Sample records for susceptibility chisub spin

  1. Susceptibilities and Spin Gaps of Weakly Coupled Spin Ladders

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    Larochelle, S.


    We calculate the uniform and staggered susceptibilities of two-chain spin-1/2 Heisenberg ladders using Monte-Carlo simulations. We show that the gap extracted from the uniform susceptibility and the saturation value of the staggered susceptibility are independent of the sign of the interchain coupling J{perpendicular} in the asymptotic limit |J{perpendicular}|/J {yields} 0. Furthermore, we examine the existence of logarithmic corrections to the linear scaling of the gap with |J{perpendicular}|.

  2. Dynamical spin dependent susceptibility of graphene like structure (United States)

    Moradian, Rostam; Rezania, Hamed; Marvi, Saeed


    Spin dependent susceptibility of gapped graphene is calculated using Hubbard model. We found that by increasing the electron density, energy gap and repulsive coulomb interaction the imaginary part of the susceptibility peaks will be shifted towards higher frequencies and by increasing the magnetization the imaginary part of the susceptibility peaks will be shifted towards lower frequencies. It means that plasmonic frequency depends on electrons band filling, electronic coulomb repulsion, magnetization and graphene initial energy gap.

  3. Spin susceptibility of Anderson impurities in arbitrary conduction bands (United States)

    Fang, Tie-Feng; Tong, Ning-Hua; Cao, Zhan; Sun, Qing-Feng; Luo, Hong-Gang


    Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution χimp to susceptibility, defined originally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in χimp, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local susceptibility χloc and to compare them with χimp obtained by the traditional NRG. Our results indicate that those exotic behaviors observed in χimp are unphysical. Instead, the low-energy excitations of the impurity in arbitrary bands only without gap at the Fermi energy are still a Fermi liquid and paramagnetic. We also demonstrate that unlike the traditional NRG yielding χloc less accurate than χimp, the FDM method allows a high-precision dynamical calculation of χloc at much reduced computational cost, with an accuracy at least one order higher than χimp. Moreover, artifacts in the FDM algorithm to χimp and origins of the spurious non-Fermi-liquid and diamagnetic features are clarified. Our work provides an efficient high-precision algorithm to calculate the spin susceptibility of impurity for arbitrary structured bands, while negating the applicability of Wilson's definition to such cases.

  4. Study of {chi}{sub c} production using HERA-B data

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    Aleksandrov, Aleksandar


    In this thesis the production of the charmonium states {chi}{sub c1} and {chi}{sub c2} in protonnucleus collisions at a proton-nucleon center-of-mass energy {radical}(s)=41.6 GeV was studied. The data used for the analysis have been taken by the fixed-target experiment HERA-B that uses the HERA proton beam to scatter protons off the nuclei of different wire targets. About 122.10{sup 3} recorded muonic J/{psi} decays, J/{psi}{yields}{mu}{sup +}{mu}{sup -}, resulted in almost 10000 reconstructed {chi}{sub c}{yields}J/{psi}{gamma}. The ratio R{sub {chi}{sub c}}= sum {sub i=1,2}{sigma}({chi}{sub ci})Br({chi}{sub ci}{yields}J/{psi}{gamma})/{sigma}(J/{psi}), which is the ratio of J/{psi} from {chi}{sub c} decays to all produced J/{psi}, was measured in the kinematical range -0.35chi}{sub c}}=0.190{sub -0.029}{sup +0.030}. Despite the small separation of the masses of the two {chi}{sub c} states, comparable to the detector resolution, the ratio R{sub 12}=R{sub {chi}{sub c}{sub 1}}/R{sub {chi}{sub c}{sub 2}} was measured yielding R{sub 12}=1.30{sub -0.37}{sup +0.59} which corresponds to a production cross section ratio ({sigma}({chi}{sub c1}))/({sigma}({chi}{sub c2}))=0.74{sub -0.22}{sup +0.34}. By using the known J/{psi} production cross section, the {chi}{sub c1} and {chi}{sub c2} production cross sections are calculated to be {sigma}({chi}{sub c1})=(153{+-}27) nb/nucleon and {sigma}({chi}{sub c2})=(207{+-}39) nb/nucleon, respectively. All results were obtained under the assumption that both the J/{psi} and {chi}{sub c} states are produced without polarization. In addition a study of possible deviations of R{sub {chi}{sub c}} and R{sub 12} due to the polarization of J/{psi} and {chi}{sub c} was performed. By varying the polarization parameter, {lambda}{sub obs}, of all produced J/{psi} by 2{sigma} around the value measured by HERA-B, and assuming fully

  5. Anomalously large spin susceptibility enhancement in n-doped CdMnTe quantum wells

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    Ben Cheikh, Z. [Laboratoire Charles Coulomb, UMR 5221, Département Semi-conducteurs, Matériaux et Capteurs, Université Montpellier 2, France and Laboratoire de Physique des Matériaux: Structures et Propriétés, Faculté (Tunisia); Cronenberger, S.; Vladimirova, M.; Scalbert, D. [Laboratoire Charles Coulomb, UMR 5221, Departement Semi-conducteurs, Materiaux et Capteurs, Universite Montpellier 2 (France); Boujdaria, K. [Laboratoire de Physique des Matériaux: Structures et Propriétés, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Zarzouna (Tunisia); Baboux, F.; Perez, F. [Institut des NanoSciences de Paris, CNRS/Université Paris 6, 4 place Jussieu, F-75005 Paris (France); Wojtowicz, T.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)


    We report on time-resolved Kerr rotation (TRKR) experiments done on n-doped CdMnTe quantum wells (QWs), in the regime where strong coupling between the electron and the Mn spin-flip excitations shows up. It has been proposed previously to deduce the 2D electron gas spin susceptibility from the coupling energy between these spin excitations. Here we measure the coupling energy on a high mobility sample down to very low excitation density, and compare the results with spin-flip Raman scattering (SFRS) on the same sample. The electron spin polarizations measured by TRKR and SFRS are found in relatively good agreement. However the spin susceptibility measured by TRKR exceeds systematically the values predicted by many-body theory. This could be an indication that the two-oscillator model used to describe mixed electron-Mn spin excitations needs to be improved.

  6. Edge state magnetism in zigzag-interfaced graphene via spin susceptibility measurements. (United States)

    Makarova, T L; Shelankov, A L; Zyrianova, A A; Veinger, A I; Tisnek, T V; Lähderanta, E; Shames, A I; Okotrub, A V; Bulusheva, L G; Chekhova, G N; Pinakov, D V; Asanov, I P; Šljivančanin, Ž


    Development of graphene spintronic devices relies on transforming it into a material with a spin order. Attempts to make graphene magnetic by introducing zigzag edge states have failed due to energetically unstable structure of torn zigzag edges. Here, we report on the formation of nanoridges, i.e., stable crystallographically oriented fluorine monoatomic chains, and provide experimental evidence for strongly coupled magnetic states at the graphene-fluorographene interfaces. From the first principle calculations, the spins at the localized edge states are ferromagnetically ordered within each of the zigzag interface whereas the spin interaction across a nanoridge is antiferromagnetic. Magnetic susceptibility data agree with this physical picture and exhibit behaviour typical of quantum spin-ladder system with ferromagnetic legs and antiferromagnetic rungs. The exchange coupling constant along the rungs is measured to be 450 K. The coupling is strong enough to consider graphene with fluorine nanoridges as a candidate for a room temperature spintronics material.

  7. Frequency dependence of the complex susceptibility for a spin-1 Ising model

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    Erdem, Riza [Department of Physics, Gaziosmanpasa University, 60250 Tokat (Turkey)], E-mail:


    The complex susceptibility or the dynamic susceptibility ({chi}({omega})={chi}'({omega})-i{chi}''({omega})) for a spin-1 Ising system with bilinear and biquadratic interactions is obtained on the basis of Onsager theory of irreversible processes. If the logarithm of the susceptibilities is plotted as a function of the logarithm of frequency, then the real part ({chi}') displays a sequence of plateau regions and the imaginary part ({chi}'') has a sequence of maxima in the ordered or ferromagnetic phase. On the other hand, only one plateau region in {chi}' and one maximum in {chi}'' is observed in the disordered or paramagnetic phase. Argand or Cole-Cole plots ({chi}''-{chi}') for a selection of temperatures are also shown, and a sequence of semicircles is illustrated in the ordered phase and only one semicircle for the disordered phase in these plots.

  8. Frequency dependence of the complex susceptibility for a spin-1 Ising model (United States)

    Erdem, Rıza


    The complex susceptibility or the dynamic susceptibility ( χ( ω)= χ'( ω)- iχ″( ω)) for a spin-1 Ising system with bilinear and biquadratic interactions is obtained on the basis of Onsager theory of irreversible processes. If the logarithm of the susceptibilities is plotted as a function of the logarithm of frequency, then the real part ( χ') displays a sequence of plateau regions and the imaginary part ( χ″) has a sequence of maxima in the ordered or ferromagnetic phase. On the other hand, only one plateau region in χ' and one maximum in χ″ is observed in the disordered or paramagnetic phase. Argand or Cole-Cole plots ( χ″- χ') for a selection of temperatures are also shown, and a sequence of semicircles is illustrated in the ordered phase and only one semicircle for the disordered phase in these plots.

  9. Scaling of the fidelity susceptibility in a disordered quantum spin chain (United States)

    Jacobson, N. Tobias; Garnerone, Silvano; Haas, Stephan; Zanardi, Paolo


    The phase diagram of a quantum XY spin chain with Gaussian-distributed random anisotropies and transverse fields is investigated, with focus on the fidelity susceptibility, a recently introduced quantum information theoretical measure. Monitoring the finite-size scaling of the probability distribution of this quantity as well as its average and typical values, we detect a disorder-induced disappearance of criticality and the emergence of Griffiths phases in this model. It is found that the fidelity susceptibility is not self-averaging near the disorder-free quantum-critical lines. At the Ising critical point the fidelity susceptibility scales as a disorder-strength independent stretched exponential of the system size, in contrast with the quadratic scaling at the corresponding point in the disorder-free XY chain. Along the line where the average anisotropy vanishes the fidelity susceptibility appears to scale extensively, whereas in the disorder-free case this point is quantum critical with quadratic finite-size scaling.

  10. Utility of susceptibility-weighted imaging and arterial spin perfusion imaging in pediatric brain arteriovenous shunting

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    Nabavizadeh, Seyed Ali; Edgar, J.C.; Vossough, Arastoo [University of Pennsylvania, Department of Radiology, Philadelphia, PA (United States); Children' s Hospital of Philadelphia, Department of Radiology, Philadelphia, PA (United States)


    The objectives of the study are to investigate the application of susceptibility-weighted imaging (SWI) and arterial spin labeling (ASL) imaging in the assessment of shunting and the draining veins in pediatric patients with arteriovenous shunting and compare the utility of SWI and ASL with conventional MR and digital subtraction angiography (DSA). This study is a retrospective study of 19 pediatric patients with arteriovenous shunting on brain MRI who were also evaluated with DSA. We assessed the ability of conventional MRI sequences, susceptibility magnitude images, phase-filtered SWI images, and pulsed ASL images in the detection of arteriovenous (AV) shunting, number of draining veins and drainage pathways in comparison to DSA. The mean number of detected draining veins on DSA (3.63) was significantly higher compared to SWI phase-filtered image (mean = 2.72), susceptibility magnitude image (mean = 2.92), ASL (mean = 1.76) and conventional MRI (2.47) (p < 0.05). Pairwise comparison of DSA difference scores (i.e., difference between MR modalities in the number of missed draining veins) revealed no difference between the MR modalities (p > 0.05). ASL was the only method that correctly identified superficial and deep venous drainage in all patients. Regarding detection of shunting, ASL, SWI phase-filtered, and magnitude images demonstrated shunting in 100, 83, and 84 % of patients, respectively. SWI depicts a higher number of draining vein compared to conventional MR pulse sequences. ASL is a sensitive approach in showing 100 % sensitivity in the detection of AV shunting and in the diagnosis of the pattern of venous drainage. The present findings suggest the added utility of both SWI and ASL in the assessment of AV shunting. (orig.)

  11. Assesment of perfusion in glial tumors with arterial spin labeling; comparison with dynamic susceptibility contrast method

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    Cebeci, H, E-mail: [Department of Radiology, Uludag University Medical School, Bursa (Turkey); Aydin, O [Department of Radiology, Uludag University Medical School, Bursa (Turkey); Ozturk-Isik, E; Gumus, C [Department of Biomedical Engineering, Yeditepe University, Istanbul (Turkey); Inecikli, F [Department of Radiology, Kanuni Sultan Suleyman Educational and Research Hospital, Istanbul (Turkey); Bekar, A; Kocaeli, H [Department of Neurosurgery, Uludag University Medical School, Bursa (Turkey); Hakyemez, B [Department of Radiology, Uludag University Medical School, Bursa (Turkey)


    Highlights: • We compared the perfusion parameters obtained with both DSC and ASL perfusion imaging methods. • In ASL perfusion imaging, we also created quantitative CBF maps. • All patients included in the study had histopathological diagnose. • All MR examinations are done with 3T MR imaging system. - Abstract: Purpose: Arterial spin labeling perfusion imaging (ASL-PI) is a non-invasive perfusion imaging method that can be used for evaluation and quantification of cerebral blood flow (CBF). Aim of our study was to evaluating the efficiency of ASL in histopathological grade estimation of glial tumors and comparing findings with dynamic susceptibility contrast perfusion imaging (DSC-PI) method. Methods: This study involved 33 patients (20 high-grade and 13 low-grade gliomas). Multiphase multislice pulsed ASL MRI sequence and a first-passage gadopentetate dimeglumine T2*-weighted gradient-echo single-shot echo-planar sequence were acquired for all the patients. For each patient, perfusion relative signal intensity (rSI), CBF and relative CBF (rCBF) on ASL-PI and relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) values on DSC-PI were determined. The relative signal intensity of each tumor was determined as the maximal SI within the tumor divided by SI within symetric region in the contralateral hemisphere on ASL-PI. rCBV and rCBF were calculated by deconvolution of an arterial input function. Relative values of the lesions were obtained by dividing the values to the normal appearing symmetric region on the contralateral hemisphere. For statistical analysis, Mann–Whitney ranksum test was carried out. Receiver operating characteristic curve (ROC) analysis was performed to assess the relationship between the rCBF-ASL, rSI-ASL, rCBV and rCBF ratios and grade of gliomas. Their cut-off values permitting best discrimination was calculated. The correlation between rCBV, rCBF, rSI-ASL and rCBF-ASL and glioma grade was assessed using

  12. Dynamical magnetic susceptibility in the spin-fermion model for cuprate superconductors (United States)

    Val'kov, V. V.; Dzebisashvili, D. M.


    Using the method of diagram techniques for the spin and Fermi operators in the framework of the SU(2)- invariant spin-fermion model of the electron structure of the CuO 2 plane of copper oxides, we obtain an exact representation of the Matsubara Green's function D ⊥( k, iω m ) of the subsystem of localized spins. This representation includes the Larkin mass operator ΣL( k, iω m ) and the strength and polarization operators P( k, iω m ) and Π( k, iω m ). The calculation in the one-loop approximation of the mass and strength operators for the Heisenberg spin system in the quantum spin-liquid state allows writing the Green's function D ⊥( k, iω m ) explicitly and establishing a relation to the result of Shimahara and Takada. An essential point in the developed approach is taking the spin-polaron nature of the Fermi quasiparticles in the spin-fermion model into account in finding the contribution of oxygen holes to the spin response in terms of the polarization operator Π( k, iω m ).

  13. Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas (United States)

    Tajima, Hiroyuki; Hanai, Ryo; Ohashi, Yoji


    We theoretically investigate magnetic properties of a trapped ultracold Fermi gas. Including pairing fluctuations within the framework of an extended T -matrix approximation, as well as effects of a harmonic trap in the local density approximation, we calculate the local spin susceptibility χt(r ,T ) in the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover region. We show that pairing fluctuations cause nonmonotonic temperature dependence of χt(r ,T ) . Although this behavior looks similar to the spin-gap phenomenon associated with pairing fluctuations in a uniform Fermi gas, the trapped case is found to also be influenced by the temperature-dependent density profile, in addition to pairing fluctuations. We demonstrate how to remove this extrinsic effect from χt(r ,T ) , to study the interesting spin-gap phenomenon purely originating from pairing fluctuations. Since experiments in cold-atom physics are always done in a trap, our results would be useful for the assessment of preformed pair scenario, from the viewpoint of spin-gap phenomenon.

  14. Alternative SAIL-Trp for robust aromatic signal assignment and determination of the {chi}{sub 2} conformation by intra-residue NOEs

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    Miyanoiri, Yohei; Takeda, Mitsuhiro [Nagoya University, Graduate School of Science, Structural Biology Research Center (Japan); Jee, JunGoo; Ono, Akira M.; Okuma, Kosuke; Terauchi, Tsutomu [Tokyo Metropolitan University, Center for Priority Areas (Japan); Kainosho, Masatsune, E-mail: [Nagoya University, Graduate School of Science, Structural Biology Research Center (Japan)


    Tryptophan (Trp) residues are frequently found in the hydrophobic cores of proteins, and therefore, their side-chain conformations, especially the precise locations of the bulky indole rings, are critical for determining structures by NMR. However, when analyzing [U-{sup 13}C,{sup 15}N]-proteins, the observation and assignment of the ring signals are often hampered by excessive overlaps and tight spin couplings. These difficulties have been greatly alleviated by using stereo-array isotope labeled (SAIL) proteins, which are composed of isotope-labeled amino acids optimized for unambiguous side-chain NMR assignment, exclusively through the {sup 13}C-{sup 13}C and {sup 13}C-{sup 1}H spin coupling networks (Kainosho et al. in Nature 440:52-57, 2006). In this paper, we propose an alternative type of SAIL-Trp with the [{zeta}2,{zeta}3-{sup 2}H{sub 2}; {delta}1,{epsilon}3,{eta}2-{sup 13}C{sub 3}; {epsilon}1-{sup 15}N]-indole ring ([{sup 12}C{sub {gamma},}{sup 12}C{sub {epsilon}2}] SAIL-Trp), which provides a more robust way to correlate the {sup 1}H{sub {beta}}, {sup 1}H{sub {alpha}}, and {sup 1}H{sub N} to the {sup 1}H{sub {delta}1} and {sup 1}H{sub {epsilon}3} through the intra-residue NOEs. The assignment of the {sup 1}H{sub {delta}1}/{sup 13}C{sub {delta}1} and {sup 1}H{sub {epsilon}3}/{sup 13}C{sub {epsilon}3} signals can thus be transferred to the {sup 1}H{sub {epsilon}1}/{sup 15}N{sub {epsilon}1} and {sup 1}H{sub {eta}2}/{sup 13}C{sub {eta}2} signals, as with the previous type of SAIL-Trp, which has an extra {sup 13}C at the C{sub {gamma}} of the ring. By taking advantage of the stereospecific deuteration of one of the prochiral {beta}-methylene protons, which was {sup 1}H{sub {beta}2} in this experiment, one can determine the side-chain conformation of the Trp residue including the {chi}{sub 2} angle, which is especially important for Trp residues, as they can adopt three preferred conformations. We demonstrated the usefulness of [{sup 12}C{sub {gamma}},{sup 12}C

  15. Measuring the {chi}{sub 1} torsion angle in protein by CH-CH cross-correlated relaxation: A new resolution-optimised experiment

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    Carlomagno, Teresa [Max Planck Institute for Biophysical Chemistry, Department of NMR-based Structural Biology (Germany)], E-mail:; Bermel, Wolfgang [Bruker Biospin GmbH (Germany); Griesinger, Christian [Max Planck Institute for Biophysical Chemistry, Department of NMR-based Structural Biology (Germany)], E-mail:


    Here we introduce an experiment with high sensitivity and resolution for the measurement of CH-CH dipolar-dipolar cross-correlated relaxation rates (CCRR) in protein side-chains. The new methodology aims to the determination of structural and dynamical parameters around the torsion angle {chi}{sub 1} by measuring C{sub {alpha}}H{sub {alpha}}-C{sub {beta}}H{sub {beta}} cross-correlated relaxation rates. The method is validated on the protein ubiquitin: the {chi}{sub 1} angles determined from the CCRR data are compared with the {chi}{sub 1} angles of a previously determined NMR structure. The agreement between the two data sets is excellent for most residues. The few discrepancies that were found between the CCR-derived {chi}{sub 1} angles and the angles of the previously determined NMR structure could be explained by taking internal motion into account. The new methodology represents a very powerful tool to determine both structure and dynamics of protein side-chains in only one experiment.

  16. Validity of the spin-susceptibility ``glue'' approximation for pairing in the two-dimensional Hubbard model (United States)

    Khatami, E.; Macridin, A.; Jarrell, M.


    We examine the validity of the weak-coupling spin-susceptibility “glue” approximation (SSGA) in a two-dimensional Hubbard model for cuprates. For comparison, we employ the well-established dynamical cluster approximation (DCA) with a quantum Monte Carlo algorithm as a cluster solver. We compare the leading eigenvalues and corresponding eigenfunctions of the DCA and SSGA pairing matrices. For realistic model parameters, we find that the SSGA fails to capture the leading pairing symmetries seen in the DCA. Furthermore, when the SSGA is improved through the addition of a term with d -wave symmetry, the strength of this additional term is found to be larger than that of the glue approximation.

  17. Magnetic susceptibility studies of the spin-glass and Verwey transitions in magnetite nanoparticles


    Lopez Maldonado, K. L.; Presa Muñoz del Toro, Patricia de la; Flores Tavizon, E.; Farias Mancilla, J: R:; Matutes Aquino, J. A.; Hernando Grande, Antonio; Elizalde Galindo, J. T.


    Magnetite nanostructured powder samples were synthesized by aging chemical method. Phase, structural, and magnetic properties were characterized. X-ray diffraction patterns showed cubic magnetite pure phase, with average crystallite size, , equal to 40 nm. Susceptibility measurements showed the well-known Verwey transition at a temperature of 90 K. The decrease of Verwey transition temperature, with respect to the one reported in literature (125 K) was attributed to the low average cryst...

  18. Arterial spin labelling MRI for assessment of cerebral perfusion in children with moyamoya disease: comparison with dynamic susceptibility contrast MRI

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    Goetti, Robert [University Children' s Hospital Zurich, Department of Diagnostic Imaging, Zurich (Switzerland); University Hospital Zurich, Department of Diagnostic and Interventional Radiology, Zurich (Switzerland); O' Gorman, Ruth [University Children' s Hospital Zurich, Center for MR Research, Zurich (Switzerland); Khan, Nadia [University Children' s Hospital Zurich, Moyamoya Center, Division of Neurosurgery, Department of Surgery, Zurich (Switzerland); Kellenberger, Christian J.; Scheer, Ianina [University Children' s Hospital Zurich, Department of Diagnostic Imaging, Zurich (Switzerland)


    This study seeks to evaluate the diagnostic accuracy of cerebral perfusion imaging with arterial spin labelling (ASL) MR imaging in children with moyamoya disease compared to dynamic susceptibility contrast (DSC) imaging. Ten children (7 females; age, 9.2 {+-} 5.4 years) with moyamoya disease underwent cerebral perfusion imaging with ASL and DSC on a 3-T MRI scanner in the same session. Cerebral perfusion images were acquired with ASL (pulsed continuous 3D ASL sequence, 32 axial slices, TR = 5.5 s, TE = 25 ms, FOV = 24 cm, matrix = 128 x 128) and DSC (gradient echo EPI sequence, 35 volumes of 28 axial slices, TR = 2,000 ms, TE = 36 ms, FOV = 24 cm, matrix = 96 x 96, 0.2 ml/kg Gd-DOTA). Cerebral blood flow maps were generated. ASL and DSC images were qualitatively assessed regarding perfusion of left and right ACA, MCA, and PCA territories by two independent readers using a 3-point-Likert scale and quantitative relative cerebral blood flow (rCBF) was calculated. Correlation between ASL and DSC for qualitative and quantitative assessment and the accuracy of ASL for the detection of reduced perfusion per territory with DSC serving as the standard of reference were calculated. With a good interreader agreement ({kappa} = 0.62) qualitative perfusion assessment with ASL and DSC showed a strong and significant correlation ({rho} = 0.77; p < 0.001), as did quantitative rCBF (r = 0.79; p < 0.001). ASL showed a sensitivity, specificity and accuracy of 94 %, 93 %, and 93 % for the detection of reduced perfusion per territory. In children with moyamoya disease, unenhanced ASL enables the detection of reduced perfusion per vascular territory with a good accuracy compared to contrast-enhanced DSC. (orig.)

  19. Investigation of the spin density wave in Na{sub x}CoO{sub 2}

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    Wooldridge, J; Paul, D McK; Balakrishnan, G; Lees, M R [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)


    Magnetic susceptibility, transport and heat capacity measurements for single-crystal Na{sub x}CoO{sub 2} (x = 0.71) are reported. A transition to a spin density wave (SDW) state at T{sub mag} = 22 K is observable in all measurements, except {chi}{sub ac} data in which a cusp is observed at 4 K and attributed to a low temperature glassy phase. M(H) loops are hysteretic below 15 K. Both the SDW transition and low temperature hysteresis are only visible along the c-axis. The system also exhibits a substantial ({approx}40%) positive magnetoresistance below this temperature. Calculations of the electronic heat capacity {gamma} above and below T{sub mag} and the size of the jump in C indicate that the onset of the SDW brings about the opening of a gap and the removal of part of the Fermi surface. Reduced in-plane electron-electron scattering counteracts the loss of carriers below the transition and as a result we see a net reduction in resistivity below T{sub mag}. Sodium ordering transitions at higher temperatures are observable as peaks in the heat capacity with a corresponding increase in resistivity.

  20. AC-Susceptibility study on vortex-molecule lattice in supermultilayer cuprate HgBa{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+2+{delta}} (n = 14)

    Energy Technology Data Exchange (ETDEWEB)

    Shivagan, D.D. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan)], E-mail:; Shirage, P.M. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Crisan, A. [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest (Romania); Department of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Tanaka, Y. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan)], E-mail:; Iyo, A. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Tokiwa, K.; Watanabe, T. [Tokyo University of Science, Noda, Chiba 278-8510 (Japan); Terada, N. [Department of Nano Structures and Advanced Materials, Kagoshima University, Kagoshima 890-0065 (Japan)


    We investigated that in HgBa{sub 2}Ca{sub n-1}Cu{sub n}O{sub 2n+2+{delta}} [Hg-12(n-1)n], for n {>=} 6, T{sub c} of about 105 K, vortex melting lines remains constant and independent of number of inner plane CuO{sub 2} layers. However the vortex dynamics of the supermultilayer system could be crucially different from that of single or double layer cuprates. Therefore we measured the fundamental and third harmonic AC susceptibility responses to see the vortex dynamics and vortex matter phase diagram of Hg-12(n-1)n (n = 14), the higher member of super-multilayered cuprate superconductors. The Lindemann type vortex melting line was estimated using onset of third harmonic susceptibility ({chi}{sub 3}), at very low h{sub AC} (50 mOe), and represented by 3D Ginzburg Landau rescaling. Frequency dependence of out of phase susceptibility {chi}''(T) measured at lower fields of 500 and 1000 Oe, for 10 Hz to 10 kHz, showed resonance behaviour in the temperature region 55-68 K, suggesting rotational and translational creep dynamics of vortex molecule, even below usual melting line. We present schematic vortex phase diagram, considering the response of vortex dynamics to applied AC frequencies, taking into account the crossover temperatures obtained from critical slowing down of spin glass model and extended thermal activated model.

  1. Magnetic Susceptibility Study of Sub-Pico-emu Sample Using a Micromagnetometer: An Investigation through Bistable Spin-Crossover Materials. (United States)

    Kamara, Souleymane; Tran, Quang-Hung; Davesne, Vincent; Félix, Gautier; Salmon, Lionel; Kim, Kunwoo; Kim, CheolGi; Bousseksou, Azzedine; Terki, Ferial


    A promising and original method to study the spin-transition in bistable spin-crossover (SCO) materials using a magnetoresistive multiring sensor and its self-generated magnetic field is reported. Qualitative and quantitative studies are carried out combining theoretical and experimental approaches. The results show that only a small part of matter dropped on the sensor surface is probed by the device. At a low bias-current range, the number of detected nanoparticles depends on the amplitude of the current. However, in agreement with the theoretical model, the stray voltage from the particles is proportional to the current squared. By changing both the bias current and the concentration of particle droplet, the thermal hysteresis of an ultrasmall volume, 1 × 10-4 mm3 , of SCO particles is measured. The local probe of the experimental setup allows a highest resolution of 4 × 10-14 emu to be reached, which is never achieved by experimental methods at room temperature. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Non-invasive assessment of intratumoral vascularity using arterial spin labeling: A comparison to susceptibility-weighted imaging for the differentiation of primary cerebral lymphoma and glioblastoma

    Energy Technology Data Exchange (ETDEWEB)

    Furtner, J., E-mail: [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Schöpf, V., E-mail: [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Preusser, M., E-mail: [Department of Medicine I, Division of Oncology, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Asenbaum, U., E-mail: [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Woitek, R., E-mail: [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Wöhrer, A., E-mail: [Institute of Neurology, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Hainfellner, J.A., E-mail: [Institute of Neurology, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Wolfsberger, S., E-mail: [Department of Neurosurgery, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria); Prayer, D., E-mail: [Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna (Austria); Comprehensive Cancer Center-Central Nervous System Tumors Unit (CCC-CNS), Medical University of Vienna (Austria)


    Using conventional MRI methods, the differentiation of primary cerebral lymphomas (PCNSL) and other primary brain tumors, such as glioblastomas, is difficult due to overlapping imaging characteristics. This study was designed to discriminate tumor entities using normalized vascular intratumoral signal intensity values (nVITS) obtained from pulsed arterial spin labeling (PASL), combined with intratumoral susceptibility signals (ITSS) from susceptibility-weighted imaging (SWI). Thirty consecutive patients with glioblastoma (n = 22) and PCNSL (n = 8), histologically classified according to the WHO brain tumor classification, were included. MRIs were acquired on a 3 T scanner, and included PASL and SWI sequences. nVITS was defined by the signal intensity ratio between the tumor and the contralateral normal brain tissue, as obtained by PASL images. ITSS was determined as intratumoral low signal intensity structures detected on SWI sequences and were divided into four different grades. Potential differences in the nVITS and ITSS between glioblastomas and PCNSLs were revealed using statistical testing. To determine sensitivity, specificity, and diagnostic accuracy, as well as an optimum cut-off value for the differentiation of PCNSL and glioblastoma, a receiver operating characteristic analysis was used. We found that nVITS (p = 0.011) and ITSS (p = 0.001) values were significantly higher in glioblastoma than in PCNSL. The optimal cut-off value for nVITS was 1.41 and 1.5 for ITSS, with a sensitivity, specificity, and accuracy of more than 95%. These findings indicate that nVITS values have a comparable diagnostic accuracy to ITSS values in differentiating glioblastoma and PCNSL, offering a completely non-invasive and fast assessment of tumoral vascularity in a clinical setting.

  3. Studies of vanadium-phosphorus-oxygen selective oxidation catalysts by sup 31 P and sup 51 V NMR spin-echo and volume susceptibility measurements

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juan.


    The purpose of this work is to characterize the vanadium-phosphorous oxide (V-P-O) catalysts for the selective oxidation of n-butane and 1-butene to maleic anhydride. The utility of solid state nuclear magnetic resonance as an analytical tool in this investigation lies in its sensitivity to the electronic environment surrounding the phosphorous and vanadium nuclei, and proximity of paramagnetic species. Spin-echo mapping NMR of {sup 31}p and {sup 51}v and volume magnetic susceptibility measurements were used as local microscopic probes of the presence of V{sup 5+}, V{sup 4+}, V{sup 3+} species in the model compounds: {beta}-VOPO{sub 4}, {beta}-VOPO{sub 4} treated with n-butane/1-butene, (VO){sub 2}P{sub 2}O{sub 7} treated with n-butane/1-butene; and industrial catalysts with P/V (phosphorus to vanadium) ratio of 0.9, 1.0 and 1.1, before and after treatment with n-butane and 1-butene. The NMR spectra provide a picture of how the oxidation states of vanadium are distributed in these catalysts. 73 refs., 32 figs., 8 tabs.

  4. Effect of magnetic susceptibility contrast medium on myocardial signal intensity with fast gradient-recalled echo and spin-echo MR imaging: initial experience in humans. (United States)

    Sakuma, H; O'Sullivan, M; Lucas, J; Wendland, M F; Saeed, M; Dulce, M C; Watson, A; Bleyl, K L; LaFrance, N D; Higgins, C B


    To show the effect of dysprosium diethylenetriaminepentaacetic acid bis-methylamine injection on the images of normal human myocardium. T2-sensitive fast gradient-recalled echo (GRE) (repetition time [TR], 10.8 msec; echo time [TE], 4.2 msec) and spin-echo (SE) (TR, three RR intervals; TE, 60 msec) magnetic resonance (MR) imaging with driven equilibrium-preparation pulse was used to produce T2 contrast material enhancement. The contrast agent was injected into 12 healthy subjects at doses of 0.05, 0.1, 0.2, 0.4, and 0.6 mmol/kg. Driven equilibrium-prepared GRE images showed a transient decrease of myocardial signal intensity at doses of 0.2-0.6 mmol/kg. Postcontrast T2-weighted SE images showed a myocardial signal attenuation (30%-45% decrease) at a dose of 0.4 mmol/kg or higher. Dynamic MR imaging with a magnetic susceptibility contrast medium can be used to monitor the first pass of contrast media through human myocardium with a conventional MR imager and a fast GRE sequence.

  5. Astrocytic tumour grading: a comparative study of three-dimensional pseudocontinuous arterial spin labelling, dynamic susceptibility contrast-enhanced perfusion-weighted imaging, and diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hua-Feng [302 Hospital of Chinese People' s Liberation Army, Department of Radiology, Beijing (China); Chen, Zhi-Ye; Wang, Yu-Lin; Wang, Yan; Ma, Lin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); Lou, Xin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); University of California, Department of Neurology, Los Angeles, CA (United States); Gui, Qiu-Ping [People' s Liberation Army General Hospital, Department of Pathology, Beijing (China); Shi, Kai-Ning; Zhou, Zhen-Yu; Zheng, Dan-Dan [General Electric Healthcare (China) Co., Ltd., Beijing; Wang, Danny J.J. [University of California, Department of Neurology, Los Angeles, CA (United States)


    We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 x 10{sup -3} mm{sup 2}/s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. (orig.)

  6. Astrocytic tumour grading: a comparative study of three-dimensional pseudocontinuous arterial spin labelling, dynamic susceptibility contrast-enhanced perfusion-weighted imaging, and diffusion-weighted imaging. (United States)

    Xiao, Hua-Feng; Chen, Zhi-Ye; Lou, Xin; Wang, Yu-Lin; Gui, Qiu-Ping; Wang, Yan; Shi, Kai-Ning; Zhou, Zhen-Yu; Zheng, Dan-Dan; Wang, Danny J J; Ma, Lin


    We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 × 10(-3) mm(2)/s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. • pCASL shows positive correlation with DSC-PWI in astrocytic tumour grading. • ADC values based on ADC histograms can be an objective method. • Combination of DWI and pCASL or DSC-PWI can improve grading accuracy.

  7. Three-dimensional arterial spin labeling imaging and dynamic susceptibility contrast perfusion-weighted imaging value in diagnosing glioma grade prior to surgery. (United States)

    Ma, Hong; Wang, Zizheng; Xu, Kai; Shao, Zefeng; Yang, Chun; Xu, Peng; Liu, Xiaohua; Hu, Chunfeng; Lu, Xin; Rong, Yutao


    The current study aimed to investigate whole-brain three-dimensional arterial spin labeling imaging (3D ASL) and dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI), in regards to their diagnostic value of preoperative glioma grade. The parameter values obtained after correction will be correlated with the diagnostic value of 3D ASL and DSC-PWI perfusion. In the current study, 50 patients with gliomas confirmed by pathology were used, including 27 low-grade gliomas (LGGs) and 23 high-grade gliomas (HGGs). Prior to surgery all patients underwent 3 Tesla magnetic resonance imaging (MRI), 3D ASL, DSC-PWI and conventional enhanced MRI scans to obtain original 3D ASL and DSC-PWI images, and the tumor regions with the most obvious parenchyma perfusion and contralateral normal white matter were selected. In these areas, the ASL-relative cerebral blood flow (ASL-rCBF), DSC-relative cerebral blood flow (DSC-rCBF) and DSC-relative cerebral blood volume (DSC-rCBV) parameter values were then obtained after correction for individual differences. The results of the present study show that ASL-CBF, DSC-CBF, DSC-CBV values and ASL-rCBF, DSC-rCBF, DSC-rCBV values increased as the grade of the glioma being imaged increased, and there was a marked difference between the HGGs and the LGGs. ASL-rCBF was significantly positively correlated with DSC-rCBF (r=0.580, PPWI and 3D ASL in the diagnosis of glioma grade. ASL-rCBF had the highest area value under the ROC curve (0.836). The areas under the ROC curve of DSC-rCBF and DSC-rCBV were analyzed using the Z test, but the difference was not statistically significant. When ASL-rCBF, DSC-rCBF and DSC-rCBV were cutoff at 2.24, 1.85 and 1.68, the sensitivity of HGG diagnosis was 83.2, 91.3 and 91.3%, and the specificity was 77.7, 63.9 and 66.7%, respectively.

  8. On the tail of the overlap probability distribution in the Sherrington-Kirkpatrick model 75.50.Lk Spin glasses and other random magnets; 75.10.Nr Spin-glass and other random models; 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.);

    CERN Document Server

    Billoire, A; Marinari, E


    We investigate the large deviation behaviour of the overlap probability density in the Sherrington-Kirkpatrick (SK) model using the coupled replica scheme, and we compare with the results of a large-scale numerical simulation. In the spin glass phase we show that, generically, for any model with continuous replica symmetry breaking (RSB), 1/N log P sub N (q)approx -A(|q| - q sub E sub A) sup 3 , and we compute the first correction to the expansion of A in powers of T sub c - T for the SK model. We also study the paramagnetic phase, where results are obtained in the replica symmetric scheme that do not involve an expansion in powers of q - q sub E sub A or T sub c - T. Finally we give precise semi-analytical estimates of P(|q| = 1). The overall agreement between the various points of view is very satisfactory.

  9. Spin current

    CERN Document Server

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


    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.

  10. Spin-current probe for phase transition in an insulator

    National Research Council Canada - National Science Library

    Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'Diaye, Alpha T; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z Q; Saitoh, Eiji


    .... Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions...

  11. Magnetic susceptibility and ground-state zero-field splitting in high-spin mononuclear manganese(III) of inverted N-methylated porphyrin complexes: Mn(2-NCH3NCTPP)Br. (United States)

    Hung, Sheng-Wei; Yang, Fuh-An; Chen, Jyh-Horung; Wang, Shin-Shin; Tung, Jo-Yu


    The crystal structures of diamagnetic dichloro(2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N',N'')-tin(IV) methanol solvate [Sn(2-NCH 3NCTPP)Cl 2.2(0.2MeOH); 6.2(0.2MeOH)] and paramagnetic bromo(2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N',N'')-manganese(III) [Mn(2-NCH 3NCTPP)Br; 5] were determined. The coordination sphere around Sn (4+) in 6.2(0.2MeOH) is described as six-coordinate octahedron ( OC-6) in which the apical site is occupied by two transoid Cl (-) ligands, whereas for the Mn (3+) ion in 5, it is a five-coordinate square pyramid ( SPY-5) in which the unidentate Br (-) ligand occupies the axial site. The g value of 9.19 (or 10.4) measured from the parallel polarization (or perpendicular polarization) of X-band EPR spectra at 4 K is consistent with a high spin mononuclear manganese(III) ( S = 2) in 5. The magnitude of axial ( D) and rhombic ( E) zero-field splitting (ZFS) for the mononuclear Mn(III) in 5 were determined approximately as -2.4 cm (-1) and -0.0013 cm (-1), respectively, by paramagnetic susceptibility measurements and conventional EPR spectroscopy. Owing to weak C(45)-H(45A)...Br(1) hydrogen bonds, the mononuclear Mn(III) neutral molecules of 5 are arranged in a one-dimensional network. A weak Mn(III)...Mn(III) ferromagnetic interaction ( J = 0.56 cm (-1)) operates via a [Mn(1)-C(2)-C(1)-N(4)-C(45)-H(45A)...Br(1)-Mn(1)] superexchange pathway in complex 5.

  12. Spin current

    CERN Document Server

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


    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.

  13. Spin multiplicities

    Energy Technology Data Exchange (ETDEWEB)

    Curtright, T.L., E-mail: [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); Van Kortryk, T.S., E-mail: [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439-4815 (United States); Zachos, C.K., E-mail: [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439-4815 (United States)


    The number of times spin s appears in the Kronecker product of n spin j representations is computed, and the large n asymptotic behavior of the result is obtained. Applications are briefly sketched. - Highlights: • We give a self-contained derivation of the spin multiplicities that occur in n-fold tensor products of spin-j representations. • We make use of group characters, properties of special functions, and asymptotic analysis of integrals. • We emphasize patterns that arise when comparing different values of j, and asymptotic behavior for large n. • Our methods and results should be useful for various statistical and quantum information theory calculations.

  14. Spin Electronics (United States)


    spin resonance of rare earth and transition metal impurities in chalcopyrite semiconductors. They also have worked in diluted magnetic...past, the ferromagnetic injector had been a ferromagnetic metal or alloy containing 3d transition elements with fractional spin polarization of the...polarized carriers. There have been numerous attempts to inject transition metals or their alloys into semiconductors, either directly (Johnson and

  15. Spin glasses

    CERN Document Server

    Bovier, Anton


    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.

  16. Spin-current probe for phase transition in an insulator (United States)

    Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'Diaye, Alpha T.; Tan, Ali; Uchida, Ken-ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z. Q.; Saitoh, Eiji


    Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is a flux of spin without an electric charge and its transport reflects spin excitation. We demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices. PMID:27573443

  17. Spin-current noise from fluctuation relations

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jong Soo [Institut de Fisica Interdisciplinària i Sistemes Complexos IFISC (UIB-CSIC), E-07122 Palma de Mallorca (Spain); Sánchez, David; López, Rosa [Institut de Fisica Interdisciplinària i Sistemes Complexos IFISC (UIB-CSIC), E-07122 Palma de Mallorca, Spain and Departement de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)


    We present fluctuation relations that connect spin-polarized current and noise in mesoscopic conductors. In linear response, these relations are equivalent to the fluctuation-dissipation theorem that relates equilibrium current-current correlations to the linear conductance. More interestingly, in the weakly nonlinear regime of transport, these relations establish a connection between the leading-order rectification spin conductance, the spin noise susceptibility and the third cumulant of spin current fluctuations at equilibrium. Our results are valid even for systems in the presence of magnetic fields and coupled to ferromagnetic electrodes.

  18. Spin dynamics in the anisotropic spin glass Fe2TiO5

    DEFF Research Database (Denmark)

    Yeshurun, Y.; Tholence, J. L.; Kjems, Jørgen


    We have studied spin-freezing phenomena along the magnetic easy axis of the insulating spin glass Fe2TiOS by magnetisation, AC susceptibility and neutron scattering experiments. The characteristic measurement time for these techniques varies over more than fourteen orders of magnitude. The result...

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

    Directory of Open Access Journals (Sweden)

    Saburo Takahashi and Sadamichi Maekawa


    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.

  20. Spin electronics

    CERN Document Server

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


    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...

  1. Spin ejector (United States)

    Andersen, John A.; Flanigan, John J.; Kindley, Robert J.


    The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.

  2. Spinning worlds

    NARCIS (Netherlands)

    Schwarz, H.


    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

  3. Spin currents, spin torques, and the concept of spin superfluidity


    Rückriegel, Andreas; Kopietz, Peter


    In magnets with non-collinear spin configuration the expectation value of the conventionally defined spin current operator contains a contribution which renormalizes an external magnetic field and hence affects only the precessional motion of the spin polarization. This term, which has been named angular spin current by Sun and Xie [Phys. Rev B 72, 245305 (2005)], does not describe the translational motion of magnetic moments. We give a prescription how to separate these two types of spin tra...

  4. Flying spin qualities testing of airplane

    Directory of Open Access Journals (Sweden)

    Kostić Čedomir J.


    Full Text Available In this paper is presented the theoretical analysis of origins and characteristics of spinning motion. There are precise explanation of every stage spin flight and basic meaning of notion. Personated equation of motion in spin and equitation of motion airplane in settled spin motion, analysis of them and general recommendation for pilots for recovering from spins. Introduced in valid military and civil specifications flight test demonstration requirements for departure resistance and flying stall and spin qualities testing of airplane. Special attention was given on predicting departure, stall and spin susceptibility and theoretical analysis in the name of magnify flight testing security. There are explanation of test equipment and methodology of flying qualities testing of airplanes. Like a support of this theme are described method and results of flight stall and spin qualities testing of airplane G-4(N-62 super see-gull with precise recommendation for pilots for recovering from spins, from TOC SLI VS (Technical testing center, department for fight testing Air Force of Serbia.

  5. Relationship between the complex susceptibility and the plasma dispersion function

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez D, H.; Cabral P, A


    It is shown that when magnetization processes in a spin system and resonant excitation of spin n states occur in the presence of internal and or external random line-broadening mechanisms, the complex magnetic susceptibility of the plasma dispersion function. letter could be useful spin in system is proportional to the relationship found in this spectroscopies such as EPR and NMR, for example, as its fitting to experimental absorption and dispersion profiles produces their Lorentzian and Gaussian contents. (Author)

  6. spin coating

    African Journals Online (AJOL)


    Intense UV photoluminescence is observed for intrinsic ZnO film. Keywords : thin films, oxidize zinc doped aluminium (ZnO:Al), sol-gel, spin coating, structural analysis, electric and optical properties. 1. Introduction. Depuis ces vingt dernières années les couches minces d'oxyde de zinc ont connu un intérêt croissant dans ...

  7. Spin-Circuit Representation of Spin Pumping (United States)

    Roy, Kuntal


    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.

  8. Fractional Spin Fluctuations as a Precursor of Quantum Spin Liquids: Majorana Dynamical Mean-Field Study for the Kitaev Model. (United States)

    Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi


    Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.

  9. Fractional Spin Fluctuations as a Precursor of Quantum Spin Liquids: Majorana Dynamical Mean-Field Study for the Kitaev Model (United States)

    Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi


    Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.

  10. Spin currents, spin torques, and the concept of spin superfluidity (United States)

    Rückriegel, Andreas; Kopietz, Peter


    In magnets with noncollinear spin configuration the expectation value of the conventionally defined spin current operator contains a contribution which renormalizes an external magnetic field and hence affects only the precessional motion of the spin polarization. This term, which has been named angular spin current by Sun and Xie [Phys. Rev. B 72, 245305 (2005)], 10.1103/PhysRevB.72.245305, does not describe the translational motion of magnetic moments. We give a prescription for how to separate these two types of spin transport and show that the translational movement of the spin is always polarized along the direction of the local magnetization. We also show that at vanishing temperature the classical magnetic order parameter in magnetic insulators cannot carry a translational spin current and elucidate how this affects the interpretation of spin supercurrents.

  11. Phase transitions and thermal entanglement of the distorted Ising-Heisenberg spin chain: topology of multiple-spin exchange interactions in spin ladders. (United States)

    Arian Zad, Hamid; Ananikian, Nerses


    We consider a symmetric spin-1/2 Ising-XXZ double sawtooth spin ladder obtained from distorting a spin chain, with the XXZ interaction between the interstitial Heisenberg dimers (which are connected to the spins based on the legs via an Ising-type interaction), the Ising coupling between nearest-neighbor spins of the legs and rungs spins, respectively, and additional cyclic four-spin exchange (ring exchange) in the square plaquette of each block. The presented analysis supplemented by results of the exact solution of the model with infinite periodic boundary implies a rich ground state phase diagram. As well as the quantum phase transitions, the characteristics of some of the thermodynamic parameters such as heat capacity, magnetization and magnetic susceptibility are investigated. We prove here that among the considered thermodynamic and thermal parameters, solely heat capacity is sensitive versus the changes of the cyclic four-spin exchange interaction. By using the heat capacity function, we obtain a singularity relation between the cyclic four-spin exchange interaction and the exchange coupling between pair spins on each rung of the spin ladder. All thermal and thermodynamic quantities under consideration should be investigated by regarding those points which satisfy the singularity relation. The thermal entanglement within the Heisenberg spin dimers is investigated by using the concurrence, which is calculated from a relevant reduced density operator in the thermodynamic limit.

  12. Phase transitions and thermal entanglement of the distorted Ising–Heisenberg spin chain: topology of multiple-spin exchange interactions in spin ladders (United States)

    Arian Zad, Hamid; Ananikian, Nerses


    We consider a symmetric spin-1/2 Ising-XXZ double sawtooth spin ladder obtained from distorting a spin chain, with the XXZ interaction between the interstitial Heisenberg dimers (which are connected to the spins based on the legs via an Ising-type interaction), the Ising coupling between nearest-neighbor spins of the legs and rungs spins, respectively, and additional cyclic four-spin exchange (ring exchange) in the square plaquette of each block. The presented analysis supplemented by results of the exact solution of the model with infinite periodic boundary implies a rich ground state phase diagram. As well as the quantum phase transitions, the characteristics of some of the thermodynamic parameters such as heat capacity, magnetization and magnetic susceptibility are investigated. We prove here that among the considered thermodynamic and thermal parameters, solely heat capacity is sensitive versus the changes of the cyclic four-spin exchange interaction. By using the heat capacity function, we obtain a singularity relation between the cyclic four-spin exchange interaction and the exchange coupling between pair spins on each rung of the spin ladder. All thermal and thermodynamic quantities under consideration should be investigated by regarding those points which satisfy the singularity relation. The thermal entanglement within the Heisenberg spin dimers is investigated by using the concurrence, which is calculated from a relevant reduced density operator in the thermodynamic limit.

  13. spin coating

    African Journals Online (AJOL)


    Dans ce travail nous avons préparé des couches minces de l'oxyde de zinc ZnO dopées à l'aluminium et non dopées par la technique Sol-Gel associée au « spin coating » sur des substrats en verre « pyrex » à partir de l'acétate de zinc dissous dans une solution de l'éthanol. Nous avons ensuite effectué des analyses ...

  14. Study of higher-order harmonics of complex ac susceptibility in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films by the mutual inductive method

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Israel, E-mail: iperez@mda.cinvestav.m [Applied Physics Department, Cinvestav Unidad Merida, Km 6 Ant., Carretera a Progreso, A.P. 73, C.P. 97310, Merida, Yucatan (Mexico); Sosa, Victor [Applied Physics Department, Cinvestav Unidad Merida, Km 6 Ant., Carretera a Progreso, A.P. 73, C.P. 97310, Merida, Yucatan (Mexico); Gamboa, Fidel, E-mail: ffgamboa@mda.cinvestav.m [Applied Physics Department, Cinvestav Unidad Merida, Km 6 Ant., Carretera a Progreso, A.P. 73, C.P. 97310, Merida, Yucatan (Mexico); Physics of Materials Department, Centro de Investigacion en Materiales Avanzados, S.C. (CIMAV) Ave. Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua (Mexico)


    We have applied the mutual inductive method to study higher-order harmonics of complex ac susceptibility {chi}{sub n}={chi}{sub n}{sup '}-i{chi}{sub n}{sup ''} for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films as function of the temperature and the applied magnetic field. The experimental results were compared with analytical and numerical results obtained from the Ishida-Mazaki model and the solution of the integral equation for the current density, respectively. Both models allow us to reproduce the main experimental features, however, as n increases the numerical model shows notable discrepancies. This failure can be attributed to the current-voltage characteristics. Also this investigation yields the activation energy U{sub c} and the critical current density J{sub c} both at T = 0 for two samples.

  15. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael


    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.

  16. Thermodynamical analysis of spin-state transitions in LaCo O3 : Negative energy of mixing to assist thermal excitation to the high-spin excited state (United States)

    Kyômen, Tôru; Asaka, Yoshinori; Itoh, Mitsuru


    Magnetic susceptibility and heat capacity due to the spin-state transition in LaCoO3 were calculated by a molecular-field model in which the energy-level diagram of high-spin state reported by Ropka and Radwanski [Phys. Rev. B 67, 172401 (2003)] is assumed for the excited state, and the energy and entropy of mixing of high-spin Co ions and low-spin Co ions are introduced phenomenologically. The experimental data below 300K were well reproduced by this model, which proposes that the high-spin excited state can be populated even if the energy of high-spin state is much larger than that of low-spin state, because the negatively large energy of mixing reduces the net excitation energy. The stability of each spin state including the intermediate-spin state is discussed based on the present results and other reports.


    Energy Technology Data Exchange (ETDEWEB)

    BAI,M.; ROSER, T.


    This paper proposes a new design of spin flipper for RHIC to obtain full spin flip with the spin tune staying at half integer. The traditional technique of using an rf dipole or solenoid as spin flipper to achieve full spin flip in the presence of full Siberian snake requires one to change the snake configuration to move the spin tune away from half integer. This is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. The design of the new spin flipper as well as numerical simulations are presented.

  18. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

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


    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

  19. Spin-fluctuation theory beyond Gaussian approximation

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, N B [Moscow State University, 119992 Moscow (Russian Federation); Reser, B I; Grebennikov, V I, E-mail: melnikov@cs.msu.s, E-mail: reser@imp.uran.r, E-mail: greben@imp.uran.r [Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, 620041 Ekaterinburg (Russian Federation)


    A characteristic feature of the Gaussian approximation in the functional-integral approach to the spin-fluctuation theory is the jump phase transition to the paramagnetic state. We eliminate the jump and obtain a continuous second-order phase transition by taking into account high-order terms in the expansion of the free energy in powers of the fluctuating exchange field. The third-order term of the free energy renormalizes the mean field, and the fourth-order term, responsible for the interaction of the fluctuations, renormalizes the spin susceptibility. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar.

  20. Spin-Mechatronics (United States)

    Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi


    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.

  1. Finite temperature spin-dynamics and phase transitions in spin-orbital models

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.-C.


    We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a 2D Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze-out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin-waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.

  2. Higher spin black holes

    National Research Council Canada - National Science Library

    Gutperle, Michael; Kraus, Per


    .... We find solutions that generalize the BTZ black hole and carry spin-3 charge. The black hole entropy formula yields a result for the asymptotic growth of the partition function at finite spin-3 chemical potential...

  3. Summary: symmetries and spin

    Energy Technology Data Exchange (ETDEWEB)

    Haxton, W.C. (Institute for Nuclear Theory, Department of Physcis, FM-15, University of Washington, Seattle, Washington 98195 (US))


    I discuss a number of the themes of the Symmetries and Spin session of the 8th International Symposium on High Energy Spin Physics: parity non-conservation, CP/T nonconservation, and tests of charge symmetry and charge independence.

  4. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  5. Quantum Spin Liquids


    Savary, Lucile; Balents, Leon


    Quantum spin liquids may be considered "quantum disordered" ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, such as non-local e...

  6. Spinning eggs and ballerinas (United States)

    Cross, Rod


    Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction between the egg and the surface on which it spins.

  7. Susceptibilities for the Müller-Hartmann-Zitartz countable infinity of phase transitions on a Cayley tree. (United States)

    Sharma, Auditya


    We obtain explicit susceptibilities for the countable infinity of phase transition temperatures of Müller-Hartmann-Zitartz on a Cayley tree. The susceptibilities are a product of the zeroth spin with the sum of an appropriate set of averages of spins on the outermost layer of the tree. A clear physical understanding for these strange phase transitions emerges naturally. In the thermodynamic limit, the susceptibilities tend to zero above the transition and to infinity below it.

  8. Spin-Caloritronic Batteries

    DEFF Research Database (Denmark)

    Yu, Xiao-Qin; Zhu, Zhen-Gang; Su, Gang


    The thermoelectric performance of a topological energy converter is analyzed. The H-shaped device is based on a combination of transverse topological effects involving the spin: the inverse spin Hall effect and the spin Nernst effect. The device can convert a temperature drop in one arm into an e...

  9. Frozen spin targets

    CERN Document Server

    Parsons, A S L


    Describes six projects which use the frozen-spin principle: Helium-3 R.M.S. and longitudinally polarized frozen spin targets at Rutherford Laboratory, and the frozen spin targets at KEK, Saclay and the one used by the CERN-Helsinki collaboration. (7 refs).

  10. Concepts in spin electronics

    CERN Document Server


    A new branch of physics and nanotechnology called spin electronics has emerged, which aims at simultaneously exploiting the charge and spin of electrons in the same device. The aim of this book is to present new directions in the development of spin electronics in both the basic physics and the future electronics.

  11. Spinning Eggs and Ballerinas (United States)

    Cross, Rod


    Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…

  12. Crystalline Kitaev spin liquids (United States)

    Yamada, Masahiko G.; Dwivedi, Vatsal; Hermanns, Maria


    Frustrated magnetic systems exhibit many fascinating phases. Prime among them are quantum spin liquids, where the magnetic moments do not order even at zero temperature. A subclass of quantum spin liquids called Kitaev spin liquids are particularly interesting, because they are exactly solvable, can be realized in certain materials, and show a large variety of gapless and gapped phases. Here we show that nonsymmorphic symmetries can enrich spin liquid phases, such that the low-energy spinon degrees of freedom form three-dimensional Dirac cones or nodal chains. In addition, we suggest a realization of such Kitaev spin liquids in metal-organic frameworks.

  13. Spin physics in semiconductors

    CERN Document Server


    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.

  14. Temperature dependence of the spin state of a Co3+ Ion in RCoO3 ( R = La, Gd) cobaltites (United States)

    Babkin, R. Yu.; Lamonova, K. V.; Orel, S. M.; Ovchinnikov, S. G.; Pashkevich, Yu. G.


    Changes in the spin state of Co3+ ions in LaCoO3 and GdCoO3 compounds are studied through the use of the temperature dependence of the magnetic susceptibility and the modified crystal field theory. It is shown that the spin subsystem of Co3+ ions in LaCoO3 and GdCoO3 undergoes the spin-crossover type transition between the high-spin ( S = 2) and low-spin ( S = 0) states without any contribution of the intermediate-spin state ( S = 1).

  15. Spin-orbit scattering in superconducting nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Alhassid, Y. [Center for Theoretical Physics, Sloane Physics Laboratory, Yale University, New Haven, Connecticut, 06520 (United States); Nesterov, K.N. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin, 53706 (United States)


    We review interaction effects in chaotic metallic nanoparticles. Their single-particle Hamiltonian is described by the proper random-matrix ensemble while the dominant interaction terms are invariants under a change of the single-particle basis. In the absence of spin-orbit scattering, the nontrivial invariants consist of a pairing interaction, which leads to superconductivity in the bulk, and a ferromagnetic exchange interaction. Spin-orbit scattering breaks spin-rotation invariance and when it is sufficiently strong, the only dominant nontrivial interaction is the pairing interaction. We discuss how the magnetic response of discrete energy levels of the nanoparticle (which can be measured in single-electron tunneling spectroscopy experiments) is affected by such pairing correlations and how it can provide a signature of pairing correlations. We also consider the spin susceptibility of the nanoparticle and discuss how spin-orbit scattering changes the signatures of pairing correlations in this observable. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Imaging the real space structure of the spin fluctuations in an iron-based superconductor. (United States)

    Chi, Shun; Aluru, Ramakrishna; Grothe, Stephanie; Kreisel, A; Singh, Udai Raj; Andersen, Brian M; Hardy, W N; Liang, Ruixing; Bonn, D A; Burke, S A; Wahl, Peter


    Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonance comes almost exclusively from neutron scattering. Here we demonstrate that by using low-temperature scanning tunnelling microscopy and spectroscopy we can characterize the spin resonance in real space. We show that inelastic tunnelling leads to the characteristic dip-hump feature seen in tunnelling spectra in high temperature superconductors and that this feature arises from excitations of the spin fluctuations. Spatial mapping of this feature near defects allows us to probe non-local properties of the spin susceptibility and to image its real space structure.

  17. Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4

    DEFF Research Database (Denmark)

    Toft-Petersen, Rasmus; Reehuis, Manfred; Jensen, Thomas Bagger Stibius


    with earlier susceptibility measurements. Using a spin Hamiltonian, we show that the spin dimensionality is intermediate between XY- and Ising-like, with an easy b axis and a hard c axis. It is shown that both next-nearest neighbor exchange couplings in the bc plane are in competition with the strongest...

  18. Quantum Entanglement of a Tunneling Spin with Mechanical Modes of a Torsional Resonator

    Directory of Open Access Journals (Sweden)

    D. A. Garanin


    Full Text Available We solve the Schrödinger equation for various quantum regimes describing a tunneling macrospin coupled to a torsional oscillator. The energy spectrum and freezing of spin tunneling are studied. Magnetic susceptibility, noise spectrum, and decoherence due to entanglement of spin and mechanical modes are computed. We show that the presence of a tunneling spin can be detected via splitting of the mechanical mode at the resonance. Our results apply to experiments with magnetic molecules coupled to nanoresonators.

  19. Higher Spin Matrix Models

    Directory of Open Access Journals (Sweden)

    Mauricio Valenzuela


    Full Text Available We propose a hybrid class of theories for higher spin gravity and matrix models, i.e., which handle simultaneously higher spin gravity fields and matrix models. The construction is similar to Vasiliev’s higher spin gravity, but part of the equations of motion are provided by the action principle of a matrix model. In particular, we construct a higher spin (gravity matrix model related to type IIB matrix models/string theory that have a well defined classical limit, and which is compatible with higher spin gravity in A d S space. As it has been suggested that higher spin gravity should be related to string theory in a high energy (tensionless regime, and, therefore to M-Theory, we expect that our construction will be useful to explore concrete connections.

  20. 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)


    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.

  1. Higher spin gauge theories

    CERN Document Server

    Henneaux, Marc; Vasiliev, Mikhail A


    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...

  2. Silicon spin communication


    Dery, Hanan; Song, Yang; Li, Pengke; Zutic, Igor


    Recent experimental breakthroughs have demonstrated that the electron spin in silicon can be reliably injected and detected as well as transferred over distances exceeding 1 mm. We propose an on-chip communication paradigm which is based on modulating spin polarization of a constant current in silicon wires. We provide figures of merit for this scheme by studying spin relaxation and drift-diffusion models in silicon.

  3. Spin coating apparatus (United States)

    Torczynski, John R.


    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.

  4. Local Noncollinear Spin Analysis. (United States)

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


    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.

  5. Spin Waves in Terbium

    DEFF Research Database (Denmark)

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


    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...

  6. PREFACE: Spin Electronics (United States)

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


    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

  7. Spin Current Noise of the Spin Seebeck Effect and Spin Pumping. (United States)

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


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

  8. Quantum spin liquid states (United States)

    Zhou, Yi; Kanoda, Kazushi; Ng, Tai-Kai


    This is an introductory review of the physics of quantum spin liquid states. Quantum magnetism is a rapidly evolving field, and recent developments reveal that the ground states and low-energy physics of frustrated spin systems may develop many exotic behaviors once we leave the regime of semiclassical approaches. The purpose of this article is to introduce these developments. The article begins by explaining how semiclassical approaches fail once quantum mechanics become important and then describe the alternative approaches for addressing the problem. Mainly spin-1 /2 systems are discussed, and most of the time is spent in this article on one particular set of plausible spin liquid states in which spins are represented by fermions. These states are spin-singlet states and may be viewed as an extension of Fermi liquid states to Mott insulators, and they are usually classified in the category of so-called S U (2 ), U (1 ), or Z2 spin liquid states. A review is given of the basic theory regarding these states and the extensions of these states to include the effect of spin-orbit coupling and to higher spin (S >1 /2 ) systems. Two other important approaches with strong influences on the understanding of spin liquid states are also introduced: (i) matrix product states and projected entangled pair states and (ii) the Kitaev honeycomb model. Experimental progress concerning spin liquid states in realistic materials, including anisotropic triangular-lattice systems [κ -(ET )2Cu2(CN )3 and EtMe3Sb [Pd (dmit )2]2 ], kagome-lattice system [ZnCu3(OH )6Cl2 ], and hyperkagome lattice system (Na4 Ir3 O8 ), is reviewed and compared against the corresponding theories.

  9. Spin-spin correlations in ferromagnetic nanosystems (United States)

    Vedmedenko, E. Y.; Mikuszeit, N.; Stapelfeldt, T.; Wieser, R.; Potthoff, M.; Lichtenstein, A. I.; Wiesendanger, R.


    Using exact diagonalization, Monte-Carlo, and mean-field techniques, characteristic temperature scales for ferromagnetic order are discussed for the Ising and the classical anisotropic Heisenberg model on finite lattices in one and two dimensions. The interplay between nearest-neighbor exchange, anisotropy and the presence of surfaces leads, as a function of temperature, to a complex behavior of the distance-dependent spin-spin correlation function, which is very different from what is commonly expected. A finite experimental observation time is considered in addition, which is simulated within the Monte-Carlo approach by an incomplete statistical average. We find strong surface effects for small nanoparticles, which cannot be explained within a simple Landau or mean-field concept and which give rise to characteristic trends of the spin-correlation function in different temperature regimes. Unambiguous definitions of crossover temperatures for finite systems and an effective method to estimate the critical temperature of corresponding infinite systems are given.

  10. Universal spin transport in a strongly interacting Fermi gas. (United States)

    Sommer, Ariel; Ku, Mark; Roati, Giacomo; Zwierlein, Martin W


    Transport of fermions, particles with half-integer spin, is central to many fields of physics. Electron transport runs modern technology, defining states of matter such as superconductors and insulators, and electron spin is being explored as a new carrier of information. Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma governed the expansion of the early Universe. However, our understanding of non-equilibrium dynamics in such strongly interacting fermionic matter is still limited. Ultracold gases of fermionic atoms realize a pristine model for such systems and can be studied in real time with the precision of atomic physics. Even above the superfluid transition, such gases flow as an almost perfect fluid with very low viscosity when interactions are tuned to a scattering resonance. In this hydrodynamic regime, collective density excitations are weakly damped. Here we experimentally investigate spin excitations in a Fermi gas of (6)Li atoms, finding that, in contrast, they are maximally damped. A spin current is induced by spatially separating two spin components and observing their evolution in an external trapping potential. We demonstrate that interactions can be strong enough to reverse spin currents, with components of opposite spin reflecting off each other. Near equilibrium, we obtain the spin drag coefficient, the spin diffusivity and the spin susceptibility as a function of temperature on resonance and show that they obey universal laws at high temperatures. In the degenerate regime, the spin diffusivity approaches a value set by [planck]/m, the quantum limit of diffusion, where [planck]/m is Planck's constant divided by 2π and m the atomic mass. For repulsive interactions, our measurements seem to exclude a metastable ferromagnetic state.

  11. Spin Switching via Quantum Dot Spin Valves (United States)

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


    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.

  12. 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


    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.

  13. Spin, mass, and symmetry

    Energy Technology Data Exchange (ETDEWEB)

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


    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. Spin coating of electrolytes (United States)

    Stetter, Joseph R.; Maclay, G. Jordan


    Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

  15. Antiferromagnetic Spin Seebeck Effect. (United States)

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


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

  16. Physics lab in spin

    CERN Multimedia

    Hawkes, N


    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).

  17. Spin Hall and spin swapping torques in diffusive ferromagnets

    KAUST Repository

    Pauyac, C. O.


    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.

  18. Strongly correlated quantum spin liquid in herbertsmithite

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, V. R., E-mail: [Petersburg Nuclear Physics Institute (Russian Federation); Popov, K. G. [Ural Branch of Russian Academy of Sciences, Komi Science Center (Russian Federation); Khodel, V. A. [Russian Research Centre Kurchatov Institute (Russian Federation)


    Strongly correlated Fermi systems are among the most intriguing and fundamental systems in physics. We show that the herbertsmithite ZnCu{sub 3}(OH){sub 6}Cl{sub 2} can be regarded as a new type of strongly correlated electrical insulator that possesses properties of heavy-fermion metals with one exception: it resists the flow of electric charge. We demonstrate that herbertsmithite's low-temperature properties are defined by a strongly correlated quantum spin liquid made with hypothetic particles such as fermionic spinons that carry spin 1/2 and no charge. Our calculations of its thermodynamic and relaxation properties are in good agreement with recent experimental facts and allow us to reveal their scaling behavior, which strongly resembles that observed in heavy-fermion metals. Analysis of the dynamic magnetic susceptibility of strongly correlated Fermi systems suggests that there exist at least two types of its scaling.

  19. Extended dynamic spin-fluctuation theory of metallic magnetism. (United States)

    Melnikov, N B; Reser, B I; Grebennikov, V I


    A dynamic spin-fluctuation theory that directly takes into account nonlocality of thermal spin fluctuations and their mode-mode interactions is developed. The Gaussian approximation in the theory is improved by a self-consistent renormalization of the mean field and spin susceptibility due to the third-and fourth-order terms of the free energy, respectively. This eliminates the fictitious first-order phase transition, which is typical for the Gaussian approximation, and yields a proper second-order phase transition. The effect of nonlocal spin correlations is enhanced by taking into account uniform fluctuations in the single-site mean Green function. Explicit computational formulae for basic magnetic characteristics are obtained. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar. Almost full agreement with experiment is achieved for the magnetization, Curie temperature, and local and effective magnetic moments.

  20. Extended dynamic spin-fluctuation theory of metallic magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, N B [Moscow State University, Moscow 119991 (Russian Federation); Reser, B I; Grebennikov, V I, E-mail:, E-mail:, E-mail: [Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg 620990 (Russian Federation)


    A dynamic spin-fluctuation theory that directly takes into account nonlocality of thermal spin fluctuations and their mode-mode interactions is developed. The Gaussian approximation in the theory is improved by a self-consistent renormalization of the mean field and spin susceptibility due to the third- and fourth-order terms of the free energy, respectively. This eliminates the fictitious first-order phase transition, which is typical for the Gaussian approximation, and yields a proper second-order phase transition. The effect of nonlocal spin correlations is enhanced by taking into account uniform fluctuations in the single-site mean Green function. Explicit computational formulae for basic magnetic characteristics are obtained. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar. Almost full agreement with experiment is achieved for the magnetization, Curie temperature, and local and effective magnetic moments.

  1. Anomalous metallic behaviour in the doped spin liquid candidate κ-(ET)4Hg2.89Br8. (United States)

    Oike, Hiroshi; Suzuki, Yuji; Taniguchi, Hiromi; Seki, Yasuhide; Miyagawa, Kazuya; Kanoda, Kazushi


    Quantum spin liquids are exotic Mott insulators that carry extraordinary spin excitations. Therefore, when doped, they are expected to afford metallic states with unconventional magnetic excitations. Here, we report experimental results which are suggestive of a doped spin liquid with anomalous metallicity in a triangular-lattice organic conductor. The spin susceptibility is nearly perfectly scaled to that of a non-doped spin liquid insulator in spite of the metallic state. Furthermore, the charge transport that is confined in the layer at high temperatures becomes sharply deconfined on cooling, coinciding with the rapid growth of spin correlations or coherence as signified by a steep decrease in spin susceptibility. The present results substantiate the desired doped spin liquid and suggest a strange metal, in which the coherence of the underlying spin liquid promotes the deconfinement of charge from the layers while preserving the non-Fermi-liquid nature.It is expected that introducing charge carriers into an exotic quantum spin liquid state may lead to an unconventional metal but there are no clear realizations of a metallic spin liquid. Here, the authors present a spin liquid candidate that also shows evidence of strange metal behavior.

  2. Higher spins and holography (United States)

    Kraus, Per; Ross, Simon F.


    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

  3. Partition functions of classical Heisenberg spin chains with arbitrary and different exchange

    Energy Technology Data Exchange (ETDEWEB)

    Cregg, P J [Materials Characterisation and Processing Group, Waterford Institute of Technology, Waterford (Ireland); GarcIa-Palacios, J L [Instituto de Ciencia de Materiales de Aragon, Consejo Superior de Investigaciones Cientificas-Universidad de Zaragoza, 50009 Zaragoza (Spain); Svedlindh, P [Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden)], E-mail:


    The classical Heisenberg model has been effective in modelling exchange interactions in molecular magnets. In this model, the partition function is important as it allows the calculation of the magnetization and susceptibility. For an ensemble of N-spin sites, this typically involves integrals in 2N dimensions. Here, for two-, three- and four-spin nearest neighbour open linear Heisenberg chains these integrals are reduced to sums of known functions, using a result due to Gegenbauer. For the case of the three- and four-spin chains, the sums are equivalent in form to the results of Joyce. The general result for an N-spin chain is also obtained.

  4. Determination of Spin State in Dinuclear Iron(II) Coordination Compounds Using Applied Field Moessbauer Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ksenofontov, V.; Spiering, H.; Reiman, S.; Garcia, Y. [Johannes-Gutenberg Universitaet, Institut fuer Anorganische Chemie und Analytische Chemie (Germany); Gaspar, A. B.; Real, J. A. [Universitat de Valencia, Departament de Quimica Inorganica (Spain); Guetlich, P. [Johannes-Gutenberg Universitaet, Institut fuer Anorganische Chemie und Analytische Chemie (Germany)


    So far there has been no direct method to determine the spin state of molecules in dinuclear iron(II) compounds. The molecular fractions of high spin (HS) and low spin (LS) species have been deduced from magnetic susceptibility and zero field Moessbauer spectroscopy data irrespective of whether they belong to LS-LS, LS-HS and HS-HS pairs. However, the distinction of pairs becomes possible if Moessbauer measurements are carried out in an external magnetic field. The proposed method opens new possibilities in the study of spin crossover phenomena in dinuclear compounds.

  5. Susceptibility to malignant hyperthermia

    NARCIS (Netherlands)

    Snoeck, Marcus Matheus Johannes


    In this thesis the author studied the diagnostic procedures for susceptibility to malignant hyperthermia (MH), with special emphasis upon refining the biological diagnostic test and improving protocols and guidelines for investigation of MH susceptibility. MH is a pharmacogenetic disease of skeletal

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

    KAUST Repository

    Manchon, Aurelien


    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.

  7. Spin transverse force on spin current in an electric field. (United States)

    Shen, Shun-Qing


    As a relativistic quantum mechanical effect, it is shown that the electron field exerts a transverse force on an electron spin 1/2 only if the electron is moving. The spin force, analogue to the Lorentz for an electron charge in a magnetic field, is perpendicular to the electric field and the spin current whose spin polarization is projected along the electric field. This spin-dependent force can be used to understand the Zitterbewegung of the electron wave packet with spin-orbit coupling and is relevant to the generation of the charge Hall effect driven by the spin current in semiconductors.

  8. Spins in chemistry

    CERN Document Server

    McWeeny, Roy


    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

  9. Quantum Spin Hall Effect

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.


    The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

  10. Quantum spin liquids

    Energy Technology Data Exchange (ETDEWEB)

    Mila, Frederic [Institut de Physique Theorique, Universite de Lausanne, BSP, Lausanne (Switzerland)


    This paper presents an overview of the properties of magnetic insulators, with emphasis on quantum effects. In particular, the consequences of strong quantum fluctuations on the low-energy properties of a number of systems are reviewed: the occurrence of a spin gap in spin-1 chains and other low-dimensional magnets; the presence of low-lying singlet excitations in several frustrated magnets; the interplay of orbital and spin fluctuations in orbitally degenerate Mott insulators. This review is intended as a pedagogical introduction to the field, and the formalism has been kept at a minimal level. (author)

  11. Frustrated spin systems

    CERN Document Server


    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

  12. Magnetic properties and Binder cumulants of a mixed spin-2 and spin-5/2 Ising diamond chain (United States)

    Jabar, A.; Masrour, R.; Benyoussef, A.; Hamedoun, M.


    The mixed spin-2 and spin-5/2 Ising diamond chain is studied using Monte Carlo simulation. The thermal variation of magnetization and magnetic susceptibilities are obtained in diamond chain. The values of transition temperatures of a mixed spin-2 and spin-5/2 Ising diamond chain have been obtained for different sizes of system N, for different crystal field and for different exchange interactions. The Binder cumulant of magnetization 〈M〉 is investigated. The magnetization with the crystal field and the exchange interaction has been established. The magnetic hysteresis cycle is determined for different values of the crystal field, exchange interactions and temperatures. The system presents the superparamagnetic behavior for a fixed crystal field and temperature value.

  13. Method for estimating spin-spin interactions from magnetization curves (United States)

    Tamura, Ryo; Hukushima, Koji


    We develop a method to estimate the spin-spin interactions in the Hamiltonian from the observed magnetization curve by machine learning based on Bayesian inference. In our method, plausible spin-spin interactions are determined by maximizing the posterior distribution, which is the conditional probability of the spin-spin interactions in the Hamiltonian for a given magnetization curve with observation noise. The conditional probability is obtained with the Markov chain Monte Carlo simulations combined with an exchange Monte Carlo method. The efficiency of our method is tested using synthetic magnetization curve data, and the results show that spin-spin interactions are estimated with a high accuracy. In particular, the relevant terms of the spin-spin interactions are successfully selected from the redundant interaction candidates by the l1 regularization in the prior distribution.

  14. Radiation reaction for spinning bodies in effective field theory. II. Spin-spin effects (United States)

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


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

  15. Estimating the spin diffusion length and the spin Hall angle from spin pumping induced inverse spin Hall voltages (United States)

    Roy, Kuntal


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

  16. Vacuum spin squeezing (United States)

    Hu, Jiazhong; Chen, Wenlan; Vendeiro, Zachary; Urvoy, Alban; Braverman, Boris; Vuletić, Vladan


    We investigate the generation of entanglement (spin squeezing) in an optical-transition atomic clock through the coupling to an optical cavity in its vacuum state. We show that if each atom is prepared in a superposition of the ground state and a long-lived electronic excited state, and viewed as a spin-1/2 system, then the collective vacuum light shift entangles the atoms, resulting in a squeezed distribution of the ensemble collective spin, without any light applied. This scheme reveals that even an electromagnetic vacuum can constitute a useful resource for entanglement and quantum manipulation. By rotating the spin direction while coupling to the vacuum, the scheme can be extended to implement two-axis twisting resulting in stronger squeezing.

  17. Silicon takes a spin

    NARCIS (Netherlands)

    Jansen, R.

    An efficient way to transport electron spins from a ferromagnet into silicon essentially makes silicon magnetic, and provides an exciting step towards integration of magnetism and mainstream semiconductor electronics.

  18. Compact photonic spin filters (United States)

    Ke, Yougang; Liu, Zhenxing; Liu, Yachao; Zhou, Junxiao; Shu, Weixing; Luo, Hailu; Wen, Shuangchun


    In this letter, we propose and experimentally demonstrate a compact photonic spin filter formed by integrating a Pancharatnam-Berry phase lens (focal length of ±f ) into a conventional plano-concave lens (focal length of -f). By choosing the input port of the filter, photons with a desired spin state, such as the right-handed component or the left-handed one, propagate alone its original propagation direction, while the unwanted spin component is quickly diverged after passing through the filter. One application of the filter, sorting the spin-dependent components of vector vortex beams on higher-order Poincaré sphere, is also demonstrated. Our scheme provides a simple method to manipulate light, and thereby enables potential applications for photonic devices.

  19. Spin Physics at COMPASS

    CERN Document Server

    Schill, C


    The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics program is the study of the spin of the nucleon in terms of its constituents, quarks and gluons. COMPASS has accumulated data during 6 years scattering polarized muons off a longitudinally or a transversely polarized deuteron (6LiD) or proton (NH3) target. Results for the gluon polarization are obtained from longitudinal double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton and the deuteron were measured in parallel as well as the helicity distributions for the three lightest quark flavors. With a transversely polarized target, results were obtained with proton and deuteron targets for the Collins an...

  20. Picosecond Spin Seebeck Effect. (United States)

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


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

  1. Itinerant spin ice (United States)

    Udagawa, Masafumi


    Spin ice is a prototypical frustrated magnet defined on a pyrochlore lattice. The ground state of spin ice is described by a simple rule called ``ice rule'': out of four spins on a tetrahedron, two spins point inward, while the other two outward. This simple rule is not sufficient to determine the spin configuration uniquely, but it leaves macroscopic degeneracy in the ground state. Despite the macroscopic degeneracy, however, the ground state is not completely disordered, but it exhibits algebraic spatial correlation, which characterizes this state as ``Coulomb phase'' where various exotic properties, such as monopole excitations and unusual magnetic responses are observed. Given the peculiar spatial correlation, it is interesting to ask what happens if itinerant electrons coexist and interact with spin ice. Indeed, this setting is relevant to several metallic Ir pyrochlore oxides, such as Ln2Ir2O7 (Ln=Pr, Nd), where Ir 5d itinerant electrons interact with Ln 4f localized moments. In these compounds, anomalous transport phenomena have been reported, such as non-monotonic magnetic field dependence of Hall conductivity and low-temperature resistivity upturn. To address these issues, we adopt a spin-ice-type Ising Kondo lattice model on a pyrochlore lattice, and solve this model by applying the cluster dynamical mean-field theory and the perturbation expansion in terms of the spin-electron coupling. As a result, we found that (i) the resistivity shows a minimum at a characteristic temperature below which spin ice correlation sets in. Moreover, (ii) the Hall conductivity shows anisotropic and non-monotonic magnetic field dependence due to the scattering from the spatially extended spin scalar chirality incorporated in spin ice manifold. These results give unified understanding to the thermodynamic and transport properties of Ln2Ir2O7 (Ln=Pr, Nd), and give new insights into the role of geometrical frustration in itinerant systems. This work has been done in

  2. Higher Spins & Strings

    CERN Multimedia

    CERN. Geneva


    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.

  3. Quantum Spin Gyroscope (United States)


    Progress Report (ONR Award No. N00014-14-1-0804) Quantum Spin Gyroscope August 2014-July 2015 Report Type: Annual Report Primary Contact E-mail...Quantum Spin Gyroscope Grant/Contract Number: N00014-14-1-0804 Principal Investigator Name: Paola Cappellaro Program Manager: Richard Tommy Willis...Abstract Gyroscopes find wide application in everyday life, from navigation to rotation sensors in hand-held devices and automobiles. In addition, they can

  4. Massive spin-2 theories

    CERN Document Server

    Folkerts, Sarah; Wintergerst, Nico


    We give an introduction to massive spin-2 theories (including massive gravity) and the problem of their non-linear completion. We review the Boulware-Deser ghost problem and two ways to circumvent classic no-go theorems. In turn, massive spin-2 theories are not uniquely defined. In the case of truncated theories, we show that the Boulware-Deser ghost may only be avoided if the derivative structure of the theory is not tuned to be Einsteinian.

  5. Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling (United States)

    Caetano, R. A.


    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.

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

    KAUST Repository

    Ortiz Pauyac, Christian


    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.

  7. Magnetic properties of a classical XY spin dimer in a “planar” magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ciftja, Orion, E-mail: [Department of Physics, Prairie View A& M University, Prairie View, TX 77446 (United States); Prenga, Dode [Department of Physics, Faculty of Natural Sciences, University of Tirana, Bul. Zog I, Tirana (Albania)


    Single-molecule magnetism originates from the strong intra-molecular magnetic coupling of a small number of interacting spins. Such spins generally interact very weakly with the neighboring spins in the other molecules of the compound, therefore, inter-molecular spin couplings are negligible. In certain cases the number of magnetically coupled spins is as small as a dimer, a system that can be considered the smallest nanomagnet capable of storing non-trivial magnetic information on the molecular level. Additional interesting patterns arise if the spin motion is confined to a two-dimensional space. In such a scenario, clusters consisting of spins with large-spin values are particularly attractive since their magnetic interactions can be described well in terms of classical Heisenberg XY spins. In this work we calculate exactly the magnetic properties of a nanomagnetic dimer of classical XY spins in a “planar” external magnetic field. The problem is solved by employing a mathematical approach whose idea is the introduction of auxiliary spin variables into the starting expression of the partition function. Results for the total internal energy, total magnetic moment, spin–spin correlation function and zero-field magnetic susceptibility can serve as a basis to understand the magnetic properties of large-spin dimer building blocks. - Highlights: • Exact magnetic properties of a dimer system of classical XY spins in magnetic field. • Partition function in nonzero magnetic field obtained in closed-form. • Novel exact analytic results are important for spin models in a magnetic field. • Result provides benchmarks to gauge the accuracy of computational techniques.

  8. Dynamic magnetic susceptibility and electrical detection of ferromagnetic resonance (United States)

    Zhang, Yin; Wang, X. S.; Yuan, H. Y.; Kang, S. S.; Zhang, H. W.; Wang, X. R.


    The dynamic magnetic susceptibility of magnetic materials near ferromagnetic resonance (FMR) is very important in interpreting the dc voltage obtained in its electrical detection. Based on the causality principle and the assumption that the usual microwave absorption lineshape of a homogeneous magnetic material around FMR is Lorentzian, the general forms of the dynamic magnetic susceptibility of an arbitrary sample and the corresponding dc voltage lineshapes of its electrical detection were obtained. Our main findings are as follows. (1) The dynamic magnetic susceptibility is not a Polder tensor for a material with an arbitrary magnetic anisotropy. The two off-diagonal matrix elements of the tensor near FMR are not, in general, opposite to each other. However, the linear response coefficient of the magnetization to the total radio frequency (rf) field (the sum of the external and internal rf fields due to precessing magnetization is a quantity which cannot be measured directly) is a Polder tensor. This may explain why the two off-diagonal susceptibility matrix elements were always wrongly assumed to be opposite to each other in almost all analyses. (2) The frequency dependence of dynamic magnetic susceptibility near FMR is fully characterized by six real numbers, while its field dependence is fully characterized by seven real numbers. (3) A recipe of how to determine these numbers by standard microwave absorption measurements for a sample with an arbitrary magnetic anisotropy is proposed. Our results allow one to unambiguously separate the contribution of the anisotropic magnetoresistance to the dc voltage signals from the anomalous Hall effect. With these results, one can reliably extract the information of spin pumping and the inverse spin-Hall effect, and determine the spin-Hall angle. (4) In the case that resonance frequency is not sensitive to the applied static magnetic field, the field dependence of the matrix elements of dynamic magnetic susceptibility, as

  9. A Two Rotor Model with spin for magnetic Nanoparticles


    Hatada, Keisuke; Hayakawa, Kuniko; Marcelli, Augusto; Palumbo, Fabrizio


    We argue that for some species of magnetic nanoparticles the macrospin can have a nonvanishing moment of inertia and then an orbital angular momentum. We represent such nanoparticles by two interacting rigid rotors one of which has a large spin attached to the body, namely by a Two Rotor Model with spin. By this model we can describe in a unified way the cases of nanoparticles free and stuck in an elastic or rigid matrix. We evaluate the magnetic susceptibilities for the latter case and under...

  10. Measurements of nuclear spin dynamics by spin-noise spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); Kavokin, K. V.; Glazov, M. M. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); Ioffe Institute, Russian Academy of Sciences, 26 Polytechnicheskaya, St.-Petersburg 194021 (Russian Federation); Vladimirova, M.; Scalbert, D.; Cronenberger, S. [Laboratoire Charles Coulomb UMR 5221 CNRS/Université de Montpellier, Place Eugene Bataillon, 34095 Montpellier Cedex 05 (France); Kavokin, A. V. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); School of Physics and Astronomy, University of Southampton, SO17 1NJ Southampton (United Kingdom); Lemaître, A.; Bloch, J. [Laboratoire de Photonique et de Nanostructures, UPR CNRS, Route de Nozay, 91460 Marcoussis (France)


    We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.

  11. Gapless Spin Excitations in the Field-Induced Quantum Spin Liquid Phase of α -RuCl3 (United States)

    Zheng, Jiacheng; Ran, Kejing; Li, Tianrun; Wang, Jinghui; Wang, Pengshuai; Liu, Bin; Liu, Zheng-Xin; Normand, B.; Wen, Jinsheng; Yu, Weiqiang


    α -RuCl3 is a leading candidate material for the observation of physics related to the Kitaev quantum spin liquid (QSL). By combined susceptibility, specific-heat, and nuclear-magnetic-resonance measurements, we demonstrate that α -RuCl3 undergoes a quantum phase transition to a QSL in a magnetic field of 7.5 T applied in the a b plane. We show further that this high-field QSL phase has gapless spin excitations over a field range up to 16 T. This highly unconventional result, unknown in either Heisenberg or Kitaev magnets, offers insight essential to establishing the physics of α -RuCl3 .

  12. Giant Spin Accumulation in Silicon Nonlocal Spin-Transport Devices (United States)

    Spiesser, A.; Saito, H.; Fujita, Y.; Yamada, S.; Hamaya, K.; Yuasa, S.; Jansen, R.


    Although the electrical injection, transport, and detection of spins in silicon have been achieved, the induced spin accumulation is much smaller than expected and desired, limiting the potential impact of Si-based spintronic devices. Here, using nonlocal spin-transport devices with an n -type Si channel and Fe /MgO magnetic tunnel contacts, we demonstrate that it is possible to create a giant spin accumulation in Si, with the spin splitting reaching 13 meV at 10 K and 3.5 meV at room temperature. The nonlocal spin signals are in good agreement with a numerical evaluation of spin injection and diffusion that explicitly takes the size of the injector contact into account. The giant spin accumulation originates from the large tunnel spin polarization of the Fe /MgO contacts (53% at 10 K and 18% at 300 K) and from the spin-density enhancement that is achieved by using a spin injector with a size comparable to the spin-diffusion length of the Si. The ability to induce a giant spin accumulation enables the development of Si spintronic devices with a large magnetic response.

  13. Nuclear Spin Isomers: Engineering a Et4 N[DyPc2 ] Spin Qudit. (United States)

    Moreno-Pineda, Eufemio; Damjanović, Marko; Fuhr, Olaf; Wernsdorfer, Wolfgang; Ruben, Mario


    Two dysprosium isotopic isomers were synthesized: Et4 N[163 DyPc2 ] (1) with I=5/2 and Et4 N[164 DyPc2 ] (2) with I=0 (where Pc=phthalocyaninato). Both isotopologues are single-molecule magnets (SMMs); however, their relaxation times as well as their magnetic hystereses differ considerably. Quantum tunneling of the magnetization (QTM) at the energy level crossings is found for both systems via ac-susceptibility and μ-SQUID measurements. μ-SQUID studies of 1(I=5/2) reveal several nuclear-spin-driven QTM events; hence determination of the hyperfine coupling and the nuclear quadrupole splitting is possible. Compound 2(I=0) shows only strongly reduced QTM at zero magnetic field. 1(I=5/2) could be used as a multilevel nuclear spin qubit, namely qudit (d=6), for quantum information processing (QIP) schemes and provides an example of novel coordination-chemistry-discriminating nuclear spin isotopes. Our results show that the nuclear spin of the lanthanide must be included in the design principles of molecular qubits and SMMs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Spin Structures in Magnetic Nanoparticles

    DEFF Research Database (Denmark)

    Mørup, Steen; Brok, Erik; Frandsen, Cathrine


    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....... Here, we give a short review of anomalous spin structures in nanoparticles....

  15. Three-electron spin qubits (United States)

    Russ, Maximilian; Burkard, Guido


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

  16. Spinning Them Off: Entrepreneuring practices in Corporate Spin-Offs

    National Research Council Canada - National Science Library

    Hydle, Katja Maria; Meland, Kjersti Vikse; Haus-Reve, Silje


    .... 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...

  17. Quantum spin transistor with a Heisenberg spin chain (United States)

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


    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

  18. Mechanisms of Spin-Dependent Heat Generation in Spin Valves (United States)

    Zhang, Xiao-Xue; Zhu, Yao-Hui; He, Pei-Song; Li, Bao-He


    The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. By reformulating the heat generation rate, we found alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One of them is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrated the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.

  19. Demonstration of the spin solar cell and spin photodiode effect (United States)

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


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

  20. Chiral higher spin gravity (United States)

    Krishnan, Chethan; Raju, Avinash


    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.

  1. Spinning fluids reactor (United States)

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


    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.

  2. SPIN-selling

    CERN Document Server

    Rackham, Neil


    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.

  3. Perspectives on spin glasses

    CERN Document Server

    Contucci, Pierluigi


    Presenting and developing the theory of spin glasses as a prototype for complex systems, this book is a rigorous and up-to-date introduction to their properties. The book combines a mathematical description with a physical insight of spin glass models. Topics covered include the physical origins of those models and their treatment with replica theory; mathematical properties like correlation inequalities and their use in the thermodynamic limit theory; main exact solutions of the mean field models and their probabilistic structures; and the theory of the structural properties of the spin glass phase such as stochastic stability and the overlap identities. Finally, a detailed account is given of the recent numerical simulation results and properties, including overlap equivalence, ultrametricity and decay of correlations. The book is ideal for mathematical physicists and probabilists working in disordered systems.

  4. Accuracy of MRI-based Magnetic Susceptibility Measurements (United States)

    Russek, Stephen; Erdevig, Hannah; Keenan, Kathryn; Stupic, Karl

    Magnetic Resonance Imaging (MRI) is increasingly used to map tissue susceptibility to identify microbleeds associated with brain injury and pathologic iron deposits associated with neurologic diseases such as Parkinson's and Alzheimer's disease. Field distortions with a resolution of a few parts per billion can be measured using MRI phase maps. The field distortion map can be inverted to obtain a quantitative susceptibility map. To determine the accuracy of MRI-based susceptibility measurements, a set of phantoms with paramagnetic salts and nano-iron gels were fabricated. The shapes and orientations of features were varied. Measured susceptibility of 1.0 mM GdCl3 solution in water as a function of temperature agreed well with the theoretical predictions, assuming Gd+3 is spin 7/2. The MRI susceptibility measurements were compared with SQUID magnetometry. The paramagnetic susceptibility sits on top of the much larger diamagnetic susceptibility of water (-9.04 x 10-6), which leads to errors in the SQUID measurements. To extract out the paramagnetic contribution using standard magnetometry, measurements must be made down to low temperature (2K). MRI-based susceptometry is shown to be as or more accurate than standard magnetometry and susceptometry techniques.

  5. Tuning size and thermal hysteresis in bistable spin crossover nanoparticles. (United States)

    Galán-Mascarós, José Ramón; Coronado, Eugenio; Forment-Aliaga, Alicia; Monrabal-Capilla, María; Pinilla-Cienfuegos, Elena; Ceolin, Marcelo


    Nanoparticles of iron(II) triazole salts have been prepared from water-organic microemulsions. The mean size of the nanoparticles can be tuned down to 6 nm in diameter, with a narrow size distribution. A sharp spin transition from the low spin (LS) to the high spin (HS) state is observed above room temperature, with a 30-40-K-wide thermal hysteresis. The same preparation can yield second generation nanoparticles containing molecular alloys by mixing triazole with triazole derivatives, or from metallic mixtures of iron(II) and zinc(II). In these nanoparticles of 10-15 nm, the spin transition "moves" towards lower temperatures, reaching a 316 K limit for the cooling down transition and maintaining a thermal hysteresis over 15-20-K-wide. The nanoparticles were characterized by dynamic light scattering, TEM, and AFM, after deposition on gold or silicon surfaces. The spin transition was characterized by magnetic susceptibility measurements and EXAFS (in solid samples after solvent removal) and also by the color change between the LS (violet) and HS (colorless) states in an organic solvent suspension. The discovery of bistable magnetic nanoparticles of 6 nm with a wide thermal hysteresis above room temperature showcases the actual possibilities of spin crossover materials for nanotechnological applications.

  6. Paramagnetic spin seebeck effect. (United States)

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


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

  7. Spin injection and perpendicular spin transport in graphite nanostructures

    NARCIS (Netherlands)

    Banerjee, T.; van der Wiel, Wilfred Gerard; Jansen, R.


    Organic- and carbon-based materials are attractive for spintronics because their small spin-orbit coupling and low hyperfine interaction is expected to give rise to large spin-relaxation times. However, the corresponding spin-relaxation length is not necessarily large when transport is via weakly

  8. Aspects of spin polarised transport

    CERN Document Server

    Allen, W D


    Spin electronics is the emerging discipline which seeks to exploit the spin of the electron in the pursuit of new areas of physics and of novel devices and applications. It can be broadly defined as the technology which differentially manipulates the two families of electronic carriers, the up and down spins. The technical basis for Spin Electronics resides in the transport properties of metallic ferromagnets which are central to the discipline and are used as sources and analysers of spin-polarised currents. We have developed a totally new model for domain wall resistance in the framework of the two spin channel model which invokes spin mixing which derives from the deviation of spin direction from the local magnetisation direction in passage through the wall

  9. Spin-flipping polarized electrons

    Directory of Open Access Journals (Sweden)

    V. S. Morozov


    Full Text Available We recently used a prototype rf dipole magnet to study the spin flipping of a 669 MeV horizontally polarized electron beam stored in the presence of a nearly full Siberian snake in the new MIT-Bates storage ring. We flipped the spin by ramping the rf dipole's frequency through an rf-induced depolarizing resonance. After optimizing the frequency ramp parameters, we used multiple spin flipping to measure a spin-flip efficiency of 94.5±2.5%. The spin-flip efficiency was apparently limited by the field strength in the air-core prototype rf dipole magnet. This unexpectedly high efficiency indicates that very efficient spin flipping of the ring's stored polarized electron beam should be possible using the much stronger ferrite spin flipper, which is now being built by the University of Michigan's Spin Physics Center.

  10. Bidirectional resonant tunneling spin pump


    Ting, David Z. -Y.; Cartoixà Soler, Xavier


    We propose a mechanism for achieving bidirectional spin pumping in conventional nonmagnetic semiconductorresonant tunnelingheterostructures under zero magnetic field. The device is designed specifically to take advantage of the special spin configuration described by the Rashba effect in asymmetric quantum wells. It induces the simultaneous flow of oppositely spin-polarized current components in opposite directions through spin-dependent resonant tunneling, and can thus generate significant l...


    Energy Technology Data Exchange (ETDEWEB)



    The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.

  12. Spin physics in semiconductors

    CERN Document Server

    Dyakonov, Mikhail I


    This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Recent results on quantum wells and quantum dots are reviewed. The book is intended for students and researchers in the fields of semiconductor physics and nanoelectronics.

  13. Antiferromagnetic spin-orbitronics

    KAUST Repository

    Manchon, Aurelien


    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.

  14. A two rotor model with spin for magnetic nanoparticles. (United States)

    Hatada, Keisuke; Hayakawa, Kuniko; Marcelli, Augusto; Palumbo, Fabrizio


    We argue that a kind of magnetic nanoparticle might exist characterized by the locking of the constituent spins with the density profile of the macrospin. We represent such a nanoparticle by two interacting rigid rotors, one of which has a large spin attached to the body, namely a two rotor model with spin. By this model we can describe in a unified way the cases of nanoparticles free and stuck in an elastic or a rigid matrix. We evaluate the magnetic susceptibility for the latter case and under some realistic assumptions we get results in closed form. A crossover between thermal and purely quantum hopping occurs at a temperature much higher than that at which tunneling becomes important. Agreement with some experimental data is remarkable.

  15. High spin states in Cu

    Indian Academy of Sciences (India)

    up of high-spin configurations outlined above, a detailed and careful study of the medium spin, near yrast states in this nucleus is important for reliable assignments of spins and parities to states in superdeformed bands [1,6] in mass region 60. Also, the observation of direct proton decay from excited states in Cu nuclei [14] ...

  16. Spin Injection in Indium Arsenide

    Directory of Open Access Journals (Sweden)

    Mark eJohnson


    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.

  17. Spin diffusion in Fermi gases

    DEFF Research Database (Denmark)

    Bruun, Georg


    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...

  18. Mechanical generation of spin current

    Directory of Open Access Journals (Sweden)

    Mamoru eMatsuo


    Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.

  19. Spin dynamics in general relativity

    NARCIS (Netherlands)

    Saravanan, S.


    Since all astrophysical objects spin, it is important to study the dynamics of spinning objects in curved space-time. The dynamics of spinning particles are described with a covariant Hamiltonian formalism. In this formalism, the closed set of equations of motion are obtained from Poisson-Dirac

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

    Directory of Open Access Journals (Sweden)

    Katja Maria Hydle


    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.

  1. Microwave generation by spin Hall nanooscillators with nanopatterned spin injector

    Energy Technology Data Exchange (ETDEWEB)

    Zholud, A., E-mail:; Urazhdin, S. [Department of Physics, Emory University, Atlanta, Georgia 30322 (United States)


    We experimentally study spin Hall nano-oscillators based on Pt/ferromagnet bilayers with nanopatterned Pt spin injection layer. We demonstrate that both the spectral characteristics and the electrical current requirements can be simultaneously improved by reducing the spin injection area. Moreover, devices with nanopatterned Pt spin injector exhibit microwave generation over a wide temperature range that extends to room temperature. Studies of devices with additional Pt spacers under the device electrodes show that the oscillation characteristics are affected not only by the spin injection geometry but also by the effects of Pt/ferromagnet interface on the dynamical properties of the ferromagnet.

  2. Competition between spin and charge order in a one-dimensional lattice (United States)

    Talebi, Amir Hossein; Davoudi, Bahman; Rahimitabar, M. Reza


    In this paper, we study the presence of competing instabilities in one-dimensional (1D) extended Hubbard model (EHM). Using the extended two-particle self-consistent approximation (ETPSC), we derive the density and interaction dependent crossover diagram for spin and charge density wave fluctuations at arbitrary wave number. We determine the phase transitions of the system by means of spin and charge susceptibilities. We draw the phase diagram which separates different phases of the model for several effective particle densities.

  3. Spinor Analysis Calculation of the Spin Correlation of the Two-Dimensional Ising Model (United States)

    Tanaka, Yoshiaki


    For the Ising model on the two-dimensional lattice with M×N lattice sites (M is a finite number; N→∞), a new method is presented by which the two-spin correlations at arbitrary distances are evaluated exactly. We make use of spinor analysis, which was employed by Kaufman and Onsager. The zero-field magnetic susceptibility χ0 that is equal to the sum of all the two-spin correlations, is calculated.

  4. Scaling in dynamic susceptibility of herbertsmithite and heavy-fermion metals

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, V.R., E-mail: [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation); Clark Atlanta University, Atlanta, GA 30314 (United States); Msezane, A.Z. [Clark Atlanta University, Atlanta, GA 30314 (United States); Popov, K.G. [Komi Science Center, Ural Division, RAS, Syktyvkar 167982 (Russian Federation); Khodel, V.A. [Russian Research Center Kurchatov Institute, Moscow 123182 (Russian Federation); McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States)


    We present a theory of the dynamic magnetic susceptibility of quantum spin liquid. The obtained results are in good agreement with experimental facts collected on herbertsmithite ZnCu{sub 3}(OH){sub 6}Cl{sub 2} and on heavy-fermion metals, and allow us to predict a new scaling in magnetic fields in the dynamic susceptibility. Under the application of strong magnetic fields quantum spin liquid becomes completely polarized. We show that this polarization can be viewed as a manifestation of gapped excitations when investigating the spin-lattice relaxation rate. -- Highlights: ► We present a theory of the dynamic magnetic susceptibility of quantum spin liquid. ► We calculate the dynamic susceptibility of ZnCu{sub 3}(OH){sub 6}Cl{sub 2} as a function of temperature versus energy. ► Our calculations are in good agreement with experimental facts. ► We explain the scaling of the dynamic susceptibility and predict a new scaling in magnetic fields. ► The polarization in magnetic fields can be viewed as a manifestation of gapped excitations.

  5. Spin superconductors in double-layer ferromagnetic graphene (United States)

    Chen, Hua; Sun, Qingfeng; Xie, X. C.


    We study double-layer ferromagnetic graphene with asymmetric gate voltage applied on top and bottom layers. By employing general random phase approximation (GRPA), the interaction dressed susceptibility shows that the leading instability is of Stoner type: the Hubbard interaction drives the electron-hole (e-h) pairs condense and leads to the coherence between top and bottom layers. These e-h excitons are charge neutral but spin polarized, and their condensation can be viewed as a spin superconductor. The Goldstone mode associated with spontaneous symmetry breaking is revealed by calculating the dynamical susceptibility. An in-plane magnetic field couples the intra-spin component to the Goldstone mode and induces a zero bias voltage tunneling peak, realizing an analogue of tunneling current in bilayer quantum Hall systems. The inter-layer tunneling current is calculated by following linear response theory, which recovers the results of Fermi's golden rule. As a complementary of susceptibility calculation, mean field approximation, which ignores fluctuations, is also applied. It precisely recovers the critical Coulomb interaction as predicted by GRPA results and comfirms the existence of symmetry breaking ground states as a saddle point solution.

  6. Spin-optical metamaterial route to spin-controlled photonics. (United States)

    Shitrit, Nir; Yulevich, Igor; Maguid, Elhanan; Ozeri, Dror; Veksler, Dekel; Kleiner, Vladimir; Hasman, Erez


    Spin optics provides a route to control light, whereby the photon helicity (spin angular momentum) degeneracy is removed due to a geometric gradient onto a metasurface. The alliance of spin optics and metamaterials offers the dispersion engineering of a structured matter in a polarization helicity-dependent manner. We show that polarization-controlled optical modes of metamaterials arise where the spatial inversion symmetry is violated. The emerged spin-split dispersion of spontaneous emission originates from the spin-orbit interaction of light, generating a selection rule based on symmetry restrictions in a spin-optical metamaterial. The inversion asymmetric metasurface is obtained via anisotropic optical antenna patterns. This type of metamaterial provides a route for spin-controlled nanophotonic applications based on the design of the metasurface symmetry properties.

  7. Spin-wave-induced spin torque in Rashba ferromagnets (United States)

    Umetsu, Nobuyuki; Miura, Daisuke; Sakuma, Akimasa


    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.

  8. Genetic susceptibility of periodontitis

    NARCIS (Netherlands)

    Laine, M.L.; Crielaard, W.; Loos, B.G.


    In this systematic review, we explore and summarize the peer-reviewed literature on putative genetic risk factors for susceptibility to aggressive and chronic periodontitis. A comprehensive literature search on the PubMed database was performed using the keywords ‘periodontitis’ or ‘periodontal

  9. Fourie susceptible.pmd

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    a number of cultivars exhibited field resistance to halo blight and bacterial brown spot, all cultivars were more or less susceptible to .... Cerillos. Alubia. I. 91. 57. Kranskop. Red speckled sugar. II. 97. 63. OPS-RS1. Red speckled sugar. II. 96. 63. OPS-RS2. Red speckled sugar. I. 100. 61. OPS-RS3. Red speckled sugar. II. 97.

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

    Directory of Open Access Journals (Sweden)

    L. D. C. Jaubert


    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.

  11. RHIC spin flipper commissioning results

    Energy Technology Data Exchange (ETDEWEB)

    Bai M.; Roser, T.; Dawson, C.; Kewisch, J.; Makdisi, Y.; Oddo, P.; Pai, C.; Pile, P.


    The five AC dipole RHIC spin flipper design in the RHIC Blue ring was first tested during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper. The closure of each ac dipole vertical bump was measured with orbital response as well as spin. The effect of the rotating field on the spin motion by the spin flipper was also confirmed by measuring the suppressed resonance at Q{sub s} = 1 - Q{sub osc}.

  12. Orientational Glasses: NMR and Electric Susceptibility Studies

    Directory of Open Access Journals (Sweden)

    Neil Sullivan


    Full Text Available We review the results of a wide range of nuclear magnetic resonance (NMRmeasurements of the local order parameters and the molecular dynamics of solid ortho-para hydrogen mixtures and solid nitrogen-argon mixtures that form novel molecular orientational glass states at low temperatures. From the NMR measurements, the distribution of the order parameters can be deduced and, in terms of simple models, used to analyze the thermodynamic measurements of the heat capacities of these systems. In addition, studies of the dielectric susceptibilities of the nitrogen-argon mixtures are reviewed in terms of replica symmetry breaking analogous to that observed for spin glass states. It is shown that this wide set of experimental results is consistent with orientation or quadrupolar glass ordering of the orientational degrees of freedom.

  13. Doping induced spin state transition in LaCoO3: dynamical mean-field study. (United States)

    Augustinský, P; Křápek, V; Kuneš, J


    Hole and electron doped LaCoO3 is studied using dynamical mean-field theory. The one-particle spectra are analyzed and compared to the available experimental data, in particular the x-ray absorption spectra. Analyzing the temporal spin-spin correlation functions we find the atomic intermediate spin state is not important for the observed Curie-Weiss susceptibility. Contrary to the commonly held view about the roles played by the t2g and eg electrons we find narrow quasiparticle bands of t2g character crossing the Fermi level accompanied by strongly damped eg excitations.

  14. A high-temperature quantum spin liquid with polaron spins (United States)

    Klanjšek, Martin; Zorko, Andrej; Žitko, Rok; Mravlje, Jernej; Jagličić, Zvonko; Biswas, Pabitra Kumar; Prelovšek, Peter; Mihailovic, Dragan; Arčon, Denis


    The existence of a quantum spin liquid (QSL) in which quantum fluctuations of spins are sufficiently strong to preclude spin ordering down to zero temperature was originally proposed theoretically more than 40 years ago, but its experimental realization turned out to be very elusive. Here we report on an almost ideal spin liquid state that appears to be realized by atomic-cluster spins on the triangular lattice of a charge-density wave state of 1T-TaS2. In this system, the charge excitations have a well-defined gap of ~0.3 eV, while nuclear quadrupole resonance and muon-spin-relaxation experiments reveal that the spins show gapless QSL dynamics and no long-range magnetic order at least down to 70 mK. Canonical T2 power-law temperature dependence of the spin relaxation dynamics characteristic of a QSL is observed from 200 K to Tf = 55 K. Below this temperature, we observe a new gapless state with reduced density of spin excitations and high degree of local disorder signifying new quantum spin order emerging from the QSL.

  15. Spin Funneling for Enhanced Spin Injection into Ferromagnets (United States)

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


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

  16. Orphan Spins in the S =5/2 Antiferromagnet CaFe2O4 (United States)

    Stock, C.; Rodriguez, E. E.; Lee, N.; Demmel, F.; Fouquet, P.; Laver, M.; Niedermayer, Ch.; Su, Y.; Nemkovski, K.; Green, M. A.; Rodriguez-Rivera, J. A.; Kim, J. W.; Zhang, L.; Cheong, S.-W.


    CaFe2O4 is an anisotropic S =5/2 antiferromagnet with two competing A (↑↑↓↓) and B (↑↓↑↓) magnetic order parameters separated by static antiphase boundaries at low temperatures. Neutron diffraction and bulk susceptibility measurements, show that the spins near these boundaries are weakly correlated and a carry an uncompensated ferromagnetic moment that can be tuned with a magnetic field. Spectroscopic measurements find these spins are bound with excitation energies less than the bulk magnetic spin waves and resemble the spectra from isolated spin clusters. Localized bound orphaned spins separate the two competing magnetic order parameters in CaFe2 O4 .

  17. Orphan Spins in the S=5/2 Antiferromagnet CaFe_{2}O_{4}. (United States)

    Stock, C; Rodriguez, E E; Lee, N; Demmel, F; Fouquet, P; Laver, M; Niedermayer, Ch; Su, Y; Nemkovski, K; Green, M A; Rodriguez-Rivera, J A; Kim, J W; Zhang, L; Cheong, S-W


    CaFe_{2}O_{4} is an anisotropic S=5/2 antiferromagnet with two competing A (↑↑↓↓) and B (↑↓↑↓) magnetic order parameters separated by static antiphase boundaries at low temperatures. Neutron diffraction and bulk susceptibility measurements, show that the spins near these boundaries are weakly correlated and a carry an uncompensated ferromagnetic moment that can be tuned with a magnetic field. Spectroscopic measurements find these spins are bound with excitation energies less than the bulk magnetic spin waves and resemble the spectra from isolated spin clusters. Localized bound orphaned spins separate the two competing magnetic order parameters in CaFe_{2}O_{4}.

  18. Spin diffusion length of Permalloy using spin absorption in lateral spin valves (United States)

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


    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.

  19. Weyl spin liquids. (United States)

    Hermanns, M; O'Brien, K; Trebst, S


    The fractionalization of quantum numbers in interacting quantum many-body systems is a central motif in condensed-matter physics with prominent examples including the fractionalization of the electron in quantum Hall liquids or the emergence of magnetic monopoles in spin-ice materials. Here, we discuss the fractionalization of magnetic moments in three-dimensional Kitaev models into Majorana fermions (and a Z_{2} gauge field) and their emergent collective behavior. We analytically demonstrate that the Majorana fermions form a Weyl superconductor for the Kitaev model on the recently synthesized hyperhoneycomb structure of β-Li_{2}IrO_{3} when applying a magnetic field. We characterize the topologically protected bulk and surface features of this state, which we dub a Weyl spin liquid, including thermodynamic and transport signatures.

  20. Spin Glass Patch Planting (United States)

    Wang, Wenlong; Mandra, Salvatore; Katzgraber, Helmut G.


    In this paper, we propose a patch planting method for creating arbitrarily large spin glass instances with known ground states. The scaling of the computational complexity of these instances with various block numbers and sizes is investigated and compared with random instances using population annealing Monte Carlo and the quantum annealing DW2X machine. The method can be useful for benchmarking tests for future generation quantum annealing machines, classical and quantum mechanical optimization algorithms.

  1. Spin and gravitation (United States)

    Ray, J. R.


    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.

  2. Spinning out a star. (United States)

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


    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.

  3. Progressive freezing of interacting spins in isolated finite magnetic ensembles (United States)

    Bhattacharya, Kakoli; Dupuis, Veronique; Le-Roy, Damien; Deb, Pritam


    Self-organization of magnetic nanoparticles into secondary nanostructures provides an innovative way for designing functional nanomaterials with novel properties, different from the constituent primary nanoparticles as well as their bulk counterparts. Collective magnetic properties of such complex closed packing of magnetic nanoparticles makes them more appealing than the individual magnetic nanoparticles in many technological applications. This work reports the collective magnetic behaviour of magnetic ensembles comprising of single domain Fe3O4 nanoparticles. The present work reveals that the ensemble formation is based on the re-orientation and attachment of the nanoparticles in an iso-oriented fashion at the mesoscale regime. Comprehensive dc magnetic measurements show the prevalence of strong interparticle interactions in the ensembles. Due to the close range organization of primary Fe3O4 nanoparticles in the ensemble, the spins of the individual nanoparticles interact through dipolar interactions as realized from remnant magnetization measurements. Signature of super spin glass like behaviour in the ensembles is observed in the memory studies carried out in field cooled conditions. Progressive freezing of spins in the ensembles is corroborated from the Vogel-Fulcher fit of the susceptibility data. Dynamic scaling of relaxation reasserted slow spin dynamics substantiating cluster spin glass like behaviour in the ensembles.

  4. A spin transition molecular material with a wide bistability domain. (United States)

    Garcia, Yann; Moscovici, Jacques; Michalowicz, Alain; Ksenofontov, Vadim; Levchenko, Georg; Bravic, Georges; Chasseau, Daniel; Gütlich, Philipp


    [Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and Mössbauer, optical, and EXAFS spectroscopy. Compound 1 exhibits a spin transition below room temperature, together with a very wide thermal hysteresis of about 50 K. This represents the widest hysteresis loop ever observed for an FeII-1,2,4-triazole spin transition material. The cooperativity is discussed on the basis of temperature-dependent EXAFS studies and of the structural features of a CuII analogue. The EXAFS structural model of (1) in both spin states is compared to that obtained for a related material whose spin transition occurs above room temperature. EXAFS spectroscopy suggests that 1,2,4-triazole chain compounds retain a linear character whatever the spin state of the iron(II).

  5. Genetic Susceptibility to Atherosclerosis

    Directory of Open Access Journals (Sweden)

    Sanja Kovacic


    Full Text Available Atherosclerosis is a complex multifocal arterial disease involving interactions of multiple genetic and environmental factors. Advances in techniques of molecular genetics have revealed that genetic ground significantly influences susceptibility to atherosclerotic vascular diseases. Besides further investigations of monogenetic diseases, candidate genes, genetic polymorphisms, and susceptibility loci associated with atherosclerotic diseases have been identified in recent years, and their number is rapidly increasing. This paper discusses main genetic investigations fields associated with human atherosclerotic vascular diseases. The paper concludes with a discussion of the directions and implications of future genetic research in arteriosclerosis with an emphasis on prospective prediction from an early age of individuals who are predisposed to develop premature atherosclerosis as well as to facilitate the discovery of novel drug targets.

  6. Spinning particle approach to higher spin field theory

    Energy Technology Data Exchange (ETDEWEB)

    Corradini, Olindo, E-mail: [Centro de Estudios en Fisica y Matematicas Basicas y Aplicadas Universidad Autonoma de Chiapas, Tuxtla Gutierrez, Chiapas (Mexico); Dipartimento di Fisica, Universita di Bologna via Irnerio 46, I-40126 Bologna (Italy); INFN, Sezione di Bologna via Irnerio 46, I-40126 Bologna (Italy)


    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.

  7. Marijuana Usage and Hypnotic Susceptibility (United States)

    Franzini, Louis R.; McDonald, Roy D.


    Anonymous self-reported drug usage data and hypnotic susceptibility scores were obtained from 282 college students. Frequent marijuana users (more than 10 times) showed greater susceptibility to hypnosis than nonusers. (Author)

  8. Quantum annealing with manufactured spins. (United States)

    Johnson, M W; Amin, M H S; Gildert, S; Lanting, T; Hamze, F; Dickson, N; Harris, R; Berkley, A J; Johansson, J; Bunyk, P; Chapple, E M; Enderud, C; Hilton, J P; Karimi, K; Ladizinsky, E; Ladizinsky, N; Oh, T; Perminov, I; Rich, C; Thom, M C; Tolkacheva, E; Truncik, C J S; Uchaikin, S; Wang, J; Wilson, B; Rose, G


    Many interesting but practically intractable problems can be reduced to that of finding the ground state of a system of interacting spins; however, finding such a ground state remains computationally difficult. It is believed that the ground state of some naturally occurring spin systems can be effectively attained through a process called quantum annealing. If it could be harnessed, quantum annealing might improve on known methods for solving certain types of problem. However, physical investigation of quantum annealing has been largely confined to microscopic spins in condensed-matter systems. Here we use quantum annealing to find the ground state of an artificial Ising spin system comprising an array of eight superconducting flux quantum bits with programmable spin-spin couplings. We observe a clear signature of quantum annealing, distinguishable from classical thermal annealing through the temperature dependence of the time at which the system dynamics freezes. Our implementation can be configured in situ to realize a wide variety of different spin networks, each of which can be monitored as it moves towards a low-energy configuration. This programmable artificial spin network bridges the gap between the theoretical study of ideal isolated spin networks and the experimental investigation of bulk magnetic samples. Moreover, with an increased number of spins, such a system may provide a practical physical means to implement a quantum algorithm, possibly allowing more-effective approaches to solving certain classes of hard combinatorial optimization problems.

  9. Spin-stripe phase in a frustrated zigzag spin-1/2 chain (United States)

    Pregelj, M.; Zorko, A.; Zaharko, O.; Nojiri, H.; Berger, H.; Chapon, L. C.; Arčon, D.


    Motifs of periodic modulations are encountered in a variety of natural systems, where at least two rival states are present. In strongly correlated electron systems, such behaviour has typically been associated with competition between short- and long-range interactions, for example, between exchange and dipole-dipole interactions in the case of ferromagnetic thin films. Here we show that spin-stripe textures may develop also in antiferromagnets, where long-range dipole-dipole magnetic interactions are absent. A comprehensive analysis of magnetic susceptibility, high-field magnetization, specific heat and neutron diffraction measurements unveils β-TeVO4 as a nearly perfect realization of a frustrated (zigzag) ferromagnetic spin-1/2 chain. Notably, a narrow spin-stripe phase develops at elevated magnetic fields due to weak frustrated short-range interchain exchange interactions, possibly assisted by the symmetry-allowed electric polarization. This concept provides an alternative route for the stripe formation in strongly correlated electron systems and may help understanding of other widespread, yet still elusive, stripe-related phenomena.

  10. Spin glass-like behavior in spin-density-wave CrCoMn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Galkin, Vladimir Yu. E-mail:; Ortiz, Wilson A.; Ali, Naushad


    Magnetic susceptibility and magnetization of spin-density-wave (SDW) alloy systems (Cr+3.2%Co){sub 1-x}Mn{sub x} and (Cr+6.5%Co){sub 1-x}Mn{sub x} have been measured with a SQUID magnetometer. Magnetic properties of the studied alloys are compared with those exhibited by binary Cr{sub 1-x}Mn{sub x} and ternary (CrFe){sub 1-x}Mn{sub x} and (CrSi){sub 1-x}Mn{sub x} alloys. All these alloys show spin glass (SG)-like behavior; however, some of their magnetic properties are quite different from those exhibited by conventional metallic spin glasses. Though both Fe and Co produce a local moment in Cr and CrMn, addition of Co to CrMn does not result in suppression of SG-like phase like that in (CrFe){sub 1-x}Mn{sub x}. This seems to be a result of essentially different strengths of Fe-Cr and Co-Cr couplings. All alloys studied show a low-temperature SG-like magnetic hysteresis. Such hysteresis is shifted to negative fields by cooling the alloys in a strong magnetic field through the Neel temperature. This effect is caused by unidirectional anisotropy of Co atoms frozen in the SDW matrix.

  11. Non-self-averaging in Ising spin glasses and hyperuniversality. (United States)

    Lundow, P H; Campbell, I A


    Ising spin glasses with bimodal and Gaussian near-neighbor interaction distributions are studied through numerical simulations. The non-self-averaging (normalized intersample variance) parameter U_{22}(T,L) for the spin glass susceptibility [and for higher moments U_{nn}(T,L)] is reported for dimensions 2,3,4,5, and 7. In each dimension d the non-self-averaging parameters in the paramagnetic regime vary with the sample size L and the correlation length ξ(T,L) as U_{nn}(β,L)=[K_{d}ξ(T,L)/L]^{d} and so follow a renormalization group law due to Aharony and Harris [Phys. Rev. Lett. 77, 3700 (1996)PRLTAO0031-900710.1103/PhysRevLett.77.3700]. Empirically, it is found that the K_{d} values are independent of d to within the statistics. The maximum values [U_{nn}(T,L)]_{max} are almost independent of L in each dimension, and remarkably the estimated thermodynamic limit critical [U_{nn}(T,L)]_{max} peak values are also practically dimension-independent to within the statistics and so are "hyperuniversal." These results show that the form of the spin-spin correlation function distribution at criticality in the large L limit is independent of dimension within the ISG family. Inspection of published non-self-averaging data for three-dimensional Heisenberg and XY spin glasses the light of the Ising spin glass non-self-averaging results show behavior which appears to be compatible with that expected on a chiral-driven ordering interpretation but incompatible with a spin-driven ordering scenario.

  12. Entanglement in a Spin-$s$ Antiferromagnetic Heisenberg Chain


    Hao, Xiang; Zhu, Shiqun


    The entanglement in a general Heisenberg antiferromagnetic chain of arbitrary spin-$s$ is investigated. The entanglement is witnessed by the thermal energy which equals to the minimum energy of any separable state. There is a characteristic temperature below that an entangled thermal state exists. The characteristic temperature for thermal entanglement is increased with spin $s$. When the total number of lattice is increased, the characteristic temperature decreases and then approaches a cons...

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

    DEFF Research Database (Denmark)

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


    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......: it equilibrates the spin density imbalance and, provided it has a non-s-wave component, also a current imbalance....

  14. Spin injection and spin transport in paramagnetic insulators


    Okamoto, Satoshi


    We investigate the spin injection and the spin transport in paramagnetic insulators described by simple Heisenberg interactions using auxiliary particle methods. Some of these methods allow access to both paramagnetic states above magnetic transition temperatures and magnetic states at low temperatures. It is predicted that the spin injection at an interface with a normal metal is rather insensitive to temperatures above the magnetic transition temperature. On the other hand below the transit...

  15. Spin sensitive bleaching and monopolar spin orientation in quantum wells


    Ganichev, Sergey; Danilov, Sergey; Belkov, Vassilij; Ivchenko, Eougenious; Bichler, Max; Wegscheider, Werner; Weiss, Dieter; Prettl, Wilhelm


    Spin sensitive bleaching of the absorption of far-infrared radiation has been observed in $p$-type GaAs/AlGaAs quantum well structures. The absorption of circularly polarized radiation saturates at lower intensities than that of linearly polarized light due to monopolar spin orientation in the first heavy hole subband. Spin relaxation times of holes in $p$-type material in the range of tens of ps were derived from the intensity dependence of the absorption.

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

    DEFF Research Database (Denmark)

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


    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...... 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...

  17. Spin-seebeck effect: a phonon driven spin distribution. (United States)

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


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

  18. Spin-orbit mediated control of spin qubits

    DEFF Research Database (Denmark)

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


    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....

  19. Spin Polarization Oscillations without Spin Precession: Spin-Orbit Entangled Resonances in Quasi-One-Dimensional Spin Transport

    Directory of Open Access Journals (Sweden)

    D. H. Berman


    Full Text Available Resonant behavior involving spin-orbit entangled states occurs for spin transport along a narrow channel defined in a two-dimensional electron gas, including an apparent rapid relaxation of the spin polarization for special values of the channel width and applied magnetic field (so-called ballistic spin resonance. A fully quantum-mechanical theory for transport using multiple subbands of the one-dimensional system provides the dependence of the spin density on the applied magnetic field and channel width and position along the channel. We show how the spatially nonoscillating part of the spin density vanishes when the Zeeman energy matches the subband energy splittings. The resonance phenomenon persists in the presence of disorder.

  20. Multiferroics with spiral spin orders. (United States)

    Tokura, Yoshinori; Seki, Shinichiro


    Cross correlation between magnetism and electricity in a solid can host magnetoelectric effects, such as magnetic (electric) induction of polarization (magnetization). A key to attain the gigantic magnetoelectric response is to find the efficient magnetism-electricity coupling mechanisms. Among those, recently the emergence of spontaneous (ferroelectric) polarization in the insulating helimagnet or spiral-spin structure was unraveled, as mediated by the spin-exchange and spin-orbit interactions. The sign of the polarization depends on the helicity (spin rotation sense), while the polarization direction itself depends on further details of the mechanism and the underlying lattice symmetry. Here, we describe some prototypical examples of the spiral-spin multiferroics, which enable some unconventional magnetoelectric control such as the magnetic-field-induced change of the polarization direction and magnitude as well as the electric-field-induced change of the spin helicity and magnetic domain.

  1. Vaporization of Kitaev spin liquids. (United States)

    Nasu, Joji; Udagawa, Masafumi; Motome, Yukitoshi


    The quantum spin liquid is an exotic quantum state of matter in magnets. This state is a spin analog of liquid helium that does not solidify down to the lowest temperature due to strong quantum fluctuations. In conventional fluids, the liquid and gas possess the same symmetry and adiabatically connect to each other by bypassing the critical end point. We find that the situation is qualitatively different in quantum spin liquids realized in a three-dimensional Kitaev model; both gapless and gapped quantum spin liquid phases at low temperatures are always distinguished from the high-temperature paramagnet (spin gas) by a phase transition. The results challenge the common belief that the absence of thermodynamic singularity down to the lowest temperature is a symptom of a quantum spin liquid.

  2. Spin liquids in frustrated magnets. (United States)

    Balents, Leon


    Frustrated magnets are materials in which localized magnetic moments, or spins, interact through competing exchange interactions that cannot be simultaneously satisfied, giving rise to a large degeneracy of the system ground state. Under certain conditions, this can lead to the formation of fluid-like states of matter, so-called spin liquids, in which the constituent spins are highly correlated but still fluctuate strongly down to a temperature of absolute zero. The fluctuations of the spins in a spin liquid can be classical or quantum and show remarkable collective phenomena such as emergent gauge fields and fractional particle excitations. This exotic behaviour is now being uncovered in the laboratory, providing insight into the properties of spin liquids and challenges to the theoretical description of these materials.

  3. Misjudging frustrations in spin liquids from oversimplified use of Curie-Weiss law

    Energy Technology Data Exchange (ETDEWEB)

    Nag, Abhishek, E-mail: [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Ray, Sugata [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)


    Absence of a single smoking-gun experiment to identify a quantum spin liquid, has kept their characterisation difficult till date. Featureless dc magnetic susceptibility and large antiferromagnetic frustration are always considered as the essential pointers to these systems. However, we show that the amount of frustration estimated by using generalised Curie-Weiss law on these susceptibility data are prone to errors and thus should be dealt with caution. We measure and analyse susceptibility data of Ba{sub 3}ZnIr{sub 2}O{sub 9}, a spin orbital liquid candidate and Gd{sub 2}O{sub 3}, a 1.5 K antiferromagnet and show the distinguishing features between them. A continuous and significant change in Curie and Weiss constants is seen to take place in Ba{sub 3}ZnIr{sub 2}O{sub 9} and other reported spin liquids with the change in the range of fitting temperatures showing the need of a temperature ‘range-of-fit’ analysis before commenting on the Weiss constants of spin liquids. The variation observed is similar to fluctuations among topological sectors persisting over a range of temperature in spin-ice candidates. On the other hand, even though we find correlations to exist at even 100 times the ordering temperature in Gd{sub 2}O{sub 3}, no such fluctuation is observed which may be used as an additional distinguishing signature of spin liquids over similarly featureless correlated paramagnets. - Highlights: • Curie-Weiss fitting may give erroneous frustration parameters in spin-liquids. • The results depend upon choice of fitting method and temperature range used. • More appropriate method is to use a ʽrange of fit’ analysis. • Can distinguish between spin-liquids and correlated paramagnets.

  4. Direct measurement of the low-temperature spin-state transition in LaCoO3. (United States)

    Klie, R F; Zheng, J C; Zhu, Y; Varela, M; Wu, J; Leighton, C


    LaCoO3 exhibits an anomaly in its magnetic susceptibility around 80 K associated with a thermally excited transition of the Co3+-ion spin. We show that electron energy-loss spectroscopy is sensitive to this Co3+-ion spin-state transition, and that the O K edge prepeak provides a direct measure of the Co3+ spin state in LaCoO3 as a function of temperature. Our experimental results are confirmed by first-principles calculations, and we conclude that the thermally excited spin-state transition occurs from a low to an intermediate spin state, which can be distinguished from the high-spin state.

  5. Observation of the spin Nernst effect (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.


    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.

  6. Spin currents in metallic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Czeschka, Franz Dominik


    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.)

  7. Two magnetic orderings and a spin-flop transition in spin-1 system SrNi2(PO4)2 (United States)

    He, Zhangzhen; Chen, S. C.; Lue, C. S.; Cheng, Wendan; Ueda, Yutaka


    Magnetic properties of SrNi2(PO4)2 are investigated by means of susceptibility, magnetization, heat-capacity, and P31 NMR measurements. Our experimental results show that SrNi2(PO4)2 is a three-dimensional antiferromagnet with two magnetic orderings at ˜23 and ˜10K . It is suggested that canted antiferromagnetic ordering at ˜23K may correspond to a Néel noncollinear spin arrangements of Ni2+ ions, and such noncollinear spin arrangements further induce spin rotations into a steady collinear antiferromagnetic phase below ˜10K with decreasing temperature. Also, spin-flop transition is observed at a critical field below ˜10K , showing magnetic anisotropy in the system.

  8. Spin-photon entangling diode

    DEFF Research Database (Denmark)

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


    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....

  9. Towards spin injection into silicon

    Energy Technology Data Exchange (ETDEWEB)

    Dash, S.P.


    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.)

  10. Spin superconductor in ferromagnetic graphene


    Sun, Qing-feng; Jiang, Zhao-tan; Yu, Yue; Xie, X. C.


    We show a spin superconductor (SSC) in ferromagnetic graphene as the counterpart to the charge superconductor, in which a spin-polarized electron-hole pair plays the role of the spin $2 (\\hbar/2)$ `Cooper pair' with a neutral charge. We present a BCS-type theory for the SSC. With the `London-type equations' of the super-spin-current density, we show the existence of an electric `Meissner effect' against a spatial varying electric field. We further study a SSC/normal conductor/SSC junction and...

  11. Spinning particles coupled to gravity

    CERN Document Server

    Hojman, Sergio A


    Recent experimental work has determined that free falling $^{87}$Rb atoms on Earth, with vertically aligned spins, follow geodesics, thus apparently ruling out spin--gravitation interactions. It is showed that while some spinning matter models coupled to gravitation referenced to in that work seem to be ruled out by the experiment, those same experimental results confirm theoretical results derived from a Lagrangian description of spinning particles coupled to gravity constructed over forty years ago. A proposal to carry out (similar but) different experiments which will help to test the validity of the Universality of Free Fall as opposed to the correctness of the aforementioned Lagrangian theory, is presented.

  12. Detecting phase transitions and crossovers in Hubbard models using the fidelity susceptibility

    CERN Document Server

    Huang, Li; Wang, Lei; Werner, Philipp


    A generalized version of the fidelity susceptibility of single-band and multi-orbital Hubbard models is systematically studied using single-site dynamical mean-field theory in combination with a hybridization expansion continuous-time quantum Monte Carlo impurity solver. We find that the fidelity susceptibility is extremely sensitive to changes in the state of the system. It can be used as a numerically inexpensive tool to detect and characterize a broad range of phase transitions and crossovers in Hubbard models, including (orbital-selective) Mott metal-insulator transitions, high-spin to low-spin transitions, Fermi-liquid to non-Fermi-liquid crossovers, and spin-freezing crossovers.

  13. Elements of spin motion (United States)

    Fukushima, Toshio; Ishizaki, Hideharu


    For use in numerical studies of rotational motion, a set of elements is introduced for the torque-free rotational motion of a rigid body around its barycenter. The elements are defined as the initial values of a modification of the Andoyer canonical variables. A computational procedure is obtained for determining these elements from the combination of the spin angular momentum vector and a triad defining the orientation of the rigid body. A numerical experiment shows that the errors of transformation between the elements and variables are sufficiently small. The errors increase linearly with time for some elements and quadratically for some others.

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

    KAUST Repository

    Lee, Ki-Seung


    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.

  15. Designing Electron Spin Textures and Spin Interferometers by Shape Deformations

    NARCIS (Netherlands)

    Ying, Zu-Jian; Gentile, Paola; Ortix, Carmine; Cuoco, Mario


    We demonstrate that the spin orientation of an electron propagating in a one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be manipulated on demand by changing the geometry of the nanosystem. Shape deformations that result in a non-uniform curvature give rise to complex

  16. Robust spin current generated by the spin Seebeck effect (United States)

    Chang, Feng-Jen; Lin, Jauyn Grace; Huang, Ssu-Yen


    Spin pumping (SP) and the spin Seebeck effect (SSE), two of the most common methods for generating a pure spin current from ferromagnetic insulators, are considered to share similar physical mechanisms. However, a systematic study of the fundamental difference of their working principle is missing. In this Rapid Communication, we present experimental evidence of the contrast in a pure spin current generated by SP and SSE, based on results from yttrium iron garnet (YIG) with various crystalline properties. It is shown that while the SP-induced spin current could be two-orders-of-magnitude different between the polycrystalline and epitaxial films, the SSE-excited spin current is surprisingly insensitive to the different crystal structures. Our results clearly distinguish the coherent mechanism of SP from the noncoherent mechanism of the SSE. Consequently, the robust SSE voltage against poor crystallinity proves that the SSE is a powerful tool to explore pure spin current physics, and suggests that polycrystalline YIG films are a promising candidate for spin caloritronic applications.

  17. Bias-dependent spin relaxation in a Spin-LED

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, C.A. C. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands)]. E-mail:; Snouck, D. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Van Dorpe, P. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Van Roy, W. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Koopmans, B. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands)


    We have investigated the bias-dependent spin relaxation in Cu-CoFe-AlO{sub x}-GaAs/AlGaAs-type of Spin-LEDs using microscopic time-resolved magnetization modulation spectroscopy (TIMMS). We observed a significant dependence of the electron spin relaxation time (effects as large as 40%) as a function of applied bias. The additional spin relaxation at non-zero bias is found to scale almost linearly with the injection current, and thereby with the current-induced hole density in the active region. This observation is indicative for a dominant contribution by Bir-Aronov-Pikus (BAP) electron-hole spin-flip scattering. In agreement with this observation, a similar BAP-enhanced spin relaxation shows up at increased laser fluence. From spatio-temporal imaging of spin relaxation, scanning pump and probe beams across the {approx}50{mu} m outside of optical window, we found a significant position dependence (lateral effects) of the spin dynamics.

  18. Spin-liquid Mott quantum criticality in two dimensions: Destabilization of a spinon Fermi surface and emergence of one-dimensional spin dynamics (United States)

    Han, Jae-Ho; Cho, Yong-Heum; Kim, Ki-Seok


    Resorting to a recently developed theoretical device called dimensional regularization for quantum criticality with a Fermi surface, we examine a metal-insulator quantum phase transition from a Landau's Fermi-liquid state to a U(1) spin-liquid phase with a spinon Fermi surface in two dimensions. Unfortunately, we fail to approach the spin-liquid Mott quantum critical point from the U(1) spin-liquid state within the dimensional regularization technique. Self-interactions between charge fluctuations called holons are not screened, which shows a run-away renormalization group flow, interpreted as holons remain gapped. This leads us to consider another fixed point, where the spinon Fermi surface can be destabilized across the Mott transition. Based on this conjecture, we reveal the nature of the spin-liquid Mott quantum critical point: Dimensional reduction to one dimension occurs for spin dynamics described by spinons. As a result, Landau damping for both spin and charge dynamics disappear in the vicinity of the Mott quantum critical point. When the flavor number of holons is over its critical value, an interacting fixed point appears to be identified with an inverted X Y universality class, controlled within the dimensional regularization technique. On the other hand, a fluctuation-driven first order metal-insulator transition results when it is below the critical number. We propose that the destabilization of a spinon Fermi surface and the emergence of one-dimensional spin dynamics near the spin-liquid Mott quantum critical point can be checked out by spin susceptibility with a 2 kF transfer momentum, where kF is a Fermi momentum in the U(1) spin-liquid state: The absence of Landau damping in U(1) gauge fluctuations gives rise to a divergent behavior at zero temperature while it vanishes in the presence of a spinon Fermi surface.

  19. Spin-spin correlation functions of the q-VBS state of an integer spin model


    Arita, Chikashi; Motegi, Kohei


    We consider the valence-bond-solid ground state of the q-deformed higher-spin AKLT model (q-VBS state). We investigate the eigenvalues and eigenvectors of a matrix (G matrix), which is constructed from the matrix product representation of the q-VBS state. We compute the longitudinal and transverse spin-spin correlation functions, and determine the correlation amplitudes and correlation lengths for real q.

  20. Correlation and disorder-enhanced nematic spin response in superconductors with weakly broken rotational symmetry

    DEFF Research Database (Denmark)

    Andersen, Brian Møller; Graser, S.; Hirschfeld, P. J.


    Recent experimental and theoretical studies have highlighted the possible role of an electronic nematic liquid in underdoped cuprate superconductors. We calculate, within a model of d-wave superconductor with Hubbard correlations, the spin susceptibility in the case of a small explicitly broken...

  1. Spin wave collapse and incommensurate fluctuations in URu2Si2

    DEFF Research Database (Denmark)

    Buyers, W.J.L.; Tun, Z.; Petersen, T.


    To test if the T(N) = 17.7 K transition in URu2Si2 is driven by a divergence of a magnetic order parameter we performed high-resolution neutron scattering. At the ordering wave vector the spin-wave energy collapsed. and the susceptibility diverged as T(N) was approached. This confirms...

  2. Topological Invariant and Quantum Spin Models from Magnetic π Fluxes in Correlated Topological Insulators

    Directory of Open Access Journals (Sweden)

    F. F. Assaad


    Full Text Available The adiabatic insertion of a π flux into a quantum spin Hall insulator gives rise to localized spin and charge fluxon states. We demonstrate that π fluxes can be used in exact quantum Monte Carlo simulations to identify a correlated Z_{2} topological insulator using the example of the Kane-Mele-Hubbard model. In the presence of repulsive interactions, a π flux gives rise to a Kramers doublet of spin-fluxon states with a Curie-law signature in the magnetic susceptibility. Electronic correlations also provide a bosonic mode of magnetic excitons with tunable energy that act as exchange particles and mediate a dynamical interaction of adjustable range and strength between spin fluxons. π fluxes can therefore be used to build models of interacting spins. This idea is applied to a three-spin ring and to one-dimensional spin chains. Because of the freedom to create almost arbitrary spin lattices, correlated topological insulators with π fluxes represent a novel kind of quantum simulator, potentially useful for numerical simulations and experiments.

  3. Spin caloritronics, origin and outlook

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haiming, E-mail: [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: [Institute of Physics, station 3, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne-EPFL (Switzerland)


    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

  4. Spin independent magnetoresistance effects in vertical graphene spin valves (United States)

    Bodepudi, Srikrishna; Pratap Singh, Abhay; Pramanik, Sandipan


    Vertical spin valve device configuration with multilayer graphene (MLG) as spacer has drawn significant attention in recent years because of its potential to produce large magnetoresistance (MR) effect due to perfect spin filtering. However, demonstration of this effect has remained elusive so far. Here we consider MLG vertical spin valve structures and show that they exhibit spin independent MR effects, which are orders of magnitude stronger than the spin dependent effects reported to date. These effects manifest within a moderate field range of 10 kG and depend on various factors such as hybridization near the top graphene surface, doping, defects and interlayer coupling. These effects highlight the rich spectrum of physical phenomena that manifest in such systems, which could be exploited in low to moderate magnetic field sensing applications.

  5. Synthesis of Nanocrystals and Particle Size Effects Studies on the Thermally Induced Spin Transition of the Model Spin Crossover Compound [Fe(phen)2(NCS)2]. (United States)

    Valverde-Muñoz, Francisco Javier; Gaspar, Ana B; Shylin, Sergii I; Ksenofontov, Vadim; Real, José A


    Surfactant-free nanocrystals of the model spin-crossover compound [Fe(phen)2(NCS)2] (phen: 1,10-phenanthroline) have been synthesized applying the reverse micelle technique. The morphology of the nanocrystals, characterized by scanning electronic microscopy, corresponds to rhombohedric platelets with dimensions ranging from 203 × 203 × 106 nm to 142 × 142 × 74 nm. Variation of the concentration of the Fe(BF4)2·6H2O salt in the synthesis has been found to have little influence on the crystallite size. In contrast, the solvent-surfactant ratio (ω) is critical for a good particle growth. The spin transition of the nanocrystals has been characterized by magnetic susceptibility measurements and Mössbauer spectroscopy. The nanocrystals undergo an abrupt and more cooperative spin transition in comparison with the bulk compound. The spin transition is centered in the interval of temperature of 175-185 K and is accompanied by 8 K of thermal hysteresis width. The crystallite quality more than the crystallite size is responsible for the higher cooperativity. The magnetic properties of the nanocrystals embedded in organic polymers such as polyethylene glycol, nujol, glycerol, and triton have been studied as well. The spin transition in the nanocrystals is affected by the polymer coating. The abrupt and first-order spin transition transforms into a more continuous spin transition as a result of the chemical pressure asserted by the organic polymers on the Fe(II) centers.

  6. Electron-spin resonance, nuclear polarization, and spin relaxation of spin-polarized atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Statt, B.W.; Berlinsky, A.J.; Hardy, W.N.


    Electron-spin-resonance measurements of spin-polarized hydrogen are presented. Excellent signal-to-noise ratio, previously obtainable only in pressure studies, allows quantitative fits to the separate a and b (proton up and down) decays of the nuclear-spin-polarized samples, yielding separate temperature dependences of the recombination rate constants K/sub a/a and K/sub a/b. Spin relaxation due to magnetic particles in the substrate is studied for different thicknesses of solid H/sub 2/ wall coating, and the results are compared with a new theoretical model.

  7. Magnetic susceptibilities of minerals (United States)

    Rosenblum, Sam; Brownfield, I.K.


    Magnetic separation of minerals is a topic that is seldom reported in the literature for two reasons. First, separation data generally are byproducts of other projects; and second, this study requires a large amount of patience and is unusually tedious. Indeed, we suspect that most minerals probably are never investigated for this property. These data are timesaving for mineralogists who concentrate mono-mineralic fractions for chemical analysis, age dating, and for other purposes. The data can certainly be used in the ore-beneficiation industries. In some instances, magnetic-susceptibility data may help in mineral identification, where other information is insufficient. In past studies of magnetic separation of minerals, (Gaudin and Spedden, 1943; Tille and Kirkpatrick, 1956; Rosenblum, 1958; Rubinstein and others, 1958; Flinter, 1959; Hess, 1959; Baker, 1962; Meric and Peyre, 1963; Rojas and others, 1965; and Duchesne, 1966), the emphasis has been on the ferromagnetic and paramagnetic ranges of extraction. For readers interested in the history of magnetic separation of minerals, Krumbein and Pettijohn (1938, p. 344-346) indicated nine references back to 1848. The primary purpose of this paper is to report the magnetic-susceptibility data on as many minerals as possible, similar to tables of hardness, specific gravity, refractive indices, and other basic physical properties of minerals. A secondary purpose is to demonstrate that the total and best extraction ranges are influenced by the chemistry of the minerals. The following notes are offered to help avoid problems in separating a desired mineral concentrate from mixtures of mineral grains.

  8. Alcohol increases hypnotic susceptibility. (United States)

    Semmens-Wheeler, Rebecca; Dienes, Zoltán; Duka, Theodora


    One approach to hypnosis suggests that for hypnotic experience to occur frontal lobe activity must be attenuated. For example, cold control theory posits that a lack of awareness of intentions is responsible for the experience of involuntariness and/or the subjective reality of hypnotic suggestions. The mid-dorso-lateral prefrontal cortex and the ACC are candidate regions for such awareness. Alcohol impairs frontal lobe executive function. This study examined whether alcohol affects hypnotisability. We administered 0.8 mg/kg of alcohol or a placebo to 32 medium susceptible participants. They were subsequently hypnotised and given hypnotic suggestions. All participants believed they had received some alcohol. Participants in the alcohol condition were more susceptible to hypnotic suggestions than participants in the placebo condition. Impaired frontal lobe activity facilitates hypnotic responding, which supports theories postulating that attenuation of executive function facilitates hypnotic response, and contradicts theories postulating that hypnotic response involves enhanced inhibitory, attentional or other executive function. Copyright © 2013. Published by Elsevier Inc.

  9. Measurements of the magnetic susceptibility and anisotropy of Tb{sub 2}Ge{sub 2}O{sub 7} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Jana, Y.M.; Ghosh, M.; Ghosh, D. E-mail:; Wanklyn, B.M


    Magnetic susceptibilities {chi}{sub a} and the anisotropy {chi}{sub a}-{chi}{sub c}={delta}{chi} in the ac-plane of the tetragonal crystal of Tb{sub 2}Ge{sub 2}O{sub 7} or TbPG were measured between 300 and 23 K. The crystal field (CF) at the site of the Tb{sup 3+} ion has a unique D{sub 5h} symmetry and the D{sub 5h} axis coincides with the c-axis of the tetragonal (D{sup 4}{sub 4}) crystal, which permitted easy determination of the thermal characteristics of molecular susceptibilities K{sub parallel}, K{sub perpendicular}, K-bar and the anisotropy {delta}K=K{sub perpendicular}-K{sub parallel}. It was found that at 300 K, {delta}K was 31.3% of K-bar and increased by 34.5 times at 23 K, becoming 107% of K-bar, suggesting strong CF effect in TbPG. For analysing these results and the optical spectra reported earlier, the total Hamiltonian, consisting of the atomic and CF interactions, was diagonalized considering 66 intermediately coupled (IC) basis states of the 4f{sup 8} ground configuration of Tb{sup 3+} in the PG host, allowing J-mixing between the IC states. The best-fitted values of the atomic and CF parameters were E{sup 1}=6030, E{sup 2}=35, E{sup 3}=605, {xi}{sub so}=1749, {alpha}=18, {beta}=-673, {gamma}=1918, B{sub 20}=470, B{sub 40}=571, B{sub 60}=2500, B{sub 65}=915 (all in cm{sup -1}). The lowest CF level was found to be a singlet followed by a doublet at 19.5 cm{sup -1} above and the total CF splitting of the {sup 7}F{sub 6} ground term was 280 cm{sup -1}. The calculated value of the nuclear quadrupole splitting <{delta}E{sub Q}> of the ground nuclear level of {sup 159}Tb in TbPG changed from 3.186x10{sup -4} cm{sup -1} (=0.204 mm/s) to 89.65x10{sup -4} cm{sup -1} between 300 and 2 K. The Schottky specific heat C{sub sh} showed a maximum at 26 K and a hump is expected around 14 K in the C{sub p} versus T curve, calculated by substituting the value of the lattice component C{sub L}/R=3.2{+-}0.2 T{sup 3}x10{sup -5} of GdPG.

  10. Extremal Higher Spin Black Holes

    NARCIS (Netherlands)

    Bañados, M.; Castro, A.; Faraggi, A.; Jottar, J.I.

    The gauge sector of three-dimensional higher spin gravities can be formulated as a Chern-Simons theory. In this context, a higher spin black hole corresponds to a flat connection with suitable holonomy (smoothness) conditions which are consistent with the properties of a generalized thermal

  11. Decoherence in quantum spin systems

    NARCIS (Netherlands)

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


    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

  12. Hybrid spin-crossover nanostructures. (United States)

    Quintero, Carlos M; Félix, Gautier; Suleimanov, Iurii; Sánchez Costa, José; Molnár, Gábor; Salmon, Lionel; Nicolazzi, William; Bousseksou, Azzedine


    This review reports on the recent progress in the synthesis, modelling and application of hybrid spin-crossover materials, including core-shell nanoparticles and multilayer thin films or nanopatterns. These systems combine, often in synergy, different physical properties (optical, magnetic, mechanical and electrical) of their constituents with the switching properties of spin-crossover complexes, providing access to materials with unprecedented capabilities.

  13. Hybrid spin-crossover nanostructures


    Quintero, Carlos M; Gautier Félix; Iurii Suleimanov; José Sánchez Costa; Gábor Molnár; Lionel Salmon; William Nicolazzi; Azzedine Bousseksou


    Summary This review reports on the recent progress in the synthesis, modelling and application of hybrid spin-crossover materials, including core?shell nanoparticles and multilayer thin films or nanopatterns. These systems combine, often in synergy, different physical properties (optical, magnetic, mechanical and electrical) of their constituents with the switching properties of spin-crossover complexes, providing access to materials with unprecedented capabilities.

  14. Black Hole Spin Measurement Uncertainty (United States)

    Salvesen, Greg; Begelman, Mitchell C.


    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.

  15. The spin-valve transistor

    NARCIS (Netherlands)

    Anil Kumar, P.S.; Lodder, J.C.


    The spin-valve transistor is a magnetoelectronic device that can be used as a magnetic field sensor. It has a ferromagnet-semiconductor hybrid structure. Using a vacuum metal bonding technique, the spin-valve transistor structure Si/Pt/NiFe/Au/Co/Au/Si is obtained. It employs hot electron transport

  16. Spin conversion on the nanoscale (United States)

    Otani, Yoshichika; Shiraishi, Masashi; Oiwa, Akira; Saitoh, Eiji; Murakami, Shuichi


    Spins can act as mediators to interconvert electricity, light, sound, vibration and heat. Here, we give an overview of the recent advances in different sub-disciplines of spintronics that can be associated with the developing field of spin conversion, and discuss future prospects.

  17. Nuclear Spins in Quantum Dots

    NARCIS (Netherlands)

    Erlingsson, S.I.


    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,

  18. Josephson spin current in triplet superconductor junctions


    Asano, Yasuhiro


    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.

  19. Disorder and Quantum Spin Ice

    Directory of Open Access Journals (Sweden)

    N. Martin


    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.

  20. Disorder and Quantum Spin Ice (United States)

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


    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.

  1. Spin Foams and Canonical Quantization

    Directory of Open Access Journals (Sweden)

    Sergei Alexandrov


    Full Text Available This review is devoted to the analysis of the mutual consistency of the spin foam and canonical loop quantizations in three and four spacetime dimensions. In the three-dimensional context, where the two approaches are in good agreement, we show how the canonical quantization à la Witten of Riemannian gravity with a positive cosmological constant is related to the Turaev-Viro spin foam model, and how the Ponzano-Regge amplitudes are related to the physical scalar product of Riemannian loop quantum gravity without cosmological constant. In the four-dimensional case, we recall a Lorentz-covariant formulation of loop quantum gravity using projected spin networks, compare it with the new spin foam models, and identify interesting relations and their pitfalls. Finally, we discuss the properties which a spin foam model is expected to possess in order to be consistent with the canonical quantization, and suggest a new model illustrating these results.

  2. Spin Hanle effect in mesoscopic superconductors (United States)

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


    We present a theoretical study of spin transport in a superconducting mesoscopic spin valve under the action of a magnetic field misaligned with respect to the injected spin. We demonstrate that superconductivity can either strongly enhance or suppress the coherent spin rotation, depending on the type of spin relaxation mechanism being dominated either by spin-orbit coupling or spin-flip scattering at impurities. We also predict a subgap contribution to the nonlocal conductance in multiterminal superconducting hybrid structures which completely eliminates the effect of spin rotation at sufficiently low temperatures.

  3. Theory of the spin Seebeck effect. (United States)

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


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

  4. Graphene susceptibility in Holstein model

    Energy Technology Data Exchange (ETDEWEB)

    Mousavi, Hamze, E-mail: [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Nano Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of)


    We study the effects of the electron-phonon interaction on the temperature dependence of the orbital magnetic susceptibility of monolayer graphene. We use the linear response theory and Green's function formalism within the Holstein Hamiltonian model. The results show that the effects of the electron-phonon interaction on the susceptibility of graphene sheet have different behaviors in two temperature regions. In the low temperature region, susceptibility increases when the electron-phonon coupling strength increases. On the other hand, the susceptibility reduces with increasing the electron-phonon coupling strength in the high temperature region. - Highlights: Effect of electron-phonon interaction on the susceptibility of graphene is studied. Linear response theory and Green's function technique in Holstein model are used. Effect of electron-phonon on susceptibility has different behaviors in two temperature regions.

  5. Topological susceptibility from slabs

    Energy Technology Data Exchange (ETDEWEB)

    Bietenholz, Wolfgang [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A.P. 70-543, Distrito Federal, C.P. 04510 (Mexico); Forcrand, Philippe de [Institute for Theoretical Physics, ETH Zürich,CH-8093 Zürich (Switzerland); CERN, Physics Department, TH Unit, CH-1211 Geneva 23 (Switzerland); Gerber, Urs [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A.P. 70-543, Distrito Federal, C.P. 04510 (Mexico); Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo,Edificio C-3, Apdo. Postal 2-82, Morelia, Michoacán, C.P. 58040 (Mexico)


    In quantum field theories with topological sectors, a non-perturbative quantity of interest is the topological susceptibility χ{sub t}. In principle it seems straightforward to measure χ{sub t} by means of Monte Carlo simulations. However, for local update algorithms and fine lattice spacings, this tends to be difficult, since the Monte Carlo history rarely changes the topological sector. Here we test a method to measure χ{sub t} even if data from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as slabs. Assuming a Gaussian distribution of these charges, this method enables the evaluation of χ{sub t}, as we demonstrate with numerical results for non-linear σ-models.

  6. Topological Susceptibility from Slabs

    CERN Document Server

    Bietenholz, Wolfgang; Gerber, Urs


    In quantum field theories with topological sectors, a non-perturbative quantity of interest is the topological susceptibility chi_t. In principle it seems straightforward to measure chi_t by means of Monte Carlo simulations. However, for local update algorithms and fine lattice spacings, this tends to be difficult, since the Monte Carlo history rarely changes the topological sector. Here we test a method to measure chi_t even if data from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as slabs. Assuming a Gaussian distribution of these charges, this method enables the evaluation of chi_t, as we demonstrate with numerical results for non-linear sigma-models.

  7. Spin flexoelectricity and chiral spin structures in magnetic films

    Energy Technology Data Exchange (ETDEWEB)

    Pyatakov, A.P., E-mail: [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)


    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.

  8. Quantum Spin Liquids in Frustrated Spin-1 Diamond Antiferromagnets (United States)

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


    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.

  9. Proximal Bright Vessel Sign on Arterial Spin Labeling Magnetic Resonance Imaging in Acute Cardioembolic Cerebral Infarction. (United States)

    Kato, Ayumi; Shinohara, Yuki; Kuya, Keita; Sakamoto, Makoto; Kowa, Hisanori; Ogawa, Toshihide


    The congestion of spin-labeled blood at large-vessel occlusion can present as hyperintense signals on perfusion magnetic resonance imaging with 3-dimensional pseudo-continuous arterial spin labeling (proximal bright vessel sign). The purpose of this study was to clarify the difference between proximal bright vessel sign and susceptibility vessel sign in acute cardioembolic cerebral infarction. Forty-two patients with cardioembolic cerebral infarction in the anterior circulation territory underwent magnetic resonance imaging including diffusion-weighted imaging, 3-dimensional pseudo-continuous arterial spin labeling perfusion magnetic resonance imaging, T2*-weighted imaging, and 3-dimensional time-of-flight magnetic resonance angiography using a 3-T magnetic resonance scanner. Visual assessments of proximal bright vessel sign and the susceptibility vessel sign were performed by consensus of 2 experienced neuroradiologists. The relationship between these signs and the occlusion site of magnetic resonance angiography was also investigated. Among 42 patients with cardioembolic cerebral infarction, 24 patients showed proximal bright vessel sign (57.1%) and 25 showed susceptibility vessel sign (59.5%). There were 19 cases of proximal bright vessel sign and susceptibility vessel sign-clear, 12 cases of proximal bright vessel sign and susceptibility vessel sign-unclear, and 11 mismatched cases. Four out of 6 patients with proximal bright vessel sign-unclear and susceptibility vessel sign-clear showed distal middle cerebral artery occlusion, and 2 out of 5 patients with proximal bright vessel sign-clear and susceptibility vessel sign-unclear showed no occlusion on magnetic resonance angiography. Proximal bright vessel sign is almost compatible with susceptibility vessel sign in patients with cardioembolic cerebral infarction. Copyright © 2017 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  10. Spin Orbit Interaction Engineering for beyond Spin Transfer Torque memory (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.

  11. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev


    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.

  12. Superconductivity and spin excitations in orbitally ordered FeSe

    Energy Technology Data Exchange (ETDEWEB)

    Kreisel, Andreas; Andersen, Brian M. [Niels Bohr Institute, University of Copenhagen (Denmark); Mukherjee, Shantanu [Niels Bohr Institute, University of Copenhagen (Denmark); Dept. of Physics, State University of New York at Binghamton, Binghamton, NY (United States); Hirschfeld, Peter J. [University of Florida, Gainesville, FL (United States)


    We provide a band-structure with low-energy properties consistent with recent photoemission and quantum oscillations measurements on the Fe-based superconductor FeSe, including a mean-field like orbital ordering in the d{sub xz}/d{sub yz} channel, and show that this model also accounts for the temperature dependence of the measured Knight shift and the spin-relaxation rate. An RPA calculation of the dynamical spin susceptibility yields spin excitations which are peaked at wave vector (π,0) in the 1-Fe Brillouin zone, with a broad maximum at energies of order a few meV. Furthermore, the superconducting gap structure obtained from spin fluctuation theory exhibits nodes on the electron pockets, consistent with the 'V'-shaped density of states measured by tunneling spectroscopy on this material. The redistribution of spectral weight in the superconducting state creates a (π,0) ''neutron resonance'' as seen in recent experiments. Comparing to various experimental results, we give predictions for further studies.

  13. Superconductivity and spin excitations in orbitally ordered FeSe (United States)

    Kreisel, Andreas; Mukherjee, Shantanu; Hirschfeld, P. J.; Andersen, B. M.

    We provide a band-structure with low-energy properties consistent with recent photoemission and quantum oscillations measurements on the Fe-based superconductor FeSe, including a mean-field like orbital ordering in the dxz /dyz channel, and show that this model also accounts for the temperature dependence of the measured Knight shift and the spin-relaxation rate. An RPA calculation of the dynamical spin susceptibility yields spin excitations which are peaked at wave vector (π , 0) in the 1-Fe Brillouin zone, with a broad maximum at energies of order a few meV. Furthermore, the superconducting gap structure obtained from spin fluctuation theory exhibits nodes on the electron pockets, consistent with the 'V'-shaped density of states measured by tunneling spectroscopy on this material. The redistribution of spectral weight in the superconducting state creates a (π , 0) ''neutron resonance'' as seen in recent experiments. Comparing to various experimental results, we give predictions for further studies A.K. and B.M.A. acknowledge financial support from a Lundbeckfond fellowship (Grant No. A9318). P.J.H. was partially supported by the Department of Energy under Grant No. DE-FG02-05ER46236.

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

    Directory of Open Access Journals (Sweden)

    Mathieu Taillefumier


    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.

  15. Spin Splitting and Spin Current in Strained Bulk Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.


    We present a theory for two recent experiments in bulk strained semiconductors and show that a new, previously overlooked, strain spin-orbit coupling term may play a fundamental role. We propose simple experiments that could clarify the origin of strain-induced spin-orbit coupling terms in inversion asymmetric semiconductors. We predict that a uniform magnetization parallel to the electric field will be induced in the samples studied in for specific directions of the applied electric field. We also propose special geometries to detect spin currents in strained semiconductors.

  16. Crossbreeding between experiment and theory on orthogonal dimer spin system

    Energy Technology Data Exchange (ETDEWEB)

    Kageyama, Hiroshi; Ueda, Yutaka [Tokyo Univ., Inst. for Solid State Physics, Material Design and Characterization Laboratory, Kashiwa, Chiba (Japan); Narumi, Yasuo; Kindo, Koichi [Osaka Univ., Research Center for Materials Science at Extreme Conditions, Toyonaka, Osaka (Japan); Kosaka, Masashi; Uwatoko, Yoshiya [Saitama Univ., Dept. of Physics, Saitama (Japan)


    We have investigated two-dimensional spin systems SrCu{sub 2}(BO{sub 3}){sub 2} and Nd{sub 2}BaZnO{sub 5}, both of which have a unique topology that is equivalent to the Shastry-Sutherland lattice. The magnetization curve of SrCu{sub 2} (BO{sub 3}){sub 2} reveals that, unlike 1/8 and 1/4 plateaux, a 1/3 plateau is very stable, surviving at least up to 69T. The pressure dependence of susceptibility up to 10 kbar indicates that the pressure causes the system to approach the critical point to some other states. On the other hand, Nd{sub 2}BaZnO{sub 5} with rather classical spins exhibits an antiferromagnetic long range ordering at 2.4 K. Finally, other experimental candidates of extended Shastry-Sutherland system will be briefly presented. (author)

  17. Visualization of spin dynamics in single nanosized magnetic elements

    Energy Technology Data Exchange (ETDEWEB)

    Banholzer, A; Hassel, C; Meckenstock, R; Stienen, S; Posth, O; Farle, M; Lindner, J [Faculty of Physics and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, D-47048 Duisburg (Germany); Narkowicz, R; Suter, D, E-mail: [Department of Physics, Technical University of Dortmund, D-44221 Dortmund (Germany)


    The design of future spintronic devices requires a quantitative understanding of the microscopic linear and nonlinear spin relaxation processes governing the magnetization reversal in nanometer-scale ferromagnetic systems. Ferromagnetic resonance is the method of choice for a quantitative analysis of relaxation rates, magnetic anisotropy and susceptibility in a single experiment. The approach offers the possibility of coherent control and manipulation of nanoscaled structures by microwave irradiation. Here, we analyze the different excitation modes in a single nanometer-sized ferromagnetic stripe. Measurements are performed using a microresonator set-up which offers a sensitivity to quantitatively analyze the dynamic and static magnetic properties of single nanomagnets with volumes of (100 nm){sup 3}. Uniform as well as non-uniform volume modes of the spin wave excitation spectrum are identified and found to be in excellent agreement with the results of micromagnetic simulations which allow the visualization of the spatial distribution of these modes in the nanostructures.

  18. Critical behavior of dissipative two-dimensional spin lattices (United States)

    Rota, R.; Storme, F.; Bartolo, N.; Fazio, R.; Ciuti, C.


    We explore critical properties of two-dimensional lattices of spins interacting via an anisotropic Heisenberg Hamiltonian that are subject to incoherent spin flips. We determine the steady-state solution of the master equation for the density matrix via the corner-space renormalization method. We investigate the finite-size scaling and critical exponent of the magnetic linear susceptibility associated with a dissipative ferromagnetic transition. We show that the von Neumann entropy increases across the critical point, revealing a strongly mixed character of the ferromagnetic phase. Entanglement is witnessed by the quantum Fisher information, which exhibits a critical behavior at the transition point, showing that quantum correlations play a crucial role in the transition.

  19. Dynamic specific heat of frustrated Ising spin rings

    CERN Document Server

    Ismail, G


    The dynamic specific heat C(omega) is calculated exactly for rings of six coupled Ising spins within Glauber dynamics. We used the response of the internal energy to small temperature oscillations to find C(omega). The spin glass (SG) and disordered ferromagnetic (DFM) rings showed here have four energy minima and thus four diverging relaxation times in the time evolution of magnetization and three such times in the evolution of energy. The properties of the real and imaginary parts of dynamic specific heat are investigated for different temperatures and frequencies. The dynamic susceptibility is affected by the longest relaxing mode while the dynamic specific heat is not. Our results confirm that C(omega) is sensitive only to rapidly relaxing processes for ferromagnetic (FM) and anti-ferromagnetic (AFM) cases. (Author)

  20. Nonlinear dynamic susceptibilities of interacting and noninteracting magnetic nanoparticles

    CERN Document Server

    Joensson, P; García-Palacios, J L; Svedlindh, P


    The linear and cubic dynamic susceptibilities of solid dispersions of nanosized maghemite gamma-Fe sub 2 O sub 3 particles have been measured for three samples with a volume concentration of magnetic particles ranging from 0.3% to 17%, in order to study the effect of dipole-dipole interactions. Significant differences between the dynamic response of the samples are observed. While the linear and cubic dynamic susceptibilities of the most dilute sample compare reasonably well with the corresponding expressions proposed by Raikher and Stepanov for noninteracting particles, the nonlinear dynamic response of the most concentrated sample exhibits at low temperatures similar features as observed in a Ag(11 at% Mn) spin glass.

  1. Quantum spin liquids: a review. (United States)

    Savary, Lucile; Balents, Leon


    Quantum spin liquids may be considered 'quantum disordered' ground states of spin systems, in which zero-point fluctuations are so strong that they prevent conventional magnetic long-range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, which is of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, such as non-local excitations, topological properties, and more. In this review, we discuss the nature of such phases and their properties based on paradigmatic models and general arguments, and introduce theoretical technology such as gauge theory and partons, which are conveniently used in the study of quantum spin liquids. An overview is given of the different types of quantum spin liquids and the models and theories used to describe them. We also provide a guide to the current status of experiments in relation to study quantum spin liquids, and to the diverse probes used therein.

  2. Quantum spin liquids: a review (United States)

    Savary, Lucile; Balents, Leon


    Quantum spin liquids may be considered ‘quantum disordered’ ground states of spin systems, in which zero-point fluctuations are so strong that they prevent conventional magnetic long-range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, which is of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, such as non-local excitations, topological properties, and more. In this review, we discuss the nature of such phases and their properties based on paradigmatic models and general arguments, and introduce theoretical technology such as gauge theory and partons, which are conveniently used in the study of quantum spin liquids. An overview is given of the different types of quantum spin liquids and the models and theories used to describe them. We also provide a guide to the current status of experiments in relation to study quantum spin liquids, and to the diverse probes used therein.

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

    KAUST Repository

    Manchon, Aurelien


    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.

  4. Spin precession in anisotropic cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Kamenshchik, A.Yu. [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); L. D. Landau Institute for Theoretical Physics, Moscow (Russian Federation); INFN, Bologna (Italy); Teryaev, O.V. [Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation); Lomonosov Moscow State University, Moscow (Russian Federation)


    We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early universe may produce the sterile particles contributing to dark matter. (orig.)

  5. Ferroelectric control of spin polarization. (United States)

    Garcia, V; Bibes, M; Bocher, L; Valencia, S; Kronast, F; Crassous, A; Moya, X; Enouz-Vedrenne, S; Gloter, A; Imhoff, D; Deranlot, C; Mathur, N D; Fusil, S; Bouzehouane, K; Barthélémy, A


    A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on "zero-current," gate-controlled operations. Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control.

  6. Spin and torsion in gravitation

    CERN Document Server

    De Sabbata, Venzo


    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

  7. Spin superfluid Josephson quantum devices (United States)

    Takei, So; Tserkovnyak, Yaroslav; Mohseni, Masoud


    A macroscopic spintronic qubit based on spin superfluidity and spin Hall phenomena is proposed. This magnetic quantum information processing device realizes the spin-supercurrent analog of the superconducting phase qubit and allows for full electrical control and readout. We also show that an array of interacting magnetic phase qubits can realize a quantum annealer. These devices can be built through standard solid-state fabrication technology, allowing for scalability. However, the upper bound for the operational temperature can, in principle, be higher than the superconducting counterpart, as it is ultimately governed by the magnetic ordering temperatures, which could be much higher than the critical temperatures of the conventional superconducting devices.

  8. Fast switching of bistable magnetic nanowires through collective spin reversal (United States)

    Vindigni, Alessandro; Rettori, Angelo; Bogani, Lapo; Caneschi, Andrea; Gatteschi, Dante; Sessoli, Roberta; Novak, Miguel A.


    The use of magnetic nanowires as memory units is made possible by the exponential divergence of the characteristic time for magnetization reversal at low temperature, but the slow relaxation makes the manipulation of the frozen magnetic states difficult. We suggest that finite-size segments can show a fast switching if collective reversal of the spins is taken into account. This mechanism gives rise at low temperatures to a scaling law for the dynamic susceptibility that has been experimentally observed for the dilute molecular chain Co(hfac)2NitPhOMe. These results suggest a possible way of engineering nanowires for fast switching of the magnetization.

  9. Spin Equilibria in Monomeric Manganocenes: Solid State Magnetic and EXAFS Studies

    Energy Technology Data Exchange (ETDEWEB)

    Walter, M. D.; Sofield, C. D.; Booth, C. H.; Andersen, R. A.


    Magnetic susceptibility measurements and X-ray data confirm that tert-butyl-substituted manganocenes [(Me{sub 3}C){sub n}C{sub 5}H{sub 5?n}]{sub 2}Mn (n = 1, 2) follow the trend previously observed with the methylated manganocenes; that is, electron-donating groups attached to the Cp ring stabilize the low-spin (LS) electronic ground state relative to Cp{sub 2}Mn and exhibit higher spin-crossover (SCO) temperatures. However, introducing three CMe{sub 3} groups on each ring gives a temperature-invariant high-spin (HS) state manganocene. The origin of the high-spin state in [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sub 2}Mn is due to the significant bulk of the [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sup -} ligand, which is sufficient to generate severe inter-ring steric strain that prevents the realization of the low-spin state. Interestingly, the spin transition in [1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}]{sub 2}Mn is accompanied by a phase transition resulting in a significant irreversible hysteresis ({Delta}T{sub c} = 16 K). This structural transition was also observed by extended X-ray absorption fine-structure (EXAFS) measurements. Magnetic susceptibility studies and X-ray diffraction data on SiMe{sub 3}-substituted manganocenes [(Me{sub 3}Si){sub n}C{sub 5}H{sub 5-n}]{sub 2}Mn (n = 1, 2, 3) show high-spin configurations in these cases. Although tetra- and hexasubstituted manganocenes are high-spin at all accessible temperatures, the disubstituted manganocenes exhibit a small low-spin admixture at low temperature. In this respect it behaves similarly to [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn, which has a constant low-spin admixture up to 90 K and then gradually converts to high-spin. Thermal spin-trapping can be observed for [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn on rapid cooling.

  10. Microwave susceptibility experiments

    Energy Technology Data Exchange (ETDEWEB)

    McConaghy, C.


    In certain experimental environments, systems can be affected or damaged by microwave pulses. I have conducted tests at LLNL to understand the phenomenology of microwave susceptibility of system components and subsystem components. To date, my experiments have concentrated on bipolar transistors, similar to what might be used in discrete analog circuits, and on CMOS RAM chips, which might be used in a computer memory system. I observed a decrease in failure energies for both the transistor and the integrated curcuit as I shortened the microwave pulse width. An S band (2.86 GHz) transmit/receive (T/R) tube has also been tested both at S band and at X band (8.16 GHz). The S band pulse had limitations in rise-time from zero power, which had an effect on the amount of power that could be transmitted through the T/R tube, as much as 0.7% of the incident power passed through the tube. All tests were conducted in closed-waveguide or coax test-fixtures, in contrast to the anechoic chambers utilized by other experimenters. I have used both S band and X band Klystron generators. For very high power (greater than 1 MW), I used an additional pulse-compression cavity at S band. Other subsystem components such as an X band mixer and an X band T/R tube will be tested in the future. 8 references.

  11. [Antimicrobial susceptibility cumulative reports]. (United States)

    Canut-Blasco, Andrés; Calvo, Jorge; Rodríguez-Díaz, Juan Carlos; Martínez-Martínez, Luis


    Cumulative reports on antimicrobial susceptibility tests data are important for selecting empirical treatments, as an educational tool in programs on antimicrobial use, and for establishing breakpoints defining clinical categories. These reports should be based on data validated by clinical microbiologists using diagnostic samples (not surveillance samples). In order to avoid a bias derived from including several isolates obtained from the same patient, it is recommended that, for a defined period, only the first isolate is counted. A minimal number of isolates per species should be presented: a figure of >=30 isolates is statistically acceptable. The report is usually presented in a table format where, for each cell, information on clinically relevant microorganisms-antimicrobial agents is presented. Depending on particular needs, multiple tables showing data related to patients, samples, services or special pathogens can be prepared. Copyright © 2015 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

  12. Neuroanatomic Differences Associated With Stress Susceptibility and Resilience. (United States)

    Anacker, Christoph; Scholz, Jan; O'Donnell, Kieran J; Allemang-Grand, Rylan; Diorio, Josie; Bagot, Rosemary C; Nestler, Eric J; Hen, René; Lerch, Jason P; Meaney, Michael J


    We examined the neurobiological mechanisms underlying stress susceptibility using structural magnetic resonance imaging and diffusion tensor imaging to determine neuroanatomic differences between stress-susceptible and resilient mice. We also examined synchronized anatomic differences between brain regions to gain insight into the plasticity of neural networks underlying stress susceptibility. C57BL/6 mice underwent 10 days of social defeat stress and were subsequently tested for social avoidance. For magnetic resonance imaging, brains of stressed (susceptible, n = 11; resilient, n = 8) and control (n = 12) mice were imaged ex vivo at 56 µm resolution using a T2-weighted sequence. We tested for behavior-structure correlations by regressing social avoidance z-scores against local brain volume. For diffusion tensor imaging, brains were scanned with a diffusion-weighted fast spin echo sequence at 78 μm isotropic voxels. Structural covariance was assessed by correlating local volume between brain regions. Social avoidance correlated negatively with local volume of the cingulate cortex, nucleus accumbens, thalamus, raphe nuclei, and bed nucleus of the stria terminals. Social avoidance correlated positively with volume of the ventral tegmental area (VTA), habenula, periaqueductal gray, cerebellum, hypothalamus, and hippocampal CA3. Fractional anisotropy was increased in the hypothalamus and hippocampal CA3. We observed synchronized anatomic differences between the VTA and cingulate cortex, hippocampus and VTA, hippocampus and cingulate cortex, and hippocampus and hypothalamus. These correlations revealed different structural covariance between brain regions in susceptible and resilient mice. Stress-integrative brain regions shape the neural architecture underlying individual differences in susceptibility and resilience to chronic stress. Copyright © 2016. Published by Elsevier Inc.

  13. 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 ...

  14. 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 ...


    Energy Technology Data Exchange (ETDEWEB)



    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.

  16. Spin Physics with the PHENIX Detector System


    Saito, N.; Collaboration, for the PHENIX


    The PHENIX experiment at RHIC has extended its scope to cover spin physics using polarized proton beams. The major goals of the spin physics at RHIC are elucidation of the spin structure of the nucleon and precision tests of the symmetries. Sensitivities of the spin physics measurements with the PHENIX detector system are reviewed.

  17. Fidelity Susceptibility Made Simple: A Unified Quantum Monte Carlo Approach

    Directory of Open Access Journals (Sweden)

    Lei Wang


    Full Text Available The fidelity susceptibility is a general purpose probe of phase transitions. With its origin in quantum information and in the differential geometry perspective of quantum states, the fidelity susceptibility can indicate the presence of a phase transition without prior knowledge of the local order parameter, as well as reveal the universal properties of a critical point. The wide applicability of the fidelity susceptibility to quantum many-body systems is, however, hindered by the limited computational tools to evaluate it. We present a generic, efficient, and elegant approach to compute the fidelity susceptibility of correlated fermions, bosons, and quantum spin systems in a broad range of quantum Monte Carlo methods. It can be applied to both the ground-state and nonzero-temperature cases. The Monte Carlo estimator has a simple yet universal form, which can be efficiently evaluated in simulations. We demonstrate the power of this approach with applications to the Bose-Hubbard model, the spin-1/2 XXZ model, and use it to examine the hypothetical intermediate spin-liquid phase in the Hubbard model on the honeycomb lattice.

  18. 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)


    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.

  19. Hybrid spin-crossover nanostructures

    National Research Council Canada - National Science Library

    Quintero, Carlos M; Félix, Gautier; Suleimanov, Iurii; Sánchez Costa, José; Molnár, Gábor; Salmon, Lionel; Nicolazzi, William; Bousseksou, Azzedine


    This review reports on the recent progress in the synthesis, modelling and application of hybrid spin-crossover materials, including core-shell nanoparticles and multilayer thin films or nanopatterns...

  20. Putting a spin on photons (United States)

    Burk, S.; Fedder, H.; Wrachtrup, J.


    We demonstrate the voltage induced switching of single defect centers between its charge states. The individual charge states do show different emission wavelengths and are identified by their ground state spin properties.

  1. Spin and exotic Galilean symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Duval, C.; Horvathy, P.A


    A slightly modified and regularized version of the non-relativistic limit of the relativistic anyon model considered by Jackiw and Nair yields particles associated with the twofold central extension of the Galilei group, with independent spin and exotic structure.

  2. Electrical and thermal spin accumulation in germanium (United States)

    Jain, A.; Vergnaud, C.; Peiro, J.; Le Breton, J. C.; Prestat, E.; Louahadj, L.; Portemont, C.; Ducruet, C.; Baltz, V.; Marty, A.; Barski, A.; Bayle-Guillemaud, P.; Vila, L.; Attané, J.-P.; Augendre, E.; Jaffrès, H.; George, J.-M.; Jamet, M.


    In this letter, we first show electrical spin injection in the germanium conduction band at room temperature and modulate the spin signal by applying a gate voltage to the channel. The corresponding signal modulation agrees well with the predictions of spin diffusion models. Then, by setting a temperature gradient between germanium and the ferromagnet, we create a thermal spin accumulation in germanium without any charge current. We show that temperature gradients yield larger spin accumulations than electrical spin injection but, due to competing microscopic effects, the thermal spin accumulation remains surprisingly unchanged under the application of a gate voltage.

  3. Spin current swapping and Hanle spin Hall effect in a two-dimensional electron gas

    NARCIS (Netherlands)

    Shen, K.; Raimondi, R.; Vignale, G.


    We analyze the effect known as “spin current swapping” (SCS) due to electron-impurity scattering in a uniform spin-polarized two-dimensional electron gas. In this effect a primary spin current Jai (lower index for spatial direction, upper index for spin direction) generates a secondary spin current

  4. Spin Hall effect by surface roughness

    KAUST Repository

    Zhou, Lingjun


    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.

  5. Hybrid spin-crossover nanostructures

    Directory of Open Access Journals (Sweden)

    Carlos M. Quintero


    Full Text Available This review reports on the recent progress in the synthesis, modelling and application of hybrid spin-crossover materials, including core–shell nanoparticles and multilayer thin films or nanopatterns. These systems combine, often in synergy, different physical properties (optical, magnetic, mechanical and electrical of their constituents with the switching properties of spin-crossover complexes, providing access to materials with unprecedented capabilities.

  6. Tailoring spin defects in diamond


    F?varo de Oliveira, Felipe; Antonov, Denis; Wang, Ya; Neumann, Philipp; Momenzadeh, Seyed Ali; H?u?ermann, Timo; Pasquarelli, Alberto; Denisenko, Andrej; Wrachtrup, J?rg


    Atomic-size spin defects in solids are unique quantum systems. Most applications require nanometer positioning accuracy, which is typically achieved by low energy ion implantation. So far, a drawback of this technique is the significant residual implantation-induced damage to the lattice, which strongly degrades the performance of spins in quantum applications. In this letter we show that the charge state of implantation-induced defects drastically influences the formation of lattice defects ...

  7. Analytic definition of spin structure (United States)

    Avetisyan, Zhirayr; Fang, Yan-Long; Saveliev, Nikolai; Vassiliev, Dmitri


    We work on a parallelizable time-orientable Lorentzian 4-manifold and prove that in this case, the notion of spin structure can be equivalently defined in a purely analytic fashion. Our analytic definition relies on the use of the concept of a non-degenerate two-by-two formally self-adjoint first order linear differential operator and gauge transformations of such operators. We also give an analytic definition of spin structure for the 3-dimensional Riemannian case.

  8. Spin dynamics of bilayer manganites

    Indian Academy of Sciences (India)

    However, the spin wave dispersion in La1.2Sr1.8Mn2O7 shows softening close to .... The dispersion of the optic spin-wave branch along [100] has also been measured. Figure 4 shows the dispersions of both the branches along [100]. The continuous ... However, it has been realized that the population of the dz2−3r2 and ...

  9. Spin qubits in antidot lattices

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Flindt, Christian; Mortensen, Niels Asger


    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...... 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....

  10. Spin photocurrents in quantum wells

    CERN Document Server

    Ganichev, S D


    Spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs) are reviewed. The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas. It is shown that in QWs belonging to one of the gyrotropic crystal classes a non-equilibrium spin polarization of uniformly distributed electrons causes a directed motion of electrons in the plane of the QW. A characteristic feature of this electric current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a QW: the spin polarization-induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asymmetric distribut...

  11. Quantum Spin Glasses, Annealing and Computation (United States)

    Tanaka, Shu; Tamura, Ryo; Chakrabarti, Bikas K.


    List of tables; List of figures, Preface; 1. Introduction; Part I. Quantum Spin Glass, Annealing and Computation: 2. Classical spin models from ferromagnetic spin systems to spin glasses; 3. Simulated annealing; 4. Quantum spin glass; 5. Quantum dynamics; 6. Quantum annealing; Part II. Additional Notes: 7. Notes on adiabatic quantum computers; 8. Quantum information and quenching dynamics; 9. A brief historical note on the studies of quantum glass, annealing and computation.

  12. The effective potential of squeezed spin states

    Energy Technology Data Exchange (ETDEWEB)

    Bilge Ocak, S.; Altanhan, T


    Coherent spin states are considered through the spin operator representation in differential equation, which give quantum mechanical potentials. Squeezed spin states are defined through a canonical transformation. The defined concept of squeezed spin states has been applied to a spin system describing a magnetic system with S=1. The effective Schroedinger equation is obtained and the squeezed potential has been constructed for the model Hamiltonian. It is found that squeezing acts as a symmetry breaking process.

  13. Spin selective filtering of polariton condensate flow

    Energy Technology Data Exchange (ETDEWEB)

    Gao, T. [FORTH-IESL, P.O. Box 1385, 71110 Heraklion, Crete (Greece); Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Crete (Greece); Antón, C.; Martín, M. D. [Departamento de Física de Materiales, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Instituto de Ciencia de Materiales “Nicolás Cabrera,” Universidad Autónoma de Madrid, Madrid 28049 (Spain); Liew, T. C. H. [School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Hatzopoulos, Z. [FORTH-IESL, P.O. Box 1385, 71110 Heraklion, Crete (Greece); Department of Physics, University of Crete, 71003 Heraklion, Crete (Greece); Viña, L. [Departamento de Física de Materiales, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Instituto de Ciencia de Materiales “Nicolás Cabrera,” Universidad Autónoma de Madrid, Madrid 28049 (Spain); Instituto de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Eldridge, P. S., E-mail: [FORTH-IESL, P.O. Box 1385, 71110 Heraklion, Crete (Greece); Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States); Savvidis, P. G., E-mail: [FORTH-IESL, P.O. Box 1385, 71110 Heraklion, Crete (Greece); Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Crete (Greece); Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom)


    Spin-selective spatial filtering of propagating polariton condensates, using a controllable spin-dependent gating barrier, in a one-dimensional semiconductor microcavity ridge waveguide is reported. A nonresonant laser beam provides the source of propagating polaritons, while a second circularly polarized weak beam imprints a spin dependent potential barrier, which gates the polariton flow and generates polariton spin currents. A complete spin-based control over the blocked and transmitted polaritons is obtained by varying the gate polarization.

  14. Theory of the Spin Seebeck Effect


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


    The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental eff...

  15. Quantum spin transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Christoph


    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.

  16. Experimental Realization of a Quantum Spin Pump

    DEFF Research Database (Denmark)

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


    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....

  17. Candidate quantum spin liquid due to dimensional reduction of a two-dimensional honeycomb lattice. (United States)

    Zhang, Bin; Zhang, Yan; Wang, Zheming; Wang, Dongwei; Baker, Peter J; Pratt, Francis L; Zhu, Daoben


    As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2[Cu2(C2O4)3](H2O)2.2 containing hexagonal layers of Cu(2+) was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu(2+) and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with θ = -120 (1) K. Orbital analysis of the Cu(2+) interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids.

  18. [Antimicrobial susceptibility in Chile 2012]. (United States)

    Cifuentes-D, Marcela; Silva, Francisco; García, Patricia; Bello, Helia; Briceño, Isabel; Calvo-A, Mario; Labarca, Jaime


    Bacteria antimicrobial resistance is an uncontrolled public health problem that progressively increases its magnitude and complexity. The Grupo Colaborativo de Resistencia, formed by a join of experts that represent 39 Chilean health institutions has been concerned with bacteria antimicrobial susceptibility in our country since 2008. In this document we present in vitro bacterial susceptibility accumulated during year 2012 belonging to 28 national health institutions that represent about 36% of hospital discharges in Chile. We consider of major importance to report periodically bacteria susceptibility so to keep the medical community updated to achieve target the empirical antimicrobial therapies and the control measures and prevention of the dissemination of multiresistant strains.

  19. Spin-inversion in nanoscale graphene sheets with a Rashba spin-orbit barrier

    Directory of Open Access Journals (Sweden)

    Somaieh Ahmadi


    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.

  20. Spin-transfer torque in spin filter tunnel junctions

    KAUST Repository

    Ortiz Pauyac, Christian


    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.

  1. Detecting spin fractionalization in a spinon Fermi surface spin liquid (United States)

    Li, Yao-Dong; Chen, Gang


    Motivated by the recent proposal that several candidate materials such as YbMgGaO4 could be spinon Fermi surface spin liquids, we explore the experimental consequences of the external magnetic fields on this exotic state. Specifically, we focus on the weak field regime where the spin-liquid state is well preserved and the spinon remains to be a good description of the magnetic excitations. From the spin-1/2 nature of the spinon excitation, we predict the unique features of the spinon continuum when the weak magnetic field is applied to the system. Due to the small energy scale of the exchange interactions between the local moments in the spin-liquid candidate like YbMgGaO4, our proposal for the spectral weight shifts and spectral crossing in the magnetic fields can be immediately tested by inelastic neutron scattering experiments. Several other experimental aspects about the spinon Fermi surface and the spinon excitations are discussed and proposed. Our work provides an experimental scheme to examine the fractionalized spinon excitation and the candidate spin-liquid states in YbMgGaO4, the 6H-B phase of Ba3NiSb2O9 , and other relevant materials.

  2. Beyond Gaussian approximation in the spin-fluctuation theory of metallic ferromagnetism

    Energy Technology Data Exchange (ETDEWEB)

    Reser, B I; Grebennikov, V I [Institute of Metal Physics, Russian Academy of Sciences, Ekaterinburg (Russian Federation); Melnikov, N B, E-mail: reser@imp.uran.r [Lomonosov Moscow State University, Moscow (Russian Federation)


    A characteristic feature of the Gaussian spin-fluctuation theory is the jump transition into the paramagnetic state. We eliminate the jump and obtain a continuous second-order phase transition by taking into account the high-order terms of the free energy of electrons in the fluctuating exchange field. The third-order term of the free energy yields a renormalization of the mean field, and fourth-order term, responsible for the interaction of the fluctuations, gives a renormalization of the spin susceptibility. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar.

  3. Spin Fluctuations in the 0.7 Anomaly in Quantum Point Contacts (United States)

    Schimmel, Dennis H.; Bruognolo, Benedikt; von Delft, Jan


    It has been argued that the 0.7 anomaly in quantum point contacts (QPCs) is due to an enhanced density of states at the top of the QPC barrier (the van Hove ridge), which strongly enhances the effects of interactions. Here, we analyze their effect on dynamical quantities. We find that they pin the van Hove ridge to the chemical potential when the QPC is subopen, cause a temperature dependence for the linear conductance that qualitatively agrees with experiments, strongly enhance the magnitude of the dynamical spin susceptibility, and significantly lengthen the QPC traversal time. We conclude that electrons traverse the QPC via a slowly fluctuating spin structure of finite spatial extent.

  4. Conduction electron spin resonance in Mg 1 - x Al x B2 (United States)

    Likodimos, V.; Koutandos, S.; Pissas, M.; Papavassiliou, G.; Prassides, K.


    Conduction electron spin resonance is employed to study the interplay of the electronic and structural properties in the normal state of Mg 1 - x Al x B2 alloys as a function of Al-doping for 0 <= x <= 1. The x-dependence of the spin susceptibility reveals considerable reduction of the total density of states N(EF) with increasing Al concentration, complying with theoretical predictions for a predominant filling effect of the hole σ bands by electron doping. The CESR linewidth exhibits significant broadening, especially prominent in the high-Al-content region, indicative of the presence of enhanced structural disorder, consistent with the presence of compositional fluctuations.


    African Journals Online (AJOL)

    isolates vere made using standard methods, Antibiotic susceptibility tests against commonly prescribed ... Acute otitis media is rapid with short .... sensitivity tests. Antimicrobial susceptibility tests: The antimicrobial susceptibility patterns of major Gram positive and negative bacterial isolates obtained from clinical specimens.

  6. Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism. (United States)

    Haverkort, M W; Hu, Z; Cezar, J C; Burnus, T; Hartmann, H; Reuther, M; Zobel, C; Lorenz, T; Tanaka, A; Brookes, N B; Hsieh, H H; Lin, H-J; Chen, C T; Tjeng, L H


    Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.

  7. World sheets of spinning particles (United States)

    Kaparulin, D. S.; Lyakhovich, S. L.


    The classical spinning particles are considered such that quantization of classical model leads to an irreducible massive representation of the Poincaré group. The class of gauge equivalent classical particle world lines is shown to form a [(d +1 )/2 ]-dimensional world sheet in d -dimensional Minkowski space, irrespectively to any specifics of the classical model. For massive spinning particles in d =3 , 4, the world sheets are shown to be circular cylinders. The radius of the cylinder is fixed by representation. In higher dimensions, the particle's world sheet turns out to be a toroidal cylinder R ×TD, D =[(d -1 )/2 ]. Proceeding from the fact that the world lines of irreducible classical spinning particles are cylindrical curves, while all the lines are gauge equivalent on the same world sheet, we suggest a method to deduce the classical equations of motion for particles and also to find their gauge symmetries. In d =3 Minkowski space, the spinning particle path is defined by a single fourth-order differential equation having two zero-order gauge symmetries. The equation defines the particle's path in Minkowski space, and it does not involve auxiliary variables. A special case is also considered of cylindric null curves, which are defined by a different system of equations. It is shown that the cylindric null curves also correspond to irreducible massive spinning particles. For the higher-derivative equation of motion of the irreducible massive spinning particle, we deduce the equivalent second-order formulation involving an auxiliary variable. The second-order formulation agrees with a previously known spinning particle model.

  8. Calculations of spin response functions in rings with Siberian Snakes and spin rotators

    Directory of Open Access Journals (Sweden)

    Yu. M. Shatunov


    Full Text Available The so-called spin response formalism, which is linear response theory applied to spin dynamics in storage rings, can calculate the resonance strengths for spin flippers in storage rings of arbitrary structure, including rings with Siberian Snakes and spin rotators. We calculate so-called spin response functions for a model of the RHIC lattice, for various scenarios of spin rotator settings.

  9. Hypnotic susceptibility and dream characteristics. (United States)

    Zamore, N; Barrett, D


    This study examined the relationship of hypnotic susceptibility to a variety of dream characteristics and types of dream content. A Dream Questionnaire was constructed synthesizing Gibson's dream inventory and Hilgard's theoretical conceptions of hypnosis. Employing the Harvard Group Scale of Hypnotic Susceptibility and the Field Inventory for evaluating hypnotic response, several dream dimensions correlated significantly with hypnotizability. For subjects as a whole, the strongest correlates were the frequency of dreams which they believed to be precognitive and out-of-body dreams. Ability to dream on a chosen topic also correlated significantly with hypnotic susceptibility for both genders. For females only, there was a negative correlation of hypnotic susceptibility to flying dreams. Absorption correlated positively with dream recall, ability to dream on a chosen topic, reports of conflict resolution in dreams, creative ideas occurring in dreams, amount of color in dreams, pleasantness of dreams, bizarreness of dreams, flying dreams and precognitive dreams.

  10. Spin and tunneling dynamics in an asymmetrical double quantum dot with spin-orbit coupling: Selective spin transport device (United States)

    Singh, Madhav K.; Jha, Pradeep K.; Bhattacherjee, Aranya B.


    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.

  11. Ancestral susceptibility to colorectal cancer

    Czech Academy of Sciences Publication Activity Database

    Huhn, S.; Pardini, Barbara; Naccarati, Alessio; Vodička, Pavel (ed.); Hemminki, K.; Försti, A.


    Roč. 27, č. 2 (2012), s. 197-204 ISSN 0267-8357 R&D Projects: GA ČR GA310/07/1430; GA ČR GAP304/10/1286 Grant - others:EU FP7(XE) HEALTH-F4-2007-200767 Institutional research plan: CEZ:AV0Z50390512 Keywords : cancer susceptibility * molecular epidemiology * genetic susceptibility Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.500, year: 2012

  12. Generalized boundary conditions for spin transfer (United States)

    Tserkovnyak, Yaroslav; Ochoa, Hector


    We develop a comprehensive description of static and dynamic spin-transfer torque at interfaces between a normal metal and a magnetic material. Specific examples of the latter include ferromagnets, collinear and noncollinear antiferromagnets, general ferrimagnets, and spin glasses. We study the limit of the exchange-dominated interactions, so that the full system is isotropic in spin space, apart from a possible symmetry-breaking order. A general such interface yields three coefficients (corresponding to three independent generators of rotations) generalizing the well-established notion of the spin-mixing conductance, which pertains to the collinear case. We develop a nonequilibrium thermodynamic description of the emerging interfacial spin transfer and its effect on the collective spin dynamics, while circumventing the usual discussion of spin currents and net spin dynamics. Instead, our focus is on the dissipation and work effectuated by the interface. Microscopic scattering-matrix based expressions are derived for the generalized spin-transfer coefficients.

  13. Universal spin dynamics in quantum wires (United States)

    Fajardo, E. A.; Zülicke, U.; Winkler, R.


    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.

  14. Fractionalized Z_{2} Classical Heisenberg Spin Liquids. (United States)

    Rehn, J; Sen, Arnab; Moessner, R


    Quantum spin systems are by now known to exhibit a large number of different classes of spin liquid phases. By contrast, for classical Heisenberg models, only one kind of fractionalized spin liquid phase, the so-called Coulomb or U(1) spin liquid, has until recently been identified: This exhibits algebraic spin correlations and impurity moments, "orphan spins," whose size is a fraction of that of the underlying microscopic degrees of freedom. Here, we present two Heisenberg models exhibiting fractionalization in combination with exponentially decaying correlations. These can be thought of as a classical continuous spin version of a Z_{2} spin liquid. Our work suggests a systematic search and classification of classical spin liquids as a worthwhile endeavor.

  15. Spin relaxation 1/f noise in graphene (United States)

    Omar, S.; Guimarães, M. H. D.; Kaverzin, A.; van Wees, B. J.; Vera-Marun, I. J.


    We report the first measurement of 1/f type noise associated with electronic spin transport, using single layer graphene as a prototypical material with a large and tunable Hooge parameter. We identify the presence of two contributions to the measured spin-dependent noise: contact polarization noise from the ferromagnetic electrodes, which can be filtered out using the cross-correlation method, and the noise originated from the spin relaxation processes. The noise magnitude for spin and charge transport differs by three orders of magnitude, implying different scattering mechanisms for the 1/f fluctuations in the charge and spin transport processes. A modulation of the spin-dependent noise magnitude by changing the spin relaxation length and time indicates that the spin-flip processes dominate the spin-dependent noise.

  16. Effective spin-spin interaction in neutron matter

    Energy Technology Data Exchange (ETDEWEB)

    Zverev, M.V. [Moscow Engineering Physics Institute, Moscow (Russian Federation); Khafizov, R.U.; Khodel, V.A. [Kurchatov Institute Russian Research Centre, Moscow (Russian Federation); Shaginyan, V.R. [Petersburg Institute of Nuclear Physics, Gatchina (Russian Federation)


    A set of equations for calculating the effective-interaction matrix R{sup ik}(q, {omega}) and the response function X{sup ik}(q, {omega}) is derived. These equations take into account the spin degrees of freedom of infinite neutron matter. For isotropic neutron matter with the Bethe interaction, the effective spin-spin interaction g(k) is calculated in the local approximation of the functional approach in the density range from {rho} = 0.17 to 25 fm{sup -3}. It is shown that this interaction weakly depends on the density within the range under consideration and that neither ferromagnetic nor antiferromagnetic phase transitions occur in the system. 7 refs., 2 figs.

  17. Spin-orbit-based device for electron spin polarization (United States)

    Avishai, Y.; Band, Y. B.


    We propose quantum devices having spin-orbit coupling (but no magnetic fields or magnetic materials) that, when attached to leads, yield a high degree of transmitted electron polarization. An example of such a simple device is treated within a tight binding model composed of two one-dimensional chains coupled by several consecutive rungs (i.e., a ladder) and subject to a gate voltage. The ensuing scattering problem (with Rashba spin-orbit coupling) is solved, and a sizable polarization is predicted. When the ladder is twisted into a helix (as in DNA), the curvature energy augments the polarization. For a system with random spin-orbit coupling, the distribution of polarization is broad; hence a high degree of polarization can be obtained in a measurement of a given disorder realization. When disorder occurs in a double helix structure then, depending on scattering energy, the variance of the polarization distribution can increase even further due to helix curvature.

  18. Heavy spin-2 Dark Matter

    Energy Technology Data Exchange (ETDEWEB)

    Babichev, Eugeny [Laboratoire de Physique Théorique, CNRS, Univ. Paris-Sud, Université Paris-Saclay,91405 Orsay (France); UPMC-CNRS, UMR7095, Institut d’Astrophysique de Paris, GReCO,98bis boulevard Arago, F-75014 Paris (France); Marzola, Luca; Raidal, Martti [National Institute of Chemical Physics and Biophysics,Rävala 10, 10143 Tallinn (Estonia); Laboratory of Theoretical Physics, Institute of Physics, University of Tartu,Ravila 14c, 50411 Tartu (Estonia); Schmidt-May, Angnis [Institut für Theoretische Physik, Eidgenössische Technische Hochschule Zürich,Wolfgang-Pauli-Strasse 27, 8093 Zürich (Switzerland); Urban, Federico; Veermäe, Hardi [National Institute of Chemical Physics and Biophysics,Rävala 10, 10143 Tallinn (Estonia); Strauss, Mikael von [UPMC-CNRS, UMR7095, Institut d’Astrophysique de Paris, GReCO,98bis boulevard Arago, F-75014 Paris (France)


    We provide further details on a recent proposal addressing the nature of the dark sectors in cosmology and demonstrate that all current observations related to Dark Matter can be explained by the presence of a heavy spin-2 particle. Massive spin-2 fields and their gravitational interactions are uniquely described by ghost-free bimetric theory, which is a minimal and natural extension of General Relativity. In this setup, the largeness of the physical Planck mass is naturally related to extremely weak couplings of the heavy spin-2 field to baryonic matter and therefore explains the absence of signals in experiments dedicated to Dark Matter searches. It also ensures the phenomenological viability of our model as we confirm by comparing it with cosmological and local tests of gravity. At the same time, the spin-2 field possesses standard gravitational interactions and it decays universally into all Standard Model fields but not into massless gravitons. Matching the measured DM abundance together with the requirement of stability constrains the spin-2 mass to be in the 1 to 100 TeV range.

  19. 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.


    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.)

  20. Spin Superfluidity in Biaxial Antiferromagnetic Insulators (United States)

    Qaiumzadeh, Alireza; Skarsvâg, Hans; Holmqvist, Cecilia; Brataas, Arne


    Antiferromagnets may exhibit spin superfluidity since the dipole interaction is weak. We seek to establish that this phenomenon occurs in insulators such as NiO, which is a good spin conductor according to previous studies. We investigate nonlocal spin transport in a planar antiferromagnetic insulator with a weak uniaxial anisotropy. The anisotropy hinders spin superfluidity by creating a substantial threshold that the current must overcome. Nevertheless, we show that applying a high magnetic field removes this obstacle near the spin-flop transition of the antiferromagnet. Importantly, the spin superfluidity can then persist across many micrometers, even in dirty samples.

  1. Spin Waves in Ho2Co17

    DEFF Research Database (Denmark)

    Clausen, Kurt Nørgaard; Lebech, Bente


    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....

  2. Spin echo magnetic resonance imaging. (United States)

    Jung, Bernd André; Weigel, Matthias


    The spin echo sequence is a fundamental pulse sequence in MRI. Many of today's applications in routine clinical use are based on this elementary sequence. In this review article, the principles of the spin echo formation are demonstrated on which the generation of the fundamental image contrasts T1, T2, and proton density is based. The basic imaging parameters repetition time (TR) and echo time (TE) and their influence on the image contrast are explained. Important properties such as the behavior in multi-slice imaging or in the presence of flow are depicted and the basic differences with gradient echo imaging are illustrated. The characteristics of the spin echo sequence for different magnetic field strengths with respect to clinical applications are discussed. Copyright © 2013 Wiley Periodicals, Inc.

  3. Next generation spin torque memories

    CERN Document Server

    Kaushik, Brajesh Kumar; Kulkarni, Anant Aravind; Prajapati, Sanjay


    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. Spin structures in antiferromagnetic nanoparticles

    DEFF Research Database (Denmark)

    Brok, Erik

    in plate-shaped NiO nanoparticles with thicknesses down to 2.0 nm is investigated with the XY Z-neutron polarisation analysis technique. This provides an effective way of separating the different scattering contributions (magnetic, nuclear and spin incoherent), and thus significantly improve the earlier......In this thesis magnetic structures of antiferromagnetic nanoparticles are studied as a function of particle size and aggregation. In nanoparticles the magnetic structure can be different from that of the corresponding bulk system due to the following reasons: a) a significant surface contribution...... to the magnetic anisotropy, b) the low symmetry environment of surface atoms or defects in the interior of particles leading to non collinear spin structures, and c) exchange interactions between neighbouring particles. Determining the spin structures of antiferromagnetic particles is difficult, however...

  5. Crossover from Spin Accumulation into Interface States to Spin Injection in the Germanium Conduction Band (United States)

    Rojas-Sanchez, Juan-Carlos; Jain, Abhinav; Cubukcu, Murat; Peiro, Julian; Le Breton, Jean-Christophe; Prestat, Eric; Vergnaud, Céline; Bayle-Guillemaud, Pascale; Vila, Laurent; Attané, Jean-Philippe; Augendre, Emmanuel; Gambarelli, Serge; Jaffrès, Henri; George, Jean-Marie; Jamet, Matthieu


    Spin injection into semiconductors is crucial for exploring spin physics and new spintronic devices. Ge is of great interest for high carrier mobilities, long spin diffusion length and large spin-orbit coupling to perform electric field spin manipulation. However the exact role of interface states in spin injection mechanism in n-Ge has not been clarified yet. Here we show a clear transition from spin accumulation into interface states to spin injection in the Ge conduction band. For this purpose, we have grown CoFeB/MgO as a spin injector on Germanium On Insulator. We observe spin signal amplification at low temperature due to spin accumulation into interface states. At 150 K, we find a clear transition to spin injection in the conduction band up to room temperature: the measured spin signal is compatible with the spin diffusion model. We could in particular demonstrate spin signal modulation applying a back gate voltage and spin-pumping by the ferromagnetic resonance of the CoFeB layer which are clear manifestations of spin accumulation in the Ge conduction band.

  6. Efficient thermal spin injection in metallic nanostructures (United States)

    Nomura, Tatsuya; Ariki, Taisei; Hu, Shaojie; Kimura, Takashi


    Thermal spin injection is a unique and fascinating method for generating spin current. If magnetization can be controlled by thermal spin injection, various advantages will be provided in spintronic devices, through its wireless controllability. However, the generation efficiency of thermal spin injection is believed to be lower than that of electrical spin injection. Here, we explore a suitable ferromagnetic metal for an efficient thermal spin injection, via systematic experiments based on diffusive spin transport under temperature gradients. Since a ferromagnetic metal with strong spin splitting is expected to have a large spin-dependent Seebeck coefficient, a lateral spin valve based on CoFe electrodes has been fabricated. However, the superior thermal spin injection property has not been observed, because the CoFe electrode retained its crystalline signature—where s-like electrons dominate the transport property in the ferromagnet. To suppress the crystalline signature, we adopt a CoFeAl electrode, in which the Al impurity significantly reduces the contribution from s-like electrons. Highly efficient thermal spin injection has been demonstrated using this CoFeAl electrode. Further optimization for thermal spin injection has been demonstrated by adjusting the Co and Fe composition.

  7. Neutron spin evolution through broadband current sheet spin flippers. (United States)

    Stonaha, P; Hendrie, J; Lee, W T; Pynn, Roger


    Controlled manipulation of neutron spin is a critical tool for many neutron scattering techniques. We have constructed current-sheet, neutron spin flippers for use in Spin Echo Scattering Angle Measurement (SESAME) that comprise pairs of open-faced solenoids which introduce an abrupt field reversal at a shared boundary. The magnetic fields generated by the coils have been mapped and compared with both an analytical approximation and a numerical boundary integral calculation. The agreement is generally good, allowing the former method to be used for rapid calculations of the Larmor phase acquired by a neutron passing through the flipper. The evolution of the neutron spin through the current sheets inside the flipper is calculated for various geometries of the current-carrying conductors, including different wire shapes, arrangements, and common imperfections. The flipping efficiency is found to be sensitive to gaps between wires and between current sheets. SESAME requires flippers with high fields and flipping planes inclined to the neutron beam. To avoid substantial neutron depolarization, such flippers require an interdigitated arrangement of wires.

  8. Long-range spin Seebeck effect and acoustic spin pumping. (United States)

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


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

  9. Modelling Infectious Disease Spreading Dynamic via Magnetic Spin Distribution: The Stochastic Monte Carlo and Neural Network Analysis (United States)

    Laosiritaworn, Yongjua; Laosiritaworn, Yongyut; Laosiritaworn, Wimalin S.


    In this work, the disease spreading under SIR framework (susceptible-infected-recovered) agent-based model was investigated via magnetic spin model, stochastic Monte Carlo simulation, and Neural Network analysis. The defined systems were two-dimensional lattice-like, where the spins (representing susceptible, infected, and recovered agents) were allocated on lattice cells. The lattice size, spin density, and infectious period were varied to observe its influence on disease spreading period. In the simulation, each spin was randomly allocated on the lattice and interacted with its first neighbouring spins for disease spreading. The subgroup magnetization profiles were recorded. From the results, numbers of agents in each subgroup as a function of time was found to depend on all considered parameters. Specifically, the disease spreading period slightly increases with increasing system size, decreases with increasing spin density, and exponentially decays with increasing infectious period. Due to many degrees of freedom associated, Neural Network was used to establish complex relationship among parameters. Multi-layer perceptron was considered, where optimized network architecture of 3-19-15-1 was found. Good agreement between predicted and actual outputs was evident. This confirms the validity of using Neural Network as supplements in modelling SIR disease spreading and provides profound database for future deployment.

  10. Spin-Wave Analysis for Kagome-Triangular Spin System and Coupled Spin Tubes: Low-Energy Excitation for the Cuboc Order (United States)

    Ochiai, Masahiro; Seki, Kouichi; Okunishi, Kouichi


    The coupled spin tube system, which is equivalent to a stacked Kagome-triangular spin system, exhibits the cuboc order — a non-coplanar spin order with a twelve-sublattice structure accompanying spontaneous breaking of the translational symmetry — in the Kagome-triangular plane. On the basis of the spin-wave theory, we analyze spin-wave excitations of the planar Kagome-triangular spin system, where the geometric phase characteristic to the cuboc spin structure emerges. We further investigate spin-wave excitations and dynamical spin structure factors for the coupled spin tubes, assuming the staggered cuboc order.

  11. Gapped Spin-1/2 Spinon Excitations in a New Kagome Quantum Spin Liquid Compound Cu3Zn(OH)6FBr (United States)

    Feng, Zili; Li, Zheng; Meng, Xin; Yi, Wei; Wei, Yuan; Zhang, Jun; Wang, Yan-Cheng; Jiang, Wei; Liu, Zheng; Li, Shiyan; Liu, Feng; Luo, Jianlin; Li, Shiliang; Zheng, Guo-qing; Meng, Zi Yang; Mei, Jia-Wei; Shi, Youguo


    We report a new kagome quantum spin liquid candidate Cu3Zn(OH)6FBr, which does not experience any phase transition down to 50 mK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (∼200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fractionalization in the fractional quantum Hall state. Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0300502, 2016YFA0300503, 2016YFA0300604, 2016YF0300300 and 2016YFA0300802, the National Natural Science Foundation of China under Grant Nos 11421092, 11474330, 11574359, 11674406, 11374346 and 11674375, the National Basic Research Program of China (973 Program) under Grant No 2015CB921304, the National Thousand-Young-Talents Program of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences under Grant Nos XDB07020000, XDB07020200 and XDB07020300. The work in Utah is supported by DOE-BES under Grant No DE-FG02-04ER46148.

  12. Susceptibility Genes in Thyroid Autoimmunity

    Directory of Open Access Journals (Sweden)

    Yoshiyuki Ban


    Full Text Available The autoimmune thyroid diseases (AITD are complex diseases which are caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility in combination with external factors (e.g. dietary iodine is believed to initiate the autoimmune response to thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITD. Various techniques have been employed to identify the genes contributing to the etiology of AITD, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions that are linked with AITD, and in some of these loci, putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD and Hashimoto's thyroiditis (HT and some are common to both the diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune modifying genes (e.g. HLA, CTLA-4 and thyroid specific genes (e.g. TSHR, Tg. Most likely, these loci interact and their interactions may influence disease phenotype and severity.

  13. Geometric spin echo under zero field (United States)

    Sekiguchi, Yuhei; Komura, Yusuke; Mishima, Shota; Tanaka, Touta; Niikura, Naeko; Kosaka, Hideo


    Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors.

  14. Universal Spin-Momentum Locked Optical Forces

    CERN Document Server

    Kalhor, Farid; Jacob, Zubin


    Evanescent electromagnetic waves possess spin-momentum locking, where the direction of propagation (momentum) is locked to the inherent polarization of the wave (transverse spin). We study the optical forces arising from this universal phenomenon and show that the fundamental origin of recently reported non-trivial optical chiral forces is spin-momentum locking. For evanescent waves, we show that the direction of energy flow, direction of decay, and direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and $HE_{11}$ mode of an optical fiber. Furthermore, we explain how the recently reported phenomena of lateral optical force on chiral and achiral particles is caused by the transverse spin of the evanescent field and the spin-momentum locking phenomenon. Finally, we propose an experiment to identify the unique lateral forces arising from the transverse spin in the optical fiber and point to fundamental differences of the spin density from...

  15. Spin diffusion and torques in disordered antiferromagnets

    KAUST Repository

    Manchon, Aurelien


    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.

  16. Doppler effect induced spin relaxation boom

    National Research Council Canada - National Science Library

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong


    .... We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom...

  17. Spin flipping in rings with Siberian Snakes

    Energy Technology Data Exchange (ETDEWEB)

    Mane, S.R. [Convergent Computing Inc., P.O. Box 561, Shoreham, NY 11786 (United States)], E-mail:


    I display numerical spin tracking simulations for spin flippers in model storage rings with full or nearly full Siberian Snakes. In many cases, the results differ from the predictions using the Froissart-Stora formula.

  18. Magneto-Seebeck effect in spin valves (United States)

    Zhang, X. M.; Wan, C. H.; Wu, H.; Tang, P.; Yuan, Z. H.; Zhang, Q. T.; Zhang, X.; Tao, B. S.; Fang, C.; Han, X. F.


    The magneto-Seebeck (MS) effect, which is also called magneto-thermo-power, was observed in Co/Cu/Co and NiFe/Cu/Co spin valves. Their Seebeck coefficients in the parallel state were larger than those in the antiparallel state, and the MS ratio defined as (SAP -SP)/SP could reach -9% in our case. The MS effect originated not only from trivial giant magnetoresistance but also from spin current generated due to spin-polarized thermoelectric conductivity of ferromagnetic materials and subsequent modulation of the spin current by different spin configurations in spin valves. A simple Mott two-channel model reproduced a -11% MS effect for the Co/Cu/Co spin valves, qualitatively consistent with our observations. The MS effect could be applied for simultaneously sensing the temperature gradient and the magnetic field and also be possibly applied to determine spin polarization of thermoelectric conductivity and the Seebeck coefficient of ferromagnetic thin films.

  19. Line profile analysis and low temperature AC susceptibility of Cu-Zn ferrites (United States)

    Lamani, Ashok. R.; Jayanna, H. S.; Prasanna, G. D.


    The Cu1-xZnxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) samples were prepared using double sintering ceramic method by adding Zn2+ at different concentration. The X-ray line profile analysis were carried out to confirm the spinel phase formation as well as to know the (%) strain in the crystal. The real and imaginary part of a.c. susceptibility measured from77K to room temperature. The high temperature peak corresponds to magnetic blocking of individual particles, while the low temperature peak is attributed to surface spin-glass freezing. To prove the dynamics of the spin (dis)order in both regimes of freezing and blocking, the frequency dependent ac susceptibility is investigated under a biasing dc field. The frequency shift in the "frozen" low-temperature ac susceptibility peak is fitted to a dynamic scaling law which indicates a spin-glass phase. Exchange bias is turned on at low temperature which signifies the existence of a strong core-shell interaction.

  20. Transverse dipole spin modes in quantum dots (United States)

    Lipparini, E.; Barranco, M.; Emperador, A.; Pi, M.; Serra, Ll.


    We have carried out a systematic analysis of the transverse dipole spin response of a large-size quantum dot within time-dependent current density functional theory. Results for magnetic fields corresponding to integer filling factors are reported, as well as a comparison with the longitudinal dipole spin response. As in the two-dimensional electron gas, the spin response at high-spin magnetization is dominated by a low-energy transverse mode.

  1. Spin response of unpolarized quantum dots (United States)

    Serra, L.; Lipparini, E.


    The spin response function for electrons confined in a quantum dot is studied within the time-dependent local spin density approximation (TDLSDA) of density functional theory. In the long-wavelength regime we predict the existence of a low-energy collective dipole (ell = 1) spin mode. The evolution with electron number of the spin response is studied and compared with that of the density response. Predictions for the static dipole polarizability are given.

  2. Spin response formalism in circular accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ptitsyn, V.I. [Brookhaven National Laboratory, Upton, NY 11973 (United States)], E-mail:; Shatunov, Yu.M. [Budker Institute of Nuclear Physics, Novosibirsk, 630090 (Russian Federation); Mane, S.R. [Convergent Computing Inc., P. O. Box 561, Shoreham, NY 11786 (United States)], E-mail:


    We present the principal features of the so-called 'spin response formalism', which is linear response theory applied to the spin dynamics in circular accelerators. The formalism is useful for calculating the resonance strengths of several classes of first-order spin resonances in rings, including those for spin flippers. We describe some of the successful applications of the formalism to various storage rings. We include a brief comparison with other formalisms and indicate topics for future work.

  3. Deformed Fredkin spin chain with extensive entanglement (United States)

    Salberger, Olof; Udagawa, Takuma; Zhang, Zhao; Katsura, Hosho; Klich, Israel; Korepin, Vladimir


    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\

  4. Symmetry enriched U(1) quantum spin liquids


    Zou, Liujun; Wang, Chong; Senthil, T.


    We classify and characterize three dimensional $U(1)$ quantum spin liquids (deconfined $U(1)$ gauge theories) with global symmetries. These spin liquids have an emergent gapless photon and emergent electric/magnetic excitations (which we assume are gapped). We first discuss in great detail the case with time reversal and $SO(3)$ spin rotational symmetries. We find there are 15 distinct such quantum spin liquids based on the properties of bulk excitations. We show how to interpret them as gaug...

  5. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes (United States)

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


    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.

  6. Spin switching in semiconductor quantum dots through spin-orbit coupling (United States)

    Valín-Rodríguez, Manuel; Puente, Antonio; Serra, Llorenç; Lipparini, Enrico


    The spin-orbit coupling influences the total spin of semiconductor quantum dots. We analyze the theoretical prediction for the combined effects of spin-orbit coupling, weak vertical magnetic fields and deformation of the dot. Our results allow the characterization of the quantum dots as the spin switches, controllable with electric gates.

  7. Electronic spin precession in semiconductor quantum dots with spin-orbit coupling (United States)

    Valín-Rodríguez, Manuel; Puente, Antonio; Serra, Llorenç; Lipparini, Enrico


    The electronic spin precession in semiconductor dots is strongly affected by the spin-orbit coupling. We present a theory of the electronic spin resonance at low magnetic fields that predicts a strong dependence on the dot occupation, the magnetic field and the spin-orbit coupling strength. Coulomb interaction effects are also taken into account in a numerical approach.

  8. Spin and energy correlations in the one dimensional spin 1/2 Heisenberg model


    Naef, F.; Zotos, X.


    In this paper, we study the spin and energy dynamic correlations of the one dimensional spin 1/2 Heisenberg model, using mostly exact diagonalization numerical techniques. In particular, observing that the uniform spin and energy currents decay to finite values at long times, we argue for the absence of spin and energy diffusion in the easy plane anisotropic Heisenberg model.

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

    DEFF Research Database (Denmark)

    Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst


    and photons in a nanophotonic waveguide. The spin can be deterministically prepared with a fidelity of 96\\%. Subsequently the system is used to implement a "single-spin photonic switch", where the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may...

  10. Thermal spin pumping and magnon-phonon-mediated spin-Seebeck effect

    NARCIS (Netherlands)

    Uchida, K.; Ota, T.; Adachi, H.; Xiao, J.; Nonaka, T.; Kajiwara, Y.; Bauer, G.E.W.; Maekawa, S.; Saitoh, E.


    The spin-Seebeck effect (SSE) in ferromagnetic metals and insulators has been investigated systematically by means of the inverse spin-Hall effect (ISHE) in paramagnetic metals. The SSE generates a spin voltage as a result of a temperature gradient in a ferromagnet, which injects a spin current into

  11. Spin Echo of a Single Electron Spin in a Quantum Dot

    NARCIS (Netherlands)

    Koppens, F.H.L.; Nowack, K.C.; Vandersypen, L.M.K.


    We report a measurement of the spin-echo decay of a single electron spin confined in a semiconductor quantum dot. When we tip the spin in the transverse plane via a magnetic field burst, it dephases in 37 ns due to the Larmor precession around a random effective field from the nuclear spins in the

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

    Indian Academy of Sciences (India)

    We present the study of spin and charge transport in nanostructures in the presence of spin-orbit (SO) interaction. Single band tight binding Hamiltonians for Elliot–Yafet and Rashba SO interaction are derived. Using these tight binding Hamiltonians and spin resolved Landauer–Büttiker formula, spin and charge transport is ...

  13. 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


    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.

  14. PREFACE: Muon spin rotation, relaxation or resonance (United States)

    Heffner, Robert H.; Nagamine, Kanetada


    ), is currently being built to replace the current Japanese muSR capability at KEK. These muSR institutions provide scientists a variety of sample environments, including a range of temperatures, magnetic fields and applied pressure. In addition, very low-energy muon beams (physics of strongly correlated electrons in solids, one of the most active fields of condensed matter research today. Strong electron correlations arise from (Coulomb) interactions which render Landau's theory of electron transport for weakly interacting systems invalid. Included in this category are unconventional heavy-fermion superconductors, high-temperature copper-oxide superconductors, non-Fermi liquid (NFL) systems and systems with strong electron-lattice-spin coupling, such as the colossal magnetoresistance manganites. Two key properties often make the muon a unique probe of these materials: (1) the muon's large magnetic moment (~3 mup) renders it extremely sensitive to the tiny magnetic fields (~1 Gauss) found, for example, in many NFL systems and in superconductors possessing time-reversal-violating order parameters, and (2) the muon's spin 1/2 creates a simple muSR lineshape (no quadrupolar coupling), ideal for measuring spin-lattice-relaxation, local susceptibilities and magnetic-field distributions in ordered magnets and superconductors. Section II contains studies which exploit the unique sensitivities of muSR just noted to elucidate new and hidden properties of novel magnetic materials, including the use of very low energy muons to study thin films. Sections I and II are concerned with the bare positive muon as a probe of internal magnetic fields in metals. The papers in section III describe studies which exploit the fact that in semiconductors the muon appears as a light isotope of the hydrogen atom, called muonium. These studies provide important new information regarding the electronic structure and motion of light, dilute hydrogen-like impurities in semiconductors, which is useful

  15. Spin-canting and magnetic anisotropy in ultrasmall CoFe2O4 nanoparticles

    DEFF Research Database (Denmark)

    Peddis, Davide; Vasquaz Mansilla, M.; Fiorani, D.


    The magnetic properties of cobalt ferrite nanoparticles dispersed in a silica matrix in samples with different concentrations (5 and 10 wt % CoFe2O4) and same particle size (3 nm) were studied by magnetization, DC and AC susceptibility, and Mossbauer spectroscopy measurements. The results indicate...... that the particles are very weakly interacting. The magnetic properties (saturation magnetization, anisotropy constant, and spin-canting) are discussed in relation to the cation distribution....

  16. Neutron spin-echo on magnetic single crystals in the quantum limit

    Energy Technology Data Exchange (ETDEWEB)

    Blackburn, E. [Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 0319 (United States) and Institut Laue-Langevin, Boite Postale 156, F-38042 Grenoble (France) and European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (Germany)]. E-mail:; Hiess, A. [Institut Laue-Langevin, Boite Postale 156, F-38042 Grenoble (France); Bernhoeft, N. [Departement de la Recherche Fondamentale sur la Matiere Condensee, CEA-Grenoble, F-38054 Grenoble (France); Rheinstaedter, M.C. [Institut Laue-Langevin, Boite Postale 156, F-38042 Grenoble (France); Fouquet, P. [Institut Laue-Langevin, Boite Postale 156, F-38042 Grenoble (France); Lander, G.H. [European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, D-76125 Karlsruhe (Germany)


    As interest in low-temperature physics increases, whether for the study of frustrated magnets or for quantum effects, neutron spin-echo will become increasingly important, because of the high-energy resolution achievable. The behaviour of quasielastic scattering for low temperatures relative to the energy scale of interest is investigated. In addition, we note that momentum-transfer selective magnetic scattering may be susceptible to parasitic echoes in certain experimental configurations.

  17. High spin properties of Ba

    Indian Academy of Sciences (India)

    Abstract. The 124Ba nucleus is investigated on the basis of the method of statistical mechanics by assuming the nucleons to move in triaxially deformed Nilsson potential. The variation in the Fermi energies of protons and neutrons is studied as a function of spin and temperature. The Fermi energies determined as a function ...

  18. Interfering with the neutron spin

    Indian Academy of Sciences (India)

    Permanent link: Keywords. Neutron interferometry; spinor; Pauli anticommutation; geometic phase; non-cyclic evolution; Pancharatnam connection; neutron polarimetry. Abstract. Charge neutrality, a spin 1 2 and an associated magnetic moment of the neutron make ...

  19. 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, ...

  20. Spin-crossover coordination nanoparticles. (United States)

    Volatron, Florence; Catala, Laure; Rivière, Eric; Gloter, Alexandre; Stéphan, Odile; Mallah, Talal


    Spin-crossover coordination nanoparticles of the cyanide-bridged three-dimensional network Fe(pyrazine){Pt(CN) 4} were prepared at three different sizes using a microemulsion. The 14 nm particles present a transition centered around 265 K with a hysteresis of 6 K.

  1. Transverse Spin Results From PHENIX

    CERN Document Server

    Wei, Feng


    The PHENIX experiment at the Relativistic Heavy Ion Collider explores the spin structure of the proton in polarized p+p collisions at center-of-mass energies up to 500 GeV. Tremendous experimental and theoretical progress has been made toward understanding the physics involved with transversely polarized beams or targets in recent years. Not only nucleon structure and parton distribution functions but also QCD dynamics have been studied in various physics processes in high-energy polarized DIS and p+p collisions. In the 2006 and 2008 RHIC runs, the PHENIX experiment took a significant amount of transversely polarized p+p collision data at 200 GeV center-of-mass energy, with an integrated luminosity of 8 $pb^{-1}$ and beam polarizations up to 50%. Single spin asymmetries of different probes have been measured in mid- and forward-rapidities. In this report, we present the latest transverse spin results from the PHENIX experiment and discuss briefly the prospects of future transverse spin physics with the PHENIX...

  2. High-spin nuclear spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diamond, R.M.


    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)

  3. Coupling spin qubits via superconductors

    DEFF Research Database (Denmark)

    Leijnse, Martin; Flensberg, Karsten


    We show how superconductors can be used to couple, initialize, and read out spatially separated spin qubits. When two single-electron quantum dots are tunnel coupled to the same superconductor, the singlet component of the two-electron state partially leaks into the superconductor via crossed...

  4. Inherited susceptibility and radiation exposure

    Energy Technology Data Exchange (ETDEWEB)

    Little, J.B. [Harvard School of Public Health, Boston, MA (United States)


    There is continuing concern that some people in the general population may have genetic makeups that place them at particularly high risk for radiation-induced cancer. The existence of such a susceptible subpopulation would have obvious implications for the estimation of risks of radiation exposure. Although it has been long known that familial aggregations of cancer do sometimes occur, recent evidence suggests that a general genetic predisposition to cancer does not exist; most cancers occur sporadically. On the other hand, nearly 10% of the known Mendelian genetic disorders are associated with cancer. A number of these involve a familial predisposition to cancer, and some are characterized by an enhanced susceptibility to the induction of cancer by various physical and chemical carcinogens, including ionizing radiation. Such increased susceptibility will depend on several factors including the frequency of the susceptibility gene in the population and its penetrance, the strength of the predisposition, and the degree to which the cancer incidence in susceptible individuals may be increased by the carcinogen. It is now known that these cancer-predisposing genes may be responsible not only for rare familial cancer syndromes, but also for a proportion of the common cancers. Although the currently known disorders can account for only a small fraction of all cancers, they serve as models for genetic predisposition to carcinogen-induced cancer in the general population. In the present report, the author describes current knowledge of those specific disorders that are associated with an enhanced predisposition to radiation-induced cancer, and discusses how this knowledge may bear on the susceptibility to radiation-induced cancer in the general population and estimates of the risk of radiation exposure.

  5. Evidence for spin-phonon coupling

    Indian Academy of Sciences (India)

    We attribute this anomalous softening to the spin-phonon coupling caused by phonon modulation of the superexchange integral be- tween the Mn3+ spins. The effective charge of oxygen (ZO) calculated using the measured. LO–TO splitting increases below TN. Keywords. Spin-phonon coupling; longitudinal and transverse ...

  6. Two spinning ways for precession dynamo. (United States)

    Cappanera, L; Guermond, J-L; Léorat, J; Nore, C


    It is numerically demonstrated by means of a magnetohydrodynamic code that precession can trigger dynamo action in a cylindrical container. Fixing the angle between the spin and the precession axis to be 1/2π, two limit configurations of the spinning axis are explored: either the symmetry axis of the cylinder is parallel to the spin axis (this configuration is henceforth referred to as the axial spin case), or it is perpendicular to the spin axis (this configuration is referred to as the equatorial spin case). In both cases, the centro-symmetry of the flow breaks when the kinetic Reynolds number increases. Equatorial spinning is found to be more efficient in breaking the centro-symmetry of the flow. In both cases, the average flow in the reference frame of the mantle converges to a counter-rotation with respect to the spin axis as the Reynolds number grows. We find a scaling law for the average kinetic energy in term of the Reynolds number in the axial spin case. In the equatorial spin case, the unsteady asymmetric flow is shown to be capable of sustaining dynamo action in the linear and nonlinear regimes. The magnetic field is mainly dipolar in the equatorial spin case, while it is is mainly quadrupolar in the axial spin case.

  7. Simple classical approach to spin resonance phenomena

    DEFF Research Database (Denmark)

    Gordon, R A


    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...

  8. Observation of the spin Seebeck effect. (United States)

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


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

  9. Topological Order in Spin Liquids with Chirality


    Scharfenberger, Burkhard


    We use the Kalmeyer-Laughlin Chiral Spin Liquid as building block to construct a hierarchy of higher-spin spin liquids and determine numerically their topological properties. We compute the entanglement spectra of some of these liquids as well as of ground states of critically frustrated quantum magnets. From the comparison, we find preliminary evidence for a topological phase transition in these systems.

  10. Spin resonance strengths for radiative polarization and vertical momentum recoils using the spin response formalism

    Energy Technology Data Exchange (ETDEWEB)

    Mane, S.R. [Convergent Computing Inc., P.O. Box 561, Shoreham, NY 11786 (United States)], E-mail:


    The radiative polarization of electrons and positrons in storage rings includes spin resonances driven by vertical momentum recoils due to spin flip photon emissions. This is in addition to the spin resonances driven by longitudinal momentum recoils. The underlying physics for the vertical momentum recoils is similar to the perturbations induced by a radial field (rf) dipole spin flipper. This paper derives the spin resonance strengths driven by the vertical momentum recoils using known techniques for spin flippers, such as the spin response formalism.

  11. An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled System

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, Andrei


    Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constant (the ReD model), and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions, and is generated by operators whose wavevector depends on the coupling strength. It renders the spin lifetime infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We obtain the spin fluctuation dynamics at, and away, from the symmetry point, and suggest experiments to observe the PSH.

  12. An Exact SU(2) Symmetry and Persistent Spin Helix ina Spin-orbit Coupled System

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.A.; /Stanford U., Phys. Dept. /Santa Barbara, KITP; Orenstein, J.; /LBL, Berkeley /UC, Berkeley; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.


    Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constant (the ReD model), and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions, and is generated by operators whose wavevector depends on the coupling strength. It renders the spin lifetime infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We obtain the spin fluctuation dynamics at, and away, from the symmetry point, and suggest experiments to observe the PSH.

  13. pitting corrosion susceptibility pitting corrosion susceptibility of aisi ...

    African Journals Online (AJOL)


    Abstract. The susceptibility of austenitic (AISI 301) stainless steel to pitting corrosion was evaluated in sodium chloride. (NaCl) solutions ... AISI 301 steel suffers from pitting corrosion in all the investigated solutions. AISI 301 steel suffers from ..... [1] Ijeomah, M.N.C. Elements of Corrosion and Protection. Theory, Auto Century ...

  14. Magnetic Susceptability Measurements in Superconductors (United States)

    Kim, Jason; Mallory, Kendall; Seim, Ryan


    A new undergraduate research facility in magnetic susceptability measurements on superconductors is being developed at the University of Northern Colorado. Initial data measurements of the magnetic susceptability of various superconductors will be presented. These measurements were obtained with a liquid helium/nitrogen dewar that was reassembled for use in this project. The cryostat consists of two separate dewars, the first of which contains liquid nitrogen, the second, liquid helium. The liquid nitrogen dewar is used to keep the helium bath from evaporating off too quickly. Data on the evaporation rates of the two liquids will also be presented.

  15. Ultra-cold fermions in the flatland: evolution from BCS to Bose superfluidity in two-dimensions with spin-orbit and Zeeman fields (United States)

    Han, Li; Sa de Melo, Carlos


    We discuss the evolution from BCS to Bose superfluidity for ultracold fermions in two-dimensions and in the presence of simultaneous spin-orbit and Zeeman fields. We analyze several thermodynamic properties to characterize different superfluid phases including pressure, compressibility, induced polarization, and spin susceptibility. Furthermore, we compute the momentum distribution and construct topological invariants for each of the superfluid phases. We thank ARO (Contract No. W911NF-09-1-0220) for support.

  16. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover


    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.

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

    DEFF Research Database (Denmark)

    Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst


    Access to the electron spin is at the heart of many protocols for integrated and distributed quantum-information processing [1-4]. For instance, interfacing the spin-state of an electron and a photon can be utilized to perform quantum gates between photons [2,5] or to entangle remote spin states [6......-9]. Ultimately, a quantum network of entangled spins constitutes a new paradigm in quantum optics [1]. Towards this goal, an integrated spin-photon interface would be a major leap forward. Here we demonstrate an efficient and optically programmable interface between the spin of an electron in a quantum dot...... and photons in a nanophotonic waveguide. The spin can be deterministically prepared with a fidelity of 96\\%. Subsequently the system is used to implement a "single-spin photonic switch", where the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may...

  18. Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque (United States)

    Zhang, G. P.; Bai, Y. H.; George, Thomas F.


    Faster magnetic recording technology is indispensable to massive data storage and big data sciences. All-optical spin switching offers a possible solution, but at present it is limited to a handful of expensive and complex rare-earth ferrimagnets. The spin switching in more abundant ferromagnets may significantly expand the scope of all-optical spin switching. Here by studying 40000 ferromagnetic spins, we show that it is the optical spin-orbit torque that determines the course of spin switching in both ferromagnets and ferrimagnets. Spin switching occurs only if the effective spin angular momentum of each constituent in an alloy exceeds a critical value. Because of the strong exchange coupling, the spin switches much faster in ferromagnets than weakly coupled ferrimagnets. This establishes a paradigm for all-optical spin switching. The resultant magnetic field (65 T) is so big that it will significantly reduce high current in spintronics, thus representing the beginning of photospintronics.

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

    Energy Technology Data Exchange (ETDEWEB)

    Stejskal, Ondřej [Nanotechnology Centre and IT4Innovations, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Hamrle, Jaroslav [Nanotechnology Centre and IT4Innovations, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Institute of Physics, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Pištora, Jaromír [Nanotechnology Centre and IT4Innovations, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Otani, Yoshichika [Center of Emergent Matter Science, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Institute for Solid State Physics, University of Tokyo, Kashiwa-shi, Chiba 277-8581 (Japan)


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

  20. Simulating spin dynamics with spin-dependent cross sections in heavy-ion collisions (United States)

    Xia, Yin; Xu, Jun; Li, Bao-An; Shen, Wen-Qing


    We have incorporated the spin-dependent nucleon-nucleon cross sections into a Boltzmann-Uehling-Uhlenbeck transport model for the first time, using the spin-singlet and spin-triplet nucleon-nucleon elastic scattering cross sections extracted from the phase-shift analyses of nucleon-nucleon scatterings in free space. We found that the spin splitting of the collective flows is not affected by the spin-dependent cross sections, justifying it as a good probe of the in-medium nuclear spin-orbit interaction. With the in-medium nuclear spin-orbit mean-field potential that leads to local spin polarization, we found that the spin-averaged observables, such as elliptic flows of free nucleons and light clusters, becomes smaller with the spin-dependent differential nucleon-nucleon scattering cross sections.

  1. Extremal higher spin black holes

    Energy Technology Data Exchange (ETDEWEB)

    Bañados, Máximo [Instituto de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago (Chile); Castro, Alejandra [Institute for Theoretical Physics, University of Amsterdam,Science Park 904, Postbus 94485, Amsterdam, 1090 GL (Netherlands); Faraggi, Alberto [Instituto de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago (Chile); Jottar, Juan I. [Institut für Theoretische Physik, ETH Zürich,Zürich, CH-8093 (Switzerland)


    The gauge sector of three-dimensional higher spin gravities can be formulated as a Chern-Simons theory. In this context, a higher spin black hole corresponds to a flat connection with suitable holonomy (smoothness) conditions which are consistent with the properties of a generalized thermal ensemble. Building on these ideas, we discuss a definition of black hole extremality which is appropriate to the topological character of 3d higher spin theories. Our definition can be phrased in terms of the Jordan class of the holonomy around a non-contractible (angular) cycle, and we show that it is compatible with the zero-temperature limit of smooth black hole solutions. While this notion of extremality does not require supersymmetry, we exemplify its consequences in the context of sl(3|2)⊕sl(3|2) Chern-Simons theory and show that, as usual, not all extremal solutions preserve supersymmetries. Remarkably, we find in addition that the higher spin setup allows for non-extremal supersymmetric black hole solutions. Furthermore, we discuss our results from the perspective of the holographic duality between sl(3|2)⊕sl(3|2) Chern-Simons theory and two-dimensional CFTs with W{sub (3|2)} symmetry, the simplest higher spin extension of the N=2 super-Virasoro algebra. In particular, we compute W{sub (3|2)} BPS bounds at the full quantum level, and relate their semiclassical limit to extremal black hole or conical defect solutions in the 3d bulk. Along the way, we discuss the role of the spectral flow automorphism and provide a conjecture for the form of the semiclassical BPS bounds in general N=2 two-dimensional CFTs with extended symmetry algebras.

  2. Magnetic properties of alternating spin-1/2 chain compound AgVOAsO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Nath, Ramesh [School of Physics, IISER, Thiruvananthapuram-695016 Kerala (India); Tsirlin, Alexander; Khuntia, Panchanana; Baenitz, Michael; Geibel, Christoph; Rosner, Helge [MPI-CPFS, 01187 Dresden (Germany); Skourski, Yurii [HLD, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany)


    We investigate the magnetic properties of a one-dimensional (1D) spin-1/2 alternating chain compound AgVOAsO{sub 4} via magnetic susceptibility, high-field magnetization, and {sup 75}As NMR measurements. Temperature dependence of the magnetic susceptibility ({chi}(T)) and NMR shift (K(T)) were fitted well by the expression for the 1D spin-1/2 alternating chain. The exchange couplings along the chain are estimated to be J {approx_equal} 40 K and J' {approx_equal} 25 K, with a spin gap {Delta} {approx_equal} 13 K. The high-field magnetization measurement at 1.4 K confirms the ground state to be a non-magnetic singlet, and reveals the critical field H{sub c} {approx_equal} 10 T of the gap closing and a saturation field {mu}{sub 0}H{sub s} {approx_equal} 48.5 T. These values are largely consistent with the estimated {Delta} and (J, J') values based on the fit of {chi}(T) and K(T). The {sup 75}As spin-lattice relaxation rate (1/T{sub 1}) follows an activated behavior at low temperatures giving rise to the same {Delta} value. Our experimental investigations are supported by band structure calculations that additionally reveal weak and frustrated interchain couplings, thus making this compound a promising candidate for Bose-Einstein condensation of magnons in high magnetic fields.

  3. Spin glass behavior in frustrated quantum spin system CuAl2O4 with a possible orbital liquid state. (United States)

    Nirmala, R; Jang, Kwang-Hyun; Sim, Hasung; Cho, Hwanbeom; Lee, Junghwan; Yang, Nam-Geun; Lee, Seongsu; Ibberson, R M; Kakurai, K; Matsuda, M; Cheong, S-W; Gapontsev, V V; Streltsov, S V; Park, Je-Geun


    CuAl2O4 is a normal spinel oxide having quantum spin, S  =  1/2 for Cu2+. It is a rather unique feature that the Cu2+ ions of CuAl2O4 sit at a tetrahedral position, not like the usual octahedral position for many oxides. At low temperatures, it exhibits all the thermodynamic evidence of a quantum spin glass. For example, the polycrystalline CuAl2O4 shows a cusp centered at ~2 K in the low-field dc magnetization data and a clear frequency dependence in the ac magnetic susceptibility while it displays logarithmic relaxation behavior in a time dependence of the magnetization. At the same time, there is a peak at ~2.3 K in the heat capacity, which shifts towards a higher temperature with magnetic fields. On the other hand, there is no evidence of new superlattice peaks in the high-resolution neutron powder diffraction data when cooled from 40 to 0.4 K. This implies that there is no long-ranged magnetic order down to 0.4 K, thus confirming a spin glass-like ground state for CuAl2O4. Interestingly, there is no sign of structural distortion either although Cu2+ is a Jahn-Teller active ion. Thus, we claim that an orbital liquid state is the most likely ground state in CuAl2O4. Of further interest, it also exhibits a large frustration parameter, f  =  |θ CW/T m| ~ 67, one of the largest values reported for spinel oxides. Our observations suggest that CuAl2O4 should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state.

  4. Spinnability Investigation of High Strength Steel in Draw-spinning and Flow-spinning (United States)

    Shi, L.; Xiao, H.; Xu, D. K.


    High strength steels are difficult to process in spinning due to their high yield and tensile strength, poor ductility and large springback. In this paper, formability of dual phase steel has been investigated on the basis of spinnability evaluation in draw-spinning and flow-spinning processes. The influences of key process parameters such as feed ratio and wheel fillet radius on forming limit coefficient in draw-spinning and maximum thinning ratio in flow-spinning are studied in detail.

  5. Experimental Verification of Comparability between Spin-Orbit and Spin-Diffusion Lengths


    Niimi, Yasuhiro; Wei, Dahai; Idzuchi, Hiroshi; Wakamura, Taro; Kato, Takeo; Otani, YoshiChika


    We experimentally confirmed that the spin-orbit lengths of noble metals obtained from weak anti-localization measurements are comparable to the spin diffusion lengths determined from lateral spin valve ones. Even for metals with strong spin-orbit interactions such as Pt, we verified that the two methods gave comparable values which were much larger than those obtained from recent spin torque ferromagnetic resonance measurements. To give a further evidence for the comparability between the two...

  6. Spin, Isospin and Strong Interaction Dynamics

    Directory of Open Access Journals (Sweden)

    Comay E.


    Full Text Available The structure of spin and isospin is analyzed. Although both spin and isospin are related to the same SU(2 group, they represent different dynamical effects. The Wigner-Racah algebra is used for providing a description of bound states of several Dirac particles in general and of the proton state in particular. Isospin states of the four ∆ (1232 baryons are discussed. The work explains the small contribution of quarks spin to the overall proton spin (the proton spin crisis. It is also proved that the addition of QCD’s color is not required for a construction of an antisymmetric state for the ∆ ++ (1232 baryon.

  7. Scalar scattering via conformal higher spin exchange

    Energy Technology Data Exchange (ETDEWEB)

    Joung, Euihun [School of Physics and Astronomy,Seoul National University, Seoul 151-747 (Korea, Republic of); Gauge, Gravity & Strings, Center for Theoretical Physics of the Universe,Institute for Basic Sciences, Daejeon 34047 (Korea, Republic of); Nakach, Simon; Tseytlin, Arkady A. [Theoretical physics group, Blackett Laboratory,Imperial College London, SW7 2AZ (United Kingdom)


    Theories containing infinite number of higher spin fields require a particular definition of summation over spins consistent with their underlying symmetries. We consider a model of massless scalars interacting (via bilinear conserved currents) with conformal higher spin fields in flat space. We compute the tree-level four-scalar scattering amplitude using a natural prescription for summation over an infinite set of conformal higher spin exchanges and find that it vanishes. Independently, we show that the vanishing of the scalar scattering amplitude is, in fact, implied by the global conformal higher spin symmetry of this model. We also discuss one-loop corrections to the four-scalar scattering amplitude.

  8. Topological susceptibility from the overlap

    DEFF Research Database (Denmark)

    Del Debbio, Luigi; Pica, Claudio


    The chiral symmetry at finite lattice spacing of Ginsparg-Wilson fermionic actions constrains the renormalization of the lattice operators; in particular, the topological susceptibility does not require any renormalization, when using a fermionic estimator to define the topological charge. Theref...

  9. Quantum Spin Lenses in Atomic Arrays

    Directory of Open Access Journals (Sweden)

    A. W. Glaetzle


    Full Text Available We propose and discuss quantum spin lenses, where quantum states of delocalized spin excitations in an atomic medium are focused in space in a coherent quantum process down to (essentially single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D, and 3D, and with strings of trapped ions. We discuss both linear and nonlinear quantum spin lenses: in a nonlinear lens, repulsive spin-spin interactions lead to focusing dynamics conditional to the number of spin excitations. This allows the mapping of quantum superpositions of delocalized spin excitations to superpositions of spatial spin patterns, which can be addressed by light fields and manipulated. Finally, we propose multifocal quantum spin lenses as a way to generate and distribute entanglement between distant atoms in an atomic lattice array.

  10. Domain wall fringe field coupled spin logic

    Directory of Open Access Journals (Sweden)

    Yu-Ming Hung


    Full Text Available A class of spin logic devices based on the spin-orbit induced spin-transfer torques requires magnetic coupling between electrically isolated ferromagnetic elements. Here we use micromagnetic modeling to study the magnetic coupling induced by fringe fields from chiral domain walls in perpendicularly magnetized nanowires. These domains can be displaced using spin-orbit torques from a proximal heavy metal layer. For a 16 nm width wire that is 1 nm thick, we find that spin-orbit torques induced domain wall propagation can reliably switch a proximal 16 nm diameter 1 nm thick nanomagnet. These results show a promising means of implementing spin logic with spin-orbit torques using elements with perpendicular magnetization, which does not require an applied magnetic field.

  11. Charge and spin transport in mesoscopic superconductors

    Directory of Open Access Journals (Sweden)

    M. J. Wolf


    Full Text Available Background: Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin.Results: We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models.Conclusion: The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures.

  12. Magnetic susceptibility of the Kagome antiferromagnet ZnCu3(OH)6Cl2. (United States)

    Rigol, Marcos; Singh, Rajiv R P


    We analyze the experimental data for the magnetic susceptibility of the material ZnCu3(OH)6Cl2 in terms of the Kagome Lattice Heisenberg model (KLHM), discussing possible role of impurity spins, dilution, exchange anisotropy, and both out-of-plane and in-plane Dzyloshinski-Moriya (DM) anisotropies, with explicit theoretical calculations using the numerical linked cluster method and exact diagonalization. The high-temperature experimental data are well described by the pure Heisenberg model with J=170 K. We show that the sudden upturn in the susceptibility around T=75 K is due to DM interactions. We also observe that at intermediate temperatures, below T=J, our calculated susceptibility for KLHM fits well with a power law T(-0.25).

  13. Spin liquid ground state in the frustrated S = 1/2 square lattice compound PbVO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Tsirlin, A. [MPI CPfS, Dresden (Germany); Dept. of Chemistry, MSU (Russian Federation); Shpanchenko, R.; Antipov, E. [Dept. of Chemistry, MSU (Russian Federation); Belik, A.; Takayama-Muromachi, E. [NIMS, Tsukuba (Japan); Rosner, H. [MPI CPfS, Dresden (Germany)


    The S=1/2 square lattice is known to be one of the simplest models of low-dimensional spin systems depicting the magnetic properties of many transition metal compounds like La{sub 2}CuO{sub 4}. If one considers nearest-neighbor (NN) interactions only, long-range spin order is established in the square lattice. Nevertheless, taking into account next-nearest neighbor (NNN) interactions may result in strong frustration of the spin system and give rise to unusual collinear magnetic order or spin liquid ground states. Here, we present a joint experimental and computational study of a novel layered vanadium oxide PbVO{sub 3} realizing a square lattice of magnetic V{sup +4} atoms. Our results show that in PbVO{sub 3} antiferromagnetic NN (J{sub 1}) as well as NNN (J{sub 2}) interactions are present. The J{sub 2}/J{sub 1} ratio is about 0.3 corresponding to a boundary between AFM ordered and spin liquid ground states. This conclusion is in a perfect agreement with magnetic susceptibility and specific heat measurements showing no sign of long-range spin order down to 2 K. PbVO{sub 3} is likely to be the first system showing spin liquid ground state for the frustrated S=1/2 square lattice. (orig.)

  14. High spin isomer beam line at RIKEN

    Energy Technology Data Exchange (ETDEWEB)

    Kishida, T.; Ideguchi, E.; Wu, H.Y. [Institute of Physical and Chemical Research, Saitama (Japan)] [and others


    Nuclear high spin states have been the subject of extensive experimental and theoretical studies. For the production of high spin states, fusion reactions are usually used. The orbital angular momentum brought in the reaction is changed into the nuclear spin of the compound nucleus. However, the maximum induced angular momentum is limited in this mechanism by the maximum impact parameter of the fusion reaction and by the competition with fission reactions. It is, therefore, difficult to populate very high spin states, and as a result, large {gamma}-detector arrays have been developed in order to detect subtle signals from such very high spin states. The use of high spin isomers in the fusion reactions can break this limitation because the high spin isomers have their intrinsic angular momentum, which can bring the additional angular momentum without increasing the excitation energy. There are two methods to use the high spin isomers for secondary reactions: the use of the high spin isomers as a target and that as a beam. A high spin isomer target has already been developed and used for several experiments. But this method has an inevitable shortcoming that only {open_quotes}long-lived{close_quotes} isomers can be used for a target: {sup 178}Hf{sup m2} (16{sup +}) with a half-life of 31 years in the present case. By developing a high spin isomer beam, the authors can utilize various short-lived isomers with a short half-life around 1 {mu}s. The high spin isomer beam line of RIKEN Accelerator Facility is a unique apparatus in the world which provides a high spin isomer as a secondary beam. The combination of fusion-evaporation reaction and inverse kinematics are used to produce high spin isomer beams; in particular, the adoption of `inverse kinematics` is essential to use short-lived isomers as a beam.

  15. Strontium Oxide Tunnel Barriers for High Quality Spin Transport and Large Spin Accumulation in Graphene. (United States)

    Singh, Simranjeet; Katoch, Jyoti; Zhu, Tiancong; Wu, Ryan J; Ahmed, Adam S; Amamou, Walid; Wang, Dongying; Mkhoyan, K Andre; Kawakami, Roland K


    The quality of the tunnel barrier at the ferromagnet/graphene interface plays a pivotal role in graphene spin valves by circumventing the impedance mismatch problem, decreasing interfacial spin dephasing mechanisms and decreasing spin absorption back into the ferromagnet. It is thus crucial to integrate superior tunnel barriers to enhance spin transport and spin accumulation in graphene. Here, we employ a novel tunnel barrier, strontium oxide (SrO), onto graphene to realize high quality spin transport as evidenced by room-temperature spin relaxation times exceeding a nanosecond in graphene on silicon dioxide substrates. Furthermore, the smooth and pinhole-free SrO tunnel barrier grown by molecular beam epitaxy (MBE), which can withstand large charge injection current densities, allows us to experimentally realize large spin accumulation in graphene at room temperature. This work puts graphene on the path to achieve efficient manipulation of nanomagnet magnetization using spin currents in graphene for logic and memory applications.

  16. Spin chains and string theory. (United States)

    Kruczenski, Martin


    Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit.

  17. Oscillating spin-2 dark matter (United States)

    Marzola, Luca; Raidal, Martti; Urban, Federico R.


    The negative outcomes of laboratory searches, juxtaposed with cosmological observations, may indicate that dark matter has a gravitational origin. We show that coherent oscillations of a massive spin-2 field emerging from bimetric theory can easily account for the observed dark matter abundance. The framework, based on the only known consistent extension of general relativity to interacting spin-2 fields, is testable in precision measurements of the electric charge variation by means of atomic clocks, molecular systems, dedicated resonant mass detectors, as well as gravity interferometers and axionlike-particle experiments. These searches, therefore, provide a new window into the phenomenology of gravity which complements the results of dedicated tests of gravitation. We also present a multimetric extension of the scenario that straightforwardly implements the clockwork mechanism for gravity, explaining the apparent weakness of this force.

  18. Transition from spin accumulation into interface states to spin injection in silicon and germanium conduction bands (United States)

    Jain, Abhinav; Rojas-Sanchez, Juan-Carlos; Cubukcu, Murat; Peiro, Julian; Le Breton, Jean-Christophe; Vergnaud, Céline; Augendre, Emmanuel; Vila, Laurent; Attané, Jean-Philippe; Gambarelli, Serge; Jaffrès, Henri; George, Jean-Marie; Jamet, Matthieu


    Electrical spin injection into semiconductors paves the way for exploring new phenomena in the area of spin physics and new generations of spintronic devices. However the exact role of interface states in the electrical spin injection mechanism from a magnetic tunnel junction into a semiconductor is still under debate. Here we demonstrate a clear transition from spin accumulation into interface states to spin injection in the conduction band of n-Si and n-Ge using a CoFeB/MgO tunnel contact. We observe spin signal amplification at low temperature due to spin accumulation into interface states followed by a clear transition towards spin injection in the conduction band from approximately 150 K up to room temperature. In this regime, the spin signal is reduced down to a value compatible with the standard spin diffusion model. More interestingly, in the case of germanium, we demonstrate a significant modulation of the spin signal by applying a back-gate voltage to the conduction channel. We also observe the inverse spin Hall effect in Ge by spin pumping from the CoFeB electrode. Both observations are consistent with spin accumulation in the Ge conduction band.

  19. Spin precession and spin Hall effect in monolayer graphene/Pt nanostructures (United States)

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


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

  20. Spin current swapping and Hanle spin Hall effect in a two-dimensional electron gas (United States)

    Shen, Ka; Raimondi, R.; Vignale, G.


    We analyze the effect known as "spin current swapping" (SCS) due to electron-impurity scattering in a uniform spin-polarized two-dimensional electron gas. In this effect a primary spin current Jia (lower index for spatial direction, upper index for spin direction) generates a secondary spin current Jai if i ≠a , or Jjj, with j ≠i , if i =a . Contrary to naive expectation, the homogeneous spin current associated with the uniform drift of the spin polarization in the electron gas does not generate a swapped spin current by the SCS mechanism. Nevertheless, a swapped spin current will be generated, if a magnetic field is present, by a completely different mechanism, namely, the precession of the spin Hall spin current in the magnetic field. We refer to this second mechanism as Hanle spin Hall effect, and we notice that it can be observed in an experiment in which a homogeneous drift current is passed through a uniformly magnetized electron gas. In contrast to this, we show that an unambiguous observation of SCS requires inhomogeneous spin currents, such as those that are associated with spin diffusion in a metal, and no magnetic field. An experimental setup for the observation of the SCS is therefore proposed.

  1. Snell's Law for Spin Waves


    Stigloher, Johannes; Decker, Martin; Körner, Helmut S.; TANABE, Kenji; Moriyama, Takahiro; Taniguchi, Takuya; Hata, Hiroshi; Madami, Marco; Gubbiotti, Gianluca; Kobayashi, Kensuke; Ono, Teruo; Back, Christian H.


    We report the experimental observation of Snell's law for magneto-static 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 relation. Since the dispersion relation for magneto-static 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\\textdegree{} with resp...

  2. Demand Response Spinning Reserve Demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Eto, Joseph H.; Nelson-Hoffman, Janine; Torres, Carlos; Hirth,Scott; Yinger, Bob; Kueck, John; Kirby, Brendan; Bernier, Clark; Wright,Roger; Barat, A.; Watson, David S.


    The Demand Response Spinning Reserve project is a pioneeringdemonstration of how existing utility load-management assets can providean important electricity system reliability resource known as spinningreserve. Using aggregated demand-side resources to provide spinningreserve will give grid operators at the California Independent SystemOperator (CAISO) and Southern California Edison (SCE) a powerful, newtool to improve system reliability, prevent rolling blackouts, and lowersystem operating costs.

  3. Neutralino spin measurement with ATLAS

    CERN Document Server

    Ventura, A; Borjanovic, I; Carlino, G; Chiodini, G; Conventi, F; Gorini, E; Grancagnolo, S; Migliaccio, A; Musto, E; Primavera, M; Spagnolo, S; Villella, I


    One of the goals of the ATLAS experiment at the CERN Large Hadron Collider is to search for evidence of Supersymmetry (SUSY) signals. If SUSY would be discovered, it will be fundamental to measure the spin of the new particles in order to prove that they are indeed supersymmetric partners. Left squark cascade decay to second lightest neutralino which further decays to slepton can represent a good opportunity for SUSY particles' spin measurement. Assuming the neutralino spin to be 1/2, the invariant mass distributions of some detectable final products of the reactions have to be charge asymmetric. In the present work the detectability of this charge asymmetry is analysed in the stau-coannihilation region and in the bulk region of the minimal Supergravity parameter space allowed by the latest experimental constraints. The criteria used to isolate the decay chain of interest and to reject the background, coming from both Standard Model and different SUSY decay channels, are described as obtained by suitable opti...

  4. Transverse spin effects at COMPASS

    CERN Document Server

    Pesaro, G


    The COMPASS experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and on hadron spectroscopy, using both muon and hadron beams. One of the main objectives for the spin program with the muon beam is the measurement of transverse spin effects in semi inclusive deep inelastic scattering. A longitudinally polarized 160 GeV/c muon beam is impinging on a transversely polarized target: from 2002 to 2004 a $^{6}$LiD (deuteron) target has been used, while during 2007 data taking a NH$_{3}$ (proton) target was put in place. All measured transverse asymmetries on deuteron have been found to be small, and compatible with zero, within the few percent statistical errors. These results, which are currently used as input for global fits, can be interpreted as cancellation between u and d quark contribution in the deuteron. The first results for the Collins and Sivers asymmetries for charged hadrons from the 2007 proton COMPASS data are also presented and discussed.

  5. 3D Spin-Liquid State in an Organic Hyperkagome Lattice of Mott Dimers (United States)

    Mizuno, Asato; Shuku, Yoshiaki; Matsushita, Michio M.; Tsuchiizu, Masahisa; Hara, Yuuki; Wada, Nobuo; Shimizu, Yasuhiro; Awaga, Kunio


    We report the first 3D spin liquid state of isotropic organic spins. Structural analysis, and magnetic and heat-capacity measurements were carried out for a chiral organic radical salt, (TBA) 1.5[(-)-NDI -Δ ] (TBA denotes tetrabutylammonium and NDI denotes naphthalene diimide), in which (-)-NDI -Δ forms a K4 structure due to its triangular molecular structure and an intermolecular π -π overlap between the NDI moieties. This lattice was identical to the hyperkagome lattice of S =1 /2 Mott dimers, and should exhibit 3D spin frustration. In fact, even though the high-temperature magnetic susceptibility followed the Curie-Weiss law with a negative Weiss constant of θ =-15 K , the low-temperature magnetic measurements revealed no long-range magnetic ordering down to 70 mK, and suggested the presence of a spin liquid state with a large residual paramagnetism χ0 of 8.5 ×10-6 emu g-1 at the absolute zero temperature. This was supported by the N 14 NMR measurements down to 0.38 K. Further, the low-temperature heat capacities cp down to 68 mK clearly indicated the presence of cp for the spin liquid state, which can be fitted to the power law of T0.62 in the wide temperature range 0.07-4.5 K.

  6. Ground state and magnetic phase transitions of the spin Lieb nanolattice: Monte Carlo simulations (United States)

    Masrour, R.; Jabar, A.


    We study the ground state and magnetic properties of the spin Lieb nanolattice with three lattice sites with spins (S = 2 , σ = 1 / 2 , q = 3 / 2) using Monte Carlo simulations. The ground state phase diagrams of the Lieb nanolattice have been studied. The phase diagrams show some key features: coexistence between regions, points where six, eight and ten states can coexist. The total and partial magnetization of each sublattice is given and the corresponding magnetic susceptibility is also found. The variation of total magnetization with the exchange interaction RSq and Rσq of the Lieb nanolattice with three lattice sites with spins (S , σ , q) has been studied. Moreover, the total magnetization versus the fields Δ /JSσ of the Lieb nanolattice with three lattice sites with spins (S , σ , q) are established for several values of Rσq and Rsq. Magnetic hysteresis cycles of the Lieb nanolattice with three lattice sites with spins (S , σ , q) are found for several values of Rsq and temperature. We show that the superparamagnetism behaviour appears for a weak coupling value between S and q thus around the transition temperature.

  7. Unconventional spin-charge phase separation in a model 2D cuprate (United States)

    Panov, Yu. D.; Budrin, K. S.; Chikov, A. A.; Moskvin, A. S.


    In this Letter we address a challenging problem of a competition of charge and spin orders for high-Tc cuprates within a simplified 2D spin-pseudospin model which takes into account both conventional Heisenberg Cu2+-Cu2+ antiferromagnetic spin exchange coupling (J) and the on-site (U) and inter-site (V) charge correlations in the CuO2 planes with the on-site Hilbert space reduced to only three effective charge states (nominally Cu1+;2+;3+). We performed classical Monte-Carlo calculations for large square lattices implying the mobile doped charges and focusing on a case of a small inter-site repulsion V ≪ J. The on-site attraction (U 0) the homogeneous ground state antiferromagnetic solutions of the doped system found in a mean-field approximation are shown to be unstable with respect to a phase separation with the charge and spin subsystems behaving like immiscible quantum liquids. Puzzlingly, with lowering the temperature one can observe two sequential phase transitions: first, an antiferromagnetic ordering in the spin subsystem diluted by randomly distributed charges, then, a charge condensation in the charge droplets. The effects are illustrated by the Monte-Carlo calculations of the specific heat and longitudinal magnetic susceptibility.

  8. Surface spin-glass in cobalt ferrite nanoparticles dispersed in silica matrix

    Energy Technology Data Exchange (ETDEWEB)

    Zeb, F.; Sarwer, W. [Materials Research Laboratory, Department of Physics, International Islamic University, Islamabad (Pakistan); Nadeem, K., E-mail: [Materials Research Laboratory, Department of Physics, International Islamic University, Islamabad (Pakistan); Kamran, M.; Mumtaz, M. [Materials Research Laboratory, Department of Physics, International Islamic University, Islamabad (Pakistan); Krenn, H. [Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, A-8010 Graz (Austria); Letofsky-Papst, I. [Institute for Electron Microscopy, University of Technology Graz, Steyrergasse 17, A-8010 Graz (Austria)


    Surface effects in cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles dispersed in a silica (SiO{sub 2}) matrix were studied by using AC and DC magnetization. Nanoparticles with different concentration of SiO{sub 2} were synthesized by using sol–gel method. Average crystallite size lies in the range 25–34 nm for different SiO{sub 2} concentration. TEM image showed that particles are spherical and elongated in shape. Nanoparticles with higher concentration of SiO{sub 2} exhibit two peaks in the out-of-phase ac-susceptibility. First peak lies in the high temperature regime and corresponds to average blocking temperature of the nanoparticles. Second peak lies in the low temperature regime and is attributed to surface spin-glass freezing in these nanoparticles. Low temperature peak showed SiO{sub 2} concentration dependence and was vanished for large uncoated nanoparticles. The frequency dependence of the AC-susceptibility of low temperature peak was fitted with dynamic scaling law which ensures the presence of spin-glass behavior. With increasing applied DC field, the low temperature peak showed less shift as compared to blocking peak, broaden, and decreased in magnitude which also signifies its identity as spin-glass peak for smaller nanoparticles. M–H loops showed the presence of more surface disorder in nanoparticles dispersed in 60% SiO{sub 2} matrix. All these measurements revealed that surface effects become strengthen with increasing SiO{sub 2} matrix concentration and surface spins freeze in to spin-glass state at low temperatures. - Highlights: • Surface effects in CoFe{sub 2}O{sub 4} nanoparticles dispersed in a SiO{sub 2} matrix were studied. • Out-of-phase AC-susceptibility exhibits two peaks for SiO{sub 2} coated nanoparticles. • First peak corresponds to average blocking temperature. • Second peak is attributed to surface spin-glass freezing • The spin-glass behavior depends upon the SiO{sub 2} matrix concentration.

  9. Spin-Light Coherence for Single-Spin Measurement and Control in Diamond (United States)

    Buckley, B. B.; Fuchs, G. D.; Bassett, L. C.; Awschalom, D. D.


    The exceptional spin coherence of nitrogen-vacancy centers in diamond motivates their function in emerging quantum technologies. Traditionally, the spin state of individual centers is measured optically and destructively. We demonstrate dispersive, single-spin coupling to light for both nondestructive spin measurement, through the Faraday effect, and coherent spin manipulation, through the optical Stark effect. These interactions can enable the coherent exchange of quantum information between single nitrogen-vacancy spins and light, facilitating coherent measurement, control, and entanglement that is scalable over large distances.

  10. Spin torque on the surface of graphene in the presence of spin orbit splitting

    Directory of Open Access Journals (Sweden)

    Ji Chen


    Full Text Available We study theoretically the spin transfer torque of a ferromagnetic layer coupled to (deposited onto a graphene surface in the presence of the Rashba spin orbit coupling (RSOC. We show that the RSOC induces an effective magnetic field, which will result in the spin precession of conduction electrons. We derive correspondingly the generalized Landau-Lifshitz-Gilbert (LLG equation, which describes the precessional motion of local magnetization under the influence of the spin orbit effect. Our theoretical estimate indicates that the spin orbit spin torque may have significant effect on the magnetization dynamics of the ferromagnetic layer coupled to the graphene surface.

  11. Spin torque on the surface of graphene in the presence of spin orbit splitting (United States)

    Chen, Ji; Jalil, Mansoor Bin Abdul; Tan, Seng Ghee


    We study theoretically the spin transfer torque of a ferromagnetic layer coupled to (deposited onto) a graphene surface in the presence of the Rashba spin orbit coupling (RSOC). We show that the RSOC induces an effective magnetic field, which will result in the spin precession of conduction electrons. We derive correspondingly the generalized Landau-Lifshitz-Gilbert (LLG) equation, which describes the precessional motion of local magnetization under the influence of the spin orbit effect. Our theoretical estimate indicates that the spin orbit spin torque may have significant effect on the magnetization dynamics of the ferromagnetic layer coupled to the graphene surface.

  12. Optical Orientation and Inverse Spin Hall Effect as Effective Tools to Investigate Spin-Dependent Diffusion

    Directory of Open Access Journals (Sweden)

    Marco Finazzi


    Full Text Available In this work we address optical orientation, a process consisting in the excitation of spin polarized electrons across the gap of a semiconductor. We show that the combination of optical orientation with spin-dependent scattering leading to the inverse spin-Hall effect, i.e., to the conversion of a spin current into an electrical signal, represents a powerful tool to generate and detect spin currents in solids. We consider a few examples where these two phenomena together allow addressing the spin-dependent transport properties across homogeneous samples or metal/semiconductor Schottky junctions.

  13. Spin-torque switching of a nano-magnet using giant spin hall effect

    Directory of Open Access Journals (Sweden)

    Ashish V. Penumatcha


    Full Text Available The Giant Spin Hall Effect(GSHE in metals with high spin-orbit coupling is an efficient way to convert charge currents to spin currents, making it well-suited for writing information into magnets in non-volatile magnetic memory as well as spin-logic devices. We demonstrate the switching of an in-plane CoFeB magnet using a combination of GSHE and an external magnetic field. The magnetic field dependence of the critical current is used to estimate the spin hall angle with the help of a thermal activation model for spin-transfer torque switching of a nanomagnet.

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

    DEFF Research Database (Denmark)

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


    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...

  15. Non-Abelian spin liquid in a spin-one quantum magnet. (United States)

    Grover, Tarun; Senthil, T


    We study a time-reversal invariant non-Abelian spin-liquid state in an SU(2) symmetric spin S=1 quantum magnet on a triangular lattice. The spin liquid is obtained by quantum disordering a noncollinear nematic state. We show that such a spin liquid cannot be obtained by the standard projective construction for spin liquids. We also study the phase transition between the spin liquid and the noncollinear nematic state and show that it cannot be described within the Landau-Ginzburg-Wilson paradigm.

  16. High resolution spin- and angle-resolved photoelectron spectroscopy for 3D spin vectorial analysis (United States)

    Okuda, Taichi; Miyamoto, Koji; Kimura, Akio; Namatame, Hirofumi; Taniguchi, Masaki


    Spin- and angle-resolved photoelectron spectroscopy (SARPES) is the excellent tool which can directly observe the band structure of crystals with separating spin-up and -down states. Recent findings of new class of materials possessing strong spin orbit interaction such as Rashba spin splitting systems or topological insulators stimulate to develop new SARPES apparatuses and many sophisticated techniques have been reported recently. Here we report our newly developed a SARPES apparatus for spin vectorial analysis with high precision at Hiroshima Synchrotron Radiation Center. Highly efficient spin polarimeter utilizing very low energy electron diffraction (VLEED) makes high resolution (ΔE Japan Society for the Promotion of Science.

  17. Spin-dependent semiconductor Bloch equations: Microscopic theory of Bir-Aronov-Pikus spin relaxation (United States)

    Lechner, C.; Rössler, U.


    Semiconductor Bloch equations, in their extension including the spin degree of freedom of the carriers, are capable to describe spin dynamics on a microscopic level. In the presence of free holes, electron spins can flip simultaneously with hole spins due to electron-hole exchange interaction. This mechanism named after Bir, Aronov, and Pikus is described here by using the extended semiconductor Bloch equations [Phys. Status Solidi B 234, 385 (2002)] and considering carrier-carrier interaction beyond the Hartree-Fock truncation. As a result we derive microscopic expressions for spin-relaxation and spin-dephasing rates.

  18. Spin-Peierls transition in low-dimensional quantum spin systems: a Green's function approach. (United States)

    Ding, L J; Yao, K L; Fu, H H


    We study the spin-Peierls (SP) transition of one-dimensional chain polymeric complexes coupled to lattice by means of many-body Green's function theory. The chain effective elastic constant is an intrinsic factor that determines the order of SP transition. It is found that the SP transition temperature T(SP) and the susceptibility-maximum temperature T(max) are in agreement with the experimental results. When an external magnetic field is applied to the chain, it makes T(SP) and T(max) decrease, and drives the SP transition from the second order to the first order. Besides, we show that the two-site thermal entanglement entropy is a good indicator of SP transition. Further considering the effect of interchain coupling on SP transition, with weak coupling of double-chain, the theoretical values are closer to the experimental results. We also calculate the density of states and spectral functions, which show that the energy gap vanishes at a critical temperature lower than T(SP), indicating a gapless SP phase lies in the gapped dimerized phase. The interchain coupling can drive the SP transition from the second order to the first order, while the SP dimerization may collapse for large interchain couplings.

  19. Large Spin Hall Angle in Vanadium Film (United States)

    Wang, Tao; Fan, Xin; Wang, Wenrui; Xie, Yunsong; Warsi, Muhammad A.; Wu, Jun; Chen, Yunpeng; Lorenz, Virginia O.; Xiao, John Q.

    We report the large spin Hall angle observed in Vanadium film with small grain size and distorted lattice parameter. The spin Hall angle is quantified by measuring current-induced spin-orbit torque in V/CoFeB bilayer using optical spin torque magnetometer based on polar magneto-optical Kerr effect (MOKE). The spin Hall angle as large as θSH = -0.071 has been observed in V/CoFeB bilayer Structural analysis, using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), confirms films grown at room temperature have very small grain size and enlarged lattice parameter. The Vanadium films with distorted crystal structure also have high resistivity (>200 μΩ cm) and long spin diffusion length (~16.3 nm) measured via spin pumping experiment. This finding of spin Hall effect enhancement in more disordered structure will provide insights for understanding and exploiting materials with strong spin orbit interaction, especially in light 3d transition metals which promise long spin diffusion length.

  20. Reducing Susceptibility to Courtesy Stigma. (United States)

    Bachleda, Catherine L; El Menzhi, Leila


    In light of the chronic shortage of health professionals willing to care for HIV/AIDS patients, and rising epidemics in many Muslim countries, this qualitative study examined susceptibility and resistance to courtesy stigma as experienced by nurses, doctors, and social workers in Morocco. Forty-nine in-depth interviews provided rich insights into the process of courtesy stigma and how it is managed, within the context of interactions with Islam, interactions within the workplace (patients, other health professionals), and interactions outside the workplace (the general public, friends, and family). Theoretically, the findings extend understanding of courtesy stigma and the dirty work literature. The findings also offer practical suggestions for the development of culturally appropriate strategies to reduce susceptibility to courtesy stigmatization. This study represents the first to explore courtesy stigma as a process experienced by health professionals providing HIV/AIDS care in an Islamic country.

  1. Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves. (United States)

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


    Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe/Au/Fe/MgO(001) spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe/Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses. The demonstrated rotation of spin polarization of hot electrons upon interaction with noncollinear magnetization at Au/Fe interfaces holds high potential for future spintronic devices.

  2. Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.M., E-mail: [School of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Pang, M.Q. [School of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Liu, S.Y.; Lei, X.L. [Department of Physics, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)


    The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.

  3. Generation of an external magnetic field with the spin orientation effect in a single layer Ising nanographene (United States)

    Şarlı, Numan


    In this work, the magnetic properties of the single layer Ising nanogaphene (SLING) are investigated by using Kaneyoshi approach (KA) within the effective field theory for different spin orientations of its magnetic atoms. We find that the magnetizations of the SLING has no phase transition, certain Curie temperature and distinct peak of susceptibility at Tc for the some spin orientations at the zero external magnetic field (H=0.0). Because these behaviors occur at H≠0.0, we suggest that the SLING generates an external magnetic field and behaves as an external magnetic field generator for these spin orientations. However, the SLING exhibits ferromagnetic behaviors for only one spin orientations. But, it exhibits antiferromagnetic behaviors for the others. For the AFM cases, diamagnetic susceptibility behaviors and type II superconductivity hysteresis behaviors are obtained. We hope that these results can open a door to obtain new class of single layer graphene and graphene-based magnetic field generator devices with the spin orientation effect.

  4. Antimycotics susceptibility testing of dermatophytes

    Directory of Open Access Journals (Sweden)

    Arsić-Arsenijević Valentina


    Full Text Available Dermatophytes are moulds that produce infections of the skin, hair and nails of humans and animals. The most common forms among these infections are onychomycosis and tinea pedis affecting 20% of world population. These infections are usually chronic. The treatment of dermatophytoses tends to be prolonged partly because available treatments are not very effective. Antifungal drug consumption and public health expenditure are high worldwide, as well as in Serbia. For adequate therapy, it is necessary to prove infection by isolation of dermatophytes and to test the antifungal susceptibility of isolates. Susceptibility testing is important for the resistance monitoring, epidemiological research and to compare in vitro activities of new antifungal agents. The diffusion and dilution methods of susceptibility tests are used, and technical issues of importance for the proper performance and interpretation of test results are published in the document E.DEF 9.1 (EUCAST and M38-A2 (CLSI. The aim of our paper is to promptly inform the public about technical achievements in this area, as well as the new organization of laboratory for medical mycology in our country. The formation of laboratory networks coordinated by the National Reference Laboratory for the cause of mycosis need to enable interlaboratory studies and further standardization of methods for antifungal susceptibility testing of dermatophytes, reproducibility of tests and clinical correlation monitoring (MIK values and clinical outcome of dermatophytosis. The importance of the new organization is expected efficient improvement in the dermatophytosis therapy at home, better quality of patient's life and the reduction of the cost of treatment.

  5. Antibiotic susceptibility of Atopobium vaginae

    Directory of Open Access Journals (Sweden)

    Verschraegen Gerda


    Full Text Available Abstract Background Previous studies have indicated that a recently described anaerobic bacterium, Atopobium vaginae is associated with bacterial vaginosis (BV. Thus far the four isolates of this fastidious micro-organism were found to be highly resistant to metronidazole and susceptible for clindamycin, two antibiotics preferred for the treatment of BV. Methods Nine strains of Atopobium vaginae, four strains of Gardnerella vaginalis, two strains of Lactobacillus iners and one strain each of Bifidobacterium breve, B. longum, L. crispatus, L. gasseri and L. jensenii were tested against 15 antimicrobial agents using the Etest. Results All nine strains of A. vaginae were highly resistant to nalidixic acid and colistin while being inhibited by low concentrations of clindamycin (range: G. vaginalis strains were also susceptible for clindamycin ( 256 μg/ml but susceptible to clindamycin (0.023 – 0.125 μg/ml. Conclusion Clindamycin has higher activity against G. vaginalis and A. vaginae than metronidazole, but not all A. vaginae isolates are metronidazole resistant, as seemed to be a straightforward conclusion from previous studies on a more limited number of strains.

  6. Four-body model study of competition between YN spin-spin and spin-orbit interactions in light hypernuclei

    Energy Technology Data Exchange (ETDEWEB)

    Hiyama, E.; Kamimura, M. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics; Motoba, T. [Lab. of Physics, Osaka E.C. Univ., Neyagawa (Japan); Yamada, T. [Lab. of Physics, Kanto Gakuin Univ., Yokohama (Japan); Yamamoto, Y. [Physics Section, Tsuru Univ., Tsuru Yamanashi (Japan)


    Since YN scattering data are extremely limited, the YN interactions proposed so-far suffer from many ambiguities. Therefore, as a complementary approach, the detailed study of hypernuclear structure should be helpful in elucidating the YN interaction properties. The purpose of this work is to make such a structure study on the basis of a newly developed method of four-body calculation and examine the spin-spin and spin-orbit parts of the YN interaction. (orig.) 8 refs.

  7. Measurements of temperature dependence of 'localized susceptibility'

    CERN Document Server

    Shiozawa, H; Ishii, H; Takayama, Y; Obu, K; Muro, T; Saitoh, Y; Matsuda, T D; Sugawara, H; Sato, H


    The magnetic susceptibility of some rare-earth compounds is estimated by measuring magnetic circular dichroism (MCD) of rare-earth 3d-4f absorption spectra. The temperature dependence of the magnetic susceptibility obtained by the MCD measurement is remarkably different from the bulk susceptibility in most samples, which is attributed to the strong site selectivity of the core MCD measurement.

  8. A Study Of The Internal Energy And Magnetic Spin Susceptibility Of ...

    African Journals Online (AJOL)

    An exact approach is re-visited in performing a comparative analysis of the attractive and repulsive 2-D Hubbard model (AHM and RHM respectively) which is used in describing a simplified 2x1 (Cu-O-Cu) lattice (known to play significant role in HTc-superconductivity in cuprates) with the use of the MATLAB. The response ...

  9. Physical properties of the spin Hamiltonian on honeycomb lattice samples with Kekulé and vacuum polarization corrections (United States)

    Martins, Ricardo Spagnuolo; Konstantinova, Elena; Belich, Humberto; Helayël-Neto, José Abdalla


    Magnetic and thermodynamical properties of a system of spins in a honeycomb lattice, such as magnetization, magnetic susceptibility and specific heat, in a low-temperature regime are investigated by considering the effects of a Kekulé scalar exchange and QED vacuum polarization corrections to the interparticle potential. The spin lattice calculations are carried out by means of Monte Carlo simulations. We present a number of comparative plots of all the physical quantities we have considered and a detailed analysis is presented to illustrate the main features and the variation profiles of the properties with the applied external magnetic field and temperature.

  10. Theory of electron spin echoes in solids

    CERN Document Server

    Asadullina, N Y; Asadullin, Y Y


    We propose modified Bloch equations (MBEs) with specific power-dependent relaxation and dispersion parameters characteristic for two-pulse excitation and when the magnetic dipole-dipole interactions in the electron spin system control the dephasing. We discriminate between the 'active' (excited by both pulses) and 'passive' (excited by the second pulse only) spins: it is shown that the 'active' spins participate in a new effect, an active spin frequency modulation effect giving rise to the power-dependent dispersion and multiple electron spin echoes (ESEs); the 'passive' spins contribute to the power-dependent relaxation. The MBEs are solved and a general expression for the two-pulse ESEs is obtained. Detailed numerical analysis of this expression gives results in good quantitative agreement with the recent experiments on the two-pulse ESEs at conventional low applied fields. The developed theory is applied also to high field ESEs, which are promising for future investigations. On the basis of published resul...

  11. Effects of interface geometry on spin injection (United States)

    Lee, B. C.


    Spin-injection efficiency may be affected by interface geometry and it was investigated theoretically by considering a nonmagnetic (NM) sphere embedded in a ferromagnetic (FM) host. When spin-polarized current is injected into the NM sphere from the FM host, it is found that spinsplitting of the electrochemical potential is enhanced at the interface while the spin polarization of the electrical current is reduced compared with the flat interface. In the Co/Cu and the Py/Cu systems, the values are different from those of the flat interface even when the sphere radius is 3 μm. Attachment of another NM electrode to the NM sphere changes the spin-splitting of the electrochemical potential, which may be critical for the nonlocal spin signal in the lateral spin valve.

  12. Spin-Valley Beam Splitter in Graphene

    CERN Document Server

    Song, Yu; Shi, Zhi-Gui; Li, Shun; Zhang, Jian


    The fourfold spin-valley degenerate degrees of freedom in bulk graphene can support rich physics and novel applications associated with multicomponent quantum Hall effects and linear conductance filtering. In this work, we study how to break the spin-valley degeneracy of electron beams spatially. We propose a spin-valley beam splitter in a gated ferromagnetic/pristine/strained graphene structure. We demonstrate that, in a full resonant tunneling regime for all spin-valley beam components, the formation of quasi-standing waves can lead four giant lateral Goos-H\\"{a}nchen shifts as large as the transverse beam width, while the interplay of the two modulated regions can lead difference of resonant angles or energies for the four spin-valley flavors, manifesting an effective spin-valley beam splitting effect. The beam splitting effect is found to be controllable by the gating and strain.

  13. Controlling a nuclear spin in a nanodiamond (United States)

    Knowles, Helena S.; Kara, Dhiren M.; Atatüre, Mete


    The sensing capability of a single optically bright electronic spin in diamond can be enhanced by making use of proximal dark nuclei as ancillary spins. Such systems, so far realized only in bulk diamond, can provide orders of magnitude higher sensitivity and spectral resolution in the case of magnetic sensing, as well as improved readout fidelity and state storage time in quantum information schemes. Nanodiamonds offer opportunities for scanning and embedded nanoscale probes, yet electronic-nuclear spin complexes have so far remained inaccessible. Here, we demonstrate coherent control of a 13C nuclear spin located 4 Å from a nitrogen-vacancy center in a nanodiamond and show coherent exchange between the two components of this hybrid spin system. We extract a free precession time T2* of 26 μ s for the nuclear spin, which exceeds the bare-electron free-precession time in nanodiamond by two orders of magnitude.

  14. Hard Probes and Spin Physics at STAR

    CERN Document Server

    Tokarev, M V


    Spin is one of the most enigmatic and least understandable properties of elementary particles. The study of the proton spin puzzle is an important part of the physics program at the Relativistic Heavy Ion Collider (RHIC) accelerating both nuclei and polarized protons. STAR is one of the two large detectors at RHIC. It has an excellent capability for spin physics. In the present work the overview of the STAR spin physics program is given. It includes the highest priority measurements of single- and double-spin asymmetries allowing one to determine gluon contribution to proton spin, to separate sea and valence quark flavor polarizations, to measure quark transversity. A brief description of the RHIC accelerator complex, some detail of the STAR detector and its perfomance are presented.

  15. Chiral Spin Pairing in Helical Magnets (United States)

    Onoda, Shigeki; Nagaosa, Naoto


    A concept of chiral spin pairing is introduced to describe a vector-chiral liquid-crystal order in frustrated spin systems. It is found that the chiral spin pairing is induced by the coupling to phonons through the Dzyaloshinskii-Moriya interaction and the four-spin exchange interaction of the Coulomb origin under the edge-sharing network of magnetic and ligand ions. This produces two successive second-order phase transitions upon cooling: an O(2) chiral spin nematic, i.e., spin cholesteric, order appears with an either parity, and then the O(2) symmetry is broken to yield a helical magnetic order. Possible candidate materials are also discussed as new multiferroic systems.

  16. Plasmonic diabolo cavity enhanced spin pumping (United States)

    Qian, Jie; Gou, Peng; Gui, Y. S.; Hu, C. M.; An, Zhenghua


    Low spin-current generation efficiency has impeded further progress in practical spin devices, especially in the form of wireless excitation. To tackle this problem, a unique Plasmonic Diabolo Cavity (PDC) is proposed to enhance the spin pumping (SP) signal. The SP microwave photovoltage is enhanced ˜22-fold by PDC at ferromagnetic resonance (FMR). This improvement owes to the localization of the microwave magnetic field, which drives the spin precession process to more effectively generate photovoltage at the FMR condition. The in-plane anisotropy of spin pumping is found to be suppressed by PDC. Our work suggests that metamaterial resonant structures exhibit rich interactions with spin dynamics and could potentially be applied in future high-frequency spintronics.

  17. Cross relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek


    Cross relaxation, and mI-dependence of the intrinsic electron spin-lattice relaxation rate We, are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin......-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from...... the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI-dependent....

  18. Hole spin relaxation in quantum dots (United States)

    Woods, L. M.; Reinecke, T. L.; Kotlyar, R.


    We present results for relaxation of the spin of a hole in a cylindrical quantum dot due to acoustic phonon assisted spin flips at low temperatures with an applied magnetic field. The hole dispersion is calculated by numerical diagonalization of the Luttinger Hamiltonian and applying perturbation theory with respect to the magnetic field, and the hole-phonon coupling is described by the Bir-Pikus Hamiltonian. We find that the decoherence time for hole spins for dots ≲20 nm is on the order of 10-8 s. This is several orders smaller than the decoherence time due to phonon assisted processes for electron spins in similar dots and is comparable to the total decoherence time of an electron spin in a quantum dot, which is controlled by the hyperfine interaction with nuclei. We obtain the dependence of the relaxation rate of the hole spin on dot size and hole mass.

  19. Spin of Planetary Probes in Atmospheric Flight (United States)

    Lorenz, R. D.

    Probes that enter planetary atmospheres are often spun during entry or descent for a variety of reasons. Their spin rate histories are influenced by often subtle effects. The spin requirements, control methods and flight experience from planetary and earth entry missions are reviewed. An interaction of the probe aerodynamic wake with a drogue parachute, observed in Gemini wind tunnel tests, is discussed in connection with the anomalous spin behaviour of the Huygens probe.

  20. Spin Forming of Aluminum Metal Matrix Composites (United States)

    Lee, Jonathan A.; Munafo, Paul M. (Technical Monitor)


    An exploratory effort between NASA-Marshall Space Flight Center (MSFC) and SpinCraft, Inc., to experimentally spin form cylinders and concentric parts from small and thin sheets of aluminum Metal Matrix Composites (MMC), successfully yielded good microstructure data and forming parameters. MSFC and SpinCraft will collaborate on the recent technical findings and develop strategy to implement this technology for NASA's advanced propulsion and airframe applications such as pressure bulkheads, combustion liner assemblies, propellant tank domes, and nose cone assemblies.

  1. Quantum spin Hall phase in multilayer graphene


    García-Martínez, N. A.; Lado, Jose L.; Fernández Rossier, Joaquín


    The so-called quantum spin Hall phase is a topologically nontrivial insulating phase that is predicted to appear in graphene and graphenelike systems. In this paper we address the question of whether this topological property persists in multilayered systems. We consider two situations: purely multilayer graphene and heterostructures where graphene is encapsulated by trivial insulators with a strong spin-orbit coupling. We use a four-orbital tight-binding model that includes full atomic spin-...

  2. Nature vs. Nurture in Discrete Spin Dynamics


    Stein, D. L.


    The problem of predictability, or "nature vs. nurture", in both ordered and disordered Ising systems following a deep quench from infinite to zero temperature is reviewed. Two questions are addressed. The first deals with the nature of the final state: for an infinite system, does every spin flip infinitely often, or does every spin flip only finitely many times, or do some spins flip infinitely often and others finitely often? Once this question is determined, the evolution of the system fro...

  3. Spin effects in perturbative quantum chromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, S.J.; Lepage, G.P.


    The spin dependence of large momentum transfer exclusive and inclusive reactions can be used to test the gluon spin and other basic elements of QCD. In particular, exclusive processes including hadronic decays of heavy quark resonances have the potential of isolating QCD hard scattering subprocesses in situations where the helicities of all the interacting constituents are controlled. The predictions can be summarized in terms of QCD spin selection rules. The calculation of magnetic moment and other hadronic properties in QCD are mentioned.

  4. Spin state switching in iron coordination compounds

    Directory of Open Access Journals (Sweden)

    Philipp Gütlich


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

  5. Spin-drift transport in semiconductors (United States)

    Idrish Miah, M.


    We present a study on spin transport in semiconductors under applied electric fields. Our experiments detect photoinjected electron spins and their relaxation during drift transport in intrinsic and moderately n-doped GaAs, based on the extraordinary Hall (eH) effect. For relatively low electric field (E), the optically spin-induced eH effect in n-doped GaAs is found to be enhanced with increasing doping density and not to depend much on E, indicating that a substantial amount of optical spin polarization is preserved during the drift transport in these extrinsic semiconductors. However, when the spin-oriented electrons are injected with a high E, a very significant decrease is observed in the eH voltage (VeH) due to an increase in the spin precession frequency of the hot electrons. Spin relaxation by the D'yakonov-Perel' mechanism is calculated, and is suggested to be the reason for such a rapid spin relaxation for hot electrons under a high E. However, in an intrinsic GaAs (i-GaAs), a much weaker VeH is observed and, as the electron spins scattered by holes due to the Coulomb interaction in i-GaAs, the spin relaxation by the Bir-Aronov-Pikus mechanism is considered. Skew scattering and side jump as possible mechanisms of the optically spin-induced transverse Hall currents are discussed. Based on a spin drift-diffusion model, drift and diffusion contributions to the VeH are examined. The results are also discussed in comparison with theoretical investigations.

  6. Spin-drift transport in 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, Chittagong-4331 (Bangladesh)


    We present a study on spin transport in semiconductors under applied electric fields. Our experiments detect photoinjected electron spins and their relaxation during drift transport in intrinsic and moderately n-doped GaAs, based on the extraordinary Hall (eH) effect. For relatively low electric field (E), the optically spin-induced eH effect in n-doped GaAs is found to be enhanced with increasing doping density and not to depend much on E, indicating that a substantial amount of optical spin polarization is preserved during the drift transport in these extrinsic semiconductors. However, when the spin-oriented electrons are injected with a high E, a very significant decrease is observed in the eH voltage (V{sub eH}) due to an increase in the spin precession frequency of the hot electrons. Spin relaxation by the D'yakonov-Perel' mechanism is calculated, and is suggested to be the reason for such a rapid spin relaxation for hot electrons under a high E. However, in an intrinsic GaAs (i-GaAs), a much weaker V{sub eH} is observed and, as the electron spins scattered by holes due to the Coulomb interaction in i-GaAs, the spin relaxation by the Bir-Aronov-Pikus mechanism is considered. Skew scattering and side jump as possible mechanisms of the optically spin-induced transverse Hall currents are discussed. Based on a spin drift-diffusion model, drift and diffusion contributions to the V{sub eH} are examined. The results are also discussed in comparison with theoretical investigations.

  7. Strong Linear Dichroism in Spin-Polarized Photoemission from Spin-Orbit-Coupled Surface States (United States)

    Bentmann, H.; Maaß, H.; Krasovskii, E. E.; Peixoto, T. R. F.; Seibel, C.; Leandersson, M.; Balasubramanian, T.; Reinert, F.


    A comprehensive understanding of spin-polarized photoemission is crucial for accessing the electronic structure of spin-orbit coupled materials. Yet, the impact of the final state in the photoemission process on the photoelectron spin has been difficult to assess in these systems. We present experiments for the spin-orbit split states in a Bi-Ag surface alloy showing that the alteration of the final state with energy may cause a complete reversal of the photoelectron spin polarization. We explain the effect on the basis of ab initio one-step photoemission theory and describe how it originates from linear dichroism in the angular distribution of photoelectrons. Our analysis shows that the modulated photoelectron spin polarization reflects the intrinsic spin density of the surface state being sampled differently depending on the final state, and it indicates linear dichroism as a natural probe of spin-orbit coupling at surfaces.

  8. Electronic spin storage in an electrically readable nuclear spin memory with a lifetime >100 seconds. (United States)

    McCamey, D R; Van Tol, J; Morley, G W; Boehme, C


    Electron spins are strong candidates with which to implement spintronics because they are both mobile and able to be manipulated. The relatively short lifetimes of electron spins, however, present a problem for the long-term storage of spin information. We demonstrated an ensemble nuclear spin memory in phosphorous-doped silicon, which can be read out electrically and has a lifetime exceeding 100 seconds. The electronic spin information can be mapped onto and stored in the nuclear spin of the phosphorus donors, and the nuclear spins can then be repetitively read out electrically for time periods that exceed the electron spin lifetime. We discuss how this memory can be used in conjunction with other silicon spintronic devices.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gladii, O.; Henry, Y.; Bailleul, M. [Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2 (France); Collet, M.; Garcia-Hernandez, K.; Cheng, C.; Bortolotti, P.; Cros, V.; Anane, A. [Unité Mixte de Physique CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767 Palaiseau (France); Xavier, S. [Thales Research and Technology, 1 Av. A. Fresnel, Campus de l' Ecole Polytechnique, 91767 Palaiseau (France); Kim, J.-V. [Institut d' Electronique Fondamentale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)


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

  10. Spin states of multielectron systems and the action of multi-spin bans (United States)

    Arifullin, M. R.; Berdinskii, V. L.


    Magnetic and spin effects in chemical reactions are caused by the effect of spin bans, which control the elementary acts of radical and ion-radical reactions involving, as a rule, two paramagnetic particles. Any description of spin bans acting in chemical and enzymatic reactions, which is accompanied by transfer of several electrons, as well as in the reactions of high spin molecules, requires knowledge of spin states. It is shown that spin states of multi-electron states should be described by a spin density matrix; rules for their construction are given and their properties are described. As a first step, the construction of four-density matrix is described in detail. The application of four- and three-spin density matrixes is shown for analyzing the formation of superoxide anion in respiratory chains of mitochondria.

  11. Graphene-WS2 heterostructures for tunable spin injection and spin transport (United States)

    Omar, S.; van Wees, B. J.


    We report the first measurements of spin injection into graphene through a 20-nm-thick tungsten disulphide (WS2) layer, along with a modified spin relaxation time (τs) in graphene in the WS2 environment, via spin-valve and Hanle spin-precession measurements, respectively. First, during the spin injection into graphene through a WS2-graphene interface, we can tune the interface resistance at different current bias and modify the spin injection efficiency, in a correlation with the conductivity-mismatch theory. Temperature assisted tunneling is identified as a dominant mechanism for the charge transport across the interface. Second, we measure the spin transport in graphene, underneath the WS2 crystal, and observe a significant reduction in the τs down to 17 ps in graphene in the WS2 covered region, compared to that in its pristine state. The reduced τs indicates the WS2-proximity induced additional dephasing of the spins in graphene.

  12. Spin-orbit-coupled transport and spin torque in a ferromagnetic heterostructure

    KAUST Repository

    Wang, Xuhui


    Ferromagnetic heterostructures provide an ideal platform to explore the nature of spin-orbit torques arising from the interplay mediated by itinerant electrons between a Rashba-type spin-orbit coupling and a ferromagnetic exchange interaction. For such a prototypic system, we develop a set of coupled diffusion equations to describe the diffusive spin dynamics and spin-orbit torques. We characterize the spin torque and its two prominent—out-of-plane and in-plane—components for a wide range of relative strength between the Rashba coupling and ferromagnetic exchange. The symmetry and angular dependence of the spin torque emerging from our simple Rashba model is in an agreement with experiments. The spin diffusion equation can be generalized to incorporate dynamic effects such as spin pumping and magnetic damping.

  13. Higher spin black holes with soft hair

    Energy Technology Data Exchange (ETDEWEB)

    Grumiller, Daniel [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Pérez, Alfredo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile); Prohazka, Stefan [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Tempo, David; Troncoso, Ricardo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile)


    We construct a new set of boundary conditions for higher spin gravity, inspired by a recent “soft Heisenberg hair”-proposal for General Relativity on three-dimensional Anti-de Sitter space. The asymptotic symmetry algebra consists of a set of affine û(1) current algebras. Its associated canonical charges generate higher spin soft hair. We focus first on the spin-3 case and then extend some of our main results to spin-N, many of which resemble the spin-2 results: the generators of the asymptotic W{sub 3} algebra naturally emerge from composite operators of the û(1) charges through a twisted Sugawara construction; our boundary conditions ensure regularity of the Euclidean solutions space independently of the values of the charges; solutions, which we call “higher spin black flowers”, are stationary but not necessarily spherically symmetric. Finally, we derive the entropy of higher spin black flowers, and find that for the branch that is continuously connected to the BTZ black hole, it depends only on the affine purely gravitational zero modes. Using our map to W-algebra currents we recover well-known expressions for higher spin entropy. We also address higher spin black flowers in the metric formalism and achieve full consistency with previous results.

  14. The quark fraction of the proton spin (United States)

    Mandula, Jeffrey E.

    We report on a lattice QCD estimate of the fraction of the proton spin that the quark spin is responsible for. The estimate is arrived at by means of a lattice QCD simulation of the polarized proton matrix element of the anomaly, F μνoverlineFμν. The preliminary result of the simulation is that this fraction is rather small. This is in accord with the interpretation of the EMC experiment that the quark spins are responsible for very little, if any, of the proton spin.

  15. Top Quark Spin Correlations at the Tevatron

    Energy Technology Data Exchange (ETDEWEB)

    Head, Tim; /Manchester U.


    Recent measurements of the correlation between the spin of the top and the spin of the anti-top quark produced in proton anti-proton scattering at a center of mass energy of {radical}s = 1.96 Tev by the CDF and D0 collaborations are discussed. using up to 4.3 fb{sup -1} of data taken with the CDF and D0 detectors the spin correlation parameter C, the degree to which the spins are correlated, is measured in dileptonic and semileptonic final states. The measurements are found to be in agreement with Standard Model predictions.

  16. Evaluation of layback spin in figure skating

    Directory of Open Access Journals (Sweden)

    Jastšenjski Ksenija


    Full Text Available Layback spin is considered as one of the most beautiful and elegant spins performed in figure skating. It is also one of the required spins in competitive short program in female category. Different techniques of executing layback spin with variations in changing the positions of free parts of the body, as well as the evaluation of layback spin in accordance with ISU rules and regulations, which have been used in all International Skating Federation competitions since 2004 (World and European championships, Olympic Games are presented in this paper. Due to very difficult position of the body while performing a layback spin, it is essential that the skaters who want to master it should have excellent agility (especially of the spinal column and shoulder and knee joints and balance. Layback spin performance requires significant skating knowledge, so it cannot be performed by beginners. Depending on the fl exibility and creativity, a skater can execute various positions of the head, arms, body and free leg while performing a layback spin. In some cases, these variations can increase the level of difficulty, and in others only the mark given for executing this spin.

  17. 21st International Symposium on Spin Physics

    CERN Document Server

    Ma, Bo-Qiang; SPIN 2014; SPIN2014


    This special volume collected important papers written by leading experts, highlighting the latest research findings in various topics of spin phenomena in particle and nuclear physics. The contents are originated from the plenary talks at the latest symposium of the Spin Physics series (SPIN2014) which was held in Beijing, China, October 20-24, 2014.The volume also comprises a special collection of contributions in memory of the late Professor Michel Borghini, an outstanding physicist well remembered for his great contributions to the progress of high energy spin physics.

  18. Quantum interference effects in molecular spin hybrids (United States)

    Esat, Taner; Friedrich, Rico; Matthes, Frank; Caciuc, Vasile; Atodiresei, Nicolae; Blügel, Stefan; Bürgler, Daniel E.; Tautz, F. Stefan; Schneider, Claus M.


    We have studied by means of low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) single molecular spin hybrids formed upon chemisorbing a polycyclic aromatic, threefold symmetric hydrocarbon molecule on Co(111) nanoislands. The spin-dependent hybridization between the Co d states and the π orbitals of the molecule leads to a spin-imbalanced electronic structure of the chemisorbed organic molecule. Spin-sensitive measurements reveal that the spin polarization shows intramolecular variations among the different aromatic rings in spite of the highly symmetric adsorption geometry promoted by symmetry matching of the threefold symmetric molecule and the sixfold symmetric Co(111) lattice. Hence the varying degree of spin polarization on the organic molecule does not stem from a different hybridization of the aromatic rings with the Co atoms, but is proposed to be a consequence of the superposition of the spin polarization of the molecule and the spatially modulated spin polarization of the spin-dependent quantum interference pattern of the Co(111) surface state.

  19. Spin-crossover materials properties and applications

    CERN Document Server

    Halcrow, Malcolm A


    The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved. Spin-Crossover Materials: Properties and Applicat

  20. Spin transport in tilted electron vortex beams


    Basu, Banasri; Chowdhury, Debashree


    In this paper we have enlightened the spin related issues of tilted Electron vortex beams. We have shown that in the skyrmionic model of electron we can have the spin Hall current considering the tilted type of electron vortex beam. We have considered the monopole charge of the tilted vortex as time dependent and through the time variation of the monopole charge we can explain the spin Hall effect of electron vortex beams. Besides, with an external magnetic field we can have a spin filter con...

  1. Long-range spin transport in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Beckmann, Detlef; Wolf, Michael J. [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Huebler, Florian [Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Loehneysen, Hilbert von [Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany)


    Recently, there has been some controversy about spin-polarized quasiparticle transport and relaxation in superconductors, with reports of both anomalously short or anomalously long relaxation times as compared to the normal state. Here, we report on non-local transport in multiterminal superconductor-ferromagnet structures. We find signatures of spin transport over distances much larger than the normal-state spin-diffusion length in the presence of a large Zeeman splitting of the quasiparticle states. The relaxation length shows a nearly linear increase with magnetic field, hinting at a freeze-out of spin relaxation by the Zeeman splitting.

  2. Relativistic dynamical spin excitations of magnetic adatoms (United States)

    dos Santos Dias, M.; Schweflinghaus, B.; Blügel, S.; Lounis, S.


    We present a first-principles theory of dynamical spin excitations in the presence of spin-orbit coupling. The broken global spin rotational invariance leads to a new sum rule. We explore the competition between the magnetic anisotropy energy and the external magnetic field, as well as the role of electron-hole excitations, through calculations for 3 d -metal adatoms on the Cu(111) surface. The spin excitation resonance energy and lifetime display nontrivial behavior, establishing the strong impact of relativistic effects. We legitimate the use of the Landau-Lifshitz-Gilbert equation down to the atomic limit, but with parameters that differ from a stationary theory.

  3. Constraints on vector meson photoproduction spin observables (United States)

    Kloet, W. M.; Tabakin, Frank


    Extraction of spin observables from vector meson photoproduction on a nucleon target is described. Starting from density matrix elements in the vector meson's rest frame, we transform to spin observables in the photon-nucleon c.m. frame. Several constraints on the transformed density matrix and on the spin observables follow from requiring that the angular distribution and the density matrix be positive definite. A set of constraints that are required in order to extract meaningful spin observables from forthcoming data are enunciated.

  4. Coherent manipulation of single spins in semiconductors. (United States)

    Hanson, Ronald; Awschalom, David D


    During the past few years, researchers have gained unprecedented control over spins in the solid state. What was considered almost impossible a decade ago, in both conceptual and practical terms, is now a reality: single spins can be isolated, initialized, coherently manipulated and read out using both electrical and optical techniques. Progress has been made towards full control of the quantum states of single and coupled spins in a variety of semiconductors and nanostructures, and towards understanding the mechanisms through which spins lose coherence in these systems. These abilities will allow pioneering investigations of fundamental quantum-mechanical processes and provide pathways towards applications in quantum information processing.

  5. Handbook of spin transport and magnetism

    CERN Document Server

    Tsymbal, Evgeny Y


    In the past several decades, the research on spin transport and magnetism has led to remarkable scientific and technological breakthroughs, including Albert Fert and Peter Grünberg's Nobel Prize-winning discovery of giant magnetoresistance (GMR) in magnetic metallic multilayers. Handbook of Spin Transport and Magnetism provides a comprehensive, balanced account of the state of the art in the field known as spin electronics or spintronics. It reveals how key phenomena first discovered in one class of materials, such as spin injection in metals, have been revisited decades later in other materia

  6. A molecular spin-photovoltaic device (United States)

    Sun, Xiangnan; Vélez, Saül; Atxabal, Ainhoa; Bedoya-Pinto, Amilcar; Parui, Subir; Zhu, Xiangwei; Llopis, Roger; Casanova, Fèlix; Hueso, Luis E.


    We fabricated a C60 fullerene-based molecular spin-photovoltaic device that integrates a photovoltaic response with the spin transport across the molecular layer. The photovoltaic response can be modified under the application of a small magnetic field, with a magnetophotovoltage of up to 5% at room temperature. Device functionalities include a magnetic current inverter and the presence of diverging magnetocurrent at certain illumination levels that could be useful for sensing. Completely spin-polarized currents can be created by balancing the external partially spin-polarized injection with the photogenerated carriers.

  7. Spin-Seebeck effect in a strongly interacting Fermi gas

    NARCIS (Netherlands)

    Wong, C.H.; Stoof, H.T.C.|info:eu-repo/dai/nl/074851357; Duine, R.A.|info:eu-repo/dai/nl/304830127


    We study the spin-Seebeck effect in a strongly interacting, two-component Fermi gas and propose an experiment to measure this effect by relatively displacing spin-up and spin-down atomic clouds in a trap using spin-dependent temperature gradients. We compute the spin-Seebeck coefficient and related

  8. High spin ↔ low spin ultrafast excitation and relaxation of an isolated iron(II complex.

    Directory of Open Access Journals (Sweden)

    Létard J.F.


    Full Text Available Picosecond and femtosecond time resolved pump-probe experiments make it possible to study both the low spin (LS to high spin (HS and high spin to low spin excitation and relaxation processes in the same isolated iron(II complex. We demonstrate that both LS → HS and HS → LS can be recorded by changing the pump wavelength and occur on the same time scale.

  9. Impact of the spin state switching on the dielectric constant of iron (II) spin crossover nanoparticles


    Iazzolino, Antonio; Galle, Geoffrey; Degert, Jérôme; Létard, Jean François; Freysz, Eric


    International audience; A simple model makes it possible to relate the dielectric constant of spin-crossover nanoparticles to the indices of refraction and the absorption coefficients of solutions containing such nanoparticles. Using this model we show that in the visible spectral range, the switching from a diamagnetic (low spin state) to a paramagnetic (high spin state) state results in a noticeable change of the dielectric constants of the spin crossover nanoparticles containing 3, 5 and 7...

  10. Spin Squeezing of Atomic Ensembles via Nuclear-Electronic Spin Entanglement

    DEFF Research Database (Denmark)

    Fernholz, Thomas; Krauter, Hanna; Jensen, K.


    We demonstrate spin squeezing in a room temperature ensemble of ≈1012 cesium atoms using their internal structure, where the necessary entanglement is created between nuclear and electronic spins of each individual atom. This state provides improvement in measurement sensitivity beyond the standard...... quantum limit for quantum memory experiments and applications in quantum metrology and is thus a complementary alternative to spin squeezing obtained via interatom entanglement. Squeezing of the collective spin is verified by quantum state tomography....

  11. Do Spin-Offs Make the Academics’ Heads Spin? (United States)

    Jongbloed, Ben W. A.; Enders, Jürgen


    As public research organisations are increasingly driven by their national and regional governments to engage in knowledge transfer, they have started to support the creation of companies. These research based spin-off companies (RBSOs) often keep contacts with the research institutes they originate from. In this paper we present the results of a study of four research institutes within two universities and two non-university public research organisations (PROs) in the Netherlands. We show that research organisations have distinct motivations to support the creation of spin-off companies. In terms of resources RBSOs contribute, mostly in a modest way, to research activities by providing information, equipment and monetary resources. In particular, RBSOs are helpful for researchers competing for research grants that demand participation of industry. Furthermore, RBSOs may be seen as a proactive response by Dutch public research organisations to demands of economic relevance from their institutional environment. RBSOs enhance the prestige of their parent organisations and create legitimacy for public funds invested in PROs. At the same time, most RBSOs do not have a significant impact on the direction of the research conducted at the PROs. PMID:20936164

  12. Quantum Spin Stabilized Magnetic Levitation (United States)

    Rusconi, C. C.; Pöchhacker, V.; Kustura, K.; Cirac, J. I.; Romero-Isart, O.


    We theoretically show that, despite Earnshaw's theorem, a nonrotating single magnetic domain nanoparticle can be stably levitated in an external static magnetic field. The stabilization relies on the quantum spin origin of magnetization, namely, the gyromagnetic effect. We predict the existence of two stable phases related to the Einstein-de Haas effect and the Larmor precession. At a stable point, we derive a quadratic Hamiltonian that describes the quantum fluctuations of the degrees of freedom of the system. We show that, in the absence of thermal fluctuations, the quantum state of the nanomagnet at the equilibrium point contains entanglement and squeezing.

  13. Charged Polaritons with Spin 1

    Directory of Open Access Journals (Sweden)

    Samoilov V.


    Full Text Available We present a new model for metal which is based on the stimulated vibration of independent charged Fermi-ions, representing as independent harmonic oscillators with natural frequencies, under action of longitudinal and transverse elastic waves. Due to application of the elastic wave-particle principle and ion-wave dualities, we predict the existence of two types of charged Polaritons with spin 1 which are induced by longitudinal and transverse elastic fields. As result of presented theory, at small wavenumbers, these charged polaritons represent charged phonons.

  14. Pauli spin blockade in the presence of strong spin-orbit coupling

    NARCIS (Netherlands)

    Danon, J.; Nazarov, Y.V.

    We study electron transport in a double quantum dot in the Pauli spin blockade regime in the presence of strong spin-orbit coupling. The effect of spin-orbit coupling is incorporated into a modified interdot tunnel coupling. We elucidate the role of the external magnetic field, the nuclear fields in

  15. Quasiperiodic spin-orbit motion and spin tunes in storage rings

    Directory of Open Access Journals (Sweden)

    D. P. Barber


    Full Text Available We present an in-depth analysis of the concept of spin precession frequency for integrable orbital motion in storage rings. Spin motion on the periodic closed orbit of a storage ring can be analyzed in terms of the Floquet theorem for equations of motion with periodic parameters, and a spin precession frequency emerges in a Floquet exponent as an additional frequency of the system. To define a spin precession frequency on nonperiodic synchrobetatron orbits we exploit the important concept of quasiperiodicity. This allows a generalization of the Floquet theorem so that a spin precession frequency can be defined in this case, too. This frequency appears in a Floquet-like exponent as an additional frequency in the system in analogy with the case of motion on the closed orbit. These circumstances lead naturally to the definition of the uniform precession rate and a definition of spin tune. A spin tune is a uniform precession rate obtained when certain conditions are fulfilled. Having defined spin tune we define spin-orbit resonance on synchrobetatron orbits and examine its consequences. We give conditions for the existence of uniform precession rates and spin tunes (e.g., where small divisors are controlled by applying a Diophantine condition and illustrate the various aspects of our description with several examples. The formalism also suggests the use of spectral analysis to “measure” spin tune during computer simulations of spin motion on synchrobetatron orbits.

  16. Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets (United States)

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


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

  17. Spin polarizabilities and characteristics of spin-1 hadrons related to parity nonconservation in the Duffin-Kemmer-Petiau formalism (United States)

    Vakulina, E. V.; Maksimenko, N. V.


    Spin polarizabilities of spin-1 particles typical of spin-1/2 hadrons are established within the Duffin-Kemmer-Petiau formalism using the relativistically invariant effective tensor representation of Lagrangians of two-photon interaction with hadrons. New spin polarizabilities of spin-1 particles associated with the presence of tensor polarizabilities are also determined.

  18. Circuit Simulation of All-Spin Logic

    KAUST Repository

    Alawein, Meshal


    With the aggressive scaling of complementary metal-oxide semiconductor (CMOS) nearing an inevitable physical limit and its well-known power crisis, the quest for an alternative/augmenting technology that surpasses the current semiconductor electronics is needed for further technological progress. Spintronic devices emerge as prime candidates for Beyond CMOS era by utilizing the electron spin as an extra degree of freedom to decrease the power consumption and overcome the velocity limit connected with the charge. By using the nonvolatility nature of magnetization along with its direction to represent a bit of information and then manipulating it by spin-polarized currents, routes are opened for combined memory and logic. This would not have been possible without the recent discoveries in the physics of nanomagnetism such as spin-transfer torque (STT) whereby a spin-polarized current can excite magnetization dynamics through the transfer of spin angular momentum. STT have expanded the available means of switching the magnetization of magnetic layers beyond old classical techniques, promising to fulfill the need for a new generation of dense, fast, and nonvolatile logic and storage devices. All-spin logic (ASL) is among the most promising spintronic logic switches due to its low power consumption, logic-in-memory structure, and operation on pure spin currents. The device is based on a lateral nonlocal spin valve and STT switching. It utilizes two nanomagnets (whereby information is stored) that communicate with pure spin currents through a spin-coherent nonmagnetic channel. By using the well-known spin physics and the recently proposed four-component spin circuit formalism, ASL can be thoroughly studied and simulated. Previous attempts to model ASL in the linear and diffusive regime either neglect the dynamic characteristics of transport or do not provide a scalable and robust platform for full micromagnetic simulations and inclusion of other effects like spin Hall

  19. Spin Orbit Torque in Ferromagnetic Semiconductors

    KAUST Repository

    Li, Hang


    Electrons not only have charges but also have spin. By utilizing the electron spin, the energy consumption of electronic devices can be reduced, their size can be scaled down and the efficiency of `read\\' and `write\\' in memory devices can be significantly improved. Hence, the manipulation of electron spin in electronic devices becomes more and more appealing for the advancement of microelectronics. In spin-based devices, the manipulation of ferromagnetic order parameter using electrical currents is a very useful means for current-driven operation. Nowadays, most of magnetic memory devices are based on the so-called spin transfer torque, which stems from the spin angular momentum transfer between a spin-polarized current and the magnetic order parameter. Recently, a novel spin torque effect, exploiting spin-orbit coupling in non-centrosymmetric magnets, has attracted a massive amount of attention. This thesis addresses the nature of spin-orbit coupled transport and torques in non-centrosymmetric magnetic semiconductors. We start with the theoretical study of spin orbit torque in three dimensional ferromagnetic GaMnAs. Using the Kubo formula, we calculate both the current-driven field-like torque and anti-damping-like torque. We compare the numerical results with the analytical expressions in the model case of a magnetic Rashba two-dimensional electron gas. Parametric dependencies of the different torque components and similarities to the analytical results of the Rashba two-dimensional electron gas in the weak disorder limit are described. Subsequently we study spin-orbit torques in two dimensional hexagonal crystals such as graphene, silicene, germanene and stanene. In the presence of staggered potential and exchange field, the valley degeneracy can be lifted and we obtain a valley-dependent Berry curvature, leading to a tunable antidamping torque by controlling the valley degree of freedom. This thesis then addresses the influence of the quantum spin Hall

  20. Spin lattices of walking droplets (United States)

    Saenz, Pedro; Pucci, Giuseppe; Goujon, Alexis; Dunkel, Jorn; Bush, John


    We present the results of an experimental investigation of the spontaneous emergence of collective behavior in spin lattice of droplets walking on a vibrating fluid bath. The bottom topography consists of relatively deep circular wells that encourage the walking droplets to follow circular trajectories centered at the lattice sites, in one direction or the other. Wave-mediated interactions between neighboring drops are enabled through a thin fluid layer between the wells. The sense of rotation of the walking droplets may thus become globally coupled. When the coupling is sufficiently strong, interactions with neighboring droplets may result in switches in spin that lead to preferred global arrangements, including correlated (all drops rotating in the same direction) or anti-correlated (neighboring drops rotating in opposite directions) states. Analogies with ferromagnetism and anti-ferromagnetism are drawn. Different spatial arrangements are presented in 1D and 2D lattices to illustrate the effects of topological frustration. This work was supported by the US National Science Foundation through Grants CMMI-1333242 and DMS-1614043.

  1. Spin canting in ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Marx, J., E-mail:; Huang, H.; Salih, K. S. M.; Thiel, W. R.; Schünemann, V. [University of Kaiserslautern, Department of Physics (Germany)


    Recently, an easily scalable process for the production of small (3 −7 nm) monodisperse superparamagnetic ferrite nanoparticles MeFe{sub 2}O{sub 4} (Me = Zn, Mn, Co) from iron metal and octanoic acid has been reported (Salih et al., Chem. Mater. 25 1430–1435 2013). Here we present a Mössbauer spectroscopic study of these ferrite nanoparticles in external magnetic fields of up to B = 5 T at liquid helium temperatures. Our analysis shows that all three systems show a comparable inversion degree and the cationic distribution for the tetrahedral A and the octahedral B sites has been determined to (Zn{sub 0.19}Fe{sub 0.81}){sup A}[Zn{sub 0.81}Fe{sub 1.19}] {sup B}O{sub 4}, (Mn{sub 0.15}Fe{sub 0.85}){sup A}[Mn{sub 0.85}Fe{sub 1.15}] {sup B}O{sub 4} and (Co{sub 0.27}Fe{sub 0.73}){sup A}[Co{sub 0.73}Fe{sub 1.27}] {sup B}O{sub 4}. Spin canting occurs presumably in the B-sites and spin canting angles of 33°, 51° and 59° have been determined for the zinc, the manganese, and the cobalt ferrite nanoparticles.

  2. Spin canting in ferrite nanoparticles (United States)

    Marx, J.; Huang, H.; Salih, K. S. M.; Thiel, W. R.; Schünemann, V.


    Recently, an easily scalable process for the production of small (3 -7 nm) monodisperse superparamagnetic ferrite nanoparticles MeFe2O4 (Me = Zn, Mn, Co) from iron metal and octanoic acid has been reported (Salih et al., Chem. Mater. 25 1430-1435 2013). Here we present a Mössbauer spectroscopic study of these ferrite nanoparticles in external magnetic fields of up to B = 5 T at liquid helium temperatures. Our analysis shows that all three systems show a comparable inversion degree and the cationic distribution for the tetrahedral A and the octahedral B sites has been determined to (Zn0.19Fe0.81) A [Zn0.81Fe1.19] B O4, (Mn0.15Fe0.85) A [Mn0.85Fe1.15] B O4 and (Co0.27Fe0.73) A [Co0.73Fe1.27] B O4. Spin canting occurs presumably in the B-sites and spin canting angles of 33°, 51° and 59° have been determined for the zinc, the manganese, and the cobalt ferrite nanoparticles.

  3. PREFACE: SPIN2010 - Preface for Conference Proceedings (United States)

    Ströher, Hans; Rathmann, Frank


    SPIN2010, the 19th International Spin Physics Symposium, took place between 27 September and 2 October, 2010 on the campus of Forschungszentrum Jülich GmbH (FZJ) in Jülich, Germany. The scientific program of this Symposium included many topics related to spin phenomena in particle and nuclear physics as well as those in related fields. The International Spin Physics Symposium series has combined the High Energy Spin Symposia and the Nuclear Polarization Conferences since 2000. The most recent two Symposia were held in Virginia, USA (October 2008) and in Kyoto, Japan (October 2006). The meeting was opened by the chairman of the Board of Management of Jülich Forschungszentrum, Professor Achim Bachem, who cordially welcomed the participants from all over the world and gave a brief introduction to the Center and the research conducted there. The scientific program consisted of plenary sessions and parallel sessions and included the following topics: Fundamental symmetries and spin Spin structure of hadrons Spin physics beyond the Standard Model Spin in hadronic reactions Spin physics with photons and leptons Spin physics in nuclear reactions and nuclei Acceleration, storage, and polarimetry of polarized beams Polarized ion and lepton sources and targets Future facilities and experiments Medical and technological applications of spin physics The 6-day symposium had about 300 participants. In total 35 plenary talks (including 3 summaries of other spin physics meetings) and 163 contributed talks were given. The contents of many of these can be found in the present contributions, arranged according to the above topics and the time sequence. In addition, a public lecture on "Drall in der Quantenwelt", presented by H O Meyer (Bloomington) was received very well. Participants had the option to visit the Cooler synchrotron COSY at the Nuclear Physics Institute (IKP) and the 9.4 T MRT-PET hybrid scanner at the Institute of Neuroscience and Medicine (INM), two unique

  4. Spin transport properties in a double quantum ring with Rashba spin-orbit interaction (United States)

    Naeimi, Azadeh S.; Eslami, Leila; Esmaeilzadeh, Mahdi; Abolhassani, Mohammad Reza


    We study spin-resolved electron transport in a double quantum ring in the presence of Rashba spin-orbit interaction and a magnetic flux using quantum waveguide theory. We show that, at the proper values of the system parameters such as the Rashba coupling constant, the radius of the rings, and the angle between the leads, the double quantum ring can act as a perfect electron spin-inverter with very high efficiency. Also, the double quantum ring can work as a spin switch. The spin polarization of transmitted electrons can be controlled and changed from -1 to +1 by using a magnetic flux.

  5. Zeeman and spin orbit effects on the spin-Hall conductance (United States)

    Lipparini, Enrico; Barranco, Manuel


    We show that when a two-dimensional interacting electron gas is submitted to a perpendicular magnetic field, the application of an in-plane electric field E induces a spin current perpendicular to E whose conductivity is quantized. This current can lead to spin accumulation that might be detected by means of optical experiments. The appearance of this intrinsic spin-Hall effect is crucially based on the validity of Kohn's theorem and on the presence of the Zeeman term in the electron Hamiltonian. The possibility of resonant effects in the spin-Hall conductivity due to the combined effect of Rashba and Dresselhaus spin-orbit couplings is discussed.

  6. Spin-to-orbital angular momentum conversion and spin-polarization filtering in electron beams. (United States)

    Karimi, Ebrahim; Marrucci, Lorenzo; Grillo, Vincenzo; Santamato, Enrico


    We propose the design of a space-variant Wien filter for electron beams that induces a spin half-turn and converts the corresponding spin angular momentum variation into orbital angular momentum of the beam itself by exploiting a geometrical phase arising in the spin manipulation. When applied to a spatially coherent input spin-polarized electron beam, such a device can generate an electron vortex beam, carrying orbital angular momentum. When applied to an unpolarized input beam, the proposed device, in combination with a suitable diffraction element, can act as a very effective spin-polarization filter. The same approach can also be applied to neutron or atom beams.

  7. The quark fraction of the proton spin

    Energy Technology Data Exchange (ETDEWEB)

    Mandula, J.E. (Department of Energy, Washington, DC (United States). Div. of High Energy Physics)


    We report on a lattice QCD estimate of the fraction of the proton spin that the quark spin is responsible for. The estimate is arrived at by means of a lattice QCD simulation of the polarized proton matrix element of the anomaly, F[sub [mu][nu

  8. Bethe vectors for XXX-spin chain (United States)

    Burdík, Čestmír; Fuksa, Jan; Isaev, Alexei


    The paper deals with algebraic Bethe ansatz for XXX-spin chain. Generators of Yang-Baxter algebra are expressed in basis of free fermions and used to calculate explicit form of Bethe vectors. Their relation to N-component models is used to prove conjecture about their form in general. Some remarks on inhomogeneous XXX-spin chain are included.

  9. The Spin : Poincaré seminar

    CERN Document Server

    Rivasseau, Vincent; Duplantier, Bertrand; Le spin : séminaire Poincaré


    The book contains articles from leading experts in different areas for which the Spin principle is the common denominator. Theoretical as well as practical topics are discussed, such as the relationship between Spin and Quantum Statistics. Furthermore, current developments of practical applications like Spintronic or medical imaging are presented.

  10. Iron(III) spin crossover compounds

    NARCIS (Netherlands)

    van Koningsbruggen, PJ; Maeda, Y; Oshio, H


    In this chapter, selected results obtained so far on Fe(III) spin crossover compounds are summarized and discussed. Fe(III) spin transition materials of ligands containing chalcogen donor atoms are considered with emphasis on those of N,N-disubstituted-dithiocarbamates,

  11. A New Spin on Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, Chris [Univ. of California, Berkeley, CA (United States)


    The electronic spin degree of freedom is of general fundamental importance to all matter. Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking. Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by-continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority . This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

  12. Antigravity: Spin-gravity coupling in action (United States)

    Plyatsko, Roman; Fenyk, Mykola


    The typical motions of a spinning test particle in Schwarzschild's background which show the strong repulsive action of the highly relativistic spin-gravity coupling are considered using the exact Mathisson-Papapetrou equations. An approximated approach to choice solutions of these equations which describe motions of the particle's proper center of mass is developed.

  13. Electron Spins in Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Hanson, R.


    This thesis describes a series of experiments aimed at understanding and controlling the behavior of the spin degree of freedom of single electrons, confined in semiconductor quantum dots. This research work is motivated by the prospects of using the electron spin as a quantum bit (qubit), the basic

  14. Mechanism of Tennis Racket Spin Performance (United States)

    Kawazoe, Yoshihiko; Okimoto, Kenji; Okimoto, Keiko

    Players often say that some strings provide a better grip and more spin than others, but ball spin did not depend on string type, gauge, or tension in pervious laboratory experiments. There was no research work on spin to uncover what is really happening during an actual tennis impact because of the difficulty of performing the appropriate experiments. The present paper clarified the mechanism of top spin and its improvement by lubrication of strings through the use of high-speed video analysis. It also provided a more detailed explanation of spin behavior by comparing a racket with lubricated strings with the famous “spaghetti” strung racket, which was banned in 1978 by the International Tennis Federation because it used plastic spaghetti tubing over the strings to reduce friction, resulting in excessive ball spin. As the main strings stretch and slide sideways more, the ball is given additional spin due to the restoring force parallel to the string face when the main strings spring back and the ball is released from the strings. Herein, we also showed that the additional spin results in a reduction of shock vibrations of the wrist joint during impact.

  15. Generic spin model on a pyrochlore lattice (United States)

    Sim, Gibaik; Lee, Sungbin

    Motivated by several pyrochlores, we discuss generic spin model considering nearest and next nearest neighbors. Both Luttinger-Tisza analysis and simulated annealing, we analyze the phase diagram of classical spin model and discuss new types of non-coplanar order induced by anisotropic interactions. KAIST startup funding.

  16. Spin dynamics in 122-type iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jitae


    In this thesis, we present the experimental data on four different iron-based SC materials. It is mainly about the magnetic-dynamics study in the FeSC that is assumed to be among the most crucial ingredients for superconductivity in this system. Thus, the main goal of this thesis is to figure out the exact relationship between spin dynamics and superconductivity, and then further to realize what is the contribution of magnetic fluctuations for superconductivity by providing experimental data for modeling a microscopic mechanism of electron pairing in the FeSC system. In Chap. 2, we first discuss basic characteristics of FeSC, such as crystal structure and electron band-structure by briefly reviewing the relevant literature. Then, an introduction about magnetic and SC phases will follow based on the generic phase diagram. Details about current understanding of magnetic ground state in the parent compounds will be discussed in terms of spin-wave excitations which would be important when we are considering the spin dynamics in doped materials. To study magnetic dynamics in FeSC, we employed the inelastic-neutron-scattering (INS) method which can uniquely probe the underlying spin dynamics in the four dimensional energy and momentum space in a wide range. By taking advantage of the well developed theory for the magnetic neutron-scattering process, one can quantify the imaginary part of spin susceptibility that is an essential physical quantity the description of elementary magnetic excitations and can be compared with theoretical calculations directly. Moreover, the technique's energy-resolving scale spans over the most relevant energy range of magnetic fluctuations (from 0 to 100 meV). For these reasons, neutron scattering is a very powerful technique for magnetism study, and we introduce how neutron-scattering experiment works theoretically and practically in Chap. 3. For a slightly underdoped Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} compound, we report the phase

  17. Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films

    NARCIS (Netherlands)

    Aqeel, A.; Vlietstra, N.; Heuver, J.A.; Bauer, G.E.W.; Noheda, B.; Van Wees, B.J.; Palstra, T.T.M.


    We report on the spin-Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) in multiferroic CoCr2O4 (CCO) spinel thin films with Pt contacts. We observe a large enhancement of both signals below the spin-spiral (Ts=28K) and the spin lock-in (Tlock?in=14K) transitions. The SMR and SSE responses

  18. Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films

    NARCIS (Netherlands)

    Aqeel, A.; Vlietstra, N.; Heuver, J. A.; Bauer, G. E. W.; Noheda, B.; van Wees, B. J.; Palstra, T. T. M.


    We report on the spin-Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) in multiferroic CoCr2O4 (CCO) spinel thin films with Pt contacts. We observe a large enhancement of both signals below the spin-spiral (T-s = 28 K) and the spin lock-in (Tlock-in = 14 K) transitions. The SMR and SSE

  19. Long-distance spin transport in a disordered magnetic insulator


    Wesenberg, Devin; Liu, Tao; Balzar, Davor; Wu, Mingzhong; Zink, Barry L.


    Spin transport through magnetic insulators via magnons has recently been explored for a growing variety of magnetic systems with long-range order and well-understood spin excitation spectra. Here we show dramatic effects of spin transport through an amorphous magnetic insulator, which is both magnetically and structurally disordered. We generate and detect spin flow though amorphous yttrium-iron-garnet ($a$-YIG) thin films in a non-local geometry by use of the spin Hall and inverse spin Hall ...

  20. Modelling Electron Spin Accumulation in a Metallic Nanoparticle


    Wei, Y.G.; Malec, C. E.; Davidović, D.


    A model describing spin-polarized current via discrete energy levels of a metallic nanoparticle, which has strongly asymmetric tunnel contacts to two ferromagnetic leads, is presented. In absence of spin-relaxation, the model leads to a spin-accumulation in the nanoparticle, a difference ($\\Delta\\mu$) between the chemical potentials of spin-up and spin-down electrons, proportional to the current and the Julliere's tunnel magnetoresistance. Taking into account an energy dependent spin-relaxati...