    Starting from the Pauli current the decomposition of the non-relativistic local velocity has been obtained in two parts (in the ordinary tensorial language): one parallel and the other orthogonal to the impulse. The former is recognized to be the classical part, that is, the center-of-mass (CM) velocity, and the latter the quantum one, that is, the velocity of the motion in the CM frame (namely, the internal spin motion or Zitterbewegung). Inserting this complete, composite expression of the velocity into the kinetic energy term of the classical non-relativistic (i.e. Newtonian) Lagrangian, the author straightforwardly get the appearance of the so called quantum potential associates as it is known, to the Madelung fluid. In such a way, the quantum mechanical behaviour of particles appears to be strictly correlated to the existence of spin and Zitterbewegung

  20. Pangaea, She No Spin

    Science.gov (United States)

    McDowell, M.

    2002-12-01

    Looking at lopsided Pangaea, shown imaginatively on many illustrated proposals, I wondered what would happen if the configuration were put in high relief on a globe and spun on axis. Then I wondered if the present configuration of land masses would itself balance as a spinning top. So I got two Replogle globes, two boxes of colored modeling clay sticks, and two fat knitting needles, to fit through the capped holes at the poles of the globes. The clay sticks I cut up into 3 mm. (1/8") slices, using a different color for each continent, and applied to the first globe, assuming the extreme exaggeration above the geoid, no matter how crude, would tell the story. Inserting one needle through the globe and securing it, I balanced the globe on the point of the needle and twirled it like a top. Result: Wobbly! Top end of needle gyrated unevenly, and here it was supposed to make a smooth precessional cone. Oh boy. For the second globe, I used a Scotese "free stuff" interpretation of Pangaea, which I had to augment considerably using USGS, DuToit, Irving and other references, fitting it on the globe and applying identical clay color slices to what I judged generally accepted land surfaces. Result: the thing would hardly stand up, let alone spin. Conclusion: Although a refinement of application on the "today" globe might eliminate nutation, creating a smoother spin, there is no way any refinement of Pangaea on the same size globe can come close. While the concept of a supercontinent may be viable, I theorize that it had to have evolved on a far smaller globe, where land mass could balance, and the "breakup" would not have caused us to wildly gyrate on our axis. Because Pangaea, she no spin.

  1. Spin Hall effect

    Czech Academy of Sciences Publication Activity Database

    Sinova, Jairo; Valenzuela, O.V.; Wunderlich, Joerg; Back, C.H.; Jungwirth, Tomáš

    2015-01-01

    Roč. 87, č. 4 (2015), s. 1213-1259 ISSN 0034-6861 R&D Projects: GA MŠk(CZ) LM2011026; GA ČR GB14-37427G EU Projects: European Commission(XE) 268066 - 0MSPIN Institutional support: RVO:68378271 Keywords : spin Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 33.177, year: 2015

  2. Spin and gravitation

    Science.gov (United States)

    Ray, J. R.

    1982-01-01

    The fundamental variational principle for a perfect fluid in general relativity is extended so that it applies to the metric-torsion Einstein-Cartan theory. Field equations for a perfect fluid in the Einstein-Cartan theory are deduced. In addition, the equations of motion for a fluid with intrinsic spin in general relativity are deduced from a special relativistic variational principle. The theory is a direct extension of the theory of nonspinning fluids in special relativity.

  3. Spinning Disk Confocal System

    Science.gov (United States)

    2006-06-01

    high temporal resolution. An instrument has been developed for exactly this type of live-cell imaging. This new instrument scans 1000 microbeams across...Imaging System. Instead of scanning a single laser beam across the cell, this new instrument scans 1000 microbeams simultaneously using a spinning...multipoint-excitation, multipoint- emission characteristics of UltraView RS, which confers three main advantages over traditional beam scanning LSCMs for

  4. Spinning out a star.

    Science.gov (United States)

    Lord, Michael D; Mandel, Stanley W; Wager, Jeffrey D

    2002-06-01

    Spinouts rarely take off; most, in fact, fall into one or more of four traps that doom them from the start. Some companies spin out ventures that are too close to the core of their businesses, in effect selling off their crown jewels. Sometimes, a parent company uses the spinout primarily to pawn off debt or expenses or to quickly raise external capital for itself. Other times, a company may try to spin out an area of its business that lacks one or more of the critical legs of a successful company--a coherent business model, say, or a solid financial base. And in many cases, parent companies can't bring themselves to sever their ownership ties and give up control of their spinouts. R.J. Reynolds, the tobacco giant, managed to avoid these traps when it successfully spun out a most unlikely venture, the pharmaceutical company Targacept. As the story illustrates, the problem with spinouts is similar to the problem of rich children. Their parents have the wherewithal to spoil them or shelter them or cling to them, but what they need is tough love and discipline--much the same discipline that characterizes successful start-ups. R.J. Reynolds recognized that it didn't know that much about the pharmaceutical business and couldn't merely try to spin out a small clone of itself. It had to treat the venture as if it were essentially starting from scratch, with a passionate entrepreneurial leader, a solid business plan, help from outside partners in the industry, and ultimately substantial venture backing. That these lessons are less obvious to executives contemplating spinning out ventures closer to their core businesses may be why so many spinouts fail.

  5. Effect of crystallinity and morphology of TiO2 nano-structures on TiO2:P3HT hybrid photovoltaic solar cells

    International Nuclear Information System (INIS)

    Boroomandnia, A.; Kasaeian, A.B.; Nikfarjam, A. et al.

    2015-01-01

    A comparative study has been made of hybrid solar cells based on poly(3-hexyl thiophene) (P3HT) and different nano-structures of TiO 2 . Electrospinning, which is a low cost production method for large area nanofibrous films, was employed to fabricate TiO 2 nanofibers and spin coating method was employed to fabricate organic-inorganic hybrid solar cells based on P3HT and TiO 2 nanostructures. The performance of the hybrid solar cells was analyzed for four density levels of the TiO 2 nanostructure. It was found that higher densities of TiO 2 leads to more interface area and generates excitons, so that the power conversion efficiency increases to 0.13. TiO 2 nanoparticles with power conversion efficiency of 0.15 showed better performance than TiO 2 nanofibers because of greater interface area. Also the crystallinity effect of the TiO 2 nanostructure on solar cell performance was investigated. Moreover, an improved photovoltaic performance was achieved after the interface modification, and the highest conversion efficiency was obtained from the N719 modified device at 241 nm, short-circuit photocurrent (J sc ) of 3.88 mA cm -2 , open-circuit voltage (V oc ) of 0.09 V and fill factor of 0.16; so that an overall conversion efficiency (η) of 0.35% was obtained. (author)

  6. Spinning geometry = Twisted geometry

    International Nuclear Information System (INIS)

    Freidel, Laurent; Ziprick, Jonathan

    2014-01-01

    It is well known that the SU(2)-gauge invariant phase space of loop gravity can be represented in terms of twisted geometries. These are piecewise-linear-flat geometries obtained by gluing together polyhedra, but the resulting geometries are not continuous across the faces. Here we show that this phase space can also be represented by continuous, piecewise-flat three-geometries called spinning geometries. These are composed of metric-flat three-cells glued together consistently. The geometry of each cell and the manner in which they are glued is compatible with the choice of fluxes and holonomies. We first remark that the fluxes provide each edge with an angular momentum. By studying the piecewise-flat geometries which minimize edge lengths, we show that these angular momenta can be literally interpreted as the spin of the edges: the geometries of all edges are necessarily helices. We also show that the compatibility of the gluing maps with the holonomy data results in the same conclusion. This shows that a spinning geometry represents a way to glue together the three-cells of a twisted geometry to form a continuous geometry which represents a point in the loop gravity phase space. (paper)

  7. Spin Foam Models

    CERN Document Server

    Krasnov, K V

    1999-01-01

    The term ‘spin foam models’ was invented only a couple years ago by Baez to refer to a new approach to quantization of general relativity that appeared as an offsping of loop quantum gravity. Although this new approach was motivated, both logically and historically, by loop quantum gravity, it became clear by now that the two approaches are rather independent. While loop quantum gravity attempts to give a canonical quantization of general relativity, spin foam model approach is set to make sense of the path integral for gravity. Eventually, the two approaches will probably be shown to be equivalent, but no rigorous result to this effect exists as for now. In this thesis I develop the spin foam quantization of gravity from scratch, referring to results from loop quantum gravity only for comparison. I start from a review of 2 + 1 gravity and discuss different roots to quantize it. While some of them, as, for example, using Chern-Simons theory, only exist in 2 + 1, others can be generalized t...

  8. Is Cu60Ti10Zr30 a bulk glass-forming alloy?

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Saida, J.; Kato, H.

    2003-01-01

    The microstructures of Cu60Ti10Zr30 alloys fabricated by using two different methods, (rods of 2.5 mm in diameter prepared by a copper-mold casting method, and ribbons of about 0.03 mm in thickness prepared by the melt-spinning method), have been investigated by transmission electron microscopy a...

  9. The Photocatalytic Activity and Compact Layer Characteristics of TiO2 Films Prepared Using Radio Frequency Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    H. C. Chang

    2014-01-01

    Full Text Available TiO2 compact layers are used in dye-sensitized solar cells (DSSCs to prevent charge recombination between the electrolyte and the transparent conductive substrate (indium tin oxide, ITO; fluorine-doped tin oxide, FTO. Thin TiO2 compact layers are deposited onto ITO/glass by means of radio frequency (rf magnetron sputtering, using deposition parameters that ensure greater photocatalytic activity and increased DSSC conversion efficiency. The photoinduced decomposition of methylene blue (MB and the photoinduced hydrophilicity of the TiO2 thin films are also investigated. The photocatalytic performance characteristics for the deposition of TiO2 films are improved by using the Grey-Taguchi method. The average transmittance in the visible region exceeds 85% for all samples. The XRD patterns of the TiO2 films, for sol-gel with spin coating of porous TiO2/TiO2 compact/ITO/glass, show a good crystalline structure. In contrast, without the TiO2 compact layer (only porous TiO2, the peak intensity of the anatase (101 plane in the XRD patterns for the TiO2 film has a lower value, which demonstrates inferior crystalline quality. With a TiO2 compact layer to prevent charge recombination, a higher short-circuit current density is obtained. The DSSC with the FTO/glass and Pt counter electrode demonstrates the energy conversion efficiency increased.

  10. Nanomechanical properties of TiCN and TiCN/Ti coatings on Ti prepared by Filtered Arc Deposition

    International Nuclear Information System (INIS)

    Sun, Yong; Lu, Cheng; Yu, Hailiang; Kiet Tieu, A.; Su, Lihong; Zhao, Yue; Zhu, Hongtao; Kong, Charlie

    2015-01-01

    Monolayer TiCN and multilayer TiCN/Ti coatings were deposited on the surface of Ti using the Filtered Arc Deposition System (FADS). Nanoindentation tests were performed on both coatings. The multilayer TiCN/Ti coating exhibited better ductility than the monolayer TiCN coating. The lattice constants of the coatings were characterized by X-ray diffraction. Transmission Electron Microscopy (TEM) was used to investigate the fracture behavior of the coatings. Inter-columnar, inclined and lateral cracks were found to be the dominant crack modes in the monolayer TiCN coatings while small bending crack and radial crack were the dominant crack modes in the multilayer TiCN/Ti coatings. The Finite Element Method (FEM) was used to simulate the indentation process. It was found that the Ti interlayer in the multilayer TiCN/Ti coating could efficiently suppress the fracture, which is responsible for the improved ductility of the multilayer TiCN/Ti coating

  11. Nanomechanical properties of TiCN and TiCN/Ti coatings on Ti prepared by Filtered Arc Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yong [School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Lu, Cheng, E-mail: chenglu@uow.edu.au [School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Yu, Hailiang [School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); School of Mechanical Engineering, Shenyang University, Shenyang 110044 (China); Kiet Tieu, A.; Su, Lihong; Zhao, Yue; Zhu, Hongtao [School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Kong, Charlie [Electron Microscope Unit, University of New South Wales, Sydney, NSW 2052 (Australia)

    2015-02-11

    Monolayer TiCN and multilayer TiCN/Ti coatings were deposited on the surface of Ti using the Filtered Arc Deposition System (FADS). Nanoindentation tests were performed on both coatings. The multilayer TiCN/Ti coating exhibited better ductility than the monolayer TiCN coating. The lattice constants of the coatings were characterized by X-ray diffraction. Transmission Electron Microscopy (TEM) was used to investigate the fracture behavior of the coatings. Inter-columnar, inclined and lateral cracks were found to be the dominant crack modes in the monolayer TiCN coatings while small bending crack and radial crack were the dominant crack modes in the multilayer TiCN/Ti coatings. The Finite Element Method (FEM) was used to simulate the indentation process. It was found that the Ti interlayer in the multilayer TiCN/Ti coating could efficiently suppress the fracture, which is responsible for the improved ductility of the multilayer TiCN/Ti coating.

  12. Spinning particle approach to higher spin field theory

    International Nuclear Information System (INIS)

    Corradini, Olindo

    2011-01-01

    We shortly review on the connection between higher-spin gauge field theories and supersymmetric spinning particle models. In such approach the higher spin equations of motion are linked to the first-class constraint algebra associated with the quantization of particle models. Here we consider a class of spinning particle models characterized by local O(N)-extended supersymmetry since these models are known to provide an alternative approach to the geometric formulation of higher spin field theory. We describe the canonical quantization of the models in curved target space and discuss the obstructions that appear in presence of an arbitrarily curved background. We then point out the special role that conformally flat spaces appear to have in such models and present a derivation of the higher-spin curvatures for maximally symmetric spaces.

  13. Entanglement entropy in random quantum spin-S chains

    International Nuclear Information System (INIS)

    Saguia, A.; Boechat, B.; Continentino, M. A.; Sarandy, M. S.

    2007-01-01

    We discuss the scaling of entanglement entropy in the random singlet phase (RSP) of disordered quantum magnetic chains of general spin S. Through an analysis of the general structure of the RSP, we show that the entanglement entropy scales logarithmically with the size of a block, and we provide a closed expression for this scaling. This result is applicable for arbitrary quantum spin chains in the RSP, being dependent only on the magnitude S of the spin. Remarkably, the logarithmic scaling holds for the disordered chain even if the pure chain with no disorder does not exhibit conformal invariance, as is the case for Heisenberg integer-spin chains. Our conclusions are supported by explicit evaluations of the entanglement entropy for random spin-1 and spin-3/2 chains using an asymptotically exact real-space renormalization group approach

  14. Spin current through quantum-dot spin valves

    International Nuclear Information System (INIS)

    Wang, J; Xing, D Y

    2006-01-01

    We report a theoretical study of the influence of the Coulomb interaction on the equilibrium spin current in a quantum-dot spin valve, in which the quantum dot described by the Anderson impurity model is coupled to two ferromagnetic leads with noncollinear magnetizations. In the Kondo regime, electrons transmit through the quantum dot via higher-order virtual processes, in which the spin of either lead electrons or a localized electron on the quantum dot may reverse. It is found that the magnitude of the spin current decreases with increasing Coulomb interactions due to spin flip effects on the dot. However, the spatial direction of the spin current remains unchanged; it is determined only by the exchange coupling between two noncollinear magnetizations

  15. Spin Transfer Torque in Graphene

    Science.gov (United States)

    Lin, Chia-Ching; Chen, Zhihong

    2014-03-01

    Graphene is an idea channel material for spin transport due to its long spin diffusion length. To develop graphene based spin logic, it is important to demonstrate spin transfer torque in graphene. Here, we report the experimental measurement of spin transfer torque in graphene nonlocal spin valve devices. Assisted by a small external in-plane magnetic field, the magnetization reversal of the receiving magnet is induced by pure spin diffusion currents from the injector magnet. The magnetization switching is reversible between parallel and antiparallel configurations by controlling the polarity of the applied charged currents. Current induced heating and Oersted field from the nonlocal charge flow have also been excluded in this study. Next, we further enhance the spin angular momentum absorption at the interface of the receiving magnet and graphene channel by removing the tunneling barrier in the receiving magnet. The device with a tunneling barrier only at the injector magnet shows a comparable nonlocal spin valve signal but lower electrical noise. Moreover, in the same preset condition, the critical charge current density for spin torque in the single tunneling barrier device shows a substantial reduction if compared to the double tunneling barrier device.

  16. Spin waves and spin instabilities in quantum plasmas

    OpenAIRE

    Andreev, P. A.; Kuz'menkov, L. S.

    2014-01-01

    We describe main ideas of method of many-particle quantum hydrodynamics allows to derive equations for description of quantum plasma evolution. We also present definitions of collective quantum variables suitable for quantum plasmas. We show that evolution of magnetic moments (spins) in quantum plasmas leads to several new branches of wave dispersion: spin-electromagnetic plasma waves and self-consistent spin waves. Propagation of neutron beams through quantum plasmas is also considered. Inst...

  17. Hardy's argument and successive spin-s measurements

    International Nuclear Information System (INIS)

    Ahanj, Ali

    2010-01-01

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

  18. Spin transport in spin filtering magnetic tunneling junctions.

    Science.gov (United States)

    Li, Yun; Lee, Eok Kyun

    2007-11-01

    Taking into account spin-orbit coupling and s-d interaction, we investigate spin transport properties of the magnetic tunneling junctions with spin filtering barrier using Landauer-Büttiker formalism implemented with the recursive algorithm to calculate the real-space Green function. We predict completely different bias dependence of negative tunnel magnetoresistance (TMR) between the systems composed of nonmagnetic electrode (NM)/ferromagnetic barrier (FB)/ferromagnet (FM) and NM/FB/FM/NM spin filtering tunnel junctions (SFTJs). Analyses of the results provide us possible ways of designing the systems which modulate the TMR in the negative magnetoresistance regime.

  19. Spin-orbit mediated control of spin qubits

    DEFF Research Database (Denmark)

    Flindt, Christian; Sørensen, A.S; Flensberg, Karsten

    2006-01-01

    We propose to use the spin-orbit interaction as a means to control electron spins in quantum dots, enabling both single-qubit and two-qubit operations. Very fast single-qubit operations may be achieved by temporarily displacing the electrons. For two-qubit operations the coupling mechanism is based...... on a combination of the spin-orbit coupling and the mutual long-ranged Coulomb interaction. Compared to existing schemes using the exchange coupling, the spin-orbit induced coupling is less sensitive to random electrical fluctuations in the electrodes defining the quantum dots....

  20. High-field spin dynamics of antiferromagnetic quantum spin chains

    DEFF Research Database (Denmark)

    Enderle, M.; Regnault, L.P.; Broholm, C.

    2000-01-01

    present recent work on the high-field spin dynamics of the S = I antiferromagnetic Heisenberg chains NENP (Haldane ground state) and CsNiCl3 (quasi-1D HAF close to the quantum critical point), the uniform S = 1/2 chain CTS, and the spin-Peierls system CuGeO3. (C) 2000 Elsevier Science B,V. All rights......The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quantum phase transitions are expected. We...

  1. Visualizing spin states using the spin coherent state representation

    Science.gov (United States)

    Lee Loh, Yen; Kim, Monica

    2015-01-01

    Orbital angular momentum eigenfunctions are readily understood in terms of spherical harmonics. However, the quantum mechanical phenomenon of spin is often said to be mysterious and hard to visualize, with no classical analog. Many textbooks give a heuristic and somewhat unsatisfying picture of a precessing spin vector. Here, we show that the spin-coherent-state representation is a striking, elegant, and mathematically meaningful tool for visualizing spin states. We also demonstrate that cartographic projections such as the Hammer projection are useful for visualizing functions defined on spherical surfaces.

  2. Spin Currents and Spin Orbit Torques in Ferromagnets and Antiferromagnets

    Science.gov (United States)

    Hung, Yu-Ming

    This thesis focuses on the interactions of spin currents and materials with magnetic order, e.g., ferromagnetic and antiferromagnetic thin films. The spin current is generated in two ways. First by spin-polarized conduction-electrons associated with the spin Hall effect in heavy metals (HMs) and, second, by exciting spin-waves in ferrimagnetic insulators using a microwave frequency magnetic field. A conduction-electron spin current can be generated by spin-orbit coupling in a heavy non-magnetic metal and transfer its spin angular momentum to a ferromagnet, providing a means of reversing the magnetization of perpendicularly magnetized ultrathin films with currents that flow in the plane of the layers. The torques on the magnetization are known as spin-orbit torques (SOT). In the first part of my thesis project I investigated and contrasted the quasistatic (slowly swept current) and pulsed current-induced switching characteristics of micrometer scale Hall crosses consisting of very thin (thesis project studies and considers applications of SOT-driven domain wall (DW) motion in a perpendicularly magnetized ultrathin ferromagnet sandwiched between a heavy metal and an oxide. My experiment results demonstrate that the DW motion can be explained by a combination of the spin Hall effect, which generates a SOT, and Dzyaloshinskii-Moriya interaction, which stabilizes chiral Neel-type DW. Based on SOT-driven DW motion and magnetic coupling between electrically isolated ferromagnetic elements, I proposed a new type of spin logic devices. I then demonstrate the device operation by using micromagnetic modeling which involves studying the magnetic coupling induced by fringe fields from chiral DWs in perpendicularly magnetized nanowires. The last part of my thesis project reports spin transport and spin-Hall magnetoresistance (SMR) in yttrium iron garnet Y3Fe5O 12 (YIG)/NiO/Pt trilayers with varied NiO thickness. To characterize the spin transport through NiO we excite

  3. QED approach to the nuclear spin-spin coupling tensor

    International Nuclear Information System (INIS)

    Romero, Rodolfo H.; Aucar, Gustavo A.

    2002-01-01

    A quantum electrodynamical approach for the calculation of the nuclear spin-spin coupling tensor of nuclear-magnetic-resonance spectroscopy is given. Quantization of radiation fields within the molecule is considered and expressions for the magnetic field in the neighborhood of a nucleus are calculated. Using a generalization of time-dependent response theory, an effective spin-spin interaction is obtained from the coupling of nuclear magnetic moments to a virtual quantized magnetic field. The energy-dependent operators obtained reduce to usual classical-field expressions at suitable limits

  4. Spin State Control using Oxide Interfaces in LaCoO3-based Heterostructures

    Science.gov (United States)

    Lee, Sangjae; Disa, Ankit; Walker, Frederick; Ahn, Charles

    The flexibility of the spin degree of freedom of the Co 3d orbitals in LaCoO3 suggests that they can be changed through careful design of oxide heterostructures. Interfacial coupling and dimensional confinement can be used to control the magnetic exchange, crystal fields, and Hund's coupling, through orbital and charge reconstructions. These parameters control the balance between multiple spin configurations, thereby modifying the magnetic ordering of LaCoO3. We study (LaCoO3)m /(LaTiO3)2 heterostructures grown by molecular beam epitaxy, which allow interfacial charge transfer from Ti to Co, in addition to structural and dimensional constraints. The electronic polarization at the interface and consequent structural distortions suppress the ferromagnetism in the LaCoO3 layers. This effect extends well beyond the interface, with ferromagnetic order absent up to LaCoO3 layer thickness of m =10. We compare the properties of the LaCoO3/LaTiO3heterostructureswithLaCoO3/SrTiO3, to untangle how charge transfer and structural modifications control the spin and magnetic configuration in cobaltates.

  5. Superconducting fluctuations in systems with Rashba-spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Beyl, Stefan [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Orth, Peter P.; Scheurer, Mathias; Schmalian, Joerg [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie (Germany)

    2015-07-01

    We investigate the BEC-BCS crossover in a two-dimensional system with Rashba-spin-orbit coupling. To include the effects of phase and amplitude fluctuations of the superconducting order parameter we perform a loop expansion of the effective field theory. We analyze in particular the probability of a low density superconducting quantum phase transition. The theory is relevant to LaAlO{sub 3}/SrTiO{sub 3} interfaces and two-dimensional cold atom systems with synthetic gauge fields.

  6. Synthesis and characterization of Ag doped TiO{sub 2} heterojunction films and their photocatalytic performances

    Energy Technology Data Exchange (ETDEWEB)

    Demirci, Selim, E-mail: selim.demirci@marmara.edu.tr [Marmara University, Department of Metallurgical and Materials Engineering, Kadiköy, 34722 Istanbul (Turkey); Dikici, Tuncay [Izmir Katip Celebi University, Department of Materials Science and Engineering, Cigli, 35620 Izmir (Turkey); Yurddaskal, Metin [Department of Metallurgical and Materials Engineering, Dokuz Eylul University, 35390 Izmir (Turkey); Center for Fabrication and Application of Electronic Materials, Dokuz Eylul University, 35390 Izmir (Turkey); Gultekin, Serdar [Department of Nanoscience and Nanoengineering, Dokuz Eylul University, 35390 İzmir (Turkey); Experimental Science Applications and Research Center, Celal Bayar University, 45140 Manisa (Turkey); Toparli, Mustafa; Celik, Erdal [Department of Metallurgical and Materials Engineering, Dokuz Eylul University, 35390 Izmir (Turkey); Department of Nanoscience and Nanoengineering, Dokuz Eylul University, 35390 İzmir (Turkey); Center for Fabrication and Application of Electronic Materials, Dokuz Eylul University, 35390 Izmir (Turkey)

    2016-12-30

    Highlights: • Ag doped TiO{sub 2} films were successfully synthesized by sol–gel spin coating method. • Ag in TiO{sub 2} lattice enters in intermediate states to decrease TiO{sub 2} bandgap energy. • Ag dopants increase the photoactivity and superhydrophilicity. • The degradation kinetics of methylene blue was studied. • The 0.7 mol% of Ag was found to be the optimum concentration. - Abstract: In this study, undoped and silver (Ag) doped titanium dioxide (TiO{sub 2}) films were successfully synthesized by sol-gel spin coating technique on the Si substrates. Photocatalytic activities of the TiO{sub 2} films with different Ag content were investigated for the degradation of methylene blue (MB) under UV light irradiation. The crystal phase structure, surface morphology, chemical and optical properties of Ag-doped TiO{sub 2} films were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis spectrophotometer, and FTIR spectrophotometer. The results showed that the Ag-doped TiO{sub 2} films calcined at 500 °C had the crystalline anatase phases and the surface morphologies with some cracks. Ag substitution into TiO{sub 2} matrix enhanced the photocatalytic activity of TiO{sub 2} films under UV light irradiation as compared to the undoped TiO{sub 2} film. Furthermore, the results indicated that the 0.7% Ag doped TiO{sub 2} film exhibited a superior photocatalytic activity than that of undoped and other Ag-doped TiO{sub 2} films. This study demonstrated the potential of an application of Ag doped films to efficiently treat dissolved organic contaminants in water.

  7. Frost formation and defrost control parameters for open multideck refrigerated food display cabinets

    Energy Technology Data Exchange (ETDEWEB)

    Tassou, S.A.; Datta, D. [Brunel Univ., Dept. of Mechanical Engineering, Uxbridge (United Kingdom); Marriott, D. [Safeway Stores plc, Hayes (United Kingdom)

    2001-04-03

    In order to achieve the required air and product temperatures in refrigerated food display cabinets, the evaporator coils, which are normally located in the base of the cabinets, operate at temperatures below the freezing point of water. The air which is circulated over the evaporator coil is cooled below its dew point and water vapour present in the air condenses and eventually freezes on the coil surface. With continuous operation of the coil, frost will accumulate on the coil surface leading to a decrease both in the air flowrate and in the overall heat transfer coefficient. In order to maintain satisfactory performance, evaporator coils are defrosted periodically. Although different defrost control strategies can be employed, for simplicity and cost considerations, defrosting in supermarket refrigeration systems is usually controlled by a pre-set time cycle. It is widely acknowledge, however, that time-based defrost may cause a number of unnecessary defrost cycles and this reduces the energy efficiency of the refrigeration systems as well as the accuracy of temperature control of the cabinets. Implementing defrost only when it is needed or on 'demand' should reduce the number of defrost cycles and lead to savings in energy and improved product quality. This paper reports on field and experimental investigations on the processes of frosting and defrosting of medium-temperature display cabinet evaporator coils. The results show that for medium-temperature refrigeration applications where the environment temperature is kept reasonably constant, the store humidity is the primary parameter influencing the rate of frost formation. Using relative humidity as a control parameter the defrost frequency can be reduced considerably without affecting cabinet performance and product integrity. Alongside the effect of relative humidity, the paper also considers the effects of other performance parameters on the processes of frosting and defrosting such as cooling time and length of previous defrost cycle, and discusses ways in which some of these parameters may be used to implement defrost on demand. (Author)

  8. Lateral electric-field control of giant magnetoresistance in Co/Cu/Fe/BaTiO{sub 3} multiferroic heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Savitha Pillai, S.; Kojima, H.; Itoh, M.; Taniyama, T., E-mail: taniyama.t.aa@m.titech.ac.jp [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8503 (Japan)

    2015-08-17

    We report lateral electric-field-driven sizable changes in the magnetoresistance of Co/Cu/Fe tri-layered wires on BaTiO{sub 3} single crystal. While the observed change is marginal in the tetragonal phase of BaTiO{sub 3}, it reaches over 40% in the orthorhombic and rhombohedral phases with an electric field of 66 kV/cm. We attribute it to possible electric-field-induced variations of the spin-dependent electronic structures, i.e., spin polarization, of the Fe via interfacial strain transfer from BaTiO{sub 3}. The contrasting results for the different phases of BaTiO{sub 3} are discussed, associated with the distinct aspects of the ferroelectric polarization switching processes in each phase.

  9. Lateral electric-field control of giant magnetoresistance in Co/Cu/Fe/BaTiO3 multiferroic heterostructure

    International Nuclear Information System (INIS)

    Savitha Pillai, S.; Kojima, H.; Itoh, M.; Taniyama, T.

    2015-01-01

    We report lateral electric-field-driven sizable changes in the magnetoresistance of Co/Cu/Fe tri-layered wires on BaTiO 3 single crystal. While the observed change is marginal in the tetragonal phase of BaTiO 3 , it reaches over 40% in the orthorhombic and rhombohedral phases with an electric field of 66 kV/cm. We attribute it to possible electric-field-induced variations of the spin-dependent electronic structures, i.e., spin polarization, of the Fe via interfacial strain transfer from BaTiO 3 . The contrasting results for the different phases of BaTiO 3 are discussed, associated with the distinct aspects of the ferroelectric polarization switching processes in each phase

  10. Lateral electric-field control of giant magnetoresistance in Co/Cu/Fe/BaTiO3 multiferroic heterostructure

    Science.gov (United States)

    Savitha Pillai, S.; Kojima, H.; Itoh, M.; Taniyama, T.

    2015-08-01

    We report lateral electric-field-driven sizable changes in the magnetoresistance of Co/Cu/Fe tri-layered wires on BaTiO3 single crystal. While the observed change is marginal in the tetragonal phase of BaTiO3, it reaches over 40% in the orthorhombic and rhombohedral phases with an electric field of 66 kV/cm. We attribute it to possible electric-field-induced variations of the spin-dependent electronic structures, i.e., spin polarization, of the Fe via interfacial strain transfer from BaTiO3. The contrasting results for the different phases of BaTiO3 are discussed, associated with the distinct aspects of the ferroelectric polarization switching processes in each phase.

  11. ac spin-Hall effect

    International Nuclear Information System (INIS)

    Entin-Wohlman, O.

    2005-01-01

    Full Text:The spin-Hall effect is described. The Rashba and Dresselhaus spin-orbit interactions are both shown to yield the low temperature spin-Hall effect for strongly localized electrons coupled to phonons. A frequency-dependent electric field E(ω) generates a spin-polarization current, normal to E, due to interference of hopping paths. At zero temperature the corresponding spin-Hall conductivity is real and is proportional to ω 2 . At non-zero temperatures the coupling to the phonons yields an imaginary term proportional to ω. The interference also yields persistent spin currents at thermal equilibrium, at E = 0. The contributions from the Dresselhaus and Rashba interactions to the interference oppose each other

  12. Magnetocrystalline anisotropy and magnetic domain structure of ErFe{sub 11}Ti and HoFe{sub 11}Ti compounds

    Energy Technology Data Exchange (ETDEWEB)

    Pastushenkov, Yury G. [Physics Department of Tver State University, 17000 Tver (Russian Federation); Skokov, Konstantin P. [Physics Department of Tver State University, 17000 Tver (Russian Federation); Skourski, Yury [Leibniz-Institute for Solid State and Material Research, 01171 Dresden (Germany); Lebedeva, Ludmila [Physics Department of Tver State University, 17000 Tver (Russian Federation); Ivanova, Tatyana [Physics Department of Moscow Stae University, 119889 Moscow (Russian Federation); Grushichev, Anton [Physics Department of Tver State University, 17000 Tver (Russian Federation)]. E-mail: yupast@tversu.ru; Mueller, Karl-Hartmut [Leibniz-Institute for Solid State and Material Research, 01171 Dresden (Germany)

    2006-05-15

    Tetragonal ThMn{sub 12}-type single crystalline ErFe{sub 11}Ti and HoFe{sub 11}Ti samples have been investigated by magnetization measurements and by observations of the magnetic domain structure at various temperatures between 10 and 300K. The magnetic structure of ErFe{sub 11}Ti changes from room temperature 'easy axis' (c-axis) type to conical at spin-reorientation temperature T{sub SR}=50K. The HoFe{sub 11}Ti has a metastable anisotropy energy minimum in the a-direction at T<40K. It leads to a first-order magnetization process detected by magnetization measurements along the a-axis in this temperature region.

  13. Observation of the spin Nernst effect

    Science.gov (United States)

    Meyer, S.; Chen, Y.-T.; Wimmer, S.; Althammer, M.; Wimmer, T.; Schlitz, R.; Geprägs, S.; Huebl, H.; Ködderitzsch, D.; Ebert, H.; Bauer, G. E. W.; Gross, R.; Goennenwein, S. T. B.

    2017-10-01

    The observation of the spin Hall effect triggered intense research on pure spin current transport. With the spin Hall effect, the spin Seebeck effect and the spin Peltier effect already observed, our picture of pure spin current transport is almost complete. The only missing piece is the spin Nernst (-Ettingshausen) effect, which so far has been discussed only on theoretical grounds. Here, we report the observation of the spin Nernst effect. By applying a longitudinal temperature gradient, we generate a pure transverse spin current in a Pt thin film. For readout, we exploit the magnetization-orientation-dependent spin transfer to an adjacent yttrium iron garnet layer, converting the spin Nernst current in Pt into a controlled change of the longitudinal and transverse thermopower voltage. Our experiments show that the spin Nernst and the spin Hall effect in Pt are of comparable magnitude, but differ in sign, as corroborated by first-principles calculations.

  14. Symplectic integrators for spin systems

    Science.gov (United States)

    McLachlan, Robert I.; Modin, Klas; Verdier, Olivier

    2014-06-01

    We present a symplectic integrator, based on the implicit midpoint method, for classical spin systems where each spin is a unit vector in R3. Unlike splitting methods, it is defined for all Hamiltonians and is O (3)-equivariant, i.e., coordinate-independent. It is a rare example of a generating function for symplectic maps of a noncanonical phase space. It yields a new integrable discretization of the spinning top.

  15. Asymptotics of relativistic spin networks

    International Nuclear Information System (INIS)

    Barrett, John W; Steele, Christopher M

    2003-01-01

    The stationary phase technique is used to calculate asymptotic formulae for SO(4) relativistic spin networks. For the tetrahedral spin network this gives the square of the Ponzano-Regge asymptotic formula for the SU(2) 6j-symbol. For the 4-simplex (10j-symbol) the asymptotic formula is compared with numerical calculations of the spin network evaluation. Finally, we discuss the asymptotics of the SO(3, 1) 10j-symbol

  16. Spin currents in metallic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Czeschka, Franz Dominik

    2011-09-05

    A pure spin current, i.e., a flow of angular momentum without accompanying net charge current, is a key ingredient in the field of spintronics. In this thesis, we experimentally investigated two different concepts for pure spin current sources suggested by theory. The first is based on a time-dependent magnetization precession which ''pumps'' a pure spin current into an adjacent non-magnetic conductor. Our experiments quantitatively corroborated important predictions expected theoretically for this approach, including the dependence of the spin current on the sample geometry and the microwave power. Even more important, we could show for the first time that the spin pumping concept is viable in a large variety of ferromagnetic materials and that it only depends on the magnetization damping. Therefore, our experiments established spin pumping as generic phenomenon and demonstrated that it is a powerful way to generate pure spin currents. The second theoretical concept is based on the conversion of charge currents into spin currents in non-magnetic nanostructures via the spin Hall effect. We experimentally investigated this approach in H-shaped, metallic nanodevices, and found that the predictions are linked to requirements not realizable with the present experimental techniques, neither in sample fabrication nor in measurement technique. Indeed, our experimental data could be consistently understood by a spin-independent transport model describing the transition from diffusive to ballistic transport. In addition, the implementation of advanced fabrication and measurement techniques allowed to discover a new non-local phenomenon, the non-local anisotropic magnetoresistance. Finally, we also studied spin-polarized supercurrents carried by spin-triplet Cooper pairs. We found that low resistance interfaces are a key requirement for further experiments in this direction. (orig.)

  17. Effect of nano-CeO 2 on microstructure properties of TiC/TiN+TiCN ...

    Indian Academy of Sciences (India)

    TiC/TiN+TiCN-reinforced composite coatings were fabricated on Ti–6Al–4V alloy by laser cladding, which improved surface performance of the substrate. ... X-ray diffraction results indicated that Al3Ti+TiC/TiN+nano-CeO2 laser-cladded coating consisted of Ti3Al, TiC, TiN, Ti2Al20Ce, TiC0.3N0.7, Ce(CN)3 and CeO2, this ...

  18. Towards spin injection into silicon

    Energy Technology Data Exchange (ETDEWEB)

    Dash, S.P.

    2007-08-15

    Si has been studied for the purpose of spin injection extensively in this thesis. Three different concepts for spin injection into Si have been addressed: (1) spin injection through a ferromagnet-Si Schottky contact, (2) spin injection using MgO tunnel barriers in between the ferromagnet and Si, and (3) spin injection from Mn-doped Si (DMS) as spin aligner. (1) FM-Si Schottky contact for spin injection: To be able to improve the interface qualities one needs to understand the atomic processes involved in the formation of silicide phases. In order to obtain more detailed insight into the formation of such phases the initial stages of growth of Co and Fe were studied in situ by HRBS with monolayer depth resolution.(2) MgO tunnel barrier for spin injection into Si: The fabrication and characterization of ultra-thin crystalline MgO tunnel barriers on Si (100) was presented. (3) Mn doped Si for spin injection: Si-based diluted magnetic semiconductor samples were prepared by doping Si with Mn by two different methods i) by Mn ion implantation and ii) by in-diffusion of Mn atoms (solid state growth). (orig.)

  19. Spin-photon entangling diode

    DEFF Research Database (Denmark)

    Flindt, Christian; Sørensen, A. S.; Lukin, M. D.

    2007-01-01

    We propose a semiconductor device that can electrically generate entangled electron spin-photon states, providing a building block for entanglement of distant spins. The device consists of a p-i-n diode structure that incorporates a coupled double quantum dot. We show that electronic control...... of the diode bias and local gating allow for the generation of single photons that are entangled with a robust quantum memory based on the electron spins. Practical performance of this approach to controlled spin-photon entanglement is analyzed....

  20. Spin diffusion in Fermi gases

    DEFF Research Database (Denmark)

    Bruun, Georg

    2011-01-01

    We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures......, strong correlation effects are included through the Landau parameters which we extract from Monte Carlo results. We show that the spin diffusion coefficient has a minimum for a temperature somewhat below the Fermi temperature with a value that approaches the quantum limit ~/m in the unitarity regime...

  1. Dipolar Spin Ice States with a Fast Monopole Hopping Rate in CdEr2X4 (X =Se , S)

    Science.gov (United States)

    Gao, Shang; Zaharko, O.; Tsurkan, V.; Prodan, L.; Riordan, E.; Lago, J.; Fâk, B.; Wildes, A. R.; Koza, M. M.; Ritter, C.; Fouquet, P.; Keller, L.; Canévet, E.; Medarde, M.; Blomgren, J.; Johansson, C.; Giblin, S. R.; Vrtnik, S.; Luzar, J.; Loidl, A.; Rüegg, Ch.; Fennell, T.

    2018-03-01

    Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr2 Se4 is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy2 Ti2 O7 . In this Letter we use diffuse neutron scattering to show that both CdEr2 Se4 and CdEr2 S4 support a dipolar spin ice state—the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy2 Ti2 O7 , i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er3 + ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr2X4 (X =Se , S) are primarily due to much faster monopole hopping. Our work suggests that CdEr2X4 offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples.

  2. Electron spin resonance

    International Nuclear Information System (INIS)

    Wasson, J.R.; Salinas, J.E.

    1980-01-01

    Published literature concerning electron spin resonance (ESR) from July 1977 to July 1979 is reviewed. The 108 literature sources cited were chosen from literally thousands and are intended to serve as a guide to the current literature and to provide an eclectic selection of publications cited for their contributions to the advance and/or applications of ESR spectroscopy. 40 of the sources are reviews, and a table is included to indicate the topic(s) mainly covered in each review. Other divisions of the material reviewed are apparatus and spectral analysis, analytical applications, and selected paramagnetic materials

  3. Synthesis and characterization of multilayered BaTiO3/NiFe2O4 thin films

    Directory of Open Access Journals (Sweden)

    Branimir Bajac

    2013-03-01

    Full Text Available Presented research was focused on the fabrication of multiferroic thin film structures, composed of ferrielectric barium titanate perovskite phase and magnetostrictive nickel ferrite spinel phase. The applicability of different, solution based, deposition techniques (film growth from solution, dip coating and spin coating for thefabrication of multilayered BaTiO3 /NiFe2O4 thin films was investigated. It was shown that only spin coating produces films of desired nanostructure, thickness and smooth and crackfree surfaces.

  4. Mesoporous Bioactive Glass Functionalized 3D Ti-6Al-4V Scaffolds with Improved Surface Bioactivity.

    Science.gov (United States)

    Ye, Xiaotong; Leeflang, Sander; Wu, Chengtie; Chang, Jiang; Zhou, Jie; Huan, Zhiguang

    2017-10-27

    Porous Ti-6Al-4V scaffolds fabricated by means of selective laser melting (SLM), having controllable geometrical features and preferable mechanical properties, have been developed as a class of biomaterials that hold promising potential for bone repair. However, the inherent bio-inertness of the Ti-6Al-4V alloy as the matrix of the scaffolds results in a lack in the ability to stimulate bone ingrowth and regeneration. The aim of the present study was to develop a bioactive coating on the struts of SLM Ti-6Al-4V scaffolds in order to add the desired surface osteogenesis ability. Mesoporous bioactive glasses (MBGs) coating was applied on the strut surfaces of the SLM Ti-6Al-4V scaffolds through spin coating, followed by a heat treatment. It was found that the coating could maintain the characteristic mesoporous structure and chemical composition of MBG, and establish good interfacial adhesion to the Ti-6Al-4V substrate. The compressive strength and pore interconnectivity of the scaffolds were not affected by the coating. Moreover, the results obtained from in vitro cell culture experiments demonstrated that the attachment, proliferation, and differentiation of human bone marrow stromal cells (hBMSCs) on the MBG-coated Ti-6Al-4V scaffolds were improved as compared with those on the conventional bioactive glass (BG)-coated Ti-6Al-4V scaffolds and bare-metal Ti-6Al-4V scaffolds. Our results demonstrated that the MBG coating by using the spinning coating method could be an effective approach to achieving enhanced surface biofunctionalization for SLM Ti-6Al-4V scaffolds.

  5. Mesoporous Bioactive Glass Functionalized 3D Ti-6Al-4V Scaffolds with Improved Surface Bioactivity

    Directory of Open Access Journals (Sweden)

    Xiaotong Ye

    2017-10-01

    Full Text Available Porous Ti-6Al-4V scaffolds fabricated by means of selective laser melting (SLM, having controllable geometrical features and preferable mechanical properties, have been developed as a class of biomaterials that hold promising potential for bone repair. However, the inherent bio-inertness of the Ti-6Al-4V alloy as the matrix of the scaffolds results in a lack in the ability to stimulate bone ingrowth and regeneration. The aim of the present study was to develop a bioactive coating on the struts of SLM Ti-6Al-4V scaffolds in order to add the desired surface osteogenesis ability. Mesoporous bioactive glasses (MBGs coating was applied on the strut surfaces of the SLM Ti-6Al-4V scaffolds through spin coating, followed by a heat treatment. It was found that the coating could maintain the characteristic mesoporous structure and chemical composition of MBG, and establish good interfacial adhesion to the Ti-6Al-4V substrate. The compressive strength and pore interconnectivity of the scaffolds were not affected by the coating. Moreover, the results obtained from in vitro cell culture experiments demonstrated that the attachment, proliferation, and differentiation of human bone marrow stromal cells (hBMSCs on the MBG-coated Ti-6Al-4V scaffolds were improved as compared with those on the conventional bioactive glass (BG-coated Ti-6Al-4V scaffolds and bare-metal Ti-6Al-4V scaffolds. Our results demonstrated that the MBG coating by using the spinning coating method could be an effective approach to achieving enhanced surface biofunctionalization for SLM Ti-6Al-4V scaffolds.

  6. 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.

  7. Diffusion equation and spin drag in spin-polarized transport

    DEFF Research Database (Denmark)

    Flensberg, Karsten; Jensen, Thomas Stibius; Mortensen, Asger

    2001-01-01

    We study the role of electron-electron interactions for spin-polarized transport using the Boltzmann equation, and derive a set of coupled transport equations. For spin-polarized transport the electron-electron interactions are important, because they tend to equilibrate the momentum of the two-s...

  8. Magic-Angle-Spinning NMR Magnet Development: Field Analysis and Prototypes

    Science.gov (United States)

    Voccio, John; Hahn, Seungyong; Park, Dong Keun; Ling, Jiayin; Kim, Youngjae; Bascuñán, Juan; Iwasa, Yukikazu

    2013-01-01

    We are currently working on a program to complete a 1.5 T/75 mm RT bore magic-angle-spinning nuclear magnetic resonance magnet. The magic-angle-spinning magnet comprises a z-axis 0.866-T solenoid and an x-axis 1.225-T dipole, each to be wound with NbTi wire and operated at 4.2 K in persistent mode. A combination of the fields creates a 1.5-T field pointed at 54.74 degrees (magic angle) from the rotation (z) axis. In the first year of this 3-year program, we have completed magnetic analysis and design of both coils. Also, using a winding machine of our own design and fabrication, we have wound several prototype dipole coils with NbTi wire. As part of this development, we have repeatedly made successful persistent NbTi-NbTi joints with this multifilamentary NbTi wire. PMID:24058275

  9. Stress analysis and microstructure of PVD monolayer TiN and multilayer TiN/(Ti,Al)N coatings

    NARCIS (Netherlands)

    Carvalho, NJM; Zoestbergen, E; Kooi, BJ; De Hosson, JTM

    2003-01-01

    Two PVD titanium nitride based coatings; monolayer TiN and multilayer resulting from the stacking of TiN and (Ti,Al)N layers were evaluated with respect to their stress state and microstructure. The TiN was deposited by triode evaporation ion plating, whereas the TiN/(Ti,AI)N was deposited using a

  10. Fabrication and characterization of laminated Ti-(TiB+La2O3/Ti composite

    Directory of Open Access Journals (Sweden)

    Yuanfei Han

    2015-10-01

    Full Text Available The incorporation of ceramic particulate reinforcements into titanium alloys can improve the specific strength and specific stiffness, while inevitably reduce the plasticity and ductility. In this study, in situ synthesized multilayer Ti-(TiB+La2O3/Ti composite was designed by learning from the microstructure of nature biological materials with excellent mechanical properties. The Ti-(TiB+La2O3/Ti composite with unique characteristic of laminated structure was prepared by combined powder metallurgy and hot rolling. The method has the synthesize advantages with in-situ reaction of Ti and LaB6 at high temperature and controllability of reinforcements size and constituent phases in composites. The result shows that the pores in the as sintered laminated structure composite completely disappeared after hot rolling at 1050 °C. The agglomerated reinforcement particles were well dispersed and distributed uniformly along the rolling direction. The thickness of pure Ti layer and (TiB+La2O3/Ti composite layer decreased from 1 mm to about 200 μm. Meanwhile, the grains size was refined obviously after rolling deformation. The room temperature tensile test indicates that the elongation of the laminated Ti-(TiB+La2O3/Ti composite improved from 13% to 17% in comparison with the uniform (TiB+La2O3/Ti composite, while the tensile strength had little change. It provides theoretical and experimental basis for fabricating the novel high performance laminated Ti-(TiB+La2O3/Ti composites.

  11. NMR relaxation in spin ice at low temperature due to diffusing emergent monopoles

    Science.gov (United States)

    Henley, Christopher L.

    2013-03-01

    At low temperatures, spin dynamics in ideal spin ice is due mainly to dilute, thermally excited magnetic ``monopole'' excitations. I consider how these will affect the longitudinal (T1) and dephasing (T2) relaxation functions of a nuclear spin in the spin-ice pyrochlore Dy2Ti2O4. Up to the time scale for nearby monopoles to be rearranged, a stretched-exponential form of the relaxation functions is expected, due to averaging over nuclei that have different local environments. ror the dephasing (T2) relaxation, the power of time in the stretched exponential is 3/2 in the case of diffusing monopoles, but 1/2 in the case of fixed, fluctuating magnetic impurities. The flip rate and density of fluctuating spins (whatever their nature) can be extracted from the measured relaxation times T1 and T2, and from known parameters. However, the actual experimental relaxation measured by Kitagawa and Takigawa becomes temperature independent in the very low T limit, and the T2 has a power t 1 / 2 in the exponential, neither of which can be explained by monopoles. I suggest the very low T behavior could be due to magnetic impurities on the (normally nonmagnetic) Ti sites. Supported by NSF grant DMR-1005466.

  12. Spin caloritronics, origin and outlook

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haiming, E-mail: haiming.yu@buaa.edu.cn [Fert Beijing Institute, School of Electronic and Information Engineering, BDBC, Beihang University (China); Brechet, Sylvain D. [Institute of Physics, station 3, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne-EPFL (Switzerland); Ansermet, Jean-Philippe, E-mail: jean-philippe.ansermet@epfl.ch [Institute of Physics, station 3, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne-EPFL (Switzerland)

    2017-03-03

    Spin caloritronics refers to research efforts in spintronics when a heat current plays a role. In this review, we start out by reviewing the predictions that can be drawn from the thermodynamics of irreversible processes. This serves as a conceptual framework in which to analyze the interplay of charge, spin and heat transport. This formalism predicts tensorial relations between vectorial quantities such as currents and gradients of chemical potentials or of temperature. Transverse effects such as the Nernst or Hall effects are predicted on the basis that these tensors can include an anti-symmetric contribution, which can be written with a vectorial cross-product. The local symmetry of the system may determine the direction of the vector defining such transverse effects, such as the surface of an isotropic medium. By including magnetization as state field in the thermodynamic description, spin currents appear naturally from the continuity equation for the magnetization, and dissipative spin torques are derived, which are charge-driven or heat-driven. Thermodynamics does not give the strength of these effects, but may provide relationships between them. Based on this framework, the review proceeds by showing how these effects have been observed in various systems. Spintronics has become a vast field of research, and the experiments highlighted in this review pertain only to heat effects on transport and magnetization dynamics, such as magneto-thermoelectric power, or the spin-dependence of the Seebeck effect, the spin-dependence of the Peltier effect, the spin Seebeck effect, the magnetic Seebeck effect, or the Nernst effect. The review concludes by pointing out predicted effects that are yet to be verified experimentally, and in what novel materials the standard thermal spin effects could be investigated. - Highlights: • Thermodynamic description of transport: three-current model. • Magneto-thermoelectric power and spin-dependent Peltier effects. • Thermal

  13. Nuclear Spin-Spin Coupling in HD, HT, and DT

    Science.gov (United States)

    Puchalski, Mariusz; Komasa, Jacek; Pachucki, Krzysztof

    2018-02-01

    The interaction between nuclear spins in a molecule is exceptionally sensitive to the physics beyond the standard model. However, all present calculations of the nuclear spin-spin coupling constant J are burdened by computational difficulties, which hinders the comparison to experimental results. Here, we present a variational approach and calculate the constant J in the hydrogen molecule with the controlled numerical precision, using the adiabatic approximation. The apparent discrepancy with experimental result is removed by an analysis of nonadiabatic effects based on the experimental values of the J constant for HD, HT, and DT molecules. This study significantly improves the reliability of the NMR theory for searching new physics in the spin-spin coupling.

  14. Spin-state blockade in Te6+-substituted electron-doped LaCoO3

    Science.gov (United States)

    Tomiyasu, Keisuke; Koyama, Shun-Ichi; Watahiki, Masanori; Sato, Mika; Nishihara, Kazuki; Onodera, Mitsugi; Iwasa, Kazuaki; Nojima, Tsutomu; Yamasaki, Yuuichi; Nakao, Hironori; Murakami, Youichi

    2015-03-01

    Perovskite-type LaCoO3 (Co3+: d6) is a rare inorganic material with sensitive and characteristic responses among low, intermediate, and high spin states. For example, in insulating nonmagnetic low-spin states below about 20 K, light hole doping (Ni substitution) induces much larger magnetization than expected; over net 10μB/hole (5μB/Ni) for 1μB/hole (1μB/Ni), in which the nearly isolated dopants locally change the surrounding Co low-spin states to magnetic ones and form spin molecules with larger total spin. Further, the former is isotropic, whereas the latter exhibits characteristic anisotropy probably because of Jahn-Teller distortion. In contrast, for electron doping, relatively insensitive spin-state responses were reported, as in LaCo(Ti4+) O3, but are not clarified, and are somewhat controversial. Here, we present macroscopic measurement data of another electron-doped system LaCo(Te6+) O3 and discuss the spin-state responses. This study was financially supported by Grants-in-Aid for Young Scientists (B) (No. 22740209 and 26800174) from the MEXT of Japan.

  15. Structural evolution of Ti/TiC multilayers

    International Nuclear Information System (INIS)

    Dahan, I.; Frage, N.; Dariel, M.P.

    2004-01-01

    Hard coatings based on metal/ceramic multilayers with periods in the nanometer range have been shown to possess some potential for improved tribological and mechanical properties. The present work is concerned with the structural evolution of (Ti/TiC) multilayers. Two kinds of multilayers consisting of 30 equithick (40 nm)TiC layers and 20 and 60 nm thick Ti layers, respectively, were sputter deposited on Mo substrates. The structural and the compositional evolution of these multilayers were examined by x-ray diffraction, transition electron microscopy (TEM), high-resolution TEM, Auger electron microscopy spectroscopy and differential thermal analysis (DTA), in the as-deposited state and after various heat treatments up to 500 deg. C. Initially, the Ti layers had a crystalline columnar grain structure displaying a (002) texture. The TiC layers displayed weak crystallinity with a pronounced (111) texture. In the course of the heat treatments, carbon diffused from the carbide layer into the adjacent Ti layers transforming the latter into off-stoichiometric TiC x with x≅0.5 and simultaneously depleting the carbon content of the initial carbide layer. The formed TiC x layers maintained the textural relationship with the neighboring TiC layers, consistent with a transformation that involved only a ABAB to ABC stacking change of the Ti sublattice. Increased mobility of the Ti atoms in carbon-depleted original TiC layers led to their full or partial recrystallization. The thermal effects associated both with the transformation of Ti layers into TiC, due to the influx of carbon atoms, and with the recrystallization of the original TiC layers were clearly revealed by the DTA measurements

  16. Snakes and spin rotators

    International Nuclear Information System (INIS)

    Lee, S.Y.

    1990-01-01

    The generalized snake configuration offers advantages of either shorter total snake length and smaller orbit displacement in the compact configuration or the multi-functions in the split configuration. We found that the compact configuration can save about 10% of the total length of a snake. On other hand, the spilt snake configuration can be used both as a snake and as a spin rotator for the helicity state. Using the orbit compensation dipoles, the spilt snake configuration can be located at any distance on both sides of the interaction point of a collider provided that there is no net dipole rotation between two halves of the snake. The generalized configuration is then applied to the partial snake excitation. Simple formula have been obtained to understand the behavior of the partial snake. Similar principle can also be applied to the spin rotators. We also estimate the possible snake imperfections are due to various construction errors of the dipole magnets. Accuracy of field error of better than 10 -4 will be significant. 2 refs., 5 figs

  17. (Ti, O)/Ti and (Ti, O, N)/Ti composite coatings fabricated via PIIID for the medical application of NiTi shape memory alloy.

    Science.gov (United States)

    Sun, Tao; Wang, Lang-Ping; Wang, Min

    2011-02-01

    In this investigation, the plasma immersion ion implantation and deposition (PIIID) technique was used to fabricate (Ti, O)/Ti or (Ti, O, N)/Ti coatings on a NiTi shape memory alloy (SMA, 50.8 at.% Ni) to improve its corrosion, wear resistance, and bioactivity. After coating fabrication, the structure and properties of composite coatings were studied, and the coated and uncoated NiTi SMA samples were compared with each other. Scanning electron microscopic (SEM) examination of coating surfaces and cross-sections showed that (Ti, O)/Ti and (Ti, O, N)/Ti composite coatings were dense and uniform, having thickness values of 1.16 ± 0.08 μm and 0.95 ± 0.06 μm, respectively. X-ray diffraction (XRD) results revealed that there were no diffraction peaks corresponding to TiO(2) or TiN for (Ti, O)/Ti and (Ti, O, N)/Ti composite coatings, suggesting that after the PIIID treatment, TiO(2) and TiN were amorphous or nanosized in the coatings. Energy dispersive X-ray (EDX) analysis indicated that the interface between the coating and NiTi SMA substrate was gradual rather than sharp. In addition, EDX elemental mapping of coating cross-sections showed that Ni was depleted from the surface. Differential scanning calorimetry (DSC) curves revealed that the shape memory ability of NiTi SMA was not degraded by the PIIID treatment. The width of wear tracks on (Ti, O, N)/Ti coated NiTi SMA samples was reduced 6.5-fold, in comparison with that on uncoated samples. The corrosion potential (E(corr) ) was improved from -466.20 ± 37.82 mV for uncoated samples to 125.50 ± 21.49 mV and -185.40 ± 37.05 mV for (Ti, O)/Ti coated and (Ti, O, N)/Ti coated samples, respectively. Both types of coatings facilitated bone-like apatite formation on the surface of NiTi SMA in simulated body fluid (SBF), indicating their in vitro bioactivity. Copyright © 2010 Wiley Periodicals, Inc.

  18. The transverse spin

    Energy Technology Data Exchange (ETDEWEB)

    Artru, X. [Institut de Physique Nucleaire de Lyon, IN2P3-CNRS, Universite Claude Bernard, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne (France)

    2002-07-01

    The aim of this introduction, which is far from exhaustive, was to give an overview on the richness of transverse spin quantity and its differences in comparison with helicity. From the experimental point of view, the physics of quark transversity in deep inelastic reaction is still practically unexplored. This situation will certainly change rapidly, with planned experiments at DESY (HERMES), Brookhaven (RHIC) and CERN (COMPAS), but there is a long way before knowing the transversity distribution, {delta}q(x), as precisely as the helicity distribution, {delta}q(x), now. Unless polarized anti-proton beams become feasible, experiments probing quark transversity will rely mainly on 'quark polarimeters', like {lambda}'s or the Collins effect. These polarimeters will have to be calibrated at e{sup +}e{sup -} colliders. The Collins polarimeter will by the way allow the flavor decomposition of {delta}q(x), using mesons of various charging and strangeness. Quark polarimetry is by itself an interesting topic of non-perturbative QCD, and may teach us something about the breaking of chiral symmetry. Let us recall that, if chiral symmetry were unbroken, transversity would be undefined. The transversity physics program is not at all a 'remake' of the helicity one. Helicity and transversity probe rather different aspects of the hadron structure. Differences between {delta}q(x) and {delta}q(x) will reveal non-relativistic effects in the baryon wave function. Also {delta}q(x) does not couples to gluon distributions, thus it is free from anomaly. In that respect it is a more clean probe than {delta}q(x). In fact, the combination of helicity and transversity measurements will perhaps be the most interesting. Polarized parton densities taking only the helicity degree of freedom are almost 'classical'. Quantum aspects of spin correlations, like violation of Bell's inequality, can be found only when varying the spin quantification axis

  19. Solar-light photocatalytic disinfection using crystalline/amorphous low energy bandgap reduced TiO2.

    Science.gov (United States)

    Kim, Youngmin; Hwang, Hee Min; Wang, Luyang; Kim, Ikjoon; Yoon, Yeoheung; Lee, Hyoyoung

    2016-04-28

    A generation of reactive oxygen species (ROS) from TiO2 under solar light has been long sought since the ROS can disinfect organic pollutants. We found that newly developed crystalline/amorphous reduced TiO2 (rTiO2) that has low energy bandgap can effectively generate ROS under solar light and successfully remove a bloom of algae. The preparation of rTiO2 is a one-pot and mass productive solution-process reduction using lithium-ethylene diamine (Li-EDA) at room temperature. Interestingly only the rutile phase of TiO2 crystal was reduced, while the anatase phase even in case of both anatase/rutile phased TiO2 was not reduced. Only reduced TiO2 materials can generate ROS under solar light, which was confirmed by electron spin resonance. Among the three different types of Li-EDA treated TiO2 (anatase, rutile and both phased TiO2), the both phased rTiO2 showed the best performance to produce ROS. The generated ROS effectively removed the common green algae Chlamydomonas. This is the first report on algae degradation under solar light, proving the feasibility of commercially available products for disinfection.

  20. Half metallic antiferromagnetic behavior in doped TiO2 rutile with double impurities (Os, Mo) from ab initio calculations

    International Nuclear Information System (INIS)

    Fakhim Lamrani, A.; Ouchri, M.; Belaiche, M.; El Kenz, A.

    2014-01-01

    Electronic and magnetic calculations were based on density functional theory within the generalized gradient approximation for II–VI compound semiconductor TiO 2 doped with single impurity Os and Mo; these compounds are half-metallic ferromagnets in their ground state with a total magnetic moment of 2μ B for both systems. Then, doping TiO 2 with double impurities (Os, Mo) was performed. As a result, Ti 1−2x Os x Mo x O 2 with x = 0.065 is a half-metallic antiferromagnet with 100% spin polarization of the conduction electrons crossing the Fermi level, without showing a net magnetization. Moreover, the Ti 14 OsMoO 32 compound is stable energetically than Ti 1−x Mo x O 2 and Ti 1−x Os x O 2 . The antiferromagnetic interaction in the Ti 1−2x Os x Mo x O 2 system is attributed to the double exchange mechanism, and the latter could also be the origin of their half-metallic behavior. - Highlights: • TiO 2 codoped with Os and Mo exhibits half-metallic diluted antiferromagnetic behavior. • TiO 2 doped with Mo exhibits half-metallic diluted ferromagnetic behavior. • TiO 2 doped with Os exhibits half-metallic diluted ferromagnetic behavior

  1. Domain growth by isothermal aging in 3D Ising and Heisenberg spin glasses.

    Science.gov (United States)

    Jönsson, P E; Yoshino, H; Nordblad, P; Aruga Katori, H; Ito, A

    2002-06-24

    Nonequilibrium dynamics of three-dimensional model spin glasses, the Ising system Fe0.50Mn0.50TiO3 and the Heisenberg-like system Ag(11 at % Mn), has been investigated by measurements of the isothermal time decay of the low frequency ac susceptibility after a quench from the paramagnetic to the spin-glass phase. It is found that the relaxation data measured at different temperatures can be scaled according to predictions from the droplet scaling model, provided that critical fluctuations are accounted for in the analyses.

  2. An injection modelocked Ti-sapphire laser for synchronous photoinjection

    International Nuclear Information System (INIS)

    Hovater, C.; Poelker, M.

    1997-01-01

    The CEBAF 4 GeV accelerator has recently begun delivering spin-polarized electrons for nuclear physics experiments. Spin-polarized electrons are emitted from a GaAs photocathode that is illuminated with pulsed laser light from a diode laser system synchronized to the injector chopping frequency (499 MHz). The present diode laser system is compact, reliable and relatively maintenance-free; however, output power is limited to less than 500 mW. In an effort to obtain higher average power and thereby prolong the effective operating lifetime of the source, they have constructed an injection modelocked Ti-sapphire laser with picosecond pulsewidths and gigahertz repetition rates. Modelocked operation is obtained through gain modulation within the Ti-sapphire crystal as a result of injection seeding with a gain-switched diode laser. Unlike conventional modelocked lasers, the pulse repetition rate of this laser can be discretely varied by setting the seed laser repetition rate equal to multiples of the Ti-sapphire laser cavity fundamental frequency. They observe pulse repetition rates from 223 MHz (fundamental) to 1,560 MHz (seventh harmonic) with average output power of 700 mW for all repetition rates. Pulsewidths ranged from 21 to 39 ps (FWHM) under various pump laser conditions

  3. Superconductive analogue of spin glasses

    International Nuclear Information System (INIS)

    Feigel'man, M.; Ioffe, L.; Vinokur, V.; Larkin, A.

    1987-07-01

    The properties of granular superconductors in magnetic fields, namely the existence of a new superconductive state analogue of the low-temperature superconductive state in spin glasses are discussed in the frame of the infinite-range model and the finite-range models. Experiments for elucidation of spin-glass superconductive state in real systems are suggested. 30 refs

  4. Spinning top—the question

    Science.gov (United States)

    Featonby, David

    2017-11-01

    The motion of a spinning top can be mystifying at times until some basic principles are understood. In this question the key to understanding what happens is the nature of the bottom tip of the top in contact with the surface on which it spins.

  5. Decoherence in Quantum Spin Systems

    NARCIS (Netherlands)

    De Raedt, H; Dobrovitski, VV; Landau, DP; Lewis, SP; Schuttler, HB

    2003-01-01

    Computer simulations of decoherence in quantum spin systems require the solution of the time-dependent Schrodinger equation for interacting quantum spin systems over extended periods of time. We use exact diagonalization, the Chebyshev polynomial technique, four Suzuki-formula algorithms, and the

  6. Nuclear Spins in Quantum Dots

    NARCIS (Netherlands)

    Erlingsson, S.I.

    2003-01-01

    The main theme of this thesis is the hyperfine interaction between the many lattice nuclear spins and electron spins localized in GaAs quantum dots. This interaction is an intrinsic property of the material. Despite the fact that this interaction is rather weak, it can, as shown in this thesis,

  7. Black Hole Spin Measurement Uncertainty

    Science.gov (United States)

    Salvesen, Greg; Begelman, Mitchell C.

    2018-01-01

    Angular momentum, or spin, is one of only two fundamental properties of astrophysical black holes, and measuring its value has numerous applications. For instance, obtaining reliable spin measurements could constrain the growth history of supermassive black holes and reveal whether relativistic jets are powered by tapping into the black hole spin reservoir. The two well-established techniques for measuring black hole spin can both be applied to X-ray binaries, but are in disagreement for cases of non-maximal spin. This discrepancy must be resolved if either technique is to be deemed robust. We show that the technique based on disc continuum fitting is sensitive to uncertainties regarding the disc atmosphere, which are observationally unconstrained. By incorporating reasonable uncertainties into black hole spin probability density functions, we demonstrate that the spin measured by disc continuum fitting can become highly uncertain. Future work toward understanding how the observed disc continuum is altered by atmospheric physics, particularly magnetic fields, will further strengthen black hole spin measurement techniques.

  8. SPIN PHYSICS: Lasers at work

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Lasers are now an everyday tool in particle physics, particularly for the spin polarization of beams, targets, and even short-lived particles. Development has been boosted in recent years by the availability of reliable multiwatt tunable lasers to select spin in an experimentally useful sample

  9. Josephson spin current in triplet superconductor junctions

    OpenAIRE

    Asano, Yasuhiro

    2006-01-01

    This paper theoretically discusses the spin current in spin-triplet superconductor / insulator / spin-triplet superconductor junctions. At low temperatures, a midgap Andreev resonant state anomalously enhances not only the charge current but also the spin current. The coupling between the Cooper pairs and the electromagnetic fields leads to the Frounhofer pattern in the direct current spin flow in magnetic fields and the alternative spin current under applied bias-voltages.

  10. Disorder and Quantum Spin Ice

    Science.gov (United States)

    Martin, N.; Bonville, P.; Lhotel, E.; Guitteny, S.; Wildes, A.; Decorse, C.; Ciomaga Hatnean, M.; Balakrishnan, G.; Mirebeau, I.; Petit, S.

    2017-10-01

    We report on diffuse neutron scattering experiments providing evidence for the presence of random strains in the quantum spin-ice candidate Pr2Zr2O7 . Since Pr3 + is a non-Kramers ion, the strain deeply modifies the picture of Ising magnetic moments governing the low-temperature properties of this material. It is shown that the derived strain distribution accounts for the temperature dependence of the specific heat and of the spin-excitation spectra. Taking advantage of mean-field and spin-dynamics simulations, we argue that the randomness in Pr2Zr2O7 promotes a new state of matter, which is disordered yet characterized by short-range antiferroquadrupolar correlations, and from which emerge spin-ice-like excitations. Thus, this study gives an original research route in the field of quantum spin ice.

  11. Disorder and Quantum Spin Ice

    Directory of Open Access Journals (Sweden)

    N. Martin

    2017-10-01

    Full Text Available We report on diffuse neutron scattering experiments providing evidence for the presence of random strains in the quantum spin-ice candidate Pr_{2}Zr_{2}O_{7}. Since Pr^{3+} is a non-Kramers ion, the strain deeply modifies the picture of Ising magnetic moments governing the low-temperature properties of this material. It is shown that the derived strain distribution accounts for the temperature dependence of the specific heat and of the spin-excitation spectra. Taking advantage of mean-field and spin-dynamics simulations, we argue that the randomness in Pr_{2}Zr_{2}O_{7} promotes a new state of matter, which is disordered yet characterized by short-range antiferroquadrupolar correlations, and from which emerge spin-ice-like excitations. Thus, this study gives an original research route in the field of quantum spin ice.

  12. Spin-lattice relaxation of individual solid-state spins

    Science.gov (United States)

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

    2018-03-01

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

  13. A Probabilistic Model of Spin and Spin Measurements

    Science.gov (United States)

    Niehaus, Arend

    2016-01-01

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

  14. Quantum Spin Liquids in Frustrated Spin-1 Diamond Antiferromagnets

    Science.gov (United States)

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

    2018-01-01

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

  15. Spin flexoelectricity and chiral spin structures in magnetic films

    International Nuclear Information System (INIS)

    Pyatakov, A.P.; Sergeev, A.S.; Mikailzade, F.A.; Zvezdin, A.K.

    2015-01-01

    In this short review a broad range of chiral phenomena observed in magnetic films (spin cycloid and skyrmion structures formation as well as chirality dependent domain wall motion) is considered under the perspective of spin flexoelectricity, i.e. the relation between bending of magnetization pattern and electric polarization. The similarity and the difference between the spin flexoelectricity and the newly emerged notion of spin flexomagnetism are discussed. The phenomenological arguments based on the geometrical idea of curvature-induced effects are supported by analysis of the microscopic mechanisms of spin flexoelectricity based on three-site ion indirect exchange and twisted RKKY interaction models. - Highlights: • Magnetic structure formation in thin films is analogous to flexoelectric phenomena in crystals. • The microscopic mechanism of spin flexoelectricity is the antisymmetric exchange. • Spin cycloid in thin film of metals can be the result of Rashba interaction in 2DEG. • The chirality-dependent Néel-type magnetic domain wall motion is observed in electric field

  16. Spin flexoelectricity and chiral spin structures in magnetic films

    Energy Technology Data Exchange (ETDEWEB)

    Pyatakov, A.P., E-mail: pyatakov@physics.msu.ru [M.V. Lomonosov Moscow State University, Leninskie gori, Moscow 119991 (Russian Federation); Sergeev, A.S. [M.V. Lomonosov Moscow State University, Leninskie gori, Moscow 119991 (Russian Federation); Mikailzade, F.A. [Department of Physics, Gebze Technical University, Gebze, 41400 Kocaeli (Turkey); Zvezdin, A.K. [A.M. Prokhorov General Physics Institute, Vavilova St., 38, Moscow 119991 (Russian Federation)

    2015-06-01

    In this short review a broad range of chiral phenomena observed in magnetic films (spin cycloid and skyrmion structures formation as well as chirality dependent domain wall motion) is considered under the perspective of spin flexoelectricity, i.e. the relation between bending of magnetization pattern and electric polarization. The similarity and the difference between the spin flexoelectricity and the newly emerged notion of spin flexomagnetism are discussed. The phenomenological arguments based on the geometrical idea of curvature-induced effects are supported by analysis of the microscopic mechanisms of spin flexoelectricity based on three-site ion indirect exchange and twisted RKKY interaction models. - Highlights: • Magnetic structure formation in thin films is analogous to flexoelectric phenomena in crystals. • The microscopic mechanism of spin flexoelectricity is the antisymmetric exchange. • Spin cycloid in thin film of metals can be the result of Rashba interaction in 2DEG. • The chirality-dependent Néel-type magnetic domain wall motion is observed in electric field.

  17. Spin Physics at COMPASS

    CERN Document Server

    Bradamante, Franco

    2005-01-01

    COMPASS is a new fixed target experiment presently in operation at CERN. It has the goal to investigate hadron structure and hadron spectroscopy by using either muon or hadron beams. From measurements of various hadron asymmetries in polarized muon - nucleon scattering it will be possible to determine the contribution of the gluons to the nucleon spin. Main objective of the hadron program is the search of exotic states, and glueballs in particular. This physics programme is carried out with a two-stage magnetic spectrometer, with particle identification and calorimetry in both stages, which has started collecting physics data in 2002, and will run at the CERN SPS at least until 2010. Preliminary results from the 2002 run with a 160 GeV muon beam are presented for several physics channels under investigation.

  18. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev

    2008-09-01

    Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.

  19. Gyroscopes may cease spinning

    Science.gov (United States)

    Martin, G. J.

    1986-02-01

    Laser gyroscopes have advantages compared to mechanical gyroscopes. Thus, they are more rugged and reliable, and, therefore, offer lower life-cycle costs. They are not yet more accurate than high-quality mechanical systems, but they have excellent development potential. Problems which can arise in the case of the spinning-rotor systems are related to their sensitivity to gravitational fields in the increasingly high-g environment of modern military aircraft. Optically based systems, on the other hand, have, in principle, no gravitational sensitivity and are in addition highly linear over a large dynamic range. The principles of operation of ring laser gyros (RLG) are discussed, taking into account the utilization of the Sagnac effect. Attention is given to the approaches found to overcome a number of engineering difficulties which arose in connection with the construction of RLG, techniques for limiting laser beam competition, aspects of geometry, and the current state of the art.

  20. Minimal model of spin-transfer torque and spin pumping caused by the spin Hall Effect

    Czech Academy of Sciences Publication Activity Database

    Chen, W.; Sigrist, M.; Sinova, Jairo; Manske, D.

    2016-01-01

    Roč. 115, č. 21 (2016), 1-5, č. článku 217203. ISSN 0031-9007 Institutional support: RVO:68378271 Keywords : spin tronics * spin Hall effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 8.462, year: 2016

  1. SpinS: Extending LTSmin with Promela through SpinJa

    NARCIS (Netherlands)

    van der Berg, Freark; van der Berg, Freark Iwert; Laarman, Alfons; Heljanko, K.; Knottenbelt, W.J.

    2012-01-01

    We show how PROMELA can be supported by the high-performance generic model checking tools of LTSMIN. The success of the SPIN model checker has made PROMELA an important modeling language. SPINJA was created as a Java implementation of SPIN, in an effort to make the model checker easily extendible

  2. Synthesis and characterization of TiO{sub 2} nanoparticle films coated with organic dyes

    Energy Technology Data Exchange (ETDEWEB)

    Rika [College of Engineering, Universiti Tenaga Nasional, 43009, Kajang, Selangor (Malaysia); Rahman, M.Y.A., E-mail: yusri@uniten.edu.m [College of Engineering, Universiti Tenaga Nasional, 43009, Kajang, Selangor (Malaysia); Salleh, M.M.; Umar, A.A. [Pusat Pengajian Fizik Gunaan, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia); Ahmad, A. [Pusat Pengajian Sains Kimia dan Teknologi Makanan, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia)

    2009-05-01

    The synthesis and characterization of TiO{sub 2} nanoparticle coated with organic dyes, coumarin and methyl orange was reported. The films were deposited onto ITO-covered glass substrate by controlled hydrolysis technique assisted with spin coating technique. The films were characterized by scanning electron microscope (SEM), X-ray dispersive (XRD) technique and ultraviolet-visible (UV-Vis) spectrophotometer. The average grain size of the TiO{sub 2} films is about 76 nm. The uncoated TiO{sub 2} film is crystalline with anatase and rutile structure. The coated TiO{sub 2} films with dye are also crystalline since the diffraction peaks have been observed at three angles. The maximum absorption of the film coated with coumarine dye is at 480 nm.

  3. Synthesis and characterization of TiO 2 nanoparticle films coated with organic dyes

    Science.gov (United States)

    Rika; Rahman, M. Y. A.; Salleh, M. M.; Umar, A. A.; Ahmad, A.

    2009-05-01

    The synthesis and characterization of TiO 2 nanoparticle coated with organic dyes, coumarin and methyl orange was reported. The films were deposited onto ITO-covered glass substrate by controlled hydrolysis technique asssited with spin coating technique. The films were characterized by scanning electron microscope (SEM), X-ray dispersive (XRD) technique and ultraviolet-visible (UV-Vis) spectrophotometer. The average grain size of the TiO 2 films is about 76 nm. The uncoated TiO 2 film is crystalline with anatase and rutile structure. The coated TiO 2 films with dye are also crystalline since the diffraction peaks have been observed at three angles. The maximum absorption of the film coated with coumarine dye is at 480 nm.

  4. Ferroelectric Properties of Nanoscale PbTiO3 Films by Hydrothemal Method

    International Nuclear Information System (INIS)

    Htet Htet Nwe; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

    2011-12-01

    Lead (II) nitride (Pb(NO3)2), titanium dioxide (TiO2) and potassium hydroxide (KOH) were used as starting materials. Lead titanate powder was formed by hydrothermal method at 150 C for 6h. The calcuim fluoride (CaF2) and titanium dioxide (TiO2) were separately adapted as intermediate layer on p-Si (100) substrate. Lead titanate thin film was formed onto CaF2/Si and TiO2/Si substrates by spin processor. 100kHz C-V characteristics of PbTiO3 films were measured by impedance analyzer (LCR meter). Polarization-electric field (P-E) characteristics were measured for both MFIS (Metal/ Ferroelectric/ Insulator/ Semiconductor) structures by applying the same triangular wave electric field in order to allow their application in NVFRAM (Non Volatile Ferroelectric Random Access Memory).

  5. The continuous spin limit of higher spin field equations

    Energy Technology Data Exchange (ETDEWEB)

    Bekaert, Xavier [Institut des Hautes Etudes Scientifiques, Le Bois-Marie, 35 route de Chartres, 91440 Bures-sur-Yvette (France); Mourad, Jihad [APC, Universite Paris VII, 2 place Jussieu, 75251 Paris Cedex 05 (France); LPT, Bat. 210, Universite Paris XI, 91405 Orsay Cedex (France)

    2006-01-15

    We show that the Wigner equations describing the continuous spin representations can be obtained as a limit of massive higher-spin field equations. The limit involves a suitable scaling of the wave function, the mass going to zero and the spin to infinity with their product being fixed. The result allows to transform the Wigner equations to a gauge invariant Fronsdal-like form. We also give the generalisation of the Wigner equations to higher dimensions with fields belonging to arbitrary representations of the massless little group.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    We develop a method for universally resolving the important issue of separating the inverse spin Hall effect (ISHE) from the spin rectification effect (SRE) signal. This method is based on the consideration that the two effects depend on the spin injection direction: The ISHE is an odd function of the spin injection direction while the SRE is independent on it. Thus, the inversion of the spin injection direction changes the ISHE voltage signal, while the SRE voltage remains. It applies generally to analyzing the different voltage contributions without fitting them to special line shapes. This fast and simple method can be used in a wide frequency range and has the flexibility of sample preparation.

  7. Generating magnetic response and half-metallicity in GaP via dilute Ti-doping for spintronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Hardev S. [Department of Physics, Panjab University, Chandigarh 160014 (India); Kashyap, Manish K., E-mail: manishdft@gmail.com [Department of Physics, Kurukshetra University, Kurukshetra 136119, Haryana (India); Kumar, Manoj [Department of Physics, Panjab University, Chandigarh 160014 (India); Kendriya Vidyalya No. 1, Kanchrapara, 743193 West Bengal (India); Thakur, Jyoti [Department of Physics, Kurukshetra University, Kurukshetra 136119, Haryana (India); Singh, Mukhtiyar [Department of Physics, Dyanand Postgraduate College, Hisar, 125001 Haryana (India); Reshak, Ali H. [New Technologies – Research Centre, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Saini, G.S.S. [Department of Physics, Panjab University, Chandigarh 160014 (India)

    2015-11-15

    Existence of band gap in one spin channel and metallic character in other leads to interesting magnetic and optical properties of any material. These materials are capable to generate fully spin polarized current and are responsible for maximizing the efficiency of spintronic devices. The present work explores the electronic and magnetic properties of Ti-doped GaP compound with dopant concentrations; x = 0.02, 0.03 and 0.06 in order to search new Diluted Magnetic Semiconductor (DMS) compounds as spintronic materials using full potential linearized augmented plane wave plus local orbitals (FPLAPW + lo) method. The generalized gradient approximation (GGA) is used to decide exact exchange-correlation (XC) potentials. The calculated results showed that the total magnetic moment of ∼1.00 μ{sub B} gets induced after Ti-doping in GaP at all dopant concentrations, irrespective of any magnetic element present. Further, this doping also generates half-metallicity in GaP with a half-metallic (HM) gap at Fermi level (E{sub F}) in minority spin channel. The half metallicity is originated by the hybridization of Ti-d states with P–p states. This induced magnetism appeared in the systems is the result of exchange interactions between host (GaP) and Ti-atom. - Highlights: • Dilute doping of Ti in Gap is addressed to produce authenticate theoretical data. • Ti-doping generates band gap at Fermi level in minority spin channel. • Magnetism appeared is the result of exchange interactions between host (GaP) and Ti. • Magnetic moment remains constant within studied dopant concentrations.

  8. Spin Hall effect, Hall effect and spin precession in diffusive normal metals

    OpenAIRE

    Shchelushkin, R. V.; Brataas, Arne

    2005-01-01

    We study transport in normal metals in an external magnetic field. This system exhibits an interplay between a transverse spin imbalance (spin Hall effect) caused by the spin-orbit interaction, a Hall effect via the Lorentz force, and spin precession due to the Zeeman effect. Diffusion equations for spin and charge flow are derived. The spin and charge accumulations are computed numerically in experimentally relevant thin film geometries. The out-of-plane spin Hall potential is suppressed whe...

  9. Spin transport in epitaxial graphene

    Science.gov (United States)

    Tbd, -

    2014-03-01

    Spintronics is a paradigm focusing on spin as the information vector in fast and ultra-low-power non volatile devices such as the new STT-MRAM. Beyond its widely distributed application in data storage it aims at providing more complex architectures and a powerful beyond CMOS solution for information processing. The recent discovery of graphene has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices. We will present experimental results allowing us to assess the potential of graphene for spintronics. We will show that unprecedented highly efficient spin information transport can occur in epitaxial graphene leading to large spin signals and macroscopic spin diffusion lengths (~ 100 microns), a key enabler for the advent of envisioned beyond-CMOS spin-based logic architectures. We will also show that how the device behavior is well explained within the framework of the Valet-Fert drift-diffusion equations. Furthermore, we will show that a thin graphene passivation layer can prevent the oxidation of a ferromagnet, enabling its use in novel humide/ambient low-cost processes for spintronics devices, while keeping its highly surface sensitive spin current polarizer/analyzer behavior and adding new enhanced spin filtering property. These different experiments unveil promising uses of graphene for spintronics.

  10. The Rashba spin-orbit coupling for superconductivity in oxide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Beyl, Stefan; Orth, Peter P.; Schmalian, Joerg [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie, Karlsruhe (Germany)

    2014-07-01

    We investigate the role of the Rashba spin-orbit coupling on the superconducting order parameter and the phase stiffness at the interface of LaAlO{sub 3} and SrTiO{sub 3}. In particular, we analyze the gate controlled crossover between BCS superconductivity and Bose-Einstein condensation of Cooper pairs, amplified by the Rashba coupling and the possibility of a phase fluctuation induced quantum critical point.

  11. High-Spin States in Odd-Odd N=Z {sup 46}V

    Energy Technology Data Exchange (ETDEWEB)

    O' Leary, C.D.; Bentley, M.A.; Appelbe, D.E.; Bark, R.A.; Cullen, D.M.; Erturk, S.; Maj. A.; Sheikh, J.A.; Warner, D.D.

    1999-12-31

    High-spin states up to the F{sub 7/2}-shell band termination at J{pi}=15+ have been observed for the first time in the odd-odd N=Z=23 nucleous {sup 46}V. The new level scheme has two separate structures corresponding to spherical and prolate shapes. A rotational band has very similar energies to the yrast sequence in {sup 46}Ti and is therefore assumed to be a T=1 configuration.

  12. Spin Hall effect-driven spin torque in magnetic textures

    KAUST Repository

    Manchon, Aurelien

    2011-07-13

    Current-induced spin torque and magnetization dynamics in the presence of spin Hall effect in magnetic textures is studied theoretically. The local deviation of the charge current gives rise to a current-induced spin torque of the form (1 - ΒM) × [(u 0 + αH u 0 M) ∇] M, where u0 is the direction of the injected current, H is the Hall angle and is the non-adiabaticity parameter due to spin relaxation. Since αH and ×can have a comparable order of magnitude, we show that this torque can significantly modify the current-induced dynamics of both transverse and vortex walls. © 2011 American Institute of Physics.

  13. Spin and torsion in gravitation

    CERN Document Server

    De Sabbata, Venzo

    1994-01-01

    This book gives an exposition of both the old and new results of spin and torsion effects on gravitational interactions with implications for particle physics, cosmology etc. Physical aspects are stressed and measurable effects in relation to other areas of physics are discussed.Among the topics discussed are: alternative ways of unifying gravity with electroweak and strong interactions by an energy dependent spin torsion coupling constant; the idea that all interactions can be understood as originating from spin curvature coupling; the possibility of cosmological models with torsion providing

  14. Spinning fluids in general relativity

    Science.gov (United States)

    Ray, J. R.; Smalley, L. L.

    1982-01-01

    General relativity field equations are employed to examine a continuous medium with internal spin. A variational principle formerly applied in the special relativity case is extended to the general relativity case, using a tetrad to express the spin density and the four-velocity of the fluid. An energy-momentum tensor is subsequently defined for a spinning fluid. The equations of motion of the fluid are suggested to be useful in analytical studies of galaxies, for anisotropic Bianchi universes, and for turbulent eddies.

  15. Spectroscopic study of 44Ti by reactions 40Ca(α,γ)44Ti, 40Ca(7Li,p2nγ)44Ti and 42Ca(α,2nγ)44Ti

    International Nuclear Information System (INIS)

    Britz, Jean.

    1980-01-01

    The first reaction allowed to populate states of excitation energies between 9.2 and 9.8 MeV and to measure their γ-decays to low-lying states in 44 Ti. Moreover this reaction helps in measuring the mean lifetime of 12 states by using the Doppler shift attenuation method. The second reaction was used to find the levels predicted by the shell model and among them the highest spin allowed Jsup(π)=12 + . The third reaction helps in measuring the mean lifetime tau=3.0+-0.6 ns of the Jsup(π)=(12 + ) state at Esub(x)=8.040 MeV. In this measurement the delayed coincidence technique with a pulsed beam was used. A confrontation of the experimental and theoretical studies on the 44 Ti nucleus is presented in this work [fr

  16. Spin-spin correlations in the tt'-Hubbard model

    International Nuclear Information System (INIS)

    Husslein, T.; Newns, D.M.; Mattutis, H.G.; Pattnaik, P.C.; Morgenstern, I.; Singer, J.M.; Fettes, W.; Baur, C.

    1994-01-01

    We present calculations of the tt'-Hubbard model using Quantum Monte Carlo techniques. The parameters are chosen so that the van Hove Singularity in the density of states and the Fermi level coincide. We study the behaviour of the system with increasing Hubbard interaction U. Special emphasis is on the spin-spin correlation (SSC). Unusual behaviour for large U is observed there and in the momentum distribution function (n(q)). (orig.)

  17. Protein Corona Prevents TiO2 Phototoxicity.

    Directory of Open Access Journals (Sweden)

    Maja Garvas

    Full Text Available TiO2 nanoparticles have generally low toxicity in the in vitro systems although some toxicity is expected to originate in the TiO2-associated photo-generated radical production, which can however be modulated by the radical trapping ability of the serum proteins. To explore the role of serum proteins in the phototoxicity of the TiO2 nanoparticles we measure viability of the exposed cells depending on the nanoparticle and serum protein concentrations.Fluorescence and spin trapping EPR spectroscopy reveal that the ratio between the nanoparticle and protein concentrations determines the amount of the nanoparticles' surface which is not covered by the serum proteins and is proportional to the amount of photo-induced radicals. Phototoxicity thus becomes substantial only at the protein concentration being too low to completely coat the nanotubes' surface.These results imply that TiO2 nanoparticles should be applied with ligands such as proteins when phototoxic effects are not desired - for example in cosmetics industry. On the other hand, the nanoparticles should be used in serum free medium or any other ligand free medium, when phototoxic effects are desired - as for efficient photodynamic cancer therapy.

  18. Spin tunneling and manipulation in nanostructures.

    Science.gov (United States)

    Sherman, E Ya; Ban, Yue; Gulyaev, L V; Khomitsky, D V

    2012-09-01

    The results for joint effects of tunneling and spin-orbit coupling on spin dynamics in nanostructures are presented for systems with discrete and continuous spectra. We demonstrate that tunneling plays the crucial role in the spin dynamics and the abilities of spin manipulation by external electric field. This result can be important for design of nanostructures-based spintronics devices.

  19. RESEARCH PLAN FOR SPIN PHYSICS AT RHIC.

    Energy Technology Data Exchange (ETDEWEB)

    AIDALA, C.; BUNCE, G.; ET AL.

    2005-02-01

    In this report we present the research plan for the RHIC spin program. The report covers (1) the science of the RHIC spin program in a world-wide context; (2) the collider performance requirements for the RHIC spin program; (3) the detector upgrades required, including timelines; (4) time evolution of the spin program.

  20. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

    I give some experimental and theoretical background to spin glasses, and then discuss the nature of the phase transition in spin glasses with vector spins. Results of Monte Carlo simulations of the Heisenberg spin glass model in three dimensions are presented. A finite-size scaling analysis of the correlation length of the ...

  1. Some recent developments in spin glasses

    Indian Academy of Sciences (India)

    Abstract. I give some experimental and theoretical background to spin glasses, and then discuss the nature of the phase transition in spin glasses with vector spins. Results of Monte Carlo simulations of the Heisenberg spin glass model in three dimensions are presented. A finite-size scaling analysis of the correlation length ...

  2. Phase space representations for spin23

    International Nuclear Information System (INIS)

    Polubarinov, I.V.

    1991-01-01

    General properties of spin matrices and density ones are considered for any spin s. For spin 2 3 phase space representations are constructed. Representations, similar to the Bell one, for the correlator of projections of two spins 2 3 in the singlet state are found. Quantum analogs of the Bell inequality are obtained. 14 refs

  3. SPIN SUSCEPTIBILITY IN HIGH - TC SUPERCONDUCTIVITY

    African Journals Online (AJOL)

    USER

    2012-07-05

    Jul 5, 2012 ... Anderson (KGA)rules(Suzuki,Suzuki,2009) will upturn the. Cu spins. It turns that this process introduces the now measurable spin fluctuations in the cuprates. The AFM sublattices contain two spin magnetic moments as we know and according to basic theory of magnetism, equal and opposite spin currents ...

  4. Hierarchical structure and photocatalysis performance of the photo-anode TiO2 film

    Science.gov (United States)

    Guli, Mina; Deng, Minghan; Bimenyimana, Theogene; Hu, Zhe

    2017-11-01

    We herein present a useful technique to design photo-anode films by composing P25 nanoparticles (NPs) with TiO2 nanorod or TiO2 nanotube arrays to optimize the photocatalysis property and overall property of dye-sensitized solar cells (DSSCs). After solvothermal and spin-coating process, an interesting hierarchical film containing one-dimensional (1D) TiO2 film and P25 NPs (1D TiO2/P25) was obtained on a fluorine-doped tin oxide substrate. In our study, P25 NPs with high specific surface area can potentially adsorb large numbers of dye molecules when 1D TiO2 arrays provide a straight path for rapid transmission of photo-generated electrons. From the experiment results, the hierarchical photo-anodes indeed exhibit superior properties than that of pristine 1D films. The photoelectric conversion efficiency improves up to 3.96 and 3.69% based on 1D TiO2/P25 DSSCs, which are significantly higher than those of 3.21 and 2.70% of the DSSCs based on 1D TiO2 photoanodes.

  5. Topological-Sector Fluctuations and Curie-Law Crossover in Spin Ice

    Directory of Open Access Journals (Sweden)

    L. D. C. Jaubert

    2013-02-01

    Full Text Available At low temperatures, a spin ice enters a Coulomb phase—a state with algebraic correlations and topologically constrained spin configurations. We show how analytical and numerical approaches for model spin-ice systems reveal a crossover between two Curie laws. One of these laws characterizes the high-temperature paramagnetic regime, while the other, which we call the “spin-liquid Curie law,” characterizes the low-temperature Coulomb-phase regime, which provides implicit evidence that the topological sector fluctuates. We compare our theory with experiment for Ho_{2}Ti_{2}O_{7}, where this process leads to a nonstandard temperature evolution of the bulk susceptibility and the wave-vector-dependent magnetic susceptibility, as measured by neutron scattering. Theory and experiment agree for bulk quantities and at large scattering wave vectors, but differences at small wave vectors indicate that the classical spin-ice states are not equally populated at low temperatures. More generally, the crossover appears to be a generic property of the emergent gauge field for a classical spin liquid, and it sheds light on the experimental difficulty of measuring a precise Curie-Weiss temperature in frustrated materials. The susceptibility at finite wave vectors is shown to be a local probe of fluctuations among topological sectors on varying length scales.

  6. Magnetoelectric control of spin currents

    Energy Technology Data Exchange (ETDEWEB)

    Gómez, J. E.; Vargas, J. M.; Avilés-Félix, L.; Butera, A. [Centro Atómico Bariloche, Instituto de Nanociencia y Nanotecnología (CNEA) and Conicet, 8400 Bariloche, Río Negro (Argentina)

    2016-06-13

    The ability to control the spin current injection has been explored on a hybrid magnetoelectric system consisting of a (011)-cut ferroelectric lead magnesium niobate-lead titanate (PMNT) single crystal, a ferromagnetic FePt alloy, and a metallic Pt. With this PMNT/FePt/Pt structure we have been able to control the magnetic field position or the microwave excitation frequency at which the spin pumping phenomenon between FePt and Pt occurs. We demonstrate that the magnetoelectric heterostructure operating in the L-T (longitudinal magnetized-transverse polarized) mode couples the PMNT crystal to the magnetostrictive FePt/Pt bilayer, displaying a strong magnetoelectric coefficient of ∼140 Oe cm kV{sup −1}. Our results show that this mechanism can be effectively exploited as a tunable spin current intensity emitter and open the possibility to create an oscillating or a bistable switch to effectively manipulate spin currents.

  7. Magnetoelectric control of spin currents

    International Nuclear Information System (INIS)

    Gómez, J. E.; Vargas, J. M.; Avilés-Félix, L.; Butera, A.

    2016-01-01

    The ability to control the spin current injection has been explored on a hybrid magnetoelectric system consisting of a (011)-cut ferroelectric lead magnesium niobate-lead titanate (PMNT) single crystal, a ferromagnetic FePt alloy, and a metallic Pt. With this PMNT/FePt/Pt structure we have been able to control the magnetic field position or the microwave excitation frequency at which the spin pumping phenomenon between FePt and Pt occurs. We demonstrate that the magnetoelectric heterostructure operating in the L-T (longitudinal magnetized-transverse polarized) mode couples the PMNT crystal to the magnetostrictive FePt/Pt bilayer, displaying a strong magnetoelectric coefficient of ∼140 Oe cm kV −1 . Our results show that this mechanism can be effectively exploited as a tunable spin current intensity emitter and open the possibility to create an oscillating or a bistable switch to effectively manipulate spin currents.

  8. Spin Structure Analyses of Antiferromagnets

    International Nuclear Information System (INIS)

    Chung, Jae Ho; Song, Young Sang; Lee, Hak Bong

    2010-05-01

    We have synthesized series of powder sample of incommensurate antiferromagnetic multiferroics, (Mn, Co)WO 4 and Al doped Ba 0.5 Sr 1.5 Zn 2 Fe 12 O 22 , incommensurate antiferromagnetic multiferroics. Their spin structure was studied by using the HRPD. In addition, we have synthesized series of crystalline samples of incommensurate multiferroics, (Mn, Co)WO 4 and olivines. Their spin structure was investigated using neutron diffraction under high magnetic field. As a result, we were able to draw the phase diagram of (Mn, Co)WO 4 as a function of composition and temperature. We learned the how the spin structure changes with increased ionic substitution. Finally we have drawn the phase diagram of the multicritical olivine Mn2SiS4/Mn2GeS4 as a function of filed and temperature through the spin structure studies

  9. spinning self-dual particles

    International Nuclear Information System (INIS)

    Gamboa, J.; Rivelles, V.O.

    1989-01-01

    Self-dual particles in two-dimensions are presented. They were obtained from chiral boson particle by square root technique. The propagator of spinning self-dual particle is calculated using the BFV formalism. (M.C.K.)

  10. The strain induced band gap modulation from narrow gap semiconductor to half-metal on Ti2CrGe: A first principles study

    Directory of Open Access Journals (Sweden)

    Jia Li

    2015-11-01

    Full Text Available The Heusler alloy Ti2CrGe is a stable L21 phase with antiferromagnetic ordering. With band-gap energy (∼ 0.18 eV obtained from a first-principles calculation, it belongs to the group of narrow band gap semiconductor. The band-gap energy decreases with increasing lattice compression and disappears until a strain of −5%; moreover, gap contraction only occurs in the spin-down states, leading to half-metallic character at the −5% strain. The Ti1, Ti2, and Cr moments all exhibit linear changes in behavior within strains of −5%– +5%. Nevertheless, the total zero moment is robust for these strains. The imaginary part of the dielectric function for both up and down spin states shows a clear onset energy, indicating a corresponding electronic gap for the two spin channels.

  11. Spin and charge transport in the presence of spin-orbit interaction

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 2. Spin and ... We present the study of spin and charge transport in nanostructures in the presence of spin-orbit (SO) interaction. ... Using these tight binding Hamiltonians and spin resolved Landauer–Büttiker formula, spin and charge transport is studied.

  12. Formation of TiO2 domains in Poly (9-vinylcarbazole) thin film by hydrolysis-condensation of a metal alkoxide

    International Nuclear Information System (INIS)

    Barlier, V.; Bounor-Legare, V.; Alcouffe, P.; Boiteux, G.; Davenas, J.

    2007-01-01

    New organic-inorganic hybrid thin films based on Poly (9-vinylcarbazole) (P9VK) and Dioxide titanium (TiO 2 ) bulk-heterojunction were obtained by a hydrolysis-condensation (H-C) process of titanium (IV) isopropoxide in thin film. The TiO 2 distribution in the film was investigated by scanning electron microscopy. The results indicated that homogeneous TiO 2 particles around 100 nm were formed on the surface of the polymer thin film. Photoluminescence spectroscopy has been used to study the charge transfer efficiency in the photoactive layer and results were compared with a simplest elaboration route, the dispersion of TiO 2 anatase in a P9VK solution before spin coating. Results showed that TiO 2 elaborated by H-C exhibits a competitive quenching effect with TiO 2 anatase

  13. Formation of TiO{sub 2} domains in Poly (9-vinylcarbazole) thin film by hydrolysis-condensation of a metal alkoxide

    Energy Technology Data Exchange (ETDEWEB)

    Barlier, V. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Bounor-Legare, V. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Alcouffe, P. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Boiteux, G. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Davenas, J. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France)]. E-mail: joel.davenas@univ-lyon1.fr

    2007-06-04

    New organic-inorganic hybrid thin films based on Poly (9-vinylcarbazole) (P9VK) and Dioxide titanium (TiO{sub 2}) bulk-heterojunction were obtained by a hydrolysis-condensation (H-C) process of titanium (IV) isopropoxide in thin film. The TiO{sub 2} distribution in the film was investigated by scanning electron microscopy. The results indicated that homogeneous TiO{sub 2} particles around 100 nm were formed on the surface of the polymer thin film. Photoluminescence spectroscopy has been used to study the charge transfer efficiency in the photoactive layer and results were compared with a simplest elaboration route, the dispersion of TiO{sub 2} anatase in a P9VK solution before spin coating. Results showed that TiO{sub 2} elaborated by H-C exhibits a competitive quenching effect with TiO{sub 2} anatase.

  14. Spin Hall effect by surface roughness

    KAUST Repository

    Zhou, Lingjun

    2015-01-08

    The spin Hall and its inverse effects, driven by the spin orbit interaction, provide an interconversion mechanism between spin and charge currents. Since the spin Hall effect generates and manipulates spin current electrically, to achieve a large effect is becoming an important topic in both academia and industries. So far, materials with heavy elements carrying a strong spin orbit interaction, provide the only option. We propose here a new mechanism, using the surface roughness in ultrathin films, to enhance the spin Hall effect without heavy elements. Our analysis based on Cu and Al thin films suggests that surface roughness is capable of driving a spin Hall angle that is comparable to that in bulk Au. We also demonstrate that the spin Hall effect induced by surface roughness subscribes only to the side-jump contribution but not the skew scattering. The paradigm proposed in this paper provides the second, not if only, alternative to generate a sizable spin Hall effect.

  15. Spin-controlled atom-ion chemistry.

    Science.gov (United States)

    Sikorsky, Tomas; Meir, Ziv; Ben-Shlomi, Ruti; Akerman, Nitzan; Ozeri, Roee

    2018-03-02

    Quantum control of chemical reactions is an important goal in chemistry and physics. Ultracold chemical reactions are often controlled by preparing the reactants in specific quantum states. Here we demonstrate spin-controlled atom-ion inelastic (spin-exchange) processes and chemical (charge-exchange) reactions in an ultracold Rb-Sr + mixture. The ion's spin state is controlled by the atomic hyperfine spin state via spin-exchange collisions, which polarize the ion's spin parallel to the atomic spin. We achieve ~ 90% spin polarization due to the absence of strong spin-relaxation channel. Charge-exchange collisions involving electron transfer are only allowed for (RbSr) + colliding in the singlet manifold. Initializing the atoms in various spin states affects the overlap of the collision wave function with the singlet molecular manifold and therefore also the reaction rate. Our observations agree with theoretical predictions.

  16. Muon spin rotation in solids

    Science.gov (United States)

    Stronach, C. E.

    1983-01-01

    The muon spin rotation (MuSR) technique is used to probe the microscopic electron density in materials. High temperature MuSR and magnetization measurements in nickel are in progress to allow an unambiguous determination of the muon impurity interaction and the impurity induced change in local spin density. The first results on uniaxial stress induced frequency shifts in an Fe single crystal are also reported.

  17. Excitations and spin waves

    International Nuclear Information System (INIS)

    Lindgaard, P.-A.

    1978-01-01

    When neutron scattering data became available for the light rare earths (REs) and the RE compounds, a need was felt for a systematic theory for excitations in crystal-field dominated systems. The crystal field mixes the wavefunctions and provides a coupling between the ground state and the excited states for many operators, whereas for the Heisenberg system only J - has a nonzero matrix element to the first excited state. A review is given of successful applications of the theory in the interpretation of several experiments. The excitation spectrum for neutron scattering is simply given by the poles of the imaginary part of the enhanced wave-vector-dependent susceptibility tensor calculated in the random-phase approximation. A discussion of the effect of two-ion anisotropy is given. The formalism reduces to the conventional spin wave theory for the Heisenberg system when the crystal field is negligible compared to the exchange interaction. However, this theory has the drawback that it is necessary to know the crystal field in advance and each value of J must then be treated separately. A review of the results in the RE Laves-phase compounds and in the heavy rare earths is given, and the status of the current understanding of the interactions is rare earths and their compounds is discussed. (author)

  18. Spin physics at RHIC

    International Nuclear Information System (INIS)

    Tannenbaum, M.J.

    1996-01-01

    Operation of RHIC with two beams of highly polarized protons (70%, either longitudinal or transverse) at high luminosity L = 2 x 10 32 cm -2 sec -1 for two months/year will allow the STAR and PHENIX detectors to perform high statististics studies of polarization phenomena in the perturbative region of hard scattering where both QCD and ElectroWeak theory make detailed predictions for polarization effects. The collision c.m. energy, √s = 200 - 500 GeV, represents a new domain for the study of spin. Direct photon production will be used to measure the gluon polarization in the polarized proton. A new twist comes from W-boson production which is expected to be 100% parity violating and will thus allow measurements of flavor separated Quark and antiquark (u, bar u, d, bar d) polarization distributions. Searches for parity violation in strong interaction processes such as jet and leading particle production will be a sensitive way to look for new physics beyond the standard model, one possibility being quark substructure

  19. Two Wien Filter Spin Flipper

    Energy Technology Data Exchange (ETDEWEB)

    Grames, J M; Benesch, J F; Clark, J; Hansknecht, J; Kazimi, R; Machie, D; Poelker, M; Stutzman, M L; Suleiman, R

    2011-03-01

    A new 4pi spin manipulator composed of two Wien filters oriented orthogonally and separated by two solenoids has been installed at the CEBAF/Jefferson Lab photoinjector. The new spin manipulator is used to precisely set the electron spin direction at an experiment in any direction (in or out of plane of the accelerator) and provides the means to reverse, or flip, the helicity of the electron beam on a daily basis. This reversal is being employed to suppress systematic false asymmetries that can jeopardize challenging parity violation experiments that strive to measure increasingly small physics asymmetries [*,**,***]. The spin manipulator is part of the ultra-high vacuum polarized electron source beam line and has been successfully operated with 100keV and 130keV electron beam at high current (>100 microAmps). A unique feature of the device is that spin-flipping requires only the polarity of one solenoid magnet be changed. Performance characteristics of the Two Wien Filter Spin Flipper will be summarized.

  20. Positivity of spin foam amplitudes

    International Nuclear Information System (INIS)

    Baez, John C; Christensen, J Daniel

    2002-01-01

    The amplitude for a spin foam in the Barrett-Crane model of Riemannian quantum gravity is given as a product over its vertices, edges and faces, with one factor of the Riemannian 10j symbols appearing for each vertex, and simpler factors for the edges and faces. We prove that these amplitudes are always nonnegative for closed spin foams. As a corollary, all open spin foams going between a fixed pair of spin networks have real amplitudes of the same sign. This means one can use the Metropolis algorithm to compute expectation values of observables in the Riemannian Barrett-Crane model, as in statistical mechanics, even though this theory is based on a real-time (e iS ) rather than imaginary-time e -S path integral. Our proof uses the fact that when the Riemannian 10j symbols are nonzero, their sign is positive or negative depending on whether the sum of the ten spins is an integer or half-integer. For the product of 10j symbols appearing in the amplitude for a closed spin foam, these signs cancel. We conclude with some numerical evidence suggesting that the Lorentzian 10j symbols are always nonnegative, which would imply similar results for the Lorentzian Barrett-Crane model

  1. Experimental Realization of a Quantum Spin Pump

    DEFF Research Database (Denmark)

    Watson, Susan; Potok, R.; M. Marcus, C.

    2003-01-01

    We demonstrate the operation of a quantum spin pump based on cyclic radio-frequency excitation of a GaAs quantum dot, including the ability to pump pure spin without pumping charge. The device takes advantage of bidirectional mesoscopic fluctuations of pumped current, made spin......-dependent by the application of an in-plane Zeeman field. Spin currents are measured by placing the pump in a focusing geometry with a spin-selective collector....

  2. Spin stabilized magnetic levitation of horizontal rotors.

    Energy Technology Data Exchange (ETDEWEB)

    Romero, Louis Anthony

    2004-10-01

    In this paper we present an analysis of a new configuration for achieving spin stabilized magnetic levitation. In the classical configuration, the rotor spins about a vertical axis; and the spin stabilizes the lateral instability of the top in the magnetic field. In this new configuration the rotor spins about a horizontal axis; and the spin stabilizes the axial instability of the top in the magnetic field.

  3. Thermal entanglement properties of small spin clusters

    OpenAIRE

    Bose, Indrani; Tribedi, Amit

    2005-01-01

    Exchange interactions in spin systems can give rise to quantum entanglement in the ground and thermal states of the systems. In this paper, we consider a spin tetramer, with spins of magnitude 1/2, in which the spins interact via nearest-neighbour, diagonal and four-spin interactions of strength J1, J2 and K respectively. The ground and thermal state entanglement properties of the tetramer are calculated analytically in the various limiting cases. Signatures of quantum phase transition (QPT) ...

  4. Quantum spin transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Christoph

    2012-05-15

    In this work, we study and quantitatively predict the quantum spin Hall effect, the spin-orbit interaction induced intrinsic spin-Hall effect, spin-orbit induced magnetizations, and spin-polarized electric currents in nanostructured two-dimensional electron or hole gases with and without the presence of magnetic fields. We propose concrete device geometries for the generation, detection, and manipulation of spin polarization and spin-polarized currents. To this end a novel multi-band quantum transport theory, that we termed the multi-scattering Buettiker probe model, is developed. The method treats quantum interference and coherence in open quantum devices on the same footing as incoherent scattering and incorporates inhomogeneous magnetic fields in a gauge-invariant and nonperturbative manner. The spin-orbit interaction parameters that control effects such as band energy spin splittings, g-factors, and spin relaxations are calculated microscopically in terms of an atomistic relativistic tight-binding model. We calculate the transverse electron focusing in external magnetic and electric fields. We have performed detailed studies of the intrinsic spin-Hall effect and its inverse effect in various material systems and geometries. We find a geometry dependent threshold value for the spin-orbit interaction for the inverse intrinsic spin-Hall effect that cannot be met by n-type GaAs structures. We propose geometries that spin polarize electric current in zero magnetic field and analyze the out-of-plane spin polarization by all electrical means. We predict unexpectedly large spin-orbit induced spin-polarization effects in zero magnetic fields that are caused by resonant enhancements of the spin-orbit interaction in specially band engineered and geometrically designed p-type nanostructures. We propose a concrete realization of a spin transistor in HgTe quantum wells, that employs the helical edge channel in the quantum spin Hall effect.

  5. Amplification of spin-current polarization

    Science.gov (United States)

    Saha, D.; Holub, M.; Bhattacharya, P.

    2007-08-01

    A ferromagnet/semiconductor based electrically controlled spin-current amplifier using a dual-drain nonlocal lateral spin valve is demonstrated. The spin polarization injected by the source into the channel is amplified at the second drain contact. An amplified current spin polarization of 100% is measured. The controlled variation of amplifier gain with bias is also demonstrated. The observations are explained in the framework of the spin drift-diffusion model.

  6. Quantum spin transport in semiconductor nanostructures

    International Nuclear Information System (INIS)

    Schindler, Christoph

    2012-01-01

    In this work, we study and quantitatively predict the quantum spin Hall effect, the spin-orbit interaction induced intrinsic spin-Hall effect, spin-orbit induced magnetizations, and spin-polarized electric currents in nanostructured two-dimensional electron or hole gases with and without the presence of magnetic fields. We propose concrete device geometries for the generation, detection, and manipulation of spin polarization and spin-polarized currents. To this end a novel multi-band quantum transport theory, that we termed the multi-scattering Buettiker probe model, is developed. The method treats quantum interference and coherence in open quantum devices on the same footing as incoherent scattering and incorporates inhomogeneous magnetic fields in a gauge-invariant and nonperturbative manner. The spin-orbit interaction parameters that control effects such as band energy spin splittings, g-factors, and spin relaxations are calculated microscopically in terms of an atomistic relativistic tight-binding model. We calculate the transverse electron focusing in external magnetic and electric fields. We have performed detailed studies of the intrinsic spin-Hall effect and its inverse effect in various material systems and geometries. We find a geometry dependent threshold value for the spin-orbit interaction for the inverse intrinsic spin-Hall effect that cannot be met by n-type GaAs structures. We propose geometries that spin polarize electric current in zero magnetic field and analyze the out-of-plane spin polarization by all electrical means. We predict unexpectedly large spin-orbit induced spin-polarization effects in zero magnetic fields that are caused by resonant enhancements of the spin-orbit interaction in specially band engineered and geometrically designed p-type nanostructures. We propose a concrete realization of a spin transistor in HgTe quantum wells, that employs the helical edge channel in the quantum spin Hall effect.

  7. Magnetic Anisotropy, Damping and Interfacial Spin Transport in Pt/LSMO Bilayers

    Science.gov (United States)

    Lee, Han Kyu

    In this thesis, I describe ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO 3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal significant negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that both are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low alpha = 1.9(1) x 10-3, and two-magnon scattering is determined to be significant and strongly anisotropic in the plane of the film. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. This work demonstrates efficient spin transport across the Pt/LSMO interface.

  8. The critical properties of the BaxSr1-xTiO3 solid solution

    International Nuclear Information System (INIS)

    Saber, M.; Ainane, A.; Essaoudi, I.; Baerner, K.; Gonzalez, J.

    2009-01-01

    Within the framework of the transverse spin -1/2 Ising model and by using the effective field theory with a probability distribution technique that accounts for the self-spin correlations, we have studied the critical properties of the Ba x Sr 1-x TiO 3 system. In particular, we have studied the polarization as function of both the temperature T and the Ba concentration x, the critical temperature T c (x) as function of x, and also the dielectric susceptibility χ(T,x) for different values of the strength of the applied electric field E

  9. Tailoring ultrafine grained and dispersion-strengthened Ti2AlC/TiAl ...

    Indian Academy of Sciences (India)

    Abstract. In situ Ti2AlC/TiAl composite was fabricated by hot-pressing method via the reaction system of Ti3AlC2 and Ti-Al pre-alloyed powders at low temperature of 1150◦C. The composite mainly consisted of TiAl, Ti3Al and. Ti2AlC phases. Fine Ti2AlC particles were homogeneously distributed and dispersed in the matrix.

  10. Ti/TiO 2 nanotube array electrode as a new sensor to ...

    Indian Academy of Sciences (India)

    The photoelectrocatalytic oxidation behaviour of ethylene glycol (EG) was studied in the present work using the TiO2-modified Ti foil (Ti/TiO2) electrode. The Ti/TiO2 nanotube array (Ti-NTA) electrode was prepared by anodizing of the Ti foil in the HF aqueous solution (0.2% v/v). The anodization was conducted in the ...

  11. Tailoring ultrafine grained and dispersion-strengthened Ti 2 AlC/TiAl ...

    Indian Academy of Sciences (India)

    In situ Ti 2 AlC/TiAl composite was fabricated by hot-pressing method via the reaction system of Ti 3 AlC 2 and Ti-Al pre-alloyed powders at low temperature of 1150 ∘ C. The composite mainly consisted of TiAl, Ti 3 Al and Ti 2 AlC phases. Fine Ti 2 AlC particles were homogeneously distributed and dispersed in the matrix.

  12. Ti/TiO2 nanotube array electrode as a new sensor to ...

    Indian Academy of Sciences (India)

    The photoelectrocatalytic oxidation behaviour of ethylene glycol (EG) was studied in the present work using the TiO2-modified Ti foil (Ti/TiO2) electrode. The Ti/TiO2 nanotube array (Ti-NTA) electrode was prepared by anodizing of the Ti foil in the HF aqueous solution (0.2% v/v). The anodization was conducted in the ...

  13. The interplay between dopants and oxygen vacancies in the magnetism of V-doped TiO2

    KAUST Repository

    Grau-Crespo, Ricardo

    2011-08-03

    Density functional theory calculations indicate that the incorporation of V into Ti lattice positions of rutile TiO2 leads to magnetic V 4 + species, but the extension and sign of the coupling between dopant moments confirm that ferromagnetic order cannot be reached via low-concentration doping in the non-defective oxide. Oxygen vacancies can introduce additional magnetic centres, and we show here that one of the effects of vanadium doping is to reduce the formation energies of these defects. In the presence of both V dopants and O vacancies all the spins tend to align with the same orientation. We conclude that V doping favours the ferromagnetic behaviour of TiO2 not only by introducing spins associated with the dopant centres but also by increasing the concentration of oxygen vacancies with respect to the pure oxide. © 2001 IOP Publishing Ltd.

  14. Microstructural features in a laser clad TiB-Ti composite coating

    NARCIS (Netherlands)

    Kooi, B.J.; Pei, Y.T.; de Hosson, J.T.M.; Brebbia, CA; DeHosson, JTM; Nishida, SI

    2003-01-01

    The microstructure of a TiB/Ti composite coating, obtained by laser cladding a Ti-6Al-4V substrate with a Ti/TiB2 powder mixture, was scrutinized using transmission electron microscopy (TEM). TiB showed three different morphologies: fine needles (200 nm diameter, 15 mum length), plates (thickness 1

  15. Enhancement and destruction of spin-Peierls physics in a one-dimensional quantum magnet under pressure

    Science.gov (United States)

    Rotundu, Costel R.; Wen, Jiajia; He, Wei; Choi, Yongseong; Haskel, Daniel; Lee, Young S.

    2018-02-01

    The application of pressure reveals a rich phase diagram for the quantum S =1 /2 spin chain material TiOCl. We performed x-ray diffraction on single-crystal samples in a diamond-anvil cell down to T =4 K and pressures up to 14.5 GPa. Remarkably, the magnetic interaction scale increases dramatically with increasing pressure, as indicated by the high onset temperature of the spin-Peierls phase. The spin-Peierls phase was probed at ˜6 GPa up to 215 K but possibly extends in temperature to above T =300 K, indicating the possibility of a quantum singlet state at room temperature. Near the critical pressure for the transition to the more metallic phase, coexisting phases are exemplified by incommensurate order in two directions. Further comparisons are made with the phase diagrams of related spin-Peierls systems that display metallicity and superconductivity under pressure.

  16. Spin-inversion in nanoscale graphene sheets with a Rashba spin-orbit barrier

    Directory of Open Access Journals (Sweden)

    Somaieh Ahmadi

    2012-03-01

    Full Text Available Spin-inversion properties of an electron in nanoscale graphene sheets with a Rashba spin-orbit barrier is studied using transfer matrix method. It is found that for proper values of Rashba spin-orbit strength, perfect spin-inversion can occur in a wide range of electron incident angle near the normal incident. In this case, the graphene sheet with Rashba spin-orbit barrier can be considered as an electron spin-inverter. The efficiency of spin-inverter can increase up to a very high value by increasing the length of Rashba spin-orbit barrier. The effect of intrinsic spin-orbit interaction on electron spin inversion is then studied. It is shown that the efficiency of spin-inverter decreases slightly in the presence of intrinsic spin-orbit interaction. The present study can be used to design graphene-based spintronic devices.

  17. Spin-transfer torque in spin filter tunnel junctions

    KAUST Repository

    Ortiz Pauyac, Christian

    2014-12-08

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

  18. Spin relaxation in quantum dots: Role of the phonon modulated spin-orbit interaction

    Science.gov (United States)

    Alcalde, A. M.; Romano, C. L.; Sanz, L.; Marques, G. E.

    2010-01-01

    We calculate the spin relaxation rates in a parabolic InSb quantum dots due to the spin interaction with acoustical phonons. We considered the deformation potential mechanism as the dominant electron-phonon coupling in the Pavlov-Firsov spin-phonon Hamiltonian. We analyze the behavior of the spin relaxation rates as a function of an external magnetic field and mean quantum dot radius. Effects of the spin admixture due to Dresselhaus contribution to spin-orbit interaction are also discussed.

  19. Theory of spin-selective Andreev reflection in the vortex core of a topological superconductor

    Science.gov (United States)

    Hu, Lun-Hui; Li, Chuang; Xu, Dong-Hui; Zhou, Yi; Zhang, Fu-Chun

    2016-12-01

    Majorana zero modes (MZMs) have been predicted to exist in a topological insulator (TI)/superconductor (SC) heterostructure. A recent spin-polarized scanning tunneling microscope (STM) experiment [Sun et al., Phys. Rev. Lett. 116, 257003 (2016), 10.1103/PhysRevLett.116.257003] has observed a spin-polarization dependence of the zero bias differential tunneling conductance at the center of a vortex core. Here, we consider a helical electron system described by a Rashba spin-orbit coupling Hamiltonian on a spherical surface with an s -wave superconducting pairing due to proximity effect. We examine the in-gap excitations of a pair of vortices with one at the north pole and the other at the south pole. While the MZM is not a spin eigenstate, the spin wave function of the MZM at the center of the vortex core, r =0 , is parallel to the magnetic field, and the local Andreev reflection of the MZM is spin selective, namely, occurs only when the STM tip has the spin polarization parallel to the magnetic field, similar to the case in a one-dimensional nanowire [He et al., Phys. Rev. Lett. 112, 037001 (2014), 10.1103/PhysRevLett.112.037001]. The total local differential tunneling conductance consists of the normal term proportional to the local density of states and an additional term arising from the Andreev reflection. We also discuss the finite size effect, for which the MZM at the north pole is hybridized with the MZM at the south pole. We apply our theory to examine the recently reported spin-polarized STM experiments and show good agreement with the experiments.

  20. Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

    Science.gov (United States)

    2016-10-14

    KEYWORDS Ferroelectric liquid crystals; solid state ferroelectrics; FLC- nanocomposites ; surface phenomena Introduction Nematic Liquid Crystals are...FLC/ BaTiO3 nanocolloids were investigated. Similar results were obtained in [10] and [11] for FLC/BaTiO3 nanocomposites studied on non- harvested...polymer concentrations were spin coated at 3500 rpm for three minutes on the ITO coated glass plates to obtain films of different thick- ness

  1. Spin and tunneling dynamics in an asymmetrical double quantum dot with spin-orbit coupling: Selective spin transport device

    Science.gov (United States)

    Singh, Madhav K.; Jha, Pradeep K.; Bhattacherjee, Aranya B.

    2017-09-01

    In this article, we study the spin and tunneling dynamics as a function of magnetic field in a one-dimensional GaAs double quantum dot with both the Dresselhaus and Rashba spin-orbit coupling. In particular, we consider different spatial widths for the spin-up and spin-down electronic states. We find that the spin dynamics is a superposition of slow as well as fast Rabi oscillations. It is found that the Rashba interaction strength as well as the external magnetic field strongly modifies the slow Rabi oscillations which is particularly useful for implementing solid state selective spin transport device.

  2. Spin dynamics with inertia in metallic ferromagnets

    Science.gov (United States)

    Kikuchi, Toru; Tatara, Gen

    2015-11-01

    The nonadiabatic contribution of environmental degrees of freedom yields an effective inertia of spin in the effective spin dynamics. In this paper, we study several aspects of the inertia of spin in metallic ferromagnets: (i) a concrete expression of the spin inertia ms: ms=ℏ Sc/(2 gsd) , where Sc is the spin polarization of conduction electrons and gsd is the s d coupling constant; (ii) a dynamical behavior of spin with inertia, discussed from the viewpoints of a spinning top and of a particle on a sphere; (iii) the behavior of spin waves and domain walls in the presence of inertia and the behavior of spin with inertia under a time-dependent magnetic field.

  3. Vibration dependence of the tensor spin-spin and scalar spin-spin hyperfine interactions by precision measurement of hyperfine structures of 127I2 near 532 nm

    International Nuclear Information System (INIS)

    Hong Fenglei; Zhang Yun; Ishikawa, Jun; Onae, Atsushi; Matsumoto, Hirokazu

    2002-01-01

    Hyperfine structures of the R(87)33-0, R(145)37-0, and P(132)36-0 transitions of molecular iodine near 532 nm are measured by observing the heterodyne beat-note signal of two I 2 -stabilized lasers, whose frequencies are bridged by an optical frequency comb generator. The measured hyperfine splittings are fit to a four-term Hamiltonian, which includes the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions, with an accuracy of ∼720 Hz. High-accurate hyperfine constants are obtained from this fit. Vibration dependences of the tensor spin-spin and scalar spin-spin hyperfine constants are determined for molecular iodine, for the first time to our knowledge. The observed hyperfine transitions are good optical frequency references in the 532-nm region

  4. Universal spin dynamics in quantum wires

    Energy Technology Data Exchange (ETDEWEB)

    Fajardo, E. A.; Zülicke, U.; Winkler, R.

    2017-10-01

    We discuss the universal spin dynamics in quasi-one-dimensional systems including the real spin in narrow-gap semiconductors like InAs and InSb, the valley pseudospin in staggered single-layer graphene, and the combination of real spin and valley pseudospin characterizing single-layer transition metal dichalcogenides (TMDCs) such as MoS2, WS2, MoS2, and WSe2. All these systems can be described by the same Dirac-like Hamiltonian. Spin-dependent observable effects in one of these systems thus have counterparts in each of the other systems. Effects discussed in more detail include equilibrium spin currents, current-induced spin polarization (Edelstein effect), and spin currents generated via adiabatic spin pumping. Our work also suggests that a long-debated spin-dependent correction to the position operator in single-band models should be absent.

  5. Spin transport in benzofurane bithiophene based organic spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Palosse, Mathieu; Séguy, Isabelle; Bedel-Pereira, Élena [CNRS, LAAS, 7 avenue du Colonel Roche, F-31400 Toulouse (France); Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); Villeneuve-Faure, Christina [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); LAPLACE, Université Paul Sabatier, 118, route de Narbonne 31062 Toulouse Cedex 9 (France); Mallet, Charlotte; Frère, Pierre [MOLTECH-Anjou, UMR CNRS 6200, Université d’Angers, 2 Bd Lavoisier 49045 ANGERS Cedex (France); Warot-Fonrose, Bénédicte; Biziere, Nicolas [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); CNRS, CEMES-CNRS UPR 8011, 29 rue Jeanne Marvig, BP 94347, FR-31055 Toulouse Cedex 4 (France); Bobo, Jean-François, E-mail: jfbobo@cemes.fr [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); CNRS, CEMES-ONERA, NMH, 2 avenue Edouard Belin, FR-31055 Toulouse Cedex 4 (France)

    2014-01-15

    In this paper we present spin transport in organic spin-valves using benzofurane bithiophene (BF3) as spacer layer between NiFe and Co ferromagnetic electrodes. The use of an AlO{sub x} buffer layer between the top electrode and the organic layer is discussed in terms of improvements of stacking topology, electrical transport and oxygen contamination of the BF3 layer. A study of magnetic hysteresis cycles evidences spin-valve behaviour. Transport properties are indicative of unshorted devices with non-linear I-V characteristics. Finally we report a magnetoresistance of 3% at 40 K and 10 mV in a sample with a 50 nm thick spacer layer, using an AlO{sub x} buffer layer.

  6. Enhancing the efficiency of dye-sensitized solar cells by adding diatom frustules into TiO{sub 2} working electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Der-Ray, E-mail: derray@mail.ndhu.edu.tw; Jiang, Yan-Jang; Liou, Run-Lin; Chen, Chih-Han; Chen, Yi-An; Tsai, Chih-Hung, E-mail: cht@mail.ndhu.edu.tw

    2015-08-30

    Graphical abstract: - Highlights: • High-speed centrifugal processing and sedimentation-rate separation techniques were used to obtain diatom frustules. • Diatom frustules were added into TiO{sub 2} paste to prepare a TiO{sub 2}-diatom paste mixture. • TiO{sub 2}-diatom paste mixture was used to fabricate working electrodes for DSSCs. • TiO{sub 2}-diatom electrodes improved the light-trapping effect and DSSC efficiency. • DSSCs with using the TiO{sub 2}-diatom electrode exhibited a 38% increase in efficiency. - Abstract: In this study, diatom frustules were added into TiO{sub 2} paste to prepare a TiO{sub 2}-diatom paste mixture. Spin-coating and high-temperature sintering techniques were then used to fabricate working electrodes for dye-sensitized solar cells (DSSCs). Mixing the diatom frustules with the TiO{sub 2} paste improved the light-trapping effect and scattering properties of the incident light in the TiO{sub 2}-diatom working electrodes, thereby enhancing the power conversion efficiency of the DSSCs. In this study, a high-speed centrifugal processing technology and sedimentation-rate separation techniques were first used to obtain the diatom frustules, which were then mixed with the TiO{sub 2} paste at a weight ratio of 1:50; a spin-coating technique was then used to fabricate the working electrodes. Finally, a high-temperature sintering process (500 °C) was performed. In this study, optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and a surface profiler and spectrometer were used to analyze the characteristics of the working electrodes. The TiO{sub 2} or TiO{sub 2}-diatom working electrodes were prepared under various spin-coating conditions for fabricating and analyzing the characteristics of the DSSCs. The results indicated that under identical conditions, the power conversion efficiency of the DSSCs was 3.81% when coated three times with a conventional TiO{sub 2

  7. Spin relaxation in disordered media

    International Nuclear Information System (INIS)

    Dzheparov, F S

    2011-01-01

    A review is given on theoretical grounds and typical experimental appearances of spin dynamics and relaxation in solids containing randomly distributed nuclear and/or electronic spins. Brief content is as follows. Disordered and magnetically diluted systems. General outlines of the spin transport theory. Random walks in disordered systems (RWDS). Observable values in phase spin relaxation, free induction decay (FID). Interrelation of longitudinal and transversal relaxation related to dynamics of occupancies and phases. Occupation number representation for equations of motion. Continuum media approximation and inapplicability of moment expansions. Long-range transitions vs percolation theory. Concentration expansion as a general constructive basis for analytical methods. Scaling properties of propagators. Singular point. Dynamical and kinematical memory in RWDS. Ways of regrouping of concentration expansions. CTRW and semi-phenomenology. Coherent medium approximation for nuclear relaxation via paramagnetic impurities. Combining of memory functions and cumulant expansions for calculation of FID. Path integral representations for RWDS. Numerical simulations of RWDS. Spin dynamics in magnetically diluted systems with low Zeeman and medium low dipole temperatures. Cluster expansions, regularization of dipole interactions and spectral dynamics.

  8. Spin-Spin Cross Relaxation in Single-Molecule Magnets

    Science.gov (United States)

    Wernsdorfer, W.; Bhaduri, S.; Tiron, R.; Hendrickson, D. N.; Christou, G.

    2002-10-01

    The one-body tunnel picture of single-molecule magnets (SMMs) is not always sufficient to explain the measured tunnel transitions. An improvement to the picture is proposed by including also two-body tunnel transitions such as spin-spin cross relaxation (SSCR) which are mediated by dipolar and weak superexchange interactions between molecules. A Mn4 SMM is used as a model system. At certain external fields, SSCRs lead to additional quantum resonances which show up in hysteresis loop measurements as well-defined steps. A simple model is used to explain quantitatively all observed transitions.

  9. Non magnetic neutron spin quantum precession using multilayer spin splitter and a phase-spin echo interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Ebisawa, T.; Tasaki, S.; Kawai, T.; Akiyoshi, T. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Achiwa, N.; Hino, M.; Otake, Y.; Funahashi, H.

    1996-08-01

    The authors have developed cold neutron optics and interferometry using multilayer mirrors. The advantages of the multilayer mirrors are their applicability to long wavelength neutrons and a great variety of the mirror performance. The idea of the present spin interferometry is based on nonmagnetic neutron spin quantum precession using multilayer spin splitters. The equation for polarized neutrons means that the polarized neutrons are equivalent to the coherent superposition of two parallel spin eigenstates. The structure and principle of a multilayer spin splitter are explained, and the nonmagnetic gap layer of the multilayer spin splitter gives rise to neutron spin quantum precession. The performance test of the multilayer spin splitter were made with a new spin interferometer, which is analogous optically to a spin echo system with vertical precession field. The spin interferometers were installed at Kyoto University research reactor and the JRR-3. The testing method and the results are reported. The performance tests on a new phase-spin echo interferometer are described, and its applications to the development of a high resolution spin echo system and a Jamin type cold neutron interferometer are proposed. (K.I.)

  10. DUBNA: Spin effects

    International Nuclear Information System (INIS)

    Anon.

    1995-01-01

    energies of 1.2, 2.5 et 3.6 GeV, underline that spin effects decrease with energy and tend to zero in agreement with the prediction of a nonpertubative quantum chromodynamics (QCD) model, where the strong fluctuations of vacuum gluon fields (instantons) provide the main contribution. The rapid vanishing of neutron-proton difference, observed for the first time, suggests that the prediction is valid for both isospin 0 and 1 states. It will be interesting to take measurements using a transversely polarized beam and target, where different behaviour is expected. With the polarizing solenoid shipped to Mainz for another experiment, the JINR setup needs a new solenoid and superconducting coils for transverse target polarization. Construction has begun in Dubna and Kharkov, respectively. Additional INTAS financial support will be requested

  11. Orthorhombic Ti2O3: A Polymorph-Dependent Narrow-Bandgap Ferromagnetic Oxide

    KAUST Repository

    Li, Yangyang

    2017-12-16

    Magnetic semiconductors are highly sought in spintronics, which allow not only the control of charge carriers like in traditional electronics, but also the control of spin states. However, almost all known magnetic semiconductors are featured with bandgaps larger than 1 eV, which limits their applications in long-wavelength regimes. In this work, the discovery of orthorhombic-structured Ti2O3 films is reported as a unique narrow-bandgap (≈0.1 eV) ferromagnetic oxide semiconductor. In contrast, the well-known corundum-structured Ti2O3 polymorph has an antiferromagnetic ground state. This comprehensive study on epitaxial Ti2O3 thin films reveals strong correlations between structure, electrical, and magnetic properties. The new orthorhombic Ti2O3 polymorph is found to be n-type with a very high electron concentration, while the bulk-type trigonal-structured Ti2O3 is p-type. More interestingly, in contrast to the antiferromagnetic ground state of trigonal bulk Ti2O3, unexpected ferromagnetism with a transition temperature well above room temperature is observed in the orthorhombic Ti2O3, which is confirmed by X-ray magnetic circular dichroism measurements. Using first-principles calculations, the ferromagnetism is attributed to a particular type of oxygen vacancies in the orthorhombic Ti2O3. The room-temperature ferromagnetism observed in orthorhombic-structured Ti2O3, demonstrates a new route toward controlling magnetism in epitaxial oxide films through selective stabilization of polymorph phases.

  12. Graphene Oxide-TiO2 Nanocomposite Films for Electron Transport Applications

    Science.gov (United States)

    Saleem, Abida; Ullah, Naveed; Khursheed, Kamran; Iqbal, Tahir; Shah, Saqlain A.; Asjad, Muhammad; Sarwar, Nazim; Saleem, Murtaza; Arshad, Muhammad

    2018-03-01

    Graphene oxide-titanium dioxide (GO-TiO2) nanocomposite thin films were prepared for application as the window layer of perovskite solar cells. Graphene oxide (GO) was prepared by a modified Hummer's method, and titanium dioxide (TiO2) nanoparticles were synthesized by hydrothermal solution method. Thin films of GO-TiO2 nanocomposite were prepared with different wt.% of GO by spin coating on indium tin oxide (ITO) substrate followed by annealing at 150°C. X-ray diffraction analysis revealed rutile phase of TiO2 nanostructures. The bandgap of the pure TiO2 thin film was found to be 3.5 eV, reducing to 2.9 eV for the GO-TiO2 nanocomposites with a red-shift towards higher wavelength. Furthermore, thermal postannealing at 400°C improved the transparency in the visible region and decreased the sheet resistance. Morphological and elemental analysis was performed by scanning electron microscopy and energy-dispersive x-ray spectroscopy, respectively. The current-voltage characteristic of the GO-TiO2 nanocomposites indicated Ohmic contact with the ITO substrate. The chemical composition of the as-synthesized GO-TiO2 nanocomposites was investigated by x-ray photoelectron spectroscopy (XPS). The results presented herein demonstrate a new, low-temperature solution-processing approach to obtain rGO-TiO2 composite material for use as the electron transport layer of perovskite solar cells.

  13. Coercivity and nanostructure of melt-spun Ti-Fe-Co-B-based alloys

    Directory of Open Access Journals (Sweden)

    W. Y. Zhang

    2016-05-01

    Full Text Available Nanocrystalline Ti-Fe-Co-B-based alloys, prepared by melt spinning and subsequent annealing, have been characterized structurally and magnetically. X-ray diffraction and thermomagnetic measurements show that the ribbons consist of tetragonal Ti3(Fe,Co5B2, FeCo-rich bcc, and NiAl-rich L21 phases; Ti3(Fe,Co5B2, is a new substitutional alloy series whose end members Ti3Co5B2 and Ti3Fe5B2 have never been investigated magnetically and may not even exist, respectively. Two compositions are considered, namely Ti11+xFe37.5-0.5xCo37.5−0.5xB14 (x = 0, 4 and alnico-like Ti11Fe26Co26Ni10Al11Cu2B14, the latter also containing an L21-type alloy. The volume fraction of the Ti3(Fe,Co5B2 phase increases with x, which leads to a coercivity increase from 221 Oe for x = 0 to 452 Oe for x = 4. Since the grains are nearly equiaxed, there is little or no shape anisotropy, and the coercivity is largely due to the magnetocrystalline anisotropy of the tetragonal Ti3(Fe,Co5B2 phase. The alloy containing Ni, Al, and Cu exhibits a magnetization of 10.6 kG and a remanence ratio of 0.59. Our results indicate that magnetocrystalline anisotropy can be introduced in alnico-like magnets, adding to shape anisotropy that may be induced by field annealing.

  14. Interphase Constituent of Laminated Composites Ti46Zr26Cu17Ni11

    Directory of Open Access Journals (Sweden)

    XU Bingtong

    2017-10-01

    Full Text Available Thermal analysis of the Ti46Zr26Cu17Ni11 amorphous ribbon prepared by melt spinning was conducted by using DSC. Accordingly the amorphous alloy was treated by vacuum heat treatment at 693 K (Tg, 753 K (Tg-Tx1 and 813 K (> Tx1 for different time to analyze the crystallization behavior. Taking Ti46Zr26Cu17Ni11 amorphous alloy, TA2 and pure Al as raw materials, laminated composites were fabricated by Gleeble-3500 thermal simulator at 873 K, 10 MPa and 8 h. The phase composition, precipitation order and properties of interface layers were investigated by SEM, TEM, micro hardness tester, combined thermodynamics and element diffusion theory. The results indicate that the glass transition temperature Tg of Ti46Zr26Cu17Ni11 amorphous is 720 K and the initial crystallization temperature Tx1 is 788 K. The I phase is crystallized from the amorphous at first, followed by a ternary or quaternary Laves phase and a TiNi phase precipited. After hot pressing, the interface between pure Al and crystallization layer is divided into two parts, which are Al3Ni with small thickness and Al3(Ti0.6Zr0.4 with fine grain and uniform microstructure. The interfaces are straight and there are no defects, with a thickness ratio of about 6.5:1 compared with interface layer between pure Ti with Al. The hardness of Al3(Ti0.6Zr0.4 and Al3Ti are 564.2HV and 579.8HV respectively. The plasticity of Al3(Ti0.6Zr0.4 layer is better.

  15. ZnO@TiO2 Architectures for a High Efficiency Dye-Sensitized Solar Cell

    International Nuclear Information System (INIS)

    Lei, Jianfei; Liu, Shuli; Du, Kai; Lv, Shijie; Liu, Chaojie; Zhao, Lingzhi

    2015-01-01

    Graphical Abstract: A fast and improved electrochemical process was reported to fabricate ZnO@TiO 2 heterogeneous architectures with enhanced power conversion efficiency (ƞ = 2.16%). This paper focuses on achieving high dye loading via binding noncorrosive TiO 2 nanocones to the outermost layer, while retaining the excellent electron transport behavior of the ZnO-based internal layer. Display Omitted -- Highlights: • Nanoconic TiO 2 particles are loaded on the surface of aligned ZnO NWs successfully by a liquid phase deposition method. • ZnO@TiO 2 architectures exhibit high efficiency of the DSSCs. -- Abstract: Instead of the spin coating step, an improved electrochemical process is reported in this paper to prepare ZnO seeded substrates and ZnO nanowires (ZnO NWs). Vertically aligned ZnO NWs are deposited electrochemically on the ZnO seeded substrates directly forming backbones for loading nanoconic TiO 2 particles, and hence ZnO@TiO 2 heterogeneous architectures are obtained. When used as photoanode materials of the dye-sensitized solar cells (DSSCs), ZnO@TiO 2 architectures exhibit enhanced power conversion efficiency (PCE) of the DSSCs. Results of the solar cell testing show that addition of TiO 2 shells to the ZnO NWs significantly increases short circuit current (from 2.6 to 4.7 mA cm −2 ), open circuit voltage (from 0.53 V to 0.77 V) and fill factor (from 0.30 to 0.59). The PCE jumped from 0.4% for bare ZnO NWs to 2.16% for ZnO@TiO 2 architectures under 100 mW cm −2 of AM 1.5 G illumination

  16. QCD SPIN PHYSICS IN HADRONIC INTERACTIONS.

    Energy Technology Data Exchange (ETDEWEB)

    VOGELSANG,W.

    2007-06-19

    We discuss spin phenomena in high-energy hadronic scattering, with a particular emphasis on the spin physics program now underway at the first polarized proton-proton collider, RHIC. Experiments at RHIC unravel the spin structure of the nucleon in new ways. Prime goals are to determine the contribution of gluon spins to the proton spin, to elucidate the flavor structure of quark and antiquark polarizations in the nucleon, and to help clarify the origin of transverse-spin phenomena in QCD. These lectures describe some aspects of this program and of the associated physics.

  17. Spin Waves in Ho2Co17

    DEFF Research Database (Denmark)

    Clausen, Kurt Nørgaard; Lebech, Bente

    1980-01-01

    Spin wave excitations in a single crystal of Ho2Co17 have been studied at 4.8 and 78 K. The results are discussed in terms of a linear spin wave model. At 78 K both ground state and excited state spin waves are observed.......Spin wave excitations in a single crystal of Ho2Co17 have been studied at 4.8 and 78 K. The results are discussed in terms of a linear spin wave model. At 78 K both ground state and excited state spin waves are observed....

  18. Fabrication and Film Qualification of Sr Modified Pb(Ca) TiO3 Thin Films

    International Nuclear Information System (INIS)

    Naw Hla Myat San; Khin Aye Thwe; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

    2011-12-01

    Strontium and calcium - modified lead titanate (Pb0.7 Ca0.15 Sr0.15 ) TiO3 (PCST)thin films were prepared by using spin coating technique. Phase transition of PCST was interpreted by means of Er-T characteristics. Process temperature dependence on micro-structure of PCST film was studied. Charge conduction mechanism of PCST thin film was also investigated for film qualification.

  19. Electrical Properties of Ultra-thin TiO2 Compact Layer on FTO for Perovskite Solar cells

    Science.gov (United States)

    Songtanasit, R.; Taychatanapat, T.; Chatraphorn, S.

    2017-09-01

    A TiO2 compact layer or blocking layer plays a crucial role in a hybrid organic-inorganic lead halide perovskite solar cell because it can prevent the carrier recombination at the interface of fluorine-doped tin oxide (FTO) and perovskite layers. There are several methods to fabricate this layer such as spray pyrolysis or spin-coating which is solution-based synthesis that is difficult to avoid pinholes in the surface of the blocking layer. In this work, TiO2 blocking layers are fabricated by radio-frequency (RF) magnetron sputtering using Ti metallic target with O2 partial pressure in Ar atmosphere on FTO coated glasses. The controlled parameters for the deposition of TiO2 compact layer are RF power, O2 partial pressure, and deposition time. The optimization of the TiO2 compact layers are found from the diode I-V characteristics between the TiO2/FTO interfaces. The resistance between the TiO2/FTO interfaces deviates from an ohmic contact towards a diode behavior when the thickness of TiO2 is increased. The thickness of the films is directly measured by surface profilometer. In addition, the UV-VIS-NIR spectroscopy is used to observe the optical transmission of the films.

  20. Flame-Made Pt-Loaded TiO2 Thin Films and Their Application as H2 Gas Sensors

    Directory of Open Access Journals (Sweden)

    Weerasak Chomkitichai

    2013-01-01

    Full Text Available The hydrogen gas sensors were developed successfully using flame-made platinum-loaded titanium dioxide (Pt-loaded TiO2 nanoparticles as the sensing materials. Pt-loaded TiO2 thin films were prepared by spin-coating technique onto Al2O3 substrates interdigitated with Au electrodes. Structural and gas-sensing characteristics were examined by using scanning electron microscopy (SEM and showed surface morphology of the deposited film. X-ray diffraction (XRD patterns can be confirmed to be the anatase and rutile phases of TiO2. High-resolution transmission electron microscopy (HRTEM showed that Pt nanoparticles deposited on larger TiO2 nanoparticles. TiO2 films loaded with Pt nanoparticles were used as conductometric sensors for the detection of H2. The gas sensing of H2 was studied at the operating temperatures of 300, 350, and 400°C in dry air. It was found that 2.00 mol% Pt-loaded TiO2 sensing films showed higher response towards H2 gas than the unloaded film. In addition, the responses of Pt-loaded TiO2 films at all operating temperatures were higher than that of unloaded TiO2 film. The response increased and the response time decreased with increasing of H2 concentrations.

  1. Benign Synthesis of Black Microspheres of Anatase TiO2with Paramagnetic Oxygen Vacancies through NH3Treatment.

    Science.gov (United States)

    Maqbool, Qysar; Srivastava, Aasheesh

    2017-10-09

    Coloured TiO 2 is coveted for its ability to extract energy from the visible region of electromagnetic spectrum. Here a facile synthesis of black anatase titania microspheres (B-TiO 2 ) through a two-step process is reported. In the first step, amorphous white TiO 2 microspheres (W-TiO 2 ) are obtained by hydrolysing titanium tetraisopropoxide by ammonia vapours in ethanol. In the second step, the W-TiO 2 is thermally annealed at 500 °C to obtain B-TiO 2 . The diffuse reflectance analysis showed that B-TiO 2 absorbs across visible spectrum with absorption extending well into NIR region. Raman scattering together with EPR analysis showed compelling evidence of the existence of oxygen deficiency within the crystal in B-TiO 2 that induces black colouration in the sample. The defects present in the black anatase sample were confirmed to be single-electron-trapped (or paramagnetic) oxygen vacancies (V o ⋅) by XPS and EPR studies. The magnetic susceptibility studies showed existence of antiferromagnetic interactions between these unpaired electron spins. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Spin qubits in antidot lattices

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Flindt, Christian; Mortensen, Niels Asger

    2008-01-01

    We suggest and study designed defects in an otherwise periodic potential modulation of a two-dimensional electron gas as an alternative approach to electron spin based quantum information processing in the solid-state using conventional gate-defined quantum dots. We calculate the band structure a...... electron transport between distant defect states in the lattice, and for a tunnel coupling of neighboring defect states with corresponding electrostatically controllable exchange coupling between different electron spins.......We suggest and study designed defects in an otherwise periodic potential modulation of a two-dimensional electron gas as an alternative approach to electron spin based quantum information processing in the solid-state using conventional gate-defined quantum dots. We calculate the band structure...

  3. Next generation spin torque memories

    CERN Document Server

    Kaushik, Brajesh Kumar; Kulkarni, Anant Aravind; Prajapati, Sanjay

    2017-01-01

    This book offers detailed insights into spin transfer torque (STT) based devices, circuits and memories. Starting with the basic concepts and device physics, it then addresses advanced STT applications and discusses the outlook for this cutting-edge technology. It also describes the architectures, performance parameters, fabrication, and the prospects of STT based devices. Further, moving from the device to the system perspective it presents a non-volatile computing architecture composed of STT based magneto-resistive and all-spin logic devices and demonstrates that efficient STT based magneto-resistive and all-spin logic devices can turn the dream of instant on/off non-volatile computing into reality.

  4. High-spin nuclear traps

    International Nuclear Information System (INIS)

    Walker, P.; Dracoulis, G.

    1994-01-01

    The reaction pathways in stars, where all the heavy elements in the Universe were formed, are inextricably linked with isomers that live long enough to capture a neutron or proton before they decay. These isomers usually have excitation energies below 0.1 MeV. It is also possible to find highly excited isomers, with several MeV of excitation energy, that are trapped because of their large angular momentum (or spin). But attempts to understand the long-lived highly excited isomers, sometimes known as ''spin traps'', have been hampered by the difficulty of producing this exotic form of nuclear matter. Now, a new generation of radioactive ion beams promises a revolution in the study of high-spin nuclear traps. (author)

  5. Spin structures in antiferromagnetic nanoparticles

    DEFF Research Database (Denmark)

    Brok, Erik

    a detailed knowledge of it can be important for applications of antiferromagnetic nanoparticles for example combined with ferromagnetic nanoparticles in nanocomposite devices. In this thesis the magnetic structure, in particular the orientation of the spins in the antiferromagnetic sublattices......, proposed to explain the unusual magnetic properties of the mineral. In summary the thesis have demonstrated methods for investigation of spin structures in magnetic nanoparticles. In particular, the classical model of the temperature dependence of canted spin structures sucessfully explains many...... experimental observations of anomalous temperature dependence in nanoparticle and bulk systems. Morover, XY Z neutron polarisation analysis have been demonstrated to be an effective way of investigating the magnetic properties of antiferromagnetic nanoparticles, significantly improving the unpolarised neutron...

  6. Evolution process of the synthesis of TiC in the Cu-Ti-C system

    International Nuclear Information System (INIS)

    Liang, Y.H.; Wang, H.Y.; Yang, Y.F.; Wang, Y.Y.; Jiang, Q.C.

    2008-01-01

    The evolution process of TiC formation in the 20 wt.% Cu-Ti-C powder mixtures was studied by using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Ti x Cu y compounds (Ti 2 Cu, TiCu, Ti 3 Cu 4 and TiCu 4 ) formed initially via solid-state diffusion reactions between Cu and Ti particles; and then Ti 2 Cu and TiCu can form a Cu-Ti eutectic liquids at about 1233 K. The unreacted Ti and C particles dissolved into the Cu-Ti liquids and led to the formation of Cu-Ti-C ternary liquids; subsequently, TiC particulates precipitated out of the saturated liquids. At the same time, also the formation of Ti 2 Cu occurred at the interface between the Cu-Ti liquids and the unreacted Ti particles. As the temperature increased further, the Ti 2 Cu melted and more Cu-Ti liquids formed; and then C particles continuously dissolved into the Cu-Ti-C liquids and TiC particulates gradually precipitated out of the saturated liquids

  7. Extrinsic spin Hall effect in graphene

    Science.gov (United States)

    Rappoport, Tatiana

    The intrinsic spin-orbit coupling in graphene is extremely weak, making it a promising spin conductor for spintronic devices. In addition, many applications also require the generation of spin currents in graphene. Theoretical predictions and recent experimental results suggest one can engineer the spin Hall effect in graphene by greatly enhancing the spin-orbit coupling in the vicinity of an impurity. The extrinsic spin Hall effect then results from the spin-dependent skew scattering of electrons by impurities in the presence of spin-orbit interaction. This effect can be used to efficiently convert charge currents into spin-polarized currents. I will discuss recent experimental results on spin Hall effect in graphene decorated with adatoms and metallic cluster and show that a large spin Hall effect can appear due to skew scattering. While this spin-orbit coupling is small if compared with what it is found in metals, the effect is strongly enhanced in the presence of resonant scattering, giving rise to robust spin Hall angles. I will present our single impurity scattering calculations done with exact partial-wave expansions and complement the analysis with numerical results from a novel real-space implementation of the Kubo formalism for tight-binding Hamiltonians. The author acknowledges the Brazilian agencies CNPq, CAPES, FAPERJ and INCT de Nanoestruturas de Carbono for financial support.

  8. COMMISSIONING SPIN ROTATORS IN RHIC

    International Nuclear Information System (INIS)

    MACKAY, W.W.; AHRENS, L.; BAI, M.; COURANT, E.D.; FISCHER, W.; HUANG, H.; LUCCIO, A.; MONTAG, C.; PILAT, F.; PTITSYN, V.; ROSER, T.; SATOGATA, T.; TRBOJEVIC, D.; VANZIEJTS, J.

    2003-01-01

    During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX

  9. Snell's Law for Spin Waves

    Science.gov (United States)

    Stigloher, J.; Decker, M.; Körner, H. S.; Tanabe, K.; Moriyama, T.; Taniguchi, T.; Hata, H.; Madami, M.; Gubbiotti, G.; Kobayashi, K.; Ono, T.; Back, C. H.

    2016-07-01

    We report the experimental observation of Snell's law for magnetostatic spin waves in thin ferromagnetic Permalloy films by imaging incident, refracted, and reflected waves. We use a thickness step as the interface between two media with different dispersion relations. Since the dispersion relation for magnetostatic waves in thin ferromagnetic films is anisotropic, deviations from the isotropic Snell's law known in optics are observed for incidence angles larger than 25 ° with respect to the interface normal between the two magnetic media. Furthermore, we can show that the thickness step modifies the wavelength and the amplitude of the incident waves. Our findings open up a new way of spin wave steering for magnonic applications.

  10. Harmony of spinning conformal blocks

    Energy Technology Data Exchange (ETDEWEB)

    Schomerus, Volker [DESY Hamburg, Theory Group,Notkestraße 85, 22607 Hamburg (Germany); Sobko, Evgeny [Nordita and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Isachenkov, Mikhail [Department of Particle Physics and Astrophysics, Weizmann Institute of Science,Rehovot 7610001 (Israel)

    2017-03-15

    Conformal blocks for correlation functions of tensor operators play an increasingly important role for the conformal bootstrap programme. We develop a universal approach to such spinning blocks through the harmonic analysis of certain bundles over a coset of the conformal group. The resulting Casimir equations are given by a matrix version of the Calogero-Sutherland Hamiltonian that describes the scattering of interacting spinning particles in a 1-dimensional external potential. The approach is illustrated in several examples including fermionic seed blocks in 3D CFT where they take a very simple form.

  11. Harmony of spinning conformal blocks

    Energy Technology Data Exchange (ETDEWEB)

    Schomerus, Volker [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group; Sobko, Evgeny [Stockholm Univ. (Sweden); Nordita, Stockholm (Sweden); Isachenkov, Mikhail [Weizmann Institute of Science, Rehovoth (Israel). Dept. of Particle Physics and Astrophysics

    2016-12-07

    Conformal blocks for correlation functions of tensor operators play an increasingly important role for the conformal bootstrap programme. We develop a universal approach to such spinning blocks through the harmonic analysis of certain bundles over a coset of the conformal group. The resulting Casimir equations are given by a matrix version of the Calogero-Sutherland Hamiltonian that describes the scattering of interacting spinning particles in a 1-dimensional external potential. The approach is illustrated in several examples including fermionic seed blocks in 3D CFT where they take a very simple form.

  12. The nucleon spin crisis bible

    International Nuclear Information System (INIS)

    Close, F.E.

    1994-01-01

    When the new data on polarised lepton nucleon scattering are compared at the same value of Q 2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in 0(α s ), higher twist effects, modern data on unpolarized structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)

  13. Spin tunnelling in mesoscopic systems

    Science.gov (United States)

    Garg, Anupam

    2001-02-01

    We study spin tunnelling in molecular magnets as an instance of a mesoscopic phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel splitting between various pairs of Zeeman levels in this molecule oscillates as a function of applied magnetic field, vanishing completely at special points in the space of magnetic fields, known as diabolical points. This phenomena is explained in terms of two approaches, one based on spin-coherent-state path integrals, and the other on a generalization of the phase integral (or WKB) method to difference equations. Explicit formulas for the diabolical points are obtained for a model Hamiltonian.

  14. The nucleon spin crisis bible

    International Nuclear Information System (INIS)

    Close, F.E.

    1993-06-01

    When the new data on polarised lepton nucleon scattering are compared at the same value of Q 2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in O(α s ), higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)

  15. Proximity Band Structure and Spin Textures on Both Sides of Topological-Insulator/Ferromagnetic-Metal Interface and Their Charge Transport Probes.

    Science.gov (United States)

    Marmolejo-Tejada, Juan Manuel; Dolui, Kapildeb; Lazić, Predrag; Chang, Po-Hao; Smidstrup, Søren; Stradi, Daniele; Stokbro, Kurt; Nikolić, Branislav K

    2017-09-13

    The control of recently observed spintronic effects in topological-insulator/ferromagnetic-metal (TI/FM) heterostructures is thwarted by the lack of understanding of band structure and spin textures around their interfaces. Here we combine density functional theory with Green's function techniques to obtain the spectral function at any plane passing through atoms of Bi 2 Se 3 and Co or Cu layers comprising the interface. Instead of naively assumed Dirac cone gapped by the proximity exchange field spectral function, we find that the Rashba ferromagnetic model describes the spectral function on the surface of Bi 2 Se 3 in contact with Co near the Fermi level E F 0 , where circular and snowflake-like constant energy contours coexist around which spin locks to momentum. The remnant of the Dirac cone is hybridized with evanescent wave functions from metallic layers and pushed, due to charge transfer from Co or Cu layers, a few tenths of an electron-volt below E F 0 for both Bi 2 Se 3 /Co and Bi 2 Se 3 /Cu interfaces while hosting distorted helical spin texture wounding around a single circle. These features explain recent observation of sensitivity of spin-to-charge conversion signal at TI/Cu interface to tuning of E F 0 . Crucially for spin-orbit torque in TI/FM heterostructures, few monolayers of Co adjacent to Bi 2 Se 3 host spectral functions very different from the bulk metal, as well as in-plane spin textures (despite Co magnetization being out-of-plane) due to proximity spin-orbit coupling in Co induced by Bi 2 Se 3 . We predict that out-of-plane tunneling anisotropic magnetoresistance in Cu/Bi 2 Se 3 /Co vertical heterostructure can serve as a sensitive probe of the type of spin texture residing at E F 0 .

  16. Reactive Ni/Ti nanolaminates

    International Nuclear Information System (INIS)

    Adams, D. P.; Bai, M. M.; Rodriguez, M. A.; McDonald, J. P.; Jones, E. Jr.; Brewer, L.; Moore, J. J.

    2009-01-01

    Nickel/titanium nanolaminates fabricated by sputter deposition exhibited rapid, high-temperature synthesis. When heated locally, self-sustained reactions were produced in freestanding Ni/Ti multilayer foils characterized by average propagation speeds between ∼0.1 and 1.4 m/s. The speed of a propagating reaction front was affected by total foil thickness and bilayer thickness (layer periodicity). In contrast to previous work with compacted Ni-Ti powders, no preheating of Ni/Ti foils was required to maintain self-propagating reactions. High-temperature synthesis was also stimulated by rapid global heating demonstrating low ignition temperatures (T ig )∼300-400 deg. C for nanolaminates. Ignition temperature was influenced by bilayer thickness with more coarse laminate designs exhibiting increased T ig . Foils reacted in a vacuum apparatus developed either as single-phase B2 cubic NiTi (austenite) or as a mixed-phase structure that was composed of monoclinic B19 ' NiTi (martensite), hexagonal NiTi 2 , and B2 NiTi. Single-phase, cubic B2 NiTi generally formed when the initial bilayer thickness was made small.

  17. Structural properties of the geometrically frustrated pyrochlore Tb2Ti2O7

    International Nuclear Information System (INIS)

    Han, Sang-Wook; Gardner, Jason S.; Booth, Corwin H.

    2004-01-01

    Although materials that exhibit nearest-neighbor-only antiferromagnetic interactions and geometrical frustration theoretically should not magnetically order in the absence of disorder, few such systems have been observed experimentally. One such system appears to be the pyrochlore Tb 2 Ti 2 O 7 . However, previous structural studies indicated that Tb 2 Ti 2 O 7 is an imperfect pyrochlore. To clarify the situation, we performed neutron powder diffraction (NPD) and x-ray absorption fine structure (XAFS) measurements on samples that were prepared identically to those that show no magnetic order. The NPD measurements show that the long-range structure of Tb 2 Ti 2 O 7 is well ordered with no structural transitions between 4.5 and 600 K. In particular, mean-squared displacements (u 2 's) for each site follow a Debye model with no offsets. No evidence for Tb/Ti site interchange was observed within an upper limit of 2%. Likewise, no excess or deficiency in the oxygen stoichiometry was observed, within an upper limit of 2% of the nominal pyrochlore value. Tb L III and Ti K-edge XAFS measurements from 20-300 K similarly indicate a well-ordered local structure. Other aspects of the structure are considered. We conclude that Tb 2 Ti 2 O 7 has, within experimental error, an ideal, disorder-free pyrochlore lattice, thereby allowing the system to remain in a dynamic, frustrated spin state to the lowest observed temperatures

  18. Spin interferometry in anisotropic spin-orbit fields

    Science.gov (United States)

    Saarikoski, Henri; Reynoso, Andres A.; Baltanás, José Pablo; Frustaglia, Diego; Nitta, Junsaku

    2018-03-01

    Electron spins in a two-dimensional electron gas can be manipulated by spin-orbit (SO) fields originating from either Rashba or Dresselhaus interactions with independent isotropic characteristics. Together, though, they produce anisotropic SO fields with consequences on quantum transport through spin interference. Here we study the transport properties of modeled mesoscopic rings subject to Rashba and Dresselhaus [001] SO couplings in the presence of an additional in-plane Zeeman field acting as a probe. By means of one- and two-dimensional quantum transport simulations we show that this setting presents anisotropies in the quantum resistance as a function of the Zeeman field direction. Moreover, the anisotropic resistance can be tuned by the Rashba strength up to the point to invert its response to the Zeeman field. We also find that a topological transition in the field texture that is associated with a geometric phase switching is imprinted in the anisotropy pattern. We conclude that resistance anisotropy measurements can reveal signatures of SO textures and geometric phases in spin carriers.

  19. Electrical properties of spin coated ultrathin titanium oxide films on GaAs

    Science.gov (United States)

    Dutta, Shankar; Pal, Ramjay; Chatterjee, Ratnamala

    2015-04-01

    In recent years, ultrathin (MOS) technology. This paper discusses deposition of ultrathin TiO2 films (˜10 nm) on GaAs substrates (one sulfur-passivated, another unpassivated) by spin coating technique. The sulfur passivation is done to reduce the surface states of GaAs substrate. After annealing at 400 °C in a nitrogen environment, the TiO2 films are found to be polycrystalline in nature with rutile phase. The TiO2 films exhibit consistent grain size of 10-20 nm with thickness around 10-12 nm. Dielectric constants of the films are found to be 65.4 and 47.1 corresponding to S-passivated and unpassivated substrates, respectively. Corresponding threshold voltages of the MOS structures are measured to be -0.1 V to -0.3 V for the S-passivated and unpassivated samples, respectively. The S-passivated TiO2 film showed improved (lower) leakage current density (5.3 × 10-4 A cm-2 at 3 V) compared to the unpassivated film (1.8 × 10-3 A/cm2 at 3 V). Dielectric breakdown-field of the TiO2 films on S-passivated and unpassivated GaAs samples are found to be 8.4 MV cm-1 and 7.2 MV cm-1 respectively.

  20. In-Situ-Reduced Synthesis of Ti 3+ Self-Doped TiO 2 /g-C 3 N 4 Heterojunctions with High Photocatalytic Performance under LED Light Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kai [College; Gao, Shanmin [College; State; Wang, Qingyao [College; Xu, Hui [College; Wang, Zeyan [State; Huang, Baibiao [State; Dai, Ying [State; Lu, Jun [Chemical

    2015-04-27

    A simple one-step calcination route was used to prepare Ti3+ self-doped TiO2/g-C3N4 heterojunctions by mixture of H2Ti3O7 and melamine. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) technologies were used to characterize the structure, crystallinity, morphology, and chemical state of the as-prepared samples. The absorption of the prepared Ti3+ self-doped TiO2/g-C3N4 heterojunctions shifted to a longer wavelength region in comparison with pristine TiO2 and g-C3N4. The photocatalytic activities of the heterojunctions were studied by degrading methylene blue under a 30 W visible-light-emitting diode irradiation source. The visible-light photocatalytic activities enhanced by the prepared Ti3+ self-doped TiO2/g-C3N4 heterojunctions were observed and proved to be better than that of pure TiO2 and g-C3N4. The photocatalysis mechanism was investigated and discussed. The intensive separation efficiency of photogenerated electron-hole in the prepared heterojunction was confirmed by photoluminescence (PL) spectra. The removal rate constant reached 0.038 min(-1) for the 22.3 wt % Ti3+ self-doped TiO2/g-C3N4 heterojunction, which was 26.76 and 7.6 times higher than that of pure TiO2 and g-C3N4, respectively. The established heterojunction between the interfaces of TiO2 nanoparticles and g-C3N4 nanosheets as well as introduced Ti3+ led to the rapid electron transfer rate and improved photoinduced electron-hole pair's separation efficiency, resulting in the improved photocatalytic performance of the Ti3+ self-doped TiO2/g-C3N4 heterojunctions.

  1. The S-DALINAC polarized electron injector SPIN

    Energy Technology Data Exchange (ETDEWEB)

    Eckardt, Christian; Bahlo, Thore; Bangert, Phillip; Barday, Roman; Bonnes, Uwe; Brunken, Marco; Burandt, Christoph; Eichhorn, Ralf; Enders, Joachim; Espig, Martin; Platz, Markus; Poltoratska, Yuliya; Roth, Markus; Schneider, Fabian; Wagner, Markus; Weber, Antje; Zwicker, Benjamin [Institut fuer Kernphysik, Technische Universitaet, Darmstadt (Germany); Ackermann, Wolfgang; Mueller, Wolfgang F.O.; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, Technische Universitaet, Darmstadt (Germany); Aulenbacher, Kurt [Institut fuer Kernphysik, Johannes Gutenberg-Universitaet, Mainz (Germany)

    2011-07-01

    A source of polarized electrons has been installed at the superconducting 130 MeV Darmstadt electron linac S-DALINAC. Polarized electrons are generated by irradiating a GaAs cathode with pulsed Ti:Sapphire and diode lasers and preaccelerated to 100 keV. A Wien filter and 100 keV Mott polarimeter are used for spin manipulation and polarization measurement and various beam diagnostic elements are installed. To measure the beam polarization downstream of the superconducting injector linac a 5-10 MeV Mott polarimeter and a Compton-transmission polarimeter have been developed. We report on the status of the polarized electron source and foreseen experiments.

  2. Polarized hyperons probe dynamics of quark spin

    International Nuclear Information System (INIS)

    Daniel S. Carman; T. S. Harry Lee; Mac Mestayer; Reinhard Schumacher

    2007-01-01

    Researchers at Jefferson Laboratory demonstrate how two analyses of the same data provide two plausible models of spin transfer in exclusive hyperon production, yielding quite different pictures of quark spin dynamics and challenging existing theories

  3. Proton polarimeters for spin transfer experiments

    International Nuclear Information System (INIS)

    McNaughton, M.W.

    1985-01-01

    The design and use of proton polarimeters for spin transfer (Wolfenstein parameter) measurements is discussed. Polarimeters are compared with polarized targets for spin dependent experiments. 32 refs., 4 figs

  4. Spin diffusion and torques in disordered antiferromagnets

    KAUST Repository

    Manchon, Aurelien

    2017-02-01

    We have developed a drift-diffusion equation of spin transport in collinear bipartite metallic antiferromagnets. Starting from a model tight-binding Hamiltonian, we obtain the quantum kinetic equation within Keldysh formalism and expand it to the lowest order in spatial gradient using Wigner expansion method. In the diffusive limit, these equations track the spatio-temporal evolution of the spin accumulations and spin currents on each sublattice of the antiferromagnet. We use these equations to address the nature of the spin transfer torque in (i) a spin-valve composed of a ferromagnet and an antiferromagnet, (ii) a metallic bilayer consisting of an antiferromagnet adjacent to a heavy metal possessing spin Hall effect, and in (iii) a single antiferromagnet possessing spin Hall effect. We show that the latter can experience a self-torque thanks to the non-vanishing spin Hall effect in the antiferromagnet.

  5. Spin transport and relaxation in graphene

    International Nuclear Information System (INIS)

    Han Wei; McCreary, K.M.; Pi, K.; Wang, W.H.; Li Yan; Wen, H.; Chen, J.R.; Kawakami, R.K.

    2012-01-01

    We review our recent work on spin injection, transport and relaxation in graphene. The spin injection and transport in single layer graphene (SLG) were investigated using nonlocal magnetoresistance (MR) measurements. Spin injection was performed using either transparent contacts (Co/SLG) or tunneling contacts (Co/MgO/SLG). With tunneling contacts, the nonlocal MR was increased by a factor of ∼1000 and the spin injection/detection efficiency was greatly enhanced from ∼1% (transparent contacts) to ∼30%. Spin relaxation was investigated on graphene spin valves using nonlocal Hanle measurements. For transparent contacts, the spin lifetime was in the range of 50-100 ps. The effects of surface chemical doping showed that for spin lifetimes in the order of 100 ps, charged impurity scattering (Au) was not the dominant mechanism for spin relaxation. While using tunneling contacts to suppress the contact-induced spin relaxation, we observed the spin lifetimes as long as 771 ps at room temperature, 1.2 ns at 4 K in SLG, and 6.2 ns at 20 K in bilayer graphene (BLG). Furthermore, contrasting spin relaxation behaviors were observed in SLG and BLG. We found that Elliot-Yafet spin relaxation dominated in SLG at low temperatures whereas Dyakonov-Perel spin relaxation dominated in BLG at low temperatures. Gate tunable spin transport was studied using the SLG property of gate tunable conductivity and incorporating different types of contacts (transparent and tunneling contacts). Consistent with theoretical predictions, the nonlocal MR was proportional to the SLG conductivity for transparent contacts and varied inversely with the SLG conductivity for tunneling contacts. Finally, bipolar spin transport in SLG was studied and an electron-hole asymmetry was observed for SLG spin valves with transparent contacts, in which nonlocal MR was roughly independent of DC bias current for electrons, but varied significantly with DC bias current for holes. These results are very important for

  6. Microwave-assisted synthesis and characterization of poly(acrylic)/SiO2-TiO2 core-shell nanoparticle hybrid thin films

    International Nuclear Information System (INIS)

    Chien, Wen-Chen; Yu, Yang-Yen; Chen, Po-Kan; Yu, Hui-Huan

    2011-01-01

    In this study, poly(acrylic)/SiO 2 -TiO 2 core-shell nanoparticle hybrid thin films were successfully synthesized by microwave-assisted polymerization. The coupling agent 3-(trimethoxysilyl) propyl methacrylate (MSMA) was hydrolyzed with colloidal SiO 2 -TiO 2 core-shell nanoparticles, and then polymerized with two acrylic monomers and initiator to form a precursor solution. The results of this study showed that the spin-coated hybrid films had relatively good surface planarity, high thermal stability, a tunable refractive index (1.525 2 -TiO 2 core-shell nanoparticle hybrid thin films, for potential use in optical applications.

  7. Process of making titanium carbide (TiC) nano-fibrous felts

    Science.gov (United States)

    Fong, Hao; Zhang, Lifeng; Zhao, Yong; Zhu, Zhengtao

    2015-01-13

    A method of synthesizing mechanically resilient titanium carbide (TiC) nanofibrous felts comprising continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix, comprising: (a) electrospinning a spin dope for making precursor nanofibers with diameters less than 0.5 J.Lm; (b) overlaying the nanofibers to produce a nanofibrous mat (felt); and then (c) heating the nano-felts first at a low temperature, and then at a high temperature for making electrospun continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix; and (d) chlorinating the above electrospun nano-felts at an elevated temperature to remove titanium for producing carbide derived carbon (CDC) nano-fibrous felt with high specific surface areas.

  8. Electronic properties of Cr-, B-doped and codoped SrTiO3

    Science.gov (United States)

    Maldonado, Frank; Maza, Luz; Stashans, Arvids

    2017-01-01

    Spin-polarized density functional theory (DFT) computations have been carried out to investigate Cr-, B-doping as well as codoping in the SrTiO3 crystal. Impact of the oxygen vacancy as an intrinsic point defect has been also taken into consideration. In order to describe more precisely 3d electrons of the Ti and Cr atoms, Hubbard-like U term in the DFT has been introduced. Outcomes of the calculations reveal occupied states within the forbidden energy region arguing that these in-gap states might be responsible for visible light photocatalysis in the SrTiO3. Structural and magnetic features of the doped and codoped material are discussed as well.

  9. Asymmetric bipolar resistive switching in solution-processed Pt/TiO{sub 2}/W devices

    Energy Technology Data Exchange (ETDEWEB)

    Biju, Kuyyadi P; Bourim, El Mostafa; Hwang, Hyunsang [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro (Oryong-dong), Buk-gu, Gwangju 500-712 (Korea, Republic of); Liu, XinJun; Kim, Insung; Jung, Seungjae; Siddik, Manzar; Lee, Joonmyoung, E-mail: biju@gist.ac.k, E-mail: hwanghs@gist.ac.k [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro (Oryong-dong), Buk-gu, Gwangju 500-712 (Korea, Republic of)

    2010-12-15

    The resistive switching characteristics of Pt/TiO{sub 2}/W devices in a submicrometre via-hole structure are investigated. TiO{sub 2} film is grown by the sol-gel spin coating technique. The device exhibits reversible and reproducible bistable resistive switching with a rectifying effect. The Schottky contact at the Pt/TiO{sub 2} interface limits electron injection under reverse bias resulting in a rectification ratio of >60 at 2 V in the low-resistance state. The switching mechanism in our device can be interpreted as an anion migration-induced redox reaction at the tungsten bottom electrode (W). The rectifying effect can significantly reduce the sneak path current in a crossbar array and provide a feasible way to achieve high memory density.

  10. TiO2 Nanowires/Poly(Methyl Methacrylate) Based Hybrid Photodetector: Improved Light Detection.

    Science.gov (United States)

    Saha, S; Mondal, A; Choudhur, B; Goswami, T; Sarkar, M B; Chattopadhyay, K K

    2016-03-01

    Hybrid photodetector with a maximum external quantum efficiency of ~3.08% in the UV region at 370 nm, was fabricated by spin-coated poly(methyl methacrylate) (PMMA) polymer onto glancing angle deposited (GLAD) vertically aligned TiO2 nanowire (NW) arrays. The TiO2 NWs/PMMA detector shows excellent rectification and constant 1.3 times photo-responsivity in the reverse bias condition from -1 V to -10 V. The photodiode possesses a low ideality factor of 5.1 as compared to bared TiO2 NWs device of 7.1. The hybrid device produces sharp turn-on of -0.8 s and turn-off transient of -0.9 s respectively.

  11. ZrTiO4 nanowire growth using membrane-assisted Pechini route

    Directory of Open Access Journals (Sweden)

    P. R. de Lucena

    2014-11-01

    Full Text Available The high surface-to-volume ratio of nanowires makes them natural competitors as new device components. In this regard, a current major challenge is to produce quasi-one-dimensional nanostructures composed of well established oxide-based materials. This article reports the synthesis of ZrTiO4 nanowires on a silicon (100 wafer in a single-step deposition/thermal treatment. The template-directed membrane synthesis strategy was associated with the Pechini route and spin-coating deposition technique. ZrTiO4 nanowires were obtained at 700 ˚C with diameters in the range of 80-100 nm. FEG- SEM images were obtained to investigate ZrTiO4 nanowire formation on the silicon surface and energy dispersive x-ray detection (EDS and x-ray diffraction (XRD analyses were performed to confirm the oxide composition and structure.

  12. MOKE study of Co/Ti/(Gd-Co) multilayers near the magnetic compensation state

    International Nuclear Information System (INIS)

    Svalov, A.V.; Fernandez, A.; Vas'kovskiy, V.O.; Kurlyandskaya, G.V.; Barandiaran, J.M.; Anton, R. Lopez; Tejedor, M.

    2006-01-01

    The magnetic behaviour of [Co/Ti/a-Gd 0.36 Co 0.64 /Ti] 4 /Co layered structures was studied by means of the transversal magneto-optic Kerr effect, with Ti spacers of different thicknesses. Within the Gd 0.36 Co 0.64 amorphous layer, the Gd magnetic sub-lattice dominates at all investigated temperatures. The strong exchange interaction at the interfaces causes 'macroscopic ferrimagnetic behaviour' in the whole system. The existence of a magnetic compensation state in the complete multilayer system was manifested by the change of sign in the magneto-optic hysteresis loops and the increase of coercivity. The evolution of the critical field for a spin-orientation transition leading to a non-collinear magnetic state near the 'compensation temperature' can be described within molecular field theory. The influence of the non-magnetic spacer thickness on the characteristics of the compensation state is also discussed

  13. Bipolar resistive switching of solution processed TiO{sub 2}–graphene oxide nanocomposite for nonvolatile memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Senthilkumar, V.; Kathalingam, A.; Valanarasu, S.; Kannan, V.; Rhee, Jin-Koo, E-mail: jkrhee@dgu.edu

    2013-11-08

    In this study, we report the observation of memory effect in TiO{sub 2}–GO nanocomposite films. Electrical properties of the prepared Al/TiO{sub 2}–GO composite/ITO devices have shown stable and reproducible bipolar resistive switching behavior. The TiO{sub 2}–GO composite films were prepared using solution method by spin coating technique. Observed results have shown that the inclusion of GO in the TiO{sub 2} matrix have exhibited a significant role in the resistive switching mechanism. The device has exhibited an excellent memory characteristic with low operating voltages, good endurance up to 10{sup 5} cycles and long retention time more than 5×10{sup 3} s.

  14. Magnus effects on spinning transonic missiles

    Science.gov (United States)

    Seginer, A.; Rosenwasser, I.

    1983-01-01

    Magnus forces and moments were measured on a basic-finner model spinning in transonic flow. Spin was induced by canted fins or by full-span or semi-span, outboard and inboard roll controls. Magnus force and moment reversals were caused by Mach number, reduced spin rate, and angle of attack variations. Magnus center of pressure was found to be independent of the angle of attack but varied with the Mach number and model configuration or reduced spin rate.

  15. Electron Spin Dynamics in Semiconductor Quantum Dots

    International Nuclear Information System (INIS)

    Marie, X.; Belhadj, T.; Urbaszek, B.; Amand, T.; Krebs, O.; Lemaitre, A.; Voisin, P.

    2011-01-01

    An electron spin confined to a semiconductor quantum dot is not subject to the classical spin relaxation mechanisms known for free carriers but it strongly interacts with the nuclear spin system via the hyperfine interaction. We show in time resolved photoluminescence spectroscopy experiments on ensembles of self assembled InAs quantum dots in GaAs that this interaction leads to strong electron spin dephasing.

  16. The chirality operators for Heisenberg spin systems

    International Nuclear Information System (INIS)

    Subrahmanyam, V.

    1994-01-01

    The ground state of closed Heisenberg spin chains with an odd number of sites has a chiral degeneracy, in addition to a two-fold Kramers degeneracy. A non-zero chirality implies that the spins are not coplanar, and is a measure of handedness. The chirality operator, which can be treated as a spin-1/2 operator, is explicitly constructed in terms of the spin operators, and is given as commutator of permutation operators. (author). 3 refs

  17. Deformed Fredkin spin chain with extensive entanglement

    Science.gov (United States)

    Salberger, Olof; Udagawa, Takuma; Zhang, Zhao; Katsura, Hosho; Klich, Israel; Korepin, Vladimir

    2017-06-01

    We introduce a new spin chain which is a deformation of the Fredkin spin chain and has a phase transition between bounded and extensive entanglement entropy scaling. In this chain, spins have a local interaction of three nearest neighbors. The Hamiltonian is frustration-free and its ground state can be described analytically as a weighted superposition of Dyck paths that depends on a deformation parameter t. In the purely spin 1/2 case, whenever t\

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-10-25

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

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

    Science.gov (United States)

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

    2014-09-01

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

  20. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

    Science.gov (United States)

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

    2017-09-01

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

  1. Detection and Control of Individual Nuclear Spins Using a Weakly Coupled Electron Spin

    NARCIS (Netherlands)

    Taminiau, T.H.; Wagenaar, J.J.T.; Van der Sar, T.; Jelezko, F.; Dobrovitski, V.V.; Hanson, R.

    2012-01-01

    We experimentally isolate, characterize, and coherently control up to six individual nuclear spins that are weakly coupled to an electron spin in diamond. Our method employs multipulse sequences on the electron spin that resonantly amplify the interaction with a selected nuclear spin and at the same

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

    Science.gov (United States)

    Gulbrandsen, Sverre A.; Brataas, Arne

    2018-02-01

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

  3. Fermi surfaces and electronic structure of the Heusler alloy Co2TiSn

    International Nuclear Information System (INIS)

    Hickey, M C; Husmann, A; Holmes, S N; Jones, G A C

    2006-01-01

    The electronic structure of the Heusler alloy Co 2 TiSn is investigated here, with particular attention paid to its potential as a half-metallic ferromagnet. Ab initio calculations are performed using a plane wave pseudopotential code in the framework of density functional theory. These accurate calculations are done with convergence tolerances of 10 -5 and 10 -4 eV on the total energy and Fermi energy, respectively. The alloy is found not to be a half-metal. Minority spin electrons undergo distinctly hole-like dispersion at the Γ point in k space while the majority spin bands are metallic with a multiply connected tube-like Fermi surface. Further, the computed minority band gap and spin polarization at the Fermi level are larger when the calculation is performed using the generalized gradient approximation

  4. Electron paramagnetic resonance investigations of Fe3+ doped layered TiInS2 and TiGaSe2 single crystals

    International Nuclear Information System (INIS)

    Faik, Mikailov; Bulat, Rameev; Sinan, Kazan; Bekir, Aktash; Faik, Mikailov; Bulat, Rameev

    2005-01-01

    Full text : TiInS 2 and TiGaSe 2 single crystals doped by paramagnetic Fe ions have been studied at room temperature by Electron Paramagnetic Resonance (EPR) technique. A fine structure of EPR spectra of paramagnetic Fe 3 + ions was observed. The spectra were interpreted to correspond to the transitions among spin multiplet which are splitted by the local ligand crystal field (CF) of orthorhombic symmetry. Four equivalent Fe 3 + centers have been observed in the EPR spectra and the local symmetry of crystal field at the Fe 3 + site and CF parameters were determined. It was established that symmetry axis of the axial component in the CF is making an angle of about 48 and 43 degree with the plane of layers of TiInS 2 and TiGaSe 2 crystals respectively. Experimental results indicate that the Fe ions substitute In (GA) at the center of InS 4 (GaSe 4 ) tetrahedrons, and the rhombic distortion of the CF is caused by the TI ions located in the trigonal cavities between the tethedral complexes

  5. Magneto-electric properties and magnetic entropy change in perovskite La{sub 0.7}Sr{sub 0.3}Mn{sub 1−x}Ti{sub x}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Bau, Le Viet, E-mail: levietbau@hdu.edu.vn; An, Nguyen Manh

    2016-12-15

    The ceramic samples of La{sub 0.7}Sr{sub 0.3}Mn{sub 1−x}Ti{sub x}O{sub 3}(x=0; 0.05; 0.1; 0.2 and 0.3) were synthesized by the conventional solid state reaction method. Their electric, magnetic and magnetocaloric properties have been investigated. The transition temperature declines and a significant influence on the width of the ferro-paramagnetic phase transition is observed as increasing Ti concentration. Moreover, the sign of spin-glass is expected to exist in the high concentration samples. For fully replacing Ti{sup 4+} for Mn{sup 4+}, the canted spin state is formed. The substitution Ti for Mn increases resistivity quickly and the insulating–metallic transition temperature shifts toward lower temperature. For x>0.1 samples, the insulating state is observed even in ferromagnetic phase. The substitution Ti shifts the CME to room temperature while almost persists the value of entropy change. Although the maximum value of CME reduces slightly, the temperature range happening MCE is expended and then improves the relative cooling power. These properties could be explained in term of DE interaction and phase separation phenomenon. - Highlights: • Electro-magnetic properties and CME of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Ti{sub x}O{sub 3} have been investigated. • T{sub C} declines and the width of the F-M phase transition is observed as increasing Ti concentration. • For fully replacing Ti{sup 4+} for Mn{sup 4+}, the canted spin state is formed. • The substitution Ti for Mn increases resistivity quickly and T{sub P} shifts toward lower temperature. • The substitution Ti shifts CME to 300 K while almost persists the value of entropy change. • Relative cooling power (RCP) increases with substitution 5% Ti for Mn.

  6. Superselective pseudocontinuous arterial spin labeling

    NARCIS (Netherlands)

    Helle, M.; Norris, D.G.; Rufer, S.; Alfke, K.; Jansen, O.; van Osch, M.J.

    2010-01-01

    A new technique for the imaging of flow territories of individual extra- and intracranial arteries is presented. The method is based on balanced pseudocontinuous arterial spin labeling but employs additional time-varying gradients in between the radiofrequency pulses of the long labeling train. The

  7. Spin squeezing and quantum correlations

    Indian Academy of Sciences (India)

    Spin squeezing and quantum correlations. K S MALLESH1, SWARNAMALA SIRSI2, MAHMOUD A A SBAIH1, P N DEEPAK1 and G RAMACHANDRAN3. 1Department of Studies in Physics, University of Mysore, Mysore 570 006, India. 2 Department of Physics, Yuvaraja's College, University of Mysore, Mysore 570 005, ...

  8. High spin states in Cu

    Indian Academy of Sciences (India)

    The mechanism for the generation of high angular momentum states in the restricted va- lence space around ... The generation of higher spin states re- .... Channel Number. 1. Counts. 0. 200. 400. 600. Channel Number. 1. Counts multiplicity. 0cp. 1cp. 2cp. 3cp. 4cp. 5cp. 0a. 1a. 2a. Charged particle. 6cp. Alpha multiplicity. −.

  9. Algebraic topology of spin glasses

    International Nuclear Information System (INIS)

    Koma, Tohru

    2011-01-01

    We study the topology of frustration in d-dimensional Ising spin glasses with d ≥ 2 with nearest-neighbor interactions. We prove the following. For any given spin configuration, the domain walls on the unfrustration network are all transverse to a frustrated loop on the unfrustration network, where a domain wall is defined to be a connected element of the collection of all the (d - 1)-cells which are dual to the bonds having an unfavorable energy, and the unfrustration network is the collection of all the unfrustrated plaquettes. These domain walls are topologically nontrivial because they are all related to the global frustration of a loop on the unfrustration network. Taking account of the thermal stability for the domain walls, we can explain the numerical results that three- or higher-dimensional systems exhibit a spin glass phase, whereas two-dimensional ones do not. Namely, in two dimensions, the thermal fluctuations of the topologically nontrivial domain walls destroy the order of the frozen spins on the unfrustration network, whereas they do not in three or higher dimensions. This may be interpreted as a global topological effect of the frustrations.

  10. Spinning targets for laser fusion

    International Nuclear Information System (INIS)

    Baldwin, D.E.; Ryutov, D.D.

    1995-09-01

    Several techniques for spinning the ICF targets up prior to or in the course of their compression are suggested. Interference of the rotational shear flow with Rayleigh-Taylor instability is briefly discussed and possible consequences for the target performance are pointed out

  11. High spin spectroscopy of Pr

    Indian Academy of Sciences (India)

    2001-07-31

    Jul 31, 2001 ... c Indian Academy of Sciences. Vol. 57, No. 1. — journal of. July 2001 physics pp. 175–179. High spin spectroscopy of. 139. Pr. S CHANDA. ½. , SARMISHTHA BHATTACHARYYA. ¾. , TUMPA BHATTACHARJEE .... which is configured under LINUX platform. Around 90 x10 two and higher fold events were ...

  12. Spin physics by the SMC

    CERN Document Server

    Le Goff, J M

    2000-01-01

    The Spin Muon Collaboration at CERN has covered a wide range of spin physics. The main aim of the collaboration was the measurement of the $g_{1}$ spin structure functions of the proton and the neutron (using deuteron targets) in the range $0.003spin structure functions $g_{2}$ were also measured, which allowed for a reduction on the error in $g_{1}$. Semi-inclusive data were analyzed in order to produce the first polarized quark distributions. Data obtained with a dedicated low $x$ trigger extend down to $x=6 \\times 10^{-5}$ for $Q^{2} \\geq$ 0.01 GeV$^{2}$. Some more specifics channels are still being analyzed, they include asymmetry in diffractive $\\rho$ production, hadron azimuthal asymmetry with a transversely polarized target, measurement of the longitudinal $\\Lambda$ polarization, and the asymmetry in high $P_{t}$ hadron pair production. This last asymmetry is related to the gluon polar...

  13. Spin tunnelling in mesoscopic systems

    Indian Academy of Sciences (India)

    We study spin tunnelling in molecular magnets as an instance of a mesoscopic phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel splitting between various pairs of Zeeman levels in this molecule oscillates as a function of applied magnetic field, vanishing completely at special points in the ...

  14. Spinning pipe gas lens revisited

    CSIR Research Space (South Africa)

    Mafusire, C

    2008-01-01

    Full Text Available , there is little information on optical phase aberrations and no study to date on the propagation parameters of the laser beam, but has rather remained rooted in the domain of ray optics. Researchers revisit the spinning pipe gas lens in this paper with new...

  15. Spin determination of fission resonances

    International Nuclear Information System (INIS)

    Keyworth, G.A.

    1976-01-01

    The present status of available information on the channel quantum numbers for resonance fission and the most urgently needed additional experiments are examined. The role of spin in the 235 U + n system is emphasized. The discussion relies heavily on recent alignment measurements and polarization results

  16. High-spin nuclear spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diamond, R.M.

    1986-07-01

    High-spin spectroscopy is the study of the changes in nuclear structure, properties, and behavior with increasing angular momentum. It involves the complex interplay between collective and single-particle motion, between shape and deformation changes, particle alignments, and changes in the pairing correlations. A review of progress in theory, experimentation, and instrumentation in this field is given. (DWL)

  17. High energy spin isospin modes in nuclei

    International Nuclear Information System (INIS)

    Chanfray, G.; Ericson, M.

    1984-01-01

    The high energy response of nuclei to a spin-isospin excitation is investigated. We show the existence of a strong contrast between the spin transverse and spin longitudinal responses. The second one undergoes a shadow effect in the Δ region and displays the occurrence of the pionic branch

  18. Recent advances of spin crossover research

    NARCIS (Netherlands)

    Gutlich, P; van Koningsbruggen, PJ; Renz, F; Schonherr, T

    2004-01-01

    Thermal spin transition (spin crossover), one of the most fascinating dynamic electronic structure phenomena occurring in coordination compounds of third row transition metal ions, mostly of iron(II), iron(III) and cobalt(II) with critical ligand field strengths competing with the spin pairing

  19. Simple classical approach to spin resonance phenomena

    DEFF Research Database (Denmark)

    Gordon, R A

    1977-01-01

    A simple classical method of describing spin resonance in terms of the average power absorbed by a spin system is discussed. The method has several advantages over more conventional treatments, and a number of important spin resonance phenomena, not normally considered at the introductory level...

  20. Overview of longitudinal spin physics at PHENIX

    International Nuclear Information System (INIS)

    Liu, Mingxiong

    2007-01-01

    We present a brief overview of the longitudinal spin physics program in the PHENIX experiment at the Relativistic Heavy Ion Collider at BNL. The main goal is to study the longitudinal spin structure of the proton with strongly interacting probes at high energy to resolve the long standing 'spin crisis'. The latest results from PHENIX are presented. (author)

  1. Geometry of Spin: Clifford Algebraic Approach

    Indian Academy of Sciences (India)

    of Pauli matrices follow from the underlying algebra. Clif- ford algebraic approach provides a geometrical and hence intuitive way to understand quantum theory of spin, and is a natural formalism to study spin. Clifford algebraic formal- ism has lot of applications in every field where spin plays an important role. Introduction.

  2. Study of squeezing in spin clusters

    International Nuclear Information System (INIS)

    Reboiro, M.; Civitarese, O.; Rebon, L.

    2007-01-01

    The conditions under which spin squeezing occurs in an asymmetric chain of spins are discussed. The time evolution of the system is calculated for different initial conditions. The effects of the use of spin coherent states to model the initial condition are analyzed

  3. Spin-glass transition in disordered terbium

    International Nuclear Information System (INIS)

    Hauser, J.J.

    1985-01-01

    While crystalline Tb is a helix antiferromagnet with a Neel temperature of 229 K which becomes ferromagnetic at 222 K, disordered Tb exhibits a spin-glass transition. The spin-glass freezing temperature ranges from 183 to 53 K, the lowest temperatures corresponding to the greatest degree of atomic disorder. These experiments constitute the first evidence for an elemental spin-glass. (author)

  4. Geometry of Spin: Clifford Algebraic Approach

    Indian Academy of Sciences (India)

    ... all the propertiesof Pauli matrices follow from the underlying algebra. Cliffordalgebraic approach provides a geometrical and henceintuitive way to understand quantum theory of spin, and isa natural formalism to study spin. Clifford algebraic formalismhas lot of applications in every field where spin plays animportant role.

  5. Muon spin rotation and other microscopic probes of spin-glass dynamics

    International Nuclear Information System (INIS)

    MacLaughlin, D.E.

    1980-01-01

    A number of different microscopic probe techniques have been employed to investigate the onset of the spin-glass state in dilute magnetic alloys. Among these are Moessbauer-effect spectroscopy, neutron scattering, ESR of the impurity spins, host NMR and, most recently, muon spin rotation and depolarization. Spin probes yield information on the microscopic static and dynamic behavior of the impurity spins, and give insight into both the spin freezing process and the nature of low-lying excitations in the ordered state. Microscopic probe experiments in spin glasses are surveyed, and the unique advantages of muon studies are emphasized

  6. Electrical detection of spin current and spin relaxation in nonmagnetic semiconductors

    International Nuclear Information System (INIS)

    Miah, M Idrish

    2008-01-01

    We report an electrical method for the detection of spin current and spin relaxation in nonmagnetic semiconductors. Optically polarized spins are dragged by an electric field in GaAs. We use the anomalous Hall effect for the detection of spin current and spin relaxation. It is found that the effect depends on the electric field and doping density as well as on temperature, but not on the excitation power. A calculation for the effect is performed using the measured spin polarization by a pump-probe experiment. The results are also discussed in comparison with a quantitative evaluation of the spin lifetimes of the photogenerated electrons under drift in GaAs

  7. Electrical detection of spin current and spin relaxation in nonmagnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M Idrish [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au

    2008-09-21

    We report an electrical method for the detection of spin current and spin relaxation in nonmagnetic semiconductors. Optically polarized spins are dragged by an electric field in GaAs. We use the anomalous Hall effect for the detection of spin current and spin relaxation. It is found that the effect depends on the electric field and doping density as well as on temperature, but not on the excitation power. A calculation for the effect is performed using the measured spin polarization by a pump-probe experiment. The results are also discussed in comparison with a quantitative evaluation of the spin lifetimes of the photogenerated electrons under drift in GaAs.

  8. Inverse spin Hall effect induced by spin pumping into semiconducting ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jung-Chuan [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Huang, Leng-Wei [Graduate Institute of Applied Physics, National Chengchi University, Taipei 11605, Taiwan (China); Hung, Dung-Shing, E-mail: dshung@mail.mcu.edu.tw [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Department of Information and Telecommunications Engineering, Ming Chuan University, Taipei 111, Taiwan (China); Chiang, Tung-Han [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Huang, J. C. A., E-mail: jcahuang@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Liang, Jun-Zhi [Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Physics, Fu Jen Catholic University, Taipei 242, Taiwan (China); Lee, Shang-Fan, E-mail: leesf@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Graduate Institute of Applied Physics, National Chengchi University, Taipei 11605, Taiwan (China)

    2014-02-03

    The inverse spin Hall effect (ISHE) of n-type semiconductor ZnO thin films with weak spin-orbit coupling has been observed by utilizing the spin pumping method. In the ferromagnetic resonance condition, the spin pumping driven by the dynamical exchange interaction of a permalloy film injects a pure spin current into the adjacent ZnO layer. This spin current gives rise to a DC voltage through the ISHE in the ZnO layer, and the DC voltage is proportional to the microwave excitation power. The effect is sizeable even when the spin backflow is considered.

  9. Inverse spin Hall effect induced by spin pumping into semiconducting ZnO

    International Nuclear Information System (INIS)

    Lee, Jung-Chuan; Huang, Leng-Wei; Hung, Dung-Shing; Chiang, Tung-Han; Huang, J. C. A.; Liang, Jun-Zhi; Lee, Shang-Fan

    2014-01-01

    The inverse spin Hall effect (ISHE) of n-type semiconductor ZnO thin films with weak spin-orbit coupling has been observed by utilizing the spin pumping method. In the ferromagnetic resonance condition, the spin pumping driven by the dynamical exchange interaction of a permalloy film injects a pure spin current into the adjacent ZnO layer. This spin current gives rise to a DC voltage through the ISHE in the ZnO layer, and the DC voltage is proportional to the microwave excitation power. The effect is sizeable even when the spin backflow is considered

  10. Spinning Reserve From Responsive Loads

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, B.J.

    2003-04-08

    Responsive load is the most underutilized reliability resource available to the power system today. It is currently not used at all to provide spinning reserve. Historically there were good reasons for this, but recent technological advances in communications and controls have provided new capabilities and eliminated many of the old obstacles. North American Electric Reliability Council (NERC), Federal Energy Regulatory Commission (FERC), Northeast Power Coordinating Council (NPCC), New York State Reliability Council (NYSRC), and New York Independent System Operator (NYISO) rules are beginning to recognize these changes and are starting to encourage responsive load provision of reliability services. The Carrier ComfortChoice responsive thermostats provide an example of these technological advances. This is a technology aimed at reducing summer peak demand through central control of residential and small commercial air-conditioning loads. It is being utilized by Long Island Power Authority (LIPA), Consolidated Edison (ConEd), Southern California Edison (SCE), and San Diego Gas and Electric (SDG&E). The technology is capable of delivering even greater response in the faster spinning reserve time frame (while still providing peak reduction). Analysis of demand reduction testing results from LIPA during the summer of 2002 provides evidence to back up this claim. It also demonstrates that loads are different from generators and that the conventional wisdom, which advocates for starting with large loads as better ancillary service providers, is flawed. The tempting approach of incrementally adapting ancillary service requirements, which were established when generators were the only available resources, will not work. While it is easier for most generators to provide replacement power and non-spinning reserve (the slower response services) than it is to supply spinning reserve (the fastest service), the opposite is true for many loads. Also, there is more financial

  11. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  12. Comparison of mechanical behavior of TiN, TiNC, CrN/TiNC, TiN/TiNC films on 9Cr18 steel by PVD

    Science.gov (United States)

    Feng, Xingguo; Zhang, Yanshuai; Hu, Hanjun; Zheng, Yugang; Zhang, Kaifeng; Zhou, Hui

    2017-11-01

    TiN, TiNC, CrN/TiNC and TiN/TiNC films were deposited on 9Cr18 steel using magnetron sputtering technique. The morphology, composition, chemical state and crystalline structure of the films were observed and analyzed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Hardness and adhesion force were tested by nanoindentation and scratch tester, respectively. The friction and wear behavior of TiN, TiNC, CrN/TiNC and TiN/TiNC films sliding against GCr15 balls were investigated and compared synthetically using ball-on-disk tribometer. It was found that Tisbnd N, Tisbnd C, Tisbnd Nsbnd C and Csbnd C bonds were formed. The TiN/TiNC film was composed of TiN, TiC and TiNC phases. Hardness and adhesion force results indicated that although the TiN film possessed the highest hardness, its adhesion force was lowest among all the films. Tribological test results showed that the friction coefficient of TiN/TiNC was much lower than that of TiN and the wear rate decreases remarkably from 2.3 × 10-15 m3/Nm to 7.1 × 10-16 m3/Nm, which indicated the TiN/TiNC film has better wear resistance.

  13. Oxide Ferromagnetic Semiconductors for Spin-Electronic Transprt

    International Nuclear Information System (INIS)

    Pandey, R.K.

    2008-01-01

    The objective of this research was to investigate the viability of oxide magnetic semiconductors as potential materials for spintronics. We identified some members of the solid solution series of ilmenite (FeTiO3) and hematite (Fe2O3), abbreviated as (IH) for simplicity, for our investigations based on their ferromagnetic and semiconducting properties. With this objective in focus we limited our investigations to the following members of the modified Fe-titanates: IH33 (ilmenitehematite with 33 atomic percent hematite), IH45 (ilmenite-hematite with 45 atomic percent hematite), Mn-substituted ilmenite (Mn-FeTiO3), and Mn-substituted pseudobrookite (Mn- Fe2TiO5). All of them are: (1) wide bandgap semiconductors with band gaps ranging in values between 2.5 to 3.5 eV; (2) n-type semiconductors; (3) they exhibit well defined magnetic hysteresis loops and (4) their magnetic Curie points are greater than 400K. Ceramic, film and single crystal samples were studied and based on their properties we produced varistors (also known as voltage dependent resistors) for microelectronic circuit protection from power surges, three-terminal microelectronic devices capable of generating bipolar currents, and an integrated structured device with controlled magnetic switching of spins. Eleven refereed journal papers, three refereed conference papers and three invention disclosures resulted from our investigations. We also presented invited papers in three international conferences and one national conference. Furthermore two students graduated with Ph.D. degrees, three with M.S. degrees and one with B.S. degree. Also two post-doctoral fellows were actively involved in this research. We established the radiation hardness of our devices in collaboration with a colleague in an HBCU institution, at the Cyclotron Center at Texas A and M University, and at DOE National Labs (Los Alamos and Brookhaven). It is to be appreciated that we met most of our goals and expanded vastly the scope of

  14. Quantum spin liquid and spin ice states in new pyrochlores

    Science.gov (United States)

    Sibille, Romain

    Magnetic systems with competing interactions can adopt exotic ground states. A particularly promising class is that of the geometrically frustrated magnets, such as the A2B2O7 pyrochlores, in which unusual spin liquids appear. Some of these phases feature short-range correlated states analogous to a Coulomb phase and give rise to emergent quasiparticle excitations. Although cases like the classical spin ice are reasonably well understood, the theoretical expectation is that quantum fluctuations lead to novel phases which are quantum spin liquids (QSLs). For instance, the quantum spin ice (QSI) is a generalization of the classical spin ice state to include quantum fluctuations, such that the effective theory becomes emergent quantum electrodynamics - the classical monopoles become coherent quantum quasiparticles, and a novel excitation playing the role of the photon appears. In this talk, I will present results on three novel materials with potential for QSL states. Each of them corresponds to a way to potentially strengthen the role of quantum fluctuations on the ground state properties of pyrochlore magnets. Firstly, I will demonstrate that, in Tb2Hf2O7, where a sizeable gap isolates the non-Kramers ground state doublet at low temperature, a large amount of anion Frenkel disorder leads to quenched random crystal fields and disordered magnetic interactions. The detailed study of this material demonstrates that disorder can play a crucial role in preventing long-range magnetic order at low temperatures, and instead induces a strongly-fluctuating Coulomb spin liquid with defect-induced frozen magnetic degrees of freedom. Secondly, I will present results on another QSL candidate based on non-Kramers ions, Pr2Hf2O7, which displays striking characteristics of the ferromagnetic correlations expected in a QSI. Finally, in the pyrochlore Ce2Sn2O7, where macroscopic measurements suggest an antiferromagnetic liquid ground state with quantum fluctuations, I will present

  15. Electron-Spin Filters Would Offer Spin Polarization Greater than 1

    Science.gov (United States)

    Ting, David Z.

    2009-01-01

    A proposal has been made to develop devices that would generate spin-polarized electron currents characterized by polarization ratios having magnitudes in excess of 1. Heretofore, such devices (denoted, variously, as spin injectors, spin polarizers, and spin filters) have typically offered polarization ratios having magnitudes in the approximate range of 0.01 to 0.1. The proposed devices could be useful as efficient sources of spin-polarized electron currents for research on spintronics and development of practical spintronic devices.

  16. Transition metal atoms pathways on rutile TiO2 (110) surface: Distribution of Ti3+ states and evidence of enhanced peripheral charge accumulation

    Science.gov (United States)

    Cai, Yongqing; Bai, Zhaoqiang; Chintalapati, Sandhya; Zeng, Qingfeng; Feng, Yuan Ping

    2013-04-01

    Charge transfer between metal nanoparticles and the supported TiO2 surface is primarily important for catalytic applications as it greatly affects the catalytic activity and the thermal stability of the deposited nanoparticles on the surface. Herein, systematic spin-polarized density functional and HSE06 calculations are performed to evaluate the adsorption, diffusion, and charge state of several transition metal monomers on both stoichiometric and reduced rutile TiO2 (110) surface. Although the presence of oxygen vacancy (Ov) increases the binding of Au, Pt and Pd on the surface, it weakens the interaction thus enhancing the diffusion for Fe, Co, Ni, Ag, and Cu adatoms on the surface. For pristine reduced surface, only a small portion (around 5%) of the excess electrons occupy the topmost surface, which are mainly delocalized at the second nearest and third nearest fivefold coordinated Ti (Ti5c) atoms. Excess electrons populating at the Ti5c atoms on the basal plane can be transferred to strongly electronegative adsorbates like Au and Pt thus enabling a moderate adsorption at this site, whereas no stable adsorption is found for other less electronegative transition metal adatoms (Ag, Cu, Fe, Co, Ni, and Pd) on the reduced surface and for all the adatoms on stoichiometric surface. This result clarifies the origin of the experimental observation of the adsorption of O2 and CO molecules at Ti5c sites in connection with charge transfer. In addition, the spatial redistribution of the excess electrons around the Ov upon the adsorption of the monomers is thoroughly examined. Our finding of an accumulation of excess electrons at the Ti5c sites around the monomers explains the critical role of the perimeter interface of the deposited nanoparticles in promoting the adsorption and activation of reactants observed in experiments.

  17. Effect of mesh patterning with UV pulsed-laser on optical and electrical properties of ZnO/Ag-Ti thin films

    International Nuclear Information System (INIS)

    Kao, K.S.; Cheng, D.L.; Chang, S.H.; Hsieh, P.T.; Chin, H.S.; Lin, H.K.

    2010-01-01

    In this study, the ZnO/Ag-Ti structure for transparence conducting oxide (TCO) is investigated by optimizing the thickness of the Ag-Ti alloy and ZnO layers. The Ag-Ti thin film is deposited by DC magnetron sputtering and its thicknesses is well controlled. The ZnO thin film is prepared by sol-gel method using zinc acetate as cation source, 2-methoxiethanol as solvent and monoethanolamine as solution stabilizer. The ZnO film deposition is performed by spin-coating technique and dried at 150 deg. C on Corning 1737 glass. Due to the conductivity of ZnO/Ag-Ti is dominated by Ag-Ti, the sheet resistance of ZnO/Ag-Ti decrease dramatically as the thickness of Ag-Ti layer increases. However, the transmittances of ZnO/Ag-Ti become unacceptable for TCO application after the thickness of Ag-Ti layer beyond 6 nm. The as-deposited ZnO/Ag-Ti structure has the optical transmittance of 83% - 500 nm and the low resistivity of 1.2 x 10 -5 Ω-cm. Furthermore, for improving the optical and electrical properties of ZnO/Ag-Ti, the thermal treatment using laser is adopted. Experimental results indicate that the transmittance of ZnO/Ag-Ti is improved from 83% to 89% - 500 nm with resistivity of 1.02 x 10 -5 Ω-cm after laser drilling. The optical spectrum, the resistance, and the morphology of the ZnO/Ag-Ti will be reported in the study.

  18. Spin ice Thin Film: Surface Ordering, Emergent Square ice, and Strain Effects

    Science.gov (United States)

    Jaubert, L. D. C.; Lin, T.; Opel, T. S.; Holdsworth, P. C. W.; Gingras, M. J. P.

    2017-05-01

    Motivated by recent realizations of Dy2 Ti2 O7 and Ho2 Ti2 O7 spin ice thin films, and more generally by the physics of confined gauge fields, we study a model spin ice thin film with surfaces perpendicular to the [001] cubic axis. The resulting open boundaries make half of the bonds on the interfaces inequivalent. By tuning the strength of these inequivalent "orphan" bonds, dipolar interactions induce a surface ordering equivalent to a two-dimensional crystallization of magnetic surface charges. This surface ordering may also be expected on the surfaces of bulk crystals. For ultrathin films made of one cubic unit cell, once the surfaces have ordered, a square ice phase is stabilized over a finite temperature window. The square ice degeneracy is lifted at lower temperature and the system orders in analogy with the well-known F transition of the 6-vertex model. To conclude, we consider the addition of strain effects, a possible consequence of interface mismatches at the film-substrate interface. Our simulations qualitatively confirm that strain can lead to a smooth loss of Pauling entropy upon cooling, as observed in recent experiments on Dy2 Ti2 O7 films.

  19. EPR Investigations of G-C3N4/TiO2 Nanocomposites

    Directory of Open Access Journals (Sweden)

    Dana Dvoranová

    2018-01-01

    Full Text Available The g-C3N4/TiO2 nanopowders prepared by the annealing of melamine and TiO2 P25 at 550 °C were investigated under dark and upon UV or visible-light photoactivation using X- and Q-band electron paramagnetic resonance (EPR spectroscopy. The EPR spectra of powders monitored at room temperature and 100 K showed the impact of the initial loading ratio of melamine/TiO2 on the character of paramagnetic centers observed. For the photocatalysts synthesized using a lower titania content, the paramagnetic signals characteristic for the g-C3N4/TiO2 nanocomposites were already found before exposure. The samples annealed using the higher TiO2 loading revealed the photoinduced generation of paramagnetic nitrogen bulk centers (g-tensor components g1 = 2.005, g2 = 2.004, g3 = 2.003 and hyperfine couplings from the nitrogen A1 = 0.23 mT, A2 = 0.44 mT, A3 = 3.23 mT typical for N-doped TiO2. The ability of photocatalysts to generate reactive oxygen species (ROS upon in situ UV or visible-light photoexcitation was tested in water or dimethyl sulfoxide by EPR spin trapping using 5,5-dimethyl 1-pyrroline N-oxide. The results obtained reflect the differences in photocatalyst nanostructures caused by the differing initial ratio of melamine/TiO2; the photocatalyst prepared by the high-temperature treatment of melamine/TiO2 wt. ratio of 1:3 revealed an adequate photoactivity in both spectral regions.

  20. Spin-configurations in thermoelectric MnCoGe materials

    Science.gov (United States)

    Hahn, Konstanze; Portavoce, Alain; Bertaina, Sylvain; Charai, Ahmed

    In the last decades, research for improved thermoelectric materials focused on the introduction of nanostructures. However, only modest enhancement of the thermoelectric efficiency could be achieved. For improved thermoelectric performance another approach is required. In this respect, temperature driven spin transport in magnetic materials offers great potential. The ternary Mn-Co-Ge, for example, shows interesting magnetocaloric and thermoelectric properties. Magnetic properties of ferromagnetic CoxMnyGe1-x-y thin films, for example, have been shown experimentally to vary with composition x and y, suggesting a possible tuning of the CoxMnyGe1-x-y properties to meet application's requirements. In this study, structural and magnetic transitions in MnGe-based materials with varying composition have been investigated using ab initio calculations. In particular, the effect of chemical composition on the stability of the hexagonal Ni2In-type and the orthorhombic TiNiSi-type structure has been examined focusing on their magnetic configurations. It has been found that compressive strain promotes the formation of the Ni2In-type structure which can be advantageous for the magnetostructural transition in thermomagnetic devices. The spin-Seebeck coefficient has been estimated for several magnetic configurations of such materials based on the Boltzmann transport. This work is financed by the A*MIDEX foundation.